Spironolactone Effectively Reduces Renal ENaC Activity and Hypertension in Ang II‐Infused Female Rats in a Sex‐Specific Manner

Abstract

Hypertension is a major modifiable risk factor for cardiovascular disease that remains suboptimally controlled despite all recent advances in biomedical research. Sex differences pertaining to development of hypertension and its pathophysiological outcomes are becoming universally recognized. Mechanistic insights into those differences can be utilized to improve the existing or develop novel therapeutic interventions for both sexes. We have previously demonstrated that excessive stimulation of Epithelial Na+ Channel (ENaC), resistant to mineralocorticoid receptor (MR) inhibition, contributes to Ang II‐induced hypertension in male mice. Given the interaction between aldosterone and estrogen signaling pathways, herein, we hypothesize that resistance to MR blockade in Ang II hypertensive subjects is sex‐specific. We combined physiological, pharmacological, biochemical and biophysical approaches to compare how MR antagonism affects renal sodium handling and blood pressure in Ang II‐infused male and female Sprague Dawley rats. Patch‐clamp electrophysiology in split‐opened collecting ducts demonstrated that systemic spironolactone administration (30 mg/kgBW·day for 14 days) only partially attenuated the stimulatory effect of Ang II infusion on ENaC in males. The activity of the channel remained at least twofold higher than in untreated normotensive controls. MR inhibition was remarkably more efficient in Ang II‐infused females, suppressing renal ENaC activity to its basal levels observed in non‐hypertensive rats. In both sexes, the reduction of ENaC activity driven by spironolactone was primarily attributed to decreased functional expression of the channel. This effect was complemented by a moderate decrease of ENaC open probability in spironolactone‐treated hypertensive females. Circulating aldosterone levels were lower in Ang II‐infused females when compared to males. This difference was further accentuated by spironolactone administration. Quantitative western‐blotting revealed that only in hypertensive females MR antagonism significantly increased renal expression of Nedd4‐2, facilitating ENaC degradation and reducing Na+ reabsorption. MR blockade did not alter the abundance of active phosphorylated forms of other renal Na+ transporters – NCC and NKCC2, in both sexes. In line with our observations on renal Na+ handling, we found that spironolactone markedly attenuated hypertension in Ang II‐infused females, while MR inhibition failed to reduce blood pressure in hypertensive males. Aldosterone antagonism did not elevate plasma K+ in all animal groups. Flow cytometry showed significantly lower levels of Th17 cells in the kidneys of spironolactone‐treated females, indicating reduced inflammatory response. Overall, our findings suggest that the action of spironolactone on ENaC‐mediated renal sodium reabsorption is sex‐specific and MR antagonism can be an effective strategy to reduce blood pressure and kidney damage in females with Ang‐II induced hypertension.Support or Funding InformationAHA 15SDG25550150This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modeling Sex Differences in the Effects of Diuretics in Renal Epithelial Transport during Angiotensin II-induced Hypertension

“…In males, that is limited to a reduction in NHE3 activity, whereas in females, Na + -K + -ATPase and SGLT2 activities are also downregulated. Our simulations of the administration of diuretics on nephron transport in a hypertensive kidney indicate that the natriuretic and diuretic effects are generally stronger in females, consistent with experimental findings (46–48); more below.…”