Key Laboratory of Endemic and Ethnic Diseases, Ministry of Education, Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China.
Mol Med Rep. 2020 Sep;22(3):2063-2075. doi: 10.3892/mmr.2020.11253. Epub 2020 Jun 18.
Alzheimer's disease (AD) is a chronic neurodegenerative, and abnormal aggregation of the neurotoxic β amyloid (Aβ) peptide is an early event in AD. The present study aimed to determine the correlation between the nicotinic acetylcholine receptor α7 subunit (α7 nAChR) and Aβ in the brains of patients with AD, and to investigate whether the increased expression levels of the α7 nAChR could alter the neurotoxicity of Aβ. The expression levels of α7 nAChR and Aβ in the brains of patients with AD and healthy brains were analyzed using immunofluorescence. Moreover, SH‑SY5Y cells were used to stably overexpress or silence α7 nAChR expression levels, prior to the treatment with or without 1 µmol/l Aβ1‑42 oligomer (AβO). The mRNA and protein expression levels of α7 nAChR, synaptophysin (SYP), postsynaptic density of 95 kDa (PSD‑95) and synaptosomal‑associated protein of 25 kDa (SNAP‑25) were subsequently analyzed using reverse transcription‑quantitative PCR and western blotting. In addition, the concentration of acetylcholine (ACh) and the activity of acetylcholinesterase (AChE) were analyzed using spectrophotometry, while the cell apoptotic rate was determined using flow cytometry. The expression of Aβ in the brains of patients with AD was found to be significantly increased, whereas the expression of α7 nAChR was significantly decreased compared with the healthy control group. In vitro, the expression levels of α7 nAChR were significantly increased or decreased following the overexpression or silencing of the gene, respectively. Consistent with these observations, the mRNA and protein expression levels of SYP, PSD‑95 and SNAP‑25 were also significantly increased following the overexpression of α7 nAChR and decreased following the genetic silencing of the receptor. In untransfected or negative control cells, the expression levels of these factors and the apoptotic rate were significantly reduced following the exposure to AβO, which was found to be attenuated by α7 nAChR overexpression, but potentiated by α7 nAChR RNA silencing. However, no significant differences were observed in either the ACh concentration or AChE activity following transfection. Collectively, these findings suggested that α7 nAChR may protect the brains of patients with AD against Aβ, as α7 nAChR overexpression increased the expression levels of SYP, SNAP‑25 and PSD‑95, and attenuated the inhibitory effect of Aβ on the expression of these synaptic proteins and cell apoptosis. Overall, this indicated that α7 nAChR may serve an important neuroprotective role in AD.
阿尔茨海默病（AD）是一种慢性神经退行性疾病，神经毒性β淀粉样肽（Aβ）的异常聚集是 AD 的早期事件。本研究旨在确定 AD 患者大脑中的烟碱型乙酰胆碱受体α7 亚基（α7 nAChR）与 Aβ之间的相关性，并探讨α7 nAChR 表达水平的增加是否会改变 Aβ 的神经毒性。使用免疫荧光法分析 AD 患者和健康大脑中α7 nAChR 和 Aβ的表达水平。此外，使用 SH-SY5Y 细胞稳定过表达或沉默α7 nAChR 表达水平，然后用或不用 1μmol/l Aβ1-42 寡聚体（AβO）处理。使用逆转录-定量 PCR 和 Western blot 分析α7 nAChR、突触小泡相关蛋白 25kDa（SNAP-25）、突触后密度蛋白 95kDa（PSD-95）和突触小体相关蛋白 25kDa（SNAP-25）的 mRNA 和蛋白表达水平。此外，使用分光光度法分析乙酰胆碱（ACh）浓度和乙酰胆碱酯酶（AChE）活性，流式细胞术测定细胞凋亡率。与健康对照组相比，AD 患者大脑中 Aβ 的表达明显增加，而α7 nAChR 的表达明显降低。在体外，过表达或沉默基因后，α7 nAChR 的表达水平分别显著增加或降低。与这些观察结果一致，过表达α7 nAChR 后 SYP、PSD-95 和 SNAP-25 的 mRNA 和蛋白表达水平也显著增加，而受体基因沉默后则降低。在未转染或阴性对照细胞中，暴露于 AβO 后这些因子的表达水平和细胞凋亡率显著降低，α7 nAChR 过表达可减弱这种抑制作用，但α7 nAChR RNA 沉默可增强这种抑制作用。然而，转染后 ACh 浓度或 AChE 活性没有差异。综上所述，这些发现表明，α7 nAChR 可能保护 AD 患者的大脑免受 Aβ 的侵害，因为α7 nAChR 过表达增加了 SYP、SNAP-25 和 PSD-95 的表达水平，并减弱了 Aβ 对这些突触蛋白表达和细胞凋亡的抑制作用。总体而言，这表明α7 nAChR 在 AD 中可能发挥重要的神经保护作用。
