Effects of Fomes officinalis polysaccharide and its purified constituent on mitogen-activated protein kinases (MAPK) signaling pathway in RAW264.7 macrophages

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Objective To investigate the effects of crude Fomes officinalis polysaccharide (FOPS) and its purified constituent (FOPS-a) on mitogen-activated protein kinases (MAPK) signaling pathway and secretion of tumor necrosis factor-α (TNF-α) in RAW264.7 macrophages. Methods RAW264.7 macrophages were treated with FOPS and FOPS-a respectively at different concentrations (50, 100, 200 μg/ml) for 24 h. RT-qPCR and Western blot methods were respectively used to detect the expression at mRNA level and the phosphorylated proteins of p38, c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). Changes in the phosphorylation of these proteins and TNF-α secretion were respectively detected by Western blot and ELISA after treating the macrophages with MAPK-specific inhibitors (PD98059, SP600125, SB203580). Results Compared with the blank control group, different concentrations of FOPS and FOPS-a could significantly increase the expression at mRNA level and the phosphorylation of p38 and ERK (P<0.05). Three inhibitors of MAPK could markedly decrease the phosphorylation of ERK1/2 and p38 and TNF-α secretion that were induced by FOPS and FOPS-a (P<0.05). Conclusions FOPS and FOPS-a might have immunomodulatory effects on RAW264.7 macrophages through activating ERK1/2 and p38 MAPK signal transduction pathways. Key words: Fomes officinalis polysaccharide; RAW264.7 macrophage; Mitogen-activated protein kinases (MAPK); Tumor necrosis factor-α (TNF-α)