BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPARgamma) activation has been proposed as a potential therapeutic strategy for various types of human cancer. The aim of this study was to activate PPARgamma and overexpress PGC-1alpha in HepG2 cells in order to analyze their effects on cell motility and E-cadherin expression. MATERIALS AND METHODS: Adenovirus-mediated gene transfer was performed to overexpress PGC-1alpha in HepG2 human hepatoma cells. Small interference RNA (siRNA) was used to silence the expression of E-cadherin and PPARgamma. Cell motility was assessed by transwell cell migration analysis. Measurements of mRNA and protein expression were done by quantitative RT-PCR and Western blotting. RESULTS: Treatment with synthetic PPARgamma agonists, thiazolidinediones (rosiglitazone; troglitazone), and adenovirus-delivered overexpression of PPARgamma transcriptional coactivator-1alpha (PGC-1alpha) up-regulated E-cadherin expression and reduced motility of HepG2 cells. Using PPARgamma antagonist GW9662, we demonstrated that both PPARgamma-dependent and -independent pathways were involved in PGC-1alpha-induced up-regulation of E-cadherin. In addition, siRNA-mediated knockdown of E-cadherin expression restored the motility of PGC-1alpha-overexpressing HepG2 cells, indicating that up-regulated E-cadherin is responsible for the lower migratory ability of these cells. Intriguingly, siRNA-mediated silencing of PPARgamma abolished E-cadherin protein expression but also reduced the motility of HepG2 cells. CONCLUSION: PPARgamma/PGC-1alpha pathway plays a crucial role in modulating E-cadherin expression and motility of HepG2 cells and may be a potential target for the prevention of HCC metastasis. less...

Although thiazolidinediones (TZDs) are potent promoters of adipogenesis in the preadipocyte, they induce apoptosis in several other cell types, such as cancer cells, endothelial cells and T-lymphocytes. In this study, we investigated the proapoptotic effect of TZDs in mature 3T3-L1 adipocytes, which express high levels of the peroxisome proliferator-activated receptor-gamma (PPARgamma) protein. Apoptosis was induced in mature 3T3-L1 adipocytes by treatment with troglitazone, pioglitazone or prostaglandin J2, and could be blocked by the PPARgamma antagonist GW9662. Treatment with PPARgamma agonists also decreased Akt-1 protein and phosphorylation levels without affecting phosphoinositide 3-kinase and PTEN. Further analysis indicated that in troglitazone-treated 3T3-L1 adipocytes, Bad phosphorylation and Bcl-2 protein levels were reduced, and Bax translocation to the mitochondria was increased. Subsequently, cytochrome c release and caspase-3 cleavage were observed. TZD-induced adipocyte apoptosis could be blocked by the caspase-3 inhibitor Ac-DEVD-CHO or by overexpression of Bcl2. In cultured rat primary adipocytes, similar apoptosis-inducing effects of troglitazone were also observed. Thus, TZDs promote apoptosis in adipocytes through a PPARgamma-dependent pathway. This apoptosis is mediated by the inhibition of Akt-1, which decreases Bad phosphorylation and activates the mitochondrial apoptotic pathway. less...

Numerous recent studies indicate that most anticancer effects of PPARgamma agonists like thiazolidinediones are the result of PPARgamma-independent pathways. These conclusions were obtained by several approaches including the use of thiazolidinedione derivatives like Delta2-Troglitazone (Delta2-TGZ) that does not activate PPARgamma. Since biotinylation has been proposed as a mechanism able to increase the specificity of drug delivery to cancer cells which could express a high level of vitamin receptor, a biotinylated derivative of Delta2-TGZ (bDelta2-TGZ) has been synthetized. In the present article, we have studied the in vitro effects of this molecule on both hormone-dependent (MCF-7) and hormone-independent (MDA-MB-231) breast cancer cells. In both cell lines, bDelta2-TGZ was more efficient than Delta2-TGZ to decrease cell viability. bDelta2-TGZ was also more potent than Delta2-TGZ to induce the proteasomal degradation of cyclin D1 in both cell lines and those of ERalpha in MCF-7 cells. However, in competition experiments, the presence of free biotin in the culture medium did not decrease the antiproliferative action of bDelta2-TGZ. Besides, other compounds that had no biotin but that were substituted at the same position of the phenolic group of the chromane moiety of Delta2-TGZ decreased cell viability similarly to bDelta2-TGZ. Hence, we concluded that the increased antiproliferative action of bDelta2-TGZ was not due to biotin itself but to the functionalization of the terminal hydroxyl group. This should be taken into account for the design of new thiazolidinedione derivatives able to affect not only hormone-dependent but also hormone-independent breast cancer cells in a PPARgamma-independent pathway. less...

