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Maffini MV, Vandenberg LN. Failure to Launch: The Endocrine Disruptor Screening Program at the U.S. Environmental Protection Agency. FRONTIERS IN TOXICOLOGY 2022; 4:908439. [PMID: 35707496 PMCID: PMC9189695 DOI: 10.3389/ftox.2022.908439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
It has been 25 years since the U.S. Congress passed the Food Quality Protection Act of 1996, an amendment to the Food Drug and Cosmetic Act, which mandated that the US Environmental Protection Agency (EPA) test all pesticide chemicals used in food for endocrine disruption. Soon after the law passed, EPA established the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) to provide recommendations to the agency on how its Endocrine Disruptor Screening Program (EDSP) should work. Among them, the committee recommended that EDSP screening should 1) evaluate both human and ecological effects; 2) test for disruption of the estrogen, androgen, and thyroid systems; 3) evaluate pesticide and non-pesticide chemicals; and 4) implement a tiered approach. EPA adopted the recommendations and the EDSP was created in 1998. To date, the EPA has yet to fully implement the law; in other words, it has failed to test all pesticide chemicals for endocrine disruption. Of the small number that have been tested, not a single pesticide chemical has been determined to be an endocrine disruptor, and no regulatory actions have been taken. Here, we review the missed opportunities EPA had to make the EDSP a functional and effective program aimed at protecting human health and the environment. Two reports by the EPA’s Office of Inspector General from 2011 to 2021 provide the framework for our discussion.
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Affiliation(s)
- Maricel V. Maffini
- Independent Consultant, Frederick, MD, United States
- *Correspondence: Maricel V. Maffini,
| | - Laura N. Vandenberg
- University of Massachusetts—Amherst, School of Public Health and Health Sciences, Amherst, MA, United States
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Thambirajah AA, Wade MG, Verreault J, Buisine N, Alves VA, Langlois VS, Helbing CC. Disruption by stealth - Interference of endocrine disrupting chemicals on hormonal crosstalk with thyroid axis function in humans and other animals. ENVIRONMENTAL RESEARCH 2022; 203:111906. [PMID: 34418447 DOI: 10.1016/j.envres.2021.111906] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/04/2021] [Accepted: 08/16/2021] [Indexed: 06/13/2023]
Abstract
Thyroid hormones (THs) are important regulators of growth, development, and homeostasis of all vertebrates. There are many environmental contaminants that are known to disrupt TH action, yet their mechanisms are only partially understood. While the effects of Endocrine Disrupting Chemicals (EDCs) are mostly studied as "hormone system silos", the present critical review highlights the complexity of EDCs interfering with TH function through their interactions with other hormonal axes involved in reproduction, stress, and energy metabolism. The impact of EDCs on components that are shared between hormone signaling pathways or intersect between pathways can thus extend beyond the molecular ramifications to cellular, physiological, behavioral, and whole-body consequences for exposed organisms. The comparatively more extensive studies conducted in mammalian models provides encouraging support for expanded investigation and highlight the paucity of data generated in other non-mammalian vertebrate classes. As greater genomics-based resources become available across vertebrate classes, better identification and delineation of EDC effects, modes of action, and identification of effective biomarkers suitable for HPT disruption is possible. EDC-derived effects are likely to cascade into a plurality of physiological effects far more complex than the few variables tested within any research studies. The field should move towards understanding a system of hormonal systems' interactions rather than maintaining hormone system silos.
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Affiliation(s)
- Anita A Thambirajah
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Michael G Wade
- Environmental Health Science & Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
| | - Jonathan Verreault
- Centre de Recherche en Toxicologie de l'environnement (TOXEN), Département des Sciences Biologiques, Université du Québec à Montréal, Succursale Centre-ville, Montréal, QC, H3C 3P8, Canada
| | - Nicolas Buisine
- UMR7221 Physiologie Moléculaire et Adaptation, Centre National de la Recherche Scientifique, Muséum National d'Histoire Naturelle, Paris Cedex 05, France
| | - Verônica A Alves
- Centre Eau Terre Environnement, Institut National de La Recherche Scientifique (INRS), Québec City, QC, G1K 9A9, Canada
| | - Valerie S Langlois
- Centre Eau Terre Environnement, Institut National de La Recherche Scientifique (INRS), Québec City, QC, G1K 9A9, Canada
| | - Caren C Helbing
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8P 5C2, Canada.
