Vitamin E inhibition of platelet aggregation is independent of antioxidantactivity

Vitamin E is the principal lipid-soluble antioxidant in human plasma, and s ome studies indicate that it may provide cardiovascular protection. To inve stigate putative mechanisms for vitamin E in this regard, the effect of vit amin E on vascular function and platelet aggregation was examined. In anima l models of endothelial dysfunction, vitamin E improved the activity of end othelium-derived nitric oxide, and this effect was not dependent upon the a ntioxidant protection of LDL. In fact, vitamin E improved endothelial funct ion in part due to the inhibition of protein kinase C (PKC) stimulation. Th is activity of vitamin E was examined in platelets, and vitamin E inhibited platelet aggregation in part through a mechanism that involves PKC, Moreov er, the platelet inhibitory activity of vitamin E was independent of its an tioxidant action because platelet inhibition was still observed with isofor ms of vitamin E that were devoid of antioxidant activity.