特异酶促使淀粉样前体蛋白裂解成β-淀粉样蛋白

β淀粉样蛋白的沉积是阿尔茨海默病(AD)发病的始发因素,所形成的老年斑是其最基本的病理改变。因此,靶向β淀粉样蛋白措施是AD最有潜力的治疗方法,也是AD的研究热点。淀粉样前体蛋白(APP)在γ分泌酶介导下裂解成β淀粉样蛋白,如能抑制γ分泌酶的活性,则可有助AD病的治疗。然而,     

血小板β-淀粉样肽前体蛋白异构体比率对老年期痴呆的诊断意义

阿尔茨海默病(Alzheimer disease,AD)是中枢神经系统退行性疾病,其主要病理特征是胞外老年斑和胞内神经纤维缠结以及血管壁β淀粉样蛋白(β-amyloid,Aβ)沉积,而老年斑以Aβ沉积为核心.Aβ是由其β淀粉样肽前体蛋白(amyloid precurosor protein,APP)经过β和γ分泌酶介导的蛋白裂解而成.     

γ-分泌酶抑制剂的研发现状

β淀粉样蛋白沉积是阿尔茨海默病的主要病理特征之一，β淀粉样蛋白是经β和卜分泌酶水解口淀粉样蛋白前体蛋白而产生，故β和γ-分泌酶是β淀粉样蛋白前体蛋白代谢的关键性酶，因而成为治疗阿尔茨海默病的很有潜力的靶点。根据β淀粉样蛋白前体蛋白的代谢、β淀粉样蛋白的形成过程及γ-分泌酶的结构、特性和作用机制，分类综述γ-分泌酶抑制剂抑制β淀粉样蛋白前体蛋白的活性及构效关系。     

甲硫哒嗪损伤大鼠学习记忆伴随脑β-淀粉样蛋白的升高

目的观察甲硫哒嗪损伤大鼠学习记忆是否伴随脑内β-淀粉样蛋白(β-amyloid protein,Aβ)水平的升高,探讨甲硫哒嗪引起认知功能受损的机制。方法20只大鼠随机分为对照组和甲硫哒嗪组,连续2wk分别腹腔注射生理盐水和治疗剂量的甲硫哒嗪(10mg·kg-1)。用Morris水迷宫测定大鼠学习记忆能力,用放射免疫分析法测脑组织Aβ含量,用免疫组织化学染色检测β-淀粉样前体蛋白(β-amyloid precursor protein,APP)表达,用RT-PCR方法测定脑中3种APP、α及β-分泌酶mRNA表达。结果甲硫哒嗪组大鼠学习记忆能力下降,脑组织Aβ含量升高(P<0.05),是对照组的1.3倍;脑皮质和海马区APP蛋白表达增高(P<0.05);除APP695、α-分泌酶mRNA表达变化无统计学意义外,脑组织APP751和APP770 mRNA表达升高(P<0.05),相对表达量之和是对照组的2.5倍;β-分泌酶mRNA表达升高(P<0.05),是对照组的2.6倍。结论脑内Aβ水平的增加,可能是甲硫哒嗪引起认知功能损害的原因之一。     

治疗阿尔采末病的药物靶点:β-分泌酶

近年来的研究表明,β-淀粉样蛋白(Aβ)是老年斑的主要成分,有明显的神经细胞毒性作用,在阿尔采末病(AD)的发病过程中发挥了重要作用,因此降低脑中Aβ的生成量是治疗AD的策略。Aβ是由β-和γ-分泌酶裂解其前体蛋白(APP)而生成,其中β-分泌酶(BACE)是启动Aβ形成的关键限速酶,因此BACE是开发治疗AD药物的一个具有吸引力的作用靶点。该文就近来对β-分泌酶的研究作一综述。     

