Activation of macrophages by natural TLR4 ligand isolated from Paecilomyces cicadae (P4496)

Abstract

Abstract Many polysaccharides isolated from mushroom are considered to be biological response modifiers and have been shown to enhance various immune responses. Paecilomyces cicadae have been reported to have immunomodulatory properties. In this study, we investigated the membrane receptor and intracellular signaling responsible for the activation of macrophage by polysaccharide (PCP) isolated from P. cicadae. PCP induced the production of nitric oxide (NO) and the mRNA expression of IL-1β, IL-6, and TNF-α in RAW 264.7 cells. To investigate the membrane receptor involved in the activation of NO production, we examined the effect of PCP on primary macrophages isolated from C3H/HeN mice having normal-TLR4 and C3H/HeJ mice having mutant-TLR4. PCP induced NO production and cytokine gene expression in macrophages from C3H/HeN, but not from tlr4-mutated C3H/HeJ mice, which suggests that TLR4 is the membrane receptor for PCP. As a mechanism of action, PCP induced the phosphorylation of ERK, JNK, and p38, and the nuclear translocation of NF-κB p50/p65, which are the main signaling molecules down-stream from TLR4. In addition, p38 and NF-κB inhibitor attenuated PCP-mediated induction of NO production by macrophages. These results indicate that PCP activates macrophages through the TLR4 signaling pathway