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Li X, Le Y, Li Y, Chen S, Guo L, Fu X, Manjanatha MG, Mei N. Evaluation of weak genotoxicity of hydroxychloroquine in human TK6 cells. Toxicol Lett 2024; 393:84-95. [PMID: 38311193 DOI: 10.1016/j.toxlet.2024.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/25/2024] [Accepted: 01/29/2024] [Indexed: 02/10/2024]
Abstract
Hydroxychloroquine (HCQ), a derivative of chloroquine (CQ), is an antimalarial and antirheumatic drug. Since there is limited data available on the genotoxicity of HCQ, in the current study, we used a battery of in vitro assays to systematically examine the genotoxicity of HCQ in human lymphoblastoid TK6 cells. We first showed that HCQ is not mutagenic in TK6 cells up to 80 μM with or without exogenous metabolic activation. Subsequently, we found that short-term (3-4 h) HCQ treatment did not cause DNA strand breakage as measured by the comet assay and the phosphorylation of histone H2A.X (γH2A.X), and did not induce chromosomal damage as determined by the micronucleus (MN) assay. However, after 24-h treatment, both CQ and HCQ induced comparable and weak DNA damage and MN formation in TK6 cells; upregulated p53 and p53-mediated DNA damage responsive genes; and triggered apoptosis and mitochondrial damage that may partially contribute to the observed MN formation. Using a benchmark dose (BMD) modeling analysis, the lower 95% confidence limit of BMD50 values (BMDL50) for MN induction in TK6 cells were about 19.7 μM for CQ and 16.3 μM for HCQ. These results provide additional information for quantitative genotoxic risk assessment of these drugs.
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Affiliation(s)
- Xilin Li
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
| | - Yuan Le
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
| | - Yuxi Li
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
| | - Si Chen
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
| | - Lei Guo
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
| | - Xin Fu
- Division of Pharmacology Toxicology Review, Office of Safety and Clinical Evaluation, Center for Drug Evaluation and Research, Silver Spring, MD 20993, USA
| | - Mugimane G Manjanatha
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
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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. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023. [PMID: 38115239 DOI: 10.1002/em.22582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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Menz J, Götz ME, Gündel U, Gürtler R, Herrmann K, Hessel-Pras S, Kneuer C, Kolrep F, Nitzsche D, Pabel U, Sachse B, Schmeisser S, Schumacher DM, Schwerdtle T, Tralau T, Zellmer S, Schäfer B. Genotoxicity assessment: opportunities, challenges and perspectives for quantitative evaluations of dose-response data. Arch Toxicol 2023; 97:2303-2328. [PMID: 37402810 PMCID: PMC10404208 DOI: 10.1007/s00204-023-03553-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 06/21/2023] [Indexed: 07/06/2023]
Abstract
Genotoxicity data are mainly interpreted in a qualitative way, which typically results in a binary classification of chemical entities. For more than a decade, there has been a discussion about the need for a paradigm shift in this regard. Here, we review current opportunities, challenges and perspectives for a more quantitative approach to genotoxicity assessment. Currently discussed opportunities mainly include the determination of a reference point (e.g., a benchmark dose) from genetic toxicity dose-response data, followed by calculation of a margin of exposure (MOE) or derivation of a health-based guidance value (HBGV). In addition to new opportunities, major challenges emerge with the quantitative interpretation of genotoxicity data. These are mainly rooted in the limited capability of standard in vivo genotoxicity testing methods to detect different types of genetic damage in multiple target tissues and the unknown quantitative relationships between measurable genotoxic effects and the probability of experiencing an adverse health outcome. In addition, with respect to DNA-reactive mutagens, the question arises whether the widely accepted assumption of a non-threshold dose-response relationship is at all compatible with the derivation of a HBGV. Therefore, at present, any quantitative genotoxicity assessment approach remains to be evaluated case-by-case. The quantitative interpretation of in vivo genotoxicity data for prioritization purposes, e.g., in connection with the MOE approach, could be seen as a promising opportunity for routine application. However, additional research is needed to assess whether it is possible to define a genotoxicity-derived MOE that can be considered indicative of a low level of concern. To further advance quantitative genotoxicity assessment, priority should be given to the development of new experimental methods to provide a deeper mechanistic understanding and a more comprehensive basis for the analysis of dose-response relationships.
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Affiliation(s)
- Jakob Menz
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany.
| | - Mario E Götz
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Ulrike Gündel
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Rainer Gürtler
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Kristin Herrmann
- Department of Pesticides Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Stefanie Hessel-Pras
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Carsten Kneuer
- Department of Pesticides Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Franziska Kolrep
- Department of Safety in the Food Chain, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Dana Nitzsche
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Ulrike Pabel
- Department of Safety in the Food Chain, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Benjamin Sachse
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Sebastian Schmeisser
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - David M Schumacher
- Department of Safety in the Food Chain, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Tanja Schwerdtle
- German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Tewes Tralau
- Department of Pesticides Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Sebastian Zellmer
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
| | - Bernd Schäfer
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Germany
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4
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Chepelev N, Long AS, Beal M, Barton‐Maclaren T, Johnson G, Dearfield KL, Roberts DJ, van Benthem J, White P. Establishing a quantitative framework for regulatory interpretation of genetic toxicity dose-response data: Margin of exposure case study of 48 compounds with both in vivo mutagenicity and carcinogenicity dose-response data. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:4-15. [PMID: 36345771 PMCID: PMC10107494 DOI: 10.1002/em.22517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 09/28/2022] [Accepted: 11/01/2022] [Indexed: 05/03/2023]
Abstract
Quantitative relationships between carcinogenic potency and mutagenic potency have been previously examined using a benchmark dose (BMD)-based approach. We extended those analyses by using human exposure data for 48 compounds to calculate carcinogenicity-derived and genotoxicity-derived margin of exposure values (MOEs) that can be used to prioritize substances for risk management. MOEs for 16 of the 48 compounds were below 10,000, and consequently highlighted for regulatory concern. Of these, 15 were highlighted using genotoxicity-derived (micronucleus [MN] dose-response data) MOEs. A total of 13 compounds were highlighted using carcinogenicity-derived MOEs; 12 compounds were overlapping. MOEs were also calculated using transgenic rodent (TGR) mutagenicity data. For 10 of the 12 compounds examined using TGR data, the results similarly revealed that mutagenicity-derived MOEs yield regulatory decisions that correspond with those based on carcinogenicity-derived MOEs. The effect of benchmark response (BMR) on MOE determination was also examined. Reinterpretation of the analyses using a BMR of 50% indicated that four out of 15 compounds prioritized using MN-derived MOEs based on a default BMR of 5% would have been missed. The results indicate that regulatory decisions based on in vivo genotoxicity dose-response data would be consistent with those based on carcinogenicity dose-response data; in some cases, genotoxicity-based decisions would be more conservative. Going forward, and in the absence of carcinogenicity data, in vivo genotoxicity assays (MN and TGR) can be used to effectively prioritize substances for regulatory action. Routine use of the MOE approach necessitates the availability of reliable human exposure estimates, and consensus regarding appropriate BMRs for genotoxicity endpoints.
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Affiliation(s)
- Nikolai Chepelev
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
| | - Alexandra S. Long
- Department of Pharmacology and ToxicologyUniversity of TorontoTorontoOntarioCanada
| | - Marc Beal
- Existing Substances Risk Assessment BureauHealth CanadaOttawaOntarioCanada
| | | | - George Johnson
- Swansea University Medical SchoolSwansea UniversitySwanseaUK
| | | | | | - Jan van Benthem
- National Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Paul White
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
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5
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Zhu X, Huo J, Zeng Z, Liu Y, Li R, Chen Y, Zhang L, Chen J. Determination of potential thresholds for N-ethyl-N-nitrosourea and ethyl methanesulfonate based on a multi-endpoint genotoxicity assessment platform in rats. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:85128-85142. [PMID: 35793016 PMCID: PMC9646607 DOI: 10.1007/s11356-022-21605-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
The main goal of the study was to investigate the genotoxic response of N-ethyl-N-nitrosourea (ENU) and ethyl methanesulfonate (EMS) at low doses in a multi-endpoint genotoxicity assessment platform in rats and to derive potential thresholds and related metrics. Male Sprague-Dawley rats were treated by daily oral gavage for 28 consecutive days with ENU (0.25 ~ 8 mg/kg bw) and EMS (5 ~ 160 mg/kg bw), both with six closely spaced dose levels. Pig-a gene mutation assay, micronucleus test, and comet assay were performed in several timepoints. Then, the dose-response relationships were analyzed for possible points of departure (PoD) using the no observed genotoxic effect level and benchmark dose (BMD) protocols with different critical effect sizes (CES, 0.05, 0.1, 0.5, and 1SD). Overall, dose-dependent increases in all investigated endpoints were found for ENU and EMS. PoDs varied across genetic endpoints, timepoints, and statistical methods, and selecting an appropriate lower 95% confidence limit of BMD needs a comprehensive consideration of the mode of action of chemicals, the characteristics of tests, and the model fitting methods. Under the experimental conditions, the PoDs of ENU and EMS were 0.0036 mg/kg bw and 1.7 mg/kg bw, respectively.
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Affiliation(s)
- Xuejiao Zhu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, Sichuan, China
| | - Jiao Huo
- Department of Nutrition and Food Safety, Chongqing Center for Disease Control and Prevention, Chongqing, China
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
| | - Zhu Zeng
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- Chengdu Fifth People's Hospital, Chengdu, Sichuan, China
| | - Yunjie Liu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Ruirui Li
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Yiyi Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Lishi Zhang
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Jinyao Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China.
