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Beal MA, Chen G, Dearfield KL, Gi M, Gollapudi B, Heflich RH, Horibata K, Long AS, Lovell DP, Parsons BL, Pfuhler S, Wills J, Zeller A, Johnson G, White PA. Interpretation of in vitro concentration-response data for risk assessment and regulatory decision-making: Report from the 2022 IWGT quantitative analysis expert working group meeting. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023. [PMID: 38115239 DOI: 10.1002/em.22582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 09/15/2023] [Accepted: 12/16/2023] [Indexed: 12/21/2023]
Abstract
Quantitative risk assessments of chemicals are routinely performed using in vivo data from rodents; however, there is growing recognition that non-animal approaches can be human-relevant alternatives. There is an urgent need to build confidence in non-animal alternatives given the international support to reduce the use of animals in toxicity testing where possible. In order for scientists and risk assessors to prepare for this paradigm shift in toxicity assessment, standardization and consensus on in vitro testing strategies and data interpretation will need to be established. To address this issue, an Expert Working Group (EWG) of the 8th International Workshop on Genotoxicity Testing (IWGT) evaluated the utility of quantitative in vitro genotoxicity concentration-response data for risk assessment. The EWG first evaluated available in vitro methodologies and then examined the variability and maximal response of in vitro tests to estimate biologically relevant values for the critical effect sizes considered adverse or unacceptable. Next, the EWG reviewed the approaches and computational models employed to provide human-relevant dose context to in vitro data. Lastly, the EWG evaluated risk assessment applications for which in vitro data are ready for use and applications where further work is required. The EWG concluded that in vitro genotoxicity concentration-response data can be interpreted in a risk assessment context. However, prior to routine use in regulatory settings, further research will be required to address the remaining uncertainties and limitations.
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Affiliation(s)
- Marc A Beal
- Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Guangchao Chen
- Centre for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment (RIVM), Utrecht, the Netherlands
| | - Kerry L Dearfield
- Retired from US Environmental Protection Agency and US Department of Agriculture, Washington, DC, USA
| | - Min Gi
- Department of Environmental Risk Assessment, Graduate School of Medicine, Osaka Metropolitan University, Osaka, Japan
| | | | - Robert H Heflich
- National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas, USA
| | - Katsuyoshi Horibata
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Kawasaki, Kanagawa, Japan
| | - Alexandra S Long
- Existing Substances Risk Assessment Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
| | - David P Lovell
- St George's Medical School, University of London, London, UK
| | - Barbara L Parsons
- National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas, USA
| | - Stefan Pfuhler
- Global Product Stewardship - Human Safety, Procter & Gamble, Cincinnati, Ohio, USA
| | - John Wills
- Genetic Toxicology and Photosafety, GSK Research & Development, Stevenage, UK
| | - Andreas Zeller
- Pharmaceutical Sciences, pRED Innovation Center Basel, Hoffmann-La Roche Ltd, Basel, Switzerland
| | - George Johnson
- Swansea University Medical School, Swansea University, Swansea, UK
| | - Paul A White
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada
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Yamada M, Suzuki T, Kohara A, Honma M. Carcinogenic risk of food additive AF-2 banned in Japan: a case study on reassessment of genotoxicity. Genes Environ 2023; 45:33. [PMID: 38053221 PMCID: PMC10696715 DOI: 10.1186/s41021-023-00292-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 11/27/2023] [Indexed: 12/07/2023] Open
Abstract
BACKGROUND Carcinogenic risk assessment studies have been repeatedly improved and are still being debated to find a goal. Evaluation might be changed if new approaches would be applied to some chemicals which means that new approaches may change the final assessment. In this paper, the risk assessment of a chemical, in particular the proper carcinogenicity, is examined using the long-banned food additive, 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide, AF-2, as a case study. RESULTS First, Ames tests were carried out using strains TA1535, TA100, TA1538, and TA98 and their nitroreductase-deficient strains YG7127, YG7128, YG7129, and YG7130. The results showed that mutagenic activity was reduced by about 50% in the nitroreductase-deficient strains, indicating that part of the mutagenic activity shown in Ames test was due to bacterial metabolism. Second, in vivo genotoxicity tests were conducted, including the one that had not been developed in 1970's. Both a micronucleus test and a gene mutation assay using transgenic mice were negative. Third, assuming it is a genotoxic carcinogen, the virtual safety dose of 550 μg/day was calculated from the TD50 in rats with a probability of 10-5. CONCLUSION AF-2 has been shown to be carcinogenic to rodents and has previously been indicated to be genotoxic in vitro. However, the present in vivo genotoxicity study, it was negative in the forestomach, a target organ for cancer, particularly in the gene mutation assay in transgenic mice. Considering the daily intake of AF-2 in the 1970s and its virtually safety dose, the carcinogenic risk of AF-2 could be considered acceptable.
