Comparative microarray analyses of mono(2-ethylhexyl)phthalate impacts on fat cell bioenergetics and adipokine network.

Cellular accumulation of mono(2-ethylhexyl)phthalate (MEHP) has been recently demonstrated to disturb fat cell energy metabolism; however, the underlying mechanism remained unclear. The study aimed to determine how MEHP influenced fat cell transcriptome and how the changes might contribute to bioenergetics. Because of the pivotal role of PPARγ in energy metabolism of fat cells, comparative microarray analysis of gene expression in 3T3-L1 adipocytes treated with both MEHP and rosiglitazone was performed. Pathway enrichment analysis and gene ontology (GO) enrichment analysis revealed that both treatments caused up-regulation of genes involved in PPAR signaling/energy metabolism-related pathways and down-regulation of genes related to adipokine/inflammation signals. MEHP/rosiglitazone-treated adipocytes exhibited increased levels of lipolysis, glucose uptake, and glycolysis; the gene expression profiles provided molecular basis for the functional changes. Moreover, MEHP was shown to induce nuclear translocation and activation of PPARγ. The similarity in gene expression and functional changes in response to MEHP and rosiglitazone suggested that MEHP influenced bioenergetics and adipokine network mainly via PPARγ. Importantly, adipokine levels in C57BL/6J mice with di(2-ethylhexyl)phthalate (DEHP) treatments provided in vivo evidence for microarray results. On the basis of correlation between gene expression and functional assays, possible involvements of genes in bioenergetics of MEHP-treated adipocytes were proposed.

Estrogenic chemicals at body burden levels attenuate energy metabolism in 3T3-L1 adipocytes.

The study aimed to examine effects of environmental estrogens at body burden levels on energy metabolism in fat cells. Acclimation of T47D-KBluc cells in estrogen-deprived medium was established for high performance of estrogen-responsive luciferase reporter assay. With the assay, relative estrogenic potency of four selected estrogen receptor (ER) agonists, i.e. diethylstilbestrol, ß-estradiol, 4-nonylphenol and bisphenol A, were determined. Immunoblot analysis revealed that the ER agonists at both EC80 and EC100 caused rapid and transient phosphorylation of extracellular signal-regulated kinases (ERK) in an ER-dependent manner. 3T3-L1 adipocytes treated with the ER agonists at EC80 for 24 hours exhibited significant downregulation in mitochondrial respiration and glycolytic function. Importantly, EC80 values of 4-nonylphenol (6.0 × 10-10  m) and bisphenol A (1.0 × 10-8  m) are in the range of human body burdens. The finding that estrogenic chemicals at body burden levels cause significant impact on fat cell energy metabolism raises an important public health issue that deserves more attention.

Crucial role of Toll-like receptors in the zinc/nickel-induced inflammatory response in vascular endothelial cells.

Our previous studies indicated that zinc induced inflammatory response in both vascular endothelial cells and promonocytes. Here, we asked if other metals could cause the similar effect on vascular endothelial cells and tried to determine its underlying mechanism. Following screening of fifteen metals, zinc and nickel were identified with a marked proinflammatory effect, as determined by ICAM-1 and IL-8 induction, on human umbilical vein endothelial cells (HUVECs). Inhibiting protein expression of myeloid differentiation primary response protein-88 (MyD88), a Toll-like receptor (TLR) adaptor acting as a TLR-signaling transducer, significantly attenuated the zinc/nickel-induced inflammatory response, suggesting the critical roles of TLRs in the inflammatory response. Blockage of TLR-4 signaling by CLI-095, a TLR-4 inhibitor, completely inhibited the nickel-induced ICAM-1 and IL-8 expression and NFκB activation. The same CLI-095 treatment significantly blocked the zinc-induced IL-8 expression, however with no significant effect on the ICAM-1 expression and a minor inhibitory effect on the NFκB activation. The finding demonstrated the differential role of TLR-4 in regulation of the zinc/nickel-induced inflammatory response, where TLR-4 played a dominant role in NFκB activation by nickel, but not by zinc. Moreover, inhibition of NFκB by adenovirus-mediated IκBα expression and Bay 11-7025, an inhibitor of cytokine-induced IκB-α phosphorylation, significantly attenuated the zinc/nickel-induced inflammatory responses, indicating the critical of NFκB in the process. The study demonstrates the crucial role of TLRs in the zinc/nickel-induced inflammatory response in vascular endothelial cells and herein deciphers a potential important difference in NFκB activation via TLRs. The study provides a molecular basis for linkage between zinc/nickel exposure and pathogenesis of the metal-related inflammatory vascular disease.

