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Patlewicz G, Karamertzanis P, Friedman KP, Sannicola M, Shah I. A systematic analysis of read-across within REACH registration dossiers. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 30:1-15. [PMID: 38993812 PMCID: PMC11235147 DOI: 10.1016/j.comtox.2024.100304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/13/2024]
Abstract
Read-across is a well-established data-gap filling technique used within analogue or category approaches. Acceptance remains an issue, mainly due to the difficulties of addressing residual uncertainties associated with a read-across prediction and because assessments are expert-driven. Frameworks to develop, assess and document read-across may help reduce variability in read-across results. Data-driven read-across approaches such as Generalised Read-Across (GenRA) include quantification of uncertainties and performance. GenRA also affords opportunities on how New Approach Method (NAM) data can be systematically incorporated to support the read-across hypothesis. Herein, a systematic investigation of differences in expert-driven read-across with data-driven approaches was pursued in terms of establishing scientific confidence in the use of read-across. A dataset of expert-driven read-across assessments that made use of registration data as disseminated in the public International Uniform Chemical Information Database (IUCLID) (version 6) of Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Study Results were compiled. A dataset of ~5000 read-across cases pertaining to repeated dose and developmental toxicity was extracted and mapped to content within EPA's Distributed Structure Searchable Toxicity database (DSSTox) to retrieve chemical name and structural identification information. Content could be mapped to ~3600 cases which when filtered for unique cases with curated quantitative structure-activity relationship-ready SMILES resulted in 389 target-source analogue pairs. The similarity between target and the source analogues on the basis of different contexts - from structural similarity using chemical fingerprints to metabolic similarity using predicted metabolic information was evaluated. An attempt was also made to quantify the relative contribution each similarity context played relative to the target-source analogue pairs by deriving a model which predicted known analogue pairs. Finally, point of departure values (PODs) were predicted using the GenRA approach underpinned by data extracted from the EPA's Toxicity Values Database (ToxValDB). The GenRA predicted PODs were compared with those reported within the REACH dossiers themselves. This study offers generalisable insights on how read-across is already applied for regulatory submissions and expectations on the levels of similarity necessary to make decisions.
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Affiliation(s)
- G Patlewicz
- Center for Computational Toxicology and Exposure (CCTE), US Environmental Protection Agency, 109 TW Alexander Dr, Research Triangle Park, USA, NC 27711
| | - P Karamertzanis
- Computational Assessment and Alternative Methods, European Chemicals Agency (ECHA), Telakkakatu 6, Helsinki, Finland, 104
| | - K Paul Friedman
- Center for Computational Toxicology and Exposure (CCTE), US Environmental Protection Agency, 109 TW Alexander Dr, Research Triangle Park, USA, NC 27711
| | - M Sannicola
- Computational Assessment and Alternative Methods, European Chemicals Agency (ECHA), Telakkakatu 6, Helsinki, Finland, 104
| | - I Shah
- Center for Computational Toxicology and Exposure (CCTE), US Environmental Protection Agency, 109 TW Alexander Dr, Research Triangle Park, USA, NC 27711
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Foley B, Hopperstad K, Gamble J, Lynn SG, Thomas RS, Deisenroth C. Technical evaluation and standardization of the human thyroid microtissue assay. Toxicol Sci 2024; 199:89-107. [PMID: 38310358 DOI: 10.1093/toxsci/kfae014] [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: 02/05/2024] Open
Abstract
The success and sustainability of U.S. EPA efforts to reduce, refine, and replace in vivo animal testing depends on the ability to translate toxicokinetic and toxicodynamic data from in vitro and in silico new approach methods (NAMs) to human-relevant exposures and health outcomes. Organotypic culture models employing primary human cells enable consideration of human health effects and inter-individual variability but present significant challenges for test method standardization, transferability, and validation. Increasing confidence in the information provided by these in vitro NAMs requires setting appropriate performance standards and benchmarks, defined by the context of use, to consider human biology and mechanistic relevance without animal data. The human thyroid microtissue (hTMT) assay utilizes primary human thyrocytes to reproduce structural and functional features of the thyroid gland that enable testing for potential thyroid-disrupting chemicals. As a variable-donor assay platform, conventional principles for assay performance standardization need to be balanced with the ability to predict a range of human responses. The objectives of this study were to (1) define the technical parameters for optimal donor procurement, primary thyrocyte qualification, and performance in the hTMT assay, and (2) set benchmark ranges for reference chemical responses. Thyrocytes derived from a cohort of 32 demographically diverse euthyroid donors were characterized across a battery of endpoints to evaluate morphological and functional variability. Reference chemical responses were profiled to evaluate the range and chemical-specific variability of donor-dependent effects within the cohort. The data-informed minimum acceptance criteria for donor qualification and set benchmark parameters for method transfer proficiency testing and validation of assay performance.
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Affiliation(s)
- Briana Foley
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - Kristen Hopperstad
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - John Gamble
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA
| | - Scott G Lynn
- Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, District of Columbia 20460, USA
| | - Russell S Thomas
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - Chad Deisenroth
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
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3
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Degitz SJ, Olker JH, Denny JS, Degoey PP, Hartig PC, Cardon MC, Eytcheson SA, Haselman JT, Mayasich SA, Hornung MW. In vitro screening of per- and polyfluorinated substances (PFAS) for interference with seven thyroid hormone system targets across nine assays. Toxicol In Vitro 2024; 95:105762. [PMID: 38072180 PMCID: PMC11081714 DOI: 10.1016/j.tiv.2023.105762] [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] [Received: 06/06/2023] [Revised: 10/31/2023] [Accepted: 12/05/2023] [Indexed: 12/30/2023]
Abstract
The US Environmental Protection Agency is evaluating the ecological and toxicological effects of per- and polyfluorinated chemicals. A number of perfluorinated chemicals have been shown to impact the thyroid axis in vivo suggesting that the thyroid hormone system is a target of these chemicals. The objective of this study was to evaluate the activity of 136 perfluorinated chemicals at seven key molecular initiating events (MIE) within the thyroid axis using nine in vitro assays. The potential MIE targets investigated are Human Iodothyronine Deiodinase 1 (hDIO1), Human Iodothyronine Deiodinase 2 (hDIO2), Human Iodothyronine Deiodinase 3 (hDIO3), Xenopus Iodothyronine Deiodinase (xDIO3); Human Iodotyrosine Deiodinase (hIYD), Xenopus Iodotyrosine Deiodinase (xIYD), Human Thyroid Peroxidase (hTPO); and the serum binding proteins Human Transthyretin (hTTR) and Human Thyroxine Binding Globulin (hTBG). Of the 136 PFAS chemicals tested, 85 had sufficient activity to produce a half-maximal effect concentration (EC50) in at least one of the nine assays. In general, most of these PFAS chemicals did not have strong potency towards the seven MIEs examined, apart from transthyretin binding, for which several PFAS had potency similar to the respective model inhibitor. These data sets identify potentially active PFAS chemicals to prioritize for further testing in orthogonal in vitro assays and at higher levels of biological organization to evaluate their capacity for altering the thyroid hormone system and causing potential adverse health and ecological effects.
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Affiliation(s)
- Sigmund J Degitz
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA.
| | - Jennifer H Olker
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA
| | - Jeffery S Denny
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA
| | - Philip P Degoey
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA
| | - Phillip C Hartig
- US Environmental Protection Agency, Office of Research and Development Center for Public Health and Environmental Assessment, Public Health and Integrated Toxicology Division, Research Triangle Park, NC 27709, USA
| | - Mary C Cardon
- US Environmental Protection Agency, Office of Research and Development Center for Public Health and Environmental Assessment, Public Health and Integrated Toxicology Division, Research Triangle Park, NC 27709, USA
| | - Stephanie A Eytcheson
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA; Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA
| | - Jonathan T Haselman
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA
| | - Sally A Mayasich
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA; Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA
| | - Michael W Hornung
- US Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure (CCTE), Great Lakes Toxicology and Ecology Division (GLTED), Duluth, MN 55804, USA
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4
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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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5
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Davidsen N, Ramhøj L, Ballegaard ASR, Rosenmai AK, Henriksen CS, Svingen T. Perfluorooctanesulfonic acid (PFOS) disrupts cadherin-16 in the developing rat thyroid gland. Curr Res Toxicol 2024; 6:100154. [PMID: 38352163 PMCID: PMC10861841 DOI: 10.1016/j.crtox.2024.100154] [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: 11/23/2023] [Revised: 02/01/2024] [Accepted: 02/05/2024] [Indexed: 02/16/2024] Open
Abstract
Perfluorooctanesulfonic acid (PFOS) can disrupt the thyroid hormone (TH) system in rodents, potentially affecting perinatal growth and neurodevelopment. Some studies also suggest that gestational exposure to PFOS can lead to lower TH levels throughout life, indicating that PFOS may compromise thyroid gland development. To address this question, we utilized a rat thyroid gland ex vivo culture system to study direct effects of PFOS on the developing thyroid. No significant changes to follicular structure or size were observed with 1 µM or 10 µM PFOS exposure. However, the transcription factor Foxe1, together with Tpo and Lrp2, were upregulated, whereas the key transcription factor Pax8 and its downstream target gene Cdh16 were significantly downregulated at the transcript level, observed with both RT-qPCR and RNAscope. Notably, Cdh16 expression was not uniformly downregulated across Cdh16-postive cells, but instead displayed a patchy expression pattern across the thyroid gland. This is a significant change in expression pattern compared to control thyroids where Cdh16 is expressed relatively uniformly. The disrupted expression pattern was also seen at the protein level. This suggests that PFOS exposure can impact follicular growth and structure. Compromised follicle integrity, if irreversible, could help explain reduced TH synthesis postnatally. This view is supported by observed changes to Tpo and Lrp2 expression, two factors that play a role in TH synthesis.
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Affiliation(s)
- Nichlas Davidsen
- National Food Institute, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
| | - 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
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6
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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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Arturi K, Hollender J. Machine Learning-Based Hazard-Driven Prioritization of Features in Nontarget Screening of Environmental High-Resolution Mass Spectrometry Data. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:18067-18079. [PMID: 37279189 PMCID: PMC10666537 DOI: 10.1021/acs.est.3c00304] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 05/15/2023] [Accepted: 05/15/2023] [Indexed: 06/08/2023]
Abstract
Nontarget high-resolution mass spectrometry screening (NTS HRMS/MS) can detect thousands of organic substances in environmental samples. However, new strategies are needed to focus time-intensive identification efforts on features with the highest potential to cause adverse effects instead of the most abundant ones. To address this challenge, we developed MLinvitroTox, a machine learning framework that uses molecular fingerprints derived from fragmentation spectra (MS2) for a rapid classification of thousands of unidentified HRMS/MS features as toxic/nontoxic based on nearly 400 target-specific and over 100 cytotoxic endpoints from ToxCast/Tox21. Model development results demonstrated that using customized molecular fingerprints and models, over a quarter of toxic endpoints and the majority of the associated mechanistic targets could be accurately predicted with sensitivities exceeding 0.95. Notably, SIRIUS molecular fingerprints and xboost (Extreme Gradient Boosting) models with SMOTE (Synthetic Minority Oversampling Technique) for handling data imbalance were a universally successful and robust modeling configuration. Validation of MLinvitroTox on MassBank spectra showed that toxicity could be predicted from molecular fingerprints derived from MS2 with an average balanced accuracy of 0.75. By applying MLinvitroTox to environmental HRMS/MS data, we confirmed the experimental results obtained with target analysis and narrowed the analytical focus from tens of thousands of detected signals to 783 features linked to potential toxicity, including 109 spectral matches and 30 compounds with confirmed toxic activity.
