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Abstract
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The constitutive androstane receptor
(CAR; NR1I3) contributes important
regulatory roles in biotransformation, xenobiotic transport function,
energy metabolism and lipid homeostasis. In this investigation, global
serum and liver tissue metabolomes were assessed analytically in wild
type and CAR-null transgenic mice using NMR, GC–MS and UPLC–MS/MS-based
metabolomics. Significantly, CAR activation increased serum levels
of fatty acids, lactate, ketone bodies and tricarboxylic acid cycle
products, whereas levels of phosphatidylcholine, sphingomyelin, amino
acids and liver glucose were decreased following short-term activation
of CAR. Mechanistically, quantitative mRNA analysis demonstrated significantly
decreased expression of key gluconeogenic pathways, and increased
expression of glucose utilization pathways, changes likely resulting
from down-regulation of the hepatic glucose sensor and bidirectional
transporter, Glut2. Short-term CAR activation also
resulted in enhanced fatty acid synthesis and impaired β-oxidation.
In summary, CAR contributes an expansive role regulating energy metabolism,
significantly impacting glucose and monocarboxylic acid utilization,
fatty acid metabolism and lipid homeostasis, through receptor-mediated
regulation of several genes in multiple associated pathways.
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Affiliation(s)
- Fengming Chen
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.,Department of Pathology , Penn State Milton S. Hershey Medical Center , Hershey , Pennsylvania 17033 , United States
| | - Denise M Coslo
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Tao Chen
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Limin Zhang
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.,CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics , Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences (CAS) , Wuhan 430070 , China
| | - Yuan Tian
- The Huck Institutes of the Life Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Philip B Smith
- The Huck Institutes of the Life Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Andrew D Patterson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
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2
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Niu B, Coslo DM, Bataille AR, Albert I, Pugh BF, Omiecinski CJ. In vivo genome-wide binding interactions of mouse and human constitutive androstane receptors reveal novel gene targets. Nucleic Acids Res 2018; 46:8385-8403. [PMID: 30102401 PMCID: PMC6144799 DOI: 10.1093/nar/gky692] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/17/2018] [Accepted: 07/20/2018] [Indexed: 12/13/2022] Open
Abstract
The constitutive androstane receptor (CAR; NR1I3) is a nuclear receptor orchestrating complex roles in cell and systems biology. Species differences in CAR's effector pathways remain poorly understood, including its role in regulating liver tumor promotion. We developed transgenic mouse models to assess genome-wide binding of mouse and human CAR, following receptor activation in liver with direct ligands and with phenobarbital, an indirect CAR activator. Genomic interaction profiles were integrated with transcriptional and biological pathway analyses. Newly identified CAR target genes included Gdf15 and Foxo3, important regulators of the carcinogenic process. Approximately 1000 genes exhibited differential binding interactions between mouse and human CAR, including the proto-oncogenes, Myc and Ikbke, which demonstrated preferential binding by mouse CAR as well as mouse CAR-selective transcriptional enhancement. The ChIP-exo analyses also identified distinct binding motifs for the respective mouse and human receptors. Together, the results provide new insights into the important roles that CAR contributes as a key modulator of numerous signaling pathways in mammalian organisms, presenting a genomic context that specifies species variation in biological processes under CAR's control, including liver cell proliferation and tumor promotion.
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Affiliation(s)
- Ben Niu
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Denise M Coslo
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Alain R Bataille
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Istvan Albert
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - B Franklin Pugh
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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3
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Abstract
Humans in industrialized areas are continuously exposed to phthalate plasticizers, prompting concerns of their potential toxicities. Previous studies from our laboratory and others have shown that various phthalates activate several mammalian nuclear receptors, in particular the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), and the peroxisomal proliferator-activated receptors (PPARs), although often at concentration levels of questionable relevance to human exposure. We discovered that di(2-ethylhexyl) phthalate (DEHP) and di-isononyl phthalate (DiNP), two of the highest volume production agents, were potent activators of human CAR2 (hCAR2), a unique human CAR splice variant and, to a lesser degree, human PXR (hPXR). These diphthalates undergo rapid metabolism in mammalian systems, initially to their major monophthalate derivatives MEHP and MiNP. Although MEHP and MiNP are reported activators of the rodent PPARs, with lower affinities for the corresponding human PPARs, it remains unclear whether these monophthalate metabolites activate hCAR2 or hPXR. In this investigation, we assessed the relative activation potential of selected monophthalates and other low molecular weight phthalates against hCAR, the most prominent hCAR splice variants, as well as hPXR and human PPAR. Using transactivation and mammalian two-hybrid protein interaction assays, we demonstrate that these substances indeed activate hCARs and hPXR but to varying degrees. MEHP and MiNP exhibit potent activation of hCAR2 and hPXR with higher affinities for these receptors than for the hPPARs. The rank order potency for MEHP and MiNP was hCAR2 > hPXR > hPPARs. Results from primary hepatocyte experiments also reflect the MEHP and MiNP upregulation of the respective human target genes. We conclude that both di- and monophthalates are potently selective hCAR2 activators and effective hPXR activators. These results implicate these targets as important mediators of selective phthalate effects in humans. The striking differential affinities for these compounds between human and rodent nuclear receptors further implies that biological results obtained from rodent models may be of only limited relevance for interpolating phthalate-mediated effects in humans.
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Affiliation(s)
- Elizabeth M Laurenzana
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Denise M Coslo
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - M Veronica Vigilar
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Anthony M Roman
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
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Girer NG, Murray IA, Omiecinski CJ, Perdew GH. Hepatic Aryl Hydrocarbon Receptor Attenuates Fibroblast Growth Factor 21 Expression. J Biol Chem 2016; 291:15378-87. [PMID: 27226639 DOI: 10.1074/jbc.m116.715151] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Indexed: 12/13/2022] Open
Abstract
The Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor involved in many physiological processes. Several studies indicate that AHR is also involved in energy homeostasis. Fibroblast growth factor 21 (FGF21) is an important regulator of the fasting and feeding responses. When administered to various genetic and diet-induced mouse models of obesity, FGF21 can attenuate obesity-associated morbidities. Here, we explore the role of AHR in hepatic Fgf21 expression through the use of a conditional, hepatocyte-targeted AHR knock-out mouse model (Cre(Alb)Ahr(Fx/Fx)). Compared with the congenic parental strain (Ahr(Fx/Fx)), non-fasted Cre(Alb)Ahr(Fx/Fx) mice exhibit a 4-fold increase in hepatic Fgf21 expression, as well as elevated expression of the FGF21-target gene Igfbp1 Furthermore, in vivo agonist activation of AHR reduces hepatic Fgf21 expression during a fast. The Fgf21 promoter contains several putative dioxin response elements (DREs). Using EMSA, we demonstrate that the AHR-ARNT heterodimer binds to a specific DRE that overlaps binding sequences for peroxisome proliferator-activated receptor α (PPARα), carbohydrate response element-binding protein (ChREBP), and cAMP response element-binding protein, hepatocyte specific (CREBH). In addition, we reveal that agonist-activated AHR impairs PPARα-, ChREBP-, and CREBH-mediated promoter activity in Hepa-1 cells. Accordingly, agonist treatment in Hepa-1 cells ablates potent ER stress-driven Fgf21 expression, and pre-treatment with AHR antagonist blocks this effect. Finally, we show that pre-treatment of primary human hepatocytes with AHR agonist diminishes PPARα-, glucose-, and ER stress-driven induction of FGF21 expression, indicating the effect is not mouse-specific. Together, our data show that AHR contributes to hepatic energy homeostasis, partly through the regulation of FGF21 expression and signaling.
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Affiliation(s)
| | - Iain A Murray
- the Department of Veterinary and Biomedical Sciences, and the Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Curtis J Omiecinski
- the Department of Veterinary and Biomedical Sciences, and the Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Gary H Perdew
- the Department of Veterinary and Biomedical Sciences, and the Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
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Takeda S, Ikeda E, Su S, Harada M, Okazaki H, Yoshioka Y, Nishimura H, Ishii H, Kakizoe K, Taniguchi A, Tokuyasu M, Himeno T, Watanabe K, Omiecinski CJ, Aramaki H. Δ(9)-THC modulation of fatty acid 2-hydroxylase (FA2H) gene expression: possible involvement of induced levels of PPARα in MDA-MB-231 breast cancer cells. Toxicology 2014; 326:18-24. [PMID: 25291031 DOI: 10.1016/j.tox.2014.09.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 09/09/2014] [Accepted: 09/29/2014] [Indexed: 12/21/2022]
Abstract
We recently reported that Δ(9)-tetrahydrocannabinol (Δ(9)-THC), a major cannabinoid component in Cannabis Sativa (marijuana), significantly stimulated the expression of fatty acid 2-hydroxylase (FA2H) in human breast cancer MDA-MB-231 cells. Peroxisome proliferator-activated receptor α (PPARα) was previously implicated in this induction. However, the mechanisms mediating this induction have not been elucidated in detail. We performed a DNA microarray analysis of Δ(9)-THC-treated samples and showed the selective up-regulation of the PPARα isoform coupled with the induction of FA2H over the other isoforms (β and γ). Δ(9)-THC itself had no binding/activation potential to/on PPARα, and palmitic acid (PA), a PPARα ligand, exhibited no stimulatory effects on FA2H in MDA-MB-231 cells; thus, we hypothesized that the levels of PPARα induced were involved in the Δ(9)-THC-mediated increase in FA2H. In support of this hypothesis, we herein demonstrated that; (i) Δ(9)-THC activated the basal transcriptional activity of PPARα in a concentration-dependent manner, (ii) the concomitant up-regulation of PPARα/FA2H was caused by Δ(9)-THC, (iii) PA could activate PPARα after the PPARα expression plasmid was introduced, and (iv) the Δ(9)-THC-induced up-regulation of FA2H was further stimulated by the co-treatment with L-663,536 (a known PPARα inducer). Taken together, these results support the concept that the induced levels of PPARα may be involved in the Δ(9)-THC up-regulation of FA2H in MDA-MB-231 cells.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan; Laboratory of Xenobiotic Metabolism and Environmental Toxicology, Faculty of Pharmaceutical Sciences, Hiroshima International University (HIU), 5-1-1 Hiro-koshingai, Kure, Hiroshima 737-0112, Japan
| | - Eriko Ikeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Shengzhong Su
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, United States
| | - Mari Harada
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hiroyuki Okazaki
- Drug Innovation Research Center, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Yasushi Yoshioka
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hajime Nishimura
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hiroyuki Ishii
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazuhiro Kakizoe
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Aya Taniguchi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Miki Tokuyasu
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Taichi Himeno
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazuhito Watanabe
- Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3 Kanagawa-machi, Kanazawa 920-1181, Japan
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, United States
| | - Hironori Aramaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan; Drug Innovation Research Center, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan.
