加兰他敏抗β淀粉样蛋白的神经保护机制研究

目的观察加兰他敏(Gal)对β淀粉样蛋白(Aβ)损伤人神经母细胞瘤细胞(SH-SY5Y)后β淀粉样前体蛋白(APP)代谢通路的影响,探讨Gal的神经保护机制。方法采用5μMAβ_(1-40)作用于SH-SY5Y细胞制备体外细胞损伤模型,0.3μM加兰他敏对Aβ_(1-40)处理的细胞进行干预并与正常细胞进行对照研究。倒置显微镜下观察细胞形态,应用噻唑蓝比色法(MTT)检测细胞活力,Western-blot技术定量检测各组APP,sAPPα,β-淀粉样前体蛋白剪切酶-1(BACE1)表达水平。结果 Aβ_(1-40)孵育细胞24h之后,细胞损伤明显,存活率从95.78.±2.5%降到62.93±2.1%,与对照组相比差异显著(P0.01);Western-blot显示细胞内BACE1表达增加,APP表达无明显改变,细胞分泌sAPPα降低;在Aβ_(1-40)孵育之前给予加兰他敏作用24h,细胞损伤程度减轻,细胞的存活率上升(85.26±5.3%)(P0.01),细胞内BACE1表达较Aβ组下降,APP表达无明显改变,细胞分泌sAPPα升高。结论加兰他敏通过抑制Aβ_(1-40)诱导的APP的异常代谢发挥神经保护作用。     

α-分泌酶与阿尔茨海默病的治疗

淀粉样前体蛋白(APP)在脑内经β和γ分泌酶的作用生成β淀粉样蛋白(Aβ),也可在α和γ分泌酶的作用下从Aβ序列内部进行降解,生成sAPPα而避免Aβ的生成,sAPPα可对神经细胞产生神经营养和神经保护作用。Aβ在脑内沉积从而对细胞造成毒性作用即Aβ毒性学说被认为是阿尔茨海默病(AD)发病机制之一。目前AD的治疗策略主要集中于抑制β分泌酶和γ分泌酶的研究。新近的研究显示,一类属于解聚素和金属蛋白酶(主要指ADAM10、ADAM17和ADAM9)分子具有α分泌酶的功能,提高α分泌酶的表达可以降低Aβ,有可能在AD的治疗中具有潜在作用。     

缺氧及复氧对淀粉样前体蛋白、去整合蛋白和金属蛋白水解酶10和淀粉样β分泌酶蛋白表达的影响

目的研究缺氧及复氧损伤对淀粉样前体蛋白(APP)、去整合蛋白和金属蛋白水解酶10(ADAM 10)和淀粉样β分泌酶(BACE 1)蛋白表达的影响。方法分为缺氧组和对照组。缺氧组在缺氧条件下(95%N2,5%CO2)培养SH-SY 5Y细胞24h后复氧,分别于0h、12h、24h利用W estern-b lot方法检测APP、ADAM 10和BACE 1蛋白表达;对照组在正常情况下培养,与缺氧组同一时间进行接种和处理。结果缺氧培养SH-SY 5Y细胞24h后复氧各时间点APP蛋白表达与对照组相比差别无统计学意义(P=0.818,0.728和0.674);ADAM 10蛋白表达分别较对照组下降25.5%,67.3%和75.9%(P=0.001,0.001,0.000);BACE 1蛋白表达分别较对照组增加22%,42%和51.5%(P=0.021,0.000和P=0.000)。结论缺氧及复氧可以降低ADAM 10蛋白表达和增加BACE 1蛋白表达。提示血管因素可能使APP更易通过产生淀粉样肽(Aβ)途径裂解,而参与SAD的病理过程。     

阿尔茨海默病的干预与α分泌酶ADAM10

阿尔茨海默病（Alzheimer＇s Disease, AD）是老年人最常见的神经变性疾病.整合素和金属蛋白酶10（ADAM10）是一种α分泌酶,也是淀粉样前体蛋白（APP）的代谢中的一种关键蛋白酶,在AD中具有重要作用.在过表达ADAM10的动物模型中发现这种金属蛋白酶可以促进学习记忆和突触生成.因此,ADAM10在神经退行性病（如AD）中是一个有价值的靶点.ADAM10有很多底物,其中以APP最为显著.因此在治疗性提高ADAM10α分泌酶活性时任何副作用都要纳入考虑的范畴.这篇综述总结了目前有关ADAM10的结构和功能的信息,并进一步探讨提高α分泌酶的表达和/或活性作为治疗靶点的可能性.     

