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Yokota, Yuichiro; Funayama, Tomoo; Muto, Yasuko*; Ikeda, Hiroko; Kobayashi, Yasuhiko
International Journal of Radiation Biology, 91(5), p.383 - 388, 2015/05
Times Cited Count：11 Percentile：64.26(Biology)We investigated the dependence of the bystander cell-killing effect on radiation dose and quality, and related molecular mechanisms. Human fibroblasts were irradiated with 
-rays or carbon ions and co-cultured with non-irradiated cells. Survival rates of non-irradiated cells decreased and nitrite concentrations in culture medium increased with increasing doses. Their dose responses were similar between -rays and carbon ions. Treatment of the specific nitric oxide (NO) radical scavenger prevented reductions in survival rates of non-irradiated cells. Negative relationships were observed between survival rates and nitrite concentrations. From these results, it was concluded that the bystander cell-killing effect mediated by NO radicals in human fibroblasts depends on irradiation doses, but not on radiation quality. NO radical production appears to be an important determinant of -ray- and carbon-ion-induced bystander effects.
Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Sakashita, Tetsuya; Suzuki, Michiyo; Kobayashi, Yasuhiko
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 75, 2015/03
We investigated the bystander effect induced by -rays or carbon ions and analyzed the role of nitric oxide (NO) in the effect. Normal human fibroblasts were used. Cells inoculated on a porous membrane were irradiated with varying doses of -rays or carbon ions. Irradiated cells were then non-contact co-cultured with non-irradiated cells for 24 h. After co-culture, the survival rates of non-irradiated bystander cells co-cultured with irradiated cells decreased with increasing dose and bottomed out at 0.5 Gy or higher doses. This indicates that the bystander effect is dependent on irradiation dose but independent of radiation quality. Next, a specific NO scavenger c-PTIO was added to the culture medium during irradiation and co-culture. This treatment prevented the reduction in survival rates of bystander cells, clearly indicating that NO has an important role in the bystander effect.
Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Sakashita, Tetsuya; Suzuki, Michiyo; Kobayashi, Yasuhiko
no journal, ,
Here, we investigate bystander effect. Normal human fibroblast WI-38 cells were irradiated with carbon ions or -rays. Irradiated cells and non-irradiated cells were co-cultured. The survival rates of bystander cells decreased with dose at lower than 0.5 Gy and bottomed out at around 80%. In addition, the survival rates of bystander cells were not significantly different between carbon ions and -rays at the same doses. These indicated the bystander cell-killing effect depends on irradiation dose but not on radiation quality. c-PTIO, a specific scavenger of nitric oxides (NO), suppressed the reduction of survival rates of bystander cells, showing NO has an important role to induce the bystander effect. The concentrations of nitrite, an oxide of NO, were measured. There were negative relationships between the survival rates of bystander cells and the nitrite concentrations of the medium. NO released to the medium maybe an important factor related to the bystander effect.