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
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6
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Li X, He X, Le Y, Guo X, Bryant MS, Atrakchi AH, McGovern TJ, Davis-Bruno KL, Keire DA, Heflich RH, Mei N. Genotoxicity evaluation of nitrosamine impurities using human TK6 cells transduced with cytochrome P450s. Arch Toxicol 2022; 96:3077-3089. [PMID: 35882637 DOI: 10.1007/s00204-022-03347-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/14/2022] [Indexed: 12/15/2022]
Abstract
Many nitrosamines are recognized as mutagens and potent rodent carcinogens. Over the past few years, nitrosamine impurities have been detected in various drugs leading to drug recalls. Although nitrosamines are included in a 'cohort of concern' because of their potential human health risks, most of this concern is based on rodent cancer and bacterial mutagenicity data, and there are little data on their genotoxicity in human-based systems. In this study, we employed human lymphoblastoid TK6 cells transduced with human cytochrome P450 (CYP) 2A6 to evaluate the genotoxicity of six nitrosamines that have been identified as impurities in drug products: N-nitrosodiethylamine (NDEA), N-nitrosoethylisopropylamine (NEIPA), N-nitroso-N-methyl-4-aminobutanoic acid (NMBA), N-nitrosomethylphenylamine (NMPA), N-nitrosodiisopropylamine (NDIPA), and N-nitrosodibutylamine (NDBA). Using flow cytometry-based assays, we found that 24-h treatment with NDEA, NEIPA, NMBA, and NMPA caused concentration-dependent increases in the phosphorylation of histone H2A.X (γH2A.X) in CYP2A6-expressing TK6 cells. Metabolism of these four nitrosamines by CYP2A6 also caused significant increases in micronucleus frequency as well as G2/M phase cell-cycle arrest. In addition, nuclear P53 activation was found in CYP2A6-expressing TK6 cells exposed to NDEA, NEIPA, and NMPA. Overall, the genotoxic potency of the six nitrosamine impurities in our test system was NMPA > NDEA ≈ NEIPA > NMBA > NDBA ≈ NDIPA. This study provides new information on the genotoxic potential of nitrosamines in human cells, complementing test results generated from traditional assays and partially addressing the issue of the relevance of nitrosamine genotoxicity for humans. The metabolically competent human cell system reported here may be a useful model for risk assessment of nitrosamine impurities found in drugs.
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Affiliation(s)
- Xilin Li
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Xiaobo He
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Yuan Le
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Xiaoqing Guo
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Matthew S Bryant
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Aisar H Atrakchi
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Timothy J McGovern
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Karen L Davis-Bruno
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - David A Keire
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Robert H Heflich
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Nan Mei
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA.
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7
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Zeng Z, Huo J, Zhu X, Liu Y, Li R, Chen Y, Zhang L, Chen J. Characterization of benzo[ a]pyrene and colchicine based on an in vivo repeat-dosing multi-endpoint genotoxicity quantitative assessment platform. Mutagenesis 2022; 37:213-225. [PMID: 35869703 DOI: 10.1093/mutage/geac012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Two prototypical genotoxicants, benzo[a]pyrene (B[a]P) and colchicine (COL), were selected as model compounds to deduce their quantitative genotoxic dose–response relationship at low doses in a multi-endpoint genotoxicity assessment platform. Male Sprague-Dawley rats were treated with B[a]P (2.5–80 mg/kg bw/day) and COL (0.125–2 mg/kg bw/day) daily for 28 days. The parameters included were as follows: comet assay in the peripheral blood and liver, Pig-a gene mutation assay in the peripheral blood, and micronucleus test in the peripheral blood and bone marrow. A significant increase was observed in Pig-a mutant frequency in peripheral blood for B[a]P (started at 40 mg/kg bw/day on Day 14, started at 20 mg/kg bw/day on Day 28), whereas no statistical difference for COL was observed. Micronucleus frequency in reticulocytes of the peripheral blood and bone marrow increased significantly for B[a]P (80 mg/kg bw/day on Day 4, started at 20 mg/kg bw/day on Days 14 and 28 in the blood; started at 20 mg/kg bw/day on Day 28 in the bone marrow) and COL (started at 2 mg/kg bw/day on Day 14, 1 mg/kg bw/day on Day 28 in the blood; started at 1 mg/kg bw/day on Day 28 in the bone marrow). No statistical variation was found in indexes of comet assay at all time points for B[a]P and COL in the peripheral blood and liver. The dose–response relationships of Pig-a and micronucleus test data were analyzed for possible point of departures using three quantitative approaches, i.e., the benchmark dose, breakpoint dose, and no observed genotoxic effect level. The practical thresholds of the genotoxicity of B[a]P and COL estimated in this study were 0.122 and 0.0431 mg/kg bw/day, respectively, and our results also provided distinct genotoxic mode of action of the two chemicals.
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Affiliation(s)
- Zhu Zeng
- Department of Clinical Nutrition, Chengdu Fifth People’s Hospital , Chengdu, Sichuan , China
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
| | - Jiao Huo
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Department of Nutrition and Food Safety, Chongqing Center for Disease Control and Prevention , Chongqing , China
| | - Xuejiao Zhu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University , Chengdu, Sichuan , China
| | - Yunjie Liu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
| | - Ruirui Li
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
| | - Yiyi Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Infections Disease Prevention and Immunization Program Office, ChengHua Center for Disease Control and Prevention , Chengdu, Sichuan , China
| | - Lishi Zhang
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
| | - Jinyao Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
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8
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Tang X, Chen Y, Zhu X, Miao Y, Wang D, Zhang J, Li R, Zhang L, Chen J. Alternariol monomethyl ether toxicity and genotoxicity in male Sprague-Dawley rats: 28-Day in vivo multi-endpoint assessment. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2022; 873:503435. [PMID: 35094809 DOI: 10.1016/j.mrgentox.2021.503435] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/29/2021] [Accepted: 11/30/2021] [Indexed: 01/08/2023]
Abstract
Alternariol monomethyl ether (AME), a typical Alternaria toxin, has often been detected in grains. We have measured the general toxicity and genotoxicity of AME with a 28-day multi-endpoint (Pig-a assay + in vivo micronucleus [MN] test + comet assay) platform. Male Sprague-Dawley rats were administered AME (1.84, 3.67, or 7.35 μg/kg body weight/day), N-Ethyl-N-nitrosourea (40 mg/kg body weight/day), or corn oil by gavage for 28 consecutive days. Another group (AME-high-dose + recovery) was maintained for a further 14 days after the end of the AME administration. Hematology and serum biochemistry results suggested that AME might compromise the immune system. The histopathology results indicated that AME can cause liver (inflammatory cell infiltration, steatosis, and edema), kidney (renal glomerular atrophy), and spleen (white pulp atrophy) damage. The genotoxicity results showed that AME can induce gene mutations, chromosome breakage, and DNA damage, but the effects were diminished after the recovery period. According to point-of-departure analysis (BMDL10), the risk to the population of exposure to AME cannot be ignored and further assessment is needed.
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Affiliation(s)
- Xinyao Tang
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Yiyi Chen
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Chenghua Center for Disease Control and Prevention, Chengdu, Sichuan, China.
| | - Xia Zhu
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Yeqiu Miao
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Dongxia Wang
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Jing Zhang
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Ruirui Li
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Lishi Zhang
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
| | - Jinyao Chen
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China; Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
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9
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Yamamoto H, Shibuya K, Fukushima T, Hashizume T. Effects of antioxidant capacity on micronucleus induction by cigarette smoke in mammalian cells. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2022; 873:503427. [PMID: 35094812 DOI: 10.1016/j.mrgentox.2021.503427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 06/14/2023]
Abstract
We have compared micronucleus (MN) induction by cigarette smoke in the L5178Y, TK6, and CHL/IU cell lines. The test sample was total particulate matter of 3R4F reference cigarette smoke, suspended in DMSO. After 3-h treatment, with or without a rat liver S9 metabolic activation system, followed by 24-h recovery, dose-dependent MN increases were seen in all cell lines. However, CHL/IU and TK6 cells were more resistant than L5178Y cells (comparison by Benchmark Doses with PROAST software). 3R4F smoke generates reactive oxygen species (ROS). Therefore, we explored the relationship between the sensitivities to 3R4F smoke and the antioxidant capacities of the cell lines. While the total antioxidant capacities were not significantly different among the cell lines, cellular glutathione (GSH) was higher in CHL/IU cells than in L5178Y cells. Pretreatment of CHL/IU cells with a GSH precursor, N-acetylcysteine (NAC), reduced the genotoxicity/cytotoxicity of 3R4F, whereas an inhibitor of GSH biosynthesis, buthionine sulfoximine (BSO), enhanced it. The effects of NAC and BSO were also seen after treatment with allyl isothiocyanate, a ROS-generating chemical, but not with mitomycin C, a ROS-independent genotoxicant. Pretreatment with NAC increased cellular thiol levels. From the present results, the genotoxicity and cytotoxicity of cigarette smoke differs among these cell lines in a manner that may be related to their antioxidant thiol levels.