DC-81-enediyne induces apoptosis of human melanoma A375 cells: involvement of the ROS, p38 MAPK, and AP-1 signaling pathways.

Melanoma is one of the most chemoresistant cancers in patient care. The remission rate of current therapy remains low. DC-81, an antitumor antibiotic produced by Streptomyces species, belongs to pyrrolo[2,1-c][1,4]benzodiazepine (PBD), which is a potent inhibitor of nucleic acid synthesis. An enediyne contains either DNA intercalating groups or DNA minor groove binding functions and these are potent DNA-damaging agents due to their ability to generate benzenoid diradicals. We have previously reported an efficient synthesis and antitumor activity of a series of novel PBD hybrids linked with enediyne. The purpose of this study was to examine the mechanism of the antiproliferative effect of DC-81-enediyne agent on human melanoma A375 cells. DC-81-enediyne induced an increase in Ca(2+) level and reactive oxygen species (ROS) generation as detected by flow cytometric assay. Western blot analysis showed that DC-81-enediyne induced the phosphorylation of p38 and activating transcription factor 2 (ATF-2). By using the luciferase reporter assay, activating protein-1 (AP-1) activity was further enhanced after A375 cells were treated with graded concentrations of DC-81-enediyne. DC-81-enediyne treatment-induced A375 cell apoptosis was significantly abrogated by the addition of Ca(2+), ROS, and p38 inhibitors. Collectively, our studies indicate that DC-81-enediyne induces A375 cell apoptosis through an increased Ca(2+) and ROS generation, which involves p38 phosphorylation and enhanced ATF-2/AP-1 expressions, leading to caspase-3 activity, poly(ADP-ribose)polymerase cleavage, M30 CytoDeath staining, and subsequent apoptotic cell death.

Zinc ions induce inflammatory responses in vascular endothelial cells.

Using one particulate zinc oxide (ZnO) and two soluble zinc compounds (Zn(NO(3))(2) and Zn(CH(3)COO)(2)), we aimed to clarify if zinc ions (Zn(2+)), like particulate ZnO, caused inflammatory responses in vascular endothelial cells. Treatments of human umbilical vein endothelial cells (HUVECs) with 368.6 µM of each zinc compound caused marked increases in IκBα phosphorylation and intercellular adhesion molecule-1 (ICAM-1) expression. Treatments with Zn(CH(3)COO)(2) (50-350 µM) induced a dose-dependent ICAM-1 expression. These results show that Zn(2+) alone is sufficient to induce similar levels of ICAM-1 expression as ZnO particles, suggesting that dissolved Zn(2+) may play the major role in inflammatory effect of ZnO particles on vascular endothelial cells.

Di(2-ethylhexyl)phthalate exposure exacerbates metabolic disorders in diet-induced obese mice.

Both phthalate exposure and obesity are positively associated with metabolic disorders. The study aimed to investigate whether DEHP exposure caused metabolic disorders in an obesity-dependent manner. Both lean and diet-induced obese mice were subjected to environmentally relevant DEHP exposure. DEHP-treated obese mice exhibited higher glucose intolerance and insulin resistance than obese mice; the metabolic disorders were accompanied by increased blood levels of leptin, LDL cholesterol, and alanine transaminase. In obese mice, DEHP enhanced macrophage infiltration into epididymal white adipose tissue (eWAT) and hepatic tissue, and promoted hepatic steatosis/steatohepatitis. The DEHP effects were not observed in lean mice. Transcriptomic changes in eWAT and hepatic tissue were determined with microarray analysis. Results indicated that obesity and DEHP synergistically regulated carbohydrate uptake, lipolysis, and abnormality of adipose tissue, via the upstream regulators Pparg, Lipe, Cd44, and Irs1. Meanwhile, obesity and DEHP differentially modulated transcriptomic changes in hepatic tissue. Obesity was associated with lipid/cholesterol synthesis, lipid accumulation, and inflammation in hepatic tissue via the upstream regulators Zbtb20 and Nr1i2. In obese mice, DEHP exposure caused hepatic injury, cell migration, and changes in glycogen quantity mainly via Cd44. Microarray analysis suggested the potential mechanism underlying the early onset of metabolic disorders in DEHP-treated obese mice.

