李亮, 薛星莉, 李亚芹, 李欢, 潘宝龙, 牛侨. 亚慢性铝染毒对转人载脂蛋白E4基因小鼠β-淀粉样蛋白含量及低密度脂蛋白家族的影响[J]. 环境与职业医学, 2020, 37(2): 103-110. DOI: 10.13213/j.cnki.jeom.2020.19565
引用本文: 李亮, 薛星莉, 李亚芹, 李欢, 潘宝龙, 牛侨. 亚慢性铝染毒对转人载脂蛋白E4基因小鼠β-淀粉样蛋白含量及低密度脂蛋白家族的影响[J]. 环境与职业医学, 2020, 37(2): 103-110. DOI: 10.13213/j.cnki.jeom.2020.19565
LI Liang, XUE Xing-li, LI Ya-qin, LI Huan, PAN Bao-long, NIU Qiao. Effects of subchronic aluminum exposure on β-amyloid protein and low density lipoprotein family in transgenic mice with human apolipoprotein E4 gene[J]. Journal of Environmental and Occupational Medicine, 2020, 37(2): 103-110. DOI: 10.13213/j.cnki.jeom.2020.19565
Citation: LI Liang, XUE Xing-li, LI Ya-qin, LI Huan, PAN Bao-long, NIU Qiao. Effects of subchronic aluminum exposure on β-amyloid protein and low density lipoprotein family in transgenic mice with human apolipoprotein E4 gene[J]. Journal of Environmental and Occupational Medicine, 2020, 37(2): 103-110. DOI: 10.13213/j.cnki.jeom.2020.19565

亚慢性铝染毒对转人载脂蛋白E4基因小鼠β-淀粉样蛋白含量及低密度脂蛋白家族的影响

Effects of subchronic aluminum exposure on β-amyloid protein and low density lipoprotein family in transgenic mice with human apolipoprotein E4 gene

  • 摘要: 背景

    铝是阿尔兹海默病的重要环境因素,载脂蛋白E4基因(ApoE4)是阿尔兹海默病的重要遗传因素。近年来铝和ApoE4基因如何导致学习记忆损伤引起了广泛关注。铝和ApoE4基因分别对β-淀粉样蛋白(Aβ)清除和神经元突触可塑性的影响有待进一步研究。

    目的

    探究铝与ApoE4基因联合作用对小鼠Aβ及载脂蛋白E受体2(ApoER2)等低密度脂蛋白家族含量的影响。

    方法

    野生型和转人ApoE4基因型的C57BL/6小鼠各16只,每种类型小鼠随机分为染铝组40 μmol·kg-1 Al(mal)3、对照组(生理盐水),每组8只。染毒方式为腹腔注射,每注射5d停止2 d,染毒时间为60 d。采用Morris水迷宫试验检测小鼠学习记忆能力,以高尔基染色检测海马CA1区突触可塑性,采用Western blotting法检测海马组织中ApoER2、低密度脂蛋白受体相关蛋白-1(LRP1)、极低密度脂蛋白受体(VLDLRs)、淀粉样前体蛋白(APP)的蛋白表达情况,用Elisa方法检测海马中Aβ40和Aβ42蛋白含量。

    结果

    Morris水迷宫试验结果显示野生型小鼠对照组和染铝组、转ApoE4基因型小鼠对照组和染铝组染毒结束后第1天逃避潜伏期分别为(48.56±18.31)、(46.77±19.91)、(45.13±19.07)、(46.81±18.04)s,至染毒结束后第5天分别下降至(19.43±13.28)、(27.03±17.47)、(21.27±20.17)、(30.06±20.02)s。方差分析显示,染毒结束后第4、5天各组逃避潜伏期差异有统计学意义(P < 0.05);同类型小鼠对照组低于染铝组,同处理条件下野生型小鼠低于转基因型小鼠,但基因类型和铝之间交互作用无统计学意义(P>0.05)。野生型小鼠对照组和染铝组、转基因型小鼠对照组和染铝组穿越平台次数分别为(2.86±0.99)、(1.88±0.64)、(2.63±0.77)、(0.50±0.53)次,基因类型和铝之间交互作用有统计学意义(P < 0.05)。野生型小鼠对照组和染铝组、转基因型小鼠对照组和染铝组树突棘密度分别为每微米(0.57±0.06)、(0.34±0.05)、(0.39±0.05)、(0.26±0.04)个,基因类型和铝之间交互作用有统计学意义(P < 0.05)。Westernblotting结果显示,染铝与基因类型对ApoER2和LRP1的蛋白表达存在交互作用(P < 0.05),且均会导致ApoER2和LRP1蛋白表达下降,对APP和VLDLRs的蛋白表达无交互作用(P < 0.05)。Elisa检测结果表明,β40蛋白表达在各组间差异无统计学意义(P>0.05);而Aβ42蛋白表达在各组间差异有统计学意义,且基因类型和铝之间存在交互作用(P < 0.05)。

