Targeting amyloid precursor protein shuttling and processing-long before amyloid beta formation

Targeting early steps in amyloid-beta production：Alzheimer’s disease（AD）has a long history as the＂amyloid deposit＂disorder.Many disorders are now known to be caused by proteinβ-sheet misfolding and aggregation（e.g.,Parkinson’s disease：α-synuclein;Huntington’s disease：Huntingtin;

Effects of long-term estrogen replacement therapy on beta-amyloid precursor protein and mRNA expression in ovariectomized rat hippocampus

BACKGROUND： In vitro cultures of neural stem cells have shown that estrogen can regulate beta-amyloid precursor protein （β-APP） metabolism and reduce amyloid-beta production. OBJECTIVE： To investigate the effects of long-term oral administration of compound nylestriol or low-dose 17beta-estradiol on β-APP and mRNA expression in the hippocampus of ovariectomized （OVX） rats. DESIGN, TIME AND SETTING： This randomized and controlled experiment was performed at the Animal Laboratory and Laboratory of Endocrine and Metabolic Disease, Xiangya Second Hospital of Central South University between April 2003 and May 2004. MATERIALS： According to body mass, 50 six-month-old female Sprague-Dawley rats were randomly divided into five groups （n = 10 per group）： normal control, sham operation, OVX model, 17beta-estradiol （Sigma, USA）, and compound nylestriol tablet （Laboratory of Endocrine and Metabolic Disease, Xiangya Second Hospital of Central South University） groups. METHODS： Rats in OVX plus 17beta-estradiol and OVX plus compound nylestriol tablet groups underwent ovariectomy. On the second day after surgery, rats were intragastrically given 17beta-estradiol （100 μg/kg）, once per day or compound nylestriol tablet （0.5 mg/kg） and levonorgestrel （0.15 mg/kg） every 2 days. MAIN OUTCOME MEASURES： β-APP expression in the hippocampus of OVX rats was determined using immunohistochemistry （SABC method） and β-APP mRNA expression was analyzed by in situ hybridization. The results were quantitatively analyzed using cell counting and average optical density. RESULTS： The number and optical density of β-APP-positive neurons in every subregion of the hippocampus of OVX rats was dramatically increased compared with normal and sham operation groups following 35 weeks of administration （P 〈 0.05）. Levels of β-APP were decreased following oral administration of compound nylestriol or 17beta-estradiol. In situ hybridization showed that long-term estrogen deficiency and oral administration of compound nylestriol or 17beta-estradiol did not alter the number of β-APP mRNA-positive neurons. CONCLUSION： The results show that long-term estrogen deficiency results in an increase of expression of β-APP though no changes in the expression of β-APP mRNA are detected. Replacement of estrogen with low-dose 17 beta-estradiol or compound nylestriol tablet inhibits the expression of β-APP in the hippocampus to the same extent.

Observation of amyloid precursor protein cleavage and Aβ generation in living cells by using multiphoton laser scanning microscopy

Objective To investigate the proteolytic mechanism of amyloid precursor protein （APP） and to explore amyloidbeta （Aβ） generation in living neurons. Methods DNA fragments were amplified by PCR or synthesized. The four fragments, CFP, 54bp, YFP and C99 were ligated into pcDNA3.0 vector to construct the recombinant plasmids pcDNA3.0-CFP-54bp- YFP and pcDNA3.0-CFP-54bp-YFP-C99. The SH-SY5Y cells were transiently transfected with pcDNA3.0-CFP-54bp-YFP or pcDNA3.0-CFP-54bp-YFP-C99. The expression of fusion gene was examined under a multiphoton laser scanning microscope. Fluorescence resonance energy transfer （FRET） was used to measure the β cleavage and γ cleavage of APE Aβ generation was confirmed by immunocytochemistry and multiphoton laser scanning microscopy. Cell viability was tested by MTT assay at different time points. Results （1） The double restriction endonuclease digestion and sequencing analysis confirmed the authenticity of the recombinant plasmids pcDNA3.0-CFP-54bp-YFP and pcDNA3.0-CFP-54bp- YFP-C99. （2） Blue and yellow fluorescences were detected in the transfected cells. （3） FRET occurred in pcDNA3.0-CFP- 54bp-YFP-transfected cells but not in pcDNA3.0-CFP-54bp-YFP-C99-transfected cells. （4） Aβ was produced in the pcDNA3.0- CFP-54bp-YFP-C99 transfected cells. （5） Aβ-deposition was widespread in the cell. （6） Cell viability decreased along with the intracellular Aβ deposition. Conclusion C99 is important for the APP β cleavage. Aβ may be generated and deposited in cells at the early stage of Alzheimer＇s disease. Intracellular Aβ accumulation brings deleterious effects on cells.

