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Vandenberg LN. Endocrine disrupting chemicals: strategies to protect present and future generations. Expert Rev Endocrinol Metab 2021; 16:135-146. [PMID: 33973826 DOI: 10.1080/17446651.2021.1917991] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 04/12/2021] [Indexed: 12/22/2022]
Abstract
Introduction: Endocrine-disrupting chemicals (EDCs) are chemicals that alter the actions of hormones. In the 21st Century, numerous expert groups of clinicians, scientists, and environmental activists have called for action to protect present and future generations from the harm induced by EDC exposures. These demands for regulatory responses come because of the strong weight of the evidence from epidemiology, wildlife, and controlled laboratory studies.Areas covered: In this review, we examine the conclusions drawn by experts from different scientific and medical disciplines. We also address several areas where recent findings or work has changed the landscape of EDC work including new approaches to identify and evaluate the evidence for EDCs using a key characteristics approach, the need to expand our understanding of vulnerable periods of development, and the increasing concern that traditional methods used to evaluate toxicity of environmental chemicals are insufficient for EDCs and how collaborative science could help to address these gaps.Expert opinion: The science is clear: there is more than enough evidence to demonstrate that EDCs affect the health of humans and wildlife. Waiting to act is a decision that puts the health of current and future generations at risk.
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Affiliation(s)
- Laura N Vandenberg
- School of Public Health & Health Sciences, Department of Environmental Health Sciences, University of Massachusetts, Amherst, MA USA
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Vandenberg LN, Najmi A, Mogus JP. Agrochemicals with estrogenic endocrine disrupting properties: Lessons Learned? Mol Cell Endocrinol 2020; 518:110860. [PMID: 32407980 PMCID: PMC9448509 DOI: 10.1016/j.mce.2020.110860] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 04/16/2020] [Accepted: 05/04/2020] [Indexed: 02/07/2023]
Abstract
Many agrochemicals have endocrine disrupting properties. A subset of these chemicals is characterized as "estrogenic". In this review, we describe several distinct ways that chemicals used in crop production can affect estrogen signaling. Using three agrochemicals as examples (DDT, endosulfan, and atrazine), we illustrate how screening tests such as the US EPA's EDSP Tier 1 assays can be used as a first-pass approach to evaluate agrochemicals for endocrine activity. We then apply the "Key Characteristics" approach to illustrate how chemicals like DDT can be evaluated, together with the World Health Organization's definition of an endocrine disruptor, to identify data gaps. We conclude by describing important issues that must be addressed in the evaluation and regulation of hormonally active agrochemicals including mixture effects, efforts to reduce vertebrate animal use, chemical prioritization, and improvements in hazard, exposure, and risk assessments.
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Affiliation(s)
- Laura N Vandenberg
- Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst, USA.
| | - Aimal Najmi
- Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst, USA
| | - Joshua P Mogus
- Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst, USA
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Rehberger K, Baumann L, Hecker M, Braunbeck T. Intrafollicular thyroid hormone staining in whole-mount zebrafish (Danio rerio) embryos for the detection of thyroid hormone synthesis disruption. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:997-1010. [PMID: 29568982 DOI: 10.1007/s10695-018-0488-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 02/26/2018] [Indexed: 06/08/2023]
Abstract
Endocrine-disrupting chemicals are known to impact multiple hormonal axes of vertebrates, among which the thyroid system is crucial for multiple developmental and physiological processes. Thus, the present study focused on the semi-quantitative visualization of intrafollicular triiodothyronine (T3) and thyroxin (T4) in zebrafish embryos as a potential test system for the detection of disrupted thyroid hormone synthesis. To this end, an antibody-based fluorescence double-staining protocol for whole-mount zebrafish embryos and larvae was adapted to simultaneously detect intrafollicular T3 and T4. During normal development until 10 days post-fertilization (dpf), the number of thyroid follicles increased along the ventral aorta. Concentrations of T4 and T3, measured by fluorescence intensity, increased until 6 dpf, but decreased thereafter. Exposure of zebrafish embryos to propylthiouracil (PTU), a known inhibitor of TH synthesis, resulted in a significant decrease in the number of follicles that stained for T3, whereas a trend for increase in follicles that stained for T4 was observed. In contrast, fluorescence intensity for both thyroid hormones decreased significantly after exposure to PTU. Overall, the zebrafish embryo appears to be suitable for the simultaneous visualization and detection of changing intrafollicular TH contents during normal development and after PTU treatment.
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Affiliation(s)
- Kristina Rehberger
- Centre for Organismal Studies, Aquatic Ecology and Toxicology, University of Heidelberg, Im Neuenheimer Feld 504, 69120, Heidelberg, Germany
- Vetsuisse Faculty, Centre for Fish and Wildlife Health, University of Bern, Länggassstrasse122, 3012, Bern, Switzerland
| | - Lisa Baumann
- Centre for Organismal Studies, Aquatic Ecology and Toxicology, University of Heidelberg, Im Neuenheimer Feld 504, 69120, Heidelberg, Germany.
| | - Markus Hecker
- School of the Environment & Sustainability and Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, SK, S7N 5B3, Canada
| | - Thomas Braunbeck
- Centre for Organismal Studies, Aquatic Ecology and Toxicology, University of Heidelberg, Im Neuenheimer Feld 504, 69120, Heidelberg, Germany.
