Elena Tremoli

Plasma lipoproteins affect platelet malondialdehyde and thromboxane B2 production

Platelet interaction with plasma lipoproteins was studied using gel-filtered platelets free of plasma constituents and purified lipoproteins. On incubation of gel-filtered platelets with plasma lipoproteins at 30 degrees C for 30 min, 100 micrograms of protein/ml of very-low as well as low-density lipoprotein caused 10% increment in platelet aggregation and [14C]serotonin release in parallel to elevation of around 15% of malondialdehyde and thromboxane B2 production. High-density lipoprotein showed the opposite effect and reduced platelet aggregation as well as thromboxane B2 synthesis by 17 and 32%, respectively. Lipoprotein-deficient plasma enhanced platelet function. Preincubation of the platelet suspension with prostacyclin did not prevent the effect of the lipoproteins on the in vitro platelet response as well as on the platelet prostaglandin pathway. Our results suggest that the formation of thromboxane B2 and malondialdehyde is influenced by plasma lipoproteins and that these, in turn, affect platelet aggregation and the release reaction. The possible significance of these results to platelet function in hyperlipidemic patients is discussed.

Influence of Atherogenic Lipoproteins on The Thrombotic Potential of Endothelial Cells

In this article the relationship between atherogenic lipoproteins, i.e. VLDL LDL and modified LDL, and “endothelial cell perturbation” is discussed. Data in the literature indicate that LDL as well as modified LDL influence a variety of functional aspects of endothelial cells, that include adhesive properties for monocytes/macrophages and regulation of vascular tone. In addition these lipoproteins influence the capacity of endothelial cells both to generate and to remove fibrin. The data so far available indicate that atherogenic lipoproteins influence both tissue factor expression and the release of plasminogen activator inhibitor type a by endothelial cells, thus increasing the prothrombotic potential of vascular endothelium.