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6
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Wahlang B, Falkner KC, Clair HB, Al-Eryani L, Prough RA, States JC, Coslo DM, Omiecinski CJ, Cave MC. Human receptor activation by aroclor 1260, a polychlorinated biphenyl mixture. Toxicol Sci 2014; 140:283-97. [PMID: 24812009 DOI: 10.1093/toxsci/kfu083] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental toxicants, present in 100% of U.S. adults and dose-dependently associated with obesity and non-alcoholic fatty liver disease (NAFLD). PCBs are predicted to interact with receptors previously implicated in xenobiotic/energy metabolism and NAFLD. These receptors include the aryl hydrocarbon receptor (AhR), pregnane xenobiotic receptor (PXR), constitutive androstane receptor (CAR), peroxisome proliferator-activated receptors (PPARs), liver-X-receptor (LXRα), and farnesoid-X-receptor (FXR). This study evaluates Aroclor 1260, a PCB mixture with congener composition mimicking that of human adipose tissue, and selected congeners, as potential ligands for these receptors utilizing human hepatoma-derived (HepG2) and primate-derived (COS-1) cell lines, and primary human hepatocytes. Aroclor 1260 (20 μg/ml) activated AhR, and PCB 126, a minor component, was a potent inducer. Aroclor 1260 activated PXR in a simple concentration-dependent manner at concentrations ≥10 μg/ml. Among the congeners tested, PCBs 138, 149, 151, 174, 183, 187, and 196 activated PXR. Aroclor 1260 activated CAR2 and CAR3 variants at lower concentrations and antagonize CAR2 activation by the CAR agonist, CITCO, at higher concentrations (≥20 μg/ml). Additionally, Aroclor 1260 induced CYP2B6 in primary hepatocytes. At subtoxic doses, Aroclor 1260 did not activate LXR or FXR and had no effect on LXR- or FXR-dependent induction by the agonists T0901317 or GW4064, respectively. Aroclor 1260 (20 μg/ml) suppressed PPARα activation by the agonist nafenopin, although none of the congeners tested demonstrated significant inhibition. The results suggest that Aroclor 1260 is a human AhR, PXR and CAR3 agonist, a mixed agonist/antagonist for CAR2, and an antagonist for human PPARα.
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Affiliation(s)
| | - K Cameron Falkner
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition
| | - Heather B Clair
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Russell A Prough
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Denise M Coslo
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Curtis J Omiecinski
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Matthew C Cave
- Department of Pharmacology and Toxicology Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition The Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky 40206
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Su S, Yang X, Omiecinski CJ. Intronic DNA elements regulate Nrf2 chemical responsiveness of the human microsomal epoxide hydrolase gene (EPHX1) through a far upstream alternative promoter. Biochim Biophys Acta 2014; 1839:493-505. [PMID: 24704207 DOI: 10.1016/j.bbagrm.2014.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/16/2014] [Accepted: 03/26/2014] [Indexed: 10/25/2022]
Abstract
In humans, microsomal epoxide hydrolase (mEH) contributes important biological functions that underlie both detoxification and bioactivation fates arising from exposures to foreign chemicals. Previously, we discovered that human mEH gene transcription is initiated from alternative promoters. The respective transcripts are programmed with tissue specificity and the upstream E1b promoter contributes predominantly to mEH expression. The results presented demonstrate that exposures to the Nrf2 activators, sulforaphane (SFN) and tert-butylhydroquinone (tBHQ), markedly activate E1b transcription in human lung and liver cells. Genomic analyses identified two major DNase I hypersensitive regions (HS-1 and HS-2) within the ~15 kb intervening sequence separating E1b from the downstream E1 promoter. In BEAS-2B cells, the Nrf2 effectors, SFN and tBHQ, selectively activated the more distal HS-2 through an antioxidant response element (ARE). An activator protein 1/12-O-tetradecanoylphorbol-13-acetate interaction was further identified within the HS-2 enhancer that functioned to additionally contribute to ARE-mediated induction responsiveness of the E1b promoter. The results demonstrate that ARE modulation, integrated with additional transcriptional complexes, regulates the tissue-specific expression of mEH and that these processes likely coordinate both the protective and bioactivation functions contributed by mEH activities in human tissues.
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Affiliation(s)
- Shengzhong Su
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Xi Yang
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Curtis J Omiecinski
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
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8
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Currie RA, Peffer RC, Goetz AK, Omiecinski CJ, Goodman JI. Phenobarbital and propiconazole toxicogenomic profiles in mice show major similarities consistent with the key role that constitutive androstane receptor (CAR) activation plays in their mode of action. Toxicology 2014; 321:80-8. [PMID: 24675475 DOI: 10.1016/j.tox.2014.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 03/05/2014] [Accepted: 03/15/2014] [Indexed: 01/10/2023]
Abstract
Toxicogenomics (TGx) is employed frequently to investigate underlying molecular mechanisms of the compound of interest and, thus, has become an aid to mode of action determination. However, the results and interpretation of a TGx dataset are influenced by the experimental design and methods of analysis employed. This article describes an evaluation and reanalysis, by two independent laboratories, of previously published TGx mouse liver microarray data for a triazole fungicide, propiconazole (PPZ), and the anticonvulsant drug phenobarbital (PB). Propiconazole produced an increase incidence of liver tumors in male CD-1 mice only at a dose that exceeded the maximum tolerated dose (2500 ppm). Firstly, we illustrate how experimental design differences between two in vivo studies with PPZ and PB may impact the comparisons of TGx results. Secondly, we demonstrate that different researchers using different pathway analysis tools can come to different conclusions on specific mechanistic pathways, even when using the same datasets. Finally, despite these differences the results across three different analyses also show a striking degree of similarity observed for PPZ and PB treated livers when the expression data are viewed as major signaling pathways and cell processes affected. Additional studies described here show that the postulated key event of hepatocellular proliferation was observed in CD-1 mice for both PPZ and PB, and that PPZ is also a potent activator of the mouse CAR nuclear receptor. Thus, with regard to the events which are hallmarks of CAR-induced effects that are key events in the mode of action (MOA) of mouse liver carcinogenesis with PB, PPZ-induced tumors can be viewed as being promoted by a similar PB-like CAR-dependent MOA.
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Affiliation(s)
- Richard A Currie
- Syngenta Ltd., Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK.
| | - Richard C Peffer
- Syngenta Crop Protection, LLC, P.O. Box 18300, Greensboro, NC 27419-8300, United States.
| | - Amber K Goetz
- Syngenta Crop Protection, LLC, P.O. Box 18300, Greensboro, NC 27419-8300, United States.
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Penn State University, University Park, PA 16802, United States.
| | - Jay I Goodman
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, United States.
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9
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Su S, Omiecinski CJ. Sp1 and Sp3 transcription factors regulate the basal expression of human microsomal epoxide hydrolase (EPHX1) through interaction with the E1b far upstream promoter. Gene 2013; 536:135-44. [PMID: 24315822 DOI: 10.1016/j.gene.2013.11.053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/28/2013] [Accepted: 11/18/2013] [Indexed: 11/24/2022]
Abstract
Microsomal epoxide hydrolase (mEH, EPHX1) is a critical biotransformation enzyme, catalyzing the metabolism of many xenobiotics. Human mEH is transcribed using alternative promoters. The upstream E1 promoter is active in liver while the far upstream E1b promoter drives the expression of mEH in all tissues, including liver. Although several liver-specific transcription factors have been identified in the regulation of E1 transcription, little is known regarding the mechanisms of E1b transcriptional regulation. Genome-wide mapping of DNase I hypersensitive sites revealed an open chromatin region between nucleotide -300 upstream and +400 downstream of E1b. This area coincides with a previously described promoter region responsible for maintaining high basal promoter activity. In silico analysis of this location revealed several Sp1/Sp3 binding sites. Site-directed mutagenesis of these motifs suppressed the transactivation activity of the E1b proximal promoter, indicating their importance as contributors to E1b promoter regulation. Further, E1b promoter activities were increased significantly following Sp1 and Sp3 overexpression, while Mithramycin A, a selective Sp1 inhibitor, reduced the promoter activities. EMSA studies demonstrated that Sp1 bound to two putative Sp1/Sp3 binding sites. ChIP analysis confirmed that both endogenous Sp1 and Sp3 were bound to the proximal promoter region of E1b. Knockdown of Sp1 expression using siRNA did not alter the endogenous E1b transcriptional level, while knockdown of Sp3 greatly decreased E1b expression in different human cell lines. Taken together, these results support the concept that Sp1 and Sp3 are functionally involved as transcriptional integrators regulating the basal expression of the derived mEH E1b variant transcript.
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Affiliation(s)
- Shengzhong Su
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
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10
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Elcombe CR, Peffer RC, Wolf DC, Bailey J, Bars R, Bell D, Cattley RC, Ferguson SS, Geter D, Goetz A, Goodman JI, Hester S, Jacobs A, Omiecinski CJ, Schoeny R, Xie W, Lake BG. Mode of action and human relevance analysis for nuclear receptor-mediated liver toxicity: A case study with phenobarbital as a model constitutive androstane receptor (CAR) activator. Crit Rev Toxicol 2013; 44:64-82. [PMID: 24180433 DOI: 10.3109/10408444.2013.835786] [Citation(s) in RCA: 188] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are important nuclear receptors involved in the regulation of cellular responses from exposure to many xenobiotics and various physiological processes. Phenobarbital (PB) is a non-genotoxic indirect CAR activator, which induces cytochrome P450 (CYP) and other xenobiotic metabolizing enzymes and is known to produce liver foci/tumors in mice and rats. From literature data, a mode of action (MOA) for PB-induced rodent liver tumor formation was developed. A MOA for PXR activators was not established owing to a lack of suitable data. The key events in the PB-induced liver tumor MOA comprise activation of CAR followed by altered gene expression specific to CAR activation, increased cell proliferation, formation of altered hepatic foci and ultimately the development of liver tumors. Associative events in the MOA include altered epigenetic changes, induction of hepatic CYP2B enzymes, liver hypertrophy and decreased apoptosis; with inhibition of gap junctional intercellular communication being an associative event or modulating factor. The MOA was evaluated using the modified Bradford Hill criteria for causality and other possible MOAs were excluded. While PB produces liver tumors in rodents, important species differences were identified including a lack of cell proliferation in cultured human hepatocytes. The MOA for PB-induced rodent liver tumor formation was considered to be qualitatively not plausible for humans. This conclusion is supported by data from a number of epidemiological studies conducted in human populations chronically exposed to PB in which there is no clear evidence for increased liver tumor risk.
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11
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Takeda S, Yoshida K, Nishimura H, Harada M, Okajima S, Miyoshi H, Okamoto Y, Amamoto T, Watanabe K, Omiecinski CJ, Aramaki H. Δ(9)-Tetrahydrocannabinol disrupts estrogen-signaling through up-regulation of estrogen receptor β (ERβ). Chem Res Toxicol 2013; 26:1073-9. [PMID: 23718638 DOI: 10.1021/tx4000446] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Δ(9)-Tetrahydrocannabinol (Δ(9)-THC) has been reported as possessing antiestrogenic activity, although the mechanisms underlying these effects are poorly delineated. In this study, we used the estrogen receptor α (ERα)-positive human breast cancer cell line, MCF-7, as an experimental model and showed that Δ(9)-THC exposures markedly suppresses 17β-estradiol (E2)- induced MCF-7 cell proliferation. We demonstrate that these effects result from Δ(9)-THC's ability to inhibit E2-liganded ERα activation. Mechanistically, the data obtained from biochemical analyses revealed that (i) Δ(9)-THC up-regulates ERβ, a repressor of ERα, inhibiting the expression of E2/ERα-regulated genes that promote cell growth and that (ii) Δ(9)-THC induction of ERβ modulates E2/ERα signaling in the absence of direct interaction with the E2 ligand binding site. Therefore, the data presented support the concept that Δ(9)-THC's antiestrogenic activities are mediated by the ERβ disruption of E2/ERα signaling.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy , 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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12
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Nguyen HL, Yang X, Omiecinski CJ. Expression of a novel mRNA transcript for human microsomal epoxide hydrolase (EPHX1) is regulated by short open reading frames within its 5'-untranslated region. RNA 2013; 19:752-66. [PMID: 23564882 PMCID: PMC3683910 DOI: 10.1261/rna.037036.112] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Microsomal epoxide hydrolase (mEH, EPHX1) is a critical xenobiotic-metabolizing enzyme, catalyzing both detoxification and bioactivation reactions that direct the disposition of chemical epoxides, including the carcinogenic metabolites of several polycyclic aromatic hydrocarbons. Recently, we discovered that a previously unrecognized and primate-specific EPHX1 transcript, termed E1-b, was actually the predominant driver of EPHX1 expression in all human tissues. In this study, we identify another human EPHX1 transcript, designated as E1-b'. Unusually, both the E1-b and E1-b' mRNA transcripts are generated from the use of a far upstream gene promoter, localized ∼18.5 kb 5'-upstream of the EPHX1 protein-coding region. Although expressed at comparatively lower levels than E1-b, the novel E1-b' transcript is readily detected in all tissues examined, with highest levels maintained in human ovary. The E1-b' mRNA possesses unusual functional features in its 5'-untranslated region, including a GC-rich leader sequence and two upstream AUGs that encode for short peptides of 26 and 17 amino acids in length, respectively. Results from in vitro transcription/translation assays and direct transfection in mammalian cells of either the E1-b' transcript or the encoded peptides demonstrated that the E1-b' upstream open reading frames (uORFs) are functional, with their presence markedly inhibiting the translation of EPHX1 protein, both in cis and in trans configurations. These unique uORF peptides exhibit no homology to any other known uORF sequences but likely function to mediate post-transcription regulation of EPHX1 and perhaps more broadly as translational regulators in human cells.
