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Ramhøj L, Svingen T, Evrard B, Chalmel F, Axelstad M. Two thyroperoxidase-inhibiting chemicals induce shared transcriptional changes in hippocampus of developing rats. Toxicology 2024; 505:153822. [PMID: 38685447 DOI: 10.1016/j.tox.2024.153822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 04/25/2024] [Accepted: 04/26/2024] [Indexed: 05/02/2024]
Abstract
Thyroid hormone (TH) system disrupting compounds can impair brain development by perturbing TH action during critical life stages. Human exposure to TH system disrupting chemicals is therefore of great concern. To better protect humans against such chemicals, sensitive test methods that can detect effects on the developing brain are critical. Worryingly, however, current test methods are not sensitive and specific towards TH-mediated effects. To address this shortcoming, we performed RNA-sequencing of rat brains developmentally exposed to two different thyroperoxidase (TPO) inhibiting compounds, the medical drug methimazole (MMI) or the pesticide amitrole. Pregnant and lactating rats were exposed to 8 and 16 mg/kg/day(d) MMI or 25 and 50 mg/kg/d amitrole from gestational day 7 until postnatal day 16. Bulk-RNA-seq was performed on hippocampus from the 16-day old male pups. MMI and amitrole caused pronounced changes to the transcriptomes; 816 genes were differentially expressed, and 425 gene transcripts were similarly affected by both chemicals. Functional terms indicate effects from key cellular functions to changes in cell development, migration and differentiation of several cell populations. Of the total number of DEGs, 106 appeared to form a consistent transcriptional fingerprint of developmental hypothyroidism as they were similarly and dose-dependently expressed across all treatment groups. Using a filtering system, we identified 20 genes that appeared to represent the most sensitive, robust and dose-dependent markers of altered TH-mediated brain development. These markers provide inputs to the adverse outcome pathway (AOP) framework where they, in the context of linking TPO inhibiting compounds to adverse cognitive function, can be used to assess altered gene expression in the hippocampus in rat toxicity studies.
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Affiliation(s)
- Louise Ramhøj
- National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark.
| | - Terje Svingen
- National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Bertrand Evrard
- Univ Rennes, Inserm, EHESP, Irset (Institut de Recherche en Santé, Environnement et Travail), UMR_S 1085, Rennes, F-35000, France
| | - Frédéric Chalmel
- Univ Rennes, Inserm, EHESP, Irset (Institut de Recherche en Santé, Environnement et Travail), UMR_S 1085, Rennes, F-35000, France
| | - Marta Axelstad
- National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
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Wiklund L, Pípal M, Weiss J, Beronius A. Exploring a mechanism-based approach for the identification of endocrine disruptors using Adverse Outcome Pathways (AOPs) and New Approach Methodologies (NAMs) : A perfluorooctane sulfonic acid case study. Toxicology 2024; 504:153794. [PMID: 38580097 DOI: 10.1016/j.tox.2024.153794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 03/21/2024] [Accepted: 04/01/2024] [Indexed: 04/07/2024]
Abstract
Endocrine disruptors (EDs) pose a serious threat to human health and the environment and require a comprehensive evaluation to be identified. The identification of EDs require a substantial amount of data, both in vitro and in vivo, due to the current scientific criteria in the EU. At the same time, the EU strives to reduce animal testing due to concerns regarding animal welfare and sensitivity of animal studies to adequately detect adverse effects relevant for human health. Perfluorooctane sulfonic acid (PFOS) is a persistent organic pollutant that is suspected to be an ED based on academic research, however it is not identified as such from a regulatory perspective. It has previously been shown that PFOS has the potential to cause neurotoxicity as well as affect the thyroid system, and it is known that specific thyroid hormone levels are critical in the development of the brain during. In this work, the aim was to evaluate a mechanism-based approach to identify ED properties of PFOS based on the Adverse Outcome Pathway (AOP) framework and using New Approach Methods (NAMs), by comparing this approach to an ED assessment based on the currently available guidance document. An AOP network (AOPN) was generated for the thyroid modality, and AOPs leading to developmental neurotoxicity (DNT) were identified. A literature search and screening process based on the AOPN, and systematic review methodology, was performed, followed by a rigorous Weight-of-Evidence (WoE) assessment. Evidence was mapped back onto the AOPN used for the literature search, to identify possible endocrine Modes-of-Action (MoAs) for PFOS and data gaps in the two assessments. It could be concluded that PFOS fulfils the criteria for ED classification in the standard ED assessment, but not in the mechanism-based assessment. The need for quantitative information, such as quantitative AOPs, for the mechanism-based approach is discussed. The possibility of a directly neurotoxic alternative MoA was also highlighted based on available in vitro data. Opportunities and challenges with implementing AOPs and NAMs into the regulatory assessment of EDs, and assessing hazard in the Next Generation Risk Assessment, is discussed. This case study exploring the mechanism-based approach to ED identification represents an important step toward more accurate and predictive assessment of EDs based on AOPs and NAMs, and to the Next Generation Risk Assessment (NGRA) concept.
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Affiliation(s)
- Linus Wiklund
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
| | - Marek Pípal
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Jana Weiss
- Department of Environmental Science, Stockholm University, Stockholm, Sweden
| | - Anna Beronius
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
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Minami K, Sato A, Tomiyama N, Ogata K, Kosaka T, Hojo H, Takahashi N, Suto H, Aoyama H, Yamada T. Prenatal test cohort of a modified rat comparative thyroid assay adding brain thyroid hormone measurements and histology but lowering group size appears able to detect disruption by sodium phenobarbital. Curr Res Toxicol 2024; 6:100168. [PMID: 38693933 PMCID: PMC11061706 DOI: 10.1016/j.crtox.2024.100168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 04/04/2024] [Accepted: 04/16/2024] [Indexed: 05/03/2024] Open
Abstract
The Comparative Thyroid Assay (CTA, USEPA) is a screening test for thyroid hormone (TH) disruption in peripheral blood of dams and offspring. Recently, we began investigating feasible improvements to the CTA by adding examination of offspring brain TH concentrations and brain histopathology. In addition, we hypothesize that the number of animals required could be reduced by 50 % while still maintaining sensitivity to characterize treatment related changes in THs. Previously, we showed that the prenatal test cohort of the modified CTA could detect 1000 ppm sodium phenobarbital (NaPB)-induced suppression of brain T3 (by 9 %) and T4 (by 33 %) with no significant changes in serum T3 and T4 (less than 8 %). In the current study we expanded the dose response in a prenatal test cohort. Pregnant SD rats (N = 10/group) were exposed to 0, 1000 or 1500 ppm NaPB in the diet from gestational days (GD) 6 to GD20. Serum THs concentrations in GD20 dams together with serum/brain THs concentrations and brain histopathology in the GD20 fetuses were examined. NaPB dose-dependently suppressed serum T3 (up to -26 %) and T4 (up to -44 %) in dams, with suppression of T3 in serum (up to -26 %) and brain (up to -18 %) and T4 in serum (up to -26 %) and brain (up to -29 %) of fetuses but without clear dose dependency. There were no remarkable findings that deviated significantly from controls in GD20 fetal brain by qualitative histopathology. Overall, the present study suggests that the prenatal test cohort of this modified CTA is able to detect the expected fetal TH disruptions by prenatal exposure to NaPB, while also reducing the number of animals used by 50 %, consistent with the results of our previous study. These findings add to the suggestion that lowering group sizes and adding endpoints may be a useful alternative to the original CTA design.
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Affiliation(s)
- Kenta Minami
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
| | - Akira Sato
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Naruto Tomiyama
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Keiko Ogata
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
| | - Tadashi Kosaka
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Hitoshi Hojo
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Naofumi Takahashi
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Hidenori Suto
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
| | - Hiroaki Aoyama
- The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Tomoya Yamada
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
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O'Shaughnessy KL, Sasser AL, Bell KS, Riutta C, Ford JL, Grindstaff RD, Gilbert ME. Bypassing the brain barriers: upregulation of serum miR-495 and miR-543-3p reflects thyroid-mediated developmental neurotoxicity in the rat. Toxicol Sci 2024; 198:128-140. [PMID: 38070162 DOI: 10.1093/toxsci/kfad125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024] Open
Abstract
Evaluating the neurodevelopmental effects of thyroid-disrupting chemicals is challenging. Although some standardized developmental and reproductive toxicity studies recommend serum thyroxine (T4) measures in developing rats, extrapolating between a serum T4 reduction and neurodevelopmental outcomes is not straightforward. Previously, we showed that the blood-brain and blood-cerebrospinal fluid barriers may be affected by developmental hypothyroidism in newborn rats. Here, we hypothesized that if the brain barriers were functionally disturbed by abnormal thyroid action, then small molecules may escape from the brain tissue and into general circulation. These small molecules could then be identified in blood samples, serving as a direct readout of thyroid-mediated developmental neurotoxicity. To address these hypotheses, pregnant rats were exposed to propylthiouracil (PTU, 0 or 3 ppm) to induce thyroid hormone insufficiency, and dams were permitted to give birth. PTU significantly reduced serum T4 in postnatal offspring. Consistent with our hypothesis, we show that tight junctions of the brain barriers were abnormal in PTU-exposed pups, and the blood-brain barrier exhibited increased permeability. Next, we performed serum microRNA Sequencing (miRNA-Seq) to identify noncoding RNAs that may reflect these neurodevelopmental disturbances. Of the differentially expressed miRNAs identified, 7 were upregulated in PTU-exposed pups. Validation by qRT-PCR shows that miR-495 and miR-543-3p were similarly upregulated in males and females. Interestingly, these miRNAs have been linked to cell junction dysfunction in other models, paralleling the identified abnormalities in the rat brain. Taken together, these data show that miR-495 and miR-543-3p may be novel in vivo biomarkers of thyroid-mediated developmental neurotoxicity.
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Affiliation(s)
- Katherine L O'Shaughnessy
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Aubrey L Sasser
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA
| | - Kiersten S Bell
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA
| | - Cal Riutta
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA
| | - Jermaine L Ford
- Chemical Characterization and Exposure Division, Center for Computational Toxicology and Exposure, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Rachel D Grindstaff
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Mary E Gilbert
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
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Gilbert ME, Hassan I, O'Shaughnessy KL, Wood C, Stoker TE, Riutta C, Ford JL. Ammonium perchlorate: serum dosimetry, neurotoxicity, and resilience of the neonatal rat thyroid system. Toxicol Sci 2024; 198:113-127. [PMID: 38145495 DOI: 10.1093/toxsci/kfad133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2023] Open
Abstract
The environmental contaminant perchlorate impairs the synthesis of thyroid hormones by reducing iodine uptake into the thyroid gland. Despite this known action, moderate doses of perchlorate do not significantly alter serum thyroid hormone in rat pups born to exposed dams. We examined perchlorate dosimetry and responsivity of the thyroid gland and brain in offspring following maternal exposure to perchlorate. Pregnant rat dams were delivered perchlorate in drinking water (0, 30, 100, 300, 1000 ppm) from gestational day 6 to postnatal day (PN) 21. Perchlorate was present in the placenta, milk, and serum, the latter declining in pups over the course of lactation. Serum and brain thyroid hormone were reduced in pups at birth but recovered to control levels by PN2. Dramatic upregulation of Nis was observed in the thyroid gland of the exposed pup. Despite the return of serum thyroid hormone to control levels by PN2, expression of several TH-responsive genes was altered in the PN14 pup brain. Contextual fear learning was unimpaired in the adults, supporting previous reports. Declining levels of serum perchlorate and a profound upregulation of Nis gene expression in the thyroid gland are consistent with the rapid return to the euthyroid state in the neonate. However, despite this recovery, thyroid hormone insufficiencies in serum and brain beginning in utero and present at birth appear sufficient to alter TH action in the fetus and subsequent trajectory of brain development. Biomarkers of that altered trajectory remain in the brain of the neonate, demonstrating that perchlorate is not devoid of effects on the developing brain.
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Affiliation(s)
- Mary E Gilbert
- Office of Research and Development, Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Iman Hassan
- Office of Air Quality, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Katherine L O'Shaughnessy
- Office of Research and Development, Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Carmen Wood
- Office of Research and Development, Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Tammy E Stoker
- Office of Research and Development, Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Cal Riutta
- Office of Research and Development, Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830, USA
| | - Jermaine L Ford
- Office of Research and Development, Center for Computational Toxicology and Exposure, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
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Hindrichs C, Walk T, Landsiedel R, Kamp H, Schneider S, Melching-Kollmuss S, Funk-Weyer D. Thyroid Hormone Metabolites Quantified in Pup and Adult Rat Cerebellum, Cortex and Whole-Brain Samples Using an Automated Online SPE-LC-MS/MS Method. Metabolites 2024; 14:61. [PMID: 38248864 PMCID: PMC10820277 DOI: 10.3390/metabo14010061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 01/23/2024] Open
Abstract
Changes in thyroid hormone (TH) levels in rat brain at early developmental stages are correlated with adverse effects on offspring development. To characterize the ability of substances to interfere with the TH concentrations in, e.g., rat brain, it is essential to know the mean TH concentrations in this tissue under control conditions. In this publication, an online solid-phase extraction (SPE) liquid chromatography (LC) tandem mass spectrometry (MS/MS) method was validated and used to measure TH metabolites (T4, T3, rT3, T2 and T1) in the brains of untreated rats. Data on TH concentrations in the whole brain and separate data from the cerebellum and the cortex are shown. The corresponding samples were gathered from young rats at postnatal days (PND) 4 and 21/22 and from adult rats. The results show inter alia the high accuracy and precision of the method, and LOQs of 0.02 ng/mL were determined for T1, T2 and rT3 and of 0.15 ng/mL for T3 and T4. Technical variability is low, as shown by the relative standard deviations of 7.5-20%. For our rat model, we found that T4, T3 and T2 concentrations rise from PND4 to PND21, whereas the rT3 concentration decreases; as well as there is no statistical difference between TH concentrations in the male and female rat brain. This method is suitable to analyze TH metabolites in the brain and build up a database of historical TH concentrations in control rats. Together, this yields a robust diagnostic tool to detect potentially adverse disturbances of TH homeostasis in the most vulnerable anatomic structure.
