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Opitz CA, Holfelder P, Prentzell MT, Trump S. The complex biology of aryl hydrocarbon receptor activation in cancer and beyond. Biochem Pharmacol 2023; 216:115798. [PMID: 37696456 PMCID: PMC10570930 DOI: 10.1016/j.bcp.2023.115798] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/08/2023] [Accepted: 09/08/2023] [Indexed: 09/13/2023]
Abstract
The aryl hydrocarbon receptor (AHR) signaling pathway is a complex regulatory network that plays a critical role in various biological processes, including cellular metabolism, development, and immune responses. The complexity of AHR signaling arises from multiple factors, including the diverse ligands that activate the receptor, the expression level of AHR itself, and its interaction with the AHR nuclear translocator (ARNT). Additionally, the AHR crosstalks with the AHR repressor (AHRR) or other transcription factors and signaling pathways and it can also mediate non-genomic effects. Finally, posttranslational modifications of the AHR and its interaction partners, epigenetic regulation of AHR and its target genes, as well as AHR-mediated induction of enzymes that degrade AHR-activating ligands may contribute to the context-specificity of AHR activation. Understanding the complexity of AHR signaling is crucial for deciphering its physiological and pathological roles and developing therapeutic strategies targeting this pathway. Ongoing research continues to unravel the intricacies of AHR signaling, shedding light on the regulatory mechanisms controlling its diverse functions.
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Affiliation(s)
- Christiane A Opitz
- German Cancer Research Center (DKFZ), Heidelberg, Division of Metabolic Crosstalk in Cancer and the German Cancer Consortium (DKTK), DKFZ Core Center Heidelberg, 69120 Heidelberg, Germany; Neurology Clinic and National Center for Tumor Diseases, 69120 Heidelberg, Germany.
| | - Pauline Holfelder
- German Cancer Research Center (DKFZ), Heidelberg, Division of Metabolic Crosstalk in Cancer and the German Cancer Consortium (DKTK), DKFZ Core Center Heidelberg, 69120 Heidelberg, Germany; Faculty of Bioscience, Heidelberg University, 69120 Heidelberg, Germany
| | - Mirja Tamara Prentzell
- German Cancer Research Center (DKFZ), Heidelberg, Division of Metabolic Crosstalk in Cancer and the German Cancer Consortium (DKTK), DKFZ Core Center Heidelberg, 69120 Heidelberg, Germany; Faculty of Bioscience, Heidelberg University, 69120 Heidelberg, Germany
| | - Saskia Trump
- Molecular Epidemiology Unit, Berlin Institute of Health at Charité and the German Cancer Consortium (DKTK), Partner Site Berlin, a partnership between DKFZ and Charité -Universitätsmedizin Berlin, 10117 Berlin, Germany
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Bileck A, Bortel P, Kriz M, Janker L, Kiss E, Gerner C, Del Favero G. Inward Outward Signaling in Ovarian Cancer: Morpho-Phospho-Proteomic Profiling Upon Application of Hypoxia and Shear Stress Characterizes the Adaptive Plasticity of OVCAR-3 and SKOV-3 Cells. Front Oncol 2022; 11:746411. [PMID: 35251951 PMCID: PMC8896345 DOI: 10.3389/fonc.2021.746411] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 12/27/2021] [Indexed: 12/26/2022] Open
Abstract
With the onset of resistance, ovarian cancer cells display almost unpredictable adaptive potential. This may derive from the tumor genetic ancestry and can be additionally tailored by post translational protein modifications (PTMs). In this study, we took advantage of high-end (phospho)-proteome analysis combined with multiparametric morphometric profiling in high-grade serous (OVCAR-3) and non-serous (SKOV-3) ovarian carcinoma cells. For functional experiments, we applied two different protocols, representing typical conditions of the abdominal cavity and of the growing tumor tissue: on the one side hypoxia (oxygen 1%) which develops within the tumor mass or is experienced during migration/extravasation in non-vascularized areas. On the other hand, fluid shear stress (250 rpm, 2.8 dyn/cm2) which affects tumor surface in the peritoneum or metastases in the bloodstream. After 3 hours incubation, treatment groups were clearly distinguishable by PCA analysis. Whereas basal proteome profiles of OVCAR-3 and SKOV-3 cells appeared almost unchanged, phosphoproteome analysis revealed multiple regulatory events. These affected primarily cellular structure and proliferative potential and consolidated in the proteome signature after 24h treatment. Upon oxygen reduction, metabolism switched toward glycolysis (e.g. upregulation hexokinase-2; HK2) and cell size increased, in concerted regulation of pathways related to Rho-GTPases and/or cytoskeletal elements, resembling a vasculogenic mimicry response. Shear stress regulated proteins governing cell cycle and structure, as well as the lipid metabolism machinery including the delta(14)-sterol reductase, kinesin-like proteins (KIF-22/20A) and the actin-related protein 2/3 complex. Independent microscopy-based validation experiments confirmed cell-type specific morphometric responses. In conclusion, we established a robust workflow enabling the description of the adaptive potential of ovarian cancer cells to physical and chemical stressors typical for the abdominal cavity and supporting the identification of novel molecular mechanisms sustaining tumor plasticity and pharmacologic resistance.
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Affiliation(s)
- Andrea Bileck
- Department of Analytical Chemistry, Faculty of Chemistry University of Vienna, Vienna, Austria
- Joint Metabolome Facility, University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Patricia Bortel
- Department of Analytical Chemistry, Faculty of Chemistry University of Vienna, Vienna, Austria
| | - Michelle Kriz
- Department of Analytical Chemistry, Faculty of Chemistry University of Vienna, Vienna, Austria
- Department of Food Chemistry and Toxicology, Faculty of Chemistry University of Vienna, Vienna, Austria
| | - Lukas Janker
- Department of Analytical Chemistry, Faculty of Chemistry University of Vienna, Vienna, Austria
| | - Endre Kiss
- Core Facility Multimodal Imaging, Faculty of Chemistry University of Vienna, Vienna, Austria
| | - Christopher Gerner
- Department of Analytical Chemistry, Faculty of Chemistry University of Vienna, Vienna, Austria
- Joint Metabolome Facility, University of Vienna and Medical University of Vienna, Vienna, Austria
- Core Facility Multimodal Imaging, Faculty of Chemistry University of Vienna, Vienna, Austria
- *Correspondence: Giorgia Del Favero, ; Christopher Gerner,
| | - Giorgia Del Favero
- Department of Food Chemistry and Toxicology, Faculty of Chemistry University of Vienna, Vienna, Austria
- Core Facility Multimodal Imaging, Faculty of Chemistry University of Vienna, Vienna, Austria
- *Correspondence: Giorgia Del Favero, ; Christopher Gerner,
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Avilla MN, Malecki KMC, Hahn ME, Wilson RH, Bradfield CA. The Ah Receptor: Adaptive Metabolism, Ligand Diversity, and the Xenokine Model. Chem Res Toxicol 2020; 33:860-879. [PMID: 32259433 PMCID: PMC7175458 DOI: 10.1021/acs.chemrestox.9b00476] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Indexed: 12/12/2022]
Abstract
The Ah receptor (AHR) has been studied for almost five decades. Yet, we still have many important questions about its role in normal physiology and development. Moreover, we still do not fully understand how this protein mediates the adverse effects of a variety of environmental pollutants, such as the polycyclic aromatic hydrocarbons (PAHs), the chlorinated dibenzo-p-dioxins ("dioxins"), and many polyhalogenated biphenyls. To provide a platform for future research, we provide the historical underpinnings of our current state of knowledge about AHR signal transduction, identify a few areas of needed research, and then develop concepts such as adaptive metabolism, ligand structural diversity, and the importance of proligands in receptor activation. We finish with a discussion of the cognate physiological role of the AHR, our perspective on why this receptor is so highly conserved, and how we might think about its cognate ligands in the future.
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Affiliation(s)
- Mele N. Avilla
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Kristen M. C. Malecki
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Mark E. Hahn
- Biology
Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543-1050, United States
| | - Rachel H. Wilson
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Christopher A. Bradfield
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
- McArdle
Laboratory for Cancer Research, University of Wisconsin School of Medicine
and Public Health, Madison, Wisconsin 53705-227, United States
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4
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Ibrahim M, MacFarlane EM, Matteo G, Hoyeck MP, Rick KRC, Farokhi S, Copley CM, O'Dwyer S, Bruin JE. Functional cytochrome P450 1A enzymes are induced in mouse and human islets following pollutant exposure. Diabetologia 2020; 63:162-178. [PMID: 31776611 PMCID: PMC6890627 DOI: 10.1007/s00125-019-05035-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 08/30/2019] [Indexed: 02/08/2023]
Abstract
AIMS/HYPOTHESIS Exposure to environmental pollution has been consistently linked to diabetes incidence in humans, but the potential causative mechanisms remain unclear. Given the critical role of regulated insulin secretion in maintaining glucose homeostasis, environmental chemicals that reach the endocrine pancreas and cause beta cell injury are of particular concern. We propose that cytochrome P450 (CYP) enzymes, which are involved in metabolising xenobiotics, could serve as a useful biomarker for direct exposure of islets to pollutants. Moreover, functional CYP enzymes in islets could also impact beta cell physiology. The aim of this study was to determine whether CYP1A enzymes are activated in islets following direct or systemic exposure to environmental pollutants. METHODS Immortalised liver (HepG2) and rodent pancreatic endocrine cell lines (MIN6, βTC-6, INS1, α-TC1, α-TC3), as well as human islets, were treated in vitro with known CYP1A inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3-methylcholanthrene (3-MC). In addition, mice were injected with either a single high dose of TCDD or multiple low doses of TCDD in vivo, and islets were isolated 1, 7 or 14 days later. RESULTS CYP1A enzymes were not activated in any of the immortalised beta or alpha cell lines tested. However, both 3-MC and TCDD potently induced CYP1A1 gene expression and modestly increased CYP1A1 enzyme activity in human islets after 48 h. The induction of CYP1A1 in human islets by TCDD was prevented by cotreatment with a cytokine mixture. After a systemic single high-dose TCDD injection, CYP1A1 enzyme activity was induced in mouse islets ~2-fold, ~40-fold and ~80-fold compared with controls after 1, 7 and 14 days, respectively, in vivo. Multiple low-dose TCDD exposure in vivo also caused significant upregulation of Cyp1a1 in mouse islets. Direct TCDD exposure to human and mouse islets in vitro resulted in suppressed glucose-induced insulin secretion. A single high-dose TCDD injection resulted in lower plasma insulin levels, as well as a pronounced increase in beta cell death. CONCLUSIONS/INTERPRETATION Transient exposure to TCDD results in long-term upregulation of CYP1A1 enzyme activity in islets. This provides evidence for direct exposure of islets to lipophilic pollutants in vivo and may have implications for islet physiology.
