Eight weeks of treatment with mineralocorticoid receptor blockade does not alter vascular function in individuals with and without type 2 diabetes.

Aldosterone has been suggested to be involved in the microvascular complications observed in type 2 diabetes. We aimed to investigate the effect of mineralocorticoid receptor (MR) blockade on endothelial function in individuals with type 2 diabetes compared to healthy controls. We included 12 participants with type 2 diabetes and 14 controls. We measured leg hemodynamics at baseline and during femoral arterial infusion of acetylcholine and sodium nitroprusside before and 8 weeks into treatment with MR blockade (eplerenone). Acetylcholine infusion was repeated with concomitant n-acetylcysteine (antioxidant) infusion. No difference in leg blood flow or vascular conductance was detected before or after the treatment with MR blockade in both groups and there was no difference between groups. Infusion of n-acetylcysteine increased baseline blood flow and vascular conductance, but did not change the vascular response to acetylcholine before or after treatment with MR blockade. Skeletal muscle eNOS content was unaltered by MR blockade and no difference between groups was detected. In conclusion, we found no effect of MR blockade endothelial function in individuals with and without type 2 diabetes. As the individuals with type 2 diabetes did not have vascular dysfunction, these results might not apply to individuals with vascular dysfunction.

D-Pinitol mitigates post-traumatic stress disorder-like behaviors induced by single prolonged stress in mice through mineralocorticoid receptor antagonism.

Post-traumatic stress disorder (PTSD) is a mental illness that can occur in individuals who have experienced trauma. Current treatments for PTSD, typically serotonin reuptake inhibitors, have limited effectiveness for patients and often cause serious adverse effects. Therefore, a novel class of treatment with better pharmacological profile is necessary. D-Pinitol has been reported to be effective for depression and anxiety disorders, but there are no reports associated with PTSD. In the present study, we investigated the effects of D-pinitol in a mouse model of PTSD induced by a single prolonged stress (SPS) protocol. We examined the therapeutic effects of D-pinitol on emotional and cognitive impairments in the SPS mouse model. We also investigated the effects of D-pinitol on fear memory formation. Mineralocorticoid receptor transactivation assay, Western blot, and quantitative PCR were employed to investigate how D-pinitol exerts its pharmacological activities. D-Pinitol ameliorated PTSD-like behaviors in a SPS mouse model. D-Pinitol also normalized the increased mRNA expression levels and protein levels of the mineralocorticoid receptor in the amygdala. A mineralocorticoid receptor agonist reversed the effects of D-pinitol on fear extinction and recall, and the antagonistic property of D-pinitol against the mineralocorticoid receptor was confirmed in vitro. Our findings suggest that D-pinitol could serve as a potential therapeutic agent for PTSD due to its antagonistic effect on the mineralocorticoid receptor.

Adverse Effects of Aldosterone: Beyond Blood Pressure.

Aldosterone is a steroid hormone that primarily acts through activation of the mineralocorticoid receptor (MR), a nuclear receptor responsible for downstream genomic regulation. Classically, activation of the MR in the renal tubular epithelium is responsible for sodium retention and volume expansion, raising systemic blood pressure. However, activation of the MR across a wide distribution of tissue types has been implicated in multiple adverse consequences for cardiovascular, cerebrovascular, renal, and metabolic disease, independent of blood pressure alone. Primary aldosteronism, heart failure, and chronic kidney disease are states of excessive aldosterone production and MR activity where targeting MR activation has had clinical benefits out of proportion to blood pressure lowering. The growing list of established and emerging therapies that target aldosterone and MR activation may provide new opportunities to improve clinical outcomes and enhance cardiovascular and renal health.

Atlas of cardiac endothelial cell enhancer elements linking the mineralocorticoid receptor to pathological gene expression.

