Estrogen negatively regulates the renal epithelial sodium channel (ENaC) by promoting Derlin-1 expression and AMPK activation

The main functions of the epithelial sodium channel (ENaC) in the kidney distal nephron are mediation of sodium and water balance and stabilization of blood pressure. Estrogen has important effects on sodium and water balance and on premenopausal blood pressure, but its role in the regulation of ENaC function is not fully understood. Female Sprague-Dawley rats were treated with 17 beta-estradiol for 6 weeks following bilateral ovariectomy. Plasma estrogen, aldosterone, creatinine, and electrolytes were analyzed, and alpha-ENaC and derlin-1 protein expression in the kidney was determined by immunohistochemistry and western blotting. The expression levels of alpha-ENaC, derlin-1, AMPK, and related molecules were also examined by western blotting and real-time PCR in cultured mouse renal collecting duct (mpkCCDc14) epithelial cells following estrogen treatment. Immunofluorescence and coimmunoprecipitation were performed to detect a-ENaC binding with derlin-1 and alpha-ENaC ubiquitination. The results demonstrated that the loss of estrogen elevated systolic blood pressure in ovariectomized (OVX) rats. OVX rat kidneys showed increased alpha-ENaC expression but decreased derlin-1 expression. In contrast, estrogen treatment decreased alpha-ENaC expression but increased derlin-1 expression in mpkCCDc14 cells. Moreover, estrogen induced alpha-ENaC ubiquitination by promoting the interaction of alpha-ENaC with derlin-1 and evoked phosphorylation of AMPK in mpkCCDc14 cells. Our study indicates that estrogen reduces ENaC expression and blood pressure in OVX rats through derlin-1 upregulation and AMPK activation.