Endothelial specific epithelial sodium channel activation prompts vascular stiffness in female mice

Abstract

Our research suggests that enhanced endothelium mineralocorticoid receptor (ECMR) signaling induces endothelium epithelial sodium channel (EnNaC) activation to promote vascular stiffness. This occurs, in part, by reduction of endothelial nitric oxide (NO) synthase (eNOS) activity and bioavailable NO. This study demonstrated that consumption of a Western Diet (WD) containing excess fat and refined sugar for 16 weeks increases aldosterone level and MR activation resulting in impaired NO mediated vascular relaxation and aortic stiffness in females. These abnormalities were prevented by low doses of the MR antagonist, spironolactone. As ECMR KO also prevented these abnormalities we posited that ECMR/EnNaC activation was critical. Accordingly, we hypothesized that EC‐specific EnNaC activation would mediate vascular stiffness and impair flow‐mediated vasodilation through reduction of bioavailable NO. Four week old C57BL6/J mice were fed a WD containing high fat (46%), sucrose (17.5%), and high fructose corn syrup (17.5%) with or without a very low dose of amiloride (1 mg/kg/day) for 16 weeks. Female EnNaC KO (EnNaC−/−) and wild‐type littermate females were treated with aldosterone (250 μg/kg/day) via osmotic minipumps for 3 weeks. Amiloride, an antagonist for EnNaC for 16 weeks, could significantly attenuate WD‐induced increases in aortic stiffness in vivo as measured by pulse wave velocity and in vitro endothelial stiffness measured by atomic force microscopy. Meanwhile, amiloride further improved flow mediated dilation in mesenteric arteries and endothelium‐dependent relaxation with acetylcholine (10−9–10−4 mol/L) stimulation in wire myograph. Importantly, EnNaC KO mice also prevent aldosterone‐induced endothelium stiffness and impairment of endothelium‐dependent relaxation. These data suggest that the sequence of activated ECMR leading to cell specific EnNaC activation and signaling decreases bioavailable NO. This cascade plays a key role in the development of vascular stiffness and dysfunction.Support or Funding InformationNIH (R01 HL73101‐01A and R01 HL107910‐01) and the Veterans Affairs Merit System (0018) to Dr. Sowers