PPARs and atherosclerosis

PPARs and atherosclerosis Coralie Fontaine, Caroline Duval, Olivier Barbier, Giulia Chinetti, Jean-Charles Fruchart and Bart Staels* UR545 INSERM, Faculte´ de Pharmacie, De´partement d’Athe´roscle´rose, Institut Pasteur de Lille, Universite´ de Lille II, 1 rue Calmette, 59019 Lille, France p Correspondence address: Tel.: þ33-3-20-87-73-88; fax: þ33-3-20-87-71-98 E-mail: [email protected](B.S.)

1. Introduction Atherosclerosis is a chronic disease characterized by the accumulation of lipids and fibrous connective tissue in the large arteries, accompanied by a local inflammatory response [1]. Atherosclerosis is the main origin of cardiovascular diseases, such as myocardial infarction and stroke, the major causes of mortality and morbidity in industrialized countries. Epidemiological studies have revealed several genetic and environmental risk factors predisposing to atherosclerosis. The metabolic syndrome, which is characterized by the simultaneous presence of one or more metabolic disorders, such as glucose intolerance, hyperinsulinemia, dyslipidemia, coagulation disturbances and hypertension, is defined as the clustering of cardiovascular risk factors with insulin resistance. Activators of peroxisome proliferator-activated receptors (PPARs), transcription factors, belonging to the superfamily of nuclear receptors, modulate several of these metabolic risk factors. Numerous studies have illustrated the role of PPARs in the control of glucose homeostasis, insulin resistance and hypertension (for review, see Refs. [2 – 4]). The PPAR subfamily consists of three distinct subtypes termed a (NR1C1), b/d (NR1C2) and g (NR1C3), which display tissue-selective expression patterns reflecting their biological functions [4]. While PPARa is expressed preferentially in tissues where fatty acids are catabolized, PPARg is mainly present in adipose tissue and PPARb/d is ubiquitously expressed (for review, see Refs. [4,5]). PPARs are expressed in most cell types of the vascular wall as well as in atherosclerotic lesions (for review, see Ref. [6]), where they affect atherogenic processes. Most of the physiological functions of PPARs can be explained by their activity as transcription factors, modulating the expression of specific target genes (for reviews see Refs. [4,5]). Upon ligand activation, PPARs regulate gene transcription by dimerizing with the retinoid X receptor (RXR) and binding to PPAR response elements (PPREs) Advances in Molecular and Cell Biology, Vol. 33, pages 543–560 q 2004 Elsevier B.V. All rights of reproduction in any form reserved. ISSN: 1569-2558 / DOI: 10.1016/S1569-2558(03)33026-7

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within the regulatory regions of target genes [4]. These PPREs usually consist of a direct repeat of the hexanucleotide sequence, AGGTCA, separated by one or two nucleotides (DR1 or DR2) (Fig. 1). PPARs can also repress gene transcription in a DNA bindingindependent manner by interfering with the nuclear factor-kappa B (NF-kB), signal transducer and activator of transcription (STAT), activator protein-1 (AP-1), nuclear factor of activated T cells (NFAT), CCAAT/enhancer-binding proteins (C/EBP) and Smad3 signaling pathways via protein –protein interactions and cofactor competition [6 –9]. Such transrepression mechanism is likely to participate in the anti-inflammatory actions of PPARs (for review, see Ref. [6]). Fatty acids (FA) and FA-derived compounds are natural ligands for PPARa and PPARg. Similarly, PPARb/d is a receptor for unsaturated FA. Natural eicosanoids derived from arachidonic acid via the lipoxygenase pathway, such as 8-S-hydroxytetraenoic acid (8-S-HETE) and leukotrien B4 (LTB4), activate PPARa [4]. Oxidized phospholipids derived from oxidized lipoproteins are natural ligands for both PPARa and PPARg [10,11]. In addition, PPARg is a receptor for eicosanoid metabolites formed via the cycloxygenase pathway, e.g. prostaglandins (PG) such as PG-J2, PG-H1 and PG-H2, and also via the lipoxygenase pathway (15-HETE) [4] (Fig. 1). Synthetic agonists of PPARs are used in the treatment of metabolic diseases, such as dyslipidemia and type 2 diabetes. The anti-diabetic glitazones, which are insulin sensitizers, are synthetic high-affinity ligands for PPARg [12 –14]. The hypolipidemic

Fig. 1. Schematic representation of the mechanism of action and ligands of PPARs. PPARs act in a transcriptional complex as a heterodimer with RXR. The PPAR/RXR complex is activated by 9-cis retinoic acid, and either natural or synthetic agonists that bind to PPARs. Both RXR and PPAR possess a ligand-binding domain (LBD) and a DNA-binding domain (DBD).

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fibrate drugs are PPARa ligands [15]. Recently, novel high-affinity subtype-specific PPAR agonists have been synthesized, including the human PPARa ligand GW7647 [16], the PPARg activators GW1929 and GW7845 [17,18] and the PPARb/d-specific agonist GW501516 [19] (Fig. 1). PPARs are exciting therapeutic targets for the treatment of disorders predisposing to atherosclerosis. We will focus on their role in the control of atherogenesis, by discussing their effects on each step of the atherogenic process.

2. PPARs modulate early stages of atherogenesis Under basal conditions, the endothelium forms a relatively impermeable barrier between the circulating blood and the vessel wall. Endothelial injury is thought to be the primary event in atherosclerosis, which leads to the attraction, recruitment and activation of different cell types including monocytes/macrophages, T-lymphocytes, endothelial cells (ECs) and smooth muscle cells (SMCs) (Fig. 2). The recruitment of monocytes to the intima requires the interaction of locally produced chemokines with specific cell surface receptors, such as the CCR2, the receptor for the monocyte chemoattractant protein-1 (MCP-1). MCP-1 expression is inhibited by PPARg ligands [20] and glitazones decrease monocyte CCR2 expression [21,22], which demonstrates that the chemotaxis mediated by MCP-1 is blocked by PPARg activation. In vivo, troglitazone reduces monocyte/macrophage homing to atherosclerotic plaques in apolipoprotein E (apoE) deficient mice [23]. Furthermore, glitazones also inhibit MCP-1 directed transendothelial migration of monocytes in low-density lipoproteins (LDL)receptor deficient mice [24]. PPARa effects on monocyte recruitment are more controversial. Indeed, whereas both natural and synthetic PPARa ligands stimulate basal expression of MCP-1 in human aortic ECs [25,26], Pasceri et al. [26] have demonstrated that CRP-induced MCP-1 expression in human ECs is inhibited by synthetic PPARa ligands. In addition T-cell recruitment to inflammation sites is modulated by PPARg, which inhibits interferon gamma (IFNg)-induced expression of certain CXC chemokines, such as IFNg-inducible protein-10 (IP-10), monokine induced by IFNg (Mig) and IFNg-inducible T-cell a-chemoattractant (I-TAC) [27]. Furthermore, PPARg agonists decrease EC expression of interleukin (IL)-8, a cytokine exerting chemotactic effects on Tlymphocytes, whereas PPARa ligands may induce its expression [25]. PPARa and PPARg activators also decrease EC migration [28,29] by inhibiting vascular endothelial growth factor (VEGF)-induced Akt phosphorylation, one pathway required for the chemotactic signaling of ECs. Rolling and adhesion of circulating monocytes to the ECs is the next critical early step in atherogenesis, and several cell adhesion molecules are involved in this process including intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1). PPARa and PPARg activators inhibit cytokine-induced expression of VCAM-1 [30,31]. Furthermore, although expression of ICAM-1 is unaffected by PPARa activators, PPARg agonists inhibit TNFa-induced ICAM-1 [23,32].

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Fig. 2. Description of the atherosclerotic process. Atherosclerosis is a complex vascular disease initiated by oxidation and accumulation of low-density lipoproteins (LDL) in the subendothelial space of the vessels, followed by endothelial cell (EC) activation resulting in the recruitment of circulating monocytes. Trapped monocytes differentiate into macrophages, which take up oxidized LDL (OxLDL) through scavenger receptors (SRs), thus forming foam cells. Activated smooth muscle cells (SMCs) proliferate and migrate from the media, thus leading to fibrous cap formation. Activation of these cells leads to the release of pro-inflammatory cytokines, which combined with the secretion of metalloproteases and expression of pro-coagulant factors results in chronic inflammation and plaque instability. This can further evolve to plaque rupture and acute occlusion by thrombosis, resulting in myocardial infarction and stroke.