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Affiliation(s)
- Haruna Yamamoto
- Scientific Product Assessment Center, R&D Group, Japan Tobacco Inc., 6-2 Umegaoka, Aoba-ku, Yokohama, Kanagawa, 227-8512, Japan.
| | - Kaori Shibuya
- Scientific Product Assessment Center, R&D Group, Japan Tobacco Inc., 6-2 Umegaoka, Aoba-ku, Yokohama, Kanagawa, 227-8512, Japan.
| | - Toshiro Fukushima
- Scientific Product Assessment Center, R&D Group, Japan Tobacco Inc., 6-2 Umegaoka, Aoba-ku, Yokohama, Kanagawa, 227-8512, Japan.
| | - Tsuneo Hashizume
- Scientific Product Assessment Center, R&D Group, Japan Tobacco Inc., 6-2 Umegaoka, Aoba-ku, Yokohama, Kanagawa, 227-8512, Japan.
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10
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Cao Y, Xi J, You X, Liu W, Luan Y. Dose-response genotoxicity of triclosan in mice: an estimate of acceptable daily intake based on organ toxicity. Toxicol Res (Camb) 2021; 10:1153-1161. [PMID: 34956618 PMCID: PMC8692727 DOI: 10.1093/toxres/tfab098] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/23/2021] [Accepted: 10/10/2021] [Indexed: 11/13/2022] Open
Abstract
Triclosan (TCS) is widely used and it bioaccumulates in humans. We found that TCS induced DNA damage in TK6 cell in our previous work. Herein, we performed a pilot assay of the TK6 cell/TK gene (TK+/-) mutation assay without metabolic activation for 24 h and found that TCS significantly induced mutation frequency. We further investigated the dose-response toxicity and genotoxicity of TCS. We combined the newly developed Pig-a gene mutation assay with bone marrow micronucleus (MN) test in a 19-day short-term study. ICR mice were administered orally with TCS at six dose levels from 0 to1000 mg/kg/day. We quantitatively assessed the dose-response relationships for the Pig-a assay, MN test, and organ coefficient data for possible points of departure (PoDs) by estimating the benchmark dose using PROAST software. We did not observe elevated Pig-a mutant frequency or MN frequency in TCS-treated mice. But a dose-dependent and statistically significant increase in liver organ coefficient data was observed. The PoD and acceptable daily intake based on organ toxicity were further developed and no greater than 1.82 and 0.00182 mg/kg/day, respectively, indicating that the toxicity of TCS may has been underestimated in previous studies and greater attention should be paid to low-level TCS exposure.
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Affiliation(s)
- Yiyi Cao
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Jing Xi
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Xinyue You
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Weiying Liu
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Yang Luan
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai 200025, People’s Republic of China
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11
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Mittelstaedt RA, Dad A, Pearce MG, Heflich RH, Cao X. Effect of life stage and target tissue on dose-response assessment of ethyl methane sulfonate-induced genotoxicity. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2021; 62:482-489. [PMID: 34647641 DOI: 10.1002/em.22465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 09/17/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
In order to investigate the possibility that treatment age affects the genotoxic response to ethyl methane sulfonate (EMS) exposure, we dosed gpt-delta neonatal mice on postnatal days 1-28 with 5-100 mg/kg/day of EMS and measured micronucleus (MN) induction in peripheral blood and gpt gene mutation in liver, lung, bone marrow, small intestine, spleen, and kidney. The data were compared to measurements from similarly exposed adult gpt-delta mice. Our results indicate that the peripheral blood MN frequencies in mice treated as neonates are not substantially different from those measured in mice treated as adults. There were, however, differences in tissue-specific gpt mutation responses in mice treated with EMS as neonates and adults. Greater mutant frequencies were seen in DNA isolated from kidney of mice treated as neonates, whereas the mutant frequencies in bone marrow, liver, and spleen were greater in the animals treated as adults. Benchmark dose potency ranking indicated that the differences for kidney were significant. Our data indicate that there are differences in EMS-induced genotoxicity between mice treated as adults and neonates; the differences, however, are relatively small.
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Affiliation(s)
- Roberta A Mittelstaedt
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Azra Dad
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Mason G Pearce
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Robert H Heflich
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Xuefei Cao
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
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12
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Chen R, You X, Cao Y, Masumura K, Ando T, Hamada S, Horibata K, Wan J, Xi J, Zhang X, Honma M, Luan Y. Benchmark dose analysis of multiple genotoxicity endpoints in gpt delta mice exposed to aristolochic acid I. Mutagenesis 2021; 36:87-94. [PMID: 33367723 DOI: 10.1093/mutage/geaa034] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 11/24/2020] [Indexed: 11/12/2022] Open
Abstract
As the carcinogenic risk of herbs containing aristolochic acids (AAs) is a global health issue, quantitative evaluation of toxicity is needed for the regulatory decision-making and risk assessment of AAs. In this study, we selected AA I (AAI), the most abundant and representative compound in AAs, to treat transgenic gpt delta mice at six gradient doses ranging from 0.125 to 4 mg/kg/day for 28 days. AAI-DNA adduct frequencies and gpt gene mutation frequencies (MFs) in the kidney, as well as Pig-a gene MFs and micronucleated reticulocytes (MN-RETs) frequencies in peripheral blood, were monitored. The dose-response (DR) relationship data for these in vivo genotoxicity endpoints were quantitatively evaluated using an advanced benchmark dose (BMD) approach with different critical effect sizes (CESs; i.e., BMD5, BMD10, BMD50 and BMD100). The results showed that the AAI-DNA adduct frequencies, gpt MFs and the MN-RETs presented good DR relationship to the administrated doses, and the corresponding BMDL100 (the lower 90% confidence interval of the BMD100) values were 0.017, 0.509 and 3.9 mg/kg/day, respectively. No positive responses were observed in the Pig-a MFs due to bone marrow suppression caused by AAI. Overall, we quantitatively evaluated the genotoxicity of AAI at low doses for multiple endpoints for the first time. Comparisons of BMD100 values across different endpoints provide a basis for the risk assessment and regulatory decision-making of AAs and are also valuable for understanding the genotoxicity mechanism of AAs.
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Affiliation(s)
- Ruixue Chen
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xinyue You
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yiyi Cao
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Kenichi Masumura
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, Japan
| | - Tomoko Ando
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, Japan
| | - Shuichi Hamada
- Tokyo Laboratory BoZo Research Center Inc., Hanegi, Setagaya, Tokyo, Japan
| | - Katsuyoshi Horibata
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, Japan
| | - Jingjing Wan
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing Xi
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xinyu Zhang
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Masamitsu Honma
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, Japan
| | - Yang Luan
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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13
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Kluxen FM, Weber K, Strupp C, Jensen SM, Hothorn LA, Garcin JC, Hofmann T. Using historical control data in bioassays for regulatory toxicology. Regul Toxicol Pharmacol 2021; 125:105024. [PMID: 34364928 DOI: 10.1016/j.yrtph.2021.105024] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 06/21/2021] [Accepted: 07/30/2021] [Indexed: 12/12/2022]
Abstract
Historical control data (HCD) consist of pooled control group responses from bioassays. These data must be collected and are often used or reported in regulatory toxicology studies for multiple purposes: as quality assurance for the test system, to help identify toxicological effects and their effect-size relevance and to address the statistical multiple comparison problem. The current manuscript reviews the various classical and potential new approaches for using HCD. Issues in current practice are identified and recommendations for improved use and discussion are provided. Furthermore, stakeholders are invited to discuss whether it is necessary to consider uncertainty when using HCD formally and statistically in toxicological discussions and whether binary inclusion/exclusion criteria for HCD should be revised to a tiered information contribution to assessments. Overall, the critical value of HCD in toxicological bioassays is highlighted when used in a weight-of-evidence assessment.
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Affiliation(s)
| | | | | | - Signe M Jensen
- Department of Plant and Efoldnvironmental Sciences, University of Copenhagen, Copenhagen, Denmark
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14
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Johnson GE, Dobo K, Gollapudi B, Harvey J, Kenny J, Kenyon M, Lynch A, Minocherhomji S, Nicolette J, Thybaud V, Wheeldon R, Zeller A. Permitted daily exposure limits for noteworthy N-nitrosamines. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2021; 62:293-305. [PMID: 34089278 DOI: 10.1002/em.22446] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/07/2021] [Accepted: 05/11/2021] [Indexed: 06/12/2023]
Abstract
A genotoxic carcinogen, N-nitrosodimethylamine (NDMA), was detected as a synthesis impurity in some valsartan drugs in 2018, and other N-nitrosamines, such as N-nitrosodiethylamine (NDEA), were later detected in other sartan products. N-nitrosamines are pro-mutagens that can react with DNA following metabolism to produce DNA adducts, such as O6 -alkyl-guanine. The adducts can result in DNA replication miscoding errors leading to GC>AT mutations and increased risk of genomic instability and carcinogenesis. Both NDMA and NDEA are known rodent carcinogens in male and female rats. The DNA repair enzyme, methylguanine DNA-methyltransferase can restore DNA integrity via the removal of alkyl groups from guanine in an error-free fashion and this can result in nonlinear dose responses and a point of departure or "practical threshold" for mutation at low doses of exposure. Following International recommendations (ICHM7; ICHQ3C and ICHQ3D), we calculated permissible daily exposures (PDE) for NDMA and NDEA using published rodent cancer bioassay and in vivo mutagenicity data to determine benchmark dose values and define points of departure and adjusted with appropriate uncertainty factors (UFs). PDEs for NDMA were 6.2 and 0.6 μg/person/day for cancer and mutation, respectively, and for NDEA, 2.2 and 0.04 μg/person/day. Both PDEs are higher than the acceptable daily intake values (96 ng for NDMA and 26.5 ng for NDEA) calculated by regulatory authorities using simple linear extrapolation from carcinogenicity data. These PDE calculations using a bench-mark approach provide a more robust assessment of exposure limits compared with simple linear extrapolations and can better inform risk to patients exposed to the contaminated sartans.
