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Schiering C, Vonk A, Das S, Stockinger B, Wincent E. Cytochrome P4501-inhibiting chemicals amplify aryl hydrocarbon receptor activation and IL-22 production in T helper 17 cells. Biochem Pharmacol 2018; 151:47-58. [PMID: 29501585 DOI: 10.1016/j.bcp.2018.02.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 02/23/2018] [Indexed: 02/07/2023]
Abstract
The aryl hydrocarbon receptor (AHR) controls interleukin 22 production by T helper 17 cells (Th17). IL-22 contributes to intestinal homeostasis but has also been implicated in chronic inflammatory disorders and colorectal cancer, highlighting the need for appropriate regulation of IL-22 production. Upon activation, the AHR induces expression of cytochrome P4501 (CYP1) enzymes which in turn play an important feedback role that curtails the duration of AHR signaling by metabolizing AHR ligands. Recently we described how agents that inhibit CYP1 function potentiate AHR signaling by disrupting metabolic clearance of the endogenous ligand 6-formylindolo[3,2-b]carbazole (FICZ). In the present study, we investigated the immune-modulating effects of environmental pollutants such as polycyclic aromatic hydrocarbons on Th17 differentiation and IL-22 production. Using Th17 cells deficient in CYP1 enzymes (Cyp1a1/1a2/1b1-/-) we show that these chemicals potentiate AHR activation through inhibition of CYP1 enzymes which leads to increases in intracellular AHR agonists. Our findings demonstrate that IL-22 production by Th17 cells is profoundly enhanced by impaired CYP1-function and strongly suggest that chemicals able to modify CYP1 function or expression may disrupt AHR-mediated immune regulation by altering the levels of endogenous AHR agonist(s).
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Affiliation(s)
- Chris Schiering
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
| | - Anne Vonk
- Swetox, Karolinska Institutet, Unit of Toxicology Sciences, Forskargatan 20, 151 36 Södertälje, Sweden.
| | - Srustidhar Das
- Karolinska Institutet, Department of Medicine, Solna (MedS), K2, L2:04 171 76 Stockholm, Sweden.
| | | | - Emma Wincent
- Swetox, Karolinska Institutet, Unit of Toxicology Sciences, Forskargatan 20, 151 36 Södertälje, Sweden; Karolinska Institutet, Institute of Environmental Medicine, Box 210, 171 77 Stockholm, Sweden.
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2
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Alhouayek M, Gouveia-Figueira S, Hammarström ML, Fowler CJ. Involvement of CYP1B1 in interferon γ-induced alterations of epithelial barrier integrity. Br J Pharmacol 2018; 175:877-890. [PMID: 29232759 DOI: 10.1111/bph.14122] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 11/24/2017] [Accepted: 11/24/2017] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE CYP1B1 and CYP1A1 are important extra-hepatic cytochromes, expressed in the colon and involved in the metabolism of dietary constituents and exogenous compounds. CYP1B1 expression is increased by pro-inflammatory cytokines, and it has been recently implicated in regulation of blood brain barrier function. We investigated its involvement in the increased permeability of the intestinal epithelial barrier observed in inflammatory conditions. EXPERIMENTAL APPROACH Epithelial monolayers formed by human T84 colon carcinoma cells cultured on transwells, were disrupted by incubation with IFNγ (10 ng·mL-1 ). Monolayer integrity was measured using transepithelial electrical resistance. CYP1A1 and CYP1B1 inhibitors or inducers were applied apically. Potential mechanisms of action were investigated using RT-qPCR. KEY RESULTS IFNγ disrupts the barrier integrity of the T84 monolayers and increases CYP1B1 and HIF1α mRNA expression. CYP1B1 induction is inhibited by the NF-κB inhibitor ammonium pyrrolidinedithiocarbamate (100 μM) but not by the HIF1α inhibitor 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (50 μM). Inhibition of CYP1B1 with the selective inhibitor 2,4,3',5'-tetramethoxystilbene (100 nM) partly reverses the effects of IFNγ on epithelial permeability. CONCLUSIONS AND IMPLICATIONS These data suggest that increased expression of CYP1B1 is involved in the effects of IFNγ on epithelial permeability. Inhibition of CYP1B1 counteracts the alterations of epithelial barrier integrity induced by IFNγ and could thus have a therapeutic potential in disorders of intestinal permeability associated with inflammation.
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Affiliation(s)
- Mireille Alhouayek
- Department of Pharmacology and Clinical Neuroscience, Pharmacology Unit, Umeå University, Umeå, Sweden.,Bioanalysis and Pharmacology of Bioactive Lipids Research Group, Louvain Drug Research Institute, Université catholique de Louvain, Bruxelles, Belgium
| | - Sandra Gouveia-Figueira
- Department of Chemistry, Umeå University, Umeå, Sweden.,Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden
| | | | - Christopher J Fowler
- Department of Pharmacology and Clinical Neuroscience, Pharmacology Unit, Umeå University, Umeå, Sweden
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3
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Yun C, Weiner JA, Chun DS, Yun J, Cook RW, Schallmo MS, Kannan AS, Mitchell SM, Freshman RD, Park C, Hsu WK, Hsu EL. Mechanistic insight into the effects of Aryl Hydrocarbon Receptor activation on osteogenic differentiation. Bone Rep 2017; 6:51-59. [PMID: 28377982 PMCID: PMC5365310 DOI: 10.1016/j.bonr.2017.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 01/18/2017] [Accepted: 02/14/2017] [Indexed: 12/31/2022] Open
Abstract
While inhibition of bone healing and increased rates of pseudarthrosis are known adverse outcomes associated with cigarette smoking, the underlying mechanisms by which this occurs are not well understood. Recent work has implicated the Aryl Hydrocarbon Receptor (Ahr) as one mediator of the anti-osteogenic effects of cigarette smoke (CS), which contains numerous toxic ligands for the Ahr. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a high-affinity Ahr ligand frequently used to evaluate Ahr pathway activation. The purpose of this study was to elucidate the downstream mechanisms of dioxin action on bone regeneration and investigate Ahr antagonism as a potential therapeutic approach to mitigate the effects of dioxin on bone. Markers of osteogenic activity and differentiation were assessed in primary rat bone marrow stromal cells (BMSC) after exposure to dioxin, Ahr antagonists, or antagonist + dioxin. Four Ahr antagonists were evaluated: α-Naphthoflavone (ANF), resveratrol (Res), 3,3′-Diindolylmethane (DIM), and luteolin (Lut). Our results demonstrate that dioxin inhibited ALP activity, migratory capacity, and matrix mineralization, whereas co-treatment with each of the antagonists mitigated these effects. Dioxin also inhibited BMSC chemotaxis, while co-treatment with several antagonists partially rescued this effect. RNA and protein expression studies found that dioxin down-regulated numerous pro-osteogenic targets, whereas co-treatment with Ahr antagonists prevented these dioxin-induced expression changes to varying degrees. Our results suggest that dioxin adversely affects bone regeneration in a myriad of ways, many of which appear to be mediated by the Ahr. Our work suggests that the Ahr should be investigated as a therapeutic target to combat the adverse effects of CS on bone healing. Dioxin, a potent Ahr ligand, inhibits osteogenic differentiation of BMSC. “Nutraceutical” Ahr antagonists found in red wine and broccoli protected against dioxin action. Targets of dioxin action included Collagens, MMPs, Phex, CXCR4/CXCL12 axis. The Ahr may in part mediate the adverse effects of cigarette smoke on osteogenic differentiation and bone healing.
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Affiliation(s)
- Chawon Yun
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Joseph A Weiner
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Danielle S Chun
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Jonghwa Yun
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Ralph W Cook
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Michael S Schallmo
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Abhishek S Kannan
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Sean M Mitchell
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Ryan D Freshman
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Christian Park
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Wellington K Hsu
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
| | - Erin L Hsu
- Northwestern University Department of Orthopaedic Surgery, Chicago, IL, USA
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4
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Park S. Cyclic Glucans Enhance Solubility of Bioavailable Flavonoids. Molecules 2016; 21:molecules21111556. [PMID: 27854350 PMCID: PMC6273393 DOI: 10.3390/molecules21111556] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 12/12/2022] Open
Abstract
Diverse flavonoids are abundant in dietary food constituents and possess useful biological activities. However, some flavonoids have limited bioavailability due to their low solubility in water. As an important approach to enhance aqueous solubility, inclusion of hydrophobic guest molecules in hydrophilic hosts such as cyclic glucans has been used. This review summarizes applications of β-cyclodextrin, synthetic β-cyclodextrin derivatives, and newly synthesized derivatives of cyclosophoraoses as complexing agents to enhance the bioavailability of flavonoids such as baicalein, kaempferol, and naphthoflavones.
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Affiliation(s)
- Seyeon Park
- Department of Applied Chemistry, Dongduk Women's University, Seoul 136-714, Korea.
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5
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Cort A, Ozben T, Saso L, De Luca C, Korkina L. Redox Control of Multidrug Resistance and Its Possible Modulation by Antioxidants. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:4251912. [PMID: 26881027 PMCID: PMC4736404 DOI: 10.1155/2016/4251912] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/14/2015] [Accepted: 11/18/2015] [Indexed: 12/13/2022]
Abstract
Clinical efficacy of anticancer chemotherapies is dramatically hampered by multidrug resistance (MDR) dependent on inherited traits, acquired defence against toxins, and adaptive mechanisms mounting in tumours. There is overwhelming evidence that molecular events leading to MDR are regulated by redox mechanisms. For example, chemotherapeutics which overrun the first obstacle of redox-regulated cellular uptake channels (MDR1, MDR2, and MDR3) induce a concerted action of phase I/II metabolic enzymes with a temporal redox-regulated axis. This results in rapid metabolic transformation and elimination of a toxin. This metabolic axis is tightly interconnected with the inducible Nrf2-linked pathway, a key switch-on mechanism for upregulation of endogenous antioxidant enzymes and detoxifying systems. As a result, chemotherapeutics and cytotoxic by-products of their metabolism (ROS, hydroperoxides, and aldehydes) are inactivated and MDR occurs. On the other hand, tumour cells are capable of mounting an adaptive antioxidant response against ROS produced by chemotherapeutics and host immune cells. The multiple redox-dependent mechanisms involved in MDR prompted suggesting redox-active drugs (antioxidants and prooxidants) or inhibitors of inducible antioxidant defence as a novel approach to diminish MDR. Pitfalls and progress in this direction are discussed.
