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Sample records for amyloid peptide 1-42-stimulated

  1. Amyloid peptide channels.

    PubMed

    Kagan, B L; Azimov, R; Azimova, R

    2004-11-01

    At least 16 distinct clinical syndromes including Alzheimer's disease (AD), Parkinson's disease (PD), rheumatoid arthritis, type II diabetes mellitus (DM), and spongiform encephelopathies (prion diseases), are characterized by the deposition of amorphous, Congo red-staining deposits known as amyloid. These "misfolded" proteins adopt beta-sheet structures and aggregate spontaneously into similar extended fibrils despite their widely divergent primary sequences. Many, if not all, of these peptides are capable of forming ion-permeable channels in vitro and possibly in vivo. Common channel properties include irreversible, spontaneous insertion into membranes, relatively large, heterogeneous single-channel conductances, inhibition of channel formation by Congo red, and blockade of inserted channels by Zn2+. Physiologic effects of amyloid, including Ca2+ dysregulation, membrane depolarization, mitochondrial dysfunction, inhibition of long-term potentiation (LTP), and cytotoxicity, suggest that channel formation in plasma and intracellular membranes may play a key role in the pathophysiology of the amyloidoses. PMID:15702375

  2. Antimicrobial Properties of Amyloid Peptides

    PubMed Central

    Kagan, Bruce L.; Jang, Hyunbum; Capone, Ricardo; Arce, Fernando Teran; Ramachandran, Srinivasan; Lal, Ratnesh; Nussinov, Ruth

    2011-01-01

    More than two dozen clinical syndromes known as amyloid diseases are characterized by the buildup of extended insoluble fibrillar deposits in tissues. These amorphous Congo red staining deposits known as amyloids exhibit a characteristic green birefringence and cross-β structure. Substantial evidence implicates oligomeric intermediates of amyloids as toxic species in the pathogenesis of these chronic disease states. A growing body of data has suggested that these toxic species form ion channels in cellular membranes causing disruption of calcium homeostasis, membrane depolarization, energy drainage, and in some cases apoptosis. Amyloid peptide channels exhibit a number of common biological properties including the universal U-shape β-strand-turn-β-strand structure, irreversible and spontaneous insertion into membranes, production of large heterogeneous single-channel conductances, relatively poor ion selectivity, inhibition by Congo red, and channel blockade by zinc. Recent evidence has suggested that increased amounts of amyloids are not only toxic to its host target cells but also possess antimicrobial activity. Furthermore, at least one human antimicrobial peptide, protegrin-1, which kills microbes by a channel-forming mechanism, has been shown to possess the ability to form extended amyloid fibrils very similar to those of classic disease-forming amyloids. In this paper, we will review the reported antimicrobial properties of amyloids and the implications of these discoveries for our understanding of amyloid structure and function. PMID:22081976

  3. Amyloid fibrils compared to peptide nanotubes.

    PubMed

    Zganec, Matjaž; Zerovnik, Eva

    2014-09-01

    Prefibrillar oligomeric states and amyloid fibrils of amyloid-forming proteins qualify as nanoparticles. We aim to predict what biophysical and biochemical properties they could share in common with better researched peptide nanotubes. We first describe what is known of amyloid fibrils and prefibrillar aggregates (oligomers and protofibrils): their structure, mechanisms of formation and putative mechanism of cytotoxicity. In distinction from other neuronal fibrillar constituents, amyloid fibrils are believed to cause pathology, however, some can also be functional. Second, we give a review of known biophysical properties of peptide nanotubes. Finally, we compare properties of these two macromolecular states side by side and discuss which measurements that have already been done with peptide nanotubes could be done with amyloid fibrils as well.

  4. Amyloid beta peptide immunotherapy in Alzheimer disease.

    PubMed

    Delrieu, J; Ousset, P J; Voisin, T; Vellas, B

    2014-12-01

    Recent advances in the understanding of Alzheimer's disease pathogenesis have led to the development of numerous compounds that might modify the disease process. Amyloid β peptide represents an important molecular target for intervention in Alzheimer's disease. The main purpose of this work is to review immunotherapy studies in relation to the Alzheimer's disease. Several types of amyloid β peptide immunotherapy for Alzheimer's disease are under investigation, active immunization and passive administration with monoclonal antibodies directed against amyloid β peptide. Although immunotherapy approaches resulted in clearance of amyloid plaques in patients with Alzheimer's disease, this clearance did not show significant cognitive effect for the moment. Currently, several amyloid β peptide immunotherapy approaches are under investigation but also against tau pathology. Results from amyloid-based immunotherapy studies in clinical trials indicate that intervention appears to be more effective in early stages of amyloid accumulation in particular solanezumab with a potential impact at mild Alzheimer's disease, highlighting the importance of diagnosing Alzheimer's disease as early as possible and undertaking clinical trials at this stage. In both phase III solanezumab and bapineuzumab trials, PET imaging revealed that about a quarter of patients lacked fibrillar amyloid pathology at baseline, suggesting that they did not have Alzheimer's disease in the first place. So a new third phase 3 clinical trial for solanezumab, called Expedition 3, in patients with mild Alzheimer's disease and evidence of amyloid burden has been started. Thus, currently, amyloid intervention is realized at early stage of the Alzheimer's disease in clinical trials, at prodromal Alzheimer's disease, or at asymptomatic subjects or at risk to develop Alzheimer's disease and or at asymptomatic subjects with autosomal dominant mutation.

  5. Amyloid inspired self-assembled peptide nanofibers.

    PubMed

    Cinar, Goksu; Ceylan, Hakan; Urel, Mustafa; Erkal, Turan S; Deniz Tekin, E; Tekinay, Ayse B; Dâna, Aykutlu; Guler, Mustafa O

    2012-10-01

    Amyloid peptides are important components in many degenerative diseases as well as in maintaining cellular metabolism. Their unique stable structure provides new insights in developing new materials. Designing bioinspired self-assembling peptides is essential to generate new forms of hierarchical nanostructures. Here we present oppositely charged amyloid inspired peptides (AIPs), which rapidly self-assemble into nanofibers at pH 7 upon mixing in water caused by noncovalent interactions. Mechanical properties of the gels formed by self-assembled AIP nanofibers were analyzed with oscillatory rheology. AIP gels exhibited strong mechanical characteristics superior to gels formed by self-assembly of previously reported synthetic short peptides. Rheological studies of gels composed of oppositely charged mixed AIP molecules (AIP-1 + 2) revealed superior mechanical stability compared to individual peptide networks (AIP-1 and AIP-2) formed by neutralization of net charges through pH change. Adhesion and elasticity properties of AIP mixed nanofibers and charge neutralized AIP-1, AIP-2 nanofibers were analyzed by high resolution force-distance mapping using atomic force microscopy (AFM). Nanomechanical characterization of self-assembled AIP-1 + 2, AIP-1, and AIP-2 nanofibers also confirmed macroscopic rheology results, and mechanical stability of AIP mixed nanofibers was higher compared to individual AIP-1 and AIP-2 nanofibers self-assembled at acidic and basic pH, respectively. Experimental results were supported with molecular dynamics simulations by considering potential noncovalent interactions between the amino acid residues and possible aggregate forms. In addition, HUVEC cells were cultured on AIP mixed nanofibers at pH 7 and biocompatibility and collagen mimetic scaffold properties of the nanofibrous system were observed. Encapsulation of a zwitterionic dye (rhodamine B) within AIP nanofiber network was accomplished at physiological conditions to demonstrate that this

  6. Tanshinones inhibit amyloid aggregation by amyloidpeptide, disaggregate amyloid fibrils, and protect cultured cells.

    PubMed

    Wang, Qiuming; Yu, Xiang; Patal, Kunal; Hu, Rundong; Chuang, Steven; Zhang, Ge; Zheng, Jie

    2013-06-19

    The misfolding and aggregation of amyloid-β (Aβ) peptides into amyloid fibrils is regarded as one of the causative events in the pathogenesis of Alzheimer's disease (AD). Tanshinones extracted from Chinese herb Danshen (Salvia Miltiorrhiza Bunge) were traditionally used as anti-inflammation and cerebrovascular drugs due to their antioxidation and antiacetylcholinesterase effects. A number of studies have suggested that tanshinones could protect neuronal cells. In this work, we examine the inhibitory activity of tanshinone I (TS1) and tanshinone IIA (TS2), the two major components in the Danshen herb, on the aggregation and toxicity of Aβ1-42 using atomic force microscopy (AFM), thioflavin-T (ThT) fluorescence assay, cell viability assay, and molecular dynamics (MD) simulations. AFM and ThT results show that both TS1 and TS2 exhibit different inhibitory abilities to prevent unseeded amyloid fibril formation and to disaggregate preformed amyloid fibrils, in which TS1 shows better inhibitory potency than TS2. Live/dead assay further confirms that introduction of a very small amount of tanshinones enables protection of cultured SH-SY5Y cells against Aβ-induced cell toxicity. Comparative MD simulation results reveal a general tanshinone binding mode to prevent Aβ peptide association, showing that both TS1 and TS2 preferentially bind to a hydrophobic β-sheet groove formed by the C-terminal residues of I31-M35 and M35-V39 and several aromatic residues. Meanwhile, the differences in binding distribution, residues, sites, population, and affinity between TS1-Aβ and TS2-Aβ systems also interpret different inhibitory effects on Aβ aggregation as observed by in vitro experiments. More importantly, due to nonspecific binding mode of tanshinones, it is expected that tanshinones would have a general inhibitory efficacy of a wide range of amyloid peptides. These findings suggest that tanshinones, particularly TS1 compound, offer promising lead compounds with dual

  7. Size Effect of Graphene Oxide on Modulating Amyloid Peptide Assembly.

    PubMed

    Wang, Jie; Cao, Yunpeng; Li, Qiang; Liu, Lei; Dong, Mingdong

    2015-06-26

    Protein misfolding and abnormal assembly could lead to aggregates such as oligomer, proto-fibril, mature fibril, and senior amyloid plaques, which are associated with the pathogenesis of many amyloid diseases. These irreversible amyloid aggregates typically form in vivo and researchers have been endeavoring to find new modulators to invert the aggregation propensity in vitro, which could increase understanding in the mechanism of the aggregation of amyloid protein and pave the way to potential clinical treatment. Graphene oxide (GO) was shown to be a good modulator, which could strongly control the amyloidosis of Aβ (33-42). In particular, quartz crystal microbalance (QCM), circular dichroism (CD) spectroscopy, and atomic force microscopy (AFM) measurements revealed the size-dependent manner of GO on modulating the assembly of amyloid peptides, which could be a possible way to regulate the self-assembled nanostructure of amyloid peptide in a predictable manner. PMID:26031933

  8. Kisspeptin prevention of amyloidpeptide neurotoxicity in vitro.

    PubMed

    Milton, Nathaniel G N; Chilumuri, Amrutha; Rocha-Ferreira, Eridan; Nercessian, Amanda N; Ashioti, Maria

    2012-09-19

    Alzheimer's disease (AD) onset is associated with changes in hypothalamic-pituitary-gonadal (HPG) function. The 54 amino acid kisspeptin (KP) peptide regulates the HPG axis and alters antioxidant enzyme expression. The Alzheimer's amyloid-β (Aβ) is neurotoxic, and this action can be prevented by the antioxidant enzyme catalase. Here, we examined the effects of KP peptides on the neurotoxicity of Aβ, prion protein (PrP), and amylin (IAPP) peptides. The Aβ, PrP, and IAPP peptides stimulated the release of KP and KP 45-54. The KP peptides inhibited the neurotoxicity of Aβ, PrP, and IAPP peptides, via an action that could not be blocked by kisspeptin-receptor (GPR-54) or neuropeptide FF (NPFF) receptor antagonists. Knockdown of KiSS-1 gene, which encodes the KP peptides, in human neuronal SH-SY5Y cells with siRNA enhanced the toxicity of amyloid peptides, while KiSS-1 overexpression was neuroprotective. A comparison of the catalase and KP sequences identified a similarity between KP residues 42-51 and the region of catalase that binds Aβ. The KP peptides containing residues 45-50 bound Aβ, PrP, and IAPP, inhibited Congo red binding, and were neuroprotective. These results suggest that KP peptides are neuroprotective against Aβ, IAPP, and PrP peptides via a receptor independent action involving direct binding to the amyloid peptides.

  9. The immune system, amyloid-beta peptide, and Alzheimer's disease.

    PubMed

    Weksler, Marc E; Gouras, Gunnar; Relkin, Norman R; Szabo, Paul

    2005-06-01

    In this review, the case is made that amyloid-beta peptide in the brain of patients with Alzheimer's disease is a primary cause of the disease and that immunotherapy directed against this peptide has the potential to halt and/or reverse disease progression. This supposition is supported by the capacity of anti-beta-amyloid peptide antibodies to prevent or reverse the disease in mouse models of Alzheimer's disease. Furthermore, preliminary results obtained in a small number of patients with Alzheimer's disease are consistent with the observations made in the mouse model of this disease. We review the relationship between the immune system, amyloid-beta peptide, and Alzheimer's disease and the progress made in applying immunotherapy to patients with Alzheimer's disease.

  10. Prediction of Peptide and Protein Propensity for Amyloid Formation.

    PubMed

    Família, Carlos; Dennison, Sarah R; Quintas, Alexandre; Phoenix, David A

    2015-01-01

    Understanding which peptides and proteins have the potential to undergo amyloid formation and what driving forces are responsible for amyloid-like fiber formation and stabilization remains limited. This is mainly because proteins that can undergo structural changes, which lead to amyloid formation, are quite diverse and share no obvious sequence or structural homology, despite the structural similarity found in the fibrils. To address these issues, a novel approach based on recursive feature selection and feed-forward neural networks was undertaken to identify key features highly correlated with the self-assembly problem. This approach allowed the identification of seven physicochemical and biochemical properties of the amino acids highly associated with the self-assembly of peptides and proteins into amyloid-like fibrils (normalized frequency of β-sheet, normalized frequency of β-sheet from LG, weights for β-sheet at the window position of 1, isoelectric point, atom-based hydrophobic moment, helix termination parameter at position j+1 and ΔG° values for peptides extrapolated in 0 M urea). Moreover, these features enabled the development of a new predictor (available at http://cran.r-project.org/web/packages/appnn/index.html) capable of accurately and reliably predicting the amyloidogenic propensity from the polypeptide sequence alone with a prediction accuracy of 84.9 % against an external validation dataset of sequences with experimental in vitro, evidence of amyloid formation. PMID:26241652

  11. Prediction of Peptide and Protein Propensity for Amyloid Formation.

    PubMed

    Família, Carlos; Dennison, Sarah R; Quintas, Alexandre; Phoenix, David A

    2015-01-01

    Understanding which peptides and proteins have the potential to undergo amyloid formation and what driving forces are responsible for amyloid-like fiber formation and stabilization remains limited. This is mainly because proteins that can undergo structural changes, which lead to amyloid formation, are quite diverse and share no obvious sequence or structural homology, despite the structural similarity found in the fibrils. To address these issues, a novel approach based on recursive feature selection and feed-forward neural networks was undertaken to identify key features highly correlated with the self-assembly problem. This approach allowed the identification of seven physicochemical and biochemical properties of the amino acids highly associated with the self-assembly of peptides and proteins into amyloid-like fibrils (normalized frequency of β-sheet, normalized frequency of β-sheet from LG, weights for β-sheet at the window position of 1, isoelectric point, atom-based hydrophobic moment, helix termination parameter at position j+1 and ΔG° values for peptides extrapolated in 0 M urea). Moreover, these features enabled the development of a new predictor (available at http://cran.r-project.org/web/packages/appnn/index.html) capable of accurately and reliably predicting the amyloidogenic propensity from the polypeptide sequence alone with a prediction accuracy of 84.9 % against an external validation dataset of sequences with experimental in vitro, evidence of amyloid formation.

  12. Surface Mediated Self-Assembly of Amyloid Peptides

    NASA Astrophysics Data System (ADS)

    Fakhraai, Zahra

    2015-03-01

    Amyloid fibrils have been considered as causative agents in many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, type II diabetes and amyloidosis. Amyloid fibrils form when proteins or peptides misfold into one dimensional crystals of stacked beta-sheets. In solution, amyloid fibrils form through a nucleation and growth mechanism. The rate limiting nucleation step requires a critical concentration much larger than those measured in physiological conditions. As such the exact origins of the seeds or oligomers that result in the formation of fully mature fibrils in the body remain topic intense studies. It has been suggested that surfaces and interfaces can enhance the fibrillization rate. However, studies of the mechanism and kinetics of the surface-mediated fibrillization are technologically challenging due to the small size of the oligomer and protofibril species. Using smart sample preparation technique to dry the samples after various incubation times we are able to study the kinetics of fibril formation both in solution and in the vicinity of various surfaces using high-resolution atomic force microscopy. These studies elucidate the role of surfaces in catalyzing amyloid peptide formation through a nucleation-free process. The nucleation free self-assembly is rapid and requires much smaller concentrations of peptides or proteins. We show that this process resembles diffusion limited aggregation and is governed by the peptide adhesion rate, two -dimensional diffusion of the peptides on the surface, and preferential interactions between the peptides. These studies suggest an alternative pathway for amyloid formation may exist, which could lead to new criteria for disease prevention and alternative therapies. Research was partially supported by a seed grant from the National Institute of Aging of the National Institutes of Health (NIH) under Award Number P30AG010124 (PI: John Trojanowski) and the University of Pennsylvania.

  13. Peptide concentration alters intermediate species in amyloid β fibrillation kinetics

    SciTech Connect

    Garvey, M.; Morgado, I.

    2013-04-12

    Highlights: ► Aβ(1–40) aggregation in vitro has been monitored at different concentrations. ► Aβ(1–40) fibrillation does not always follow conventional kinetic mechanisms. ► We demonstrate non-linear features in the kinetics of Aβ(1–40) fibril formation. ► At high Aβ(1–40) concentrations secondary processes dictate fibrillation speed. ► Intermediate species may play significant roles on final amyloid fibril development. -- Abstract: The kinetic mechanism of amyloid aggregation remains to be fully understood. Investigations into the species present in the different kinetic phases can assist our comprehension of amyloid diseases and further our understanding of the mechanism behind amyloid β (Aβ) (1–40) peptide aggregation. Thioflavin T (ThT) fluorescence and transmission electron microscopy (TEM) have been used in combination to monitor Aβ(1–40) aggregation in vitro at both normal and higher than standard concentrations. The observed fibrillation behaviour deviates, in several respects, from standard concepts of the nucleation–polymerisation models and shows such features as concentration-dependent non-linear effects in the assembly mechanism. Aβ(1–40) fibrillation kinetics do not always follow conventional kinetic mechanisms and, specifically at high concentrations, intermediate structures become populated and secondary processes may further modify the fibrillation mechanism.

  14. Specific binding of DNA to aggregated forms of Alzheimer's disease amyloid peptides.

    PubMed

    Camero, Sergio; Ayuso, Jose M; Barrantes, Alejandro; Benítez, María J; Jiménez, Juan S

    2013-04-01

    Anomalous protein aggregation is closely associated to age-related mental illness. Extraneuronal plaques, mainly composed of aggregated amyloid peptides, are considered as hallmarks of Alzheimer's disease. According to the amyloid cascade hypothesis, this disease starts as a consequence of an abnormal processing of the amyloid precursor protein resulting in an excess of amyloid peptides. Nuclear localization of amyloid peptide aggregates together with amyloid-DNA interaction, have been repeatedly reported. In this paper we have used surface plasmon resonance and electron microscopy to study the structure and behavior of different peptides and proteins, including β-lactoglobulin, bovine serum albumin, myoglobin, histone, casein and the amyloidpeptides related to Alzheimer's disease Aβ25-35 and Aβ1-40. The main purpose of this study is to investigate whether proneness to DNA interaction is a general property displayed by aggregated forms of proteins, or it is an interaction specifically related to the aggregated forms of those particular proteins and peptides related to neurodegenerative diseases. Our results reveal that those aggregates formed by amyloid peptides show a particular proneness to interact with DNA. They are the only aggregated structures capable of binding DNA, and show more affinity for DNA than for other polyanions like heparin and polyglutamic acid, therefore strengthening the hypothesis that amyloid peptides may, by means of interaction with nuclear DNA, contribute to the onset of Alzheimer's disease.

  15. Alzheimer's disease amyloid peptides interact with DNA, as proved by surface plasmon resonance.

    PubMed

    Barrantes, Alejandro; Camero, Sergio; Garcia-Lucas, Angel; Navarro, Pedro J; Benitez, María J; Jiménez, Juan S

    2012-10-01

    According to the amyloid hypothesis, abnormal processing of the β-amyloid precursor protein in Alzheimer's disease patients increases the production of β-amyloid toxic peptides, which, after forming highly aggregated fibrillar structures, lead to extracellular plaques formation, neuronal loss and dementia. However, a great deal of evidence has point to intracellular small oligomers of amyloid peptides, probably transient intermediates in the process of fibrillar structures formation, as the most toxic species. In order to study the amyloid-DNA interaction, we have selected here three different forms of the amyloid peptide: Aβ1-40, Aβ25-35 and a scrambled form of Aβ25-35. Surface Plasmon Resonance was used together with UV-visible spectroscopy, Electrophoresis and Electronic Microscopy to carry out this study. Our results prove that, similarly to the full length Aβ1-42, all conformations of toxic amyloid peptides, Aβ1-40 and Aβ25-35, may bind DNA. In contrast, the scrambled form of Aβ25-35, a non-aggregating and nontoxic form of this peptide, could not bind DNA. We conclude that although the amyloid-DNA interaction is closely related to the amyloid aggregation proneness, this cannot be the only factor which determines the interaction, since small oligomers of amyloid peptides may also bind DNA if their predominant negatively charged amino acid residues are previously neutralized.

  16. Natural human antibodies to amyloid beta peptide.

    PubMed

    Szabo, Paul; Relkin, Norman; Weksler, Marc E

    2008-06-01

    Properties of human, natural anti-Abeta antibodies and commercially available intravenous immunoglobulin (IVIg) have been examined in light of the beneficial effects of passive immunotherapy with IVIg for patients with mild to moderate Alzheimer's disease (AD). Anti-Abeta antibodies in IVIg recognize conformation-specific epitopes as well as linear epitopes from different regions of the Abeta peptide. Anti-Abeta antibodies in circulation, especially those with high avidity, are often masked by ligands and the avidity of these antibodies increases upon dissociation of the bound ligands from the antibodies. Such natural anti-Abeta antibodies have the capacity to prevent Abeta oligomer-induced neurotoxicity in N2A neuroblastoma cells. This neuro-protective effect may reflect the therapeutic potential of the natural anti-Abeta antibodies found in IVIg for the treatment of patients with AD.

  17. Short peptides self-assemble to produce catalytic amyloids

    NASA Astrophysics Data System (ADS)

    Rufo, Caroline M.; Moroz, Yurii S.; Moroz, Olesia V.; Stöhr, Jan; Smith, Tyler A.; Hu, Xiaozhen; Degrado, William F.; Korendovych, Ivan V.

    2014-04-01

    Enzymes fold into unique three-dimensional structures, which underlie their remarkable catalytic properties. The requirement to adopt a stable, folded conformation is likely to contribute to their relatively large size (>10,000 Da). However, much shorter peptides can achieve well-defined conformations through the formation of amyloid fibrils. To test whether short amyloid-forming peptides might in fact be capable of enzyme-like catalysis, we designed a series of seven-residue peptides that act as Zn2+-dependent esterases. Zn2+ helps stabilize the fibril formation, while also acting as a cofactor to catalyse acyl ester hydrolysis. These results indicate that prion-like fibrils are able to not only catalyse their own formation, but they can also catalyse chemical reactions. Thus, they might have served as intermediates in the evolution of modern-day enzymes. These results also have implications for the design of self-assembling nanostructured catalysts including ones containing a variety of biological and non-biological metal ions.

  18. Amyloid Beta Peptides Differentially Affect Hippocampal Theta Rhythms In Vitro

    PubMed Central

    Gutiérrez-Lerma, Armando I.; Ordaz, Benito; Peña-Ortega, Fernando

    2013-01-01

    Soluble amyloid beta peptide (Aβ) is responsible for the early cognitive dysfunction observed in Alzheimer's disease. Both cholinergically and glutamatergically induced hippocampal theta rhythms are related to learning and memory, spatial navigation, and spatial memory. However, these two types of theta rhythms are not identical; they are associated with different behaviors and can be differentially modulated by diverse experimental conditions. Therefore, in this study, we aimed to investigate whether or not application of soluble Aβ alters the two types of theta frequency oscillatory network activity generated in rat hippocampal slices by application of the cholinergic and glutamatergic agonists carbachol or DHPG, respectively. Due to previous evidence that oscillatory activity can be differentially affected by different Aβ peptides, we also compared Aβ25−35 and Aβ1−42 for their effects on theta rhythms in vitro at similar concentrations (0.5 to 1.0 μM). We found that Aβ25−35 reduces, with less potency than Aβ1−42, carbachol-induced population theta oscillatory activity. In contrast, DHPG-induced oscillatory activity was not affected by a high concentration of Aβ25−35 but was reduced by Aβ1−42. Our results support the idea that different amyloid peptides might alter specific cellular mechanisms related to the generation of specific neuronal network activities, instead of exerting a generalized inhibitory effect on neuronal network function. PMID:23878547

  19. Dimensionality of carbon nanomaterial impacting on the modulation of amyloid peptide assembly.

    PubMed

    Wang, J; Zhu, Z; Bortolini, C; Hoffmann, S V; Amari, A; Zhang, H X; Liu, L; Dong, M D

    2016-07-29

    A wide variety of inorganic nanomaterials have been exploited so far for their great potential for biological applications. Some of these materials could be valid candidates to modulate the assembly of amyloid peptides, which is relevant to amyloid-related diseases. In this work, we reveal that a carbon nanomaterial can indeed modulate the assembly of amyloid peptides and, additionally, we show that this modulating effect is closely related to the dimensionality of the nanomaterials.

  20. Dimensionality of carbon nanomaterial impacting on the modulation of amyloid peptide assembly

    NASA Astrophysics Data System (ADS)

    Wang, J.; Zhu, Z.; Bortolini, C.; Hoffmann, S. V.; Amari, A.; Zhang, H. X.; Liu, L.; Dong, M. D.

    2016-07-01

    A wide variety of inorganic nanomaterials have been exploited so far for their great potential for biological applications. Some of these materials could be valid candidates to modulate the assembly of amyloid peptides, which is relevant to amyloid-related diseases. In this work, we reveal that a carbon nanomaterial can indeed modulate the assembly of amyloid peptides and, additionally, we show that this modulating effect is closely related to the dimensionality of the nanomaterials.

  1. Dimensionality of carbon nanomaterial impacting on the modulation of amyloid peptide assembly.

    PubMed

    Wang, J; Zhu, Z; Bortolini, C; Hoffmann, S V; Amari, A; Zhang, H X; Liu, L; Dong, M D

    2016-07-29

    A wide variety of inorganic nanomaterials have been exploited so far for their great potential for biological applications. Some of these materials could be valid candidates to modulate the assembly of amyloid peptides, which is relevant to amyloid-related diseases. In this work, we reveal that a carbon nanomaterial can indeed modulate the assembly of amyloid peptides and, additionally, we show that this modulating effect is closely related to the dimensionality of the nanomaterials. PMID:27302044

  2. Membrane Pore Formation by Amyloid beta (25-35) Peptide

    NASA Astrophysics Data System (ADS)

    Kandel, Nabin; Tatulian, Suren

    Amyloid (A β) peptide contributes to Alzheimer's disease by a yet unidentified mechanism. One of the possible mechanisms of A β toxicity is formation of pores in cellular membranes. We have characterized the formation of pores in phospholipid membranes by the Aβ25 - 35 peptide (GSNKGAIIGLM) using fluorescence, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) techniques. CD and FTIR identified formation of β-sheet structure upon incubation of the peptide in aqueous buffer for 2 hours. Unilamellar vesicles composed of a zwitterionic lipid, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and 70 % POPC plus 30 % of an acidic lipid, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), are made in 30 mM CaCl2. Quin-2, a fluorophore that displays increased fluorescence upon Ca2+ binding, is added to the vesicles externally. Peptide addition results in increased Quin-2 fluorescence, which is interpreted by binding of the peptide to the vesicles, pore formation, and Ca2+ leakage. The positive and negative control measurements involve addition of a detergent, Triton X-100, which causes vesicle rupture and release of total calcium, and blank buffer, respectively.

  3. Cytochrome c peroxidase activity of heme bound amyloid β peptides.

    PubMed

    Seal, Manas; Ghosh, Chandradeep; Basu, Olivia; Dey, Somdatta Ghosh

    2016-09-01

    Heme bound amyloid β (Aβ) peptides, which have been associated with Alzheimer's disease (AD), can catalytically oxidize ferrocytochrome c (Cyt c(II)) in the presence of hydrogen peroxide (H2O2). The rate of catalytic oxidation of Cyt(II) c has been found to be dependent on several factors, such as concentration of heme(III)-Aβ, Cyt(II) c, H2O2, pH, ionic strength of the solution, and peptide chain length of Aβ. The above features resemble the naturally occurring enzyme cytochrome c peroxidase (CCP) which is known to catalytically oxidize Cyt(II) c in the presence of H2O2. In the absence of heme(III)-Aβ, the oxidation of Cyt(II) c is not catalytic. Thus, heme-Aβ complex behaves as CCP.

  4. Cytochrome c peroxidase activity of heme bound amyloid β peptides.

    PubMed

    Seal, Manas; Ghosh, Chandradeep; Basu, Olivia; Dey, Somdatta Ghosh

    2016-09-01

    Heme bound amyloid β (Aβ) peptides, which have been associated with Alzheimer's disease (AD), can catalytically oxidize ferrocytochrome c (Cyt c(II)) in the presence of hydrogen peroxide (H2O2). The rate of catalytic oxidation of Cyt(II) c has been found to be dependent on several factors, such as concentration of heme(III)-Aβ, Cyt(II) c, H2O2, pH, ionic strength of the solution, and peptide chain length of Aβ. The above features resemble the naturally occurring enzyme cytochrome c peroxidase (CCP) which is known to catalytically oxidize Cyt(II) c in the presence of H2O2. In the absence of heme(III)-Aβ, the oxidation of Cyt(II) c is not catalytic. Thus, heme-Aβ complex behaves as CCP. PMID:27270708

  5. Stabilization of a β-hairpin in monomeric Alzheimer's amyloidpeptide inhibits amyloid formation

    PubMed Central

    Hoyer, Wolfgang; Grönwall, Caroline; Jonsson, Andreas; Ståhl, Stefan; Härd, Torleif

    2008-01-01

    According to the amyloid hypothesis, the pathogenesis of Alzheimer's disease is triggered by the oligomerization and aggregation of the amyloid-β (Aβ) peptide into protein plaques. Formation of the potentially toxic oligomeric and fibrillar Aβ assemblies is accompanied by a conformational change toward a high content of β-structure. Here, we report the solution structure of Aβ(1–40) in complex with the phage-display selected affibody protein ZAβ3, a binding protein of nanomolar affinity. Bound Aβ(1–40) features a β-hairpin comprising residues 17–36, providing the first high-resolution structure of Aβ in β conformation. The positions of the secondary structure elements strongly resemble those observed for fibrillar Aβ. ZAβ3 stabilizes the β-sheet by extending it intermolecularly and by burying both of the mostly nonpolar faces of the Aβ hairpin within a large hydrophobic tunnel-like cavity. Consequently, ZAβ3 acts as a stoichiometric inhibitor of Aβ fibrillation. The selected Aβ conformation allows us to suggest a structural mechanism for amyloid formation based on soluble oligomeric hairpin intermediates. PMID:18375754

  6. Strong inhibition of beta-amyloid peptide aggregation realized by two-steps evolved peptides.

    PubMed

    Ghimire Gautam, Sunita; Komatsu, Masayuki; Nishigaki, Koichi

    2015-03-01

    Several decades of cumulated research evidence have proven that aggregation of beta-amyloid 42 (Aβ42) is the main cause of neuronal death in the brains of patients with Alzheimer's disease. Therefore, inhibition of Aβ42 aggregation holds great promise for the prevention and treatment of Alzheimer's disease. To this end, we used a systematic in vitro evolution including a paired peptide library method. We identified two peptides with high binding affinity (with Kd in the nm range) for Aβ42. Functionally, these peptides strongly inhibited the aggregation of Aβ42 as shown by the thioflavin T assay and atomic force microscopy. Moreover, these peptides rescued PC12 cells from the cytotoxic effect of aggregated Aβ42 in vitro. Our results suggest that these novel peptides may be potential therapeutic seeds for the treatment of Alzheimer's disease.

  7. Copper(II) ions and the Alzheimer's amyloidpeptide: Affinity and stoichiometry of binding

    NASA Astrophysics Data System (ADS)

    Tõugu, Vello; Friedemann, Merlin; Tiiman, Ann; Palumaa, Peep

    2014-10-01

    Deposition of amyloid beta (Aβ) peptides into amyloid plaques is the hallmark of Alzheimer's disease. According to the amyloid cascade hypothesis this deposition is an early event and primary cause of the disease, however, the mechanisms that cause this deposition remain elusive. An increasing amount of evidence shows that the interactions of biometals can contribute to the fibrillization and amyloid formation by amyloidogenic peptides. From different anions the copper ions deserve the most attention since it can contribute not only toamyloid formation but also to its toxicity due to the generation of ROS. In this thesis we focus on the affinity and stoichiometry of copper(II) binding to the Aβ molecule.

  8. De novo design of self-assembled hexapeptides as β-amyloid (Aβ) peptide inhibitors.

    PubMed

    Wang, Qiuming; Liang, Guizhao; Zhang, Mingzhen; Zhao, Jun; Patel, Kunal; Yu, Xiang; Zhao, Chao; Ding, Binrong; Zhang, Ge; Zhou, Feimeng; Zheng, Jie

    2014-10-15

    The ability of peptides to construct specific secondary structures provides a useful function for biomaterial design that cannot be achieved with traditional organic molecules and polymers. Inhibition of amyloid formation is a promising therapeutic approach for the treatment of neurodegenerative diseases. Existing peptide-based inhibitors are mainly derived from original amyloid sequences, which have very limited sequence diversity and activity. It is highly desirable to explore other peptide-based inhibitors that are not directly derived from amyloid sequences. Here, we develop a hybrid high-throughput computational method to efficiently screen and design hexapeptide inhibitors against amyloid-β (Aβ) aggregation and toxicity from the first principle. Computationally screened/designed inhibitors are then validated for their inhibition activity using biophysical experiments. We propose and demonstrate a proof-of-concept of the "like-interacts-like" design principle that the self-assembling peptides are able to interact strongly with conformationally similar motifs of Aβ peptides and to competitively reduce Aβ-Aβ interactions, thus preventing Aβ aggregation and Aβ-induced toxicity. Such a de novo design can also be generally applicable to design new peptide inhibitors against other amyloid diseases, beyond traditional peptide inhibitors with homologous sequences to parent amyloid peptides.

