Interaction of miRNA, Endothelial Mineralocorticoid Receptor and Epithelial Sodium Channel in Endothelium Stiffness and Aortic Dysfunction.

Excessive endothelial cell (EC) mineralocorticoid receptor (ECMR) and epithelial sodium channel activation in endothelium (EnNaC) increase oxidative stress and inflammation with associated cardiovascular abnormalities. Previous studies implicate elevations in circulating aldosterone (Aldo) in obesity enhance ECMR/EnNaC signaling that contribute to the development of vascular stiffness, in part, by reducing endothelial nitric oxide (NO) synthase (eNOS) activity and NO production. However, the specific role of ECMR/EnNaC signaling and its molecular mechanisms have not been explored. We hypothesized interactions between ECMR, dysregulation of miRNA expression, and EnNaC contribute to obese-/Aldo-induced endothelium dysfunction and aortic stiffness. Six week-old ECMR -/- and wild type littermate mice were fed a mouse chow or Western diet (WD) containing excess fat (46%) and fructose (17.5%) for 16 weeks. The EnNaC alpha subunit KO (EnNaC -/- ) and EnNaC +/+ female mice were administrated Aldo (250 μg/kg/day) via osmotic minipumps for 3 weeks beginning at 25-28 weeks of age. RNA sequencing showed that in ECMR +/+ mice WD induced increased miR-7a, miR-34, and miR-6973a and reduced miR-99, miR-486a, miR-6904, miR-6916, miR-6240 that potentially target EnNaC expression. For EnNaC in vascular function, EnNaC -/- significantly reduced inward sodium currents by patch clamp in isolated mouse ECs. Meanwhile, EnNaC -/- significantly inhibited Aldo-induced endothelium stiffness and endothelium dependent relaxation observed in EnNaC +/+ . Further, chronic Aldo infusion induced aortic endoplasmic reticulum stress, reduced eNOS activation, endothelium permeability, expression of pro-inflammatory cytokines IL1 and IL6, oxidative stress, and aortic collagen 1 deposition and these abnormalities were attenuated in EnNaC -/- mice. These data indicate that interaction of endothelial specific ECMR/miRNA/EnNaC mediates vascular endothelium dysfunction and prompts aortic stiffness.