A 3-O-methylated heterogalactan from Pleurotus eryngii activates macrophages

Mushroom-derived polysaccharides exhibit various biological activities owing to their diverse structural features. Here, we purified a 3-O-methylated heterogalactan (WPEP-N-b, Mw 21.4 kDa) from the fruiting bodies of Pleurotus eryngii. WPEP-N-b is composed primarily of galactose (43.8%), mannose (39.3%), methyl-galactose (11.7%) and glucose (9.2%) residues, with the main chain being composed of alpha-1,6-linked D-Galp and 3-O-MeD-Galp, branched at O-2 with single t-beta-D-Manp as major the side chain. beta-1,6-D-Glcp residues are present as minor components either in side-chains or backbone. WPEP-N-b increases macrophage phagocytosis and secretion of NO, TNF-alpha, IL-6 and IL-1 beta. Mechanistic studies demonstrate that WPEP-N-b promotes the degradation of I kappa B-alpha, and enhances phosphorylation of MAPKs and the NF-kappa B p65 subunit Our results also indicate that this polysaccharide activates RAW264.7 cells via MAPK and NF-kappa B signaling pathways and the Toll-like receptor 2(TLR2). These results increase our understanding as to how mushroom-derived polysaccharides modulate the immunologic process.