Effects of arecoline on adipogenesis, lipolysis, and glucose uptake of adipocytes-A possible role of betel-quid chewing in metabolic syndrome.

To investigate the possible involvement of betel-quid chewing in adipocyte dysfunction, we determined the effects of arecoline, a major alkaloid in areca nuts, on adipogenic differentiation (adipogenesis), lipolysis, and glucose uptake by fat cells. Using mouse 3T3-L1 preadipocytes, we showed that arecoline inhibited adipogenesis as determined by oil droplet formation and adipogenic marker gene expression. The effects of arecoline on lipolysis of differentiated 3T3-L1 adipocytes were determined by the glycerol release assay, indicating that arecoline induced lipolysis in an adenylyl cyclase-dependent manner. The diabetogenic effects of arecoline on differentiated 3T3-L1 adipocytes were evaluated by the glucose uptake assay, revealing that > or = 300 microM arecoline significantly attenuated insulin-induced glucose uptake; however, no marked effect on basal glucose uptake was detected. Moreover, using 94 subjects that were randomly selected from a health check-up, we determined the association of betel-quid chewing with hyperlipidemia and its related risk factors. Hyperlipidemia frequency and serum triglyceride levels of betel-quid chewers were significantly higher than those of non-betel-quid chewers. In this study, we demonstrated that arecoline inhibits adipogenic differentiation, induces adenylyl cyclase-dependent lipolysis, and interferes with insulin-induced glucose uptake. Arecoline-induced fat cell dysfunction may lead to hyperlipidemia and hyperglycemia/insulin-resistance. These findings provide the first in vitro evidence of betel-quid chewing modulation of adipose cell metabolism that could contribute to the explanation of the association of this habit with metabolic syndrome disorders.

Synthesis, and biological evaluation of 2-(4-aminophenyl)benzothiazole derivatives as photosensitizing agents.

Photodynamic therapy (PDT) employing exogenous photosensitizers is currently being approved for treatment of basal cell carcinoma (BCC). 2-(4-Aminophenyl)benzothiazoles (6) consist of chromophoric structure and absorb light in the UVA (315-400 nm). These results encouraged us to design and synthesize a diversity of 2-phenylbenzothiazoles (6). Studies on the apoptotic mechanism involved in photosensitive effects induced by UVA-activated 6 in BCC cells are carried out in the present article. 6-UVA-treated cells displayed several features of apoptosis, including an increase in the sub-G1 population, a significantly increased annexin V binding, and activation of caspase-3. 6-UVA induced a decrease in mitochondrial membrane potential (Deltapsi(mt)) and ATP via enhanced ROS generation and promoted phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK expression. These results suggest that 6-UVA elicits photosensitive effects in mitochondria processes which involve ERK and p38 activation, and ultimately lead to BCC cell apoptosis.

Primary Amine Modified Gold Nanodots Regulate Macrophage Function and Antioxidant Response: Potential Therapeutics Targeting of Nrf2.

