Interactions of Zn(II) and Cu(II) ions with Alzheimer's amyloid-beta peptide. Metal ion binding, contribution to fibrillization and toxicity

Amyloid-β peptides (Aβ) are key molecules in Alzheimer's disease (AD) pathology as they form amyloid plaques that are primary hallmarks of AD. There is increasing evidence demonstrating that the biometals zinc(ii) and copper(ii) interact with Aβ peptides and have an influence on their fibrillization and toxicity. Zinc and copper ions are abundantly present in the synaptic areas of the brain, and it is likely that the age-related dyshomeostasis of these biometals is associated with AD pathology. In this review we summarize the knowledge of the interactions of zinc and copper ions with Aβ peptides, their role in Aβ fibrillization and toxicity and provide a critical analysis of the conflicting results in the field. Copper ions entrapped in Aβ fibrils are electrochemically active and can generate ROS in the presence of hydrogen peroxide and reducing agents. This might provide a key for understanding the putative role of copper in Aβ toxicity and AD pathology.     

Neglected N-Truncated Amyloid-β Peptide and Its Mixed Cu–Zn Complexes

The Protein Journal - Amyloid-β (Aβ) peptides are involved in Alzheimer’s disease (AD) development. The interactions of these peptides with copper and zinc ions also seem to be...     

Amyloid precursor protein is required for in vitro platelet adhesion to amyloid peptides and potentiation of thrombus formation

Amyloid precursor protein (APP) is the precursor of amyloid β (Aβ) peptides, whose accumulation in the brain is associated with Alzheimer's disease. APP is also expressed on the platelet surface and Aβ peptides are platelet agonists. The physiological role of APP is largely unknown. In neurons, APP acts as an adhesive receptor, facilitating integrin-mediated cell adhesion, while in platelets it regulates coagulation and venous thrombosis. In this work, we analyzed platelets from APP KO mice to investigate whether membrane APP supports platelet adhesion to physiological and pathological substrates. We found that APP-null platelets adhered and spread normally on collagen, von Willebrand Factor or fibrinogen. However, adhesion on immobilized Aβ peptides Aβ_1–40, Aβ_1–42 and Aβ_25–35 was completely abolished in platelets lacking APP. By contrast, platelet activation and aggregation induced by Aβ peptides occurred normally in the absence of APP. Adhesion of APP-transfected HEK293 to Aβ peptides was significantly higher than that of control cells expressing low levels of APP. Co-coating of Aβ_1–42 and Aβ_25–35 with collagen strongly potentiated platelet adhesion when whole blood from wild type mice was perfused at arterial shear rate, but had no effects with blood from APP KO mice. These results demonstrate that APP selectively mediates platelet adhesion to Aβ under static condition but not platelet aggregation, and is responsible for Aβ-promoted potentiation of thrombus formation under flow. Therefore, APP may facilitate an early step in thrombus formation when Aβ peptides accumulate in cerebral vessel walls or atherosclerotic plaques.     

β-淀粉样蛋白-血红素复合物和蛋白质酪氨酸硝化及其与阿尔茨海默症的关系

β-淀粉样蛋白(Amyloid-β,Aβ)是阿尔茨海默症(Alzheimer’s disease,AD)病人大脑中淀粉样斑块的主要组成部分。β-淀粉样蛋白级联假说指出,Aβ在脑实质的沉积是最终导致阿尔茨海默症的一个关键步骤。目前的大量研究表明,相对于高度聚集的Aβ,可溶性的Aβ低聚物可能与认知功能障碍的关联性更强。血红素(heme)的代谢在AD患者大脑中发生了改变。近来发现heme可与Aβ结合,形成一个复合物Aβ-heme,该复合物拥有显著高于heme的过氧化物酶活性,具有比heme更强的催化蛋白质酪氨酸硝化的能力。这个结果提示,Aβ-heme可能是联系Aβ与AD中大量蛋白质发生硝化的关键分子。同时,Aβ与heme的结合改变了heme催化蛋白质硝化的位点选择性。这些研究对于阐明Aβ和heme在体内可能的生理作用具有重要意义。     

Distinct inflammatory phenotypes of microglia and monocyte‐derived macrophages in Alzheimer's disease models: effects of aging and amyloid pathology