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Affiliation(s)
- George E Johnson
- Swansea University Medical School, Swansea University, Swansea, Wales, UK
| | - Krista Dobo
- Genetic Toxicology, Drug Safety Research and Development, Pfizer, Groton, Connecticut, USA
| | - Bhaskar Gollapudi
- Center for Toxicology and Mechanistic Biology, Exponent Consulting, Midland, Michigan, USA
| | | | | | - Michelle Kenyon
- Genetic Toxicology, Drug Safety Research and Development, Pfizer, Groton, Connecticut, USA
| | | | | | - John Nicolette
- Genetic, Environmental and Occupational Toxicology, AbbVie, Chicago, Illinois, USA
| | | | - Ryan Wheeldon
- Swansea University Medical School, Swansea University, Swansea, Wales, UK
| | - Andreas Zeller
- Pharmaceutical Sciences, pRED Innovation Center Basel, Hoffmann-La Roche Ltd, Basel, Switzerland
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15
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Schuler M, Tomlinson L, Homiski M, Cheung J, Zhan Y, Coffing S, Engel M, Rubitski E, Seitis G, Hales K, Robertson A, Vispute S, Cook J, Radi Z, Hollingshead B. Experiments in the EpiDerm 3D Skin In Vitro Model and Minipigs In Vivo Indicate Comparatively Lower In Vivo Skin Sensitivity of Topically Applied Aneugenic Compounds. Toxicol Sci 2021; 180:103-121. [PMID: 33481035 DOI: 10.1093/toxsci/kfaa189] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Risk management of in vitro aneugens for topically applied compounds is not clearly defined because there is no validated methodology to accurately measure compound concentration in proliferating stratum basale keratinocytes of the skin. Here, we experimentally tested several known aneugens in the EpiDerm reconstructed human skin in vitro micronucleus assay and compared the results to flow cytometric mechanistic biomarkers (phospho-H3; MPM2, DNA content). We then evaluated similar biomarkers (Ki-67, nuclear area) using immunohistochemistry in skin sections of minipigs following topical exposure the potent aneugens, colchicine, and hesperadin. Data from the EpiDerm model showed positive micronucleus responses for all aneugens tested following topical or direct media dosing with similar sensitivity when adjusted for applied dose. Quantitative benchmark dose-response analysis exhibited increases in the mitotic index biomarkers phospho-H3 and MPM2 for tubulin binders and polyploidy for aurora kinase inhibitors are at least as sensitive as the micronucleus endpoint. By comparison, the aneugens tested did not induce histopathological changes, increases in Ki-67 immunolabeling or nuclear area in skin sections from the in vivo minipig study at doses in significant excess of those eliciting a response in vitro. Results indicate the EpiDerm in vitro micronucleus assay is suitable for the hazard identification of aneugens. The lack of response in the minipig studies indicates that the barrier function of the minipig skin, which is comparable to human skin, protects from the effects of aneugens in vivo. These results provide a basis for conducting additional studies in the future to further refine this understanding.
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Affiliation(s)
- Maik Schuler
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Lindsay Tomlinson
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Michael Homiski
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Jennifer Cheung
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Yutian Zhan
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Stephanie Coffing
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Maria Engel
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Elizabeth Rubitski
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Gary Seitis
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Katherine Hales
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Andrew Robertson
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Saurabh Vispute
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Jon Cook
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Zaher Radi
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
| | - Brett Hollingshead
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340 and Cambridge, Massachusetts 02139, USA
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16
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A weight of evidence assessment of the genotoxicity of 2,6-xylidine based on existing and new data, with relevance to safety of lidocaine exposure. Regul Toxicol Pharmacol 2021; 119:104838. [DOI: 10.1016/j.yrtph.2020.104838] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 10/31/2020] [Accepted: 12/03/2020] [Indexed: 12/25/2022]
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17
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Cordelli E, Bignami M, Pacchierotti F. Comet assay: a versatile but complex tool in genotoxicity testing. Toxicol Res (Camb) 2021; 10:68-78. [PMID: 33613974 DOI: 10.1093/toxres/tfaa093] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/26/2020] [Accepted: 11/12/2020] [Indexed: 12/11/2022] Open
Abstract
The comet assay is a versatile method for measuring DNA strand breaks in individual cells. It can also be applied to cells isolated from treated animals. In this review, we highlight advantages and limitations of this in vivo comet assay in a regulatory context. Modified versions of the standard protocol detect oxidized DNA bases and may be used to reveal sites of DNA base loss, DNA interstrand crosslinks, and the extent of DNA damage induced indirectly by reactive oxygen species elicited by chemical-induced oxidative stress. The assay is, however, at best semi-quantitative, and we discuss possible approaches to improving DNA damage quantitation and highlight the necessity of optimizing protocol standardization to enhance the comparability of results between laboratories. As a genotoxicity test in vivo, the in vivo comet assay has the advantage over the better established micronucleus erythrocyte test that it can be applied to any organ, including those that are specific targets of chemical carcinogens or those that are the first sites of contact of ingested or inhaled mutagens. We illustrate this by examples of its use in risk assessment for the food contaminants ochratoxin and furan. We suggest that improved quantitation is required to reveal the full potential of the comet assay and enhance its role in the battery of in vivo approaches to characterize the mechanisms of toxicity and carcinogenicity of chemicals and to aid the determination of safe human exposure limits.
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Affiliation(s)
- Eugenia Cordelli
- Territorial and Production Systems Sustainability Department, Health Protection Technology Division, ENEA, CR Casaccia, Via Anguillarese 301, Rome 00123, Italy
| | - Margherita Bignami
- Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome 00161, Italy
| | - Francesca Pacchierotti
- Territorial and Production Systems Sustainability Department, Health Protection Technology Division, ENEA, CR Casaccia, Via Anguillarese 301, Rome 00123, Italy
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18
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Guo X, Seo JE, Petibone D, Tryndyak V, Lee UJ, Zhou T, Robison TW, Mei N. Performance of HepaRG and HepG2 cells in the high-throughput micronucleus assay for in vitro genotoxicity assessment. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2020; 83:702-717. [PMID: 32981483 DOI: 10.1080/15287394.2020.1822972] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The micronucleus (MN) assay is a core test used to evaluate genotoxic potential of xenobiotics. The traditional in vitro MN assay is usually conducted in cells lacking metabolic competency or by supplementing cultures with an exogenous rat S9 metabolic system, which creates a significant assay limitation for detecting genotoxic metabolites. Our previous study demonstrated that compared to HepG2, HepaRG cells exhibited a significantly higher level of CYP450 enzyme activities and detected a greater portion of genotoxic carcinogens requiring metabolic activation using the Comet assay. The aim of this study was to assess the performance of HepaRG cells in the flow cytometry-based MN assay by testing 28 compounds with known genotoxic or carcinogenic modes of action (MoA). HepaRG cells exhibited higher sensitivity (83%) than HepG2 cells (67%) in detecting 12 indirect-acting genotoxicants or carcinogens. The HepaRG MN assay was 100% specific and 93% accurate in detecting genotoxic potential of the 28 compounds. Quantitative comparison of the MN concentration-response data using benchmark dose analysis showed that most of the tested compounds induced higher % MN in HepaRG than HepG2 cells. In addition, HepaRG cells were compatible with the Multiflow DNA damage assay, which predicts the genotoxic MoA of compounds tested. These results suggest that high-throughput flow cytometry-based MN assay may be adapted using HepaRG cells for genotoxicity assessment, and that HepaRG cells appear to be more sensitive than HepG2 cells in detecting genotoxicants or carcinogens that require metabolic activation.
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Affiliation(s)
- Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration , Jefferson, AR, USA
| | - Ji-Eun Seo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration , Jefferson, AR, USA
| | - Dayton Petibone
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration , Jefferson, AR, USA
| | - Volodymyr Tryndyak
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration , Jefferson, AR, USA
| | - Un Jung Lee
- Department of Medicine, Epidemiology and Population Health, Albert Einstein College of Medicine , Bronx, NY, USA
| | - Tong Zhou
- Center for Veterinary Medicine, U.S. Food and Drug Administration , Rockville, MD, USA
| | - Timothy W Robison
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration , Silver Spring, MD, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration , Jefferson, AR, USA
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19
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Gollapudi BB, Su S, Li AA, Johnson GE, Reiss R, Albertini RJ. Genotoxicity as a toxicologically relevant endpoint to inform risk assessment: A case study with ethylene oxide. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:852-871. [PMID: 32926486 PMCID: PMC7756744 DOI: 10.1002/em.22408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 05/05/2023]
Abstract
The purpose of the present investigation is to analyze the in vivo genotoxicity dose-response data of ethylene oxide (EO) and the applicability of the derived point-of-departure (PoD) values when estimating permitted daily exposure (PDE) values. A total of 40 data sets were identified from the literature, and benchmark dose analyses were conducted using PROAST software to identify a PoD value. Studies employing the inhalation route of exposure and assessing gene or chromosomal mutations and chromosomal damage in various tissues were considered the most relevant for assessing risk from EO, since these effects are likely to contribute to adverse health consequences in exposed individuals. The PoD estimates were screened for precision and the values were divided by data-derived adjustment factors. For gene mutations, the lowest PDE was 285 parts per trillion (ppt) based on the induction of lacI mutations in the testes of mice following 48 weeks of exposure to EO. The corresponding lowest PDE value for chromosomal mutations was 1,175 ppt for heritable translocations in mice following 8.5 weeks of EO exposure. The lowest PDE for chromosomal aberrations was 238 ppt in the mouse peripheral blood lymphocytes following 48 weeks of inhalation exposure. The diverse dose-response data for EO-induced genotoxicity enabled the derivation of PoDs for various endpoints, tissues, and species and identified 238 ppt as the lowest PDE in this retrospective analysis.
