title: Vitamin E inhibition of platelet aggregation is independent of antioxidant activity.
abstract: Vitamin E is the principal lipid-soluble antioxidant in human plasma, and some studies indicate that it may provide cardiovascular protection. To investigate putative mechanisms for vitamin E in this regard, the effect of vitamin E on vascular function and platelet aggregation was examined. In animal models of endothelial dysfunction, vitamin E improved the activity of endothelium-derived nitric oxide, and this effect was not dependent upon the antioxidant protection of LDL. In fact, vitamin E improved endothelial function in part due to the inhibition of protein kinase C (PKC) stimulation. This activity of vitamin E was examined in platelets, and vitamin E inhibited platelet aggregation in part through a mechanism that involves PKC. Moreover, the platelet inhibitory activity of vitamin E was independent of its antioxidant action because platelet inhibition was still observed with isoforms of vitamin E that were devoid of antioxidant activity.
authors.affiliation: Department of Pharmacology, Georgetown University Medical Center, Washington, DC , USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Freedman
authors.forename: J F
authors.initials: JF
authors.lastname: Keaney
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D002318:Cardiovascular Diseases / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D013927:Thrombosis / Q000517:prevention & control; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000975:Antioxidants; D010975:Platelet Aggregation Inhibitors; D014810:Vitamin E; D011493:Protein Kinase C