Effects Of Peroxisome Proliferator-activated Receptor Research Articles

Large‐Scale Screening of Natural Products Transactivating Peroxisome Proliferator‐Activated Receptor α Identifies 9S‐Hydroxy‐10E,12Z,15Z‐Octadecatrienoic Acid and Cymarin as Potential Compounds Capable of Increasing Apolipoprotein A‐I Transcription in Human Liver Cells

Increasing apolipoprotein A-I (apoA-I), the predominant protein of high-density lipoprotein (HDL) particles, has favorable effects on atherogenic risk factors. Here, we investigated the effects of peroxisome proliferator-activated receptor α (PPARα) transactivating compounds on apoA-I transcription in HepG2 cells. A transient PPARα agonist transactivation assay was used to screen 2500 natural compounds. To analyze the effects on apoA-I transcription, human hepatocellular liver carcinoma (HepG2) were exposed to 0.1, 1, and 10 μg/mL of the natural PPARα transactivators. ApoA-I mRNA expression was determined by quantitative polymerase chain reaction. Extensive dose-response experiments were performed using compounds that increased apoA-I transcription by minimally 20%. Kelch-like ECH-associated protein 1 (KEAP) and carnitine palmitoyltransferase 1 alpha (CPT1α) expression were used respectively to confirm Bromodomain-containing protein 4 inhibition or PPARα activation. Twenty-eight natural compounds increased PPARα transactivation by at least twofold. Despite the increased CPT1α expression seen after the addition of most PPARα activating compounds, CPT1α expression and PPARα transactivation did not correlate. Addition of 0.05 μg/mL 9S-hydroxy-10E,12Z,15Z-octadecatrienoic acid (9(S)-HOTrE) increased apoA-I mRNA expression by 35%, whereas 10-25 μg/mL of cymarin increased apoA-I transcription by 37%. However, combining cymarin and 9(S)-HOTrE did not result in a synergistic effect, in contrast this combination even decreased apoA-I transcription. ApoA-I transcription involves multiple regulatory players, and PPARα transactivation alone is not sufficient. A search for natural compounds resembling the molecular structure of 9(S)-HOTrE or cymarin could aid to find additional components that increase apoA-I transcription.

Effects of peroxisome proliferator-activated receptor γ-toll-like receptor 4-tumor necrosis factor-α targeted pathway on hyperglycemia induced myocardium inflammation and oxidative stress

To investigate the potential effects and mechanism on peroxisome proliferator-activated receptor γ-toll-like receptor 4-tumor necrosis factor-α (PPARγ-TLR4-TNF-α) targeted pathway on hyperglycemia induced myocardium inflammation and oxidative stress. Thirty-two Japanese healthy adult rabbits were randomly divided into four groups with 8 rabbits in each group: normal control group (NC group), diabetes mellitus group (DM group), diabetes mellitus + pioglitazone 4 mg×kg-1×d-1 and 8 mg×kg-1×d-1 groups (DM+PGZ 4 mg and 8 mg groups). DM model was reproduced by alloxan of 150 mg/kg through auricular vein injection. On the same day of successful DM model reproduction, the diabetic rabbits were fed with corresponding dose of pioglitazone in DM+PGZ 4 mg and 8 mg groups, but the rabbits in NC group were not challenged. After 8 weeks of feeding, venous blood of left jugular vein bifurcation and myocardium tissue were harvested respectively for the determination of inflammation and oxidative stress parameters. TNF-α, interleukin-1 (IL-1), adiponectin (ADP), nitric oxide (NO) and total nitric oxide synthase (NOS) levels were determined by enzyme linked immunosorbent assay (ELISA), myeloperoxidase (MPO) activity was determined by colorimetric method, superoxide dismutase (SOD) activity was determined by hydroxylamine method, malondialdehyde (MDA) was determined by thiobarbituric acid colorimetric method, and catalase (CAT) activity was determined by UV spectrophotometry method. In addition, the mRNA expressions of TNF-α and TLR4 were determined by real-time quantitate reverse transcription-polymerase chain reaction (RT-qPCR). (1) IL-1 and TNF-α in serum and myocardium of model rabbits were significantly increased, ADP was significantly decreased, and the mRNA expressions of TNF-α and TLR4 in myocardium were significantly increased, indicating a significant inflammatory reaction. The inflammatory reaction in pioglitazone intervention groups was significantly reduced, TNF-α and IL-1 levels in serum and myocardium of DM+PGZ 4 mg and 8 mg groups were significantly decreased as compared with those of DM group [serum: TNF-α (ng/L) was 268.33±46.57, 261.34±33.73 vs. 331.40±69.05, myocardium: TNF-α (ng/L) was 144.72±26.90, 139.59±14.59 vs. 177.48±27.40; serum: IL-1 (ng/L) was 24.40±2.56, 23.35±3.13 vs. 30.08±5.44, myocardium: IL-1 (ng/L) was 21.26±2.85, 20.54±2.75 vs. 24.78±3.60, all P < 0.05], and ADP levels were significantly increased [serum (μg/L): 19.64±8.85, 20.54±7.47 vs. 15.45±3.06, myocardium (μg/L): 10.31±2.22, 11.49±3.42 vs. 7.76±1.77, all P < 0.05], and the mRNA expressions of TNF-α and TLR4 in myocardium were significantly decreased (TNF-α mRNA: 0.15±0.05, 0.14±0.06 vs. 0.25±0.09; TLR4 mRNA: 0.57±0.17, 0.40±0.18 vs. 0.75±0.35, all P < 0.05). (2) Oxidative stress in serum and myocardium of model rabbits was significantly increased, SOD, NO, and total NOS levels were significantly decreased while the serum CAT and MDA levels were significantly increased without effect on MPO. Compared with the DM group, SOD and NO levels in serum and myocardium were significantly increased in DM+PGZ 4 mg and 8 mg groups [serum: SOD (U/L) was 571.39±40.85, 609.28±54.47 vs. 535.10±37.08, myocardium: SOD (U/mg) was 55.74±8.12, 53.60±9.87 vs. 42.26±12.34; serum: NO (μmol/L) was 2.95±0.51, 2.99±0.43 vs. 2.03±0.78, myocardium: NO (nmol/mg) was 1.95±0.37, 2.11±0.26 vs. 1.56±0.33, all P < 0.05], the serum MDA levels were significantly decreased (μmol/L: 20.11±2.34, 19.70±2.02 vs. 23.07±3.06, both P < 0.05), while no significant effect on CAT. There was no significant difference in parameter of inflammatory and oxidative stress between the two pioglitazone intervention groups. 4 mg×kg-1×d-1 pioglitazone could activate PPARγ-TLR4-TNF-α targeted pathway, thus inhibit inflammatory and oxidative stress factors expression, and down-regulate hyperglycemia induced myocardium inflammatory and oxidative stress level, but the effect did not show a dose dependent manner.

