Aldosterone regulates vascular gene transcription via oxidative stress-dependent and -independent pathways

Mineralocorticoid Receptors in Vascular Smooth Muscle: Blood Pressure and Beyond

After half a century of evidence suggesting the existence of mineralocorticoid receptors (MR) in the vasculature, the advent of technology to specifically knockout the MR from smooth muscle cells (SMCs) in mice has elucidated contributions of SMC-MR to cardiovascular function and disease, independent of the kidney. This review summarizes the latest understanding of the molecular mechanisms by which SMC-MR contributes to (1) regulation of vasomotor function and blood pressure to contribute to systemic and pulmonary hypertension; (2) vascular remodeling in response to hypertension, vascular injury, obesity, and aging, and the impact on vascular calcification; and (3) cardiovascular pathologies including aortic aneurysm, heart valve dysfunction, and heart failure. Data are reviewed from in vitro studies using SMCs and in vivo findings from SMC-specific MR-knockout mice that implicate target genes and signaling pathways downstream of SMC-MR. By regulating expression of the L-type calcium channel subunit Cav1.2 and angiotensin II type-1 receptor, SMC-MR contributes to myogenic tone and vasoconstriction, thereby contributing to systemic blood pressure. MR activation also promotes SMC proliferation, migration, production and degradation of extracellular matrix, and osteogenic differentiation by regulating target genes including connective tissue growth factor, osteopontin, bone morphogenetic protein 2, galectin-3, and matrix metallopeptidase-2. By these mechanisms, SMC-MR promotes disease progression in models of aging-associated vascular stiffness, vascular calcification, mitral and aortic valve disease, pulmonary hypertension, and heart failure. While rarely tested, when sexes were compared, the mechanisms of SMC-MR-mediated disease were sexually dimorphic. These advances support targeting SMC-MR-mediated mechanisms to prevent and treat diverse cardiovascular disorders.

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).

NGAL is a Novel Target in Hypertension by Modulating the NCC-Mediated Renal Na Balance

BACKGROUND

The expression of NGAL/lcn2 (neutrophil gelatinase-associated lipocalin) is directly modulated by mineralocorticoid receptor activation but its role in blood pressure control is unclear.

METHODS

a potential relationship between NGAL plasma levels, systolic blood pressure and urinary Na excretion was assessed in the STANISLAS cohort. The specific role of NGAL/lcn2 in salt-sensitive hypertension was studied using lcn2-knockout mice (lcn2 KO) fed with low-Na diet (0Na).

RESULTS

we show that NGAL plasma levels positively correlate with systolic blood pressure, whereas they negatively correlate with urinary Na excretion in subjects of the STANISLAS cohort. Prolonged feeding of lcn2 KO mice with a 0Na diet induced lower systolic blood pressure than that of the control group (wildtype), suggesting a role for NGAL/lcn2 in Na-balance homeostasis. Short-term or prolonged 0Na increased Na-Cl cotransporter (NCC) phosphorylation in the cortex of wildtype mice, which was prevented in lcn2 KO mice. Recombinant mouse lcn2 injections in lcn2 KO mice induced NCC phosphorylation in the kidney cortex, associated with decreased urinary Na excretion. Ex vivo experiments using kidney slices from lcn2 KO mice showed increased NCC phosphorylation by recombinant murine lcn2. In addition, recombinant murine lcn2 induced activation of CamK2β (calcium/calmodulin-dependent protein kinase II β subunit) phosphorylation in lcn2 KO mice and in kidney slices, providing an underlying mechanism involved in lcn2-induced NCC phosphorylation. Indeed, the inhibition of CamK2β prevented NCC phosphorylation induced by recombinant lcn2 in kidney slices.

CONCLUSIONS

we highlight a novel role of NGAL/lcn2 as a modulator of the activity of the renal sodium transporter NCC affecting salt-sensitive blood pressure.

Smooth Muscle Mineralocorticoid Receptor Promotes Hypertension After Preeclampsia

BACKGROUND

Preeclampsia is a syndrome of high blood pressure (BP) with end organ damage in late pregnancy that is associated with high circulating soluble VEGF receptor (sFlt1 [soluble Fms-like tyrosine kinase 1]). Women exposed to preeclampsia have a substantially increased risk of hypertension after pregnancy, but the mechanism remains unknown, leaving a missed interventional opportunity. After preeclampsia, women have enhanced sensitivity to hypertensive stress. Since smooth muscle cell mineralocorticoid receptors (SMC-MR) are activated by hypertensive stimuli, we hypothesized that high sFlt1 exposure in pregnancy induces a postpartum state of enhanced SMC-MR responsiveness.

METHODS

Postpartum BP response to high salt intake was studied in women with prior preeclampsia. MR transcriptional activity was assessed in vitro in sFlt1-treated SMC by reporter assays and PCR. Preeclampsia was modeled by transient sFlt1 expression in pregnant mice. Two months post-partum, mice were exposed to high salt and then to AngII (angiotensin II) and BP and vasoconstriction were measured.

RESULTS

Women exposed to preeclampsia had significantly enhanced salt sensitivity of BP verses those with a normotensive pregnancy. sFlt1 overexpression during pregnancy in mice induced elevated BP and glomerular endotheliosis, which resolved post-partum. The sFlt1 exposed post-partum mice had significantly increased BP response to 4% salt diet and to AngII infusion. In vitro, SMC-MR transcriptional activity in response to aldosterone or AngII was significantly increased after transient exposure to sFlt1 as was aldosterone-induced expression of AngII type 1 receptor. Post-partum, SMC-MR-KO mice were protected from the enhanced response to hypertensive stimuli after preeclampsia. Mechanistically, preeclampsia mice exposed to postpartum hypertensive stimuli develop enhanced aortic stiffness, microvascular myogenic tone, AngII constriction, and AngII type 1 receptor expression, all of which were prevented in SMC-MR-KO littermates.

CONCLUSIONS

These data support that sFlt1-induced vascular injury during preeclampsia produces a persistent state of enhanced sensitivity of SMC-MR to activation. This contributes to postpartum hypertension in response to common stresses and supports testing of MR antagonism to mitigate the increased cardiovascular risk in women after PE.

Aldosterone and cardiovascular diseases

Aldosterone's role in the kidney and its pathophysiologic actions in hypertension are well known. However, its role or that of its receptor [minieralocorticoid receptor (MR)] in other cardiovascular (CV) disease are less well described. To identify their potential roles in six CV conditions (heart failure, myocardial infarction, atrial fibrillation, stroke, atherosclerosis, and thrombosis), we assessed these associations in the following four areas: (i) mechanistic studies in rodents and humans; (ii) pre-clinical studies of MR antagonists; (iii) clinical trials of MR antagonists; and (iv) genetics. The data were acquired from an online search of the National Library of Medicine using the PubMed search engine from January 2011 through June 2021. There were 3702 publications identified with 200 publications meeting our inclusion and exclusion criteria. Data strongly supported an association between heart failure and dysregulated aldosterone/MR. This association is not surprising given aldosterone/MR's prominent role in regulating sodium/volume homeostasis. Atrial fibrillation and myocardial infarction are also associated with dysregulated aldosterone/MR, but less strongly. For the most part, the data were insufficient to determine whether there was a relationship between atherosclerosis, stroke, or thrombosis and aldosterone/MR dysregulation. This review clearly documented an expanding role for aldosterone/MR's dysregulation in CV diseases beyond hypertension. How expansive it might be is limited by the currently available data. It is anticipated that with an increased focus on aldosterone/MR's potential roles in these diseases, additional clinical and pre-clinical data will clarify these relationships, thereby, opening approaches to use modulators of aldosterone/MR's action to more precisely treat these CV conditions.

