Influence of vitamin E on the antiplatelet effect of acetylsalicylic acid in human blood

We analysed the in vitro interaction between acetylsalicylic acid and vitamin E on the principal antiplatelet sites of action of acetylsalicylic acid, i.e., platelet aggregation, prostanoid production in platelets and leukocytes, and nitric oxide synthesis. Aggregation was measured in whole blood and in platelet-rich plasma (PRP) with ADP, collagen or arachidonic acid as platelet inducers, and we measured the production of thromboxane B2, prostacyclin and nitric oxide. Vitamin E potentiated the antiplatelet effect of acetylsalicylic acid in both whole blood and PRP. In PRP induced with collagen the IC50 for acetylsalicylic acid alone was 339 � 11.26, and that of acetylsalicylic acid þ vitamin E was 0.89 � 0.09 (P < 0.05). Vitamin E did not enhance inhibition of platelet thromboxane production by acetylsalicylic acid. Vitamin E spared or even increased prostacyclin levels, and acetylsalicylic acid þ vitamin E diminished the inhibition of prostacyclin synthesis by acetylsalicylic acid (IC50 acetylsalicylic acid alone ¼ 1.81 � 0.15mM; IC50 acetylsalicylic acid þ vitamin E ¼ 12.92 � 1.10mM, P < 0.05). Vitamin E increased the effect of acetylsalicylic acid on neutrophil nitric oxide production 42-fold (P < 0.05). We conclude that vitamin E potentiates the antiplatelet effect of acetylsalicylic acid in vitro, and thus merits further research in ex vivo studies.