ABSTRACT

Aldosterone is crucial for regulating sodium conservation in the kidney, salivary glands, sweat glands, and colon. This adrenal steroid hormone acts via the mineralocorticoid receptor (MR) to promote active transport of sodium and potassium excretion in its target tissues, through activation of specific amiloride-sensitive sodium channels (ENaC) and a Na-K ATP-ase pump. Defective aldosterone biosynthesis or action results in various clinical and laboratory test manifestations, such as hypotension, hyponatremia, hyperkalemia, and acidosis. Primary adrenal insufficiency and congenital adrenal hypoplasia are discussed in other chapters. In this chapter the mechanisms underlying aldosterone-deficient conditions, such as hyporeninemic hypoaldosteronism, primary hypoaldosteronism, including aldosterone synthase deficiency (ASD), acquired forms of the disease, and pseudohypoaldosteronism, an aldosterone resistance syndrome due to insensitivity of target tissues to aldosterone, are reviewed. 

INTRODUCTION

ALDOSTERONE BIOSYNSTHESIS

All human steroid hormones are derived from cholesterol. Aldosterone is synthesized in the zona glomerulosa of the adrenal cortex through four enzymes, cholesterol desmolase (CYP11A1), 21-hydroxylase (CYP21A2), aldosterone synthase (CYP11B2), and 3β-hydroxysteroid dehydrogenase (3β-HSD) (Figure 1). CYP11A1, CYP21A2 and CYP11B2 are cytochrome 450 enzymes (CYP), which are membrane-bound, heme-containing enzymes that accept electrons from NADPH through accessory proteins and use molecular oxygen to perform hydroxylation or other oxidative conversions (1). CYP11A1, which is a side-chain cleavage enzyme, cleaves the side chain from C21 of cholesterol, converting cholesterol to pregnenolone in adrenal mitochondria and this is the first step in steroidogenesis. The CYP11A1 gene is located on the long arm of human chromosome 15q24-q25 (2). Pregnenolone is returned to the cytosolic compartment and is converted to progesterone by 3β-HSD. Progesterone is then hydroxylated at C21 by CYP21A2, an enzyme located in the smooth endoplasmic reticulum, to yield deoxycorticosterone (DOC). The CYP21A2 gene is located on the short arm of human chromosome 6 (3). Only CYP21A2 is active in humans, the other, CYP21A1P is a pseudogene (4). CYP11B1, which is a mitochondrial enzyme, catalyzes β-hydroxylation at C11 and converts DOC to corticosterone. The terminal two steps in the conversion of corticosterone to aldosterone (18-hydroxylation and 18-methyloxidation) are catalyzed by CYP11B2 (aldosterone synthase) (5) which was previously named corticosterone 18-hydroxylase/18-methyloxidase (CMO I/CMO II) or 18-hydroxylase/isomerase. These two steps previously proposed to be catalyzed by separate enzyme, CMO 1 and II, are known to involve only one enzyme substrate interaction, aldosterone synthase encoded by CYP11B2 gene (6). The CYP11B1 and CYP11B2 genes are located on the long arm of chromosome 8 and the amino acid sequence of CYP11B2 shares more than 90% homology with that of CYP11B1 (7). In humans, the expression of CYP11B1 and CYP11B2 in the adrenal glands is spatially separated. While expression of CYP11B1 takes place in the zona reticularis/fasciculata, CYP11B2 expression and aldosterone synthesis are restricted to the zona glomerulus (8).

Figure 1. Aldosterone Biosynthesis. Aldosterone is derived from cholesterol. Biosynthetic pathway of aldosterone and structure of adrenal steroids and their biosynthetic precursors are shown in the figure. The enzymes that catalyze each step are listed in the adjacent box at the right side of the figure.

Epigenetic Regulation Of Cyp11b2 Expression

CYP11B2 gene expression is epigenetically controlled. DNA methylation at CpG dinucleotides alter gene expression by affecting transcription factor binding activity (9). Cyclic AMP responsive element binding protein 1 (CREB 1) /ATF family members and nuclear receptor subfamily 4, group A (NR4A) members bind the CYP11B2 promoter at Ad1  (cAMP response element at -71/-64) and Ad5 (cAMP response element at -129/-114), respectively, leading to activation of transcription. DNA methylation at CpG1 greatly decreased CREB 1 binding to Ad1 in the promoter lesion of CYP11B2  gene (10). In addition, DNA methylation at CpG2 reduced basal binding activities of NR4A1 and NR4A2 with Ad5 by 30% and 50%, respectivly (10). Ang II infusion in the rat decreased the methylation ratio of CYP11B2 gene  and increased gene expression in the adrenal gland (10). A low-salt diet induced hypomethylation of rat CYP11B2 and increased CYP11B2 mRNA levels parallel with aldosterone synthesis (10).

REGULATION OF ALDOSTERONE SECRETION

Aldosterone secretion is regulated by multiple factors. The renin-angiotensin system and potassium ion are the major regulators, whereas ACTH and other POMC peptides, sodium ion, vasopressin, dopamine, ANP, β-adrenergic agents, serotonin and somatostatin are minor modulators.

The Renin-Angiotensin System

Renin is a 430 amino acid enzyme that cleaves renin substrate or angiotensinogen, which is a 453 amino acid alpha-globulin product of the liver, to produce the decapeptide, angiotensin I. Angiotensin I is rapidly cleaved by angiotensin-converting enzyme (ACE) in the lung and other tissues to form the octapeptide, angiotensin II. Moreover, angiotensinase cleaves the NH2-terminal Asp residue from angiotensin II and produces the heptapeptide, angiotensin III, then to the hexapeptide angiotensin IV. The circulating levels of angiotensin III are 15 to 25% of those of angiotensin II. Angiotensin II, III and IV stimulate aldosterone secretion and vasoconstriction, while angiotensin II is more potent for vasoconstriction. The angiotensins are inactivated within minutes by tissue and plasma peptidase. The levels of the circulating renin are the rate-limiting factor in this process.

Renin is synthesized by the juxtaglomerular cells in the renal cortex and its secretion is controlled by renal arterial blood pressure, sodium concentrations of tubular fluid sensed by the macula densa, and renal sympathetic nervous activity (11). Factors that decrease renal blood flow, such as hemorrhage, dehydration, salt restriction, upright posture, and renal artery narrowing, increase renin levels. In contrast, factors that increase blood pressure, such as high salt intake, peripheral vasoconstrictors, and supine posture, decrease renin levels. Hypokalemia increases and hyperkalemia decreases renin release.

The effect of angiotensin II and III on the adrenal glomerulosa is initiated by binding to G-protein coupled receptors. The first mechanism of the intracellular signal transduction is activation of phospholipase C, which hydrolyzes PIP2 to IP3, which then releases intracellular calcium ions (12). Interestingly, angiotensin II does not stimulate adenylate cyclase activity. Angiotensin II stimulation leads to increased transfer of cholesterol to the inner mitochondrial membrane and increased conversion of cholesterol to pregnenolone and corticosterone to aldosterone (13).

Potassium

Potassium directly increases aldosterone secretion by the adrenal cortex and aldosterone then lowers serum potassium by stimulating its excretion by the kidney. High dietary potassium intake increases plasma aldosterone and enhances the aldosterone response to a subsequent potassium or angiotensin II infusion (12). The primary action of potassium for stimulating aldosterone secretion is to depolarize the plasma membrane, which activates voltage-dependent calcium channels, that permit influx or efflux of extracellular calcium (12–14), leading to the activation of calmodulin and calmodulin-dependent kinase, subsequently. The activated kinase phosphorylates both activating transcription factor and members of CRE-binding protein family which bind to 5’ flanking promotor regions of the CYP11B2 gene and trigger gene transcription in the zona glomerulosa, followed by increased aldosterone biosynthesis (13,14).

Pituitary Factors

ACTH and possibly other POMC-derived peptides, including α-MSH, α-MSH, β-LPH, and β-END, influence aldosterone secretion, however, the role of ACTH in aldosterone secretion is minor (12). ACTH increases aldosterone secretion by binding to glomerulosa cell-surface melanocortin-2 receptor, by activating adenylate cyclase, and increasing intracellular cAMP (15). Like other agents, ACTH stimulates the same two early and late steps of aldosterone biosynthesis.

Vasopressin has a modest and transient stimulatory effect on aldosterone secretion from zona granulosa cells in vitro. This effect is probably mediated via V2 receptors and phospholipase C generating IP3 and diacylglycerol (16).

Sodium

Sodium intake influences aldosterone secretion by an indirect effect through renin and to a minor extent by direct effects on zona glomerulosa responsiveness to angiotensin II. High sodium intake increases vascular volume, which suppresses renin secretion and angiotensin II generation and decreases the sensitivity of aldosterone response to angiotensin II.

Inhibitory Agents

Dopamine inhibits aldosterone secretion in humans by a mechanism that is independent of the effects of prolactin, ACTH, electrolytes, and the renin-angiotensin system (17,18). This inhibitory effect may involve binding to D2 receptors on glomerulosa cells (19). Atrial natriuretic peptide (ANP) directly inhibits aldosterone secretion and blocks the stimulatory effects of angiotensin II, potassium and ACTH, at least in part, by interfering with extracellular calcium influx (20).

MECHANISMS OF ALDOSTERONE ACTION

Effect of Aldosterone

Aldosterone is crucial for sodium conservation in the kidney, salivary glands, sweat glands, and colon. Aldosterone promotes active sodium transport and excretion of potassium in its major target tissues. It exerts its effects via the mineralocorticoid receptor (MR) and the resultant activation of specific amiloride-sensitive sodium channels (ENaC) and the Na-K ATP-ase pump (21). Aldosterone and the MR may be involved in the regulation of genes coding for the subunits of the amiloride sensitive sodium channel and the Na-K ATP-ase pump, serum and glucocorticoid regulated kinase (SGK), channel-inducing factor, as well as of other proteins (22,23). Activated SGK1 phosphorylates the neural precursor cell-expressed, developmentally down-regulated protein 4-2 (Nedd4-2) which allows binding of 14-3-3 proteins (24). Then, the interaction of Nedd4-2 and ENaC causes an accumulation of ENaC at the plasma membrane and enhances epithelial sodium transport by increasing open probability of ENaC. In a later phase translation and allocation of ENaC, basolateral Na-K ATP-ase and apical K channel (ROMK) are enhanced in its target tissues (25–27).

On the other hand, rapid effects in response to aldosterone but independent of the MR were described as so-called non-genomic or rapid signaling of aldosterone. The G protein-coupled estrogen receptor (GPER) [previously known as G protein-coupled receptor 30 (GPR30)], a member of the seven transmembrane domain family of cell surface receptors, has been reported to be a membrane receptor for aldosterone (28). The expression of GPER is ubiquitous, including in vascular cells (both endothelial cells and smooth muscle cells) and is required for rapid MR-independent effects of aldosterone in vascular smooth muscle cells (28). Aldosterone has both vasodilator and vasoconstrictor effects. The effect of aldosterone on endothelial function would vary depending on the balance between GPER and MR expression. In vascular endothelial cells, aldosterone activation of GPER mediates vasodilation, while activation of endothelial MR has been linked to enhanced vasoconstrictor and/or impaired vasodilator response (28–30).

Mineralocorticoid Receptor

The mineralocorticoid receptor (MR) is found in the cytoplasm and nucleus and the sodium channels are expressed in the apical membrane of epithelial cells of the distal convoluted tubule as well as in cells of other tissues involved with conservation of salt, such as colon, sweat glands, lung, and tongue. MR is a member of the nuclear receptor superfamily. Together with the glucocorticoid, progesterone, and androgen receptors, MR forms the steroid receptor subfamily (30). Steroid receptors display a modular structure comprised of five regions (A-E). The N-terminal A/B region harbors an autonomous activation function. The central C region, corresponding to the DNA-binding domain, is highly conserved and is composed of two zinc fingers involved in DNA binding and receptor dimerization. The D region is a hydrophilic region and it forms a hinge between DNA-binding domain and ligand-binding domain. The E region corresponds to the C-terminal ligand-binding domain and mediates numerous functions, including ligand binding, interaction with heat-shock proteins, dimerization, nuclear targeting, and hormone-dependent activation (31) (Figure 2). The human MR (hMR) and human glucocorticoid receptor (hGR) have almost identical DNA-binding domains (94% homology in the amino acid) and very similar ligand-binding domains (57%), but divergent N-terminal A/B regions (<15%) (32). The hMR gene was mapped on chromosome 4q31.1-31.2 (33,34) and hMR cDNA encodes a 107 kilodalton polypeptide with 984 amino acids (32). The hMR gene consists of 10 exons, including two exons 1 that encode different 5'-untranslated sequences (35). Expression of the two different hMR variants is under the control of two different promoters that contain no obvious TATA element, but multiple GC boxes. Both hMRα and hMRβ mRNAs are expressed at approximately the same level in the mineralocorticoid target tissues (36).

Figure 2. The linearized structures of the mineralocorticoid receptor gene, mRNAs and protein. The MR gene consists of 10 exons. The MR has two exons 1 (exon 1α and exon 1β), each with an alternative promoter; however, the finally translated MR protein is the same. Exons 1 are untranslated regions, exon 2 codes for the immunogenic domain (A/B), exons 3 and 4 for the DNA-binding domain (C), and exons 5-9 for the hinge region (D) and the ligand-binding domain (E) (37)

Molecular and Cellular Mechanisms of the Aldosterone Action

MRs in its unliganded state is located in the cytoplasm, as part of hetero-oligomeric complexes containing heat shock proteins 90, 70 and 50 (38). Upon binding with their ligand, the receptor-ligand complex dissociates from the heat shock proteins, homo- or heterodimerizes and translocates into the nucleus. Homodimers or heterodimers of the MR interact with hormone-responsive elements (HRE) and/or other transcription factors in the promoter regions of target genes, including the subunits of the ENaC or other proteins related to this channel and sodium transport in general, and modulates the transcription rates of these genes (39) (Figure 3).

Figure 3. Mechanism of aldosterone action on sodium reabsorption at the distal convoluted tubule of the nephron. Aldosterone binds to the MR, which is located in the cytoplasm in complex with heat shock proteins 90, 70 and 50. After binding, the receptor-ligand complex translocates into the nucleus, binds to hormone-responsive elements (HRE) of target genes where it modulates their transcription rate. Amiloride-sensitive sodium channel (ENaC) subunits or other related proteins may be targets of such regulation (40).

Pre-Receptor Regulation

Since cortisol circulates at plasma concentrations several orders of magnitude higher than those of aldosterone does, and since it has a high affinity for the MR, it would be expected to overwhelm this receptor in mineralocorticoid target tissues and cause mineralocorticoid excess. A local enzyme, 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), however, converts active cortisol to inactive cortisone, and protects the MRs from the effects of cortisol (40) 11β-HSD catalyzes the inter-conversion of hormonally active C11-hydroxylated corticosteroids (cortisol in humans or corticosterone in rodents) and their inactive C11-keto metabolites (cortisone in humans or 11-dehydrocorticosterone in rodents). Two isozymes of 11β-HSD have been identified, 11β-HSD type 1 (11β-HSD1) and 11β-HSD2, which differ in their biological properties and tissue distributions. 11β-HSD2, a potent NAD-dependent 11β-hydrogenase, rapidly inactivates glucocorticoids. The human 11β-HSD2 gene encodes 405 amino acids and its molecular weight is approximately 40-kilodalton (41). 11β-HSD2 has a hydrophilic N-terminal domain that is thought to anchor the protein into membranes (42). 11β-HSD2 is localized as a dimer in the nucleus and cytoplasm of cells of the cortical collecting duct and colon (42,43). Prednisolone and prednisone are substrates for both 11β-HSD isozymes (44,45) and dexamethasone is metabolized slightly by 11β-HSD2 (46). Licorice derivatives, such as glycyrrhizic acid, and the hemisuccinate derivative carbenoxolone are inhibitors of 11β-HSD2. Inhibition of 11β-HSD2 with such agents, confers mineralocorticoid potency to physiologic concentrations of endogenous glucocorticoids in the kidney and colon (47). Thus, in normal physiology, 11β-HSD2 protects the MR by converting cortisol to the inactive cortisone and allows aldosterone-selective access to the inherently nonselective MR in mineralocorticoid target tissues.

Amiloride-Sensitive Sodium Channel (Epithelial Sodium Channel; ENaC)

The cDNA of the α-subunit of the ENaC (αENaC) was cloned from the rat colon in 1993 (48) and soon after the cDNAs of the β- and γ-subunits of this channel were cloned for the same species (49). The human α-, β- and γ-subunits of ENaC were also cloned (50,51). In vitro studies demonstrated that the α subunit of the ENaC itself had the majority of Na channel function, while, the β- and γ- subunits alone were not shown to play as major a role in sodium transport (48). However, the β- and γ-subunits enhanced the function of the α-subunit and all subunits are required for full ENaC activity (52). It appears then that this channel consists of the α-, β- and γ-subunits and an amiloride-binding protein (Figure 4). Aldosterone increases transcription of αENaC but not β- and γ-subunits, resulting enhanced channel assembly and transported from endoplasmic reticulum to Golgi (53). In Golgi, furin proteolytically cleaves specific sites in the extracellular domains of α- and γ-ENaC, resulting in channel activation. At the cell surface, Nedd4-2 binds to ENaC, increasing endocytosis and degeneration (54).The proline-rich region of the C-terminal of the αENaC is important for binding to α-spectrin and for stabilization of the sodium channel in the membrane (55). Recently, several studies demonstrated abnormalities of the β- and γ-subunits of the ENaC in patients with Liddle's syndrome, characterized by mineralocorticoid excess (hypertension and hypokalemic alkalosis), and suppressed aldosterone secretion (56–59). The truncation caused by these mutations influenced the PY motif at the N-terminal of the molecule. This motif is responsible for the binding of the channel subunits with NEDD4, a carrier protein facilitating clearance of the channel (60). Moreover, a point mutation of the αENaC gene, located close to the N-terminal of the protein, was reported to cause a decrease of the probability of an open sodium channel, resulting in defective reabsorption (40,61).

The ENaC-Regulatory Complexes in Aldosterone-Mediated Sodium Transport

Aldosterone-induced trans-epithelial Na+ transport via ENaC involves the coordinate functioning of stimulatory signaling proteins such as serum- and glucocorticoid-induce kinase-1 (SGK1) (23,62), glucocorticoid-induced leucine zipper protein-1 (GILZ1) (63) and connector enhancer of kinase suppressor of Ras 3 (CNK3) (64), with inhibitory proteins, such as neural precursor cell expressed, developmentally downregulated protein (Nedd4-2) (24) and extracellular signal-regulated kinase (ERK) 1/2 (23,24,62,65).

SGK1 is an aldosterone-regulated protein kinase that stimulates renal ENaC through many mechanisms. First, SGK1 phosphorylates the E3 ubiquitin ligase and Nedd4-2, and inhibits its actions. Nedd4-2 interacts with the C-terminal tail of ENaC subunits, decrease surface expression of the channel via channel ubiquitinoylation (23,24,62). Second, SGK1 phosphorylates kinase with no lysine (WNK) 4 and prevents ENaC endocytosis (66). Third, SGK1 directly phosphorylates alpha ENaC and transforms silent ENaC channels to active ones (67). Then, SGK1 alters ENaC expression, trafficking and activity, and stimulates Na+ transport in the kidney cortical collecting duct (CCD) (68). However, SGK1 is a short-lived protein. Following synthesis, SGK1 is rapidly targeted to the endoplasmic reticulum (ER), where ER-associated ubiquitin ligases CHIP and HRD1 aid in its ubiquitinoylation and subsequent proteasome-mediated degradation (69). Another aldosterone-induced ENaC-regulator, GILZ, which protects SGK1 from rapid ER-associated degradation by controlling protein-protein interaction (53.6). In kidney CCD, GILZ1 is robustly induced by aldosterone (70). GILZ1 stimulates ENaC cell surface expression and activity at least in part by inhibiting ERK1/2, which abrogates ENaC function (65,71,72).

The recently identified MR target gene CNKSR3 (connector enhancer of kinase suppressor of Ras 3), commonly referred as CNK3, is highly expressed in the connecting tubule (CNT) and the CCD (73). CNK3, like SGK1 and GILZ1, is rapidly induced by physiological concentrations of aldosterone (64). CNK3 acts to assembly various ENaC-regulatory components in close vicinity of the channel and thereby exerts its stimulatory effects on channel function (74).

Epigenetic Control of  ENaC Transcription by Aldosterone-Sensitive Dot1A-Af9 Complex

Chromatin regulates gene transcription by the post-translational modification of histone N-terminal tails such as acetylation and methylation. The histone H3 Lys 79 methyltransferase disruptor of telomeric silencing alternative splice variant a (Dot1a) methylates histone H3 Lys79, which resides in the globular domain (75). ALL-1 fused gene from chromatin 9 (Af9), putative transcription factor, physically and functionally interact with Dot1a to form a nuclear repressor complex that directly or indirectly binds specific site of the alpha ENaC promoter. Aldosterone reduces the level of Af9 mRNA and protein. Then, Af9 overexpression induces hypermethylation of histone H3 Lys 79 and repression of alpha ENaC transcription (76). Aldosterone impairs the formation of Dot1a -Af9 complex associated with alpha ENaC promoter by 1) decreasing abundance of Dot1a and Af9; 2) attenuating the interaction between Dot1a and Af9 via Sgk-1-catalyzed phosphorylation of Af9 at Ser 435; 3) counterbalancing the repression through binding to mineralocorticoid receptor (MR) and facilitating its translocation into the cell nucleus, where MR and Dot1a compete for binding to Af9.  These are aldosterone-dependent and -independent mechanisms for Dot1a-Af9-mediated repression of alpha ENaC transcription. While aldosterone -independent de-repression achieved through the action of ALL-1 fused gene from chromatin 17 (Af17), Af17 upregulates alpha ENaC transcription by decreasing Af9 binding to Dot1a and relieving Dot1a-Af9-mediated repression of ENaC (77). 4) SGK1 phosphorylates Af9, thus, down-regulating Dot1a-Af9 complex, and relieving the basal repression on alpha ENaC transcription (67,78).

Figure 4. Model of a putative amiloride-sensitive sodium channel (ENaC). The amiloride-sensitive sodium channel appears to consist of the α-, β- and γ- subunits and an amiloride-binding protein. This channel is located at the apical site of the renal epithelium and plays a role in passive sodium transport, which is mainly regulated by mineralocorticoids (79).

THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM IN NEWBORNS AND INFANTS                

Aldosterone secretion rate of newborns and infants was similar to that of older children and adults. Therefore, the aldosterone secretion rate corrected by body surface was much higher in infancy than later in life (80). Urinary aldosterone at birth depends on gestational age and increases progressively, concurrently with the levels of plasma aldosterone. Plasma renin activity, plasma aldosterone and urinary excretion rate of aldosterone decrease with age (81). At  birth, human kidneys display tubular immaturity leading to sodium wasting and impaired ability to reabsorb water. Past studies showed that plasma potassium concentrations were significantly higher in newborns than in their respective mothers, while neonatal and maternal plasma sodium concentrations were closely related. Aldosterone and renin levels in newborns differs significantly from the corresponding maternal concentrations (82). The aldosterone-renin ratio significantly increases with gestational age. Thus, neonatal partial aldosterone resistance was previously suggested because of the high urinary sodium loss in the presence of hyperactivity of the renin-angiotensin-aldosterone system (83). Previous study found that the highest aldosterone levels detected in the cord blood originated from de novo synthesis by the fetal adrenal glands (84). In addition, neonatal aldosterone resistance was associated with weak or undetectable renal MR expression at birth. MR mRNA is transiently expressed between 15 and 24 weeks of gestation, but it is undetectable in late gestational age and neonatal kidney (85). 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta HSD2) and alpha ENaC are closely correlated with cyclic MR expression.

CLASSIFICATION OF HYPOALDOSTERONISM

Various syndromes are characterized by or associated with hypoaldosteronism. Hypoaldosteronism is classified in three large categories, defective stimulation of aldosterone secretion, primary defects in adrenal synthesis or secretion of aldosterone, and aldosterone resistance, according to their pathophysiology and summarized in Table 1.

Defective Stimulation of Aldosterone

The first category of conditions, which is characterized by defective stimulation of aldosterone secretion, includes the syndromes of congenital and acquired hyporeninemic hypoaldosteronism. One of these conditions is due to a defect of renin secretion such as hyporeninemia resulting from β-blockers, prostaglandin synthetase inhibitors, and calcium channel blockers. Another condition is due to decrease in the conversion of angiotensin I to angiotensin II mediated by converting enzyme inhibitor medications and is associated with hyperreninemia.

Primary Defects in Adrenal Biosynthesis or Secretion of Aldosterone

The second category of conditions, which are characterized by primary defects in adrenal synthesis or secretion of aldosterone, includes all causes of primary adrenal insufficiency and primary hypoaldosteronism caused by aldosterone synthase (CYP11B2) deficiency or as an acquired state. Primary adrenal insufficiency causes include congenital adrenal hypoplasia, congenital adrenal hyperplasia, adrenoleukodystrophy/ adrenomyeloneuropathy, acquired adrenal insufficiency due to autoimmune, infectious and infiltrative disease, bilateral adrenalectomy and use of adrenolytic agents and enzyme inhibitors that block cortisol and aldosterone biosynthesis. These conditions are usually combined with defective cortisol synthesis. Aldosterone synthase (CYP11B2) deficiency (ASD) leads to reduced aldosterone production associated with low or high levels of 18-hydroxycorticosterone, referred to as CMO I or CMO II deficiency, respectively. Several conditions may be associated with aldosterone biosynthetic activity. Heparin suppresses aldosterone synthesis. Critically ill patients with persistent hypovolemia and hypotension also have inappropriately low plasma aldosterone concentrations in relation to the activity of the renin-angiotensin system. Isolated primary hypoaldosteronism in occasionally associated with metastatic cancer of the adrenal gland.