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Affiliation(s)
- Katarzyna Arturi
- Department
of Environmental Chemistry, Swiss Federal
Institute of Aquatic Science and Technology (Eawag), Ueberlandstrasse 133, 8600 Dübendorf, Switzerland
| | - Juliane Hollender
- Department
of Environmental Chemistry, Swiss Federal
Institute of Aquatic Science and Technology (Eawag), Ueberlandstrasse 133, 8600 Dübendorf, Switzerland
- Institute
of Biogeochemistry and Pollution Dynamics, Eidgenössische Technische Hochschule Zürich (ETH Zurich), Rämistrasse 101, 8092 Zürich, Switzerland
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Khondkaryan L, Tevosyan A, Navasardyan H, Khachatrian H, Tadevosyan G, Apresyan L, Chilingaryan G, Navoyan Z, Stopper H, Babayan N. Datasets Construction and Development of QSAR Models for Predicting Micronucleus In Vitro and In Vivo Assay Outcomes. TOXICS 2023; 11:785. [PMID: 37755795 PMCID: PMC10537630 DOI: 10.3390/toxics11090785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 09/07/2023] [Accepted: 09/11/2023] [Indexed: 09/28/2023]
Abstract
In silico (quantitative) structure-activity relationship modeling is an approach that provides a fast and cost-effective alternative to assess the genotoxic potential of chemicals. However, one of the limiting factors for model development is the availability of consolidated experimental datasets. In the present study, we collected experimental data on micronuclei in vitro and in vivo, utilizing databases and conducting a PubMed search, aided by text mining using the BioBERT large language model. Chemotype enrichment analysis on the updated datasets was performed to identify enriched substructures. Additionally, chemotypes common for both endpoints were found. Five machine learning models in combination with molecular descriptors, twelve fingerprints and two data balancing techniques were applied to construct individual models. The best-performing individual models were selected for the ensemble construction. The curated final dataset consists of 981 chemicals for micronuclei in vitro and 1309 for mouse micronuclei in vivo, respectively. Out of 18 chemotypes enriched in micronuclei in vitro, only 7 were found to be relevant for in vivo prediction. The ensemble model exhibited high accuracy and sensitivity when applied to an external test set of in vitro data. A good balanced predictive performance was also achieved for the micronucleus in vivo endpoint.
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Affiliation(s)
- Lusine Khondkaryan
- Institute of Molecular Biology, NAS RA, Yerevan 0014, Armenia; (L.K.); (G.T.); (L.A.)
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
| | - Ani Tevosyan
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
- YerevaNN, Yerevan 0025, Armenia; (H.K.); (G.C.)
| | | | - Hrant Khachatrian
- YerevaNN, Yerevan 0025, Armenia; (H.K.); (G.C.)
- Department of Informatics and Applied Mathematics, Yerevan State University, Yerevan 0025, Armenia
| | - Gohar Tadevosyan
- Institute of Molecular Biology, NAS RA, Yerevan 0014, Armenia; (L.K.); (G.T.); (L.A.)
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
| | - Lilit Apresyan
- Institute of Molecular Biology, NAS RA, Yerevan 0014, Armenia; (L.K.); (G.T.); (L.A.)
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
| | | | - Zaven Navoyan
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
| | - Helga Stopper
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany;
| | - Nelly Babayan
- Institute of Molecular Biology, NAS RA, Yerevan 0014, Armenia; (L.K.); (G.T.); (L.A.)
- Toxometris.ai, Yerevan 0009, Armenia; (A.T.); (H.N.); (Z.N.)
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9
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Haselman JT, Nichols JW, Mattingly KZ, Hornung MW, Degitz SJ. A biologically based computational model for the hypothalamic-pituitary-thyroid (HPT) axis in Xenopus laevis larvae. Math Biosci 2023:109021. [PMID: 37201649 DOI: 10.1016/j.mbs.2023.109021] [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: 02/17/2023] [Revised: 04/28/2023] [Accepted: 05/11/2023] [Indexed: 05/20/2023]
Abstract
A biologically based computational model was developed to describe the hypothalamic-pituitary-thyroid (HPT) axis in developing Xenopus laevis larvae. The goal of this effort was to develop a tool that can be used to better understand mechanisms of thyroid hormone-mediated metamorphosis in X. laevis and predict organismal outcomes when those mechanisms are perturbed by chemical toxicants. In this report, we describe efforts to simulate the normal biology of control organisms. The structure of the model borrows from established models of HPT axis function in mammals. Additional features specific to X. laevis account for the effects of organism growth, growth of the thyroid gland, and developmental changes in regulation of thyroid stimulating hormone (TSH) by circulating thyroid hormones (THs). Calibration was achieved by simulating observed changes in stored and circulating levels of THs during a critical developmental window (Nieuwkoop and Faber stages 54-57) that encompasses widely used in vivo chemical testing protocols. The resulting model predicts that multiple homeostatic processes, operating in concert, can act to preserve circulating levels of THs despite profound impairments in TH synthesis. Represented in the model are several biochemical processes for which there are high-throughput in vitro chemical screening assays. By linking the HPT axis model to a toxicokinetic model of chemical uptake and distribution, it may be possible to use this vitro effects information to predict chemical effects in X. laevis larvae resulting from defined chemical exposures.
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Affiliation(s)
- Jonathan T Haselman
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN, 55804, United States of America.
| | - John W Nichols
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN, 55804, United States of America
| | - Kali Z Mattingly
- SpecPro Professional Services (SPS), Contractor to U.S. Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN, 55804, United States of America
| | - Michael W Hornung
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN, 55804, United States of America
| | - Sigmund J Degitz
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN, 55804, United States of America
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10
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Patlewicz G, Paul-Friedman K, Houck K, Zhang L, Huang R, Xia M, Brown J, Simmons SO. Evaluating the utility of a high throughput thiol-containing fluorescent probe to screen for reactivity: A case study with the Tox21 library. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2023; 26:10.1016/j.comtox.2023.100271. [PMID: 37388277 PMCID: PMC10304587 DOI: 10.1016/j.comtox.2023.100271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
High-throughput screening (HTS) assays for bioactivity in the Tox21 program aim to evaluate an array of different biological targets and pathways, but a significant barrier to interpretation of these data is the lack of high-throughput screening (HTS) assays intended to identify non-specific reactive chemicals. This is an important aspect for prioritising chemicals to test in specific assays, identifying promiscuous chemicals based on their reactivity, as well as addressing hazards such as skin sensitisation which are not necessarily initiated by a receptor-mediated effect but act through a non-specific mechanism. Herein, a fluorescence-based HTS assay that allows the identification of thiol-reactive compounds was used to screen 7,872 unique chemicals in the Tox21 10K chemical library. Active chemicals were compared with profiling outcomes using structural alerts encoding electrophilic information. Random Forest classification models based on chemical fingerprints were developed to predict assay outcomes and evaluated through 10-fold stratified cross validation (CV). The mean CV Balanced Accuracy of the validation set was 0.648. The model developed shows promise as a tool to screen untested chemicals for their potential electrophilic reactivity based solely on chemical structural features.
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Affiliation(s)
- Grace Patlewicz
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Katie Paul-Friedman
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Keith Houck
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Li Zhang
- National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, Bethesda, MD 20892, USA
| | - Ruili Huang
- National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, Bethesda, MD 20892, USA
| | - Menghang Xia
- National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, Bethesda, MD 20892, USA
| | - Jason Brown
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Steven O. Simmons
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
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11
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Mitchell CA, Burden N, Bonnell M, Hecker M, Hutchinson TH, Jagla M, LaLone CA, Lagadic L, Lynn SG, Shore B, Song Y, Vliet SM, Wheeler JR, Embry MR. New Approach Methodologies for the Endocrine Activity Toolbox: Environmental Assessment for Fish and Amphibians. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2023; 42:757-777. [PMID: 36789969 PMCID: PMC10258674 DOI: 10.1002/etc.5584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/07/2022] [Accepted: 02/06/2023] [Indexed: 06/14/2023]
Abstract
Multiple in vivo test guidelines focusing on the estrogen, androgen, thyroid, and steroidogenesis pathways have been developed and validated for mammals, amphibians, or fish. However, these tests are resource-intensive and often use a large number of laboratory animals. Developing alternatives for in vivo tests is consistent with the replacement, reduction, and refinement principles for animal welfare considerations, which are supported by increasing mandates to move toward an "animal-free" testing paradigm worldwide. New approach methodologies (NAMs) hold great promise to identify molecular, cellular, and tissue changes that can be used to predict effects reliably and more efficiently at the individual level (and potentially on populations) while reducing the number of animals used in (eco)toxicological testing for endocrine disruption. In a collaborative effort, experts from government, academia, and industry met in 2020 to discuss the current challenges of testing for endocrine activity assessment for fish and amphibians. Continuing this cross-sector initiative, our review focuses on the current state of the science regarding the use of NAMs to identify chemical-induced endocrine effects. The present study highlights the challenges of using NAMs for safety assessment and what work is needed to reduce their uncertainties and increase their acceptance in regulatory processes. We have reviewed the current NAMs available for endocrine activity assessment including in silico, in vitro, and eleutheroembryo models. New approach methodologies can be integrated as part of a weight-of-evidence approach for hazard or risk assessment using the adverse outcome pathway framework. The development and utilization of NAMs not only allows for replacement, reduction, and refinement of animal testing but can also provide robust and fit-for-purpose methods to identify chemicals acting via endocrine mechanisms. Environ Toxicol Chem 2023;42:757-777. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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Affiliation(s)
| | - Natalie Burden
- National Centre for the 3Rs (NC3Rs), London, United Kingdom
| | - Mark Bonnell
- Environment and Climate Change Canada, Ottawa, Canada
| | - Markus Hecker
- Toxicology Centre and School of the Environment & Sustainability, University of Saskatchewan, Saskatoon, Canada
| | | | | | - Carlie A. LaLone
- Office of Research and Development, Great Lakes Toxicology & Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
| | - Laurent Lagadic
- Research and Development, Crop Science, Environmental Safety, Bayer, Monheim am Rhein, Germany
| | - Scott G. Lynn
- Office of Pesticide Programs, US Environmental Protection Agency, Washington, DC
| | - Bryon Shore
- Environment and Climate Change Canada, Ottawa, Canada
| | - You Song
- Norwegian Institute for Water Research, Oslo, Norway
| | - Sara M. Vliet
- Office of Research and Development, Scientific Computing and Data Curation Division, US Environmental Protection Agency, Duluth, Minnesota
| | | | - Michelle R. Embry
- The Health and Environmental Sciences Institute, Washington, DC, USA
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12
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Stoker TE, Wang J, Murr AS, Bailey JR, Buckalew AR. High-Throughput Screening of ToxCast PFAS Chemical Library for Potential Inhibitors of the Human Sodium Iodide Symporter. Chem Res Toxicol 2023; 36:380-389. [PMID: 36821091 DOI: 10.1021/acs.chemrestox.2c00339] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Over the past decade, there has been increased concern for environmental chemicals that can target various sites within the hypothalamic-pituitary-thyroid axis to potentially disrupt thyroid synthesis, transport, metabolism, and/or function. One well-known thyroid target in both humans and wildlife is the sodium iodide symporter (NIS) that regulates iodide uptake into the thyroid gland, the first step of thyroid hormone synthesis. Our laboratory previously developed and validated a radioactive iodide uptake (RAIU) high-throughput assay in a stably transduced human NIS cell line (hNIS-HEK293T-EPA) to identify chemicals with potential for NIS inhibition. So far, we have tested over 2000 chemicals (US EPA's ToxCast chemical libraries PI_v2, PII, and e1K) and discovered a subset of chemicals that significantly inhibit iodide uptake in the hNIS assay. Here, we utilized this screening assay to test a set of 149 unique per- and polyfluoroalkyl substances (PFAS) (ToxCast PFAS library) for potential NIS inhibition. For this evaluation, the 149 blinded samples were screened in a tiered approach, first in an initial single-concentration (≤100 μM) RAIU assay and subsequent evaluation of the chemicals that produced ≥20% inhibition using multiconcentration (MC) response (0.001-100 μM) testing in parallel RAIU and cell viability assays. Of this set, 38 of the PFAS chemicals inhibited iodide uptake ≥20% in the MC testing with 25 displaying inhibition ≥50%. To prioritize the most potent PFAS NIS inhibitors in this set, chemicals were ranked based on outcomes of both iodide uptake and cytotoxicity and normalized to perchlorate, a known positive control. Consistent with previous findings, PFOS and PFHxS were again found to be potent NIS inhibitors, yet significant inhibition was also observed for several other screened PFAS chemicals. Although further studies are clearly warranted, this initial screening effort identifies NIS as a molecular target for potential thyroid disruption by this persistent and structurally diverse class of chemicals.
