The Impact of Dose Rate on DNA Double-Strand Break Formation and Repair in Human Lymphocytes Exposed to Fast Neutron Irradiation

The lack of information on how biological systems respond to low-dose and low dose-rate exposures makes it difficult to accurately assess the carcinogenic risks. This is of critical importance to space radiation, which remains a serious concern for long-term manned space exploration. In this study,...

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Bibliographic Details
Main Authors: Shankari Nair, Monique Engelbrecht, Xanthene Miles, Roya Ndimba, Randall Fisher, Peter du Plessis, Julie Bolcaen, Jaime Nieto-Camero, Evan de Kock, Charlot Vandevoorde
Format: Article
Language:English
Published: MDPI AG 2019-10-01
Series:International Journal of Molecular Sciences
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Online Access:https://www.mdpi.com/1422-0067/20/21/5350
Description
Summary:The lack of information on how biological systems respond to low-dose and low dose-rate exposures makes it difficult to accurately assess the carcinogenic risks. This is of critical importance to space radiation, which remains a serious concern for long-term manned space exploration. In this study, the &#947;-H2AX foci assay was used to follow DNA double-strand break (DSB) induction and repair following exposure to neutron irradiation, which is produced as secondary radiation in the space environment. Human lymphocytes were exposed to high dose-rate (HDR: 0.400 Gy/min) and low dose-rate (LDR: 0.015 Gy/min) <i>p</i>(66)/Be(40) neutrons. DNA DSB induction was investigated 30 min post exposure to neutron doses ranging from 0.125 to 2 Gy. Repair kinetics was studied at different time points after a 1 Gy neutron dose. Our results indicated that &#947;-H2AX foci formation was 40% higher at HDR exposure compared to LDR exposure. The maximum &#947;-H2AX foci levels decreased gradually to 1.65 &#177; 0.64 foci/cell (LDR) and 1.29 &#177; 0.45 (HDR) at 24 h postirradiation, remaining significantly higher than background levels. This illustrates a significant effect of dose rate on neutron-induced DNA damage. While no significant difference was observed in residual DNA damage after 24 h, the DSB repair half-life of LDR exposure was slower than that of HDR exposure. The results give a first indication that the dose rate should be taken into account for cancer risk estimations related to neutrons.
ISSN:1422-0067