  9. Unwinding fibril formation of medin, the peptide of the most common form of human amyloid

    SciTech Connect

    Larsson, Annika; Soederberg, Linda; Westermark, Gunilla T.; Sletten, Knut; Engstroem, Ulla; Tjernberg, Lars O.; Naeslund, Jan; Westermark, Per

    2007-10-05

    Medin amyloid affects the medial layer of the thoracic aorta of most people above 50 years of age. The consequences of this amyloid are not completely known but the deposits may contribute to diseases such as thoracic aortic aneurysm and dissection or to the general diminished elasticity of blood vessels seen in elderly people. We show that the 50-amino acid residue peptide medin forms amyloid-like fibrils in vitro. With the use of Congo red staining, Thioflavin T fluorescence, electron microscopy, and a solid-phase binding assay on different synthetic peptides, we identified the last 18-19 amino acid residues to constitute the amyloid-promoting region of medin. We also demonstrate that the two C-terminal phenylalanines, previously suggested to be of importance for amyloid formation, are not required for medin amyloid formation.

  10. Amyloidpeptide: Dr. Jekyll or Mr. Hyde?

    PubMed

    Puzzo, Daniela; Arancio, Ottavio

    2013-01-01

    Amyloidpeptide (Aβ) is considered a key protein in the pathogenesis of Alzheimer's disease (AD) because of its neurotoxicity and capacity to form characteristic insoluble deposits known as senile plaques. Aβ derives from amyloid-β protein precursor (AβPP), whose proteolytic processing generates several fragments including Aβ peptides of various lengths. The normal function of AβPP and its fragments remains poorly understood. While some fragments have been suggested to have a function in normal physiological cellular processes, Aβ has been widely considered as a "garbage" fragment that becomes toxic when it accumulates in the brain, resulting in impaired synaptic function and memory. Aβ is produced and released physiologically in the healthy brain during neuronal activity. In the last 10 years, we have been investigating whether Aβ plays a physiological role in the brain. We first demonstrated that picomolar concentrations of a human Aβ42 preparation enhanced synaptic plasticity and memory in mice. Next, we investigated the role of endogenous Aβ in healthy murine brains and found that treatment with a specific antirodent Aβ antibody and an siRNA against murine AβPP impaired synaptic plasticity and memory. The concurrent addition of human Aβ42 rescued these deficits, suggesting that in the healthy brain, physiological Aβ concentrations are necessary for normal synaptic plasticity and memory to occur. Furthermore, the effect of both exogenous and endogenous Aβ was seen to be mediated by modulation of neurotransmitter release and α7-nicotinic receptors. These findings need to be taken into consideration when designing novel therapeutic strategies for AD.

  11. AmyloidPeptide: Dr. Jekyll or Mr. Hyde?

    PubMed Central

    Puzzo, Daniela; Arancio, Ottavio

    2013-01-01

    Amyloidpeptide (Aβ) is considered a key protein in the pathogenesis of Alzheimer’s disease (AD) because of its neurotoxicity and capacity to form characteristic insoluble deposits known as senile plaques. Aβ derives from amyloid-β protein precursor (AβPP), whose proteolytic processing generates several fragments including Aβ peptides of various lengths. The normal function of AβPP and its fragments remains poorly understood. While some fragments has been suggested to have a function in normal physiological cellular processes, Aβ has been widely considered as a “garbage” fragment that becomes toxic when it accumulates in the brain, resulting in impaired synaptic function and memory. Aβ is produced and released physiologically in the healthy brain during neuronal activity. In the last 10 years, we have been investigating whether Aβ plays a physiological role in the brain. We first demonstrated that picomolar concentrations of a human Aβ42 preparation enhanced synaptic plasticity and memory in mice. Next, we investigated the role of endogenous Aβ in healthy murine brains and found that treatment with a specific antirodent Aβ antibody and an siRNA against murine AβPP impaired synaptic plasticity and memory. The concurrent addition of human Aβ42 rescued these deficits, suggesting that in the healthy brain, physiological Aβ concentrations are necessary for normal synaptic plasticity and memory to occur. Furthermore, the effect of both exogenous and endogenous Aβ was seen to be mediated by modulation of neurotransmitter release and α7-nicotinic receptors. These findings need to be taken into consideration when designing novel therapeutic strategies for AD. PMID:22735675

  12. Amyloidpeptide: Dr. Jekyll or Mr. Hyde?

    PubMed

    Puzzo, Daniela; Arancio, Ottavio

    2013-01-01

    Amyloidpeptide (Aβ) is considered a key protein in the pathogenesis of Alzheimer's disease (AD) because of its neurotoxicity and capacity to form characteristic insoluble deposits known as senile plaques. Aβ derives from amyloid-β protein precursor (AβPP), whose proteolytic processing generates several fragments including Aβ peptides of various lengths. The normal function of AβPP and its fragments remains poorly understood. While some fragments have been suggested to have a function in normal physiological cellular processes, Aβ has been widely considered as a "garbage" fragment that becomes toxic when it accumulates in the brain, resulting in impaired synaptic function and memory. Aβ is produced and released physiologically in the healthy brain during neuronal activity. In the last 10 years, we have been investigating whether Aβ plays a physiological role in the brain. We first demonstrated that picomolar concentrations of a human Aβ42 preparation enhanced synaptic plasticity and memory in mice. Next, we investigated the role of endogenous Aβ in healthy murine brains and found that treatment with a specific antirodent Aβ antibody and an siRNA against murine AβPP impaired synaptic plasticity and memory. The concurrent addition of human Aβ42 rescued these deficits, suggesting that in the healthy brain, physiological Aβ concentrations are necessary for normal synaptic plasticity and memory to occur. Furthermore, the effect of both exogenous and endogenous Aβ was seen to be mediated by modulation of neurotransmitter release and α7-nicotinic receptors. These findings need to be taken into consideration when designing novel therapeutic strategies for AD. PMID:22735675

  13. Identification of a Novel Parallel β‐Strand Conformation within Molecular Monolayer of Amyloid Peptide

    PubMed Central

    Liu, Lei; Li, Qiang; Zhang, Shuai; Wang, Xiaofeng; Hoffmann, Søren Vrønning; Li, Jingyuan; Liu, Zheng

    2016-01-01

    The differentiation of protein properties and biological functions arises from the variation in the primary and secondary structure. Specifically, in abnormal assemblies of protein, such as amyloid peptide, the secondary structure is closely correlated with the stable ensemble and the cytotoxicity. In this work, the early Aβ33‐42 aggregates forming the molecular monolayer at hydrophobic interface are investigated. The molecular monolayer of amyloid peptide Aβ33‐42 consisting of novel parallel β‐strand‐like structure is further revealed by means of a quantitative nanomechanical spectroscopy technique with force controlled in pico‐Newton range, combining with molecular dynamic simulation. The identified parallel β‐strand‐like structure of molecular monolayer is distinct from the antiparallel β‐strand structure of Aβ33‐42 amyloid fibril. This finding enriches the molecular structures of amyloid peptide aggregation, which could be closely related to the pathogenesis of amyloid disease.

  14. Common molecular mechanism of amyloid pore formation by Alzheimer’s β-amyloid peptide and α-synuclein

    PubMed Central

    Di Scala, Coralie; Yahi, Nouara; Boutemeur, Sonia; Flores, Alessandra; Rodriguez, Léa; Chahinian, Henri; Fantini, Jacques

    2016-01-01

    Calcium-permeable pores formed by small oligomers of amyloid proteins are the primary pathologic species in Alzheimer’s and Parkinson’s diseases. However, the molecular mechanisms underlying the assembly of these toxic oligomers in the plasma membrane of brain cells remain unclear. Here we have analyzed and compared the pore-forming capability of a large panel of amyloid proteins including wild-type, variant and truncated forms, as well as synthetic peptides derived from specific domains of Aβ1-42 and α-synuclein. We show that amyloid pore formation involves two membrane lipids, ganglioside and cholesterol, that physically interact with amyloid proteins through specific structural motifs. Mutation or deletion of these motifs abolished pore formation. Moreover, α-synuclein (Parkinson) and Aβ peptide (Alzheimer) did no longer form Ca2+-permeable pores in presence of drugs that target either cholesterol or ganglioside or both membrane lipids. These results indicate that gangliosides and cholesterol cooperate to favor the formation of amyloid pores through a common molecular mechanism that can be jammed at two different steps, suggesting the possibility of a universal therapeutic approach for neurodegenerative diseases. Finally we present the first successful evaluation of such a new therapeutic approach (coined “membrane therapy”) targeting amyloid pores formed by Aβ1-42 and α-synuclein. PMID:27352802

  15. Monoclonal Antibodies Inhibit in vitro Fibrillar Aggregation of the Alzheimer β -Amyloid Peptide

    NASA Astrophysics Data System (ADS)

    Solomon, Beka; Koppel, Rela; Hanan, Eilat; Katzav, Tamar

    1996-01-01

    The β -amyloid peptide, the hallmark of Alzheimer disease, forms fibrillar toxic aggregates in brain tissue that can be dissolved only by strong denaturing agents. To study β -amyloid formation and its inhibition, we prepared immune complexes with two monoclonal antibodies (mAbs), AMY-33 and 6F/3D, raised against β -amyloid fragments spanning amino acid residues 1-28 and 8-17 of the β -amyloid peptide chain, respectively. In vitro aggregation of β -amyloid peptide was induced by incubation for 3 h at 37 degrees C and monitored by ELISA, negative staining electron microscopy, and fluorimetric studies. We found that the mAbs prevent the aggregation of β -amyloid peptide and that the inhibitory effect appears to be related to the localization of the antibody-binding sites and the nature of the aggregating agents. Preparation of mAbs against ``aggregating epitopes,'' defined as sequences related to the sites where protein aggregation is initiated, may lead to the understanding and prevention of protein aggregation. The results of this study may provide a foundation for using mAbs in vivo to prevent the β -amyloid peptide aggregation that is associated with Alzheimer disease.

  16. Neurotrophic effects of amyloid precursor protein peptide 165 in vitro.

    PubMed

    Yao, Jie; Ma, Lina; Wang, Rong; Sheng, Shuli; Ji, Zhijuan; Zhang, Jingyan

    2016-01-01

    Diabetic encephalopathy is one of the risk factors for Alzheimer's disease. Our previous findings indicated that animals with diabetic encephalopathy exhibit learning and memory impairment in addition to hippocampal neurodegeneration, both of which are ameliorated with amyloid precursor protein (APP) 17-mer (APP17) peptide treatment. Although APP17 is neuroprotective, it is susceptible to enzymatic degradation. Derived from the active sequence structure of APP17, we have previously structurally transformed and modified several APP5-mer peptides (APP328-332 [RERMS], APP 5). We have developed seven different derivatives of APP5, including several analogs. Results from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on human neuroblastoma SH-SY5Y cells in the present study showed that P165 was the most neuroprotective APP5 derivative. Furthermore, we tested the effects of APP5 and P165 on the number of cells and the release of lactate dehydrogenase. Western immunoblot analyses were also performed. The digestion rates of P165 and APP5 were determined by the pepsin digestion test. P165 resisted pepsin digestion significantly more than APP5. Therefore, P165 may be optimal for oral administration. Overall, these findings suggest that P165 may be a potential drug for the treatment of diabetic encephalopathy. PMID:26551064

  17. The Aβ peptide forms non-amyloid fibrils in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Luo, Jinghui; Wärmländer, Sebastian K. T. S.; Yu, Chien-Hung; Muhammad, Kamran; Gräslund, Astrid; Pieter Abrahams, Jan

    2014-05-01

    Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils.Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00291a

  18. Conversion of non-fibrillar {beta}-sheet oligomers into amyloid fibrils in Alzheimer's disease amyloid peptide aggregation

    SciTech Connect

    Benseny-Cases, Nuria; Cocera, Mercedes; Cladera, Josep

    2007-10-05

    A{beta}(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular {beta}-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the A{beta}(1-40) fibril formation process. A unique sample containing 90 {mu}M peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar {beta}-structures. The number of oligomers and the amount of non-fibrillar {beta}-structures grows throughout the lag phase and during the elongation phase these non-fibrillar {beta}-structures are transformed into fibrillar (amyloid) {beta}-structures, formed by association of high molecular weight intermediates.

  19. Destruction of amyloid fibrils by graphene through penetration and extraction of peptides.

    PubMed

    Yang, Zaixing; Ge, Cuicui; Liu, Jiajia; Chong, Yu; Gu, Zonglin; Jimenez-Cruz, Camilo A; Chai, Zhifang; Zhou, Ruhong

    2015-11-28

    Current therapies for Alzheimer's disease (AD) can provide a moderate symptomatic reduction or delay progression at various stages of the disease, but such treatments ultimately do not arrest the advancement of AD. As such, novel approaches for AD treatment and prevention are urgently needed. We here provide both experimental and computational evidence that pristine graphene and graphene-oxide nanosheets can inhibit Aβ peptide monomer fibrillation and clear mature amyloid fibrils, thus impacting the central molecular superstructures correlated with AD pathogenesis. Our molecular dynamics simulations for the first time reveal that graphene nanosheets can penetrate and extract a large number of peptides from pre-formed amyloid fibrils; these effects seem to be related to exceptionally strong dispersion interactions between peptides and graphene that are further enhanced by strong π-π stacking between the aromatic residues of extracted Aβ peptides and the graphene surface. Atomic force microscopy images confirm these predictions by demonstrating that mature amyloid fibrils can be cut into pieces and cleared by graphene oxides. Thioflavin fluorescence assays further illustrate the detailed dynamic processes by which graphene induces inhibition of monomer aggregation and clearance of mature amyloid fibrils, respectively. Cell viability and ROS assays indicate that graphene oxide can indeed mitigate cytotoxicity of Aβ peptide amyloids. Our findings provide new insights into the underlying molecular mechanisms that define graphene-amyloid interaction and suggest that further research on nanotherapies for Alzheimer's and other protein aggregation-related diseases is warranted.

  20. Peptide p5 binds both heparinase-sensitive glycosaminoglycans and fibrils in patient-derived AL amyloid extracts.

    PubMed

    Martin, Emily B; Williams, Angela; Heidel, Eric; Macy, Sallie; Kennel, Stephen J; Wall, Jonathan S

    2013-06-21

    In previously published work, we have described heparin-binding synthetic peptides that preferentially recognize amyloid deposits in a mouse model of reactive systemic (AA) amyloidosis and can be imaged by using positron and single photon emission tomographic imaging. We wanted to extend these findings to the most common form of visceral amyloidosis, namely light chain (AL); however, there are no robust experimental animal models of AL amyloidosis. To further define the binding of the lead peptide, p5, to AL amyloid, we characterized the reactivity in vitro of p5 with in situ and patient-derived AL amyloid extracts which contain both hypersulfated heparan sulfate proteoglycans as well as amyloid fibrils. Histochemical staining demonstrated that the peptide specifically localized with tissue-associated AL amyloid deposits. Although we anticipated that p5 would undergo electrostatic interactions with the amyloid-associated glycosaminoglycans expressing heparin-like side chains, no significant correlation between peptide binding and glycosaminoglycan content within amyloid extracts was observed. In contrast, following heparinase I treatment, although overall binding was reduced, a positive correlation between peptide binding and amyloid fibril content became evident. This interaction was further confirmed using synthetic light chain fibrils that contain no carbohydrates. These data suggest that p5 can bind to both the sulfated glycosaminoglycans and protein fibril components of AL amyloid. Understanding these complex electrostatic interactions will aid in the optimization of synthetic peptides for use as amyloid imaging agents and potentially as therapeutics for the treatment of amyloid diseases.

  1. Amyloid Beta Peptide Slows Down Sensory-Induced Hippocampal Oscillations

    PubMed Central

    Peña-Ortega, Fernando; Bernal-Pedraza, Ramón

    2012-01-01

    Alzheimer's disease (AD) progresses with a deterioration of hippocampal function that is likely induced by amyloid beta (Aβ) oligomers. Hippocampal function is strongly dependent on theta rhythm, and disruptions in this rhythm have been related to the reduction of cognitive performance in AD. Accordingly, both AD patients and AD-transgenic mice show an increase in theta rhythm at rest but a reduction in cognitive-induced theta rhythm. We have previously found that monomers of the short sequence of Aβ (peptide 25–35) reduce sensory-induced theta oscillations. However, considering on the one hand that different Aβ sequences differentially affect hippocampal oscillations and on the other hand that Aβ oligomers seem to be responsible for the cognitive decline observed in AD, here we aimed to explore the effect of Aβ oligomers on sensory-induced theta rhythm. Our results show that intracisternal injection of Aβ1–42 oligomers, which has no significant effect on spontaneous hippocampal activity, disrupts the induction of theta rhythm upon sensory stimulation. Instead of increasing the power in the theta band, the hippocampus of Aβ-treated animals responds to sensory stimulation (tail pinch) with an increase in lower frequencies. These findings demonstrate that Aβ alters induced theta rhythm, providing an in vivo model to test for therapeutic approaches to overcome Aβ-induced hippocampal and cognitive dysfunctions. PMID:22611415

  2. Specific interactions between amyloidpeptide and curcumin derivatives: Ab initio molecular simulations

    NASA Astrophysics Data System (ADS)

    Ishimura, Hiromi; Kadoya, Ryushi; Suzuki, Tomoya; Murakawa, Takeru; Shulga, Sergiy; Kurita, Noriyuki

    2015-07-01

    Alzheimer's disease is caused by accumulation of amyloid-β (Aβ) peptides in a brain. To suppress the production of Aβ peptides, it is effective to inhibit the cleavage of amyloid precursor protein (APP) by secretases. However, because the secretases also play important roles to produce vital proteins for human body, inhibitors for the secretases may have side effects. To propose new agents for protecting the cleavage site of APP from the attacking of the γ-secretase, we have investigated here the specific interactions between a short APP peptide and curcumin derivatives, using protein-ligand docking as well as ab initio molecular simulations.

  3. Peptide p5 binds both heparinase-sensitive glycosaminoglycans and fibrils in patient-derived AL amyloid extracts

    SciTech Connect

    Martin, Emily B.; Williams, Angela; Heidel, Eric; Macy, Sallie; Kennel, Stephen J.; Wall, Jonathan S.

    2013-06-21

    Highlights: •Polybasic peptide p5 binds human light chain amyloid extracts. •The binding of p5 with amyloid involves both glycosaminoglycans and fibrils. •Heparinase treatment led to a correlation between p5 binding and fibril content. •p5 binding to AL amyloid requires electrostatic interactions. -- Abstract: In previously published work, we have described heparin-binding synthetic peptides that preferentially recognize amyloid deposits in a mouse model of reactive systemic (AA) amyloidosis and can be imaged by using positron and single photon emission tomographic imaging. We wanted to extend these findings to the most common form of visceral amyloidosis, namely light chain (AL); however, there are no robust experimental animal models of AL amyloidosis. To further define the binding of the lead peptide, p5, to AL amyloid, we characterized the reactivity in vitro of p5 with in situ and patient-derived AL amyloid extracts which contain both hypersulfated heparan sulfate proteoglycans as well as amyloid fibrils. Histochemical staining demonstrated that the peptide specifically localized with tissue-associated AL amyloid deposits. Although we anticipated that p5 would undergo electrostatic interactions with the amyloid-associated glycosaminoglycans expressing heparin-like side chains, no significant correlation between peptide binding and glycosaminoglycan content within amyloid extracts was observed. In contrast, following heparinase I treatment, although overall binding was reduced, a positive correlation between peptide binding and amyloid fibril content became evident. This interaction was further confirmed using synthetic light chain fibrils that contain no carbohydrates. These data suggest that p5 can bind to both the sulfated glycosaminoglycans and protein fibril components of AL amyloid. Understanding these complex electrostatic interactions will aid in the optimization of synthetic peptides for use as amyloid imaging agents and potentially as

  4. Methionine oxidation of amyloid peptides by peroxovanadium complexes: inhibition of fibril formation through a distinct mechanism.

    PubMed

    He, Lei; Wang, Xuesong; Zhu, Dengsen; Zhao, Cong; Du, Weihong

    2015-12-01

    Fibril formation of amyloid peptides is linked to a number of pathological states. The prion protein (PrP) and amyloid-β (Aβ) are two remarkable examples that are correlated with prion disorders and Alzheimer's disease, respectively. Metal complexes, such as those formed by platinum and ruthenium compounds, can act as inhibitors against peptide aggregation primarily through metal coordination. This study revealed the inhibitory effect of two peroxovanadium complexes, (NH4)[VO(O2)2(bipy)]·4H2O (1) and (NH4)[VO(O2)2(phen)]·2H2O (2), on amyloid fibril formation of PrP106-126 and Aβ1-42via site-specific oxidation of methionine residues, besides direct binding of the complexes with the peptides. Complexes 1 and 2 showed higher anti-amyloidogenic activity on PrP106-126 aggregation than on Aβ1-42, though their regulation on the cytotoxicity induced by the two peptides could not be differentiated. The action efficacy may be attributed to the different molecular structures of the vanadium complex and the peptide sequence. Results reflected that methionine oxidation may be a crucial action mode in inhibiting amyloid fibril formation. This study offers a possible application value for peroxovanadium complexes against amyloid proteins. PMID:26444976

  5. Methionine oxidation of amyloid peptides by peroxovanadium complexes: inhibition of fibril formation through a distinct mechanism.

    PubMed

    He, Lei; Wang, Xuesong; Zhu, Dengsen; Zhao, Cong; Du, Weihong

    2015-12-01

    Fibril formation of amyloid peptides is linked to a number of pathological states. The prion protein (PrP) and amyloid-β (Aβ) are two remarkable examples that are correlated with prion disorders and Alzheimer's disease, respectively. Metal complexes, such as those formed by platinum and ruthenium compounds, can act as inhibitors against peptide aggregation primarily through metal coordination. This study revealed the inhibitory effect of two peroxovanadium complexes, (NH4)[VO(O2)2(bipy)]·4H2O (1) and (NH4)[VO(O2)2(phen)]·2H2O (2), on amyloid fibril formation of PrP106-126 and Aβ1-42via site-specific oxidation of methionine residues, besides direct binding of the complexes with the peptides. Complexes 1 and 2 showed higher anti-amyloidogenic activity on PrP106-126 aggregation than on Aβ1-42, though their regulation on the cytotoxicity induced by the two peptides could not be differentiated. The action efficacy may be attributed to the different molecular structures of the vanadium complex and the peptide sequence. Results reflected that methionine oxidation may be a crucial action mode in inhibiting amyloid fibril formation. This study offers a possible application value for peroxovanadium complexes against amyloid proteins.

  6. Amyloidpeptide aggregation and the influence of carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Wen-Hui, Xi; Guang-Hong, Wei

    2016-01-01

    Soluble peptides or proteins can self-aggregate into insoluble, ordered amyloid fibrils under appropriate conditions. These amyloid aggregates are the hallmarks of several human diseases ranging from neurodegenerative disorders to systemic amyloidoses. In this review, we first introduce the common structural features of amyloid fibrils and the amyloid fibrillation kinetics determined from experimental studies. Then, we discuss the structural models of Alzheimer’s amyloid-β (Aβ) fibrils derived from solid-state nuclear magnetic resonance spectroscopy. On the computational side, molecular dynamics simulations can provide atomic details of structures and the underlying oligomerization mechanisms. We finally summarize recent progress in atomistic simulation studies on the oligomerization of Aβ (including full-length Aβ and its fragments) and the influence of carbon nanoparticles. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274075 and 91227102).

  7. Bexarotene blocks calcium-permeable ion channels formed by neurotoxic Alzheimer's β-amyloid peptides.

    PubMed

    Fantini, Jacques; Di Scala, Coralie; Yahi, Nouara; Troadec, Jean-Denis; Sadelli, Kevin; Chahinian, Henri; Garmy, Nicolas

    2014-03-19

    The anticancer drug bexarotene has been shown to restore cognitive functions in animal models of Alzheimer's disease, but its exact mechanism of action remains elusive. In the present report, we have used a combination of molecular, physicochemical, and cellular approaches to elucidate the mechanisms underlying the anti-Alzheimer properties of bexarotene in neural cells. First of all, we noticed that bexarotene shares a structural analogy with cholesterol. We showed that cholesterol and bexarotene compete for the same binding site in the C-terminal region of Alzheimer's β-amyloid peptide 1-42 (Aβ1-42). This common bexarotene/cholesterol binding domain was characterized as a linear motif encompassing amino acid residues 25-35 of Aβ1-42. Because cholesterol is involved in the oligomerization of Alzheimer's β-amyloid peptides into neurotoxic amyloid channels, we studied the capability of bexarotene to interfere with this process. We showed that nanomolar concentrations of bexarotene efficiently prevented the cholesterol-dependent increase of calcium fluxes induced by β-amyloid peptides Aβ1-42 and Aβ25-35 in SH-SY5Y cells, suggesting a direct effect of the drug on amyloid channel formation. Molecular dynamics simulations gave structural insights into the role of cholesterol in amyloid channel formation and explained the inhibitory effect of bexarotene. Because it is the first drug that can both inhibit the binding of cholesterol to β-amyloid peptides and prevent calcium-permeable amyloid pore formation in the plasma membrane of neural cells, bexarotene might be considered as the prototype of a new class of anti-Alzheimer compounds. The experimental approach developed herein can be used as a screening strategy to identify such compounds. PMID:24383913

  8. Bexarotene blocks calcium-permeable ion channels formed by neurotoxic Alzheimer's β-amyloid peptides.

    PubMed

    Fantini, Jacques; Di Scala, Coralie; Yahi, Nouara; Troadec, Jean-Denis; Sadelli, Kevin; Chahinian, Henri; Garmy, Nicolas

    2014-03-19

    The anticancer drug bexarotene has been shown to restore cognitive functions in animal models of Alzheimer's disease, but its exact mechanism of action remains elusive. In the present report, we have used a combination of molecular, physicochemical, and cellular approaches to elucidate the mechanisms underlying the anti-Alzheimer properties of bexarotene in neural cells. First of all, we noticed that bexarotene shares a structural analogy with cholesterol. We showed that cholesterol and bexarotene compete for the same binding site in the C-terminal region of Alzheimer's β-amyloid peptide 1-42 (Aβ1-42). This common bexarotene/cholesterol binding domain was characterized as a linear motif encompassing amino acid residues 25-35 of Aβ1-42. Because cholesterol is involved in the oligomerization of Alzheimer's β-amyloid peptides into neurotoxic amyloid channels, we studied the capability of bexarotene to interfere with this process. We showed that nanomolar concentrations of bexarotene efficiently prevented the cholesterol-dependent increase of calcium fluxes induced by β-amyloid peptides Aβ1-42 and Aβ25-35 in SH-SY5Y cells, suggesting a direct effect of the drug on amyloid channel formation. Molecular dynamics simulations gave structural insights into the role of cholesterol in amyloid channel formation and explained the inhibitory effect of bexarotene. Because it is the first drug that can both inhibit the binding of cholesterol to β-amyloid peptides and prevent calcium-permeable amyloid pore formation in the plasma membrane of neural cells, bexarotene might be considered as the prototype of a new class of anti-Alzheimer compounds. The experimental approach developed herein can be used as a screening strategy to identify such compounds.

  9. Direct electrochemical and AFM detection of amyloidpeptide aggregation on basal plane HOPG.

    PubMed

    Lopes, Paula; Xu, Meng; Zhang, Min; Zhou, Ting; Yang, Yanlian; Wang, Chen; Ferapontova, Elena E

    2014-07-21

    Amyloidogenesis is associated with more than 30 human diseases, including Alzheimer's which is related to aggregation of β-amyloid peptide (Aβ). Here, consecutive stages of Aβ42 aggregation and amyloid fibril formation were followed electrochemically via oxidation of tyrosines in Aβ42 adsorbed on the basal plane graphite electrode and directly correlated with Aβ42 morphological changes observed by atomic force microscopy of the same substrate. The results offer new tools for analysis of mechanisms of Aβ aggregation.

  10. [The influence of dipole modifiers on the channel-forming activity of amyloid and amyloid-like peptides in lipid bilayers].

    PubMed

    Efimova, S S; Zakharov, V V; Ostroumova, O S

    2015-01-01

    We have studied the steady-state transmembrane current induced by amyloid and amyloid-like peptides in lipid bilayers in the presence of dipole modifiers. It has been shown that the addition of dipole modifier, phloretin, to the membrane bathing solutions leads to an increase in the multichannel activity of amyloid beta-peptide fragment 25-35, [Gly35]-amyloid beta-peptide fragment 25--35, prion protein fragment 106-126 and amyloid-like peptides myr-BASP1 (1--13), myr-BASP1(1--19) and GAP-43(1--40). We have found that the effect of phloretin is not the result of dipole potential changes due to adsorption of this modifier on the membrane. Using the various fragments of amyloid beta-peptide, presenilin, prion protein and neuronal proteins BASP1 and GAP-43 allowes to conclude that the steady-state peptide-induced transmembrane current in the case of addition of phloretin is due to the electrostatic interaction between the positively charged channel-forming agents and negatively charged dipole modifier. The results obtained by electron microscopy have demonstrated that this interaction increases degree of peptide oligomerization. PMID:26035972

  11. Pro-Cognitive Effects of Non-Peptide Analogues of Soluble Amyloid Peptide Precursor Fragment sAPP.

    PubMed

    Tiunova, A A; Komissarova, N V; Nenaidenko, V G; Makhmutova, A A; Beznosko, B K; Bachurin, S O; Anokhin, K V

    2016-08-01

    We studied pro-cognitive effect of two heterocyclic low-molecular-weight compounds that serve as non-peptide analogues of soluble fragment of amyloid peptide precursor (sAPP). Intracerebroventricular and systemic administration of peptide mimetics P2 and P5 improved weak memory on the model of passive avoidance in chicks and in the object location task in mice. Both compounds were effective if administered close to the moment of training or 4 h after it. The time windows and dose range for the pro-cognitive effects of the mimetics were similar to those observed in previous studies with sAPP peptide fragments. PMID:27590763

  12. Action of Caffeine as an Amyloid Inhibitor in the Aggregation of Aβ16-22 Peptides.

    PubMed

    Sharma, Bhanita; Paul, Sandip

    2016-09-01

    Alzheimer's disease (AD) is a neurodegenerative disease caused due to aggregation of Aβ peptides in the brain tissues. Recently, several studies on AD transgenic mice have shown the effect of caffeine in significantly reducing the Aβ amyloid level in their brains. However, the mechanism and mode of caffeine action on amyloid aggregation are not known. Therefore, in this study, we have carried out molecular dynamics simulations of five amyloid-forming Aβ16-22 peptides in pure water and in a regime of caffeine solutions, with different caffeine/peptide stoichiometric ratios. The secondary structure analyses of peptides in pure water show the formation of β-sheet conformations, whereas on addition of caffeine, these ordered conformations become negligible. The radial distribution function, contact map, nonbonding interaction energy, hydrogen bonding, potential of mean force, and hydration analyses show that there is less interpeptide interaction in the presence of caffeine, and the effect is greater with an increasing caffeine ratio. The interaction of aromatic phenylalanine residues of peptides with caffeine restricts the interpeptide interaction tendency. Upon increasing the number of caffeine molecules, interaction of caffeine with other hydrophobic residues also increases. Thus, the hydrophobic core-recognition motif of amyloid formation of peptides is physically blocked by caffeine, thereby abolishing the self-assembly formation. PMID:27487451

  13. The Aβ peptide forms non-amyloid fibrils in the presence of carbon nanotubes.

    PubMed

    Luo, Jinghui; Wärmländer, Sebastian K T S; Yu, Chien-Hung; Muhammad, Kamran; Gräslund, Astrid; Pieter Abrahams, Jan

    2014-06-21

    Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils.

  14. Structural Transformation and Aggregation of cc-beta Peptides Into Amyloid Proto-fibrils

    NASA Astrophysics Data System (ADS)

    Bhandari, Yuba; Steckmann, Timothy; Chapagain, Prem; Gerstman, Bernard

    2013-03-01

    The study of amyloid fibrils has important implications in understanding and treatment of various neurodegenerative diseases such as Alzheimer's and Parkinson's. During the formation of amyloid fibrils, peptide polymers manifest fascinating physical behavior by undergoing complicated structural transformations. We examine the behavior of a small engineered peptide called cc-beta, that was designed to mimic the structural changes of the much larger, naturally occurring amyloid beta proteins. Molecular dynamics (MD) simulations are performed to uncover the underlying physics that is responsible for the large scale structural transformations. By using implicit solvent replica exchange MD simulations, we examined the behavior of 12 peptides, initially arranged in four different cc-beta alpha helix trimers. We observed various intermediate stages of aggregation, as well as an organized proto-fibril beta aggregate. We discuss the time evolution and the various interactions involved in the structural transformation.

  15. Investigating the binding interactions of galantamine with β-amyloid peptide.

    PubMed

    Rao, Praveen P N; Mohamed, Tarek; Osman, Wesseem

    2013-01-01

    The anti-Alzheimer's agent galantamine is known to possess anti-amyloid properties. However the exact mechanisms are not clear. We studied the binding interactions of galantamine with amyloid peptide dimer (Aβ(1-40)) through molecular docking and molecular dynamics simulations. Galantamine's binding site within the amyloid peptide dimer was identified by docking experiments and the most stable complex was analyzed by molecular dynamics simulation. These studies show that galantamine was interacting with the central region of the amyloid dimer (Lys16-Ala21) and the C-terminal region (Ile31-Val36) with minimum structural drift of Cα atom in those regions. Strikingly, a significant drift was observed at the turn region from Asp23-Gly29 (Cα atom RMSD=9.2 Å and 11.6 Å at 50 fs and 100 fs respectively). Furthermore, galantamine's binding mode disrupts the key pi-pi stacking interaction between aromatic rings of Phe19 (chain A) and Phe19 (chain B) and intermolecular hydrogen bonds seen in unbound peptide dimer. Noticeably, the azepine tertiary nitrogen of galantamine was in close proximity to backbone CO of Leu34 (distance <3.5 Å) to stabilize the dimer conformation. In summary, the results indicate that galantamine binding to amyloid peptide dimer leads to a significant conformational change at the turn region (Asp23-Gly29) that disrupts interactions between individual β-strands and promotes a nontoxic conformation of Aβ(1-40) to prevent the formation of neurotoxic oligomers.

