Endothelial Cell Mineralocorticoid Receptor Research Articles

Cell-specific mineralocorticoid receptors: future therapeutic targets for stroke?

The mineralocorticoid receptor (MR), well known to be expressed in renal epithelial cells where it is important in fluid and electrolyte homeostasis, has aldosterone as one of its main agonists. Much research in the last 10–15 years indicates that MRs are also expressed outside of the kidney, including in the brain, vasculature and heart, where they contribute to the pathophysiology of disease (Dinh et al., 2012; Jaisser and Farman, 2016). Excess aldosterone is a cardiovascular risk factor, and MR antagonism is beneficial in the setting of cardiovascular disease (both clinically and experimentally), including in experimental stroke, whereby MR antagonism is beneficial in reducing both cerebral infarct size (Iwanami et al., 2007; Oyamada et al., 2008) and cerebral vascular remodeling (reviewed in Dinh et al., 2012) following cerebral ischemia. MR antagonism also reverses remodeling, both during aldosterone/mineralocorticoid excess and following cerebral ischemia. The advent of technology to generate mice which lack specific genes in specific cell types has allowed investigation into the contribution of MR in cell types such as vascular endothelial and myeloid cells to the pathophysiology of cerebrovascular disease and stroke (Frieler et al., 2011, 2012; Dinh et al., 2016). Endothelial cell MRs mediate cerebrovascular oxidative stress and brain inflammation in response to excess aldosterone (Dinh et al., 2016), and myeloid MR contribute to the ischemic damage, inflammation and neurological impairment following cerebral ischemia/reperfusion (Frieler et al., 2011, 2012). These and further investigations into the contribution of cell-specific MRs to cerebrovascular disease and stroke can help guide the future design of therapeutic strategies for stroke treatment.

Deoxycorticosterone Acetate/Salt–Induced Cardiac But Not Renal Injury Is Mediated By Endothelial Mineralocorticoid Receptors Independently From Blood Pressure

Chronic kidney disease has a tremendously increasing prevalence and requires novel therapeutic approaches. Mineralocorticoid receptor (MR) antagonists have proven highly beneficial in the therapy of cardiac disease. The cellular and molecular events leading to cardiac inflammation and remodeling are proposed to be similar to those mediating renal injury. Thus, this study was designed to evaluate and directly compare the effect of MR deletion in endothelial cells on cardiac and renal injury in a model of deoxycorticosterone acetate-induced hypertension. Endothelial MR deletion ameliorated deoxycorticosterone acetate/salt-induced cardiac remodeling. This was associated with a reduced expression of the vascular cell adhesion molecule Vcam1 in MR-deficient cardiac endothelial cells. Ambulatory blood pressure telemetry revealed that the protective effect of MR deletion was independent from blood pressure. Similar to the heart, deoxycorticosterone acetate/salt-induced severe renal injury, including inflammation, fibrosis, glomerular injury, and proteinuria. However, no differences in renal injury were observed between genotypes. In conclusion, MR deletion from endothelial cells ameliorated deoxycorticosterone acetate/salt-induced cardiac inflammation and remodeling independently from alterations in blood pressure but it did not affect renal injury. These findings suggest that the anti-inflammatory mechanism mediating organ protection after endothelial cell MR deletion is specific for the heart versus the kidney.

Endothelial Mineralocorticoid Receptor Deletion Prevents Diet-Induced Cardiac Diastolic Dysfunction in Females.

