细胞质受照射的遗传损伤效应

GENOTOXIC EFFECTS OF CYTOPLASMIC IRRADIATION

通过使用精确单粒子微束装置照射人与中国仓鼠杂交AL 细胞细胞质 ,显示α粒子照射细胞质只有轻微的致死率 ,照射 16个α粒子后仍有 76%的细胞可以存活。诱变试验结果发现 ,尽管单个α粒子照射细胞质在CD59基因位点诱变频率较低 ,但 8个或多于 8个α粒子可诱导出高于未受照射对照 3倍的诱变频率聚合酶链式反应 (PCR)分析发现 ,照射细胞质诱导的CD59- 基因突变子其 11号染色体上Wilms肿瘤 (WT)、过氧化氢酶 (CAT)、(H -rasRAS)、甲状旁腺激素(PTH)、(脱脂蛋白 -A1APO -A1)等基因缺失率很小 ,其突变谱类似于自发突变子的突变谱。DMSO或BSO处理细胞的研究显示 ,自由基清除剂DMSO可降低照射细胞质所诱发的CD59基因突变频率 ;与此相反 ,能与细胞内的谷胱甘肽结合的BSO可增加突变频率。结果表明 ,自由基很可能是照射细胞质诱发突变的主要原因之一。此外 ,用IF7单克隆抗体进行的 8-羟基脱氧鸟苷免疫过氧化物酶染色反应发现照射细胞质可在核内引起DNA的氧化损伤。

Abstract: Using a charged particle microbeam whereby individual cell's cytoplasm could be irradiated with a single or an exact number of α particles, cell lethality, mutation induction and the functional role of reactive oxygen species in mediating the mutagenic response in the human-hamster hybrid (A L) cell assay system were assayed. The results showed that cytoplasm irradiation induced very little toxicity such that traversal through the cytoplasm with 16 alpha particles resulted in a cell survival fraction of -0.76. While cytoplasmic traversal with one particles induced relatively few CD59 - mutant cells, those irradiated with 8 or more particles had an induced mutant frequency that was -3 fold higher than the background incidence. PCR analysis showed that CD59 - mutation induced by cytoplasmic radiation involved almost exclusively small alterations similar to those of spontaneous origin. Treatment of cells with dimethyl sulfoxide (DMSO) suppressed the mutant frequency induced by cytoplasmic irradiation, whereas buthionine S-R-sulfoximine (BSO) treatment which reduces intracellular glutathione level, increased the mutation frequency. These novel findings showed that the mechanism of mutation by cytoplasmic irradiation was heavily dependent on oxyradicals. Moreover, using IF 7 monoclonal antibody to detect 8-OHdG induction, the data indicated that cytoplasmic irradiation generate oxidative DNA damage in the nuclei of the target cells.