Aldosterone Synthase in Peripheral Sensory Neurons Contributes to Mechanical Hypersensitivity during Local Inflammation in Rats.

BACKGROUND: Recent emerging evidence suggests that extra-adrenal synthesis of aldosterone occurs (e.g., within the failing heart and in certain brain areas). In this study, the authors investigated evidence for a local endogenous aldosterone production through its key processing enzyme aldosterone synthase within peripheral nociceptive neurons. METHODS: In male Wistar rats (n = 5 to 8 per group) with Freund's complete adjuvant hind paw inflammation, the authors examined aldosterone, aldosterone synthase, and mineralocorticoid receptor expression in peripheral sensory neurons using quantitative reverse transcriptase-polymerase chain reaction, Western blot, immunohistochemistry, and immunoprecipitation. Moreover, the authors explored the nociceptive behavioral changes after selective mineralocorticoid receptor antagonist, canrenoate-K, or specific aldosterone synthase inhibitor application. RESULTS: In rats with Freund's complete adjuvant-induced hind paw inflammation subcutaneous and intrathecal application of mineralocorticoid receptor antagonist, canrenoate-K, rapidly and dose-dependently attenuated nociceptive behavior (94 and 48% reduction in mean paw pressure thresholds, respectively), suggesting a tonic activation of neuronal mineralocorticoid receptors by an endogenous ligand. Indeed, aldosterone immunoreactivity was abundant in peptidergic nociceptive neurons of dorsal root ganglia and colocalized predominantly with its processing enzyme aldosterone synthase and mineralocorticoid receptors. Moreover, aldosterone and its synthesizing enzyme were significantly upregulated in peripheral sensory neurons under inflammatory conditions. The membrane mineralocorticoid receptor consistently coimmunoprecipitated with endogenous aldosterone, confirming a functional link between mineralocorticoid receptors and its endogenous ligand. Importantly, inhibition of endogenous aldosterone production in peripheral sensory neurons by a specific aldosterone synthase inhibitor attenuated nociceptive behavior after hind paw inflammation (a 32% reduction in paw pressure thresholds; inflammation, 47 ± 2 [mean ± SD] vs. inflammation + aldosterone synthase inhibitor, 62 ± 2). CONCLUSIONS: Local production of aldosterone by its processing enzyme aldosterone synthase within peripheral sensory neurons contributes to ongoing mechanical hypersensitivity during local inflammation via intrinsic activation of neuronal mineralocorticoid receptors.

Somatic CACNA1H Mutation As a Cause of Aldosterone-Producing Adenoma.

Driver somatic mutations for aldosterone excess have been found in ≈90% of aldosterone-producing adenomas (APAs) using an aldosterone synthase (CYP11B2)-guided sequencing approach. In the present study, we identified a novel somatic CACNA1H mutation (c.T4289C, p.I1430T) in an APA without any currently known aldosterone-driver mutations using CYP11B2 immunohistochemistry-guided whole exome sequencing. The CACNA1H gene encodes a voltage-dependent T-type calcium channel alpha-1H subunit. Germline variants in this gene are known as a cause of familial hyperaldosteronism IV. Targeted next-generation sequencing detected identical CACNA1H variants in 2 additional APAs in a cohort of the University of Michigan, resulting in a prevalence of 4% (3/75) in APAs. We tested the functional effect of the variant on adrenal cell aldosterone production and CYP11B2 mRNA expression using the human adrenocortical HAC15 cell line with a doxycycline-inducible CACNA1HI1430T mutation. Doxycycline treatment increased CYP11B2 mRNA levels as well as aldosterone production, supporting a pathological role of the CACNA1H p.I1430T mutation on the development of primary aldosteronism. In conclusion, somatic CACNA1H mutation is a genetic cause of APAs. Although the prevalence of this mutation is low, this study will provide better understanding of molecular mechanism of inappropriate aldosterone production in APAs.

Impact of immunohistochemistry on the diagnosis and management of primary aldosteronism: An important tool for improved patient follow-up.

