Irisin mitigates salt-sensitive hypertension via regulating renal AMPK-Rac1 pathway.

BACKGROUND: Irisin, as a myokine, plays a protective role against cardiovascular disease, including myocardial infarction, atherosclerosis and hypertension. However, whether irisin attenuates salt-sensitive hypertension and the related underlying mechanisms is unknown. METHODS: Male Dahl salt-resistant (DSR) and Dahl salt-sensitive (DSS) (12 weeks) rats were fed a high salt diet (8% NaCl) with or without irisin treatment by intraperitoneal injection for 8 weeks. RESULTS: Compared with DSR rats, DSS rats showed higher systolic blood pressure (SBP), impaired natriuresis and diuresis and renal dysfunction. In addition, it was accompanied by downregulation of renal p-AMPKα and upregulation of renal RAC1 and nuclear mineralocorticoid receptor (MR). Irisin intervention could significantly up-regulated renal p-AMPKα level and down-regulated renal RAC1-MR signal, thereby improving renal sodium excretion and renal function, and ultimately reducing blood pressure in DSS rats. Ex vivo treatment with irisin reduced the expression of RAC1 and nuclear MR in primary renal distal convoluted tubule cells from DSS rats and the effects of irisin were abolished by cotreatment of compound C (AMPK inhibitor), indicating that the regulation of RAC1-MR signals by irisin depended on the activation of AMPK. CONCLUSIONS: Irisin administration lowered salt-sensitive hypertension through regulating RAC1-MR signaling via activation of AMPK, which may be a promising therapeutic approach for salt-sensitive hypertension.

Mineralocorticoid Receptor Blocker Prevents Mineralocorticoid Receptor-Mediated Inflammation by Modulating Transcriptional Activity of Mineralocorticoid Receptor-p65-Signal Transducer and Activator of Transcription 3 Complex.

BACKGROUND: Mineralocorticoid receptor (MR) induces cardiac inflammation cooperatively with nuclear factor-κB and signal transducer and activator of transcription 3 (STAT3); MR blockers exert anti-inflammatory effects. However, the underlying mechanism remains unclear. We investigated the anti-inflammatory effect of esaxerenone, a novel MR blocker, in experimental myocardial infarction (MI) and its underlying mechanisms. METHODS AND RESULTS: Male C57BL/6J mice subjected to ligation of the left anterior descending artery were randomly assigned to either the vehicle or esaxerenone group. Esaxerenone was provided with a regular chow diet. The mice were euthanized at either 4 or 15 days after MI. Cardiac function, fibrosis, and inflammation were evaluated. Esaxerenone significantly improved cardiac function and attenuated cardiac fibrosis at 15 days after MI independently of its antihypertensive effect. Inflammatory cell infiltration, inflammatory-related gene expression, and elevated serum interleukin-6 levels at 4 days after MI were significantly attenuated by esaxerenone. In vitro experiments using mouse macrophage-like cell line RAW264.7 cells demonstrated that esaxerenone- and spironolactone-attenuated lipopolysaccharide-induced interleukin-6 expression without altering the posttranslational modification and nuclear translocation of p65 and STAT3. Immunoprecipitation assays revealed that MR interacted with both p65 and STAT3 and enhanced the p65-STAT3 interaction, leading to a subsequent increase in interleukin-6 promoter activity, which was reversed by esaxerenone. CONCLUSIONS: Esaxerenone ameliorated postinfarct remodeling in experimental MI through its anti-inflammatory properties exerted by modulating the transcriptional activity of the MR-p65-STAT3 complex. These results suggest that the MR-p65-STAT3 complex can be a novel therapeutic target for treating MI.

Functional redundancy between glucocorticoid and mineralocorticoid receptors in mature corticotropin-releasing hormone neurons protects from obesity.

