tau蛋白和磷酸化tau蛋白对神经系统疾病的影响

tau蛋白是一种神经元微管相关蛋白,参与轴突微管组装的调节。其磷酸化水平的增高与多种神经退行性疾病息息相关,如阿尔茨海默病、帕金森病、额颞叶痴呆、亨廷顿病,等。有研究表明其与脑血管病的发生发展密不可分。而昼夜节律作为维持机体日常生命活动以及体内稳态的重要调节器,受昼夜节律因子的调节,其紊乱可诱发神经退行性疾病相关致病蛋白的积累和相关致病激素的异常分泌,从而加剧疾病的进展。文中主要围绕磷酸化tau蛋白和昼夜节律对神经系统疾病的影响进行论述。     

tau 蛋白在阿尔茨海默病中的病理生理机制及 tau 示踪剂研究现状

随着社会人口老龄化,老年性痴呆的患病率逐年增加,已成为继心血管疾病和肿瘤后第三大危及人类生命健康的疾病。通过近二、三十年来对阿尔茨海默病（A D ）的深入研究,已明确了细胞外淀粉样老年斑（Senile Plaques ,SP ）和细胞内神经原纤维缠结（Neurofibrillary Tangles ,NFTs）是AD患者脑中最经典的组织病理变化,也是AD区别于其他痴呆最显著的特征。尸解研究显示,大脑皮质过度磷酸化tau的密度与生前认知障碍及神经元丢失的病理改变明确相关［1］,tau异常是神经退行性变的主要介质,由于匹兹堡化合物B （Pittsburgh Compound B , PiB）对淀粉样蛋白β（Amyloid β,Aβ）的成像成功地用于临床,促进了世界范围内对tau示踪剂及tau成像的纵向研究。目前利用已发现的选择性正电子发射断层扫描（Positron Emission Tomography ,PET ）配体,包括18 F － T HK523,18 F － T HK5105,18 F －T HK5117,18 F － T HK5351,18 F － T807和18 F －T808,进一步确定了 tau蛋白在不同阶段 AD患者脑中的沉积及病理机制,揭示了选择性 tau PET 示踪剂在活体内评估 tau沉积的作用及其与 Aβ的关系［2－4］,tau和 Aβ成像的结合将提高 AD 诊断的特异性,有助于进一步阐明部分认知功能正常个体中无Aβ沉积,但发生AD样神经变性改变的病理学机制［5］,目前认为 tau PET 示踪剂可以作为预测认知功能减退和疾病进展的替代性标记物［6］,对AD和非AD tau病的早期诊断和鉴别诊断具有重要的临床意义。     

tau蛋白和中枢神经系统变性疾病

tau蛋白是脑内神经元细胞支架蛋白之一。其正常功能是促进微管蛋白组成微管 ,并维持已形成微管的稳定性。参与维持细胞形态、信息传递、细胞分裂等重要生物学过程 ,是轴突生长发育和神经元极性形成的不可缺少因素。近年来发现tau蛋白与一些中枢神经系统变性疾病密切相关。我们将综述此方面的研究进展。一、tau蛋白的生物学结构tau蛋白是一种神经元微管相关蛋白 ,由微管相关蛋白和管蛋白组成的微管是细胞骨架的重要组成成分 ,与细胞有丝分裂、细胞内物质转运等多种功能有关。正常情况下广泛存在于神经元内 ,在脑内主要集中在神经细胞轴突之中…     

广泛性脑萎缩者血浆tau蛋白、磷酸化tau蛋白水平与认知功能的关系

目的探讨血浆tau蛋白、磷酸化tau蛋白(p-tau)蛋白与广泛性脑萎缩者认知功能的关系。方法纳入100名中、重度广泛性脑萎缩者,记录性别、年龄、受教育程度等一般情况,按认知功能不同分为两组:正常组(n=50例)和痴呆组(n=50例)。应用双抗体夹心酶联免疫吸附法测定血浆tau蛋白、p-tau蛋白含量,分析两组患者血浆tau蛋白、p-tau蛋白的表达差异及其与认知功能的关系。结果痴呆组血浆tau蛋白、p-tau蛋白水平[(210.92±43.79)pg/m L、(81.15±16.85)pg/m L]较正常组[(210.92±43.79)pg/m L、(81.15±16.85)pg/m L]明显升高(P0.05),tau蛋白、p-tau蛋白水平均与MMSE评分值呈负相关(均P0.05),与脑萎缩程度无明显相关性(P0.05)。结论广泛性脑萎缩患者出现认知损害可能与tau蛋白水平升高有关。     