Endothelial cells play crucial roles in physiology and are increasingly recognized as therapeutic targets in cardiovascular disease. Here, we analyzed the regulatory landscape of cardiac endothelial cells by assessing chromatin accessibility, histone modifications, and 3D chromatin organization and confirmed the functional relevance of enhancer-promoter interactions by CRISPRi-mediated enhancer silencing. We used this dataset to explore mechanisms of transcriptional regulation in cardiovascular disease and compared six different experimental models of heart failure, hypertension, or diabetes. Enhancers that regulate gene expression in diseased endothelial cells were enriched with binding sites for a distinct set of transcription factors, including the mineralocorticoid receptor (MR), a known drug target in heart failure and hypertension. For proof of concept, we applied endothelial cell-specific MR deletion in mice to confirm MR-dependent gene expression and predicted direct MR target genes. Overall, we have compiled here a comprehensive atlas of cardiac endothelial cell enhancer elements that provides insight into the role of transcription factors in cardiovascular disease.

Comprehensive characterization of the effect of mineralocorticoid receptor antagonism with spironolactone on the renin-angiotensin-aldosterone system in healthy dogs.

OBJECTIVE: To characterize the dose-exposure-response effect of spironolactone on biomarkers of the classical and alternative arms of the renin-angiotensin-aldosterone system (RAAS) in healthy dogs. ANIMALS: Ten healthy purpose-bred Beagle dogs. PROCEDURES: Study dogs were randomly allocated to 2 spironolactone dosing groups (2 mg/kg PO q24hr, 4 mg/kg PO q24hr). The dogs received 7-day courses of spironolactone followed by a 14-day washout period in a crossover (AB/BA) design. Angiotensin peptides and aldosterone were measured in serum using equilibrium analysis, and plasma canrenone and 7-α-thiomethyl spironolactone (TMS) were quantified via liquid chromatography-mass spectrometry/mass spectroscopy (LC-MS/MS). Study results were compared before and after dosing and between groups. RESULTS: Following spironolactone treatment, dogs had a significant increase in serum aldosterone concentration (P = 0.07), with no statistical differences between dosing groups. Significant increases in angiotensin II (P = 0.09), angiotensin I (P = 0.08), angiotensin 1-5 (P = 0.08), and a surrogate marker for plasma renin activity (P = 0.06) were detected compared to baseline following spironolactone treatment during the second treatment period only. Overall, changes from baseline did not significantly differ between spironolactone dosages. RAAS analytes were weakly correlated (R < 0.4) with spironolactone dosage and plasma canrenone or plasma TMS. There were no adverse clinical or biochemical effects seen at any spironolactone dosage during treatment. CONCLUSIONS: Treatment with spironolactone increased serum aldosterone concentration in healthy dogs and impacted other biomarkers of the classical and alternative arms of the RAAS. There was no difference in effect on the RAAS between 2 and 4 mg/kg/day dosing. Dosage of 4 mg/kg/day was safe and well-tolerated in healthy dogs.

Mineralocorticoid promotes intestinal inflammation through receptor dependent IL17 production in ILC3s.

Aldosterone is a key mineralocorticoid involved in regulating the concentration of blood electrolytes and physiological volume balance. Activation of mineralocorticoid receptor (MR) has been recently reported to participate in adaptive and innate immune responses under inflammation. Here, we evaluated the role of aldosterone and MR in inflammation bowel diseases (IBD). Aldosterone elevated in the colon of DSS-induced colitis mice. Aldosterone addition induced IL17 production and ROS/RNS level in group 3 innate lymphoid cells (ILC3s) and exacerbated intestinal injury. A selective mineralocorticoid receptor antagonism, eplerenone, inhibited IL17-producing ILC3s and its ROS/RNS production, protected mice from DSS-induced colitis. Mice lacking Nr3c2 (MR coding gene) in ILC3s exhibited decreased IL17 and ROS/RNS production, which alleviated colitis and colitis-associated colorectal cancer (CAC). Further experiments revealed that MR could directly bind to IL17A promoter and facilitate its transcription, which could be enhanced by aldosterone. Thus, our findings demonstrated the critical role of aldosterone-MR-IL17 signaling in ILC3s and gut homeostasis, indicating the therapeutic strategy of eplerenone in IBD clinical trial.

mTOR Regulates Mineralocorticoid Receptor Transcriptional Activity by ULK1-Dependent and -Independent Mechanisms.