新型γ-分泌酶调节剂SPI-1865的研发历程概述

阿尔茨海默症(Alzheimer's disease,AD)为进行性的神经退行性疾病,目前缺乏有效的治疗手段.β淀粉样蛋白(β-amyloid,Aβ)在脑神经细胞外过度沉积形成的寡聚体和淀粉样斑块与阿尔茨海默症的发生、发展密切相关.γ-分泌酶是β淀粉样蛋白代谢过程中的关键酶,为研发阿尔茨海默症治疗药物的关键靶点.针对此靶点研发的γ-分泌酶调节剂(γ-secretase modulators,GSM)因对Notch等蛋白影响较小,有广阔的应用前景.本文总结了源于黑升麻(Black cohosh,Cimicifuga racemosa)的环阿尔廷型三萜为先导物的结构优化历程,最终获得γ-分泌酶调节剂药物候选物SPI-1865,以期为γ-分泌酶调节剂的开发与改造提供有价值的参考.     

β-淀粉样蛋白前体蛋白裂解酶1相关干预策略在阿尔采末病治疗的研究进展

阿尔采末病(AD)是一种进行性的神经退行性疾病,其发病原因是脑内β淀粉样蛋白(Aβ)的聚集和沉积。Aβ是由淀粉样蛋白前体经β-分泌酶和γ-分泌酶剪切代谢生成,而β-淀粉样蛋白前体蛋白裂解酶1(BACE1)是该过程的限速酶,抑制BACE1的活性可减少Aβ的产生,因此BACE1成为人们关注治疗AD的热门靶点。本文对近年来BACE1靶点在阿尔采末病治疗中的研究和进展进行综述。     

还脑益聪方提取物含药血清对APP/PS1双基因转染细胞γ分泌酶活性及相关蛋白表达的影响

目的观察中药复方-还脑益聪方提取物(Huannao Yicong decoction,HYD)含药血清对β-淀粉样前蛋白swe基因(APPswe)人类早老素(PSEN1d E9,PS1)和早老蛋白1d E9基因(PSEN1d E9)人鼠淀粉样前蛋白融合体(APPswe,APP)双基因转染人胚肾293(human embryonic kidney 293,HEK293)细胞γ分泌酶活性及相关蛋白的影响,分析含药血清影响γ分泌酶活性相关蛋白的作用机制。方法以人APP/PS1双基因转染(HEK293)人胚肾细胞株为载体,将其分为5组,分别为空白组,7.5%HYD含药血清组,15%HYD含药血清组,HYD直接给药组,γ分泌酶抑制剂-DAPT组,复苏传代后采用细胞计数试剂盒CCK-8(cell counting kit-8,CCK-8)法检测HYD含药血清(大鼠灌胃10 d,取血清并进行血药成分检测)对人APP/PS1双基因转染细胞的生长活力和超微结构的影响;透射电镜观察各组细胞超微结构;双荧光素酶基因检测γ分泌酶活性;蛋白质印迹法(Western blot)检测γ分泌酶组件及相关蛋白早老素1(Presenilin 1,PS1)、鸟苷酸结合蛋白(GTP binding protein,CDC42)、热休克蛋白70羧基端作用蛋白(carboxyl terminus of Hsc70-interacting protein,CHIP)、前咽缺陷蛋白-1α(anterior pharynx defective-1α,Aph-1α)和低氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α)的表达。结果 15%HYD含药血清组对细胞株的增殖作用高于其余各血清浓度组(P<0.05,P<0.01);透射电镜显示模型组线粒体膜不完整,有轻微肿胀,线粒体嵴模糊,胞质内有较多的脂褐素沉积,其余各组数量均有一定程度的好转和减轻。γ分泌酶活性结果,给药后24 h和48 h,与模型组比较,直接给药组、DAPT组差异有统计学意义(P<0.05或P<0.01);与DAPT组比较,15%HYD含药血清组差异有统计学意义(P<0.05)。γ分泌酶结果与模型组比较,各给药组的PS1蛋白、CDC42蛋白表达差异有统计学意义(P<0.05,P<0.01),CHIP蛋白表达和Aph-1α蛋白表达无统计学意义(P>0.05),而HYD直接给药组HIF-1α蛋白差异有统计学意义(P<0.05)。结论HYD含药血清具有改善人APP/PS1双基因转染细胞超微结构、抑制γ分泌酶活性的作用,其机制涉及促进CDC42蛋白的表达,抑制PS1蛋白水解生成PS1 CTF/NTF异二聚体,同时抑制HIF-1α蛋白的生成,进而降低γ分泌酶的活性。     