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Affiliation(s)
- Aysegul Cort
- Department of Nutrition and Dietetics, Faculty of Health Sciences, Sanko University, İncili Pınar, Gazi Muhtar Paşa Bulvarı, Sehitkamil, 27090 Gaziantep, Turkey
| | - Tomris Ozben
- Department of Biochemistry, Akdeniz University Medical Faculty, Campus, Dumlupınar Street, 07070 Antalya, Turkey
| | - Luciano Saso
- Department of Physiology and Pharmacology “Vittorio Erspamer”, La Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Chiara De Luca
- Evidence-Based Well-Being (EB-WB) Ltd., 31 Alt-Stralau, 10245 Berlin, Germany
| | - Liudmila Korkina
- Centre of Innovative Biotechnological Investigations Nanolab, 197 Vernadskogo Prospekt, Moscow 119571, Russia
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6
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Wang GZ, Cheng X, Zhou B, Wen ZS, Huang YC, Chen HB, Li GF, Huang ZL, Zhou YC, Feng L, Wei MM, Qu LW, Cao Y, Zhou GB. The chemokine CXCL13 in lung cancers associated with environmental polycyclic aromatic hydrocarbons pollution. eLife 2015; 4:e09419. [PMID: 26565418 PMCID: PMC4764582 DOI: 10.7554/elife.09419] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Accepted: 11/04/2015] [Indexed: 12/16/2022] Open
Abstract
More than 90% of lung cancers are caused by cigarette smoke and air pollution, with polycyclic aromatic hydrocarbons (PAHs) as key carcinogens. In Xuanwei City of Yunnan Province, the lung cancer incidence is among the highest in China, attributed to smoky coal combustion-generated PAH pollution. Here, we screened for abnormal inflammatory factors in non-small cell lung cancers (NSCLCs) from Xuanwei and control regions (CR) where smoky coal was not used, and found that a chemokine CXCL13 was overexpressed in 63/70 (90%) of Xuanwei NSCLCs and 44/71 (62%) of smoker and 27/60 (45%) of non-smoker CR patients. CXCL13 overexpression was associated with the region Xuanwei and cigarette smoke. The key carcinogen benzo(a)pyrene (BaP) induced CXCL13 production in lung epithelial cells and in mice prior to development of detectable lung cancer. Deficiency in Cxcl13 or its receptor, Cxcr5, significantly attenuated BaP-induced lung cancer in mice, demonstrating CXCL13's critical role in PAH-induced lung carcinogenesis.
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Affiliation(s)
- Gui-Zhen Wang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Xin Cheng
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Bo Zhou
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Zhe-Sheng Wen
- Department of Thoracic Surgery, Sun Yat-Sen University Cancer Center, Guangzhou, China
| | - Yun-Chao Huang
- Department of Thoracic Surgery, The Third Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Hao-Bin Chen
- Department of Pathology, The First People’s Hospital of Qu Jing City, Qu Jing, China
| | - Gao-Feng Li
- Department of Thoracic Surgery, The Third Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Zhi-Liang Huang
- Department of Thoracic Surgery, Sun Yat-Sen University Cancer Center, Guangzhou, China
| | - Yong-Chun Zhou
- Department of Thoracic Surgery, The Third Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Lin Feng
- Department of Pathology, Chinese PLA General Hospital, Beijing, China
| | - Ming-Ming Wei
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Li-Wei Qu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Yi Cao
- Laboratory of Molecular and Experimental Pathology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Guang-Biao Zhou
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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7
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Pernomian L, da Silva CHTP. Current basis for discovery and development of aryl hydrocarbon receptor antagonists for experimental and therapeutic use in atherosclerosis. Eur J Pharmacol 2015; 764:118-123. [PMID: 26142084 DOI: 10.1016/j.ejphar.2015.06.058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 06/25/2015] [Accepted: 06/29/2015] [Indexed: 12/11/2022]
Abstract
The important role played by aryl hydrocarbon receptor activation in the pathophysiology of atherosclerosis induced by cigarette smoke exposure has spurred the clinical interest in the development of aryl hydrocarbon receptor antagonists with atheroprotective efficacy. A few aryl hydrocarbon receptor antagonists were developed but the lack of structural information regarding the receptor ligand binding domain resulted in several limitations in the pharmacological properties of these compounds including partial agonism, allosterism, non-selectivity, cytotoxicity and susceptibility to bioactivation. These limitations make the progress of preclinical and clinical assays with the available aryl hydrocarbon receptor antagonists difficult. There is a great interest in developing pure, competitive, selective, nontoxic and resistant to bioactivation aryl hydrocarbon receptor antagonists. Current technology permits the development of pharmacologically ideal antagonists based on the chemical features of the aryl hydrocarbon receptor ligand binding domain. According to these characteristics, chlorinated derivatives of trans-stilbene meta-substituted with electrophilic aromatic directing groups would be effective prototypes for pure, competitive, selective, nontoxic and resistant to bioactivation antagonists for such receptor.
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Affiliation(s)
- Larissa Pernomian
- Computational Laboratory of Pharmaceutical Chemistry, Faculdade de Ciências Farmacêuticas de Ribeirão Preto (FCFRP), Universidade de São Paulo (USP), Avenida do Café s/n, 14040-903 Ribeirão Preto, SP, Brazil.
| | - Carlos H T P da Silva
- Computational Laboratory of Pharmaceutical Chemistry, Faculdade de Ciências Farmacêuticas de Ribeirão Preto (FCFRP), Universidade de São Paulo (USP), Avenida do Café s/n, 14040-903 Ribeirão Preto, SP, Brazil
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8
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Gábelová A, Poláková V, Prochazka G, Kretová M, Poloncová K, Regendová E, Luciaková K, Segerbäck D. Sustained induction of cytochrome P4501A1 in human hepatoma cells by co-exposure to benzo[a]pyrene and 7H-dibenzo[c,g]carbazole underlies the synergistic effects on DNA adduct formation. Toxicol Appl Pharmacol 2013; 271:1-12. [DOI: 10.1016/j.taap.2013.04.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 04/09/2013] [Accepted: 04/10/2013] [Indexed: 12/11/2022]
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9
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Aryl hydrocarbon receptor contributes to the MEK/ERK-dependent maintenance of the immature state of human dendritic cells. Blood 2013; 121:e108-17. [PMID: 23430108 DOI: 10.1182/blood-2012-07-445106] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Dendritic cells (DCs) promote tolerance or immunity depending on their maturation state, which is enhanced or accelerated upon MEK-ERK signaling pathway inhibition. We have determined the contribution of MEK-ERK activation to the profile of gene expression of human immature monocyte-derived dendritic cells (MDDCs) and peripheral blood myeloid DCs. ERK inhibition altered the expression of genes that mediate Chemokine (C-C motif) ligand 19 (CCL19)-directed migration (CCR7) and low-density lipoprotein (LDL) binding (CD36, SCARB1, OLR1, CXCL16) by immature DCs. In addition, ERK upregulated CCL2 expression while impairing the expression of DC maturation markers (RUNX3, ITGB7, IDO1). MEK-ERK-regulated genes exhibited an overrepresentation of cognate sequences for the aryl hydrocarbon receptor (AhR) transcription factor, whose transcriptional and DNA-binding activities increased in MDDCs upon exposure to the MEK1/2 inhibitor U0126. Therefore, the MEK-ERK signaling pathway regulates antigen capture, lymph node homing, and acquisition of maturation-associated genes, and its contribution to the maintenance of the immature state of MDDCs and myeloid DCs is partly dependent on the activity of AhR. Since pharmacologic modulation of the MEK-ERK signaling pathway has been proposed as a potential therapeutic strategy for cancer, our findings indicate that ERK inhibitors might influence antitumor responses through regulation of critical DC effector functions.
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10
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Busbee PB, Rouse M, Nagarkatti M, Nagarkatti PS. Use of natural AhR ligands as potential therapeutic modalities against inflammatory disorders. Nutr Rev 2013; 71:353-69. [PMID: 23731446 DOI: 10.1111/nure.12024] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The aim of this review is to discuss research involving ligands for the aryl hydrocarbon receptor (AhR) and their role in immunomodulation. While activation of the AhR is well known for its ability to regulate the biochemical and toxic effects of environmental chemicals, more recently an exciting discovery has been made indicating that AhR ligation can also regulate T-cell differentiation, specifically through activation of Foxp3(+) regulatory T cells (Tregs) and downregulation of the proinflammatory Th17 cells. Such findings have opened new avenues of research on the possibility of targeting the AhR to treat inflammatory and autoimmune diseases. Specifically, this review will discuss the current research involving natural and dietary AhR ligands. In addition, evidence indicating the potential use of these ligands in regulating inflammation in various diseases will be highlighted. The importance of the AhR in immunological processes can be illustrated by expression of this receptor on a majority of immune cell types. In addition, AhR signaling pathways have been reported to influence a number of genes responsible for mediating inflammation and other immune responses. As interest in the AhR and its ligands increases, it seems prudent to consolidate current research on the contributions of these ligands to immune regulation during the course of inflammatory diseases.
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Affiliation(s)
- Philip B Busbee
- Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina 29208, USA
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11
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Bussmann UA, Pérez Sáez JM, Bussmann LE, Barañao JL. Aryl hydrocarbon receptor activation leads to impairment of estrogen-driven chicken vitellogenin promoter activity in LMH cells. Comp Biochem Physiol C Toxicol Pharmacol 2013; 157:111-8. [PMID: 23103859 DOI: 10.1016/j.cbpc.2012.10.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 10/20/2012] [Accepted: 10/20/2012] [Indexed: 01/05/2023]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates most of the toxic effects of environmental contaminants. Among the multiple pleiotropic responses elicited by AHR agonists, the antiestrogenic and endocrine-disrupting action of the receptor activation is one of the most studied. It has been demonstrated that some AHR agonists disrupt estradiol-induced vitellogenin synthesis in the fish liver via a mechanism that involves crosstalk between the AHR and the estrogen receptor (ER). Chicken hepatocytes have become a model for the study of AHR action in birds and the induction of the signal and its effect in these cells are well established. However, the impact of AHR activation on estradiol-regulated responses in the chicken liver remains to be demonstrated. The aim of the present study was, therefore, to determine the effect of AHR action on ER-driven transcription in a convenient model of chicken liver cells. For this purpose, we designed a reporter construct bearing the 5' regulatory region of the chicken vitellogenin II gene and used it to transfect chicken hepatoma LMH cells. We found that β-naphthoflavone represses ER-driven vitellogenin promoter activity and that this action is mediated by the AHR. This inhibitory crosstalk between both pathways appears to be unidirectional, since estradiol did not alter the transcript levels of an AHR target gene. Besides, and highly relevant, we show that LMH cell line transfected with a reporter construct bearing the chicken vitellogenin promoter sequence is a useful and convenient model for the study of AHR-ER interaction in chicken liver-derived cells.
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12
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Ma Q. Influence of light on aryl hydrocarbon receptor signaling and consequences in drug metabolism, physiology and disease. Expert Opin Drug Metab Toxicol 2011; 7:1267-93. [DOI: 10.1517/17425255.2011.614947] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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13
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Sacks PG, Zhao ZL, Kosinska W, Fleisher KE, Gordon T, Guttenplan JB. Concentration dependent effects of tobacco particulates from different types of cigarettes on expression of drug metabolizing proteins, and benzo(a)pyrene metabolism in primary normal human oral epithelial cells. Food Chem Toxicol 2011; 49:2348-55. [PMID: 21722697 PMCID: PMC3182574 DOI: 10.1016/j.fct.2011.06.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 06/14/2011] [Accepted: 06/15/2011] [Indexed: 01/10/2023]
Abstract
The ability of tobacco smoke (TS) to modulate phase I and II enzymes and affect metabolism of tobacco carcinogens is likely an important factor in its carcinogenicity. For the first time several types of TS particulates (TSP) were compared in different primary cultured human oral epithelial cells (NOE) for their abilities to affect metabolism of the tobacco carcinogen, (BaP) to genotoxic products, and expression of drug metabolizing enzymes. TSP from, reference filtered (2RF4), mentholated (MS), reference unfiltered, (IR3), ultra low tar (UL), and cigarettes that primarily heat tobacco (ECL) were tested. Cells pretreated with TSP concentrations of 0.2-10 μg/ml generally showed increased rates of BaP metabolism; those treated with TSP concentrations above 10 μg/ml showed decreased rates. Effects of TSPs were similar when expressed on a weight basis. Weights of TSP/cigarette varied in the order: MS≈IR3>2RF4>ECL>UL. All TSPs induced the phase I proteins, cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1), phase II proteins, NAD(P)H dehydrogenase quinone 1 (NQO1), and microsomal glutathione S-transferase 1 (MGST1), and additionally, hydroxysteroid (17-beta) dehydrogenase 2 (HSD17B2), as assessed by qRT-PCR. The pattern of gene induction at probable physiological levels favored activation over detoxification.
