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O009 - THE EFFECT OF LDL OR HDL-ASSOCIATED PCSK9 ON PLATELET AGGREGATION AND INFLAMMATORY STIMULATION OF ENDOTHELIAL CELLS, IN VITRO (ID 209)
Abstract
Background and Aims
PCSK9 is a serine protease that increases LDL-cholesterol levels due to endosomal and lysosomal degradation of the LDL-receptor. Studies have shown that PCSK9 is attached in all plasma lipoproteins. We investigated the effect of LDL and HDL-associated PCSK9 on platelet aggregation and on endothelial cell activation.
Methods
Washed platelets (WP), isolated from healthy volunteers, were incubated with 0.1mg/ml LDL or HDL in the presence or absence of 2.5μg/ml polyclonal antibody against PCSK9 (anti-PCSK9pAb) and activated with 0.1 units/ml thrombin or 0.25mM AA and monitored using Light Transmittance Aggregometry. Human Umbilical Vein Endothelial Cells (HUVECs) were cultured and pre-incubated with 0.1mg/ml LDL or HDL in the presence or absence of anti-PCSK9pAb for 5min followed by activation with 0.25ng/ml Tumor Necrosis Factor-α (TNF-α) for 6h. Cell activation was studied by flow cytometry for the membrane expression of ICAM-1 (Intercellular Adhesion Molecule-1).
Results
Thrombin and AΑ-induced platelet aggregation was inhibited by 50±19% and 38±11%, respectively in the presence of HDL and by 28±15 and 39±12%, respectively in the presence of LDL. These effects were not significantly influenced in the presence of anti-PCSK9pAb. ICAM-1 membrane expression was inhibited by 49±7.5% and 20±1.7% in the presence of HDL and LDL respectively, whereas these inhibitions were significantly reduced (p<0.05) in the presence of anti-PCSK9pAb by 22±6.9% and 9.2±0.8%, respectively.
Conclusions
HDL and LDL-associated PCSK9 does not affect the inhibitory effect of these lipoproteins on platelet activation whereas it significantly increases their inhibitory effect on inflammatory stimulation of endothelial cells.