title: Emodin inhibits ATP-induced IL-1β secretion, ROS production and phagocytosis attenuation in rat peritoneal macrophages via antagonizing P2X₇ receptor.
abstract: BACKGROUND
  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.
  
  
  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 Ca²⁺ concentration ([Ca²⁺]c) was detected by fluorescent Ca²⁺ imaging. Interleukin-1β (IL-1β) release was measured by rat IL-1β 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 [Ca²⁺](c) increase evoked by ATP (5 mM) was inhibited by emodin, in a dose-dependent manner with IC₅₀ of 0.5 μM. Furthermore, emodin reduced the IL-1β release induced by ATP (2 mM) in lipopolysaccharide (LPS)-activated macrophages, with an IC₅₀ of 1.6 μM. Emodin also strongly suppressed the ROS production and phagocytosis attenuation triggered by ATP (1 mM), with IC₅₀ values of 1 μM and 0.7 μM, respectively. Besides, BBG, a specific antagonist of P2X₇R, exhibited similar suppressive effects on these inflammation responses.
  
  
  CONCLUSIONS
  These results showed the inhibitory effects of emodin on ATP-induced [Ca²⁺](c) increase, IL-1β release, ROS production and phagocytosis attenuation in rat peritoneal macrophages, by inhibiting the activation of P2X₇R.
authors.affiliation: Department of Biophysics, School of Physics and.
authors.forename: Shuyan
authors.initials: S
authors.lastname: Zhu
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Wang
authors.forename: Xinyu
authors.initials: X
authors.lastname: Wang
authors.forename: Junying
authors.initials: J
authors.lastname: Li
authors.forename: Fen
authors.initials: F
authors.lastname: Hu
mesh_terms: D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004642:Emodin / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D007249:Inflammation / Q000517:prevention & control; D020128:Inhibitory Concentration 50; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects*; D008297:Male; D010587:Phagocytosis / Q000187:drug effects; D058920:Purinergic P2X Receptor Antagonists / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D058486:Receptors, Purinergic P2X7 / Q000187:drug effects* / Q000378:metabolism; D012250:Rheum / Q000737:chemistry
chemical_list: D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D058920:Purinergic P2X Receptor Antagonists; D017382:Reactive Oxygen Species; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D004642:Emodin; D002118:Calcium