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Eaton DL, Simon TW, Kaminski NE, Perdew GH, Nebert DW. The 2022 revised WHO TEFs for dioxins and dioxin-like chemicals: The importance of considering the use of species-specific information to determine relative effective potency for human-based risk assessment. Regul Toxicol Pharmacol 2024; 149:105599. [PMID: 38490576 DOI: 10.1016/j.yrtph.2024.105599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/25/2024] [Accepted: 03/05/2024] [Indexed: 03/17/2024]
Affiliation(s)
- David L Eaton
- Dept. Environmental Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA, USA.
| | | | - Norbert E Kaminski
- Food and Consumer Product Ingredient Safety Endowed Chair, Department of Pharmacology and Toxicology, Institute for Integrative Toxicology, Director, Center for Reseaerch on Ingredient Safety, Michigan State University, East Lansing, MI, USA
| | - Gary H Perdew
- H. Thomas and Dorothy Willits Hallowell Chair in Agricultural Sciences, The Pennsylvania State University, State College, PA, USA
| | - Daniel W Nebert
- Department of Environmental and Public Health Sciences, Center for Environmental Genetics, University of Cincinnati College of Medicine, Department of Pediatrics & Molecular Developmental Biology, Division of Human Genetics, Cincinnati Children's Research Foundation, Cincinnati, OH, USA
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2
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Sahebnasagh A, Hashemi J, Khoshi A, Saghafi F, Avan R, Faramarzi F, Azimi S, Habtemariam S, Sureda A, Khayatkashani M, Safdari M, Rezai Ghaleno H, Soltani H, Khayat Kashani HR. Aromatic hydrocarbon receptors in mitochondrial biogenesis and function. Mitochondrion 2021; 61:85-101. [PMID: 34600156 DOI: 10.1016/j.mito.2021.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 09/17/2021] [Accepted: 09/27/2021] [Indexed: 12/11/2022]
Abstract
Mitochondria are ubiquitous membrane-bound organelles that not only play a key role in maintaining cellular energy homeostasis and metabolism but also in signaling and apoptosis. Aryl hydrocarbons receptors (AhRs) are ligand-activated transcription factors that recognize a wide variety of xenobiotics, including polyaromatic hydrocarbons and dioxins, and activate diverse detoxification pathways. These receptors are also activated by natural dietary compounds and endogenous metabolites. In addition, AhRs can modulate the expression of a diverse array of genes related to mitochondrial biogenesis and function. The aim of the present review is to analyze scientific data available on the AhR signaling pathway and its interaction with the intracellular signaling pathways involved in mitochondrial functions, especially those related to cell cycle progression and apoptosis. Various evidence have reported the crosstalk between the AhR signaling pathway and the nuclear factor κB (NF-κB), tyrosine kinase receptor signaling and mitogen-activated protein kinases (MAPKs). The AhR signaling pathway seems to promote cell cycle progression in the absence of exogenous ligands, whereas the presence of exogenous ligands induces cell cycle arrest. However, its effects on apoptosis are controversial since activation or overexpression of AhR has been observed to induce or inhibit apoptosis depending on the cell type. Regarding the mitochondria, although activation by endogenous ligands is related to mitochondrial dysfunction, the effects of endogenous ligands are not well understood but point towards antiapoptotic effects and inducers of mitochondrial biogenesis.
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Affiliation(s)
- Adeleh Sahebnasagh
- Clinical Research Center, Department of Internal Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Javad Hashemi
- Department of Pathobiology and Laboratory Sciences, School of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Amirhosein Khoshi
- Department of Clinical Biochemistry, School of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Fatemeh Saghafi
- Department of Clinical Pharmacy, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Razieh Avan
- Assistant Professor of Clinical Pharmacy, Department of Clinical Pharmacy, Medical Toxicology and Drug Abuse Research Center (MTDRC), Faculty of Pharmacy, Birjand University of Medical Sciences, Birjand, Iran
| | - Fatemeh Faramarzi
- Clinical Pharmacy Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Saeed Azimi
- Student Research Committee, Department of Clinical Pharmacy, Faculty of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Solomon Habtemariam
- Pharmacognosy Research Laboratories and Herbal Analysis Services, School of Science, University of Greenwich, Central Avenue, Chatham-Maritime, Kent ME4 4TB, United Kingdom
| | - Antoni Sureda
- Research Group in Community Nutrition and Oxidative Stress, University of the Balearic Islands and Health Research Institute of Balearic Islands (IdISBa), Palma de Mallorca, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Maryam Khayatkashani
- School of Iranian Traditional Medicine, Tehran University of Medical Sciences, 14155-6559 Tehran, Iran
| | - Mohammadreza Safdari
- Department of Orthopedic Surgery, Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Hassan Rezai Ghaleno
- Department of Surgery, Faculty of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran
| | - Hosseinali Soltani
- Department of General Surgery, Imam Ali Hospital, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Hamid Reza Khayat Kashani
- Department of Neurosurgery, Imam Hossein Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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3
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Liu JR, Miao H, Deng DQ, Vaziri ND, Li P, Zhao YY. Gut microbiota-derived tryptophan metabolism mediates renal fibrosis by aryl hydrocarbon receptor signaling activation. Cell Mol Life Sci 2021; 78:909-922. [PMID: 32965514 PMCID: PMC11073292 DOI: 10.1007/s00018-020-03645-1] [Citation(s) in RCA: 94] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 08/31/2020] [Accepted: 09/12/2020] [Indexed: 02/06/2023]
Abstract
The gut microbiota has a crucial effect on regulating the intestinal mucosal immunity and maintaining intestinal homeostasis both in health and in disease state. Many effects are mediated by gut microbiota-derived metabolites and tryptophan, an essential aromatic amino acid, is considered important among many metabolites in the crosstalk between gut microbiota and the host. Kynurenine, serotonin, and indole derivatives are derived from the three major tryptophan metabolism pathways modulated by gut microbiota directly or indirectly. Aryl hydrocarbon receptor (AHR) is a cytoplasmic ligand-activated transcription factor involved in multiple cellular processes. Tryptophan metabolites as ligands can activate AHR signaling in various diseases such as inflammation, oxidative stress injury, cancer, aging-related diseases, cardiovascular diseases (CVD), and chronic kidney diseases (CKD). Accumulated uremic toxins in the body fluids of CKD patients activate AHR and affect disease progression. In this review, we will elucidate the relationship between gut microbiota-derived uremic toxins by tryptophan metabolism and AHR activation in CKD and its complications. This review will provide therapeutic avenues for targeting CKD and concurrently present challenges and opportunities for designing new therapeutic strategies against renal fibrosis.
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Affiliation(s)
- Jing-Ru Liu
- Faculty of Life Science, & Medicine, Northwest University, No. 229 Taibai North Road, Xi'an, 710069, Shaanxi, China
| | - Hua Miao
- Faculty of Life Science, & Medicine, Northwest University, No. 229 Taibai North Road, Xi'an, 710069, Shaanxi, China
| | - De-Qiang Deng
- Department of Nephrology, Urumqi Chinese Medicine Hospital, No. 590 Fridenly South Road, Urumqi, 830000, Xinjiang Uygur Autonomous Region, China
| | - Nosratola D Vaziri
- Division of Nephrology and Hypertension, School of Medicine, University of California Irvine, Irvine, CA, 92897, USA
| | - Ping Li
- Beijing Key Lab for Immune-Mediated Inflammatory Diseases, Department of Nephrology, Institute of Clinical Medical Science, China-Japan Friendship Hospital, Beijing, 100029, China.
| | - Ying-Yong Zhao
- Faculty of Life Science, & Medicine, Northwest University, No. 229 Taibai North Road, Xi'an, 710069, Shaanxi, China.