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13
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Takeda S, Noguchi M, Matsuo K, Yamaguchi Y, Kudo T, Nishimura H, Okamoto Y, Amamoto T, Shindo M, Omiecinski CJ, Aramaki H. (-)-Xanthatin up-regulation of the GADD45γ tumor suppressor gene in MDA-MB-231 breast cancer cells: role of topoisomerase IIα inhibition and reactive oxygen species. Toxicology 2013; 305:1-9. [PMID: 23313378 PMCID: PMC4030303 DOI: 10.1016/j.tox.2012.12.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Revised: 12/26/2012] [Accepted: 12/31/2012] [Indexed: 11/23/2022]
Abstract
Previously, we reported that (-)-xanthatin, a naturally occurring xanthanolide present in the Cocklebur plant, exhibits potent anti-proliferative effects on human breast cancer cells, accompanied by an induction of the growth arrest and DNA damage-inducible gene 45γ (GADD45γ), recognized recently as a novel tumor suppressor gene. However, the mechanisms mediating this activation were unknown. Topoisomerase IIα (Topo IIα) inhibition has been reported to produce a cell death response accompanied by an atypical DNA laddering fragmentation profile, similar to that noted previously for (-)-xanthatin. Therefore we hypothesized that (-)-xanthatin's GADD45γ activation was mediated through the Topo IIα pathway. Here, we identify that (-)-xanthatin does function as a catalytic inhibitor of Topo IIα, promoting DNA damage. In addition, reactive oxygen species (ROS) were elevated in cells treated with this agent. Mechanistically, it was determined that the induced levels of GADD45γ mRNA resulting from (-)-xanthatin exposures were stabilized by coordinately produced ROS, and that the consequent induction of GADD45γ mRNA, GADD45γ protein and ROS generation were abrogated by co-treatment with N-acetyl-l-cysteine. Taken together, the data support the concept that Topo IIα inhibition by (-)-xanthatin is a trigger that stimulates expression of DNA damage-inducible GADD45γ mRNA and that concomitantly produced ROS act downstream to further enhance the GADD45γ mRNA/GADD45γ protein induction process, resulting in breast cancer cell death.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Momoko Noguchi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazumasa Matsuo
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
| | - Yasuhiro Yamaguchi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Taichi Kudo
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hajime Nishimura
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Yoshiko Okamoto
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Toshiaki Amamoto
- NEUES Corporation, Yaesu Center Building 3F, 1-6-6 Yaesu, Chuo-ku, Tokyo 103-0028, Japan
| | - Mitsuru Shindo
- Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, United States
| | - Hironori Aramaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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14
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Takeda S, Harada M, Su S, Okajima S, Miyoshi H, Yoshida K, Nishimura H, Okamoto Y, Amamoto T, Watanabe K, Omiecinski CJ, Aramaki H. Induction of the fatty acid 2-hydroxylase (FA2H) gene by Δ(9)-tetrahydrocannabinol in human breast cancer cells. J Toxicol Sci 2013; 38:305-8. [PMID: 23535410 PMCID: PMC4018719 DOI: 10.2131/jts.38.305] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
To investigate gene(s) being regulated by ∆(9)-tetrahydrocannabinol (∆(9)-THC), we performed DNA microarray analysis of human breast cancer MDA-MB-231 cells, which are poorly differentiated breast cancer cells, treated with ∆(9)-THC for 48 hr at an IC50 concentration of approximately 25 µM. Among the highly up-regulated genes (> 10-fold) observed, fatty acid 2-hydroxylase (FA2H) was significantly induced (17.8-fold). Although the physiological role of FA2H has not yet been fully understood, FA2H has been shown to modulate cell differentiation. The results of Oil Red O staining after ∆(9)-THC exposure showed the distribution of lipid droplets (a sign of the differentiated phenotype) in cells. Taken together, the results obtained here indicate that FA2H is a novel ∆(9)-THC-regulated gene, and that ∆(9)-THC induces differentiation signal(s) in poorly differentiated MDA-MB-231 cells.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Mari Harada
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Shengzhong Su
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, USA
| | - Shunsuke Okajima
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hiroko Miyoshi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazutaka Yoshida
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hajime Nishimura
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Yoshiko Okamoto
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Toshiaki Amamoto
- NEUES Corporation, Yaesu Center Building 3F, 1-6-6 Yaesu, Chuo-ku, Tokyo 103-0028, Japan
| | - Kazuhito Watanabe
- Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3 Kanagawa-machi, Kanazawa 920-1181, Japan
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, USA
| | - Hironori Aramaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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15
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Takeda S, Okajima S, Miyoshi H, Yoshida K, Okamoto Y, Okada T, Amamoto T, Watanabe K, Omiecinski CJ, Aramaki H. Cannabidiolic acid, a major cannabinoid in fiber-type cannabis, is an inhibitor of MDA-MB-231 breast cancer cell migration. Toxicol Lett 2012; 214:314-9. [PMID: 22963825 DOI: 10.1016/j.toxlet.2012.08.029] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 08/31/2012] [Accepted: 08/31/2012] [Indexed: 12/19/2022]
Abstract
Cannabidiol (CBD), a major non-psychotropic constituent of fiber-type cannabis plant, has been reported to possess diverse biological activities, including anti-proliferative effect on cancer cells. Although CBD is obtained from non-enzymatic decarboxylation of its parent molecule, cannabidiolic acid (CBDA), few studies have investigated whether CBDA itself is biologically active. Results of the current investigation revealed that CBDA inhibits migration of the highly invasive MDA-MB-231 human breast cancer cells, apparently through a mechanism involving inhibition of cAMP-dependent protein kinase A, coupled with an activation of the small GTPase, RhoA. It is established that activation of the RhoA signaling pathway leads to inhibition of the mobility of various cancer cells, including MDA-MB-231 cells. The data presented in this report suggest for the first time that as an active component in the cannabis plant, CBDA offers potential therapeutic modality in the abrogation of cancer cell migration, including aggressive breast cancers.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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16
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Laurenzana EM, Chen T, Kannuswamy M, Sell BE, Strom SC, Li Y, Omiecinski CJ. The orphan nuclear receptor DAX-1 functions as a potent corepressor of the constitutive androstane receptor (NR1I3). Mol Pharmacol 2012; 82:918-28. [PMID: 22896671 DOI: 10.1124/mol.112.080721] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Regulation of gene transcription is controlled in part by nuclear receptors that function coordinately with coregulator proteins. The human constitutive androstane receptor (CAR; NR1I3) is expressed primarily in liver and regulates the expression of genes involved in xenobiotic metabolism as well as hormone, energy, and lipid homeostasis. In this report, DAX-1, a nuclear receptor family member with corepressor properties, was identified as a potent CAR regulator. Results of transaction and mutational studies demonstrated that both DAX-1's downstream LXXLL and its PCFQVLP motifs were critical contributors to DAX-1's corepression activities, although two other LXXM/LL motifs located nearer the N terminus had no impact on the CAR functional interaction. Deletion of DAX-1's C-terminal transcription silencing domain restored CAR1 transactivation activity in reporter assays to approximately 90% of control, demonstrating its critical function in mediating the CAR repression activities. Furthermore, results obtained from mammalian two-hybrid experiments assessing various domain configurations of the respective receptors showed that full-length DAX-1 inhibited the CAR-SRC1 interaction by approximately 50%, whereas the same interaction was restored to 90% of control when the DAX-1 transcription silencing domain was deleted. Direct interaction between CAR and DAX-1 was demonstrated with both alpha-screen and coimmunoprecipitation experiments, and this interaction was enhanced in the presence of the CAR activator 6-(4-chlorophenyl)imidazo[2,1-b]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO). Results obtained in primary human hepatocytes further demonstrated DAX-1 inhibition of CAR-mediated CITCO induction of the CYP2B6 target gene. The results of this investigation identify DAX-1 as a novel and potent CAR corepressor and suggest that DAX-1 functions as a coordinate hepatic regulator of CAR's biological function.
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Affiliation(s)
- Elizabeth M Laurenzana
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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17
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Laurenzana EM, Chen T, Sell B, Kannuswamy M, Li Y, Omiecinski CJ. The Orphan Receptor/Corepressor DAX‐1 Modulates Human CAR Transcriptional Activity. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.673.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Elizabeth M Laurenzana
- Center for Toxciology and Molecular CarcinogenesisPennsylvania State UniversityUniversity ParkPA
| | - Tao Chen
- Center for Toxciology and Molecular CarcinogenesisPennsylvania State UniversityUniversity ParkPA
| | - Brian Sell
- Center for Toxciology and Molecular CarcinogenesisPennsylvania State UniversityUniversity ParkPA
| | - Malavika Kannuswamy
- Center for Toxciology and Molecular CarcinogenesisPennsylvania State UniversityUniversity ParkPA
| | - Yong Li
- Pharmaceutical SciencesUniversity of PittsburghPittsburghPA
| | - Curtis J Omiecinski
- Center for Toxciology and Molecular CarcinogenesisPennsylvania State UniversityUniversity ParkPA
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18
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Omiecinski CJ, Coslo DM, Chen T, Laurenzana EM, Peffer RC. Multi-species analyses of direct activators of the constitutive androstane receptor. Toxicol Sci 2011; 123:550-62. [PMID: 21778469 DOI: 10.1093/toxsci/kfr191] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The constitutive androstane receptor (CAR; NR1I3) is a member of the nuclear receptor superfamily and functions as an important xenochemical sensor and transcriptional modulator in mammalian cells. Upon chemical activation, CAR undergoes nuclear translocation and heterodimerization with the retinoid X receptor subsequent to its DNA target interaction. CAR is unusual among nuclear receptors in that it possesses a high level of constitutive activity in cell-based assays, obscuring the detection of ligand activators. However, a human splice variant of CAR, termed CAR3, exhibits negligible constitutive activity. In addition, CAR3 is activated by ligands with similar specificity as the reference form of the receptor. In this study, we hypothesized that similar CAR3 receptors could be constructed across various mammalian species' forms of CAR that would preserve species-specific ligand responses, thus enabling a more sensitive and differential screening assessment of CAR response among animal models. A battery of CAR3 receptors was produced in mouse, rat, and dog and comparatively evaluated with selected ligands together with human CAR1 and CAR3 in mammalian cell reporter assays. The results demonstrate that the 5-amino acid insertion that typifies human CAR3 also imparts ligand-activated receptor function in other species' CAR while maintaining signature responses in each species to select CAR ligands. These variant constructs permit in vitro evaluation of differential chemical effector responses across species and coupled with in vivo assays, the species-selective contributions of CAR in normal physiology and in disease processes such as hepatocarcinogenesis.
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Affiliation(s)
- Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Penn State University, University Park, Pennsylvania 16802, USA.