OBJECTIVE: Here, we aimed to investigate the role of glucocorticoid and mineralocorticoid receptors (GRs and MRs, respectively) in the regulation of energy homeostasis. METHODS: We used three mouse models with simultaneous deletion of GRs and MRs in either forebrain neurons, the paraventricular nucleus, or corticotropin-releasing hormone (CRH) neurons and compared them with wild-type controls or isolated knockout groups. In addition to body weight, food intake, energy expenditure, insulin sensitivity, fat/lean mass distribution, and plasma corticosterone levels, we also performed transcriptomic analysis of CRH neurons and assessed their response to melanocortinergic stimulation. RESULTS: Similar to global double-knockout models, deletion of GRs and MRs specifically in mature CRH neurons resulted in obesity. Importantly, the latter was accompanied by insulin resistance, but not increased plasma corticosterone levels. Transcriptomic analysis of these neurons revealed upregulation of several genes involved in postsynaptic signal transduction, including the Ptk2b gene, which encodes proline-rich tyrosine kinase 2. Knockout of both nuclear receptors leads to upregulation of Ptk2b in CRH neurons, which results in their diminished responsiveness to melanocortinergic stimulation. CONCLUSIONS: Our data demonstrate the functional redundancy of GRs and MRs in CRH neurons to maintain energy homeostasis and prevent obesity. Simultaneous targeting of both receptors might represent an unprecedented approach to counteract obesity.

Early metabolic and transcriptomic regulation in rainbow trout (Oncorhynchus mykiss) liver by 11-deoxycorticosterone through two corticosteroid receptors pathways.

Cortisol hormone is considered the main corticosteroid in fish stress, acting through glucocorticoid (GR) or mineralocorticoid (MR) receptor. The 11-deoxycorticosterone (DOC) corticosteroid is also secreted during stress and could complement the cortisol effects, but this still not fully understood. Hence, we evaluated the early transcriptomic response of rainbow trout (Oncorhynchus mykiss) liver by DOC through GR or MR. Thirty juvenile trout were pretreated with an inhibitor of endogenous cortisol synthesis (metyrapone) by intraperitoneal injection in presence or absence of GR (mifepristone) and MR (eplerenone) pharmacological antagonists for one hour. Then, fish were treated with a physiological DOC dose or vehicle (DMSO-PBS1X as control) for three hours (n = 5 per group). We measured several metabolic parameters in plasma, together with the liver glycogen content. Additionally, we constructed cDNA libraries from liver of each group, sequenced by HiseqX Illumina technology and then analyzed by RNA-seq. Plasma pyruvate and cholesterol levels decreased in DOC-administered fish and only reversed by eplerenone. Meanwhile, DOC increased liver glycogen contents depending on both corticosteroid receptor pathways. RNA-seq analysis revealed differential expressed transcripts induced by DOC through GR (448) and MR (1901). The enriched biological processes to both were mainly related to stress response, protein metabolism, innate immune response and carbohydrates metabolism. Finally, we selected sixteen genes from enriched biological process for qPCR validation, presenting a high Pearson correlation (0.8734 average). These results describe novel physiological effects of DOC related to early metabolic and transcriptomic responses in fish liver and differentially modulated by MR and GR.

Mineralocorticoid Receptor Signaling in Peripheral Blood Cells in Patients with Multiple Sclerosis.

Multiple sclerosis (MS) is associated with alterations in neuroendocrine function, primarily the hypothalamic-pituitary-adrenal axis, including lower expression of the glucocorticoid receptor (GR) and its target genes in peripheral blood mononuclear cells (PBMC) or full blood. We previously found reduced mineralocorticoid receptor (MR) expression in MS patients' peripheral blood. MS is being treated with a widening variety of disease-modifying treatments (DMT), some of which have similar efficacy but different mechanisms of action; body-fluid biomarkers to support the choice of the optimal initial DMT and/or to indicate an unsatisfactory response before clinical activity are unavailable. Using cell culture of volunteers' PBMCs and subsequent gene expression analysis (microarray and qPCR validation), we identified the mRNA expression of OTUD1 to represent MR signaling. The MR and MR target gene expression levels were then measured in full blood samples. In 119 MS (or CIS) patients, the expression of both MR and OTUD1 was lower than in 42 controls. The expression pattern was related to treatment, with the MR expression being particularly low in patients treated with fingolimod. While MR signaling may be involved in the therapeutic effects of some disease-modifying treatments, MR and OTUD1 expression can complement the neuroendocrine assessment of MS disease course. If confirmed, such assessment may support clinical decision-making.