In addition, the expression [33] and the secretion [34 –36] of endothelin-1 (ET-1), a vasoconstrictor peptide chemotactic to monocytes and a potent inducer of cell adhesion molecules (for review, see Ref. [37]), is repressed by both PPARa and PPARg ligands in ECs. Since there is no PPRE in the ET-1 promoter, PPARs appear to act indirectly on the expression by blocking the AP-1 signaling pathway [33]. Iglarz et al. [38] have recently shown the beneficial effect of PPARa and PPARg activators in vivo on vascular effects in deoxycorticosterone acetate (DOCA)-salt rats, a model of endothelin-dependent hypertension. This inhibition of ET-1 by PPARa and PPARg activators has been previously demonstrated in rats with cardiac hypertrophy due to pressure overload provoked by abdominal aortic banding [39,40]. PPARg agonists also enhance EC growth and secretion of C-type natriuretic peptide (CNP), an endothelium-derived relaxing peptide, in ECs [40]. Altogether, these effects might contribute to the slight decrease of blood pressure observed in diabetic patients treated with glitazones [41,42].

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Under basal conditions, endothelium-derived nitric oxide (NO), produced by endothelial NO synthase (eNOS), inhibits leukocyte attachment and promotes vascular relaxation (for reviews, see Refs. [43,44]). However, NO may present pro-atherogenic effects, since it promotes oxidative stress and inflammation when produced at high concentration by inducible NO synthase (iNOS). PPARg ligands increase NO release from ECs, thus inducing NO-dependent vasoprotective effects [45]. On the contrary, both PPARa and PPARg ligands inhibit iNOS expression in macrophages and as such reduce inflammatory NO production [46,47]. Thus, PPAR-dependent regulation of chemokines, adhesion molecules and NO suggests that PPARa and PPARg exert inhibitory effects on chemoattraction and cellular adhesion to ECs. PPARs may also have a protective action on the endothelium, thus decreasing endothelial injury.

3. PPARs control lipid accumulation and reverse cholesterol transport After recruitment into the subendothelium, monocytes differentiate into macrophages. Accumulation of cholesterol in these cells leads to the formation of foam cells (Fig. 3).

Fig. 3. Role of PPARa and PPARg on cholesterol homeostasis in macrophages. Whereas PPARg increases CD36 gene expression, SR-A expression is decreased. As net effect, no induction of foam cell formation is observed after treatment with PPARg or PPARa. Moreover, both passive and active efflux are potentiated by PPARa and PPARg agonists. In addition, the proportion of cholesteryl ester (CE) is decreased by PPARa and PPARg ligands in macrophages, resulting in an enhanced availability of free cholesterol (FC) for efflux.

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To be recognized by macrophages, LDL undergo modification, such as oxidation, glycosylation and aggregation. In ECs, PPARa and PPARg modulate the generation of free radicals, which contributes to oxidized LDL (OxLDL) formation. Indeed, PPARa and PPARg activators increase the expression of the Cu2þ, Zn2þ superoxide dismutase (CuZnSOD), a superoxide scavenger enzyme, which protects arteries from the deleterious effects of reactive oxygen species (ROS) [48]. In addition, PPARa and PPARg agonists decrease the NADPH oxidase expression, which contributes to superoxide formation [49]. Moreover, in macrophages, PPARg activation attenuated ROS formation [49]. By contrast, in THP-1 macrophages, PPARa and not PPARg activation induced generation of hydrogen peroxide, a marker of ROS [50]. Finally, PPARa activation by OxLDL leads to the downregulation of platelet-activating factor (PAF)-receptor gene expression in human monocytes and macrophages [51]. PAF is a potent pro-inflammatory substance playing an important role in LDL oxidation and whose effects are mediated by a specific cell receptor (PAF-receptor). In addition, PPARs play an important role in regulating cholesterol uptake and homeostasis in macrophages. PPARa and PPARg agonists upregulate human macrophage lipoprotein lipase (LPL) expression [52,53], but decrease LPL secretion and enzyme activity in differentiated macrophages [53]. Since LPL is required for the uptake of glycated LDL by macrophages [54], this downregulation may explain the decreased uptake of glycated LDL by macrophages after PPARa and PPARg stimulation [53]. PPARg ligands have been suggested to promote lipid accumulation in macrophages by inducing the receptor scavenger CD36 [55] and the adipocyte lipid-binding protein (ALBP/aP2) [56], both of which enhance cholesterol ester accumulation. However, PPARg repression of the scavenger receptor A (SR-A) counterbalances CD36 induction [57]. Indeed, by acting through post-transcriptional mechanisms, PPARg ligands decrease SRA protein levels, which is involved in the uptake of modified LDL. Overall, there is no stimulatory effect of PPARg or PPARa activation on LDL accumulation in macrophages [57,58]. Moreover, PPARa and PPARg inhibit apoB48 receptor expression, which mediates lipid accumulation of triglyceride-rich lipoproteins in THP-1 cells [59]. On the contrary, Vosper et al. [60] have found that PPARb/d agonists promote lipid loading in human macrophages by oxLDL and that over-expression of PPARb/d in human differentiated THP-1 monocytes provokes a profound increase in lipid accumulation. Finally, PPARg activators inhibit TNFa-induced expression of the OxLDL receptor, lectin-like OxLDL receptor-1 (LOX-1) in ECs, an effect with potential beneficial consequences on cholesterol concentration in the endothelium [61]. Cholesterol efflux is the first step of the reverse cholesterol transport, which mediates the centripetal transport of cholesterol from peripheral cells back to the liver. Macrophage cholesterol efflux to high-density lipoprotein (HDL) occurs either via passive diffusion facilitated or not by protein, such as SR-B1/CLA-1, or via active efflux mediated by the ATP-binding cassette (ABC) proteins. In human macrophages, both PPARa and PPARg activators induce protein levels of SR-B1/CLA-1 [62]. Moreover, the apoE expression is upregulated by PPARg in macrophages [63], whereas PPARb/d downregulates genes involved in lipid efflux such as apoE and cholesterol 27-hydroxylase (CYP27) [60]. Interestingly, ligands of all three PPAR isotypes induce ABCA-1 expression [19,58] and as such stimulate cholesterol efflux from macrophages. PPARa and PPARg induce

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ABCA-1 by an indirect mechanism via induction of the liver X receptor a (LXRa) [58]. However, the molecular mechanism of ABCA1 induction by PPARb/d activators appears to be LXRa-independent [19]. Finally, PPARa and PPARg-specific ligands decrease the cholesteryl ester (CE):free cholesterol (FC) ratio in macrophages resulting in an enhanced availability of FC for efflux through the ABCA-1 pathway [64,65]. In addition to the protective actions of HDL against atherosclerosis through the removal of excess cholesterol from the atherosclerotic lesion (for review, see Ref. [66]), HDL also exerts various other anti-atherogenic properties, such as the inhibition of monocyte chemotaxis, leukocyte adhesion, LDL oxidation and endothelial dysfunction (for review, see Ref. [67]). PPARa and PPARg (for review, see Refs. [68,69]) and, more recently, PPARb/d ([for review, see Refs. [70,71]) are known to influence HDL-cholesterol metabolism in humans. Fibrates influence the expression of HDL remodeling enzymes, such as the phospholipid transfer lipoprotein (PLTP) [72], an enzyme transferring phospholipids from VLDL/LDL to HDL, and lecithin:cholesterol acyl transferase (LCAT) [73], respectively, in mice and rats. PPARb/d-specific agonists also increase plasma HDL-cholesterol concentrations in insulin resistant mice and obese rhesus monkeys [19,74]. The molecular mechanisms behind this induction remain to be clarified. ApoAI and apoAII are the major HDL apolipoproteins. In humans, PPARa activation increases the transcription of these two genes via binding to PPREs in their promoters [75, 76], an effect that contributes to the increase of HDL concentrations following fibrate treatment. In addition, fenofibrate increases apoAI plasma and hepatic expression levels in apoE deficient mice expressing a human apoAI transgene, which is associated with decreased atherosclerotic lesion formation [77]. Although the increase of plasma apoAI is undoubtedly beneficial, substantial controversy exists on the role of apoAII in atherosclerosis. Indeed, whereas transgenic mice over-expressing murine apoAII are more prone to develop atherosclerosis [78], over-expression of human apoAII protects against atherogenesis [79]. Thus, PPARa and PPARg appear to be protective against accumulation of cholesterol formation into macrophages. Whereas they do not influence cholesterol accumulation, PPARa and PPARg agonists promote cholesterol efflux, decrease cholesterol esterification and increase HDL concentrations. The role of PPARb/d in these processes is less clear, and more studies are required to specify its role in the control of atherogenesis.

