Peroxisome Proliferator Response Element Research Articles

Differential regulation of hepatic SH3 domain binding kinase 1 (SBK1) expression in mouse and goldfish

SH3 domain binding kinase 1 (SBK1) is a serine/threonine kinase that belongs to the new kinase family (NFK) with limited information on its function. Previous studies reported that SBK1 plays a role in memory formation, lipid metabolism, and cancer cell progression. Nevertheless, the regulatory mechanism of Sbk1 expression in various tissues remains unknown. We report here that Sbk1 expression in mouse hepatocytes was downregulated by glucocorticoid, whereas saturated and unsaturated fatty acids were stimulators of Sbk1 expression. The regulatory role of glucocorticoid and fatty acid was further confirmed by the Sbk1 promoter assay, which aligned with the presence of several glucocorticoid-response elements (GRE) and peroxisome proliferator responsive elements (PPRE) in the mouse Sbk1 promoter. The inhibitory effect of glucocorticoids on hepatic Sbk1 expression and protein content could also be demonstrated in vivo after prednisolone injection. Moreover, the expression of SBK1 in goldfish (gfSBK1) was also sensitive to glucocorticoid suppression as their mouse orthologues. In contrast, insulin had a differential action on SBK1 expression that it promoted the expression of all SBK1 isoforms in the goldfish hepatocytes but inhibited Sbk1 expression in the mouse hepatocytes. Together, our findings indicate that SBK1 expression is hormone- and nutrient-sensitive with a species-specific response.

Sinomenine alleviates lipopolysaccharide-induced acute lung injury via a PPARβ/δ-dependent mechanism

Evidence is mounting that sinomenine and peroxisome proliferator-activated receptor β/δ (PPARβ/δ) are effective against lipopolysaccharide (LPS)-induced acute lung injury (ALI) via anti-inflammatory properties. However, it is unknown whether PPARβ/δ plays a role in the protective effect of sinomenine on ALI. Here, we initially observed that preemptive administration of sinomenine markedly alleviated lung pathological changes, pulmonary edema and neutrophil infiltration, accompanied by inhibition of the expression of the pro-inflammatory cytokines Tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6), which were largely reversed following the addition of a PPARβ/δ antagonist. Subsequently, we also noticed that sinomenine upregulated adenosine A2A receptor expression in a PPARβ/δ-dependent manner in LPS-stimulated bone marrow-derived macrophages (BMDMs). Further investigation indicated that PPARβ/δ directly bound to the functional peroxisome proliferator responsive element (PPRE) in the adenosine A2A receptor gene promoter region to enhance the expression of the adenosine A2A receptor. Sinomenine was identified as a PPARβ/δ agonist. It could bind with PPARβ/δ, and promote the nuclear translocation and transcriptional activity of PPARβ/δ. In addition, combined treatment with sinomenine and an adenosine A2A receptor agonist exhibited synergistic effects and better protective roles than their single use against ALI. Taken together, our results reveal that sinomenine exerts advantageous effects on ALI by activating of PPARβ/δ, with the subsequent upregulation of adenosine A2A receptor expression, and provide a novel and potential therapeutic application for ALI.

Ursolic acid promotes microglial polarization toward the M2 phenotype via PPARγ regulation of MMP2 transcription

