Sublethal Total Body Irradiation Leads to Early Cerebellar Damage and Oxidative Stress

The present study aimed at identifying early damage index in the cerebellum following total body irradiation (TBI). Adult male CD2F1 mice (n=18) with or without TBI challenge (8.5 Gy irradiation) were assessed for histology and expression of selected immunohistochemical markers including malondiadehyde (MDA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), protein 53 (p53), vascular endothelial growth factor receptor 2 (VEGF-R2), CD45, calbindin D-28k (CB- 28) and vesicular glutamate transport-2 (VGLUT2) in cerebellar folia II to IV. Compared to sham-controls, TBI significantly increased vacuolization of the molecular layer. At high magnification, deformed fiber-like structures were found along with the empty matrix space. Necrotic Purkinje cells were identified on 3.5 days after TBI, but not on 1 day. Purkinje cell count was reduced significantly 3.5 days after TBI. Compared with sham control, overall intensities of MDA and 8-OHdG immunoreactivities were increased dramatically on 1 and 3.5 days after TBI. Expression of VEGF-R2 was identified to be co-localized with 8-OHdG after TBI. This validates microvessel endothelial damage. The p53 immunoreactivities mainly deposited in the granular layer and microvessels after TBI and co-localization of the p53 with the CD45, both which were found within the microvessels. After TBI, CB28 expression decreased whereas the VGLUT2 expression increased significantly; Purkinje cells exhibited a reduced body size and deformity of dendritic arbor, delineated by CB28 immunoreactivity. Substantial damage to the cerebellum can be detectable as early as 1- 3.5 days in adult animals following sublethal TBI. Oxidative stress, inflammatory response and calcium neurotoxicity-associated mechanisms are involved in radiation-induced neuronal damage.