Activation Of Peroxisome Proliferator-activated Receptor Alpha Research Articles

Abstract 19434: The Novel PPARalpha-Selective Agonist K-877 Improves Dyslipidemia, Enhances Reverse Cholesterol Transport and Decreases Inflammation and Atherosclerosis

Background: Atherosclerosis is characterized by lipid accumulation and chronic inflammation in the arterial wall. Elevated levels of apolipoprotein (apo) B-containing lipoproteins are a risk factor for cardiovascular disease (CVD). By contrast, plasma levels of high-density lipoprotein (HDL) and apoA-I are protective against CVD by enhancing HDL functionality and reverse cholesterol transport (RCT). Activation of peroxisome proliferator-activated receptor-alpha (PPARalpha), a ligand-activated transcription factor, controls plasma lipid metabolism, macrophage cholesterol handling as well as the inflammatory response. Objective: To study whether pharmacological activation of PPARalpha with the highly potent PPARalpha ligand, K-877, improves lipid metabolism, macrophage cholesterol efflux, inflammation and consequently atherosclerosis development in human apoA-I transgenic mice and in the human apolipoprotein E2 knock-in mouse (apo E2KI) model of mixed dyslipidemia and atherosclerosis. Methods and results: In polarized Caco-2/TC7 human intestinal epithelium cells, K-877 treatment decreased apoB secretion and increased the expression of PPARalpha target genes involved in fatty acid oxidation and intestinal HDL production. Moreover, K-877 induced secretion of apoA-I in HDL particles. In primary human macrophages, K-877 promoted macrophage cholesterol efflux to HDL. K-877 treatment of human apoA-I transgenic mice induced plasma HDL cholesterol and apoA-I levels. Moreover, K-877 stimulated in vivo RCT in these mice. In addition, K-877 treatment exerted anti-inflammatory properties in murine and human macrophages. K-877 treatment not only improved the lipid profile, but also reduced inflammatory and macrophage marker gene expression in the aortic crosses as well as aortic atherosclerotic lesion burden in western diet-fed apo E2KI mice. Conclusion: These results demonstrate that the novel PPARalpha agonist K-877 exerts beneficial effects on lipid metabolism, RCT and inflammation resulting in anti-atherogenic properties.

Urotensin II exerts antiapoptotic effect on NRK-52E cells through prostacyclin-mediated peroxisome proliferator-activated receptor alpha and Akt activation

Urotensin II (UII) is a cyclic vasoactive peptide which is mainly expressed in kidneys. Although elevated plasma UII levels are associated with renal impairment, the influence of UII on renal injury is unclear. In this study, we monitored the influence of UII on gentamicin-induced apoptosis in rat tubular cells (NRK-52E). We found that UII significantly reduced gentamicin-induced apoptosis and apoptotic signals. Blocking endogenous UII secretion caused cells to be more susceptible to gentamicin. In gentamicin-treated mice, UII also expressed protective effect on renal tubular cells. UII was also found to induce prostacyclin (PGI2) production, which caused peroxisomal proliferator-activated receptor α (PPARα) activation as revealed by both PGI2 synthase siRNA transfection and piroxicam treatment. Blockage of PPARα by siRNA transfection inhibited UII-induced Akt phosphorylation and the antiapoptotic effect of UII. Our results suggest that UII can protect renal tubular cells from gentamicin-induced apoptosis through PGI2-mediated PPARα and Akt activation.

Design and Synthesis of Potent N-Acylethanolamine-hydrolyzing Acid Amidase (NAAA) Inhibitor as Anti-Inflammatory Compounds