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Babalola OO, Truter JC, Archer E, van Wyk JH. Exposure Impacts of Environmentally Relevant Concentrations of a Glufosinate Ammonium Herbicide Formulation on Larval Development and Thyroid Histology of Xenopus laevis. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2021; 80:717-725. [PMID: 32948887 DOI: 10.1007/s00244-020-00758-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Accepted: 09/05/2020] [Indexed: 06/11/2023]
Abstract
Thyroid hormones play critical roles in body growth and development as well as reproduction. They also influence the activities of a wider variety of tissues and biological functions, such as osmoregulation, metabolism, and especially metamorphosis in organisms, such as frogs. These complex activities of thyroid hormones are prone to disruption by agricultural pesticides, often leading to modulation of growth and the reproductive system in particular. These substances include Glufosinate ammonium, Glyphosates, Imazapyr, Penoxsulam, and Diquat dibromide among other herbicides. In this study, the standardized Xenopus Metamorphosis Assay protocol was used to assess the potential thyroid-modulatory properties of the Glufosinate ammonium Basta formulation, at relevant environmental concentrations (0.05 mg/L, 0.15 mg/L, and 0.25 mg/L) for 21 days. The results showed that this formulation only reduced the hind-limb length among the morphological endpoints. Histological evaluation showed that the mean thyroid gland area and the mean thyroidal follicle epithelium height were significantly increased following 0.15 and 0.25 mg/L exposures. The present study confirmed that this Basta formulation interacts with the thyroid axis and therefore potentially pose health hazard to amphibian in particular and potentially metamorphic aquatic vertebrates. Furthermore, the result is a signal of inherent potential thyroid disrupting activities that must be further investigated and characterised in some of the aquatic herbicide formulations to safeguard the aquatic biodiversity.
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Affiliation(s)
- Oluwaseun O Babalola
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa.
- Zoology and Environmental Biology, Lagos State University, Lagos, Nigeria.
| | - J Christoff Truter
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
- Department of Paraclinical Sciences, University of Pretoria, Pretoria, South Africa
| | - Edward Archer
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Johannes H van Wyk
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
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Korkmaz N, Örün İ. Effects of pesticide NeemAzal-T/S on thyroid, stress hormone and some cytokines levels in freshwater common carp, Cyprinus carpio L. TOXIN REV 2021. [DOI: 10.1080/15569543.2021.1895841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Nuh Korkmaz
- Department of Biology, Faculty of Arts and Sciences, Osmaniye Korkut Ata University, Osmaniye, Turkey
| | - İbrahim Örün
- Department of Biology, Faculty of Science and Letters, Aksaray University, Aksaray, Turkey
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Nugegoda D, Kibria G. Effects of environmental chemicals on fish thyroid function: Implications for fisheries and aquaculture in Australia. Gen Comp Endocrinol 2017; 244:40-53. [PMID: 26921447 DOI: 10.1016/j.ygcen.2016.02.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 02/22/2016] [Accepted: 02/24/2016] [Indexed: 12/14/2022]
Abstract
Numerous environmental stressors exert acute or chronic effects on the fish thyroid cascade. Such effects could be mediated via thyroidal alterations, imbalance of plasma T4 and T3 levels or damage to the structure of the thyroidal tissues (thyroid hypertrophy, hyperplasia). The thyroidal system is intricately linked to other endocrine systems in vertebrates including the control of reproduction. Disruption of fish thyroid function by environmental stressors has the potential to result in deleterious effects including the inhibition of sperm production, reduction in egg production, gonad development, ovarian growth, swimming activity, fertilisation and increase in larval mortality. Thyroid hormones play a major role in the development and growth of fish, particularly during their early life stages, thus, thyroid disruption by environmental stressors could inhibit the growth of fish larvae and juveniles in wild fish and cultured species, limit fish seed production and result in a decline in wild fisheries. This review highlights the effects of several environmental toxicants including PBDE, PCBs, PCDD and PCDF, PAH/oil, phthalates, metals, pesticides, mixed pollutants/chemicals, cyanide; and other stressors including acid (low pH) and ammonia, on fish thyroid function. Environmental sources of chemical stressors and appropriate water quality guidelines to protect the freshwater and marine species for the relevant pollutants are also discussed including (when available) the Australian guidelines (2000) and Canadian water quality guidelines (where Australian guidelines are not available). To date there has been no published research on the effects of anthropogenic environmental pollutants on the thyroid system of any native Australian fish species. However, the detection of high risk chemicals (notably PBDEs, PCBs, PAHs, metals and pesticides) in Australian waterways and Australian fish and shellfish implies that thyroid disruption of Australian wild fish and aquacultured species could occur. It is therefore imperative that the effects of such pollutants on the thyroid system of Australian native fish be investigated.
