1
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Hendriks G, Adriaens E, Allemang A, Clements J, Cole G, Derr R, Engel M, Hamel A, Kidd D, Kellum S, Kiyota T, Myhre A, Naëssens V, Pfuhler S, Roy M, Settivari R, Schuler M, Zeller A, van Benthem J, Vanparys P, Kirkland D. Interlaboratory validation of the ToxTracker assay: An in vitro reporter assay for mechanistic genotoxicity assessment. Environ Mol Mutagen 2024; 65:4-24. [PMID: 38545858 DOI: 10.1002/em.22592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/11/2024]
Abstract
ToxTracker is a mammalian cell reporter assay that predicts the genotoxic properties of compounds with high accuracy. By evaluating induction of various reporter genes that play a key role in relevant cellular pathways, it provides insight into chemical mode-of-action (MoA), thereby supporting discrimination of direct-acting genotoxicants and cytotoxic chemicals. A comprehensive interlaboratory validation trial was conducted, in which the principles outlined in OECD Guidance Document 34 were followed, with the primary objectives of establishing transferability and reproducibility of the assay and confirming the ability of ToxTracker to correctly classify genotoxic and non-genotoxic compounds. Reproducibility of the assay to predict genotoxic MoA was confirmed across participating laboratories and data were evaluated in terms of concordance with in vivo genotoxicity outcomes. Seven laboratories tested a total of 64 genotoxic and non-genotoxic chemicals that together cover a broad chemical space. The within-laboratory reproducibility (WLR) was up to 98% (73%-98% across participants) and the overall between-laboratory reproducibility (BLR) was 83%. This trial confirmed the accuracy of ToxTracker to predict in vivo genotoxicants with a sensitivity of 84.4% and a specificity of 91.2%. We concluded that ToxTracker is a robust in vitro assay for the accurate prediction of in vivo genotoxicity. Considering ToxTracker's robust standalone accuracy and that it can provide important information on the MoA of chemicals, it is seen as a valuable addition to the regulatory in vitro genotoxicity battery that may even have the potential to replace certain currently used in vitro battery assays.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Jan van Benthem
- National Institute for Public Health and the Environment, The Netherlands
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2
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Beal MA, Chen G, Dearfield KL, Gi M, Gollapudi B, Heflich RH, Horibata K, Long AS, Lovell DP, Parsons BL, Pfuhler S, Wills J, Zeller A, Johnson G, White PA. Interpretation of in vitro concentration-response data for risk assessment and regulatory decision-making: Report from the 2022 IWGT quantitative analysis expert working group meeting. Environ Mol Mutagen 2023. [PMID: 38115239 DOI: 10.1002/em.22582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 09/15/2023] [Accepted: 12/16/2023] [Indexed: 12/21/2023]
Abstract
Quantitative risk assessments of chemicals are routinely performed using in vivo data from rodents; however, there is growing recognition that non-animal approaches can be human-relevant alternatives. There is an urgent need to build confidence in non-animal alternatives given the international support to reduce the use of animals in toxicity testing where possible. In order for scientists and risk assessors to prepare for this paradigm shift in toxicity assessment, standardization and consensus on in vitro testing strategies and data interpretation will need to be established. To address this issue, an Expert Working Group (EWG) of the 8th International Workshop on Genotoxicity Testing (IWGT) evaluated the utility of quantitative in vitro genotoxicity concentration-response data for risk assessment. The EWG first evaluated available in vitro methodologies and then examined the variability and maximal response of in vitro tests to estimate biologically relevant values for the critical effect sizes considered adverse or unacceptable. Next, the EWG reviewed the approaches and computational models employed to provide human-relevant dose context to in vitro data. Lastly, the EWG evaluated risk assessment applications for which in vitro data are ready for use and applications where further work is required. The EWG concluded that in vitro genotoxicity concentration-response data can be interpreted in a risk assessment context. However, prior to routine use in regulatory settings, further research will be required to address the remaining uncertainties and limitations.
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Affiliation(s)
- Marc A Beal
- Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Guangchao Chen
- Centre for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment (RIVM), Utrecht, the Netherlands
| | - Kerry L Dearfield
- Retired from US Environmental Protection Agency and US Department of Agriculture, Washington, DC, USA
| | - Min Gi
- Department of Environmental Risk Assessment, Graduate School of Medicine, Osaka Metropolitan University, Osaka, Japan
| | | | - Robert H Heflich
- National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas, USA
| | - Katsuyoshi Horibata
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Kawasaki, Kanagawa, Japan
| | - Alexandra S Long
- Existing Substances Risk Assessment Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | - David P Lovell
- St George's Medical School, University of London, London, UK
| | - Barbara L Parsons
- National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas, USA
| | - Stefan Pfuhler
- Global Product Stewardship - Human Safety, Procter & Gamble, Cincinnati, Ohio, USA
| | - John Wills
- Genetic Toxicology and Photosafety, GSK Research & Development, Stevenage, UK
| | - Andreas Zeller
- Pharmaceutical Sciences, pRED Innovation Center Basel, Hoffmann-La Roche Ltd, Basel, Switzerland
| | - George Johnson
- Swansea University Medical School, Swansea University, Swansea, UK
| | - Paul A White
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
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3
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Dertinger SD, Li D, Beevers C, Douglas GR, Heflich RH, Lovell DP, Roberts DJ, Smith R, Uno Y, Williams A, Witt KL, Zeller A, Zhou C. Assessing the quality and making appropriate use of historical negative control data: A report of the International Workshop on Genotoxicity Testing (IWGT). Environ Mol Mutagen 2023:10.1002/em.22541. [PMID: 37097075 PMCID: PMC10598234 DOI: 10.1002/em.22541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 04/12/2023] [Accepted: 04/20/2023] [Indexed: 05/03/2023]
Abstract
Historical negative control data (HCD) have played an increasingly important role in interpreting the results of genotoxicity tests. In particular, Organisation for Economic Co-operation and Development (OECD) genetic toxicology test guidelines recommend comparing responses produced by exposure to test substances with the distribution of HCD as one of three criteria for evaluating and interpreting study results (referred to herein as "Criterion C"). Because of the potential for inconsistency in how HCD are acquired, maintained, described, and used to interpret genotoxicity testing results, a workgroup of the International Workshops for Genotoxicity Testing was convened to provide recommendations on this crucial topic. The workgroup used example data sets from four in vivo tests, the Pig-a gene mutation assay, the erythrocyte-based micronucleus test, the transgenic rodent gene mutation assay, and the in vivo alkaline comet assay to illustrate how the quality of HCD can be evaluated. In addition, recommendations are offered on appropriate methods for evaluating HCD distributions. Recommendations of the workgroup are: When concurrent negative control data fulfill study acceptability criteria, they represent the most important comparator for judging whether a particular test substance induced a genotoxic effect. HCD can provide useful context for interpreting study results, but this requires supporting evidence that (i) HCD were generated appropriately, and (ii) their quality has been assessed and deemed sufficiently high for this purpose. HCD should be visualized before any study comparisons take place; graph(s) that show the degree to which HCD are stable over time are particularly useful. Qualitative and semi-quantitative assessments of HCD should also be supplemented with quantitative evaluations. Key factors in the assessment of HCD include: (i) the stability of HCD over time, and (ii) the degree to which inter-study variation explains the total variability observed. When animal-to-animal variation is the predominant source of variability, the relationship between responses in the study and an HCD-derived interval or upper bounds value (i.e., OECD Criterion C) can be used with a strong degree of confidence in contextualizing a particular study's results. When inter-study variation is the major source of variability, comparisons between study data and the HCD bounds are less useful, and consequentially, less emphasis should be placed on using HCD to contextualize a particular study's results. The workgroup findings add additional support for the use of HCD for data interpretation; but relative to most current OECD test guidelines, we recommend a more flexible application that takes into consideration HCD quality. The workgroup considered only commonly used in vivo tests, but it anticipates that the same principles will apply to other genotoxicity tests, including many in vitro tests.
