Aldosterone Biosynthesis Research Articles

RF33 | PSAT79 Chronic Activation of Gq-Signaling in the Mouse Adrenal Cortex Disrupts Zonation and Causes Aldosterone Production in the Zona Fasciculata

Abstract Background The mammalian adrenal cortex is composed of the zona glomerulosa (ZG), zona fasciculata (ZF), and in some species the zona reticularis (ZR). Each layer is characterized by a specific steroidogenic enzyme expression pattern that leads to selective production of mineralocorticoids, glucocorticoids or adrenal androgens. ZG-specific expression of cytochrome P450 aldosterone synthase (Cyp11b2) and aldosterone biosynthesis are renin-angiotensin-dependent processes in which the Gq-signaling pathway is activated by angiotensin II (AngII). Gq-signaling can be exogenously activated using Gq-coupled designer receptors exclusively activated by designer drug (GqDREADD) technology. Using transgenic mice with targeted expression of GqDREADD to the adrenal cortex, we previously demonstrated that short-term receptor activation increased adrenal Cyp11b2 and aldosterone production. Herein, we hypothesized that prolonged activation of mouse adrenal cortex Gq-signaling would exacerbate the aldosterone levels and promote the transdifferentiation of ZF cells to ZG cells. Methods Transgenic AS+/Cre hM3Dq (GqDREADD) female mice were engineered through crossing GqDREADD mice with Cyp11b2-regulated Cre recombinase mice. Mice were placed on a high sodium diet (to suppress physiologic renin) and orally provided the GqDREADD ligand, clozapine N-oxide (CNO; n=10) or control (n=8) for 6 weeks followed by collection of blood and adrenals. Mineralocorticoid levels were quantified using LC-MS/MS. Adrenal RNA was isolated and assessed by RNAseq for transcriptomic changes, and RT-qPCR analysis for ZG- and ZF-specific transcript markers, Cyp11b2 and Cyp11b1 (marker of ZF), respectively. Transcripts for β-catenin (Ctnnb1) and axin-2 (Axin2) (markers of the WNT signaling pathway) were also analyzed. Immunofluorescence (IF) studies examined adrenal expression of Cyp11b1 and Cyp11b2 in mice treated for 1 month. Results CNO treatment caused plasma aldosterone to increase 613-fold from 7.9 ±2.5 pg/mL to 4810.7 ±1110.7 pg/mL (p<0.01). Levels of 18-hydroxycorticosterone increased 70-fold from 144.9 ±22.0 to 10143.2 ±1479.6 pg/mL (p<0.0001). Corticosterone levels were unaffected. RT-qPCR analysis showed adrenal Cyp11b2 transcripts to be 224-fold higher (p<0.0001) in the CNO-treated group while a 30% decrease in Cyp11b1 levels was observed (p<0.01) compared to the controls. IF demonstrated hybrid ZF cells aberrantly expressing both Cyp11b2 and Cyp11b1. Within the normal mouse adrenal, the outer ZG exhibits high WNT/β-catenin (Ctnnb1) activation. To determine if chronic CNO treatment impacted overall adrenal WNT signaling, Ctnnb1 and Axin2 (a downstream β-catenin gene target) were examined. Analysis revealed no statistical difference in Ctnnb1 and Axin2 transcript levels in treated mice. RNAseq revealed that 242 transcripts were increased in adrenals from treated mice, while 109 decreased (>3-fold change; p<0.01). Induced transcripts include Cyp11b2 and its transcriptional regulators, Nr4a1 and Nr4a2. Conclusion Overall, these findings demonstrate that chronic Gq-signaling is sufficient to cause ZF cells to produce aldosterone and express Cyp11b2. The findings also suggest that the adrenocortical WNT signaling pathway is not increased by the activation of Gq-signaling. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 12:36 p.m. - 12:41 p.m.

Potassium homeostasis: sensors, mediators, and targets.

