Effects Of Troglitazone Research Articles

The antidiabetic drug troglitazone protects against PrP (106‑126)‑induced neurotoxicity via thePPARγ‑autophagy pathway in neuronal cells.

Prion diseases, which involve the alteration of cellular prion protein into a misfolded isoform, disrupt the central nervous systems of humans and animals alike. Prior research has suggested that peroxisome proliferator-activator receptor (PPAR)γ and autophagy provide some protection against neurodegeneration. PPARs are critical to lipid metabolism regulation and autophagy is one of the main cellular mechanisms by which cell function and homeostasis is maintained. The present study examined the effect of troglitazone, a PPARγ agonist, on autophagy flux in a prion peptide (PrP) (106–126)-mediated neurodegeneration model. Western blot analysis confirmed that treatment with troglitazone increased LC3-II and p62 protein expression, whereas an excessive increase in autophagosomes was verified by transmission electron microscopy. Troglitazone weakened PrP (106–126)-mediated neurotoxicity via PPARγ activation and autophagy flux inhibition. A PPARγ antagonist blocked PPARγ activation as well as the neuroprotective effects induced by troglitazone treatment, indicating that PPARγ deactivation impaired troglitazone-mediated protective effects. In conclusion, the present study demonstrated that troglitazone protected primary neuronal cells against PrP (106–126)-induced neuronal cell death by inhibiting autophagic flux and activating PPARγ signals. These results suggested that troglitazone may be a useful therapeutic agent for the treatment of neurodegenerative disorders and prion diseases.

Mechanistic Insights into Side Effects of Troglitazone and Rosiglitazone Using a Novel Inverse Molecular Docking Protocol.

Thiazolidinediones form drugs that treat insulin resistance in type 2 diabetes mellitus. Troglitazone represents the first drug from this family, which was removed from use by the FDA due to its hepatotoxicity. As an alternative, rosiglitazone was developed, but it was under the careful watch of FDA for a long time due to suspicion, that it causes cardiovascular diseases, such as heart failure and stroke. We applied a novel inverse molecular docking protocol to discern the potential protein targets of both drugs. Troglitazone and rosiglitazone were docked into predicted binding sites of >67,000 protein structures from the Protein Data Bank and examined. Several new potential protein targets with successfully docked troglitazone and rosiglitazone were identified. The focus was devoted to human proteins so that existing or new potential side effects could be explained or proposed. Certain targets of troglitazone such as 3-oxo-5-beta-steroid 4-dehydrogenase, neutrophil collagenase, stromelysin-1, and VLCAD were pinpointed, which could explain its hepatoxicity, with additional ones indicating that its application could lead to the treatment/development of cancer. Results for rosiglitazone discerned its interaction with members of the matrix metalloproteinase family, which could lead to cancer and neurodegenerative disorders. The concerning cardiovascular side effects of rosiglitazone could also be explained. We firmly believe that our results deepen the mechanistic understanding of the side effects of both drugs, and potentially with further development and research maybe even help to minimize them. On the other hand, the novel inverse molecular docking protocol on the other hand carries the potential to develop into a standard tool to predict possible cross-interactions of drug candidates potentially leading to adverse side effects.

Troglitazone, a Selective Ligand for PPARγ, Induces Cell-cycle Arrest in Human Oral SCC Cells.

We attempted to clarify the role of Peroxisome proliferator-activated receptor γ (PPARγ) and its ligand, troglitazone (TRO) on oral squamous cell carcinoma (SCC). The expression of PPARγ gene was examined in 47 human oral SCC tissues and two human oral SCC cell lines, CA9-22 and HSC-4. The effects of TRO on the growth and cell-cycle progression of human oral SCC cells were examined. PPARγ mRNA was detected in 20 of 47 oral SCC tissues and two human oral SCC cells. TRO significantly suppressed the growth of the cells, but did not induce apoptosis. CA9-22 cells treated with TRO showed an increased fraction in the G1 phase and decreased fractions in the S and G2-M phases. TRO did not induce apoptosis in oral SCC cells, but did inhibit the growth of the cells by arresting the cell cycle at G1 phase.