BACKGROUND AND AIMS: Primary aldosteronism is a common cause of secondary hypertension. Primary aldosteronism is caused by an aldosterone-producing adenoma or bilateral hyperplasia that in some cases is asymmetrical with one adrenal dominating aldosterone secretion. Most patients with aldosterone-producing adenoma are biochemically cured by unilateral adrenalectomy, but patients with bilateral hyperplasia have a significant risk of residual or recurrent disease. Here, immunohistochemistry of CYP11B1 and B2 was used to investigate whether these markers could aid in the diagnostic workup of primary aldosteronism patients. MATERIALS AND METHODS: A total of 39 patients with primary aldosteronism who underwent unilateral adrenalectomy for a presumed adenoma during 2013-2016 were included. Immunohistochemistry using monoclonal antibodies identifying the enzymes CYP11B1 and B2 was part of routine histopathological workup in 6 cases; in 33 cases, it was applied retrospectively. The hyperplasia diagnosis was suggested when there was no dominating nodule but immunoreactivity for CYP11B2 was seen in several nodules, which were also seen on routine sections. To distinguish between adenoma and hyperplasia, a ratio between the largest and second largest CYP11B2-positive nodules was calculated. RESULTS: In all, 22 patients had an aldosterone-producing adenoma, while 13 patients were judged to have hyperplasia. In four cases, a final diagnosis could not be established, thus these were judged equivocal. Among the 33 cases investigated retrospectively, the primary histopathological diagnosis was altered from hyperplasia to aldosterone-producing adenoma in 9 cases (27%) after immunohistochemistry, and the immunohistochemically rectified adenoma group displayed improved clinical cure rates compared to the routine H&E-diagnosed cohort. Moreover, the B2 ratio was significantly higher in adenoma than in hyperplasia and equivocal cases. CONCLUSION: Immunohistochemistry detecting CYP11B1 and B2 expression is of great help in establishing a final histopathological diagnosis in patients with primary aldosteronism. This procedure should be part of the histopathological routine in all operated primary aldosteronism patients.

Effects of Adipocyte-derived Factors on the Adrenal Cortex.

BACKGROUND AND OBJECTIVE: Obesity is highly complicated by hypertension and hyperglycemia. In particular, it has been proposed that obesity-related hypertension is caused by adipocyte-derived factors that are recognized as undetermined proteins secreted from adipocytes. Adipocyte-derived factors have been known to be related to aldosterone secretion in the adrenal gland. So far, Wnt proteins, CTRP-1, VLDL, LDL, HDL and leptin have been demonstrated to stimulate aldosterone secretion. In contrast, it has not yet been clarified whether adipocyte-derived factors also affect adrenal cortisol secretion. METHODS AND RESULTS: In the present study, we investigated the effect of adipocyte-derived factors on cortisol synthase gene CYP11B1 mRNA expression in vitro study using adrenocortical carcinoma H295R cells and mouse fibroblast 3T3-L1cells. Interestingly, adipocyte-derived factors were demonstrated to have the ability to stimulate CYP11B1 mRNA expression. CONCLUSION: Since CYP11B1 is well known as a limiting enzyme of cortisol synthesis, our study suggests that adipocyte-derived factors may stimulate cortisol secretion, as well as aldosterone secretion. Taken together, adipocyte-derived factors may be the cause of metabolic syndrome due to their stimulating effects on aldosterone/cortisol secretion. Therefore, the innovation of novel drugs against them may possibly be a new approach against metabolic syndrome.

Steroid Profiling and Immunohistochemistry for Subtyping and Outcome Prediction in Primary Aldosteronism-a Review.

PURPOSE OF REVIEW: Steroid profiling and immunohistochemistry are both promising new tools used to improve diagnostic accuracy in the work-up of primary aldosteronism (PA) and to predict treatment outcomes. Herein, we review the recent literature and present an outlook to the future of diagnostics and therapeutic decision-making in patients with PA. RECENT FINDING: PA is the most common endocrine cause of arterial hypertension and unilateral forms of the disease are potentially curable by surgical resection of the overactive adrenal. Recent studies have shown that adrenal steroid profiling by liquid chromatography-tandem mass spectrometry (LC-MS/MS) can be helpful for subtyping unilateral and bilateral forms of PA, classifying patients with a unilateral aldosterone-producing adenoma (APA) according to the presence of driver mutations of aldosterone production in APAs, and potentially predicting the outcomes of surgical treatment for unilateral PA. Following adrenalectomy, immunohistochemistry of aldosterone synthase (CYP11B2) in resected adrenals is a new tool to analyze "functional" histopathology and may be an indicator of biochemical outcomes after surgery. Biochemical and clinical outcomes of therapy in PA vary widely among patients. Peripheral venous steroid profiling at baseline could improve diagnostic accuracy and help in surgical decision-making in cases of a suspected APA; results of "functional" histopathology could help determine which patients are likely to need close post-surgical follow-up for persistent aldosteronism.

