PPARgamma activation primes human monocytes into alternative M2 macrophages with anti-inflammatory properties.

Th1 cytokines promote monocyte differentiation into proatherogenic M1 macrophages, while Th2 cytokines lead to an "alternative" anti-inflammatory M2 macrophage phenotype. Here we show that in human atherosclerotic lesions, the expression of M2 markers and PPARgamma, a nuclear receptor controlling macrophage inflammation, correlate positively. Moreover, PPARgamma activation primes primary human monocytes into M2 differentiation, resulting in a more pronounced anti-inflammatory activity in M1 macrophages. However, PPARgamma activation does not influence M2 marker expression in resting or M1 macrophages, nor does PPARgamma agonist treatment influence the expression of M2 markers in atherosclerotic lesions, indicating that only native monocytes can be primed by PPARgamma activation to an enhanced M2 phenotype. Furthermore, PPARgamma activation significantly increases expression of the M2 marker MR in circulating peripheral blood mononuclear cells. These data demonstrate that PPARgamma activation skews human monocytes toward an anti-inflammatory M2 phenotype.

TReP-132 is a novel progesterone receptor coactivator required for the inhibition of breast cancer cell growth and enhancement of differentiation by progesterone.

The sex steroid progesterone is essential for the proliferation and differentiation of the mammary gland epithelium during pregnancy. In relation to this, in vitro studies using breast carcinoma T47D cells have demonstrated a biphasic progesterone response, consisting of an initial proliferative burst followed by a sustained growth arrest. However, the transcriptional factors acting with the progesterone receptor (PR) to mediate the progesterone effects on mammary cell growth and differentiation remain to be determined. Recently, it has been demonstrated that the transcriptional regulating protein of 132 kDa (TReP-132), initially identified as a regulator of steroidogenesis, is also a cell growth suppressor. Similar to progesterone-bound PR, TReP-132 acts by inducing the gene expression of the G1 cyclin-dependent kinase inhibitors p21WAF1/Cip1 (p21) and p27Kip1 (p27). The putative interaction between TReP-132 and progesterone pathways in mammary cells was therefore analyzed in the present study. Our results show that TReP-132 interacts in vitro and in T47D cells with progesterone-activated PR. TReP-132 synergizes with progesterone-bound PR to trans activate the p21 and p27 gene promoters at proximal Sp1-binding sites. Moreover, TReP-132 overexpression and knockdown, respectively, increased or prevented the induction of p21 and p27 gene expression by progesterone. As a consequence, TReP-132 knockdown also resulted in the loss of the inhibitory effects of progesterone on pRB phosphorylation, G1/S cell cycle progression, and cell proliferation. Furthermore, the knockdown of TReP-132 expression also prevented the induction of both early and terminal markers of breast cell differentiation which had been previously identified as progesterone target genes. As well, the progesterone-induced accumulation of lipid vacuoles was inhibited in the TReP-132-depleted cells. Finally, TReP-132 gene expression levels increased following progesterone treatment, indicating the existence of a positive auto-regulatory loop between PR and TReP-132. Taken together, these data identify TReP-132 as a coactivator of PR mediating the growth-inhibitory and differentiation effects of progesterone on breast cancer cells.

PPAR alpha inhibits vascular smooth muscle cell proliferation underlying intimal hyperplasia by inducing the tumor suppressor p16INK4a.

Vascular SMC proliferation is a crucial event in occlusive cardiovascular diseases. PPARalpha is a nuclear receptor controlling lipid metabolism and inflammation, but its role in the regulation of SMC growth remains to be established. Here, we show that PPARalpha controls SMC cell-cycle progression at the G1/S transition by targeting the cyclin-dependent kinase inhibitor and tumor suppressor p16(INK4a) (p16), resulting in an inhibition of retinoblastoma protein phosphorylation. PPARalpha activates p16 gene transcription by both binding to a canonical PPAR-response element and interacting with the transcription factor Sp1 at specific proximal Sp1-binding sites of the p16 promoter. In a carotid arterial-injury mouse model, p16 deficiency results in an enhanced SMC proliferation underlying intimal hyperplasia. Moreover, PPARalpha activation inhibits SMC growth in vivo, and this effect requires p16 expression. These results identify an unexpected role for p16 in SMC cell-cycle control and demonstrate that PPARalpha inhibits SMC proliferation through p16. Thus, the PPARalpha/p16 pathway may be a potential pharmacological target for the prevention of cardiovascular occlusive complications of atherosclerosis.

