铅对小鼠海马β-位点-淀粉样前体蛋白剪切酶-1和Bax及β淀粉样蛋白42蛋白表达以及学习记忆能力的影响

Effects of Lead Acetate on BACE1,Bax and Aβ42 Protein Expression in Hippocampus and Learning and Memory Ability among Mice

目的探讨乙酸铅对小鼠海马β-位点-淀粉样前体蛋白剪切酶-1(β-site-APP cleavage enzyme-1,BACE-1)、Bax、β淀粉样蛋白42(β-amyloid protein,Aβ42)蛋白表达以及学习记忆能力的影响。方法将44只6月龄SPF级雄性C57BL/6小鼠随机分成4组,分别为对照(生理盐水)组和低(10 mg/kg)、中(30 mg/kg)、高(60 mg/kg)剂量乙酸铅染毒组,每组11只。采用腹腔注射方式进行染毒,染毒容量为20 ml/kg,隔日染毒1次,共注射7次。采用Western blot法检测小鼠海马组织内BACE1、sAPPβ和Bax蛋白的表达情况;采用ELISA法检测Aβ42蛋白的表达情况;采用免疫组化双标染色观察BACE1和Neuronal ClassⅢβ-Tubulin(Tuj1)阳性定位情况;末次染毒后,采用Morris水迷宫实验检测小鼠的学习记忆能力变化。结果与对照组相比,30和60 mg/kg乙酸铅染毒组小鼠海马内BACE1、sAPPβ、Bax和Aβ42蛋白的表达水平均显著升高,差异有统计学意义(P<0.01);而10 mg/kg乙酸铅染毒组小鼠海马内BACE1、sAPPβ、Bax蛋白的表达水平无显著改变。且随着乙酸铅染毒剂量的升高,小鼠海马内BACE1、sAPPβ、Bax和Aβ42蛋白的表达水平均呈上升趋势。BACE1阳性和Tuj1阳性存在共定位现象。与对照组比较,30、60 mg/kg乙酸铅染毒组小鼠的逃避潜伏期显著延长,穿越平台次数显著减少,差异有统计学意义(P<0.05),10 mg/kg乙酸铅染毒组与对照组差异无统计学意义。结论铅暴露可引起海马BACE1和Bax及Aβ42蛋白表达上调,并可引起小鼠学习记忆能力降低。

Objective To investigate the effects of lead acetate on BACE1, Bax protein expression, and Aβ42 expression in the hippocampus of mice. Methods Forty-four C57BL/6 SPF mice were randomly divided into four groups, 11 in each, vehicle-treated group and lead acetate-treated group （10, 30 and 60 mg/kg, through intraperitoneal injection, every two days for seven times, 20 mg/kg for each mice）. The protein expression changes of BACE1, sAPPβ and Bax in hippocampus were tested by Western blot. The Aβ42 protein expression was observed by ELISA,the relations of BACE1 and Neuronal Class Ⅲ β-Tubulin （Tujl） were tested by double immunofluorescence staining,and the changes of learning and memory were tested by Morris water maze after the last injection of lead acetate. Results The protein expression of BACE1, sAPPβ and Bax and also the protein expression of Aβ42 were increased in 30 mg/kg and 60 mg/kg lead acetate-treated groups compared with control group （P〈 0.05）, and increased accompanied by the increasing concentration of lead acetate. BACE1 expression co-localized with that of Tujl; The escape latency increased and the crossing times decreased in lead acetate-treated groups（p〈0.05）. While there were no significant differences between 10 mg/kg lead acetate-treated group and control-group. Conclusion Lead exposure may increase the protein expression of BACE1 and Bax, increase the Aβ42 protein expression and decrease the learning and memory ability.