Angiotensin 1-7 suppresses angiotensin II mediated aldosterone production via JAK/STAT signaling inhibition.

Angiotensin 1-7 (Ang 1-7), which is a protein cleaved from angiotensin II (A-II), binds to the MAS receptor. Ang 1-7 has been demonstrated to exert protective effects against A-II-mediated cardiac, atherosclerotic, and renal damages. The aims of our study were to demonstrate the inhibitory role of Ang 1-7 in A-II-mediated aldosterone production by interacting with the MAS receptor in human adrenocortical carcinoma (HAC15) cells, and clarify the intracellular signaling mechanisms underlying the inhibition of aldosterone production by Ang 1-7. Ang 1-7 significantly suppressed A-II-stimulated aldosterone production, and partially abrogated A-II-induced upregulation of CYP11B2 expression. Treatment with a selective Ang 1-7 antagonist abrogated Ang 1-7-mediated inhibition of aldosterone production in HAC15 cells. Incubation of A-II-treated HAC15 cells with conditioned medium containing Ang 1-7 was demonstrated to suppress A-II-mediated aldosterone production and CYP11B2 expression. Proteomic analysis showed that Ang 1-7 predominantly inhibited the phosphorylation of JAK-STAT proteins in A-II stimulated HAC15 cells. Treatment of HAC15 cells with a STAT3 inhibitor partially but significantly repressed A-II-mediated aldosterone production by 63.2%. Similarly, treatment with a STAT5 inhibitor significantly abrogated A-II-stimulated aldosterone production in HAC15 cells by 60.7%. In conclusion, we demonstrated that Ang 1-7 negatively regulates A-II-mediated aldosterone production, and the observed inhibition of aldosterone production was associated with JAK/STAT signaling in human adrenal cells. Therefore, activation of Ang 1-7 or stimulation of the MAS receptor, which inhibits aldosterone production, is a promising therapeutic approach for the prevention of cardiovascular events that can directly affect the target organs.

GSTA1 Expression Is Correlated With Aldosterone Level in KCNJ5-Mutated Adrenal Aldosterone-Producing Adenoma.

Context: KCNJ5 mutation is a major cause of aldosterone-producing adenomas (APAs). The development of APA apart from KCNJ5 mutation is less investigated. Objective: To investigate other mechanisms affecting aldosterone secretion apart from KCNJ5. Patients and Methods: Six pairs of KCNJ5-mutated, high and low aldosterone-secreting APAs, five non-KCNJ5-mutated APAs, and four normal adrenal glands were assayed by Affymetrix GeneChip Human Transcriptome Array 2.0. A total of 113 APA samples were investigated to explore the expression of glutathione-S-transferase A1 (GSTA1). H295R cells were used to verify the function of GSTA1. Results: GSTA1 was the top gene downregulated in high-aldosterone KCNJ5-mutated APAs. GSTA1 was also downregulated in KCNJ5-mutated APAs compared with wild-type KCNJ5 APAs. Accordingly, mutant KCNJ5 decreased GSTA1 messenger RNA and protein expression levels. GSTA1 overexpression suppressed aldosterone secretion whether in wild-type or mutant KCNJ5 H295R cells. Adding ethacrynic acid or silencing of GSTA1 increased aldosterone secretion by increasing reactive oxygen species (ROS), superoxide, H2O2 levels, and Ca2+ influx. The expression of the transcription factors NR4A1, NR4A2, and CAMK1 and intracellular Ca2+ were significantly upregulated by GSTA1 inhibition. The reduced form of NAD phosphate oxidase inhibitor or H2O2 scavenger or blocking calmodulin or calcium channels could significantly reduce aldosterone secretion in GSTA1-inhibited cells. Conclusions: (1) GSTA1 expression is reversely correlated with aldosterone level in KCNJ5-mutated APAs, (2) GSTA1 regulates aldosterone secretion by ROS and Ca2+ signaling, and (3) KCNJ5 mutation downregulates GSTA1 expression, and overexpression of GSTA1 reverses increased aldosterone in KCNJ5-mutated adrenal cells.