Cardiovascular Disease in Obstructive Sleep Apnea: Putative Contributions of Mineralocorticoid Receptors

Obstructive sleep apnea (OSA) is a chronic and highly prevalent condition that is associated with oxidative stress, inflammation, and fibrosis, leading to endothelial dysfunction, arterial stiffness, and vascular insulin resistance, resulting in increased cardiovascular disease and overall mortality rates. To date, OSA remains vastly underdiagnosed and undertreated, with conventional treatments yielding relatively discouraging results for improving cardiovascular outcomes in OSA patients. As such, a better mechanistic understanding of OSA-associated cardiovascular disease (CVD) and the development of novel adjuvant therapeutic targets are critically needed. It is well-established that inappropriate mineralocorticoid receptor (MR) activation in cardiovascular tissues plays a causal role in a multitude of CVD states. Clinical studies and experimental models of OSA lead to increased secretion of the MR ligand aldosterone and excessive MR activation. Furthermore, MR activation has been associated with worsened OSA prognosis. Despite these documented relationships, there have been no studies exploring the causal involvement of MR signaling in OSA-associated CVD. Further, scarce clinical studies have exclusively assessed the beneficial role of MR antagonists for the treatment of systemic hypertension commonly associated with OSA. Here, we provide a comprehensive overview of overlapping mechanistic pathways recruited in the context of MR activation- and OSA-induced CVD and propose MR-targeted therapy as a potential avenue to abrogate the deleterious cardiovascular consequences of OSA.

Smooth muscle mineralocorticoid receptor as an epigenetic regulator of vascular ageing

AIMS

Vascular stiffness increases with age and independently predicts cardiovascular disease risk. Epigenetic changes, including histone modifications, accumulate with age but the global pattern has not been elucidated nor are the regulators known. Smooth muscle cell-mineralocorticoid receptor (SMC-MR) contributes to vascular stiffness in ageing mice. Thus, we investigated the regulatory role of SMC-MR in vascular epigenetics and stiffness.

METHODS AND RESULTS

Mass spectrometry-based proteomic profiling of all histone modifications completely distinguished 3 from 12-month-old mouse aortas. Histone-H3 lysine-27 (H3K27) methylation (me) significantly decreased in ageing vessels and this was attenuated in SMC-MR-KO littermates. Immunoblotting revealed less H3K27-specific methyltransferase EZH2 with age in MR-intact but not SMC-MR-KO vessels. These ageing changes were examined in primary human aortic (HA)SMC from adult vs. aged donors. MR, H3K27 acetylation (ac), and stiffness gene (connective tissue growth factor, integrin-α5) expression significantly increased, while H3K27me and EZH2 decreased, with age. MR inhibition reversed these ageing changes in HASMC and the decline in stiffness genes was prevented by EZH2 blockade. Atomic force microscopy revealed that MR antagonism decreased intrinsic stiffness and the probability of fibronectin adhesion of aged HASMC. Conversely, ageing induction in young HASMC with H2O2; increased MR, decreased EZH2, enriched H3K27ac and MR at stiffness gene promoters by chromatin immunoprecipitation, and increased stiffness gene expression. In 12-month-old mice, MR antagonism increased aortic EZH2 and H3K27 methylation, increased EZH2 recruitment and decreased H3K27ac at stiffness genes promoters, and prevented ageing-induced vascular stiffness and fibrosis. Finally, in human aortic tissue, age positively correlated with MR and stiffness gene expression and negatively correlated with H3K27me3 while MR and EZH2 are negatively correlated.

CONCLUSION

These data support a novel vascular ageing model with rising MR in human SMC suppressing EZH2 expression thereby decreasing H3K27me, promoting MR recruitment and H3K27ac at stiffness gene promoters to induce vascular stiffness and suggests new targets for ameliorating ageing-associated vascular disease.

Mechanism by Which Inflammation and Oxidative Stress Induce Mineralocorticoid Receptor Gene Expression in Aging Vascular Smooth Muscle Cells

BACKGROUND

Vascular MR (mineralocorticoid receptor) expression increases with age driving aging-associated vascular stiffness and hypertension. MR has two isoforms (1α and 1β) with distinct 5'-untranslated and promoter sequences (P1 and P2), but the gene regulatory mechanisms remain unknown. We investigated mechanisms driving MR gene transcriptional regulation in aging human smooth muscle cells (SMC).

METHODS

MR was quantified in aortic tissue and primary human aortic SMC (HASMC) comparing adult and aged donors and adult HASMC treated with H2O2, to induce aging. Predicted transcription factor (TF) binding sites in the MR gene were validated using chromatin immunoprecipitations and reporter assays. The impact of TF inhibitors on MR isoforms and fibrosis target gene expression was examined.

RESULTS

Expression of both MR mRNA isoforms increased with donor age or H2O2 treatment in HASMCs. HIF1α (hypoxia-inducible factor) and the inflammatory TF NFκB (nuclear factor kappa B) both increased with age in HASMCs and are predicted to bind MR promoters. H2O2 induced HIF1α and NFκB expression and DNA binding of HIF1α to the MR P1 promoter and of NFκB to both MR promoters in HASMCs. HIF1α inhibition decreased MR-1α isoform expression while NFκB inhibition decreased both MR isoforms. HIF1α, NFκB, and MR inhibition decreased the expression of a SMC-MR target gene implicated in vascular fibrosis. In human aortic tissues, expression of HIF1α and NFκB each positively correlated with donor age and MR expression (P<0.0001).

CONCLUSIONS

These data implicate the inflammatory TF, NFκB, and oxidative stress-induced TF, HIF1α, in regulating SMC MR transcription in aging HASMCs, which drives aging-related vascular stiffness and cardiovascular disease.

Aldosterone as a Mediator of Cardiovascular Damage

Besides the physiological regulation of water, sodium, and potassium homeostasis, aldosterone modulates several physiological and pathological processes in the cardiovascular system. At the vascular level, aldosterone excess stimulates endothelial dysfunction and infiltration of inflammatory cells, enhances the development of the atherosclerotic plaque, and favors plaque instability, arterial stiffness, and calcification. At the cardiac level, aldosterone increases cardiac inflammation, fibrosis, and myocardial hypertrophy. As a clinical consequence, high aldosterone levels are associated with enhanced risk of cardiovascular events and mortality, especially when aldosterone secretion is inappropriate for renin levels and sodium intake, as in primary aldosteronism. Several clinical trials showed that mineralocorticoid receptor antagonists reduce cardiovascular mortality in patients with heart failure and reduced ejection fraction, but inconclusive results were reported for other cardiovascular conditions, such as heart failure with preserved ejection fraction, myocardial infarction, and atrial fibrillation. In patients with primary aldosteronism, adrenalectomy or treatment with mineralocorticoid receptor antagonists significantly mitigate adverse aldosterone effects, reducing the risk of cardiovascular events, mortality, and incident atrial fibrillation. In this review, we will summarize the major preclinical and clinical studies investigating the cardiovascular damage mediated by aldosterone and the protective effect of mineralocorticoid receptor antagonists for the reduction of cardiovascular risk in patients with cardiovascular diseases and primary aldosteronism.

Dexamethasone-associated metabolic effects in male mice are partially caused by depletion of endogenous corticosterone

Synthetic glucocorticoids are clinically used to treat auto-immune and inflammatory disease. Despite the high efficacy, glucocorticoid treatments causes side effects such as obesity and insulin resistance in many patients. Via their pharmacological target, the glucocorticoid receptor (GR), glucocorticoids suppress endogenous glucocorticoid secretion. Endogenous, but not synthetic, glucocorticoids activate the mineralocorticoid receptor (MR) and side effects of synthetic glucocorticoids may thus not only result from GR hyperactivation but also from MR hypoactivation. Here, we tested the hypothesis that reactivation of MR with corticosterone add-on treatment can attenuate the metabolic effects of the synthetic glucocorticoid dexamethasone. Male 8-week-old C57Bl/6J mice received a high-fat diet supplemented with dexamethasone or vehicle, and were subcutaneously implanted with low-dose corticosterone- or vehicle-containing pellets. Dexamethasone strongly reduced body weight and fat mass gain, while corticosterone add-on partially normalized this. Dexamethasone-induced hyperglycemia and hyperinsulinemia were exacerbated by corticosterone add-on, which was prevented by MR antagonism. In subcutaneous white adipose tissue, corticosterone add-on prevented the dexamethasone-induced expression of intracellular lipolysis genes. In brown adipose tissue, dexamethasone also upregulated gene expression of brown adipose tissue identity markers, lipid transporters and lipolysis enzymes, which was prevented by corticosterone add-on. In conclusion, corticosterone add-on treatment prevents several, while exacerbating other metabolic effects of dexamethasone. While the exact role of MR remains elusive, this study suggests that corticosterone suppression by dexamethasone contributes to its effects in mice.