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Popova EV, Tinkov AA, Ajsuvakova OP, Skalnaya MG, Skalny AV. Boron – A potential goiterogen? Med Hypotheses 2017; 104:63-67. [DOI: 10.1016/j.mehy.2017.05.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 05/12/2017] [Accepted: 05/25/2017] [Indexed: 01/19/2023]
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Comparative analysis of goitrogenic effects of phenylthiourea and methimazole in zebrafish embryos. Reprod Toxicol 2015; 57:10-20. [DOI: 10.1016/j.reprotox.2015.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 04/19/2015] [Accepted: 04/29/2015] [Indexed: 11/24/2022]
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Scientific Opinion on the risks to public health related to the presence of perchlorate in food, in particular fruits and vegetables. EFSA J 2014. [DOI: 10.2903/j.efsa.2014.3869] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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Zhang J, Hisada A, Yoshinaga J, Shiraishi H, Shimodaira K, Okai T, Noda Y, Shirakawa M, Kato N. Exposure to pyrethroids insecticides and serum levels of thyroid-related measures in pregnant women. ENVIRONMENTAL RESEARCH 2013; 127:16-21. [PMID: 24210131 DOI: 10.1016/j.envres.2013.10.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/29/2013] [Accepted: 10/03/2013] [Indexed: 06/02/2023]
Abstract
Possible association between environmental exposure to pyrethroid insecticides and serum thyroid-related measures was explored in 231 pregnant women of 10-12 gestational weeks recruited at a university hospital in Tokyo during 2009-2011. Serum levels of free thyroxine (fT4), thyroid stimulating hormone (TSH) and thyroid biding globulin (TBG) and urinary pyrethroid insecticide metabolite (3-phenoxybenzoic acid, 3-PBA) were measured. Obstetrical information was obtained from medical records and dietary and lifestyle information was collected by self-administered questionnaire. Geometric mean concentration of creatinine-adjusted urinary 3-PBA was 0.363 (geometric standard deviation: 3.06) μg/g cre, which was consistent with the previously reported levels for non-exposed Japanese adult females. The range of serum fT4, TSH and TBG level was 0.83-3.41 ng/dL, 0.01-27.4 μIU/mL and 16.4-54.4 μg/mL, respectively. Multiple regression analysis was carried out by using either one of serum levels of thyroid-related measures as a dependent variable and urinary 3-PBA as well as other potential covariates (age, pre-pregnancy BMI, parity, urinary iodine, smoking and drinking status) as independent variables: 3-PBA was not found as a significant predictor of serum level of thyroid-related measures. Lack of association may be due to lower pyrethroid insecticide exposure level of the present subjects. Taking the ability of pyrethroid insecticides and their metabolite to bind to nuclear thyroid hormone (TH) receptor, as well as their ability of placental transfer, into consideration, it is warranted to investigate if pyrethroid pesticides do not have any effect on TH actions in fetus brain even though maternal circulating TH level is not affected.
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Affiliation(s)
- Jie Zhang
- Department of Environmental Studies, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan
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Bisphenol A interferes with thyroid specific gene expression. Toxicology 2013; 304:21-31. [DOI: 10.1016/j.tox.2012.12.001] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 11/30/2012] [Accepted: 12/01/2012] [Indexed: 11/21/2022]
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Oka T, Mitsui-Watanabe N, Tatarazako N, Onishi Y, Katsu Y, Miyagawa S, Ogino Y, Yatsu R, Kohno S, Takase M, Kawashima Y, Ohta Y, Aoki Y, Guillette LJ, Iguchi T. Establishment of transactivation assay systems using fish, amphibian, reptilian and human thyroid hormone receptors. J Appl Toxicol 2012; 33:991-1000. [DOI: 10.1002/jat.2825] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 08/24/2012] [Accepted: 08/24/2012] [Indexed: 11/09/2022]
Affiliation(s)
- Tomohiro Oka
- Integrated Environmental Risk Research Section, Research Center for Environmental Risk; National Institute for Environmental Studies; 16-2 Onogawa; Tsukuba; Ibaraki; 305-8506; Japan
| | - Naoko Mitsui-Watanabe
- Environmental Risk Research Center, Institute of Environmental Ecology; IDEA Consultants, Inc.; 1334-5 Riemon; Yaizu; Shizuoka; 421-0212; Japan
| | - Norihisa Tatarazako
- Integrated Environmental Risk Research Section, Research Center for Environmental Risk; National Institute for Environmental Studies; 16-2 Onogawa; Tsukuba; Ibaraki; 305-8506; Japan
| | - Yuta Onishi
- Environmental Risk Research Center, Institute of Environmental Ecology; IDEA Consultants, Inc.; 1334-5 Riemon; Yaizu; Shizuoka; 421-0212; Japan
| | | | - Shinichi Miyagawa
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences; The Graduate University for Advanced Studies; 5-1 Higashiyama, Myodaiji; Okazaki; Aichi; 444-8787; Japan
| | - Yukiko Ogino
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences; The Graduate University for Advanced Studies; 5-1 Higashiyama, Myodaiji; Okazaki; Aichi; 444-8787; Japan
| | - Ryohei Yatsu
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences; The Graduate University for Advanced Studies; 5-1 Higashiyama, Myodaiji; Okazaki; Aichi; 444-8787; Japan
| | - Satomi Kohno
- Department of Obstetrics and Gynecology & Marine Biomedicine and Environmental Science Center; Medical University of South Carolina and Hollings Marine Laboratory; 221 Ft. Johnson Rd.; Charleston; SC; 29412; USA
| | - Minoru Takase
- Institute for Amphibian Biology, Graduate School of Science; Hiroshima University; 1-3-1 Higashi-Hiroshima; Hiroshima; 739-8526; Japan
| | - Yukio Kawashima
- Japan NUS Co. Ltd.; 7-5-25 Nishi-Shinjyuku, Shinjyuku-ku; Tokyo; 160-0023; Japan
| | - Yasuhiko Ohta
- Department of Veterinary Medicine, Faculty of Agriculture; Tottori University; Koyama, Tottori; Tottori; 680-8553; Japan
| | - Yasunobu Aoki