Macrolides Blunt Aldosterone Biosynthesis: A Proof-of-Concept Study in KCNJ5 Mutated Adenoma Cells Ex Vivo.

Aldosterone-producing adenoma (APA), a major subtype of primary hyperaldosteronism, the main curable cause of human endocrine hypertension, involves somatic mutations in the potassium channel Kir3.4 (KCNJ5) in 30% to 70% of cases, typically the more florid phenotypes. Because KCNJ5 mutated channels were reported to be specifically sensitive to inhibition by macrolide antibiotics, which concentration dependently blunts aldosterone production in HAC15 transfected with the G151R and L168R mutated channel, we herein tested the effect of clarithromycin on aldosterone synthesis and secretion in a pure population of aldosterone-secreting cells obtained by immunoseparation (CD56+ cells) from APA tissues with/without the 2 most common KCNJ5 mutations. From a large cohort of patients with an unambiguous APA diagnosis, we recruited those who were wild type (n=3) or had G151R (n=2) and L168R (n=2) mutations. We found that clarithromycin concentration dependently lowered CYP11B2 gene expression (by 60%) and aldosterone secretion (by 70%; P<0.001 for both) in CD56+ cells isolated ex vivo from KCNJ5 mutated APAs, although it was ineffective in CD56+ cells from wild-type APAs. By proving the principle that the oversecretion of aldosterone can be specifically blunted in APA cells ex vivo with G151R and L168R mutations, these results provide compelling evidence of the possibility of specifically correcting aldosterone excess in patients with APA carrying the 2 most common KCNJ5 somatic mutations.

Macrolides selectively inhibit mutant KCNJ5 potassium channels that cause aldosterone-producing adenoma.

Aldosterone-producing adenomas (APAs) are benign tumors of the adrenal gland that constitutively produce the salt-retaining steroid hormone aldosterone and cause millions of cases of severe hypertension worldwide. Either of 2 somatic mutations in the potassium channel KCNJ5 (G151R and L168R, hereafter referred to as KCNJ5MUT) in adrenocortical cells account for half of APAs worldwide. These mutations alter channel selectivity to allow abnormal Na+ conductance, resulting in membrane depolarization, calcium influx, aldosterone production, and cell proliferation. Because APA diagnosis requires a difficult invasive procedure, patients often remain undiagnosed and inadequately treated. Inhibitors of KCNJ5MUT could allow noninvasive diagnosis and therapy of APAs carrying KCNJ5 mutations. Here, we developed a high-throughput screen for rescue of KCNJ5MUT-induced lethality and identified a series of macrolide antibiotics, including roxithromycin, that potently inhibit KCNJ5MUT, but not KCNJ5WT. Electrophysiology demonstrated direct KCNJ5MUT inhibition. In human aldosterone-producing adrenocortical cancer cell lines, roxithromycin inhibited KCNJ5MUT-induced induction of CYP11B2 (encoding aldosterone synthase) expression and aldosterone production. Further exploration of macrolides showed that KCNJ5MUT was similarly selectively inhibited by idremcinal, a macrolide motilin receptor agonist, and by synthesized macrolide derivatives lacking antibiotic or motilide activity. Macrolide-derived selective KCNJ5MUT inhibitors thus have the potential to advance the diagnosis and treatment of APAs harboring KCNJ5MUT.

Age-Related Autonomous Aldosteronism.