Physiological effects of amyloid precursor protein and its derivatives on neural stem cell biology and signaling pathways involved

The pathological implication of amyloid precursor protein(APP)in Alzheimer’s disease has been widely documented due to its involvement in the generation of amyloid-β peptide.However,the physiological functions of APP are still poorly understood.APP is considered a multimodal protein due to its role in a wide variety of processes,both in the embryo and in the adult brain.Specifically,APP seems to play a key role in the proliferation,differentiation and maturation of neural stem cells.In addition,APP can be processed through two canonical processing pathways,generating different functionally active fragments:soluble APP-α,soluble APP-β,amyloid-β peptide and the APP intracellular C-terminal domain.These fragments also appear to modulate various functions in neural stem cells,including the processes of proliferation,neurogenesis,gliogenesis or cell death.However,the molecular mechanisms involved in these effects are still unclear.In this review,we summarize the physiological functions of APP and its main proteolytic derivatives in neural stem cells,as well as the possible signaling pathways that could be implicated in these effects.The knowledge of these functions and signaling pathways involved in the onset or during the development of Alzheimer’s disease is essential to advance the understanding of the pathogenesis of Alzheimer’s disease,and in the search for potential therapeutic targets.

Divalent cation tolerance protein binds to β-secretase and inhibits the processing of amyloid precursor protein

The deposition of amyloid-beta is a pathological hallmark of Alzheimer＇s disease, Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase （beta-site amyloid precursor protein-cleaving enzyme 1） and r-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of AIzheimer＇s disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer＇s disease.

Lipid rafts participate in aberrant degradative autophagic-lysosomal pathway of amyloid-beta peptide in Alzheimer's disease

Amyloid-beta peptide is the main component of amyloid plaques, which are found in Alzhei- mer＇s disease. The generation and deposition of amyloid-beta is one of the crucial factors for the onset and progression of Alzheimer＇s disease. Lipid rafts are glycolipid-rich liquid domains of the plasma membrane, where certain types of protein tend to aggregate and intercalate. Lipid rafts are involved in the generation of amyloid-beta oligomers and the formation of amyloid-beta peptides. In this paper, we review the mechanism by which lipid rafts disturb the aberrant deg- radative autophagic-lysosomal pathway of amyloid-beta, which plays an important role in the pathological process of Alzheimer＇s disease. Moreover, we describe this mechanism from the view of the Two-system Theory of fasciology and thus, suggest that lipid rafts may be a new target of Alzheimer＇s disease treatment.

circBIRC6 contributes to the development of non-small cell lung cancer via regulating microRNA-217/amyloid beta precursor protein binding protein 2 axis

