ATM对辐射后AT细胞端粒酶活性的影响

Effect of ATM on telomerase activity in AT cells exposed to ionizing radiation

目的:探讨ATM对电离辐射照射的毛细血管扩张共济失调症(ataxia telangiectasia,AT)患者皮肤的成纤维细胞系AT细胞(ATSBIVA)端粒酶活性的影响。方法:以源于正常人皮肤的成纤维细胞系GM细胞(GM0639)为对照,应用基于PCR的端粒重复扩增技术(telomeric repeat amplification protocal,TRAP)与高效液相色谱(HPLC)技术,定量分析细胞分别经0、1、3、5 Gy 60Coγ射线照射后以及经3 Gy 60Coγ射线照射后继续培养2、24、48、72 h,AT、空载体AT、ATM+-AT和GM细胞的端粒酶活性的变化。结果:未照射时,除GM细胞外,AT、空载体AT、ATM+-AT细胞均呈现较高的端粒酶活性表达,但ATM+-AT细胞的端粒酶活性明显低于AT和空载体AT细胞的端粒酶活性(P<0．01),而后二者无明显差异(P> 0．05);电离辐射照射后,AT、空载体AT、ATM+-AT和GM细胞的端粒酶活性均呈剂量依赖性和时间依赖性增强,且在相同剂量点与时间点,ATM+-AT细胞的端粒酶活性高于GM细胞(P<0．01)(除5 Gy计量点外),但低于AT和空载体AT细胞(P<0．01),而后二者无明显差异(P>0．05)。结论:电离辐射可诱导细胞端粒酶活性表达;并且细胞端粒酶活性水平随剂量与时间的增加而增加;ATM可下调AT细胞端粒酶活性水平。推测端粒酶参与电离辐射诱导DNA损伤的修复。

Objective：To investigate the effect of ataxia telangiectasia mutated （ATM） genes on telomerase activity of fibroblast cell line （ATSBIVA cells） from the skin of patients with ataxia-telangiectasia （AT） induced by ionizing radiation. Methods： Fibroblast cell line GM0639 originated from the skin of normal people was used as control. Cells were exposed to ^60Coγ irradiation at 0, 1, 3 and 5 Gy. The cells exposed to 3 Gy of ^60Coγ-rays were re-cultured for 2, 24, 48 and 72 h, respectively. PCR based telomeric repeat amplification protocol （TRAP） and HPLC methods were used to determine the telomerase activity in AT, ATM＋AT and GM0639 cells, respectively. Results：Except for GM0639 cells, AT, PEBS7- AT ATM＋AT cells showed high telomerase activity before ionizing radiation. But the ielomerase activity in ATM＋AT cells was significantly lower than that of AT and PEBS7-AT cells （P〈0.01）. The difference in telomerase activity between AT and PEBS7-AT cells was not significant （P〉0.05）. After exposure to ionizing radiation the telomerase activity in AT, PEBS7-AT, ATM ＋AT, and GM0639 cells were significantly increased in a dose- and time-dependent manners. At the same dose point and time point, the telomerase activity in ATM ＋AT cells were significantly higher than that of GM0639 cells （except 5 Gy point）, but still lower than that of AT and PEBS7 AT cells （P〈 0. 01）. But the telomerase activity in AT cells were not significantly different from that in PEBS7-AT cells （P）0.05）. Conclusion： Ionizing radiation induces the increase in telomerase activity in a dose- and time-dependent manners. ATM can down-regulate telomerase activity of AT cells before and after ionizing radiation. It indicates that telomerase participates in the repair process of DNA injury induced by ionizing radiation.