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Thematic Review ,Thematic Review Series: High Density Lipoprotein Structure, Function, and Metabolism| Volume 54, ISSUE 12, P3227-3243, December 2013

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High density lipoproteins and endothelial functions: mechanistic insights and alterations in cardiovascular disease1

Open AccessPublished:July 20, 2013DOI:https://doi.org/10.1194/jlr.R037762
      Prospective population studies in the primary prevention setting have shown that reduced plasma levels of HDL cholesterol are associated with an increased risk of coronary disease and myocardial infarction. Experimental and translational studies have further revealed several potential anti-atherogenic effects of HDL, including protective effects on endothelial cell functions. HDL has been suggested to protect endothelial cell functions by prevention of oxidation of LDL and its adverse endothelial effects. Moreover, HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and anti-inflammatory, anti-apoptotic, and anti-thrombotic effects as well as endothelial repair processes. However, several recent clinical trials using HDL cholesterol-raising agents, such as torcetrapib, dalcetrapib, and niacin, did not demonstrate a significant reduction of cardiovascular events in patients with coronary disease. Of note, growing evidence suggests that the vascular effects of HDL can be highly heterogeneous and vasoprotective properties of HDL are altered in patients with coronary disease. Characterization of underlying mechanisms and understanding of the clinical relevance of this “HDL dysfunction” is currently an active field of cardiovascular research. Notably, in some recent studies no clear association of higher HDL cholesterol levels with a reduced risk of cardiovascular events was observed in patients with already established coronary disease. A greater understanding of mechanisms of action of HDL and its altered vascular effects is therefore critical within the context of HDL-targeted therapies. In this review, we will address different effects of HDL on endothelial cell functions potentially relevant to atherosclerotic vascular disease and explore molecular mechanisms leading to “dysfunctional HDL”.
      Large prospective studies of cardiovascular risk factors have shown that reduced plasma levels of HDL cholesterol are associated with an increased risk of coronary artery disease (CAD) (
      • Gordon T.
      • Castelli W.P.
      • Hjortland M.C.
      • Kannel W.B.
      • Dawber T.R.
      High density lipoprotein as a protective factor against coronary heart disease. The Framingham Study.
      ,
      • Castelli W.P.
      • Garrison R.J.
      • Wilson P.W.
      • Abbott R.D.
      • Kalousdian S.
      • Kannel W.B.
      Incidence of coronary heart disease and lipoprotein cholesterol levels. The Framingham Study.
      ,
      • Cullen P.
      • Schulte H.
      • Assmann G.
      The Munster Heart Study (PROCAM): total mortality in middle-aged men is increased at low total and LDL cholesterol concentrations in smokers but not in nonsmokers.
      ,
      • Sharrett A.R.
      • Ballantyne C.M.
      • Coady S.A.
      • Heiss G.
      • Sorlie P.D.
      • Catellier D.
      • Patsch W.
      Coronary heart disease prediction from lipoprotein cholesterol levels, triglycerides, lipoprotein(a), apolipoproteins A-I and B, and HDL density subfractions: the Atherosclerosis Risk in Communities (ARIC) Study.
      ,
      • Di Angelantonio E.
      • Sarwar N.
      • Perry P.
      • Kaptoge S.
      • Ray K.K.
      • Thompson A.
      • Wood A.M.
      • Lewington S.
      • Sattar N.
      • Packard C.J.
      • et al.
      Major lipids, apolipoproteins, and risk of vascular disease.
      ). In recent years, several biological functions of HDL have been identified, whereby HDL may exert anti-atherogenic effects (
      • Rader D.J.
      Molecular regulation of HDL metabolism and function: implications for novel therapies.
      ,
      • Mineo C.
      • Deguchi H.
      • Griffin J.H.
      • Shaul P.W.
      Endothelial and antithrombotic actions of HDL.
      ,
      • Barter P.J.
      • Nicholls S.
      • Rye K.A.
      • Anantharamaiah G.M.
      • Navab M.
      • Fogelman A.M.
      Antiinflammatory properties of HDL.
      ); e.g., HDL from healthy subjects has been shown to directly promote endothelial anti-inflammatory, anti-apoptotic, and anti-thrombotic effects (
      • Mineo C.
      • Deguchi H.
      • Griffin J.H.
      • Shaul P.W.
      Endothelial and antithrombotic actions of HDL.
      ,
      • Yuhanna I.S.
      • Zhu Y.
      • Cox B.E.
      • Hahner L.D.
      • Osborne-Lawrence S.
      • Lu P.
      • Marcel Y.L.
      • Anderson R.G.
      • Mendelsohn M.E.
      • Hobbs H.H.
      • et al.
      High-density lipoprotein binding to scavenger receptor-BI activates endothelial nitric oxide synthase.
      ,
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ,
      • Tall A.R.
      • Yvan-Charvet L.
      • Terasaka N.
      • Pagler T.
      • Wang N.
      HDL, ABC transporters, and cholesterol efflux: implications for the treatment of atherosclerosis.
      ,
      • Rye K.A.
      • Barter P.J.
      Antiinflammatory actions of HDL: a new insight.
      ) (Fig. 1). Accordingly, interventions to increase HDL cholesterol levels and/or HDL function are being intensely evaluated as a potential therapeutic strategy to reduce cardiovascular risk. However, recent evidence suggests that the endothelial and vascular effects of HDL are highly heterogeneous and vasoprotective properties of HDL are impaired in patients with diabetes, coronary disease, or chronic kidney dysfunction (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Khera A.V.
      • Cuchel M.
      • de la Llera-Moya M.
      • Rodrigues A.
      • Burke M.F.
      • Jafri K.
      • French B.C.
      • Phillips J.A.
      • Mucksavage M.L.
      • Wilensky R.L.
      • et al.
      Cholesterol efflux capacity, high-density lipoprotein function, and atherosclerosis.
      ,
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      ) (Fig. 1).
      Figure thumbnail gr1
      Fig. 1Left panel: HDL from healthy subjects exerts direct vasoprotective effects such as endothelial anti-inflammatory, anti-oxidative, anti-apoptotic, and anti-thrombotic effects. HDL from healthy subjects stimulates endothelial cell NO production and promotes endothelial repair after vascular injury. Right panel: Accumulating evidence suggests that the vascular effects of HDL can be highly heterogeneous. HDL loses potential anti-atherosclerotic properties in patients with chronic inflammatory diseases, such as CAD, that has been termed HDL dysfunction. Of note, HDL may also become a pro-inflammatory particle in certain pathophysiological conditions.
      Various studies have examined the association of genetic variations leading to altered HDL cholesterol plasma levels with coronary disease risk (
      • Thompson A.
      • Di Angelantonio E.
      • Sarwar N.
      • Erqou S.
      • Saleheen D.
      • Dullaart R.P.
      • Keavney B.
      • Ye Z.
      • Danesh J.
      Association of cholesteryl ester transfer protein genotypes with CETP mass and activity, lipid levels, and coronary risk.
      ,
      • Ridker P.M.
      • Pare G.
      • Parker A.N.
      • Zee R.Y.
      • Miletich J.P.
      • Chasman D.I.
      Polymorphism in the CETP gene region, HDL cholesterol, and risk of future myocardial infarction: genomewide analysis among 18 245 initially healthy women from the Women's Genome Health Study.
      ,
      • Frikke-Schmidt R.
      • Nordestgaard B.G.
      • Stene M.C.
      • Sethi A.A.
      • Remaley A.T.
      • Schnohr P.
      • Grande P.
      • Tybjaerg-Hansen A.
      Association of loss-of-function mutations in the ABCA1 gene with high-density lipoprotein cholesterol levels and risk of ischemic heart disease.
      ). These studies suggest that some genetic variations associated with higher HDL cholesterol plasma levels may not necessarily be asso­ciated with a reduced risk of coronary disease or myocardial infarction, although this does not apply for all associations [e.g., cholesteryl ester transfer protein (CETP)], and for some genes remains inconclusive (
      • Voight B.F.
      • Peloso G.M.
      • Orho-Melander M.
      • Frikke-Schmidt R.
      • Barbalic M.
      • Jensen M.K.
      • Hindy G.
      • Holm H.
      • Ding E.L.
      • Johnson T.
      • et al.
      Plasma HDL cholesterol and risk of myocardial infarction: a Mendelian randomisation study.
      ,
      • Singaraja R.R.
      • Sivapalaratnam S.
      • Hovingh K.
      • Dube M.P.
      • Castro-Perez J.
      • Collins H.L.
      • Adelman S.J.
      • Riwanto M.
      • Manz J.
      • Hubbard B.
      • et al.
      The impact of partial and complete loss-of-function mutations in endothelial lipase on high-density lipoprotein levels and functionality in humans.
      ).
      Of note, several recent clinical trials have not been able to demonstrate that therapies that increase HDL cholesterol levels reduce cardiovascular risk in patients with coronary disease. The Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events (ILLUMINATE) trial testing the impact of the CETP inhibitor torcetrapib on clinical outcome showed an increase in cardiovascular events and total mortality despite elevations in HDL cholesterol, that was, however, at least in part attributed to toxic effects of the compound (
      • Barter P.J.
      • Caulfield M.
      • Eriksson M.
      • Grundy S.M.
      • Kastelein J.J.
      • Komajda M.
      • Lopez-Sendon J.
      • Mosca L.
      • Tardif J.C.
      • Waters D.D.
      • et al.
      Effects of torcetrapib in patients at high risk for coronary events.
      ). Dalcetrapib, another CETP inhibitor, raised the HDL cholesterol level in patients hospitalized with an acute coronary syndrome (ACS), but the trial was terminated before completion due to lack of clinical benefit (
      • Schwartz G.G.
      • Olsson A.G.
      • Abt M.
      • Ballantyne C.M.
      • Barter P.J.
      • Brumm J.
      • Chaitman B.R.
      • Holme I.M.
      • Kallend D.
      • Leiter L.A.
      • et al.
      Effects of dalcetrapib in patients with a recent acute coronary syndrome.
      ). And very recently, the HPS2-THRIVE trial results showed that adding extended-release niacin/laropiprant, another HDL-raising agent, to statins did not reduce the risk of cardiovascular events (
      • Armitage J.
      Niacin causes serious unexpected side effects, but no worthwhile benefits.
      ). Taken together, these observations strongly suggest that plasma levels of HDL cholesterol alone are not an optimal therapeutic target.
      Importantly, accumulating evidence suggests that the vascular effects of HDL can be highly heterogeneous. We and others have observed that HDL loses potential anti-atherosclerotic properties in patients with chronic inflammatory disorders such as the antiphospholipid syndrome (
      • Charakida M.
      • Besler C.
      • Batuca J.R.
      • Sangle S.
      • Marques S.
      • Sousa M.
      • Wang G.
      • Tousoulis D.
      • Delgado Alves J.
      • Loukogeorgakis S.P.
      • et al.
      Vascular abnormalities, paraoxonase activity, and dysfunctional HDL in primary antiphospholipid syndrome.
      ), systemic lupus erythematosus and rheumatoid arthritis (
      • McMahon M.
      • Grossman J.
      • FitzGerald J.
      • Dahlin-Lee E.
      • Wallace D.J.
      • Thong B.Y.
      • Badsha H.
      • Kalunian K.
      • Charles C.
      • Navab M.
      • et al.
      Proinflammatory high-density lipoprotein as a biomarker for atherosclerosis in patients with systemic lupus erythematosus and rheumatoid arthritis.
      ), scleroderma (
      • Weihrauch D.
      • Xu H.
      • Shi Y.
      • Wang J.
      • Brien J.
      • Jones D.W.
      • Kaul S.
      • Komorowski R.A.
      • Csuka M.E.
      • Oldham K.T.
      • et al.
      Effects of D-4F on vasodilation, oxidative stress, angiostatin, myocardial inflammation, and angiogenic potential in tight-skin mice.
      ), the metabolic syndrome (
      • de Souza J.A.
      • Vindis C.
      • Hansel B.
      • Negre-Salvayre A.
      • Therond P.
      • Serrano Jr, C.V.
      • Chantepie S.
      • Salvayre R.
      • Bruckert E.
      • Chapman M.J.
      • et al.
      Metabolic syndrome features small, apolipoprotein A-I-poor, triglyceride-rich HDL3 particles with defective anti-apoptotic activity.
      ), diabetes (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Perségol L.
      • Vergès B.
      • Foissac M.
      • Gambert P.
      • Duvillard L.
      Inability of HDL from type 2 diabetic patients to counteract the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation.
      ), and coronary disease (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      ,
      • Ansell B.J.
      • Navab M.
      • Hama S.
      • Kamranpour N.
      • Fonarow G.
      • Hough G.
      • Rahmani S.
      • Mottahedeh R.
      • Dave R.
      • Reddy S.T.
      • et al.
      Inflammatory/antiinflammatory properties of high-density lipoprotein distinguish patients from control subjects better than high-density lipoprotein cholesterol levels and are favorably affected by simvastatin treatment.
      ). Notably, in a study of 189 patients with chronic kidney disease on hemodialysis, an impaired anti-inflammatory capacity of HDL was correlated with a poor clinical outcome (
      • Kalantar-Zadeh K.
      • Kopple J.D.
      • Kamranpour N.
      • Fogelman A.M.
      • Navab M.
      HDL-inflammatory index correlates with poor outcome in hemodialysis patients.
      ). Furthermore, HDL isolated from subjects with type 1 or type 2 diabetes mellitus or abdominal obesity had reduced capacity to reverse the inhibition of aortic ring endothelium-dependent relaxation by oxidized LDL (oxLDL) as compared with HDL from healthy control subjects (
      • Perségol L.
      • Vergès B.
      • Foissac M.
      • Gambert P.
      • Duvillard L.
      Inability of HDL from type 2 diabetic patients to counteract the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation.
      ,
      • Perségol L.
      • Foissac M.
      • Lagrost L.
      • Athias A.
      • Gambert P.
      • Vergès B.
      • Duvillard L.
      HDL particles from type 1 diabetic patients are unable to reverse the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation.
      ,
      • Perségol L.
      • Vergès B.
      • Gambert P.
      • Duvillard L.
      Inability of HDL from abdominally obese subjects to counteract the inhibitory effect of oxidized LDL on vasorelaxation.
      ). These pro-inflammatory HDL particles have been termed “dysfunctional” HDL (Fig. 1). The heterogeneity of the vascular effects of HDL may be attributed to changes in the HDL-associated proteome and lipids, i.e., posttranslational protein modifications and changes in the amount and type of proteins and lipids bound to the HDL particle. In particular, HDL is susceptible to oxidation/modification in vitro by a variety of oxidants, such as metal ions, peroxyl and hydroxyl radicals, aldehydes, various myeloperoxidase (MPO)-generated oxidants, lipoxygenase, phospholipase A2, elastase, nonenzymatic glycation, and homocysteinylation (
      • Ferretti G.
      • Bacchetti T.
      • Negre-Salvayre A.
      • Salvayre R.
      • Dousset N.
      • Curatola G.
      Structural modifications of HDL and functional consequences.
      ). In the present review, we will address different mechanisms whereby HDL exerts effects on endothelial cell functions. In particular, the effects of HDL on regulation of endothelial nitric oxide synthase (eNOS) and endothelial cell nitric oxide (NO) production, endothelial inflammatory activation, endothelial apoptotic regulation, endothelial repair from vascular injury, lipid oxidation, and endothelial thrombotic activation will be discussed. Importantly, recent insights into molecular mechanisms leading to HDL dysfunction in different pathophysiological states will be described.

