Structural Characterization and Anti-Colitis Mechanisms ofPolysaccharides via Modulation of Neutrophil Extracellular Traps (NETs)-Macrophage Crosstalk.

Abstract

BACKGROUND: (PS), a perennial herbaceous plant belonging to the Liliaceae family, is widely distributed in China and other East Asian countries. PS has been used as food and medicine for thousands of years, and its rhizomes are rich inpolysaccharides (PSP), which exhibit various bioactivities, yet their structural features and therapeutic mechanisms against ulcerative colitis (UC) remain unclear. METHODS: A homogeneous polysaccharide, PSP-1b (57.45 kDa), was isolated from the rhizomes of PS via ion-exchange and gel filtration chromatography and structurally characterized using chromatographic and spectroscopic methods. In vivo, its effects were evaluated in a dextran sulfate sodium (DSS)-induced mouse model of UC, while in vitro mechanisms were explored using macrophages stimulated with lipopolysaccharide (LPS) and neutrophil extracellular traps (NETs). RESULTS: PSP-1b was identified as a neutral polysaccharide with minimal branching. Its primary structural backbone was largely composed of →4)-β-D-Gal-(1→ residues. A portion of these backbone residues was substituted at the O-6 position by side chains primarily composed of β-D-Gal-(1→ units. In vivo, PSP-1b significantly alleviated DSS-induced colitis by reducing inflammatory cytokine secretion, suppressing colonic macrophage infiltration, and reversing neutrophil extracellular traps (NETs) deposition. In vitro, PSP-1b directly interacted with TLR4, inhibited the MAPK/NF-κB signaling pathway, and attenuated LPS- and NET-induced macrophage polarization and inflammation. CONCLUSIONS: PSP-1b as a promising candidate for functional foods or therapeutic agents targeting inflammatory bowel disease.