Alzheimer's disease (AD) is a neurodegenerative disease characterized by formation of amyloid‐β (Aβ) plaques, activated microglia, and neuronal cell death leading to progressive dementia. Recent data indicate that microglia and monocyte‐derived macrophages (MDM) are key players in the initiation and progression of AD, yet their respective roles remain to be clarified. As AD occurs mostly in the elderly and aging impairs myeloid functions, we addressed the inflammatory profile of microglia and MDM during aging in TgAPP/PS1 and TgAPP/PS1dE9, two transgenic AD mouse models, compared to WT littermates. We only found MDM infiltration in very aged mice. We determined that MDM highly expressed activation markers at basal state. In contrast, microglia exhibited an activated phenotype only with normal aging and Aβ pathology. Our study showed that CD14 and CD36, two receptors involved in phagocytosis, were upregulated during Aβ pathogenesis. Moreover, we observed, at the protein levels in AD models, higher production of pro‐inflammatory mediators: IL‐1β, p40, iNOS, CCL‐3, CCL‐4, and CXCL‐1. Taken together, our data indicate that microglia and MDM display distinct phenotypes in AD models and highlight the specific effects of normal aging vs Aβ peptides on inflammatory processes that occur during the disease progression. These precise phenotypes of different subpopulations of myeloid cells in normal and pathologic conditions may allow the design of pertinent therapeutic strategy for AD.     

Anti-oligomeric Abeta single-chain variable domain antibody blocks Abeta-induced toxicity against human neuroblastoma cells

The Amyloid-β (Aβ) peptide is a major component of the amyloid plaques associated with Alzheimer's disease (AD). Recent studies suggest that the most toxic forms of Aβ are small, soluble oligomeric aggregates. Here, we report the isolation and characterization of a single-chain variable domain (scFv) antibody isolated against oligomeric Aβ using a protocol developed in our laboratory that combines phage display technology and atomic force microscopy (AFM). Starting with a randomized, single framework phage display library, after three rounds of selection against oligomeric Aβ, we identified an scFv that bound oligomeric Aβ specifically, but not monomeric or fibrillar forms. The anti-oligomeric scFv inhibits Aβ aggregation and toxicity, and reduces the toxicity of preformed oligomeric Aβ towards human neuroblastoma cells. When used to probe samples of human brain tissue, the scFv reacted with AD tissue but not a healthy control or Parkinson's disease brain samples. The anti-oligomeric Aβ scFv therefore has potential therapeutic and diagnostic applications in specifically targeting or identifying the toxic morphologies of Aβ in AD brains.     

β-淀粉样肽的细胞内毒性与线粒体通透性转变孔道

β-淀粉样肽（amyloid—β peptide,Aβ）是阿尔采末病患者脑内老年斑的主要成分,具有很强的神经毒性。近年来,研究发现细胞内产生和聚集的Aβ可以通过多种途径发挥其神经毒性作用。利用离体线粒体模型发现,Aβ可以导致线粒体通透性转变孔道（mitochondrial permeability transition pore,MPTP）开放。MPTP开放会进一步加剧线粒体功能的损伤,并可导致细胞色素c和凋亡诱导因子释放,在线粒体介导的细胞死亡中具有重要作用。Aβ引起的MPTP开放可能是胞内Aβ导致神经元死亡的重要通路,研究Aβ对该孔道的影响将有助于阐明Aβ的毒性机理并以期找到减轻Aβ损伤的新策略。     

Role of thrombin in the pathogenesis of atherosclerosis

Atherosclerosis is an arterial disease associated with inflammation. Thrombin is a procoagulant and proinflammatory serine protease that contributes to the pathology of atherosclerosis by enhancing the expression of cell adhesion molecules, inducing the secretion of proinflammatory cytokines, activating inflammatory responses in atherosclerotic plaques, stimulating proliferation of aortic smooth muscle cells, and exacerbating vascular lesions at sites of injury. Hence, thrombin appears to be an important target for treatment of atherosclerosis and thrombin pharmacological inhibitors have significant therapeutic potency for suppressing inflammatory responses in cardiovascular diseases. This review summarizes the proinflammatory signaling functions of thrombin as well as the therapeutic potency of thrombin inhibitors in the pathogenesis of atherosclerosis and hence their potential therapeutic value in this condition.     