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Affiliation(s)
- Peter G. Sacks
- New York University College of Dentistry, Dept of Basic Science, New York, NY 10010
| | - Zhong-Lin Zhao
- New York University College of Dentistry, Dept of Basic Science, New York, NY 10010
| | - Wieslawa Kosinska
- New York University College of Dentistry, Dept of Basic Science, New York, NY 10010
| | - Kenneth E. Fleisher
- New York University College of Dentistry, Dept of Basic Science, New York, NY 10010
| | - Terry Gordon
- NYU School of Medicine, Dept of Environmental Medicine, New York, NY 10010
| | - Joseph B. Guttenplan
- New York University College of Dentistry, Dept of Basic Science, New York, NY 10010
- NYU School of Medicine, Dept of Environmental Medicine, New York, NY 10010
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14
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Soshilov A, Denison MS. Ligand displaces heat shock protein 90 from overlapping binding sites within the aryl hydrocarbon receptor ligand-binding domain. J Biol Chem 2011; 286:35275-82. [PMID: 21856752 DOI: 10.1074/jbc.m111.246439] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hsp90 (heat shock protein of 90 kDa) is often found associated with functional domains of client proteins, including those for ligand binding, dimerization, DNA binding, and enzymatic activity. Although Hsp90 can maintain the conformation of functionally important domains prior to activation of the client protein, its specific binding site and the mechanism(s) of Hsp90 dissociation during activation are unknown. Here, we have identified and characterized residues involved in Hsp90 binding within the aryl hydrocarbon receptor (AhR) ligand-binding domain and demonstrate that they overlap with those involved in ligand binding. In agreement with this spatial model, ligand binding results in Hsp90 dissociation from the AhR Per-ARNT-Sim B fragment. Interestingly, whereas Hsp90-binding residues within the ligand-binding domain were not involved in Hsp90-dependent AhR protein stability, several of these residues are important for ligand-dependent AhR activation, and their mutation resulted in conversion of two AhR antagonists/partial agonists into full AhR agonists. These studies reveal co-localization of a tentative Hsp90-binding site with that for AhR ligand binding and provide the first molecular mechanism for Hsp90 dissociation in the activation of a client protein.
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Affiliation(s)
- Anatoly Soshilov
- Department of Environmental Toxicology, University of California, Davis, California 95616-8588, USA
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15
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Smith KJ, Murray IA, Tanos R, Tellew J, Boitano AE, Bisson WH, Kolluri SK, Cooke MP, Perdew GH. Identification of a high-affinity ligand that exhibits complete aryl hydrocarbon receptor antagonism. J Pharmacol Exp Ther 2011; 338:318-27. [PMID: 21493753 DOI: 10.1124/jpet.110.178392] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The biological functions of the aryl hydrocarbon receptor (AHR) can be delineated into dioxin response element (DRE)-dependent or -independent activities. Ligands exhibiting either full or partial agonist activity, e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin and α-naphthoflavone, have been demonstrated to potentiate both DRE-dependent and -independent AHR function. In contrast, the recently identified selective AHR modulators (SAhRMs), e.g., 1-allyl-3-(3,4-dimethoxyphenyl)-7-(trifluoromethyl)-1H-indazole (SGA360), bias AHR toward DRE-independent functionality while displaying antagonism with regard to ligand-induced DRE-dependent transcription. Recent studies have expanded the physiological role of AHR to include modulation of hematopoietic progenitor expansion and immunoregulation. It remains to be established whether such physiological roles are mediated through DRE-dependent or -independent pathways. Here, we present evidence for a third class of AHR ligand, "pure" or complete antagonists with the capacity to suppress both DRE-dependent and -independent AHR functions, which may facilitate dissection of physiological AHR function with regard to DRE or non-DRE-mediated signaling. Competitive ligand binding assays together with in silico modeling identify N-(2-(1H-indol-3-yl)ethyl)-9-isopropyl-2-(5-methylpyridin-3-yl)-9H-purin-6-amine (GNF351) as a high-affinity AHR ligand. DRE-dependent reporter assays, in conjunction with quantitative polymerase chain reaction analysis of AHR targets, reveal GNF351 as a potent AHR antagonist that demonstrates efficacy in the nanomolar range. Furthermore, unlike many currently used AHR antagonists, e.g., α-naphthoflavone, GNF351 is devoid of partial agonist potential. It is noteworthy that in a model of AHR-mediated DRE-independent function, i.e., suppression of cytokine-induced acute-phase gene expression, GNF351 has the capacity to antagonize agonist and SAhRM-mediated suppression of SAA1. Such data indicate that GNF351 is a pure antagonist with the capacity to inhibit both DRE-dependent and -independent activity.
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Affiliation(s)
- Kayla J Smith
- Department of Veterinary and Biomedical Sciences, Center for Molecular Toxicology and Carcinogenesis, Pennsylvania StateUniversity, University Park, Pennsylvania 16802, USA
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Wang X, Hawkins BT, Miller DS. Aryl hydrocarbon receptor-mediated up-regulation of ATP-driven xenobiotic efflux transporters at the blood-brain barrier. FASEB J 2010; 25:644-52. [PMID: 21048045 DOI: 10.1096/fj.10-169227] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Many widespread and persistent organic pollutants, e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), activate the aryl hydrocarbon receptor (AhR), causing it to translocate to the cell nucleus, where it transactivates target genes. AhR's ability to target the blood-brain barrier is essentially unexplored. We show here that exposing isolated rat brain capillaries to 0.05-0.5 nM TCDD roughly doubled transport activity and protein expression of P-glycoprotein, an ATP-driven drug efflux pump and a critical determinant of drug entry into the CNS. These effects were abolished by actinomycin D or cycloheximide or by the AhR antagonists resveratrol and α-naphthoflavone. Brain capillaries from TCDD-dosed rats (1-5 μg/kg, i.p.) exhibited increased transport activity and protein expression of 3 xenobiotic efflux pumps, P-glycoprotein, multidrug resistance-associated protein 2, and breast cancer resistance polypeptide, as well as expression of Cyp1a1 and Cyp1b1, both AhR target genes. Consistent with increased P-glycoprotein expression in capillaries from TCDD-dosed rats, in situ brain perfusion indicated significantly reduced brain accumulation of verapamil, a P-glycoprotein substrate. These findings suggest a new paradigm for the field of environmental toxicology: toxicants acting through AhR to target xenobiotic efflux transporters at the blood-brain barrier and thus reduce brain accumulation of CNS-acting therapeutic drugs.
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Affiliation(s)
- Xueqian Wang
- Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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17
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Singh NP, Singh US, Nagarkatti M, Nagarkatti PS. Resveratrol (3,5,4'-trihydroxystilbene) protects pregnant mother and fetus from the immunotoxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Mol Nutr Food Res 2010; 55:209-19. [PMID: 20715097 DOI: 10.1002/mnfr.201000206] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 06/07/2010] [Accepted: 06/23/2010] [Indexed: 01/21/2023]
Abstract
SCOPE The "fetal basis of adult disease" hypothesis proposes that prenatal exposure to environmental stress can lead to increased susceptibility to clinical disorders later in life. In utero exposure of fetus to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to alterations in T-cell differentiation in the thymus and increased susceptibility to autoimmune disease later in life. TCDD triggers toxicity through activation of aryl hydrocarbon receptor and severely affects maternal and fetal immune system during pregnancy. METHODS AND RESULTS In this study, using a mouse model, we investigated if administration of resveratrol (RES; 3,5,4'-trihydroxystilbene) would inhibit immunotoxicity induced by TCDD during pregnancy in the mother and fetus. We observed that RES protected not only normal nonpregnant mice but also pregnant mothers and their fetuses from TCDD-induced thymic atrophy, apoptosis, and alterations in the expression of T-cell receptor and costimulatory molecules as well as T-cell differentiation. In addition, there was significantly reduced expression of CYP1A1 in thymi of both the mother and the fetus when RES was used in vivo post-TCDD exposure. CONCLUSION In conclusion, these studies demonstrate that consumption of RES, a natural plant product, during pregnancy, may afford protection to the mother and the fetus from the toxicity induced by environmental pollutants that mediate their effects through activation of aryl hydrocarbon receptor.
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Affiliation(s)
- Narendra P Singh
- Department of Pathology, Microbiology & Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA
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18
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Hamada M, Satsu H, Ashida H, Sugita-Konishi Y, Shimizu M. Metabolites of galangin by 2,3,7,8-tetrachlorodibenzo-p-dioxin-inducible cytochrome P450 1A1 in human intestinal epithelial Caco-2 cells and their antagonistic activity toward aryl hydrocarbon receptor. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:8111-8118. [PMID: 20550209 DOI: 10.1021/jf100778f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Galangin, a dietary flavonoid, inhibited cytochrome P450 1A1 (CYP1A1) expression induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This inhibitory activity remained after permeating human intestinal epithelial Caco-2 cell monolayers, but was reduced when galangin permeated TCDD-pretreated Caco-2 cells. The present study tested whether TCDD affected the intestinal metabolism of flavonoids. LC-MS/MS analyses showed that galangin and two galangin glucuronoconjugates were reduced 0.7-fold, whereas kaempferol (a galangin oxidate) and kaempferol glucuronoconjugate were increased 1.5-fold by permeating TCDD-pretreated Caco-2 cells, as compared to untreated Caco-2 cells. An assay using recombinant human CYP1A1 and the CYP1A1 inhibitor alpha-naphthoflavone revealed that CYP1A1 oxidized galangin to kaempferol. These results indicated that galangin was metabolized to kaempferol by TCDD-inducible CYP1A1 in Caco-2 cells. A previous study revealed that kaempferol had much weaker inhibitory activity than galangin toward TCDD-induced CYP1A1 expression. Therefore, the oxidative metabolism of galangin to kaempferol in TCDD-pretreated Caco-2 cells implicated reduction in the inhibitory activity of galangin.