Overnutrition and insulin resistance are especially prominent risk factors for the development of cardiac diastolic dysfunction in females. We recently reported that consumption of a Western diet (WD) containing excess fat (46%), sucrose (17.5%), and high fructose corn syrup (17.5%) for 16 weeks resulted in cardiac diastolic dysfunction and aortic stiffening in young female mice and that these abnormalities were prevented by mineralocorticoid receptor blockade. Herein, we extend those studies by testing whether WD-induced diastolic dysfunction and factors contributing to diastolic impairment, such as cardiac fibrosis, hypertrophy, inflammation, and impaired insulin signaling, are modulated by excess endothelial cell mineralocorticoid receptor signaling. Four-week-old female endothelial cell mineralocorticoid receptor knockout and wild-type mice were fed mouse chow or WD for 4 months. WD feeding resulted in prolonged relaxation time, impaired diastolic septal wall motion, and increased left ventricular filling pressure indicative of diastolic dysfunction. This occurred in concert with myocardial interstitial fibrosis and cardiomyocyte hypertrophy that were associated with enhanced profibrotic (transforming growth factor β1/Smad) and progrowth (S6 kinase-1) signaling, as well as myocardial oxidative stress and a proinflammatory immune response. WD also induced cardiomyocyte stiffening, assessed ex vivo using atomic force microscopy. Conversely, endothelial cell mineralocorticoid receptor deficiency prevented WD-induced diastolic dysfunction, profibrotic, and progrowth signaling, in conjunction with reductions in macrophage proinflammatory polarization and improvements in insulin metabolic signaling. Therefore, our findings indicate that increased endothelial cell mineralocorticoid receptor signaling associated with consumption of a WD plays a key role in the activation of cardiac profibrotic, inflammatory, and growth pathways that lead to diastolic dysfunction in female mice.

Abstract 131: Endothelial Cell Mineralocorticoid Receptor: A Critical Player in Aortic Stiffness and Cardiac Diastolic Dysfunction in Female Mice

Enhanced activation of mineralocorticoid receptors (MRs) impairs insulin metabolic signaling, increases oxidative stress, and induces maladaptive immune responses with associated CV abnormalities. Emerging information suggests that obesity and insulin resistance predict CV stiffness in females. However, the specific role of endothelial cell MR (ECMR) has not been explored. Accordingly, we hypothesized that ECMR signaling modulated by a western diet (WD) impairs insulin signaling and increases inflammation, fibrosis and CV stiffness in females. Four week-old ECMR knockout (ECMR -/- ) and wild-type female mice were fed a mouse chow or WD containing fat (46%), sucrose (17.5%), and high fructose (17.5%) for 16 weeks. WD prompted MR to bind the hormone response element (nGnACAnnnTGTnCn) on the site of ENaC promoter and induced an increase in ENaC expression that was associated with increased aortic and EC stiffness as determined by in vivo pulse wave velocity and ex vivo atomic force microscopy techniques, respectively The elevated aortic stiffness was accompanied by increased expression of cytokines IL-17, MCP-1 and M1 markers CD 86, and CD11c. ENaC expression was reduced in the ECMR -/- vasculature with a decrease in WD-increase in aortic and EC stiffness.. ECMR -/- also improved aortic vasorelaxation to Ach, SNP (10 -9 -10 -4 mol/L), and insulin (0.1- 300 ng/ml), which were impaired by WD. Additionally, ECMR -/- restored WD-induced cardiac diastolic dysfunction assessed by cardiac MRI and echocardiography. Diastolic dysfunction was related to cardiomyocyte hypertrophy, oxidative stress, and fibrosis and occurred with enhanced activation of S6 kinase-1, Erk 1/2, serine phosphorylation of IRS-1, inactivation of PI3K-AKT-eNOS signaling pathways and the pro-fibrotic TGF-β1/ Smad signaling pathway and increased macrophage pro-inflammatory polarization. ECMR -/- markedly attenuated the cardiac functional and changes signaling induced by WD. These findings suggest that increased ECMR signaling and associated ENaC activation plays a key role in WD induced insulin metabolic sinaling impairment, adaptive pro-inflammatory responses, macrophage polarization and associated aortic stiffness and cardiac diastolic dysfunction in females.

Mineralocorticoid receptor: a critical player in vascular remodeling.

