Host: The Japan Radiation Research Society
Acquisition of radioresistance of cultured cells to high-dose irradiation induced by low-dose preirradiation is known to the adaptive response. It was found that not only cultured cells but also the survival rate of lethally irradiated mice was significantly improved by low-dose (0.45 Gy) preirradiation and that this phenomenon had a specific window of priming dose and interval until the acquisition of radioresistance. This type of whole-body adaptive response is sometimes referred to as the "Yonezawa effect". However, the mechanism of Yonezawa effect is still remained unknown. We focused on the regulation of hematopoietic cell differentiation after high-dose irradiation, and we found that myeloid cells (Gr-1+/Mac-1+) in femur were rapidly recovered after high-dose (6 Gy) irradiation in low-dose (0.5 Gy) preirradiated mice. According to those myeloid recovery, myeloid-stimulating cytokines in blood plasma also up-regulated after high-dose irradiation in low-dose preirradiated mice. Furthermore, the reduction of peripheral blood erythrocytes two weeks after high-dose irradiation was significantly suppressed, which is a possible mechanism that improved the survival rate of mice after high-dose irradiation. We would like to discuss the mechanism of Yonezawa effect regulated by those hematopoietic cell differentiation after high-dose irradiation in low-dose preirradiated mice.