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Affiliation(s)
- Muna Ibrahim
- Laboratory of Molecular and Cellular Medicine, Department of Cellular & Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Erin M MacFarlane
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Geronimo Matteo
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Myriam P Hoyeck
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Kayleigh R C Rick
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Salar Farokhi
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Catherine M Copley
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Shannon O'Dwyer
- Laboratory of Molecular and Cellular Medicine, Department of Cellular & Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Jennifer E Bruin
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
- Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
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Tsai CH, Li CH, Liao PL, Chang YW, Cheng YW, Kang JJ. Aza-PBHA, a potent histone deacetylase inhibitor, inhibits human gastric-cancer cell migration via PKCα-mediated AHR-HDAC interactions. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118564. [PMID: 31672612 DOI: 10.1016/j.bbamcr.2019.118564] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/16/2019] [Accepted: 10/23/2019] [Indexed: 12/19/2022]
Abstract
Recently, histone deacetylase inhibitors (HDACi) have become widely used in anti-cancer treatment; however, due to acquired drug resistance and their relatively low specificity, they are largely ineffective against late-stage cancer. Thus, it is critical to elucidate the molecular mechanisms underlying these issues, so as to identify novel therapeutic targets to prevent late-stage cancer progression and resistance acquisition. The present study investigated the Aryl hydrocarbon receptor (AHR), that has been shown to mediate histone acetylation by regulating histone deacetylase (HDAC) activity during HDACi treatment in human gastric-cancer cell lines (i.e. AGS and NCI-N87 cells). The potent HDACi, Aza-PBHA, was thus shown to upregulate AHR expression in both AGS and NCI-N87 cell lines, and to increase histone acetylation levels by facilitating AHR/HDAC interactions. Conversely, AHR knockdown increased HDAC activity. Aza-PBHA also increased PKCα phosphorylation and membrane translocation; however, interestingly, PKCα inhibition reduced the Aza-PBHA-increased AHR and histone acetylation levels, and inhibited the formation of the AHR/HDAC complex, likely upregulating Aza-PBHA-inhibited cell migration. Thus, our results suggest that Aza-PBHA treatment increased AHR levels to suppress HDAC activity, and inhibited cell migration by activating PKCα activation. These findings support the use of drugs to control AHR-related epigenetic regulation as a promising potential method to prevent acquired resistance to cancer treatments.
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Affiliation(s)
- Chi-Hao Tsai
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan; School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan.
| | - Ching-Hao Li
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taiwan.
| | - Po-Lin Liao
- Institute of Food Safety and Health Assessment, National Yang-Ming University, Taipei, Taiwan
| | - Yu-Wei Chang
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
| | - Yu-Wen Cheng
- School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan; Ph.D. Program for the Clinical Drug Discovery from Botanical Herbs, College of Pharmacy, Taipei Medical University, Taiwan; Ph.D. Program in Biotechnology Research and Development, College of Pharmacy, Taipei Medical University, Taiwan.
| | - Jaw-Jou Kang
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan; Faculty of Pharmacy, National Yang-Ming University, Taipei, Taiwan.
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6
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Han EH, Kim HG, Lee EJ, Jeong HG. Endosulfan Induces CYP1A1 Expression Mediated through Aryl Hydrocarbon Receptor Signal Transduction by Protein Kinase C. Toxicol Res 2016; 31:339-45. [PMID: 26877836 PMCID: PMC4751443 DOI: 10.5487/tr.2015.31.4.339] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CYP1A1 is a phase I xenobiotic-metabolizing enzyme whose expression is mainly driven by AhR. Endosulfan is an organochlorine pesticide used agriculturally for a wide range of crops. In this study, we investigated the effect of endosulfan on CYP1A1 expression and regulation. Endosulfan significantly increased CYP1A1 enzyme activity as well as mRNA and protein levels. In addition, endosulfan markedly induced XRE transcriptional activity. CH-223191, an AhR antagonist, blocked the endosulfan-induced increase in CYP1A1 mRNA and protein expression. Moreover, endosulfan did not induce CYP1A1 gene expression in AhR-deficient mutant cells. Furthermore, endosulfan enhanced the phosphorylation of calcium calmodulin (CaM)-dependent protein kinase (CaMK) and protein kinase C (PKC). In conclusion, endosulfan-induced up-regulation of CYP1A1 is associated with AhR activation, which may be mediated by PKC-dependent pathways.
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Affiliation(s)
- Eun Hee Han
- Drug & Disease Target Group, Division of Bioconvergence Analysis, Korea Basic Science Institute, Daejeon, Korea; Biological Analysis Science, University of Science and Technology, Daejeon, Korea
| | - Hyung Gyun Kim
- Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Korea
| | - Eun Ji Lee
- Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Korea
| | - Hye Gwang Jeong
- Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Korea
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7
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Aftabi Y, Colagar AH, Mehrnejad F. An in silico approach to investigate the source of the controversial interpretations about the phenotypic results of the human AhR-gene G1661A polymorphism. J Theor Biol 2016; 393:1-15. [PMID: 26776670 DOI: 10.1016/j.jtbi.2016.01.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Revised: 12/11/2015] [Accepted: 01/01/2016] [Indexed: 12/21/2022]
Abstract
Aryl hydrocarbon receptor (AhR) acts as an enhancer binding ligand-activated intracellular receptor. Chromatin remodeling components and general transcription factors such as TATA-binding protein (TBP) are evoked on AhR-target genes by interaction with its flexible transactivation domain (TAD). AhR-G1661A single nucleotide polymorphism (SNP: rs2066853) causes an arginine to lysine substitution in the acidic sub-domain of TAD at position 554 (R554K). Although, numerous studies associate the SNP with some abnormalities such as cancer, other reliable investigations refuse the associations. Consequently, the interpretation of the phenotypic results of G1661A-transition has been controversial. In this study, an in silico analysis were performed to investigate the possible effects of the transition on AhR-mRNA, protein structure, interaction properties and modifications. The analysis revealed that the R554K substitution affects secondary structure and solvent accessibility of adjacent residues. Also, it causes to decreasing of the AhR stability; altering the hydropathy features of the local sequence and changing the pattern of the residues at the binding site of the TAD-acidic sub-domain. Generating of new sites for ubiquitination and acetylation for AhR-K554 variant respectively at positions 544 and 560 was predicted. Our findings intensify the idea that the AhR-G1661A transition may affects AhR-TAD interactions, especially with the TBP, which influence AhR-target genes expression. However, the previously reported flexibility of the modular TAD could act as an intervening factor, moderate the SNP effects and causes distinct outcomes in different individuals and tissues.
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Affiliation(s)
- Younes Aftabi
- Department of Molecular and Cell Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Post Code: 47416-95447, Mazandaran, Iran
| | - Abasalt Hosseinzadeh Colagar
- Department of Molecular and Cell Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Post Code: 47416-95447, Mazandaran, Iran.
| | - Faramarz Mehrnejad
- Department of Life Science Engineering, Faculty of New Sciences & Technologies, University of Tehran, P.O. Box: 14395-1561, Tehran, Iran
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Gebraël C, Jumarie C. Cadmium interference with ERK1/2 and AhR signaling without evidence for cross-talk. Toxicol Res (Camb) 2015. [DOI: 10.1039/c5tx00284b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The possibility that Cd may activate AhR indirectlyviaERK1/2 phosphorylation was tested as a function of enterocytic differentiation status in the human Caco-2 cells.
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Affiliation(s)
- C. Gebraël
- Département des Sciences Biologiques
- Centre TOXEN
- Université du Québec à Montréal
- Montréal
- Canada
| | - C. Jumarie
- Département des Sciences Biologiques
- Centre TOXEN
- Université du Québec à Montréal
- Montréal
- Canada
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Vogel CFA, Khan EM, Leung PSC, Gershwin ME, Chang WLW, Wu D, Haarmann-Stemmann T, Hoffmann A, Denison MS. Cross-talk between aryl hydrocarbon receptor and the inflammatory response: a role for nuclear factor-κB. J Biol Chem 2014; 289:1866-75. [PMID: 24302727 PMCID: PMC3894361 DOI: 10.1074/jbc.m113.505578] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/26/2013] [Indexed: 01/13/2023] Open
Abstract
The aryl hydrocarbon receptor (AhR) is involved in the regulation of immune responses, T-cell differentiation, and immunity. Here, we show that inflammatory stimuli such as LPS induce the expression of AhR in human dendritic cells (DC) associated with an AhR-dependent increase of CYP1A1 (cytochrome P4501A1). In vivo data confirmed the elevated expression of AhR by LPS and the LPS-enhanced 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated induction of CYP1A1 in thymus of B6 mice. Inhibition of nuclear factor-κB (NF-κB) repressed both normal and LPS-enhanced, TCDD-inducible, AhR-dependent gene expression and canonical pathway control of RelA-regulated AhR-responsive gene expression. LPS-mediated induction of AhR was NF-κB-dependent, as shown in mouse embryonic fibroblasts (MEFs) derived from Rel null mice. AhR expression and TCDD-mediated induction of CYP1A1 was significantly reduced in RelA-deficient MEF compared with wild type MEF cells and ectopic expression of RelA restored the expression of AhR and induction of CYP1A1 in MEF RelA null cells. Promoter analysis of the human AhR gene identified three putative NF-κB-binding elements upstream of the transcription start site. Mutation analysis of the AhR promoter identified one NF-κB site as responsible for mediating the induction of AhR expression by LPS and electrophoretic shift assays demonstrated that this NF-κB motif is recognized by the RelA/p50 heterodimer. Our results show for the first time that NF-κB RelA is a critical component regulating the expression of AhR and the induction of AhR-dependent gene expression in immune cells illustrating the interaction of AhR and NF-κB signaling.
