Human liver PPARα gene expression negatively correlates with NASH severity, visceral adiposity and insulin resistance and positively with adiponectin. Histological improvement is associated with an increase in expression of PPARα and its target genes. These data might suggest that PPARα is a potential therapeutic target in NASH.

Abstract-Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase used in the prevention of cardiovascular disease (CVD). In addition to their cholesterol-lowering activities, statins exert pleiotropic antiinflammatory effects, which might contribute to their beneficial effects not only on CVD but also on lipid-unrelated immune and inflammatory diseases, such as rheumatoid arthritis, asthma, stroke, and transplant rejection. However, the molecular mechanisms involved in these antiinflammatory properties of statins are unresolved. Here we show that the peroxisome proliferator-activated receptor (PPAR) ␣ mediates antiinflammatory effects of simvastatin in vivo in models of acute inflammation. The inhibitory effects of statins on lipopolysaccharide-induced inflammatory response genes were abolished in PPAR␣-deficient macrophages and neutrophils. Moreover, simvastatin inhibited PPAR␣ phosphorylation by lipopolysaccharide-activated protein kinase C (PKC) ␣. A constitutive active form of PKC␣ inhibited nuclear factor B transrepression by PPAR␣ whereas simvastatin enhanced transrepression activity of wild-type PPAR␣, but not of PPAR␣ mutated in its PKC phosphorylation sites. These data indicate that the acute antiinflammatory effect of simvastatin occurs via PPAR␣ by a mechanism involving inhibition of PKC␣ inactivation of PPAR␣ transrepression activity. Key Words: inflammation Ⅲ macrophages Ⅲ neutrophils Ⅲ nuclear receptors Ⅲ statins Ⅲ PKC S tatins, competitive inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the ratelimiting enzyme in cholesterol synthesis, are widely prescribed for the treatment of hypercholesterolemia. 1 In addition to plasma lipid-modulating action, statins exert pleiotropic antiinflammatory effects, which might contribute to their beneficial effects on cardiovascular disease (CVD). 2 Emerging evidences also suggest beneficial therapeutic activities of statins in immune and inflammatory diseases such as multiple sclerosis, Alzheimer's disease, ischemic stroke, transplant rejection, rheumatoid arthritis, and asthma. [3][4][5][6] Several clinical observations indicate that these effects cannot be attributed to their cholesterol-lowering activities only. 7 Statin therapy decreases plasma concentrations of inflammatory markers, such as C-reactive protein (CRP), within 1 week after treatment initiation, before any lipid changes are observed. 8 Statin treatment reduces the incidence of ischemic stroke for which plasma cholesterol levels are not considered a risk factor. 9 Moreover, statins also exert antiinflammatory actions in animal models, which are resistant to their hypolipidemic actions. 10 In models of acute and chronic inflammation, statins inhibit endothelial adhesion and transendothelial migration of leukocytes to sites of inflammation, 10 acting both on endothelial cells and leukocytes. Statins modulate macrophage functions by inhibiting the activation of inflammatory response genes, such as interleukin (IL)-1b and IL-6, tumor necrosis...

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Hepatocyte growth factor/scatter factor (HGF/SF) induces scattering and morphogenesis of epithelial cells through the activation of the MET tyrosine kinase receptor. Although the activated MET receptor recruits a number of signaling proteins, little is known of the downstream signaling pathways activated by HGF/SF. In this study, we wished to examine the signaling pathway leading to activation of the ETS1 transcription factor. Using in vitro and in vivo kinase assays, we found that HGF/SF activates the ERK1 MAP kinase, leading to the phosphorylation of the threonine 38 residue of ETS1 within a putative MAP kinase phosphorylation site (PLLT38P). This threonine residue was neither phosphorylated by JNK1, nor by p38 MAP kinases and was required for the induction of transcriptional activity of ETS1 by HGF/SF. Using kinase and transcription assays, we further demonstrated that phosphorylation and activation of ETS1 occurs downstream of a RAS-RAF-MEK-ERK pathway. The functional involvement of this pathway in HGF/SF action was demonstrated using U0126, a pharmacological inhibitor of MEK, which blocked phosphorylation and activation of ETS1, RASdependent transcriptional responses, cell scattering and morphogenesis. These data demonstrated that ETS1 is a downstream target of HGF/SF acting through a RAS-RAF-MEK-ERK pathway and provides a signaling pathway leading to the regulation of gene expression by HGF/SF.