Peroxisome proliferator-activated receptor alpha improves pancreatic adaptation to insulin resistance in obese mice and reduces lipotoxicity in human islets.

Peroxisome proliferator-activated receptor (PPAR) alpha is a transcription factor controlling lipid and glucose homeostasis. PPARalpha-deficient (-/-) mice are protected from high-fat diet-induced insulin resistance. However, the impact of PPARalpha in the pathophysiological setting of obesity-related insulin resistance is unknown. Therefore, PPARalpha(-/-) mice in an obese (ob/ob) background were generated. PPARalpha deficiency did not influence the growth curves of the obese mice but surprisingly resulted in a severe, age-dependent hyperglycemia. PPARalpha deficiency did not aggravate peripheral insulin resistance. By contrast, PPARalpha(-/-) ob/ob mice developed pancreatic beta-cell dysfunction characterized by reduced mean islet area and decreased insulin secretion in response to glucose in vitro and in vivo. In primary human pancreatic islets, PPARalpha agonist treatment prevented fatty acid-induced impairment of glucose-stimulated insulin secretion, apoptosis, and triglyceride accumulation. These results indicate that PPARalpha improves the adaptative response of the pancreatic beta-cell to pathological conditions. PPARalpha could thus represent a promising target in the prevention of type 2 diabetes.

The RXR agonist bexarotene improves cholesterol homeostasis and inhibits atherosclerosis progression in a mouse model of mixed dyslipidemia.

OBJECTIVE: The activity of the antitumoral agent bexarotene (Targretin, Bexarotene) depends on its binding to the nuclear retinoid-X receptor (RXR) and subsequent transcriptional regulation of target genes. Through RXR activation, bexarotene may modulate numerous metabolic pathways involved in atherosclerosis. Here, we investigated the effect of bexarotene on atherosclerosis progression in a dyslipidemic murine model, the human apolipoprotein E2 knockin mouse, that develops essentially macrophage-laden lesions. METHODS AND RESULTS: Atherosclerotic lesions together with different metabolic pathways involved in atherosclerosis were investigated in mice treated or not with bexarotene. Bexarotene protects from atherosclerosis development in mice, at least in part by improving the circulating cholesterol distribution profile likely via a marked decrease of dietary cholesterol absorption caused by modulation of intestinal expression of genes recently identified as major players in this process, Niemann-Pick-C1-Like1 (NPC1L1) and CD13. This atheroprotection appears despite a strong hypertriglyceridemia. Moreover, bexarotene treatment only modestly modulates inflammatory gene expression in the vascular wall, but markedly enhanced the capacity of macrophages to efflux cellular lipids. CONCLUSIONS: These data provide evidence of a favorable pharmacological effect of bexarotene on atherosclerosis despite the induction of hypertriglyceridemia, likely via a beneficial action on intestinal absorption and macrophage efflux.

PPARalpha, but not PPARgamma, activators decrease macrophage-laden atherosclerotic lesions in a nondiabetic mouse model of mixed dyslipidemia.