N-acylethanolamine-hydrolyzing acid amidase (NAAA) is a lysosomal enzyme involved in biological deactivation of N-palmitoylethanolamide (PEA), which exerts anti-inflammatory and analgesic effects through the activation of nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR-α). To develop selective and potent NAAA inhibitors, we designed and synthesized a series of derivatives of 1-pentadecanyl-carbonyl pyrrolidine (compound 1), a general amidase inhibitor. Structure activity relationship (SAR) studies have identified a compound 16, 1-(2-Biphenyl-4-yl)ethyl-carbonyl pyrrolidine, which has shown the highest inhibition on NAAA activity (IC50 = 2.12±0.41 µM) and is characterized as a reversible and competitive NAAA inhibitor. Computational docking analysis and mutagenesis study revealed that compound 16 interacted with Asparagine 209 (Asn209) residue flanking the catalytic pocket of NAAA so as to block the substrate entrance. In vitro pharmacological studies demonstrated that compound 16 dose-dependently reduced mRNA expression levels of iNOS and IL-6, along with an increase of intracellular PEA levels, in mouse macrophages with lipopolysaccharides (LPS) induced inflammation. Our study discovered a novel NAAA inhibitor, compound 16, that could serve as a potential anti-inflammatory agent.

Salacia oblonga ameliorates hypertriglyceridemia and excessive ectopic fat accumulation in laying hens

Ethnopharmacological relevanceSalacia oblonga root (SOR) is an Ayurvedic medicine for obesity and diabetes, those are associated with glucose and lipid metabolism. Aim of the studySOR has been demonstrated previously to improve glucose and lipid metabolism in animal models of obesity and diabetes and to be a peroxisome proliferator-activated receptor-alpha activator. However, the anti-obesogenic and anti-diabetic mechanisms of SOR are still not largely understood. Here, we investigated the effects of SOR on lipid metabolism using laying hen, a unique animal model with a very high rate of triglyceride synthesis in the liver. Materials and methodsLaying hens and preadolescent pullets were treated with the layer ration containing 0%, 0.5%, or 1% SOR water extract for 4 weeks. Biochemical variables were determined enzymatically. ResultsLaying hens showed much higher fasted triglyceride concentrations (increased by 5–13 folds) in plasma, liver, skeletal muscle and heart than pullets. 1% SOR extract treatment inhibited body weight increase without affecting food intake. Importantly, this treatment substantially attenuated hypertriglyceridemia and inhibited increases in triglyceride contents in the non-adipose tissues. However, SOR extract did not induce change in plasma glucose concentration. Moreover, SOR extract did not alter all variables in pullets. ConclusionsThese results demonstrate that SOR ameliorates hypertriglyceridemia and excessive ectopic fat accumulation in laying hens. These findings suggest that the triglyceride-lowering property is one of the primary effects of SOR, possibly via hepatic mechanisms.

S6 kinase 2 deficiency enhances ketone body production and increases peroxisome proliferator-activated receptor alpha activity in the liver

Nutrient homeostasis is tightly regulated by the balance between energy production and utilization. During fasting, production of ketone bodies as an alternative energy source is critical to maintain nutrient homeostasis. An important component in the nutrient-sensitive signaling pathway is S6 kinase 2 (S6K2), a downstream effector of mammalian target of rapamycin. Here, we show that mice lacking S6K2 exhibit elevated levels of ketone bodies and enhanced peroxisome proliferator-activated receptor alpha (PPARα) activity upon nutrient availability. Consistent with this, knockdown of S6K2 increases the transcriptional activity of PPARα. S6K2 suppresses PPARα by associating with its corepressor, nuclear receptor corepressor 1 (NCoR1), and by inducing the recruitment of NCoR1 to the nucleus. Moreover, ob/ob mice, a genetic model of obesity, have markedly elevated S6K2 activity, and S6K2 was strongly associated with NCoR1 in the nucleus of liver cells. Our findings suggest that S6K2 regulates hepatic energy homeostasis by repressing PPARα activity and point to its potential relevance for therapeutic strategies designed to modulate S6K2 activity as a treatment for deregulated ketone body production.

Effect of acute administration of Pistacia lentiscus L. essential oil on rat cerebral cortex following transient bilateral common carotid artery occlusion.