  16. Tau/Amyloid Beta 42 Peptide Test (Alzheimer Biomarkers)

    MedlinePlus

    ... page: Was this page helpful? Also known as: Alzheimer Biomarkers Formal name: Tau Protein and Amyloid Beta ... supplemental tests to help establish a diagnosis of Alzheimer disease and to distinguish between AD and other ...

  17. Surface Behavior and Lipid Interaction of Alzheimer β-Amyloid Peptide 1–42: A Membrane-Disrupting Peptide

    PubMed Central

    Ambroggio, Ernesto E.; Kim, Dennis H.; Separovic, Frances; Barrow, Colin J.; Barnham, Kevin J.; Bagatolli, Luis A.; Fidelio, Gerardo D.

    2005-01-01

    Amyloid aggregates, found in patients that suffer from Alzheimer's disease, are composed of fibril-forming peptides in a β-sheet conformation. One of the most abundant components in amyloid aggregates is the β-amyloid peptide 1–42 (Aβ 1–42). Membrane alterations may proceed to cell death by either an oxidative stress mechanism, caused by the peptide and synergized by transition metal ions, or through formation of ion channels by peptide interfacial self-aggregation. Here we demonstrate that Langmuir films of Aβ 1–42, either in pure form or mixed with lipids, develop stable monomolecular arrays with a high surface stability. By using micropipette aspiration technique and confocal microscopy we show that Aβ 1–42 induces a strong membrane destabilization in giant unilamellar vesicles composed of palmitoyloleoyl-phosphatidylcholine, sphingomyelin, and cholesterol, lowering the critical tension of vesicle rupture. Additionally, Aβ 1–42 triggers the induction of a sequential leakage of low- and high-molecular-weight markers trapped inside the giant unilamellar vesicles, but preserving the vesicle shape. Consequently, the Aβ 1–42 sequence confers particular molecular properties to the peptide that, in turn, influence supramolecular properties associated to membranes that may result in toxicity, including: 1), an ability of the peptide to strongly associate with the membrane; 2), a reduction of lateral membrane cohesive forces; and 3), a capacity to break the transbilayer gradient and puncture sealed vesicles. PMID:15681641

  18. Destruction of amyloid fibrils by graphene through penetration and extraction of peptides

    NASA Astrophysics Data System (ADS)

    Yang, Zaixing; Ge, Cuicui; Liu, Jiajia; Chong, Yu; Gu, Zonglin; Jimenez-Cruz, Camilo A.; Chai, Zhifang; Zhou, Ruhong

    2015-11-01

    Current therapies for Alzheimer's disease (AD) can provide a moderate symptomatic reduction or delay progression at various stages of the disease, but such treatments ultimately do not arrest the advancement of AD. As such, novel approaches for AD treatment and prevention are urgently needed. We here provide both experimental and computational evidence that pristine graphene and graphene-oxide nanosheets can inhibit Aβ peptide monomer fibrillation and clear mature amyloid fibrils, thus impacting the central molecular superstructures correlated with AD pathogenesis. Our molecular dynamics simulations for the first time reveal that graphene nanosheets can penetrate and extract a large number of peptides from pre-formed amyloid fibrils; these effects seem to be related to exceptionally strong dispersion interactions between peptides and graphene that are further enhanced by strong π-π stacking between the aromatic residues of extracted Aβ peptides and the graphene surface. Atomic force microscopy images confirm these predictions by demonstrating that mature amyloid fibrils can be cut into pieces and cleared by graphene oxides. Thioflavin fluorescence assays further illustrate the detailed dynamic processes by which graphene induces inhibition of monomer aggregation and clearance of mature amyloid fibrils, respectively. Cell viability and ROS assays indicate that graphene oxide can indeed mitigate cytotoxicity of Aβ peptide amyloids. Our findings provide new insights into the underlying molecular mechanisms that define graphene-amyloid interaction and suggest that further research on nanotherapies for Alzheimer's and other protein aggregation-related diseases is warranted.Current therapies for Alzheimer's disease (AD) can provide a moderate symptomatic reduction or delay progression at various stages of the disease, but such treatments ultimately do not arrest the advancement of AD. As such, novel approaches for AD treatment and prevention are urgently needed. We

  19. Solvent effects on self-assembly of beta-amyloid peptide.

    PubMed Central

    Shen, C L; Murphy, R M

    1995-01-01

    beta-amyloid peptide (A beta) is the primary protein component of senile plaques in Alzheimer's disease patients. Synthetic A beta spontaneously assembles into amyloid fibrils and is neurotoxic to cortical cultures. Neurotoxicity has been associated with the degree of peptide aggregation, yet the mechanism of assembly of A beta into amyloid fibrils is poorly understood. In this work, A beta was dissolved in several different solvents commonly used in neurotoxicity assays. In pure dimethylsulfoxide (DMSO), A beta had no detectable beta-sheet content; in 0.1% trifluoroacetate, the peptide contained one-third beta-sheet; and in 35% acetonitrile/0.1% trifluoroacetate, A beta was two-thirds beta-sheet, equivalent to the fibrillar peptide in physiological buffer. Stock solutions of peptide were diluted into phosphate-buffered saline, and fibril growth was followed by static and dynamic light scattering. The growth rate was substantially faster when the peptide was predissolved in 35% acetonitrile/0.1% trifluoroacetate than in 0.1% trifluoroacetate, 10% DMSO, or 100% DMSO. Differences in growth rate were attributed to changes in the secondary structure of the peptide in the stock solvent. These results suggest that formation of an intermediate with a high beta-sheet content is a controlling step in A beta self-assembly. PMID:8527678

  20. Competitive Mirror Image Phage Display Derived Peptide Modulates Amyloid Beta Aggregation and Toxicity

    PubMed Central

    Rudolph, Stephan; Klein, Antonia Nicole; Tusche, Markus; Schlosser, Christine; Elfgen, Anne; Brener, Oleksandr; Teunissen, Charlotte; Gremer, Lothar; Funke, Susanne Aileen; Kutzsche, Janine; Willbold, Dieter

    2016-01-01

    Alzheimer´s disease is the most prominent type of dementia and currently no causative treatment is available. According to recent studies, oligomeric species of the amyloid beta (Aβ) peptide appear to be the most toxic Aβ assemblies. Aβ monomers, however, may be not toxic per se and may even have a neuroprotective role. Here we describe a competitive mirror image phage display procedure that allowed us to identify preferentially Aβ1–42 monomer binding and thereby stabilizing peptides, which destabilize and thereby eliminate toxic oligomer species. One of the peptides, called Mosd1 (monomer specific d-peptide 1), was characterized in more detail. Mosd1 abolished oligomers from a mixture of Aβ1–42 species, reduced Aβ1–42 toxicity in cell culture, and restored the physiological phenotype in neuronal cells stably transfected with the gene coding for human amyloid precursor protein. PMID:26840229

  1. Amyloid-beta peptide binds to microtubule-associated protein 1B (MAP1B).

    PubMed

    Gevorkian, Goar; Gonzalez-Noriega, Alfonso; Acero, Gonzalo; Ordoñez, Jorge; Michalak, Colette; Munguia, Maria Elena; Govezensky, Tzipe; Cribbs, David H; Manoutcharian, Karen

    2008-05-01

    Extracellular and intraneuronal formation of amyloid-beta aggregates have been demonstrated to be involved in the pathogenesis of Alzheimer's disease. However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of targets have deleterious effects on cellular functions. In the present study we have shown for the first time that amyloid-beta 1-42 bound to a peptide comprising the microtubule binding domain of the heavy chain of microtubule-associated protein 1B by the screening of a human brain cDNA library expressed on M13 phage. This interaction may explain, in part, the loss of neuronal cytoskeletal integrity, impairment of microtubule-dependent transport and synaptic dysfunction observed previously in Alzheimer's disease.

  2. AMYLOIDPEPTIDE BINDS TO MICROTUBULE-ASSOCIATED PROTEIN 1B (MAP1B)

    PubMed Central

    Gevorkian, Goar; Gonzalez-Noriega, Alfonso; Acero, Gonzalo; Ordoñez, Jorge; Michalak, Colette; Munguia, Maria Elena; Govezensky, Tzipe; Cribbs, David H.; Manoutcharian, Karen

    2008-01-01

    Extracellular and intraneuronal formation of amyloid-beta aggregates have been demonstrated to be involved in the pathogenesis of Alzheimer’s disease. However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of targets have deleterious effects on cellular functions. In the present study we have shown for the first time that amyloid-beta 1-42 bound to a peptide comprising the microtubule binding domain of the heavy chain of microtubule-associated protein 1B by the screening of a human brain cDNA library expressed on M13 phage. This interaction may explain, in part, the loss of neuronal cytoskeletal integrity, impairment of microtubule-dependent transport and synaptic dysfunction observed previously in Alzheimer’s disease. PMID:18079022

  3. Glutamate system, amyloid ß peptides and tau protein: functional interrelationships and relevance to Alzheimer disease pathology.

    PubMed

    Revett, Timothy J; Baker, Glen B; Jhamandas, Jack; Kar, Satyabrata

    2013-01-01

    Alzheimer disease is the most prevalent form of dementia globally and is characterized premortem by a gradual memory loss and deterioration of higher cognitive functions and postmortem by neuritic plaques containing amyloid ß peptide and neurofibrillary tangles containing phospho-tau protein. Glutamate is the most abundant neurotransmitter in the brain and is essential to memory formation through processes such as long-term potentiation and so might be pivotal to Alzheimer disease progression. This review discusses how the glutamatergic system is impaired in Alzheimer disease and how interactions of amyloid ß and glutamate influence synaptic function, tau phosphorylation and neurodegeneration. Interestingly, glutamate not only influences amyloid ß production, but also amyloid ß can alter the levels of glutamate at the synapse, indicating that small changes in the concentrations of both molecules could influence Alzheimer disease progression. Finally, we describe how the glutamate receptor antagonist, memantine, has been used in the treatment of individuals with Alzheimer disease and discuss its effectiveness.

  4. Acetylcholinesterase, a senile plaque component, affects the fibrillogenesis of amyloid-beta-peptides.

    PubMed

    Alvarez, A; Bronfman, F; Pérez, C A; Vicente, M; Garrido, J; Inestrosa, N C

    1995-12-01

    Acetylcholinesterase (AChE) colocalizes with amyloid-beta peptide (A beta) deposits present in the brain of Alzheimer's patients. Recent studies showed that A beta 1-40 can adopt two different conformational states in solution (an amyloidogenic conformer, A beta ac, and a non-amyloidogenic conformer, A beta nac) which have distinct abilities to form amyloid fibrils. We report here that AChE binds A beta nac and accelerates amyloid formation by the same peptide. No such effect was observed with A beta ac, the amyloidogenic conformer, suggesting that AChE acts as a 'pathological chaperone' inducing a conformational transition from A beta nac into A beta ac in vitro.

  5. The rheological properties of beta amyloid Langmuir monolayers: Comparative studies with melittin peptide.

    PubMed

    Caruso, Benjamín; Ambroggio, Ernesto E; Wilke, Natalia; Fidelio, Gerardo Daniel

    2016-10-01

    We determined the rheological properties of β-amyloid Langmuir films at the air/water interface, a peptide whose interfacial structure is extended β-sheet, and compared them with those of films composed of Melittin (Mel), which adopts an α-helical conformation at neutral pH. To determine the dilatational and shear moduli we evaluated the response of pure peptide monolayers to an oscillatory anisotropic compressive work. Additionally, a micro-rheological characterization was performed by tracking the diffusion of micrometer sized latex beads onto the interface. This technique allowed us the detection of different rheological behaviour between monolayers presenting a low shear response. Monolayers of the β-sheet structure-adopting peptides, such as β-amyloid peptides, exhibited a marked shear (elastic) modulus even at low surface pressures. In contrast, Mel monolayers exhibited negligible shear modulus and the micro-rheological shear response was markedly lower than that observed for either Aβ1-40 or Aβ1-42 amyloid peptides. When Mel monolayers were formed at the interface of an aqueous solution at pH 11, we observed an increase in both the lateral stability and film viscosity as detected by a slower diffusion of the latex beads, in keeping with an increase in β-sheet structure at this high pH (verified by ATR and FT-IR measurements). We suggest that the interactions responsible for the marked response upon shear observed for β-amyloid peptide monolayers are the hydrogen bonds of the β-sheet structure that can form an infinite planar network at the interface. Conversely, α-helical Mel peptide lack of these inter-molecular interactions and, therefore the shear contribution was negligible. We propose that the secondary structure is important for modulating the rheological behavior of short peptide monolayers regardless of the mass density or surface charge at the surface.

  6. Amyloidpeptide active site: theoretical Cu K-edge XANES study

    NASA Astrophysics Data System (ADS)

    Chaynikov, A. P.; Soldatov, M. A.; Streltsov, V.; Soldatov, A. V.

    2013-04-01

    This article is dedicated to the local atomic structure analysis of the copper binding site in amyloidpeptide. Here we considered two possible structural models that were previously obtained by means of EXAFS analysis and density functional theory simulations. We present the calculations of Cu K-edge XANES spectra for both models and make comparison of these spectra with experiment.

  7. Studies of Polymorphism of Amyloid-β42 Peptide from Different Suppliers.

    PubMed

    Suvorina, Mariya Yu; Selivanova, Olga M; Grigorashvili, Elizaveta I; Nikulin, Alexey D; Marchenkov, Victor V; Surin, Alexey K; Galzitskaya, Oxana V

    2015-01-01

    The aim of this study was to investigate the process of amyloidogenesis of amyloid-β (Aβ)42 peptide, by means of fluorescence spectroscopy, electron microscopy, X-ray diffraction, and mass spectrometry. It has been repeatedly reported in the literature that the process of fibril formation by Aβ42 peptide depends considerably not only upon the specific conditions (ionic conditions, pH, temperature, mixing, etc.), as well as the manufacturing route (synthetic or recombinant), but also on the methods of synthesis and purification. We have, for the first time, systematically analyzed samples of Aβ42 peptide supplied by five different companies (Anaspec, Invitrogen, Enzo, Sigma-Aldrich, and SynthAssist) and obtained evidence of significant variability, including lot to lot variations. All studied samples formed amyloid-like fibrils at pH3-6, and the fibrils contained cross-β structures. Samples from Anaspec, Invitrogen, and Enzo formed one particular type of amyloid-like fibrils, while the samples from Sigma-Aldrich and SynthAssist formed another distinct type of fibrils. The observed polymorphism emphasizes the capacity of the Aβ42 peptide to act as a prion agent with varying structural characteristics. The presented data have allowed us to propose a possible mechanism of formation of amyloid-like fibrils. PMID:26401694

  8. Biochemical Identification of a Linear Cholesterol-Binding Domain within Alzheimer’s β Amyloid Peptide

    PubMed Central

    2012-01-01

    Alzheimer’s β-amyloid (Aβ) peptides can self-organize into amyloid pores that may induce acute neurotoxic effects in brain cells. Membrane cholesterol, which regulates Aβ production and oligomerization, plays a key role in this process. Although several data suggested that cholesterol could bind to Aβ peptides, the molecular mechanisms underlying cholesterol/Aβ interactions are mostly unknown. On the basis of docking studies, we identified the linear fragment 22–35 of Aβ as a potential cholesterol-binding domain. This domain consists of an atypical concatenation of polar/apolar amino acid residues that was not previously found in cholesterol-binding motifs. Using the Langmuir film balance technique, we showed that synthetic peptides Aβ17–40 and Aβ22–35, but not Aβ1–16, could efficiently penetrate into cholesterol monolayers. The interaction between Aβ22–35 and cholesterol was fully saturable and lipid-specific. Single-point mutations of Val-24 and Lys-28 in Aβ22–35 prevented cholesterol binding, whereas mutations at residues 29, 33, and 34 had little to no effect. These data were consistent with the in silico identification of Val-24 and Lys-28 as critical residues for cholesterol binding. We conclude that the linear fragment 22–35 of Aβ is a functional cholesterol-binding domain that could promote the insertion of β-amyloid peptides or amyloid pore formation in cholesterol-rich membrane domains. PMID:23509984

  9. Inhibition of fibril formation in beta-amyloid peptide by a novel series of benzofurans.

    PubMed Central

    Howlett, D R; Perry, A E; Godfrey, F; Swatton, J E; Jennings, K H; Spitzfaden, C; Wadsworth, H; Wood, S J; Markwell, R E

    1999-01-01

    A series of benzofuran derivatives have been identified as inhibitors of fibril formation in the beta-amyloid peptide. The activity of these compounds has been assessed by a novel fibril-formation-specific immunoassay and for their effects on the production of a biologically active fibril product. The inhibition afforded by the compounds seems to be associated with their binding to beta-amyloid, as identified by scintillation proximity binding assay. Binding assays and NMR studies also indicate that the inhibition is associated with self-aggregation of the compounds. There is a close correlation between the activity of the benzofurans as inhibitors of fibril formation and their ability to bind to beta-amyloid. Non-benzofuran inhibitors of the fibril formation process do not seem to bind to the same site on the beta-amyloid molecule as the benzofurans. Thus a specific recognition site might exist for benzofurans on beta-amyloid, binding to which seems to interfere with the ability of the peptide to form fibrils. PMID:10229684

  10. Acetylcholinesterase accelerates assembly of amyloid-beta-peptides into Alzheimer's fibrils: possible role of the peripheral site of the enzyme.

    PubMed

    Inestrosa, N C; Alvarez, A; Pérez, C A; Moreno, R D; Vicente, M; Linker, C; Casanueva, O I; Soto, C; Garrido, J

    1996-04-01

    Acetylcholinesterase (AChE), an important component of cholinergic synapses, colocalizes with amyloid-beta peptide (A beta) deposits of Alzheimer's brain. We report here that bovine brain AChE, as well as the human and mouse recombinant enzyme, accelerates amyloid formation from wild-type A beta and a mutant A beta peptide, which alone produces few amyloid-like fibrils. The action of AChE was independent of the subunit array of the enzyme, was not affected by edrophonium, an active site inhibitor, but it was affected by propidium, a peripheral anionic binding site ligand. Butyrylcholinesterase, an enzyme that lacks the peripheral site, did not affect amyloid formation. Furthermore, AChE is a potent amyloid-promoting factor when compared with other A beta-associated proteins. Thus, in addition to its role in cholinergic synapses, AChE may function by accelerating A beta formation and could play a role during amyloid deposition in Alzheimer's brain.

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

    PubMed Central

    Zhou, Xin; Yang, Chun; Liu, Yufeng; Li, Peng; Yang, Huiying; Dai, Jingxing; Qu, Rongmei; Yuan, Lin

    2014-01-01

    Amyloid-beta peptide is the main component of amyloid plaques, which are found in Alzheimer'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 degradative 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. PMID:25206748

  12. Amyloidpeptides in interaction with raft-mime model membranes: a neutron reflectivity insight.

    PubMed

    Rondelli, Valeria; Brocca, Paola; Motta, Simona; Messa, Massimo; Colombo, Laura; Salmona, Mario; Fragneto, Giovanna; Cantù, Laura; Del Favero, Elena

    2016-01-01

    The role of first-stage β-amyloid aggregation in the development of the Alzheimer disease, is widely accepted but still unclear. Intimate interaction with the cell membrane is invoked. We designed Neutron Reflectometry experiments to reveal the existence and extent of the interaction between β-amyloid (Aβ) peptides and a lone customized biomimetic membrane, and their dependence on the aggregation state of the peptide. The membrane, asymmetrically containing phospholipids, GM1 and cholesterol in biosimilar proportion, is a model for a raft, a putative site for amyloid-cell membrane interaction. We found that the structured-oligomer of Aβ(1-42), its most acknowledged membrane-active state, is embedded as such into the external leaflet of the membrane. Conversely, the Aβ(1-42) unstructured early-oligomers deeply penetrate the membrane, likely mimicking the interaction at neuronal cell surfaces, when the Aβ(1-42) is cleaved from APP protein and the membrane constitutes a template for its further structural evolution. Moreover, the smaller Aβ(1-6) fragment, the N-terminal portion of Aβ, was also used. Aβ N-terminal is usually considered as involved in oligomer stabilization but not in the peptide-membrane interaction. Instead, it was seen to remove lipids from the bilayer, thus suggesting its role, once in the whole peptide, in membrane leakage, favouring peptide recruitment. PMID:26880066

  13. Surface plasmon resonance for the label-free detection of Alzheimer's β-amyloid peptide aggregation.

    PubMed

    Palladino, Pasquale; Aura, Angela M; Spoto, Giuseppe

    2016-01-01

    Amyloid peptide oligomers and fibrils are studied as targets for therapy and diagnosis of Alzheimer's disease. They are usually detected by amyloid incubation, but such method is necessarily associated with Aβ1-42 depletion and dye binding or conjugation, which have a complex influence on fibril growth, provide information about fibril elongation over long time periods only, and might lead to false-positive results in amyloid inhibition assay. Surface plasmon resonance (SPR) is used to study with no labelling and in real time the aggregation of Aβ1-42 amyloid on specific antibodies. SPR data show, for the first time by using SPR, a multi-phase association behavior for Aβ1-42 oligomers accounting for a sigmoidal growth of amyloid as a function of time, with two antibody-dependent aggregation patterns. The new method represents an advantageous alternative to traditional procedures for investigating amyloid self-assembly and inhibition from early-stage oligomer association, on the time scale of seconds to minutes, to long-term polymerization, on the time scale of hours to days. PMID:26558762

  14. Structural and Thermodynamic Properties of AmyloidPeptides: Impact of Fragment Size

    NASA Astrophysics Data System (ADS)

    Kitahara, T.; Wise-Scira, O.; Coskuner, O.

    2010-10-01

    Alzheimer's disease is a progressive neurodegenerative disease whose physiological characteristics include the accumulation of amyloid-containing deposits in the brain and consequent synapse and neuron loss. Unfortunately, most widely used drugs for the treatment can palliate the outer symptoms but cannot cure the disease itself. Hence, developing a new drug that can cure it. Most recently, the ``early aggregation and monomer'' hypothesis has become popular and a few drugs have been developed based on this hypothesis. Detailed understanding of the amyloidpeptide structure can better help us to determine more effective treatment strategies; indeed, the structure of Amyloid has been studied extensively employing experimental and theoretical tools. Nevertheless, those studies have employed different fragment sizes of Amyloid and characterized its conformational nature in different media. Thus, the structural properties might be different from each other and provide a reason for the existing debates in the literature. Here, we performed all-atom MD simulations and present the structural and thermodynamic properties of Aβ1-16, Aβ1-28, and Aβ1-42 in the gas phase and in aqueous solution. Our studies show that the overall structures, secondary structures, and the calculated thermodynamic properties change with increasing peptide size. In addition, we find that the structural properties of those peptides are different from each other in the gas phase and in aqueous solution.

  15. Insights into the molecular interactions between aminopeptidase and amyloid beta peptide using molecular modeling techniques.

    PubMed

    Dhanavade, Maruti J; Sonawane, Kailas D

    2014-08-01

    Amyloid beta (Aβ) peptides play a central role in the pathogenesis of Alzheimer's disease. The accumulation of Aβ peptides in AD brain was caused due to overproduction or insufficient clearance and defects in the proteolytic degradation of Aβ peptides. Hence, Aβ peptide degradation could be a promising therapeutic approach in AD treatment. Recent experimental report suggests that aminopeptidase from Streptomyces griseus KK565 (SGAK) can degrade Aβ peptides but the interactive residues are yet to be known in detail at the atomic level. Hence, we developed the three-dimensional model of aminopeptidase (SGAK) using SWISS-MODEL, Geno3D and MODELLER. Model built by MODELLER was used for further studies. Molecular docking was performed between aminopeptidase (SGAK) with wild-type and mutated Aβ peptides. The docked complex of aminopeptidase (SGAK) and wild-type Aβ peptide (1IYT.pdb) shows more stability than the other complexes. Molecular docking and MD simulation results revealed that the residues His93, Asp105, Glu139, Glu140, Asp168 and His255 are involved in the hydrogen bonding with Aβ peptide and zinc ions. The interactions between carboxyl oxygen atoms of Glu139 of aminopeptidase (SGAK) with water molecule suggest that the Glu139 may be involved in the nucleophilic attack on Ala2-Glu3 peptide bond of Aβ peptide. Hence, amino acid Glu139 of aminopeptidase (SGAK) might play an important role to degrade Aβ peptides, a causative agent of Alzheimer's disease.

  16. Dynamics of the formation of a hydrogel by a pathogenic amyloid peptide: islet amyloid polypeptide

    PubMed Central

    Jean, Létitia; Lee, Chiu Fan; Hodder, Peter; Hawkins, Nick; Vaux, David J.

    2016-01-01

    Many chronic degenerative diseases result from aggregation of misfolded polypeptides to form amyloids. Many amyloidogenic polypeptides are surfactants and their assembly can be catalysed by hydrophobic-hydrophilic interfaces (an air-water interface in-vitro or membranes in-vivo). We recently demonstrated the specificity of surface-induced amyloidogenesis but the mechanisms of amyloidogenesis and more specifically of adsorption at hydrophobic-hydrophilic interfaces remain poorly understood. Thus, it is critical to determine how amyloidogenic polypeptides behave at interfaces. Here we used surface tensiometry, rheology and electron microscopy to demonstrate the complex dynamics of gelation by full-length human islet amyloid polypeptide (involved in type II diabetes) both in the bulk solution and at hydrophobic-hydrophilic interfaces (air-water interface and phospholipids). We show that the hydrogel consists of a 3D supramolecular network of fibrils. We also assessed the role of solvation and dissected the evolution over time of the assembly processes. Amyloid gelation could have important pathological consequences for membrane integrity and cellular functions. PMID:27535008

  17. Dynamics of the formation of a hydrogel by a pathogenic amyloid peptide: islet amyloid polypeptide.

    PubMed

    Jean, Létitia; Lee, Chiu Fan; Hodder, Peter; Hawkins, Nick; Vaux, David J

    2016-01-01

    Many chronic degenerative diseases result from aggregation of misfolded polypeptides to form amyloids. Many amyloidogenic polypeptides are surfactants and their assembly can be catalysed by hydrophobic-hydrophilic interfaces (an air-water interface in-vitro or membranes in-vivo). We recently demonstrated the specificity of surface-induced amyloidogenesis but the mechanisms of amyloidogenesis and more specifically of adsorption at hydrophobic-hydrophilic interfaces remain poorly understood. Thus, it is critical to determine how amyloidogenic polypeptides behave at interfaces. Here we used surface tensiometry, rheology and electron microscopy to demonstrate the complex dynamics of gelation by full-length human islet amyloid polypeptide (involved in type II diabetes) both in the bulk solution and at hydrophobic-hydrophilic interfaces (air-water interface and phospholipids). We show that the hydrogel consists of a 3D supramolecular network of fibrils. We also assessed the role of solvation and dissected the evolution over time of the assembly processes. Amyloid gelation could have important pathological consequences for membrane integrity and cellular functions. PMID:27535008

  18. Amnesia induced in mice by centrally administered beta-amyloid peptides involves cholinergic dysfunction.

    PubMed

    Maurice, T; Lockhart, B P; Privat, A

    1996-01-15

    Substantial evidences suggest that the increased cerebral deposition, and neurotoxic action of the beta-amyloid peptide, the major constituent of senile plaques, may represent the underlying cause of the cognitive deficits observed in Alzheimer's disease. Herein, we attempted to verify this hypothesis by inducing a potential Alzheimer's-type amnesia after direct intracerebroventricular administration of aggregated beta 25-35-amyloid peptide in mice. In this aim, mnesic capacities were evaluated after 6-13 days, using spontaneous alternation in the Y-maze, step-down type passive avoidance and place learning in a water-maze. Pretraining administration of aggregated beta 25-35 peptide induced dose-dependent decreases in both alternation behaviour and passive avoidance, at doses of 3 and 9 nmol/mouse. A reduced but still significant impairment was observed when the peptide was not aggregated, or 'aged', by preincubation for 4 days at 37 degrees C. The beta 1-28 peptide, at 3 nmol/mouse, also induced a marked decrease in step-down latency. Posttraining, but not preretention, administration of beta 25-35 peptide also significantly impaired learning. The beneficial effects of cholinergic agents on beta 25-35-induced amnesia was examined using the cholinesterase inhibitor tacrine (THA, 1.3 and 4.3 mumol/kg i.p.) and the nicotinic receptor agonist (-)-nicotine (NIC, 0.06 and 0.2 mumol/kg i.p.). Both drugs induced a dose-dependent abrogation of the beta 25-35-induced decreases in alternation behaviour and passive avoidance. Furthermore, THA, at 1.3 mumol/kg, and NIC, at 0.2 mumol/kg, also reversed the beta 25-35-induced impairment of place learning and retention in the water-maze. Histological examination of Cresyl violet-stained brain sections indicated a moderate but significant cell loss within the frontoparietal cortex and the hippocampal formation of mice treated with aged beta 25-35 peptide (9 nmol). Examination of Congo red-stained sections in the same animals

  19. Reduced aggregation and cytotoxicity of amyloid peptides by graphene oxide/gold nanocomposites prepared by pulsed laser ablation in water.

    PubMed

    Li, Jingying; Han, Qiusen; Wang, Xinhuan; Yu, Ning; Yang, Lin; Yang, Rong; Wang, Chen

    2014-11-12

    A novel and convenient method to synthesize the nanocomposites combining graphene oxides (GO) with gold nanoparticles (AuNPs) is reported and their applications to modulate amyloid peptide aggregation are demonstrated. The nanocomposites produced by pulsed laser ablation (PLA) in water show good biocompatibility and solubility. The reduced aggregation of amyloid peptides by the nanocomposites is confirmed by Thioflavin T fluorescence and atomic force microscopy. The cell viability experiments reveals that the presence of the nanocomposites can significantly reduce the cytotoxicity of the amyloid peptides. Furthermore, the depolymerization of peptide fibrils and inhibition of their cellular cytotoxicity by GO/AuNPs is also observed. These observations suggest that the nanocomposites combining GO and AuNPs have a great potential for designing new therapeutic agents and are promising for future treatment of amyloid-related diseases.

  20. Solid-state NMR sequential assignment of the β-endorphin peptide in its amyloid form.

    PubMed

    Seuring, Carolin; Gath, Julia; Verasdonck, Joeri; Cadalbert, Riccardo; Rivier, Jean; Böckmann, Anja; Meier, Beat H; Riek, Roland

    2016-10-01

    Insights into the three-dimensional structure of hormone fibrils are crucial for a detailed understanding of how an amyloid structure allows the storage of hormones in secretory vesicles prior to hormone secretion into the blood stream. As an example for various hormone amyloids, we have studied the endogenous opioid neuropeptide β-endorphin in one of its fibril forms. We have achieved the sequential assignment of the chemical shifts of the backbone and side-chain heavy atoms of the fibril. The secondary chemical shift analysis revealed that the β-endorphin peptide adopts three β-strands in its fibril state. This finding fosters the amyloid nature of a hormone at the atomic level.

  1. Nuclear translocation uncovers the amyloid peptide Aβ42 as a regulator of gene transcription.

    PubMed

    Barucker, Christian; Harmeier, Anja; Weiske, Joerg; Fauler, Beatrix; Albring, Kai Frederik; Prokop, Stefan; Hildebrand, Peter; Lurz, Rudi; Heppner, Frank L; Huber, Otmar; Multhaup, Gerhard

    2014-07-18

    Although soluble species of the amyloidpeptide Aβ42 correlate with disease symptoms in Alzheimer disease, little is known about the biological activities of amyloid-β (Aβ). Here, we show that Aβ peptides varying in lengths from 38 to 43 amino acids are internalized by cultured neuroblastoma cells and can be found in the nucleus. By three independent methods, we demonstrate direct detection of nuclear Aβ42 as follows: (i) biochemical analysis of nuclear fractions; (ii) detection of biotin-labeled Aβ in living cells by confocal laser scanning microscopy; and (iii) transmission electron microscopy of Aβ in cultured cells, as well as brain tissue of wild-type and transgenic APPPS1 mice (overexpression of amyloid precursor protein and presenilin 1 with Swedish and L166P mutations, respectively). Also, this study details a novel role for Aβ42 in nuclear signaling, distinct from the amyloid precursor protein intracellular domain. Chromatin immunoprecipitation showed that Aβ42 specifically interacts as a repressor of gene transcription with LRP1 and KAI1 promoters. By quantitative RT-PCR, we confirmed that mRNA levels of the examined candidate genes were exclusively decreased by the potentially neurotoxic Aβ42 wild-type peptide. Shorter peptides (Aβ38 or Aβ40) and other longer peptides (nontoxic Aβ42 G33A substitution or Aβ43) did not affect mRNA levels. Overall, our data indicate that the nuclear translocation of Aβ42 impacts gene regulation, and deleterious effects of Aβ42 in Alzheimer disease pathogenesis may be influenced by altering the expression profiles of disease-modifying genes.

  2. Effect of Curcumin on the metal ion induced fibrillization of Amyloidpeptide

    NASA Astrophysics Data System (ADS)

    Banerjee, Rona

    2014-01-01

    The effect of Curcumin on Cu(II) and Zn(II) induced oligomerization and protofibrillization of the amyloid-beta (Aβ) peptide has been studied by spectroscopic and microscopic methods. Curcumin could significantly reduce the β-sheet content of the peptide in a time dependent manner. It also plays an antagonistic role in β-sheet formation that is promoted by metal ions like Cu(II) and Zn(II) as observed by Circular Dichroism (CD) spectroscopy. Atomic force microscopic (AFM) images show that spontaneous fibrillization of the peptide occurs in presence of Cu(II) and Zn(II) but is inhibited on incubation of the peptide with Curcumin indicating the beneficial role of Curcumin in preventing the aggregation of Aβ peptide.

