Inhibition Of Aldosterone Production Research Articles

Perfluorotetradecanoic acid exposure to adult male rats stimulates corticosterone biosynthesis but inhibits aldosterone production.

Perfluorotetradecanoic acid (PFTeDA) is a novel perfluoroalkyl substance that ubiquitously exists in the environment. However, whether PFTeDA affects adrenal cortex function remains unclear. Male Sprague-Dawley rats (age of 60 days) were daily administered with PFTeDA (0, 1, 5, and 10 mg/kg body weight) through gavage for 28 days. PFTeDA did not change body and adrenal gland weights. PFTeDA markedly elevated serum corticosterone level at 10 mg/kg but lowering serum aldosterone level at this dosage without influencing serum adrenocorticotropic hormone level. PFTeDA thickened zona fasciculata without affecting zona glomerulosa. PFTeDA remarkably upregulated the expression of corticosterone biosynthetic genes (Mc2r, Scarb1, Star, Cyp21, Cyp11b1, and Hsd11b1) and their proteins, whereas downregulating aldosterone biosynthetic enzyme Cyp11b2 and its protein, thereby distinctly altering their serum levels. PFTeDA markedly downregulated the expression of antioxidant genes (Sod1 and Sod2) and their proteins at 10 mg/kg. PFTeDA significantly decreased SIRT1/PGC1α and AMPK signaling while stimulating AKT1/mTOR signaling. Corticosterone significantly inhibited testosterone production by adult Leydig cells at >0.1 μM in vitro; however aldosterone significantly stimulated testosterone production at 0.1 nM. In conclusion, exposure to PFTeDA at male rat adulthood causes corticosterone excess and aldosterone deficiency via SIRT1/PGC1α, AMPK, and AKT1/mTOR signals, which in turn additively leads to testosterone deficiency.

FRI144 Using Single Cell Technology To Predict The Cell Of Origin Of Aldosterone-producing Adrenal Adenomas

Abstract Disclosure: K. Laycock: None. C. Cabrera: None. E. Wozniak: None. C. Mein: None. E. Azizan: None. X. Wu: None. G. Argentesi: None. E. Goodchild: None. W. Drake: None. M.J. Brown: None. Background: Aldosterone-producing adrenal adenomas (APAs) are the commonest surgically curable cause of hypertension, but individual prediction of postoperative outcome is challenging. Emerging data suggest that outcomes are influenced by APA genotype; identifying the cell of origin of APAs could facilitate a greater understanding of why certain genotypes are more/less likely to be associated with residual/recurrent autonomous aldosterone production(1, 2). Aims: 1. To develop an adult adrenal single cell atlas. 2. To identify the likely cell of origin for APAs with different mutations. Methodology: Bulk RNA sequencing from 67 APAs discovered known or novel somatic genotypes in 55, and replicated or discovered distinctive transcriptomes for each genotype. Single nuclei RNA sequencing was performed on 13 adrenals adjacent to the genotyped APAs. After aggregation of all 13 datasets, cluster analysis was undertaken to identify cell types and some of the transitions between these. Similarities were sought between the genotype-enriched transcriptomes of APAs, and the transcriptomes of individual cell clusters in adjacent adrenal. Results: A single nuclei atlas of 56,442 nuclei was developed. Clusters included each of the 3 cortical zones, aldosterone-producing micronodules, capsular cells, adrenal medulla, macrophages, T cells, stromal cells, endothelial cells and neurones. Several zona glomerulosa selective transcripts in previous laser-capture studies(3, 4) clustered separately from CYP11B2-positive cells (e.g. LGR5, GABBR2) or in distinct non-steroidogenic clusters (e.g. KIAA1210, RSPO3, PTGDS).A sub-cluster of stromal cells, positive for KIAA1210, RSPO3, CDH13 and MFAP5 (each p<10-254 cf other clusters) is likely to represent the distinctive KIAA1210+ capsular/interstitial cells on adrenal immunohistochemistry (www.proteinatlas.org). Bulk RNA sequencing of a rare CLCN2-mutant APA showed 13-30-fold higher expression of these and multiple other genes localising to the single nuclei stromal-cell cluster. Conclusion: Single nuclei sequencing documents the heterogeneity of adrenal cells, and potential for multiple different cell-types to develop into APAs. Ongoing analysis is underway to replicate the CLCN2-mutant transcriptome and identify cells-of-origins for tumours with commoner mutations. 1.Wu X et al. 11C metomidate PET-CT versus AVS for diagnosing surgically curable PA: a prospective within-patient trial. Nat Med. In press 2.Zhou J et al. Somatic mutations of GNA11 and GNAQ in CTNNB1-mutant APAs presenting in puberty, pregnancy or menopause. Nat Genet. 2021 3.Nishimoto K et al. Aldosterone-stimulating somatic gene mutations are common in normal adrenal glands. Proc Natl Acad Sci USA. 2015 4.Shaikh LH et al. LGR5 Activates Noncanonical Wnt Signaling and Inhibits Aldosterone Production in the Human Adrenal. J Clin Endocrinol Metab. 2015 Presentation: Friday, June 16, 2023