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Affiliation(s)
- Masami Yamada
- Department of Applied Chemistry, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa, 239-8686, Japan.
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan.
| | - Takayoshi Suzuki
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan
| | - Arihiro Kohara
- JCRB Cell Bank, National Institute of Biomedical Innovation, 7-6-8, Saito-asagi, Osaka, Ibaraki, 567-0085, Japan
| | - Masamitsu Honma
- Division of General Affairs, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan
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Bates CA, Haber LT, Moore MM, Schoeny R, Maier A. Development of a framework for risk assessment of dietary carcinogens. Food Chem Toxicol 2023; 180:114022. [PMID: 37716495 DOI: 10.1016/j.fct.2023.114022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 08/09/2023] [Accepted: 09/01/2023] [Indexed: 09/18/2023]
Abstract
Although there are a number of guidance documents and frameworks for evaluation of carcinogenicity, none of the current methods fully reflects the state of the science. Common limitations include the absence of dose-response assessment and not considering the impact of differing exposure patterns (e.g., intermittent, high peaks vs. lower, continuous exposures). To address these issues, we have developed a framework for risk assessment of dietary carcinogens. This framework includes an enhanced approach for weight of evidence (WOE) evaluation for genetic toxicology data, with a focus on evaluating studies based on the most recent testing guidance to determine whether a chemical is a mutagen. Included alongside our framework is a discussion of resources for evaluating tissue dose and the temporal pattern of internal dose, taking into account the chemical's toxicokinetics. The framework then integrates the mode of action (MOA) and associated dose metric category with the exposure data to identify the appropriate approach(es) to low-dose extrapolation and level of concern associated with the exposure scenario. This framework provides risk managers with additional flexibility in risk management and risk communication options, beyond the binary choice of linear low-dose extrapolation vs. application of uncertainty factors.
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Affiliation(s)
| | - Lynne T Haber
- Risk Science Center, University of Cincinnati College of Medicine, USA
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Fishbein A, Hammock BD, Serhan CN, Panigrahy D. Carcinogenesis: Failure of resolution of inflammation? Pharmacol Ther 2021; 218:107670. [PMID: 32891711 PMCID: PMC7470770 DOI: 10.1016/j.pharmthera.2020.107670] [Citation(s) in RCA: 91] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2020] [Indexed: 02/06/2023]
Abstract
Inflammation in the tumor microenvironment is a hallmark of cancer and is recognized as a key characteristic of carcinogens. However, the failure of resolution of inflammation in cancer is only recently being understood. Products of arachidonic acid and related fatty acid metabolism called eicosanoids, including prostaglandins, leukotrienes, lipoxins, and epoxyeicosanoids, critically regulate inflammation, as well as its resolution. The resolution of inflammation is now appreciated to be an active biochemical process regulated by endogenous specialized pro-resolving lipid autacoid mediators which combat infections and stimulate tissue repair/regeneration. Environmental and chemical human carcinogens, including aflatoxins, asbestos, nitrosamines, alcohol, and tobacco, induce tumor-promoting inflammation and can disrupt the resolution of inflammation contributing to a devastating global cancer burden. While mechanisms of carcinogenesis have focused on genotoxic activity to induce mutations, nongenotoxic mechanisms such as inflammation and oxidative stress promote genotoxicity, proliferation, and mutations. Moreover, carcinogens initiate oxidative stress to synergize with inflammation and DNA damage to fuel a vicious feedback loop of cell death, tissue damage, and carcinogenesis. In contrast, stimulation of resolution of inflammation may prevent carcinogenesis by clearance of cellular debris via macrophage phagocytosis and inhibition of an eicosanoid/cytokine storm of pro-inflammatory mediators. Controlling the host inflammatory response and its resolution in carcinogen-induced cancers will be critical to reducing carcinogen-induced morbidity and mortality. Here we review the recent evidence that stimulation of resolution of inflammation, including pro-resolution lipid mediators and soluble epoxide hydrolase inhibitors, may be a new chemopreventive approach to prevent carcinogen-induced cancer that should be evaluated in humans.
