Iyer Rashi, Lehnert Bruce E
Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Radiat Res. 2002 Jan;157(1):3-7. doi: 10.1667/0033-7587(2002)157[0003:apiiit]2.0.co;2.
Numerous investigators have reported that direct exposure of cells to a low dose of ionizing radiation can induce a condition of enhanced radioresistance, i.e. a "radioadaptive" response. In this report, we investigated the hypothesis that a radioadaptive bystander effect may be induced in unirradiated cells by a transmissible factor(s) present in the supernatants of cells exposed to a low dose of alpha particles. Normal human lung fibroblasts (HFL-1) were irradiated with 1 cGy of alpha particles and their supernatants were transferred to unirradiated HFL-1 cells as a bystander cell model. Compared to directly irradiated cells that were not treated with supernatants from HFL-1 cells exposed to low-dose radiation, such treatment resulted in increased clonogenic survival after subsequent exposure to 10 and 19 cGy of alpha particles. Increases in protein levels of AP-endonuclease, a redox and DNA base excision repair protein, were found in the bystander cells, but not in directly irradiated cells. Supernatants from alpha-particle-irradiated cells were also found to increase the clonogenicity of unirradiated cells. These results, in conjunction with our earlier findings that supernatants from cells exposed to a low dose of alpha particles contain growth-promoting activity, suggest that this new bystander effect may be related to an increase in DNA repair and cell growth/cell cycle regulation.
许多研究人员报告称，将细胞直接暴露于低剂量电离辐射可诱导一种增强的辐射抗性状态，即“辐射适应性”反应。在本报告中，我们研究了一种假说，即暴露于低剂量α粒子的细胞上清液中存在的可传递因子可能会在未受辐照的细胞中诱导辐射适应性旁观者效应。将正常人肺成纤维细胞（HFL-1）用1 cGy的α粒子进行辐照，并将其上清液转移至未受辐照的HFL-1细胞作为旁观者细胞模型。与未用暴露于低剂量辐射的HFL-1细胞的上清液处理的直接辐照细胞相比，这种处理导致在随后暴露于10和19 cGy的α粒子后克隆形成存活率增加。在旁观者细胞中发现了AP内切核酸酶（一种氧化还原和DNA碱基切除修复蛋白）的蛋白质水平升高，但在直接辐照的细胞中未发现。还发现α粒子辐照细胞的上清液可增加未受辐照细胞的克隆形成能力。这些结果，连同我们早期的发现，即暴露于低剂量α粒子的细胞的上清液含有促进生长的活性，表明这种新的旁观者效应可能与DNA修复增加以及细胞生长/细胞周期调控有关。