Transmembrane potassium (K) gradients are key determinants of membrane potential that can modulate action potentials, control muscle contractility, and influence ion channel and transporter activity.Daily K intake is normally equal to the amount of K in the entire extracellular fluid (ECF) creating a critical challenge - how to maintain ECF [K] and membrane potential in a narrow range during feast and famine.Adaptations to maintain ECF [K] include sensing the K intake, sensing ECF [K] vs. desired set-point and activating mediators that regulate K distribution between ECF and ICF, and regulate renal K excretion. In this focused review, we discuss the basis of these adaptions, including (1) potential mechanisms for rapid feedforward signaling to kidney and muscle after a meal (before a rise in ECF [K]), (2) how skeletal muscles sense and respond to changes in ECF [K], (3) effects of K on aldosterone biosynthesis, and (4) how the kidney responds to changes in ECF [K] to modify K excretion. The concepts of sexual dimorphisms in renal K handling adaptation are introduced, and the molecular mechanisms that can account for the benefits of a K-rich diet to maintain cardiovascular health are discussed. Although the big picture of K homeostasis is becoming more clear, we also highlight significant pieces of the puzzle that remain to be solved, including knowledge gaps in our understanding of initiating signals, sensors and their connection to homeostatic adjustments of ECF [K].

A Novel Somatic Mutation of CACNA1H p.V1937M in Unilateral Primary Hyperaldosteronism.

BackgroundSomatic mutations for excess aldosterone production have been frequently identified as important roles in the pathogenesis of unilateral primary hyperaldosteronism (uPA). Although CACNA1H mutation represents a minor etiology in primary aldosteronism, it plays a significant role in causing uPAs in sporadic cases.ObjectiveTo identify novel somatic CACNA1H mutation in patients with uPA and investigate the pathophysiological, immunohistological, and clinical characteristics of the variant.MethodsWe applied a customized and targeted gene panel next-generation sequencing approach to detect mutations from the uPA cohort in Taiwan Primary Aldosteronism Investigation study group. Information from pre-diagnostic to postoperative data was collected, including past history, medications, blood pressure readings, biochemical data, and image studies. The functional role of the variant was confirmed by in vitro studies, demonstrating aldosterone production in variant-transfected human adrenal cell lines.ResultsWe identified a novel somatic CACNA1H mutation c.5809G>A (p.Val1937Met) in a uPA case. The CACNA1H gene encodes the pore-forming alpha-1H subunit of the voltage-dependent T-type calcium channel Cav3.2. This somatic CACNA1H p.V1937M variant showed excellent clinical and biochemical outcomes after ipsilateral adrenalectomy. The functional effect of somatic CACNA1H p.V1937M variant results in increased CYP11B2 expression and aldosterone biosynthesis in HAC15 cells. A distinct heterogeneous foamy pattern of CYP11B2 and CYP17A1 expression was identified in immunohistological staining, supporting the pathological evidence of aldosterone synthesis.ConclusionsThe somatic mutation of CACNA1H p.V1937M might be a pathogenic driver in aldosterone overproduction. This study provides new insight into the molecular mechanism and disease outcomes of uPA.

DEVELOPMENT OF AN ADRENOCORTICAL CELL MODEL OF CALCIUM SIGNALING MODULATION TO DECIPHER THE MOLECULAR MECHANISMS RESPONSIBLE FOR PRIMARY ALDOSTERONISM

Objective: Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels (KCNJ5, CACNA1D, CACNA1H and CLCN2) and ATPases (ATP1A1 and ATP2B3) defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. Design and method: We have developed an adrenocortical H295R_S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7–5HT3. Mutations have been introduced in the ligand binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7–5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Results: Treatment of α7–5HT3 expressing cells with increasing concentration of PSEM-817 (from 10–9 to 10–5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10–8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10–8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10–7 M, suggesting a dose dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around -60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around -10 mV. Conclusions: This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Development of an adrenocortical cell model of calcium signaling modulation to decipher the molecular mechanisms responsible for primary aldosteronism

Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels and defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. We have developed an adrenocortical H295R-S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7-5HT3. Mutations have been introduced in the ligand-binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7-5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Treatment of α7-5HT3 expressing cells with increasing concentration of PSEM-817 (from 10-9 to 10-5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10-8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10-8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10-7 M, suggesting a dose-dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around −60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around −10 mV. This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

CYP21A2 Gene Expression in a Humanized 21-Hydroxylase Mouse Model Does Not Affect Adrenocortical Morphology and Function.

