State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People’s Republic of China.
J Radiat Res. 2011;52(2):159-67. doi: 10.1269/jrr.10087. Epub 2011 Feb 19.
Non-targeted effects induced by ionizing radiation have been demonstrated both in vitro and in vivo. Previously, we have also demonstrated the existence of non-targeted effects in intact Arabidopsis seeds following low-energy heavy-ion radiation. In the present study, 6.5 MeV protons with 8 × 10(11) ions/cm(2) and 2 × 10(11) ions/cm(2) fluence respectively were used to irradiate non-shielded or partial-shielded Arabidopsis seeds to further explore the mechanisms which regulate in vivo non-targeted effects and to investigate the difference between damage caused by non-targeted effects and direct irradiation. Results showed that excess reactive oxygen species (ROS) are present in the non-irradiated part of the partially irradiated samples, indicating that in vivo non-targeted effects can promote the generation of excess metabolic ROS in the non-irradiated shoot apical meristem/root apical meristem cells. Furthermore, pretreatment with 0.5% ROS scavenger dimethyl sulfoxide (DMSO) or 0.02 mM reactive nitrogen species (RNS) scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) significantly suppresses the non-targeted effects in the partially irradiated samples, while in the whole-body irradiated samples, the cPTIO pretreatment has no effect. On the other hand using antioxidant enzyme assays, superoxide dismutase activity was found to increase for partial irradiated samples and decrease for the whole-body exposed seeds. Taken together, these results implicate that damage caused by non-targeted effects is different from that induced by direct irradiation in vivo. Metabolic products such as ROS and RNS are involved in the in vivo non-targeted effects.
电离辐射诱导的非靶向效应已在体外和体内得到证实。以前，我们还在低能重离子辐射后的完整拟南芥种子中证明了非靶向效应的存在。在本研究中，使用 6.5 MeV 质子，剂量分别为 8×10(11)ions/cm(2)和 2×10(11)ions/cm(2)，对非屏蔽或部分屏蔽的拟南芥种子进行辐照，以进一步探索调节体内非靶向效应的机制，并研究非靶向效应引起的损伤与直接辐照之间的差异。结果表明，部分辐照样品的非照射部分存在过量的活性氧（ROS），表明体内非靶向效应可以促进非照射茎尖分生组织/根尖分生组织细胞中过量代谢 ROS 的产生。此外，用 0.5%ROS 清除剂二甲亚砜（DMSO）或 0.02 mM 活性氮物质（RNS）清除剂 2-4-羧基苯基-4,4,5,5-四甲基咪唑啉-1-氧-3-氧化物（cPTIO）预处理可以显著抑制部分辐照样品中的非靶向效应，而在全身辐照样品中，cPTIO 预处理没有影响。另一方面，通过抗氧化酶测定发现，超氧化物歧化酶活性在部分辐照样品中增加，而在全身暴露种子中减少。总之，这些结果表明，非靶向效应引起的损伤与体内直接辐射诱导的损伤不同。ROS 和 RNS 等代谢产物参与了体内非靶向效应。