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Affiliation(s)
- Mika Hamada
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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Murray IA, Flaveny CA, DiNatale BC, Chairo CR, Schroeder JC, Kusnadi A, Perdew GH. Antagonism of aryl hydrocarbon receptor signaling by 6,2',4'-trimethoxyflavone. J Pharmacol Exp Ther 2009; 332:135-44. [PMID: 19828881 DOI: 10.1124/jpet.109.158261] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) is regarded as an important homeostatic transcriptional regulator within physiological and pathophysiological processes, including xenobiotic metabolism, endocrine function, immunity, and cancer. Agonist activation of the AHR is considered deleterious based on toxicological evidence obtained with environmental pollutants, which mediate toxic effects through AHR. However, a multitude of plant-derived constituents, e.g., polyphenols that exhibit beneficial properties, have also been described as ligands for the AHR. It is conceivable that some of the positive aspects of such compounds can be attributed to suppression of AHR activity through antagonism. Therefore, we conducted a dioxin response element reporter-based screen to assess the AHR activity associated with a range of flavonoid compounds. Our screen identified two flavonoids (5-methoxyflavone and 7,4'-dimethoxyisoflavone) with previously unidentified AHR agonist potential. In addition, we have identified and characterized 6,2',4'-trimethoxyflavone (TMF) as an AHR ligand that possesses the characteristics of an antagonist having the capacity to compete with agonists, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo[a]pyrene, thus effectively inhibiting AHR-mediated transactivation of a heterologous reporter and endogenous targets, e.g., CYP1A1, independent of cell lineage or species. Furthermore, TMF displays superior action by virtue of having no partial agonist activity, in contrast to other documented antagonists, e.g., alpha-napthoflavone, which are partial weak agonists. TMF also exhibits no species or promoter dependence with regard to AHR antagonism. TMF therefore represents an improved tool allowing for more precise dissection of AHR function in the absence of any conflicting agonist activity.
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Affiliation(s)
- Iain A Murray
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary Sciences, The Pennsylvania State University, Pennsylvania 16802, USA
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20
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Bisson WH, Koch DC, O'Donnell EF, Khalil SM, Kerkvliet NI, Tanguay RL, Abagyan R, Kolluri SK. Modeling of the aryl hydrocarbon receptor (AhR) ligand binding domain and its utility in virtual ligand screening to predict new AhR ligands. J Med Chem 2009; 52:5635-41. [PMID: 19719119 DOI: 10.1021/jm900199u] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor; the AhR Per-AhR/Arnt-Sim (PAS) domain binds ligands. We developed homology models of the AhR PAS domain to characterize previously observed intra- and interspecies differences in ligand binding using molecular docking. In silico structure-based virtual ligand screening using our model resulted in the identification of pinocembrin and 5-hydroxy-7-methoxyflavone, which promoted nuclear translocation and transcriptional activation of AhR and AhR-dependent induction of endogenous target genes.
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Affiliation(s)
- William H Bisson
- Cancer Biology Laboratory, Environmental Health Sciences Center, Oregon State University, Corvallis, Oregon 97331, USA
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21
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Collins NH, Lessey EC, DuSell CD, McDonnell DP, Fowler L, Palomino WA, Illera MJ, Yu X, Mo B, Houwing AM, Lessey BA. Characterization of antiestrogenic activity of the Chinese herb, prunella vulgaris, using in vitro and in vivo (Mouse Xenograft) models. Biol Reprod 2008; 80:375-83. [PMID: 18923163 DOI: 10.1095/biolreprod.107.065375] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Prunella vulgaris (PV), a commonly used Chinese herb, also known as Self-heal, has a wide range of reported medicinal activities. By screening multiple herbs using the endometrial cancer cell line, ECC-1, and an alkaline phosphatase detection assay, we found that PV displayed significant antiestrogenic activity. We investigated the possible usefulness of antiestrogenic activity using both in vitro and in vivo models of endometrial function. Using the well-differentiated, hormone-responsive endometrial cell line, ECC-1, PV extract, at concentrations that were not toxic to the cells, significantly reduced alkaline phosphatase activity and cell proliferation in response to estrogen in a dose-dependent manner. The expression of CYR61, an estrogen-induced protein, was blocked in ECC-1 cells by both the antiestrogen ICI 182,780 and PV extract. Interestingly, PV extract did not appear to directly inhibit estrogen signaling. Rather, we found that its activities were probably related to an ability to function as an aryl hydrocarbon receptor (AHR) agonist in ECC-1 cells. In support of this hypothesis, we noted that PV induced CYP1A1, CYP1B1, and AHR repressor expression in a dose-dependent manner--responses that were blocked by small interfering RNA treatment to reduce AHR and specific AHR antagonists. Ovariectomized immunodeficient RAG-2/gamma(c) knockout mice implanted with human endometrial xenografts developed implants only when treated with estrogen. Mice treated with estrogen and PV tea in their drinking water had fewer and smaller xenograft implants compared with their estrogen-treated counterparts that drank only water (P < 0.05). Analysis of the resulting implants by immunohistochemistry demonstrated persistent estrogen receptor (ER), but reduced proliferation and CYR61 expression. Mouse uterine tissue weight in PV-treated mice was not different from controls, and cycle fecundity of intact C57 female mice was unaffected by PV tea treatment. PV, or Self-heal, exhibits significant antiestrogenic properties, both in vitro and in vivo. This activity is likely due to the ability of PV-activated AHR to interfere with estrogen. This herb may be useful as an adjunct for the treatment of estrogen-dependent processes like endometriosis and breast and uterine cancers. Full characterization of this herb will likely provide new insights into the crosstalk between AHR and ESR1, with potential for therapeutic applications in women.
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Affiliation(s)
- Nancy H Collins
- Department of Obstetrics and Gynecology, Greenville Hospital System, Greenville, South Carolina 29605, USA
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Oikawa K, Yoshida K, Takanashi M, Tanabe H, Kiyuna T, Ogura M, Saito A, Umezawa A, Kuroda M. Dioxin interferes in chromosomal positioning through the aryl hydrocarbon receptor. Biochem Biophys Res Commun 2008; 374:361-4. [DOI: 10.1016/j.bbrc.2008.07.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Accepted: 07/09/2008] [Indexed: 12/15/2022]
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Scott JA, Hodson PV. Evidence for multiple mechanisms of toxicity in larval rainbow trout (Oncorhynchus mykiss) co-treated with retene and alpha-naphthoflavone. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2008; 88:200-206. [PMID: 18511136 DOI: 10.1016/j.aquatox.2008.04.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Revised: 04/09/2008] [Accepted: 04/11/2008] [Indexed: 05/26/2023]
Abstract
Alkylated polycyclic aromatic hydrocarbons, such as retene (7-isopropyl-1-methylphenanthrene), induce cytochrome P450 1A (CYP1A) enzymes and produce dioxin-like toxicity in the embryo-larval stages of fish characterized by the signs of blue sac disease (BSD). The signs of toxicity are well characterized; however, the mechanism is not well understood. To elucidate the role of CYP1A in retene toxicity, larval rainbow trout (Oncorhynchus mykiss) were co-treated with a range of concentrations of alpha-naphthoflavone (ANF), a known CYP1A inhibitor. The co-treatment produced synergistic toxicity at 3.2-100 microg/L ANF, after which toxicity at 180 microg/L ANF dropped to levels typical of retene-only. At 320 microg/L ANF, toxicity increased with or without retene, indicating that ANF alone was capable of inducing BSD. In addition, the additive toxicity of retene-only and 320 microg/L ANF-only approximately equalled that of the co-exposed larvae (100 microg/L retene+320 microg/L ANF), indicating response addition. Thus, two mechanisms of action occurred in co-exposed larvae at different concentrations of ANF. In trout larvae, there was a correlation between toxicity and CYP1A protein concentrations, and in juvenile trout, ANF produced a concentration-dependent inhibition of ethoxyresorufin-O-deethylase (EROD) activity without a measurable drop in CYP1A protein. Taken together, the mechanism underlying the synergistic toxicity is EROD-independent and may be AhR-dependent. This study demonstrated that multiple, exposure-dependent mechanisms can occur in mixture toxicity, suggesting that current risk assessment models may drastically underestimate toxicity, particularly of mixtures containing both CYP1A inducers and inhibitors.
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Affiliation(s)
- Jason A Scott
- Department of Biology, Queen's University, Kingston, ON, Canada
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24
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Jang JY, Park D, Shin S, Jeon JH, Choi BI, Joo SS, Hwang SY, Nahm SS, Kim YB. Antiteratogenic effect of resveratrol in mice exposed in utero to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Eur J Pharmacol 2008; 591:280-3. [PMID: 18571640 DOI: 10.1016/j.ejphar.2008.05.033] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 04/21/2008] [Accepted: 05/20/2008] [Indexed: 11/17/2022]
Abstract
The effect of resveratrol, an aryl hydrocarbon receptor antagonist, on the teratogenicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated. Pregnant C57BL/6J mice were orally administered resveratrol (50 mg/kg) for 6 consecutive days, from gestational day (GD) 8 to GD13, followed by an oral challenge with TCDD (14 mug/kg) on GD12. TCDD caused severe fetal malformations including cleft palate (40.7%), renal pelvic dilatation (100%, mean score 3.060), and ureteric dilatation (100%, mean score 3.210) and tortuosity (95.1%). Resveratrol significantly reduced both the incidence of TCDD-induced cleft palate to 18.4% and the degrees of renal pelvic and ureteric dilatations caused by TCDD. The results suggest that pretreatment with resveratrol might bring a beneficial outcome for reducing the incidence and severity of fetal malformations caused by TCDD exposure in utero.
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Affiliation(s)
- Ja Young Jang
- College of Veterinary Medicine and Research Institute of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Republic of Korea
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Zatloukalová J, Svihálková-Sindlerová L, Kozubík A, Krcmár P, Machala M, Vondrácek J. β-Naphthoflavone and 3′-methoxy-4′-nitroflavone exert ambiguous effects on Ah receptor-dependent cell proliferation and gene expression in rat liver ‘stem-like’ cells. Biochem Pharmacol 2007; 73:1622-34. [PMID: 17324381 DOI: 10.1016/j.bcp.2007.01.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 01/24/2007] [Accepted: 01/24/2007] [Indexed: 10/23/2022]
Abstract
Both natural and synthetic flavonoids are known to interact with the aryl hydrocarbon receptor (AhR); however, their agonist/antagonist properties in vitro have been so far studied mostly in the context of cytochrome P450 1A1 gene (Cyp1a1) regulation. We investigated effects of two synthetic flavones known either as AhR agonist (beta-naphthoflavone; BNF) or antagonist (3'-methoxy-4'-nitroflavone; 3M4NF), using an in vitro model of liver 'stem-like' cells, on expression of various AhR target genes and AhR-dependent cell proliferation. We found that the presumed antagonist 3M4NF induces a partial nuclear translocation and activation of AhR. Although inhibiting the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced Cyp1a1 expression, 3M4NF alone induced a minor increase of CYP1A1 mRNA and protein. However, 3M4NF did not induce AhR binding to synthetic dioxin response elements (DRE). In contrast to Cyp1a1, 3M4NF induced a marked expression of other AhR-regulated genes, such as Cyp1b1 and Nqo1, as well as transcriptional repression of Cdh13 gene, confirming that its effects may be promoter-context specific. Like BNF, 3M4NF induced AhR-dependent cell proliferation of contact-inhibited rat liver 'stem-like' WB-F344 cells, associated with a marked upregulation of Cyclin A, as well as the downregulation of proteins involved in formation of cell-cell contacts. Based on these experimental findings, we conclude that partial agonists/antagonists of AhR can increase cell proliferation rate and AhR-dependent genes expression in both cell type- and gene-specific manner. The specificity of effects of flavones on diverse AhR targets should be taken into account, when studying AhR signaling using presumed AhR antagonists.