BACKGROUND: Gold nanoparticles with high biocompatibility and immunomodulatory properties have potential applications in the development of new diagnostic and therapeutic strategies for nanomedicine. Nanoparticles targeting macrophages can manipulate or control immunological diseases. This study assessed the activity of dendrimer-encapsulated gold nanodots (AuNDs) with three surface modifications [ie, outfacing groups with primary amine (AuNDs-NH2), hydroxyl (AuNDs-OH), and quaternary ammonium ions (AuNDs-CH3)] regulated macrophage function and antioxidant response through Nrf2-dependent pathway. METHODS: AuNDs were prepared and characterized. Intracellular distribution of AuNDs in human macrophages was observed through confocal microscopy. The activity of AuNDs was evaluated using macrophage functions and antioxidant response in the human macrophage cell line THP-1. RESULTS: AuNDs-NH2 and AuNDs-CH3, but not AuNDs-OH, drove the obvious Nrf2-antioxidant response element pathway in THP-1 cells. Of the three, AuNDs-NH2 considerably increased mRNA levels and antioxidant activities of heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1 in THP-1 cells. IL-6 mRNA and protein expression was mediated through Nrf2 activation in AuNDs-NH2-treated macrophages. Furthermore, Nrf2 activation by AuNDs-NH2 increased the phagocytic ability of THP-1 macrophages. CONCLUSION: AuNDs-NH2 had immunomodulatory activities in macrophages. The findings of the present work suggested that AuNDs have potential effects against chronic inflammatory diseases via the Nrf2 pathway.

Phthalate exposure causes browning-like effects on adipocytes in vitro and in vivo.

Mono(2-ethylhexyl)phthalate (MEHP) promotes adipogenesis via PPARγ. PPARγ agonists, e.g., rosiglitazone (RSG), enhance adipocyte browning. However, scientific evidence regarding MEHP as a browning chemical is lacking. This study combined 3T3-L1 adipocytes and C57BL/6J mice to examine the potential roles of MEHP in browning. MEHP and the browning agent RSG caused similar energy metabolism in adipocytes. Both MEHP and RSG caused transcriptional changes involved in browning-associated thermogenesis, energy homeostasis, inflammatory response, and glucose uptake. MEHP-treated adipocytes exhibited brown adipocyte-like characteristics, i.e., increased mitochondrial proton leak, triiodothyronine-induced Bmp8b expression, decreased inflammation, and smaller lipid droplets. Increased PDK4 and PEPCK1 in MEHP/RSG-treated adipocytes could block glucose utilization for mitochondrial respiration. Mitochondrial/peroxisomal biogenesis and fatty acid ß-oxidation in MEHP-treated adipocytes were enhanced. Candidate genes in promoting browning of MEHP-treated adipocytes were highlighted. In di(2-ethylhexyl)phthalate (DEHP)-treated mice, transcriptional changes in white adipose tissue (WAT) were associated with adipocyte differentiation, lipid synthesis, carbohydrate uptake, and WAT/brown adipose tissue (BAT) quantity. PPARγ and NR4A1 were predicted as the top two upstream regulators in orchestrating transcriptional changes. DEHP-treated mice exhibited actively expressed browning marker genes (i.e., Pparg, Adrb1, Adrb3, Ppargc1a, and Ucp1) in WAT, increased blood FGF21 levels, and higher amounts of BAT, supporting the browning-like effects in vivo.

Synthesis and antitumor activity of novel enediyne-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrids.

A series of novel pyrrolo[2,1-c][1,4]benzodiazepine (PBD) hybrids linked with enediyne is described. These compounds were prepared by linking C-8 of DC-81 (1) with an enediyne (10-16) through carbon chain linkers to afford PBD hybrid agents 17-23 in good yields. Most of the hybrids on human cancer cell lines exhibited higher cytotoxicity, and an increase in the sub-G1 population than 1. In a previous article, we have demonstrated that DC-81-indole conjugate agents (3-6) are potent inducers of cell apoptosis in melanoma. In the present article, we investigated whether DC-81-enediyne agents possess more cytotoxicity than 6 on human 293T cells. Our data revealed that treatment of 293T cells with DC-81-enediyne resulted in a significant increase of annexin V binding, caspase-3 degradation, and p53 arrest to identify apoptotic cells than 6. These results suggest that the DC-81-enediyne agents are more efficient in inducing apoptosis than DC-81-indole in 293T cells.

