冈田酸和β-淀粉样蛋白对大鼠CaMKⅡ与Tau蛋白磷酸化的影响

目的探讨冈田酸和β-淀粉样蛋白对大鼠CaMKⅡ与Tau蛋白磷酸化的影响。方法用立体定向方法将β-淀粉样蛋白(β-amyloid protein,Aβ)(1mg/ml、5μl/只)注入SD大鼠海马CA1区,1w后注射冈田酸(OA)0.4nmol/L、2μl/只,隔天注射共注射7次,以建立类AD动物模型。采用水迷宫、Western blotting和Real-time等方法对类AD模型进行行为学和分子生物学分析,检测类AD大鼠海马组织CaMKⅡ、磷酸化Tau蛋白的表达水平以及大鼠学习记忆力的变化。结果与对照组相比Aβ1-42海马注射组、OA注射组及共同注射Aβ1-42和OA组均能引起大鼠学习记忆力降低,CaMKⅡmRNA及蛋白表达增加(P0.01),Tau蛋白Ser404磷酸化增加(P0.05)。Aβ1-42与OA具有协同增加CaMKⅡmRNA及蛋白表达及Tau蛋白Ser404磷酸化的作用。结论 Aβ1-42和OA可降低大鼠学习记忆能力,增加CaMKⅡ表达和Tau蛋白Ser404磷酸化。     

轻度认知障碍患者认知水平与血清淀粉样蛋白42磷酸化Tau同型半胱氨酸水平相关性分析

目的探讨轻度认知障碍患者认知水平与血清淀粉样蛋白42、磷酸化Tau、同型半胱氨酸水平的相关性。方法选择2008-2011年济宁各社区近1 100例50~80岁的中老年人,筛选出MCI患者36例,并选取年龄、学历相匹配的健康对照组36例。检测MCI组与对照组的认知功能水平与血清Aβ-42、p-tan、Hcy水平,使用相关性分析MMSE水平与血清指标的关系。结果 2组患者性别比例、平均年龄、受教育年限方面比较差异无统计学意义(P0.05),对照组平均MMSE明显高于MCI组,差异有统计学意义(P≤0.05),MCI组平均Aβ-42、p-tan、Hcy水平明显高于对照组,差异有统计学意义(P≤0.05),MCI组及对照组的Aβ-42、p-tan、Hcy均与患者的MMSE得分呈相关性(P≤0.05),其中MMSE得分与Aβ-42、p-tan、Hcy为负相关。结论血清Aβ-42、p-tan、Hcy可指示认知功能水平。     

β-淀粉样蛋白诱导骨髓间充质干细胞向神经元样细胞分化过程中Tau蛋白的过度磷酸化

背景：大多数学者认为β-淀粉样蛋白是阿尔茨海默病发病的始动因素,而Tau蛋白过度磷酸化可能是阿尔茨海默病最重要的分子病理变化之一。目的：观察β-淀粉样蛋白25~35对大鼠骨髓间充质干细胞分化的神经元样细胞Tau蛋白磷酸化的影响。 方法：体外分离纯化大鼠骨髓间充质干细胞,将第4代骨髓间充质干细胞分为两组：实验组中加入预诱导培养基和20 μmol/L β-淀粉样蛋白25~35,24 h后用含2%二甲基亚砜和200 μmol/L丁羟茴醚的DMEM诱导其向神经细胞分化,5 h后收取细胞。对照组诱导方法同实验组,但在诱导过程中未加入β-淀粉样蛋白25~35。结果与结论：光镜下可见纺锤状的骨髓间充质干细胞诱导后出现长突起,呈现神经细胞样形态,但实验组突起数量和长度均少于对照组;免疫细胞化学法检测两组诱导后的神经元样细胞为神经元特异性烯醇化酶阳性;免疫蛋白印记法证明实验组的GSK-3β、Tau[pSer262]和Tau[pSer396]表达均显著高于对照组。结果提示β-淀粉样蛋白25~35能够通过GSK-3β途径诱导骨髓间充质干细胞分化的神经元样细胞Tau蛋白过度磷酸化。     