降低细胞胆固醇水平对β-淀粉样肽生成的影响

目的观察降低细胞胆固醇水平对β-淀粉样肽(β-amyloid,Aβ)生成的影响,初步探讨胆固醇和阿尔茨海默病(Alzheimer's disease,AD)的相关性。方法以稳定表达人野生型淀粉样前体蛋白(amyloid precursor protein,APP)的神经母细胞瘤SH-SY5Y细胞为模型,分别给予β-甲基环糊精或洛伐他汀对细胞系进行处理;胆固醇定量试剂盒测定细胞内胆固醇水平的变化,放射免疫法测定细胞培养液中Aβ的含量,Western Blot方法半定量检测全长型APP和可溶性APPα的水平。结果β-甲基环糊精和洛伐他汀处理组分别降低细胞胆固醇水平67.5%和49.5%(P<0.05),细胞培养液中Aβ含量分别降低39.5%和25.7%(P<0.05),sAPPα含量分别增加3.5倍和2.0倍(P<0.05)。结论降低细胞胆固醇水平使细胞外Aβ含量减少,sAPPα含量增加,这提示胆固醇可能通过影响APP代谢途径而参与AD的病理过程。     

鱼藤酮建立帕金森病细胞模型的方法研究

目的探讨鱼藤酮诱导SH-SY5Y细胞建立帕金森病(Parkinson disease,PD)细胞模型的方法。方法实验分为空白对照组及鱼藤酮0.5μmol/L、1.0μmol/L、2.5μmol/L、5.0μmol/L组共5组,各组分别于鱼藤酮加入24h、48h点,观察SH-SY5Y细胞形态变化,采用MTT比色法检测细胞活力;于24h时采用Western blot法检测细胞α-突触核蛋白(α-synuclein)表达量;对空白对照组及鱼藤酮0.5μmol/L、1.0μmol/L组于24h、48h行HE染色观察细胞内包涵体形成情况。以激光共聚焦免疫荧光法观察鱼藤酮1.0μmol/L组24h时α-synuclein的分布情况。结果空白对照组细胞生长较密,神经突起细长;在鱼藤酮药物组24时,0.5μmol/L组细胞突起变短,1.0μmol/L组细胞突起短缩更明显,2.5μmol/L组胞体肿胀明显,5.0μmol/L组圆缩细胞增多;各浓度组48h时与24h时比较,细胞突起变短、细胞肿胀、圆缩更明显。MTT试验显示1.0μmol/L鱼藤酮24h组和0.5μmol/L鱼藤酮48h组分别使细胞活性下降到空白对照组的(86.06±9.06)%和(62.06±7.13)%,与对照组比较差异均具有统计学意义(P0.05)。Western blot结果显示鱼藤酮0.5、1.0、2.5和5.0μmol/L组SH-SY5Y细胞内α-synuclein相对表达水平分别为(1.23±0.11)、(1.41±0.20)、(1.77±0.09)和(1.31±0.28),其中1.0μmol/L、2.5μmol/L鱼藤酮组α-synuclein水平高于空白对照组(P0.05);HE染色显示,在1.0μmol/L鱼藤酮24h组和0.5μmol/L鱼藤酮48h组均观察到细胞质内出现嗜伊红、边界清楚的类路易小体样包涵体;免疫荧光染色显示在1.0μmol/L鱼藤酮24h组观察到细胞内出现颗粒状α-synuclein免疫染色阳性聚集体,可被Thioflavin S共定位。结论 1.0μmol/L鱼藤酮24h诱导SH-SY5Y细胞所建立的PD模型能够很好地模拟PD病理改变,可作为研究PD发病机制的细胞模型。     

