Contributions of Direct and Indirect Actions in Cell Killing by High-LET Radiations
Contributions of Direct and Indirect Actions in Cell Killing by High-LET Radiations
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DOI：
10.1667/rr1490.1
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发表时间：
2009-02-01
影响因子：
3.4
通讯作者：
Furusawa, Yoshiya
中科院分区：
文献类型：
--
作者：
Hirayama, Ryoichi;Ito, Atsushi;Furusawa, Yoshiya
平山河，伊藤，A.，Tomita，M.，Tsukada，T.，Yatagai，F.，野口，M.，松本，Y.，Kase，Y.，Ando，K.，Okayasu河，和Furusawa，F.直接和间接作用在高LET辐射杀死细胞中的作用。Radiat. Res. 171，212-218（2009）.辐射的生物效应主要源于对DNA的损伤。X射线和重离子对DNA的损伤是由直接和间接作用共同引起的。间接作用在细胞杀伤中的贡献可以从二甲基亚砜（DMSO）的最大保护程度来估计，二甲基亚砜抑制间接作用而不影响直接作用。指数生长的中国仓鼠V79细胞暴露于高LET辐射的20至2106千电子伏/μ m的存在或不存在的DMSO和它们的生存使用集落形成测定。间接作用对细胞杀伤的贡献随着LET的增加而降低。然而，即使在非常高的LET的贡献没有达到零，估计为32%的LET为2106千电子伏/亩米。因此，即使放射化学估计的G值的OH自由基是几乎为零，在LET为1000千电子伏/μ m，间接作用的OH自由基的生物效应的高LET辐射贡献了很大一部分。在10%的存活水平下测定的RBE随着LET的增加而增加，在200 keV/mu m时达到最大值2.88，此后下降。当分别估算直接作用（RBE（D））和间接作用（RBE，）的RBE时，两者都表现出与RBE相似的LET依赖性，峰值为200 keV/μ m。然而，RBE（D）（5.99）的峰值远高于RBE（I）（1.89）。因此，直接作用比间接作用对高LET辐射的高RBE贡献更大。(C)2009年，辐射研究学会
Hirayama, R., Ito, A., Tomita, M., Tsukada, T., Yatagai, F., Noguchi, M., Matsumoto, Y., Kase, Y., Ando, K., Okayasu, R., and Furusawa, F. Contributions of Direct and Indirect Actions in Cell Killing by High-LET Radiations. Radiat. Res. 171, 212-218 (2009).The biological effects of radiation originate principally in damages to DNA. DNA damages by X rays as well as heavy ions are induced by a combination of direct and indirect actions. The contribution of indirect action in cell killing can be estimated from the maximum degree of protection by dimethylsulfoxide (DMSO), which suppresses indirect action without affecting direct action. Exponentially growing Chinese hamster V79 cells were exposed to high-LET radiations of 20 to 2106 keV/mu m in the presence or absence of DMSO and their survival was determined using a colony formation assay. The contribution of indirect action to cell killing decreased with increasing LET. However, the contribution did not reach zero even at very high LETs and was estimated to be 32% at an LET of 2106 keV/mu m. Therefore, even though the radiochemically estimated G value of OH radicals was nearly zero at an LET of 1000 keV/mu m, indirect action by OH radicals contributed to a substantial fraction of the biological effects of high-LET radiations. The RBE determined at a survival level of 10% increased with LET, reaching a maximum value of 2.88 at 200 keV/mu m, and decreased thereafter. When the RBE was estimated separately for direct action (RBE(D)) and indirect action (RBE,); both exhibited an LET dependence similar to that of the RBE, peaking at 200 keV/mu m. However, the peak value was much higher for RBE(D) (5.99) than RBE(I) (1.89). Thus direct action contributes more to the high RBE of high-LET radiations than indirect action does. (C) 2009 by Radiation Research Society