alitretinoin and ciglitazone

Insulin resistance is the failure of insulin to stimulate the transport of glucose into its target cells. A highly regulatable supply of glucose is important for cardiomyocytes to cope with situations of metabolic stress. We recently observed that isolated adult rat cardiomyocytes become insulin resistant in vitro. Insulin resistance is combated at the whole body level with agonists of the nuclear receptor complex peroxisome proliferator-activated receptor gamma (PPARgamma)/retinoid X receptor (RXR). We investigated the effects of PPARgamma/RXR agonists on the insulin-stimulated glucose transport and on insulin signaling in insulin-resistant adult rat cardiomyocytes. Treatment of cardiomyocytes with ciglitazone, a PPARgamma agonist, or 9-cis retinoic acid (RA), a RXR agonist, increased insulin- and metabolic stress-stimulated glucose transport, whereas agonists of PPARalpha or PPARbeta/delta had no effect. Stimulation of glucose transport in response to insulin requires the phosphorylation of the signaling intermediate Akt on the residues Thr308 and Ser473 and, downstream of Akt, AS160 on several Thr and Ser residues. Phosphorylation of Akt and AS160 in response to insulin was lower in insulin-resistant cardiomyocytes. However, treatment with 9-cis RA markedly increased phosphorylation of both proteins. Treatment with 9-cis RA also led to better preservation of microtubules in cultured cardiomyocytes. Disruption of microtubules in insulin-responsive cardiomyocytes abolished insulin-stimulated glucose transport and reduced phosphorylation of AS160 but not Akt. Metabolic stress-stimulated glucose transport also involved AS160 phosphorylation in a microtubule-dependent manner. Thus, the stimulation of glucose uptake in response to insulin or metabolic stress is dependent in cardiomyocytes on the presence of intact microtubules.

Topics: Alitretinoin; AMP-Activated Protein Kinase Kinases; Animals; Cells, Cultured; Cytoskeleton; Glucose; Glucose Transporter Type 4; Insulin; Insulin Resistance; Male; Microtubules; Myocytes, Cardiac; Phenoxyacetates; PPAR gamma; Protein Kinases; Pyrimidines; Rats; Rats, Sprague-Dawley; Retinoid X Receptors; Signal Transduction; Thiazolidinediones; Tretinoin

Melanoma represents one of the most rapidly metastasizing, hence deadly tumors due to its high proliferation rate and invasiveness, characteristics of undifferentiated embryonic tissues. Given the absence of effective therapy for metastatic melanoma, understanding more fully the molecular mechanisms underlying melanocyte differentiation may provide opportunities for novel therapeutic intervention. Here we show that in mouse melanoma S91 cells activation of the peroxisome proliferator activated receptor (PPAR) gamma induces events resembling differentiation, such as growth arrest accompanied by apoptosis, spindle morphology and enhanced tyrosinase expression. These events are preceded by an initial transient increase in expression from the Microphthalmia-associated transcription factor gene, (MITF) promoter, whereas exposure to a PPAR gamma ligand- ciglitazone that exceeds 8 h, causes a gradual decrease of MITF, until by 48 h MITF expression is substantially reduced. Beta-catenin, an MITF transcriptional activator, shows a similar pattern of decline during ciglitazone treatment, consistent with previous reports that activated PPAR gamma inhibits the Wnt/beta-catenin pathway through induction of beta-catenin proteasomal degradation. We suggest that the PPAR gamma-mediated beta-catenin down-regulation is likely to be responsible for changes in MITF levels. The data suggest that PPAR gamma, besides its well-established role in mesenchymal cell differentiation towards adipocytes, might regulate differentiation in the melanocytic lineage.

Topics: Alitretinoin; Animals; Antigens, Differentiation; Antineoplastic Agents; beta Catenin; Blotting, Western; Cell Cycle; Cell Differentiation; Cell Line, Tumor; Cell Shape; Fluorescent Antibody Technique; Gene Expression Regulation, Neoplastic; Melanocytes; Melanoma; Mice; Microphthalmia-Associated Transcription Factor; Monophenol Monooxygenase; Phenotype; PPAR gamma; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; Thiazolidinediones; Tretinoin; Up-Regulation

