亚低温对脑缺血大鼠脑组织富含脯氨酸的Akt底物40与磷酸化的富含脯氨酸的Akt底物40表达的影响及其脑保护作用的研究

Study of mild hypothermia on changes of proline-rich Akt substrate of 40-kD a and phospho-proline-rich Akt substrate of 40-kD a protein in rats and the neuroprotectivemechanism after cerebral ischemia

目的：研究亚低温对脑缺血大鼠富含脯氨酸的Akt底物40（ PRAS40）与磷酸化的PRAS40（ p-PRAS40）表达的影响及其脑保护作用。方法56只大鼠随机分为正常对照组、假手术组、脑缺血组和脑缺血亚低温治疗组（亚低温组），后两组又分为缺血3h、6h、12h、24h、72h、7d亚组，每个亚组4只大鼠。用线栓法制作大鼠局灶脑缺血模型。亚低温组于缺血后30 min实施脑部亚低温（32～33℃）并持续4 h。在相应时间点行神经功能缺损评分，用免疫组化染色检测PRAS40及p-PRAS40的表达。结果脑缺血大鼠PRAS40和p-PRAS40的表达呈时间依赖性变化。 PRAS40在缺血12 h开始减少，至缺血72 h表达最低，亚低温组12 h、24 h、72 h、7 d亚组与脑缺血组的差异有统计学意义（均P＜0.05）；p-PRAS40在缺血3 h开始减少，至缺血24 h表达最低，亚低温组3 h、6 h、12 h、24 h、72 h亚组与脑缺血组的差异有统计学意义（均P＜0.05）。神经功能缺损评分比较，亚低温组各亚组均明显低于脑缺血组（均P＜0.05）。结论脑缺血大鼠PRAS40和p-PRAS40表达减少；亚低温能延缓其表达减少。亚低温能明显减轻脑缺血所致的神经功能缺损。

Objective To study the effects of mild hypothermia on proline-rich Akt substrate of 40-kDa （ PRAS40 ） and phospho-PRAS40 （ p-PRAS40 ） expression and their role in brain protection following cerebral ischemia in rats.Methods Fifty-six rats were randomly divided into normal group ,sham-operation group,ischemia group and ischemia mild hypothermia treatment group （ mild hypothermia group ） .The last two groups were divided into ischemia 3 h, 6 h, 12 h, 24 h, 72 h and 7 d sub-groups, 4 rats in each sub-group.The focal cerebral ischemia models of rats were achieved by modified thread embolism .Mild hypothermia group was performed mild hypothermia （32-33℃） 30 min after ischemia lasted for 4 h.Neurological function defect scale was performed at the corresponding time point .The expression of PRAS40 and p-PRAS40 were detected with immunohistochemical method . Results The expression levels of PRAS 4 and p-PRAS40 in rats with cerebral ischemia were in time-dependent manner .The level of PRAS40 was decreased in 12 h post-ischemia initially and reached the lowest point in 72 h post-ischemia.It was significantly higher in the mild hypothermia group than that in the ischemia group in 12 h, 24 h, 72 h and 7 d post-ischemia （all P〈0.05）.The level of p-PRAS40 was decreased in 3 h post-ischemia and reached the lowest point in 24 h post-ischemia .It was significantly higher in the mild hypothermia group than that in the ischemia group in 3 h, 6 h, 12 h, 24 h and 72 h post-ischemia （all P〈0.05）.The assessment of neural functional defect was significantly lower in the mild hypothermia group than those in ischemic group （ all P〈0.05 ） .Conclusions The expression levels of PRAS 4 and p-PRAS40 are decreased in cerebral ischemia rats .Mild hypothermia treatment could significantly rescue the decrease .Meanwhile , mild hypothermia treatment can significantly improved neurologic impairment resulted from cerebral ischemia .