Tau蛋白过度磷酸化对脑淀粉样蛋白生成的影响

目的研究tau蛋白过度磷酸化对脑淀粉样蛋白生成的影响。方法用蛋白磷酸酯酶抑制剂冈田酸（OA）在大鼠侧脑室内注射,每天1次连续8周。用Morris水迷宫和免疫组化方法观察OA组大鼠行为学改变、神经原纤维缠结及淀粉样蛋白的表达;并与对照组比较。结果与对照组相比,OA组大鼠Morris水迷宫平均潜伏期显著延长,学习获取能力较差,空间记忆能力衰退。OA组大鼠的海马CA1区、CA3区、CA4区、齿状回、大脑皮质出现tau蛋白磷酸化,神经原纤维缠结;大脑皮质及海马CA1区、CA3区、齿状回等部位出现β淀粉样蛋白沉积。结论Tau蛋白过度磷酸化可以增加脑部淀粉样蛋白的沉积。     

Tau蛋白与Alzheimer病

1 Tau的分子生物学 Tau蛋白由17号染色体长臂上的单基因编码,经可变剪接产生6种同型。成人脑可表达tau的6种异构,分别由352～441个不等的氨基酸构成,tau羧基末端可见1个重复片段,内含3～4个相同的氨基酸重复序列,每个序列由31～32个氨基酸残基组成。氨基末端含有1个29～58个氨基酸残基的插入序列,CSFtau蛋白形成不同的异构体。外周神经系统主要表达较大的tau异构体,其氨基末端插入254个氨     

MCI患者血清中Tau蛋白 Aβ1-42P-tau的检测价值分析

目的 探讨血清磷酸化Tau（P-tau）、β淀粉样蛋白1-42（Aβ1-42）以及Tau蛋白在轻度认知障碍（MCI）患者中的临床应用价值.方法 采用酶联免疫法测定主诉健忘组（SMC）30例,MCI患者30例,阿尔茨海默病组（AD）68例（轻度AD 24例,中度AD 22例,重度AD 22例）以及健康对照组35例血清中P-tau、Aβ1-42、Tau蛋白水平,并分析三种标记物与疾病的相关性.结果 与对照组及MCI组相比,MCI组、AD组MMSE评分显著上升,差异有统计学意义（P〈0.05）,重度AD组MMSE评分显著高于轻度、中度AD组,两两比较差异有统计学意义（P〈0.05）.与对照组相比,MCI组、AD组P-tau、Tau蛋白水平显著上升,且AD组高于MCI组,而Aβ1-42水平显著下降,且AD组下降幅度大于MCI组,差异有统计学意义（P〈0.05）.其中重度AD组P-tau、Tau蛋白水平高于轻度、中度AD组,而Aβ1-42水平低于轻、中度组,差异有统计学意义（P〈0.05）.SMC 组与对照组相比,各标记物水平差异无统计学意义（P〉0.05）.与单纯Tau蛋白、Aβ1-42、P-tau诊断相比,Tau蛋白、Aβ1-42、P-tau联合诊断的灵敏性、特异性、准确性显著增加,差异有统计学意义（P〈0.05）.结论 MCI病情发生及发展过程可能与血清P-tau、Aβ1-42、Tau蛋白水平异常有关,通过测定这三种标记物可有效预测MCI患者病情进展情况.     

抑制Tau蛋白过度磷酸化治疗阿尔茨海默病的研究进展

阿尔茨海默病(AD)是一种神经退行性疾病,在疾病早期出现记忆障碍,随着病情进展出现严重的认知衰退,并最终导致患者在确诊后的平均9年内死亡[1].AD是成人老年痴呆症最常见的原因.全球患病率高达2400万,由于本病的机制尚不清楚,目前还没有治愈的方法,预计到2050年将翻两番[1].仅在美国,估计每年用于阿尔茨海默病的医疗保健费用高达17.2亿,因此迫切需要寻找治疗AD的新途径.现就近几年针对抑制Tau蛋白过度磷酸化治疗AD的研究做一综述.     