Troglitazone exerts metabolic and antitumor effects on T47D breast cancer cells by suppressing mitochondrial pyruvate availability.

The aim of the present study was to investigate the metabolic and anticancer effects of troglitazone (TGZ) with a focus on the potential role of mitochondrial pyruvate utilization. 2‑Deoxyglucose (2‑DG) was more cytotoxic in CT26 cancer cells compared with T47D cells, despite a smaller suppression of glucose uptake. On the other hand, TGZ caused a more prominent shift to glycolytic metabolism and was more cytotoxic in T47D cells. Both effects of TGZ on T47D cells were dose‑dependently reversed by addition of methyl pyruvate (mPyr), indicating suppression of mitochondrial pyruvate availability. Furthermore, UK5099, a specific mitochondrial pyruvate carrier inhibitor, closely simulated the metabolic and antitumor effects of TGZ and their reversal by mPyr. This was accompanied by a substantial reduction of activated p70S6K. In CT26 cells, UK5099 did not reduce activated p70S6K and only modestly decreased cell proliferation. In these cells, combining glutamine restriction with UK5099 further increased glucose uptake and completely suppressed cell proliferation. Thus, TGZ‑mediated inhibition of mitochondrial pyruvate utilization is an effective treatment for cancer cells that are more dependent on mitochondrial glucose metabolism. By contrast, cancer cells that are more glycolysis‑dependent may require suppression of glutamine utilization in addition to blocking mitochondrial pyruvate availability for a full antitumor effect.

Troglitazone activates TRPV1 and causes deacetylation of PPARγ in 3T3-L1 cells

Published research suggests that activation of transient receptor potential vanilloid subfamily 1 (TRPV1) enhances the expression and deacetylation of peroxisome proliferator-activated receptor gamma (PPARγ) to cause browning of white adipose tissue. Here, we show that TRPV1 activation by capsaicin significantly prevents high fat diet-induced obesity in mice. This is associated with an increase in the expression and deacetylation of PPARγ in the epididymal fat of these mice. Consistent with the TRPV1 activation in vivo, overexpression of TRPV1 enhanced the PPARγ and other thermogenic genes in cultured 3T3-L1 preadipocytes. To determine the interaction between TRPV1 and PPARγ signaling, we analyzed the effect of Troglitazone (Trog; a thiazolidinedione derivative and an agonist of PAARγ) treatment on cultured 3T3-L1 cells. Trog enhanced the expression of TRPV1, PPARγ and thermogenic proteins in undifferentiated 3T3-L1 cells but not in differentiated cells. Acute application of Trog stimulated a robust Ca2+ influx into 3T3-L1 cells and TRPV1 inhibition by capsazepine prevented this. More interestingly, Trog or capsaicin treatment caused the deacetylation of PPARγ in 3T3-L1 cells and inhibition of TRPV1 or Sirtuin 1 - prevented this. Our data suggest a novel effect of Trog to induce PPARγ deacetylation by activating TRPV1. This research has a significant implication on the role of TRPV1 and PPARγ signaling in the browning of white adipose tissue.

A Synergistic Anti-Cancer Effect of Troglitazone and Lovastatin in a Human Anaplastic Thyroid Cancer Cell Line and in a Mouse Xenograft Model.

Anaplastic thyroid cancer (ATC) is a malignant subtype of thyroid cancers and its mechanism of development remains inconclusive. Importantly, there is no effective strategy for treatment since ATC is not responsive to conventional therapies, including radioactive iodine therapy and thyroid-stimulating hormone suppression. Here, we report that a combinational approach consisting of drugs designed for targeting lipid metabolism, lovastatin (an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, HMGCR) and troglitazone (an agonist of peroxisome proliferator-activated receptor gamma, PPARγ), exhibits anti-proliferation in cell culture systems and leads to tumor regression in a mouse xenograft model. The composition contains a sub-lethal concentration of both drugs and exhibits low toxicity to certain types of normal cells. Our results support a hypothesis that the inhibitory effect of the combination is partly through a cell cycle arrest at G0/G1 phase, as evidenced by the induction of cyclin-dependent kinase inhibitors, p21cip and p27kip, and the reduction of hyperphosphorylated retinoblastoma protein (pp-Rb)-E2F1 signaling. Therefore, targeting two pathways involved in lipid metabolism may provide a new direction for treating ATC.