GM1 locates to mature amyloid structures implicating a prominent role for glycolipid-protein interactions in Alzheimer pathology

While the molecular mechanisms underlying Alzheimer's disease (AD) remain largely unknown, abnormal accumulation and deposition of beta amyloid (Aβ) peptides into plaques has been proposed as a critical pathological process driving disease progression. Over the last years, neuronal lipid species have been implicated in biological mechanisms underlying amyloid plaque pathology. While these processes comprise genetic features along with lipid signaling as well as direct chemical interaction of lipid species with Aβ mono- and oligomers, more efforts are needed to spatially delineate the exact lipid-Aβ plaque interactions in the brain. Chemical imaging using mass spectrometry (MS) allows to probe the spatial distribution of lipids and peptides in complex biological tissues comprehensively and at high molecular specificity. As different imaging mass spectrometry (IMS) modalities provide comprehensive molecular and spatial information, we here describe a multimodal ToF-SIMS- and MALDI-based IMS strategy for probing lipid and Aβ peptide changes in a transgenic mouse model of AD (tgAPP_ArcSwe). Both techniques identified a general AD-associated depletion of cortical sulfatides, while multimodal MALDI IMS revealed plaque specific lipid as well as Aβ peptide isoforms. In addition, MALDI IMS analysis revealed chemical features associated with morphological heterogeneity of individual Aβ deposits. Here, an altered GM1 to GM2/GM3 ganglioside metabolism was observed in the diffuse periphery of plaques but not in the core region. This was accompanied by an enrichment of Aβ1–40arc peptide at the core of these deposits. Finally, a localization of arachidonic acid (AA) conjugated phosphatidylinositols (PI) and their corresponding degradation product, lyso-phosphatidylinositols (LPI) to the periphery of Aβ plaques was observed, indicating site specific macrophage activation and ganglioside processing.     

Intravenous Administration of Human Umbilical Cord Mesenchymal Stem Cells Improves Cognitive Impairments and Reduces Amyloid-Beta Deposition in an AβPP/PS1 Transgenic Mouse Model

Alzheimer’s disease (AD) is characterized by Amyloid-β (Aβ) deposition in senile plaques in specific areas of the brain and by intraneuronal p-tau accumulation in neurofibrillary tangles. Cumulative evidence supports that oxidative stress is an important factor in the pathogenesis of AD and contributes to Aβ generation. However, there is no effective treatment for AD. Human umbilical cord mesenchymal stem cells (HUMSCs) have potential therapeutic value for the treatment of neurological disease. However, the therapeutic impact of systemic administration of HUMSCs and their mechanism of action in AD have not yet been determined. Here, we found that intravenous infusion of HUMSCs significantly improved spatial learning and alleviated memory decline in an AβPP/PS1 mouse model of AD. HUMSC treatment also increased glutathione (GSH) activity and ratio of GSH to oxidative glutathione as well as superoxide dismutase activity, while decreasing malondialdehyde activity and protein carbonyl level, which suggests that HUMSC infusion alleviated oxidative stress in AβPP/PS1 mice. In addition, HUMSC infusion reduced β-secretase 1 and CTFβ, thus reducing Aβ deposition in mice. HUMSCs may have beneficial effects in the prevention and treatment of AD.     

Reduction of amyloid β-peptide accumulation in Tg2576 transgenic mice by oral vaccination

Alzheimer’s disease (AD) is pathologically characterized by the presence of extracellular senile plaques and intracellular neurofibrillary tangles. Amyloid β-peptide (Aβ) is the main component of senile plaques, and the pathological load of Aβ in the brain has been shown to be a marker of the severity of AD. Aβ is produced from the amyloid precursor protein by membrane proteases and is known to aggregate. Recently, immune-mediated cerebral clearance of Aβ has been studied extensively as potential therapeutic strategy. In previous studies that used a purified Aβ challenge in a mouse model of AD, symptomatic improvement was reported. However, a clinical Alzheimer’s vaccine trial in the United States was stopped because of severe side effects. Immunization with the strong adjuvant used in these trials might have activated an inflammatory Th1 response.In this study, to establish a novel, safer, lower-cost therapy for AD, we tested an oral vaccination in a wild-type and a transgenic mouse model of AD administered via green pepper leaves expressing GFP-Aβ. Anti-Aβ antibodies were effectively induced after oral immunization. We examined the immunological effects in detail and identified no inflammatory reactions. Furthermore, we demonstrated a reduction of Aβ in the immunized AD-model mice. These results suggest this edible vehicle for Aβ vaccination has a potential clinical application in the treatment of AD.     

