Ginkgo biloba modulates glutathione redox cycle in vascular endothelial cells

We recently reported that Ginkgo biloba extract (GEE) suppressed oxidative burst in macrophages and protected bovine pulmonary artery endothelial cells (PAEC) from oxidant injury. In this study the effects of GBE on glutathione (GSH) redox cycle and activity of antioxidant enzymes were investigated. Confluent monolayers of PAEC were incubated with GEE for 8-48 h, washed, and then lysed with Triton X-100. Biochemical assays were performed with the lysate. GEE caused both dose- and time-dependent increase in GSH level and glutathione disulfide (GSSG) reductase activity while GSH peroxidase and superoxide dismutase activity remained unaffected. Exposure of PAEC to an organic oxidant tert-butyl hydroperoxide (tBHP) resulted in decreased GSH level, increased lipid peroxidation, and elevated leakage of intracellular lactate dehydrogenase. Preincubation or simultaneous treatment of PAEC with GEE prevented these changes induced by tBHP. Our data suggest that the antioxidant effect of GBE may be due to its modulation of the GSH redox cycle in PAEC as well as direct scavenging of the oxidant. Copyright (C) 1996 Elsevier Science Inc.