Vitamin E inhibits collagen-induced platelet activation by blunting hydrogen peroxide

In this study, we investigated whether vitamin E at concentrations achievab le in blood after supplementation inhibits platelet function in humans. Gel -filtered platelets were incubated 30 minutes with scalar concentrations (5 0 to 250 mmol/L) of vitamin E and then stimulated with collagen. Compared w ith controls, vitamin E inhibited collagen-induced platelet aggregation and thromboxane A2 formation in a dose-dependent manner. Furthermore, vitamin E inhibited, in a dose-dependent manner, Ca2+ mobilization and formation of inositol 1,4,5-triphosphate, Because it was previously shown that hydrogen peroxide formation mediates arachidonic acid metabolism and phospholipase C activation in collagen-induced platelet activation, we investigated wheth er vitamin E was able to blunt hydrogen peroxide. In experiments performed in unstimulated platelets supplemented with hydrogen peroxide and in collag en-stimulated platelets, vitamin E was able to blunt hydrogen peroxide. In 6 healthy subjects given vitamin E for 2 weeks.(600 mg/d), we found a signi ficant decrease of collagen-induced H2O2 formation, platelet aggregation, a nd calcium mobilization. This study demonstrated in vitro and ex vivo that vitamin E inhibits collagen-induced platelet activation by blunting hydroge n peroxide formation.