Vascular remodeling is a pathological condition with structural changes of blood vessels. Both inside-out and outside-in hypothesis have been put forward to describe mechanisms of vascular remodeling. An integrated model of these two hypotheses emphasizes the importance of immune cells such as monocytes/macrophages, T cells, and dendritic cells. These immune cells are at the center stage to orchestrate cellular proliferation, migration, and interactions of themselves and other vascular cells including endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and fibroblasts. These changes on vascular wall lead to inflammation and oxidative stress that are largely responsible for vascular remodeling. Mineralocorticoid receptor (MR) is a classic nuclear receptor. MR agonist promotes inflammation and oxidative stress and therefore exacerbates vascular remodeling. Conversely, MR antagonists have the opposite effects. MR has direct roles on vascular cells through non-genomic or genomic actions to modulate inflammation and oxidative stress. Recent studies using genetic mouse models have revealed that MR in myeloid cells, VSMCs and ECs all contribute to vascular remodeling. In conclusion, data in the past years have demonstrated that MR is a critical control point in modulating vascular remodeling. Studies will continue to provide evidence with more detailed mechanisms to support this notion.

Endothelial Cell Mineralocorticoid Receptors Regulate Deoxycorticosterone/Salt-Mediated Cardiac Remodeling and Vascular Reactivity But Not Blood Pressure

Recent studies have identified novel pathological roles for mineralocorticoid receptors (MR) in specific cell types in cardiovascular disease. The mechanisms by which MR promotes inflammation and fibrosis involve multiple cell-specific events. To identify the role of MR in endothelial cells (EC-MR), the current study explored the vascular responses to aldosterone in wild-type (WT) and EC-null mice (EC-MRKO). Nitric oxide function was impaired in the thoracic aorta and mesenteric arteries of aldosterone-treated WT mice. Although endothelial nitric oxide function was equivalently impaired in the mesenteric arteries of aldosterone-treated EC-MRKO mice, endothelial function was unaffected in the aorta, suggesting a differential role for EC-MR depending on the vascular bed. Second, the contribution of EC-MR to cardiovascular inflammation, fibrosis, and hypertension was determined in WT and EC-MRKO treated with deoxycorticosterone/salt for 8 days or 8 weeks. At 8 days, loss of EC-MR prevented macrophage infiltration and the expression of proinflammatory genes in the myocardium. Increased cardiac fibrosis was not detected in either genotype at this time, mRNA levels of profibrotic genes were significantly lower in EC-MRKO mice versus WT. At 8 weeks, deoxycorticosterone/salt treatment increased macrophage recruitment and proinflammatory gene expression in WT but not in EC-MRKO. Collagen deposition and connective tissue growth factor expression were significantly reduced in EC-MRKO versus WT. Interestingly, systolic blood pressure was equivalently elevated in deoxycorticosterone/salt treated WT and EC-MRKO. Our data demonstrate that (1) EC-MR signaling contributes to vascular nitric oxide function in large conduit arteries but not in resistance vessels and (2) an independent role for EC-MR in the inflammatory and profibrotic response to deoxycorticosterone/salt.

Mineralokortikoidrezeptorantagonisten als Therapieoption bei akuter und chronischer Chorioretinopathia centralis serosa

It is well known that central serous chorioretinopathy (CSCR) is triggered by endogenous and exogenous glucocorticoids but the exact pathomechanism is not completely understood. According to the results of previous studies overactivation of mineralocorticoid receptors may play a decisive role in the pathogenesis of CSCR. Experimental studies have shown that overactivation of mineralocorticoid receptors in endothelial cells of the choroid induces increased permeability. In a pilot study inhibition of mineralocorticoid receptors was successful in treating CSCR. This article reports about the use of spironolactone in the treatment of CSCR. In this observational case series spectral-domain optical coherence tomographv (SD-OCT) showed either reduction or complete reabsorption of subretinal fluid. In pilot studies and in this case series inhibition of mineralocorticoid receptors as a therapeutic option was effective and safe; however, the efficacy is difficult to distinguish from spontaneous recovery, especially in acute CSCR. For further assessment of this treatment controlled clinical trials are urgently required as this therapy would offer a new approach for patients with chronic CSCR and no tendency towards recovery.

