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Waters MD, Warren S, Hughes C, Lewis P, Zhang F. Human genetic risk of treatment with antiviral nucleoside analog drugs that induce lethal mutagenesis: The special case of molnupiravir. Environ Mol Mutagen 2022; 63:37-63. [PMID: 35023215 DOI: 10.1002/em.22471] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/28/2021] [Accepted: 01/08/2022] [Indexed: 06/14/2023]
Abstract
This review considers antiviral nucleoside analog drugs, including ribavirin, favipiravir, and molnupiravir, which induce genome error catastrophe in SARS-CoV or SARS-CoV-2 via lethal mutagenesis as a mode of action. In vitro data indicate that molnupiravir may be 100 times more potent as an antiviral agent than ribavirin or favipiravir. Molnupiravir has recently demonstrated efficacy in a phase 3 clinical trial. Because of its anticipated global use, its relative potency, and the reported in vitro "host" cell mutagenicity of its active principle, β-d-N4-hydroxycytidine, we have reviewed the development of molnupiravir and its genotoxicity safety evaluation, as well as the genotoxicity profiles of three congeners, that is, ribavirin, favipiravir, and 5-(2-chloroethyl)-2'-deoxyuridine. We consider the potential genetic risks of molnupiravir on the basis of all available information and focus on the need for additional human genotoxicity data and follow-up in patients treated with molnupiravir and similar drugs. Such human data are especially relevant for antiviral NAs that have the potential of permanently modifying the genomes of treated patients and/or causing human teratogenicity or embryotoxicity. We conclude that the results of preclinical genotoxicity studies and phase 1 human clinical safety, tolerability, and pharmacokinetics are critical components of drug safety assessments and sentinels of unanticipated adverse health effects. We provide our rationale for performing more thorough genotoxicity testing prior to and within phase 1 clinical trials, including human PIG-A and error corrected next generation sequencing (duplex sequencing) studies in DNA and mitochondrial DNA of patients treated with antiviral NAs that induce genome error catastrophe via lethal mutagenesis.
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Affiliation(s)
- Michael D Waters
- Michael Waters Consulting USA, Hillsborough, North Carolina, USA
| | | | - Claude Hughes
- Duke University Medical Center, Durham, North Carolina, USA
| | | | - Fengyu Zhang
- Global Clinical and Translational Research Institute, Bethesda, Maryland, USA
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Chen R, Zhou C, Cao Y, Xi J, Ohira T, He L, Huang P, You X, Liu W, Zhang X, Ma S, Xie T, Chang Y, Luan Y. Assessment of Pig-a, Micronucleus, and Comet Assay Endpoints in Tg.RasH2 Mice Carcinogenicity Study of Aristolochic Acid I. Environ Mol Mutagen 2020; 61:266-275. [PMID: 31443125 DOI: 10.1002/em.22325] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/16/2019] [Accepted: 08/19/2019] [Indexed: 06/10/2023]
Abstract
A newly developed in vivo Pig-a gene mutation assay displays great potential for integration into genotoxicity tests. To obtain more evidence for application of the Pig-a assay, we integrated this assay, micronucleus test in peripheral blood (MN-pb test) and bone marrow (MN-bm test), as well as a Comet assay into a transgenic RasH2 mice carcinogenicity study. Fourteen male RasH2 mice and five wild-type (WT) mice were treated with a strong mutagen aristolochic acid I at a dose of 5 mg/kg/day for 4 consecutive weeks. Mice recovered in 5 weeks. Peripheral bloods were collected for Pig-a assay, MN-pb test, and Comet assay at several time points, while bone marrow and target organs were harvested for the MN-bm test and pathological diagnosis after mice were euthanized. Finally, 13 of the 14 RasH2 mice developed squamous cell carcinomas in the forestomach, while there were no carcinomas in the WT mice. Pig-a mutant frequencies (MFs) consecutively increased throughout the study to a maximum value of approximately 63-fold more than background. These frequencies were relative to the incidence, size, and malignant degree of tumors. Micronucleated reticulocytes increased from Day 1 to Day 49, before returning to background levels. No positive responses were observed in either the MN-bm test or the Comet assay. Results suggested that, when compared with the other two tests, the Pig-a assay persistently contributed to sustaining MFs, enhanced detection sensitivity due to the accumulation of Pig-a mutations, and demonstrated better predictability for tumorigenicity. Environ. Mol. Mutagen. 61:266-275, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Ruixue Chen
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Changhui Zhou
- Shanghai InnoStar Bio-Tech Co., Ltd., National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai, People's Republic of China
| | - Yiyi Cao
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Jing Xi
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Toko Ohira
- Shanghai InnoStar Bio-Tech Co., Ltd., National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai, People's Republic of China
| | - Liang He
- Shanghai InnoStar Bio-Tech Co., Ltd., National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai, People's Republic of China
| | - Pengcheng Huang
- Shanghai InnoStar Bio-Tech Co., Ltd., National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai, People's Republic of China
| | - Xinyue You
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Weiying Liu
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Xinyu Zhang
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Shuangcheng Ma
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- National Institutes for Food and Drug Control, Beijing, China
| | - Tianpei Xie
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- Shanghai Standard Technology Co., Ltd., Shanghai, People's Republic of China
| | - Yan Chang
- Shanghai InnoStar Bio-Tech Co., Ltd., National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai, People's Republic of China
| | - Yang Luan
- School of Public Health, Hongqiao International Institute of Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- Joint Laboratory on Herbal Safety, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
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Ji Z, Settivari RS, LeBaron MJ. Pilot studies evaluating the nongenotoxic rodent carcinogens phenobarbital and clofibrate in the rat Pig-a assay. Environ Mol Mutagen 2019; 60:42-46. [PMID: 30338550 DOI: 10.1002/em.22232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/16/2018] [Accepted: 07/17/2018] [Indexed: 06/08/2023]
Abstract
The Pig-a assay is an emerging and promising in vivo method to determine mutagenic potential of chemicals. Since its development in 2008, remarkable progress has been made in harmonizing and characterizing the test procedures, primarily using known mutagenic chemicals. The purpose of the present study was to evaluate specificity of the Pig-a assay using two nongenotoxic and well-characterized rodent liver carcinogens, phenobarbital and clofibrate, in male F344/DuCrl rats. Daily oral administration of phenobarbital or clofibrate at established hepatotoxic doses for 28 days resulted in substantial hepatic alterations, however, did not increase the frequency of Pig-a mutation markers (RETCD59- and RBCCD59- ) compared to vehicle control or pre-exposure (Day -5) mutant frequencies. These results are consistent with the existing literature on the nonmutagenic mode of action (MoA) of phenobarbital and clofibrate liver tumors. The present study contributes to the limited, but expanding evidence on the specificity of the Pig-a assay and further for the investigations of carcinogenic MoAs, i.e., mutagenic or nonmutagenic potential of chemicals. Environ. Mol. Mutagen. 60:42-46, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Zhiying Ji
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
| | - Raja S Settivari
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
| | - Matthew J LeBaron
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
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Qin M, Chen R, Huang Z, Wang J, Xu S, Jiang R, Li J, Xian J, Wang X, Lu Y, Xu L, Chen N, Chen X, Wang P, Wang T. Application of the in vivo Pig-a gene mutation assay to test the potential genotoxicity of p-phenylenediamine. Food Chem Toxicol 2019; 123:424-30. [PMID: 30439388 DOI: 10.1016/j.fct.2018.10.061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/17/2018] [Accepted: 10/27/2018] [Indexed: 11/21/2022]
Abstract
Currently, it remains controversial whether p-phenylenediamine (PPD) is genotoxic. In this study, we evaluated the potential genotoxicity of PPD using the newly-developed Pig-a gene mutation assay. The results of three classical genetic toxicity tests (bacterial reverse mutation assay, mammalian cell chromosomal aberration test, and mammalian erythrocyte micronucleus test) are all positive, suggesting that PPD is potentially genotoxic. In Pig-a assay, Sprague-Dawley rats are orally administered with PPD for 28 consecutive days at three doses (12.5, 25, and 50 mg/kg/day). Our result shows that PPD (25 and 50 mg/kg/day) dose-dependently increases RETCD59- value over controls on Day 8. RETCD59- keeps increasing to the maximum on Day 15 and then decreases until Day 29. PPD also dose-dependently increase RBCCD59- value on Day 15, which keeps elevating until Day 29. The time-course of RETCD59- and RBCCD59- induced by PPD are similar with that induced by N-ethyl-N-nitrosourea (ENU) treatment for 3 days. Our data suggests that PPD has potential genotoxic effects, and the Pig-a assay is sensitive to assess mutagenicity. However, further investigation of the changes of RETCD59- and RBCCD59- induced by hair dyes containing PPD should be detected by Pig-a assay in occupational exposure population to confirm the safety of PPD usage.
