亚低温对局灶性脑缺血大鼠模型C3表达的影响

Effect of mild hypothermia on the expression of C3 after MCAO in rats

目的观察亚低温(32～35℃)对局灶性脑缺血后大鼠脑组织C3表达的影响。方法 100只大鼠随机分成假手术组、常温组和亚低温组,各组根据观察时间点分为术后6h、1d、2d、3d、7d五个亚组。建立大鼠左侧大脑中动脉闭塞(MCAO)模型,应用冰袋降温的方法使亚低温组大鼠肛温10min内降至(33℃±1℃),维持低温6h后复温。假手术组和常温组大鼠保持肛温(37℃±0.5℃)。在各时间点采用神经缺陷评分对各大鼠进行神经功能评分后断头取脑,行苏木素伊红染色观察脑缺血病理学改变,免疫组织化学染色观察不同时间点C3表达情况。结果假手术组大鼠清醒后无神经功能障碍,常温组及亚低温组大鼠清醒后均出现左侧Horner征及不同程度右侧前肢为重的偏瘫,两组大鼠神经功能缺损3d时最明显,7d时均有所减轻。除6h外各时间点亚低温组大鼠神经功能缺损评分均较常温组低(P<0.05),各时间点亚低温组大鼠脑组织病理学损伤较常温组轻。在各时间点假手术组大鼠脑组织中C3可见少许表达,各组间比较差异无统计学意义(P>0.05)。常温组和亚低温组大鼠缺血侧脑组织于缺血后6h补体C3阳性细胞数均开始增加,至3d均达到高峰,到7d时C3阳性细胞数明显减少,与常温组相比,亚低温组各时间点缺血侧脑组织C3表达明显减少(P<0.05)。结论脑缺血时,缺血侧脑组织C3有表达,亚低温可使C3表达减少。亚低温可能通过降低C3的表达减轻补体级联反应起脑保护作用。

Objective To observe the effect of mild hypothermia on the expression of C3 in focal cerebral ischemic rats. Methods One hundred rats were randomly divided into 3 groups： sham operative group,ordinary temperature group,and mild hypothermia group.Every group was divided into 5 subgroups by different time points,that was 6th hour,1st,2nd,3rd,7th day after sham operation and cerebral ischemia.Left middle cerebral artery occlusion models were established.The rats in mild hypothermia group were treated by ice bag,and the rectal temperature were kept at（33±1） centigrade in ten minutes,hypothermia was maintained for 6 hours,then we made the rats rewarming slowly.The rats in sham operative and ordinary temperature group were treated by ordinary temperature consple,and the rectal temperature were kept at（37±0.5） centigrade.Functional deficits were quantified by Zea Longa five point scale（ZFPS） before the rats were killed at every time point.The pathological changes of cerebral ischemia were observed by hematoxylin-eosin staining（HE）.The expressions of complement C3 were assessed by immunohistochemistry staining. Results After recovery from anesthesia,the nerve functional deficit of rats were not seen in sham operative group.But left Horner syndrome and different severity of right hemiparalysis,especially right anterior limb palsy were seen in mild hypothermia group and ordinary temperature group.The nerve functional deficit was the most obvious at the third day after middle cerebral artery occlusion（MACO）,and it recovered at the seventh day after MACO.In addition to the 6th hour subgroup,different degree of neurologic impairment was seen both in mild hypothermia group and in ordinary temperature group,but the score of neurological deficit in the former was less than that in the latter（P0.05）.The pathological damage of brain tissue in normal temperature group was more severe than that in hypothermia group at each time point.The changes of C3 positive cells in brain tissue at the 6th hour,1st,2nd,3rd,7th day after sham operation were slight in sham operative group,and there were no differences between these subgroups（P0.05）.The positive cells of C3 in cerebral ischemic focus began to increase at sixth hour after MACO and progressively increased,then,they reached a peak at the third day after MACO.At the seven day after MACO,the positive cells of C3 significantly reduced.At each different time point,the number of C3 positive cells in brain tissue in mild hypothermia group were obviously fewer than that in ordinary temperature group（P0.05）. Conclusion The expression of C3 in brain tissue increases after cerebral ischemia,mild hypothermia can reduce the expression of C3 in brain tissue after cerebral ischemia in brain tissue after cerebral ischemia.Mild hypothermia maybe reduce complement cascade reaction by reducing the expression of C3.