- Integrated Environmental Risk Research Section, Research Center for Environmental Risk; National Institute for Environmental Studies; 16-2 Onogawa; Tsukuba; Ibaraki; 305-8506; Japan
| | - Louis J. Guillette
- Department of Obstetrics and Gynecology & Marine Biomedicine and Environmental Science Center; Medical University of South Carolina and Hollings Marine Laboratory; 221 Ft. Johnson Rd.; Charleston; SC; 29412; USA
| | - Taisen Iguchi
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences; The Graduate University for Advanced Studies; 5-1 Higashiyama, Myodaiji; Okazaki; Aichi; 444-8787; Japan
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Raldúa D, Thienpont B, Babin PJ. Zebrafish eleutheroembryos as an alternative system for screening chemicals disrupting the mammalian thyroid gland morphogenesis and function. Reprod Toxicol 2012; 33:188-97. [DOI: 10.1016/j.reprotox.2011.09.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Revised: 08/16/2011] [Accepted: 09/08/2011] [Indexed: 01/09/2023]
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Andra SS, Makris KC. Thyroid disrupting chemicals in plastic additives and thyroid health. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, ENVIRONMENTAL CARCINOGENESIS & ECOTOXICOLOGY REVIEWS 2012; 30:107-151. [PMID: 22690712 DOI: 10.1080/10590501.2012.681487] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The globally escalating thyroid nodule incidence rates may be only partially ascribed to better diagnostics, allowing for the assessment of environmental risk factors on thyroid disease. Endocrine disruptors or thyroid-disrupting chemicals (TDC) like bisphenol A, phthalates, and polybrominated diphenyl ethers are widely used as plastic additives in consumer products. This comprehensive review studied the magnitude and uncertainty of TDC exposures and their effects on thyroid hormones for sensitive subpopulation groups like pregnant women, infants, and children. Our findings qualitatively suggest the mixed, significant (α = 0.05) TDC associations with natural thyroid hormones (positive or negative sign). Future studies should undertake systematic meta-analyses to elucidate pooled TDC effect estimates on thyroid health indicators and outcomes.
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Affiliation(s)
- Syam S Andra
- Water and Health Laboratory, Cyprus International Institute for Environmental and Public Health in association with Harvard School of Public Health, Cyprus University of Technology, Limassol, Cyprus
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Thienpont B, Tingaud-Sequeira A, Prats E, Barata C, Babin PJ, Raldúa D. Zebrafish eleutheroembryos provide a suitable vertebrate model for screening chemicals that impair thyroid hormone synthesis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:7525-7532. [PMID: 21800831 DOI: 10.1021/es202248h] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Thyroxine-immunofluorescence quantitative disruption test (TIQDT) was designed to provide a simple, rapid, alternative bioassay for assessing the potential of chemical pollutants and drugs to disrupt thyroid gland function. This study demonstrated that zebrafish eleutheroembryos provided a suitable vertebrate model, not only for screening the potential thyroid disrupting effect of molecules, but also for estimating the potential hazards associated with exposure to chemicals directly impairing thyroxine (T4) synthesis. Amitrole, potassium perchlorate, potassium thiocyanate, methimazole (MMI), phloroglucinol, 6-propyl-2-thiouracil, ethylenethiourea, benzophenone-2, resorcinol, pyrazole, sulfamethoxazole, sodium bromide, mancozeb, and genistein were classified as thyroid gland function disruptors. Concordance between TIQDT on zebrafish and mammalian published data was very high and the physiological relevance of T4-intrafollicular content was clearly higher than regulation at the transcriptional level of tg or slc5a5. Moreover, concentration-response analysis provided information about the thyroid disrupting potency and hazard of selected positive compounds. Finally, the effect of perchlorate, but not MMI, was completely rescued by low-micromolar amounts of iodide. TIQDT performed on zebrafish eleutheroembryos is an alternative whole-organism screening assay that provides relevant information for environmental and human risk assessments.
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Affiliation(s)
- Benedicte Thienpont
- Institute of Environmental Assessment and Water Research, IDÆA-CSIC, Jordi Girona 18, 08034 Barcelona, Spain
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Schmidt F, Braunbeck T. Alterations along the Hypothalamic-Pituitary-Thyroid Axis of the Zebrafish (Danio rerio) after Exposure to Propylthiouracil. J Thyroid Res 2011; 2011:376243. [PMID: 21860775 PMCID: PMC3153923 DOI: 10.4061/2011/376243] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 04/17/2011] [Accepted: 05/11/2011] [Indexed: 11/29/2022] Open
Abstract
In the past, various approaches have been developed to detect adverse effects of pollutants on the thyroid of vertebrates, most of these with special emphasis on the South African clawed frog, Xenopus laevis. Although fish are primarily affected by thyroid-disrupting chemicals, studies into alterations of the thyroid of fish are scarce. Therefore, effects of the reference compound propylthiouracil on histopathology of the thyroid axis were analyzed in a modified early life-stage test with zebrafish (Danio rerio) exposed to propylthiouracil. The test substance induced dose-dependent alterations of thyroidal tissue concomitant with increases in the number of surrounding blood vessels. Despite this massive proliferation of the thyroid, zebrafish were not able to maintain thyroxin concentrations. The pituitary was affected displaying significant alterations in thyroid-stimulating hormone cell counts. Quantitative evaluation of pituitary surface areas revealed a dose-dependent increase of adenohypophyseal tissue. Distinct histopathological effects may contribute to a more easy identification and interpretation of alterations induced by thyroid-disrupting chemicals.
