15-deoxy-delta(12-14)-prostaglandin-j2 and pirinixic-acid

In this study, experiments were designed to determine if peroxisome proliferator-activated receptor (PPAR) alpha agonists could decrease myocardial ischemia/reperfusion injury after cardioplegia-induced cardiac arrest under cardiopulmonary bypass, attenuate the appearance of cardiomyocytic apoptosis, and decrease the damage of reactive oxygen species. Cardiomyocytic apoptosis occurs after cardiopulmonary bypass surgery. Reactive oxygen species and peroxynitrite generated during ischemia/reperfusion initiate the formation of single-strand DNA breaks. Peroxisome proliferator-activated receptors (PPARs) activators had an important role in alleviating myocardial apoptosis. Four groups of New Zealand white rabbits (10 in each group, each 2.5-3.5 kg) underwent cardiopulmonary bypass. Thirty minutes before surgery, one group received WY14643 (a PPAR-alpha agonist, 1 mg kg(-1)) and another received 15D-PGJ2 (a PPAR-gamma agonist; 0.3 mg kg(-1)). The ascending aorta was cross-clamped for 60 min, whereas intermittent cold crystalloid cardioplegic solution was infused into the aortic root every 20 min. The myocardium of the reperfused hearts and control hearts were harvested and studied in vitro for evidence of apoptosis using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling method and Western blot analyses of cytochrome c and apoptosis-inducing factor. The reactive oxidative insults were checked using enzyme-linked immunosorbent assay to detect plasma cytokine levels. The occurrence of cardiomyocytic apoptosis and elevation of plasma cytokines were significantly lower in the group receiving PPAR-alpha agonists than in the other groups. Western blot analysis of apoptosis-inducing factor and cytochrome c revealed similar patterns. PPAR-alpha activation could diminish postischemic cardiomyocytic apoptosis and reactive oxygen species injuries after global cardiac arrest under cardiopulmonary bypass, possibly via prevention of both caspase-dependent and caspase-independent apoptotic pathways.

Topics: Animals; Apoptosis; Cardiopulmonary Bypass; Caspase 3; Caspases; Cell Adhesion Molecules; Cytokines; Fas Ligand Protein; Gene Expression; Heart; Heart Arrest, Induced; In Situ Nick-End Labeling; Male; Membrane Glycoproteins; Myocardial Reperfusion Injury; Myocytes, Cardiac; NF-kappa B; Peroxidase; Peroxisome Proliferators; PPAR alpha; PPAR gamma; Prostaglandin D2; Proto-Oncogene Proteins c-jun; Pyrimidines; Rabbits; Troponin I; Tumor Necrosis Factors

Chemokine-mediated inflammatory cell infiltration is a hallmark of asthma. We recently demonstrated that glucocorticoids and beta(2)-agonists additively or synergistically suppress tumor necrosis factor-alpha (TNFalpha)-induced production of chemokines eotaxin and interleukin-8 (IL-8), respectively, in human airway smooth muscle (HASM) cells, which may partly explain their combined benefits in asthma. Peroxisome proliferator-activated receptors (PPARs) also modulate inflammatory gene expression. We reported here that the PPARgamma agonists 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) and troglitazone, but not PPARalpha agonist WY-14643, inhibited TNFalpha-induced production of eotaxin and monocyte chemotactic protein-1 (MCP-1) but not IL-8. Eotaxin inhibition was transcriptional and additively enhanced by the glucocorticoid fluticasone and the beta(2)-agonist salmeterol, whereas MCP-1 inhibition was post-transcriptional and additively and synergistically enhanced by fluticasone and salmeterol, respectively. Coimmunoprecipitation revealed that 15d-PGJ(2) induced a protein-protein interaction between PPARgamma and the glucocorticoid receptor (GR) in TNFalpha-treated HASM cells, which was enhanced by fluticasone and salmeterol. 15d-PGJ(2), fluticasone, and salmeterol all inhibited TNFalpha-induced histone H4 acetylation at the eotaxin promoter and NF-kappaB p65 binding to the eotaxin promoter and induced PPARgamma and GR association with the eotaxin promoter, as analyzed by chromatin immunoprecipitation assay. Our data suggest that chemokine expression in HASM cells is differentially regulated by PPARgamma agonists and that the interaction between PPARgamma and GR may be responsible for the additive and synergistic inhibition of chemokine expression by PPARgamma agonists, glucocorticoids, and beta(2)-agonists, particularly the chromatin-dependent suppression of eotaxin gene transcription. The interaction may have wide applications and may provide a potential target for pharmacological and molecular intervention.

