Effects of Low-Dose Irradiation Using Unsealed Caesium-137 on Cultured Normal Human Cells. Homo sapiens

Caesium-137 (Cs-137) is one of the major radionuclides appearing in the natural environment after nuclear power plant accidents. However, the biological effects of low-dose internal irradiation with this radionuclide remain unclear. We developed an experimental model for studying low-dose internal irradiation using cultured human cells. The cells were incubated in the culture medium supplemented with unsealed Cs-137 chloride. We used the Monte Carlo simulation method for measuring internal irradiation because making direct measurements was not possible. The simulation revealed that 96.40%?99.70% of the internal irradiation involved ?-particles and other electrons. During the experiment, a gradual incorporation of Cs-137 in the cells, and the absorbed dose rate increased in a time-dependent manner. In addition, the number of ?-H2AX and 53BP1 nuclear foci in the cells increased by internal irradiation in a dose-dependent manner. Microarray analysis revealed time-dependent alterations in gene expression caused by the radiation. These results demonstrate that our experimental system can be useful in the investigation of the effects of low-dose internal irradiation. Overall design: HUVECs synchronized in G1 cell cycle phase were irradiated by unsealed cesium-137 in culture medium at 0.0146 mGy per minute (0.675 mGy) externally and 0.0152 mGy per minute (2.09 mGy/ hr), 0.0159 mGy per minute (4.66 mGy/ hr)for 1, 3 and 6 h, respectively. Experiments were biologically duplicated.

铯-137（Caesium-137，Cs-137）是核电站事故后自然环境中出现的主要放射性核素之一。然而，该放射性核素低剂量内照射的生物学效应仍不明确。我们构建了一套基于体外培养人类细胞的低剂量内照射研究实验模型，将细胞置于添加了未密封氯化铯-137的培养基中进行孵育培养。鉴于无法直接开展内照射剂量测量，我们采用蒙特卡洛（Monte Carlo）模拟法进行剂量测算。模拟结果显示，96.40%~99.70%的内照射贡献来自β粒子及其他电子辐射。实验过程中，细胞对Cs-137的摄取量逐渐升高，细胞吸收剂量率呈时间依赖性递增。此外，经内照射处理的细胞中，γ-H2AX与53BP1核焦点的数量呈剂量依赖性增加。基因芯片（Microarray）分析结果显示，辐射诱导的基因表达变化呈时间依赖性特征。上述结果证实，本实验系统可有效用于低剂量内照射效应的相关研究。实验总体设计：将同步化于G1细胞周期时相的人脐静脉内皮细胞（Human Umbilical Vein Endothelial Cells, HUVECs）置于培养基中，分别以0.0146 mGy/分钟（总剂量0.675 mGy）、0.0152 mGy/分钟（2.09 mGy/小时）及0.0159 mGy/分钟（4.66 mGy/小时）的剂量率，通过添加未密封氯化铯-137的培养基进行1小时、3小时及6小时的内照射处理。本实验设置生物学重复。