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Affiliation(s)
- Anna Fishbein
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA; Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
| | - Bruce D. Hammock
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, CA 95616, USA
| | - Charles N. Serhan
- Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Dipak Panigrahy
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA,Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, 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. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 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] [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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Kang DS, Yang JH, Kim HS, Koo BK, Lee CM, Ahn YS, Jung JH, Seo YR. Application of the Adverse Outcome Pathway Framework to Risk Assessment for Predicting Carcinogenicity of Chemicals. J Cancer Prev 2018; 23:126-133. [PMID: 30370257 PMCID: PMC6197844 DOI: 10.15430/jcp.2018.23.3.126] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 09/25/2018] [Accepted: 09/27/2018] [Indexed: 12/26/2022] Open
Abstract
As industry develops in modern society, many chemicals are being used. The safety of chemicals is an important issue because humans are constantly exposed to chemicals throughout their daily life. Through a risk assessment, the hazardous human effects of chemicals can be identified. Recently, the adverse outcome pathway (AOP) framework has been used to predict the adverse effects of chemicals. As a conceptual framework for organizing existing biological knowledge, the AOP consists of a molecular initiating event, key events, and an adverse outcome. These independent elements represent biological responses and are connected by key event relationships. This AOP framework provides intuitive hazard identification that can be helpful for carcinogenic risk assessment of chemicals. In this review, we introduce the application of the AOP framework to risk assessment for predicting carcinogenicity of chemicals and illustrate the utility of this approach for cancer prevention.
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Affiliation(s)
- Doo Seok Kang
- Institute of Environmental Medicine for Green Chemistry, Department of Life Science, Dongguk University Biomedi Campus, Goyang, Korea
| | - Jun Hyuek Yang
- Institute of Environmental Medicine for Green Chemistry, Department of Life Science, Dongguk University Biomedi Campus, Goyang, Korea
| | - Hyun Soo Kim
- Institute of Environmental Medicine for Green Chemistry, Department of Life Science, Dongguk University Biomedi Campus, Goyang, Korea
| | - Bon Kon Koo
- Institute of Environmental Medicine for Green Chemistry, Department of Life Science, Dongguk University Biomedi Campus, Goyang, Korea
| | - Cheol Min Lee
- Department of Chemical and Biological Engineering, College of Natural Science and Engineering, Seokyeong University, Seoul, Korea
| | - Yeon-Soon Ahn
- Department of Preventive Medicine and Institute of Occupational and Environmental Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea
| | - Jong-Hyeon Jung
- Faculty of Health Science, Daegu Haany University, Gyeongsan, Korea
| | - Young Rok Seo
- Institute of Environmental Medicine for Green Chemistry, Department of Life Science, Dongguk University Biomedi Campus, Goyang, Korea
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7
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Manjanatha MG, Shelton SD, Chen Y, Parsons BL, Myers MB, McKim KL, Gollapudi BB, Moore NP, Haber LT, Allen B, Moore MM. Dose and temporal evaluation of ethylene oxide-induced mutagenicity in the lungs of male big blue mice following inhalation exposure to carcinogenic concentrations. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:122-134. [PMID: 28326610 DOI: 10.1002/em.22080] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 02/13/2017] [Indexed: 06/06/2023]
Abstract
Ethylene oxide (EO) is a direct acting alkylating agent; in vitro and in vivo studies indicate that it is both a mutagen and a carcinogen. However, it remains unclear whether the mode of action (MOA) for cancer for EO is a mutagenic MOA, specifically via point mutation. To investigate the MOA for EO-induced mouse lung tumors, male Big Blue (BB) B6C3F1 mice (10/group) were exposed to EO by inhalation, 6 hr/day, 5 days/week for 4 (0, 10, 50, 100, or 200 ppm EO), 8, or 12 weeks (0, 100, or 200 ppm EO). Lung DNA samples were analyzed for cII mutant frequency (MF) at 4, 8 and 12 weeks of exposure; the mutation spectrum was analyzed for mutants from control and 200 ppm EO treatments. Although EO-induced cII MFs were 1.5- to 2.7-fold higher than the concurrent controls at 4 weeks, statistically significant increases in the cII MF were found only after 8 and 12 weeks of exposure and only at 200 ppm EO (P ≤ 0.05), which is twice the highest concentration used in the cancer bioassay. Consistent with the positive response, DNA sequencing of cII mutants showed a significant shift in the mutational spectra between control and 200 ppm EO following 8 and 12 week exposures (P ≤ 0.035), but not at 4 weeks. Thus, EO mutagenic activity in vivo was relatively weak and required higher than tumorigenic concentrations and longer than 4 weeks exposure durations. These data do not follow the classical patterns for a MOA mediated by point mutations. Environ. Mol. Mutagen. 58:122-134, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Mugimane G Manjanatha
