人皮肤成纤维细胞和脐带间充质干细胞分泌蛋白差异比较研究

该文探讨人皮肤成纤维细胞(NCF)和脐带间充质干细胞(hUC-MSCs)分泌蛋白的差异,从而初步阐明脐带间充质干细胞分泌蛋白对于治疗退行性疾病的可能分子机理。基于串联质谱(LC-MS/MS)的方法,收集用无血清培养基培养48 h的NCF和hUC-MSCs上清样品,进行TMT(tandem mass tags for relative and absolute quantitation)检测,从而对蛋白质酶解之后的肽段进行同位素标记,之后对分泌蛋白的表达差异进行精确的鉴定和定量。通过生物信息学分析,建立NCF和hUC-MSCs分泌蛋白谱图,并通过GO(gene ontology)对这些分泌蛋白进行功能分析,对于在蛋白分子互作图中处于中心位置的CCL2、COL4A1、TGFβ1、SERPINE1、SEMA7A我们进行了Real-time PCR定量分析。通过TMT以及生物信息学分析,该文鉴定出1 000多种共有蛋白,其中有704种蛋白在hUC-MSCs中的表达量比NCF中高。通过Real-time PCR,我们证实了CCL2、COL4A1在hUC-MSCs中的分泌量的确高于其在NCF中的分泌量,且差异具有显著性。通过检索文献以及Uniprot的相应数据库数据,该文发现,这两种分子在炎症的消除方面起到十分重要的作用,而炎症反应在帕金森病等退行性疾病的发生与发展过程中起到重要作用。通过对NCF和hUC-MSCs培养基中分泌的蛋白进行检测分析,该研究为探讨脐带间充质干细胞分泌蛋白治疗神经退行性疾病的可能分子机制提供启示。     

β-分泌酶抑制剂研究进展

阿尔兹海默病(Alzheimer's disease,AD)是一种退行性的神经性疾病,其主要病理特征为β-淀粉样蛋白(β-amyloid protein,Aβ)的异常聚集及tau蛋白的过度磷酸化。研究发现,β-分泌酶上调在Aβ沉积发生发展过程中具有重要作用。抑制β-分泌酶活性有可能减少淀粉样病变,从而延缓AD病理发生。现结合AD的发病机制对β-分泌酶的特点及β-分泌酶抑制剂的研究进展进行综述。     

α分泌酶在阿尔茨海默病治疗中的作用

阿尔茨海默病(Alzheimer!sdisease,AD)是老年人常见的一种神经系统变性疾病,其特征性病理变化是患者脑内的神经炎性斑,神经炎性斑的主要成分是细胞外β淀粉样蛋白(βamyloid,Aβ)的沉积.Aβ由其前体物质——淀粉样前体蛋白(amyloidprecursorprotein,APP)经β分泌酶和γ分泌酶系列水解而来.APP也可在α分泌酶和γ分泌酶的序列作用下水解,既避免了完整Aβ分子的产生,又产生了对细胞有益的胞外片段(sAPPα),因此这条代谢途径已成为研究AD治疗的靶点.较多的实验结果显示,一类解聚素和金属蛋白酶(adisintegrinandmetalloproteinase,ADAM)分子具有α分泌酶的功能,α分泌酶有可能成为AD治疗的潜在药物靶点.     

单纯生物学制剂诱导人脐带间充质干细胞向胰岛素分泌细胞快速分化

为探讨用单纯生物学制剂诱导人脐带间充质干细胞(mesenchymal stem cells derived from human umbilical cord,hUC-MSCs)向胰岛素分泌细胞分化的可行性,本研究用胶原酶Ⅱ、胰蛋白酶次序消化及两步离心法从人胎儿完整脐带中分离、纯化出hUC-MSCs;用表皮生长因子、碱性成纤维生长因子、银杏提取液和高糖培养基IMDM诱导hUC-MSCs向胰岛素分泌细胞分化。在hUC-MSCs诱导前后,用倒置显微镜观察其形态变化,RT-PCR检测其胰岛相关基因的表达;双硫腙染色鉴定胰岛样细胞团(islet-like clusters,ILCs);细胞免疫荧光染色检测ILCs中PDX-1和免疫活性胰岛素(immunoreactive insulin,IRI)的表达;化学发光法检测ILCs的IRI分泌量;Western blot鉴定IRI的性质。结果显示:纯化的hUC-MSCs呈间充质干细胞特有的形态特征:长梭形,平行或螺旋形排列;在上述单纯生物学制剂的诱导下,hUC-MSCs逐渐变圆并聚集成团;在25cm2培养瓶的细胞生长面可见上百个ILCs;ILCs表达胰岛特异性基因pdx-1、insulin;ILCs呈PDX-1和IRI免疫染色阳性反应,双硫腙染色呈阳性;ILCs可分泌IRI,但多为胰岛素原(proinsulin,PI)。以上结果提示,用表皮生长因子、碱性成纤维生长因子、银杏提取液和高糖培养基IMDM可诱导hUC-MSCs快速分化为胰岛素分泌细胞,但ILCs功能不够成熟,难以产生足量真胰岛素。     