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Affiliation(s)
- Tammy E Stoker
- Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Jun Wang
- Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
- Oak Ridge Institute for Science and Education, US Department of Energy, Oak Ridge, Tennessee 37831, United States
| | - Ashley S Murr
- Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Jarod R Bailey
- Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
- Oak Ridge Institute for Science and Education, US Department of Energy, Oak Ridge, Tennessee 37831, United States
| | - Angela R Buckalew
- Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
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13
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Gundacker C, Audouze K, Widhalm R, Granitzer S, Forsthuber M, Jornod F, Wielsøe M, Long M, Halldórsson TI, Uhl M, Bonefeld-Jørgensen EC. Reduced Birth Weight and Exposure to Per- and Polyfluoroalkyl Substances: A Review of Possible Underlying Mechanisms Using the AOP-HelpFinder. TOXICS 2022; 10:toxics10110684. [PMID: 36422892 PMCID: PMC9699222 DOI: 10.3390/toxics10110684] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 11/04/2022] [Accepted: 11/07/2022] [Indexed: 05/14/2023]
Abstract
Prenatal exposure to per- and polyfluorinated substances (PFAS) may impair fetal growth. Our knowledge of the underlying mechanisms is incomplete. We used the Adverse Outcome Pathway (AOP)-helpFinder tool to search PubMed for studies published until March 2021 that examined PFAS exposure in relation to birth weight, oxidative stress, hormones/hormone receptors, or growth signaling pathways. Of these 1880 articles, 106 experimental studies remained after abstract screening. One clear finding is that PFAS are associated with oxidative stress in in vivo animal studies and in vitro studies. It appears that PFAS-induced reactive-oxygen species (ROS) generation triggers increased peroxisome proliferator-activated receptor (PPAR)γ expression and activation of growth signaling pathways, leading to hyperdifferentiation of pre-adipocytes. Fewer proliferating pre-adipocytes result in lower adipose tissue weight and in this way may reduce birth weight. PFAS may also impair fetal growth through endocrine effects. Estrogenic effects have been noted in in vivo and in vitro studies. Overall, data suggest thyroid-damaging effects of PFAS affecting thyroid hormones, thyroid hormone gene expression, and histology that are associated in animal studies with decreased body and organ weight. The effects of PFAS on the complex relationships between oxidative stress, endocrine system function, adipogenesis, and fetal growth should be further explored.
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Affiliation(s)
- Claudia Gundacker
- Institute of Medical Genetics, Medical University of Vienna, 1090 Vienna, Austria
- Correspondence: ; Tel.: +43-1-40160-56503
| | - Karine Audouze
- Unit T3S, Université Paris Cité, Inserm U1124, 75006 Paris, France
| | - Raimund Widhalm
- Institute of Medical Genetics, Medical University of Vienna, 1090 Vienna, Austria
| | - Sebastian Granitzer
- Institute of Medical Genetics, Medical University of Vienna, 1090 Vienna, Austria
| | - Martin Forsthuber
- Institute of Medical Genetics, Medical University of Vienna, 1090 Vienna, Austria
| | - Florence Jornod
- Unit T3S, Université Paris Cité, Inserm U1124, 75006 Paris, France
| | - Maria Wielsøe
- Department of Public Health, Aarhus University, 8000 Aarhus, Denmark
| | - Manhai Long
- Department of Public Health, Aarhus University, 8000 Aarhus, Denmark
| | - Thórhallur Ingi Halldórsson
- Faculty of Food Science and Nutrition, University of Iceland, 102 Reykjavík, Iceland
- Department of Epidemiology Research, Statens Serum Institut, 2300 Copenhagen, Denmark
| | - Maria Uhl
- Environment Agency Austria, 1090 Vienna, Austria
| | - Eva Cecilie Bonefeld-Jørgensen
- Department of Public Health, Aarhus University, 8000 Aarhus, Denmark
- Greenland Center for Health Research, Greenland University, Nuuk 3905, Greenland
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14
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Wlodkowic D, Jansen M. High-throughput screening paradigms in ecotoxicity testing: Emerging prospects and ongoing challenges. CHEMOSPHERE 2022; 307:135929. [PMID: 35944679 DOI: 10.1016/j.chemosphere.2022.135929] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 06/09/2022] [Accepted: 07/31/2022] [Indexed: 06/15/2023]
Abstract
The rapidly increasing number of new production chemicals coupled with stringent implementation of global chemical management programs necessities a paradigm shift towards boarder uses of low-cost and high-throughput ecotoxicity testing strategies as well as deeper understanding of cellular and sub-cellular mechanisms of ecotoxicity that can be used in effective risk assessment. The latter will require automated acquisition of biological data, new capabilities for big data analysis as well as computational simulations capable of translating new data into in vivo relevance. However, very few efforts have been so far devoted into the development of automated bioanalytical systems in ecotoxicology. This is in stark contrast to standardized and high-throughput chemical screening and prioritization routines found in modern drug discovery pipelines. As a result, the high-throughput and high-content data acquisition in ecotoxicology is still in its infancy with limited examples focused on cell-free and cell-based assays. In this work we outline recent developments and emerging prospects of high-throughput bioanalytical approaches in ecotoxicology that reach beyond in vitro biotests. We discuss future importance of automated quantitative data acquisition for cell-free, cell-based as well as developments in phytotoxicity and in vivo biotests utilizing small aquatic model organisms. We also discuss recent innovations such as organs-on-a-chip technologies and existing challenges for emerging high-throughput ecotoxicity testing strategies. Lastly, we provide seminal examples of the small number of successful high-throughput implementations that have been employed in prioritization of chemicals and accelerated environmental risk assessment.
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Affiliation(s)
- Donald Wlodkowic
- The Neurotox Lab, School of Science, RMIT University, Melbourne, VIC, 3083, Australia.
| | - Marcus Jansen
- LemnaTec GmbH, Nerscheider Weg 170, 52076, Aachen, Germany
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15
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Koval LE, Dionisio KL, Friedman KP, Isaacs KK, Rager JE. Environmental mixtures and breast cancer: identifying co-exposure patterns between understudied vs breast cancer-associated chemicals using chemical inventory informatics. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2022; 32:794-807. [PMID: 35710593 DOI: 10.15139/s3/umpckw] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/27/2022] [Accepted: 05/31/2022] [Indexed: 05/28/2023]
Abstract
BACKGROUND Although evidence linking environmental chemicals to breast cancer is growing, mixtures-based exposure evaluations are lacking. OBJECTIVE This study aimed to identify environmental chemicals in use inventories that co-occur and share properties with chemicals that have association with breast cancer, highlighting exposure combinations that may alter disease risk. METHODS The occurrence of chemicals within chemical use categories was characterized using the Chemical and Products Database. Co-exposure patterns were evaluated for chemicals that have an association with breast cancer (BC), no known association (NBC), and understudied chemicals (UC) identified through query of the Silent Spring Institute's Mammary Carcinogens Review Database and the U.S. Environmental Protection Agency's Toxicity Reference Database. UCs were ranked based on structure and physicochemical similarities and co-occurrence patterns with BCs within environmentally relevant exposure sources. RESULTS A total of 6793 chemicals had data available for exposure source occurrence analyses. 50 top-ranking UCs spanning five clusters of co-occurring chemicals were prioritized, based on shared properties with co-occuring BCs, including chemicals used in food production and consumer/personal care products, as well as potential endocrine system modulators. SIGNIFICANCE Results highlight important co-exposure conditions that are likely prevalent within our everyday environments that warrant further evaluation for possible breast cancer risk. IMPACT STATEMENT Most environmental studies on breast cancer have focused on evaluating relationships between individual, well-known chemicals and breast cancer risk. This study set out to expand this research field by identifying understudied chemicals and mixtures that may occur in everyday environments due to their patterns of commercial use. Analyses focused on those that co-occur alongside chemicals associated with breast cancer, based upon in silico chemical database querying and analysis. Particularly in instances when understudied chemicals share physicochemical properties and structural features with carcinogens, these chemical mixtures represent conditions that should be studied in future clinical, epidemiological, and toxicological studies.
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Affiliation(s)
- Lauren E Koval
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- The Institute for Environmental Health Solutions, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kathie L Dionisio
- Immediate Office of the Assistant Administrator, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Katie Paul Friedman
- Center for Computational Toxicology and Exposure, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Kristin K Isaacs
- Center for Computational Toxicology and Exposure, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Julia E Rager
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- The Institute for Environmental Health Solutions, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Curriculum in Toxicology and Environmental Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC, USA.