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4
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Aida-Yasuoka K, Yoshioka W, Kawaguchi T, Ohsako S, Tohyama C. A mouse strain less responsive to dioxin-induced prostaglandin E2 synthesis is resistant to the onset of neonatal hydronephrosis. Toxicol Sci 2014; 141:465-74. [PMID: 25015655 DOI: 10.1093/toxsci/kfu142] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Dioxin is a ubiquitous environmental pollutant that induces toxicity when bound to the aryl hydrocarbon receptor (AhR). Significant differences in susceptibility of mouse strains to dioxin toxicity are largely accounted for by the dissociation constant of binding to dioxins of AhR subtypes encoded by different alleles. We showed that cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1), components of a prostanoid synthesis pathway, play essential roles in the onset of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced hydronephrosis of neonatal mice. Although C57BL/6J and BALB/cA mice harbor AhR receptors highly responsive to TCDD, they were found by chance to differ significantly in the incidence of TCDD-induced hydronephrosis. Therefore, the goal of the present study was to determine the molecular basis of this difference in susceptibility to TCDD toxicity. For this purpose, we administered C57BL/6J and BALB/cA dams' TCDD at an oral dose of 15 or 80 μg/kg on postnatal day (PND) 1 to expose pups to TCDD via lactation, and the pups' kidneys were collected on PND 7. The incidence of hydronephrosis in C57BL/6J pups (64%) was greater than in BALB/cA pups (0%, p < 0.05), despite similarly increased levels of COX-2 mRNA. The incidence of hydronephrosis in these mouse strains paralleled the levels of renal mPGES-1 mRNA and early growth response 1 (Egr-1) that modulates mPGES-1 gene expression, as well as PGE2 concentrations in urine. Although these mouse strains possess AhR alleles tightly bound to TCDD, their difference in incidence and severity of hydronephrosis can be explained, in part, by differences in the expression of mPGES-1 and Egr-1.
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Affiliation(s)
- Keiko Aida-Yasuoka
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Wataru Yoshioka
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan Department of Pathophysiology, Tokyo University of Pharmacy and Life Sciences, Tokyo 192-0392, Japan
| | - Tatsuya Kawaguchi
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Seiichiroh Ohsako
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Chiharu Tohyama
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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5
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DeGroot DE, Hayashi A, Denison MS. Lack of ligand-selective binding of the aryl hydrocarbon receptor to putative DNA binding sites regulating expression of Bax and paraoxonase 1 genes. Arch Biochem Biophys 2014; 541:13-20. [PMID: 24200861 PMCID: PMC3875388 DOI: 10.1016/j.abb.2013.10.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 10/25/2013] [Accepted: 10/28/2013] [Indexed: 12/29/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates the biological and toxicological effects of structurally diverse chemicals through its ability to bind specific DNA recognition sites (dioxin responsive elements (DREs)), and activate transcription of adjacent genes. While the DRE has a highly conserved consensus sequence, it has been suggested that the nucleotide specificity of AhR DNA binding may be ligand-dependent. The upstream regulatory regions of the murine Bax and human paraoxonase 1 (PON1) genes reportedly contain unique DRE-like sequences that respond to AhRs activated by some ligands but not others. Given the significant implications of this observation to understanding the diversity in AhR responses and that of other ligand-dependent nuclear receptors, a combination of DNA binding, nuclear translocation and gene expression analysis was used to investigate the molecular mechanisms underlying these ligand-selective responses. Although known AhR agonists stimulated AhR nuclear translocation, DRE binding and gene expression, the ligand-selective DRE-like DNA elements identified in the Bax and PON1 upstream regulatory regions failed to bind ligand-activated AhR or confer AhR-responsiveness upon a reporter gene. These results argue against the reported ligand-selectivity of AhR DNA binding and suggest DNA binding by ligand activated AhR involves DRE-containing DNA.
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Affiliation(s)
- Danica E DeGroot
- Department of Environmental Toxicology, University of California, Davis, CA 95616, United States
| | - Ai Hayashi
- Department of Environmental Toxicology, University of California, Davis, CA 95616, United States
| | - Michael S Denison
- Department of Environmental Toxicology, University of California, Davis, CA 95616, United States.
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6
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Denison MS, Soshilov AA, He G, DeGroot DE, Zhao B. Exactly the same but different: promiscuity and diversity in the molecular mechanisms of action of the aryl hydrocarbon (dioxin) receptor. Toxicol Sci 2011; 124:1-22. [PMID: 21908767 DOI: 10.1093/toxsci/kfr218] [Citation(s) in RCA: 567] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Ah receptor (AhR) is a ligand-dependent transcription factor that mediates a wide range of biological and toxicological effects that result from exposure to a structurally diverse variety of synthetic and naturally occurring chemicals. Although the overall mechanism of action of the AhR has been extensively studied and involves a classical nuclear receptor mechanism of action (i.e., ligand-dependent nuclear localization, protein heterodimerization, binding of liganded receptor as a protein complex to its specific DNA recognition sequence and activation of gene expression), details of the exact molecular events that result in most AhR-dependent biochemical, physiological, and toxicological effects are generally lacking. Ongoing research efforts continue to describe an ever-expanding list of ligand-, species-, and tissue-specific spectrum of AhR-dependent biological and toxicological effects that seemingly add even more complexity to the mechanism. However, at the same time, these studies are also identifying and characterizing new pathways and molecular mechanisms by which the AhR exerts its actions and plays key modulatory roles in both endogenous developmental and physiological pathways and response to exogenous chemicals. Here we provide an overview of the classical and nonclassical mechanisms that can contribute to the differential sensitivity and diversity in responses observed in humans and other species following ligand-dependent activation of the AhR signal transduction pathway.
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Affiliation(s)
- Michael S Denison
- Department of Environmental Toxicology, University of California, Davis, California 95616, USA.
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7
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Mullen Grey AK, Riddick DS. Glucocorticoid and adrenalectomy effects on the rat aryl hydrocarbon receptor pathway depend on the dosing regimen and post-surgical time. Chem Biol Interact 2009; 182:148-58. [PMID: 19615983 DOI: 10.1016/j.cbi.2009.07.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Accepted: 07/10/2009] [Indexed: 01/21/2023]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the effects of aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin and 3-methylcholanthrene (MC); the prototypical response is induction of drug-metabolizing enzymes. Factors that regulate AHR levels in vivo are poorly understood and it is also not clear how AHR levels affect aromatic hydrocarbon responsiveness. Our interest in pituitary-dependent regulation of AHR levels was prompted by two findings from our laboratory: (1) hypophysectomized rats have reduced hepatic levels of AHR protein; and (2) glucocorticoids increase AHR expression and aromatic hydrocarbon responsiveness in rodent hepatoma cells. To study whether adrenalectomy and glucocorticoids contribute to hormone-dependent regulation of the hepatic AHR pathway, male adrenalectomized (ADX) or SHAM-ADX rats were treated with dexamethasone (DEX) or vehicle. AHR protein was depleted by 50-60% at 4 days after ADX, but was not altered by DEX treatment. To assess whether the observed AHR depletion affected aromatic hydrocarbon responsiveness, the induction of hepatic cytochrome P450 1B1 (CYP1B1) mRNA by MC was measured as an AHR-mediated adaptive response. MC-induced hepatic CYP1B1 mRNA was reduced by 50% in ADX rats relative to SHAM-ADX. Exogenous glucocorticoid treatment (DEX - 1.5mg/kg) induced hepatic AHR nuclear translocator (ARNT) mRNA by up to 9-fold at 3 and 6h after dosing, with no corresponding change in ARNT protein levels. These data demonstrate that: (1) adrenal-dependent factors contribute to the physiological maintenance of hepatic AHR protein levels; (2) the depletion of hepatic AHR protein in ADX rats coincided with a diminished adaptive response to MC; and (3) exogenous glucocorticoid treatment increases hepatic ARNT mRNA levels regardless of adrenal status. This model is useful for studying the mechanisms of AHR and ARNT regulation and for further characterization of the impact of AHR protein depletion on the response to aromatic hydrocarbons in vivo.