4. PPARs, local immune and inflammatory responses Atherosclerosis is characterized by a local immune response which occured via the recruitment, activation and proliferation of cells of the immune system. Dendritic cells (DCs) are critical initiators of the immune response by activating T-lymphocytespresenting antigen. Activated T-lymphocytes differentiate into two subpopulations differing in their profiles of secreted cytokines. Th1 cells mediate the cellular immune response whereas Th2 cells potentiate the humoral response (Fig. 4). In DCs, PPARg activation inhibits the production of IL-12 [80,81], a pro-inflammatory cytokine known to play a role in the polarization of the acquired immune (Th1) response

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Fig. 4. Effects of PPARs on inflammation. PPARg ligands deviate away from Th1 towards Th2 cytokine production. In addition, the anti-inflammatory activities of PPARs leads to the inhibition ( # ) of pro-inflammatory molecule release by endothelial cells (ECs), macrophages, smooth muscle cells (SMCs), dendritic cells (DCs) and T-lymphocytes (T-Lc). Acute inflammation is neutralized by PPARs through the diminution of circulating interleukin (IL)-6, fibrinogen, C reactive protein (CRP) and serum amyloid A (SAA) plasma levels.

in mice and human. Moreover, PPARg activation lowers the surface expression of the costimulatory molecules CD80, CD86, CD64, and the synthesis of chemokines involved in the Th1 immune response, such as RANTES, IP-10 and IL1-b [81 – 83]. In T-lymphocytes, activated PPARg negatively interacts with T-cell-specific transcription factor NFAT-stimulated IL-2 transcription [7,83], and thus reduces the proliferative effect of this cytokine. The major histocompatibility complex class II, directly involved in T-lymphocyte activation, is inhibited by PPARg ligands [84]. In addition, PPARg increases T-lymphocyte apoptosis, thus decreasing their viability [85]. Altogether, the protective effects of PPARg ligands on the immune response associated with atherogenesis may be due, on the one hand, to immune deviation from Th1 to Th2-type cytokine production and, on the other hand, to a global decrease of the immune response. The role of PPARa in the immune response is less documented. PPARa inhibits IL-2 secretion via NF-kB transrepression and also decreases IFNg production in T-lymphocytes [83,86]. The PPARa-dependent suppression of adaptive immune responses was evidenced in vivo using the PPARa deficient mouse model [87].

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The activation of ECs, macrophages, SMCs, T-lymphocytes leads to the release of proinflammatory molecules, such as cytokines, and the onset of a chronic inflammatory response (Fig. 4). In inflammation, the transcription factor NF-kB is activated and increases the expression of multiple pro-inflammatory genes. PPARa and PPARg activation results in a negative cross-talk with inflammatory transcription factors, such as NF-kB, STAT-1 and AP-1, to block their downstream target genes (for review, see Ref. [6]). In human monocytes/macrophages, PPARg activators inhibit the activation of inflammatory cytokines, such as IL-1b, IL-6, IL-8, IL-10 and TNFa (for review, see Refs. [6,83]). In addition, PPARg activation induces the production of IL-1 receptor antagonist in THP-1 cells, providing a new anti-inflammatory action mechanism [88]. In macrophages, PG-J2 and thiazolidinediones (at high concentration) inhibit lipopolysaccharide (LPS) and IFNg-induced macrophage activation [47,89]. The anti-inflammatory activity of PPARg is also monitored by the downregulation of iNOS, COX2 and metalloproteinase 9 (MMP9) [47,90], three important actors of the inflammatory response. However, the most pronounced anti-inflammatory effects are observed with PG-J2, which is not selective for PPARg and acts also via PPAR-independent mechanisms [91,92]. Nevertheless, PPARg activation suppresses zinc finger transcription factor early growth response gene-1 (Egr-1) expression and, as such, inhibits expression of Egr-1-induced inflammatory target genes [93]. The interaction between activated PPARg and C/EBPd is another mechanism by which PPARg may downregulate the production of inflammatory cytokines [94]. Thus, PPARg ligands appear to exert anti-inflammatory activities via both PPARg dependent and independent mechanisms. Activated PPARa inhibits inflammatory response markers, such as ET-1, VCAM-1, IL-6, TF, MMP9, COX2 and iNOS in ECs, SMCs and macrophages [25,30,31,33,34,95– 99]. Zuckerman et al. [100] have recently shown that the synthesis of both NO and b-2 integrin CD11 induced by IFNg is inhibited in peritoneal macrophages from apoE deficient mice treated with a PPARa/g coagonist, thus leading to the inhibition of macrophage activation. The anti-inflammatory activities of PPARa and PPARg activators have been evidenced in humans. In patients with hyperlipidemia, fenofibrate treatment decreases circulating levels of IL-6 as well as fibrinogen and CRP, whose production is controlled by cytokines such as IL-1b and IL-6 [26,96]. PPARa activation reduces CRP expression in human umbilical vein ECs [26]. In addition, fibrates reduce nuclear CEBPb-p50NF-kB complex formation, which enhances hepatic CRP promoter activity in response to IL-1b [101]. Moreover, fenofibrate treatment of mice abrogates the acute phase-induced elevation of plasma serum amyloid A (SAA) [102]. Ex vivo, isolated aortas from PPARa deficient mice show an exacerbated response to LPS, as measured by IL-6 secretion, thus demonstrating a role for PPARa in the control of vascular inflammation [103]. Similarly, rosiglitazone treatment of patients with type 2 diabetes significantly reduces plasma levels of IL-6, CRP, MMP9, NF-kB and SAA [90,104]. Thus, adaptive immune and chronic inflammatory responses involved in the process of atherogenesis are inhibited by both PPARa and PPARg activation via direct and indirect mechanisms. The anti-inflammatory properties of PPARa and PPARg may contribute to their protective role against atherogenesis.

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5. Role of PPARs in plaque development and stability Formation of the fibrous plaque is due to SMC migration and proliferation in the intima. These cells secrete an extracellular matrix (ECM) and give rise to a fibrous cap. The role of PPARg in this stage of the atherosclerosis is well described. PPARg ligands inhibit the proliferation and the migration of vascular SMCs (VSMCs), a phenomenon that may be of particular relevance for restenosis prevention [105 – 107]. PPARg ligands inhibit migration of SMCs by inhibiting Ets-1 expression, a transcription factor required for matrix metalloprotease induction [108,109]. Inhibition of the ET-1 secretion, a potent inducer of SMC proliferation, by PPARa and PPARg agonists [33 –36,38] represents another way by which PPARa and PPARg interfere with proliferation of SMCs. In addition, IL-1b-induced expression of the platelet-derived growth factor-a receptor (PDGFaR) – PDGFa being a potent mitogen for VSMCs – is suppressed by PPARg activation via transrepression of CCAAT/enhancer-binding protein-dC/EBPd) [110]. Furthermore, PPARg inhibits the mitogenic induction of the cyclin-dependent kinase inhibitor p21 by modulating the protein kinase C delta (PKCd) pathway in VSMCs [111]. Moreover, PPARg ligands may inhibit angiotensin II-induced cell growth and hypertrophy in VSMCs by suppression of its receptor, the angiotensin II type 1 receptor (ATR1) [112, 113]. Recently, Abe et al. [114] have proposed another mechanism explaining the PPARgmediated growth inhibition of VSMCs through a GATA-6-dependent transcriptional mechanism. In addition, integrins play an important role in VSMC migration, and PPARa activation inhibits TGF-b-induced beta5 integrin expression [115]. Moreover, a PPARa/g coagonist inhibits the beta2 integrin CD11 induced by IFNg [100]. By contrast, PPARb/d induces post-confluent VSMC proliferation by increasing cyclinA and cyclin-dependent kinase CDK2, which are implicated in cell cycle regulation, as well as decreasing p57kip2, a kinase activity inhibitor [116]. Plaque rupture is the end-stage of the atherogenic process, leading to thrombus formation, occlusion and the clinical sequels of atherosclerosis. Plaque instability is partly due to the degradation of the ECM in the fibrous cap. PPARa and PPARg ligands inhibit gene expression [47], secretion and gelatinolytic activity [90,117,118] of MMP9, a matrix degrading protein secreted in response to inflammatory activation. In addition, PPARa agonists decrease expression of PAF receptor expression in macrophages [51,119]. PAF stimulates the secretion of elastase-type enzymes, which contribute to plaque stability and rupture. In addition, PPARg activators reduce osteopontin [120] and osteoprotegerin [121] gene expression, respectively, in macrophages and VSMCs, suggesting that PPARg could influence vascular calcification, since osteopontin and osteoprotegerin are described as inhibitors of arterial calcification [122,123]. Gemfibrozil, a PPARa agonist, significantly decreases vascular proteoglycan biosynthesis and glucosaminoglycan synthesis [124], two important components of the ECM. Neovascularisation is also an important process that influences plaque stability. Even though VEGF appears protective against EC injury in the early stages of atherosclerosis by protecting ECs against oxLDL toxicity [125], this protein may exert pro-atherogenic activities, since VEGF induces angiogenesis leading to plaque destabilization and rupture. PPARg induces VEGF production in VSMCs and macrophages, and thus may induce angiogenesis [126]. However, PPARg ligands have been shown to inhibit tumor

