Agrocybe cylindracea Polysaccharides Ameliorate DSS-Induced Colitis by Restoring Intestinal Barrier Function and Reprogramming Immune Homeostasis via the Gut–Liver Axis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease driven by immune dysregulation, microbiota imbalance, and intestinal barrier dysfunction. Despite its global burden, effective therapies remain limited. This study explores the therapeutic potential of <i>Agrocybe cylindracea</i> polysaccharides (ACP) in a dextran sulfate sodium (DSS)-induced murine colitis model. High-performance liquid chromatography (HPLC)-characterized ACP was administered orally to BALB/c mice following colitis induction. ACP treatment significantly reduced Disease Activity Index (DAI) scores, preserved colon length, and restored intestinal barrier integrity by upregulating tight junction proteins. Mechanistically, ACP modulated immune homeostasis, suppressing pro-inflammatory cytokines (IL-17, IL-23, CRP) while enhancing anti-inflammatory mediators (IL-4, TGF-β). Furthermore, ACP inhibited hepatic TLR4/MyD88/NF-κB signaling, attenuated systemic inflammation, and reshaped gut microbiota composition by enriching beneficial taxa and reducing pathogenic <i>Bacteroides</i>. These findings demonstrate ACP multi-target efficacy in colitis, positioning it as a promising natural therapeutic for UC.