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Affiliation(s)
- Anne K Mullen Grey
- Department of Pharmacology and Toxicology, Medical Sciences Building, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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8
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Zhao B, Baston DS, Hammock B, Denison MS. Interaction of diuron and related substituted phenylureas with the Ah receptor pathway. J Biochem Mol Toxicol 2006; 20:103-13. [PMID: 16788953 PMCID: PMC3032054 DOI: 10.1002/jbt.20126] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates many of the biological and toxicological actions of structurally diverse chemicals, including the ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin. Here, we have examined the ability of diuron, a widely used herbicide, and several structurally related substituted phenylureas to bind to and activate/inhibit the AhR and AhR signal transduction. Diuron induced CYP1A1 mRNA levels in mouse hepatoma (Hepa1c1c7) cells and AhR-dependent luciferase reporter gene expression in stably transfected mouse, rat, guinea pig, and human cell lines. In addition, ligand binding and gel retardation analysis demonstrated the ability of diuron to competitively bind to and stimulate AhR transformation and DNA binding in vitro and in intact cells. Several structurally related substituted phenylureas competitively bound to the guinea pig hepatic cytosolic AhR, inhibited 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced AhR-dependent luciferase reporter gene expression in a species-specific manner and stimulated AhR transformation and DNA binding, consistent with their role as partial AhR agonists. These results demonstrate not only that diuron and related substituted phenylureas are AhR ligands but also that exposure to these chemicals could induce/inhibit AhR-dependent biological effects.
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Affiliation(s)
- Bin Zhao
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
| | - David S. Baston
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
| | - Bruce Hammock
- Department of Entomology, University of California, Davis, CA, USA
- University of California Davis Cancer Center, Sacramento, CA, USA
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California, Davis, CA 95616-8588, USA
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9
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Brevini TAL, Cillo F, Antonini S, Gandolfi F. Effects of endocrine disrupters on the oocytes and embryos of farm animals. Reprod Domest Anim 2005; 40:291-9. [PMID: 16008759 DOI: 10.1111/j.1439-0531.2005.00592.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Currently, approximately 60 chemicals have been identified as endocrine disruptors (EDs): exogenous agents that interfere with the synthesis, secretion, transport, metabolism, binding, action, or elimination of natural blood-borne hormones. Farm animals ingest these substances with food and drinking water. Their stability and lipid solubility has led to increased concern that these substances may compromise the reproductive health of both humans and animals. Oocytes are a permanent cell population established before birth which is exposed to environmental stimuli for a period that, in farm animals, can be as long as several years. Oocyte competence is acquired within the ovary during the developmental stages that precede ovulation and its role is critical during the interval between fertilization and the so-called maternal to embryonic transition, when the transcriptional activity of the embryonic genome becomes fully functional. Any perturbation of these delicate process is likely to reduce oocyte developmental competence and, therefore, to cause an arrest of embryonic development at any given stage. A critical analysis of the doses and time of exposure is presented together with a description of the effects of different EDs on farm animal oocytes and early embryonic development. Finally some of the mechanisms mediating EDs effects on the oocytes will be described. In particular the role of arylhydrocarbon receptor, maternal mRNA stability and cytoplasmic remodelling during oocyte maturation will be discussed in some details.
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Affiliation(s)
- T A L Brevini
- Department of Anatomy of Domestic Animals, University of Milan, Milan, Italy
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Ziccardi MH, Gardner IA, Mazet JAK, Denison MS. Application of the luciferase cell culture bioassay for the detection of refined petroleum products. MARINE POLLUTION BULLETIN 2002; 44:983-991. [PMID: 12474956 DOI: 10.1016/s0025-326x(02)00128-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A luciferase cell culture-based bioassay, developed to detect 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like activity of halo-genated and polycyclic aromatic hydrocarbons, was optimized to detect refined petroleum products and to determine their relative inducing potency. Quality control standards from 32 refined products (gasolines and diesels, jet fuels, lubricating oils, fuel oils and weathered products) and three commercial products were evaluated. Induction equivalents (I-EQs) were determined by direct comparison of the EC50 and EC20 values (based on the median and 20% TCDD maximal response, respectively) from dose-response curves for each product to those obtained with TCDD. Most petroleum products were active in the luciferase bioassay, with those products composed of fractions produced later in the distillation process (i.e. fuel oils) inducing higher levels. Additionally, weathering of products reduced their induction potency. Based on the high I-EQ estimates of many products, biological effects associated with exposure may have been previously underestimated using other diagnostic methods.
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Affiliation(s)
- Michael H Ziccardi
- Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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Denison MS, Pandini A, Nagy SR, Baldwin EP, Bonati L. Ligand binding and activation of the Ah receptor. Chem Biol Interact 2002; 141:3-24. [PMID: 12213382 DOI: 10.1016/s0009-2797(02)00063-7] [Citation(s) in RCA: 320] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The Ah receptor (AhR) is a ligand-dependent transcription factor that can be activated by structurally diverse synthetic and naturally-occurring chemicals. Although a significant amount of information is available with respect to the planar aromatic hydrocarbon AhR ligands, the actual spectrum of chemicals that can bind to and activate the AhR is only now being elucidated. In addition, the lack of information regarding the actual three-dimensional structure of the AhR ligand binding domain (LBD) has hindered detailed analysis of the molecular mechanisms by which these ligands bind to and active AhR signal transduction. In this review we describe the current state of knowledge with respect to naturally occurring AhR ligands and present and discuss the first theoretical model of the AhR LBD based on crystal structures of homologous PAS family members.
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Affiliation(s)
- Michael S Denison
- Department of Environmental Toxicology, Meyer Hall, One Shields Avenue, University of California, Davis 95616-8588, USA.
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12
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Ziccardi MH, Mazet JAK, Gardner IA, Boyce WM, Denison MS. Validation of a cell culture bioassay for detection of petroleum exposure in mink (Mustela vison) as a model for detection in sea otters (Enhydra lutris). Am J Vet Res 2002; 63:963-8. [PMID: 12118676 DOI: 10.2460/ajvr.2002.63.963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To validate a luciferase bioassay, which is based on a recombinant mouse hepatoma cell line, for the detection of exposure to petroleum in mustelid species. ANIMALS 122 American mink (Mustela vison) and 15 sea otters (Enhydra lutris). PROCEDURES Mink were exposed to Bunker C fuel oil or Alaska North Slope crude oil externally as a single exposure or internally via low dose concentrations in their ration for 6 months. Serum samples were analyzed for cytochrome P450 1A1 induction by quantification of luciferase activity in the bioassay. Mink liver specimens were also evaluated for cytochrome P450 1A1 induction by quantification of ethoxyresorufin-o-deethylase activity. Serum collected from exposed and unexposed sea otters was also analyzed using the luciferase bioassay. RESULTS Serum samples from mink externally exposed to petroleum had significantly increased luciferase activities at 1 week after exposure. Serum samples taken at later time points or from mink exposed to either product in the ration did not cause significant luciferase induction. Samples from otters exposed to petroleum had significantly higher luciferase induction as compared with samples from otters not exposed to petroleum at 2 and 8 years after the spill. Cytochrome P450 1A1 activity in liver specimens collected from mink that were internally exposed through diet was significantly increased at the conclusion of our study. CONCLUSION AND CLINICAL RELEVANCE The luciferase bioassay is a sensitive and specific method for determining recent exposure to petroleum in mink. The lack of luciferase activity in serum samples collected from mink greater than 1 week after experimental exposure was likely attributable to lower overall petroleum exposure in our trial, compared with natural exposures.