RNA-Binding Protein Musashi-2 Inhibits Aldosterone Production

The adrenal cortex is the site of steroid hormone synthesis. These hormones control important physiological processes like metabolism, blood pressure and volume, and sexual characteristic development. While the signaling pathways, transcription factors, and steroidogenic enzymes are well-characterized, surprisingly little is known about the contribution RNA-binding proteins (RBPs). RBPs exert post-transcriptional control by interacting with specific elements within target mRNAs. Here we focus on the RBP, Mushashi-2 (MSI2), which binds to UAG sequences in the 3’UTR of its target transcripts. MSI2 is required for development of steroidogenic tissues which is consistent with its higher mRNA levels in human ovaries and testis. MSI2 also exhibits high expression levels in human adrenal tissue and the immortalized human adrenocortical cell line (H295R). Based on the compelling MSI2 expression pattern, we set out to determine the role of MSI2 on aldosterone production. Depletion of MSI2 using siRNA led to significantly lower aldosterone levels in H295R cells stimulated with AngII. We also employed an orthogonal loss-of-function approach by co-treating cells with AngII and increasing concentrations of Ro-08-2750 (Ro), a direct and selective inhibitor of MSI2-RNA interactions. Ro inhibited aldosterone production in a dose-dependent manner at 1 µM with almost complete inhibition at 5 µM. The molecular mechanism by which MSI2 regulates target RNA translation and/or decay is unknown. Moreover, whether MSI2 acts as a repressor or activator appears to be context dependent. Our goal is to determine the precise molecular mechanism by which MSI2 promotes aldosterone production. Specifically, we will identify MSI2 targets, temporally resolved consequences of MSI2 inhibition, and protein interaction partners. This work will impact our understanding of fundamental principles of RBP-mediated regulation, as well as novel regulatory mechanisms underlying human steroid hormone synthesis. Indeed, Ro (or further optimized compounds) may represent new therapeutic avenues for adrenal disease.

Novel molecular mechanisms in the inhibition of adrenal aldosterone synthesis: Action of tolvaptan via vasopressin V2 receptor‐independent pathway