Peroxisome proliferator-activated receptor γ plays dual roles on experimental periodontitis in rats.

To investigate the effects of peroxisome proliferator-activated receptor γ (PPARγ) on inflammation control and bone remodelling in experimental periodontitis in rats. Experimental periodontitis was induced in rats by thread ligation around cervixes of mandibular first molars. PPARγ agonist, antagonist and vehicle were intraperitoneally administrated, respectively, into rats. Ninety-six male SD rats were randomly divided into control, ligation+vehicle, ligation+agonist and ligation+antagonist groups. After 1, 4 and 8weeks, alveolar bone loss was assessed by Micro-CT and HE staining. Inflammation and bone metabolism factors were evaluated by ELISA and immunohistochemical examination. Osteoclasts were quantified by tartrate-resistant acid phosphatase (TRAP) staining. Alveolar bone loss was significantly reduced after 1week, while significantly increased after 8weeks in agonist group, but antagonist group showed the opposite trend. Agonist decreased some inflammatory cytokines expression after 1 and 4weeks, downregulated OPG, RUNX2, BMP-2 and upregulated RANKL after 8weeks, but antagonist brought the opposite effect. PPARγ agonist significantly reduced osteoclast counting after 1week, while increased it after 8weeks. During periodontitis progression, PPARγ could inhibit inflammation, prevent bone resorption within a short time, while the long-term PPARγ activation would lead to increased bone resorption, and PPARγ repression by antagonist would enhance alveolar bone formation.

Activation of PPARα by Oral Clofibrate Increases Renal Fatty Acid Oxidation in Developing Pigs.

The objective of this study was to evaluate the effects of peroxisome proliferator-activated receptor α (PPARα) activation by clofibrate on both mitochondrial and peroxisomal fatty acid oxidation in the developing kidney. Ten newborn pigs from 5 litters were randomly assigned to two groups and fed either 5 mL of a control vehicle (2% Tween 80) or a vehicle containing clofibrate (75 mg/kg body weight, treatment). The pigs received oral gavage daily for three days. In vitro fatty acid oxidation was then measured in kidneys with and without mitochondria inhibitors (antimycin A and rotenone) using [1-14C]-labeled oleic acid (C18:1) and erucic acid (C22:1) as substrates. Clofibrate significantly stimulated C18:1 and C22:1 oxidation in mitochondria (p < 0.001) but not in peroxisomes. In addition, the oxidation rate of C18:1 was greater in mitochondria than peroxisomes, while the oxidation of C22:1 was higher in peroxisomes than mitochondria (p < 0.001). Consistent with the increase in fatty acid oxidation, the mRNA abundance and enzyme activity of carnitine palmitoyltransferase I (CPT I) in mitochondria were increased. Although mRNA of mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase (mHMGCS) was increased, the β-hydroxybutyrate concentration measured in kidneys did not increase in pigs treated with clofibrate. These findings indicate that PPARα activation stimulates renal fatty acid oxidation but not ketogenesis.

