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Schiffman SS, Scholl EH, Furey TS, Nagle HT. Toxicological and pharmacokinetic properties of sucralose-6-acetate and its parent sucralose: in vitro screening assays. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2023; 26:307-341. [PMID: 37246822 DOI: 10.1080/10937404.2023.2213903] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The purpose of this study was to determine the toxicological and pharmacokinetic properties of sucralose-6-acetate, a structural analog of the artificial sweetener sucralose. Sucralose-6-acetate is an intermediate and impurity in the manufacture of sucralose, and recent commercial sucralose samples were found to contain up to 0.67% sucralose-6-acetate. Studies in a rodent model found that sucralose-6-acetate is also present in fecal samples with levels up to 10% relative to sucralose which suggest that sucralose is also acetylated in the intestines. A MultiFlow® assay, a high-throughput genotoxicity screening tool, and a micronucleus (MN) test that detects cytogenetic damage both indicated that sucralose-6-acetate is genotoxic. The mechanism of action was classified as clastogenic (produces DNA strand breaks) using the MultiFlow® assay. The amount of sucralose-6-acetate in a single daily sucralose-sweetened drink might far exceed the threshold of toxicological concern for genotoxicity (TTCgenotox) of 0.15 µg/person/day. The RepliGut® System was employed to expose human intestinal epithelium to sucralose-6-acetate and sucralose, and an RNA-seq analysis was performed to determine gene expression induced by these exposures. Sucralose-6-acetate significantly increased the expression of genes associated with inflammation, oxidative stress, and cancer with greatest expression for the metallothionein 1 G gene (MT1G). Measurements of transepithelial electrical resistance (TEER) and permeability in human transverse colon epithelium indicated that sucralose-6-acetate and sucralose both impaired intestinal barrier integrity. Sucralose-6-acetate also inhibited two members of the cytochrome P450 family (CYP1A2 and CYP2C19). Overall, the toxicological and pharmacokinetic findings for sucralose-6-acetate raise significant health concerns regarding the safety and regulatory status of sucralose itself.
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Affiliation(s)
- Susan S Schiffman
- Joint Department of Biomedical Engineering, University of North Carolina/North Carolina State University, Raleigh, NC, USA
| | | | - Terrence S Furey
- Departments of Genetics and Biology, University of North Carolina, Chapel Hill, NC, USA
| | - H Troy Nagle
- Joint Department of Biomedical Engineering, University of North Carolina/North Carolina State University, Raleigh, NC, USA
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC, USA
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2
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Li X, Le Y, Seo JE, Guo X, Li Y, Chen S, Mittelstaedt RA, Moore N, Guerrero S, Sims A, King ST, Atrakchi AH, McGovern TJ, Davis-Bruno KL, Keire DA, Elespuru RK, Heflich RH, Mei N. Revisiting the mutagenicity and genotoxicity of N-nitroso propranolol in bacterial and human in vitro assays. Regul Toxicol Pharmacol 2023; 141:105410. [PMID: 37210026 DOI: 10.1016/j.yrtph.2023.105410] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 05/05/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
Propranolol is a widely used β-blocker that can generate a nitrosated derivative, N-nitroso propranolol (NNP). NNP has been reported to be negative in the bacterial reverse mutation test (the Ames test) but genotoxic in other in vitro assays. In the current study, we systematically examined the in vitro mutagenicity and genotoxicity of NNP using several modifications of the Ames test known to affect the mutagenicity of nitrosamines, as well as a battery of genotoxicity tests using human cells. We found that NNP induced concentration-dependent mutations in the Ames test, both in two tester strains that detect base pair substitutions, TA1535 and TA100, as well as in the TA98 frameshift-detector strain. Although positive results were seen with rat liver S9, the hamster liver S9 fraction was more effective in bio-transforming NNP into a reactive mutagen. NNP also induced micronuclei and gene mutations in human lymphoblastoid TK6 cells in the presence of hamster liver S9. Using a panel of TK6 cell lines that each expresses a different human cytochrome P450 (CYP), CYP2C19 was identified as the most active enzyme in the bioactivation of NNP to a genotoxicant among those tested. NNP also induced concentration-dependent DNA strand breakage in metabolically competent 2-dimensional (2D) and 3D cultures of human HepaRG cells. This study indicates that NNP is genotoxic in a variety of bacterial and mammalian systems. Thus, NNP is a mutagenic and genotoxic nitrosamine and a potential human carcinogen.
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Affiliation(s)
- Xilin Li
- 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
| | - Ji-Eun Seo
- 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
| | - Yuxi Li
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Si Chen
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Roberta A Mittelstaedt
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Nyosha Moore
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Sharon Guerrero
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Audrey Sims
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Sruthi T King
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, 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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3
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Smith-Roe SL, Swartz CD, Rashid A, Christy NC, Sly JE, Chang X, Sipes NS, Shockley KR, Harris SF, McBride SJ, Larson GJ, Collins BJ, Mutlu E, Witt KL. Evaluation of the herbicide glyphosate, (aminomethyl)phosphonic acid, and glyphosate-based formulations for genotoxic activity using in vitro assays. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:202-233. [PMID: 36880770 PMCID: PMC10266336 DOI: 10.1002/em.22534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 02/03/2023] [Accepted: 02/14/2023] [Indexed: 05/03/2023]
Abstract
Glyphosate, the most heavily used herbicide world-wide, is applied to plants in complex formulations that promote absorption. The National Toxicology Program reported in 1992 that glyphosate, administered to rats and mice at doses up to 50,000 ppm in feed for 13 weeks, showed little evidence of toxicity, and no induction of micronuclei was observed in the mice in this study. Subsequently, mechanistic studies of glyphosate and glyphosate-based formulations (GBFs) that have focused on DNA damage and oxidative stress suggest that glyphosate may have genotoxic potential. However, few of these studies directly compared glyphosate to GBFs, or effects among GBFs. To address these data gaps, we tested glyphosate, glyphosate isopropylamine (IPA), and (aminomethyl)phosphonic acid (AMPA, a microbial metabolite of glyphosate), 9 high-use agricultural GBFs, 4 residential-use GBFs, and additional herbicides (metolachlor, mesotrione, and diquat dibromide) present in some of the GBFs in bacterial mutagenicity tests, and in human TK6 cells using a micronucleus assay and a multiplexed DNA damage assay. Our results showed no genotoxicity or notable cytotoxicity for glyphosate or AMPA at concentrations up to 10 mM, while all GBFs and herbicides other than glyphosate were cytotoxic, and some showed genotoxic activity. An in vitro to in vivo extrapolation of results for glyphosate suggests that it is of low toxicological concern for humans. In conclusion, these results demonstrate a lack of genotoxicity for glyphosate, consistent with observations in the NTP in vivo study, and suggest that toxicity associated with GBFs may be related to other components of these formulations.
