56Fe irradiation-induced cognitive deficits through oxidative stress in mice.

The rapid growth of manned space flight results in more concerns about health risks and an urgent need for health assessment for space travel. The cosmic environment is complicated and full of radiation. Because of their strong biological effects, heavy ions such as 56Fe ions are considered to be an important component of these lethal galactic rays. Due to the importance of brain function to astronauts, we explored the long-term effects and potential mechanisms of 56Fe ion radiation on mice brains containing the hippocampus. In our study, radiation doses were carried out with 0.5 Gy, 1 Gy or 2 Gy. One month after whole-body 56Fe ion exposure, the Morris water maze test was performed to assess the ability of spatial learning and memory. A histological study was used for pathology analysis of the hippocampus. Alteration of oxidative stress was reflected by MDA and GSH and oxidative DNA damage marked by 8-OHdG was detected by biochemical and immunofluorescence methods. In our results, irradiated groups exhibited significant changes in behavioral performance and also showed loose and edematous arrangement in the pathological characteristics. Furthermore, whole brain levels of MDA, GSH and 8-OHdG increased in the irradiated groups. In addition, increased expression of 8-OHdG can also be detected by immunofluorescence in the hippocampus. Our findings revealed a linkage between radiation-induced oxidative stress and behavioral deficits. This may suggest an underlying mechanism of brain tissue protection and risk assessment in manned space flight.