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Affiliation(s)
- Dayanthi Nugegoda
- School of Applied Sciences, RMIT University, Bundoora West Campus, Plenty Road, Melbourne, Australia.
| | - Golam Kibria
- School of Applied Sciences, RMIT University, Bundoora West Campus, Plenty Road, Melbourne, Australia.
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Wegner S, Browne P, Dix D. Identifying reference chemicals for thyroid bioactivity screening. Reprod Toxicol 2016; 65:402-413. [PMID: 27589887 DOI: 10.1016/j.reprotox.2016.08.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 08/19/2016] [Accepted: 08/29/2016] [Indexed: 12/20/2022]
Abstract
Reference chemicals were selected based on thyroid bioactivity in 'Tier 1' screening assays used by the U.S. EPA's Endocrine Disruptor Screening Program. Active reference chemicals had significant effects on thyroid-responsive endpoints in the amphibian metamorphosis assay, and the male and female pubertal rat assays. In the absence of thyroid weight or histopathological effects, additional published studies providing mechanistic data on thyroid activity were required for active chemicals. Inactive reference chemicals had no significant effects on thyroid-responsive endpoints in Tier 1 assays, or in amphibian or rodent studies from several online databases. The 34 reference chemicals (29 active and five inactive) will be useful for performance-based validation of alternative, high throughput screening assays for thyroid bioactivity.
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Affiliation(s)
- Susanna Wegner
- Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN, United States.
| | - Patience Browne
- Office of Science Coordination and Policy (OSCP), Office of Chemical Safety and Pollution Prevention, U.S. EPA, Washington, D.C., United States
| | - David Dix
- Office of Science Coordination and Policy (OSCP), Office of Chemical Safety and Pollution Prevention, U.S. EPA, Washington, D.C., United States
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Lou Q, Cao S, Xu W, Zhang Y, Qin Z, Wei W. Molecular characterization and mRNA expression of ribosomal protein L8 in Rana nigromaculata during development and under exposure to hormones. J Environ Sci (China) 2014; 26:2331-2339. [PMID: 25458689 DOI: 10.1016/j.jes.2014.09.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 01/22/2014] [Accepted: 02/24/2014] [Indexed: 06/04/2023]
Abstract
Like Xenopus laevis, some species of the Rana genus are also used to study endocrine disrupting chemicals (EDCs). Although ribosomal protein L8 (rpl8) is the most-used reference gene for analyzing gene expression by quantitative reverse transcription polymerase chain reaction in Rana, its suitability as the reference gene has never been validated in any species of the Rana genus. We characterized rpl8 cDNA in Rana nigromaculata, a promising native species in East Asia for assaying endocrine disrupting effects. We found that the rpl8 cDNA consisted of 919bp and encoded 257 amino acids, exhibiting high identities of amino acid sequence with known rpl8 in other Rana species. Then, we examined the stability of mRNA expression during development. Compared with elongation factor 1 alpha 1, another common housekeeping gene, neither stage-specific nor tissue-specific expression of the rpl8 gene was found in all tissues examined (brain, liver, intestine, tail, testis and ovary) during R. nigromaculata development. Finally, we investigated rpl8 expression under exposure to hormones. No change in rpl8 mRNA expression was found under exposure to thyroid hormone (T4) and estrogen (estradiol), whereas expression of the corresponding biomarker genes was induced. Our results show that rpl8 is an appropriate reference gene for analyzing gene expression by quantitative reverse transcription polymerase chain reaction for assaying EDCs using R. nigromaculata, and might also provide support for using rpl8 as a reference gene in other Rana species due to the high conservation of rpl8 among the Rana genus.
