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(Arteriosclerosis, Thrombosis, and Vascular Biology. 1999;19:2542-2547.)
© 1999 American Heart Association, Inc.

Thrombosis

Vitamin E Inhibits Collagen-Induced Platelet Activation by Blunting Hydrogen Peroxide

Pasquale Pignatelli; Fabio M. Pulcinelli; Luisa Lenti; Pier Paolo Gazzaniga; Francesco Violi

Correspondence to Prof Pier Paolo Gazzaniga, Dipartimento di Medicina Sperimentale e Patologia, Università degli Studi di Roma "La Sapienza," Viale Regina Elena 324, 00161 Roma, Italy. E-mail gazzaniga{at}axrma.uniroma1.it

Abstract—In this study, we investigated whether vitamin E at concentrations achievable in blood after supplementation inhibits platelet function in humans. Gel-filtered platelets were incubated 30 minutes with scalar concentrations (50 to 250 mmol/L) of vitamin E and then stimulated with collagen. Compared with 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 whether vitamin E was able to blunt hydrogen peroxide. In experiments performed in unstimulated platelets supplemented with hydrogen peroxide and in collagen-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 significant decrease of collagen-induced H₂O₂ formation, platelet aggregation, and calcium mobilization. This study demonstrated in vitro and ex vivo that vitamin E inhibits collagen-induced platelet activation by blunting hydrogen peroxide formation.

Key Words: antioxidants • platelet aggregation • arachidonic acid metabolism • phospholipase C enzyme • thromboxane A2

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