Steroid 21-hydroxylase is an enzyme of the steroid pathway that is involved in the biosynthesis of cortisol and aldosterone by hydroxylation of 17α-hydroxyprogesterone and progesterone at the C21 position. Mutations in CYP21A2, the gene encoding 21-hydroxylase, cause the most frequent form of the autosomal recessive disorder congenital adrenal hyperplasia (CAH). In this study, we generated a humanized 21-hydroxylase mouse model as the first step to the generation of mutant mice with different CAH-causing mutations. We replaced the mouse Cyp21a1 gene with the human CYP21A2 gene using homologous recombination in combination with CRISPR/Cas9 technique. The aim of this study was to characterize the new humanized mouse model. All results described are related to the homozygous animals in comparison with wild-type mice. We show analogous expression patterns of human 21-hydroxylase by the murine promoter and regulatory elements in comparison to murine 21-hydroxylase in wild-type animals. As expected, no Cyp21a1 transcript was detected in homozygous CYP21A2 adrenal glands. Alterations in adrenal gene expression were observed for Cyp11a1, Star, and Cyb11b1. These differences, however, were not pathological. Outward appearance, viability, growth, and fertility were not affected in the humanized CYP21A2 mice. Plasma steroid levels of corticosterone and aldosterone showed no pathological reduction. In addition, adrenal gland morphology and zonation were similar in both the humanized and the wild-type mice. In conclusion, humanized homozygous CYP21A2 mice developed normally and showed no differences in histological analyses, no reduction in adrenal and gonadal gene expression, or in plasma steroids in comparison with wild-type littermates.

Visualization of calcium channel blockers in human adrenal tissues and their possible effects on steroidogenesis in the patients with primary aldosteronism (PA)

Voltage-gated L-type calcium channel (CaV) isoforms are well known to play pivotal tissue-specific roles not only in vasoconstriction but also in adrenocortical steroidogenesis including aldosterone biosynthesis. Alpha-1C subunit calcium channel (CC) (CaV1.2) is the specific target of anti-hypertensive CC blockers (CCBs) and its Alpha-1D subunit (CaV1.3) regulates depolarization of cell membrane in aldosterone-producing cells. Direct effects of CCBs on aldosterone biosynthesis were previously postulated but their intra-adrenal distribution and effects on steroid production in primary aldosteronism (PA) patients have remained virtually unknown. In this study, frozen tissue specimens constituting tumor, adjacent adrenal gland and peri-adrenal adipose tissues of nine aldosterone-producing adenoma (APA) cases were examined for visualization of amlodipine and aldosterone themselves using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Liquid chromatography-mass spectrometry (LC–MS) analysis was also performed to quantify amlodipine and 17 adrenal steroids in those cases above and compared the findings with immunohistochemical analysis of steroidogenic enzymes and calcium channels (CaV1.2 and CaV1.3). Effects of amlodipine on mRNA level of aldosterone biosynthetic enzymes were also explored using human adrenocortical carcinoma cell line (H295R). Amlodipine-specific peak (m/z 407.1 > 318.1) was detected only in amlodipine treated cases. Accumulation of amlodipine was marked in adrenal cortex compared to peri-adrenal adipose tissues but not significantly different between APA tumors and adjacent adrenal glands, which was subsequently confirmed by LC–MS quantification. Intra-adrenal distribution of amlodipine was generally consistent with that of CCs. In addition, quantitative steroid profiles using LC–MS and in vitro study demonstrated the lower HSD3B activities in amlodipine treated cases. Immunoreactivity of CaV1.2 and HSD3B2 were also correlated. We report the first demonstration of specific visualization of amlodipine in human adrenal tissues by MALDI-MSI. Marked amlodipine accumulation in the adrenal glands suggested its direct effects on steroidogenesis in PA patients, possibly targeting on CaV1.2 and suppressing HSD3B activity.

Biological sex modifies aldosterone's secretion at a cellular level.

Inconsistencies have been reported on the effect of sex on aldosterone (ALDO) levels leading to clinical confusion. The reasons for these inconsistencies are uncertain but include estrogen and/or its receptor modulating target gene responses to mineralocorticoid receptor activation and ALDO secretagogues' levels. This study's goal was to determine whether ALDO's biosynthesis also differed by sex. Two approaches were used. First, plasma renin activity and aldosterone were measured in rats. Both were significantly higher in males. Secondly, using rat zona glomerulosa (ZG) cells, we assessed three ex vivo areas: (1) activity/levels of early steps in ALDO's biosynthesis (StAR and CYP11A1); (2) activity/levels of a late step (CYP11B2); and (3) the status of the mineralocorticoid receptor (MR)-mediated, ultrashort feedback loop. Females had higher expression of CYP11A1 and StAR and increased CYP11A1 activity (increased pregnenolone/corticosterone levels) but did not differ in CYP11B2 expression or activity (ALDO levels). Activating the ZG's MR (thereby activating the ultrashort feedback loop) reduced CYP11B2's activity similarly in both sexes. Exvivo, these molecular effects were accompanied, in females, by lower ALDO basally but higher ALDO with angiotensin II stimulation. In conclusion, we documented that not only was there a sex-mediated difference in the activity of ALDO's biosynthesis but also these differences at the molecular level help explain the variable reports on ALDO's circulating levels. Basally, both in vivo and ex vivo, males had higher ALDO levels, likely secondary to higher ALDO secretagogue levels. However, in response to acute stimulation, ALDO levels are higher in females because of the greater levels and/or activity of their StAR/CYP11A1.

