An extract of Phellinus linteus grown on germinated brown rice inhibits inflammation markers in RAW264.7 macrophages by suppressing inflammatory cytokines, chemokines, and mediators and up-regulating antioxidant activity

Abstract

The immunomodulatory activity of an organic extract of Phellinus linteus grown on slightly germinated brown rice (PBR) was previously demonstrated. Here, we investigated the possible anti-inflammatory activity of the PBR extract by analyzing its effect on the expression of macrophage-derived cytokines, chemokines, and mediator genes that participate in immune and inflammatory responses and diseases. The extract profoundly inhibited the induction of cytokines and chemokines, including tumor necrosis factor-α, chemokine (C-X-C motif) ligand-10, granulocyte-macrophage colony-stimulating factor, and interleukin-6, in lipopolysaccharide (LPS)-stimulated RAW264.7 mouse macrophage cells. It also greatly inhibited LPS-stimulated production of nitric oxide (NO) and prostaglandin E(2) in RAW264.7 cells by suppressing the expression of inducible NO synthase and cyclooxygenase-2. PBR extract inhibited NO production with a twofold lower half-maximal inhibitory concentration value than P. linteus extract. To elucidate the underlying mechanism of action, we examined the effect of the PBR extract on the LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs) in RAW264.7 cells. PBR extract greatly inhibited extracellular signal-regulated kinase and c-Jun N-terminal kinase phosphorylation and slightly inhibited p38 MAPK phosphorylation. It also significantly increased intracellular glutathione peroxidase activity and heme oxygenase-1 protein expression. Thus, the PBR extract has anti-inflammatory activity in LPS-stimulated RAW264.7 cells by virtue of its ability to suppress the production of inflammatory cytokines and chemokines via inhibition of MAPK activation and up-regulation of antioxidant activities.