The liver X receptors (LXRalpha and LXRbeta), ligand-activated transcription factors, belong to the superfamily of nuclear hormone receptors and have been shown to play a major role in atherosclerosis by modulating cholesterol and triglyceride metabolism. In this report, we describe a novel LXR target, the adipocyte fatty acid binding protein (aP2), which plays an important role in fatty acid metabolism, adipocyte differentiation and atherosclerosis. While LXR agonists induce aP2 mRNA expression in human monocytes (THP-1 cells) and macrophages in a time- and concentration-dependent manner, they have no effect on aP2 expression in human adipocytes. The increase in aP2 mRNA level was additive when THP-1 cells were treated with LXR and PPARgamma agonists. Also, an RXR agonist induced aP2 expression in these cells. While no additive effect was observed with LXR and RXR agonists, additive effects were observed with RXR and PPARgamma agonists. GW9662, a potent PPARgamma antagonist, inhibited PPARgamma-induced aP2 expression without affecting LXR-mediated aP2 expression indicating the induction is mediated directly through LXR activation. Analysis of human aP2 promoter revealed a potential LXR response element (LXRE). Gel shift data showed that the LXRalpha/RXRalpha heterodimer bound to the LXRE motif in aP2 promoter in vitro in a sequence-specific manner. Deletion and mutation analyses of the proximal aP2 promoter confirm that this is a functional LXRE. These data indicate for the first time that human macrophage aP2 promoter is a direct target for the regulation by LXR/RXR heterodimers.

Topics: 5' Flanking Region; Adipocytes; Alitretinoin; Base Sequence; Binding Sites; Cell Differentiation; Cell Line; Dimerization; DNA-Binding Proteins; Drug Synergism; Fatty Acid-Binding Proteins; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Liver X Receptors; Macrophages; Molecular Sequence Data; Orphan Nuclear Receptors; PPAR gamma; Protein Binding; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Response Elements; Sequence Deletion; Sulfonamides; Thiazolidinediones; Tretinoin

Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a critical albeit poorly defined role in the development and progression of several cancer types including those of the breast, colon, and lung. A PPAR response element (PPRE) reporter assay was utilized to evaluate the selective transactivation of PPARgamma in 10 different cell lines including normal mammary epithelial, breast, lung, and colon cancer cells. Cells were treated with one of four compounds including rosglitizone (Ros), ciglitizone (Cig), 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2), or GW 9662 (GW). We observed differences in transactivation between cell lines from different tissue origin, across cell lines from a single tissue type, and selective modulation of PPARgamma within a single cell line by different ligands. Interestingly, GW, a PPARgamma antagonist in adipocytes, enhanced PPRE reporter activation in normal mammary epithelial cells while it had virtually no effect in any of the cancer cell lines tested. Within each cancer type, individual cell lines were found to respond differently to distinct PPARgamma ligands. For instance, Ros, Cig, and PGJ2 were all potent agonist of PPARgamma transactivation in lung adenocarcinoma cell lines while these same ligands had no effect in squamous cell or large cell carcinomas of the lung. Message levels of PPARgamma and retinoid X receptor alpha (RXRalpha) in the individual cell lines were quantitated by real time-polymerase chain reaction (RT-PCR). The ratio of PPARgamma to RXRalpha was predictive of how cells responded to co-treatment of Ros and 9-cis-retinoic acid, an RXRalpha agonist, in two out of three cell lines tested. These data indicate that PPARgamma can be selectively modulated and suggests that it may be used as a therapeutic target for individual tumors.

Topics: Alitretinoin; Anilides; Breast Neoplasms; Caco-2 Cells; Cell Line, Tumor; Colonic Neoplasms; Female; Gene Expression Regulation, Neoplastic; Genes, Reporter; HT29 Cells; Humans; Ligands; Lung Neoplasms; PPAR gamma; Prostaglandin D2; Retinoid X Receptor alpha; RNA, Messenger; Rosiglitazone; Thiazolidinediones; Transfection; Tretinoin

This study was designed to investigate whether nuclear receptor agonists can be used as potential differentiation therapy agents for human osteosarcoma.. Four osteosarcoma cell lines (143B, MNNG/HOS, MG-63, and TE-85) were treated with proliferator-activated receptor (PPAR)gamma agonists, troglitazone and ciglitazone, and a retinoid X receptor (RXR) ligand, 9-cis retinoic acid. The proliferation and induction of apoptosis in the treated cells were assessed, as was the induction of alkaline phosphatase, a differentiation marker of osteoblasts.. The expression of PPARgamma was readily detected in all tested osteosarcoma lines. On treatment with the PPARgamma and RXR ligands, all four osteosarcoma lines exhibited a significantly reduced proliferation rate and cell viability. Among the four lines, 143B and MNNG/HOS were shown to be more sensitive to ligand-induced apoptosis, as demonstrated by the Crystal Violet and Hoechst staining assays. Of the three tested ligands, troglitazone was shown to be the most effective in inducing cell death, followed by 9-cis retinoic acid. Moreover, a strong synergistic effect on the induction of cell death was observed when both troglitazone and 9-cis retinoic acid or ciglitazone and 9-cis retinoic acid were administered to osteosarcoma cells. Troglitazone was shown to effectively induce alkaline phosphatase activity, a well-characterized hallmark for osteoblastic differentiation.. Our findings suggest that PPARgamma and/or RXR ligands may be used as efficacious adjuvant therapeutic agents for primary osteosarcoma, as well as potential chemopreventive agents for preventing the recurrence and metastasis of osteosarcoma after the surgical removal of the primary tumors.