Long Noncoding RNA Tug1 Promotes Angiotensin II-Induced Renal Fibrosis by Binding to Mineralocorticoid Receptor and Negatively Regulating MicroR-29b-3p

[Figure: see text].

Nondipping Blood Pressure: Predictive or Reactive Failure of Renal Sodium Handling?

Blood pressure follows a daily rhythm, dipping during nocturnal sleep in humans. Attenuation of this dip (nondipping) is associated with increased risk of cardiovascular disease. Renal control of sodium homeostasis is essential for long-term blood pressure control. Sodium reabsorption and excretion have rhythms that rely on predictive/circadian as well as reactive adaptations. We explore how these rhythms might contribute to blood pressure rhythm in health and disease.

Sex differences in the time course and mechanisms of vascular and cardiac aging in mice: role of the smooth muscle cell mineralocorticoid receptor

Aging is associated with heart and vascular dysfunction that contributes to cardiovascular disease (CVD) risk. Clinical data support a sexual dimorphism in the time course of aging-associated CVD. However, the mechanisms driving sex differences in cardiovascular aging and whether they can be modeled in mice have not been explored. Mineralocorticoid receptors (MRs) regulate blood pressure, and we previously demonstrated in male mice that MR expression increases in aging mouse vessels and smooth muscle cell-specific MR deletion (SMC-MR-KO) protects from cardiovascular aging. This study characterizes sex differences in murine cardiovascular aging and the associated sex-specific role of SMC-MR. Aortic stiffness, measured by pulse wave velocity, increased from 3 to 12 mo of age in males but not until 18 mo in females. The timing of the rise in aortic stiffening correlated with the timing of increased aortic MR expression, and aortic stiffness did not increase with age in SMC-MR-KO mice of both sexes. Vascular fibrosis increased at 12 mo in males and later at 18 mo in females; however, fibrosis was attenuated by SMC-MR-KO in males only. In resistance vessels, angiotensin type 1 receptor (AT1R)-mediated vasoconstriction also increased at 12 mo in males and 18 mo in females. ANG II-induced vasoconstriction was decreased in SMC-MR-KO specifically in males in association with decreased AT1R expression. Cardiac systolic function declined in males and females by 18 mo of age, which was prevented by SMC-MR-KO specifically in females. Cardiac perivascular fibrosis increased with age in both sexes accompanied by sex-specific changes in the expression levels of MR-regulated profibrotic genes.NEW & NOTEWORTHY These data demonstrate that the delayed and steeper decline in cardiovascular function observed in aging females can be modeled in aging mice. Moreover, the mechanisms driving vascular and cardiac aging phenotypes are distinct between males and females. Mineralocorticoid receptors in smooth muscle cells play a significant role in cardiovascular aging in both sexes; however, they do so by distinct mechanisms. Overall, these findings suggest that sex-specific therapies may be necessary to retard the aging process and improve cardiovascular disease outcomes in the aging population.

Knockout of the circadian clock protein PER1 results in sex-dependent alterations of ET-1 production in mice in response to a high-salt diet plus mineralocorticoid treatment

Previously, we showed that global knockout (KO) of the circadian clock transcription factor PER1 in male, but not female, mice fed a high-salt diet plus mineralocorticoid treatment (HS/DOCP) resulted in nondipping hypertension and decreased night/day ratio of sodium (Na) excretion. Additionally, we have shown that the endothelin-1 (ET-1) gene is targeted by both PER1 and aldosterone. We hypothesized that ET-1 would exhibit a sex-specific response to HS/DOCP treatment in PER1 KO. Here we show that male, but not female, global PER1 KO mice exhibit a decreased night/day ratio of urinary ET-1. Gene expression analysis revealed significant genotype differences in ET-1 and endothelin A receptor (ET_A) expression in male, but not female, mice in response to HS/DOCP. Additionally, both wild-type and global PER1 KO male mice significantly increase endothelin B receptor (ET_B) expression in response to HS/DOCP, but female mice do not. Finally, siRNA-mediated knockdown of PER1 in mouse cortical collecting duct cells (mpkCCDc14) resulted in increased ET-1 mRNA expression and peptide secretion in response to aldosterone treatment. These data suggest that PER1 is a negative regulator of ET-1 expression in response to HS/DOCP, revealing a novel mechanism for the regulation of renal Na handling in response to HS/DOCP treatment.

Obesity and cardiovascular disease in women

As the prevalence of obesity continues to grow worldwide, the health and financial burden of obesity-related comorbidities grows too. Cardiovascular disease (CVD) is clearly associated with increased adiposity. Importantly, women are at higher risk of CVD when obese and insulin resistant, in particular at higher risk of developing heart failure with preserved ejection fraction and ischemic heart disease. Increased aldosterone and mineralocorticoid receptor activation, aberrant estrogenic signaling and elevated levels of androgens are among some of the proposed mechanisms explaining the heightened CVD risk. In addition to traditional cardiovascular risk factors, understanding nontraditional risk factors specific to women, like excess weight gain during pregnancy, preeclampsia, gestational diabetes, and menopause are central to designing personalized interventions aimed to curb the epidemic of CVD. In the present review, we examine the available evidence supporting a differential cardiovascular impact of increased adiposity in women compared with men and the proposed pathophysiological mechanisms behind these differences. We also discuss women-specific cardiovascular risk factors associated with obesity and insulin resistance.

Mineralocorticoid Receptors in Metabolic Syndrome: From Physiology to Disease

Over the past decade, several studies have shown that activity of extra-renal mineralocorticoid receptors (MR) regulates vascular tone, adipogenesis, adipose tissue function, and cardiomyocyte contraction. In mice, abnormal activation of MR in the vasculature and in adipose tissue favors the occurrence of several components of the metabolic syndrome (MetS), such as hypertension, obesity, and glucose intolerance. Accordingly, high levels of aldosterone are associated with obesity and MetS in humans, suggesting that altered activation of aldosterone-MR system in extra-renal tissues leads to profound metabolic dysfunctions. In this context, in addition to the classical indications for heart failure and hypertension, MR antagonists (MRAs) nowadays represent a promising approach to tackle cardiovascular and metabolic disorders occurring in the MetS.

Vascular and inflammatory mineralocorticoid receptors in kidney disease

Mineralocorticoid receptor (MR) activation in the kidney can occur outside the aldosterone-sensitive distal nephron in sites including the endothelium, smooth muscle and inflammatory cells. MR activation in these cells has deleterious effects on kidney structure and function by promoting oxidative injury, endothelial dysfunction and stiffness, vascular remodelling and calcification, decreased relaxation and activation of T cells and pro-inflammatory macrophages. Here, we review the data showing the cellular consequences of MR activation in endothelial, smooth muscle and inflammatory cells and how this affects the kidney in pathological situations. The evidence demonstrating a benefit of pharmacological or genetic MR inhibition in various models of kidney disease is also discussed.

Vascular mineralocorticoid receptor activation and disease

Mineralocorticoid receptor activation in endothelial and smooth muscle cells can promote vascular disease by increasing oxidative stress, promoting inflammation, accelerating vascular stiffness, remodeling, and calcification, altering vessel responsiveness to various vasoactive factors, thus altering vascular tone and blood pressure, and by altering angiogenesis. Here, we review the recent evidence highlighting the impact of vascular mineralocorticoid receptor activation in pathological situations, including kidney injury, vascular injury associated with metabolic diseases, atherosclerosis, cerebral vascular injury during hypertension, vascular stiffening and aging, pulmonary hypertension, vascular calcification, cardiac remodeling, wound healing, inflammation, thrombosis, and disorders related to angiogenic defects in the eye. The possible mechanisms implicating mineralocorticoid receptor activation in various vascular disorders are discussed. Altogether, recent evidence points towards pharmacological mineralocorticoid receptor inhibition as a strategy to treat diseases in which overactivation of the mineralocorticoid receptor in endothelial and/or smooth muscle cells may play a pivotal role.

