Costes Sylvain V, Boissière Arnaud, Ravani Shraddha, Romano Raquel, Parvin Bahram, Barcellos-Hoff Mary Helen
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Radiat Res. 2006 May;165(5):505-15. doi: 10.1667/RR3538.1.
In this study, we investigated the formation of radiation-induced foci in normal human fibroblasts exposed to X rays or 130 keV/mum nitrogen ions using antibodies to phosphorylated protein kinase ataxia telangiectasia mutated (ATMp) and histone H2AX (gamma-H2AX). High-content automatic image analysis was used to quantify the immunofluorescence of radiation-induced foci. The size of radiation-induced foci increased for both proteins over a 2-h period after nitrogen-ion irradiation, while the size of radiation-induced foci did not change after exposure to low-LET radiation. The number of radiation-induced ATMp foci showed a more rapid rise and greater frequency after X-ray exposure and was resolved more rapidly such that the frequency of radiation-induced foci decreased by 90% compared to 60% after exposure to high-LET radiation 2 h after 30 cGy. In contrast, the kinetics of radiation-induced gamma-H2AX focus formation was similar for high- and low-LET radiation in that it reached a plateau early and remained constant for up to 2 h. High-resolution 3D images of radiation-induced gamma-H2AX foci and dosimetry computation suggest that multiple double-strand breaks from nitrogen ions are encompassed within large nuclear domains of 4.4 Mbp. Our work shows that the size and frequency of radiation-induced foci vary as a function of radiation quality, dose, time and protein target. Thus, even though double-strand breaks and radiation-induced foci are correlated, the dynamic nature of both contradicts their accepted equivalence for low doses of different radiation qualities.
在本研究中，我们使用针对磷酸化共济失调毛细血管扩张突变蛋白激酶（ATMp）和组蛋白H2AX（γ-H2AX）的抗体，研究了正常人类成纤维细胞在暴露于X射线或130 keV/μm氮离子后辐射诱导灶的形成。采用高内涵自动图像分析对辐射诱导灶的免疫荧光进行定量。氮离子照射后2小时内，两种蛋白的辐射诱导灶大小均增加，而低线性能量传递辐射暴露后辐射诱导灶大小未发生变化。X射线照射后，辐射诱导的ATMp灶数量上升更快且频率更高，并且消散更快，以至于在30 cGy照射后2小时，与高LET辐射后60%相比，辐射诱导灶的频率降低了90%。相比之下，高LET和低LET辐射诱导的γ-H2AX灶形成动力学相似，即早期达到平台期并在长达2小时内保持恒定。辐射诱导的γ-H2AX灶的高分辨率3D图像和剂量学计算表明，氮离子产生的多个双链断裂包含在4.4 Mbp的大核区域内。我们的研究表明，辐射诱导灶的大小和频率随辐射质量、剂量、时间和蛋白质靶点而变化。因此，尽管双链断裂与辐射诱导灶相关，但两者的动态特性与它们在低剂量不同辐射质量下被认可的等效性相矛盾。
