Effects of the mineralocorticoid receptor antagonist eplerenone in experimental autoimmune encephalomyelitis.

There is growing evidence indicating that mineralocorticoid receptor (MR) expression influences a wide variety of functions in metabolic and immune response. The present study explored if antagonism of the MR reduces neuroinflammation in the spinal cord of mice with experimental autoimmune encephalomyelitis (EAE). Eplerenone (EPLE) (100 mg/kg dissolved in 30% 2-hydroxypropyl-ß-cyclodextrin) was administered intraperitoneally (i.p.) daily from EAE induction (day 0) until sacrificed on day 17 post-induction. The MR blocker (a) significantly decreased the inflammatory parameters TLR4, MYD88, IL-1ß, and iNOS mRNAs; (b) attenuated HMGB1, NLRP3, TGF-ß mRNAs, microglia, and aquaporin4 immunoreaction without modifying GFAP. Serum IL-1ß was also decreased in the EAE+EPLE group. Moreover, EPLE treatment prevented demyelination and improved clinical signs of EAE mice. Interestingly, MR was decreased and GR remained unchanged in EAE mice while EPLE treatment restored MR expression, suggesting that a dysbalanced MR/GR was associated with the development of neuroinflammation. Our results indicated that MR blockage with EPLE attenuated inflammation-related spinal cord pathology in the EAE mouse model of Multiple Sclerosis, supporting a novel therapeutic approach for immune-related diseases.

Effect of 11-Deoxycorticosterone in the Transcriptomic Response to Stress in Rainbow Trout Skeletal Muscle.

In aquaculture, many stressors can negatively affect growth in teleosts. It is believed that cortisol performs glucocorticoid and mineralocorticoid functions because teleosts do not synthesize aldosterone. However, recent data suggest that 11-deoxycorticosterone (DOC) released during stress events may be relevant to modulate the compensatory response. To understand how DOC modifies the skeletal muscle molecular response, we carried out a transcriptomic analysis. Rainbow trout (Oncorhynchus mykiss) were intraperitoneally treated with physiological doses of DOC in individuals pretreated with mifepristone (glucocorticoid receptor antagonist) or eplerenone (mineralocorticoid receptor antagonist). RNA was extracted from the skeletal muscles, and cDNA libraries were constructed from vehicle, DOC, mifepristone, mifepristone plus DOC, eplerenone, and eplerenone plus DOC groups. The RNA-seq analysis revealed 131 differentially expressed transcripts (DETs) induced by DOC with respect to the vehicle group, mainly associated with muscle contraction, sarcomere organization, and cell adhesion. In addition, a DOC versus mifepristone plus DOC analysis revealed 122 DETs related to muscle contraction, sarcomere organization, and skeletal muscle cell differentiation. In a DOC versus eplerenone plus DOC analysis, 133 DETs were associated with autophagosome assembly, circadian regulation of gene expression, and regulation of transcription from RNA pol II promoter. These analyses indicate that DOC has a relevant function in the stress response of skeletal muscles, whose action is differentially modulated by GR and MR and is complementary to cortisol.

Eplerenone Implantation Improved Adipose Dysfunction Averting RAAS Activation and Cell Division.

Introduction: Mineralocorticoid receptor (MR) activation within adipose tissue, triggers inflammation and metabolic syndrome development. The pharmacological blockade of MR provides beneficial effects for adipose tissue. Our study evaluates the impact of eplerenone implantation upon obesity. Experimental approach: A group of mice with implanted placebo pellets were fed using two types of diet, a normal (ND) or a high fat (HFD) diet. Additionally, a group of mice fed HFD were implanted with an eplerenone pellet. Metabolic and biochemical parameters were assessed in each animal group. Adipocyte size and lipid accumulation were investigated in the liver and adipose tissue. We evaluated the components of renin-angiotensin-aldosterone system (RAAS) locally in adipose tissue. Key results: Eplerenone reduced HFD-induced body weight gain, fasting glucose levels, fat accumulation, HFD-induced adipocyte size and liver lipid accumulation and improved glucose tolerance. In the adipose tissue, HFD significantly increased the mRNA levels of the RAAS molecules relative to the ND group. Eplerenone lowered RAAS mRNA levels, components of lipid metabolism and markers of inflammation in HFD-fed animals. Conclusion: MR antagonism with eplerenone diminishes insulin resistance that is related to obesity partly via a reduction of RAAS activation, inflammatory progression and cytokines induction. This suggests that eplerenone should be further studied as a therapeutic option for obesity and overweight.

The activation of the G protein-coupled estrogen receptor (GPER) prevents and regresses cardiac hypertrophy.

Ventricular hypertrophy is a risk factors for arrhythmias, ischemia and sudden death. It involves cellular modifications leading to a pathological remodeling and is associated with heart failure. The activation of the G protein-coupled estrogen receptor (GPER) mediates beneficial actions in the cardiovascular system. Our goal was to prevent and regress the hypertrophy by the activation of GPER in neonatal cardiac myocytes (NRCM) and SHR male rats. Aldosterone increased the neonatal cardiomyocytes cell surface area after 48 h of incubation. The aldo-induced hypertrophy was blocked by the mineralocorticoid receptor (MR) inhibitor Eplererone or the reduction of MR expression by siRNA. The activation of GPER by the agonist G-1 totally prevented the increase surface area by Ald. The transfection of neonatal rat cardiac myocytes with a siRNA against GPER or the incubation with GPER blockers G-15 and G-36 inhibited the protection of G-1. The significant increase of cell surface area after 48 h of incubation with Ald was totally regressed in 24 h by the presence of G-1, indicating that the activation of GPER not only prevent the hypertrophy but also regress the hypertrophy when it is already established. In the in vivo model, G-1 or Vehicle was constantly infused via the minipump to SHR. The reduction of the hypertrophy by G-1 was evident by the cross-sectional area, BNP and ANP markers and by echocardiography. In this studied we demonstrated that the activation of GPER prevented and regressed the hypertrophy induced by Ald in NRCM and regressed hypertrophy in SHR rats.

Mineralocorticoid receptor antagonists lead to increased adenosine bioavailability and modulate contractile cardiac parameters.

Activation of mineralocorticoid receptor antagonists (MRAs) is cardioprotective; however, this property is lost upon blockade or inactivation of adenosine (ADO) receptor A2b. In this study, we investigated whether the effects of MRAs are mediated by an interaction between cardioprotective ADO receptors A1 and A3. Spironolactone (SPI) or eplerenone (EPL) increased ADO levels in the plasma of treated animals compared to control animals. SPI or EPL increased the protein and activity levels of ecto-5'-nucleotidase (NT5E), an enzyme that synthesizes ADO, compared to control. The levels of ADO deaminase (ADA), which degrades ADO, were not affected by SPI or EPL; however, the activity of ADA was reduced in SPI-treated rats compared to control. Using an isolated cardiomyocyte model, we found inotropic and chronotropic effects, and increased calcium transient [Ca2+]i in cells treated with ADO receptor A1 or A3 antagonists compared to control groups. Upon co-treatment with MRAs, EPL and SPI fully and partially reverted the effects of receptor A1 or A3 antagonism, respectively. Collectively, MRAs in vivo lead to increased ADO bioavailability. In vitro, the rapid effects of SPI and EPL are mediated by an interaction between ADO receptors A1 and A3.