The microRNA cluster miR-17~92 is induced by aldosterone and estrogen and inhibits aldosterone signaling in the kidney distal nephron

Background: Hypertension affects more than one billion people worldwide. A key regulator of blood pressure homeostasis is aldosterone, the final signaling hormone of the renin-angiotensin-aldosterone-signaling (RAAS) system. Aldosterone increases sodium (Na+) transport in the kidney distal nephron to regulate blood volume. We previously demonstrated that aldosterone alters the expression of microRNAs (miRs) in collecting duct epithelial cells to modulate the Na+ transport response to aldosterone. In this study a novel miR cluster, miR-17~92, is investigated for its ability to alter aldosterone signaling in the kidney in a sex-specific manner. Methods: The cortical collecting duct (CCD), mCCD-cl1, cell line were cultured on permeable filter supports to measure Na+ transport by short-circuit current recordings in Ussing chambers. In vivo regulation of miRs by aldosterone was confirmed using freshly isolated CCD cells from male and female mice placed on low Na+ diets. Dual-luciferase assays validated miR targeting of the serum and glucocorticoid kinase (SGK1). CCD cells were treated with estrogen to determine the impact on aldosterone stimulation and Na+ transport. RT-qPCR quantified miR and mRNA expression and western blot analysis quantified protein expression of the RAAS signaling cascade in mCCD cells after aldosterone and estrogen stimulation. Results: The miR-17~92 cluster expression is increased after aldosterone and estrogen stimulation in cultured mCCD cells. A sex-specific upregulation of the miR-17~92 cluster was observed in isolated CCD cells from female mice placed on a low-Na+ diet to stimulate aldosterone release. This increase was not observed in male mice. Members of the miR cluster, miRs-19a&b, are predicted to bind to the 3’-untranslated region of SGK1 and this was confirmed using luciferase assays. Overexpression of miR-19 in mCCD cells using miR mimics significantly inhibited aldosterone stimulation of Na+ transport via the epithelial sodium channel (ENaC). Estrogen pretreatment of mCCD blunted a subsequent aldosterone stimulation. This blunting of aldosterone signaling was due to a decrease in SGK1 mRNA and protein levels, for both estrogen stimulated and miR-19 mimic overexpressing cells. Conclusion: The miR-17~92 cluster is regulated by aldosterone and estrogen. Mir-19 targets SGK1 and reduces its expression. This, in turn, reduces the aldosterone-induced ENaC transport. The regulation of miR-17~92 is sex-specific and estrogen responsive, and targets SGK1 to downregulate sodium transport in the CCD. This could contribute to sex differences in sodium homeostasis. NIH 5T32DK061296-20 This is the full abstract presented at the American Physiology Summit 2023 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.