We investigated the inhibitory effect and associated molecular mechanisms of tolvaptan on angiotensin II (AngII)-induced aldosterone production in vitro and in vivo. In vitro, H295R human adrenocarcinoma cells were incubated with 1μmol·L-1 arginine vasopressin (AVP) or dDAVP, or tolvaptan (0.1, 1, and 3μmol·L-1 ) in the presence and absence of 100nmol·L-1 of AngII. In vivo, Sprague-Dawley rats were treated with tolvaptan 0.05% in the diet for 6days in the presence and absence of 200pmol·min-1 AngII. Tolvaptan suppressed AngII-induced aldosterone production in a dose-dependent manner in H295R cells, whereas neither AVP nor dDAVP in the presence or absence of AngII altered aldosterone production, suggesting the vasopressin V2 receptor was not involved in the inhibitory effect of tolvaptan on aldosterone synthesis. In addition, tolvaptan inhibited the AngII-induced increase in aldosterone synthase (CYP11B2) protein levels without suppressing CYP11B2 mRNA expression. Notably, tolvaptan increased the levels of unfolded protein response (UPR) marker DDIT3 and eIF2α phosphorylation (a UPR-induced event), which could block the translation of CYP11B2 mRNA into protein and thereby inhibit aldosterone production. In vivo, tolvaptan significantly inhibited AngII-induced increases in serum and adrenal aldosterone levels and CYP11B2 protein levels. This anti-aldosterone effect was associated with a reduction in the elevated systolic and diastolic BP. Tolvaptan inhibited AngII-stimulated aldosterone production via a V2 receptor-independent pathway, which can counteract or even surpass its potential activating effect of diuresis-induced aldosterone secretion in certain aldosterone-mediated pathological conditions.

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.

L-Lysine Acts as a Serotonin Type 4 Receptor Antagonist to Counteract In Vitro and In Vivo the Stimulatory Effect of Serotonergic Agents on Aldosterone Secretion in Man.

In the normal human adrenal gland, serotonin (5-HT) stimulates aldosterone secretion through the 5-HT4 receptor (5-HT4R). However, the physiological role of the serotonergic control of adrenocortical function is not known. In the present study, we have investigated the ability of l-Lysine, which has been shown to act as a 5-HT4 receptor antagonist, to counteract in vitro and in vivo the stimulatory effect of 5-HT4R agonists on aldosterone production. l-Lysine was found to inhibit aldosterone production induced by 5-HT and the 5-HT4R agonists BIMU8 from cultured human adrenocortical cells. The action of l-Lysine (4.95 g/day orally) on the adrenal cortex was also evaluated in 20 healthy volunteers in a double blind, cross-over, placebo controlled study. l-Lysine had no significant influence on basal plasma aldosterone levels and the aldosterone responses to upright posture, tetracosactide, and low sodium diet (10 mmol/day for 3 days). Conversely, l-Lysine significantly reduced the surge of plasma aldosterone induced by metoclopramide indicating that l-Lysine is able to efficiently antagonize the adrenal 5-HT4 receptors in vivo. These results suggest that l-Lysine supplementation may represent a new treatment of primary adrenal diseases in which corticosteroid hypersecretion is driven by overexpressed 5-HT4 receptors.

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.

Calpain-10 Activity Underlies Angiotensin II-Induced Aldosterone Production in an Adrenal Glomerulosa Cell Model.

Aldosterone is a steroid hormone important in the regulation of blood pressure. Aberrant production of aldosterone results in the development and progression of diseases including hypertension and congestive heart failure; therefore, a complete understanding of aldosterone production is important for developing more effective treatments. Angiotensin II (AngII) regulates steroidogenesis, in part through its ability to increase intracellular calcium levels. Calcium can activate calpains, proteases classified as typical or atypical based on the presence or absence of penta-EF-hands, which are involved in various cellular responses. We hypothesized that calpain, in particular calpain-10, is activated by AngII in adrenal glomerulosa cells and underlies aldosterone production. Our studies showed that pan-calpain inhibitors reduced AngII-induced aldosterone production in 2 adrenal glomerulosa cell models, primary bovine zona glomerulosa and human adrenocortical carcinoma (HAC15) cells, as well as CYP11B2 expression in the HAC15 cells. Although AngII induced calpain activation in these cells, typical calpain inhibitors had no effect on AngII-elicited aldosterone production, suggesting a lack of involvement of classical calpains in this process. However, an inhibitor of the atypical calpain, calpain-10, decreased AngII-induced aldosterone production. Consistent with this result, small interfering RNA (siRNA)-mediated knockdown of calpain-10 inhibited aldosterone production and CYP11B2 expression, whereas adenovirus-mediated overexpression of calpain-10 resulted in increased AngII-induced aldosterone production. Our results indicate that AngII-induced activation of calpain-10 in glomerulosa cells underlies aldosterone production and identify calpain-10 or its downstream pathways as potential targets for the development of drug therapies for the treatment of hypertension.