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Affiliation(s)
- Florian Schmidt
- Aquatic Ecology and Toxicology Group, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
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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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Zewdie T, Smith CM, Hutcheson M, West CR. Basis of the Massachusetts reference dose and drinking water standard for perchlorate. ENVIRONMENTAL HEALTH PERSPECTIVES 2010; 118:42-48. [PMID: 20056583 PMCID: PMC2831965 DOI: 10.1289/ehp.0900635] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 01/30/2009] [Accepted: 07/13/2009] [Indexed: 05/28/2023]
Abstract
OBJECTIVE Perchlorate inhibits the uptake of iodide in the thyroid. Iodide is required to synthesize hormones critical to fetal and neonatal development. Many water supplies and foods are contaminated with perchlorate. Exposure standards are needed but controversial. Here we summarize the basis of the Massachusetts (MA) perchlorate reference dose (RfD) and drinking water standard (DWS), which are considerably lower and more health protective than related values derived by several other agencies. We also review information regarding perchlorate risk assessment and policy. DATA SOURCES MA Department of Environmental Protection (DEP) scientists, with input from a science advisory committee, assessed a wide range of perchlorate risk and exposure information. Health outcomes associated with iodine insufficiency were considered, as were data on perchlorate in drinking water disinfectants. DATA SYNTHESIS We used a weight-of-the-evidence approach to evaluate perchlorate risks, paying particular attention to sensitive life stages. A health protective RfD (0.07 microg/kg/day) was derived using an uncertainty factor approach with perchlorate-induced iodide uptake inhibition as the point of departure. The MA DWS (2 microg/L) was based on risk management decisions weighing information on perchlorate health risks and its presence in certain disinfectant solutions used to treat drinking water for pathogens. CONCLUSIONS Current data indicate that perchlorate exposures attributable to drinking water in individuals at sensitive life stages should be minimized and support the MA DEP perchlorate RfD and DWS. Widespread exposure to perchlorate and other thyroid toxicants in drinking water and foods suggests that more comprehensive policies to reduce overall exposures and enhance iodine nutrition are needed.
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Affiliation(s)
| | - C. Mark Smith
- Address correspondence to C.M. Smith, Massachusetts Department of Environmental Protection, Office of Research and Standards, 1 Winter St., Boston, MA 02108 USA. Telephone: (617) 292-5509. Fax: (617) 556-1006. E-mail:
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Salay E, Garabrant D. Polychlorinated biphenyls and thyroid hormones in adults: a systematic review appraisal of epidemiological studies. CHEMOSPHERE 2009; 74:1413-9. [PMID: 19108870 DOI: 10.1016/j.chemosphere.2008.11.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2008] [Revised: 10/27/2008] [Accepted: 11/17/2008] [Indexed: 05/04/2023]
Abstract
Reported evidence regarding relationships between polychlorinated biphenyls (PCBs) and thyroid homeostasis in adults has been considered contradictory. The objective of this systematic review is to determine a possible association between PCB exposure and the circulating thyroid hormones and thyrotropin (TSH) levels in adults, by analyzing the quality of published studies. A systematic review of epidemiological papers was conducted using PubMed. An evaluation of the quality of 22 studies was performed, and the papers were classified into two tiers: Tier I for studies with higher quality scores (eight) and Tier II for studies with lower quality scores (14). It appears that PCBs can interfere with thyroid hormone homeostasis; however epidemiological evidence is not entirely clear. For triiodothyronine (T3) and thyroxine (T4), Tier I studies showed either an inverse (four cases for T3; five cases for T4) or no significant association (two cases for T3; five cases for T4) with PCBs. In the case of free thyroxine and TSH, the Tier I papers observed no clear association with PCB levels. Rigorous study design, assessment of potential confounding factors, and fuller reporting of methods and results in future studies will facilitate understanding of whether PCB exposure is associated with changes in thyroid function.
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Affiliation(s)
- Elisabete Salay
- Department of Food and Nutrition, University of Campinas, CP 6121, Campinas, SP, CEP 13083-862, Brazil.
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Zoeller RT, Crofton KM. Mode of Action: Developmental Thyroid Hormone Insufficiency—Neurological Abnormalities Resulting From Exposure to Propylthiouracil. Crit Rev Toxicol 2008; 35:771-81. [PMID: 16417044 DOI: 10.1080/10408440591007313] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Because thyroid hormone is essential for normal brain development before and after birth, environmental chemicals that interfere with thyroid hormone signaling can adversely affect brain development. Adverse consequences of thyroid hormone insufficiency depend both on severity and developmental timing, indicating that environmental antithyroid factors may produce different effects at different developmental windows of exposure. Mechanistic studies can provide important insight into the potential impact of chemicals on human thyroid function, but relevance to humans must be systematically evaluated. This kind of analysis depends on data sets that include information about animals and humans. The drug 6-n-propyl-2-thiouracil (PTU) is used in animals to experimentally manipulate serum thyroid hormone levels, and in humans to treat patients, including pregnant women, with Graves' disease. A systematic analysis of the mode of action (MOA) of PTU in rats and in humans discloses similar modes of action. While the analysis predicts that PTU doses that produce thyroid hormone insufficiency in humans would adversely affect the developing brain, careful monitoring of PTU administration in pregnant and lactating humans keeps infant serum thyroid hormone levels within the normal range.