Eplerenone–A novel Mineralocorticoid receptor antagonist for the clinical application

Aldosterone is produced from the zona glomerulosa of the adrenal cortex in the adrenal gland, which is main mineralocorticoid hormone. Upon binding the mineralocorticoid receptor, it regulates sodium and potassium absorption, secretion, and retention, thereby maintaining stable blood pressure levels. However, abnormal aldosterone synthesis and metabolism could be pathogenic and contribute to multiple organ fibrosis and structural remodeling. For instance, hyperaldosteronemia is critically involved in the development of hypertension, heart failure (HF), and renal disease. Therefore, mineralocorticoid receptor antagonists (MRAs) that could fight against high concentrations of aldosterone play an important role in the treatment of diseases caused by hyperaldosteronism. Eplerenone, as a novel selective MRA, has better therapeutic efficiency and fewer side effects comparing to the classical drug spironolactone. In this review, first, we go through the biosynthesis and biologic properties of aldosterone and then introduce how hyperaldosteronemia facilitates certain diseases progression. Aldosterone is an important part of the renin-angiotensin-aldosterone system (RAAS), which plays a crucial role in essential hypertension, atrial tremor, and tissue fibrosis. Second, we summarize current evidence of clinical application of eplerenone in the control of primary aldosteronism, hypertension, HF, nephropathy, insulin resistance, and liver damage. It is exciting that many studies have shown that the use of eplerenone in these diseases yields good outcomes accompanied with fewer adverse effects such as hyperkalemia, metabolic acidosis, hypotension, and acute kidney failure, which indicates that eplerenone is a strong and safe MRA and inhibitor of RAAS system. This review focuses on therapeutic efficacy and disadvantages of eplerenone when treating a series of different diseases. Ultimately, we hope to shed light on future therapeutic strategies in diseases associated with hyperaldosteronemia.

CCN2 (Cellular Communication Network Factor 2) Deletion Alters Vascular Integrity and Function Predisposing to Aneurysm Formation.

CCN2 (cellular communication network factor 2) is a matricellular protein involved in cell communication and microenvironmental signaling responses. CCN2 is known to be overexpressed in several cardiovascular diseases, but its role is not completely understood. Here, CCN2 involvement in aortic wall homeostasis and response to vascular injury was investigated in inducible <i>Ccn2</i>-deficient mice, with induction of vascular damage by infusion of Ang II (angiotensin II; 15 days), which is known to upregulate CCN2 expression in the aorta. Ang II infusion in CCN2-silenced mice lead to 60% mortality within 10 days due to rapid development and rupture of aortic aneurysms, as evidenced by magnetic resonance imaging, echography, and histological examination. <i>Ccn2</i> deletion decreased systolic blood pressure and caused aortic structural and functional changes, including elastin layer disruption, smooth muscle cell alterations, augmented distensibility, and increased metalloproteinase activity, which were aggravated by Ang II administration. Gene ontology analysis of RNA sequencing data identified aldosterone biosynthesis as one of the most enriched terms in CCN2-deficient aortas. Consistently, treatment with the mineralocorticoid receptor antagonist spironolactone before and during Ang II infusion reduced aneurysm formation and mortality, underscoring the importance of the aldosterone pathway in Ang II-induced aorta pathology. CCN2 is critically involved in the functional and structural homeostasis of the aorta and in maintenance of its integrity under Ang II-induced stress, at least, in part, by disruption of the aldosterone pathway. Thus, this study opens new avenues to future studies in disorders associated to vascular pathologies.