Background:Circular RNAs(circRNAs)are considered to be important regulators in cancer biology.In this study,we focused on the effect of circRNA baculoviral inhibitor of apoptosis protein(IAP)repeat containing 6(circBIRC6)on non-small cell lung cancer(NSCLC)progression.Methods:The NSCLC and adjacent non-tumor tissues were collected at Shanghai Ninth People's Hospital.Quantitative real-time polymerase chain reaction was conducted for assessing the levels of circBIRC6,amyloid beta precursor protein binding protein 2(APPBP2)messenger RNA(mRNA),baculoviral IAP repeat containing 6 mRNA(BIRC6),and microRNA-217(miR-217).Western blot assay was adopted for measuring the protein levels of APPBP2,E-cadherin,N-cadherin,and vimentin.Colony formation assay,transwell assay,and flow cytometry analysis were utilized for evaluating cell colony formation,metastasis,and apoptosis.Dualluciferase reporter assay and RNA immunoprecipitation assay were carried out to determine the interaction between miR-217 and circBIRC6 and APPBP2 in NSCLC tissues.The murine xenograft model assay was used to investigate the function of circBIRC6 in tumor formation in vivo.Differences were analyzed via Student's t test or one-way analysis of variance.Pearson's correlation coefficient analysis was used to analyze linear correlation.Results:CircBIRC6 was overexpressed in NSCLC tissues and cells.Knockdown of circBIRC6 repressed the colony formation and metastasis and facilitated apoptosis of NSCLC cells in vitro and restrained tumorigenesis in vivo.Mechanically,circBIRC6 functioned as miR-217 sponge to promote APPBP2 expression in NSCLC cells.MiR-217 inhibition rescued circBIRC6 knockdown-mediated effects on NSCLC cell colony formation,metastasis,and apoptosis.Overexpression of miR-217 inhibited the malignant phenotypes of NSCLC cells,while the effects were abrogated by elevating APPBP2.Conclusion:CircBIRC6 aggravated NSCLC cell progression by elevating APPBP2 via sponging miR-217,which might provide a fresh perspective on NSCLC therapy.

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer＇s disease （AD）, although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β2-adrenergic receptor antagonist, ICI 118551 （ICI）, on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic （TG） mice treated with ICI （AD-TG/ICI） was significantly poorer compared with NaCl-treated AD-TG mice （AD-TG/NaCl）, suggesting that β2-adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β2-adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β2-adrener- gic receptor increased amyloid-β accumulation by downregulating hippocampal a-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β2-adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD.

T cells promote the regeneration of neural precursor cells in the hippocampus of Alzheimer's disease mice

Alzheimer＇s disease is closely associated with disorders of neurogenesis in the brain, and growing evidence supports the involvement of immunological mechanisms in the development of the disease. However, at present, the role of T cells in neuronal regeneration in the brain is unknown. We injected amyloid-beta 1-42 peptide into the hippocampus of six BALB/c wild-type mice and six BALB/c-nude mice with T-cell immunodeficiency to establish an animal model of Alzhei- mer＇s disease. A further six mice of each genotype were injected with same volume of normal saline. Immunohistochemistry revealed that the number of regenerated neural progenitor cells in the hippocampus of BALB/c wild-type mice was significantly higher than that in BALB/c-nude mice. Quantitative fluorescence PCR assay showed that the expression levels of peripheral T cell-associated cytokines （interleukin-2, interferon-y） and hippocampal microglia-related cyto- kines （interleukin-113, tumor necrosis factor-a） correlated with the number of regenerated neural progenitor cells in the hippocampus. These results indicate that T cells promote hippocampal neurogenesis in Alzheimer＇s disease and T-cell immunodeficiency restricts neuronal regeneration in the hippocampus. The mechanism underlying the promotion of neuronal regeneration by T cells is mediated by an increased expression of peripheral T cells and central microglial cytokines in Alzheimer＇s disease mice. Our findings provide an experimental basis for understanding the role of T cells in Alzheimer＇s disease.

Beta secretase activity in peripheral nerve regeneration

While the peripheral nervous system has the capacity to regenerate following a nerve injury,it is often at a slow rate and results in unsatisfactory recovery,leaving patients with reduced function.Many regeneration associated genes have been identified over the years,which may shed some insight into how we can manipulate this intrinsic regenerative ability to enhance repair following peripheral nerve injuries.Our lab has identified the membrane bound protease beta-site amyloid precursor protein-cleaving enzyme 1（BACE1）,or beta secretase,as a potential negative regulator of peripheral nerve regeneration.When beta secretase activity levels are abolished via a null mutation in mice,peripheral regeneration is enhanced following a sciatic nerve crush injury.Conversely,when activity levels are greatly increased by overexpressing beta secretase in mice,nerve regeneration and functional recovery are impaired after a sciatic nerve crush injury.In addition to our work,many substrates of beta secretase have been found to be involved in regulating neurite outgrowth and some have even been identified as regeneration associated genes.In this review,we set out to discuss BACE1 and its substrates with respect to axonal regeneration and speculate on the possibility of utilizing BACE1 inhibitors to enhance regeneration following acute nerve injury and potential uses in peripheral neuropathies.

