Radiation Safety Research Center, Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry, CRIEPI, Komae-shi, Tokyo 201-8511, Japan.
Radiat Res. 2010 Jul;174(1):37-45. doi: 10.1667/RR2086.1.
Radiation-induced bystander effects are the biological responses exhibited by cells adjacent to cells that have been traversed by charged particles. Using a synchrotron X-ray microbeam irradiation system, we irradiated five cells in two different ways: by targeting the nuclei with 10 microm x 10-microm 5.35 keV X-ray beams and by irradiating the whole cells with 50 microm x 50-microm 5.35 keV X-ray beams. Then we measured the clonogenic survival of the bystander cells. When only the nuclei were irradiated, a parabolic enhancement of bystander cell death was observed in a dose-dependent manner in the low-dose region around 1 Gy. In contrast, the surviving fraction of bystander cells decreased monotonically when whole cells were irradiated. Addition of carboxy-PTIO, a specific scavenger of nitric oxide (NO), suppressed bystander cell death in both cases. These results indicate that NO is a mediator in the induction of the parabolic and monotonic types of bystander cell death. Moreover, from the spatial analysis, we found that the parabolic type of bystander cell death was induced primarily within 1 mm of irradiated cells. Our findings demonstrate that the induction of bystander cell death depends on the sites of energy deposition in irradiated cells.
辐射诱导的旁观者效应是指细胞受到带电粒子穿过的细胞的影响而表现出的生物学反应。使用同步辐射 X 射线微束辐照系统，我们以两种不同的方式辐照了五个细胞：用 10 微米 x 10 微米 5.35 千电子伏特 X 射线束靶向细胞核，并用 50 微米 x 50 微米 5.35 千电子伏特 X 射线束辐照整个细胞。然后，我们测量了旁观者细胞的集落形成存活能力。当仅辐照细胞核时，在低剂量区域（约 1 Gy 左右），旁观者细胞死亡呈抛物线增强，呈剂量依赖性。相比之下，当整个细胞被辐照时，旁观者细胞的存活分数呈单调递减。添加羧基-PTIO，一种特定的一氧化氮（NO）清除剂，抑制了两种情况下的旁观者细胞死亡。这些结果表明，NO 是诱导抛物线和单调型旁观者细胞死亡的介质。此外，从空间分析中，我们发现抛物线型旁观者细胞死亡主要发生在辐照细胞的 1 毫米范围内。我们的研究结果表明，旁观者细胞死亡的诱导取决于辐照细胞中能量沉积的部位。
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