Newman Jennifer P A, Banerjee Birendranath, Fang Wanru, Poonepalli Anuradha, Balakrishnan Lakshmidevi, Low Grace Kah Mun, Bhattacharjee Rabindra N, Akira Shizuo, Jayapal Manikandan, Melendez Alirio J, Baskar Rajamanickam, Lee Han-Woong, Hande M Prakash
Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
J Cell Physiol. 2008 Mar;214(3):796-809. doi: 10.1002/jcp.21276.
Telomeres and telomerase appear to participate in the repair of broken DNA ends produced by oxidative damage. Arsenite is an environmental contaminant and a potent human carcinogen, which induces oxidative stress on cells via the generation of reactive oxygen species affecting cell viability and chromosome stability. It promotes telomere attrition and reduces cell survival by apoptosis. In this study, we used mouse embryonic fibroblasts (MEFs) from mice lacking telomerase RNA component (mTERC(-/-) mice) with long (early passage or EP) and short (late passage or LP) telomeres to investigate the extent of oxidative damage by comparing the differences in DNA damage, chromosome instability, and cell survival at 24 and 48 h of exposure to sodium arsenite (As3+; NaAsO2). There was significantly high level of DNA damage in mTERC(-/-) cells with short telomeres as determined by alkaline comet assay. Consistent with elevated DNA damage, increased micronuclei (MN) induction reflecting gross genomic instability was also observed. Fluorescence in situ hybridization (FISH) analysis revealed that increasing doses of arsenite augmented the chromosome aberrations, which contributes to genomic instability leading to possibly apoptotic cell death and cell cycle arrest. Microarray analysis has revealed that As3+ treatment altered the expression of 456 genes of which 20% of them have known functions in cell cycle and DNA damage signaling and response, cell growth, and/or maintenance. Results from our studies imply that short dysfunctional telomeres impair the repair of oxidative damage caused by arsenite. The results will have implications in risk estimation as well as cancer chemotherapy.
端粒和端粒酶似乎参与了由氧化损伤产生的断裂DNA末端的修复过程。亚砷酸盐是一种环境污染物和强效人类致癌物，它通过产生活性氧对细胞诱导氧化应激，从而影响细胞活力和染色体稳定性。它会促进端粒损耗，并通过凋亡降低细胞存活率。在本研究中，我们使用来自缺乏端粒酶RNA组分的小鼠（mTERC(-/-)小鼠）的小鼠胚胎成纤维细胞（MEF），这些细胞具有长（早期传代或EP）和短（晚期传代或LP）端粒，通过比较暴露于亚砷酸钠（As3+；NaAsO2）24小时和48小时后DNA损伤、染色体不稳定性和细胞存活的差异，来研究氧化损伤的程度。通过碱性彗星试验测定，具有短端粒的mTERC(-/-)细胞中DNA损伤水平显著较高。与DNA损伤增加一致，还观察到反映总体基因组不稳定性的微核（MN）诱导增加。荧光原位杂交（FISH）分析表明，亚砷酸盐剂量增加会加剧染色体畸变，这会导致基因组不稳定，可能导致凋亡细胞死亡和细胞周期停滞。微阵列分析显示，As3+处理改变了456个基因的表达，其中20%在细胞周期、DNA损伤信号传导与反应、细胞生长和/或维持方面具有已知功能。我们的研究结果表明，功能失调的短端粒会损害亚砷酸盐引起的氧化损伤的修复。这些结果将对风险评估以及癌症化疗产生影响。