Defective Aldosterone Actions

The third category which is characterized by defective aldosterone action includes syndromes of aldosterone resistance such as pseudohypoaldosteronism type 1 and sodium-wasting states resulting from excessive amounts of circulating mineralocorticoid antagonists, such as spironolactone and its analogues, and synthetic progestin or natural agonists, such as progesterone or 17-hydroxyprogesterone. These mineralocorticoid antagonists may antagonize aldosterone at the levels of mineralocorticoid receptor (86) and frequently, these states are compensated for by elevated concentrations of plasma aldosterone.

HYPORENINEMIC HYPOALDOSTERONISM

The most common form of isolated hypoaldosteronism is caused by impaired renin release from the kidney. Hudson et al. first described this syndrome in 1957 (87), however, hyporeninemia was first recognized in 1972 (88) (89). The typical patient is 50 to 70 years old and usually presents with chronic and asymptomatic hyperkalemia and mild to moderate renal insufficiency with a 40-70% decrease in the glomerular filtration rate when compared to that of age matched healthy subjects. Hyperchloremic metabolic acidosis is seen in approximately half of the patients. This acidosis is classified as a renal tubular acidosis type IV (90). The acidosis is a consequence of decreased renal ammonia neogenesis, reduced hydrogen ion-secretory capacity in the distal nephron, and mild reduction in the proximal tubular threshold for bicarbonate reabsorption. Occasionally, muscle weakness or cardiac arrhythmias are present in some patients. More than a half of the patients have diabetes mellitus (91). Other frequently associated states include autonomic neuropathy, hypotension, and various nephropathies such as glomerulonephritis, gouty nephropathy, and pyelonephritis. Also, this syndrome is associated with nephropathies associated with multiple myeloma and systemic lupus erythematosus, mixed cryoglobulinemia, nephrolithiasis, analgesic nephropathy, renal amyloidosis, IgA nephropathy, cirrhosis, sickle cell anemia, acquired immune deficiency syndrome (AIDS), polyneuropathy, organomegaly, endocrinopathy, M protein and skin changes (POEMS) syndrome, lead poisoning, excess sodium bicarbonate, and Sjogren’s syndrome (90,92–101) . Moreover, this syndrome occurs transiently in association with use of non-steroidal anti-inflammatory drugs, cyclosporin A, mitomycin C, cosyntropin, and other agents in susceptible individuals (102–104).

Pathophysiology

Urinary aldosterone excretion is low under basal conditions and fails to increase after sodium restriction. Plasma renin activity is also low and does not increase appropriately during sodium restriction, periods of prolonged upright posture, or diuretic administration (88). Interstitial renal disease and damage to the juxtaglomerular apparatus seems the most likely cause for the primary defect in renin generation or release and secondary deficiency of aldosterone. However, in some patients with this syndrome there is an absent or blunted aldosterone response to angiotensin II (94,104), suggesting a coexisting primary defect in aldosterone secretion or it reflects atrophy of the zona glomerulosa caused by chronic renin deficiency.

There are various mechanisms to be explained for the hyporeninemia. First possible mechanism is the hypervolemia. The expanded extracellular fluid volume due to hypertension may suppress renin. In fact, long-term sodium restriction and diuretic administration increase plasma renin activity in these patients, however, the increments of plasma renin activity are less than those of normal subjects (97). A second possible mechanism is insufficiency of the autonomic nervous system, particularly in patients with diabetic neuropathy. Impaired adrenergic response to postural change may contribute to insufficient renin release. Besides, these patients exhibit decreased sensitivity to β-adrenergic agonists, suggesting defects in both production and action of catecholamines (96). A third proposed mechanism is secretion of abnormal forms of renin, such as a defect in the conversion of prorenin to renin. Insufficiency of autonomic nervous system may be associated with impaired conversion of prorenin to renin. Indeed, patients with diabetes mellitus and autonomic neuropathy have elevated plasma levels of prorenin (105). A fourth possibility is prostaglandin deficiency. Production of prostaglandin I2 (prostacyclin), which mediates renin release, is apparently diminished in patients with hyporeninemic hypoaldosteronism as assessed by measurement of the stable urinary metabolite 6-keto-prostaglandin F1α (95). Furthermore, the prostaglandin I2 in these patients was unresponsive to the potent stimulator’s norepinephrine and calcium. Prostaglandin I2 deficiency may cause hyporeninemic hypoaldosteronism by causing defects in the conversion of prorenin to renin and renin release (106).

Diagnosis

The diagnosis of hyporeninemic hypoaldosteronism must be considered in any patient with unexplained hyperkalemia. Excess potassium intake from food or drugs does not cause sustained hyperkalemia, if renal function is normal. Renal function should be evaluated and drugs that impair renal potassium excretion should be excluded as a cause. The clinical diagnosis is confirmed by low plasma renin activity and low plasma concentrations or urinary aldosterone excretion under conditions that activate the renin-angiotensin-aldosterone axis by maintenance of upright posture and/or furosemide administration. A low random plasma renin concentration associated with a normal ratio of aldosterone to plasma renin activity is also useful for the diagnosis (94).

Therapy

The therapeutic approach should be chosen after taking into consideration the age of the patients and other concurrent disorders. Only monitoring potassium concentrations is enough for patients with moderate hyperkalemia and without electro-cardiographic changes. Drugs that promote hyperkalemia, such as β-adrenergic antagonists, cyclooxygenase inhibitors, angiotensin-converting enzyme inhibitors, heparin, and potassium-sparing diuretics, should be avoided. Dietary potassium intake should be reduced, if possible. Diuretics are the initial treatment for patients who have disorders associated with sodium retention, such as hypertension and congestive heart failure. Mineralocorticoid replacement with fludrocortisone is reserved for patients with severe hyperkalemia without hypertension and congestive heart failure.

PRIMARY HYPOALDOSTERONISM- ALDOSTERONE SYNTHASE DEFICIENCY (ASD)

Congenital hypoaldosteronism is a rare inherited disorder transmitted as either an autosomal recessive or autosomal dominant trait with mixed penetrance. This disorder was previously termed "corticosterone methyloxidase (CMO)” deficiency and subdivided into two types according to the relative levels of aldosterone and its precursors in an affected person. Patients with "corticosterone methyloxidase I (CMO I)" deficiency have elevated serum levels of corticosterone and low levels of 18-hydroxycorticosterone and aldosterone. In contrast, patients with "corticosterone methyloxidase II (CMO II)" deficiency have high levels of 18-hydroxycorticosterone, the immediate precursor of aldosterone (107). With greater understanding of structure-activity relationships in the CYP11B2 enzyme, this disorder may be better considered a spectrum of hormonal deficiencies, depending on the nature of the CYP11B2 gene defect (108). Two steps of aldosterone biosynthesis from corticosterone previously proposed to be catalyzed by separate enzymes, CMO I and II, previously, are known to involve only one enzyme substrate interaction (6). Isolated aldosterone deficiency results from loss of activity of aldosterone synthase encoded by CYP11B2 gene (109–118). Therefore, the term aldosterone synthase deficiency type 1 (ASD1) and type 2 (ASD2) reflects more appropriately the molecular basis of this disease. In both ASD1 and 2, glomerulosa zone corticosterone is increased and aldosterone decreased, but 18-hydroxycorticosterone is increased in ASD2 (108).  ASD1 is associated with loss of both 18-hydroxilation and 18-oxidation enzyme activities. In ASD2, the ability to convert corticosterone (B) to 18-hydorxytetrahydro11-dehydrocorticosterone (18-OH-B) is preserved with failure of further oxidation of 18-hhdroxicorticosrerone to aldosterone (119). The deficiency of aldosterone is much more severe in ASD1. In contrast, aldosterone may reach normal levels under intense stimulation of renin-angiotensin system in ASD2 (108). The clinical presentations of these deficiencies are otherwise similar.

Clinical Presentation

The clinical presentation is typical of aldosterone deficiency, including electrolyte abnormalities such as a variable degree of hyponatremia, hyperkalemia and metabolic acidosis, with poor growth in childhood, but there are usually no symptoms in adults (107,120). Miao et al. reviewed 45 ASD patients (20 of ASD1, 12 of ASD2, 13 of undefined subtype) (121).  From their review, 95% of the patients having ASD1 and all of having ASD2 and an undefined subtype had hyponatremia, while 89% showed hyperkalemia. In infants, it is characterized by recurrent dehydration, salt wasting and failure to thrive. These symptoms are present generally within the first 3 months of life, and most often after the first 5 days of life. A modest uremia with a normal creatinine level reflects dehydration in the presence of intrinsically normal renal function. Plasma renin activity might vary, while elevated plasma renin activity levels were more likely to be found in the ASD1 (121).

Diagnosis and Therapy

The diagnosis can be established by measuring the appropriate corticosteroids or their major metabolic products, such as 11-deoxycorticosterone (DOC), corticosterone, 18-hydroxycorticosterone, 18-hydroxy-DOC, and aldosterone levels in plasma. The ratio of plasma 18-hydroxycorticosterone to plasma aldosterone differentiates the two disorders; it is less than 10 in ASD1 (CMO I deficiency) and more than 100 in ASD2 (CMO II deficiency) (121,122). Patients with ASD2 (CMO II deficiency) tend to have increased plasma cortisol levels that may result from increased adrenal sensitivity to ACTH induced by the increased plasma angiotensin II levels in response to sodium depletion (123).

Both forms of the syndrome are treated by replacement of mineralocorticoid with the usual dosage of fludrocortisone (0.1-0.3 mg/ day). Almost infants and children require oral sodium supplementation (2 g/day as NaCl alone or in combination with NaHCO₃), although some infants with severe symptom need intravenous fluids. Oral sodium supplementation may be discontinued once plasma rennin activity has decreased to normal, but mineralocorticoid replacement is usually maintained through childhood.

Molecular Mechanism of CYP11B2 Deficiency

ASD has been identified in Jews of European, North American, and Iranian descent (119). In Asians, it was reported in the Thai (124), Indian (124), Japanese (125) and Chinese populations (120,126).

To date, approximately 40 mutations, such as missense and nonsense mutations, splicing mutations, small insertions/deletions, gross deletions, and complex rearrangements, in the CYP11B2 have been reported in cases of ASD; the most common mutations were missense and nonsense (121). Some variants, such as p.Q170X, p.E198D, c.1398+2T>A, p. F233fsX*295, p.L462R, p.Q337X and p.Q272W, were identified in patients without an ASD classification subtype (121). A majority of mutations led to complete loss of enzyme activity, while in some mutations, such as V386A and R181W, double homozygosity was required for clinical phenotype (112,113,121).

Some patients with ASD1 (CMO I deficiency) have a homozygous 5 nucleotide deletion in exon 1 which leads to a frameshift and premature stop codon, resulting in the complete lack of enzyme production (109,110). A male Caucasian patient with ASD1 (CMO I deficiency) had a homozygous point mutation causing a R384P substitution, resulting in complete loss of 11 β- and 18-hydroxylase activity (111) (Figure 5). This suggests that the arginine-384 in aldosterone synthase is highly conserved and apparently quite important for enzyme activity.

A male infant of Turkish parents who presented with ASD1 had a homozygous missense mutation (L451F) in exon 8 of CYP11B2 gene. The L451F mutant protein in vitro showed complete aldosterone deficiency with 11-deoxycirticosterone or corticosterone as substrates. The L451F mutation located immediately adjacent to the highly conserved heme-binding C450 of the cytochrome P450 (117). Computer modeling of the molecule suggested that this substitute my lead a steric effect resulting in preventing the activity of CYP11B2 (117).

Three siblings of Pakistan origin who presented with ASD1 had a homozygous mutation (S308P) in exon 5 of CYP11B2 gene. The S308P mutant protein in vitro showed complete loss of enzyme activity. This mutated residue is likely to locate within the a-helix I, close to the heme-binding, active site of the enzyme. This structural change may be the cause of this disorder in this family (118). 

A large number of kindreds with ASD2 (CMO II deficiency) have been identified among Jews originally from Isfahan, Iran. Such patients are all homozygous for two mutations, R181W in exon 3 and V386A in exon 7 (109,112,113) (Figure 5). These mutations together reduce aldosterone synthase activity to 0.2 % of normal without affecting 11 β-hydroxylase activity (112,113). However, one non-Iranian patient with ASD2 (CMO II deficiency) carries mutations in the paternal allele, including V386A and T318A mutations, and maternal allele, including R181W and a deletion/frameshift mutation, resulting in complete loss of enzyme activity (113). This suggests that the high levels of 18-hydroxycorticosterone seen in ASD2 (CMO II deficiency) can be synthesized by CYP11B1, which has some 18-hydroxylase activity, and not by CYP11B2. A patient with apparent ASD 1 was homozygous for the mutations E198A and V386A, yet when assayed in vitro the double mutant enzyme behaved similarly to the mutant enzyme found in the Iranian Jewish ASD 2 patients (127). Thus, a difference in expression of CYP11B1 rather than allelic variation of CYP11B2 may be involved in the mechanism underlying the different levels of 18-hydroxycorticosterone between ASD1 and 2 (CMO I and CMO II deficiency). The distinction between ASD 1 and ASD 2 is not precise, and these disorders should be regarded as different degrees of severity on a continuous clinical spectrum.

 A male Japanese patient with ASD1 (CMO I) was a compound heterozygous for W56X in exon 1 and R384W in exon 7. W56X was inherited from his mother and R384X was from his father. Since both alleles contain nonsense mutations, a lack of CYP11B2 activity was speculated to cause his condition (125).

Two male Japanese patients with ASD2 (CMO II) had homozygous missense mutation (G435S) in the exon 8 of CYP11B2 gene. The expression studies indicated that the steroid 18-hydroxylase/oxidase activities of mutant enzyme were substantially reduced.

A female infant of Albanian origin with ASD2 (CMO II) revealed homozygosity for a pathogenic T185I mutation in Exon 3 of the CYP11B2 gene and two other homozygous polymorphisms F168F and K1738 in Exon3 (128). Both healthy parents revealed heterozygous for all three substitutions.

Another female Italian Caucasian patient was diagnosed with a compound heterozygous mutation located in exon 4 causing a premature stop codon (E255X) and a further mutation in exon 5, also causing a premature stop codon (Q272X). The patient’s CYP11B2 encoded two truncated forms of aldosterone synthase predicted to be inactive because they lack critical active site residues as well as the hormone-binding site. However, this case displays biochemical features intermediate between those of ASD1 and 2 (CMO I and II).

Some cases of ASD without causative mutations in CYP11B2 have also been reported (116,119).

Figure 5. Relative positions of CYP11B1 and CYP11B2 on chromosome 8 and mutations of CYP11B2. A, The relative positions of CYP11B1 and CYP11B2 on chromosome 8q22. Arrows indicate direction of transcription. B, Mutations of CYP11B2 in reported patients with CYP11B2 deficiency are summarized in the figure (109,121,126,128).

ACQUIRED FORMS OF PRIMARY HYPOALDOSTERONISM  

Several conditions may be associated with aldosterone biosynthetic defects. The administration of heparin causes natriuresis and hyperkalemia (129). Heparin preparations suppress aldosterone synthesis, leading to a compensatory rise in plasma renin activity. However, it has been demonstrated that this suppression of enzyme activity is attributable to chlorbutol (1,1,1-trichloro-2-methyl-2-propanol), the preservative used in commercial heparin, rather than to pure heparin (130).

Persistently hypotensive, critically ill patients with sepsis, pneumonia, peritonitis, cholangitis and liver failure, also have inappropriately low plasma aldosterone concentrations in relation to elevated plasma renin activity (131). The defect is at the level of the adrenal but has not been associated with any particular disease or therapy. Plasma cortisol levels are high, reflecting the stressed state. The response to angiotensin infusion is impaired, and the ratio of plasma 18-hydroxycorticosterone to aldosterone is increased, suggesting selective insufficiency of CMO II. It is possible that the hypoxia causes a relative zona glomerulosa insufficiency (132).

ALDOSTERONE RESISTANCE

Pseudohypoaldosteronism (PHA) Type 1

Mineralocorticoid resistance (pseudohypoaldosteronism type 1, PHA1) results from inability of aldosterone to exert its effect on its target tissues and was first reported by Cheek and Perry as a sporadic occurrence in 1958 (133). This disease, usually presents in infancy with severe salt-wasting and failure to thrive, accompanied by profound urinary sodium loss, severe hyponatremia, hyperkalemia, acidosis, hyperreninemia, and paradoxically markedly elevated plasma and urinary aldosterone concentrations. Usually, renal and adrenal functions are normal. This disease has been reported in over 70 patients (134). The prevalence, as estimated from recruitment through a genetic laboratory at the Hôpital Européen Georges Pompidou in France, which is a national reference center for a rare disease, is ~1 per 80,000 newborns (135)(136). Approximately one fifth of these cases are familial, and both an autosomal dominant and a recessive form of genetic transmission have been observed. A previous study found that all patients had renal tubular unresponsiveness to aldosterone, while some had involvement of other mineralocorticoid target-tissues, including the sweat and salivary glands, and the colonic epithelium, as well. Autosomal recessive PHA1 presents in the neonatal period with hyponatremia caused by multi-organ salt loss, including kidney, colon, and sweat and salivary glands. Autosomal recessive PHA1 persists into adulthood and shows no improvement over time. However, literature regarding follow-up of these patients after diagnosis is insufficient.  In contrast, autosomal dominant PHA1 is characterized by an isolated renal resistance to aldosterone, leading to renal salt loss. Particularly autosomal dominant form of PHA1 typically shows a gradual clinical improvement during childhood, allowing the cessation of sodium supplementation. 

PATHOPHYSIOLOGY

The mechanism(s) by which aldosterone controls sodium transport in its target tissues involves the mineralocorticoid receptor (MR) and proteins that are associated with the amiloride-sensitive sodium channel (ENaC). The latter proteins are expressed in the apical membrane of epithelial cells of the distal convoluted tubule and in the membranes of cells of other tissues involved in the conservation of salt, such as colon, sweat gland, lung and tongue. Thus, the MR and the ENaC were considered as potential candidate molecules for the pathogenesis of PHA1. In fact, mutations of α- and β-subunits of the ENaC were reported in PHA patients from autosomal recessive kindreds (61,137). Mutations of the MR were also reported in the patients with autosomal dominant PHA1 (138,139). However, no molecular defects were found in either MR or ENaC in some patients with PHA1, especially in those with the sporadic form PHA1, which suggests molecular heterogeneity in PHA1 (79,140–144).

DIAGNOSIS

Electrolyte profiles suggest mineralocorticoid deficiency or end-organ resistance, along with hyperkalemia, hyponatremia and metabolic acidosis associated with profound urinary salt loss. Renal and adrenal function is normal. The diagnosis is confirmed by the markedly elevated plasma aldosterone concentrations and plasma renin activity.

The differential diagnosis of PHA1 includes salt-wasting states due to hypoaldosteronism, including several forms of congenital adrenal hyperplasia, isolated hypoaldosteronism due to corticosterone methyloxidase (CMO) I and II deficiencies and congenital adrenal hypoplasia. Normal cortisol and excessive aldosterone responses to adrenocorticotropin (ACTH) are expected in patients with congenital PHA.

THERAPY         

The standard treatment of PHA has been replacement with high doses of salt, with a variable response among patients (134). Recently, carbenoxolone, an 11β-hydroxysteroid dehydrogenase inhibitor, was employed as therapy in PHA1 and an ameliorating effect was observed which was attributed to mediation by the MR (140). We studied a 17-yr-old male patient with congenital multifocal target-organ resistance to aldosterone. We examined his clinical response to carbenoxolone, expected to increase the intracellular level of cortisol in the kidney by preventing local conversion of cortisol to cortisone, and to high doses of fludrocortisone, a synthetic mineralocorticoid. Subsequently, and for a brief period of time, we administered dexamethasone, which has no intrinsic salt-retaining activity, in addition to carbenoxolone, to suppress endogenous cortisol, along with its intrinsic mineralocorticoid activity.

Figure 6. Effect of carbenoxolone, carbenoxolone plus dexamethasone, and fludrocortisone (top panel) on the serum sodium (middle panel) and potassium (bottom panel) concentrations of a patient with PHA. Carbenoxolone normalized plasma electrolytes, addition of dexamethasone reversed this effect, while fludrocortisone at high doses also normalized plasma electrolytes (140).

Carbenoxolone normalized the patient's serum electrolyte concentrations and decreased his urinary excretion of sodium within a week (Figure 6). Subsequent long-term therapy of this patient with carbenoxolone (450 mg/day p.o.) maintained his electrolyte concentrations within the normal range. His urinary 24 h free cortisol was increased during carbenoxolone therapy. Addition of dexamethasone suppressed his urinary free cortisol excretion and reversed the beneficial effect of carbenoxolone on serum and urinary electrolytes (Figure 6). These data suggest that an increase in urinary free cortisol observed during carbenoxolone therapy was due to a localized effect of this drug on the kidney rather than on tissues involved in the negative feedback effect of glucocorticoids. The effect of carbenoxolone does not seem to be mediated by GR but seems to be exerted purely via the MR (Figure 7). There were no adverse effects of long-term carbenoxolone therapy in this patient. He also reported increased stamina, a better ability to concentrate and less anxiety. On treatment, the patient grew 6 cm/y and progressed from -4SD to -3SD scores for mean height for age. He also progressed in his pubertal development from Tanner stage III to IV for pubic hair, while his bone age advanced from 12 to 14 y.

Figure 7. Mechanism of the effect of carbenoxolone. Carbenololone inhibits of conversion of cortisol to cortisone in the kidney, resulting in the enhancement of the effect of cortisol as a ligand for MR. Dexamethasone suppressed cortisol production and reversing the beneficial effect of carbenoxolone in our patient with PHA1.

Both carbenoxolone and fludrocortisone normalized the serum electrolytes of our patient, suggesting the presence of a functional, albeit possibly defective, renal MR. Interestingly, the same patient was unresponsive to intravenous infusion of aldosterone and fludrocortisone (up to 3 mg/day) when studied in infancy (145), suggesting that the clinical improvement that has been noted in the majority of PHA patients with age may be related to changes in their responsiveness to mineralocorticoid.

On the other hand, another study reported that carbenoxolone did not show any significant salt-retaining effect in two patients with multiple PHA, while carbenoxolone significantly suppressed the renin-aldosterone system in a patient with renal-form PHA (146).  This difference of responsiveness to carbenoxolone may be due to an age-dependent change on mineralocorticoid responsiveness. Additionally, the different mineralocorticoid responsiveness of renal and multisystem PHA patients indicates a difference in their MR function. The partial response to carbenoxolone in renal PHA suggests that there is at least a partly functional MR. This is also supported by the observation that spironolactone, a mineralocorticoid antagonist, aggravated sodium loss in several patients with renal PHA (147).

MOLECULAR MECHANISM(S) OF PSEUDOHYPOALDOSTERONISM TYPE 1          

In 1996, a study reported homozygous mutations introducing a stop codon or frame shift in the αENaC gene of affected members of families with autosomal recessive PHA (61).  To date, worldwide more than 40 different mutations have been described in the coding region of ENaC subunit genes (148–150). The majority of mutations appear in the αENaC gene SCNN1A, most frequently in exon 8 (61,150–152). Mutations are nonsense, single base deletions or insertions, or splice-site mutations, leading to abnormal length of mRNA and protein. Few missense mutations in αENaC gene have also been reported (149,153). Only a few cases of mutations in β and gamma ENaC genes have been reported (149,154,155). Phenotype and genotype correlations have been noted with more severe phenotype in nonsense, frameshift, and abnormal splicing mutations than patients with missense mutations (148,154,155).

A Swedish study regarding families with autosomal recessive PHA, homozygous or compound heterozygous mutations showed that a stop codon or a frame shift in the αENaC gene was associated with pulmonary disease as well (150). The truncation caused by these mutations influenced the PY motif at the N-terminal region of the molecule. This motif is responsible for the binding of the channel subunits with Nedd4, a carrier protein facilitating clearance of the channel (60). Moreover, a point mutation of the αENaC gene, located close to the N-terminal of the protein, was reported to cause a decrease of the probability of an open sodium channel, resulting in defective reabsorption (61,153). In the other four families with autosomal recessive PHA, insertion of a T in exon 8 and nonsense mutation (R508X) in exon 11 of the αENaC gene, resulting in a truncated αENaC subunit, was found (156). A splice site mutation in intron 12 of the βENaC gene, which preventing correct splicing of the mRNA was found in a Scottish patient (156). Also, other autosomal recessive families with PHA had a homozygous splice-site mutation in the γENaC, while a Japanese sporadic patient with the systemic form of PHA was a compound heterozygote for mutations in the αENaC, which resulted in the generation of a truncated channel subunit (137,157) . Compound heterozygous mutations (Q217X in exon 4 and Y306X in exon 6) of βENaC have been reported in the patient with multi-organ PHA1 of Ashkenazi family in Israel (154). These mutations produce shortened βENaC subunits with 253 and 317 residues respectively instead of the 640 residues present in βENaC subunit. Expression of cRNA carrying these mutations in Xenopas oocytes showed that the either mutation drastically reduced to only 3% of normal ENaC activity (154).  An African American female with PHA, who had persistent and symptom hyperkalemia, had compound heterozygous mutation in the βENaC gene: c.1288delC in exon 9, a one-base deletion that generated a frameshift mutation, and c.1466+1 G>A, an intronic base substitution in intron11 that leaded to a splice site mutation (158).