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Affiliation(s)
| | | | | | - George R. Douglas
- Environmental Health Science and Research Bureau, Health
Canada, Ottawa, Canada, K1A 9K9
| | - Robert H. Heflich
- U.S. Food and Drug Administration/National Center for
Toxicological Research, Jefferson AR USA
| | - David P. Lovell
- St. George’s Medical School, University of London,
Cranmer Terrace, London, SW17 0RE, UK
| | | | - Robert Smith
- Labcorp Drug Development, Otley Road, Harrogate, HG3 1PY,
UK
| | - Yoshifumi Uno
- LSI Medience Co., 1-2-3 Shibaura, Minato-ku, Tokyo
105-0023, Japan
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health
Canada, Ottawa, Canada, K1A 9K9
| | - Kristine L. Witt
- Division of Translational Toxicology, National Institute
of Environmental Health Sciences/National Institutes of Health, Research Triangle
Park, NC, USA
| | - Andreas Zeller
- F. Hoffmann-La Roche Ltd., Pharmaceutical Sciences, pRED
Innovation Center Basel, 4070 Basel, Switzerland
| | - Changhui Zhou
- Shanghai Innostar Bio-tech Co., Ltd., China State
Institute of Pharmaceutical Industry, Shanghai, China
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4
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Beal MA, Audebert M, Barton-Maclaren T, Battaion H, Bemis JC, Cao X, Chen C, Dertinger SD, Froetschl R, Guo X, Johnson G, Hendriks G, Khoury L, Long AS, Pfuhler S, Settivari RS, Wickramasuriya S, White P. Quantitative in vitro to in vivo extrapolation of genotoxicity data provides protective estimates of in vivo dose. Environ Mol Mutagen 2023; 64:105-122. [PMID: 36495195 DOI: 10.1002/em.22521] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 11/29/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
Genotoxicity assessment is a critical component in the development and evaluation of chemicals. Traditional genotoxicity assays (i.e., mutagenicity, clastogenicity, and aneugenicity) have been limited to dichotomous hazard classification, while other toxicity endpoints are assessed through quantitative determination of points-of-departures (PODs) for setting exposure limits. The more recent higher-throughput in vitro genotoxicity assays, many of which also provide mechanistic information, offer a powerful approach for determining defined PODs for potency ranking and risk assessment. In order to obtain relevant human dose context from the in vitro assays, in vitro to in vivo extrapolation (IVIVE) models are required to determine what dose would elicit a concentration in the body demonstrated to be genotoxic using in vitro assays. Previous work has demonstrated that application of IVIVE models to in vitro bioactivity data can provide PODs that are protective of human health, but there has been no evaluation of how these models perform with in vitro genotoxicity data. Thus, the Genetic Toxicology Technical Committee, under the Health and Environmental Sciences Institute, conducted a case study on 31 reference chemicals to evaluate the performance of IVIVE application to genotoxicity data. The results demonstrate that for most chemicals considered here (20/31), the PODs derived from in vitro data and IVIVE are health protective relative to in vivo PODs from animal studies. PODs were also protective by assay target: mutations (8/13 chemicals), micronuclei (9/12), and aneugenicity markers (4/4). It is envisioned that this novel testing strategy could enhance prioritization, rapid screening, and risk assessment of genotoxic chemicals.
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Affiliation(s)
- Marc A Beal
- Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Marc Audebert
- Toxalim UMR1331, Toulouse University, INRAE, Toulouse, France
| | - Tara Barton-Maclaren
- Existing Substances Risk Assessment Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | - Hannah Battaion
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | | | - Xuefei Cao
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Connie Chen
- Health and Environmental Sciences Institute, Washington, District of Columbia, USA
| | | | | | - Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | | | | | | | - Alexandra S Long
- Existing Substances Risk Assessment Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | - Stefan Pfuhler
- Global Product Stewardship, Procter & Gamble, Cincinnati, Ohio, USA
| | - Raja S Settivari
- Mammalian Toxicology Center, Corteva Agriscience, Newark, Delaware, USA
| | - Shamika Wickramasuriya
- Existing Substances Risk Assessment Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | - Paul White
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
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5
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Fortin AMV, Long AS, Williams A, Meier MJ, Cox J, Pinsonnault C, Yauk CL, White PA. Application of a new approach methodology (NAM)-based strategy for genotoxicity assessment of data-poor compounds. Front Toxicol 2023; 5:1098432. [PMID: 36756349 PMCID: PMC9899896 DOI: 10.3389/ftox.2023.1098432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 01/02/2023] [Indexed: 01/24/2023] Open
Abstract
The conventional battery for genotoxicity testing is not well suited to assessing the large number of chemicals needing evaluation. Traditional in vitro tests lack throughput, provide little mechanistic information, and have poor specificity in predicting in vivo genotoxicity. New Approach Methodologies (NAMs) aim to accelerate the pace of hazard assessment and reduce reliance on in vivo tests that are time-consuming and resource-intensive. As such, high-throughput transcriptomic and flow cytometry-based assays have been developed for modernized in vitro genotoxicity assessment. This includes: the TGx-DDI transcriptomic biomarker (i.e., 64-gene expression signature to identify DNA damage-inducing (DDI) substances), the MicroFlow® assay (i.e., a flow cytometry-based micronucleus (MN) test), and the MultiFlow® assay (i.e., a multiplexed flow cytometry-based reporter assay that yields mode of action (MoA) information). The objective of this study was to investigate the utility of the TGx-DDI transcriptomic biomarker, multiplexed with the MicroFlow® and MultiFlow® assays, as an integrated NAM-based testing strategy for screening data-poor compounds prioritized by Health Canada's New Substances Assessment and Control Bureau. Human lymphoblastoid TK6 cells were exposed to 3 control and 10 data-poor substances, using a 6-point concentration range. Gene expression profiling was conducted using the targeted TempO-Seq™ assay, and the TGx-DDI classifier was applied to the dataset. Classifications were compared with those based on the MicroFlow® and MultiFlow® assays. Benchmark Concentration (BMC) modeling was used for potency ranking. The results of the integrated hazard calls indicate that five of the data-poor compounds were genotoxic in vitro, causing DNA damage via a clastogenic MoA, and one via a pan-genotoxic MoA. Two compounds were likely irrelevant positives in the MN test; two are considered possibly genotoxic causing DNA damage via an ambiguous MoA. BMC modeling revealed nearly identical potency rankings for each assay. This ranking was maintained when all endpoint BMCs were converted into a single score using the Toxicological Prioritization (ToxPi) approach. Overall, this study contributes to the establishment of a modernized approach for effective genotoxicity assessment and chemical prioritization for further regulatory scrutiny. We conclude that the integration of TGx-DDI, MicroFlow®, and MultiFlow® endpoints is an effective NAM-based strategy for genotoxicity assessment of data-poor compounds.
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Affiliation(s)
- Anne-Marie V. Fortin
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Alexandra S. Long
- Existing Substances Risk Assessment Bureau, Health Canada, Ottawa, ON, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Matthew J. Meier
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Julie Cox
- Bureau of Gastroenterology, Infection and Viral Diseases, Health Canada, Ottawa, ON, Canada
| | - Claire Pinsonnault
- New Substances Assessment and Control Bureau, Health Canada, Ottawa, ON, Canada
| | - Carole L. Yauk
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,*Correspondence: Carole L. Yauk, ; Paul A. White,
| | - Paul A. White
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada,*Correspondence: Carole L. Yauk, ; Paul A. White,
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Moore MM, Abraham I, Ballantyne M, Behrsing H, Cao X, Clements J, Gaca M, Gillman G, Hashizume T, Heflich RH, Hurtado S, Jordan KG, Leverette R, McHugh D, Miller-Holt J, Phillips G, Recio L, Roy S, Scian M, Simms L, Smart DJ, Stankowski LF, Tarran R, Thorne D, Weber E, Wieczorek R, Yoshino K, Curren R. Key Challenges and Recommendations for In Vitro Testing of Tobacco Products for Regulatory Applications: Consideration of Test Materials and Exposure Parameters. Altern Lab Anim 2023; 51:55-79. [PMID: 36821083 DOI: 10.1177/02611929221146536] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to identify, discuss and develop recommendations for optimal scientific and technical approaches for conducting in vitro assays, to assess potential toxicity within and across tobacco and various next generation nicotine and tobacco products (NGPs), including heated tobacco products (HTPs) and electronic nicotine delivery systems (ENDS). The third workshop (24-26 February 2020) summarised the key challenges and made recommendations concerning appropriate methods of test article generation and cell exposure from combustible cigarettes, HTPs and ENDS. Expert speakers provided their research, perspectives and recommendations for the three basic types of tobacco-related test articles: i) pad-collected material (PCM); ii) gas vapour phase (GVP); and iii) whole smoke/aerosol. These three types of samples can be tested individually, or the PCM and GVP can be combined. Whole smoke/aerosol can be bubbled through media or applied directly to cells at the air-liquid interface. Summaries of the speaker presentations and the recommendations developed by the workgroup are presented. Following discussion, the workshop concluded the following: that there needs to be greater standardisation in aerosol generation and collection processes; that methods for testing the NGPs need to be developed and/or optimised, since simply mirroring cigarette smoke testing approaches may be insufficient; that understanding and quantitating the applied dose is fundamental to the interpretation of data and conclusions from each study; and that whole smoke/aerosol approaches must be contextualised with regard to key information, including appropriate experimental controls, environmental conditioning, analytical monitoring, verification and performance criteria.