BackgroundIschemia/reperfusion leads to inflammation and oxidative stress which damages membrane highly polyunsaturated fatty acids (HPUFAs) and eventually induces neuronal death. This study evaluates the effect of the administration of Pistacia lentiscus L. essential oil (E.O.), a mixture of terpenes and sesquiterpenes, on modifications of fatty acid profile and endocannabinoid (eCB) congener concentrations induced by transient bilateral common carotid artery occlusion (BCCAO) in the rat frontal cortex and plasma.MethodsAdult Wistar rats underwent BCCAO for 20 min followed by 30 min reperfusion (BCCAO/R). 6 hours before surgery, rats, randomly assigned to four groups, were gavaged either with E.O. (200 mg/0.45 ml of sunflower oil as vehicle) or with the vehicle alone.ResultsBCCAO/R triggered in frontal cortex a decrease of docosahexaenoic acid (DHA), the membrane highly polyunsaturated fatty acid most susceptible to oxidation. Pre-treatment with E.O. prevented this change and led further to decreased levels of the enzyme cyclooxygenase-2 (COX-2), as assessed by Western Blot. In plasma, only after BCCAO/R, E.O. administration increased both the ratio of DHA-to-its precursor, eicosapentaenoic acid (EPA), and levels of palmytoylethanolamide (PEA) and oleoylethanolamide (OEA).ConclusionsAcute treatment with E.O. before BCCAO/R elicits changes both in the frontal cortex, where the BCCAO/R-induced decrease of DHA is apparently prevented and COX-2 expression decreases, and in plasma, where PEA and OEA levels and DHA biosynthesis increase. It is suggested that the increase of PEA and OEA plasma levels may induce DHA biosynthesis via peroxisome proliferator-activated receptor (PPAR) alpha activation, protecting brain tissue from ischemia/reperfusion injury.

Activation of mouse and human peroxisome proliferator-activated receptor-alpha (PPARα) by perfluoroalkyl acids (PFAAs): Further investigation of C4–C12 compounds

Perfluorinated alkyl acids (PFAAs) are manufactured surfactants found globally in the environment and in tissues of humans and wildlife. Several PFAAs adversely affect rodents and activation of PPARα is thought to be their mode of action. Our previous study demonstrated that some PFAAs activate mouse and human PPARα in transiently transfected COS-1 cells. Here, we test more PFAAs for PPARα activation in the same system. Cells were transfected with either mouse or human PPARα-luciferase reporter plasmid, exposed the next day to either vehicle, PPARα agonist (WY14643), perfluoropentanoic acid (C5), perfluoroheptanoic acid (C7), perfluorooctanoic acid (C8), perfluoroundecanoic acid (C11), or perfluorododecanoic acid (C12) at concentrations from 0.5μM to 100μM, and luminescence was measured after 24h. C8 induced the highest activity for human PPARα, followed by C7, C5, and C11. C12 had little activity. C8 induced the highest activity for mouse PPARα, followed by C11, C7, C12 and C5. The two studies together found increasing activity of PPARα with increasing chain length of the PFAA up to perfluorononanoic acid (C9) and lower activity with longer chain PFAAs with both mouse and human PPARα.

Acute Cholestatic Hepatitis Induced by Gemfibrozil - A Case Report: ACG/AstraZeneca Clinical Vignette Award