To date more than 50 different mutations in the human MR gene (NR3C2) causing autosomal dominant PHA1 have been described. NR3C2 mutations were found in 62% of patients with renal PHA1 referred to a genetics laboratory at the Hôpital Européen Georges Prompidou in France (135). Nonsense mutations, frameshift mutations, splice site mutations, and deletions of whole or part of the gene lead to gross change of the MR protein. Nonsense mutations are found in all exons and lead to truncated MR protein. A past study. reported families with autosomal dominant PHA, who had molecular defects of the MR resulting in non-expression of one of the 2 alleles (138) (Figure 8). In addition, another study reported a sporadic patient with PHA who had a heterozygous mutation in exon 9 of the MR that introduced a premature stop codon (144) (Figure 8). These results, may suggest that expression of only one allele of the MR is insufficient to prevent salt loss. Another case study did not identify any abnormalities of the MR in PHA patients from two families with the autosomal dominant form of the disease (144), while other authors reported a heterozygous missense mutation in exon 8 of the MR gene identified in PHA patients from a Japanese autosomal dominant family (139) (Figure 8). A heterozygous nonsense mutation in exon 2 (S163X, C436X) and in exon 9 (R947X) of the MR, leading to a premature stop codon of the MR gene were found in other patients with autosomal dominant PHA (159–161). It was previously reported a heterozygous splice acceptor site mutation, which results in exon 7 skipping and subsequently in premature termination in exon 8 of MR with Japanese female patients with PHA1 (162). This study showed that RT-PCR products of mRNA with that patient showed both wiled-type and mutated mRNA, suggesting that haploinsufficiency due to nonsense mediated mRNA decay with premature termination is not sufficient to give rise to the PHA phenotype (162). It was also reported that Q776R mutation in exon 5 or L979P mutation in exon 9, which is located in the ligand-binding domain of the MR, presented reduced or absent aldosterone binding, respectively (163). Three-dimensional structure of MR suggests that the residue Q776 is located in helix 3 and is locking aldosterone in the ligand-binding pocket (163). A study examined patients with PHA1 presenting isolated renal salt loss from six families in Italy and Germany and found one nonsense mutation (E378X), one frameshift mutation (A958R) and two missense mutations (S818L and E972G) (164). S818L does not bind aldosterone or activate transcription or translocate into the nucleus. Three-dimensional molecular structure showed that S818 was located in helix H5 and S818 was speculated to be necessary to stabilize helix H5 and the -sheet 1 via hydrogen bond to Y828. E972G mutation showed a significantly lower ligand-binding affinity and only 9% of wild-type transcriptional activity. Three-dimensional molecular structure showed that E972 is involved in a hydrogen-bond network with R947 anchoring helix H12 to H10. Thus, substitute of E972G suggested to be open up the hydrophobic core and displace helix H10, causing the decreased ligand-binding ability (164).

A Japanese study reported four sporadic patients and two siblings with a renal form of PHA (165). Two siblings and one sporadic patient had R651X of NR3C2 (MR) gene. One sporadic patient had R947X, another two patients had 603A deletion and 304-305CG deletion, respectively, both resulting in frameshift mutations (165).

Another study reported two female Japanese infants with the renal form of PHA1 and identified two heterozygous mutations. One had a c.4932_493insTT in Exon 2, resulting in a premature stop codon (p.Met166 LeufsX8) and another had a nonsense mutation of R861X in exon 7 (166).  These mutations resulted in haploinsufficiency of the MR and were the cause of aldosterone resistance in the kidney.

From the study of the genetics laboratory at the Hôpital Européen Georges Pompidou in France, 20 mutations were found in exon 2; all of them led to truncated receptors, Of the 22 mutations identified in exon 3 and 4, coding for the MR DBD, 11 were nonsense or frameshift mutations, the reminder missense mutations. Thirty variants were located in exon 5-9 and affected LBD; the majority were missense mutations. Nine were splice variants in different introns, 19 were large deletions encompassing single or multiple exons and the flanking intronic regions of the NR3C2 gene (135) (figure 8).

These studies suggest major molecular heterogeneity in PHA.

Figure 8. Mutations of the MR in patients with PHA1. Mutations of the MR that have been reported in patients with PHA1 are summarized in the figure (135,138,139,144,166). 

Another study investigated 5 unrelated cases of sporadic PHA (79,140,143). The researchers found a nonconservative homozygous mutation (A241V) in the MR of 4 of the patients and a conservative heterozygous mutation (I180V) in one of these patients and his asymptomatic father, while no abnormalities were found in the DNA- or ligand-binding domains of the MR. The Val241 and Val180 substitutions were found also in the norm 6al population. The heterozygosity and homozygosity frequencies of the Val241 and Val180 mutations were 48%, 38%, 22% and 1.5%, respectively. Another finding was a nonconservative amino acid substitution (T663A) in the αENaC, which was located close to the C-terminal (79). Of the 5 patients, 2 were homozygous and 3 heterozygous for this variation, respectively. This amino acid substitution was also present at high frequency in apparently normal controls. The homozygosity and heterozygosity frequencies of the αENaC Ala663 were 31% and 64%, respectively. Three of the 4 (75%) patients with multiple tissue resistance to aldosterone had both αENaC (heterozygous or homozygous) and MR (homozygous) mutations as described above, while only 7% of our controls with apparently normal salt conservation had the same concurrent abnormalities (Table 2, p < 0.025).

                (79) with permission

The researchers identified, in a Japanese patient with sporadic PHA, three homozygous substitutions in the MR gene: G215C, I180V or A241V, which had previously reported to occur in healthy populations. Luciferase activities induced by MR with either G215C, I180V or A241V substitution were significantly lower than those for wild-type MR with aldosterone at concentrations ranging from 10-11 to 10-9 M, 10-8M, or 10-11 to 10-6M, respectively. A homozygous A to G substitution of the donor splice site of αENaC intron 4 was found in the patient. These results suggest that each of three MR polymorphisms identified in our patient is functionally and structurally heterogeneous (167).

The authors suggested that the above polymorphisms may confer vulnerability in salt conservation, which might be expressed fully only when concurrently present with other genetic defects of the MR or other proteins that participate in sodium homeostasis, such as Nedd4 (168). This hypothesis, if true, would be compatible with a sporadic presentation or a digenic or multigenic expression and heredity as previously described in retinitis pigmentosa (169). In this case, hereditary transmission might be complex and appear either as a dominant and/or recessive trait with variable penetrance.

Secondary Pseudohypoaldosteronism (PHA)

Secondary PHA is a form of renal resistance to aldosterone. The cause of secondary PHA is either renal disease or medication. The clinical and laboratory findings resemble those of a transient PHA. Since Rodriguez-Soriano et al. reported the first case in 1983 (169), more than 68 cases have been reported. Secondary PHA may occur mainly in neonates and young infants with urinary tract infections, such as pyelonephritis, and/or malformation of urinary system causing obstructive uropathy, tubulointerstitial nephritis, sickle cell nephropathy, and systemic lupus erythematosus(170). Secondary PHA has been also related to drugs like non-steroidal anti-inflammatory agents and potassium-sparing diuretics (170–172). This state occurs in male infants more frequently than female infants because of the higher incidence of urinary tract infections and obstructive uropathy in male infants rather than in female infants(169). Patients present poor feeding, poor weight gain or failure to thrive, vomiting, diarrhea, polyuria, and dehydration. Acute worsening of their general condition may occur, with severe weight loss, peripheral circulatory failure, rise in serum urea and creatinine levels, and occasional life-threatening hyperkalemia (169). The laboratory features are hyponatremia, hyperkalemia, metabolic acidosis, elevation of plasma aldosterone concentrations and plasma renin activity, and inappropriately increased sodium and decreased potassium excretion in urine (173).  The aldosterone resistance of secondary PHA is transient and usually reverts with the resolution of the infection.

PATHOPHYSIOLOGY

The very high ratio of plasma aldosterone to potassium, together with diminished urinary K/Na values, strongly suggests that hyponatremia and hyperkalemia result from a lack of response of the renal tubule to endogenous mineralocorticoids (174). The intrarenal expression of several cytokines, such as tumor necrosis factor alpha, interleukin (IL) 1, IL-6, transforming growth factor beta-1, angiotensin II, endothelin, thromboxane A2, and prostaglandins, are increased in cases of urinary tract infections. These changes result in inhibition of aldosterone action through reduction of its expression and/or impairment of its receptor, vasoconstriction and reduction of glomerular filtration rate, increased natriuresis and/or decreased Na⁺-K⁺-ATPase activity(173) . A past study found that the number of mineralocorticoid receptors in obstructive uropathy were low in the acute phase but returned to normal after successful surgical correction of the obstruction (175). This suggests that a reduced aldosterone effect can also reflect down-regulation of the receptor sites, due to highly elevated aldosterone levels (175).

THERAPY

The clinical and laboratory findings improve within one or two days and disappear after the completion of medical treatment of urinary tract infection and/or surgical correction of obstructive uropathy, usually within a few days to one week after beginning of treatment (173). However, in some patients, sodium bicarbonate and/or sodium chloride supplementation may be necessary for a week or month (173)