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Affiliation(s)
| | | | - Mark Ballantyne
- 63899Labcorp Early Development Laboratories Limited, Harrogate, North Yorkshire, UK
| | - Holger Behrsing
- 329003Institute for In Vitro Sciences, Gaithersburg, MD, USA
| | - Xuefei Cao
- 4136National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR, USA
| | - Julie Clements
- 63899Labcorp Early Development Laboratories Limited, Harrogate, North Yorkshire, UK
| | - Marianna Gaca
- 195179British American Tobacco, R&D, Southampton, Hampshire, UK
| | - Gene Gillman
- 520154Enthalpy Analytical, Inc., Durham, NC, USA
| | - Tsuneo Hashizume
- 74193Japan Tobacco Inc., Scientific Product Assessment Centre, Yokohama, Kanagawa, Japan
| | - Robert H Heflich
- 4136National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR, USA
| | - Sara Hurtado
- 66661Charles River Laboratories - Skokie, LLC., Skokie, IL, USA
| | - Kristen G Jordan
- RAI Services Company, Scientific & Regulatory Affairs, Winston-Salem, NC, USA
| | - Robert Leverette
- RAI Services Company, Scientific & Regulatory Affairs, Winston-Salem, NC, USA
| | - Damian McHugh
- 161931Philip Morris International R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | | | - Gary Phillips
- Life Science Technologies Ltd, Eastleigh, Hampshire, UK
| | - Leslie Recio
- 298616ILS, PO Box 13501, Research Triangle Park, NC, USA
| | | | | | | | - Daniel J Smart
- 161931Philip Morris International R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | | | - Robert Tarran
- Department of Cell Biology and Physiology, 2332University of North Carolina, Chapel Hill, NC, USA
| | - David Thorne
- 195179British American Tobacco, R&D, Southampton, Hampshire, UK
| | - Elisabeth Weber
- 588402Oekolab Ges. f. Umweltanalytik, A Member of the JT International Group of Companies, Vienna, Austria
| | | | - Kei Yoshino
- 74193Japan Tobacco Inc., Scientific Product Assessment Centre, Yokohama, Kanagawa, Japan
| | - Rodger Curren
- 329003Institute for In Vitro Sciences, Gaithersburg, MD, USA
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7
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Allemang A, Mahony C, Pfuhler S. The in vitro genotoxicity potency of mixtures of pyrrolizidine alkaloids can be explained by dose addition of the individual mixture components. Environ Mol Mutagen 2022; 63:400-407. [PMID: 36258291 DOI: 10.1002/em.22512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 10/10/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Plant-based 1,2-unsaturated Pyrrolizidine Alkaloids (PAs) are responsible for liver genotoxicity/carcinogenicity following metabolic activation, making them a relevant concern for safety assessment. Due to 21st century toxicology approaches, risk of PAs can be better discerned though an understanding of differing toxic potencies, but it is often mixtures of PAs that are found as contaminants in foods, for example, herbal teas and honey, food supplements and herbal medicines. Our study investigated whether genotoxicity potency of PAs dosed individually or in mixtures differed when measured using micronuclei formation in vitro in HepaRG human liver cells, which we and others have shown to be suitable for observing genotoxic potency differences across different PA structural classes. When equipotent concentrations of up to six different PAs representing a wide range of potencies in vitro were tested as mixtures, the observed genotoxic potency aligned favorably with results for single PAs. Similarly, when the BMD confidence intervals of these equipotent mixtures were compared with the confidence intervals of the individual PAs, only minimal variation was observed. These data support a conclusion that for this class of plant impurities, all acting via the same DNA-reactive mode of action, genotoxic potency can be regarded as additive when assessing the risk of mixtures of PAs.
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Affiliation(s)
- Ashley Allemang
- Global Product Stewardship, Human Safety, The Procter & Gamble Company, Mason, USA
| | - Catherine Mahony
- Global Product Stewardship, Human Safety, Procter & Gamble Technical Center Ltd., Reading, UK
| | - Stefan Pfuhler
- Global Product Stewardship, Human Safety, The Procter & Gamble Company, Mason, USA
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8
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Buick JK, Williams A, Meier MJ, Swartz CD, Recio L, Gagné R, Ferguson SS, Engelward BP, Yauk CL. A Modern Genotoxicity Testing Paradigm: Integration of the High-Throughput CometChip® and the TGx-DDI Transcriptomic Biomarker in Human HepaRG™ Cell Cultures. Front Public Health 2021; 9:694834. [PMID: 34485225 PMCID: PMC8416458 DOI: 10.3389/fpubh.2021.694834] [Citation(s) in RCA: 147] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 07/14/2021] [Indexed: 12/14/2022] Open
Abstract
Higher-throughput, mode-of-action-based assays provide a valuable approach to expedite chemical evaluation for human health risk assessment. In this study, we combined the high-throughput alkaline DNA damage-sensing CometChip® assay with the TGx-DDI transcriptomic biomarker (DDI = DNA damage-inducing) using high-throughput TempO-Seq®, as an integrated genotoxicity testing approach. We used metabolically competent differentiated human HepaRG™ cell cultures to enable the identification of chemicals that require bioactivation to cause genotoxicity. We studied 12 chemicals (nine DDI, three non-DDI) in increasing concentrations to measure and classify chemicals based on their ability to damage DNA. The CometChip® classified 10/12 test chemicals correctly, missing a positive DDI call for aflatoxin B1 and propyl gallate. The poor detection of aflatoxin B1 adducts is consistent with the insensitivity of the standard alkaline comet assay to bulky lesions (a shortcoming that can be overcome by trapping repair intermediates). The TGx-DDI biomarker accurately classified 10/12 agents. TGx-DDI correctly identified aflatoxin B1 as DDI, demonstrating efficacy for combined used of these complementary methodologies. Zidovudine, a known DDI chemical, was misclassified as it inhibits transcription, which prevents measurable changes in gene expression. Eugenol, a non-DDI chemical known to render misleading positive results at high concentrations, was classified as DDI at the highest concentration tested. When combined, the CometChip® assay and the TGx-DDI biomarker were 100% accurate in identifying chemicals that induce DNA damage. Quantitative benchmark concentration (BMC) modeling was applied to evaluate chemical potencies for both assays. The BMCs for the CometChip® assay and the TGx-DDI biomarker were highly concordant (within 4-fold) and resulted in identical potency rankings. These results demonstrate that these two assays can be integrated for efficient identification and potency ranking of DNA damaging agents in HepaRG™ cell cultures.
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Affiliation(s)
- Julie K Buick
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Matthew J Meier
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Carol D Swartz
- Integrated Laboratory Systems Inc. (ILS), Research Triangle Park, Durham, NC, United States
| | - Leslie Recio
- Integrated Laboratory Systems Inc. (ILS), Research Triangle Park, Durham, NC, United States
| | - Rémi Gagné
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Stephen S Ferguson
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC, United States
| | - Bevin P Engelward
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada.,Department of Biology, University of Ottawa, Ottawa, ON, Canada
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9
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Escher J. How Family Histories Can Inform Research About Germ Cell Exposures: The Example of Autism. Biol Reprod 2021; 105:767-773. [PMID: 33959752 DOI: 10.1093/biolre/ioab092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/08/2021] [Accepted: 04/30/2021] [Indexed: 12/19/2022] Open
Abstract
Throughout the scientific literature, heritable traits are routinely presumed to be genetic in origin. However, as emerging evidence from the realms of genetic toxicology and epigenomics demonstrate, heritability may be better understood as encompassing not only DNA sequence passed down through generations, but also disruptions to the parental germ cells causing de novo mutations or epigenetic alterations, with subsequent shifts in gene expression and functions in offspring. The Beyond Genes conference highlighted advances in understanding these aspects at molecular, experimental and epidemiological levels. In this commentary I suggest that future research on this topic could be inspired by collecting parents' germ cell exposure histories, with particular attention to cases of families with multiple children suffering idiopathic disorders. In so doing I focus on the endpoint of autism spectrum disorders (ASD). Rates of this serious neurodevelopment disability have climbed around the world, a growing crisis that cannot be explained by diagnostic shifts. ASD's strong heritability has prompted a research program largely focused on DNA sequencing to locate rare and common variants, but decades of this gene-focused research have revealed surprisingly little about the molecular origins of the disorder. Based on my experience as the mother of two children with idiopathic autism, and as a research philanthropist and autism advocate, I suggest ways researchers might probe parental germ cell exposure histories to develop new hypotheses that may ultimately reveal sources of non-genetic heritability in a subset of idiopathic heritable pathologies.