Clinical Properties and Non-Clinical Testing of Mineralocorticoid Receptor Antagonists in In Vitro Cell Models.

Mineralocorticoid receptor antagonists (MRAs) are one of the renin-angiotensin-aldosterone system inhibitors widely used in clinical practice. While spironolactone and eplerenone have a long-standing profile in clinical medicine, finerenone is a novel agent within the MRA class. It has a higher specificity for mineralocorticoid receptors, eliciting less pronounced adverse effects. Although approved for clinical use in patients with chronic kidney disease and heart failure, intensive non-clinical research aims to further elucidate its mechanism of action, including dose-related selectivity. Within the field, animal models remain the gold standard for non-clinical testing of drug pharmacological and toxicological properties. Their role, however, has been challenged by recent advances in in vitro models, mainly through sophisticated analytical tools and developments in data analysis. Currently, in vitro models are gaining momentum as possible platforms for advanced pharmacological and pathophysiological studies. This article focuses on past, current, and possibly future in vitro cell models research with clinically relevant MRAs.

Aldosterone, mitochondria and regulation of cardiovascular metabolic disease.

Aldosterone is a mineralocorticoid hormone involved in controlling electrolyte balance, blood pressure, and cellular signaling. It plays a pivotal role in cardiovascular and metabolic physiology. Excess aldosterone activates mineralocorticoid receptors, leading to subsequent inflammatory responses, increased oxidative stress, and tissue remodeling. Various mechanisms have been reported to link aldosterone with cardiovascular and metabolic diseases. However, mitochondria, responsible for energy generation through oxidative phosphorylation, have received less attention regarding their potential role in aldosterone-related pathogenesis. Excess aldosterone leads to mitochondrial dysfunction, and this may play a role in the development of cardiovascular and metabolic diseases. Aldosterone has the potential to affect mitochondrial structure, function, and dynamic processes, such as mitochondrial fusion and fission. In addition, aldosterone has been associated with the suppression of mitochondrial DNA, mitochondria-specific proteins, and ATP production in the myocardium through mineralocorticoid receptor, nicotinamide adenine dinucleotide phosphate oxidase, and reactive oxygen species pathways. In this review, we explore the mechanisms underlying aldosterone-induced cardiovascular and metabolic mitochondrial dysfunction, including mineralocorticoid receptor activation and subsequent inflammatory responses, as well as increased oxidative stress. Furthermore, we review potential therapeutic targets aimed at restoring mitochondrial function in the context of aldosterone-associated pathologies. Understanding these mechanisms is vital, as it offers insights into novel therapeutic strategies to mitigate the impact of aldosterone-induced mitochondrial dysfunction, thereby potentially improving the outcomes of individuals affected by cardiovascular and metabolic disorders.

Mineralocorticoid receptor (MR) antagonist eplerenone and MR modulator balcinrenone prevent renal extracellular matrix remodeling and inflammation via the MR/proteoglycan/TLR4 pathway.

Excessive activation of the mineralocorticoid receptor (MR) is implicated in cardiovascular and renal disease. Decreasing MR activation with MR antagonists (MRA) is effective to slow chronic kidney disease (CKD) progression and its cardiovascular comorbidities in animal models and patients. The present study evaluates the effects of the MR modulator balcinrenone and the MRA eplerenone on kidney damage in a metabolic CKD mouse model combining nephron reduction and a 60% high-fat diet. Balcinrenone and eplerenone prevented the progression of renal damages, extracellular matrix remodeling and inflammation to a similar extent. We identified a novel mechanism linking MR activation to the renal proteoglycan deposition and inflammation via the TLR4 pathway activation. Balcinrenone and eplerenone similarly blunted this pathway activation.