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Affiliation(s)
- Christiane Hindrichs
- BASF Metabolome Solutions GmbH, Tegeler Weg 33, 10589 Berlin, Germany; (C.H.); (T.W.)
- Department of Chemistry, Rheinland-Pfälzischen Technischen Universität Kaiserslautern-Landau, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern, Germany
| | - Tilmann Walk
- BASF Metabolome Solutions GmbH, Tegeler Weg 33, 10589 Berlin, Germany; (C.H.); (T.W.)
| | - Robert Landsiedel
- Experimental Toxicology and Ecology, BASF SE, Im Spitzenbusch 10, 67227 Frankenthal, Germany (S.S.)
- Pharmacology and Toxicology, Institute of Pharmacy, Free University of Berlin, 14195 Berlin, Germany
| | - Hennicke Kamp
- BASF Metabolome Solutions GmbH, Tegeler Weg 33, 10589 Berlin, Germany; (C.H.); (T.W.)
| | - Steffen Schneider
- Experimental Toxicology and Ecology, BASF SE, Im Spitzenbusch 10, 67227 Frankenthal, Germany (S.S.)
| | | | - Dorothee Funk-Weyer
- Experimental Toxicology and Ecology, BASF SE, Im Spitzenbusch 10, 67227 Frankenthal, Germany (S.S.)
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Stoker T, DeVane G, Buckalew A, Bailey J, Ford J, Murr A. Evaluation of the diphenyl herbicide, oxyfluorfen, for effects on thyroid hormones in the juvenile rat. Curr Res Toxicol 2023; 6:100146. [PMID: 38223505 PMCID: PMC10787258 DOI: 10.1016/j.crtox.2023.100146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 12/17/2023] [Accepted: 12/19/2023] [Indexed: 01/16/2024] Open
Abstract
Recently, oxyfluorfen, a pre- and post-emergent diphenyl ether herbicide, was identified in our laboratory as an inhibitor of iodide uptake by the sodium iodide symporter (NIS), the first key step in the synthesis of thyroid hormones (THs). This inhibition was observed in vitro, using both a human NIS engineered cell line (hNIS-HEK293T-EPA) and a rat thyroid follicular cell line (FRTL-5). Oxyfluorfen was found to be a potent inhibitor of NIS activity with an EC50 of approximately 2 µM in both cell lines with no observed cytotoxicity at any concentration tested up to 100 μM. The current research tested the hypothesis that oxyfluorfen alters circulating concentrations of THs. This hypothesis was first tested in a pilot study with both juvenile male and female rats exposed to oxyfluorfen for 4 days at 0, 125, 250 and 500 mg/kg/day. Once we identified that this short-term 4-day oxyfluorfen exposure suppressed both total serum thyroxine (T4) and triiodothyronine (T3) at all doses, we tested seven lower concentrations of oxyfluorfen (0.8125 to 62.5 mg/kg day) in an 8-day exposure paradigm to more closely evaluate the dose-response. We found that oxyfluorfen suppressed serum T4 with a LOEL of 3.25 mg/kg/day and T3 with a LOEL 62.5 mg/kg/day. Analytical chemistry of the serum showed an accumulation over time following oral exposure to oxyfluorfen in both the 4- and 8-day groups. Analytical chemistry of the thyroid glands in the 8-day study revealed higher accumulation in the thyroid as compared to the serum (2 to 3- fold at 62.5 mg/kg). No changes in thyroid weight or serum TSH were observed following the 8-day exposure. This study is the first to demonstrate an effect of oxyfluorfen on serum thyroid hormones in the rat. Additional studies are needed to further evaluate the effects on thyroid homeostasis with extended exposures and the potential implications of the observed effects.
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Affiliation(s)
- T.E. Stoker
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA, ORD, U.S. EPA, RTP, NC, United States
| | - G.D. DeVane
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA, ORD, U.S. EPA, RTP, NC, United States
- Oak Ridge Institute, Oakridge, TN, United States
| | - A.R. Buckalew
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA, ORD, U.S. EPA, RTP, NC, United States
| | - J.R. Bailey
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA, ORD, U.S. EPA, RTP, NC, United States
- Oak Ridge Institute, Oakridge, TN, United States
| | - J.L. Ford
- Advanced Analytical Chemistry Methods Branch, Center for Computational Toxicology & Exposure Chemical Characterization & Exposure Division, CCTE, ORD, U.S. EPA, RTP, NC, United States
| | - A.S. Murr
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, CPHEA, ORD, U.S. EPA, RTP, NC, United States
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Gilbert ME, O’Shaughnessy KL, Bell KS, Ford JL. Structural Malformations in the Neonatal Rat Brain Accompany Developmental Exposure to Ammonium Perchlorate. TOXICS 2023; 11:1027. [PMID: 38133428 PMCID: PMC10747616 DOI: 10.3390/toxics11121027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/11/2023] [Accepted: 12/11/2023] [Indexed: 12/23/2023]
Abstract
Environmental contaminants are often flagged as thyroid system disruptors due to their actions to reduce serum thyroxine (T4) in rodent models. The presence of a periventricular heterotopia (PVH), a brain malformation resulting from T4 insufficiency, has been described in response to T4 decrements induced by pharmaceuticals that reduce the hormone synthesis enzyme thyroperoxidase. In this report, we extend these observations to the environmental contaminant perchlorate, an agent that interferes with thyroid status by inhibiting iodine uptake into the thyroid gland. Pregnant rat dams were administered perchlorate in their drinking water (0, 30, 100, 300, 1000 ppm) from gestational day (GD) 6 until the weaning of pups on postnatal day (PN) 21. Serum T4 was reduced in dams and fetuses in late gestation and remained lower in lactating dams. Pup serum and brain T4, however, were not reduced beyond PN0, and small PVHs were evident in the brains of offspring when assessed on PN14. To emulate the developmental time window of the brain in humans, a second study was conducted in which pups from perchlorate-exposed dams were administered perchlorate orally from PN0 to PN6. This treatment reduced serum and brain T4 in the pup and resulted in large PVH. A third study extended the period of serum and brain TH suppression in pups by coupling maternal perchlorate exposure with maternal dietary iodine deficiency (ID). No PVHs were evident in the pups from ID dams, small PVHs were observed in the offspring of dams exposed to 300 ppm of perchlorate, and very large PVHs were present in the brains of pups born to dams receiving ID and perchlorate. These findings underscore the importance of the inclusion of serum hormone profiles in pregnant dams and fetuses in in vivo screens for thyroid-system-disrupting chemicals and indicate that chemical-induced decreases in fetal rat serum that resolve in the immediate postnatal period may still harbor considerable concern for neurodevelopment in humans.
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Affiliation(s)
- Mary E. Gilbert
- Centre for Public Health and Environmental Assessment, Office of Research and Development, Environmetal Protection Agency, Research Triangle Park, NC 27709, USA;
| | - Katherine L. O’Shaughnessy
- Centre for Public Health and Environmental Assessment, Office of Research and Development, Environmetal Protection Agency, Research Triangle Park, NC 27709, USA;
| | - Kiersten S. Bell
- College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA;
| | - Jermaine L. Ford
- National Center for Computational Toxicology, Office of Research and Development, Environmental Protection Agency, Research Triangle Park, NC 27709, USA;
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9
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Saberi R, Mirazi N, Amirahmadi S, Darbandi ZK, Vafaee F, Rajabian A, Hosseini M. Ameliorative effects of thiamin on learning behavior and memory dysfunction in a rat model of hypothyroidism: implication of oxidative stress and acetylcholinesterase. Metab Brain Dis 2023; 38:2603-2613. [PMID: 37906392 DOI: 10.1007/s11011-023-01317-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 10/23/2023] [Indexed: 11/02/2023]
Abstract
Hypothyroidism causes learning and memory impairment. Considering the neuroprotective properties of thiamine (Vitamin B1), this study was conducted to investigate the effects of thiamine on acetylcholinesterase (AChE) activity, oxidative damage, and memory deficits in hypothyroid rats.In this study, 50 rats (21 days old) were randomly divided into 5 groups and treated with propylthiouracil (0.05% in drinking water) and thiamine (50, 100, and 200 mg/kg, oral) for 7 weeks. Following that, Morris water maze (MWM) and passive avoidance (PA) tests were performed. Finally, oxidative stress indicators and AChE activity were measured in brain tissue.Treatment of hypothyroid rats with thiamine, especially at 100 and 200 mg/kg, alleviated the ability to remember the location of the platform as reflected by less time spent and distance to reach the platform, during the MWM test (P < 0.05 to P < 0.001). In the PA test, the latency to enter the dark chamber and light stay time were increased in rats who received thiamine compared to the hypothyroid group (P < 0.05 to P < 0.001). In addition, thiamine increased the levels of total thiol groups and superoxide dismutase while decreasing the levels of malondialdehyde and AChE.Our results suggest that thiamine supplementation could effectively improve memory loss in a rat model of hypothyroidism. The positive effects of thiamin on the learning and memory of hypothyroid rats may be due to amelioration of redox hemostasis and cholinergic disturbance.
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Affiliation(s)
- Rasul Saberi
- Department of Biology, Faculty of Basic Sciences, Bu-Ali Sina University, Hamedan, Iran
- Psychiatry and Behavioral Sciences Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Naser Mirazi
- Department of Biology, Faculty of Basic Sciences, Bu-Ali Sina University, Hamedan, Iran
| | - Sabiheh Amirahmadi
- Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
- Department of Physiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Zahra Kioumarsi Darbandi
- Psychiatry and Behavioral Sciences Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Farzaneh Vafaee
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Arezoo Rajabian
- Department of Internal Medicine, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
| | - Mahmoud Hosseini
- Psychiatry and Behavioral Sciences Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
- Department of Physiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
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10
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O'Shaughnessy KL, Hotchkiss MG, Buckalew AK, Murr AS, Gilbert ME, Stoker TE. An optimized radioimmunoassay for quantification of total serum thyroxine (T4) in fetal, neonatal, and pregnant rats. Neurotoxicol Teratol 2023; 100:107303. [PMID: 37777095 DOI: 10.1016/j.ntt.2023.107303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 09/05/2023] [Accepted: 09/26/2023] [Indexed: 10/02/2023]
Abstract
Identifying xenobiotics that interrupt the thyroid axis has significant public health implications, given that thyroid hormones are required for brain development. As such, some developmental and reproductive toxicology (DART) studies now require or recommend serum total thyroxine (T4) measurements in pregnant, lactating, and developing rats. However, serum T4 concentrations are normally low in the fetus and pup which makes quantification difficult. These challenges can be circumvented by technologies like mass spectrometry, but these approaches are expensive and not always widely available. To demonstrate the feasibility of measuring T4 using a commercially available assay, we examine technical replicates of rat serum samples measured both by liquid chromatography mass spectrometry (LC/MS/MS) and radioimmunoassay (RIA). These samples were obtained from rats on gestational day 20 (dams and fetuses) or postnatal day 5 (pups), following maternal exposure to the goitrogen propylthiouracil (0-3 ppm) to incrementally decrease T4. We show that with assay modification, it is possible to measure serum T4 using low sample volumes (25-50 μL) by an RIA, including in the GD20 fetus exposed to propylthiouracil. This proof-of-concept study demonstrates the technical feasibility of measuring serum T4 in DART studies.
