Little John B
Harvard School of Public Health, Center for Radiation Sciences and Environmental Health, 665 Huntington Avenue, Boston, MA 02115, USA.
Health Phys. 2006 Nov;91(5):416-26. doi: 10.1097/01.HP.0000232847.23192.3e.
Traditional thinking has been that the biological effects of ionizing radiation occur in irradiated cells as a consequence of the DNA damage they incur. This implies that (1) biological effects occur only in irradiated cells, (2) radiation traversal through the nucleus of the cell is a prerequisite to produce a biological response, and (3) DNA is the target molecule in the cell. Evidence has been emerging, however, for non-DNA targeted effects of radiation; that is, effects including mutations, chromosomal aberrations, and changes in gene expression that occur in cells that in themselves receive no radiation exposure. Two of these phenomena will be described in this paper. The first is radiation-induced genomic instability whereby biological effects, including elevated frequencies of mutations and chromosomal aberrations, arise in the distant descendants of irradiated cells. The second phenomenon has been termed the "bystander effect," whereby in a mixed population of irradiated and nonirradiated cells, biological effects arise in those cells that receive no radiation exposure. The damage signals are transmitted from cell to cell through gap junction channels, and the genetic effects observed in bystander cells appear to result from an upregulation of oxidative stress. The possible influence of these nontargeted effects of radiation on the response to low-dose exposures is discussed.
传统观念认为，电离辐射的生物学效应是由于其对受照射细胞造成DNA损伤而产生的。这意味着：（1）生物学效应仅发生在受照射细胞中；（2）辐射穿过细胞核是产生生物学反应的前提条件；（3）DNA是细胞中的靶分子。然而，越来越多的证据表明存在辐射的非DNA靶向效应，即包括突变、染色体畸变以及基因表达变化等效应，这些效应出现在自身未受到辐射照射的细胞中。本文将描述其中两种现象。第一种是辐射诱导的基因组不稳定性，即受照射细胞的远代后代中出现包括突变频率和染色体畸变频率升高在内的生物学效应。第二种现象被称为“旁观者效应”，即在受照射细胞和未受照射细胞的混合群体中，未受辐射照射的细胞出现生物学效应。损伤信号通过间隙连接通道在细胞间传递，旁观者细胞中观察到的遗传效应似乎是由氧化应激上调所致。本文还讨论了辐射的这些非靶向效应可能对低剂量照射反应产生的影响。
