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 ecology. These findings highlight LSP as a promising natural therapeutic candidate for IBD. Further metabolomic and meta transcriptomic analyses are warranted to elucidate the microbial metabolites and molecular pathways mediating these protective effects.