Topics: Adrenergic beta-Agonists; Albuterol; Androstadienes; Blotting, Western; Cell Line; Chemokine CCL11; Chemokine CCL2; Chemokines; Chemokines, CC; Chromans; Chromatin; Chromatin Immunoprecipitation; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Fluticasone; Gene Expression Regulation; Glucocorticoids; Humans; Immunoprecipitation; Interleukin-8; Plasmids; PPAR alpha; PPAR gamma; Promoter Regions, Genetic; Prostaglandin D2; Protein Binding; Pyrimidines; Receptors, Glucocorticoid; Reverse Transcriptase Polymerase Chain Reaction; RNA; Salmeterol Xinafoate; Thiazolidinediones; Transcription, Genetic; Transfection; Troglitazone; Tumor Necrosis Factor-alpha

Membrane-associated prostaglandin (PG) E(2) synthase-1 (mPGES-1) catalyzes the conversion of PGH(2) to PGE(2), which contributes to many biological processes. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor and plays an important role in growth, differentiation, and inflammation in different tissues. Here, we examined the effect of PPARgamma ligands on interleukin-1beta (IL-1beta)-induced mPGES-1 expression in human synovial fibroblasts. PPARgamma ligands 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)) and the thiazolidinedione troglitazone (TRO), but not PPARalpha ligand Wy14643, dose-dependently suppressed IL-1beta-induced PGE(2) production, as well as mPGES-1 protein and mRNA expression. 15d-PGJ(2) and TRO suppressed IL-1beta-induced activation of the mPGES-1 promoter. Overexpression of wild-type PPARgamma further enhanced, whereas overexpression of a dominant negative PPARgamma alleviated, the suppressive effect of both PPARgamma ligands. Furthermore, pretreatment with an antagonist of PPARgamma, GW9662, relieves the suppressive effect of PPARgamma ligands on mPGES-1 protein expression, suggesting that the inhibition of mPGES-1 expression is mediated by PPARgamma. We demonstrated that PPARgamma ligands suppressed Egr-1-mediated induction of the activities of the mPGES-1 promoter and of a synthetic reporter construct containing three tandem repeats of an Egr-1 binding site. The suppressive effect of PPARgamma ligands was enhanced in the presence of a PPARgamma expression plasmid. Electrophoretic mobility shift and supershift assays for Egr-1 binding sites in the mPGES-1 promoter showed that both 15d-PGJ(2) and TRO suppressed IL-1beta-induced DNA-binding activity of Egr-1. These data define mPGES-1 and Egr-1 as novel targets of PPARgamma and suggest that inhibition of mPGES-1 gene transcription may be one of the mechanisms by which PPARgamma regulates inflammatory responses.

Topics: Amino Acid Motifs; Anilides; Binding Sites; Blotting, Western; Cell Division; Cell Nucleus; Chromans; DNA-Binding Proteins; DNA, Complementary; Dose-Response Relationship, Drug; Early Growth Response Protein 1; Fibroblasts; Genes, Dominant; Genes, Reporter; Humans; Immediate-Early Proteins; Immunologic Factors; Inflammation; Interleukin-1; Intramolecular Oxidoreductases; Ligands; Peroxisome Proliferators; Plasmids; Promoter Regions, Genetic; Prostaglandin D2; Prostaglandin-E Synthases; Protein Binding; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; RNA; Synovial Membrane; Thiazolidinediones; Time Factors; Transcription Factors; Transcription, Genetic; Transfection; Troglitazone

