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

The monocyte chemoattractant protein-1 (MCP-1) is produced during reperfusion injury and induces tissue factor that is the initiator of the clotting cascade. Neutrophil elastase is a crutial mediator of inflammatory tissue damage. Activation of the coagulation system stimulates cytokine production by activated leukocytes. We investigated the effects of neutrophil elastase and oxygen radicals generated by hypoxia associated with microthrombus formation on MCP-1 expression after ischemia/reperfusion in rat liver. In vitro MCP-1 production by macrophages after stimulation with human neutrophil elastase (HNE) or oxygen radicals generated by hypoxanthine and xanthine oxidase was examined. Liver ischemia was induced in rats by occluding the portal vein for 30 min. An inhibitor of human neutrophil elastase (ONO-5046 times Na, 10 mg/kg) and antithrombin III (AT-III, 250 U/kg) were injected i.v. 5 min before vascular clamping. Serum concentrations of MCP-1 were measured by enzyme-linked immunosorbent assay. Human neutrophil elastase or oxygen radicals significantly enhanced in vitro MCP-1 production by macrophages. Serum MCP-1 concentrations reached a peak at 6 hr after reperfusion and then gradually decreased. However, pretreatment of animals with AT-III or ONO-5046 times Na alone resulted in significantly smaller increases in serum concentrations of MCP-1 after reperfusion. Pretreatment with both ONO-5046 times Na and AT-III produced additive effects. The combined treatment with ONO-5046 times Na and AT-III significantly reduced MCP-1 mRNA in liver after ischemia/reperfusion. MCP-1 production by macrophages is stimulated by neutrophil elastase and oxygen radicals generated by hypoxia, probably due to microthrombus formation after ischemia/reperfusion of the rat liver.