Kanasugi Yuichi, Hamada Nobuyuki, Wada Seiichi, Funayama Tomoo, Sakashita Tetsuya, Kakizaki Takehiko, Kobayashi Yasuhiko, Takakura Kaoru
Physics Department, International Christian University, Tokyo, Japan.
Int J Radiat Biol. 2007 Feb;83(2):73-80. doi: 10.1080/09553000601121116.
To investigate the role of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) in the medium-mediated bystander effect for chromosomal aberrations induced by low-linear energy transfer (LET) X-rays and high-LET heavy ions in normal human fibroblast cells.
The recipient cells were treated for 12 h with conditioned medium, which was harvested from donor cells at 24 h after exposure to 10 Gy of soft X-rays (5 keV/microm) and 20Ne ions (437 keV/microm), followed by analyses of chromosome aberrations in recipient cells with premature chromosome condensation methods. To examine the role of DNA-PKcs and nitric oxide (NO), cells were treated with its inhibitor LY294002 (LY) and its scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (c-PTIO), respectively.
Increased frequency of chromosome aberrations in recipient cells treated with conditioned medium from irradiated but not from un-irradiated donor cells was observed which was independent of radiation type. Bystander induction of chromosome aberrations in recipient cells was mitigated when donor cells were treated with LY before irradiation and with c-PTIO after irradiation, and was enhanced when recipient cells were treated with LY before treatment of recipient cells with conditioned medium from irradiated donor cells.
Irradiated normal human cells secrete NO and other molecules which in turn transmit radiation signals to unirradiated bystander cells, leading to the induction of bystander chromosome aberrations partially repairable by DNA-PKcs-mediated DNA damage repair machinery, such as non-homologous end-joining repair pathways.
研究DNA依赖蛋白激酶催化亚基（DNA-PKcs）在低线性能量转移（LET）X射线和高线性能量转移重离子诱导正常人成纤维细胞染色体畸变的介质介导旁观者效应中的作用。
受体细胞用条件培养基处理12小时，该条件培养基是在供体细胞暴露于10 Gy软X射线（5 keV/μm）和20Ne离子（437 keV/μm）24小时后收集的，随后用早熟染色体凝聚法分析受体细胞中的染色体畸变。为了研究DNA-PKcs和一氧化氮（NO）的作用，细胞分别用其抑制剂LY294002（LY）及其清除剂2-(4-羧基苯基)-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物（c-PTIO）处理。
观察到用来自受辐照而非未受辐照供体细胞的条件培养基处理的受体细胞中染色体畸变频率增加，这与辐射类型无关。当供体细胞在辐照前用LY处理且在辐照后用c-PTIO处理时，受体细胞中旁观者诱导的染色体畸变减轻，而当受体细胞在用来自受辐照供体细胞的条件培养基处理前用LY处理时，旁观者诱导的染色体畸变增强。
受辐照的正常人细胞分泌NO和其他分子，这些分子进而将辐射信号传递给未受辐照的旁观者细胞，导致旁观者染色体畸变的诱导，部分可由DNA-PKcs介导的DNA损伤修复机制修复，如非同源末端连接修复途径。