信号转导在淀粉样前体蛋白代谢中的研究进展

淀粉样前体蛋白(APP)裂解主要经过α和β分泌酶两条途径,激活β分泌酶途径可增加β-淀粉样蛋白(Aβ)在脑组织的生成量和沉积量,而激活α分泌酶途径可增加可溶性淀粉样前体蛋白α(sAPPα)的生成,sAPPα具有保护神经元促进轴突生长并且相对地降低Aβ的生成量。体内许多神经递质等可通过相应受体偶联的G蛋白或酪氨酸激酶等激活胞浆内的各种信号蛋白来影响α或β分泌酶的活性,从而影响sAPPα或Aβ的生成量。因此,寻找APP信号转导通路上的阻断剂或激动剂以选择性增加sAPPα的生成而减少Aβ的生成量将为寻找AD治疗药物开辟一条新的途径。     

五味子乙素对Aβ_(25-35)诱导PC12细胞损伤的保护作用

目的探讨五味子乙素对Aβ25-35引起的褐家鼠肾上腺嗜铬瘤细胞PC12细胞毒性的作用,并探讨其可能机制。方法 10、25、50、75、100μmol/L五味子乙素作用于PC12细胞,MTT法筛选低毒性的五味子乙素浓度,Aβ25-35诱导PC12细胞毒性损伤建立阿尔茨海默病体外模型,加入低毒性的五味子乙素,倒置显微镜下观察细胞形态变化,MTT法检测细胞活性,RT-PCR法检测PC12细胞β淀粉样前体蛋白(amyloidβ-protein precursor,APP)基因mRNA的表达水平。结果 10、25μmol/L五味子乙素单纯处理可促进PC12细胞增殖,以10μmol/L增长作用更明显,差异具有统计学意义(P0.05),50、75、100μmol/L五味子乙素对细胞有抑制作用,抑制率10%;给予Aβ25-35诱导后PC12细胞存活率降低为(46.4±4.9)%,APP基因表达上调(105±9.3)%;给予10μmol/L的五味子乙素处理后的Aβ25-35组,细胞存活率升高至(107±5.5)%,APP基因表达减少(66.9±7.2)%。结论 10、25μmol/L五味子乙素均可以促进PC12细胞增长,但不具有浓度依赖性;10μmol/L五味子乙素可拮抗Aβ25-35对PC12细胞的损伤作用,机制可能是通过减少APP表达而起作用。     

SH-SY5Y神经细胞APP高表达对胆碱酯酶活性影响

目的研究类阿尔茨海默病(AD)神经细胞模型中APP异常代谢下胆碱酯酶活性变化,探讨AD的发病机制。方法采用脂质体转染法将含有瑞典家族性AD双突变的淀粉样蛋白前体蛋白APP670/671基因(APPSWE)转染至神经母细胞瘤细胞(SH-SY5Y)中;利用实时荧光定量PCR方法和Western blotting的方法测定APPmRNA、可溶性APP(αAPPs)和总APP蛋白表达水平;采用改进的Ellman比色法测定细胞培养基中乙酰胆碱酯酶(Acetylcholinesterase,AChE)及丁酰胆碱酯酶(Butyrylcholinesterase,BuChE)活性。结果转染APPSWE质粒的SH-SY5Y细胞APP总mRNA和蛋白表达水平显著升高,αAPPs分泌量下降。转染组SH-SY5Y细胞与对照组相比,AChE和BuChE活性都升高。结论体外神经细胞实验证明APP蛋白过度表达能升高AChE和BuChE的活性,其机制可能与APP蛋白代谢紊乱使Aβ升高及下调αAPPs分泌有关。     

