Abstract: Objective: The aim of this study was to explore the regulatory effect of Ganoderma atrum polysaccharide (PSG-1) on M1/M2 polarization in lipopolysaccharide (LPS)-simulated mouse macrophages. Methods: Neutral red assay was used to detect macrophage phagocytosis, and flow cytometry analysis was used to determine the level of reactive oxygen species (ROS) and the expression of mannose receptor (MR). Nitric oxide (NO) was analyzed by the Griess method and the levels of interleukin-1β (IL-1β) and IL-10 were determined by enzyme-linked immunosorbent assay (ELISA). Results: Compared to the LPS group, PSG-1 could remarkably reduce macrophage phagocytosis, and inhibit the secretion of IL-1β and NO, but down-regulate the generation of ROS, suggesting that PSG-1 could inhibit LPS-caused macrophage polarization into M1. Meanwhile, significant elevations of MR expression and IL-10 level were observed in the PSG-1 + LPS group compared to LPS group, indicating that PSG-1 promoted macrophage polarization into M2. Further results showed that the inhibitory effect of PSG-1 against LPS-induced inflammatory response was decreased evidently in macrophages by the treatment of anti-MR antibody. Conclusion: PSG-1 has a distinct regulatory effect on LPS-mediated macrophage polarization via inhibiting polarization into M1 and enhancing polarization into M2. Its molecular mechanism may be closely related to the regulation of MR expression on the surface of macrophages.

Key words: Ganoderma atrum polysaccharide, macrophage polarization, mannose receptor, regulatory effect, inflammatory response