  3. Amyloidpeptide binds to cytochrome C oxidase subunit 1.

    PubMed

    Hernandez-Zimbron, Luis Fernando; Luna-Muñoz, Jose; Mena, Raul; Vazquez-Ramirez, Ricardo; Kubli-Garfias, Carlos; Cribbs, David H; Manoutcharian, Karen; Gevorkian, Goar

    2012-01-01

    Extracellular and intraneuronal accumulation of amyloid-beta aggregates has been demonstrated to be involved in the pathogenesis of Alzheimer's disease (AD). However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of macromolecules has deleterious effects on cellular functions. Mitochondria were found to be the target for amyloid-beta, and mitochondrial dysfunction is well documented in AD. In the present study we have shown for the first time that Aβ 1-42 bound to a peptide comprising the amino-terminal region of cytochrome c oxidase subunit 1. Phage clone, selected after screening of a human brain cDNA library expressed on M13 phage and bearing a 61 amino acid fragment of cytochrome c oxidase subunit 1, bound to Aβ 1-42 in ELISA as well as to Aβ aggregates present in AD brain. Aβ 1-42 and cytochrome c oxidase subunit 1 co-immunoprecipitated from mitochondrial fraction of differentiated human neuroblastoma cells. Likewise, molecular dynamics simulation of the cytochrome c oxidase subunit 1 and the Aβ 1-42 peptide complex resulted in a reliable helix-helix interaction, supporting the experimental results. The interaction between Aβ 1-42 and cytochrome c oxidase subunit 1 may explain, in part, the diminished enzymatic activity of respiratory chain complex IV and subsequent neuronal metabolic dysfunction observed in AD.

  4. Surface Effects Mediate Self-Assembly of AmyloidPeptides

    PubMed Central

    2015-01-01

    Here we present a label-free method for studying the mechanism of surface effects on amyloid aggregation. In this method, spin-coating is used to rapidly dry samples, in a homogeneous manner, after various incubation times. This technique allows the control of important parameters for self-assembly, such as the surface concentration. Atomic force microscopy is then used to obtain high-resolution images of the morphology. While imaging under dry conditions, we show that the morphologies of self-assembled aggregates of a model amyloidpeptide, Aβ12–28, are strongly influenced by the local surface concentration. On mica surfaces, where the peptides can freely diffuse, homogeneous, self-assembled protofibrils formed spontaneously and grew longer with longer subsequent incubation. The surface fibrillization rate was much faster than the rates of fibril formation observed in solution, with initiation occurring at much lower concentrations. These data suggest an alternative pathway for amyloid formation on surfaces where the nucleation stage is either bypassed entirely or too fast to measure. This simple preparation procedure for high-resolution atomic force microscopy imaging of amyloid oligomers and protofibrils should be applicable to any amyloidogenic protein species. PMID:25229233

  5. Direct electrochemical and AFM detection of amyloidpeptide aggregation on basal plane HOPG

    NASA Astrophysics Data System (ADS)

    Lopes, Paula; Xu, Meng; Zhang, Min; Zhou, Ting; Yang, Yanlian; Wang, Chen; Ferapontova, Elena E.

    2014-06-01

    Amyloidogenesis is associated with more than 30 human diseases, including Alzheimer's which is related to aggregation of β-amyloid peptide (Aβ). Here, consecutive stages of Aβ42 aggregation and amyloid fibril formation were followed electrochemically via oxidation of tyrosines in Aβ42 adsorbed on the basal plane graphite electrode and directly correlated with Aβ42 morphological changes observed by atomic force microscopy of the same substrate. The results offer new tools for analysis of mechanisms of Aβ aggregation.Amyloidogenesis is associated with more than 30 human diseases, including Alzheimer's which is related to aggregation of β-amyloid peptide (Aβ). Here, consecutive stages of Aβ42 aggregation and amyloid fibril formation were followed electrochemically via oxidation of tyrosines in Aβ42 adsorbed on the basal plane graphite electrode and directly correlated with Aβ42 morphological changes observed by atomic force microscopy of the same substrate. The results offer new tools for analysis of mechanisms of Aβ aggregation. Electronic supplementary information (ESI) available: Experimental details: procedures for Aβ42 aggregation and electrode modification, DPV/AFM measurements and analysis. See DOI: 10.1039/c4nr02413c

  6. AmyloidPeptide Binds to Cytochrome C Oxidase Subunit 1

    PubMed Central

    Hernandez-Zimbron, Luis Fernando; Luna-Muñoz, Jose; Mena, Raul; Vazquez-Ramirez, Ricardo; Kubli-Garfias, Carlos; Cribbs, David H.; Manoutcharian, Karen; Gevorkian, Goar

    2012-01-01

    Extracellular and intraneuronal accumulation of amyloid-beta aggregates has been demonstrated to be involved in the pathogenesis of Alzheimer's disease (AD). However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of macromolecules has deleterious effects on cellular functions. Mitochondria were found to be the target for amyloid-beta, and mitochondrial dysfunction is well documented in AD. In the present study we have shown for the first time that Aβ 1–42 bound to a peptide comprising the amino-terminal region of cytochrome c oxidase subunit 1. Phage clone, selected after screening of a human brain cDNA library expressed on M13 phage and bearing a 61 amino acid fragment of cytochrome c oxidase subunit 1, bound to Aβ 1–42 in ELISA as well as to Aβ aggregates present in AD brain. Aβ 1–42 and cytochrome c oxidase subunit 1 co-immunoprecipitated from mitochondrial fraction of differentiated human neuroblastoma cells. Likewise, molecular dynamics simulation of the cytochrome c oxidase subunit 1 and the Aβ 1–42 peptide complex resulted in a reliable helix-helix interaction, supporting the experimental results. The interaction between Aβ 1–42 and cytochrome c oxidase subunit 1 may explain, in part, the diminished enzymatic activity of respiratory chain complex IV and subsequent neuronal metabolic dysfunction observed in AD. PMID:22927926

  7. Exploring the early steps of aggregation of amyloid-forming peptide KFFE

    NASA Astrophysics Data System (ADS)

    Wei, Guanghong; Mousseau, Normand; Derreumaux, Philippe

    2004-11-01

    It has been shown recently that even a tetrapeptide can form amyloid fibrils sharing all the characteristics of amyloid fibrils built from large proteins. Recent experimental studies also suggest that the toxicity observed in several neurodegenerative diseases, such as Alzheimer's disease and Creutzfeldt-Jakob disease, is not only related to the mature fibrils themselves, but also to the soluble oligomers formed early in the process of fibrillogenesis. This raises the interest in studying the early steps of the aggregation process. Although fibril formation follows the nucleation-condensation process, characterized by the presence of lag phase, the exact pathways remain to be determined. In this study, we used the activation-relaxation technique and a generic energy model to explore the process of self-assembly and the structures of the resulting aggregates of eight KFFE peptides. Our simulations show, starting from different states with a preformed antiparallel dimer, that eight chains can self-assemble to adopt, with various orientations, four possible distant oligomeric well-aligned structures of similar energy. Two of these structures show a double-layer β-sheet organization, in agreement with the structure of amyloid fibrils as observed by x-ray diffraction; another two are mixtures of dimers and trimers. Our results also suggest that octamers are likely to be below the critical size for nucleation of amyloid fibrils for small peptides.

  8. Heme oxygenase-1 induction and mitochondrial iron sequestration in astroglia exposed to amyloid peptides.

    PubMed

    Ham, D; Schipper, H M

    2000-05-01

    The mechanisms responsible for pathological iron deposition and mitochondrial insufficiency that have been documented in the brains of Alzheimer (AD) patients remain poorly understood. In the present study, we demonstrate that low-micromolar concentrations of amyloid1-40 (A40) and amyloid 1-42 (A42), peptides implicated in the pathogenesis of AD, increase levels of heme oxygenase-1 (HO-1) mRNA and protein in cultured rat astroglia. Furthermore, 6 days of exposure to amyloid augments the sequestration of 55FeCl3-derived iron by astroglial mitochondria without affecting the disposition of this metal in whole-cell and lysosomal compartments. Mitochondrial iron deposition was not observed in the amyloid-treated glia when diferric-transferrin served as the metal donor. We had previously shown that inhibitors of HO-1 and the mitochondrial permeability transition pore (MTP) block the uptake of mitochondrial iron in astrocytes exposed to the pro-oxidant effects of dopamine and several pro-inflammatory cytokines. Similarly, in the current study, amyloid-induced mitochondrial iron trapping was significantly attenuated by co-administration of the HO-1 transcriptional suppressor, dexamethasone (DEX) or the MTP blocker, cyclosporin A (CSA). Thus, the marked enhancement of HO-1 expression previously demonstrated in AD-affected neurons and astroglia may transduce amyloid (oxidative) stress into the abnormal patterns of iron deposition and mitochondrial insufficiency characteristic of this disease. Finally, in experiments employing cytotoxic concentrations of A40, we provide evidence that inhibition of HO-1 transcription and related mitochondrial iron deposition may be an important mechanism by which DEX protects tissues subjected to amyloid stress.

  9. Detection of β-Amyloid Peptide Dimer in Solution by Fluorescence Resonance Energy Transfer

    NASA Astrophysics Data System (ADS)

    Han, Jun; Mei, Erwen; Kung, Mei-Ping; Kung, Hank; Dai, Hai-Lung

    2006-03-01

    Studies have suggested that there is a connection between ß-amyloid-derived diffusible ligands (ADDLs), small oligomers formed from clustering of peptides with 39-42 amino acid units, and pathogenicity of Alzheimer's disease. It is believed that the soluble ADDL oligomers eventually coagulate and precipitate into fibrils that cause neurotoxicity. Although there have been studies characterizing the fibrils structure and the large coagulate formation kinetics, little experimental information exists for the oligomers in the solution phase. We report here the use of fluorescence resonance energy transfer detected through a confocal microscope under single molecule conditions for the detection of the β-amyloid (1-40) peptide dimer in solution. The structure of the dimer is characterized in terms of the distance of the two N-terminals.

  10. Insight into the stability of cross-β amyloid fibril from VEALYL short peptide with molecular dynamics simulation.

    PubMed

    Ye, Wei; Chen, Yue; Wang, Wei; Yu, Qingfen; Li, Yixue; Zhang, Jian; Chen, Hai-Feng

    2012-01-01

    Amyloid fibrils are found in many fatal neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, type II diabetes, and prion disease. The VEALYL short peptide from insulin has been confirmed to aggregate amyloid-like fibrils. However, the aggregation mechanism of amyloid fibril is poorly understood. Here, we utilized molecular dynamics simulation to analyse the stability of VEALYL hexamer. The statistical results indicate that hydrophobic residues play key roles in stabilizing VEALYL hexamer. Single point and two linkage mutants confirmed that Val1, Leu4, and Tyr5 of VEALYL are key residues. The consistency of the results for the VEALYL oligomer suggests that the intermediate states might be trimer (3-0) and pentamer(3-2). These results can help us to obtain an insight into the aggregation mechanism of amyloid fibril. These methods can be used to study the stability of amyloid fibril from other short peptides.

  11. Serum amyloid A induces contrary immune responses via formyl peptide receptor-like 1 in human monocytes.

    PubMed

    Lee, Ha Young; Kim, Mi-Kyoung; Park, Kyoung Sun; Shin, Eun Ha; Jo, Seong Ho; Kim, Sang Doo; Jo, Eun Jin; Lee, Youl-Nam; Lee, Chuhee; Baek, Suk-Hwan; Bae, Yoe-Sik

    2006-07-01

    Although the level of serum amyloid A has been reported to be up-regulated during inflammatory response, the role of serum amyloid A on the regulation of inflammation and immune response has not been elucidated. We found that serum amyloid A stimulated the production of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10, which are proinflammatory and anti-inflammatory cytokines, respectively, in human monocytes. Low concentrations of serum amyloid A stimulated TNF-alpha production with maximal activity at 6 h after stimulation, whereas high concentrations of serum amyloid A stimulated IL-10 production with maximal activity at 12 h. The activations of the two cytokines by serum amyloid A occurred at both the transcription and translational levels. Signaling events induced by serum amyloid A included the activation of two mitogen-activated protein kinases (extracellular signal-regulated kinase and p38 kinase), which were found to be required for TNF-alpha and IL-10 production, respectively. The stimulation of formyl peptide receptor-like-1-expressing RBL-2H3 cells, but not of vector-expressing RBL-2H3 cells with serum amyloid A, induced mitogen-activated protein kinases activation and the accumulation of the RNAs of these two cytokines. Together, our findings suggest that serum amyloid A modulates contrary immune responses via formyl peptide receptor-like 1, by inducing TNF-alpha or IL-10, and demonstrate that extracellular signal-regulated kinase and p38 kinase play counteracting roles in this process.

  12. All-atom molecular dynamics studies of the full-length β-amyloid peptides

    NASA Astrophysics Data System (ADS)

    Luttmann, Edgar; Fels, Gregor

    2006-03-01

    β-Amyloid peptides are believed to play an essential role in Alzheimer's disease (AD), due to their sedimentation in the form of β-amyloid aggregates in the brain of AD-patients, and the in vitro neurotoxicity of oligomeric aggregates. The monomeric peptides come in different lengths of 39-43 residues, of which the 42 alloform seems to be most strongly associated with AD-symptoms. Structural information on these peptides to date comes from NMR studies in acidic solutions, organic solvents, or on shorter fragments of the peptide. In addition X-ray and solid-state NMR investigations of amyloid fibrils yield insight into the structure of the final aggregate and therefore define the endpoint of any conformational change of an Aβ-monomer along the aggregation process. The conformational changes necessary to connect the experimentally known conformations are not yet understood and this process is an active field of research. In this paper, we report results from all-atom molecular dynamics simulations based on experimental data from four different peptides of 40 amino acids and two peptides consisting of 42 amino acids. The simulations allow for the analysis of intramolecular interactions and the role of structural features. In particular, they show the appearance of β-turn in the region between amino acid 21 and 33, forming a hook-like shape as it is known to exist in the fibrillar Aβ-structures. This folding does not depend on the formation of a salt bridge between Asp-23 and Lys-28 but requires the Aβ(1-42) as such structure was not observed in the shorter system Aβ(1-40).

  13. Amyloidogenic amyloid-β-peptide variants induce microbial agglutination and exert antimicrobial activity.

    PubMed

    Spitzer, Philipp; Condic, Mateja; Herrmann, Martin; Oberstein, Timo Jan; Scharin-Mehlmann, Marina; Gilbert, Daniel F; Friedrich, Oliver; Grömer, Teja; Kornhuber, Johannes; Lang, Roland; Maler, Juan Manuel

    2016-01-01

    Amyloid-β (Aβ) peptides are the main components of the plaques found in the brains of patients with Alzheimer's disease. However, Aβ peptides are also detectable in secretory compartments and peripheral blood contains a complex mixture of more than 40 different modified and/or N- and C-terminally truncated Aβ peptides. Recently, anti-infective properties of Aβ peptides have been reported. Here, we investigated the interaction of Aβ peptides of different lengths with various bacterial strains and the yeast Candida albicans. The amyloidogenic peptides Aβ1-42, Aβ2-42, and Aβ3p-42 but not the non-amyloidogenic peptides Aβ1-40 and Aβ2-40 bound to microbial surfaces. As observed by immunocytochemistry, scanning electron microscopy and Gram staining, treatment of several bacterial strains and Candida albicans with Aβ peptide variants ending at position 42 (Aβx-42) caused the formation of large agglutinates. These aggregates were not detected after incubation with Aβx-40. Furthermore, Aβx-42 exerted an antimicrobial activity on all tested pathogens, killing up to 80% of microorganisms within 6 h. Aβ1-40 only had a moderate antimicrobial activity against C. albicans. Agglutination of Aβ1-42 was accelerated in the presence of microorganisms. These data demonstrate that the amyloidogenic Aβx-42 variants have antimicrobial activity and may therefore act as antimicrobial peptides in the immune system. PMID:27624303

  14. Amyloidogenic amyloid-β-peptide variants induce microbial agglutination and exert antimicrobial activity

    PubMed Central

    Spitzer, Philipp; Condic, Mateja; Herrmann, Martin; Oberstein, Timo Jan; Scharin-Mehlmann, Marina; Gilbert, Daniel F.; Friedrich, Oliver; Grömer, Teja; Kornhuber, Johannes; Lang, Roland; Maler, Juan Manuel

    2016-01-01

    Amyloid-β (Aβ) peptides are the main components of the plaques found in the brains of patients with Alzheimer’s disease. However, Aβ peptides are also detectable in secretory compartments and peripheral blood contains a complex mixture of more than 40 different modified and/or N- and C-terminally truncated Aβ peptides. Recently, anti-infective properties of Aβ peptides have been reported. Here, we investigated the interaction of Aβ peptides of different lengths with various bacterial strains and the yeast Candida albicans. The amyloidogenic peptides Aβ1-42, Aβ2-42, and Aβ3p-42 but not the non-amyloidogenic peptides Aβ1-40 and Aβ2-40 bound to microbial surfaces. As observed by immunocytochemistry, scanning electron microscopy and Gram staining, treatment of several bacterial strains and Candida albicans with Aβ peptide variants ending at position 42 (Aβx-42) caused the formation of large agglutinates. These aggregates were not detected after incubation with Aβx-40. Furthermore, Aβx-42 exerted an antimicrobial activity on all tested pathogens, killing up to 80% of microorganisms within 6 h. Aβ1-40 only had a moderate antimicrobial activity against C. albicans. Agglutination of Aβ1-42 was accelerated in the presence of microorganisms. These data demonstrate that the amyloidogenic Aβx-42 variants have antimicrobial activity and may therefore act as antimicrobial peptides in the immune system. PMID:27624303

  15. Fe(2+) binding on amyloid β-peptide promotes aggregation.

    PubMed

    Boopathi, Subramaniam; Kolandaivel, Ponmalai

    2016-09-01

    The metal ions Zn(2+) , Cu(2+) , and Fe(2+) play a significant role in the aggregation mechanism of Aβ peptides. However, the nature of binding between metal and peptide has remained elusive; the detailed information on this from the experimental study is very difficult. Density functional theory (dft) (M06-2X/6-311++G (2df,2pd) +LANL2DZ) has employed to determine the force field resulting due to metal and histidine interaction. We performed 200 ns molecular dynamics (MD) simulation on Aβ1-42 -Zn(2+) , Aβ1-42 -Cu(2+) , and Aβ1-42 -Fe(2+) systems in explicit water with different combination of coordinating residues including the three Histidine residues in the N-terminal. The present investigation, the Aβ1-42 -Zn(2+) system possess three turn conformations separated by coil structure. Zn(2+) binding caused the loss of the helical structure of N-terminal residues which transformed into the S-shaped conformation. Zn(2+) has reduced the coil and increases the turn content of the peptide compared with experimental study. On the other hand, the Cu(2+) binds with peptide, β sheet formation is observed at the N-terminal residues of the peptide. Fe(2+) binding is to promote the formation of Glu22-Lys28 salt-bridge which stabilized the turn conformation in the Phe19-Gly25 residues, subsequently β sheets were observed at His13-Lys18 and Gly29-Gly37 residues. The turn conformation facilitates the β sheets are arranged in parallel by enhancing the hydrophobic contact between Gly25 and Met35, Lys16 and Met35, Leu17 and Leu34, Val18 and Leu34 residues. The Fe(2+) binding reduced the helix structure and increases the β sheet content in the peptide, which suggested, Fe(2+) promotes the oligomerization by enhancing the peptide-peptide interaction. Proteins 2016; 84:1257-1274. © 2016 Wiley Periodicals, Inc. PMID:27214008

  16. Fe(2+) binding on amyloid β-peptide promotes aggregation.

    PubMed

    Boopathi, Subramaniam; Kolandaivel, Ponmalai

    2016-09-01

    The metal ions Zn(2+) , Cu(2+) , and Fe(2+) play a significant role in the aggregation mechanism of Aβ peptides. However, the nature of binding between metal and peptide has remained elusive; the detailed information on this from the experimental study is very difficult. Density functional theory (dft) (M06-2X/6-311++G (2df,2pd) +LANL2DZ) has employed to determine the force field resulting due to metal and histidine interaction. We performed 200 ns molecular dynamics (MD) simulation on Aβ1-42 -Zn(2+) , Aβ1-42 -Cu(2+) , and Aβ1-42 -Fe(2+) systems in explicit water with different combination of coordinating residues including the three Histidine residues in the N-terminal. The present investigation, the Aβ1-42 -Zn(2+) system possess three turn conformations separated by coil structure. Zn(2+) binding caused the loss of the helical structure of N-terminal residues which transformed into the S-shaped conformation. Zn(2+) has reduced the coil and increases the turn content of the peptide compared with experimental study. On the other hand, the Cu(2+) binds with peptide, β sheet formation is observed at the N-terminal residues of the peptide. Fe(2+) binding is to promote the formation of Glu22-Lys28 salt-bridge which stabilized the turn conformation in the Phe19-Gly25 residues, subsequently β sheets were observed at His13-Lys18 and Gly29-Gly37 residues. The turn conformation facilitates the β sheets are arranged in parallel by enhancing the hydrophobic contact between Gly25 and Met35, Lys16 and Met35, Leu17 and Leu34, Val18 and Leu34 residues. The Fe(2+) binding reduced the helix structure and increases the β sheet content in the peptide, which suggested, Fe(2+) promotes the oligomerization by enhancing the peptide-peptide interaction. Proteins 2016; 84:1257-1274. © 2016 Wiley Periodicals, Inc.

  17. Local atomic structure and oxidation processes of Cu(I) binding site in amyloid beta peptide: XAS Study

    NASA Astrophysics Data System (ADS)

    Kremennaya, M. A.; Soldatov, M. A.; Stretsov, V. A.; Soldatov, A. V.

    2016-05-01

    There are two different motifs of X-ray absorption spectra for Cu(I) K-edge in amyloidpeptide which could be due to two different configurations of local Cu(I) environment. Two or three histidine ligands can coordinate copper ion in varying conformations. On the other hand, oxidation of amyloidpeptide could play an additional role in local copper environment. In order to explore the peculiarities of local atomic and electronic structure of Cu(I) binding sites in amyloidpeptide the x-ray absorption spectra were simulated for various Cu(I) environments including oxidized amyloid-β and compared with experimental data.

  18. Amyloid peptides derived from CsgA and FapC modify the viscoelastic properties of biofilm model matrices.

    PubMed

    Lembré, Pierre; Di Martino, Patrick; Vendrely, Charlotte

    2014-01-01

    The bacterial biofilm is a complex environment of cells, which secrete a matrix made of various components, mainly polysaccharides and proteins. An understanding of the precise role of these components in the stability and dynamics of biofilm architecture would be a great advantage for the improvement of anti-biofilm strategies. Here, artificial biofilm matrices made of polysaccharides and auto-assembled peptides were designed, and the influence of bacterial amyloid proteins on the mechanical properties of the biofilm matrix was studied. The model polysaccharides methylcellulose and alginate and peptides derived from the amyloid proteins curli and FapC found in biofilms of Enterobacteriaceae and Pseudomonas, respectively, were used. Rheological measurements showed that the amyloid peptides do not prevent the gelation of the polysaccharides but influence deformation of the matrices under shear stress and modify the gel elastic response. Hence the secretion of amyloids could be for the biofilm a way of adapting to environmental changes. PMID:24592895

  19. Inhibiting and reversing amyloidpeptide (1-40) fibril formation with gramicidin S and engineered analogues.

    PubMed

    Luo, Jinghui; Otero, José M; Yu, Chien-Hung; Wärmländer, Sebastian K T S; Gräslund, Astrid; Overhand, Mark; Abrahams, Jan Pieter

    2013-12-16

    In Alzheimer's disease, amyloid-β (Aβ) peptides aggregate into extracellular fibrillar deposits. Although these deposits may not be the prime cause of the neurodegeneration that characterizes this disease, inhibition or dissolution of amyloid fibril formation by Aβ peptides is likely to affect its development. ThT fluorescence measurements and AFM images showed that the natural antibiotic gramicidin S significantly inhibited Aβ amyloid formation in vitro and could dissolve amyloids that had formed in the absence of the antibiotic. In silico docking suggested that gramicidin S, a cyclic decapeptide that adopts a β-sheet conformation, binds to the Aβ peptide hairpin-stacked fibril through β-sheet interactions. This may explain why gramicidin S reduces fibril formation. Analogues of gramicidin S were also tested. An analogue with a potency that was four-times higher than that of the natural product was identified.

  20. The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's β-amyloid peptide fragment.

    PubMed

    Xie, Luogang; Luo, Yin; Lin, Dongdong; Xi, Wenhui; Yang, Xinju; Wei, Guanghong

    2014-08-21

    Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of β-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-β (Aβ) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene :  peptide molar ratio greater than 1 : 8) can dramatically prevent β-sheet formation of Aβ(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on Aβ(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the β-sheet formation of Aβ(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of β-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and Aβ(16-22) peptides significantly weaken the peptide-peptide interaction that is important for β-sheet formation, thus retarding Aβ(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of Aβ(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease.

  1. The Mechanism Underlying Amyloid Polymorphism is Opened for Alzheimer's Disease AmyloidPeptide.

    PubMed

    Selivanova, Olga M; Surin, Alexey K; Marchenkov, Victor V; Dzhus, Ulyana F; Grigorashvili, Elizaveta I; Suvorina, Mariya Yu; Glyakina, Anna V; Dovidchenko, Nikita V; Galzitskaya, Oxana V

    2016-09-01

    It has been demonstrated using Aβ40 and Aβ42 recombinant and synthetic peptides that their fibrils are formed of complete oligomer ring structures. Such ring structures have a diameter of about 8-9 nm, an oligomer height of about 2- 4 nm, and an internal diameter of the ring of about 3-4 nm. Oligomers associate in a fibril in such a way that they interact with each other, overlapping slightly. There are differences in the packing of oligomers in fibrils of recombinant and synthetic Aβ peptides. The principal difference is in the degree of orderliness of ring-like oligomers that leads to generation of morphologically different fibrils. Most ordered association of ring-like structured oligomers is observed for a recombinant Aβ40 peptide. Less ordered fibrils are observed with the synthetic Aβ42 peptide. Fragments of fibrils the most protected from the action of proteases have been determined by tandem mass spectrometry. It was shown that unlike Aβ40, fibrils of Aβ42 are more protected, showing less ordered organization compared to that of Aβ40 fibrils. Thus, the mass spectrometry data agree with the electron microscopy data and structural models presented here. PMID:27567850

  2. Analysis of amino-terminal variants of amyloidpeptides by capillary isoelectric focusing immunoassay.

    PubMed

    Haußmann, Ute; Jahn, Olaf; Linning, Philipp; Janßen, Christin; Liepold, Thomas; Portelius, Erik; Zetterberg, Henrik; Bauer, Chris; Schuchhardt, Johannes; Knölker, Hans-Joachim; Klafki, Hans; Wiltfang, Jens

    2013-09-01

    Here we present a novel assay for the separation and detection of amino-terminal amyloid-β (Aβ) peptide variants by capillary isoelectric focusing (CIEF) immunoassay. Specific amino-terminally truncated Aβ peptides appear to be generated by β-secretase (BACE1)-independent mechanisms and have previously been observed in cerebrospinal fluid (CSF) after BACE1 inhibitor treatment in an animal model. CIEF immunoassay sensitivity is sufficient to detect total Aβ in CSF without preconcentration. To analyze low-abundance amino-terminally truncated Aβ peptides from cell culture supernatants, we developed a CIEF-compatible immunoprecipitation protocol, allowing for selective elution of Aβ peptides with very low background. CIEF immunoassay and immunoprecipitation mass spectrometry analysis identified peptides starting at residue Arg(5) as the main amino-terminal Aβ variants produced in the presence of tripartite BACE1 inhibitor in our cell culture model. The CIEF immunoassay allows for robust relative quantification of Aβ peptide patterns in biological samples. To assess the future possibility of absolute quantification, we have prepared the Aβ peptides Aβ(x-10), Aβ(x-16), and Aβ(5-38(D23S)) by using solid phase peptide synthesis as internal standards for the CIEF immunoassay.

  3. A novel assay in vitro of human islet amyloid polypeptide amyloidogenesis and effects of insulin secretory vesicle peptides on amyloid formation.

    PubMed Central

    Kudva, Y C; Mueske, C; Butler, P C; Eberhardt, N L

    1998-01-01

    Human islet amyloid polypeptide (IAPP) is a 37-residue peptide that is co-secreted with insulin by the beta-cell and might be involved in the pathogenesis of non-insulin-dependent diabetes mellitus. We developed an improved assay in vitro based on the fluorescence of bound thioflavin T to study factors affecting amyloidogenesis. Monomeric IAPP formed amyloid fibrils, as detected by increased fluorescence and by electron microscopy. Fluorimetric analysis revealed that the initial rate of amyloid formation was: (1) proportional to the peptide monomer concentration, (2) maximal at pH 9.5, (3) maximal at 200 mMKCl, and (4) proportional to temperature from 4 to 37 degreesC. We found that 5-fold and 10-fold molar excesses of proinsulin inhibited fibril formation by 39% and 59% respectively. Insulin was somewhat more potent with 5-fold and 10-fold molar excesses inhibiting fibril formation by 69% and 73% respectively, whereas C-peptide had no effect at these concentrations. Thus at physiological ratios of IAPP to insulin, insulin and proinsulin, but not C-peptide, can retard amyloidogenesis. Because insulin resistance or hyperglycaemia increase the IAPP-to-insulin ratio, increased intracellular IAPP compared with insulin expression in genetically predisposed individuals might contribute to intracellular amyloid formation, beta-cell death and the genesis of non-insulin-dependent diabetes mellitus. PMID:9560308

  4. A peptide zipcode sufficient for anterograde transport within amyloid precursor protein

    PubMed Central

    Satpute-Krishnan, Prasanna; DeGiorgis, Joseph A.; Conley, Michael P.; Jang, Marcus; Bearer, Elaine L.

    2006-01-01

    Fast anterograde transport of membrane-bound organelles delivers molecules synthesized in the neuronal cell body outward to distant synapses. Identification of the molecular “zipcodes” on organelles that mediate attachment and activation of microtubule-based motors for this directed transport is a major area of inquiry. Here we identify a short peptide sequence (15 aa) from the cytoplasmic C terminus of amyloid precursor protein (APP-C) sufficient to mediate the anterograde transport of peptide-conjugated beads in the squid giant axon. APP-C beads travel at fast axonal transport rates (0.53 μm/s average velocity, 0.9 μm/s maximal velocity) whereas beads coupled to other peptides coinjected into the same axon remain stationary at the injection site. This transport appears physiologic, because it mimics behavior of endogenous squid organelles and of beads conjugated to C99, a polypeptide containing the full-length cytoplasmic domain of amyloid precursor protein (APP). Beads conjugated to APP lacking the APP-C domain are not transported. Coinjection of APP-C peptide reduces C99 bead motility by 75% and abolishes APP-C bead motility, suggesting that the soluble peptide competes with protein-conjugated beads for axoplasmic motor(s). The APP-C domain is conserved (13/15 aa) from squid to human, and peptides from either squid or human APP behave similarly. Thus, we have identified a conserved peptide zipcode sufficient to direct anterograde transport of exogenous cargo and suggest that one of APP's roles may be to recruit and activate axonal machinery for endogenous cargo transport. PMID:17062754

  5. “Clicked” Sugar–Curcumin Conjugate: Modulator of Amyloid-β and Tau Peptide Aggregation at Ultralow Concentrations

    PubMed Central

    2011-01-01

    The synthesis of a water/plasma soluble, noncytotoxic, “clicked” sugar-derivative of curcumin with amplified bioefficacy in modulating amyloid-β and tau peptide aggregation is presented. Curcumin inhibits amyloid-β and tau peptide aggregation at micromolar concentrations; the sugar–curcumin conjugate inhibits Aβ and tau peptide aggregation at concentrations as low as 8 nM and 0.1 nM, respectively. In comparison to curcumin, this conveniently synthesized Alzheimer’s drug candidate is a more powerful antioxidant. PMID:22860163

  6. "Clicked" sugar-curcumin conjugate: modulator of amyloid-β and tau peptide aggregation at ultralow concentrations.

    PubMed

    Dolai, Sukanta; Shi, Wei; Corbo, Christopher; Sun, Chong; Averick, Saadyah; Obeysekera, Dinali; Farid, Mina; Alonso, Alejandra; Banerjee, Probal; Raja, Krishnaswami

    2011-12-21

    The synthesis of a water/plasma soluble, noncytotoxic, "clicked" sugar-derivative of curcumin with amplified bioefficacy in modulating amyloid-β and tau peptide aggregation is presented. Curcumin inhibits amyloid-β and tau peptide aggregation at micromolar concentrations; the sugar-curcumin conjugate inhibits Aβ and tau peptide aggregation at concentrations as low as 8 nM and 0.1 nM, respectively. In comparison to curcumin, this conveniently synthesized Alzheimer's drug candidate is a more powerful antioxidant. PMID:22860163

  7. Structure, orientation, and surface interaction of Alzheimer amyloidpeptides on the graphite.

    PubMed

    Yu, Xiang; Wang, Qiuming; Lin, Yinan; Zhao, Jun; Zhao, Chao; Zheng, Jie

    2012-04-24

    The misfolding and aggregation of amyloid-β (Aβ) peptides into amyloid fibrils in solution and on the cell membrane has been linked to the pathogenesis of Alzheimer's disease. Although it is well-known that the presence of different surfaces can accelerate the aggregation of Aβ peptides into fibrils, surface-induced conformation, orientation, aggregation, and adsorption of Aβ peptides have not been well understood at the atomic level. Here, we perform all-atom explicit-water molecular dynamics (MD) simulations to study the orientation change, conformational dynamics, surface interaction of small Aβ aggregates with different sizes (monomer to tetramer), and conformations (α-helix and β-hairpin) upon adsorption on the graphite surface, in comparison with Aβ structures in bulk solution. Simulation results show that hydrophobic graphite induces the quick adsorption of Aβ peptides regardless of their initial conformations and sizes. Upon the adsorption, Aβ prefers to adopt random structure for monomers and to remain β-rich-structure for small oligomers, but not helical structures. More importantly, due to the amphiphilic sequence of Aβ and the hydrophobic nature of graphite, hydrophobic C-terminal residues of higher-order Aβ oligomers appear to have preferential interactions with the graphite surface for facilitating Aβ fibril formation and fibril growth. In combination of atomic force microscopy (AFM) images and MD simulation results, a postulated mechanism is proposed to describe the structure and kinetics of Aβ aggregation from aqueous solution to the graphite surface, providing parallel insights into Aβ aggregation on biological cell membranes.