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Affiliation(s)
- Michael H Ziccardi
- Wildlife Health Center, Department of Pathology, School of Veterinary Medicine, University of California, Davis 95616, USA
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13
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ARULMOZHIRAJA SUNDARAM, FUJII TOSHIHIRO, SATO GEN. Density functional theory-based reactivity descriptors for dioxins. Mol Phys 2002. [DOI: 10.1080/00268970110072395] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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14
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Matthews M, Heimler I, Fahy M, Radwanska E, Hutz R, Trewin A, Rawlins R. Effects of dioxin, an environmental pollutant, on mouse blastocyst development and apoptosis. Fertil Steril 2001; 75:1159-62. [PMID: 11384643 DOI: 10.1016/s0015-0282(01)01802-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE To evaluate the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) on mouse embryo development and apoptosis. DESIGN Controlled animal study. SETTING Academic research environment. ANIMAL(S) Female mice (CB6F1) at 3 to 6 weeks of age and proven breeders (C578B46). INTERVENTION(S) Mouse embryos were obtained at the morula stage and cultured to the blastocyst stage in a pharmacologic dose of TCDD (3.1 microM) or a control medium. The morphology was assessed, and staining for apoptosis was performed. Immunohistochemistry for the presence of aromatic hydrocarbon receptor (AhR) was performed in another set of morula-stage embryos. MAIN OUTCOME MEASURE(S) The number of embryos developing from the morula to the blastocyst stage and number of apoptotic blastomeres in control vs. TCDD culture conditions. RESULT(S) No statistically significant differences were observed in the percentage of embryos reaching the blastocyst stage: 80.9% (115 of 142) in the TCDD-treated group, vs. 82.9% (121 of 146) in the control group. There was also no difference in the degree of apoptosis: 22.6 +/- 7.3% apoptotic cells (TCDD) vs. 25.3 +/- 9.7% (controls). Staining indicated the slight presence of aromatic hydrocarbon receptor in the morula-stage mouse embryos. CONCLUSION(S) TCDD at 3.1 microM did not alter the development of early mouse morula to blastocysts and did not significantly induce apoptosis in vitro.
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Affiliation(s)
- M Matthews
- Division of Reproductive Endocrinology, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois, USA.
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Hahn ME. The aryl hydrocarbon receptor: a comparative perspective. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1998; 121:23-53. [PMID: 9972449 DOI: 10.1016/s0742-8413(98)10028-2] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The aryl hydrocarbon receptor (Ah receptor or AHR) is a ligand-activated transcription factor involved in the regulation of several genes, including those for xenobiotic-metabolizing enzymes such as cytochrome P450 1A and 1B forms. Ligands for the AHR include a variety of aromatic hydrocarbons, including the chlorinated dioxins and related halogenated aromatic hydrocarbons whose toxicity occurs through activation of the AHR. The AHR and its dimerization partner ARNT are members of the emerging bHLH-PAS family of transcriptional regulatory proteins. In this review, our current understanding of the AHR signal transduction pathway in non-mammalian and other non-traditional species is summarized, with an emphasis on similarities and differences in comparison to the AHR pathway in rodents and humans. Evidence and prospects for the presence of a functional AHR in early vertebrates and invertebrates are also examined. An overview of the bHLH-PAS family is presented in relation to the diversity of bHLH-PAS proteins and the functional and evolutionary relationships of the AHR and ARNT to the other members of this family. Finally, some of the most promising directions for future research on the comparative biochemistry and molecular biology of the AHR and ARNT are discussed.
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Affiliation(s)
- M E Hahn
- Biology Department, Woods Hole Oceanographic Institution, MA 02543-1049, USA.
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16
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Heimler I, Rawlins RG, Owen H, Hutz RJ. Dioxin perturbs, in a dose- and time-dependent fashion, steroid secretion, and induces apoptosis of human luteinized granulosa cells. Endocrinology 1998; 139:4373-9. [PMID: 9751521 DOI: 10.1210/endo.139.10.6264] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD) is the most toxic congener of a large class of environmental pollutants. Several studies have shown that TCDD exposure reduced fecundity and ovulatory rate in rats and increased the incidence of endometriosis in monkeys. Recent work suggests that TCDD's endocrine-disrupting effects are, at least in part, caused by a direct action at the ovary. Although the factors involved in TCDD-induced toxicity are still under investigation, several studies have shown that TCDD induces programmed cell death, or apoptosis, in various tissues and may act in a similar fashion in the ovary. In the present study, we set out to evaluate the in vitro effects of TCDD on steroid secretion, specifically estradiol-17beta (E2) and progesterone, by human luteinized granulosa cells (LGC), and to further determine whether TCDD is capable of inducing apoptosis in this cell type. Human LGC were obtained from women participating in an in vitro fertilization program. Medium, with or without three different concentrations of TCDD and substrates [androstenedione (A4) or pregnenolone], was added to each culture. The media were collected at 4, 8, 12, 24, 36, and 48 h and were assayed by RIA. At 24 and 48 h, the LGC were fixed for assessment of DNA fragmentation via an in situ immunofluorescence technique. Transmission electron microscopy was also performed on LGC after 24 and 48 h with TCDD. TCDD, at all concentrations tested (3.1 pM, 3.1 nM, and 3.1 microM), significantly reduced E2 accumulation in the media at 8, 12, and 24 h, compared with controls. At 36 and 48 h, TCDD treatment (at 3.1 microM) caused a significant increase in E2, compared with controls. The effect of TCDD on E2 was abolished with the addition of A4. TCDD treatment did not alter progesterone accumulation. Apoptosis increased at 24 h with 3.1 microM TCDD, with no apparent effect at 3.1 nM. By 48 h, however, TCDD increased apoptosis in a dose-dependent manner. Transmission electron microscopy showed ultrastructural differences in LGC with 3.1 microM TCDD at 24 and 48 h. Collectively, the results of the present study suggest that TCDD perturbs E2 secretion by depletion of A4 precursor and increases apoptotic cell death of human LGC in a dose- and time-dependent fashion.