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Takeda S, Matsuo K, Yaji K, Okajima-Miyazaki S, Harada M, Miyoshi H, Okamoto Y, Amamoto T, Shindo M, Omiecinski CJ, Aramaki H. (--)-Xanthatin selectively induces GADD45γ and stimulates caspase-independent cell death in human breast cancer MDA-MB-231 cells. Chem Res Toxicol 2011; 24:855-65. [PMID: 21568272 PMCID: PMC4089510 DOI: 10.1021/tx200046s] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
exo-Methylene lactone group-containing compounds, such as (--)-xanthatin, are present in a large variety of biologically active natural products, including extracts of Xanthium strumarium (Cocklebur). These substances are reported to possess diverse functional activities, exhibiting anti-inflammatory, antimalarial, and anticancer potential. In this study, we synthesized six structurally related xanthanolides containing exo-methylene lactone moieties, including (--)-xanthatin and (+)-8-epi-xanthatin, and examined the effects of these chemically defined substances on the highly aggressive and farnesyltransferase inhibitor (FTI)-resistant MDA-MB-231 cancer cell line. The results obtained demonstrate that (--)-xanthatin was a highly effective inhibitor of MDA-MB-231 cell growth, inducing caspase-independent cell death, and that these effects were independent of FTase inhibition. Further, our results show that among the GADD45 isoforms, GADD45γ was selectively induced by (--)-xanthatin and that GADD45γ-primed JNK and p38 signaling pathways are, at least in part, involved in mediating the growth inhibition and potential anticancer activities of this agent. Given that GADD45γ is becoming increasingly recognized for its tumor suppressor function, the results presented here suggest the novel possibility that (--)-xanthatin may have therapeutic value as a selective inducer of GADD45γ in human cancer cells, in particular in FTI-resistant aggressive breast cancers.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazumasa Matsuo
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816–8580, Japan
| | - Kentaro Yaji
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816–8580, Japan
| | - Shunsuke Okajima-Miyazaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Mari Harada
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hiroko Miyoshi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Yoshiko Okamoto
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Toshiaki Amamoto
- NEUES Corporation, Yaesu Center Building 3F, 1-6-6 Yaesu, Chuo-ku, Tokyo 103-0028, Japan
| | - Mitsuru Shindo
- Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga 816–8580, Japan
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Hironori Aramaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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20
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Omiecinski CJ, Vanden Heuvel JP, Perdew GH, Peters JM. Xenobiotic metabolism, disposition, and regulation by receptors: from biochemical phenomenon to predictors of major toxicities. Toxicol Sci 2011; 120 Suppl 1:S49-75. [PMID: 21059794 PMCID: PMC3145385 DOI: 10.1093/toxsci/kfq338] [Citation(s) in RCA: 235] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/01/2010] [Indexed: 02/07/2023] Open
Abstract
To commemorate the 50th anniversary of the Society of Toxicology, this special edition article reviews the history and current scope of xenobiotic metabolism and transport, with special emphasis on the discoveries and impact of selected "xenobiotic receptors." This overall research realm has witnessed dynamic development in the past 50 years, and several of the key milestone events that mark the impressive progress in these areas of toxicological sciences are highlighted. From the initial observations regarding aspects of drug metabolism dating from the mid- to late 1800's, the area of biotransformation research witnessed seminal discoveries in the mid-1900's and onward that are remarkable in retrospect, including the discovery and characterization of the phase I monooxygenases, the cytochrome P450s. Further research uncovered many aspects of the biochemistry of xenobiotic metabolism, expanding to phase II conjugation and phase III xenobiotic transport. This led to hallmark developments involving integration of genomic technologies to elucidate the basis for interindividual differences in response to xenobiotic exposures and discovery of nuclear and soluble receptor families that selectively "sense" the chemical milieu of the mammalian cell and orchestrate compensatory changes in gene expression programming to accommodate complex xenobiotic exposures. This review will briefly summarize these developments and investigate the expanding roles of xenobiotic receptor biology in the underlying basis of toxicological response to chemical agents.
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Affiliation(s)
- Curtis J Omiecinski
- Department of Veterinary and Biomedical Sciences, Center for Molecular Toxicology and Carcinogenesis, Penn State University, University Park, Pennsylvania 16802, USA.
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21
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Zamule SM, Coslo DM, Chen F, Omiecinski CJ. Differentiation of human embryonic stem cells along a hepatic lineage. Chem Biol Interact 2011; 190:62-72. [PMID: 21241686 DOI: 10.1016/j.cbi.2011.01.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 01/07/2011] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
Abstract
The limited availability of hepatic tissue suitable for the treatment of liver disease and drug discovery research advances the generation of hepatic-like cells from alternative sources as a valuable approach. In this investigation we exploited a unique hepatic differentiation approach to generate hepatocyte-like cells from human embryonic stem cells (hESCs). hESCs were cultured for 10-20 days on collagen substrate in highly defined and serum free hepatocyte media. The resulting cell populations exhibited hepatic cell-like morphology and were characterized with a variety of biological endpoint analyses. Real-time PCR analysis demonstrated that mRNA expression of the 'stemness' marker genes NANOG and alkaline phosphatase in the differentiated cells was significantly reduced, findings that were functionally validated using alkaline phosphatase activity detection measures. Immunofluorescence studies revealed attenuated levels of the 'stemness' markers OCT4, SOX2, SSEA-3, TRA-1-60, and TRA-1-81 in the hepatic-like cell population. The hepatic character of the cells was evaluated additionally by real-time PCR analyses that demonstrated increased mRNA expression of the hepatic transcription factors FOXA1, C/EBPα, and HNF1α, the nuclear receptors CAR, RXRα, PPARα, and HNF4α, the liver-generated plasma proteins α-fetoprotein, transthyretin, transferrin, and albumin, the protease inhibitor α-1-antitrypsin, metabolic enzymes HMGCS2, PEPCK, and biotransformation enzymes CYP3A7, CYP3A4, CYP3A5, and CYP2E1. Indocyanine green uptake albumin secretion and glycogen storage capacity further confirmed acquisition of hepatic function. These studies define an expeditious methodology that facilitates the differentiation of hESCs along a hepatic lineage and provide a framework for their subsequent use in pharmacological and toxicological research applications requiring a renewable supply of human hepatocytes.
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Affiliation(s)
- Stephanie M Zamule
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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22
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DeKeyser JG, Laurenzana EM, Peterson EC, Chen T, Omiecinski CJ. Selective phthalate activation of naturally occurring human constitutive androstane receptor splice variants and the pregnane X receptor. Toxicol Sci 2011; 120:381-91. [PMID: 21227907 DOI: 10.1093/toxsci/kfq394] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Phthalates and other endocrine-disruptive chemicals are manufactured in large quantities for use as plasticizers and other commercial applications, resulting in ubiquitous human exposure and thus, concern regarding their toxicity. Innate defense against small molecule exposures is controlled in large part by the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR). The human CAR gene undergoes multiple alternative splicing events resulting in the CAR2 and CAR3 variant receptors. Recent studies from our laboratory show that CAR2 is potently and specifically activated by di(2-ethylhexyl) phthalate (DEHP). We hypothesized that alternative splicing is a mechanism for increasing CAR's functional diversity, broadening the human receptors' repertoire of response to environmental xenobiotics. In these studies, we examine the interaction of alternatively spliced CARs and PXR with a range of suspected endocrine disruptors, including phthalates, bisphenol A (BPA), and 4-N-nonylphenol (NP). Transactivation and two-hybrid studies in COS-1 cells revealed differential selectivity of endocrine-disrupting chemicals for the variant CAR and PXR. Ex vivo studies showed DEHP and di-isononyl phthalate potently induced CYP2B6 and CYP3A4 expression in human hepatocytes. Mutation analysis of CAR2, in silico modeling, and ligand docking studies suggested that the SPTV amino acid insertion of CAR2 creates a unique ligand-binding pocket. Alternative gene splicing results in variant CAR receptors that selectively recognize phthalates and BPA. The interaction of phthalates with CAR and PXR suggests a xenobiotic response that is complex and biologically redundant.
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Affiliation(s)
- Joshua G DeKeyser
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Stagliano MC, DeKeyser JG, Omiecinski CJ, Jones AD. Bioassay-directed fractionation for discovery of bioactive neutral lipids guided by relative mass defect filtering and multiplexed collision-induced dissociation. Rapid Commun Mass Spectrom 2010; 24:3578-84. [PMID: 21080510 PMCID: PMC4019978 DOI: 10.1002/rcm.4796] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We report a synergistic method using bioassay-directed liquid chromatography fractionation and time-of-flight mass spectrometry to guide and accelerate bioactive compound discovery. To steer purification and assays toward anticipated neutral lipid activators of a constitutive androstane receptor splice variant, a relative mass defect filter was calculated, based on the ratio of the mass defect to the measured ion mass, and used to reduce the number of candidate ion masses. Mass measurements often lack sufficient accuracy to provide unambiguous assignments of elemental compositions, and since the relative mass defect reflects fractional hydrogen content of ions, this value is largely determined by the hydrogen content of a compound's biosynthetic precursors. A relative mass defect window ranging from 600-1000 ppm, consistent with an assortment of lipids, was chosen to assess the number of candidate ions in fractions of fetal bovine serum. This filter reduced the number of candidate ion m/z values from 1345 to 892, which was further reduced to 21 by intensity and isotope filtering. Accurate mass measurements from time-of-flight mass spectrometry and fragment ion masses generated using nonselective collision-induced dissociation suggested dioctyl phthalate as one of few neutral lipid constituents in the active fraction. The identity of this compound was determined to be di(2-ethylhexyl) phthalate using GC/MS, and it was ranked as a promising candidate for reporter assay screening.
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Affiliation(s)
- Michael C. Stagliano
- Department of Chemistry, 104 Chemistry Building, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Biochemistry & Molecular Biology, 212 Biochemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Joshua G. DeKeyser
- Center for Molecular Toxicology and Carcinogenesis, 309 Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 309 Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA
| | - A. Daniel Jones
- Department of Biochemistry & Molecular Biology, 212 Biochemistry, Michigan State University, East Lansing, MI 48824, USA
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
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Schroeder JC, Dinatale BC, Murray IA, Flaveny CA, Liu Q, Laurenzana EM, Lin JM, Strom SC, Omiecinski CJ, Amin S, Perdew GH. The uremic toxin 3-indoxyl sulfate is a potent endogenous agonist for the human aryl hydrocarbon receptor. Biochemistry 2010; 49:393-400. [PMID: 20000589 DOI: 10.1021/bi901786x] [Citation(s) in RCA: 228] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor involved in the regulation of multiple cellular pathways, such as xenobiotic metabolism and Th17 cell differentiation. Identification of key physiologically relevant ligands that regulate AHR function remains to be accomplished. Screening of indole metabolites has identified indoxyl 3-sulfate (I3S) as a potent endogenous ligand that selectively activates the human AHR at nanomolar concentrations in primary human hepatocytes, regulating transcription of multiple genes, including CYP1A1, CYP1A2, CYP1B1, UGT1A1, UGT1A6, IL6, and SAA1. Furthermore, I3S exhibits an approximately 500-fold greater potency in terms of transcriptional activation of the human AHR relative to the mouse AHR in cell lines. Structure-function studies reveal that the sulfate group is an important determinant for efficient AHR activation. This is the first phase II enzymatic product identified that can significantly activate the AHR, and ligand competition binding assays indicate that I3S is a direct AHR ligand. I3S failed to activate either CAR or PXR. The physiological importance of I3S lies in the fact that it is a key uremic toxin that accumulates to high micromolar concentrations in kidney dialysis patients, but its mechanism of action is unknown. I3S represents the first identified relatively high potency endogenous AHR ligand that plays a key role in human disease progression. These studies provide evidence that the production of I3S can lead to AHR activation and altered drug metabolism. Our results also suggest that prolonged activation of the AHR by I3S may contribute to toxicity observed in kidney dialysis patients and thus represent a possible therapeutic target.
