β-elemene attenuates macrophage activation and proinflammatory factor production via crosstalk with Wnt/β-catenin signaling pathway

beta-elemene, extracted from Rhizoma zedoariae, has been widely used as a traditional medicine for its antitumor activity against a broad range of cancers. However, the effect of beta-elemene in inflammation disorders has yet to be determined. The present study was designed to investigate the anti-inflammatory effects and potential molecular mechanisms of beta-elemene in lipopolysaccharide (LPS)-induced murine macrophage cells RAW264.7. We found that the production of pro-inflammatory mediators, including interleukin-6(IL-6), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta), induced by LPS was significantly suppressed by beta-elemene in a dose-dependent manner in RAW264.7 macrophage cell line. Also, beta-elemene inhibited LPS-induced nitric oxide synthase (iNOS) and interleukin-10 (IL-10) expression by RAW264.7, which was related to the down-regulation of Wnt/beta-catenin signaling pathway. Importantly, this study demonstrates that beta-catenin was significantly inhibited by beta-elemene, which appeared to be largely responsible for the down-regulation of Wnt/beta-catenin signaling pathway. Accordingly, the deletion of beta-catenin in primary macrophages reversed beta-catenin-elicited inhibition of immune response. Furthermore, beta-catenin expression and Wnt/beta-catenin signaling pathway induced by LPS in RAW264.7 was also significantly inhibited by alpha-humulene, one isomeric sesquiterpene of beta-elemene. alpha-humulene was also found to significantly inhibit LPS-induced production of proinflammatory cytokines. However, alpha-humulene showed more cytotoxic ability than beta-elemene. Collectively, our data illustrated that beta-elemene exerted a potent inhibitory effect on pro-inflammatory meditator and cytokines production via the inactivation of beta-catenin, and also demonstrated the protective functions of beta-elemene in endotoxin-induced inflammation. beta-elemene may serve as potential nontoxic modulatory agents for the prevention and treatment of inflammatory diseases.