REFERENCES

1. Miller WL. Molecular biology of steroid hormone synthesis. Endocrine Reviews 1988;9(3):295–318.
2. Chung BC, Matteson KJ, Voutilainen R, Mohandas TK, Miller WL. Human cholesterol side-chain cleavage enzyme, P450scc: cDNA cloning, assignment of the gene to chromosome 15, and expression in the placenta. Proceedings of the National Academy of Sciences of the United States of America 1986;83(23):8962–8966.
3. White PC, Chaplin DD, Weis JH, Dupont B, New MI, Seidman JG. Two steroid 21-hydroxylase genes are located in the murine S region. Nature 1984;312(5993):465–467.
4. White PC, New MI, Dupont B. HLA-linked congenital adrenal hyperplasia results from a defective gene encoding a cytochrome P-450 specific for steroid 21-hydroxylation. Proceedings of the National Academy of Sciences of the United States of America 1984;81(23 I):7505–7509.
5. Curnow KM, Tusie-Lunaf MT, Pascoe L, Natarajan R, Gu JL, Nadler JL, Whitef PC. The product of the CYP11B2 gene is required for aldosterone biosynthesis in the human adrenal cortex. Molecular Endocrinology 1991;5(10):1513–1522.
6. Kawamoto T, Mitsuuchi Y, Toda K, Yokoyama Y, Miyahara K, Miura S, Ohnishi T, Ichikawa Y, Nakao K, Imura H, Ulick S, Shizuta Y. Role of steroid 11β-hydroxylase and steroid 18-hydroxylase in the biosynthesis of glucocorticoids and mineralocorticoids in humans. Proceedings of the National Academy of Sciences of the United States of America 1992;89(4):1458–1462.
7. Chua SC, Szabo P, Vitek A, Grzeschik KH, John M, White PC. Cloning of cDNA encoding steroid 11 beta-hydroxylase (P450c11). Proceedings of the National Academy of Sciences of the United States of America 1987;84(20):7193–7197.
8. Rainey WE. Adrenal zonation: Clues from 11β-hydroxylase and aldosterone synthase. Molecular and Cellular Endocrinology 1999;151(1–2):151–160.
9. Demura M, Bulun SE. CpG dinucleotide methylation of the CYP19 I.3/II promoter modulates cAMP-stimulated aromatase activity. Molecular and Cellular Endocrinology 2008;283(1–2):127–132.
10. Takeda Y, Demura M, Wang F, Karashima S, Yoneda T, Kometani M, Hashimoto A, Aono D, Horike SI, Meguro-Horike M, Yamagishi M, Takeda Y. Epigenetic regulation of aldosterone synthase gene by sodium and angiotensin II. Journal of the American Heart Association 2018;7(10). doi:10.1161/JAHA.117.008281.
11. Gibbons GH, Dzau VJ, Farhi ER, Barger AC. Interaction of Signals Influencing Renin Release. Annual Review of Physiology 1984;46(1):291–308.
12. Quinn SJ, Williams GH. Regulation of aldosterone secretion. Annual Review of Physiology 1988;50:409–426.
13. Kramer E, Gallant S, Brownie AC. Actions of Angiotensin 11 on Aldosterone Adrenal Cortex Biosynthesis in the Rat AND LATE PATHWAY* Animals and Tissue Preparation-Female Sprague-Dawley rats.
14. Bassett MH, White PC, Rainey WE. The regulation of aldosterone synthase expression. In: Molecular and Cellular Endocrinology.Vol 217. Mol Cell Endocrinol; 2004:67–74.
15. Kojima I, Kojima K, Rasmussen H. Role of calcium and cAMP in the action of adrenocorticotropin on aldosterone secretion. Journal of Biological Chemistry 1985;260(7):4248–4256.
16. Woodcock EA, McLeod JK, Johnston CI. Vasopressin stimulates phosphatidylinositol turnover and aldosterone synthesis in rat adrenal glomerulosa cells: Comparison with angiotensin ii. Endocrinology 1986;118(6):2432–2436.
17. Hollenberg NK, Chenitz WR, Adams DF, Williams GH. Reciprocal influence of salt intake on adrenal glomerulosa and renal vascular responses to angiotensin II in normal man. Journal of Clinical Investigation 1974;54(1):34–42.
18. Carey RM. Acute Dopaminergic Inhibition of Aldosterone Secretion Is Independent of Angiotensin II and Adrenocorticotropin. Journal of Clinical Endocrinology and Metabolism 1982;54(2):463–469.
19. Missale C, Liberini P, Memo M, Carruba MO, Spano P. Characterization of dopamine receptors associated with aldosterone secretion in rat adrenal glomerulosa. Endocrinology 1986;119(5):2227–2232.
20. Chartier L, Schiffrin EL. Role of calcium in effects of atrial natriuretic peptide on aldosterone production in adrenal glomerulosa cells. American Journal of Physiology - Endocrinology and Metabolism 1987;252(4 (15/4)). doi:10.1152/ajpendo.1987.252.4.e485.
21. Jorgensen PL. Structure, function and regulation of Na,K-ATPase in the kidney. Kidney International 1986;29(1):10–20.
22. Oguchi A, Ikeda U, Kanbe T, Tsuruya Y, Yamamoto K, Kawakami K, Medford RM, Shimada K. Regulation of Na-K-ATPase gene expression by aldosterone in vascular smooth muscle cells. American Journal of Physiology - Heart and Circulatory Physiology 1993;265(4 34-4). doi:10.1152/ajpheart.1993.265.4.h1167.
23. Pearce D. SGK1 regulation of epithelial sodium transport. Cellular Physiology and Biochemistry 2003;13(1):13–20.
24. Bhalla V, Daidié D, Li H, Pao AC, LaGrange LP, Wang J, Vandewalle A, Stockand JD, Staub O, Pearce D. Serum- and glucocorticoid-regulated kinase 1 regulates ubiquitin ligase neural precursor cell-expressed, developmentally down-regulated protein 4-2 by inducing interaction with 14-3-3. Molecular Endocrinology 2005;19(12):3073–3084.
25. Kornel L, Smoszna-Konaszewska B. Aldosterone (ALDO) increases transmembrane influx of Na+ in vascular smooth muscle (VSM) cells through increased synthesis of Na+ channels. Steroids 1995;60(1):114–119.
26. Mick VE, Itani OA, Loftus RW, Husted RF, Schmidt TJ, Thomas CP. The α-Subunit of the Epithelial Sodium Channel Is an Aldosterone-Induced Transcript in Mammalian Collecting Ducts, and This Transcriptional Response Is Mediated via Distinct cis -Elements in the 5′-Flanking Region of the Gene . Molecular Endocrinology 2001;15(4):575–588.
27. Yoo D, Kim BY, Campo C, Nance L, King A, Maouyo D, Welling PA. Cell surface expression of the ROMK (Kir 1.1) channel is regulated by the aldosterone-induced kinase, SGK-1, and protein kinase A. Journal of Biological Chemistry 2003;278(25):23066–23075.
28. Gros R, Ding Q, Sklar LA, Prossnitz EE, Arterburn JB, Chorazyczewski J, Feldman RD. GPR30 expression is required for the mineralocorticoid receptor-independent rapid vascular effects of aldosterone. Hypertension 2011;57(3):442–451.
29. Gros R, Ding Q, Liu B, Chorazyczewski J, Feldman RD. Aldosterone mediates its rapid effects in vascular endothelial cells through GPER activation. American Journal of Physiology - Cell Physiology 2013;304(6). doi:10.1152/ajpcell.00203.2012.
30. Mangelsdorf DJ, Thummel C, Beato M, Herrlich P, Schütz G, Umesono K, Blumberg B, Kastner P, Mark M, Chambon P, Evans RM. The nuclear receptor superfamily: The second decade. Cell 1995;83(6):835–839.
31. Hellal-Levy C, Fagart J, Souque A, Rafestin-Oblin ME. Mechanistic aspects of mineralocorticoid receptor activation. In: Kidney International.Vol 57. Blackwell Publishing Inc.; 2000:1250–1255.
32. Arriza JL, Weinberger C, Cerelli G, Glaser TM, Handelin BL, Housman DE, Evans RM. Cloning of human mineralocorticoid receptor complementary DNA: Structural and functional kinship with the glucocorticoid receptor. Science 1987;237(4812):268–275.
33. Fan YS, Eddy RL, Byers MG, Haley LL, Henry WM, Novvak NJ, Shows TB. The human mineralocorticoid receptor gene (MLR) is located on chromosome 4 at q31.2. Cytogenetic and Genome Research 1989;52(1–2):83–84.
34. Morrison N, Harrap SB, Arriza JL, Boyd E, Connor JM. Regional chromosomal assignment of the human mineralocorticoid receptor gene to 4q31.1. Human Genetics 1990;85(1):130–132.
35. Zennaro MC, Keightley MC, Kotelevtsev Y, Conway GS, Soubrier F, Fuller PJ. Human mineralocorticoid receptor genomic structure and identification of expressed isoforms. Journal of Biological Chemistry 1995;270(36):21016–21020.
36. Zennaro MC, Farman N, Bonvalet JP, Lombès M. Tissue-specific expression of α and β messenger ribonucleic acid isoforms of the human mineralocorticoid receptor in normal and pathological states. Journal of Clinical Endocrinology and Metabolism 1997;82(5):1345–1352.
37. Arai K, Zachman K, Shibasaki T, Chrousos GP. Polymorphisms of Amiloride-Sensitive Sodium Channel Subunits in Five Sporadic Cases of Pseudohypoaldosteronism: Do They Have Pathologic Potential? 1 . The Journal of Clinical Endocrinology & Metabolism 1999;84(7):2434–2437.
38. Beato M, Sánchez-Pacheco A. Interaction of steroid hormone receptors with the transcription initiation complex. Endocrine Reviews 1996;17(6):587–609.
39. Bamberger CM, Bamberger AM, Wald M, Chrousos GP, Schulte HM. Inhibition of mineralocorticoid activity by the β isoform of the human glucocorticoid receptor. Journal of Steroid Biochemistry and Molecular Biology 1997;60(1–2):43–50.
40. Arai K, Chrousos GP. Aldosterone Deficiency and Resistance. MDText.com, Inc.; 2000. Available at: http://www.ncbi.nlm.nih.gov/pubmed/25905305. Accessed August 18, 2020.
41. Funder JW, Pearce PT, Myles K, Roy LP. Apparent mineralocorticoid excess, pseudohypoaldosteronism, and urinary electrolyte excretion: toward a redefinition of mineralocorticoid action. The FASEB Journal 1990;4(14):3234–3238.
42. Albiston AL, Obeyesekere VR, Smith RE, Krozowski ZS. Cloning and tissue distribution of the human 1 lβ-hydroxysteroid dehydrogenase type 2 enzyme. Molecular and Cellular Endocrinology 1994;105(2). doi:10.1016/0303-7207(94)90176-7.
43. Obeyesekere VR, Li KXZ, Ferrari P, Krozowski Z. Truncation of the N- and C-terminal regions of the human 11β-hydroxysteroid dehydrogenase type 2 enzyme and effects on solubility and bidirectional enzyme activity. Molecular and Cellular Endocrinology 1997;131(2):173–182.
44. Bujalska I, Shimojo M, Howie A, Stewart PM. Human 11β-hydroxysteroid dehydrogenase: Studies on the stably transfected isoforms and localization of the type 2 isozyme within renal tissue. In: Steroids.Vol 62. Elsevier Inc.; 1997:77–82.
45. Murphy BEP. Specificity of human 11β-hydroxysteroid dehydrogenase. Journal of Steroid Biochemistry 1981;14(8):807–809.
46. Frey FJ. Kinetics and dynamics of prednisolone. Endocrine Reviews 1987;8(4):453–473.
47. Ferrari P, Smith RE, Funder JW, Krozowski ZS. Substrate and inhibitor specificity of the cloned human 11β-hydroxysteroid dehydrogenase type 2 isoform. American Journal of Physiology - Endocrinology and Metabolism 1996;270(5). doi:10.1152/ajpendo.1996.270.5.E900.
48. Souness GW, Morris DJ. The antinatriuretic and kaliuretic effects of the glucocorticoids corticosterone and cortisol following pretreatment with carbenoxolone sodium (a liquorice derivative) in the adrenalectomized rat. Endocrinology 1989;124(3):1588–1590.
49. Canessa CM, Horisberger JD, Rossier BC. Epithelial sodium channel related to proteins involved in neurodegeneration. Nature 1993;361(6411):467–470.
50. Canessa CM, Schild L, Buell G, Thorens B, Gautschi I, Horisberger JD, Rossier BC. Amiloride-sensitive epithelial Na+ channel is made of three homologous subunits. Nature 1994;367(6462):463–467.
51. Voilley N, Lingueglia E, Champigny G, Mattéi MG, Waldmann R, Lazdunski M, Barbry P. The lung amiloride-sensitive Na+ channel: Biophysical properties, pharmacology, ontogenesis, and molecular cloning. Proceedings of the National Academy of Sciences of the United States of America 1994;91(1):247–251.
52. McDonald FJ, Price MP, Snyder PM, Welsh MJ. Cloning and expression of the β- and γ-subunits of the human epithelial sodium channel. American Journal of Physiology - Cell Physiology 1995;268(5 37-5). doi:10.1152/ajpcell.1995.268.5.c1157.
53. Snyder PM. Minireview: Regulation of epithelial Na+ channel trafficking. Endocrinology 2005;146(12):5079–5085.
54. Masilamani S, Kim GH, Mitchell C, Wade JB, Knepper MA. Aldosterone,mediated regulation of ENaC α, β, and γ subunit proteins in rat kidney. Journal of Clinical Investigation 1999;104(7). doi:10.1172/JCI7840.
55. Snyder PM, Steines JC, Olson DR. Relative Contribution of Nedd4 and Nedd4-2 to ENaC Regulation in Epithelia Determined by RNA Interference. Journal of Biological Chemistry 2004;279(6):5042–5046.
56. Rotin D, Bar-Sagi D, O’Brodovich H, Merilainen J, Lehto VP, Canessa CM, Rossier BC, Downey GP. An SH3 binding region in the epithelial Na+ channel (alpha rENaC) mediates its localization at the apical membrane. The EMBO journal 1994;13(19):4440–50.
57. Shimkets RA, Warnock DG, Bositis CM, Nelson-Williams C, Hansson JH, Schambelan M, Gill JR, Ulick S, Milora R v., Findling JW, Canessa CM, Rossier BC, Lifton RP. Liddle’s syndrome: Heritable human hypertension caused by mutations in the β subunit of the epithelial sodium channel. Cell 1994;79(3):407–414.
58. Hansson JH, Nelson-Williams C, Suzuki H, Schild L, Shimkets R, Lu Y, Canessa C, Iwasaki T, Rossier B, Lifton RP. Hypertension caused by a truncated epithelial sodium channel γ subunit: Genetic heterogeneity of Liddle syndrome. Nature Genetics 1995;11(1):76–82.
59. Hansson JH, Schild L, Lu Y, Wilson TA, Gautschi I, Shimkets R, Nelson-Williams C, Rossier BC, Lifton RP. A de novo missense mutation of the β subunit of the epithelial sodium channel causes hypertension and Liddle syndrome, identifying a proline-rich segment critical for regulation of channel activity. Proceedings of the National Academy of Sciences of the United States of America 1995;92(25):11495–11499.
60. Tamura H, Schild L, Enomoto N, Matsui N, Marumo F, Rossier BC, Sasaki S. Liddle disease caused by a missense mutation of β subunit of the epithelial sodium channel gene. Journal of Clinical Investigation 1996;97(7):1780–1784.
61. Schild L, Lu Y, Gautschi I, Schneeberger E, Lifton RP, Rossier BC. Identification of a PY motif in the epithelial Na channel subunits as a target sequence for mutations causing channel activation found in Liddle syndrome. EMBO Journal 1996;15(10):2381–2387.
62. Chang SS, Grunder S, Hanukoglu A, Rösler A, Mathew PM, Hanukoglu I, Schild L, Lu Y, Shimkets RA, Nelson-Williams C, Rossier BC, Lifton RP. Mutations in subunits of the epithelial sodium channel cause salt wasting with hyperkalaemic acidosis, pseudohypoaldosteronism type 1. Nature Genetics 1996;12(3):248–253.
63. McCormick JA, Bhalla V, Pao AC, Pearce D. SGK1: A rapid aldosterone-induced regulator of renal sodium reabsorption. Physiology 2005;20(2):134–139.
64. Muller OG, Parnova RG, Centeno G, Rossier BC, Firsov D, Horisberger JD. Mineralocorticoid effects in the kidney: Correlation between αENaC, GILZ, and Sgk-1 mRNA expression and urinary excretion of Na+ and K+. Journal of the American Society of Nephrology 2003;14(5):1107–1115.
65. Ziera T, Irlbacher H, Fromm A, Latouche C, Krug SM, Fromm M, Jaisser F, Borden SA. Cnksr3 is a direct mineralocorticoid receptor target gene and plays a key role in the regulation of the epithelial sodium channel. The FASEB Journal 2009;23(11):3936–3946.
66. Booth RE, Stockand JD. Targeted degradation of ENaC in response to PKC activation of the ERK1/2 cascade. American Journal of Physiology - Renal Physiology 2003;284(5 53-5). doi:10.1152/ajprenal.00373.2002.
67. Ring AM, Leng Q, Rinehart J, Wilson FH, Kahle KT, Hebert SC, Lifton RP. An SGK1 site in WNK4 regulates Na+ channel and K+ channel activity and has implications for aldosterone signaling and K + homeostasis. Proceedings of the National Academy of Sciences of the United States of America 2007;104(10):4025–4029.
68. Valinsky WC, Touyz RM, Shrier A. Aldosterone, SGK1, and ion channels in the kidney. Clinical Science 2018;132(2):173–183.
69. Debonneville C, Flores SY, Kamynina E, Plant PJ, Tauxe C, Thomas MA, Münster C, Chraïbi A, Pratt JH, Horisberger JD, Pearce D, Loffing J, Staub O. Phosphorylation of Nedd4-2 by Sgk1 regulates epithelial Na+ channel cell surface expression. EMBO Journal 2001;20(24):7052–7059.
70. Arteaga MF, Wang L, Ravid T, Hochstrasser M, Canessa CM. An amphipathic helix targets serum and glucocorticoid-induced kinase 1 to the endoplasmic reticulum-associated ubiquitin-conjugation machinery. Proceedings of the National Academy of Sciences of the United States of America 2006;103(30):11178–11183.
71. Robert-Nicoud M, Flahaut M, Elalouf JM, Nicod M, Salinas M, Bens M, Doucet A, Wincker P, Artiguenave F, Horisberger JD, Vandewalle A, Rossier BC, Firsov D. Transcriptome of a mouse kidney cortical collecting duct cell line: Effects of aldosterone and vasopressin. Proceedings of the National Academy of Sciences of the United States of America 2001;98(5):2712–2716.
72. Soundararajan R, Melters D, Shih IC, Wang J, Pearce D. Epithelial sodium channel regulated by differential composition of a signaling complex. Proceedings of the National Academy of Sciences of the United States of America 2009;106(19):7804–7809.
73. Soundararajan R, Wang J, Melters D, Pearce D. Glucocorticoid-induced leucine zipper 1 stimulates the epithelial sodium channel by regulating serum- and glucocorticoid-induced kinase 1 stability and subcellular localization. Journal of Biological Chemistry 2010;285(51):39905–39913.
74. Loffing J, Zecevic M, Féraille E, Kaissling B, Asher C, Rossier BC, Firestone GL, Pearce D, Verrey F. Aldosterone induces rapid apical translocation of ENaC in early portion of renal collecting system: Possible role of SGK. American Journal of Physiology - Renal Physiology 2001;280(4 49-4). doi:10.1152/ajprenal.2001.280.4.f675.
75. Soundararajan R, Pearce D, Ziera T. The role of the ENaC-regulatory complex in aldosterone-mediated sodium transport. Molecular and Cellular Endocrinology 2012;350(2):242–247.
76. Zhang W, Xia X, Jalal DI, Kuncewicz T, Xu W, Lesage GD, Kone BC. Aldosterone-sensitive repression of ENaCα transcription by a histone H3 lysine-79 methyltransferase. American Journal of Physiology - Cell Physiology 2006;290(3). doi:10.1152/ajpcell.00431.2005.
77. Zhang W, Xia X, Reisenauer MR, Hemenway CS, Kone BC. Dot1a-AF9 complex mediates histone H3 Lys-79 hypermethylation and repression of ENaCα in an aldosterone-sensitive manner. Journal of Biological Chemistry 2006;281(26):18059–18068.
78. Reisenauer MR, Anderson M, Huang L, Zhang Z, Zhou Q, Kone BC, Morris AP, LeSage GD, Dryer SE, Zhang W. AF17 competes with AF9 for binding to Dot1a to up-regulate transcription of epithelial Na+ channel α. Journal of Biological Chemistry 2009;284(51):35659–35669.
79. Zhang W, Xia X, Reisenauer MR, Rieg T, Lang F, Kuhl D, Vallon V, Kone BC. Aldosterone-induced Sgk1 relieves Dot1a-Af9-mediated transcriptional repression of epithelial Na+ channel α. Journal of Clinical Investigation 2007;117(3):773–783.
80. Arai K, Zachman K, Shibasaki T, Chrousos GP. Polymorphisms of Amiloride-Sensitive Sodium Channel Subunits in Five Sporadic Cases of Pseudohypoaldosteronism: Do They Have Pathologic Potential? 1 . The Journal of Clinical Endocrinology & Metabolism 1999;84(7):2434–2437.
81. Kowarski A, Katz H, Mlgeon CJ. Plasma aldosterone concentration in normal subjects from infancy to adulthood. Journal of Clinical Endocrinology and Metabolism 1974;38(3):489–491.
82. van Acker KJ, Scharpe SL, Deprettere AJR, Neels HM. Renin-angiotensin-aldosterone system in the healthy infant and child. Kidney International 1979;16(2):196–203.
83. Laetitia M, Eric P, Laurence FLH, Francois P, Claudine C, Pascal B, Lombès M. Physiological partial aldosterone resistance in human newborns. Pediatric Research 2009;66(3):323–328.
84. Bizzarri C, Pedicelli S, Cappa M, Cianfarani S. Water balance and “salt wasting” in the first year of life: The role of aldosterone-signaling defects. Hormone Research in Paediatrics 2016;86(3):143–153.
85. Coulter CL, Jaffe RB. Functional maturation of the primate fetal adrenal in vivo: 3. Specific zonal localization and developmental regulation of CYP21A2 (P450c21) and CYP11B1/CYP11B2 (P450c11/aldosterone synthase) lead to integrated concept of zonal and temporal steroid biosynthesis. Endocrinology 1998;139(12):5144–5150.
86. Martinerie L, Viengchareun S, Delezoide AL, Jaubert F, Sinico M, Prevot S, Boileau P, Meduri G, Lombes M. Low renal mineralocorticoid receptor expression at birth contributes to partial aldosterone resistance in neonates. Endocrinology 2009;150(9):4414–4424.
87. LANDAU RL, LUGIBIHL K. Inhibition of the sodium-retaining influence of aldosterone by progesterone. The Journal of clinical endocrinology and metabolism 1958;18(11):1237–1245.
88. HUDSON JB, CHOBANIAN A v., RELMAN AS. Hypoaldosteronism; a clinical study of a patient with an isolated adrenal mineralocorticoid deficiency, resulting in hyperkalemia and Stokes-Adams attacks. The New England journal of medicine 1957;257(12):529–536.
89. Schambelan M, Stockigt JR, Biglieri EG. Isolated Hypoaldosteronism in Adults: A Renin-Deficiency Syndrome. New England Journal of Medicine 1972;287(12):573–578.
90. Perez G, Siegel L, Schreiner GE. Selective hypoaldosteronism with hyperkalemia. Annals of internal medicine 1972;76(5):757–763.
91. Sebastian A, Schambelan M, Lindenfeild S, Morris RC. Amelioration of Metabolic Acidosis with Fludrocortisone Therapy in Hyporeninemic Hypoaldosteronism. New England Journal of Medicine 1977;297(11):576–583.
92. Perez GO, Lespier L, Jacobi J, Oster JR, Katz FH, Vaamonde CA, Fishman LM. Hyporeninemia and Hypoaldosteronism in Diabetes Mellitus. Archives of Internal Medicine 1977;137(7):852–855.
93. Kalin MF, Poretsky L, Seres DS, Zumoff B. Hyporeninemic hypoaldosteronism associated with acquired immune deficiency syndrome. The American Journal of Medicine 1987;82(5):1035–1038.
94. Onozaki A, Katoh T, Watanabe T. Hyporeninemic hypoaldosteronism associated with Sjogren’s syndrome [4]. American Journal of Medicine 2002;112(3):245–246.
95. DeFronzo RA. Hyperkalemia and hyporeninemic hypoaldosteronism. Kidney International 1980;17(1):118–134.
96. Nadler JL, Lee FO, Hsueh W, Horton R. Evidence of Prostacyclin Deficiency in the Syndrome of Hyporeninemic Hypoaldosteronism. New England Journal of Medicine 1986;314(16):1015–1020.
97. Tuck ML, Sambhi MP, Levin L. Hyporeninemic hypoaldosteronism in diabetes mellitus. Studies of the autonomic nervous system’s control of renin release. Diabetes 1979;28(3):237–241.
98. Perez GO, Lespier LE, Oster JR, Vaamonde CA. Effect of alterations of sodium intake in patients with hyporeninemic hypoaldosteronism. Nephron 1977;18(5):259–265.
99. Escarce JJ. Hyporeninemic Hypoaldosteronism in a Patient With Cirrhosis and Ascites. Archives of Internal Medicine 1986;146(12):2407–2408.
100. Nakamoto Y, Imai H, Hamanaka S, Yoshida K, Akihama T, Miura AB. IgM monoclonal gammopathy accompanied by nodular glomerulosclerosis, urine-concentrating defect, and hyporeninemic hypoaldosteronism. American Journal of Nephrology 1985;5(1):53–58.
101. Yoshino M, Amerian R, Brautbar N. Hyporeninemic hypoaldosteronism in sickle cell disease. Nephron 1982;31(3):242–244.
102. Kiley J, Zager P. Hyporeninemic Hypoaldosteronism in Two Patients With Systemic Lupus Erythematosus. American Journal of Kidney Diseases 1984;4(1):39–43.
103. Masud T, Winocour P, Clarke F. Reversible hyporeninaemic hypoaldosteronism and life-threatening cardiac dysrhythmias: The interaction of non-steroidal anti-inflammatory drugs and autonomic dysfunction. Postgraduate Medical Journal 1993;69(813):593–594.
104. Motoo Y, Sawabu N, Takemori Y, Ohta H, Okai T, Ikeda K, Yokoyama H. Long-Term Follow-Up of Mitomycin C Nephropathy. Internal Medicine 1994;33(3):180–184.
105. Sunderlin FF, Anderson GH, Streeten DHP, Blumenthal SA. The renin-angiotensin-aldosterone system in diabetic patients with hyperkalemia. Diabetes 1981;30(4):335–340.
106. Deleiva A, Christlieb AR, Melby JC, Graham CA, Day RP, Luetscher JA, Zager PG. Big Renin and Biosynthetic Defect of Aldosterone in Diabetes Mellitus. New England Journal of Medicine 1976;295(12):639–643.
107. FitzGerald GA, Hossmann V, Hummerich W, Konrads A. The renin - kallikrein - prostaglandin system: Plasma active and inactive renin and urinary kallikrein during prostacyclin infusion in man. Prostaglandines and Medicine 1980;5(6):445–456.
108. Ulick S, Wang JZ, Morton DH. The biochemical phenotypes of two inborn errors in the biosynthesis of aldosterone. Journal of Clinical Endocrinology and Metabolism 1992;74(6):1415–1420.
109. Ulick S. Correction of the nomenclature and mechanism of the aldosterone biosynthetic defects. The Journal of Clinical Endocrinology & Metabolism 1996;81(3):1299–1300.
110. Mitsuuchi Y, Kawamoto T, Miyahara K, Ulick S, Morton DH, Naiki Y, Kuribayashi I, Toda K, Hara T, Orii T, Yasuda K, Miura K, Yamamoto Y, Imura H, Shizuta Y. Congenitally defective aldosterone biosynthesis in humans: Inactivation of the P450C18 gene (CYP11B2) due to nucleotide deletion in CMO I deficient patients. Biochemical and Biophysical Research Communications 1993;190(3):864–869.
111. Shizuta Y, Kawamoto T, Mitsuuchi Y, Miyahara K, Rösler A, Ulick S, Imura H. Inborn errors of aldosterone biosynthesis in humans. Steroids 1995;60(1):15–21.
112. Geley S, Jöhrer K, Peter M, Denner K, Bernhardt R, Sippell WG, Kofler R. Amino acid substitution R384P in aldosterone synthase causes corticosterone methyloxidase type I deficiency. Journal of Clinical Endocrinology and Metabolism 1995;80(2):424–429.
113. Pascoe L, Curnow KM, Slutsker L, Rosler A, White PC. Mutations in the human CYP11B2 (aldosterone synthase) gene causing corticosterone methyloxidase II deficiency. Proceedings of the National Academy of Sciences of the United States of America 1992;89(11):4996–5000.
114. Zhang G, Rodriguez H, Fardella CE, Harris DA, Miller WL. Mutation T318M in the CYP11B2 gene encoding P450c11AS (aldosterone synthase) causes corticosterone methyl oxidase II deficiency. American Journal of Human Genetics 1995;57(5):1037–1043.
115. Kuribayashi I, Kuge H, Santa RJ, Mutlaq AZ, Yamasaki N, Furuno T, Takahashi A, Chida S, Nakamura T, Endo F, Doi Y, Onishi S, Shizuta Y. A missense mutation (GGC[435Gly]→AGC[ser]) in exon 8 of the CYP11B2 gene inherited in Japanese patients with congenital hypoaldosteronism. Hormone Research 2003;60(5):255–260.
116. Williams TA, Mulatero P, Bosio M, Lewicka S, Palermo M, Veglio F, Armanini D. A particular phenotype in a girl with aldosterone synthase deficiency. In: Journal of Clinical Endocrinology and Metabolism.Vol 89. J Clin Endocrinol Metab; 2004:3168–3172.
117. Leshinsky-Silver E, Landau Z, Unlubay S, Bistrizer T, Zung A, Tenenbaum-Rakover Y, DeVries L, Lev D, Hanukoglu A. Congenital hyperreninemic hypoaldosteronism in Israel: Sequence analysis of CYP11B2 gene. Hormone Research 2006;66(2):73–78.
118. Nguyen HH, Hannemann F, Hartmann MF, Wudy SA, Bernhardt R. Aldosterone synthase deficiency caused by a homozygous L451F mutation in the CYP11B2 gene. Molecular Genetics and Metabolism 2008;93(4):458–467.
119. Løvås K, McFarlane I, Nguyen HH, Curran S, Schwabe J, Halsall D, Bernhardts R, Wallace AM, Chatterjee VKK. A novel CYP11b2 gene mutation in an asian family with aldosterone synthase deficiency. Journal of Clinical Endocrinology and Metabolism 2009;94(3):914–919.
120. White PC. Aldosterone synthase deficiency and related disorders. In: Molecular and Cellular Endocrinology.Vol 217. Mol Cell Endocrinol; 2004:81–87.
121. Rösler A. The natural history of salt-wasting disorders of adrenal and renal origin. Journal of Clinical Endocrinology and Metabolism 1984;59(4):689–700.
122. Miao H, Yu Z, Lu L, Zhu H, Auchus RJ, Liu J, Jiang J, Pan H, Gong F, Chen S, Lu Z. Analysis of novel heterozygous mutations in the CYP11B2 gene causing congenital aldosterone synthase deficiency and literature review. Steroids 2019;150. doi:10.1016/j.steroids.2019.108448.
123. Peter M, Partsch CJ, Sippell WG. Multisteroid analysis in children with terminal aldosterone biosynthesis defects. Journal of Clinical Endocrinology and Metabolism 1995;80(5):1622–1627.
124. Ulick S. Cortisol as mineralocorticoid. The Journal of Clinical Endocrinology & Metabolism 1996;81(4):1307–1308.
125. Klomchan T, Supornsilchai V, Wacharasindhu S, Shotelersuk V, Sahakitrungruang T. Novel CYP11B2 mutation causing aldosterone synthase (P450c11AS) deficiency. European Journal of Pediatrics 2012;171(10):1559–1562.
126. Kondo E, Nakamura A, Homma K, Hasegawa T, Yamaguchi T, Narugami M, Hattori T, Aoyagi H, Ishizu K, Tajima T. Two novel mutations of the CYP11B2 gene in a Japanese patient with aldosterone deficiency type 1. Endocrine Journal 2013;60(1):51–55.
127. Hui E, Yeung MCW, Cheung PT, Kwan E, Low L, Tan KCB, Lam KSL, Chan AOK. The clinical significance of aldosterone synthase deficiency: Report of a novel mutation in the CYP11B2 gene. BMC Endocrine Disorders 2014;14. doi:10.1186/1472-6823-14-29.
128. Portrat-Doyen S, Tourniaire J, Richard O, Mulatero P, Aupetit-Faisant B, Curnow KM, Pascoe L, Morel Y. Isolated Aldosterone Synthase Deficiency Caused by Simultaneous E198D and V386A Mutations in the CYP11B2 Gene 1 . The Journal of Clinical Endocrinology & Metabolism 1998;83(11):4156–4161.
129. Jessen CL, Christensen JH, Birkebæk NH, Rittig S. Homozygosity for a mutation in the CYP11B2 gene in an infant with congenital corticosterone methyl oxidase deficiency type II. Acta Paediatrica, International Journal of Paediatrics 2012;101(11). doi:10.1111/j.1651-2227.2012.02823.x.
130. O’Kelly R, Magee F, McKenna J. Routine heparin therapy inhibits adrenal aldosterone production. Journal of Clinical Endocrinology and Metabolism 1983;56(1):173–176.
131. Sequeira SJ, McKenna TJ. Chlorbutol, a new inhibitor of aldosterone biosynthesis identified during examination of heparin effect on aldosterone production. Journal of Clinical Endocrinology and Metabolism 1986;63(3):780–784.
132. Zipser RD, Davenport MW, Martin KL, Tuck ML, Warner NE, Swinney RR, Davis CL, Horton R. Hyperreninemic hypoaldosteronism in the critically 111: A new entity. Journal of Clinical Endocrinology and Metabolism 1981;53(4):867–873.
133. Davenport MW, Zipser RD. Association of hypotension with hyperreninemic hypoaldosteronism in the critically ill patient. Archives of internal medicine 1983;143(4):735–7.
134. Cheek DB, Perry JW. A salt wasting syndrome in infancy. Archives of Disease in Childhood 1958;33(169):252–256.
135. Speiser PW, Stoner E, New MI. Pseudohypoaldosteronism: a review and report of two new cases. Advances in experimental medicine and biology 1986;196:173–195.
136. Zennaro MC, Fernandes-Rosa F. Mineralocorticoid receptor mutations. Journal of Endocrinology 2017;234(1):T93–T106.
137. Zennaro MC, Lombès M. Mineralocorticoid resistance. Trends in Endocrinology and Metabolism 2004;15(6):264–270.
138. Strautnieks SS, Thompson RJ, Gardiner RM, Chung E. A novel splice-site mutation in the γ subunit of the epithelial sodium channel gene in three pseudohypoaldosteronism type 1 families. Nature Genetics 1996;13(2):248–250.
139. Geller DS, Rodriguez-Soriano J, Vallo Boado A, Schifter S, Bayer M, Chang SS, Lifton RP. Mutations in the mineralocorticoid receptor gene cause autosomal dominant pseudohypoaldosteronism type I. Nature Genetics 1998;19(3):279–281.
140. Tajima T, Kitagawa H, Yokoya S, Tachibana K, Adachi M, Nakae J, Suwa S, Katoh S, Fujieda K. A novel missense mutation of mineralocorticoid receptor gene in one Japanese family with a renal form of pseudohypoaldosteronism type 1. Journal of Clinical Endocrinology and Metabolism 2000;85(12):4690–4694.
141. Arai K, Tsigos C, Suzuki Y, Irony I, Karl M, Listwak S, Chrousos GP. Physiological and molecular aspects of mineralocorticoid receptor action in pseudohypoaldosteronism: a responsiveness test and therapy. The Journal of Clinical Endocrinology & Metabolism 1994;79(4):1019–1023.
142. Zennaro MC, Borensztein P, Jeunemaitre X, Armanini D, Soubrier F. No alteration in the primary structure of the mineralocorticoid receptor in a family with pseudohypoaldosteronism. The Journal of Clinical Endocrinology & Metabolism 1994;79(1):32–38.
143. Komesaroff PA, Verity K, Fuller PJ. Pseudohypoaldosteronism: molecular characterization of the mineralocorticoid receptor. The Journal of Clinical Endocrinology & Metabolism 1994;79(1):27–31.
144. Arai K, Tsigos C, Suzuki Y, Listwak S, Zachman K, Zangeneh F, Rapaport R, Chanoine JP, Chrousos GP. No apparent mineralocorticoid receptor defect in a series of sporadic cases of pseudohypoaldosteronism. Journal of Clinical Endocrinology and Metabolism 1995;80(3):814–817.
145. Viemann M, Peter M, López-Siguero JP, Simic-Schleicher G, Sippell WG. Evidence for genetic heterogeneity of pseudohypoaldosteronism type 1: Identification of a novel mutation in the human mineralocorticoid receptor in one sporadic case and no mutations in two autosomal dominant kindreds. Journal of Clinical Endocrinology and Metabolism 2001;86(5):2056–2059.
146. Oberfield SE, Levine LS, Carey RM, Bejar R, New MI. Pseudohypoaldosteronism: multiple target organ unresponsiveness to mineralocorticoid hormones. The Journal of clinical endocrinology and metabolism 1979;48(2):228–34.
147. Hanukoglu A, Omana J, Steinitz M, Rosler A, Hanukoglu I. Pseudohypoaldosteronism due to renal and multisystem resistance to mineralocorticoids respond differently to carbenoxolone. Journal of Steroid Biochemistry and Molecular Biology 1997;60(1–2):105–112.
148. Postel-Vinay MC, Alberti GM, Ricour C, Limal JM, Rappaport R, Royer P. Pseudohypoaldosteronism: Persistence of hyperaldosteronism and evidence for renal tubular and intestinal responsiveness to endogenous aldosterone. Journal of Clinical Endocrinology and Metabolism 1974;39(6):1038–1044.
149. Hanukoglu I, Hanukoglu A. Epithelial sodium channel (ENaC) family: Phylogeny, structure-function, tissue distribution, and associated inherited diseases. Gene 2016;579(2):95–132.
150. Dirlewanger M, Huser D, Zennaro MC, Girardin E, Schild L, Schwitzgebel VM. A homozygous missense mutation in SCNN1A is responsible for a transient neonatal form of pseudohypoaldosteronism type 1. American Journal of Physiology - Endocrinology and Metabolism 2011;301(3). doi:10.1152/ajpendo.00066.2011.
151. Schaedel C, Marthinsen L, Kristoffersson AC, Kornfält R, Nilsson KO, Orlenius B, Holmberg L. Lung symptoms in pseudohypoaldosteronism type 1 are associated with deficiency of the α-subunit of the epithelial sodium channel. Journal of Pediatrics 1999;135(6):739–745.
152. Wang J, Yu T, Yin L, Li J, Yu L, Shen Y, Yu Y, Shen Y, Fu Q. Novel Mutations in the SCNN1A Gene Causing Pseudohypoaldosteronism Type 1. PLoS ONE 2013;8(6). doi:10.1371/journal.pone.0065676.
153. Edelheit O, Hanukoglu I, Gizewska M, Kandemir N, Tenenbaum-Rakover Y, Yurdakök M, Zajaczek S, Hanukoglu A. Novel mutations in epithelial sodium channel (ENaC) subunit genes and phenotypic expression of multisystem pseudohypoaldosteronism. Clinical Endocrinology 2005;62(5):547–553.
154. Gründer S, Firsov D, Chang SS, Jaeger NF, Gautschi I, Schild L, Lifton RP, Rossier BC. A mutation causing pseudohypoaldosteronism type 1 identifies a conserved glycine that is involved in the gating of the epithelial sodium channel. EMBO Journal 1997;16(5):899–907.
155. Edelheit O, Hanukoglu I, Shriki Y, Tfilin M, Dascal N, Gillis D, Hanukoglu A. Truncated beta epithelial sodium channel (ENaC) subunits responsible for multi-system pseudohypoaldosteronism support partial activity of ENaC. Journal of Steroid Biochemistry and Molecular Biology 2010;119(1–2):84–88.
156. Hanukoglu A, Edelheit O, Shriki Y, Gizewska M, Dascal N, Hanukoglu I. Renin-aldosterone response, urinary Na/K ratio and growth in pseudohypoaldosteronism patients with mutations in epithelial sodium channel (ENaC) subunit genes. Journal of Steroid Biochemistry and Molecular Biology 2008;111(3–5):268–274.
157. Saxena A, Hanukoglu I, Saxena D, Thompson RJ, Mark Gardiner R, Hanukoglu A. Novel mutations responsible for autosomal recessive multisystem pseudohypoaldosteronism and sequence variants in epithelial sodium channel α-, β-, and γ-subunit genes. Journal of Clinical Endocrinology and Metabolism 2002;87(7):3344–3350.
158. Adachi M, Tachibana K, Asakura Y, Abe S, Nakae J, Tajima T, Fujieda K. Compound Heterozygous Mutations in the γ Subunit Gene of ENaC (1627delG and 1570-1G→A) in One Sporadic Japanese Patient with a Systemic Form of Pseudohypoaldosteronism Type 1. The Journal of Clinical Endocrinology & Metabolism 2001;86(1):9–12.
159. Nobel YR, Lodish MB, Raygada M, del Rivero J, Faucz FR, Abraham SB, Lyssikatos C, Belyavskaya E, Stratakis CA, Zilbermint M. Pseudohypoaldosteronism type 1 due to novel variants of SCNN1B gene. Endocrinology, Diabetes and Metabolism Case Reports 2016;2016. doi:10.1530/EDM-15-0104.
160. Riepe FG, Krone N, Morlot M, Ludwig M, Sippell WG, Partsch CJ. Identification of a novel mutation in the human mineralocorticoid receptor gene in a german family with autosomal-dominant pseudohypoaldosteronism type 1: Further evidence for marked interindividual clinical heterogeneity. Journal of Clinical Endocrinology and Metabolism 2003;88(4):1683–1686.
161. Riepe FG, Krone N, Morlot M, Peter M, Sippell WG, Partsch CJ. Autosomal-Dominant Pseudohypoaldosteronism Type 1 in a Turkish Family Is Associated with a Novel Nonsense Mutation in the Human Mineralocorticoid Receptor Gene. Journal of Clinical Endocrinology and Metabolism 2004;89(5):2150–2152.
162. Nyström AM, Bondeson ML, Skanke N, Mårtensson J, Strömberg B, Gustafsson J, Annerén G. A Novel Nonsense Mutation of the Mineralocorticoid Receptor Gene in a Swedish Family with Pseudohypoaldosteronism Type I (PHA1). Journal of Clinical Endocrinology and Metabolism 2004;89(1):227–231.
163. Kanda K, Nozu K, Yokoyama N, Morioka I, Miwa A, Hashimura Y, Kaito H, Iijima K, Matsuo M. Autosomal dominant pseudohypoaldosteronism type 1 with a novel splice site mutation in MR gene. BMC Nephrology 2009;10(1). doi:10.1186/1471-2369-10-37.
164. Sartorato P, Lapeyraque AL, Armanini D, Kuhnle U, Khaldi Y, Salomon R, Abadie V, di Battista E, Naselli A, Racine A, Bosio M, Caprio M, Poulet-Young V, Chabrolle JP, Niaudet P, de Gennes C, Lecornec MH, Poisson E, Fusco AM, Loli P, Lombès M, Zennaro MC. Different inactivating mutations of the mineralocorticoid receptor in fourteen families affected by type I pseudohypoaldosteronism. Journal of Clinical Endocrinology and Metabolism 2003;88(6):2508–2517.
165. Riepe FG, Finkeldei J, de Sanctis L, Einaudi S, Testa A, Karges B, Peter M, Viemann M, Grötzinger J, Sippell WG, Fejes-Toth G, Krone N. Elucidating the underlying molecular pathogenesis of NR3C2 mutants causing autosomal dominant pseudohypoaldosteronism type 1. Journal of Clinical Endocrinology and Metabolism 2006;91(11):4552–4561.
166. Hatta Y, Nakamura A, Hara S, Kamijo T, Iwata J, Hamajima T, Abe M, Okada M, Ushio M, Tsuyuki K, Tajima T. Clinical and molecular analysis of six Japanese patients with a renal form of pseudohypoaldosteronism type 1. Endocrine Journal 2013;60(3):299–304.
167. Morikawa S, Komatsu N, Sakata S, Nakamura-Utsunomiya A, Okada S, Tajima T. Two Japanese patients with the renal form of pseudohypoaldosteronism type 1 caused by mutations of NR3C2. Clinical Pediatric Endocrinology 2015;24(3):135–138.
168. Arai K, Nakagomi Y, Iketani M, Shimura Y, Amemiya S, Ohyama K, Shibasaki T. Functional polymorphisms in the mineralocorticoid receptor and amirolide-sensitive sodium channel genes in a patient with sporadic pseudohypoaldosteronism. Human Genetics 2003;112(1):91–97.
169. Warnock DG. Accessory factors and the regulation of epithelial sodium channel activity. Journal of Clinical Investigation 1999;103(5):593.
170. Rodríguez-Soriano J, Vallo A, Oliveros R, Castillo G. Transient pseudohypoaldosteronism secondary to obstructive uropathy in infancy. The Journal of Pediatrics 1983;103(3):375–380.
171. Bizzarri C, Olivini N, Pedicelli S, Marini R, Giannone G, Cambiaso P, Cappa M. Congenital primary adrenal insufficiency and selective aldosterone defects presenting as salt-wasting in infancy: A single center 10-year experience. Italian Journal of Pediatrics 2016;42(1). doi:10.1186/s13052-016-0282-3.
172. Geller DS. Mineralocorticoid resistance. Clinical Endocrinology 2005;62(5):513–520.
173. Riepe FG. Clinical and Molecular Features of Type 1 Pseudohypoaldosteronism. Hormone Research 2009;72(1):1–9.
174. Bogdanović R, Stajić N, Putnik J, Paripović A. Transient type 1 pseudo-hypoaldosteronism: Report on an eight-patient series and literature review. Pediatric Nephrology 2009;24(11):2167–2175.
175. Adam WR. Hypothesis: A simple algorithm to distinguish between hypoaldosteronism and renal aldosterone resistance in patients with persistent hyperkalemia. Nephrology 2008;13(6):459–464.
176. Kuhnle U, Guariso G, Sonega M, Hinkel GK, Hubl W, Armanini D. Transient pseudohypoaldosteronism in obstructive renal disease with transient reduction of lymphocytic aldosterone receptors. Hormone Research in Paediatrics 1993;39(3–4):152–155.