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Affiliation(s)
- R Thomas Zoeller
- University of Massachusetts-Amherst, Department of Biology, Morrill Science Center, 01003, USA.
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Patel A, Zuo G, Lehman SG, Badruzzaman M, Clifford DA, Roberts DJ. Fluidized bed reactor for the biological treatment of ion-exchange brine containing perchlorate and nitrate. WATER RESEARCH 2008; 42:4291-4298. [PMID: 18718630 DOI: 10.1016/j.watres.2008.07.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 07/07/2008] [Accepted: 07/10/2008] [Indexed: 05/26/2023]
Abstract
The removal of perchlorate and nitrate from contaminated drinking water using regenerable ion-exchange processes produces a high salt brine (3-10% NaCl) laden with high concentrations of perchlorate and nitrate. This bench-scale research describes the operation of acetate-fed granular activated carbon (GAC) based fluidized bed reactors (FBR) for perchlorate-only, and combined nitrate and perchlorate removal from synthetic brine (6% NaCl). The GAC was inoculated with a salt-tolerant culture developed by the authors and used previously in batch systems. An FBR was an effective design for perchlorate reduction and exhibited first-order degradation kinetics with respect to perchlorate concentrations. Nitrate was also removed by the organisms in the column and had no negative effects on the removal of perchlorate using the FBR design. However, at higher concentrations of nitrate the FBR was more difficult to operate due to loss of carbon and biomass from the formation of nitrogen bubbles and the high recycle flow rates needed.
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Affiliation(s)
- A Patel
- Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204-4003, United States
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20
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Phillips KP, Foster WG. Key developments in endocrine disrupter research and human health. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2008; 11:322-344. [PMID: 18368559 DOI: 10.1080/10937400701876194] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Environmental etiologies involving exposures to chemicals that mimic endogenous hormones are proposed for a number of adverse human health effects, including infertility, abnormal prenatal and childhood development, and reproductive cancers (National Research Council, 1999; World Health Organization, 2002). Endocrine disrupters represent a significant area of environmental research with important implications for human health. This article provides an overview of some of the key developments in this field that may enhance our ability to assess the human health risks posed by exposure to endocrine disrupters. Advances in methodologies of hazard identification (toxicogenomics, transcriptomics, proteomics, metabolomics, bioinformatics) are discussed, as well as epigenetics and emerging biological endpoints.
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Affiliation(s)
- Karen P Phillips
- Faculty of Health Sciences, University of Ottawa, Ottawa, ON, Canada.
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Mori K, Yoshida K, Hoshikawa S, Ito S, Yoshida M, Satoh M, Watanabe C. Effects of perinatal exposure to low doses of cadmium or methylmercury on thyroid hormone metabolism in metallothionein-deficient mouse neonates. Toxicology 2006; 228:77-84. [PMID: 16982123 DOI: 10.1016/j.tox.2006.08.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 08/15/2006] [Accepted: 08/16/2006] [Indexed: 10/24/2022]
Abstract
Perinatal exposure to cadmium (Cd) or methylmercury (MeHg) results in impaired neurodevelopment. Thyroid hormone is essential for normal brain development. However, the issue whether Cd or MeHg, especially at low doses, interrupts thyroid hormone action remains to be investigated. In the present study, effects of perinatal exposure to low levels of Cd or MeHg on thyroid hormone metabolism were examined using metallothionein I and II (MT-I/II) null or wild-type neonatal mice. Dams were exposed to 10 mg/L water of Cd or 5 mg/kg chow of MeHg from gestational day 0 to post-natal day 10 (PND 10). Sera, livers and brains were collected from neonates on PND 10. Iodothyronine deiodinase activities and serum thyroxine (T4) concentrations were measured. MeHg exposure failed to induce changes in serum T4 levels and liver type 1 deiodinase (D1) and brain type 2 deiodinase (D2) activities regardless of the MT genotype. However, exposure to MeHg resulted in a decrease in brain type 3 deiodinase (D3) activity in MT-I/II null and wild-type neonates. In contrast, exposure to Cd resulted in a decrease in serum T4 levels in MT-I/II null neonates. Consistently, brain D2 activity was increased in Cd-exposed MT-I/II null neonates. No significant changes in liver D1 and brain D3 activities were induced by Cd administration. Our study demonstrates that perinatal exposure to low doses of Cd or MeHg can induce changes in brain deiodinase activities in the neonates, suggesting that thyroid hormone metabolism in fetuses and neonates might be a potential target of Cd and MeHg.
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Affiliation(s)
- Kouki Mori
- Division of Nephrology, Endocrinology and Vascular Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-Machi, Sendai, Japan.
