tretinoin and 2-4-thiazolidinedione

Recent studies brought adipocyte glyceroneogenesis back to the fore as an important pathway in fatty acid homeostasis and underlined the key role played by cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in this pathway. The present review analyses the mechanisms by which a series of hormones and nutrients affect PEPCK-C gene transcription and glyceroneogenesis and describes evidence for disregulation of this pathway in type 2 diabetes.

Topics: Animals; Diabetes Mellitus, Type 2; Fatty Acids; Gene Expression Regulation, Enzymologic; Glycerol; Phosphoenolpyruvate Carboxykinase (GTP); Thiazolidinediones; Tretinoin

Cancer chemopreventive agents transcriptionally induce glutathione S-transferase (GST), which can protect cells from chemical-induced carcinogenesis. Activation of either NF-E2-related factor-2 (Nrf2) or the CCAAT/enhancer binding protein-beta (C/EBPbeta) contributes to GST induction. Peroxisome proliferator-activated receptor-gamma (PPARgamma) and the retinoic acid X receptor (RXR) play roles in regulating cell differentiation and chemoprevention. This study examined GSTA2 gene induction by the PPARgamma activator and 9-cis-retinoic acid (RA), a RXR ligand, and investigated the molecular basis of PPAR-RXR-mediated GSTA2 induction in the H4IIE hepatocytes. Either 15-deoxy-delta (12, 14)-prostaglandin J(2) (PGJ(2)) or RA induced GSTA2 with Nrf2 and C/EBPbeta activation. When compared with PGJ(2) or RA alone, PGJ(2) + RA enhanced GSTA2 induction, with increases in Nrf2 and C/EBPbeta activation. PGJ(2) + RA increased the luciferase reporter gene activity in the cells transfected with the -1.65-kb flanking region of the GSTA2 gene. Thiazolidinedione PPARgamma agonists, troglitazone, rosiglitazone, and pioglitazone, in combination with RA, potentiated GSTA2 induction, confirming that the activation of the PPARgamma and RXR heterodimer contributed to GSTA2 expression. Deletion of the antioxidant response element- or C/EBP-binding sites or the overexpression of dominant-negative mutant of C/EBP abolished the reporter gene expression. PGJ2 + RA increased the binding of the PPARgamma - RXR heterodimer to the putative PPAR-response elements (PPREs) in the GSTA2 promoter. Specific mutations of these multiple PPRE sites resulted in the complete loss of its responsiveness to PGJ2 + RA, which suggests that these binding sites function as a PPRE-responsive enhancer module (PPREM). Transactivation of PPREM by the PPARgamma - RXR heterodimer was verified by the effective GSTA2 induction in the cells treated with PGJ2 + RA after transfecting them with the plasmids encoding PPARgamma1 and RXRalpha. In conclusion, the PPARgamma - RXR heterodimer promotes GSTA2 induction by activating PPREM in the GSTA2 gene, as well as inducing Nrf2 and C/EBPbeta activation.

Topics: Alitretinoin; Animals; Base Sequence; CCAAT-Enhancer-Binding Protein-beta; Cell Line; DNA-Binding Proteins; Gene Expression Regulation, Enzymologic; Glutathione Transferase; Hepatocytes; Mice; Molecular Sequence Data; NF-E2-Related Factor 2; Promoter Regions, Genetic; Prostaglandin D2; Rats; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Response Elements; Retinoid X Receptors; Thiazolidinediones; Trans-Activators; Transcription Factors; Transcriptional Activation; Tretinoin

The peroxisome proliferator-activated receptors (PPAR) alpha and gamma play key roles in the transcriptional control of contrasting metabolic pathways such as adipogenesis and fatty acid beta-oxidation. Both ligand-activated nuclear receptors bind to common target gene response elements and interact with distinct domains of the transcriptional coactivator PGC-1 to attain their full transcriptional potency. Thus, PPAR subtype specificity may be determined by ligand availability and transcription factor or coactivator expression levels. To identify other, perhaps more precise mechanisms contributing to PPAR subtype specificity, we studied PGC-1 recruitment by PPARs using a previously described hormone response element in the human UCP1 promoter and a human brown adipocyte cell line as our model system. As in rodents, PGC-1 is involved in the transcriptional regulation of the UCP1 gene in humans and mediates the effects of PPARalpha and PPARgamma agonists and retinoic acid. Interestingly, a previously postulated PGC-1 repressor selectively affects the PPARalpha-mediated activation of UCP1 gene expression. Furthermore, inhibition of p38 MAPK signaling, known to regulate the PGC-1/repressor interaction, decreases the stimulatory effect of PPARalpha agonist treatment without reducing the response to thiazolidinedione or retinoic acid. These data support a model whereby PPAR subtype specificity is regulated by recruitment of PGC-1.