ABSTRACT

The Acquired Immunodeficiency Syndrome (AIDS), caused by infection with the Human Immunodeficiency Virus Type-1 (HIV), is characterized by profound immunosuppression, particularly of the innate, and T-helper (Th) 1-directed immunity. AIDS causes multisystem dysfunction, including impairment of the hypothalamic-pituitary-adrenal (HPA) axis, a major system coordinating the resting state and the adaptive response to stress. This neuroendocrine axis consists of three components: the hypothalamus, the pituitary gland, and the adrenal cortex with its end-effector molecules, the glucocorticoids. AIDS/HIV influence the HPA axis directly, through modulation of the host immune activity and alterations of the cellular biological pathways via HIV-encoded proteins, as well as indirectly, through immunodeficiency-associated opportunistic infections and various side effects of the therapeutic compounds employed, including those used in the highly active antiretroviral therapy (HAART). In this chapter, the interaction between AIDS/HIV and the HPA axis is reviewed and discussed.

INTRODUCTION

Patients with Acquired Immunodeficiency Syndrome (AIDS), caused by infection with the Human Immunodeficiency Virus Type-1 (HIV), develop profound immunosuppression, particularly of their innate and T-helper (Th) 1-directed cellular immunity (1). These patients may also present with dysfunction of many organ systems, including the hypothalamic-pituitary-adrenal (HPA) axis (2). During the last 25 years, numerous reports have provided evidence for alterations of the HPA axis and its influence on target tissues in HIV-infected patients (Table 1). Indeed, AIDS has been associated with adrenalitis caused by opportunistic infections, adrenal dysfunction secondary to neoplastic infiltration into the adrenal cortices, and changes related to circulating cytokines and other bioactive molecules known to influence functions of the HPA axis (3). Glucocorticoid hormones secreted from the adrenal cortex act as end-effectors of the HPA axis and have strong anti-inflammatory effects (4). Thus, these hormones were considered for reversing HIV-mediated depletion of circulating CD4+ lymphocytes and slowing progression to AIDS, as well as to subside complications associated with HIV infection (5) (Table 2).

*Acceleration of Kaposi sarcoma by glucocorticoids (110)

Although development of HIV vaccines targeting components of the viral particles is still challenging, establishment and clinical introduction of the highly active antiretroviral therapy (HAART) that employs combinatory use of the three different types of antiretroviral drugs, such as nucleoside and non-nucleoside analogues acting as reverse transcriptase inhibitors, non-peptidic viral protease inhibitors (PIs) and the compounds blocking entry of HIV to CD4+ lymphocytes, efficiently suppress HIV replication in infected patients and have dramatically improved clinical course and life expectancy of AIDS patients (6-9). However, the prolongation of lives with long-term use of the above antiretroviral agents have generated novel morbidities and complications, which influence the patients’ quality of life and add new risk factors for premature death. Central among them is the quite common AIDS-related insulin resistance and lipodystrophy syndrome (ARIRLS), which is characterized by a striking phenotype and marked metabolic disturbances that are reminiscent of Cushing syndrome (10). In agreement with above-indicated clinical background, acquired alterations in the sensitivity of tissues to glucocorticoids were originally hypothesized in AIDS patients, and this concept was further extended to other nuclear receptor (NR) family proteins. In addition, some PIs inhibit the cytochrome p450 enzyme CYP3A4, which is necessary to metabolize glucocorticoids into inactive forms (11). Thus, the pharmacologic action of glucocorticoids used in the AIDS patients treated with these compounds is pronounced due to slowing of their metabolism, and “iatrogenic” Cushing syndrome is subsequently developed in these patients (12).

AIDS patients frequently develop several different types of malignancies, such as lymphoma and Kaposi sarcoma, in part due to profound destruction of host immune system by HIV (13,14). Glucocorticoids are among the central compounds for the treatment of the patients harboring these malignancies (13,15). Glucocorticoids are also pivotal for the treatment of HIV-associated nephropathy, which is observed in about 10% of AIDS patients (16). Use of glucocorticoids is further considered for the patients with HIV-associated tuberculosis and other opportunistic infections as part of the immunoadjuvant therapy (17,18).

In this chapter, we will explain known interactions between HIV infection and the HPA axis, particularly focusing on glucocorticoid hormones. We also present our understanding on some emerging concepts of such interactions, and discuss their possible mechanisms and relevance to HIV pathogenesis. 

HPA AXIS AND GLUCOCORTICOID ACTIONS

Humans face unforeseen short- and long-term environmental changes called “stressors”, which can be external (e.g. excessive heat or cold, food deprivation, trauma and invasion by pathogens) or internal (e.g. hurtful memories, splachnic injuries, neoplasia’s) (19-22). To adapt to these changes, humans have the stress-responsive system, which senses such stressors through various peripheral sensory organs, processes them in the central nervous system (CNS), and adjusts the CNS and peripheral organ activities (19-22). The hypothalamic-pituitary-adrenal (HPA) axis with its end-effectors glucocorticoids is one of the two arms of this regulatory system, together with the locus caeruleus/norepinephrine-autonomic system and their end-effectors, norepinephrine and epinephrine (19,21,22). At baseline, activity of the HPA axis and circulating glucocorticoid levels are in a typical diurnal rhythm, reaching their zenith in the early morning and their nadir in the late evening in diurnal animals including humans through input from a circadian rhythm center, the suprachiasmatic nucleus (SCN), and they participate in the maintenance of internal homeostasis (20,23,24). Upon exposure to stressors, the HPA axis is liberated from this regular circadian rhythm, and is strongly activated to modulate many biological activities including those of the CNS, intermediary metabolism, immunity and reproduction via highly elevated circulating glucocorticoids (4,19-25). However, this stress-induced activation of the HPA axis may also exert an array of adverse effects when its response is not properly tailored to the stressful stimuli (25). For example, acute hyper-activation of the HPA axis has been associated with development of post-traumatic stress disorder, while chronic activation of the HPA axis, and consequently prolonged elevation of serum glucocorticoid levels, induce visceral-type obesity and insulin resistance/dyslipidemia, which are represented as metabolic syndrome (19,21-25).

The HPA axis consists of the hypothalamic PVN parvocellular corticotropin-releasing hormone (CRH)- and arginine vasopressin (AVP)-secreting neurons, the corticotrophs of the pituitary gland, and the adrenal gland cortex (3,21-24) (Figure 1A). The PVN neurons release CRH and AVP into the hypophyseal portal system located under the median eminence of the hypothalamus in response to stimulatory signals from higher brain regulatory centers (3,21-24). Secreted CRH and AVP reach the pituitary gland and synergistically stimulate secretion of the adrenocorticotropic hormone (ACTH) from corticotrophs (19,21-24,26). ACTH released into systemic circulation finally stimulates both production and secretion of glucocorticoids (cortisol in humans and corticosterone in rodents) from the zona fasciculata of the adrenal cortex (25). Secreted glucocorticoids modulate activity of virtually all organs and tissues to adjust their functions. In addition, these hormones suppress higher regulatory centers of the HPA axis, the PVN and the pituitary gland, ultimately forming a closed negative feedback loop that aims to reset the activated HPA axis and restore its homeostasis (19).

Figure 1. The HPA axis and intracellular actions of GR

Organization of the HPA Axis

The HPA axis consists of 3 components: the PVN of hypothalamus, the anterior pituitary gland and the adrenal cortex. Neurons residing in PVN produce CRH and AVP and release them into the pituitary portal vein under the control of upper centers, including the central circadian rhythm center, hypothalamic suprachiasmatic nucleus (SCN). Released CRH and AVP stimulate secretion of ACTH from corticotrophs of the anterior pituitary gland. ACTH then stimulates the production and secretion of glucocorticoids (cortisol in humans and corticosterone in rodents) from adrenocortical cells located in zona fasciculata of the adrenal gland. Circulating glucocorticoids suppress upper regulatory centers including PVN and pituitary gland, forming a closed regulatory loop.

Intracellular Actions of GR

In the absence of glucocorticoids, GR resides in the cytoplasm forming a heterocomplex with several heat shock proteins (HSP). Upon binding to glucocorticoids, GR releases HSPs and translocates into the nucleus. In the nucleus, GR directly binds its specific sequence called glucocorticoid response elements (GREs) located in the promoter/enhancer region of glucocorticoid-responsive genes as a homodimer, and stimulates transcription by attracting many transcriptional cofactors and the RNA polymerase II complex. GR also modulates transcriptional activity of other transcription factors through physical protein-protein interaction without associating directly to DNA. After regulating transcription of glucocorticoid-responsive genes, GR moves back into the cytoplasm with help of the nuclear export system and returns to its ligand friendly condition by reforming a heterocomplex with HSPs. This complex regulatory system for the GR intracellular activity is sensitive to many inputs from other intracellular regulatory systems in order to adjust net GR actions upon local needs. [modified from (27)]

Infection of pathogens including HIV potently activates the HPA axis and induces subsequent secretion of glucocorticoids from the adrenal cortex (28,29). Pathogens generally stimulate central part of this regulatory system (e.g., brain hypothalamus and pituitary corticotrophs) directly with their structural and genetic components, and indirectly with cytokines and inflammatory mediators, such as the tumor necrosis factor a (TNFa), interleukin (IL)-1 and IL-6, secreted from activated immune cells and/or infected tissues (30). Secreted glucocorticoids in turn subside inflammation, functioning as a counter regulatory mechanism for otherwise overshooting immune response (31). Glucocorticoids do this mainly by suppressing release of humoral inflammatory mediators, granulocyte migration, cellular immunity and production of Th1 cytokines, such as IL-12, TNFa and the interferon (IFN) g, while they stimulate humoral immunity and secretion of Th2-inducing anti-inflammatory cytokines, including IL-4, IL-10 and the transforming growth factor b (4,32,33).

Glucocorticoids exert profound influences on many physiologic functions by virtue of their diverse roles in growth, development, and maintenance of cardiovascular, metabolic and immune homeostasis (4,34,35). Excess amounts of glucocorticoids have strong effects on intermediary metabolism, developing insulin resistance/overt diabetes mellitus and hyperlipidemia (especially triglycerides and free fatty acids) through modulation of their broad target regulatory systems/molecules (4). As glucocorticoids possess potent anti-inflammatory and immunosuppressive activities, they are used as invaluable therapeutic means in inflammatory and autoimmune diseases (36). In addition, glucocorticoids are central components of the anti-cancer treatment especially for hematologic malignancies, such as leukemia and lymphoma (4).

Glucocorticoids exert their effects on their target cells through the glucocorticoid receptor (GR), a ligand-specific and -dependent transcription factor, ubiquitously expressed in almost all tissues and cells (21-24,28). There are two 3’ splicing variants, GRa and GRb, through alternative use of a different terminal exon termed 9a or 9b. GRa is the classic glucocorticoid receptor, which binds glucocorticoids and transactivates or transrepresses glucocorticoid-responsive genes (37). GRa shuttles between the cytoplasm and the nucleus; Binding of glucocorticoids to GRa causes it to dissociate from the cytoplasmic hetero-oligomer containing heat shock proteins and to translocate into the nucleus through the nuclear pore (28) (Figure 1B). Ligand-bound and nucleus-translocated GRa binds as a homo-dimer to specific DNA sequences called glucocorticoid response elements (GREs) located in the promoter/enhancer regions of glucocorticoid-responsive genes to modulate their transcription (28). On the other hand, GRb does not bind glucocorticoids and functions as a dominant negative inhibitor of GRa on GRE-containing glucocorticoid-responsive promoters, together with its intrinsic transcriptional activity on the genes not related to glucocorticoid transcriptional activity (37,38). However, its physiologic and pathophysiologic roles have not been fully determined as yet (37).

The GRE-bound GR (hereafter for GRa) attracts to the promoter regions of glucocorticoid-responsive genes numerous “coactivator complexes”, including those with histone acetyltransferase (HAT) activity, such as the NR coactivator [p160, p300/CREB-binding protein (CBP) and p300/CBP-associated factor (p/CAF)] complex, the SWI/SNF and the vitamin D receptor-interacting protein/thyroid hormone receptor-associated protein (DRIP/TRAP) chromatin-remodeling complexes (39). Among them, p160-type NR coactivators bind first to the ligand-activated and DNA-bound GR through their coactivator LxxLL motifs, and attract other coactivators and chromatin modulatory complexes including p300/CBP to the promoter/enhancer region of glucocorticoid-responsive genes. Through these proteins and protein complexes, GR alters chromatin structure and facilitates access of other transcription factors, RNA polymerase II and its ancillary factors to the promoter region of glucocorticoid-responsive genes, and ultimately changes their transcription rates (28). In addition to these protein molecules, recent research identified that several long non-protein-coding RNA molecules, such as the steroid receptor RNA coactivator (SRA) and the growth arrest-specific 5 (Gas5), regulate the transcriptional activity of GR (40,41).

Complexity of the GR-signaling system residing in glucocorticoid target organs/tissues suggests that it provides potential regulatory “windows” to the GR-induced transcriptional network, which further indicates that glucocorticoid activity is under the tight regulation of numerous factors to adjust its activity upon local needs (25,28) (Figure 1B). This peripheral modulation of the glucocorticoid-signaling system is referred to as “sensitivity of tissues to glucocorticoids”, which determines effectiveness of circulating glucocorticoids in local tissues (30). Depending on its directions -decreased or increased-, it is categorized into two subgroups; resistance and hypersensitivity. Both states may be generalized or tissue-specific, as well as congenital or acquired. The generalized, congenital form of glucocorticoid resistance, namely the familial/sporadic glucocorticoid resistance syndrome or Chrousos syndrome, was described and established approximately 30 years ago (42-45). It is characterized by partial, relatively well-compensated resistance of all tissues to glucocorticoids and is mostly caused by inactivating mutations in the GR gene (42-45). On the other hand, tissue-specific, acquired forms of glucocorticoid resistance/hypersensitivity have been inferred but not fully confirmed or elucidated (46). Such states may be limited to certain tissues, as for instance leukocytes or adipocytes, and present with the manifestations associated with deficiency or excess glucocorticoids specific to respective tissues (25). Allergic, inflammatory or autoimmune diseases, such as glucocorticoid resistant asthma, Crohn’s disease, rheumatoid arthritis and systemic lupus erythematosus, may be glucocorticoid resistant states found in the components of the immune system (25,46). Conditions associated with chronic deprivation of energy resources, such as severe lean and anorexia nervosa, are considered as glucocorticoid resistance specific in the liver, fat and/or muscles, in part through activation of several kinases including the AMP-activated protein kinase and subsequent cytoplasmic segregation of a newly-identified GR coactivator, the CREB-regulated transcription coactivator 2 and/or induction of the repressive molecules, such as the RNA corepressor Gas5 (41,46-49). In contrast, the conditions associated with excess energy resources, such as central obesity-associated insulin resistance, hyperlipidemia and hypertension, may be glucocorticoid hypersensitivity states in adipose and/or vascular tissues (46).

INTERACTION OF THE HPA AXIS AND HIV INFECTION

Pathologic Conditions Associated with the Adrenal Glands in AIDS Patients

The adrenal gland is one of the organs frequently found damaged by HIV infection at autopsy, mostly caused by the opportunistic infection of other pathogens due to immunodeficiency of AIDS patients (50-52). Incidence of adrenalitis has significantly dropped recently, because the immune function of AIDS patients is much better preserved and the incidence of opportunistic infection has been dramatically reduced due to introduction of HAART (53). Pathologic findings of AIDS-associated adrenalitis are intra-adrenal inflammatory lesions with or without necrosis, thrombosis, and/or fibrosis, as well as metastases of Kaposi sarcoma. Cytomegalovirus adrenalitis is the most common cause of the adrenal insufficiency seen in AIDS patients (51,52), while cryptococcus, mycobacteria, histoplasma, Toxoplasma gondii, and Pneumocystis carinii also affect the adrenal glands (50,53,54). Pathologic findings vary from mild focal inflammation to extensive hemorrhagic necrosis. Although several cases with extensive adrenal necrosis and profound adrenal dysfunction have been reported (55-57), infectious adrenalitis does not usually cause clinical adrenal insufficiency in most of the AIDS patients (2). Indeed, 17% of 74 hospitalized AIDS patients demonstrated abnormal response of serum cortisol against ACTH injection in one early study, whereas only 4% of these patients developed adrenal insufficiency (58). However, a report on 60 advanced AIDS patients with less than 50 cells/ml of peripheral CD4+ lymphocyte counts demonstrated that over 25% of these patients had abnormally low and high levels of respectively serum cortisol and plasma ACTH, reduced excretion of urinary free cortisol and/or blunted response of serum cortisol to exogenous ACTH (59). Thirty-eight (63.3%) patients had cytomegalovirus antigenemia. Furthermore, 16 out of the 36 patients followed up for at least one year developed overt adrenal insufficiency and half of them were treated with corticosteroid replacement. In conclusion, pathologic findings of the adrenal glands are frequently encountered at autopsy, yet these are mild and are not associated with overt primary adrenal insufficiency in the majority of cases. Presence of adrenal insufficiency, and hence, glucocorticoid replacement therapy should be considered in some end-stage AIDS patients with special caution. Indeed, one fatal case with severe adrenal insufficiency due to cytomegalovirus infection even under the treatment with pharmacologic doses of glucocorticoids was reported (60).

Change of the HPA Axis/Pituitary Gland in AIDS Patients

           
Because the adrenal glands are frequently affected in AIDS patients and common manifestations of these patients, such as weakness, fatigue and body weight loss, mimic those of adrenal insufficiency, many studies have examined basal and/or reserve activity of the HPA axis (2,61-63). A majority of publications indicates that basal levels of serum cortisol and plasma ACTH are normal or slightly elevated and their circadian rhythm is preserved in AIDS patients (54,64-68). Elevations of serum cortisol have been reported both in the early stages of AIDS and in severely affected, terminal patients (63,69,70). Twenty four-hour urinary free cortisol excretion was increased depending on severity of the AIDS-associated manifestations (71). The adrenocortical reserve capacity evaluated with a standard ACTH stimulation test is preserved in the majority of patients, while it is reduced in advanced cases (59). In a large study of 350 patients with HIV infection, 30.9% of participants displayed serum cortisol levels below 100 µg/L with a median value of 55.48 µg/L (11.36-99.96 µg/L); however, only 16.3% of participants had stimulated serum cortisol levels below 180 µg/L with median of 118 µg/L (19.43-179.62) (60). Importantly, the authors found a high prevalence of hypocortisolism among HIV patients, especially in those who had been on ART for a longer time (72). Secretion of ACTH in response to CRH is blunted, especially in terminal-stage AIDS patients (62,63,73,74). Altered profiles of circulating cytokines are suggested as a cause of low responsiveness of the pituitary gland to CRH (62). Significant blunting of the ACTH response in AIDS patients was also reported in the cold immersion stress test (66).

Focal to widespread necrosis and/or fibrosis of the anterior pituitary gland was observed at autopsy in 10 out of the 88 AIDS patients; 5 showed apparent signs of cytomegalovirus infection in the absence of apparent inflammatory reaction, and one demonstrated severe cryptococcus infection (75). Based on the above evidence, it appears that the function of the pituitary gland (corticotrophs) for secretion of ACTH is generally preserved in AIDS patients. Hyponatremia and hypovolemia observed in AIDS patients at the end-stage of their disease is likely to be a result of the adrenal insufficiency due to dysfunction of the adrenal gland caused by specific adrenal lesions, such as infectious adrenalitis or neoplastic infiltration (51).

GLUCOCORTICOIDS IN THE TREATMENT OF AIDS PATIENTS

Protease Inhibitor-Mediated Inhibition of Glucocorticoid Metabolism and Development of Iatrogenic Cushing Syndrome

PIs, which inhibit activity of the viral-encoded protease and are widely used as part of HAART, act as inhibitors of one of the cytochrome P450 (CYP) enzymes, CYP3A4, which is necessary for metabolizing glucocorticoids into inactive forms in the liver (11). Ritonavir is the strongest suppressor of CYP3A4-mediated 6b-hydroxylation of steroids, while indinavir and nelfinavir are moderate suppressors and saquinavir is the weakest (11). All these PIs cause full-blown Cushing syndrome in AIDS patients treated even with inhaled or intranasal synthetic glucocorticoids (e.g., fluticasone, budesonide, mometasone and belclomethasone) by extremely reducing their metabolic clearance (12,76-82). Duration of the glucocorticoid-PI co-administration prior to the development of iatrogenic Cushing syndrome is highly variable, from 10 days to 5 years (mean: 7.1 years), while mean doses of administered glucocorticoids (e.g., fluticasone) are around 200-800 mg/day (mean: 400mg/day) in adults (12). Thus, glucocorticoids, even applied topically, should be used with caution in the patients treated with PIs. Changing ritonavir to other PIs or use of different classes of anti-viral drugs may help reducing this characteristic side effect.

Other Therapeutic Compounds That Potentially Affect Glucocorticoid Metabolism in AIDS Patients

Some other medications used for the treatment of AIDS patients are known to affect glucocorticoid metabolism and contribute to the development of adrenal insufficiency or Cushing syndrome. Ketoconazole, an anti-fungal compound frequently used for fungal skin infections especially in immunocompromised patients, such as those with HIV infection and those on chemotherapy, can suppress steroidogenesis by inhibiting the steroidogenic enzymes P450 side-chain cleavage enzyme and 17b-hydroxylase, and cause cortisol deficiency (83,84). This effect of ketoconazole is not observed with other similar compounds, such as fluconazole and itraconazole, and imidazole derivatives. Phenytoin and rifampicin, which are respectively an anticonvulsant and an antibiotic used for the treatment of tuberculosis, can accelerate cortisol metabolism, and thus, potentially cause adrenal insufficiency particularly in AIDS patients with reduced adrenal reserve (53). Megestrol acetate, a progesterone derivative also known as 17α-acetoxy-6-dehydro-6-methylprogesterone, is often used at relatively high doses to boost appetite and to induce weight gain in AIDS patients with cachexia (85). This compound has some glucocorticoid actions, therefore, causes glucocorticoid excess and subsequent adrenal insufficiency upon its withdrawal or under stress (86).

