Department of Radiochemistry, South African Nuclear Energy Corporation, Pretoria 001, South Africa.
Radiobiology, Radiation Biophysics Division, Department of Nuclear Medicine, iThemba LABS, Cape Town 7131, South Africa.
Int J Mol Sci. 2019 Oct 28;20(21):5350. doi: 10.3390/ijms20215350.
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 γ-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) (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 γ-H2AX foci formation was 40% higher at HDR exposure compared to LDR exposure. The maximum γ-H2AX foci levels decreased gradually to 1.65 ± 0.64 foci/cell (LDR) and 1.29 ± 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.
由于缺乏关于生物系统如何应对低剂量和低剂量率暴露的信息，因此难以准确评估致癌风险。这对于空间辐射至关重要，空间辐射仍然是长期载人太空探索的一个严重问题。在这项研究中，使用 γ-H2AX 焦点分析来跟踪暴露于中子辐照后 DNA 双链断裂 (DSB) 的诱导和修复，中子辐照是空间环境中产生的次级辐射。人类淋巴细胞暴露于高剂量率 (HDR：0.400 Gy/min) 和低剂量率 (LDR：0.015 Gy/min) ((66)/Be(40)) 中子。在暴露于中子剂量范围为 0.125 至 2 Gy 后 30 分钟，研究了 DNA DSB 的诱导。在 1 Gy 中子剂量后不同时间点研究了修复动力学。我们的结果表明，与 LDR 暴露相比，HDR 暴露时 γ-H2AX 焦点形成高 40%。最大 γ-H2AX 焦点水平在照射后 24 小时逐渐降低至 1.65±0.64 焦点/细胞 (LDR) 和 1.29±0.45 (HDR)，仍明显高于背景水平。这说明剂量率对中子诱导的 DNA 损伤有显著影响。尽管在 24 小时后未观察到残留 DNA 损伤的显著差异，但 LDR 暴露的 DSB 修复半衰期比 HDR 暴露慢。结果首次表明，在与中子相关的癌症风险估计中应考虑剂量率。