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22
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Mitsui N, Fujii T, Miyahara M, Oka T, Kashiwagi A, Kashiwagi K, Hanada H, Urushitani H, Santo N, Tooi O, Iguchi T. Development of metamorphosis assay using Silurana tropicalis for the detection of thyroid system-disrupting chemicals. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2006; 64:281-7. [PMID: 16139362 DOI: 10.1016/j.ecoenv.2005.07.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 05/15/2005] [Accepted: 07/05/2005] [Indexed: 05/04/2023]
Abstract
The West African clawed frog (Silurana tropicalis), which resembles the South African clawed frog (Xenopus laevis), but is somewhat smaller, has a diploid genome and a shorter generation time. Therefore, S. tropicalis has the potential for use as a new model in ecotoxicology. We demonstrated a S. tropicalis metamorphosis assay based on Xenopus Metamorphosis Assay (XEMA) using 1 microg/L thyroxine (T4) and 75 mg/L propylthiouracil (PTU). Tadpoles at developmental stages 48-50 were exposed to chemicals for 28 days and total body length, developmental stage, and hind limb length were recorded every 7 days. Significant differences in developmental stage and total body length were found for both T4 and PTU after 7-day exposure, which were similar to the results of the XEMA ring-test using the same chemicals. Moreover, in the present study, we measured hind limb length as a new endpoint of thyroid axis. Significant differences in the hind limb length were encountered in both T4 and PTU treatments after 7 days of exposure. These results suggest that S. tropicalis can be used in a XEMA-like protocol to detect agonist and antagonist effects of chemicals on the thyroid system. Hind limb length is also a suitable endpoint in such protocols. A new test protocol detecting both thyroid disruption and reproductive effects of chemicals using S. tropicalis should be established in the near future.
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Affiliation(s)
- Naoko Mitsui
- Biotechnology Research Laboratory, Towa Kagaku Co., Ltd., 3-13-26 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
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23
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Iguchi T, Watanabe H, Katsu Y. Application of ecotoxicogenomics for studying endocrine disruption in vertebrates and invertebrates. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114 Suppl 1:101-5. [PMID: 16818254 PMCID: PMC1874166 DOI: 10.1289/ehp.8061] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Chemicals released into the environment potentially disrupt the endocrine system in wild animals and humans. Developing organisms are particularly sensitive to estrogenic chemicals. Exposure to estrogens or estrogenic chemicals during critical periods of development induces persistent changes in both reproductive and nonreproductive organs, including persistent molecular alterations. Estrogen-responsive genes and critical developmental windows of various animal species, therefore, need to be identified for investigators to understand the molecular basis of estrogenic activity during embryonic development. For investigators to understand molecular mechanisms of toxicity in various species, toxicogenomics/ecotoxicogenomics, defined as the integration of genomics (transcriptomics, proteomics, metabolomics) into toxicology and ecotoxicology, need to be established as powerful tools for research. As the initial step toward using genomics to examine endocrine-disrupting chemicals, estrogen receptors and other steroid hormone receptors have been cloned in various species, including reptiles, amphibians, and fish, and alterations in the expression of these genes in response to chemicals were investigated. We are identifying estrogen-responsive genes in mouse reproductive tracts using cDNA microarrays and trying to establish microarray systems in the American alligator, roach, medaka, and water fleas (Daphnia magna). It is too early to define common estrogen-responsive genes in various animal species; however, toxicogenomics and ectotoxicogenomics provide powerful tools to help us understand the molecular mechanism of chemical toxicities in various animal species.
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Affiliation(s)
- Taisen Iguchi
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Myodaiji, Okazaki, Japan.
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Park JW, Rinchard J, Liu F, Anderson TA, Kendall RJ, Theodorakis CW. The thyroid endocrine disruptor perchlorate affects reproduction, growth, and survival of mosquitofish. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2006; 63:343-52. [PMID: 16507371 DOI: 10.1016/j.ecoenv.2005.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Revised: 04/04/2005] [Accepted: 04/05/2005] [Indexed: 05/06/2023]
Abstract
The perchlorate anion--an oxidizer found in rockets, missiles, some ammunition, flares, airbags, and fireworks--occurs as a contaminant in ground and surface water in many parts of the United States. Its toxic effects include inhibition of thyroid hormone synthesis. To investigate its chronic toxicity, mosquitofish (Gambusia holbrooki) adults and fry were exposed to aqueous sodium perchlorate at 1, 10, and 100mg/L, and growth and reproductive performance (fecundity, eggs/embryos mass, and gonadosomatic index [GSI]) were determined. Five-day acute toxicity tests were also performed. Perchlorate had a stimulatory effect on fecundity, GSI, and egg/embryo mass, at least for some treatments. The LC50 of sodium perchlorate was 404 mg/L. Growth was enhanced at 1mg/L but inhibited at 10mg/L. These results suggest that, at environmentally relevant concentrations, perchlorate does not induce acutely toxic effects but may have mild stimulatory or hormetic effects on fitness parameters in this species.
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Affiliation(s)
- June-Woo Park
- Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79409-1163, USA
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Opitz R, Hartmann S, Blank T, Braunbeck T, Lutz I, Kloas W. Evaluation of Histological and Molecular Endpoints for Enhanced Detection of Thyroid System Disruption in Xenopus laevis Tadpoles. Toxicol Sci 2006; 90:337-48. [PMID: 16396842 DOI: 10.1093/toxsci/kfj083] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Amphibian metamorphosis represents a promising model for the identification of thyroid system-disrupting chemicals due to the pivotal role played by thyroid hormones for the initiation and regulation of metamorphosis. An important aspect of bioassay development is the identification and evaluation of sensitive and diagnostic endpoints. In this study, several morphological, histological, and molecular endpoints were evaluated for their utility to detect alterations in thyroid system function after exposure of stage 51 Xenopus laevis tadpoles to various concentrations (1.0, 2.5, 10, 25, and 50 mg/l) of the anti-thyroidal compound ethylenethiourea (ETU). Analysis of developmental stages on exposure day 20 and monitoring of time to fore limb emergence (FLE) revealed retardation and complete arrest of tadpole development at 25 mg/l and 50 mg/l ETU, respectively. Development was not affected by 1.0, 2.5, and 10 mg/l ETU. Histological alterations in the thyroid gland were observed in FLE-displaying tadpoles after exposure to 2.5, 10, and 25 mg/l ETU, as well as in developmentally arrested tadpoles exposed to 50 mg/l ETU. Prevalence and severity of histological changes increased in a concentration-dependent manner. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) showed increased mRNA expression of the alpha- and beta-subunits of thyroid-stimulating hormone (TSHalpha, TSHbeta) in pituitary tissue of tadpoles exposed to 25 and 50 mg/l ETU. Results demonstrate the successful detection of anti-thyroidal effects of ETU in Xenopus laevis tadpoles using various endpoints and highlight the particular sensitivity of thyroid gland histology to detect thyroid system disruption in tadpoles.