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angiogenesis [127]. Thus, the role of PPARg in angiogenesis remains to be clarified by further studies. Finally, plaque stability is also influenced by apoptosis of SMCs and macrophages [128 – 130]. Apoptosis occurring in atherosclerotic areas is potentially involved in necrotic core formation and plaque rupture, which may trigger atherothrombotic events (for review, see Ref. [131]). PPARa and PPARg control apoptosis via negative cross-talk with the anti-apoptotic NF-kB pathway in macrophages [132]. Rosiglitazone upregulates the expression of the tumor suppressor gene, phosphatase and tensin homolog (PTEN), which modulates, at least, cell survival and proliferation, in human macrophages via a PPRE in its promoter [133]. Furthermore, PG-J2 can also trigger the apoptosis of ECs via a PPARgdependent pathway [134]. The significance of apoptosis in atherosclerosis remains unclear. Although it has been proposed that apoptotic cell death contributes to plaque instability, rupture and thrombus formation, macrophage apoptosis also decreases inflammation of macrophage origin and avoids the destruction of ECM collagen, which maintains the elasticity of the plaque [135]. Thus, PPARs, and especially PPARg, appear to reduce fibrous plaque formation by inhibiting SMC migration and proliferation. However, the role of PPARs in plaque stability or rupture and their consequences on atherogenesis are less understood. 6. PPARs and thrombosis PPARs also modulate platelet aggregation. PPARg inhibits thromboxane synthase (TXS) expression by a mechanism involving protein– protein interaction between PPARg and the nuclear factor-E2-related factor 2 [136]. Moreover, the expression of the thromboxane receptor (TXR) is inhibited by PPARg activators via an interaction with Sp1 in VSMCs [137]. Thus, PPARg activation results in a decreased synthesis and action of thromboxane A2, a potent platelet aggregation inducer and vasoconstrictor. In addition, TF is a major factor in thrombus formation and blood coagulation. PPARa agonists inhibit TF expression in monocytes and macrophages [98,99]. Finally, glitazones and fibrates also modulate the secretion of the plasminogen activator inhibitor-1 (PAI-1) [138,139]. However, the exact mechanisms and effects are still unclear [139,140], and the role of PPAR in the regulation of PAI-1 and its consequences for atherothrombosis remain to be clarified. On the whole, PPARa and PPARg activation appears protective against atherothrombosis. 7. Anti-atherosclerotic effects of PPARs: results from in vivo studies Compelling evidence for a regulatory role for PPARs on atherogenesis in vivo comes from studies in animal models of atherosclerosis and human clinical trials. Various animals models presenting accelerated atherosclerosis have been developed to study the pathophysiology of the disease and/or the evaluation of potential therapeutic strategies (for review, see Ref. [141]). PPARg ligands have been shown to prevent the progression of atherosclerotic lesions, with a concomitant decrease of macrophage

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accumulation in the plaque of both apoE and LDL receptor deficient mice [17,23,24,142]. Glitazones act by reducing monocyte/macrophage homing to atherosclerotic plaques, by inhibiting fatty streak formation, improving glucose homeostasis and enhancing reverse cholesterol transport [143]. Since rosiglitazone treatment of apoE deficient mice rendered diabetic by a low dose of streptozotocin leads to higher lipid levels and similar glucose levels but less atherosclerosis [144], the anti-atherogenic effect of glitazones seems to be mediated by direct vascular actions. In the same way, treatment of apoE deficient mice with PPARa/g coagonist results in a reduction of atherosclerosis [100,142]. Moreover, fenofibrate also reduces lesion surface area in the aortic sinus of apoE deficient mice expressing a human apoAI transgene [77]. In addition, rosiglitazone treatment reduces myocardial infarction and limits postischemic injury in rats [145,146]. Moreover, protection against myocardial ischemic injury and improvement of endothelial vasodilatation by PPARa was demonstrated in mice [147]. However, surprisingly, PPARa deficiency in the apoE null background mice results in lowered atherosclerosis [148]. These double knockout mice are characterized by higher concentrations of atherogenic lipoproteins, but also higher insulin sensitivity, lower blood pressure and fewer intimal lesions. A wealth of clinical studies have revealed that fibrates improve the cardiovascular risk profile. Several angiographic intervention trials, including the Lipid Coronary Angiographic Trial (LOCAT), the Diabetes Atherosclerosis Intervention Study (DAIS) and the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT), have demonstrated beneficial effects of fibrates on atherosclerotic lesion progression [149 –151]. Furthermore, secondary prevention trials, such as the Veterans Administration-HDL-Cholesterol Intervention Trial (VA-HIT) [152] and the Helsinki Heart Study [153], demonstrated a decreased incidence of cardiovascular events following fibrate treatment. In patients with type 2 diabetes, who are characterized by moderate hypertriglyceridemia and low HDLcholesterol concentrations, fibrates decrease the incidence of myocardial infarction, as observed in the Mary’s Ealing, Northwick Park Diabetes (SENDCAP) study [154]. Moreover, adding fenofibrate to simvastatin increases significantly HDL cholesterol levels [155]. Thus, the development of combination drugs for atherosclerosis treatment appears to be a good way to increase their efficacy (for review, see Ref. [156]). Some studies have been performed testing the effects of glitazone treatment on cardiovascular risks in various diabetic and insulin-resistant patient populations [157,158]. Glitazone therapy lowers both fasting and post-prandial glucose levels and improves insulin-stimulated glucose disposal. However, the effect of glitazones on the plasma lipid profile in humans is controversial and intervention trials assessing the influence of these compounds on the incidence of cardiovascular disease are still lacking. In patients with type 2 diabetes, pioglitazone and rosiglitazone appear to have distinct effects on the plasma levels of triglycerides and LDL. While pioglitazone treatment lowers serum concentrations of LDL and triglycerides, rosiglitazone treatment has no effect on these parameters [157,159]. Although the mechanistic basis for these differences is unclear, the fact that pioglitazone has, albeit limited, PPARa activity may be one possible explanation [160]. Nevertheless, troglitazone treatment of patients with type 2 diabetes [161] resulted in a significant reduction of intima:media thickness (IMT).

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Running trials, such as the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) and PROACTIVE trials, will provide additional evidence for possible clinical cardiovascular benefits of both PPARa and PPARg agonists in the diabetic population. PPARa/g agonists are currently in phase 3 development for the treatment of patients with type 2 diabetes [162]. 8. Conclusion Considerable evidences indicate that PPARa and PPARg have beneficial effects in inflammatory diseases, including atherosclerosis. Although molecular mechanisms are not yet fully established and the complexity of these systems appears important, PPARs interfere at different steps of atherogenesis by blocking vascular cell recruitment, modulating foam cell formation, interfering with the inflammatory response and inhibiting fibrous plaque development. Their implication in plaque stability and atherothrombosis is less clear, and its understanding requires further studies. In conclusion, PPAR agonists represent pharmacological drugs with high potential. Combination treatment and development of coagonists appear to be promising future option for an optimal treatment of atherosclerosis. Acknowledgements Support by grants from ARC (Association pour la Recherche contre le Cancer) (to CD), the Fondation Lefoulon-Delalande, Institut de France (to OB), European Community (to GC) (grant QLRT-1999-01007), Fonds Europe´ens de De´veloppement Re´gional, Conseil Re´gional Re´gion Nord/Pas-de-Calais “Genopole Project 01360124” and Leducq Foundation (to B.S. and J.C.F.) is kindly acknowledged.