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Affiliation(s)
- Stephanie L. Smith-Roe
- Division of Translational Toxicology, NIEHS, Research
Triangle Park, North Carolina, USA
| | - Carol D. Swartz
- Integrated Laboratory Systems, LLC†, Research Triangle Park, North Carolina,
USA
| | - Asma Rashid
- Integrated Laboratory Systems, LLC†, Research Triangle Park, North Carolina,
USA
| | - Nicholas C. Christy
- Integrated Laboratory Systems, LLC†, Research Triangle Park, North Carolina,
USA
| | - Jamie E. Sly
- Integrated Laboratory Systems, LLC†, Research Triangle Park, North Carolina,
USA
| | - Xiaoqing Chang
- Integrated Laboratory Systems, LLC†, Research Triangle Park, North Carolina,
USA
| | - Nisha S. Sipes
- Division of Translational Toxicology, NIEHS, Research
Triangle Park, North Carolina, USA
| | - Keith R. Shockley
- Biostatistics and Computational Biology Branch, NIEHS,
Research Triangle Park, North Carolina, USA
| | - Shawn F. Harris
- Social & Scientific Systems, Inc., Durham, North
Carolina, USA
| | | | - Gary J. Larson
- Social & Scientific Systems, Inc., Durham, North
Carolina, USA
| | - Bradley J. Collins
- Division of Translational Toxicology, NIEHS, Research
Triangle Park, North Carolina, USA
| | - Esra Mutlu
- Division of Translational Toxicology, NIEHS, Research
Triangle Park, North Carolina, USA
| | - Kristine L. Witt
- Division of Translational Toxicology, NIEHS, Research
Triangle Park, North Carolina, USA
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4
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Zhang B, Li F, Shen L, Chen L, Xia Z, Ding J, Li M, Guo LH. A cathodic photoelectrochemical immunoassay with dual signal amplification for the ultrasensitive detection of DNA damage biomarkers. Biosens Bioelectron 2023; 224:115052. [PMID: 36603285 DOI: 10.1016/j.bios.2022.115052] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 12/31/2022]
Abstract
Toxicity screening and risk assessment of an overwhelmingly large and ever-increasing number of chemicals are vitally essential for ecological safety and human health. Genotoxicity is particularly important because of its association with mutagenicity, carcinogenicity and cancer. Phosphorylated histone H2AX (γH2AX) is an early sensitive genotoxic biomarker. It is therefore highly desirable to develop analytical methods for the detection of trace γH2AX to enable screening and assessment of genotoxicity. Here, we developed a novel cathodic photoelectrochemical (PEC) immunoassay with dual signal amplification for the rapid and ultrasensitive detection of γH2AX in cell lysates. A sandwich immuno-reaction targeting γH2AX was first carried out on a 96-well plate, using a secondary antibody/gold nanoparticle/glucose oxidase conjugate as the labeled detection antibody. The conjugate increased the production of H2O2 and thus provided the first mechanism of signal amplification. The immuno-reaction product containing H2O2 was then detected on a photocathode prepared from Bi2+xWO6 rich in oxygen vacancies, with H2O2 acting as electron acceptor. The oxygen vacancies acted as both adsorption and activation sites of H2O2 and thus enhanced the photocurrent, which provided another mechanism of signal amplification. As a result, an ultrasensitive immunoassay for γH2AX determination was established with a limit of detection of 6.87 pg/mL (S/N = 3) and a wide linear range from 0.01 to 500 ng/mL. The practicability of this assay was verified by detecting γH2AX in cell lysates exposed to known genotoxic chemicals. Our work offers a promising tool for the screening of genotoxic chemicals and opening a new avenue toward environmental risk assessment.
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Affiliation(s)
- Bihong Zhang
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Fangfang Li
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Linyu Shen
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Lu Chen
- Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; College of Life Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Zhiqiang Xia
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Jinjian Ding
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China
| | - Minjie Li
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China.
| | - Liang-Hong Guo
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China; Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou, Zhejiang, 310016, PR China.
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5
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Fortin AMV, Long AS, Williams A, Meier MJ, Cox J, Pinsonnault C, Yauk CL, White PA. Application of a new approach methodology (NAM)-based strategy for genotoxicity assessment of data-poor compounds. FRONTIERS IN TOXICOLOGY 2023; 5:1098432. [PMID: 36756349 PMCID: PMC9899896 DOI: 10.3389/ftox.2023.1098432] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 01/02/2023] [Indexed: 01/24/2023] Open
Abstract
The conventional battery for genotoxicity testing is not well suited to assessing the large number of chemicals needing evaluation. Traditional in vitro tests lack throughput, provide little mechanistic information, and have poor specificity in predicting in vivo genotoxicity. New Approach Methodologies (NAMs) aim to accelerate the pace of hazard assessment and reduce reliance on in vivo tests that are time-consuming and resource-intensive. As such, high-throughput transcriptomic and flow cytometry-based assays have been developed for modernized in vitro genotoxicity assessment. This includes: the TGx-DDI transcriptomic biomarker (i.e., 64-gene expression signature to identify DNA damage-inducing (DDI) substances), the MicroFlow® assay (i.e., a flow cytometry-based micronucleus (MN) test), and the MultiFlow® assay (i.e., a multiplexed flow cytometry-based reporter assay that yields mode of action (MoA) information). The objective of this study was to investigate the utility of the TGx-DDI transcriptomic biomarker, multiplexed with the MicroFlow® and MultiFlow® assays, as an integrated NAM-based testing strategy for screening data-poor compounds prioritized by Health Canada's New Substances Assessment and Control Bureau. Human lymphoblastoid TK6 cells were exposed to 3 control and 10 data-poor substances, using a 6-point concentration range. Gene expression profiling was conducted using the targeted TempO-Seq™ assay, and the TGx-DDI classifier was applied to the dataset. Classifications were compared with those based on the MicroFlow® and MultiFlow® assays. Benchmark Concentration (BMC) modeling was used for potency ranking. The results of the integrated hazard calls indicate that five of the data-poor compounds were genotoxic in vitro, causing DNA damage via a clastogenic MoA, and one via a pan-genotoxic MoA. Two compounds were likely irrelevant positives in the MN test; two are considered possibly genotoxic causing DNA damage via an ambiguous MoA. BMC modeling revealed nearly identical potency rankings for each assay. This ranking was maintained when all endpoint BMCs were converted into a single score using the Toxicological Prioritization (ToxPi) approach. Overall, this study contributes to the establishment of a modernized approach for effective genotoxicity assessment and chemical prioritization for further regulatory scrutiny. We conclude that the integration of TGx-DDI, MicroFlow®, and MultiFlow® endpoints is an effective NAM-based strategy for genotoxicity assessment of data-poor compounds.