二苯乙烯苷对APP转基因小鼠学习记忆能力和脑内β-淀粉样肽表达的影响

目的:观察从中药何首乌提取的二苯乙烯苷(TSG)对APP转基因小鼠学习记忆能力、β-淀粉样肽(Aβ)和分泌酶的影响。方法:将APP转基因小鼠随机分为模型组,TSG 0．05和0．2 g·kg-1组,同月龄同背景C57BL／6J小鼠为对照组,各组小鼠从4月龄始连续灌胃给药6个月。用morris水迷宫观察小鼠学习记忆能力,用免疫组化法观察小鼠海马APP,Aβ,β位点剪切酶(BACE,即β-分泌酶)和代表γ-分泌酶的早老蛋白-1(PS-1)的表达。结果:10月龄转基因小鼠模型组与正常对照组相比,模型组学习记忆能力明显降低,海马APP,Aβ和PS-1的表达明显增强。TSG能显著改善模型小鼠学习记忆能力,降低脑内APP、Aβ的生成,抑制海马PS-1的表达。在正常对照组、模型组和TSG组之间,β-分泌酶表达没有明显差异。结论:TSG能减少脑内Aβ形成,改善学习记忆能力,作用机理可能与减少APP生成和抑制γ-分泌酶的表达有关。     

葛根素对阿尔茨海默病细胞模型Aβ蛋白的抑制作用

目的在过表达β淀粉样前体蛋白的SH-SY5Y细胞上(SH-SY5Y/APP695)观察葛根素对β淀粉样蛋白(β-amyloid protein,Aβ)生成的作用,探讨其防治阿尔茨海默病的机制。方法葛根素2.5,5和10μmol·L-1处理SH-SY5Y/APP细胞24 h,MTT法检测细胞活力,ELISA试剂盒测定细胞外Aβ1-40和Aβ1-42水平;Western blot蛋白质印迹法检测APP及β-分泌酶的蛋白表达变化;荧光法测β-分泌酶的活性;RT-PCR法检测β-分泌酶转录的变化。结果葛根素可剂量依赖性的减少SH-SY5Y/APP695细胞外Aβ1-40、Aβ1-42的水平;酶活性分析显示2.5,5和10μmol·L-1的葛根素分别抑制了15%,30%和40%β-分泌酶的活性。Western blot印迹结果显示,葛根素能剂量依赖性抑制β-分泌酶蛋白表达,2.5,5和10μmol·L-1的葛根素使β-分泌酶的蛋白表达分别减少至82%,71%和45%,与空白对照组比较差异均具有统计学意义(P<0.05)。结论葛根素通过下调β-分泌酶蛋白的表达、抑制β-分泌酶的活性减少Aβ的形成,这可能是葛根素防治阿尔茨海默病作用的重要机制之一。     