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Affiliation(s)
- Jennifer C Schroeder
- Center for Molecular Toxicology and Carcinogenesis and Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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DiNatale BC, Murray IA, Schroeder JC, Flaveny CA, Lahoti TS, Laurenzana EM, Omiecinski CJ, Perdew GH. Kynurenic acid is a potent endogenous aryl hydrocarbon receptor ligand that synergistically induces interleukin-6 in the presence of inflammatory signaling. Toxicol Sci 2010; 115:89-97. [PMID: 20106948 DOI: 10.1093/toxsci/kfq024] [Citation(s) in RCA: 439] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Inflammatory signaling plays a key role in tumor progression, and the pleiotropic cytokine interleukin-6 (IL-6) is an important mediator of protumorigenic properties. Activation of the aryl hydrocarbon receptor (AHR) with exogenous ligands coupled with inflammatory signals can lead to synergistic induction of IL6 expression in tumor cells. Whether there are endogenous AHR ligands that can mediate IL6 production remains to be established. The indoleamine-2,3-dioxygenase pathway is a tryptophan oxidation pathway that is involved in controlling immune tolerance, which also aids in tumor escape. We screened the metabolites of this pathway for their ability to activate the AHR; results revealed that kynurenic acid (KA) is an efficient agonist for the human AHR. Structure-activity studies further indicate that the carboxylic acid group is required for significant agonist activity. KA is capable of inducing CYP1A1 messenger RNA levels in HepG2 cells and inducing CYP1A-mediated metabolism in primary human hepatocytes. In a human dioxin response element-driven stable reporter cell line, the EC(25) was observed to be 104nM, while in a mouse stable reporter cell line, the EC(25) was 10muM. AHR ligand competition binding assays revealed that KA is a ligand for the AHR. Treatment of MCF-7 cells with interleukin-1beta and a physiologically relevant concentration of KA (e.g., 100nM) leads to induction of IL6 expression that is largely dependent on AHR expression. Our findings have established that KA is a potent AHR endogenous ligand that can induce IL6 production and xenobiotic metabolism in cells at physiologically relevant concentrations.
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Affiliation(s)
- Brett C DiNatale
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania 16803, USA
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Abstract
Increasingly, research suggests that for certain systems, animal models are insufficient for human toxicology testing. The development of robust, in vitro models of human toxicity is required to decrease our dependence on potentially misleading in vivo animal studies. A critical development in human toxicology testing is the use of human primary hepatocytes to model processes that occur in the intact liver. However, in order to serve as an appropriate model, primary hepatocytes must be maintained in such a way that they persist in their differentiated state. While many hepatocyte culture methods exist, the two-dimensional collagen "sandwich" system combined with a serum-free medium, supplemented with physiological glucocorticoid concentrations, appears to robustly maintain hepatocyte character. Studies in rat and human hepatocytes have shown that when cultured under these conditions, hepatocytes maintain many markers of differentiation including morphology, expression of plasma proteins, hepatic nuclear factors, phase I and II metabolic enzymes. Functionally, these culture conditions also preserve hepatic stress response pathways, such as the SAPK and MAPK pathways, as well as prototypical xenobiotic induction responses. This chapter will briefly review culture methodologies but will primarily focus on hallmark hepatocyte structural, expression and functional markers that characterize the differentiation status of the hepatocyte.
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Affiliation(s)
- Katy M Olsavsky Goyak
- Center for Molecular Toxicology & Carcinogenesis and Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, USA
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Moody DE, Fang WB, Lin SN, Weyant DM, Strom SC, Omiecinski CJ. Effect of rifampin and nelfinavir on the metabolism of methadone and buprenorphine in primary cultures of human hepatocytes. Drug Metab Dispos 2009; 37:2323-9. [PMID: 19773542 PMCID: PMC2784702 DOI: 10.1124/dmd.109.028605] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 09/17/2009] [Indexed: 01/09/2023] Open
Abstract
We tested the hypothesis that primary cultures of human hepatocytes could predict potential drug interactions with methadone and buprenorphine. Hepatocytes (five donors) were preincubated with dimethyl sulfoxide (DMSO) (vehicle), rifampin, or nelfinavir before incubation with methadone or buprenorphine. Culture media (0-60 min) was analyzed by liquid chromatography-tandem mass spectrometry for R- and S-methadone and R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) or for buprenorphine, norbuprenorphine, and their glucuronides [buprenorphine-3-glucuronide (B-3-G) and norbuprenorphine-3-glucuronide (N-3-G)]. R- and S-EDDP were detected in three of five, four of five, and five of five media from cells pretreated with DMSO, nelfinavir, and rifampin. R-EDDP increased 3.1- and 26.5-fold, and S-EDDP increased 2.5- and 21.3-fold after nelfinavir and rifampin. The rifampin effect was significant. B-3-G production was detected in media of all cells incubated with buprenorphine and accounted for most of the buprenorphine loss from culture media; it was not significantly affected by either pretreatment. Norbuprenorphine and N-3-G together were detected in three of five, four of five, and five of five donors pretreated with DMSO, nelfinavir and rifampin, and norbuprenorphine in one of five, one of five, and two of five donors. Although there was a trend for norbuprenorphine (2.8- and 4.9-fold) and N-3-G (1.7- and 1.9-fold) to increase after nelfinavir and rifampin, none of the changes were significant. To investigate low norbuprenorphine production, buprenorphine was incubated with human liver and small intestine microsomes fortified to support both N-dealkylation and glucuronidation; N-dealkylation predominated in small intestine and glucuronidation in liver microsomes. These studies support the hypothesis that methadone metabolism and its potential for drug interactions can be predicted with cultured human hepatocytes, but for buprenorphine the combined effects of hepatic and small intestinal metabolism are probably involved.
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Affiliation(s)
- David E Moody
- Center for Human Toxicology, Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84108, USA.
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Yang X, Liang SH, Weyant DM, Lazarus P, Gallagher CJ, Omiecinski CJ. The expression of human microsomal epoxide hydrolase is predominantly driven by a genetically polymorphic far upstream promoter. J Pharmacol Exp Ther 2009; 330:23-30. [PMID: 19364907 DOI: 10.1124/jpet.109.150870] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microsomal epoxide hydrolase (EPHX1) biotransforms epoxide derivatives of pharmaceuticals, including metabolites of certain antiepileptic medications, such as phenytoin and carbamazepine, and many environmental epoxides, such as those derived from butadiene, benzene, and carcinogenic polyaromatic hydrocarbons. We previously identified a far upstream promoter region, designated E1-b, in the EPHX1 gene that directs expression of an alternatively spliced EPHX1 mRNA transcript in human tissues. In this investigation, we characterized the structural features and expression character of the E1-b promoter region. Results of quantitative real-time polymerase chain reaction analyses demonstrated that the E1-b variant transcript is preferentially and broadly expressed in most tissues, such that it accounts for the majority of total EPHX1 transcript in vivo. Comparative genomic sequence comparisons indicated that the human EPHX1 E1-b gene regulatory region is primate-specific. Direct sequencing and genotyping approaches in 450 individuals demonstrated that the E1-b promoter region harbors a series of transposable element cassettes, including a polymorphic double Alu insertion. Results of reporter assays conducted in several human cell lines demonstrated that the inclusion of the Alu(+/+) insertion significantly decreases basal transcriptional activities. Furthermore, using haplotype block analyses, we determined that the E1-b polymorphic promoter region was not in linkage disequilibrium with two previously identified nonsynonomous single nucleotide polymorphisms (SNPs) in the coding region or with functional SNPs previously identified in the proximal promoter region of the gene. These results demonstrate that the upstream E1-b promoter is the major regulator of EPHX1 expression in human tissues and that polymorphism in this region may contribute an interindividual risk determinant to xenobiotic-induced toxicities.
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Affiliation(s)
- Xi Yang
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA 16802, USA
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DeKeyser JG, Stagliano MC, Auerbach SS, Prabhu KS, Jones AD, Omiecinski CJ. Di(2-ethylhexyl) phthalate is a highly potent agonist for the human constitutive androstane receptor splice variant CAR2. Mol Pharmacol 2009; 75:1005-13. [PMID: 19211671 DOI: 10.1124/mol.108.053702] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The human constitutive androstane receptor (CAR, CAR1) regulates the expression of genes involved in xenobiotic metabolism in the liver. The CAR gene uses multiple alternative splicing events during pre-mRNA processing, thereby enhancing the CAR transcriptome. Previous reports have identified two prominent human CAR variants, CAR2 and CAR3, that possess four- and five-amino acid insertions in their ligand binding domains, respectively. Unlike the constitutively active reference form of the receptor, we now demonstrate that CAR2 is a ligand-activated receptor and comprises approximately 30% of the reference transcript level in human liver tissues in human hepatocytes. Furthermore, we identify the common plasticizer, di(2-ethylhexyl) phthalate (DEHP), as a highly potent and uniquely selective agonist of CAR2. Results from reporter transactivation and mammalian two-hybrid assays reveal that DEHP activates CAR2 at low nanomolar concentrations, results further supported by analysis of CAR target gene expression in primary human hepatocytes. In addition, comparative genomic analyses show that the typical mouse, rat, and marmoset models of DEHP toxicity cannot accurately profile potential human toxicity because of these species' inability to generate a CAR2-like transcript. The discovery that CAR2 is an ultimate human DEHP receptor identifies a novel pathway modulating human DEHP toxicity with potential clinical implications for a subset of patients undergoing critical care medical interventions.
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Affiliation(s)
- Joshua G DeKeyser
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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Bogen KT, Benson JM, Yost GS, Morris JB, Dahl AR, Clewell HJ, Krishnan K, Omiecinski CJ. Naphthalene metabolism in relation to target tissue anatomy, physiology, cytotoxicity and tumorigenic mechanism of action. Regul Toxicol Pharmacol 2008; 51:S27-36. [PMID: 18191315 PMCID: PMC4030291 DOI: 10.1016/j.yrtph.2007.10.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 10/29/2007] [Accepted: 10/31/2007] [Indexed: 11/27/2022]
Abstract
This report provides a summary of deliberations conducted under the charge for members of Module C Panel participating in the Naphthalene State-of-the-Science Symposium (NS(3)), Monterey, CA, October 9-12, 2006. The panel was charged with reviewing the current state of knowledge and uncertainty about naphthalene metabolism in relation to anatomy, physiology and cytotoxicity in tissues observed to have elevated tumor incidence in these rodent bioassays. Major conclusions reached concerning scientific claims of high confidence were that: (1) rat nasal tumor occurrence was greatly enhanced, if not enabled, by adjacent, histologically related focal cellular proliferation; (2) elevated incidence of mouse lung tumors occurred at a concentration (30 ppm) cytotoxic to the same lung region at which tumors occurred, but not at a lower and less cytotoxic concentration (tumorigenesis NOAEL=10 ppm); (3) naphthalene cytotoxicity requires metabolic activation (unmetabolized naphthalene is not a proximate cause of observed toxicity or tumors); (4) there are clear regional and species differences in naphthalene bioactivation; and (5) target tissue anatomy and physiology is sufficiently well understood for rodents, non-human primates and humans to parameterize species-specific physiologically based pharmacokinetic (PBPK) models for nasal and lung effects. Critical areas of uncertainty requiring resolution to enable improved human cancer risk assessment were considered to be that: (1) cytotoxic naphthalene metabolites, their modes of cytotoxic action, and detailed low-dose dose-response need to be clarified, including in primate and human tissues, and neonatal tissues; (2) mouse, rat, and monkey inhalation studies are needed to better define in vivo naphthalene uptake and metabolism in the upper respiratory tract; (3) in vivo validation studies are needed for a PBPK model for monkeys exposed to naphthalene by inhalation, coupled to cytotoxicity studies referred to above; and (4) in vivo studies are needed to validate a human PBPK model for naphthalene. To address these uncertainties, the Panel proposed specific research studies that should be feasible to complete relatively promptly. Concerning residual uncertainty far less easy to resolve, the Panel concluded that environmental, non-cytotoxic exposure levels of naphthalene do not induce tumors at rates that can be predicted meaningfully by simple linear extrapolation from those observed in rodents chronically exposed to far greater, cytotoxic naphthalene concentrations.