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Valentine CC 3rd, Young RR, Fielden MR, Kulkarni R, Williams LN, Li T, Minocherhomji S, Salk JJ. Direct quantification of in vivo mutagenesis and carcinogenesis using duplex sequencing. Proc Natl Acad Sci U S A 2020; 117:33414-25. [PMID: 33318186 DOI: 10.1073/pnas.2013724117] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Error-corrected next-generation sequencing (ecNGS) can be used to rapidly detect and quantify the in vivo mutagenic impact of environmental exposures or endogenous processes in any tissue, from any species, at any genomic location. The greater speed, higher scalability, richer data outputs, and cross-species and cross-locus applicability of ecNGS compared to existing methods make it a powerful new tool for mutational research, regulatory safety testing, and emerging clinical applications. The ability to accurately measure mutations is critical for basic research and identifying potential drug and chemical carcinogens. Current methods for in vivo quantification of mutagenesis are limited because they rely on transgenic rodent systems that are low-throughput, expensive, prolonged, and do not fully represent other species such as humans. Next-generation sequencing (NGS) is a conceptually attractive alternative for detecting mutations in the DNA of any organism; however, the limit of resolution for standard NGS is poor. Technical error rates (∼1 × 10−3) of NGS obscure the true abundance of somatic mutations, which can exist at per-nucleotide frequencies ≤1 × 10−7. Using duplex sequencing, an extremely accurate error-corrected NGS (ecNGS) technology, we were able to detect mutations induced by three carcinogens in five tissues of two strains of mice within 31 d following exposure. We observed a strong correlation between mutation induction measured by duplex sequencing and the gold-standard transgenic rodent mutation assay. We identified exposure-specific mutation spectra of each compound through trinucleotide patterns of base substitution. We observed variation in mutation susceptibility by genomic region, as well as by DNA strand. We also identified a primordial marker of carcinogenesis in a cancer-predisposed strain of mice, as evidenced by clonal expansions of cells carrying an activated oncogene, less than a month after carcinogen exposure. These findings demonstrate that ecNGS is a powerful method for sensitively detecting and characterizing mutagenesis and the early clonal evolutionary hallmarks of carcinogenesis. Duplex sequencing can be broadly applied to basic mutational research, regulatory safety testing, and emerging clinical applications.
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Bline AP, Dearfield KL, DeMarini DM, Marchetti F, Yauk CL, Escher J. Heritable hazards of smoking: Applying the "clean sheet" framework to further science and policy. Environ Mol Mutagen 2020; 61:910-921. [PMID: 33064321 PMCID: PMC7756471 DOI: 10.1002/em.22412] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/26/2020] [Accepted: 10/11/2020] [Indexed: 05/06/2023]
Abstract
All the cells in our bodies are derived from the germ cells of our parents, just as our own germ cells become the bodies of our children. The integrity of the genetic information inherited from these germ cells is of paramount importance in establishing the health of each generation and perpetuating our species into the future. There is a large and growing body of evidence strongly suggesting the existence of substances that may threaten this integrity by acting as human germ cell mutagens. However, there generally are no absolute regulatory requirements to test agents for germ cell effects. In addition, the current regulatory testing paradigms do not evaluate the impacts of epigenetically mediated intergenerational effects, and there is no regulatory framework to apply new and emerging tests in regulatory decision making. At the 50th annual meeting of the Environmental Mutagenesis and Genomics Society held in Washington, DC, in September 2019, a workshop took place that examined the heritable effects of hazardous exposures to germ cells, using tobacco smoke as the example hazard. This synopsis provides a summary of areas of concern regarding heritable hazards from tobacco smoke exposures identified at the workshop and the value of the Clean Sheet framework in organizing information to address knowledge and testing gaps.
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Affiliation(s)
- Abigail P. Bline
- Fielding School of Public HealthUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | | | | | - Francesco Marchetti
- Environmental Health Science Research Bureau, Health CanadaOttawaOntarioCanada
| | - Carole L. Yauk
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
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DeMarini DM. The mutagenesis moonshot: The propitious beginnings of the environmental mutagenesis and genomics society. Environ Mol Mutagen 2020; 61:8-24. [PMID: 31294870 PMCID: PMC6949362 DOI: 10.1002/em.22313] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 06/20/2019] [Indexed: 05/05/2023]
Abstract
A mutagenesis moonshot addressing the influence of the environment on our genetic wellbeing was launched just 2 months before astronauts landed on the moon. Its impetus included the discovery that X-rays (Muller HJ. [1927]: Science 64:84-87) and chemicals (Auerbach and Robson. [1946]: Nature 157:302) were germ-cell mutagens, the introduction of a growing number of untested chemicals into the environment after World War II, and an increasing awareness of the role of environmental pollution on human health. Due to mounting concern from influential scientists that germ-cell mutagens might be ubiquitous in the environment, Alexander Hollaender and colleagues founded in 1969 the Environmental Mutagen Society (EMS), now the Environmental Mutagenesis and Genomics Society (EMGS); Frits Sobels founded the European EMS in 1970. As Fred de Serres noted, such societies were necessary because protecting populations from environmental mutagens could not be addressed by existing scientific societies, and new multidisciplinary alliances were required to spearhead this movement. The nascent EMS gathered policy makers and scientists from government, industry, and academia who became advocates for laws requiring genetic toxicity testing of pesticides and drugs and helped implement those laws. They created an electronic database of the mutagenesis literature; established a peer-reviewed journal; promoted basic and applied research in DNA repair and mutagenesis; and established training programs that expanded the science worldwide. Despite these successes, one objective remains unfulfilled: identification of human germ-cell mutagens. After 50 years, the voyage continues, and a vibrant EMGS is needed to bring the mission to its intended target of protecting populations from genetic hazards. Environ. Mol. Mutagen. 61:8-24, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- David M. DeMarini
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina
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Cox JA, Zwart EP, Luijten M, White PA. The development and prevalidation of an in vitro mutagenicity assay based on MutaMouse primary hepatocytes, Part I: Isolation, structural, genetic, and biochemical characterization. Environ Mol Mutagen 2019; 60:331-347. [PMID: 30592088 PMCID: PMC6590113 DOI: 10.1002/em.22253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/10/2018] [Accepted: 09/15/2018] [Indexed: 06/09/2023]
Abstract
To develop an improved in vitro mammalian cell gene mutation assay, it is imperative to address the known deficiencies associated with existing assays. Primary hepatocytes isolated from the MutaMouse are ideal for an in vitro gene mutation assay due to their metabolic competence, their "normal" karyotype (i.e., neither transformed nor immortalized), and the presence of the MutaMouse transgene for rapid and reliable mutation scoring. The cells were extensively characterized to confirm their utility. Freshly isolated cells were found to have a hepatocyte-like morphology, predominantly consisting of binucleated cells. These cells maintain hepatocyte-specific markers for up to 3 days in culture. Analyses revealed a normal murine hepatocyte karyotype with a modal ploidy number of 4n. Fluorescence in situ hybridization analysis confirmed the presence of the lambda shuttle vector on chromosome 3. The doubling time was determined to be 22.5 ± 3.3 h. Gene expression and enzymatic activity of key Phase I and Phase II metabolic enzymes were maintained for at least 8 and 24 h in culture, respectively. Exposure to β-naphthoflavone led to approximately 900- and 9-fold increases in Cyp1a1 and Cyp1a2 gene expression, respectively, and approximately twofold induction in cytochrome P450 (CYP) 1A1/1A2 activity. Exposure to phenobarbital resulted in an approximately twofold increase in CYP 2B6 enzyme activity. Following this characterization, it is evident that MutaMouse primary hepatocytes have considerable promise for in vitro mutagenicity assessment. The performance of these cells in an in vitro gene mutation assay is assessed in Part II. Environ. Mol. Mutagen. 60:331-347, 2019. © 2018 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
