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Nagashima H, Shiraishi K, Ohkawa S, Sakamoto Y, Komatsu K, Matsuura S, Tachibana A, Tauchi H. Induction of somatic mutations by low-dose X-rays: the challenge in recognizing radiation-induced events. JOURNAL OF RADIATION RESEARCH 2018; 59:ii11-ii17. [PMID: 29053826 PMCID: PMC5941164 DOI: 10.1093/jrr/rrx053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 08/21/2017] [Indexed: 05/24/2023]
Abstract
It is difficult to distinguish radiation-induced events from spontaneous events during induction of stochastic effects, especially in the case of low-dose or low-dose-rate exposures. By using a hypersensitive system for detecting somatic mutations at the HPRT1 locus, we investigated the frequency and spectrum of mutations induced by low-dose X-rays. The mutant frequencies induced by doses of >0.15 Gy were statistically significant when compared with the spontaneous frequency, and a clear dose dependency was also observed for mutant frequencies at doses of >0.15 Gy. In contrast, mutant frequencies at doses of <0.1 Gy occurred at non-significant levels. The mutation spectrum in HPRT-deficient mutants revealed that the type of mutations induced by low-dose exposures was similar to that seen in spontaneous mutants. An apparent change in mutation type was observed for mutants induced by doses of >0.2 Gy. Our observations suggest that there could be a critical dose for mutation induction at between 0.1 Gy and 0.2 Gy, where mutagenic events are induced by multiple DNA double-strand breaks (DSBs). These observations also suggest that low-dose radiation delivered at doses of <0.1 Gy may not result in DSB-induced mutations but may enhance spontaneous mutagenesis events.
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Affiliation(s)
- Haruki Nagashima
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
| | - Kumiko Shiraishi
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
| | - Saori Ohkawa
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
| | - Yuki Sakamoto
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
| | - Kenshi Komatsu
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida-Konoe Cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shinya Matsuura
- Department of Radiation Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553 Japan
| | - Akira Tachibana
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
| | - Hiroshi Tauchi
- Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
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Pirela SV, Miousse IR, Lu X, Castranova V, Thomas T, Qian Y, Bello D, Kobzik L, Koturbash I, Demokritou P. Effects of Laser Printer-Emitted Engineered Nanoparticles on Cytotoxicity, Chemokine Expression, Reactive Oxygen Species, DNA Methylation, and DNA Damage: A Comprehensive in Vitro Analysis in Human Small Airway Epithelial Cells, Macrophages, and Lymphoblasts. ENVIRONMENTAL HEALTH PERSPECTIVES 2016; 124:210-9. [PMID: 26080392 PMCID: PMC4749083 DOI: 10.1289/ehp.1409582] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 06/12/2015] [Indexed: 05/20/2023]
Abstract
BACKGROUND Engineered nanomaterials (ENMs) incorporated into toner formulations of printing equipment become airborne during consumer use. Although information on the complex physicochemical and toxicological properties of both toner powders and printer-emitted particles (PEPs) continues to grow, most toxicological studies have not used the actual PEPs but rather have primarily used raw toner powders, which are not representative of current exposures experienced at the consumer level during printing. OBJECTIVES We assessed the biological responses of a panel of human cell lines to PEPs. METHODS Three physiologically relevant cell lines--small airway epithelial cells (SAECs), macrophages (THP-1 cells), and lymphoblasts (TK6 cells)--were exposed to PEPs at a wide range of doses (0.5-100 μg/mL) corresponding to human inhalation exposure durations at the consumer level of 8 hr or more. Following treatment, toxicological parameters reflecting distinct mechanisms were evaluated. RESULTS PEPs caused significant membrane integrity damage, an increase in reactive oxygen species (ROS) production, and an increase in pro-inflammatory cytokine release in different cell lines at doses equivalent to exposure durations from 7.8 to 1,500 hr. Furthermore, there were differences in methylation patterns that, although not statistically significant, demonstrate the potential effects of PEPs on the overall epigenome following exposure. CONCLUSIONS The in vitro findings obtained in this study suggest that laser printer-emitted engineered nanoparticles may be deleterious to lung cells and provide preliminary evidence of epigenetic modifications that might translate to pulmonary disorders.
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Affiliation(s)
- Sandra V. Pirela
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
| | - Isabelle R. Miousse
- Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Xiaoyan Lu
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
| | - Vincent Castranova
- Department of Pharmaceutical Sciences, West Virginia University, Morgantown, West Virginia, USA
| | - Treye Thomas
- Office of Hazard Identification and Reduction, U.S. Consumer Product Safety Commission, Rockville, Maryland, USA
| | - Yong Qian
- Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA
| | - Dhimiter Bello
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
- Department of Work Environment, University of Massachusetts-Lowell, Lowell, Massachusetts, USA
| | - Lester Kobzik
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
| | - Igor Koturbash
- Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Philip Demokritou
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
- Address correspondence to P. Demokritou, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Harvard University, 665 Huntington Ave., Room 1310B, Boston, MA 02115 USA. (617) 432-3481. E-mail:
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Krutá M, Šeneklová M, Raška J, Salykin A, Zerzánková L, Pešl M, Bártová E, Franek M, Baumeisterová A, Košková S, Neelsen KJ, Hampl A, Dvořák P, Rotrekl V. Mutation frequency dynamics in HPRT locus in culture-adapted human embryonic stem cells and induced pluripotent stem cells correspond to their differentiated counterparts. Stem Cells Dev 2014; 23:2443-54. [PMID: 24836366 DOI: 10.1089/scd.2013.0611] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The genomic destabilization associated with the adaptation of human embryonic stem cells (hESCs) to culture conditions or the reprogramming of induced pluripotent stem cells (iPSCs) increases the risk of tumorigenesis upon the clinical use of these cells and decreases their value as a model for cell biology studies. Base excision repair (BER), a major genomic integrity maintenance mechanism, has been shown to fail during hESC adaptation. Here, we show that the increase in the mutation frequency (MF) caused by the inhibition of BER was similar to that caused by the hESC adaptation process. The increase in MF reflected the failure of DNA maintenance mechanisms and the subsequent increase in MF rather than being due solely to the accumulation of mutants over a prolonged period, as was previously suggested. The increase in the ionizing-radiation-induced MF in adapted hESCs exceeded the induced MF in nonadapted hESCs and differentiated cells. Unlike hESCs, the overall DNA maintenance in iPSCs, which was reflected by the MF, was similar to that in differentiated cells regardless of the time spent in culture and despite the upregulation of several genes responsible for genome maintenance during the reprogramming process. Taken together, our results suggest that the changes in BER activity during the long-term cultivation of hESCs increase the mutagenic burden, whereas neither reprogramming nor long-term propagation in culture changes the MF in iPSCs.
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Affiliation(s)
- Miriama Krutá
- 1 Department of Biology, Faculty of Medicine, Masaryk University , Brno, Czech Republic
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