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Revollo JR, Pearce MG, Dad A, Petibone DM, Robison TW, Roberts D, Dobrovolsky VN. Analysis of mutation in the rat Pig-a assay: I) studies with bone marrow erythroid cells. Environ Mol Mutagen 2018; 59:722-732. [PMID: 30091272 DOI: 10.1002/em.22211] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/08/2018] [Accepted: 05/10/2018] [Indexed: 06/08/2023]
Abstract
We have established a flow cytometry-based Pig-a assay for rat bone marrow erythroid cells (BMEs). The BME Pig-a assay uses a DNA-specific stain and two antibodies: one against the transmembrane transferrin receptor (CD71 marker) and the other against the GPI-anchored complement inhibitory protein (CD59 marker). In F344 male rats treated acutely with a total of 120 mg/kg of N-ethyl-N-nitrosourea (ENU) the frequency of CD59-deficient phenotypically mutant BMEs increased approximately 24-fold compared to the rats concurrently treated with the vehicle. Such an increase of mutant BMEs coincides with increases of CD59-deficient reticulocytes measured in rats treated with similar doses of ENU. Sequence analysis of the endogenous X-linked Pig-a gene of CD59-deficient BMEs revealed that they are Pig-a mutants. The spectrum of ENU-induced Pig-a mutations in these BMEs was consistent with the in vivo mutagenic signature of ENU: 73% of mutations occurred at A:T basepairs, with the mutated T on the nontranscribed strand of the gene. T→A transversion was the most frequent mutation followed by T→C transition; no deletion or insertion mutations were present in the spectrum. Since BMEs are precursors of peripheral red blood cells, our findings suggest that CD59-deficient erythrocytes measured in the flow cytometric erythrocyte Pig-a assay develop from BMEs containing mutations in the Pig-a gene. Thus, the erythrocyte Pig-a assay detects mutation in the Pig-a gene. Environ. Mol. Mutagen. 59:722-732, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Javier R Revollo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
| | - Mason G Pearce
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
| | - Azra Dad
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
| | - Dayton M Petibone
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
| | - Timothy W Robison
- Division of Pulmonary, Allergy, and Rheumatology Products, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland
| | - Daniel Roberts
- Charles River Laboratories, Skokie, Illinois; Joint Graduate Program of Toxicology, Rutgers University, Piscataway, New Jersey
| | - Vasily N Dobrovolsky
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
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David R, Talbot E, Allen B, Wilson A, Arshad U, Doherty A. The development of an in vitro Pig-a assay in L5178Y cells. Arch Toxicol 2018; 92:1609-1623. [PMID: 29362862 DOI: 10.1007/s00204-018-2157-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 01/17/2018] [Indexed: 12/01/2022]
Abstract
A recent flow cytometry-based in vivo mutagenicity assay involves the hemizygous phosphatidylinositol class A (Pig-a) gene. Pig-a forms the catalytic subunit of N-acetylglucosaminyltransferase required for glycophosphatidylinositol (GPI) anchor biosynthesis. Mutations in Pig-a prevent GPI-anchor synthesis resulting in loss of cell-surface GPI-linked proteins. The aim of the current study was to develop and validate an in vitro Pig-a assay in L5178Y mouse lymphoma cells. Ethyl methanesulfonate (EMS)-treated cells (186.24-558.72 µg/ml; 24 h) were used for method development and antibodies against GPI-linked CD90.2 and stably expressed CD45 were used to determine GPI-status by flow cytometry. Antibody concentration and incubation times were optimised (0.18 µg/ml, 30 min, 4 °C) and Zombie Violet™ (viability marker; 0.5%, 30 min, RT) was included. The optimum phenotypic expression period was 8 days. The low background mutation frequency of GPI-deficiency [GPI(-)] in L5178Y cells (0.1%) constitutes a rare event, thus flow cytometry acquisition parameters were optimised; 104 cells were measured at medium flow rate to ensure a CV ≤ 30%. Spiking known numbers of GPI(-) cells into a wild-type population gave high correlation between measured and spiked numbers (R2 0.999). We applied the in vitro Pig-a assay to a selection of well-validated genotoxic and non-genotoxic compounds. EMS, N-ethyl-N-nitrosourea and 4-nitroquinoline-N-oxide dose dependently increased numbers of GPI(-) cells, while etoposide, mitomycin C, and a bacterial-specific mutagen did not. Cycloheximide and sodium chloride were negative. Sanger sequencing revealed Pig-a mutations in the GPI(-) clones. In conclusion, this in vitro Pig-a assay could complement the in vivo version, and follow up weak Ames positives and late-stage human metabolites or impurities.
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Affiliation(s)
- Rhiannon David
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK.
| | - Emily Talbot
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Bethany Allen
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Amy Wilson
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Usman Arshad
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK
| | - Ann Doherty
- Genetic Toxicology, Discovery Safety, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Cambridge, UK
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Ji Z, LeBaron MJ. Applying the erythrocyte Pig-a assay concept to rat epididymal sperm for germ cell mutagenicity evaluation. Environ Mol Mutagen 2017; 58:485-493. [PMID: 28714084 DOI: 10.1002/em.22109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 05/18/2017] [Accepted: 05/18/2017] [Indexed: 06/07/2023]
Abstract
The Pig-a assay, a recently developed in vivo somatic gene mutation assay, is based on the identification of mutant erythrocytes that have an altered repertoire of glycosylphosphatidylinositol (GPI)-anchored cell surface markers. We hypothesized that the erythrocyte Pig-a assay concept could be applied to rat cauda epididymal spermatozoa (sperm) for germ cell mutagenicity evaluation. We used GPI-anchored CD59 as the Pig-a mutation marker and examined the frequency of CD59-negative sperm using flow cytometry. A reconstruction experiment that spiked un-labeled sperm (mutant-mimic) into labeled sperm at specific ratios yielded good agreement between the detected and expected frequencies of mutant-mimic sperm, demonstrating the analytical ability for CD59-negative sperm detection. Furthermore, this methodology was assessed in F344/DuCrl rats administered N-ethyl-N-nitrosourea (ENU), a prototypical mutagen, or clofibrate, a lipid-lowering drug. Rats treated with 1, 10, or 20 mg/kg body weight/day (mkd) ENU via daily oral garage for five consecutive days showed a dose-dependent increase in the frequency of CD59-negative sperm on study day 63 (i.e., 58 days after the last ENU dose). This ENU dosing regimen also increased the frequency of CD59-negative erythrocytes. In rats treated with 300 mkd clofibrate via daily oral garage for consecutive 28 days, no treatment-related changes were detected in the frequency of CD59-negative sperm on study day 85 (i.e., 57 days after the last dose) or in the frequency of CD59-negative erythrocytes on study day 29. In conclusion, these data suggest that the epidiymal sperm Pig-a assay in rats is a promising method for evaluating germ cell mutagenicity. Environ. Mol. Mutagen. 58:485-493, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Zhiying Ji
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan, 48674
| | - Matthew J LeBaron
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan, 48674
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Rees BJ, Tate M, Lynch AM, Thornton CA, Jenkins GJ, Walmsley RM, Johnson GE. Development of an in vitro PIG-A gene mutation assay in human cells. Mutagenesis 2017; 32:283-297. [PMID: 28057708 PMCID: PMC5907909 DOI: 10.1093/mutage/gew059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 11/15/2016] [Indexed: 11/12/2022] Open
Abstract
Mutagens can be carcinogens, and traditionally, they have been identified in vitro using the Salmonella 'Ames' reverse mutation assay. However, prokaryotic DNA packaging, replication and repair systems are mechanistically very different to those in the humans we inevitably seek to protect. Therefore, for many years, mammalian cell line genotoxicity assays that can detect eukaryotic mutagens as well as clastogens and aneugens have been used. The apparent lack of specificity in these largely rodent systems, due partly to their mutant p53 status, has contributed to the use of animal studies to resolve data conflicts. Recently, silencing mutations at the PIG-A locus have been demonstrated to prevent glycophosphatidylinositol (GPI) anchor synthesis and consequentially result in loss of GPI-anchored proteins from the cell's extracellular surface. The successful exploitation of this mutant phenotype in animal studies has triggered interest in the development of an analogous in vitro PIG-A mutation screening assay. This article describes the development of a robust assay design using metabolically active human cells. The assay includes viability and cell membrane integrity assessment and conforms to the future ideas of the 21st-century toxicology testing.