- Julie A. Cox
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOntarioCanada
| | - Edwin P. Zwart
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Mirjam Luijten
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Paul A. White
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOntarioCanada
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Cox JA, Zwart EP, Luijten M, White PA. The development and prevalidation of an in vitro mutagenicity assay based on MutaMouse primary hepatocytes, Part II: Assay performance for the identification of mutagenic chemicals. Environ Mol Mutagen 2019; 60:348-360. [PMID: 30714215 PMCID: PMC6593967 DOI: 10.1002/em.22277] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/23/2019] [Accepted: 01/29/2019] [Indexed: 06/09/2023]
Abstract
As demonstrated in Part I, cultured MutaMouse primary hepatocytes (PHs) are suitable cells for use in an in vitro gene mutation assay due to their metabolic competence, their "normal" phenotype, and the presence of the MutaMouse transgene for reliable mutation scoring. The performance of these cells in an in vitro gene mutation assay is evaluated in this study, Part II. A panel of 13 mutagenic and nonmutagenic compounds was selected to investigate the performance of the MutaMouse PH in vitro gene mutation assay. The nine mutagens represent a range of classes of chemicals and include mutagens that are both direct-acting and requiring metabolic activation. All the mutagens tested, except for ICR 191, elicited significant, concentration-dependent increases in mutant frequency (MF) ranging from 2.6- to 14.4-fold over the control. None of the four nonmutagens, including two misleading, or "false," positives (i.e., tertiary butylhydroquinone [TBHQ] and eugenol), yielded any significant increases in MF. The benchmark dose covariate approach facilitated ranking of the positive chemicals from most (i.e., 3-nitrobenzanthrone [3-NBA], benzo[a]pyrene [BaP], and aflatoxin B1 [AFB1]) to least (i.e., N-ethyl-N-nitrosourea [ENU]) potent. Overall, the results of this preliminary validation study suggest that this assay may serve as a complimentary tool alongside the standard genotoxicity test battery. This study, alongside Part I, illustrates the promise of MutaMouse PHs for use in an in vitro gene mutation assay, particularly for chemicals requiring metabolic activation. Environ. Mol. Mutagen. 60:348-360, 2019. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
- Julie A. Cox
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
| | - Edwin P. Zwart
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Mirjam Luijten
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Paul A. White
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
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Schisler MR, Gollapudi BB, Moore MM. Evaluation of U. S. National Toxicology Program (NTP) mouse lymphoma assay data using International Workshop on Genotoxicity Tests (IWGT) and the Organization for Economic Co-Operation and Development (OECD) criteria. Environ Mol Mutagen 2018; 59:829-841. [PMID: 30357906 DOI: 10.1002/em.22250] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/21/2018] [Accepted: 08/23/2018] [Indexed: 06/08/2023]
Abstract
The forward gene mutation mouse lymphoma assay (MLA) is widely used, as part of a regulatory test battery, to identify the genotoxic potential of chemicals. It identifies mutagens capable of inducing a variety of genetic events. During the 1980s and early 1990s, the U.S. National Toxicology Program (NTP) developed a publicly available database (https://tools.niehs.nih.gov/cebs3/ui/) of MLA results. This database is used to define the mutagenic potential of chemicals, to develop structure-activity relationships (SAR), and to draw correlations to animal carcinogenicity findings. New criteria for MLA conduct and data interpretation were subsequently developed by the International Workshop for Genotoxicity Testing (IWGT) and the Organization of Economic Cooperation and Development (OECD). These recommendations are included in a new OECD Test Guideline (TG490). It is essential that early experimental data be re-examined and classified according to the current criteria to build a curated database to better inform chemical-specific evaluations and SAR models. We re-evaluated more than 1900 experiments representing 342 chemicals against the newly defined acceptance criteria for background mutant frequency (MF), cloning efficiency (CE), positive control values (modified for this evaluation due to lack of colony sizing), appropriate dose selection, and data consistency. Only 17% of the evaluated experiments met all acceptance criteria used in this re-evaluation. Results from 211 chemicals were determined to be uninterpretable, 92 were positive, and 39 equivocal. The authors could not classify any responses as negative because colony sizing was not performed for any of these experiments and it is clear, based on many experiment with unacceptably low background and positive control MFs, that mutant colony recovery was often suboptimal. This re-evaluation provides a curated database for the MLA. A similar curation should be done for other widely used genetic toxicology assays, but will be more difficult for certain assays (e.g., in vitro chromosomal aberrations) because important parameters such as level of cytotoxicity were often not evaluated/reported. Environ. Mol. Mutagen. 59:829-841, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
| | - B B Gollapudi
- Exponent, Inc., Center for Health Sciences, Alexandria, Virginia
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Affiliation(s)
- Jeffrey M Peters
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, Maryland 20892
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Wills JW, Johnson GE, Battaion HL, Slob W, White PA. Comparing BMD-derived genotoxic potency estimations across variants of the transgenic rodent gene mutation assay. Environ Mol Mutagen 2017; 58:632-643. [PMID: 28945287 PMCID: PMC5698699 DOI: 10.1002/em.22137] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 08/04/2017] [Accepted: 08/08/2017] [Indexed: 05/07/2023]
Abstract
There is growing interest in quantitative analysis of in vivo genetic toxicity dose-response data, and use of point-of-departure (PoD) metrics such as the benchmark dose (BMD) for human health risk assessment (HHRA). Currently, multiple transgenic rodent (TGR) assay variants, employing different rodent strains and reporter transgenes, are used for the assessment of chemically-induced genotoxic effects in vivo. However, regulatory issues arise when different PoD values (e.g., lower BMD confidence intervals or BMDLs) are obtained for the same compound across different TGR assay variants. This study therefore employed the BMD approach to examine the ability of different TGR variants to yield comparable genotoxic potency estimates. Review of over 2000 dose-response datasets identified suitably-matched dose-response data for three compounds (ethyl methanesulfonate or EMS, N-ethyl-N-nitrosourea or ENU, and dimethylnitrosamine or DMN) across four commonly-used murine TGR variants (Muta™Mouse lacZ, Muta™Mouse cII, gpt delta and BigBlue® lacI). Dose-response analyses provided no conclusive evidence that TGR variant choice significantly influences the derived genotoxic potency estimate. This conclusion was reliant upon taking into account the importance of comparing BMD confidence intervals as opposed to directly comparing PoD values (e.g., comparing BMDLs). Comparisons with earlier works suggested that with respect to potency determination, tissue choice is potentially more important than choice of TGR assay variant. Scoring multiple tissues selected on the basis of supporting toxicokinetic information is therefore recommended. Finally, we used typical within-group variances to estimate preliminary endpoint-specific benchmark response (BMR) values across several TGR variants/tissues. We discuss why such values are required for routine use of genetic toxicity PoDs for HHRA. Environ. Mol. Mutagen. 58:632-643, 2017. © 2017 Her Majesty the Queen in Right of Canada. Environmental and Molecular Mutagenesis Published by Wiley Periodicals, Inc.