The effect of pioglitazone on aldosterone and cortisol production in HAC15 human adrenocortical carcinoma cells

Pioglitazone belongs to the class of drugs called thiazolidinediones (TZDs), which are widely used as insulin sensitizers in the treatment of diabetes. A major side effect of TZDs is fluid retention. The steroid hormone aldosterone also promotes sodium and fluid retention; however, the effect of pioglitazone on aldosterone production is controversial. We analyzed the effect of pioglitazone alone and in combination with angiotensin II (AngII) on the late rate-limiting step of adrenocortical steroidogenesis in human adrenocortical carcinoma HAC15 cells. Treatment with pioglitazone for 24h significantly increased the expression of CYP11B2 and enhanced AngII-induced CYP11B2 expression. Despite the observed changes in mRNA levels, pioglitazone significantly inhibited AngII-induced aldosterone production and CYP11B2 protein levels. On the other hand, pioglitazone stimulated the expression of the unfolded protein response (UPR) marker DDIT3, with this effect occurring at early times and inhibitable by the PPARγ antagonist GW9962. The levels of DDIT3 (CHOP) and phospho-eIF2α (Ser51), a UPR-induced event that inhibits protein translation, were also increased. Thus, pioglitazone promotes CYP11B2 expression but nevertheless inhibits aldosterone production in AngII-treated HAC15 cells, likely by blocking global protein translation initiation through DDIT3 and phospho-eIF2α. In contrast, pioglitazone promoted AngII-induced CYP11B1 expression and cortisol production. Since cortisol enhances lipolysis, this result suggests the possibility that PPARs, activated by products of fatty acid oxidation, stimulate cortisol secretion to promote utilization of fatty acids during fasting. In turn, the ability of pioglitazone to stimulate cortisol production could potentially underlie the effects of this drug on fluid retention.

Different effects of progesterone and estradiol on chimeric and wild type aldosterone synthase in vitro

BackgroundFamilial hyperaldosteronism type I (FH-I) is caused by the unequal recombination between the 11beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes, resulting in the generation of a CYP11B1/B2 chimeric gene and abnormal adrenal aldosterone production. Affected patients usually show severe hypertension and an elevated frequency of stroke at a young age. Aldosterone levels rise during pregnancy, yet in pregnant women with FH-1, their hypertensive condition either remains unchanged or may even improve. The purpose of this study was to investigate in vitro whether female sex steroids modulate the activity of chimeric (ASCE) or wild type (ASWT) aldosterone synthase enzymes.MethodsWe designed an in vitro assay using HEK-293 cell line transiently transfected with vectors containing the full ASCE or ASWT cDNAs. Progesterone or estradiol effects on AS enzyme activities were evaluated in transfected cells incubated with deoxycorticosterone (DOC) alone or DOC plus increasing doses of these steroids.ResultsIn our in vitro model, both enzymes showed similar apparent kinetic parameters (Km = 1.191 microM and Vmax = 27.08 microM/24 h for ASCE and Km = 1.163 microM and Vmax = 36.98 microM/24 h for ASWT; p = ns, Mann–Whitney test). Progesterone inhibited aldosterone production by ASCE- and ASWT-transfected cells, while estradiol demonstrated no effect. Progesterone acted as a competitive inhibitor for both enzymes. Molecular modelling studies and binding affinity estimations indicate that progesterone might bind to the substrate site in both ASCE and ASWT, supporting the idea that this steroid could regulate these enzymatic activities and contribute to the decay of aldosterone synthase activity in chimeric gene-positive patients.ConclusionsOur results show an inhibitory action of progesterone in the aldosterone synthesis by chimeric or wild type aldosterone synthase enzymes. This is a novel regulatory mechanism of progesterone action, which could be involved in protecting pregnant women with FH-1 against hypertension. In vitro, both enzymes showed comparable kinetic parameters, but ASWT was more strongly inhibited than ASCE. This study implicates a new role for progesterone in the regulation of aldosterone levels that could contribute, along with other factors, to the maintenance of an adequate aldosterone-progesterone balance in pregnancy.