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Affiliation(s)
- Anne-Marie V. Fortin
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Alexandra S. Long
- Existing Substances Risk Assessment Bureau, Health Canada, Ottawa, ON, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Matthew J. Meier
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | - Julie Cox
- Bureau of Gastroenterology, Infection and Viral Diseases, Health Canada, Ottawa, ON, Canada
| | - Claire Pinsonnault
- New Substances Assessment and Control Bureau, Health Canada, Ottawa, ON, Canada
| | - Carole L. Yauk
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,*Correspondence: Carole L. Yauk, ; Paul A. White,
| | - Paul A. White
- Department of Biology, University of Ottawa, Ottawa, ON, Canada,Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada,*Correspondence: Carole L. Yauk, ; Paul A. White,
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6
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Aichinger G, Pahlke G, Puntscher H, Groestlinger J, Grabher S, Braun D, Tillmann K, Plasenzotti R, Del Favero G, Warth B, Höger H, Marko D. Markers for DNA damage are induced in the rat colon by the Alternaria toxin altertoxin-II, but not a complex extract of cultured Alternaria alternata. FRONTIERS IN TOXICOLOGY 2022; 4:977147. [PMID: 36353200 PMCID: PMC9638006 DOI: 10.3389/ftox.2022.977147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/12/2022] [Indexed: 01/19/2024] Open
Abstract
Mycotoxins produced by Alternaria spp. act genotoxic in cell-based studies, but data on their toxicity in vivo is scarce and urgently required for risk assessment. Thus, male Sprague-Dawley rats received single doses of a complex Alternaria toxin extract (CE; 50 mg/kg bw), altertoxin II (ATX-II; 0.21 mg/kg bw) or vehicle by gavage, one of the most genotoxic metabolites in vitro and were sacrificed after 3 or 24 h, respectively. Using SDS-PAGE/Western Blot, a significant increase of histone 2a.X phosphorylation and depletion of the native protein was observed for rats that were exposed to ATX-II for 24 h. Applying RT-PCR array technology we identified genes of interest for qRT-PCR testing, which in turn confirmed an induction of Rnf8 transcription in the colon of rats treated with ATX-II for 3 h and CE for 24 h. A decrease of Cdkn1a transcription was observed in rats exposed to ATX-II for 24 h, possibly indicating tissue repair after chemical injury. In contrast to the observed response in the colon, no markers for genotoxicity were induced in the liver of treated animals. We hereby provide the first report of ATX-II as a genotoxicant in vivo. Deviating results for similar concentrations of ATX-II in a natural Alternaria toxin mixture argue for substantial mixture effects.
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Affiliation(s)
- Georg Aichinger
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
- Laboratory of Toxicology, Department of Health Science and Technology, ETH Zurich, Switzerland
| | - Gudrun Pahlke
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Hannes Puntscher
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Julia Groestlinger
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Stephanie Grabher
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Dominik Braun
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Katharina Tillmann
- Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Roberto Plasenzotti
- Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Giorgia Del Favero
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
- Core Facility Multimodal Imaging, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Benedikt Warth
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Harald Höger
- Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Vienna, Austria
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7
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Kowalczyk K, Roszak J, Sobańska Z, Stępnik M. Review of mechanisms of genotoxic action of dibenzo[def,p]chrysene (formerly dibenzo[a,l]pyrene). TOXIN REV 2022. [DOI: 10.1080/15569543.2022.2124419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
| | - J. Roszak
- Department of Translational Research, Nofer Institute of Occupational Medicine, Łódź, Poland
| | - Z. Sobańska
- Department of Translational Research, Nofer Institute of Occupational Medicine, Łódź, Poland
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8
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Rahmanian N, Shokrzadeh M, Eskandani M. Recent advances in γH2AX biomarker-based genotoxicity assays: A marker of DNA damage and repair. DNA Repair (Amst) 2021; 108:103243. [PMID: 34710661 DOI: 10.1016/j.dnarep.2021.103243] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 10/04/2021] [Accepted: 10/19/2021] [Indexed: 02/06/2023]
Abstract
The phosphorylation of histone variant H2AX and formation of γH2AX is a primary response to the DNA double-strand breaks (DSBs). Detection of γH2AX is a robust and sensitive tool for diagnosis of DNA damage and repair in pre-clinical drug discovery investigations. In addition, the replication stress also leads to the formation of γH2AX and cell death and so γH2AX can serve as a surrogate marker of drug-induced cytotoxicity. Recent advances in genomic research offer an opportunity to detect γH2AX as a specific biomarker for quantitative analysis of DNA damages and repair using high content screening technology and quantitative imaging analysis. The proposed approaches identify a wide range of genetic disorders and are applied in combination with other assays in drug discovery and also for the evaluation of the efficacy of various developmental drugs. In the current review, we provide recent insights into the potential of γH2AX biomarker as a powerful tool in genotoxicity analyses for the monitoring and managing of cancer diseases.
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Affiliation(s)
- Nazanin Rahmanian
- Pharmaceutical Sciences Research Center, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Mohammad Shokrzadeh
- Department of Toxicology and Pharmacology, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran.
| | - Morteza Eskandani
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran.
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9
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Liu C, Qie Y, Zhao L, Li M, Guo LH. A High-Throughput Platform for the Rapid Quantification of Phosphorylated Histone H2AX in Cell Lysates Based on Microplate Electrochemiluminescence Immunosensor Array. ACS Sens 2021; 6:3724-3732. [PMID: 34591450 DOI: 10.1021/acssensors.1c01502] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Sensitive detection of phosphorylated histone H2AX (γH2AX) in cells as a biomarker of DNA double-strand breaks has great significance in the field of molecular toxicology and life science research. However, current γH2AX detection methods require labor- and time-consuming steps. Here, for the first time, we designed a simple electrochemiluminescence (ECL) immunoassay integrated with a microplate-based sensor array to realize sensitive and high-throughput detection of γH2AX in cell lysates. Under the optimized conditions, this ECL immunosensor array could linearly respond to γH2AX concentrations in the range from 2 × 102 to 1 × 105 pg/mL. In addition, our approach possessed excellent specificity and satisfactory reproducibility, and its practicality was verified in real cell lysates. The whole process including instrumental and manual operation was completed in no more than 3 h. This study provides a convenient and rapid alternative method for the sensitive quantification of γH2AX, which shows promising application in high-throughput screening of genotoxic chemicals and drug candidates.