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Affiliation(s)
- Benjamin J Rees
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Matthew Tate
- Gentronix Ltd BioHub at Alderley Park, Alderley Edge, Cheshire, UK
| | | | - Catherine A Thornton
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Gareth J Jenkins
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Richard M Walmsley
- Gentronix Ltd BioHub at Alderley Park, Alderley Edge, Cheshire, UK
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - George E Johnson
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, UK
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Raschke M, Igl BW, Kenny J, Collins J, Dertinger SD, Labash C, Bhalli JA, Tebbe CCM, McNeil KM, Sutter A. In Vivo Pig-a gene mutation assay: Guidance for 3Rs-friendly implementation. Environ Mol Mutagen 2016; 57:678-686. [PMID: 27770464 DOI: 10.1002/em.22060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 09/15/2016] [Indexed: 06/06/2023]
Abstract
The rodent Pig-a assay is an in vivo method for the detection of gene mutation, where lack of glycosylphosphatidylinositol-anchored proteins on the surface of circulating red blood cells (RBCs) serves as a reporter for Pig-a gene mutation. In the case of rats, the frequency of mutant phenotype RBCs is measured via fluorescent anti-CD59 antibodies and flow cytometry. The Pig-a assay meets the growing expectations for novel approaches in animal experimentation not only focusing on the scientific value of the assay but also on animal welfare aspects (3Rs principles), for example, amenable to integration into pivotal rodent 28-day general toxicology studies. However, as recommended in the Organisation for Economic Co-operation and Development Test Guidelines for genotoxicity testing, laboratories are expected to demonstrate their proficiency. While this has historically involved the extensive use of animals, here we describe an alternative approach based on a series of blood dilutions covering a range of mutant frequencies. The experiments described herein utilized either non-fluorescent anti-CD59 antibodies to provide elevated numbers of mutant-like cells, or a low volume blood sample from a single N-ethyl-N-nitrosourea treated animal. Results from these so-called reconstruction experiments from four independent laboratories showed good overall precision (correlation coefficients: 0.9979-0.9999) and accuracy (estimated slope: 0.71-1.09) of mutant cell scoring, which was further confirmed by Bland-Altman analysis. These data strongly support the use of reconstruction experiments for training purposes and demonstrating laboratory proficiency with very few animals, an ideal situation given the typically conflicting goals of demonstrating laboratory proficiency and reducing the use of animals. Environ. Mol. Mutagen. 57:678-686, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Marian Raschke
- Bayer Pharma AG, Muellerstrasse 178, Berlin, 13353, Germany
| | - Bernd-W Igl
- Bayer Pharma AG, Muellerstrasse 178, Berlin, 13353, Germany
| | - Julia Kenny
- GlaxoSmithKline, Park Road, Ware, Hertfordshire, SG12 0DP, United Kingdom
| | - Joanne Collins
- GlaxoSmithKline, Park Road, Ware, Hertfordshire, SG12 0DP, United Kingdom
| | | | - Carson Labash
- Litron Laboratories, 3500 Winton Place, Rochester, New York, 14623
| | - Javed A Bhalli
- Covance Laboratories Inc, 671 S. Meridian Rd, Greenfield, Indiana, 46140
| | - Cameron C M Tebbe
- Covance Laboratories Inc, 671 S. Meridian Rd, Greenfield, Indiana, 46140
| | - Kylie M McNeil
- Covance Laboratories Inc, 671 S. Meridian Rd, Greenfield, Indiana, 46140
| | - Andreas Sutter
- Bayer Pharma AG, Muellerstrasse 178, Berlin, 13353, Germany
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Kimoto T, Horibata K, Miura D, Chikura S, Okada Y, Ukai A, Itoh S, Nakayama S, Sanada H, Koyama N, Muto S, Uno Y, Yamamoto M, Suzuki Y, Fukuda T, Goto K, Wada K, Kyoya T, Shigano M, Takasawa H, Hamada S, Adachi H, Uematsu Y, Tsutsumi E, Hori H, Kikuzuki R, Ogiwara Y, Yoshida I, Maeda A, Narumi K, Fujiishi Y, Morita T, Yamada M, Honma M. The PIGRET assay, a method for measuring Pig-a gene mutation in reticulocytes, is reliable as a short-term in vivo genotoxicity test: Summary of the MMS/JEMS-collaborative study across 16 laboratories using 24 chemicals. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2016; 811:3-15. [DOI: 10.1016/j.mrgentox.2016.10.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 10/18/2016] [Indexed: 10/20/2022]
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Horibata K, Ukai A, Honma M. Evaluation of mutagenicity of acrylamide using RBC Pig-a and PIGRET assays by single peroral dose in rats. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2016; 811:54-9. [DOI: 10.1016/j.mrgentox.2015.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 12/16/2015] [Indexed: 11/22/2022]
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Roberts DJ, McKeon M, Xu Y, Stankowski LF. Comparison of integrated genotoxicity endpoints in rats after acute and subchronic oral doses of 4-nitroquinoline-1-oxide. Environ Mol Mutagen 2016; 57:17-27. [PMID: 26407646 PMCID: PMC7362388 DOI: 10.1002/em.21981] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 08/17/2015] [Indexed: 05/16/2023]
Abstract
During interlaboratory validation trials for the Pig-a gene mutation assay we assessed the genotoxicity of 4-nitroquinoline-1-oxide (4NQO) across endpoints in multiple tissues: induction of Pig-a mutant red blood cells (RBCs) and reticulocytes (RETs); micronucleated RETs (MN RETs); and DNA damage in blood and liver via the alkaline Comet assay (%tail intensity [TI]). In a previous subchronic toxicity study with 28 daily doses, biologically meaningful increases were observed only for Pig-a mutant RBCs/RETs while marginal increases in the frequency of MN RET were observed, and other clastogenic endpoints were negative. Follow up acute studies were performed using the same cumulative doses (0, 35, 70, 105, and 140 mg/kg) administered in a bolus, or split over three equal daily doses, with samples collected up to 1 month after the last dose. Both of the acute dosing regimens produced similar results, in that endpoints were either positive or negative, regardless of 1 or 3 daily doses, but the three consecutive daily dose regimen yielded more potent responses in TI (in liver and blood) and Pig-a mutant frequencies. In these acute studies the same cumulative doses of 4NQO induced positive responses in clastogenic endpoints that were negative or inconclusive using a subchronic study design. Additionally, a positive control group using combination doses of cyclophosphamide and ethyl methanesulfonate was employed to assess assay validity and potentially identify a future positive control treatment for integrated genetic toxicity studies.
