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Altenburger R, Ait-Aissa S, Antczak P, Backhaus T, Barceló D, Seiler TB, Brion F, Busch W, Chipman K, de Alda ML, de Aragão Umbuzeiro G, Escher BI, Falciani F, Faust M, Focks A, Hilscherova K, Hollender J, Hollert H, Jäger F, Jahnke A, Kortenkamp A, Krauss M, Lemkine GF, Munthe J, Neumann S, Schymanski EL, Scrimshaw M, Segner H, Slobodnik J, Smedes F, Kughathas S, Teodorovic I, Tindall AJ, Tollefsen KE, Walz KH, Williams TD, Van den Brink PJ, van Gils J, Vrana B, Zhang X, Brack W. Future water quality monitoring--adapting tools to deal with mixtures of pollutants in water resource management. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 512-513:540-551. [PMID: 25644849 DOI: 10.1016/j.scitotenv.2014.12.057] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 12/18/2014] [Accepted: 12/18/2014] [Indexed: 05/18/2023]
Abstract
Environmental quality monitoring of water resources is challenged with providing the basis for safeguarding the environment against adverse biological effects of anthropogenic chemical contamination from diffuse and point sources. While current regulatory efforts focus on monitoring and assessing a few legacy chemicals, many more anthropogenic chemicals can be detected simultaneously in our aquatic resources. However, exposure to chemical mixtures does not necessarily translate into adverse biological effects nor clearly shows whether mitigation measures are needed. Thus, the question which mixtures are present and which have associated combined effects becomes central for defining adequate monitoring and assessment strategies. Here we describe the vision of the international, EU-funded project SOLUTIONS, where three routes are explored to link the occurrence of chemical mixtures at specific sites to the assessment of adverse biological combination effects. First of all, multi-residue target and non-target screening techniques covering a broader range of anticipated chemicals co-occurring in the environment are being developed. By improving sensitivity and detection limits for known bioactive compounds of concern, new analytical chemistry data for multiple components can be obtained and used to characterise priority mixtures. This information on chemical occurrence will be used to predict mixture toxicity and to derive combined effect estimates suitable for advancing environmental quality standards. Secondly, bioanalytical tools will be explored to provide aggregate bioactivity measures integrating all components that produce common (adverse) outcomes even for mixtures of varying compositions. The ambition is to provide comprehensive arrays of effect-based tools and trait-based field observations that link multiple chemical exposures to various environmental protection goals more directly and to provide improved in situ observations for impact assessment of mixtures. Thirdly, effect-directed analysis (EDA) will be applied to identify major drivers of mixture toxicity. Refinements of EDA include the use of statistical approaches with monitoring information for guidance of experimental EDA studies. These three approaches will be explored using case studies at the Danube and Rhine river basins as well as rivers of the Iberian Peninsula. The synthesis of findings will be organised to provide guidance for future solution-oriented environmental monitoring and explore more systematic ways to assess mixture exposures and combination effects in future water quality monitoring.
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Affiliation(s)
- Rolf Altenburger
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany; RWTH Aachen University, Aachen, Germany
| | - Selim Ait-Aissa
- Institut National de l'Environnement Industriel et des Risques INERIS, BP2, 60550 Verneuil-en-Halatte, France
| | - Philipp Antczak
- Centre for Computational Biology and Modelling, University of Liverpool, L69 7ZB, UK
| | - Thomas Backhaus
- Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottbergs Gata 22b, 40530 Gothenburg, Sweden
| | - Damià Barceló
- Water and Soil Quality Research Group, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain
| | | | - Francois Brion
- Institut National de l'Environnement Industriel et des Risques INERIS, BP2, 60550 Verneuil-en-Halatte, France
| | - Wibke Busch
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
| | - Kevin Chipman
- School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
| | - Miren López de Alda
- Water and Soil Quality Research Group, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain
| | | | - Beate I Escher
- National Research Centre for Environmental Toxicology (Entox), The University of Queensland, Brisbane, Australia; UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
| | - Francesco Falciani
- Centre for Computational Biology and Modelling, University of Liverpool, L69 7ZB, UK
| | - Michael Faust
- Faust & Backhaus Environmental Consulting, Fahrenheitstr. 1, 28359 Bremen, Germany
| | - Andreas Focks
- Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands
| | - Klara Hilscherova
- Masaryk University, Research Centre for Toxic Compounds in the Environment (RECETOX), Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic
| | - Juliane Hollender
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | | | - Felix Jäger
- Synchem UG & Co. KG, Am Kies 2, 34587 Felsberg-Altenburg, Germany
| | - Annika Jahnke
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
| | - Andreas Kortenkamp
- Brunel University, Institute of Environment, Health and Societies, Uxbridge UB8 3PH, United Kingdom
| | - Martin Krauss
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
| | - Gregory F Lemkine
- WatchFrog, Bâtiment Genavenir 3, 1 rue Pierre Fontaine, 91000 Evry, France
| | - John Munthe
- IVL Swedish Environmental Research Institute, P.O. Box 53021, 400 14 Göteborg, Sweden
| | - Steffen Neumann
- Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle, Germany
| | - Emma L Schymanski
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Mark Scrimshaw
- Brunel University, Institute of Environment, Health and Societies, Uxbridge UB8 3PH, United Kingdom
| | - Helmut Segner
- University of Bern, Centre for Fish and Wildlife Health, PO Box 8466, CH-3001 Bern, Switzerland
| | | | - Foppe Smedes
- Masaryk University, Research Centre for Toxic Compounds in the Environment (RECETOX), Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic
| | - Subramaniam Kughathas
- Brunel University, Institute of Environment, Health and Societies, Uxbridge UB8 3PH, United Kingdom
| | - Ivana Teodorovic
- University of Novi Sad, Faculty of Sciences¸ Trg Dositeja Obradovića, 321000 Novi Sad, Serbia
| | - Andrew J Tindall
- WatchFrog, Bâtiment Genavenir 3, 1 rue Pierre Fontaine, 91000 Evry, France
| | - Knut Erik Tollefsen
- Norwegian Institute for Water Research NIVA, Gaustadalléen 21, N-0349 Oslo, Norway
| | - Karl-Heinz Walz
- MAXX Mess- und Probenahmetechnik GmbH, Hechinger Straße 41, D-72414 Rangendingen, Germany
| | - Tim D Williams
- School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
| | - Paul J Van den Brink
- Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands
| | - Jos van Gils
- Foundation Deltares, Potbus 177, 277 MH Delft, The Netherlands
| | - Branislav Vrana
- Masaryk University, Research Centre for Toxic Compounds in the Environment (RECETOX), Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic
| | - Xiaowei Zhang
- State Key Laboratory of Pollution Control & Resource Reuse, School of the Environment, Collaborative Innovation Center for Regional Environmental Quality, Nanjing University, Nanjing 210023, PR China
| | - Werner Brack
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany
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Annamalai J, Namasivayam V. Endocrine disrupting chemicals in the atmosphere: Their effects on humans and wildlife. ENVIRONMENT INTERNATIONAL 2015; 76:78-97. [PMID: 25569353 DOI: 10.1016/j.envint.2014.12.006] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 12/17/2014] [Accepted: 12/20/2014] [Indexed: 05/20/2023]
Abstract
Endocrine disrupting chemicals (EDCs) are exogenous agents that interfere or disrupt the normal synthesis, secretion, transportation, binding and metabolism of natural hormones; eventually dysregulating homeostatic mechanisms, reproduction and development. They are emitted into the atmosphere during anthropogenic activities and physicochemical reactions in nature. Inhalation of these EDCs as particulate and gaseous vapors triggers their interaction with endocrine glands and exerts agonist or antagonists actions at hormone receptors. The endocrine disruption at nanogram levels of EDC's has gained concern in the last decade, due to infertility among men and women, early puberty, obesity, diabetes and cancer. Thus, the review explores the literature that addresses the major occurring EDCs in the atmosphere including phthalates, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), brominated flame retardants (BFRs), dioxins, alkylphenols (APs) and perfluorinated chemicals (PFCs). Sources, fate, half-life, mechanism, measured concentrations in air, bioaccumulation in tissues, laboratory exposures correlating to toxicological effects of these EDCs in humans and wildlife are discussed.