Integrating Genetics and Genomics in Primary Aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension, with an estimated prevalence of ≈10% in referred patients and 4% in primary care1,2 but as high as 20% in patients with resistant hypertension.3,4 It is characterized by hypertension with low plasma renin and elevated aldosterone that is often seen with hypokalemia. PA occurs as a result of a dysregulation of the normal mechanisms controlling adrenal aldosterone production. The 2 major causes are aldosterone-producing adenomas (APAs) and bilateral adrenal hyperplasia (BAH), also called idiopathic hyperaldosteronism. The early detection of PA has an enormous impact on clinical outcome and survival, given the major cardiovascular adverse effects of aldosterone excess, which are independent of blood pressure,5,6 and predict outcome after surgical treatment.7,8 Patients with PA have a significantly higher risk of nonfatal myocardial infarction, atrial fibrillation, and stroke compared with age-, sex-, and blood pressure–matched essential hypertensives.5 Furthermore, changes in cardiac structure and function9 and partially reversible renal dysfunction10 have been described, whereas the increased occurrence of metabolic abnormalities in patients with PA is still a matter of debate.11,12 Although the 2008 guidelines for the management of PA have been pivotal for homogenizing screening procedures and treatment among specialized centers,13 there remain a few critical issues related to diagnosis, subtype differentiation, and treatment of nonsurgically correctable forms. Reliable diagnostic and prognostic biomarkers are lacking for more sensitive and specific screening, as well as new therapeutic avenues, because medical and/or surgical treatment of PA leads to normotension in only a minority of patients. This may come from a better understanding of the pathogenic mechanisms of the disease, in particular, identification of the genetic and molecular determinants leading to the development of APA and …

Drosha‐dependent miRNA regulate aldosterone synthesis by increasing StAR and HSD3B2 expression

Drosha initiates the production of miRNAs from precursors. To study the functions of miRNA in adrenal steroid production, we knocked down Drosha expression in the HAC15 cell, a subclone of the H295R human adrenocortical cell, using lentiviral vectors to deliver shRNA of Drosha. Drosha protein levels in the infected HAC15 cells were reduced by 74.3% compared to empty vector infected control cells. Drosha knock‐down led to 36.3% and 46.4% suppression of aldosterone production under basal and after angiotensin II (A‐II) stimulated conditions, respectively. Basal and A‐II stimulated StAR and HSD3B2 mRNA expression levels in the Drosha knock‐down cells were also significantly suppressed; expression of other enzymes required for aldosterone synthesis were not altered. In conclusion, suppression of Drosha significantly diminished basal and A‐II stimulated StAR and HSD3B2 mRNA expression and aldosterone production, suggesting that at least one miRNA is essential for aldosterone production.Support: VA Medical Research Funds, NIH HL27255 & HL75321

Benidipine reduces ischemia reperfusion-induced systemic oxidative stress through suppression of aldosterone production in mice

Aldosterone is implicated in the pathogenesis of several cardiovascular diseases, including ischemia reperfusion (I/R) and myocardial infarction, and also causes oxidative stress and inflammation in cardiovascular systems. Benidipine, a long-acting T- and L-type calcium channel blocker, reduces infarct size following myocardial I/R in rabbits. Benidipine also inhibits the production of aldosterone in vitro. However, the precise mechanism of this phenomenon in vivo remains unknown. We therefore evaluated whether benedipine has a beneficial role through the regulation of oxidative stress in myocardial I/R. C57BL/6J mice were subjected to 30 min of left ascending coronary I/R. Benidipine was administered orally at 3 mg kg(-1) daily for 3 weeks without any changes in hemodynamic variables. Benidipine significantly reduced infarction size (13.4±2.5%) compared with controls (25.5±3.6%). Urinary 8-hydroxy-2' deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, increased significantly after I/R. I/R induced increases in 8-OHdG were significantly lower with benidipine. Local myocardial 8-OHdG was also elevated in I/R, but this augmentation was significantly suppressed with benidipine. The plasma aldosterone concentration (PAC) significantly increased 2 days after I/R and remained elevated at least 7 days after I/R. Treatment with benidipine significantly decreased I/R-induced elevation of the PAC. I/R-induced markers of fibrosis in hearts also reduced in benidipine. These results suggest that the administration of benidipine reduces myocardial infarct size as well as systemic oxidative stress after I/R. These phenomena are partially linked to reduced plasma aldosterone levels.