α-分泌酶ADAM10对APP转基因小鼠情绪和学习行为的影响

目的探讨α-分泌酶ADAM10对阿尔茨海默病发生的作用。方法采用开场实验、高架十字迷宫和水迷宫实验测试并比较APP转基因小鼠和APP/ADAM10双转基因小鼠的行为学差异。结果与对照组小鼠相比,APP转基因小鼠焦虑性增高,自主活动力减弱,空间学习记忆力下降,差异有显著性(P<0.05);而APP/ADAM10双转基因小鼠各种行为和对照组相比无显著性差异(P>0.05)。结论α-分泌酶ADAM10能显著改善小鼠的情绪,提高APP转基因小鼠的自主活动力和学习、记忆能力,开发激活AD-AM10酶活性的药物或者在神经细胞表达ADAM10可望成为治疗阿尔茨海默病的新途径。     

ERK1-independent α-secretase cut of β-amyloid precursor protein via M1 muscarinic receptors and PKCα/ε

The amyloid precursor protein (βAPP) undergoes several proteolytic cleavages. While β- and γ-secretases are responsible for the production of the 40-43 amino-acid long amyloid β peptide (Aβ), the α-secretase cut performed by the disintegrins ADAM10 and ADAM17, occurs in the middle of the Aβ sequence, thereby preventing its formation and leading to the secretion of the large sAPPα neuroprotective fragment. Here we showed that a series of M1 muscarinic receptor agonists dose-dependently stimulated sAPPα secretion without interfering with βAPP subcellular distribution. Carbachol- and PDBu-induced sAPPα secretions were blocked by the general PKC inhibitor GF109203X. We established that HEK293 and rhabdhomyosarcoma cells overexpressing constitutively active (CA) PKCα or PKCε secrete increased amounts of sAPPα while those expressing PKCδ were unable to modify sAPPα recovery. Conversely, the overexpression of PKCα or PKCε dominant negative (DN) constructs abolished PDBU-stimulated sAPPα secretion, whereas DN-PKCδ remained inert. In agreement, PKCα knockout lowered sAPPα recovery in primary cultured fibroblasts. We also demonstrated that the regulated α-secretase processing of βAPP is not controlled by the Extracellular-Regulated Kinase-1/MAP-ERK Kinase (ERK1/MEK) cascade and likely does not require ADAM17 phosphorylation on its threonine735 residue. Because the muscarinic-dependent α-secretase-like processing of PrP(c) is fully dependent on ADAM17 phosphorylation on its threonine735 residue by ERK1, these results indicate that a single extracellular signal triggers ADAM17-dependent regulated cleavages of βAPP and PrP(c) through distinct signalling cascades. This opens new potential therapeutic strategies aimed, in the context of Alzheimer's disease, at selectively activating ADAM17 towards βAPP without affecting the cleavages of its numerous other substrates.     

Cilostazol suppresses β‐amyloid production by activating a disintegrin and metalloproteinase 10 via the upregulation of SIRT1‐coupled retinoic acid receptor‐β

The accumulation of plaques of β‐amyloid (Aβ) peptides, a hallmark of Alzheimer's disease, results from the sequential cleavage of amyloid precursor protein (APP) by activation of β‐ and γ‐secretases. However, the production of Aβ can be avoided by alternate cleavage of APP by α‐and γ‐secretases. We hypothesized that cilostazol attenuates Aβ production by increasing a disintegrin and metalloproteinase 10 (ADAM10)/α‐secretase activity via SIRT1‐coupled retinoic acid receptor‐β (RARβ) activation in N2a cells expressing human APP Swedish mutation (N2aSwe). To evoke endogenous Aβ overproduction, the culture medium was switched from medium containing 10% fetal bovine serum (FBS) to medium containing 1% FBS, and cells were cultured for 3～24 hr. After depletion of FBS in media, N2aSwe cells showed increased accumulations of full‐length APP (FL‐APP) and Aβ in a time‐dependent manner (3–24 hr) in association with decreased ADAM10 protein expression. When pretreated with cilostazol (10–30 μM), FL‐APP and Aβ levels were significantly reduced, and ADAM10 and α‐secretase activities were restored. Furthermore, the effect of cilostazol on ADAM10 expression was antagonized by pretreating Rp‐cAMPS and sirtinol and by SIRT1‐gene silencing. In the N2aSwe cells overexpressing the SIRT1 gene, ADAM10, and sAPPα levels were significantly elevated. In addition, like all‐trans retinoic acid, cilostazol enhanced the protein expressions of RARβ and ADAM10, and the cilostazol‐stimulated ADAM10 elevation was significantly attenuated by LE135 (a RARβ inhibitor), sirtinol, and RARβ‐gene silencing. In conclusion, cilostazol suppresses the accumulations of FL‐APP and Aβ by activating ADAM10 via the upregulation of SIRT1‐coupled RARβ. © 2014 Wiley Periodicals, Inc.     