Dual PPARα/γ ligand TZD18 improves myocardial metabolic remodeling after myocardial infarction in rats.

To investigate the changes in myocardial energy metabolism and the effect of peroxisome proliferator-activated receptor alpha/gamma (PPARα/γ) dual agonist TZD18 on myocardial energy metabolism in rats with heart failure after myocardial infarction. The myocardial infarction model was established by ligating the left anterior descending coronary artery. The rats were randomly divided into the myocardial infarction group (MI group), the TZD18 intervention group (TZD18 group), and the shame surgery group (sham group). 8 weeks later, the blood flow parameters were measured by carotid arterial cannulas, and ventricular remodeling indexes were calculated. Hearts were extracted from rats after the execution. The expressions of PPARα/γ mRNA and α/β-MHC mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). The mitochondrial oxidative respiration activity was measured by a bio-tissue oxygen consumption meter, the content of adenosine in mitochondria was measured by high-performance liquid chromatography, and tritium-labeled adenosine diphosphate incorporation assay was used to detect the transport activity of adenosine nucleotide translocases (ANT). The expression of PPARα/γ mRNA and the ratio of α/β-MHC mRNA in the MI group were significantly decreased, the content of high energy phosphates, respiration activity, ANT transport activity in mitochondria were significantly decreased, the hemodynamic indexes were disturbed and left ventricular weight/body weight ratio (LVW/BW) significantly became higher. TZD18 intervention could increase the expression level of PPARα/γ mRNA and up-regulate the ratio of α/β-MHC mRNA, thus improving mitochondrial respiratory activity and ANT transport activity in rats with heart failure after myocardial infarction, increasing the content of high energy phosphates in mitochondria and improving the remodeling indexes in the ventricle. TZD18 increases both the expression of enzymes related to myocardial energy metabolism and the content of high-energy phosphates in mitochondria. Also, it improves the respiratory activity and ANT transport activity by activating PPARα/γ genes, thus improving the generation and delivery of myocardial energy and protecting the myocardial cells.

Dose-dependent effects of peroxisome proliferator-activated receptors β/δ agonist on systemic inflammation after haemorrhagic shock

IntroductionPPARβ/δ agonists are known to modulate the systemic inflammatory response after sepsis. In this study, inflammation modulation effects of PPARβ/δ are investigated using the selective PPARβ/δ agonist (GW0742) in a model of haemorrhagic shock (HS)-induced sterile systemic inflammation. MethodsBlood pressure-controlled (35±5mmHg) HS was performed in C57/BL6 mice for 90min. Low-dose GW0742 (0.03mg/kg/BW) and high-dose GW0742 (0.3mg/kg/BW) were then administered at the beginning of resuscitation. Mice were sacrificed 6h after induction of HS. Plasma levels of IL-6, IL-1β, IL-10, TNFα, KC, MCP-1, and GM-CSF were determined by ELISA. Myeloperoxidase (MPO) activity in pulmonary and liver tissues was analysed with standardised MPO kits. ResultsIn mice treated with high-dose GW0742, plasma levels of IL-6, IL-1β, and MCP-1 were significantly increased compared to the control group mice. When compared to mice treated with low-dose GW0742 plasma levels of IL-6, IL-1β, GM-CSF, KC, and MCP-1 were significantly elevated in high-dose-treated mice. Low-dose GW0742 treatment was associated with a non-significant downtrend of inflammatory factors in mice with HS. No significant changes of MPO activity in lung and liver were observed between the control group and the GW0742 treatment groups. ConclusionThis study identified dose-dependent effects of GW0742 on systemic inflammation after HS. While high-dose GW0742 substantially enhanced the systemic inflammatory response, low-dose GW0742 led to a downtrend of pro-inflammation cytokine expression. The exact mechanisms are yet unknown and need to be assessed in further studies.