PKCδ Mediates Mineralocorticoid Receptor Activation by Angiotensin II to Modulate Smooth Muscle Cell Function

Angiotensin II (AngII) and the mineralocorticoid receptor (MR) ligand aldosterone both contribute to cardiovascular disorders, including hypertension and adverse vascular remodeling. We previously demonstrated that AngII activates MR-mediated gene transcription in human vascular smooth muscle cells (SMCs), yet the mechanism and the impact on SMC function are unknown. Using an MR-responsive element-driven transcriptional reporter assay, we confirm that AngII induces MR transcriptional activity in vascular SMCs and endothelial cells, but not in Cos1 or human embryonic kidney-293 cells. AngII activation of MR was blocked by the MR antagonist spironolactone or eplerenone and the protein kinase C-δ (PKCδ) inhibitor rottlerin, implicating both in the mechanism. Similarly, small interfering RNA knockdown of PKCδ in SMCs prevented AngII-mediated MR activation, whereas knocking down of MR blocked both aldosterone- and AngII-induced MR function. Coimmunoprecipitation studies reveal that endogenous MR and PKCδ form a complex in SMCs that is enhanced by AngII treatment in association with increased serine phosphorylation of the MR N terminus. AngII increased mRNA expression of the SMC-MR target gene, FKBP51, via an MR-responsive element in intron 5 of the FKBP51 gene. The impact of AngII on FKBP51 reporter activity and gene expression in SMCs was inhibited by spironolactone and rottlerin. Finally, the AngII-induced increase in SMC number was also blocked by the MR antagonist spironolactone and the PKCδ inhibitor rottlerin. These data demonstrate that AngII activates MR transcriptional regulatory activity, target gene regulation, and SMC proliferation in a PKCδ-dependent manner. This new mechanism may contribute to synergy between MR and AngII in driving SMC dysfunction and to the cardiovascular benefits of MR and AngII receptor blockade in humans.

The endothelial mineralocorticoid receptor: Contributions to sex differences in cardiovascular disease

Cardiovascular disease remains the leading cause of death for both men and women. The observation that premenopausal women are protected from cardiovascular disease relative to age-matched men, and that this protection is lost with menopause, has led to extensive study of the role of sex steroid hormones in the pathogenesis of cardiovascular disease. However, the molecular basis for sex differences in cardiovascular disease is still not fully understood, limiting the ability to tailor therapies to male and female patients. Therefore, there is a growing need to investigate molecular pathways outside of traditional sex hormone signaling to fully understand sex differences in cardiovascular disease. Emerging evidence points to the mineralocorticoid receptor (MR), a steroid hormone receptor activated by the adrenal hormone aldosterone, as one such mediator of cardiovascular disease risk, potentially serving as a sex-dependent link between cardiovascular risk factors and disease. Enhanced activation of the MR by aldosterone is associated with increased risk of cardiovascular disease. Emerging evidence implicates the MR specifically within the endothelial cells lining the blood vessels in mediating some of the sex differences observed in cardiovascular pathology. This review summarizes the available clinical and preclinical literature concerning the role of the MR in the pathophysiology of endothelial dysfunction, hypertension, atherosclerosis, and heart failure, with a special emphasis on sex differences in the role of endothelial-specific MR in these pathologies. The available data regarding the molecular mechanisms by which endothelial-specific MR may contribute to sex differences in cardiovascular disease is also summarized. A paradigm emerges from synthesis of the literature in which endothelial-specific MR regulates vascular function in a sex-dependent manner in response to cardiovascular risk factors to contribute to disease. Limitations in this field include the relative paucity of women in clinical trials and, until recently, the nearly exclusive use of male animals in preclinical investigations. Enhanced understanding of the sex-specific roles of endothelial MR could lead to novel mechanistic insights underlying sex differences in cardiovascular disease incidence and outcomes and could identify additional therapeutic targets to effectively treat cardiovascular disease in men and women.

Endothelial cell mineralocorticoid receptors oppose VEGF-induced gene expression and angiogenesis

Aldosterone is a key factor in adverse cardiovascular remodeling by acting on the mineralocorticoid receptor (MR) in different cell types. Endothelial MR activation mediates hypertrophy, inflammation and fibrosis. Cardiovascular remodeling is often accompanied by impaired angiogenesis, which is a risk factor for the development of heart failure. In this study, we evaluated the impact of MR in endothelial cells on angiogenesis. Deoxycorticosterone acetate (DOCA)-induced hypertension was associated with capillary rarefaction in the heart of WT mice but not of mice with cell type-specific MR deletion in endothelial cells. Consistently, endothelial MR deletion prevented the inhibitory effect of aldosterone on the capillarization of subcutaneously implanted silicon tubes and on capillary sprouting from aortic ring segments. We examined MR-dependent gene expression in cultured endothelial cells by RNA-seq and identified a cluster of differentially regulated genes related to angiogenesis. We found opposing effects on gene expression when comparing activation of the mineralocorticoid receptor in ECs to treatment with vascular endothelial growth factor (VEGF), a potent activator of angiogenesis. In conclusion, we demonstrate here that activation of endothelial cell MR impaired angiogenic capacity and lead to capillary rarefaction in a mouse model of MR-driven hypertension. MR activation opposed VEGF-induced gene expression leading to the dysregulation of angiogenesis-related gene networks in endothelial cells. Our findings underscore the pivotal role of endothelial cell MR in the pathophysiology of hypertension and related heart disease.

Role of Aldosterone and Mineralocorticoid Receptor in Cardiovascular Aging

The mineralocorticoid receptor (MR) was originally identified as a regulator of blood pressure, able to modulate renal sodium handling in response to its principal ligand aldosterone. MR is expressed in several extra-renal tissues, including the heart, vasculature, and adipose tissue. More recent studies have shown that extra-renal MR plays a relevant role in the control of cardiovascular and metabolic functions and has recently been implicated in the pathophysiology of aging. MR activation promotes vasoconstriction and acts as a potent pro-fibrotic agent in cardiovascular remodeling. Aging is associated with increased arterial stiffness and vascular tone, and modifications of arterial structure and function are responsible for these alterations. MR activation contributes to increase blood pressure with aging by regulating myogenic tone, vasoconstriction, and vascular oxidative stress. Importantly, aging represents an important contributor to the increased prevalence of cardiometabolic syndrome. In the elderly, dysregulation of MR signaling is associated with hypertension, obesity, and diabetes, representing an important cause of increased cardiovascular risk. Clinical use of MR antagonists is limited by the adverse effects induced by MR blockade in the kidney, raising the risk of hyperkalaemia in older patients with reduced renal function. Therefore, there is an unmet need for the enhanced understanding of the role of MR in aging and for development of novel specific MR antagonists in the context of cardiovascular rehabilitation in the elderly, in order to reduce relevant side effects.

Mineralocorticoid receptor: A hidden culprit for hemodialysis vascular access dysfunction

Hemodialysis vascular access dysfunction is a common and intractable problem in clinical practice with no definitive therapy yet available. As a key mediator of vascular and cardiac maladaptive remodeling, mineralocorticoid receptor (MR) plays a pivotal role in vascular fibrosis and intimal hyperplasia (IH) and is potentiated locally in hemodialysis vascular access following diverse injuries, like barotrauma, cannulation and shear stress. MR-related genomic and non-genomic pathways are responsible for triggering vascular smooth muscle cell activation, proliferation, migration and extracellular matrix overproduction. In endothelial cells, MR signaling diminishes nitric oxide production and its bioavailability, but amplifies reactive oxygen species, leading to an inflammatory state. Moreover, MR favors macrophage polarization towards a pro-inflammatory phenotype. In clinical settings like post-angioplasty or stenting restenosis, the beneficial effect of MR antagonists on vascular fibrosis and IH has been validated. In aggregate, therapeutic targeting of MR may provide a new avenue to prevent hemodialysis vascular access dysfunction.

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MR signaling is instrumental in both insufficient outward remodeling and exuberant inward remodeling of AVF.

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The effects of MR in VSMC, endothelial cell, and macrophage act synergistically to promote IH and vascular fibrosis in AVF.

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Pharmacological targeting of MR represents a novel therapeutic strategy to prevent hemodialysis vascular access dysfunction.

Mineralocorticoids and Cardiovascular Disease in Females with Insulin Resistance and Obesity

PURPOSE OF THE REVIEW

In the present review, we will discuss the evidence and the mechanisms underlying the complex interplay between obesity, mineralocorticoid receptor activation, and cardiovascular dysfunction with special emphasis on the pathogenesis of cardiovascular disease (CVD) in obese and insulin-resistant females.