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16
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Koval LE, Dionisio KL, Friedman KP, Isaacs KK, Rager JE. Environmental mixtures and breast cancer: identifying co-exposure patterns between understudied vs breast cancer-associated chemicals using chemical inventory informatics. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2022; 32:794-807. [PMID: 35710593 PMCID: PMC9742149 DOI: 10.1038/s41370-022-00451-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/27/2022] [Accepted: 05/31/2022] [Indexed: 05/15/2023]
Abstract
BACKGROUND Although evidence linking environmental chemicals to breast cancer is growing, mixtures-based exposure evaluations are lacking. OBJECTIVE This study aimed to identify environmental chemicals in use inventories that co-occur and share properties with chemicals that have association with breast cancer, highlighting exposure combinations that may alter disease risk. METHODS The occurrence of chemicals within chemical use categories was characterized using the Chemical and Products Database. Co-exposure patterns were evaluated for chemicals that have an association with breast cancer (BC), no known association (NBC), and understudied chemicals (UC) identified through query of the Silent Spring Institute's Mammary Carcinogens Review Database and the U.S. Environmental Protection Agency's Toxicity Reference Database. UCs were ranked based on structure and physicochemical similarities and co-occurrence patterns with BCs within environmentally relevant exposure sources. RESULTS A total of 6793 chemicals had data available for exposure source occurrence analyses. 50 top-ranking UCs spanning five clusters of co-occurring chemicals were prioritized, based on shared properties with co-occuring BCs, including chemicals used in food production and consumer/personal care products, as well as potential endocrine system modulators. SIGNIFICANCE Results highlight important co-exposure conditions that are likely prevalent within our everyday environments that warrant further evaluation for possible breast cancer risk. IMPACT STATEMENT Most environmental studies on breast cancer have focused on evaluating relationships between individual, well-known chemicals and breast cancer risk. This study set out to expand this research field by identifying understudied chemicals and mixtures that may occur in everyday environments due to their patterns of commercial use. Analyses focused on those that co-occur alongside chemicals associated with breast cancer, based upon in silico chemical database querying and analysis. Particularly in instances when understudied chemicals share physicochemical properties and structural features with carcinogens, these chemical mixtures represent conditions that should be studied in future clinical, epidemiological, and toxicological studies.
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Affiliation(s)
- Lauren E Koval
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- The Institute for Environmental Health Solutions, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kathie L Dionisio
- Immediate Office of the Assistant Administrator, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Katie Paul Friedman
- Center for Computational Toxicology and Exposure, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Kristin K Isaacs
- Center for Computational Toxicology and Exposure, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Julia E Rager
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- The Institute for Environmental Health Solutions, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Curriculum in Toxicology and Environmental Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC, USA.
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17
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Foster MJ, Patlewicz G, Shah I, Haggard DE, Judson RS, Paul Friedman K. Evaluating structure-based activity in a high-throughput assay for steroid biosynthesis. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 24:1-23. [PMID: 37841081 PMCID: PMC10569244 DOI: 10.1016/j.comtox.2022.100245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Data from a high-throughput human adrenocortical carcinoma assay (HT-H295R) for steroid hormone biosynthesis are available for >2000 chemicals in single concentration and 654 chemicals in multi-concentration (mc). Previously, a metric describing the effect size of a chemical on the biosynthesis of 11 hormones was derived using mc data referred to as the maximum mean Mahalanobis distance (maxmMd). However, mc HT-H295R assay data remain unavailable for many chemicals. This work leverages existing HT-H295R assay data by constructing structure-activity relationships to make predictions for data-poor chemicals, including: (1) identification of individual structural descriptors, known as ToxPrint chemotypes, associated with increased odds of affecting estrogen or androgen synthesis; (2) a random forest (RF) classifier using physicochemical property descriptors to predict HT-H295R maxmMd binary (positive or negative) outcomes; and, (3) a local approach to predict maxmMd binary outcomes using nearest neighbors (NNs) based on two types of chemical fingerprints (chemotype or Morgan). Individual chemotypes demonstrated high specificity (85-98%) for modulators of estrogen and androgen synthesis but with low sensitivity. The best RF model for maxmMd classification included 13 predicted physicochemical descriptors, yielding a balanced accuracy (BA) of 71% with only modest improvement when hundreds of structural features were added. The best two NN models for binary maxmMd prediction demonstrated BAs of 85 and 81% using chemotype and Morgan fingerprints, respectively. Using an external test set of 6302 chemicals (lacking HT-H295R data), 1241 were identified as putative estrogen and androgen modulators. Combined results across the three classification models (global RF model and two local NN models) predict that 1033 of the 6302 chemicals would be more likely to affect HT-H295R bioactivity. Together, these in silico approaches can efficiently prioritize thousands of untested chemicals for screening to further evaluate their effects on steroid biosynthesis.
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Affiliation(s)
- M J Foster
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
- National Student Services Contractor, Oak Ridge Associated Universities
| | - G Patlewicz
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
| | - I Shah
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
| | - D E Haggard
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
| | - R S Judson
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
| | - K Paul Friedman
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA
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18
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El-Masri H, Paul Friedman K, Isaacs K, Wetmore BA. Advances in computational methods along the exposure to toxicological response paradigm. Toxicol Appl Pharmacol 2022; 450:116141. [PMID: 35777528 PMCID: PMC9619339 DOI: 10.1016/j.taap.2022.116141] [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] [Received: 04/12/2022] [Revised: 05/27/2022] [Accepted: 06/23/2022] [Indexed: 10/17/2022]
Abstract
Human health risk assessment is a function of chemical toxicity, bioavailability to reach target biological tissues, and potential environmental exposure. These factors are complicated by many physiological, biochemical, physical and lifestyle factors. Furthermore, chemical health risk assessment is challenging in view of the large, and continually increasing, number of chemicals found in the environment. These challenges highlight the need to prioritize resources for the efficient and timely assessment of those environmental chemicals that pose greatest health risks. Computational methods, either predictive or investigative, are designed to assist in this prioritization in view of the lack of cost prohibitive in vivo experimental data. Computational methods provide specific and focused toxicity information using in vitro high throughput screening (HTS) assays. Information from the HTS assays can be converted to in vivo estimates of chemical levels in blood or target tissue, which in turn are converted to in vivo dose estimates that can be compared to exposure levels of the screened chemicals. This manuscript provides a review for the landscape of computational methods developed and used at the U.S. Environmental Protection Agency (EPA) highlighting their potentials and challenges.
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Affiliation(s)
- Hisham El-Masri
- Center for Computational Toxicology and Exposure, Office of Research and Development, U. S. Environmental Protection Agency, Research Triangle Park, NC, USA.
| | - Katie Paul Friedman
- Center for Computational Toxicology and Exposure, Office of Research and Development, U. S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Kristin Isaacs
- Center for Computational Toxicology and Exposure, Office of Research and Development, U. S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Barbara A Wetmore
- Center for Computational Toxicology and Exposure, Office of Research and Development, U. S. Environmental Protection Agency, Research Triangle Park, NC, USA
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19
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Cronin MTD, Bauer FJ, Bonnell M, Campos B, Ebbrell DJ, Firman JW, Gutsell S, Hodges G, Patlewicz G, Sapounidou M, Spînu N, Thomas PC, Worth AP. A scheme to evaluate structural alerts to predict toxicity - Assessing confidence by characterising uncertainties. Regul Toxicol Pharmacol 2022; 135:105249. [PMID: 36041585 PMCID: PMC9585125 DOI: 10.1016/j.yrtph.2022.105249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/12/2022] [Accepted: 08/17/2022] [Indexed: 11/26/2022]
Abstract
Structure-activity relationships (SARs) in toxicology have enabled the formation of structural rules which, when coded as structural alerts, are essential tools in in silico toxicology. Whilst other in silico methods have approaches for their evaluation, there is no formal process to assess the confidence that may be associated with a structural alert. This investigation proposes twelve criteria to assess the uncertainty associated with structural alerts, allowing for an assessment of confidence. The criteria are based around the stated purpose, description of the chemistry, toxicology and mechanism, performance and coverage, as well as corroborating and supporting evidence of the alert. Alerts can be given a confidence assessment and score, enabling the identification of areas where more information may be beneficial. The scheme to evaluate structural alerts was placed in the context of various use cases for industrial and regulatory applications. The analysis of alerts, and consideration of the evaluation scheme, identifies the different characteristics an alert may have, such as being highly specific or generic. These characteristics may determine when an alert can be used for specific uses such as identification of analogues for read-across or hazard identification. Structural alerts are useful tools for predictive toxicology. 12 criteria to evaluate structural alerts have been identified. A strategy to determine confidence of structural alerts is presented. Different use cases require different characteristics of structural alerts. A Scheme to Evaluate Structural Alerts to Predict Toxicity – Assessing Confidence By Characterising Uncertainties.
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Affiliation(s)
- Mark T D Cronin
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Franklin J Bauer
- KREATiS SAS, 23 rue du Creuzat, ZAC de St-Hubert, 38080, L'Isle d'Abeau, France
| | - Mark Bonnell
- Science and Risk Assessment Directorate, Environment & Climate Change Canada, 351 St. Joseph Blvd, Gatineau, Quebec, K1A 0H3, Canada
| | - Bruno Campos
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Bedfordshire, MK44 1LQ, UK
| | - David J Ebbrell
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - James W Firman
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Steve Gutsell
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Bedfordshire, MK44 1LQ, UK
| | - Geoff Hodges
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Bedfordshire, MK44 1LQ, UK
| | - Grace Patlewicz
- Center for Computational Toxicology and Exposure (CCTE), US Environmental Protection Agency, 109 TW Alexander Dr, RTP, NC, 27709, USA
| | - Maria Sapounidou
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Nicoleta Spînu
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK
| | - Paul C Thomas
- KREATiS SAS, 23 rue du Creuzat, ZAC de St-Hubert, 38080, L'Isle d'Abeau, France
| | - Andrew P Worth
- European Commission, Joint Research Centre (JRC), Ispra, Italy.
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20
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Amphibian Metamorphosis Assay: Investigation of the potential effects of five chemicals on the hypothalamic-pituitary thyroid axis of Xenopus laevis. Regul Toxicol Pharmacol 2022; 134:105241. [PMID: 35940297 PMCID: PMC10389063 DOI: 10.1016/j.yrtph.2022.105241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/24/2022] [Accepted: 07/25/2022] [Indexed: 11/20/2022]
Abstract
2-Ethylhexyl 4-hydroxybenzoate (2-EHHB), 4-tert-octylphenol (4-OP), 4-nonylphenol-branched (4-NP), benzyl butyl phthalate (BBP) and dibutyl phthalate (DBP) were evaluated using a 21-day Amphibian Metamorphosis Assay (AMA). Xenopus laevis larvae were exposed nominally to each chemical at 3.6, 10.9, 33.0, and 100 μg/L, except 4-NP concentrations were 1.8, 5.5, 16.5 and 50 μg/L. Endpoints included mortality, developmental stage, hind limb length (HLL), snout-vent length (SVL), body weight (BW), and thyroid histopathology. BBP and 4-OP accelerated development compared to controls at the mean measured concentration of 3.5 and 39.8 μg/L, respectively. An increase in developmental stage frequency distribution was observed for 4-OP at 39.8 and 103 µg/L, BBP at all concentrations and DBP at 143 µg/L. Normalized HLL was increased on study day (SD) 21 for all tested substances except 4-NP. Histopathology revealed accelerated development and mild thyroid follicular cell hypertrophy at all BBP concentrations, but moderate severity at 105 μg/L. Increased BW occurred for all chemicals except 4-OP. Increased SVL was observed for 4-NP, BBP and DBP on SD 21. There was insufficient evidence that 4-NP and 2-EHHB affected the hypothalamic-pituitary thyroid axis, however, BBP, DBP and 4-OP showed potential effects on amphibian metamorphosis and thyroid activity, albeit through different lines of evidence.