Cis-bifenthrin inhibits cortisol and aldosterone biosynthesis in human adrenocortical H295R cells via cAMP signaling cascade

Cis-bifenthrin (cis-BF) is a common-used pyrethroid insecticide frequently detected in environmental and biological matrices. Mounting evidence highlights the endocrine disrupting effects of cis-BF due to anti-estrogenic or anti-androgenic activity. However, little is known about the exposure effects of cis-BF on adrenal cortex function. In this study, effects of cis-BF on biosynthesis of adrenal steroids, as well as the potential mechanisms were investigated in human adrenocortical carcinoma (H295R) cells. Cis-BF decreased basal production levels of cortisol and aldosterone, as well as cAMP-induced production of cortisol. Both he basal and cAMP-stimulated transcriptional levels of several steroidogenic genes were significantly down-regulated by cis-BF. As an important rate-limiting enzyme in steroidogenesis, the protein level of StAR was prohibited by cis-BF on both basal and cAMP-induced conditions. Intracellular level of cAMP was significantly reduced by cis-BF. Overall, these data suggest that cis-BF may inhibit the biosynthesis of cortisol and aldosterone via disrupting cAMP signaling cascade.

Colocalization of Wnt/β-Catenin and ACTH Signaling Pathways and Paracrine Regulation in Aldosterone-producing Adenoma.

Aldosterone-producing adenomas (APAs) are a common cause of primary aldosteronism (PA). Despite the discovery of somatic mutations in APA and the characterization of multiple factors regulating adrenal differentiation and function, the sequence of events leading to APA formation remains to be determined. We investigated the role of Wnt/β-catenin and adrenocorticotropin signaling, as well as elements of paracrine regulation of aldosterone biosynthesis in adrenals with APA and their relationship to intratumoral heterogeneity and mutational status. We analyzed the expression of aldosterone-synthase (CYP11B2), CYP17A1, β-catenin, melanocortin type 2 receptor (MC2R), phosphorlyated cAMP response element-binding protein (pCREB), tryptase, S100, CD34 by multiplex immunofluorescence, and immunohistochemistry-guided reverse transcription-quantitative polymerase chain reaction. Eleven adrenals with APA and 1 with micronodular hyperplasia from patients with PA were analyzed. Main outcome measures included localization of CYP11B2, CYP17A1, β-catenin, MC2R, pCREB, tryptase, S100, CD34 in APA and aldosterone-producing cell clusters (APCCs). Immunofluorescence revealed abundant mast cells and a dense vascular network in APA, independent of mutational status. Within APA, mast cells were localized in areas expressing CYP11B2 and were rarely colocalized with nerve fibers, suggesting that their degranulation is not controlled by innervation. In these same areas, ß-catenin was activated, suggesting a zona glomerulosa cell identity. In heterogeneous APA with KCNJ5 mutations, MC2R and vascular endothelial growth factor A expression was higher in areas expressing CYP11B2. A similar pattern was observed in APCC, with high expression of CYP11B2, activated β-catenin, and numerous mast cells. Our results suggest that aldosterone-producing structures in adrenals with APA share common molecular characteristics and cellular environment, despite different mutation status, suggesting common developmental mechanisms.

Aldosterone and Primary Aldosteronism: Star Performers in Hypertension Research

Aldosterone and Primary Aldosteronism: Star Performers in Hypertension Research

Interaction Between Wnt/β-catenin and ACTH Signaling Pathways and Paracrine Regulation in Aldosterone Producing Adenoma

Primary aldosteronism (PA) is the most frequent form of secondary arterial hypertension and is caused in the majority of cases by an aldosterone producing adenoma (APA) or bilateral adrenal hyperplasia. Different somatic mutations have been identified in APA and in other aldosterone producing structures, which can be distinct within the same adrenal, suggesting multiple mechanisms underlying APA development. Also, APA show important cellular and molecular heterogeneity which may be due to interaction of different signaling pathways involved in adrenal cortex cell differentiation and function. The aim of this study was to investigate the role of Wnt/β-catenin and ACTH signaling as well as elements of paracrine regulation of aldosterone biosynthesis and vascularization in the development of APA and aldosterone producing cell clusters (APCC) and their relationship with intratumoral heterogeneity and mutational status. We performed immunohistochemistry and multiplex immunofluorescence (CYP11B2, CYP17A1, β-catenin, MC2R, pCREB, Tryptase, S100, CD34) multispectral image analysis on 11 adrenals with APA and one with micronodular hyperplasia from patients with PA. CYP11B2 (aldosterone synthase) IHC guided RT-qPCR was performed on RNA extracted from formalin-fixed paraffin-embedded tissues in 7 adrenals. Multiplex immunofluorescence revealed high abundance of tryptase positive mast cells and a dense vascular component in APA, which were independent of the mutational status. Within APA, mast cells were mainly localized in zones expressing CYP11B2, but not in areas expressing CYP17A1, and were rarely colocalized with nerve fibers, suggesting that their activity is not controlled by innervation. In cells expressing aldosterone synthase, β-catenin was activated, i.e. shows nuclear and/or cytoplasmic staining, features suggestive of a zona glomerulosa cell identity; MC2R was found at the cell membrane. Expression of MC2R mRNA was observed at different levels in APA, similar to expression of MRAP and VEGFA; MRAP2 was not detected. Within heterogeneous APA carrying KCNJ5 mutations, both MC2R and VEGFA expression was higher in areas expressing CYP11B2. Remarkably, this pattern was maintained in APCC, where cells show high CYP11B2 expression, together with activated β-catenin, independently of the mutation status. In addition, a high number of mast cells was detected around APCC, with a reorganization of the capillaries around the CYP11B2 positive cells. Our results suggest that aldosterone producing structures in adrenals with APA share common molecular characteristics and cellular environment, despite different mutation status. Mast cells appear to be closely associated with cells expressing aldosterone synthase, both in APA and APCC, and their role in regulating aldosterone biosynthesis in the context of somatic mutations in PA remains to be established.

