Effect of hypothermia on Calpain and MAP-2 after trauma brain injury in rats

Objective To determine the effect of hypothermia on gene transcription and protein expression of calpain and MAP-2 after traumatic brain injury. Methods Fifty-four rats were randomly divided into 3 groups: sham-operated group (n=6), normothermia group (n=24) and hypothermia group (n=24). Hypothermia intervention for 4 h immediately initiated after trauma brain injury in hypothermia group. At every time point (6, 12, 24 and 72 h after traumatic brain injury), respective 3 rats from normothermia group and hypothermia group were sacrificed. The brain tissue were prepared for fluorescence PCR and Western blot analysis to semi-quantitate gene transcription and protein expression of calpain and MAP-2. Results Hypothermia group showed increased calpain gene transcription at 12 and 24 h after traumatic brain injury respectively (P0.05). The increase in calpain protein expression also had been reduced by hypothermia after traumatic brain injury at all the time points, specially this intervention completely inhibited increase of calpain protein at 12 and 72 h after traumatic brain injury (P0.05). Compared with sham-operated group, rats showed reduced MAP-2 gene transcription in either normothermia group or hypothermia group (P0.05), and the reduction in hypothermia group was less than normothermia group at 6, 12 and 24 h. It was evident that cortex MAP-2 protein expression decreased no matter hypothermia existed after traumatic brain injury, but its expression in the hypothermia group was always less than their corresponding normothermia group (P0.05). Conclusion Neuroprotection of hypothermia may relate to the decrease of calpain protein expression after traumatic brain injury. The relation between hypothermia and MAP-2 will be investigated ulteriorly.