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Affiliation(s)
- John W. Wills
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
| | - George E. Johnson
- Institute of Life Science, Swansea University Medical SchoolSwanseaUnited Kingdom
| | - Hannah L. Battaion
- Department of Chemistry and Biomolecular SciencesUniversity of OttawaOttawaOntarioCanada
| | - Wout Slob
- National Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Paul A. White
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
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Dearfield KL, Gollapudi BB, Bemis JC, Benz RD, Douglas GR, Elespuru RK, Johnson GE, Kirkland DJ, LeBaron MJ, Li AP, Marchetti F, Pottenger LH, Rorije E, Tanir JY, Thybaud V, van Benthem J, Yauk CL, Zeiger E, Luijten M. Next generation testing strategy for assessment of genomic damage: A conceptual framework and considerations. Environ Mol Mutagen 2017; 58:264-283. [PMID: 27650663 DOI: 10.1002/em.22045] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 08/08/2016] [Indexed: 06/06/2023]
Abstract
For several decades, regulatory testing schemes for genetic damage have been standardized where the tests being utilized examined mutations and structural and numerical chromosomal damage. This has served the genetic toxicity community well when most of the substances being tested were amenable to such assays. The outcome from this testing is usually a dichotomous (yes/no) evaluation of test results, and in many instances, the information is only used to determine whether a substance has carcinogenic potential or not. Over the same time period, mechanisms and modes of action (MOAs) that elucidate a wider range of genomic damage involved in many adverse health outcomes have been recognized. In addition, a paradigm shift in applied genetic toxicology is moving the field toward a more quantitative dose-response analysis and point-of-departure (PoD) determination with a focus on risks to exposed humans. This is directing emphasis on genomic damage that is likely to induce changes associated with a variety of adverse health outcomes. This paradigm shift is moving the testing emphasis for genetic damage from a hazard identification only evaluation to a more comprehensive risk assessment approach that provides more insightful information for decision makers regarding the potential risk of genetic damage to exposed humans. To enable this broader context for examining genetic damage, a next generation testing strategy needs to take into account a broader, more flexible approach to testing, and ultimately modeling, of genomic damage as it relates to human exposure. This is consistent with the larger risk assessment context being used in regulatory decision making. As presented here, this flexible approach for examining genomic damage focuses on testing for relevant genomic effects that can be, as best as possible, associated with an adverse health effect. The most desired linkage for risk to humans would be changes in loci associated with human diseases, whether in somatic or germ cells. The outline of a flexible approach and associated considerations are presented in a series of nine steps, some of which can occur in parallel, which was developed through a collaborative effort by leading genetic toxicologists from academia, government, and industry through the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) Genetic Toxicology Technical Committee (GTTC). The ultimate goal is to provide quantitative data to model the potential risk levels of substances, which induce genomic damage contributing to human adverse health outcomes. Any good risk assessment begins with asking the appropriate risk management questions in a planning and scoping effort. This step sets up the problem to be addressed (e.g., broadly, does genomic damage need to be addressed, and if so, how to proceed). The next two steps assemble what is known about the problem by building a knowledge base about the substance of concern and developing a rational biological argument for why testing for genomic damage is needed or not. By focusing on the risk management problem and potential genomic damage of concern, the next step of assay(s) selection takes place. The work-up of the problem during the earlier steps provides the insight to which assays would most likely produce the most meaningful data. This discussion does not detail the wide range of genomic damage tests available, but points to types of testing systems that can be very useful. Once the assays are performed and analyzed, the relevant data sets are selected for modeling potential risk. From this point on, the data are evaluated and modeled as they are for any other toxicology endpoint. Any observed genomic damage/effects (or genetic event(s)) can be modeled via a dose-response analysis and determination of an estimated PoD. When a quantitative risk analysis is needed for decision making, a parallel exposure assessment effort is performed (exposure assessment is not detailed here as this is not the focus of this discussion; guidelines for this assessment exist elsewhere). Then the PoD for genomic damage is used with the exposure information to develop risk estimations (e.g., using reference dose (RfD), margin of exposure (MOE) approaches) in a risk characterization and presented to risk managers for informing decision making. This approach is applicable now for incorporating genomic damage results into the decision-making process for assessing potential adverse outcomes in chemically exposed humans and is consistent with the ILSI HESI Risk Assessment in the 21st Century (RISK21) roadmap. This applies to any substance to which humans are exposed, including pharmaceuticals, agricultural products, food additives, and other chemicals. It is time for regulatory bodies to incorporate the broader knowledge and insights provided by genomic damage results into the assessments of risk to more fully understand the potential of adverse outcomes in chemically exposed humans, thus improving the assessment of risk due to genomic damage. The historical use of genomic damage data as a yes/no gateway for possible cancer risk has been too narrowly focused in risk assessment. The recent advances in assaying for and understanding genomic damage, including eventually epigenetic alterations, obviously add a greater wealth of information for determining potential risk to humans. Regulatory bodies need to embrace this paradigm shift from hazard identification to quantitative analysis and to incorporate the wider range of genomic damage in their assessments of risk to humans. The quantitative analyses and methodologies discussed here can be readily applied to genomic damage testing results now. Indeed, with the passage of the recent update to the Toxic Substances Control Act (TSCA) in the US, the new generation testing strategy for genomic damage described here provides a regulatory agency (here the US Environmental Protection Agency (EPA), but suitable for others) a golden opportunity to reexamine the way it addresses risk-based genomic damage testing (including hazard identification and exposure). Environ. Mol. Mutagen. 58:264-283, 2017. © 2016 The Authors. Environmental and Molecular Mutagenesis Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Kerry L Dearfield
- U.S. Department of Agriculture, Food Safety and Inspection Service, Washington, District of Columbia
| | - B Bhaskar Gollapudi
- Exponent® Inc, Center for Toxicology and Mechanistic Biology, Midland, Michigan
| | | | | | - George R Douglas
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
| | - Rosalie K Elespuru
- U.S. Food and Drug Administration, CDRH/OSEL DBCMS, Silver Spring, Maryland
| | - George E Johnson
- Institute of Life Science, College of Medicine, Swansea University, Swansea, SA2 8PP, United Kingdom
| | | | - Matthew J LeBaron
- The Dow Chemical Company, Molecular, Cellular, and Biochemical Toxicology, Midland, Michigan
| | - Albert P Li
- In Vitro ADMET Laboratories LLC, Columbia, Maryland
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
| | - Lynn H Pottenger
- Formerly of The Dow Chemical Company, Toxicology & Environmental Research and Consulting now with Olin Corporation, Midland, Michigan
| | - Emiel Rorije
- National Institute for Public Health and the Environment (RIVM), Center for Safety of Substances and Products, Bilthoven, 3720 BA, The Netherlands
| | - Jennifer Y Tanir
- ILSI Health and Environmental Sciences Institute (HESI), Washington, District of Columbia
| | - Veronique Thybaud
- Sanofi, Drug Disposition, Safety and Animal Research, Vitry-sur-Seine, France
| | - Jan van Benthem
- National Institute for Public Health and the Environment (RIVM), Center for Health Protection, Bilthoven, 3720 BA, The Netherlands
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
| | - Errol Zeiger
- Errol Zeiger Consulting, Chapel Hill, North Carolina
| | - Mirjam Luijten
- National Institute for Public Health and the Environment (RIVM), Center for Health Protection, Bilthoven, 3720 BA, The Netherlands
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Abstract
The ability of non-genotoxic agents to induce cancer has been documented and clearly requires a reassessment of testing for environmental and human safety. Drug safety testing has historically relied on test batteries designed to detect DNA damage leading to mutation and cancer. The standard genetic toxicology testing battery has been a reliable tool set to identify small molecules/chemicals as hazards that could lead to genetic changes in organisms and induction of cancer. While pharmaceutical companies and regulatory agencies have extensively used the standard battery, it is not suitable for compounds that may induce epigenetic changes. Additionally, many pharmaceutical companies have changed their product portfolios to include peptides and/or other biological molecules, which are not expected to be genotoxic in their own right. If we are to best use our growing knowledge regarding chemicals and biomolecules that induce heritable changes via epigenetic mechanisms, then we must ask what changes may be needed in our testing paradigm to predict long-term downstream effects through epigenetic mechanisms.
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Affiliation(s)
- Kevin Sweder
- Forensic and National Security Sciences Institute, Center for Science & Technology, Syracuse University, Syracuse, NY, USA
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Fellows MD. Targeting safety in the clinic for precise genome editing using CRISPR: a genotoxicologist's perspective. Per Med 2016; 13:279-282. [PMID: 29749810 DOI: 10.2217/pme-2016-0026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Mick D Fellows
- AstraZeneca Innovative Medicines & Early Development Darwin Building 310, Milton Science Park, Cambridge, CB4 OWG, UK
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Yauk CL, Buick JK, Williams A, Swartz CD, Recio L, Li H, Fornace AJ, Thomson EM, Aubrecht J. Application of the TGx-28.65 transcriptomic biomarker to classify genotoxic and non-genotoxic chemicals in human TK6 cells in the presence of rat liver S9. Environ Mol Mutagen 2016; 57:243-60. [PMID: 26946220 PMCID: PMC5021161 DOI: 10.1002/em.22004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/03/2016] [Accepted: 02/04/2016] [Indexed: 05/05/2023]
Abstract
In vitro transcriptional signatures that predict toxicities can facilitate chemical screening. We previously developed a transcriptomic biomarker (known as TGx-28.65) for classifying agents as genotoxic (DNA damaging) and non-genotoxic in human lymphoblastoid TK6 cells. Because TK6 cells do not express cytochrome P450s, we confirmed accurate classification by the biomarker in cells co-exposed to 1% 5,6 benzoflavone/phenobarbital-induced rat liver S9 for metabolic activation. However, chemicals may require different types of S9 for activation. Here we investigated the response of TK6 cells to higher percentages of Aroclor-, benzoflavone/phenobarbital-, or ethanol-induced rat liver S9 to expand TGx-28.65 biomarker applicability. Transcriptional profiles were derived 3 to 4 hr following a 4 hr co-exposure of TK6 cells to test chemicals and S9. Preliminary studies established that 10% Aroclor- and 5% ethanol-induced S9 alone did not induce the TGx-28.65 biomarker genes. Seven genotoxic and two non-genotoxic chemicals (and concurrent solvent and positive controls) were then tested with one of the S9s (selected based on cell survival and micronucleus induction). Relative survival and micronucleus frequency was assessed by flow cytometry in cells 20 hr post-exposure. Genotoxic/non-genotoxic chemicals were accurately classified using the different S9s. One technical replicate of cells co-treated with dexamethasone and 10% Aroclor-induced S9 was falsely classified as genotoxic, suggesting caution in using high S9 concentrations. Even low concentrations of genotoxic chemicals (those not causing cytotoxicity) were correctly classified, demonstrating that TGx-28.65 is a sensitive biomarker of genotoxicity. A meta-analysis of datasets from 13 chemicals supports that different S9s can be used in TK6 cells, without impairing classification using the TGx-28.65 biomarker.