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Affiliation(s)
- Jayshree Annamalai
- Centre for Environmental Studies, CEG Campus, Anna University, Guindy, Chennai 600 025, Tamil Nadu, India.
| | - Vasudevan Namasivayam
- Centre for Environmental Studies, CEG Campus, Anna University, Guindy, Chennai 600 025, Tamil Nadu, India.
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Guyot R, Chatonnet F, Gillet B, Hughes S, Flamant F. Toxicogenomic analysis of the ability of brominated flame retardants TBBPA and BDE-209 to disrupt thyroid hormone signaling in neural cells. Toxicology 2014; 325:125-32. [DOI: 10.1016/j.tox.2014.08.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/22/2014] [Accepted: 08/23/2014] [Indexed: 10/24/2022]
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Zhang YF, Xu W, Lou QQ, Li YY, Zhao YX, Wei WJ, Qin ZF, Wang HL, Li JZ. Tetrabromobisphenol A disrupts vertebrate development via thyroid hormone signaling pathway in a developmental stage-dependent manner. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:8227-34. [PMID: 24963557 DOI: 10.1021/es502366g] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Data concerning effects of tetrabromobisphenol A (TBBPA) on thyroid hormone (TH)-dependent vertebrate development have been limited, although TBBPA has been demonstrated in vitro to disrupt the TH signaling pathway at the transcriptional level. In this study, we investigated the effects of TBBPA on T3-induced and spontaneous Xenopus laevis metamorphosis, which share many similarities with TH-dependent development in higher vertebrates. In a 6-day T3-induced metamorphosis assay using premetamorphic tadpoles, 10-1000 nM TBBPA exhibited inhibitory effects on T3-induced expression of TH-response genes and morphological changes in a concentration-dependent manner, with a weak stimulatory action on tadpole development and TH-response gene expression in the absence of T3 induction. In a spontaneous metamorphosis assay, we further found that TBBPA promoted tadpole development from stage 51 to 56 (pre- and prometamorphic stages) but inhibited metamorphic development from stage 57 to 66 (metamorphic climax). These results strongly show that TBBPA, even at low concentrations, disrupts TH-dependent development in a developmental stage-dependent manner, i.e., TBBPA exhibits an antagonistic activity at the developmental stages when animals have high endogenous TH levels, whereas it acts as an agonist at the developmental stages when animals have low endogenous TH levels. Our study highlights the adverse influences of TBBPA on TH-dependent development in vertebrates.
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Affiliation(s)
- Yin-Feng Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences and ‡Department of Environmental Bio-Technology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
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Préau L, Fini JB, Morvan-Dubois G, Demeneix B. Thyroid hormone signaling during early neurogenesis and its significance as a vulnerable window for endocrine disruption. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:112-21. [PMID: 24980696 DOI: 10.1016/j.bbagrm.2014.06.015] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/14/2014] [Accepted: 06/20/2014] [Indexed: 12/11/2022]
Abstract
The essential roles of thyroid hormone (TH) in perinatal brain development have been known for decades. More recently, many of the molecular mechanisms underlying the multiple effects of TH on proliferation, differentiation, migration, synaptogenesis and myelination in the developing nervous system have been elucidated. At the same time data from both epidemiological studies and animal models have revealed that the influence of thyroid signaling on development of the nervous system, extends to all periods of life, from early embryogenesis to neurogenesis in the adult brain. This review focuses on recent insights into the actions of TH during early neurogenesis. A key concept is that, in contrast to the previous ideas that only the unliganded receptor was implicated in these early phases, a critical role of the ligand, T3, is increasingly recognized. These findings are considered in the light of increasing knowledge of cell specific control of T3 availability as a function of deiodinase activity and transporter expression. These requirements for TH in the early stages of neurogenesis take on new relevance given the increasing epidemiological data on adverse effects of TH lack in early pregnancy on children's neurodevelopmental outcome. These ideas lead logically into a discussion on how the actions of TH during the first phases of neurogenesis can be potentially disrupted by gestational iodine lack and/or chemical pollution. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
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Affiliation(s)
- Laetitia Préau
- UMR CNRS 7221, Evolution des Régulations Endocriniennes, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Jean Baptiste Fini
- UMR CNRS 7221, Evolution des Régulations Endocriniennes, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Ghislaine Morvan-Dubois
- UMR CNRS 7221, Evolution des Régulations Endocriniennes, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Barbara Demeneix
- UMR CNRS 7221, Evolution des Régulations Endocriniennes, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75231 Paris, France.
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Delfosse V, Grimaldi M, le Maire A, Bourguet W, Balaguer P. Nuclear Receptor Profiling of Bisphenol-A and Its Halogenated Analogues. VITAMINS & HORMONES 2014; 94:229-51. [DOI: 10.1016/b978-0-12-800095-3.00009-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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57
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Perkins EJ, Ankley GT, Crofton KM, Garcia-Reyero N, LaLone CA, Johnson MS, Tietge JE, Villeneuve DL. Current perspectives on the use of alternative species in human health and ecological hazard assessments. ENVIRONMENTAL HEALTH PERSPECTIVES 2013; 121:1002-10. [PMID: 23771518 PMCID: PMC3764090 DOI: 10.1289/ehp.1306638] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 06/12/2013] [Indexed: 05/17/2023]
Abstract
BACKGROUND Traditional animal toxicity tests can be time and resource intensive, thereby limiting the number of chemicals that can be comprehensively tested for potential hazards to humans and/or to the environment. OBJECTIVE We compared several types of data to demonstrate how alternative models can be used to inform both human and ecological risk assessment. METHODS We reviewed and compared data derived from high throughput in vitro assays to fish reproductive tests for seven chemicals. We investigated whether human-focused assays can be predictive of chemical hazards in the environment. We examined how conserved pathways enable the use of nonmammalian models, such as fathead minnow, zebrafish, and Xenopus laevis, to understand modes of action and to screen for chemical risks to humans. RESULTS We examined how dose-dependent responses of zebrafish embryos exposed to flusilazole can be extrapolated, using pathway point of departure data and reverse toxicokinetics, to obtain human oral dose hazard values that are similar to published mammalian chronic toxicity values for the chemical. We also examined how development/safety data for human health can be used to help assess potential risks of pharmaceuticals to nontarget species in the environment. DISCUSSION Using several examples, we demonstrate that pathway-based analysis of chemical effects provides new opportunities to use alternative models (nonmammalian species, in vitro tests) to support decision making while reducing animal use and associated costs. CONCLUSIONS These analyses and examples demonstrate how alternative models can be used to reduce cost and animal use while being protective of both human and ecological health.
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Affiliation(s)
- Edward J Perkins
- US Army Engineer Research and Development Center, Vicksburg, Mississippi, USA.
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58
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Punzon I, Latapie V, Le Mével S, Hagneau A, Jolivet P, Palmier K, Fini JB, Demeneix BA. Towards a humanized PPARγ reporter system for in vivo screening of obesogens. Mol Cell Endocrinol 2013; 374:1-9. [PMID: 23603401 DOI: 10.1016/j.mce.2013.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 04/08/2013] [Accepted: 04/08/2013] [Indexed: 12/30/2022]
Abstract
Overeating and lack of exercise are major contributors to the current obesity epidemic, but environmental contaminants, or obesogens, are also considered to be potential actors. A common obesogen target is the Peroxisome Proliferator Activated Receptor Gamma (PPARγ). Screening for exogenous obesogens requires in vivo systems as many xenobiotics exert their effects through metabolites. We thus developed a humanized in vivo PPARγ reporter model, using Xenopus laevis larvae, a species possessing metabolic capacities comparable to mammals. A somatic transgenesis approach was used to co-express an expression vector for the human PPARγ protein simultaneously with one of a series of reporter vectors, each containing a PPARγ Response Element (PPRE)-eGFP sequence. Treatment of tadpoles with PPARγ agonists, antagonists or candidate obesogens, significantly modulated eGFP expression. Thus, the system provides a promising proof of principle for a sensitive and reliable humanized in vivo tool to screen both novel PPARγ drug ligands and potential endocrine disruptors or obesogens targeting this receptor.