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - Sharon D Shelton
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - Ying Chen
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - Barbara L Parsons
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - Meagan B Myers
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - Karen L McKim
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
| | - B Bhaskar Gollapudi
- Toxicology and Environmental Research and Consulting, Dow Chemical Company, Midland, Michigan
| | - Nigel P Moore
- Toxicology and Environmental Research and Consulting, Dow Europe GmbH, Horgen, Switzerland
| | - Lynne T Haber
- Environmental Health, Toxicology Excellence for Risk Assessment, Cincinnati, Ohio
| | - Bruce Allen
- Independent Consultant, Chapel Hill, North Carolina
| | - Martha M Moore
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US FDA, Jefferson, Arkansas
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Ding W, Levy DD, Bishop ME, Pearce MG, Davis KJ, Jeffrey AM, Duan JD, Williams GM, White GA, Lyn-Cook LE, Manjanatha MG. In vivo genotoxicity of estragole in male F344 rats. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2015; 56:356-365. [PMID: 25361439 DOI: 10.1002/em.21918] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 10/03/2014] [Indexed: 06/04/2023]
Abstract
Estragole, a naturally occurring constituent of various herbs and spices, is a rodent liver carcinogen which requires bio-activation. To further understand the mechanisms underlying its carcinogenicity, genotoxicity was assessed in F344 rats using the comet, micronucleus (MN), and DNA adduct assays together with histopathological analysis. Oxidative damage was measured using human 8-oxoguanine-DNA-N-glycosylase (hOGG1) and EndonucleaseIII (EndoIII)-modified comet assays. Results with estragole were compared with the structurally related genotoxic carcinogen, safrole. Groups of seven-week-old male F344 rats received corn oil or corn oil containing 300, 600, or 1,000 mg/kg bw estragole and 125, 250, or 450 mg/kg bw safrole by gavage at 0, 24, and 45 hr and terminated at 48 hr. Estragole-induced dose-dependent increases in DNA damage following EndoIII or hOGG1 digestion and without enzyme treatment in liver, the cancer target organ. No DNA damage was detected in stomach, the non-target tissue for cancer. No elevation of MN was observed in reticulocytes sampled from peripheral blood. Comet assays, both without digestion or with either EndoIII or hOGG1 digestion, also detected DNA damage in the liver of safrole-dosed rats. No DNA damage was detected in stomach, nor was MN elevated in peripheral blood following dosing with safrole suggesting that, as far both safrole and estragole, oxidative damage may contribute to genotoxicity. Taken together, these results implicate multiple mechanisms of estragole genotoxicity. DNA damage arises from chemical-specific interaction and is also mediated by oxidative species.
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Affiliation(s)
- Wei Ding
- Division of Genetic and Molecular Toxicology, US FDA/National Center for Toxicological Research, Jefferson, Arkansas
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Schulte PA, Whittaker C, Curran CP. Considerations for Using Genetic and Epigenetic Information in Occupational Health Risk Assessment and Standard Setting. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S69-S81. [PMID: 26583908 PMCID: PMC4685594 DOI: 10.1080/15459624.2015.1060323#.xhlte1uzbx4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Risk assessment forms the basis for both occupational health decision-making and the development of occupational exposure limits (OELs). Although genetic and epigenetic data have not been widely used in risk assessment and ultimately, standard setting, it is possible to envision such uses. A growing body of literature demonstrates that genetic and epigenetic factors condition biological responses to occupational and environmental hazards or serve as targets of them. This presentation addresses the considerations for using genetic and epigenetic information in risk assessments, provides guidance on using this information within the classic risk assessment paradigm, and describes a framework to organize thinking about such uses. The framework is a 4 × 4 matrix involving the risk assessment functions (hazard identification, dose-response modeling, exposure assessment, and risk characterization) on one axis and inherited and acquired genetic and epigenetic data on the other axis. The cells in the matrix identify how genetic and epigenetic data can be used for each risk assessment function. Generally, genetic and epigenetic data might be used as endpoints in hazard identification, as indicators of exposure, as effect modifiers in exposure assessment and dose-response modeling, as descriptors of mode of action, and to characterize toxicity pathways. Vast amounts of genetic and epigenetic data may be generated by high-throughput technologies. These data can be useful for assessing variability and reducing uncertainty in extrapolations, and they may serve as the foundation upon which identification of biological perturbations would lead to a new paradigm of toxicity pathway-based risk assessments.