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Affiliation(s)
- Christoph F. A. Vogel
- From the Department of Environmental Toxicology
- Center for Health and the Environment
| | | | | | | | - W. L. William Chang
- Center for Comparative Medicine, University of California, Davis, California 95616
| | - Dalei Wu
- the Sanford-Burnham Medical Research Institute, Orlando, Florida 32827
| | | | - Alexander Hoffmann
- the Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90025
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Li ZH, Xu H, Zheng W, Lam SH, Gong Z. RNA-sequencing analysis of TCDD-induced responses in zebrafish liver reveals high relatedness to in vivo mammalian models and conserved biological pathways. PLoS One 2013; 8:e77292. [PMID: 24204792 PMCID: PMC3813628 DOI: 10.1371/journal.pone.0077292] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/01/2013] [Indexed: 12/15/2022] Open
Abstract
TCDD is one of the most persistent environmental toxicants in biological systems and its effect through aryl hydrocarbon receptor (AhR) has been well characterized. However, the information on TCDD-induced toxicity in other molecular pathways is rather limited. To fully understand molecular toxicity of TCDD in an in vivo animal model, adult zebrafish were exposed to TCDD at 10 nM for 96 h and the livers were sampled for RNA-sequencing based transcriptomic profiling. A total of 1,058 differently expressed genes were identified based on fold-change>2 and TPM (transcripts per million) >10. Among the top 20 up-regulated genes, 10 novel responsive genes were identified and verified by RT-qPCR analysis on independent samples. Transcriptomic analysis indicated several deregulated pathways associated with cell cycle, endocrine disruptors, signal transduction and immune systems. Comparative analyses of TCDD-induced transcriptomic changes between fish and mammalian models revealed that proteomic pathway is consistently up-regulated while calcium signaling pathway and several immune-related pathways are generally down-regulated. Finally, our study also suggested that zebrafish model showed greater similarity to in vivo mammalian models than in vitro models. Our study indicated that the zebrafish is a valuable in vivo model in toxicogenomic analyses for understanding molecular toxicity of environmental toxicants relevant to human health. The expression profiles associated with TCDD could be useful for monitoring environmental dioxin and dioxin-like contamination.
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Affiliation(s)
- Zhi-Hua Li
- Department of Biological Sciences, National University of Singapore, Singapore
- Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan, China
| | - Hongyan Xu
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Weiling Zheng
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Siew Hong Lam
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Zhiyuan Gong
- Department of Biological Sciences, National University of Singapore, Singapore
- * E-mail:
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11
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Solaimani P, Damoiseaux R, Hankinson O. Genome-wide RNAi high-throughput screen identifies proteins necessary for the AHR-dependent induction of CYP1A1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Sci 2013; 136:107-19. [PMID: 23997114 DOI: 10.1093/toxsci/kft191] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) has a plethora of physiological roles, and upon dysregulation, carcinogenesis can occur. One target gene of AHR encodes the xenobiotic and drug-metabolizing enzyme CYP1A1, which is inducible by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) via the AHR. An siRNA library targeted against over 5600 gene candidates in the druggable genome was used to transfect mouse Hepa-1 cells, which were then treated with TCDD, and subsequently assayed for CYP1A1-dependent ethoxyresorufin-o-deethylase (EROD) activity. Following redundant siRNA activity (RSA) statistical analysis, we identified 93 hits that reduced EROD activity with a p value ≤ .005 and substantiated 39 of these as positive hits in a secondary screening using endoribonuclease-prepared siRNAs (esiRNAs). Twelve of the corresponding gene products were subsequently confirmed to be necessary for the induction of CYP1A1 messenger RNA by TCDD. None of the candidates were deficient in aryl hydrocarbon nuclear translocator expression. However 6 gene products including UBE2i, RAB40C, CRYGD, DCTN4, RBM5, and RAD50 are required for the expression of AHR as well as for induction of CYP1A1. We also found 2 gene products, ARMC8 and TCF20, to be required for the induction of CYP1A1, but our data are ambiguous as to whether they are required for the expression of AHR. In contrast, SIN3A, PDC, TMEM5, and CD9 are not required for AHR expression but are required for the induction of CYP1A1, implicating a direct role in Cyp1a1 transcription. Our methods, although applied to Cyp1a1, could be modified for identifying proteins that regulate other inducible genes.
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Affiliation(s)
- Parrisa Solaimani
- * Molecular Toxicology Interdepartmental Program, Department of Pathology and Laboratory Medicine, and the Jonsson Comprehensive Cancer Center and
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12
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Zhao B, Bohonowych JES, Timme-Laragy A, Jung D, Affatato AA, Rice RH, Di Giulio RT, Denison MS. Common commercial and consumer products contain activators of the aryl hydrocarbon (dioxin) receptor. PLoS One 2013; 8:e56860. [PMID: 23441220 PMCID: PMC3575475 DOI: 10.1371/journal.pone.0056860] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 01/15/2013] [Indexed: 01/27/2023] Open
Abstract
Activation of the Ah receptor (AhR) by halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), can produce a wide variety of toxic and biological effects. While recent studies have shown that the AhR can bind and be activated by structurally diverse chemicals, how widespread of these AhR agonists are in environmental, biological and synthetic materials remains to be determined. Using AhR-based assays, we demonstrate the presence of potent AhR agonists in a variety of common commercial and consumer items. Solvent extracts of paper, rubber and plastic products contain chemicals that can bind to and stimulate AhR DNA binding and/or AhR-dependent gene expression in hepatic cytosol, cultured cell lines, human epidermis and zebrafish embryos. In contrast to TCDD and other persistent dioxin-like HAHs, activation of AhR-dependent gene expression by these extracts was transient, suggesting that the agonists are metabolically labile. Solvent extracts of rubber products produce AhR-dependent developmental toxicity in zebrafish in vivo, and inhibition of expression of the metabolic enzyme CYP1A, significantly increased their toxic potency. Although the identity of the responsible AhR-active chemicals and their toxicological impact remain to be determined, our data demonstrate that AhR active chemicals are widely distributed in everyday products.
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Affiliation(s)
- Bin Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- Department of Environmental Toxicology, University of California Davis, Davis, California, United States of America
| | - Jessica E. S. Bohonowych
- Department of Environmental Toxicology, University of California Davis, Davis, California, United States of America
| | - Alicia Timme-Laragy
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Dawoon Jung
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Alessandra A. Affatato
- Department of Environmental Toxicology, University of California Davis, Davis, California, United States of America
| | - Robert H. Rice
- Department of Environmental Toxicology, University of California Davis, Davis, California, United States of America
| | - Richard T. Di Giulio
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California Davis, Davis, California, United States of America
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13
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Kolasa E, Balaguer P, Houlbert N, Fardel O. Phorbol ester-modulation of estrogenic genomic effects triggered by the environmental contaminant benzanthracene. Toxicol In Vitro 2012; 26:807-16. [DOI: 10.1016/j.tiv.2012.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 05/11/2012] [Accepted: 05/18/2012] [Indexed: 12/29/2022]
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14
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Inoue H, Mishima K, Yamamoto-Yoshida S, Ushikoshi-Nakayama R, Nakagawa Y, Yamamoto K, Ryo K, Ide F, Saito I. Aryl hydrocarbon receptor-mediated induction of EBV reactivation as a risk factor for Sjögren's syndrome. THE JOURNAL OF IMMUNOLOGY 2012; 188:4654-62. [PMID: 22467650 DOI: 10.4049/jimmunol.1101575] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a variety of biological effects by binding to environmental pollutants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin). Although numerous animal studies have demonstrated the harmful effects of dioxins, it remains controversial whether dioxins pose a risk to human health. Enhanced lytic replication of EBV is a risk factor for the development of autoimmune diseases and cancers. This study evaluated the possibility that ligand-activated AhR reactivates EBV. EBV reactivation and AhR transactivation were evaluated with luciferase assays. Saliva samples were collected from 19 patients with primary Sjögren's syndrome (SS). Control saliva samples were obtained from 10 healthy individuals and nine patients with severe dry mouth. TCDD enhanced BZLF1 transcription, which mediates the switch from the latent to the lytic form of EBV infection in EBV-positive B cell lines and in a salivary gland epithelial cell line. Moreover, TCDD-induced increases in BZLF1 mRNA and EBV genomic DNA levels were confirmed in the B cell lines. Saliva from SS patients activated the transcription of both CYP1A1 and BZLF1. Additionally, there was a positive correlation between CYP1A1 and BZLF1 promoter activities. AhR ligands elicited the reactivation of EBV in activated B cells and salivary epithelial cells, and these ligands are involved in SS. Our findings reveal novel aspects of the biological effects of dioxin and the AhR-dependent pathogenesis of autoimmune diseases.
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Affiliation(s)
- Hiroko Inoue
- Department of Pathology, Tsurumi University School of Dental Medicine, Kanagawa 230-8501, Japan
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15
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Elliott A, Joiakim A, Mathieu PA, Duniec-Dmuchowski Z, Kocarek TA, Reiners JJ. p-Anilinoaniline enhancement of dioxin-induced CYP1A1 transcription and aryl hydrocarbon receptor occupancy of CYP1A1 promoter: role of the cell cycle. Drug Metab Dispos 2012; 40:1032-40. [PMID: 22344700 DOI: 10.1124/dmd.111.042549] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is targeted by ubiquitination for degradation by the proteasome shortly after its activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In silico screening identified p-anilinoaniline (pAA) as a putative inhibitor of an E2 ligase that partners with an E3 ligase implicated in AhR ubiquitination. We investigated whether pAA could modify AhR-dependent activation of its target gene CYP1A1. pAA (1-200 μM) alone did not affect AhR content, or stimulate CYP1A1 mRNA accumulation in human mammary epithelial MCF10A cultures. However, pretreatment with ≥100 μM pAA suppressed TCDD-induced CYP1A1 activation and AhR degradation via its functioning as an AhR antagonist. At a lower concentration (25 μM), pAA cotreatment increased TCDD-induced CYP1A1 mRNA accumulation, without inhibiting AhR turnover or altering CYP1A1 mRNA half-life. Whereas TCDD alone did not affect MCF10A proliferation, 25 μM pAA was cytostatic and induced a G(1) arrest that lasted ∼7 h and induced an S phase arrest that peaked 5 to 8 h later. TCDD neither affected MCF10A cell cycle progression nor did it alter pAA effects on the cell cycle. The magnitude of CYP1A1 activation depended upon the time elapsed between pAA pretreatment and TCDD addition. Maximal AhR occupancy of the CYP1A1 promoter and accumulation of CYP1A1 heterogeneous nuclear RNA and mRNA occurred when pAA-pretreated cultures were exposed to TCDD in late G(1) and early/mid S phase. TCDD-mediated induction of CYP2S1 was also cell cycle-dependent in MCF10A cultures. Similar studies with HepG2 cultures indicated that the cell cycle dependence of CYP1A1 induction is cell context-dependent.