      IMPACT OF HDL ON LDL OXIDATION AND ITS ENDOTHELIAL EFFECTS

      Lessons from experimental studies and alterations of HDL from patients with coronary disease or diabetes

      HDL may exert endothelial-protective effects by limiting oxidation of LDL. Oxidation of LDL has long been suggested as a relevant mechanism for atherogenesis (
      • Witztum J.L.
      • Steinberg D.
      Role of oxidized low density lipoprotein in atherogenesis.
      ,
      • Heinecke J.W.
      Oxidants and antioxidants in the pathogenesis of atherosclerosis: implications for the oxidized low density lipoprotein hypothesis.
      ). LDL is entrapped in the subendothelial space where it is subject to oxidative modifications by reactive nitrogen species, MPO pathways, and others (
      • Diaz M.N.
      • Frei B.
      • Vita J.A.
      • Keaney Jr, J.F.
      Antioxidants and atherosclerotic heart disease.
      ). Once formed, oxLDL is a potent inducer of endothelial expression of inflammatory molecules (
      • Navab M.
      • Berliner J.A.
      • Watson A.D.
      • Hama S.Y.
      • Territo M.C.
      • Lusis A.J.
      • Shih D.M.
      • Van Lenten B.J.
      • Frank J.S.
      • Demer L.L.
      • et al.
      The Yin and Yang of oxidation in the development of the fatty streak. A review based on the 1994 George Lyman Duff Memorial Lecture.
      ). OxLDL also promotes the differentiation of monocytes into macrophages that take up oxLDL in a process that converts them into foam cells, hallmark cells of atherosclerotic plaques (
      • Chisolm 3rd, G.M.
      • Hazen S.L.
      • Fox P.L.
      • Cathcart M.K.
      The oxidation of lipoproteins by monocytes-macrophages. Biochemical and biological mechanisms.
      ).
      Hessler, Robertson, and Chisolm (
      • Hessler J.R.
      • Robertson Jr, A.L.
      • Chisolm 3rd, G.M.
      LDL-induced cytotoxicity and its inhibition by HDL in human vascular smooth muscle and endothelial cells in culture.
      ) reported early on that HDL protects against LDL-induced cytotoxicity on endothelial cells. HDL was demonstrated to prevent copper-induced LDL oxidation or LDL oxidation by cultured endothelial cells (
      • van Hinsbergh V.W.
      • Scheffer M.
      • Havekes L.
      • Kempen H.J.
      Role of endothelial cells and their products in the modification of low-density lipoproteins.
      ,
      • Ohta T.
      • Takata K.
      • Horiuchi S.
      • Morino Y.
      • Matsuda I.
      Protective effect of lipoproteins containing apoprotein A-I on Cu2+-catalyzed oxidation of human low density lipoprotein.
      ,
      • Parthasarathy S.
      • Barnett J.
      • Fong L.G.
      High-density lipoprotein inhibits the oxidative modification of low-density lipoprotein.
      ) (Table 1). HDL is a major carrier of lipid peroxidation products (
      • Bowry V.W.
      • Stanley K.K.
      • Stocker R.
      High density lipoprotein is the major carrier of lipid hydroperoxides in human blood plasma from fasting donors.
      ,
      • Proudfoot J.M.
      • Barden A.E.
      • Loke W.M.
      • Croft K.D.
      • Puddey I.B.
      • Mori T.A.
      HDL is the major lipoprotein carrier of plasma F2-isoprostanes.
      ) which are thought to play a role in the initiation and progression of atherosclerotic vascular disease (
      • Hansson G.K.
      Inflammation, atherosclerosis, and coronary artery disease.
      ). HDL can directly inhibit oxidation of LDL via transfer of oxidation products from LDL to HDL (
      • Bowry V.W.
      • Stanley K.K.
      • Stocker R.
      High density lipoprotein is the major carrier of lipid hydroperoxides in human blood plasma from fasting donors.
      ). In addition, circulating HDL accumulates oxidized phospholipids, such as hydroperoxides, lysophosphatidylcholine, and F2-isoprostanes (
      • Bowry V.W.
      • Stanley K.K.
      • Stocker R.
      High density lipoprotein is the major carrier of lipid hydroperoxides in human blood plasma from fasting donors.
      ,
      • Proudfoot J.M.
      • Barden A.E.
      • Loke W.M.
      • Croft K.D.
      • Puddey I.B.
      • Mori T.A.
      HDL is the major lipoprotein carrier of plasma F2-isoprostanes.
      ). The transfer of lipid hydroperoxides from LDL prevents the initiation of a free radical chain reaction of oxidation (
      • Navab M.
      • Hama S.Y.
      • Cooke C.J.
      • Anantharamaiah G.M.
      • Chaddha M.
      • Jin L.
      • Subbanagounder G.
      • Faull K.F.
      • Reddy S.T.
      • Miller N.E.
      • et al.
      Normal high density lipoprotein inhibits three steps in the formation of mildly oxidized low density lipoprotein: step 1.
      ). Furthermore, some of the advanced products of phospholipid oxidation may serve as ligands for scavenger receptors and promote uptake of modified lipoproteins by macro­phages as well as pro-thrombotic effects mediated by platelet scavenger receptor CD36 (
      • Podrez E.A.
      • Poliakov E.
      • Shen Z.
      • Zhang R.
      • Deng Y.
      • Sun M.
      • Finton P.J.
      • Shan L.
      • Gugiu B.
      • Fox P.L.
      • et al.
      Identification of a novel family of oxidized phospholipids that serve as ligands for the macrophage scavenger receptor CD36.
      ,
      • Valiyaveettil M.
      • Podrez E.A.
      Platelet hyperreactivity, scavenger receptors and atherothrombosis.
      ).
      TABLE 1Summary of the endothelial vasoprotective effects of HDL and its alterations in pathophysiological states
      Endothelial FunctionMechanisms of Effects of HDLKey ComponentsAlterations in Pathophysiological Settings
      Endothelial protection by limiting LDL oxidationHDL prevents oxidation of LDL in vitro (
      • van Hinsbergh V.W.
      • Scheffer M.
      • Havekes L.
      • Kempen H.J.
      Role of endothelial cells and their products in the modification of low-density lipoproteins.
      • Parthasarathy S.
      • Barnett J.
      • Fong L.G.
      High-density lipoprotein inhibits the oxidative modification of low-density lipoprotein.
      )
      ApoA-I, ApoE, ApoJ, PON1, LCAT, and PAF-AHImpaired antioxidant capacity of HDL in patients with CAD (
      • Navab M.
      • Berliner J.A.
      • Subbanagounder G.
      • Hama S.
      • Lusis A.J.
      • Castellani L.W.
      • Reddy S.
      • Shih D.
      • Shi W.
      • Watson A.D.
      • et al.
      HDL and the inflammatory response induced by LDL-derived oxidized phospholipids.
      ,
      • Navab M.
      • Hama S.Y.
      • Hough G.P.
      • Subbanagounder G.
      • Reddy S.T.
      • Fogelman A.M.
      A cell-free assay for detecting HDL that is dysfunctional in preventing the formation of or inactivating oxidized phospholipids.
      ,
      • Patel P.J.
      • Khera A.V.
      • Jafri K.
      • Wilensky R.L.
      • Rader D.J.
      The anti-oxidative capacity of high-density lipoprotein is reduced in acute coronary syndrome but not in stable coronary artery disease.
      ) and ischemic cardiomyopathy (
      • Patel P.J.
      • Khera A.V.
      • Wilensky R.L.
      • Rader D.J.
      Anti-oxidative and cholesterol efflux capacities of high-density lipoprotein are reduced in ischaemic cardiomyopathy.
      )
      HDL is a major carrier of lipid peroxidation products (
      • Bowry V.W.
      • Stanley K.K.
      • Stocker R.
      High density lipoprotein is the major carrier of lipid hydroperoxides in human blood plasma from fasting donors.
      ,
      • Proudfoot J.M.
      • Barden A.E.
      • Loke W.M.
      • Croft K.D.
      • Puddey I.B.
      • Mori T.A.
      HDL is the major lipoprotein carrier of plasma F2-isoprostanes.
      )
      Loss of antioxidant capacity of HDL after surgery in humans and rabbits (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ) and after acute influenza in mice (
      • Van Lenten B.J.
      • Wagner A.C.
      • Nayak D.P.
      • Hama S.
      • Navab M.
      • Fogelman A.M.
      High-density lipoprotein loses its anti-inflammatory properties during acute influenza a infection.
      )
      Stimulation of endothelial NO productionDirect stimulation of eNOS via SR-BI and S1P3 (
      • Yuhanna I.S.
      • Zhu Y.
      • Cox B.E.
      • Hahner L.D.
      • Osborne-Lawrence S.
      • Lu P.
      • Marcel Y.L.
      • Anderson R.G.
      • Mendelsohn M.E.
      • Hobbs H.H.
      • et al.
      High-density lipoprotein binding to scavenger receptor-BI activates endothelial nitric oxide synthase.
      ,
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ,
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Kuvin J.T.
      • Ramet M.E.
      • Patel A.R.
      • Pandian N.G.
      • Mendelsohn M.E.
      • Karas R.H.
      A novel mechanism for the beneficial vascular effects of high-density lipoprotein cholesterol: enhanced vasorelaxation and increased endothelial nitric oxide synthase expression.
      • Rämet M.E.
      • Rämet M.
      • Lu Q.
      • Nickerson M.
      • Savolainen M.J.
      • Malzone A.
      • Karas R.H.
      High-density lipoprotein increases the abundance of eNOS protein in human vascular endothelial cells by increasing its half-life.
      )
      ApoA-I, S1P, and PON1Impaired capacity of HDL to simulate endothelial NO production in patients with CAD (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ), diabetes (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ), CKD (
      • Speer T.
      • Rohrer L.
      • Blyszczuk P.
      • Shroff R.
      • Kuschnerus K.
      • Krankel N.
      • Kania G.
      • Zewinger S.
      • Akhmedov A.
      • Shi Y.
      • et al.
      Abnormal high-density lipoprotein induces endothelial dysfunction via activation of Toll-like receptor-2.
      ), and antiphospholipid syndrome (
      • Charakida M.
      • Besler C.
      • Batuca J.R.
      • Sangle S.
      • Marques S.
      • Sousa M.
      • Wang G.
      • Tousoulis D.
      • Delgado Alves J.
      • Loukogeorgakis S.P.
      • et al.
      Vascular abnormalities, paraoxonase activity, and dysfunctional HDL in primary antiphospholipid syndrome.
      )
      Reduce inhibitory interaction of eNOS with caveolin-1 via ABCG1-mediated oxysterol efflux (
      • Terasaka N.
      • Yu S.
      • Yvan-Charvet L.
      • Wang N.
      • Mzhavia N.
      • Langlois R.
      • Pagler T.
      • Li R.
      • Welch C.L.
      • Goldberg I.J.
      • et al.
      ABCG1 and HDL protect against endothelial dysfunction in mice fed a high-cholesterol diet.
      ,
      • Terasaka N.
      • Westerterp M.
      • Koetsveld J.
      • Fernandez-Hernando C.
      • Yvan-Charvet L.
      • Wang N.
      • Sessa W.C.
      • Tall A.R.
      ATP-binding cassette transporter G1 and high-density lipoprotein promote endothelial NO synthesis through a decrease in the interaction of caveolin-1 and endothelial NO synthase.
      )
      Prevention of oxLDL-mediated eNOS displacement from caveolae (
      • Uittenbogaard A.
      • Shaul P.W.
      • Yuhanna I.S.
      • Blair A.
      • Smart E.J.
      High density lipoprotein prevents oxidized low density lipoprotein-induced inhibition of endothelial nitric-oxide synthase localization and activation in caveolae.
      )
      Impact on endothelial inflammatory activationInhibition of endothelial monocyte adhesion in vitro (
      • Navab M.
      • Imes S.S.
      • Hama S.Y.
      • Hough G.P.
      • Ross L.A.
      • Bork R.W.
      • Valente A.J.
      • Berliner J.A.
      • Drinkwater D.C.
      • Laks H.
      • et al.
      Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.
      ,
      • Mackness B.
      • Hine D.
      • Liu Y.
      • Mastorikou M.
      • Mackness M.
      Paraoxonase-1 inhibits oxidised LDL-induced MCP-1 production by endothelial cells.
      • Park S.H.
      • Park J.H.
      • Kang J.S.
      • Kang Y.H.
      Involvement of transcription factors in plasma HDL protection against TNF-alpha-induced vascular cell adhesion molecule-1 expression.
      )
      ApoA-I and phosphatidylcholineImpaired anti-inflammatory capacity of HDL in patients with CAD (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ), diabetes (
      • Morgantini C.
      • Natali A.
      • Boldrini B.
      • Imaizumi S.
      • Navab M.
      • Fogelman A.M.
      • Ferrannini E.
      • Reddy S.T.
      Anti-inflammatory and antioxidant properties of HDLs are impaired in type 2 diabetes.
      ), and ESRD (
      • Tölle M.
      • Huang T.
      • Schuchardt M.
      • Jankowski V.
      • Prüfer N.
      • Jankowski J.
      • Tietge U.J.
      • Zidek W.
      • van der Giet M.