Microglia, which are the primary inflammatory cells of the brain, can undergo phenotypic switching between M1 and M2 polarization, which have opposing effects on inflammation. Peroxisome proliferator-activated receptor gamma (PPARγ) is a member of the nuclear receptor family of ligand-inducible transcription factors, and PPARγ is known to regulate M2 macrophage polarization. Previous studies have shown that the natural pentacyclic triterpenoid ursolic acid (3β-hydroxy-urs-12-en-28-oic acid; UA) influences microglial activation. Additionally, UA increases tissue inhibitor matrix metalloproteinase 1 (TIMP1), while greatly reducing the release of matrix metalloproteinase 2 (MMP2) and MMP9 in a PPARγ-dependent manner. Here, we examined the anti-inflammatory properties of UA by observing how well it promotes the phenotypic transition of lipopolysaccharide (LPS) and interferon gamma (IFNγ)-activated BV2 microglia from M1 to M2 polarization. To determine if PPARγ is involved in the underlying molecular pathway, we treated rats with UA and the PPARγ inhibitor BADGE. We also investigated the mechanisms by which PPARγ controls transcription from the MMP2 promoter. The in-vitro experiments showed that UA shifted LPS/IFNγ-activated BV2 microglia from the M1 to the M2 phenotype, which was associated with a reduction in the neurotoxic factors MMP2 and MMP9, and an increase in the anti-inflammatory factor TIMP1. Co-treatment with increased MMP2 and MMP9 synthesis while decreasing TIMP1 release, indicating that UA has anti-inflammatory effects on LPS/IFNγ-activated BV2 cells via activation of PPARγ. Next, we found that PPARγ directly influences MMP2 transcriptional activity by identifying the crucial peroxisome proliferator response element (PPRE) among five potential PPREs in the MMP2 promoter. These results suggest that UA has a protective anti-inflammatory effect against neuroinflammatory toxicity, which is exerted by direct activation of PPARγ and selectively modulates microglial polarization and suppresses MMP2 formation.

DNA-Protein-Interaction (DPI)-ELISA Assay for PPAR-γ Receptor Binding.

Dysregulation of peroxisome proliferator-activated receptor (PPAR)-γ has been described in a plethora of pathological conditions, such as diabetes, obesity, inflammatory-related diseases, and cancer. Therefore, identifying novel drugs that are able to restore PPAR-γ activity is a current challenge, which is however slowed down by the lack of a rapid and reproducible activity assay. To date, only a few methods are able to characterize PPAR-γ activity and most of them are expensive, time-consuming, and not always quantitative.Herein, we presented a sensitive multi-well colorimetric assay, termed DNA-Protein-Interaction enzyme-linked immunosorbent assay (DPI-ELISA). This method is based on the ELISA principle, except that it allows to detect only activated PPAR-γ because, unlike classical ELISA, PPAR-γ is not captured by an antibody but by a double-stranded oligonucleotide probe containing its peroxisome proliferator response elements (PPRE) consensus sequence. Thus, DPI-ELISA represents a useful assay for PPAR-γ studies, as well as for the identification of novel PPAR-γ ligands for the development of innovative therapeutic approaches to human diseases where PPAR-γ signaling is dysregulated.

Auraptene, a citrus peel-derived natural product, prevents myocardial infarction-induced heart failure by activating PPARα in rats

BackgroundAuraptene derived from the peel of Citrus hassaku possesses anti-tumor, anti-inflammatory, and neuroprotective activities. Thus, it could be a valuable pharmacological alternative to treat some diseases. However, the therapeutic value of auraptene for heart failure (HF) is unknown. Study design/methodsIn cultured cardiomyocytes from neonatal rats, the effect of auraptene on phenylephrine-induced hypertrophic responses and peroxisome proliferator-activated receptor-alpha (PPARα)-dependent gene transcriptions. To investigate whether auraptene prevents the development of heart failure after myocardial infarction (MI) in vivo, Sprague–Dawley rats with moderate MI (fractional shortening < 40%) were randomly assigned for treatment with low- or high-dose auraptene (5 or 50 mg/kg/day, respectively) or vehicle for 6 weeks. The effects of auraptene were evaluated by echocardiography, histological analysis, and the measurement of mRNA levels of hypertrophy, fibrosis, and PPARα-associated genes. ResultsIn cultured cardiomyocytes, auraptene repressed phenylephrine-induced hypertrophic responses, such as increases in cell size and activities of atrial natriuretic factor and endothelin-1 promoters. Auraptene induced PPARα-dependent gene activation by enhancing cardiomyocyte peroxisome proliferator-responsive element reporter activity. The inhibition of PPARα abrogated the protective effect of auraptene on phenylephrine-induced hypertrophic responses. In rats with MI, auraptene significantly improved MI-induced systolic dysfunction and increased posterior wall thickness compared to the vehicle. Auraptene treatment also suppressed MI-induced increases in myocardial cell diameter, perivascular fibrosis, and expression of hypertrophy and fibrosis response markers at the mRNA level compared with vehicle treatment. MI-induced decreases in the expression of PPARα-dependent genes were improved by auraptene treatment. ConclusionsAuraptene has beneficial effects on MI-induced cardiac hypertrophy and left ventricular systolic dysfunction in rats, at least partly due to PPARα activation. Further clinical studies are required to evaluate the efficacy of auraptene in patients with HF.

