Ginkgo biloba extract inhibits tumor necrosis factor-α-induced reactive oxygen species generation, transcription factor activation, and cell adhesion molecule expression in human aortic endothelial cells

Objective - This study was conducted to examination whether Ginkgo biloba extract (GBE), a Chinese herb with antioxidant activity, could reduce cytokine-induced monocyte/human aortic endothelial cell ( HAEC) interaction, a pivotal early event in atherogenesis. Methods and Results - Pretreatment of HAECs with GBE (50 and 100 mug/mL for 18 hours) significantly suppressed cellular binding between the human monocytic cell line U937 and tumor necrosis factor-alpha (TNF-alpha)-stimulated HAECs by using in vitro binding assay (68.7% and 60.1% inhibitions, respectively). Cell enzyme - linked immunosorbent assay and immunoblot analysis showed that GBE (50 mug/mL for 18 hours) significantly attenuated TN-alpha-induced cell surface and total protein expression of vascular cellular adhesion molecule-1 and intracellular adhesion molecule-1 (63.5% and 69.2%, respectively; P < 0.05). However, pretreatment with probucol (5 mu mol/L for 18 hours) reduced the expression of vascular cellular adhesion molecule-1 but not intracellular adhesion molecule-1. Preincubation of HAECs with GBE or probucol significantly reduced intracellular reactive oxygen species formation induced by TNF-alpha (76.8% and 68.2% inhibitions, respectively; P < 0.05). Electrophoretic mobility shift assay demonstrated that both GBE and probucol inhibited transcription factor nuclear factor-kappaB activation in TNF-alpha-stimulated HAECs (55.2% and 65.6% inhibitions, respectively) but only GBE could inhibit the TNF-alpha-stimulated activator protein 1 activation (45.1% inhibition, P < 0.05). Conclusions - GBE could reduce cytokine-stimulated endothelial adhesiveness by downregulating intracellular reactive oxygen species formation, nuclear factor-kappa B and activator protein 1 activation, and adhesion molecule expression in HAECs, supporting the notion that the natural compound Ginkgo biloba may have potential implications in clinical atherosclerosis disease.