      High-density lipoprotein loses its anti-inflammatory capacity by accumulation of pro-inflammatory-serum amyloid A.
      )
      Inhibition of endothelial VCAM-1 and ICAM-1 expression in vitro and in vivo (
      • Dimayuga P.
      • Zhu J.
      • Oguchi S.
      • Chyu K.Y.
      • Xu X.O.
      • Yano J.
      • Shah P.K.
      • Nilsson J.
      • Cercek B.
      Reconstituted HDL containing human apolipoprotein A-1 reduces VCAM-1 expression and neointima formation following periadventitial cuff-induced carotid injury in apoE null mice.
      • Patel S.
      • Drew B.G.
      • Nakhla S.
      • Duffy S.J.
      • Murphy A.J.
      • Barter P.J.
      • Rye K.A.
      • Chin-Dusting J.
      • Hoang A.
      • Sviridov D.
      • et al.
      Reconstituted high-density lipoprotein increases plasma high-density lipoprotein anti-inflammatory properties and cholesterol efflux capacity in patients with type 2 diabetes.
      )
      Displacement of apoA-I by SAA in rabbits and mice (
      • Khovidhunkit W.
      • Kim M.S.
      • Memon R.A.
      • Shigenaga J.K.
      • Moser A.H.
      • Feingold K.R.
      • Grunfeld C.
      Effects of infection and inflammation on lipid and lipoprotein metabolism: mechanisms and consequences to the host.
      • Cabana V.G.
      • Reardon C.A.
      • Wei B.
      • Lukens J.R.
      • Getz G.S.
      SAA-only HDL formed during the acute phase response in apoA-I+/+ and apoA-I−/− mice.
      )
      Impaired anti-inflammatory capacity of apoA-I after MPO-mediated oxidation in vitro (
      • Undurti A.
      • Huang Y.
      • Lupica J.A.
      • Smith J.D.
      • DiDonato J.A.
      • Hazen S.L.
      Modification of high density lipoprotein by myeloperoxidase generates a pro-inflammatory particle.
      ) and of HDL after glycation in vitro (
      • Nobécourt E.
      • Tabet F.
      • Lambert G.
      • Puranik R.
      • Bao S.
      • Yan L.
      • Davies M.J.
      • Brown B.E.
      • Jenkins A.J.
      • Dusting G.J.
      • et al.
      Nonenzymatic glycation impairs the antiinflammatory properties of apolipoprotein A-I.
      ,
      • Hedrick C.C.
      • Thorpe S.R.
      • Fu M.X.
      • Harper C.M.
      • Yoo J.
      • Kim S.M.
      • Wong H.
      • Peters A.L.
      Glycation impairs high-density lipoprotein function.
      )
      Impact of endothelial apoptotic pathwaysInhibition of endothelial apoptosis mediated by TNF-α, oxLDL, and growth factor deprivation in vitro (
      • Nofer J.R.
      • Levkau B.
      • Wolinska I.
      • Junker R.
      • Fobker M.
      • von Eckardstein A.
      • Seedorf U.
      • Assmann G.
      Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids.
      • Suc I.
      • Escargueil-Blanc I.
      • Troly M.
      • Salvayre R.
      • Negre-Salvayre A.
      HDL and ApoA prevent cell death of endothelial cells induced by oxidized LDL.
      )
      ApoA-I, lysosphingolipids, and clusterinImpaired anti-apoptotic capacity of HDL in patients with CAD with reduced clusterin and increased apoC-III content (
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      )
      Reduced anti-apoptotic capacity of HDL after MPO-catalyzed oxidation in vitro (
      • Undurti A.
      • Huang Y.
      • Lupica J.A.
      • Smith J.D.
      • DiDonato J.A.
      • Hazen S.L.
      Modification of high density lipoprotein by myeloperoxidase generates a pro-inflammatory particle.
      )
      Impact on endothelial repair after vascular injuryStimulation of endothelial cell proliferation, migration and recruitment of EOC in vitro and in vivo (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Seetharam D.
      • Mineo C.
      • Gormley A.K.
      • Gibson L.L.
      • Vongpatanasin W.
      • Chambliss K.L.
      • Hahner L.D.
      • Cummings M.L.
      • Kitchens R.L.
      • Marcel Y.L.
      • et al.
      High-density lipoprotein promotes endothelial cell migration and reendothelialization via scavenger receptor-B type I.
      ,
      • Zhu W.
      • Saddar S.
      • Seetharam D.
      • Chambliss K.L.
      • Longoria C.
      • Silver D.L.
      • Yuhanna I.S.
      • Shaul P.W.
      • Mineo C.
      The scavenger receptor class B type I adaptor protein PDZK1 maintains endothelial monolayer integrity.
      )
      ApoA-I and S1PImpaired HDL capacity to stimulate endothelial repair after vascular injury in patients with type 2 diabetes (
      • Tepper O.M.
      • Galiano R.D.
      • Capla J.M.
      • Kalka C.
      • Gagne P.J.
      • Jacobowitz G.R.
      • Levine J.P.
      • Gurtner G.C.
      Human endothelial progenitor cells from type II diabetics exhibit impaired proliferation, adhesion, and incorporation into vascular structures.
      ,
      • Pan B.
      • Ma Y.
      • Ren H.
      • He Y.
      • Wang Y.
      • Lv X.
      • Liu D.
      • Ji L.
      • Yu B.
      • Chen Y.E.
      • et al.
      Diabetic HDL is dysfunctional in stimulating endothelial cell migration and proliferation due to down regulation of SR-BI expression.
      ) and CAD (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      )
      Prevention of apoptosis of circulating EOCs (
      • Noor R.
      • Shuaib U.
      • Wang C.X.
      • Todd K.
      • Ghani U.
      • Schwindt B.
      • Shuaib A.
      High-density lipoprotein cholesterol regulates endothelial progenitor cells by increasing eNOS and preventing apoptosis.
      )
      Impact on endothelial thrombotic activationIncreased prostacyclin synthesis in vitro (
      • Fleisher L.N.
      • Tall A.R.
      • Witte L.D.
      • Miller R.W.
      • Cannon P.J.
      Stimulation of arterial endothelial cell prostacyclin synthesis by high density lipoproteins.
      ,
      • Spector A.A.
      • Scanu A.M.
      • Kaduce T.L.
      • Figard P.H.
      • Fless G.M.
      • Czervionke R.L.
      Effect of human plasma lipoproteins on prostacyclin production by cultured endothelial cells.
      ) and in vivo (
      • Van Sickle W.A.
      • Wilcox H.G.
      • Malik K.U.
      • Nasjletti A.
      High density lipoprotein-induced cardiac prostacyclin synthesis in vitro: relationship to cardiac arachidonate mobilization.
      ,
      • Calabresi L.
      • Rossoni G.
      • Gomaraschi M.
      • Sisto F.
      • Berti F.
      • Franceschini G.
      High-density lipoproteins protect isolated rat hearts from ischemia-reperfusion injury by reducing cardiac tumor necrosis factor-alpha content and enhancing prostaglandin release.
      )
      ApoA-I and phospholipidsOxidized HDL strongly inhibits platelet activation and aggregation (
      • Valiyaveettil M.
      • Kar N.
      • Ashraf M.Z.
      • Byzova T.V.
      • Febbraio M.
      • Podrez E.A.
      Oxidized high-density lipoprotein inhibits platelet activation and aggregation via scavenger receptor BI.
      )
      Stimulation of Cox-2 expression (
      • Norata G.D.
      • Callegari E.
      • Inoue H.
      • Catapano A.L.
      HDL3 induces cyclooxygenase-2 expression and prostacyclin release in human endothelial cells via a p38 MAPK/CRE-dependent pathway: effects on COX-2/PGI-synthase coupling.
      • Martínez-González J.
      • Escudero I.
      • Badimon L.
      Simvastatin potenciates PGI(2) release induced by HDL in human VSMC: effect on Cox-2 up-regulation and MAPK signalling pathways activated by HDL.
      ) and inhibition of E-selectin expression (
      • Barter P.J.
      • Nicholls S.
      • Rye K.A.
      • Anantharamaiah G.M.
      • Navab M.
      • Fogelman A.M.
      Antiinflammatory properties of HDL.
      ,
      • Cockerill G.W.
      • Saklatvala J.
      • Ridley S.H.
      • Yarwood H.
      • Miller N.E.
      • Oral B.
      • Nithyanathan S.
      • Taylor G.
      • Haskard D.O.
      High-density lipoproteins differentially modulate cytokine-induced expression of E-selectin and cyclooxygenase-2.
      )
      HDL isolated from patients with type 2 diabetes upregulates Cox-2 expression and prostacyclin release (
      • Tong X.
      • Peng H.
      • Liu D.
      • Ji L.
      • Niu C.
      • Ren J.
      • Pan B.
      • Hu J.
      • Zheng L.
      • Huang Y.
      High-density lipoprotein of patients with type 2 diabetes mellitus upregulates cyclooxgenase-2 expression and prostacyclin I-2 release in endothelial cells: relationship with HDL-associated sphingosine-1-phosphate.
      )
      Downregulation of endothelial cell tissue factor expression in vitro (
      • Viswambharan H.
      • Ming X.F.
      • Zhu S.
      • Hubsch A.
      • Lerch P.
      • Vergeres G.
      • Rusconi S.
      • Yang Z.
      Reconstituted high-density lipoprotein inhibits thrombin-induced endothelial tissue factor expression through inhibition of RhoA and stimulation of phosphatidylinositol 3-kinase but not Akt/endothelial nitric oxide synthase.
      )
      A study by Navab et al. (
      • Navab M.
      • Hama S.Y.
      • Cooke C.J.
      • Anantharamaiah G.M.
      • Chaddha M.
      • Jin L.
      • Subbanagounder G.
      • Faull K.F.
      • Reddy S.T.
      • Miller N.E.
      • et al.
      Normal high density lipoprotein inhibits three steps in the formation of mildly oxidized low density lipoprotein: step 1.
      ) demonstrated that apoA-I binds to and removes lipid hydroperoxides of LDL in vitro and in vivo. Treatment of human artery wall cells with apoA-I, but not apoA-II, or treatment with an apoA-I peptide mimetic, or with normal HDL or paraoxonase, also rendered the cells unable to oxidize LDL (
      • Navab M.
      • Hama S.Y.
      • Anantharamaiah G.M.
      • Hassan K.
      • Hough G.P.
      • Watson A.D.
      • Reddy S.T.
      • Sevanian A.
      • Fonarow G.C.
      • Fogelman A.M.
      Normal high density lipoprotein inhibits three steps in the formation of mildly oxidized low density lipoprotein: steps 2 and 3.
      ).
      Human HDL can also directly reduce cholesteryl ester hydroperoxides and phosphatidylcholine hydroperoxides via Met residues 112 and 148 of apoA-I (
      • Garner B.
      • Waldeck A.R.
      • Witting P.K.
      • Rye K.A.
      • Stocker R.
      Oxidation of high density lipoproteins. II. Evidence for direct reduction of lipid hydroperoxides by methionine residues of apolipoproteins AI and AII.
      ). Recombinant HDL containing only apoA-I and 1-palmitoyl-2-oleoyl-pho­sphatidylcholine (POPC) was as effective as native HDL in preventing LDL oxidation, supporting a key anti-oxidant role for apoA-I (
      • Zerrad-Saadi A.
      • Therond P.
      • Chantepie S.
      • Couturier M.
      • Rye K.A.
      • Chapman M.J.
      • Kontush A.
      HDL3-mediated inactivation of LDL-associated phospholipid hydroperoxides is determined by the redox status of apolipoprotein A-I and HDL particle surface lipid rigidity: relevance to inflammation and atherogenesis.
      ). In vivo studies have demonstrated that apoA-I can act as an anti-oxidative, anti-inflammatory, and anti-atherosclerotic agent (
      • Pászty C.
      • Maeda N.
      • Verstuyft J.
      • Rubin E.M.
      Apolipoprotein AI transgene corrects apolipoprotein E deficiency-induced atherosclerosis in mice.
      ,
      • Nicholls S.J.
      • Dusting G.J.
      • Cutri B.
      • Bao S.
      • Drummond G.R.
      • Rye K.A.
      • Barter P.J.
      Reconstituted high-density lipoproteins inhibit the acute pro-oxidant and proinflammatory vascular changes induced by a periarterial collar in normocholesterolemic rabbits.
      ,
      • Nicholls S.J.
      • Cutri B.
      • Worthley S.G.
      • Kee P.
      • Rye K.A.
      • Bao S.
      • Barter P.J.
      Impact of short-term administration of high-density lipoproteins and atorvastatin on atherosclerosis in rabbits.
      ). Recent clinical studies have suggested that although very high HDL cholesterol and large-size HDL particle levels may be associated with an increased cardiovascular risk; a high concentration of apoA-I was an independent negative predictor of cardiovascular risk (
      • van der Steeg W.A.
      • Holme I.
      • Boekholdt S.M.
      • Larsen M.L.
      • Lindahl C.
      • Stroes E.S.
      • Tikkanen M.J.
      • Wareham N.J.
      • Faergeman O.
      • Olsson A.G.
      • et al.
      High-density lipoprotein cholesterol, high-density lipoprotein particle size, and apolipoprotein A-I: significance for cardiovascular risk: the IDEAL and EPIC-Norfolk studies.
      ).
      Interestingly, several other HDL-associated apolipoproteins have also been shown to exert anti-oxidant effects. ApoA-II-enriched HDL from mice transgenic for human apoA-II protected VLDL from oxidation more efficiently than control HDL (