RECENT FINDINGS

Since the initial isolation of aldosterone in 1953 and the cloning of the mineralocorticoid receptor (MR) decades later, our understanding has expanded tremendously regarding their involvement in the pathogenesis of CVD. Recent results from both pre-clinical and clinical studies support a close correlation between increase adiposity and enhanced aldosterone production (MR activation). Importantly, insulin resistance and obese females are more prone to the deleterious cardiovascular effects of MR activation, and enhanced MR activation in females has emerged as an important causative event in the genesis of a more severe CVD in diabetic women. Different clinical trials have been completed examining the effect of MR blockade in subjects with CVD. Despite its important beneficial mortality impact, side effects are frequent and a newer MR antagonist, finerenone, with less risk of hyperkalemia is currently being tested in large clinical trials.

New roles of aldosterone and mineralocorticoid receptors in cardiovascular disease: translational and sex-specific effects

Recent advances in the field of mineralocorticoid receptor (MR) and its ligand aldosterone expanded the role of this hormone and its receptor far beyond their initial function as a regulator of Na⁺ and K⁺ homeostasis in epithelial cells. The symposium "New Roles of Aldosterone and Mineralocorticoid Receptors in Cardiovascular Disease: Translational and Sex-Specific Effects" presented at the 38th World Congress of the International Union of Physiological Sciences (Rio de Janeiro, Brazil) highlighted the contribution of extrarenal MRs to cardiovascular disease. This symposium showcased how MRs expressed in endothelial, vascular smooth muscle, and immune cells plays a critical role in the development of vascular disease associated with aging, obesity, and chronic aldosterone stimulation and demonstrated that MR antagonism prevents the acute renal dysfunction and tubular injury induced by ischemia-reperfusion injury. It was also shown that the adipocyte-derived hormone leptin is a new direct regulator of aldosterone secretion and that leptin-mediated aldosterone production is a major contributor to obesity-associated hypertension in women. Sex differences in the role of aldosterone and of endothelial MR in the cardiovascular outcomes of obesity were highlighted. This review summarizes these important emerging concepts regarding the contribution of aldosterone and cell-specific MR to cardiovascular disease in male and female subjects and further supports sex-specific benefits of MR antagonist drugs to be tested in additional populations.

Mineralocorticoid receptor antagonism reverses diabetes-related coronary vasodilator dysfunction: A unique vascular transcriptomic signature

Coronary microvascular dysfunction predicts and may be a proximate cause of cardiac dysfunction and mortality in diabetes; however, few effective treatments exist for these conditions. We recently demonstrated that mineralocorticoid receptor (MR) antagonism reversed cardiovascular dysfunction in early-stage obesity/insulin resistance. The mechanisms underlying this benefit of MR antagonism and its relevance in the setting of long-term obesity complications like diabetes; however, remain unclear. Thus, the present study evaluated the impact of MR antagonism on diabetes-related coronary dysfunction and defines the MR-dependent vascular transcriptome in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat recapitulating later stages of human diabetes. OLETF rats were treated with spironolactone (Sp) and compared to untreated OLETF and lean Long-Evans Tokushima Otsuka rats. Sp treatment attenuated diabetes-associated adipose and cardiac inflammation/fibrosis and improved coronary endothelium-dependent vasodilation but did not alter enhanced coronary vasoconstriction, blood pressure, or metabolic parameters in OLETF rats. Further mechanistic studies using RNA deep sequencing of OLETF rat aortas revealed 157 differentially expressed genes following Sp including upregulation of genes involved in the molecular regulation of nitric oxide bioavailability (Hsp90ab1, Ahsa1, Ahsa2) as well as novel changes in α_1D adrenergic receptors (Adra1d), cyclooxygenase-2 (Ptgs2), and modulatory factors of these pathways (Ackr3, Acsl4). Further, Ingenuity Pathway Analysis predicted inhibition of upstream inflammatory regulators by Sp and inhibition of 'migration of endothelial cells', 'differentiation of smooth muscle', and 'angiogenesis' biological functions by Sp in diabetes. Thus, this study is the first to define the MR-dependent vascular transcriptome underlying treatment of diabetes-related coronary microvascular dysfunction by Sp.

Smooth Muscle Cell-Mineralocorticoid Receptor as a Mediator of Cardiovascular Stiffness With Aging

Stiffening of the vasculature with aging is a strong predictor of adverse cardiovascular events, independent of all other risk factors including blood pressure, yet no therapies target this process. MRs (mineralocorticoid receptors) in smooth muscle cells (SMCs) have been implicated in the regulation of vascular fibrosis but have not been explored in vascular aging. Comparing SMC-MR-deleted male mice to MR-intact littermates at 3, 12, and 18 months of age, we demonstrated that aging-associated vascular stiffening and fibrosis are mitigated by MR deletion in SMCs. Progression of cardiac stiffness and fibrosis and the decline in exercise capacity with aging were also mitigated by MR deletion in SMC. Vascular gene expression profiling analysis revealed that MR deletion in SMC is associated with recruitment of a distinct antifibrotic vascular gene expression program with aging. Moreover, long-term pharmacological inhibition of MR in aged mice prevented the progression of vascular fibrosis and stiffness and induced a similar antifibrotic vascular gene program. Finally, in a small trial in elderly male humans, short-term MR antagonism produced an antifibrotic signature of circulating biomarkers similar to that observed in the vasculature of SMC-MR-deleted mice. These findings suggest that SMC-MR contributes to vascular stiffening with aging and is a potential therapeutic target to prevent the progression of aging-associated vascular fibrosis and stiffness.

The Renin-Angiotensin-Aldosterone System as a Therapeutic Target in Late Injury Caused by Ischemia-Reperfusion

Ischemia-reperfusion (I/R) injury is a well-known phenomenon that involves different pathophysiological processes. Connection in diverse systems of survival brings about cellular dysfunction or even apoptosis. One of the survival systems of the cells, to the assault caused by ischemia, is the activation of the renin-angiotensin-aldosterone system (also known as an axis), which is focused on activating diverse signaling pathways to favor adaptation to the decrease in metabolic supports caused by the hypoxia. In trying to adapt to the I/R event, great changes occur that unchain cellular dysfunction with the capacity to lead to cell death, which translates into a poor prognosis due to the progression of dysfunction of the cellular activity. The search for the understanding of the diverse therapeutic alternatives in molecular coupling could favor the prognosis and evolution of patients who are subject to the I/R process.

Evidence for the use of mineralocorticoid receptor antagonists in the treatment of coronary artery disease and post-angioplasty restenosis

Mineralocorticoid receptor antagonists (MRAs), such as spironolactone and eplerenone have an established role in the treatment of heart failure. However, many experimental and clinical studies have shown that aldosterone also plays a pivotal role in a variety of other pathophysiological conditions within the cardiovascular system. Aldosterone has been suggested to promote inflammation, endothelial dysfunction and smooth muscle cell hyperplasia during the development of atherosclerosis, thereby promoting the development of coronary artery disease (CAD). Since CAD and subsequent ischemic cardiomyopathy are the major causes of heart failure, it is of major interest, whether pharmacological therapy with MRAs among heart failure patients will also affect the common underlying conditions, namely, atherosclerosis and subsequent coronary vessel narrowing/rarefication. Therefore, in this article, we reviewed and discussed the preclinical and clinical evidence of MRAs for the treatment of acute or chronic vascular remodeling processes, such as atherosclerosis and post-angioplasty restenosis, which determine the progression of CAD and subsequent ischemic cardiomyopathy.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: The role of the mineralocorticoid receptor in the vasculature

Since the mineralocorticoid receptor (MR) was cloned 30 years ago, it has become clear that MR is expressed in extra-renal tissues, including the cardiovascular system, where it is expressed in all cells of the vasculature. Understanding the role of MR in the vasculature has been of particular interest as clinical trials show that MR antagonism improves cardiovascular outcomes out of proportion to changes in blood pressure. The last 30 years of research have demonstrated that MR is a functional hormone-activated transcription factor in vascular smooth muscle cells and endothelial cells. This review summarizes advances in our understanding of the role of vascular MR in regulating blood pressure and vascular function, and its contribution to vascular disease. Specifically, vascular MR contributes directly to blood pressure control and to vascular dysfunction and remodeling in response to hypertension, obesity and vascular injury. The literature is summarized with respect to the role of vascular MR in conditions including: pulmonary hypertension; cerebral vascular remodeling and stroke; vascular inflammation, atherosclerosis and myocardial infarction; acute kidney injury; and vascular pathology in the eye. Considerations regarding the impact of age and sex on the function of vascular MR are also described. Further investigation of the precise molecular mechanisms by which MR contributes to these processes will aid in the identification of novel therapeutic targets to reduce cardiovascular disease (CVD)-related morbidity and mortality.

