Bidirectional immunomodulatory activities of polysaccharides purified from Pleurotus nebrodensis

A novel Pleurotus nebrodensis polysaccharide (PN50G) was purified, characterized, and cultured with RAW264.7 macrophages to evaluate its bidirectional immunostimulating characteristics. PN50G was purified by using Sepharose 4B gel filtration; the molecular weight of PN50G was distributed at 2,000 kDa. The total protein and carbohydrate constituent ratios in PN50G were 2.6 ± 0.9 % and 92.4 ± 6.1 % (w/w), respectively, which suggests that PN50G may be a major proteo-polysaccharide component. The phagocytosis of macrophages was improved significantly, and remarkable changes were observed in the morphology of PN50G-treated cells. Compared with the control group, the productions of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and inducible nitric oxide synthase (iNOS) in the macrophages as well as the messenger RNA expressions were strongly induced by PN50G. Pro-/anti-inflammatory (IL-6/IL-10, TNF-α/IL-10, NO/IL-10) cytokine secretion ratios by lipopolysaccharide-stimulated RAW264.7 macrophages were significantly decreased by PN50G treatments in a dose-dependent manner under an excessive immune experimental model. This study suggests that purified PN50G can improve immunity and suppress immune overactivity in LPS-induced macrophages in a preventive manner to coordinate innate immunity and inflammatory responses.