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Affiliation(s)
| | - Steave Su
- Exponent, Inc., Center for Health SciencesNew YorkNew YorkUSA
| | - Abby A. Li
- Exponent, Inc., Center for Health SciencesOaklandCaliforniaUSA
| | | | - Richard Reiss
- Exponent, Inc., Center for Health SciencesAlexandriaVirginiaUSA
| | - Richard J. Albertini
- Department of PathologyUniversity of Vermont College of MedicineBurlingtonVermontUSA
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Li X, He X, Chen S, Guo X, Bryant MS, Guo L, Manjanatha MG, Zhou T, Witt KL, Mei N. Evaluation of pyrrolizidine alkaloid-induced genotoxicity using metabolically competent TK6 cell lines. Food Chem Toxicol 2020; 145:111662. [PMID: 32798647 PMCID: PMC9969979 DOI: 10.1016/j.fct.2020.111662] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 07/21/2020] [Accepted: 07/26/2020] [Indexed: 12/12/2022]
Abstract
Pyrrolizidine alkaloid (PA)-containing plants are among the most common poisonous plants affecting humans, livestock, and wildlife worldwide. A large number of PAs are known to induce genetic damage after metabolic activation. In the present study, using a battery of fourteen newly developed TK6 cell lines, each expressing a single human cytochrome P450 (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C18, 2C9, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7), we identified specific CYPs responsible for bioactivating three PAs - lasiocarpine, riddelliine, and senkirkine. Among the fourteen cell lines, cells expressing CYP3A4 showed significant increases in PA-induced cytotoxicity, evidenced by decreased ATP production and cell viability, and increased caspase 3/7 activities. LC-MS/MS analysis revealed the formation of 1-hydroxymethyl-7-hydroxy-6,7-dihydropyrrolizine (DHP), the main reactive metabolite of PAs, in CYP3A4-expressing TK6 cells. DHP was also detected in CYP3A5- and 3A7-expressing cells after PA exposure, but to a much lesser extent. Subsequently, using a high-throughput micronucleus assay, we demonstrated that PAs induced concentration-dependent increases in micronuclei and G2/M phase cell cycle arrest in three CYP3A variant-expressing TK6 cell lines. Using Western blotting, we observed that PA-induced apoptosis, cell cycle changes, and DNA damage were primarily mediated by CYP3A4. Benchmark dose (BMD) modeling demonstrated that lasiocarpine, of the three PAs, was the most potent inducer of micronuclei, with a BMD100 of 0.036 μM. These results indicate that our TK6 cell system holds promise for genotoxicity screening of compounds requiring metabolic activation, identifying specific CYPs involved in bioactivation, and discriminating the genotoxic compounds that have different chemical structures.
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Affiliation(s)
- Xilin Li
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Xiaobo He
- Office of Scientific Coordination, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Si Chen
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Matthew S. Bryant
- Office of Scientific Coordination, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Lei Guo
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Mugimane G. Manjanatha
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
| | - Tong Zhou
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, MD 20855, USA
| | - Kristine L. Witt
- Divison of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA.
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21
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Gi M, Fujioka M, Totsuka Y, Matsumoto M, Masumura K, Kakehashi A, Yamaguchi T, Fukushima S, Wanibuchi H. Quantitative analysis of mutagenicity and carcinogenicity of 2-amino-3-methylimidazo[4,5-f]quinoline in F344 gpt delta transgenic rats. Mutagenesis 2020; 34:279-287. [PMID: 31233596 DOI: 10.1093/mutage/gez015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 06/09/2019] [Indexed: 11/13/2022] Open
Abstract
Quantitative analysis of the mutagenicity and carcinogenicity of the low doses of genotoxic carcinogens present in food is of pressing concern. The purpose of the present study was to determine the mutagenicity and carcinogenicity of low doses of the dietary genotoxic carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Male F344 gpt delta transgenic rats were fed diets supplemented with 0, 0.1, 1, 10 or 100 ppm IQ for 4 weeks. The frequencies of gpt transgene mutations in the liver were significantly increased in the 10 and 100 ppm groups. In addition, the mutation spectra was altered in the 1, 10 and 100 ppm groups: frequencies of G:C to T:A transversion were significantly increased in groups administered 1, 10 and 100 ppm IQ in a dose-dependent manner, and the frequencies of G:C to A:T transitions, A:T to T:A transversions and A:T to C:G transversions were significantly increased in the 100 ppm group. Increased frequencies of single base pair deletions and Spi- mutants in the liver, and an increase in glutathione S-transferase placental form (GST-P)-positive foci, a preneoplastic lesion of the liver in rats, was also observed in the 100 ppm group. In contrast, neither mutations nor mutation spectra or GST-P-positive foci were statistically altered by administration of IQ at 0.1 ppm. We estimated the point of departure for the mutagenicity and carcinogenicity of IQ using the no-observed-effect level approach and the Benchmark dose approach to characterise the dose-response relationship of low doses of IQ. Our findings demonstrate the existence of no effect levels of IQ for both in vivo mutagenicity and hepatocarcinogenicity. The findings of the present study will facilitate an understanding of the carcinogenic effects of low doses of IQ and help to determine a margin of exposure that may be useful for practical human risk assessment.
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Affiliation(s)
- Min Gi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Masaki Fujioka
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Yukari Totsuka
- Division of Carcinogenesis and Cancer Prevention, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
| | - Michiharu Matsumoto
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, Japan
| | - Kenichi Masumura
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Kawasaki-ku, Kawasaki, Kanagawa, Japan
| | - Anna Kakehashi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Takashi Yamaguchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Shoji Fukushima
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, Japan.,Association for Promotion of Research on Risk Assessment, Nakagawa-ku, Nagoya, Japan
| | - Hideki Wanibuchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
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Performance of high-throughput CometChip assay using primary human hepatocytes: a comparison of DNA damage responses with in vitro human hepatoma cell lines. Arch Toxicol 2020; 94:2207-2224. [PMID: 32318794 DOI: 10.1007/s00204-020-02736-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/06/2020] [Indexed: 10/24/2022]
Abstract
Primary human hepatocytes (PHHs) are considered the "gold standard" for evaluating hepatic metabolism and toxicity of xenobiotics. In the present study, we evaluated the genotoxic potential of four indirect-acting (requiring metabolic activation) and six direct-acting genotoxic carcinogens, one aneugen, and five non-carcinogens that are negative or equivocal for genotoxicity in vivo in cryopreserved PHHs derived from three individual donors. DNA damage was determined over a wide range of concentrations using the CometChip technology and the resulting dose-responses were quantified using benchmark dose (BMD) modeling. Following a 24-h treatment, nine out of ten genotoxic carcinogens produced positive responses in PHHs, while negative responses were found for hydroquinone, aneugen colchicine and five non-carcinogens. Overall, PHHs demonstrated a higher sensitivity (90%) for detecting DNA damage from genotoxic carcinogens than the sensitivities previously reported for HepG2 (60%) and HepaRG (70%) cells. Quantitative analysis revealed that most of the compounds produced comparable BMD10 values among the three types of hepatocytes, while PHHs and HepaRG cells produced similar BMD1SD values. Evidence of sex- and ethnicity-related interindividual variation in DNA damage responses was also observed in the PHHs. A literature search for in vivo Comet assay data conducted in rodent liver tissues demonstrated consistent positive/negative calls for the compounds tested between in vitro PHHs and in vivo animal models. These results demonstrate that CometChip technology can be applied using PHHs for human risk assessment and that PHHs had higher sensitivity than HepaRG cells for detecting genotoxic carcinogens in the CometChip assay.
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Wheeldon RP, Bernacki DT, Dertinger SD, Bryce SM, Bemis JC, Johnson GE. Benchmark Dose Analysis of DNA Damage Biomarker Responses Provides Compound Potency and Adverse Outcome Pathway Information for the Topoisomerase II Inhibitor Class of Compounds. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:396-407. [PMID: 31983063 DOI: 10.1002/em.22360] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 01/11/2020] [Accepted: 01/21/2020] [Indexed: 06/10/2023]
Abstract
Genetic toxicology data have traditionally been utilized for hazard identification to provide a binary call for a compound's risk. Recent advances in the scientific field, especially with the development of high-throughput methods to quantify DNA damage, have influenced a change of approach in genotoxicity assessment. The in vitro MultiFlow® DNA Damage Assay is one such method which multiplexes γH2AX, p53, phospho-histone H3 biomarkers into a single-flow cytometric analysis (Bryce et al., [2016]: Environ Mol Mutagen 57:546-558). This assay was used to study human TK6 cells exposed to each of eight topoisomerase II poisons for 4 and 24 hr. Using PROAST v65.5, the Benchmark Dose approach was applied to the resulting flow cytometric datasets. With "compound" serving as covariate, all eight compounds were combined into a single analysis, per time point and endpoint. The resulting 90% confidence intervals, plotted in Log scale, were considered as the potency rank for the eight compounds. The in vitro MultiFlow data showed a maximum confidence interval span of 1Log, which indicates data of good quality. Patterns observed in the compound potency rank were scrutinized by using the expert rule-based software program Derek Nexus, developed by Lhasa Limited. Compound sub-classification and structural alerts were considered contributory to the potencies observed for the topoisomerase II poisons studied herein. The Topo II poison Adverse Outcome Pathway was evaluated with MultiFlow endpoints serving as Key Events. The step-wise approach described herein can be considered as a foundation for risk assessment of compounds within a specific mode of action of interest. Environ. Mol. Mutagen. 2020. © 2020 Wiley Periodicals, Inc.
