Emodin inhibits ATP-induced IL-1? secretion, ROS production and phagocytosis attenuation in rat peritoneal macrophages via antagonizing P2X7 receptor.
Abstract Context: Previous in vitro studies have demonstrated that emodin (1,3,8-trihydroxy-6-methyl-anthraquinone), an anthraquinone derivative from the rhizome of Rheum palmatum L., can inhibit the activation of P2X7 receptors (P2X7R) as a potential antagonist. However, the effects of emodin on P2X7R-related inflammatory processes remain unclear. Objective: This study aimed to investigate the effects of emodin on different inflammation responses of macrophages induced by ATP, the natural ligand of P2X7R. Materials and methods: Rat peritoneal macrophages were treated with millimolar ATP and emodin (0.1, 0.3,?1,?3,?10?µM) or brilliant blue G (BBG, 0.1,?1,?10?µM). Cytosolic Ca(2+) concentration ([Ca(2+)]c) was detected by fluorescent Ca(2+) imaging. Interleukin-1? (IL-1?) release was measured by rat IL-1? ELISA kits. Reactive oxygen species (ROS) generation was examined by dihydroethidium (DHE) fluorescent staining. Phagocytic activity was tested by neutral red uptake assay. Results: We found that the [Ca(2+)]c increase evoked by ATP (5?mM) was inhibited by emodin, in a dose-dependent manner with IC50 of 0.5??M. Furthermore, emodin reduced the IL-1? release induced by ATP (2?mM) in lipopolysaccharide (LPS)-activated macrophages, with an IC50 of 1.6??M. Emodin also strongly suppressed the ROS production and phagocytosis attenuation triggered by ATP (1?mM), with IC50 values of 1??M and 0.7??M, respectively. Besides, BBG, a specific antagonist of P2X7R, exhibited similar suppressive effects on these inflammation responses. Conclusion: These results showed the inhibitory effects of emodin on ATP-induced [Ca(2+)]c increase, IL-1? release, ROS production and phagocytosis attenuation in rat peritoneal macrophages, by inhibiting the activation of P2X7R.