Abstract: Objective: To explore the in vivo anti-inflammatory activity of a water-soluble polysaccharide purified from Ganoderma atrum, named PSG-1, and its effect on mannose receptor (MR) expression. Methods: In the present study, lipopolysaccharide (LPS) via intraperitoneal injection was applied to establish a mouse model of inflammation. Mice were randomly divided into five groups: control group, LPS group, high-dose PSG-1 (100 mg/(kg·d)) + LPS group, mediumdose PSG-1 (50 mg/(kg·d)) + LPS group and low-dose PSG-1 (25 mg/(kg·d)) + LPS group. MR expression, phagocytosis and the level of reactive oxygen species (ROS) in macrophages were analyzed by flow cytometry. The levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in serum were determined by enzyme-linked immunosorbent assay (ELISA). Results: Compared with the control group, MR expression on the macrophage surface was decreased in the LPS group. In contrast, MR expression on the macrophage surface was significantly increased in the PSG-1 + LPS group in comparison with the LPS group (P < 0.01). Macrophage phagocytosis and the level of ROS in the LPS group were higher than in the control group, which were significantly decreased after administration of PSG-1 (P＜0.05, P＜0.01). After mice were administrated with LPS, the levels of TNF-α, IL-1β and IL-6 were significantly increased in serum in comparison with the control group (P < 0.01). Compared with the LPS group, the expression level of TNF-α was significantly decreased after administration of high-dose PSG-1 (P < 0.05), but the expression levels of IL-1β and IL-6 did not significantly change. Conclusion: PSG-1 had an anti-inflammatory effect, being able to partly suppress inflammation induced by LPS in vivo, by promoting MR expression on the peritoneal macrophage surface in mice and suppressing macrophage polarization to M1 phenotype.

Key words: Ganoderma atrum polysaccharide, lipopolysaccharide, macrophage, mannose receptor, phagocytosis, cytokine, polarization