Molecular evidence of altered stress responsivity related to neuroinflammation in the schizophrenia midbrain.

Stress and inflammation are risk factors for schizophrenia. Chronic psychosocial stress is associated with subcortical hyperdopaminergia, a core feature of schizophrenia. Hyperdopaminergia arises from midbrain neurons, leading us to hypothesise that changes in stress response pathways may occur in this region. To identify whether transcriptional changes in glucocorticoid and mineralocorticoid receptors (NR3C1/GR, NR3C2/MR) or other stress signalling molecules (FKBP4, FKBP5) exist in schizophrenia midbrain, we measured gene expression in the human brain (N = 56) using qRT-PCR. We assessed whether alterations in these mRNAs were related to previously identified high/low inflammatory status. We investigated relationships between stress-related transcripts themselves, and between FKBP5 mRNA, dopaminergic, and glial cell transcripts in diagnostic and inflammatory subgroups. Though unchanged by diagnosis, GR mRNA levels were reduced in high inflammatory compared to low inflammatory schizophrenia cases (p = 0.026). We found no effect of diagnosis or inflammation on MR mRNA. FKBP4 mRNA was decreased and FKBP5 mRNA was increased in schizophrenia (p < 0.05). FKBP5 changes occurred in high inflammatory (p < 0.001), whereas FKBP4 changes occurred in low inflammatory schizophrenia cases (p < 0.05). The decrease in mRNA encoding the main stress receptor (GR), as well as increased transcript levels of the stress-responsive negative regulator (FKBP5), may combine to blunt the midbrain response to stress in schizophrenia when neuroinflammation is present. Negative correlations between FKBP5 mRNA and dopaminergic transcripts in the low inflammatory subgroup suggest higher levels of FKBP5 mRNA may also attenuate dopaminergic neurotransmission in schizophrenia even when inflammation is absent. We report alterations in GR-mediated stress signalling in the midbrain in schizophrenia.

Discovering novel targets of abscisic acid using computational approaches.

Abscisic acid (ABA) is a crucial plant hormone that is naturally produced in various mammalian tissues and holds significant potential as a therapeutic molecule in humans. ABA is selected for this study due to its known roles in essential human metabolic processes, such as glucose homeostasis, immune responses, cardiovascular system, and inflammation regulation. Despite its known importance, the molecular mechanism underlying ABA's action remain largely unexplored. This study employed computational techniques to identify potential human ABA receptors. We screened 64 candidate molecules using online servers and performed molecular docking to assess binding affinity and interaction types with ABA. The stability and dynamics of the best complexes were investigated using molecular dynamics simulation over a 100 ns time period. Root mean square fluctuations (RMSF), root mean square deviation (RMSD), solvent-accessible surface area (SASA), radius of gyration (Rg), free energy landscape (FEL), and principal component analysis (PCA) were analyzed. Next, the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method was employed to calculate the binding energies of the complexes based on the simulated data. Our study successfully pinpointed four key receptors responsible for ABA signaling (androgen receptor, glucocorticoid receptor, mineralocorticoid receptor, and retinoic acid receptor beta) that have a strong affinity for binding with ABA and remained structurally stable throughout the simulations. The simulations with Hydralazine as an unrelated ligand were conducted to validate the specificity of the identified receptors for ABA. The findings of this study can contribute to further experimental validation and a better understanding of how ABA functions in humans.

New ways of mitigating aldosterone in cardiorenal disease.