Long non-coding RNA G23Rik attenuates fasting-induced lipid accumulation in mouse liver

Peroxisome proliferator-activated receptor α (PPARα) is a key mediator of lipid metabolism and metabolic stress in the liver. A recent study revealed that PPARα-dependent long non-coding RNAs (lncRNAs) play an important role in modulating metabolic stress and inflammation in the livers of fasted mice. Here hepatic lncRNA 3930402G23Rik (G23Rik) was found to have active peroxisome proliferator response elements (PPREs) within its promoter and is directly regulated by PPARα. Although G23Rik RNA was expressed to varying degrees in several tissues, the PPARα-dependent regulation of this lncRNA was only observed in the liver. Pharmacological activation of PPARα induced PPARα recruitment at the G23Rik promoter and a pronounced increase in hepatic G23Rik lncRNA expression. A G23Rik-null mouse line was developed to further characterize the function of this lncRNA in the liver. G23Rik-null mice were more susceptible to hepatic lipid accumulation in response to acute fasting. Histological analysis further revealed a pronounced buildup of lipid droplets and a significant increase in neutral triglycerides and lipids as indicated by enhanced oil red O staining of liver sections. Hepatic cholesterol, non-esterified fatty acid, and triglyceride levels were significantly elevated in G23Rik-null mice and associated with induction of the lipid-metabolism related gene Cd36. These findings provide evidence for a lncRNA dependent mechanism by which PPARα attenuates hepatic lipid accumulation in response to metabolic stress through lncRNA G23Rik induction.

Anti-influenza A Virus Effects and Mechanisms of Emodin and Its Analogs via Regulating PPARα/γ-AMPK-SIRT1 Pathway and Fatty Acid Metabolism.

The peroxisome proliferator-activated receptor (PPAR) α/γ-adenosine 5′-monophosphate- (AMP-) activated protein kinase- (AMPK-) sirtuin-1 (SIRT1) pathway and fatty acid metabolism are reported to be involved in influenza A virus (IAV) replication and IAV-pneumonia. Through a cell-based peroxisome proliferator responsive element- (PPRE-) driven luciferase bioassay, we have investigated 145 examples of traditional Chinese medicines (TCMs). Several TCMs, such as Polygonum cuspidatum, Rheum officinale Baillon, and Aloe vera var. Chinensis (Haw.) Berg., were found to possess high activity. We have further detected the anti-IAV activities of emodin (EMO) and its analogs, a group of common important compounds of these TCMs. The results showed that emodin and its several analogs possess excellent anti-IAV activities. The pharmacological tests showed that emodin significantly activated PPARα/γ and AMPK, decreased fatty acid biosynthesis, and increased intracellular ATP levels. Pharmaceutical inhibitors, siRNAs for PPARα/γ and AMPKα1, and exogenous palmitate impaired the inhibition of emodin. The in vivo test also showed that emodin significantly protected mice from IAV infection and pneumonia. Pharmacological inhibitors for PPARα/γ and AMPK signal and exogenous palmitate could partially counteract the effects of emodin in vivo. In conclusion, emodin and its analogs are a group of promising anti-IAV drug precursors, and the pharmacological mechanism of emodin is linked to its ability to regulate the PPARα/γ-AMPK pathway and fatty acid metabolism.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα.

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

Upregulation of IL-1 Receptor Antagonist by Aspirin in Glial Cells via Peroxisome Proliferator-Activated Receptor-Alpha.

