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

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.

This study sought to clarify the molecular mechanisms and therapeutic targets responsible for DSG's protective effects against UC.

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.

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.

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.