硒酸钠抑制阿尔茨海默症模型小鼠海马β-淀粉样蛋白产生及嗅球病变的分子机制

发布时间：2018-02-21 19:09

本文关键词： 阿尔茨海默症(AD) 硒酸钠 Wnt/β-catenin信号通路蛋白磷酸酯酶2A(PP2A) β-淀粉样蛋白前体(APP) β-淀粉样蛋白(Aβ)　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：阿尔茨海默症(Alzheimer’s disease,AD)是一种与年龄相关的渐行性神经退行性疾病,最初表现为进行性记忆力减退、获得性知识丧失,最终发展为日常生活活动能力完全丧失,给社会和家庭带来沉重负担。越来越多的研究表明硒的日摄入量与AD的发病率密切相关。研究发现硒酸钠能够显著降低微管相关蛋白tau病变模型鼠脑内tau蛋白的过度磷酸化,减少神经纤维缠结,但是硒酸钠对AD病理过程中Wnt/β-catenin信号通路的影响以及对淀粉样蛋白前体(APP)的剪切过程的影响并不清楚。同时,AD病变过程与嗅球的关系、硒对AD鼠脑中嗅球病变的影响,目前报道甚少。本论文围绕这两方面开展了相关研究。本研究采用三转基因AD模型鼠,从2月龄开始给予含6?g/ml硒酸钠的饮用水,给药10个月后检测其海马区的病理指标。研究发现,12月龄AD模型鼠海马区出现大量β-淀粉样蛋白(Aβ)及神经元凋亡,并且出现Wnt/β-catenin信号通路活性下调。给予硒酸钠的AD模型鼠,其海马区神经元突触密度增加,β-淀粉样蛋白减少,神经元凋亡降低。进一步研究发现:硒酸钠显著激活AD模型鼠脑内蛋白磷酸酶(PP2A)的活性、降低糖元合成酶激酶3β(GSK3β)的磷酸化,提高β-链蛋白(β-catenin)的表达水平,从而激活Wnt/β-catenin信号通路及其下游靶基因的转录,使基因c-myc、survivin、TXNRD2表达水平上调,基因BACE1的表达水平下调。AD模型鼠脑内APP在其第668位的苏氨酸残基的磷酸化(APP-pT668)易被BACE1识别并剪切,造成Aβ的产生增加,本研究发现AD模型鼠硒酸钠处理组APP-pT668的表达水平显著降低,降低Aβ的产生。以上结果表明Wnt/β-catenin信号通路对阻止AD的病理变化具有重要作用,硒酸钠有可能是治疗AD的一种潜在药物。AD的早期病理变化中嗅觉功能受损,为了探究硒酸钠对嗅球早期病理变化的影响,本研究给予2月龄三转基因AD模型鼠3?g/ml硒酸钠饮用水,饲养4个月后检测相关指标。结果发现,硒酸钠显著提高小鼠的空间记忆能力,相比野生型小鼠,AD组嗅球内Aβ及Tau-pS231的表达显著升高,硒酸钠处理组AD模型鼠嗅球内二者的表达水平显著降低。分别取野生型小鼠、AD模型鼠及硒酸钠饲养AD组小鼠的嗅球组织,从中提取总RNA进行转录组测序和生物信息学分析,发现与野生型小鼠相比,AD小鼠嗅球中Grin2a、Grin2b、Creb1、Gng13及Chrm2基因表达水平降低,Gfap基因表达水平升高;给予硒酸钠的AD模型小鼠,嗅球中显著上调的基因有Grin2a、Grin2b、Creb1、Gng13及Chrm2,下调基因有Gfap,硒酸钠给药组逆转了AD模型鼠嗅球内上述基因的表达水平。采用Q-PCR及Western blotting验证了与突触相关的基因Grin2a和Grin2b与转录组显示的结果一致。为了在细胞水平上验证这一结果,用0.1?M硒酸钠处理从AD小鼠嗅球中分离培养的原代神经元,与从野生型小鼠嗅球中分离培养的原代神经元相比较,发现AD组嗅球内神经元突触素蛋白显著下降,硒酸钠处理AD组,突触素的表达增加。综上,硒酸钠能够激活AD模型鼠脑内降低的Wnt/β-catenin信号通路,抑制APP剪切形成Aβ、减少神经元的凋亡。同时,硒酸钠降低嗅球内Aβ的产生及tau蛋白的过度磷酸化,提高嗅球中Grin2a和Grin2b基因和蛋白的表达,并且提高突触素蛋白的表达。在已有硒酸钠抑制AD病理特征的基础上,进一步揭示了硒酸钠对AD上游信号通路和早期病变组织的作用和机理。
[Abstract]:Blzheimer ("Alzheimer s disease, AD) is more of a neurodegenerative disease associated with age, initially characterized by progressive loss of memory, loss of acquired knowledge, and ultimately the development of activities of daily living completely lost, bring heavy burden to society and family. More and more studies show that the incidence of selenium on intake and rate of AD are closely related. The study found that sodium selenite can significantly reduce tau hyperphosphorylation of microtubule associated protein tau in brain of rat model, reduce neurofibrillary tangles, but the sodium selenite AD pathological effects of Wnt/ during beta -catenin signaling pathway and the amyloid precursor protein (APP) effect the shearing process is not clear. At the same time, the relationship between AD and pathological changes of the olfactory bulb, effects of selenium on AD in rat brain in the olfactory bulb lesion, rarely reported. This paper carried out the research on the two aspects Study. This study used three AD transgenic mouse model, starting from 2 month old to 6 with g/ml? Sodium selenite in drinking water, detection of pathological index in their hippocampus after 10 months of administration. The study found that 12 month old of the AD model in hippocampus of the emergence of a large number of amyloid beta (A beta) and neuronal apoptosis, and downregulation of Wnt/ beta -catenin signaling pathway activity. AD model rats were given sodium selenite, the hippocampal synaptic density increased, amyloid beta protein decreased, apoptosis of neurons decreased. Further studies showed that sodium selenite significantly activated AD model rat brain protein phosphatase (PP2A) activity, reduced glycogen