      • Boisfer E.
      • Stengel D.
      • Pastier D.
      • Laplaud P.M.
      • Dousset N.
      • Ninio E.
      • Kalopissis A.D.
      Antioxidant properties of HDL in transgenic mice overexpressing human apolipoprotein A-II.
      ). However, in other studies, over­expression of human apoA-II in dyslipidemic mice accelerated atherosclerosis and reduced anti-oxidative activity of HDL (
      • Ribas V.
      • Sanchez-Quesada J.L.
      • Anton R.
      • Camacho M.
      • Julve J.
      • Escola-Gil J.C.
      • Vila L.
      • Ordonez-Llanos J.
      • Blanco-Vaca F.
      Human apolipoprotein A-II enrichment displaces paraoxonase from HDL and impairs its antioxidant properties: a new mechanism linking HDL protein composition and antiatherogenic potential.
      ,
      • Rotllan N.
      • Ribas V.
      • Calpe-Berdiel L.
      • Martin-Campos J.M.
      • Blanco-Vaca F.
      • Escola-Gil J.C.
      Overexpression of human apolipoprotein A-II in transgenic mice does not impair macrophage-specific reverse cholesterol transport in vivo.
      ). The authors postulated that the pro-atherogenic actions of apoA-II may be related to the displacement of apoA-I and paraoxonase-1 (PON1) by apoA-II from HDL particles (
      • Ribas V.
      • Sanchez-Quesada J.L.
      • Anton R.
      • Camacho M.
      • Julve J.
      • Escola-Gil J.C.
      • Vila L.
      • Ordonez-Llanos J.
      • Blanco-Vaca F.
      Human apolipoprotein A-II enrichment displaces paraoxonase from HDL and impairs its antioxidant properties: a new mechanism linking HDL protein composition and antiatherogenic potential.
      ). Of note, in a nested case-control study of the European Prospective Investigation into Cancer and Nutrition-Norfolk (EPIC-Norfolk) cohort, apoA-II was found to be associated with a decreased risk of future CAD in apparently healthy subjects (
      • Birjmohun R.S.
      • Dallinga-Thie G.M.
      • Kuivenhoven J.A.
      • Stroes E.S.
      • Otvos J.D.
      • Wareham N.J.
      • Luben R.
      • Kastelein J.J.
      • Khaw K.T.
      • Boekholdt S.M.
      Apolipoprotein A-II is inversely associated with risk of future coronary artery disease.
      ).
      ApoE has been shown to have allele-specific anti-oxidant activity (
      • Miyata M.
      • Smith J.D.
      Apolipoprotein E allele-specific antioxidant activity and effects on cytotoxicity by oxidative insults and beta-amyloid peptides.
      ). ApoE2 can stimulate endothelial NO release and has anti-inflammatory activities (
      • Sacre S.M.
      • Stannard A.K.
      • Owen J.S.
      Apolipoprotein E (apoE) isoforms differentially induce nitric oxide production in endothelial cells.
      ). In contrast, apoE4 has been described as pro-inflammatory (
      • Ophir G.
      • Amariglio N.
      • Jacob-Hirsch J.
      • Elkon R.
      • Rechavi G.
      • Michaelson D.M.
      Apolipoprotein E4 enhances brain inflammation by modulation of the NF-kappaB signaling cascade.
      ). It has also been reported that HDL-associated apoJ can inhibit LDL oxidation by artery wall cells (
      • Navab M.
      • Hama-Levy S.
      • Van Lenten B.J.
      • Fonarow G.C.
      • Cardinez C.J.
      • Castellani L.W.
      • Brennan M.L.
      • Lusis A.J.
      • Fogelman A.M.
      • La Du B.N.
      Mildly oxidized LDL induces an increased apolipoprotein J/paraoxonase ratio.
      ). In addition, apoA-IV has been demonstrated to exert anti-oxidant, anti-inflammatory, and anti-atherosclerotic actions in vivo (
      • Ostos M.A.
      • Conconi M.
      • Vergnes L.
      • Baroukh N.
      • Ribalta J.
      • Girona J.
      • Caillaud J.M.
      • Ochoa A.
      • Zakin M.M.
      Antioxidative and antiatherosclerotic effects of human apolipoprotein A-IV in apolipoprotein E-deficient mice.
      ,
      • Recalde D.
      • Ostos M.A.
      • Badell E.
      • Garcia-Otin A.L.
      • Pidoux J.
      • Castro G.
      • Zakin M.M.
      • Scott-Algara D.
      Human apolipoprotein A-IV reduces secretion of proinflammatory cytokines and atherosclerotic effects of a chronic infection mimicked by lipopolysaccharide.
      ,
      • Vowinkel T.
      • Mori M.
      • Krieglstein C.F.
      • Russell J.
      • Saijo F.
      • Bharwani S.
      • Turnage R.H.
      • Davidson W.S.
      • Tso P.
      • Granger D.N.
      • et al.
      Apolipoprotein A-IV inhibits experimental colitis.
      ).
      Notably, HDL also carries anti-oxidant enzymes that may be involved in prevention of lipid oxidation or degradation of lipid hydroperoxides such as PON1, LCAT, and platelet-activating factor acetylhydrolase (PAF-AH). In particular, PON1 has been suggested to be an important regulator of the potential anti-atherogenic capacity of HDL (
      • Shih D.M.
      • Gu L.
      • Xia Y.R.
      • Navab M.
      • Li W.F.
      • Hama S.
      • Castellani L.W.
      • Furlong C.E.
      • Costa L.G.
      • Fogelman A.M.
      • et al.
      Mice lacking serum paraoxonase are susceptible to organophosphate toxicity and atherosclerosis.
      ,
      • Tward A.
      • Xia Y.R.
      • Wang X.P.
      • Shi Y.S.
      • Park C.
      • Castellani L.W.
      • Lusis A.J.
      • Shih D.M.
      Decreased atherosclerotic lesion formation in human serum paraoxonase transgenic mice.
      ). Various studies have suggested that the direct anti-oxidant effect of HDL on LDL oxidation, measured as a reduction in lipid peroxides, is to a significant extent mediated by PON1 (
      • Mackness M.I.
      • Arrol S.
      • Durrington P.N.
      Paraoxonase prevents accumulation of lipoperoxides in low-density lipoprotein.
      ,
      • Watson A.D.
      • Berliner J.A.
      • Hama S.Y.
      • La Du B.N.
      • Faull K.F.
      • Fogelman A.M.
      • Navab M.
      Protective effect of high density lipoprotein associated paraoxonase. Inhibition of the biological activity of minimally oxidized low density lipoprotein.
      ,
      • Shih D.M.
      • Xia Y.R.
      • Wang X.P.
      • Miller E.
      • Castellani L.W.
      • Subbanagounder G.
      • Cheroutre H.
      • Faull K.F.
      • Berliner J.A.
      • Witztum J.L.
      • et al.
      Combined serum paraoxonase knockout/apolipoprotein E knockout mice exhibit increased lipoprotein oxidation and atherosclerosis.
      ). In human studies, higher PON1 activity is associated with a lower incidence of major cardiovascular events and conversely reduced activity of PON1 is associated with pathological conditions such as chronic renal failure, rheumatoid arthritis, and Alzheimer's disease, as reviewed elsewhere (
      • Soran H.
      • Younis N.N.
      • Charlton-Menys V.
      • Durrington P.
      Variation in paraoxonase-1 activity and atherosclerosis.
      ).
      Biochemical studies have suggested the anti-oxidant role of LCAT through its capacity to hydrolyze oxidized acyl chains from phosphatidylcholine-based oxidized phospholipids and oxidized free fatty acids (
      • Subramanian V.S.
      • Goyal J.
      • Miwa M.
      • Sugatami J.
      • Akiyama M.
      • Liu M.
      • Subbaiah P.V.
      Role of lecithin-cholesterol acyltransferase in the metabolism of oxidized phospholipids in plasma: studies with platelet-activating factor-acetyl hydrolase-deficient plasma.
      ,
      • Goyal J.
      • Wang K.
      • Liu M.
      • Subbaiah P.V.
      Novel function of lecithin-cholesterol acyltransferase. Hydrolysis of oxidized polar phospholipids generated during lipoprotein oxidation.
      ). In vivo study in mice deficient for LDL receptor and leptin showed that LCAT overexpression decreased autoantibodies to oxLDL (
      • Mertens A.
      • Verhamme P.
      • Bielicki J.K.
      • Phillips M.C.
      • Quarck R.
      • Verreth W.
      • Stengel D.
      • Ninio E.
      • Navab M.
      • Mackness B.
      • et al.
      Increased low-density lipoprotein oxidation and impaired high-density lipoprotein antioxidant defense are associated with increased macrophage homing and atherosclerosis in dyslipidemic obese mice: LCAT gene transfer decreases atherosclerosis.
      ). PAF-AH is another HDL-associated enzyme that can hydrolyze oxidized phospholipids (
      • Marathe G.K.
      • Zimmerman G.A.
      • McIntyre T.M.
      Platelet-activating factor acetylhydrolase, and not paraoxonase-1, is the oxidized phospholipid hydrolase of high density lipoprotein particles.
      ,
      • Noto H.
      • Hara M.
      • Karasawa K.
      • Iso O.N.
      • Satoh H.
      • Togo M.
      • Hashimoto Y.
      • Yamada Y.
      • Kosaka T.
      • Kawamura M.
      • et al.
      Human plasma platelet-activating factor acetylhydrolase binds to all the murine lipoproteins, conferring protection against oxidative stress.
      ). In arteries of non­hyperlipidemic rabbits, local expression of PAF-AH reduced the accumulation of oxidatively modified LDL without changing plasma levels of PAF-AH and reduced the expression of endothelial cell adhesion molecules (
      • Arakawa H.
      • Qian J.Y.
      • Baatar D.
      • Karasawa K.
      • Asada Y.
      • Sasaguri Y.
      • Miller E.R.
      • Witztum J.L.
      • Ueno H.
      Local expression of platelet-activating factor-acetylhydrolase reduces accumulation of oxidized lipoproteins and inhibits inflammation, shear stress-induced thrombosis, and neointima formation in balloon-injured carotid arteries in nonhyperlipidemic rabbits.
      ). In human studies, PAF-AH deficiency through a missense mutation of the gene is an independent risk factor for CAD in Japanese men (
      • McIntyre T.M.
      • Prescott S.M.
      • Stafforini D.M.
      The emerging roles of PAF acetylhydrolase.
      ). Circulating levels of PAF-AH is also shown to be an independent marker of the risk of CAD (
      • Garza C.A.
      • Montori V.M.
      • McConnell J.P.
      • Somers V.K.
      • Kullo I.J.
      • Lopez-Jimenez F.
      Association between lipoprotein-associated phospholipase A2 and cardiovascular disease: a systematic review.
      ). However, in a recent study by Holleboom et al. (
      • Holleboom A.G.
      • Daniil G.
      • Fu X.
      • Zhang R.
      • Hovingh G.K.
      • Schimmel A.W.
      • Kastelein J.J.
      • Stroes E.S.
      • Witztum J.L.
      • Hutten B.A.
      • et al.
      Lipid oxidation in carriers of lecithin:cholesterol acyltransferase gene mutations.
      ), reduced LCAT activity and PAF-AH activity due to LCAT mutations was not associated with increased plasma lipid peroxidation.
      HDL has also been shown to promote efflux of 7-ketocholesterol (
      • Terasaka N.
      • Yu S.
      • Yvan-Charvet L.
      • Wang N.
      • Mzhavia N.
      • Langlois R.
      • Pagler T.
      • Li R.
      • Welch C.L.
      • Goldberg I.J.
      • et al.
      ABCG1 and HDL protect against endothelial dysfunction in mice fed a high-cholesterol diet.
      ,
      • Terasaka N.
      • Wang N.
      • Yvan-Charvet L.
      • Tall A.R.
      High-density lipoprotein protects macrophages from oxidized low-density lipoprotein-induced apoptosis by promoting efflux of 7-ketocholesterol via ABCG1.
      ) at sites of inflammation and thereby reduces endothelial cell inflammatory activation (
      • Shao B.
      • Heinecke J.W.
      HDL, lipid peroxidation, and atherosclerosis.
      ). Accordingly, Nicholls et al. (
      • Nicholls S.J.
      • Dusting G.J.
      • Cutri B.
      • Bao S.
      • Drummond G.R.
      • Rye K.A.
      • Barter P.J.
      Reconstituted high-density lipoproteins inhibit the acute pro-oxidant and proinflammatory vascular changes induced by a periarterial collar in normocholesterolemic rabbits.
      ) have reported that reconstituted HDL inhibits superoxide production and vascular inflammation induced by a nonocclusive carotid periarterial collar in normocholesterolemic rabbits. In addition, Van Linthout et al. (
      • Van Linthout S.
      • Spillmann F.
      • Lorenz M.
      • Meloni M.
      • Jacobs F.
      • Egorova M.
      • Stangl V.
      • De Geest B.
      • Schultheiss H.P.
      • Tschope C.
      Vascular-protective effects of high-density lipoprotein include the downregulation of the angiotensin II type 1 receptor.
      ) have observed that human apoA-I gene transfer in rats with streptozotocin-induced diabetes mellitus resulted in a 1.9-fold increase in HDL cholesterol levels and inhibition of angiotensin II type 1 receptor-mediated NAD(P)H oxidase activation and generation of reactive oxygen species.