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Affiliation(s)
- P. A. Schulte
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. Whittaker
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. P. Curran
- Northern Kentucky University, Department of Biological Sciences, Highland Heights, Kentucky
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Schulte PA, Whittaker C, Curran CP. Considerations for Using Genetic and Epigenetic Information in Occupational Health Risk Assessment and Standard Setting. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S69-81. [PMID: 26583908 PMCID: PMC4685594 DOI: 10.1080/15459624.2015.1060323] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Risk assessment forms the basis for both occupational health decision-making and the development of occupational exposure limits (OELs). Although genetic and epigenetic data have not been widely used in risk assessment and ultimately, standard setting, it is possible to envision such uses. A growing body of literature demonstrates that genetic and epigenetic factors condition biological responses to occupational and environmental hazards or serve as targets of them. This presentation addresses the considerations for using genetic and epigenetic information in risk assessments, provides guidance on using this information within the classic risk assessment paradigm, and describes a framework to organize thinking about such uses. The framework is a 4 × 4 matrix involving the risk assessment functions (hazard identification, dose-response modeling, exposure assessment, and risk characterization) on one axis and inherited and acquired genetic and epigenetic data on the other axis. The cells in the matrix identify how genetic and epigenetic data can be used for each risk assessment function. Generally, genetic and epigenetic data might be used as endpoints in hazard identification, as indicators of exposure, as effect modifiers in exposure assessment and dose-response modeling, as descriptors of mode of action, and to characterize toxicity pathways. Vast amounts of genetic and epigenetic data may be generated by high-throughput technologies. These data can be useful for assessing variability and reducing uncertainty in extrapolations, and they may serve as the foundation upon which identification of biological perturbations would lead to a new paradigm of toxicity pathway-based risk assessments.
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Affiliation(s)
- P. A. Schulte
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
- Address correspondence to Paul A. Schulte, Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, 4676 Columbia Parkway, MS-C14 Cincinnati, OH45226, . E-mail:
| | - C. Whittaker
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. P. Curran
- Northern Kentucky University, Department of Biological Sciences, Highland Heights, Kentucky
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11
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Sex-specific dose-response analysis of genotoxicity in cyproterone acetate-treated F344 rats. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2014; 774:1-7. [DOI: 10.1016/j.mrgentox.2014.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/18/2014] [Accepted: 08/23/2014] [Indexed: 11/19/2022]
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Dertinger SD, Phonethepswath S, Avlasevich SL, Torous DK, Mereness J, Cottom J, Bemis JC, Macgregor JT. Pig-a gene mutation and micronucleated reticulocyte induction in rats exposed to tumorigenic doses of the leukemogenic agents chlorambucil, thiotepa, melphalan, and 1,3-propane sultone. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2014; 55:299-308. [PMID: 24449360 DOI: 10.1002/em.21846] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/13/2013] [Accepted: 12/17/2013] [Indexed: 06/03/2023]
Abstract
To evaluate whether blood-based genotoxicity endpoints can provide temporal and dose-response data within the low-dose carcinogenic range that could contribute to carcinogenic mode of action (MoA) assessments, we evaluated the sensitivity of flow cytometry-based micronucleus and Pig-a gene mutation assays at and below tumorigenic dose rate 50 (TD50) levels. The incidence of micronucleated reticulocytes (MN-RET) was used to evaluate chromosomal damage, and the frequency of CD59-negative reticulocytes (RET(CD59-) ) and erythrocytes (RBC(CD59-) ) served as phenotypic reporters of mutation at the X-linked Pig-a gene. Several leukemogenic agents with a presumed genotoxic MoA were studied. Specifically, male Sprague Dawley rats were treated via oral gavage for 28 days with chlorambucil, thiotepa, melphalan, and 1,3-propane sultone at doses corresponding to 0.33x, 1x, and 3x TD50, as well as at the maximum tolerated dose. Frequencies of MN-RET were determined at Days 4 and 29, and RET(CD59-) and RBC(CD59-) data were collected pretreatment as well as Days 15/16, 29, and 56/57. Dose-related increases were observed for each endpoint, and time to maximal effect was consistently: MN-RET < RET(CD59-) < RBC(CD59-) . For each of the chemicals studied, the genotoxic events occurred long before tumors or preneoplastic lesions would be expected. Furthermore, in the case of Pig-a gene mutation, the responses were observed at or below the TD50 dose for three out of the four chemicals studied. These data illustrate the potential for quantitative blood-based analyses to provide dose-response and temporality information that relates genetic damage to cancer induction.
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von Stackelberg K. A Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment. J Toxicol 2013; 2013:371610. [PMID: 23533401 PMCID: PMC3600329 DOI: 10.1155/2013/371610] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 05/18/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022] Open
Abstract
Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown.