References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

Lusis, A.J., 2000. Nature 407, 233 –241. Torra, I.P., Chinetti, G., Duval, C., Fruchart, J.C., Staels, B., 2001. Curr. Opin. Lipidol. 12, 245–254. Willson, T.M., Lambert, M.H., Kliewer, S.A., 2001. Annu. Rev. Biochem. 70, 341–367. Barbier, O., Torra, I.P., Duguay, Y., Blanquart, C., Fruchart, J.C., Glineur, C., Staels, B., 2002. Arterioscler. Thromb. Vasc. Biol. 22, 717–726. Duval, C., Chinetti, G., Trottein, F., Fruchart, J.C., Staels, B., 2002. Trends. Mol. Med. 8, 422–430. Chinetti, G., Fruchart, J.C., Staels, B., 2000. Inflamm. Res. 49, 497 –505. Yang, X.Y., Wang, L.H., Chen, T., Hodge, D.R., Resau, J.H., DaSilva, L., Farrar, W.L., 2000. J. Biol. Chem. 275, 4541– 4544. Gervois, P., Vu-Dac, N., Kleemann, R., Kockx, M., Dubois, G., Laine, B., Kosykh, V., Fruchart, J.C., Kooistra, T., Staels, B., 2001. J. Biol. Chem. 276, 33471–33477. Fu, M., Zhang, J., Zhu, X., Myles, D.E., Willson, T.M., Liu, X., Chen, Y.E., 2001. J. Biol. Chem. 276, 45888–45894. Delerive, P., Furman, C., Teissier, E., Fruchart, J., Duriez, P., Staels, B., 2000. FEBS Lett. 471, 34–38. Davies, S.S., Pontsler, A.V., Marathe, G.K., Harrison, K.A., Murphy, R.C., Hinshaw, J.C., Prestwich, G.D., Hilaire, A.S., Prescott, S.M., Zimmerman, G.A., McIntyre, T.M., 2001. J. Biol. Chem. 276, 16015–16023.

556

C. Fontaine et al.

[12] Lehmann, J.M., Moore, L.B., Smith-Oliver, T.A., Wilkison, W.O., Willson, T.M., Kliewer, S.A., 1995. J. Biol. Chem. 270, 12953–12956. [13] Raji, A., Plutzky, J., 2002. Curr. Cardiol. Rep. 4, 514– 521. [14] Martens, F.M., Visseren, F.L., Lemay, J., de Koning, E.J., Rabelink, T.J., 2002. Drugs 62, 1463–1480. [15] Willson, T.M., Brown, P.J., Sternbach, D.D., Henke, B.R., 2000. J. Med. Chem. 43, 527– 550. [16] Brown, P.J., Stuart, L.W., Hurley, K.P., Lewis, M.C., Winegar, D.A., Wilson, J.G., Wilkison, W.O., Ittoop, O.R., Willson, T.M., 2001. Bioorg. Med. Chem. Lett. 11, 1225–1227. [17] Li, A.C., Brown, K.K., Silvestre, M.J., Willson, T.M., Palinski, W., Glass, C.K., 2000. J. Clin. Invest. 106, 523– 531. [18] Brown, K.K., Henke, B.R., Blanchard, S.G., Cobb, J.E., Mook, R., Kaldor, I., Kliewer, S.A., Lehmann, J.M., Lenhard, J.M., Harrington, W.W., Novak, P.J., Faison, W., Binz, J.G., Hashim, M.A., Oliver, W.O., Brown, H.R., Parks, D.J., Plunket, K.D., Tong, W.Q., Menius, J.A., Adkison, K., Noble, S.A., Willson, T.M., 1999. Diabetes 48, 1415– 1424. [19] Oliver, W.R. Jr., Shenk, J.L., Snaith, M.R., Russell, C.S., Plunket, K.D., Bodkin, N.L., Lewis, M.C., Winegar, D.A., Sznaidman, M.L., Lambert, M.H., Xu, H.E., Sternbach, D.D., Kliewer, S.A., Hansen, B.C., Willson, T.M., 2001. Proc. Natl Acad. Sci. USA 98, 5306–5311. [20] Murao, K., Imachi, H., Momoi, A., Sayo, Y., Hosokawa, H., Sato, M., Ishida, T., Takahara, J., 1999. FEBS Lett. 454, 27–30. [21] Ishibashi, M., Egashira, K., Hiasa, K., Inoue, S., Ni, W., Zhao, Q., Usui, M., Kitamoto, S., Ichiki, T., Takeshita, A., 2002. Hypertension 40, 687 –693. [22] Han, K.H., Quehenberger, O., 2000. Trends Cardiovasc. Med. 10, 209–216. [23] Pasceri, V., Wu, H.D., Willerson, J.T., Yeh, E.T., 2000. Circulation 101, 235 –238. [24] Collins, A.R., Meehan, W.P., Kintscher, U., Jackson, S., Wakino, S., Noh, G., Palinski, W., Hsueh, W.A., Law, R.E., 2001. Arterioscler. Thromb. Vasc. Biol. 21, 365–371. [25] Lee, H., Shi, W., Tontonoz, P., Wang, S., Subbanagounder, G., Hedrick, C.C., Hama, S., Borromeo, C., Evans, R.M., Berliner, J.A., Nagy, L., 2000. Circ. Res. 87, 516–521. [26] Pasceri, V., Cheng, J.S., Willerson, J.T., Yeh, E.T., Chang, J., 2001. Circulation 103, 2531–2534. [27] Marx, N., Mach, F., Sauty, A., Leung, J.H., Sarafi, M.N., Ransohoff, R.M., Libby, P., Plutzky, J., Luster, A.D., 2000. J. Immunol. 164, 6503– 6508. [28] Goetze, S., Bungenstock, A., Czupalla, C., Eilers, F., Stawowy, P., Kintscher, U., Spencer-Hansch, C., Graf, K., Nurnberg, B., Law, R.E., Fleck, E., Grafe, M., 2002. Hypertension 40, 748–754. [29] Goetze, S., Eilers, F., Bungenstock, A., Kintscher, U., Stawowy, P., Blaschke, F., Graf, K., Law, R.E., Fleck, E., Grafe, M., 2002. Biochem. Biophys. Res. Commun. 293, 1431– 1437. [30] Jackson, S.M., Parhami, F., Xi, X.P., Berliner, J.A., Hsueh, W.A., Law, R.E., Demer, L.L., 1999. Arterioscler. Thromb. Vasc. Biol. 19, 2094–2104. [31] Marx, N., Sukhova, G.K., Collins, T., Libby, P., Plutzky, J., 1999. Circulation 99, 3125–3131. [32] Chen, N.G., Han, X., 2001. Biochem. Biophys. Res. Commun. 282, 717–722. [33] Delerive, P., Martin-Nizard, F., Chinetti, G., Trottein, F., Fruchart, J.C., Najib, J., Duriez, P., Staels, B., 1999. Circ. Res. 85, 394 –402. [34] Satoh, H., Tsukamoto, K., Hashimoto, Y., Hashimoto, N., Togo, M., Hara, M., Maekawa, H., Isoo, N., Kimura, S., Watanabe, T., 1999. Biochem. Biophys. Res. Commun. 254, 757–763. [35] Martin-Nizard, F., Furman, C., Delerive, P., Kandoussi, A., Fruchart, J.C., Staels, B., Duriez, P., 2002. J. Cardiovasc. Pharmacol. 40, 822– 831. [36] Kandoussi, A., Martin, F., Hazzan, M., Noel, C., Fruchart, J.C., Staels, B., Duriez, P., 2002. Clin. Sci. (Lond.) 103(Suppl. 48), 81S–83S. [37] Agapitov, A.V., Haynes, W.G., 2002. J. Renin Angiotensin Aldosterone Syst. 3, 1–15. [38] Iglarz, M., Touyz, R.M., Amiri, F., Lavoie, M.F., Diep, Q.N., Schiffrin, E.L., 2003. Arterioscler. Thromb. Vasc. Biol. 23, 45–51. [39] Ogata, T., Miyauchi, T., Sakai, S., Irukayama-Tomobe, Y., Goto, K., Yamaguchi, I., 2002. Clin. Sci. (Lond.) 103(Suppl. 48), 284S– 288S. [40] Sakai, S., Miyauchi, T., Irukayama-Tomobe, Y., Ogata, T., Goto, K., Yamaguchi, I., 2002. Clin. Sci. (Lond.) 103(Suppl. 48), 16S–20S. [41] Itoh, H., Nakao, K., 2000. Nippon Rinsho 58(Suppl. 1), 214 –224.