Cellular distribution and interaction between extended renin-angiotensin-aldosterone system pathways in atheroma

The importance of the renin-angiotensin-aldosterone system (RAAS) in the development of atherosclerotic has been experimentally documented. In fact, RAAS components have been shown to be locally expressed in the arterial wall and to be differentially regulated during atherosclerotic lesion progression. RAAS transcripts and proteins were shown to be differentially expressed and to interact in the 3 main cells of atheroma: endothelial cells, vascular smooth muscle cells, and macrophages. This review describes the local expression and cellular distribution of extended RAAS components in the arterial wall and their differential regulation during atherosclerotic lesion development.

Dipeptidyl peptidase-4 (DPP-4) inhibition with linagliptin reduces western diet-induced myocardial TRAF3IP2 expression, inflammation and fibrosis in female mice

Background

Diastolic dysfunction (DD), a hallmark of obesity and primary defect in heart failure with preserved ejection fraction, is a predictor of future cardiovascular events. We previously reported that linagliptin, a dipeptidyl peptidase-4 inhibitor, improved DD in Zucker Obese rats, a genetic model of obesity and hypertension. Here we investigated the cardioprotective effects of linagliptin on development of DD in western diet (WD)-fed mice, a clinically relevant model of overnutrition and activation of the renin-angiotensin-aldosterone system.

Methods

Female C56Bl/6 J mice were fed an obesogenic WD high in fat and simple sugars, and supplemented or not with linagliptin for 16 weeks.

Results

WD induced oxidative stress, inflammation, upregulation of Angiotensin II type 1 receptor and mineralocorticoid receptor (MR) expression, interstitial fibrosis, ultrastructural abnormalities and DD. Linagliptin inhibited cardiac DPP-4 activity and prevented molecular impairments and associated functional and structural abnormalities. Further, WD upregulated the expression of TRAF3IP2, a cytoplasmic adapter molecule and a regulator of multiple inflammatory mediators. Linagliptin inhibited its expression, activation of its downstream signaling intermediates NF-κB, AP-1 and p38-MAPK, and induction of multiple inflammatory mediators and growth factors that are known to contribute to development and progression of hypertrophy, fibrosis and contractile dysfunction. Linagliptin also inhibited WD-induced collagens I and III expression. Supporting these in vivo observations, linagliptin inhibited aldosterone-mediated MR-dependent oxidative stress, upregulation of TRAF3IP2, proinflammatory cytokine, and growth factor expression, and collagen induction in cultured primary cardiac fibroblasts. More importantly, linagliptin inhibited aldosterone-induced fibroblast activation and migration.

Conclusions

Together, these in vivo and in vitro results suggest that inhibition of DPP-4 activity by linagliptin reverses WD-induced DD, possibly by targeting TRAF3IP2 expression and its downstream inflammatory signaling.

Mineralocorticoid regulation of cell function: the role of rapid signalling and gene transcription pathways

The mineralocorticoid receptor (MR) and mineralocorticoids regulate epithelial handling of electrolytes, and induces diverse effects on other tissues. Traditionally, the effects of MR were ascribed to ligand-receptor binding and activation of gene transcription. However, the MR also utilises a number of intracellular signalling cascades, often by transactivating unrelated receptors, to change cell function more rapidly. Although aldosterone is the physiological mineralocorticoid, it is not the sole ligand for MR. Tissue-selective and mineralocorticoid-specific effects are conferred through the enzyme 11β-hydroxysteroid dehydrogenase 2, cellular redox status and properties of the MR itself. Furthermore, not all aldosterone effects are mediated via MR, with implication of the involvement of other membrane-bound receptors such as GPER. This review will describe the ligands, receptors and intracellular mechanisms available for mineralocorticoid hormone and receptor signalling and illustrate their complex interactions in physiology and disease.

Effect of hormone replacement therapy with the anti-mineralocorticoid progestin Drospirenone compared to tibolone on endothelial function and central haemodynamics in post-menopausal women

Drospirenone (DRSP) is an antialdosterone agent with progestogenic and antiandrogenic effects. This compound, has been recently used in combination with 17β-estradiol (E2) as hormonal therapy in postmenopausal women and has been shown to exert a significant antihypertensive effect in hypertensive post-menopausal women. Aim of the present study was to compare the effect of DRSP/E2 with those of Tibolone (T) on endothelial function, arterial stiffness, and lipid profile of early postmenopausal women naïve on post-menopausal hormonal therapy. Twenty-four women met the inclusion criteria and entered the study. Women were randomized to receive either DRSP/E2 or T for 6months. Blood pressure and heart rate were similar in both groups at baseline and at the end of the study. Compared to baseline, endothelial function assessed by Reactive Hyperemia (RH) significantly improved in women receiving E2/DRSP, whereas no significant differences between baseline and follow up were detected in women receiving Tibolone. Women receiving E2/DRSP showed a significant decrease in pulse wave velocity and Augmentation Index compared to baseline while no changes were observed in women receiving Tibolone. The capacity of sera to trigger endothelial cells apoptosis in vitro measured by cell death assay was significantly reduced by E/DRSP but not by T (HFA-E 70±5,6% vs HFD-E 41±4,5%, p<0,001). In conclusion, the present study shows that the association of Estradiol and Drospirenone as hormonal replacement therapy significantly improves vascular parameters and the composition of sera relevant for vascular protection in early post-menopausal normotensive women. These effects are not shared by Tibolone.

Vascular mineralocorticoid receptor regulates microRNA-155 to promote vasoconstriction and rising blood pressure with aging

Hypertension is nearly universal yet poorly controlled in the elderly despite proven benefits of intensive treatment. Mice lacking mineralocorticoid receptors in smooth muscle cells (SMC-MR-KO) are protected from rising blood pressure (BP) with aging, despite normal renal function. Vasoconstriction is attenuated in aged SMC-MR-KO mice, thus they were used to explore vascular mechanisms that may contribute to hypertension with aging. MicroRNA (miR) profiling identified miR-155 as the most down-regulated miR with vascular aging in MR-intact but not SMC-MR-KO mice. The aging-associated decrease in miR-155 in mesenteric resistance vessels was associated with increased mRNA abundance of MR and of predicted miR-155 targets Cav1.2 (L-type calcium channel (LTCC) subunit) and angiotensin type-1 receptor (AgtR1). SMC-MR-KO mice lacked these aging-associated vascular gene expression changes. In HEK293 cells, MR repressed miR-155 promoter activity. In cultured SMCs, miR-155 decreased Cav1.2 and AgtR1 mRNA. Compared to MR-intact littermates, aged SMC-MR-KO mice had decreased systolic BP, myogenic tone, SMC LTCC current, mesenteric vessel calcium influx, LTCC-induced vasoconstriction and angiotensin II-induced vasoconstriction and oxidative stress. Restoration of miR-155 specifically in SMCs of aged MR-intact mice decreased Cav1.2 and AgtR1 mRNA and attenuated LTCC-mediated and angiotensin II-induced vasoconstriction and oxidative stress. Finally, in a trial of MR blockade in elderly humans, changes in serum miR-155 predicted the BP treatment response. Thus, SMC-MR regulation of miR-155, Cav1.2 and AgtR1 impacts vasoconstriction with aging. This novel mechanism identifies potential new treatment strategies and biomarkers to improve and individualize antihypertensive therapy in the elderly.