Purpose: Gemfibrozil is a fibric acid derivative and an activator of peroxisome proliferator-activated receptor-alpha (PPARα), a nuclear receptor involved in the metabolism of carbohydrates and fats.We report a rare case of cholestatic hepatitis due to gemfibrozil. A 55-year-old African-American man presented with abdominal pain, fatigue, pruritis and jaundice over the preceding month. He had a past medical history including HTN, DM type 2 and hypertriglyceridemia. He also reports a history of chronic hepatitis C previously treated with interferon but discontinued due to intolerance. Three months prior to presentation he was prescribed gemfibrozil 600 mg twice daily for hypertriglyceridemia. Upon presentation, his physical examination was unremarkable. Laboratory data over several months revealed peak values of ALT 241 IU/L, ALKP 359 IU/L, and TB 11.5 mg/dL. His coagulation profile, acute hepatitis serology, and amylase/lipase were normal. Work-up for other etiologies were negative including autoimmune, toxic and genetic causes. Malignancy was also excluded. Liver ultrasound showed normal blood flow but mild, diffuse increased echogenicity consistent with fatty infiltration. CT abdomen revealed cholelithiasis without cholecystitis and no ascites. Liver biopsy was performed revealing chronic portal inflammation with interface hepatitis and bridging fibrosis (METVIR grade 2-3, stage II). Few eosinophils and rare neutrophils were seen among the lymphocytes. Prominent hepatocellular and canalicular bilirubinostasis with the formation of “cholestatic” rosettes, neocholangiolar proliferation, and focal duct injury were seen. Early collagen deposits in areas of collapse with pericellular and perisinusoidal fibrosis were noted indicating a possible drug injury on top of a pre-existing chronic liver disease. Upon discontinuation of gemfibrozil, liver enzymes trended down with normalization over 8 weeks with the exception of alkaline phosphatase which remained elevated at 305 IU/L. Further review of this patient's record revealed two prior incidents of gemfibrozil initiation resulting in liver injury attributed to chronic hepatitis C. The product information for gemfibrozil indicates elevations in liver function tests have been observed previously for which periodic monitoring is recommended. This case represents the first report of gemfibrozil-induced cholestasis in a patient with chronic hepatitis C. By presenting this case, we hope to characterize the pattern of liver damage and to increase the awareness of hepatotoxicity associated with gemfibrozil. Early recognition, withdrawing the use of gemfibrozil, and supportive treatment play an important role in preventing further liver injury.

Multiplicity of nuclear receptor activation by PFOA and PFOS in primary human and rodent hepatocytes

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are surface active fluorochemicals that, due to their exceptional stability to degradation, are persistent in the environment. Both PFOA and PFOS are eliminated slowly in humans, with geometric mean serum elimination half-lives estimated at 3.5 and 4.8 years, respectively. The biological activity of PFOA and PFOS in rodents is attributed primarily to transactivation of the nuclear receptor peroxisome proliferator activated receptor alpha (PPARA), which is an important regulator of lipid and carbohydrate metabolism. However, there are significant species-specific differences in the response to PFOA and PFOS exposure; non-rodent species, including humans, are refractory to several but not all of these effects. Many of the metabolic effects have been attributed to the activation of PPARA; however, recent studies using PPARα knockout mice demonstrate residual PPARA-independent effects, some of which may involve the activation of alternate nuclear receptors, including NR1I2 (PXR), NR1I3 (CAR), NR1H3 (LXRA), and NR1H4 (FXR). The objective of this investigation was to characterize the activation of multiple nuclear receptors and modulation of metabolic pathways associated with exposure to PFOA and PFOS, and to compare and contrast the effects between rat and human primary liver cells using quantitative reverse transcription PCR (RT-qPCR). Our results demonstrate that multiple nuclear receptors participate in the metabolic response to PFOA and PFOS exposure resulting in a substantial shift from carbohydrate metabolism to fatty acid oxidation and hepatic triglyceride accumulation in rat liver cells. This shift in intermediary metabolism was more pronounced for PFOA than PFOS. Furthermore, while there is some similarity in the activation of metabolic pathways between rat and humans, particularly in PPARA regulated responses; the changes in primary human cells were more subtle and possibly reflect an adaptive metabolic response rather than an overt metabolic regulation observed in rodents.

Activation of peroxisome proliferator-activated receptor-alpha stimulates both differentiation and fatty acid oxidation in adipocytes