Apicidin attenuates memory deficits by reducing the Aβ load in APP/PS1 mice

Aims

Amyloid beta (Aβ) is an important pathological feature of Alzheimer's disease (AD). A disintegrin and metalloproteinase 10 (ADAM10) can reduce the production of toxic Aβ by activating the nonamyloidogenic pathway of amyloid precursor protein (APP). We previously found that apicidin, which is a histone deacetylase (HDAC) inhibitor, can promote the expression of ADAM10 and reduce the production of Aβ in vitro. This study was designed to determine the potential of apicidin treatment to reverse learning and memory impairments in an AD mouse model and the possible correlation of these effects with ADAM10.

Methods

Nine-month-old APP/PS1 mice and C57 mice received intraperitoneal injections of apicidin or vehicle for 2 months. At 11 months of age, we evaluated the memory performance of mice with Morris water maze (MWM) and context fear conditioning tests. The Aβ levels were assessed in mouse brain using the immunohistochemical method and ELISA. The expression of corresponding protein involved in proteolytic processing of APP and the phosphorylation of tau were assessed by Western blotting.

Results

Apicidin reversed the deficits of spatial reference memory and contextual fear memory, attenuated the formation of Aβ-enriched plaques, and decreased the levels of soluble and insoluble Aβ40/42 in APP/PS1 mice. Moreover, apicidin significantly increased the expression of ADAM10, improved the level of sAPPα, and reduced the production of sAPPβ, but did not affect the levels of phosphorylated tau in APP/PS1 mice.

Conclusion

Apicidin significantly improves the AD symptoms of APP/PS1 mice by regulating the expression of ADAM10, which may contribute to decreasing the levels of Aβ rather than decreasing the phosphorylation of tau.     

氟西汀对大鼠星形胶质细胞分泌的胶质源性神经营养因子的影响

目的 探讨氟西汀对大鼠星形胶质细胞分泌的胶质源性神经营养因子(GDNF)的影响.方法 以氟西汀干预体外培养的大鼠海马星形胶质细胞,通过四甲基偶氮唑盐法(MTT)检测不同浓度氟西汀对细胞活力的影响;采用酶联免疫吸附测定法(ELISA)检测细胞培养液GDNF浓度及Real-time PCR法检测GDNFmRNA的表达.结果 (1)氟西汀浓度超过35 μmol/L浓度时,可降低细胞活性,差异有统计学意义(P<0.01或P<0.05);(2)10 μmol/L氟西汀干预星形胶质细胞不同时间后,48 h组细胞培养液GDNF浓度[(68±13)fg/L]高于0 h组[(32±11)fg/L]、6 h组[(34±12)fg/L]、12 h组[(41±17)fg/L]、24 h组[(45±13)fg/L],差异均有统计学意义(P均<0.01);(3)不同浓度氟西汀作用星形胶质细胞48 h后,10 μmol/L浓度组的细胞培养液GDNF浓度[(64±17)fg/L]高于0 μmol/L[(39±15)fg/L]和1 μmoVL浓度组[(39±18)fg/L],差异均有统计学意义(P均<0.05);(4)氟西汀作用星形胶质细胞48 h后,撤离氟西汀24 h后星形胶质细胞仍明显分泌GDNF,差异有统计学意义(P<0.01或P<0.05);(5)不同浓度氟西汀作用星形胶质细胞24 h后,10 μmol/L和20 μmol/L浓度组细胞GDNFmRNA表达量[分别为(0.008 1±0.001 1)和(0.006 3±0.000 3)]高于0 μmol/L、1 μmol/L及5 μmol/L浓度组[分别为(0.003 1±0.000 7)、(0.003 9±0.000 3)和(0.004 1±0.000 2)],差异均有统计学意义(P均<0.01).结论 氟西汀可能通过促进星形胶质细胞GDNF的分泌来发挥其神经保护作用.     