      Alterations of the effects of HDL from patients after surgery, with CAD or diabetes on LDL oxidation

      Early studies by van Lenten et al. (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ) have demonstrated that the anti-inflammatory capacity of HDL is affected by acute phase responses in both humans and rabbits. The authors isolated human HDL from the patients before and immediately after surgery and characterized the effects of HDL on LDL-induced monocyte transmigration and lipid hydroperoxide formation (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ). Before cardiac surgery, HDL completely inhibited the LDL-induced increase in monocyte transmigration and lipid hydroperoxide formation. In marked contrast, “acute phase” HDL obtained from the same patients 2–3 days after surgery amplified the LDL-induced monocyte transmigration and was less effective in inhibiting lipid hydroperoxide formation, i.e., HDL in the same patient had been transformed from an anti-inflammatory toward a pro-inflammatory particle (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ). Interestingly, the changes in HDL functionality in this study were paralleled by an increase in HDL-associated acute phase reactants [i.e., ceruloplasmin and serum amyloid A (SAA)], while the activities of the HDL-associated anti-oxidant enzymes, paraoxonase and platelet-factor activating acetylhydrolase, were reduced in acute phase HDL (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ). Similarly, an acute influenza A infection in wild-type mice progressively impaired the ability of HDL to inhibit LDL oxidation and LDL-induced monocyte chemotactic activity in human artery wall cell cocultures up to 9 days after inoculation (
      • Van Lenten B.J.
      • Wagner A.C.
      • Nayak D.P.
      • Hama S.
      • Navab M.
      • Fogelman A.M.
      High-density lipoprotein loses its anti-inflammatory properties during acute influenza a infection.
      ).
      HDL from patients with CAD failed to prevent LDL oxidation (
      • Navab M.
      • Hama S.Y.
      • Anantharamaiah G.M.
      • Hassan K.
      • Hough G.P.
      • Watson A.D.
      • Reddy S.T.
      • Sevanian A.
      • Fonarow G.C.
      • Fogelman A.M.
      Normal high density lipoprotein inhibits three steps in the formation of mildly oxidized low density lipoprotein: steps 2 and 3.
      ), and HDL from mice genetically predisposed to diet-induced atherosclerosis became pro-inflammatory when the mice were fed an atherogenic diet (
      • Navab M.
      • Berliner J.A.
      • Subbanagounder G.
      • Hama S.
      • Lusis A.J.
      • Castellani L.W.
      • Reddy S.
      • Shih D.
      • Shi W.
      • Watson A.D.
      • et al.
      HDL and the inflammatory response induced by LDL-derived oxidized phospholipids.
      ). A subsequent study by Ansell et al. (
      • Ansell B.J.
      • Navab M.
      • Hama S.
      • Kamranpour N.
      • Fonarow G.
      • Hough G.
      • Rahmani S.
      • Mottahedeh R.
      • Dave R.
      • Reddy S.T.
      • et al.
      Inflammatory/antiinflammatory properties of high-density lipoprotein distinguish patients from control subjects better than high-density lipoprotein cholesterol levels and are favorably affected by simvastatin treatment.
      ) suggested that the capacity of HDL to alter LDL-induced monocyte chemotactic activity in patients with CAD was somewhat improved after 6 weeks of simvastatin therapy. However, HDL from patients with CAD on statin therapy remained pro-inflammatory in contrast to HDL from age- and sex-matched healthy subjects.
      Navab et al. (
      • Navab M.
      • Hama S.Y.
      • Hough G.P.
      • Subbanagounder G.
      • Reddy S.T.
      • Fogelman A.M.
      A cell-free assay for detecting HDL that is dysfunctional in preventing the formation of or inactivating oxidized phospholipids.
      ) developed a fluorescent cell-free assay to detect the capacity of HDL to inhibit the oxidation of LDL, or inhibit the oxidation of L-α-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC) by hydroperoxyoctadecadienoic acid, or inactivate oxidized PAPC. Using this assay, HDL isolated from 27 patients with coronary atherosclerosis failed to inhibit the fluorescent signal generated by a control LDL, whereas HDL from 31 matched normal subjects with the same levels of HDL cholesterol significantly inhibited the signal (
      • Navab M.
      • Hama S.Y.
      • Hough G.P.
      • Subbanagounder G.
      • Reddy S.T.
      • Fogelman A.M.
      A cell-free assay for detecting HDL that is dysfunctional in preventing the formation of or inactivating oxidized phospholipids.
      ).
      The presence of oxidized lipids in HDL has been proposed to play a role in the altered anti-oxidant properties of HDL (
      • Navab M.
      • Imes S.S.
      • Hama S.Y.
      • Hough G.P.
      • Ross L.A.
      • Bork R.W.
      • Valente A.J.
      • Berliner J.A.
      • Drinkwater D.C.
      • Laks H.
      • et al.
      Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.
      ). Administration of apoA-1 mimetic peptides, L-4F, to apoE-deficient mice has been shown to reduce plasma levels of oxidized fatty acids [15-hydroxyeicosatetraenoic acid (HETE), 5-HETE, 13-hydroxyocta-decadienoic acid (HODE), and 9-HODE] and improve the HDL anti-oxidant capacity and the capacity of HDL to inhibit LDL-induced monocyte chemotactic activity in cultured human aortic endothelial cells (
      • Imaizumi S.
      • Grijalva V.
      • Navab M.
      • Van Lenten B.J.
      • Wagner A.C.
      • Anantharamiah G.M.
      • Fogelman A.M.
      • Reddy S.T.
      L-4F differentially alters plasma levels of oxidized fatty acids resulting in more anti-inflammatory HDL in mice.
      ). Moreover, in a recent study by Morgantini et al. (
      • Morgantini C.
      • Natali A.
      • Boldrini B.
      • Imaizumi S.
      • Navab M.
      • Fogelman A.M.
      • Ferrannini E.
      • Reddy S.T.
      Anti-inflammatory and antioxidant properties of HDLs are impaired in type 2 diabetes.
      ), HDL from patients with type 2 diabetes had impaired anti-oxidant properties and increased oxidized fatty acid content. The authors postulated that elevated content of oxidized fatty acids (5-HETE, 9-HETE, 12-HETE, 15-HETE, 9-HODE, and 13-HODE) in HDL isolated from the type 2 diabetic patients may account for the impaired anti-oxidant properties of the lipoprotein (
      • Morgantini C.
      • Natali A.
      • Boldrini B.
      • Imaizumi S.
      • Navab M.
      • Fogelman A.M.
      • Ferrannini E.
      • Reddy S.T.
      Anti-inflammatory and antioxidant properties of HDLs are impaired in type 2 diabetes.
      ). In another study, the ability of HDL to inhibit LDL oxidation was found to be reduced in ACS but not in stable CAD patients (
      • Patel P.J.
      • Khera A.V.
      • Jafri K.
      • Wilensky R.L.
      • Rader D.J.
      The anti-oxidative capacity of high-density lipoprotein is reduced in acute coronary syndrome but not in stable coronary artery disease.
      ). Very recently, the same group also reported that the anti-oxidative and cholesterol efflux capacities of HDL are reduced in ischemic cardiomyopathy (
      • Patel P.J.
      • Khera A.V.
      • Wilensky R.L.
      • Rader D.J.
      Anti-oxidative and cholesterol efflux capacities of high-density lipoprotein are reduced in ischaemic cardiomyopathy.
      ).

      EFFECTS OF HDL ON eNOS-DEPENDENT NO PRODUCTION

      Experimental studies and altered effects of HDL from patients with cardiovascular disease

      Endothelial NO plays a crucial role in the regulation of vascular tone and structure. eNOS-derived NO has been shown to exert a variety of atheroprotective effects in the vasculature, such as anti-inflammatory and anti-thrombotic effects (
      • Landmesser U.
      • Hornig B.
      • Drexler H.
      Endothelial function: a critical determinant in atherosclerosis?.
      ). Reduced endothelial NO bioavailability has therefore been suggested to promote initiation and progression of atherosclerosis (
      • Landmesser U.
      • Hornig B.
      • Drexler H.
      Endothelial function: a critical determinant in atherosclerosis?.
      ).
      Accumulating evidence suggests that HDL can directly stimulate eNOS-mediated NO production via endothelial scavenger receptor class B type I (SR-BI) (
      • Yuhanna I.S.
      • Zhu Y.
      • Cox B.E.
      • Hahner L.D.
      • Osborne-Lawrence S.
      • Lu P.
      • Marcel Y.L.
      • Anderson R.G.
      • Mendelsohn M.E.
      • Hobbs H.H.
      • et al.
      High-density lipoprotein binding to scavenger receptor-BI activates endothelial nitric oxide synthase.
      ). Several experimental studies have consistently demonstrated the capacity of HDL to modulate eNOS expression and to stimulate endothelial NO production in vitro and in vivo (
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ,
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Kuvin J.T.
      • Ramet M.E.
      • Patel A.R.
      • Pandian N.G.
      • Mendelsohn M.E.
      • Karas R.H.
      A novel mechanism for the beneficial vascular effects of high-density lipoprotein cholesterol: enhanced vasorelaxation and increased endothelial nitric oxide synthase expression.
      ,
      • Mineo C.
      • Yuhanna I.S.
      • Quon M.J.
      • Shaul P.W.
      High density lipoprotein-induced endothelial nitric-oxide synthase activation is mediated by Akt and MAP kinases.
      ,
      • Rämet M.E.
      • Rämet M.
      • Lu Q.
      • Nickerson M.
      • Savolainen M.J.
      • Malzone A.
      • Karas R.H.
      High-density lipoprotein increases the abundance of eNOS protein in human vascular endothelial cells by increasing its half-life.
      ). Moreover, in human studies, administration of reconstituted HDL has been shown to improve endothelial function in subjects with hypercholesterolemia and in subjects with isolated low HDL due to heterozygous loss-of-function mutations in the ABCA-1 gene locus (
      • Bisoendial R.J.
      • Hovingh G.K.
      • Levels J.H.
      • Lerch P.G.
      • Andresen I.
      • Hayden M.R.
      • Kastelein J.J.
      • Stroes E.S.
      Restoration of endothelial function by increasing high-density lipoprotein in subjects with isolated low high-density lipoprotein.
      ,
      • Spieker L.E.
      • Sudano I.
      • Hurlimann D.
      • Lerch P.G.
      • Lang M.G.
      • Binggeli C.
      • Corti R.
      • Ruschitzka F.
      • Luscher T.F.
      • Noll G.
      High-density lipoprotein restores endothelial function in hypercholesterolemic men.
      ). It is worth noting that one can only speculate on how exactly the reconstituted HDL mixes with endogenous circulating HDL.
      Several mechanisms have been proposed to account for the endothelial NO-stimulating capacity of HDL. Early studies have shown that HDL prevents oxLDL-mediated eNOS displacements from caveolae and restores enzyme stimulation (
      • Uittenbogaard A.
      • Shaul P.W.
      • Yuhanna I.S.
      • Blair A.
      • Smart E.J.
      High density lipoprotein prevents oxidized low density lipoprotein-induced inhibition of endothelial nitric-oxide synthase localization and activation in caveolae.
      ). A study by Yuhanna et al. (
      • Yuhanna I.S.
      • Zhu Y.
      • Cox B.E.
      • Hahner L.D.
      • Osborne-Lawrence S.
      • Lu P.
      • Marcel Y.L.
      • Anderson R.G.
      • Mendelsohn M.E.
      • Hobbs H.H.
      • et al.
      High-density lipoprotein binding to scavenger receptor-BI activates endothelial nitric oxide synthase.
      ) suggested that HDL can bind to endothelial SR-BI and thus directly stimulate eNOS-mediated NO production. HDL binding to SR-BI initiates tyrosine kinase Src-mediated activation of phosphoinositide 3-kinase (PI3K), which in turn activates Akt and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway (
      • Mineo C.
      • Yuhanna I.S.
      • Quon M.J.
      • Shaul P.W.
      High density lipoprotein-induced endothelial nitric-oxide synthase activation is mediated by Akt and MAP kinases.
      ). Activation of endothelial Akt by HDL stimulates phosphorylation of eNOS at serine residue 1177 (Fig. 2) (
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ,
      • Mineo C.
      • Yuhanna I.S.
      • Quon M.J.
      • Shaul P.W.
      High density lipoprotein-induced endothelial nitric-oxide synthase activation is mediated by Akt and MAP kinases.
      ), which is known to be an important regulatory mechanism leading to eNOS activation (
      • Dimmeler S.
      • Fleming I.
      • Fisslthaler B.
      • Hermann C.
      • Busse R.
      • Zeiher A.M.
      Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation.
      ).
      Figure thumbnail gr2
      Fig. 2Signaling pathways mediating the effects of HDL on endothelial NO production and endothelial apoptosis. HDL from healthy subjects binds to SR-BI via apoA-I, leading to PDZK1-dependent activation of Src family kinases, PI3K and Akt, which phosphorylate eNOS at serine residue 1177, therefore increasing eNOS activity. PI3K-dependent MAPK activation and binding of HDL-associated lysophospholipids to the S1P3 receptor also activate eNOS. In contrast, HDL from patients with CAD can suppress eNOS activation. Inactivation of PON1 and greater accumulation of MDA in HDL lead to LOX-1-mediated activation of PKCβII and inhibition of eNOS by phosphorylation at threonine 495. HDL-associated clusterin (Clu) promotes endothelial anti-apoptotic signaling via activation of PI3K and Akt leading to increased expression of anti-apoptotic Bcl-xL. Akt activation also phosphorylates Bcl-2-associated death promoter Bad preventing it from binding to Bcl-xL, which is then free to inhibit mitochondria-mediated apoptosis. In CAD, the level of HDL-associated clusterin is reduced, whereas HDL-associated apoC-III content is increased. HDL-associated apoC-III activates MAPK signaling via phosphorylation of p38 leading to increased activation of pro-apoptotic tBid, which promotes cytochrome C release from the mitochondria and downstream caspase-3-mediated apoptosis.
      Another mechanism has also been identified whereby HDL can maintain endothelial cell NO production and availability in mice fed a high-cholesterol diet (
      • Terasaka N.
      • Yu S.
      • Yvan-Charvet L.
      • Wang N.
      • Mzhavia N.
      • Langlois R.
      • Pagler T.
      • Li R.
      • Welch C.L.
      • Goldberg I.J.
      • et al.
      ABCG1 and HDL protect against endothelial dysfunction in mice fed a high-cholesterol diet.
      ). These authors suggested that HDL-induced ABCG1-mediated efflux of oxysterols from endothelial cells plays a role because 7-ketosterol, a dietary oxysterol, accumulated in endothelial cells of ABCG1-deficient mice on a Western diet (
      • Terasaka N.
      • Yu S.
      • Yvan-Charvet L.
      • Wang N.
      • Mzhavia N.
      • Langlois R.
      • Pagler T.
      • Li R.
      • Welch C.L.
      • Goldberg I.J.
      • et al.
      ABCG1 and HDL protect against endothelial dysfunction in mice fed a high-cholesterol diet.
      ). Interestingly, incubation of human aortic endothelial cells with HDL prevented 7-ketosterol-induced production of reactive oxygen species and disruption of the active eNOS dimer. Furthermore, HDL-mediated cholesterol efflux via ABCG1 reduced the inhibitory interaction of eNOS with caveolin-1 and thereby restored eNOS activity in cholesterol-loaded endothelial cells (
      • Terasaka N.
      • Westerterp M.
      • Koetsveld J.
      • Fernandez-Hernando C.
      • Yvan-Charvet L.
      • Wang N.
      • Sessa W.C.
      • Tall A.R.
      ATP-binding cassette transporter G1 and high-density lipoprotein promote endothelial NO synthesis through a decrease in the interaction of caveolin-1 and endothelial NO synthase.
      ). These data suggest that the ability of HDL to preserve endothelial function in the presence of hypercholesterolemia may, at least in part, relate to an increased endothelial efflux of oxysterols.
      Various components of HDL have been suggested to play a role in its endothelial NO-stimulating capacity. In cultured endothelial cells, the potential interaction of apoA-I with eNOS has been reported (
      • Rämet M.E.
      • Rämet M.
      • Lu Q.
      • Nickerson M.
      • Savolainen M.J.
      • Malzone A.
      • Karas R.H.
      High-density lipoprotein increases the abundance of eNOS protein in human vascular endothelial cells by increasing its half-life.
      ). However, despite being the ligand for SR-BI, a major HDL receptor, lipid-free apoA-I failed to activate eNOS, suggesting that other HDL components may be important or are required to support the conformation of apoA-1 to allow it to interact with SR-BI and to stimulate eNOS (
      • de Beer M.C.
      • Durbin D.M.
      • Cai L.
      • Jonas A.
      • de Beer F.C.
      • van der Westhuyzen D.R.
      Apolipoprotein A-I conformation markedly influences HDL interaction with scavenger receptor BI.
      ). In isolated endothelial cell plasma membranes, anti-apoA-I antibody inhibits eNOS activation by HDL, whereas anti-apoA-II anti­body further enhances eNOS stimulation by HDL (
      • Yuhanna I.S.
      • Zhu Y.
      • Cox B.E.
      • Hahner L.D.
      • Osborne-Lawrence S.
      • Lu P.
      • Marcel Y.L.
      • Anderson R.G.
      • Mendelsohn M.E.
      • Hobbs H.H.
      • et al.
      High-density lipoprotein binding to scavenger receptor-BI activates endothelial nitric oxide synthase.
      ). Several studies have suggested that HDL-associated lysophospholipids may play a role in eNOS activation. Of note, HDL-associated sphingosylphosphorylcholine, sphingosine-1-phosphate (S1P), and lysosulfatide may cause eNOS-dependent relaxation of precontracted aortic rings from mice via binding to the lysophospholipid receptor S1P3 expressed on endothelial cells (
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ). The vasodilatory response to HDL, however, was not completely inhibited in S1P3-deficient mice (
      • Nofer J.R.
      • van der Giet M.
      • Tolle M.
      • Wolinska I.
      • von Wnuck Lipinski K.
      • Baba H.A.
      • Tietge U.J.
      • Godecke A.
      • Ishii I.
      • Kleuser B.
      • et al.
      HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.
      ).
      Recently, we observed that the HDL-associated antioxidant enzyme PON1 is an important determinant of the capacity of HDL to stimulate endothelial NO production and to exert NO-dependent endothelial-atheroprotective effects (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ). Inhibition of PON1 in HDL from healthy subjects impaired the capacity of HDL to stimulate endothelial NO production and HDL isolated from PON1-deficient mice failed to stimulate NO production in mouse aortic endothelial cells (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ). Furthermore, inhibition of eNOS-mediated NO production prevented the inhibitory effects of HDL from healthy subjects on nuclear factor κB (NF-κB) activity, vascular cell adhesion molecule (VCAM)-1 expression, and endothelial monocyte adhesion, suggesting that the capacity of HDL to stimulate endothelial NO production is important for these endothelial anti-inflammatory effects of HDL (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ).