Topics: Alitretinoin; Antineoplastic Agents; Apoptosis; Cell Differentiation; Cell Division; Chromans; Dose-Response Relationship, Drug; Drug Synergism; Gene Expression Regulation, Neoplastic; HT29 Cells; Humans; Osteosarcoma; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Retinoid X Receptors; RNA, Neoplasm; Thiazoles; Thiazolidinediones; Time Factors; Transcription Factors; Tretinoin; Troglitazone; Tumor Cells, Cultured

The gamma isoform of the peroxisome proliferator-activated receptor (PPARgamma) is a nuclear receptor that regulates adipocyte differentiation. Recently it has been shown to be expressed in human colonic mucosa and cancer, but its role in colon carcinogenesis and progression is still unclear. We demonstrate that activation of PPARgamma by ciglitazone (cig), a selective PPARgamma ligand, induces HT-29 human colon cancer cells to undergo apoptosis. Treatment with cig also down-regulates expression of cyclooxygenase-2 (COX-2) protein. Simultaneous exposure of cells to cig and 9-cis-retinoic acid (9-cis-RA), a ligand for retinoid X receptor, results in an increased apoptotic effect and increased inhibition of COX-2 expression, compared with cells treated with either cig or 9-cis-RA alone. As COX-2 is overexpressed in human colon cancer and has been implicated in augmenting invasiveness and tumorigenecity, the ability of PPARgamma activation to decrease COX-2 expression and induce apoptosis suggests that the PPARgamma pathway may be considered as a therapeutic target for colon cancer.

Topics: Alitretinoin; Antineoplastic Agents; Apoptosis; Cell Division; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; DNA Fragmentation; Down-Regulation; Drug Synergism; Enzyme-Linked Immunosorbent Assay; Genes, cdc; HT29 Cells; Humans; Isoenzymes; Membrane Proteins; Prostaglandin-Endoperoxide Synthases; Receptors, Cytoplasmic and Nuclear; Thiazoles; Thiazolidinediones; Transcription Factors; Tretinoin

Release of arachidonic acid from rat liver cells is stimulated after a 6-hour incubation with 9-cis retinoic acid, all trans retinoic acid, the selective peroxisome proliferator-activated receptor-gamma synthetic thiazolidinedione, ciglitazone, the cyclopentenones, 15-deoxy-Delta(12,14) PGJ2 and PGA1 and the non-steroidal anti-inflammatory drugs, celecoxib and indomethacin. The rates of the release stimulated by 15-deoxy-Delta(12,14) PGJ2 differ from those observed with celecoxib. Arachidonic acid release by9-cis retinoic acid in the presence of either ciglitazone or trans retinoic acid is synergistic. It is additive in the presence of celecoxib. Cycloheximide and actinomycin inhibit the release of arachidonic acid stimulated by 15-deoxy-Delta(12,14) PGJ2 but not by celecoxib. The findings indicate that agonists of the peroxisome proliferator-activated receptor-gamma and retinoic acid receptors stimulate the release of arachidonic acid. The mechanisms involved may differ in the cases of 15-deoxy-Delta(12,14) PGJ2 and celecoxib.

Topics: Alitretinoin; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Celecoxib; Cell Line; Cycloheximide; Dactinomycin; Dose-Response Relationship, Drug; Drug Synergism; Indomethacin; Kinetics; Liver; Prostaglandin D2; Prostaglandins A; Pyrazoles; Rats; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Sulfonamides; Thiazoles; Thiazolidinediones; Transcription Factors; Tretinoin

The peroxisome proliferator-activated receptor-gamma (PPARgamma) is activated by 15-deoxy-delta(12,14) prostaglandin J2 (15d-PGJ2), anti-diabetic thiazolidinediones and several non-steroidal anti-inflammatory drugs (NSAIDs). In rat glial cells, lipopolysaccharide and interferon-gamma (LPS/IFN-gamma) induced expression of both inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1). PPARgamma activators inhibited iNOS expression by LPS and IFN-gamma. However, PPARgamma activator alone induced HO-1 expression and further enhanced LPS/IFN-gamma-induced HO-1 expression. These results suggest that activation of PPARgamma negatively regulate iNOS expression and positively regulates HO-1 expression in glial cells.

Topics: Alitretinoin; Animals; Anti-Inflammatory Agents, Non-Steroidal; Brain; Cells, Cultured; Dinoprostone; Enzyme Induction; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Interferon-gamma; Lipopolysaccharides; Neuroglia; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitrites; Prostaglandin D2; Pyrimidines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Thiazoles; Thiazolidinediones; Transcription Factors; Tretinoin