张淑惠, 张慧芳, 徐义荣, 王姗姗, 赵宇卿, 牛侨. 慢性铝染毒对大鼠海马突触可塑性及神经连接蛋白1表达的影响[J]. 环境与职业医学, 2019, 36(7): 621-626. DOI: 10.13213/j.cnki.jeom.2019.18715
引用本文: 张淑惠, 张慧芳, 徐义荣, 王姗姗, 赵宇卿, 牛侨. 慢性铝染毒对大鼠海马突触可塑性及神经连接蛋白1表达的影响[J]. 环境与职业医学, 2019, 36(7): 621-626. DOI: 10.13213/j.cnki.jeom.2019.18715
ZHANG Shu-hui, ZHANG Hui-fang, XU Yi-rong, WANG Shan-shan, ZHAO Yuqing, NIU Qiao. Effects of chronic aluminum exposure on hippocampal synaptic plasticity and neuroligin 1 expression in rats[J]. Journal of Environmental and Occupational Medicine, 2019, 36(7): 621-626. DOI: 10.13213/j.cnki.jeom.2019.18715
Citation: ZHANG Shu-hui, ZHANG Hui-fang, XU Yi-rong, WANG Shan-shan, ZHAO Yuqing, NIU Qiao. Effects of chronic aluminum exposure on hippocampal synaptic plasticity and neuroligin 1 expression in rats[J]. Journal of Environmental and Occupational Medicine, 2019, 36(7): 621-626. DOI: 10.13213/j.cnki.jeom.2019.18715

慢性铝染毒对大鼠海马突触可塑性及神经连接蛋白1表达的影响

Effects of chronic aluminum exposure on hippocampal synaptic plasticity and neuroligin 1 expression in rats

  • 摘要: 背景 铝抑制海马长时程增强(LTP)的功能,表明铝可能损伤突触可塑性。神经连接蛋白1(NLGN1)能通过募集N-甲基-D-天冬氨酸受体(NMDAR)及突触后致密蛋白95(PSD-95)等影响树突棘的发育、成熟。

    目的 探讨慢性铝染毒对大鼠海马突触可塑性和NLGN1表达的影响,揭示NLGN1在其中的作用。

    方法 取清洁雄性SD大鼠48只随机分为对照组,低、中、高剂量铝染毒组,每组12只。对照组给予生理盐水,低、中、高剂量组分别给予10、20、40 μmol/kg麦芽酚铝溶液,采用染5 d停2 d模式腹腔注射麦芽酚铝溶液建立慢性铝染毒模型,染毒时长3个月。染毒周期结束后,用Morris水迷宫检测逃避潜伏期、穿越平台次数,反映大鼠学习记忆功能。用LTP实验记录海马CA1区场兴奋性突触后电位(fEPSP)。用高尔基染色观察海马CA1区神经元树突棘的形态和数量改变。Western blot检测大鼠海马NLGN1、NMDAR-2A、NMDAR-2B以及PSD-95的表达。

    结果 随着训练天数的增加,对照组及铝染毒组大鼠潜伏期用时逐渐减少。与对照组相比,20 μmol/kg和40 μmol/kg染铝组大鼠在Morris水迷宫检测中潜伏期明显延长(第2、3、4天分别延长19.67、5.96、6.49 s和21.77、10.20、9.91 s,P < 0.05),穿越平台的次数分别减少了2.14次和3.93次(P < 0.05)。30 min高频刺激后,20 μmol/kg及40 μmol/kg染铝组大鼠fEPSP分别为1.15±0.03、1.10±0.06,60 min高频刺激后则下降为1.03±0.18、0.98±0.22,均低于对照组(1.41±0.05、1.47±0.11,P < 0.05)。与对照组(1.302±0.111)/μm相比,20μmol/kg及40μmol/kg染铝组大鼠树突棘密度(0.790±0.056)、(0.725±0.152)/μm明显降低(P < 0.05)。慢性铝染毒后,与对照组(1.00±0.00)相比,20 μmol/kg铝染毒组(0.80±0.07)、40 μmol/kg铝染毒组(0.55±0.05)NLGN1表达降低(P < 0.05);与对照组(1.00±0.00)相比,20 μmol/kg铝染毒组NMDAR-2A(0.58±0.08)、NMDAR-2B(0.56±0.04)、PSD-95(0.76±0.01)表达降低(P < 0.05)。