BACKGROUND: Both aging and inappropriate secretion of aldosterone increase the risk for developing cardiovascular disease; however, the influence of aging on aldosterone secretion and physiology is not well understood. METHODS: The relationship between age and adrenal aldosterone synthase (CYP11B2) expression was evaluated in 127 normal adrenal glands from deceased kidney donors (age, 9 months to 68 years). Following immunohistochemistry, CYP11B2-expressing area and areas of abnormal foci of CYP11B2-expressing cells, called aldosterone-producing cell clusters, were analyzed. In a separate ancillary clinical study of 677 participants without primary aldosteronism, who were studied on both high and restricted sodium diets (age, 18-71 years), we used multivariable linear regression to assess the independent associations between age and renin-angiotensin-aldosterone system physiology. RESULTS: In adrenal tissue, the total CYP11B2-expressing area was negatively correlated with age (r=-0.431, P<0.0001), whereas the total aldosterone-producing cell cluster area was positively correlated with age (r=0.390, P<0.0001). The integrated ratio of aldosterone-producing cell cluster to CYP11B2-expressing area was most strongly and positively correlated with age (r=0.587, P<0.0001). When participants in the clinical study were maintained on a high sodium balance, renin activity progressively declined with older age, whereas serum and urinary aldosterone did not significantly decline. Correspondingly, the aldosterone-to-renin ratio was positively and independently associated with older age (adjusted ß=+5.54 ng/dL per ng/mL per hour per 10 years, P<0.001). In contrast, when participants were assessed under sodium-restricted conditions, physiological stimulation of aldosterone was blunted with older age (ß=-4.6 ng/dL per 10 years, P<0.0001). CONCLUSIONS: Aging is associated with a pattern of decreased normal zona glomerulosa CYP11B2 expression and increased aldosterone-producing cell cluster expression. This histopathologic finding parallels an age-related autonomous aldosteronism and abnormal aldosterone physiology that provides 1 potential explanation for age-related cardiovascular risk.

A ubiquitin-proteasome inhibitor bortezomib suppresses the expression of CYP11B2, a key enzyme of aldosterone synthesis.

CYP11B2 is a key enzyme involved in the synthesis of the mineralocorticoid aldosterone. CYP11B2 expression in the adrenal glands is controlled by the renin-angiotensin system (RAS), and plays an important role in the maintenance of electrolyte metabolism in higher organisms. Abnormal overexpression of CYP11B2 results in the disruption of mineral balance and can lead to hypertension. Though the molecular mechanism of the regulation of CYP11B2 expression has remained elusive, we hypothesize that compounds that prevent CYP11B2 expression could represent a novel class of antihypertensive drugs. In this study, we established a high-throughput screening system to identify such compounds, and subsequently carried out chemical screening. We found that the ubiquitin-proteasome inhibitor bortezomib could suppress CYP11B2 expression and secretion of aldosterone induced by angiotensin II (Ang II) in adrenocortical H295R cells. Moreover, bortezomib down-regulated the Cyp11b2 mRNA expression facilitated in the adrenal gland of Tsukuba hypertensive mice, resulting in subsequent lowering of their blood pressures. Furthermore, we observed the characteristic alteration of H3K27ac in the adrenal CYP11B2 gene promoter induced by Ang II stimulation, which was found to be disrupted by bortezomib. Taken together, these results suggest the possibility of developing novel antihypertensive drugs that prevent CYP11B2 expression.

Disorganized Steroidogenesis in Adrenocortical Carcinoma, a Case Study.

Most adrenocortical carcinomas (ACCs) produce excessive amounts of steroid hormones including aldosterone, cortisol, and steroid precursors. However, aldosterone- and cortisol-producing cells in ACCs have not yet been immunohistochemically described. We present a case of ACC causing mild primary aldosteronism and subclinical Cushing's syndrome. Removal of the tumor cured both conditions. In order to examine the expression patterns of the steroidogenic enzymes responsible for adrenocortical hormone production, 10 tumor portions were immunohistochemically analyzed for aldosterone synthase (CYP11B2), 11ß-hydroxylase (CYP11B1, cortisol-synthesizing enzyme), 3ß-hydroxysteroid dehydrogenase (3ßHSD, upstream enzyme for both CYP11B2 and CYP11B1), and 17α-hydroxylase/C17-20 lyase (CYP17, upstream enzyme for CYP11B1, but not for CYP11B1). CYP11B2, CYP11B1, and 3ßHSD were expressed sporadically, and their expression patterns varied significantly among the different tumor portions examined. The expression of these enzymes was random and not associated with each other. CYP17 was expressed throughout the tumor, even in CYP11B2-positive cells. Small tumor cell populations were aldosterone- or cortisol-producing cells, as judged by 3ßHSD coinciding with either CYP11B2 or CYP11B1, respectively. These results suggest that the tumor produced limited amounts of aldosterone and cortisol due to the lack of the coordinated expression of steroidogenic enzymes, which led to mild clinical expression in this case. We delineated the expression patterns of steroidogenic enzymes in ACC. The coordinated expression of steroidogenic enzymes in normal and adenoma cells was disturbed in ACC cells, resulting in the inefficient production of steroid hormones in relation to the large tumor volume.