Background:Neuroinflammation is a recognized aspect of Alzheimer’s disease (AD) and other neurological illnesses. Interleukin 1 receptor antagonist (IL-1Ra) is an anti-inflammatory molecule, which inhibits inflammatory molecules in different cells including brain cells. However, mechanisms for upregulating IL-1Ra in brain cells are poorly understood.Objective:Since aspirin is a widely available pain reliever that shows promise beyond its known pain-relieving capacity, we examined whether aspirin could upregulate the IL-1Ra in the brain.Methods:We employed PCR, real-time PCR, western blot, immunostaining, chromatin immunoprecipitation (ChIP), and lentiviral transduction in glial cells. 5xFAD mice, an animal model of AD, were treated with aspirin orally via gavage.Results:Aspirin increased the expression of IL-1Ra mRNA and protein in primary mouse astrocytes and mouse BV-2 microglial cells. While investigating the mechanism, we found that the IL-1Ra gene promoter harbors peroxisome proliferator response element (PPRE) and that aspirin upregulated IL-1Ra in astrocytes isolated from peroxisome proliferator-activated receptor-beta knockout (PPARβ–/–), but not PPARα–/–, mice. Moreover, we observed that aspirin bound to tyrosine 314 residue of PPARα to stimulate IL-1Ra and that aspirin treatment also increased the recruitment of PPARα to the IL-1Ra promoter. Accordingly, aspirin increased IL-1Ra in vivo in the brain of wild type and PPARβ–/–, but not in PPARα–/– mice. Similarly, aspirin treatment also increased astroglial and microglial IL-1Ra in the cortex of 5xFAD, but not 5xFAD/PPARα–/– mice.Conclusion:Aspirin may reduce the severity of different neurological conditions by upregulating IL-1Ra and reducing the inflammation.

Natural Compound 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al from Momordica charantia Acts as PPARγ Ligand.

Momordica charantia is a popular vegetable associated with effective complementary and alternative diabetes management in some parts of the world. However, the molecular mechanism is less commonly investigated. In this study, we investigated the association between a major cucurbitane triterpenoid isolated from M. charantia, 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al (THCB) and peroxisome proliferator activated receptor gamma (PPARγ) activation and its related activities using cell culture and molecular biology techniques. In this study, we report on both M. charantia fruit crude extract and THCB in driving the luciferase activity of Peroxisome Proliferator Response Element, associated with PPARγ activation. Other than that, THCB also induced adipocyte differentiation at far less intensity as compared to the full agonist rosiglitazone. In conjunction, THCB treatment on adipocytes also resulted in upregulation of PPAR gamma target genes expression; AP2, adiponectin, LPL and CD34 at a lower magnitude compared to rosiglitazone’s induction. THCB also induced glucose uptake into muscle cells and the mechanism is via Glut4 translocation to the cell membrane. In conclusion, THCB acts as one of the many components in M. charantia to induce hypoglycaemic effect by acting as PPARγ ligand and inducing glucose uptake activity in the muscles by means of Glut4 translocation.

Synthesis of DHA (omega-3 fatty acid): FADS2 gene polymorphisms and regulation by PPARα

