叶酸对AD模型小鼠脑内Aβ沉积及BACE1表达影响

田甜; 孙杨; 王渭诗; 刘欢; 黄国伟

doi:10.11847/zgggws1114187

叶酸对AD模型小鼠脑内Aβ沉积及BACE1表达影响

Effects of folic acid on Aβ deposition and BACE1 expression in brain of APP/PS1 transgenic mouse

摘要

摘要:
目的探讨叶酸对阿尔茨海默病（AD）小鼠脑内β–淀粉样蛋白（Aβ）沉积影响及机制。
方法将6月龄雄性APP/PS1模型小鼠随机分为4组：叶酸缺乏组、叶酸对照组、叶酸低、高剂量组（120、600 μg/kg）；同月龄野生型小鼠作为阴性对照组。叶酸缺乏组小鼠饲以叶酸缺乏饲料，其他各组饲以普通饲料，干预60 d。采用实时荧光定量PCR法（RT-PCR）检测β位淀粉样前体裂解酶–1（BACE1）mRNA水平；免疫印迹法（WB）检测脑组织BACE1蛋白表达；免疫组化法检测脑组织Aβ表达；酶联免疫吸附法检测脑组织中Aβ_1–40和Aβ_1–42含量。
结果与叶酸对照组比较，叶酸高剂量组小鼠脑组织中Aβ蛋白表达降低，叶酸缺乏组Aβ蛋白表达升高（P < 0.05）；与叶酸对照组（0.295 ± 0.034）比较，叶酸高剂量组小鼠脑组织Aβ_1–42含量（0.209 ± 0.041）降低，叶酸缺乏组Aβ_1–42含量（0.396 ± 0.043）升高（P < 0.05）；与叶酸对照组（15.99 ± 1.434）比较，叶酸缺乏组小鼠脑组织BACE1 mRNA水平（21.97 ± 4.396）升高，叶酸低、高剂量组小鼠脑组织中BACE1 mRNA表达水平分别为（9.932 ± 1.903）、（10.53 ± 2.750）均降低（均P < 0.05）；与叶酸对照组（1.371 ± 0.213）比较，叶酸缺乏组小鼠脑组织中BACE1蛋白表达水平（1.655 ± 0.241）升高，叶酸低、高剂量组小鼠脑组织中BACE1蛋白表达水平分别为（1.003 ± 0.271）、（0.906 ± 0.188）均降低，差异均有统计学意义（均P < 0.05）。
结论补充叶酸可减少AD小鼠脑组织中Aβ沉积及Aβ_1–42含量，其机制可能与叶酸抑制小鼠脑组织中淀粉样蛋白生成途径的分泌酶BACE1表达有关。

Abstract:
Objective To explore the effect and mechanisms of folic acid on deposition of amyloid β-protein (Aβ) in brain tissues of mice with Alzheimer’s disease.
Methods Forty 6-month-old male APP/PS1 mice were randomly assigned into four groups: a folate deficiency group (AD + FA-D) with folic acid deficient feed and daily gavage of water, a folate control group (AD + FA-N) with normal feed and daily gavage with water, and low- and high-dose folate groups (AD + FA-L and AD + FA-H) with normal feed and daily gavage of 120 and 600 μg/kg folic acid; ten 6-month-old male wild type mice with normal feed and daily gavage of water (WT + FA-N) were used as negative controls. The treatments were performed consecutively for 60 days. By the end of the treatments, the mRNA expression of β-site amyloid precursor protein cleaving enzyme-1 (BACE1) in brain tissues was quantified by real-time PCR. The protein expression level of β-site amyloid precursor protein cleaving enzyme-1 (BACE1) in brain tissues was detected with Western blot; the expression of Aβ in brain tissues was measured with immunohistochemistry; the expression levels of Aβ_1–40 and Aβ_1–42 in brain tissues were measured with enzyme-linked immunosorbent assay (ELISA).
Results The expression of Aβ decreased in AD+FA-H group and increased in AD+FA-D group significantly compared to that in AD+FA-N group (P < 0.05); the content of Aβ_1–42 (0.209 ± 0.041) decreased in AD + FA-H group and increased (0.396 ± 0.043) in AD + FA-D group significantly compared to that (0.295 ± 0.034) in AD + FA-N group (P < 0.05); the expression of BACE1 mRNA increased in AD + FA-D group (21.97 ± 4.396) but decreased in AD + FA-L and AD + FA-H groups (9.932 ± 1.903 and 10.53 ± 2.750) significantly compared to that (15.99 ± 1.434) in AD + FA-N group (P < 0.05 for all); the expression of BACE1 protein increased in AD + FA-D group (1.655 ± 0.241) but decreased in AD + FA-L and AD + FA-H groups (1.003 ± 0.271 and 0.906 ± 0.188) significantly compared to that (1.371 ± 0.213) in AD + FA-N group (P < 0.05 for all).
Conclusion The study results show that folic acid supplementation can reduce brain Aβ deposition and Aβ_1–42 content and the mechanism of the effects may be related to folic acid-induced inhibition of BACE1 expression associated with Aβ formation in brain tissue of mice.

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