基于GEO数据库构建APP、APBA和APBB家族的胃癌预后评估模型

目的基于淀粉样β前体蛋白(amyloid beta precursor protein,APP)家族、淀粉样β前体蛋白结合蛋白A(amyloid beta precursor protein binding family A,APBA)家族和淀粉样β前体蛋白结合蛋白B(amyloid beta precursor protein binding family B,APBB)家族构建胃癌预后评估模型。方法从基因表达综合(gene expression omnibus,GEO)数据库下载GSE62254胃癌数据集作为训练集,GSE15459作为验证集。利用Cox回归分析筛选APP家族、APBA家族和APBB家族中胃癌预后的独立危险因素;分别建立基于三家族独立预后因素的风险评分1(risk score 1,RS1)、RS1联合病理学参数的RS2、传统TNM分期的RS3;卡方检验分析RS1与胃癌患者临床病理特征的关系;利用单细胞在线分析网站,分析纳入RS1模型的基因在不同细胞亚群中的表达情况;利用CIBERSORT分析RS1对不同免疫细胞浸润的影响;利用基因集富集分析(gene set enrichment analysis,GSEA)进行通路富集分析。结果APLP2、APBB1、APBB2是胃癌患者预后的独立危险因素(P<0.05),基于三者的风险评分RS1高组患者生存期明显短于RS1低组患者。联合临床病理学参数的Cox回归分析显示,N分期、M分期、Lauren分型和RS1是胃癌患者预后的独立危险因素(P<0.05)。基于此构建的RS2(AUC=0.767)比仅基于T分期、N分期、M分期构建的RS3(AUC=0.719)预测准确率提高了4.8%。RS1和肿瘤T分期呈正相关(P<0.05),RS1高组CD4静息细胞浸润较高,激活细胞浸润较低,M2巨噬细胞浸润较高。GSEA通路分析显示,高RS1组患者富集于MAPK、MTOR和WNT等通路。结论本研究成功构建了基于APP、APBA和APBB家族的胃癌预后评估模型,该模型能够较准确地判断胃癌患者预后。

广东海风藤提取物对痴呆鼠脑内β淀粉样前体蛋白基因表达的影响

目的 研究老年痴呆鼠脑内 β淀粉样前体蛋白基因 (β APP)表达的改变 ;及广东海风藤提取物 (HS2 )对老年痴呆鼠学习记忆及脑内 β APP基因表达的影响。方法 选用昆明种小鼠 ,腹腔注射D 半乳糖和灌胃三氯化铝制备老年痴呆小鼠模型 ,三个治疗组在造模的同时分别灌胃低、中、高剂量的HS2 。通过Morris水迷宫和半定量反转录聚合酶链反应 (RT PCR)来测定HS2 对老年痴呆模型小鼠学习记忆和脑内 β APPmRNA含量的影响。结果 老年痴呆模型小鼠学习记忆成绩下降 ,脑内 β APP基因表达增强。模型小鼠口服低、中、高剂量HS2 能提高其学习记忆成绩 ,降低脑内β APPmRNA含量并呈现一定的量效关系。 结论 HS2 能改善老年痴呆鼠学习记忆能力并下调β APP基因的表达。

人参皂苷Rg1对脂多糖诱导的C6细胞株淀粉样前体蛋白和脑啡肽酶表达的影响

目的 :为寻找治疗阿尔茨海默病的有效药物 ,探讨人参皂苷Rg1对脂多糖 (LPS)诱导的C6细胞株淀粉样前体蛋白 (APP)和脑啡肽酶 (NEP)表达的影响。方法 :应用MTT比色法检测一定剂量LPS(10 0mg·L-1)和不同浓度人参皂苷Rg1(2 5、5、10、2 0 μmol·L-1)对C6细胞存活率的影响 ,应用RT -PCR观察细胞中APP、NEP表达的变化。结果 :LPS作用于C6细胞株 ,C6细胞存活率下降 ,细胞内APP的表达增加 ,NEP的表达降低。人参皂苷Rg1能提高LPS处理的C6细胞存活率 ,使细胞内APP的表达降低 ,NEP的表达升高。结论 :LPS造成细胞损伤和细胞内APP表达增加、NEP表达降低 ,人参皂苷Rg1对LPS造成的细胞毒性具有拮抗作用 ,可减弱LPS引起的细胞内APP表达增强 ,减轻LPS对细胞内NEP表达的抑制。