BACKGROUND: The present study was conducted to assess the effect of Pioglitazone, an oral antidiabetic drug with selective PPAR-gamma agonist effect; in a dose of 4 mg/kg B.W. once a day orally for eight weeks on the liver of streptozotocin-induced diabetic rats. MATERIAL AND METHODS: Sixty male adult albino Wistar rats were equally randomly into six groups (n=10). Group I: normal control group was received no medication. Group II: distilled water control group, they are non diabetic group and received distilled water once a day orally by gastric tube for 8 weeks. Group III: citrate buffer control group, they are non diabetic received a single intraperitoneal injection of an equivalent amount of vehicle (citrate buffer, pH 4.5) 1 ml/kg at the time of induction. Group IV: Pioglitazone control group, they are non diabetic received pioglitazone HCl, single dose of 4 mg/kg b.w. once a day orally by gastric tube for eight weeks. Group V: diabetic control group, they are streptozotocin-induced diabetic rats that received no medication. Group VI: diabetic treated group, they are streptozotocin-induced diabetic rats treated by pioglitazone for eight weeks. RESULTS: At the end of the experiment microscopic examination of the liver sections in the diabetic control group, showed mild to moderate portal inflammatory infiltrate, mostly lymphocytic as well as intralobular cell necrosis and apoptosis as well as bile stasis. These results were associated serologically with elevation of all liver parameters. Pioglitazone administration in the normal rats for eight weeks didn't show any significant difference neither serologically nor histopathologically compared with normal control group. Moreover, pioglitazone administration caused statistically significant reduction in the mean levels of liver tests, as well as fasting blood glucose of the STZ-induced diabetic rats. CONCLUSION: There is no evidence that pioglitazone administration has a harmful effect on the liver. On the other hand, it has a potential beneficial effects on the liver during treatment of STZ-induced diabetic rats, suggesting that liver toxicity isn't a class effect of the thiazolidinediones but rather a unique effect of troglitazone. less...

Adipocyte dysfunction is strongly associated with the development of insulin resistance and diabetes, and regulation of adipogenesis is important in prevention of diabetes We prepared a 100% methanol fraction of methanolic extract from unripe kiwi fruit (Actinidia deliciosa), designated KMF (kiwi fruit methanol fraction). When applied to 3T3-L1 preadipocyte cells, KMF promoted adipocyte differentiation, increased glycerol-3-phosphate dehydrogenase (GPDH) activity, and increased triglyceride (TG) content KMF markedly increased mRNA expression of peroxisome proliferator-activated receptor gamma (PPARgamma)-the master adipogenic transcription factor-and its target genes. Moreover, KMF increased mRNA expression and protein secretion of adiponectin, whereas mRNA expression and secretion of monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) were decreased. Compared with troglitazone, KMF decreased the production of reactive oxygen species (ROS) and nuclear factor-kappaB (NFkappaB) activation. Glucose uptake was stimulated by KMF in differentiated 3T3-L1 adipocytes. Taken together, these results indicate that KMF may exert beneficial effects against diabetes via its ability to regulate adipocyte differentiation and function. less...