Metalloprotease-disintegrin (ADAM) genes are widely and differentially expressed in the adult CNS

ADAM family of metalloprotease-disintegrins, including enzymes that process TNF-alpha and beta-amyloid precursor protein, has been indicated in neuronal development, but the role of these protease/adhesion/signaling proteins in adult nervous system remains poorly understood. Present study provides a systematic examination of ADAM gene expression in rodent CNS, showing the first quantitative characterization of ADAM mRNA distribution therein. At least 17 ADAM mRNAs were expressed. Individual ADAM mRNAs and their isoforms showed strikingly different expression patterns. Expression of mRNAs for ADAM10, the putative alpha-secretase, and ADAM17 (TACE), also indicated in APP processing, was further characterized using in situ hybridization. Expression of ADAM10 mRNA was widespread, while ADAM17 showed a more restricted pattern. Altogether, the wide and differential expression of ADAM mRNAs suggests versatile roles for ADAMs in the adult CNS.     

加兰他敏对APP/PS1转基因小鼠海马区星形胶质细活化及C/EBPβ表达的影响

目的研究加兰他敏对APP/PS1转基因小鼠海马区星形胶质细胞活化、C/EBPβ表达及行为学的影响。方法选取10月龄雄性APP/PS1转基因小鼠20只,随机分为模型对照组(10只)和治疗组(10只),同月龄、同背景的C57BL/6野生型雄性小鼠10只作为正常对照组。治疗组皮下注射加兰他敏溶液5mg/kg,2次/d,连续治疗8周,正常对照组和模型对照组给予皮下注射等量生理盐水。应用Morris水迷宫实验于干预治疗8周后开始测定各组小鼠空间学习记忆能力,连续7d,采用免疫组织化学、免疫荧光及Western-blot方法观察各组小鼠海马区星形胶质细胞活化及C/EBPβ表达水平。结果与正常对照组相比,模型对照组和治疗组小鼠Morris检测第5、6天平均逃避潜伏期延长,穿越平台次数减少(P0.05,P0.05),而治疗组其逃避潜伏期较模型对照组缩短(P0.05),穿越平台次数增多(P0.05);同时治疗组小鼠星形胶质细胞活化被明显抑制,胶质纤维酸性蛋白(GFAP)的阳性表达面积〔(5.003±0.823)%〕及C/EBPβ的表达量(87.711±14.622)较模型对照组〔(7.116±1.040)%,119.920±16.901〕明显减少(P0.05,P0.05)。结论加兰他敏改善APP/PS1转基因AD小鼠的学习记忆能力可能与其抑制星形胶质细胞的活化及C/EBPβ的表达有关。     

神经肽Y对海马神经元“癫痫样”动作电位的影响

目的探讨神经肽Y(neuropeptide Y,NPY)对海马神经元"癫痫样"动作电位的影响。方法用无镁细胞外液处理原代培养12 d的海马神经元3 h,诱导海马神经元癫痫样放电,建立海马神经元癫痫样放电模型;用全细胞膜片钳电流钳模式检测神经元动作电位,分别给予0.1μmol/L和1μmol/L NPY各1μL,给药时间10 s,观察其对神经元动作电位频率及波幅的影响。结果无镁细胞外液处理神经元3 h,可以形成稳定的海马神经元癫痫样放电模型,频率16～23 Hz,波幅75～96 mV。模型组神经元动作电位频率为(18.00±2.32)Hz,而0.1μmol/L和1μmol/L NPY组分别为(4.75±1.04)Hz和(1.50±0.75)Hz。与模型组相比较,两种浓度NPY组均降低了动作电位发放的频率(P<0.05)。模型组神经元动作电位波幅为(82.25±5.17)mV,而0.1μmol/L和1μmol/L NPY组分别为(49.75±2.49)mV和(40.00±2.20)mV。与模型组相比较,两种浓度NPY组均降低了动作电位发放的波幅(P<0.05)。两种浓度NPY之间相比较,也有统计学差异(P<0.05)。1μmol/LNPY明显抑制了动作电位发放的频率和波幅。结论 NPY能够抑制无镁细胞外液诱发的神经元癫痫样电活动,为应用NPY抑制癫痫发作提供了细胞电生理学证据。     