Peroxisome proliferator-activated receptor-α (PPARα) is a dietary lipid sensor, whose activation results in hypolipidemic effects. In this study, we investigated whether PPARα activation affects energy metabolism in white adipose tissue (WAT). Activation of PPARα by its agonist (bezafibrate) markedly reduced adiposity in KK mice fed a high-fat diet. In 3T3-L1 adipocytes, addition of GW7647, a highly specific PPARα agonist, during adipocyte differentiation enhanced glycerol-3-phosphate dehydrogenase activity, insulin-stimulated glucose uptake, and adipogenic gene expression. However, triglyceride accumulation was not increased by PPARα activation. PPARα activation induced expression of target genes involved in FA oxidation and stimulated FA oxidation. In WAT of KK mice treated with bezafibrate, both adipogenic and FA oxidation-related genes were significantly upregulated. These changes in mRNA expression were not observed in PPARα-deficient mice. Bezafibrate treatment enhanced FA oxidation in isolated adipocytes, suppressing adipocyte hypertrophy. Chromatin immunoprecipitation (ChIP) assay revealed that PPARα was recruited to promoter regions of both adipogenic and FA oxidation-related genes in the presence of GW7647 in 3T3-L1 adipocytes. These findings indicate that the activation of PPARα affects energy metabolism in adipocytes, and PPARα activation in WAT may contribute to the clinical effects of fibrate drugs.

Peroxisome Proliferator-Activated Receptor-αActivation Decreases Mean Arterial Pressure, Plasma Interleukin-6, and COX-2 While Increasing Renal CYP4A Expression in an Acute Model of DOCA-Salt Hypertension

Peroxisome proliferator-activated receptor-alpha (PPAR-α) activation by fenofibrate reduces blood pressure and sodium retention during DOCA-salt hypertension. PPAR-α activation reduces the expression of inflammatory cytokines, such as interleukin-6 (IL-6). Fenofibrate also induces cytochrome P450 4A (CYP4A) and increases 20-hydroxyeicosatetraenoic acid (20-HETE) production. This study tested whether the administration of fenofibrate would reduce blood pressure by attenuating plasma IL-6 and renal expression of cyclooxygenase-2 (COX-2), while increasing expression of renal CYP4A during 7 days of DOCA-salt hypertension. We performed uni-nephrectomy on 12–14 week old male Swiss Webster mice and implanted biotelemetry devices in control, DOCA-salt (1.5 mg/g) treated mice with or without fenofibrate (500 mg/kg/day in corn oil, intragastrically). Fenofibrate significantly decreased mean arterial pressure and plasma IL-6. In kidney homogenates, fenofibrate increased CYP4A and decreased COX-2 expression. There were no differences in renal cytochrome P450, family 2, subfamily c, polypeptide 23 (CYP2C23) and soluble expoxide hydrolase (sEH) expression between the groups. Our results suggest that the blood pressure lowering effect of PPAR-α activation by fenofibrate involves the reduction of plasma IL-6 and COX-2, while increasing CYP4A expression during DOCA-salt hypertension. Our results may also suggest that PPAR-α activation protects the kidney against renal injury via decreased COX-2 expression.

Peroxisome proliferator-activated receptor gamma and early folliculogenesis during an acute hyperandrogenism condition

Acute hyperandrogenism decreases serum P levels and induces early apoptosis of antral follicles by a mechanism mediated by the peroxisome proliferator-activated receptor gamma system and independent of the steroidogenic acute regulator protein.

Fenofibrate Increases Very Low Density Lipoprotein Triglyceride Production Despite Reducing Plasma Triglyceride Levels in APOE*3-Leiden.CETP Mice

The peroxisome proliferator-activated receptor alpha (PPARalpha) activator fenofibrate efficiently decreases plasma triglycerides (TG), which is generally attributed to enhanced very low density lipoprotein (VLDL)-TG clearance and decreased VLDL-TG production. However, because data on the effect of fenofibrate on VLDL production are controversial, we aimed to investigate in (more) detail the mechanism underlying the TG-lowering effect by studying VLDL-TG production and clearance using APOE*3-Leiden.CETP mice, a unique mouse model for human-like lipoprotein metabolism. Male mice were fed a Western-type diet for 4 weeks, followed by the same diet without or with fenofibrate (30 mg/kg bodyweight/day) for 4 weeks. Fenofibrate strongly lowered plasma cholesterol (-38%) and TG (-60%) caused by reduction of VLDL. Fenofibrate markedly accelerated VLDL-TG clearance, as judged from a reduced plasma half-life of glycerol tri[(3)H]oleate-labeled VLDL-like emulsion particles (-68%). This was associated with an increased post-heparin lipoprotein lipase (LPL) activity (+110%) and an increased uptake of VLDL-derived fatty acids by skeletal muscle, white adipose tissue, and liver. Concomitantly, fenofibrate markedly increased the VLDL-TG production rate (+73%) but not the VLDL-apolipoprotein B (apoB) production rate. Kinetic studies using [(3)H]palmitic acid showed that fenofibrate increased VLDL-TG production by equally increasing incorporation of re-esterified plasma fatty acids and liver TG into VLDL, which was supported by hepatic gene expression profiling data. We conclude that fenofibrate decreases plasma TG by enhancing LPL-mediated VLDL-TG clearance, which results in a compensatory increase in VLDL-TG production by the liver.