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Affiliation(s)
- Katherine L O'Shaughnessy
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Michelle G Hotchkiss
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Angela K Buckalew
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Ashley S Murr
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Mary E Gilbert
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Tammy E Stoker
- Neurological and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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11
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Melching-Kollmuss S, Bothe K, Charlton A, Gangadharan B, Ghaffari R, Jacobi S, Marty S, Marxfeld HA, McInnes EF, Sauer UG, Sheets LP, Strupp C, Tinwell H, Wiemann C, Botham PA, van Ravenzwaay B. Towards a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny - Part IV: the ECETOC and CLE Proposal for a Thyroid Function-Related Neurodevelopmental Toxicity Testing and Assessment Scheme (Thyroid-NDT-TAS). Crit Rev Toxicol 2023; 53:339-371. [PMID: 37554099 DOI: 10.1080/10408444.2023.2231033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/22/2023] [Accepted: 06/22/2023] [Indexed: 08/10/2023]
Abstract
Following the European Commission Endocrine Disruptor Criteria, substances shall be considered as having endocrine disrupting properties if they (a) elicit adverse effects, (b) have endocrine activity, and (c) the two are linked by an endocrine mode-of-action (MoA) unless the MoA is not relevant for humans. A comprehensive, structured approach to assess whether substances meet the Endocrine Disruptor Criteria for the thyroid modality (EDC-T) is currently unavailable. Here, the European Centre for Ecotoxicology and Toxicology of Chemicals Thyroxine Task Force and CropLife Europe propose a Thyroid Function-Related Neurodevelopmental Toxicity Testing and Assessment Scheme (Thyroid-NDT-TAS). In Tier 0, before entering the Thyroid-NDT-TAS, all available in vivo, in vitro and in silico data are submitted to weight-of-evidence (WoE) evaluations to determine whether the substance of interest poses a concern for thyroid disruption. If so, Tier 1 of the Thyroid-NDT-TAS includes an initial MoA and human relevance assessment (structured by the key events of possibly relevant adverse outcome pathways) and the generation of supportive in vitro/in silico data, if relevant. Only if Tier 1 is inconclusive, Tier 2 involves higher-tier testing to generate further thyroid- and/or neurodevelopment-related data. Tier 3 includes the final MoA and human relevance assessment and an overarching WoE evaluation to draw a conclusion on whether, or not, the substance meets the EDC-T. The Thyroid-NDT-TAS is based on the state-of-the-science, and it has been developed to minimise animal testing. To make human safety assessments more accurate, it is recommended to apply the Thyroid-NDT-TAS during future regulatory assessments.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Ursula G Sauer
- Scientific Consultancy - Animal Welfare, Neubiberg, Germany
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12
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Liu M, Yu Z, Yang F, Zhao Z, Zhou M, Wang C, Zhang B, Liang G, Liu X, Shao J. BDE209-promoted Dio2 degradation in H4 glioma cells through the autophagy pathway, resulting in hypothyroidism and leading to neurotoxicity. Toxicology 2023:153581. [PMID: 37330034 DOI: 10.1016/j.tox.2023.153581] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 06/07/2023] [Accepted: 06/15/2023] [Indexed: 06/19/2023]
Abstract
Decabromodiphenyl ether (BDE209), the homologue with the highest number of brominates in polybrominated diphenyl ethers (PBDEs), is one of the most widespread environmental persistent organic pollutants (POPs) due to its mass production and extensive application in recent decades. BDE209 is neurotoxic, possibly related to its interference with the thyroid hormone (TH) system. However, the underlying molecular mechanisms of BDE209-induced TH interference and neurobehavioral disorders remains unknown. Here, we explored how BDE209 manipulated the major enzyme, human type II iodothyronine deiodinase (Dio2), that is most important in regulating local cerebral TH equilibrium by neuroglial cells, using an in vitro model of human glioma H4 cells. Clonogenic cell survival assay and LC/MS/MS analysis showed that BDE209 could induce chronic neurotoxicity by inducing TH interference. Co-IP assay, RT-qPCR and confocal assay identified that BDE209 destroyed the stability of Dio2 without affecting its expression, and promoted its binding to p62, thereby enhancing its autophagic degradation, thus causing TH metabolism disorder and neurotoxicity. Furthermore, molecular docking studies predicted that BDE209 could effectively suppress Dio2 activity by competing with tetraiodothyronine (T4). Collectively, our study demonstrates that BDE209-induced Dio2 degradation and loss of its enzymatic activity in neuroglial cells are the fundamental pathogenic basis for BDE209-mediated cerebral TH disequilibrium and neurotoxicity, providing a target of interest for further investigation using glial/neuronal cell co-culture system and in vivo models.
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Affiliation(s)
- Min Liu
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China; Neurology Department, Dalian University Affiliated Xinhua Hospital, Dalian, 116021, China
| | - Zhenlong Yu
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Fangyu Yang
- General Hospital of Northern Theater Command (General Hospital of Shenyang Military Command), Department of Neurosurgery, Shenyang, China
| | - Zikuang Zhao
- School of Pharmacy, Hangzhou Normal University, Hangzhou, 116000, China
| | - Meirong Zhou
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Chao Wang
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Baojing Zhang
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Guobiao Liang
- General Hospital of Northern Theater Command (General Hospital of Shenyang Military Command), Department of Neurosurgery, Shenyang, China.
| | - Xiaohui Liu
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China
| | - Jing Shao
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China; Liaoning Key Laboratory of Hematopoietic Stem Cell Transplantation and Translational Medicine; Liaoning Medical Center for Hematopoietic Stem Cell Transplantation; Dalian Key Laboratory of Hematology; Diamond Bay Institute of Hematology; Second Hospital of Dalian Medical University, Dalian, 116027, China.
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13
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Ford J, Riutta C, Kosian PA, O'Shaughessy K, Gilbert M. Reducing uncertainties in quantitative adverse outcome pathways by analysis of thyroid hormone in the neonatal rat brain. Toxicol Sci 2023; 193:192-203. [PMID: 37099719 PMCID: PMC10732312 DOI: 10.1093/toxsci/kfad040] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023] Open
Abstract
A number of xenobiotics interfere with thyroid hormone (TH) signaling. Although adequate supplies of TH are necessary for normal brain development, regulatory reliance on serum TH as proxies for brain TH insufficiency is fraught with significant uncertainties. A more direct causal linkage to neurodevelopmental toxicity induced by TH-system disrupting chemicals is to measure TH in the target organ of most concern, the brain. However, the phospholipid-rich matrix of brain tissue presents challenges for TH extraction and measurement. We report optimized analytical procedures to extract TH in brain tissue of rats with recoveries >80% and low detection limits for T3, rT3, and T4 (0.013, 0.033, and 0.028 ng/g, respectively). Recovery of TH is augmented by enhancing phospholipid separation from TH using an anion exchange column coupled with a stringent column wash. Quality control measures incorporating a matrix-matched calibration procedure revealed excellent recovery and consistency across a large number of samples. Application of optimized procedures revealed age-dependent increases in neonatal brain T4, T3, and rT3 on the day of birth (postnatal day, PN0), PN2, PN6, and PN14. No sex-dependent differences in brain TH were observed at these ages, and similar TH levels were evident in perfused versus non-perfused brains. Implementation of a robust and reliable method to quantify TH in the fetal and neonatal rat brain will aid in the characterization of the thyroid-dependent chemical interference on neurodevelopment. A brain- in addition to a serum-based metric will reduce uncertainties in assessment of hazard and risk on the developing brain posed by thyroid system-disrupting chemicals.
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Affiliation(s)
- Jermaine Ford
- Center for Computational Toxicology and Exposure, Chemical Characterization and Exposure Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Cal Riutta
- Oak Ridge Institute for Science Education, Oak Ridge, Tennessee 37830, USA
| | - Patricia A Kosian
- Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, US Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Katherine O'Shaughessy
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Mary Gilbert
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
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14
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Liu M, Yu Z, Zhao Z, Yang F, Zhou M, Wang C, Tian X, Zhang B, Liang G, Liu X, Shao J. MiR-24-3p/Dio3 axis is essential for BDE47 to induce local thyroid hormone disorder and neurotoxicity. Toxicology 2023; 491:153527. [PMID: 37116683 DOI: 10.1016/j.tox.2023.153527] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/21/2023] [Accepted: 04/25/2023] [Indexed: 04/30/2023]
Abstract
BDE47 (2,2,4,4-tetrabromodiphenyl ether) is a member of the most important congeners of polybrominated diphenyl ethers (PBDEs) and has been identified as a developmental, reproductive and nervous system toxicant and endocrine system disruptor due to its frequent detection in human tissue and environmental samples. Our preliminary work suggested that high- and low-level of bromodiphenyl ethers have different effects on neuronal cells with differential targets of actions on neural tissues. In this study, we presented the underlying mechanism of BDE47 neurotoxicity from the perspective of thyroid hormone (TH) metabolism using in vitro model of human SK-N-AS neuronal cells. BDE47 could induce local TH metabolism disorder in neuronal cells by inhibiting the expression of the main enzyme, human type III iodothyronine deiodinase (Dio3). Further elucidation revealed that BDE47 effectively up-regulating miR-24-3p, which binds to the 3'-UTR of Dio3 and inhibits its expression. In addition, BDE47 could also inhibit the deiodinase activity of Dio3. Collectively, our study demonstrates the molecular mechanism of BDE47 regulating Dio3-induced TH metabolism disorder through inducing miR-24-3p, providing new clues for the role of miRNAs in neurodevelopmental toxicity mediated by environmental pollutants.
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Affiliation(s)
- Min Liu
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China; Neurology Department, Dalian University Affiliated Xinhua Hospital, Dalian, 116021, China
| | - Zhenlong Yu
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Zikuang Zhao
- School of Pharmacy, Hangzhou Normal University, Hangzhou, 116000, China
| | - Fangyu Yang
- General Hospital of Northern Theater Command (General Hospital of Shenyang Military Command), Department of Neurosurgery, Shenyang, China
| | - Meirong Zhou
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Chao Wang
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Xiangge Tian
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Baojing Zhang
- College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Guobiao Liang
- General Hospital of Northern Theater Command (General Hospital of Shenyang Military Command), Department of Neurosurgery, Shenyang, China.
| | - Xiaohui Liu
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China
| | - Jing Shao
- Department of Environmental Health and Toxicology, School of Public Health, Dalian Medical University, Dalian, 116044, China; Liaoning Key Laboratory of Hematopoietic Stem Cell Transplantation and Translational Medicine; Liaoning Medical Center for Hematopoietic Stem Cell Transplantation; Dalian Key Laboratory of Hematology; Diamond Bay Institute of Hematology; Second Hospital of Dalian Medical University, Dalian, 116027, China.
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15
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Minami K, Suto H, Sato A, Ogata K, Kosaka T, Hojo H, Takahashi N, Tomiyama N, Fukuda T, Iwashita K, Aoyama H, Yamada T. Feasibility study for a downsized comparative thyroid assay with measurement of brain thyroid hormones and histopathology in rats: Case study with 6-propylthiouracil and sodium phenobarbital at high dose. Regul Toxicol Pharmacol 2022; 137:105283. [PMID: 36372265 DOI: 10.1016/j.yrtph.2022.105283] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 10/12/2022] [Accepted: 10/29/2022] [Indexed: 11/13/2022]
Abstract
Concern has been raised that thyroid hormone disruptors (THDs) may potentially interfere with the developing brain, but effects of mild suppression of maternal THs by environmental contaminants on neonatal brain development are not fully understood. The comparative thyroid assay (CTA) is a screening test for offspring THDs, but it requires several animals and is criticized that reliance on serum THs alone as predictive markers of brain malfunction is inadequate. To verify feasibility of the downsized CTA but additional examination of brain THs levels and histopathology, we commenced internal-validation studies. This paper presents the data of the study where 6-propylthiouracil (6-PTU, 10 ppm) and sodium phenobarbital (NaPB, 1000 ppm) were dosed by feeding from gestational days (GD)6-20, and from GD6 to lactation day 21. The modified CTA detected 6-PTU-induced severe (>70%) suppression of serum THs in dams, with >50% suppressed serum/brain TH levels in offspring and brain heterotopia in postnatal day 21 pups. The modified CTA also detected NaPB-induced mild (<35%) suppression of serum THs in dams, with mild (<35%) reduction of serum/brain TH levels in fetuses but not in pups. These findings suggest that the modified CTA may have a potential as a screening test for offspring THDs.
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Affiliation(s)
- Kenta Minami
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Hidenori Suto
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Akira Sato
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Keiko Ogata
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Tadashi Kosaka
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Hitoshi Hojo
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Naofumi Takahashi
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Naruto Tomiyama
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Takako Fukuda
- Bioscience Research Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka, 554-8558, Japan
| | - Katsumasa Iwashita
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Hiroaki Aoyama
- Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki, 303-0043, Japan
| | - Tomoya Yamada
- Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan.
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16
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Gölz L, Baumann L, Pannetier P, Braunbeck T, Knapen D, Vergauwen L. AOP Report: Thyroperoxidase Inhibition Leading to Altered Visual Function in Fish Via Altered Retinal Layer Structure. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2022; 41:2632-2648. [PMID: 35942927 DOI: 10.1002/etc.5452] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
Thyroid hormones (THs) are involved in the regulation of many important physiological and developmental processes, including vertebrate eye development. Thyroid hormone system-disrupting chemicals (THSDCs) may have severe consequences, because proper functioning of the visual system is a key factor for survival in wildlife. However, the sequence of events leading from TH system disruption (THSD) to altered eye development in fish has not yet been fully described. The development of this adverse outcome pathway (AOP) was based on an intensive literature review of studies that focused on THSD and impacts on eye development, mainly in fish. In total, approximately 120 studies (up to the end of 2021) were used in the development of this AOP linking inhibition of the key enzyme for TH synthesis, thyroperoxidase (TPO), to effects on retinal layer structure and visual function in fish (AOP-Wiki, AOP 363). In a weight-of-evidence evaluation, the confidence levels were overall moderate, with ample studies showing the link between reduced TH levels and altered retinal layer structure. However, some uncertainties about the underlying mechanism(s) remain. Although the current weight-of-evidence evaluation is based on fish, the AOP is plausibly applicable to other vertebrate classes. Through the re-use of several building blocks, this AOP is connected to the AOPs leading from TPO and deiodinase inhibition to impaired swim bladder inflation in fish (AOPs 155-159), together forming an AOP network describing THSD in fish. This AOP network addresses the lack of thyroid-related endpoints in existing fish test guidelines for the evaluation of THSDCs. Environ Toxicol Chem 2022;41:2632-2648. © 2022 SETAC.