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Affiliation(s)
- Chang Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People’s Republic of China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Yu Qie
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People’s Republic of China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Lixia Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People’s Republic of China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310007, P. R. China
| | - Minjie Li
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou 310018, Zhejiang, People’s Republic of China
| | - Liang-Hong Guo
- College of Quality and Safety Engineering, China Jiliang University, Hangzhou 310018, Zhejiang, People’s Republic of China
- Institute of Environmental and Health Sciences, China Jiliang University, Hangzhou 310018, Zhejiang, People’s Republic of China
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10
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Desaulniers D, Vasseur P, Jacobs A, Aguila MC, Ertych N, Jacobs MN. Integration of Epigenetic Mechanisms into Non-Genotoxic Carcinogenicity Hazard Assessment: Focus on DNA Methylation and Histone Modifications. Int J Mol Sci 2021; 22:10969. [PMID: 34681626 PMCID: PMC8535778 DOI: 10.3390/ijms222010969] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 12/15/2022] Open
Abstract
Epigenetics involves a series of mechanisms that entail histone and DNA covalent modifications and non-coding RNAs, and that collectively contribute to programing cell functions and differentiation. Epigenetic anomalies and DNA mutations are co-drivers of cellular dysfunctions, including carcinogenesis. Alterations of the epigenetic system occur in cancers whether the initial carcinogenic events are from genotoxic (GTxC) or non-genotoxic (NGTxC) carcinogens. NGTxC are not inherently DNA reactive, they do not have a unifying mode of action and as yet there are no regulatory test guidelines addressing mechanisms of NGTxC. To fil this gap, the Test Guideline Programme of the Organisation for Economic Cooperation and Development is developing a framework for an integrated approach for the testing and assessment (IATA) of NGTxC and is considering assays that address key events of cancer hallmarks. Here, with the intent of better understanding the applicability of epigenetic assays in chemical carcinogenicity assessment, we focus on DNA methylation and histone modifications and review: (1) epigenetic mechanisms contributing to carcinogenesis, (2) epigenetic mechanisms altered following exposure to arsenic, nickel, or phenobarbital in order to identify common carcinogen-specific mechanisms, (3) characteristics of a series of epigenetic assay types, and (4) epigenetic assay validation needs in the context of chemical hazard assessment. As a key component of numerous NGTxC mechanisms of action, epigenetic assays included in IATA assay combinations can contribute to improved chemical carcinogen identification for the better protection of public health.
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Affiliation(s)
- Daniel Desaulniers
- Environmental Health Sciences and Research Bureau, Hazard Identification Division, Health Canada, AL:2203B, Ottawa, ON K1A 0K9, Canada
| | - Paule Vasseur
- CNRS, LIEC, Université de Lorraine, 57070 Metz, France;
| | - Abigail Jacobs
- Independent at the Time of Publication, Previously US Food and Drug Administration, Rockville, MD 20852, USA;
| | - M. Cecilia Aguila
- Toxicology Team, Division of Human Food Safety, Center for Veterinary Medicine, US Food and Drug Administration, Department of Health and Human Services, Rockville, MD 20852, USA;
| | - Norman Ertych
- German Centre for the Protection of Laboratory Animals (Bf3R), German Federal Institute for Risk Assessment, Diedersdorfer Weg 1, 12277 Berlin, Germany;
| | - Miriam N. Jacobs
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton OX11 0RQ, UK;
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Bryce SM, Dertinger SD, Bemis JC. Kinetics of γH2AX and phospho-histone H3 following pulse treatment of TK6 cells provides insights into clastogenic activity. Mutagenesis 2021; 36:255-264. [PMID: 33964157 DOI: 10.1093/mutage/geab014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 05/07/2021] [Indexed: 11/14/2022] Open
Abstract
The desire for in vitro genotoxicity assays to provide higher information content, especially regarding chemicals' predominant genotoxic mode of action, has led to the development of a novel multiplexed assay available under the trade name MultiFlow®. We report here on an experimental design variation that provides further insight into clastogens' genotoxic activity. First, the standard MultiFlow DNA Damage Assay-p53, γ H2AX, phospho-histone H3 was used with human TK6 lymphoblastoid cells that were exposed for 24 continuous hours to each of 50 reference clastogens. This initial analysis correctly identified 48/50 compounds as clastogenic. These 48 compounds were then evaluated using a short-term, 'pulse' treatment protocol whereby cells were exposed to test chemical for 4 h, a centrifugation/washout step was performed, and cells were allowed to recover for 20 h. MultiFlow analyses were accomplished at 4 and 24 h. The γ H2AX and phospho-histone H3 biomarkers were found to exhibit distinct differences in terms of their persistence across chemical classes. Unsupervised hierarchical clustering analysis identified three groups. Examination of the compounds within these groups showed one cluster primarily consisting of alkylators that directly target DNA. The other two groups were dominated by non-DNA alkylators and included anti-metabolites, oxidative stress inducers and chemicals that inhibit DNA-processing enzymes. These results are encouraging, as they suggest that a simple follow-up test for in vitro clastogens provides mechanistic insights into their genotoxic activity. This type of information will contribute to improve decision-making and help guide further testing.
