2-Phenylnaphthalene Derivatives Inhibit Lipopolysaccharide-Induced Pro-Inflammatory Mediators by Downregulating of MAPK/NF-κB Pathways in RAW 264.7 Macrophage Cells

The anti-inflammatory pharmacological effect of eight 2-phenylnaphthalenes (PNAP-1−PNAP-8) on lipopolysaccharide (LPS)-induced RAW 264.7 (a mouse cell line) was investigated. Among them, 6,7-dihydroxy-2-(4′-hydroxyphenyl)naphthalene (PNAP-6) and 2-(4′-aminophenyl)-6,7-dimethoxynaphthalene (PNAP-8) exhibited the best anti-inflammatory activity in this study. PNAP-6 and PNAP-8 not only significantly decreased the expression of inducible nitric oxide synthase and cyclooxygenase-II, but also inhibited the production of nitric oxide, interleukin-6, and tumor necrosis factor-α in LPS stimulated cells. Moreover, PNAP-6 and PNAP-8 inhibited nuclear factor (NF)-κB activation by decreasing the degradation of IκB and nuclear translocation of NF-κB subunit (p65). In addition, PNAP-6 and PNAP-8 also attenuated the phosphorylation of ERK, p38, and JNK. These results suggest that PNAP-6 and PNAP-8 exert anti-inflammatory activities by down regulating NF-κB activation and the mitogen-activated protein kinase signaling pathway in LPS-stimulated Raw 264.7 cells. This is the first study demonstrating that PNAPs can inhibit LPS-induced pro-inflammatory mediators in macrophages cells.