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Affiliation(s)
- Katherine von Stackelberg
- E Risk Sciences, LLP, 12 Holton Street, Allston, MA 02134, USA
- Harvard Center for Risk Analysis, 401 Park Drive, Landmark 404J, Boston, MA 02215, USA
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Ding W, Petibone DM, Latendresse JR, Pearce MG, Muskhelishvili L, White GA, Chang CW, Mittelstaedt RA, Shaddock JG, McDaniel LP, Doerge DR, Morris SM, Bishop ME, Manjanatha MG, Aidoo A, Heflich RH. In vivo genotoxicity of furan in F344 rats at cancer bioassay doses. Toxicol Appl Pharmacol 2012; 261:164-71. [DOI: 10.1016/j.taap.2012.03.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/27/2012] [Accepted: 03/29/2012] [Indexed: 10/28/2022]
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McDaniel LP, Ding W, Dobrovolsky VN, Shaddock JG, Mittelstaedt RA, Doerge DR, Heflich RH. Genotoxicity of furan in Big Blue rats. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2012; 742:72-8. [DOI: 10.1016/j.mrgentox.2011.12.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 12/09/2011] [Accepted: 12/10/2011] [Indexed: 01/01/2023]
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Strategies in case of positive in vivo results in genotoxicity testing. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2011; 723:121-8. [DOI: 10.1016/j.mrgentox.2010.09.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 09/08/2010] [Indexed: 01/23/2023]
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17
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Dearfield KL, Thybaud V, Cimino MC, Custer L, Czich A, Harvey JS, Hester S, Kim JH, Kirkland D, Levy DD, Lorge E, Moore MM, Ouédraogo-Arras G, Schuler M, Suter W, Sweder K, Tarlo K, van Benthem J, van Goethem F, Witt KL. Follow-up actions from positive results of in vitro genetic toxicity testing. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2011; 52:177-204. [PMID: 20963811 DOI: 10.1002/em.20617] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 06/16/2010] [Accepted: 06/18/2010] [Indexed: 05/30/2023]
Abstract
Appropriate follow-up actions and decisions are needed when evaluating and interpreting clear positive results obtained in the in vitro assays used in the initial genotoxicity screening battery (i.e., the battery of tests generally required by regulatory authorities) to assist in overall risk-based decision making concerning the potential effects of human exposure to the agent under test. Over the past few years, the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) Project Committee on the Relevance and Follow-up of Positive Results in In Vitro Genetic Toxicity (IVGT) Testing developed a decision process flow chart to be applied in case of clear positive results in vitro. It provides for a variety of different possibilities and allows flexibility in choosing follow-up action(s), depending on the results obtained in the initial battery of assays and available information. The intent of the Review Subgroup was not to provide a prescriptive testing strategy, but rather to reinforce the concept of weighing the totality of the evidence. The Review Subgroup of the IVGT committee highlighted the importance of properly analyzing the existing data, and considering potential confounding factors (e.g., possible interactions with the test systems, presence of impurities, irrelevant metabolism), and chemical modes of action when analyzing and interpreting positive results in the in vitro genotoxicity assays and determining appropriate follow-up testing. The Review Subgroup also examined the characteristics, strengths, and limitations of each of the existing in vitro and in vivo genotoxicity assays to determine their usefulness in any follow-up testing.
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Affiliation(s)
- Kerry L Dearfield
- U.S. Department of Agriculture, Food Safety and Inspection Service, Washington, District of Columbia, USA
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Boverhof DR, Chamberlain MP, Elcombe CR, Gonzalez FJ, Heflich RH, Hernández LG, Jacobs AC, Jacobson-Kram D, Luijten M, Maggi A, Manjanatha MG, Benthem JV, Gollapudi BB. Transgenic animal models in toxicology: historical perspectives and future outlook. Toxicol Sci 2011; 121:207-33. [PMID: 21447610 DOI: 10.1093/toxsci/kfr075] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Transgenic animal models are powerful tools for developing a more detailed understanding on the roles of specific genes in biological pathways and systems. Applications of these models have been made within the field of toxicology, most notably for the screening of mutagenic and carcinogenic potential and for the characterization of toxic mechanisms of action. It has long been a goal of research toxicologists to use the data from these models to refine hazard identification and characterization to better inform human health risk assessments. This review provides an overview on the applications of transgenic animal models in the assessment of mutagenicity and carcinogenicity, their use as reporter systems, and as tools for understanding the roles of xenobiotic-metabolizing enzymes and biological receptors in the etiology of chemical toxicity. Perspectives are also shared on the future outlook for these models in toxicology and risk assessment and how transgenic technologies are likely to be an integral tool for toxicity testing in the 21st century.
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Affiliation(s)
- Darrell R Boverhof
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674, USA.