Peroxisome proliferator-activated receptor-gamma: potential molecular therapeutic target for HIV-1-associated brain inflammation

BackgroundDespite the use of combination antiretroviral therapy for the treatment of HIV-1 infection, cognitive impairments remain prevalent due to persistent viral replication and associated brain inflammation. Primary cellular targets of HIV-1 in the brain are macrophages, microglia, and to a certain extent astrocytes which in response to infection release inflammatory markers, viral proteins [i.e., glycoprotein 120 (gp120)] and exhibit impaired glutamate uptake. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily of ligand-activated transcription factors. Compelling evidence suggests that PPARγ exerts anti-inflammatory properties in neurological disorders. The goal of this study was to examine the role of PPARγ in the context of HIV-1ADA gp120-induced inflammation in vitro, in primary cultures of rat astrocytes and microglia, and in vivo, in a rodent model of HIV-1ADA gp120-associated brain inflammation.MethodsPrimary mixed cultures of rat astrocytes and microglia were treated with PPARγ agonists (rosiglitazone or pioglitazone) and exposed to HIV-1ADA gp120. Inflammatory cytokines and indicator of oxidative stress response (TNFα, IL-1β, iNOS) were measured using qPCR, and glutamate transporter (GLT-1) was quantified by immunoblotting. In vivo, rats were administered an intracerebroventricular injection of HIV-1ADA gp120 and an intraperitoneal injection of PPARγ agonist (rosiglitazone) or co-administration with PPARγ antagonist (GW9662). qPCR and immunoblotting analyses were applied to measure inflammatory markers, GLT-1 and PPARγ.ResultsIn primary mixed cultures of rat astrocytes and microglia, HIV-1ADA gp120 exposure resulted in a significant elevation of inflammatory markers and a decrease in GLT-1 expression which were significantly attenuated with rosiglitazone or pioglitazone treatment. Similarly, in vivo, treatment with rosiglitazone reversed the gp120-mediated inflammatory response and downregulation of GLT-1. Furthermore, we demonstrated that the anti-inflammatory effects of PPARγ agonist rosiglitazone were mediated through inhibition of NF-κB.ConclusionOur data demonstrate that gp120 can induce an inflammatory response and decrease expression of GLT-1 in the brain in vitro and in vivo. We have also successfully shown that these effects can be reversed by treatment with PPARγ agonists, rosiglitazone or pioglitazone. Together our data suggest that targeting PPARγ signaling may provide an option for preventing/treating HIV-associated brain inflammation.

PPAR\u03b1 activation protects against cholestatic liver injury

Intrahepatic cholestasis induced by drug toxicity, bile salt export pump (BSEP) deficiency, or pregnancy frequently causes cholestatic liver damage, which ultimately may lead to liver fibrosis and cirrhosis. Here, the preventive and therapeutic effects of peroxisome proliferator-activated receptor α (PPARα) signaling activated by fenofibrate was evaluated on cholestatic liver damage. Metabolomic analysis revealed that alpha-naphthyl isothiocyanate (ANIT)-induced intrahepatic cholestasis resulted in the accumulation of serum long-chain acylcarnitines and triglyceride, and the reduced expression of four fatty acid β-oxidation (β-FAO) relevant genes (Cpt1b, Cpt2, Mcad and Hadha), indicating the disruption of β-FAO. The increase of acylcarnitines in hepatic cell resulted in the enhanced expression of anti-oxidative genes glutathione S-transferases (Gsta2 and Gstm3) directly. As direct PPARα-regulated genes, Cpt1b, Cpt2, and Mcad were up-regulated after pretreatment with PPARα agonist, fenofibrate, indicating the improvement of β-FAO. In the end, the disrupted bile acid metabolism in the enterohepatic circulation and the enhanced oxidative stress and inflammation cytokines induced by ANIT exposure were significantly recovered with the improvement of β-FAO using fenofibrate treatment. These findings provide the rationale for the use of PPARα agonists as therapeutic alternatives for cholestatic liver damage.

Renoprotective effect of a novel selective PPARα modulator K-877 in db/db mice: A role of diacylglycerol-protein kinase C-NAD(P)H oxidase pathway

ObjectiveSeveral clinical studies have shown the beneficial effects of peroxisome proliferator-activated receptor α (PPARα) agonists on diabetic nephropathy. However, the molecular mechanism is not fully understood. Here we show that K-877, a novel selective PPARα modulator, ameliorates nephropathy in db/db mice via inhibition of renal lipid content and oxidative stress. Methods and resultsK-877 (0.5mg/kg/day) was administered to db/db mice for 2 or 12weeks. Short-term treatment did not affect body weight or plasma glucose levels in db/db mice, but attenuated albuminuria, along with improvement of plasma lipid profiles, lipid content including total diacylglycerol (DAG) levels, protein kinase C (PKC) activity, NAD(P)H oxidase-4 expression, and oxidative stress markers, all of which were significantly increased in diabetic kidneys. It increased phosphorylation of 5′-AMP activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), and expression of several genes mediating fatty acid β-oxidation. In addition, long-term treatment ameliorated renal mesangial expansion in db/db mice and improved glycemic control. ConclusionsK-877 administration ameliorates diabetic nephropathy, at least in part, via inhibition of renal lipid content and oxidative stress. The underlying mechanism may be mediated by modulating the renal AMPK-ACC pathway, subsequent acceleration of fatty acid β-oxidation and inhibition of fatty acid synthesis, and thus inhibition of the DAG-PKC-NAD(P)H oxidase pathway, in addition to its systemic effect including improvement of the plasma lipid profile and glycemic control.