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Affiliation(s)
- Steven M Bryce
- Litron Laboratories, 3500 Winton Place, Suite 1B, Rochester, NY 14623, USA
| | | | - Jeffrey C Bemis
- Litron Laboratories, 3500 Winton Place, Suite 1B, Rochester, NY 14623, USA
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12
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Shao Y, Schiwy A, Glauch L, Henneberger L, König M, Mühlenbrink M, Xiao H, Thalmann B, Schlichting R, Hollert H, Escher BI. Optimization of a pre-metabolization procedure using rat liver S9 and cell-extracted S9 in the Ames fluctuation test. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 749:141468. [PMID: 32827816 DOI: 10.1016/j.scitotenv.2020.141468] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 08/01/2020] [Accepted: 08/02/2020] [Indexed: 06/11/2023]
Abstract
Many environmental pollutants pose a toxicological hazard only after metabolic activation. In vitro bioassays using cell lines or bacteria have often no or reduced metabolic activity, which impedes their use in the risk assessment. To improve the predictive capability of in vitro assays, external metabolization systems like the liver S9 fraction are frequently combined with in vitro toxicity assays. While it is typical for S9 fractions that samples and testing systems are combined in the same exposure system, we propose to separate the metabolism step and toxicity measurement. This allows for a modular combination of metabolic activation by enzymes isolated from rat liver (S9) or a biotechnological alternative (ewoS9R) with in vitro bioassays that lack metabolic capacity. Benzo(a)pyrene and 2-aminoanthracene were used as model compounds to optimize the conditions for the S9 metabolic degradation/activation step. The Ames assay with Salmonella typhimurium strains TA98 and TA100 was applied to validate the set-up of decoupling the S9 activation/metabolism from the bioassay system. S9 protein concentration of 0.25 mgprotein/mL, a supplement of 0.13 mM NADPH and a pre-incubation time of 100 min are recommended for activation of samples prior to dosing them to in vitro bioassays using the regular dosing protocols of the respective bioassay. EwoS9R performed equally well as Moltox S9, which is a step forward in developing true animal-free in vitro bioassays. After pre-incubation with S9 fraction, chemicals induced bacteria revertants in both the TA98 and the TA100 assay as efficiently as the standard Ames assay. The pre-incubation of chemicals with S9 fraction could serve for a wide range of cellular in vitro assays to efficiently combine activation and toxicity measurement, which may greatly facilitate the application of these assays for chemical hazard assessment and monitoring of environmental samples.
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Affiliation(s)
- Ying Shao
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany; Key Laboratory of the Three Gorges Reservoir Eco-environment, Ministry of Education, Chongqing University, Shazheng street 174, Shapingba, 400044 Chongqing, China.
| | - Andreas Schiwy
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Department of Evolutionary Ecology and Ecotoxicology, Goethe University, Max-von-Laue-Str. 13, 60438 Frankfurt/Main, Germany
| | - Lisa Glauch
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Luise Henneberger
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Maria König
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Marie Mühlenbrink
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Hongxia Xiao
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany
| | - Beat Thalmann
- EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany
| | - Rita Schlichting
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Henner Hollert
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Department of Evolutionary Ecology and Ecotoxicology, Goethe University, Max-von-Laue-Str. 13, 60438 Frankfurt/Main, Germany
| | - Beate I Escher
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Eberhard Karls University of Tübingen, Environmental Toxicology, Centre for Applied Geosciences, 72074 Tubingen, Germany
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13
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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: 19] [Impact Index Per Article: 4.8] [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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14
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Hung PH, Savidge M, De M, Kang JC, Healy SM, Valerio LG. In vitro and in silico genetic toxicity screening of flavor compounds and other ingredients in tobacco products with emphasis on ENDS. J Appl Toxicol 2020; 40:1566-1587. [PMID: 32662109 DOI: 10.1002/jat.4020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/12/2020] [Accepted: 05/16/2020] [Indexed: 12/16/2022]
Abstract
Electronic nicotine delivery systems (ENDS) are regulated tobacco products and often contain flavor compounds. Given the concern of increased use and the appeal of ENDS by young people, evaluating the potential of flavors to induce DNA damage is important for health hazard identification. In this study, alternative methods were used as prioritization tools to study the genotoxic mode of action (MoA) of 150 flavor compounds. In particular, clastogen-sensitive (γH2AX and p53) and aneugen-sensitive (p-H3 and polyploidy) biomarkers of DNA damage in human TK6 cells were aggregated through a supervised three-pronged ensemble machine learning prediction model to prioritize chemicals based on genotoxicity. In addition, in silico quantitative structure-activity relationship (QSAR) models were used to predict genotoxicity and carcinogenic potential. The in vitro assay identified 25 flavors as positive for genotoxicity: 15 clastogenic, eight aneugenic and two with a mixed MoA (clastogenic and aneugenic). Twenty-three of these 25 flavors predicted to induce DNA damage in vitro are documented in public literature to be in e-liquid or in the aerosols produced by ENDS products with youth-appealing flavors and names. QSAR models predicted 46 (31%) of 150 compounds having at least one positive call for mutagenicity, clastogenicity or rodent carcinogenicity, 49 (33%) compounds were predicted negative for all three endpoints, and remaining compounds had no prediction call. The parallel use of these predictive technologies to elucidate MoAs for potential genetic damage, hold utility as a screening strategy. This study is the first high-content and high-throughput genotoxicity screening study with an emphasis on flavors in ENDS products.
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Affiliation(s)
- Pei-Hsuan Hung
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - Matthew Savidge
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - Mamata De
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - Jueichuan Connie Kang
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA.,US Public Health Service Commissioned Corps, Rockville, MD, USA
| | - Sheila M Healy
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - Luis G Valerio
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, United States Food and Drug Administration, Silver Spring, Maryland, USA
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15
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Tian S, Cyr A, Zeise K, Bryce SM, Hall N, Bemis JC, Dertinger SD. 3Rs-friendly approach to exogenous metabolic activation that supports high-throughput genetic toxicology testing. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:408-432. [PMID: 32039521 DOI: 10.1002/em.22361] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 01/29/2020] [Accepted: 02/05/2020] [Indexed: 06/10/2023]
Abstract
MultiFlow® DNA Damage-p53, γH2AX, Phospho-Histone H3 is a miniaturized, flow cytometry-based assay that provides genotoxic mode of action information by distinguishing clastogens, aneugens, and nongenotoxicants. Work to date has focused on the p53-competent human cell line TK6. While mammalian cell genotoxicity assays typically supply exogenous metabolic activation in the form of concentrated rat liver S9, this is a less-than-ideal approach for several reasons, including 3Rs considerations. Here, we describe our experiences with low concentration S9 and saturating co-factors which were allowed to remain in contact with cells and test chemicals for 24 continuous hours. We exposed TK6 cells in 96-well plates to each of 15 reference chemicals over a range of concentrations, both in the presence and absence of 0.25% v/v phenobarbital/β-naphthoflavone-induced rat liver S9. After 4 and 24 hr of treatment cell aliquots were added to wells of a microtiter plate containing the working detergent/stain/antibody cocktail. After a brief incubation robotic sampling was employed for walk-away flow cytometric data acquisition. PROAST benchmark dose (BMD) modeling was used to characterize the resulting dose-response curves. For each of the 8 reference pro-genotoxicants studied, relative nuclei count, γH2AX, and/or p53 biomarker BMD values were order(s) of magnitude lower for 0.25% S9 conditions compared to 0% S9. Conversely, several of the direct-acting reference chemicals exhibited appreciably lower cytotoxicity and/or genotoxicity BMD values in the presence of S9 (eg, resorcinol). These results prove the efficacy of the low concentration S9 system, and indicate that an efficient and highly scalable multiplexed assay can effectively identify chemicals that require bioactivation to exert their genotoxic effects.