Local renal aldosterone production induces inflammation and matrix formation in kidneys of diabetic rats

Recently, we reported the presence of a local renal aldosterone production. In the present study, we tested the hypothesis that local aldosterone production in the kidney contributes to renal inflammation, matrix formation and albuminuria associated with diabetes. We evaluated changes in renal aldosterone content (RAC), aldosterone synthase expression, nuclear factor kappaB (NFkappaB), tumour necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), transforming growth factor beta (TGFbeta), glomerular fibronectin, collagen type IV and urinary albumin extraction (UAE) in response to the aldosterone synthase inhibitor FAD286. Studies were conducted in adrenalectomized, normoglycaemic (control) or diabetic rats for 14 weeks. The FAD286 was administered during the last 10 weeks of the study. Plasma aldosterone levels were not detectable in any of the study groups. Compared with control rats, diabetic rats had higher levels of RAC by 488% (P < 0.01), NFkappaB by 293% (P < 0.01), TNFalpha by 356% (P < 0.01), IL-6 by 378% (P < 0.01), TGFbeta by 337% (P < 0.01) and UAE by 1122% (P < 0.01), and increased glomerular fibronectin and collagen type IV immunostaining. In diabetic rats, FAD286 reduced RAC (P < 0.01), UAE (P < 0.05), NFkappaB mRNA, TNFalpha mRNA, IL-6 mRNA and TGFbeta mRNA by 51, 41, 41 and 52% and also their proteins and decreased glomerular fibronectin and collagen type IV immunostaining. In conclusion, diabetes increases local aldosterone production in the kidney, which contributes to development of renal inflammation, matrix formation and albuminuria. Inhibition of aldosterone production in the kidney could be helpful in management of diabetic nephropathy.

Blockade of T-type voltage-dependent Ca2+ channels by benidipine, a dihydropyridine calcium channel blocker, inhibits aldosterone production in human adrenocortical cell line NCI-H295R

Benidipine, a long-lasting dihydropyridine calcium channel blocker, is used for treatment of hypertension and angina. Benidipine exerts pleiotropic pharmacological features, such as renoprotective and cardioprotective effects. In pathophysiological conditions, the antidiuretic hormone aldosterone causes development of renal and cardiovascular diseases. In adrenal glomerulosa cells, aldosterone is produced in response to extracellular potassium, which is mainly mediated by T-type voltage-dependent Ca2+ channels. More recently, it has been demonstrated that benidipine inhibits T-type Ca2+ channels in addition to L-type Ca2+ channels. Therefore, effect of calcium channel blockers, including benidipine, on aldosterone production and T-type Ca2+ channels using human adrenocortical cell line NCI-H295R was investigated. Benidipine efficiently inhibited KCl-induced aldosterone production at low concentration (3 and 10 nM), with inhibitory activity more potent than other calcium channel blockers. Patch clamp analysis indicated that benidipine concentration-dependently inhibited T-type Ca2+ currents at 10, 100 and 1000 nM. As for examined calcium channel blockers, inhibitory activity for T-type Ca2+ currents was well correlated with aldosterone production. L-type specific calcium channel blockers calciseptine and nifedipine showed no effect in both assays. These results indicate that inhibition of T-type Ca2+ channels is responsible for inhibition of aldosterone production in NCI-H295R cells. Benidipine efficiently inhibited KCl-induced upregulation of 11-β-hydroxylase mRNA and aldosterone synthase mRNA as well as KCl-induced Ca2+ influx, indicating it as the most likely inhibition mechanism. Benidipine partially inhibited angiotensin II-induced aldosterone production, plus showed additive effects when used in combination with the angiotensin II type I receptor blocker valsartan. Benidipine also partially inhibited angiotensin II-induced upregulation of the above mRNAs and Ca2+ influx inhibitory activities of benidipine for aldosterone production. T-type Ca2+ channels may contribute to additional benefits of this drug for treating renal and cardiovascular diseases, beyond its primary anti-hypertensive effects from blocking L-type Ca2+ channels.

