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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 PMCID: PMC11369915 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] [Grants] [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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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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3
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Wilde S, Dambowsky M, Hempt C, Sutter A, Queisser N. Classification of in vitro genotoxicants using a novel multiplexed biomarker assay compared to the flow cytometric micronucleus test. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:662-677. [PMID: 28940655 DOI: 10.1002/em.22130] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/26/2017] [Accepted: 07/28/2017] [Indexed: 06/07/2023]
Abstract
Regulatory in vitro genotoxicity testing exhibits shortcomings in specificity and mode of action (MoA) information. Thus, the aim of this work was to evaluate the performance of the novel MultiFlow® assay composed of mechanistic biomarkers quantified in TK6 cells after treatment (4 and 24 hr): γH2AX (DNA double strand breaks), phosphorylated H3 (mitotic cells), translocated p53 (genotoxicity), and cleaved PARP1 (apoptosis). A reference dataset of 31 compounds with well-established MoA was studied using the MicroFlow® micronucleus assay. A positive call was raised following the earlier published criteria from Litron Laboratories. In the light of our data, these evaluation criteria should probably be adjusted since only 8/11 (73%) nongenotoxicants and 18/20 (90%) genotoxicants were correctly identified. Moreover, there is a need for new in vitro tools to delineate the predominant MoA as in the MicroFlow® assay only 5/9 (56%) aneugens and 4/11 (36%) clastogens were correctly classified. In contrast, the MultiFlow® assay provides more in-depth information about the MoA and therefore reliably discriminates clastogens, aneugens, and nongenotoxicants. By using a lab-specific, practical threshold for the aforementioned biomarkers, 10/11 (91%) nongenotoxicants and 19/20 genotoxicants (95%), 9/11 (82%) clastogens, and 8/9 (89%) aneugens were correctly categorized, suggesting a clear improvement over the MicroFlow® . Furthermore, the MultiFlow markers were benchmarked against established methods to assess the validity of the data. Altogether, these findings demonstrated good agreement between the MultiFlow® assay and the benchmarking methods. Finally, p21 may improve class discrimination given the correct identification of 4/4 (100%) aneugens and 2/5 (40%) clastogens. Environ. Mol. Mutagen. 58:662-677, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sabrina Wilde
- Investigational Toxicology, Bayer AG, Berlin, Germany
| | | | - Claudia Hempt
- Investigational Toxicology, Bayer AG, Berlin, Germany
| | | | - Nina Queisser
- Investigational Toxicology, Bayer AG, Berlin, Germany
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4
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Etter S, Birrell L, Cahill P, Scott H, Billinton N, Walmsley RM, Smith B. The ‘BlueScreen HC’ assay as a decision making test in the genotoxicity assessment of flavour and fragrance materials. Toxicol In Vitro 2015; 29:1425-35. [DOI: 10.1016/j.tiv.2015.05.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 05/01/2015] [Accepted: 05/03/2015] [Indexed: 11/28/2022]
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5
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Hornberg JJ, Laursen M, Brenden N, Persson M, Thougaard AV, Toft DB, Mow T. Exploratory toxicology as an integrated part of drug discovery. Part II: Screening strategies. Drug Discov Today 2013; 19:1137-44. [PMID: 24374152 DOI: 10.1016/j.drudis.2013.12.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 11/18/2013] [Accepted: 12/18/2013] [Indexed: 12/31/2022]
Abstract
In an effort to reduce toxicity-related attrition, different strategies have been implemented throughout the pharmaceutical industry. Previously (in Part I), we have outlined our 'integrated toxicology' strategy, which aims to provide timely go/no-go decisions (fail early) but also to show a direction to the drug discovery teams (showing what will not fail). In this review (Part II of the series) we describe our compound testing strategies with respect to cardiovascular safety, hepatotoxicity, genotoxicity, immunotoxicity and exploratory in vivo toxicity. We discuss the in vitro, ex vivo and in vivo assays and models we employ to assess safety risks and optimize compound series during the drug discovery process, including their predictivity and the decisions they generate.
