Presentation 成体マウスにおいて重粒子線によって誘導された適応応答の機構研究

田中, 薫  ,  王, 冰  ,  二宮, 康晴  ,  丸山, 耕一  ,  劉, 強  ,  藤田, 和子  ,  笠井, 清美  ,  根井, 充

Radiation-induced adaptive response (AR) is a phenomenon that a priming low dose induces radioresistance against the subsequent challenge radiation at higher doses. In a series of investigation, successful induction of AR by certain combinations of X-rays and heavy ions was demonstrated in mice using suppression of bone marrow death in thirty-day survival test as the criterion. As increased number of endogenous spleen colonies (CFU-S, a measure of viable pluripotent hematopoietic stem cells) was closely related to the suppression of challenge radiation-induced lethality when X-rays were used as both the priming and challenge doses, in this work, as the first approach to exploration of the AR mechanisms with high LET heavy-ion irradiations (HIR) involved, the number of endogenous CFU-S was examined. In addition to X-rays, accelerated HIR of carbon (15keV/μm) and iron (200KeV/μm) particles were used. Female mice of C57BL/6J strain were irradiated with the priming and challenge doses at postnatal ages of 6 and 8 weeks, respectively. Results showed that under AR-inducible conditions, i.e., X-rays+carbon, carbon+X-rays, carbon+carbon, significantly increased number of endogenous CFU-S was observed, while under AR-uninducible condition, i.e., X-rays+iron, no increase was detectable. These findings indicate that under AR-inducible conditions with high LET HIR involved, the increased number of endogenous CFU-S was also closely related to the suppression of challenge radiation-induced lethality. These findings would provide a new insight into further mechanistic study on high LET radiation-induced AR.

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