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21
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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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22
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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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23
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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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24
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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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25
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Paul Friedman K, Gagne M, Loo LH, Karamertzanis P, Netzeva T, Sobanski T, Franzosa JA, Richard AM, Lougee RR, Gissi A, Lee JYJ, Angrish M, Dorne JL, Foster S, Raffaele K, Bahadori T, Gwinn MR, Lambert J, Whelan M, Rasenberg M, Barton-Maclaren T, Thomas RS. Utility of In Vitro Bioactivity as a Lower Bound Estimate of In Vivo Adverse Effect Levels and in Risk-Based Prioritization. Toxicol Sci 2021; 173:202-225. [PMID: 31532525 DOI: 10.1093/toxsci/kfz201] [Citation(s) in RCA: 131] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Use of high-throughput, in vitro bioactivity data in setting a point-of-departure (POD) has the potential to accelerate the pace of human health safety evaluation by informing screening-level assessments. The primary objective of this work was to compare PODs based on high-throughput predictions of bioactivity, exposure predictions, and traditional hazard information for 448 chemicals. PODs derived from new approach methodologies (NAMs) were obtained for this comparison using the 50th (PODNAM, 50) and the 95th (PODNAM, 95) percentile credible interval estimates for the steady-state plasma concentration used in in vitro to in vivo extrapolation of administered equivalent doses. Of the 448 substances, 89% had a PODNAM, 95 that was less than the traditional POD (PODtraditional) value. For the 48 substances for which PODtraditional < PODNAM, 95, the PODNAM and PODtraditional were typically within a factor of 10 of each other, and there was an enrichment of chemical structural features associated with organophosphate and carbamate insecticides. When PODtraditional < PODNAM, 95, it did not appear to result from an enrichment of PODtraditional based on a particular study type (eg, developmental, reproductive, and chronic studies). Bioactivity:exposure ratios, useful for identification of substances with potential priority, demonstrated that high-throughput exposure predictions were greater than the PODNAM, 95 for 11 substances. When compared with threshold of toxicological concern (TTC) values, the PODNAM, 95 was greater than the corresponding TTC value 90% of the time. This work demonstrates the feasibility, and continuing challenges, of using in vitro bioactivity as a protective estimate of POD in screening-level assessments via a case study.
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Affiliation(s)
- Katie Paul Friedman
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
| | - Matthew Gagne
- Healthy Environments and Consumer Safety Branch, Health Canada, Government of Canada, Ottawa, Ontario, Canada, K1A0K9
| | - Lit-Hsin Loo
- Innovations in Food and Chemical Safety Programme and Bioinformatics Institute, Agency for Science, Technology and Research, Singapore, 138671, Singapore
| | - Panagiotis Karamertzanis
- Computational Assessment Unit, European Chemicals Agency, European Chemicals Agency Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Uusimaa, Finland
| | - Tatiana Netzeva
- Computational Assessment Unit, European Chemicals Agency, European Chemicals Agency Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Uusimaa, Finland
| | - Tomasz Sobanski
- Computational Assessment Unit, European Chemicals Agency, European Chemicals Agency Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Uusimaa, Finland
| | - Jill A Franzosa
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
| | - Ann M Richard
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
| | - Ryan R Lougee
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711.,Oak Ridge Institute for Science and Education, U.S. Department of Energy, Oak Ridge, TN 37831, USA
| | - Andrea Gissi
- Computational Assessment Unit, European Chemicals Agency, European Chemicals Agency Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Uusimaa, Finland
| | - Jia-Ying Joey Lee
- Innovations in Food and Chemical Safety Programme and Bioinformatics Institute, Agency for Science, Technology and Research, Singapore, 138671, Singapore
| | - Michelle Angrish
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Washington, DC, 20004 and Research Triangle Park, NC 27711
| | - Jean Lou Dorne
- Scientific Committee and Emerging Risks Unit Department of Risk Assessment and Scientific Assistance, Via Carlo Magno 1A, 43126 Parma, Italy
| | - Stiven Foster
- Office of Land and Emergency Management, U.S. Environmental Protection Agency, Washington, DC, 20004
| | - Kathleen Raffaele
- Office of Land and Emergency Management, U.S. Environmental Protection Agency, Washington, DC, 20004
| | - Tina Bahadori
- Oak Ridge Institute for Science and Education, U.S. Department of Energy, Oak Ridge, TN 37831, USA
| | - Maureen R Gwinn
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
| | - Jason Lambert
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
| | - Maurice Whelan
- European Commission, Joint Research Centre (JRC), Via Enrico Fermi, 2749, I - 21027 Ispra, Italy
| | - Mike Rasenberg
- Computational Assessment Unit, European Chemicals Agency, European Chemicals Agency Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Uusimaa, Finland
| | - Tara Barton-Maclaren
- Healthy Environments and Consumer Safety Branch, Health Canada, Government of Canada, Ottawa, Ontario, Canada, K1A0K9
| | - Russell S Thomas
- National Center for Computational Toxicology, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711
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26
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Dawson D, Ingle BL, Phillips KA, Nichols JW, Wambaugh JF, Tornero-Velez R. Designing QSARs for Parameters of High-Throughput Toxicokinetic Models Using Open-Source Descriptors. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:6505-6517. [PMID: 33856768 PMCID: PMC8548983 DOI: 10.1021/acs.est.0c06117] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The intrinsic metabolic clearance rate (Clint) and the fraction of the chemical unbound in plasma (fup) serve as important parameters for high-throughput toxicokinetic (TK) models, but experimental data are limited for many chemicals. Open-source quantitative structure-activity relationship (QSAR) models for both parameters were developed to offer reliable in silico predictions for a diverse set of chemicals regulated under the U.S. law, including pharmaceuticals, pesticides, and industrial chemicals. As a case study to demonstrate their utility, model predictions served as inputs to the TK component of a risk-based prioritization approach based on bioactivity/exposure ratios (BERs), in which a BER < 1 indicates that exposures are predicted to exceed a biological activity threshold. When applied to a subset of the Tox21 screening library (6484 chemicals), we found that the proportion of chemicals with BER <1 was similar using either in silico (1133/6484; 17.5%) or in vitro (148/848; 17.5%) parameters. Further, when considering only the chemicals in the Tox21 set with in vitro data, there was a high concordance of chemicals classified with either BER <1 or >1 using either in silico or in vitro parameters (767/848, 90.4%). Thus, the presented QSARs may be suitable for prioritizing the risk posed by many chemicals for which measured in vitro TK data are lacking.
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Affiliation(s)
- Daniel Dawson
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
| | - Brandall L. Ingle
- U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
| | - Katherine A. Phillips
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
| | - John W. Nichols
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
| | - John F. Wambaugh
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
| | - Rogelio Tornero-Velez
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709
- Corresponding Author Address correspondence to Rogelio Tornero-Velez at 109 T.W. Alexander Drive, Mail Code E205-01, Research Triangle Park, NC, 27709;
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27
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de Lima Junior NC, Camilo JF, do Carmo PR, de Andrade MN, Braz BF, Santelli RE, de Brito Gitirana L, Ferreira ACF, de Carvalho DP, Miranda-Alves L, Dias GRM. Subacute exposure to lead promotes disruption in the thyroid gland function in male and female rats. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 274:115889. [PMID: 33223335 DOI: 10.1016/j.envpol.2020.115889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 06/11/2023]
Abstract
Exposure to heavy metals, such as lead, is a global public health problem. Lead has a long historic relation to several adverse health conditions and was recently classified as an endocrine disruptor. The aim of this study was to investigate the effects of subacute exposure to lead on the thyroid gland function. Adult male and female Wistar rats received a lead acetate solution containing 10 or 25 mg/kg, by gavage, three times a week, for 14 days. One week later, behavioral testing showed no alterations in anxiety and motor-exploratory parameters, as evaluated by Open-Field and Plus-Maze Tests, but impairment in learning and memory was found in the male 25 mg/kg lead-treated group and in both female lead-treated groups, as evaluated by the Inhibitory Avoidance Test. After one week, serum levels of tT3 were reduced in the 25 mg/kg female group and in the 10 mg∕ kg male group. However, tT4 levels were increased in the 25 mg/kg male group and in both female treated groups. TSH levels did not change and lead serum levels were undetectable. Morphologic alterations were observed in the thyroid gland, including abnormal thyroid parenchyma follicles of different sizes, epithelial stratification and vacuolization of follicular cells, decrease in colloid eosinophilia and vascular congestion, accompanied by morphometric alterations. An increase in collagen deposition was also observed. No differences were observed in TPO activity or protein expression, H2O2 generation by NADPH oxidases or hepatic D1 mRNA expression. However, thyroid NIS protein expression was considerably decreased in the male and female lead-treated groups, while TSHr expression was decreased in the 25 mg/kg female lead-treated group. These findings demonstrated that subacute exposure to lead acetate disrupts thyroid gland function in both sexes, leading to morphophysiological impairment and to changes in learning and memory abilities.
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Affiliation(s)
- Niedson Correia de Lima Junior
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Endocrinology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Juliana Franco Camilo
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Pâmella Rodrigues do Carmo
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Marcelle Novaes de Andrade
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Pharmacology and Medicinal Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Bernardo Ferreira Braz
- Department of Analytical Chemistry, Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Ricardo Erthal Santelli
- Department of Analytical Chemistry, Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Lycia de Brito Gitirana
- Laboratory of Integrative Histology, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Andrea Claudia Freitas Ferreira
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Endocrinology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Denise Pires de Carvalho
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Endocrinology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Leandro Miranda-Alves
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Endocrinology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Pharmacology and Medicinal Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Glaecir Roseni Mundstock Dias
- Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Postgraduate Program in Endocrinology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
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Mayasich SA, Korte JJ, Denny JS, Hartig PC, Olker JH, DeGoey P, O'Flanagan J, Degitz SJ, Hornung MW. Xenopus laevis and human type 3 iodothyronine deiodinase enzyme cross-species sensitivity to inhibition by ToxCast chemicals. Toxicol In Vitro 2021; 73:105141. [PMID: 33713820 DOI: 10.1016/j.tiv.2021.105141] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 02/12/2021] [Accepted: 03/08/2021] [Indexed: 11/15/2022]
Abstract
Deiodinase enzymes are critical for tissue-specific and temporal control of activation or inactivation of thyroid hormones during vertebrate development, including amphibian metamorphosis. We previously screened ToxCast chemicals for inhibitory activity toward human recombinant Type 3 iodothyronine deiodinase enzyme (hDIO3) and subsequently produced Xenopus laevis recombinant dio3 enzyme (Xldio3) with the goals to identify specific chemical inhibitors of Xldio3, to evaluate cross-species sensitivity and explore whether the human assay results are predictive of the amphibian. We identified a subset of 356 chemicals screened against hDIO3 to test against Xldio3, initially at a single concentration (200 μM), and further tested 79 in concentration-response mode. Most chemicals had IC50 values lower for hDIO3 than for Xldio3 and many had steep Hill slopes (a potential indication of non-specific inhibition). However, eight of the most potent chemicals are likely specific inhibitors, with IC50 values of 14 μM or less, Hill slopes near -1 and curves not significantly different between species likely due to conservation of catalytically active amino acids. Controlling for assay conditions, human in vitro screening results can be predictive of activity in the amphibian assay. This study lays the groundwork for future studies using recombinant non-mammalian proteins to test cross-species sensitivity to chemicals. DISCLAIMER: The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
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Affiliation(s)
- Sally A Mayasich
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA; Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Joseph J Korte
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Jeffrey S Denny
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Phillip C Hartig
- Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Jennifer H Olker
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Philip DeGoey
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Joseph O'Flanagan
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA; Oak Ridge Associated Universities, Oak Ridge, TN, USA
| | - Sigmund J Degitz
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA
| | - Michael W Hornung
- Great Lakes Toxicology and Ecology Division, Center for Computational Toxicology and Ecology, Office of Research and Development, U.S. Environmental Protection Agency, Duluth, MN, USA.