Effect of Troglitazone (Tz) and N‐Acetyl Cysteine (Nac) Treatment on Beta Cells' Survival, and Insulin Production Under Hyperglycaemic Conditions

BackgroundType I diabetes mellitus is characterized by the deficiency of insulin‐producing beta cells but there is still a substantial number of beta cells found in the pancreas and secrete insulin at the time of diagnosis. The mTOR pathway can directly influence insulin production by affecting multiple translation factors, one of which is decreasing eIF‐4E inhibition which, in the same time, can be activated by the indirect insulin production enhancer, ERK phosphorylation pathway.AimThe purpose of this study is to find out the combined effects of TZ and NAC on Beta‐cells insulin production and survival under hyperglycemic conditions (24 hours and 72 hours) and explore the effect of different TZ concentrations under 72h hyperglycemic conditions.MethodsGRINCH cells were prepared, cultured, and divided into separate 24‐well plates (200,000 cell/well) and 96‐well plates (10,000 cell/well). The experiment was performed on a total of 8 wells, 4 for each type of well plates; 2 for 24hrs, and 2 for 72hrs treatments; 1 being normoglycemic and 1 being a hyperglycemic well for each time condition. Apart from the controls, each plate had 3 treatment groups. The first group was the cells treated with TZ (10μM). The second group was the cells treated with NAC (2mM). The third group was the combination of NAC with TZ along with the cells. All groups contained an adequate amount of media in relation to the treatment. To explore the effects of different TZ concentrations, two extra 24‐well plates with GRINCH cells were prepared, one for each environment (hyper and normoglycemic conditions). 3 different TZ concentrations were used, 10, 5, and 2.5μM along with their respective vehicle controls. measurements were taken at 24 and 72 hours.ResultsAll the three groups showed increased insulin production in normoglycemic 24hrs condition, however, in 24hrs hyperglycemia, only NAC and the combination of NAC and TZ showed an increase while TZ stayed the same. In 72hrs normoglycemia, TZ and NAC showed a decrease while their combination showed no change. While in 72hrs hyperglycemia both TZ and the combination decreased but NAC increased. The only 2 conditions with increased survival were NAC and TZ individual treatment in 72hrs normoglycemic conditions. Concerning the second part of the experiment; 2.5μM showed an increase in insulin production.ConclusionThere was no positive proof of the combination (TZ and NAC) effect in chronic 72hrs hyperglycemia which possibly excludes its use in diabetics, however, there positive effects in acute 24hrs hyperglycemia should be further investigated. Furthermore, the fact that at a certain concentration TZ was able to increase insulin proves that there is a point at which by using TZ, ERK and mTOR pathways both would be enhanced to increase insulin production which gives more incite of Thiazolidinediones effects in diabetic patients.Support or Funding InformationThis work was supported by the University of Sharjah and the Boehringer Ingelheim Pharmaceutical company.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Troglitazone Inhibits Matrix Metalloproteinase-9 Expression and Invasion of Breast Cancer Cell through a Peroxisome Proliferator-Activated Receptor γ-Dependent Mechanism.

PurposePeroxisome proliferator-activated receptor γ (PPARγ) is involved in the pathology of numerous diseases including atherosclerosis, diabetes, obesity, and cancer. Matrix metalloproteinases (MMPs) play a significant role in tissue remodeling related to various processes such as morphogenesis, angiogenesis, tissue repair, invasion, and metastasis. We investigated the effects of PPARγ on MMP expression and invasion in breast cancer cells.MethodsMCF-7 cells were cultured and then cell viability was monitored in an MTT assay. Western blotting, gelatin zymography, real-time polymerase chain reaction, and luciferase assays were performed to investigate the effect of the synthetic PPARγ ligand troglitazone on MMP expression. Transcription factor DNA binding was analyzed by electrophoretic mobility shift assay. A Matrigel invasion assay was used to assess the effects of troglitazone on MCF-7 cells.ResultsTroglitazone did not affect MCF-7 cell viability. 12-O-tetradecanoylphorbol-13-acetate (TPA) induced MMP-9 expression and invasion in MCF-7 cell. However, these effects were decreased by troglitazone. TPA increased nuclear factor κB and activator protein-1 DNA binding, while troglitazone inhibited these effects. The selective PPARγ antagonist GW9662 reversed MMP-9 inhibition by troglitazone in TPA-treated MCF-7 cells.ConclusionTroglitazone inhibited nuclear factor κB and activator protein-1-mediated MMP-9 expression and invasion of MCF-7 cells through a PPARγ-dependent mechanism.