Emerging Roles of the Mineralocorticoid Receptor in Pathology: Toward New Paradigms in Clinical Pharmacology

The mineralocorticoid receptor (MR) and its ligand aldosterone are the principal modulators of hormone-regulated renal sodium reabsorption. In addition to the kidney, there are several other cells and organs expressing MR, in which its activation mediates pathologic changes, indicating potential therapeutic applications of pharmacological MR antagonism. Steroidal MR antagonists have been used for decades to fight hypertension and more recently heart failure. New therapeutic indications are now arising, and nonsteroidal MR antagonists are currently under development. This review is focused on nonclassic MR targets in cardiac, vascular, renal, metabolic, ocular, and cutaneous diseases. The MR, associated with other risk factors, is involved in organ fibrosis, inflammation, oxidative stress, and aging; for example, in the kidney and heart MR mediates hormonal tissue-specific ion channel regulation. Genetic and epigenetic modifications of MR expression/activity that have been documented in hypertension may also present significant risk factors in other diseases and be susceptible to MR antagonism. Excess mineralocorticoid signaling, mediated by aldosterone or glucocorticoids binding, now appears deleterious in the progression of pathologies that may lead to end-stage organ failure and could therefore benefit from the repositioning of pharmacological MR antagonists.

MicroRNA-34b/c inhibits aldosterone-induced vascular smooth muscle cell calcification via a SATB2/Runx2 pathway

Increasing evidence shows that aldosterone and specific microRNAs (miRs) contribute to vascular smooth muscle cell (VSMC) calcification. In this study, we aim to explore the mechanistic links between miR-34b/c and aldosterone in VSMC calcification. VSMC calcification models were established both in vitro and in vivo. First, the levels of aldosterone, miR-34b/c and special AT-rich sequence-binding protein 2 (SATB2) were measured. Then, miR-34b/c mimics or inhibitors were transfected into VSMCs to evaluate the function of miR-34b/c. Luciferase reporter assays were used to demonstrate whether SATB2 was a direct target of miR-34b/c. Aldosterone and SATB2 were found to be markedly upregulated during VSMC calcification, whereas miR-34b/c expression was downregulated. Treatment with the mineralocorticoid receptor (MR) antagonist eplerenone inhibited VSMC calcification. In aldosterone-induced VSMC calcification, miR-34b/c levels were downregulated and SATB2 protein was upregulated. Furthermore, miR-34b/c overexpression alleviated aldosterone-induced VSMC calcification as well as inhibited the expression of SATB2 protein, whereas miR-34b/c inhibition markedly enhanced VSMC calcification and upregulated SATB2 protein. In addition, luciferase reporter assays showed that SATB2 is a direct target of miR-34b/c in VSMCs. Overexpression of SATB2 induced Runx2 overproduction and VSMC calcification. Therefore, miR-34b/c participates in aldosterone-induced VSMC calcification via a SATB2/Runx2 pathway. As miR-34b/c appears to be a negative regulator, it has potential as a therapeutic target of VSMC calcification.

Activated mineralocorticoid receptor regulates micro-RNA-29b in vascular smooth muscle cells

Inappropriately activated mineralocorticoid receptor (MR) is a risk factor for vascular remodeling with unclear molecular mechanism. Recent findings suggest that post-transcriptional regulation by micro-RNAs (miRs) may be involved. Our aim was to search for MR-dependent miRs in vascular smooth muscle cells (VSMCs) and to explore the underlying molecular mechanism and the pathologic relevance. We detected that aldosteroneviathe MR reduces miR-29bin vivoin murine aorta and in human primary and cultured VSMCs (ED50= 0.07 nM) but not in endothelial cells [quantitative PCR (qPCR), luciferase assays]. This effect was mediated by an increased decay of miR-29b in the cytoplasm with unchanged miR-29 family member or primary-miR levels. Decreased miR-29b led to an increase in extracellular matrix measured by ELISA and qPCR and enhanced VSMC migration in single cell-tracking experiments. Additionally, cell proliferation and the apoptosis/necrosis ratio (caspase/lactate dehydrogenase assay) was modulated by miR-29b. Enhanced VSMC migration by aldosterone required miR-29b regulation. Control experiments were performed with scrambled RNA and empty plasmids, by comparing aldosterone-stimulated with vehicle-incubated cells. Overall, our findings provide novel insights into the molecular mechanism of aldosterone-mediated vascular pathogenesis by identifying miR-29b as a pathophysiologic relevant target of activated MR in VSMCs and by highlighting the importance of miR processing for miR regulation.-Bretschneider, M., Busch, B., Mueller, D., Nolze, A., Schreier, B., Gekle, M., Grossmann, C. Activated mineralocorticoid receptor regulates micro-RNA-29b in vascular smooth muscle cells.

Novel Pathophysiological Mechanisms in Hypertension

Hypertension is the most common disease affecting humans and imparts a significant cardiovascular and renal risk to patients. Extensive research over the past few decades has enhanced our understanding of the underlying mechanisms in hypertension. However, in most instances, the cause of hypertension in a given patient continues to remain elusive. Nevertheless, achieving aggressive blood pressure goals significantly reduces cardiovascular morbidity and mortality, as demonstrated in the recently concluded SPRINT trial. Since a large proportion of patients still fail to achieve blood pressure goals, knowledge of novel pathophysiologic mechanisms and mechanism based treatment strategies is crucial. The following chapter will review the novel pathophysiological mechanisms in hypertension, with a focus on role of immunity, inflammation and vascular endothelial homeostasis. The therapeutic implications of these mechanisms will be discussed where applicable.

Spironolactone ameliorates arterial medial calcification in uremic rats: the role of mineralocorticoid receptor signaling in vascular calcification

Vascular calcification (VC) is a critical complication in patients with chronic kidney disease (CKD). The effects of spironolactone (SPL), a mineralocorticoid receptor (MR) antagonist, on VC have not been fully investigated in CKD. The present in vivo study determined the protective effects of SPL on VC in CKD rats. Rats were divided into a control group and four groups of rats with adenine-induced CKD. Three groups were treated with 0, 50, and 100 mg·kg(-1)·day(-1) SPL for 8 wk, and one group was treated with 100 mg·kg(-1)·day(-1) SPL for the last 2 wk of the 8-wk treatment period. After 8 wk, CKD rats developed azotemia and hyperphosphatemia, with increases in the expression of serum and glucocorticoid-regulated kinase-1 and sodium-phosphate cotransporter, in inflammation and oxidative stress level, in osteogenic signaling and apoptosis, and in aortic calcification, compared with control rats. SPL dose dependently decreased these changes in the aortas, concomitant with improvements in renal inflammation, tubulointerstitial nephritis, and kidney function. SPL neither lowered blood pressure level nor induced hyperkalemia. Treatment of CKD rats for the last 2 wk with 100 mg·kg(-1)·day(-1) SPL attenuated VC compared with CKD rats with the same degree of kidney function and hyperphosphatemia. In conclusion, SPL dose dependently inhibits the progression of VC by suppressing MR signaling, local inflammation, osteogenic transition, and apoptosis in the aortas of CKD rats.

Neutrophil Gelatinase-Associated Lipocalin, a Novel Mineralocorticoid Biotarget, Mediates Vascular Profibrotic Effects of Mineralocorticoids

Activation of the mineralocorticoid receptor has been shown to be deleterious in cardiovascular diseases (CVDs). We have recently shown that lipocalin 2 (Lcn2), or neutrophil gelatinase-associated lipocalin (NGAL), is a primary target of aldosterone/mineralocorticoid receptor in the cardiovascular system. Lcn2 is a circulating protein, which binds matrix metalloproteinase 9 and modulates its stability. We hypothesized that Lcn2 could be a mediator of aldosterone/mineralocorticoid receptor profibrotic effects in the cardiovascular system. Correlations between aldosterone and profibrotic markers, such as procollagen type I N-terminal peptide, were investigated in healthy subjects and subjects with abdominal obesity. The implication of Lcn2 in the mineralocorticoid pathway was studied using Lcn2 knockout mice subjected to a nephrectomy/aldosterone/salt (NAS) challenge for 4 weeks. In human subjects, NGAL/matrix metalloproteinase 9 was positively correlated with plasma aldosterone and fibrosis biomarkers. In mice, loss of Lcn2 prevented the NAS-induced increase of plasma procollagen type I N-terminal peptide, as well as the increase of collagen fibers deposition and collagen I expression in the coronary vessels and the aorta. The lack of Lcn2 also blunted the NAS-induced increase in systolic blood pressure. Ex vivo, treatment of human fibroblasts with recombinant Lcn2 induced the expression of collagen I and the profibrotic galectin-3 and cardiotrophin-1 molecules. Our results showed that Lcn2 plays a key role in aldosterone/mineralocorticoid receptor-mediated vascular fibrosis. The clinical data indicate that this may translate in human patients. Lcn2 is, therefore, a new biotarget in cardiovascular fibrosis induced by mineralocorticoid activation.