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Affiliation(s)
- Carole L. Yauk
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Julie K. Buick
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Carol D. Swartz
- Integrated Laboratory Systems IncResearch Triangle ParkNorth Carolina
| | - Leslie Recio
- Integrated Laboratory Systems IncResearch Triangle ParkNorth Carolina
| | - Heng‐Hong Li
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Albert J. Fornace
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Errol M. Thomson
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Jiri Aubrecht
- Drug Safety Research and Development, Pfizer IncGrotonConnecticut
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22
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Abstract
Incorporating phenotypic screening as a key strategy enhances predictivity and translatability of drug discovery efforts. Cellular imaging serves as a "phenotypic anchor" to identify important toxicologic pathology that encompasses an array of underlying mechanisms, thus provides an effective means to reduce drug development failures due to insufficient safety. This mini-review highlights the latest advances in hepatotoxicity, cardiotoxicity, and genetic toxicity tests that utilized cellular imaging as a screening strategy, and recommends path forward for further improvement.
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23
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Buick JK, Moffat I, Williams A, Swartz CD, Recio L, Hyduke DR, Li H, Fornace AJ, Aubrecht J, Yauk CL. Integration of metabolic activation with a predictive toxicogenomics signature to classify genotoxic versus nongenotoxic chemicals in human TK6 cells. Environ Mol Mutagen 2015; 56:520-34. [PMID: 25733247 PMCID: PMC4506226 DOI: 10.1002/em.21940] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 12/24/2014] [Accepted: 01/14/2015] [Indexed: 05/21/2023]
Abstract
The use of integrated approaches in genetic toxicology, including the incorporation of gene expression data to determine the molecular pathways involved in the response, is becoming more common. In a companion article, a genomic biomarker was developed in human TK6 cells to classify chemicals as genotoxic or nongenotoxic. Because TK6 cells are not metabolically competent, we set out to broaden the utility of the biomarker for use with chemicals requiring metabolic activation. Specifically, chemical exposures were conducted in the presence of rat liver S9. The ability of the biomarker to classify genotoxic (benzo[a]pyrene, BaP; aflatoxin B1, AFB1) and nongenotoxic (dexamethasone, DEX; phenobarbital, PB) agents correctly was evaluated. Cells were exposed to increasing chemical concentrations for 4 hr and collected 0 hr, 4 hr, and 20 hr postexposure. Relative survival, apoptosis, and micronucleus frequency were measured at 24 hr. Transcriptome profiles were measured with Agilent microarrays. Statistical modeling and bioinformatics tools were applied to classify each chemical using the genomic biomarker. BaP and AFB1 were correctly classified as genotoxic at the mid- and high concentrations at all three time points, whereas DEX was correctly classified as nongenotoxic at all concentrations and time points. The high concentration of PB was misclassified at 24 hr, suggesting that cytotoxicity at later time points may cause misclassification. The data suggest that the use of S9 does not impair the ability of the biomarker to classify genotoxicity in TK6 cells. Finally, we demonstrate that the biomarker is also able to accurately classify genotoxicity using a publicly available dataset derived from human HepaRG cells.
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Affiliation(s)
- Julie K. Buick
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Ivy Moffat
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Water and Air Quality Bureau, Health CanadaOttawaOntarioCanada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Carol D. Swartz
- Integrated Laboratory Systems Inc.Research Triangle ParkNorth Carolina
| | - Leslie Recio
- Integrated Laboratory Systems Inc.Research Triangle ParkNorth Carolina
| | - Daniel R. Hyduke
- Biological Engineering DepartmentUtah State UniversityLoganUtah
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Heng‐Hong Li
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Albert J. Fornace
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Jiri Aubrecht
- Drug Safety Research and Development, Pfizer Inc.GrotonConnecticut
| | - Carole L. Yauk
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
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24
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Buick JK, Moffat I, Williams A, Swartz CD, Recio L, Hyduke DR, Li H, Fornace AJ, Aubrecht J, Yauk CL. Integration of metabolic activation with a predictive toxicogenomics signature to classify genotoxic versus nongenotoxic chemicals in human TK6 cells. Environ Mol Mutagen 2015; 56:520-534. [PMID: 25733247 PMCID: PMC4506226 DOI: 10.1002/em.21940|] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 12/24/2014] [Accepted: 01/14/2015] [Indexed: 06/10/2023]
Abstract
The use of integrated approaches in genetic toxicology, including the incorporation of gene expression data to determine the molecular pathways involved in the response, is becoming more common. In a companion article, a genomic biomarker was developed in human TK6 cells to classify chemicals as genotoxic or nongenotoxic. Because TK6 cells are not metabolically competent, we set out to broaden the utility of the biomarker for use with chemicals requiring metabolic activation. Specifically, chemical exposures were conducted in the presence of rat liver S9. The ability of the biomarker to classify genotoxic (benzo[a]pyrene, BaP; aflatoxin B1, AFB1) and nongenotoxic (dexamethasone, DEX; phenobarbital, PB) agents correctly was evaluated. Cells were exposed to increasing chemical concentrations for 4 hr and collected 0 hr, 4 hr, and 20 hr postexposure. Relative survival, apoptosis, and micronucleus frequency were measured at 24 hr. Transcriptome profiles were measured with Agilent microarrays. Statistical modeling and bioinformatics tools were applied to classify each chemical using the genomic biomarker. BaP and AFB1 were correctly classified as genotoxic at the mid- and high concentrations at all three time points, whereas DEX was correctly classified as nongenotoxic at all concentrations and time points. The high concentration of PB was misclassified at 24 hr, suggesting that cytotoxicity at later time points may cause misclassification. The data suggest that the use of S9 does not impair the ability of the biomarker to classify genotoxicity in TK6 cells. Finally, we demonstrate that the biomarker is also able to accurately classify genotoxicity using a publicly available dataset derived from human HepaRG cells.
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Affiliation(s)
- Julie K. Buick
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Ivy Moffat
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
- Water and Air Quality Bureau, Health CanadaOttawaOntarioCanada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
| | - Carol D. Swartz
- Integrated Laboratory Systems Inc.Research Triangle ParkNorth Carolina
| | - Leslie Recio
- Integrated Laboratory Systems Inc.Research Triangle ParkNorth Carolina
| | - Daniel R. Hyduke
- Biological Engineering DepartmentUtah State UniversityLoganUtah
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Heng‐Hong Li
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Albert J. Fornace
- Department of Biochemistry and Molecular and Cellular BiologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
- Department of OncologyGeorgetown University Medical CenterWashingtonDistrict of Columbia
| | - Jiri Aubrecht
- Drug Safety Research and Development, Pfizer Inc.GrotonConnecticut
| | - Carole L. Yauk
- Environmental Health Science and Research Bureau, Health CanadaOttawaOntarioCanada
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25
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Abstract
Chlorpyrifos (CPF), methyl parathion (MPT), and malathion (MLT) are among the most extensively used organophosphate (OP) pesticides in India. DNA protein cross-links (DPC) and DNA strand breaks are toxic lesions associated with the mechanism(s) of toxicity of carcinogenic compounds. In the present study, we examined the hypothesis that individual and interactive genotoxic effects of CPF, MPT, and MLT are involved in the formation of DPC and DNA strand break. The DNA strand break was measured by comet assay and expressed as DNA damage index, while DPC estimation was carried out by fluorescence emission assay. The results showed that exposure of rat lymphocytes with CPF, MPT, and MLT caused significantly marked increase in DNA damage and DPC formation in time-dependent manner. MPT caused the highest damage, and these pesticides do not potentiate the toxicity of each other.
