A novel naturally occurring salicylic acid analogue acts as an anti-inflammatory agent by inhibiting nuclear factor-kappaB activity in RAW264.7 macrophages

Methyl salicylate 2-O-β-d-lactoside (DL0309), is a molecule chemically related to salicylic acid that is isolated from Gaultheria yunnanensis (FRANCH.) REHDER (G. yunnanensis). G. yunnanensis, a traditional Chinese herbal medicine, is widely used for treating rheumatoid arthritis, swelling, pain, trauma, and chronic tracheitis. In the present study, we explored the mechanism whereby DL0309 exerts anti-inflammatory effects, using the model of lipopolysaccharide (LPS)-treated RAW264.7 cells. We examined the effects of DL0309 on LPS-induced nuclear factor-kappaB (NF-κB) activity by Western blot analysis, cell imaging analysis and an electrophoretic mobility shift assay (EMSA). Production of pro-inflammatory cytokines was also measured. Our observations indicate that DL0309 suppressed production of nitric oxide (NO), reactive oxygen species (ROS) and the pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), in a concentration-dependent manner. The phosphorylation of IKK-β and degradation of IκB-α by LPS were both inhibited by DL0309 in the cytoplasm. The increased protein level of NF-κB by LPS in the nucleus was also reduced by DL0309. Consistent with these results, we found that DL0309 prevents the nuclear translocation and DNA binding activity of NF-κB. Finally, our results demonstrate that DL0309 exerts anti-inflammatory effects, by inhibiting the production of pro-inflammatory cytokines and suppressing of the activation of the NF-κB signaling pathway in LPS-treated macrophage cells. Therefore, DL0309 may have therapeutic potential for treating inflammatory diseases by regulating the NF-κB pathway and pro-inflammatory cytokine production.