The mineralocorticoid receptor (MR) is a transcription factor for genes mediating diverse, cell-specific functions, including trophic effects as well as promoting fluid/electrolyte homeostasis. It was reported that in intercalated cells, phosphorylation of the MR at serine 843 (S843) by Unc-51-like kinase (ULK1) inhibits MR activation and that phosphorylation of ULK1 by mechanistic target of rapamycin (mTOR) inactivates ULK1, and thereby prevents MR inactivation. We extended these findings with studies in M1 mouse cortical collecting duct cells stably expressing the rat MR and a reporter gene. Pharmacological inhibition of ULK1 dose-dependently increased ligand-induced MR transactivation, while ULK1 activation had no effect. Pharmacological inhibition of mTOR and CRISPR/gRNA gene knockdown of rapamycin-sensitive adapter protein of mTOR (Raptor) or rapamycin-insensitive companion of mTOR (Rictor) decreased phosphorylated ULK1 and ligand-induced activation of the MR reporter gene, as well as transcription of endogenous MR-target genes. As predicted, ULK1 inhibition had no effect on aldosterone-mediated transcription in M1 cells with the mutated MR-S843A (alanine cannot be phosphorylated). In contrast, mTOR inhibition dose-dependently decreased transcription in the MR-S843A cells, though not as completely as in cells with the wild-type MR-S843. mTOR, Raptor, and Rictor coprecipitated with the MR and addition of aldosterone increased their phosphorylated, active state. These results suggest that mTOR significantly regulates MR activity in at least 2 ways: by suppressing MR inactivation by ULK1, and by a yet ill-defined mechanism that involves direct association with MR. They also provide new insights into the diverse functions of ULK1 and mTOR, 2 key enzymes that monitor the cell's energy status.

Mineralocorticoid receptor promotes cardiac macrophage inflammaging.

Inflammaging, a pro-inflammatory status that characterizes aging and primarily involving macrophages, is a master driver of age-related diseases. Mineralocorticoid receptor (MR) activation in macrophages critically regulates inflammatory and fibrotic processes. However, macrophage-specific mechanisms and the role of the macrophage MR for the regulation of inflammation and fibrotic remodeling in the aging heart have not yet been elucidated. Transcriptome profiling of cardiac macrophages from male/female young (4 months-old), middle (12 months-old) and old (18 and 24 months-old) mice revealed that myeloid cell-restricted MR deficiency prevents macrophage differentiation toward a pro-inflammatory phenotype. Pathway enrichment analysis showed that several biological processes related to inflammation and cell metabolism were modulated by the MR in aged macrophages. Further, transcriptome analysis of aged cardiac fibroblasts revealed that macrophage MR deficiency reduced the activation of pathways related to inflammation and upregulation of ZBTB16, a transcription factor involved in fibrosis. Phenotypic characterization of macrophages showed a progressive replacement of the TIMD4+MHC-IIneg/low macrophage population by TIMD4+MHC-IIint/high and TIMD4-MHC-IIint/high macrophages in the aging heart. By integrating cell sorting and transwell experiments with TIMD4+/TIMD4-macrophages and fibroblasts from old MRflox/MRLysMCre hearts, we showed that the inflammatory crosstalk between TIMD4- macrophages and fibroblasts may imply the macrophage MR and the release of mitochondrial superoxide anions. Macrophage MR deficiency reduced the expansion of the TIMD4- macrophage population and the emergence of fibrotic niches in the aging heart, thereby protecting against cardiac inflammation, fibrosis, and dysfunction. This study highlights the MR as an important mediator of cardiac macrophage inflammaging and age-related fibrotic remodeling.