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Affiliation(s)
| | - Aiyana Cyr
- Litron Laboratories, Rochester, New York
| | | | | | - Nikki Hall
- Litron Laboratories, Rochester, New York
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16
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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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17
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Benchmark dose analyses of γH2AX and pH3 endpoints for quantitative comparison of in vitro genotoxicity potential of lipophilic phycotoxins. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2020; 852:503169. [PMID: 32265043 DOI: 10.1016/j.mrgentox.2020.503169] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/28/2020] [Accepted: 03/06/2020] [Indexed: 12/30/2022]
Abstract
The phycotoxins, okadaic acid (OA) and dinophysistoxins 1 and 2 (DTX-1 and -2), are protein phosphatase PP2A and PP1 inhibitors involved in diarrhetic shellfish poisoning (DSP) in humans. Data on the in vivo acute toxicity of the OA-group toxins show some differences and the European Food Safety Authority (EFSA) has determined toxicity equivalent factors (TEFs) of one for the reference toxin, OA, as well as for DTX-1 and 0.6 for DTX-2. However, recent in vitro studies indicated that DTX-1 seems to be more toxic than OA. As OA was described as apoptotic and aneugenic compound, we analyzed the DNA damage responses induced by the 3 toxins through γH2AX and pH3 biomarkers on proliferative HepaRG cells using High Content Analysis. We quantitatively examined the responses for γH2AX and pH3 by benchmark dose analyzing (BMD) using PROAST software. We found that the three toxins increased both γH2AX- and pH3-positive cells populations in a concentration-dependent manner. The 3 toxins induced mitotic arrest, characteristic of aneugenic compounds, as well as DNA strand-breaks concomitantly to cytotoxicity. BMD analysis showed that DTX-1 is the most potent inducer of DNA damage, followed by OA and DTX-2. The quantitative genotoxic data provided in this study are additional findings for reconsidering the estimated TEFs of this group of phycotoxins.
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Khoury L, Zalko D, Audebert M. Evaluation of the genotoxic potential of apoptosis inducers with the γH2AX assay in human cells. Mutat Res 2020; 852:503165. [PMID: 32265046 DOI: 10.1016/j.mrgentox.2020.503165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/26/2020] [Accepted: 02/28/2020] [Indexed: 11/19/2022]
Abstract
Human risk assessment of genotoxic chemicals is an important area of research. However, the specificity of in vitro mammalian genotoxicity assays is sometime low, as they yield to misleading positive results that are not observe in in vivo studies. Apoptosis can be a confounding factor in the interpretation of the results. Recently, a new strategy for genotoxicity screening, based on the combined analysis of phosphorylated histones H2AX (γH2AX) and H3 (pH3), was proposed to discriminate efficiently aneugenic from clastogenic compounds. However, γH2AX biomarker could also be induce by apoptosis. The aim of the present study was to investigate the specificity of this genotoxic biomarker. For this purpose, we analyzed 26 compounds inducing apoptosis by different mechanism of action, with the γH2AX assay in three human cell lines after 24 h treatment. Most of the tested chemicals were negative in the assay, whatever the cell line tested. The few compounds that generated positive data have also been report positive in other genotoxicity assays. The data presented here demonstrate that the γH2AX assay is not vulnerable to the generation of misleading positive results by apoptosis inducers. Currently, no formal guidelines have been approve for the γH2AX assay for regular genotoxicity studies, but we suggest that this biomarker could be used as a new standard genotoxicity assay.
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Affiliation(s)
- Laure Khoury
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France
| | - Daniel Zalko
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France
| | - Marc Audebert
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France.
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19
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The effect of inhibitors of phosphatidylinositol 3-kinase-related kinases on dibenzo[def,p]chrysene genotoxicity measured by γH2AX levels and neutral comet assay in HepG2 human hepatocellular cancer cells. Toxicol In Vitro 2019; 63:104749. [PMID: 31838185 DOI: 10.1016/j.tiv.2019.104749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 12/11/2019] [Accepted: 12/11/2019] [Indexed: 12/12/2022]
Abstract
In the study the modulating effect of inhibition of phosphatidylinositol 3-kinase-related kinases (PIKK): ATM (Ataxia Telangiectasia Mutated), ATR (Ataxia Telangiectasia and Rad3 Related) and DNA-PK (DNA-dependent protein kinase) on genotoxicity of dibenzo[def,p]chrysene (DBC) in HepG2 human hepatocellular cancer cells was investigated. The cytotoxicity of DBC was determined, also in combination with PIKK inhibitors, using the MTT reduction assay. The high cytotoxicity of DBC was observed after 72 h incubation (IC50 = 0.06 μM). The PIKK inhibitors applied at non-cytotoxic concentrations: caffeine (1 mM) and KU55933 (2.5 μM) had no significant influence on the DBC cytotoxicity, however NU7026 (5 μM) caused significant increase in the cell viability by about 25%. The combinations of the inhibitors (double or triple) where NU7026 was present also caused increase in the cell viability (i.e. cytoprotective effect) compared to the effect of DBC. The level of damage to the genetic material (DNA double strand breaks, DSB) was assessed by measuring levels of phosphorylated form of H2A histone (γH2AX) and neutral comet assay. DBC induced DSB in a concentration and time-dependent manner. NU7026 considerably reduced the level of DSB level measured by γH2AX and comet assay. The obtained results confirm that DBC is cytotoxic and causes damage to the genetic material including DSB. The DNA-PK inhibitor NU7026 increases cell viability after exposure to DBC and reduces DNA damage, what indicates an important role of the sensor kinase in mediating the effect.