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Affiliation(s)
- Ryan P Wheeldon
- Institute of Life Science, Swansea University Medical School, Swansea University, Wales, United Kingdom
| | | | | | | | | | - George E Johnson
- Institute of Life Science, Swansea University Medical School, Swansea University, Wales, United Kingdom
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Strategies in genotoxicology: Acceptance of innovative scientific methods in a regulatory context and from an industrial perspective. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2020; 853:503171. [PMID: 32522346 DOI: 10.1016/j.mrgentox.2020.503171] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/08/2020] [Accepted: 03/09/2020] [Indexed: 12/13/2022]
Abstract
The tests used and the general principles behind test strategies are now often over 30 years old. It may be time by now, given that our knowledge of genetic toxicology has improved and that we also technically are better able to investigate DNA damage making use of modern molecular biological techniques, to start thinking on a new test strategy. In the present paper, it is discussed that the time is there to consider a new approach for genotoxicity assessment of substances. A fit for all test strategy was discussed making use of the most recent technological methods and techniques. It was also indicated that in silico tools should be more accepted by regulatory institutes/bodies as supporting information to better conclude which tests should be required for each separate substance to demonstrate its genotoxic potency. Next to that there should be a good rationale for performing in vivo studies. Finally, the need for germ cell genotoxicity testing, essential when classification and labeling of substances is mandatory, was discussed. It was suggested to change the GHS for genotoxicity classification and labelling from in vivo tests in germ cells into in vivo tests in somatic cells. Quantitative genotoxicology was also discussed. It appeared that we are currently at a transition, where the science developing to justify carrying out human health risk assessments based on genetic toxicology data sets supported by mechanistic data and exposure data. However, implementation will take time, and acceptance will be supported through the development of numerous case studies. Major remaining questions are: is genetic damage a relevant endpoint in itself, or should the risk assessment be carried out on the apical endpoint of cancer and which genotoxic endpoint should be used to derive the point of departure (PoD) for the human exposure limit?
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Jalili P, Huet S, Lanceleur R, Jarry G, Hegarat LL, Nesslany F, Hogeveen K, Fessard V. Genotoxicity of Aluminum and Aluminum Oxide Nanomaterials in Rats Following Oral Exposure. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E305. [PMID: 32053952 PMCID: PMC7075173 DOI: 10.3390/nano10020305] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 01/27/2020] [Accepted: 02/02/2020] [Indexed: 02/06/2023]
Abstract
Due to several gaps remaining in the toxicological evaluation of nanomaterials (NMs), consumers and public health agencies have shown increasing concern for human health protection. In addition to aluminum (Al) microparticles, Al-containing nanomaterials (Al NMs) have been applied by food industry as additives and contact materials. Due to the limited amount of literature on the toxicity of Al NMs, this study aimed to evaluate the in vivo genotoxic potential of Al0 and Al2O3 NMs after acute oral exposure. Male Sprague-Dawley rats were administered three successive gavages at 6, 12.5 and 25 mg/kg bw. A comparison with AlCl3 was done in order to assess the potential effect of dissolution into Al ions. Both DNA strand breaks and oxidative DNA damage were investigated in six organs/tissues (duodenum, liver, kidney, spleen, blood and bone marrow) with the alkaline and the Fpg-modified comet assays. Concomitantly, chromosomal damage was investigated in bone marrow and colon with the micronucleus assay. The comet assay only showed DNA damage with Al2O3 NMs in bone marrow (BM), while AlCl3 induced slight but non-significant oxidative DNA damage in blood. No increase of chromosomal mutations was observed after treatment with the two Al MNs either in the BM or in the colons of rats.
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Affiliation(s)
- Pégah Jalili
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Sylvie Huet
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Rachelle Lanceleur
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Gérard Jarry
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Ludovic Le Hegarat
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Fabrice Nesslany
- Institut Pasteur de Lille, Laboratoire de toxicologie génétique, 1 Rue du Professeur Calmette, 59019 Lille CEDEX, France;
| | - Kevin Hogeveen
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
| | - Valérie Fessard
- Unité de Toxicologie des Contaminants, Agence Nationale de Sécurité Sanitaire (ANSES), 10 B rue Claude Bourgelat, 35306 Fougères, France (S.H.); (R.L.); (G.J.); (L.L.H.); (K.H.)
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26
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Pouzou JG, Kissel J, Yost MG, Fenske RA, Cullen AC. Use of benchmark dose models in risk assessment for occupational handlers of eight pesticides used in pome fruit production. Regul Toxicol Pharmacol 2020; 110:104504. [PMID: 31655092 PMCID: PMC6937384 DOI: 10.1016/j.yrtph.2019.104504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 10/12/2019] [Accepted: 10/15/2019] [Indexed: 11/27/2022]
Abstract
The benchmark dose has been frequently recommended for the creation of points of departure for regulatory dose limits, but many regulations, including pesticide risk assessment and registration in the United States, continues to rely on NOAEL methods as the OECD toxicological standard methods recommend. This study used data from studies in support of pesticide registration for eight different compounds to build dose-response models and calculate benchmark doses and confidence limits. The results were compared to the NOAEL of the same study. A probabilistic estimate of dose was compared with all points of departure to demonstrate differences in the protective ability of each different selected limit. While neither the BMD/BMDL nor the NOAEL was consistently more protective, the advantage of using the BMD in quantifying the uncertainty of the point of departure is highlighted, and the feasibility of using current OECD-guideline studies for derivation of a BMD is demonstrated in these cases.
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27
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White PA, Long AS, Johnson GE. Quantitative Interpretation of Genetic Toxicity Dose-Response Data for Risk Assessment and Regulatory Decision-Making: Current Status and Emerging Priorities. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:66-83. [PMID: 31794061 DOI: 10.1002/em.22351] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 11/27/2019] [Accepted: 11/30/2019] [Indexed: 06/10/2023]
Abstract
The screen-and-bin approach for interpretation of genotoxicity data is predicated on three false assumptions: that genotoxicants are rare, that genotoxicity dose-response functions do not contain a low-dose region mechanistically characterized by zero-order kinetics, and that genotoxicity is not a bona fide toxicological endpoint. Consequently, there is a need to develop and implement quantitative methods to interpret genotoxicity dose-response data for risk assessment and regulatory decision-making. Standardized methods to analyze dose-response data, and determine point-of-departure (PoD) metrics, have been established; the most robust PoD is the benchmark dose (BMD). However, there are no standards for regulatory interpretation of mutagenicity BMDs. Although 5-10% is often used as a critical effect size (CES) for BMD determination, values for genotoxicity endpoints have not been established. The use of BMDs to determine health-based guidance values (HBGVs) requires assessment factors (AFs) to account for interspecies differences and variability in human sensitivity. Default AFs used for other endpoints may not be appropriate for interpretation of in vivo mutagenicity BMDs. Analyses of published dose-response data showing the effects of compensatory pathway deficiency indicate that AFs for sensitivity differences should be in the range of 2-20. Additional analyses indicate that the AF to compensate for short treatment durations should be in the range of 5-15. Future work should use available data to empirically determine endpoint-specific CES values; similarly, to determine AF values for BMD adjustment. Future work should also evaluate the ability to use in vitro dose-response data for risk assessment, and the utility of probabilistic methods for determination of mutagenicity HBGVs. Environ. Mol. Mutagen. 61:66-83, 2020. © 2019 Her Majesty the Queen in Right of Canada.