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Affiliation(s)
- Daniel J Roberts
- Bristol-Myers Squibb, New Brunswick, NJ, USA
- Joint Graduate Program of Toxicology, Rutgers, NJ, USA
| | | | - Yong Xu
- BioReliance Corporation, Rockville, MD, USA
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Zeller A, Tang L, Dertinger SD, Funk J, Duran-Pacheco G, Guérard M. A proposal for a novel rationale for critical effect size in dose–response analysis based on a multi-endpointin vivostudy with methyl methanesulfonate. Mutagenesis 2015; 31:239-53. [DOI: 10.1093/mutage/gev077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dertinger SD, Avlasevich SL, Bemis JC, Chen Y, MacGregor JT. Human erythrocyte PIG-A assay: an easily monitored index of gene mutation requiring low volume blood samples. Environ Mol Mutagen 2015; 56:366-77. [PMID: 25412990 PMCID: PMC4406781 DOI: 10.1002/em.21924] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/29/2014] [Indexed: 05/21/2023]
Abstract
This laboratory has previously described a method for scoring the incidence of rodent blood Pig-a mutant phenotype erythrocytes using immunomagnetic separation in conjunction with flow cytometric analysis (In Vivo MutaFlow®). The current work extends this approach to human blood. The frequencies of CD59- and CD55-negative reticulocytes (RET(CD59-/CD55-)) and erythrocytes (RBC(CD59-/CD55-)) serve as phenotypic reporters of PIG-A gene mutation. Immunomagnetic separation was found to provide an effective means of increasing the number of reticulocytes and erythrocytes evaluated. Technical replicates were utilized to provide a sufficient number of cells for precise scoring while at the same time controlling for procedural accuracy by allowing comparison of replicate values. Cold whole blood samples could be held for at least one week without affecting reticulocyte, RET(CD59-/CD55-) or RBC(CD59-/CD55-) frequencies. Specimens from a total of 52 nonsmoking, self-reported healthy adult subjects were evaluated. The mean frequency of RET(CD59-/CD55-) and RBC(CD59-/CD55-) were 6.0 × 10(-6) and 2.9 × 10(-6), respectively. The difference is consistent with a modest selective pressure against mutant phenotype erythrocytes in the circulation, and suggests advantages of studying both populations of erythrocytes. Whereas intra-subject variability was low, inter-subject variability was relatively high, with RET(CD59-/CD55-) frequencies differing by more than 30-fold. There was an apparent correlation between age and mutant cell frequencies. Taken together, the results indicate that the frequency of human PIG-A mutant phenotype cells can be efficiently and reliably estimated using a labeling and analysis protocol that is well established for rodent-based studies. The applicability of the assay across species, its simplicity and statistical power, and the relatively non-invasive nature of the assay should benefit myriad research areas involving DNA damage, including studies of environmental factors that modify "spontaneous" mutation frequencies.
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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.
| | | | | | - Yuhchyau Chen
- Department of Radiation Oncology, University of Rochester Medical Center, Rochester, New York
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Gollapudi BB, Lynch AM, Heflich RH, Dertinger SD, Dobrovolsky VN, Froetschl R, Horibata K, Kenyon MO, Kimoto T, Lovell DP, Stankowski LF, White PA, Witt KL, Tanir JY. The in vivo Pig-a assay: A report of the International Workshop On Genotoxicity Testing (IWGT) Workgroup. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2015; 783:23-35. [DOI: 10.1016/j.mrgentox.2014.09.007] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 09/15/2014] [Indexed: 12/01/2022]
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Stankowski LF, Aardema MJ, Lawlor TE, Pant K, Roy S, Xu Y, Elbekai R. Integration of Pig-a, micronucleus, chromosome aberration and comet assay endpoints in a 28-day rodent toxicity study with urethane. Mutagenesis 2015; 30:335-42. [PMID: 25934985 PMCID: PMC4506322 DOI: 10.1093/mutage/gev013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
As part of the international Pig-a validation trials, we examined the induction of Pig-a mutant reticulocytes and red blood cells (RET(CD59-) and RBC(CD59-), respectively) in peripheral blood of male Sprague Dawley(®) rats treated with urethane (25, 100 and 250mg/kg/day) or saline by oral gavage for 29 days. Additional endpoints integrated into this study were: micronucleated reticulocytes (MN-RET) in peripheral blood; chromosome aberrations (CAb) and DNA damage (%tail intensity via the comet assay) in peripheral blood lymphocytes (PBL); micronucleated polychromatic erythrocytes (MN-PCE) in bone marrow; and DNA damage (comet) in various organs at termination (the 29th dose was added for the comet endpoint at sacrifice). Ethyl methanesulfonate (EMS; 200mg/kg/day on Days 3, 4, 13, 14, 15, 27, 28 and 29) was evaluated as the concurrent positive control (PC). All animals survived to termination and none exhibited overt toxicity, but there were significant differences in body weight and body weight gain in the 250-mg/kg/day urethane group, as compared with the saline control animals. Statistically significant, dose-dependent increases were observed for urethane for: RET(CD59-) and RBC(CD59-) (on Days 15 and 29); MN-RET (on Days 4, 15 and 29); and MN-PCE (on Day 29). The comet assay yielded positive results in PBL (Day 15) and liver (Day 29), but negative results for PBL (Days 4 and 29) and brain, kidney and lung (Day 29). No significant increases in PBL CAb were observed at any sample time. Except for PBL CAb (likely due to excessive cytotoxicity), EMS-induced significant increases in all endpoints/tissues. These results compare favorably with earlier in vivo observations and demonstrate the utility and sensitivity of the Pig-a in vivo gene mutation assay, and its ability to be easily integrated, along with other standard genotoxicity endpoints, into 28-day rodent toxicity studies.
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Affiliation(s)
| | - Marilyn J Aardema
- BioReliance Corporation, Rockville, MD 20850, USA, Marilyn Aardema Consulting LLC, Fairfield, OH 45014, USA
| | | | - Kamala Pant
- BioReliance Corporation, Rockville, MD 20850, USA
| | - Shambhu Roy
- BioReliance Corporation, Rockville, MD 20850, USA
| | - Yong Xu
- BioReliance Corporation, Rockville, MD 20850, USA
| | - Reem Elbekai
- BioReliance Corporation, Rockville, MD 20850, USA
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Labash C, Avlasevich SL, Carlson K, Torous DK, Berg A, Bemis JC, MacGregor JT, Dertinger SD. Comparison of male versus female responses in the Pig-a mutation assay. Mutagenesis 2015; 30:349-57. [PMID: 25833915 DOI: 10.1093/mutage/geu055] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Validation of the Pig-a gene mutation assay has been based mainly on studies in male rodents. To determine if the mutagen-induced responses of the X-linked Pig-a gene differ in females compared to males, 7- or 14-week old male and female Sprague Dawley rats were exposed to N-ethyl-N-nitrosourea (ENU). In the study with the 7-week old rats, exposure was to 0, 1, 5 or 25mg ENU/kg/day for three consecutive days (study Days 1-3). Pig-a mutant phenotype reticulocyte (RET(CD59-)) and mutant phenotype erythrocyte (RBC(CD59-)) frequencies were determined on study Days -4, 15, 29 and 46 using immunomagnetic separation in conjunction with flow cytometric analysis (In Vivo MutaFlow®). Additionally, blood samples collected on Day 4 were analysed for micronucleated reticulocyte (MN-RET) frequency (In Vivo MicroFlow®). The percentage of reticulocytes (%RET) was markedly higher in the 7-week old males compared to females through Day 15 (2.39-fold higher on Day -4). At 25mg/kg/day, ENU reduced Day 4 RET frequencies in both sexes, and the two highest dose levels resulted in elevated MN-RET frequencies, with no sex or treatment × sex interaction. The two highest dose levels significantly elevated the frequencies of mean RET(CD59-) and RBC(CD59-) in both sexes from Day 15 onward. RET(CD59-) and RBC(CD59-) frequencies were somewhat lower for females compared to males at the highest dose level studied, and differences in RET(CD59-) resulted in a statistically significant interaction effect of treatment × sex. In the study with 14-week old rats, treatment was for 3 days with 0 or 25mg ENU/kg/day. RET frequencies differed to a lesser degree between the sexes, and in this case there was no evidence of a treatment × sex interaction. These results suggest that the slightly higher response in younger males than in the younger females may be related to differences in erythropoiesis function at that age. In conclusion, while some quantitative differences were noted, there were no qualitative differences in how males and females responded to a prototypical mutagen, and support the contention that both sexes are equally acceptable for Pig-a gene mutation studies.