Increased peroxisome proliferator-activated receptor γ activity reduces imatinib uptake and efficacy in chronic myeloid leukemia mononuclear cells.

Imatinib is actively transported by organic cation transporter-1 (OCT-1) influx transporter, and low OCT-1 activity in diagnostic chronic myeloid leukemia blood mononuclear cells is significantly associated with poor molecular response to imatinib. Herein we report that, in diagnostic chronic myeloid leukemia mononuclear cells and BCR-ABL1+ cell lines, peroxisome proliferator-activated receptor γ agonists (GW1929, rosiglitazone, pioglitazone) significantly decrease OCT-1 activity; conversely, peroxisome proliferator-activated receptor γ antagonists (GW9662, T0070907) increase OCT-1 activity. Importantly, these effects can lead to corresponding changes in sensitivity to BCR-ABL kinase inhibition. Results were confirmed in peroxisome proliferator-activated receptor γ-transduced K562 cells. Furthermore, we identified a strong negative correlation between OCT-1 activity and peroxisome proliferator-activated receptor γ transcriptional activity in diagnostic chronic myeloid leukemia patients (n=84; P<0.0001), suggesting that peroxisome proliferator-activated receptor γ activation has a negative impact on the intracellular uptake of imatinib and consequent BCR-ABL kinase inhibition. The inter-patient variability of peroxisome proliferator-activated receptor γ activation likely accounts for the heterogeneity observed in patient OCT-1 activity at diagnosis. Recently, the peroxisome proliferator-activated receptor γ agonist pioglitazone was reported to act synergistically with imatinib, targeting the residual chronic myeloid leukemia stem cell pool. Our findings suggest that peroxisome proliferator-activated receptor γ ligands have differential effects on circulating mononuclear cells compared to stem cells. Since the effect of peroxisome proliferator-activated receptor γ activation on imatinib uptake in mononuclear cells may counteract the clinical benefit of this activation in stem cells, caution should be applied when combining these therapies, especially in patients with high peroxisome proliferator-activated receptor γ transcriptional activity.

Inhibition of ERK activity enhances the cytotoxic effect of peroxisome proliferator-activated receptor γ (PPARγ) agonists in HeLa cells

In this study, we examined whether the peroxisome proliferator-activated receptor γ (PPARγ) agonists, ciglitazone (CGZ) and troglitazone (TGZ), induce cell death in human cervical cancer HeLa cells. The cells were treated with a range of CGZ or TGZ doses for 24 or 48 h. Low concentrations of CGZ (≤10 μM) or TGZ (≤20 μM) had no effect on cell viability whereas higher doses induced cell death in a time- and dose-dependent manner as evidenced by the detection of activated caspase-3 and PARP cleavage. Treatment with the PPARγ antagonist GW9662 followed by PPARγ agonists did not increase CGZ- or TGZ-induced cell death, indicating that PPARγ agonists induced HeLa cell death independently of PPARγ. Moreover, ERK1/2 activation was observed at a CGZ concentration of 25 μM and a TGZ concentration of 35 μM, both of which induced cell death. To elucidate the role of ERK1/2 activated by the two PPARγ agonists, the effect of U0126, an inhibitor of ERK1/2, on PPARγ-agonist-induced cell death was examined. Treatment with 10 or 20 μM U0126 followed by CGZ or TGZ induced the down-regulation of ERK1/2 activity and a decrease in Bcl-2 expression accompanied by the collapse of mitochondrial membrane potential, which in turn significantly enhanced CGZ- or TGZ-induced apoptotic cell death. Our results suggest that PPARγ agonists are capable of inducing apoptotic cell death in HeLa cells independently of PPARγ and that inhibition of ERK1/2 activity offers a strategy to enhance the cytotoxicity of PPARγ agonists in the treatment of cervical cancer.

Role of UCP2 in the protective effects of PPARβ/δ activation on lipopolysaccharide-induced endothelial dysfunction