PPARs and Atherosclerosis

557

[42] Parulkar, A.A., Pendergrass, M.L., Granda-Ayala, R., Lee, T.R., Fonseca, V.A., 2001. Ann. Intern. Med. 134, 61–71. [43] Russo, G., Leopold, J.A., Loscalzo, J., 2002. Vascul. Pharmacol. 38, 259–269. [44] Napoli, C., 2002. J. Card. Surg. 17, 355–362. [45] Calnek, D.S., Mazzella, L., Roser, S., Roman, J., Hart, C.M., 2003. Arterioscler. Thromb. Vasc. Biol. 23, 52 –57. [46] Colville-Nash, P.R., Qureshi, S.S., Willis, D., Willoughby, D.A., 1998. J. Immunol. 161, 978– 984. [47] Ricote, M., Li, A.C., Willson, T.M., Kelly, C.J., Glass, C.K., 1998. Nature 391, 79–82. [48] Inoue, I., Goto, S., Matsunaga, T., Nakajima, T., Awata, T., Hokari, S., Komoda, T., Katayama, S., 2001. Metabolism. 50, 3–11. [49] Fischer, B., von Knethen, A., Brune, B., 2002. J. Immunol. 168, 2828–2834. [50] Teissier, E., Chinetti, G., Staels, B., 2002. Circulation 106, II-261. [51] Hourton, D., Delerive, P., Stankova, J., Staels, B., Chapman, M.J., Ninio, E., 2001. Biochem. J. 354, 225 –232. [52] Li, L., Beauchamp, M.C., Renier, G., 2002. Atherosclerosis. 165, 101– 110. [53] Gbaguidi, F.G., Chinetti, G., Milosavljevic, D., Teissier, E., Chapman, J., Olivecrona, G., Fruchart, J.C., Griglio, S., Fruchart-Najib, J., Staels, B., 2002. FEBS Lett. 512, 85 –90. [54] Zimmermann, R., Panzenbock, U., Wintersperger, A., Levak-Frank, S., Graier, W., Glatter, O., Fritz, G., Kostner, G.M., Zechner, R., 2001. Diabetes. 50, 1643–1653. [55] Tontonoz, P., Nagy, L., Alvarez, J.G., Thomazy, V.A., Evans, R.M., 1998. Cell 93, 241 –252. [56] Fu, Y., Luo, N., Lopes-Virella, M.F., Garvey, W.T., 2002. Atherosclerosis 165, 259 –269. [57] Moore, K.J., Rosen, E.D., Fitzgerald, M.L., Randow, F., Andersson, L.P., Altshuler, D., Milstone, D.S., Mortensen, R.M., Spiegelman, B.M., Freeman, M.W., 2001. Nat. Med. 7, 41–47. [58] Chinetti, G., Lestavel, S., Bocher, V., Remaley, A.T., Neve, B., Torra, I.P., Teissier, E., Minnich, A., Jaye, M., Duverger, N., Brewer, H.B., Fruchart, J.C., Clavey, V., Staels, B., 2001. Nat. Med. 7, 53 –58. [59] Haraguchi, G., Kobayashi, Y., Brown, M.L., Tanaka, A., Isobe, M., Gianturco, S.H., Bradley, W.A., 2003. J. Lipid Res. 16, 16. [60] Vosper, H., Patel, L., Graham, T.L., Khoudoli, G.A., Hill, A., Macphee, C.H., Pinto, I., Smith, S.A., Suckling, K.E., Wolf, C.R., Palmer, C.N., 2001. J. Biol. Chem. 276, 44258–44265. [61] Chiba, Y., Ogita, T., Ando, K., Fujita, T., 2001. Biochem. Biophys. Res. Commun. 286, 541 –546. [62] Chinetti, G., Gbaguidi, F.G., Griglio, S., Mallat, Z., Antonucci, M., Poulain, P., Chapman, J., Fruchart, J.C., Tedgui, A., Najib-Fruchart, J., Staels, B., 2000. Circulation 101, 2411–2417. [63] Galetto, R., Albajar, M., Polanco, J.I., Zakin, M.M., Rodriguez-Rey, J.C., 2001. Biochem. J. 357, 521 –527. [64] Chinetti, G., Lestavel, S., Fruchart, J.C., Clavey, V., Staels, B., 2003. Circ. Res. 92, 212–217. [65] Argmann, C.A., Sawyez, C.G., McNeil, C.J., Hegele, R.A., Huff, M.W., 2003. Arterioscler. Thromb. Vasc. Biol. 23, 475 –482. [66] von Eckardstein, A., Nofer, J.R., Assmann, G., 2001. Arterioscler. Thromb. Vasc. Biol. 21, 13–27. [67] Nofer, J.R., Kehrel, B., Fobker, M., Levkau, B., Assmann, G., von Eckardstein, A., 2002. Atherosclerosis 161, 1–16. [68] Xie, Y., Yang, Q., DePierre, J.W., 2002. Ann. N. Y. Acad. Sci. 973, 17–25. [69] van Bilsen, M., van der Vusse, G.J., Gilde, A.J., Lindhout, M., van der Lee, K.A., 2002. Mol. Cell. Biochem. 239, 131 –138. [70] Michalik, L., Desvergne, B., Wahli, W., 2003. Curr. Opin. Lipidol. 14, 129–135. [71] Skogsberg, J., Kannisto, K., Cassel, T.N., Hamsten, A., Eriksson, P., Ehrenborg, E., 2003. Arterioscler. Thromb. Vasc. Biol. 27, 27. [72] Bouly, M., Masson, D., Gross, B., Jiang, X.C., Fievet, C., Castro, G., Tall, A.R., Fruchart, J.C., Staels, B., Lagrost, L., Luc, G., 2001. J. Biol. Chem. 276, 25841–25847. [73] Staels, B., van Tol, A., Skretting, G., Auwerx, J., 1992. J. Lipid Res. 33, 727–735. [74] Leibowitz, M.D., Fievet, C., Hennuyer, N., Peinado-Onsurbe, J., Duez, H., Bergera, J., Cullinan, C.A., Sparrow, C.P., Baffic, J., Berger, G.D., Santini, C., Marquis, R.W., Tolman, R.L., Smith, R.G., Moller, D.E., Auwerx, J., 2000. FEBS Lett. 473, 333–336.