Clinical and neurobiological correlates of soluble amyloid precursor proteins in the cerebrospinal fluid

BackgroundAccording to a widely accepted hypothesis, the amyloid precursor protein (APP) is processed by two competing pathways: the amyloidogenic β-secretase–mediated pathway or the nonamyloidogenic α-secretase–mediated pathway. APP is cleaved preferentially through the nonamyloidogenic pathway in normal brain, whereas the balance shifts to the amyloidogenic pathway in Alzheimer’s disease (AD). The levels of the α-secretase–cleaved soluble APP (sAPPα) and β-secretase–cleaved soluble APP (sAPPβ) in cerebrospinal fluid (CSF) are likely to reflect these competing mechanisms.MethodsWe investigated the levels and the relationship between sAPPα and sAPPβ in the CSF of 64 patients with mild AD, 76 patients with mild cognitive impairment, and 12 cognitively healthy control subjects, as well as the effect of apolipoprotein E genotype and sex on soluble APP levels.ResultsThere was a significant positive correlation between sAPPα and sAPPβ levels in all three groups. sAPPα and sAPPβ concentrations were higher in patients with mild cognitive impairment compared with patients with AD. In the AD group, females exhibited higher sAPPα and sAPPβ levels than males. No influence of the apolipoprotein E genotype on soluble APP concentrations was detected.DiscussionThe positive correlation between sAPPα and sAPPβ challenges the hypothesis that AD is caused by an imbalance of the α- and β-secretase APP proteolysis through competing mechanisms. Moreover, the differences in CSF levels of sAPPα and sAPPβ between male and female patients with AD may reflect a “sexual dimorphism” in the activity of the two APP processing pathways in AD.     

Part-time alpha-secretases: the functional biology of ADAM 9, 10 and 17

Disintegrin metalloproteases of the ADAM family form a large (at present > 40 members in mammals) family of multidomain membrane proteins that in their ectodomain combine a cystein-rich, disintegrin and a zinc metalloprotease domain. Via their metalloprotease domain, ADAMs are often implicated in ectodomain shedding, either to release e.g. growth factors or to initiate further intracellular signalling via regulated intramembrane proteolysis. Mainly based upon overexpression studies in vehicle cells, three of them, ADAMs 9, 10 and 17, have been proposed to act as alpha-secretases for amyloid precursor protein (APP). It is striking thereby that this role has since then remained somewhat ill-defined, as APP processing in ADAM9 deficient neurons is unaltered, and also ADAM10 deficient murine embryonic fibroblasts exhibit at best a highly variable reduction in alpha-secretase activity. However, during the past years, numerous other substrates have been linked to all three sheddases, the cleavage of which in some cases appears to be strikingly more important for the organism than APP processing. Most notably, the perinatally lethal phenotype of ADAM17 knockout mice is dominated by a loss of growth factor shedding, while the even earlier fatal effects of ADAM10 deficiency exhibit key features of disabled Notch signalling and possibly also cadherin processing defects. In this review, we will summarize the published data on the "non-APP" functions of all three ADAMs, the further evaluation of which may be crucial when attempting to treat Alzheimer s Disease by increasing their expression and/or activity. As the knockouts of ADAM10 and ADAM17 are only informative for their roles in (early) development, while a number of recently assigned new substrates play crucial roles in the normal and/or diseased adult organism as well, work on conditional knockout models will be crucial to fully characterize both the full functional portfolio of (candidate) alpha-secretases as well as their clinical relevance, which may go way beyond Alzheimer s Disease.