肠道菌群相关代谢物丁酸的量效和时效对人脐带间充质干细胞增殖的影响

目的探讨人肠道菌相关代谢物丁酸对人脐带间充质干细胞(human umbilical cord mesenchymal stem cells,hUC-MSCs)增殖的影响。方法用含不同浓度丁酸(0.02、0.08、0.32、1.25和5.00 mmol/L)的干细胞培养基培养hUC-MSCs,采用CCK-8增殖实验检测24、48和72 h细胞增殖情况,并与正常对照组比较。结果 hUC-MSCs的增殖与丁酸的量效和时效均有关系,作用24 h内抑制hUC-MSCs增殖,到48 h则表现出低浓度促进细胞增殖、高浓度抑制细胞增殖的作用;当时间达到72 h,则低浓度丁酸对hUC-MSCs的促增殖作用减弱,高浓度组对其增殖抑制的作用有所增强。结论丁酸对hUC-MSCs增殖的影响存在量效和时效的共同作用,适宜的丁酸浓度和作用时间对机体肠道的功能维持及平衡有重要影响。     

PPARα与阿尔茨海默病的研究进展

阿尔茨海默病(Alzheimer's disease,AD)是一种进行性、破坏认知与记忆功能的持续性神经退行性疾病.它的主要病理特征是以β淀粉样蛋白(β-amyloid protein,Aβ)沉积和Tau蛋白过度磷酸化形成神经原纤维缠结(neurofibrillary tangle,NFT)为主,是一种日益严重的全球健康性问题.过氧化物酶体增殖物激活受体(peroxisome proliferators-activated receptor,PPAR)是在中枢神经系统(CNS)中表达,调节能量代谢、神经传递、氧化还原稳态、线粒体功能等生理过程的一种核受体. PPARα作为其中一个亚型,在AD控制突触可塑性和调节神经元认知功能中有重要作用,说明PPARα是治疗AD的一个很有前途的靶点.这篇综述探讨了Aβ、氧化应激、神经炎症、脂质代谢在AD中的意义,以及PPARα的潜在价值及其在AD中的作用,揭示了未来PPARα作为AD治疗靶点的可能性.     

β淀粉样蛋白的分泌酶与阿尔采末病的治疗

β淀粉样蛋白(Aβ)级联反应在阿尔采末病(AD)发病过程中起主要作用,Aβ由分泌酶中的β和γ分泌酶水解β淀粉样蛋白前体蛋白(APP)而来。本文综述了参与APP水解的三种分泌酶(α、β和γ)的发现、研究进展及其在调节β淀粉样蛋白过程中的作用。选择性地激活α分泌薄或抑制β和γ分泌酶格减少Aβ产生,为AD治疗提供新的研究思路,以分泌酶为靶点可能成为治疗AD的理想途径。     

人脐带间充质干细胞内源性SDF-1α促进HIBD大鼠神经功能修复的实验研究

该文主要研究人脐带间充质干细胞(human umbilical cord mesenchymal stem cells,hUC-MSCs)促进缺氧缺血性脑损伤(Hypoxic-ischemicbraindamage,HIBD)神经功能修复的作用及机制。hUC-MSCs移植后,对大鼠进行行为学观察,运用HE(hematoxylin-eosin)染色观察海马组织病理改变, Western blot检测hUC-MSCs与氧糖剥夺(oxygen glucose deprivation,OGD)神经干细胞分离共培养体系、HIBD大鼠海马组织中SDF-1α、CXCR4、PI3K/AKT表达;CCK-8测定干细胞增殖情况。结果显示, hUC-MSCs移植后:HIBD大鼠学习记忆功能和海马组织病变改善;海马区Nestin表达和海马齿状回区再生神经干细胞数量升高;海马组织hSDF-1α、SDF-1α、CXCR4、PI3K、AKT及p-AKT表达上调。hUC-MSCs促进OGD损伤神经干细胞增殖及hSDF-1α分泌,上调PI3K和p-AKT表达。该文结果提示, hUC-MSCs移植上调HIBD大鼠海马组织hSDF-1α分泌,激活PI3K/AKT通路,诱导内源性神经干细胞再生,改善HIBD大鼠学习记忆功能。     

