9-deoxy-delta-9-prostaglandin-d2 and pirinixic-acid

In the present study we investigated the effect of peroxisome proliferator activated receptor (PPAR) ligands on progesterone (P4) and 17β-estradiol (E2) secretion and 3b-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3β-HSD) mRNA abundance in porcine corpora lutea (CL) collected on days 10-12 and 14-16 of the estrous cycle or pregnancy. The PPAR agonists reduced P4 secretion by the CL during pregnancy whereas they were ineffective during the estrous cycle. An inhibitory effect of WY-14643 (PPARα agonist) on P4 release was noted on days 14-16 of pregnancy. The treatment of the CL with L-165,045 (PPARβ agonist) diminished P4 release by the tissue during both stages of pregnancy. A natural PPARγ agonist, PGJ2, reduced P4 release on days 14-16 or days 10-12 of pregnancy, respectively. Rosiglitazone (PPARγ agonist) inhibited P4 secretion by the CL on days 10-12 of pregnancy. In turn, PPARα ligands effect on E2 release was differential. While PPARγ activator diminished E2 secretion by the CL explants during all tested stages of the estrous cycle and pregnancy, PPARβ ligands did not induce any change in E2 level. In turn, PPARβ agonist reduced E2 release by the tissue during both stages of pregnancy but did not affect the secretion during the estrous cycle. In the present study there was a lack of PPAR ligands effect on 3β-HSD mRNA abundance. In summary, the results suggest that PPARs are involved in the regulation of progesterone and 17β-estradiol release by porcine CL. Porcine CL indicates a different receptivity to PPAR ligands depending on the reproductive status of animals.

Topics: 3-Hydroxysteroid Dehydrogenases; Anilides; Animals; Benzamides; Corpus Luteum; Estradiol; Estrous Cycle; Female; Gene Expression; Indoles; Ligands; Peroxisome Proliferator-Activated Receptors; Phenoxyacetates; Pregnancy; Progesterone; Prostaglandin D2; Pyridines; Pyrimidines; RNA, Messenger; Rosiglitazone; Swine; Thiazolidinediones

Arachidonic acid (AA) metabolizing enzymes and peroxisome proliferator-activated receptors (PPARs) have been shown to regulate the growth of epithelial cells. We have previously reported that exposure to the 5-lipoxygenase activating protein-directed inhibitor MK886 but not the cyclooxygenase inhibitor, indomethacin, reduced growth, increased apoptosis, and up-regulated PPARalpha and gamma expression in breast cancer cell lines. In the present study, we explore approaches to maximizing the proapoptotic effects of PPARgamma on lung cancer cell lines. Non-small-cell cancer cell line A549 revealed dose-dependent PPARgamma reporter activity after treatment with MK886. The addition of indomethacin in combination with MK886 further increases reporter activity. We also show increased growth inhibition and up-regulation of apoptosis after exposure to MK886 alone, or in combination with indomethacin and the PPAR ligand, 15-deoxy-Delta12,14-prostaglandin J2 compared with single drug exposures on the adenocarcinoma cell line A549 and small-cell cancer cell lines H345, N417, and H510. Real-time PCR analyses showed increased PPAR mRNA and retinoid X receptor (RXR)alpha mRNA expression after exposure to MK886 and indomethacin in a time-dependent fashion. The results suggest that the principal proapoptotic effect of these drugs may be mediated through the known antiproliferative effects of the PPARgamma-RXR interaction. We therefore explored a three-drug approach to attempt to maximize this effect. The combination of low-dose MK886, ciglitazone, and 13-cis-retinoic acid interacted at least in a superadditive fashion to inhibit the growth of lung cancer cell lines A549 and H1299, suggesting that targeting PPARgamma and AA action is a promising approach to lung cancer growth with a favorable therapeutic index.