Airway smooth muscle is actively involved in the inflammatory process in diseases such as chronic obstructive pulmonary disease and asthma by 1) contributing to airway narrowing through hyperplasia and hypertrophy and 2) the release of GM-CSF and G-CSF, which promotes the survival and activation of infiltrating leukocytes. Thus, the identification of novel anti-inflammatory pathways in airway smooth muscle will have important implications for the treatment of inflammatory airway disease. This study identifies such a pathway in the activation of peroxisome proliferator-activated receptors (PPARs). PPAR ligands are known therapeutic agents in the treatment of diabetes; however, their role in human airway disease is unknown. We demonstrate, for the first time, that human airway smooth muscle cells express PPAR alpha and -gamma subtypes. Activation of PPAR gamma by natural and synthetic ligands inhibits serum-induced cell growth more effectively than does the steroid dexamethasone, and induces apoptosis. Moreover, PPAR gamma activation, like dexamethasone, inhibits the release of GM-CSF. However, PPAR gamma ligands, but not dexamethasone, similarly inhibits G-CSF release. These results reveal a novel anti-inflammatory pathway in human airway smooth muscle, where PPAR gamma activation has additional anti-inflammatory effects to those of steroids. Hence, PPAR ligands might act as potential treatments in human respiratory diseases.

Topics: Adolescent; Adult; Anti-Inflammatory Agents; Apoptosis; Blotting, Western; Cell Division; Cells, Cultured; Dexamethasone; DNA Fragmentation; Female; Granulocyte Colony-Stimulating Factor; Granulocyte-Macrophage Colony-Stimulating Factor; Growth Inhibitors; Humans; Interleukin-1; Ligands; Male; Middle Aged; Muscle, Smooth; Peroxisomes; Prostaglandin D2; Protein Isoforms; Pulmonary Disease, Chronic Obstructive; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thiazoles; Thiazolidinediones; Trachea; Transcription Factors

Phytohemagglutinin (PHA) elicited expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in primary human T cells via the PPARgamma3 promoter, as shown by reverse transcription-polymerase chain reaction. Electrophoretic mobility shift assay demonstrated no correlation between PPARgamma expression and its activation. However, addition of specific PPARgamma agonists such as ciglitazone or 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) for 1 h following PHA pretreatment provoked PPARgamma activation verified by supershift analysis. Taking the proapoptotic properties of PPARgamma into consideration, we analyzed induction of apoptosis in activated T cells in response to PPARgamma agonists. Cells exposed to PPARgamma agonists alone revealed minor cell death compared with controls, whereas treatment with 15d-PGJ(2) or ciglitazone for 4 h subsequent to PHA stimulation significantly increased cell demise, which was attenuated by the pan-caspase inhibitor zVAD, pointing to apoptosis as the underlying mechanism. These data may be relevant for pathophysiological conditions accompanied with lymphopenia of T cells under conditions such as sepsis.

Topics: Apoptosis; Cysteine Proteinase Inhibitors; Gene Expression Regulation; Humans; Hydrazines; Jurkat Cells; Lymphocyte Activation; Lymphopenia; Nitrogen Oxides; Phytohemagglutinins; Promoter Regions, Genetic; Prostaglandin D2; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; T-Lymphocytes; Thiazoles; Thiazolidinediones; Transcription Factors