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Coffing SL, Kenyon MO, Ackerman JI, Shutsky TJ, Dobo KL. Evaluation of the in vivo mutagenicity of isopropyl methanesulfonate in acute and 28-day studies. Environ Mol Mutagen 2015; 56:322-332. [PMID: 25229874 DOI: 10.1002/em.21910] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 08/21/2014] [Accepted: 08/22/2014] [Indexed: 06/03/2023]
Abstract
Understanding the mutagenic dose response could prove beneficial in the management of pharmaceutically relevant impurities. For most alkyl ester impurities, such as isopropyl methanesulfonate (IPMS), little in vivo mutagenicity data exist for dose analysis. The likelihood of a sublinear dose response for IPMS was assessed by comparing the Swain Scott constant, the SN 1/SN 2 reaction mechanism and the O(6) :N(7) guanine adduct ratio to that of more well-known alkyl esters. Based on available information, IPMS was predicted to have a mutagenic profile most like ethyl nitrosourea. To test this hypothesis, mature male Wistar Han rats were administered IPMS using acute (single administration at 3.5 to 56 mg/kg) or subchronic (28 days at 0.125 to 2 mg/kg/day) exposures. The in vivo Pig-a mutation assay was used to identify mutant phenotype reticulocyte (Ret) and red blood cell (RBC) populations. The maximum mutant response occurred approximately 15 and 28 days after the last dose administration in the mutant Ret and RBC populations respectively in the acute study and on Day 29 and 56 in the mutant Ret and RBC populations, respectively, in the subchronic study. A comparison of RBC mutant frequencies from acute and subchronic protocols suggests a sublinear response; however, this was not substantiated by statistical analysis. A No Observed Effect Level (NOEL) of 0.25 mg/kg/day resulted in a Permitted Daily Exposure equivalent to the Threshold of Toxicological Concern. An estimate of the NOEL based on the previously mentioned factors, in practice, would have pre-empted further investigation of the potent mutagen IPMS.
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Affiliation(s)
- Stephanie L Coffing
- Pfizer Worldwide Research and Development, Genetic Toxicology, Groton, Connecticut
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Kenyon MO, Coffing SL, Ackerman JI, Gunther WC, Dertinger SD, Criswell K, Dobo KL. Compensatory erythropoiesis has no impact on the outcome of the in vivo Pig-a mutation assay in rats following treatment with the haemolytic agent 2-butoxyethanol. Mutagenesis 2015; 30:325-34. [PMID: 25820171 DOI: 10.1093/mutage/geu051] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Pig-a assay has rapidly gained international interest as a useful tool for assessing the mutagenic potential of compounds in vivo. Although a large number of compounds, including both mutagens and non-mutagens, have been tested in the rat Pig-a assay in haematopoietic cells, there is limited understanding of how perturbations in haematopoiesis affect assay performance. Of particular concern is the possibility that regenerative haematopoiesis alone, without exposure to a genotoxic agent, could result in elevated Pig-a mutant cell frequencies. To address this concern, Wistar-Han rats were dosed by oral gavage with a non-genotoxic haemolytic agent, 2-butoxyethanol (2-BE). Dose levels ranging from 0 to 450 mg/kg were tested using both single administration and 28-day treatment regimens. Haematology parameters were assessed at minimum within the first 24h of treatment and 8 days after the final administration. Pig-a mutant frequencies were assessed on Days 15 and ~30 for both treatment protocols and also on Days 43 and 57 for the 28-day protocol. Even at doses of 2-BE that induced marked intravascular lysis and strong compensatory erythropoiesis, the average Pig-a mutant phenotype red blood cell and reticulocyte frequencies were within the historical vehicle control distribution. 2-BE therefore showed no evidence of in vivo mutagenicity in these studies. The data suggest that perturbations in haematopoiesis alone do not lead to an observation of increased mutant frequency in the Pig-a assay.
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Affiliation(s)
- Michelle O Kenyon
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
| | - Stephanie L Coffing
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
| | - Joel I Ackerman
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
| | - William C Gunther
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
| | | | - Kay Criswell
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
| | - Krista L Dobo
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, MS-8274-1317, Groton, CT 06340, USA and Litron Laboratories, 3500 Winton Place, Rochester, NY 14623, USA
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Godin-Ethier J, Leroux F, Wang N, Thébaud S, Merah F, Nelson A. Characterisation of an in vivo Pig-a gene mutation assay for use in regulatory toxicology studies. Mutagenesis 2015; 30:359-63. [DOI: 10.1093/mutage/gev005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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21
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Tu H, Zhang M, Zhou C, Wang Z, Huang P, Ou H, Chang Y. Genotoxicity assessment of melamine in the in vivo Pig-a mutation assay and in a standard battery of assays. Mutat Res Genet Toxicol Environ Mutagen 2014; 777:62-7. [PMID: 25726176 DOI: 10.1016/j.mrgentox.2014.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 11/26/2014] [Accepted: 12/03/2014] [Indexed: 10/24/2022]
Abstract
The genotoxicity of melamine was evaluated with the combined Pig-a mutation/micronucleus assay, the bacterial reverse mutation assay, and the in vitro cytokinesis-block micronucleus assay (CBMN). Five groups of six- to eight-week-old male Sprague-Dawley (SD) rats were given three daily doses of vehicle control (100% pure sesame oil), melamine (500, 1000, and 2000 mg/kg) or positive control (N-ethyl-N-nitrosourea, ENU, 20 mg/kg) by oral gavage. Peripheral blood was sampled pre-dose (day -1) and at time points up to day 60. Pig-a mutant frequencies were determined in total red blood cells (RBCs) and reticulocytes (RETs) as RBC(CD59-) and RET(CD59-) frequencies, on days -1, 15, 29 and 60, and micronucleus frequencies were measured in RETs on day 4. No significant increases in RBC(CD59-) or RET(CD59-) frequencies were observed for the melamine-treated group at any of the time points studied, but the positive control, ENU, induced statistically significant increases compared with the vehicle control. Similar results were obtained in the micronucleus assay. Melamine did not induce statistically significant increases in %MN-RET. In the bacterial reverse mutation assay, melamine was tested from 62.5 to 1000 μg/plate in tester strains TA97a, TA98, TA100, TA102, and TA1535, with and without metabolic activation, and no evidence of toxicity or mutagenicity was observed at any dose tested. In the in vitro CBMN assay, in Chinese hamster ovary (CHO) cells, melamine was tested (75, 150, and 300 μg/mL) in the presence and absence of S9 mix, and no positive increases in the number of cells containing micronuclei were seen. These results suggest that melamine does not exhibit significant genotoxic potential. These data could be valuable for risk assessment purposes and also for further characterizing the new in vivoPig-a gene mutation assay.
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Affiliation(s)
- Honggang Tu
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Ming Zhang
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Changhui Zhou
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Zheng Wang
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Pengcheng Huang
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Hongmei Ou
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Yan Chang
- National Shanghai Center for New Drug Safety Evaluation & Research, China State Institute of Pharmaceutical Industry, Shanghai, China.
