Alterations in brain-derived neurotrophic factor and insulin-like growth factor-1 protein levels after penetrating ballistic-like brain injury in rats

BACKGROUND: Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) are essential for neuroplasticity and neuronal survival. Despite the importance of these endogenous factors in mediating posttraumatic recovery, little is known about their response after penetrating type traumatic brain injury. The objective of this study was to quantify the expression levels BDNF and IGF-1, two well-known neuroplasticity mediators, after penetrating ballistic-like brain injury (PBBI). METHODS: Rats were randomly assigned to receive unilateral sham or PBBI injuries. Using enzyme-linked immunosorbent assay and immunohistochemistry, we performed a comprehensive evaluation of BDNF and IGF-1 expression at acute (1 hour, 6 hours, 1 day) and subacute (2, 3, 7, and 14 days) timepoints after injury. RESULTS: BDNF and IGF-1 expression was transiently upregulated in both cortex and hippocampus after PBBI. Although BDNF levels increased at acute timepoints, IGF-1 expression peaked at 3 days in cortical homogenates. Although there was loss of staining in cells bordering the cavity, increased BDNF and IGF-1 immunoreactivity was observed in scattered neurons away from the contusion site. Glial upregulation of both growth factors was observed at early timepoints in the hippocampus. CONCLUSION: Our findings demonstrate that PBBI results in a brief upregulation of BDNF and IGF-1 during early posttraumatic period, providing critical information for interventions aiming to enhance neuronal survival and brain plasticity. (Copyright (C) 2017 Wolters Kluwer Health, Inc. All rights reserved.)