褪黑素对Alzheimer病模型大鼠认知功能和海马tau蛋白过度磷酸化的影响

目的 研究褪黑素(MT)对Alzheimer病(AD)模型大鼠认知功能和海马tau蛋白过度磷酸化的影响.方法 给大鼠海马内注射凝聚态β-淀粉样蛋白(Aβ)25-35制作AD模型;MT组大鼠从制模前7 d至制模后19 d每日腹腔注射MT,AD组大鼠制模后腹腔注射生理盐水;用Morris水迷宫试验检测大鼠的认知功能,银染法观察海马神经元形态,免疫组化法观察过度磷酸化tau蛋白的表达,并与正常对照组比较.结果 MT组大鼠Morris水迷宫试验结果明显好于AD组(均P＜0.001);海马CA1区磷酸化tau蛋白阳性细胞数(60.0±2.3)明显少于AD组(98.4±3.0)(P＜0.001),与正常对照组比较差异无统计学意义;海马CA1区神经元纤维形态较AD组规则.结论 MT可明显改善AD大鼠的认知功能,并且抑制海马tau蛋白的过度磷酸化.     

Tau蛋白过度磷酸化对阿尔茨海默病微兴奋性突触后电流的影响

目的探讨Tau蛋白过度磷酸化对阿尔茨海默病微兴奋性突触后电流的影响。方法 2月龄健康雄性Wistar大鼠20只,随机分为AD模型组和对照组。海马脑片膜片钳全细胞记录mEPSCs。观察2组mEPSCs频率、幅值、半衰期以及上升时间、曲线下面积的变化,并进行比较。结果①mEPSCs频率:实验组(0.043±0.002)Hz,对照组(0.17±0.006)Hz,P<0.05。②mEPSCs幅值:实验组(7.458±0.381)pA,对照组(14.054±0.356)pA,减少46%,P<0.05。③mEPSCs半衰期:实验组(6.724±1.331)ms,对照组(13.289±2.325)ms,减少49%,P<0.05。④mEPSCs上升时间:实验组(4.382±1.032)ms,对照组(6.343±0.942)ms,减少31%,P<0.05。⑤mEPSCs曲线下面积:实验组(118.903±37.054)pAms,对照组(321.334±87.542)pAms,减少63%,P<0.05。结论 Tau蛋白过度磷酸化后能减少微兴奋性突触后电流的产生,从而从神经电生理的角度降低了突触的兴奋性,进而降低了患者的记忆力,加速了细胞的凋亡。     

阿尔茨海默病的脑脊液标志：总Tau蛋白，磷酸化Tau蛋白和Aβ42

早期和精确地诊断AD非常重要,也最为困难。所以脑脊液的生物学标记将有特别价值。本文综述AD的脑脊液生物学标志物Aβ42和Tau蛋白在临床诊断中的作用。     

Tau protein in normal and Alzheimer's disease brain

In 1975, Weingarten and colleagues isolated a protein factor that was able to induce microtubule formation. They called this factor tau (t). Some ten years later a new era of research on this microtubule-associated protein was launched when several groups almost simultaneously discovered that tau was the predominant protein component of the paired helical filaments (PHFs) and neurofibrillary tangles (NFTs) which are characteristic pathological lesions of the Alzheimer's disease brain. Subsequent findings that PHF-tau isolated from Alzheimer's disease brain was phosphorylated to a greater extent than non-PHF tau, led to extensive investigation into the posttranslational modifications (mainly phosphorylation) of tau in normal and Alzheimer's disease brain. The present review highlights the literature concerning the normal functioning and processing of tau protein, and examines the evidence for the involvement of the abnormal posttranslational processing of tau in the pathology of Alzheimer's disease. Finally, speculation as to the relationship between abnormal processing of tau, other subcellular abnormalities seen in Alzheimer's disease, and the pathological causes of the disease are discussed.     

Tau isoform profile and phosphorylation state in dementia pugilistica recapitulate Alzheimer's disease

Insights into mechanisms of familial Alzheimer's disease (AD) caused by genetic mutations have emerged rapidly compared to sporadic AD. Indeed, despite identification of several sporadic AD risk factors, it remains enigmatic how or why they predispose to neurodegenerative disease. For example, traumatic brain injury (TBI) predisposes to AD, and recurrent TBI in career boxers may cause a progressive memory disorder associated with AD-like brain pathology known as dementia pugilistica (DP). Although the reasons for this are unknown, repeated TBI may cause DP by mechanisms similar to those involved in AD. To investigate this possibility, we compared the molecular profile of tau pathologies in DP with those in AD and showed that the same tau epitopes map to filamentous tau inclusions in AD and DP brains, while the abnormal tau proteins isolated from DP brains are indistinguishable from the six abnormally phosphorylated brain tau isoforms in AD brains. Thus, these data suggest that recurrent TBI may cause DP by activating pathological mechanisms similar to those that cause brain degeneration due to accumulations of filamentous tau lesions in AD, and similar, albeit attenuated, activation of these processes by a single TBI may increase susceptibility to sporadic AD decades after the event.     