The search for gamma-secretase and development of inhibitors

A considerable body of evidence has accumulated in recent years implicating the beta-amyloid protein (Abeta) in the etiology of Alzheimer s disease (AD). The highly hydrophobic Abeta can nucleate and form neurotoxic fibrils that are the principal components of the cerebral plaques characteristic of AD. Abeta is formed from the amyloid-beta precursor protein (APP) through two protease activities. First, beta-secretase cleaves APP at the Abeta N-terminus, resulting in a soluble, secreted APP derivative (beta-APPs) and a 12 kDa membrane-retained C-terminal fragment. The latter is further processed to Abeta by gamma secretases, which cleave within the single transmembrane region. Other APP molecules can be cleaved by alpha-secretase within the Abeta region, thus precluding Abeta formation. Both beta- and gamma- secretase have become prime targets for the development of therapeutic agent that reduce Abeta production. Beta-secretase has recently been identified as a new membrane-anchored aspartyl protease in the cathepsin D family. Inhibitor profiling, site-directed mutagenesis, and affinity labeling together have suggested that the multi-pass presenilins are gamma-secretases, novel intramembrane-cleaving aspartyl proteases activated through autoproteolysis. In this article, we review the current knowledge of gamma-secretase biochemistry and cell biology and the development of inhibitors of this important therapeutic target.     

γ分泌酶调控剂的研究进展

老年痴呆症是影响老年人健康的一个重要疾病,普遍认为淀粉样蛋白（amyloid beta protein, Aβ）与其发病密切相关。γ分泌酶作为Aβ产生途径中一个关键的蛋白酶,其剪切作用决定Aβ不同短肽的形成。本文综述近年来γ分泌酶调控剂的研究进展,总结归纳其构效关系,并探讨其未来的研究方向。     

The role of heparan sulfate in the generation of Abeta

Alzheimer's disease is a fatal neurodegenerative disorder for which there are currently few treatments and no cure. Heparan sulfate, a heterogeneously sulfated glycosaminoglycan, has been identified as the first naturally occurring inhibitor of beta secretase, the rate-limiting step in the formation of Abeta, the peptide core of the amyloid plaques that cause Alzheimer's disease. Though heparan sulfate has frequently been implicated in the formation of fibrils, only fairly recently has its role as an inhibitor of beta secretase been recognized. This inhibitory activity is dependent on the structure and size of the heparan sulfate chain, with emphasis placed on the position of the sulfates. Heparan sulfate directly binds to beta secretase and causes a closed configuration of the catalytic site. Regulation of amyloid precursor protein (APP) beta secretase cleavage could occur at a number of cellular locations, including the Golgi complex, endosomal system and cell surface. Heparan sulfate also binds to APP and may sequester it away from beta secretase. These findings have led to the examination of heparan sulfate analogues, such as beta-secretase inhibitors, as a potential therapeutic approach to treat Alzheimer's disease.     

Modulation of neutrophil apoptosis by beta-amyloid proteins

This study examined the effect of amyloid beta peptide (Abeta) and the secretase inhibitors of amyloid precursor proteins (APP) on the spontaneous apoptosis of neutrophils. Abeta(1-40) decreased the apoptotic rate of neutrophils. The delayed apoptosis by Abeta was not blocked by pertussis toxin and N-formyl peptide receptor-like 1 antagonistic peptide, WRWWWW. The inhibitors of phoshoinositide 3-kinase (LY294002), phospholipase C (U73122), or Ca++-dependent protein kinase C (Go6976) abrogated the anti-apoptotic effect of Abeta on neutrophils. Moreover, the Abeta-induced delay of apoptosis was inhibited by a calcium chelator, BAPTA/AM. The amount of the APP protein was reduced in the cultured neutrophils and the APP level in the Abeta or pancaspase-treated neutrophils was lower than that in the cultured neutrophils. However, the reduction in APP level was recovered after treating them with the secretase inhibitors or anti-Fas antibody. The exogenous addition of cell permeable beta- and gamma-secretase inhibitors resulted in an increase in the rate of the apoptosis. The regulation of neutrophil apoptosis by the addition of Abeta and secretase inhibitors occurred via the caspase -8, -9, -3, and mitochondrial-dependent pathways. This suggests that the intracellular beta-amyloid proteins play a role as regulating factor of neutrophil survival and that Abeta-induced delay of apoptosis is mediated by other receptors rather than a seven-transmembrane G protein-coupled receptor(s).     