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Affiliation(s)
- I Punzon
- UMR CNRS 7221, Evolution des Régulations Endocriniennes CNRS UMR 7221/Muséum National d'Histoire Naturelle, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75231 Paris, France
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Viguié C, Collet SH, Gayrard V, Picard-Hagen N, Puel S, Roques BB, Toutain PL, Lacroix MZ. Maternal and fetal exposure to bisphenol a is associated with alterations of thyroid function in pregnant ewes and their newborn lambs. Endocrinology 2013; 154:521-8. [PMID: 23150491 DOI: 10.1210/en.2012-1401] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The putative thyroid-disrupting properties of bisphenol A (BPA) highlight the need for an evaluation of fetal exposure and its consequence on the mother/newborn thyroid functions in models relevant to human. The goals of this study were to characterize in sheep a relevant model for human pregnancy and thyroid physiology, the internal exposures of the fetuses and their mothers to BPA and its main metabolite BPA-glucuronide (Gluc), and to determine to what extent it might be associated with thyroid disruption. Ewes were treated with BPA [5 mg/(kg · d) sc] or vehicle from d 28 until the end of pregnancy. Unconjugated BPA did not appear to accumulate in pregnant ewes, and its concentration was similar in the newborns and their mothers (0.13 ± 0.02 and 0.18 ± 0.03 nmol/ml in cord and maternal blood, respectively). In amniotic fluid and cord blood, BPA-Gluc concentrations were about 1300-fold higher than those of BPA. Total T(4) concentrations were decreased in BPA-treated pregnant ewes and in the cord and the jugular blood of their newborns (30% decrease). A similar difference was observed for free T(4) plasma concentrations in the jugular blood of the newborns. Our results show in a long-gestation species with a similar regulatory scheme of thyroid function as humans that BPA in utero exposure can be associated with hypothyroidism in the newborns. If such an effect were to be confirmed for a more relevant exposure scheme to BPA, this would constitute a major issue for BPA risk assessment.
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Affiliation(s)
- Catherine Viguié
- Institut National de la Recherche Agronomique/Institut National Polytechnique/Université Paul Sabatire, Ecole Nationale Vétérinaire de Toulouse, Laboratoire de Physiologie, 23 chemin des Capelles, BP 87614, F-31076 Toulouse cedex 3, France.
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61
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Scholz S, Renner P, Belanger SE, Busquet F, Davi R, Demeneix BA, Denny JS, Léonard M, McMaster ME, Villeneuve DL, Embry MR. Alternatives to in vivo tests to detect endocrine disrupting chemicals (EDCs) in fish and amphibians--screening for estrogen, androgen and thyroid hormone disruption. Crit Rev Toxicol 2012. [PMID: 23190036 DOI: 10.3109/10408444.2012.737762] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Endocrine disruption is considered a highly relevant hazard for environmental risk assessment of chemicals, plant protection products, biocides and pharmaceuticals. Therefore, screening tests with a focus on interference with estrogen, androgen, and thyroid hormone pathways in fish and amphibians have been developed. However, they use a large number of animals and short-term alternatives to animal tests would be advantageous. Therefore, the status of alternative assays for endocrine disruption in fish and frogs was assessed by a detailed literature analysis. The aim was to (i) determine the strengths and limitations of alternative assays and (ii) present conclusions regarding chemical specificity, sensitivity, and correlation with in vivo data. Data from 1995 to present were collected related to the detection/testing of estrogen-, androgen-, and thyroid-active chemicals in the following test systems: cell lines, primary cells, fish/frog embryos, yeast and cell-free systems. The review shows that the majority of alternative assays measure effects directly mediated by receptor binding or resulting from interference with hormone synthesis. Other mechanisms were rarely analysed. A database was established and used for a quantitative and comparative analysis. For example, a high correlation was observed between cell-free ligand binding and cell-based reporter cell assays, between fish and frog estrogenic data and between fish embryo tests and in vivo reproductive effects. It was concluded that there is a need for a more systematic study of the predictive capacity of alternative tests and ways to reduce inter- and intra-assay variability.
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Affiliation(s)
- S Scholz
- Department of Bioanalytical Ecotoxicology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany.
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Fini JB, Le Mével S, Palmier K, Darras VM, Punzon I, Richardson SJ, Clerget-Froidevaux MS, Demeneix BA. Thyroid hormone signaling in the Xenopus laevis embryo is functional and susceptible to endocrine disruption. Endocrinology 2012; 153:5068-81. [PMID: 22968643 DOI: 10.1210/en.2012-1463] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (TH) is essential for vertebrate brain development. Most research on TH and neuronal development focuses on late development, mainly the perinatal period in mammals. However, in human infants neuromotor development correlates best with maternal TH levels in the first trimester of pregnancy, suggesting that TH signaling could affect early brain development. Studying TH signaling in early embryogenesis in mammals is experimentally challenging. In contrast, free-living embryos, such as Xenopus laevis, permit physiological experimentation independent of maternal factors. We detailed key elements of TH signaling: ligands, receptors (TR), and deiodinases during early X. laevis development, before embryonic thyroid gland formation. Dynamic profiles for all components were found. Between developmental stages 37 and 41 (~48 h after hatching, coincident with a phase of continuing neurogenesis) significant increases in T(3) levels as well as in mRNA encoding deiodinases and TR occurred. Exposure of embryos at this developmental stage for 24 h to either a TH antagonist, NH-3, or to tetrabromobisphenol A, a flame retardant and known TH disruptor, differentially modulated the expression of a number of TH target genes implicated in neural stem cell function or neural differentiation. Moreover, 24-h exposure to either NH-3 or tetrabromobisphenol A diminished cell proliferation in the brain. Thus, these data show first, that TH signaling exerts regulatory roles in early X. laevis neurogenesis and second, that this period represents a potential window for endocrine disruption.
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Affiliation(s)
- J B Fini
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 7221, Evolution des Régulations Endocriniennes CNRS UMR 7221/Muséum National d'Histoire Naturelle Département Régulations, Développement et Diversité Moléculaire, 75231 Paris, France
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Zatecka E, Ded L, Elzeinova F, Kubatova A, Dorosh A, Margaryan H, Dostalova P, Peknicova J. Effect of tetrabrombisphenol A on induction of apoptosis in the testes and changes in expression of selected testicular genes in CD1 mice. Reprod Toxicol 2012; 35:32-9. [PMID: 22677475 DOI: 10.1016/j.reprotox.2012.05.095] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 05/18/2012] [Accepted: 05/25/2012] [Indexed: 11/30/2022]
Abstract
Tetrabromobisphenol A (TBBPA) is a substance widely used in industry as a flame retardant. TBBPA was found in the environment and was detected even in the human body. The effect of this chemical was observed in different cell lines in vitro and it is supposed that TBBPA may affect various hormonal systems in vivo. In this study we examined the effect of TBBPA on the reproductive parameters of two generations of outbred mice in vivo. Experimental and control animals of F1 generation were bred in various conditions to enable evaluation of the possible trans-generational effect. An increased incidence of apoptosis in the testes and changes in the morphometry of seminiferous tubules was detected in the experimental animals. In addition, changes in the expression pattern of selected genes encoding proteins that play an important role during spermatogenesis were observed. In contrast, sperm quality and reproduction were not affected by TBBPA.
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Affiliation(s)
- Eva Zatecka
- Laboratory of Reproductive Biology, Institute of Biotechnology, Academy of Sciences of the Czech Republic, vvi, Prague 4, Czech Republic
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Boas M, Feldt-Rasmussen U, Main KM. Thyroid effects of endocrine disrupting chemicals. Mol Cell Endocrinol 2012; 355:240-8. [PMID: 21939731 DOI: 10.1016/j.mce.2011.09.005] [Citation(s) in RCA: 421] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 05/29/2011] [Accepted: 09/02/2011] [Indexed: 11/17/2022]
Abstract
In recent years, many studies of thyroid-disrupting effects of environmental chemicals have been published. Of special concern is the exposure of pregnant women and infants, as thyroid disruption of the developing organism may have deleterious effects on neurological outcome. Chemicals may exert thyroid effects through a variety of mechanisms of action, and some animal experiments and in vitro studies have focused on elucidating the mode of action of specific chemical compounds. Long-term human studies on effects of environmental chemicals on thyroid related outcomes such as growth and development are still lacking. The human exposure scenario with life long exposure to a vast mixture of chemicals in low doses and the large physiological variation in thyroid hormone levels between individuals render human studies very difficult. However, there is now reasonably firm evidence that PCBs have thyroid-disrupting effects, and there is emerging evidence that also phthalates, bisphenol A, brominated flame retardants and perfluorinated chemicals may have thyroid disrupting properties.