OBJECTIVE: Peroxisome proliferator-activated receptor (PPAR) alpha and gamma are nuclear receptors that may modulate atherogenesis, not only by correcting metabolic disorders predisposing to atherosclerosis but also by directly acting at the level of the vascular wall. The accumulation of lipid-laden macrophages in the arterial wall is an early pivotal event participating in the initiation and promotion of atherosclerotic lesion formation. Because PPARalpha and gamma modulate macrophage gene expression and cellular function, it has been suggested that their ligands may modulate atherosclerosis development via direct effects on macrophages. In this report, we investigated the effect of a PPARalpha ligand (fenofibrate) and 2 PPARgamma ligands (rosiglitazone and pioglitazone) on atherogenesis in a dyslipidemic nondiabetic murine model that develops essentially macrophage-laden lesions. METHODS AND RESULTS: Mice were fed a Western diet supplemented or not with fenofibrate (100 mpk), rosiglitazone (10 mpk), or pioglitazone (40 mpk) for 10 weeks. Atherosclerotic lesions together with metabolic parameters were measured after treatment. Fenofibrate treatment significantly improved lipoprotein metabolism toward a less atherogenic phenotype but did not affect insulin sensitivity. Contrarily, rosiglitazone and pioglitazone improved glucose homeostasis, whereas they did not improve lipoprotein metabolism. Fenofibrate treatment significantly decreased the accumulation of lipids and macrophages in the aortic sinus. However, surprisingly, neither rosiglitazone nor pioglitazone had an effect on lesion lipid accumulation or macrophage content. CONCLUSIONS: These results indicate that in a dyslipidemic nondiabetic murine model, PPARalpha, but not PPARgamma, activators protect against macrophage foam cell formation.

SR-BI does not require raft/caveola localisation for cholesteryl ester selective uptake in the human adrenal cell line NCI-H295R.

Class B type I scavenger receptor (SR-BI) mediates the selective uptake of high-density lipoprotein (HDL)-derived cholesteryl esters (HDL-CE) in steroidogenic cells and hepatocytes. SR-BI is enriched in the caveolae of some cell types, genetically modified or not, and these domains have already been shown to constitute primary acceptors for HDL-CE. Nevertheless, the fate of caveola-free cell types has not yet been discussed.NCI-H295R, a human adrenal cell line, highly active in HDL-CE uptake via SR-BI, does not display any morphologically defined caveolae and expresses caveolin at a very low level. Using two different fractionation protocols, we have shown, in this cell type, that SR-BI is homogeneously distributed along the plasma membrane and consists principally of a non-raft membrane-associated pool. Raft destabilisation and caveolin-1 displacement from plasma membrane did not modify the SR-BI-mediated HDL-CE selective uptake. Moreover, the induction of SR-BI expression that is associated with increased CE selective uptake was not associated with any modification in caveolin-1 expression or any raft-targeting mechanism of SR-BI in NCI-H295R. In conclusion, we provide evidence that SR-BI does not require raft/caveola localisation to be implicated in CE selective uptake either in basal or in induced conditions.

Human free apolipoprotein A-I and artificial pre-beta-high-density lipoprotein inhibit eNOS activity and NO release.

Little is known about the effects of human free apolipoprotein A-I (Free-Apo A-I) and pre-beta-high density lipoprotein (pre-beta-HDL) on the endothelium function. In this study, we have investigated the effects of Free-Apo A-I and artificial pre-beta-HDL on endothelial NO synthase (eNOS) activity and on NO production by endothelial cells. Free-Apo A-I drastically inhibited NO production in human umbilical cord vein endothelial cells (HUVECs) and eNOS activity in bovine aortic endothelial cells (BAECs). Pre-beta-HDL and serum from human apolipoprotein A-I transgenic rabbits inhibited eNOS activity in BAECs but HDL3 did not. Free-Apo A-I displaced eNOS from BAEC plasma membrane towards intracellular pools without affecting eNOS activity and eNOS mass in BAEC crude homogenates. Free-Apo A-I and HDL3 did not decrease either caveolin bound to BAEC plasma membrane or caveola cholesterol content. As previously described, we showed that HDL3 directly induced endothelium-dependent relaxation of rings from rat aorta. We observed that pre-beta-HDL significantly decreased endothelium-dependent relaxation of rat aortic rings ex vivo.

Tissue factor pathway inhibitor-2 gene methylation is associated with low expression in carotid atherosclerotic plaques.