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Affiliation(s)
- I Heimler
- Department of Biological Sciences, University of Wisconsin-Milwaukee, 53211, USA
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17
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Wilson CL, Safe S. Mechanisms of ligand-induced aryl hydrocarbon receptor-mediated biochemical and toxic responses. Toxicol Pathol 1998; 26:657-71. [PMID: 9789953 DOI: 10.1177/019262339802600510] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a member of a broad group of halogenated aromatic hydrocarbons (HAHs) that is known to induce a wide range of toxic and biochemical responses in laboratory animals and humans. The effects of HAH exposure are mediated by binding to the cytosolic aryl hydrocarbon receptor (AhR), which is expressed in a tissue- and cell type-specific manner. The AhR is a ligand-activated transcription factor belonging to the basic helix-loop-helix/Per-AhR-Arnt-Sim (bHLH/PAS) superfamily of proteins. The mechanism of induction of gene transcription by TCDD involves ligand recognition and binding by the AhR, nuclear translocation, and dimerization with the AhR cofactor, AhR nuclear translocator (Arnt). The nuclear heterodimer interacts with cognate xenobiotic responsive elements (XREs) in promoter/enhancer regions of multiple Ah-responsive genes. Subsequent changes in chromatin structure and/or interaction of the AhR complex with the basal transcriptional machinery play a significant role in AhR-mediated gene expression. Although Arnt is a necessary component of a functional nuclear AhR complex, this protein also forms transcriptionally active heterodimers with other bHLH/PAS factors, including those involved in the transcriptional response to hypoxia. Arnt is ubiquitously expressed in mammalian systems, and results from transgenic mouse studies suggest that this protein plays a vital role in early mammalian embryonic development. Similar experiments suggest that the AhR may be involved in development of various organ systems. Thus, molecular mechanistic studies of TCDD action have contributed significantly to an improved understanding of the role of at least 2 bHLH/PAS proteins, as well as organ- and tissue-specific biochemical and toxic responses to this class of environmental toxins.
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Affiliation(s)
- C L Wilson
- Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station 77843-4466, USA
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18
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Abstract
We have provided a historical perspective on a body of steroid receptor research dealing with the structure and physiological significance of the untransformed 9S receptor that has often confused both novice and expert investigators. The frequent controversies and equivocations of earlier studies were due to the fact that the native, hormone-free state of these receptors is a large multiprotein complex that resisted description for many years because of its unstable and dynamic nature. The untransformed 9S state of the steroid and dioxin receptors has provided a unique system for studying the function of the ubiquitous, abundant, and conserved heat shock protein, hsp90. The hormonal control of receptor association with hsp90 provided a method of manipulating the receptor heterocomplex in a manner that was physiologically meaningful. For several steroid receptors, binding to hsp90 was required for the receptor to be in a native hormone-binding state, and for all of the receptors, hormone binding promoted dissociation of the receptor from hsp90 and conversion of the receptor to the DNA-binding state. Although the complexes between tyrosine kinases and hsp90 were discovered earlier, the hormonal regulation or steroid receptor association with hsp90 permitted much more rapid and facile study of hsp90 function. The observations that hsp90 binds to the receptors through their HBDs and that these domains can be fused to structurally different proteins bringing their function under hormonal control provided a powerful linkage between the hormonal regulation of receptor binding to hsp90 and the initial step in steroid hormone action. Because the 9S receptor hsp90 heterocomplexes could be physically stabilized by molybdate, their protein composition could be readily studied, and it became clear that these complexes are multiprotein structures containing a number of unique proteins, such as FKBP51, FKBP52, CyP-40, and p23, that were discovered because of their presence in these structures. Further analysis showed that hsp90 itself exists in a variety of native multiprotein heterocomplexes independent of steroid receptors and other 'substrate' proteins. Cell-free systems can now be used to study the formation of receptor heterocomplexes. As we outlined in the scheme of Fig. 1, the multicomponent receptor-hsp90 heterocomplex assembly system is being reconstituted, and the importance of individual proteins, such as hsp70, p60, and p23, in the assembly process is becoming recognized. It should be noted that our understanding of the mechanism and purpose of steroid receptor heterocomplex assembly is still at an early stage. We can now speculate on the roles of receptor-associated proteins in receptor action, both as individuals and as a group, but their actual functions are still vague or unknown. We can make realistic models about the chaperoning and trafficking of steroid receptors, but we don't yet know how these processes occur, we don't know where chaperoning occurs in the cell (e.g. Is it limited to the cytoplasm? Is it a diffuse process or does chaperoning occur in association with structural elements?), and, with the exception of the requirement for hormone binding, we don't know the extent to which the hsp90-based chaperone system impacts on steroid hormone action. It is not yet clear how far the discovery of this hsp90 heterocomplex assembly system will be extended to the development of a general understanding of protein processing in the cell. Because this assembly system is apparently present in all eukaryotic cells, it probably performs an essential function for many proteins. The bacterial homolog of hsp90 is not an essential protein, but hsp90 is essential in eukaryotes, and recent studies indicate that the development of the cell nucleus from prokaryotic progenitors was accompanied by the duplication of genes for hsp90 and hsp70 (698). (ABSTRACT TRUNCATED)
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Affiliation(s)
- W B Pratt
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109, USA
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19
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Santodonato J. Review of the estrogenic and antiestrogenic activity of polycyclic aromatic hydrocarbons: relationship to carcinogenicity. CHEMOSPHERE 1997; 34:835-48. [PMID: 9569946 DOI: 10.1016/s0045-6535(97)00012-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Human exposure to nonsteroidal estrogens in the environment has recently been proposed as a risk factor for endocrine disruption and the development of cancers of the breast and reproductive tract. Certain polycyclic aromatic hydrocarbons (PAHs), which closely resemble steroid hormones, are ubiquitous environmental contaminants whose carcinogenicity has been extensively studied. This review examines the available evidence regarding the actions of PAHs on estrogen receptor activity, estrogen metabolism and the hypothalamo-pituitary axis. In most studies, PAHs exhibited either weakly estrogenic or antiestrogenic responses. The possibility is raised that the endocrine toxicology of certain PAHs reflects both genotoxic and non-genotoxic components which may be interrelated, particularly with regard to carcinogenesis.
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Affiliation(s)
- J Santodonato
- New York State Electric and Gas Corporation, Binghamton 13903, USA
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20
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Bank PA, Yao EF, Phelps CL, Harper PA, Denison MS. Species-specific binding of transformed Ah receptor to a dioxin responsive transcriptional enhancer. Eur J Pharmacol 1992; 228:85-94. [PMID: 1332880 DOI: 10.1016/0926-6917(92)90016-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The Ah receptor (AhR) mediates many, if not all, of the toxic and biological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related halogenated aromatic hydrocarbons. Although wide variations in species sensitivity to these compounds have been observed, numerous biochemical and physiochemical characteristics of the AhR appear similar among species. We have examined the ability of cytosolic AhR, from a variety of species (rat, rabbit, guinea pig, hamster, mouse, cow, sheep, fish, chicken and human), to transform and bind to its cognate DNA recognition sequence, the dioxin responsive enhancer (DRE), to evaluate the importance of these events in species variations in TCDD responsiveness. Gel retardation analysis using a murine DRE oligonucleotide has revealed that cytosolic AhR from a wide variety of species can transform in vitro and bind to the DRE and demonstrates that all of the factors necessary for AhR transformation and DNA binding are present in cytosol. In addition, DNA-binding analysis using a series of mutant DRE oligonucleotides has indicated no apparent species- or ligand-dependent, nucleotide-specific difference in AhR binding to the DRE. These studies support a highly conserved nature of the DRE and AhR (at least in DNA binding) and imply that a sequence closely related to the murine consensus DRE sequence is responsible for conferring AhR-dependent, TCDD responsiveness in each of these species.