间充质干细胞旁分泌作用治疗阿尔茨海默病的临床前研究进展

阿尔茨海默病(Alzheimer’s disease,AD)是最常见的神经退行性疾病之一,严重损害患者的记忆和认知能力。研究者经过多年探索仍无法找到治愈AD的有效药物。源于间充质干细胞(mesenchymal stem cells,MSCs)旁分泌的生长因子、细胞因子、趋化因子等生物因子及外泌体具有抗炎、清除β-淀粉样蛋白(β-amyloid peptide,Aβ)、促进神经生长以及抑制细胞凋亡等作用,MSCs的旁分泌作用被认为是治疗AD最有前途的临床疗法之一。该文首先总结了AD的发病机制,然后根据MSCs所具有的特征和优势,综述了利用MSCs的旁分泌作用治疗AD的临床前研究,期望为将来临床上治疗AD提供有价值的信息。     

褪黑素对异丙肾上腺素诱导大鼠tau蛋白过度磷酸化的预防作用

异常过度磷酸化的微管相关蛋白tau是阿尔茨海默病(Alzheimer's disease,AD)患者大脑中神经原纤维缠结的主要组成部分.迄今为止,尚无有效的措施阻止tau蛋白的过度磷酸化.为探讨褪黑素(melatonin,Mel)对AD样tau蛋白过度磷酸化的预防作用,我们以β受体激动剂异丙肾上腺素(isoproterenol,IP)来复制AD样tau蛋白过度磷酸化的动物模型,在大鼠双侧海马注射IP前,以褪黑素作为保护组药物,于腹腔连续注射5 d.应用磷酸化位点特异性抗体(PHF-1和Tau-1)作免疫印迹和免疫组织化学检测tau蛋白的磷酸化水平,并用非磷酸化依赖的总tau蛋白抗体(111e)进行标准化.免疫印迹结果显示在注射IP 48 h后,tau蛋白在PHF-1表位的免疫反应显著增强,在Tau-1表位显著减弱,表明tau蛋白在Ser396/Ser404(PHF-1)和Ser199/Ser202(Tau-1)位点有过度磷酸化.免疫组织化学染色结果与免疫印迹结果相似,主要检测到在大鼠海马CA3区的神经纤维有tau蛋白过度磷酸化.褪黑素预处理大鼠可有效地阻止IP诱导tau蛋白在Tau-1和PHF-1位点的过度磷酸化.上述结果提示褪黑素可预防大鼠脑组织中由异丙肾上腺素引起的AD样tau蛋白的过度磷酸化.     

Tau function and dysfunction in neurons: its role in neurodegenerative disorders

Alzheimer’s disease (AD) is the most usual neurodegenerative disorder leading to dementia in the aged human population. It is characterized by the presence of two main brain pathological hallmarks: senile plaques and neurofibrillary tangles (NFTs). NFTs are composed of fibrillar polymers of the abnormally phosphorylated cytoskeletal protein tau.     

Tau PET Imaging for Staging of Alzheimer's Disease in Down Syndrome

Alzheimer's disease (AD) pathology and early‐onset dementia develop almost universally in Down syndrome (DS). AD is defined neuropathologically by the presence of extracellular plaques of aggregated amyloid β protein and intracellular neurofibrillary tangles (NFTs) of aggregated hyperphosphorylated tau protein. The development of radiolabeled positron emission tomography (PET) ligands for amyloid plaques and tau tangles enables the longitudinal assessment of the spatial pattern of their accumulation in relation to symptomatology. Recent work indicates that amyloid pathology develops 15–20 years before neurodegeneration and symptom onset in the sporadic and autosomal dominant forms of AD, while tau pathology correlates more closely with symptomatic stages evidenced by cognitive decline and dementia. Recent work on AD biomarkers in DS illustrates similarities between DS and sporadic AD. It may soon be possible to apply recently developed staging classifications to DS to obtain a more nuanced understanding of the development AD in DS and to provide more accurate diagnosis and prognosis in the clinic.     