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29
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Expanded high-throughput screening and chemotype-enrichment analysis of the phase II: e1k ToxCast library for human sodium-iodide symporter (NIS) inhibition. Arch Toxicol 2021; 95:1723-1737. [PMID: 33656581 DOI: 10.1007/s00204-021-03006-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 02/16/2021] [Indexed: 12/19/2022]
Abstract
The sodium-iodide symporter (NIS) mediates the uptake of iodide into the thyroid. Inhibition of NIS function by xenobiotics has been demonstrated to suppress circulating thyroid hormones and perturb related physiological functions. Until recently, few environmental chemicals had been screened for NIS inhibition activity. We previously screened over 1000 chemicals from the ToxCast Phase II (ph1v2 and ph2) libraries using an in vitro radioactive iodide uptake (RAIU) with the hNIS-HEK293T cell line to identify NIS inhibitors. Here, we broaden the chemical space by expanding screening to include the ToxCast e1k library (804 unique chemicals) with initial screening for RAIU at 1 × 10-4 M. Then 209 chemicals demonstrating > 20% RAIU inhibition were further tested in multiple-concentration, parallel RAIU and cell viability assays. This identified 55 chemicals as active, noncytotoxic RAIU inhibitors. Further cytotoxicity-adjusted potency scoring (with NaClO4 having a reference score of 200) revealed five chemicals with moderate to strong RAIU inhibition (scored > 100). These data were combined with our previous PhII screening data to produce binary hit-calls for ~ 1800 unique chemicals (PhII + e1k) with and without cytotoxicity filtering. Results were analyzed with a ToxPrint chemotype-enrichment workflow to identify substructural features significantly enriched in the NIS inhibition hit-call space. We assessed the applicability of enriched PhII chemotypes to prospectively predict NIS inhibition in the e1k dataset. Chemotype enrichments derived for the combined ~ 1800 dataset also identified additional enriched features, as well as chemotypes affiliated with cytotoxicity. These enriched chemotypes provide important new information that can support future data interpretation, structure-activity relationship, chemical use, and regulation.
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30
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Richard AM, Huang R, Waidyanatha S, Shinn P, Collins BJ, Thillainadarajah I, Grulke CM, Williams AJ, Lougee RR, Judson RS, Houck KA, Shobair M, Yang C, Rathman JF, Yasgar A, Fitzpatrick SC, Simeonov A, Thomas RS, Crofton KM, Paules RS, Bucher JR, Austin CP, Kavlock RJ, Tice RR. The Tox21 10K Compound Library: Collaborative Chemistry Advancing Toxicology. Chem Res Toxicol 2021. [PMID: 33140634 DOI: 10.1021/acs.chemrestox.0c0026410.1021/acs.chemrestox.0c00264.s003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Since 2009, the Tox21 project has screened ∼8500 chemicals in more than 70 high-throughput assays, generating upward of 100 million data points, with all data publicly available through partner websites at the United States Environmental Protection Agency (EPA), National Center for Advancing Translational Sciences (NCATS), and National Toxicology Program (NTP). Underpinning this public effort is the largest compound library ever constructed specifically for improving understanding of the chemical basis of toxicity across research and regulatory domains. Each Tox21 federal partner brought specialized resources and capabilities to the partnership, including three approximately equal-sized compound libraries. All Tox21 data generated to date have resulted from a confluence of ideas, technologies, and expertise used to design, screen, and analyze the Tox21 10K library. The different programmatic objectives of the partners led to three distinct, overlapping compound libraries that, when combined, not only covered a diversity of chemical structures, use-categories, and properties but also incorporated many types of compound replicates. The history of development of the Tox21 "10K" chemical library and data workflows implemented to ensure quality chemical annotations and allow for various reproducibility assessments are described. Cheminformatics profiling demonstrates how the three partner libraries complement one another to expand the reach of each individual library, as reflected in coverage of regulatory lists, predicted toxicity end points, and physicochemical properties. ToxPrint chemotypes (CTs) and enrichment approaches further demonstrate how the combined partner libraries amplify structure-activity patterns that would otherwise not be detected. Finally, CT enrichments are used to probe global patterns of activity in combined ToxCast and Tox21 activity data sets relative to test-set size and chemical versus biological end point diversity, illustrating the power of CT approaches to discern patterns in chemical-activity data sets. These results support a central premise of the Tox21 program: A collaborative merging of programmatically distinct compound libraries would yield greater rewards than could be achieved separately.
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Affiliation(s)
- Ann M Richard
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Ruili Huang
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Suramya Waidyanatha
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Paul Shinn
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Bradley J Collins
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Inthirany Thillainadarajah
- Senior Environmental Employment Program, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Christopher M Grulke
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Antony J Williams
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Ryan R Lougee
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
- Oak Ridge Institute for Science and Education, United States Department of Energy, Oak Ridge, Tennessee 37830, United States
| | - Richard S Judson
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Keith A Houck
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Mahmoud Shobair
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Chihae Yang
- Altamira, LLC, Columbus, Ohio 43235, United States
- Molecular Networks, GmbH, Erlangen 90411, Germany
| | - James F Rathman
- Altamira, LLC, Columbus, Ohio 43235, United States
- Molecular Networks, GmbH, Erlangen 90411, Germany
| | - Adam Yasgar
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Suzanne C Fitzpatrick
- Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, Maryland 20740, United States
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Russell S Thomas
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Kevin M Crofton
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
- R3Fellows, LLC, Durham, North Carolina 27701, United States
| | - Richard S Paules
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - John R Bucher
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Christopher P Austin
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Robert J Kavlock
- Center for Computational Toxicology and Exposure, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
- Kavlock Consulting, LLC, Washington, DC 20001, United States
| | - Raymond R Tice
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
- RTice Consulting, Hillsborough, North Carolina 27278, United States
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31
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Richard AM, Huang R, Waidyanatha S, Shinn P, Collins BJ, Thillainadarajah I, Grulke CM, Williams AJ, Lougee RR, Judson RS, Houck KA, Shobair M, Yang C, Rathman JF, Yasgar A, Fitzpatrick SC, Simeonov A, Thomas RS, Crofton KM, Paules RS, Bucher JR, Austin CP, Kavlock RJ, Tice RR. The Tox21 10K Compound Library: Collaborative Chemistry Advancing Toxicology. Chem Res Toxicol 2021; 34:189-216. [PMID: 33140634 PMCID: PMC7887805 DOI: 10.1021/acs.chemrestox.0c00264] [Citation(s) in RCA: 106] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Indexed: 12/13/2022]
Abstract
Since 2009, the Tox21 project has screened ∼8500 chemicals in more than 70 high-throughput assays, generating upward of 100 million data points, with all data publicly available through partner websites at the United States Environmental Protection Agency (EPA), National Center for Advancing Translational Sciences (NCATS), and National Toxicology Program (NTP). Underpinning this public effort is the largest compound library ever constructed specifically for improving understanding of the chemical basis of toxicity across research and regulatory domains. Each Tox21 federal partner brought specialized resources and capabilities to the partnership, including three approximately equal-sized compound libraries. All Tox21 data generated to date have resulted from a confluence of ideas, technologies, and expertise used to design, screen, and analyze the Tox21 10K library. The different programmatic objectives of the partners led to three distinct, overlapping compound libraries that, when combined, not only covered a diversity of chemical structures, use-categories, and properties but also incorporated many types of compound replicates. The history of development of the Tox21 "10K" chemical library and data workflows implemented to ensure quality chemical annotations and allow for various reproducibility assessments are described. Cheminformatics profiling demonstrates how the three partner libraries complement one another to expand the reach of each individual library, as reflected in coverage of regulatory lists, predicted toxicity end points, and physicochemical properties. ToxPrint chemotypes (CTs) and enrichment approaches further demonstrate how the combined partner libraries amplify structure-activity patterns that would otherwise not be detected. Finally, CT enrichments are used to probe global patterns of activity in combined ToxCast and Tox21 activity data sets relative to test-set size and chemical versus biological end point diversity, illustrating the power of CT approaches to discern patterns in chemical-activity data sets. These results support a central premise of the Tox21 program: A collaborative merging of programmatically distinct compound libraries would yield greater rewards than could be achieved separately.
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Affiliation(s)
- Ann M. Richard
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Ruili Huang
- National
Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Suramya Waidyanatha
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Paul Shinn
- National
Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Bradley J. Collins
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Inthirany Thillainadarajah
- Senior
Environmental Employment Program, United
States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
| | - Christopher M. Grulke
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Antony J. Williams
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Ryan R. Lougee
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
- Oak
Ridge Institute for Science and Education, United States Department
of Energy, Oak Ridge, Tennessee 37830, United States
| | - Richard S. Judson
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Keith A. Houck
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Mahmoud Shobair
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Chihae Yang
- Altamira,
LLC, Columbus, Ohio 43235, United States
- Molecular Networks, GmbH, Erlangen 90411, Germany
| | - James F. Rathman
- Altamira,
LLC, Columbus, Ohio 43235, United States
- Molecular Networks, GmbH, Erlangen 90411, Germany
| | - Adam Yasgar
- National
Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Suzanne C. Fitzpatrick
- Center
for Food Safety and Applied Nutrition, United
States Food and Drug Administration, College Park, Maryland 20740, United States
| | - Anton Simeonov
- National
Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Russell S. Thomas
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
| | - Kevin M. Crofton
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
- R3Fellows,
LLC, Durham, North Carolina 27701, United States
| | - Richard S. Paules
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - John R. Bucher
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Christopher P. Austin
- National
Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
| | - Robert J. Kavlock
- Center
for Computational Toxicology and Exposure, Office of Research and
Development, United States Environmental
Protection Agency, Research
Triangle Park, North Carolina 27711, United States
- Kavlock
Consulting, LLC, Washington, DC 20001, United States
| | - Raymond R. Tice
- Division
of the National Toxicology Program, National
Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
- RTice Consulting, Hillsborough, North Carolina 27278, United States
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32
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Panieri E, Buha-Đorđevic A, Saso L. Endocrine disruption by PFAS: A major concern associated with legacy and replacement substances. ARHIV ZA FARMACIJU 2021. [DOI: 10.5937/arhfarm71-34197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Perand poly-fluorinated alkyl substances (PFAS) have been used for decades in a great variety of processes and products by virtue of their exceptional properties, versatility and chemical stability. Nevertheless, it is increasingly recognized that these substances can represent a serious hazard to human health and living organisms due to their persistence, long-range transport potential and tendency to accumulate in biota. For this reason, some efforts have been made across the EU to identify alternative molecules, with a shorter carbon chain and theoretically safer profile, that might replace the previous generation of legacy PFAS. Unfortunately, this strategy has not been entirely successful and serious concerns are still posed by PFAS in different human populations. Among others, an emerging aspect is represented by the adverse effects that both legacy and alternative PFAS can exert on the human endocrine system, with respect to vulnerable target subpopulations. In this review we will briefly summarize PFAS properties, uses and environmental fate, focusing on their effects on human reproductive capacity and fertility, body weight control and obesity as well as thyroid function.