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Krüger CT, Hofmann M, Hartwig A. The in vitro PIG-A gene mutation assay: mutagenicity testing via flow cytometry based on the glycosylphosphatidylinositol (GPI) status of TK6 cells. Arch Toxicol 2014; 89:2429-43. [PMID: 25417052 DOI: 10.1007/s00204-014-1413-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 11/06/2014] [Indexed: 11/28/2022]
Abstract
The X-linked PIG-A gene is involved in the biosynthesis of the cell surface anchor GPI, and its inactivation may serve as a new marker for mutagenicity. The in vivo PIG-A gene mutation assay is currently being validated by several groups. In this study, we established a corresponding in vitro variant of the PIG-A assay applying B-lymphoblastoid TK6 cells. PE-conjugated antibodies against the GPI-anchored proteins CD55 and CD59 were used to determine the GPI status via multicolor flow cytometry. Mutant spiked TK6 cell samples were analyzed, and mutants were quantified with even small numbers being quantitatively recovered. To validate our approach, mutant spiked cell samples were analyzed by flow cytometry and proaerolysin selection in parallel, yielding a high correlation. Further, we developed a procedure to reduce the background level of preexisting mutant cells to lower than 20 in 10(6) cells to increase the sensitivity of the assay. Spontaneous rate of GPI deficiency was investigated being 0.76 × 10(-6)/cell/generation for TK6 cells. The optimal phenotype expression time after ethyl methanesulfonate treatment was found to be 10 days. We applied the in vitro PIG-A assay to demonstrate the mutagenicity of ethyl methanesulfonate, 4-nitroquinoline 1-oxide and UV-C irradiation in a dose-dependent and statistically significant manner. Pyridine and cycloheximide were included as negative controls providing negative test results up to 10 mM. These data suggest that the in vitro PIG-A assay could complement the in vivo PIG-A assay with some distinct advantages compared to other in vitro mammalian mutagenicity tests.
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Affiliation(s)
- Christopher T Krüger
- Department of Food Chemistry and Toxicology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131, Karlsruhe, Germany
| | - Mareike Hofmann
- Department of Food Chemistry and Toxicology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131, Karlsruhe, Germany
| | - Andrea Hartwig
- Department of Food Chemistry and Toxicology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131, Karlsruhe, Germany.
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Gunther WC, Coffing SL, Dickinson DA, Engel ME, Fiedler RD, O'Lone SD, Sanok KE, Thiffeault CJ, Shutsky TJ, Schuler MJ, Dobo KL. Evaluation of the Pig-a, micronucleus, and comet assay endpoints in a 28-day study with ethyl methanesulfonate. Environ Mol Mutagen 2014; 55:492-499. [PMID: 24599777 DOI: 10.1002/em.21863] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 02/06/2014] [Indexed: 06/03/2023]
Abstract
Ethyl methanesulfonate (EMS) was evaluated as part of the validation effort for the rat Pig-a mutation assay and compared with other well-established in vivo genotoxicity endpoints. Male Sprague-Dawley (SD) rats were given a daily dose of 0, 6.25, 12.5, 25, 50, or 100 mg/kg/day EMS for 28 days, and evaluated for a variety of genotoxicity endpoints in peripheral blood, liver, and colon. Blood was sampled pre-dose (Day 1) and at various time points up to Day 105. Pig-a mutant frequencies were determined in total red blood cells (RBCs) and reticulocytes (RETs) as RBC(CD59-) and RET(CD59-) frequencies. The first statistically significant increases in mutant frequencies were seen in RETs on Day 15 and in RBCs on Day 29 with the maximum RET(CD59-) on Day 29 and of RBC(CD59-) on Day 55. The lowest dose producing a statistically significant increase of RET(CD59-) was 12.5 mg/kg on Day 55 and 25 mg/kg for RBC(CD59-) on Day 55. EMS also induced significant increases in % micronucleated RETs (MN-RETs) in peripheral blood on Days 3, 15, and 28. No statistically significant increases in micronuclei were seen in liver or colon. Results from the in vivo Comet assay on Day 29 showed generally weak increases in DNA damage in all tissues evaluated with little evidence for accumulation of damage seen over time. The results with EMS indicate that the assessment of RBC(CD59-) and/or RET(CD59-) in the Pig-a assay could be a useful and sensitive endpoint for a repeat dose protocol and complements other genotoxicity endpoints.
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Affiliation(s)
- William C Gunther
- Pfizer Global Research and Development, Genetic Toxicology, Groton, Connecticut
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Avlasevich SL, Phonethepswath S, Labash C, Carlson K, Torous DK, Cottom J, Bemis JC, MacGregor JT, Dertinger SD. Diethylnitrosamine genotoxicity evaluated in sprague dawley rats using pig-a mutation and reticulocyte micronucleus assays. Environ Mol Mutagen 2014; 55:400-406. [PMID: 24574022 DOI: 10.1002/em.21862] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 02/12/2014] [Accepted: 02/12/2014] [Indexed: 06/03/2023]
Abstract
Diethylnitrosamine (DEN) is a genotoxic carcinogen, but in vivo DNA-damaging activities are not usually evident in hematopoietic cells because the short-lived active metabolite is formed mainly in the liver. DEN therefore represented an interesting case for evaluating the performance characteristics of blood-based endpoints of genotoxicity that have been automated using flow cytometric analysis-frequency of micronucleated reticulocytes and Pig-a mutant phenotype reticulocytes (RET(CD59-) ) and erythrocytes (RBC(CD59-) ). Male Sprague Dawley rats were treated for 28 consecutive days with DEN at levels up to 12.5 mg/kg/day. Serial blood samples were collected and micronucleus frequencies were determined on Days 4 and 29, while RET(CD59-) and RBC(CD59-) frequencies were determined on Days 15, 29, and 42. The Pig-a analyses were conducted with an enrichment step based on immunomagnetic column separation to increase the statistical power of the assay. Modest but significant reductions to reticulocyte frequencies demonstrated that bone marrow was exposed to reactive intermediates. Even so, DEN did not affect micronucleus frequencies at any dose level tested. However, RET(CD59-) frequencies were significantly elevated in the high dose group on Day 29, and RBC(CD59-) were increased at this same dose level on Days 29 and 42. These results demonstrate that the Pig-a assay is sufficiently sensitive to evaluate chemicals for genotoxic potential, even in the case of a promutagen that has traditionally required direct assessment(s) of liver tissue for detection of DNA-damage.
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Horibata K, Ukai A, Honma M. Evaluation of Rats' In Vivo Genotoxicity Induced by N-ethyl-N-nitrosourea in the RBC Pig-a, PIGRET, and gpt Assays. Genes Environ 2014. [DOI: 10.3123/jemsge.2014.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Tang L, Guérard M, Zeller A. Quantitative assessment of the dose-response of alkylating agents in DNA repair proficient and deficient ames tester strains. Environ Mol Mutagen 2014; 55:15-23. [PMID: 24273186 DOI: 10.1002/em.21825] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 10/04/2013] [Accepted: 10/04/2013] [Indexed: 06/02/2023]
Abstract
Mutagenic and clastogenic effects of some DNA damaging agents such as methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS) have been demonstrated to exhibit a nonlinear or even "thresholded" dose-response in vitro and in vivo. DNA repair seems to be mainly responsible for these thresholds. To this end, we assessed several mutagenic alkylators in the Ames test with four different strains of Salmonella typhimurium: the alkyl transferases proficient strain TA1535 (Ogt+/Ada+), as well as the alkyl transferases deficient strains YG7100 (Ogt+/Ada-), YG7104 (Ogt-/Ada+) and YG7108 (Ogt-/Ada-). The known genotoxins EMS, MMS, temozolomide (TMZ), ethylnitrosourea (ENU) and methylnitrosourea (MNU) were tested in as many as 22 concentration levels. Dose-response curves were statistically fitted by the PROAST benchmark dose model and the Lutz-Lutz "hockeystick" model. These dose-response curves suggest efficient DNA-repair for lesions inflicted by all agents in strain TA1535. In the absence of Ogt, Ada is predominantly repairing methylations but not ethylations. It is concluded that the capacity of alkyl-transferases to successfully repair DNA lesions up to certain dose levels contributes to genotoxicity thresholds.