脑脊液磷酸化tau蛋白与总tau蛋白比值对散发性Creutzfeldt-Jakob病的诊断价值

目的通过对CJD病人脑脊液磷酸化tau蛋白与总tau蛋白比值的研究,探讨其对散发性CJD的诊断价值。方法采用双抗体夹心酶联免疫吸附法(ELISA)检测13例散发性CJD、11例其它痴呆及29例非痴呆脑脊液磷酸化tau蛋白。同时测定脑脊液磷酸化tau蛋白与总tau蛋白的比值。结果1.CJD组与其它两组相比,p-tau/t-tau的比值有明显差异(P<0.05)。2.在CJD组高浓度的磷酸化tau蛋白与进展快,病程短有关(P<0.01)。结论测定p-tau/t-tau的比值有助于CJD与AD等痴呆类疾病的鉴别,对判定预后有一定帮助。     

Is tau aggregation toxic or protective?

Abnormal protein deposits are a common feature of many human diseases including Alzheimer's disease. In Alzheimer's disease, the appearance of tangles, composed of the microtubule associated protein tau, correlates with both cell death and symptom severity. However, are tau filaments simply markers of disease progression, or are they directly responsible for cell death? Due to conflicting findings from cell and animal models, it remains controversial whether tau polymers or smaller pre-fibrillar aggregates or tau monomers are the toxic species. Indeed, if monomeric or oligomeric species are mediators of disease, formation of larger tau filaments may prove beneficial to affected cells. This review will examine the findings regarding the toxicity of various tau species.     

Endogenous overproduction of β-amyloid induces tau hyperphosphorylation and decreases the solubility of tau in N2a cells

Summary. Although neurofibrillary tangles and senile plaques have been identified as the hallmark pathological changes in the brain of Alzheimer’s disease (AD), the relationship between them is still not fully understood. In the present study, we have studied the effect of endogenously overproduced amyloid β (Aβ) on tau by using wild type amyloid precursor protein (APP) transfected (N2a/APP695), or Swedish mutant APP plus Δ9 deleted presenilin-1 co-transfected (N2a/APPswe.Δ9) and APP vector transfected (N2a/vector) cell lines. We measured the secreted and intracellular Aβ, including Aβ_1–40 and Aβ_1–42, by Sandwich ELISA assay. It was shown that the levels of Aβ were increased time-dependently in N2a/APP695 and N2a/APPswe.Δ9 but not in N2a/vector upon butyric acid (BA) treatment. Compared with N2a/vector cells, tau in N2a/APP695 and N2a/APPswe.Δ9 cells was not extracted by RIPA buffer, and the SDS-extracted tau protein was hyperphosphorylated at Tau-1 and PHF-1 epitopes upon BA treatment. Obvious accumulation of the hyperphosphorylated tau in N2a/APP695 and N2a/APPswe.Δ9 cells was observed at 48 h after BA treatment. The total level of the extracted tau was reduced in N2a/APP695 and N2a/APPswe.Δ9 lines compared with N2a/vector cells by Western blot, and this reduction of total tau was also detected by immunofluorescence staining. No obvious alteration of tau mRNA was observed in both N2a/APP695 and N2a/APPswe.Δ9 cells compared with N2a/vector. This study provides direct evidence demonstrating that endogenously overproduced Aβ not only induces tau hyperphosphorylation but also decreases the level and solubility of tau in N2a cell lines. The first and second authors contributed equally to the paper     

阿尔茨海默病中针对tau蛋白治疗的研究进展

tau蛋白异常过度磷酸化被认为是阿尔茨海默病（AD）发病的重要因素,细胞内神经元纤维缠结（NFT）是AD脑中最经典的组织病理学变化,而NFT的主要成分是过度磷酸化tau蛋白。此文围绕针对tau蛋白治疗有关问题进行综述。     