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Affiliation(s)
- Robert Opitz
- Department of Inland Fisheries, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, D-12587 Berlin, Germany
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Scinicariello F, Murray HE, Smith L, Wilbur S, Fowler BA. Genetic factors that might lead to different responses in individuals exposed to perchlorate. ENVIRONMENTAL HEALTH PERSPECTIVES 2005; 113:1479-84. [PMID: 16263499 PMCID: PMC1310906 DOI: 10.1289/ehp.8076] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Perchlorate has been detected in groundwater in many parts of the United States, and recent detection in vegetable and dairy food products indicates that contamination by perchlorate is more widespread than previously thought. Perchlorate is a competitive inhibitor of the sodium iodide symporter, the thyroid cell-surface protein responsible for transporting iodide from the plasma into the thyroid. An estimated 4.3% of the U.S. population is subclinically hypothyroid, and 6.9% of pregnant women may have low iodine intake. Congenital hypothyroidism affects 1 in 3,000 to 1 in 4,000 infants, and 15% of these cases have been attributed to genetic defects. Our objective in this review is to identify genetic biomarkers that would help define subpopulations sensitive to environmental perchlorate exposure. We review the literature to identify genetic defects involved in the iodination process of the thyroid hormone synthesis, particularly defects in iodide transport from circulation into the thyroid cell, defects in iodide transport from the thyroid cell to the follicular lumen (Pendred syndrome), and defects of iodide organification. Furthermore, we summarize relevant studies of perchlorate in humans. Because of perchlorate inhibition of iodide uptake, it is biologically plausible that chronic ingestion of perchlorate through contaminated sources may cause some degree of iodine discharge in populations that are genetically susceptible to defects in the iodination process of the thyroid hormone synthesis, thus deteriorating their conditions. We conclude that future studies linking human disease and environmental perchlorate exposure should consider the genetic makeup of the participants, actual perchlorate exposure levels, and individual iodine intake/excretion levels.
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Affiliation(s)
- Franco Scinicariello
- Division of Toxicology, Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.
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27
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Opitz R, Lutz I, Nguyen NH, Scanlan TS, Kloas W. Analysis of thyroid hormone receptor betaA mRNA expression in Xenopus laevis tadpoles as a means to detect agonism and antagonism of thyroid hormone action. Toxicol Appl Pharmacol 2005; 212:1-13. [PMID: 16040072 DOI: 10.1016/j.taap.2005.06.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 05/17/2005] [Accepted: 06/09/2005] [Indexed: 11/25/2022]
Abstract
Amphibian metamorphosis represents a unique biological model to study thyroid hormone (TH) action in vivo. In this study, we examined the utility of thyroid hormone receptors alpha (TRalpha) and betaA (TRbetaA) mRNA expression patterns in Xenopus laevis tadpoles as molecular markers indicating modulation of TH action. During spontaneous metamorphosis, only moderate changes were evident for TRalpha gene expression whereas a marked up-regulation of TRbetaA mRNA occurred in hind limbs (prometamorphosis), head (late prometamorphosis), and tail tissue (metamorphic climax). Treatment of premetamorphic tadpoles with 1 nM 3,5,3'-triiodothyronine (T3) caused a rapid induction of TRbetaA mRNA in head and tail tissue within 6 to 12 h which was maintained for at least 72 h after initiation of T3 treatment. Developmental stage had a strong influence on the responsiveness of tadpole tissues to induce TRbetaA mRNA during 24 h treatment with thyroxine (0, 1, 5, 10 nM T4) or T3 (0, 1, 5, 10 nM). Premetamorphic tadpoles were highly sensitive in their response to T4 and T3 treatments, whereas sensitivity to TH was decreased in early prometamorphic tadpoles and strongly diminished in late prometamorphic tadpoles. To examine the utility of TRbetaA gene expression analysis for detection of agonistic and antagonistic effects on T3 action, mRNA expression was assessed in premetamorphic tadpoles after 48 h of treatment with the synthetic agonist GC-1 (0, 10, 50, 250 nM), the synthetic antagonist NH-3 (0, 40, 200, 1000 nM), and binary combinations of NH-3 (0, 40, 200, 1000 nM) and T3 (1 nM). All tested concentrations of GC-1 as well as the highest concentration of NH-3 caused an up-regulation of TRbetaA expression. Co-treatment with NH-3 and T3 revealed strong antagonistic effects by NH-3 on T3-induced TRbetaA mRNA up-regulation. Results of this study suggest that TRbetaA mRNA expression analysis could serve as a sensitive molecular testing approach to study effects of environmental compounds on the thyroid system in X. laevis tadpoles.
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Affiliation(s)
- Robert Opitz
- Department of Inland Fisheries, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Mueggelseedamm 301, Berlin D-12587, Germany.