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Affiliation(s)
- Lisa Gölz
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Lisa Baumann
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Pauline Pannetier
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
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17
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Jin Y, Qi G, Feng M, Yu D. The path via pathway-based approaches towards safety assessment: A concise review. Toxicol Appl Pharmacol 2022; 452:116195. [PMID: 35977605 DOI: 10.1016/j.taap.2022.116195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 07/26/2022] [Accepted: 08/10/2022] [Indexed: 10/15/2022]
Abstract
For decades, chemical safety assessment has been proposed to shift from animal testing to in vitro testing systems in response to the call for the 3R. In Europe, the answer was to combine various information sources in integrated testing strategies (ITS); In the US, it was in 2007 when the landmark report by the National Research Council put forward a vision of in vitro toxicity testing paradigm. Since then, efforts to develop pathway-based assessment framework have been on the track. In 2010, systems biology brought out a conceptual framework called adverse outcome pathway (AOP), which took one step further from toxicity pathway to regulatory toxicology. Computational modeling, high-throughput screening, high-content omics have all been approached to facilitate this progress. This paper briefly reviewed the achievement of pathway-based chemical assessment since 2007, discussed potential pitfalls and challenges that mechanism-driven chemical assessment may undergo, and presented future perspectives of safety assessment that is to be based on computational system biology.
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Affiliation(s)
- Yuan Jin
- School of Public Health, Qingdao University, Qingdao, China
| | - Guangshuai Qi
- School of Public Health, Qingdao University, Qingdao, China
| | - Meiyao Feng
- Department of Environmental Health, Qingdao Municipal Center for Disease Control and Prevention, Qingdao Institute of Preventive Medicine, Qingdao, China
| | - Dianke Yu
- School of Public Health, Qingdao University, Qingdao, China..
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18
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Marty MS, Sauer UG, Charlton A, Ghaffari R, Guignard D, Hallmark N, Hannas BR, Jacobi S, Marxfeld HA, Melching-Kollmuss S, Sheets LP, Urbisch D, Botham PA, van Ravenzwaay B. Towards a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny-part III: how is substance-mediated thyroid hormone imbalance in pregnant/lactating rats or their progeny related to neurodevelopmental effects? Crit Rev Toxicol 2022; 52:546-617. [PMID: 36519295 DOI: 10.1080/10408444.2022.2130166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This review investigated which patterns of thyroid- and brain-related effects are seen in rats upon gestational/lactational exposure to 14 substances causing thyroid hormone imbalance by four different modes-of-action (inhibition of thyroid peroxidase, sodium-iodide symporter and deiodinase activities, enhancement of thyroid hormone clearance) or to dietary iodine deficiency. Brain-related parameters included motor activity, cognitive function, acoustic startle response, hearing function, periventricular heterotopia, electrophysiology and brain gene expression. Specific modes-of-action were not related to specific patterns of brain-related effects. Based upon the rat data reviewed, maternal serum thyroid hormone levels do not show a causal relationship with statistically significant neurodevelopmental effects. Offspring serum thyroxine together with offspring serum triiodothyronine and thyroid stimulating hormone appear relevant to predict the likelihood for neurodevelopmental effects. Based upon the collated database, thresholds of ≥60%/≥50% offspring serum thyroxine reduction and ≥20% and statistically significant offspring serum triiodothyronine reduction indicate an increased likelihood for statistically significant neurodevelopmental effects; accuracies: 83% and 67% when excluding electrophysiology (and gene expression). Measurements of brain thyroid hormone levels are likely relevant, too. The extent of substance-mediated thyroid hormone imbalance appears more important than substance mode-of-action to predict neurodevelopmental impairment in rats. Pertinent research needs were identified, e.g. to determine whether the phenomenological offspring thyroid hormone thresholds are relevant for regulatory toxicity testing. The insight from this review shall be used to suggest a tiered testing strategy to determine whether gestational/lactational substance exposure may elicit thyroid hormone imbalance and potentially also neurodevelopmental effects.
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Affiliation(s)
| | - Ursula G Sauer
- Scientific Consultancy-Animal Welfare, Neubiberg, Germany
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19
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Gilbert ME, Hassan I, Wood C, O'Shaughnessy KL, Spring S, Thomas S, Ford J. Gestational Exposure to Perchlorate in the Rat: Thyroid Hormones in Fetal Thyroid Gland, Serum, and Brain. Toxicol Sci 2022; 188:117-130. [PMID: 35385113 PMCID: PMC10732305 DOI: 10.1093/toxsci/kfac038] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Iodine is essential for the production of thyroid hormones. Perchlorate is an environmental contaminant that interferes with iodine uptake into the thyroid gland to reduce thyroid hormone synthesis. As thyroid hormones are critical for brain development, exposure to perchlorate during pregnancy is of concern for the developing fetal brain. In this study, we (1) define profiles of thyroid hormone in the maternal and fetal compartments of pregnant rats in response to inhibition of the sodium-iodide symporter (NIS) by perchlorate and (2) expand inquiry previously limited to serum to include fetal thyroid gland and brain. Perchlorate was added to the drinking water (0, 1, 30, 300, and 1000 ppm) of pregnant rat dams from gestational days (GD) 6-20. On GD20, blood, thyroid gland, and brain were collected from the fetus and dam for thyroid hormone and molecular analyses. Thyroid gland and serum thyroid hormones were dose-dependently reduced, with steeper declines evident in the fetus than in the dam. The thyroid gland revealed perturbations of thyroid hormone-action with greater sensitivity in the fetus than the dam. Thyroid hormones and thyroid hormone-responsive gene expression were reduced in the fetal cortex portending effects on brain development. These findings are the first quantitative assessments of perchlorate-induced deficits in the fetal thyroid gland and fetal brain. We provide a conceptual framework to develop a quantitative NIS adverse outcome pathway for serum thyroid hormone deficits and the potential to impact the fetal brain. Such a framework may also serve to facilitate the translation of in vitro bioactivity to the downstream in vivo consequences of NIS inhibition in the developing fetus.
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Affiliation(s)
- Mary E Gilbert
- Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina 27711, USA
| | - Iman Hassan
- Office of Air Quality Planning and Standards, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Carmen Wood
- Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina 27711, USA
| | - Katherine L O'Shaughnessy
- Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina 27711, USA
| | - Stephanie Spring
- Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina 27711, USA
- Oak Ridge Institute for Student Education, Oak Ridge, Tennessee, USA
| | - Susan Thomas
- Centre for Public Health and Environmental Assessment, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina 27711, USA
- Oak Ridge Institute for Student Education, Oak Ridge, Tennessee, USA
| | - Jermaine Ford
- National Center for Computational Toxicology, US Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina, USA
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20
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Liu A, Han N, Munoz-Muriedas J, Bender A. Deriving time-concordant event cascades from gene expression data: A case study for Drug-Induced Liver Injury (DILI). PLoS Comput Biol 2022; 18:e1010148. [PMID: 35687583 PMCID: PMC9292124 DOI: 10.1371/journal.pcbi.1010148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 07/18/2022] [Accepted: 04/26/2022] [Indexed: 01/10/2023] Open
Abstract
Adverse event pathogenesis is often a complex process which compromises multiple events ranging from the molecular to the phenotypic level. In toxicology, Adverse Outcome Pathways (AOPs) aim to formalize this as temporal sequences of events, in which event relationships should be supported by causal evidence according to the tailored Bradford-Hill criteria. One of the criteria is whether events are consistently observed in a certain temporal order and, in this work, we study this time concordance using the concept of “first activation” as data-driven means to generate hypotheses on potentially causal mechanisms. As a case study, we analysed liver data from repeat-dose studies in rats from the TG-GATEs database which comprises measurements across eight timepoints, ranging from 3 hours to 4 weeks post-treatment. We identified time-concordant gene expression-derived events preceding adverse histopathology, which serves as surrogate readout for Drug-Induced Liver Injury (DILI). We find known mechanisms in DILI to be time-concordant, and show further that significance, frequency and log fold change (logFC) of differential expression are metrics which can additionally prioritize events although not necessary to be mechanistically relevant. Moreover, we used the temporal order of transcription factor (TF) expression and regulon activity to identify transcriptionally regulated TFs and subsequently combined this with prior knowledge on functional interactions to derive detailed gene-regulatory mechanisms, such as reduced Hnf4a activity leading to decreased expression and activity of Cebpa. At the same time, also potentially novel events are identified such as Sox13 which is highly significantly time-concordant and shows sustained activation over time. Overall, we demonstrate how time-resolved transcriptomics can derive and support mechanistic hypotheses by quantifying time concordance and how this can be combined with prior causal knowledge, with the aim of both understanding mechanisms of toxicity, as well as potential applications to the AOP framework. We make our results available in the form of a Shiny app (https://anikaliu.shinyapps.io/dili_cascades), which allows users to query events of interest in more detail. Understanding mechanisms from systems-scale biological data is of great relevance in toxicology as well as drug discovery; however how to generate causal hypotheses instead of correlations is by no means clear. In this work, we study the conserved temporal order of events and present an automatable framework to quantify and characterize time concordance across a large set of time-series. We apply this concept to events derived from time-resolved gene expression and histopathology from the TG-GATEs in vivo liver data as a case study. We were able to recover known events involved in the pathogenesis of Drug-Induced Liver Injury (DILI), and identify potentially novel pathway and transcription factors (TFs) which precede adverse histopathology. As complementary sources of evidence for causality, we additionally show how time concordance and prior knowledge on plausible interactions between TFs can be combined to derive causal hypotheses on the TFs’ mode of regulation and interaction partners. Overall, the results derived in our case study can serve as valuable hypothesis-free starting points for the development of Adverse Outcome Pathways for DILI, and demonstrate that our approach provides a novel angle to prioritize mechanistically relevant events.
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Affiliation(s)
- Anika Liu
- Milner Therapeutics Institute, University of Cambridge, Cambridge, United Kingdom
- Systems Modelling and Translational Biology, Data and Computational Sciences, GSK, London, United Kingdom
- Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (AL); (AB)
| | - Namshik Han
- Milner Therapeutics Institute, University of Cambridge, Cambridge, United Kingdom
- Cambridge Centre for AI in Medicine, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Jordi Munoz-Muriedas
- Systems Modelling and Translational Biology, Data and Computational Sciences, GSK, London, United Kingdom
- Computer-Aided Drug Design, UCB, Slough, United Kingdom
| | - Andreas Bender
- Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (AL); (AB)
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21
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Tebby C, Gao W, Delp J, Carta G, van der Stel W, Leist M, Jennings P, van de Water B, Bois FY. A quantitative AOP of mitochondrial toxicity based on data from three cell lines. Toxicol In Vitro 2022; 81:105345. [PMID: 35278637 DOI: 10.1016/j.tiv.2022.105345] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/22/2022] [Accepted: 03/07/2022] [Indexed: 11/30/2022]
Abstract
Adverse Outcome Pathways (AOPs) are increasingly used to support the integration of in vitro data in hazard assessment for chemicals. Quantitative AOPs (qAOPs) use mathematical models to describe the relationship between key events (KEs). In this paper, data obtained in three cell lines, LHUMES, HepG2 and RPTEC/TERT1, using similar experimental protocols, was used to calibrate a qAOP of mitochondrial toxicity for two chemicals, rotenone and deguelin. The objectives were to determine whether the same qAOP could be used for the three cell types, and to test chemical-independence by cross-validation with a dataset obtained on eight other chemicals in LHUMES cells. Repeating the calibration approach for both chemicals in three cell lines highlighted various practical difficulties. Even when the same readouts of KEs are measured, the mathematical functions used to describe the key event relationships may not be the same. Cross-validation in LHUMES cells was attempted by estimating chemical-specific potency at the molecular initiating events and using the rest of the calibrated qAOP to predict downstream KEs: toxicity of azoxystrobin, carboxine, mepronil and thifluzamide was underestimated. Selection of most relevant readouts and accurate characterization of the molecular initiating event for cross-validation are critical when designing in vitro experiments targeted at calibrating qAOPs.
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Affiliation(s)
- Cleo Tebby
- Experimental Toxicology and Modeling (TEAM) Unit, Ineris, rue Jacques Taffanel, 60550 Verneuil-en-Halatte, France.
| | - Wang Gao
- Experimental Toxicology and Modeling (TEAM) Unit, Ineris, rue Jacques Taffanel, 60550 Verneuil-en-Halatte, France; Applied Mathematics Laboratory (LMAC EA 2222), Université Technologique de Compiègne (UTC), 57 avenue de Landshut, 60203 Compiègne Cedex, France
| | - Johannes Delp
- In Vitro Toxicology and Biomedicine, Department inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78464, Konstanz, Germany; Cooperative Doctorate College InViTe, University of Konstanz, Konstanz, Germany
| | - Giada Carta
- Division of Molecular and Computational Toxicology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Wanda van der Stel
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, the Netherlands
| | - Marcel Leist
- In Vitro Toxicology and Biomedicine, Department inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78464, Konstanz, Germany
| | - Paul Jennings
- Division of Molecular and Computational Toxicology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Bob van de Water
- Division of Drug Discovery and Safety, Leiden Academic Centre of Drug Research, Leiden University, Leiden, the Netherlands
| | - Frederic Y Bois
- Experimental Toxicology and Modeling (TEAM) Unit, Ineris, rue Jacques Taffanel, 60550 Verneuil-en-Halatte, France; Certara, Simcyp, Sheffield, United Kingdom
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22
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Jin Y, Qi G, Shou Y, Li D, Liu Y, Guan H, Zhang Q, Chen S, Luo J, Xu L, Li C, Ma W, Chen N, Zheng Y, Yu D. High throughput data-based, toxicity pathway-oriented development of a quantitative adverse outcome pathway network linking AHR activation to lung damages. JOURNAL OF HAZARDOUS MATERIALS 2022; 425:128041. [PMID: 34906874 DOI: 10.1016/j.jhazmat.2021.128041] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 12/05/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
The quantitative adverse outcome pathway (qAOP) is proposed to inform dose-responses at multiple biological levels for the purpose of toxicity prediction. So far, qAOP models concerning human health are scarce. Previously, we proposed 5 key molecular pathways that led aryl hydrogen receptor (AHR) activation to lung damages. The present study assembled an AOP network based on the gene expression signatures of these toxicity pathways, and validated the network using publicly available high throughput data combined with machine learning models. In addition, the AOP network was quantitatively evaluated with omics approaches and bioassays, using 16HBE-CYP1A1 cells exposed to benzo(a)pyrene (BaP), a prototypical AHR activator. Benchmark dose (BMD) analysis of transcriptomics revealed that AHR gene held the lowest BMD value, whereas AHR pathway held the lowest point of departure (PoD) compared to the other 4 pathways. Targeted bioassays were further performed to quantitatively understand the cellular responses, including ROS generation, DNA damage, interleukin-6 production, and extracellular matrix increase marked by collagen expression. Eventually, response-response relationships were plotted using nonlinear model fitting. The present study developed a highly reliable AOP model concerning human health, and validated as well as quantitatively evaluated it, and such a method is likely to be adoptable for risk assessment.