The impact of parental and developmental stress on DNA methylation in the avian hypothalamic-pituitary-adrenal axis.

The hypothalamic-pituitary-adrenal (HPA) axis coordinates an organism's response to environmental stress. The responsiveness and sensitivity of an offspring's stress response may be shaped not only by stressors encountered in their early post-natal environment but also by stressors in their parent's environment. Yet, few studies have considered how stressors encountered in both of these early life environments may function together to impact the developing HPA axis. Here, we manipulated stressors in the parental and post-natal environments in a population of house sparrows (Passer domesticus) to assess their impact on changes in DNA methylation (and corresponding gene expression) in a suite of genes within the HPA axis. We found that nestlings that experienced early life stress across both life-history periods had higher DNA methylation in a critical HPA axis gene, the glucocorticoid receptor (NR3C1). In addition, we found that the life-history stage when stress was encountered impacted some genes (HSD11B1, NR3C1 and NR3C2) differently. We also found evidence for the mitigation of parental stress by post-natal stress (in HSD11B1 and NR3C2). Finally, by assessing DNA methylation in both the brain and blood, we were able to evaluate cross-tissue patterns. While some differentially methylated regions were tissue-specific, we found cross-tissue changes in NR3C2 and NR3C1, suggesting that blood is a suitable tissue for assessing DNA methylation as a biomarker of early life stress. Our results provide a crucial first step in understanding the mechanisms by which early life stress in different life-history periods contributes to changes in the epigenome of the HPA axis.

Mineralocorticoid Receptor Antagonism Reduces Inflammatory Pain Measures in Mice Independent of the Receptors on Sensory Neurons.

Corticosteroids are commonly used in the treatment of inflammatory low back pain, and their nominal target is the glucocorticoid receptor (GR) to relieve inflammation. They can also have similar potency at the mineralocorticoid receptor (MR). The MR has been shown to be widespread in rodent and human dorsal root ganglia (DRG) neurons and non-neuronal cells, and when MR antagonists are administered during a variety of inflammatory pain models in rats, pain measures are reduced. In this study we selectively knockout (KO) the MR in sensory neurons to determine the role of MR in sensory neurons of the mouse DRG in pain measures as MR antagonism during the local inflammation of the DRG (LID) pain model. We found that MR antagonism using eplerenone reduced evoked mechanical hypersensitivity during LID, but MR KO in paw-innervating sensory neurons only did not. This could be a result of differences between prolonged (MR KO) versus acute (drug) MR block or an indicator that non-neuronal cells in the DRG are driving the effect of MR antagonists. MR KO unmyelinated C neurons are more excitable under normal and inflamed conditions, while MR KO does not affect excitability of myelinated A cells. MR KO in sensory neurons causes a reduction in overall GR mRNA but is protective against reduction of the anti-inflammatory GRα isoform during LID. These effects of MR KO in sensory neurons expanded our understanding of MR's functional role in different neuronal subtypes (A and C neurons), and its interactions with the GR.

Myosin Light Chain Phosphatase Plays an Important Role in Cardiac Fibrosis in a Model of Mineralocorticoid Receptor-Associated Hypertension.