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Bansal R, You SH, Herzig CTA, Zoeller RT. Maternal thyroid hormone increases HES expression in the fetal rat brain: an effect mimicked by exposure to a mixture of polychlorinated biphenyls (PCBs). BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 156:13-22. [PMID: 15862623 DOI: 10.1016/j.devbrainres.2005.01.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2004] [Revised: 01/17/2005] [Accepted: 01/20/2005] [Indexed: 11/22/2022]
Abstract
Thyroid hormone is known to be essential for normal brain development both before and after birth, but much less is known about the role of thyroid hormone development before birth. In rodents, thyroid hormone of maternal origin can selectively regulate gene expression in the fetal cortex; HES1 was identified as a putative thyroid hormone responsive gene in the fetal cortex. Using in situ hybridization, we now confirm that thyroid hormone administration to pregnant rats can increase the abundance of HES1 mRNA in the fetal cortex on gestational day 16 (G16). In separate experiments, we found that maternal exposure to polychlorinated biphenyls (PCBs) increases HES expression similarly. Western analysis of proteins extracted from fetal cortex did not confirm that Notch-1 or Notch-3 activation was associated with treatment effects on HES expression. However, considering the role of HES proteins in fate specification of cortical neurons, these findings suggest that thyroid hormone, and PCB exposure, may influence fate specification of cortical neurons.
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Affiliation(s)
- Ruby Bansal
- Department of Biology, University of Massachusetts-Amherst, Morrill Science Center, Amherst, MA 01003, USA
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29
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Lewandowski TA, Seeley MR, Beck BD. Interspecies differences in susceptibility to perturbation of thyroid homeostasis: a case study with perchlorate. Regul Toxicol Pharmacol 2004; 39:348-62. [PMID: 15135213 DOI: 10.1016/j.yrtph.2004.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Indexed: 11/22/2022]
Abstract
Despite many physiological similarities, humans and rats exhibit notably different susceptibilities to thyroid perturbation. Considerable research has recently been conducted on the thyroid-active chemical perchlorate, a chemical of emerging environmental and regulatory interest. While the data indicate humans and rats exhibit similar dose-response relationships in terms of acute inhibition of thyroidal iodide uptake, the two species appear to exhibit notable differences in terms of thyroid hormone response, the toxicologically significant consequence of iodide uptake inhibition. We analyzed dose-response data for changes in serum T(3), T(4), and TSH levels from studies in humans, rats, mice, and rabbits. We found that thyroid homeostasis in the rat appears to be strikingly more sensitive to perchlorate than any of the other species. Rats exhibited an increase in serum TSH at 0.1mg/kg-day whereas other species remained unresponsive even at doses of 10mg/kg-day. Less pronounced but consistent effects were seen with serum T(3) and T(4). These cross-species comparisons provide strong evidence that data obtained from rat studies should be critically evaluated for their relevance to humans. If rat data are used to develop toxicity criteria for perchlorate, we propose that this is an instance where an inter-species uncertainty factor less than one is supportable. DISCLOSURE STATEMENT: One of the authors (BDB) has been hired by Lockheed Martin Corporation as an expert in litigation involving perchlorate. A portion of the initial research presented in this paper was conducted in conjunction with her role in that matter.
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Affiliation(s)
- T A Lewandowski
- Gradient Corporation, 600 Stewart St., Suite 803, Seattle, WA 98101, USA.
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Gilbert ME. Alterations in synaptic transmission and plasticity in area CA1 of adult hippocampus following developmental hypothyroidism. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 148:11-8. [PMID: 14757514 DOI: 10.1016/j.devbrainres.2003.09.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Transient reductions in thyroid hormone during critical periods of brain development can have devastating and irreversible effects on neurological function. The hippocampus is a brain region sensitive to thyroid hormones and is a necessary substrate for some forms of learning and memory. Subregions within the hippocampus display distinct ontogenetic profiles and have shown differential vulnerability to some indices of thyrotoxic insult. Synaptic function can be readily assessed in the hippocampus, yet little information exists on the consequences of early thyroid hormone insufficiency on the neurophysiological integrity of this structure. Previous work has examined the long-term consequences of perinatal hypothyroidism on neurophysiology of the dentate gyrus of the hippocampal formation. The current study reveals that alterations in synaptic function also exist in area CA1, and some differences in the pattern of effects are evident between the two hippocampal subfields. Developing rats were transiently exposed to the thyrotoxicant, propylthiouracil (PTU; 0 or 15 ppm), through the drinking water of pregnant dams beginning on gestational day 18. This regimen markedly reduced circulating levels of thyroid hormones and stunted pup growth. PTU exposure was terminated on postnatal day (PN) 21 and electrophysiological assessments were conducted by recording field potentials in area CA1 of hippocampal slices derived from adult male offspring. Synaptic transmission, short-term, and long-term synaptic plasticity were assessed. Consistent with observations in the dentate gyrus, somatic population spike amplitudes were reduced in assessments of baseline synaptic transmission of slices from PTU-exposed animals. No differences were identified in excitatory postsynaptic potentials (EPSP). Short-term plasticity of the EPSP as indexed by paired pulse facilitation was markedly impaired by PTU exposure. Long-term potentiation (LTP) of the population spike was enhanced, consistent with findings in dentate gyrus, but no change in EPSP LTP was detected. Perturbations in synaptic function in the hippocampus of adult rats transiently exposed to a period of hormone insufficiency during the perinatal period are likely to contribute to cognitive deficits associated with developmental hypothyroidism.
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Affiliation(s)
- M E Gilbert
- Neurotoxicology Division (MD-B105-05), National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Heindel JJ, Zoeller RT. Thyroid hormone and brain development: translating molecular mechanisms to population risk. Thyroid 2003; 13:1001-4. [PMID: 14651783 DOI: 10.1089/105072503770867165] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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