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Affiliation(s)
- Qinqin Lou
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Environment, Nanjing University of Technology, Nanjing 210009, China.
| | - Shan Cao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Environment, Nanjing University of Technology, Nanjing 210009, China
| | - Wei Xu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Environment, Nanjing University of Technology, Nanjing 210009, China
| | - Yinfeng Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Zhanfen Qin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| | - Wuji Wei
- College of Environment, Nanjing University of Technology, Nanjing 210009, China
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9
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Abstract
Endogenous hormones have effects on tissue morphology, cell physiology, and behaviors at low doses. In fact, hormones are known to circulate in the part-per-trillion and part-per-billion concentrations, making them highly effective and potent signaling molecules. Many endocrine-disrupting chemicals (EDCs) mimic hormones, yet there is strong debate over whether these chemicals can also have effects at low doses. In the 1990s, scientists proposed the "low-dose hypothesis," which postulated that EDCs affect humans and animals at environmentally relevant doses. This chapter focuses on data that support and refute the low-dose hypothesis. A case study examining the highly controversial example of bisphenol A and its low-dose effects on the prostate is examined through the lens of endocrinology. Finally, the chapter concludes with a discussion of factors that can influence the ability of a study to detect and interpret low-dose effects appropriately.
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Affiliation(s)
- Laura N Vandenberg
- Department of Public Health, Division of Environmental Health Sciences, University of Massachusetts - Amherst, Amherst, Massachusetts, USA.
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Muzzio AM, Noyes PD, Stapleton HM, Lema SC. Tissue distribution and thyroid hormone effects on mRNA abundance for membrane transporters Mct8, Mct10, and organic anion-transporting polypeptides (Oatps) in a teleost fish. Comp Biochem Physiol A Mol Integr Physiol 2013; 167:77-89. [PMID: 24113777 DOI: 10.1016/j.cbpa.2013.09.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 09/26/2013] [Accepted: 09/27/2013] [Indexed: 11/18/2022]
Abstract
Many of the actions of thyroid hormones (THs) occur via TH binding to intracellular receptors. Although it was long thought that THs diffused passively across plasma membranes, it is now recognized that cellular entry is mediated by a variety of membrane transporter proteins. In this study, we identified cDNAs encoding the TH transporters monocarboxylate transferases 8 (mct8) and 10 (mct10) as well as eight distinct organic anion-transporting polypeptide (oatp) proteins from fathead minnow (Pimephales promelas). Analysis of the tissue distribution of transporter mRNAs revealed that mct8 and mct10 transcripts were both abundant in liver, but also present at lower levels in brain, gonad and other tissues. Transcripts encoding oatp1c1 were highly abundant in brain, liver and gonad, and exhibited significant sex differences in the liver and gonad. Treatment of adult male minnows with 3,5,3'-triiodothyronine (T3) or the goitrogen methimazole altered gene transcript abundance for several transporters. Fish given exogenous T3 had reduced mct8 and oapt1c1 mRNA levels in the liver compared to methimazole-treated fish. In the brain, transcripts for mct8, mct10, oatp2b1, and oatp3a1 were each reduced in abundance in fish with elevated T3. As a whole, these results provide evidence that TH status influences the transcriptional dynamics of mct8, mct10 and several Oatp genes including oatp1c1 in teleost fish.