Aβ_(1-42)诱导阿尔茨海默病模型大鼠海马内细胞因子表达变化的研究

目的探讨β淀粉样蛋白(Aβ)1-42诱导的阿尔茨海默病(AD)模型大鼠海马内致炎细胞因子和抗炎细胞因子表达的变化。方法 24只SD大鼠随机分为正常对照组(intact组)、PBS对照组和AD模型组。PBS对照组为海马CA1区注射PBS,AD模型组为海马CA1区注射Aβ1-42。应用Morris水迷宫测试大鼠逃避潜伏期;Nissl染色观察海马CA1区神经元的损害情况;Western blot方法检测海马组织中淀粉样前体蛋白(APP)以及蛋白质磷酸酶-2A(PP2A)的表达量;Real-time PCR法检测海马内细胞因子白介素(IL)-1β、肿瘤坏死因子(TNF)-α、干扰素(IFN)-γ、IL-4、IL-10和转化生长因子(TGF)-β的mRNA水平。结果大鼠双侧海马内注射Aβ1-42后,动物的空间学习记忆能力降低、海马CA1区神经元胞体丢失、海马内APP表达上调而PP2A表达下调。AD模型大鼠的海马内,致炎细胞因子IL-1β、TNF-α和IFN-γ的mRNA表达上调,而抗炎细胞因子IL-4、IL-10和TGF-β的mRNA表达下调。结论 AD大鼠脑内存在致炎/抗炎失衡的神经炎症,它参与了AD的发病机制。

大鼠弥漫性轴突损伤早期淀粉样前体蛋白(β-APP)表达的实验研究

目的观察大鼠弥漫性轴突损伤(DAI)早期脑内各部位淀粉样前体蛋白(β-APP)表达的变化。方法应用瞬间旋转致伤装置使16只SD大鼠发生DAI,并于伤后3h、6h分批处死(每时间点8只),另取8只大鼠作为正常对照,在24h后处死。取各组大鼠脑标本进行免疫组织化学观察,检查损伤后早期不同时间皮质下白质、海马、胼胝体、脑干区域的病理学改变。各部位(胼胝体、海马、脑干)的切片在显微镜下(200倍)进行半定量分析。结果损伤后3h,大脑皮质下白质、胼胝体和脑干β-APP呈弱阳性表达;损伤后6h,轴突局部免疫反应阳性较前明显增强,范围增大,半定量分析显示,胼胝体、海马、脑干的免疫反应均强于3h组。结论β-APP在DAI早期(伤后3h)即有明确表达,并呈逐渐增强趋势,可作为DAI早期的标志物。

可溶性α淀粉样前体蛋白对蛛网膜下腔出血大鼠神经细胞凋亡及神经功能的影响

目的探讨可溶性α淀粉样前体蛋白(solubleαform of amyloid precursor protein,sAPPα)对蛛网膜下腔出血(subarachnoid hemorrhage,SAH)大鼠神经细胞凋亡及神经功能的影响。方法选择雄性SD大鼠60只,随机分为对照组、生理盐水组(SAH+生理盐水)和sAPPα组(SAH+sAPPα),每组20只。大鼠自体血于视交叉前池建立SAH模型,生理盐水组在SAH模型建立后脑室注入生理盐水,sAPPα组在SAH模型建立后脑室注入sAPPα。各组分别于模型建立后取大鼠10只,注药3d后行组织凋亡细胞检测,采用TUNEL法测定凋亡细胞,并进行免疫荧光检测;各组分别于模型建立后取大鼠10只,注药3d后进行神经功能评分。结果对照组大鼠颞叶脑组织仅有很少量阳性凋亡细胞,而生理盐水组脑组织阳性凋亡细胞较对照组明显增多,差异有统计学意义(P<0.05)。与生理盐水组比较,sAPPα组脑组织阳性凋亡细胞明显降低,差异有统计学意义(P<0.05)。对照组、生理盐水组和sAPPα组用药3d后神经功能评分分别为(26.7±0.5)分、(13.9±0.7)分和(23.0±0.8)分。sAPPα组神经功能评分较生理盐水组明显增高,差异有统计学意义(P<0.05)。结论 sAPPα可通过抑制SAH后神经细胞凋亡,减轻继发损伤,从而改善神经功能恢复。