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Affiliation(s)
- Leilei Tang
- pRED, Pharma Research and Early Development, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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Horibata K, Ukai A, Kimoto T, Suzuki T, Kamoshita N, Masumura K, Nohmi T, Honma M. Evaluation of in vivo genotoxicity induced by N-ethyl-N-nitrosourea, benzo[a]pyrene, and 4-nitroquinoline-1-oxide in the Pig-a and gpt assays. Environ Mol Mutagen 2013; 54:747-754. [PMID: 24105957 DOI: 10.1002/em.21818] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 08/14/2013] [Accepted: 08/20/2013] [Indexed: 06/02/2023]
Abstract
The recently developed Pig-a mutation assay is based on flow cytometric enumeration of glycosylphosphatidylinositol (GPI) anchor-deficient red blood cells caused by a forward mutation in the Pig-a gene. Because the assay can be conducted in nontransgenic animals and the mutations accumulate with repeat dosing, we believe that the Pig-a assay could be integrated into repeat-dose toxicology studies and provides an alternative to transgenic rodent (TGR) mutation assays. The capacity and characteristics of the Pig-a assay relative to TGR mutation assays, however, are unclear. Here, using transgenic gpt delta mice, we compared the in vivo genotoxicity of single oral doses of N-ethyl-N-nitrosourea (ENU, 40 mg/kg), benzo[a]pyrene (BP, 100 and 200 mg/kg), and 4-nitroquinoline-1-oxide (4NQO, 50 mg/kg) in the Pig-a (peripheral blood) and gpt (bone marrow and liver) gene mutation assays. Pig-a assays were conducted at 2, 4, and 7 weeks after the treatment, while gpt assays were conducted on tissues collected at the 7-week terminal sacrifice. ENU increased both Pig-a and gpt mutant frequencies (MFs) at all sampling times, and BP increased MFs in both assays but the Pig-a MFs peaked at 2 weeks and then decreased. Although 4NQO increased gpt MFs in the liver, only weak, nonsignificant increases (two- or threefold above control) were detected in the bone marrow in both the Pig-a and the gpt assay. These findings suggest that further studies are needed to elucidate the kinetics of the Pig-a mutation assay in order to use it as an alternative to the TGR mutation assay.
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Affiliation(s)
- Katsuyoshi Horibata
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
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Bhalli JA, Shaddock JG, Pearce MG, Dobrovolsky VN. Sensitivity of the Pig-a assay for detecting gene mutation in rats exposed acutely to strong clastogens. Mutagenesis 2013; 28:447-55. [PMID: 23677247 DOI: 10.1093/mutage/get022] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Clastogens are potential human carcinogens whose detection by genotoxicity assays is important for safety assessment. Although some endogenous genes are sensitive to the mutagenicity of clastogens, many genes that are used as reporters for in vivo mutation (e.g. transgenes) are not. In this study, we have compared responses in the erythrocyte Pig-a gene mutation assay with responses in a gene mutation assay that is relatively sensitive to clastogens, the lymphocyte Hprt assay, and in the reticulocyte micronucleus (MN) assay, which provides a direct measurement of clastogenicity. Male F344 rats were treated acutely with X-rays, cyclophosphamide (CP) and Cis-platin (Cis-Pt), and the frequency of micronucleated reticulocytes (MN RETs) in peripheral blood was measured 1 or 2 days later. The frequencies of CD59-deficient Pig-a mutant erythrocytes and 6-thioguanine-resistant Hprt mutant T-lymphocytes were measured at several times up to 16 weeks after the exposure. All three clastogens induced strong increases in the frequency of MN RETs, with X-rays and Cis-Pt producing near linear dose responses. The three agents also were positive in the two gene mutation assays although the assays detected them with different efficiencies. The Pig-a assay was more efficient in detecting the effect of Cis-Pt treatment, whereas the Hprt assay was more efficient for X-rays and CP. The results indicate that the erythrocyte Pig-a assay can detect the in vivo mutagenicity of clastogens although its sensitivity is variable in comparison with the lymphocyte Hprt assay.
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Affiliation(s)
- Javed A Bhalli
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, HFT-120, Jefferson, AR 72079, USA
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Bhalli JA, Ding W, Shaddock JG, Pearce MG, Dobrovolsky VN, Heflich RH. Evaluating the weak in vivo micronucleus response of a genotoxic carcinogen, Aristolochic acids. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2013; 753:82-92. [DOI: 10.1016/j.mrgentox.2013.03.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 03/01/2013] [Accepted: 03/03/2013] [Indexed: 02/08/2023]
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Dertinger SD, Phonethepswath S, Avlasevich SL, Torous DK, Mereness J, Bryce SM, Bemis JC, Bell S, Weller P, Macgregor JT. Efficient monitoring of in vivo pig-a gene mutation and chromosomal damage: summary of 7 published studies and results from 11 new reference compounds. Toxicol Sci 2012; 130:328-48. [PMID: 22923490 PMCID: PMC3498746 DOI: 10.1093/toxsci/kfs258] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 08/17/2012] [Indexed: 11/12/2022] Open
Abstract
The ability to effectively monitor gene mutation and micronucleated reticulocyte (MN-RET) frequency in short-term and repeated dosing schedules was investigated using the recently developed flow cytometric Pig-a mutation assay and flow cytometric micronucleus analysis. Eight reference genotoxicants and three presumed nongenotoxic compounds were studied: chlorambucil, melphalan, thiotepa, cyclophosphamide, azathioprine, 2-acetylaminofluorene, hydroxyurea, methyl methanesulfonate, o-anthranilic acid, sulfisoxazole, and sodium chloride. These experiments extend previously published results with seven other chemicals. Male Sprague Dawley rats were treated via gavage for 3 or 28 consecutive days with several dose levels of each chemical up to the maximum tolerated dose. Blood samples were collected at several time points up to day 45 and were analyzed for Pig-a mutation with a dual-labeling method that facilitates mutant cell frequency measurements in both total erythrocytes and the reticulocyte subpopulation. An immunomagnetic separation technique was used to increase the efficiency of scoring mutant cells. Blood samples collected on day 4, and day 29 for the 28-day study, were evaluated for MN-RET frequency. The three nongenotoxicants did not induce Pig-a or MN-RET responses. All genotoxicants except hydroxyurea increased the frequency of Pig-a mutant reticulocytes and erythrocytes. Significant increases in MN-RET frequency were observed for each of the genotoxicants at both time points. Whereas the highest Pig-a responses tended to occur in the 28-day studies, when total dose was greatest, the highest induction of MN-RET was observed in the 3-day studies, when dose per day was greatest. There was no clear relationship between the maximal Pig-a response of a given chemical and its corresponding maximal MN-RET response, despite the fact that both endpoints were determined in the same cell lineage. Taken with other previously published results, these data demonstrate the value of integrating Pig-a and micronucleus endpoints into in vivo toxicology studies, thereby providing information about mutagenesis and chromosomal damage in the same animals from which toxicity, toxicokinetics, and metabolism data are obtained.
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Ohtani S, Unno A, Ushiyama A, Kimoto T, Miura D, Kunugita N. The in vivo Pig-a gene mutation assay is useful for evaluating the genotoxicity of ionizing radiation in mice. Environ Mol Mutagen 2012; 53:579-588. [PMID: 22911630 DOI: 10.1002/em.21724] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 07/09/2012] [Accepted: 07/10/2012] [Indexed: 06/01/2023]
Abstract
The in vivo Pig-a mutation assay has been adapted for measuring mutation in rats, mice, monkeys, and humans. To date, the assay has been used mainly to assess the mutagenicity of chemicals that are known to be powerful point mutagens. The assay has not been used to measure the biological effects associated with ionizing radiation. In this study, we modified the Pig-a gene mutation assay (Kimoto et al. [2011b]: Mutat Res 723:36-42) and used 3-color staining with fluorescently labeled anti-CD24, anti-TER-119, and anti-CD71 to detect the Pig-a mutant frequencies in total red blood cells (RBCs) and in reticulocytes (RETs) from X-irradiated mice. Single exposures to X-irradiation resulted in dose- and time-dependent increases in Pig-a mutant frequencies, and these subsequently declined over time returning to background frequencies. The same total amount of radiation, delivered either as a single dose or as four repeat doses at weekly intervals, increased Pig-a mutant frequencies to comparable levels, reaching maxima 2-3 weeks after the single dose or 2-3 weeks after the last of the repeat doses. These increased frequencies subsequently returned to background levels. Our results indicated that the 3-color Pig-a assay was useful for evaluating the in vivo genotoxicity of radiation.
