低線量放射線の生体影響の解明

抄録

After the accident of Fukushima Daiichi nuclear power plant, many people in Japan have a concern about biological effect with low dose and low dose rate radiation. In such situation, some people also have concerns to radiation usage for diagnostics and therapies. As the current amendment of medical law provides the rules of radiation diagnostics strictly, medical workers, treating radiation for medical, have to understand the biological effects with exposure to ionizing radiation to explain the effects of medical radiation to patients.
Acute irradiation of high dose radiation induces several types of DNA damages. Among of them, DNA doble-strand breaks （DSBs） are most serious damages to cells and constructing organs, because remaining of DSB damages could lead to cell death, subsequently dysfunction of organs （deterministic effects）. Therefore, living beings are developing DNA repair systems such as non-homologous end-joining and homologous recombination. Miss-repair and non-repair could generate gene mutation, and subsequently lead to tumorigenesis （stochastic effects）.
Exposure of radiation also causes excess accumulation of ROS （reactive oxygen species）/oxidative stress, which may lead to biological effects of low dose rate radiation. We found that mitochondria damage contributed to accumulation of ROS and activation of oxidative stress in human normal fibroblasts under low dose rate irradiation. We also observed that low dose rate irradiation also caused gamma-H2AX positive micronuclei in the presence of ATM inhibitor. As ATM is an important protein kinase of oxidative stress responses as well as DNA damage responses, anti-oxidative stress function may be important to repress micronuclei formation. In order to provide relief to concerning people, we have to clarify the biological effects of low dose and low dose rate radiation more.