Steroidal mineralocorticoid receptor antagonists (MRAs) bind to the mineralocorticoid receptor and antagonize the effects of aldosterone, which contributes to the development and progression of cardio- and renovascular diseases. Guidelines recommend steroidal MRAs in patients with heart failure with reduced or mildly reduced ejection fraction, as they reduce morbidity and mortality. In heart failure with preserved ejection fraction, MRAs have not convincingly shown to improve prognosis. Steroidal MRAs delay the progression of chronic kidney disease, reduce proteinuria and lower blood pressure in resistant hypertension but can induce hyperkalaemia. Due to their limited selectivity to the mineralocorticoid receptor, steroidal MRAs can cause significant adverse effects, i.e. libido loss, erectile dysfunction, gynaecomastia, and amenorrhoea, leading to low rates of persistance. Against this background, new avenues for developing non-steroidal, selective (ns)MRAs and aldosterone-synthase inhibitors have been taken. Finerenone has been shown to delay the progression of diabetic nephropathy and lower the incidence of heart failure hospitalizations in patients with chronic kidney disease and diabetes compared with placebo. Finerenone has therefore been recommended by the 2023 European Society of Cardiology Guidelines for the management of diabetes in patients with type 2 diabetes and chronic kidney disease. Further randomized controlled trials assessing the safety and effectiveness of finerenone in patients with heart failure are currently ongoing. Esaxerenone provides antihypertensive effects and has been approved for the treatment of hypertension in Japan. Baxdrostat and lorundostat, novel selective aldosterone-synthase inhibitors, are currently under investigation. In phase II trials, baxdrostat and lorundostat were safe and effective in lowering blood pressure in resistant hypertension. In this review, we summarize and critically discuss the evidence for new drugs mitigating aldosterone in heart failure, hypertension, and chronic kidney disease.

The mineralocorticoid receptor in diabetic kidney disease.

Diabetes mellitus is one of the leading causes of chronic kidney disease and its progression to end-stage kidney disease (ESKD). Diabetic kidney disease (DKD) is characterized by glomerular hypertrophy, hyperfiltration, inflammation, and the onset of albuminuria, together with a progressive reduction in glomerular filtration rate. This progression is further accompanied by tubulointerstitial inflammation and fibrosis. Factors such as genetic predisposition, epigenetic modifications, metabolic derangements, hemodynamic alterations, inflammation, and inappropriate renin-angiotensin-aldosterone system (RAAS) activity contribute to the onset and progression of DKD. In this context, decades of work have focused on glycemic and blood pressure reduction strategies, especially targeting the RAAS to slow disease progression. Although much of the work has focused on targeting angiotensin II, emerging data support that the mineralocorticoid receptor (MR) is integral in the development and progression of DKD. Molecular mechanisms linked to the underlying pathophysiological changes derived from MR activation include vascular endothelial and epithelial cell responses to oxidative stress and inflammation. These responses lead to alterations in the microcirculatory environment, the abnormal release of extracellular vesicles, gut dysbiosis, epithelial-mesenchymal transition, and kidney fibrosis. Herein, we present recent experimental and clinical evidence on the MR in DKD onset and progress along with new MR-based strategies for the treatment and prevention of DKD.

Interplay between caveolin-1 and mineralocorticoid receptor in cardiometabolic disease.

Over the past decades, research has clearly established the important role of the mineralocorticoid receptor (MR) in both renal and extra-renal tissues. Recently, caveolin-1 (Cav-1) has emerged as a mediator of MR signaling in several tissues, with implications on cardiovascular and metabolic dysfunction. The main structural component of caveolae (plasma membrane invaginations with diverse functions), Cav-1 is a modulator of cardiovascular function, cellular glucose, and lipid homeostasis, via its effects on signal transduction pathways that mediate inflammatory responses and oxidative stress. In this review, we present evidence indicating an overlap between the roles of the MR and Cav-1 in cardiometabolic disease and the relevant signaling pathways involved. Furthermore, we discuss the potential use of Cav-1 as a biomarker and/or target for MR-mediated dysfunction.

Toll-like receptor 4-dependent innate immune responses are mediated by intracrine corticosteroids and activation of glycogen synthase kinase-3ß in astrocytes.