BACKGROUND: Myosin phosphatase targeting subunit 2 (MYPT2) is an important subunit of cardiac MLC (myosin light chain) phosphatase, which plays a crucial role in regulating the phosphorylation of MLC to phospho-MLC (p-MLC). A recent study demonstrated mineralocorticoid receptor-related hypertension is associated with RhoA/Rho-associated kinase/MYPT1 signaling upregulation in smooth muscle cells. Our purpose is to investigate the effect of MYPT2 on cardiac function and fibrosis in mineralocorticoid receptor-related hypertension. METHODS AND RESULTS: HL-1 murine cardiomyocytes were incubated with different concentrations or durations of aldosterone. After 24-hour stimulation, aldosterone increased CTGF (connective tissue growth factor) and MYPT2 and decreased p-MLC in a dose-dependent manner. MYPT2 knockdown decreased CTGF. Cardiac-specific MYPT2-knockout (c-MYPT2-/-) mice exhibited decreased type 1 phosphatase catalytic subunit ß and increased p-MLC. A disease model of mouse was induced by subcutaneous aldosterone and 8% NaCl food for 4 weeks after uninephrectomy. Blood pressure elevation and left ventricular hypertrophy were observed in both c-MYPT2-/- and MYPT2+/+ mice, with no difference in heart weights or nuclear localization of mineralocorticoid receptor in cardiomyocytes. However, c-MYPT2-/- mice had higher ejection fraction and fractional shortening on echocardiography after aldosterone treatment. Histopathology revealed less fibrosis, reduced CTGF, and increased p-MLC in c-MYPT2-/- mice. Basal global radial strain and global longitudinal strain were higher in c-MYPT2-/- than in MYPT2+/+ mice. After aldosterone treatment, both global radial strain and global longitudinal strain remained higher in c-MYPT2-/- mice compared with MYPT2+/+ mice. CONCLUSIONS: Cardiac-specific MYPT2 knockout leads to decreased myosin light chain phosphatase and increased p-MLC. MYPT2 deletion prevented cardiac fibrosis and dysfunction in a model of mineralocorticoid receptor-associated hypertension.

Potential of Modulating Aldosterone Signaling and Mineralocorticoid Receptor with microRNAs to Attenuate Diabetic Kidney Disease.

Diabetic Kidney Disease (DKD) is a significant complication of diabetes and primary cause of end-stage renal disease globally. The exact mechanisms underlying DKD remain poorly understood, but multiple factors, including the renin-angiotensin-aldosterone system (RAAS), play a key role in its progression. Aldosterone, a mineralocorticoid steroid hormone, is one of the key components of RAAS and a potential mediator of renal damage and inflammation in DKD. miRNAs, small noncoding RNA molecules, have attracted interest due to their regulatory roles in numerous biological processes. These processes include aldosterone signaling and mineralocorticoid receptor (MR) expression. Numerous miRNAs have been recognized as crucial regulators of aldosterone signaling and MR expression. These miRNAs affect different aspects of the RAAS pathway and subsequent molecular processes, which impact sodium balance, ion transport, and fibrosis regulation. This review investigates the regulatory roles of particular miRNAs in modulating aldosterone signaling and MR activation, focusing on their impact on kidney injury, inflammation, and fibrosis. Understanding the complex interaction between miRNAs and the RAAS could lead to a new strategy to target aldosterone signaling and MR activation using miRNAs. This highlights the potential of miRNA-based interventions for DKD, with the aim of enhancing kidney outcomes in individuals with diabetes.

First Evidence of Mineralocorticoid Receptor Gene and Protein Expression in Rat and Human Thyroid Tissues and Cell Cultures.

Aldosterone (Aldo) exerts its action through binding with the mineralocorticoid receptor (MR). Clinically, a link between primary aldosteronism (PA) and thyroid diseases has been hypothesised. However, the presence and activity of MR on the thyroid have not yet been demonstrated. We investigated the gene/protein expression and activation of MR in primary thyroid cell cultures (normal rat thyroid [FRTL-5] and human papillary thyroid cancer [PTC] cell lines, BCPAP and K1) through qRT-PCR analysis, immunofluorescence, and confocal microscopy. We also studied the effects of Aldo on thyroid-specific and inflammation genes in vitro. Paired human normal and neoplastic thyroid tissues were also studied. We demonstrated both gene and protein expression and activation of MR in normal rat thyroid and human PTC lines. Incubation with Aldo induced an acute increase in IL-6 expression in both the FRTL-5 and BCPAP lines, which was antagonised by spironolactone, and an acute and late upregulation of thyroid-specific genes in FRTL-5. MR was also expressed at both gene and protein levels in normal human thyroid tissues and in PTC, with a progressive decline during neoplastic tumourigenesis, particularly in more aggressive histotypes. We present the first evidence of MR gene and protein expression in both normal and pathological thyroid cells and tissues. We have shown that MR is present and functionally activated in thyroid tissue. Binding of Aldo to MR induces the expression of inflammatory and thyroid-specific genes, and the thyroid may thus be considered a novel mineralocorticoid target tissue.

