Therapies that raise levels of HDL, which is thought to exert atheroprotective effects via effects on endothelium, are being examined for the treatment or prevention of coronary artery disease (CAD). However, the endothelial effects of HDL are highly heterogeneous, and the impact of HDL of patients with CAD on the activation of endothelial eNOS and eNOS-dependent pathways is unknown. Here we have demonstrated that, in contrast to HDL from healthy subjects, HDL from patients with stable CAD or an acute coronary syndrome (HDL CAD ) does not have endothelial antiinflammatory effects and does not stimulate endothelial repair because it fails to induce endothelial NO production. Mechanistically, this was because HDL CAD activated endothelial lectin-like oxidized LDL receptor 1 (LOX-1), triggering endothelial PKCβII activation, which in turn inhibited eNOS-activating pathways and eNOS-dependent NO production. We then identified reduced HDL-associated paraoxonase 1 (PON1) activity as one molecular mechanism leading to the generation of HDL with endothelial PKCβII-activating properties, at least in part due to increased formation of malondialdehyde in HDL. Taken together, our data indicate that in patients with CAD, HDL gains endothelial LOX-1-and thereby PKCβII-activating properties due to reduced HDL-associated PON1 activity, and that this leads to inhibition of eNOS-activation and the subsequent loss of the endothelial antiinflammatory and endothelial repair-stimulating effects of HDL.

Objective-MicroRNAs are important intracellular regulators of gene expression, but also circulate in the blood being protected by extracellular vesicles, proteins, or high-density lipoprotein (HDL). Here, we evaluate the regulation and potential function of HDL-and low-density lipoprotein-bound miRs isolated from healthy subjects and patients with coronary artery disease. Approach and Results-HDL-bound miRs with known effects in the cardiovascular system were analyzed in HDL isolated from healthy subjects (n=10), patients with stable coronary artery disease (n=10), and patients with an acute coronary syndrome (n=10). In HDL from healthy subjects, miR-223 was detected at concentrations >10 000 copies/µg HDL, and miR-126 and miR-92a at about 3000 copies/µg HDL. Concentrations of most miRs were substantially higher in HDL as compared with low-density lipoprotein. However, HDL-bound miR-223 contributed to only 8% of the total circulating miRs. The signatures of miRs varied only slightly in HDL derived from patients with coronary artery disease. We did not observe a significant uptake of HDL-bound miRs into endothelial cells, smooth muscle cells, or peripheral blood mononuclear cells. However, patient-derived HDL transiently reduced miR expression particularly when incubated with smooth muscle and peripheral blood mononuclear cells. Conclusions-Circulating

R educed plasma levels of high-density lipoprotein (HDL) cholesterol are associated with an increased risk of coronary artery disease (CAD).1 Moreover, in patients with CAD that are treated with statin and have low levels of low-density lipoprotein (LDL) cholesterol, reduced HDL cholesterol levels were predictive of major cardiovascular events.2 Besides promoting reverse cholesterol transport, 3,4 HDL has been demonstrated to exert antiatherosclerotic effects, including antiinflammatory properties and stimulation of endothelial nitric oxide (NO) production. [5][6][7][8][9] However, these effects of HDL have been observed to be highly heterogenous in patients with CAD or diabetes mellitus. 10-12 Editorial see p 868 Clinical Perspective on p 904Endothelial dysfunction and injury are thought to contribute importantly to the progression of CAD. [13][14][15] Experimental studies have indicated that atherosclerotic lesion-prone vascular regions are characterized by a high endothelial cell turnover, 16 which has been attributed to an increased rate of endothelial cell apoptosis. Moreover, superficial atherosclerotic plaque erosion with the loss of an intact endothelial cell monolayer is observed quite frequently in patients with an acute coronary syndrome (ACS) based on pathological studies, 17,18 and on 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 d...

Myeloperoxidase (MPO) and paraoxonase 1 (PON1) are high-density lipoprotein-associated (HDL-associated) proteins mechanistically linked to inflammation, oxidant stress, and atherosclerosis. MPO is a source of ROS during inflammation and can oxidize apolipoprotein A1 (APOA1) of HDL, impairing its atheroprotective functions. In contrast, PON1 fosters systemic antioxidant effects and promotes some of the atheroprotective properties attributed to HDL. Here, we demonstrate that MPO, PON1, and HDL bind to one another, forming a ternary complex, wherein PON1 partially inhibits MPO activity, while MPO inactivates PON1. MPO oxidizes PON1 on tyrosine 71 (Tyr 71 ), a modified residue found in human atheroma that is critical for HDL binding and PON1 function. Acute inflammation model studies with transgenic and knockout mice for either PON1 or MPO confirmed that MPO and PON1 reciprocally modulate each other's function in vivo. Further structure and function studies identified critical contact sites between APOA1 within HDL, PON1, and MPO, and proteomics studies of HDL recovered from acute coronary syndrome (ACS) subjects revealed enhanced chlorotyrosine content, site-specific PON1 methionine oxidation, and reduced PON1 activity. HDL thus serves as a scaffold upon which MPO and PON1 interact during inflammation, whereupon PON1 binding partially inhibits MPO activity, and MPO promotes site-specific oxidative modification and impairment of PON1 and APOA1 function.