Fetal alcohol-induced hyperactivity is reversed by treatment with the PPARα agonist fenofibrate in a rat model

Exposure to alcohol in utero is linked to the development of a wide range of psychobehavioral changes, notably hyperactivity and attention deficit, with complex underlying pathological and functional mechanisms. Although the currently available treatments for hyperactivity have been studied in children exposed to alcohol in utero, the efficacy of these compounds is subject to debate and has prompted efforts to identify new pharmacological targets. In a rat model of early alcohol exposure (i.e., in utero and during lactation), we studied the effect of the lipid-lowering peroxisome proliferator-activated receptor (PPAR) alpha activator fenofibrate on psychobehavioral impairments. In the young rat, early exposure to alcohol perturbs locomotor behavior and induces prepubertal hyperactivity and postpubertal hypoactivity. The hyperactivity, usually observed at the end of the fifth week of life, was prevented by the administration of fenofibrate, which also had a beneficial effect on the accompanying attention deficit by reinforcing sustained attention. Our results with fenofibrate suggest that the pharmacological modulation of nuclear receptors such as PPAR-alpha may constitute a new therapeutic approach to managing the psychobehavioral disorders associated with early alcohol exposure.

Influence of peroxisome proliferator-activated receptor-alpha (PPARα) activity on adverse effects associated with amiodarone exposure in mice

Although amiodarone is the most effective antiarrhythmic agent currently available, concerns regarding adverse effects, including liver, lung and thyroid toxicity, often limit its use. Previously, we reported that amiodarone-induced hepatic steatosis in mice was associated with an upregulation of target genes modulated by peroxisome proliferator-activated receptor-alpha (PPARα). Because amiodarone does not directly stimulate PPARα, target gene induction may reflect a compensatory reaction countering some adverse effects of amiodarone. To test this, we examined co-treatment with the PPARα agonist, fenofibrate, and amiodarone in both PPARα(+/+) and PPARα(−/−) mice. Amiodarone treated PPARα(−/−) mice exhibited significantly greater weight loss and higher serum aspartate aminotransferase (AST) compared to PPARα(+/+) mice. Fenofibrate co-treatment reduced weight loss in amiodarone treated PPARα(−/−) mice, but not PPARα(+/+) mice. Fenofibrate stimulation of PPARα reduced serum amiodarone concentrations in normal mice. Serum amiodarone concentrations were higher in mice without PPARα expression given at 40–80 mg/kg amiodarone doses. These results are consistent with a protective influence of PPARα in reducing amiodarone-induced hepatic toxicity. In addition to PPARα-dependent effects, fenofibrate also demonstrated PPARα-independent actions that suggest a complex interaction modulating both hepatic lipid metabolism and amiodarone disposition. Further studies of the beneficial effect of fenofibrate and the interplay between lipid metabolism and amiodarone pharmacokinetics are required.