Expression changes of the mRNA of Alzheimer's disease related factors in the permanent ischemic rat brain

The rat with permanent occlusion of the bilateral common carotid arteries (2VO) is useful model for the study of dementia. The expression changes of amyloid precursor protein (APP), secretase, alpha7 nicotinic acetylcholine receptor (alpha7NicR) and acetylcholine esterase (AChE), which are involved in Alzheimer's disease, were examined by quantitative RT/PCR in this model rat brain. The expression of APP, alpha7NicR and secretase were increased 4 d after 2VO. The alpha7NicR level at 2 d after operation already tended to increase. These result suggest that alpha7NicR expression was enhanced at early stage of brain ischemia. Using this model to find drugs which regulate the alpha7NicR expression will be useful to assay the materials with anti-dementive effect.     

阿尔采末病淀粉样前体蛋白(APP)和早老素-1(PS-1)双重基因稳定转染细胞系的建立

目的　构建APP751和PS 1(M14 6L)双重基因稳定转染的中国仓鼠卵巢 (CHO)细胞系 ,以用于 β 分泌酶或γ 分泌酶抑制剂的研究和相关药物的筛选。方法　从人胎盘基因文库中用多聚酶链反应 (PCR)方法扩增野生型和突变型PS 1(M14 6L)基因 ,并重组克隆到PCI neo质粒 ,用脂质体 (Lipo fectAmine)法将野生型和突变型 (M14 6L)PS 1转染至含APP751表达基因的CHO细胞 ,选择培养液筛选能稳定表达目的基因的CHO细胞株。用免疫沉淀和ELISA测定分析细胞表达产物。结果　建立了数株能表达Aβ和PS 1的CHO细胞。在转染细胞株中高表达的SP 1为全长 4 5kd的PS 1蛋白 ;野生型PS 1和突变型PS 1(M14 6L)以及单纯APP751转染的CHO细胞株均可分泌Aβ多肽 ,且突变型PS 1(M14 6L)转染的细胞株分泌到条件培养液中的Aβ1～ 42 比其它细胞株增加了近两倍。结论　突变型PS 1(M14 6L)的高表达可促使Aβ1～ 42 的分泌增加。我们建立的PS 1和APP双重基因稳定转染的CHO细胞株模型 ,可用于 β 分泌酶或γ 分泌酶抑制剂的研究和相关药物的筛选     

Syntheses and in-vitro evaluation of novel adamantane based γ-secretase inhibitors

Abnormal processing of amyloid precursor protein (APP) by β - and γ -secretases to produce excess amyloid-β-peptide is believed to contribute to the pathophysiological cascade that results in Alzheimer's disease. γ -Secretase inhibition or modulation therefore represents a rational approach to the prevention and/or management of AD. Here, we present the discovery and SAR of a class of novel adamantanyl sulfonamide based γ -secretase inhibitors. Activity evaluation was conducted on cell lines overexpressing APP (wild type and Swedish mutation). Our results suggest size threshold and hydrogen bond formation are necessary for inhibitory activity. There was no correlation between compound activity, Log P, and the electronic effect of substituents on the aromatic ring. These compounds possess desirable drug like properties and results of the study can guide a pharmacophore based design of γ -secretase inhibitors.     

Molecular and biochemical features in Alzheimer's disease

The purpose of this review is to discuss the pathophysiological pathways involved in pathogenesis of Alzheimer's disease pointing out current and future pharmacological targets. Alzheimer's disease is one of the most important neurodegenerative disorders in the developed world together with Parkinson's disease. Although this disease was described almost a century ago, the molecular mechanisms that lead to the development of the neuronal pathology are not clear at the moment. Furthermore, although enormous efforts have been done, an efficient treatment for the disease does not exist yet because the mechanism of neuronal cell death is unknown. In the present work we discuss, in depth, the potential mechanisms involved in apoptosis and neuronal death in Alzheimer's disease. The biology, structure and physiological properties of beta-amyloid peptide and related proteases (secretases) are discussed, as well as existing therapeutics and future strategies for the treatment of Alzheimer's disease. Inhibition of production of amyloid peptides by secretase inhibitors has been suggested as one of the most rational and specific therapeutic approaches. Inhibition of apoptosis mediated by oxidative stress generation and mitochondrial alteration, or blockade of NMDA receptors could constitute suitable therapeutic strategies for Alzheimer's disease. Finally, a multiple therapy with antioxidants, cell cycle inhibitors and other drugs modulating APP processing could be, in the future, a suitable strategy in order to delay Alzheimer's disease progression.     