In humans, in several biological systems, in particular the nervous system, the FADS2 gene transcribes Δ6-desaturase, which is the rate-limiting enzyme for converting α-linolenic acid into docosahexaenoic acid (an n-3 fatty acid). The peroxisome proliferator-activated receptor α (PPARα) modulates the transcription of FADS2 gene by interacting with a second transcription factor: the retinoid X receptor α (RXRα). These transcription factors take the form of a PPARα-RXRα heterodimer and are modulated by the ligands that modify their respective structures and enable them to bind to the peroxisome proliferator response element (PPRE) located in the promoter region of the FADS2 gene. Free estradiol induces the activation of PPARα via two pathways (i) transcription through genomic action mediated by an estrogen receptor; (ii) a non-genomic effect that allows for phosphorylation and activates PPARα via the ERK1/2-MAPK pathway. Phosphorylation is an on/off switch for PPARα transcription activity. Since Δ6-desaturase expression is retro-inhibited by free intracellular DHA in a dose-dependent manner, this position paper proposes an original hypothesis: if DHA simultaneously binds to both phosphorylated PPARα and RXRα, the resulting DHA-PPARαP-RXRα-DHA heterodimer represses FADS2 gene via PPRE. The retinoic acids-RARα-RXRα-DHA heterodimer would not dissociate from corepressors and would prevent coactivators from binding to FADS2. We speculate that SNPs, which are mostly located on PPRE, modulate the binding affinities of DHA-PPARαP-RXRα-DHA heterodimer to PPRE. The DHA-PPARαP-RXRα-DHA heterodimer’s greater affinity for PPRE results in a decreased production of D6D and DHA. FADS2 promoter polymorphism would increase the competition between DHA and other ligands, in accordance with their concentrations and affinities.

The Role of Nrf2 and PPARγ in the Improvement of Oxidative Stress in Hypertension and Cardiovascular Diseases

Reactive oxygen species are an important element of redox regulation in cells and tissues. During physiological processes, molecules undergo chemical changes caused by reduction and oxidation reactions. Free radicals are involved in interactions with other molecules, leading to oxidative stress. Oxidative stress works two ways depending on the levels of oxidizing agents and products. Excessive action of oxidizing agents damages biomolecules, while a moderate physiological level of oxidative stress (oxidative eustress) is necessary to control life processes through redox signaling required for normal cellular operation. High levels of reactive oxygen species (ROS) mediate pathological changes. Oxidative stress helps to regulate cellular phenotypes in physiological and pathological conditions. Nrf2 (nuclear factor erythroid 2-related factor 2, NFE2L2) transcription factor functions as a target nuclear receptor against oxidative stress and is a key factor in redox regulation in hypertension and cardiovascular disease. Nrf2 mediates transcriptional regulation of a variety of target genes. The Keap1-Nrf2-ARE system regulates many detoxification and antioxidant enzymes in cells after the exposure to reactive oxygen species and electrophiles. Activation of Nrf2/ARE signaling is differentially regulated during acute and chronic stress. Keap1 normally maintains Nrf2 in the cytosol and stimulates its degradation through ubiquitination. During acute oxidative stress, oxidized molecules modify the interaction of Nrf2 and Keap1, when Nrf2 is released from the cytoplasm into the nucleus where it binds to the antioxidant response element (ARE). This triggers the expression of antioxidant and detoxification genes. The consequence of long-term chronic oxidative stress is activation of glycogen synthase kinase 3β (GSK-3β) inhibiting Nrf2 activity and function. PPARγ (peroxisome proliferator-activated receptor gamma) is a nuclear receptor playing an important role in the management of cardiovascular diseases, hypertension and metabolic syndrome. PPARγ targeting of genes with peroxisome proliferator response element (PPRE) has led to the identification of several genes involved in lipid metabolism or oxidative stress. PPARγ stimulation is triggered by endogenous and exogenous ligands – agonists and it is involved in the activation of several cellular signaling pathways involved in oxidative stress response, such as the PI3K/Akt/NOS pathway. Nrf2 and PPARγ are linked together with their several activators and Nrf2/ARE and PPARγ/PPRE pathways can control several types of diseases.

Fenofibrate Reduces the Severity of Neuroretinopathy in a Type 2 Model of Diabetes without Inducing Peroxisome Proliferator-Activated Receptor Alpha-Dependent Retinal Gene Expression.