Increased aquaglyceroporin 9 expression disrupts arsenic resistance in human lung cancer cells.

Resistance to chemotherapy is one of the major problems in treatment responses of lung cancer. This study explored the mechanism underlying the arsenic resistance of lung cancer. Four lung cancer cells with different proliferation activity were characterized for cytotoxicity, arsenic influx/efflux, and arsenic effects on intracellular glutathione and 8-hydroxy-2'-deoxyguanosine (8-OHdG) production. Our data revealed that relative proliferation potency of these cells was H1299>A549>CL3>H1355. Moreover, A549, H1299, and H1355 were markedly resistant to As(2)O(3) with IC50 approximately 100 microM, whereas CL3 was sensitive to As(2)O(3) with IC50 approximately 11.8 microM. After treatment with the respective As(2)O(3) at IC50, arsenic influx/efflux activity in CL3 was comparable to those in the other three arsenic-resistant cells. However, differences in glutathione levels and 8-OHdG production were also detected either before or after arsenic treatment, indicating that a certain degree of variation in anti-oxidative systems and/or 8-OHdG repair activity existed in these cell lines. By transfection of an aquaglyceroporin 9 (AQP9) gene, we showed that increased AQP9 expression significantly enhanced arsenic uptake and disrupted arsenic resistance of A549. The present study strongly suggests that membrane transporters responsible for arsenic uptake, such as AQP9, may play a critical role in development of arsenic resistance in human lung cancer cells.

Co-production of gamma-glutamylcysteine and glutathione by mutant strain Saccharomyces cerevisiae FC-3 and its kinetic analysis.

Co-production of gamma -glutamylcysteine (gamma -GC) and glutathione (GSH) by a novel mutant strain Saccharomyces cerevisiae FC-3 and its kinetic analysis were investigated. The strain could produce gamma -GC and GSH with high yields (4.22 and 14.3 mg/g-DCW, respectively) in batch submerged cultures. Effects of medium components and cultivation conditions on cell growth and the contents of intracellular gamma -GC and GSH were examined. Results show that 2% (w/v) sucrose and 2.5% (w/v) yeast extract are the best carbon and nitrogen sources, respectively, and supplement of three amino acids (glycine, cysteine and glutamate), each at 0.08% (w/v), in the medium could enhance gamma -GC and GSH production. In addition, optimal operating conditions are at the initial pH value of 7.0, 30 degrees C and 200 rev/min. Moreover, results obtained from kinetic analyses reveal that gamma -GC production is mixed-type growth associated, but GSH production is growth-associated.

Fibroblast growth factor 21 secretion enhances glucose uptake in mono(2-ethylhexyl)phthalate-treated adipocytes.

Previous studies revealed that cellular accumulation of mono(2-ethylhexyl)phthalate (MEHP) disturbed energy metabolism in adipocytes, where glucose uptake was significantly increased. The present study aimed to determine the mechanisms underlying the increased glucose uptake. MEHP-treated 3T3-L1 adipocytes exhibited a significantly increased glucose uptake activity. Immunoblot analysis suggested that the insulin-induced signals were not responsible for the increased glucose uptake. qPCR analysis revealed that both Glut1 and Glut4 genes were highly expressed during adipogenesis; Glut1 mRNA levels in MEHP-treated adipocytes were significantly increased. Moreover, MEHP-treated adipocytes exhibited significantly increased levels of fibroblast growth factor 21 (FGF21) in both mRNA and secreted protein. FGF21 is a peptide hormone with pleiotropic effects on regulation of insulin sensitivity and glucose/lipid homeostasis. We found that MEHP, FGF21, and lactate in culture medium together enhanced Fgf21 gene expression in MEHP-treated adipocytes. FGF21 signaling requires fibroblast growth factor receptor (FGFR) and ßKlotho. Fgfr family and ßKlotho genes were actively expressed during adipogenesis; mRNA levels of Fgfr3 and Fgfr4 genes in MEHP-treated adipocytes were significantly increased. Roles of FGF21/FGFR and phosphoinositide 3-kinase (PI3K)/AKT signal axes in regulation of glucose uptake were determined. We demonstrated that FGF21/FGFR signals played the major roles in up-regulation of the basal glucose uptake in MEHP-treated adipocytes. The in vitro evidence suggests that cellular FGF21 secretion enhances the basal glucose uptake in MEHP-treated adipocytes.