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Affiliation(s)
- Yuan Jin
- School of Public Health, Qingdao University, Qingdao, China
| | - Guangshuai Qi
- School of Public Health, Qingdao University, Qingdao, China
| | - Yingqing Shou
- School of Public Health, Qingdao University, Qingdao, China
| | - Daochuan Li
- School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Yuzhen Liu
- School of Public Health, Qingdao University, Qingdao, China
| | - Heyuan Guan
- School of Public Health, Qingdao University, Qingdao, China
| | - Qianqian Zhang
- School of Public Health, Qingdao University, Qingdao, China
| | - Shen Chen
- School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Jiao Luo
- School of Public Health, Qingdao University, Qingdao, China
| | - Lin Xu
- School of Public Health, Qingdao University, Qingdao, China
| | - Chuanhai Li
- School of Public Health, Qingdao University, Qingdao, China
| | - Wanli Ma
- School of Public Health, Qingdao University, Qingdao, China
| | - Ningning Chen
- School of Public Health, Qingdao University, Qingdao, China
| | - Yuxin Zheng
- School of Public Health, Qingdao University, Qingdao, China
| | - Dianke Yu
- School of Public Health, Qingdao University, Qingdao, China.
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23
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Haselman JT, Olker JH, Kosian PA, Korte JJ, Denny JS, Tietge JE, Hornung MW, Degitz SJ. Characterization of the mechanistic linkages between iodothyronine deiodinase inhibition and impaired thyroid-mediated growth and development in Xenopus laevis using iopanoic acid. Toxicol Sci 2022; 187:139-149. [PMID: 35179606 PMCID: PMC9254162 DOI: 10.1093/toxsci/kfac014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Iodothyronine deiodinases (DIO) are key enzymes that influence tissue-specific thyroid hormone levels during thyroid-mediated amphibian metamorphosis. Within the larger context of evaluating chemicals for thyroid system disrupting potential, chemical activity toward DIOs is being evaluated using high-throughput in vitro screening assays as part of U.S. EPA's ToxCast program. However, existing data gaps preclude any inferences between in vitro chemical inhibition of DIOs and in vivo outcomes relevant to ecological risk assessment. This study aimed to generate targeted data in a laboratory model species (Xenopus laevis) using a model DIO inhibitor, iopanoic acid (IOP), to characterize linkages between in vitro potency, in vivo biochemical responses, and adverse organismal outcomes. In vitro potency of IOP toward DIOs was evaluated using previously developed in vitro screening assays, which showed concentration-dependent inhibition of human DIO1 (IC50: 97 µM) and DIO2 (IC50: 231 µM) but did not inhibit human or X. laevis DIO3 under the assay conditions. In vivo exposure of larval X. laevis to 0, 2.6, 5.3 and 10.5 µM IOP caused thyroid-related biochemical profiles in the thyroid gland and plasma consistent with hyperthyroxinemia but resulted in delayed metamorphosis and significantly reduced growth in the highest two exposure concentrations. Independent evaluations of dio gene expression ontogeny, together with existing literature, supported interpretation of IOP-mediated effects resulting in a proposed adverse outcome pathway for DIO2 inhibition leading to altered amphibian metamorphosis. This study highlights the types of mechanistic data needed to move toward predicting in vivo outcomes of regulatory concern from in vitro bioactivity data.
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Affiliation(s)
- Jonathan T Haselman
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Jennifer H Olker
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Patricia A Kosian
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Joseph J Korte
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Jeffrey S Denny
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Joseph E Tietge
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Michael W Hornung
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Sigmund J Degitz
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
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24
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Paini A, Campia I, Cronin MT, Asturiol D, Ceriani L, Exner TE, Gao W, Gomes C, Kruisselbrink J, Martens M, Meek MB, Pamies D, Pletz J, Scholz S, Schüttler A, Spînu N, Villeneuve DL, Wittwehr C, Worth A, Luijten M. Towards a qAOP framework for predictive toxicology - Linking data to decisions. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 21:100195. [PMID: 35211660 PMCID: PMC8850654 DOI: 10.1016/j.comtox.2021.100195] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/23/2021] [Accepted: 10/09/2021] [Indexed: 12/22/2022]
Abstract
The adverse outcome pathway (AOP) is a conceptual construct that facilitates organisation and interpretation of mechanistic data representing multiple biological levels and deriving from a range of methodological approaches including in silico, in vitro and in vivo assays. AOPs are playing an increasingly important role in the chemical safety assessment paradigm and quantification of AOPs is an important step towards a more reliable prediction of chemically induced adverse effects. Modelling methodologies require the identification, extraction and use of reliable data and information to support the inclusion of quantitative considerations in AOP development. An extensive and growing range of digital resources are available to support the modelling of quantitative AOPs, providing a wide range of information, but also requiring guidance for their practical application. A framework for qAOP development is proposed based on feedback from a group of experts and three qAOP case studies. The proposed framework provides a harmonised approach for both regulators and scientists working in this area.
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Affiliation(s)
- Alicia Paini
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | - Ivana Campia
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | | | - David Asturiol
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | | | - Thomas E. Exner
- Edelweiss Connect GmbH, Technology Park Basel, Basel, Switzerland
| | - Wang Gao
- Institut National de l'Environnement Industriel et des Risques (INERIS), Verneuil-en-Halatte, France
| | | | | | | | | | - David Pamies
- Department of Physiology, Lausanne and Swiss Centre for Applied Human Toxicology (SCAHT), University of Lausanne, Lausanne, Switzerland
| | - Julia Pletz
- Liverpool John Moores University, Liverpool, United Kingdom
| | - Stefan Scholz
- Helmholtz Centre for Environmental Research GmbH – UFZ, Leipzig, Germany
| | - Andreas Schüttler
- Helmholtz Centre for Environmental Research GmbH – UFZ, Leipzig, Germany
| | - Nicoleta Spînu
- Liverpool John Moores University, Liverpool, United Kingdom
| | - Daniel L. Villeneuve
- US Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, Duluth, MN, USA
| | | | - Andrew Worth
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | - Mirjam Luijten
- National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
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25
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Ramhøj L, Svingen T, Frädrich C, Rijntjes E, Wirth EK, Pedersen K, Köhrle J, Axelstad M. Perinatal exposure to the thyroperoxidase inhibitors methimazole and amitrole perturbs thyroid hormone system signaling and alters motor activity in rat offspring. Toxicol Lett 2021; 354:44-55. [PMID: 34757178 DOI: 10.1016/j.toxlet.2021.10.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/15/2021] [Accepted: 10/26/2021] [Indexed: 01/12/2023]
Abstract
Disruption of the thyroid hormone system during development can impair brain development and cause irreversible damage. Some thyroid hormone system disruptors act by inhibiting the thyroperoxidase (TPO) enzyme, which is key to thyroid hormone synthesis. For the potent TPO-inhibiting drug propylthiouracil (PTU) this has been shown to result in thyroid hormone system disruption and altered brain development in animal studies. However, an outstanding question is which chemicals beside PTU can cause similar effects on brain development and to what degree thyroid hormone insufficiency must be induced to be able to measure adverse effects in rats and their offspring. To start answering these questions, we performed a perinatal exposure study in pregnant rats with two TPO-inhibitors: the drug methimazole (MMI) and the triazole herbicide amitrole. The study involved maternal exposure from gestational day 7 through to postnatal day 22, to MMI (8 and 16 mg/kg body weight/day) or amitrole (25 and 50 mg/kg body weight/day). Both MMI and amitrole reduced serum T4 concentrations in a dose-dependent manner in dams and offspring, with a strong activation of the hypothalamic-pituitary-thyroid axis. This reduction in serum T4 led to decreased thyroid hormone-mediated gene expression in the offspring's brains and caused adverse effects on brain function, seen as hyperactivity and decreased habituation in preweaning pups. These dose-dependent effects induced by MMI and amitrole are largely the same as those observed with PTU. This demonstrates that potent TPO-inhibitors can induce effects on brain development in rats and that these effects are driven by T4 deficiency. This knowledge will aid the identification of TPO-inhibiting thyroid hormone system disruptors in a regulatory context and can serve as a starting point in search of more sensitive markers of developmental thyroid hormone system disruption.
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Affiliation(s)
- Louise Ramhøj
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Terje Svingen
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Caroline Frädrich
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Institut für Experimentelle Endokrinologie, 10115, Berlin, Germany
| | - Eddy Rijntjes
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Institut für Experimentelle Endokrinologie, 10115, Berlin, Germany
| | - Eva K Wirth
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, Department of Endocrinology and Metabolism and Charité Center for Cardiovascular Research, 10115, Berlin, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Berlin, Germany
| | - Katrine Pedersen
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Josef Köhrle
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Institut für Experimentelle Endokrinologie, 10115, Berlin, Germany
| | - Marta Axelstad
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark.
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26
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Gilbert ME, O'Shaughnessy KL, Thomas SE, Riutta C, Wood CR, Smith A, Oshiro WO, Ford RL, Hotchkiss MG, Hassan I, Ford JL. Thyroid Disruptors: Extrathyroidal Sites of Chemical Action and Neurodevelopmental Outcome-An Examination Using Triclosan and Perfluorohexane Sulfonate. Toxicol Sci 2021; 183:195-213. [PMID: 34460931 PMCID: PMC9038230 DOI: 10.1093/toxsci/kfab080] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Many xenobiotics are identified as potential thyroid disruptors due to their action to reduce circulating levels of thyroid hormone, most notably thyroxine (T4). Developmental neurotoxicity is a primary concern for thyroid disrupting chemicals yet correlating the impact of chemically induced changes in serum T4 to perturbed brain development remains elusive. A number of thyroid-specific neurodevelopmental assays have been proposed, based largely on the model thyroid hormone synthesis inhibitor propylthiouracil (PTU). This study examined whether thyroid disrupting chemicals acting distinct from synthesis inhibition would result in the same alterations in brain as expected with PTU. The perfluoroalkyl substance perfluorohexane sulfonate (50 mg/kg/day) and the antimicrobial Triclosan (300 mg/kg/day) were administered to pregnant rats from gestational day 6 to postnatal day (PN) 21, and a number of PTU-defined assays for neurotoxicity evaluated. Both chemicals reduced serum T4 but did not increase thyroid stimulating hormone. Both chemicals increased expression of hepatic metabolism genes, while thyroid hormone-responsive genes in the liver, thyroid gland, and brain were largely unchanged. Brain tissue T4 was reduced in newborns, but despite persistent T4 reductions in serum, had recovered in the PN6 pup brain. Neither treatment resulted in a low dose PTU-like phenotype in either brain morphology or neurobehavior, raising questions for the interpretation of serum biomarkers in regulatory toxicology. They further suggest that reliance on serum hormones as prescriptive of specific neurodevelopmental outcomes may be too simplistic and to understand thyroid-mediated neurotoxicity we must expand our thinking beyond that which follows thyroid hormone synthesis inhibition.
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Affiliation(s)
- Mary E Gilbert
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Katherine L O'Shaughnessy
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Susan E Thomas
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830, USA
| | - Cal Riutta
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830, USA
| | - Carmen R Wood
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Alicia Smith
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830, USA
| | - Wendy O Oshiro
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Richard L Ford
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830, USA
| | - Michelle Gatien Hotchkiss
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Iman Hassan
- Center for Public Health and Environmental Assessment, Public Health Integrated Toxicology Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
| | - Jermaine L Ford
- Center for Computational Toxicology and Exposure, Chemical Characterization and Exposure Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709, USA
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27
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Huisinga M, Bertrand L, Chamanza R, Damiani I, Engelhardt J, Francke S, Freyberger A, Harada T, Harleman J, Kaufmann W, Keane K, Köhrle J, Lenz B, Marty MS, Melching-Kollmuss S, Palazzi X, Pohlmeyer-Esch G, Popp A, Rosol TJ, Strauss V, Van den Brink-Knol H, Wood CE, Yoshida M. Adversity Considerations for Thyroid Follicular Cell Hypertrophy and Hyperplasia in Nonclinical Toxicity Studies: Results From the 6th ESTP International Expert Workshop. Toxicol Pathol 2021; 48:920-938. [PMID: 33334259 DOI: 10.1177/0192623320972009] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The European Society of Toxicologic Pathology organized an expert workshop in May 2018 to address adversity considerations related to thyroid follicular cell hypertrophy and/or hyperplasia (FCHH), which is a common finding in nonclinical toxicity studies that can have important implications for risk assessment of pharmaceuticals, food additives, and environmental chemicals. The broad goal of the workshop was to facilitate better alignment in toxicologic pathology and regulatory sciences on how to determine adversity of FCHH. Key objectives were to describe common mechanisms leading to thyroid FCHH and potential functional consequences; provide working criteria to assess adversity of FCHH in context of associated findings; and describe additional methods and experimental data that may influence adversity determinations. The workshop panel was comprised of representatives from the European Union, Japan, and the United States. Participants shared case examples illustrating issues related to adversity assessments of thyroid changes. Provided here are summary discussions, key case presentations, and panel recommendations. This information should increase consistency in the interpretation of adverse changes in the thyroid based on pathology findings in nonclinical toxicity studies, help integrate new types of biomarker data into the review process, and facilitate a more systematic approach to communicating adversity determinations in toxicology reports.
