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Ogata K, Suto H, Sato A, Maeda K, Minami K, Tomiyama N, Kosaka T, Hojo H, Takahashi N, Aoyama H, Yamada T. Optimal testing time for cerebral heterotopia formation in the rat comparative thyroid assay, a downstream indicator for perinatal thyroid hormone insufficiency. J Toxicol Pathol 2024; 37:173-187. [PMID: 39359896 PMCID: PMC11442261 DOI: 10.1293/tox.2024-0004] [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: 01/17/2024] [Accepted: 06/25/2024] [Indexed: 10/04/2024] Open
Abstract
In a past study, we proposed a modified Comparative Thyroid Assay (CTA) with additional examinations of brain thyroid hormone (TH) concentrations and brain histopathology but with smaller group sizes. The results showed that the modified CTA in Sprague Dawley rats detected 10 ppm 6-propylthiouracil (6-PTU)-induced significant suppressions of serum/brain TH concentrations in offspring. To confirm the reliability of qualitative brain histopathology and identify the optimal testing time for heterotopia (a cluster of ectopic neurons) in the modified CTA, brain histopathology together with serum/brain TH concentrations were assessed in GD20 fetuses and PND2, 4, 21, and 28 pups using a similar study protocol but with a smaller number of animals (N=3-6/group/time). Significant hypothyroidism was observed and brain histopathology revealed cerebral heterotopia formation in PND21 and PND28 pups, with likely precursor findings in PND2 and PND4 pups but not in GD20 fetuses. This study confirmed that the optimal testing time for cerebral heterotopia in rat CTA was PND21 and thereafter. These findings suggest that cerebral heterotopia assessment at appropriate times may be a useful alternative to the original CTA design.
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Affiliation(s)
- Keiko Ogata
- 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
- Current address: Registration & Regulatory Affairs
Department, AgroSolutions Division-International, Sumitomo Chemical Company, Ltd., Tokyo
Nihombashi Tower, 2-7-1 Nihonbashi, Chuo-ku, Tokyo 103-6020, Japan
| | - Akira Sato
- Institute of Environmental Toxicology, 4321
Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan
| | - Keiko Maeda
- Environmental Health Science Laboratory, Sumitomo Chemical
Company, Ltd., 3-1-98 Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
| | - Kenta Minami
- Environmental Health Science Laboratory, Sumitomo Chemical
Company, Ltd., 3-1-98 Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan
| | - Naruto Tomiyama
- Institute of Environmental Toxicology, 4321
Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, 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
| | - 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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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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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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O’Shaughnessy KL, McMichael BD, Sasser AL, Bell KS, Riutta C, Ford JL, Stoker TE, Grindstaff RD, Pandiri AR, Gilbert ME. Thyroid hormone action controls multiple components of cell junctions at the ventricular zone in the newborn rat brain. Front Endocrinol (Lausanne) 2023; 14:1090081. [PMID: 36843608 PMCID: PMC9950412 DOI: 10.3389/fendo.2023.1090081] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 01/09/2023] [Indexed: 02/12/2023] Open
Abstract
Thyroid hormone (TH) action controls brain development in a spatiotemporal manner. Previously, we demonstrated that perinatal hypothyroidism led to formation of a periventricular heterotopia in developing rats. This heterotopia occurs in the posterior telencephalon, and its formation was preceded by loss of radial glia cell polarity. As radial glia mediate cell migration and originate in a progenitor cell niche called the ventricular zone (VZ), we hypothesized that TH action may control cell signaling in this region. Here we addressed this hypothesis by employing laser capture microdissection and RNA-Seq to evaluate the VZ during a known period of TH sensitivity. Pregnant rats were exposed to a low dose of propylthiouracil (PTU, 0.0003%) through the drinking water during pregnancy and lactation. Dam and pup THs were quantified postnatally and RNA-Seq of the VZ performed in neonates. The PTU exposure resulted in a modest increase in maternal thyroid stimulating hormone and reduced thyroxine (T4). Exposed neonates exhibited hypothyroidism and T4 and triiodothyronine (T3) were also reduced in the telencephalon. RNA-Seq identified 358 differentially expressed genes in microdissected VZ cells of hypothyroid neonates as compared to controls (q-values ≤0.05). Pathway analyses showed processes like maintenance of the extracellular matrix and cytoskeleton, cell adhesion, and cell migration were significantly affected by hypothyroidism. Immunofluorescence also demonstrated that collagen IV, F-actin, radial glia, and adhesion proteins were reduced in the VZ. Immunohistochemistry of integrin αvβ3 and isoforms of both thyroid receptors (TRα/TRβ) showed highly overlapping expression patterns, including enrichment in the VZ. Taken together, our results show that TH action targets multiple components of cell junctions in the VZ, and this may be mediated by both genomic and nongenomic mechanisms. Surprisingly, this work also suggests that the blood-brain and blood-cerebrospinal fluid barriers may also be affected in hypothyroid newborns.
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Affiliation(s)
- Katherine L. O’Shaughnessy
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
- *Correspondence: Katherine L. O’Shaughnessy,
| | - Benjamin D. McMichael
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
- Oak Ridge Institute for Science Education, Oak Ridge, TN, United States
| | - Aubrey L. Sasser
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
- Oak Ridge Institute for Science Education, Oak Ridge, TN, United States
| | - Kiersten S. Bell
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
- Oak Ridge Institute for Science Education, Oak Ridge, TN, United States
| | - Cal Riutta
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
- Oak Ridge Institute for Science Education, Oak Ridge, TN, United States
| | - Jermaine L. Ford
- Chemical Characterization and Exposure Division, Center for Computational Toxicology and Exposure, United States Environmental Protection Agency, Research Triangle Park, NC, United States
| | - Tammy E. Stoker
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
| | - Rachel D. Grindstaff
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
| | - Arun R. Pandiri
- Comparative and Molecular Pathogenesis Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States
| | - Mary E. Gilbert
- United States Environmental Protection Agency, Public Health Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, United States
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