Vanguards of paradigm shift in radiation biology; Radiation-induced adaptive and bystander responses

放射線誘発バイスタンダー効果と適応応答

松本 英樹*; 浜田 信行*; 高橋 昭久*; 小林 泰彦; 大西 武雄*

Matsumoto, Hideki*; Hamada, Nobuyuki*; Takahashi, Akihisa*; Kobayashi, Yasuhiko; Onishi, Takeo*

細胞に低線量の放射線をあらかじめ照射しておくと、高線量の放射線に抵抗性を示すことが知られており、この現象は放射線適応応答と呼ばれている。本総説では、放射線適応応答と、バイスタンダー効果(放射線の生物効果が、直接照射された細胞から、その周囲の非照射細胞に伝達される現象)との関連性を概説する。

The risks of low dose ionizing irradiation ( 100 mSv) have been estimated using a linear no-threshold model by extrapolating from data obtained after high dose irradiation. The validity of this dose-response model is, however, controversial because evidence accumulated for over the past decade has shown that response of living organisms including humans to low dose/low dose-rate radiation is different from that to high dose/high dose-rate radiation. In another words, findings that cannot be explained by the classical "target theory" of radiobiology have accumulated. The radiation-induced adaptive response, bystander effects, low-dose radio-hypersensitivity, and genomic instability are specifically observed in response to low dose/low dose-rate radiation, and underpinnings of these responses often involve biochemical/molecular signals responding to targeted and non-targeted events. Recently, interrelations between the radioadaptive and bystander responses have been increasingly reported. We review observations supporting the existence of the latter two phenomena, and discuss the possible link between them from the aspect of production of reactive oxygen and nitrogen species.