Apoptosis supression of cultured mouse brain cells by low dose rate irradiation of heavy particles

An environment of low dose rate radiation of heavy particles was achieved in an incubator by using off-centered scattered beam of accelerator (HIMAC). Cultured hole brain cells prepared from newborn mice of C3H, SCID and B6 were incubated in 10% FBS-DMEM medium for five days in the HIMAC incubator irradiating the low dose rate of heavy particles. The heavy particle irradiation was passively occurred while the HIMAC beam port was activated during the other experiments in the night period. The radiation doses inside and outside the incubator were continuously measured by LIULIN detectors. The accumulated dose during incubation varied 0.5-10mGy depend on the frequency of HIMAC operations. The apoptotic sensitivities of the brain cells were evaluated by fixing and Hoechst33342 staining after additional acute exposure of 200 KV X-ray within 4 Gy. A slight increase in apoptotic fraction without the acute irradiation was observed in cells inside the incubator compared to the laboratory control. The apoptosis induction was however suppressed when the additional X-ray irradiation was applied in a range of 0.25- 0.75Gy. This suggested that an adaptive response may be induced when heavy particle irradiation of the low dose rate was applied prior to the acute X-ray irradiation. This paper will discuss effects of the accumulated doses of the preceding irradiation of heavy particles and periods until the subsequent acute irradiation