Mineralocorticoid receptor blockade prevents Western diet-induced diastolic dysfunction in female mice

Overnutrition/obesity predisposes individuals, particularly women, to diastolic dysfunction (DD), an independent predictor of future cardiovascular disease. We examined whether low-dose spironolactone (Sp) prevents DD associated with consumption of a Western Diet (WD) high in fat, fructose, and sucrose. Female C57BL6J mice were fed a WD with or without Sp (1 mg·kg(-1)·day(-1)). After 4 mo on the WD, mice exhibited increased body weight and visceral fat, but similar blood pressures, compared with control diet-fed mice. Sp prevented the development of WD-induced DD, as indicated by decreased isovolumic relaxation time and an improvement in myocardial performance (<Tei index) and septal annular velocity (<E'-to-A' ratio), as assessed by echocardiography, as well as decreased diastolic relaxation time/increased diastolic initial filling rate, as assessed by MRI. The relationship between passive sarcomere length of cardiac myocytes and ventricular pressure was monitored using di-8-ANEPPS staining of the t-tubule network in hearts ex vivo. Sp administration led to longer sarcomere lengths at each pressure indicative of improved ventricular compliance in WD-fed mice. Sp also prevented left ventricular hypertrophy, interstitial fibrosis, and oxidative stress. Sp prevented the WD-induced increased expression of myocardial proinflammatory M1 macrophage markers monocyte chemoattractant protein-1 and CD11c and increased the expression of the anti-inflammatory M2 macrophage marker CD206. These findings demonstrate that WD-induced DD is associated with increased oxidant stress, fibrosis, and immune dysregulation. Mineralocorticoid receptor antagonism enhanced M2 macrophage polarization and ameliorated oxidant stress and fibrosis. This work supports a novel blood pressure-independent effect of MR antagonism as a strategy to prevent diet-induced DD in women. Mineralocorticoid antagonism; low-dose spironolactone; aldosterone;high-fat diet; high-fructose diet; oxidative stress; inflammation; cardiac hypertrophy; myocardial compliance.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis

BACKGROUND

Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'.

RESULTS

Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability.

CONCLUSIONS

Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Mineralocorticoid receptors in the heart: lessons from cell-selective transgenic animals

The clinical impact of cardiovascular disease cannot be underestimated. Equally, the importance of cost-effective management of cardiac failure is a pressing issue in the face of an ageing population and the increasing incidence of metabolic disorders worldwide. Targeting the mineralocorticoid receptor (MR) offers one approach for the treatment of heart failure with current strategies for novel MR therapeutics focusing on harnessing their cardio-protective benefits, but limiting the side effects of existing agents. It is now well accepted that activation of the MR in the cardiovascular system promotes tissue inflammation and fibrosis and has negative consequences for cardiac function and patient outcomes following cardiac events. Indeed, blockade of the MR using one of the two available antagonists (spironolactone and eplerenone) provides significant cardio-protective effects in the clinical and experimental setting. Although the pathways downstream of MR that translate receptor activation into tissue inflammation, fibrosis and dysfunction are still being elucidated, a series of recent studies using cell-selective MR (NR3C2)-null or MR-overexpressing mice have offered many new insights into the role of MR in cardiovascular disease and the control of blood pressure. Dissecting the cell-specific roles of MR signalling in the heart and vasculature to identify those pathways that are critical for MR-dependent responses is an important step towards achieving cardiac-selective therapeutics. The goal of this review is to discuss recent advances in this area that have emerged from the study of tissue-selective MR-null mice, and other targeted transgenic models and their relevance to clinical disease.

Direct role for smooth muscle cell mineralocorticoid receptors in vascular remodeling: novel mechanisms and clinical implications

The mineralocorticoid receptor (MR) is a key regulator of blood pressure. MR antagonist drugs are used to treat hypertension and heart failure, resulting in decreased mortality by mechanisms that are not completely understood. In addition to the kidney, MR is also expressed in the smooth muscle cells (SMCs) of the vasculature, where it is activated by the hormone aldosterone and affects the expression of genes involved in vascular function at the cellular and systemic levels. Following vascular injury due to mechanical or physiological stresses, vessels undergo remodeling resulting in SMC hypertrophy, migration, and proliferation, as well as vessel fibrosis. Exuberant vascular remodeling is associated with poor outcomes in cardiovascular patients. This review compiles recent findings on the specific role of SMC-MR in the vascular remodeling process. The development and characterization of a SMC-specific MR-knockout mouse has demonstrated a direct role for SMC-MR in vascular remodeling. Additionally, several novel mechanisms contributing to SMC-MR-mediated vascular remodeling have been identified and are reviewed here, including Rho-kinase signaling, placental growth factor signaling through vascular endothelial growth factor type 1 receptor, and galectin signaling.

Impact of aldosterone on osteoinductive signaling and vascular calcification

Vascular calcification is frequently found already in early stages of chronic kidney disease (CKD) patients and is associated with high cardiovascular risk. The process of vascular calcification is not considered a passive phenomenon but involves, at least in part, phenotypical transformation of vascular smooth muscle cells (VSMCs). Following exposure to excessive extracellular phosphate concentrations, VSMCs undergo a reprogramming into osteo-/chondroblast-like cells. Such 'vascular osteoinduction' is characterized by expression of osteogenic transcription factors and triggered by increased phosphate concentrations. A key role in this process is assigned to cellular phosphate transporters, most notably the type III sodium-dependent phosphate transporter Pit1. Pit1 expression is stimulated by mineralocorticoid receptor activation. Therefore, aldosterone participates in the phenotypical transformation of VSMCs. In preclinical models, aldosterone antagonism reduces vascular osteoinduction. Patients with CKD suffer from hyperphosphatemia predisposing to vascular osteogenic transformation, potentially further fostered by concomitant hyperaldosteronism. Clearly, additional research is required to define the role of aldosterone in the regulation of osteogenic signaling and the consecutive vascular calcification in CKD, but more generally also other diseases associated with excessive vascular calcification and even in individuals without overt disease.

Estrogen receptor inhibits mineralocorticoid receptor transcriptional regulatory function

The steroid hormone aldosterone (aldo) contributes to cardiovascular disease in animal models and in humans. Aldo activates the mineralocorticoid receptor (MR), a hormone-activated transcription factor, and indeed, pharmacological MR inhibition improves cardiovascular outcomes. Because the incidence of cardiovascular disease is lower in premenopausal women, we hypothesized that estrogen (E2) signaling through the estrogen receptor (ER) may protect the vasculature by inhibiting the detrimental effects of aldo signaling through the MR. We demonstrate that E2-activated ER inhibits MR-mediated gene transcription from the mouse mammary tumor virus reporter in human embryonic kidney-293 cells. In contrast, aldo-activated MR does not affect ER-mediated gene transcription. The ERα N terminus (amino acids 1-253) containing part of the DNA-binding domain is sufficient to inhibit MR genomic function, although point mutations reveal that DNA binding, ligand-independent activation, and rapid nongenomic ERα signaling are not required for this effect. Furthermore, ERα and MR are part of a complex in cell lysates, with amino acids 1-233 of the ERα N terminus being sufficient to complex with the MR. Overall, the ability of ERα to inhibit MR-mediated gene transcription correlates with the ability of ERα segments to both localize to the nucleus and complex with the MR. In cultured vascular endothelial cells expressing ERα, E2 inhibits aldo induction of the vascular MR target gene intercellular adhesion molecule-1 (ICAM-1). ICAM-1 induction by endothelial MR is known to promote vascular inflammation that could contribute to the mechanism of aldo-induced atherosclerosis. E2 also inhibits aldo induction of ICAM-1 protein and prevents aldo-enhanced leukocyte adhesion to endothelial cells. These studies support a new model in which E2-activated ER in endothelial cells forms a complex with MR in the nucleus to modulate MR regulation of the proinflammatory gene ICAM-1. Estrogen inhibition of MR regulation of genes that contribute to cardiovascular disease may be a new mechanism by which premenopausal women are protected from cardiovascular disease.