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Affiliation(s)
- Malene Boas
- Department of Growth and Reproduction GR, Rigshospitalet, University of Copenhagen, Denmark.
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65
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Wheeler GN, Liu KJ. Xenopus: An ideal system for chemical genetics. Genesis 2012; 50:207-18. [DOI: 10.1002/dvg.22009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/21/2011] [Accepted: 12/23/2011] [Indexed: 02/05/2023]
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Fini JB, Riu A, Debrauwer L, Hillenweck A, Le Mével S, Chevolleau S, Boulahtouf A, Palmier K, Balaguer P, Cravedi JP, Demeneix BA, Zalko D. Parallel biotransformation of tetrabromobisphenol A in Xenopus laevis and mammals: Xenopus as a model for endocrine perturbation studies. Toxicol Sci 2011; 125:359-67. [PMID: 22086976 DOI: 10.1093/toxsci/kfr312] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The flame retardant tetrabromobisphenol A (TBBPA) is a high production flame retardant that interferes with thyroid hormone (TH) signaling. Despite its rapid metabolism in mammals, TBBPA is found in significant amounts in different tissues. Such findings highlight first a need to better understand the effects of TBBPA and its metabolites and second the need to develop models to address these questions experimentally. We used Xenopus laevis tadpoles to follow radiolabeled (14)C-TBBPA uptake and metabolism. Extensive and rapid uptake of radioactivity was observed, tadpoles metabolizing > 94% of (14)C-TBBPA within 8 h. Four metabolites were identified in water and tadpole extracts: TBBPA-glucuronide, TBBPA-glucuronide-sulfate, TBBPA-sulfate, and TBBPA-disulfate. These metabolites are identical to the TBBPA conjugates characterized in mammals, including humans. Most radioactivity (> 75%) was associated with sulfated conjugates. The antithyroid effects of TBBPA and the metabolites were compared using two in vivo measures: tadpole morphology and an in vivo tadpole TH reporter gene assay. Only TBBPA, and not the sulfated metabolites, disrupted thyroid signaling. Moreover, TBBPA treatment did not affect expression of phase II enzymes involved in TH metabolism, suggesting that the antithyroid effects of TBBPA are not due to indirect effects on TH metabolism. Finally, we show that only the parent TBBPA inhibits T3-induced transactivation in cells expressing human, zebrafish, or X. laevis TH receptor, TRα. We conclude, first, that perturbation of thyroid signaling by TBBPA is likely due to rapid direct action of the parent compound, and second, that Xenopus is an excellent vertebrate model for biotransformation studies, displaying homologous pathways to mammals.
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Affiliation(s)
- Jean-Baptiste Fini
- UMR CNRS 7221, Evolution des Régulations Endocriniennes Department of Regulations, Development and Molecular Diversity, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France
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Riu A, Grimaldi M, le Maire A, Bey G, Phillips K, Boulahtouf A, Perdu E, Zalko D, Bourguet W, Balaguer P. Peroxisome proliferator-activated receptor γ is a target for halogenated analogs of bisphenol A. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:1227-32. [PMID: 21561829 PMCID: PMC3230400 DOI: 10.1289/ehp.1003328] [Citation(s) in RCA: 238] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 05/11/2011] [Indexed: 05/18/2023]
Abstract
BACKGROUND The occurrence of halogenated analogs of the xenoestrogen bisphenol A (BPA) has been recently demonstrated both in environmental and human samples. These analogs include brominated [e.g., tetrabromobisphenol A (TBBPA)] and chlorinated [e.g., tetrachlorobisphenol A (TCBPA)] bisphenols, which are both flame retardants. Because of their structural homology with BPA, such chemicals are candidate endocrine disruptors. However, their possible target(s) within the nuclear hormone receptor superfamily has remained unknown. OBJECTIVES We investigated whether BPA and its halogenated analogs could be ligands of estrogen receptors (ERs) and peroxisome proliferator-activated receptors (PPARs) and act as endocrine-disrupting chemicals. METHODS We studied the activity of compounds using reporter cell lines expressing ERs and PPARs. We measured the binding affinities to PPARγ by competitive binding assays with [3H]-rosiglitazone and investigated the impact of TBBPA and TCBPA on adipocyte differentiation using NIH3T3-L1 cells. Finally, we determined the binding mode of halogenated BPAs to PPARγ by X-ray crystallography. RESULTS We observed that TBBPA and TCBPA are human, zebrafish, and Xenopus PPARγ ligands and determined the mechanism by which these chemicals bind to and activate PPARγ. We also found evidence that activation of ERα, ERβ, and PPARγ depends on the degree of halogenation in BPA analogs. We observed that the bulkier brominated BPA analogs, the greater their capability to activate PPARγ and the weaker their estrogenic potential. CONCLUSIONS Our results strongly suggest that polyhalogenated bisphenols could function as obesogens by acting as agonists to disrupt physiological functions regulated by human or animal PPARγ.
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Affiliation(s)
- Anne Riu
- INRA (National Institute of Agronomic Research), UMR 1089 Xénobiotiques, Toulouse, France
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68
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Terrien X, Fini JB, Demeneix BA, Schramm KW, Prunet P. Generation of fluorescent zebrafish to study endocrine disruption and potential crosstalk between thyroid hormone and corticosteroids. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2011; 105:13-20. [PMID: 21684237 DOI: 10.1016/j.aquatox.2011.04.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/05/2011] [Accepted: 04/09/2011] [Indexed: 05/28/2023]
Abstract
Several environmental chemicals disrupt thyroid function, a key regulator of normal development involved in many physiological processes in fish. We studied the effects of such chemicals in vivo using transient transgenic zebrafish (Danio rerio), expressing Green Fluorescent Protein (GFP) under the control of a TH/bZIP promoter from Xenopus laevis. Exposure to thyroid hormone (T3) at 10(-8)M increased GFP fluorescence in F0 embryos and larvae. Transient transgenic embryos were exposed to a T3 signaling agonist (TRIAC) or antagonists (NH(3) or NaClO(4)), or to the endocrine disruptor Bisphenol A (BPA). When tested alone, TRIAC increased fluorescence, confirming the specificity of our model. Exposure to NH(3) or NaClO(4) decreased fluorescence, reflecting inhibition of thyroid function. When tested alone, BPA did not modify fluorescence, but when tested with T3, it significantly reduced T3-induced fluorescence, suggesting disruption of the thyroid function by BPA. The expression of genes involved in the TH axis (TR-alpha, TR-beta, TSH) and the corticoid axis (GR and MR) was followed by q-PCR after T3 or BPA exposure (24 or 48h) and at different developmental stages (0, 1, or 5 days post-fertilization). Expression of TR-alpha, TR-beta, and TSH genes increased after 48h T3 exposure in 1-day-old larvae. When tested alone, BPA only slightly affected gene expression. When applied with T3, BPA decreased expression of all candidate genes in 1-day-old embryos compared to the T3 treated group, in agreement with data obtained with the TH/bZIP-eGFP zebrafish model. Finally, we show that T3 exposure leads to up-regulation of MR and GR genes. This study provides a new rapid diagnostic tool for characterizing the disrupting effects of toxicants on thyroid function and suggests possible crosstalk between the TR and Corticoid Signaling system.
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Affiliation(s)
- Xavier Terrien
- INRA UR 1037 SCRIBE, IFR 140, 35042 Rennes Cedex, France.