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20
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Bernacki DT, Bryce SM, Bemis JC, Dertinger SD, Witt KL, Smith‐Roe SL. Evidence for an Aneugenic Mechanism of Action for Micronucleus Induction by Black Cohosh Extract. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2019; 60:845-856. [PMID: 31569270 PMCID: PMC6900087 DOI: 10.1002/em.22334] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/03/2019] [Accepted: 09/07/2019] [Indexed: 06/10/2023]
Abstract
Black cohosh extract (BCE) is a popular botanical dietary supplement marketed to relieve symptoms of various gynecological ailments. Studies conducted by the National Toxicology Program (NTP) showed that BCE induces micronucleated erythrocytes in female rats and mice. Subsequently, the NTP showed that a variety of BCEs, including the sample that induced micronuclei (MN) in vivo ("NTP BCE") had a similar effect in human TK6 cells. Further testing with the MultiFlow® DNA Damage Assay revealed that TK6 cells exposed to NTP BCE, as well as a BCE reference material (BC XRM), exhibited a signature consistent with aneugenic activity in TK6 cells. Results from experiments reported herein confirmed these in vitro observations with NTP BCE and BC XRM. We extended these studies to include a novel test system, the MultiFlow Aneugen Molecular Mechanism Assay. For these experiments, TK6 cells were exposed to NTP BCE and BC XRM over a range of concentrations in the presence of fluorescent Taxol (488 Taxol). After 4 h, nuclei from lysed cells were stained with a nucleic acid dye and labeled with fluorescent antibodies against phospho-histone H3 (p-H3) and Ki-67. Whereas BCEs did not affect p-H3:Ki-67 ratios (a signature of aneugenic mitotic kinase inhibitors), 488 Taxol-associated fluorescence (a tubulin binder-sensitive endpoint) was affected. More specifically, 488 Taxol-associated fluorescence was reduced over the same concentration range that was previously observed to induce MN. These results provide direct evidence that BCEs destabilize microtubules in vitro, and this is the molecular mechanism responsible for the aneugenicity findings. Environ. Mol. Mutagen. 2019. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
| | | | | | | | - Kristine L. Witt
- Division of the National Toxicology ProgramNIEHSResearch Triangle ParkNorth Carolina
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Smart DJ, Helbling FR, McHugh D, Vanscheeuwijck P. Baseline effects of non-flavored e-liquids in the in vitro micronucleus assay. TOXICOLOGY RESEARCH AND APPLICATION 2019. [DOI: 10.1177/2397847319887904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Electronic nicotine delivery systems (ENDSs; e.g. e-cigarettes) are being developed as potentially reduced-risk alternatives to the continued use of conventional tobacco products. They typically comprise a device that heats an e-liquid to generate inhalable vapor. E-liquids and ENDS-derived vapor have been the focus of toxicological assessment; in particular, their DNA-damaging potential has been investigated with varying outcomes and conclusions. In vitro genetic toxicology assays have formed a part of these assessments. However, they are susceptible to producing misleading or false positive results, especially under extreme conditions. In the present study, we evaluated a series of six neat (non-vaporized) non-flavored e-liquids (NFEL-A to F) in a flow cytometry version of the in vitro micronucleus assay in order to characterize their baseline effects on Chinese hamster ovary cells under hazard identification conditions. The NFELs induced cytotoxicity universally despite differing in propylene glycol (PG), vegetable glycerin (VG), and nicotine content. In addition, significant genotoxic responses were also detected with the PG-predominant e-liquids NFEL-A, D, and F but not with NFEL-B, C, or E, which contained higher proportions of VG. All six NFELs induced extreme cell culture conditions (i.e. increases in pH and osmolality) at the concentrations assessed. They also exhibited nonbiologically relevant effects on the mechanistic endpoints (i.e. cell cycle and phosphorylated histones H2AX and H3). In conclusion, although the PG component of the NFELs drove micronucleus formation in the assay, data on the complementary mechanistic endpoints suggest that this apparent DNA damage is potentially misleading and of negligible biological relevance as a risk for DNA integrity. In future assessments, any adverse changes (such as signatures of micronuclei induction, G2M arrest, and increases in γH2AX) relative to this reference data set might indicate a possible genotoxic hazard and would prompt further investigations for exploring the extent of risk.
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Affiliation(s)
- Daniel J Smart
- Philip Morris International Research and Development, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Fabian R Helbling
- Philip Morris International Research and Development, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Damian McHugh
- Philip Morris International Research and Development, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Patrick Vanscheeuwijck
- Philip Morris International Research and Development, Philip Morris Products S.A., Neuchâtel, Switzerland
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22
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Bernacki DT, Bryce SM, Bemis JC, Dertinger SD. Aneugen Molecular Mechanism Assay: Proof-of-Concept With 27 Reference Chemicals. Toxicol Sci 2019; 170:382-393. [PMID: 31132080 PMCID: PMC6657583 DOI: 10.1093/toxsci/kfz123] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A tiered bioassay and data analysis scheme is described for elucidating the most common molecular targets responsible for chemical-induced in vitro aneugenicity: tubulin destabilization, tubulin stabilization, and inhibition of mitotic kinase(s). To evaluate this strategy, TK6 cells were first exposed to each of 27 presumed aneugens over a range of concentrations. After 4 and 24 h of treatment, γH2AX, p53, phospho-histone H3 (p-H3), and polyploidization biomarkers were evaluated using the MultiFlow DNA Damage Assay Kit. The assay identified 27 of 27 chemicals as genotoxic, with 25 exhibiting aneugenic signatures, 1 aneugenic and clastogenic, and 1 clastogenic. Subsequently, a newly described follow-up assay was employed to investigate the aneugenic agents' molecular targets. For these experiments, TK6 cells were exposed to each of 26 chemicals in the presence of 488 Taxol. After 4 h, cells were lysed and the liberated nuclei and mitotic chromosomes were stained with a nucleic acid dye and labeled with fluorescent antibodies against p-H3 and Ki-67. Flow cytometric analyses revealed that alterations to 488 Taxol-associated fluorescence were only observed with tubulin binders-increases in the case of tubulin stabilizers, decreases with destabilizers. Mitotic kinase inhibitors with known Aurora kinase B inhibiting activity were the only aneugens that dramatically decreased the ratio of p-H3-positive to Ki-67-positive nuclei. Unsupervised hierarchical clustering based on 488 Taxol fluorescence and p-H3: Ki-67 ratios clearly distinguished compounds with these disparate molecular mechanisms. Furthermore, a classification algorithm based on an artificial neural network was found to effectively predict molecular target, as leave-one-out cross-validation resulted in 25/26 agreement with a priori expectations. These results are encouraging, as they suggest that an adequate number of training set chemicals, in conjunction with a machine learning algorithm based on 488 Taxol, p-H3, and Ki-67 responses, can reliably elucidate the most commonly encountered aneugenic molecular targets.