  8. Amyloid fibril formation of peptides derived from the C-terminus of CETP modulated by lipids

    SciTech Connect

    García-González, Victor; Mas-Oliva, Jaime

    2013-04-26

    Highlights: •The secondary structure of a C-terminal peptide derived from CETP was studied. •Lipids modulate secondary structure changes of a C-terminal peptide derived from CETP. •Lysophosphatidic acid maintains a functional α-helix and prevents fibril formation. •Transfer of lipids by CETP is related to the presence of an α-helix at its C-end. -- Abstract: Cholesteryl-ester transfer protein (CETP) is a plasmatic protein involved in neutral lipid transfer between lipoproteins. Focusing on the last 12 C-terminus residues we have previously shown that mutation D{sub 470}N promotes a conformational change towards a β-secondary structure. In turn, this modification leads to the formation of oligomers and fibrillar structures, which cause cytotoxic effects similar to the ones provoked by amyloid peptides. In this study, we evaluated the role of specific lipid arrangements on the structure of peptide helix-Z (D{sub 470}N) through the use of thioflavin T fluorescence, peptide bond absorbance, circular dichroism and electron microscopy. The results indicate that the use of micelles formed with lysophosphatidylcholine and lysophosphatidic acid (LPA) under neutral pH induce a conformational transition of peptide helix-Z containing a β-sheet conformation to a native α-helix structure, therefore avoiding the formation of amyloid fibrils. In contrast, incubation with phosphatidic acid does not change the profile for the β-sheet conformation. When the electrostatic charge at the surface of micelles or vesicles is regulated through the use of lipids such as phospholipid and LPA, minimal changes and the presence of β-structures were recorded. Mixtures with a positive net charge diminished the percentage of β-structure and the amount of amyloid fibrils. Our results suggest that the degree of solvation determined by the presence of a free hydroxyl group on lipids such as LPA is a key condition that can modulate the secondary structure and the consequent formation of

  9. Amyloid beta (Aβ) peptide modulators and other current treatment strategies for Alzheimer’s disease (AD)

    PubMed Central

    Lukiw, Walter J.

    2012-01-01

    Introduction Alzheimer’s disease (AD) is a common, progressive neurological disorder whose incidence is reaching epidemic proportions. The prevailing ‘amyloid cascade hypothesis’, which maintains that the aberrant proteolysis of beta-amyloid precursor protein (βAPP) into neurotoxic amyloid beta (Aβ)-peptides is central to the etiopathology of AD, continues to dominate pharmacological approaches to the clinical management of this insidious disorder. This review is a compilation and update on current pharmacological strategies designed to down-regulate Aβ42-peptide generation in an effort to ameliorate the tragedy of AD. Areas Covered This review utilized on-line data searches at various open online-access websites including the Alzheimer Association, Alzheimer Research Forum; individual drug company databases; the National Institutes of Health (NIH) Medline; Pharmaprojects database; Scopus; inter-University research communications and unpublished research data. Expert Opinion Aβ immunization-, anti-acetylcholinesterase-, β-secretase-, chelation-, γ-secretase-, N-methyl D-aspartate (NMDA) receptor antagonist-, statin-based and other strategies to modulate βAPP processing have dominated pharmacological approaches directed against AD-type neurodegenerative pathology. Cumulative clinical results of these efforts remain extremely disappointing, and have had little overall impact on the clinical management of AD. While a number of novel approaches are in consideration and development, to date there is still no effective treatment or cure for this expanding healthcare concern. PMID:22439907

  10. Measurement of beta-amyloid peptides in specific cells using a photo thin-film transistor

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Beom; Chae, Cheol-Joo; Shin, Hye-Rim; Song, Ki-Bong

    2012-01-01

    The existence of beta-amyloid [Aβ] peptides in the brain has been regarded as the most archetypal biomarker of Alzheimer's disease [AD]. Recently, an early clinical diagnosis has been considered a great importance in identifying people who are at high risk of AD. However, no microscale electronic sensing devices for the detection of Aβ peptides have been developed yet. In this study, we propose an effective method to evaluate a small quantity of Aβ peptides labeled with fluorescein isothiocyanate [FITC] using a photosensitive field-effect transistor [p-FET] with an on-chip single-layer optical filter. To accurately evaluate the quantity of Aβ peptides within the cells cultured on the p-FET device, we measured the photocurrents which resulted from the FITC-conjugated Aβ peptides expressed from the cells and measured the number of photons of the fluorochrome in the cells using a photomultiplier tube. Thus, we evaluated the correlation between the generated photocurrents and the number of emitted photons. We also evaluated the correlation between the number of emitted photons and the amount of FITC by measuring the FITC volume using AFM. Finally, we estimated the quantity of Aβ peptides of the cells placed on the p-FET sensing area on the basis of the binding ratio between FITC molecules and Aβ peptides.

  11. β-Amyloid: the key peptide in the pathogenesis of Alzheimer’s disease

    PubMed Central

    Sun, Xiaojuan; Chen, Wei-Dong; Wang, Yan-Dong

    2015-01-01

    The amyloid β peptide (Aβ) is a critical initiator that triggers the progression of Alzheimer’s Disease (AD) via accumulation and aggregation, of which the process may be caused by Aβ overproduction or perturbation clearance. Aβ is generated from amyloid precursor protein through sequential cleavage of β- and γ-secretases while Aβ removal is dependent on the proteolysis and lysosome degradation system. Here, we overviewed the biogenesis and toxicity of Aβ as well as the regulation of Aβ production and clearance. Moreover, we also summarized the animal models correlated with Aβ that are essential in AD research. In addition, we discussed current immunotherapeutic approaches targeting Aβ to give some clues for exploring the more potentially efficient drugs for treatment of AD. PMID:26483691

  12. Hydrodynamic effects on β-amyloid (16-22) peptide aggregation

    NASA Astrophysics Data System (ADS)

    Chiricotto, Mara; Melchionna, Simone; Derreumaux, Philippe; Sterpone, Fabio

    2016-07-01

    Computer simulations based on simplified representations are routinely used to explore the early steps of amyloid aggregation. However, when protein models with implicit solvent are employed, these simulations miss the effect of solvent induced correlations on the aggregation kinetics and lifetimes of metastable states. In this work, we apply the multi-scale Lattice Boltzmann Molecular Dynamics technique (LBMD) to investigate the initial aggregation phases of the amyloid Aβ16-22 peptide. LBMD includes naturally hydrodynamic interactions (HIs) via a kinetic on-lattice representation of the fluid kinetics. The peptides are represented by the flexible OPEP coarse-grained force field. First, we have tuned the essential parameters that control the coupling between the molecular and fluid evolutions in order to reproduce the experimental diffusivity of elementary species. The method is then deployed to investigate the effect of HIs on the aggregation of 100 and 1000 Aβ16-22 peptides. We show that HIs clearly impact the aggregation process and the fluctuations of the oligomer sizes by favouring the fusion and exchange dynamics of oligomers between aggregates. HIs also guide the growth of the leading largest cluster. For the 100 Aβ16-22 peptide system, the simulation of ˜300 ns allowed us to observe the transition from ellipsoidal assemblies to an elongated and slightly twisted aggregate involving almost the totality of the peptides. For the 1000 Aβ16-22 peptides, a system of unprecedented size at quasi-atomistic resolution, we were able to explore a branched disordered fibril-like structure that has never been described by other computer simulations, but has been observed experimentally.

  13. Hydrodynamic effects on β-amyloid (16-22) peptide aggregation.

    PubMed

    Chiricotto, Mara; Melchionna, Simone; Derreumaux, Philippe; Sterpone, Fabio

    2016-07-21

    Computer simulations based on simplified representations are routinely used to explore the early steps of amyloid aggregation. However, when protein models with implicit solvent are employed, these simulations miss the effect of solvent induced correlations on the aggregation kinetics and lifetimes of metastable states. In this work, we apply the multi-scale Lattice Boltzmann Molecular Dynamics technique (LBMD) to investigate the initial aggregation phases of the amyloid Aβ16-22 peptide. LBMD includes naturally hydrodynamic interactions (HIs) via a kinetic on-lattice representation of the fluid kinetics. The peptides are represented by the flexible OPEP coarse-grained force field. First, we have tuned the essential parameters that control the coupling between the molecular and fluid evolutions in order to reproduce the experimental diffusivity of elementary species. The method is then deployed to investigate the effect of HIs on the aggregation of 100 and 1000 Aβ16-22 peptides. We show that HIs clearly impact the aggregation process and the fluctuations of the oligomer sizes by favouring the fusion and exchange dynamics of oligomers between aggregates. HIs also guide the growth of the leading largest cluster. For the 100 Aβ16-22 peptide system, the simulation of ∼300 ns allowed us to observe the transition from ellipsoidal assemblies to an elongated and slightly twisted aggregate involving almost the totality of the peptides. For the 1000 Aβ16-22 peptides, a system of unprecedented size at quasi-atomistic resolution, we were able to explore a branched disordered fibril-like structure that has never been described by other computer simulations, but has been observed experimentally. PMID:27448906

  14. Hydrodynamic effects on β-amyloid (16-22) peptide aggregation.

    PubMed

    Chiricotto, Mara; Melchionna, Simone; Derreumaux, Philippe; Sterpone, Fabio

    2016-07-21

    Computer simulations based on simplified representations are routinely used to explore the early steps of amyloid aggregation. However, when protein models with implicit solvent are employed, these simulations miss the effect of solvent induced correlations on the aggregation kinetics and lifetimes of metastable states. In this work, we apply the multi-scale Lattice Boltzmann Molecular Dynamics technique (LBMD) to investigate the initial aggregation phases of the amyloid Aβ16-22 peptide. LBMD includes naturally hydrodynamic interactions (HIs) via a kinetic on-lattice representation of the fluid kinetics. The peptides are represented by the flexible OPEP coarse-grained force field. First, we have tuned the essential parameters that control the coupling between the molecular and fluid evolutions in order to reproduce the experimental diffusivity of elementary species. The method is then deployed to investigate the effect of HIs on the aggregation of 100 and 1000 Aβ16-22 peptides. We show that HIs clearly impact the aggregation process and the fluctuations of the oligomer sizes by favouring the fusion and exchange dynamics of oligomers between aggregates. HIs also guide the growth of the leading largest cluster. For the 100 Aβ16-22 peptide system, the simulation of ∼300 ns allowed us to observe the transition from ellipsoidal assemblies to an elongated and slightly twisted aggregate involving almost the totality of the peptides. For the 1000 Aβ16-22 peptides, a system of unprecedented size at quasi-atomistic resolution, we were able to explore a branched disordered fibril-like structure that has never been described by other computer simulations, but has been observed experimentally.

  15. Bexarotene Blocks Calcium-Permeable Ion Channels Formed by Neurotoxic Alzheimer’s β-Amyloid Peptides

    PubMed Central

    2014-01-01

    The anticancer drug bexarotene has been shown to restore cognitive functions in animal models of Alzheimer’s disease, but its exact mechanism of action remains elusive. In the present report, we have used a combination of molecular, physicochemical, and cellular approaches to elucidate the mechanisms underlying the anti-Alzheimer properties of bexarotene in neural cells. First of all, we noticed that bexarotene shares a structural analogy with cholesterol. We showed that cholesterol and bexarotene compete for the same binding site in the C-terminal region of Alzheimer’s β-amyloid peptide 1–42 (Aβ1–42). This common bexarotene/cholesterol binding domain was characterized as a linear motif encompassing amino acid residues 25–35 of Aβ1–42. Because cholesterol is involved in the oligomerization of Alzheimer’s β-amyloid peptides into neurotoxic amyloid channels, we studied the capability of bexarotene to interfere with this process. We showed that nanomolar concentrations of bexarotene efficiently prevented the cholesterol-dependent increase of calcium fluxes induced by β-amyloid peptides Aβ1–42 and Aβ25–35 in SH-SY5Y cells, suggesting a direct effect of the drug on amyloid channel formation. Molecular dynamics simulations gave structural insights into the role of cholesterol in amyloid channel formation and explained the inhibitory effect of bexarotene. Because it is the first drug that can both inhibit the binding of cholesterol to β-amyloid peptides and prevent calcium-permeable amyloid pore formation in the plasma membrane of neural cells, bexarotene might be considered as the prototype of a new class of anti-Alzheimer compounds. The experimental approach developed herein can be used as a screening strategy to identify such compounds. PMID:24383913

  16. In vitro fibrillization of Alzheimer's amyloidpeptide (1-42)

    NASA Astrophysics Data System (ADS)

    Tiiman, Ann; Krishtal, Jekaterina; Palumaa, Peep; Tõugu, Vello

    2015-09-01

    The amyloid deposition in the form of extracellular fibrillar aggregates of amyloid-β (Aβ) peptide is a critical pathological event in Alzheimer's disease. Here, we report a systematic investigation of the effects of environmental factors on the kinetics of Aβ fibrillization in vitro. The effects of Aβ42 peptide concentration, temperature, pH, added solvents and the ratio of Aβ40 and Aβ42 on the peptide fibrillization under agitated conditions was studied. The analysis show that the rate of fibril growth by monomer addition is not limited by diffusion but by rearrangement in the monomer structure, which is enhanced by low concentrations of fluorinated alcohols and characterized by the activation energy of 12 kcal/mol. Fibrillization rate decreases at pH values below 7.0 where simultaneous protonation of His 13 and 14 inhibits fibril formation. The lag period for Aβ42 was only twofold shorter and the fibril growth rate twofold faster than those of Aβ40. Lag period was shortened and the fibrillization rate was increased only at 90% content of Aβ42.

  17. Indexing amyloid peptide diffraction from serial femtosecond crystallography: new algorithms for sparse patterns

    SciTech Connect

    Brewster, Aaron S.; Sawaya, Michael R.; Rodriguez, Jose; Hattne, Johan; Echols, Nathaniel; McFarlane, Heather T.; Cascio, Duilio; Adams, Paul D.; Eisenberg, David S.; Sauter, Nicholas K.

    2015-02-01

    Special methods are required to interpret sparse diffraction patterns collected from peptide crystals at X-ray free-electron lasers. Bragg spots can be indexed from composite-image powder rings, with crystal orientations then deduced from a very limited number of spot positions. Still diffraction patterns from peptide nanocrystals with small unit cells are challenging to index using conventional methods owing to the limited number of spots and the lack of crystal orientation information for individual images. New indexing algorithms have been developed as part of the Computational Crystallography Toolbox (cctbx) to overcome these challenges. Accurate unit-cell information derived from an aggregate data set from thousands of diffraction patterns can be used to determine a crystal orientation matrix for individual images with as few as five reflections. These algorithms are potentially applicable not only to amyloid peptides but also to any set of diffraction patterns with sparse properties, such as low-resolution virus structures or high-throughput screening of still images captured by raster-scanning at synchrotron sources. As a proof of concept for this technique, successful integration of X-ray free-electron laser (XFEL) data to 2.5 Å resolution for the amyloid segment GNNQQNY from the Sup35 yeast prion is presented.

  18. Proteolytically Inactive Insulin-Degrading Enzyme Inhibits Amyloid Formation Yielding Non-Neurotoxic Aβ Peptide Aggregates

    PubMed Central

    de Tullio, Matias B.; Castelletto, Valeria; Hamley, Ian W.; Martino Adami, Pamela V.; Morelli, Laura; Castaño, Eduardo M.

    2013-01-01

    Insulin-degrading enzyme (IDE) is a neutral Zn2+ peptidase that degrades short peptides based on substrate conformation, size and charge. Some of these substrates, including amyloid β (Aβ) are capable of self-assembling into cytotoxic oligomers. Based on IDE recognition mechanism and our previous report of the formation of a stable complex between IDE and intact Aβ in vitro and in vivo, we analyzed the possibility of a chaperone-like function of IDE. A proteolytically inactive recombinant IDE with Glu111 replaced by Gln (IDEQ) was used. IDEQ blocked the amyloidogenic pathway of Aβ yielding non-fibrillar structures as assessed by electron microscopy. Measurements of the kinetics of Aβ aggregation by light scattering showed that 1) IDEQ effect was promoted by ATP independent of its hydrolysis, 2) end products of Aβ-IDEQ co-incubation were incapable of “seeding” the assembly of monomeric Aβ and 3) IDEQ was ineffective in reversing Aβ aggregation. Moreover, Aβ aggregates formed in the presence of IDEQ were non-neurotoxic. IDEQ had no conformational effects upon insulin (a non-amyloidogenic protein under physiological conditions) and did not disturb insulin receptor activation in cultured cells. Our results suggest that IDE has a chaperone-like activity upon amyloid-forming peptides. It remains to be explored whether other highly conserved metallopeptidases have a dual protease-chaperone function to prevent the formation of toxic peptide oligomers from bacteria to mammals. PMID:23593132

  19. Catalytic antibodies to amyloid β peptide in defense against Alzheimer disease

    PubMed Central

    Taguchi, Hiroaki; Planque, Stephanie; Nishiyama, Yasuhiro; Szabo, Paul; Weksler, Marc E.; Friedland, Robert P.; Paul, Sudhir

    2008-01-01

    Immunoglobulins (Igs) that bind amyloid β peptide (Aβ) are under clinical trials for immunotherapy of Alzheimer disease (AD). We have identified IgMs and recombinant Ig fragments that hydrolyze Aβ. Hydrolysis of peripheral Aβ by the IgMs may induce increased Aβ release from the brain. The catalytic IgMs are increased in AD patients, presumably reflecting a protective autoimmune response. Reduced Aβ aggregation and neurotoxicity attributable to the catalytic function were evident. These findings provide a foundation for development of catalytic Igs for AD immunotherapy. PMID:18486927

  20. Amyloidpeptide structure in aqueous solution varies with fragment size

    NASA Astrophysics Data System (ADS)

    Wise-Scira, Olivia; Xu, Liang; Kitahara, Taizo; Perry, George; Coskuner, Orkid

    2011-11-01

    Various fragment sizes of the amyloid-β (Aβ) peptide have been utilized to mimic the properties of the full-length Aβ peptide in solution. Among these smaller fragments, Aβ16 and Aβ28 have been investigated extensively. In this work, we report the structural and thermodynamic properties of the Aβ16, Aβ28, and Aβ42 peptides in an aqueous solution environment. We performed replica exchange molecular dynamics simulations along with thermodynamic calculations for investigating the conformational free energies, secondary and tertiary structures of the Aβ16, Aβ28, and Aβ42 peptides. The results show that the thermodynamic properties vary from each other for these peptides. Furthermore, the secondary structures in the Asp1-Lys16 and Asp1-Lys28 regions of Aβ42 cannot be completely captured by the Aβ16 and Aβ28 fragments. For example, the β-sheet structures in the N-terminal region of Aβ16 and Aβ28 are either not present or the abundance is significantly decreased in Aβ42. The α-helix and β-sheet abundances in Aβ28 and Aβ42 show trends - to some extent - with the potential of mean forces but no such trend could be obtained for Aβ16. Interestingly, Arg5 forms salt bridges with large abundances in all three peptides. The formation of a salt bridge between Asp23-Lys28 is more preferred over the Glu22-Lys28 salt bridge in Aβ28 but this trend is vice versa for Aβ42. This study shows that the Asp1-Lys16 and Asp1-Lys28 regions of the full length Aβ42 peptide cannot be completely mimicked by studying the Aβ16 and Aβ28 peptides.

  1. Zinc-induced interaction of the metal-binding domain of amyloidpeptide with DNA.

    PubMed

    Khmeleva, Svetlana A; Mezentsev, Yuri V; Kozin, Sergey A; Tsvetkov, Philipp O; Ivanov, Alexis S; Bodoev, Nikolay V; Makarov, Alexander A; Radko, Sergey P

    2013-01-01

    The interaction of the 16-mer synthetic peptide (Aβ16), which represents the metal-binding domain of the amyloid-β with DNA, was studied employing the surface plasmon resonance technique. It has been shown that Aβ16 binds to the duplex DNA in the presence of zinc ions and thus the metal-binding domain can serve as a zinc-dependent DNA-binding site of the amyloid-β. The interaction of Aβ16 with DNA most probably depends on oligomerization of the peptide and is dominated by interaction with phosphates of the DNA backbone.

  2. Beta-amyloid peptides undergo regulated co-secretion with neuropeptide and catecholamine neurotransmitters.

    PubMed

    Toneff, Thomas; Funkelstein, Lydiane; Mosier, Charles; Abagyan, Armen; Ziegler, Michael; Hook, Vivian

    2013-08-01

    Beta-amyloid (Aβ) peptides are secreted from neurons, resulting in extracellular accumulation of Aβ and neurodegeneration of Alzheimer's disease. Because neuronal secretion is fundamental for the release of neurotransmitters, this study assessed the hypothesis that Aβ undergoes co-release with neurotransmitters. Model neuronal-like chromaffin cells were investigated, and results illustrate regulated, co-secretion of Aβ(1-40) and Aβ(1-42) with peptide neurotransmitters (galanin, enkephalin, and NPY) and catecholamine neurotransmitters (dopamine, norepinephrine, and epinephrine). Regulated secretion from chromaffin cells was stimulated by KCl depolarization and nicotine. Forskolin, stimulating cAMP, also induced co-secretion of Aβ peptides with peptide and catecholamine neurotransmitters. These data suggested the co-localization of Aβ with neurotransmitters in dense core secretory vesicles (DCSV) that store and secrete such chemical messengers. Indeed, Aβ was demonstrated to be present in DCSV with neuropeptide and catecholamine transmitters. Furthermore, the DCSV organelle contains APP and its processing proteases, β- and γ-secretases, that are necessary for production of Aβ. Thus, Aβ can be generated in neurotransmitter-containing DCSV. Human IMR32 neuroblastoma cells also displayed regulated secretion of Aβ(1-40) and Aβ(1-42) with the galanin neurotransmitter. These findings illustrate that Aβ peptides are present in neurotransmitter-containing DCSV, and undergo co-secretion with neuropeptide and catecholamine neurotransmitters that regulate brain functions.

  3. A Cocoa Peptide Protects Caenorhabditis elegans from Oxidative Stress and β-Amyloid Peptide Toxicity

    PubMed Central

    Martorell, Patricia; Bataller, Esther; Llopis, Silvia; Gonzalez, Núria; Álvarez, Beatriz; Montón, Fernando; Ortiz, Pepa; Ramón, Daniel; Genovés, Salvador

    2013-01-01

    Background Cocoa and cocoa-based products contain different compounds with beneficial properties for human health. Polyphenols are the most frequently studied, and display antioxidant properties. Moreover, protein content is a very interesting source of antioxidant bioactive peptides, which can be used therapeutically for the prevention of age-related diseases. Methodology/Principal Findings A bioactive peptide, 13L (DNYDNSAGKWWVT), was obtained from a hydrolyzed cocoa by-product by chromatography. The in vitro inhibition of prolyl endopeptidase (PEP) was used as screening method to select the suitable fraction for peptide identification. Functional analysis of 13L peptide was achieved using the transgenic Caenorhabditis elegans strain CL4176 expressing the human Aβ1–42 peptide as a pre-clinical in vivo model for Alzheimer's disease. Among the peptides isolated, peptide 13L (1 µg/mL) showed the highest antioxidant activity (P≤0.001) in the wild-type strain (N2). Furthermore, 13L produced a significant delay in body paralysis in strain CL4176, especially in the 24–47 h period after Aβ1–42 peptide induction (P≤0.0001). This observation is in accordance with the reduction of Aβ deposits in CL4176 by western blot. Finally, transcriptomic analysis in wild-type nematodes treated with 13L revealed modulation of the proteosomal and synaptic functions as the main metabolic targets of the peptide. Conclusions/Significance These findings suggest that the cocoa 13L peptide has antioxidant activity and may reduce Aβ deposition in a C. elegans model of Alzheimer's disease; and therefore has a putative therapeutic potential for prevention of age-related diseases. Further studies in murine models and humans will be essential to analyze the effectiveness of the 13L peptide in higher animals. PMID:23675471

  4. Charge-pairing mechanism of phosphorylation effect upon amyloid fibrillation of human tau core peptide.

    PubMed

    Inoue, Masafumi; Hirata, Akiyoshi; Tainaka, Kazuki; Morii, Takashi; Konno, Takashi

    2008-11-11

    Phosphorylation of a fibrillogenic protein, human tau, is believed to play crucial roles in the pathogenesis of Alzheimer's disease. For elucidating molecular mechanisms of the phosphorylation effect on tau fibrillation, we synthesized a peptide, VQIVY 310K (PHF6) and its phosphorylated derivative (PHF6pY). PHF6 is a partial peptide surrounding a plausible in vivo phosphorylation site Tyr310 and forms amyloid-type fibrils similar to those generated by full-length tau. Fibrillation of PHF6 and PHF6pY were studied by spectroscopic and microscopic methods, and the critical concentration of the fibrillation was determined for comparing the fibril stability. The results showed that the phosphorylation strongly influenced the fibrillation propensity of PHF6 by changing its dependency on pH and ionic strength. On the basis of the observations, we suggested that charged sites on the phosphate group and its electrostatic pairing with the neighboring charged residues were physical origins of the phosphorylation effect. To verify this charge-pairing mechanism, we conducted experiments using a series of PHF6 derivatives with non-native charge distributions. The electrostatic interaction in an intermolecular mode was also demonstrated by the system composed of two different peptide species, which found that fibrillation of nonphosphorylated PHF6 was drastically enhanced when a trace amount of phosphorylated PHF6 molecules coexisted. A simulation analysis utilizing crystal coordinates of the PHF6 fibril was also performed for interpreting the experimental results in a molecular level. The present study using the model peptide system gave us a microscopically insightful view on the roles of tau phosphorylation in amyloid-related diseases.

  5. Synthetic peptide homologous to. beta. protein from Alzheimer's disease forms amyloid-like fibrils in vitro

    SciTech Connect

    Kirschner, D.A.; Inouye, H.; Duffy, L.K.; Sinclair, A.; Lind, M.; Selkoe, D.J.

    1987-10-01

    Progressive amyloid deposition in senile plaques and cortical blood vessels may play a central role in the pathogenesis of Alzheimer's disease. The authors have used x-ray diffraction and electron microscopy to study the molecular organization and morphology of macromolecular assemblies formed by three synthetic peptides homologous to ..beta.. protein of brain amyloid: ..beta..-(1-28), residues 1-28 of the ..beta.. protein; (Ala/sup 1 -/..beta..-(1-28), ..beta..-(1-28) with alanine substituted for lysine at position 16; and ..beta..-(18-28), residues 18-28 of the ..beta.. protein. ..beta..-(1-28) readily formed fibrils in vitro that were similar in ultrastructure to the in vivo amyloid and aggregated into large bundles resembling those of senile plaque cores. X-ray patterns from partially dried, oriented pellets showed a cross-..beta..-conformation. (Ala/sup 16/)..beta..-(1-28) formed ..beta..-pleated sheet assemblies that were dissimilar to in vivo fibrils. The width of the 10-A spacing indicated stacks of about six sheets. Thus, substitution of the uncharged alanine for the positively charged lysine in the ..beta..-strand region enhances the packing of the sheets and dramatically alters the type of macromolecular aggregate formed. BETA-(18-28) formed assemblies that had even a greater number of stacked sheets. The findings on these homologous synthetic assemblies help to define the specific sequence that is required to form Alzheimer's-type amyloid fibrils, thus providing an in vitro model of age-related cerebral amyloidogenesis.

  6. Synthetic peptide homologous to beta protein from Alzheimer disease forms amyloid-like fibrils in vitro.

    PubMed Central

    Kirschner, D A; Inouye, H; Duffy, L K; Sinclair, A; Lind, M; Selkoe, D J

    1987-01-01

    Progressive amyloid deposition in senile plaques and cortical blood vessels may play a central role in the pathogenesis of Alzheimer disease. We have used x-ray diffraction and electron microscopy to study the molecular organization and morphology of macromolecular assemblies formed by three synthetic peptides homologous to beta protein of brain amyloid: beta-(1-28), residues 1-28 of the beta protein; [Ala16]beta-(1-28), beta-(1-28) with alanine substituted for lysine at position 16; and beta-(18-28), residues 18-28 of the beta protein. beta-(1-28) readily formed fibrils in vitro that were similar in ultrastructure to the in vivo amyloid and aggregated into large bundles resembling those of senile plaque cores. X-ray patterns from partially dried, oriented pellets showed a cross-beta-conformation. A series of small-angle, equatorial maxima were consistent with a tubular fibril having a mean diameter of 86 A and a wall composed of pairs of cross-beta-pleated sheets. The data may also be consistent with pairs of cross-beta-sheets that are centered 71-A apart. [Ala16]beta-(1-28) formed beta-pleated sheet assemblies that were dissimilar to in vivo fibrils. The width of the 10-A spacing indicated stacks of about six sheets. Thus, substitution of the uncharged alanine for the positively charged lysine in the beta-strand region enhances the packing of the sheets and dramatically alters the type of macromolecular aggregate formed. beta-(18-28) formed assemblies that had even a greater number of stacked sheets, approximately equal to 24 per diffracting domain as indicated by the sharp intersheet reflection. Our findings on these homologous synthetic assemblies help to define the specific sequence that is required to form Alzheimer-type amyloid fibrils, thus providing an in vitro model of age-related cerebral amyloidogenesis. Images PMID:3477820

  7. Interaction with amyloid beta peptide compromises the lipid binding function of apolipoprotein E.

    PubMed

    Tamamizu-Kato, Shiori; Cohen, Jenny K; Drake, Carolyn B; Kosaraju, Malathi G; Drury, Jessica; Narayanaswami, Vasanthy

    2008-05-01

    Apolipoprotein (apo) E is an exchangeable apolipoprotein that plays an integral role in cholesterol transport in the plasma and the brain. It is also associated with protein misfolding or amyloid proteopathy of the beta amyloid peptide (Abeta) in Alzheimer's disease (AD) and cerebral amyloid angiopathy. The C-terminal domain (CT) of apoE encompasses two types of amphipathic alpha helices: a class A helix (residues 216-266) and a class G* helix (residues 273-299). This domain also harbors high-affinity lipoprotein binding and apoE self-association sites that possibly overlap. The objective of this study is to examine if the neurotoxic oligomeric Abeta interacts with apoE CT and if this association affects the lipoprotein binding function of recombinant human apoE CT. Site-specific fluorescence labeling of single cysteine-containing apoE CT variants with donor probes were employed to identify the binding of Abeta bearing an acceptor probe by intermolecular fluorescence resonance energy-transfer analysis. A higher efficiency of energy transfer was noted with probes located in the class A helix than with those located in the class G* helix of apoE CT. In addition, incubation of apoE CT with Abeta severely impaired the lipid binding ability and the overall amount of lipid-associated apoE CT. However, when apoE CT is present in a lipid-bound state, Abeta appears to be localized within the lipid milieu of the lipoprotein particle and not associated with any specific segments of the protein. When our data are taken together, they suggest that Abeta association compromises the fundamental lipoprotein binding function of apoE, which may have implications not only in terms of amyloid buildup but also in terms of the accumulation of cholesterol at extracellular sites.

  8. Feasibility of β-Sheet Breaker Peptide-H102 Treatment for Alzheimer's Disease Based on β-Amyloid Hypothesis

    PubMed Central

    Tan, Yuan-zhen; Sun, Feng-xian; Song, Ming; Zhao, Juan; Ma, Zhi-hong; Li, Mei; Zheng, Kai-jun; Xu, Shu-mei

    2014-01-01

    β-amyloid hypothesis is the predominant hypothesis in the study of pathogenesis of Alzheimer's disease. This hypothesis claims that aggregation and neurotoxic effects of amyloid β (Aβ) is the common pathway in a variety of etiological factors for Alzheimer's disease. Aβ peptide derives from amyloid precursor protein (APP). β-sheet breaker peptides can directly prevent and reverse protein misfolding and aggregation in conformational disorders. Based on the stereochemical structure of Aβ1-42 and aggregation character, we had designed a series of β-sheet breaker peptides in our previous work and screened out a 10-residue peptide β-sheet breaker peptide, H102. We evaluated the effects of H102 on expression of P-tau, several associated proteins, inflammatory factors and apoptosis factors, and examined the cognitive ability of APP transgenic mice by behavioral test. This study aims to validate the β-amyloid hypothesis and provide an experimental evidence for the feasibility of H102 treatment for Alzheimer's disease. PMID:25372040

  9. Patterning nanofibrils through the templated growth of multiple modified amyloid peptides.

    PubMed

    Sakai, Hiroki; Watanabe, Ken; Kudoh, Fuki; Kamada, Rui; Chuman, Yoshiro; Sakaguchi, Kazuyasu

    2016-01-01

    There has been considerable interest in the patterning of functionalized nanowires because of the potential applications of these materials to the construction of nanodevices. A variety of biomolecular building blocks containing amyloid peptides have been used to functionalize nanowires. However, the patterning of self-assembled nanowires can be challenging because of the difficulties associated with controlling the self-assembly of these functionalized building blocks. Herein, we present a versatile approach for the patterning of nanowires based on the combination of templated fibril growth with a versatile functionalization method using our structure-controllable amyloid peptides (SCAPs). Using this approach, we have succeeded in the formation of multi-type nanowires with tandem domain structures in high yields. Given that the mixing-SCAP method can lead to the formation of tandem fibrils, it is noteworthy that our method allowed us to control the initiation of fibril formation from the gold nanoparticles, which were attached to a short fibril as initiation points. This approach could be used to prepare a wide variety of fibril patterns, and therefore holds great potential for the development of novel self-assembled nanodevices. PMID:27559011

  10. Effect of osmolytes on the conformation and aggregation of some amyloid peptides: CD spectroscopic data.

    PubMed

    Inayathullah, Mohammed; Rajadas, Jayakumar

    2016-06-01

    Protein misfolding and aggregation are responsible for a large number of diseases called protein conformational diseases or disorders that include Alzheimer׳s disease, Huntington׳s diseases, Prion related encephalopathies and type-II diabetes (http://dx.doi.org/10.1038/35041139) (Kopito and Ron, 2000) [1]. A variety of studies have shown that some small organic molecules, known as osmolytes have the ability to stabilize native conformation of proteins and prevent misfolding and aggregation (http://www.la-press.com/article.php?article_id=447) (Zhao et al., 2008) [2]. It has been shown that certain short segment or fragment of respective proteins can also form amyloids, and the segments also promote the aggregation in the full-length protein (http://dx.doi.org/10.2174/0929867023369187) (Gazit, 2002) [3]. This article presents circular dichroism spectroscopic data on conformational analysis and effect of osmolytes on Aβ peptide fragments, different lengths of polyglutamine peptide and the amyloidogenic segment of islet amyloid polypeptide. PMID:27222868

  11. Patterning nanofibrils through the templated growth of multiple modified amyloid peptides

    NASA Astrophysics Data System (ADS)

    Sakai, Hiroki; Watanabe, Ken; Kudoh, Fuki; Kamada, Rui; Chuman, Yoshiro; Sakaguchi, Kazuyasu

    2016-08-01

    There has been considerable interest in the patterning of functionalized nanowires because of the potential applications of these materials to the construction of nanodevices. A variety of biomolecular building blocks containing amyloid peptides have been used to functionalize nanowires. However, the patterning of self-assembled nanowires can be challenging because of the difficulties associated with controlling the self-assembly of these functionalized building blocks. Herein, we present a versatile approach for the patterning of nanowires based on the combination of templated fibril growth with a versatile functionalization method using our structure-controllable amyloid peptides (SCAPs). Using this approach, we have succeeded in the formation of multi-type nanowires with tandem domain structures in high yields. Given that the mixing-SCAP method can lead to the formation of tandem fibrils, it is noteworthy that our method allowed us to control the initiation of fibril formation from the gold nanoparticles, which were attached to a short fibril as initiation points. This approach could be used to prepare a wide variety of fibril patterns, and therefore holds great potential for the development of novel self-assembled nanodevices.

