Phellinus linteus inhibits inflammatory mediators by suppressing redox-based NF-κB and MAPKs activation in lipopolysaccharide-induced RAW 264.7 macrophage

Abstract

The mushroom Phellinus linteus has been known to exhibit potent biological activity. In contrast to the immuno-potentiating properties of Phellinus linteus, the anti-inflammatory properties of Phellinus linteus have rarely been investigated. Recently, ethanol extract and n-BuOH fractions from Phellinus linteus were deemed most effective in anti-inflammatory activity in RAW 264.7 macrophages. The regulatory mechanisms of Phellinus linteus butanol fractions (PLBF) on the pharmacological and biochemical actions of macrophages involved in inflammation have not been clearly defined yet. In the present study, we tested the role of PLBF on anti-inflammation patterns in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. To investigate the mechanism by which PLBF inhibits NO and PGE 2 production as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, we examined the activation of IκB and MAPKs in LPS-activated macrophages. PLBF clearly inhibited nuclear translocation of NF-κB p65 subunits, which correlated with PLBF's inhibitory effects on IκBα phosphorylation and degradation. PLBF also suppressed the activation of mitogen-activated protein (MAP) kinases including p38 and stress-activated protein kinase/c-Jun NH 2-terminal kinase (SAPK/JNK). Furthermore, macrophages stimulated with LPS generated ROS via activation of membrane-bound NADPH oxidase, and ROS played an important role in the activation of nuclear factor-κB (NF-κB) and MAPKs. We demonstrated that PLBF directly blocked intracellular accumulation of reactive oxygen species in RAW 264.7 cells stimulated with LPS much as the NADPH oxidase inhibitors, diphenylene iodonium, and antioxidant pyrrolidine dithiocarbamate did. The suppression of NADPH oxidase also inhibited NO production and iNOS protein expression. Cumulatively, these results suggest that PLBF inhibits the production of NO and PGE 2 through the down-regulation of iNOS and COX-2 gene expression via ROS-based NF-κB and MAPKs activation. Thus, PLBF may provide a potential therapeutic approach for inflammation-associated disorders.