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Background: Relationships of radiation induced oxidative stress and the redox status in the cerebral nervous system has been reported.
Aim: Daily time courses of the redox status in the brains of mice, which were irradiated X-ray or carbon-ion beam (C-beam), were observed by magnetic resonance redox imaging (MRRI) technique.
Methods: The mice were irradiated by 8 Gy X-ray or C-beam on their head under anesthesia. C-beam irradiation was done at Heavy-Ion Medical Accelerator in Chiba (HIMAC) (NIRS/QST, Chiba, Japan). MRRI measurements using a blood-brain-barrier permeable nitroxyl contrast agent, MC-PROXYL or TEMPOL, were performed at a 7 T scanner on several deferent timings, i.e. several hours, 1, 2, 4, and 8 day(s) after irradiation. Signal decay curves of both nitroxyl radical probes in brains of mice showed typical 2-phase decay profiles. Decay rate k1, which is mainly reflects reduction of the nitroxyl radical, and decay rate k2, which is mainly reflects clearance of the nitroxyl radical, were observed form the initial fast decay phase and second slow decay phase of the decay curves, respectively.
Results/Conclusions: The k1, i.e. pseudo reduction rate, of MC-PROXYL was become slower several hours after X-irradiation, and then it looked gradually recovered during 8 days. C-beam also reduced k1 of MC-PROXYL several hours after irradiation; however, it was recovered to the control level day after, and then kept control or little increased levels until day 8. The time courses of k2, i.e. pseudo clearance rate, of MC-PROXYL were showed a similar pattern, which was once reduced hours after either X- or C-irradiation, and then it was recovered after 1 day, and kept control level until day 8. The k1 of TEMPOL showed similar responses as shown in MC-PROXYL. X-ray and C-beam gave different redox responses, which was probably due to different oxidative stress/injury, in mouse brain.
会議概要（会議名, 開催地, 会期, 主催者等）
16th International Congress of Radiation Research (ICRR2019)
Comparison of X-ray and Carbon-Ion Beam Induced Alterations of RedOx Status in Mouse Brain