  12. Indexing amyloid peptide diffraction from serial femtosecond crystallography: New algorithms for sparse patterns

    DOE PAGESBeta

    Brewster, Aaron S.; Sawaya, Michael R.; Rodriguez, Jose; Hattne, Johan; Echols, Nathaniel; McFarlane, Heather T.; Cascio, Duilio; Adams, Paul D.; Eisenberg, David S.; Sauter, Nicholas K.

    2015-01-23

    Still diffraction patterns from peptide nanocrystals with small unit cells are challenging to index using conventional methods owing to the limited number of spots and the lack of crystal orientation information for individual images. New indexing algorithms have been developed as part of theComputational Crystallography Toolbox(cctbx) to overcome these challenges. Accurate unit-cell information derived from an aggregate data set from thousands of diffraction patterns can be used to determine a crystal orientation matrix for individual images with as few as five reflections. These algorithms are potentially applicable not only to amyloid peptides but also to any set of diffraction patternsmore » with sparse properties, such as low-resolution virus structures or high-throughput screening of still images captured by raster-scanning at synchrotron sources. As a proof of concept for this technique, successful integration of X-ray free-electron laser (XFEL) data to 2.5 Å resolution for the amyloid segment GNNQQNY from the Sup35 yeast prion is presented.« less

  13. Indexing amyloid peptide diffraction from serial femtosecond crystallography: New algorithms for sparse patterns

    SciTech Connect

    Brewster, Aaron S.; Sawaya, Michael R.; Rodriguez, Jose; Hattne, Johan; Echols, Nathaniel; McFarlane, Heather T.; Cascio, Duilio; Adams, Paul D.; Eisenberg, David S.; Sauter, Nicholas K.

    2015-01-23

    Still diffraction patterns from peptide nanocrystals with small unit cells are challenging to index using conventional methods owing to the limited number of spots and the lack of crystal orientation information for individual images. New indexing algorithms have been developed as part of theComputational Crystallography Toolbox(cctbx) to overcome these challenges. Accurate unit-cell information derived from an aggregate data set from thousands of diffraction patterns can be used to determine a crystal orientation matrix for individual images with as few as five reflections. These algorithms are potentially applicable not only to amyloid peptides but also to any set of diffraction patterns with sparse properties, such as low-resolution virus structures or high-throughput screening of still images captured by raster-scanning at synchrotron sources. As a proof of concept for this technique, successful integration of X-ray free-electron laser (XFEL) data to 2.5 Å resolution for the amyloid segment GNNQQNY from the Sup35 yeast prion is presented.

  14. Indexing amyloid peptide diffraction from serial femtosecond crystallography: new algorithms for sparse patterns.

    PubMed

    Brewster, Aaron S; Sawaya, Michael R; Rodriguez, Jose; Hattne, Johan; Echols, Nathaniel; McFarlane, Heather T; Cascio, Duilio; Adams, Paul D; Eisenberg, David S; Sauter, Nicholas K

    2015-02-01

    Still diffraction patterns from peptide nanocrystals with small unit cells are challenging to index using conventional methods owing to the limited number of spots and the lack of crystal orientation information for individual images. New indexing algorithms have been developed as part of the Computational Crystallography Toolbox (cctbx) to overcome these challenges. Accurate unit-cell information derived from an aggregate data set from thousands of diffraction patterns can be used to determine a crystal orientation matrix for individual images with as few as five reflections. These algorithms are potentially applicable not only to amyloid peptides but also to any set of diffraction patterns with sparse properties, such as low-resolution virus structures or high-throughput screening of still images captured by raster-scanning at synchrotron sources. As a proof of concept for this technique, successful integration of X-ray free-electron laser (XFEL) data to 2.5 Å resolution for the amyloid segment GNNQQNY from the Sup35 yeast prion is presented.

  15. Patterning nanofibrils through the templated growth of multiple modified amyloid peptides

    PubMed Central

    Sakai, Hiroki; Watanabe, Ken; Kudoh, Fuki; Kamada, Rui; Chuman, Yoshiro; Sakaguchi, Kazuyasu

    2016-01-01

    There has been considerable interest in the patterning of functionalized nanowires because of the potential applications of these materials to the construction of nanodevices. A variety of biomolecular building blocks containing amyloid peptides have been used to functionalize nanowires. However, the patterning of self-assembled nanowires can be challenging because of the difficulties associated with controlling the self-assembly of these functionalized building blocks. Herein, we present a versatile approach for the patterning of nanowires based on the combination of templated fibril growth with a versatile functionalization method using our structure-controllable amyloid peptides (SCAPs). Using this approach, we have succeeded in the formation of multi-type nanowires with tandem domain structures in high yields. Given that the mixing-SCAP method can lead to the formation of tandem fibrils, it is noteworthy that our method allowed us to control the initiation of fibril formation from the gold nanoparticles, which were attached to a short fibril as initiation points. This approach could be used to prepare a wide variety of fibril patterns, and therefore holds great potential for the development of novel self-assembled nanodevices. PMID:27559011

  16. Double-stranded DNA stereoselectively promotes aggregation of amyloid-like fibrils and generates peptide/DNA matrices.

    PubMed

    Yamada, Masanori; Hara, Sachiko; Yamada, Tetsuya; Katagiri, Fumihiko; Hozumi, Kentaro; Nomizu, Motoyoshi

    2014-11-01

    An amyloidogenic LAM-L peptide (AASIKVAVSADR, all-L configuration) derived from laminin promoted cell adhesion, neurite outgrowth, and angiogenesis. Here, we prepared novel matrices using double-stranded DNA and the LAM-L peptide. Double-stranded DNA promoted aggregation of amyloid-like fibrils and generated a LAM-L/DNA matrix through electrostatic interactions between the phosphate groups of DNA and the amino groups of LAM-L. This formation of peptide/DNA matrix depends on the Ile-Lys-Val-Ala-Val (IKVAV) sequence in the peptide, since LAM-RM peptide (AASVVIAKSADR), which is scrambled peptide of LAM-L, did not form a matrix with DNA. Further, LAM-D (all-D configuration of LAM-L), which forms amyloid-like fibrils and promotes similar biological activities as LAM-L, did not form amyloid-like fibrils with DNA, suggesting that DNA selectively interacts with the L-configured peptide. Moreover, the LAM-L/DNA matrices showed stronger cell attachment activity compared with LAM-L alone, suggesting the LAM-L/DNA matrices have potential for use as a novel biomaterial in tissue engineering.

  17. Peripherally administered antibodies against amyloid beta-peptide enter the central nervous system and reduce pathology in a mouse model of Alzheimer disease.

    PubMed

    Bard, F; Cannon, C; Barbour, R; Burke, R L; Games, D; Grajeda, H; Guido, T; Hu, K; Huang, J; Johnson-Wood, K; Khan, K; Kholodenko, D; Lee, M; Lieberburg, I; Motter, R; Nguyen, M; Soriano, F; Vasquez, N; Weiss, K; Welch, B; Seubert, P; Schenk, D; Yednock, T

    2000-08-01

    One hallmark of Alzheimer disease is the accumulation of amyloid beta-peptide in the brain and its deposition as plaques. Mice transgenic for an amyloid beta precursor protein (APP) mini-gene driven by a platelet-derived (PD) growth factor promoter (PDAPP mice), which overexpress one of the disease-linked mutant forms of the human amyloid precursor protein, show many of the pathological features of Alzheimer disease, including extensive deposition of extracellular amyloid plaques, astrocytosis and neuritic dystrophy. Active immunization of PDAPP mice with human amyloid beta-peptide reduces plaque burden and its associated pathologies. Several hypotheses have been proposed regarding the mechanism of this response. Here we report that peripheral administration of antibodies against amyloid beta-peptide, was sufficient to reduce amyloid burden. Despite their relatively modest serum levels, the passively administered antibodies were able to enter the central nervous system, decorate plaques and induce clearance of preexisting amyloid. When examined in an ex vivo assay with sections of PDAPP or Alzheimer disease brain tissue, antibodies against amyloid beta-peptide triggered microglial cells to clear plaques through Fc receptor-mediated phagocytosis and subsequent peptide degradation. These results indicate that antibodies can cross the blood-brain barrier to act directly in the central nervous system and should be considered as a therapeutic approach for the treatment of Alzheimer disease and other neurological disorders. PMID:10932230

  18. Effect of agitation on the peptide fibrillization: Alzheimer's amyloidpeptide 1-42 but not amylin and insulin fibrils can grow under quiescent conditions.

    PubMed

    Tiiman, Ann; Noormägi, Andra; Friedemann, Merlin; Krishtal, Jekaterina; Palumaa, Peep; Tõugu, Vello

    2013-06-01

    Many peptides and proteins can form fibrillar aggregates in vitro, but only a limited number of them are forming pathological amyloid structures in vivo. We studied the fibrillization of four peptides--Alzheimer's amyloid-β (Aβ) 1-40 and 1-42, amylin and insulin. In all cases, intensive mechanical agitation of the solution initiated fast fibrillization. However, when the mixing was stopped during the fibril growth phase, the fibrillization of amylin and insulin was practically stopped, and the rate for Aβ40 substantially decreased, whereas the fibrillization of Aβ42 peptide continued to proceed with almost the same rate as in the agitated conditions. The reason for the different sensitivity of the in vitro fibrillization of these peptides towards agitation in the fibril growth phase remains elusive. PMID:23609985

  19. The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's β-amyloid peptide fragment

    NASA Astrophysics Data System (ADS)

    Xie, Luogang; Luo, Yin; Lin, Dongdong; Xi, Wenhui; Yang, Xinju; Wei, Guanghong

    2014-07-01

    Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of β-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-β (Aβ) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent β-sheet formation of Aβ(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on Aβ(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the β-sheet formation of Aβ(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of β-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and Aβ(16-22) peptides significantly weaken the peptide-peptide interaction that is important for β-sheet formation, thus retarding Aβ(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of Aβ(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease.Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of

  20. Iron and aluminum interaction with amyloid-beta peptides associated with Alzheimer’s disease

    SciTech Connect

    Drochioiu, Gabi; Ion, Laura; Murariu, Manuela; Habasescu, Laura

    2014-10-06

    An elevation in the concentration of heavy metal ions in Alzheimer’s disease (AD) brain has been demonstrated in many studies. Aβ precipitation and toxicity in AD brains seem to be caused by abnormal interactions with neocortical metal ions, especially iron, copper, zinc, and aluminum [1–3]. There is increasing evidence that iron and aluminum ions are involved in the mechanisms that underlie the neurodegenerative diseases [4,5]. However, evidence was brought to demonstrate that some Aβ fragments, at physiological pH, are not able to form binary complexes with Fe(III) ions of sufficient stability to compete with metal hydroxide precipitation [6]. On the contrary, multiple metal ions are known to interact with Aβ peptides [7]. Consequently, we investigated here the interaction of Fe(II/III) and Al(III) ions with some amyloidpeptides and fragments that results in peptide aggregation and fibrillation [8,9]. Infrared spectroscopy, atomic force microscopy, scanning electron microscopy, electrophoresis and mass spectrometry demonstrated conformational changes of peptides in the presence of such metals.

  1. Iron and aluminum interaction with amyloid-beta peptides associated with Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Drochioiu, Gabi; Murariu, Manuela; Ion, Laura; Habasescu, Laura

    2014-10-01

    An elevation in the concentration of heavy metal ions in Alzheimer's disease (AD) brain has been demonstrated in many studies. Aβ precipitation and toxicity in AD brains seem to be caused by abnormal interactions with neocortical metal ions, especially iron, copper, zinc, and aluminum [1-3]. There is increasing evidence that iron and aluminum ions are involved in the mechanisms that underlie the neurodegenerative diseases [4,5]. However, evidence was brought to demonstrate that some Aβ fragments, at physiological pH, are not able to form binary complexes with Fe(III) ions of sufficient stability to compete with metal hydroxide precipitation [6]. On the contrary, multiple metal ions are known to interact with Aβ peptides [7]. Consequently, we investigated here the interaction of Fe(II/III) and Al(III) ions with some amyloidpeptides and fragments that results in peptide aggregation and fibrillation [8,9]. Infrared spectroscopy, atomic force microscopy, scanning electron microscopy, electrophoresis and mass spectrometry demonstrated conformational changes of peptides in the presence of such metals.

  2. Dynamic behavior of small heat shock protein inhibition on amyloid fibrillization of a small peptide (SSTSAA) from RNase A

    SciTech Connect

    Xi, Dong; Dong, Xiao; Deng, Wei; Lai, Luhua

    2011-12-09

    Highlights: Black-Right-Pointing-Pointer Mechanism of small heat shock protein inhibition on fibril formation was studied. Black-Right-Pointing-Pointer Peptide SSTSAA with modified ends was used for amyloid fibril formation. Black-Right-Pointing-Pointer FRET signal was followed during the fibril formation. Black-Right-Pointing-Pointer Mj HSP16.5 inhibits fibril formation when introduced in the lag phase. Black-Right-Pointing-Pointer Mj HSP16.5 slows down fibril formation when introduced after the lag phase. -- Abstract: Small heat shock proteins, a class of molecular chaperones, are reported to inhibit amyloid fibril formation in vitro, while the mechanism of inhibition remains unknown. In the present study, we investigated the mechanism by which Mj HSP16.5 inhibits amyloid fibril formation of a small peptide (SSTSAA) from RNase A. A model peptide (dansyl-SSTSAA-W) was designed by introducing a pair of fluorescence resonance energy transfer (FRET) probes into the peptide, allowing for the monitoring of fibril formation by this experimental model. Mj HSP16.5 completely inhibited fibril formation of the model peptide at a molar ratio of 1:120. The dynamic process of fibril formation, revealed by FRET, circular dichroism, and electron microscopy, showed a lag phase of about 2 h followed by a fast growth period. The effect of Mj HSP16.5 on amyloid fibril formation was investigated by adding it into the incubation solution during different growth phases. Adding Mj HSP16.5 to the incubating peptide before or during the lag phase completely inhibited fibril formation. However, introducing Mj HSP16.5 after the lag phase only slowed down the fibril formation process by adhering to the already formed fibrils. These findings provide insight into the inhibitory roles of small heat shock proteins on amyloid fibril formation at the molecular level.

  3. Effect of graphene oxide on the conformational transitions of amyloid beta peptide: A molecular dynamics simulation study.

    PubMed

    Baweja, Lokesh; Balamurugan, Kanagasabai; Subramanian, Venkatesan; Dhawan, Alok

    2015-09-01

    The interactions between nanomaterials (NMs) and amyloid proteins are central to the nanotechnology-based diagnostics and therapy in neurodegenerative disorders such as Alzheimer's and Parkinson's. Graphene oxide (GO) and its derivatives have shown to modulate the aggregation pattern of disease causing amyloid beta (Aβ) peptide. However, the mechanism is still not well understood. Using molecular dynamics simulations, the effect of graphene oxide (GO) and reduced graphene oxide (rGO) having carbon:oxygen ratio of 4:1 and 10:1, respectively, on the conformational transitions (alpha-helix to beta-sheet) and the dynamics of the peptide was investigated. GO and rGO decreased the beta-strand propensity of amino acid residues in Aβ. The peptide displayed different modes of adsorption on GO and rGO. The adsorption on GO was dominated by electrostatic interactions, whereas on rGO, both van der Waals and electrostatic interactions contributed in the adsorption of the peptide. Our study revealed that the slight increase in the hydrophobic patches on rGO made it more effective inhibitor of conformational transitions in the peptide. Alpha helix-beta sheet transition in Aβ peptide could be one of the plausible mechanism by which graphene oxide may inhibit amyloid fibrillation. PMID:26275931

  4. Effect of graphene oxide on the conformational transitions of amyloid beta peptide: A molecular dynamics simulation study.

    PubMed

    Baweja, Lokesh; Balamurugan, Kanagasabai; Subramanian, Venkatesan; Dhawan, Alok

    2015-09-01

    The interactions between nanomaterials (NMs) and amyloid proteins are central to the nanotechnology-based diagnostics and therapy in neurodegenerative disorders such as Alzheimer's and Parkinson's. Graphene oxide (GO) and its derivatives have shown to modulate the aggregation pattern of disease causing amyloid beta (Aβ) peptide. However, the mechanism is still not well understood. Using molecular dynamics simulations, the effect of graphene oxide (GO) and reduced graphene oxide (rGO) having carbon:oxygen ratio of 4:1 and 10:1, respectively, on the conformational transitions (alpha-helix to beta-sheet) and the dynamics of the peptide was investigated. GO and rGO decreased the beta-strand propensity of amino acid residues in Aβ. The peptide displayed different modes of adsorption on GO and rGO. The adsorption on GO was dominated by electrostatic interactions, whereas on rGO, both van der Waals and electrostatic interactions contributed in the adsorption of the peptide. Our study revealed that the slight increase in the hydrophobic patches on rGO made it more effective inhibitor of conformational transitions in the peptide. Alpha helix-beta sheet transition in Aβ peptide could be one of the plausible mechanism by which graphene oxide may inhibit amyloid fibrillation.

  5. Osmolyte Induced Changes in Peptide Conformational Ensemble Correlate with Slower Amyloid Aggregation: A Coarse-Grained Simulation Study.

    PubMed

    Sukenik, Shahar; Sapir, Liel; Harries, Daniel

    2015-12-01

    Stabilizing osmolytes are known to impact the process of amyloid aggregation, often altering aggregation kinetics. Recent evidence further suggests that osmolytes modify the peptide conformational dynamics, as well as change the physical characteristics of assembling amyloid fibrils. To resolve how these variations emerge on the molecular level, we simulated the initial aggregation steps of an amyloid-forming peptide in the presence and absence of the osmolyte sorbitol, a naturally occurring polyol. To this end, a coarse-grained force field was extended and implemented to access larger aggregate sizes and longer time scales. The force field optimization procedure placed emphasis on calibrating the solution thermodynamics of sorbitol, the aggregating peptide in its monomeric form, and the interaction of both of these components with each other and with water. Our simulations show a difference in aggregation kinetics and structural parameters in the presence of sorbitol compared to water, which qualitatively agree well with our experimentally resolved aggregation kinetics of the same peptide. The kinetic changes induced by sorbitol can be traced in our simulations to changes in monomer conformations resulting from osmolyte presence. These translate into changes in peptide conformations within the aggregated clusters and into differences in rates of monomer nucleation and of association to formed fibrils. We find that, compared to pure water as solvent, the presence of sorbitol induces formation of more aggregates each containing fewer peptides, with an increased tendency toward parallel interpeptide contacts. PMID:26587669

  6. Spectroscopic investigation of Ginkgo biloba terpene trilactones and their interaction with amyloid peptide Aβ(25-35)

    NASA Astrophysics Data System (ADS)

    He, Jiangtao; Petrovic, Ana G.; Dzyuba, Sergei V.; Berova, Nina; Nakanishi, Koji; Polavarapu, Prasad L.

    2008-04-01

    The beneficial effects of Ginkgo biloba extract in the "treatment" of dementia are attributed to its terpene trilactone (TTL) constituents. The interactions between TTLs and amyloid peptide are believed to be responsible in preventing the aggregation of peptide. These interactions have been investigated using infrared vibrational absorption (VA) and circular dichroism (VCD) spectra. Four TTLs, namely ginkgolide A (GA), ginkgolide B (GB), ginkgolide C (GC) and bilobalide (BB) and amyloid Aβ(25-35) peptide, as a model for the full length peptide, are used in this study. GA-monoether and GA-diether have also been synthesized and investigated to help understand the role of individual carbonyl groups in these interactions. The precipitation and solubility issues encountered with the mixture of ginkgolide + Aβ peptide for VA and VCD studies were overcome using binary ethanol-D 2O solvent mixture. The experimental VA and VCD spectra of GA, GB, GC and BB, GA-monoether and GA-diether have been analyzed using the corresponding spectra predicted with density functional theory. The time-dependent experimental VA and VCD spectra of Aβ(25-35) peptide and the corresponding experimental spectra in the presence of TTLs indicated that the effect of the TTLs in modulating the aggregation of Aβ(25-35) peptide is relatively small. Such small effects might indicate the absence of a specific interaction between the TTLs and Aβ(25-35) peptide as a major force leading to the reduced aggregation of amyloid peptides. It is possible that the therapeutic effect of G. biloba extract does not originate from direct interactions between TTLs and the Aβ(25-35) peptide and is more complex.

  7. Surfaces modulate beta-amyloid peptide aggregation associated with Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Yates, Elizabeth Anne

    A hallmark of Alzheimer's disease, a late onset neurodegenerative disease, is the presence of neuritic amyloid plaques deposited within the brain composed of beta-amyloid (Abeta) peptide aggregates. Abeta can aggregate into a variety of polymorphic aggregate structures under different chemical environments, specifically affected by the presence of differing surfaces. There are several point mutations clustered around the central hydrophobic core of Abeta (E22G Arctic mutation, E22K Italian mutation, D23N Iowa mutation, and A21G Flemish mutation). These mutations are associated with hereditary diseases ranging from almost pure cerebral amyloid angiopathy to typical Alzheimer's disease pathology with both plaques and tangles. To determine how these different point mutations, which modify both peptide charge and hydrophobic character, altered Abeta aggregation and morphology under free solution conditions, at an anionic surface/liquid interface and in the presence of supported lipid bilayers, atomic force microscopy was used. Additionally, the non-native conformation of Abeta leads to the formation of nanoscale, toxic aggregates which have been shown to strongly interact with supported lipid bilayers, which may represent a key step in potential toxic mechanisms. Understanding how specific regions of Abeta regulate its aggregation in the absence and presence of surfaces can provide insight into the fundamental interaction of Abeta with cellular surfaces. Specific fragments of Abeta (Abeta1-11, Abeta 1-28, Abeta10-26, Abeta12-24, Abeta 16-22, Abeta22-35, and Abeta1-40), represent a variety of chemically unique regions along Abeta, i.e., the extracellular domain, the central hydrophobic core, and transmembrane domain. Using various scanning probe microscopic techniques, the interaction of these Abeta sequences with lipid membranes was shown to alter aggregate morphology and induce mechanical changes of lipid bilayers compared to aggregates formed under free solution

  8. The interaction with gold suppresses fiber-like conformations of the amyloid β (16-22) peptide

    NASA Astrophysics Data System (ADS)

    Bellucci, Luca; Ardèvol, Albert; Parrinello, Michele; Lutz, Helmut; Lu, Hao; Weidner, Tobias; Corni, Stefano

    2016-04-01

    Inorganic surfaces and nanoparticles can accelerate or inhibit the fibrillation process of proteins and peptides, including the biomedically relevant amyloid β peptide. However, the microscopic mechanisms that determine such an effect are still poorly understood. By means of large-scale, state-of-the-art enhanced sampling molecular dynamics simulations, here we identify an interaction mechanism between the segments 16-22 of the amyloid β peptide, known to be fibrillogenic by itself, and the Au(111) surface in water that leads to the suppression of fiber-like conformations from the peptide conformational ensemble. Moreover, thanks to advanced simulation analysis techniques, we characterize the conformational selection vs. induced fit nature of the gold effect. Our results disclose an inhibition mechanism that is rooted in the details of the microscopic peptide-surface interaction rather than in general phenomena such as peptide sequestration from the solution.Inorganic surfaces and nanoparticles can accelerate or inhibit the fibrillation process of proteins and peptides, including the biomedically relevant amyloid β peptide. However, the microscopic mechanisms that determine such an effect are still poorly understood. By means of large-scale, state-of-the-art enhanced sampling molecular dynamics simulations, here we identify an interaction mechanism between the segments 16-22 of the amyloid β peptide, known to be fibrillogenic by itself, and the Au(111) surface in water that leads to the suppression of fiber-like conformations from the peptide conformational ensemble. Moreover, thanks to advanced simulation analysis techniques, we characterize the conformational selection vs. induced fit nature of the gold effect. Our results disclose an inhibition mechanism that is rooted in the details of the microscopic peptide-surface interaction rather than in general phenomena such as peptide sequestration from the solution. Electronic supplementary information (ESI

  9. Recombinant amyloid beta-peptide production by coexpression with an affibody ligand

    PubMed Central

    Macao, Bertil; Hoyer, Wolfgang; Sandberg, Anders; Brorsson, Ann-Christin; Dobson, Christopher M; Härd, Torleif

    2008-01-01

    Background Oligomeric and fibrillar aggregates of the amyloid β-peptide (Aβ) have been implicated in the pathogenesis of Alzheimer's disease (AD). The characterization of Aβ assemblies is essential for the elucidation of the mechanisms of Aβ neurotoxicity, but requires large quantities of pure peptide. Here we describe a novel approach to the recombinant production of Aβ. The method is based on the coexpression of the affibody protein ZAβ3, a selected affinity ligand derived from the Z domain three-helix bundle scaffold. ZAβ3 binds to the amyloidogenic central and C-terminal part of Aβ with nanomolar affinity and consequently inhibits aggregation. Results Coexpression of ZAβ3 affords the overexpression of both major Aβ isoforms, Aβ(1–40) and Aβ(1–42), yielding 4 or 3 mg, respectively, of pure 15N-labeled peptide per liter of culture. The method does not rely on a protein-fusion or -tag and thus does not require a cleavage reaction. The purified peptides were characterized by NMR, circular dichroism, SDS-PAGE and size exclusion chromatography, and their aggregation propensities were assessed by thioflavin T fluorescence and electron microscopy. The data coincide with those reported previously for monomeric, largely unstructured Aβ. ZAβ3 coexpression moreover permits the recombinant production of Aβ(1–42) carrying the Arctic (E22G) mutation, which causes early onset familial AD. Aβ(1–42)E22G is obtained in predominantly monomeric form and suitable, e.g., for NMR studies. Conclusion The coexpression of an engineered aggregation-inhibiting binding protein offers a novel route to the recombinant production of amyloidogenic Aβ peptides that can be advantageously employed to study the molecular basis of AD. The presented expression system is the first for which expression and purification of the aggregation-prone Arctic variant (E22G) of Aβ(1–42) is reported. PMID:18973685

  10. A novel antagonistic role of natural compound icariin on neurotoxicity of amyloid β peptide

    PubMed Central

    Liu, Jianhui; Liu, Zixuan; Zhang, Yonglan; Yin, Fei

    2015-01-01

    Background & objectives: Amyloid β-peptide (Aβ) has been shown to be responsible for senile plaque formation and cell damage in Alzheimer's disease (AD). This study was aimed to explore the role of natural compound icariin on the aggregation and the cytotoxicity of Aβ in vitro. Methods: Thioflavin T (ThT) fluorescence assay and transmission electron microscopy (TEM) imaging were done to determine the influence of icariin on the aggregation of Aβ1-42 peptide. MTT assay was used to evaluate the protective effect of icariin on Aβ1-42 induced cytotoxicity in neuroblastoma SH-SY5Y cells. Results: Icariin inhibited Aβ1-42 aggregation in a dose-dependent manner. Additionally, icariin also prevented the cytotoxicity of Aβ1-42 in SH-SY5Y cells by decreasing the production of peroxide hydrogen during the aggregation of this peptide. Interpretation & conclusions: The results indicated a novel antagonistic role of icariin in the neurotoxicity of Aβ1-42 via inhibiting its aggregation, suggesting that icariin might have potential therapeutic benefits to delay or modify the progression of AD. PMID:26354216

  11. Structure-Based Peptide Design to Modulate Amyloid Beta Aggregation and Reduce Cytotoxicity

    PubMed Central

    Kumar, Jitendra; Namsechi, Risa; Sim, Valerie L.

    2015-01-01

    The deposition of Aβ peptide in the brain is the key event in Alzheimer disease progression. Therefore, the prevention of Aβ self assembly into disease-associated oligomers is a logical strategy for treatment. π stacking is known to provide structural stability to many amyloids; two phenylalanine residues within the Aβ 14–23 self recognition element are in such an arrangement in many solved structures. Therefore, we targeted this structural stacking by substituting these two phenylalanine residues with their D-enantiomers. The resulting peptides were able to modulate Aβ aggregation in vitro and reduce Aβ cytotoxicity in primary neuronal cultures. Using kinetic analysis of fibril formation, electron microscopy and dynamic light scattering characterization of oligomer size distributions, we demonstrate that, in addition to altering fibril structural characteristics, these peptides can induce the formation of larger amorphous aggregates which are protective against toxic oligomers, possibly because they are able to sequester the toxic oligomers during co-incubation. Alternatively, they may alter the surface structure of the oligomers such that they can no longer interact with cells to induce toxic pathways. PMID:26070139

  12. Salts drive controllable multilayered upright assembly of amyloid-like peptides at mica/water interface

    PubMed Central

    Dai, Bin; Kang, Seung-gu; Huynh, Tien; Lei, Haozhi; Castelli, Matteo; Hu, Jun; Zhang, Yi; Zhou, Ruhong

    2013-01-01

    Surface-assisted self-assembly of amyloid-like peptides has received considerable interest in both amyloidosis research and nanotechnology in recent years. Despite extensive studies, some controlling factors, such as salts, are still not well understood, even though it is known that some salts can promote peptide self-assemblies through the so-called “salting-out” effect. However, they are usually noncontrollable, disordered, amorphous aggregates. Here, we show via a combined experimental and theoretical approach that a conserved consensus peptide NH2-VGGAVVAGV-CONH2 (GAV-9) (from representative amyloidogenic proteins) can self-assemble into highly ordered, multilayered nanofilaments, with surprising all-upright conformations, under high-salt concentrations. Our atomic force microscopy images also demonstrate that the vertical stacking of multiple layers is highly controllable by tuning the ionic strength, such as from 0 mM (monolayer) to 100 mM (mainly double layer), and to 250 mM MgCl2 (double, triple, quadruple, and quintuple layers). Our atomistic molecular dynamics simulations then reveal that these individual layers have very different internal nanostructures, with parallel β-sheets in the first monolayer but antiparallel β-sheets in the subsequent upper layers due to their different microenvironment. Further studies show that the growth of multilayered, all-upright nanostructures is a common phenomenon for GAV-9 at the mica/water interface, under a variety of salt types and a wide range of salt concentrations. PMID:23650355

  13. Salts drive controllable multilayered upright assembly of amyloid-like peptides at mica/water interface.

    PubMed

    Dai, Bin; Kang, Seung-gu; Huynh, Tien; Lei, Haozhi; Castelli, Matteo; Hu, Jun; Zhang, Yi; Zhou, Ruhong

    2013-05-21

    Surface-assisted self-assembly of amyloid-like peptides has received considerable interest in both amyloidosis research and nanotechnology in recent years. Despite extensive studies, some controlling factors, such as salts, are still not well understood, even though it is known that some salts can promote peptide self-assemblies through the so-called "salting-out" effect. However, they are usually noncontrollable, disordered, amorphous aggregates. Here, we show via a combined experimental and theoretical approach that a conserved consensus peptide NH2-VGGAVVAGV-CONH2 (GAV-9) (from representative amyloidogenic proteins) can self-assemble into highly ordered, multilayered nanofilaments, with surprising all-upright conformations, under high-salt concentrations. Our atomic force microscopy images also demonstrate that the vertical stacking of multiple layers is highly controllable by tuning the ionic strength, such as from 0 mM (monolayer) to 100 mM (mainly double layer), and to 250 mM MgCl2 (double, triple, quadruple, and quintuple layers). Our atomistic molecular dynamics simulations then reveal that these individual layers have very different internal nanostructures, with parallel β-sheets in the first monolayer but antiparallel β-sheets in the subsequent upper layers due to their different microenvironment. Further studies show that the growth of multilayered, all-upright nanostructures is a common phenomenon for GAV-9 at the mica/water interface, under a variety of salt types and a wide range of salt concentrations. PMID:23650355

  14. The irreversible binding of amyloid peptide substrates to insulin-degrading enzyme

    PubMed Central

    de Tullio, Matías B; Morelli, Laura

    2008-01-01

    Insulin-degrading enzyme (IDE) is a conserved Zn2+metalloendopeptidase involved in insulin degradation and in the maintenance of brain steady-state levels of amyloid β peptide (Aβ) of Alzheimer's disease (AD). Our recent demonstration that IDE and Aβ are capable of forming a stoichiometric and extremely stable complex raises several intriguing possibilities regarding the role of this unique protein-peptide interaction in physiological and pathological conditions. These include a protective cellular function of IDE as a “dead-end chaperone” alternative to its proteolytic activity and the potential impact of the irreversible binding of Aβ to IDE upon its role as a varicella zoster virus receptor. In a pathological context, the implications for insulin signaling and its relationship to AD pathogenesis are discussed. Moreover, our findings warrant further research regarding a possible general and novel interaction between amyloidogenic peptides and other Zn2+metallopeptidases with an IDE-like fold and a substrate conformation-dependent recognition mechanism. PMID:19098445

  15. Impact of sequence on the molecular assembly of short amyloid peptides.

    PubMed

    Wagoner, Victoria A; Cheon, Mookyung; Chang, Iksoo; Hall, Carol K

    2014-07-01

    The goal of this work is to understand how the sequence of a protein affects the likelihood that it will form an amyloid fibril and the kinetics along the fibrillization pathway. The focus is on very short fragments of amyloid proteins since these play a role in the fibrillization of the parent protein and can form fibrils themselves. Discontinuous molecular dynamics simulations using the PRIME20 force field were performed of the aggregation of 48-peptide systems containing SNQNNF (PrP (170-175)), SSTSAA (RNaseA(15-20)), MVGGVV (Aβ(35-40)), GGVVIA (Aβ(37-42)), and MVGGVVIA (Aβ(35-42)). In our simulations SNQQNF, SSTTSAA, and MVGGVV form large numbers of fibrillar structures spontaneously (as in experiment). GGVVIA forms β-sheets that do not stack into fibrils (unlike experiment). The combination sequence MVGGVVIA forms less fibrils than MVGGVV, hindered by the presence of the hydrophobic residues at the C-terminal. Analysis of the simulation kinetics and energetics reveals why MVGGVV forms fibrils and GGVVIA does not, and why adding I and A to MVGGVVIA reduces fibrillization and enhances amorphous aggregation into oligomeric structures. The latter helps explain why Aβ(1-42) assembles into more complex oligomers than Aβ(1-40), a consequence of which is that it is more strongly associated with Alzheimer's disease.