558

C. Fontaine et al.

[75] Vu-Dac, N., Schoonjans, K., Laine, B., Fruchart, J.C., Auwerx, J., Staels, B., 1994. J. Biol. Chem. 269, 31012–31018. [76] Vu-Dac, N., Schoonjans, K., Kosykh, V., Dallongeville, J., Fruchart, J.C., Staels, B., Auwerx, J., 1995. J. Clin. Invest. 96, 741–750. [77] Duez, H., Chao, Y.S., Hernandez, M., Torpier, G., Poulain, P., Mundt, S., Mallat, Z., Teissier, E., Burton, C.A., Tedgui, A., Fruchart, J.C., Fievet, C., Wright, S.D., Staels, B., 2002. J. Biol. Chem. 277, 48051–48057. [78] Warden, C.H., Hedrick, C.C., Qiao, J.H., Castellani, L.W., Lusis, A.J., 1993. Science 261, 469 –472. [79] Tailleux, A., Bouly, M., Luc, G., Castro, G., Caillaud, J.M., Hennuyer, N., Poulain, P., Fruchart, J.C., Duverger, N., Fievet, C., 2000. Arterioscler. Thromb. Vasc. Biol. 20, 2453–2458. [80] Faveeuw, C., Fougeray, S., Angeli, V., Fontaine, J., Chinetti, G., Gosset, P., Delerive, P., Maliszewski, C., Capron, M., Staels, B., Moser, M., Trottein, F., 2000. FEBS Lett. 486, 261–266. [81] Gosset, P., Charbonnier, A.S., Delerive, P., Fontaine, J., Staels, B., Pestel, J., Tonnel, A.B., Trottein, F., 2001. Eur. J. Immunol. 31, 2857–2865. [82] Hornung, D., Chao, V.A., Vigne, J.L., Wallwiener, D., Taylor, R.N., 2003. Gynecol. Obstet. Invest. 55, 20– 24. [83] Marx, N., Kehrle, B., Kohlhammer, K., Grub, M., Koenig, W., Hombach, V., Libby, P., Plutzky, J., 2002. Circ. Res. 90, 703–710. [84] Kwak, B.R., Myit, S., Mulhaupt, F., Veillard, N., Rufer, N., Roosnek, E., Mach, F., 2002. Circ. Res. 90, 356– 362. [85] Harris, S.G., Phipps, R.P., 2001. Eur. J. Immunol. 31, 1098–1105. [86] Jones, D.C., Ding, X., Daynes, R.A., 2002. J. Biol. Chem. 277, 6838–6845. [87] Yang, Q., Xie, Y., Alexson, S.E., Nelson, B.D., DePierre, J.W., 2002. Biochem. Pharmacol. 63, 1893–1900. [88] Meier, C.A., Chicheportiche, R., Juge-Aubry, C.E., Dreyer, M.G., Dayer, J.M., 2002. Cytokine 18, 320– 328. [89] Jiang, C., Ting, A.T., Seed, B., 1998. Nature 391, 82–86. [90] Marx, N., Froehlich, J., Siam, L., Ittner, J., Wierse, G., Schmidt, A., Scharnagl, H., Hombach, V., Koenig, W., 2003. Arterioscler. Thromb. Vasc. Biol. 23, 283 –288. [91] Hinz, B., Brune, K., Pahl, A., 2003. Biochem. Biophys. Res. Commun. 302, 415–420. [92] Park, E.J., Park, S.Y., Joe, E.H., Jou, I., 2003. J. Biol. Chem. 12, 12. [93] Okada, M., Yan, S.F., Pinsky, D.J., 2002. FASEB J. 16, 1861–1868. [94] Takata, Y., Kitami, Y., Yang, Z.H., Nakamura, M., Okura, T., Hiwada, K., 2002. Circ. Res. 91, 427– 433. [95] Xu, X., Otsuki, M., Saito, H., Sumitani, S., Yamamoto, H., Asanuma, N., Kouhara, H., Kasayama, S., 2001. Endocrinology 142, 3332–3339. [96] Staels, B., Koenig, W., Habib, A., Merval, R., Lebret, M., Torra, I.P., Delerive, P., Fadel, A., Chinetti, G., Fruchart, J.C., Najib, J., Maclouf, J., Tedgui, A., 1998. Nature 393, 790 –793. [97] Delerive, P., Gervois, P., Fruchart, J.C., Staels, B., 2000. J. Biol. Chem. 275, 36703–36707. [98] Marx, N., Mackman, N., Schonbeck, U., Yilmaz, N., Hombach, V.V., Libby, P., Plutzky, J., 2001. Circulation 103, 213–219. [99] Neve, B.P., Corseaux, D., Chinetti, G., Zawadzki, C., Fruchart, J.C., Duriez, P., Staels, B., Jude, B., 2001. Circulation 103, 207–212. [100] Zuckerman, S.H., Kauffman, R.F., Evans, G.F., 2002. Lipids 37, 487–494. [101] Kleemann, R., Gervois, P.P., Verschuren, L., Staels, B., Princen, H.M., Kooistra, T., 2003. Blood 101, 545– 551. [102] Yamazaki, K., Kuromitsu, J., Tanaka, I., 2002. Biochem. Biophys. Res. Commun. 290, 1114–1122. [103] Delerive, P., De Bosscher, K., Besnard, S., Vanden Berghe, W., Peters, J.M., Gonzalez, F.J., Fruchart, J.C., Tedgui, A., Haegeman, G., Staels, B., 1999. J. Biol. Chem. 274, 32048–32054. [104] Fuell DL, F.M., Greenberg, A.S., Haffner, S., Chen, H., 2001. Diabetes 50, A435. [105] Marx, N., Schonbeck, U., Lazar, M.A., Libby, P., Plutzky, J., 1998. Circ. Res. 83, 1097–1103. [106] Law, R.E., Goetze, S., Xi, X.P., Jackson, S., Kawano, Y., Demer, L., Fishbein, M.C., Meehan, W.P., Hsueh, W.A., 2000. Circulation 101, 1311– 1318.

PPARs and Atherosclerosis

559

[107] de Dios, S.T., Hannan, K.M., Dilley, R.J., Hill, M.A., Little, P.J., 2001. J. Diabetes Complications 15, 120 –127. [108] Goetze, S., Kim, S., Xi, X.P., Graf, K., Yang, D.C., Fleck, E., Meehan, W.P., Hsueh, W.A., Law, R.E., 2000. J. Cardiovasc. Pharmacol. 35, 749–757. [109] Goetze, S., Kintscher, U., Kim, S., Meehan, W.P., Kaneshiro, K., Collins, A.R., Fleck, E., Hsueh, W.A., Law, R.E., 2001. J. Cardiovasc. Pharmacol. 38, 909–921. [110] Takata, Y., Kitami, Y., Okura, T., Hiwada, K., 2001. J. Biol. Chem. 276, 12893–12897. [111] Wakino, S., Kintscher, U., Liu, Z., Kim, S., Yin, F., Ohba, M., Kuroki, T., Schonthal, A.H., Hsueh, W.A., Law, R.E., 2001. J. Biol. Chem. 276, 47650–47657. [112] Takeda, K., Ichiki, T., Tokunou, T., Funakoshi, Y., Iino, N., Hirano, K., Kanaide, H., Takeshita, A., 2000. Circulation 102, 1834–1839. [113] Sugawara, A., Takeuchi, K., Uruno, A., Ikeda, Y., Arima, S., Sato, K., Kudo, M., Taniyama, Y., Ito, S., 2001. Hypertens. Res. 24, 229–233. [114] Abe, M., Hasegawa, K., Wada, H., Morimoto, T., Yanazume, T., Kawamura, T., Hirai, M., Furukawa, Y., Kita, T., 2003. Arterioscler. Thromb. Vasc. Biol. 23, 404 –410. [115] Kintscher, U., Lyon, C., Wakino, S., Bruemmer, D., Feng, X., Goetze, S., Graf, K., Moustakas, A., Staels, B., Fleck, E., Hsueh, W.A., Law, R.E., 2002. Circ. Res. 91, e35–e44. [116] Zhang, J., Fu, M., Zhu, X., Xiao, Y., Mou, Y., Zheng, H., Akinbami, M.A., Wang, Q., Chen, Y.E., 2002. J. Biol. Chem. 277, 11505–11512. [117] Shu, H., Wong, B., Zhou, G., Li, Y., Berger, J., Woods, J.W., Wright, S.D., Cai, T.Q., 2000. Biochem. Biophys. Res. Commun. 267, 345–349. [118] Marx, N., Sukhova, G., Murphy, C., Libby, P., Plutzky, J., 1998. Am. J. Pathol. 153, 17– 23. [119] Hourton, D., Stengel, D., Chapman, M.J., Ninio, E., 2001. Eur. J. Biochem. 268, 4489– 4496. [120] Oyama, Y., Kurabayashi, M., Akuzawa, N., Nagai, R., 2000. J. Atheroscler. Thromb. 7, 77–82. [121] Fu, M., Zhang, J., Lin Yg, Y., Zhu, X., Willson, T.M., Chen, Y.E., 2002. Biochem. Biophys. Res. Commun. 294, 597–601. [122] Browner, W.S., Lui, L.Y., Cummings, S.R., 2001. J. Clin. Endocrinol. Metab. 86, 631–637. [123] Speer, M.Y., McKee, M.D., Guldberg, R.E., Liaw, L., Yang, H.Y., Tung, E., Karsenty, G., Giachelli, C.M., 2002. J. Exp. Med. 196, 1047–1055. [124] Nigro, J., Dilley, R.J., Little, P.J., 2002. Atherosclerosis 162, 119–129. [125] Kuzuya, M., Ramos, M.A., Kanda, S., Koike, T., Asai, T., Maeda, K., Shitara, K., Shibuya, M., Iguchi, A., 2001. Arterioscler. Thromb. Vasc. Biol. 21, 765 –770. [126] Jozkowicz, A., Dulak, J., Piatkowska, E., Placha, W., Dembinska-Kiec, A., 2000. Acta Biochim. Pol. 47, 1147–1157. [127] Panigrahy, D., Singer, S., Shen, L.Q., Butterfield, C.E., Freedman, D.A., Chen, E.J., Moses, M.A., Kilroy, S., Duensing, S., Fletcher, C., Fletcher, J.A., Hlatky, L., Hahnfeldt, P., Folkman, J., Kaipainen, A., 2002. J. Clin. Invest. 110, 923– 932. [128] Kockx, M.M., De Meyer, G.R., Muhring, J., Jacob, W., Bult, H., Herman, A.G., 1998. Circulation 97, 2307–2315. [129] Roberts, R.A., Chevalier, S., Hasmall, S.C., James, N.H., Cosulich, S.C., Macdonald, N., 2002. Toxicology 181–182, 167–170. [130] Boitier, E., Gautier, J.C., Roberts, R., 2003. Comp. Hepatol. 2, 3. [131] Geng, Y.J., Libby, P., 2002. Arterioscler. Thromb. Vasc. Biol. 22, 1370–1380. [132] Chinetti, G., Griglio, S., Antonucci, M., Torra, I.P., Delerive, P., Majd, Z., Fruchart, J.C., Chapman, J., Najib, J., Staels, B., 1998. J. Biol. Chem. 273, 25573–25580. [133] Patel, L., Pass, I., Coxon, P., Downes, C.P., Smith, S.A., Macphee, C.H., 2001. Curr. Biol. 11, 764 –768. [134] Bishop-Bailey, D., Hla, T., 1999. J. Biol. Chem. 274, 17042–17048. [135] Martinet, W., Kockx, M.M., 2001. Curr. Opin. Lipidol. 12, 535–541. [136] Ikeda, Y., Sugawara, A., Taniyama, Y., Uruno, A., Igarashi, K., Arima, S., Ito, S., Takeuchi, K., 2000. J. Biol. Chem. 275, 33142–33150. [137] Sugawara, A., Uruno, A., Kudo, M., Ikeda, Y., Sato, K., Taniyama, Y., Ito, S., Takeuchi, K., 2002. J. Biol. Chem. 277, 9676– 9683.