Overexpression of the inducible cyclooxygenase (COX-2) and inducible NO synthase (iNOS) in activated brain macrophages (microglia) and astrocytes appears central to many neuroinflammatory conditions. 15-Deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) is a ligand for the peroxisome proliferator-activated receptor (PPAR)gamma. It has been proposed as an inhibitor of microglial activation, based on the study of iNOS down-regulation in rodent microglia. Because iNOS induction after cytokine activation remains controversial in human microglia, we examined the effect of 15d-PGJ(2) and other PPAR agonists on human microglia and astrocytes, using COX-2 induction as an index of activation. We found that PPAR alpha ligands (clofibrate and WY14643) enhanced IL-1 beta-induced COX-2 expression in human astrocytes and microglia, while inhibiting IL-1 beta plus IFN-gamma induction of iNOS in astrocytes. This is the first description of an inhibition of iNOS uncoupled from that of COX-2. 15d-PGJ(2) suppressed COX-2 induction in human astrocytes. It prevented NF-kappa B binding to the COX-2 promoter through a new pathway that is the repression of NF-kappa Bp50 induction by IL-1 beta. In contrast, 15d-PGJ(2) increased c-Jun and c-Fos DNA-binding activity in astrocytes, which may result in the activation of other inflammatory pathways. In human microglia, no effect of 15d-PGJ(2) on COX-2 and NF-kappa Bp65/p50 induction was observed. However, the entry of 15d-PGJ(2) occurred in microglia because STAT-1 and c-Jun expression was modulated. Our data suggest the existence of novel pathways mediated by 15d-PGJ(2) in human astrocytes. They also demonstrate that, unlike astrocytes and peripheral macrophages or rodent brain macrophages, human microglia are not subject to the anti-inflammatory effect of 15d-PGJ(2) in terms of COX-2 inhibition.

Topics: Anti-Inflammatory Agents; Astrocytes; Brain; Cells, Cultured; Clofibrate; Cyclooxygenase 2; Cytokines; Gene Silencing; Humans; Isoenzymes; Membrane Proteins; Microglia; NF-kappa B; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Promoter Regions, Genetic; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Pyrimidines; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Transcription Factors

This study was designed to investigate the effects of various chemically distinct activators of PPAR-gamma and PPAR-alpha in a rat model of acute myocardial infarction. Using Northern blot analysis and RT-PCR in samples of rat heart, we document the expression of the mRNA for PPAR-gamma (isoform 1 but not isoform 2) as well as PPAR-beta and PPAR-alpha in freshly isolated cardiac myocytes and cardiac fibroblasts and in the left and right ventricles of the heart. Using a rat model of regional myocardial ischemia and reperfusion (in vivo), we have discovered that various chemically distinct ligands of PPAR-gamma (including the TZDs rosiglitazone, ciglitazone, and pioglitazone, as well as the cyclopentanone prostaglandins 15D-PGJ2 and PGA1) cause a substantial reduction of myocardial infarct size in the rat. We demonstrate that two distinct ligands of PPAR-alpha (including clofibrate and WY 14643) also cause a substantial reduction of myocardial infarct size in the rat. The most pronounced reduction in infarct size was observed with the endogenous PPAR-gamma ligand, 15-deoxyDelta12,14-prostagalndin J2 (15D-PGJ2). The mechanisms of the cardioprotective effects of 15D-PGJ2 may include 1) activation of PPAR-alpha, 2) activation of PPAR-gamma, 3) expression of HO-1, and 4) inhibition of the activation of NF-kappaB in the ischemic-reperfused heart. Inhibition by 15D-PGJ2 of the activation of NF-kappaB in turn results in a reduction of the 1) expression of inducible nitric oxide synthase and the nitration of proteins by peroxynitrite, 2) formation of the chemokine MCP-1, and 3) expression of the adhesion molecule ICAM-1. We speculate that ligands of PPAR-gamma and PPAR-alpha may be useful in the therapy of conditions associated with ischemia-reperfusion of the heart and other organs. Our findings also imply that TZDs and fibrates may help protect the heart against ischemia-reperfusion injury. This beneficial effect of 15D-PGJ2 was associated with a reduction in the expression of the 1) adhesion molecules ICAM-1 and P-selectin, 2) chemokine macrophage chemotactic protein 1, and 3) inducible isoform of nitric oxide synthase. 15D-PGJ2 reduced the nitration of proteins (immunohistological analysis of nitrotyrosine formation) caused by ischemia-reperfusion, likely due to the generation of peroxynitrite. Not all of the effects of 15D-PGJ2, however, are due to the activation of PPAR-gamma. For instance, exposure of rat cardiac myocytes to 15D-PGJ2, but not to rosiglitazon