Induction of apoptosis by DC-81-indole conjugate agent through NF-kappaB and JNK/AP-1 pathway.

DC-81, an antitumor antibiotic produced by Streptomyces species, belongs to the pyrrolo[2,1- c][1,4]benzodiazepine (PBD) family, which are potent inhibitors of nucleic acid synthesis. We previously reported an efficient synthesis of PBD hybrids linked with indole carboxylates. Recently, we have also shown that a PBD hybrid (IN6CPBD) agent can activate the apoptotic pathway mediated by mitochondria. In this study, we will examine the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) that functionally regulate cell proliferation, transformation, and apoptosis. To investigate the IN6CPBD-induced alterations in NF-kappaB and AP-1 activity that involve cell cycle regulation, we exposed human melanoma A375 cells to different concentrations of IN6CPBD. Our data revealed that treatment of A375 cells with IN6CPBD resulted in a marked loss of cells from the G2/M phase of the cell cycle and an increase in Ca (2+) and cAMP and promoted phosphorylation of Jun N-terminal kinase (JNK) expression. By using the luciferase reporter assay, the NF-kappaB activities were decreased; however, AP-1 activity was further enhanced after A375 cells were treated with graded concentrations of IN6CPBD. Blockade of NF-kappaB or JNK activity further enhanced caspase-3 substrate PARP cleavage and subsequent apoptotic cell death.

Arecoline inhibits the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced cytochrome P450 1A1 activation in human hepatoma cells.

In the present study, we investigated the effect of arecoline, a major areca nut alkaloid, on the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced activation of cytochrome P4501A1 (CYP1A1) in a human hepatoma cell line Huh-7. We treated Huh-7 cells with 10nM TCDD in the presence of different concentrations of arecoline (50-300 microM). Our results indicated that arecoline attenuated the TCDD-induced CYP1A1 enzyme activation with an inhibitory effect on cell proliferation. By using real-time RT-PCR, we demonstrated that arecoline inhibited the TCDD-induced activations of CYP1A1 and AhR repressor (AhRR) mRNA expression in a similar pattern. Our results revealed that arecoline inhibited AhR mRNA expression with no direct effect on CYP1A1 enzyme activity. Therefore, in our present study, the observed inhibitory effect of arecoline on CYP1A1 activation was not due to the up-regulation of AhRR or direct inhibitory effect on CYP1A1. Taken together, here we have demonstrated that arecoline attenuates the TCDD-induced CYP1A1 activation mainly via down-regulation of AhR expression in human hepatoma cells, suggesting the possible involvement of arecoline in the AhR-mediated metabolism of environmental toxicants in liver.

Differential effect of arecoline on the endogenous dioxin-responsive cytochrome P450 1A1 and on a stably transfected dioxin-responsive element-driven reporter in human hepatoma cells.

Dioxin-responsive element-mediated chemical activated luciferase expression (DRE-CALUX) is one of alternative bioassays for the determination of dioxin levels. We have previously established a DRE-CALUX cell line, Huh7-DRE-Luc, by using stable transfection of Huh-7 cells with a reporter plasmid (4xDRE-TATA-Luc) carrying a DRE-driven firefly luciferase gene. It was also shown that arecoline, a major areca nut alkaloid, inhibited the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cytochrome P450 1A1 (CYP1A1) activation in Huh-7 cells. The TCDD-activated aryl hydrocarbon receptor (AhR) induces the DRE-CALUX activation and CYP1A1 gene expression via binding to DRE in promoter regions of these dioxin-responsive genes. In the present study, the effect of arecoline on the TCDD-induced activation of DRE-CALUX and CYP1A1 enzyme in Huh7-DRE-Luc and Huh-7 cells, respectively, was examined. It was found that arecoline inhibited TCDD-induced CYP1A1 activation and however enhanced TCDD-induced DRE-CALUX activation. This finding indicates the differential effect of arecoline on the endogenous dioxin-responsive CYP1A1 and on a stably transfected DRE-driven reporter in human hepatoma cells. The present study suggests that induction of DRE-CALUX alone does not necessarily parallel with endogenous CYP1A1 gene expression, and that the reporter assay may detect interactions that are not functional in endogenous gene.