Myeloid cells are capable of synthesizing aldosterone to exacerbate damage in muscular dystrophy.

FDA-approved mineralocorticoid receptor (MR) antagonists are used to treat heart failure. We have recently demonstrated efficacy of MR antagonists for skeletal muscles in addition to heart in Duchenne muscular dystrophy mouse models and that mineralocorticoid receptors are present and functional in skeletal muscles. The goal of this study was to elucidate the underlying mechanisms of MR antagonist efficacy on dystrophic skeletal muscles. We demonstrate for the first time that infiltrating myeloid cells clustered in damaged areas of dystrophic skeletal muscles have the capacity to produce the natural ligand of MR, aldosterone, which in excess is known to exacerbate tissue damage. Aldosterone synthase protein levels are increased in leukocytes isolated from dystrophic muscles compared with controls and local aldosterone levels in dystrophic skeletal muscles are increased, despite normal circulating levels. All genes encoding enzymes in the pathway for aldosterone synthesis are expressed in muscle-derived leukocytes. 11ß-HSD2, the enzyme that inactivates glucocorticoids to increase MR selectivity for aldosterone, is also increased in dystrophic muscle tissues. These results, together with the demonstrated preclinical efficacy of antagonists, suggest MR activation is in excess of physiological need and likely contributes to the pathology of muscular dystrophy. This study provides new mechanistic insight into the known contribution of myeloid cells to muscular dystrophy pathology. This first report of myeloid cells having the capacity to produce aldosterone may have implications for a wide variety of acute injuries and chronic diseases with inflammation where MR antagonists may be therapeutic.

High risk of adrenal toxicity of N1-desoxy quinoxaline 1,4-dioxide derivatives and the protection of oligomeric proanthocyanidins (OPC) in the inhibition of the expression of aldosterone synthetase in H295R cells.

Quinoxaline 1,4-dioxide derivatives (QdNOs) with a wide range of biological activities are used in animal husbandry worldwide. It was found that QdNOs significantly inhibited the gene expression of CYP11B1 and CYP11B2, the key aldosterone synthases, and thus reduced aldosterone levels. However, whether the metabolites of QdNOs have potential adrenal toxicity and the role of oxidative stress in the adrenal toxicity of QdNOs remains unclear. The relatively new QdNOs, cyadox (CYA), mequindox (MEQ), quinocetone (QCT) and their metabolites, were selected for elucidation of their toxic mechanisms in H295R cells. Interestingly, the results showed that the main toxic metabolites of QCT, MEQ, and CYA were their N1-desoxy metabolites, which were more harmful than other metabolites and evoked dose and time-dependent cell damage on adrenal cells and inhibited aldosterone production. Gene and protein expression of CYP11B1 and CYP11B2 and mRNA expression of transcription factors, such as NURR1, NGFIB, CREB, SF-1, and ATF-1, were down regulated by N1-desoxy QdNOs. The natural inhibitors of oxidant stress, oligomeric proanthocyanidins (OPC), could upregulate the expression of diverse transcription factors, including CYP11B1 and CYP11B2, and elevated aldosterone levels to reduce adrenal toxicity. This study demonstrated for the first time that N1-desoxy QdNOs have the potential to be the major toxic metabolites in adrenal toxicity, which may shed new light on the adrenal toxicity of these fascinating compounds and help to provide a basic foundation for the formulation of safety controls for animal products and the design of new QdNOs with less harmful effects.

Antiaging Gene Klotho Regulates Adrenal CYP11B2 Expression and Aldosterone Synthesis.