synthase kinase 3 beta (GSK3 beta) phosphorylation, improved beta chain protein (beta -catenin) expression levels and transcriptional activation of Wnt/ -catenin signaling pathway and its downstream target genes, the genes c-myc, survivin, TXNRD2 expression level increased, the expression level of BACE1 gene down regulated. AD APP in the brain of rat model of threonine residues 668th phosphorylation of BACE1 (APP-pT668) is easily identified and cut, resulting in the increase of A beta, the study found that the AD rat model of sodium selenite treatment group the expression level of APP-pT668 decreased significantly, decreased the production of A 3. The above results showed that Wnt/ beta -catenin the signal pathway plays an important role in the pathological changes of block AD, sodium selenite may be the early pathological changes in olfactory function damaged a potential drug for treatment of.AD AD, in order to explore the effect of sodium selenate on early pathological changes of the olfactory bulb, this study gives 2 month old three transgenic rat model of AD 3? G/ml sodium selenite in drinking water. Detection of relevant indicators after 4 months of feeding. The results showed that sodium selenite significantly improve the spatial memory ability of mice, compared with wild type mice, AD group in the olfactory bulb of the expression of A beta and Tau-pS231 increased significantly, sodium selenite treated group AD rats in the olfactory bulb The expression level of two was significantly reduced. Were collected from wild type mice, the olfactory bulb tissue in AD rats and sodium selenite feeding AD mice, extraction of total RNA from in transcriptome sequencing and bioinformatics analysis, found that compared with wild type mice, Grin2a AD mice, the olfactory bulb in Grin2b, Creb1, Gng13 expression and the level of Chrm2 gene decreased, the expression level of Gfap gene increased; AD mice given sodium selenite, significantly increased in the olfactory bulb gene Grin2a, Grin2b, Creb1, Gng13 and Chrm2, were down regulated Gfap, sodium selenite reversed the expression level of AD rats in the olfactory bulb of the gene delivery by Q-PCR group. Western and blotting show and synapse related genes Grin2a and Grin2b and transcription group showed the consistency of the results. In order to verify the results, at the cellular level by 0.1? M sodium selenite treatment cultured primary neurons from the olfactory bulb of AD mice, and from the wild Cultured primary neurons in the olfactory bulb type mice compared to AD group of neurons in the olfactory bulb of synaptophysin decreased significantly in treatment group AD of sodium selenite, increase the expression of synaptophysin. Therefore, sodium selenite can activate Wnt/ beta -catenin signaling pathway in AD rat brain decreased, the inhibition of APP formation of shear A beta. Reduce neuronal apoptosis. At the same time, sodium selenite reduced phosphorylation in the olfactory bulb of A beta and tau protein, enhance the expression of Grin2a and Grin2b in the olfactory bulb of gene and protein, and increase the expression of synaptophysin. Inhibition of AD based histopathological features in existing sodium selenite, and further reveal the mechanism of selenium AD sodium on the upstream signaling pathways and early lesions.

【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R749.16;R-332

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