    结论 慢性铝染毒可能通过下调NLGN1、NMDAR-2A、NMDAR-2B以及PSD-95蛋白表达水平损伤海马突触功能,导致大鼠学习记忆功能受损。

     

    Abstract: Background Aluminum inhibits hippocampal long-term potentiation (LTP), suggesting that aluminum may impair synaptic plasticity. Neuroligin 1 (NLGN1) can affect the development and maturation of dendritic spines by recruiting N-methyl-D-aspartic acid receptor (NMDAR) and postsynaptic density protein 95 (PSD-95).

    Objective The purpose of this study is to investigate the effect of chronic aluminum exposure on hippocampal synaptic plasticity and NLGN1 expression in rats, and reveal the role of NLGN1 in this process.

    Methods Forty-eight clean male SD rats were randomly divided into control group, and low, medium, and high dose aluminum groups, with 12 rats in each group. The control group was given normal saline, and the low, medium, and high dose groups were given 10, 20, 40 μmol/kg aluminum-maltolate complexAl(mal)3, respectively. A chronic aluminum exposure model was established by weekly intraperitoneal injection of Al(mal)3 for 5 days and rest for 2 days. The duration of the exposure was 3 months. After the exposure, Morris water maze was used to evaluate escape latency and the number of crossing, indicators of learning and memory function of rats. Field excitatory postsynaptic potential (fEPSP) in CA1 region of hippocampus was measured by LTP assay in vivo. The morphological presentation and number change of dendritic spine of CA1 neurons in hippocampus were detected with Golgi staining. The expressions of hippocampal NLGN1, NMDAR-2A, NMDAR-2B, and PSD-95 were examined by Western blot.

    Results As the training days increased, the latencies of the control group and the aluminum exposure groups gradually decreased. Compared with the control group, the latencies of the 20 and 40μmol/kg aluminum exposure groups significantly prolonged in the Morris water maze (on day 2, 3, and 4, 19.67, 5.96, and 6.49s increased of the 20μmol/kg group; 21.77, 10.20, and 9.91 s increased of the 40μmol/kg group; P < 0.05), and the numbers of crossing the original platform decreased by 2.14 times and 3.93 times, respectively (P < 0.05). In 30 min post high frequency stimulation, the fEPSPs of the 20 and 40 μmol/kg aluminum exposure groups were 1.15±0.03 and 1.10±0.06 respectively, and the fEPSPs decreased to 1.03±0.18 and 0.98±0.22 respectively after 60 min, with significant differences compared with the control group (1.41±0.05 and 1.47±0.11, P < 0.05). Compared with the control group(1.302±0.111)/μm, the dendritic spine densities of the 20 and 40 μmol/kg aluminum exposure groups(0.790±0.056), (0.725±0.152)/μm decreased significantly (P < 0.05). After chronic aluminum exposure, compared with the control group (1.00±0.00), the NLGN1 expression levels in the 20 μmol/kg group (0.80±0.07) and in the 40μmol/kg group (0.55±0.05) were reduced significantly (P < 0.05); compared with the control group (1.00±0.00), the expression levels of NMDAR-2A (0.58±0.08), NMDAR-2B (0.56±0.04), and PSD-95 (0.76±0.01) in the 20μmol/kg group were reduced significantly (P < 0.05).

    Conclusion Chronic aluminum exposure may impair hippocampal synaptic function by down-regulating NLGN1, NMDAR-2A, NMDAR-2B, and PSD-95 protein expressions, resulting in impaired learning and memory.

     

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