Changes of autophagy in injured cortex after trauma and radiation injury of brain

Objective To clarify the expression of autophagy related proteins in cortical neurons following trauma combined with radiation injury of brain (TRI) and the underlying clinical significance. Methods Fifty-eight male SD adult rats were divided into sham group (n=15), traumatic brain injury group (TBI group, n=15), radiation-induced brain injury group (RBI group, n=14), and TRI group (n=14), according to the random number table. Rats in TBI group were subjected to lateral fluid percussion injury in the cortex, in RBI group whole body 4.5 Gy single dose irradiation to 60Co, and in TRI group whole body 4.5 Gy single dose irradiation to 60Co within 30 minutes after the lateral fluid percussion injury in the cortex. Six weeks after the modeling in each group, neuronal injury was detected with HE staining and expressions of autophagy-related proteins, LC3- II and Beclin-1, were detected through Western blotting. Results TBI group cortical neurons was reduced compared to sham group[(68.7±7.8) vs (96.9±9.6)] (P 0.05), vacuoles, pyknosis and dissolution were not obvious, and expressions of Beclin-1 and LC3-Ⅱ were significantly increased in contrast with sham and TBI groups (P<0. 01). In TRI group number of cortical was grossly reduced to 45.8±7.8 in contrast with TBI and RBI groups (P<0. 05), vacuoles, pyknosis and dissolution were obvious, expressions of Beclin-1 and LC3-Ⅱ decreased significantly as compared to TBI and RBI groups ( P<0. 01). Conclusion Autophagy in the injured cortex is increased after the separate TBI or RBI, but the combined injury of TRI results in significantly reduced autophagy in the injured cortex along with increased neuron degeneration which suggests a protective role of autophagy in brain injuries. Key words: Brain injuries; Radiation injuries; Autophagy