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69
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Chatonnet F, Picou F, Fauquier T, Flamant F. Thyroid hormone action in cerebellum and cerebral cortex development. J Thyroid Res 2011; 2011:145762. [PMID: 21765985 PMCID: PMC3134109 DOI: 10.4061/2011/145762] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 04/09/2011] [Indexed: 01/30/2023] Open
Abstract
Thyroid hormones (TH, including the prohormone thyroxine (T4) and its active deiodinated derivative 3,3′,5-triiodo-L-thyronine (T3)) are important regulators of vertebrates neurodevelopment. Specific transporters and deiodinases are required to ensure T3 access to the developing brain. T3 activates a number of differentiation processes in neuronal and glial cell types by binding to nuclear receptors, acting directly on transcription. Only few T3 target genes are currently known. Deeper investigations are urgently needed, considering that some chemicals present in food are believed to interfere with T3 signaling with putative neurotoxic consequences.
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Affiliation(s)
- Fabrice Chatonnet
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Université de Lyon, UMR CNRS 5242, 46 allée d'Italie, 69364 Lyon Cedex 07, France
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Willett CE, Bishop PL, Sullivan KM. Application of an integrated testing strategy to the U.S. EPA endocrine disruptor screening program. Toxicol Sci 2011; 123:15-25. [PMID: 21642633 DOI: 10.1093/toxsci/kfr145] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
New approaches to generating and evaluating toxicity data for chemicals are needed to cope with the ever-increasing demands of new programs. One such approach involves the use of an integrated testing and evaluation strategy based on the specific properties and activities of a chemical. Such an integrated strategy, whether applied to existing or future programs, can promote efficient use of resources and save animals. We demonstrate the utility of such a strategy by applying it to the current U.S. Environmental Protection Agency Endocrine Disruptor Screening Program (EDSP). Launched in October 2009, the EDSP utilizes a two-tiered approach, whereby each tier requires a battery of animal-intensive and expensive tests. Tier 1 consists of five in vitro and six in vivo assays that are intended to determine a chemical's potential to interact with the estrogen (E), androgen (A), or thyroid (T) hormone pathways. Tier 2 is proposed to consist of multigenerational reproductive and developmental toxicity tests in several species and is intended to determine whether a chemical can cause adverse effects resulting from E, A, or T modulation. In contrast to the existing EDSP structure, we show, using the pesticide atrazine as an example, that a multilevel testing framework combined with an integrated evaluation process would significantly increase efficiency by minimizing testing.
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Affiliation(s)
- Catherine E Willett
- Regulatory Testing Division, People for the Ethical Treatment of Animals, Norfolk, Virginia 23510, USA
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71
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Shen O, Wu W, Du G, Liu R, Yu L, Sun H, Han X, Jiang Y, Shi W, Hu W, Song L, Xia Y, Wang S, Wang X. Thyroid disruption by Di-n-butyl phthalate (DBP) and mono-n-butyl phthalate (MBP) in Xenopus laevis. PLoS One 2011; 6:e19159. [PMID: 21544203 PMCID: PMC3081329 DOI: 10.1371/journal.pone.0019159] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 03/28/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Di-n-butyl phthalate (DBP), a chemical widely used in many consumer products, is estrogenic and capable of producing seriously reproductive and developmental effects in laboratory animals. However, recent in vitro studies have shown that DBP and mono-n-butyl phthalate (MBP), the major metabolite of DBP, possessed thyroid hormone receptor (TR) antagonist activity. It is therefore important to consider DBP and MBP that may interfere with thyroid hormone system. METHODOLOGY/PRINCIPAL FINDINGS Nieuwkoop and Faber stage 51 Xenopus laevis were exposed to DBP and MBP (2, 10 or 15 mg/L) separately for 21 days. The two test chemicals decelerated spontaneous metamorphosis in X. laevis at concentrations of 10 and 15 mg/L. Moreover, MBP seemed to possess stronger activity. The effects of DBP and MBP on inducing changes of expression of selected thyroid hormone response genes: thyroid hormone receptor-beta (TRβ), retinoid X receptor gamma (RXRγ), alpha and beta subunits of thyroid-stimulating hormone (TSHα and TSHβ) were detected by qPCR at all concentrations of the compounds. Using mammalian two-hybrid assay in vitro, we found that DBP and MBP enhanced the interactions between co-repressor SMRT (silencing mediator for retinoid and thyroid hormone receptors) and TR in a dose-dependent manner, and MBP displayed more markedly. In addition, MBP at low concentrations (2 and 10 mg/L) caused aberrant methylation of TRβ in head tissue. CONCLUSIONS The current findings highlight potential disruption of thyroid signalling by DBP and MBP and provide data for human risk assessment.
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Affiliation(s)
- Ouxi Shen
- The Center for Disease Control and Prevention of Suzhou Industrial Park,
Suzhou, China
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Wei Wu
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Guizhen Du
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Renping Liu
- The Center for Disease Control and Prevention of Suzhou Industrial Park,
Suzhou, China
| | - Lugang Yu
- The Center for Disease Control and Prevention of Suzhou Industrial Park,
Suzhou, China
| | - Hong Sun
- Jiangsu Provincial Center for Disease Control and Prevention, Nanjing,
China
| | - Xiumei Han
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Yi Jiang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of
Nanjing Medical University, Nanjing, China
| | - Wei Shi
- State Key Laboratory of Pollution Control and Resource Reuse, School of
the Environment, Nanjing University, Nanjing, China
| | - Wei Hu
- State Key Laboratory of Pollution Control and Resource Reuse, School of
the Environment, Nanjing University, Nanjing, China
| | - Ling Song
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Yankai Xia
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Shoulin Wang
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
| | - Xinru Wang
- Key Laboratory of Reproductive Medicine, Institute of Toxicology, School
of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University),
Ministry of Education, China
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Gibert Y, Sassi-Messai S, Fini JB, Bernard L, Zalko D, Cravedi JP, Balaguer P, Andersson-Lendahl M, Demeneix B, Laudet V. Bisphenol A induces otolith malformations during vertebrate embryogenesis. BMC DEVELOPMENTAL BIOLOGY 2011; 11:4. [PMID: 21269433 PMCID: PMC3040707 DOI: 10.1186/1471-213x-11-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 01/26/2011] [Indexed: 01/09/2023]
Abstract
Background The plastic monomer and plasticizer bisphenol A (BPA), used for manufacturing polycarbonate plastic and epoxy resins, is produced at over 2.5 million metric tons per year. Concerns have been raised that BPA acts as an endocrine disruptor on both developmental and reproductive processes and a large body of evidence suggests that BPA interferes with estrogen and thyroid hormone signaling. Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models. Results We report that BPA exposure leads to severe malformations of the otic vesicle. In zebrafish and in Xenopus embryos, exposure to BPA during the first developmental day resulted in dose-dependent defects in otolith formation. Defects included aggregation, multiplication and occasionally failure to form otoliths. As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors. Na+/K+ ATPases are crucial for otolith formation in zebrafish. Pharmacological inhibition of the major Na+/K+ ATPase with ouabain can rescue the BPA-induced otolith phenotype. Conclusions The data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.
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Affiliation(s)
- Yann Gibert
- Institut de Génomique Fonctionnelle de Lyon; Université de Lyon; Université Lyon 1; CNRS; INRA; Ecole Normale Supérieure de Lyon; 46 allée d'Italie, 69364 Lyon Cedex 07, France.
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Carr JA, Patiño R. The hypothalamus-pituitary-thyroid axis in teleosts and amphibians: endocrine disruption and its consequences to natural populations. Gen Comp Endocrinol 2011; 170:299-312. [PMID: 20566362 DOI: 10.1016/j.ygcen.2010.06.001] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 06/01/2010] [Indexed: 11/29/2022]
Abstract
Teleosts and pond-breeding amphibians may be exposed to a wide variety of anthropogenic, waterborne contaminants that affect the hypothalamus-pituitary-thyroid (HPT) axis. Because thyroid hormone is required for their normal development and reproduction, the potential impact of HPT-disrupting contaminants on natural teleost and amphibian populations raises special concern. There is laboratory evidence indicating that persistent organic pollutants, heavy metals, pharmaceutical and personal care products, agricultural chemicals, and aerospace products may alter HPT activity, development, and reproduction in teleosts and amphibians. However, at present there is no evidence to clearly link contaminant-induced HPT alterations to impairments in teleost or amphibian population health in the field. Also, with the exception of perchlorate for which laboratory studies have shown a direct link between HPT disruption and adverse impacts on development and reproductive physiology, little is known about if or how other HPT-disrupting contaminants affect organismal performance. Future field studies should focus on establishing temporal associations between the presence of HPT-disrupting chemicals, the occurrence of HPT alterations, and adverse effects on development and reproduction in natural populations; as well as determining how complex mixtures of HPT contaminants affect organismal and population health.