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Affiliation(s)
- Jorrit J Hornberg
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Morten Laursen
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Nina Brenden
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Mikael Persson
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Annemette V Thougaard
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Dorthe B Toft
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Tomas Mow
- Department of Exploratory Toxicology, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
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Bryce SM, Avlasevich SL, Bemis JC, Tate M, Walmsley RM, Saad F, Van Dijck K, De Boeck M, Van Goethem F, Lukamowicz-Rajska M, Elhajouji A, Dertinger SD. Flow cytometric 96-well microplate-based in vitro micronucleus assay with human TK6 cells: protocol optimization and transferability assessment. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2013; 54:180-194. [PMID: 23447390 DOI: 10.1002/em.21760] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 12/17/2012] [Accepted: 12/17/2012] [Indexed: 06/01/2023]
Abstract
An automated approach for scoring in vitro micronuclei (MN) has been described in which flow cytometric analysis is combined with compound exposure, processing, and sampling in a single 96-well plate (Bryce SM et al. [2010]: Mutat Res 703:191-199). The current report describes protocol optimization and an interlaboratory assessment of the assay's transferability and reproducibility. In a training phase, the methodology was refined and collaborating laboratories were qualified by repeatedly testing three compounds. Second, a set of 32 chemicals comprised of reference genotoxicants and presumed non-genotoxicants was tested at each of four sites. TK6 cells were exposed to 10 closely spaced compound concentrations for 1.5- to 2-cell population doublings, and were then stained and lysed for flow cytometric analysis. MN frequencies were determined by evaluating ≥ 5,000 cells per replicate well, and several indices of cytotoxicity were acquired. The prevalence of positive results varied according to the MN-fold increase used to signify a genotoxic result, as well as the endpoint used to define a cytotoxicity limit. By varying these parameters, assay sensitivity and specificity values ranged from 82 to 98%, and 86 to 97%, respectively. In a third phase, one laboratory tested a further six genotoxicants and five non-genotoxic apoptosis inducers. In these experiments assay specificity was markedly improved when top concentration selection was based on two cytotoxicity endpoints-relative survival and quantification of ethidium monoazide-positive events. Collectively, the results indicate that the miniaturized assay is transferable across laboratories. The 96-well format consumes considerably less compound than conventional in vitro MN test methods, and the high information content provided by flow cytometry helps guard against irrelevant positive results arising from overt toxicity.
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Johnson D, Walmsley R. Histone-deacetylase inhibitors produce positive results in the GADD45a-GFP GreenScreen HC assay. Mutat Res 2013; 751:96-100. [PMID: 23340162 DOI: 10.1016/j.mrgentox.2012.12.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/29/2012] [Accepted: 12/05/2012] [Indexed: 11/25/2022]
Abstract
Histone-deacetylase inhibitors (HDACi) are able to induce cell-cycle arrest, apoptosis and differentiation in a variety of tumour cell lines. The mechanisms leading to these cellular outcomes are not fully understood, however, it is has been proposed that induction of cell-cycle arrest might be a result of genotoxic stress. Despite the potential for genotoxic activity of this class of compounds, there are very few data available to provide evidence for this, either in vitro or in vivo. In this study, four HDACi, viz. trichostatin A, sodium butyrate, APHA compound 8 and apicidin, were tested in the human lymphoblastoid TK6 cell line-hosted GADD45a-GFP assay, which has high sensitivity and specificity in the detection of genotoxic carcinogens and in vivo genotoxicants. All four compounds produced positive genotoxicity results within the acceptable toxic dose range of the assay, with APHA compound 8 producing the weakest response. Taken alongside recent evidence demonstrating that GADD45a is not induced by non-genotoxic apoptogens, this study suggests that genotoxicity contributes to the anti-tumour activity of HDACi drugs.
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Affiliation(s)
- Donna Johnson
- Harper Adams University College, Newport, Shropshire, UK.
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Allsup J, Billinton N, Scott H, Walmsley RM. Applicability domain of the GADD45a reporter assays: non-steroidal anti-inflammatory drugs do not produce misleading genotoxicity results. Toxicol Res (Camb) 2013. [DOI: 10.1039/c3tx50029b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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