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Affiliation(s)
| | - Lise Bertrand
- 57146Charles River Laboratories, Saint-Germain-Nuelles, France
| | - Ronnie Chamanza
- 50148Janssen Pharmaceutical Companies of Johnson & Johnson, Beerse, Belgium
| | | | | | - Sabine Francke
- Center for Food Safety and Applied Nutrition (CFSAN), 4137US Food and Drug Administration, College Park, MD, USA
| | | | | | | | | | | | - Josef Köhrle
- 72217Charité University Medicine Berlin, Berlin, Germany
| | - Barbara Lenz
- Roche Pharma Research and Development, Basel, Switzerland
| | - M Sue Marty
- 540144The Dow Chemical Company, Midland, MI, USA
| | | | | | | | | | | | | | | | - Charles E Wood
- 6893Boehringer Ingelheim Pharmaceuticals Inc, Ridgefield, CT, USA
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28
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Haselman JT, Olker JH, Kosian PA, Korte JJ, Swintek JA, Denny JS, Nichols JW, Tietge JE, Hornung MW, Degitz SJ. Targeted Pathway-based In Vivo Testing Using Thyroperoxidase Inhibition to Evaluate Plasma Thyroxine as a Surrogate Metric of Metamorphic Success in Model Amphibian Xenopus laevis. Toxicol Sci 2021; 175:236-250. [PMID: 32176285 DOI: 10.1093/toxsci/kfaa036] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chemical safety evaluation is in the midst of a transition from traditional whole-animal toxicity testing to molecular pathway-based in vitro assays and in silico modeling. However, to facilitate the shift in reliance on apical effects for risk assessment to predictive surrogate metrics having characterized linkages to chemical mechanisms of action, targeted in vivo testing is necessary to establish these predictive relationships. In this study, we demonstrate a means to predict thyroid-related metamorphic success in the model amphibian Xenopus laevis using relevant biochemical measurements during early prometamorphosis. The adverse outcome pathway for thyroperoxidase inhibition leading to altered amphibian metamorphosis was used to inform a pathway-based in vivo study design that generated response-response relationships. These causal relationships were used to develop Bayesian probabilistic network models that mathematically determine conditional dependencies between biochemical nodes and support the predictive capability of the biochemical profiles. Plasma thyroxine concentrations were the most predictive of metamorphic success with improved predictivity when thyroid gland sodium-iodide symporter gene expression levels (a compensatory response) were used in conjunction with plasma thyroxine as an additional regressor. Although thyroid-mediated amphibian metamorphosis has been studied for decades, this is the first time a predictive relationship has been characterized between plasma thyroxine and metamorphic success. Linking these types of biochemical surrogate metrics to apical outcomes is vital to facilitate the transition to the new paradigm of chemical safety assessments.
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Affiliation(s)
- Jonathan T Haselman
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Jennifer H Olker
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Patricia A Kosian
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Joseph J Korte
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Joseph A Swintek
- Badger Technical Services, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Jeffrey S Denny
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - John W Nichols
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Joseph E Tietge
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Michael W Hornung
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
| | - Sigmund J Degitz
- Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Duluth, Minnesota 55804
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Marty S, Beekhuijzen M, Charlton A, Hallmark N, Hannas BR, Jacobi S, Melching-Kollmuss S, Sauer UG, Sheets LP, Strauss V, Urbisch D, Botham PA, van Ravenzwaay B. Towards a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny - part II: how can key events of relevant adverse outcome pathways be addressed in toxicological assessments? Crit Rev Toxicol 2021; 51:328-358. [PMID: 34074207 DOI: 10.1080/10408444.2021.1910625] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The current understanding of thyroid-related adverse outcome pathways (AOPs) with adverse neurodevelopmental outcomes in mammals has been reviewed. This served to establish if standard rodent toxicity test methods and in vitro assays allow identifying thyroid-related modes-of-action potentially leading to adverse neurodevelopmental outcomes, and the human relevance of effects - in line with the European Commission's Endocrine Disruptor Criteria. The underlying hypothesis is that an understanding of the key events of relevant AOPs provides insight into differences in incidence, magnitude, or species sensitivity of adverse outcomes. The rodent studies include measurements of serum thyroid hormones, thyroid gland pathology and neurodevelopmental assessments, but do not directly inform on specific modes-of-action. Opportunities to address additional non-routine parameters reflecting critical events of AOPs in toxicological assessments are presented. These parameters appear relevant to support the identification of specific thyroid-related modes-of-action, provided that prevailing technical limitations are overcome. Current understanding of quantitative key event relationships is often weak, but would be needed to determine if the triggering of a molecular initiating event will ultimately result in an adverse outcome. Also, significant species differences in all processes related to thyroid hormone signalling are evident, but the biological implications thereof (including human relevance) are often unknown. In conclusion, careful consideration of the measurement (e.g. timing, method) and interpretation of additional non-routine parameters is warranted. These findings will be used in a subsequent paper to propose a testing strategy to identify if a substance may elicit maternal thyroid hormone imbalance and potentially also neurodevelopmental effects in the progeny.
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Affiliation(s)
- Sue Marty
- The Dow Chemical Company, Midland, MI, USA
| | | | | | | | | | | | | | - Ursula G Sauer
- Scientific Consultancy - Animal Welfare, Neubiberg, Germany
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30
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A review of species differences in the control of, and response to, chemical-induced thyroid hormone perturbations leading to thyroid cancer. Arch Toxicol 2021; 95:807-836. [PMID: 33398420 DOI: 10.1007/s00204-020-02961-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 11/26/2020] [Indexed: 12/13/2022]
Abstract
This review summarises the current state of knowledge regarding the physiology and control of production of thyroid hormones, the effects of chemicals in perturbing their synthesis and release that result in thyroid cancer. It does not consider the potential neurodevelopmental consequences of low thyroid hormones. There are a number of known molecular initiating events (MIEs) that affect thyroid hormone synthesis in mammals and many chemicals are able to activate multiple MIEs simultaneously. AOP analysis of chemical-induced thyroid cancer in rodents has defined the key events that predispose to the development of rodent cancer and many of these will operate in humans under appropriate conditions, if they were exposed to high enough concentrations of the affecting chemicals. There are conditions however that, at the very least, would indicate significant quantitative differences in the sensitivity of humans to these effects, with rodents being considerably more sensitive to thyroid effects by virtue of differences in the biology, transport and control of thyroid hormones in these species as opposed to humans where turnover is appreciably lower and where serum transport of T4/T3 is different to that operating in rodents. There is heated debate around claimed qualitative differences between the rodent and human thyroid physiology, and significant reservations, both scientific and regulatory, still exist in terms of the potential neurodevelopmental consequences of low thyroid hormone levels at critical windows of time. In contrast, the situation for the chemical induction of thyroid cancer, through effects on thyroid hormone production and release, is less ambiguous with both theoretical, and actual data, showing clear dose-related thresholds for the key events predisposing to chemically induced thyroid cancer in rodents. In addition, qualitative differences in transport, and quantitative differences in half life, catabolism and turnover of thyroid hormones, exist that would not operate under normal situations in humans.
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31
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Hassan I, El-Masri H, Ford J, Brennan A, Handa S, Paul Friedman K, Gilbert ME. Extrapolating In Vitro Screening Assay Data for Thyroperoxidase Inhibition to Predict Serum Thyroid Hormones in the Rat. Toxicol Sci 2020; 173:280-292. [PMID: 31697382 DOI: 10.1093/toxsci/kfz227] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Thyroperoxidase (TPO) is an enzyme essential for thyroid hormone (TH) synthesis and a target site for a number of xenobiotics that disrupt TH homeostasis. An in vitro high-throughput screening assay for TPO inhibition, the Amplex UltraRed-TPO (AUR-TPO), has been used to screen the ToxCast chemical libraries for this action. Output from this assay would be most useful if it could be readily translated into an in vivo response, namely a reduction of TH in serum. To this end, the relationship between TPO inhibition in vitro and serum TH decreases was examined in rats exposed to 2 classic TPO inhibitors, propylthiouracil (PTU) and methimazole (MMI). Serum and gland PTU, MMI, and TH levels were quantified using tandem liquid chromatography mass spectrometry. Thyroperoxidase activity was determined in thyroid gland microsomes treated with PTU or MMI in vitro and ex vivo from thyroid gland microsomes prepared from exposed animals. A quantitative model was constructed by contrasting in vitro and ex vivo AUR-TPO results and the in vivo time-course and dose-response analysis. In vitro:ex vivo correlations of AUR-TPO outputs indicated that less than 30% inhibition of TPO in vitro was sufficient to reduce serum T4 by 20%, a degree of regulatory significance. Although further testing of model estimates using other TPO inhibitors is essential for verification of these initial findings, the results of this study provide a means to translate in vitro screening assay results into predictions of in vivo serum T4 changes to inform risk assessment.
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Affiliation(s)
- Iman Hassan
- Toxicity Assessment Division.,National Health and Environmental Effects Research Laboratory
| | - Hisham El-Masri
- National Health and Environmental Effects Research Laboratory.,Integrated Systems Toxicology Division
| | - Jermaine Ford
- National Health and Environmental Effects Research Laboratory.,Analytical Chemistry Research Core/Research Cores Unit, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Amanda Brennan
- National Health and Environmental Effects Research Laboratory.,Analytical Chemistry Research Core/Research Cores Unit, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Sakshi Handa
- National Health and Environmental Effects Research Laboratory.,Integrated Systems Toxicology Division.,Oak Ridge Institute for Science Education, Oak Ridge, Tennessee
| | - Katie Paul Friedman
- National Center for Computational Toxicology, US Environmental Protection Agency, Research Triangle Park, North Carolina, 27711
| | - Mary E Gilbert
- Toxicity Assessment Division.,National Health and Environmental Effects Research Laboratory
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Lewis RW, Hill T, Corton JC. A set of six Gene expression biomarkers and their thresholds identify rat liver tumorigens in short-term assays. Toxicology 2020; 443:152547. [PMID: 32755643 PMCID: PMC10439517 DOI: 10.1016/j.tox.2020.152547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/23/2020] [Accepted: 07/28/2020] [Indexed: 02/01/2023]
Abstract
Traditional methods for cancer risk assessment are retrospective, resource-intensive, and not feasible for the vast majority of environmental chemicals. In earlier studies, we used a set of six biomarkers to accurately identify liver tumorigens in transcript profiles derived from chemically-treated rats using either a Toxicological Priority Index (ToxPi) approach or using derived biomarker thresholds for cancer. The biomarkers consisting of 7-113 genes are used to predict the most common liver cancer molecular initiating events: genotoxicity, cytotoxicity and activation of the xenobiotic receptors AhR, CAR, ER, and PPARα. In the present study, we apply and evaluate the performance of these methods for cancer prediction in an independent rat liver study of 44 chemicals (6 h-7d exposures) examined by Affymetrix arrays. In the first approach, ToxPi ranking of biomarker scores consistently gave the highest scores to tumorigenic chemical-dose pairs; balanced accuracies for identification of liver tumorigenic chemicals were up to 89 %. The second approach used tumorigenic thresholds derived in the present study or from our earlier study that were set at the maximum value for chemical-dose exposures without detectable liver tumor outcomes. Using these thresholds, balanced accuracies were up to 90 %. Both approaches identified all tumorigenic chemicals. Almost all of the tumorigenic chemicals activated more than one MIE. We also compared biomarker responses between two types of profiling platforms (Affymetrix full-genome array, TempO-Seq 1500+ array containing ∼2600 genes) and found that the lack of the full set of biomarker genes on the 1500+ array resulted in decreased ability to identify chemicals that activate the MIEs. Overall, these results demonstrate that predictive approaches based on the 6 biomarkers could be used in short-term assays to identify chemicals and their doses that induce liver tumors, the most common endpoint in rodent bioassays.
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Affiliation(s)
- Robert W Lewis
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States.
| | - Thomas Hill
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States; Oak Ridge Institute for Science and Education (ORISE) fellow Office of Research and Development, U.S. Environmental Protection Agency (EPA), Research Triangle Park, NC, United States.
| | - J Christopher Corton
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States.
