Quantitative detection of γ-radiation-induced DNA double-strand breaks using γ-H2AX foci in mouse organs, lymphocytes and scid lymphoma cell line

一些生物标记，突变，染色体畸变，微核，菌落形成等已被用于测量辐射剂量。然而，需要大量的动物或细胞来测量这种由辐射引起的低频率事件。为了更精确和灵敏地测量辐射损伤，最好检测辐照后细胞的第一个或最早的事件（DNA双链断裂），特别是在修复缺陷细胞或动物中。小鼠（C.B17株）和scid淋巴瘤细胞（来自C.B17-scid小鼠）暴露于^<137 bb0（0.1、0.2、0.5、1、2和4 Gy）的cs γ射线中。通过测量细胞内γ-H2AX灶的信号强度或计数荧光信号数，定量测定scid淋巴瘤细胞、C.B17外周淋巴细胞和器官的DNA双链断裂。γ-H2AX聚焦在照射后3 min内出现，60 min达到最大荧光。在淋巴细胞、淋巴瘤细胞和来自小鼠器官（脑、肝、肾、睾丸）的细胞中，发现γ-H2AX病灶数量与辐射剂量之间的关系在整个剂量范围内呈线性关系。这些结果表明，用γ-H2AX焦点定量DNA双链断裂是检测小鼠高、低剂量辐射损伤的一种有用的生物剂量计。有趣的是，在小肠绒毛细胞中，辐照后γ-H2AX灶未见增加。与γ-H2AX磷酸化相关的基因应该在器官的所有细胞中表达，以修复由辐射和化学物质等环境影响引起的自发DNA双链断裂，然而，这些必要的系统似乎并不是在所有器官中都起作用。

Several biological markers, mutation, chromosome aberration, microneuclei, colony formation, etc. have been used to measure radiation doses. However, enormous numbers of animals or cells are required to measure such low frequent events induced by radiations. To measure the radiation damage more precisely and sensitively, it is better to detect the first or earliest events in cells after irradiation (DNA double-strand breaks), especially in repair deficient cells or animals. Mice (C.B17 strain) and scid lymphoma cells (from C.B17-scid mice) were exposed to ^<137>Csγ-rays (0.1, 0.2, 0.5, 1, 2 and 4 Gy). Quantitation of DNA double-strand breaks in scid lymphoma cells, C.B17 peripheral lymphocytes, and organs was carried out by measuring signal intensity or counting fluorescence signal number of γ-H2AX foci in cells. The γ-H2AX foci appeared within 3 min after irradiation and reached a maximum fluorescence in 60 min. In lymphocytes, lymphoma cells, and cells from the mouse organs (brain, liver, kidney, testis), the relationships between the numbers of γ-H2AX foci and radiation dose was found to be linear over the entire dose range studied. These results suggest that quantitation of DNA double-strand breaks by the γ-H2AX foci is an useful biodosimeter for detecting high and low dose radiation damage in mice. Intriguingly, in the villi cells from the small intestine, no increase of γ-H2AX foci was found after irradiation. Genes related to the γ-H2AX phosphorylation are supposed to express in all cells of organs to repair spontaneous DNA double-strand breaks caused environmental effects, e.g. radiation and chemicals, however, it seems that theses essential systems are not working in all organs.