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Affiliation(s)
- P A Bank
- Department of Biochemistry, Michigan State University, East Lansing 48824
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21
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Denison MS. Heterogeneity of rat hepatic Ah receptor: identification of two receptor forms which differ in their biochemical properties. JOURNAL OF BIOCHEMICAL TOXICOLOGY 1992; 7:249-56. [PMID: 1338110 DOI: 10.1002/jbt.2570070408] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In cytosol, the rat hepatic Ah receptor (AhR) appears to exist in two distinct forms (AhR alpha, AhR beta) in similar concentration. The binding of ligand (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)) to AhR alpha requires the receptor be in its oligomeric 8-10 to S conformation (bound to other protein subunits), while ligand binding to AhR beta can occur with the dissociated 5-6 S form. Occupancy of AhR alpha by ligand (TCDD) protects it from salt-dependent inactivation; AhR beta is not inactivated by high salt conditions. The addition of molybdate to cytosol during tissue homogenization stabilized AhR alpha against salt-dependent inactivation and subunit dissociation but did not prevent dissociation of AhR beta by high salt. Although the presence of molybdate appears to stabilize AhR alpha in its oligomeric 8-10 S, it had no significant effect on the overall amount of TCDD:AhR complex which bound to its specific DNA recognition site, the dioxin responsive element (DRE). These results suggest that AhR alpha, unlike AhR beta, is either unable to transform or bind to the DRE with high affinity.
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Affiliation(s)
- M S Denison
- Department of Biochemistry, Michigan State University, East Lansing 48824
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22
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Denison MS, Yao EF. Characterization of the interaction of transformed rat hepatic cytosolic Ah receptor with a dioxin responsive transcriptional enhancer. Arch Biochem Biophys 1991; 284:158-66. [PMID: 1846511 DOI: 10.1016/0003-9861(91)90278-q] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Many of the biological and toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), a highly toxic environmental contaminant, are mediated by a soluble intracellular protein (the Ah receptor (AhR)). Following a poorly defined process of transformation, during which the TCDD:AhR complex acquires the ability to bind to DNA with high affinity, TCDD:AhR complexes activate gene transcription by binding to dioxin responsive enhancers (DREs) adjacent to the responsive gene. Here we have utilized gel retardation analysis to study the interaction of rat hepatic cytosolic TCDD:AhR complexes, transformed in vitro, with dioxin responsive enhancer DNA. Cytosol contains a protein(s) that binds to the DRE in a TCDD-inducible, sequence-specific, time- and temperature-dependent manner and exhibits AhR ligand binding specificity. These results imply that this inducible protein-DNA complex represents the binding of liganded:AhR complex to the DRE. The TCDD:AhR complex bound to the DRE with an equilibrium dissociation constant of 1.2 +/- 0.1 nM, an affinity at least 3800-fold stronger than that for binding to nonspecific DNA. Assuming one DNA binding site per AhR molecule, the total concentration of transformed AhR in these studies was approximately 56.1 +/- 6.6 fmol/mg protein (representing transformation of 45% of the total amount of AhR present in the same cytosolic preparations). Inhibition of AhR transformation, but not ligand or DNA binding, by EDTA and EGTA suggests that a chelatable divalent cation(s) may play a critical role in the transformation process.
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Affiliation(s)
- M S Denison
- Department of Biochemistry, Michigan State University, East Lansing 48824
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23
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Denison MS, Vella LM. The hepatic Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin: species differences in subunit dissociation. Arch Biochem Biophys 1990; 277:382-8. [PMID: 2155580 DOI: 10.1016/0003-9861(90)90594-o] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) produces many of its biological effects by binding to a soluble, intracellular protein (the Ah receptor (AhR]. The hepatic AhR, from a variety of species, is present in low salt cytosol as a form which sediments at 8-10 S. High salt (0.4 M KCL) dissociates the rat, guinea pig, and rabbit cytosolic TCDD:AhR complex to a form which sediments at 5-6 S. In contrast, high salt conditions failed to dissociate the 8-10 S TCDD:AhR complex present in any of the mouse strains studied. Incubation of cytosol with heparin resulted in a shift of the [3H]TCDD:AhR complex to a smaller sedimenting form in all species. Mouse TCDD:AhR complex sedimented at 8-10 S when cytosol was simultaneously incubated with high salt and heparin, indicating that the interaction of heparin with the AhR was electrostatic in nature. Incubation of heparin-dissociated mouse TCDD:AhR complex (5-6 S) with high salt resulted in reassociation of AhR to a form which sediments at 8-10 S. Our data suggests that the resistance of mouse AhR to salt-mediated dissociation may be due to a property of the receptor protein itself and also indicates that mouse hepatic cytosolic AhR is distinctly different from that present in all other species examined to date.
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Affiliation(s)
- M S Denison
- Department of Biochemistry, Michigan State University, East Lansing 48824
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24
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Beebe L, Park SS, Anderson LM. Differential enzyme induction of mouse liver and lung following a single low or high dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). JOURNAL OF BIOCHEMICAL TOXICOLOGY 1990; 5:211-9. [PMID: 2096217 DOI: 10.1002/jbt.2570050403] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The induction response of cytochrome P-450-dependent enzyme activities to a single low (5 nmol/kg) or high (50 nmol/kg, intraperitoneal [ip] dose of TCDD was examined in liver and lung homogenates over a 12-week time course in an outbred, Ah-responsive strain of mice (National Institutes of Health [NIH] Swiss). Total hepatic cytochrome P-450 was quantified, and the dealkylation of ethoxy- and benzyloxyresorufin (activities of P-450 IA1 and IIB1, respectively) were measured in both tissues at 48 and 96 hr and at 1, 4, and 12 weeks post-TCDD administration. Western immunoblotting with monoclonal antibody 1-7-1 was conducted to confirm the specific IA1-inductive effects of each dose of TCDD over the same time course. Following the low dose, specific IA1 induction was apparent in liver at the earliest time point, was maximal at 1 week, and declined to control values at 12 weeks. Pulmonary IA1 was near-maximally induced at 48 hr, and remained at that level for 4 weeks. In contrast, a tenfold higher dose of TCDD elicited similar IA1 induction profiles for both tissues, with a maximum at 1 week and a progressive loss at 4 and 12 weeks postexposure. P-450 IIB1 activity was elevated in TCDD-treated animals by enzymatic assay; however, Western immunoblotting did not confirm this finding. These data demonstrate persistent dose-dependent P450 induction over many weeks by a single TCDD dose, with significant organ-specific differences: (a) lung is more sensitive than liver to a nonmaximal inducing dose of TCDD, and (b) at a maximally inducing dose of TCDD, lung is very similar to liver in both the level and time course of IA1 induction.
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Affiliation(s)
- L Beebe
- Laboratory of Comparative Carcinogenesis, National Cancer Institute-Frederick Cancer Research and Development Center, MD 21702
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25
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Prokipcak RD, Faber LE, Okey AB. Characterization of the Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin: use of chemical crosslinking and a monoclonal antibody directed against a 59-kDa protein associated with steroid receptors. Arch Biochem Biophys 1989; 274:648-58. [PMID: 2552929 DOI: 10.1016/0003-9861(89)90480-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The Ah receptor regulates induction of cytochrome P450IA1 (aryl hydrocarbon hydroxylase) by "3-methylcholanthrene-type" compounds and mediates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related halogenated aromatic hydrocarbons. Hepatic Ah receptor from untreated rodents is localized in the cytosol and has an apparent molecular mass of 250 to 300 kDa. This large form can be dissociated into a smaller ligand-binding subunit upon exposure to high ionic strength. The Ah receptor displays many structural similarities to the receptors for steroid hormones. Two non-ligand-binding proteins have been identified to be associated with the cytosolic forms of the steroid hormone receptors. The first is a 90-kDa heat shock protein (hsp 90); the second is a 59-kDa protein (p59) of unknown function. The cytosolic Ah receptor ligand-binding subunit previously has been shown to be associated with hsp 90. In the present study, we used a monoclonal antibody, KN 382/EC1, generated against the 59-kDa protein which is associated with rabbit steroid receptors to determine if p59 also is a component of the large cytosolic Ah receptor complex. Cytosolic forms of rabbit progesterone receptor, glucocorticoid receptor, and Ah receptor were analyzed by velocity sedimentation on sucrose gradients under low-ionic-strength conditions and in the presence of molybdate. Progesterone receptor from rabbit uterine cytosol and glucocorticoid receptor from rabbit liver each had a sedimentation coefficient of approximately 9 S. In the presence of KN 382/EC1 antibody the progesterone receptor and the glucocorticoid receptor both underwent a shift in sedimentation to a value of approximately 11 S. The increase in sedimentation velocity is an indication that the receptor-protein complexes are interacting with the antibody. Under low-ionic-strength conditions the Ah receptors from rabbit uterine cytosol and liver cytosol had a sedimentation coefficient of approximately 9 S. However, in contrast to the steroid receptors, the Ah receptor showed no change in its sedimentation properties in either tissue in the presence of KN 382/EC1, indicating that the antibody is not interacting with the Ah receptor. Multimeric Ah receptor complexes that were chemically crosslinked still did not show any interaction with KN 382/EC1. These data indicate that the 59-kDa protein either is not associated with the Ah receptor or is present in an altered form which the antibody cannot recognize.
