A (1 6) Branched (1 4) b d Glucan from Grifola frondosa Inhibits Lipopolysaccharide Induced Cytokine Production in RAW264.7 Macrophages by Binding to TLR2 Rather than Dectin 1 or CR3 Receptors.
Mushroom polysaccharides including b glucans possess various health promoting properties and are known to be the major bioactive constituents of Grifola frondosa (GF) which is a popular edible and medicinal mushroom. Dectin 1, a pattern recognition receptor, is responsible for recognizing b glucans. In this study, parental RAW264.7 macrophages and Dectin 1 expressing RAW264.7 macrophages were used to investigate the anti inflammatory activity and receptor involvement of the water soluble polysaccharides from GF. Results indicated that the high molecular weight fraction of GF (GF70 F1; 1260 kDa) inhibited TNF a and IL 6 production as well as NF kB activation in lipopolysaccharide induced macrophages. Chemical and enzymatic linkage analyses indicated that GF70 F1 mainly contained the known (1 3)(1 6) b d glucan and a polysaccharide not previously isolated from GF, a nondigestible glucan with a b (1 4) linked backbone and b (1 6) linked branches. The ability of GF70 F1 to inhibit cytokine production was not affected by the expression level of Dectin 1 in cells, and a similar inhibitory activity was observed after removing the (1 3)(1 6) b d glucan from GF70 F1. Blockade of Toll like receptor 2 (TLR2) but not Dectin 1 or complement receptor 3 (CR3) attenuated the inhibitory activity of GF70 F1. The nondigestible (1 6) branched (1 4) b d glucan in GF70 F1 may contribute to the anti inflammatory activity via interacting with TLR2 rather than Dectin 1 or CR3 receptors.
Journal of natural products