Altered Activation of Endothelial Anti- and Proapoptotic Pathways by High-Density Lipoprotein from Patients with Coronary Artery Disease

Abstract

Background— Endothelial dysfunction and injury are thought to play an important role in the progression of coronary artery disease (CAD). High-density lipoprotein from healthy subjects (HDL Healthy ) has been proposed to exert endothelial antiapoptotic effects that may represent an important antiatherogenic property of the lipoprotein. The present study therefore aimed to compare effects of HDL CAD and HDL Healthy on the activation of endothelial anti- and proapoptotic pathways and to determine which changes of the lipoprotein are relevant for these processes. Methods and Results— HDL was isolated from patients with stable CAD (HDL sCAD ), an acute coronary syndrome (HDL ACS ), and healthy subjects. HDL Healthy induced expression of the endothelial antiapoptotic Bcl-2 protein Bcl-xL and reduced endothelial cell apoptosis in vitro and in apolipoprotein E–deficient mice in vivo. In contrast, HDL sCAD and HDL ACS did not inhibit endothelial apoptosis, failed to activate endothelial Bcl-xL, and stimulated endothelial proapoptotic pathways, in particular, p38-mitogen-activated protein kinase–mediated activation of the proapoptotic Bcl-2 protein tBid. Endothelial antiapoptotic effects of HDL Healthy were observed after inhibition of endothelial nitric oxide synthase and after delipidation, but not completely mimicked by apolipoprotein A-I or reconstituted HDL, suggesting an important role of the HDL proteome. HDL proteomics analyses and subsequent validations and functional characterizations suggested a reduced clusterin and increased apolipoprotein C-III content of HDL sCAD and HDL ACS as mechanisms leading to altered effects on endothelial apoptosis. Conclusions— The present study demonstrates for the first time that HDL CAD does not activate endothelial antiapoptotic pathways, but rather stimulates potential endothelial proapoptotic pathways. HDL-proteome remodeling plays an important role for these altered functional properties of HDL. These findings provide novel insights into mechanisms leading to altered vascular effects of HDL in coronary disease.