Increased susceptibility to troglitazone-induced mitochondrial permeability transition in type 2 diabetes mellitus model rat.

Troglitazone, a member of the thiazolidinedione class of antidiabetic drugs, was withdrawn from the market because it causes severe liver injury. One of the mechanisms for this adverse effect is thought to be mitochondrial toxicity. To investigate the characteristics of troglitazone-induced liver toxicity in more depth, the toxicological effects of troglitazone on hepatocytes and liver mitochondria were investigated using a rat model of type 2 diabetes mellitus (T2DM). Troglitazone was found to increase mitochondrial permeability transition (MPT) in the liver mitochondria of diabetic rats to a greater extent than in control rats, whereas mitochondrial membrane potential and oxidative phosphorylation were not affected. To identify the factors associated with this increase in susceptibility to MPT in diabetic rats, we assessed the oxidative status of the liver mitochondria and found a decrease in mitochondrial glutathione content and an increase in phospholipid peroxidation. Moreover, incorporation of oxidized cardiolipin, a mitochondrion-specific phospholipid, was involved in the troglitazone-induced alteration in susceptibility to MPT. In conclusion, liver mitochondria display disease-associated mitochondrial lipid peroxidation in T2DM, which facilitates the higher susceptibility to troglitazone-induced MPT. Thus, greater susceptibility of liver mitochondria may be a host factor leading to troglitazone-induced hepatotoxicity in T2DM.

The effects of troglitazone on AMPK in HepG2 cells

AMP-activated protein kinase (AMPK) is an enzyme crucial in cellular metabolism found to be inhibited in many metabolic diseases including type 2 diabetes. Thiazolidinediones (TZDs) are a class of anti-diabetic drug known to activate AMPK through increased phosphorylation at Thr172, however there has been no research to date on whether they have any effect on inhibition of AMPK's lesser known site of inhibition, Ser485/491. HepG2 cells were treated with troglitazone and phosphorylation of AMPK was found to increase at both Thr172 and Ser485 in a dose- and time-dependent manner. Treatment of HepG2 cells with insulin and PMA led to increases in p-AMPK Ser485 via Akt and PKD1 respectively; however these kinases were not found to be implicated in increases seen from troglitazone. Incubation with the other TZDs, rosiglitazone and pioglitazone, let to a minor increase in p-AMPK Ser485 phosphorylation as well as AMPK activity; however these findings were significantly less than those of troglitazone under equal conditions. These data suggest that the effects of troglitazone on AMPK are more complex than previously thought. Phosphorylation at sites of both activation and inhibition can occur in tandem, although the mechanism by which this occurs has not yet been elucidated.

Troglitazone Inhibits Bile Acid Amidation: A Possible Risk Factor for Liver Injury

