[Time course of calpain activity changes in rat neurons following fluid percussion injury and the interventional effect of mild hypothermia].

OBJECTIVE: To investigate the time course of calpain activity changes in rat neurons following fluid percussion injury (FPI) under normothermia (37 degrees celsius;) and mild hypothermia (32-/+0.5) degrees celsius;. METHODS: In vitro cultured rat neurons were subjected to FPI followed by application of mild hypothermia for intervention at different time points, and the changes in intraneuronal calpain activity following FPI and the interventional effect of mild hypothermia on calpain activity were evaluated by UV-spectrophotometry at different time points. RESULTS: Remarkable changes occurred in calpain activity in the neurons following FPI at 37 degrees celsius;, and mild hypothermia produced obvious interventional effect on calpain activity in close relation to the timing of intervention initiation. CONCLUSION: Intraneuronal calpain activity changes following FPI are involved in the pathological process of cellular injury, and mild hypothermia might offer protection against traumatic brain injury to some extent by regulating calpain activity. The interventional effect of mild hypothermia is associated with the timing of the intervention initiation.

[Effect of intraischemic mild hypothermia on interleukin-1beta and monocyte chemoattractant protein-1 contents in ischemic core of rat cortex after transient focal cerebral ischemia].

OBJECTIVE: To investigate the effect of intraischemic mild hypothermia on the protein levels of interleukin (IL)-1beta and monocyte chemoattractant protein (MCP)-1 in the ischemic core of rat cortex after transient focal cerebralischemia. METHODS: Eighty male Wistar rats were randomly divided into normothermic (37 degrees C) and mild hypothermic (32 - 33 degrees C) groups. The normothermic group was redivided into six subgroups of 8 rats: sham operation, ischemia for 2 hours without reperfusion, and reperfusion for 6 hours, 16 hours, 24 hours, and 48 hours respectively after ischemia; and the mild hypothermic group was redivided into 4 group with 8 rats: reperfusion for 6, 16, 24, and 48 hours. The rats except those in the sham operation subgroup were subjected to right middle cerebral artery occlusion by insertion a specially prepared nylon filament for two hours. Ice bag was used to lower the brain temperature and anal temperature soon after ischemia to 32.0 - 33.0 degrees C within 10 minutes in the mild hypothermic subgroups. The brain and anal temperature remained at 37.0 - 37.5 degrees C in all normothermic subgroups. Then the rats were killed 0, 6, 16, 24 and 48 hours after reperfusion respectively and their brains were taken out to examine the size of brain infarct by 2,3,5-triphenyltetrazolium chloride (TTC) staining reaction. The protein levels of IL-1beta and MCP-1 in the cortical ischemic core were measured by ELISA. RESULTS: No significant change of IL-1beta protein level was found in the cortical ischemic cores at any time point after reperfusion among the normothermic subgroups. The IL-1beta protein levels at different time points were not significantly different between the intraischemic mild hypothermia subgroups and the normothermic subgroups (all P > 0.05). The MCP-1 protein level in the cortical ischemic cores of the normothermic subgroups began to increase since the 6th hour afer reperfusion (22.5 +/- 8.7 ng x g tissue(-1), 17 times that in the sham operation samples, P < 0.05), peaked in 48 hours (110.9 +/- 47.0 ng x g tissue(-1), 83.7 times that in the sham operation sample, P < 0.001). The protein level of MCP-1 in the mild hypothermic subgroups was 8.7 +/- 7.6 ng x g tissue(-1) 6 h after reperfusion (P < 0.005 in comparison with those in sham operation subgroup and ischemia subgroup) and was 56.0 +/- 40.3 ng x g tissue(-1), 48 hours after reperfusion (P < 0.05) incomparison with those in the normothermic subgroups). The sizes of cortical infarct at different time points in the mild hypothermic subgroups were significantly smaller than those in the normothermic subgroups (P < 0.05). CONCLUSION: Mild hypothermia reduces the level of MCP-1 in the cortex after cerebral ischemia/reperfusion which may be one of the important mechanisms of the neuroprotective effects of mild hypothermia.