560

C. Fontaine et al.

[138] Durrington, P.N., Mackness, M.I., Bhatnagar, D., Julier, K., Prais, H., Arrol, S., Morgan, J., Wood, G.N., 1998. Atherosclerosis 138, 217–225. [139] Kato, K., Satoh, H., Endo, Y., Yamada, D., Midorikawa, S., Sato, W., Mizuno, K., Fujita, T., Tsukamoto, K., Watanabe, T., 1999. Biochem. Biophys. Res. Commun. 258, 431–435. [140] Marx, N., Bourcier, T., Sukhova, G.K., Libby, P., Plutzky, J., 1999. Arterioscler. Thromb. Vasc. Biol. 19, 546– 551. [141] Mehta, D., Angelini, G.D., Bryan, A.J., 1996. Int. J. Cardiol. 56, 235– 257. [142] Claudel, T., Leibowitz, M.D., Fievet, C., Tailleux, A., Wagner, B., Repa, J.J., Torpier, G., Lobaccaro, J.M., Paterniti, J.R., Mangelsdorf, D.J., Heyman, R.A., Auwerx, J., 2001. Proc. Natl Acad. Sci. USA 98, 2610–2615. [143] Chen, Z., Ishibashi, S., Perrey, S., Osuga, J., Gotoda, T., Kitamine, T., Tamura, Y., Okazaki, H., Yahagi, N., Iizuka, Y., Shionoiri, F., Ohashi, K., Harada, K., Shimano, H., Nagai, R., Yamada, N., 2001. Arterioscler. Thromb. Vasc. Biol. 21, 372–377. [144] Levi, Z., Shaish, A., Yacov, N., Levkovitz, H., Trestman, S., Gerber, Y., Cohen, H., Dvir, A., Rhachmani, R., Ravid, M., Harats, D., 2003. Diabetes Obes. Metab. 5, 45–50. [145] Yue Tl, T.L., Chen, J., Bao, W., Narayanan, P.K., Bril, A., Jiang, W., Lysko, P.G., Gu, J.L., Boyce, R., Zimmerman, D.M., Hart, T.K., Buckingham, R.E., Ohlstein, E.H., 2001. Circulation 104, 2588–2594. [146] Khandoudi, N., Delerive, P., Berrebi-Bertrand, I., Buckingham, R.E., Staels, B., Bril, A., 2002. Diabetes 51, 1507–1514. [147] Tabernero, A., Schoonjans, K., Jesel, L., Carpusca, I., Auwerx, J., Andriantsitohaina, R., 2002. BMC Pharmacol. 2, 10. [148] Tordjman, K., Bernal-Mizrachi, C., Zemany, L., Weng, S., Feng, C., Zhang, F., Leone, T.C., Coleman, T., Kelly, D.P., Semenkovich, C.F., 2001. J. Clin. Invest. 107, 1025–1034. [149] Steiner, G., 1996. Diabetologia 39, 1655–1661. [150] Ericsson, C.G., Hamsten, A., Nilsson, J., Grip, L., Svane, B., de Faire, U., 1996. Lancet 347, 849–853. [151] Frick, M.H., Syvanne, M., Nieminen, M.S., Kauma, H., Majahalme, S., Virtanen, V., Kesaniemi, Y.A., Pasternack, A., Taskinen, M.R., 1997. Circulation 96, 2137–2143. [152] Rubins, H.B., Robins, S.J., Collins, D., Fye, C.L., Anderson, J.W., Elam, M.B., Faas, F.H., Linares, E., Schaefer, E.J., Schectman, G., Wilt, T.J., Wittes, J., 1999. N. Engl. J. Med. 341, 410–418. [153] Frick, M.H., Elo, O., Haapa, K., Heinonen, O.P., Heinsalmi, P., Helo, P., Huttunen, J.K., Kaitaniemi, P., Koskinen, P., Manninen, V., Ma¨enpa¨a¨, H., Ma¨lko¨nen, M., Ma¨ntta¨ri, M., Norola, S., Pasternack, A., Pikkarainen, J., Romo, M., Jjo¨blom, T., Nikkila¨, E.A., 1987. Helsinki Heart Study: primary-prevention trial with gemfibrozil in middle-aged men with dyslipidemia. Safety of treatment, changes in risk factors, and incidence of coronary heart disease. N. Engl. J. Med. 317, 1237–1245. [154] Elkeles, R.S., Diamond, J.R., Poulter, C., Dhanjil, S., Nicolaides, A.N., Mahmood, S., Richmond, W., Mather, H., Sharp, P., Feher, M.D., 1998. Diabetes Care 21, 641–648. [155] Vega, G.L., Ma, P.T., Cater, N.B., Filipchuk, N., Meguro, S., Garcia-Garcia, A.B., Grundy, S.M., 2003. Am. J. Cardiol. 91, 956 –960. [156] Black, D.M., 2003. Curr. Atheroscler. Rep. 5, 29–32. [157] Kipnes, M.S., Krosnick, A., Rendell, M.S., Egan, J.W., Mathisen, A.L., Schneider, R.L., 2001. Am. J. Med. 111, 10–17. [158] Kaplan, F., Al-Majali, K., Betteridge, D.J., 2001. J. Cardiovasc. Risk 8, 211 –217. [159] Gegick, C.G., Altheimer, M.D., 2001. Endocr. Pract. 7, 162–169. [160] Smith, U., 2001. Int. J. Clin. Pract. Suppl., 121, 13 –18. [161] Minamikawa, J., Tanaka, S., Yamauchi, M., Inoue, D., Koshiyama, H., 1998. J. Clin. Endocrinol. Metab. 83, 1818–1820. [162] Ebdrup, S., Pettersson, I., Rasmussen, H.B., Deussen, H.J., Frost Jensen, A., Mortensen, S.B., Fleckner, J., Pridal, L., Nygaard, L., Sauerberg, P., 2003. J. Med. Chem. 46, 1306–1317.