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Affiliation(s)
- Kenneth T Bogen
- Exponent Health & Environmental, 500 12th Street, Suite 220, Oakland, CA 94607, USA.
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Zamule SM, Strom SC, Omiecinski CJ. Preservation of hepatic phenotype in lentiviral-transduced primary human hepatocytes. Chem Biol Interact 2008; 173:179-86. [PMID: 18468591 PMCID: PMC2749468 DOI: 10.1016/j.cbi.2008.03.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 03/13/2008] [Accepted: 03/14/2008] [Indexed: 01/11/2023]
Abstract
Lentiviral vectors effectively transduce both dividing and non-dividing cells and stably integrate into the genome of the host cell. In this study, we evaluated the usefulness of a lentiviral system for genetic modulation of primary human hepatocyte cultures. Infection with GFP-expressing lentivectors shows that Huh7 and HepG2 cell lines, as well as primary cultures of human hepatocytes, are efficiently transduced by lentiviral vectors. Real-time RT-PCR analyses demonstrate that infection with lentivectors does not alter hepatic hallmarks such as the expression of the nuclear receptors CAR, PXR, RXR alpha, or HNF4 alpha, or expression of the secretory protein, albumin. Additionally, infected hepatocytes retain the capacity for CYP3A4 induction in response to treatment with phenobarbital, a uniquely sensitive indicator of hepatic differentiation status. Lentivectors may be used for both over-expression and knockdown analyses in primary hepatocytes, as demonstrated in this study by >200-fold CAR over-expression and knockdown of CAR to less than 40% of endogenous levels, with corresponding effects on CYP2B6 expression. In summary, lentiviral vectors provide a novel methodology by which primary human hepatocytes may be stably genetically manipulated, with minimal effects on the differentiated hepatic phenotype. These approaches offer considerable advantage over current methodologies, providing a valuable alternative for use in pharmacological and toxicological investigations involving primary human hepatocyte models and potentially for cell-based therapeutics to treat hepatic dysfunction in vivo.
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Affiliation(s)
- Stephanie M. Zamule
- Center for Molecular Toxicology & Carcinogenesis and the Department of Veterinary & Biomedical Sciences, Pennsylvania State University, 101 Life Sciences Building, University Park, PA, 16802
| | - Stephen C. Strom
- Department of Pathology, University of Pittsburgh, S407 S-BST, 200 Lothrop Street, Pittsburgh, PA, 15261
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology & Carcinogenesis and the Department of Veterinary & Biomedical Sciences, Pennsylvania State University, 101 Life Sciences Building, University Park, PA, 16802
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DeKeyser JG, Bryant SD, Omiecinski CJ. Distinct pharmacological activities associated with naturally occurring splice variants of the human constitutive androstane receptor. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.921.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joshua G DeKeyser
- Veterinary and Biomedical SciencesPennsylvania State UniversityUniversity ParkPA
| | - Sharon D Bryant
- National Institute of Environmental Health SciencesResearch Triangle ParkNC
| | - Curtis J Omiecinski
- Veterinary and Biomedical SciencesPennsylvania State UniversityUniversity ParkPA
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Zamule SM, Weyant DM, Omiecinski CJ. Culturing conditions conducive to the differentiation of hESCs along a hepatic lineage. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.921.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Stephanie Mary Zamule
- Department of Veterinary and Biomedical SciencesPennsylvania State UniversityUniversity ParkPA
| | - Denise M Weyant
- Department of Veterinary and Biomedical SciencesPennsylvania State UniversityUniversity ParkPA
| | - Curtis J Omiecinski
- Department of Veterinary and Biomedical SciencesPennsylvania State UniversityUniversity ParkPA
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Page JL, Strom SC, Omiecinski CJ. Regulation of the human cathepsin E gene by the constitutive androstane receptor. Arch Biochem Biophys 2007; 467:132-8. [PMID: 17888866 PMCID: PMC4064465 DOI: 10.1016/j.abb.2007.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Revised: 08/02/2007] [Accepted: 08/03/2007] [Indexed: 01/28/2023]
Abstract
Cathepsin E (CTSE) is an aspartic protease that has been linked to antigen processing and innate immunity. Elevated levels of CTSE expression have also been associated with several forms of cancer, including carcinomas exhibiting highly invasive character. In this study, we performed DNA microarray experiments, together with quantitative reverse transcriptase PCR analyses and enzymatic activity determinations to identify human CTSE as a novel target gene for regulation by the constitutive androstane receptor (CAR), a nuclear receptor activated by the liver tumor promoting agent, phenobarbital. In particular, two motifs within the 5'-flanking region of the human CTSE gene were identified as direct sites of interaction with CAR/RXRalpha heterodimers, a direct repeat-3 site at position -766 and a direct repeat-4 site at position -1407. Thus, these studies demonstrate CAR-mediated regulation of CTSE within primary hepatocyte cultures from several individual donors and suggest that elevated CTSE activity may play a functional role in the etiology of hepatocarcinogenesis.
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Affiliation(s)
- Jeanine L. Page
- Center for Molecular Toxicology & Carcinogenesis and the Department of Veterinary & Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA
| | - Stephen C. Strom
- Department of Pathology, University of Pittsburgh, 210 Lothrop Street, 450 BST, Pittsburgh, PA 15261, USA
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology & Carcinogenesis and the Department of Veterinary & Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA
- Corresponding author. Fax: +1 814 863 1696. (C.J. Omiecinski)
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Patel RD, Hollingshead BD, Omiecinski CJ, Perdew GH. Aryl-hydrocarbon receptor activation regulates constitutive androstane receptor levels in murine and human liver. Hepatology 2007; 46:209-18. [PMID: 17596880 PMCID: PMC4098831 DOI: 10.1002/hep.21671] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED The aryl-hydrocarbon receptor (AhR) is a basic helix-loop-helix/Per-Arnt-Sim transcription factor that can be activated by exogenous as well as endogenous ligands. AhR is traditionally associated with xenobiotic metabolism. In an attempt to identify novel target genes, C57BL/6J mice were treated with beta-naphthoflavone (BNF), a known AhR ligand, and genome-wide expression analysis studies were performed using high-density microarrays. Constitutive androstane receptor (CAR) was found to be one of the differentially regulated genes. Real-time quantitative polymerase chain reaction (qPCR) verified the increase in CAR messenger RNA (mRNA) level. BNF treatment did not increase CAR mRNA in AhR-null mice. Time-course studies in mice revealed that the regulation of CAR mRNA mimicked that of Cyp1A1, a known AhR target gene. To demonstrate that the increase in CAR mRNA translates to an increase in functional CAR protein, mice were sequentially treated with BNF (6 hours) followed by the selective CAR agonist, TCPOBOP (3 hours). qPCR revealed an increase in the mRNA level of Cyp2b10, previously known to be regulated by CAR. This also suggests that CAR protein is present in limiting amounts with respect to its transactivation ability. Finally, CAR was also up-regulated in primary human hepatocytes in response to AhR activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo[a]pyrene. CONCLUSION This study identifies a mode of up-regulating CAR and potentially expands the role of AhR in drug metabolism. This study also demonstrates in vivo up-regulation of CAR through chemical exposure.
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Affiliation(s)
- Rushang D Patel
- Department of Veterinary and Biomedical Sciences and the Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA
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Olsavsky KM, Page JL, Johnson MC, Zarbl H, Strom SC, Omiecinski CJ. Gene expression profiling and differentiation assessment in primary human hepatocyte cultures, established hepatoma cell lines, and human liver tissues. Toxicol Appl Pharmacol 2007; 222:42-56. [PMID: 17512962 PMCID: PMC2974173 DOI: 10.1016/j.taap.2007.03.032] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 03/13/2007] [Accepted: 03/14/2007] [Indexed: 12/12/2022]
Abstract
Frequently, primary hepatocytes are used as an in vitro model for the liver in vivo. However, the culture conditions reported vary considerably, with associated variability in performance. In this study, we characterized the differentiation character of primary human hepatocytes cultured using a highly defined, serum-free two-dimensional sandwich system, one that configures hepatocytes with collagen I as the substratum together with a dilute extracellular matrix (Matrigeltrade mark) overlay combined with a defined serum-free medium containing nanomolar levels of dexamethasone. Gap junctional communication, indicated by immunochemical detection of connexin 32 protein, was markedly enhanced in hepatocytes cultured in the Matrigel sandwich configuration. Whole genome expression profiling enabled direct comparison of liver tissues to hepatocytes and to the hepatoma-derived cell lines, HepG2 and Huh7. PANTHER database analyses were used to identify biological processes that were comparatively over-represented among probe sets expressed in the in vitro systems. The robustness of the primary hepatocyte cultures was reflected by the extent of unchanged expression character when compared directly to liver, with more than 77% of the probe sets unchanged in each of the over-represented categories, representing such genes as C/EBPalpha, HNF4alpha, CYP2D6, and ABCB1. In contrast, HepG2 and Huh7 cells were unchanged from the liver tissues for fewer than 48% and 55% of these probe sets, respectively. Further, hierarchical clustering of the hepatocytes, but not the cell lines, shifted from donor-specific to treatment-specific when the probe sets were filtered to focus on phenobarbital-inducible genes, indicative of the highly differentiated nature of the hepatocytes when cultured in a highly defined two-dimensional sandwich system.
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Affiliation(s)
- Katy M. Olsavsky
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802
| | - Jeanine L. Page
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802
| | - Mary C. Johnson
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802
| | - Helmut Zarbl
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Mailstop C1-015, P.O. Box 19024, Seattle WA, 98109
| | - Stephen C. Strom
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Curtis J. Omiecinski
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802
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Su S, Omiecinski CJ. Differential splicing of the human peroxisome proliferator‐activated receptor, PPARβ/δ. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a419-d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shengzhong Su
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University101 Life Sciences BuildingUniversity ParkPA16802
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University101 Life Sciences BuildingUniversity ParkPA16802
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Zamule SM, Strom SC, Omiecinski CJ. High efficiency transduction and stable gene expression of primary human hepatocytes with lentiviral vectors. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Stephanie M. Zamule
- Department of Veterinary & Biomedical SciencesPennsylvania State University304 Life Sciences BuildingUniversity ParkPA16802
| | - Stephen C. Strom
- Department of PathologyUniversity of PittsburghS407 S‐BST, 200 Lothrop StreetPittsburghPA15261
| | - Curtis J. Omiecinski
- Department of Veterinary & Biomedical SciencesPennsylvania State University304 Life Sciences BuildingUniversity ParkPA16802
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Stoner MA, Auerbach SS, Zamule SM, Strom SC, Omiecinski CJ. Transactivation of a DR-1 PPRE by a human constitutive androstane receptor variant expressed from internal protein translation start sites. Nucleic Acids Res 2007; 35:2177-90. [PMID: 17355985 PMCID: PMC1874654 DOI: 10.1093/nar/gkm090] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Downstream in-frame start codons produce amino-terminal-truncated human constitutive androstane receptor protein isoforms (ΔNCARs). The ΔNCARs are expressed in liver and in vitro cell systems following translation from in-frame methionine AUG start codons at positions 76, 80, 125, 128, 168 and 265 within the full-length CAR mRNA. The resulting CAR proteins lack the N-terminal DNA-binding domain (DBD) of the receptor, yielding ΔNCAR variants with unique biological function. Although the ΔNCARs maintain full retinoid X receptor alpha (RXRα) heterodimerization capacity, the ΔNCARs are inactive on classical CAR-inducible direct repeat (DR)-4 elements, yet efficiently transactivate a DR-1 element derived from the endogenous PPAR-inducible acyl-CoA oxidase gene promoter. RXRα heterodimerization with CAR1, CAR76 and CAR80 isoforms is necessary for the DR-1 PPRE activation, a function that exhibits absolute dependence on both the respective RXRα DBD and CAR activation (AF)-2 domains, but not the AF-1 or AF-2 domain of RXRα, nor CAR's DBD. A new model of CAR DBD-independent transactivation is proposed, such that in the context of a DR-1 peroxisome proliferator-activated response element, only the RXRα portion of the CAR-RXRα heterodimer binds directly to DNA, with the AF-2 domain of tethered CAR mediating transcriptional activation of the receptor complex.
