Mitigation of Iron-irradiation-induced Genotoxicity by Post-exposure Diet Restriction in Bone Marrow Erythrocytes in Mice

Purpose: Effect from post-exposure onset of diet restriction on genotoxicity induced by high LET iron particles was studied using total body irradiation (TBI) of mice and micronucleus frequency in bone marrow erythrocytes as the endpoint.Materials and Methods: C57BL/6J Jms strain female mice of 8 weeks old were irradiated with iron particles (initial energy=500 MeV/nucleon, LET=200 keV/μm; HIMAC) at a dose of 2.0 Gy. Induction of acute genotoxicity and late residual damage in the hematopoietic system was determined respectively at one and two months after TBI. After TBI, mice were either allowed to free access to a standard laboratory chow MB-1 (Funabashi Farm Co., Japan) or treated under a diet restriction (DR) to 75% of the amount that the animals took under free access.Results and Conclusions: Reduction of body weight gain after TBI was observed in the groups that were exposed to TBI alone, under DR alone, and under DR after TBI. TBI alone caused a significant increase in micronucleus induction. DR alone did not alter the micronucleus frequency. On the other hand, DR after TBI induced a significant decrease in micronucleus induction compared to the treatment by TBI alone. These findings indicated that post-exposure onset of diet restriction could relieve the genotoxicity induced by TBI to high LET iron particles.Acknowledgments: This work was partially supported by both the MEXT Grant-in-Aid for Scientific Research on Innovative Areas, Grant Number 15H05935 “Living in Space” and three HIMAC Research Project Grants (22B258, 14J286 and 16J295).日本放射線影響学会第63回大