Anti-resorptive saurolactam exhibits in vitro anti-inflammatory activity via ERK–NF-κB signaling pathway

Natural products and their derivatives have historically been an invaluable a source of therapeutic agents. In this report, we demonstrated the anti-inflammatory activity of saurolactam, a compound isolated from the aerial portions of the Chinese lizard, Saururus chinensis. In RAW264.7 macrophage cells, saurolactam significantly inhibited the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase and cyclooxygenase-2 and, consequently, inhibited the release of NO and prostaglandin E2. Moreover, real-time PCR and multiplex cytokine assays showed that saurolactam (10 µM) significantly inhibited the LPS-induced mRNA and protein expression levels of pro-inflammatory genes, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. Finally, western blot analysis showed that saurolactam dose-dependently inhibited LPS-induced extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase activation and nuclear factor (NF)-κB translocation into the nucleus. The inhibitory activity of saurolactam on the activation of NF-κB was confirmed by a NF-κB luciferase reporter gene assay. In conclusion, we propose that the in vitro anti-inflammatory activity of saurolactam is produced by blocking ERK/MAP kinase and NF-κB activation.