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23
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Kopp B, Khoury L, Audebert M. Validation of the γH2AX biomarker for genotoxicity assessment: a review. Arch Toxicol 2019; 93:2103-2114. [DOI: 10.1007/s00204-019-02511-9] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 07/04/2019] [Indexed: 12/12/2022]
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24
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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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25
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Maranghi F, Tassinari R, Narciso L, Tait S, Rocca CL, Felice GD, Butteroni C, Corinti S, Barletta B, Cordelli E, Pacchierotti F, Eleuteri P, Villani P, Hegarat LL, Fessard V, Reale O. In vivo toxicity and genotoxicity of beauvericin and enniatins. Combined approach to study in vivo toxicity and genotoxicity of mycotoxins beauvericin (BEA) and enniatin B (ENNB). ACTA ACUST UNITED AC 2018. [DOI: 10.2903/sp.efsa.2018.en-1406] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Eugenia Cordelli
- Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) Italy
| | - Francesca Pacchierotti
- Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) Italy
| | - Patrizia Eleuteri
- Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) Italy
| | - Paola Villani
- Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) Italy
| | - Ludovic Le Hegarat
- French Agency for Food, Environmental and Occupational Health & Safety (ANSES) France
| | - Valérie Fessard
- French Agency for Food, Environmental and Occupational Health & Safety (ANSES) France
| | - Océane Reale
- French Agency for Food, Environmental and Occupational Health & Safety (ANSES) France
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26
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Bryce SM, Bernacki DT, Smith-Roe SL, Witt KL, Bemis JC, Dertinger SD. Investigating the Generalizability of the MultiFlow ® DNA Damage Assay and Several Companion Machine Learning Models With a Set of 103 Diverse Test Chemicals. Toxicol Sci 2018; 162:146-166. [PMID: 29106658 PMCID: PMC6059150 DOI: 10.1093/toxsci/kfx235] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The in vitro MultiFlow DNA Damage assay multiplexes p53, γH2AX, phospho-histone H3, and polyploidization biomarkers into 1 flow cytometric analysis (Bryce, S. M., Bernacki, D. T., Bemis, J. C., and Dertinger, S. D. (2016). Genotoxic mode of action predictions from a multiplexed flow cytometric assay and a machine learning approach. Environ. Mol. Mutagen. 57, 171-189). The work reported herein evaluated the generalizability of the method, as well as several data analytics strategies, to a range of chemical classes not studied previously. TK6 cells were exposed to each of 103 diverse chemicals, 86 of which were supplied by the National Toxicology Program (NTP) and selected based upon responses in genetic damage assays conducted under the Tox21 program. Exposures occurred for 24 h over a range of concentrations, and cell aliquots were removed at 4 and 24 h for analysis. Multiplexed response data were evaluated using 3 machine learning models designed to predict genotoxic mode of action based on data from a training set of 85 previously studied chemicals. Of 54 chemicals with sufficient information to make an a priori call on genotoxic potential, the prediction models' accuracies were 79.6% (random forest), 88.9% (logistic regression), and 90.7% (artificial neural network). A majority vote ensemble of the 3 models provided 92.6% accuracy. Forty-nine NTP chemicals were not adequately tested (maximum concentration did not approach assay's cytotoxicity limit) and/or had insufficient conventional genotoxicity data to allow their genotoxic potential to be defined. For these chemicals MultiFlow data will be useful in future research and hypothesis testing. Collectively, the results suggest the MultiFlow assay and associated data analysis strategies are broadly generalizable, demonstrating high predictability when applied to new chemicals and classes of compounds.
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Affiliation(s)
| | | | - Stephanie L Smith-Roe
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Kristine L Witt
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
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27
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Bryce SM, Bernacki DT, Bemis JC, Spellman RA, Engel ME, Schuler M, Lorge E, Heikkinen PT, Hemmann U, Thybaud V, Wilde S, Queisser N, Sutter A, Zeller A, Guérard M, Kirkland D, Dertinger SD. Interlaboratory evaluation of a multiplexed high information content in vitro genotoxicity assay. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:146-161. [PMID: 28370322 PMCID: PMC5436310 DOI: 10.1002/em.22083] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 05/18/2023]
Abstract
We previously described a multiplexed in vitro genotoxicity assay based on flow cytometric analysis of detergent-liberated nuclei that are simultaneously stained with propidium iodide and labeled with fluorescent antibodies against p53, γH2AX, and phospho-histone H3. Inclusion of a known number of microspheres provides absolute nuclei counts. The work described herein was undertaken to evaluate the interlaboratory transferability of this assay, commercially known as MultiFlow® DNA Damage Kit-p53, γH2AX, Phospho-Histone H3. For these experiments, seven laboratories studied reference chemicals from a group of 84 representing clastogens, aneugens, and nongenotoxicants. TK6 cells were exposed to chemicals in 96-well plates over a range of concentrations for 24 hr. At 4 and 24 hr, cell aliquots were added to the MultiFlow reagent mix and following a brief incubation period flow cytometric analysis occurred, in most cases directly from a 96-well plate via a robotic walk-away data acquisition system. Multiplexed response data were evaluated using two analysis approaches, one based on global evaluation factors (i.e., cutoff values derived from all interlaboratory data), and a second based on multinomial logistic regression that considers multiple biomarkers simultaneously. Both data analysis strategies were devised to categorize chemicals as predominately exhibiting a clastogenic, aneugenic, or nongenotoxic mode of action (MoA). Based on the aggregate 231 experiments that were performed, assay sensitivity, specificity, and concordance in relation to a priori MoA grouping were ≥ 92%. These results are encouraging as they suggest that two distinct data analysis strategies can rapidly and reliably predict new chemicals' predominant genotoxic MoA based on data from an efficient and transferable multiplexed in vitro assay. Environ. Mol. Mutagen. 58:146-161, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
| | | | | | | | - Maria E Engel
- Pfizer Worldwide Research and Development, Groton, Connecticut
| | - Maik Schuler
- Pfizer Worldwide Research and Development, Groton, Connecticut
| | | | | | | | | | | | | | | | - Andreas Zeller
- Roche Pharma Research and Early Development, Basel, Switzerland
| | - Melanie Guérard
- Roche Pharma Research and Early Development, Basel, Switzerland
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