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Affiliation(s)
- Matthew A. Stoner
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Scott S. Auerbach
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Stephanie M. Zamule
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Stephen C. Strom
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, USA
- *To whom correspondence should be addressed. 814-863-1625814-863-1696
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Page JL, Johnson MC, Olsavsky KM, Strom SC, Zarbl H, Omiecinski CJ. Gene expression profiling of extracellular matrix as an effector of human hepatocyte phenotype in primary cell culture. Toxicol Sci 2007; 97:384-97. [PMID: 17329237 PMCID: PMC4098128 DOI: 10.1093/toxsci/kfm034] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Previously, we demonstrated that primary cultures of rat hepatocytes evidence higher levels of differentiated function when cultured in the presence of a dilute overlay of extracellular matrix (Matrigel). In this investigation, we used DNA microarrays, quantitative RT-PCR, immunoblotting, and cell morphology analyses to evaluate the biological responses imparted by Matrigel overlays on primary cultures of human hepatocytes from five independent donors. Although interindividual variability in responses was evident, our results demonstrated that Matrigel additions typically improved hepatocyte morphology and differentiation character. Results from RNA-profiling experiments indicated that Matrigel additions enhanced hepatocyte RNA expression levels associated with a battery of differentiated features, to levels comparable to those seen in vivo, for genes such as the cytochrome P450s, solute carrier family members, sulfotransferases, certain nuclear transcription factors, and other liver-specific markers, such as albumin, transferrin, and response to the inducer, phenobarbital. In contrast, Matrigel additions were generally associated with reduced RNA expression levels for several cytokeratins, integrins, and a number of stress-related pathways. Decreases in integrin protein expression were similarly detected, although enhanced levels of the gap junction-associated protein, connexin 32, were detected in Matrigel-treated cultures. These data support the concept that ECM functions mechanistically to augment the differentiation character of primary human hepatocytes in culture by mediating a reduction in cellular stress response signaling and by enhancing gap junctional cell-cell communication.
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Affiliation(s)
- Jeanine L. Page
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Mary C. Johnson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Katy M. Olsavsky
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Steven C. Strom
- Department of Pathology, University of Pittsburgh, 200 Lothrop Street, 450 BST, Pittsburgh, Pennsylvania 15261
| | - Helmut Zarbl
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Mailstop C1-015, PO Box 19024, Seattle, Washington 98109-1024
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, 101 Life Sciences Building, The Pennsylvania State University, University Park, Pennsylvania 16802
- To whom correspondence should be addressed. Fax: (814) 863-1696.
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Dekeyser JG, Auerbach SS, Stoner MA, Omiecinski CJ. CAR2 displays unique ligand binding and RXRα heterodimerization characteristics. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a1184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joshua Gordon Dekeyser
- Department of Veterinary ScienceThe Pennsylvania State UniversityDepartment of Veterinary Science201 Life Sciences BuildingUniversity ParkPA16802
| | - Scott S. Auerbach
- Department of PharmacologyUniversity of WashingtonDepartment of PharmacologyUniversity of WashingtonBox 357280SeattleWA98195‐7280
| | - Matthew A. Stoner
- Department of Veterinary ScienceThe Pennsylvania State UniversityDepartment of Veterinary Science201 Life Sciences BuildingUniversity ParkPA16802
| | - Curtis J. Omiecinski
- Department of Veterinary ScienceThe Pennsylvania State UniversityDepartment of Veterinary Science201 Life Sciences BuildingUniversity ParkPA16802
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Abstract
The constitutive androstane receptor (CAR; NR1I3) regulates the expression of genes involved in xenobiotic metabolism. Alternative splicing of the human CAR gene yields an array of mRNAs that encode structurally diverse proteins. One form of CAR, termed CAR2, contains an additional four amino acids (SPTV) that are predicted to reshape the ligand-binding pocket. The current studies show a marked, ligand-independent, CAR2-mediated transactivation of reporters containing optimal DR-3, DR-4, and DR-5 response elements, and reporters derived from the natural CYP2B6 and CYP3A4 gene promoters. Overexpression of the RXRalpha ligand binding domain was critical for achieving these effects. CAR2 interaction with SRC-1 was similarly dependent on the coexpression of RXRalpha. Mutagenesis of Ser233 (SPTV) to an alanine residue yielded a receptor possessing higher constitutive activity. Alternatively, mutating Ser233 to an aspartate residue drastically reduced the transactivation capacity of CAR2. The respective abilities of these mutagenized forms of CAR2 to transactivate a DR-4 x 3 reporter element correlated with their ability to interact with RxRalpha and to recruit SRC-1 in a ligand-regulated manner. Together, these results demonstrate a robust RXRalpha-dependent recruitment of coactivators and transactivation by CAR2. In addition, CAR2 displays novel dose responses to clotrimazole and androstanol compared with the reference form of the receptor while at the same time retaining the ability to bind CITCO. This result supports a hypothesis whereby the four-amino-acid insertion in CAR2 structurally modifies its ligand binding pocket, suggesting that CAR2 is regulated by a set of ligands distinct from those governing the activity of reference CAR.
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Affiliation(s)
- Scott S Auerbach
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary & Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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Faucette SR, Zhang TC, Moore R, Sueyoshi T, Omiecinski CJ, LeCluyse EL, Negishi M, Wang H. Relative activation of human pregnane X receptor versus constitutive androstane receptor defines distinct classes of CYP2B6 and CYP3A4 inducers. J Pharmacol Exp Ther 2006; 320:72-80. [PMID: 17041008 PMCID: PMC4091905 DOI: 10.1124/jpet.106.112136] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Both the human pregnane X receptor (hPXR) and constitutive androstane receptor (hCAR) are capable of regulating CYP3A4 and CYP2B6 gene expression. However, the majority of currently identified CYP3A4 and CYP2B6 inducers are confirmed activators of hPXR but not hCAR. To compare these receptors with respect to their chemical selectivities, 16 drugs known to induce CYP3A4 and/or CYP2B expression were evaluated for relative activation of hPXR versus hCAR. Because of the high basal but low chemical-induced activation of hCAR in immortalized cells, alternative methods were used to evaluate hCAR activation potential. Thirteen of the 16 compounds were classified as moderate to strong hPXR activators. In contrast, carbamazepine (CMZ), efavirenz (EFV), and nevirapine (NVP) were classified as negligible or weak hPXR activators at concentrations associated with efficacious CYP2B6 reporter or endogenous gene induction in primary human hepatocytes, suggesting potential activation of hCAR. Subsequent experiments demonstrated that these three drugs efficiently induced nuclear accumulation of in vivo-transfected enhanced yellow fluorescent protein-hCAR and significantly increased expression of a CYP2B6 reporter gene when hCAR was expressed in CAR-/- mice. In addition, using a recently identified, chemically responsive splice variant of hCAR (hCAR3), the hCAR activation profiles of the 16 compounds were evaluated. By combining results from the hPXR- and hCAR3-based reporter gene assays, these inducers were classified as hPXR, hCAR, or hPXR/hCAR dual activators. Our results demonstrate that CMZ, EFV, and NVP induce CYP2B6 and CYP3A4 preferentially through hCAR and that hCAR3 represents a sensitive tool for in vitro prediction of chemical-mediated human CAR activation.
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Affiliation(s)
- Stephanie R Faucette
- Division of Molecular Pharmaceutics, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina, USA
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Auerbach SS, Stoner MA, Su S, Omiecinski CJ. Retinoid X receptor-alpha-dependent transactivation by a naturally occurring structural variant of human constitutive androstane receptor (NR1I3). Mol Pharmacol 2005; 68:1239-53. [PMID: 16099843 PMCID: PMC4064472 DOI: 10.1124/mol.105.013417] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The constitutive androstane receptor (CAR) mediates the hepatic induction of various xenobiotic metabolizing enzymes and transporters after specific chemical exposures. Recent reports have established the existence of several human CAR mRNA splice variants, including a prominently expressed form termed CAR3, a receptor that possesses a 5 amino acid insertion within its ligand binding domain. In this study, we demonstrate that, in contrast to the constitutively active reference form of the receptor, CAR3 is ligand-activated, transactivating an optimized DR-4 x 3 reporter in response to the human CAR ligand 6-(4-chlorophenyl)imidazo[2,1-b]thiazole-5-carbaldehyde O-(3, 4-dichlorobenzyl)oxime (CITCO). The transactivation response requires the DNA binding domain and AF-2 motif of CAR3 and is markedly enhanced by retinoid X receptor-alpha (RXR) cotransfection. The stimulatory effects of RXR involve a unique mechanism, because they were completely dependent on the RXR AF-2 function but independent of both the RXR A/B domain and its C domain/heterodimerization region. Mammalian two-hybrid results demonstrated that RXR enhanced CITCO-dependent interaction of CAR3 with the receptor interaction domain of SRC-1, indicating that RXR augments CAR3 activity by facilitating coactivator recruitment. It is noteworthy that clotrimazole also functions as a ligand activator of CAR3, in contrast to the inverse agonist activity exhibited by this agent on the reference form of the receptor. Furthermore, results of transfection assays reveal that CAR3 is capable of transactivating the natural CYP2B6 and CYP3A4 gene enhancers, exhibiting both ligand- and RXR-dependence. These results demonstrate that CAR3, unlike CAR1, is a ligand-activated receptor and that CAR3 may regulate gene expression in vivo in a manner distinct from the reference form of the receptor.
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Affiliation(s)
- Scott S Auerbach
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 201 Life Sciences Bldg., University Park, PA 16802, USA
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Hosagrahara VP, Rettie AE, Hassett C, Omiecinski CJ. Functional analysis of human microsomal epoxide hydrolase genetic variants. Chem Biol Interact 2005; 150:149-59. [PMID: 15535985 PMCID: PMC4091877 DOI: 10.1016/j.cbi.2004.07.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Revised: 07/30/2004] [Accepted: 07/30/2004] [Indexed: 11/22/2022]
Abstract
Human microsomal epoxide hydrolase (EPHX1) is active in the metabolism of many potentially carcinogenic or otherwise genotoxic epoxides, such as those derived from the oxidation of polyaromatic hydrocarbons. EPHX1 is polymorphic and encodes allelic variation at least two amino acid positions, Y113H and H139R. In a number of recent molecular epidemiological investigations, EPHX1 polymorphism has been suggested as a susceptibility factor for several human diseases. To better evaluate the functional contribution of EPHX1 genetic polymorphism, we characterized the enzymatic properties associated with each of the respective variant proteins. Enzymatic profiles were evaluated with cis-stilbene oxide (cSO) and benzo[a]pyrene-4,5-epoxide (BaPO), two prototypical substrates for the hydrolase. In one series of experiments, activities of recombinant EPHX1 proteins were analyzed subsequent to their expression using the pFastbac baculovirus vector in Spodoptera frugiperda-9 (Sf9) insect cells, and purification by column chromatography. In parallel studies, EPHX1 activities were evaluated with human liver microsomes derived from individuals of known EPHX1 genotype. Using the purified protein preparations, rates of cSO and BaPO hydrolysis for the reference protein, Y113/H139, were approximately 2-fold greater than those measured with the other EPHX1 allelic variants. However, when activities were analyzed using human liver microsomal fractions, no major differences were evident in the reaction rates generated among preparations representing the different EPHX1 alleles. Collectively, these results suggest that the structural differences encoded by the Y113H and H139R variant alleles exert only modest impact on EPHX1-specific enzymatic activities in vivo.
