氯化锂对沙土鼠前脑缺血后神经细胞凋亡及P53、核转录因子κB蛋白表达的影响

背景:氯化锂能抑制各种原因引起的神经细胞凋亡,其确切的脑保护作用较复杂.目的:观察氯化锂预处理后,短暂前脑缺血沙土鼠脑海马CA1区神经细胞凋亡及促凋亡基因P53、核转录因子κB蛋白表达的变化.设计:随机对照实验.单位:南京医科大学人体解剖学教研室.材料:实验于2003-10/2004-03在南京医科大学人体解剖学教研室实验室完成.选择清洁级雄性健康沙土鼠54只,体质量55～70 g.方法:54只沙土鼠随机分为3组,假手术组、缺血再灌注组和氯化锂组,每组18只.各组又分别依假手术后或脑缺血再灌注后处死动物时间的不同分为1,3,7 d组,每组6只.氯化锂组腹腔注射氯化锂3 mEq/kg,1次/d,连续7 d.缺血再灌注组、假手术组以生理盐水代替氯化锂.于第8天晨开始制作前脑缺血再灌注动物模型:沙土鼠经戊巴比妥钠麻醉后,应用微动脉夹同时夹闭双侧颈总动脉,夹闭5 min,松开动脉夹恢复脑血流即为再灌注.假手术组仅游离双侧颈总动脉但不夹闭.各组沙土鼠于脑缺血再灌注后各规定时间点处死,于视交叉后1.7～4.0 mm行冠状切块,切片,片厚4μm.测定凋亡细胞应用原位末端标记染色法,测定P53、核转录因子κB阳性细胞表达应用免疫组织化学染色法.计数单位面积(1 mm2)内凋亡细胞数及P53、核转录因子κB阳性细胞数.主要观察指标:脑缺血再灌注后神经细胞凋亡及P53、核转录因子κB蛋白的表达.结果:54只沙土鼠全部进入结果分析.①脑海马CA1区凋亡细胞表达情况:缺血再灌注3 d组显著高于氯化锂3 d组(552.0±145.5,142.4±103.5)个/mm2,(t=5.623,P＜0.01)].脑缺血再灌注7 d组凋亡细胞有所减少,但仍显著高于氯化锂7 d组(408.0±119.8,156.0±1082)个/mm2,(t=8.242,P＜0.01)].②脑海马CA1区P53阳性细胞表达情况:缺血再灌注1,3,7 d组表达显著高于相应的假手术组和氯化锂组(F=37.668～89.545,P＜0.01).③脑海马CA1区核转录因子κB阳性细胞表达情况:缺血再灌注1 d,3 d组表达均增高(78.5±25.2),(176.5±35.5)个/mm2,再灌注7 d组表达消失.氯化锂3 d组显著低于缺血再灌注3 d组(64.5±30.8)个/mm2,(t=5.824,P＜0.01)].结论:氯化锂预处理能显著减轻沙土鼠短暂前脑缺血后海马CA1区神经元凋亡,下调促凋亡基因P53蛋白及核转录因子κB蛋白的表达可能是氯化锂产生脑保护作用的原因之一.

Effect of lithium chloride on neuronal apoptosis and expression of P53 and nuclear factor kappa B after forebrain ischemia in gerbils

BACKGROUND: Recently, lithium was reported shown neuroprotective effect against apoptosis induced by a variety of insults in vitro and in vitro,but the precise mechanisms underlying its neuroprotective effect remain unknown.OBJECTIVE: To observe the effect of lithium chloride on neuronal apoptosis and the expression of P53 or nuclear factor kappa B (NF-κB) protein in the CA1 region of the hippocampus after global ischemia in gerbils.DESIGN: A randomized controlled experimental research.SETTING: Department of Anatomy of Nanjing Medical University.MATERIALS: Fifty-four healthy male gerbils weighing 50-70 g, clearing grade, were purchased from Experimental Animal Center of Zhejiang Province.METHODS: Totally 54 gerbils were randomly divided into three groups namely: sham-operation group (SH group), ischemia-reperfusion group (IR group) and lithium chloride group (LI group), with 18 in each group. SH group, IR group and LI group were further divided into 3 subgroups respectively (SH1d, SH3d, SH7d; IR1d, IR3d, IR7d; LI1d, LI3d, LI7d), according to the time of reperfusion, with 6 gerbils in each. Gerbils in LI group were injected intraperitoneally with lithium chloride 3 mEq /kg, once a day for 7consecutive days before operation. Normal saline was used instead of lithium in SH group and IR group as vehicle control. Forebrain ischemia was induced at 24 hours after the last injection of lithium chloride. After gerbils being anesthetized, the bilateral common carotid arteries were blocked with micro aneurysm clips for 5 minutes, and the micro aneurysm clips were removed and the cerebral blood flow restored. Sham-operation animals were underwent the same operation except occlusion of bilateral common carotid arteries. Gerbils in each group were killed at every time points.4 μm coronal sections at 1.7-4.0 mm visual cross were cut at the level of the dorsal hippocampus. The apoptosis cells were assayed with in situ Cell Death Detection Kit, and assay of positive cell in cell apoptosis, P53 and positive NF-κB was performed with immunohistochemistry staining. The total number of TUNEL positive cells, P53 or NF-κB positive cells per image (area of 1 mm2) was counted.MAIN OUTCOME MEASURES: Neuronal apoptosis and expression of P53 or NF-κB protein in the CA1 region after cerebral ischemic reperfusion.apoptosis cell in cerebral hippocampus CA1 region: No TUNEL positive cells were detected in SH group, a large majority of TUNEL positive cells were detected in the CA1 region in IR group on the 3rd day after reperfusion (552.0±145.5, 142.4±103.5) pcs/mm2, t= 5.623, P ＜ 0.01], and TUNEL positive cells declined on the 7th day after reperfusion. The numbers of TUNEL positive cells in the CA1 region of LI3d, LI7d group were significantly lower than those of IR3d, IR7d group (408.0±119.8, 156.0±108.2) pcs/mm2,CA1 region: In IR group, the expression of P53 protein was increased on the 1st, 3rd and 7th day after reperfusion compared with that in SH group and cerebral hippocampus CA1 region: No NF-κB protein was expressed in SH group. In IR group, the expression of NF-κB protein was increased on the 1st day after reperfusion (78.5±25.2)/mm2, significantly increased on the 3rd day after reperfusion (176.5±35.5)/mm2 and on the 7th day after reperfusion, the expression of NF-κB protein disappeared. There were no significant statistical difference between LI group and IR group on the 1st day after reperfusion. The expression of NF-κB protein in LI group was significantly lower than that in IR group on the 3rd day after reperfusion (64.5±30.8)/mm2,t=5.824, P ＜ 0.01].CONCLUSION: Lithium chloride can significantly suppress neuronal apoptosis after global ischemia in gerbils. The down-regulation of expression of P53 or NF-κB protein is one of the mechanisms of the neuroprotective effect by lithium chloride.