Potential Use of Glucocorticoids for Slowing AIDS Progression and Treatment of AIDS Complications

Current therapeutic regimens, including HAART, have enabled us to control viremia and viral replication in HIV-infected patients, and thus, have expanded their life expectancy significantly (6,8). However, these therapeutic regimens are expensive and their adherence rates are sometimes low (87-89). In addition, compounds used for the treatment of AIDS often have chronic toxic side effects, such as the characteristic AIDS-related insulin resistance and lipodystrophy syndrome (ARIRLS), which will be discussed in a later section, as well as mitochondrial toxicity, lactic acidosis, hepatotoxicity, and cardiomyopathy (90). Thus, other antiretroviral agents have been developed, including inhibitors of viral integrase, host CXCR4 and CCR5, and fusion of HIV to CD4+ lymphocytes (91). In addition to these compounds that directly interfere with viral activities, immunosuppressive agents, such as glucocorticoids and cyclosporine A, have been tested in HIV-infected patients, as these agents may suppress HIV-mediated immune activation, which is one of the major factors for AIDS progression and reduction of peripheral CD4+ lymphocytes (5,92-95); The synthetic glucocorticoid prednisone at 0.3-0.5 mg/kg/day successfully increases peripheral CD4+ lymphocyte counts and prevents their reduction for up to 10 years (5,96). It also suppresses circulating levels of TNFa and IL-6, known indicators of HIV-mediated host immune activation and possible causative agents for AIDS-associated wasting syndrome (92,97,98). These cytokines may also participate in HIV replication by potentiating Tat-mediated activation of the HIV long terminal repeat (LTR) promoter via stimulation of the nuclear factor-kB (NF-kB) (99). This beneficial effect of glucocorticoids is more obvious in patients whose immune system is less damaged (5,95). Glucocorticoids do not alter peripheral viral load in the patients who have already been treated with antiretroviral drugs, and thus, have low viral load before initiation of therapy (5,94,95). However, one case report indicated that high doses of prednisone (100 mg for 9 consecutive days) demonstrated extremely strong suppression on the circulating virus titer of the patient infected with multi-drug-resistant HIV (100). The synthetic glucocorticoid dexamethasone inhibits elimination of CD4+ lymphocytes by macrophages isolated from HIV-infected patients in vitro (101). Glucocorticoids reduce circulating mature monocytes in monkeys (sooty magabey) infected with the simian immunodeficiency virus, a model virus of HIV used in animal studies (102). These monocytes act as the HIV reservoirs due to their ability to transfer the virus to CD4+ lymphocytes and their relatively long life (103). Furthermore, reduced diurnal amplitude of circulating cortisol in HIV-infected patients is correlated with their greater T cell immune activation, which is a known risk factor for immunologic and clinical progression of AIDS (104). This evidence suggests that healthy diurnal cortisol production is beneficial for slowing down the AIDS progression. Thus, at treatment-naïve or equivalent states, glucocorticoids appear to inhibit viral replication by suppressing HIV-mediated inflammation, subsequent production of inflammatory cytokines and viral transmission from monocytes to CD4+ lymphocytes. However, glucocorticoids are also risk factors for AIDS-associated complications, including sarcopenia, osteoporosis and/or osteonecrosis of the hip, and are reported to accelerate development of human herpes virus-8 (HHV8)-associated Kaposi sarcoma in the patients with pleural tuberculosis, interstitial pneumonia and glomerulonephritis (105-113). Indeed, HHV8 encodes the latency-associated nuclear antigen (LANA), which functions as a coactivator of GR through direct physical interaction (114). Glucocorticoids are also risk factors for elective hip surgery (total hip arthroplasty and resurfacing), and may be a potential factor for the development of CD8 encephalitis in HIV-infected patients (111,115).

Thus, the therapeutic use of glucocorticoids in AIDS patients appears to be quite limited by several factors, particularly in the era of improved HAART, which can control viral replication with less side effects. Selective glucocorticoids or other non-steroidal compounds, with immunosuppressive actions but not metabolic side effects, might be beneficial in the treatment of AIDS patients. Indeed, some of such compounds (e.g., Compound Abbott-Ligand (AL)-438, ZK216348 and the hydroxyl phenyl aziridine precursor analogue Compound A) are under investigation for their selective glucocorticoid effects (116) (please see Endotext chapter in the Adrenal Diseases and Function section entitled “Glucocorticoid Receptor”).

In addition to the effect on circulating CD4+ lymphocyte counts, glucocorticoids act as central components in the treatment regimens for HIV-associated lymphoma (such as Hodgkin and non-Hodgkin lymphoma and latter’s subtypes Burkitt lymphoma and plasmablastic lymphoma), multi-centric, HHV8-associated Castleman’s disease (also known as giant or angiofollicular lymph node hyperplasia, lymphoid hamartoma, angiofollicular lymph node hyperplasia) and HIV-associated nephropathy (13,16,117-120). Glucocorticoids are also used to subside some complications of opportunistic infections, such as those by Pneumocystis carinii and mycobacteria (pleuritis and pericarditis), and those associated with immune reconstitution inflammatory syndrome (IRIS), which sometimes happens in AIDS patients upon recovery of their immune system with antiretroviral treatment (121-124). One clinical study examining the beneficial effects of glucocorticoids for the treatment of AIDS-associated cryptococcal meningitis was performed (18). Moreover, a recent double-blind, placebo-controlled, cross-over study investigated the effects of a single low-dose administration of hydrocortisone (10 mg oral) on cognition in 36 HIV-infected women (125). The authors found that this low dose had beneficial effects in verbal learning and delayed memory, working memory, visuospatial abilities and behavioral inhibition (125). Further larger studies are clearly needed to verify these promising results. Finally, glucocorticoids are prescribed empirically for AIDS patients to treat their fatigue and appetite loss (126-130).

Adverse Effects of the Contraceptive Medroxyprogesterone Acetate for Increasing the Chance of HIV Infection through GR Activation

It is important for the HIV endemic area whether contraceptives increase/reduce the chance of HIV infection, therefore several clinical studies were previously performed to address this possibility (131). These compounds, regularly mixtures of progestins and estrogens, stimulate the progesterone (PR) and estrogen receptor for mimicking the hormonal profiles of pregnancy (132). There are 2 types of contraceptives with regard to their routes of administration; injection and oral intake (131). Recent studies revealed that one of the injectable contraceptives, medroxyprogesterone acetate (MPA), a compound widely used in sub-Saharan Africa, increases a chance of HIV infection particularly in young women with high exposure to this virus (131). Subsequent research revealed that MPA can bind GR in addition to PR with high affinity in contrast to other progestins, such as progesterone and norethisterone acetate, and strongly suppresses inflammatory response in endocervical cells by activating local GR (131,133). Moreover, medroxyprogesterone acetate was found to increase HIV-1 replication in human peripheral blood mononuclear cells through mechanisms involving the glucocorticoid receptor, increased CD4/CD8 ratios and CCR5 levels (134). Further, this compound enhances Vpr-mediated apoptosis of human CD4+ lymphocytes by cooperating with GR, which further affects clinical course of HIV-infected patients (133).

GLUCOCORTICOIDS RESISTANCE/HYPERSENSITIVITY ASSOCIATED WITH AIDS PATIENTS

Glucocorticoid Resistance with Reduced GR Affinity to its Ligands

Norbiato et al. reported a distinct subgroup of AIDS patients who showed apparent adrenal insufficiency with fatigue, weakness, body weight loss, hypotension, and skin and mucosal hyperpigmentation associated with markedly elevated levels of serum cortisol and moderately increased levels of plasma ACTH (135). In these patients, affinity of the GR to its ligand was markedly decreased in peripheral leukocytes with concurrent elevations of receptor numbers, suggesting that the apparent adrenal insufficiency seen in these patients might be caused by decreased sensitivity of peripheral tissues to glucocorticoids. This research group estimated that up to 17 % of AIDS patients are likely to have altered GR actions (136).

Pathologic mechanism(s) underlying this characteristic condition with markedly reduced receptor affinity has(have) not been elucidated as yet. A similar glucocorticoid resistance state associated with reduced receptor affinity was previously reported in glucocorticoid resistant asthma patients. In the latter patients, the affinity change is limited to immune tissues, such as peripheral leukocytes, and is progressively reverted to normal when cells are incubated ex vivo (137). Since incubation of patients’ peripheral lymphocytes with IL-2 and IL-4 preserves the decrease in receptor affinity (137,138), and since elevation of these cytokine levels is generally observed in asthma patients (139), it is likely that cytokine-related mechanisms are involved in the development/maintenance of the receptor affinity change observed in AIDS patients. It was subsequently reported that glucocorticoid resistant asthma was also associated with increased expression of the GRb isoform, suggesting that this splicing variant receptor might participate in the pathogenesis of the glucocorticoid resistance of AIDS patients as well (140). Because many kinases and other molecules important for the cytokine and growth factor signaling potentially modulate GR activity (28,30), and cytomegalovirus alters GR transcriptional activity by phosphorylating this receptor through activation of the extracellular signal-regulated kinases (141), it is possible that some of such molecules might also contribute to the alteration of the receptor affinity in AIDS patients.

The exact prevalence of this glucocorticoid resistance associated with reduced receptor affinity observed in AIDS patients is not known. Although similar patients were reported by another group just after appearance of the initial cases (142), very few reports followed subsequently, suggesting that this characteristic AIDS-related pathologic condition may be rare and/or associated with some special condition of AIDS patients, which may be disappeared after introduction of HAART. In this instance, severe uncontrollable immune dysregulation and/or inflammation by HIV observed at an early and/or specific period may be required for developing this characteristic phenotype. 

AIDS-Related Insulin Resistance and Lipodystrophy Syndrome (ARIRLS): A Complex Pathologic Condition to Which Dysregulation of the Glucocorticoid/GR Signaling System Contributes

In late ’90s, an acquired form of lipodystrophy, which partially mimics the clinical presentation of Cushing syndrome, was reported in AIDS patients (10,143-146). The patients had a characteristic redistribution of their adipose tissue, with an enlargement of their dorsocervical fat pad (“buffalo hump”), axial fat pads (bilateral symmetric lipomatosis), lipomastia, and expansion in their abdominal girth ("Crix-belly" or "protease paunch") [lipohypertrophy in trunk and abdomen]. Since these manifestations are reminiscent of the typical phenotype of chronic glucocorticoid excess or Cushing syndrome, this condition was initially referred as a pseudo-Cushing state, a term reserved for obese, depressive or alcoholic patients with biochemical hypercortisolism who are frequently hard to differentiate from true Cushing syndrome (31). In addition to these initial characteristic manifestations, some patients develop lipoatrophy in face, buttocks and limbs (147). Furthermore, they frequently demonstrate metabolic complications, such as severe insulin resistance, hyperlipidemia and hepatic steatosis, similar to some of the congenital lipodystrophy syndromes (29,46,147). Taken together, this AIDS-related characteristic syndrome has 3 major components in its manifestations, lipohypertrophy, lipoatrophy and metabolic complication, such as insulin resistance and dyslipidemia.

Pathologic causes of ARIRLS are not known, but appear to be multifactorial. ARIRLS patients demonstrate manifestations shared with or district from those of other lipodystrophies unrelated to HIV infection, suggesting that it is caused by the pathologic mechanisms somewhat different from the latter conditions (148). Alteration of the HPA axis and/or the glucocorticoid/GR signaling system appear(s) to be involved in the development of certain part of this syndrome, as we will discuss below. 

Factors Contributing to the Development of ARIRLS

ANTIRETROVIRAL DRUGS

Protease Inhibitors (PIs)

Possible mechanisms contributing to this characteristic syndrome are listed in Table 3 and summarized in Figure 2. As several previous reports indicated, one of the earlier suggestions was that the syndrome was outcome of adverse effects of antiretroviral drugs including PIs, nucleoside reverse transcriptase inhibitors (NRTIs) and/or non-nucleoside reverse transcriptase inhibitors (NNRTIs) (147,149). PIs interfere with viral replication by efficiently inhibiting the activity of the viral-encoded protease, which normally digests the Gag-Pol p160 kDa precursor protein, producing several polypeptide fragments with distinct functions (149,150). NRTIs and NNRTIs, on the other hand, inhibit viral replication by suppressing the activity of the reverse transcriptase also encoded by HIV (149). The effects of various antiretroviral drugs on the development of lipodystrophy and metabolic complications are listed in Table 4. Since prototype drugs were significantly associated with the development of ARIRLS, new compounds with less association were subsequently developed.

Figure 2. Major proposed mechanisms in the genesis of ARIRLS. Three major components, antiretroviral drugs, viral factors and host factors differentially contribute to the development of ARIRLS by respectively modulating adipogenesis, lipogenesis, and tissue insulin action through induction of/responsiveness to inflammatory cytokines, damage to adipocytes (e.g. by mitochondrial toxicity and reactive oxygen species) and/or through modulation of host cellular mechanisms, such as NR (GR, PPAR, PXR and LXR) signaling systems and inhibition/modulation of p450 enzyme activity (such as CYP3A and steroidogenic enzymes). Some changes can also alter tissue glucocorticoid action (glucocorticoid sensitivity) through expression of the GR and/or 11bHSD1 that converts inactive cortisone to active cortisol. As sum of these changes, major manifestations, lipohypertrophy, lipoatrophy and insulin resistance/dyslipidemia are finally developed in which modulation of the glucocorticoid metabolism/signaling system play a significant part. Their specific actions on visceral and subcutaneous fat may contribute to the development of lipohypertrophy and lipoatrophy in different body areas. [from (29,46,147,151)]

+: presence, -: absence, ?: unknown, * During stress and starvation, both fat and lean body mass are lost. Post stress and starvation body weight gain is primarily due to fat accumulation. 

Modified from (147) (Permission for re-use was obtained from Elsevier with the license number: 3012541054207)

* These data should be considered with caution because discrepancies exist among studies that cannot be presented in one table. 

Mechanistically, PIs act as inhibitors of the CYP3A4 enzyme, which metabolizes and inactivates glucocorticoids as we discussed above (11). Thus, these compounds may slightly increase circulating levels of endogenously produced cortisol by reducing its clearance in the liver, and participate in the development of ARIRLS. PIs also decrease hepatic lipase activity and modulate differentiation of pre-adipocytes (152-154). A possible underlying mechanism for this PI-mediated modulation of adipocyte activity is that these compounds change the expression levels of the peroxisome proliferation receptor (PPAR) g and the CAAT/enhancer-binding protein (C/EBP) a (148). PPARg is a NR family protein and acts as a pivotal regulator of glucose and lipid metabolism and development/differentiation of adipocytes (155). C/EBPa is a bZip family transcription factor, and plays also a key role in adipogenesis and adipocyte differentiation (156). In addition, PIs increase IL-6 and TNFa production by activating the NF-kB pathway in subcutaneous fat (157). These cytokines are known to play important roles in local inflammation and lipid accumulation in adipose tissue (158). The adverse effect of PIs may also result from induction of the endoplasmic reticulum stress or inhibition of the proteosomes (159,160).

NRTIs and NNRTIs

In addition to PIs, these classes of antiretroviral drugs are also associated strongly with development of ARIRLS. Among them, thymidine NRTI (tNRTI) stavudine and zidovudine cause severe lipoatrophy in AIDS patients, thus they were removed from the list of the first-line antiretroviral compounds in Western countries (161). These compounds demonstrate mitochondrial toxicity by inhibiting the mitochondrial DNA polymerase g, facilitating generation of the reactive oxygen species in adipose tissues and possibly causing lipoatrophy in AIDS patients (147). Although weak, NNRTIs, such as efavirenz and nevirapine, also have an activity to develop lipodystrophy and dyslipidemia (147).

Modulation of NR Activity by Antiretroviral Drugs

In addition to above-indicated potential actions of antiretroviral drugs on the development of ARIRLS, some of these compounds can modulate the transcriptional activity of several NRs, such as the pregnane X receptor (PXR), constitutive androstane receptor (CAR), liver X receptors (LXRs) and the estrogen receptor a (ERa), and directly stimulate their transcriptional activity. Interestingly, these antiretroviral drugs were demonstrated to act potentially as ligands for the receptors in in silico structural analysis on the ligand-binding pocket of these receptors (154). PXR and CAR act as xenobiotic sensing receptors and induce drug metabolizing enzymes with broad ligand specificity for many chemical compounds, and several PIs can stimulate CYP3A4 and CYP2B6 promoter activity through activation of these receptors (154). Activation of PXR, either by its known ligands or transgenic expression of PXR, increases production of glucocorticoids in the adrenal glands by stimulating expression of the steroidogenic enzymes, such as CYP11A, CYP11B1, CYP11B2 and 3b-hydroxysteroid dehydrogenase, and develops Cushingoid manifestations in rodents (162), suggesting that PIs may increase cortisol production and participate in the development of ARIRLS indirectly through activation of PXR. Furthermore, PIs (ritonavir, atazanavir and darunavir) and maraviroc (CCR5 antagonist) activate the transcriptional activity of LXRa and/or LXRb, while NNRTIs (tenofovir and efavirenz) stimulate ERa (but not ERb) (154). Since LXRs are the receptors for regulating cholesterol/fatty acid metabolism and insulin actions, activation of these receptors by antiretroviral drugs may underlie pathophysiology of ARIRLS (163). In addition, LXRs and ERa cooperate with GR for expression of glucocorticoid-responsive genes, thus it is likely that these antiretroviral drugs enhance glucocorticoid actions indirectly through stimulating these NRs (164,165).

VIRAL FACTORS

Although antiretroviral drugs are generally accepted for causing ARIRLS, a small percentage of HIV-infected patients develop characteristic features of this syndrome prior to their introduction; HIV-infected patients who are not receiving antiretroviral therapy often have lipid abnormality, including elevated triglyceride levels, a high proportion of small and dense LDL particles, and low HDL cholesterol levels, similar to ARIRLS patients (166). Furthermore, different classes of chemical compounds that target different components of HIV/adipocyte biological pathways can develop similar ARIRLS manifestations in AIDS patients (147). These pieces of evidence thus suggest that the HIV infection itself could nonspecifically, -in part via inflammatory cytokine elevations and stress induced cortisol hypersecretion-, induce an insulin resistant phenotype (31). Pro-inflammatory cytokines, such as TNFa, IL-1 and IL-6, which are released from the HIV-infected macrophages localized in adipose tissues, do cause resistance to insulin and fat accumulation in neighboring adipocytes (158). In addition, these cytokines indirectly activate GR in adipose tissues by stimulating expression of the 11b-hydroxysteroid dehydrogenase-1 (11bHSD1), which converts inactive cortisone into active cortisol (167). Moreover, increased expression of GR is also reported in subcutaneous fat of zidovudine-treated AIDS patients (168). In this context, antiretroviral drugs might just exacerbate already present, smoldering insulin resistance and lipodystrophy, not expressed because of the known malnutrition of sick AIDS patients and the absence of sufficient calories to build visceral and other fat deposits (10,30,169). As manifestations of the sickness syndrome subside with treatment, the emaciated patient goes through refeeding with body weight gain of mostly fat, tilting the ratio of fat to lean body mass upward, further worsening insulin resistance.

HIV, in its 9.8 kb genomic information, encodes and produces 3 precursor proteins, the Gag, RNA polymerase and envelope polypeptides, whose processed products are the reverse transcriptase, protease, integrase, matrix, and capsid, as well as 6 accessory proteins, Tat, Rev, Nef, Vif, Vpr and Vpu (170) (Figure 3). Some of these polypeptides are virion-associated proteins incorporated in the viral particle and others are expressed in host cells where they direct viral replication and gene expression and several host cell functions. Since infection with HIV has a dramatic impact on host target cells, it is quite possible that some of these viral proteins modulate host cell glucose and lipid metabolism by changing the activity of GR in local tissues, such as in adipose tissue, skeletal muscles and liver, and participate in the development of ARIRLS. Indeed, there are several pieces of evidence indicating that AIDS patients have altered tissue sensitivity to glucocorticoids. First of all, they all develop reduction of innate and Th1-directed cellular immunity. Levels of plasma IL-2, IL-12 and IFN-g, which direct cellular immunity, are suppressed in AIDS patients, while levels of IL-4 are increased (171,172). All changes can be induced by exogenously introduced glucocorticoids and are seen in hypercortisolemic patients with classic Cushing syndrome (173). AIDS patients also frequently present with muscle wasting and myopathy, as well as dyslipidemia and visceral obesity-related insulin resistance (174-176). Therefore, some unknown viral factor(s) might modulate tissue sensitivity to glucocorticoids in AIDS patients in a tissue-specific fashion, sparing their HPA axis preserving normal negative feedback sensitivity to glucocorticoids.

Figure 3. Lineralized structure of the HIV genome and localization of vpr and tat coding region (shown in black boxes). HIV, in its 9.8 kb genomic information, encodes and produces 3 precursor proteins, the Gag (gag), RNA polymerase (pol) and envelope polypeptides (env), whose processed products are the reverse transcriptase, protease, integrase, matrix, and capsid, as well as 6 accessory proteins, Tat, Rev, Nef, Vif, Vpr and Vpu. LTR: long terminal repeat [modified from (170,177)]

In agreement with these reported findings, one of the HIV proteins, Vpr, which is a 96-amino acid virion-associated accessory protein with multiple functions, including influencing transcriptional activity and having a cell cycle-arresting effect, increases the action of GR by several fold, functioning as a potent GR coactivator (178). The GR coactivator activity of Vpr is biologically evident in the suppression of IL-12 production from monocytes and the expression of activated NF-kB ligand (RANKL) in lymphocytes (179,180). Similar to host p160 type coactivators, Vpr contains one LxxLL coactivator motif through which it binds to the ligand-activated and promoter-bound GR (178). GR-bound Vpr then attracts p300/CBP, and ultimately potentiates the transcriptional activity of GR by acting as a molecular adaptor between GR and p300/CBP (177,181) (Figure 4). p300/CBP are HAT coactivators also known as integrators or regulatory “platforms” for many signal transduction cascades by providing docking sites for many transcription factors, including NRs, CRE-binding protein (CREB), activator protein-1 (AP-1), NF-kB and the signal transducers and activators of transcription (STATs) (182) (Figure 4). Vpr easily penetrates the cell membrane to exert its biologic effects (183,184), thus its effects may be extended to tissues not infected with HIV.

Figure 4. Linearized Vpr, Tat and p300 molecules and their mutual interaction domains. Vpr interacts with cellular molecules, such as NR, p300/CBP coactivators and 14-3-3, while Tat is physically associated with pTEFb elongation factor through its component Cyclin T1. Tat also binds p300/CBP and p160 type coactivators. Numerous transcription factors, transcriptional regulators and viral molecules bind the transcriptional coactivator p300. Binding sites of p160 NR coactivators and Vpr overlap with each other and they both bind NRs and p300/CBP. Thus, Vpr mimics the host p160 NR coactivators and enhances NR transcriptional activity. p300 facilitates attraction of transcription factors, cofactors and general transcription complexes by loosening the histone/DNA interaction through acetylation of histone tails by its histone acetyltransferase (HAT) domain. [modified from (29,30)]. CREB: CRE-binding protein, HAT: histone acetyltransferase, NF-kB: nuclear factor-kB, NR: nuclear hormone receptor, p/CAF: p300/CBP-associating factor, pTEFb: positive-acting transcription elongation factor b, Rb: retinoblastoma protein, SF-1: steroidogenic factor-1, STAT2: signal transducer and activator of transcription 2, TFIIB: transcription factor IIB.

Another HIV accessory protein, Tat, the most potent transactivator of the HIV long terminal repeat promoter, also moderately potentiates GR-induced transcriptional activity, possibly through accumulation of the positive-acting transcription elongation factor b (pTEFb) complex, that is comprised by the cyclin-dependent kinase 9 and its partner molecule cyclin T, on glucocorticoid responsive promoters (185) (Figure 4). Because Tat, like Vpr, also circulates in blood and exerts its actions as an auto/paracrine or endocrine factor by penetrating the cell membrane (186), it is possible that Tat modulates tissue sensitivity to glucocorticoids irrespectively of a cell’s infection by HIV. Concomitantly with Vpr, Tat may induce tissue hypersensitivity to glucocorticoids that might contribute to viral proliferation indirectly, by suppressing local immune system activity and by altering the host’s metabolic balance, with both functions being governed by glucocorticoids (30,46).

Vpr reduces tissue sensitivity to insulin not only through potentiating the actions of glucocorticoids, but also by modulating insulin’s transcriptional activity via interaction with the protein of the 14-3-3 family, which participates in the cell cycle arrest activity of Vpr (29,187). Insulin uses the forkhead transcription factors (FoxOs) to control gene induction; baseline unphosphorylated FoxOs are active, reside in the nucleus, and bind to their responsive sequences in the promoter region of insulin-responsive genes; in contrast, insulin activates Akt kinase, which phosphorylates specific serine and threonine residues of FoxOs rendering it inactive (188). Indeed, once FoxOs are phosphorylated at specific residues, they lose their transcriptional activity, by binding with 14-3-3 through phosphorylated residues and subsequently segregated into the cytoplasm (188). We found that Vpr moderately inhibited insulin-induced translocation of FoxO3a into the cytoplasm through inhibiting its association with 14-3-3 (187). Thus, Vpr may participate in the induction of insulin resistance by interfering with the insulin signaling through FoxOs/14-3-3 (29,151,177). 

We further found that Vpr-mediated insulin resistance might be compounded by the ability of the viral protein to interfere with the signal transduction of PPARg (183). Indeed, Vpr suppresses the c-Cbl associating protein (CAP) mRNA expression in pre-adipocyte cells and associated with the PPAR-binding site located in the promoter region of this gene. CAP is predominantly expressed in insulin-sensitive tissues and positively regulates insulin action, directly associating with both the insulin receptor and the c-Cbl proto-oncogene product (189). Vpr delivered either by exogenous expression or as a peptide added to media suppresses PPARg agonist-induced adipocyte differentiation (183). Thus, circulating Vpr, or alternatively Vpr produced as a consequence of direct infection of adipocytes, may suppress differentiation of preadipocytes by acting as a corepressor of PPARg-mediated gene transcription (29,183,190). We further found that Vpr regulates the transcriptional activity of PPARb/d as well, and alters cellular energy metabolism organized by mitochondria (191). Vpr disturbs the insulin signaling and induces hepatic steatosis by disrupting the transcriptional program of PPARs in the liver and adipose tissue in the animal models, such as the transgenic mice expressing Vpr specifically in these organ and tissue and the mice inoculated with the pump that continuously releases the synthetic Vpr peptide into circulation (192). Moreover, Vpr was demonstrated to induce fatty liver in mice via LXRα and PPARα dysregulation (193). Taken together, based on these pieces of evidence, Vpr may be a key factor for the development of lipodystrophy, insulin resistance and hyperlipidemia observed in HIV-infected patients through modulation of the GR/PPARs/LXR and FoxOs/14-3-3 activities.