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Affiliation(s)
- Amanda M Muzzio
- Biological Sciences Department, Center for Coastal Marine Sciences, California Polytechnic State University, San Luis Obispo, CA, USA
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Torres L, Orazio CE, Peterman PH, Patiño R. Effects of dietary exposure to brominated flame retardant BDE-47 on thyroid condition, gonadal development and growth of zebrafish. FISH PHYSIOLOGY AND BIOCHEMISTRY 2013; 39:1115-1128. [PMID: 23334565 DOI: 10.1007/s10695-012-9768-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 12/31/2012] [Indexed: 06/01/2023]
Abstract
Little is known about the effects of brominated flame retardants in teleosts and some of the information currently available is inconsistent. This study examined effects of dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on thyroid condition, body mass and size, and gonadal development of zebrafish. Pubertal, 49-day-old (posthatch) fish were fed diets without BDE-47 (control) or with 1, 5 or 25 μg/g BDE-47/diet. Treatments were conducted in triplicate 30-L tanks each containing 50 zebrafish, and 15 fish per treatment (5 per tank) were sampled at days 40, 80 and 120 of exposure. Measurements were taken of body mass, standard length, head depth and head length. Sex (at 40-120 days of exposure), germ cell stage (at 40 days) and thyroid condition (at 120 days; follicular cell height, colloid depletion, angiogenesis) were histologically determined. Whole-body BDE-47 levels at study completion were within the high end of levels reported in environmentally exposed (wild) fishes. Analysis of variance was used to determine differences among treatments at each sampling time. No effects were observed on thyroid condition or germ cell stage in either sex. Reduced head length was observed in females exposed to BDE-47 at 80 days but not at 40 or 120 days. In males, no apparent effects of BDE-47 were observed at 40 and 80 days, but fish exposed to 25 μg/g had lower body mass at 120 days compared to control fish. These observations suggest that BDE-47 at environmentally relevant whole-body concentrations does not affect thyroid condition or pubertal development of zebrafish but does affect growth during the juvenile-to-adult transition, especially in males.
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Affiliation(s)
- Leticia Torres
- Department of Biological Sciences and Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, TX, 79409-3131, USA
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Tassinari R, Cubadda F, Moracci G, Aureli F, D’Amato M, Valeri M, De Berardis B, Raggi A, Mantovani A, Passeri D, Rossi M, Maranghi F. Oral, short-term exposure to titanium dioxide nanoparticles in Sprague-Dawley rat: focus on reproductive and endocrine systems and spleen. Nanotoxicology 2013; 8:654-62. [DOI: 10.3109/17435390.2013.822114] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Searcy BT, Beckstrom-Sternberg SM, Beckstrom-Sternberg JS, Stafford P, Schwendiman AL, Soto-Pena J, Owen MC, Ramirez C, Phillips J, Veldhoen N, Helbing CC, Propper CR. Thyroid hormone-dependent development in Xenopus laevis: a sensitive screen of thyroid hormone signaling disruption by municipal wastewater treatment plant effluent. Gen Comp Endocrinol 2012; 176:481-92. [PMID: 22248444 DOI: 10.1016/j.ygcen.2011.12.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 12/27/2011] [Indexed: 11/20/2022]
Abstract
Because thyroid hormones (THs) are conserved modulators of development and physiology, identification of compounds adversely affecting TH signaling is critical to human and wildlife health. Anurans are an established model for studying disruption of TH signaling because metamorphosis is dependent upon the thyroid system. In order to strengthen this model and identify new gene transcript biomarkers for TH disruption, we performed DNA microarray analysis of Xenopus laevis tadpole tail transcriptomes following treatment with triiodothyronine (T(3)). Comparison of these results with previous studies in frogs and mammals identified 36 gene transcripts that were TH-sensitive across clades. We then tested molecular biomarkers for sensitivity to disruption by exposure to wastewater effluent (WWE). X. laevis tadpoles, exposed to WWE from embryo through metamorphosis, exhibited an increased developmental rate compared to controls. Cultured tadpole tails showed dramatic increases in levels of four TH-sensitive gene transcripts (thyroid hormone receptor β (TRβ), deiodinase type II (DIO2), and corticotropin releasing hormone binding protein (CRHBP), fibroblast activation protein α (FAPα)) when exposed to T(3) and WWE extracts. TRβ, DIO2, and CRHBP were identified as TH sensitive in other studies, while FAPα mRNA transcripts were highly TH sensitive in our array. The results validate the array and demonstrate TH-disrupting activity by WWE. Our findings demonstrate the usefulness of cross-clade analysis for identification of gene transcripts that provide sensitivity to endocrine disruption. Further, the results suggest that development is disrupted by exposure to complex mixes of compounds found in WWE possibly through interference with TH signaling.
