HYDROGEN-PEROXIDE INDUCES UP-REGULATION OF FAS IN HUMAN ENDOTHELIAL-CELLS

Hydrogen peroxide (H2O2), an oxidant generated by inflammatory cells, is an important mediator of injury of endothelial cells (ECs), Here we show that H2O2 induces up-regulation of the expression of Fas, a deat h signal, in human ECs in culture. Flow cytometric analysis with a mAb against human Fas showed that incubation for 21h with H2O2 induced a dose-dependent increase in the level of Fas in ECs, Coincubation with catalase, which rapidly degrades H2O2, inhibited H2O2-induced up-regul ation of Fas, H2O2 also induced a dose-dependent increase in Fas mRNA level. A significant increase in Fas mRNA. levels was observed from 6 h after stimulation with H2O2. Vanadate, a protein phosphatase inhibit or, significantly enhanced Fas mRNA and protein levels in H2O2-treated ECs, On the other hand, genistein, a tyrosine kinase inhibitor, inhib ited H2O2-induced Fas mRNA. expression, Furthermore, a flow cytometric method with propidium iodide staining and electron microscopic analys is showed that incubation with an agonistic Ab against Fas (anti-Fas I gM) induced apoptosis in H2O2-treated cells, These findings suggest th at H2O2 induces up-regulation of Fas in ECs and that activation of pro tein tyrosine kinase may be involved in the mechanism of H2O2-induced Fas expression. Therefore, Fas-mediated apoptosis may have a pathologi c role in H2O2-induced EC injury and thereby provide a new therapeutic target.