Treadmill exercise inhibits traumatic brain injury-induced hippocampal apoptosis

Traumatic brain injury (TBI) occurs when an outside force impacts the brain. The main problem associated with TBI is neuronal cell death of the brain, and the outcome of TBI ranges from complete recovery to permanent disability, and sometimes death. Physical exercise is known to ameliorate neurologic impairment induced by various brain insults. In the present study, we investigated the effects of treadmill exercise on short-term memory and apoptosis in the hippocampus following TBI in rats. TBI was induced by an electromagnetic-controlled cortical impact. The rats in the exercise group were forced to run on a treadmill for 30 min once daily for 10 consecutive days, beginning 2 days after induction of TBI. For the current study, a step-down avoidance task, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, Western blot for Bcl-2 and Bax, and immunohistochemistry for caspase-3 were conducted. The present results revealed that TBI impaired short-term memory, and increased DNA fragmentation and caspase-3 expression in the hippocampus. Induction of TBI also enhanced expression of pro-apoptotic factor Bax protein and suppressed expression of anti-apoptotic factor Bcl-2 protein in the hippocampus. Treadmill exercise alleviated short-term memory impairment, and decreased DNA fragmentation and caspase-3 expression in the hippocampus. In addition, treadmill exercise remarkably suppressed expression of Bax protein and slightly increased expression of Bcl-2 protein in TBI-induced rats. The present study showed that treadmill exercise might overcome TBI-induced apoptotic neuronal cell death, thus facilitating recovery following TBI.

Research Highlights
► In the present study, traumatic brain injury (TBI) impaired short-term memory.
► TBI also increased apoptotic neuronal cell death in the hippocampus.
► Treadmill exercise alleviated short-term memory impairment with decreased apoptosis.
► The present results show that treadmill exercise may overcome TBI-induced apoptosis.