Bacterial endotoxin lipopolysaccharide (LPS) activates inflammatory pathways, induces cytokine expression in the endothelium, augments reactive oxygen species (ROS) production in the vascular wall, and induces endothelial dysfunction. The aim of the present study was to analyze the effects of peroxisome proliferator-activated receptor (PPAR)β/δ activation on LPS-induced inflammation, oxidative stress and endothelial dysfunction and to determine whether uncoupling protein-2 (UCP2) plays a role in these effects. In vivo, the PPARβ/δ agonist GW0742 treatment prevented the LPS-induced reduction in aortic relaxation, the increase in vascular ROS production, the upregulation of NOX1, NOX2, p47phox, and p22phox mRNA levels, and the endoplasmic reticulum (ER) stress markers in mice. We show that in mouse aortic endothelial cells (MAECs), GW0742 prevented the decreased A23187-stimulated nitric oxide (NO) production, and the increased intracellular ROS levels caused by exposure to LPS in vitro. The PPARβ/δ antagonist GSK0660 abolished all these in vivo and in vitro protective effects induced by GW0742. This agonist also restored the reduced expression of UCP2 and mitofusin-2 induced by LPS. The effects of GW0742 on NO and ROS production in MAEC exposed to LPS were abolished by the UCP2 inhibitor genipin or by siRNA targeting UCP-2. Genipin also suppressed the expressional changes on NADPH oxidase and ER stress markers induced by GW0742. In conclusion, PPARβ/δ activation restored the LPS-induced endothelial dysfunction by upregulation of UCP2, with the subsequent alleviation of ER stress and NADPH oxidase activity, thus reducing intracellular ROS production and increasing NO bioavailability.

PPARγ Inhibits VSMC Proliferation and Migration via Attenuating Oxidative Stress through Upregulating UCP2.

Increasing evidence showed that abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) are common event in the pathophysiology of many vascular diseases, including atherosclerosis and restenosis after angioplasty. Among the underlying mechanisms, oxidative stress is one of the principal contributors to the proliferation and migration of VSMCs. Oxidative stress occurs as a result of persistent production of reactive oxygen species (ROS). Recently, the protective effects of peroxisome proliferator-activated receptor γ (PPARγ) against oxidative stress/ROS in other cell types provide new insights to inhibit the suggests that PPARγ may regulate VSMCs function. However, it remains unclear whether activation of PPARγ can attenuate oxidative stress and further inhibit VSMC proliferation and migration. In this study, we therefore investigated the effect of PPARγ on inhibiting VSMC oxidative stress and the capability of proliferation and migration, and the potential role of mitochondrial uncoupling protein 2 (UCP2) in oxidative stress. It was found that platelet derived growth factor-BB (PDGF-BB) induced VSMC proliferation and migration as well as ROS production; PPARγ inhibited PDGF-BB-induced VSMC proliferation, migration and oxidative stress; PPARγ activation upregulated UCP2 expression in VSMCs; PPARγ inhibited PDGF-BB-induced ROS in VSMCs by upregulating UCP2 expression; PPARγ ameliorated injury-induced oxidative stress and intimal hyperplasia (IH) in UCP2-dependent manner. In conclusion, our study provides evidence that activation of PPARγ can attenuate ROS and VSMC proliferation and migration by upregulating UCP2 expression, and thus inhibit IH following carotid injury. These findings suggest PPARγ may represent a prospective target for the prevention and treatment of IH-associated vascular diseases.

Metabolic and Inflammatory Adaptation of Reactive Astrocytes: Role of PPARs.

Astrocyte-mediated inflammation is associated with degenerative pathologies such as Alzheimer's and Parkinson's diseases and multiple sclerosis. The acute inflammation and morphological and metabolic changes that astrocytes develop after the insult are known as reactive astroglia or astrogliosis that is an important response to protect and repair the lesion. Astrocytes optimize their metabolism to produce lactate, glutamate, and ketone bodies in order to provide energy to the neurons that are deprived of nutrients upon insult. Firstly, we review the basis of inflammation and morphological changes of the different cell population implicated in reactive gliosis. Next, we discuss the more active metabolic pathways in healthy astrocytes and explain the metabolic response of astrocytes to the insult in different pathologies and which metabolic alterations generate complications in these diseases. We emphasize the role of peroxisome proliferator-activated receptors isotypes in the inflammatory and metabolic adaptation of astrogliosis developed in ischemia or neurodegenerative diseases. Based on results reported in astrocytes and other cells, we resume and hypothesize the effect of peroxisome proliferator-activated receptor (PPAR) activation with ligands on different metabolic pathways in order to supply energy to the neurons. The activation of selective PPAR isotype activity may serve as an input to better understand the role played by these receptors on the metabolic and inflammatory compensation of astrogliosis and might represent an opportunity to develop new therapeutic strategies against traumatic brain injuries and neurodegenerative diseases.

Role of peroxisome proliferator-activated receptor alpha and gamma in antiangiogenic effect of pomegranate peel extract.