Mechanisms of adiponectin‐mediated COX‐2 induction and protection against iron injury in mouse hepatocytes

Adiponectin (APN)-mediated cyclooxygenase (COX)-2 induction is known to have various protective effects on cardiovascular diseases. However, the molecular mechanisms of APN-mediated COX-2 induction and its protection against iron-mediated injury in hepatocytes are still unclear. Herein, we show that AMP-mediated peroxisome proliferator-activated receptor (PPAR)alpha activation was attributable to COX-2 induction by APN, which was further confirmed by identifying novel functional PPAR responsive elements (PPREs) in the mouse COX-2 promoter region. Prostaglandin (PG)I2 and PGE2, metabolites of COX-2, time-dependently increased in hepatocytes treated with APN. Interestingly, beraprost and misoprostol, respective agonists for PGI2 and PGE2, mimicked the protective effects of APN in iron-mediated inflammation in hepatocytes. The iron dextran-activated nuclear factor (NF)-kappaB pathway was correlated with the increased production of inflammatory cytokines including tumor necrosis factor-alpha, intercellular adhesion molecule-1, and monocyte chemotactic protein-1. This was eliminated by administration of APN, whereas blockage of PPARalpha activation, an upstream regulator of COX-2 induction by APN, and COX-2 activation reversed the anti-inflammatory effect of APN, suggesting the crucial role of COX-2 in this event. Herein, we demonstrate that APN-mediated COX-2 induction through a PPARalpha-dependent mechanism, and COX-2 exerted an anti-inflammatory effect of APN in hepatocytes subjected to iron challenge.

Protective role of palmitoylethanolamide in contact allergic dermatitis

Palmitoylethanolamide (PEA) is an anti-inflammatory mediator that enhances the activation by anandamide (AEA) of cannabinoid receptors and transient receptor potential vanilloid type-1 (TRPV1) channels, and directly activates peroxisome proliferator-activated receptor-alpha (PPAR-alpha). In mice, 2,4-dinitrofluorobenzene (DNFB)-induced contact allergic dermatitis (CAD) in inflamed ears is partly mediated by the chemokine Monocyte Chemotactic Protein-2 (MCP-2) and accompanied by elevation of AEA levels. No datum is available on PEA regulation and role in CAD. We examined whether PEA is produced during DNFB-induced CAD, and if it has any direct protective action in keratinocytes in vitro. Eight- to ten-week-old female C57BL/6J wild-type and CB(1)/CB(2) double knock-out mice were used to measure PEA levels and the expression of TRPV1, PPAR-alpha receptors and enzymes responsible for PEA biosynthesis and degradation. Human keratinocytes (HaCaT) cells were stimulated with polyinosinic polycytidylic acid [poly-(I:C)], and the expression and release of MCP-2 were measured in the presence of PEA and antagonists of its proposed receptors. 2,4-Dinitrofluorobenzene increased ear skin PEA levels and up-regulated TRPV1, PPAR-alpha and a PEA-biosynthesizing enzyme in ear keratinocytes. In HaCaT cells, stimulation with poly-(I:C) elevated the levels of both PEA and AEA, and exogenous PEA (10 microM) inhibited poly-(I:C)-induced expression and release of MCP-2 in a way reversed by antagonism at TRPV1, but not PPAR-alpha. PEA (5-10 mg/kg, intraperitoneal) also inhibited DNFB-induced ear inflammation in mice in vivo, in a way attenuated by TRPV1 antagonism. We suggest that PEA is an endogenous protective agent against DNFB-induced keratinocyte inflammation and could be considered for therapeutic use against CAD.

Control of Steroid 21-oic Acid Synthesis by Peroxisome Proliferator-activated Receptor α and Role of the Hypothalamic-Pituitary-Adrenal Axis

