Forsythin inhibits lipopolysaccharide-induced inflammation by suppressing JAK-STAT and p38 MAPK signalings and ROS production

Forsythin (FOR) is an active ingredient extracted from the fruit of the medicinal plant Forsythia suspensa (Thunb.) Vahl. Here, we investigated the effect of FOR on LPS-induced inflammatory response and the underlying molecular mechanisms in RAW264.7 macrophages. RAW264.7 cells were pre-treated with or without FOR and then stimulated with or without LPS. The productions of TNF-alpha, IL-1 beta, IL-6, PGE(2) and NO were determined by ELISA and nitrite analysis, respectively. The expressions of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were measured by Western blotting and RT-PCR analysis. The activations of signaling molecules were detected by Western blotting using phosphorylation specific antibodies. Reactive oxygen species (ROS) production was determined by ROS assay. LPS-induced productions of IL-1 beta, IL-6, TNF-alpha, NO and PGE(2) were inhibited by FOR in a dose-dependent manner. FOR also suppressed the LPS-elevated expressions of iNOS and COX-2. Further investigations revealed that FOR significantly inhibited the LPS-induced activations of JAK-STATs and p38 MAPKs, but not of IKK alpha/beta in LPS-stimulated RAW264.7 cells. Additionally, FOR interfered with both JAK-STATs and p38 MAPKs signaling pathways to modulate the expressions of IL-1 beta, IL-6, TNF-alpha, iNOS and COX-2. Furthermore, FOR reduced the LPS-induced ROS accumulation, validating that FOR serves as an antioxidant. Our data suggested that FOR exerts anti-inflammatory action, at least in part, via suppressing LPS-induced activation of JAK-STATs and p38 MAPKs signalings and production of ROS in macrophage cells.