还脑益聪方组分对β淀粉样前体蛋白转基因痴呆小鼠行为学及胆碱能系统的早期干预作用

目的:观察还脑益聪方复方组分早期干预对阿尔茨海默病(Alzhei mer disease,AD)模型β淀粉样前体蛋白(β-amyloid precursor protein,APP)转基因小鼠行为学及脑胆碱能系统的影响。方法:将60只3月龄APP695V717I转基因小鼠随机分为4组:模型组、大剂量还脑益聪方组[2.80g/(kg.d)]、小剂量还脑益聪方组[1.40g/(kg.d)]及盐酸多奈哌齐阳性对照组[0.65mg/(kg.d)],每组15只。15只遗传背景相同的非转基因C57BL/6J小鼠作为正常对照组。所试药物稀释至相同体积灌胃给药,正常组和模型组给以等体积蒸馏水灌胃,连续灌胃6个月。采用Morris水迷宫实验和避暗实验进行小鼠行为学测试,采用酶联免疫吸附测定法分别检测小鼠大脑皮层和海马组织的乙酰胆碱(acetylcholine,ACh)、乙酰胆碱酯酶(acetylcholinesterase,AChE)含量及胆碱乙酰转移酶(choline acetyltransferase,ChAT)的活性,采用考马斯亮蓝法测定脑组织中蛋白的含量。结果:与正常对照组比较,模型组小鼠学习记忆成绩均显著下降(P<0.05,P<0.01),海马和皮层组织的ACh含量和ChAT活性显著降低,AChE含量显著增加(P<0.01,P<0.05)。与模型组比较,盐酸多奈哌齐组、还脑益聪方组小鼠的学习记忆能力均有明显提高(P<0.05);盐酸多奈哌齐组、还脑益聪方大剂量组小鼠海马ACh含量明显提高(P<0.05),盐酸多奈哌齐组、还脑益聪方组小鼠海马AChE含量显著降低,ChAT活性显著升高(P<0.01,P<0.05);盐酸多奈哌齐组和还脑益聪方两组小鼠皮层ACh含量均明显提高(P<0.05),AChE含量有不同程度的降低,还脑益聪方两组小鼠皮层ChAT活性均明显提高(P<0.05)。结论:还脑益聪方能明显改善APP转基因小鼠的学习记忆能力,其作用机制可能与调控小鼠海马与皮层胆碱能系统相关酶的含量有关。

蛇床子素通过上调微RNA-101a-3p抑制阿尔茨海默病细胞淀粉样前体蛋白表达

目的:研究阿尔茨海默病细胞模型中蛇床子素抑制淀粉样前体蛋白(APP)的作用及机制。方法:脂质体2000转染建立APP高表达的SH-SY5Y细胞模型。利用MTT和乳酸脱氢酶(LDH)法检测蛇床子素对APP高表达细胞的存活率和损伤程度的影响。利用基因芯片技术筛选给予蛇床子素治疗后差异表达的微RNA(miRNA),然后通过生物信息学分析预测与差异表达miRNA靶向结合的基因。细胞内转入差异表达miRNA的抑制剂,然后采用免疫荧光细胞化学法观察细胞中APP、β淀粉样蛋白(Aβ)表达情况,RT-PCR法检测细胞中APP mRNA表达。结果:实验成功构建了APP高表达的阿尔茨海默病细胞模型。MTT和LDH法检测结果显示,蛇床子素对于APP高表达的细胞具有一定的保护作用,可以减轻细胞的损伤。miRNA-101a-3p是蛇床子素调控较明显的miRNA,其与APP的3'非翻译区靶向结合。与模型对照组比较,miR-101a-3p抑制剂组APP和Aβ蛋白荧光强度增加,APP mRNA表达量增加(均P<0.01);加入蛇床子素后细胞中APP和Aβ蛋白荧光强度降低,APP mRNA表达量减少(均P<0.01)。结论:在阿尔茨海默病细胞模型中,蛇床子素通过上调miR-101a-3p抑制APP表达。