The relationship between subcortical tau pathology and Alzheimer's disease

The stepwise progression of tau pathology [NFTs (neurofibrillary tangles) and NTs (neuropil threads)] in AD (Alzheimer's disease) is generally assumed to begin in the transentorhinal region (entorhinal stage) from which it progresses to the hippocampus (limbic stage) and to neocortical regions (neocortical stage). This stepwise progression is reflected in the NFT Braak stages. However, it has been shown recently that tau pathology is frequently seen in subcortical nuclei, in particular the LC (locus coeruleus) in over 90% of individuals under 30 years of age, suggesting that AD-associated tau pathology begins in the LC and not in the transentorhinal region. On the other hand, only minimal amounts of tau pathology are seen in the LC in cases with considerable entorhinal tau pathology, while the severity of tau pathology in the LC significantly increases with increasing NFT Braak stages. These findings suggest that the LC becomes increasingly involved during AD progression rather than representing the site initially affected. Further studies are warranted to answer the question of whether tau pathology in the LC of young individuals is associated with AD or whether it rather reflects non-specific neuronal damage.     

The toxicity of tau in Alzheimer disease: turnover, targets and potential therapeutics

It has been almost 25 years since the initial discovery that tau was the primary component of the neurofibrillary tangles (NFTs) in Alzheimer disease (AD) brain. Although AD is defined by both β-amyloid (Aβ) pathology (Aβ plaques) and tau pathology (NFTs), whether or not tau played a critical role in disease pathogenesis was a subject of discussion for many years. However, given the increasing evidence that pathological forms of tau can compromise neuronal function and that tau is likely an important mediator of Aβ toxicity, there is a growing awareness that tau is a central player in AD pathogenesis. In this review we begin with a brief history of tau, then provide an overview of pathological forms of tau, followed by a discussion of the differential degradation of tau by either the proteasome or autophagy and possible mechanisms by which pathological forms of tau may exert their toxicity. We conclude by discussing possible avenues for therapeutic intervention based on these emerging themes of tau's role in AD.     

Chronic lithium administration to FTDP-17 tau and GSK-3beta overexpressing mice prevents tau hyperphosphorylation and neurofibrillary tangle formation, but pre-formed neurofibrillary tangles do not revert

Glycogen synthase kinase-3 (GSK-3) has been proposed as the main kinase able to aberrantly phosphorylate tau in Alzheimer's disease (AD) and related tauopathies, raising the possibility of designing novel therapeutic interventions for AD based on GSK-3 inhibition. Lithium, a widely used drug for affective disorders, inhibits GSK-3 at therapeutically relevant concentrations. Therefore, it was of great interest to test the possible protective effects of lithium in an AD animal model based on GSK-3 overexpression. We had previously generated a double transgenic model, overexpressing GSK-3beta in a conditional manner, using the Tet-off system and tau protein carrying a triple FTDP-17 (frontotemporal dementia and parkinsonism linked to chromosome 17) mutation. This transgenic line shows tau hyperphosphorylation in hippocampal neurones accompanied by neurofibrillary tangles (NFTs). We used this transgenic model to address two issues: first, whether chronic lithium treatment is able to prevent the formation of aberrant tau aggregates that result from the overexpression of FTDP-17 tau and GSK-3beta; second, whether lithium is able to change back already formed NFTs in aged animals. Our data suggest that progression of the tauopathy can be prevented by administration of lithium when the first signs of neuropathology appear. Furthermore, it is still possible to partially reverse tau pathology in advanced stages of the disease, although NFT-like structures cannot be changed. The same results were obtained after shut-down of GSK-3beta overexpression, supporting the possibility that GSK-3 inhibition is not sufficient to reverse NFT-like aggregates.     