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Affiliation(s)
- Althea Elliott
- Institute of Environmental Health Sciences, 259 Mack Ave., Wayne State University, Detroit, MI 48201, USA
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16
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Denison MS, Soshilov AA, He G, DeGroot DE, Zhao B. Exactly the same but different: promiscuity and diversity in the molecular mechanisms of action of the aryl hydrocarbon (dioxin) receptor. Toxicol Sci 2011; 124:1-22. [PMID: 21908767 DOI: 10.1093/toxsci/kfr218] [Citation(s) in RCA: 567] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Ah receptor (AhR) is a ligand-dependent transcription factor that mediates a wide range of biological and toxicological effects that result from exposure to a structurally diverse variety of synthetic and naturally occurring chemicals. Although the overall mechanism of action of the AhR has been extensively studied and involves a classical nuclear receptor mechanism of action (i.e., ligand-dependent nuclear localization, protein heterodimerization, binding of liganded receptor as a protein complex to its specific DNA recognition sequence and activation of gene expression), details of the exact molecular events that result in most AhR-dependent biochemical, physiological, and toxicological effects are generally lacking. Ongoing research efforts continue to describe an ever-expanding list of ligand-, species-, and tissue-specific spectrum of AhR-dependent biological and toxicological effects that seemingly add even more complexity to the mechanism. However, at the same time, these studies are also identifying and characterizing new pathways and molecular mechanisms by which the AhR exerts its actions and plays key modulatory roles in both endogenous developmental and physiological pathways and response to exogenous chemicals. Here we provide an overview of the classical and nonclassical mechanisms that can contribute to the differential sensitivity and diversity in responses observed in humans and other species following ligand-dependent activation of the AhR signal transduction pathway.
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Affiliation(s)
- Michael S Denison
- Department of Environmental Toxicology, University of California, Davis, California 95616, USA.
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17
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Regulation of cytochrome P4501A by protein kinase C: the role of heat shock protein70. J Cell Commun Signal 2011; 6:37-44. [PMID: 21725659 DOI: 10.1007/s12079-011-0143-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Accepted: 06/20/2011] [Indexed: 10/18/2022] Open
Abstract
Carbofuran is a pesticide, which is used throughout the world as a nematicide and an acaricide. This pesticide integrates into living organisms through aquatic ecosystem. In earlier report, we had demonstrated that cytochrome P4501A was induced in cultured catfish hepatocytes in response to carbofuran, which might be responsible for the detoxification of this pesticide. As the underlying signaling mechanism associated with induction and regulation of cytochrome P4501A has not yet been well defined, we therefore in the present study have investigated to identify the regulatory network of cytochrome P4501A in catfish liver or cultured hepatocytes by targeting several key signaling molecules such as phosphatidyl inositol (PI) or protein kinase C (PKC), which are critical molecules for many important pathways. PKC and heat shock protein70 (HSP70) have been shown to be induced in response to carbofuran in catfish hepatocytes. Results also indicate that induction of CYP1A is modulated by HSP70 and PKC in fish hepatocytes. Thus our data shed light on the regulation of EROD activity, which has been used as a bio-monitoring tool for measuring aquatic pollution.
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18
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Powis M, Celius T, Matthews J. Differential ligand-dependent activation and a role for Y322 in aryl hydrocarbon receptor-mediated regulation of gene expression. Biochem Biophys Res Commun 2011; 410:859-65. [PMID: 21703235 DOI: 10.1016/j.bbrc.2011.06.079] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 06/09/2011] [Indexed: 01/23/2023]
Abstract
The aryl hydrocarbon receptor (AHR) mediates the toxic effects of halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PeCDF) and 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF). Non-traditional activators, including omeprazole (Omp), are thought to regulate AHR action through phosphorylation rather than binding to the receptor. In this study, we examined the ability of these compounds to induce AHR-dependent regulation of cytochrome P450 1A1 (CYP1A1) and CYP1B1 in T-47D human breast cancer cells. The role of Y322, a residue implicated in Omp-dependent activation of AHR was also investigated. All four compounds induced CYP1A1 and CYP1B1 mRNA expression, with Omp differing from the HAHs. Chromatin immunoprecipitation assays revealed ligand- and gene-selectivity in the recruitment patterns of AHR coactivators. We also found that residue Y322 of human AHR was important for maximum activation of AHR by 2,3,7,8-TCDD and 2,3,4,7,8-PeCDF, but required for 2,3,7,8-TCDF and Omp in an AHR-deficient MCF-7 human breast cancer cell line. In summary, this study provides evidence for context- and ligand-selective differences in coactivator recruitment in AHR-regulated gene expression and reveal an important role of Y322 in AHR activation.
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Affiliation(s)
- Melanie Powis
- Department of Pharmacology and Toxicology, Medical Sciences Building, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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19
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Baston DS, Denison MS. Considerations for potency equivalent calculations in the Ah receptor-based CALUX bioassay: normalization of superinduction results for improved sample potency estimation. Talanta 2011; 83:1415-21. [PMID: 21238730 PMCID: PMC3036574 DOI: 10.1016/j.talanta.2010.11.035] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 11/11/2010] [Accepted: 11/12/2010] [Indexed: 10/18/2022]
Abstract
The chemically activated luciferase expression (CALUX) system is a mechanistically based recombinant luciferase reporter gene cell bioassay used in combination with chemical extraction and clean-up methods for the detection and relative quantitation of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxin-like halogenated aromatic hydrocarbons in a wide variety of sample matrices. While sample extracts containing complex mixtures of chemicals can produce a variety of distinct concentration-dependent luciferase induction responses in CALUX cells, these effects are produced through a common mechanism of action (i.e. the Ah receptor (AhR)) allowing normalization of results and sample potency determination. Here we describe the diversity in CALUX response to PCDD/Fs from sediment and soil extracts and not only report the occurrence of superinduction of the CALUX bioassay, but we describe a mechanistically based approach for normalization of superinduction data that results in a more accurate estimation of the relative potency of such sample extracts.
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Affiliation(s)
- David S. Baston
- Department of Environmental Toxicology, University of California, Davis, CA 95616, USA
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California, Davis, CA 95616, USA
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20
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Abel J, Haarmann-Stemmann T. An introduction to the molecular basics of aryl hydrocarbon receptor biology. Biol Chem 2011; 391:1235-48. [PMID: 20868221 DOI: 10.1515/bc.2010.128] [Citation(s) in RCA: 208] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Depending on their chemical structure and properties, environmental chemicals and other xenobiotics that enter the cell can affect cellular function by either nonselective binding to cellular macromolecules or by interference with cellular receptors, which would initiate a more defined cell biological response. One of these intracellular chemosensor molecules is the aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family that is known to mediate the biochemical and toxic effects of dioxins, polyaromatic hydrocarbons and related compounds. Numerous investigations have revealed that the AhR is not only a master regulator of drug metabolism activated by anthropogenic chemicals, but is also triggered by natural and endogenous ligands and can influence cell biological endpoints such as growth and differentiation. Cutting-edge research has identified new intriguing functions of the AhR, such as during proteasomal degradation of steroid hormone receptors, the cellular UVB stress response and the differentiation of certain T-cell subsets. In this review we provide both a survey of the fundamental basics of AhR biology and an insight into new functional aspects of AhR signaling to further stimulate research on this intriguing transcription factor at the interface between toxicology, cell biology and immunology.
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Affiliation(s)
- Josef Abel
- Institut für Umweltmedizinische Forschung (IUF) an der Heinrich-Heine-Universität Düsseldorf gGmbH, Auf'm Hennekamp 50, Düsseldorf, Germany
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21
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Niestroy J, Barbara A, Herbst K, Rode S, van Liempt M, Roos PH. Single and concerted effects of benzo[a]pyrene and flavonoids on the AhR and Nrf2-pathway in the human colon carcinoma cell line Caco-2. Toxicol In Vitro 2011; 25:671-83. [PMID: 21256954 DOI: 10.1016/j.tiv.2011.01.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Revised: 01/10/2011] [Accepted: 01/11/2011] [Indexed: 01/07/2023]
Abstract
As phytochemicals have the potential to counteract adverse effects of carcinogens we investigated the influence of the flavonoids quercetin and kaempferol on benzo[a]pyrene (BaP) mediated effects on human colon cancer cells, Caco-2. We focused on concerted effects on the expression of AhR and Nrf2 pathway components. In contrast to kaempferol, BaP and quercetin efficiently induced CYP1A1, CYP1A2 and CYP1B1-mRNA in Caco-2 cells. BaP not only acted via AhR activation but sustainably also by increasing AhR and by down-regulating AhRR mRNA. The flavonoids did not affect AhR expression but counteracted the BaP mediated AhRR repression. Only quercetin was found to induce AhRR mRNA. ARNT mRNA appeared to be slightly but significantly down-regulated by BaP as well as by flavonoids while expression of AIP was not or only slightly modulated. The Nrf2 pathway was activated by BaP and by the flavonoids shown by induction of Nrf2 and several of its target genes such as NQO1, GSTP1, GSTA1 and GCLC. Induction effects of 10 μm BaP on Nrf2, GSTP1 and NQO1 were abolished by the flavonoids. In summary, we show that quercetin supports AhR mediated effects. Both flavonoids, however, may counteract the effects of BaP on expression of AhR, AhRR, Nrf2, GSTP1 and NQO1. In conclusion, quercetin appears to have two faces, a flavonoid-like one and a PAH-like one which supports Ahr-mediated effects while kaempferol acts "just like a flavonoid". Thus, flavonoids have to be treated individually with respect to their anti-adverse activity.
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Affiliation(s)
- Jeanette Niestroy
- Leibniz Research Centre for Working Environment and Human Factors, D-44139 Dortmund, Germany
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22
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Enhancing the response of CALUX and CAFLUX cell bioassays for quantitative detection of dioxin-like compounds. Sci China Chem 2010; 53:1010-1016. [PMID: 21394221 DOI: 10.1007/s11426-010-0142-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Reporter genes produce a protein product in transfected cells that can be easily measured in intact or lysed cells and they have been extensively used in numerous basic and applied research applications. Over the past 10 years, reporter gene assays have been widely accepted and used for analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxin-like compounds in various types of matrices, such as biological, environmental, food and feed samples, given that high-resolution instrumental analysis techniques are impractical for large-scale screening analysis. The most sensitive cell-based reporter gene bioassay systems developed are the mechanism-based CALUX (Chemically Activated Luciferase Expression) and CAFLUX (Chemically Activated Fluorescent Expression) bioassays, which utilize recombinant cell lines containing stably transfected dioxin (AhR)-responsive firefly luciferase or enhanced green fluorescent protein (EGFP) reporter genes, respectively. While the current CALUX and CAFLUX bioassays are very sensitive, increasing their lower limit of sensitivity, magnitude of response and dynamic range for chemical detection would significantly increase their utility, particularly for those samples that contain low levels of dioxin-like HAHs (i.e., serum). In this study, we report that the addition of modulators of cell signaling pathways or modification of cell culture conditions results in significant improvement in the magnitude and overall responsiveness of the existing CALUX and CAFLUX cell bioassays.
