Diosgenin ameliorates colitis by inhibiting mitochondrial DNA synthesis in macrophages via STAT2-CMPK2 pathway.

Abstract

BACKGROUND: Ulcerative colitis (UC) is a chronic inflammatory bowel disease with rising global prevalence, posing ongoing therapeutic challenges. Diosgenin (DSG), a natural steroidal saponin, exhibits anti-inflammatory properties. However, its molecular mechanisms in UC are poorly understood. PURPOSE: This study sought to clarify the molecular mechanisms and therapeutic targets responsible for DSG's protective effects against UC. METHODS: A murine colitis model induced by dextran sulfate sodium was used to assess DSG efficacy. Mechanistic insights were obtained from RNA sequencing analysis and confirmed in RAW264.7 and bone marrow-derived macrophages through Stat2 knockdown/overexpression experiments. Chromatin immunoprecipitation and surface plasmon resonance assays were used to investigate DSG-STAT2 interactions. RESULTS: DSG markedly alleviated colonic inflammation and tissue damage in DSS-treated mice. It significantly modulated macrophage polarization in colonic lamina propria lymphocytes. RNA-seq and Western blotting revealed that DSG selectively suppressed STAT2 phosphorylation and CMPK2 expression in macrophages, while attenuated LPS-induced mitochondrial DNA (mtDNA) synthesis and mitochondrial ROS (mtROS) production. STAT2 directly bound to the Cmpk2 promoter, and Stat2 silencing abolished LPS-driven Cmpk2 transcription and mtDNA synthesis. DSG interacted with STAT2 at Pro630 and Lys689 residues, and its inhibitory effects on CMPK2 and mtDNA were reversed by STAT2 overexpression. CONCLUSIONS: DSG exerts its anti-colitis effects by selectively targeting STAT2 at Pro630 and Lys689, thereby suppressing CMPK2-mediated mtDNA overproduction. The discovery of a STAT2-dependent mechanism in DSG presents a potential therapeutic approach for UC.