L-精氨酸对局灶性脑缺血大鼠神经元凋亡的影响

Effect of L-arginine on neuronal apoptosis induced by focal cerebral ischemia in rats

目的 评价L-精氨酸（L-arg）对局灶性脑缺血大鼠神经元凋亡的影响。方法 健康雄性SD大鼠56只，体重250～300g，随机分为7组（n=8）：假手术组（SH组）、脑缺血2h组（IS1组）、脑缺血2h L-arg治疗组（L—arg1组）、脑缺血6h组（IS2组）、脑缺血6h L—arg治疗组（L-arg2组）、脑缺血12h组（IS1组）及脑缺血12h L-arg治疗组（L-arg3组）。采用线栓法制备大鼠大脑中动脉阻塞模型。各L-arg治疗组分别于脑缺血后腹腔注射L-精氨酸500mg/kg，2次／d，治疗3d；IS组给予等容量生理盐水。治疗3d后取脑，测定缺血区域神经元凋亡率、Caspase-3蛋白、Bcl-2蛋白和Bax蛋白的表达水平。结果 与SH组比较，IS1组、IS2组和IS2组神经元凋亡率升高，Caspase-3蛋白和Bax蛋白表达上调，Bcl-2／Bax蛋白比值降低（P〈0．01）；与IS1组和IS2组比较，L—arg．组和L-arg2组神经元凋亡率降低，Caspase-3蛋白和Bax蛋白表达下调，Bcl-2蛋白表达上调，Bcl-2／Bax蛋白比值升高（P〈0．01）。IS3组与L-arg3组上述指标差异无统计学意义（P〉0．05）。结论L-arg可减少脑缺血早期大鼠神经元凋亡，具有一定的治疗作用，其机制可能与下调Caspase-3蛋白表达、调节Bcl-2／Bax蛋白平衡有关。

Objective To investigate the effect of L-arginine （L-arg） on neuronal apoptosis induced by focal cerebral ischemia in rats.Methods Fifty-six male SD rats, weighing 250-300 g, were randomly divided into 7 groups （n = 8 each）： sham operation group （SH）, 2 h cerebral ischemia group （ISi）, 2 h cerebral ischemia and L-arg treatment group （ L-arg1 ）, 6 h cerebral ischemia group （ IS2 ）, 6 h cerebral ischemia and L-arg treatment group （L-arg2）, 12 h cerebral ischemia group （IS3）, and 12 h cerebral ischemia and L-arg treatment group （L-arg3 ）. Focal cerebral ischemia was produced by middle cerebral artery occlusion for 12 h. A nylon thread with rounded tip was inserted into left internal carotid artery cranial until resistance was met. The distance from bifurcation of common carotid artery to the tip of the thread was about 18-19 mm. Focal cerebral ischemia was confirmed by left Hornet＇s syndrome and right side hemiplegia. In each L-arg group, L-arg 500 mg/kg was given intraperitoneally after cerebral ischemia twice a day for 3 days. In IS group, normal saline was given instead of Larg. The animals were decapitated 3 days after treatment. The brains were immediately removed for the determination of the neuronal apoptosis rate in the ischemic region and the expression of Caspase-3, Bcl-2 and Bax protein. Results The neuronal apoptosis rate and the expression of Caspase-3 and Bax protein were significantly higher, while the ratio of Bcl-2/Bax protein was significantly lower in IS1, IS2 and IS3 group than in SH group （ P 〈 0.01 ）. The neuronal apoptosis rate and the expression of Caspase-3 and Bax protein were significantly lower, while the expression of Bcl-2 protein and the ratio of Bcl-2/Bax protein were significantly higher in L-arg1 and L-arg2 group than in IS, and IS2 group （P 〈 0.01）. There was no significant difference in the indexes mentioned above between IS3 and L-arg3 group （ P 〉 0.05） . Conclusion L-arg can reduce the neuronal apoptosis and has certain therapeutic effect during the early cerebral ischemia period. The underlying mechanism may be related to the down-regulation of Caspase-3 protein expression and the balance regulation of Bcl-2/Bax protein.