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Affiliation(s)
- Vinayak P. Hosagrahara
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98105, USA
| | - Allan E. Rettie
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98105, USA
| | - Christopher Hassett
- Center for Molecular Toxicology, 115 Henning, The Pennsylvania State University, University Park, PA 16802, USA
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology, 115 Henning, The Pennsylvania State University, University Park, PA 16802, USA
- Corresponding author. Tel.: +1 814 8631625; fax.:+1 814 8636140. (C.J. Omiecinski)
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Abdel-Rahman SZ, Ammenheuser MM, Omiecinski CJ, Wickliffe JK, Rosenblatt JI, Ward JB. Variability in human sensitivity to 1,3-butadiene: influence of polymorphisms in the 5'-flanking region of the microsomal epoxide hydrolase gene (EPHX1). Toxicol Sci 2005; 85:624-31. [PMID: 15716486 PMCID: PMC4091891 DOI: 10.1093/toxsci/kfi115] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The carcinogenic effects of 1,3-butadiene (BD), a mutagenic chemical widely used in the manufacture of synthetic rubber, are likely initiated through its epoxide metabolites. In humans, these epoxides are detoxified predominantly by hydrolysis, a reaction mediated by the microsomal epoxide hydrolase (mEH; EPHX1) enzyme. It appears reasonable to hypothesize that BD-exposed individuals possessing lower mEH detoxification capacity may have elevated risk of adverse health effects. The interindividual levels of mEH enzymatic activity vary considerably, and polymorphisms in the mEH gene may contribute to this variability. In addition to the well-studied coding region polymorphisms encoding Tyr113His and His139Arg substitutions, seven other polymorphic sites in the 5'-flanking region of the mEH gene have been reported. These polymorphisms appear to differentially affect mEH gene transcriptional activities. The 5'-flanking region polymorphisms exist in two linkages, the -200 linkage (-200C/T, -259C/T, -290T/G) and the -600 linkage (-362A/G, -613T/C, -699T/C), whereas the -399T/C polymorphism exists as an independent site. Because these polymorphisms may affect total mEH enzymatic activity, we hypothesized that they influence the mutagenic response associated with occupational exposure to BD. We genotyped the 5'-region of the mEH gene in 49 non-smoking workers from two styrene-butadiene rubber facilities in southeast Texas and evaluated the linkage patterns against results obtained from an autoradiographic HPRT mutant lymphocyte assay, used as a biomarker of genotoxic effect. In the study population, 67% were exposed to low BD levels, <150 parts per billion, and 33% were exposed to >150 ppb. We used the observed HPRT mutant (variant) frequency (VF) in the studied population and a 4-way first-order interaction statistical model to estimate parameters that describe the influence of exposure, genotypes and the interaction between the two on the HPRT VF in the target population. The background (baseline) VF, defined as the VF (x 10(-6)) +/- S.E.M. at low levels of BD exposure (<150 ppb) where all the genotypes under study are homozygous wild-type, was estimated to be 4.02 +/- 1.32. Exposure to >150 ppb of BD alone resulted in an estimated increase in VF of 3.42 +/- 2.47 above the baseline level. Inheritance of the variant ATT allele in the -600 linkages resulted in an estimated increase in VF of 3.39 +/- 1.67 above the baseline level. When the interaction between BD exposure and the ATT allele in the -600 linkage group was considered, a statistically significant positive interaction was observed, with an estimated increase in the VF of 10.89 +/- 2.16 (95% CI = 6.56-15.20; p = 0.0027) above baseline. These new data confirm and extend our previous findings that sensitivity to the genotoxic effects of BD is inversely correlated with predicted mEH activity.
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Affiliation(s)
- Sherif Z Abdel-Rahman
- Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, Texas 77555-1110, USA.
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Liang SH, Hassett C, Omiecinski CJ. Alternative promoters determine tissue-specific expression profiles of the human microsomal epoxide hydrolase gene (EPHX1). Mol Pharmacol 2004; 67:220-30. [PMID: 15465926 PMCID: PMC4091896 DOI: 10.1124/mol.104.005579] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microsomal epoxide hydrolase (EPHX1) catalyzes hydration reactions that determine the cellular disposition of reactive epoxide derivatives. Whereas the previously defined EPHX1 exon 1 sequence (E1) is derived from a promoter proximal to exon 2 of the EPHX1 coding region, in this investigation, we identified an alternative EPHX1 exon 1 sequence, E1-b, originating from a gene promoter localized approximately 18.5 kb upstream of exon 2. Northern hybridizations demonstrated that the E1-b variant is widely expressed and that the E1-b promoter functions as the primary driver of EPHX1 expression in human tissues. In contrast, the E1 promoter directs expression only in the liver. To examine the basis for liver-specific usage of the E1 promoter, we identified several potential cis-regulatory elements that included GATA (-110/-105) and hepatocyte nuclear factor 3 (HNF3) (-96/-88) motifs. GATA-4 was the principal GATA family member interacting with its respective motif, whereas both HNF3alpha and HNF3beta were capable of interacting with the HNF3 element. GATA-4 and HNF3alpha/HNF3beta DNA binding complexes were enriched in hepatic cells. Site-directed mutagenesis and transactivation analyses of the E1 promoter revealed that GATA-4 is probably a principal factor that regulates liver-specific expression of the E1 variant, with HNF3alpha and HNF3beta acting to negatively regulate GATA-4 function in hepatic cells.
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Affiliation(s)
- Shun-Hsin Liang
- Center of Molecular Toxicology, 115 Henning, Pennsylvania State University, University Park, PA 16802, USA
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Yamamoto M, Mise M, Matsumoto S, Ito S, Gohyama N, Ishida S, Sagara Y, Omiecinski CJ, Oguri K, Yamada H. Comparison of genomic and cDNA sequences of guinea pig CYP2B18 and rat CYP2B2: absence of a phenobarbital-responsive enhancer module in the upstream region of the CYP2B18 gene. J Biochem Mol Toxicol 2004; 18:124-30. [PMID: 15252867 DOI: 10.1002/jbt.20016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Potential mechanisms were investigated whereby CYP2B18, a cytochrome P450 gene exhibiting high constitutive expression but only low levels of phenobarbital-inducibility in the guinea pig liver, may be differentially regulated versus the highly inducible rat CYP2B2 gene. To comparatively assess potential regulatory sequences associated with CYP2B18, a guinea pig genomic library was screened enabling isolation of the CYP2B18 gene. The genomic screening process resulted in the identification of at least four closely-related CYP2B18 genes, designated here as CYP2B18A-D. Of these isolates, CYP2B18A exhibited sequence identical to that of the CYP2B18 cDNA. Further, the deduced amino acid sequence of the CYP2B18 cDNA was identical to that of N-terminal and internally-derived peptide sequences obtained in this investigation from CYP2B18 protein isolated from guinea pig liver. Genomic structural sequences were derived for CYP2B18A, together with the respective 5'-upstream and intronic regions of the gene. Comparison of the CYP2B18A and CYP2B2 gene sequences revealed the lack of repetitive LINE gene sequences in CYP2B18A, putative silencing elements that effect neighboring genes, although these sequences were present in both 5'-upstream and 3'-downstream regions of CYP2B2. We determined that the phenobarbital-responsive enhancer module was absent from the 5'-upstream region as well as the intronic regions of CYP2B18A gene. We hypothesize that the compromised phenobarbital inducibility of CYP2B18A stems from its lack of a functional phenobarbital responsive enhancer module.
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Affiliation(s)
- Midori Yamamoto
- Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Sidhu JS, Liu F, Omiecinski CJ. Phenobarbital responsiveness as a uniquely sensitive indicator of hepatocyte differentiation status: requirement of dexamethasone and extracellular matrix in establishing the functional integrity of cultured primary rat hepatocytes. Exp Cell Res 2004; 292:252-64. [PMID: 14697333 DOI: 10.1016/j.yexcr.2003.09.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We used a serum-free, highly defined primary hepatocyte culture model to investigate the mechanisms whereby dexamethasone (Dex) and extracellular matrix (ECM) coordinate cell differentiation and transcriptional responsiveness to the inducer, phenobarbital (PB). Low nanomolar levels of Dex and dilute concentrations of ECM overlay were essential in the maintenance of normal hepatocyte physiology, as assessed by cell morphology, LDH release, expression of the hepatic nuclear factors C/EBPalpha, -beta, -gamma, HNF-1alpha, -1beta, -4alpha, and RXRalpha, expression of prototypical hepatic marker genes, including albumin and transferrin, and ultimately, cellular capacity to respond to PB. The loss of hepatocyte integrity produced by deficiency of these components correlated with the activation of several stress signaling pathways including the MAPK, SAPK/JNK, and c-Jun signaling pathways, with resulting nuclear recruitment of the activated protein-1 (AP-1) complex. In Dex-deficient cultures, normal cellular function, including the PB induction response, was largely restored in a dose-dependent manner by reintroduction of nanomolar additions of the hormone, in the presence of ECM. Our results demonstrate critical and cooperative roles for Dex and ECM in establishing hepatocyte integrity and in the coordination of an array of liver-specific functions. These studies further establish the PB gene induction response as an exceptionally sensitive indicator of hepatocyte differentiation status.
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Affiliation(s)
- Jaspreet S Sidhu
- Department of Environmental Health, University of Washington, Seattle, WA 98105, USA
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Auerbach SS, Ramsden R, Stoner MA, Verlinde C, Hassett C, Omiecinski CJ. Alternatively spliced isoforms of the human constitutive androstane receptor. Nucleic Acids Res 2003; 31:3194-207. [PMID: 12799447 PMCID: PMC162252 DOI: 10.1093/nar/gkg419] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The nuclear receptor CAR (NR1I3) regulates transcription of genes encoding xenobiotic- and steroid-metabolizing enzymes. Regulatory processes that are mediated by CAR are modulated by a structurally diverse array of chemicals including common pharmaceutical and environmental agents. Here we describe four in-frame splice variants of the human CAR receptor gene. The variant mRNA splice transcripts were expressed in all human livers evaluated. Molecular modeling of the splice variant proteins predicts that the structural effects are localized within the receptor's ligand-binding domain. Assays to assess function indicate that the variant proteins, when compared with the reference protein isoform, exhibit compromised activities with respect to DNA binding, transcriptional activation and coactivator recruitment.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- Blotting, Western
- COS Cells
- Cloning, Molecular
- Constitutive Androstane Receptor
- DNA/metabolism
- Histone Acetyltransferases
- Humans
- Ligands
- Liver/chemistry
- Models, Molecular
- Molecular Sequence Data
- Nuclear Receptor Coactivator 1
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Protein Structure, Tertiary
- RNA, Messenger/analysis
- RNA, Messenger/chemistry
- RNA, Messenger/metabolism
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Recombinant Proteins/metabolism
- Sequence Alignment
- Transcription Factors/chemistry
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcriptional Activation
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Affiliation(s)
- Scott S Auerbach
- Department of Pharmacology, University of Washington, Seattle, WA, USA
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