Deficiency of the antiaging gene Klotho (KL) induces renal damage and hypertension through unknown mechanisms. In this study, we assessed whether KL regulates expression of CYP11B2, a key rate-limiting enzyme in aldosterone synthesis, in adrenal glands. We found that haplodeficiency of KL(+/-) in mice increased the plasma level of aldosterone by 16 weeks of age, which coincided with spontaneous and persistent elevation of BP. Blockade of aldosterone actions by eplerenone reversed KL deficiency-induced hypertension and attenuated the kidney damage. Protein expression of CYP11B2 was upregulated in adrenal cortex of KL(+/-) mice. KL and CYP11B2 proteins colocalized in adrenal zona glomerulosa cells. Silencing of KL upregulated and overexpression of KL downregulated CYP11B2 expression in human adrenocortical cells. Notably, silencing of KL decreased expression of SF-1, a negative transcription factor of CYP11B2, but increased phosphorylation of ATF2, a positive transcription factor of CYP11B2, which may contribute to upregulation of CYP11B2 expression. Therefore, these results show that KL regulates adrenal CYP11B2 expression. KL deficiency-induced spontaneous hypertension and kidney damage may be partially attributed to the upregulation of CYP11B2 expression and aldosterone synthesis.

Variable transcriptional regulation of the human aldosterone synthase gene causes salt-dependent high blood pressure in transgenic mice.

BACKGROUND: Aldosterone, synthesized in the adrenal cortex by the enzyme CYP11B2, induces positive sodium balance and predisposes to hypertension. Various investigators, using genomic DNA analyses, have linked -344T polymorphism in the human CYP11B2 (hCYP11B2) gene to human hypertension. hCYP11B2 gene promoter has 3 single-nucleotide polymorphisms in linkage disequilibrium: T/A at -663, T/C at -470, and C/T at -344. Variants ACT occur together and form the haplotype-I (Hap-I), whereas variants TTC constitute Hap-II. We hypothesize that these single-nucleotide polymorphisms, when present together, will lead to haplotype-dependent differences in the transcriptional regulation of the hCYP11B2 gene and affect blood pressure regulation. METHODS AND RESULTS: We evaluated differences in tissue expression in vivo and consequential effects on blood pressure stemming from the 2 haplotypes. Novel transgenic mice with the hCYP11B2 gene, targeted to the mouse HPRT locus, with either Hap-II or Hap-I variant are used in this study. Our results show increased adrenal and renal expression of hCYP11B2 in transgenic mice with Hap-I when compared with mice with Hap-II. Importantly, we observed increased baseline blood pressure in Hap-I transgenic mice, an effect accentuated by a high-salt diet. Pathophysiological effects of elevated aldosterone were corroborated by our results showing upregulation of proinflammatory markers in renal tissues from the transgenic mice with Hap-I. CONCLUSIONS: These findings characterize the haplotype-dependent regulation of the hCYP11B2 gene where -344T serves as a reporter polymorphism and show that Hap-I leads to increased expression of hCYP11B2, with permissive effects on blood pressure and inflammatory milieu.

Akt-mediated cardioprotective effects of aldosterone in type 2 diabetic mice.

Studies have shown that aldosterone would have angiogenic effects and therefore would be beneficial in the context of cardiovascular diseases. We thus investigated the potential involvement of aldosterone in triggering a cardiac angiogenic response in the context of type-2 diabetes and the molecular pathways involved. Male 3-wk-old aldosterone synthase (AS)-overexpressing mice and their control wild-type (WT) littermates were fed a standard or high-fat, high-sucrose (HFHS) diet. After 6 mo of diet treatment, mice were euthanized, and cardiac samples were assayed by RT-PCR, immunoblotting, and immunohistology. HFHS diet induced type-2 diabetes in WT (WT-D) and AS (AS-D) mice. VEGFa mRNAs decreased in WT-D (-43%, P<0.05 vs. WT) and increased in AS-D mice (+236%, P< 0.01 vs. WT-D). In WT-D mouse hearts, the proapoptotic p38MAPK was activated (P<0.05 vs. WT and AS-D), whereas Akt activity decreased (-64%, P<0.05 vs. WT). The AS mice, which exhibited a cardiac up-regulation of IGF1-R, showed an increase in Akt phosphorylation when diabetes was induced (P<0.05 vs. WT and AS-D). Contrary to WT-D mice, AS-D mouse hearts did not express inflammatory markers and exhibited a normal capillary density (P<0.05 vs. WT-D). To our knowledge, this is the first study providing new insights into the mechanisms whereby aldosterone prevents diabetes-induced cardiac disorders.