  16. Folic acid administration inhibits amyloid β-peptide accumulation in APP/PS1 transgenic mice.

    PubMed

    Li, Wen; Liu, Huan; Yu, Min; Zhang, Xumei; Zhang, Meilin; Wilson, John X; Huang, Guowei

    2015-08-01

    Alzheimer's disease (AD) is associated with malnutrition, altered one-carbon metabolism and increased hippocampal amyloidpeptide (Aβ) accumulation. Aberrant DNA methylation may be an epigenetic mechanism that underlies AD pathogenesis. We hypothesized that folic acid acts through an epigenetic gene silencing mechanism to lower Aβ levels in the APP/PS1 transgenic mouse model of AD. APP/PS1 mice were fed either folate-deficient or control diets and gavaged daily with 120 μg/kg folic acid, 13.3mg/kg S-adenosylmethionine (SAM) or both. Examination of the mice after 60 days of treatment showed that serum folate concentration increased with intake of folic acid but not SAM. Folate deficiency lowered endogenous SAM concentration, whereas neither intervention altered S-adenosylhomocysteine concentration. DNA methyltransferase (DNMT) activity increased with intake of folic acid raised DNMT activity in folate-deficient mice. DNA methylation rate was stimulated by folic acid in the amyloid precursor protein (APP) promoter and in the presenilin 1 (PS1) promoter. Folate deficiency elevated hippocampal APP, PS1 and Aβ protein levels, and these rises were prevented by folic acid. In conclusion, these findings are consistent with a mechanism in which folic acid increases methylation potential and DNMT activity, modifies DNA methylation and ultimately decreases APP, PS1 and Aβ protein levels.

  17. Mitofusin-2 knockdown increases ER-mitochondria contact and decreases amyloid β-peptide production.

    PubMed

    Leal, Nuno Santos; Schreiner, Bernadette; Pinho, Catarina Moreira; Filadi, Riccardo; Wiehager, Birgitta; Karlström, Helena; Pizzo, Paola; Ankarcrona, Maria

    2016-09-01

    Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum (ER). Such contacts are formed between mitochondria-associated ER membranes (MAM), specialized subregions of ER, and the outer mitochondrial membrane (OMM). We have previously shown increased expression of MAM-associated proteins and enhanced ER to mitochondria Ca(2+) transfer from ER to mitochondria in Alzheimer's disease (AD) and amyloid β-peptide (Aβ)-related neuronal models. Here, we report that siRNA knockdown of mitofusin-2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca(2+) transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra- and extracellular Aβ40 and Aβ42 . Analysis of γ-secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ-secretase complex function. Amyloid-β precursor protein (APP), β-site APP-cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 siRNA treatment. In summary, our data shows that modulation of ER-mitochondria contact affects γ-secretase activity and Aβ generation. Increased ER-mitochondria contact results in lower γ-secretase activity suggesting a new mechanism by which Aβ generation can be controlled. PMID:27203684

  18. Efficient four-drug cocktail therapy targeting amyloidpeptide for Alzheimer's disease.

    PubMed

    Asai, Masashi; Iwata, Nobuhisa; Tomita, Taisuke; Iwatsubo, Takeshi; Ishiura, Shoichi; Saido, Takaomi C; Maruyama, Kei

    2010-12-01

    Cocktail treatment is an effective multidrug medication therapy for some diseases, such as cancer and AIDS, because of the additive or synergistic effect of each medicine and relief from adverse effects. Amyloidpeptide (Aβ), which is now recognized as central to the development of Alzheimer's disease (AD), is derived from the sequential proteolysis of amyloid precursor protein (APP) by β- and γ-secretases. Secretase inhibitors are one of most attractive targets for therapeutic intervention in AD. However, because β- and γ-secretases cleave not only APP but also other substrate proteins, strong inhibition of these secretases leads to severe adverse effects. Some nonsteroidal antiinflammatory drugs (NSAIDs) and cholesterol-lowering drugs (statins) can modify the production of Aβ. Here, we report that a cocktail treatment with four drugs (NSAID, statin, and β- and γ-secretase inhibitors) had additive effects on the reduction of Aβ levels in cultured cells without competing with each other. Moreover, the four-drug cocktail treatment caused no changes in processing of the γ-secretase substrate Notch. This is suggests that this cocktail treatment could be a new therapeutic approach for AD. PMID:20890992

  19. Peptidomimetic β-Secretase Inhibitors Comprising a Sequence of AmyloidPeptide for Alzheimer's Disease.

    PubMed

    Vila-Real, Helder; Coelho, Helena; Rocha, João; Fernandes, Adelaide; Ventura, M Rita; Maycock, Christopher D; Iranzo, Olga; Simplício, Ana L

    2015-07-23

    Alzheimer's disease is a grave social problem in an aging population. A major problem is the passage of drugs through the blood-brain barrier. This work tests the hypothesis that the conjugation of peptidomimetic β-secretase inhibitors with a fragment of amyloidpeptide facilitates entrance into the central nervous system. HVR-3 (compound 4), one of the conjugation products, was found to be as potent as OM00-3, a known peptidomimetic inhibitor, 4-fold more selective toward β-secretase 1 in relation to β-secretase 2 and 3-fold more resistant to in vitro metabolization in human serum. Its intravenous administration to mice and Wistar rats generated an active metabolite recovered from the rodent's brains. PMID:26061085

  20. Amyloid beta-peptide and oxidative cellular injury in Alzheimer's disease.

    PubMed

    Mark, R J; Blanc, E M; Mattson, M P

    1996-06-01

    Alzheimer's disease is a progressive neurodegenerative disorder that affects primarily learning and memory functions. There is significant neuronal loss and impairment of metabolic functioning in the temporal lobe, an area believed to be crucial for learning and memory tasks. Aggregated deposits of amyloid beta-peptide may have a causative role in the development and progression of AD. We review the cellular actions of A beta and how they can contribute to the cytotoxicity observed in AD. A beta causes plasma membrane lipid peroxidation, impairment of ion-motive ATPases, glutamate uptake, uncoupling of a G-protein linked receptor, and generation of reactive oxygen species. These effects contribute to the loss of intracellular calcium homeostasis reported in cultured neurons. Many cell types other than neurons show alterations in the Alzheimer's brain. The effects of A beta on these cell types is also reviewed. PMID:8884749

  1. NADPH oxidase mediates β-amyloid peptide-induced activation of ERK in hippocampal organotypic cultures

    PubMed Central

    Serrano, Faridis; Chang, Angela; Hernandez, Caterina; Pautler, Robia G; Sweatt, J David; Klann, Eric

    2009-01-01

    Background Previous studies have shown that beta amyloid (Aβ) peptide triggers the activation of several signal transduction cascades in the hippocampus, including the extracellular signal-regulated kinase (ERK) cascade. In this study we sought to characterize the cellular localization of phosphorylated, active ERK in organotypic hippocampal cultures after acute exposure to either Aβ (1-42) or nicotine. Results We observed that Aβ and nicotine increased the levels of active ERK in distinct cellular localizations. We also examined whether phospho-ERK was regulated by redox signaling mechanisms and found that increases in active ERK induced by Aβ and nicotine were blocked by inhibitors of NADPH oxidase. Conclusion Our findings indicate that NADPH oxidase-dependent redox signaling is required for Aβ-induced activation of ERK, and suggest a similar mechanism may occur during early stages of Alzheimer's disease. PMID:19804648

  2. Two nitrogen-containing ligands as inhibitors of metal-induced amyloid β-peptide aggregation.

    PubMed

    Chen, Tingting; Zhu, Shajun; Liu, Siyuan; Lu, Yapeng; Zhu, Li

    2014-02-01

    Abnormal interactions of Zn(2+) and Cu(2+) with the amyloid β-peptide (Aβ) are proposed to play an important role in the neuropathogenesis of Alzheimer's disease (AD). Metal chelators are potential therapeutic agents for AD because they could sequester metals ions from Aβ aggregates and reverse the aggregation. In this study, two nitrogencontaining ligands, TACN and BPA, have been investigated as possible metal chelators in the therapy of Alzheimer's disease. The interactions between the chelators and Aβ40 aggregates are studied by turbidometry, thioflavin T (ThT) fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), BCA protein assay, circular dichroism spectroscopy (CD), and atomic force microscopy (AFM). The results demonstrates that TACN and BPA are capable of both disrupting and preventing Zn(2+) or Cu(2+)-induced Aβ40 aggregation. Moreover, they can also suppress the production of H2O2 induced by Cu-Aβ40, associated with toxic oxidative stress in AD. PMID:23844690

  3. Common benzothiazole and benzoxazole fluorescent DNA intercalators for studying Alzheimer Aβ1-42 and prion amyloid peptides.

    PubMed

    Stefansson, Steingrimur; Adams, Daniel L; Tang, Cha-Mei

    2012-05-01

    Amyloids are fibrillar protein aggregates associated with a number of neurodegenerative pathologies including Alzheimer and Creutzfeldt-Jakob disease. The study of amyloids is usually based on fluorescence with the dye thioflavin-T. Although a number of amyloid binding compounds have been synthesized, many are nonfluorescent or not readily available for research use. Here we report on a class of commercial benzothiazole/benzoxazole containing fluorescent DNA intercalators from Invitrogen that possess the ability to bind amyloid Aβ1-42 peptide and hamster prion. These dyes fluoresce from 500-750 nm and are available as dimers or monomers. We demonstrate that these dyes can be used as acceptors for thioflavin-T fluorescence resonance energy transfer as well as reporter groups for binding studies with Congo red and chrysamine G. As more potential therapeutic compounds for these diseases are generated, there is a need for simple and inexpensive methods to monitor their interactions with amyloids. The fluorescent dyes reported here are readily available and can be used as tools for biochemical studies of amyloid structures and in vitro screening of potential therapeutics.

  4. Lattice model for amyloid peptides: OPEP force field parametrization and applications to the nucleus size of Alzheimer's peptides.

    PubMed

    Tran, Thanh Thuy; Nguyen, Phuong H; Derreumaux, Philippe

    2016-05-28

    Coarse-grained protein lattice models approximate atomistic details and keep the essential interactions. They are, therefore, suitable for capturing generic features of protein folding and amyloid formation at low computational cost. As our aim is to study the critical nucleus sizes of two experimentally well-characterized peptide fragments Aβ16-22 and Aβ37-42 of the full length Aβ1-42 Alzheimer's peptide, it is important that simulations with the lattice model reproduce all-atom simulations. In this study, we present a comprehensive force field parameterization based on the OPEP (Optimized Potential for Efficient protein structure Prediction) force field for an on-lattice protein model, which incorporates explicitly the formation of hydrogen bonds and directions of side-chains. Our bottom-up approach starts with the determination of the best lattice force parameters for the Aβ16-22 dimer by fitting its equilibrium parallel and anti-parallel β-sheet populations to all-atom simulation results. Surprisingly, the calibrated force field is transferable to the trimer of Aβ16-22 and the dimer and trimer of Aβ37-42. Encouraged by this finding, we characterized the free energy landscapes of the two decamers. The dominant structure of the Aβ16-22 decamer matches the microcrystal structure. Pushing the simulations for aggregates between 4-mer and 12-mer suggests a nucleus size for fibril formation of 10 chains. In contrast, the Aβ37-42 decamer is largely disordered with mixed by parallel and antiparallel chains, suggesting that the nucleus size is >10 peptides. Our refined force field coupled to this on-lattice model should provide useful insights into the critical nucleation number associated with neurodegenerative diseases. PMID:27250331

  5. Lattice model for amyloid peptides: OPEP force field parametrization and applications to the nucleus size of Alzheimer's peptides

    NASA Astrophysics Data System (ADS)

    Tran, Thanh Thuy; Nguyen, Phuong H.; Derreumaux, Philippe

    2016-05-01

    Coarse-grained protein lattice models approximate atomistic details and keep the essential interactions. They are, therefore, suitable for capturing generic features of protein folding and amyloid formation at low computational cost. As our aim is to study the critical nucleus sizes of two experimentally well-characterized peptide fragments Aβ16-22 and Aβ37-42 of the full length Aβ1-42 Alzheimer's peptide, it is important that simulations with the lattice model reproduce all-atom simulations. In this study, we present a comprehensive force field parameterization based on the OPEP (Optimized Potential for Efficient protein structure Prediction) force field for an on-lattice protein model, which incorporates explicitly the formation of hydrogen bonds and directions of side-chains. Our bottom-up approach starts with the determination of the best lattice force parameters for the Aβ16-22 dimer by fitting its equilibrium parallel and anti-parallel β-sheet populations to all-atom simulation results. Surprisingly, the calibrated force field is transferable to the trimer of Aβ16-22 and the dimer and trimer of Aβ37-42. Encouraged by this finding, we characterized the free energy landscapes of the two decamers. The dominant structure of the Aβ16-22 decamer matches the microcrystal structure. Pushing the simulations for aggregates between 4-mer and 12-mer suggests a nucleus size for fibril formation of 10 chains. In contrast, the Aβ37-42 decamer is largely disordered with mixed by parallel and antiparallel chains, suggesting that the nucleus size is >10 peptides. Our refined force field coupled to this on-lattice model should provide useful insights into the critical nucleation number associated with neurodegenerative diseases.

  6. Molecular Dynamics Simulations of Amyloid β-Peptide (1-42): Tetramer Formation and Membrane Interactions.

    PubMed

    Brown, Anne M; Bevan, David R

    2016-09-01

    The aggregation cascade and peptide-membrane interactions of the amyloid β-peptide (Aβ) have been implicated as toxic events in the development and progression of Alzheimer's disease. Aβ42 forms oligomers and ultimately plaques, and it has been hypothesized that these oligomeric species are the main toxic species contributing to neuronal cell death. To better understand oligomerization events and subsequent oligomer-membrane interactions of Aβ42, we performed atomistic molecular-dynamics (MD) simulations to characterize both interpeptide interactions and perturbation of model membranes by the peptides. MD simulations were utilized to first show the formation of a tetramer unit by four separate Aβ42 peptides. Aβ42 tetramers adopted an oblate ellipsoid shape and showed a significant increase in β-strand formation in the final tetramer unit relative to the monomers, indicative of on-pathway events for fibril formation. The Aβ42 tetramer unit that formed in the initial simulations was used in subsequent MD simulations in the presence of a pure POPC or cholesterol-rich raft model membrane. Tetramer-membrane simulations resulted in elongation of the tetramer in the presence of both model membranes, with tetramer-raft interactions giving rise to the rearrangement of key hydrophobic regions in the tetramer and the formation of a more rod-like structure indicative of a fibril-seeding aggregate. Membrane perturbation by the tetramer was manifested in the form of more ordered, rigid membranes, with the pure POPC being affected to a greater extent than the raft membrane. These results provide critical atomistic insight into the aggregation pathway of Aβ42 and a putative toxic mechanism in the pathogenesis of Alzheimer's disease. PMID:27602722

  7. Location and conformation of amyloid β(25-35) peptide and its sequence-shuffled peptides within membranes: implications for aggregation and toxicity in PC12 cells.

    PubMed

    Tsai, Hui-Hsu Gavin; Lee, Jian-Bin; Shih, Yuan-Ci; Wan, Lei; Shieh, Fa-Kuen; Chen, Chin-Yu

    2014-05-01

    Extracellular deposits of amyloid β (Aβ) aggregates in the brain is the hallmark of Alzheimer's disease. We present the configurations (location and conformation) and the interfacial folding and membrane insertion mechanisms of Aβ fragments, wild-type Aβ(25-35), Aβ(35-25), and a sequence-shuffled peptide [Aβ(25-35)-shuffled] from Aβ(25-35) within membranes by replica-exchange molecular dynamics simulations. Although these peptides have the same amino acid composition, simulations show they have distinct locations and conformations within membranes. Moreover, our in vitro experiments show that these peptides have distinct neurotoxicities. We rationalize the distinct neurotoxicities of these peptides in terms of their simulated locations and conformations in membranes. This work provides another view that complements the general hydrophobicity-toxicity views, to better explain the neurotoxicity of Aβ peptides.

  8. Amyloid peptide Aβ40 inhibits aggregation of Aβ42: Evidence from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Viet, Man Hoang; Li, Mai Suan

    2012-06-01

    Effects of amyloid beta (Aβ) peptide Aβ40 on secondary structures of Aβ42 are studied by all-atom simulations using the GROMOS96 43a1 force field with explicit water. It is shown that in the presence of Aβ40 the beta-content of monomer Aβ42 is reduced. Since the fibril-prone conformation N* of full-length Aβ peptides has the shape of beta strand-loop-beta strand this result suggests that Aβ40 decreases the probability of observing N* of Aβ42 in monomer state. Based on this and the hypothesis that the higher is the population of N* the higher fibril formation rates, one can expect that, in agreement with the recent experiment, Aβ40 inhibit fibril formation of Aβ42. It is shown that the presence of Aβ40 makes the salt bridge D23-K28 and fragment 18-33 of Aβ42 more flexible providing additional support for this experimental fact. Our estimation of the binding free energy by the molecular mechanics-Poisson-Boltzmann surface area method reveals the inhibition mechanism that Aβ40 binds to Aβ42 modifying its morphology.

  9. Zn(2+) effect on structure and residual hydrophobicity of amyloid β-peptide monomers.

    PubMed

    Shi, Hu; Kang, Baotao; Lee, Jin Yong

    2014-09-01

    The aggregation of amyloid β-peptide (Aβ peptide) has been associated with the pathogenesis of Alzheimer's disease (AD). In the present study, we aimed to disclose how Zn(2+) affects the Aβ aggregation in detail. Thus, molecular dynamics simulation was implemented to elucidate the changes of structure and residual hydrophobicity upon Zn(2+) coordination. Our results show that Zn(2+) can strongly influence the structural properties of Aβ40 and Aβ42 by reducing helical formation and increasing turn formation to expose the hydrophobic regions. Furthermore, hydrophobicity of Zn(2+)-Aβ40 and Zn(2+)-Aβ42 was much higher than that of each monomer, since Zn(2+) binding can significantly influence the hydrophilic domains of Aβ. The further analyses indicate that not only four residues (H6, E11, H13, and H14) but also R5, D7, K16, K28, and terminal residues influence hydrophobicity upon Zn(2+) coordination. Importantly, R5, K16, and K28 play a crucial role to regulate solvation-free energies. This work is helpful to understand the fundamental role of Zn(2+) in aggregation, which could be useful for further development of new drugs to inhibit Zn(2+)-Aβ aggregation.

  10. Mechanisms of Ultrasonically Induced Fibrillation of Amyloid β1-40 Peptides

    NASA Astrophysics Data System (ADS)

    Uesugi, Kentaro; Ogi, Hirotsugu; Fukushima, Masahiko; So, Masatomo; Yagi, Hisashi; Goto, Yuji; Hirao, Masahiko

    2013-07-01

    We systematically study the relationship between the ultrasonically induced aggregation behavior of amyloid β1-40 peptide and acoustic pressures to clarify the dominant mechanism of the aggregation. With ultrasonic irradiation, the thioflavin-T (ThT) level of the Aβ solution rises after a lag time, takes a maximum at ˜5 h, and remains unchanged or decreases. Thus, we monitor the ThT level at 5 h to evaluate the progress of the β-sheet structure and investigate its correlation with the acoustic pressures of fundamental and harmonics waves. The second-harmonics-wave amplitude shows the highest correlation with the ThT level, indicating the dominant contribution of cavitation bubbles to the fibrillation phenomenon. The influence of solution pH and Ar gas are investigated to identify the aggregation mechanism. As a result, local condensation of the peptide due to the high affinity of hydrophobic residues to the bubble-solution interface causes a highly supersaturated solution, leading to precipitation of β-sheet-rich nuclei.

  11. Probing Alzheimer amyloid peptide aggregation using a cell-free fluorescent protein refolding method.

    PubMed

    Arslan, Pharhad Eli; Chakrabartty, Avijit

    2009-08-01

    Fibrillation of the Alzheimer beta-amyloid peptide (Abeta) and (or) formation of toxic oligomers are key pathological events in Alzheimer's disease. Several strategies have been introduced to identify small molecule aggregation inhibitors, and based on these methods, a number of aggregation inhibitors have been identified. However, most of these methods use chemically synthesized Abeta42 peptides, which are difficult to maintain in a monomeric state at neutral pH where anti-aggregation screening is usually carried out. We have developed a cell-free Abeta42 aggregation assay based on fluorescence protein refolding. This assay utilizes nanomolar concentrations of protein. We genetically fused Abeta42 to the N-terminus of vYFP, a variant of of GFP, and expressed and purified the folded fusion protein. The refolding efficiency of Abeta42-vYFP fusion was inversely correlated with the solubility of Abeta42. Using fluorescence to monitor refolding of Abeta42-vYFP, we confirmed that Zn2+ binds to Abeta42 and increases its aggregation. The IC50 value estimated for Zn binding is 3.03 +/- 0.65 micromol/L. We also show that this technique is capable of monitoring the aggregation of chemically synthesized Abeta42.

  12. DCP-LA neutralizes mutant amyloid beta peptide-induced impairment of long-term potentiation and spatial learning.

    PubMed

    Nagata, Tetsu; Tomiyama, Takami; Tominaga, Takemi; Mori, Hiroshi; Yaguchi, Takahiro; Nishizaki, Tomoyuki

    2010-01-01

    Long-term potentiation (LTP) was monitored from the CA1 region of the intact rat hippocampus by delivering high frequency stimulation (HFS) to the Schaffer collateral commissural pathway. Intraventricular injection with mutant amyloid beta(1-42) peptide lacking glutamate-22 (Abeta(1-42)E22Delta), favoring oligomerization, 10 min prior to HFS, inhibited expression of LTP, with the potency more than wild-type amyloid beta(1-42) peptide. Intraperitoneal injection with the linoleic acid derivative 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) 70 min prior to HFS neutralized mutant Abeta(1-42)E22Delta peptide-induced LTP inhibition. In the water maze test, continuous intraventricular injection with mutant Abeta(1-42)E22Delta peptide for 14 days prolonged the acquisition latency as compared with that for control, with the potency similar to wild-type Abeta(1-42) peptide, and intraperitoneal injection with DCP-LA shortened the prolonged latency to control levels. The results of the present study indicate that DCP-LA neutralizes mutant Abeta(1-42)E22Delta peptide-induced impairment of LTP and spatial learning.

  13. P3 beta-amyloid peptide has a unique and potentially pathogenic immunohistochemical profile in Alzheimer's disease brain.

    PubMed Central

    Higgins, L. S.; Murphy, G. M.; Forno, L. S.; Catalano, R.; Cordell, B.

    1996-01-01

    The presence of beta-amyloid in brain tissue is characteristic of Alzheimer's disease (AD). A naturally occurring derivative of the beta-amyloid peptide, p3, possesses all of the structural determinants required for fibril assembly and neurotoxicity. p3-specific antibodies were used to examine the distribution of this peptide in brain. p3 reactivity was absent or sparse in aged non-AD brains but was prevalent in selected areas of AD brain in diffuse deposits and in a subset of dystrophic neurites. p3-reactive dystrophic neurites were found both independent in the neuropil and associated with plaques. Little or no reactivity was observed to amyloid cores in classical plaques or to amyloid in the cerebral vasculature. The exclusive appearance of p3 reactivity in AD brain plus the selective localization of p3 reactivity to abnormal structures in the temporal lobe limbic system suggests that p3 may be a contributing factor to AD pathology. Images Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 PMID:8701997

  14. Exploiting the therapeutic potential of 8-β-d-glucopyranosylgenistein: synthesis, antidiabetic activity, and molecular interaction with islet amyloid polypeptide and amyloid β-peptide (1-42).

    PubMed

    Jesus, Ana R; Dias, Catarina; Matos, Ana M; de Almeida, Rodrigo F M; Viana, Ana S; Marcelo, Filipa; Ribeiro, Rogério T; Macedo, Maria P; Airoldi, Cristina; Nicotra, Francesco; Martins, Alice; Cabrita, Eurico J; Jiménez-Barbero, Jesús; Rauter, Amélia P

    2014-11-26

    8-β-d-Glucopyranosylgenistein (1), the major component of Genista tenera, was synthesized and showed an extensive therapeutical impact in the treatment of STZ-induced diabetic rats, producing normalization of fasting hyperglycemia and amelioration of excessive postprandial glucose excursions and and increasing β-cell sensitivity, insulin secretion, and circulating insulin within 7 days at a dose of 4 (mg/kg bw)/day. Suppression of islet amyloid polypeptide (IAPP) fibril formation by compound 1 was demonstrated by thioflavin T fluorescence and atomic force microscopy. Molecular recognition studies with IAPP and Aβ1-42 employing saturation transfer difference (STD) confirmed the same binding mode for both amyloid peptides as suggested by their deduced epitope. Insights into the preferred conformation in the bound state and conformers' geometry resulting from interaction with Aβ1-42 were also given by STD, trNOESY, and MM calculations. These studies strongly support 8-β-d-glucopyranosylgenistein as a promising molecular entity for intervention in amyloid events of both diabetes and the frequently associated Alzheimer's disease. PMID:25347820

  15. Aloe arborescens Extract Protects IMR-32 Cells against Alzheimer Amyloid Beta Peptide via Inhibition of Radical Peroxide Production.

    PubMed

    Clementi, Maria Elisabetta; Tringali, Giuseppe; Triggiani, Doriana; Giardina, Bruno

    2015-11-01

    Aloe arborescens is commonly used as a pharmaceutical ingredient for its effect in burn treatment and ability to increase skin wound healing properties. Besides, it is well known to have beneficial phytotherapeutic, anticancer, and radio-protective properties. In this study, we first provided evidence that A. arborescens extract protects IMR32, a neuroblastoma human cellular line, from toxicity induced by beta amyloid, the peptide responsible for Alzheimer's disease. In particular, pretreatment with A. arborescens maintains an elevated cell viability and exerts a protective effect on mitochondrial functionality, as evidenced by oxygen consumption experiments. The protective mechanism exerted by A. arborescens seems be related to lowering of oxidative potential of the cells, as demonstrated by the ROS measurement compared with the results obtained in the presence of amyloid beta (1-42) peptide alone. Based on these preliminary observations we suggest that use ofA. arborescens extract could be developed as agents for the management of AD. PMID:26749845

  16. Molecular cloning and characterization of a cDNA encoding the cerebrovascular and the neuritic plaque amyloid peptides

    SciTech Connect

    Robakis, N.K.; Ramakrishna, N.; Wolfe, G.; Wisniewski, H.M.

    1987-06-01

    Deposits of amyloid fibers are found in large numbers in the walls of blood vessels and in neuritic plaques in the brains of patients with Alzheimer disease and adults with Down syndrome. The authors used the amino acid sequence of the amyloid peptide to synthesize oligonucleotide probes specific for the gene encoding this peptide. When a human brain cDNA library was screened with this probe, a clone was found with a 1.7-kilobase insert that contains a long open reading frame coding for 412 amino acid residues including the 28 amino acids of the amyloid peptide. RNA gel blots revealed that a 3.3-kilobase mRNA species was present in the brains of individuals with Alzheimer disease, with Down syndrome, or with not apparent neurological disorders. Southern blots showed that homologous genes are present in the genomic DNA of humans, rabbits, sheep, hamsters, and mice, suggesting that this gene has been conserved through mammalian evolution. Localization of the corresponding genomic sequences on human chromosome 21 suggest a genetic relationship between Alzheimer disease and Down syndrome, and it may explain the early appearance of large numbers of neuritic plaques in adult Down syndrome patients.

  17. Molecular cloning and characterization of a cDNA encoding the cerebrovascular and the neuritic plaque amyloid peptides.

    PubMed

    Robakis, N K; Ramakrishna, N; Wolfe, G; Wisniewski, H M

    1987-06-01

    Deposits of amyloid fibers are found in large numbers in the walls of blood vessels and in neuritic plaques in the brains of patients with Alzheimer disease and adults with Down syndrome. We used the amino acid sequence of the amyloid peptide to synthesize oligonucleotide probes specific for the gene encoding this peptide. When a human brain cDNA library was screened with this probe, a clone was found with a 1.7-kilobase insert that contains a long open reading frame coding for 412 amino acid residues including the 28 amino acids of the amyloid peptide. RNA gel blots revealed that a 3.3-kilobase mRNA species was present in the brains of individuals with Alzheimer disease, with Down syndrome, or with no apparent neurological disorders. Southern blots showed that homologous genes are present in the genomic DNA of humans, rabbits, sheep, hamsters, and mice, suggesting that this gene has been conserved through mammalian evolution. Localization of the corresponding genomic sequences on human chromosome 21 suggests a genetic relationship between Alzheimer disease and Down syndrome, and it may explain the early appearance of large numbers of neuritic plaques in adult Down syndrome patients.

  18. Inhibitory Effect of Curcumin-Cu(II) and Curcumin-Zn(II) Complexes on Amyloid-Beta Peptide Fibrillation

    PubMed Central

    2014-01-01

    Mononuclear complexes of Curcumin with Cu(II) and Zn(II) have been synthesized and, characterized and their effects on the fibrillization and aggregation of amyloid-beta (Aβ) peptide have been studied. FTIR spectroscopy and atomic force microscopy (AFM) observations demonstrate that the complexes can inhibit the transition from less structured oligomers to β-sheet rich protofibrils which act as seeding factors for further fibrillization. The metal complexes also impart more improved inhibitory effects than Curcumin on peptide fibrillization. PMID:25147492

  19. Assessment of the aggregation propensity of the β -amyloid peptide during the synthesis and when free in solution.

    PubMed

    Malavolta, Luciana; Pinto, Marcelo R S; Nakaie, Clóvis R

    2013-08-01

    This work developed an alternative approach targeting the evaluation of the aggregation propensity of the (1-42) β-amyloid peptide (Alzheimer's disease) and some segments, either attached to a polymer during their synthesis or when free in solution. The solvation behavior of peptide-resins was gauged by measuring the swelling of beads in a microscope and the degree of chain motion through EPR spectra of previously labeled resins with an amino acid-type probe. In terms of comparative solvent dissociation power towards aggregated structures, the findings revealed greater values of peptide-resin swelling, peptide chain mobility and solubility when in strong electron donor dimethylsulfoxide than in strong electron acceptor trifluoroethanol. Otherwise, the weakest chain-chain disruption power was verified for acetonitrile, an internally neutral solvent in terms of Lewis acid/base properties. In complement, fluorescence and light scattering experiments depicted that the 15-35 region plays an essential role in the amyloid peptide fibril formation capacity. PMID:23458076

  20. Antimicrobial peptide (Cn-AMP2) from liquid endosperm of Cocos nucifera forms amyloid-like fibrillar structure.

    PubMed

    Gour, Shalini; Kaushik, Vibha; Kumar, Vijay; Bhat, Priyanka; Yadav, Subhash C; Yadav, Jay K

    2016-04-01

    Cn-AMP2 is an antimicrobial peptide derived from liquid endosperm of coconut (Cocos nucifera). It consists of 11 amino acid residues and predicted to have high propensity for β-sheet formation that disposes this peptide to be amyloidogenic. In the present study, we have examined the amyloidogenic propensities of Cn-AMP2 in silico and then tested the predictions under in vitro conditions. The in silico study revealed that the peptide possesses high amyloidogenic propensity comparable with Aβ. Upon solubilisation and agitation in aqueous buffer, Cn-AMP2 forms visible aggregates that display bathochromic shift in the Congo red absorbance spectra, strong increase in thioflavin T fluorescence and fibrillar morphology under transmission electron microscopy. All these properties are typical of an amyloid fibril derived from various proteins/peptides including Aβ. PMID:27028204

  1. Deciphering the Glycolipid Code of Alzheimer's and Parkinson's Amyloid Proteins Allowed the Creation of a Universal Ganglioside-Binding Peptide

    PubMed Central

    Yahi, Nouara; Fantini, Jacques

    2014-01-01

    A broad range of microbial and amyloid proteins interact with cell surface glycolipids which behave as infectivity and/or toxicity cofactors in human pathologies. Here we have deciphered the biochemical code that determines the glycolipid-binding specificity of two major amyloid proteins, Alzheimer's β-amyloid peptide (Aβ) and Parkinson's disease associated protein α-synuclein. We showed that both proteins interact with selected glycolipids through a common loop-shaped motif exhibiting little sequence homology. This 12-residue domain corresponded to fragments 34-45 of α-synuclein and 5-16 of Aβ. By modulating the amino acid sequence of α-synuclein at only two positions in which we introduced a pair of histidine residues found in Aβ, we created a chimeric α-synuclein/Aβ peptide with extended ganglioside-binding properties. This chimeric peptide retained the property of α-synuclein to recognize GM3, and acquired the capacity to recognize GM1 (an Aβ-inherited characteristic). Free histidine (but not tryptophan or asparagine) and Zn2+ (but not Na+) prevented this interaction, confirming the key role of His-13 and His-14 in ganglioside binding. Molecular dynamics studies suggested that the chimeric peptide recognized cholesterol-constrained conformers of GM1, including typical chalice-shaped dimers, that are representative of the condensed cholesterol-ganglioside complexes found in lipid raft domains of the plasma membrane of neural cells. Correspondingly, the peptide had a particular affinity for raft-like membranes containing both GM1 and cholesterol. The chimeric peptide also interacted with several other gangliosides, including major brain gangliosides (GM4, GD1a, GD1b, and GT1b) but not with neutral glycolipids such as GlcCer, LacCer or asialo-GM1. It could inhibit the binding of Aβ1-42 onto neural SH-SY5Y cells and did not induce toxicity in these cells. In conclusion, deciphering the glycolipid code of amyloid proteins allowed us to create a universal

  2. Amyloid beta-peptide possesses a transforming growth factor-beta activity.

    PubMed

    Huang, S S; Huang, F W; Xu, J; Chen, S; Hsu, C Y; Huang, J S

    1998-10-16

    Amyloid beta-peptide (Abeta) of 39-42 amino acid residues is a major constituent of Alzheimer's disease neurite plaques. Abeta aggregates (fibrils) are believed to be responsible for neuronal damage and dysfunction, as well as microglia and astrocyte activation in disease lesions by multiple mechanisms. Since Abeta aggregates possess the multiple valencies of an FAED motif (20th to 23rd amino acid residues), which resembles the putative transforming growth factor-beta (TGF-beta) active site motif, we hypothesize that Abeta monomers and Abeta aggregates may function as TGF-beta antagonists and partial agonists, analogous to previously described monovalent and multivalent TGF-beta peptide antagonists and agonists (Huang, S. S., Liu, Q., Johnson, F. E., Konish, Y., and Huang, J. S. (1997) J. Biol. Chem. 272, 27155-27159). Here, we report that the Abeta monomer, Abeta-(1-40) and its fragment, containing the motif inhibit radiolabeled TGF-beta binding to cell-surface TGF-beta receptors in mink lung epithelial cells (Mv1Lu cells). Abeta-(1-40)-bovine serum albumin conjugate (Abeta-(1-40)-BSA), a multivalent synthetic analogue of Abeta aggregates, exhibited cytotoxicity toward bovine cerebral endothelial cells and rat post-mitotic differentiated hippocampal neuronal cells (H19-7 cells) and inhibitory activities of radiolabeled TGF-beta binding to TGF-beta receptors and TGF-beta-induced plasminogen activator inhibitor-1 expression, that were approximately 100-670 times more potent than those of Abeta-(1-40) monomers. At less than micromolar concentrations, Abeta-(1-40)-BSA but not Abeta-(1-40) monomers inhibited proliferation of Mv1Lu cells. Since TGF-beta is an organizer of responses to neurodegeneration and is also found in neurite plaques, the TGF-beta antagonist and partial agonist activities of Abeta monomers and aggregates may play an important role in the pathogenesis of the disease.