Fenofibrate slows the progression of clinical diabetic retinopathy (DR), but its mechanism of action in the retina remains unclear. Fenofibrate is a known agonist of peroxisome proliferator-activated receptor alpha (PPARα), a transcription factor critical for regulating metabolism, inflammation and oxidative stress. Using a DR mouse model, db/db, we tested the hypothesis that fenofibrate slows early DR progression by activating PPARα in the retina. Relative to healthy littermates, six-month-old db/db mice exhibited elevated serum triglycerides and cholesterol, retinal gliosis, and electroretinography (ERG) changes including reduced b-wave amplitudes and delayed oscillatory potentials. These pathologic changes in the retina were improved by oral fenofibrate. However, fenofibrate did not induce PPARα target gene expression in whole retina or isolated Müller glia. The capacity of the retina to respond to PPARα was further tested by delivering the PPARα agonist GW590735 to the intraperitoneal or intravitreous space in mice carrying the peroxisome proliferator response element (PPRE)-luciferase reporter. We observed strong induction of the reporter in the liver, but no induction in the retina. In summary, fenofibrate treatment of db/db mice prevents the development of early DR but is not associated with induction of PPARα in the retina.

Evaluation of a Putative PPAR Modulator

BackgroundPeroxisome Proliferative‐Activated Receptors (PPAR) are part of a superfamily of receptors. Of the PPARs, three forms are most prevalent, PPAR‐a, PPAR‐b/d and PPAR‐g that bind FA &amp; FA‐derivatives to their receptor domains. Each PPAR consists of an AF‐1 domain, DNA‐binding domain, dimerization domain, and ligand‐binding domain. (1) When a lipid‐derived ligand binds to a PPAR, the PPAR heterodimerizes with a retinoid X receptor (2). This heterodimer will bind a co‐activator protein (3), which in turn activates a peroxisome proliferator response element (PPRE) (1,2). The PPRE is located in a promoter region of the target genes of a DNA sequence that will allow for trans‐activation or ‐repression of gene expression. (4.) Previous data has been collected regarding a drug compound called Compound 9, which was a dual agonist of PPARg and PPARd. The compound tested, benzyl derivative, called BMZ is a derivative of compound 9.ObjectivesTest novel compound, a demethylated derivative of a previously used compound, called BMZ, to determine its activation of PPAR receptors.MethodsTo test BMZ activation of PPAR receptors, HeLa cells were plated into 96 well plates and transfected with PPRE‐3x‐TK‐luciferase (520ng/l), Trans IT‐X2 transfection reagent, and serum reduced media. The cells were then treated with troglitazone, pioglitazone, and BMZ with the following concentration in separate wells in triplicate, 0.1mM, 0.3 mM, 1.0 mM, 3.0 mM, 10 mM, 30 mM. Triplicate wells were also treated with 10 mM of BMZ with 10 mM of troglitazone. Finally, a separate triplicate of Compound 9 was added. A luciferase assay was conducted 24 hours after application of drug in five, five minute intervals.ResultsThe results showed that there was some activation of PPAR receptors for the novel BMZ compound. Furthermore, when BMZ was added to troglitazone, there was an decreased activation of the receptors.Support or Funding InformationMarian University College of Osteopathic Medicine Internal GrantRelative Luminescence Units of various PPAR‐gamma agonistsFigure 1

Synthesis and evaluation of novel peptidomimetics bearing p-aminobenzoic acid moiety as potential antidiabetic agents.

Aim: Search for a new class of potential antidiabetic agents. Methodology: A series of novel peptidomimetics bearing the p-aminobenzoic acid moiety (TM3-TM6) were designed and synthesized. For all synthetic target molecules, the peroxisome proliferator response element (PPRE) activated activities have been evaluated and the toxicity were computed. Results & discussion: 46 new p-aminobenzoic acid derivatives have been characterized by 1H NMR, 13C NMR and high-resolution mass spectrometry (HRMS). The results of in vitro PPRE-activated activity, molecular docking study and toxicity prediction revealed that these compounds had potential antidiabetic activities and low toxicity. In particular compound 3b had up to 87% PPRE-activated activity compared with pioglitazone. This discovery may provide new insights for finding novel PPRE lead compound.

WY-14643 Regulates CYP1B1 Expression through Peroxisome Proliferator-Activated Receptor α-Mediated Signaling in Human Breast Cancer Cells.

