Structural elucidation of Lyophyllum Decastes polysaccharide LP1-1 and its mechanism of macrophage activation mediated through TLR2/4.

Lyophyllum decastes polysaccharides have demonstrated immunostimulatory activities, but a clear understanding of their mechanism of action is lacking. In this study, a neutral polysaccharide, LP1-1, was isolated from the fruiting bodies of Lyophyllum decastes, and its structural characteristics and immunostimulatory activity were investigated. The results showed that LP1-1 had a molecular weight of 17.4 kDa and was composed of glucose, galactose, mannose, and fucose at a molar ratio of 91.53:4.63:2.72:1.12. LP1-1 was identified with a repeating unit of →3)-β-D-Glcp-(1→, 3,6)-β-D-Galp-(1→, and the terminal α-D-Glcp-(1 → 4)-α-D-Glcp-(1 → is linked to the repeating unit via O-6 position of the →3,6)-β-D-Galp-(1→. LP1-1 significantly enhanced the phagocytic activity of RAW264.7 macrophages and promoted the secretion of IL-6, TNF-α, and nitric oxide (NO). LP1-1 exerted its immunostimulatory effects primarily through Toll-like receptors TLR2 and TLR4, leading to the activation of the IκBα and MAPK signaling pathways. These findings provide a theoretical basis for the development of Lyophyllum decastes polysaccharides as a potential immunostimulatory agent in functional foods and pharmaceuticals.