Herbal medicines are promising cancer preventive candidates. It has been shown that Punica granatum L. could inhibit angiogenesis and tumor invasion. In this study, we investigated whether the anti-angiogenic effect of pomegranate peel extract (PPE) is partly attributable to Peroxisome proliferator-activated receptors (PPARs) activation in the Human Umbilical Vein Endothelial Cells (HUVECs). Ethanol extract from PPE was prepared. HUVECs were treated in four groups (with PPE (10 μg/ml) alone, PPE with or without PPARγ (T0070907) and α (GW6471) antagonists, and control group). The possible effect of PPARs on angiogenic regulation was checked by Matrigel assay. The mRNA expression levels of vascular endothelial growth factor (VEGF) was detected by Quantitative reverse transcription-polymerase chain reaction (QRT-PCR). PPE significantly inhibited both tube formation (size, length, and junction of tubes) and VEGF mRNA expression (P<0.05). Our results showed that the anti-angiogenic effects of PPE were significantly reversed by both PPAR antagonists (P<0.05). There was no difference between PPE plus antagonists groups and the control group. In summary our results showed that the anti-angiogenic effects of PPE could be mediated in part through PPAR dependent pathway.

Protective Effect of Peroxisome Proliferator-Activated Receptor α Activation against Cardiac Ischemia-Reperfusion Injury Is Related to Upregulation of Uncoupling Protein-3.

Activation of peroxisome proliferator-activated receptor α (PPARα) confers cardioprotection, while its mechanism remains elusive. We investigated the protective effect of PPARα activation against cardiac ischemia-reperfusion injury in terms of the expression of uncoupling protein (UCP). Myocardial infarct size and UCP expression were measured in rats treated with WY-14643 20 mg/kg, a PPARα ligand, or vehicle. WY-14643 increased UCP3 expression in vivo. Myocardial infarct size was decreased in the WY-14643 group (76 ± 8% versus 42 ± 12%, P<0.05). During reperfusion, the incidence of arrhythmia was higher in the control group compared with the WY-14643 group (9/10 versus 3/10, P<0.05). H9c2 cells were incubated for 24 h with WY-14643 or vehicle. WY-14643 increased UCP3 expression in H9c2 cells. WY-14643 decreased hypoxia-stimulated ROS production. Cells treated with WY-14643 were more resistant to hypoxia-reoxygenation than the untreated cells. Knocking-down UCP3 by siRNA prevented WY-14643 from attenuating the production of ROS. UCP3 siRNA abolished the effect of WY-14643 on cell viability against hypoxia-reoxygenation. In summary, administration of PPARα agonist WY-14643 mitigated the extent of myocardial infarction and incidence of reperfusion-induced arrhythmia. PPARα activation conferred cytoprotective effect against hypoxia-reoxygenation. Associated mechanisms involved increased UCP3 expression and resultant attenuation of ROS production.

Effects of peroxisome proliferator-activated receptor (PPAR)delta agonist on sternohyoid muscle in MS model rats

Effects of peroxisome proliferator-activated receptor (PPAR)delta agonist on sternohyoid muscle in MS model rats

Bovine (Bos taurus) Bone Marrow Mesenchymal Cell Differentiation to Adipogenic and Myogenic Lineages

Purpose: We evaluated the effect of peroxisome proliferator-activated receptor (PPAR) agonists on the differentiation and metabolic features of bovine bone marrow-derived mesenchymal cells induced to adipogenic or myogenic lineages. Methods: Cells isolated from 7-day-old calves were cultured in basal medium (BM). For adipogenic differentiation, cells were cultured for one passage in BM and then transferred to a medium supplemented with either rosiglitazone, telmisartan, sirtinol or conjugated c-9, t-11 linoleic acid; for myogenic differentiation, third-passage cells were added with either bezafibrate, telmisartan or sirtinol. The expression of PPARγ (an adipogenic differentiation marker), myosin heavy chain (MyHC; a myogenic differentiation marker) and genes related to energy metabolism were measured by quantitative real-time PCR in a completely randomized design. Results: For adipogenic differentiation, 20 µM telmisartan showed the highest PPARγ expression (15.58 ± 0.62-fold, p < 0.0001), and differences in the expression of energy metabolism-related genes were found for hexokinase II, phosphofructokinase, adipose triglyceride lipase, acetyl-CoA carboxylase α(ACACα) and fatty acid synthase (p < 0.001), but not for ACACβ (p = 0.4275). For myogenic differentiation, 200 µM bezafibrate showed the highest MyHC expression (73.98 ± 11.79-fold), and differences in the expression of all energy metabolism-related genes were found (p < 0.05). Conclusions: Adipocyte and myocyte differentiation are enhanced with telmisartan and bezafibrate, respectively, and energy uptake, storage and mobilization are improved with both.

Effects of macrophage-dependent peroxisome proliferator-activated receptor γ signalling on adhesion formation after abdominal surgery in an experimental model.