Tau蛋白与阿尔茨海默病关系研究进展

阿尔茨海默病(Alzheimer's disease,AD)是一种以进行性痴呆(记忆减退、认知障碍以及人格改变1为临床特征,大脑皮质和海马区域出现细胞外老年斑、细胞内神经元纤维缠结(neurofibrillary tangle,NFT)和营养不良性轴突改变为病理特征的神经变性疾病[1],并且其痴呆症状的严重程度与NFT的多少有关[2].     

Tau protein in normal and Alzheimer's disease brain: an update

Tau is a microtubule-associated protein that, in a hyperphosphorylated form, comprises the main component of the paired helical filaments and neurofibrillary tangles found in Alzheimer's Disease (AD) brain. It is therefore important to understand the normal functioning and processing of tau protein, and the abnormal posttranslational processing of tau in AD pathology. In 1996, Johnson and Jenkins reviewed the literature on the biochemistry, function, and phosphorylation of tau in normal and AD brain. Since that time, numerous publications have come out further elucidating the properties of tau. The present review updates the topics originally covered in the 1996 review, as well as presents a number of new topics. For example, mutations in the tau gene have been found in several non-AD, autosomal dominant neurodegenerative disorders that exhibit extensive neurofibrillary pathology. In addition, there is increasing evidence that tau may be involved in signal transduction, organelle transport, and cell growth, independent of its microtubule-binding functions. Taken together, the research reviewed here demonstrates that tau is a very complex protein with various functions that are intricately regulated. It is clear that more research is required to completely understand the functions and regulation of tau in normal and AD brain.     

葛根素对Alzheimer病大鼠海马tau蛋白过度磷酸化及胆碱乙酰转移酶活性的影响

目的探讨葛根素(Pue)对Alzheimer病(AD)大鼠海马色氨酸404位点tau蛋白过度磷酸化(Pser404tau)及胆碱乙酰转移酶(ChAT)活性的影响。方法将SD大鼠随机分为假手术组、AD组和Pue组;右侧杏仁核注射β淀粉样肽(Aβ2535)制备AD大鼠模型,假手术组同样部位注射三氟乙酸;用Y型迷宫检测各组大鼠学习记忆能力;应用免疫组化方法检测各组大鼠海马Pser404tau阳性细胞及ChAT阳性细胞的表达。结果(1)与假手术组相比,AD组大鼠迷宫试验成绩下降,海马Pser404tau阳性细胞数明显增加,ChAT阳性细胞数明显减少(均P<0.01);(2)与AD组相比,Pue组学习记忆成绩明显提高(P<0.05),Pser404tau阳性细胞数明显降低,ChAT阳性细胞数明显增加(均P<0.01)。结论Pue明显改善AD大鼠学习记忆能力,可能与其抑制tau蛋白过磷酸化反应、减轻胆碱能神经元损伤、增加ChAT活性和功能、催化Ach合成有关。     

Effect of tibolone pretreatment on kinases and phosphatases that regulate the expression and phosphorylation of Tau in the hippocampus of rats exposed to ozone

