Abstract
We have studied whether the p53-dependent apoptosis induced by acute radiation is interfered with pre-irradiation at a low dose or a low dose-rate in human cultured cells and whole body of mouse. In human cultured cells, we found that a challenge irradiation with X-ray immediately after chronic irradiation resulted in lower levels of p53 and p53-dependent apoptosis than those observed after the challenge irradiation alone. In mouse spleen, we found significant suppression of them induced by challenge irradiation at a high dose-rate when mice were pre-irradiated with a low dose or a low dose-rate irradiation. In addition, we did not find any radioadaptive response in DNA-PKcs deficient scid mice. These findings suggest that pre-irradiation at a low dose or a low dose-rate suppressed the p53-dependent apoptosis through the post-translational modification of target molecules by DNA-PK. We expect that the present findings will provide useful information in the health care of radiation workers and the general population. [J Radiat Res 44:376 (2003)]