Expression of CD36 scavenger receptors on macrophages is involved in oxidized low-density lipoprotein uptake and foam cell formation during atherosclerotic lesion development. We examined the effects of aged garlic extract (AGE), a garlic preparation enriched in water-soluble cysteinyl moieties that increases cellular total thiols and glutathione concentrations, on CD36 expression in human monocytes/macrophages (THP-1 cells and primary human monocytes). Compared to control, AGE (1-5 mg/mL) dose-dependently and significantly suppressed CD36 expression up to by 61.8 +/- 7.4% in THP-1-derived macrophages and up to 50.5 +/- 7.1% in primary human macrophages, respectively. Furthermore, AGE prevented induction of CD36 expression by the peroxisome proliferator activator receptor (PPAR) gamma agonist troglitazone, and decreased binding of nuclear proteins to a PPARgamma response element. AGE showed a stronger inhibitory effect on CD36 expression in THP-1 cells during simultaneous incubation with phorbol 12-myristate 13-acetate (PMA) compared to cells that had been pre-incubated with PMA. Furthermore, AGE decreased CD11b expression in a dose-dependent manner. These data indicate that AGE inhibits CD36 expression by modulating the PPARgamma pathway in human macrophages and monocytes differentiation into macrophages, and suggests that the extract could be useful for the prevention of atherosclerotic lesions. Copyright (c) 2010 John Wiley & Sons, Ltd. less...

Cancer cells gain growth advantages in the microenvironment by shifting cellular metabolism to aerobic glycolysis, the so-called Warburg effect. There is a growing interest in targeting aerobic glycolysis for cancer therapy by exploiting the differential susceptibility of malignant versus normal cells to glycolytic inhibition, of which the proof-of-concept is provided by the in vivo efficacy of dietary caloric restriction and natural product-based energy restriction-mimetic agents (ERMAs) such as resveratrol and 2-deoxyglucose in suppressing carcinogenesis in animal models. Here, we identified thiazolidinediones (TZDs) as a novel class of ERMAs in that they elicited hallmark cellular responses characteristic of energy restriction, including transient induction of silent information regulator (Sirt)1 expression, activation of the intracellular fuel sensor AMP-activated protein kinase, and endoplasmic reticulum stress, the interplay among which culminated in autophagic and apoptotic death. The translational implications of this finding are multifold. First, the novel function of troglitazone and ciglitazone in targeting energy restriction provides a mechanistic basis to account for their peroxisome proliferator-activated receptor (PPAR)gamma-independent effects on a broad spectrum of signaling targets. Second, we demonstrated that Sirt1-mediated upregulation of beta-transducin repeat-containing protein-facilitated proteolysis of cell cycle- and apoptosis-regulatory proteins is an energy restriction-elicited signaling event and is critical for the antitumor effects of ERMAs. Third, it provides a molecular rationale for using TZDs as scaffolds to develop potent ERMAs, of which the proof-of-principle is demonstrated by OSU-CG12. OSU-CG12, a PPARgamma-inactive ciglitazone derivative, exhibits one- and three-orders-of-magnitude higher potency in eliciting starvation-like cellular responses relative to resveratrol and 2-deoxyglucose, respectively. less...

Thiazolidinediones, including rosiglitazone, troglitazone, are insulin-sensitizing drugs and high-affinity ligands for the Peroxisome Proliferator-Activated Receptor gamma (PPARgamma). Apart from their antidiabetic activity, these molecules possess antitumor properties. We investigated their potential apoptotic effects on RT4 (derived from a well differentiated grade I papillary tumor) and T24 (derived from an undifferentiated grade III carcinoma) bladder cancer cells. Rosiglitazone induced G2/M or G0/G1 phase cell cycle arrest in RT4 and T24 cells respectively. Only troglitazone triggered apoptosis via extrinsic and intrinsic pathways in both cell lines. Interestingly, rosiglitazone amplified TRAIL-induced apoptosis in TRAIL-sensitive RT4 cells or let TRAIL-resistant T24 cells to respond to TRAIL. Thiazolidinediones acted through PPARgamma activation-independent mechanisms. The underlying mechanisms involved for the first time in cancer cells the up-regulation of soluble and/or membrane-bound TRAIL. This was associated with increased cell surface death receptor 5 expression and c-FLIP and survivin down-regulation, mediated in part through proteasome-dependent degradation in troglitazone-promoted cell death. Therefore, the combination of rosiglitazone and TRAIL could be clinically relevant as chemopreventive or therapeutic agents for the treatment of TRAIL-resistant high grade urothelial cancers. (c) 2010 UICC. less...

