叠氮胸苷对人胶质瘤细胞辐射后DNA双链损伤修复的影响

Effects of AZT on the Repair of DNA Double-strand Breaks of Human Malignant Glioma Cells after Radiation

目的观察逆转录酶抑制剂叠氮胸苷(AZT)对人脑胶质瘤U251放射性DNA损伤双链修复(DSB),探讨其放射增敏的机制。方法实验分为4个组:空白组:未行AZT与γ-射线处理;放射组:细胞接受2 Gyγ射线单次照射;加药组:细胞培养液中加入终浓度为0.8 mm/L的AZT,作用24 h;药放组:细胞经过0.8 mm/L的AZT作用24 h后,再行2 Gyγ射线单次照射。用中性单细胞凝胶电泳方法检测辐射后DNA双链断裂(尾矩)。结果空白组与加药组细胞无慧尾,表明AZT本身不会导致DNADSB。而放射组和药放组均出现明显的彗星图象,药放组的初始DSB与放射组相比无显著性差异(P>0.05)。但前者的修复速度较慢,照射后2 h放射组的DSB基本修复完全,而药放组仍有50%的残留。结论AZT的放射增敏作用机制与其对DNA DSB的修复有关。

Objective To investigate the effect of AZT（3＇-azido-3＇- deoxythmidine） combined with irradiation on the repair of DNA double-strand breaks of U251 cells（Human Malignant Glioma Cells）,and discuss the mechanism of its radiosensitization. Methods There are four groups in the experiment：control group：no disposal of AZT or 7-irradiation. radiation group：cells accept 2 Gy 7-irradiation as single fraction irradiation. AZT group ： adding the final concentration of 0.8 mm/L AZT in the cell culture fluid in 24 h. AZT combined with radiation group：after dealt with 0.8 mm/L AZT 24 h, cells are given to 2 Gy ）＇-irradiation assingle fraction irradiation. Detecting DNA double-strand breaks（tail moment,TM） after radiation with neutral single cell gel electrophoresis. Results The cells in control group and radiation group don＇ t exist rational awareness tail,it shows that AZT itself don＇ t result to DNA double-strand breaks. Nevertheless radiation group and AZT combined with radiation group all show up obvious comet figure, the incipient DSB of AZT combined with radiation group compared with radiation group is not significant dlfference（P 〉 0.05）. But the former＇s repair speed is slow,after 2 h with radiation, the DSB of radiation group is basically repaired completely,as a contrast, there is 50% remained in AZT combined with radiation group. Conclusion The role of AZT radiosensitization mechanisms may be related with its role of DNA DSB repair.