Authors' reply: Nonselective nonsteroidal anti‐inflammatory drugs and increased cardiovascular events: emotional stress could be the explanation

We noted with interest the comments of Dr Sutton [1] that ‘a Google search on aldosterone, stress, mood produced ‘52 000 English or French pages’ in 0.33 s' and that our paper [2] ‘made no mention of stress as a possible cause of increases in aldosterone during NSAID treatment’. Our research [2] was conducted in vitro using human kidney (and liver) microsomes and demonstrated that nonselective NSAIDs inhibit the glucuronidation of aldosterone, predicating an increase in plasma and tissue (renal) aldosterone concentration in vivo. To suggest that stress is an explantion for our in vitro data indicates that Dr Sutton either did not read or understand the article and its conclusions. Although aldosterone synthesis and secretion is regulated principally by angiotensin II, extracellular potassium and ACTH we concur with Dr Sutton that other factors can stimulate or inhibit aldosterone production in vivo including catecholamines, 5-hydroxytryptamine, heparin and vasoactive intestinal polypeptide [3]. Undoubtedly aldosterone is a key cardiovascular hormone contributing to the pathophysiology of heart failure [3] and the development of hypertension [4]. The potential for a synergistic effect of NSAIDs and ‘stress’ on aldosterone concentration in vivo might lead us to conclude that in stressful situations the adage ‘take an aspirin and lie down’ should be revised simply to ‘lie down’!

Aldosterone and magnesium

Magnesium ion (Mg) directly inhibits aldosterone production in rat adrenal glomerulosa cells, while potassium ion directly stimulates aldosterone production. It is reported that Mg shows antihypertensive effect in patients with essential hypertension. Secondary hyperaldosteronism induced by diuretic treatment in patients with congestive heart failure accelerates potassium and magnesium ions' excretion in urine. Diuretic-induced falls in potassium and magnesium ions and aldosterone-induced cardiac fibrosis and remodelling are associated with fatal ventricular arrhythmia. Aldosterone antagonists, such as spironolactone and eplerenone, correct not only potassium deficiency but also magnesium deficiency induced by diuretics. Mg supplementation also may be useful procedure to correct potassium and magnesium deficiency, because Mg itself inhibits aldosterone release from the adrenal glands.

Regulation of adrenocortical cardiotonic steroid production by dopamine and PKA signaling

There is growing evidence that the adrenal cortex is the source of cardiotonic steroid (CS) regulators of sodium, potassium-ATPase (NKA). The control of adrenocortical production CS may play a critical role in mediating renal and vascular responses involved in arterial hypertension. Dopamine (DA) controls renal NKA by direct regulatory phosphorylation and indirectly by modification of aldosterone release. In the present studies, Y-1 adrenocortical cell cultures which have been shown to produce a cardiotonic steroid indistinguishable from the known vertebrate steroid, marinobufagenin (MBG), were treated with various agents to stimulate or antagonize dopamine signaling pathways. We demonstrate that Y-1 cells express both pharmacological types of dopamine receptor (DA1 and DA2). Treatment of Y-1 cells with DA stimulated MBG production in a dose range similar to that shown to inhibit aldosterone production by the adrenal cortex. Experiments with specific DA1 and DA2 receptor agonists and antagonists were performed and allowed us to attribute the DA stimulatory effect to a DA1 type receptor. The DA stimulatory effect on MBG depended on protein kinase A (PKA) and could be blocked by Rp-cAMPS. Although both basal and forskolin-stimulated progesterone production by Y-1 cells were profoundly inhibited in Y-1 cell lines expressing the dominant negative type I regulatory subunit of PKA, both basal and forskolin-stimulated MBG production were demonstrated in these lines. This evidence suggests a possible role of DA1 signaling through camp-mediated activation of the type II PKA holoenzyme in the adrenal cortex.