Human cytochrome P450 1B1 (CYP1B1)-mediated biotransformation of endobiotics and xenobiotics plays an important role in the progression of human breast cancer. In this study, we investigated the effects of WY-14643, a peroxisome proliferator-activated receptor α (PPARα) agonist, on CYP1B1 expression and the related mechanism in MCF7 breast cancer cells. We performed quantitative reverse transcription-polymerase chain reaction, transient transfection, and chromatin immunoprecipitation to evaluate the effects of PPARα on peroxisome proliferator response element (PPRE)-mediated transcription. WY-14643 increased the protein and mRNA levels of CYP1B1, as well as promoter activity, in MCF-7 cells. Moreover, WY-14643 plus GW6471, a PPARα antagonist, significantly inhibited the WY-14643-mediated increase in CYP1B1 expression. PPARα knockdown by a small interfering RNA markedly suppressed the induction of CYP1B1 expression by WY-14643, suggesting that WY-14643 induces CYP1B1 expression via a PPARα-dependent mechanism. Bioinformatics analysis identified putative PPREs (−833/−813) within the promoter region of the CYP1B1 gene. Inactivation of these putative PPREs by deletion mutagenesis suppressed the WY-14643-mediated induction of CYP1B1 promoter activation. Furthermore, WY-14643 induced PPARα to assume a form capable of binding specifically to the PPRE-binding site in the CYP1B1 promoter. Our findings suggest that WY-14643 induces the expression of CYP1B1 through activation of PPARα.

Prostaglandin D2 stimulates phenotypic changes in vascular smooth muscle cells

Since chronic inflammation is associated with the pathogenesis of atherosclerosis, inflammatory cytokines might contribute to the phenotypic modulation of vascular smooth muscle cells (VSMCs). Tumor necrosis factor α (TNFα) facilitated the transformation of contractile VSMCs to the synthetic phenotype, as determined by the expression of marker proteins and a collagen gel contraction assay. Western blot analysis and a cyclooxygenase-2 (COX2) promoter assay revealed that TNFα stimulation resulted in the induction of COX2. The overexpression, silencing, or pharmacological inhibition of COX2 significantly affected TNFα-induced phenotypic conversion, and of the tested prostaglandins, only PGD2 significantly induced phenotypic conversion. ERK was significantly activated by PGD2 stimulation, and the pharmacological inhibition of ERK blocked the PGD2-induced phenotypic conversion of VSMCs. However, antagonists or agonists of PGD2 receptors did not affect VSMC conversion. In contrast, spontaneously dehydrated forms of PGD2, such as PGJ2, Δ12-PGJ2, and 15-d-PGJ2, strongly induced phenotypic conversion. A reporter gene assay showed that TNFα, PGD2, and 15-d-PGJ2 significantly activated the peroxisome proliferator-responsive element (PPRE) promoter. In addition, the overexpression or silencing of peroxisome proliferator-activated receptor δ (PPARδ) significantly influenced 15-d-PGJ2-induced phenotypic conversion. Finally, atherosclerotic neointima formation was significantly suppressed in mice lacking TNFα. In addition, mice fed celecoxib exhibited complete inhibition of carotid artery ligation-induced neointima formation. This study shows that PGD2 regulates the phenotypic conversion of VSMCs by generating an endogenous ligand of PPAR, and that this leads to neointima formation in occlusive arterial disease.

Nutritional strategies to modulate inflammation pathways via regulation of peroxisome proliferator-activated receptor β/δ

The peroxisome proliferator-activated receptor (PPAR) β/δ has an important role in multiple inflammatory conditions, including obesity, hypertension, cancer, cardiovascular disease, diabetes mellitus, and autoimmune diseases. PPARβ/δ forms a heterodimer with the retinoic acid receptor and binds to peroxisome proliferator response elements to initiate transcription of its target genes. PPARβ/δ is also able to suppress the activities of several transcription factors, including nuclear factor κB, and activator protein 1, thus regulating anti-inflammatory cellular responses and playing a protective role in several diseases. Recent studies have shown that nutritional compounds, including nutrients and bioactive compounds, can regulate PPARβ/δ expression. This review discusses key nutritional compounds that are known to modulate PPARβ/δ and are likely to affect human health.