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33
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Gilbert ME, O'Shaughnessy KL, Axelstad M. Regulation of Thyroid-disrupting Chemicals to Protect the Developing Brain. Endocrinology 2020; 161:bqaa106. [PMID: 32615585 PMCID: PMC8650774 DOI: 10.1210/endocr/bqaa106] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/30/2020] [Indexed: 12/18/2022]
Abstract
Synthetic chemicals with endocrine disrupting properties are pervasive in the environment and are present in the bodies of humans and wildlife. As thyroid hormones (THs) control normal brain development, and maternal hypothyroxinemia is associated with neurological impairments in children, chemicals that interfere with TH signaling are of considerable concern for children's health. However, identifying thyroid-disrupting chemicals (TDCs) in vivo is largely based on measuring serum tetraiodothyronine in rats, which may be inadequate to assess TDCs with disparate mechanisms of action and insufficient to evaluate the potential neurotoxicity of TDCs. In this review 2 neurodevelopmental processes that are dependent on TH action are highlighted, neuronal migration and maturation of gamma amino butyric acid-ergic interneurons. We discuss how interruption of these processes by TDCs may contribute to abnormal brain circuitry following developmental TH insufficiency. Finally, we identify issues in evaluating the developmental neurotoxicity of TDCs and the strengths and limitations of current approaches designed to regulate them. It is clear that an enhanced understanding of how THs affect brain development will lead to refined toxicity testing, reducing uncertainty and improving our ability to protect children's health.
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Affiliation(s)
- Mary E Gilbert
- Center for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Katherine L O'Shaughnessy
- Center for Public Health and Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Marta Axelstad
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, Denmark
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34
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Hill T, Rooney J, Abedini J, El-Masri H, Wood CE, Corton JC. Gene Expression Thresholds Derived From Short-term Exposures Identify Rat Liver Tumorigens. Toxicol Sci 2020; 177:41-59. [PMID: 32603419 DOI: 10.1093/toxsci/kfaa102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Traditional methods for cancer risk assessment are resource-intensive, retrospective, and not feasible for the vast majority of environmental chemicals. In this study, we investigated whether quantitative genomic data from short-term studies may be used to set protective thresholds for potential tumorigenic effects. We hypothesized that gene expression biomarkers measuring activation of the key early events in established pathways for rodent liver cancer exhibit cross-chemical thresholds for tumorigenesis predictive for liver cancer risk. We defined biomarker thresholds for 6 major liver cancer pathways using training sets of chemicals with short-term genomic data (3-29 days of exposure) from the TG-GATES (n = 77 chemicals) and DrugMatrix (n = 86 chemicals) databases and then tested these thresholds within and between datasets. The 6 pathway biomarkers represented genotoxicity, cytotoxicity, and activation of xenobiotic, steroid, and lipid receptors (aryl hydrocarbon receptor, constitutive activated receptor, estrogen receptor, and peroxisome proliferator-activated receptor α). Thresholds were calculated as the maximum values derived from exposures without detectable liver tumor outcomes. We identified clear response values that were consistent across training and test sets. Thresholds derived from the TG-GATES training set were highly predictive (97%) in a test set of independent chemicals, whereas thresholds derived from the DrugMatrix study were 96%-97% predictive for the TG-GATES study. Threshold values derived from an abridged gene list (2/biomarker) also exhibited high predictive accuracy (91%-94%). These findings support the idea that early genomic changes can be used to establish threshold estimates or "molecular tipping points" that are predictive of later-life health outcomes.
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Affiliation(s)
- Thomas Hill
- Center for Computational Toxicology and Exposure.,Oak Ridge Institute for Science and Education (ORISE), NHEERL, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - John Rooney
- Center for Computational Toxicology and Exposure.,Oak Ridge Institute for Science and Education (ORISE), NHEERL, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.,Integrated Laboratory Systems, Morrisville, North Carolina
| | - Jaleh Abedini
- Center for Computational Toxicology and Exposure.,Integrated Laboratory Systems, Morrisville, NC
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35
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Knapen D, Stinckens E, Cavallin JE, Ankley GT, Holbech H, Villeneuve DL, Vergauwen L. Toward an AOP Network-Based Tiered Testing Strategy for the Assessment of Thyroid Hormone Disruption. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:8491-8499. [PMID: 32584560 PMCID: PMC7477622 DOI: 10.1021/acs.est.9b07205] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A growing number of environmental pollutants are known to adversely affect the thyroid hormone system, and major gaps have been identified in the tools available for the identification, and the hazard and risk assessment of these thyroid hormone disrupting chemicals. We provide an example of how the adverse outcome pathway (AOP) framework and associated data generation can address current testing challenges in the context of fish early life stage tests, and fish tests in general. We demonstrate how a suite of assays covering biological processes involved in the underlying toxicological pathways can be implemented in a tiered screening and testing approach for thyroid hormone disruption, using the levels of assessment of the OECD's Conceptual Framework for the Testing and Assessment of Endocrine Disrupting Chemicals as a guide.
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Affiliation(s)
- Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Evelyn Stinckens
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Jenna E Cavallin
- Badger Technical Services, United States Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Gerald T Ankley
- United States Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Henrik Holbech
- Ecotoxicology Lab, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Daniel L Villeneuve
- United States Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
- Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
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36
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Spinu N, Cronin MTD, Enoch SJ, Madden JC, Worth AP. Quantitative adverse outcome pathway (qAOP) models for toxicity prediction. Arch Toxicol 2020; 94:1497-1510. [PMID: 32424443 PMCID: PMC7261727 DOI: 10.1007/s00204-020-02774-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/04/2020] [Indexed: 01/06/2023]
Abstract
The quantitative adverse outcome pathway (qAOP) concept is gaining interest due to its potential regulatory applications in chemical risk assessment. Even though an increasing number of qAOP models are being proposed as computational predictive tools, there is no framework to guide their development and assessment. As such, the objectives of this review were to: (i) analyse the definitions of qAOPs published in the scientific literature, (ii) define a set of common features of existing qAOP models derived from the published definitions, and (iii) identify and assess the existing published qAOP models and associated software tools. As a result, five probabilistic qAOPs and ten mechanistic qAOPs were evaluated against the common features. The review offers an overview of how the qAOP concept has advanced and how it can aid toxicity assessment in the future. Further efforts are required to achieve validation, harmonisation and regulatory acceptance of qAOP models.
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Affiliation(s)
- Nicoleta Spinu
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Mark T D Cronin
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Steven J Enoch
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Judith C Madden
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Andrew P Worth
- European Commission, Joint Research Centre (JRC), Ispra, Italy.
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37
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Olker JH, Haselman JT, Kosian PA, Donnay KG, Korte JJ, Blanksma C, Hornung MW, Degitz SJ. Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians. Toxicol Sci 2019; 166:318-331. [PMID: 30137636 DOI: 10.1093/toxsci/kfy203] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The enzyme iodotyrosine deiodinase (dehalogenase, IYD) catalyzes iodide recycling and promotes iodide retention in thyroid follicular cells. Loss of function or chemical inhibition of IYD reduces available iodide for thyroid hormone synthesis, which leads to hormone insufficiency in tissues and subsequent negative developmental consequences. IYD activity is especially critical under conditions of lower dietary iodine and in low iodine environments. Our objective was to evaluate the toxicological relevance of IYD inhibition in a model amphibian (Xenopus laevis) used extensively for thyroid disruption research. First, we characterized IYD ontogeny through quantification of IYD mRNA expression. Under normal development, IYD was expressed in thyroid glands, kidneys, liver, and intestines, but minimally in the tail. Then, we evaluated how IYD inhibition affected developing larval X. laevis with an in vivo exposure to a known IYD inhibitor (3-nitro-l-tyrosine, MNT) under iodine-controlled conditions; MNT concentrations were 7.4-200 mg/L, with an additional 'rescue' treatment of 200 mg/L MNT supplemented with iodide. Chemical inhibition of IYD resulted in markedly delayed development, with larvae in the highest MNT concentrations arrested prior to metamorphic climax. This effect was linked to reduced glandular and circulating thyroid hormones, increased thyroidal sodium-iodide symporter gene expression, and follicular cell hypertrophy and hyperplasia. Iodide supplementation negated these effects, effectively rescuing exposed larvae. These results establish toxicological relevance of IYD inhibition in amphibians. Given the highly conserved nature of the IYD protein sequence and scarcity of environmental iodine, IYD should be further investigated as a target for thyroid axis disruption in freshwater organisms.
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Affiliation(s)
- Jennifer H Olker
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Jonathan T Haselman
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Patricia A Kosian
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Kelby G Donnay
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Joseph J Korte
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Chad Blanksma
- Badger Technical Services, U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Michael W Hornung
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
| | - Sigmund J Degitz
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
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38
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Noyes PD, Friedman KP, Browne P, Haselman JT, Gilbert ME, Hornung MW, Barone S, Crofton KM, Laws SC, Stoker TE, Simmons SO, Tietge JE, Degitz SJ. Evaluating Chemicals for Thyroid Disruption: Opportunities and Challenges with in Vitro Testing and Adverse Outcome Pathway Approaches. ENVIRONMENTAL HEALTH PERSPECTIVES 2019; 127:95001. [PMID: 31487205 PMCID: PMC6791490 DOI: 10.1289/ehp5297] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 07/01/2019] [Accepted: 08/13/2019] [Indexed: 05/19/2023]
Abstract
BACKGROUND Extensive clinical and experimental research documents the potential for chemical disruption of thyroid hormone (TH) signaling through multiple molecular targets. Perturbation of TH signaling can lead to abnormal brain development, cognitive impairments, and other adverse outcomes in humans and wildlife. To increase chemical safety screening efficiency and reduce vertebrate animal testing, in vitro assays that identify chemical interactions with molecular targets of the thyroid system have been developed and implemented. OBJECTIVES We present an adverse outcome pathway (AOP) network to link data derived from in vitro assays that measure chemical interactions with thyroid molecular targets to downstream events and adverse outcomes traditionally derived from in vivo testing. We examine the role of new in vitro technologies, in the context of the AOP network, in facilitating consideration of several important regulatory and biological challenges in characterizing chemicals that exert effects through a thyroid mechanism. DISCUSSION There is a substantial body of knowledge describing chemical effects on molecular and physiological regulation of TH signaling and associated adverse outcomes. Until recently, few alternative nonanimal assays were available to interrogate chemical effects on TH signaling. With the development of these new tools, screening large libraries of chemicals for interactions with molecular targets of the thyroid is now possible. Measuring early chemical interactions with targets in the thyroid pathway provides a means of linking adverse outcomes, which may be influenced by many biological processes, to a thyroid mechanism. However, the use of in vitro assays beyond chemical screening is complicated by continuing limits in our knowledge of TH signaling in important life stages and tissues, such as during fetal brain development. Nonetheless, the thyroid AOP network provides an ideal tool for defining causal linkages of a chemical exerting thyroid-dependent effects and identifying research needs to quantify these effects in support of regulatory decision making. https://doi.org/10.1289/EHP5297.
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Affiliation(s)
- Pamela D Noyes
- National Center for Environmental Assessment, Office of Research and Development (ORD), U.S. Environmental Protection Agency (EPA), Washington, DC, USA
| | - Katie Paul Friedman
- National Center for Computational Toxicology, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Patience Browne
- Environment Health and Safety Division, Environment Directorate, Organisation for Economic Co-operation and Development (OECD), Paris, France
| | - Jonathan T Haselman
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory (NHEERL), ORD, U.S. EPA, Duluth, Minnesota, USA
| | - Mary E Gilbert
- Toxicity Assessment Division, NHEERL, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Michael W Hornung
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory (NHEERL), ORD, U.S. EPA, Duluth, Minnesota, USA
| | - Stan Barone
- Office of Pollution Prevention and Toxics, Office of Chemical Safety and Pollution Prevention, U.S. EPA, Washington, DC, USA
| | - Kevin M Crofton
- National Center for Computational Toxicology, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Susan C Laws
- Toxicity Assessment Division, NHEERL, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Tammy E Stoker
- Toxicity Assessment Division, NHEERL, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Steven O Simmons
- National Center for Computational Toxicology, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | - Joseph E Tietge
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory (NHEERL), ORD, U.S. EPA, Duluth, Minnesota, USA
| | - Sigmund J Degitz
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory (NHEERL), ORD, U.S. EPA, Duluth, Minnesota, USA
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Spinu N, Bal-Price A, Cronin MTD, Enoch SJ, Madden JC, Worth AP. Development and analysis of an adverse outcome pathway network for human neurotoxicity. Arch Toxicol 2019; 93:2759-2772. [DOI: 10.1007/s00204-019-02551-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 08/14/2019] [Indexed: 12/21/2022]
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Zgheib E, Gao W, Limonciel A, Aladjov H, Yang H, Tebby C, Gayraud G, Jennings P, Sachana M, Beltman JB, Bois FY. Application of three approaches for quantitative AOP development to renal toxicity. ACTA ACUST UNITED AC 2019. [DOI: 10.1016/j.comtox.2019.02.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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41
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Beekhuijzen M, Rijk JCW, Meijer M, de Raaf MA, Pelgrom S. A critical evaluation of thyroid hormone measurements in OECD test guideline studies: Is there any added value? Reprod Toxicol 2019; 88:56-66. [PMID: 31348994 DOI: 10.1016/j.reprotox.2019.07.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/28/2019] [Accepted: 07/19/2019] [Indexed: 01/14/2023]
Abstract
Recently several OECD test guidelines were updated to include thyroid hormone measurements for assessing endocrine disruptor potency, which led to an imperative need to align interpretation of these results by the different stakeholders. We therefore evaluated 124 repro screening studies, which showed in 38% of the studies a statistical significant finding for T4 in at least one treatment group, probably due to disturbances of normal homeostasis causing high variation. Consequently, for a thorough evaluation it is extremely important to take the historical control range into account. In conclusion, the current testing approach is not providing specific information needed to assess endocrine disruption, as too often a statistical significant finding is noted and as down-stream adverse effects are not evaluated. Therefore, major modifications are urgently needed. Instead of extending the in vivo experiments, it should be investigated if in vitro assessments will provide more relevant information on human endocrine disruptor potential.