BACKGROUND: The tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine-protease inhibitor which is expressed in atherosclerotic plaques. Epigenetic regulation of the TFPI-2 gene, through methylation of CpG islands, has been advocated in cancer. We hypothesized that TFPI-2 gene methylation could regulate TFPI-2 expression in atherosclerosis. METHODS: We used Methylation Specific PCR (MSP) and pyrosequencing in order to identify 18 CpG of the TFPI-2 promoter, in 59 carotid atherosclerotic plaques and 26 control mammary arteries. RESULTS: MSP showed methylation of the TFPI-2 gene (MSP+) in 16 plaques (27%), while no methylation (MSP-) was found in control arteries. Pyrosequencing confirmed that MSP+ plaques presented higher methylation levels than MSP- ones and arteries (p=0.03 and 0.01). Moreover, the TFPI-2 mRNA levels were lower in methylated plaques than in unmethylated ones and than in arteries (p=0.04 and <0.0001). The methylated plaques contained less lipids and macrophage infiltration than unmethylated ones. Their TFPI-2 immunoreactivity was mainly detected in the macrophages located in the media on the adventitial side, rather than in the lipid-rich core. CONCLUSION: Methylation of the TFPI-2 gene takes place in atherosclerotic plaques and is associated with decreased TFPI-2 expression. The place of this process in atherosclerosis progression remains to be investigated.

Physiological pathway for low-density lipoproteins across the blood-brain barrier: transcytosis through brain capillary endothelial cells in vitro.

Although an immense knowledge has accumulated concerning regulation of cholesterol homeostasis in the body, this does not include the brain, where details are just emerging. Using an in vitro blood-brain barrier model, the authors have demonstrated that low-density lipoprotein (LDL) underwent transcytosis through the endothelial cells (ECs) by a receptor-mediated process, bypassing the lysosomal compartment. Moreover, caveolae might be involved in these blood-borne molecule transports from the blood to the brain. Although several ligands are known to be internalized through cell surface caveolae, the subsequent intracellular pathways have remained elusive. By cell fractionation experiment and Western blot, the authors have demonstrated that the LDL receptor is located in the caveolae membrane fraction. Then, LDLs internalized were detected by electron microscopy in multivesicular bodies. The authors identified in brain capillary ECs a novel endosomal compartment, mildly acidic, positive for marker Lamp-1 but devoid of any degradative capability. From the point of view of pH, cellular location, and caveolae-derived formation, the multivesicular organelles described here can be related to the caveosome structure. These results could provide clues to physiological functions of caveolae-caveosome transcellular pathway in brain capillary ECs and may help in the rational design of more effective therapeutic drugs to the brain.

The PPARalpha activator fenofibrate slows down the progression of the left ventricular dysfunction in porcine tachycardia-induced cardiomyopathy.

It has been reported that high intramyocardial peroxisome proliferator-activated receptor alpha (PPARalpha) stimulation or overexpression altered cardiac contractile function in mouse models of cardiac hypertrophy and heart failure. Nevertheless, it has never been demonstrated that clinically relevant doses of drugs stimulating PPARalpha activity such as fenofibrate increase the risk to develop heart failure in humans. To determine if fenofibrate accelerates the development of heart failure in large mammals, we have tested its effects on the progression of left ventricular dysfunction in pacing-induced heart failure in pigs. Fenofibrate treatment blunted reduction in left ventricular ejection fraction, reduced cardiac hypertrophy, and attenuated clinical signs of heart failure. Fenofibrate impeded the increase in atrial natriuretic peptide, brain natriuretic peptide, and endothelin-1 plasma levels. The expression of PPARalpha, fatty acyl-CoA-oxidase, and carnitine palmitoyltransferase-Ibeta was reduced at mRNA levels in the left ventricle from untreated heart failure pigs but maintained near normal values with fenofibrate. Fenofibrate prevented heart failure-induced overexpression of TNFalpha mRNA and enhanced catalase activity in left ventricle compared to placebo. These data suggest that a clinically relevant dose of fenofibrate does not accelerate but slows down heart failure development in the model of pacing-induced heart failure in large mammals.

