Reactive oxygen intermediates induce monocyte chemotactic protein-1 in vascular endothelium after brief ischemia

Chemokine expression is associated with reperfusion of infarcted myocardium . in the setting of tissue necrosis, intense inflammation, and inflammatory cytokine release. The specific synthesis of monocyte chemotactic protein ( MCP)-1 mRNA by cardiac venules in reperfused infarcts corresponded to the r egion where leukocytes; normally localize. MCP-1 could be induced by exogen ous. tumor necrosis factor (TNF)-alpha or by postischemic cardiac lymph con taining TNF-alpha. However, the release of TNF-alpha during early reperfusi on did not explain the venular localization of MCP-1 induction. To better u nderstand the factors mediating MCP-1 induction, we examined the role of is chemia/reperfusion in a model of brief coronary occlusion in which no necro sis or inflammatory response is seen. Adult mongrel dogs were subjected to 15 minutes of coronary occlusion and 5 hours of reperfusion. Ribonuclease p rotection assay revealed up-regulation of MCP-1 mRNA only in ischemic. segm ents of reperfused canine myocardium. Pretreatment with the reactive oxygen scavenger N-(2-mercaptopropionyl)-glycine completely inhibited MCP-1 induc tion. In situ hybridization localized MCP-1 message to small venular endoth elium ischemic areas without myocyte necrosis. Get shift analysis of nuclea r extracts from the ischemic area showed enhanced DNA binding of the transc ription factors AP-1 and nuclear factor (NF)-kappaB, crucial for MCP-1 expr ession, in ischemic myocardial regions. Immunohistochemical staining demons trated reperfusion-dependent nuclear translocation of c-Jun and NF-kappaB ( p65) in small venular endothelium., only in the ischemic regions of the myo cardium, that was inhibited by N-(2-mercaptopropionyl)-glycine. in vitro, t reatment of cultured canine jugular vein endothelial cells with the reactiv e oxygen intermediate H2O2 induced a concentration-dependent increase in MC P-1 mRNA levels, which was inhibited by the antioxidant N-acetyl-L-cysteine , a precursor of glutathione, but not pyrrolidine dithiocarbamate, an inhib itor of NF-kappaB and activator of AP-1. In contrast to our studies with in farction, incubation of canine jugular vein endothelial. cells with postisc hemic cardiac lymph did not induce MCP-1 mRNA expression suggesting the abs ence of cytokine-mediated MCP-1 induction after a sublethal ischemic period . These results suggest that reactive oxygen intermediate generation, after a brief ischemic episode, is capable of inducing MCP-1 expression in venul ar endothelium through AP-1 and NF-kappaB. Short periods of ischemia/reperf usion, insufficient to produce a myocardial infarction, induce MCP-1 expres sion, potentially mediating angiogenesis in the ischemic noninfarcted heart .