The wall of the seminiferous tubules contains contractile smooth-muscle-like peritubular cells, thought to be important for sperm transport. Impaired spermatogenesis in men typically involves remodeling of this wall, and we now found that smooth muscle cell (SMC) markers, namely myosin heavy chain (MYH11) and smooth muscle actin (SMA) are often lost or diminished in peritubular cells of testes of men with impaired spermatogenesis. This suggests reduced contractility of the peritubular wall, which may contribute to sub- or infertility. In these cases, testicular expression of cyclooxygenase-2 (COX-2) implies formation of prostaglandins (PGs). When screening different PGs for their ability to target human testicular peritubular cells (HTPCs), only a PG metabolite, 15-deoxy-Delta(12-14)-prostaglandin-J2 (15dPGJ2), was effective. In primary cultures of HTPCs, 15dPGJ2 increased cell size in a reversible manner. Importantly, 15dPGJ2 treatment resulted in a loss of typical differentiation markers for SMCs, namely MYH11, calponin, and SMA, whereas fibroblast markers were unchanged. Collagen gel contraction assays revealed that this loss correlates with a reduced ability to contract. Experiments with an antagonist (bisphenol A diglycidyl ether) and agonist (troglitazone) for a cognate 15dPGJ2 receptor (i.e. peroxisome proliferator-activated receptor-gamma) indicated that peroxisome proliferator-activated receptor-gamma is not directly involved. Rather, the mode of action of 15dPGJ2 involves reactive oxygen species. The antioxidant N-acetylcysteine not only blocked ROS formation but also prevented the increase in cell size and the loss of contractility in HTPCs challenged with 15dPGJ2. We conclude that 15dPGJ2, via reactive oxygen species, influences SMC phenotype and contractility of human peritubular cells and possibly is involved in the development of human male sub-/infertility. less...

The transcription factor CREB is diminished in smooth muscle cells (SMCs) in remodeled, hypertensive pulmonary arteries (PAs) in animals exposed to chronic hypoxia. Forced depletion of CREB in PA SMCs stimulates their proliferation and migration in vitro. PDGF produced in the hypoxic PA wall promotes CREB proteasomal degradation in SMCs via PI3Kinase/Akt signaling, which promotes phosphorylation of CREB at two casein kinase 2 (CK2) sites. Here we tested whether thiazolidinediones, agents that inhibit hypoxia-induced PA remodeling, attenuate SMC CREB loss. We found that the thiazolidinedione rosiglitazone prevented PA remodeling and SMC CREB loss in rats exposed to chronic hypoxia. Likewise, the thiazolidinedione troglitazone blocked PA SMC proliferation and CREB depletion induced by PDGF in vitro. Thiazolidinediones did not repress Akt activation by hypoxia in vivo or by PDGF in vitro. However, PDGF induced CK2 alpha' catalytic subunit expression and activity in PA SMCs, and depletion of CK2 alpha' subunit prevented PDGF-stimulated CREB loss. Troglitazone inhibited PDGF-induced CK2 alpha' subunit expression in vitro and rosiglitazone blocked induction of CK2 catalytic subunit expression by hypoxia in PA SMCs in vivo. We conclude that thiazolidinediones prevent PA remodeling in part by suppressing upregulation of CK2 and loss of CREB in PA SMCs. less...