氨基胍对局灶性脑缺血诱导大鼠脑神经元凋亡的影响

Effect of aminoguanidine on neuronal apoptosis induced by focal cerebral ischemia in rats

目的观察选择性诱导型一氧化氮合酶抑制剂氨基胍(AG)对局灶性脑缺血诱导大鼠脑神经元凋亡的影响,探讨AG对脑缺血大鼠脑神经元的保护作用及其机制。方法健康雄性SD大鼠54只,体重250-300 g,随机分为3组:假手术组(SH组)、缺血组(IS组)、AG治疗组(AG组),每组18只。每组按给药时机分为3个亚组:缺血2 h组、缺血6 h组、缺血12 h组,每亚组6只。IS、AG组采用插线法制备大鼠大脑中动脉阻断模型。AG组每次腹腔注射AG 100 mg/kg,每日2次,连续3 d。IS 组给予等量的生理盐水。治疗后大鼠断头取脑,采用流式细胞仪测定脑组织神经元凋亡率、Bcl-2蛋白、Bax蛋白表达及Bcl-2蛋白与Bax蛋白比值(Bcl-2/Bax)。结果与SH组比较,IS、AG组各亚组神经元凋亡率及Bax蛋白表达升高,AG组各亚组Bcl-2蛋白表达升高,IS、AG组各亚组Bcl-2/Bax降低(P <0.01);与IS组比较,AG组各亚组神经元凋亡率降低,AG组各亚组Bcl-2蛋白表达及Bcl-2/Bax升高,AG组Bax蛋白表达降低(P<0.05或0.01)。结论AG通过增加Bcl-2蛋白表达,降低Bax蛋白表达,调节Bcl-2/Bax平衡,对脑缺血大鼠脑神经元产生一定程度的保护作用。

Objective To evaluate the effect of aminoguanidine (AG) on neuronal apoptosis induced by focal cerebral ischemia in rats and the possible mechanism of protective effect of AG against cerebral ischemic injury.Methods Fifty-four male SD rats weighing 250-290 g were randomly divided into 3 groups: (1) sham operated group (SH group, n = 18); (2) ischemic group (IS group, n = 18) and (3) AG group(n = 18). SH, IS and AG groups were further divided into 3 subgroups according to the administration time:2, 6 or 12 h following cerebral ischemia. In AG group AG 100 mg· kg-1 was given intraperitoneally twice a day for 3 consecutive days. In IS group normal saline was given instead of AG. Focal cerebral ischemia was produced by middle cerebral artery occlusion (MCAO). A nylon thread with rounded tip which was inserted into left internal carotid artery cranially until resistance was felt. 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 Homer's syndrome and right side hemiplegia. In SH group the carotid artery was exposed but no thread was inserted. The nylon thread was with drawn to allow reperfusion after 2, 6 or 12 h MCAO. The animals were detected by flow cytometry. Results Significantly increased DNA fragmentation indicative of apoptosis was detected after MCAO. The percentage of apoptotic cells and expression of Bax protein were significantly lower after 2, 6 and 12 h ischemia in AG group than in IS group but still significantly higher than in SH group. The expression of Bcl-2 protein was significantly higher after 2,6 and 12 h in AG group than in IS group. There was no significant difference in the expression of Bcl-2 protein between IS and SH group. Conclusion AG can protect neurons from apoptosis through increasing the Bcl-2 protein expression and inhibiting the Bax protein expression.