阿尔茨海默病与炎性调控

阿尔茨海默病 （AD） 是毁灭性的神经退行性损伤疾病,其特点是细胞外聚积β淀粉样蛋白（Aβ）形成淀粉样斑块和细胞内异常高度磷酸化 tau 蛋白导致神经纤维缠结(neurobrillary tangles）.基于上述特点提出的β淀粉样蛋白假说和tau的高度磷酸化假说,仍不能完全解释其发病机理和神经元的退行性损伤.目前,炎症小体在阿尔茨海默病的病理过程中引起的炎症和组织损伤引起高度关注.因此研究AD患者中炎症小体如何激活、组装、并诱发细胞炎性介质的高表达,可能对深入研究AD病理机制和治疗靶点的突破提供一种新的解释,本文主要针对这一研究领域的进展加以简要的概述介绍.     

TGF-β1 is an organizer of responses to neurodgeneration

TGF-β1 mRNA and protein were recently found to increase in animal brains after experimental lesions that cause local deafferentation or neuron death. Elevations of TGF-β1 mRNA after lesions are prominent in microglia but are also observed in neurons and astrocytes. Moreover, TGF-β1 mRNA autoinduces its own mRNA in the brain. These responses provide models for studying the increases of TGF-β1 protein observed in βA/amyloid-containing extracellular plaques of Alzheimer's disease (AD) and Down's syndrome (DS) and in brain cells of AIDS victims. Involvement of TGF-β1 in these human brain disorders is discussed in relation to the potent effects of TGF-β1 on wound healing and inflammatory responses in peripheral tissues. We hypothesize that TGF-β1 and possibly other TGF-β peptides have organizing roles in responses to neurodegeneration and brain injury that are similar to those observed in non-neural tissues. Work from many laboratories has shown that activities of TGF-β peptides on brain cells include chemotaxis, modification of extracellular matrix, and regulation of cytoskeletal gene expression and of neurotrophins. Similar activities of the TGF-β's are well established in other tissues.     

Aspirin prevents adhesion of T lymphoblasts to vascular smooth muscle cells

In the development of atherosclerosis, inflammatory cells adhere to and migrate into the vascular walls by interacting with vascular smooth muscle cells. To investigate the mechanism of aspirin’s anti-atherogenic activity, we examined whether aspirin inhibits the adhesion of lymphocytes to human aortic smooth muscle cells (AoSMC). Aspirin inhibited T-cell adhesion to AoSMC activated by interleukin 1β (IL-1β) in a dose-dependent manner. Antibodies to the adhesion molecules ICAM-1 or VCAM-1, but not to E-selectin, prevented T-cell adhesion. ICAM-1 and VCAM-1 expression stimulated by IL-1β was reduced by the treatment with aspirin, whereas the expression of E-selectin was unaffected. Nuclear factor κB (NF-κB) activity was enhanced by IL-1β and reduced by aspirin, indicating that decreased ICAM-1 and VCAM-1 expression was due to reduced NF-κB activity.Thus, aspirin inhibits the adhesion of Jurkat T cells to IL-1β-activated AoSMC by reducing NF-κB activity and decreasing expression of ICAM-1 and VCAM-1, and may prevent the development of atherosclerosis.     

Site-specific aspartic acid isomerization regulates self-assembly and neurotoxicity of amyloid-β

Amyloid-β (Aβ) proteins, which consist of 42 amino acids (Aβ_1–42), are the major constituent of neuritic plaques that form in the brains of senile patients with Alzheimer’s disease (AD). Several reports state that three aspartic acid (Asp) residues at positions 1, 7, and 23 in Aβ_1–42 in the plaques of patients with AD are highly isomerized from the l- to d-form. Using biophysical experiments, the present study shows that simultaneous d-isomerization of Asp residues at positions 7 and 23 (d-Asp^7,23) enhances oligomerization, fibril formation, and neurotoxic effect of Aβ_1–42. In addition, d-isomerization of Asp at position 1 (d-Asp¹) suppresses malignant effects induced by d-Asp^7,23 of Aβ_1–42. These results provide fundamental information to elucidate molecular mechanisms of AD pathogenesis and to develop potent inhibitors of amyloid aggregates and Aβ neurotoxicity.     