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Affiliation(s)
- Jirina Zatloukalová
- Laboratory of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Czech Republic
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Kasai A, Hiramatsu N, Meng Y, Yao J, Maeda S, Kitamura M. Fast-track DRESSA: a bioassay for fast, sensitive, and selective detection of halogenated and polycyclic aromatic hydrocarbons. Anal Biochem 2005; 337:84-8. [PMID: 15649379 DOI: 10.1016/j.ab.2004.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Indexed: 10/26/2022]
Abstract
Dioxin and related chemicals cause a variety of toxic and biological effects via the aryl hydrocarbon receptor (AhR). We recently reported a mammalian cell-based bioassay system (dioxin-responsive-element-based sensing via secreted alkaline phosphatase; DRESSA) that can detect dioxin and dioxin-like chemicals with high sensitivity. In this report, we describe an advanced method (designated "fast-track DRESSA") that achieves fast, selective, and sensitive detection of dioxin and other toxic compounds. By optimization of assay conditions on cell number and serum concentration, the fast-track DRESSA enabled detection of 0.5 pM 2,3,7,8-tetrachlorodibenzo-p-dioxin within 6 h. It also enabled detection of 10 pM 3-methylcholanthrene, 100 pM benzo[a]pyrene, and 100 pM beta-naphthoflavone within 6-16 h. By combination with the AhR antagonist alpha-naphthoflavone, nonspecific, false-positive responses could be eliminated. Because of its time-saving property and easiness, sensitiveness, and specificity, the fast-track DRESSA would be advantageous for high-throughput screening of dioxin and dioxin-like compounds in environmental samples.
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Affiliation(s)
- Ayumi Kasai
- Department of Biochemistry, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Tamaho, Yamanashi 409-3898, Japan
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Kasai A, Yao J, Yamauchi K, Hiramatsu N, Hayakawa K, Meng Y, Maeda S, Kitamura M. Influence of cAMP on reporter bioassays for dioxin and dioxin-like compounds. Toxicol Appl Pharmacol 2005; 211:11-9. [PMID: 15972221 DOI: 10.1016/j.taap.2005.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 05/10/2005] [Accepted: 05/12/2005] [Indexed: 11/15/2022]
Abstract
In reporter assays for detection of dioxins, the dioxin-responsive element (DRE) is generally used as a sensor sequence. In several systems, the CYP1A1 promoter containing DREs (DRE(cyp)) is inserted into a part of the long terminal repeat of mouse mammary tumor virus (LTR(MMTV)) to improve sensitivity of assays. We found that DRE(cyp)-LTR(MMTV) responds not only to dioxins and dioxin-like compounds but also to forskolin, a cAMP-elevating agent. This effect was dose-dependent and reproduced by other cAMP-elevating agents including 8-bromo-cAMP and 3-isobutyl-methylxanthine. The cAMP response element (CRE) and CRE-like sequences were absent in DRE(cyp)-LTR(MMTV) and not involved in this process. In contrast to the effect of dioxin, the activation of DRE(cyp)-LTR(MMTV) by cAMP was independent of the aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor for DRE. Furthermore, neither DRE(cyp), LTR(MMTV) nor the consensus sequence of DRE alone was activated in response to cAMP. These data elucidated for the first time that the combination of DRE(cyp) with LTR(MMTV) causes a peculiar response to cAMP and suggested that use of AhR antagonists is essential to exclude false-positive responses of DRE(cyp)-LTR(MMTV)-based bioassays for detection and quantification of dioxins and dioxin-like compounds.
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Affiliation(s)
- Ayumi Kasai
- Department of Biochemistry, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato1110, Tamaho, Yamanashi 409-3898, Japan
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28
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Ferraris M, Flora A, Chiesara E, Fornasari D, Lucchetti H, Marabini L, Frigerio S, Radice S. Molecular mechanism of the aryl hydrocarbon receptor activation by the fungicide iprodione in rainbow trout (Oncorhynchus mykiss) hepatocytes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2005; 72:209-220. [PMID: 15820101 DOI: 10.1016/j.aquatox.2004.12.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 12/10/2004] [Accepted: 12/19/2004] [Indexed: 05/24/2023]
Abstract
The dicarboximide fungicide iprodione (Ip) causes oxidative damage as a result of the production of free oxygen radicals, and induces cytochrome P4501A3 (CYP1A3) in cultured rainbow trout hepatocytes. The aim of this study was to characterise some of the molecular mechanisms by means of which Ip activates the aryl hydrocarbon receptor (AhR) and subsequently induces the CYP1A3 gene in rainbow trout (Oncorhynchus mykiss). The study was performed using primary hepatocytes and transfected HepG2 cells with a reporter construct, in which luciferase gene expression is under the transcriptional control of a multimerised xenobiotic response elements (4XREs), or a 2.3 Kb DNA fragment (corresponding to the trout CYP1A3 gene promoter). Ip exposure increased rainbow trout hepatocyte CYP1A3 mRNA over time and increased the expression of reporter gene in HepG2, thus suggesting that Ip induces the CYP1A3 gene by activating the AhR. Genistein, a tyrosine kinase inhibitor, efficiently inhibited the Ip-mediated induction of the CYP1A3 gene as demonstrated by mRNA level decrease and the impaired activation of the luciferase reporter gene constructs. Staurosporine, an inhibitor of protein kinase C, also suppressed the induction by Ip. When the AhR antagonist alpha-naphthoflavone was added to the cultures, Ip-mediated CYP1A3 induction was suppressed. These findings are consistent with a mechanism of Ip-mediated CYP1A3 gene induction that involves the activation of the AhR complex via phosphorylation-dephosphorylation reactions.
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Affiliation(s)
- Michela Ferraris
- Department of Pharmacology, Chemotherapy and Medical Toxicology E. Trabucchi, University of Milan, Via Vanvitelli 32, 20129 Milan, Italy.
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Windal I, Van Wouwe N, Eppe G, Xhrouet C, Debacker V, Baeyens W, De Pauw E, Goeyens L. Validation and interpretation of CALUX as a tool for the estimation of dioxin-like activity in marine biological matrixes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:1741-8. [PMID: 15819233 DOI: 10.1021/es049182d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Among the different analytical tools proposed as an alternative to the very expensive gas chromatography high-resolution mass spectrometry (GC-HRMS) analyses of polychlorodibenzo-p-dioxin and polychlorodibenzofurans, Chemically Activated LUciferase gene eXpression (CALUX) in vitro cell bioassay is very promising. It allows the analyses of a high number of samples since it is relatively fast, inexpensive, and sensitive. However, this technique is not yet widely applied for screening or environmental monitoring. The main reasons are probably the lack of validation and the difficulty in interpreting the global biological response of the bioassay. In this paper, the strict quality control criteria set up for the validation of CALUX are described. The validation has shown good repeatability (relative standard deviation (RSD) = 9%) and good within-lab reproducibility (RSD = 15%) of the results. The quantification limit, in the conditions applied in this paper, is 1.25 pg CALUX-TEQ/g fat. Comparison of CALUX and GC-HRMS analysis was made forvarious marine matrixes (fishes, mussels, starfishes, sea birds, and marine mammals). Good correlations are usually observed, but there are systematic differences between the results. Attempts are made to identify the origin of the discrepancy between the two methods.
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Affiliation(s)
- Isabelle Windal
- Scientific Institute of Public Health, 1050 Brussels, Belgium.
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Schreurs RHMM, Sonneveld E, van der Saag PT, van der Burg B, Seinen W. Examination of the in vitro (anti)estrogenic, (anti)androgenic and (anti)dioxin-like activities of tetralin, indane and isochroman derivatives using receptor-specific bioassays. Toxicol Lett 2005; 156:261-75. [PMID: 15737489 DOI: 10.1016/j.toxlet.2004.11.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 11/30/2004] [Accepted: 11/30/2004] [Indexed: 11/22/2022]
Abstract
Molecules derived from tetralin, indane and isochroman are often used in the synthesis of fragrance materials. The two polycyclic musk fragrances AHTN (6-acetyl-1,1,2,4,4,7-hexamethyltetralin), HHCB (1,2,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-benzopyran) and ADBI (4-acetyl-1,1-dimethyl-6-tert-butylindane) are derived from tetralin, isochroman and indane, respectively. In previous studies, AHTN and HHCB have been shown to antagonize estrogen receptors (ERs), both in vitro and in vivo. Here, we used two newly developed reporter gene assays, to examine the agonistic and antagonistic properties of several indane, tetralin and isochroman derivatives towards the human androgen receptor (AR) and aryl hydrocarbon receptor (AhR). Additionally, we also assessed (anti)estrogenicity of these compounds. A number of compounds showed weak estrogenic activity towards the human ER alpha. Several compounds showed (anti)estrogenic effects, starting at a concentration of 0.1 microM. Surprisingly, almost all compounds were found to be AR antagonists, starting at 0.1 microM. None of the compounds tested, showed either agonism or antagonism towards the AhR. Non-specific effects via crosstalk of the AhR and the ER or AR can therefore be ruled out. As far as we are aware, molecules derived from indane, tetralin and isochroman showing direct interaction with the ER and AR have not been reported previously.
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Affiliation(s)
- Richard H M M Schreurs
- Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80176, 3508 TD, Utrecht, The Netherlands
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31
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Chen G, Bunce NJ. Interaction between halogenated aromatic compounds in the Ah receptor signal transduction pathway. ENVIRONMENTAL TOXICOLOGY 2004; 19:480-9. [PMID: 15352264 DOI: 10.1002/tox.20053] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Many toxic and biochemical responses to halogenated aromatic compounds (HACs) such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins (PCDDs) are mediated through the aryl hydrocarbon receptor (AhR), which is an intracellular cytosolic target for HACs. Environmental exposure to HACs almost always involves complex mixtures of congeners, some of which can antagonize the action of potent HACs such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this work we studied TCDD and representative PCB congeners, alone and in mixture, for their effect on CYP1A gene transcription and protein levels in primary rat hepatocytes. Together with our previous work, our results suggest that formation of the Ah receptor-ligand-DRE (dioxin response element) complex is the principal point of divergence in the mechanism between an AhR agonist and an AhR antagonist. The coplanar PCBs 77 and 126 and the mono-ortho PCB 156 were full agonists toward CYP1A1 gene transcription and CYP1A protein levels, showing typical additive behavior with TCDD to the target molecule AhR. In contrast, the nonplanar PCB 153 antagonized the action of TCDD, even at concentrations that occupied a significant fraction of AhR molecules. Competitive inhibition explains the commonly reported decrease of ethoxyresorufin-O-deethylase (EROD) activity when PCBs are present in high concentrations and the antagonism of PCBs to the EROD activity of TCDD. The result is that Western blotting offers a much more reliable measure of CYP1A protein concentration than does the EROD assay, despite the greater convenience of the latter.