The endothelial mineralocorticoid receptor regulates vasoconstrictor tone and blood pressure

Pathophysiological aldosterone (aldo)/mineralocorticoid receptor (MR) signaling has significant effects on the cardiovascular system, resulting in hypertension and cardiovascular remodeling; however, the specific contribution of the vascular MR to blood pressure regulation remains to be established. To address this question, we generated a mouse model with conditional overexpression of the MR in endothelial cells (MR-EC). In basal conditions, MR-EC mice developed moderate hypertension that could be reversed by canrenoate, a pharmacological MR antagonist. MR-EC mice presented increased contractile response of resistance arteries to vasoconstrictors (phenylephrine, thromboxane A(2) analog, angiotensin II, and endothelin 1) in the absence of vascular morphological alterations. The acute blood pressure response to angiotensin II or endothelin 1 infusion was increased in MR-EC mice compared with that in littermate controls. These observations demonstrate that enhanced MR activation in the endothelium generates an increase in blood pressure, independent of stimulation of renal tubular Na(+) transport by aldo/MR or direct activation of smooth muscle MR and establish one mechanism by which endothelial MR activation per se may contribute to impaired vascular reactivity.

Functional Mineralocorticoid Receptors in Human Vascular Endothelial Cells Regulate Intercellular Adhesion Molecule-1 Expression and Promote Leukocyte Adhesion

In clinical trials, aldosterone antagonists decrease cardiovascular mortality and ischemia by unknown mechanisms. The steroid hormone aldosterone acts by binding to the mineralocorticoid receptor (MR), a ligand-activated transcription factor. In humans, aldosterone causes MR-dependent endothelial cell (EC) dysfunction and in animal models, aldosterone increases vascular macrophage infiltration and atherosclerosis. MR antagonists inhibit these effects without changing blood pressure, suggesting a direct role for vascular MR in EC function and atherosclerosis. Whether human vascular ECs express functional MR is not known. Here, we show that human coronary artery and aortic ECs express MR mRNA and protein and that EC MR mediates aldosterone-dependent gene transcription. Human ECs also express the enzyme 11-beta-hydroxysteroid dehydrogenase-2 (11betaHSD2), and inhibition of 11betaHSD2 in aortic ECs enhances gene transactivation by cortisol, supporting that EC 11betaHSD2 is functional. Furthermore, aldosterone stimulates transcription of the proatherogenic leukocyte-EC adhesion molecule intercellular adhesion molecule (ICAM)1 gene and protein expression on human coronary artery ECs, an effect inhibited by the MR antagonist spironolactone and by MR knock down with small interfering RNA. Cell adhesion assays demonstrate that aldosterone promotes leukocyte-EC adhesion, an effect that is inhibited by spironolactone and ICAM1 blocking antibody, supporting that aldosterone induction of EC ICAM1 surface expression via MR mediates leukocyte-EC adhesion. These data show that aldosterone activates endogenous EC MR and proatherogenic gene expression in clinically important human ECs. These studies describe a novel mechanism by which aldosterone may influence ischemic cardiovascular events and support a new explanation for the decrease in ischemic events in patients treated with aldosterone antagonists.

Enhancement of glucocorticoid and mineralocorticoid receptor density in the microcirculation of the spontaneously hypertensive rat.

Elevated blood pressure and abnormal physiological parameters in the microcirculation of the spontaneously hypertensive rat (SHR) can be normalized by adrenalectomy. Thus glucocorticoids and mineralocorticoids may have major control over blood pressure status and organ injury mechanisms in SHRs. As background, this study was designed to examine the distribution of the glucocorticoid and mineralocorticoid receptors in a microvascular network. Mature SHR and their normotensive controls, the Wistar-Kyoto (WKY) rat, were studied. An immunohistochemical method was developed that provides a comprehensive display of the receptors in all segments of the mesentery microcirculation and the surrounding tissue parenchyma. All cells in the mesentery exhibit immunolabeling of the glucocorticoid receptor with predominant expression in the nuclei of parenchymal and endothelial cells. The mineralocorticoid receptor is expressed also in most cells of the microcirculation and adjacent parenchymal tissue. Both receptors exhibit the highest levels of immunolabel in the wall of the arterioles and venules, with lower levels in capillaries. Compared with WKY rats, the SHRs exhibit significantly enhanced density of glucocorticoid and mineralocorticoid receptors in endothelial cells of arterioles and venules as well as in parenchymal cells. These results suggest that the enhanced sensitivity of the SHR to glucocorticoids and aldosterone may be in part associated with enhanced glucocorticoid and mineralocorticoid receptor densities in the microcirculation.