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23
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Fernandez-Salguero PM. A remarkable new target gene for the dioxin receptor: The Vav3 proto-oncogene links AhR to adhesion and migration. Cell Adh Migr 2010; 4:172-5. [PMID: 20190565 DOI: 10.4161/cam.4.2.10387] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The dioxin receptor (AhR) is possibly the best characterized xenobiotic receptor because of its essential role in mediating the harmful effects of highly toxic environmental pollutants. Despite the fact that AhR-dependent toxicity is a major environmental concern, compelling evidence has recently been produced unveiling novel and remarkable endogenous functions of AhR in cell physiology and tissue homeostasis. Adding to its role in cell proliferation and differentiation, AhR is also involved in the control of cell adhesion and migration, both highly relevant tasks in development and in disease states such as cancer. Interestingly, the effect of AhR on cell migration is cell-type specific because it can sustain or slow down cell motility. Here, I will comment on our recent report showing that AhR is a positive regulator of fibroblast cells migration. Besides characterizing the phenotype of such mesenchymal cells, the most important single finding of our study is that AhR uses the cytoskeleton regulator and oncogen Vav3 to signal through small Rho GTPases, ultimately leading to the physiological control of cell adhesion and migration. These data reveal that AhR activity is required to maintain signaling pathways governing normal cell function and open the question of whether AhR plays a role in cell migration during development and in pathological conditions such as tumor metastasis.
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Affiliation(s)
- Pedro M Fernandez-Salguero
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
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24
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Deb S, Bandiera SM. Characterization and expression of extrahepatic CYP2S1. Expert Opin Drug Metab Toxicol 2010; 5:367-80. [PMID: 19368491 DOI: 10.1517/17425250902865586] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND About one-third of the CYP enzymes identified so far, including several novel CYP enzymes such as CYP2S1, CYP2U1 and CYP2W1, belong to the CYP2 family. As with other recently discovered CYP enzymes, detailed information about the catalytic activity and function of CYP2S1 is lacking. OBJECTIVE To review and compare the expression of CYP2S1 mRNA and protein in humans, mice and rats, and to critically examine evidence pertaining to CYP2S1 regulation and its catalytic activity. METHODS Information about mouse and human CYP2S1 was summarized from published reports. Data about rat CYP2S1 expression was taken from recent work by the authors. RESULTS/CONCLUSIONS CYP2S1 shares molecular characteristics of both CYP1 and CYP2 family enzymes but shows a unique tissue profile of expression. Further studies are needed to identify selective substrates and to measure CYP2S1 protein levels before the role of CYP2S1 in xenobiotic metabolism and its relevance to physiological pathways and disease states can be determined.
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Affiliation(s)
- Subrata Deb
- University of British Columbia, Faculty of Pharmaceutical Sciences, 2146 East Mall, Vancouver, British Columbia, V6T 1Z3, Canada
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25
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Deb S, Bandiera SM. Characterization of a new cytochrome P450 enzyme, CYP2S1, in rats: its regulation by aryl hydrocarbon receptor agonists. Toxicology 2009; 267:91-8. [PMID: 19883719 DOI: 10.1016/j.tox.2009.10.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 10/19/2009] [Accepted: 10/21/2009] [Indexed: 11/26/2022]
Abstract
In the present study, we examined the expression of CYP2S1 mRNA and protein in tissues from male and female rats and investigated aryl hydrocarbon receptor (AhR)-mediated regulation. CYP2S1 mRNA was detected by RT-PCR in all rat tissues examined, except for the adrenal gland, and no sex-dependent differences were observed. To study the regulation of CYP2S1 mRNA expression by AhR agonists, rats were treated with 3-methylcholanthrene (3-MC; 25mg/kg/dayx3 days) or with a single intraperitoneal injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at various dosages (0, 1, 5, 10, 50, 100mug/kg). CYP2S1 mRNA levels were increased in lung, stomach, jejunum and ileum following treatment with 3-MC and in lung, liver and kidney tissues following treatment with TCDD. Induction of CYP2S1 mRNA was greater with TCDD than 3-MC treatment and was more pronounced in lung than other tissues. Antiserum raised against a peptide corresponding to the C-terminus of CYP2S1 was used to measure relative CYP2S1 protein expression by immunoblot analysis. An immunoreactive CYP2S1 protein band with an approximate molecular weight of 50kDa was detected in microsomes of rat lung, stomach and kidney, but not other tissues. Unlike CYP2S1 mRNA, CYP2S1 protein levels were not increased after treatment with 3-MC or the highest dosage of TCDD, indicating that CYP2S1 protein expression was less sensitive than mRNA expression to AhR-mediated regulation. Our study is the first to characterize CYP2S1 mRNA and protein expression in rats, and from the results obtained, we conclude that AhR is involved in the transcriptional regulation of CYP2S1 in rats.
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Affiliation(s)
- Subrata Deb
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T1Z3
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26
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Ascorbic acid suppresses the 2,3,7,8-tetrachloridibenxo-p-dioxin (TCDD)-induced CYP1A1 expression in human HepG2 cells. Toxicol In Vitro 2009; 23:622-6. [DOI: 10.1016/j.tiv.2009.02.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 02/02/2009] [Accepted: 02/22/2009] [Indexed: 11/18/2022]
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27
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Bekki K, Takigami H, Suzuki G, Tang N, Hayakawa K. Evaluation of Toxic Activities of Polycyclic Aromatic Hydrocarbon Derivatives Using In Vitro Bioassays. ACTA ACUST UNITED AC 2009. [DOI: 10.1248/jhs.55.601] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Kanae Bekki
- Graduate School of Natural Science and Technology, Kanazawa University
- Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies
| | - Hidetaka Takigami
- Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies
| | - Go Suzuki
- Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies
- Center for Marine Environmental Studies, Ehime University
| | - Ning Tang
- Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University
| | - Kazuichi Hayakawa
- Graduate School of Natural Science and Technology, Kanazawa University
- Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University
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28
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Ma C, Marlowe JL, Puga A. The aryl hydrocarbon receptor at the crossroads of multiple signaling pathways. EXS 2009; 99:231-57. [PMID: 19157064 DOI: 10.1007/978-3-7643-8336-7_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The aryl hydrocarbon receptor (AHR) has long been recognized as a ligand-activated transcription factor responsible for the induction of drug-metabolizing enzymes. Its role in the combinatorial matrix of cell functions was established long before the first report of an AHR cDNA sequence was published. It is only recently that other functions of this protein have begun to be recognized, and it is now clear that the AHR also functions in pathways outside of its well-characterized role in xenobiotic enzyme induction. Perturbation of these pathways by xenobiotic ligands may ultimately explain much of the toxicity of these compounds. This chapter focuses on the interactions of the AHR in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, differentiation and apoptosis. Ultimately, the effect of a particular AHR ligand on the biology of the organism will depend on the milieu of critical pathways and proteins expressed in specific cells and tissues with which the AHR itself interacts.
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Affiliation(s)
- Ci Ma
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45220, USA.
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Oesch-Bartlomowicz B, Oesch F. Role of cAMP in mediating AHR signaling. Biochem Pharmacol 2008; 77:627-41. [PMID: 19013136 DOI: 10.1016/j.bcp.2008.10.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 10/11/2008] [Accepted: 10/13/2008] [Indexed: 01/30/2023]
Abstract
Regulation of the nuclear import of many transcription factors represents a step in gene regulation which is crucial for a number of cellular processes. The aryl hydrocarbon receptor (AHR), a basic helix-loop-helix protein of the PAS (PER-ARNT-SIM) family of transcriptional regulators is a cytosol-associated and ligand-activated receptor. The environmental toxin dioxin binds with high affinity to AHR rendering it nuclear and leading to the activation of AHR sensitive genes. However, the fact, that the AHR mediates a large variety of physiological events without the involvement of any known exogenous ligand, including liver and vascular system development, maturation of the immune system, regulation of genes involved in cellular growth, cell differentiation and circadian rhythm, speaks for an important role of AHR in cell biology independent of the presence of an exogenous ligand. Different approaches were applied to study mechanism(s) which render AHR nuclear and design its function in absence of exogenous ligands. We found that AHR is sensitive to cAMP signaling mediated by cAMP-dependent protein kinase (PKA) which fundamentally differs from AHR signaling mediated by the exogenous ligand dioxin. It has been shown that PKA mediated signaling can be confined by compartmentalization of signaling components in microdomains conferring specificity to signaling by the ubiquitous second messenger cAMP. Moreover, A-kinase-anchoring proteins (AKAPs) and newly discovered cAMP receptors, Epac (exchange protein directly activated by cAMP), may give us a further chance to enter into new dimensions of cAMP signal transmissions that potentially may bring us closer to AHR physiology.
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Ashida H, Nishiumi S, Fukuda I. An update on the dietary ligands of the AhR. Expert Opin Drug Metab Toxicol 2008; 4:1429-47. [DOI: 10.1517/17425255.4.11.1429] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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31
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Puga A, Ma C, Marlowe JL. The aryl hydrocarbon receptor cross-talks with multiple signal transduction pathways. Biochem Pharmacol 2008; 77:713-22. [PMID: 18817753 DOI: 10.1016/j.bcp.2008.08.031] [Citation(s) in RCA: 288] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 08/20/2008] [Accepted: 08/21/2008] [Indexed: 12/13/2022]
Abstract
Exposure to toxic polycyclic aromatic hydrocarbons raises a number of toxic and carcinogenic responses in experimental animals and humans mediated for the most part by the aryl hydrocarbon -- or dioxin -- receptor (AHR). The AHR is a ligand-activated transcription factor whose central role in the induction of drug-metabolizing enzymes has long been recognized. For quite some time now, it has become clear that the AHR also functions in pathways outside of its role in detoxification and that perturbation of these pathways by xenobiotic ligands may be an important part of the toxicity of these compounds. AHR activation by some of its ligands participates among others in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, immediate-early gene induction, cross-talk within the RB/E2F axis and mobilization of crucial calcium stores. Ultimately, the effect of a particular AHR ligand may depend as much on the adaptive interactions that it established with pathways and proteins expressed in a specific cell or tissue as on the toxic responses that it raises.
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Affiliation(s)
- Alvaro Puga
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45220, USA.