Dyslipidemia shifts the tissue factor/tissue factor pathway inhibitor balance toward increased thrombogenicity in atherosclerotic plaques: evidence for a corrective effect of statins.

BACKGROUND: Tissue factor (TF) is a key mediator of atherosclerotic plaque thrombogenicity and may be regulated by plaque TF pathway inhibitor (TFPI). High atherogenic lipoproteins are a well-known arterial risk factor, but their effects on the TF/TFPI balance in atherosclerotic plaques, as well as those of widely used lipid-lowering agents such as statins, are incompletely understood. OBJECTIVES: We analyzed the TF/TFPI balance in carotid plaques from 86 patients, according to the presence of dyslipidemia and statin therapy. RESULTS: In patients with untreated dyslipidemia (ApoB/ApoA1 ratio >0.7) (D+) (n=44), TF antigen (TF) tended to be higher than in those without dyslipidemia (D-) (n=16). In patients with statins (S+) (n=26), TF was lower than in D+ (p=0.02) and similar to that of D- patients. TFPI antigen was higher in D- than in D+ and S+ patients (p

S 26948: a new specific peroxisome proliferator activated receptor gamma modulator with potent antidiabetes and antiatherogenic effects.

OBJECTIVE: Rosiglitazone displays powerful antidiabetes benefits but is associated with increased body weight and adipogenesis. Keeping in mind the concept of selective peroxisome proliferator-activated receptor (PPAR)gamma modulator, the aim of this study was to characterize the properties of a new PPARgamma ligand, S 26948, with special attention in body-weight gain. RESEARCH DESIGN AND METHODS: We used transient transfection and binding assays to characterized the binding characteristics of S 26948 and GST pull-down experiments to investigate its pattern of coactivator recruitment compared with rosiglitazone. We also assessed its adipogenic capacity in vitro using the 3T3-F442A cell line and its in vivo effects in ob/ob mice (for antidiabetes and antiobesity properties), as well as the homozygous human apolipoprotein E2 knocking mice (E2-KI) (for antiatherogenic capacity). RESULTS: S 26948 displayed pharmacological features of a high selective ligand for PPARgamma with low potency in promoting adipocyte differentiation. It also displayed a different coactivator recruitment profile compared with rosiglitazone, being unable to recruit DRIP205 or PPARgamma coactivator-1 alpha. In vivo experiments showed that S 26948 was as efficient in ameliorating glucose and lipid homeostasis as rosiglitazone, but it did not increase body and white adipose tissue weights and improved lipid oxidation in liver. In addition, S 26948 represented one of the few molecules of the PPARgamma ligand class able to decrease atherosclerotic lesions. CONCLUSIONS: These findings establish S 26948 as a selective PPARgamma ligand with distinctive coactivator recruitment and gene expression profile, reduced adipogenic effect, and improved biological responses in vivo.

Characterization of a new mouse model for human apolipoprotein A-I/C-III/A-IV deficiency.

Human data raised the possibility that coronary heart disease is associated with mutations in the apolipoprotein gene cluster APOA1/C3/A4 that result in multideficiency of cluster-encoded apolipoproteins and hypoalphalipoproteinemia. To test this hypothesis, we generated a mouse model for human apolipoprotein A-I (apoA-I)/C-III/A-IV deficiency. Homozygous mutants (Apoa1/c3/a4(-/-)) lacking the three cluster-encoded apolipoproteins were viable and fertile. In addition, feeding behavior and growth were apparently normal. Total cholesterol (TC), high density lipoprotein cholesterol (HDLc), and triglyceride levels in the plasma of fasted mutants fed a regular chow were 32% (P < 0.001), 17% (P < 0.001), and 70% (P < 0.01), respectively, those of wild-type mice. When fed a high-fat Western-type (HFW) diet, Apoa1/c3/a4(-/-) mice showed a further decrease in HDLc concentration and a moderate increase in TC, essentially in non-HDL fraction. The capacity of Apoa1/c3/a4(-/-) plasma to promote cholesterol efflux in vitro was decreased to 75% (P < 0.001), and LCAT activity was decreased by 38% (P < 0.01). Despite the very low total plasma cholesterol, the imbalance in lipoprotein distribution caused small but detectable aortic lesions in one-third of Apoa1/c3/a4(-/-) mice fed a HFW diet. In contrast, none of the wild-type mice had lesions. These results demonstrate that Apoa1/c3/a4(-/-) mice display clinical features similar to human apoA-I/C-III/A-IV deficiency (i.e., marked hypoalphalipoproteinemia) and provide further support for the apoa1/c3/a4 gene cluster as a minor susceptibility locus for atherosclerosis in mice.