A previous study identified the peroxisome proliferator-activated receptor alpha (PPARalpha) activation biomarkers 21-steroid carboxylic acids 11beta-hydroxy-3,20-dioxopregn-4-en-21-oic acid (HDOPA) and 11beta,20-dihydroxy-3-oxo-pregn-4-en-21-oic acid (DHOPA). In the present study, the molecular mechanism and the metabolic pathway of their production were determined. The PPARalpha-specific time-dependent increases in HDOPA and 20alpha-DHOPA paralleled the development of adrenal cortex hyperplasia, hypercortisolism, and spleen atrophy, which was attenuated in adrenalectomized mice. Wy-14,643 activation of PPARalpha induced hepatic FGF21, which caused increased neuropeptide Y and agouti-related protein mRNAs in the hypothalamus, stimulation of the agouti-related protein/neuropeptide Y neurons, and activation of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in increased adrenal cortex hyperplasia and corticosterone production, revealing a link between PPARalpha and the HPA axis in controlling energy homeostasis and immune regulation. Corticosterone was demonstrated as the precursor of 21-carboxylic acids both in vivo and in vitro. Under PPARalpha activation, the classic reductive metabolic pathway of corticosterone was suppressed, whereas an alternative oxidative pathway was uncovered that leads to the sequential oxidation on carbon 21 resulting in HDOPA. The latter was then reduced to the end product 20alpha-DHOPA. Hepatic cytochromes P450, aldehyde dehydrogenase (ALDH3A2), and 21-hydroxysteroid dehydrogenase (AKR1C18) were found to be involved in this pathway. Activation of PPARalpha resulted in the induction of Aldh3a2 and Akr1c18, both of which were confirmed as target genes through introduction of promoter luciferase reporter constructs into mouse livers in vivo. This study underscores the power of mass spectrometry-based metabolomics combined with genomic and physiologic analyses in identifying downstream metabolic biomarkers and the corresponding upstream molecular mechanisms.

OR8,47 IGF-I:Vitronectin interactions modulate breast cancer cell survival, migration and epithelial to mesenchymal transition

anticancer potential. Fenofibrate is a potent agonist of peroxisome proliferator activated receptor alpha (PPARa) that can switch energy metabolism from glycolysis to fatty acid b-oxidation, and has low systemic toxicity. Fenofibrate also attenuates IGF-I-mediated cellular responses, which could be relevant in the process of glioblastoma cell dispersal. Methods: The effects of fenofibrate on glioma cell motility, IGF-I receptor (IGF-IR) signaling, PPARa activity, reactive oxygen species (ROS) metabolism, mitochondrial potential, and ATP production were analyzed in human glioma cell lines. Results: Fenofibrate treatment attenuated IGF-I signaling responses and repressed cell motility of LN-229 and T98G Glioma cell lines. In the absence of fenofibrate, specific inhibition of the IGF-IR had only modest effects on Glioma cell motility. Further experiments revealed that PPARa-dependent accumulation of ROS is a strong contributing factor in Glioma cell lines responses to fenofibrate. The ROS scavenger, N-acetyl-cysteine (NAC), restored cell motility, improved mitochondrial potential, and increased ATP levels in fenofibrate treated G9lioma cell lines. Conclusions: Our results indicate that although fenofibratemediated inhibition of the IGF-IR may not be sufficient in counteracting Glioma cell dispersal, PPARa-dependent metabolic switch and the resulting ROS accumulation strongly contribute to the inhibition of these devastating brain tumor cells.

Fenofibrate Treatment Enhances Antioxidant Status and Attenuates Endothelial Dysfunction in Streptozotocin-Induced Diabetic Rats

Diabetic endothelial dysfunction is accompanied by increased oxidative stress and upregulated proinflammatory and inflammatory mediators in the vasculature. Activation of peroxisome proliferator-activated receptor-alpha (PPAR-α) results in antioxidant and anti-inflammatory effects. This study was designed to investigate the effect of fenofibrate, a PPAR-α activator, on the endothelial dysfunction, oxidative stress, and inflammation in streptozotocin diabetic rats. Diabetic rats received fenofibrate (150 mg kg−1 day−1) for 4 weeks. Fenofibrate treatment restored the impaired endothelium-dependent relaxation and increased basal nitric oxide availability in diabetic aorta, enhanced erythrocyte/liver superoxide dismutase and catalase levels, ameliorated the abnormal serum/aortic thiobarbituric acid reactive substances, and prevented the increased aortic myeloperoxidase without a significant change in serum total cholesterol and triglyceride levels. It did not affect the decreased total homocysteine level and the increased tumor necrosis factor-α level in the serum of diabetic rats. Fenofibrate-induced prevention of the endothelial function seems to be related to its potential antioxidant and antiinflammatory activity.