      Alterations of the effects of HDL from patients with cardiovascular disease on endothelial NO availability

      We and others have recently shown that direct endothelial effects of HDL from patients with CAD or diabetes are markedly altered when compared with HDL from healthy subjects. In contrast to HDL from healthy subjects, HDL from patients with diabetes or chronic kidney disease failed to stimulate endothelial cell NO production and to promote endothelial repair in a carotid artery injury model in mice (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Speer T.
      • Rohrer L.
      • Blyszczuk P.
      • Shroff R.
      • Kuschnerus K.
      • Krankel N.
      • Kania G.
      • Zewinger S.
      • Akhmedov A.
      • Shi Y.
      • et al.
      Abnormal high-density lipoprotein induces endothelial dysfunction via activation of Toll-like receptor-2.
      ). Moreover, HDL from patients with either stable CAD or an ACS, in contrast to HDL from age- and gender-matched healthy subjects, inhibited rather than stimulated endothelial cell NO production and lost the capacity to limit endothelial inflammatory activation as well as to promote endothelial repair in vivo (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ).
      Notably, we have observed that malondialdehyde (MDA) content is elevated in HDL from patients with coronary disease as compared with HDL from healthy subjects, which may limit endothelial NO production (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ) (Fig. 2). The antagonistic action of MDA was determined to be mediated by lectin-type oxLDL receptor 1 activation of protein kinase C-βII, which inhibits Akt-activating phosphorylation at Ser473 and eNOS-activating phospho­rylation at Ser1177 (Fig. 2). Because MDA formation is decreased by HDL-associated PON1 (
      • Aviram M.
      • Rosenblat M.
      • Bisgaier C.L.
      • Newton R.S.
      • Primo-Parmo S.L.
      • La Du B.N.
      Paraoxonase inhibits high-density lipoprotein oxidation and preserves its functions. A possible peroxidative role for paraoxonase.
      ), PON1 activity was evaluated and was found to be markedly decreased in HDL from patients with coronary disease (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ). Furthermore, PON1 inactivation in HDL from healthy subjects results in greater protein kinase C-βII activation in cultured endothelial cells, decreased activating eNOS-Ser1177 phosphorylation, and increased inactivating eNOS-Thr495 phosphorylation, resulting in attenuated NO production. Furthermore, HDL from PON1-deficient mice failed to stimulate endothelial cell NO production (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ). These observations suggest that alterations of HDL-associated PON1 may have a major impact on endothelial effects of HDL.
      An inverse relationship between PON1 serum activity and cardiovascular events has been reported (
      • Regieli J.J.
      • Jukema J.W.
      • Doevendans P.A.
      • Zwinderman A.H.
      • Kastelein J.J.
      • Grobbee D.E.
      • van der Graaf Y.
      Paraoxonase variants relate to 10-year risk in coronary artery disease: impact of a high-density lipoprotein-bound antioxidant in secondary prevention.
      ,
      • Bhattacharyya T.
      • Nicholls S.J.
      • Topol E.J.
      • Zhang R.
      • Yang X.
      • Schmitt D.
      • Fu X.
      • Shao M.
      • Brennan D.M.
      • Ellis S.G.
      • et al.
      Relationship of paraoxonase 1 (PON1) gene polymorphisms and functional activity with systemic oxidative stress and cardiovascular risk.
      ). A recent analysis of SNPs for PON1 identified in genome-wide association studies did not reveal a significant association between the lead SNPs for PON1 that was associated with mildly reduced paraoxonase activity and the risk of cardiovascular events (
      • Tang W.H.
      • Hartiala J.
      • Fan Y.
      • Wu Y.
      • Stewart A.F.
      • Erdmann J.
      • Kathiresan S.
      • Roberts R.
      • McPherson R.
      • Allayee H.
      • et al.
      Clinical and genetic association of serum paraoxonase and arylesterase activities with cardiovascular risk.
      ). A difficulty with respect to PON1 is that it is not known to what extent the paraoxonase and arylesterase activities of the enzyme represent biologically relevant functions. We and others have observed important posttranslational modifications of the enzyme, which could lead to further alterations of biological properties of the enzyme (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Aviram M.
      • Rosenblat M.
      • Billecke S.
      • Erogul J.
      • Sorenson R.
      • Bisgaier C.L.
      • Newton R.S.
      • La Du B.
      Human serum paraoxonase (PON 1) is inactivated by oxidized low density lipoprotein and preserved by antioxidants.
      ).

      EFFECTS OF HDL ON ENDOTHELIAL CELL INFLAMMATORY ACTIVATION

      Experimental studies and alterations of the effects of HDL from patients with cardiovascular disease

      Atherosclerosis is a chronic inflammatory disease. Endothelial adhesion and subsequent infiltration and accumulation of monocytes/macrophages and T lymphocytes into the arterial intima represent critical steps in initiation and progression of atherosclerotic lesions (
      • Hansson G.K.
      Inflammation, atherosclerosis, and coronary artery disease.
      ). HDL has been shown to inhibit the expression of monocyte che­moattractant protein-1, an important pro-inflammatory chemokine in endothelial cells (
      • Navab M.
      • Imes S.S.
      • Hama S.Y.
      • Hough G.P.
      • Ross L.A.
      • Bork R.W.
      • Valente A.J.
      • Berliner J.A.
      • Drinkwater D.C.
      • Laks H.
      • et al.
      Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.
      ,
      • Mackness B.
      • Hine D.
      • Liu Y.
      • Mastorikou M.
      • Mackness M.
      Paraoxonase-1 inhibits oxidised LDL-induced MCP-1 production by endothelial cells.
      ). Studies have demonstrated that native HDL and reconstituted HDL containing apoA-I or the apoA-I Milano mutant inhibit the expression of leukocyte adhesion molecules in endothelial cells that are activated by pro-inflammatory stimuli (
      • Cockerill G.W.
      • Rye K.A.
      • Gamble J.R.
      • Vadas M.A.
      • Barter P.J.
      High-density lipoproteins inhibit cytokine-induced expression of endothelial cell adhesion molecules.
      ,
      • Calabresi L.
      • Franceschini G.
      • Sirtori C.R.
      • De Palma A.
      • Saresella M.
      • Ferrante P.
      • Taramelli D.
      Inhibition of VCAM-1 expression in endothelial cells by reconstituted high density lipoproteins.
      ). Furthermore, HDL has been suggested to inhibit endothelial monocyte adhesion induced by oxLDL (
      • Maier J.A.
      • Barenghi L.
      • Pagani F.
      • Bradamante S.
      • Comi P.
      • Ragnotti G.
      The protective role of high-density lipoprotein on oxidized-low-density-lipoprotein-induced U937/endothelial cell interactions.
      ) or tumor necrosis factor-α (TNF-α) (
      • Park S.H.
      • Park J.H.
      • Kang J.S.
      • Kang Y.H.
      Involvement of transcription factors in plasma HDL protection against TNF-alpha-induced vascular cell adhesion molecule-1 expression.
      ) and monocyte transmigration in cocultures of human aortic endothelial cells and smooth muscle cells stimulated with LDL (
      • Navab M.
      • Imes S.S.
      • Hama S.Y.
      • Hough G.P.
      • Ross L.A.
      • Bork R.W.
      • Valente A.J.
      • Berliner J.A.
      • Drinkwater D.C.
      • Laks H.
      • et al.
      Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.
      ).
      The potential anti-inflammatory effects of HDL have also been demonstrated by several in vivo studies. Administration of reconstituted human HDL in apoE-deficient mice reduced VCAM-1 expression and decreased monocyte/macrophage infiltration following carotid artery cuff injury (
      • Dimayuga P.
      • Zhu J.
      • Oguchi S.
      • Chyu K.Y.
      • Xu X.O.
      • Yano J.
      • Shah P.K.
      • Nilsson J.
      • Cercek B.
      Reconstituted HDL containing human apolipoprotein A-1 reduces VCAM-1 expression and neointima formation following periadventitial cuff-induced carotid injury in apoE null mice.
      ). Recently, it was shown that apoA-I gene transfer resulting in increased HDL cholesterol plasma levels inhibited diabetes-induced myocardial mRNA expression of VCAM-1 and intercellular adhesion molecule-1 in mice with streptozotocin-induced diabetic cardiomyopathy (
      • Van Linthout S.
      • Spillmann F.
      • Riad A.
      • Trimpert C.
      • Lievens J.
      • Meloni M.
      • Escher F.
      • Filenberg E.
      • Demir O.
      • Li J.
      • et al.
      Human apolipoprotein A-I gene transfer reduces the development of experimental diabetic cardiomyopathy.
      ). In contrast, in a study in apoE-deficient mice with transgenic overexpression of human apoA-I, endothelial VCAM-1 expression monocyte adherence was not reduced in early atherosclerotic lesions at the aortic branch sites, despite reducing aortic atherosclerotic lesion formation (
      • Dansky H.M.
      • Charlton S.A.
      • Barlow C.B.
      • Tamminen M.
      • Smith J.D.
      • Frank J.S.
      • Breslow J.L.
      Apo A-I inhibits foam cell formation in Apo E-deficient mice after monocyte adherence to endothelium.
      ). Hence, these observations support the concept that the anti-inflammatory capacity of HDL is heterogeneous, depending on the pathophysiological conditions, that is also consistent with findings of recent studies demonstrating that the inhibitory effects of HDL isolated from different human subjects on TNF-α-stimulated endothelial VCAM-1 expression varied considerably (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ,
      • Ashby D.T.
      • Rye K.A.
      • Clay M.A.
      • Vadas M.A.
      • Gamble J.R.
      • Barter P.J.
      Factors influencing the ability of HDL to inhibit expression of vascular cell adhesion molecule-1 in endothelial cells.
      ). In human studies, it has been suggested that administration of reconstituted HDL increased the anti-inflammatory capacity of HDL from patients with type 2 diabetes (
      • Patel S.
      • Drew B.G.
      • Nakhla S.
      • Duffy S.J.
      • Murphy A.J.
      • Barter P.J.
      • Rye K.A.
      • Chin-Dusting J.
      • Hoang A.
      • Sviridov D.
      • et al.
      Reconstituted high-density lipoprotein increases plasma high-density lipoprotein anti-inflammatory properties and cholesterol efflux capacity in patients with type 2 diabetes.
      ).
      Several mechanisms have been suggested to explain the inhibitory effects of HDL on endothelial inflammatory activation (
      • Barter P.J.
      • Nicholls S.
      • Rye K.A.
      • Anantharamaiah G.M.
      • Navab M.
      • Fogelman A.M.
      Antiinflammatory properties of HDL.
      ). HDL can inhibit activation of the endothelial pro-inflammatory transcription factor NF-κB (
      • Park S.H.
      • Park J.H.
      • Kang J.S.
      • Kang Y.H.
      Involvement of transcription factors in plasma HDL protection against TNF-alpha-induced vascular cell adhesion molecule-1 expression.
      ,
      • Xia P.
      • Vadas M.A.
      • Rye K.A.
      • Barter P.J.
      • Gamble J.R.
      High density lipoproteins (HDL) interrupt the sphingosine kinase signaling pathway. A possible mechanism for protection against atherosclerosis by HDL.
      ). Impaired endothelial NO bioavailability and increased endothelial superoxide production have been implicated in activation of NF-κB (
      • Collins T.
      • Cybulsky M.I.
      NF-kappaB: pivotal mediator or innocent bystander in atherogenesis?.
      ). Furthermore, it was demonstrated that endothelial anti-inflammatory effects of HDL are mediated via SR-BI, PDZK1, PI3K, eNOS, and S1P receptors (
      • Kimura T.
      • Tomura H.
      • Mogi C.
      • Kuwabara A.
      • Damirin A.
      • Ishizuka T.
      • Sekiguchi A.
      • Ishiwara M.
      • Im D.S.
      • Sato K.
      • et al.
      Role of scavenger receptor class B type I and sphingosine 1-phosphate receptors in high density lipoprotein-induced inhibition of adhesion molecule expression in endothelial cells.
      ). Recently, we have observed that inhibition of eNOS-mediated NO production reduced the inhibitory effects of HDL from healthy subjects on NF-κB activity, VCAM-1 expression, and endothelial monocyte adhesion, suggesting that the capacity of HDL to stimulate endo­thelial NO production contributes to these endothelial anti-inflammatory effects of HDL (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ).
      It has been proposed that apoA-1, the major protein constituent of HDL, is able to recapitulate the anti-inflammatory capacity of HDL. In an in vivo study, infusion of apoA-I to rabbits subjected to acute vascular inflammation reduced neutrophil infiltration and endothelial cell inflammatory activation (
      • Puranik R.
      • Bao S.
      • Nobecourt E.
      • Nicholls S.J.
      • Dusting G.J.
      • Barter P.J.
      • Celermajer D.S.
      • Rye K.A.
      Low dose apolipoprotein A-I rescues carotid arteries from inflammation in vivo.
      ). Furthermore, administration of apoA-1 mimetic peptides D-4F and L-4F has been shown to reduce vascular inflammation in type I diabetic rats and improved insulin sensitivity in obese mice (
      • Peterson S.J.
      • Husney D.
      • Kruger A.L.
      • Olszanecki R.
      • Ricci F.
      • Rodella L.F.
      • Stacchiotti A.
      • Rezzani R.
      • McClung J.A.
      • Aronow W.S.
      • et al.
      Long-term treatment with the apolipoprotein A1 mimetic peptide increases antioxidants and vascular repair in type I diabetic rats.
      ,
      • Peterson S.J.
      • Drummond G.
      • Kim D.H.
      • Li M.
      • Kruger A.L.
      • Ikehara S.
      • Abraham N.G.
      L-4F treatment reduces adiposity, increases adiponectin levels, and improves insulin sensitivity in obese mice.
      ). Furthermore, lipid-free apoA-I and reconstituted HDL treatment reduced the expression of chemokines and chemokine receptors in vivo and in vitro via modulation of NF-κB and peroxisome proliferator-activated receptor γ (
      • Bursill C.A.
      • Castro M.L.
      • Beattie D.T.
      • Nakhla S.
      • van der Vorst E.
      • Heather A.K.
      • Barter P.J.
      • Rye K.A.
      High-density lipoproteins suppress chemokines and chemokine receptors in vitro and in vivo.
      ). One of the potential mechanisms for the anti-inflammatory effect of apoA-I is by mediating cellular cholesterol efflux through ABCA1, an ATP-binding transporter (
      • Tang C.
      • Liu Y.
      • Kessler P.S.
      • Vaughan A.M.
      • Oram J.F.
      The macrophage cholesterol exporter ABCA1 functions as an anti-inflammatory receptor.
      ,
      • Zhu X.
      • Owen J.S.
      • Wilson M.D.
      • Li H.
      • Griffiths G.L.
      • Thomas M.J.
      • Hiltbold E.M.
      • Fessler M.B.
      • Parks J.S.
      Macrophage ABCA1 reduces MyD88-dependent Toll-like receptor trafficking to lipid rafts by reduction of lipid raft cholesterol.
      ). Interestingly, apoA-I has also been shown to attenuate palmitate-induced NF-κB activation by reducing toll-like receptor-4 recruitment into lipid rafts (
      • Cheng A.M.
      • Handa P.
      • Tateya S.
      • Schwartz J.
      • Tang C.
      • Mitra P.
      • Oram J.F.
      • Chait A.
      • Kim F.
      Apolipoprotein A-I attenuates palmitate-mediated NF-kappaB activation by reducing Toll-like receptor-4 recruitment into lipid rafts.
      ).
      Besides apoA-I, the lipid component of HDL has also been proposed to be important for the anti-inflammatory effects of HDL. In vitro studies using discoidal reconstituted HDL containing apoA-I as the sole protein suggested that inhibitory effects of HDL on endothelial cell adhesion molecule expression are also, at least in part, dependent on HDL-associated phospholipid species (
      • Baker P.W.
      • Rye K.A.
      • Gamble J.R.
      • Vadas M.A.
      • Barter P.J.
      Phospholipid composition of reconstituted high density lipoproteins influences their ability to inhibit endothelial cell adhesion molecule expression.
      ). The inhibition of cytokine-induced expression of VCAM-1 by reconstituted HDL varied substantially when different phospha­tidylcholine species were compared, indicating that the lipid composition of HDL influences its anti-inflammatory capacity and might be an important determinant of HDL functionality (
      • Barter P.J.
      • Nicholls S.
      • Rye K.A.
      • Anantharamaiah G.M.
      • Navab M.
      • Fogelman A.M.
      Antiinflammatory properties of HDL.
      ,
      • Baker P.W.
      • Rye K.A.
      • Gamble J.R.
      • Vadas M.A.
      • Barter P.J.
      Phospholipid composition of reconstituted high density lipoproteins influences their ability to inhibit endothelial cell adhesion molecule expression.
      ).

