Wang Lu, Kuwahara Yoshikazu, Li Li, Baba Taisuke, Shin Ryong-Woon, Ohkubo Yasuhito, Ono Koji, Fukumoto Manabu
Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Seiryo-machi, Sendai, Japan.
Int J Radiat Biol. 2007 Jul;83(7):433-42. doi: 10.1080/09553000701370878.
In order to identify supportive evidence of radiation exposure to cells, we analyzed the relationship between exposure to ionizing radiation and the induction of deletions in mitochondrial DNA (mtDNA).
Using human hepatoblastoma cell line, HepG2 and its derivatives, HepG2-A, -89 and -400, established after long term exposure to X-ray, mtDNA deletions were analyzed by polymerase chain reaction (PCR) and real-time PCR after cells were subjected to radiation and genotoxic treatments.
Common Deletion (CD), the most extensively studied deletion of mtDNA, was induced within 24 h after exposure to 5 Gray (Gy) of X-rays and was associated with replication of mtDNA. CD became undetectable several days after the exposure due to the death of cells containing mitochondria within which CD had been induced. Furthermore, we found a novel mtDNA deletion that consisted of a 4934 base-pair deletion (4934del) between nucleotide position 8435 and 13,368. A lower dose of ionizing radiation was required to induce the 4934del than for CD and this was independent of the quality of radiation used and was not induced by treatments with hydrogen peroxide (H(2)O(2)) and other genotoxic reagents including bleomycin.
CD is induced by ionizing radiation, however, the amount of CD detected at a certain point in time after radiation exposure is dependent on the initial frequency of CD induced and the death rate of cells with mtDNA containing CD. The novel mtDNA deletion found in this study, therefore, will be used to determine whether cells were exposed to ionizing radiation.
为了确定细胞辐射暴露的支持性证据，我们分析了电离辐射暴露与线粒体DNA（mtDNA）缺失诱导之间的关系。
使用人肝癌细胞系HepG2及其衍生物HepG2-A、-89和-400，这些细胞系是在长期暴露于X射线后建立的。在细胞接受辐射和基因毒性处理后，通过聚合酶链反应（PCR）和实时PCR分析mtDNA缺失情况。
常见缺失（CD）是mtDNA中研究最广泛的缺失，在暴露于5格雷（Gy）X射线后24小时内被诱导，并且与mtDNA的复制有关。由于含有已诱导出CD的线粒体的细胞死亡，暴露几天后CD变得无法检测到。此外，我们发现了一种新的mtDNA缺失，它由核苷酸位置8435和13368之间4934个碱基对的缺失（4934del）组成。诱导4934del所需的电离辐射剂量低于CD，这与所使用辐射的质量无关，并且不会由过氧化氢（H₂O₂）和包括博来霉素在内的其他基因毒性试剂处理诱导产生。
CD由电离辐射诱导，然而，辐射暴露后某一时刻检测到的CD量取决于诱导的CD初始频率以及含有CD的mtDNA的细胞死亡率。因此，本研究中发现的新的mtDNA缺失将用于确定细胞是否暴露于电离辐射。