Troglitazone and pioglitazone were developed as thiazolidinedione-type antidiabetes drugs, but only troglitazone was withdrawn from the markets due to severe liver injury. As both troglitazone and its sulfate metabolite are strong inhibitors of the bile salt export pump (BSEP), troglitazone-induced bile acid (BA) retention is thought to be one of the underlying mechanisms of liver injury. However, pioglitazone is also a strong BSEP inhibitor, indicating other mechanisms may also be involved in troglitazone-induced BA retention. Although retention of hydrophobic BAs (eg, chenodeoxycholic acid [CDCA]: a nonamidated BA) is known to cause hepatocyte injury, little is known about the hepatic conversion of nonamidated, hydrophobic BA species into less toxic hydrophilic BAs (eg, glycochenodeoxycholic acid: amidated BA) as a mechanism of drug-induced liver injury. In this study, we, therefore, investigated the effects of troglitazone and pioglitazone on BA amidation and the role of amidated BAs in troglitazone-associated BA-mediated hepatotoxicity. We also evaluated the intracellular BA composition of human hepatocytes treated with nonamidated BA species (CDCA or deoxycholic acid [DCA]) in the presence of troglitazone or pioglitazone. Amidation of CDCA and DCA was significantly inhibited by troglitazone (IC50: 5 and 3 µmol/l, respectively), but not pioglitazone. Moreover, treatment with troglitazone led to the retention of CDCA and DCA and decrease of glycine-amidation in hepatocytes. From these results, we suggest that troglitazone-induced liver injury might be caused by the accumulation of nonamidated BAs in hepatocytes due to inhibition of BA amidation.

The effect of PPARγ agonist on SGLT2 and glucagon expressions in alpha cells under hyperglycemia.

Although sodium glucose cotransporter 2 (SGLT2) inhibitors have many beneficial effects for type 2 diabetes, including decreased cardiovascular death, recent reports that they increased glucagon through SGLT2 inhibition raised some concern. Troglitazone, Peroxisome proliferator-activated receptor γ (PPAR-γ) agonist, was reported to increase SGLT2 in renal proximal tubule cells, but its role on pancreatic alpha cells have not been reported. We investigated the effect of troglitazone on SGLT2 expression in alpha cells and subsequent glucagon regulation in hyperglycemia. An Alpha TC1-6 cell line was cultured in control (5 mM) or hyperglycemia (HG, 15mM) for 72h. We applied troglitazone with or without PPARγ antagonist (GW9662 10 μM). To investigate the involvement of PI3K/Akt pathway, we applied troglitazone with or without Wortmanin. We measured sodium glucose transporter 2 (SGLT2) and glucagon (GCG) mRNA and protein expression. PPAR gamma, PI3K and Akt protein were also measured. Exposure of alpha TC cells to HG for 72h increased glucagon mRNA and protein expression. HG decreased SGLT2 mRNA and protein expression. Troglitazone significantly reversed HG-induced reduction of SGLT2 expression and increase of glucagon secretion. PPARγ antagonist (GW9662 10μM) decreased the expression of SGLT2 and increased glucagon as HG did. Hyperglycemia increased PI3K and pAkt expression in alpha cells. Wortmanin (PI3K inhibitor, 1 μM) reversed HG-induced SGLT2 decrease and glucagon increase. Troglitazone treatment decreased PI3K and pAkt expression in HG. In conclusion, PPARγ agonist, troglitazone improved glucose transport SGLT2 dysfunction and subsequent glucagon dysregulation in alpha cell under hyperglycemia. Those effects were through the involvement of PI3K/pAkt signaling pathway. This study may add one more reason for the ideal combination of PPARγ agonist and SGLT2 inhibitor in clinical practice.

Effects of troglitazone on bile acid disposition in Bsep KO rats

The inhibition of bile salt export pump (BSEP) by troglitazone (TGZ) and its sulfate metabolite (TS) is one of the mechanisms for TGZ‐induced hepatotoxicity. Here, we evaluated the bile acid profiles in wild type (WT) and Bsep knock‐out (KO) rats following repeated oral dose of TGZ (200 mg/kg/day, 7 days). With the remove of 8 base‐pair of nuclear acids, the mRNA levels of Shp, Mrp2, Mrp3 and Sult2A1 were significantly upregulated in KO rats. Following 7 day TGZ treatment, no signs of liver toxicity were observed in WT and KO rats, but Cyp7A1 was significantly increased in both groups. The plasma exposures of TGZ were not different between WT and KO rats, and are similar on Day‐1 and Day‐7. The exposures of TS were 7.6 and 9.3 fold lower in KO rats than in WT on Day‐1 and Day‐7, respectively. However, the formation of TS in liver S9 incubation was similar between WT and KO, indicating that the decreased TS plasma exposures in KO rats could be from increased biliary excretion, rather than altered metabolism. In general, dosing vehicle had minimal effects on bile acid profiles in WT and KO rats, but plasma exposure of individual bile acids demonstrated variable changes in KO rats when compared with WT rats. Many bile acids were increased with the first dose of TGZ in WT, but the increases were partially restored on last dose. In KO rats, alterations of most bile acids were only observed after 7 doses of TGZ. Therefore, rats seem able to regulate bile acid homeostasis through bile acid synthesis and transporter regulation in the presence of Bsep impairment caused by genetic modification or drug inhibition.

