Abstract 5486: High Density Lipoprotein (HDL) From Healthy Subjects, but Not From Patients With Coronary Artery Disease, Exerts Anti-thrombotic Effects on Human Endothelial Cells

Abstract

Background: Arterial thrombus formation is determined by the balance between pro-thrombotic mediators such as tissue factor (TF) and plasminogen activator inhibitor type 1 (PAI-1), and anti-thrombotic factors like tissue factor pathway inhibitor (TFPI) or tissue plasminogen activator (tPA). Native HDL from healthy subjects (HS) has anti-thrombotic properties; however, it remains unknown whether this is the case for HDL from patients with stable coronary disease (CAD) or acute coronary syndrome (ACS). Methods: HDL was isolated by sequential ultracentrifugation from HS and patients with CAD and ACD. The effects of HDL (50 μ g/ml) on TF, TFPI, and PAI-1 expression in human endothelial cells were determined by Western blot analysis; tPA release was measured by ELISA. Results: HDL from HS impaired thrombin-induced TF expression (−45±5%, p<0.05, n=16) and activity (−33±8%, p<0.05, n±7); in contrast, HDL from CAD and ACS patients did not (p=NS, n=12 and n=8). Similarly, HDL from HS increased TFPI expression by 2-fold (p<0.01, n=8), while HDL from CAD and ACS patients had no effect (p=NS). HDL from HS enhanced tPA release (+26±3%; p=0.05, n=8); in contrast, HDL from CAD and ACS patients did not (p=NS, n=6). Furthermore, HDL from HS did not affect PAI-1 expression, while HDL from CAD patients enhanced PAI-1 expression by 62% (p<0.05 vs. healthy, n=12) and HDL from ACS patients by 2 fold (p<0.05 vs. control and p<0.05 vs. healthy, n=8). Pretreatment with the inhibitor of NO formation, L-NAME (100 μ M), abolished the anti-thrombotic effects of HDL from HS on TF, TFPI, and tPA expression. The exogenous nitric oxide donor, DETANO, mimicked the effects of HDL from HS on TF, TFPI, and tPA. Conclusion: This study demonstrates that HDL from healthy subjects exerts anti-thrombotic effects on endothelial cells. In contrast, HDL from CAD and ACS patients loses these antithrombotic properties and instead enhances PAI-1 expression, thereby becoming pro-thrombotic. This observation might be highly relevant for HDL-targeted therapies.