Objective-The objective of this study was to determine whether the potent selective cannabinoid receptor-1 antagonist rimonabant has antiatherosclerotic properties. Methods and Results-Rimonabant (50 mg/kg/d in the diet) significantly reduced food intake (from 3.35Ϯ.04 to 2.80Ϯ0.03 g/d), weight gain (from 14.6Ϯ0.7 g to Ϫ0.6Ϯ0.3 g), serum total cholesterol (from 8.39Ϯ0.54 to 5.32Ϯ0.18 g/L), and atherosclerotic lesion development in the aorta (from 1.7Ϯ0.22 to 0.21Ϯ0.037 mm 2 ) and aortic sinus (from 101 000Ϯ7800 to 27 000Ϯ2900 m 2 ) of LDLR Ϫ/Ϫ mice fed a Western-type diet for 3 months. Rimonabant also reduced plasma levels of the proinflammatory cytokines MCP-1 and IL12 by 85% (PϽ0.05) and 76% (PϽ0.05), respectively. Pair-fed animals had reduced weight gain (6.2Ϯ0.6 g gain), but developed atherosclerotic lesions which were as large as those of untreated animals, showing that the antiatherosclerotic effect of rimonabant is not related to reduced food intake. Interestingly, rimonabant at a lower dose (30 mg/kg/d in the diet) reduced atherosclerosis development in the aortic sinus (from 121 000Ϯ20 000 to 62 000Ϯ11 000 m 2 , 49% reduction, PϽ0.05), without affecting serum total cholesterol (7.8Ϯ0.7 g/L versus 8.1Ϯ1.3 g/L in the control group). Rimonabant decreased lipopolysaccharide (LPS)-and IL1␤-induced proinflammatory gene expression in mouse peritoneal macrophages in vitro as well as thioglycollateinduced recruitment of macrophages in vivo (10 mg/kg, po bolus). Conclusions-These results show that rimonabant has antiatherosclerotic effects in LDLRϪ/Ϫ mice. These effects are partly unrelated to serum cholesterol modulation and could be related to an antiinflammatory effect.

Abstract-Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors controlling lipid and glucose metabolism as well as inflammation. PPARs are expressed in macrophages, cells that also generate reactive oxygen species (ROS). In this study, we investigated whether PPARs regulate ROS production in macrophages. Different PPAR-␣, but not PPAR-␥ agonists, increased the production of ROS (H 2 O 2 and O 2 . ) in human and murine macrophages.PPAR-␣ activation did not induce cellular toxicity, but significantly decreased intracellular glutathione levels. The increase in ROS production was not attributable to inherent prooxidant effects of the PPAR-␣ agonists tested, but was mediated by PPAR-␣, because the effects were lost in bone marrow-derived macrophages from PPAR-␣ Ϫ/Ϫ mice. The PPAR-␣-induced increase in ROS was attributable to the induction of NADPH oxidase, because (1) preincubation with the NADPH oxidase inhibitor diphenyleneiodinium prevented the increase in ROS production; (2) PPAR-␣ agonists increased O 2 . production measured by superoxide dismutase-inhibitable cytochrome c reduction; (3) PPAR-␣ agonists induced mRNA levels of the NADPH oxidase subunits p47 phox , p67 phox , and gp91 phox and membrane p47 phox protein levels; and (4) induction of ROS production was abolished in p47 phoxϪ/Ϫ and gp91 phoxϪ/Ϫ macrophages. Finally, induction of NADPH oxidase by PPAR-␣ agonists resulted in the formation of oxidized LDL metabolites that exert PPAR-␣-independent proinflammatory and PPAR-␣-dependent decrease of lipopolysaccharide-induced inducible nitric oxide synthase expression in macrophages. These data identify a novel mechanism of autogeneration of endogenous PPAR-␣ ligands via stimulation of NADPH oxidase activity. Key Words: macrophages Ⅲ nuclear receptors Ⅲ NADPH oxidase Ⅲ reactive oxygen species Ⅲ inflammation P eroxisome proliferator-activated receptor ␣ (PPAR-␣) is a transcription factor belonging to the superfamily of ligandactivated nuclear receptors that heterodimerizes with the retinoid X receptor. In rodents, but not in humans, PPAR-␣ activation causes hepatomegaly attributable to parenchymal peroxisome proliferation, resulting in a marked increase in oxidative stress. 1 In humans, PPAR-␣ agonists are used for the treatment of dyslipidemia. PPAR-␣ regulates the expression of genes controlling lipid and lipoprotein metabolism and cholesterol and glucose homeostasis. PPAR-␣ activation results in decreased plasma triglyceride and small dense LDL levels and increased HDL. 2 PPAR-␣ also exerts antiinflammatory activities by transrepressing inflammatory signaling pathways. 2 PPAR-␣ is also expressed in vascular wall cells, including monocyte-derived macrophages, where it modulates cholesterol homeostasis. In macrophages, PPAR-␣ regulates the expression of the HDL receptor CLA-1/SR-B1 and the cholesterol/phospholipid transporter ABCA1. 3 Moreover, PPAR-␣ inhibits cholesterol esterification, resulting in an enhanced availability of free cholesterol for efflux through the ABCA1 pathway. 3 P...