    结论

    铝和ApoE4基因对小鼠学习记忆能力存在一定程度的影响,尤其是空间学习记忆能力。铝和ApoE4基因对海马CA1区突触可塑性可能存在交互作用,表明铝和ApoE4基因联合作用可能对突触可塑性造成影响;铝和ApoE4基因对Aβ含量变化可能存在交互作用,尤其是Aβ42含量的变化,其原因可能是铝和ApoE4基因联合作用导致低密度脂蛋白家族中ApoER2和LRP1降低。

     

    Abstract: Background

    Aluminum is an important environmental risk factor for Alzheimer's disease, and ApoE4 gene is an important genetic determinant of Alzheimer's disease. In recent years, how aluminum and ApoE4 gene lead to learning and memory impairment has drawn wide attention. Aluminum and ApoE4 gene play important roles in β-amyloid protein (Aβ) clearance and neuronal synaptic plasticity, which needs further exploration.

    Objective

    This experiment explores the effects of aluminum and ApoE4 gene on the content of Aβ and the content of low density lipoprotein family, such as apolipoprotein E receptor 2 (ApoER2), in mice.

    Methods

    Sixteen wild type C57BL/6 mice and 16 transgenic mice with human ApoE4 gene were included in this study. Both types of mice were randomly divided into aluminum exposure group40 μmol·kg-1 Al(mal)3 and control group (normal saline) with 8 mice in each group. Intraperitoneal injection of Al(mal)3 solution was successively performed for 5 d and rested for 2 d, and the exposure time was 60 d in total. The learning and memory ability of mice was detected with Morris water maze; the synaptic plasticity in CA1 area of hippocampus was detected with Golgi staining; the protein expressions of ApoER2, low density lipoprotein receptor-related protein 1 (LRP1), very low density lipoprotein receptor (VLDLR s), and amyloid protein precursor (APP) in hippocampus were detected by Western blotting; and the levels of Aβ40 and Aβ42 proteins in hippocampus was detected by Elisa.

    Results

    The results of Morris water maze showed that the escape latencies of the C57BL/6 control group, the C57BL/6 aluminum group, the ApoE4 control group, and the ApoE4 aluminum group on the first day after the end of exposure were (48.56±18.31), (46.77±19.91), (45.13±19.07), and (46.81±18.04) s, respectively; on the fifth day after the end of exposure, the results were decreased to (19.43±13.28), (27.03±17.47), (21.27±20.17), and (30.06±20.02) s, respectively. The results of analysis of variance showed that the differences of escape latency between groups were statistically significant on the fourth and fifth days after the end of exposure (P < 0.05); the control group showed lower values than the aluminum group, and the wild type C57BL/6 mice showed lower values than the ApoE4 transgenic type mice; however, the interaction between genotype and aluminum was not statistically significant (P>0.05). The frequencies of crossing the platform in the C57BL/6 control group, the C57BL/6 aluminum group, the ApoE4 control group, and the ApoE4 aluminum group were (2.86±0.99), (1.88±0.64), (2.63±0.77), and (0.50±0.53), respectively; the interaction between genotype and aluminum was statistically significant (P < 0.05). The densities of dendritic spines in the C57BL/6 control group and aluminum group as well as the ApoE4 control group and aluminum group were (0.57±0.06), (0.34±0.05), (0.39±0.05), and (0.26±0.04) spines per μm, respectively; the interaction between genotype and aluminum was statistically significant (P < 0.05). Western blotting results showed that aluminum and ApoE4 gene had interactions with ApoER2 and LRP1 protein expressions (P < 0.05), and both aluminum exposure and ApoE4 genotype led to decreased expression levels of ApoER2 and LRP1 proteins, but had no interaction with APP or VLDLRs protein expressions (P < 0.05). The results of Elisa showed that there was an interaction between aluminum and ApoE4 gene in Aβ42 protein (P < 0.05), but not in Aβ40 (P>0.05).

    Conclusion

    Aluminum and ApoE4 gene interact with each other on learning and memory in mice, especially on spatial learning and memory ability. The interaction between aluminum and ApoE4 gene on synaptic plasticity in hippocampal CA1 region indicates that the combined action may have an effect on synaptic plasticity. The interaction between aluminum and ApoE4 gene on Aβ content, especially on Aβ42 content, may be related to the decrease in ApoER2 and LRP1 of the low density lipoprotein family.

     

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