HOST FACTORS

Several host factors may influence susceptibility and manifestation of ARIRLS. Variant alleles of APOC3, APOE contribute to an unfavorable lipid profile in patients with HIV infection, while application of antiretroviral therapy further worsens it (194). Another study identified that APOE polymorphism is also associated with the dyslipidemia seen in AIDS patients treated with PIs (195). One recent study demonstrated that polymorphisms of the genes involved in apoptosis and adipocyte metabolism are significantly related to the development of ARIRLS (196). Among the polymorphisms examined, ApoC3-455 variant is associated with lipoatrophy, while two variants of the adrenergic receptor b2 influence fat accumulation in ARIRLS patients (196). A polymorphism in the TNFa gene promoter is associated with development of lipodystrophy in one study, while this association was not confirmed in larger studies (194). Stavudine-induced lipoatrophy is associated with the HLA-B100*4001 allele among the genetic variants of HLA-A, HLA-B HLA-C, HLA-DRB1, HLA-DQB1 and HLA-DPB1 (190). A newly identified polymorphism (Tth111I) in the GR gene is negatively associated with the development of some manifestations of ARIRLS in the African-American population (197). Finally, toxicity of antiretroviral drugs depends on their metabolism in each patient, which is partly determined genetically (196).

Summary for ARIRLS

Above pieces of evidence indicate that ARIRLS is most likely caused by multiple factors, including the infection itself, - via nonspecific inflammatory cytokine - and stress-induced hypercortisolism causing insulin resistance-, several HIV products disturbing the cellular functions of the host, and antiretroviral drugs, all acting on a genetic and constitutional background of variable predisposition to the syndrome. It is highly possible that alteration of glucocorticoid/GR signaling system by any of the above indicated factors contributes to the development of ARIRLS. Further studies are necessary to characterize this syndrome further, to better define the mechanisms involved in its development, and devise ways to prevent it from occurring or for reversing it.

ACKNOWLEDGEMENTS

This literary work was supported by the intramural fund of the Sidra Medical and Research Center to T. Kino.