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Piersma AH, van Benthem J, Ezendam J, Staal YCM, Kienhuis AS. The virtual human in chemical safety assessment. CURRENT OPINION IN TOXICOLOGY 2019. [DOI: 10.1016/j.cotox.2019.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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43
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Li AA, Makris SL, Marty MS, Strauss V, Gilbert ME, Blacker A, Zorrilla LM, Coder PS, Hannas B, Lordi S, Schneider S. Practical considerations for developmental thyroid toxicity assessments: What's working, what's not, and how can we do better? Regul Toxicol Pharmacol 2019; 106:111-136. [PMID: 31018155 DOI: 10.1016/j.yrtph.2019.04.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 04/11/2019] [Accepted: 04/14/2019] [Indexed: 12/26/2022]
Abstract
Thyroid hormones (THs; T3 and T4) play a role in development of cardiovascular, reproductive, immune and nervous systems. Thus, interpretation of TH changes from rodent studies (during pregnancy, in fetuses, neonates, and adults) is critical in hazard characterization and risk assessment. A roundtable session at the 2017 Society of Toxicology (SOT) meeting brought together academic, industry and government scientists to share knowledge and different perspectives on technical and data interpretation issues. Data from a limited group of laboratories were compiled for technical discussions on TH measurements, including good practices for reliable serum TH data. Inter-laboratory historical control data, derived from immunoassays or mass spectrometry methods, revealed: 1) assay sensitivities vary within and across methodologies; 2) TH variability is similar across animal ages; 3) laboratories generally achieve sufficiently sensitive TH quantitation levels, although issues remain for lower levels of serum TH and TSH in fetuses and postnatal day 4 pups; thus, assay sensitivity is critical at these life stages. Best practices require detailed validation of rat serum TH measurements across ages to establish assay sensitivity and precision, and identify potential matrix effects. Finally, issues related to data interpretation for biological understanding and risk assessment were discussed, but their resolution remains elusive.
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Affiliation(s)
- Abby A Li
- Exponent Inc., 1010 14th Street, San Francisco, CA, 94114, USA.
| | - Susan L Makris
- US Environmental Protection Agency Office of Research and Development, 1200 Pennsylvania Ave NW 8623R, Washington, DC, 20460, USA.
| | - M Sue Marty
- The Dow Chemical Company, Toxicology & Environmental Research and Consulting, 1803 Building, Midland, MI, 48674, USA.
| | - Volker Strauss
- BASF SE, Experimental Toxicology and Ecology, 67056, Ludwigshafen, Germany.
| | - Mary E Gilbert
- US Environmental Protection Agency, National Health Environmental Effects Research Lab, 109 T.W. Alexander Drive, MD B105 05, Research Triangle Park, NC, 27711, USA.
| | - Ann Blacker
- Bayer CropScience, P.O. Box 12014, RTP, NC, 27709, USA.
| | | | - Pragati S Coder
- Charles River Laboratories, Developmental and Reproductive Toxicology, 1407 George Road, Ashland, OH, 44805, USA.
| | - Bethany Hannas
- The Dow Chemical Company, Toxicology & Environmental Research and Consulting, 1803 Building, Midland, MI, 48674, USA.
| | - Sheri Lordi
- Charles River Laboratories International, 251 Ballardvale Street, Wilmington, MA, 01887, USA.
| | - Steffen Schneider
- BASF SE, Experimental Toxicology and Ecology, 67056, Ludwigshafen, Germany.
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O'Shaughnessy KL, Kosian PA, Ford JL, Oshiro WM, Degitz SJ, Gilbert ME. Developmental Thyroid Hormone Insufficiency Induces a Cortical Brain Malformation and Learning Impairments: A Cross-Fostering Study. Toxicol Sci 2019; 163:101-115. [PMID: 29385626 DOI: 10.1093/toxsci/kfy016] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Thyroid hormones (THs) are essential for brain development, but few rodent models exist that link TH inefficiency to apical neurodevelopmental endpoints. We have previously described a structural anomaly, a heterotopia, in the brains of rats treated in utero with propylthiouracil (PTU). However, how the timing of an exposure relates to this birth defect is unknown. This study seeks to understand how various temporal treatments of the mother relates to TH insufficiency and adverse neurodevelopment of the offspring. Pregnant rats were exposed to PTU (0 or 3 ppm) through the drinking water from gestational day 6 until postnatal day (PN) 14. On PN2 a subset of pups was cross-fostered to a dam of the opposite treatment, to create 4 conditions: pups exposed to PTU prenatally, postnatally, during both periods, or not at all (control). Both PTU and TH concentrations were characterized in the mother and offspring over time, to capture the dynamics of a developmental xenobiotic exposure. Brains of offspring were examined for heterotopia presence and severity, and adult littermates were assessed for memory impairments. Heterotopia were observed under conditions of prenatal exposure, and its severity increased in animals in the most prolonged exposure group. This malformation was also permanent, but not sex biased. In contrast, behavioral impairments were limited to males, and only in animals exposed to PTU during both the gestational and postnatal periods. This suggests a distinct TH-dependent etiology for both phenotypes, and illustrates how timing of hypothyroxinemia can induce abnormal brain structure and function.
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Affiliation(s)
- Katherine L O'Shaughnessy
- National Health and Environmental Effects Research Laboratory, Toxicity Assessment Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709.,Oak Ridge Institute for Science Education, Oak Ridge, Tennessee 37803
| | - Patricia A Kosian
- National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota 55804
| | - Jermaine L Ford
- Analytical Chemistry Core, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709
| | | | - Sigmund J Degitz
- National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota 55804
| | - Mary E Gilbert
- National Health and Environmental Effects Research Laboratory, Toxicity Assessment Division, US Environmental Protection Agency, Research Triangle Park, North Carolina 27709
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Characterization of non-radiolabeled Thyroxine (T 4) uptake in cryopreserved rat hepatocyte suspensions: Pharmacokinetic implications for PFOA and PFOS chemical exposure. Toxicol In Vitro 2019; 58:230-238. [PMID: 30930230 DOI: 10.1016/j.tiv.2019.03.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/28/2019] [Accepted: 03/18/2019] [Indexed: 11/22/2022]
Abstract
The alteration of thyroxine (T4) cellular uptake by an environmental chemical can serve as a contributing factor in thyroid hormone (TH) disruption. Herein, we describe a non-radiolabeled (LC-MS/MS) oil-filtration technique designed to characterize the mechanism(s) responsible for T4 cellular uptake in cryopreserved rat hepatocyte suspensions. The environmental chemicals perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) were evaluated for their effect on T4 hepatic uptake. At 37 °C, hepatic assays demonstrated saturable kinetics with increasing T4 concentrations, while a linear uptake rate consistent with passive diffusion was detected at 4 °C. Carrier-mediated (37-4 °C) transport of T4 was the predominant hepatic uptake process versus passive diffusion. Cyclosporin A (CsA) chemically inhibited T4 hepatic uptake, whereas PFOA/PFOS displayed no inhibition of T4 translocation. Increasing PFOA/PFOS concentration levels with the T4 serum carrier-protein transthyretin (TTR) present resulted in a dose-response increase in T4 hepatic uptake rates, correlating with increased T4 free fraction values. Hepatic assays conducted in the presence of PFOA/PFOS and TTR displayed an enhanced first-order T4 hepatic uptake rate consistent with carrier-mediated transport. These in vitro findings characterizing increased T4 hepatic uptake provides mechanistic insight regarding decreased T4 serum levels (hypothyroxinemia) previously observed within in vivo rodent studies following perfluorinated chemical exposure.
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46
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A transient window of hypothyroidism alters neural progenitor cells and results in abnormal brain development. Sci Rep 2019; 9:4662. [PMID: 30874585 PMCID: PMC6420655 DOI: 10.1038/s41598-019-40249-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/07/2019] [Indexed: 12/19/2022] Open
Abstract
Cortical heterotopias are clusters of ectopic neurons in the brain and are associated with neurodevelopmental disorders like epilepsy and learning disabilities. We have previously characterized the robust penetrance of a heterotopia in a rat model, induced by thyroid hormone (TH) disruption during gestation. However, the specific mechanism by which maternal TH insufficiency results in this birth defect remains unknown. Here we first determined the developmental window susceptible to endocrine disruption and describe a cellular mechanism responsible for heterotopia formation. We show that five days of maternal goitrogen treatment (10 ppm propylthiouracil) during the perinatal period (GD19-PN2) induces a periventricular heterotopia in 100% of the offspring. Beginning in the early postnatal brain, neurons begin to aggregate near the ventricles of treated animals. In parallel, transcriptional and architectural changes of this region were observed including decreased Sonic hedgehog (Shh) expression, abnormal cell adhesion, and altered radial glia morphology. As the ventricular epithelium is juxtaposed to two sources of brain THs, the cerebrospinal fluid and vasculature, this progenitor niche may be especially susceptible to TH disruption. This work highlights the spatiotemporal vulnerabilities of the developing brain and demonstrates that a transient period of TH perturbation is sufficient to induce a congenital abnormality.
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O’Shaughnessy KL, Wood CR, Ford RL, Kosian PA, Hotchkiss MG, Degitz SJ, Gilbert ME. Thyroid Hormone Disruption in the Fetal and Neonatal Rat: Predictive Hormone Measures and Bioindicators of Hormone Action in the Developing Cortex. Toxicol Sci 2018; 166:163-179. [PMID: 30085217 PMCID: PMC6727986 DOI: 10.1093/toxsci/kfy190] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Adverse neurodevelopmental consequences remain a primary concern when evaluating the effects of thyroid hormone (TH) disrupting chemicals. Though the developing brain is a known target of TH insufficiency, the relationship between THs in the serum and the central nervous system is not well characterized. To address this issue, dose response experiments were performed in pregnant rats using the goitrogen propylthiouracil (PTU) (dose range 0.1-10 ppm). THs were quantified in the serum and brain of offspring at gestational day 20 (GD20) and postnatal day 14 (PN14), two developmental stages included in OECD and EPA regulatory guideline/guidance studies. From the dose response data, the quantitative relationships between THs in the serum and brain were determined. Next, targeted gene expression analyses were performed in the fetal and neonatal cortex to test the hypothesis that TH action in the developing brain is linked to changes in TH concentrations within the tissue. Results show a significant reduction of T4/T3 in the serum and brain of the GD20 fetus in response to low doses of PTU; interestingly, very few genes were significantly different at any dose tested. In the PN14 pup significant reductions of T4/T3 in the serum and brain were also detected; however, twelve transcriptional targets were identified in the neonatal cortex that correlated well with reduced brain THs. These results show that serum T4 is a good predictor of brain THs, and offer several target genes that could serve as pragmatic readouts of T4/T3 dysfunction within the PN14 cortex.
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Affiliation(s)
- Katherine L. O’Shaughnessy
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830
| | - Carmen R. Wood
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Richard L. Ford
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
- Oak Ridge Institute for Science Education, Oak Ridge, Tennesse 37830
| | - Patricia A. Kosian
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Duluth, Minnesota 55804
| | - Michelle G. Hotchkiss
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Sigmund J. Degitz
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Duluth, Minnesota 55804
| | - Mary E. Gilbert
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
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48
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Boyes WK, Degn L, George BJ, Gilbert ME. Moderate perinatal thyroid hormone insufficiency alters visual system function in adult rats. Neurotoxicology 2018; 67:73-83. [PMID: 29684405 PMCID: PMC6733525 DOI: 10.1016/j.neuro.2018.04.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 12/25/2022]
Abstract
Thyroid hormone (TH) is critical for many aspects of neurodevelopment and can be disrupted by a variety of environmental contaminants. Sensory systems, including audition and vision are vulnerable to TH insufficiencies, but little data are available on visual system development at less than severe levels of TH deprivation. The goal of the current experiments was to explore dose-response relations between graded levels of TH insufficiency during development and the visual function of adult offspring. Pregnant Long Evans rats received 0 or 3 ppm (Experiment 1), or 0, 1, 2, or 3 ppm (Experiment 2) of propylthiouracil (PTU), an inhibitor of thyroid hormone synthesis, in drinking water from gestation day (GD) 6 to postnatal day (PN) 21. Treatment with PTU caused dose-related reductions of serum T4, with recovery on termination of exposure, and euthyroidism by the time of visual function testing. Tests of retinal (electroretinograms; ERGs) and visual cortex (visual evoked potentials; VEPs) function were assessed in adult offspring. Dark-adapted ERG a-waves, reflecting rod photoreceptors, were increased in amplitude by PTU. Light-adapted green flicker ERGs, reflecting M-cone photoreceptors, were reduced by PTU exposure. UV-flicker ERGs, reflecting S-cones, were not altered. Pattern-elicited VEPs were significantly reduced by 2 and 3 ppm PTU across a range of stimulus contrast values. The slope of VEP amplitude-log contrast functions was reduced by PTU, suggesting impaired visual contrast gain. Visual contrast gain primarily reflects function of visual cortex, and is responsible for adjusting sensitivity of perceptual mechanisms in response to changing visual scenes. The results indicate that moderate levels of pre-and post-natal TH insufficiency led to alterations in visual function of adult rats, including both retinal and visual cortex sites of dysfunction.
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Affiliation(s)
- William K Boyes
- Toxicity Assessment Division, Neurotoxicology Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA.
| | - Laura Degn
- Toxicity Assessment Division, Neurotoxicology Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Barbara Jane George
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Mary E Gilbert
- Toxicity Assessment Division, Neurotoxicology Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA
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