Neutrophil elastase and oxygen radicals enhance monocyte chemoattractant protein-1 expression after ischemia/reperfusion in rat liver

Background The monocyte chemoattractant protein-1 (MCP-1) is produced durin g reperfusion injury and induces tissue factor that is the initiator of the clotting cascade. Neutrophil elastase is a crucial mediator of inflammator y tissue damage. Activation of the coagulation system stimulates cytokine p roduction by activated leukocytes. We investigated the effects of neutrophi l elastase and oxygen radicals generated by hypoxia associated with microth rombus formation on MCP-1 expression after ischemia/reperfusion in rat live r. Methods. In vitro MCP-1 production by macrophages after stimulation with hu man neutrophil elastase (HNE) or oxygen radicals generated by hypoxanthine and xanthine oxidase was examined. Liver ischemia was induced in rats by oc cluding the portal vein for 30 min. An inhibitor of human neutrophil elasta se (ONO-5046 Na, 10 mg/kg) and antithrombin III (AT-III, 250 U/kg) were inj ected i.v. 5 min before vascular clamping. Serum concentrations of MCP-1 we re measured by enzyme-linked immunosorbent assay. Results. Human neutrophil elastase or oxygen radicals significantly enhance d in vitro MCP-1 production by macrophages. Serum MCP-1 concentrations reac hed a peak at 6 hr after reperfusion and then gradually decreased. However, pretreatment of animals with AT-III or ONO-5046 Na alone resulted in signi ficantly smaller increases in serum concentrations of MCP-1 after reperfusi on. Pretreatment with both ONO-5046 Na and AT-III produced additive effects . The combined treatment with ONO-5046 Na and AT-III significantly reduced MCP-1 mRNA in liver after ischemia/reperfusion. Conclusion MCP-1 production by macrophages is stimulated by neutrophil elas tase and oxygen radicals generated by hypoxia, probably due to microthrombu s formation after isohemia/reperfusion of the rat liver.