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Affiliation(s)
- Paul A White
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Alexandra S Long
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - George E Johnson
- Swansea University Medical School, Swansea, Wales, United Kingdom
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Luijten M, Ball NS, Dearfield KL, Gollapudi BB, Johnson GE, Madia F, Peel L, Pfuhler S, Settivari RS, ter Burg W, White PA, van Benthem J. Utility of a next generation framework for assessment of genomic damage: A case study using the industrial chemical benzene. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:94-113. [PMID: 31709603 PMCID: PMC6972600 DOI: 10.1002/em.22346] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/31/2019] [Accepted: 11/06/2019] [Indexed: 05/22/2023]
Abstract
We recently published a next generation framework for assessing the risk of genomic damage via exposure to chemical substances. The framework entails a systematic approach with the aim to quantify risk levels for substances that induce genomic damage contributing to human adverse health outcomes. Here, we evaluated the utility of the framework for assessing the risk for industrial chemicals, using the case of benzene. Benzene is a well-studied substance that is generally considered a genotoxic carcinogen and is known to cause leukemia. The case study limits its focus on occupational and general population health as it relates to benzene exposure. Using the framework as guidance, available data on benzene considered relevant for assessment of genetic damage were collected. Based on these data, we were able to conduct quantitative analyses for relevant data sets to estimate acceptable exposure levels and to characterize the risk of genetic damage. Key observations include the need for robust exposure assessments, the importance of information on toxicokinetic properties, and the benefits of cheminformatics. The framework points to the need for further improvement on understanding of the mechanism(s) of action involved, which would also provide support for the use of targeted tests rather than a prescribed set of assays. Overall, this case study demonstrates the utility of the next generation framework to quantitatively model human risk on the basis of genetic damage, thereby enabling a new, innovative risk assessment concept. Environ. Mol. Mutagen. 61:94-113, 2020. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
- Mirjam Luijten
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | | | | | | | - George E. Johnson
- Swansea University Medical School, Swansea UniversitySwanseaUnited Kingdom
| | - Federica Madia
- European Commission, Joint Research Centre (JRC)IspraItaly
| | - Lauren Peel
- Health and Environmental Sciences InstituteWashingtonDistrict of Columbia
| | | | | | - Wouter ter Burg
- Centre for Safety of Substances and ProductsNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Paul A. White
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
| | - Jan van Benthem
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
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Zeller A, Brigo A, Brink A, Guerard M, Lang D, Muster W, Runge F, Sutter A, Vock E, Wichard J, Schadt S. Genotoxicity Assessment of Drug Metabolites in the Context of MIST and Beyond. Chem Res Toxicol 2019; 33:10-19. [DOI: 10.1021/acs.chemrestox.9b00348] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andreas Zeller
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Alessandro Brigo
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Andreas Brink
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Melanie Guerard
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Dieter Lang
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Wolfgang Muster
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Frank Runge
- Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, 88400 Biberach, Germany
| | - Andreas Sutter
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Esther Vock
- Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, 88400 Biberach, Germany
| | - Jörg Wichard
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Simone Schadt
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
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30
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Guo X, Seo JE, Li X, Mei N. Genetic toxicity assessment using liver cell models: past, present, and future. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2019; 23:27-50. [PMID: 31746269 DOI: 10.1080/10937404.2019.1692744] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Genotoxic compounds may be detoxified to non-genotoxic metabolites while many pro-carcinogens require metabolic activation to exert their genotoxicity in vivo. Standard genotoxicity assays were developed and utilized for risk assessment for over 40 years. Most of these assays are conducted in metabolically incompetent rodent or human cell lines. Deficient in normal metabolism and relying on exogenous metabolic activation systems, the current in vitro genotoxicity assays often have yielded high false positive rates, which trigger unnecessary and costly in vivo studies. Metabolically active cells such as hepatocytes have been recognized as a promising cell model in predicting genotoxicity of carcinogens in vivo. In recent years, significant advances in tissue culture and biological technologies provided new opportunities for using hepatocytes in genetic toxicology. This review encompasses published studies (both in vitro and in vivo) using hepatocytes for genotoxicity assessment. Findings from both standard and newly developed genotoxicity assays are summarized. Various liver cell models used for genotoxicity assessment are described, including the potential application of advanced liver cell models such as 3D spheroids, organoids, and engineered hepatocytes. An integrated strategy, that includes the use of human-based cells with enhanced biological relevance and throughput, and applying the quantitative analysis of data, may provide an approach for future genotoxicity risk assessment.
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Affiliation(s)
- Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
| | - Ji-Eun Seo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
| | - Xilin Li
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
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Jensen SM, Kluxen FM, Ritz C. A Review of Recent Advances in Benchmark Dose Methodology. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:2295-2315. [PMID: 31046141 DOI: 10.1111/risa.13324] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 02/01/2019] [Accepted: 04/03/2019] [Indexed: 06/09/2023]
Abstract
In this review, recent methodological developments for the benchmark dose (BMD) methodology are summarized. Specifically, we introduce the advances for the main steps in BMD derivation: selecting the procedure for defining a BMD from a predefined benchmark response (BMR), setting a BMR, selecting a dose-response model, and estimating the corresponding BMD lower limit (BMDL). Although the last decade has shown major progress in the development of BMD methodology, there is still room for improvement. Remaining challenges are the implementation of new statistical methods in user-friendly software and the lack of consensus about how to derive the BMDL.
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Affiliation(s)
- Signe M Jensen
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Christian Ritz
- Department of Nutrition, Sports and Exercise, University of Copenhagen, Copenhagen, Denmark
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Dertinger SD, Kraynak AR, Wheeldon RP, Bernacki DT, Bryce SM, Hall N, Bemis JC, Galloway SM, Escobar PA, Johnson GE. Predictions of genotoxic potential, mode of action, molecular targets, and potency via a tiered multiflow® assay data analysis strategy. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2019; 60:513-533. [PMID: 30702769 PMCID: PMC6880310 DOI: 10.1002/em.22274] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/14/2019] [Accepted: 01/23/2019] [Indexed: 05/08/2023]
Abstract
The in vitro MultiFlow® DNA Damage Assay multiplexes γH2AX, p53, phospho-histone H3, and polyploidization biomarkers into a single flow cytometric analysis. The current report describes a tiered sequential data analysis strategy based on data generated from exposure of human TK6 cells to a previously described 85 chemical training set and a new pharmaceutical-centric test set (n = 40). In each case, exposure was continuous over a range of closely spaced concentrations, and cell aliquots were removed for analysis following 4 and 24 hr of treatment. The first data analysis step focused on chemicals' genotoxic potential, and for this purpose, we evaluated the performance of a machine learning (ML) ensemble, a rubric that considered fold increases in biomarkers against global evaluation factors (GEFs), and a hybrid strategy that considered ML and GEFs. This first tier further used ML output and/or GEFs to classify genotoxic activity as clastogenic and/or aneugenic. Test set results demonstrated the generalizability of the first tier, with particularly good performance from the ML ensemble: 35/40 (88%) concordance with a priori genotoxicity expectations and 21/24 (88%) agreement with expected mode of action (MoA). A second tier applied unsupervised hierarchical clustering to the biomarker response data, and these analyses were found to group certain chemicals, especially aneugens, according to their molecular targets. Finally, a third tier utilized benchmark dose analyses and MultiFlow biomarker responses to rank genotoxic potency. The relevance of these rankings is supported by the strong agreement found between benchmark dose values derived from MultiFlow biomarkers compared to those generated from parallel in vitro micronucleus analyses. Collectively, the results suggest that a tiered MultiFlow data analysis pipeline is capable of rapidly and effectively identifying genotoxic hazards while providing additional information that is useful for modern risk assessments-MoA, molecular targets, and potency. Environ. Mol. Mutagen. 60:513-533, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Stephen D. Dertinger
- Litron Laboratories, Rochester, New York
- Correspondence to: Stephen D. Dertinger, Litron Laboratories, 3500 Winton Place, Rochester, NY 14623.
| | | | - Ryan P. Wheeldon
- Institute of Life Science, Swansea University Medical School, Swansea University, Swansea, Wales, United Kingdom
| | | | | | - Nikki Hall
- Litron Laboratories, Rochester, New York
| | | | | | | | - George E. Johnson
- Institute of Life Science, Swansea University Medical School, Swansea University, Swansea, Wales, United Kingdom
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Goumenou M, Tsatsakis A. Proposing new approaches for the risk characterisation of single chemicals and chemical mixtures: The source related Hazard Quotient (HQ S) and Hazard Index (HI S) and the adversity specific Hazard Index (HI A). Toxicol Rep 2019; 6:632-636. [PMID: 31334033 PMCID: PMC6616343 DOI: 10.1016/j.toxrep.2019.06.010] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Indexed: 11/26/2022] Open
Abstract
A hazard quotient (HQ) for a single chemical and the hazard index (HI) for a mixture of chemicals were first described as approaches for risk characterisation by the EPA. HQ is defined as the ratio of exposure to an appropriate reference dose such as the ADI. HI is the sum of the HQs of the chemicals in a mixture. HQ and HI have been used to characterise risk after various exposure scenarios. However, both approaches have a significant limitation in the way they are used. The accurate use of HQ or HI requires estimation of aggregate exposure, that is, exposure to a given chemical(s) from all possible relevant sources. In many studies, risk is assessed assuming exposure from a specific source such as, consumption of water or a specific food item, in which chemical(s) concentration(s) have been measured. In this case the classic HQ/HI approach can result in significant underestimation of risk. For this purpose, we developed an alternative approach, named as Source Related HQ (HQs) where HQS is the ratio of the exposure from the specific source of interest to the respected reference values. According to our approach the HQS, before being compared to the reference dose, should be adjusted by a correction factor, in order to simulate aggregated exposure. A correction factor can be calculated based on the permitted exposure contribution from the specific source to the permitted aggregated exposure. Another important limitation specific to the HI approach is the use of chemical specific ADIs that do not correspond to the same critical effect. In this study, we present an analysis based on the individual critical effects, in order to derive the critical effect and an adversity specific Hazard Index (HIA) and risk characterisation for the whole mixture.
