Abstract

Background Inflammatory bowel disease (IBD) involves epithelial barrier disruption, immune dysregulation, and microbial imbalance. The present study investigated the protective mechanisms of Laetiporus sulphureus polysaccharides (LSP) in dextran sulfate sodium (DSS)-induced colitis, focusing on intestinal barrier restoration, immunomodulation, and gut microbiota remodeling. Methods LSP was structurally characterized using HPLC, FTIR, and SEM analyses, revealing a heteropolysaccharide primarily composed of glucose (55.16%), galactose (16.55%), and mannose (13.52%). Experimental colitis was induced in BALB/c mice with 3% DSS, followed by oral LSP administration (200 or 400 mg/kg). Disease severity, histopathology, barrier markers, cytokine profiles, macrophage polarization, and gut microbiota composition were evaluated using biochemical assays, immunofluorescence, IHC, and 16S rRNA sequencing. Results LSP significantly mitigated DSS-induced colitis by reducing the disease activity index by approximately 60% (∼2.5-fold, p < 0.001) and restoring colon length (∼1.5-fold, p < 0.01). Barrier integrity improved via enhanced mucin-2 expression (∼3.5-fold) and tight junction proteins Occludin, Claudin-1, and ZO-1 (∼5–9-fold). LSP suppressed pro-inflammatory cytokines TNF-α, IL-6, and IL-1β (∼2–3-fold) while upregulating anti-inflammatory mediators IL-10 and TGF-β (∼2.5–3-fold), reflecting a rebalanced mucosal immune milieu. 16S rRNA sequencing demonstrated reversal of DSS-induced dysbiosis, characterized by a reduction in pathogenic Escherichia–Shigella (∼3.8-fold) and Enterobacteriaceae (∼3.5-fold), and enrichment of beneficial taxa including Lactobacillus , Bifidobacterium, and Ruminococcus (∼2–4-fold). Conclusion LSP exerts multi-targeted protection against colitis by reinforcing epithelial barrier function, attenuating inflammation, and reshaping gut microbial ecol