REFERENCES

1. Graziosi C, Soudeyns H, Rizzardi GP, Bart PA, Chapuis A, Pantaleo G. Immunopathogenesis of HIV infection. AIDS Res Hum Retroviruses 1998; 14 Suppl 2:S135-142
2. Sellmeyer DE, Grunfeld C. Endocrine and metabolic disturbances in human immunodeficiency virus infection and the acquired immune deficiency syndrome. Endocr Rev 1996; 17:518-532
3. Chrousos GP. The hypothalamic-pituitary-adrenal axis and immune-mediated inflammation. N Engl J Med 1995; 332:1351-1362
4. Glucocorticoids, Overview. Nicolaides NC, Charmandari E, Chrousos GP. In Encyclopedia of Endocrine Diseases (2nd Edition), edited by Ilpo Huhtaniemi and Luciano Martini, New York 2018, pp. 64-71.
5. Andrieu JM, Lu W. Long-term clinical, immunologic and virologic impact of glucocorticoids on the chronic phase of HIV infection. BMC Med 2004; 2:17
6. Morris AB, Cu-Uvin S, Harwell JI, Garb J, Zorrilla C, Vajaranant M, Dobles AR, Jones TB, Carlan S, Allen DY. Multicenter review of protease inhibitors in 89 pregnancies. J Acquir Immune Defic Syndr 2000; 25:306-311
7. Nannini EC, Okhuysen PC. HIV1 and the gut in the era of highly active antiretroviral therapy. Curr Gastroenterol Rep 2002; 4:392-398
8. Tashima KT, Flanigan TP. Antiretroviral therapy in the year 2000. Infect Dis Clin North Am 2000; 14:827-849
9. Collins SE, Grant PM, Shafer RW. Modifying Antiretroviral Therapy in Virologically Suppressed HIV-1-Infected Patients. Drugs 2016; 76:75-98
10. Lo JC, Mulligan K, Tai VW, Algren H, Schambelan M. "Buffalo hump" in men with HIV-1 infection. Lancet 1998; 351:867-870
11. Malaty LI, Kuper JJ. Drug interactions of HIV protease inhibitors. Drug Saf 1999; 20:147-169
12. Saberi P, Phengrasamy T, Nguyen DP. Inhaled corticosteroid use in HIV-positive individuals taking protease inhibitors: a review of pharmacokinetics, case reports and clinical management. HIV Med 2013; 14:519-529
13. Weiss R, Mitrou P, Arasteh K, Schuermann D, Hentrich M, Duehrsen U, Sudeck H, Schmidt-Wolf IG, Anagnostopoulos I, Huhn D. Acquired immunodeficiency syndrome-related lymphoma: simultaneous treatment with combined cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy and highly active antiretroviral therapy is safe and improves survival -results of the German Multicenter Trial. Cancer 2006; 106:1560-1568
14. Carbone A, Cesarman E, Spina M, Gloghini A, Schulz TF. HIV-associated lymphomas and g-herpesviruses. Blood 2009; 113:1213-1224
15. Dezube BJ. Acquired immunodeficiency syndrome-related Kaposi's sarcoma: clinical features, staging, and treatment. Semin Oncol 2000; 27:424-430
16. Pope SD, Johnson MD, May DB. Pharmacotherapy for human immunodeficiency virus-associated nephropathy. Pharmacotherapy 2005; 25:1761-1772
17. Mayanja-Kizza H, Jones-Lopez E, Okwera A, Wallis RS, Ellner JJ, Mugerwa RD, Whalen CC. Immunoadjuvant prednisolone therapy for HIV-associated tuberculosis: a phase 2 clinical trial in Uganda. J Infect Dis 2005; 191:856-865
18. Day J, Imran D, Ganiem AR, Tjahjani N, Wahyuningsih R, Adawiyah R, Dance D, Mayxay M, Newton P, Phetsouvanh R, Rattanavong S, Chan AK, Heyderman R, van Oosterhout JJ, Chierakul W, Day N, Kamali A, Kibengo F, Ruzagira E, Gray A, Lalloo DG, Beardsley J, Binh TQ, Chau TT, Chau NV, Cuc NT, Farrar J, Hien TT, Van Kinh N, Merson L, Phuong L, Tho LT, Thuy PT, Thwaites G, Wertheim H, Wolbers M. CryptoDex: a randomised, double-blind, placebo-controlled phase III trial of adjunctive dexamethasone in HIV-infected adults with cryptococcal meningitis: study protocol for a randomised control trial. Trials 2014; 15:441
19. Chrousos GP. Stress and disorders of the stress system. Nat Rev Endocrinol 2009; 5:374-381
20. Nader N, Chrousos GP, Kino T. Interactions of the circadian CLOCK system and the HPA axis. Trends Endocrinol Metab 2010; 21:277-286
21. Nicolaides NC, Kyratzi E, Lamprokostopoulou A, Chrousos GP, Charmandari E. Stress, the stress system and the role of glucocorticoids. Neuroimmunomodulation. 2015; 22(1-2):6-19
22. Stavrou S, Nicolaides NC, Critselis E, Darviri C, Charmandari E, Chrousos GP. Paediatric stress: from neuroendocrinology to contemporary disorders. Eur J Clin Invest 2017; 47(3):262-269
23. Nicolaides NC, Charmandari E, Kino T, Chrousos GP. Stress-Related and Circadian Secretion and Target Tissue Actions of Glucocorticoids: Impact on Health. Front Endocrinol (Lausanne). 2017; 8:70
24. Agorastos A, Nicolaides NC, Bozikas VP, Chrousos GP, Pervanidou P. Multilevel Interactions of Stress and Circadian System: Implications for Traumatic Stress. Front Psychiatry. 2020; 10:1003
25. Chrousos GP, Kino T. Glucocorticoid action networks and complex psychiatric and/or somatic disorders. Stress 2007; 10:213-219
26. Bao AM, Meynen G, Swaab DF. The stress system in depression and neurodegeneration: focus on the human hypothalamus. Brain Res Rev 2008; 57:531-553
27. Kino T. Stress, glucocorticoid hormones, and hippocampal neural progenitor cells: implications to mood disorders. Front Physiol 2015; 6:230
28. Chrousos GP, Kino T. Intracellular glucocorticoid signaling: a formerly simple system turns stochastic. Sci STKE 2005; 2005:pe48
29. Kino T, Chrousos GP. Virus-mediated modulation of the host endocrine signaling systems: clinical implications. Trends Endocrinol Metab 2007; 18:159-166
30. Kino T. Tissue glucocorticoid sensitivity: beyond stochastic regulation on the diverse actions of glucocorticoids. Horm Metab Res 2007; 39:420-424
31. Chrousos GP. Stress, chronic inflammation, and emotional and physical well-being: Concurrent effects and chronic sequelae. J Allergy Clin Immunol 2000; 106:S275-S291
32. Elenkov IJ. Glucocorticoids and the Th1/Th2 balance. Ann N Y Acad Sci 2004; 1024:138-146
33. Elenkov IJ, Chrousos GP. Stress hormones, proinflammatory and antiinflammatory cytokines, and autoimmunity. Ann N Y Acad Sci 2002; 966:290-303
34. Clark JK, Schrader WT, O'Malley BW. Mechanism of steroid hormones. In: Wilson JD, Foster DW, eds. Williams Textbook of Endocrinology. Philadelphia: WB Sanders Co.; 1992:35-90.
35. Munck A, Guyre PM, Holbrook NJ. Physiological functions of glucocorticoids in stress and their relation to pharmacological actions. Endocr Rev 1984; 5:25-44
36. Boumpas DT, Chrousos GP, Wilder RL, Cupps TR, Balow JE. Glucocorticoid therapy for immune-mediated diseases: basic and clinical correlates. Ann Intern Med 1993; 119:1198-1208
37. Kino T, Su YA, Chrousos GP. Human glucocorticoid receptor isoform b: recent understanding of its potential implications in physiology and pathophysiology. Cell Mol Life Sci 2009; 66:3435-3448
38. Kino T, Manoli I, Kelkar S, Wang Y, Su YA, Chrousos GP. Glucocorticoid receptor (GR) b has intrinsic, GRa-independent transcriptional activity. Biochem Biophys Res Commun 2009; 381:671-675
39. McKenna NJ, Lanz RB, O'Malley BW. Nuclear receptor coregulators: cellular and molecular biology. Endocr Rev 1999; 20:321-344
40. Lanz RB, McKenna NJ, Onate SA, Albrecht U, Wong J, Tsai SY, Tsai MJ, O'Malley BW. A steroid receptor coactivator, SRA, functions as an RNA and is present in an SRC-1 complex. Cell 1999; 97:17-27
41. Kino T, Hurt DE, Ichijo T, Nader N, Chrousos GP. Noncoding RNA gas5 is a growth arrest- and starvation-associated repressor of the glucocorticoid receptor. Sci Signal 2010; 3:ra8
42. Charmandari E, Kino T. Chrousos syndrome: a seminal report, a phylogenetic enigma and the clinical implications of glucocorticoid signalling changes. Eur J Clin Invest 2010; 40:932-942
43. Charmandari E, Kino T, Ichijo T, Chrousos GP. Generalized glucocorticoid resistance: clinical aspects, molecular mechanisms, and implications of a rare genetic disorder. J Clin Endocrinol Metab 2008; 93:1563-1572
44. Nicolaides NC, Charmandari E. Chrousos syndrome: from molecular pathogenesis to therapeutic management. Eur J Clin Invest 2015; 45(5):504-514
45. Nicolaides NC, Charmandari E. Novel insights into the molecular mechanisms underlying generalized glucocorticoid resistance and hypersensitivity syndromes. Hormones (Athens) 2017; 16(2):124-138
46. Kino T, De Martino MU, Charmandari E, Mirani M, Chrousos GP. Tissue glucocorticoid resistance/hypersensitivity syndromes. J Steroid Biochem Mol Biol 2003; 85:457-467
47. Nader N, Ng SS, Lambrou GI, Pervanidou P, Wang Y, Chrousos GP, Kino T. AMPK regulates metabolic actions of glucocorticoids by phosphorylating the glucocorticoid receptor through p38 MAPK. Mol Endocrinol 2010; 24:1748-1764
48. Laue L, Gold PW, Richmond A, Chrousos GP. The hypothalamic-pituitary-adrenal axis in anorexia nervosa and bulimia nervosa: pathophysiologic implications. Adv Pediatr 1991; 38:287-316
49. Hill MJ, Suzuki S, Segars JH, Kino T. CRTC2 Is a coactivator of GR and couples GR and CREB in the regulation of hepatic gluconeogenesis. Mol Endocrinol 2016; 30:104-117
50. Bricaire F, Marche C, Zoubi D, Regnier B, Saimot AG. Adrenocortical lesions and AIDS. Lancet 1988; 1:881
51. Glasgow BJ, Steinsapir KD, Anders K, Layfield LJ. Adrenal pathology in the acquired immune deficiency syndrome. Am J Clin Pathol 1985; 84:594-597
52. Nassoro DD, Mkhoi ML, Sabi I, Meremo AJ, Lawala PS, Mwakyula IH. Adrenal Insufficiency: A Forgotten Diagnosis in HIV/AIDS Patients in Developing Countries. Int J Endocrinol. 2019; 2019:2342857
53. Lo J, Grinspoon SK. Adrenal function in HIV infection. Curr Opin Endocrinol Diabetes Obes 2010; 17:205-209
54. Hawken MP, Ojoo JC, Morris JS, Kariuki EW, Githui WA, Juma ES, Gathua SN, Kimari JN, Thiong'o LN, Raynes JG, Broadbent P, Gilks CF, Otieno LS, McAdam KP. No increased prevalence of adrenocortical insufficiency in human immunodeficiency virus-associated tuberculosis. Tuber Lung Dis 1996; 77:444-448
55. Seel K, Guschmann M, van Landeghem F, Grosch-Worner I. Addison-disease - an unusual clinical manifestation of CMV-end organ disease in pediatric AIDS. Eur J Med Res 2000; 5:247-250
56. Angulo JC, Lopez JI, Flores N. Lethal cytomegalovirus adrenalitis in a case of AIDS. Scand J Urol Nephrol 1994; 28:105-106
57. Greene LW, Cole W, Greene JB, Levy B, Louie E, Raphael B, Waitkevicz J, Blum M. Adrenal insufficiency as a complication of the acquired immunodeficiency syndrome. Ann Intern Med 1984; 101:497-498
58. Membreno L, Irony I, Dere W, Klein R, Biglieri EG, Cobb E. Adrenocortical function in acquired immunodeficiency syndrome. J Clin Endocrinol Metab 1987; 65:482-487
59. Hoshino Y, Yamashita N, Nakamura T, Iwamoto A. Prospective examination of adrenocortical function in advanced AIDS patients. Endocr J 2002; 49:641-647
60. Uno K, Konishi M, Yoshimoto E, Kasahara K, Mori K, Maeda K, Ishida E, Konishi N, Murakawa K, Mikasa K. Fatal cytomegalovirus-associated adrenal insufficiency in an AIDS patient receiving corticosteroid therapy. Intern Med 2007; 46:617-620
61. Verges B, Chavanet P, Desgres J, Vaillant G, Waldner A, Brun JM, Putelat R. Adrenal function in HIV infected patients. Acta Endocrinol (Copenh) 1989; 121:633-637
62. Biglino A, Limone P, Forno B, Pollono A, Cariti G, Molinatti GM, Gioannini P. Altered adrenocorticotropin and cortisol response to corticotropin-releasing hormone in HIV-1 infection. Eur J Endocrinol 1995; 133:173-179
63. Lortholary O, Christeff N, Casassus P, Thobie N, Veyssier P, Trogoff B, Torri O, Brauner M, Nunez EA, Guillevin L. Hypothalamo-pituitary-adrenal function in human immunodeficiency virus-infected men. J Clin Endocrinol Metab 1996; 81:791-796
64. Coodley GO, Loveless MO, Nelson HD, Coodley MK. Endocrine function in the HIV wasting syndrome. J Acquir Immune Defic Syndr 1994; 7:46-51
65. Findling JW, Buggy BP, Gilson IH, Brummitt CF, Bernstein BM, Raff H. Longitudinal evaluation of adrenocortical function in patients infected with the human immunodeficiency virus. J Clin Endocrinol Metab 1994; 79:1091-1096
66. Kumar M, Kumar AM, Morgan R, Szapocznik J, Eisdorfer C. Abnormal pituitary-adrenocortical response in early HIV-1 infection. J Acquir Immune Defic Syndr 1993; 6:61-65
67. Malone JL, Oldfield ECd, Wagner KF, Simms TE, Daly R, O'Brian J, Burke DS. Abnormalities of morning serum cortisol levels and circadian rhythms of CD4+ lymphocyte counts in human immunodeficiency virus type 1-infected adult patients. J Infect Dis 1992; 165:185-186
68. Yanovski JA, Miller KD, Kino T, Friedman TC, Chrousos GP, Tsigos C, Falloon J. Endocrine and metabolic evaluation of human immunodeficiency virus-infected patients with evidence of protease inhibitor-associated lipodystrophy. J Clin Endocrinol Metab 1999; 84:1925-1931
69. Christeff N, Gherbi N, Mammes O, Dalle MT, Gharakhanian S, Lortholary O, Melchior JC, Nunez EA. Serum cortisol and DHEA concentrations during HIV infection. Psychoneuroendocrinology 1997; 22:S11-18
70. de la Torre B, von Krogh G, Svensson M, Holmberg V. Blood cortisol and dehydroepiandrosterone sulphate (DHEAS) levels and CD4 T cell counts in HIV infection. Clin Exp Rheumatol 1997; 15:87-90
71. Stolarczyk R, Rubio SI, Smolyar D, Young IS, Poretsky L. Twenty-four-hour urinary free cortisol in patients with acquired immunodeficiency syndrome. Metabolism 1998; 47:690-694
72. Akase IE, Habib AG, Bakari AG, Muhammad H, Gezawa I, Nashabaru I, Iliyasu G, Mohammed AA. Occurrence of hypocortisolism in HIV patients: Is the picture changing? Ghana Med J. 2018; 52(3):147-152
73. Dobs AS, Dempsey MA, Ladenson PW, Polk BF. Endocrine disorders in men infected with human immunodeficiency virus. Am J Med 1988; 84:611-616
74. Raffi F, Brisseau JM, Planchon B, Remi JP, Barrier JH, Grolleau JY. Endocrine function in 98 HIV-infected patients: a prospective study. AIDS 1991; 5:729-733
75. Ferreiro J, Vinters HV. Pathology of the pituitary gland in patients with the acquired immune deficiency syndrome (AIDS). Pathology 1988; 20:211-215
76. Rouanet I, Peyriere H, Mauboussin JM, Vincent D. Cushing's syndrome in a patient treated by ritonavir/lopinavir and inhaled fluticasone. HIV Med 2003; 4:149-150
77. Chen F, Kearney T, Robinson S, Daley-Yates PT, Waldron S, Churchill DR. Cushing's syndrome and severe adrenal suppression in patients treated with ritonavir and inhaled nasal fluticasone. Sex Transm Infect 1999; 75:274
78. Hillebrand-Haverkort ME, Prummel MF, ten Veen JH. Ritonavir-induced Cushing's syndrome in a patient treated with nasal fluticasone. AIDS 1999; 13:1803
79. Dubrocq G, Estrada A, Kelly S, Rakhmanina N. Acute development of Cushing syndrome in an HIV-infected child on atazanavir/ritonavir based antiretroviral therapy. Endocrinol Diabetes Metab Case Rep. 2017; 2017:17-0076
80. Colpitts L, Murray TB, Tahhan SG, Boggs JP. Iatrogenic Cushing Syndrome in a 47-Year-Old HIV-Positive Woman on Ritonavir and Inhaled Budesonide. J Int Assoc Provid AIDS Care. 2017; 16(6):531-534
81. Alidoost M, Conte GA, Agarwal K, Carson MP, Lann D, Marchesani D. Iatrogenic Cushing's Syndrome Following Intra-Articular Triamcinolone Injection in an HIV-Infected Patient on Cobicistat Presenting as a Pulmonary Embolism: Case Report and Literature Review. Int Med Case Rep J. 2020; 13:229-235
82. Figueiredo J, Serrado M, Khmelinskii N, do Vale S. Iatrogenic Cushing syndrome and multifocal osteonecrosis caused by the interaction between inhaled fluticasone and ritonavir. BMJ Case Rep. 2020; 13(5):e233712
83. Veytsman I, Nieman L, Fojo T. Management of endocrine manifestations and the use of mitotane as a chemotherapeutic agent for adrenocortical carcinoma. J Clin Oncol 2009; 27:4619-4629
84. Fassnacht M, Hahner S, Beuschlein F, Klink A, Reincke M, Allolio B. New mechanisms of adrenostatic compounds in a human adrenocortical cancer cell line. Eur J Clin Invest 2000; 30 Suppl 3:76-82
85. Chidakel AR, Zweig SB, Schlosser JR, Homel P, Schappert JW, Fleckman AM. High prevalence of adrenal suppression during acute illness in hospitalized patients receiving megestrol acetate. J Endocrinol Invest 2006; 29:136-140
86. Gonzalez Villarroel P, Fernandez Perez I, Paramo C, Gentil Gonzalez M, Carnero Lopez B, Vazquez Tunas ML, Carrasco Alvarez JA. Megestrol acetate-induced adrenal insufficiency. Clin Transl Oncol 2008; 10:235-237
87. d'Arminio Monforte A, Lepri AC, Rezza G, Pezzotti P, Antinori A, Phillips AN, Angarano G, Colangeli V, De Luca A, Ippolito G, Caggese L, Soscia F, Filice G, Gritti F, Narciso P, Tirelli U, Moroni M. Insights into the reasons for discontinuation of the first highly active antiretroviral therapy (HAART) regimen in a cohort of antiretroviral naive patients. I.CO.N.A. Study Group. Italian Cohort of Antiretroviral-Naive Patients. AIDS 2000; 14:499-507
88. Deloria-Knoll M, Chmiel JS, Moorman AC, Wood KC, Holmberg SD, Palella FJ. Factors related to and consequences of adherence to antiretroviral therapy in an ambulatory HIV-infected patient cohort. AIDS Patient Care STDS 2004; 18:721-727
89. Brook MG, Dale A, Tomlinson D, Waterworth C, Daniels D, Forster G. Adherence to highly active antiretroviral therapy in the real world: experience of twelve English HIV units. AIDS Patient Care STDS 2001; 15:491-494
90. Hawkins T. Understanding and managing the adverse effects of antiretroviral therapy. Antiviral Res 2010; 85:201-209
91. Tang MW, Shafer RW. HIV-1 antiretroviral resistance: scientific principles and clinical applications. Drugs 2012; 72:e1-25
92. Tavel JA, Sereti I, Walker RE, Hahn B, Kovacs JA, Jagannatha S, Davey RT, Jr., Falloon J, Polis MA, Masur H, Metcalf JA, Stevens R, Rupert A, Baseler M, Lane HC. A randomized, double-blinded, placebo-controlled trial of intermittent administration of interleukin-2 and prednisone in subjects infected with human immunodeficiency virus. J Infect Dis 2003; 188:531-536
93. Rizzardi GP, Harari A, Capiluppi B, Tambussi G, Ellefsen K, Ciuffreda D, Champagne P, Bart PA, Chave JP, Lazzarin A, Pantaleo G. Treatment of primary HIV-1 infection with cyclosporin A coupled with highly active antiretroviral therapy. J Clin Invest 2002; 109:681-688
94. McComsey GA, Whalen CC, Mawhorter SD, Asaad R, Valdez H, Patki AH, Klaumunzner J, Gopalakrishna KV, Calabrese LH, Lederman MM. Placebo-controlled trial of prednisone in advanced HIV-1 infection. AIDS 2001; 15:321-327
95. Wallis RS, Kalayjian R, Jacobson JM, Fox L, Purdue L, Shikuma CM, Arakaki R, Snyder S, Coombs RW, Bosch RJ, Spritzler J, Chernoff M, Aga E, Myers L, Schock B, Lederman MM. A study of the immunology, virology, and safety of prednisone in HIV-1-infected subjects with CD4 cell counts of 200 to 700 mm(-3). J Acquir Immune Defic Syndr 2003; 32:281-286
96. Ulmer A, Muller M, Bertisch-Mollenhoff B, Frietsch B. Low-dose prednisolone has a CD4-stabilizing effect in pre-treated HIV-patients during structured therapy interruptions (STI). Eur J Med Res 2005; 10:227-232
97. Dudgeon WD, Phillips KD, Carson JA, Brewer RB, Durstine JL, Hand GA. Counteracting muscle wasting in HIV-infected individuals. HIV Med 2006; 7:299-310
98. Belec L, Meillet D, Hernvann A, Gresenguet G, Gherardi R. Differential elevation of circulating interleukin-1b, tumor necrosis factor a, and interleukin-6 in AIDS-associated cachectic states. Clin Diagn Lab Immunol 1994; 1:117-120
99. Osborn L, Kunkel S, Nabel GJ. Tumor necrosis factor a and interleukin 1 stimulate the human immunodeficiency virus enhancer by activation of the nuclear factor kB. Proc Natl Acad Sci U S A 1989; 86:2336-2340
100. Ansari AW, Schmidt RE, Heiken H. Prednisolone mediated suppression of HIV-1 viral load strongly correlates with C-C chemokine CCL2: In vivo and in vitro findings. Clin Immunol 2007; 125:1-4
101. Orlikowsky TW, Wang ZQ, Dudhane A, Dannecker GE, Niethammer D, Wormser GP, Hoffmann MK, Horowitz HW. Dexamethasone inhibits CD4 T cell deletion mediated by macrophages from human immunodeficiency virus-infected persons. J Infect Dis 2001; 184:1328-1330
102. Moniuszko M, Liyanage NP, Doster MN, Parks RW, Grubczak K, Lipinska D, McKinnon K, Brown C, Hirsch V, Vaccari M, Gordon S, Pegu P, Fenizia C, Flisiak R, Grzeszczuk A, Dabrowska M, Robert-Guroff M, Silvestri G, Stevenson M, McCune J, Franchini G. Glucocorticoid treatment at moderate doses of SIVmac251-infected rhesus macaques decreases the frequency of circulating CD14+CD16++ monocytes but does not alter the tissue virus reservoir. AIDS Res Hum Retroviruses 2015; 31:115-126
103. Ellery PJ, Tippett E, Chiu YL, Paukovics G, Cameron PU, Solomon A, Lewin SR, Gorry PR, Jaworowski A, Greene WC, Sonza S, Crowe SM. The CD16+ monocyte subset is more permissive to infection and preferentially harbors HIV-1 in vivo. J Immunol 2007; 178:6581-6589
104. Patterson S, Moran P, Epel E, Sinclair E, Kemeny ME, Deeks SG, Bacchetti P, Acree M, Epling L, Kirschbaum C, Hecht FM. Cortisol patterns are associated with T cell activation in HIV. PLoS One 2013; 8:e63429
105. Miller KD, Masur H, Jones EC, Joe GO, Rick ME, Kelly GG, Mican JM, Liu S, Gerber LH, Blackwelder WC, Falloon J, Davey RT, Polis MA, Walker RE, Lane HC, Kovacs JA. High prevalence of osteonecrosis of the femoral head in HIV-infected adults. Ann Intern Med 2002; 137:17-25
106. Scribner AN, Troia-Cancio PV, Cox BA, Marcantonio D, Hamid F, Keiser P, Levi M, Allen B, Murphy K, Jones RE, Skiest DJ. Osteonecrosis in HIV: a case-control study. J Acquir Immune Defic Syndr 2000; 25:19-25
107. Glesby MJ, Hoover DR, Vaamonde CM. Osteonecrosis in patients infected with human immunodeficiency virus: a case-control study. J Infect Dis 2001; 184:519-523
108. Panayotakopoulos GD, Day S, Peters BS, Kulasegaram R. Severe osteoporosis and multiple fractures in an AIDS patient treated with short-term steroids for lymphoma: a need for guidelines. Int J STD AIDS 2006; 17:567-568
109. Elliott AM, Luzze H, Quigley MA, Nakiyingi JS, Kyaligonza S, Namujju PB, Ducar C, Ellner JJ, Whitworth JA, Mugerwa R, Johnson JL, Okwera A. A randomized, double-blind, placebo-controlled trial of the use of prednisolone as an adjunct to treatment in HIV-1-associated pleural tuberculosis. J Infect Dis 2004; 190:869-878
110. Jinno S, Goshima C. Progression of Kaposi sarcoma associated with iatrogenic Cushing syndrome in a person with HIV/AIDS. AIDS Read 2008; 18:100-104
111. Kerr E, Middleton A, Churchill D, Reading I, Walker-Bone K. A case-control study of elective hip surgery among HIV-infected patients: exposure to systemic glucocorticoids significantly increases the risk. HIV Med 2014; 15:182-188
112. Joo M, Soon Lee S, Jin Park H, Shin HS. Iatrogenic Kaposi's sarcoma following steroid therapy for nonspecific interstitial pneumonia with HHV-8 genotyping. Pathol Res Pract 2006; 202:113-117
113. Agbaht K, Pepedil F, Kirkpantur A, Yilmaz R, Arici M, Turgan C. A case of Kaposi's sarcoma following treatment of membranoproliferative glomerulonephritis and a review of the literature. Ren Fail 2007; 29:107-110
114. Togi S, Nakasuji M, Muromoto R, Ikeda O, Okabe K, Kitai Y, Kon S, Oritani K, Matsuda T. Kaposi's sarcoma-associated herpesvirus-encoded LANA associates with glucocorticoid receptor and enhances its transcriptional activities. Biochem Biophys Res Commun 2015; 463:395-400
115. Lescure FX, Moulignier A, Savatovsky J, Amiel C, Carcelain G, Molina JM, Gallien S, Pacanovski J, Pialoux G, Adle-Biassette H, Gray F. CD8 encephalitis in HIV-infected patients receiving cART: a treatable entity. Clin Infect Dis 2013; 57:101-108
116. Rosen J, Miner JN. The search for safer glucocorticoid receptor ligands. Endocr Rev 2005; 26:452-464
117. Mounier N, Spina M, Gabarre J, Raphael M, Rizzardini G, Golfier JB, Vaccher E, Carbone A, Coiffier B, Chichino G, Bosly A, Tirelli U, Gisselbrecht C. AIDS-related non-Hodgkin lymphoma: final analysis of 485 patients treated with risk-adapted intensive chemotherapy. Blood 2006; 107:3832-3840
118. Castillo J, Pantanowitz L, Dezube BJ. HIV-associated plasmablastic lymphoma: lessons learned from 112 published cases. Am J Hematol 2008; 83:804-809
119. Jacomet C, Lesens O, Villemagne B, Darcha C, Tournilhac O, Henquell C, Cormerais L, Gourdon F, Peigue-Lafeuille H, Travade P, Beytout J, Laurichesse H. Non Hodgkin's and Hodgkin's lymphomas and HIV: frequency, outcome and immune response under HAART; Clermont-Ferrand University Hospital, 1991-2003. Med Mal Infect 2006; 36:157-162
120. Soumerai JD, Sohani AR, Abramson JS. Diagnosis and management of Castleman disease. Cancer Control 2014; 21:266-278
121. Martin-Blondel G, Mars LT, Liblau RS. Pathogenesis of the immune reconstitution inflammatory syndrome in HIV-infected patients. Curr Opin Infect Dis 2012; 25:312-320
122. Newsome SD, Nath A. Varicella-zoster virus vasculopathy and central nervous system immune reconstitution inflammatory syndrome with human immunodeficiency virus infection treated with steroids. J Neurovirol 2009; 15:288-291
123. Mayosi BM, Ntsekhe M, Bosch J, Pandie S, Jung H, Gumedze F, Pogue J, Thabane L, Smieja M, Francis V, Joldersma L, Thomas KM, Thomas B, Awotedu AA, Magula NP, Naidoo DP, Damasceno A, Chitsa Banda A, Brown B, Manga P, Kirenga B, Mondo C, Mntla P, Tsitsi JM, Peters F, Essop MR, Russell JB, Hakim J, Matenga J, Barasa AF, Sani MU, Olunuga T, Ogah O, Ansa V, Aje A, Danbauchi S, Ojji D, Yusuf S. Prednisolone and Mycobacterium indicus pranii in tuberculous pericarditis. N Engl J Med 2014; 371:1121-1130
124. Cotton MF, Rabie H, Nemes E, Mujuru H, Bobat R, Njau B, Violari A, Mave V, Mitchell C, Oleske J, Zimmer B, Varghese G, Pahwa S; P1073 team. A prospective study of the immune reconstitution inflammatory syndrome (IRIS) in HIV-infected children from high prevalence countries. PLoS One. 2019; 14(7):e0211155
125. Rubin LH, Phan KL, Keating SM, Maki PM. A single low dose of hydrocortisone enhances cognitive functioning in HIV-infected women. AIDS. 2018; 32(14):1983-1993
126. Dichter JR, Lundgren JD, Nielsen TL, Jensen BN, Schattenkerk J, Benfield TL, Lawrence M, Shelhamer J. Pneumocystis carinii pneumonia in HIV-infected patients: effect of steroid therapy on surfactant level. Respir Med 1999; 93:373-378
127. Thwaites GE, Nguyen DB, Nguyen HD, Hoang TQ, Do TT, Nguyen TC, Nguyen QH, Nguyen TT, Nguyen NH, Nguyen TN, Nguyen NL, Nguyen HD, Vu NT, Cao HH, Tran TH, Pham PM, Nguyen TD, Stepniewska K, White NJ, Tran TH, Farrar JJ. Dexamethasone for the treatment of tuberculous meningitis in adolescents and adults. N Engl J Med 2004; 351:1741-1751
128. Aster RH. Thrombocytopenia in the HIV-infected patient. Hosp Pract (Off Ed) 1994; 29:81-86
129. Koduri PR, Singa P, Nikolinakos P. Autoimmune hemolytic anemia in patients infected with human immunodeficiency virus-1. Am J Hematol 2002; 70:174-176
130. Levy R, Colonna P, Tourani JM, Gastaut JA, Brice P, Raphael M, Taillan B, Andrieu JM. Human immunodeficiency virus associated Hodgkin's disease: report of 45 cases from the French Registry of HIV-Associated Tumors. Leuk Lymphoma 1995; 16:451-456
131. Hapgood JP, Ray RM, Govender Y, Avenant C, Tomasicchio M. Differential glucocorticoid receptor-mediated effects on immunomodulatory gene expression by progestin contraceptives: implications for HIV-1 pathogenesis. Am J Reprod Immunol 2014; 71:505-512
132. Sech LA, Mishell DR, Jr. Oral steroid contraception. Womens Health (Lond Engl) 2015; 11:743-748
133. Govender Y, Avenant C, Verhoog NJ, Ray RM, Grantham NJ, Africander D, Hapgood JP. The injectable-only contraceptive medroxyprogesterone acetate, unlike norethisterone acetate and progesterone, regulates inflammatory genes in endocervical cells via the glucocorticoid receptor. PLoS One 2014; 9:e96497
134. Maritz MF, Ray RM, Bick AJ, Tomasicchio M, Woodland JG, Govender Y, Avenant C, Hapgood JP. Medroxyprogesterone acetate, unlike norethisterone, increases HIV-1 replication in human peripheral blood mononuclear cells and an indicator cell line, via mechanisms involving the glucocorticoid receptor, increased CD4/CD8 ratios and CCR5 levels. PLoS One. 2018 Apr 26;13(4):e0196043
135. Norbiato G, Bevilacqua M, Vago T, Baldi G, Chebat E, Bertora P, Moroni M, Galli M, Oldenburg N. Cortisol resistance in acquired immunodeficiency syndrome. J Clin Endocrinol Metab 1992; 74:608-613
136. Norbiato G, Bevilacqua M, Vago T, Clerici M. Glucocorticoids and Th-1, Th-2 type cytokines in rheumatoid arthritis, osteoarthritis, asthma, atopic dermatitis and AIDS. Clin Exp Rheumatol 1997; 15:315-3123
137. Sher ER, Leung DY, Surs W, Kam JC, Zieg G, Kamada AK, Szefler SJ. Steroid-resistant asthma. Cellular mechanisms contributing to inadequate response to glucocorticoid therapy. J Clin Invest 1994; 93:33-39
138. Kam JC, Szefler SJ, Surs W, Sher ER, Leung DY. Combination IL-2 and IL-4 reduces glucocorticoid receptor-binding affinity and T cell response to glucocorticoids. J Immunol 1993; 151:3460-3466
139. Leung DY, Martin RJ, Szefler SJ, Sher ER, Ying S, Kay AB, Hamid Q. Dysregulation of interleukin 4, interleukin 5, and interferon g gene expression in steroid-resistant asthma. J Exp Med 1995; 181:33-40
140. Leung DYM, Hamid Q, Vottero A, Szefler SJ, Surs W, Minshall E, Chrousos GP, Klemm DJ. Association of glucocorticoid insensitivity with increased expression of glucocorticoid receptor b. J Exp Med 1997; 186:1567-1574
141. Ng SS, Li A, Pavlakis GN, Ozato K, Kino T. Viral infection increases glucocorticoid-induced interleukin-10 production through ERK-mediated phosphorylation of the glucocorticoid receptor in dendritic cells: potential clinical implications. PLoS One 2013; 8:e63587
142. Vagnucci AH, Winkelstein A. Circadian rhythm of lymphocytes and their glucocorticoid receptors in HIV-infected homosexual men. J Acquir Immune Defic Syndr 1993; 6:1238-1247
143. Christeff N, Melchior JC, de Truchis P, Perronne C, Nunez EA, Gougeon ML. Lipodystrophy defined by a clinical score in HIV-infected men on highly active antiretroviral therapy: correlation between dyslipidaemia and steroid hormone alterations. AIDS 1999; 13:2251-2260
144. Saint-Marc T, Touraine JL. "Buffalo hump" in HIV-1 infection. Lancet 1998; 352:319-320
145. De Luca A, Murri R, Damiano F, Ammassari A, Antinori A. "Buffalo hump" in HIV-1 infection. Lancet 1998; 352:320
146. Darvay A, Acland K, Lynn W, Russell-Jones R. Striae formation in two HIV-positive persons receiving protease inhibitors. J Am Acad Dermatol 1999; 41:467-469
147. Caron-Debarle M, Lagathu C, Boccara F, Vigouroux C, Capeau J. HIV-associated lipodystrophy: from fat injury to premature aging. Trends Mol Med 2010; 16:218-229
148. Nolis T. Exploring the pathophysiology behind the more common genetic and acquired lipodystrophies. J Hum Genet 2014; 59:16-23
149. De Clercq E. Antiretroviral drugs. Curr Opin Pharmacol 2010; 10:507-515
150. Carr A, Samaras K, Chisholm DJ, Cooper DA. Pathogenesis of HIV-1-protease inhibitor-associated peripheral lipodystrophy, hyperlipidaemia, and insulin resistance. Lancet 1998; 351:1881-1883
151. Kino T, Chrousos GP. Human immunodeficiency virus type-1 accessory protein Vpr: a causative agent of the AIDS-related insulin resistance/lipodystrophy syndrome? Ann N Y Acad Sci 2004; 1024:153-167
152. Lenhard JM, Furfine ES, Jain RG, Ittoop O, Orband-Miller LA, Blanchard SG, Paulik MA, Weiel JE. HIV protease inhibitors block adipogenesis and increase lipolysis in vitro. Antiviral Res 2000; 47:121-129
153. Zhang B, MacNaul K, Szalkowski D, Li Z, Berger J, Moller DE. Inhibition of adipocyte differentiation by HIV protease inhibitors. J Clin Endocrinol Metab 1999; 84:4274-4277
154. Svard J, Blanco F, Nevin D, Fayne D, Mulcahy F, Hennessy M, Spiers JP. Differential interactions of antiretroviral agents with LXR, ER and GR nuclear receptors: potential contributing factors to adverse events. Br J Pharmacol 2014; 171:480-497
155. Ahmadian M, Suh JM, Hah N, Liddle C, Atkins AR, Downes M, Evans RM. PPARg signaling and metabolism: the good, the bad and the future. Nat Med 2013; 19:557-566
156. Ramji DP, Foka P. CCAAT/enhancer-binding proteins: structure, function and regulation. Biochem J 2002; 365:561-575
157. Vatier C, Leroyer S, Quette J, Brunel N, Capeau J, Antoine B. HIV protease inhibitors differently affect human subcutaneous and visceral fat: they induce IL-6 production and later lipid storage capacity in subcutaneous but not visceral adipose tissue explants. Antiviral Therapy 2008; 13:A3
158. Ouchi N, Parker JL, Lugus JJ, Walsh K. Adipokines in inflammation and metabolic disease. Nat Rev Immunol 2011; 11:85-97
159. Flint OP, Noor MA, Hruz PW, Hylemon PB, Yarasheski K, Kotler DP, Parker RA, Bellamine A. The role of protease inhibitors in the pathogenesis of HIV-associated lipodystrophy: cellular mechanisms and clinical implications. Toxicol Pathol 2009; 37:65-77
160. Djedaini M, Peraldi P, Drici MD, Darini C, Saint-Marc P, Dani C, Ladoux A. Lopinavir co-induces insulin resistance and ER stress in human adipocytes. Biochem Biophys Res Commun 2009; 386:96-100
161. Nolan D, Mallal S. Complications associated with NRTI therapy: update on clinical features and possible pathogenic mechanisms. Antivir Ther 2004; 9:849-863
162. Zhai Y, Pai HV, Zhou J, Amico JA, Vollmer RR, Xie W. Activation of pregnane X receptor disrupts glucocorticoid and mineralocorticoid homeostasis. Mol Endocrinol 2007; 21:138-147
163. Lee SD, Tontonoz P. Liver X receptors at the intersection of lipid metabolism and atherogenesis. Atherosclerosis 2015; 242:29-36
164. Nader N, Ng SS, Wang Y, Abel BS, Chrousos GP, Kino T. Liver x receptors regulate the transcriptional activity of the glucocorticoid receptor: implications for the carbohydrate metabolism. PLoS One 2012; 7:e26751
165. Miranda TB, Voss TC, Sung MH, Baek S, John S, Hawkins M, Grontved L, Schiltz RL, Hager GL. Reprogramming the chromatin landscape: interplay of the estrogen and glucocorticoid receptors at the genomic level. Cancer Res 2013; 73:5130-5139
166. Riddler SA, Smit E, Cole SR, Li R, Chmiel JS, Dobs A, Palella F, Visscher B, Evans R, Kingsley LA. Impact of HIV infection and HAART on serum lipids in men. Jama 2003; 289:2978-2982
167. Sutinen J, Kannisto K, Korsheninnikova E, Nyman T, Ehrenborg E, Andrew R, Wake DJ, Hamsten A, Walker BR, Yki-Jarvinen H. In the lipodystrophy associated with highly active antiretroviral therapy, pseudo-Cushing's syndrome is associated with increased regeneration of cortisol by 11b-hydroxysteroid dehydrogenase type 1 in adipose tissue. Diabetologia 2004; 47:1668-1671
168. Boothby M, McGee KC, Tomlinson JW, Gathercole LL, McTernan PG, Shojaee-Moradie F, Umpleby AM, Nightingale P, Shahmanesh M. Adipocyte differentiation, mitochondrial gene expression and fat distribution: differences between zidovudine and tenofovir after 6 months. Antivir Ther 2009; 14:1089-1100
169. Miller KK, Daly PA, Sentochnik D, Doweiko J, Samore M, Basgoz NO, Grinspoon SK. Pseudo-Cushing's syndrome in human immunodeficiency virus-infected patients. Clin Infect Dis 1998; 27:68-72
170. Pavlakis GN. The molecular biology of HIV-1. In: DeVita VT, Hellman S, Rosenberg SA, eds. AIDS: Diagnosis, Treatment and Prevention. 4 ed. Philadelphia: Lippincott Raven; 1996:45-74.
171. Norbiato G, Bevilacqua M, Vago T, Taddei A, Clerici. Glucocorticoids and the immune function in the human immunodeficiency virus infection: a study in hypercortisolemic and cortisol-resistant patients. J Clin Endocrinol Metab 1997; 82:3260-3263
172. Norbiato G, Bevilacqua M, Vago T, Clerici M. Glucocorticoids and interferon-a in the acquired immunodeficiency syndrome. J Clin Endocrinol Metab 1996; 81:2601-2606
173. Elenkov IJ, Chrousos GP. Stress Hormones, Th1/Th2 patterns, Pro/Anti-inflammatory Cytokines and Susceptibility to Disease. Trends Endocrinol Metab 1999; 10:359-368
174. Hadigan C, Miller K, Corcoran C, Anderson E, Basgoz N, Grinspoon S. Fasting hyperinsulinemia and changes in regional body composition in human immunodeficiency virus-infected women. J Clin Endocrinol Metab 1999; 84:1932-1937
175. Belec L, Mhiri C, DiCostanzo B, Gherardi R. The HIV wasting syndrome. Muscle Nerve 1992; 15:856-857
176. Simpson DM, Bender AN, Farraye J, Mendelson SG, Wolfe DE. Human immunodeficiency virus wasting syndrome may represent a treatable myopathy. Neurology 1990; 40:535-538
177. Kino T, Pavlakis GN. Partner molecules of accessory protein Vpr of the human immunodeficiency virus type 1. DNA Cell Biol 2004; 23:193-205
178. Kino T, Gragerov A, Kopp JB, Stauber RH, Pavlakis GN, Chrousos GP. The HIV-1 virion-associated protein vpr is a coactivator of the human glucocorticoid receptor. J Exp Med 1999; 189:51-62
179. Mirani M, Elenkov I, Volpi S, Hiroi N, Chrousos GP, Kino T. HIV-1 protein Vpr suppresses IL-12 production from human monocytes by enhancing glucocorticoid action: potential implications of Vpr coactivator activity for the innate and cellular immunity deficits observed in HIV-1 infection. J Immunol 2002; 169:6361-6368
180. Fakruddin JM, Laurence J. HIV-1 Vpr enhances production of receptor of activated NF-kB ligand (RANKL) via potentiation of glucocorticoid receptor activity. Arch Virol 2005; 150:67-78
181. Kino T, Gragerov A, Slobodskaya O, Tsopanomichalou M, Chrousos GP, Pavlakis GN. Human immunodeficiency virus type-1 (HIV-1) accessory protein Vpr induces transcription of the HIV-1 and glucocorticoid-responsive promoters by binding directly to p300/CBP coactivators. J Virol 2002; 76:9724-9734
182. Goodman RH, Smolik S. CBP/p300 in cell growth, transformation, and development. Genes Dev 2000; 14:1553-1577
183. Shrivastav S, Kino T, Cunningham T, Ichijo T, Schubert U, Heinklein P, Chrousos GP, Kopp JB. Human immunodeficiency virus (HIV)-1 viral protein R suppresses transcriptional activity of peroxisome proliferator-activated receptor g and inhibits adipocyte differentiation: implications for HIV-associated lipodystrophy. Mol Endocrinol 2008; 22:234-247
184. Sherman MP, Schubert U, Williams SA, de Noronha CM, Kreisberg JF, Henklein P, Greene WC. HIV-1 Vpr displays natural protein-transducing properties: implications for viral pathogenesis. Virology 2002; 302:95-105
185. Kino T, Slobodskaya O, Pavlakis GN, Chrousos GP. Nuclear receptor coactivator p160 proteins enhance the HIV-1 long terminal repeat promoter by bridging promoter-bound factors and the Tat-P-TEFb complex. J Biol Chem 2002; 277:2396-2405
186. Fawell S, Seery J, Daikh Y, Moore C, Chen LL, Pepinsky B, Barsoum J. Tat-mediated delivery of heterologous proteins into cells. Proc Natl Acad Sci U S A 1994; 91:664-668
187. Kino T, De Martino MU, Charmandari E, Ichijo T, Outas T, Chrousos GP. HIV-1 accessory protein Vpr inhibits the effect of insulin on the Foxo subfamily of forkhead transcription factors by interfering with their binding to 14-3-3 proteins: potential clinical implications regarding the insulin resistance of HIV-1-infected patients. Diabetes 2005; 54:23-31
188. Barthel A, Schmoll D, Unterman TG. FoxO proteins in insulin action and metabolism. Trends Endocrinol Metab 2005; 16:183-189
189. Baumann CA, Chokshi N, Saltiel AR, Ribon V. Cloning and characterization of a functional peroxisome proliferator activator receptor-g-responsive element in the promoter of the CAP gene. J Biol Chem 2000; 275:9131-9135
190. Wangsomboonsiri W, Mahasirimongkol S, Chantarangsu S, Kiertiburanakul S, Charoenyingwattana A, Komindr S, Thongnak C, Mushiroda T, Nakamura Y, Chantratita W, Sungkanuparph S. Association between HLA-B*4001 and lipodystrophy among HIV-infected patients from Thailand who received a stavudine-containing antiretroviral regimen. Clin Infect Dis 2010; 50:597-604
191. Shrivastav S, Zhang L, Okamoto K, Lee H, Lagranha C, Abe Y, Balasubramanyam A, Lopaschuk GD, Kino T, Kopp JB. HIV-1 Vpr enhances PPARb/d-mediated transcription, increases PDK4 expression, and reduces PDC activity. Mol Endocrinol 2013; 27:1564-1576
192. Agarwal N, Iyer D, Patel SG, Sekhar RV, Phillips TM, Schubert U, Oplt T, Buras ED, Samson SL, Couturier J, Lewis DE, Rodriguez-Barradas MC, Jahoor F, Kino T, Kopp JB, Balasubramanyam A. HIV-1 Vpr induces adipose dysfunction in vivo through reciprocal effects on PPAR/GR co-regulation. Sci Transl Med 2013; 5:213ra164
193. Agarwal N, Iyer D, Gabbi C, Saha P, Patel SG, Mo Q, Chang B, Goswami B, Schubert U, Kopp JB, Lewis DE, Balasubramanyam A. HIV-1 viral protein R (Vpr) induces fatty liver in mice via LXRα and PPARα dysregulation: implications for HIV-specific pathogenesis of NAFLD. Sci Rep. 2017; 7(1):13362
194. Tarr PE, Taffe P, Bleiber G, Furrer H, Rotger M, Martinez R, Hirschel B, Battegay M, Weber R, Vernazza P, Bernasconi E, Darioli R, Rickenbach M, Ledergerber B, Telenti A. Modeling the influence of APOC3, APOE, and TNF polymorphisms on the risk of antiretroviral therapy-associated lipid disorders. J Infect Dis 2005; 191:1419-1426
195. Behrens GM, Stoll M, Schmidt RE. Lipodystrophy syndrome in HIV infection: what is it, what causes it and how can it be managed? Drug Saf 2000; 23:57-76
196. Zanone Poma B, Riva A, Nasi M, Cicconi P, Broggini V, Lepri AC, Mologni D, Mazzotta F, Monforte AD, Mussini C, Cossarizza A, Galli M. Genetic polymorphisms differently influencing the emergence of atrophy and fat accumulation in HIV-related lipodystrophy. Aids 2008; 22:1769-1778
197. Manenschijn L, Scherzer R, Koper JW, Danoff A, van Rossum EF, Grunfeld C. Association of glucocorticoid receptor haplotypes with body composition and metabolic parameters in HIV-infected patients from the FRAM study. Pharmacogenet Genomics 2014; 24:156-161