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Hashimoto K, Takeda S, Swenberg JA, Nakamura J. Incorporation of metabolic activation potentiates cyclophosphamide-induced DNA damage response in isogenic DT40 mutant cells. Mutagenesis 2015; 30:821-8. [PMID: 26085549 DOI: 10.1093/mutage/gev042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Elucidating the DNA repair pathways that are activated in the presence of genotoxic agents is critical to understand their modes of action. Although the DT40 cell-based DNA damage response (DDR) assay provides rapid and sensitive results, the assay cannot be used on genotoxic compounds that require metabolic activation to be reactive. Here, we applied the metabolic activation system to a DDR and micronucleus (MN) assays in DT40 cells. Cyclophosphamide (CP), a well-known cross-linking agent requiring metabolic activation, was preincubated with liver S9 fractions. When DT40 cells and mutant cells were exposed to the preactivated CP, CP caused increased cytotoxicity in FANC-, RAD9-, REV3- and RAD18-mutant cells compared to isogenic wild-type cells. We then performed a MN assay on DT40 cells treated with preactivated CP. An increase in the MN was observed in REV3- and FANC-mutant cells at lower concentrations of activated CP than in the parental DT40 cells. These results demonstrated that the incorporation of metabolic preactivation system using S9 fractions significantly potentiates DDR caused by CP in DT40 cells and their mutants. In addition, our data suggest that the metabolic preactivation system for DDR and MN assays has a potential to increase the relevance of this assay to screening various compounds for potential genotoxicity.
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Affiliation(s)
- Kiyohiro Hashimoto
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA, Drug Safety Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - James A Swenberg
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jun Nakamura
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA,
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Krewski D, Westphal M, Andersen ME, Paoli GM, Chiu WA, Al-Zoughool M, Croteau MC, Burgoon LD, Cote I. A framework for the next generation of risk science. ENVIRONMENTAL HEALTH PERSPECTIVES 2014; 122:796-805. [PMID: 24727499 PMCID: PMC4123023 DOI: 10.1289/ehp.1307260] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 04/09/2014] [Indexed: 05/19/2023]
Abstract
OBJECTIVES In 2011, the U.S. Environmental Protection Agency initiated the NexGen project to develop a new paradigm for the next generation of risk science. METHODS The NexGen framework was built on three cornerstones: the availability of new data on toxicity pathways made possible by fundamental advances in basic biology and toxicological science, the incorporation of a population health perspective that recognizes that most adverse health outcomes involve multiple determinants, and a renewed focus on new risk assessment methodologies designed to better inform risk management decision making. RESULTS The NexGen framework has three phases. Phase I (objectives) focuses on problem formulation and scoping, taking into account the risk context and the range of available risk management decision-making options. Phase II (risk assessment) seeks to identify critical toxicity pathway perturbations using new toxicity testing tools and technologies, and to better characterize risks and uncertainties using advanced risk assessment methodologies. Phase III (risk management) involves the development of evidence-based population health risk management strategies of a regulatory, economic, advisory, community-based, or technological nature, using sound principles of risk management decision making. CONCLUSIONS Analysis of a series of case study prototypes indicated that many aspects of the NexGen framework are already beginning to be adopted in practice.
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Affiliation(s)
- Daniel Krewski
- McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada
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Gentry PR, Yager JW, Clewell RA, Clewell HJ. Use of mode of action data to inform a dose-response assessment for bladder cancer following exposure to inorganic arsenic. Toxicol In Vitro 2014; 28:1196-205. [PMID: 24937311 DOI: 10.1016/j.tiv.2014.05.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 05/19/2014] [Accepted: 05/21/2014] [Indexed: 01/15/2023]
Abstract
In the recent National Research Council report on conducting a dose-response assessment for inorganic arsenic, the committee remarked that mode of action data should be used, to the extent possible, to extrapolate below the observed range for epidemiological studies to inform the shape of the dose-response curve. Recent in vitro mode of action studies focused on understanding the development of bladder cancer following exposure to inorganic arsenic provide data to inform the dose-response curve. These in vitro data, combined with results of bladder cancer epidemiology studies, inform the dose-response curve in the low-dose region, and include values for both pharmacokinetic and pharmacodynamic variability. Integration of these data provides evidence of a range of concentrations of arsenic for which no effect on the bladder would be expected. Specifically, integration of these results suggest that arsenic exposures in the range of 7-43 ppb in drinking water are exceedingly unlikely to elicit changes leading to key events in the development of cancer or noncancer effects in bladder tissue. These findings are consistent with the lack of evidence for bladder cancer following chronic ingestion of arsenic water concentrations <100 ppb in epidemiological studies.