Arsenic inhibits induction of cytochrome P450 1A1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin in human hepatoma cells.

The aim of this study was to examine the arsenic effect on activation of aryl hydrocarbon receptor (AhR)-mediated gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in human hepatoma cells. The human hepatoma Huh7 cells were treated with sodium arsenite (NaAsO2) from 0.5 to 20 microM for 24 h. Our data revealed that NaAsO2 < or = 10 microM caused no significant cytotoxic effect on Huh7 cells (p>0.05). We also established a dioxin-responsive element (DRE)-mediated Chemical Activated LUciferase eXpression (CALUX) cell line, Huh7-DRE-Luc, by stable transfection of Huh7 with a DRE-driven firefly luciferase reporter plasmid (4xDRE-TATA-Luc). Treatments of Huh7-DRE-Luc and Huh7 with NaAsO2 attenuated the 2,3,7,8-TCDD-induced DRE-CALUX and cytochrome P450 1A1 (CYP1A1) activations, respectively, in a dose-dependent manner. We found that the calculated CALUX-toxic equivalent (TEQ) levels induced by cotreatment of NaAsO2 > or = 3.0 microM and 10 nM 2,3,7,8-TCDD were significantly lower than that induced by 2,3,7,8-TCDD alone (p<0.05). In the present study, we demonstrated that arsenic not only inhibited the TCDD-induced CYP1A1 activation but also interfered with DRE-CALUX bioassay in human hepatoma cells. Our finding also suggests that extensive cleanup of sample for removal of any possible interfering factor is critical to guarantee the accuracy of dioxin-TEQ levels using DRE-CALUX bioassay.

Steroidogenic factor 1 differentially regulates basal and inducible steroidogenic gene expression and steroid synthesis in human adrenocortical H295R cells.

The significance of steroidogenic factor 1 (SF-1) in adrenal steroidogenesis was studied using adrenocortical cell lines transformed with a dominant negative mutant of SF-1. Constitutive expression of the mutant did not only impair the activity of endogenous SF-1 but also diminish its own expression, suggesting that SF-1 was under autoregulation. Inhibition of the endogenous SF-1 activity significantly reduced basal and inducible transcription of CYP17, CYP21B and CYP11B1, but exhibited little effects on StAR and CYP11A1 expression. Stimulating the transformed cells with potassium and cAMP freed CYP11B2 from the mutant-caused transcriptional inhibition, whereas the transformation abolished induction of CYP17 by both stimulants. Consistent with the transcriptional changes of steroidogenic genes, basal and inducible synthesis of cortisol and androgens drastically declined in the transformed cell lines. The relief of CYP11B2 repression following the potassium and cAMP stimulation removed the restraint the mutant exerted on aldosterone synthesis, and resulted in aldosterone overproduction in the stimulated transformed cells. SF-1 also plays a role in regulating the adrenocorticotrophic hormone (ACTH) responsiveness of the adrenocortical cells. Inhibition of SF-1 activity significantly decreased basal expression of ACTH receptor and its induction by potassium and cAMP.

A recombinant PPRE-driven luciferase bioassay for identification of potential PPAR agonists.

A recombinant Huh7-PPRE-Luc cell line, carrying a peroxisome proliferator response element (PPRE)-driven luciferase gene, is an efficient tool for evaluation of potential peroxisome proliferator-activated receptor (PPAR) agonists. The cells exhibited a good dose-response induction in PPRE-driven luciferase activity by three subtypes of PPAR agonists as well as by a retinoid X receptor agonist, 9-cis-retinoic acid. Here, the bioassay is fitted into a 96-well plate format for high-throughput screening purpose.