Oxidative stress(OS) is a key process in the development of many neurodegenerative diseases, memory disorders, and other pathological processes related to aging. Tibolone(TIB), a synthetic hormone used as a treatment for menopausal symptoms, decreases lipoperoxidation levels, prevents memory impairment and learning disability caused by ozone(O_3) exposure. However, it is not clear if TIB could prevent the increase in phosphorylation induced by oxidative stress of the microtubule-associated protein Tau. In this study, the effects of TIB at different times of administration on the phosphorylation of Tau, the activation of glycogen synthase kinase-3β(GSK3β), and the inactivation of Akt and phosphatases PP2 A and PTEN induced by O_3 exposure were assessed in adult male Wistar rats. Rats were divided into 10 groups: control group(ozone-free air plus vehicle [C]), control + TIB group(ozone-free air plus TIB 1 mg/kg [C + TIB]); 7,15, 30, and 60 days of ozone exposure groups [O_3] and 7, 15, 30, and 60 days of TIB 1 mg/kg before ozone exposure groups [O_3 + TIB]. The effects of O_3 exposure and TIB administration were assessed by western blot analysis of total and phosphorylated Tau, GSK3β, Akt, PP2 A, and PTEN proteins and oxidative stress marker nitrotyrosine, and superoxide dismutase activity and lipid peroxidation of malondialdehyde by two different spectrophotometric methods(Marklund and TBARS, respectively). We observed that O_3 exposure increases Tau phosphorylation, which is correlated with decreased PP2 A and PTEN protein levels, diminished Akt protein levels, and increased GSK3β protein levels in the hippocampus of adult male rats. The effects of O_3 exposure were prevented by the long-term treatment(over 15 days) with TIB. Malondialdehyde and nitrotyrosine levels increased from 15 to 60 days of exposure to O_3 in comparison to C group, and superoxide dismutase activity decreased. Furthermore, TIB administration limited the changes induced by O_3 exposure. Our results suggest a beneficial use of hormone replacement therapy with TIB to prevent neurodegeneration caused by O_3 exposure in rats.     

高胆固醇对AD大鼠海马神经元缺失和Tau蛋白异常磷酸化的影响

目的 研究高胆固醇饮食对阿尔茨海默病(AD)大鼠海马神经元缺失和Tau(ser202)异常磷酸化的影响.方法 海马齿状同注射B淀粉样蛋白(A13)建立AD大鼠模型,根据不同饮食,将动物分为高胆同醇AD组、高胆同醇磷酸盐缓冲液(PBS)组、标准饮食AD组和标准饮食PBS组;采用尼氏染色方法检测海马神经元缺失率,应用免疫组织化学方法检测海马及皮层Tau(ser202)磷酸化水平.结果 高胆固醇饮食增加海马神经元缺失,高胆固醇饮食AD组海马神经元缺失率(30.9%±4.6%)明显大于标准饮食AD组(22.7%±1.9%)、高胆同醇饮食PBS组(7.O%±1.5%)和标准饮食PBS组(5.4%±1.1%),差异均有统计学意义(P＜0.05);高胆固醇AD组、标准饮食AD组、高胆固醇PBS组、标准饮食PBS组海马齿状回(Pser202)Tau阳性细胞数分别为65.5±6.2、48.8±4.8、22.5±3.1和12.7±1.7,比较差异均有统计学意义(P＜0,05).结论 高胆固醇饮食促进Aβ诱导神经元缺失和Tau蛋白异常磷酸化.     

Activation of protein phosphatase 2B and hyperphosphorylation of Tau in Alzheimer's disease

Protein phosphatase 2B (PP2B) is one of the major brain phosphatases and can dephosphorylate tau at several phosphorylation sites in vitro. Previous studies that measured PP2B activity in human brain crude extracts showed that PP2B activity was either unchanged or decreased in Alzheimer's disease (AD) brain. These results led to the speculation that PP2B might regulate tau phosphorylation and that a down-regulation of PP2B might contribute to abnormal hyperphosphorylation of tau. In this study, we immunoprecipitated PP2B from brains of six AD subjects and seven postmortem- and age-matched controls and then measured the phosphatase activity. We found a three-fold increase in PP2B activity in AD brain as compared with control brains. The activation was due to the partial cleavage of PP2B by calpain I that was activated in AD brain. The truncation of PP2B appeared to alter its intracellular distribution in the brain. In human brains, PP2B activity correlated positively, rather than negatively, to the levels of tau phosphorylation at several sites that can be dephosphorylated by PP2B in vitro. Truncation of PP2B in the frontal cortex was more than in the temporal cortex, and tau phosphorylation was also more in the frontal cortex. Taken together, these results indicate that truncation of PP2B by calpain I elevates its activity but does not counteract the abnormal hyperphosphorylation tau in AD brain.