L-精氨酸对局灶性脑缺血损伤大鼠脑组织TNF-α、IL-1β及神经元凋亡的影响

Effect of L-arginine on cerebral TNF-α and IL-1β content and neuronal apoptosis after cerebral ischemic injury in rats

目的探讨L-精氨酸对局灶性脑缺血损伤大鼠脑组织肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）及神经元凋亡的影响。方法健康雄性SD大鼠30只,体重250～280g,随机分为3组（n=10）：假手术组（SH组）、缺血组（IS组）和L-广精氨酸治疗组（L-arg组）。L-arg组腹腔注射L-精氨酸500mg/kg,每日2次,连续3d;IS组给予等容量的生理盐水;2组均采用线栓法制备大鼠局灶性脑缺血损伤模型。将大鼠断头取脑,采用免疫组化法检测脑组织TNF-α表达,放免法检测脑组织IL-1β含量,流式细胞仪测定神经元凋亡情况、Bcl-2蛋白、Bax蛋白表达计算Bcl-2/Bax蛋白比值。结果与SH组比较,IS组脑组织TNF-α表达、IL-1β含量、神经元凋亡率升高,Bax蛋白表达上调,Bcl-2/Bax蛋白比值降低（P〈0.01）;与IS组比较,L-arg组脑组织TNF-α表达、IL-1β含量、神经元凋亡率降低,Bcl-2蛋白表达上调,Bax蛋白表达下调,Bcl-2/Bax蛋白比值升高（P〈0.01）。结论L-精氨酸通过抑制脑组织TNF-α和IL-1β水平的升高,上调Bcl-2蛋白表达,下调Bax蛋白表达,调节Bcl-2/Bax蛋白比值平衡,抑制神经元凋亡,从而对脑缺血大鼠神经元产生一定程度的保护作用。

Objective To investigate the effect of L-arginine （L-arg） on inflammatory factors in the brain tissue and neuronal apoptosis after focal cerebral ischemic injury and the possible mechanism of protective effect of L-arg against cerebral ischemic injury.Methods Thirty male SD rats weighing 250-280 g were randomly divided into 3 groups （n = 10 each）： （1） sham operation group （SH）; （2） I/R group and （3） L-arg group. Focal cerebral ischemia was produced by middle cerebral artery occlusion （MCAO） for 12 h. A nylon thread with rounded tip was inserted into left internal carotid artery craniad until resistance was left. The distance from fibureation of common carotid artery to the tip of the thread was about 18-19 mm. Focal cerebral ischemia was confirmed by left Homer＇s syndrome and right side hemiplegia. In SH group the carotid artery was exposed but no nylon thread was inserted. In L-arg group L-arg 500 mg/kg was given intraperitoneally twice a day for 3 days starting from 12 h after MCAO. In I/R group normal saline was given instead of L-arg. The animals were decapitated 3 days after treatment. The brains were immediately removed for determination of TNF-α expression （,by immuno histo-chemistry） and IL-1β content （by radio-immuno assay） in the brain tissue and neuronal apoptosis and the expression of Bcl-2 and Bax protein （by flow cytometry） . Results The expression of TNF-α and the IL-1β content were significantly increased after MCAO. The significantly increased DNA fragmentation indicating apoptosis was detected after MCAO. The expression of TNF-α and IL-1β content were significantly lower in L-arg group than in I/R group. The percentage of apoptotic cells and expression of Bax protein were significantly lower in L-arg group than in I/R group but still significantly higher than in SH group. There was no significant difference in the expression of Bcl-2 protein between I/R and SH group. Conclusion L-arg can inhibit the increase in the expression of TNF-α and IL-1β content in the brain tissue and protect neurons from apoptosis induced by focal cerebral ischemia through increasing Bcl-2 protein expression and decreasing Bax protein expression.