Temporal expression of cyclooxygenase-2 in peritoneal macrophages of rats and effects of panax notoginseng saponins

Objective:  To explore the temporal expression pattern of cyclooxygenase (COX)-2 and effects of panax notogensing saponins (PNS) in peritoneal macrophages of rats. Materials and methods:  Phagocytosis function of peritoneal macrophages was measured by chicken red blood cell phagocytosis assay in vitro. Expression of COX-2 mRNA and protein, PGE₂ and PGD₂ production were determined with real-time PCR, Western blotting and radioimmunoassay, respectively. Results:  Phagocytosis function of macrophages increased significantly after stimulation and reached peak during 2–3h. Expression of COX-2 mRNA and its protein increased markedly after stimulation and reached the first peak at 2 h and 3h, respectively; and then decreased to reach a minimum at 24h. The second peak appeared at 36h. PNS (50, 100, 200 mg/kg) increased the phagocytosis function obviously at 2h, decreased the expression level of COX-2 and PGE₂ production at 2 h and elevated COX-2 expression and PGD₂ production at 36 h, respectively. Conclusion:  COX-2 expression in peritoneal macrophages has a double-hump feature after stimulation. PNS enhanced phagocytosis, inhibiting COX-2 expression at an early stage and elevating it at a later stage. Received 29 February 2008; returned for revision 27 March 2008; received from final revision 14 May 2008; accepted by G. Wallace 9 June 2008 The first two authors contributed equally to this work.