      Alterations of effects of HDL from patients with coronary disease, diabetes, or chronic kidney dysfunction on endothelial inflammatory activation

      Early studies have demonstrated that the anti-inflammatory capacity of HDL is lost during acute phase responses in both humans and rabbits, as shown by the impaired ability of the isolated HDL to protect LDL from oxidation and inhibit the adhesion of monocytes to endothelial cells (
      • Van Lenten B.J.
      • Hama S.Y.
      • de Beer F.C.
      • Stafforini D.M.
      • McIntyre T.M.
      • Prescott S.M.
      • La Du B.N.
      • Fogelman A.M.
      • Navab M.
      Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.
      ,
      • Van Lenten B.J.
      • Wagner A.C.
      • Nayak D.P.
      • Hama S.
      • Navab M.
      • Fogelman A.M.
      High-density lipoprotein loses its anti-inflammatory properties during acute influenza a infection.
      ). Furthermore, the capacity of HDL to inhibit LDL-induced monocyte chemotactic activity has also been shown to be impaired in CAD patients (
      • Navab M.
      • Berliner J.A.
      • Subbanagounder G.
      • Hama S.
      • Lusis A.J.
      • Castellani L.W.
      • Reddy S.
      • Shih D.
      • Shi W.
      • Watson A.D.
      • et al.
      HDL and the inflammatory response induced by LDL-derived oxidized phospholipids.
      ), which can be improved following simvastatin therapy (
      • Ansell B.J.
      • Navab M.
      • Hama S.
      • Kamranpour N.
      • Fonarow G.
      • Hough G.
      • Rahmani S.
      • Mottahedeh R.
      • Dave R.
      • Reddy S.T.
      • et al.
      Inflammatory/antiinflammatory properties of high-density lipoprotein distinguish patients from control subjects better than high-density lipoprotein cholesterol levels and are favorably affected by simvastatin treatment.
      ). Recent studies have also described that the HDL capacity to inhibit the expression of adhesion molecules and monocyte chemotactic activity is lost in patients with CAD and diabetes, as well as end-stage renal disease (ESRD) (
      • Besler C.
      • Heinrich K.
      • Rohrer L.
      • Doerries C.
      • Riwanto M.
      • Shih D.M.
      • Chroni A.
      • Yonekawa K.
      • Stein S.
      • Schaefer N.
      • et al.
      Mechanisms underlying adverse effects of HDL on eNOS-activating pathways in patients with coronary artery disease.
      ,
      • Morgantini C.
      • Natali A.
      • Boldrini B.
      • Imaizumi S.
      • Navab M.
      • Fogelman A.M.
      • Ferrannini E.
      • Reddy S.T.
      Anti-inflammatory and antioxidant properties of HDLs are impaired in type 2 diabetes.
      ,
      • Tölle M.
      • Huang T.
      • Schuchardt M.
      • Jankowski V.
      • Prüfer N.
      • Jankowski J.
      • Tietge U.J.
      • Zidek W.
      • van der Giet M.
      High-density lipoprotein loses its anti-inflammatory capacity by accumulation of pro-inflammatory-serum amyloid A.
      ).
      Various mechanisms have been proposed to account for the impaired endothelial anti-inflammatory effects of HDL. The decrease in HDL apoA-I levels in inflammatory states has been related to decreased apoA-I synthesis in the liver, accelerated HDL catabolism, and apoA-I replacement in HDL particles by SAA (
      • Khovidhunkit W.
      • Kim M.S.
      • Memon R.A.
      • Shigenaga J.K.
      • Moser A.H.
      • Feingold K.R.
      • Grunfeld C.
      Effects of infection and inflammation on lipid and lipoprotein metabolism: mechanisms and consequences to the host.
      ,
      • Esteve E.
      • Ricart W.
      • Fernandez-Real J.M.
      Dyslipidemia and inflammation: an evolutionary conserved mechanism.
      ). Upon induction of the acute phase, SAA is able to replace apoA-I in small dense HDL, resulting in reduced plasma levels of apoA-I (
      • Parks J.S.
      • Rudel L.L.
      Alteration of high density lipoprotein subfraction distribution with induction of serum amyloid A protein (SAA) in the nonhuman primate.
      ). In rabbits and mice, SAA can completely replace apoA-I in a subset of small dense HDL particles, therefore functioning as a structural apolipoprotein (
      • Cabana V.G.
      • Reardon C.A.
      • Wei B.
      • Lukens J.R.
      • Getz G.S.
      SAA-only HDL formed during the acute phase response in apoA-I+/+ and apoA-I−/− mice.
      ). Accordingly, SAA was recently found to be enriched in HDL from end-stage renal disease patients, which correlated with its reduced anti-inflammatory capacity to inhibit monocyte chemoattractant protein-1 formation in vascular smooth muscle cells (
      • Tölle M.
      • Huang T.
      • Schuchardt M.
      • Jankowski V.
      • Prüfer N.
      • Jankowski J.
      • Tietge U.J.
      • Zidek W.
      • van der Giet M.
      High-density lipoprotein loses its anti-inflammatory capacity by accumulation of pro-inflammatory-serum amyloid A.
      ).
      In addition, certain amino acid residues in apoA-I, such as methionine, cysteine, tyrosine, and lysine residues, are susceptible to oxidative modifications (
      • Bergt C.
      • Pennathur S.
      • Fu X.
      • Byun J.
      • O'Brien K.
      • McDonald T.O.
      • Singh P.
      • Anantharamaiah G.M.
      • Chait A.
      • Brunzell J.
      • et al.
      The myeloperoxidase product hypochlorous acid oxidizes HDL in the human artery wall and impairs ABCA1-dependent cholesterol transport.
      ,
      • Zheng L.
      • Nukuna B.
      • Brennan M.L.
      • Sun M.
      • Goormastic M.
      • Settle M.
      • Schmitt D.
      • Fu X.
      • Thomson L.
      • Fox P.L.
      • et al.
      Apolipoprotein A-I is a selective target for myeloperoxidase-catalyzed oxidation and functional impairment in subjects with cardiovascular disease.
      ). In vitro study has demonstrated that MPO-catalyzed oxidative modification of HDL or apoA-I converts HDL into a pro-inflammatory particle which promotes NF-κB activation and endothelial VCAM-1 expression (
      • Undurti A.
      • Huang Y.
      • Lupica J.A.
      • Smith J.D.
      • DiDonato J.A.
      • Hazen S.L.
      Modification of high density lipoprotein by myeloperoxidase generates a pro-inflammatory particle.
      ). Furthermore, glycation of HDL and apoA-I, a process that is known to occur in diabetes in vivo (
      • Curtiss L.K.
      • Witztum J.L.
      Plasma apolipoproteins AI, AII, B, CI, and E are glucosylated in hyperglycemic diabetic subjects.
      ), has also been proposed to impact on the anti-inflammatory capacity of HDL (
      • Nobécourt E.
      • Tabet F.
      • Lambert G.
      • Puranik R.
      • Bao S.
      • Yan L.
      • Davies M.J.
      • Brown B.E.
      • Jenkins A.J.
      • Dusting G.J.
      • et al.
      Nonenzymatic glycation impairs the antiinflammatory properties of apolipoprotein A-I.
      ). In contrast to normal lipid-free ApoA-I, glycated lipid-free apoA-I infusion did not decrease adhesion molecule expression following vascular injury (
      • Nobécourt E.
      • Tabet F.
      • Lambert G.
      • Puranik R.
      • Bao S.
      • Yan L.
      • Davies M.J.
      • Brown B.E.
      • Jenkins A.J.
      • Dusting G.J.
      • et al.
      Nonenzymatic glycation impairs the antiinflammatory properties of apolipoprotein A-I.
      ). Glycation of HDL has also been shown to impair the HDL's capacity to inhibit oxLDL-induced monocyte adhesion to human aortic endothelial cells in vitro (
      • Hedrick C.C.
      • Thorpe S.R.
      • Fu M.X.
      • Harper C.M.
      • Yoo J.
      • Kim S.M.
      • Wong H.
      • Peters A.L.
      Glycation impairs high-density lipoprotein function.
      ).