Reactive astrocytes are important pathophysiologically and synthesize neurosteroids. We observed that LPS increased immunoreactive TLR4 and key steroidogenic enzymes in cortical astrocytes of rats and investigated whether corticosteroids are produced and mediate astrocytic TLR4-dependent innate immune responses. We found that LPS increased steroidogenic acute regulatory protein (StAR) and StAR-dependent aldosterone production in purified astrocytes. Both increases were blocked by the TLR4 antagonist TAK242. LPS also increased 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) and corticosterone production, and both were prevented by TAK242 and by siRNAs against 11ß-HSD1, StAR, or aldosterone synthase (CYP11B2). Knockdown of 11ß-HSD1, StAR, or CYP11B2 or blocking either mineralocorticoid receptors (MR) or glucocorticoid receptors (GR) prevented dephosphorylation of p-Ser9GSK-3ß, activation of NF-κB, and the GSK-3ß-dependent increases of C3, IL-1ß, and TNF-α caused by LPS. Exogenous aldosterone mimicked the MR- and GSK-3ß-dependent pro-inflammatory effects of LPS in astrocytes, but corticosterone did not. Supernatants from astrocytes treated with LPS reduced MAP2 and viability of cultured neurons except when astrocytic StAR or MR was inhibited. In adrenalectomized rats, intracerebroventricular injection of LPS increased astrocytic TLR4, StAR, CYP11B2, and 11ß-HSD1, NF-κB, C3 and IL-1ß, decreased astrocytic p-Ser9GSK-3ß in the cortex and was neurotoxic, except when spironolactone was co-injected, consistent with the in vitro results. LPS also activated NF-κB in some NeuN+ and CD11b+ cells in the cortex, and these effects were prevented by spironolactone. We conclude that intracrine aldosterone may be involved in the TLR4-dependent innate immune responses of astrocytes and can trigger paracrine effects by activating astrocytic MR/GSK-3ß/NF-κB signaling.

Novel Evolution of Mineralocorticoid Receptor in Humans Compared to Chimpanzees, Gorillas, and Orangutans.

We identified five distinct full-length human mineralocorticoid receptor (MR) genes containing either 984 amino acids (MR-984) or 988 amino acids (MR-988), which can be distinguished by the presence or absence of Lys, Cys, Ser, and Trp (KCSW) in their DNA-binding domain (DBD) and mutations at codons 180 and 241 in their amino-terminal domain (NTD). Two human MR-KCSW genes contain either (Val-180, Val-241) or (Ile-180, Val-241) in their NTD, and three human MR-984 genes contain either (Ile-180, Ala-241), (Val-180, Val-241), or (Ile-180, Val-241). Human MR-KCSW with (Ile-180, Ala-241) has not been cloned. In contrast, chimpanzees contain four MRs: two MR-988s with KCSW in their DBD, or two MR-984s without KCSW in their DBD. Chimpanzee MRs only contain (Ile180, Val-241) in their NTD. A chimpanzee MR with either (Val-180, Val-241) or (Ile-180, Ala-241) in the NTD has not been cloned. Gorillas and orangutans each contain one MR-988 with KCSW in the DBD and one MR-984 without KCSW, and these MRs only contain (Ile-180, Val-241) in their NTD. A gorilla MR or orangutan MR with either (Val-180, Val-241) or (Ile-180, Ala-241) in the NTD has not been cloned. Together, these data suggest that human MRs with (Val-180, Val-241) or (Ile-180, Ala-241) in the NTD evolved after humans and chimpanzees diverged from their common ancestor. Considering the multiple functions in human development of the MR in kidney, brain, heart, skin, and lungs, as well as MR activity in interaction with the glucocorticoid receptor, we suggest that the evolution of human MRs that are absent in chimpanzees may have been important in the evolution of humans from chimpanzees. Investigation of the physiological responses to corticosteroids mediated by the MR in humans, chimpanzees, gorillas, and orangutans may provide insights into the evolution of humans and their closest relatives.

