Aldosterone suppresses Na⁺/H⁺ exchanger-3 expression through miR-204-5P-mediated post-transcriptional regulation in distal colon

Na⁺/H⁺ exchanger-3 (NHE3) is a major mediator of electroneutral NaCl absorption in the intestine and colon. In distal colon, chronic aldosterone exposure suppresses NHE3 expression, but the molecular mechanism responsible for this regulation remains unclear. Here, we tested whether aldosterone represses NHE3 through microRNA-dependent post-transcriptional regulation. Transcriptomic analysis of distal colon from dietary Na⁺-depleted rats identified miR-204-5P (miR-204-5P) as markedly upregulated. Aldosterone increased miR-204-5P abundance and concomitantly reduced NHE3 mRNA, protein expression, and transport activity in rat and human distal colonic epithelium and in SK-CO15 cells. Bioinformatic and reporter analyses identified a conserved miR-204-5P binding site within the NHE3 3'-untranslated region, and miR-204-5P mimic transfection markedly suppressed NHE3 expression and transport activity without affecting other Na⁺/H⁺ exchanger isoforms. These findings identify a previously unrecognized aldosterone-miRNA signaling pathway that mediates chronic repression of NHE3 and provide new insight into hormonal regulation of colonic Na⁺ absorption.