Vitamin E Protects Against Oxidative Damage and Learning Disability After Mild Traumatic Brain Injury in Rats

Background. Reactive oxygen species induce neuronal damage, and their role in reducing synaptic plasticity and function is beginning to be understood. Vitamin E is a potent reactive oxygen species scavenger, which has the potential to reduce oxidative damage encountered after traumatic brain injury (TBI). Brain-derived neurotrophic factor (BDNF) can facilitate synaptic function and support learning by modulating the CaMKII system, synapsin I, and cAMP-response element-binding protein (CREB). The elevation of superoxide dismutase (SOD) and Sir2 (silent information regulator 2) play an important role in resistance to oxidative stress. Objective. We examined the possibility that vitamin E supplemented in the diet may help counteract the effects of TBI on the molecular substrates underlying synaptic plasticity and cognitive function in the hippocampus. Methods. Rats were fed a regular diet with or without 500 IU/kg of vitamin E for 4 weeks (n = 6-8 per group) before a mild fluid percussion injury (FPI) was performed. Results. FPI increased protein oxidation as evidenced by elevated levels of protein carbonyls and reduced levels of SOD and Sir2. In addition, FPI resulted in poor performance in the Morris water maze, which was accompanied by reduced levels of BDNF and its downstream effectors on synaptic plasticity, synapsin I, CREB, and CaMKII. Supplementation of vitamin E in the diet counteracted all the observed effects of FPI. Conclusions. These results suggest that vitamin E dietary supplementation can protect the brain against the effects of mild TBI on synaptic plasticity and cognition, using molecular systems associated with the maintenance of long-term plasticity, such as BDNF and Sir2.