The influence of pharmacological mineralocorticoid and glucocorticoid receptor blockade on the cortisol response to psychological stress.

The glucocorticoid cortisol is the end product of the hypothalamic-pituitary-adrenal (HPA) axis and crucial for the stress response in humans. Cortisol regulates numerous biological functions by binding to two different types of receptors: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). Both receptors are found in the brain where they are crucially involved in various mental functions and in feedback inhibition of cortisol release. The precise role of both receptors in the human stress response is not completely understood. In this study, we examined the effects of pharmacological blockade of the MR or the GR on stress-induced cortisol release in a sample of 318 healthy young men (M = 25.42, SD = 5.01). Participants received the MR antagonist spironolactone (300 mg), the GR antagonist mifepristone (600 mg), or a placebo and were subjected 90 min later to a social-evaluative stressor (Trier Social Stress Test) or a non-stressful control condition. We found significantly higher stress-induced cortisol release in the spironolactone group, whereas participants after mifepristone administration did not differ from the control groups. These results suggest that MR blockade results in attenuated fast negative feedback processes and emphasize the important role of the MR during the early phase of the stress response.

Glucocorticoids with or without fludrocortisone in septic shock: a narrative review from a biochemical and molecular perspective.

Two randomised controlled trials have reported a reduction in mortality when adjunctive hydrocortisone is administered in combination with fludrocortisone compared with placebo in septic shock. A third trial did not support this finding when hydrocortisone administered in combination with fludrocortisone was compared with hydrocortisone alone. The underlying mechanisms for this mortality benefit remain poorly understood. We review the clinical implications and potential mechanisms derived from laboratory and clinical data underlying the beneficial role of adjunctive fludrocortisone with hydrocortisone supplementation in septic shock. Factors including distinct biological effects of glucocorticoids and mineralocorticoids, tissue-specific and mineralocorticoid receptor-independent effects of mineralocorticoids, and differences in downstream signalling pathways between mineralocorticoid and glucocorticoid binding at the mineralocorticoid receptor could contribute to this interaction. Furthermore, pharmacokinetic and pharmacodynamic disparities exist between aldosterone and its synthetic counterpart fludrocortisone, potentially influencing their effects. Pending publication of well-designed, randomised controlled trials, a molecular perspective offers valuable insights and guidance to help inform clinical strategies.

The Mineralocorticoid Receptor in the Vasculature: Friend or Foe?

Originally described as the renal aldosterone receptor that regulates sodium homeostasis, it is now clear that mineralocorticoid receptors (MRs) are widely expressed, including in vascular endothelial and smooth muscle cells. Ample data demonstrate that endothelial and smooth muscle cell MRs contribute to cardiovascular disease in response to risk factors (aging, obesity, hypertension, atherosclerosis) by inducing vasoconstriction, vascular remodeling, inflammation, and oxidative stress. Extrapolating from its role in disease, evidence supports beneficial roles of vascular MRs in the context of hypotension by promoting inflammation, wound healing, and vasoconstriction to enhance survival from bleeding or sepsis. Advances in understanding how vascular MRs become activated are also reviewed, describing transcriptional, ligand-dependent, and ligand-independent mechanisms. By synthesizing evidence describing how vascular MRs convert cardiovascular risk factors into disease (the vascular MR as a foe), we postulate that the teleological role of the MR is to coordinate responses to hypotension (the MR as a friend).