Topics: Acetophenones; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Arachidonic Acid; Caspases; Cell Growth Processes; Cell Line, Tumor; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Indoles; Isotretinoin; Ligands; Lung Neoplasms; Peroxisome Proliferator-Activated Receptors; Prostaglandin D2; Pyrimidines; Retinoid X Receptor alpha; RNA, Messenger; Tetrazoles; Thiazolidinediones

Previous studies have demonstrated that inflammatory cytokines such as interleukin-1beta (IL-1beta) promote lipid accumulation in human mesangial cells (HMC) by dysregulating the expression of lipoprotein receptors. Intracellular lipid accumulation is governed by both influx and efflux; therefore, the effect of IL-1beta on the efflux of lipid from HMC was investigated. IL-1beta was shown to inhibit (3)H-cholesterol efflux from HMC and increase total intracellular cholesterol concentration, probably as a result of reduced expression of the adenosine triphosphate (ATP) binding cassette A1 (ABCA1), a transporter protein involved in apolipoprotein-A1 (apo-A1)-mediated lipid efflux. To ascertain the molecular mechanisms involved, expression of peroxisome proliferator-activated receptors (PPAR) and liver X receptoralpha (LXRalpha) were examined. IL-1beta (5 ng/ml) reduced PPARalpha, PPARgamma, and LXRalpha mRNA expression. Activation of PPARgamma with the agonist prostaglandin J2 (10 micro M) and of PPARalpha with either bezafibrate (100 micro M) or Wy14643 (100 micro M) both increased LXRalpha and ABCA1 gene expression also and enhanced apoA1-mediated cholesterol efflux from lipid-loaded cells, even in the presence of IL-1beta. A natural ligand of LXRalpha, 25-hydroxycholesterol (25-OHC), had similar effects; when used together with PPAR agonists, an additive effect was observed, indicating co-operation between PPAR and LXRalpha in regulating ABCA1 gene expression. This was supported by the observation that overexpression of either PPARalpha or PPARgamma by transfection enhanced LXRalpha and ABCA1 gene induction by PPAR agonists. Taken together with previous data, it appears that, in addition to increasing lipid uptake, inflammatory cytokines promote intracellular lipid accumulation by inhibiting cholesterol efflux through the PPAR-LXRalpha-ABCA1 pathway. These results suggest potential mechanisms whereby inflammation may exacerbate lipid-mediated cellular injury in the glomerulus and in other tissues and indicate that PPAR agonists may have a protective effect.

Topics: Anticholesteremic Agents; Antineoplastic Agents; ATP-Binding Cassette Transporters; Bezafibrate; Biological Transport; Cell Line, Transformed; Cholesterol; DNA-Binding Proteins; Glomerular Mesangium; Humans; Hydroxycholesterols; Hypolipidemic Agents; Interleukin-1; Liver X Receptors; Orphan Nuclear Receptors; Prostaglandin D2; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Transcription Factors

Malignant astrocytomas are among the most common brain tumours and few therapeutic options exist. It has recently been recognized that the ligand-activated nuclear receptor PPARgamma can regulate cellular proliferation and induce apoptosis in different malignant cells. We report the effect of three structurally different PPARgamma agonists inducing apoptosis in human (U87MG and A172) and rat (C6) glioma cells. The PPARgamma agonists ciglitazone, LY171 833 and prostaglandin-J2, but not the PPARalpha agonist WY14643, inhibited proliferation and induced cell death. PPARgamma agonist-induced cell death was characterized by DNA fragmentation and nuclear condensation, as well as inhibited by the synthetic receptor-antagonist bisphenol A diglycidyl ether (BADGE). In contrast, primary murine astrocytes were not affected by PPARgamma agonist treatment. The apoptotic death in the glioma cell lines treated with PPARgamma agonists was correlated with the transient up-regulation of Bax and Bad protein levels. Furthermore, inhibition of Bax expression by specific antisense oligonucleotides protected glioma cells against PPARgamma-mediated apoptosis, indicating an essential role of Bax in PPARgamma-induced apoptosis. However, PPARgamma agonists not only induced apoptosis but also caused redifferentiation as indicated by outgrowth of long processes and expression of the redifferentiation marker N-cadherin in response to PPARgamma agonists. Taken together, treatment of glioma cells with PPARgamma agonists may hold therapeutic potential for the treatment of gliomas.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; bcl-Associated Death Protein; Cadherins; Carrier Proteins; Cell Division; Cell Survival; DNA Fragmentation; Drug Evaluation, Preclinical; Glioma; Humans; Nuclear Proteins; Oligonucleotides, Antisense; Prostaglandin D2; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Pyrimidines; Rats; Receptors, Cytoplasmic and Nuclear; Thiazoles; Thiazolidinediones; Transcription Factors; Tumor Cells, Cultured

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