Cellular Effects of Troglitazone on YD15 Tongue Carcinoma Cells

Cellular Effects of Troglitazone on YD15 Tongue Carcinoma Cells

Cancer drug troglitazone stimulates the growth and response of renal cells to hypoxia inducible factors

Troglitazone has been used to suppress the growth of a number of tumors through apoptosis and autophagy. However, previous in vitro studies have employed very high concentrations of troglitazone (≥10−5 M) in order to elicit growth inhibitory effects. In this report, when employing lower concentrations of troglitazone in defined medium, troglitazone was observed to stimulate the growth of primary renal proximal tubule (RPT) cells. Rosiglitazone, like troglitazone, is a thiazolidinedione (TZD) that is known to activate Peroxisome Proliferator Activated Receptor Υ (PPARΥ). Notably, rosiglitazone also stimulates RPT cell growth, as does Υ-linolenic acids, another PPARΥ agonist. The PPARΥ antagonist GW9662 inhibited the growth stimulatory effect of troglitazone. In addition, troglitazone stimulated transcription by a PPAR Response Element/Luciferase construct. These results are consistent with the involvement of PPARΥ as a mediator of the growth stimulatory effect of troglitazone. In a number of tumor cells, the expression of hypoxia inducible factor (HIF) is increased, promoting the expression of HIF inducible genes, and vascularization. Troglitazone was observed to stimulate transcription by a HIF/luciferase construct. These observations indicate that troglitazone not only promotes growth, also the survival of RPT cells under conditions of hypoxia.

Troglitazone Enhances the Apoptotic Response of DLD-1 Colon Cancer Cells to Photodynamic Therapy.

PurposeThe aim of this study was to investigate whether the peroxisomal proliferator-activated receptor gamma (PPARγ) ligand troglitazone in combination with photodynamic therapy (PDT) enhances the apoptotic response of DLD-1 colon cancer cells.Materials and MethodsThe effects of troglitazone, PDT, and troglitazone in combination with PDT on cell viability and apoptosis were assessed in DLD-1 cells. Cell viability and proliferation were evaluated using the tetrazolium-based MTT assay, and apoptosis was evaluated via cell staining with propidium iodide (PI) and annexin V-FITC. The levels of pro-caspase-3 were measured via Western blot analyses.ResultsTreatment of troglitazone and PDT induced the growth retardation and cell death of DLD-1 cells in a dose-dependent manner, respectively. The combination treatment significantly suppressed cell growth and increased the apoptotic response of DLD-1 and resulted in apoptosis rather than necrosis, as shown by PI/annexin V staining and degradation of procaspase-3.ConclusionConclusion: These results document the anti-proliferative and apoptotic activities of PDT in combination with the PPARγ ligand troglitazone and provide a strong rationale for testing the therapeutic potential of combination treatment in colon cancer.

Development of an optimized cytotoxicity assay system for CYP3A4-mediated metabolic activation via modified piggyBac transposition

Drug-induced hepatotoxicity is often caused by cytochrome P450 (CYP)-dependent metabolism of drugs into reactive metabolites. Assessment of hepatotoxicity induced by bioactive compounds is hampered by low CYP expression within in vitro cell lines. To overcome this limitation, piggyBac transposition and monoclonal expansion were used to generate a HepG2 cell line with stable and homogenously high expression of CYP3A4, a prominent CYP isoform. Our studies demonstrate the generated line's constant CYP3A4 expression and activity for over 40 cell passages; to date, it has been in subculture for more than a year without addition of Puromycin. This cell line was utilized to evaluate cytotoxicity of two bioactive (troglitazone and acetaminophen) and two non-bioactive (citrate and galactosamine) compounds by MTT assay. Cell viability significantly decreased upon treatment with bioactive drugs. Moreover, cell lines used in the present study were more sensitive to toxic effects of troglitazone than previously reported. Therefore, this HepG2 cell-based assay system may provide a suitable hepatic model for predicting CYP3A4-mediated hepatotoxicity during preclinical drug development.