An in Vitro triple screen model for human mineralocorticoid receptor activity.

The mineralocorticoid receptor (MR, NR3C2) mediates ion and water homeostasis in epithelial cells of the distal nephron and other tissues. Aldosterone, the prototypical mineralocorticoid, regulates electrolyte and fluid balance. Cortisol binds to MR with equal affinity to aldosterone, but many MR-expressing tissues inactivate cortisol to cortisone via 11ß-hydroxysteroid dehydrogenase type 2 (HSD11B2). Dysregulated MR activation contributes to direct cardiovascular tissue insults. Besides aldosterone and cortisol, a variety of MR agonists and/or HSD11B2 inhibitors are putative players in the pathophysiology of low-renin hypertension (LRH), and cardiovascular and metabolic pathology. We developed an in vitro human MR (hMR) model, to facilitate screening for MR agonists, antagonists, and HSD11B2 inhibitors. The CV1 monkey kidney cells were transduced with lentivirus to stably express hMR and an MR-responsive gaussia luciferase gene. Clonal populations of MR-expressing cells (CV1-MRluc) were further transduced to express HSD11B2 (CV1-MRluc-HSD11B2). CV1-MRluc and CV1-MRluc-HSD11B2 cells were treated with aldosterone, cortisol, 11-deoxycorticosterone (DOC), 18-hydroxycorticosterone (18OHB), 18-hydroxycortisol (18OHF), 18-oxocortisol (18oxoF), progesterone, or 17-hydroxyprogesterone (17OHP). In CV1-MRLuc cells, aldosterone and DOC displayed similar potency (EC50: 0.45 nM and 0.30 nM) and maximal response (31- and 23-fold increase from baseline) on hMR; 18oxoF and 18OHB displayed lower potency (19.6 nM and 56.0 nM, respectively) but similar maximal hMR activation (25- and 27-fold increase, respectively); cortisol and corticosterone exhibited higher maximal responses (73- and 52-fold, respectively); 18OHF showed no MR activation. Progesterone and 17OHP inhibited aldosterone-mediated MR activation. In the MRluc-HSD11B2 model, the EC50 of cortisol for MR activation increased from 20 nM (CV1-MRLuc) to ∼2000 nM, while the EC50 for aldosterone remained unchanged. The addition of 18ß-glycyrrhetinic acid (18ß-GA), a HSD11B2 inhibitor, restored the potency of cortisol back to ∼70 nM in CV1-hMRLuc-HSD11B2 cells. Together, these two cell models will facilitate the discovery of novel MR-modulators, informing MR-mediated pathophysiology mechanisms and drug development efforts.

Lysine-Cysteine-Serine-Tryptophan inserted into the DNA-binding domain of human mineralocorticoid receptor increases transcriptional activation by aldosterone.

Due to alternative splicing in an ancestral DNA-binding domain (DBD) of the mineralocorticoid receptor (MR), humans contain two almost identical MR transcripts with either 984 amino acids (MR-984) or 988 amino acids (MR-988), in which their DBDs differ by only four amino acids, Lys,Cys,Ser,Trp (KCSW). Human MRs also contain mutations at two sites, codons 180 and 241, in the amino terminal domain (NTD). Together, there are five distinct full-length human MR genes in GenBank. Human MR-984, which was cloned in 1987, has been extensively studied. Human MR-988, cloned in 1995, contains KCSW in its DBD. Neither this human MR-988 nor the other human MR-988 genes have been studied for their response to aldosterone and other corticosteroids. Here, we report that transcriptional activation of human MR-988 by aldosterone is increased by about 50 % compared to activation of human MR-984 in HEK293 cells transfected with the TAT3 promoter, while the half-maximal response (EC50) is similar for aldosterone activation of MR-984 and MR-988. Transcriptional activation of human MR also depends on the amino acids at codons 180 and 241. Interestingly, in HEK293 cells transfected with the MMTV promoter, transcriptional activation by aldosterone of human MR-988 is similar to activation of human MR-984, indicating that the promoter has a role in the regulation of the response of human MR-988 to aldosterone. The physiological responses to aldosterone and other corticosteroids in humans with MR genes containing KCSW and with differences at codons 180 and 241 in the NTD warrant investigation.