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Affiliation(s)
- Guosheng Chen
- Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Gozgit JM, Nestor KM, Fasco MJ, Pentecost BT, Arcaro KF. Differential action of polycyclic aromatic hydrocarbons on endogenous estrogen-responsive genes and on a transfected estrogen-responsive reporter in MCF-7 cells. Toxicol Appl Pharmacol 2004; 196:58-67. [PMID: 15050408 DOI: 10.1016/j.taap.2003.12.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2003] [Accepted: 12/15/2003] [Indexed: 11/23/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants that have been extensively studied for multiple toxicological endpoints in both laboratory animals and humans. The purpose of this study was to investigate the estrogenicity of PAHs in the human breast cancer cell line MCF-7. We investigated 14 PAHs for their ability to bind either the estrogen receptor (ER) or the aryl hydrocarbon receptor (AhR) and to activate target gene expression. PAHs were tested in a human recombinant estrogen receptor (hrER) competitive binding assay, and in both an estrogen response element (ERE)- and xenobiotic response element (XRE)-mediated reporter gene assay. We used quantitative RT-PCR to examine selected PAHs that showed activity in the ERE reporter gene assay for their ability to upregulate estrogen-responsive genes HEM45, progesterone receptor, and pS2, and the aryl hydrocarbon-responsive CYP1A1 gene. None of the 14 PAHs bound the hrER, but five of the PAHs (anthracene, B[a]A, chrysene, B[b]F, and B[a]P) induced ER-reporter activity. This activity was dependent on the metabolism of PAHs in MCF-7 cells via the AhR pathway, which resulted in the formation of metabolites that bound the ER. None of the five PAHs that induced the ER-reporter were found to upregulate estrogen-responsive genes, yet four of the five PAHs induced AhR-dependent CYP1A1 gene expression. In contrast, a metabolite of B[a]P, 3'OH-B[a]P, and a PCB metabolite, 4'OH-2,4,6-BP, did weakly upregulate all three estrogen-responsive genes. Data from these studies indicate that induction of ER-reporter activity alone does not necessarily parallel endogenous gene transcription, and that the reporter gene assay may detect interactions that are not functional in vivo.
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Affiliation(s)
- Joseph M Gozgit
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA 01003-9298, USA
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33
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Shibazaki M, Takeuchi T, Ahmed S, Kikuchi H. Suppression by p38 MAP Kinase Inhibitors (Pyridinyl Imidazole Compounds) of Ah Receptor Target Gene Activation by 2,3,7,8-Tetrachlorodibenzo-p-dioxin and the Possible Mechanism. J Biol Chem 2004; 279:3869-76. [PMID: 14594946 DOI: 10.1074/jbc.m305880200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome P-450 1A1 (CYP1A1) is known to be induced by aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), through activation of the aryl hydrocarbon receptor (AhR). We found that p38 MAP kinase inhibitors (SB203580 and SB202190; 40 microm each; pyridinyl imidazole compounds) suppressed CYP1A1-mRNA induction by TCDD (2 nm) in mouse hepatoma Hepa-1 cells and in human hepatoma HepG2 cells, and also suppressed CYP1B1-mRNA induction by TCDD (2 nm) in human breast adenocarcinoma MCF7 cells. An analogue compound, SB202474, which does not inhibit p38 MAP kinase, also suppressed CYP1A1-mRNA induction by TCDD. Moreover, overexpression of a dominant-negative gene for p38 MAP kinase in Hepa-1 cells did not suppress Cyp1a1 reporter gene induction by TCDD. Therefore, the suppression of Cyp1a1 transcription by pyridinyl imidazole compounds is not because of their inhibition of p38 MAP kinase activity. Because SB203580 did not inhibit in vitro AhR transformation by TCDD, this compound was not acting as a simple AhR antagonist. SB203580 decreased TCDD-induced histone acetylation levels in the region of the Cyp1a1 gene promoter, especially around the TATA box sequence. This result suggests the possibility that pyridinyl imidazole compounds suppress the recruitment of some co-activator that has the histone acetyltransferase activity necessary for CYP1A1-mRNA transcription.
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Affiliation(s)
- Masahiko Shibazaki
- Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan
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Savouret JF, Berdeaux A, Casper RF. The aryl hydrocarbon receptor and its xenobiotic ligands: a fundamental trigger for cardiovascular diseases. Nutr Metab Cardiovasc Dis 2003; 13:104-13. [PMID: 12929624 DOI: 10.1016/s0939-4753(03)80026-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This review reconsiders a major cause of cardiovascular diseases, tobacco smoking, as the activation of the Aryl hydrocarbon Receptor (AhR), also known as the dioxin receptor, by aryl hydrocarbons from the tar fraction of tobacco in various organs of the cardiovascular domain. This concept sheds new light on well-known albeit controversial epidemiological concepts such as the Mediterranean diet and the French paradox. We also review the discovery that resveratrol, a natural AhR antagonist, may be of interest in the prevention and treatment of cardiovascular diseases.
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Affiliation(s)
- J F Savouret
- Unité de recherche mixte UMR-S 530, Inserm, Université Paris 5, Centre Universitaire-UFR Biomedicale, 45 rue des Saints-Pères, 75006 Paris, France.
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Moorthy B, Miller KP, Jiang W, Williams ES, Kondraganti SR, Ramos KS. Role of cytochrome P4501B1 in benzo[a]pyrene bioactivation to DNA-binding metabolites in mouse vascular smooth muscle cells: evidence from 32P-postlabeling for formation of 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-3,6-quinone as major proximate genotoxic intermediates. J Pharmacol Exp Ther 2003; 305:394-401. [PMID: 12649394 DOI: 10.1124/jpet.102.044271] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Benzo[a]pyrene (BP), a polycylic aromatic hydrocarbon (PAH), is a potent atherogen and carcinogen in laboratory animals. Since genotoxic mechanisms may contribute to the development of atherosclerosis by PAHs, we have tested the hypotheses that: 1) BP induces DNA adducts in mouse aortic smooth muscle cells (SMCs); 2) 3-hydroxybenzo[a]pyrene (3-OH-BP) and benzo[a]pyrene-3,6-quinone (BPQ) are proximate genotoxic metabolites; and 3) cytochrome P4501B1 (CYP1B1) mediates the activation of BP and its metabolites to ultimate genotoxic intermediates. Cultured mouse aortic SMCs were treated with BP, 3-OH-BP, or BPQ for 24 h, and DNA adduct formation was analyzed by (32)P-postlabeling. In some experiments, cells were pretreated with the CYP1B1 inhibitor 1-ethynylpyrene (EP) prior to exposure to BP or its metabolites. BP, 3-OH-BP, and BPQ induced formation of several DNA adducts that were not observed in dimethylsulfoxide-treated cells. Re- and cochromatography experiments indicated that 3-OH-BP and BPQ were proximate genotoxic metabolites of BP. DNA adduct formation was strongly inhibited by EP, a specific inhibitor of CYP1B1. BP treatment of SMCs resulted in induction of aryl hydrocarbon hydroxylase (AHH) activity and CYP1B1, but not CYP1A1, apoprotein. EP also blocked AHH induction by BP. In conclusion, the results of this study support the hypothesis that in SMCs, which are target sites for the development of atherosclerosis, the major bioactivation pathway of BP entails CYP1B1-mediated formation of the 3-OH-BP and BPQ, which are proximate genotoxic metabolites that may in turn get transformed to ultimate DNA-binding metabolites, which may contribute to atherogenesis by PAHs.
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Affiliation(s)
- Bhagavatula Moorthy
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA.
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36
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Ishida S, Jinno H, Tanaka-Kagawa T, Ando M, Ohno Y, Ozawa S, Sawada JI. Characterization of human CYP1A1/1A2 induction by DNA microarray and alpha-naphthoflavone. Biochem Biophys Res Commun 2002; 296:172-7. [PMID: 12147246 DOI: 10.1016/s0006-291x(02)00856-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DNA microarrays and real time PCR were used to analyze the mechanism of gene induction by CYP1A1 inducers, beta-naphthoflavone, and omeprazole, in the human hepatocellular carcinoma HepG2 cells. Reproducible and significant inductions were observed in a limited number of genes including CYP1A1 and CYP1A2. Genes induced by omeprazole included several protein tyrosine kinase targets. This result confirmed that omeprazole could modulate gene expressions through protein tyrosine kinase-mediated pathway. Induction ratios were considerably different from CYP1A1 and CYP1A2 (>10-fold) to other induced genes (<5-fold). alpha-Naphthoflavone, which is known as an antagonist to 2,3,7,8-tetrachlorodibenzo-p-dioxin, inhibited the inductions of heme oxygenase 1, glutamate-cysteine ligase (modifier unit), and thioredoxin reductase by beta-naphthoflavone but not those of CYP1A1 and CYP1A2. It unexpectedly enhanced the beta-naphthoflavone-mediated CYP1A1 and CYP1A2 induction. These results suggest that the CYP1A1 and CYP1A2 genes, which share their 5(') enhancer regions, are regulated differently from the other genes.
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Affiliation(s)
- Seiichi Ishida
- Project Team for Pharmacogenetics, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, 158-8501, Tokyo, Japan.
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Rushing SR, Denison MS. The silencing mediator of retinoic acid and thyroid hormone receptors can interact with the aryl hydrocarbon (Ah) receptor but fails to repress Ah receptor-dependent gene expression. Arch Biochem Biophys 2002; 403:189-201. [PMID: 12139968 DOI: 10.1016/s0003-9861(02)00233-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related chemicals causes a variety of tissue- and species-specific biological and toxicological effects, most of which are mediated by the aryl hydrocarbon receptor (AhR). The AhR complex is a ligand-dependent transcription factor that binds to its specific DNA recognition site as a dimer with the AhR nuclear translocator (ARNT) and activates gene transcription. Here, we have examined the ability of a nuclear corepressor, the silencing mediator of retinoic acid and thyroid hormone receptors (SMRT), to interact with and modulate AhR-dependent gene expression. Using glutathione S-transferase (GST) "pull-down" binding assays, we have mapped a major interaction between these factors to the silencing domain of SMRT and the PAS B ligand binding domain of AhR, and this interaction is unaffected by the addition of an AhR ligand. Association of SMRT with the AhR:ARNT:DNA complex was not detected by GST pull-down or gel retardation assays. Transient cotransfections of mammalian cells (Hepa1c1c7, MCF-7, and BG-1) with SMRT and a TCDD-inducible luciferase reporter containing the dioxin-responsive domain from the mouse CYP1A1 regulatory region revealed that SMRT does not repress, but enhances, AhR signaling. However, when a reporter containing a human CYP1A1 upstream region was cotransfected with SMRT into human MCF-7 cells, AhR-driven reporter activity was decreased by half, suggesting that SMRT acts on the human CYP1A1 promoter via a factor other than the AhR in MCF-7 cells. Furthermore, the interaction between SMRT and the AhR may have implications in pathways other than the AhR signaling pathway.