The farnesoid X receptor modulates adiposity and peripheral insulin sensitivity in mice.

The farnesoid X receptor (FXR) is a bile acid (BA)-activated nuclear receptor that plays a major role in the regulation of BA and lipid metabolism. Recently, several studies have suggested a potential role of FXR in the control of hepatic carbohydrate metabolism, but its contribution to the maintenance of peripheral glucose homeostasis remains to be established. FXR-deficient mice display decreased adipose tissue mass, lower serum leptin concentrations, and elevated plasma free fatty acid levels. Glucose and insulin tolerance tests revealed that FXR deficiency is associated with impaired glucose tolerance and insulin resistance. Moreover, whole-body glucose disposal during a hyperinsulinemic euglycemic clamp is decreased in FXR-deficient mice. In parallel, FXR deficiency alters distal insulin signaling, as reflected by decreased insulin-dependent Akt phosphorylation in both white adipose tissue and skeletal muscle. Whereas FXR is not expressed in skeletal muscle, it was detected at a low level in white adipose tissue in vivo and induced during adipocyte differentiation in vitro. Moreover, mouse embryonic fibroblasts derived from FXR-deficient mice displayed impaired adipocyte differentiation, identifying a direct role for FXR in adipocyte function. Treatment of differentiated 3T3-L1 adipocytes with the FXR-specific synthetic agonist GW4064 enhanced insulin signaling and insulin-stimulated glucose uptake. Finally, treatment with GW4064 improved insulin resistance in genetically obese ob/ob mice in vivo. Although the underlying molecular mechanisms remain to be unraveled, these results clearly identify a novel role of FXR in the regulation of peripheral insulin sensitivity and adipocyte function. This unexpected function of FXR opens new perspectives for the treatment of type 2 diabetes.

Increased susceptibility of low-density lipoprotein to ex vivo oxidation in mice transgenic for human apolipoprotein B treated with 1 melatonin-related compound is not associated with atherosclerosis progression.

Considerable evidence supports the hypothesis that LDL oxidation has an important role in atherosclerosis. It has been demonstrated that the feeding of hypercholesterolemic mice on an atherogenic diet supplemented with melatonin highly increases the surface of atherosclerotic lesions in aorta and the sensitivity of atherogenic lipoprotein to ex vivo oxidation even though high melatonin doses inhibit lipoprotein oxidation in vitro. A melatonin-related compound (DTBHB: N-[2-(5-methoxy-1H-indol-3-yl)ethyl]-3,5-di-tert-butyl-4-hydroxybenzamide) has been reported to strongly inhibit lipid peroxidation in vitro. In the present study, DTBHB treatment considerably increased the sensitivity of atherogenic lipoproteins to ex vivo oxidation but did not modify atherosclerotic lesion development in mice. Moreover, DTBHB treatment did not induce detectable lipidic alteration. These data confirm that the capacity of molecules to inhibit atherogenic lipoprotein oxidation in vitro offers no prediction of their capacity to inhibit in vivo atherosclerosis development.

Protective effect of glial cells against lipopolysaccharide-mediated blood-brain barrier injury.

