Immunomodulatory Activity of Polysaccharide-Protein Complex from the Mushroom Sclerotia of Polyporus rhinocerus in Murine Macrophages

摘要

A novel water-soluble polysaccharide-protein complex (PRW1) isolated from the sclerotia of an edible mushroom Polyporus rhinocerus which was purified by membrane ultrafiltration could significantly activate murine macrophages RAW264.7 in vitro. PRW1 had a molecular weight of less than SO kDa and was found to be a highly branched heteropolysaccharide-protein complex composed of 45.7 +/- 0.97% polysaccharide and 44.2 +/- 0.41% protein. Based on the results of total acid hydrolysis, methylation analysis, and Fourier transform infrared spectroscopy, the carbohydrate moiety of PRW1 was found to be a beta-D-mannoglucan with its backbone containing -> 1)-D-Glcp-(4 ->, -> 1)-D-Glcp-(6 ->, and -> 1)-D-Manp-(2 -> residues (molar ratio of 5:4:6) and having terminal D-Glcp as side chain (degree of branching of 0.62). In vitro studies showed that PRW1 significantly induced NO production and enhanced the release of a variety of cytokines including G-CSF, GM-CSF, IL-6, IL12p40/70, MCP-1, MCP-5, MIP-1-alpha, MIP-2, RANTES, sTNFRI, and TNF-alpha. Mechanistically, PRW1 treatment triggered ERK phosphorylation to activate macrophages within 15 min and significantly increased the expression level of inducible NOS after 6 h. In summary, this study indicates that PRW1 derived from the sclerotia of P. rhinocerus is a potential immunomodulatory agent for cancer immunotherapy.