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Affiliation(s)
- Brian T Searcy
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, United States
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Schreinemachers DM. Association between Perchlorate and Indirect Indicators of Thyroid Dysfunction in NHANES 2001-2002, a Cross-Sectional, Hypothesis-Generating Study. Biomark Insights 2011; 6:135-46. [PMID: 22174568 PMCID: PMC3235992 DOI: 10.4137/bmi.s7985] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND A previous study based on NHANES 2001-2002 observed that increased levels of urinary perchlorate were associated with increased levels of thyroid stimulating hormone among all women, and with decreased levels of thyroxine among women with low urinary iodine. No associations were observed for men. METHODS Using the same NHANES 2001-2002 data, associations of urinary perchlorate with indirect biomarkers of thyroid hormone disruption were investigated. Decreased levels of hemoglobin (HGB), hematocrit (HCT), and high density lipoprotein (HDL) have been observed among subjects with subclinical hypothyroidism. To investigate the suitability of these indicators for use in observational studies, subjects were divided into six groups: boys, age 6-19; men, age 20-85; girls, age 6-14; non-pregnant women, age 15-49; women, age 50-85; and pregnant women. Use of perchlorate quintiles (Q1-Q5) and continuous log-transformed perchlorate in the regression models allowed investigation of both non-linear and linear associations. Adjustments were made for age, urinary creatinine, race/ethnicity, body mass index, cotinine, poverty index, hours of fasting, thiocyanate, nitrate, daily kcal intake, C-reactive protein. Adjustment for alcohol consumption depended on availability. Adjustment for prescription drugs (beta-blockers, sex hormones, antihyperlipidemic and antidiabetic drugs) was made if it changed the perchlorate estimate by ≥10%. RESULTS Statistically significant decreases were observed for HGB and HCT among boys, men, women age 15-49, and pregnant women, and for HDL among men. CONCLUSIONS Although the mean response biomarkers were within normal range, their association with urinary perchlorate is of interest. HGB and HCT among pregnant women showed a stronger association with urinary perchlorate than non-pregnant women age 15-49. Statistically significant associations were observed for individual perchlorate quintiles. Assumption of linearity of log-transformed perchlorate may result in underestimation of some associations.
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Affiliation(s)
- Dina M Schreinemachers
- Epidemiology Branch, Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA
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Curran CP, Vorhees CV, Williams MT, Genter MB, Miller ML, Nebert DW. In utero and lactational exposure to a complex mixture of polychlorinated biphenyls: toxicity in pups dependent on the Cyp1a2 and Ahr genotypes. Toxicol Sci 2010; 119:189-208. [PMID: 20961953 DOI: 10.1093/toxsci/kfq314] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Polychlorinated biphenyls (PCBs) are persistent toxic pollutants occurring as complex mixtures in the environment. Humans are known genetically to have > 60-fold differences in hepatic cytochrome P450 1A2 (CYP1A2) levels and > 12-fold differences in aryl hydrocarbon receptor (AHR) affinity, both of which could affect PCB pharmacokinetics. Thus, we compared Ahr(b1)_Cyp1a2(+/+) high-affinity AHR wild-type, Ahr(d)_Cyp1a2(+/+) poor affinity AHR wild-type, Ahr(b1)_Cyp1a2(-/-) knockout, and Ahr(d)_Cyp1a2(-/-) knockout mouse lines. We chose a mixture of three coplanar and five noncoplanar PCBs to reproduce that seen in human tissues, breast milk, and the food supply. The mixture was given by gavage to the mother on gestational day 10.5 (GD10.5) and postnatal day 5 (PND5); tissues were collected from pups and mothers at GD11.5, GD18.5, PND6, PND13, and PND28. Ahr(b1)_Cyp1a2(-/-) pups showed lower weight at birth and slower rate of growth postnatally. Absence of CYP1A2 resulted in significant splenic atrophy at PND13 and PND28. Presence of high-affinity AHR enhanced thymic atrophy and liver hypertrophy in the pups. Concentrations of each congener were analyzed at all time points: maximal noncoplanar congener levels in maternal tissues were observed from GD18 until PND6, whereas the highest levels in pups were found between PND6 and PND28. Coplanar PCB concentrations were generally higher in Ahr(d)-containing pup tissues; these findings are consistent with earlier studies demonstrating the crucial importance of AHR-mediated inducible CYP1 in the gastrointestinal tract as a means of detoxication of oral planar polycyclic aromatic hydrocarbons.