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Affiliation(s)
- Shin Ohtani
- Department of Environmental Health, National Institute of Public Health, Saitama, Japan
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Torous DK, Phonethepswath S, Avlasevich SL, Mereness J, Bryce SM, Bemis JC, Weller P, Bell S, Gleason C, Custer LL, MacGregor JT, Dertinger SD. In vivo flow cytometric Pig-a and micronucleus assays: highly sensitive discrimination of the carcinogen/noncarcinogen pair benzo(a)pyrene and pyrene using acute and repeated-dose designs. Environ Mol Mutagen 2012; 53:420-428. [PMID: 22730284 DOI: 10.1002/em.21709] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 05/11/2012] [Accepted: 05/12/2012] [Indexed: 06/01/2023]
Abstract
Combining multiple genetic toxicology endpoints into a single in vivo study, and/or integrating one or more genotoxicity assays into general toxicology studies, is attractive because it reduces animal use and enables comprehensive comparative analysis using toxicity, metabolism, and pharmacokinetic information from the same animal. This laboratory has developed flow cytometric scoring techniques for monitoring two blood-based genotoxicity endpoints-micronucleated reticulocyte frequency and gene mutation at the Pig-a locus-thereby making combination and integration studies practical. The ability to effectively monitor these endpoints in short-term and repeated dosing schedules was investigated with the carcinogen/noncarcinogen pair benzo(a)pyrene (BP) and pyrene (Pyr). Male Sprague-Dawley rats were treated via oral gavage for 3 or 28 consecutive days with several dose levels of Pyr, including maximum tolerated doses. BP exposure was administered by the same route but at one dose level, 250 or 125 mg/kg/day for 3-day and 28-day studies, respectively. Serial blood samples were collected up to Day 45, and were analyzed for Pig-a mutation with a dual labeling method (SYTO 13 in combination with anti-CD59-PE) that facilitated mutant cell frequency measurements in both total erythrocytes and the reticulocyte subpopulation. A mutant cell enrichment step based on immunomagnetic column separation was used to increase the statistical power of the assay. BP induced robust mutant reticulocyte responses by Day 15, and elevated frequencies persisted until study termination. Mutant erythrocyte responses lagged mutant reticulocyte responses, with peak incidences observed on Day 30 of the 3-day study (43-fold increase) and on Day 42 of the 28-day study (171-fold increase). No mutagenic effects were apparent for Pyr. Blood samples collected on Day 4, and Day 29 for the 28-day study, were evaluated for micronucleated reticulocyte frequency. Significant increases in micronucleus frequencies were observed with BP, whereas Pyr had no effect. These results demonstrate that Pig-a and micronucleus endpoints discriminate between these structurally related carcinogenic and noncarcinogenic agents. Furthermore, the high sensitivity demonstrated with the enrichment protocol indicates that the Pig-a endpoint is suitable for both repeated-dose and acute studies, allowing integration of mutagenic and clastogenic endpoints into on-going toxicology studies, and use as a short-term assay that provides efficient screening and mechanistic information in vivo.
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Kimoto T, Chikura S, Suzuki-Okada K, Kobayashi XM, Itano Y, Miura D, Kasahara Y. Effective use of the Pig-a gene mutation assay for mutagenicity screening: measuring CD59-deficient red blood cells in rats treated with genotoxic chemicals. J Toxicol Sci 2012; 37:943-55. [DOI: 10.2131/jts.37.943] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Dertinger SD, Heflich RH. In vivo assessment of Pig-a gene mutation-recent developments and assay validation. Environ Mol Mutagen 2011; 52:681-684. [PMID: 22167884 DOI: 10.1002/em.20685] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Bhalli JA, Shaddock JG, Pearce MG, Dobrovolsky VN, Cao X, Heflich RH, Vohr HW. Report on stage III Pig-a mutation assays using benzo[a]pyrene. Environ Mol Mutagen 2011; 52:731-737. [PMID: 22052432 DOI: 10.1002/em.20675] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/15/2011] [Accepted: 07/15/2011] [Indexed: 05/31/2023]
Abstract
Genotoxicity assays were conducted on rats treated with benzo[a]pyrene (BaP) as part of Stage III of a validation study on the Pig-a gene mutation assay. Assays were performed at the U.S. FDA-NCTR and Bayer-Germany. Starting on Day 1, groups of five 6- to 7-week-old male Fischer 344 (F344, used at FDA-NCTR) and Han Wistar rats (Bayer) were given 28 daily doses of 0, 37.5, 75, or 150 mg/kg BaP; blood was sampled on Days -1, 4, 15, 29, and 56. Pig-a mutant frequencies were determined on Days -1, 15, 29, and 56 in total red blood cells (RBCs) and reticulocytes (RETs) as RBC(CD59-) and RET(CD59-) frequencies; percent micronucleated-RETs (%MN-RET) were measured on Days 4 and 29. RBC(CD59-) and RET(CD59-) frequencies increased in a dose- and time-dependent manner, producing significant increases by Day 29 in both rat models. The responses for RETs were stronger than those for RBCs, and the responses in F344 rats were stronger than in Han Wistar rats. BaP also produced significant increases in %MN-RET frequency at Days 4 and 29, with the responses being greater in F344 than Han Wistar rats. The overall findings were consistent with those of the reference laboratory using Han Wistar rats. Finally, mutation assays performed on splenocytes from Day 56 F344 rats indicated that BaP mutant frequencies were three to fivefold higher for the Hprt gene than the Pig-a gene. The results indicate that the Pig-a RET and RBC assays are reproducible, transferable, and show promise for integrating gene mutation into 28-day repeat-dose studies.
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Affiliation(s)
- Javed A Bhalli
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas 72079, USA
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Stankowski LF, Roberts DJ, Chen H, Lawlor T, McKeon M, Murli H, Thakur A, Xu Y. Integration of Pig-a, micronucleus, chromosome aberration, and Comet assay endpoints in a 28-day rodent toxicity study with 4-nitroquinoline-1-oxide. Environ Mol Mutagen 2011; 52:738-747. [PMID: 22020836 DOI: 10.1002/em.20692] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 09/08/2011] [Accepted: 09/08/2011] [Indexed: 05/31/2023]
Abstract
As part of the Stage III Pig-a multilaboratory validation trial, we examined the induction of CD59-negative reticulocytes and total red blood cells (RET(CD59-) and RBC(CD59-) , respectively) in male Sprague Dawley(®) rats treated with 4-nitroquinoline-1-oxide (4NQO), for 28 consecutive days by oral gavage, at doses of 1.25, 2.50, 3.75, 5.00, and 7.50 mg kg(-1) day(-1) (the high dose group was sacrificed on Day 15 due to excessive morbidity/mortality). Animals also were evaluated for: micronucleated reticulocytes (mnRET) by flow cytometry; DNA damage in peripheral blood, liver, and stomach using the Comet assay; and chromosome aberrations (CAb) in peripheral blood lymphocytes (PBL). All endpoints were analyzed at two or more timepoints where possible. Mortality, body and organ weights, food consumption, and clinical pathology also were evaluated, and demonstrated that the maximum tolerated dose was achieved at 5.00 mg kg(-1) day(-1) . The largest increases observed for the genetic toxicology endpoints (fold-increase compared to control, where significant; all at 5.00 mg kg(-1) day(-1) on Day 29) were: RET(CD59-) (21X), RBC(CD59-) (9.0X), and mnRET (2.0X). In contrast, no significant increases were observed for the CAb or Comet response, in any tissue analyzed, at any timepoint. Because 4NQO is a well known mutagen, clastogen, and carcinogen, the lack of response for these latter endpoints was unexpected. These results emphasize the extreme care that must betaken in dose and endpoint selection when incorporating genotoxicity endpoints into routine toxicity studies as has been recommended or is under consideration by various regulatory and industrial bodies.
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