Reestablishing microglia function: good news for Alzheimer's therapy?

Alzheimer's disease (AD) is the most common form of age‐related neurodegenerative disease resulting in dementia. The current notion is that AD is based on a pathological plaque‐forming accumulation of amyloid‐β (Aβ) peptides that originate from a disturbed balance between production and removal of Aβ peptides. Loss of Aβ uptake capacity by brain microglia is linked to Aβ plaque formation and AD onset. In this issue of The EMBO Journal, Daria and colleagues show that this microglia dysfunction is reversible and that existing Aβ plaques can be cleared, suggesting that restoring microglia function may be vital for treating AD.     

Interleukin-1β modulates smooth muscle cell phenotype to a distinct inflammatory state relative to PDGF-DD via NF-κB-dependent mechanisms

Smooth muscle cell (SMC) phenotypic modulation in atherosclerosis and in response to PDGF in vitro involves repression of differentiation marker genes and increases in SMC proliferation, migration, and matrix synthesis. However, SMCs within atherosclerotic plaques can also express a number of proinflammatory genes, and in cultured SMCs the inflammatory cytokine IL-1β represses SMC marker gene expression and induces inflammatory gene expression. Studies herein tested the hypothesis that IL-1β modulates SMC phenotype to a distinct inflammatory state relative to PDGF-DD. Genome-wide gene expression analysis of IL-1β- or PDGF-DD-treated SMCs revealed that although both stimuli repressed SMC differentiation marker gene expression, IL-1β distinctly induced expression of proinflammatory genes, while PDGF-DD primarily induced genes involved in cell proliferation. Promoters of inflammatory genes distinctly induced by IL-1β exhibited over-representation of NF-κB binding sites, and NF-κB inhibition in SMCs reduced IL-1β-induced upregulation of proinflammatory genes as well as repression of SMC differentiation marker genes. Interestingly, PDGF-DD-induced SMC marker gene repression was not NF-κB dependent. Finally, immunofluorescent staining of mouse atherosclerotic lesions revealed the presence of cells positive for the marker of an IL-1β-stimulated inflammatory SMC, chemokine (C-C motif) ligand 20 (CCL20), but not the PDGF-DD-induced gene, regulator of G protein signaling 17 (RGS17). Results demonstrate that IL-1β- but not PDGF-DD-induced phenotypic modulation of SMC is characterized by NF-κB-dependent activation of proinflammatory genes, suggesting the existence of a distinct inflammatory SMC phenotype. In addition, studies provide evidence for the possible utility of CCL20 and RGS17 as markers of inflammatory and proliferative state SMCs within atherosclerotic plaques in vivo.     

Oligomeric amyloid-β peptide affects the expression of genes involved in steroid and lipid metabolism in primary neurons

Amyloid-β peptide (Aβ) is the principal component of plaques in the brains of patients with Alzheimer's disease (AD), and the most toxic form of Aβ may be as soluble oligomers. We report here the results of a microarray study of gene expression profiles in primary mouse cortical neurons in response to oligomeric Aβ(1-42). A major and unexpected finding was the down-regulation of genes involved in the biosynthesis of cholesterol and other steroids and lipids (such as Fdft1, Fdps, Idi1, Ldr, Mvd, Mvk, Nsdhl, Sc4mol), the expression of which was verified by quantitative real-time RT-PCR (qPCR). The ATP-binding cassette gene Abca1, which has a major role in cholesterol transport in brain and other tissues and has been genetically linked to AD, was notably up-regulated. The possible involvement of cholesterol and other lipids in Aβ synthesis and action in Alzheimer's disease has been studied and debated extensively but remains unresolved. These new data suggest that Aβ may influence steroid and lipid metabolism in neurons via multiple gene-expression changes.