Topics: Adult; Animals; Cardiotonic Agents; Cell Adhesion Molecules; Cell Line; Cells, Cultured; Chemokine CCL2; Clofibrate; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Humans; Ligands; Male; Membrane Proteins; Myocardial Infarction; Myocardial Reperfusion Injury; Pioglitazone; Prostaglandin D2; Prostaglandins A; Protein Isoforms; Pyrimidines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Rosiglitazone; Thiazoles; Thiazolidinediones; Transcription Factors

Peroxisome proliferator-activated receptor (PPAR)-gamma is a nuclear hormone receptor that serves as a trans factor to regulate lipid metabolism. Intense interest is focused on PPAR-gamma and its ligands owing to its putative role in adipocyte differentiation. Little is known, however, about the functions of PPAR-gamma in the immune system, especially in T lymphocytes. We demonstrate that both naive and activated ovalbumin-specific T cells from DO11.10-transgenic mice express PPAR-gamma mRNA and protein. In order to determine the function of PPAR-gamma, T cells were stimulated with phorbol 12-myristate 13-acetate and ionomycin or antigen and antigen-presenting cells. Simultaneous exposure to PPAR-gamma ligands (e. g. 15-deoxy-Delta(12, 14)-prostaglandin J(2), troglitazone) showed drastic inhibition of proliferation and significant decreases in cell viability. The decrease in cell viability was due to apoptosis of the T lymphocytes, and occurred only when cells were treated with PPAR-gamma, and not PPAR-alpha agonists, revealing specificity of this response for PPAR-gamma. These observations suggest that PPAR-gamma agonists play an important role in regulating T cell-mediated immune responses by inducing apoptosis. T cell death via PPAR-gamma ligation may act as a potent anti-inflammatory signal in the immune system, and ligands could possibly be used to control disorders in which excessive inflammation occurs.

Topics: Animals; Antigen Presentation; Apoptosis; Cell Division; Cell Survival; Cells, Cultured; Chromans; Flow Cytometry; Immunohistochemistry; In Situ Nick-End Labeling; Ionomycin; Ligands; Lymphocyte Activation; Mice; Mice, Inbred BALB C; Mice, Transgenic; Prostaglandin D2; Pyrimidines; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Specific Pathogen-Free Organisms; T-Lymphocytes; Tetradecanoylphorbol Acetate; Thiazoles; Thiazolidinediones; Transcription Factors; Troglitazone

Peroxisome proliferator-activated receptor-gamma (PPARgamma), a member of the nuclear hormone receptor superfamily originally shown to play an important role in adipocyte differentiation and glucose homeostasis, is now known to regulate inflammatory responses. Given the importance of endothelial cell (EC)-derived chemokines in regulating leukocyte function and trafficking, we studied the effects of PPARgamma ligands on the expression of chemokines induced in ECs by the Th1 cytokine IFN-gamma. Treatment of ECs with PPARgamma activators significantly inhibited IFN-gamma-induced mRNA and protein expression of the CXC chemokines IFN-inducible protein of 10 kDa (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha-chemoattractant (I-TAC), whereas expression of the CC chemokine monocyte chemoattractant protein-1 was not altered. PPARgamma activators decreased IFN-inducible protein of 10 kDa promoter activity and inhibited protein binding to the two NF-kappaB sites but not to the IFN-stimulated response element ISRE site. Furthermore, PPARgamma ligands inhibited the release of chemotactic activity for CXC chemokine receptor 3 (CXCR3)-transfected lymphocytes from IFN-gamma-stimulated ECs. These data suggest that anti-diabetic PPARgamma activators might attenuate the recruitment of activated T cells at sites of Th1-mediated inflammation.