Numerous infections of the central nervous system are characterized by altered blood-brain barrier (BBB) functions leading to brain damage. To study the mechanisms that cause BBB disruption in these pathologies, we used an in vitro BBB model consisting of a coculture of brain capillary endothelial cells and glial cells. When these endothelial cells were submitted alone to lipopolysaccharide (LPS), added in the luminal compartment, a huge increase in the paracellular permeability of the monolayer was observed. As glial cells surrounding the brain capillaries are of prime importance in specifying at least some cellular properties, we investigated whether glial cells would be able to modulate this endothelial cell response to LPS. When endothelial cells were incubated with LPS added luminally, in the presence of glial cells, LPS surprisingly had no effect on the endothelial cell monolayer permeability, suggesting a protective effect of glial cells on the LPS-mediated injury. As in our experiments, the endotoxin does not interact with the glial cell population. This protective effect suggests a close communication between cerebral endothelial cells and brain parenchymal cells. In our coculture model, the glial cell population is a mixture of astrocytes, oligodendrocytes, and microglial cells. Further experiments performed with purified astrocytes showed that microglial cells or oligodendrocytes, or both, are essential for the complete protection of the endothelial cell monolayer integrity. All these results are direct evidence for a modulatory effect of glial cells on brain capillary endothelial cell response in the pathogenesis of endotoxemia.

Reduction of atherosclerosis by the peroxisome proliferator-activated receptor alpha agonist fenofibrate in mice.

Several clinical and angiographic intervention trials have shown that fibrate treatment leads to a reduction of the coronary events associated to atherosclerosis. Fibrates are ligands for peroxisome proliferator-activated receptor alpha (PPARalpha) that modulate risk factors related to atherosclerosis by acting at both systemic and vascular levels. Here, we investigated the effect of treatment with the PPARalpha agonist fenofibrate (FF) on the development of atherosclerotic lesions in apolipoprotein (apo) E-deficient mice and human apoA-I transgenic apoE-deficient (hapoA-I Tg x apoE-deficient) mice fed a Western diet. In apoE-deficient mice, plasma lipid levels were increased by FF treatment with no alteration in the cholesterol distribution profile. FF treatment did not reduce atherosclerotic lesion surface area in the aortic sinus of 5-month-old apoE-deficient mice. By contrast, FF treatment decreased total cholesterol and esterified cholesterol contents in descending aortas of these mice, an effect that was more pronounced in older mice exhibiting more advanced lesions. Furthermore, FF treatment reduced MCP-1 mRNA levels in the descending aortas of apoE-deficient mice, whereas ABCA-1 expression levels were maintained despite a significant reduction of aortic cholesterol content. In apoE-deficient mice expressing a human apoA-I transgene, FF increased human apoA-I plasma and hepatic mRNA levels without affecting plasma lipid levels. This increase in human apoA-I expression was accompanied by a significant reduction in the lesion surface area in the aortic sinus. These data indicate that the PPARalpha agonist fenofibrate reduces atherosclerosis in these animal models of atherosclerosis.

Daily melatonin supplementation in mice increases atherosclerosis in proximal aorta.

Considerable evidence supports the hypothesis that LDL oxidation plays an important role in atherosclerosis. Even though high melatonin doses inhibit LDL oxidation in vitro, the effect of melatonin on atherosclerosis has never been studied. We have demonstrated that the feeding of hypercholesterolemic mice with an atherogenic diet supplemented with melatonin highly increases the surface of atherosclerotic lesions in the proximal aorta. These observations occur without detectable lipidic or glucidic phenotype alteration. Melatonin treatment increased highly the sensitivity of atherogenic lipoprotein to Cu(2+) and gamma-radiolysis generated oxyradical ex vivo oxidation during the fasting period. Moreover, these altered lipoproteins were less recognized by the LDL receptor metabolic pathway of murine fibroblasts while they transferred many more cholesteryl esters to murine macrophages. This study suggests that caution should be taken as regards high melatonin dosage in hypercholesterolemic patients.