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Affiliation(s)
- A Ojha
- Department of Pharmacology, All India Institute of Medical Sciences, New Delhi, India
| | - Y K Gupta
- Department of Pharmacology, All India Institute of Medical Sciences, New Delhi, India
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26
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de Conti A, Kobets T, Tryndyak V, Burnett SD, Han T, Fuscoe JC, Beland FA, Doerge DR, Pogribny IP. Persistence of furan-induced epigenetic aberrations in the livers of F344 rats. Toxicol Sci 2014; 144:217-26. [PMID: 25539665 DOI: 10.1093/toxsci/kfu313] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Furan is a heterocyclic organic compound produced in the chemical manufacturing industry and also found in a broad range of food products, including infant formulas and baby foods. Previous reports have indicated that the adverse biological effects of furan, including its liver tumorigenicity, may be associated with epigenetic abnormalities. In the present study, we investigated the persistence of epigenetic alterations in rat liver. Male F344 rats were treated by gavage 5 days per week with 8 mg furan/kg body weight (bw)/day for 90 days. After the last treatment, rats were divided randomly into 4 groups; 1 group of rats was sacrificed 24 h after the last treatment, whereas other groups were maintained without further furan treatment for an additional 90, 180, or 360 days. Treatment with furan for 90 days resulted in alterations in histone lysine methylation and acetylation, induction of base-excision DNA repair genes, suggesting oxidative damage to DNA, and changes in the gene expression in the livers. A majority of these furan-induced molecular changes was transient and disappeared after the cessation of furan treatment. In contrast, histone H3 lysine 9 and H3 lysine 56 showed a sustained and time-depended decrease in acetylation, which was associated with formation of heterochromatin and altered gene expression. These results indicate that furan-induced adverse effects may be mechanistically related to sustained changes in histone lysine acetylation that compromise the ability of cells to maintain and control properly the expression of genetic information.
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Affiliation(s)
- Aline de Conti
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Tetyana Kobets
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Volodymyr Tryndyak
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Sarah D Burnett
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Tao Han
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - James C Fuscoe
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Frederick A Beland
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Daniel R Doerge
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
| | - Igor P Pogribny
- *Division of Biochemical Toxicology and Division of Systems Biology, National Center for Toxicological Research, Jefferson, Arkansas 72079
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27
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Arencibia-Arrebola DF, Rosario-Fernández LA, Suárez-Fernández YE, Vidal-Novoa A, Delgado-Roche L. Comparison in the efficiency of different murine lines for genotoxicity assays. Interdiscip Toxicol 2012; 5:141-9. [PMID: 23554554 PMCID: PMC3600514 DOI: 10.2478/v10102-012-0023-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 09/10/2012] [Accepted: 09/25/2012] [Indexed: 11/21/2022] Open
Abstract
The aim of this research was to compare the efficiency of different murine lines for genotoxicity assays. Rats and mice of different murine lines were used. The spontaneous and induced indexes were evaluated according to alkaline comet assay of peripheral blood leukocytes, micronucleus and chromosomic aberration assay of bone marrow cell, and sperm head morphology assay. In most of the evaluated assays the line of Balb/c mice turned out to be the ideal biomodel, with less spontaneous indexes and high induced indexes to the mutagen used; allowing to detect in a narrow error margin those substances that are classified of very low genotoxicity. These results demonstrate that genetically the line of Balb/c mice in both sexes is more stable than the other ones evaluated. This suggests the use of the Balb/c line on in vivo genotoxicity assay will increase sensibility and robustness.
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Affiliation(s)
| | | | | | | | - Livan Delgado-Roche
- Center of Study for the Research and Biological Evaluations (CEIEB-U.H), Havana, Cuba
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28
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Claxton LD, de A. Umbuzeiro G, DeMarini DM. The Salmonella mutagenicity assay: the stethoscope of genetic toxicology for the 21st century. Environ Health Perspect 2010; 118:1515-22. [PMID: 20682480 PMCID: PMC2974687 DOI: 10.1289/ehp.1002336] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 06/09/2010] [Accepted: 08/02/2010] [Indexed: 05/03/2023]
Abstract
OBJECTIVES According to the 2007 National Research Council report Toxicology for the Twenty-First Century, modern methods (e.g., "omics," in vitro assays, high-throughput testing, computational methods) will lead to the emergence of a new approach to toxicology. The Salmonella mammalian microsome mutagenicity assay has been central to the field of genetic toxicology since the 1970s. Here we document the paradigm shifts engendered by the assay, the validation and applications of the assay, and how the assay is a model for future in vitro toxicology assays. DATA SOURCES We searched PubMed, Scopus, and Web of Knowledge using key words relevant to the Salmonella assay and additional genotoxicity assays. DATA EXTRACTION We merged the citations, removing duplicates, and categorized the papers by year and topic. DATA SYNTHESIS The Salmonella assay led to two paradigm shifts: that some carcinogens were mutagens and that some environmental samples (e.g., air, water, soil, food, combustion emissions) were mutagenic. Although there are > 10,000 publications on the Salmonella assay, covering tens of thousands of agents, data on even more agents probably exist in unpublished form, largely as proprietary studies by industry. The Salmonella assay is a model for the development of 21st century in vitro toxicology assays in terms of the establishment of standard procedures, ability to test various agents, transferability across laboratories, validation and testing, and structure-activity analysis. CONCLUSIONS Similar to a stethoscope as a first-line, inexpensive tool in medicine, the Salmonella assay can serve a similar, indispensable role in the foreseeable future of 21st century toxicology.
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Affiliation(s)
- Larry D. Claxton
- Genetic and Cellular Toxicology Branch, Integrated Systems Toxicology Division, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Gisela de A. Umbuzeiro
- Laboratório de Ecotoxicologia Aquática e Limnologia, Faculdade de Tecnologia, Universidade Estadual de Campinas, Limeira, São Paulo, Brazil
| | - David M. DeMarini
- Genetic and Cellular Toxicology Branch, Integrated Systems Toxicology Division, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Address correspondence to D.M. DeMarini, B105-03, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711 USA. Telephone: (919) 541-1510. Fax: (919) 541-0694. E-mail:
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29
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Matson CW, Clark BW, Jenny MJ, Fleming CR, Hahn ME, Di Giulio RT. Development of the morpholino gene knockdown technique in Fundulus heteroclitus: a tool for studying molecular mechanisms in an established environmental model. Aquat Toxicol 2008; 87:289-95. [PMID: 18378331 PMCID: PMC2413436 DOI: 10.1016/j.aquatox.2008.02.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 02/13/2008] [Accepted: 02/19/2008] [Indexed: 05/06/2023]
Abstract
A significant challenge in environmental toxicology is that many genetic and genomic tools available in laboratory models are not developed for commonly used environmental models. The Atlantic killifish (Fundulus heteroclitus) is one of the most studied teleost environmental models, yet few genetic or genomic tools have been developed for use in this species. The advancement of genetic and evolutionary toxicology will require that many of the tools developed in laboratory models be transferred into species more applicable to environmental toxicology. Antisense morpholino oligonucleotide (MO) gene knockdown technology has been widely utilized to study development in zebrafish and has been proven to be a powerful tool in toxicological investigations through direct manipulation of molecular pathways. To expand the utility of killifish as an environmental model, MO gene knockdown technology was adapted for use in Fundulus. Morpholino microinjection methods were altered to overcome the significant differences between these two species. Morpholino efficacy and functional duration were evaluated with molecular and phenotypic methods. A cytochrome P450-1A (CYP1A) MO was used to confirm effectiveness of the methodology. For CYP1A MO-injected embryos, a 70% reduction in CYP1A activity, a 86% reduction in total CYP1A protein, a significant increase in beta-naphthoflavone-induced teratogenicity, and estimates of functional duration (50% reduction in activity 10 dpf, and 86% reduction in total protein 12 dpf) conclusively demonstrated that MO technologies can be used effectively in killifish and will likely be just as informative as they have been in zebrafish.
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Affiliation(s)
- Cole W. Matson
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708
| | - Bryan W. Clark
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708
| | - Matthew J. Jenny
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - Carrie R. Fleming
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708
| | - Mark E. Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - Richard T. Di Giulio
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708
- Corresponding Author: Richard T. Di Giulio, Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708-0328, (919) 613-8024,
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