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Affiliation(s)
- P R Gentry
- ENVIRON International Corporation, 1900 N. 18th Street, Suite 804, Monroe, LA 71201, United States.
| | - J W Yager
- ENVIRON International Corporation, 2200 Powell Street, Suite 700, Emeryville, CA 94608, United States; University of New Mexico, MSC 10 5550, 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
| | - R A Clewell
- The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709-2137, United States
| | - H J Clewell
- The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709-2137, United States
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The impact of recent advances in research on arsenic cancer risk assessment. Regul Toxicol Pharmacol 2014; 69:91-104. [DOI: 10.1016/j.yrtph.2014.02.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/05/2014] [Accepted: 02/07/2014] [Indexed: 11/23/2022]
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Strengthening the foundation of next generation risk assessment. Regul Toxicol Pharmacol 2014; 68:160-70. [DOI: 10.1016/j.yrtph.2013.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 12/04/2013] [Accepted: 12/08/2013] [Indexed: 12/20/2022]
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Abstract
Toxicology is and will be heavily influenced by advances in many scientific disciplines. For toxicologic pathology, particularly relevant are the increasing array of molecular methods providing deeper insights into toxicity pathways, in vivo imaging techniques visualizing toxicodynamics and more powerful computers anticipated to allow (partly) automated morphological diagnoses. It appears unlikely that, in a foreseeable future, animal studies can be replaced by in silico and in vitro studies or longer term in vivo studies by investigations of biomarkers including toxicogenomics of shorter term studies, though the importance of such approaches will continue to increase. In addition to changes based on scientific progress, the work of toxicopathologists is and will be affected by social and financial factors, among them stagnating budgets, globalization, and outsourcing. The number of toxicopathologists in North America, Europe, and the Far East is not expected to grow. Many toxicopathologists will likely spend less time at the microscope but will be more heavily involved in early research activities, imaging, and as generalists with a broad biological understanding in evaluation and management of toxicity. Toxicologic pathology will remain important and is indispensable for validation of new methods, quality assurance of established methods, and for areas without good alternative methods.
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Bhattacharya S, Zhang Q, Carmichael PL, Boekelheide K, Andersen ME. Toxicity testing in the 21 century: defining new risk assessment approaches based on perturbation of intracellular toxicity pathways. PLoS One 2011; 6:e20887. [PMID: 21701582 PMCID: PMC3118802 DOI: 10.1371/journal.pone.0020887] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 05/11/2011] [Indexed: 01/15/2023] Open
Abstract
The approaches to quantitatively assessing the health risks of chemical exposure have not changed appreciably in the past 50 to 80 years, the focus remaining on high-dose studies that measure adverse outcomes in homogeneous animal populations. This expensive, low-throughput approach relies on conservative extrapolations to relate animal studies to much lower-dose human exposures and is of questionable relevance to predicting risks to humans at their typical low exposures. It makes little use of a mechanistic understanding of the mode of action by which chemicals perturb biological processes in human cells and tissues. An alternative vision, proposed by the U.S. National Research Council (NRC) report Toxicity Testing in the 21(st) Century: A Vision and a Strategy, called for moving away from traditional high-dose animal studies to an approach based on perturbation of cellular responses using well-designed in vitro assays. Central to this vision are (a) "toxicity pathways" (the innate cellular pathways that may be perturbed by chemicals) and (b) the determination of chemical concentration ranges where those perturbations are likely to be excessive, thereby leading to adverse health effects if present for a prolonged duration in an intact organism. In this paper we briefly review the original NRC report and responses to that report over the past 3 years, and discuss how the change in testing might be achieved in the U.S. and in the European Union (EU). EU initiatives in developing alternatives to animal testing of cosmetic ingredients have run very much in parallel with the NRC report. Moving from current practice to the NRC vision would require using prototype toxicity pathways to develop case studies showing the new vision in action. In this vein, we also discuss how the proposed strategy for toxicity testing might be applied to the toxicity pathways associated with DNA damage and repair.
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Affiliation(s)
- Sudin Bhattacharya
- Program in Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Qiang Zhang
- Program in Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Paul L. Carmichael
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedford, United Kingdom
| | - Kim Boekelheide
- Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island, United States of America
| | - Melvin E. Andersen
- Program in Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina, United States of America
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Krewski D, Westphal M, Al-Zoughool M, Croteau MC, Andersen ME. New Directions in Toxicity Testing. Annu Rev Public Health 2011; 32:161-78. [DOI: 10.1146/annurev-publhealth-031210-101153] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Daniel Krewski
- McLaughlin Center for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5; , , ,
| | - Margit Westphal
- McLaughlin Center for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5; , , ,
| | - Mustafa Al-Zoughool
- McLaughlin Center for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5; , , ,
| | - Maxine C. Croteau
- McLaughlin Center for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5; , , ,
| | - Melvin E. Andersen
- Program in Chemical Safety Sciences, Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709, USA;
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