γ-secretase inhibitors and modulators for the treatment of Alzheimer's disease: disappointments and hopes

According to the β-amyloid (Aβ) hypothesis, compounds that inhibit or modulate γ secretase, the pivotal enzyme that generates Aβ, are potential therapeutics for Alzheimer's disease (AD). Studies in both transgenic and non-transgenic animal models of AD have indicated that γ-secretase inhibitors, administered by the oral route, are able to lower brain Aβ concentrations. However, scanty data are available on the effects of these compounds on brain Aβ deposition after chronic administration. Behavioral studies are also scarce with only one study indicating positive cognitive effects of a peptidomimetic compound acutely administered (DAPT). γ-Secretase inhibitors may cause abnormalities in the gastrointestinal tract, thymus, spleen and skin in experimental animals and in man. These toxic effects are likely due to inhibition of Notch cleavage, a transmembrane receptor involved in regulating cell-fate decisions. Some non-steroidal anti-inflammatory drugs (NSAIDs) and other small organic molecules have been found to modulate γ secretase shifting its cleavage activity from longer to shorter β-amyloid species without affecting Notch cleavage. Long-term histopathological and behavioral animal studies are available with these NSAIDs (mainly ibuprofen) but it is unclear if the observed in vivo effects on Aβ brain pathology and learning depend on their activity on γ-secretase or on other biological targets. The most studied γ-secretase inhibitor, semagacestat (LY-450139), was shown to dose-dependently decrease the generation of Aβ in the cerebrospinal fluid of healthy humans. Unfortunately, two large Phase 3 clinical trials of semagacestat in mild-to-moderate AD patients were prematurely interrupted because of the observation of detrimental effects on cognition and functionality in patients receiving the drug compared to those receiving placebo. These detrimental effects were mainly ascribed to the inhibition of Notch processing and to the accumulation of the neurotoxic precursor of Aβ (the carboxy-terminal fragment of APP, or CTFβ) resulting from the block of the γ-secretase cleavage activity on APP. Two large Phase 3 studies in mild AD patients with tarenflurbil (R flurbiprofen), a putative γ-secretase modulator, were also completely negative. The failure of tarenflurbil was ascribed to low potency and brain penetration. New Notch-sparing γ-secretase inhibitors and more potent, more brain penetrant γ-secretase modulators are being developed with the hope of overcoming the previous setbacks.     

Human beta-secretase (BACE) and BACE inhibitors: progress report

A key step in the processing of the integral membrane protein APP, or Amyloid Precursor Protein is through the proteolytic cleavage by the enzyme beta-Secretase (BACE). The proteolysis of APP by BACE, followed by subsequent C-terminal cleavage(s) by gamma-secretase, results in the formation of the amyloid beta (Abeta) peptide. The principal component of the neuritic plaque found in the brains of Alzheimer's Disease (AD) patients is Abeta which is a neurotoxic and highly aggregatory peptide segment of APP. The amyloid hypothesis holds that the neuronal dysfunction and clinical manifestation of AD is a consequence of the long term deposition and accumulation of 40-42 amino-acid long Abeta peptides, and that this process leads to the onset and progression of AD. Due to the apparent causal relationship between Abeta and AD, the so-called "secretases" that produce Abeta have been targeted for development of inhibitors that might serve as therapeutic agents for treatment of this dreaded, and ever more prevalent disease. Herein will be discussed our current understanding of BACE, its role in the formation of neuritic plaques and the known inhibitors of the enzyme.