The role of apoE in inhibitory effects of apoE-rich HDL on platelet function.

Apolipoprotein E- (ApoE-) rich high-density lipoprotein (HDL), which was prepared from the bound fraction of normolipemic volunteers on heparin-Sepharose and from a hyperalphalipoproteinemic patient, potently inhibited aggregation of human platelets in a dose-dependent fashion. Dimyristoyl phosphatidylcholine liposome with apoE (apoE.DMPC) also inhibited platelet aggregation, and incubation of washed platelets with apoE.DMPC resulted in the release of cholesterol into the supernatant in a time- and dose-dependent manner. These results suggest that apoE plays a major role in the inhibitory effect of apoE-rich HDL in platelet function, presumably due to the release of cholesterol from the plasma membrane.