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Affiliation(s)
- James A Carr
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, USA.
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Decherf S, Demeneix BA. The obesogen hypothesis: a shift of focus from the periphery to the hypothalamus. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2011; 14:423-448. [PMID: 21790320 DOI: 10.1080/10937404.2011.578561] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The obesogen concept proposes that environmental contaminants may be contributing to the epidemic of obesity and its related pathology, metabolic disorder. The first references to such a notion appeared at the beginning of the current decade, with the hypothesis that the correlation between increasing incidence of obesity and enhanced industrial chemical production was not simply coincidental, but potentially causally related. The next event was the introduction of the term "obesogen" as representing an environmental pollutant that adversely affects various aspects of adipose tissue functions. More recently, the concept was extended to include substances that may modify metabolic balance at the central, hypothalamic level. The actions of two prime candidate obesogens, tributyltin (TBT) and tetrabromobisphenol A (TBBPA), acting at the central level are the main focus of this review. Having discussed the evidence for contaminant accumulation in the environment and in human tissues and the potential mechanisms of action, data are provided showing that these two widespread pollutants modify hypothalamic gene regulations. Our studies are based on maternal exposure and measurement of effects in the progeny, mainly based on in vivo gene reporter assays. Such models are obviously pertinent to testing current hypotheses that propose that early exposure might exert effects on later development and physiological functions. The potential molecular mechanisms involved are discussed, as are the broader physiological consequences of these hypothalamic dysregulations.
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Affiliation(s)
- Stéphanie Decherf
- CNRS UMR 7221 «Evolution of Endocrine Regulations», Department Regulations, Development and Molecular Diversity, Muséum National d'Histoire Naturelle, Paris, France.
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Heimeier RA, Shi YB. Amphibian metamorphosis as a model for studying endocrine disruption on vertebrate development: effect of bisphenol A on thyroid hormone action. Gen Comp Endocrinol 2010; 168:181-9. [PMID: 20178801 DOI: 10.1016/j.ygcen.2010.02.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 02/17/2010] [Accepted: 02/18/2010] [Indexed: 10/19/2022]
Abstract
Thyroid hormone (TH) is essential for proper development in vertebrates. TH deficiency during gestation and early postnatal development produces severe neurological, skeletal, metabolism and growth abnormalities. It is therefore important to consider environmental chemicals that may interfere with TH signaling. Exposure to environmental contaminants that disrupt TH action may underlie the increasing incidence of human developmental disorders worldwide. One contaminant of concern is the xenoestrogen bisphenol A (BPA), a chemical widely used to manufacture polycarbonate plastics and epoxy resins. The difficulty in studying uterus-enclosed mammalian embryos has hampered the analysis on the direct effects of BPA during vertebrate development. As TH action at the cellular level is highly conserved across vertebrate species, amphibian metamorphosis serves as an important TH-dependent in vivo vertebrate model for studying potential contributions of BPA toward human developmental disorders. Using Xenopus laevis as a model, we and others have demonstrated the inhibitory effects of BPA exposure on metamorphosis. Genome-wide gene expression analysis revealed that surprisingly, BPA primarily targets the TH-signaling pathway essential for metamorphosis in Xenopus laevis. Given the importance of the genomic effects of TH during metamorphosis and the conservation in its regulation in higher vertebrates, these observations suggest that the effect of BPA in human embryogenesis is through the inhibition of the TH pathway and warrants further investigation. Our findings further argue for the critical need to use in vivo animal models coupled with systematic molecular analysis to determine the developmental effects of endocrine disrupting compounds.
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Affiliation(s)
- Rachel A Heimeier
- Institute of Environmental Medicine, Karolinska Institutet, Nobels väg 13, S-171 77 Stockholm, Sweden.
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Helbing CC, Maher SK, Han J, Gunderson MP, Borchers C. Peering into molecular mechanisms of action with frogSCOPE. Gen Comp Endocrinol 2010; 168:190-8. [PMID: 20074577 DOI: 10.1016/j.ygcen.2010.01.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Accepted: 01/08/2010] [Indexed: 12/12/2022]
Abstract
Exposure of critical life stages to harmful chemicals at low, environmentally-relevant concentrations can alter how hormones function, and change metabolic pathways or developmental processes that impact reproduction, behavior, or susceptibility to disease later in life. These alterations can be captured through evaluation of changes to transcriptomes, proteomes, and metabolomes occurring at those critical life stages thereby enabling more effective and earlier identification of mechanism of action, individual susceptibilities and adaptation, and prediction of detrimental sublethal effects. Amphibians are "wet canaries in the coalmine" as indicators for environmental health. There are more than 6000 species living in a variety of ecological niches worldwide yet limited 'omics resources and approaches exist. To provide for a means of addressing this challenge, frogSCOPE (frog Sentinel species Comparative "Omics" for the Environment) combines transcriptomics, proteomics, and metabolomics together to form the foundation for the identification of biological response indicators of harmful effects on a species of wild frog (Rana catesbeiana) at a sensitive tadpole stage. Various exposure and sampling methodologies are possible including standard in vivo exposures, tail fin biopsies, and the C-fin assay. frogSCOPE establishes methodological and analytical approaches applicable to wildlife by using a uniquely-designed frog cDNA array developed to accommodate cross-species hybridization and quantitative real-time polymerase chain reaction (QPCR) assays on poorly genetically-characterized wildlife species. Combination with proteomics (isobaric tags for relative and absolute protein quantitation; iTRAQ) and metabolomics (mass spectrometry) enable the generation of molecular fingerprints to identify mechanisms of action in a more comprehensive fashion to better define suitable indicators of deleterious biological outcomes to wildlife.
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Affiliation(s)
- Caren C Helbing
- Department of Biochemistry & Microbiology, University of Victoria, P.O. Box 3055 Stn CSC, Victoria, BC, Canada.
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Shi H, Qian L, Guo S, Zhang X, Liu J, Cao Q. Teratogenic effects of tetrabromobisphenol A on Xenopus tropicalis embryos. Comp Biochem Physiol C Toxicol Pharmacol 2010; 152:62-8. [PMID: 20188212 DOI: 10.1016/j.cbpc.2010.02.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Revised: 02/21/2010] [Accepted: 02/21/2010] [Indexed: 11/18/2022]
Abstract
Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant and a known thyroid disruptor. We reported exposing Xenopus tropicalis embryos (NF10) to 0.01, 0.1 or 1 mg/L of TBBPA with or without 70 microg/L triiodothyronine (T(3)). Compared with the controls, 1 mg/L of TBBPA significantly reduced the body length of embryos after 24, 36 and 48 h of exposure. Embryos treated with TBBPA showed multiple malformations, including: abnormal eyes, skin hypopigmentation, enlarged proctodaeum, narrow fins and pericardial edemas. The effect of abnormal eyes manifested itself in the loss of pigmentation, reduction in size, or absence of external eyes. The degree of eye malformations was quantified with the index of eye malformations (IEM) with 0 being normal and 3 being severe. In the 1 mg/L TBBPA treatment groups, the incidence of total malformations (ITM) was 68-93%, and IEM was 0.8-0.9. T(3) showed no teratogenic effects on embryos, but it significantly enhanced TBBPA-induced teratogenic effects. In the T(3)+1 mg/L TBBPA treatment groups, ITM was 91-99%, and IEM was 1.8-1.9. Histological observations showed that the retinas were generally smaller, and the lenses were underdeveloped or even absent. These results indicate that TBBPA at relatively high concentration has teratogenic effects on X. tropicalis embryos. The results also suggest that thyroid hormone signaling might be involved in TBBPA induced-teratogenicity.