Topics: Chemokine CXCL10; Chemokine CXCL11; Chemokine CXCL9; Chemokines, CXC; Chemotaxis; Docosahexaenoic Acids; Dose-Response Relationship, Immunologic; Eicosapentaenoic Acid; Endothelium, Vascular; Humans; Intercellular Signaling Peptides and Proteins; Interferon-gamma; Microbodies; NF-kappa B; Promoter Regions, Genetic; Prostaglandin D2; Pyrimidines; Receptors, Chemokine; Receptors, CXCR3; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Saphenous Vein; T-Lymphocytes; Transcription Factors

The present study examined the roles of peroxisome proliferator-activated receptors (PPAR) in activation of hepatic stellate cells (HSC), a pivotal event in liver fibrogenesis. RNase protection assay detected mRNA for PPARgamma1 but not that for the adipocyte-specific gamma2 isoform in HSC isolated from sham-operated rats, whereas the transcripts for neither isoforms were detectable in HSC from cholestatic liver fibrosis induced by bile duct ligation (BDL). Semi-quantitative reverse transcriptase-polymerase chain reaction confirmed a 70% reduction in PPARgamma mRNA level in HSC from BDL. Nuclear extracts from BDL cells showed an expected diminution of binding to PPAR-responsive element, whereas NF-kappaB and AP-1 binding were increased. Treatment of cultured-activated HSC with ligands for PPARgamma (10 microm 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)); 0.1 approximately 10 microm BRL49653) inhibited DNA and collagen synthesis without affecting the cell viability. Suppression of HSC collagen by 15dPGJ(2) was abrogated 70% by the concomitant treatment with a PPARgamma antagonist (GW9662). HSC DNA and collagen synthesis were inhibited by WY14643 at the concentrations known to activate both PPARalpha and gamma (>100 microm) but not at those that only activate PPARalpha (<10 microm) or by a synthetic PPARalpha-selective agonist (GW9578). 15dPGJ(2) reduced alpha1(I) procollagen, smooth muscle alpha-actin, and monocyte chemotactic protein-1 mRNA levels while inducing matrix metalloproteinase-3 and CD36. 15dPGJ(2) and BRL49653 inhibited alpha1(I) procollagen promoter activity. Tumor necrosis factor alpha (10 ng/ml) reduced PPARgamma mRNA, and this effect was prevented by the treatment with 15dPGJ(2). These results demonstrate that HSC activation is associated with the reductions in PPARgamma expression and PPAR-responsive element binding in vivo and is reversed by the treatment with PPARgamma ligands in vitro. These findings implicate diminished PPARgamma signaling in molecular mechanisms underlying activation of HSC in liver fibrogenesis and the potential therapeutic value of PPARgamma ligands for liver fibrosis.

Topics: Animals; Cell Size; Cell Survival; Cells, Cultured; Collagen; DNA; Gene Expression Regulation; Liver; Liver Cirrhosis, Biliary; Liver Cirrhosis, Experimental; Male; Promoter Regions, Genetic; Prostaglandin D2; Protein Binding; Protein Isoforms; Pyrimidines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Rosiglitazone; Thiazoles; Thiazolidinediones; Transcription Factors; Tumor Necrosis Factor-alpha

A cyclopentenone-type prostaglandin, 15-deoxy-Delta(12, 14)-prostaglandin J(2) (15-d-PGJ(2)), has been shown to induce the cellular stress response and to be a ligand for the peroxisome proliferator-activated receptor (PPAR)-gamma. We studied its effect on the basal and thyrotropin (TSH)-induced production of thyroglobulin (TG) by human thyrocytes cultured in the presence of 10% FBS. In 15-d-PGJ(2)-treated cells in which the agent itself did not stimulate cAMP production, both the basal production of TG and the response to TSH were facilitated, including the production of TG and cAMP, whereas such production was decreased in untreated cells according to duration of culture. PGD(2) and PGJ(2), which are precursors to 15-d-PGJ(2), exhibited an effect similar to 15-d-PGJ(2). However, the antidiabetic thiazolidinediones known to be specific ligands for PPAR-gamma, and WY-14643, a specific PPAR-alpha ligand, lacked this effect. 15-d-PGJ(2) and its precursors, but not the thiazolidinediones, induced gene expression for heme oxygenase-1 (HO-1), a stress-related protein, and strongly inhibited interleukin-1 (IL-1)-induced nitric oxide (NO) production. Cyclopentenone-type PGs have been recently shown to inhibit nuclear factor-kappaB (NF-kappaB) activation via a direct and PPAR-independent inhibition of inhibitor-kappaB kinase, suggesting that, in human thyrocytes, such PGs may inhibit IL-1-induced NO production, possibly via an inhibition of NF-kappaB activation. On the other hand, sodium arsenite, a known activator of the stress response pathway, induced HO-1 mRNA expression but lacked a promoting effect on TG production. Thus 15-d-PGJ(2) and its precursors appear to facilitate TG production via a PPAR-independent mechanism and through a different pathway from the cellular stress response that is available to cyclopentenone-type PGs. Our findings reveal a novel role of these PGs associated with thyrocyte differentiation.