Antiproliferative effects and molecular mechanisms of troglitazone in human cervical cancer in vitro.

We investigated the effects of troglitazone on human cervical cancer SiHa cells and its mechanisms of action. SiHa cells were incubated with different concentrations of troglitazone (100, 200, or 400 μg/mL) for 24, 48, and 72 hours. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay; cell cycle and apoptosis were detected by flow cytometry; and morphology of SiHa cells was observed under an inverted microscope. pcDNA3.1 and pcDNA3.1-Skp2 plasmids were constructed and then transfected into SiHa cells. Protein expression was analyzed by Western blotting. Troglitazone inhibited the proliferation of SiHa cells in a time- and concentration-dependent manner. Troglitazone caused G0/1 phase arrest but failed to reduce apoptosis in SiHa cells. Troglitazone significantly increased expression of p27 but decreased Skp2 expression. Skp2 overexpression inhibited the role of troglitazone in increasing expression of p27, and the cell cycle inhibitory effect of troglitazone. Troglitazone can inhibit SiHa cell viability by affecting cell cycle distribution but not apoptosis, and Skp2 and p27 may play a critical role.

The inhibitory effect of troglitazone on macrophage differentiation mediated by repressing NF-κB ctivation independently of PPARγ

The synthetic thiazolidinediones (TZDs) are agonists for the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) and widely used as insulin-sensitizing drugs in type II diabetes. Troglitazone (TGZ) is a TZDs type of PPARγ ligands, which shows hepatic adverse effects in clinical practice. Liver-resident macrophages derive from monocytes and play important roles in maintaining homeostasis in the liver microenvironment. Here, we demonstrated that TGZ could significantly inhibit phorbol 12-myristate 13-acetate (PMA)-induced macrophage differentiation of monocytic cells in a dose-dependent manner with minimal cytotoxicity. However, another PPARγ ligand rosiglitazone (RSG) had only marginal impact on macrophage differentiation. Pretreatment with PPARγ antagonist GW9662 or knockdown of PPARγ could not abrogate CD11b induction. Compared with RSG, TGZ could mimic NF-κB inhibitor BAY 11-7082 to block NF-κB signaling and macrophage differentiation. Therefore, the present data has demonstrated a unique inhibitory action of TGZ on macrophage differentiation which was mediated by suppressing NF-κB activation and was independent of PPARγ. These findings suggested that the inhibitory effect on macrophage differentiation might partly account for TGZ-induced liver injury.

Troglitazone metabolism and transporter effects in chimeric mice: a comparison between chimeric humanized and chimeric murinized FRG mice

1. The biotransformation, hepatic transporter and blood chemistry effects of troglitazone were investigated following 7 days of dosing at 600 mg/kg/day to chimeric murinized or humanized FRG mice, Mo-FRG and Hu-FRG mice, respectively.2. Clinical chemistry and histopathology analysis revealed a significant drop in humanization over the time course of the study for the Hu-FRG mice but no significant changes associated with troglitazone treatment in either the Mo-FRG or the Hu-FRG models. No changes in transporter expression in livers of these mice were observed. Oxidative and conjugative metabolic pathways were identified with a 15- to 18-fold increase in formation of troglitazone sulfate in the Hu-FRG mice compared with the Mo-FRG mice in blood and bile, respectively. This resembles the troglitazone metabolism in human and these data are comparable with the formation of this metabolite in the chimeric uPA+/+/SCID mice.3. However, larger amounts of troglitazone glucuronide were also observed in the Hu-FRG mouse compared with the Mo-FRG mouse which may be an effect of the drop in humanization of the Hu-FRG mouse during the study.4. Highly humanized mice have a considerable potential in providing a useful first insight into circulating human metabolites of candidate drugs metabolized in the liver.