The vascular endothelium is a target for oxidant-induced damage in many disease states including hyperoxia, inflammation, ischemia and reperfusion injury. However, little is known concerning oxidant injury to endothelial cells and its relationship to hemostasis. Our studies have focused on the ability of oxygen free radicals to injure and/or alter selected vascular endothelial cell functions pertinent to the regulation of hemostasis. Xanthine and xanthine oxidase, a well-characterized generating system for the production of the superoxide anion radical (O−
2) was used to sublethally injure human umbilical vein endothelial cells (HUVE) in vitro. We examined the effects of a 15 min exposure of HUVE cells to xanthine (50μM), and xanthine oxidase (2.5-100mU) (previously determined to be non-toxic using trypan blue dye exclusion) on platelet adherence, and prostacyclin release using established assays. The antioxidant enzymes superoxide dismutase (SOD) 200μg/ml and catalase 50μg/ml were added to endothelium incubation systems to evaluate any protective effects upon O−
2-induced alterations. All experiments were conducted in a serum-free HEPES-Tyrode's buffer, pH 7.4 incubation system. Our results show that exposure of HUVE cells to sublethal concentrations of oxygen free radical generating systems causes significant enhancement of platelet adherence (65%) to injured endothelium. A 12-fold increase in prostacyclin release resulted after a 15 min treatment with xanthine and xanthine oxidase. The addition of exogenous PGI2 (150nM) to platelet-endothelial systems did not completely prevent the enhanced platelet adherence suggesting that lack of prostacyclin was not completely responsible for the adherence of platelets to O−
2 injured cells. When SOD and catalase, scavengers of O−
2 and H2O−
2, were added to treated cells, platelet adherence decreased by 42-77% and prostacyclin release approached that of control cultures. These data implicate an active participation of activated metabolites of molecular oxygen in the alteration of vascular endothelial cell function.
Alterations in human vascular endothelial cell function by oxygen free radicals. Platelet adherence and prostacyclin release.