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32
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Hollingshead BD, Beischlag TV, Dinatale BC, Ramadoss P, Perdew GH. Inflammatory signaling and aryl hydrocarbon receptor mediate synergistic induction of interleukin 6 in MCF-7 cells. Cancer Res 2008; 68:3609-17. [PMID: 18483242 DOI: 10.1158/0008-5472.can-07-6168] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The pleiotropic cytokine interleukin 6 (IL-6) is involved in immune cell homeostasis. Additionally, IL-6 expression and signaling in tumor cells have been shown to elicit both protumor and antitumor properties. There is a plethora of mechanistic knowledge regarding how IL-6 signal transduction translates to biological responses. However, there is little understanding as to what factors control IL-6 expression within a tumor cell environment. The studies presented herein show that, in MCF-7 breast and ECC-1 endocervical cancer cells, the stimulation of aryl hydrocarbon receptor (AHR) activity, in combination with IL-1beta or phorbol 12-myristate 13-acetate (PMA) treatment, results in a marked synergistic induction of IL-6 levels over what is seen without AHR activation. Chromatin immunoprecipitation experiments suggest that the regulation of IL-6 mRNA expression occurs at the chromatin level, as AHR presence on the IL-6 promoter was observed in response to treatment with AHR ligand. Synergistic induction of IL-6 expression was sustained for 72 hours, with accumulation of IL-6 protein reaching levels 4.8-fold above IL-1beta treatment alone. In addition, transcriptional regulation of the prototypic AHR responsive gene Cyp1a1 was negatively regulated by PMA and IL-1beta treatment. Silencing of RELA expression alleviated IL-1beta-mediated repression of AHR transcriptional activity, whereas PMA-mediated repression was maintained. Additionally, small interfering RNA studies reveal that AHR and RELA are necessary for synergistic induction of IL-6. The findings presented here reveal the AHR as a potential therapeutic target for selective modulation of IL-6 expression in some tumor cell types. The data also suggest a possible previously unrecognized mechanism of AHR-mediated tumor promotion.
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Affiliation(s)
- Brett D Hollingshead
- Department of Veterinary and Biomedical Sciences and Center for Molecular Toxicology and Carcinogenesis, Pennsylvania State University, University Park, Pennsylvania, USA
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Pharmacologic profiling of human and rat cytochrome P450 1A1 and 1A2 induction and competition. Arch Toxicol 2008; 82:909-21. [DOI: 10.1007/s00204-008-0317-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Accepted: 05/06/2008] [Indexed: 01/06/2023]
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34
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Hwang YP, Han EH, Choi JH, Kim HG, Lee KJ, Jeong TC, Lee ES, Jeong HG. Chemopreventive effects of Furan-2-yl-3-pyridin-2-yl-propenone against 7,12-dimethylbenz[a]anthracene-inducible genotoxicity. Toxicol Appl Pharmacol 2008; 228:343-50. [DOI: 10.1016/j.taap.2007.12.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 12/13/2007] [Accepted: 12/14/2007] [Indexed: 10/22/2022]
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35
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Bohonowych JES, Zhao B, Timme-Laragy A, Jung D, Di Giulio RT, Denison MS. Newspapers and newspaper ink contain agonists for the ah receptor. Toxicol Sci 2008; 102:278-90. [PMID: 18203687 PMCID: PMC2855230 DOI: 10.1093/toxsci/kfn011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Ligand-dependent activation of the aryl hydrocarbon receptor (AhR) pathway leads to a diverse array of biological and toxicological effects. The best-studied ligands for the AhR include polycyclic and halogenated aromatic hydrocarbons, the most potent of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, as new AhR ligands are identified and characterized, their structural and physiochemical diversity continues to expand. Our identification of AhR agonists in crude extracts from diverse materials raises questions as to the magnitude and extent of human exposure to AhR ligands through normal daily activities. We have found that solvent extracts of newspapers from countries around the world stimulate the AhR signaling pathway. AhR agonist activity was observed for dimethyl sulfoxide (DMSO), ethanol, and water extracts of printed newspaper, unprinted virgin paper, and black printing ink, where activation of luciferase reporter gene expression was transient, suggesting that the AhR active chemical(s) was metabolically labile. DMSO and ethanol extracts also stimulated AhR transformation and DNA binding, and also competed with [(3)H]TCDD for binding to the AhR. In addition, DMSO extracts of printed newspaper induced cytochrome P450 1A associated 7-ethoxyresorufin-O-deethylase activity in zebrafish embryos in vivo. Although the responsible bioactive chemical(s) remain to be identified, our results demonstrate that newspapers and printing ink contain relatively potent metabolically labile agonists of the AhR. Given the large amount of recycling and reprocessing of newspapers throughout the world, release of these easily extractable AhR agonists into the environment should be examined and their potential effects on aquatic organisms assessed.
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Affiliation(s)
- Jessica E S Bohonowych
- Department of Environmental Toxicology, University of California, Davis, California 95616, USA
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36
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Erichsen TJ, Ehmer U, Kalthoff S, Lankisch TO, Müller TM, Munzel PA, Manns MP, Strassburg CP. Genetic variability of aryl hydrocarbon receptor (AhR)-mediated regulation of the human UDP glucuronosyltransferase (UGT) 1A4 gene. Toxicol Appl Pharmacol 2008; 230:252-60. [PMID: 18433817 DOI: 10.1016/j.taap.2008.02.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2007] [Revised: 02/13/2008] [Accepted: 02/21/2008] [Indexed: 10/22/2022]
Abstract
UDP glucuronosyltransferases (UGTs) play an important role for drug detoxification and toxicity. UGT function is genetically modulated by single nucleotide polymorphisms (SNPs) which lead to the expression of functionally altered protein, or altered expression levels. UGT1A4 activity includes anticonvulsants, antidepressants and environmental mutagens. In this study the induction of the human UGT1A4 gene and a potential influence of genetic variation in its promoter region were analyzed. SNPs at bp -219 and -163 occurred in 9% among 109 blood donors reducing UGT1A4 transcription by 40%. UGT1A4 transcription was dioxin inducible. Reporter gene experiments identified 2 xenobiotic response elements (XRE), which were functionally confirmed by mutagenesis analyses, and binding was demonstrated by electromobility shift assays. Constitutive human UGT1A4 gene expression and induction was aryl hydrocarbon receptor (AhR)-dependent, and reduced in the presence of SNPs at bp -219 and -163. AhR-mediated regulation of the human UGT1A4 gene by two XRE and a modulation by naturally occurring genetic variability by SNPs is demonstrated, which indicates gene-environment interaction with potential relevance for drug metabolism.
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Affiliation(s)
- Thomas J Erichsen
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover, Medical School, Hannover, Germany
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37
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Dioxin-mediated tumor progression through activation of mitochondria-to-nucleus stress signaling. Proc Natl Acad Sci U S A 2008; 105:186-91. [PMID: 18172213 DOI: 10.1073/pnas.0706183104] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The environmental toxin 2,3,7,8-tetrachlorodibenzodioxin (TCDD) is a known human carcinogen; however, its precise mechanism of action remains unclear. Here we show that TCDD induces mitochondrial dysfunction, stress signaling, and tumor invasion by a mechanism similar to that described for mtDNA-depleted cells. Treatment of C2C12 cells with TCDD disrupted mitochondrial transmembrane potential in a time-dependent fashion and inhibited mitochondrial transcription and translation. TCDD also increased cytosolic [Ca(2+)](c) and RyR1-specific Ca(2+) release. These changes were associated with increased calcineurin (CnA) levels and activation of CnA-sensitive NF-kappaB/Rel (IkappaBbeta-dependent) factors. Cells treated with TCDD displayed resistance to apoptosis, increased expression of the tumor marker cathepsin L, and a high degree of invasiveness as tested by the Matrigel membrane invasion assay. These effects were reversed by the CnA inhibitor FK506, and CnA mRNA silencing suggesting that TCDD triggers a signaling pathway similar to mtDNA depletion. Taken together, these results reveal that TCDD may promote tumor progression in vivo by directly targeting mitochondrial transcription and induction of mitochondrial stress signaling.
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38
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Furness SGB, Lees MJ, Whitelaw ML. The dioxin (aryl hydrocarbon) receptor as a model for adaptive responses of bHLH/PAS transcription factors. FEBS Lett 2007; 581:3616-25. [PMID: 17459381 DOI: 10.1016/j.febslet.2007.04.011] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 04/03/2007] [Accepted: 04/04/2007] [Indexed: 11/19/2022]
Abstract
This review examines the common theme of adaptive responses of bHLH/PAS proteins, using the dioxin receptor as a prototype. The bHLH/PAS family of transcriptional regulators are a group of key developmental and environmental stress sensing proteins. They employ a variety of post-translational control mechanisms to regulate their transcriptional output. Amongst this family, the dioxin receptor is best known for its ability to elicit toxic responses to dioxin and dioxin like chemicals even though it mediates more benign adaptive responses to non-toxic xenobiotics. We discuss what is known about dioxin receptor physiology, both adaptive and inherent, along with its molecular regulation and put this into the context of the wider bHLH/PAS family. We also raise the issue of its toxic responses, in particular the idea that it is the dysregulation of its poorly characterised housekeeping functions that leads to these outcomes.
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Affiliation(s)
- Sebastian G B Furness
- Drug Discovery Laboratory, Department of Pharmacology, Building 13E, Monash University, Wellington Road, Clayton, Victoria 3800, Australia.
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39
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Hu W, Sorrentino C, Denison MS, Kolaja K, Fielden MR. Induction of Cyp1a1 Is a Nonspecific Biomarker of Aryl Hydrocarbon Receptor Activation: Results of Large Scale Screening of Pharmaceuticals and Toxicants in Vivo and in Vitro. Mol Pharmacol 2007; 71:1475-86. [PMID: 17327465 DOI: 10.1124/mol.106.032748] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Expression of Cyp1a1 and its related enzyme activity have long been used as a biomarker for aryl hydrocarbon receptor (AhR) activation and a warning of dioxin-like toxicity. As a result, induction of Cyp1a1 by pharmaceutical drug candidates or environmental contaminants raises significant concern in risk assessment. The current study evaluates the specificity of Cyp1a1 induction as a marker for AhR affinity and activation and provides context to assess the relevancy of AhR activation to risk assessment. In vivo experiments examined the expression of Cyp1a1 and other AhR-regulated genes in liver, kidney, and heart in response to 596 compounds. From this data set, a subset of 147 compounds was then evaluated for their ability to activate or bind to the AhR using a combination of gel shift, reporter gene, and competitive receptor binding assays. Whereas in vivo Cyp1a1 mRNA expression is a sensitive marker for AhR activation, it lacks specificity, because 81 (59%) of 137 compounds were found to significantly induce Cyp1a1 in vivo but were not verified to bind or activate the AhR in vitro. Combining in vivo and in vitro findings, we identified nine AhR agonists, six of which are marketed therapeutics and have been approved by the U.S. Food and Drug Administration, including leflunomide, flutamide, and nimodipine. These drugs do not produce dioxin-like toxicity in rats or in humans. These data demonstrate that induction of Cyp1a1 is a nonspecific biomarker of direct AhR affinity and activation and lend further support to the hypothesis that Cyp1a1 induction and/or AhR activation is not synonymous with dioxin-like toxicity.