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

Glucocorticoid receptor ␣ (GR␣) and peroxisome proliferatoractivated receptor ␣ (PPAR␣) are transcription factors with clinically important immune-modulating properties. Either receptor can inhibit cytokine gene expression, mainly through interference with nuclear factor B (NF-B)-driven gene expression. The present work aimed to investigate a functional cross-talk between PPAR␣-and GR␣-mediated signaling pathways. Simultaneous activation of PPAR␣ and GR␣ dose-dependently enhances transrepression of NF-B-driven gene expression and additively represses cytokine production. In sharp contrast and quite unexpectedly, PPAR␣ agonists inhibit the expression of classical glucocorticoid response element (GRE)-driven genes in a PPAR␣-dependent manner, as demonstrated by experiments using PPAR␣ wild-type and knockout mice. The underlying mechanism for this transcriptional antagonism relies on a PPAR␣-mediated interference with the recruitment of GR␣, and concomitantly of RNA polymerase II, to GRE-driven gene promoters. Finally, the biological relevance of this phenomenon is underscored by the observation that treatment with the PPAR␣ agonist fenofibrate prevents glucocorticoid-induced hyperinsulinemia of mice fed a high-fat diet. Taken together, PPAR␣ negatively interferes with GREmediated GR␣ activity while potentiating its antiinflammatory effects, thus providing a rationale for combination therapy in chronic inflammatory disorders.cross-talk ͉ gluconeogenesis ͉ inflammation ͉ hyperinsulinema ͉ side effects G lucocorticoids (GCs) are presently the most potent drugs for the treatment of acute and chronic inflammatory diseases. Nevertheless, side effects such as osteoporosis, muscle wasting, hypertension, behavioral alterations, and disorders of glucose (Glc) and lipid metabolism, burden their therapeutical use. GCs mediate their effect via the glucocorticoid receptor ␣ (GR␣), a member of the nuclear receptor superfamily. After binding of GCs, a conformational change in the receptor is induced, releasing cytosolic chaperoning proteins followed by GR␣ translocation into the nucleus. Activated GR␣ can directly regulate the expression of its target genes through GR␣ binding onto promoter-imbedded GREs. Target genes of GR␣ homodimers include proteins involved in Glc, fat, and protein metabolism. Alternatively, GR␣ can also influence gene expression by interfering with the activity of nuclear factor B (NF-B), a key regulatory proinflammatory transcription factor (1). Peroxisome proliferator-activated receptor ␣ (PPAR␣), a ligand-activated transcription factor, also belonging to the nuclear receptor superfamily, is highly expressed in liver, skeletal and cardiac muscle, kidney, and in cells involved in inflammatory processes. Besides its involvement in lipid and Glc metabolism, PPAR␣ exhibits potent antiinflammatory properties. Recently, a protective role for PPAR␣ has also been demonstrated in obesityinduced hepatic inflammation (2). Fatty acid derivates and hypolipidemic fibrates are natural and synthetic PPAR␣ ligands, respect...