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33
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Olker JH, Korte JJ, Denny JS, Haselman JT, Hartig PC, Cardon MC, Hornung MW, Degitz SJ. In vitro screening for chemical inhibition of the iodide recycling enzyme, iodotyrosine deiodinase. Toxicol In Vitro 2020; 71:105073. [PMID: 33352258 DOI: 10.1016/j.tiv.2020.105073] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/25/2020] [Accepted: 12/17/2020] [Indexed: 02/07/2023]
Abstract
The iodide recycling enzyme, iodotyrosine deiodinase (IYD), is a largely unstudied molecular mechanism through which environmental chemicals can potentially cause thyroid disruption. This highly conserved enzyme plays an essential role in maintaining adequate levels of free iodide for thyroid hormone synthesis. Thyroid disruption following in vivo IYD inhibition has been documented in mammalian and amphibian models; however, few chemicals have been tested for IYD inhibition in either in vivo or in vitro assays. Presented here are the development and application of a screening assay to assess susceptibility of IYD to chemical inhibition. With recombinant human IYD enzyme, a 96-well plate in vitro assay was developed and then used to screen over 1800 unique substances from the U.S. EPA ToxCast screening library. Through a tiered screening approach, 194 IYD inhibitors were identified (inhibited IYD enzyme activity by 20% or greater at target concentration of 200 μM). 154 chemicals were further tested in concentration-response (0.032-200 μM) to determine IC50 and rank-order potency. This work broadens the coverage of thyroid-relevant molecular targets for chemical screening, provides the largest set of chemicals tested for IYD inhibition, and aids in prioritizing chemicals for targeted in vivo testing to evaluate thyroid-related adverse outcomes.
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Affiliation(s)
- Jennifer H Olker
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA.
| | - Joseph J Korte
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA
| | - Jeffrey S Denny
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA
| | - Jonathan T Haselman
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA
| | - Phillip C Hartig
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, North Carolina 27709, USA
| | - Mary C Cardon
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, North Carolina 27709, USA
| | - Michael W Hornung
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA
| | - Sigmund J Degitz
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA
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Garcia de Lomana M, Weber AG, Birk B, Landsiedel R, Achenbach J, Schleifer KJ, Mathea M, Kirchmair J. In Silico Models to Predict the Perturbation of Molecular Initiating Events Related to Thyroid Hormone Homeostasis. Chem Res Toxicol 2020; 34:396-411. [PMID: 33185102 PMCID: PMC7887800 DOI: 10.1021/acs.chemrestox.0c00304] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Disturbance of the thyroid hormone homeostasis has been associated with adverse health effects such as goiters and impaired mental development in humans and thyroid tumors in rats. In vitro and in silico methods for predicting the effects of small molecules on thyroid hormone homeostasis are currently being explored as alternatives to animal experiments, but are still in an early stage of development. The aim of this work was the development of a battery of in silico models for a set of targets involved in molecular initiating events of thyroid hormone homeostasis: deiodinases 1, 2, and 3, thyroid peroxidase (TPO), thyroid hormone receptor (TR), sodium/iodide symporter, thyrotropin-releasing hormone receptor, and thyroid-stimulating hormone receptor. The training data sets were compiled from the ToxCast database and related scientific literature. Classical statistical approaches as well as several machine learning methods (including random forest, support vector machine, and neural networks) were explored in combination with three data balancing techniques. The models were trained on molecular descriptors and fingerprints and evaluated on holdout data. Furthermore, multi-task neural networks combining several end points were investigated as a possible way to improve the performance of models for which the experimental data available for model training are limited. Classifiers for TPO and TR performed particularly well, with F1 scores of 0.83 and 0.81 on the holdout data set, respectively. Models for the other studied targets yielded F1 scores of up to 0.77. An in-depth analysis of the reliability of predictions was performed for the most relevant models. All data sets used in this work for model development and validation are available in the Supporting Information.
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Affiliation(s)
- Marina Garcia de Lomana
- BASF SE, 67063 Ludwigshafen am Rhein, Germany.,Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, 1090 Vienna, Austria
| | | | | | | | | | | | | | - Johannes Kirchmair
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, 1090 Vienna, Austria
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35
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Nelms MD, Karmaus AL, Patlewicz G. An evaluation of the performance of selected (Q)SARs/expert systems for predicting acute oral toxicity. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2020; 16:100135. [PMID: 33163737 PMCID: PMC7641510 DOI: 10.1016/j.comtox.2020.100135] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Multiple US agencies use acute oral toxicity data in a variety of regulatory contexts. One of the ad-hoc groups that the US Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) established to implement the ICCVAM Strategic Roadmap was the Acute Toxicity Workgroup (ATWG) to support the development, acceptance, and actualisation of new approach methodologies (NAMs). One of the ATWG charges was to evaluate in vitro and in silico methods for predicting rat acute systemic toxicity. Collaboratively, the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) and the US Environmental Protection Agency (US EPA) collected a large body of rat oral acute toxicity data (~16,713 studies for 11,992 substances) to serve as a reference set to evaluate the performance and coverage of new and existing models as well as build understanding of the inherent variability of the animal data. Here, we focus on evaluating in silico models for predicting the Lethal Dose (LD50) as implemented within two expert systems, TIMES and TEST. The performance and coverage were evaluated against the reference dataset. The performance of both models were similar, but TEST was able to make predictions for more chemicals than TIMES. The subset of the data with multiple (>3) LD50 values was used to evaluate the variability in data and served as a benchmark to compare model performance. Enrichment analysis was conducted using ToxPrint chemical fingerprints to identify the types of chemicals where predictions lay outside the upper 95% confidence interval. Overall, TEST and TIMES models performed similarly but had different chemical features associated with low accuracy predictions, reaffirming that these models are complementary and both worth evaluation when seeking to predict rat LD50 values.
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Affiliation(s)
- Mark D. Nelms
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | | | - Grace Patlewicz
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
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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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Conti A, Strazzeri C, Rhoden KJ. Perfluorooctane sulfonic acid, a persistent organic pollutant, inhibits iodide accumulation by thyroid follicular cells in vitro. Mol Cell Endocrinol 2020; 515:110922. [PMID: 32621861 DOI: 10.1016/j.mce.2020.110922] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/26/2020] [Accepted: 06/23/2020] [Indexed: 12/11/2022]
Abstract
Poly- and perfluoroalkyl substances (PFAS) are a class of endocrine disrupting chemicals (EDCs) reported to alter thyroid function. Iodide uptake by thyroid follicular cells, an early step in the synthesis of thyroid hormones, is a potential target for thyroid disruption by EDCs. The aim of the present study was to evaluate the acute effects of perfluorooctane sulfonic acid (PFOS) and perfluorooctane carboxylic acid (PFOA), two of the most abundant PFAS in the environment, on iodide transport by thyroid follicular cells in vitro. Dynamic changes in intracellular iodide concentration were monitored by live cell imaging using YFP-H148Q/I152, a genetically encoded fluorescent iodide biosensor. PFOS, but not PFOA, acutely and reversibly inhibited iodide accumulation by FRTL-5 thyrocytes, as well as by HEK-293 cells transiently expressing the Sodium Iodide Symporter (NIS). PFOS prevented NIS-mediated iodide uptake and reduced intracellular iodide concentration in iodide-containing cells, mimicking the effect of the NIS inhibitor perchlorate. PFOS did not affect iodide efflux from thyroid cells. The results of this study suggest that disruption of iodide homeostasis in thyroid cells may be a potential mechanism for anti-thyroid health effects of PFOS. The study also confirms the utility of the YFP-H148Q/I152 cell-based assay to screen environmental PFAS, and other EDCs, for anti-thyroid activity.
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Affiliation(s)
- Amalia Conti
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, S. Orsola-Malpighi Hospital, via Massarenti 9, Bologna, 40138, Italy.
| | - Chiara Strazzeri
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, S. Orsola-Malpighi Hospital, via Massarenti 9, Bologna, 40138, Italy.
| | - Kerry J Rhoden
- Department of Medical and Surgical Sciences (DIMEC), and Health Sciences & Technologies Interdepartmental Center for Industrial Research (CIRI SDV), University of Bologna, S. Orsola-Malpighi Hospital, via Massarenti 9, Bologna, 40138, Italy.
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38
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Wang H, Khodaparast S, Carroll J, Kelly C, Robles ESJ, Cabral JT. A microfluidic-multiwell platform for rapid phase mapping of surfactant solutions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:045109. [PMID: 32357682 DOI: 10.1063/1.5144770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Measurement of the phase behavior and (meta)stability of liquid formulations, including surfactant solutions, is required for the understanding of mixture thermodynamics, as well as their practical utilization. We report a microfluidic platform with a stepped temperature profile, imposed by a dual Peltier module, connected to an automated multiwell plate injector and optical setup, for rapid solution phase mapping. The measurement protocol is defined by the temperature step ΔT ≡ T1 - T2 (≲100 °C), volumetric flow rate Q ≡ ΔV/Δt (≲50 μl/min), which implicitly set the thermal gradient ΔT/Δt (≃0.1-50 °C/min), and measurement time (which must exceed the intrinsic timescale of the relevant phase transformation). Furthermore, U-shaped microchannels can assess the reversibility of such transformations, yielding a facile measurement of the metastable zone width of the phase diagram. By contrast with traditional approaches, the platform precisely controls the cooling and heating rates by tuning the flow rate, and the absolute temperature excursion by the hot and cold thermal profile, which remain stationary during operation, thus allowing the sequential and reproducible screening of large sample arrays. As a model system, we examined the transition from the micellar (L1) to the liquid crystalline lamellar phase (Lα), upon cooling, of aqueous solutions of sodium linear alkylbenzene sulfonate, a biodegradable anionic surfactant extensively employed in industry. Our findings are validated with quiescent optical microscopy and small angle neutron scattering data.