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Affiliation(s)
- Christine P Curran
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0056, USA
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Palace V, Park B, Pleskach K, Gemmill B, Tomy G. Altered thyroxine metabolism in rainbow trout (Oncorhynchus mykiss) exposed to hexabromocyclododecane (HBCD). CHEMOSPHERE 2010; 80:165-169. [PMID: 20378152 DOI: 10.1016/j.chemosphere.2010.03.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/26/2010] [Accepted: 03/06/2010] [Indexed: 05/29/2023]
Abstract
Hexabromocyclododecane (HBCD) is an additive flame retardant used in consumer and industrial applications. Our earlier work suggested that fish exposed to HBCD exhibited an increase in the rate of turnover of thyroxine (T4), the precursor molecule to the active thyroid hormone triiodothyronine (T3). To examine this further, juvenile rainbow trout were held in the laboratory and fed diets containing environmentally relevant concentrations of the individual alpha, beta or gamma isomers. Thirty-two days after feeding began, 20 fish from each group were gavaged with gelatin containing 1microCi [(125)I]-T4. Uptake of [(125)I]-T4 from the gut was low and recoveries of the initial [(125)I]-T4 were <10% after 2d and <3% and <2% after 6 and 14d respectively, with no differences among groups. However, measurements of the labeled T4 in tissues 2, 4, 6 and 14d after gavage showed that tissue disposition and elimination rates of the hormone were altered by HBCD. In particular, on day 14 after gavage feeding, there was significantly lower radioactivity in the thyroid of fish exposed to the HBCD isomers relative to the reference group. This implies that either there was lower iodide uptake by the gland in fish exposed to HBCD or that the rate of thyroid hormone turnover in HBCD treated fish was elevated. There was also a significantly higher type II outer ring deiodinase enzyme activity in livers of fish exposed to the beta and gamma isomers. Taken together, these results indicate that HBCD can potentially impact the thyroid system of fish.
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Affiliation(s)
- Vince Palace
- Fisheries and Oceans Canada, Winnipeg, Manitoba, Canada.
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Is the mechanisms of fipronil-induced thyroid disruption specific of the rat: Re-evaluation of fipronil thyroid toxicity in sheep? Toxicol Lett 2010; 194:51-7. [DOI: 10.1016/j.toxlet.2010.01.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 11/23/2022]
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Ucán-Marin F, Arukwe A, Mortensen AS, Gabrielsen GW, Letcher RJ. Recombinant albumin and transthyretin transport proteins from two gull species and human: chlorinated and brominated contaminant binding and thyroid hormones. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:497-504. [PMID: 20039755 DOI: 10.1021/es902691u] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Environmentally relevant concentrations of selected polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) flame retardant congeners and their hydroxylated (OH) and methoxylated (MeO) analogues that can perturb thyroid hormone-dependent processes were comparatively examined with respect to competitive binding with thyroxine (T(4)) and 3,5,3'-triiodothyronine (T(3)) thyroid hormones (THs) on recombinant human and gull albumin and transthyretin transport proteins. The liver tissue was from glaucous gulls (Larus hyperboreus) from Norway and herring gulls (Larus argentatus) from the Great Lakes of North America. We isolated, cloned, sequenced, purified, and expressed the cDNA (cDNA) of albumin from liver of herring and glaucous gull. Albumin amino acid sequences were identical for both gull species. Concentration-dependent, competitive binding curves were generated for T(4) and T(3) binding alone and for selected substrates using gull and human recombinant albumin (recALB). Human recALB had high preference for T(4) relative to T(3), whereas it was reversed for gull recALB. Binding assays with recALB and recTTR gull proteins showed that relative to 2,2',4,4'-tetrabromoDE (BDE-47) and 2,2',3,4',5,5',6-heptaCB (CB-187) and the MeO-substituted (4-MeO-CB187 and 6-MeO-BDE47) analogues, 4-OH-CB187, 6-OH-BDE47, and 4'-OH-BDE49 had the greatest binding affinity and potency, and that competitive binding was greater for T(3) relative to T(4). These results indicate that xenobiotic ligand binding to human ALB or TTR cannot be used as a surrogate for gull binding interactions. The combination of TH-like brominated diphenyl ether backbone (relative to the chlorinated biphenyl backbone), and the presence of OH-group produced a more effective competitive ligand on human and gull recALB and recTTR relative to both T(3) and T(4). This suggests the possibility that OH-substituted organohalogen contaminants may be an exposure concern to the thyroid system in free-ranging gulls as well as for humans.