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Meng F, Wang Y, Myers MB, Wong BA, Gross EA, Clewell HJ, Dodd DE, Parsons BL. p53 codon 271 CGT to CAT mutant fraction does not increase in nasal respiratory and olfactory epithelia of rats exposed to inhaled naphthalene. Mutat Res 2011; 721:199-205. [PMID: 21324376 DOI: 10.1016/j.mrgentox.2011.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 11/17/2022]
Abstract
A 2-year rat tumor bioassay testing whole body exposure to naphthalene (NA) vapor found a significant increase in nasal respiratory epithelial adenomas in male rats and in olfactory epithelial neuroblastomas in female rats. To obtain mechanistic insight into NA-induced nasal carcinogenesis, NA dose-response was characterized in nasal epithelium using a tumor-relevant endpoint. Specifically, levels of p53 codon 271 CGT to CAT mutation were measured in nasal respiratory and olfactory epithelium of NA-exposed male and female rats by allele-specific competitive blocker-PCR (ACB-PCR). Male and female, 8-9 week-old F344 rats (5 rats/group) were exposed to 0, 0.1, 1.0, 10, and 30ppm NA vapor for 13 weeks (6h/day, 5 days/week). The geometric mean p53 mutant fraction (MF) levels in nasal epithelium of control treatment groups ranged between 2.05 × 10(-5) and 3.05 × 10(-5). No significant dose-related changes in p53 mutant fraction (MF) were observed in the olfactory or respiratory epithelia of female rats. However, statistically significant treatment-related differences were observed in male respiratory and olfactory epithelium, with the p53 MF in the respiratory epithelium of male rats exposed to 30ppm NA significantly lower than that in controls. Further, a significant trend of decreasing p53 MF with increasing dose was observed in the male respiratory epithelium. Of the tissue types analyzed, respiratory epithelium is the most sensitive to the cytotoxic effects of NA, suggesting cytotoxicity may be responsible for the loss of p53 mutation. Because ACB-PCR has been used successfully to detect the effects of known mutagenic carcinogens, the absence of any significant increases in p53 MF associated with NA exposure adds to the weight of evidence that NA does not operate through a directly mutagenic mode of action.
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Affiliation(s)
- Fanxue Meng
- National Center for Toxicological Research, US Food and Drug Administration, Jefferson, AR 72079, USA
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Parsons BL, Myers MB, Meng F, Wang Y, McKinzie PB. Oncomutations as biomarkers of cancer risk. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:836-850. [PMID: 20740637 DOI: 10.1002/em.20600] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Cancer risk assessment impacts a range of societal needs, from the regulation of chemicals to achieving the best possible human health outcomes. Because oncogene and tumor suppressor gene mutations are necessary for the development of cancer, such mutations are ideal biomarkers to use in cancer risk assessment. Consequently, DNA-based methods to quantify particular tumor-associated hotspot point mutations (i.e., oncomutations) have been developed, including allele-specific competitive blocker-PCR (ACB-PCR). Several studies using ACB-PCR and model mutagens have demonstrated that significant induction of tumor-associated oncomutations are measureable at earlier time points than are used to score tumors in a bioassay. In the particular case of benzo[a]pyrene induction of K-Ras codon 12 TGT mutation in the A/J mouse lung, measurement of tumor-associated oncomutation was shown to be an earlier and more sensitive endpoint than tumor response. The measurement of oncomutation by ACB-PCR led to two unexpected findings. First, oncomutations are present in various tissues of control rodents and "normal" human colonic mucosa samples at relatively high frequencies. Approximately 60% of such samples (88/146) have mutant fractions (MFs) >10(-5), and some have MFs as high as 10(-3) or 10(-4). Second, preliminary data indicate that oncomutations are present frequently as subpopulations in tumors. These findings are integrated into a hypothesis that the predominant preexisting mutations in particular tissues may be useful as generic reporters of carcinogenesis. Future research opportunities using oncomutation as an endpoint are described, including rodent to human extrapolation, dose-response assessment, and personalized medicine.
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Affiliation(s)
- Barbara L Parsons
- Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, Jefferson, Arkansas 72079, USA.