Intracellular Cholesterol Metabolism in Aldosterone-Producing Adenoma.~A Possible Association With Cellular Morphometry and Genotype~

Introduction: Primary aldosteronism (PA) is the most common cause of secondary hypertension. More than 70% of APAs have been reported to have KCNJ5 somatic mutation in Asian countiries. Patients with KCNJ5 mutated APAs generally harbor high plasma aldosterone concentration (PAC), and are mainly composed of clear tumor cells containing abundant lipid droplets. However, an association among intracellular cholesterol metabolism, morphological features and genotypes in tumor cells has remained virtually unknown.[Materials and methods]Three cholesterol receptors (SR-B1, LDL-R, VLDL-R) were immunolocakized in 25 APA cases (KCNJ5 mt: n= 15, WT: n=10) who underwent adrenalectomy at Tohoku University Hospital. Image analysis software (HALO, India Labs) was used to quantitatively analyze the intracellular localization and immunoreactivity and expored their correlation with genotype and clinical factors.[Results]LDL-R immunoreactivity was significantly lower in KCNJ5 mt group than WT group (P = 0.0369). In KCNJ5 mt group, a significant correlation was detected between LDL-R immunoreactivity and CYP11B2 (Aldosterone synthase), (P = 0.0271, ρ = 0.5684) but not in WT group. In addition, LDL-R immunoreactivity was significantly inversely correlated with tumor size (P = 0.0142, ρ = -0.6176) and PAC (P = <0.001, ρ = -0.7179) in mt group as well as in whole APA cases.[Discussion]This is the first study to compare cholesterol receptor expression profiles with morphological tumor cell subtype, genotype, and clinical data in APAs. Results indicated that KCNJ5 mt APAabundantly stored cholesterol ester in their cytoplasm and cholesterol uptake was less activated, resulting In rather efficient aldosterone biosynthesis in tumor cells. In addition, a significant correlation was detected between LDL-R and CYP11B2 with the abundant localization of LDL-R in tumor cells. Therefore, LDL-R could be a predominant resource of plasma lipoprotein uptake in aldosterone-producing tumor cells, especially for KCNJ5mt APAs.

Modulation of Calcium Signaling by Chemogenetic Tools to Elucidate the Pathogenesis of Primary Aldosteronism

Primary aldosteronism (PA) is the most frequent form of secondary arterial hypertension. The identification of germline or somatic mutations in different genes coding for ion channels (KCNJ5, CACNA1D, CACNA1H and CLCN2) and ATPases (ATP1A1 and ATP2B3) defines PA as a channelopathy. These mutations promote increased intracellular calcium concentrations and activation of calcium signaling, the main trigger for aldosterone biosynthesis.The aim of our study was to elucidate the mechanisms underlying the development of PA by modulating calcium signaling using chemogenetic tools.We have generated two different adrenocortical H295R_S2 cell lines stably expressing different chimeric ion channels generated by fusing the mutated extracellular ligand binding domain of the α7 nicotinic acetylcholine receptor to the ion pore domain of large Cys-loop receptor ion channel family; these receptors constitute PSAM (Pharmacologically Selective Actuator Modules). The mutations introduced in the ligand-binding domain allow to use synthetic ligands, PSEM (Pharmacologically Selective Effector Molecules) to activate the PSAM. We used two different PSAM: the chimeric receptor α7-5HT3 or a mutated acetylcholine receptor nAchR, allowing respectively modulation of sodium or calcium entry into the cells in response to the specific PSEM: Varenicline for α7-5HT3 or Compound 9S for mutated nAChR. The cells lines were characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production and steroidogenic gene expression.Cells expressing α7-5HT3 treated for 24h with increasing concentrations of Varenicline (10–9 to 10-5M) showed increased intracellular calcium concentrations and an increase in expression of steroidogenic genes such as StAR CYP17A1, CYP21A2 and CYP11B2. Cell proliferation was not affected. Calcium entry into cells expressing the mutated nAChR receptor treated for 24h with increasing concentrations of Compound 9S (10–9 to 10-5M) induced an increase in expression of steroidogenic genes such as StAR, CYP21A2 and HSD3B2, but not CYP11B2. Similarly to the results obtained in cells expressing α7-5HT3, cell proliferation was unaffected in response to Compound 9S.These cell lines, in which we can modulate the intracellular calcium concentration « on demand », are a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Structural and Functional Insights into Aldosterone Biosynthesis

