Vitamin E reduces platelet adhesion to human endothelial cells in vitro

Abstract

Although it has been reported that vitamin E (α-tocopherol) can reduce platelet adhesiveness and aggregation in vivo, the mechanism is still unknown. Therefore, the aim of the present study was to determine whether incubations of platelet-rich plasma (PRP) with vitamin E influence platelet adhesion to cultured endothelial cells. To exclude blood plasma involvement, also washed platelets were pretreated with α-tocopherol. Vitamin E (0.5-1.0 mM) was added to PRP or washed platelets. Endothelial cells in monolayer were incubated with thrombin-activated platelets (1 or 2 U/ml). After 1 hr of incubation, non-adhered platelets were removed and counted. Treating of PRP with α-tocopherol inhibited platelet adhesion to endothelial cell monolayer. This effect was dose dependent on concentrations of α-tocopherol and thrombin. In our experiments PRP was treated with α-tocopherol and endothelial cell monolayer was used as test surface. These findings agree with previous observations on the adhesivity of platelets to synthetic surfaces after dietary vitamin E in healthy volunteers. When washed platelets were incubated with α-tocopherol, no significant reduction of adhesion was detectable. As preincubation of washed platelets with α-tocopherol does not inhibit platelet adhesion, it may be supposed that the effect of vitamin E does not occur in a directly cellular mechanism. The data suggest that α-tocopherol may reduce platelet adhesiveness probably after incorporation by plasma lipoproteins. (C) 2000 Wiley-Liss, Inc.