Research Center for Radiation Protection, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan.
Radiat Res. 2010 Oct;174(4):532-6. doi: 10.1667/RR2133.1.
Induction of an adaptive response by priming X rays in combination with challenge irradiations from high-LET accelerated heavy ions was attempted in young adult female C57BL/6J Jms mice using 30-day survival after the challenge irradiations as an index. Three kinds of accelerated heavy ions from monoenergetic beams of carbon, silicon and iron ions with LETs of about 15, 55 and 200 keV/μm, respectively, were examined. A priming low dose of 0.50 Gy X rays in combination with a challenging dose of 7.50 Gy was used in the animals serving as a positive control group to confirm the successful induction of an adaptive response. The priming low dose of 0.50 Gy X rays was also used in combination with accelerated heavy ions. The priming low dose of X rays significantly reduced the mortality from the high challenge doses of carbon or silicon particles but not from iron particles. These results indicate that an adaptive response could be induced by priming low-LET X rays in combination with subsequent challenge high-LET irradiations from certain kinds of accelerated heavy ions, and successful induction of an adaptive response would possibly be an event related to the LET and/or the type of heavy ions. This is the first time that the existence of an adaptive response induced by low-LET X rays against high-LET whole-body irradiation in mice has been demonstrated. These findings would provide new insight into the radiation-induced adaptive response in vivo.
采用年轻成年雌性 C57BL/6J Jms 小鼠，以挑战照射后 30 天的存活率作为指标，尝试用低剂量 X 射线预处理联合高 LET 重离子（加速）的挑战照射来诱导适应性反应。使用三种不同 LET 的加速重离子束，即碳、硅和铁离子，LET 值分别约为 15、55 和 200 keV/μm。用 0.50 Gy X 射线预处理联合 7.50 Gy 挑战剂量的方案作为阳性对照组，用于确认适应性反应的成功诱导。X 射线的低剂量预处理（0.50 Gy）也与加速重离子联合使用。X 射线的低剂量预处理显著降低了碳或硅粒子的高挑战剂量引起的死亡率，但对铁粒子没有影响。这些结果表明，低 LET X 射线预处理联合某些种类的加速重离子的后续高 LET 照射可以诱导适应性反应，而成功诱导适应性反应可能与 LET 和/或重离子的类型有关。这是首次在小鼠中证明低 LET X 射线对高 LET 全身照射诱导适应性反应的存在。这些发现将为体内辐射诱导适应性反应提供新的见解。