Aspirin up-regulates suppressor of cytokine signaling 3 in glial cells via PPARα.

Neuroinflammation is being recognized as a hallmark of different neurodegenerative disorders, including Alzheimer's disease. Suppressor of cytokine signaling 3 (SOCS3) is an anti-inflammatory molecule, which is known to inhibit cytokine signaling and inflammatory gene expression in different cells. However, the pathways by which SOCS3 could be up-regulated in brain cells are poorly understood. Aspirin is a widely available pain reliever that is showing promise beyond its known pain-relieving capacity. This study underlines the importance of aspirin in upregulating SOCS3 in astrocytes and microglia. Aspirin increased the expression of Socs3 mRNA and protein in mouse astrocytes and BV-2 microglial cells in both a time- and dose-dependent manner. While investigating the mechanism, we found that Socs3 gene promoter harbors peroxisome proliferator response element and that aspirin up-regulated SOCS3 in astrocytes isolated from PPARβ (-/-), but not PPARα (-/-), mice. Accordingly, aspirin increased SOCS3 in vivo in the cortex of wild type and PPARβ (-/-), but not PPARα (-/-), mice. Similarly, aspirin treatment increased astroglial and microglial SOCS3 in the cortex of FAD5X, but not FAD5X/PPARα (-/-), mice. Finally, recruitment of PPARα by aspirin to the proximal, but not distal, peroxisome proliferator response element of the Socs3 promoter suggests that aspirin increases the transcription of Socs3 gene via PPARα. This study describes a novel property of aspirin in elevating SOCS3 in glial cells via PPARα and suggests that aspirin may be further considered for therapeutic application in neuroinflammatory and neurodegenerative disorders.

Mechanisms of tanshinone Ⅱ_A in reducing 4-HNE-induced hepatocyte damage by activating PPARα

Tanshinone Ⅱ_A( Tan Ⅱ_A),the liposoluble constituents of Salvia miltiorrhiza,can not only ameliorate the lipidic metabolism and decrease the concentration of lipid peroxidation,but also resist oxidation damage,scavenge free radicals and control inflammation,with a protective effect on prognosis after liver function impairment. Therefore,the studies on the exact mechanism of Tan Ⅱ_A in protecting the liver can provide important theoretical and experimental basis for the prevention and treatment effect of Tan Ⅱ_A for liver injury. In the present study,the protective effects and mechanism of Tan Ⅱ_A on 4-hydroxynonenal( 4-HNE)-induced liver injury were investigated in vitro. Normal liver tissues NCTC 1469 cells were used to induce hepatocytes oxidative damages by 4-HNE treatment. The protective effect of Tan Ⅱ_A on hepatocytes oxidative damages was detected by release amount of lactate dehydrogenase( LDH) analysis and hoechst staining. The protein expression changes of peroxisome proliferator-activated receptor α( PPARα) and peroxisome proliferator response element( PPRE) were analyzed by Western blot analysis in NCTC 1469 cells before and after Tan Ⅱ_A treatment. The gene expression changes of fatty aldehyde dehydrogenase( FALDH) were analyzed by Real-time polymerase chain reaction( PCR) analysis. The results showed that 4-HNE increased the release amount of LDH,lowered the cell viability of NCTC 1469 cells,and Tan Ⅱ_A reversed 4-HNE-induced hepatocyte damage. Western blot analysis and RT-PCR analysis results showed that 4-HNE decreased the expression of PPARα and FALDH and increased the expression of 4-HNE. However,the expression of PPARα and FALDH were increased significantly and the expression of 4-HNE was decreased obviously after Tan Ⅱ_A treatment. This study confirmed that the curative effect of Tan Ⅱ_A was obvious on hepatocytes damage,and the mechanism may be associated with activating PPARα and FALDH expression as well as scavenging 4-HNE.