Effects of Mild Hypothermia Treatment on Rat Hippocampal β-Amyloid Expression Following Traumatic Brain Injury.

Previous studies have reported that mild induced hypothermia (MIH) treatment has positive effects on traumatic brain injury (TBI) outcomes, which have recently been linked to β-amyloid (Aβ)-induced secondary brain injury (SBI) extent in hippocampal tissues. We therefore investigate the relationship between MIH treatment and expression of Aβ and related proteins following TBI. Adult Sprague-Dawley rats were randomly divided into three equal groups (S: sham-operated, N: normothermia, and H: mild hypothermia). After TBI induced by fluid percussion, group N remained at normal temperature, and group H underwent MIH (32°C) for 6 hours. Behavioral scale scores were then assessed. All rats were sacrificed 24 hours and hippocampal tissues were harvested, stained with hematoxylin and eosin. mRNA and protein expressions of Aβ, β-amyloid protein precursor (APP), and β-secretase (BACE) were analyzed. Our results revealed significantly improved behavioral scale scores and the surviving neuron numbers were observed in group H compared to group N (<0.05). Additionally, group N increased APP, Aβ, and BACE levels compared to group S (all <0.05). Reduced expression of APP-, Aβ-, and BACE were apparent in group H compared to group N (all <0.05). However, no statistically significant difference was observed between groups H and S in behavioral scale scores and the expression of APP-, Aβ-, and BACE (>0.05). In conclusion, MIH treatment significantly improves the survival of neuron and reduced Aβ, BACE, and APP upregulation after TBI, which may provide a better understanding of the mechanisms by which hypothermia reduces SBI in TBI patients.