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Affiliation(s)
- Haoyu Wang
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Sepideh Khodaparast
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - John Carroll
- National Formulation Centre, Centre for Process Innovation, Sedgefield DL1 1GL, United Kingdom
| | - Caroline Kelly
- National Formulation Centre, Centre for Process Innovation, Sedgefield DL1 1GL, United Kingdom
| | - Eric S J Robles
- Procter & Gamble, Newcastle Innovation Centre, Newcastle-Upon-Tyne NE12 9TS, United Kingdom
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
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Deisenroth C, Soldatow VY, Ford J, Stewart W, Brinkman C, LeCluyse EL, MacMillan DK, Thomas RS. Development of an In Vitro Human Thyroid Microtissue Model for Chemical Screening. Toxicol Sci 2020; 174:63-78. [PMID: 31808822 PMCID: PMC8061085 DOI: 10.1093/toxsci/kfz238] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Thyroid hormones (TH) are essential for regulating a number of diverse physiological processes required for normal growth, development, and metabolism. The US EPA Endocrine Disruptor Screening Program (EDSP) has identified several molecular thyroid targets relevant to hormone synthesis dynamics that have been adapted to high-throughput screening (HTS) assays to rapidly evaluate the ToxCast/Tox21 chemical inventories for potential thyroid disrupting chemicals (TDCs). The uncertainty surrounding the specificity of active chemicals identified in these screens and the relevance to phenotypic effects on in vivo human TH synthesis are notable data gaps for hazard identification of TDCs. The objective of this study was to develop a medium-throughput organotypic screening assay comprised of reconstructed human thyroid microtissues to quantitatively evaluate the disruptive effects of chemicals on TH production and secretion. Primary human thyroid cells procured from qualified euthyroid donors were analyzed for retention of NK2 homeobox 1 (NKX2-1), Keratin 7 (KRT7), and Thyroglobulin (TG) protein expression by high-content image analysis to verify enrichment of follicular epithelial cells. A direct comparison of 2-dimensional (2D) and 3-dimensional (3D) 96-well culture formats was employed to characterize the morphology, differential gene expression, TG production, and TH synthesis over the course of 20 days. The results indicate that modeling human thyroid cells in the 3D format was sufficient to restore TH synthesis not observed in the 2D culture format. Inhibition of TH synthesis in an optimized 3D culture format was demonstrated with reference chemicals for key molecular targets within the thyroid gland. Implementation of the assay may prove useful for interpreting phenotypic effects of candidate TDCs identified by HTS efforts currently underway in the EDSP.
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Affiliation(s)
- Chad Deisenroth
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | | | - Jermaine Ford
- Research Cores Unit, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711
| | - Wendy Stewart
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Cassandra Brinkman
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | | | - Denise K. MacMillan
- Research Cores Unit, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711
| | - Russell S. Thomas
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
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Evaluation of potential sodium-iodide symporter (NIS) inhibitors using a secondary Fischer rat thyroid follicular cell (FRTL-5) radioactive iodide uptake (RAIU) assay. Arch Toxicol 2020; 94:873-885. [PMID: 32065294 DOI: 10.1007/s00204-020-02664-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 02/03/2020] [Indexed: 12/29/2022]
Abstract
The Fischer rat thyroid follicular cell line (FRTL-5) endogenously expresses the sodium-iodide symporter (NIS) and has been used to identify environmental chemicals that perturb thyroid hormone homeostasis by disruption of NIS-mediated iodide uptake. Previously, a high-throughput radioactive iodide uptake (RAIU) screening assay incorporating the hNIS-HEK293T-EPA cell line was used to identify potential human NIS (hNIS) inhibitors in 1028 ToxCast Phase I (ph1_v2) and Phase II chemicals. In this study, the FRTL-5 cell line was evaluated and applied as a secondary RAIU assay coupled with cell viability assays to further prioritize highly active NIS inhibitors from the earlier screening. Assay validation with ten reference chemicals and performance assessment by chemical controls suggest the FRTL-5 based assays are robust and highly reproducible. Top-ranked chemicals from the ToxCast screening were then evaluated in both FRTL-5 and hNIS RAIU assays using newly sourced chemicals to strengthen the testing paradigm and to enable a rat vs. human species comparison. Eighteen of 29 test chemicals showed less than 1 order of magnitude difference in IC50 values between the two assays. Notably, two common perfluorinated compounds, perfluorooctanesulfonic acid (PFOS) and perfluorohexane sulfonate (PFHxS), demonstrated strong NIS inhibitory activity [IC50 - 6.45 (PFOS) and - 5.70 (PFHxS) log M in FRTL-5 RAIU assay]. In addition, several chemicals including etoxazole, methoxyfenozide, oxyfluorfen, triclocarban, mepanipyrim, and niclosamide also exhibited NIS inhibition with minimal cytotoxicity in both assays and are proposed for additional testing using short-term in vivo assays to characterize effects on thyroid hormone synthesis.
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41
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Ramhøj L, Hass U, Gilbert ME, Wood C, Svingen T, Usai D, Vinggaard AM, Mandrup K, Axelstad M. Evaluating thyroid hormone disruption: investigations of long-term neurodevelopmental effects in rats after perinatal exposure to perfluorohexane sulfonate (PFHxS). Sci Rep 2020; 10:2672. [PMID: 32060323 PMCID: PMC7021709 DOI: 10.1038/s41598-020-59354-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 01/24/2020] [Indexed: 12/17/2022] Open
Abstract
Thyroid hormones are critical for mammalian brain development. Thus, chemicals that can affect thyroid hormone signaling during pregnancy are of great concern. Perfluorohexane sulfonate (PFHxS) is a widespread environmental contaminant found in human serum, breastmilk, and other tissues, capable of lowering serum thyroxine (T4) in rats. Here, we investigated its effects on the thyroid system and neurodevelopment following maternal exposure from early gestation through lactation (0.05, 5 or 25 mg/kg/day PFHxS), alone or in combination with a mixture of 12 environmentally relevant endocrine disrupting compounds (EDmix). PFHxS lowered thyroid hormone levels in both dams and offspring in a dose-dependent manner, but did not change TSH levels, weight, histology, or expression of marker genes of the thyroid gland. No evidence of thyroid hormone-mediated neurobehavioral disruption in offspring was observed. Since human brain development appear very sensitive to low T4 levels, we maintain that PFHxS is of potential concern to human health. It is our view that current rodent models are not sufficiently sensitive to detect adverse neurodevelopmental effects of maternal and perinatal hypothyroxinemia and that we need to develop more sensitive brain-based markers or measurable metrics of thyroid hormone-dependent perturbations in brain development.
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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
| | - Ulla Hass
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800,, Denmark
| | - Mary E Gilbert
- Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Carmen Wood
- Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Terje Svingen
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800,, Denmark
| | - Diana Usai
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800,, Denmark
| | - Anne Marie Vinggaard
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800,, Denmark
| | - Karen Mandrup
- Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800,, Denmark
| | - 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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42
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Nelms MD, Lougee R, Roberts DW, Richard A, Patlewicz G. Comparing and contrasting the coverage of publicly available structural alerts for protein binding. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2019; 12:1-13. [PMID: 37701288 PMCID: PMC10494887 DOI: 10.1016/j.comtox.2019.100100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The molecular initiating event for many mechanisms of toxicological action comprise the reactive, covalent binding between an exogenous electrophile and an endogenous nucleophile. The target sites for electrophiles are typically peptides, proteins, enzymes or DNA. Of these, the formation of covalent adducts with proteins and DNA are perhaps the most established as they are most closely associated with skin sensitisation and genotoxicity endpoints. As such, being able to identify electrophilic features within a chemical structure provides a starting point to characterise its reactivity profile. There are a number of software tools that have been developed to help identify structural features indicative of electrophilic reactive potential to address various purposes, including: 1) to facilitate category formation for read-across of toxicity effects such as skin sensitisation potential, as well as 2) to profile substances to identify potential confounding factors to rationalise their activity in high-throughput screening (HTS) assays. Here, three such schemes that have been published in the literature as collections of SMARTS patterns and their associated chemical-biological reaction domains have been compared. The goals are 1) to better understand their scope and coverage, and 2) to assess their performance relative to a published skin sensitisation dataset where manual annotations to assign likely mechanistic domains based on expert judgement were already available. The 3 schemes were then applied to the Tox21 library and the consensus outcome was reported to highlight the proportion of chemicals likely to exhibit a reactivity response, specific to a mechanistic reaction domain, but non-specific with respect to target-tissue based activity. ToxPrint fingerprints were computed and activity enrichments computed to compare the structural features identified for the skin sensitisation dataset and Tox21 chemicals for each 'consensus' reaction domain. Enriched ToxPrints were also used to identify ToxCast assays potentially informative for reactivity.
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Affiliation(s)
- Mark D. Nelms
- Oak Ridge Institute for Science and Education (ORISE), 1299 Bethel Valley Road, Oak Ridge, TN 37830, USA
- National Center for Computational Toxicology (NCCT), Office of Research and Development, US Environmental Protection Agency (US EPA), 109 TW Alexander Dr, Research Triangle Park (RTP), NC 27711, USA
| | - Ryan Lougee
- Oak Ridge Institute for Science and Education (ORISE), 1299 Bethel Valley Road, Oak Ridge, TN 37830, USA
- National Center for Computational Toxicology (NCCT), Office of Research and Development, US Environmental Protection Agency (US EPA), 109 TW Alexander Dr, Research Triangle Park (RTP), NC 27711, USA
| | - David W. Roberts
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
| | - Ann Richard
- National Center for Computational Toxicology (NCCT), Office of Research and Development, US Environmental Protection Agency (US EPA), 109 TW Alexander Dr, Research Triangle Park (RTP), NC 27711, USA
| | - Grace Patlewicz
- National Center for Computational Toxicology (NCCT), Office of Research and Development, US Environmental Protection Agency (US EPA), 109 TW Alexander Dr, Research Triangle Park (RTP), NC 27711, USA
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43
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Nelms MD, Pradeep P, Patlewicz G. Evaluating potential refinements to existing Threshold of Toxicological Concern (TTC) values for environmentally-relevant compounds. Regul Toxicol Pharmacol 2019; 109:104505. [PMID: 31639428 DOI: 10.1016/j.yrtph.2019.104505] [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: 08/20/2019] [Revised: 10/12/2019] [Accepted: 10/15/2019] [Indexed: 11/29/2022]
Abstract
The Toxic Substances Control Act (TSCA) mandates the US EPA perform risk-based prioritisation of chemicals in commerce and then, for high-priority substances, develop risk evaluations that integrate toxicity data with exposure information. One approach being considered for data poor chemicals is the Threshold of Toxicological Concern (TTC). Here, TTC values derived using oral (sub)chronic No Observable (Adverse) Effect Level (NO(A)EL) data from the EPA's Toxicity Values database (ToxValDB) were compared with published TTC values from Munro et al. (1996). A total of 4554 chemicals with structures present in ToxValDB were assigned into their respective TTC categories using the Toxtree software tool, of which toxicity data was available for 1304 substances. The TTC values derived from ToxValDB were similar, but not identical to the Munro TTC values: Cramer I ((ToxValDB) 37.3 c. f. (Munro) 30 μg/kg-day), Cramer II (34.6 c. f. 9.1 μg/kg-day) and Cramer III (3.9 c. f. 1.5 μg/kg-day). Cramer III 5th percentile values were found to be statistically different. Chemical features of the two Cramer III datasets were evaluated to account for the differences. TTC values derived from this expanded dataset substantiated the original TTC values, reaffirming the utility of TTC as a promising tool in a risk-based prioritisation approach.
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Affiliation(s)
- Mark D Nelms
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA; Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Prachi Pradeep
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA; Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA
| | - Grace Patlewicz
- Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency, Research Triangle Park, Durham, NC, 27709, USA.
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