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Affiliation(s)
- R D Prokipcak
- Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
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26
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Labruzzo P, Yu XF, Dufresne MJ. Induction of aryl hydrocarbon hydroxylase and demonstration of a specific nuclear receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin in two human hepatoma cell lines. Biochem Pharmacol 1989; 38:2339-48. [PMID: 2546564 DOI: 10.1016/0006-2952(89)90474-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Two established human hepatoma cell lines, Hep3B and HepG2, were examined for aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) induction and for the presence of the murine-equivalent aromatic hydrocarbon (Ah) receptor. Both cell lines demonstrated polycyclic aromatic hydrocarbon (PAH)-induced AHH activity; however, assay conditions for induction were different than those established for the control mouse hepatoma cell line, Hepa c1-9. When cytosols from either cell line were exposed to tritiated 2,3,7,8-tetrachlorodibenzo-p-dioxin [( 3H]TCDD) and analyzed on sucrose gradients with or without prior charcoal treatment, two peaks were observed at positions corresponding to 4-5 S and 8-9 S. The 8-9 S peak was identified as the probable human Ah receptor equivalent since, like the mouse Ah receptor, this peak: (a) was eliminated only by cytochrome P1-450 inducers; (b) was sensitive to protease digestion; and (c) was thermolabile. Levels of TCDD specifically bound in the 8-9 S peak for HepG2 and Hep3B were 27 and 34 fmol/mg cytosolic protein respectively. The level of TCDD specifically bound was not affected by charcoal treatment or by the addition of sodium molybdate, which is known to stabilize ligand binding to steroid receptors. Incubation of Hep3B or HepG2 cells with [H]TCDD at 37 degrees for 1 hr effected a redistribution of binding from the cytosol 8-9 S peak to a nuclear 6 S peak. The nuclear peaks from both human cell lines demonstrated similar sedimentation properties, temperature-dependence and inducer-specificity, as for the mouse nuclear Ah receptor. Appearance of nuclear 6 S binding is consistent with a temperature-dependent translocation process, supporting the observation that these human hepatoma cell lines contain a binding component which is similar to the mouse Ah receptor in structure and function during AHH induction.
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Affiliation(s)
- P Labruzzo
- Department of Biological Sciences, University of Windsor, Ontario, Canada
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27
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Bunce NJ, Landers JP, Safe SH. Kinetic models for association of 2,3,7,8-tetrachlorodibenzo-p-dioxin with the Ah receptor. Arch Biochem Biophys 1988; 267:384-97. [PMID: 2848454 DOI: 10.1016/0003-9861(88)90044-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Saturation binding studies of the interaction between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the Ah receptor obtained from the hepatic cytosol of Wistar rats have been carried out. The conventional Scatchard analysis for determination of the equilibrium constant for ligand-receptor binding has been shown to be inappropriate due to thermal inactivation of the unoccupied receptor. Simulation models of the receptor-ligand binding kinetics which take into account receptor degradation have been developed and the results are consistent with two alternative kinetic models. In Model 1, reversible 2,3,7,8-TCDD-receptor binding occurs in parallel with inactivation of the unbound receptor; analysis of the observed data using this model suggests that the previously determined equilibrium constants (Kass) for association of the ligand with the receptor are orders of magnitude too low and the total initial receptor concentrations are somewhat underestimated. In Model 2, the unbound receptor is converted unimolecularly to an activated state which then undergoes competitive degradation or entrapment by ligand. Experiments have been carried out over the temperature range 4-37 degrees C, enabling activation parameters to be obtained. According to Scheme 1, the activation enthalpies for association of receptor with ligand and for thermal inactivation of the unoccupied receptor are high, and numerically almost identical (delta H++ ca 125 kJ mol-1). These reactions are strongly entropically driven and this is consistent with association being accompanied by a conformational change in the receptor protein, and the previously postulated binding of the ligand to a hydrophobic pocket. According to Scheme 2, there is only one enthalpy of activation because both inactivation and entrapment by 2,3,7,8-TCDD are fast processes which follow the same slow activation step. On the basis of this latter model, a 10(-9) M concentration of 2,3,7,8-TCDD is sufficient to trap roughly two-thirds of the activated receptors.
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Affiliation(s)
- N J Bunce
- Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Ontario, Canada
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28
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29
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Barton HA, Marletta MA. Kinetic and immunochemical studies of a receptor-like protein that binds aromatic hydrocarbons. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)60640-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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30
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Farrell K, Safe L, Safe S. Synthesis and aryl hydrocarbon receptor binding properties of radiolabeled polychlorinated dibenzofuran congeners. Arch Biochem Biophys 1987; 259:185-95. [PMID: 2825595 DOI: 10.1016/0003-9861(87)90485-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Microchlorination of 1,4,9[3H]dibenzofuran gave several polychlorinated dibenzofuran (PCDF) products and 2,3,7,8-[3H]tetrachlorodibenzofuran (TCDF), 1,2,3,7,8-[3H]pentachlorodibenzofuran (PeCDF), and 1,2,3,6,7,8-/1,2,3,4,7,8-hexachlorodibenzofuran (HCDF) of high specific activity (57, 34, and 32.5 Ci/mmol, respectively) were purified by preparative high-pressure liquid chromatography. These compounds were investigated as radioligands for the rat liver cytosolic aryl hydrocarbon (Ah) receptor protein. Like 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (TCDD), the radiolabeled PCDF congeners exhibited saturable binding with the receptor protein and sucrose density gradient analysis of the radiolabeled ligand-receptor complexes gave specific binding peaks with comparable sedimentation profiles. The rank order of radioligand binding affinities (Kd values) was 2,3,7,8-TCDD greater than 2,3,7,8-TCDF greater than 1,2,3,6,7,8-HCDF greater than 1,2,3,7,8-PeCDF and the maximum difference in Kd values for the four radioligands was less than 13-fold (0.44-5.9 nM). The interactions of the PCDF radioligands with the cytosolic receptor all exhibited saturable binding curves and linear Scatchard plots and the slopes of their Hill plots were in the range 1.0-1.1, thus indicating that cooperativity was not a factor in these binding interactions. The relative stabilities and dissociation kinetics of the radioligand-receptor complexes were highly dependent on the structure of the radioligand. The dissociation curves of the 2,3,7,8-[3H]TCDD and PCDF receptor complexes were biphasic and this suggests that there may be a temporal shift in ligand binding affinities. However, the rates of dissociation did not correlate with the rank order of ligand binding affinities. The stabilities of the radioligand-receptor complexes were also dependent on the structures of the radioligands; for example, the 2,3,7,8-[3H]TCDD-receptor complex degraded more rapidly than the PCDF-receptor complex and these relative stabilities were clearly not related to the Kd values or the relative in vivo or in vitro biologic potencies of these halogenated aryl hydrocarbons.