Both endothelial mineralocorticoid receptor expression and hyperleptinemia are required for clinical characteristics of placental ischemia in mice.

One of the initiating events in preeclampsia (PE) is placental ischemia. Rodent models of placental ischemia do not present with vascular endothelial dysfunction, a hallmark of PE. We previously demonstrated a role for leptin in endothelial dysfunction in pregnancy in the absence of placental ischemia. We hypothesized that placental ischemia requires hyperleptinemia and endothelial mineralocorticoid receptor (ECMR) expression to induce PE-associated endothelial dysfunction in pregnant mice. We induced placental ischemia via the reduced uterine perfusion pressure (RUPP) procedure in pregnant ECMR-intact (ECMR+/+) and ECMR deletion (ECMR-/-) mice at gestational day (GD) 13. ECMR+/+ RUPP pregnant mice also received concurrent leptin infusion via miniosmotic pump (0.9 mg/kg/day). RUPP increased blood pressure via radiotelemetry and decreased fetal growth in ECMR+/+ pregnant mice. Both increases in blood pressure and reduced fetal growth were abolished in RUPP ECMR-/- mice. Placental ischemia did not decrease endothelial-dependent relaxation to acetylcholine (ACh) but increased phenylephrine (Phe) contraction in mesenteric arteries of pregnant mice, which was ablated by ECMR deletion. Addition of leptin to RUPP mice significantly reduced ACh relaxation in ECMR+/+ pregnant mice, accompanied by an increase in soluble FMS-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PLGF) ratio. In conclusion, our data indicate that high leptin levels drive endothelial dysfunction in PE and that ECMR is required for clinical characteristics of hypertension and fetal growth restriction in placental ischemia PE. Collectively, we show that both ECMR and leptin play a role to mediate PE.NEW & NOTEWORTHY Leptin is a key feature of preeclampsia that initiates vascular endothelial dysfunction in preeclampsia characterized by placental ischemia. Endothelial mineralocorticoid receptor (ECMR) deletion in placental ischemia protects pregnant mice from elevations in blood pressure and fetal growth restriction in pregnancy. Increases in leptin production mediate the key pathological feature of endothelial dysfunction in preeclampsia in rodents. ECMR activation contributes to the increase in blood pressure and fetal growth restriction in preeclampsia.

Klotho is highly expressed in the chief sites of regulated potassium secretion, and it is stimulated by potassium intake.

Klotho regulates many pathways in the aging process, but it remains unclear how it is physiologically regulated. Because Klotho is synthesized, cleaved, and released from the kidney; activates the chief urinary K+ secretion channel (ROMK) and stimulates urinary K+ secretion, we explored if Klotho protein is regulated by dietary K+ and the potassium-regulatory hormone, Aldosterone. Klotho protein along the nephron was evaluated in humans and in wild-type (WT) mice; and in mice lacking components of Aldosterone signaling, including the Aldosterone-Synthase KO (AS-KO) and the Mineralocorticoid-Receptor KO (MR-KO) mice. We found the specific cells of the distal nephron in humans and mice that are chief sites of regulated K+ secretion have the highest Klotho protein expression along the nephron. WT mice fed K+-rich diets increased Klotho expression in these cells. AS-KO mice exhibit normal Klotho under basal conditions but could not upregulate Klotho in response to high-K+ intake in the K+-secreting cells. Similarly, MR-KO mice exhibit decreased Klotho protein expression. Together, i) Klotho is highly expressed in the key sites of regulated K+ secretion in humans and mice, ii) In mice, K+-rich diets increase Klotho expression specifically in the potassium secretory cells of the distal nephron, iii) Aldosterone signaling is required for Klotho response to high K+ intake.