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Affiliation(s)
- Wenyue Hu
- Iconix Biosciences, Inc., 325 E. Middlefield Road, Mountain View, CA 94043, USA
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40
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Han EH, Hwang YP, Jeong TC, Lee SS, Shin JG, Jeong HG. Eugenol inhibit 7,12-dimethylbenz[a]anthracene-induced genotoxicity in MCF-7 cells: Bifunctional effects on CYP1 and NAD(P)H:quinone oxidoreductase. FEBS Lett 2007; 581:749-56. [PMID: 17275817 DOI: 10.1016/j.febslet.2007.01.044] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Revised: 01/16/2007] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
Typically, chemopreventive agents either inhibit the cytochrome P450s (CYPs) that are essential for the metabolism of carcinogens or induce phase II detoxifying enzymes. This study examined the chemopreventive effect of eugenol on 7,12-dimethylbenz[a]anthracene (DMBA)-induced DNA damage in MCF-7 cells. Eugenol inhibited the formation of the DMBA-DNA adduct in a dose dependent manner. CYP1A1 and CYP1B1 activity, which catalyze the biotransformation of DMBA, were strongly inhibited by eugenol. Eugenol also suppressed the CYP1A induction by DMBA through decreased aryl hydrocarbon receptor activation and subsequent DNA binding. Furthermore, eugenol increased the expression and activity of NAD(P)H:quinone oxidoreductase (QR), a major detoxifying enzyme for DMBA, through NF-E2 related factor2 binding to antioxidant response element in QR gene. Therefore, eugenol has a potent protective effect against DMBA-induced genotoxicity, presumably through the suppression of the DMBA activation and the induction of its detoxification. These results suggest that eugenol has potential as a chemopreventive.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/analogs & derivatives
- 9,10-Dimethyl-1,2-benzanthracene/toxicity
- Aryl Hydrocarbon Hydroxylases/genetics
- Aryl Hydrocarbon Hydroxylases/metabolism
- Cell Line, Tumor
- Cytochrome P-450 CYP1A1/genetics
- Cytochrome P-450 CYP1A1/metabolism
- Cytochrome P-450 CYP1B1
- DNA Adducts/drug effects
- DNA Damage
- Eugenol/pharmacology
- Gene Expression Regulation, Enzymologic/drug effects
- Gene Expression Regulation, Neoplastic/drug effects
- Humans
- Microsomes/drug effects
- Microsomes/enzymology
- NAD(P)H Dehydrogenase (Quinone)/metabolism
- NF-E2-Related Factor 2/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Aryl Hydrocarbon/genetics
- Regulatory Sequences, Nucleic Acid/drug effects
- Transcriptional Activation/drug effects
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Affiliation(s)
- Eun Hee Han
- BK21 Project Team, Department of Pharmacy, College of Pharmacy, Research Center for Proteineous Materials, Chosun University, 375 Seosuk-dong, Kwangju 501-759, South Korea
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41
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Fukumori S, Murata T, Taguchi M, Hashimoto Y. Rapid and Drastic Induction of CYP3A4 mRNA Expression via Vitamin D Receptor in Human Intestinal LS180 Cells. Drug Metab Pharmacokinet 2007; 22:377-81. [DOI: 10.2133/dmpk.22.377] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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42
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Operaña TN, Nguyen N, Chen S, Beaton D, Tukey RH. Human CYP1A1GFP Expression in Transgenic Mice Serves as a Biomarker for Environmental Toxicant Exposure. Toxicol Sci 2006; 95:98-107. [PMID: 17065433 DOI: 10.1093/toxsci/kfl144] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The human CYP1A1 gene is regulated by the aryl hydrocarbon receptor (AhR), and induction of CYP1A1 is known to play an important role in xenobiotic metabolism. To examine the regulation of human CYP1A1 in vivo, we created a transgenic mouse strain (Tg-CYP1A1(GFP)) expressing a chimeric gene consisting of the entire human CYP1A1 gene (15 kb) fused with a GFP reporter gene. The treatment of Tg-CYP1A1(GFP) mice with a single intraperitoneal dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or benzo[a]pyrene (B[a]P) led to the induction of CYP1A1(GFP) in both the liver and the lung as determined by fluorescence and Western blot analysis. The localization of induced fluorescence in liver also demonstrated the usefulness of cultured hepatocytes in examining the actions of AhR agonists toward induction of CYP1A1(GFP). Other routes of B[a]P administration, such as by oral exposure at 100 mg/kg for 3 days, led to reduced induction of CYP1A1(GFP) in liver and lung. In liver, expression of CYP1A1(GFP) was a sensitive marker for oral exposure, while mouse CYP1A1 was not induced at these doses. While first pass metabolism of B[a]P in the gastrointestinal tract reduces the potential of the AhR to induce CYP1A1(GFP) in the liver, adequate concentrations reach the hepatic circulation as demonstrated by induction of human UGT1A proteins in transgenic mice that express the human UGT1 locus. The capability to identify fluorescently labeled CYP1A1 in vivo provides a sensitive measurement of gene response and links exposure to potential environmental toxicants and activation of the AhR.
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Affiliation(s)
- Theresa N Operaña
- Laboratory of Environmental Toxicology, Departments of Chemistry and Biochemistry and Pharmacology, University of California, San Diego, La Jolla, California 92093-0722, USA
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43
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Han EH, Kim JY, Jeong HG. Effect of biochanin A on the aryl hydrocarbon receptor and cytochrome P450 1A1 in MCF-7 human breast carcinoma cells. Arch Pharm Res 2006; 29:570-6. [PMID: 16903077 DOI: 10.1007/bf02969267] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Phytoestrogen biochanin A is an isoflavone derivative isolated from red clover Trifolium pratense with anticarcinogenic properties. This study examined the action of biochanin A with the carcinogen activation pathway that is mediated by the aryl hydrocarbon receptor (AhR) in MCF-7 breast carcinoma cells. Treating the cells with biochanin A alone caused the accumulation of CYP1A1 mRNA and an increase in CYP1A1-specific 7-ethoxyresorufin O-deethylase (EROD) activity in a dose dependent manner. A concomitant treatment with 7,12-dimethylbenz[a]anthracene (DMBA) and biochanin A markedly reduced the DMBA-inducible EROD activity and CYP1A1 mRNA level. In addition, the biochanin A treatment alone activated the DNA-binding capacity of the AhR for the dioxin-response element (DRE) of CYP1A1, as measured by the electrophoretic-mobility shift assay (EMSA). EMSA revealed that biochanin A reduced the level of the DMBA-inducible AhR-DRE binding complex. Furthermore, biochanin A competed with the prototypical AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), for binding to the AhR in an isolated rat cytosol. The biochanin A competitively inhibited the metabolic activation of DMBA, as measured by the formation of the DMBA-DNA adducts. These results suggest that biochanin A may thus be a natural ligand to bind on AhR. Therefore, biochanin A may be due to act an antagonist/agonist of the AhR pathway.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/metabolism
- 9,10-Dimethyl-1,2-benzanthracene/pharmacology
- Animals
- Antineoplastic Agents, Phytogenic/metabolism
- Antineoplastic Agents, Phytogenic/pharmacology
- Binding, Competitive
- Breast Neoplasms/enzymology
- Breast Neoplasms/genetics
- Carcinogens/metabolism
- Carcinogens/pharmacology
- Cell Line, Tumor
- Cytochrome P-450 CYP1A1/antagonists & inhibitors
- Cytochrome P-450 CYP1A1/genetics
- Cytochrome P-450 CYP1A1/metabolism
- DNA/metabolism
- DNA Adducts
- Dose-Response Relationship, Drug
- Gene Expression Regulation, Neoplastic/drug effects
- Genistein/metabolism
- Genistein/pharmacology
- Humans
- Liver/drug effects
- Liver/metabolism
- Male
- Oxazines/metabolism
- Polychlorinated Dibenzodioxins/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Aryl Hydrocarbon/drug effects
- Receptors, Aryl Hydrocarbon/metabolism
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Affiliation(s)
- Eun Hee Han
- Department of Pharmacy, College of Pharmacy, Research Center for Proteineous Materials, Chosun University, Kwangju, Korea
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44
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Petersen SL, Krishnan S, Hudgens ED. The aryl hydrocarbon receptor pathway and sexual differentiation of neuroendocrine functions. Endocrinology 2006; 147:S33-42. [PMID: 16690800 DOI: 10.1210/en.2005-1157] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Historically, much of the research on health effects of environmental pollutants focused on ascertaining whether compounds were carcinogenic. More recent findings show that environmental contaminants also exert insidious effects by disrupting hormone action. Of particular concern are findings that developmental exposure to dioxins, chemicals that act through the aryl hydrocarbon receptor pathway, permanently alters sexually differentiated neural functions in animal models. In this review, we focus on mechanisms through which dioxins disrupt neuroendocrine development as exemplified by effects on a brain region critical for ovulation in rodents. We also provide evidence that dysregulation of GABAergic neural development may be a general mechanism underlying a broad spectrum of effects seen after perinatal dioxin exposure.
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Affiliation(s)
- Sandra L Petersen
- Department of Biology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003 USA.
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45
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N'Diaye M, Le Ferrec E, Lagadic-Gossmann D, Corre S, Gilot D, Lecureur V, Monteiro P, Rauch C, Galibert MD, Fardel O. Aryl hydrocarbon receptor- and calcium-dependent induction of the chemokine CCL1 by the environmental contaminant benzo[a]pyrene. J Biol Chem 2006; 281:19906-15. [PMID: 16679317 DOI: 10.1074/jbc.m601192200] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are widely distributed immunotoxic environmental contaminants well known to regulate expression of pro-inflammatory cytokines such as interleukine-1beta and tumor necrosis factor-alpha. In the present study, we demonstrated that the chemokine CCL1, notably involved in cardiovascular diseases and inflammatory or allergic processes, constitutes a new molecular target for PAHs. Indeed, exposure to PAHs such as benzo[a]pyrene (BP) markedly increased mRNA expression and secretion of CCL1 in primary human macrophage cultures. Moreover, intranasal administration of BP to mice enhanced mRNA levels of TCA3, the mouse orthologue of CCL1, in lung. CCL1 induction in cultured human macrophages was fully prevented by targeting the aryl hydrocarbon receptor (AhR) through chemical inhibition or small interfering RNA-mediated down-modulation of its expression. In addition, BP and the potent AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin were found to enhance activity of a CCL1 promoter sequence containing a consensus xenobiotic-responsive element known to specifically interact with AhR. Moreover, 2,3,7,8-tetrachlorodibenzo-p-dioxin triggered AhR binding to this CCL1 promoter element as revealed by chromatin immunoprecipitation experiments and electrophoretic mobility shift assays. In an attempt to further characterize the mechanism of CCL1 induction, we demonstrated that BP was able to induce an early and transient increase of intracellular calcium concentration in human macrophages. Inhibition of this calcium increase, using the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester or the calcium store-operated channel inhibitor 2-aminoethoxydiphenyl borate, fully blocked CCL1 up-regulation. Taken together, these results bring the first demonstration that PAHs induce expression of the chemokine CCL1 in an AhR- and calcium-dependent manner.