The steroid hormone aldosterone synthesized by cytochrome P450 11B2 (CYP11B2, aldosterone synthase) regulates blood pressure and mineral homeostasis. For aldosterone synthesis, CYP11B2 requires the small iron/sulfur cluster protein adrenodoxin (Adx) which provides electrons for the reaction. Overproduction of aldosterone leads to primary aldosteronism, the most common form of secondary hypertension with very limited treatment options. Herein a structure/function approach was used to examine the role of adrenodoxin as allosteric modulator of aldosterone biosynthesis and to define the structural basis for CYP11B2 interaction with adrenodoxin. Studies revealed that adrenodoxin binding on the CYP11B2 surface increases the affinity to its physiological substrate 11-deoxycorticosterone in the buried active site up to 5.5-fold. Kinetic studies showed an increase of CYP11B2 turnover and a decrease in Km values at higher adrenodoxin concentrations. When performing inhibition studies, higher concentrations of adrenodoxin enhance the inhibitory effect of the antihypertensive drug osilodrostat. To elucidate the structural basis for aldosterone biosynthesis, an adrenodoxin/CYP11B2 fusion protein was generated to examine the protein/protein interaction. An X-ray structure of this complex with the breast cancer drug fadrozole was obtained in high resolution and identified the adrenodoxin binding site on the proximal face of CYP11B2 and specific electrostatic interactions. Overall, the studies presented here improve our understanding of the aldosterone biosynthetic system and the impact of adrenodoxin on CYP11B2 interaction with substrates and drugs. This information can be exploited for an orthogonal approach to treat primary aldosteronism and associated cardiac disease.

ACE2 AND ANGIOTENSIN-(1-7) AND ALDOSTERONE BIOSYNTHESIS IN HUMAN ADRENOCORTICAL TISSUES

Objective: The angiotensin converting enzyme 2 (ACE2) and its product angiotensin-(1–7) (Ang-(1–7)) were suggested to play cardiovascular protective effects via angiotensin type 2 (AT2R), MasR and alamandine receptors. Whether this involves blunting of aldosterone biosynthesis in humans remains unknown. Design and method: We quantified ACE2 mRNA in human aldosterone-producing adenoma (APA) and APA-adjacent tissue obtained ex vivo from primary aldosteronism (PA) patients with real-time and ddPCR. We also investigated the effects of Ang-(1–7) and diminazene aceturate (DIZE), a putative ACE2 activator, on aldosterone synthase (CYP11B2) and 11b-hydroxylase (CYP11B1) as proxy for aldosterone and cortisol secretion, respectively, in the absence and presence of the AT1R antagonist irbesartan, or the MasR antagonist A779. Results: We detected ACE2 mRNA at higher amounts in APA-adjacent tissue than in APA. Functional in vitro studies with LC-MS showed active conversion of Ang II into Ang 1–7, albeit at low level, through ACE-2-independent mechanisms. At [10–8 M] Ang-(1–7) did not affect CYP11B1 and CYP11B2 gene transcripts, while at high concentration [10–6 M] it increased both mRNAs (p &lt; 0.001 vs vehicle) through an AT1-R-mediated mechanism as these stimulatory effects were abolished by irbesartan. To investigate if Ang-(1–7) could blunt aldosterone production when CYP11B2 is upregulated, we exposed H295 cells to [10–8 M] Ang II and found that Ang-(1–7) did not blunt Ang II-induced expression of CYP11B1 and CYP11B2 mRNA. Moreover, we discovered that [10–7 M] DIZE increased ACE2 mRNA by 1.5 fold from baseline (p = 0.01) but left CYP11B1 or CYP11B2 mRNA levels unaffected. DIZE did not blunt the AT1R mediated stimulatory effect of [10–6 M] Ang-(1–7) on CYP11B1 and CYP11B2 mRNA. Conclusions: Thus, although Ang-(1–7) can be locally generated at low levels and MasR and ACE2 mRNAs are detectable in APA and APA-adjacent tissue, neither Ang-(1–7) nor DIZE were able to blunt Ang II-mediated aldosterone synthase expression. Collectively these results suggest that the ACE2/Ang-(1–7)/MasR axis is unlikely to counteract aldosterone biosynthesis under conditions of enhanced aldosterone secretion as PA and heart failure.