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Affiliation(s)
- Huahong Shi
- Department of Environmental Science, Key Laboratory of Urbanization and Ecological Restoration, East China Normal University, Shanghai 200062, China.
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78
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Behavioral toxicology in the 21st century: challenges and opportunities for behavioral scientists. Summary of a symposium presented at the annual meeting of the neurobehavioral teratology society, June, 2009. Neurotoxicol Teratol 2010; 32:313-28. [PMID: 20171276 DOI: 10.1016/j.ntt.2010.02.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 01/27/2010] [Accepted: 02/06/2010] [Indexed: 12/26/2022]
Abstract
The National Research Council (NRC) of the National Academies of Science recently published a report of its vision of toxicity testing in the 21st century. The report proposes that the current toxicity testing paradigm that depends upon whole-animal tests be replaced with a strategy based upon in vitro tests, in silico models and evaluations of toxicity at the human population level. These goals are intended to set in motion changes that will transform risk assessment into a process in which adverse effects on public health are predicted by quantitative structure-activity relationship (QSAR) models and data from suites of high-throughput in vitro tests. The potential roles for whole-animal testing in this futuristic vision are both various and undefined. A symposium was convened at the annual meeting of the Neurobehavioral Teratology Society in Rio Grande, Puerto Rico in June, 2009 to discuss the potential challenges and opportunities for behavioral scientists in developing and/or altering this strategy toward the ultimate goal of protecting public health from hazardous chemicals. R. Kavlock described the NRC vision, introduced the concept of the 'toxicity pathway' (a central guiding principle of the NRC vision), and described the current status of an initial implementation this approach with the EPA's ToxCast(R) program. K. Crofton described a pathway based upon disruption of thyroid hormone metabolism during development, including agents, targets, and outcomes linked by this mode of action. P. Bushnell proposed a pathway linking the neural targets and cellular to behavioral effects of acute exposure to organic solvents, whose predictive power is limited by our incomplete understanding of the complex CNS circuitry that mediates the behavioral responses to solvents. B. Weiss cautioned the audience regarding a pathway approach to toxicity testing, using the example of the developmental toxicity of phthalates, whose effects on mammalian sexual differentiation would be difficult to identify based on screening tests in vitro. Finally, D. Rice raised concerns regarding the use of data derived from toxicity screening tests to human health risk assessments. Discussion centered around opportunities and challenges for behavioral toxicologists regarding this impending paradigm shift. Opportunities include: identifying and characterizing toxicity pathways; informing the conditions and limits of extrapolation; addressing issues of susceptibility and variability; providing reality-checks on selected positives and negatives from screens; and performing targeted testing and dose-response assessments of chemicals flagged during screening. Challenges include: predicting behavior using models of complex neurobiological pathways; standardizing study designs and dependent variables to facilitate creation of databases; and managing the cost and efficiency of behavioral assessments. Thus, while progress is being made in approaching the vision of 21st century toxicology, we remain a long way from replacing whole-animal tests; indeed, some animal testing will be essential for the foreseeable future at least. Initial advances will likely provide better prioritization tools so that animal resources are used more efficiently and effectively.
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79
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Fini JB, Pallud-Mothré S, Le Mével S, Palmier K, Havens CM, Le Brun M, Mataix V, Lemkine GF, Demeneix BA, Turque N, Johnson PE. An innovative continuous flow system for monitoring heavy metal pollution in water using transgenic Xenopus laevis tadpoles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:8895-8900. [PMID: 19943663 DOI: 10.1021/es9008954] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
While numerous detection methods exist for environmental heavy metal monitoring, easy-to-use technologies combining rapidity with in vivo measurements are lacking. Multiwell systems exploiting transgenic tadpoles are ideal but require time-consuming placement of individuals in wells. We developed a real-time flow-through system, based on Fountain Flow cytometry, which measures in situ contaminant-induced fluorescence in transgenic amphibian larvae immersed in water samples. The system maintains the advantages of transgenic amphibians, but requires minimal human intervention. Portable and self-contained, it allows on-site measurements. Optimization exploited a transgenic Xenopus laevis bearing a chimeric gene with metal responsive elements fused to eGFP. The transgene was selectively induced by 1 microM Zn(2+). Using this tadpole we show the continuous flow method to be as rapid and sensitive as image analysis. Flow-through readings thus accelerate the overall process of data acquisition and render fluorescent monitoring of tadpoles suitable for on-site tracking of heavy metal pollution.
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Affiliation(s)
- Jean-Baptiste Fini
- UMR CNRS 7221, Evolution des Regulations Endocriniennes, Departement Regulations, Developpement et Diversite Moleculaire, Museum National d'Histoire Naturelle, 75231 Paris, France
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80
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Abstract
PURPOSE OF REVIEW To overview the effects of endocrine disrupters on thyroid function. RECENT FINDINGS Studies in recent years have revealed thyroid-disrupting properties of many environmentally abundant chemicals. Of special concern is the exposure of pregnant women and infants, as thyroid disruption of the developing fetus may have deleterious effects on neurological outcome. Evidence is reviewed for the following groups of chemicals: polychlorinated biphenyls, dioxins, flame retardants, pesticides, perfluorinated chemicals, phthalates, bisphenol A and ultraviolet filters. Chemicals may exert thyroid effects through a variety of mechanisms of action, and some publications have focused on elucidating the mechanisms of specific (groups of) chemicals. SUMMARY A large variety of ubiquitous chemicals have been shown to have thyroid-disrupting properties, and the combination of mechanistic, epidemiological and exposure studies indicates that the ubiquitous human and environmental exposure to industrial chemicals may impose a serious threat to human and wildlife thyroid homeostasis. Currently, available evidence suggests that authorities need to regulate exposure to thyroid-disrupting chemicals of pregnant women, neonates and small children in order to avoid potential impairment of brain development. Future studies will indicate whether adults also are at risk of thyroid damage due to these chemicals.
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Affiliation(s)
- Malene Boas
- University Department of Growth and Reproduction, Rigshospitalet, Copenhagen, Denmark
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81
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Oehlmann J, Schulte-Oehlmann U, Kloas W, Jagnytsch O, Lutz I, Kusk KO, Wollenberger L, Santos EM, Paull GC, Van Look KJW, Tyler CR. A critical analysis of the biological impacts of plasticizers on wildlife. Philos Trans R Soc Lond B Biol Sci 2009; 364:2047-62. [PMID: 19528055 PMCID: PMC2873012 DOI: 10.1098/rstb.2008.0242] [Citation(s) in RCA: 425] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
This review provides a critical analysis of the biological effects of the most widely used plasticizers, including dibutyl phthalate, diethylhexyl phthalate, dimethyl phthalate, butyl benzyl phthalate and bisphenol A (BPA), on wildlife, with a focus on annelids (both aquatic and terrestrial), molluscs, crustaceans, insects, fish and amphibians. Moreover, the paper provides novel data on the biological effects of some of these plasticizers in invertebrates, fish and amphibians. Phthalates and BPA have been shown to affect reproduction in all studied animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations. Molluscs, crustaceans and amphibians appear to be especially sensitive to these compounds, and biological effects are observed at environmentally relevant exposures in the low ng l(-1) to microg l(-1) range. In contrast, most effects in fish (except for disturbance in spermatogenesis) occur at higher concentrations. Most plasticizers appear to act by interfering with the functioning of various hormone systems, but some phthalates have wider pathways of disruption. Effect concentrations of plasticizers in laboratory experiments coincide with measured environmental concentrations, and thus there is a very real potential for effects of these chemicals on some wildlife populations. The most striking gaps in our current knowledge on the impacts of plasticizers on wildlife are the lack of data for long-term exposures to environmentally relevant concentrations and their ecotoxicity when part of complex mixtures. Furthermore, the hazard of plasticizers has been investigated in annelids, molluscs and arthropods only, and given the sensitivity of some invertebrates, effects assessments are warranted in other invertebrate phyla.
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Affiliation(s)
- Jörg Oehlmann
- Department of Aquatic Ecotoxicology, Goethe University Frankfurt am Main, Frankfurt am Main, Germany.
