Oxidant exposure stimulates cultured coronary artery endothelial cells to release 15-HETE: differential effects on PGI2 and 15-HETE synthesis.

Oxidant stress to the endothelium is an important component of inflammatory processes involved in the pathogenesis of ischemic/reperfusion injury. The effects of acute oxidant exposure on cultured bovine coronary artery endothelial cell (BCA) functions including arachidonic acid metabolism, permeability, tissue factor expression, and viability were assessed after exposure of cells to the hydrogen peroxide-generating system of glucose-glucose oxidase (GO). GO markedly stimulated the synthesis of the arachidonic acid metabolites 15-hydroxyeicosatetraenoic acid (15-HETE) and prostacyclin (PGI2). Both sublethal and lethal concentrations of GO increased 15-HETE release from BCAs by as much as 15-fold. In contrast to 15-HETE, enhanced PGI2 synthesis occurred at concentrations of GO that did not injure the BCA monolayers, whereas lethal doses of GO had no stimulatory effect on PGI2 production. Moreover, the sublytic oxidant-induced stimulation of PGI2 synthesis in BCAs (50-fold) was significantly greater than that induced by other mediators or that observed in parallel studies with human umbilical vein endothelial cells. In vitro endothelial cell barrier function was determined by measuring iodine 125-labeled albumin clearance across confluent cell monolayers. GO increased cellular permeability in a concentration-dependent manner, although statistically significant increases were only observed at the highest (i.e., lethal) concentrations (C(alb) = 0.840 +/- 0.16 with 1.0 U/ml GO vs C(alb) = 0.24 +/- 0.02 in control cells). Finally, oxidant exposure did not induce BCA tissue factor activity at any concentration examined. These results suggest that oxidant exposure, as might occur during ischemic reperfusion, could affect subsequent coronary vascular responses by releasing the arachidonate metabolite 15-HETE, which can cause vasoconstriction as well as attract and activate leukocytes. In addition, oxidants may also modulate vascular reactivity by altering the release of the potent vasodilator and neutrophil modulator PGI2 as lower levels of oxidant generation stimulate its synthesis, whereas higher levels suppress PGI2 release. Thus the degree of oxidant stress may profoundly affect the endothelial synthesis and release of 15-HETE and PGI2, compounds with antagonist effects on vascular tone and neutrophil activation. Consequently the balance between oxidant-induced production of these mediators by the coronary endothelium may significantly affect the pathophysiology of myocardial ischemia and reperfusion injury.