尼古丁对Aβ_(25～35)细胞毒性的拮抗作用及与β-淀粉样前体蛋白代谢的关系

目的研究尼古丁对β-淀粉样蛋白(Aβ)细胞毒性的拮抗作用及与β-淀粉样前体蛋白(APP)代谢之间的关系。方法不同浓度的尼古丁分别单独或与Aβ25～35同时作用于PC12细胞24h,然后采用MTT法检测细胞活力;WesternBlot法检测PC12细胞上清液中的可溶性β-淀粉样前体蛋白α片段(sAPPα)和细胞内胰岛素降解酶的表达水平。结果(1)尼古丁浓度于0.10～500μmol/L时,对PC12细胞无明显毒性作用(均P>0.05),当浓度升至1000μmol/L时则产生一定的毒性作用(P≤0.05);Aβ25～35浓度于1～100μmol/L时对PC12细胞具有明显毒性作用(均P≤0.01),Aβ25～35浓度降至0.10μmol/L时则失去其毒性作用(P>0.05)。(2)尼古丁浓度于0.10～1000μmol/L时,对Aβ25～35诱导的细胞毒性呈现不同的作用:尼古丁浓度于0.10～100μmol/L时可部分拮抗Aβ25～35诱导的细胞毒性作用(均P<0.01),但不能使PC12细胞活力恢复至正常细胞水平(均P<0.01);而当尼古丁浓度于500μmol/L和1000μmol/L时则不产生拮抗Aβ25～35诱导的细胞毒性作用(均P>0.05)。(3)Aβ25～35(20μmol/L)和尼古丁(100μmol/L,1000μmol/L)单独或联合作用均可引起PC12细胞可溶性β-淀粉样前体蛋白α片段分泌水平升高(均P<0.01),其中以尼古丁浓度为100μmol/L时可溶性β-淀粉样前体蛋白α片段的分泌水平最高。(4)浓度为20μmol/L的Aβ25～35可导致胰岛素降解酶表达水平降低(P<0.01),而浓度为100μmol/L的尼古丁可明显拮抗这种作用(P<0.01),1000μmol/L的尼古丁则无明显拮抗作用(P>0.05);将浓度为100μmol/L和1000μmol/L的尼古丁分别单独作用于PC12细胞时,胰岛素降解酶表达水平明显升高,与正常对照组相比差异有统计学意义(P<0.01)。结论尼古丁对Aβ25～35诱导的细胞毒性的拮抗作用与可溶性β-淀粉样前体蛋白α片段的分泌水平并无直接关系,而可能与胰岛素降解酶的表达水平相关。

长期口服雌激素对去卵巢大鼠海马结构内β-淀粉样前体蛋白及其mRNA表达的影响

目的观察长期口服复方尼尔雌醇和小剂量17β-雌二醇补充治疗对去卵巢大鼠海马结构内β-淀粉样前体蛋白(β-APP)及其mRNA表达的影响。方法7月龄SD大鼠按体重随机分成5组正常对照组、假手术组(SHAM)、去卵巢组(OVX)、17β-雌二醇预防干预组(OVX/ERT)和复方尼尔雌醇预防干预组(OVX/NL)连续观察。5组均在去卵巢后35w处死。用免疫组织化学方法(SABC法)显示大鼠海马结构内β-APP,原位杂交方法显示β-APPmRNA。细胞计数及图像分析观察β-APP及其mRNA的变化。结果OVX组海马结构内各亚区β-APP阳性神经元数量和平均光密度均高于正常组、SHAM组、OVX/ERT组、OVX/NL组(P<0.05),而β-APPmRNA阳性神经元数量和平均光密度在5组之间均无显著性差异。结论长期雌激素缺乏导致了大鼠海马结构内β-APP含量的增加,长期口服复方尼尔雌醇和小剂量17β-雌二醇补充治疗可减少β-APP的含量,且二者效果相当。促进β-APP分解、减少β-APP的含量,进而减少Aβ的沉着可能是雌激素神经保护的重要机制之一。