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Meng F, Bermudez E, McKinzie PB, Andersen ME, Clewell HJ, Parsons BL. Measurement of tumor-associated mutations in the nasal mucosa of rats exposed to varying doses of formaldehyde. Regul Toxicol Pharmacol 2010; 57:274-83. [PMID: 20347909 DOI: 10.1016/j.yrtph.2010.03.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 03/15/2010] [Accepted: 03/17/2010] [Indexed: 01/09/2023]
Abstract
This study examined the potential induction of tumor-associated mutations in formaldehyde-exposed rat nasal mucosa using a sensitive method, allele-specific competitive blocker-PCR (ACB-PCR). Levels of p53 codon 271 CGT to CAT and K-Ras codon 12 GGT to GAT mutations were quantified in nasal mucosa of rats exposed to formaldehyde. In addition, nasal mucosa cell proliferation was monitored because regenerative cell proliferation is considered a key event in formaldehyde-induced carcinogenesis. Male F344 rats (6-7 weeks old, 5 rats/group) were exposed to 0, 0.7, 2, 6, 10, and 15 ppm formaldehyde for 13 weeks (6 h/day, 5 days/week). ACB-PCR was used to determine levels of p53 and K-Ras mutations. Although two of five untreated rats had measureable spontaneous p53 mutant fractions (MFs), most nasal mucosa samples had p53 MFs below 10(-5). All K-Ras MF measurements were below 10(-5). No dose-related increases in p53 or K-Ras MF were observed, even though significant increases in bromodeoxyuridine incorporation demonstrated induced cell proliferation in the 10 and 15 ppm formaldehyde-treatment groups. Therefore, induction of tumor-associated p53 mutation likely occurs after several other key events in formaldehyde-induced carcinogenesis.
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Affiliation(s)
- Fanxue Meng
- US Food and Drug Administration, National Center for Toxicological Research, Division of Genetic and Reproductive Toxicology, Jefferson, AR 72079, USA.
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Mei N, McDaniel LP, Dobrovolsky VN, Guo X, Shaddock JG, Mittelstaedt RA, Azuma M, Shelton SD, McGarrity LJ, Doerge DR, Heflich RH. The genotoxicity of acrylamide and glycidamide in big blue rats. Toxicol Sci 2010; 115:412-21. [PMID: 20200216 DOI: 10.1093/toxsci/kfq069] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Acrylamide (AA), a mutagen and rodent carcinogen, recently has been detected in fried and baked starchy foods, a finding that has prompted renewed interest in its potential for toxicity in humans. In the present study, we exposed Big Blue rats to the equivalent of approximately 5 and 10 mg/kg body weight/day of AA or its epoxide metabolite glycidamide (GA) via the drinking water, an AA treatment regimen comparable to those used to produce cancer in rats. After 2 months of dosing, the rats were euthanized and blood was taken for the micronucleus assay; spleens for the lymphocyte Hprt mutant assay; and liver, thyroid, bone marrow, testis (from males), and mammary gland (females) for the cII mutant assay. Neither AA nor GA increased the frequency of micronucleated reticulocytes. In contrast, both compounds produced small (approximately twofold to threefold above background) but significant increases in lymphocyte Hprt mutant frequency (MF, p < 0.05), with the increases having dose-related linear trends (p < 0.05 to p < 0.001). Neither compound increased the cII MF in testis, mammary gland (tumor target tissues), or liver (nontarget tissue), while both compounds induced weak positive increases in bone marrow (nontarget tissue) and thyroid (target tissue). Although the genotoxicity in tumor target tissue was weak, in combination with the responses in surrogate tissues, the results are consistent with AA being a gene mutagen in the rat via metabolism to GA.
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Affiliation(s)
- Nan Mei
- Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, Jefferson, Arkansas 72079, USA.
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Douron M. U-shaped dose-response curves: implications for risk characterization of essential elements and other chemicals. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2010; 73:181-186. [PMID: 20077289 DOI: 10.1080/15287390903340450] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The existing risk assessment and management model is a general framework that can incorporate the assessment of numerous types of chemicals, such as essential elements. The general nature of the framework, however, often precludes precise statements of risk and only gives assurances of accuracy by way of a judicious use of conservative assumptions. A mode-of-action framework may provide approaches that are both more precise and accurate, and that may be used for characterizing both risk and benefit of essential elements, but such a framework needs to address the differing severity of adverse effects. Current dose-response data gaps often hinder the evaluation of the risk and benefit of several essential elements; however, new modeling methods, such as categorical regression, need to be further explored. Finally, the essentiality of certain elements provides evidence that two thresholds likely exist in an individual for adverse effect, one at low doses for undernutrition, and another at high doses for toxicity, for the element of concern. This evidence may aid in the estimation of such thresholds in populations.
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Affiliation(s)
- Michael Douron
- Toxicology Excellence for Risk Assessment, Cincinnati, Ohio 45211, USA.
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Manjanatha MG, Shelton SD, Dobrovolsky VN, Shaddock JG, McGarrity LG, Twaddle NW, Moore MM, Mattison DR, Slikker W, Morris SM. Evaluation of mutagenic mode of action in Big Blue mice fed methylphenidate for 24 weeks. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2009; 680:43-8. [DOI: 10.1016/j.mrgentox.2009.09.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 09/05/2009] [Accepted: 09/11/2009] [Indexed: 11/16/2022]
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