@misc{oai:repo.qst.go.jp:00079457, author = {Wang, Bing and Liu, Cuihua and Tanaka, Kaoru and Katsube, Takanori and Hirakawa, Hirokazu and Ninomiya, Yasuharu and Maruyama, Kouichi and Murakami, Masahiro and Fujita, Kazuko and Qiang Liu and Fujimori, Akira and Nenoi, Mitsuru and Wang, Bing and Liu, Cuihua and Tanaka, Kaoru and Katsube, Takanori and Hirakawa, Hirokazu and Ninomiya, Yasuharu and Maruyama, Kouichi and Murakami, Masahiro and Fujita, Kazuko and Fujimori, Akira and Nenoi, Mitsuru}, month = {Sep}, note = {Background & Aim: Existence of radioadaptive response (RAR) was demonstrated in varied biosystems. RAR is capable of reducing genotoxicity, mutation and carcinogenesis but the underlying mechanisms remain fragmented. The first RAR mouse model (Yonezawa Effect) was established by Yonezawa et al. using low LET X-rays as both the priming and the challenge doses, and rescue of bone marrow death as the endpoint. The aim of this study was to characterize RAR in this model. Methods & Results: We demonstrated that existence of RAR using different types of ionizing radiation (IR) including high LET heavy ions; increase in the hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) measured as endogenous colony forming units-spleen under RAR; and reduction of delayed homologous recombination (HR) in the nucleated cells in hematopoietic tissues (bone marrow and spleen). Conclusions & Discussions: These findings suggest that RAR in mice induced by different types of IR would share a common underlying mechanism: the priming IR-induced resistance in the blood forming tissues, leading to a protective effect on the HSCs/HPCs and rescuing the animals from bone marrow death. On the other hand, reduction of delayed HR may be at least a part of the mechanisms underlying decreased carcinogenesis by RAR. These findings provide a new insight into the mechanistic study on RAR in vivo and suggest that application of RAR would contribute to a more rigorous and scientifically-grounded system of radiation protection in radiotherapy. Acknowledgement: This work was partially supported by MEXT Grant-in-Aid for Scientific Research on Innovative Areas, “Living in Space” (grant Nos. JP15K21745, 15H05944 and 15H05935)., 日本宇宙生物科学会第33回大会}, title = {New Findings in Characterization of Radioadaptive Response in Mice (Yonezawa Effect).}, year = {2019} }