Protium javanicum Burm. Methanol Extract Attenuates LPS-Induced Inflammatory Activities in Macrophage-Like RAW264.7 Cells

Protium javanicum Burm. f. is a medicinal plant used in traditional medicine. Gum and oleoresins from this plant have been used as anti-inflammatory agents for treating ulcers, headaches, eyelid inflammation, and rheumatic pain. However, its anti-inflammatory mechanism of action is still unknown. To better understand the mechanism, we used lipopolysaccharide- (LPS-) treated RAW264.7 cells to measure inflammatory mediators with the Griess assay and to identify target signaling molecules by immunoblot analysis. In this study, we report that the Protium javanicum methanol extract (Pj-ME) plays an important role in suppressing nitric oxide (NO) levels without cytotoxicity. The effect of Pj-ME in LPS-induced expression leads to reduced inflammatory cytokine expression, specifically inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and tumor necrosis factor (TNF-α). Pj-ME significantly inhibited LPS-induced protein expression of the nuclear factor-kappa B (NF-κB) signaling pathway in a time-dependent manner. Syk and Src were identified as putative signaling molecules of Pj-ME-mediated anti-inflammatory activity, which were inhibited by Pj-ME. We demonstrated that Pj-ME controls the STAT3 signaling pathway by suppressing STAT3 and JAK phosphorylation and also downregulates the gene expression of IL-6. Therefore, these results elucidate Pj-ME as a novel anti-inflammatory naturally derived drug with anti-inflammatory and antioxidant properties which may be subject to therapeutic and prognostic relevance.