Yang Z, Kodama S, Suzuki K, Watanabe M
Department of Health Sciences, School of Pharmaceutical Sciences, Nagasaki University, Japan.
J Radiat Res. 1998 Mar;39(1):35-51. doi: 10.1269/jrr.39.35.
We examined whether the shortening of telomere structure is related to in vitro cellular aging after multiple low-dose irradiation. We used three strains of HE cells (HE23, HE31, and HE40) exhibiting different levels of telomerase activity and irradiated these cells twice a week with a dose of 2 cGy or 4 cGy of X-rays until they senesced. The cells were in total exposed to doses of 52-208 cGy of X-rays. Only the HE31 cells, which had no telomerase activity, experienced an increase in the number of cell divisions, reaching a maximum of 120-124% of the non-irradiated controls. However, in two strains which did exhibit telomerase activity in an early passage in culture, no extension of cell life span was found. Telomerase-positive cells completely lost all telomerase activity when the cells were subcultured several times without irradiation. In the HE31 cells where the life span was extended, the ratio of cell having a long telomere was higher than those of the other two cells (HE23 and HE40). Cytogenetic analysis revealed that the life span extension due to multiple low-dose irradiation which was observed in HE31 cells did not correlate with specific chromosome alterations. Our results suggest that the telomerase activity remaining in the cells at an early passage does not correlate with the extension of life span in vitro by X-irradiation. The factor other than telomerase activity may play an important role in the regulation of telomere length and the extension of life span.
我们研究了多次低剂量照射后端粒结构缩短是否与体外细胞衰老相关。我们使用了三株端粒酶活性水平不同的HE细胞（HE23、HE31和HE40），每周用2 cGy或4 cGy的X射线对这些细胞照射两次，直至它们衰老。细胞总共接受了52 - 208 cGy的X射线照射。只有没有端粒酶活性的HE31细胞经历了细胞分裂次数的增加，达到未照射对照的120 - 124%的最大值。然而，在培养早期传代时确实表现出端粒酶活性的两株细胞中，未发现细胞寿命延长。当细胞在未照射的情况下传代几次时，端粒酶阳性细胞完全丧失了所有端粒酶活性。在寿命延长的HE细胞中，具有长端粒的细胞比例高于其他两株细胞（HE23和HE40）。细胞遗传学分析表明，在HE31细胞中观察到的多次低剂量照射导致的寿命延长与特定的染色体改变无关。我们的结果表明，早期传代时细胞中残留的端粒酶活性与X射线照射导致的体外寿命延长无关。除端粒酶活性外的其他因素可能在端粒长度调节和寿命延长中起重要作用。