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Affiliation(s)
- S Renée Rushing
- Department of Environmental Toxicology, University of California at Davis, Davis, CA 95616, USA
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38
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Cui X, Palamanda J, Norton L, Thomas A, Lau YY, White RE, Cheng KC. A high-throughput cell-based reporter gene system for measurement of CYP1A1 induction. J Pharmacol Toxicol Methods 2002; 47:143-51. [PMID: 12628305 DOI: 10.1016/s1056-8719(02)00222-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Enzyme induction is undesirable in new drug discovery process, with consequences spanning from auto-induction to toxicity. Cytochrome P450 (CYP) 1A1 has long been known to be one of the metabolic enzymes involved in activating many procarcinogens, the first step toward tumor formation during chemical carcinogenesis. Induction of CYP1A1 during drug treatment may predispose the patients to some risk of chemical carcinogenesis. METHODS Based on the signal-transduction mechanism of CYP1A1 induction, a high-throughput reporter-gene system was established by stable transformation of H4IIE cells to incorporate the luciferase gene under control of CYP1A1 promoter. This stable cell line was validated with known CYP1A1 inducers, such as 3-methylcholanthrene (3-MC), beta-naphthoflavone (beta-NF), alpha-naphthoflavone (alpha-NF) and 3-indocarbinol. Thirty in-house new chemical entities (NCEs) were then screened with this reporter-gene system, and also administered to rats to evaluate in vivo CYP1A1 induction. RESULTS CYP1A1 reporter gene system can be used to identify strong inducers, such as 3-MC, beta-NF and alpha-NF, and weak inducers, such as 3-indocarbinol. In vitro induction of 30 in-house compounds in reporter gene system did not correlate with in vivo induction in rat liver microsome measured by ethoxyresorufin-O-dealkylation (EROD) activity, but had a reasonable correlation with Western blot signals. DISCUSSION This reporter-gene system may be useful in eliminating compounds that can cause CYP1A1 induction at an early stage of drug discovery.
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Affiliation(s)
- Xiaoming Cui
- Department of Exploratory Drug Discovery, Schering-Plough Research Institute, D209, K15-2700, Kenilworth, NJ 07033, USA.
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Abstract
The various properties of the stilbene phytoalexin Resveratrol provide interesting new avenues of research in the field of chemoprevention and chemotherapy. A particular emphasis is given on xenobiotic-related carcinogenesis.
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Affiliation(s)
- J F Savouret
- INSERM unité 135, Hopital de Bicêtre CHU level 3, Le Kremlin-Bicêtre, France.
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Kwon YW, Ueda S, Ueno M, Yodoi J, Masutani H. Mechanism of p53-dependent apoptosis induced by 3-methylcholanthrene: involvement of p53 phosphorylation and p38 MAPK. J Biol Chem 2002; 277:1837-44. [PMID: 11706017 DOI: 10.1074/jbc.m105033200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycyclic aromatic hydrocarbons (PAHs) such as 3-methylcholanthrene (MC) cause untoward effects including carcinogenesis. Here we investigated the effect of MC on apoptosis. MC induced apoptosis, preceded by serine 15 phosphorylation and accumulation of p53. MC failed to cause apoptosis in p53-deficient MG63 cells, whereas ectopic expression of p53 in MG63 cells restored the response to MC. Therefore, MC-induced apoptosis was dependent on p53. MC also activated p38 mitogen-activated protein kinase (MAPK) at 16-24 h. Accumulation of p53 and p53 phosphorylated at serine 15 was not changed by SB203580, a specific inhibitor of p38 MAPK or overexpression of a dominant negative mutant of p38 MAPK at 8 h after MC treatment, whereas the accumulation was suppressed at 24 h. These results suggest that MC induces accumulation and phosphorylation of p53 via a p38 MAPK-independent (early) and p38 MAPK-dependent (late) pathway. SB203580 repressed MC-induced apoptosis. MC induced p38 MAPK activation in p53 expressing cells but not in p53-deficient cells, indicating that the p38 MAPK activation was dependent on early p53 activation. The current study shows that both p53 and p38 MAPK activation are required for MC-induced apoptosis and provides a novel model of a functional regulation between p53 and p38 MAPK in chemical stress-induced apoptosis.
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Affiliation(s)
- Yong-Won Kwon
- Institute for Virus Research, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
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Savouret JF, Antenos M, Quesne M, Xu J, Milgrom E, Casper RF. 7-ketocholesterol is an endogenous modulator for the arylhydrocarbon receptor. J Biol Chem 2001; 276:3054-9. [PMID: 11042205 DOI: 10.1074/jbc.m005988200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have identified 7-ketocholesterol (7-KC) as an endogenous modulator that inhibits transactivation by the arylhydrocarbon receptor (AhR) through competitive binding against xenobiotic ligands. 7-KC binds AhR and displaces labeled dioxin (2,3,7,8-tetrachlorodibenzo(p)dioxin (TCDD)). IC(50) is 5 x 10(-7) m in vivo and 7 x 10(-6) m in vitro. These figures are consistent with its concentration in human blood plasma and tissues. Association with 7-KC prevents AhR binding to DNA. 7-KC blocks the TCDD-mediated transactivation of stably expressed reporter gene constructs in T47-D cells as well as the expression of the endogenous CYP 1A1 gene in HepG2 cells and in primary porcine aortic endothelial cells. Injection of 7-KC to rats blocks the induction of CYP 1A1 messenger RNA and protein in endothelial cells from myocardial blood vessels. The differential sensitivity of mammalian species to toxic effects of AhR ligands, especially dioxin (TCDD), correlates with the expression of 7-hydroxycholesterol dehydrogenase, which synthesizes 7-KC from 7-hydroxycholesterol. The documented involvement of AhR ligands in cardiovascular diseases through lipid peroxidation and endothelium dysfunction can now be examined in the context of displacement of this protective modulator.
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Affiliation(s)
- J F Savouret
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada.
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42
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Tom DJ, Lee LE, Lew J, Bols NC. Induction of 7-ethoxyresorufin-O-deethylase activity by planar chlorinated hydrocarbons and polycyclic aromatic hydrocarbons in cell lines from the rainbow trout pituitary. Comp Biochem Physiol A Mol Integr Physiol 2001; 128:185-98. [PMID: 11223380 DOI: 10.1016/s1095-6433(00)00291-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The induction of 7-ethoxyresorufin-o-deethylase (EROD) activity was examined in three rainbow trout pituitary cell lines: RTP-91E, RTP-91F and RTP-2. RTP-91E and RTP-91F were developed from the pituitary of a male and have epithelial-like and fibroblast-like morphologies, respectively. RTP-2, which was described previously, was developed from the pituitary of a female and has an epithelial-like shape. In all cell lines EROD activity was induced by 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD). Immunoblotting with the polyclonal antibody, anti-trout CYP1A1(277-294)/KLH, confirmed induction of a 58-kDa polypeptide. Potential inhibitors of the aryl hydrocarbon receptor, geldanamycin and alpha-naphthoflavone, inhibited EROD induction by TCDD. Other compounds inducing EROD activity were 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), and 3-methylcholanthrene (3MC). When judged by the concentration eliciting 50% of the maximal response (EC50), induction was similar in RTP-2 and RTP-91E, and less effective in RTP-91F. Regardless of the cell line, the rank order from most to least potent inducer on the basis of EC50 value was TCDD> or =PCDD>TCDF>PCB 126>>3MC. When induction potencies were expressed relative to TCDD, the values obtained with the pituitary cell lines were similar to previously published values derived with a rainbow trout liver cell line.
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Affiliation(s)
- D J Tom
- Department of Biology, University of Waterloo, ON N2L 3G1, Waterloo, Canada
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Guo M, Joiakim A, Reiners JJ. Suppression of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated aryl hydrocarbon receptor transformation and CYP1A1 induction by the phosphatidylinositol 3-kinase inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1- benzopyran-4-one (LY294002). Biochem Pharmacol 2000; 60:635-42. [PMID: 10927021 DOI: 10.1016/s0006-2952(00)00379-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Numerous flavonoids are ligands of the aryl hydrocarbon receptor (AHR) and function as AHR antagonists and/or agonists. LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one] is a widely used inhibitor of phosphatidylinositol 3-kinase (PI 3-kinase), and is structurally related to members of the flavonoid family. Concentrations of LY294002 >/= 10 microM were cytostatic, but not cytotoxic, to cultures of the immortalized human breast epithelial cell line MCF10A-Neo. Treatment of MCF10A-Neo cultures with the AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) stimulated the transcriptional activation of CYP1A1, as monitored by measurements of steady-state CYP1A1 mRNA. Pretreatment of cultures with >/= 10 microM LY294002 suppressed the TCDD activation of CYP1A1 (IC(50) approximately 10 microM). Electrophoretic mobility shift assays employing rat liver cytosol demonstrated that concentrations of LY294002 </= 400 microM did not transform the AHR into a DNA-binding species. However, the addition of LY294002 to cytosol just prior to TCDD addition completely suppressed AHR transformation by TCDD (IC(50) approximately 35 microM). The PI 3-kinase inhibitor Wortmannin was weakly cytostatic, but not cytotoxic to MCF10A-Neo cultures at concentrations </= 500 nM. Exposure of cultures to Wortmannin (10-500 nM) did not suppress TCDD activation of CYP1A1. Analyses of the phosphorylation status of Akt-1, an in vivo substrate of PI 3-kinase, demonstrated that concentrations of LY294002 >/= 50 microM and Wortmannin >/= 10 nM completely suppressed PI 3-kinase activity. Hence, the ability of LY294002 to suppress TCDD-dependent activation of CYP1A1 is unrelated to PI 3-kinase inhibition. Instead, this activity reflects LY294002 functioning as an AHR antagonist. Furthermore, most of the cytostatic activity of LY294002 towards MCF10A-Neo cells is unrelated to the inhibition of PI 3-kinase.
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Affiliation(s)
- M Guo
- Institute of Chemical Toxicology, Wayne State University, Detroit, MI 48201, USA
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Reiners JJ, Clift RE. Aryl hydrocarbon receptor regulation of ceramide-induced apoptosis in murine hepatoma 1c1c7 cells. A function independent of aryl hydrocarbon receptor nuclear translocator. J Biol Chem 1999; 274:2502-10. [PMID: 9891021 DOI: 10.1074/jbc.274.4.2502] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The relationship between aryl hydrocarbon receptor (AHR) content and susceptibility to apoptosis was examined in the murine hepatoma 1c1c7 cell line and a series of variants having different levels of AHR expression. Exposure of 1c1c7 cultures to N-acetylsphingosine (C2-ceramide) caused a concentration-dependent inhibition of cell proliferation, loss of viability, and induction of apoptosis as monitored by analyses of DNA fragmentation and caspase activation. A variant cell line (Tao) having approximately 10% of the AHR content of 1c1c7 cells also arrested following exposure to C2-ceramide, but did not undergo apoptosis. Modulation of 1c1c7 and Tao AHR contents by transfection of Ahr antisense and sense constructs, respectively, confirmed the relationship between AHR content and susceptibility to C2-ceramide-induced apoptosis. C2-ceramide also induced the apoptosis of an AHR-containing cell line lacking the aryl hydrocarbon receptor nuclear translocator protein. AHR ligands (i.e. 2,3,7,8-tetrachlorodibenzo-p-dioxin and alpha-naphthoflavone) neither induced apoptosis nor modulated the development of apoptosis in C2-ceramide-treated 1c1c7 cultures. AHR content did not affect staurosporine- or doxorubicin-induced apoptosis. These results suggest the AHR modulates aspects of ceramide signaling associated with the induction of apoptosis but not cell cycle arrest, and does so by a mechanism that is independent of its interaction with aryl hydrocarbon receptor nuclear translocator and exogenous AHR ligands.