The pathophysiology of adhesion formation after abdominal and pelvic surgery is still largely unknown. The aim of the study was to investigate the role of macrophage polarization and the effect of peroxisome proliferator-activated receptor (PPAR) γ stimulation on adhesion formation in an animal model. Peritoneal adhesion formation was induced by the creation of ischaemic buttons within the peritoneal wall and the formation of a colonic anastomosis in wild-type, interleukin (IL) 10-deficient (IL-10(-/-) ), IL-4-deficient (IL-4(-/-) ) and CD11b-Cre/PPARγ(fl) (/fl) mice. Adhesions were assessed at regular intervals, and cell preparations were isolated from ischaemic buttons and normal peritoneum. These samples were analysed for macrophage differentiation and its markers, and expression of cytokines by quantitative PCR, fluorescence microscopy, arginase activity and pathological examination. Some animals underwent pioglitazone (PPAR-γ agonist) or vehicle treatment to inhibit adhesion formation. Anastomotic healing was evaluated by bursting pressure measurement and collagen gene expression. Macrophage M2 marker expression and arginase activity were raised in buttons without adhesions compared with buttons with adhesions. IL-4(-/-) and IL-10(-/-) mice were not affected, whereas CD11b-Cre/PPARγ(fl) (/fl) mice showed decreased arginase activity and increased adhesion formation. Perioperative pioglitazone treatment increased arginase activity and decreased adhesion formation in wild-type but not CD11b-Cre/PPARγ(fl) (/fl) mice. Pioglitazone had no effect on anastomotic healing. Endogenous macrophage-specific PPAR-γ signalling affected arginase activity and macrophage polarization, and counter-regulated peritoneal adhesion manifestation. Pharmacological PPAR-γ agonism induced a shift towards macrophage M2 polarization and ameliorated adhesion formation in a macrophage-dependent manner. Surgical relevance Postoperative adhesion formation is frequently seen after abdominal surgery and occurs in response to peritoneal trauma. The pathogenesis is still unknown but includes an imbalance in fibrinolysis, collagen production and inflammatory mechanisms. Little is known about the role of macrophages during adhesion formation. In an experimental model, macrophage M2 marker expression was associated with reduced peritoneal adhesion formation and involved PPAR-γ-mediated arginase activity. Macrophage-specific PPAR-γ deficiency resulted in reduced arginase activity and aggravated adhesion formation. Pioglitazone, a PPAR-γ agonist, induced M2 polarization and reduced postoperative adhesion formation without compromising anastomotic healing in mice. Pioglitazone ameliorated postoperative adhesion formation without compromising intestinal wound healing. Therefore, perioperative PPAR-γ agonism might be a promising strategy for prevention of adhesion formation after abdominal surgery.

Activated peroxisome proliferator-activated receptor α inhibiting the lipopolysaccharide-induced macrophage-mediated inflammatory responses by promoting the autophagy

Objective To investigate the effects of peroxisome proliferator-activated receptor α (PPARα) on macrophage-mediated inflammatory responses with the interference of lipopolysaccharide and the possible mechanism. Methods The bone marrow stem cells were isolated from the femora of mice. The granulocyte-macrophage colony stimulating factor (GM-CSF) was used to stimulate the in vitro differentiation from bone marrow stem cells into primary macrophages. An in vitro model with cultured cells expressing inflammatory cytokines was established by treating the primary macrophages with lipopolysaccharide (LPS). A specific chemical agonist, Wy-14643, was used to activate PPARα. Autophagy inhibitors including 3-methyladenine (3-MA) and small interfering RNA against Atg7 (Atg7 siRNA) were used to inhibit the autophagy. Western blot assay was performed to detect the expression of autophagy-related proteins (Atg5, Atg7, Beclin-1 and LC3). The transcriptional levels of TNF-α, IL-1β, IL-6, Atg5, Atg7 and Beclin-1 were analyzed by qRT-PCR. Results Compared with the macrophages treated with LPS alone, those pretreated with various concentrations of Wy-14643 (10 μmol/L, 25 μmol/L and 50 μmol/L) showed inhibited expression of proinflammatory cytokines (TNF-α, IL-1β and IL-6) and enhanced expression of autophagy-related proteins (Atg5, Atg7 and Beclin-1) at mRNA level in a dose-dependent manner. The expression of autophagy-related proteins (Atg5, Atg7, Beclin-1 and LC3) by macrophages was promoted with the pretreatment of Wy-14643 as indicated by Western blot assay. The transcriptional levels of TNF-α, IL-1β and IL-6 were increased in Wy-14643 pretreated-macrophages after stimulation with 3-MA or Atg7 siRNA. Conclusion PPARα suppressed the macrophage-mediated inflammatory responses by promoting autophagy, suggesting that the PPARα-autophagy pathway might be one of the signaling pathways regulating LPS induced-inflammatory responses. Key words: Peroxisome proliferator-activated receptor α; Autophagy; Inflammatory response; Macrophages; Lipopolysaccharide