KCNJ5 mutations in aldosterone producing adenoma and relationship with adrenal cortex remodeling.

Somatic mutations of KCNJ5, coding for the potassium channel GIRK4, have recently been implicated in the formation of aldosterone producing adenoma (APA). While a causal link between KCNJ5 mutations, membrane depolarization and aldosterone production has been established, the precise mechanism by which these mutations promote cell proliferation and APA formation remains unclear. The aim of our study was to correlate KCNJ5 mutation status with morphological and functional characteristics of the adrenal cortex adjacent to APA. While GIRK4 was expressed in APA and in the zona glomerulosa of the adjacent cortex, significantly lower levels were detected in APA harboring a KCNJ5 mutation. There was no correlation between KCNJ5 mutation status and the morphological measures of adrenal cortex remodeling, including nodulation, vascularization and expression of CYP11B2. The cell composition of APA was not significantly different between groups. These results indicate that KCNJ5 mutations are not correlated with adrenal cortex remodeling in APA.

Characterization of NCI-H295R cells as an in vitro model of hyperaldosteronism.

In depth analysis of key molecular mechanisms involved in functional autonomy of aldosterone secretion is hampered by the lack of tumor cell lines that reflect functional characteristics of aldosterone producing adenomas. Herein, we describe the characteristics of the adrenocortical carcinoma cell line NCI-H295R and its suitability as a model of hyperaldosteronism in relation to different culture conditions. Steroid profiling revealed that NCI-H295R cells predominantly secrete cortisol, while aldosterone and other steroids are released at much lower concentrations. However, aldosterone output specifically increased in response to different stimuli such as ACTH and angiotensin II, and in particular to potassium in a dose dependent manner. NCI-H295R cells readily formed spheroids under specific culture conditions, a method widely used for the enrichment of progenitor cells. Unexpectedly, spheroid cells excelled with higher aldosterone concentration and higher expression levels of the steroidogenic enzymes StAR, 3ßHSD, CYP17, SF-1, and the MC2-receptor. Further investigations revealed that this phenomenon is mainly attributed to epithelial growth factor (EGF) and particularly fibroblast growth factor (FGF), which are both essential ingredients in the spheroid culture medium. Aldosterone release under the combinatory influence of EGF and FGF was not higher than the effect of FGF alone. Spheroid growth per se, therefore, does not ensure an enrichment of less differentiated cell types in this cell line.

APEX1 regulation of aldosterone synthase gene transcription is disrupted by a common polymorphism in humans.

RATIONALE: The genetic mechanisms underlying hypertension are unclear, but relative aldosterone excess, present in ≈10% of hypertensive patients, is known to be a heritable trait. This phenotype associates with a T/C single nucleotide polymorphism (SNP) at position -344 of the aldosterone synthase gene (CYP11B2). However, deletion of this SNP has no effect on gene transcription. We have identified another T/C SNP at -1651, in tight linkage disequilibrium with the -344 SNP and here investigate its functional effect on CYP11B2 transcription. OBJECTIVE: We assessed the effect on transcriptional activity of the -1651 T/C SNP in vivo and in vitro and propose the mechanism by which transcriptional activity is altered. METHODS AND RESULTS: We demonstrated that the SNP at -1651 exerts significant allele-dependent effects on CYP11B2 transcription. We confirm binding of the transcriptional repressor APEX1 to -1651T, which is associated with reduced transcriptional activity in relation to the less strongly bound -1651C. We show that inhibiting APEX1 by small molecule inhibition or small interfering RNA (SiRNA) leads to increased CYP11B2 transcription. In addition, overexpression of APEX1 is associated with reduced transcriptional activity. Finally, we also show that -1651T associates with lower excretion rates of aldosterone metabolites in human subjects. CONCLUSIONS: We conclude that APEX1 is a novel transcriptional repressor of CYP11B2 and that differential APEX1 binding at -1651 of CYP11B2 results in altered gene expression. This mechanism may contribute to the observed relationship between CYP11B2 genotype and aldosterone phenotype in a subgroup of hypertensive patients.