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Affiliation(s)
- Francisco Ucán-Marin
- Wildlife and Landscape Science Directorate, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON, K1A 0H3, Canada
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Abstract
1. The monocarboxylate transporter (MCT, SLC16) family comprises 14 members, of which to date only MCT1-4 have been shown to carry monocarboxylates, transporting important metabolic compounds such as lactate, pyruvate and ketone bodies in a proton-coupled manner. The transport of such compounds is fundamental for metabolism, and the tissue locations, properties and regulation of these isoforms is discussed. 2. Of the other members of the MCT family, MCT8 (a thyroid hormone transporter) and TAT1 (an aromatic amino acid transporter) have been characterized more recently, and their physiological roles are reviewed herein. The endogenous substrates and functions of the remaining members of the MCT family await elucidation. 3. The MCT proteins have the typical twelve transmembrane-spanning domain (TMD) topology of membrane transporter proteins, and their structure-function relationship is discussed, especially in relation to the future impact of the single nucleotide polymorphism (SNP) databases and, given their ability to transport pharmacologically relevant compounds, the potential impact for pharmacogenomics.
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Affiliation(s)
- D Meredith
- School of Life Sciences, Oxford Brookes University, Headington, Oxford, UK.
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Santini F, Mantovani A, Cristaudo A, Rago T, Marsili A, Buselli R, Mignani A, Ceccarini G, Bastillo R, Taddei D, Ricco I, Vitti P, Pinchera A. Thyroid function and exposure to styrene. Thyroid 2008; 18:1065-9. [PMID: 18816178 DOI: 10.1089/thy.2008.0003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Many natural substances and drugs have long been known to cause goiter or thyroid dysfunction. More recently, several environmental pollutants, such as pesticides and industrial compounds, have been investigated for their thyroid-disrupting activity and related adverse effects on human health. The aim of this study was to evaluate the effects of styrene on the thyroid axis in occupationally exposed workers. METHODS Thirty-eight exposed (E) and 123 nonexposed (NE) male workers (controls) were assessed. Serum concentrations of thyrotropin (TSH; basal and after thyrotropin-releasing hormone [TRH] administration.), free thyroxine (FT(4)), free triiodothyronine (FT(3)), anti-thyroglobulin, thyroid peroxidase antibody, and calcitonin were measured. Thyroid ultrasound examination was also performed. In E workers, urinary creatinine, mandelic acid (MA), and phenylglyoxylic acid (PGA) were also measured. RESULTS No significant differences between E and NE workers were demonstrated, as far as thyroid volume, nodularity, serum thyroid antibodies, and calcitonin were analyzed. However, in the E group a positive correlation between duration of exposure and thyroid volume was detected. After exclusion of subjects with nodular or autoimmune thyroid diseases, serum concentrations of FT(4), FT(3), and TSH did not differ between the two groups. In E workers there was a positive correlation between the urinary concentrations of styrene metabolites (MA plus PGA) and FT(4) or FT(4)/FT(3) ratio (p < 0.05; r = 0.45 and p < 0.005; r = 0.61, respectively), while no correlation was observed between urinary concentrations of MA plus PGA and serum TSH (either basal and stimulated). CONCLUSIONS Chronic exposure to styrene is not associated with an increase in nodular or autoimmune thyroid diseases. However, styrene could interfere with peripheral metabolism of thyroid hormones by inhibiting T(4) to T(3) conversion. Whether this is a direct effect on iodothyronine deiodinases or a consequence of a general distress, such as in nonthyroidal illnesses, remains to be established. Further studies in a larger population of exposed workers are needed to confirm these preliminary observations.
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Affiliation(s)
- Ferruccio Santini
- Department of Endocrinology and Kidney, University Hospital of Pisa, Pisa, Italy.
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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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