ALTERATIONS IN HUMAN VASCULAR ENDOTHELIAL-CELL FUNCTION BY OXYGEN FREE-RADICALS - PLATELET ADHERENCE AND PROSTACYCLIN RELEASE

This study was directed to the ability of oxygen free radicals to cause reversible vascular endothelial cell dysfunction. A well-characterized system for the production of the superoxide anion radical (O2-.) and hydrogen peroxide (H2O2), employing xanthine and xanthine oxidase, was used to sublethally injure human umbilical vein endothelial (HUVE) cells in vitro. We examined the effects of a 15-minute incubation of HUVE cells with xanthine (50-mu-M) and xanthine oxidase (2.5-100 munits) on platelet adherence and prostacyclin (PGI2) release. All experiments were conducted in a serum-free N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid)-Tyrode buffer (pH 7.4) incubation system. Exposure of HUVE cells to sublethal concentrations of oxygen free radicals caused significant enhancement of platelet adherence (65 +/- 6.3%) to injured endothelium. A 12-fold increase in PGI2 release resulted after a 15-minute treatment with xanthine and xanthine oxidase. The addition of exogenous PGI2 (150 mM) to platelet-endothelial systems did not completely prevent the enhanced platelet adherence, suggesting that a lack of PGI2 was not completely responsible for the adherence of platelets to O2-.-injured cells. When superoxide dismutase (SOD) and catalase, scavengers of O2-. and H2O2, were added in combination to treated cells, platelet adherence decreased by 42-77% and PGI2 release approached that of control cultures. No decrease in either platelet adherence or PGI2 release occurred when chemically inactivated forms of SOD and catalase or bovine serum albumin were added to oxidant-treated cultures.