ALDOSTERONE CONTRIBUTES TO SYSTOLIC BLOOD PRESSURE ELEVATION DURING REST TIME IN MALE MICE INDUCIBLY OVEREXPRESSING HUMAN ENDOTHELIN-1 IN ENDOTHELIUM

Objective: The mechanisms of blood pressure (BP) regulation by endothelin (ET)-1 produced by endothelial cells (ECs) are complex and remain unclear. Transgenic mice with tamoxifen-inducible EC-restricted human ET-1 overexpression (ieET-1) exhibited BP elevation 3 months after induction. ET-1 has been shown to stimulate the release of aldosterone from adrenal cortex (AC). Whether aldosterone plays a role in EC ET-1 overexpression-induced BP elevation and vascular injury is still unknown. Design and method: Nine to 12-week-old male ieET-1 mice and control ieCre mice expressing a tamoxifen-inducible Cre recombinase under the control of EC-specific Tie2 promoter were treated with tamoxifen (1 mg/kg/day, SC) for 5 days and studied 3 months later. A set of mice was treated with eplerenone (100 mg/kg/day, PO), a mineralocorticoid receptor antagonist, or the ETA receptor blocker atrasentan (100 mg/kg/day) during the last 2 weeks of the study. BP was measured by telemetry and mesenteric artery function and remodeling by pressurized myography. Plasma aldosterone levels were measured by ELISA. The expression of genes involved in aldosterone biosynthesis was determined by reverse transcription-quantitative PCR in AC. CYP11B2 expression was determined in AC by immunofluorescence. Results: Plasma aldosterone levels were increased in ieET-1 vs. ieCre mice (1.21 ± 0.14 vs. 0.70 ± 0.09 ng/mL, P &lt; 0.05), which was reversed by atrasentan. Cyp11b2 (aldosterone synthase), Hsd3b6 (hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 6) and Cry1 (core-clock component cryptochrome 1) mRNA expression was decreased respectively by 50%, 39% and 31% in AC, and CYP11B2 protein expression was decreased by 51% in adrenal glomerulosa of ieET-1 vs. ieCre mice (P &lt; 0.05). Two week eplerenone treatment reduced systolic BP by 10 mm Hg in ieET-1 mice during rest time (last 3 days, P &lt; 0.05). Eplerenone abrogated the enhanced sensitivity of mesenteric arteries to contraction by norepinephrine in ieET-1 mice (P &lt; 0.05), increased the sensitivity of endothelium-independent relaxation responses to sodium nitroprusside in ieET-1 mice (P &lt; 0.05). Mesenteric artery media/lumen was reduced in eplerenone-treated ieET-1 vs. ieET-1 and ieCre mice (P &lt; 0.05). Conclusions: These results demonstrate that aldosterone contributes to human EC ET-1 overexpression-induced BP elevation and vascular remodeling and norepinephrine sensitivity.

Codonopsis Radix modulates water and electrolytes homeostasis in mice

Codonopsis Radix is a traditional Chinese medicine best known for its effects in treating digestive, cardiovascular, immunological and hematopoitic diseases. It also appears in the traditional Chinese medical prescriptions against ascites. However, the physiological effect and molecular mechanism of Codonopsis Radix in water and electrolytes homeostasis have not been well studied. We found that Codonopsis Radix decoction increased water intake and the urine volume, but decreased food intake in mice. The treatment significantly reduced angiotensin II receptor (AT1R) transcription and serum aldosterone level in animals, suggested perturbed function of renin-angiotensin system. RNAseq analysis of Codonopsis Radix treated NCI–H295R cells detected suppressed AT1R, SP1, and TEF transcription as well. Thus, Codonopsis Radix may regulate water and electrolytes homeostasis by affecting AT1R expression and aldosterone biosynthesis, possibly through downregulating SP1 and TEF transcription.