Sinomenine alleviates ulcerative colitis by targeting FXR to regulate arachidonic acid metabolism and Th17/Treg homeostasis.

Sinomenine (SIN), a bioactive alkaloid with anti-inflammatory activity, has shown therapeutic potential in ulcerative colitis (UC), but its precise molecular targets remain unclear. This study investigated the key targets and mechanisms underlying SIN-mediated protection in UC. In a dextran sulfate sodium (DSS)-induced colitis mouse model, SIN dose-dependently alleviated colitis symptoms, restored colon length, improved histopathology injury, and enhanced intestinal barrier integrity by increasing ZO-1 and claudin-1 expression. Integrated bioinformatics analyses, including differential expression analysis, WGCNA, network pharmacology, and machine-learning algorithms, identified farnesoid X receptor (FXR) as a core therapeutic target of SIN. Molecular docking predicted stable SIN-FXR binding, and cellular thermal shift assay further supported engagement of SIN with FXR. FXR expression was reduced in UC tissues and DSS-induced colitis mice but was restored after SIN treatment. Functional enrichment and single-cell RNA sequencing analyses linked FXR to lipid metabolism, immune regulation, and the Th17/Treg balance. Mechanistically, SIN suppressed arachidonic acid metabolism, reduced pro-inflammatory cytokines, increased anti-inflammatory cytokines, decreased Th17 cells, and promoted Treg accumulation. Co-administration of SIN with the FXR agonist fexaramine further potentiated its protective effects, whereas the FXR antagonist glycine-β-muricholic acid markedly reversed SIN-mediated improvements in intestinal inflammation, barrier integrity, arachidonic acid metabolism, and Th17/Treg homeostasis. Collectively, these findings demonstrate that SIN ameliorates experimental colitis, at least in part, by targeting FXR to modulate lipid metabolism and restoring Th17/Treg balance. This study provides a mechanistic basis for the therapeutic application of SIN, either alone or in combination with FXR agonists, in UC treatment.