Topics: Anticholesteremic Agents; Arsenites; Bucladesine; Cells, Cultured; Chromans; Cyclic AMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fetal Proteins; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Humans; Hypoglycemic Agents; Ligands; Membrane Proteins; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Pioglitazone; Prostaglandin D2; Pyrimidines; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Sodium Compounds; Thiazoles; Thiazolidinediones; Thyroglobulin; Thyroid Gland; Thyrotropin; Transcription Factors; Troglitazone

The peroxisome proliferator-activated receptors (PPARs) are lipid-activated transcription factors involved in the regulation of lipid metabolism and adipocyte differentiation. Little is known, however, about the control of the expression of the genes encoding each of all three receptor subtypes: alpha, delta, and gamma. We have addressed this question in the brown adipocyte, the only cell type that co-expresses high levels of the three PPAR subtypes. Differentiation of brown adipocytes is associated with enhanced expression of PPAR genes. However, whereas PPARgamma and PPARdelta genes are already expressed in preadipocytes, the mRNA for PPARalpha appears suddenly in association with the acquisition of the terminally differentiated phenotype. Both retinoic acid isomers and PPAR agonists, specific for either PPARalpha or PPARgamma, regulate expression of each PPAR subtype gene in the opposite way: they up-regulate PPARalpha and down-regulate PPARgamma. The effects on PPARalpha mRNA are independent of protein synthesis, whereas inhibition of PPARgamma mRNA expression depends on protein synthesis, except when its specific ligand prostaglandin J2 is used. Our results indicate a strictly opposite autoregulation of PPAR subtypes, which supports specific physiological roles for them in controlling brown fat differentiation and thermogenic activity.

Topics: Adipocytes; Adipose Tissue, Brown; Animals; Cell Differentiation; Cells, Cultured; DNA-Binding Proteins; Gene Expression Regulation; Ligands; Male; Mice; Prostaglandin D2; Protein Isoforms; Pyrimidines; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Transcription Factors; Tretinoin

Prostaglandins (PGs) of the J2 series form in vivo and exert effects on a variety of biological processes. While most of PGs mediate their effects through G protein-coupled receptors, the mechanism of action for the J2 series of PGs remains unclear. Here, we report the PGJ2 and its derivatives are efficacious activators of peroxisome proliferator-activated receptors alpha and gamma (PPAR alpha and PPAR gamma, respectively), orphan nuclear receptors implicated in lipid homeostasis and adipocyte differentiation. The PGJ2 metabolite 15-deoxy-delta 12,14-PGJ2 binds directly to PPAR gamma and promotes efficient differentiation of C3H10T1/2 fibroblasts to adipocytes. These data provide strong evidence that a fatty acid metabolite can function as an adipogenic agent through direct interactions with PPAR gamma and furthermore, suggest a novel mechanism of action for PGs of the J2 series.

Topics: Adipocytes; Animals; Binding, Competitive; Cell Differentiation; Cells, Cultured; Fibroblasts; Hypoglycemic Agents; Ligands; Mice; Microbodies; Prostaglandin D2; Prostaglandins; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Recombinant Fusion Proteins; Rosiglitazone; Signal Transduction; Thiazoles; Thiazolidinediones; Transcription Factors; Transcriptional Activation