Abstract: Objective:This study was to investigate the inhibitory effects of Pinus koraiensis pine nut polysaccharide(PNP40c-1)on the inflammatory response of RAW264.7 cells induced by lipopolysaccharide(LPS)and the possible mechanism. Methods:LPS was used to stimulate RAW264.7 macrophages to induce inflammation. MTT assay,colorimetric assay,enzyme-linked immunosorbent assay,RT-PCR and Western Blot were used to compare the cell viability,phagocytosis,nitric oxide/nitric oxide synthase and the expression of cytokines in macrophages before and after LPS-treatment. Furthermore,the mRNA and protein expression of Nrf2 and HO-1 in the Nrf2/HO-1 signaling pathway were also studied to explore the specific action mechanism of PNP40c-1.Results:In LPS-induced inflammatory response,PNP40c-1 significantly increased the phagocytosis(P<0.05)and inhibited the overexpression of NO and iNOS in RAW264.7 macrophages in a dose-dependent way. Moreover,PNP40c-1 also regulated the secretion of pro-inflammatory factors such as tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β)and interleukin-6(IL-6)through Nrf2/HO-1 signaling pathway to relieve inflammation induced by LPS. Conclusion:Pinus koraiensis pine nut polysaccharide PNP40c-1 possesses inhibitory effects on LPS-induced inflammatory response and the action mechanism is related to the regulation of Nrf2/HO-1 signaling pathway.