高压氧预处理对老龄大鼠全脑缺血再灌注损伤后神经可塑性的影响

Effect of hyperbaric oxygen preconditioning on expression of neuroplasticity after acute global cerebral ischemia-reperfusion in aged rats

目的研究高压氧预处理对老龄大鼠全脑缺血再灌注损伤时轴突生长抑制因子(Nogo)mRNA、Nogo-A蛋白表达的影响,探讨其影响神经可塑性的机制。方法将42只雄性SD大鼠分为4组:对照组(C组,n=6)、高压氧组(H组,n=12)、脑缺血再灌注损伤组(I/R组,n=12)、高压氧预处理+脑缺血再灌注损伤组(HOP组,n=12)。H组和HOP组每天置于高压氧舱内1h,氧压为0.2MPa,连续5d,最后1次高压氧处理后24h时I/R组和HOP组采用改良Pulsinelli四血管闭塞法制备大鼠全脑缺血再灌注损伤模型,全脑缺血10min,再灌注24h时H组、I/R组和HOP组随机取6只大鼠断头取脑,分离大脑皮质,采用实时荧光定量PCR法检测Nogo mRNA的表达水平,免疫印迹法检测Nogo-A蛋白的表达水平。各组大鼠分别行横断位及冠状位T1WI、T2WI扫描。结果 C组、H组大脑未见明显缺血梗死灶,缺血组双侧皮质区可见明显弧形缺血梗死区,HOP组双侧皮质区也可见弧形缺血梗死区,面积较I/R组小。与C组比较,Nogo mRNA及Nogo-A蛋白表达上调(P<0.05);与I/R组比较,Nogo mRNA及Nogo-A蛋白表达下调(P<0.05)。结论高压氧预处理通过抑制大脑皮质Nogo mRNA及Nogo-A蛋白表达上调,提高神经可塑性,能减少老龄大鼠急性全脑缺血后超急性期大脑皮质缺血梗死面积。

Objective To investigate the effect of hyperbaric oxygen preconditioning （HOP）on expression of Nogo mRNA,No-go-A and Ng R protein in the cerebral cortex after acute global cerebral ischemia-reperfusion （I/R）in aged rats and to study its mechanism affecting neuroplasticity.Methods Forty-two aged male SD rats were randomly divided into 4 groups：control group （C group,n=6）,hyperbaric oxygen group （H group,n=12）,cerebral I/R injury group （I/R group,n=12）and HOP group （n=12）. The H group and the HOP group were placed in the hyperbaric oxygen cabin for 1 h per day with a oxygen pressure of 0.2 Mpa for successive 5 d,at 24 h after last time of hyperbaric oxygen preconditioning the I/R group and the HOP group adopted the modified Pulsinelli vessel occlusion method for preparing the rat I/R injury model,with global cerebral ischemia for 10 min and reperfusion for 24 h,each 6 rats were randomly taken from the the H group,I/R group and HOP group and their heads were cut off for taking the brain and isolating the cerebral cortex.The real time fluorescence quantification PCR was adopted to detect the expression level of Nogo mRNA and the Nogo-A protein level was detected by Western blot.The rats in various groups were performed the T1 WI and T2WI scanning in the transection position and the coronal positions.Results There were no obvious ischemic brain infarction in the normal control group and the H group,the arc-shaped bilateral cortex ischemic infarct area was clearly seen in the ischemic group,the ischemic infarct area was also seen in the HOP ischemia group,but its area was smaller than which in the ischemic group.Compared with the C group,the expression of Nogo mRNA and the Nogo-A protein in the HOP group was up-regulated（P〈0.05）;compared with the I/R group,the expression of Nogo mRNA and the Nogo-A protein was down-regulated（P〈0.05）. Conclusion HOP increases the neuroplasticity and can reduce the cerebral ischemic infarction area in the exceed acute stage of rat acute global cerebral ischemia by inhibiting Nogo mRNA in the cerebral cortex and up-regulating the Nogo-A protein expression.