Topics: Adipocytes; Animals; Base Sequence; Carrier Proteins; Cell Line; Cell Nucleus; DNA, Complementary; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Imidazoles; Ion Channels; Ligands; MAP Kinase Signaling System; Membrane Proteins; Mitochondrial Proteins; Mitogen-Activated Protein Kinases; Molecular Sequence Data; Mutation; Oxygen; p38 Mitogen-Activated Protein Kinases; Plasmids; Promoter Regions, Genetic; Protein Structure, Tertiary; Pyridines; Rats; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Thiazoles; Thiazolidinediones; Transcription Factors; Transcription, Genetic; Transfection; Tretinoin; Uncoupling Protein 1

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 present study examined the expression and role of the thiazolidinedione (TZD)-activated transcription factor, peroxisome proliferator-activated receptor gamma (PPARgamma), in human bladder cancers. In situ hybridization shows that PPARgamma mRNA is highly expressed in all human transitional epithelial cell cancers (TCCa's) studied (n=11). PPARgamma was also expressed in five TCCa cell lines as determined by RNase protection assays and immunoblot. Retinoid X receptor alpha (RXRalpha), a 9-cis-retinoic acid stimulated (9-cis-RA) heterodimeric partner of PPARgamma, was also co-expressed in all TCCa tissues and cell lines. Treatment of the T24 bladder cancer cells with the TZD PPARgamma agonist troglitazone, dramatically inhibited 3H-thymidine incorporation and induced cell death. Addition of the RXRalpha ligands, 9-cis-RA or LG100268, sensitized T24 bladder cancer cells to the lethal effect of troglitazone and two other PPAR- activators, ciglitazone and 15-deoxy-delta(12,14)-PGJ2 (15dPGJ(2)). Troglitazone treatment increased expression of two cyclin-dependent kinase inhibitors, p21(WAF1/CIP1) and p16(INK4), and reduced cyclin D1 expression, consistent with G1 arrest. Troglitazone also induced an endogenous PPARgamma target gene in T24 cells, adipocyte-type fatty acid binding protein (A-FABP), the expression of which correlates with bladder cancer differentiation. In situ hybridization shows that A-FABP expression is localized to normal uroepithelial cells as well as some TCCa's. Taken together, these results demonstrate that PPARgamma is expressed in human TCCa where it may play a role in regulating TCCa differentiation and survival, thereby providing a potential target for therapy of uroepithelial cancers.

Topics: Alitretinoin; Antineoplastic Agents; Apoptosis; Carcinoma, Transitional Cell; Carrier Proteins; Cell Death; Chromans; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p16; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; DNA; DNA, Complementary; Dose-Response Relationship, Drug; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; G1 Phase; Humans; Immunoblotting; In Situ Hybridization; Ligands; Luciferases; Myelin P2 Protein; Neoplasm Proteins; Nicotinic Acids; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Retinoid X Receptors; Ribonucleases; Tetrahydronaphthalenes; Thiazoles; Thiazolidinediones; Transcription Factors; Transcriptional Activation; Transfection; Tretinoin; Troglitazone; Tumor Cells, Cultured; Tumor Suppressor Proteins; Urinary Bladder Neoplasms

We studied the effects of a thiazolidinedione (T-174) and retinoids on adipocyte differentiation in beef cattle. Stromal-vascular (SV) cells containing preadipocytes were prepared from perirenal adipose tissue of 21-mo-old Japanese Black steers. After confluence, these cells were cultured in 25 microM T-174, which is a specific ligand for an adipogenesis stimulating nuclear receptor (i.e., gamma subtype of peroxisome proliferator-activated receptor [PPARgamma]), with 1 microM all-trans retinoic acid (RA) or .4 to 40 microg/100 mL of retinol for 10 to 14 d. The number of cells accumulating lipid droplets was counted as morphologically differentiated adipocytes, and the activity of glycerol-3-phosphate dehydrogenase (GPDH), a biochemical index for the differentiation, was determined. The number of lipid-laden cells and GPDH activity were increased by the addition of T-174. All-trans retinoic acid completely blocked the stimulative action of T-174. The addition of retinol also decreased the number of lipid-laden cells and GPDH activity in a dose-dependent manner. These results showed that the thiazolidinedione stimulated adipocyte differentiation and the retinoids blocked the adipogenesis induced by the thiazolidinedione in primary culture of bovine SV cells. Peroxisome proliferator-activated receptor gamma may play an important role in adipocyte differentiation, and retinoids may interfere with the action of PPARgamma in cattle.

Topics: Adipocytes; Animals; Blotting, Western; Cattle; Cell Differentiation; Cells, Cultured; Dose-Response Relationship, Drug; Drug Interactions; Endothelium, Vascular; Glycerolphosphate Dehydrogenase; Ligands; Male; Receptors, Cytoplasmic and Nuclear; Stromal Cells; Thiazoles; Thiazolidinediones; Transcription Factors; Tretinoin; Vitamin A

Retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (1,25 (OH)2 D3) inhibited adipocyte differentiation of 3T3-L1 preadipocytes in the presence of thiazolidinedione, a specific ligand for peroxisome proliferator-activated receptory (PPARgamma). These fat-soluble vitamins repressed the up-regulated protein expression of PPARgamma2 during the first 40 hours of initiation of 3T3-L1 preadipocyte differentiation. Compared with RA, 1,25 (OH)2 D3 inhibited PPARgamma2 expression more effectively and caused concomitantly a greater inhibition of adipocyte differentiation. These results suggest that the inhibitory action of adipocyte differentiation by RA or 1,25 (OH)2 D3 is exhibited through direct repression of the expression of PPARgamma2 protein, even in the presence of its ligand. They also raise the intriguing possibility that attenuation or amplification of the pharmacological effects of thiazolidinedione that are dependent on PPARgamma in adipose cells is caused by alteration of the levels of these fat-soluble vitamins.

Topics: 3T3 Cells; Adipocytes; Animals; Calcitriol; Cell Differentiation; Hypoglycemic Agents; Ligands; Mice; Receptors, Cytoplasmic and Nuclear; Stem Cells; Thiazoles; Thiazolidinediones; Transcription Factors; Tretinoin; Up-Regulation