Control of aldosterone secretion: a model for convergence in cellular signaling pathways.

Aldosterone secretion by glomerulosa cells is stimulated by angiotensin II (ANG II), extracellular K(+), corticotrophin, and several paracrine factors. Electrophysiological, fluorimetric, and molecular biological techniques have significantly clarified the molecular action of these stimuli. The steroidogenic effect of corticotrophin is mediated by adenylyl cyclase, whereas potassium activates voltage-operated Ca(2+) channels. ANG II, bound to AT(1) receptors, acts through the inositol 1,4,5-trisphosphate (IP(3))-Ca(2+)/calmodulin system. All three types of IP(3) receptors are coexpressed, rendering a complex control of Ca(2+) release possible. Ca(2+) release is followed by both capacitative and voltage-activated Ca(2+) influx. ANG II inhibits the background K(+) channel TASK and Na(+)-K(+)-ATPase, and the ensuing depolarization activates T-type (Ca(v)3.2) Ca(2+) channels. Activation of protein kinase C by diacylglycerol (DAG) inhibits aldosterone production, whereas the arachidonate released from DAG in ANG II-stimulated cells is converted by lipoxygenase to 12-hydroxyeicosatetraenoic acid, which may also induce Ca(2+) signaling. Feedback effects and cross-talk of signal-transducing pathways sensitize glomerulosa cells to low-intensity stimuli, such as physiological elevations of [K(+)] (< or =1 mM), ANG II, and ACTH. Ca(2+) signaling is also modified by cell swelling, as well as receptor desensitization, resensitization, and downregulation. Long-term regulation of glomerulosa cells involves cell growth and proliferation and induction of steroidogenic enzymes. Ca(2+), receptor, and nonreceptor tyrosine kinases and mitogen-activated kinases participate in these processes. Ca(2+)- and cAMP-dependent phosphorylation induce the transfer of the steroid precursor cholesterol from the cytoplasm to the inner mitochondrial membrane. Ca(2+) signaling, transferred into the mitochondria, stimulates the reduction of pyridine nucleotides.

Effects of nitric oxide on aldosterone synthesis and nitric oxide synthase activity in glomerulosa cells from bovine adrenal gland.

This study investigated the effects of two NO-releasing agents, diethylenetriamine-NO (deta-NO) and sodium nitroprusside (SNP), on basal, ACTH-, and angiotensin II (AngII)-stimulated aldosterone production in glomerulosa cells from bovine adrenal gland. NO donors inhibited basal and ACTH- or AngII-stimulated aldosterone synthesis in a concentration-dependent manner. Deta-NO and SNP also provoked a concentration-dependent stimulation of cGMP production. However, cGMP was not responsible for the inhibition of aldosterone secretion, because a cGMP analog did not reproduce the inhibitory effect. Moreover, soluble guanylyl cyclase or protein kinase G inhibitors did not revert the inhibitory effect of NO on aldosterone production. NO donors did not modify ACTH-stimulated cAMP production or AngII-stimulated PLC activity stimulation, but inhibited 22[R] hydroxycholesterol- or pregnenolone-stimulated aldosteronogenesis. NO can be synthesized in bovine glomerulosa cells because nitrite production was determined and characterization of NOS activity was also performed. Nitrite accumulation was not modified in the presence of ACTH, AngII, or other factors used to induce iNOS. NOS activity that showed a Michaelis-Menten kinetic was NADPH- and calcium-dependent and was inhibited by two competitive inhibitors, L-NAME and L-NMMA. These results show that NO inhibits aldosterone production in glomerulosa cells acting on P450scc and other P450-dependent steroidogenic enzymes, and these cells display NOS activity suggesting that NO can be produced by constitutive NOS isozymes.