Cholesterol-dependent modulation of tau phosphorylation in cultured neurons

One of the hallmarks of Alzheimer's disease (AD) is the abnormal state of tau. It is both highly phosphorylated and aggregated into paired helical filaments (PHFs) in neurofibrillary tangles (NFTs). However, the mechanism underlying the hyperphosphorylation of tau in NFTs and neuronal degeneration in AD remains to be elucidated. The fact that hyperphosphorylation of tau in NFTs are also found in the patients with Niemann-Pick disease, type C (NPC), which is a cholesterol storage disease associated with defective intracellular trafficking of exogenous cholesterol, implies that perturbation of cholesterol metabolism may be involved in tau phosphorylation and neurodegeneration. Here, we report that cholesterol deficiency induced by inhibition of cholesterol biosynthesis in cultured neurons results in hyperphosphorylation of tau, accompanied by axonal degeneration associated with microtubule depolymerization. These changes were prevented by concurrent treatment with beta-migrating very low-density lipoprotein (beta-VLDL) or cholesterol. We propose that intracellular cholesterol plays an essential role in the modulation of tau phosphorylation and the maintenance of microtubule stability.     

New Age of Neuroproteomics in Alzheimer’s Disease Research

Alzheimer’s disease (AD) is the leading cause of dementia, a condition that gradually destroys brain cells and leads to progressive decline in mental functions. The disease is characterized by accumulation of misfolded neuronal proteins, amyloid and tau, into insoluble aggregates known as extracellular senile plaques and intracellular neurofibrillary tangles, respectively. However, only tau pathology appears to correlate with the progression of the disease and it is believed to play a central role in the progression of neurodegeneration. In AD, tau protein undergoes various types of posttranslational modifications, most notably hyperphosphorylation and truncation. Using four proteomics approaches we aimed to uncover the key steps leading to neurofibrillary degeneration and thus to identify therapeutic targets for AD. Functional neuroproteomics was employed to generate the first transgenic rat model of AD by expressing a truncated misordered form of tau, “Alzheimer’s tau”. The rat model showed that Alzheimer’s tau toxic gain of function is responsible for the induction of abnormal tau cascade and is the driving force in the development of neurofibrillary degeneration. Structural neuroproteomics allowed us to determine partial 3D structure of the Alzheimer’s filament core at a resolution of 1.6 Å. Signaling neuroproteomics data lead to the identification and characterization of relevant phosphosites (the tau phosphosignalome) contributing to neurodegeneration. Interaction neuroproteomics revealed links to a new group of proteins interacting with Alzheimer’s tau (tau interactome) under normal and pathological conditions, which would provide novel drug targets and novel biomarkers for treatment of AD and other tauopathies.     

Design, synthesis, and testing of an 6-O-linked series of benzimidazole based inhibitors of CDK5/p25

Alzheimer’s disease (AD) is a progressive neurodegenerative disease resulting in cognitive and behavioral impairment. The two classic pathological hallmarks of AD include extraneuronal deposition of amyloid ?? (A??) and intraneuronal formation of neurofibrillary tangles (NFTs). NFTs contain hyperphosphorylated tau. Tau is the major microtubule-associated protein in neurons and stabilizes microtubules (MTs). Cyclin dependent kinase 5 (CDK5), when activated by the regulatory binding protein p25, phosphorylates tau at a number of proline-directed serine/threonine residues, resulting in formation of phosphorylated tau as paired helical filaments (PHFs) then in subsequent deposition of PHFs as NFTs. Beginning with the structure of Roscovitine, a moderately selective CDK5 inhibitor, we sought to conduct structural modifications to increase inhibitory potency of CDK5 and increase selectivity over a similar enzyme, cyclin dependent kinase 2 (CDK2). The design, synthesis, and testing of a series of 1-isopropyl-4-aminobenzyl-6-ether-linked benzimidazoles is presented.     

MARKing tau for tangles and toxicity

In healthy neurons, tau proteins regulate microtubule function in the axon. In the brains of individuals with Alzheimer's disease, tau is hyperphosphorylated and aggregated into intraneuronal deposits called neurofibrillary tangles (NFTs). Hyperphosporylation dislodges tau from the microtubule surface, potentially resulting in compromised axonal integrity and the accumulation of toxic tau peptides. Recent biochemical and animal model studies have re-evaluated tau phosphorylation and other aspects of neurofibrillar pathology. The results indicate that phosphorylation of tau's microtubule-binding domain by the protein kinase MARK primes tau for hyperphosphorylation by the kinases GSK-3 and Cdk5, which in turn triggers the aggregation of tau into filaments and tangles. Toxic consequences for the neuron might be exacerbated by tangle formation but are already evident during the early steps of the process.