阿尔茨海默病患者脑液tau蛋白含量的检测

目的 探讨ＣＳＦ中ｔａｕ蛋白浓度对于诊断ＡＤ的意义，同时分析其与载旧白Ｅ（ＡＰＯＥ）的不同等位基因型之间的关系。方法 阿尔茨海默病（ＡＤ）组纳入４５例，多发性梗塞性痴呆（ＭＩＤ）组２９例，精神分裂症组３７例，其它神经系统疾病（ＯＮＤ）组２６例，正常脑脊液（ＣＳＦ）对照组（正常组）１２例。采用酶联免疫吸附分析法检测ｔａｕ蛋白浓度，采用聚合酶链式反应方法检测ＡＰＯＥ４ 基因型。结果 ＡＤ组ＣＳＦ中ｔａ     

Amyloid β accelerates phosphorylation of tau and neurofibrillary tangle formation in an amyloid precursor protein and tau double-transgenic mouse model

In Alzheimer's disease, Aβ deposits are considered the initial cardinal events that induce tauopathy secondarily. However, the relationship between Aβ amyloidosis and tauopathy has not been determined in detail. We produced double transgenic mice, 2×TgTau(+/-) APP(+/-) , by mating Tg2576 mice that exhibit Aβ amyloidosis and TgTauP301L mice that show tauopathy, and statistically analyzed the effect of Aβ accumulation on tauopathy. There was no significant difference in theprogression of Aβ accumulation among 2×TgTau(+/-) APP(+/-) and 1×TgTau(-/-) APP(+/-) , and tau accumulation among 2×TgTau(+/-) APP(+/-) and 1×Tg Tau(+/-) APP(-/-) . The appearance rates of phosphorylated tau developing in neurons and processes were significantly accelerated in 2×TgTau(+/-) APP(+/-) mice compared with those in 1×TgTau(+/-) APP(-/-) mice at 23 months of age. Accumulation of phosphorylated and confomationally altered tau and GSK3β in neuronal processes was accelerated in the white matter in 2×TgTau(+/-) APP(+/-) . The level of phosphorylated tau in the sarkosyl-insoluble fraction was increased in 2×TgTau(+/-) APP(+/-) brains compared with that in 1×TgTau(+/-) APP(-/-) brains. Thus, Aβ amyloid partially enhances tauopathy through accumulation of insoluble, phosphorylated, and conformationally changed tau in neuronal cytoplasm and processes in the late stage.     

Alzheimer病神经原纤维缠结与tau蛋白研究

Ａｌｚｈｅｉｍｅｒ病(ＡＤ)是以进行性记忆和认知功能丧失为临床特征的大脑退行性疾病,其神经病理学特征为神经细胞内神经原纤维缠结(ｎｅｕｒｏｆｉｂｒｉｌｌａｒｙｔａｎｇｌｅｓ,ＮＦＴｓ)、神经细胞外老年斑(ｓｅｎｉｌｅｐｌａｑｕｅｓ,ＳＰｓ)和神经细胞减少。尽管ＮＦ     

抑制磷酸酶和tau过度磷酸化诱导神经细胞凋亡

目的探讨磷酸酶活性抑制、tau蛋白异常磷酸化与神经细胞变性死亡的关系.方法磷酸酶(PP)-2A/PP-1抑制剂岗田酸(okadaicacid,OA)10nmol/L与成神经细胞瘤细胞(SH-SY5Y)共培养,DNA-梯带和末端转移酶标记技术.结果用10nmol/LOA与SY5Y细胞共培养24h和48h均可引起DNA-梯带出现,此时末端转移酶标记显示阳性细胞数由2.16%±0.94%分别增多至18.05%±3.57%(P＜0.01)和22.52%±4.78%(P＜0.01).结论由于上述检测指标均与细胞凋亡有关,提示抑制PP-2A和部分抑制PP-1引起tau蛋白异常磷酸化可能通过神经细胞凋亡而引起AD患者神经细胞丢失.     

