| Objective:Ischemic cerebrovascular disease is a major hazard to human health disease, as it has the characteristics of high prevalence, high mortality and high disability, medical workers has much attention on it. Neuron damage after cerebral ischemic can cause complex change in pathophysiology,including over-loading of calcium,excessive oxygen free radicals and NO,apoptosis,and damage in biomembrane.inflammation andso on,which lead to more serious braindamage. Neuroprotectants are not as effective as heyare hoped too.While the hypothermia treatment is one of the most important neuroprotective methods. Mild hypothermia therapy has been applied to the current treatment of ischemic cerebrovascular disease. Although many studies have been the done on neuroprotective mechanisms of hypothermia, there are still many puzzling phenomenon, In clinical work we found that some patients with ischemic cerebrovascular disease during the treatment of mild hypothermia in the implementation of a stable condition, but they appeared to be more seriously and even death after rewarming.The purpose of this study is observe the effect of mild hypothermia on cerebral ischemia and reperfusion in neuronal apoptosis, and study the possible internal mechanisms on the molecular level.Methods:96 cases of cerebral ischemia-reperfusion model were divided into two groups, one is mild hypothermia treatment group and the other is control group. Each group has 48 SD rats individually. Implementation of mild hypothermia to the rats in hypothermia group,and tympanic temperature is maintained at (33±0.5)℃. After 72 hours of mild hypothermia treatment,we stop it and using the natural rewarming method. While the control group has no mild hypothermia treatment. Each group of 6 randomly selected rats were anesthetized and decapitated quickly removed brain tissue for frozen sections, during the mild hypothermia 24h,48h,72h, and 24h,48h, 72h,96h and 120h after rewarming. The cell apoptosis was detected by tissue in situ apoptosis detection (TUNEL) test at all observation time points.RT-PCR method to detect the mRNA expression apoptosis gene caspase-3, Fas and Bcl-2 at all the above time points. Application of statistical software SPSS 13.0 for statistical analysis.Results:The apoptosis cell number during mild hypothermia therapy in mild hypothermia group was less than the control group (P<0.05), then increased gradually after rewarming, till to 72h there was no significant difference between two groups(P> 0.05). And the mRNA expression level of caspase-3, Fas and Bcl-2 during mild hypothermia therapy in mild hypothermia group were lower than the control group (P<0.05), and increased with rewarming, till to 72h after rewarming there was no significant difference between two groups(P>0.05).Conclusion:Mild hypothermia does have a neuroprotective function.It can reduce the number of nerve cell apoptosis in the process of cerebral ischemia and reperfusion, but the apoptosis rate rise rapidly with rewarming. Mild hypothermia can not prevents neural cell apoptosis thoroughly, and its role in protecting neuronal cells is limited to be slow the speed of apoptosis.The levels of mRNA of pro-apoptotic gene caspase-3 and Fas and the process of neuronal apoptosis are synchronous, suggesting that a possible mechanism of hypothermia delayed neuronal apoptosis in ischemia-reperfusion cell is that it can inhibite the expression of pro-apoptotic gene caspase-3 and Fas.Hypothermia can not maintain a permanent high expression of apoptosis gene, and therefore can not inhibit neuronal apoptosis in ischemia-reperfusion cell for a long time.Therefore, we should actively seek the treatment time window of mild hypothermia, the brain protection of mild hypothermia and other methods to save the function of nerve cells better integration in order to achieve a real sense protection of nerve cell structure and function of the full purposes. |
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