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Affiliation(s)
- Marina Goumenou
- Centre of Toxicology Science and Research, University of Crete, School of Medicine, Crete, Greece
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Seo JE, Tryndyak V, Wu Q, Dreval K, Pogribny I, Bryant M, Zhou T, Robison TW, Mei N, Guo X. Quantitative comparison of in vitro genotoxicity between metabolically competent HepaRG cells and HepG2 cells using the high-throughput high-content CometChip assay. Arch Toxicol 2019; 93:1433-1448. [PMID: 30788552 DOI: 10.1007/s00204-019-02406-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 01/31/2019] [Indexed: 12/18/2022]
Abstract
In vitro genotoxicity testing that employs metabolically active human cells may be better suited for evaluating human in vivo genotoxicity than current bacterial or non-metabolically active mammalian cell systems. In the current study, 28 compounds, known to have different genotoxicity and carcinogenicity modes of action (MoAs), were evaluated over a wide range of concentrations for the ability to induce DNA damage in human HepG2 and HepaRG cells. DNA damage dose-responses in both cell lines were quantified using a combination of high-throughput high-content (HTHC) CometChip technology and benchmark dose (BMD) quantitative approaches. Assays of metabolic activity indicated that differentiated HepaRG cells had much higher levels of cytochromes P450 activity than did HepG2 cells. DNA damage was observed for four and two out of five indirect-acting genotoxic carcinogens in HepaRG and HepG2 cells, respectively. Four out of seven direct-acting carcinogens were positive in both cell lines, with two of the three negatives being genotoxic mainly through aneugenicity. The four chemicals positive in both cell lines generated HTHC Comet data in HepaRG and HepG2 cells with comparable BMD values. All the non-genotoxic compounds, including six non-genotoxic carcinogens, were negative in HepaRG cells; five genotoxic non-carcinogens also were negative. Our results indicate that the HTHC CometChip assay detects a greater proportion of genotoxic carcinogens requiring metabolic activation (i.e., indirect carcinogens) when conducted with HepaRG cells than with HepG2 cells. In addition, BMD genotoxicity potency estimate is useful for quantitatively evaluating CometChip assay data in a scientifically rigorous manner.
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Affiliation(s)
- Ji-Eun Seo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Volodymyr Tryndyak
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Qiangen Wu
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Kostiantyn Dreval
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA.,Department of Internal Medicine, Division of Molecular Medicine, Program in Cancer Genetics, Epigenetics and Genomics, University of New Mexico Comprehensive Cancer Center, Albuquerque, NM, 87131, USA
| | - Igor Pogribny
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Matthew Bryant
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Tong Zhou
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, MD, 20855, USA
| | - Timothy W Robison
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA
| | - Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, 72079, USA.
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Re: Gi et al. 2018, In vivo positive mutagenicity of 1,4-dioxane and quantitative analysis of its mutagenicity and carcinogenicity in rats, Archives of Toxicology 92:3207–3221. Arch Toxicol 2018; 93:211-212. [DOI: 10.1007/s00204-018-2370-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 12/03/2018] [Indexed: 12/15/2022]
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Xiao CC, Chen MJ, Mei FB, Fang X, Huang TR, Li JL, Deng W, Li YD. Influencing factors and health risk assessment of microcystins in the Yongjiang river (China) by Monte Carlo simulation. PeerJ 2018; 6:e5955. [PMID: 30479903 PMCID: PMC6241391 DOI: 10.7717/peerj.5955] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 10/16/2018] [Indexed: 02/03/2023] Open
Abstract
The Yongjiang river is a large, shallow, hyper-trophic, freshwater river in Guangxi, China. To investigate the presence of microcystin-RR, microcystin-LR, and microcystin-YR (MC-RR, MC-LR, and MC-YR) in the Yongjiang river and describe their correlation with environmental factors, as well as, assess health risk using Monte Carlo simulation, 90 water samples were collected at three sample points from March to December 2017. Results showed that during the monitoring period, total concentrations of MC-RR (TMC-RR), MC-YR (TMC-YR), and MC-LR (TMC-LR) varied from 0.0224 to 0.3783 μg/L, 0.0329 to 0.1433 μg/L, and 0.0341 to 0.2663 μg/L, respectively. Total phosphorus (TP) content appeared to be related to TMC-LR and the total concentrations of microcystins (TMCs), while pH and total nitrogen (TN)/TP ratio appeared to be related to TMC-RR and TMC-YR, respectively. Using the professional health risk assessment software @Risk7.5, the risks of dietary intake of microcystins (MCs), including the carcinogenic risk and non-carcinogenic risk, were evaluated. It was found that the carcinogenic risk of MC-RR from drinking water was higher than MC-LR and MC-YR, and the presence of MCs would lead to high potential health risks, especially in children. The carcinogenic risk of MC-RR to children was >1 × 10-4, the maximum allowance level recommended by the US Environmental Protection Agency; as for adults, it was >5 × 10-5, the maximum allowance level recommended by the International Commission on Radiological Protection. The non-carcinogenic hazard index (HI) of MC-RR, MC-YR, and MC-LR increased successively, indicating that MC-LR was more hazardous to human health than MC-YR and MC-RR, but its HI was <1. This suggests that MCs pose less risk to health. However, it is necessary to strengthen the protection and monitoring of drinking water source for effective control of water pollution and safeguarding of human health.
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Affiliation(s)
- Chan-Chan Xiao
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Mao-Jian Chen
- Department of Breast Surgery, Affiliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Fan-Biao Mei
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Xiang Fang
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Tian-Ren Huang
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Ji-Lin Li
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Wei Deng
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
| | - Yuan-Dong Li
- Department of Experimental Research, Affliated Tumor Hospital of Guangxi Medical University, Nanning, China
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Relative potency of fifteen pyrrolizidine alkaloids to induce DNA damage as measured by micronucleus induction in HepaRG human liver cells. Food Chem Toxicol 2018; 121:72-81. [PMID: 30125636 DOI: 10.1016/j.fct.2018.08.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 07/30/2018] [Accepted: 08/02/2018] [Indexed: 01/20/2023]
Abstract
Plant-based 1,2-unsaturated Pyrrolizidine Alkaloids (PAs) can be found as contaminants in foods like teas, herbs and honey. PAs are responsible for liver genotoxicity/carcinogenicity following metabolic activation, making them a relevant concern for safety assessment. Current regulatory risk assessments take a precautionary approach and assume all PAs are as potent as the known most potent representatives: lasiocarpine and riddelliine. Our study investigated whether genotoxicity potency differed as a consequence of structural differences, assessing micronuclei in vitro in HepaRG cells which express metabolising enzymes at levels similar to primary human hepatocytes. Benchmark Dose (BMD) analysis was used to calculate the critical effect dose for 15 PAs representing 6 structural classes. When BMD confidence intervals were used to rank PAs, lasiocarpine was the most potent PA and plotted distinctly from all other PAs examined. PA-N-oxides were least potent, notably less potent than their corresponding parent PA's. The observed genotoxic potency compared favorably with existing in vitro data when metabolic competency was considered. Although further consideration of biokinetics will be needed to develop a robust understanding of relative potencies for a realistic risk assessment of PA mixtures, these data facilitate understanding of their genotoxic potencies and affirm that not all PAs are created equal.
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Ratni H, Ebeling M, Baird J, Bendels S, Bylund J, Chen KS, Denk N, Feng Z, Green L, Guerard M, Jablonski P, Jacobsen B, Khwaja O, Kletzl H, Ko CP, Kustermann S, Marquet A, Metzger F, Mueller B, Naryshkin NA, Paushkin SV, Pinard E, Poirier A, Reutlinger M, Weetall M, Zeller A, Zhao X, Mueller L. Discovery of Risdiplam, a Selective Survival of Motor Neuron-2 ( SMN2) Gene Splicing Modifier for the Treatment of Spinal Muscular Atrophy (SMA). J Med Chem 2018; 61:6501-6517. [PMID: 30044619 DOI: 10.1021/acs.jmedchem.8b00741] [Citation(s) in RCA: 282] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
SMA is an inherited disease that leads to loss of motor function and ambulation and a reduced life expectancy. We have been working to develop orally administrated, systemically distributed small molecules to increase levels of functional SMN protein. Compound 2 was the first SMN2 splicing modifier tested in clinical trials in healthy volunteers and SMA patients. It was safe and well tolerated and increased SMN protein levels up to 2-fold in patients. Nevertheless, its development was stopped as a precautionary measure because retinal toxicity was observed in cynomolgus monkeys after chronic daily oral dosing (39 weeks) at exposures in excess of those investigated in patients. Herein, we describe the discovery of 1 (risdiplam, RG7916, RO7034067) that focused on thorough pharmacology, DMPK and safety characterization and optimization. This compound is undergoing pivotal clinical trials and is a promising medicine for the treatment of patients in all ages and stages with SMA.
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Affiliation(s)
- Hasane Ratni
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Martin Ebeling
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - John Baird
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Stefanie Bendels
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Johan Bylund
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Karen S Chen
- SMA Foundation , 888 Seventh Avenue, Suite 400 , New York , New York 10019 , United States
| | - Nora Denk
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Luke Green
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Melanie Guerard
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Philippe Jablonski
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Bjoern Jacobsen
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Omar Khwaja
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Heidemarie Kletzl
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Stefan Kustermann
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Anne Marquet
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Friedrich Metzger
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Barbara Mueller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Nikolai A Naryshkin
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Sergey V Paushkin
- SMA Foundation , 888 Seventh Avenue, Suite 400 , New York , New York 10019 , United States
| | - Emmanuel Pinard
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Agnès Poirier
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Michael Reutlinger
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Marla Weetall
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Andreas Zeller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Xin Zhao
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Lutz Mueller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
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