The Epithelial Na+ Channel Is a Zn2+ Sensitive Renal Na+ Reabsorption Pathway that Mediates Zn2+ Deficiency-induced Hypertension

Abstract

Background: Zinc (Zn2+) deficiency (ZnD) is comorbid with many chronic diseases including kidney disease and diabetes. Individuals in these vulnerable populations have a higher prevalence of hypertension. Recently, we reported that ZnD induces hypertension by promoting renal Na+ reabsorption. However, the renal Na+ reabsorption mechanisms involved continue to be identified. The renal epithelial Na+ channel (ENaC) plays an essential role in regulating whole-body Na+ and water balance and is involved in hypertension. We hypothesize that ENaC is a Zn2+-sensitive channel that mediates ZnD-induced hypertension. Experimental Design: To establish the role of ENaC in ZnD-induced hypertension, WT C57Bl/6 mice were switched from a Zn2+ adequate to a Zn2+ deficient diet for 10 weeks. During weeks 9 and 10, mice were treated with benzamil, an ENaC inhibitor. Systolic blood pressure (BP) was monitored by tail-cuff plethysmography; Renal ENaC expression was examined by immunohistochemistry and Western blot. To authenticate the Zn2+ sensitivity of ENaC, mouse distal convoluted tubule cells (mDCT) were treated with a Zn2+ chelator (TPEN) or vehicle (ethanol) for 24 hours. A subset of TPEN-treated cellular monolayers were supplemented with Zn2+ for 24 hours to replete intracellular Zn2+. Cellular ENaC expression was examined by Western blot analysis. Results: 1) Blood pressure: Compared to Zn2+ adequate mice (101.4 mm Hg ± 4.225), Zn2+ deficient mice had increased BP (154.6 mm Hg ± 2.422). However, benzamil treatment lowered BP (115.0 mm Hg ± 4.626) of Zn2+ deficient mice. 2)Immunohistochemistry: Next, Zn2+ effects on ENaC expression were examined. In Zn2+ deficient mice, αENaC protein abundance significantly increased compared with Zn2+ adequate mice. 3) Western blot analysis: To directly investigate Zn2+effects on ENaC expression, in vitro studies were performed using mDCT cells. Western blot analysis showed that TPEN-induced ZnD stimulated both αENaC and βENaC protein expression. Conclusion: Collectively, our findings reveal that (1) ENaC is a Zn2+ sensitive renal Na+ reabsorption pathway and (2) ENaC mediates ZnD-induced hypertension. Significance: Understanding the renal mechanisms by which Zn2+ regulates blood pressure may have an important therapeutic impact on hypertension. Funding: R21 DK119879, R01 DK-133698 (National Institute of Diabetes and Digestive and Kidney Diseases); R25DK078381 (NIH NIDDK STEP-UP program);1742339 (National Science Foundation ASK Program). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.