      EFFECTS OF HDL ON ENDOTHELIAL CELL APOPTOTIC PATHWAYS

      Experimental studies and alterations of effects of HDL from patients with coronary disease

      Endothelial dysfunction and injury contribute to the pa­thogenesis of atherosclerosis (
      • Landmesser U.
      • Hornig B.
      • Drexler H.
      Endothelial function: a critical determinant in atherosclerosis?.
      ,
      • Ross R.
      Atherosclerosis–an inflammatory disease.
      ,
      • Nabel E.G.
      • Braunwald E.
      A tale of coronary artery disease and myocardial infarction.
      ). Experimental studies have shown that atherosclerotic lesion-prone vascular regions are characterized by a high endothelial cell turnover (
      • Caplan B.A.
      • Schwartz C.J.
      Increased endothelial cell turnover in areas of in vivo Evans Blue uptake in the pig aorta.
      ), which has been attributed to an increased rate of endothelial cell apoptosis. Endothelial cell apoptosis has also been suggested to contribute importantly to the pathophysiology of coronary disease (
      • Burke A.P.
      • Farb A.
      • Malcom G.T.
      • Liang Y.H.
      • Smialek J.
      • Virmani R.
      Coronary risk factors and plaque morphology in men with coronary disease who died suddenly.
      ,
      • Rössig L.
      • Dimmeler S.
      • Zeiher A.M.
      Apoptosis in the vascular wall and atherosclerosis.
      ). The capacity of HDL to attenuate endothelial cell apoptosis may therefore represent an anti-atherogenic property of HDL (
      • Nofer J.R.
      • Levkau B.
      • Wolinska I.
      • Junker R.
      • Fobker M.
      • von Eckardstein A.
      • Seedorf U.
      • Assmann G.
      Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids.
      ,
      • Sugano M.
      • Tsuchida K.
      • Makino N.
      High-density lipoproteins protect endothelial cells from tumor necrosis factor-alpha-induced apoptosis.
      ,
      • Suc I.
      • Escargueil-Blanc I.
      • Troly M.
      • Salvayre R.
      • Negre-Salvayre A.
      HDL and ApoA prevent cell death of endothelial cells induced by oxidized LDL.
      ,
      • de Souza J.A.
      • Vindis C.
      • Negre-Salvayre A.
      • Rye K.A.
      • Couturier M.
      • Therond P.
      • Chantepie S.
      • Salvayre R.
      • Chapman M.J.
      • Kontush A.
      Small, dense HDL 3 particles attenuate apoptosis in endothelial cells: pivotal role of apolipoprotein A-I.
      ).
      HDL inhibits apoptosis of endothelial cells induced by both death receptor-mediated and mitochondrial-mediated apoptotic pathways. HDL may inhibit apoptosis triggered by various pro-atherogenic factors, such as TNF-α, oxLDL, and growth factor deprivation (
      • Nofer J.R.
      • Levkau B.
      • Wolinska I.
      • Junker R.
      • Fobker M.
      • von Eckardstein A.
      • Seedorf U.
      • Assmann G.
      Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids.
      ,
      • Sugano M.
      • Tsuchida K.
      • Makino N.
      High-density lipoproteins protect endothelial cells from tumor necrosis factor-alpha-induced apoptosis.
      ,
      • Suc I.
      • Escargueil-Blanc I.
      • Troly M.
      • Salvayre R.
      • Negre-Salvayre A.
      HDL and ApoA prevent cell death of endothelial cells induced by oxidized LDL.
      ). Both HDL-associated proteins and lipids have been suggested to contribute to the anti-apoptotic capacity of HDL. ApoA-I has been shown to inhibit endothelial cell apoptosis induced by oxLDL, VLDL, and TNF-α (
      • Sugano M.
      • Tsuchida K.
      • Makino N.
      High-density lipoproteins protect endothelial cells from tumor necrosis factor-alpha-induced apoptosis.
      ,
      • Suc I.
      • Escargueil-Blanc I.
      • Troly M.
      • Salvayre R.
      • Negre-Salvayre A.
      HDL and ApoA prevent cell death of endothelial cells induced by oxidized LDL.
      ,
      • Speidel M.T.
      • Booyse F.M.
      • Abrams A.
      • Moore M.A.
      • Chung B.H.
      Lipolyzed hypertriglyceridemic serum and triglyceride-rich lipoprotein cause lipid accumulation in and are cytotoxic to cultured human endothelial cells. High density lipoproteins inhibit this cytotoxicity.
      ). HDL subpopulations enriched with apoA-I account for approximately 70% of the anti-apoptotic activity of HDL in human microvascular endothelial cells that were treated with mildly oxLDL and reconstitution of HDL with apoA-I, cholesterol, and phospholipids potently decreased oxLDL-induced apoptosis in these cells (
      • de Souza J.A.
      • Vindis C.
      • Negre-Salvayre A.
      • Rye K.A.
      • Couturier M.
      • Therond P.
      • Chantepie S.
      • Salvayre R.
      • Chapman M.J.
      • Kontush A.
      Small, dense HDL 3 particles attenuate apoptosis in endothelial cells: pivotal role of apolipoprotein A-I.
      ), suggesting that apoA-I plays an important role for the anti-apoptotic capacity of HDL in oxLDL-stimulated endothelial cells.
      HDL-associated lysosphingolipids have also been shown to inhibit endothelial cell apoptosis triggered by growth factor deprivation (
      • Nofer J.R.
      • Levkau B.
      • Wolinska I.
      • Junker R.
      • Fobker M.
      • von Eckardstein A.
      • Seedorf U.
      • Assmann G.
      Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids.
      ,
      • Kimura T.
      • Sato K.
      • Kuwabara A.
      • Tomura H.
      • Ishiwara M.
      • Kobayashi I.
      • Ui M.
      • Okajima F.
      Sphingosine 1-phosphate may be a major component of plasma lipoproteins responsible for the cytoprotective actions in human umbilical vein endothelial cells.
      ,
      • Kimura T.
      • Sato K.
      • Malchinkhuu E.
      • Tomura H.
      • Tamama K.
      • Kuwabara A.
      • Murakami M.
      • Okajima F.
      High-density lipoprotein stimulates endothelial cell migration and survival through sphingosine 1-phosphate and its receptors.
      ). The anti-apoptotic capacity of HDL-associated lipids was further supported by the findings that the ratio of S1P and sphingomyelin was increased in small dense HDL3 particles and positively correlated with the capacity of these HDL subpopulations to attenuate endothelial cell apoptosis (
      • Kontush A.
      • Therond P.
      • Zerrad A.
      • Couturier M.
      • Negre-Salvayre A.
      • de Souza J.A.
      • Chantepie S.
      • Chapman M.J.
      Preferential sphingosine-1-phosphate enrichment and sphingomyelin depletion are key features of small dense HDL3 particles: relevance to antiapoptotic and antioxidative activities.
      ).
      Several mechanisms have been proposed for the endothelial anti-apoptotic effects of HDL, depending on the trigger of apoptosis. OxLDL causes a delayed but sustained increase in intracellular calcium in endothelial cells, leading to cell death, and this effect is reversed by HDL and mediated by prevention of the calcium increase (
      • Suc I.
      • Escargueil-Blanc I.
      • Troly M.
      • Salvayre R.
      • Negre-Salvayre A.
      HDL and ApoA prevent cell death of endothelial cells induced by oxidized LDL.
      ). TNF-α-induced endothelial cell apoptosis is also inhibited by HDL, and this is associated with attenuated induction of CPP32-like protease (caspase 3), which is a component of all primary apoptotic pathways (
      • Sugano M.
      • Tsuchida K.
      • Makino N.
      High-density lipoproteins protect endothelial cells from tumor necrosis factor-alpha-induced apoptosis.
      ). Growth factor deprivation activates the mitochondrial pathway of apoptosis, which can be suppressed by HDL. HDL inhibits the dissipation of mitochondrial potential, oxygen-derived free radical generation, cytochrome c release to the cytoplasm, and activation of caspase 3 and caspase 9. HDL also activates Akt and causes phosphorylation of the Akt target Bcl-2-associated death promoter Bad, preventing it from binding to Bcl-xL (Fig. 2). Bcl-xL, an anti-apoptotic Bcl-2 family protein, is then free to inhibit mitochondria-mediated apoptosis (
      • Nofer J.R.
      • Levkau B.
      • Wolinska I.
      • Junker R.
      • Fobker M.
      • von Eckardstein A.
      • Seedorf U.
      • Assmann G.
      Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids.
      ). In addition, HDL causes PI3K-mediated upregulation of the Bcl-xL expression (
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      ). Interestingly, HDL retained its anti-apoptotic activity after knockdown of eNOS using specific RNA interference or pharmacological inhibition using N (G)-nitro-L- arginine methyl ester (16), suggesting that HDL may exert its anti-apoptotic activity independently of eNOS activation. Lysophospholipid S1P enhances endothelial cell survival, and this effect is inhibited by knockdown of the S1P receptor endothelial differentiation gene 1/S1P1 by pertussis toxin and by PI3K and ERK pathway antagonists, suggesting that signaling by lysophospholipid components of HDL may be important for the inhibition of apoptosis (
      • Kimura T.
      • Sato K.
      • Malchinkhuu E.
      • Tomura H.
      • Tamama K.
      • Kuwabara A.
      • Murakami M.
      • Okajima F.
      High-density lipoprotein stimulates endothelial cell migration and survival through sphingosine 1-phosphate and its receptors.
      ).

      Alterations of the effects of HDL from patients with cardiovascular disease on endothelial apoptosis

      Recently, we have observed that reduced clusterin and increased apoC-III content in HDL isolated from patients with CAD led to activation of pro-apoptotic signaling pathways in endothelial cells (
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      ). In contrast to HDL from healthy subjects, HDL isolated from patients with stable CAD or an ACS failed to inhibit endothelial cell apoptosis in vitro and in apoE-deficient mice in vivo. Instead, HDL isolated from these patients stimulated endothelial pro-apoptotic pathways, in particular p38-MAPK-mediated activation of the pro-apoptotic Bcl-2 protein tBid (Fig. 2). Our studies further suggest that differences in the proteome of HDL from patients with CAD, in particular reduced HDL-associated clusterin and increased HDL-associated apoC-III, play an important role for altered activation of endothelial anti- and pro-apoptotic signaling pathways (Fig. 2) (
      • Riwanto M.
      • Rohrer L.
      • Roschitzki B.
      • Besler C.
      • Mocharla P.
      • Mueller M.
      • Perisa D.
      • Heinrich K.
      • Altwegg L.
      • von Eckardstein A.
      • et al.
      Altered activation of endothelial anti- and pro-apoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of HDL-proteome remodeling.
      ). Furthermore, oxidative modifications of HDL may also play a role in the loss of anti-apoptotic activity of HDL, as demonstrated by Undurti et al. (
      • Undurti A.
      • Huang Y.
      • Lupica J.A.
      • Smith J.D.
      • DiDonato J.A.
      • Hazen S.L.
      Modification of high density lipoprotein by myeloperoxidase generates a pro-inflammatory particle.
      ) showing that MPO-catalyzed oxidation of HDL resulted in the impaired capacity to inhibit endothelial apoptosis in vitro.

      EFFECTS OF HDL ON ENDOTHELIAL REPAIR AFTER VASCULAR INJURY

      Experimental studies and effects of HDL from patients with cardiovascular disease

      Recent studies have also suggested that HDL may stimulate endothelial repair processes. Endothelial repair processes have long been thought to be only dependent on the proliferation and migration of local adjacent endothelial cells (
      • Caplan B.A.
      • Schwartz C.J.
      Increased endothelial cell turnover in areas of in vivo Evans Blue uptake in the pig aorta.
      ); however, several recent studies have demonstrated that bone marrow-derived mononuclear cells [early outgrowth cells (EOCs)] can promote endothelial repair after vascular injury (
      • Sorrentino S.A.
      • Bahlmann F.H.
      • Besler C.
      • Muller M.
      • Schulz S.
      • Kirchhoff N.
      • Doerries C.
      • Horvath T.
      • Limbourg A.
      • Limbourg F.
      • et al.
      Oxidant stress impairs in vivo reendothelialization capacity of endothelial progenitor cells from patients with type 2 diabetes mellitus: restoration by the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone.
      ,
      • Walter D.H.
      • Rittig K.
      • Bahlmann F.H.
      • Kirchmair R.
      • Silver M.
      • Murayama T.
      • Nishimura H.
      • Losordo D.W.
      • Asahara T.
      • Isner J.M.
      Statin therapy accelerates reendothelialization: a novel effect involving mobilization and incorporation of bone marrow-derived endothelial progenitor cells.
      ), and likely contribute to endothelial repair processes in lesion-prone areas of experimental atherosclerosis and improve endothelial function (
      • Foteinos G.
      • Hu Y.
      • Xiao Q.
      • Metzler B.
      • Xu Q.
      Rapid endothelial turnover in atherosclerosis-prone areas coincides with stem cell repair in apolipoprotein E-deficient mice.
      ,
      • Wassmann S.
      • Werner N.
      • Czech T.
      • Nickenig G.
      Improvement of endothelial function by systemic transfusion of vascular progenitor cells.
      ).
      HDL stimulates endothelial repair by promotion of endothelial cell proliferation or migration and stimulation of the recruitment and endothelial repair capacity of EOCs (
      • Sorrentino S.A.
      • Besler C.
      • Rohrer L.
      • Meyer M.
      • Heinrich K.
      • Bahlmann F.H.
      • Mueller M.
      • Horvath T.
      • Doerries C.
      • Heinemann M.
      • et al.
      Endothelial-vasoprotective effects of high-density lipoprotein are impaired in patients with type 2 diabetes mellitus but are improved after extended-release niacin therapy.
      ,
      • Seetharam D.
      • Mineo C.
      • Gormley A.K.
      • Gibson L.L.
      • Vongpatanasin W.
      • Chambliss K.L.
      • Hahner L.D.
      • Cummings M.L.
      • Kitchens R.L.
      • Marcel Y.L.
      • et al.
      High-density lipoprotein promotes endothelial cell migration and reendothelialization via scavenger receptor-B type I.
      ,
      • Zhu W.
      • Saddar S.
      • Seetharam D.
      • Chambliss K.L.
      • Longoria C.
      • Silver D.L.
      • Yuhanna I.S.
      • Shaul P.W.
      • Mineo C.
      The scavenger receptor class B type I adaptor protein PDZK1 maintains endothelial monolayer integrity.
      ). HDL induces a marked increase in endothelial cell migration in vitro with effects comparable to endothelial growth factors, such as basic fibroblast growth factor or vascular endothelial growth factor (
      • Kimura T.
      • Sato K.
      • Malchinkhuu E.
      • Tomura H.
      • Tamama K.
      • Kuwabara A.
      • Murakami M.
      • Okajima F.
      High-density lipoprotein stimulates endothelial cell migration and survival through sphingosine 1-phosphate and its receptors.
      ,
      • Seetharam D.
      • Mineo C.
      • Gormley A.K.
      • Gibson L.L.
      • Vongpatanasin W.
      • Chambliss K.L.
      • Hahner L.D.
      • Cummings M.L.
      • Kitchens R.L.
      • Marcel Y.L.
      • et al.
      High-density lipoprotein promotes endothelial cell migration and reendothelialization via scavenger receptor-B type I.
      ,
      • Murugesan G.
      • Sa G.
      • Fox P.L.
      High-density lipoprotein stimulates endothelial cell movement by a mechanism distinct from basic fibroblast growth factor.
      ). Native HDL and HDL-associated lysosphingolipid S1P stimulate endothelial cell migration via S1P receptors S1P1 and S1P3, and the effects can be blocked by pertussis toxin which inhibits the interactions between G proteins and G protein-coupled receptors (
      • Kimura T.
      • Sato K.
      • Malchinkhuu E.
      • Tomura H.
      • Tamama K.
      • Kuwabara A.
      • Murakami M.
      • Okajima F.
      High-density lipoprotein stimulates endothelial cell migration and survival through sphingosine 1-phosphate and its receptors.