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Affiliation(s)
- Monique N'Diaye
- INSERM U620, Unité Mixte de Recherche 6061, Laboratoire de Génétique et Développement, Facultéde Médecine, Université de Rennes 1, IFR140, 35043 Rennes Cedex
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Klein GP, Hodge EM, Diamond ML, Yip A, Dann T, Stern G, Denison MS, Harper PA. Gas-phase ambient air contaminants exhibit significant dioxin-like and estrogen-like activity in vitro. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:697-703. [PMID: 16675423 PMCID: PMC1459922 DOI: 10.1289/ehp.8496] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 12/29/2005] [Indexed: 05/09/2023]
Abstract
Several adverse health effects, such as respiratory and cardiovascular morbidity, have been linked to exposure to particulate matter in ambient air; however, the biologic activity of gas-phase ambient organic air contaminants has not been examined as thoroughly. Using aryl hydrocarbon receptor (AHR)-based and estrogen receptor (ER)-based cell bioassay systems, we assessed the dioxin-like and estrogenic activities of gas-phase organic ambient air contaminants compared with those of particulate-phase contaminants using samples collected between seasons over 2 years from an urban and a rural location in the Greater Toronto Area, Canada. The concentration of the sum (Sigma) of polycyclic aromatic hydrocarbons, which was highest in the gas phase, was 10-100 times more abundant than that of Sigmapolychlorinated biphenyls, Sigmanitro-polycyclic aromatic hydrocarbons, and Sigmaorganochlorine pesticides, and 10(3) to 10(4) times more abundant than Sigmapolychlorinated dibenzo-p-dioxins/dibenzofurans. Gas-phase samples induced significant AHR- and ER-dependent gene expression. The activity of the gas-phase samples was greater than that of the particulate-phase samples in the estrogen assay and, in one case, in the AHR assay. We found no strong associations between either summer or winter seasons or urban or rural locations in the relative efficacy of the extracts in either the ER or AHR assay despite differences in chemical composition, concentrations, and abundance. Our results suggest that mechanistic studies of the health effects of ambient air must consider gas and particulate phases because chemicals present in both phases can affect AHR and ER signaling pathways.
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Affiliation(s)
- Gail P Klein
- Department of Pharmacology, Centre for Urban Health Initiatives, University of Toronto, and Program in Developmental Biology, Hospital for Sick Children, Toronto, Ontario, Canada
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Schreiber TD, Köhle C, Buckler F, Schmohl S, Braeuning A, Schmiechen A, Schwarz M, Münzel PA. REGULATION OFCYP1A1GENE EXPRESSION BY THE ANTIOXIDANTTERT-BUTYLHYDROQUINONE. Drug Metab Dispos 2006; 34:1096-101. [PMID: 16581943 DOI: 10.1124/dmd.106.009662] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CYP1A1, a major phase I enzyme, plays an important role in the metabolism of polycyclic aromatic hydrocarbons and in the chemical activation of xenobiotics to carcinogenic derivatives. The phenolic antioxidant tert-butylhydroquinone (tBHQ), often used as a food preservative, is generally considered to act only as a mono-functional inducer of phase II enzymes, thereby exerting chemo-protection. However, we recently observed that tBHQ elevated the activity of an aryl hydrocarbon receptor (AhR) response element (DRE)-driven luciferase reporter in human colon carcinoma cells (Caco-2). Therefore, we studied the effects of tBHQ on the activity of a DRE-driven reporter, CYP1A1 mRNA expression, and CYP1A enzyme activity in Caco-2 cells and human HepG2 hepatoma cells. We found tBHQ caused induction of reporter activity and CYP1A1 expression and activity in Caco-2 and HepG2 cells. Moreover, tBHQ combined with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increased reporter activity and mRNA expression in Caco-2 cells in an additive manner. By contrast, tBHQ decreased TCDD-mediated induction of reporter activity and CYP1A1 mRNA expression in HepG2 cells. Resveratrol, an AhR antagonist, repressed the induction of CYP1A1 by tBHQ. Cotransfection of HepG2 cells with a dominant negative AhR nuclear translocator mutant abolished the tBHQ-induced CYP1A1 reporter activity. These findings indicate that CYP1A1 may be induced by the antioxidant tBHQ via an AhR-dependent mechanism.
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Affiliation(s)
- Thomas D Schreiber
- Institute of Pharmacology and Toxicology, Department of Toxicology, University of Tübingen, Tübingen, Germany
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Suzuki G, Takigami H, Kushi Y, Sakai SI. Time-course changes of mixture effects on AhR binding-dependent luciferase activity in a crude extract from a compost sample. Toxicol Lett 2006; 161:174-87. [PMID: 16225999 DOI: 10.1016/j.toxlet.2005.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Revised: 09/07/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022]
Abstract
Crude extracts of environmental samples contain stable and labile aryl hydrocarbon receptor (AhR) ligands, and show huge activities in the cell-based bioassay, and these activities are higher than the chemically calculated induction equivalent values. It is thought that not only unidentified AhR ligands but also mixture effect among compounds might contribute to these activities. In the previous work, we have indicated that hydrophobic compounds in household sewage sludge (HSS) compost may interact synergistically with 2,3,7,8-TCDD in the CALUX (DR-CALUX: Dioxin-Responsive Chemical-Activated Luciferase gene eXpression) assay [Suzuki, G., Takigami, H., Kushi, Y., Sakai, S., 2004. Evaluation of mixture effects in a crude extract of compost using the CALUX bioassay and HPLC fractionation. Environ. Int. 30, 1055-1066]. In this study, we focused on co-existing stable compounds such as halogenated aromatic hydrocarbons (HAHs) and labile compounds such as polyaromatic hydrocarbons (PAHs) in the crude extract and investigated the time-course changes of mixture effects among compounds in environmental samples using the CALUX assay and normal-phase high-performance liquid chromatography (NP-HPLC) fractionation. We confirmed that CYP1A-inducing PAHs and HAHs could be separated by NP-HPLC on a nitrophenylpropylsilica (NITRO) column. To determine whether the activities of AhR ligands in environmental samples (including the HSS compost) could be assessed by the additivity theory, we compared the CALUX activity of the crude extract with the arithmetical sum of the activities of all the fractions separated by NP-HPLC. We confirmed a potentiation of CALUX activity at 12-, 24- and 48-h exposure durations. In contrast, CALUX activity increased additively at 6- and 72-h exposure durations. CALUX activity was potentiated when the CALUX activity of the HPLC fractions showed a remarkable reduction resulting in a change of activity profiles. In contrast, additivity was observed at a 72-h exposure duration when the CALUX activity of the HPLC fractions showed neither remarkable reduction nor a change in profile. Our results suggest that differences in the metabolic decomposition of compounds affected mixture effects on CALUX activity in a crude extract from HSS compost.
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Affiliation(s)
- Go Suzuki
- Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
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Zhao B, Baston DS, Hammock B, Denison MS. Interaction of diuron and related substituted phenylureas with the Ah receptor pathway. J Biochem Mol Toxicol 2006; 20:103-13. [PMID: 16788953 PMCID: PMC3032054 DOI: 10.1002/jbt.20126] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates many of the biological and toxicological actions of structurally diverse chemicals, including the ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin. Here, we have examined the ability of diuron, a widely used herbicide, and several structurally related substituted phenylureas to bind to and activate/inhibit the AhR and AhR signal transduction. Diuron induced CYP1A1 mRNA levels in mouse hepatoma (Hepa1c1c7) cells and AhR-dependent luciferase reporter gene expression in stably transfected mouse, rat, guinea pig, and human cell lines. In addition, ligand binding and gel retardation analysis demonstrated the ability of diuron to competitively bind to and stimulate AhR transformation and DNA binding in vitro and in intact cells. Several structurally related substituted phenylureas competitively bound to the guinea pig hepatic cytosolic AhR, inhibited 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced AhR-dependent luciferase reporter gene expression in a species-specific manner and stimulated AhR transformation and DNA binding, consistent with their role as partial AhR agonists. These results demonstrate not only that diuron and related substituted phenylureas are AhR ligands but also that exposure to these chemicals could induce/inhibit AhR-dependent biological effects.
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Affiliation(s)
- Bin Zhao
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
| | - David S. Baston
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
| | - Bruce Hammock
- Department of Entomology, University of California, Davis, CA, USA
- University of California Davis Cancer Center, Sacramento, CA, USA
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
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Li Y, Luu TC, Chan WK. A novel Arnt-interacting protein Ainp2 enhances the aryl hydrocarbon receptor signalling. Arch Biochem Biophys 2005; 441:84-95. [PMID: 16111650 DOI: 10.1016/j.abb.2005.06.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 06/24/2005] [Accepted: 06/29/2005] [Indexed: 11/23/2022]
Abstract
In an effort to better understand the Ah receptor nuclear translocator (Arnt)-dependent signaling mechanisms, we employed a phage display system to identify Arnt-interacting peptides. Human liver cDNA library was utilized to screen for Arnt-interacting peptides using an Arnt construct fused to thioredoxin (TH-ArntCDelta418). Two clones, namely Ainp1 and Ainp2 (Arnt-interacting peptide), were identified and subsequently Ainp2 was further characterized. Ainp2 interacts with TH-ArntCDelta418 in the GST pull-down and mammalian two-hybrid assays. Northern blot results revealed that Ainp2 is predominantly expressed in human liver. The putative full-length Ainp2 cDNA sequence was subsequently cloned using RACE PCR. Endogenous expression of Ainp2 was found in Jurkat cells at the mRNA and protein levels. Results from the transient transfection studies using a DRE-driven reporter plasmid and the real-time QPCR experiments examining the endogenous CYP1A1 expression showed that Ainp2 enhances the 3-methylchloranthrene-induced activity in HepG2 cells, suggesting that Ainp2 plays a role in the Arnt-dependent function
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Affiliation(s)
- Yi Li
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211, USA
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