PrP可抑制tau介导的体外微管形成作用

目的研究朊蛋白（PrP）对微管相关蛋白（tau）介导的体外微管形成的影响。方法我们从兔脑组织中纯化出微管蛋白，并纯化出原核表达的tau和PrP蛋白。利用电子显微镜技术显示微管蛋白的聚集、tau对微管蛋白的聚集的影响，及PrP对tau介导的微管蛋白形成微管的影响。通过GST pull down实验研究tau与微管蛋白的相互作用，PrP对tau与微管蛋白相互作用的影响。结果电子显微镜负染显示纯化的微管蛋白在一定的实验条件下可聚集形成直径为25Nm的微管结构。在反应体系中加入tau后微管样结构的形成明显增加，而加入PrP后可显著地抑制tau对微管结构形成的促进作用。重组tau能与提取的天然微管蛋白在体外结合，而PrP可明显地抑制tau与微管蛋白的结合作用，并呈现剂量依赖关系。结论tau蛋白可促进微管蛋白形成微管结构，而PrP可通过与tau的相互作用抑制微管的形成。     

老年精神分裂症脑脊液中tau蛋白与认知功能

目的：探讨脑脊液中ｔａｕ蛋白与认知功能缺损之间的关系。方法：精神分裂症组３７例，其他神经系统疾病组２６例，Ａｌｚｈｅｉｍｅｒ病组４５例，对精神分裂症患者评定阳性阴性症状量表，Ｆｕｌｄ物体记忆测验，言辞流畅测验，积木测验及数字广度测验。采用酶联免疫吸附分析检测３组患者中ｔａｕ蛋白浓度。     

Alzheimer病患者脑tau、β-tubulin的表达

目的 观察Alzheimer病（AD）患者脑tau、β-tubulin的表达、分布与神经元骨架改变的关系。方法 采用免疫组织化学方法观察tau、β-tubulin,在8例AD、5例非痴呆老人（ND）脑海马、嗅球、脑室周围皮质等部位的表达并进行半定量分析。结果 （1）AD组tau蛋白与ND组相比表达明显增加（P＜0．001）,主要在额叶、颞叶、海马、脑室周及嗅球的表达增高（P＜0．05）;顶叶、枕叶无明显差异。大脑新皮层、海马神经元树突、胞膜均有表达,细胞核膜部分着色,部分神经元呈典型NET样结构;星形胶质细胞也有表达。此外,神经毡细丝、老年斑亦有广泛表达。ND组tau散在表达,无NFT样神经元。（2）AD组的β-tubulin明显减少（P＜0．001）,额叶、颞叶、顶叶、海马及脑室周表达明显下降（P＜0．05）;而枕叶与嗅球无差异。β-tubulin在ND组,主要是海马及皮质神经元树突上广泛表达,白质区轴索结构也有阳性表达。结论 AD患者脑内tau表达增高且存在区域分布差异;而tau的过度产生与β-tubulin的表达减少和晚期AD脑内广泛的神经元丢失、结构破坏相一致,提示AD脑内神经原纤维缠结形成与二者改变的机制值得进一步探讨。     

Morin attenuates tau hyperphosphorylation by inhibiting GSK3β

Alzheimer's disease (AD) is the major form of age-related dementia and is characterized by progressive cognitive impairment, the accumulation of extracellular amyloid β-peptide (Aβ), and intracellular hyperphosphorylated tau aggregates in affected brain regions. Tau hyperphosphorylation and accumulation in neurofibrillary tangles is strongly correlated with cognitive deficits, and is apparently a critical event in the dementia process because mutations in tau can cause a tangle-only form of dementia called frontotemporal lobe dementia. Among kinases that phosphorylate tau, glycogen synthase kinase 3β (GSK3β) is strongly implicated in AD pathogenesis. In the present study, we established an ELISA to screen for agents that inhibit GSK3β activity and found that the flavonoid morin effectively inhibited GSK3β activity and blocked GSK3β-induced tau phosphorylation in vitro. In addition, morin attenuated Aβ-induced tau phosphorylation and protected human neuroblastoma cells against Aβ cytotoxicity. Furthermore, treatment of 3xTg-AD mice with morin resulted in reductions in tau hyperphosphorylation and paired helical filament-like immunoreactivity in hippocampal neurons. Morin is a novel inhibitor of GSK3β that can reduce tau pathology in vivo and may have potential as a therapeutic agent in tauopathies.