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82
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Bondesson M, Jönsson J, Pongratz I, Olea N, Cravedi JP, Zalko D, Håkansson H, Halldin K, Di Lorenzo D, Behl C, Manthey D, Balaguer P, Demeneix B, Fini JB, Laudet V, Gustafsson JA. A CASCADE of effects of bisphenol A. Reprod Toxicol 2009; 28:563-7. [PMID: 19577634 DOI: 10.1016/j.reprotox.2009.06.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 05/14/2009] [Accepted: 06/25/2009] [Indexed: 11/26/2022]
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83
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Fini JB, Dolo L, Cravedi JP, Demeneix B, Zalko D. Metabolism of the endocrine disruptor BPA by Xenopus laevis tadpoles. Ann N Y Acad Sci 2009; 1163:394-7. [PMID: 19456369 DOI: 10.1111/j.1749-6632.2008.03655.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Metabolism of the plasticizer bisphenol A (BPA), a thyroid function disruptor, was investigated in Xenopus laevis tadpoles. Uptake and biotransformation of [(3)H]-BPA was followed over 72 h at 1 micromol/L and 10 micromol/L +/- triiodothyronine. A rapid decrease of radioactivity in media was observed after [(3)H]-BPA was added. [(3)H]-BPA uptake reached 25% after 24 h then ranged between 6% and 15%. Metabolic profiles of water samples at 24, 48, and 72 h as well as tadpole extracts (at 72 h) were obtained using radio-HPLC. Parent (unmodified) BPA was consistently found in water samples and within tadpoles. Six peaks corresponding to BPA metabolites were detected. Based on retention time comparison with standards isolated from rat and human material, the two main metabolites were identified as BPA-glucuronide and BPA-sulfate. Thus, Xenopus laevis provides a useful model for studying BPA effects in vertebrates, as the main BPA metabolites are similar to those produced in mammals.
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Affiliation(s)
- Jean-Baptiste Fini
- UMR CNRS 5166, Evolution des Régulations Endocriniennes, Dept. Regulations, Development and Molecular Diversity, Muséum National d'Histoire Naturelle, Paris, France
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84
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Heimeier RA, Das B, Buchholz DR, Shi YB. The xenoestrogen bisphenol A inhibits postembryonic vertebrate development by antagonizing gene regulation by thyroid hormone. Endocrinology 2009; 150:2964-73. [PMID: 19228888 PMCID: PMC2689811 DOI: 10.1210/en.2008-1503] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bisphenol A (BPA), a chemical widely used to manufacture plastics, is estrogenic and capable of disrupting sex differentiation. However, recent in vitro studies have shown that BPA can also antagonize T(3) activation of the T(3) receptor. The difficulty in studying uterus-enclosed mammalian embryos has hampered the analysis on the direct effects of BPA during vertebrate development. This study proposed to identify critical T(3) pathways that may be disrupted by BPA based on molecular analysis in vivo. Because amphibian metamorphosis requires T(3) and encompasses the postembryonic period in mammals when T(3) action is most critical, we used this unique model for studying the effect of BPA on T(3)-dependent vertebrate development at both the morphological and molecular levels. After 4 d of exposure, BPA inhibited T(3)-induced intestinal remodeling in premetamorphic Xenopus laevis tadpoles. Importantly, microarray analysis revealed that BPA antagonized the regulation of most T(3)-response genes, thereby explaining the inhibitory effect of BPA on metamorphosis. Surprisingly, most of the genes affected by BPA in the presence of T(3) were T(3)-response genes, suggesting that BPA predominantly affected T(3)-signaling pathways during metamorphosis. Our finding that this endocrine disruptor, well known for its estrogenic activity in vitro, functions to inhibit T(3) pathways to affect vertebrate development in vivo and thus not only provides a mechanism for the likely deleterious effects of BPA on human development but also demonstrates the importance of studying endocrine disruption in a developmental context in vivo.
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Affiliation(s)
- Rachel A Heimeier
- Section on Molecular Morphogenesis, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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85
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Hofmann PJ, Schomburg L, Köhrle J. Interference of Endocrine Disrupters with Thyroid Hormone Receptor–Dependent Transactivation. Toxicol Sci 2009; 110:125-37. [DOI: 10.1093/toxsci/kfp086] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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86
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Rüegg J, Penttinen-Damdimopoulou P, Mäkelä S, Pongratz I, Gustafsson JA. Receptors mediating toxicity and their involvement in endocrine disruption. EXS 2009; 99:289-323. [PMID: 19157066 DOI: 10.1007/978-3-7643-8336-7_11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Many toxic compounds exert their harmful effects by activating of certain receptors, which in turn leads to dysregulation of transcription. Some of these receptors are so called xenosensors. They are activated by external chemicals and evoke a cascade of events that lead to the elimination of the chemical from the system. Other receptors that are modulated by toxic substances are hormone receptors, particularly the ones of the nuclear receptor family. Some environmental chemicals resemble endogenous hormones and can falsely activate these receptors, leading to undesired activity in the cell. Furthermore, excessive activation of the xenosensors can lead to disturbances of the integrity of the system as well. In this chapter, the concepts of receptor-mediated toxicity and hormone disruption are introduced. We start by describing environmental chemicals that can bind to xenosensors and nuclear hormone receptors. We then describe the receptors most commonly targeted by environmental chemicals. Finally, the mechanisms by which receptor-mediated events can disrupt the system are depicted.
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Affiliation(s)
- Joëlle Rüegg
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
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87
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Legler J. New insights into the endocrine disrupting effects of brominated flame retardants. CHEMOSPHERE 2008; 73:216-22. [PMID: 18667224 DOI: 10.1016/j.chemosphere.2008.04.081] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 04/27/2008] [Accepted: 04/28/2008] [Indexed: 05/24/2023]
Abstract
The objective of this review is to provide an overview of recent studies demonstrating the endocrine disrupting (ED) effects of brominated flame retardants (BFRs), while highlighting interesting data presented at the recent international BFR workshop in Amsterdam in April, 2007. A review written in 2002 was used as a starting point and about 60 publications published since 2003 were reviewed. New insights into the in vivo effects of BFRs on thyroid hormone, estrogen and androgen pathways in both mammalian and non-mammalian models are provided, and novel (in vitro) findings on the mechanisms underlying ED effects are highlighted. Special attention is also given to reports on neurotoxicological effects at relatively low doses of BFRs, although an endocrine-related mechanism is disputable. Convincing evidence has been published showing that BFRs and importantly, BFR metabolites, have the potential to disrupt endocrine systems at multiple target sites. While some studies suggest a wide margin of safety between effect concentrations in rodent models and levels encountered in humans and the environment, other studies demonstrate that exposure to low doses relevant for humans and wildlife at critical time points in development can result in profound effects on both endocrine pathways and (neuro)development.
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Affiliation(s)
- Juliette Legler
- Institute for Environmental Studies, VU University Amsterdam, De Boelelaan 1087, Amsterdam, The Netherlands.
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88
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Abstract
Brominated flame retardants (BFR) are endocrine disrupters in experimental systems, both in vitro and in vivo. Although BFR effects on thyroid hormones are well confirmed, studies of effects on oestrogen/androgen systems are fewer but today growing in numbers. The effects of BFR on other hormone systems are still unknown. Hormonal effect levels in animals start from ca 1 mg/kg b.w., but there are exceptions: effects on spermatogenesis, suggesting hormonal causes, have been observed at a low dose (60 microg/kg b.w.) of a polybrominated diphenyl ether (PBDE) congener, BDE-99. It could be concluded that hormonal effects are of importance in risk assessment, and in some cases where effects are seen at low levels safety margins may be insufficient. One additional uncertainty is the lack of reliable human data that could be used to support animal BFR observations. In spite of the recent regulation of PBDE production, levels of both PBDE and of other BFR groups are still present in environmental samples. Thus, we have to deal with the possible effects of human BFR exposure for times to come. In order to reduce BFR exposure, the routes of exposure should be carefully examined and ways to reduce levels in major exposure routes considered.
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89
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Köhrle J. Environment and endocrinology: The case of thyroidology. ANNALES D'ENDOCRINOLOGIE 2008; 69:116-22. [DOI: 10.1016/j.ando.2008.02.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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