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Affiliation(s)
- K Farrell
- Department of Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station 77843
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Poland A, Glover E. Variation in the molecular mass of the Ah receptor among vertebrate species and strains of rats. Biochem Biophys Res Commun 1987; 146:1439-49. [PMID: 3040002 DOI: 10.1016/0006-291x(87)90811-4] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The Ah receptor in eight vertebrate species was characterized by labeling the cytosolic fraction of tissue with the photoaffinity ligand, [125I]-2-azido-3-iodo-7,8-dibromodibenzo-p-dioxin, and analysis of the products by denaturing gel electrophoresis. The apparent molecular mass of the dominant labeled peptide showed appreciable species variation: mouse-95 kDa; chicken (embryo)-101 kDa; guinea pig-103 kDa; rabbit-104 kDa; rat-106 kDa; human-106 kDa; monkey-113 kDa, and hamster-124 kDa. Seven inbred strains of rats, had a Ah receptor ligand binding peptide of 106 kDa; however outbred Long-Evans rats were shown to be polymorphic expressing a 101 kDa and/or 106 kDa allelic forms. The notable frequency of structural variation in the Ah receptor is in contrast to the analogous highly conserved steroid hormone receptors.
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Kester JE, Gasiewicz TA. Characterization of the in vitro stability of the rat hepatic receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Arch Biochem Biophys 1987; 252:606-25. [PMID: 3028272 DOI: 10.1016/0003-9861(87)90067-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The in vitro stability of the Ah receptor from rat hepatic cytosol was evaluated by [3H]TCDD binding studies, gel filtration, and sucrose density gradient ultracentrifugation. Thermal inactivation of unoccupied receptor followed first-order kinetics between 5 and 40 degrees C, with an estimated Ea for inactivation of approximately 35 kcal/mol. Protease inhibitors did not reduce and dilution slightly increased the inactivation rate at 20 degrees C. Recovery and 20 degrees C stability decreased with increasing ionic strength. The TCDD-receptor complex was less susceptible to degradation at 20 degrees C, even in the presence of 0.4 M KCl. Specific binding was markedly pH dependent, with maximum recovery at 7.6. Analysis of the pH curve suggested that cysteine sulfhydryl groups may be involved in TCDD binding. Dithiothreitol (1 mM) maximized recovery and 20 degrees C stability, and addition of the thiol largely reactivated binding sites lost from cytosol prepared without it. Removal of low molecular weight components of cytosol by gel filtration resulted in a rapid 20 degrees C inactivation rate that could not be lessened by dithiothreitol. Glycerol (10% v/v) and EDTA (1.5 mM) maximized recovery of specific binding, but both decreased 20 degrees C stability in a concentration-dependent manner. Calcium chloride (4 mM) increased stability at 20 degrees C by approximately 20%, and retarded the characteristic shift in sedimentation coefficient from approximately 9 to approximately 6 S in high-salt sucrose gradients. The fact that sodium molybdate (20 mM) decreased recovery and 20 degrees C stability when dithiothreitol was present but slightly increased stability in its absence suggested an antagonism between the two compounds. Molybdate mitigated the inactivation induced by 0.4 M KCl, an effect which may be related to the observation of dual peaks in molybdate-containing high-salt sucrose gradients. These data indicate that thermal inactivation of the unoccupied rat hepatic Ah receptor primarily may be due to physical rather than enzymatic processes; (ii) sulfhydryl oxidation, removal of low molecular weight cytosolic components, and high ionic strength result in rapid rates of inactivation at 20 degrees C; and (iii) the large degree of protection conferred by TCDD binding implies a very tight ligand-receptor interaction, and as such accords with TCDDs extraordinary potency and persistence in producing its toxic and biochemical effects.
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Aström A, DePierre JW. Rat-liver microsomal cytochrome P-450: purification, characterization, multiplicity and induction. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 853:1-27. [PMID: 3533149 DOI: 10.1016/0304-4173(86)90002-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Denison MS, Okey AB, Hamilton JW, Bloom SE, Wilkinson CF. Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin: ontogeny in chick embryo liver. JOURNAL OF BIOCHEMICAL TOXICOLOGY 1986; 1:39-49. [PMID: 2856072 DOI: 10.1002/jbt.2570010305] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Aryl hydrocarbon hydroxylase (AHH, cytochrome P1-450) is induced in chick liver very early during embryonic development if embryos are treated with 3-methylcholanthrene-type compounds such as 3,4,3'4'-tetrachlorobiphenyl. In mammals, AHH induction is known to be mediated by the Ah receptor. Liver from embryonic and newly hatched chicks was found to contain a cytosolic receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) which has properties that are very similar to properties of the Ah receptor previously characterized in mammalian tissues. In chick embryo liver, cytosolic binding sites for TCDD were of high affinity (Kd for [3-H]-TCDD = 0.2 nM) and were specific for 3-methylcholanthrene-type inducers. The specific binding component sedimented at about 9S on sucrose density gradients prepared at low ionic strength. A high level of Ah receptor was detected in chick embryo liver by the fifth day of incubation (5 DI); this is at least 24 hours prior to the onset of AHH inducibility. The Ah receptor concentration increased from 5 DI to 8 DI, the period when chick liver is undergoing early morphological differentiation. After 8 DI, Ah receptor levels dropped substantially and remained low into the posthatching period. In contrast, AHH inducibility was high by 7 DI and remained high throughout embryonic development and into the posthatching period. The discrepancy between Ah receptor levels and the degree of AHH inducibility suggests that only a small fraction of the Ah receptor population is required for maximal AHH induction.
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Affiliation(s)
- M S Denison
- Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
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Denison MS, Vella LM, Okey AB. Hepatic Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin. Partial stabilization by molybdate. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67509-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Okey AB, Roberts EA, Harper PA, Denison MS. Induction of drug-metabolizing enzymes: mechanisms and consequences. Clin Biochem 1986; 19:132-41. [PMID: 3518989 DOI: 10.1016/s0009-9120(86)80060-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The activity of many enzymes that carry out biotransformation of drugs and environmental chemicals can be substantially increased by prior exposure of humans or animals to a wide variety of foreign chemicals. Increased enzyme activity is due to true enzyme induction mediated by increased synthesis of mRNAs which code for specific drug-metabolizing enzymes. Several species of cytochrome P-450 are inducible as are certain conjugating enzymes such as glutathione S-transferases, glucuronosyl transferases, and epoxide hydrolases. Induction of drug-metabolizing enzymes has been shown in several instances to alter the efficacy of some therapeutic agents. Induction of various species of cytochrome P-450 also is known to increase the rate at which potentially toxic reactive metabolic intermediates are formed from drugs or environmental chemicals. Overall, however, induction of drug-metabolizing enzymes appears to be a beneficial adaptive response for organisms living in a "chemically-hostile" world.
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Denison MS, Vella LM, Okey AB. Structure and function of the Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin. Species difference in molecular properties of the receptors from mouse and rat hepatic cytosols. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35611-9] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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