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Affiliation(s)
- J J Reiners
- Institute of Chemical Toxicology, Wayne State University, Detroit, Michigan 48201, USA.
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Carrière V, Dussaulx E, Rousset M, Zweibaum A, Cambier D. Decreased expression of gamma-glutamyltranspeptidase in the intestinal cell line Caco-2 by inducers of cytochrome P450 1A1. Biochem Pharmacol 1998; 56:817-23. [PMID: 9774143 DOI: 10.1016/s0006-2952(98)00106-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Our purpose was to investigate whether inducers of cytochrome P450 1A1 (CYP1A1), which cause a decreased expression in Caco-2 cells, at both the mRNA and protein levels, of membrane proteins associated with the uptake and transport of hexoses, would also affect the expression of gamma-glutamyltranspeptidase (gammaGT) (EC 2.3.2.2). In Caco-2 clonal TC7 cells grown under standard conditions (25 mM glucose), exposure to beta-naphthoflavone (beta-NF), 2,3,7,8-tetrachlorodibenzo-p-dioxin, and 3-methylcholanthrene resulted in increased glucose consumption and decreased gammaGT activity in cells grown to confluence, i.e. when the differentiation is optimum. GammaGT activity was further analyzed during the time course of differentiation of TC7 cells treated or not with beta-naphthoflavone: while gammaGT activity in untreated cells showed a 10-fold increase from the exponential phase of growth until late postconfluence, gammaGT activity in beta-NF-treated cells, although increasing by 4-fold, remained at a much lower level (<25%). This decreased activity of gammaGT was associated with a decreased level of gammaGT mRNA. This inhibiting effect was not dependent on the CYP1A1 activity, as it also occurred in the presence of CYP1A1 inhibitors such as alpha-naphthoflavone, 8-methoxypsoralen or ellipticin. It was however dependent on glucose supply as it was not observed when the cells were cultured in low glucose (1 mM). These results raise the question of whether, in Caco-2 cells, CYP1A1 inducers or the signal transduction system which controls CYP1A1 are involved in the regulation of the expression of gammaGT through a mechanism involving glucose metabolism.
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Affiliation(s)
- V Carrière
- Unité de Recherches sur la Différenciation Cellulaire Intestinale, INSERM U178, Villejuif, France
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Modulation of Hepatocyte Gene Expression by the Carcinogen Benzo[a]pyrene. Toxicol In Vitro 1998; 12:395-402. [DOI: 10.1016/s0887-2333(98)00003-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/1997] [Indexed: 11/18/2022]
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Carrière V, Rodolosse A, Lacasa M, Cambier D, Zweibaum A, Rousset M. Hypoxia and CYP1A1 induction-dependent regulation of proteins involved in glucose utilization in Caco-2 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:G1101-8. [PMID: 9696711 DOI: 10.1152/ajpgi.1998.274.6.g1101] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Although induction of cytochrome P-450 1A1 (CYP1A1) in the Caco-2 clone TC7 alters glucose utilization and modifies the expression of sucrase-isomaltase (SI) and hexose transporters, nothing is known of the events that control these effects. In this study, we analyzed the effects of beta-naphthoflavone (beta-NF) and hypoxia on these parameters and expression of key enzymes of glucose metabolism. Both beta-NF and hypoxia induce similar changes: 1) induction of CYP1A1 mRNA; 2) increased glucose consumption and lactic acid production and lower glycogen content; 3) downregulation of SI and upregulation of GLUT1 mRNAs; 4) downregulation of fructose-1,6-bisphosphatase and pyruvate kinase mRNAs and upregulation of phosphoenolpyruvate carboxykinase, pyruvate dehydrogenase, lactate dehydrogenase, and phosphofructokinase mRNAs; and 5) upregulation of c-fos and c-jun mRNAs. Although addition of inhibitors of CYP1A1 catalytic activity to beta-NF-treated cells totally inhibits the enzyme activity, it does not modify CYP1A1 mRNA response and associated effects, thus excluding a direct role for the enzyme per se. These results point to a possible physiological implication of the signal-transduction pathway responsible for CYP1A1 induction.
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Affiliation(s)
- V Carrière
- Unité de Recherches sur la Différenciation Cellulaire Intestinale, Institut National de la Santé et de la Recherche Médicale, Villejuif, France
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Mounho BJ, Burchiel SW. Alterations in human B cell calcium homeostasis by polycyclic aromatic hydrocarbons: possible associations with cytochrome P450 metabolism and increased protein tyrosine phosphorylation. Toxicol Appl Pharmacol 1998; 149:80-9. [PMID: 9512730 DOI: 10.1006/taap.1997.8345] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies performed in this laboratory have shown that certain benzo(a)pyrene (BaP) metabolites, such as benzo(a)pyrene-7,8-dihydrodiol (BaP-7,8-diol) and benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), were more effective in elevating intracellular Ca2+ in normal human peripheral blood mononuclear cell (HPBMC) T and B cells than was BaP. Additionally, it has been shown that the suppression of human T cell mitogenesis produced by polycyclic aromatic hydrocarbons (PAHs) and certain BaP metabolites is reversed by treatment with alpha-naphthoflavone (ANF), a cytochrome P450 1A and 1B inhibitor. ANF also diminishes the elevation in intracellular calcium (Ca2+) produced by BaP in HPBMC. In the present studies, we further defined the relationships between intracellular Ca2+ elevation produced by BaP and two immunotoxic P450-derived metabolites, BaP-7,8-diol and BPDE in the Daudi human B cell line. At 1, 4, and 18 h, both BaP-7,8-diol and BPDE produced a significant rise in intracellular Ca2+. This effect, however, was not observed with BaP or benzo(e)pyrene (BeP), a nonimmunotoxic PAH. To evaluate the potential role of cytochrome P450 metabolism in PAH-induced Ca2+ elevation, Daudi cells were pretreated with ANF for 4 h, followed by treatment with BaP metabolites for 18 h. ANF completely reversed the rise in Ca2+ produced by BaP-7,8-diol, but had no effect on the Ca2+ elevation produced by BPDE. These results suggest that BPDE may be the ultimate P450 metabolite responsible for Ca2+ elevation in human B cells. BaP-7,8-diol and BPDE were found to increase tyrosine phosphorylation in Daudi whole cell lysates and to increase tyrosine phosphorylation of two important Src-related protein tyrosine kinases (PTKs), Lyn and Syk. Inhibition of tyrosine phosphorylation by herbimycin A was found to largely prevent the increase in intracellular Ca2+ produced by BaP-7,8-diol and BPDE, suggesting that Ca2+ elevation is coupled to increased tyrosine phosphorylation in Daudi. BPDE was found to produce a statistically significant increase in tyrosine phosphorylation of Lyn and Syk within 10 min of exposure. Collectively, these data demonstrate that certain P450-derived metabolites of BaP may be responsible for PTK activation and an increase intracellular Ca2+, which may alter antigen receptor signaling in human B cells.
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Affiliation(s)
- B J Mounho
- University of New Mexico College of Pharmacy, Toxicology Program, Albuquerque 87131-1066, USA
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Reiners JJ, Lee JY, Clift RE, Dudley DT, Myrand SP. PD98059 is an equipotent antagonist of the aryl hydrocarbon receptor and inhibitor of mitogen-activated protein kinase kinase. Mol Pharmacol 1998; 53:438-45. [PMID: 9495809 DOI: 10.1124/mol.53.3.438] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
PD98059 [2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one] is a flavonoid and a potent inhibitor of mitogen-activated protein kinase kinase (MEK). Concentrations of PD98059 of </=20 muM were not cytotoxic to cultures of the immortalized human breast epithelial cell line MCF10A. The agent was weakly cytostatic at concentrations of >/=10 microM. In vivo exposure of cultures to </=20 microM PD98059 for 2-22 hr did not affect overall extracellular signal-regulated kinase contents; however, exposure to PD98059 resulted in a rapid loss (>95%) of the dually phosphorylated forms of extracellular signal-regulated kinase (IC50 = 1 muM). Treatment of cultures with PD98059 of >/=1 muM either at the time of addition or up to 48 hr before the addition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suppressed in a concentration-dependent manner the accumulation of induced steady state CYP1A1, CYP1B1, and NQO1 mRNAs. The addition of PD98059 to rat liver cytosol just before the addition of TCDD suppressed TCDD binding (IC50 = 4 muM) and aryl hydrocarbon receptor (AHR) transformation (IC50 = 1 muM), as measured by sucrose gradient centrifugation and electrophoretic mobility shift assays. Flavone and flavanone, two closely related structural analogs of PD98059, inhibited AHR transformation by TCDD with IC50 values similar to that obtained with PD98059. However, neither analog was as potent as PD98059 in inhibiting MEK (IC50 approximately 190 muM for both). These results suggest that PD98059 is a ligand for the AHR and functions as an AHR antagonist at concentrations commonly used to inhibit MEK and signaling processes that entail MEK activation.
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Affiliation(s)
- J J Reiners
- Institute of Chemical Toxicology, Wayne State University, Detroit, Michigan 48201, USA.
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Chang CY, Puga A. Constitutive activation of the aromatic hydrocarbon receptor. Mol Cell Biol 1998; 18:525-35. [PMID: 9418899 PMCID: PMC121520 DOI: 10.1128/mcb.18.1.525] [Citation(s) in RCA: 183] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/1997] [Accepted: 10/22/1997] [Indexed: 02/05/2023] Open
Abstract
The ligand-activated aromatic hydrocarbon receptor (AHR) dimerizes with the AHR nuclear translocator (ARNT) to form a functional complex that transactivates expression of the cytochrome P-450 CYP1A1 gene and other genes in the dioxin-inducible [Ah] gene battery. Previous work from this laboratory has shown that the activity of the CYP1A1 enzyme negatively regulates this process. To study the relationship between CYP1A1 activity and Ah receptor activation we used CYP1A1-deficient mouse hepatoma c37 cells and CYP1A1- and AHR-deficient African green monkey kidney CV-1 cells. Using gel mobility shift and luciferase reporter gene expression assays, we found that c37 cells that had not been exposed to exogenous Ah receptor ligands already contained transcriptionally active AHR-ARNT complexes, a finding that we also observed in wild-type Hepa-1 cells treated with Ellipticine, a CYP1A1 inhibitor. In CV-1 cells, transient expression of AHR and ARNT leads to high levels of AHR-ARNT-dependent luciferase gene expression even in the absence of an agonist. Using a green fluorescent protein-tagged AHR, we showed that elevated reporter gene expression correlates with constitutive nuclear localization of the AHR. Transcriptional activation of the luciferase reporter gene observed in CV-1 cells is significantly decreased by (i) expression of a functional CYP1A1 enzyme, (ii) competition with chimeric or truncated AHR proteins containing the AHR ligand-binding domain, and (iii) treatment with the AHR antagonist alpha-naphthoflavone. These results suggest that a CYP1A1 substrate, which accumulates in cells lacking CYP1A1 enzymatic activity, is an AHR ligand responsible for endogenous activation of the Ah receptor.
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Affiliation(s)
- C Y Chang
- Department of Environmental Health, University of Cincinnati Medical Center, Ohio 45267-0056, USA
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