  3. Mechanisms of AmyloidPeptide Clearance: Potential Therapeutic Targets for Alzheimer’s Disease

    PubMed Central

    Yoon, Sang-Sun; Jo, Sangmee Ahn

    2012-01-01

    Amyloidpeptide (Aβ) is still best known as a molecule to cause Alzheimer’s disease (AD) through accumulation and deposition within the frontal cortex and hippocampus in the brain. Thus, strategies on developing AD drugs have been focused on the reduc-tion of Aβ in the brain. Since accumulation of Aβ depends on the rate of its synthesis and clearance, the metabolic pathway of Aβ in the brain and the whole body should be carefully explored for AD research. Although the synthetic pathway of Aβ is equally important, we summarize primarily the clearance pathway in this paper because the former has been extensively reviewed in previous studies. The clearance of Aβ from the brain is accomplished by several mechanisms which include non-enzymatic and enzymatic pathways. Nonenzymatic pathway includes interstitial fluid drainage, uptake by microglial phagocytosis, and transport across the blood vessel walls into the circulation. Multiple Aβ-degrading enzymes (ADE) implicated in the clearance process have been identified, which include neprilysin, insulin-degrading enzyme, matrix metalloproteinase-9, glutamate carboxypeptidase II and others. A series of studies on Aβ clearance mechanism provide new insight into the pathogenesis of AD at the molecular level and suggest a new target for the development of novel therapeutics. PMID:24130920

  4. Isoflurane and desflurane at clinically relevant concentrations induce amyloid {beta}-peptide oligomerization: An NMR study

    SciTech Connect

    Mandal, Pravat K Fodale, Vincenzo

    2009-02-13

    Current understanding on Alzheimer's disease (AD) reveals that soluble amyloid {beta}-peptide (A{beta}) oligomeric formation plays an important role in AD pathophysiology. A potential role for several inhaled anesthetics in promoting A{beta} oligomer formation has been suggested. Using a nuclear magnetic resonance (NMR) study, we previously demonstrated that at a high concentration (higher than clinically relevant concentrations), the inhaled anesthetics halothane and isoflurane, interact with specific amino acid residues (G29, A30, and I31) and induce A{beta} oligomerization. The present study confirms this is true at a clinically relevant concentration. Isoflurane and desflurane induce A{beta} oligomerization by inducing chemical shift changes of the critical amino acid residues (G29, A30, and I31), reinforcing the evidence that perturbation of these three crucial residues indeed plays an important role in oligomerization. These findings support the emerging hypothesis that several commonly used inhaled anesthetics could be involved in neurodegeneration, as well as risk factor for accelerating the onset of AD.

  5. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms.

    PubMed

    Iljina, Marija; Garcia, Gonzalo A; Dear, Alexander J; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C T; Dobson, Christopher M; Frenkel, Daan; Knowles, Tuomas P J; Klenerman, David

    2016-01-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer's disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer's disease. PMID:27346247

  6. Study of amyloidpeptide functional brain networks in AD, MCI and HC.

    PubMed

    Jiang, Jiehui; Duan, Huoqiang; Huang, Zheming; Yu, Zhihua

    2015-01-01

    One medical challenge in studying the amyloid-β (Aβ) peptide mechanism for Alzheimer's disease (AD) is exploring the law of beta toxic oligomers' diffusion in human brains in vivo. One beneficial means of solving this problem is brain network analysis based on graph theory. In this study, the characteristics of Aβ functional brain networks of Healthy Control (HC), Mild Cognitive Impairment (MCI), and AD groups were compared by applying graph theoretical analyses to Carbon 11-labeled Pittsburgh compound B positron emission tomography (11C PiB-PET) data. 120 groups of PiB-PET images from the ADNI database were analyzed. The results showed that the small-world property of MCI and AD were lost as compared to HC. Furthermore, the local clustering of networks was higher in both MCI and AD as compared to HC, whereas the path length was similar among the three groups. The results also showed that there could be four potential Aβ toxic oligomer seeds: Frontal_Sup_Medial_L, Parietal_Inf_L, Frontal_Med_Orb_R, and Parietal_Inf_R. These four seeds are corresponding to Regions of Interests referred by physicians to clinically diagnose AD.

  7. Anticonvulsants attenuate amyloid beta-peptide neurotoxicity, Ca2+ deregulation, and cytoskeletal pathology.

    PubMed

    Mark, R J; Ashford, J W; Goodman, Y; Mattson, M P

    1995-01-01

    Increasing evidence supports the involvement of amyloid beta-peptide (A beta) and an excitotoxic mechanism of neuronal injury in the pathogenesis of Alzheimer's disease. However, approaches aimed at preventing A beta toxicity and neurofibrillary degeneration are undeveloped. We now report that anticonvulsants (carbamazepine, phenytoin, and valproic acid) can protect cultured rat hippocampal neurons against A beta- and glutamate-induced injury. Each of the anticonvulsants attenuated the elevation of intracellular free calcium levels [(Ca2+)i] elicited by A beta or glutamate suggesting that their neuroprotective mechanism of action involved stabilization of [Ca2+]i. These compounds were effective at clinically relevant concentrations (carbamazepine, 100 nM-10 microM; phenytoin, 100 nM-1 microM; valproic acid, 100 nM-100 microM). The anticonvulsants suppressed glutamate-induced alterations in tau and buiquitin immunoreactivities. Compounds that stabilize [Ca2+]i may afford protection against the kinds of insults believed to underlie neuronal injury in Alzheimer's disease. PMID:7777136

  8. Amyloid beta-peptide disrupts carbachol-induced muscarinic cholinergic signal transduction in cortical neurons.

    PubMed

    Kelly, J F; Furukawa, K; Barger, S W; Rengen, M R; Mark, R J; Blanc, E M; Roth, G S; Mattson, M P

    1996-06-25

    Cholinergic pathways serve important functions in learning and memory processes, and deficits in cholinergic transmission occur in Alzheimer disease (AD). A subset of muscarinic cholinergic receptors are linked to G-proteins that activate phospholipase C, resulting in the liberation of inositol trisphosphate and Ca2+ release from intracellular stores. We now report that amyloid beta-peptide (Abeta), which forms plaques in the brain in AD, impairs muscarinic receptor activation of G proteins in cultured rat cortical neurons. Exposure of rodent fetal cortical neurons to Abeta25-35 and Abeta1-40 resulted in a concentration and time-dependent attenuation of carbachol-induced GTPase activity without affecting muscarinic receptor ligand binding parameters. Downstream events in the signal transduction cascade were similarly attenuated by Abeta. Carbachol-induced accumulation of inositol phosphates (IP, IP2, IP3, and IP4) was decreased and calcium imaging studies revealed that carbachol-induced release of calcium was severely impaired in neurons pretreated with Abeta. Muscarinic cholinergic signal transduction was disrupted with subtoxic levels of exposure to AP. The effects of Abeta on carbachol-induced GTPase activity and calcium release were attenuated by antioxidants, implicating free radicals in the mechanism whereby Abeta induced uncoupling of muscarinic receptors. These data demonstrate that Abeta disrupts muscarinic receptor coupling to G proteins that mediate induction of phosphoinositide accumulation and calcium release, findings that implicate Abeta in the impairment of cholinergic transmission that occurs in AD. PMID:8692890

  9. MALDI, AP/MALDI and ESI techniques for the MS detection of amyloid [beta]-peptides

    NASA Astrophysics Data System (ADS)

    Grasso, Giuseppe; Mineo, Placido; Rizzarelli, Enrico; Spoto, Giuseppe

    2009-04-01

    Amyloid [beta]-peptides (A[beta]s) are involved in several neuropathological conditions such as Alzheimer's disease and considerable experimental evidences have emerged indicating that different proteases play a major role in regulating the accumulation of A[beta]s in the brain. Particularly, insulin-degrading enzyme (IDE) has been shown to degrade A[beta]s at different cleavage sites, but the experimental results reported in the literature and obtained by mass spectrometry methods are somehow fragmentary. The detection of A[beta]s is often complicated by solubility issues, oxidation artifacts and spontaneous aggregation/cleavage and, in order to rationalize the different reported results, we analyzed A[beta]s solutions by three different MS approaches: matrix assisted laser desorption ionization-time of flight (MALDI-TOF), atmospheric pressure (AP) MALDI ion trap and electrospray ionization (ESI) ion trap. Differences in the obtained results are discussed and ESI is chosen as the most suitable MS method for A[beta]s detection. Finally, cleavage sites produced by interaction of A[beta]s with IDE are identified, two of which had never been reported in the literature.

  10. Study of amyloidpeptide functional brain networks in AD, MCI and HC.

    PubMed

    Jiang, Jiehui; Duan, Huoqiang; Huang, Zheming; Yu, Zhihua

    2015-01-01

    One medical challenge in studying the amyloid-β (Aβ) peptide mechanism for Alzheimer's disease (AD) is exploring the law of beta toxic oligomers' diffusion in human brains in vivo. One beneficial means of solving this problem is brain network analysis based on graph theory. In this study, the characteristics of Aβ functional brain networks of Healthy Control (HC), Mild Cognitive Impairment (MCI), and AD groups were compared by applying graph theoretical analyses to Carbon 11-labeled Pittsburgh compound B positron emission tomography (11C PiB-PET) data. 120 groups of PiB-PET images from the ADNI database were analyzed. The results showed that the small-world property of MCI and AD were lost as compared to HC. Furthermore, the local clustering of networks was higher in both MCI and AD as compared to HC, whereas the path length was similar among the three groups. The results also showed that there could be four potential Aβ toxic oligomer seeds: Frontal_Sup_Medial_L, Parietal_Inf_L, Frontal_Med_Orb_R, and Parietal_Inf_R. These four seeds are corresponding to Regions of Interests referred by physicians to clinically diagnose AD. PMID:26405999

  11. The Alzheimer's Disease-Associated Amyloid β-Protein Is an Antimicrobial Peptide

    PubMed Central

    Soscia, Stephanie J.; Kirby, James E.; Washicosky, Kevin J.; Tucker, Stephanie M.; Ingelsson, Martin; Hyman, Bradley; Burton, Mark A.; Goldstein, Lee E.; Duong, Scott; Tanzi, Rudolph E.; Moir, Robert D.

    2010-01-01

    Background The amyloid β-protein (Aβ) is believed to be the key mediator of Alzheimer's disease (AD) pathology. Aβ is most often characterized as an incidental catabolic byproduct that lacks a normal physiological role. However, Aβ has been shown to be a specific ligand for a number of different receptors and other molecules, transported by complex trafficking pathways, modulated in response to a variety of environmental stressors, and able to induce pro-inflammatory activities. Methodology/Principal Findings Here, we provide data supporting an in vivo function for Aβ as an antimicrobial peptide (AMP). Experiments used established in vitro assays to compare antimicrobial activities of Aβ and LL-37, an archetypical human AMP. Findings reveal that Aβ exerts antimicrobial activity against eight common and clinically relevant microorganisms with a potency equivalent to, and in some cases greater than, LL-37. Furthermore, we show that AD whole brain homogenates have significantly higher antimicrobial activity than aged matched non-AD samples and that AMP action correlates with tissue Aβ levels. Consistent with Aβ-mediated activity, the increased antimicrobial action was ablated by immunodepletion of AD brain homogenates with anti-Aβ antibodies. Conclusions/Significance Our findings suggest Aβ is a hitherto unrecognized AMP that may normally function in the innate immune system. This finding stands in stark contrast to current models of Aβ-mediated pathology and has important implications for ongoing and future AD treatment strategies. PMID:20209079

  12. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms

    PubMed Central

    Iljina, Marija; Garcia, Gonzalo A.; Dear, Alexander J.; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C. T.; Dobson, Christopher M.; Frenkel, Daan; Knowles, Tuomas P. J.; Klenerman, David

    2016-01-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer’s disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer’s disease. PMID:27346247

  13. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms

    NASA Astrophysics Data System (ADS)

    Iljina, Marija; Garcia, Gonzalo A.; Dear, Alexander J.; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C. T.; Dobson, Christopher M.; Frenkel, Daan; Knowles, Tuomas P. J.; Klenerman, David

    2016-06-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer’s disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer’s disease.

  14. Viscoelastic response of neural cells governed by the deposition of amyloidpeptides (Aβ)

    NASA Astrophysics Data System (ADS)

    Gong, Ze; You, Ran; Chang, Raymond Chuen-Chung; Lin, Yuan

    2016-06-01

    Because of its intimate relation with Alzheimer's disease (AD), the question of how amyloidpeptide (Aβ) deposition alters the membrane and cytoskeltal structure of neural cells and eventually their mechanical response has received great attention. In this study, the viscoelastic properties of primary neurons subjected to various Aβ treatments were systematically characterized using atomic force microrheology. It was found that both the storage ( G ') and loss ( G ″) moduli of neural cells are rate-dependent and grow by orders of magnitude as the driving frequency ω varies from 1 to 100 Hz. However, a much stronger frequency dependence was observed in the loss moduli (with a scaling exponent of ˜0.96) than that in G ' ( ˜ ω 0.2 ). Furthermore, both cell moduli increase gradually within the first 6 h of Aβ treatment before steady-state values are reached, with a higher dosage of Aβ leading to larger changes in cell properties. Interestingly, we showed that the measured neuron response can be well-explained by a power law structural damping model. Findings here establish a quantitative link between Aβ accumulation and the physical characteristics of neural cells and hence could provide new insights into how disorders like AD affect the progression of different neurological processes from a mechanics point of view.

  15. Induced expression of neuronal membrane attack complex and cell death by Alzheimer's beta-amyloid peptide.

    PubMed

    Shen, Y; Sullivan, T; Lee, C M; Meri, S; Shiosaki, K; Lin, C W

    1998-06-15

    beta-amyloid peptide (A beta) and complement-derived membrane attack complex (MAC) are co-localized in senile plaques of brains from Alzheimer's disease (AD) patients. But the relationship between A beta and complement activation is unclear. We have used human neurotypic cells, differentiated SH-SY5Y, as a model system to examine regulation of neuronal MAC expression and cell death by A beta. We demonstrated that mRNAs (C1q, C2, C3, C4, C5, C6, C7, C8 and C9) and proteins (C1q, C3 and C9) for the major components of the classical complement cascade are present in the SH-SY5Y neurotypic cells, indicating that neuronal cells can synthesize the necessary proteins required for MAC formation. Furthermore, immunocytochemical studies showed the A beta-induced neuronal MAC expression on the SH-SY5Y cells after CD59 was removed by PIPLC or blocked by anti-CD59 antibody. Meanwhile, increased A beta-induced neuronal cell death was observed following treatment with anti-CD59. Taken together, these results suggest that A beta activates neuronal complement cascade to induce MAC, and a deficiency of endogenous complement regulatory proteins, e.g., CD59, may increase the vulnerability of neurons to complement-mediated cytotoxicity. PMID:9689469

  16. Cytosolic amyloid-{beta} peptide 42 escaping from degradation induces cell death

    SciTech Connect

    Lee, Eun Kyung; Park, Yong Wook; Shin, Dong Yeon; Mook-Jung, Inhee; Yoo, Yung Joon . E-mail: yjyoo@gist.ac.kr

    2006-06-02

    Accumulating evidence suggests that intracellular amyloid-{beta} (A{beta}) peptide triggers the early pathological events in Alzheimer's disease (AD). However, little is known about the consequence of cytosolic A{beta}. In this study, we ectopically expressed A{beta}42 in the cytoplasm of SH-SY5Y neuroblastoma cells by expressing a fusion protein of GFP-tagged ubiquitin and A{beta}42 (GFPUb-A{beta}42). Although GFPUb and A{beta}42 are stochastically produced with the same molar ratio in the cytoplasm, A{beta}42 was completely degraded in more than 50% of the GFPUb-expressing cells. However, if A{beta}42 was not degraded in their cytoplasm, then A{beta}42-expressing cells underwent apoptosis. The number of A{beta}42-expressing cells is significantly increased by the inhibition of proteasome with MG132. Cytosolic A{beta}42 which has escaped degradation inhibits proteasome and thereby may accelerate the accumulation of A{beta}42 and its detrimental effects. Our findings suggest that cells have the potential to degrade A{beta}42 in their cytoplasm but if A{beta}42 appears in the cytoplasm due to its incomplete degradation, it accumulates and may trigger the fatal cascade of pathology of AD.

  17. Amyloidpeptides act as allosteric modulators of cholinergic signalling through formation of soluble BAβACs.

    PubMed

    Kumar, Rajnish; Nordberg, Agneta; Darreh-Shori, Taher

    2016-01-01

    Amyloidpeptides, through highly sophisticated enzymatic machinery, are universally produced and released in an action potential synchronized manner into the interstitial fluids in the brain. Yet no native functions are attributed to amyloid-β. The amyloid-β hypothesis ascribes just neurotoxicity properties through build-up of soluble homomeric amyloid-β oligomers or fibrillar deposits. Apolipoprotein-ε4 (APOE4) allele is the only confirmed genetic risk factor of sporadic Alzheimer's disease; once more it is unclear how it increases the risk of Alzheimer's disease. Similarly, central cholinergic signalling is affected selectively and early in the Alzheimer's disease brain, again why cholinergic neurons show this sensitivity is still unclear. However, the three main known Alzheimer's disease risk factors, advancing age, female gender and APOE4, have been linked to a high apolipoprotein-E and accumulation of the acetylcholine degrading enzyme, butyrylcholinesterase in cerebrospinal fluids of patients. Furthermore, numerous reports indicate that amyloid-β interacts with butyrylcholinesterase and apolipoprotein-E. We have proposed that this interaction leads to formation of soluble ultrareactive acetylcholine-hydrolyzing complexes termed BAβACs, to adjust at demand both synaptic and extracellular acetylcholine signalling. This hypothesis predicted presence of acetylcholine-synthesizing enzyme, choline acetyltransferase in extracellular fluids to allow maintenance of equilibrium between breakdown and synthesis of acetylcholine through continuous in situ syntheses. A recent proof-of-concept study led to the discovery of this enzyme in the human extracellular fluids. We report here that apolipoprotein-E, in particular ε4 isoprotein acts as one of the strongest endogenous anti-amyloid-β fibrillization agents reported in the literature. At biological concentrations, apolipoprotein-E prevented amyloid-β fibrillization for at least 65 h. We show that amyloid

  18. Amyloidpeptides act as allosteric modulators of cholinergic signalling through formation of soluble BAβACs

    PubMed Central

    Kumar, Rajnish; Nordberg, Agneta

    2016-01-01

    Amyloidpeptides, through highly sophisticated enzymatic machinery, are universally produced and released in an action potential synchronized manner into the interstitial fluids in the brain. Yet no native functions are attributed to amyloid-β. The amyloid-β hypothesis ascribes just neurotoxicity properties through build-up of soluble homomeric amyloid-β oligomers or fibrillar deposits. Apolipoprotein-ε4 (APOE4) allele is the only confirmed genetic risk factor of sporadic Alzheimer’s disease; once more it is unclear how it increases the risk of Alzheimer’s disease. Similarly, central cholinergic signalling is affected selectively and early in the Alzheimer’s disease brain, again why cholinergic neurons show this sensitivity is still unclear. However, the three main known Alzheimer’s disease risk factors, advancing age, female gender and APOE4, have been linked to a high apolipoprotein-E and accumulation of the acetylcholine degrading enzyme, butyrylcholinesterase in cerebrospinal fluids of patients. Furthermore, numerous reports indicate that amyloid-β interacts with butyrylcholinesterase and apolipoprotein-E. We have proposed that this interaction leads to formation of soluble ultrareactive acetylcholine-hydrolyzing complexes termed BAβACs, to adjust at demand both synaptic and extracellular acetylcholine signalling. This hypothesis predicted presence of acetylcholine-synthesizing enzyme, choline acetyltransferase in extracellular fluids to allow maintenance of equilibrium between breakdown and synthesis of acetylcholine through continuous in situ syntheses. A recent proof-of-concept study led to the discovery of this enzyme in the human extracellular fluids. We report here that apolipoprotein-E, in particular ε4 isoprotein acts as one of the strongest endogenous anti-amyloid-β fibrillization agents reported in the literature. At biological concentrations, apolipoprotein-E prevented amyloid-β fibrillization for at least 65 h. We show that

  19. Self-Assembly of a 9-Residue Amyloid-Forming Peptide Fragment of SARS Corona Virus E-protein: Mechanism of Self Aggregation and Amyloid-Inhibition of hIAPP

    PubMed Central

    Bhat, Jyotsna; Bera, Supriyo; Midya, Anupam; Fierke, Carol A.; Ramamoorthy, Ayyalusamy; Bhunia, Anirban

    2016-01-01

    Molecular self-assembly, a phenomenon widely observed in nature, has been exploited through organic molecules, proteins, DNA and peptides to study complex biological systems. These self-assembly systems may also be used in understanding the molecular and structural biology which can inspire the design and synthesis of increasingly complex biomaterials. Specifically, use of these building blocks to investigate protein folding and misfolding has been of particular value since it can provide tremendous insights into peptide aggregation related to a variety of protein misfolding diseases, or amyloid diseases (e.g. Alzheimer’s disease, Parkinson’s disease, type-II diabetes). Herein, the self-assembly of TK9, a 9 residue peptide of the extra membrane C-terminal tail of the SARS Corona virus envelope, and its variants were characterized through biophysical, spectroscopic and simulated studies, and it was confirmed that the structure of these peptides influence their aggregation propensity, hence, mimicking amyloid proteins. TK9, which forms a beta-sheet rich fibril, contains a key sequence motif that may be critical for beta-sheet formation, thus making it an interesting system to study amyloid fibrillation. TK9 aggregates were further examined through simulations to evaluate the possible intra- and inter peptide interactions at the molecular level. These self-assembly peptides can also serve as amyloid inhibitors through hydrophobic and electrophilic recognition interactions. Our results show that TK9 inhibits the fibrillation of hIAPP, a 37 amino acid peptide implicated in the pathology of type-II diabetes. Thus, biophysical and NMR experimental results have revealed a molecular level understanding of peptide folding events, as well as the inhibition of amyloid-protein aggregation are reported. PMID:25785896

  20. A Robust and Efficient Production and Purification Procedure of Recombinant Alzheimers Disease Methionine-Modified AmyloidPeptides.

    PubMed

    Hoarau, Marie; Malbert, Yannick; Irague, Romain; Hureau, Christelle; Faller, Peter; Gras, Emmanuel; André, Isabelle; Remaud-Siméon, Magali

    2016-01-01

    An improved production and purification method for Alzheimer's disease related methionine-modified amyloid-β 1-40 and 1-42 peptides is proposed, taking advantage of the formation of inclusion body in Escherichia coli. A Thioflavin-S assay was set-up to evaluate inclusion body formation during growth and optimize culture conditions for amyloidpeptides production. A simple and fast purification protocol including first the isolation of the inclusion bodies and second, two cycles of high pH denaturation/ neutralization combined with an ultrafiltration step on 30-kDa cut-off membrane was established. Special attention was paid to purity monitoring based on a rational combination of UV spectrophotometry and SDS-PAGE analyses at the various stages of the process. It revealed that this chromatography-free protocol affords good yield of high quality peptides in term of purity. The resulting peptides were fully characterized and are appropriate models for highly reproducible in vitro aggregation studies. PMID:27532547

  1. A Robust and Efficient Production and Purification Procedure of Recombinant Alzheimers Disease Methionine-Modified AmyloidPeptides

    PubMed Central

    Hoarau, Marie; Hureau, Christelle; Faller, Peter; Gras, Emmanuel; André, Isabelle; Remaud-Siméon, Magali

    2016-01-01

    An improved production and purification method for Alzheimer’s disease related methionine-modified amyloid-β 1–40 and 1–42 peptides is proposed, taking advantage of the formation of inclusion body in Escherichia coli. A Thioflavin-S assay was set-up to evaluate inclusion body formation during growth and optimize culture conditions for amyloidpeptides production. A simple and fast purification protocol including first the isolation of the inclusion bodies and second, two cycles of high pH denaturation/ neutralization combined with an ultrafiltration step on 30-kDa cut-off membrane was established. Special attention was paid to purity monitoring based on a rational combination of UV spectrophotometry and SDS-PAGE analyses at the various stages of the process. It revealed that this chromatography-free protocol affords good yield of high quality peptides in term of purity. The resulting peptides were fully characterized and are appropriate models for highly reproducible in vitro aggregation studies. PMID:27532547

  2. Dutch and arctic mutant peptides of β amyloid1–40 differentially affect the FGF-2 pathway in brain endothelium

    PubMed Central

    Solito, Raffaella; Corti, Federico; Fossati, Silvia; Mezhericher, Emiliya; Donnini, Sandra; Ghiso, Jorge; Giachetti, Antonio; Rostagno, Agueda; Ziche, Marina

    2009-01-01

    Single point mutations of the amyloid precursor protein generate Aβ variants bearing amino acid substitutions at positions 21–23. These mutants are associated with distinct hereditary phenotypes of cerebral amyloid angiopathy, manifesting varying degrees of tropism for brain vessels, and impaired microvessel remodeling and angiogenesis. We examined the differential effects of E22Q (Dutch), and E22G (Arctic) variants in comparison to WT Aβ on brain endothelial cell proliferation, angiogenic phenotype expression triggered by fibroblast growth factor (FGF-2), pseudo-capillary sprouting, and induction of apoptosis. E22Q exhibited a potent anti-angiogenic profile in contrast to E22G, which had a much weaker effect. Investigations on the FGF-2 signaling pathway revealed the greatest differences among the peptides: E22Q andWT peptides suppressed FGF-2 expression while E22G had barely any effect. Phosphorylation of the FGF-2 receptor, FGFR-1, and the survival signal Akt were abolished by E22Q and WT peptides, but not by E22G. The biological dissimilar effect of the mutant and WT peptides on cerebral EC cannot be assigned to a particular Aβ structure, suggesting that the toxic effect of the Aβ assemblies goes beyond mere multimerization. PMID:19061884

  3. Bilirubin and amyloid-beta peptide induce cytochrome c release through mitochondrial membrane permeabilization.

    PubMed Central

    Rodrigues, C. M.; Solá, S.; Silva, R.; Brites, D.

    2000-01-01

    BACKGROUND: The pathogenesis of bilirubin encephalopathy and Alzheimer's disease appears to result from accumulation of unconjugated bilirubin (UCB) and amyloid-beta (Abeta) peptide, respectively, which may cause apoptosis. Permeabilization of the mitochondrial membrane, with release of intermembrane proteins, has been strongly implicated in cell death. Inhibition of the mitochondrial permeability is one pathway by which ursodeoxycholate (UDC) and tauroursodeoxycholate (TUDC) protect against apoptosis in hepatic and nonhepatic cells. In this study, we further characterize UCB- and Abeta-induced cytotoxicty in isolated neural cells, and investigate membrane perturbation during incubation of isolated mitochondria with both agents. In addition, we evaluate whether the anti-apoptotic drugs UDC and TUDC prevent any changes from occurring. MATERIALS AND METHODS: Primary rat neuron and astrocyte cultures were incubated with UCB or Abeta peptide, either alone or in the presence of UDC. Apoptosis was assessed by DNA fragmentation and nuclear morphological changes. Isolated mitochondria were treated with each toxic, either alone or in combination with UDC, TUDC, or cyclosporine A. Mitochondrial swelling was measured spectrophotometrically and cytochrome c protein levels determined by Western blot. RESULTS: Incubation of neural cells with both UCB and Abeta induced apoptosis (p < 0.01). Coincubation with UDC reduced apoptosis by > 50% (p < 0.05). Both toxins caused membrane permeabilization in isolated mitochondria (p < 0.001); whereas, pretreatment with UDC was protective (p < 0.05). TUDC was even more effective at preventing matrix swelling mediated by Abeta (p < 0.01). UDC and TUDC markedly reduced cytochrome c release associated with mitochondrial permeabilization induced by UCB and Abeta, respectively (p < 0.05). Moreover, cyclosporine A significantly inhibited mitochondrial swelling and cytochrome c efflux mediated by UCB (p < 0.05). CONCLUSION: UCB and Abeta peptide

  4. The architecture of amyloid-like peptide fibrils revealed by X-ray scattering, diffraction and electron microscopy

    SciTech Connect

    Langkilde, Annette E.; Morris, Kyle L.; Serpell, Louise C.; Svergun, Dmitri I.; Vestergaard, Bente

    2015-04-01

    The aggregation process and the fibril state of an amyloidogenic peptide suggest monomer addition to be the prevailing mechanism of elongation and a model of the peptide packing in the fibrils has been obtained. Structural analysis of protein fibrillation is inherently challenging. Given the crucial role of fibrils in amyloid diseases, method advancement is urgently needed. A hybrid modelling approach is presented enabling detailed analysis of a highly ordered and hierarchically organized fibril of the GNNQQNY peptide fragment of a yeast prion protein. Data from small-angle X-ray solution scattering, fibre diffraction and electron microscopy are combined with existing high-resolution X-ray crystallographic structures to investigate the fibrillation process and the hierarchical fibril structure of the peptide fragment. The elongation of these fibrils proceeds without the accumulation of any detectable amount of intermediate oligomeric species, as is otherwise reported for, for example, glucagon, insulin and α-synuclein. Ribbons constituted of linearly arranged protofilaments are formed. An additional hierarchical layer is generated via the pairing of ribbons during fibril maturation. Based on the complementary data, a quasi-atomic resolution model of the protofilament peptide arrangement is suggested. The peptide structure appears in a β-sheet arrangement reminiscent of the β-zipper structures evident from high-resolution crystal structures, with specific differences in the relative peptide orientation. The complexity of protein fibrillation and structure emphasizes the need to use multiple complementary methods.

  5. Immunosensor for diagnosis of Alzheimer disease using amyloid-β 1-40 peptide and silk fibroin thin films.

    PubMed

    Gonçalves, J M; Lima, L R; Moraes, M L; Ribeiro, S J L

    2016-11-01

    Layer-by-Layer (LbL) films containing silk fibroin (SF) and the 40 aminoacid-long amyloidpeptide (Aβ1-40) were prepared with the purpose of developing a new prototype of an electrochemical immunosensor. The film showed a satisfactory growth in quartz substrate and screen-printed carbon electrodes, as observed by UV-vis spectroscopy and cyclic voltammetric, respectively. The peptide immobilized in LbL films in junction with SF shows secondary structure induced, as shown by circular dichroism measurements, favoring the interaction SF/peptide LbL film with the specific antibody. Immunosensor showed a linear response in the presence of the antibody with concentrations from 0 to 10ngmL(-1) both analyzed by current changes in 0.3V and voltammogram area. This system can be applied as a new prototype for preliminary diagnosis of Alzheimer's disease. PMID:27524028

  6. Familial amyloid precursor protein mutants cause caspase-6-dependent but amyloid β-peptide-independent neuronal degeneration in primary human neuron cultures.

    PubMed Central

    Sivananthan, S N; Lee, A W; Goodyer, C G; LeBlanc, A C

    2010-01-01

    Although familial Alzheimer disease (AD)-associated autosomal dominant mutants have been extensively studied, little is known about the underlying molecular mechanisms of neurodegeneration induced by these mutants in AD. Wild-type, Swedish or London amyloid precursor protein (APP) transfection in primary human neurons induced neuritic beading, in which several co-expressed proteins, such as enhanced green fluorescent protein, red fluorescent protein (RFP)-tau and RFP-ubiquitin, accumulated. APP-induced neuritic beading was dependent on caspase-6 (Casp6), because it was inhibited with 5 μM z-VEID-fmk or with dominant-negative Casp6. Neuritic beading was independent from APP-mediated amyloid β-peptide (Aβ) production, because the APPM596V (APPMV) mutant, which cannot generate Aβ, still induced Casp6-dependent neuritic beading. However, the beaded neurons underwent Casp6- and Aβ-dependent cell death. These results indicate that overexpression of wild-type or mutant APP causes Casp6-dependent but Aβ-independent neuritic degeneration in human neurons. Because Casp6 is activated early in AD and is involved in axonal degeneration, these results suggest that the inhibition of Casp6 may represent an efficient early intervention against familial forms of AD. Furthermore, these results indicate that removing Aβ without inhibiting Casp6 may have little effect in preventing the progressive dementia associated with sporadic or familial AD. PMID:21368865

  7. Self-assembly of a nine-residue amyloid-forming peptide fragment of SARS corona virus E-protein: mechanism of self aggregation and amyloid-inhibition of hIAPP.

    PubMed

    Ghosh, Anirban; Pithadia, Amit S; Bhat, Jyotsna; Bera, Supriyo; Midya, Anupam; Fierke, Carol A; Ramamoorthy, Ayyalusamy; Bhunia, Anirban

    2015-04-01

    Molecular self-assembly, a phenomenon widely observed in nature, has been exploited through organic molecules, proteins, DNA, and peptides to study complex biological systems. These self-assembly systems may also be used in understanding the molecular and structural biology which can inspire the design and synthesis of increasingly complex biomaterials. Specifically, use of these building blocks to investigate protein folding and misfolding has been of particular value since it can provide tremendous insights into peptide aggregation related to a variety of protein misfolding diseases, or amyloid diseases (e.g., Alzheimer's disease, Parkinson's disease, type-II diabetes). Herein, the self-assembly of TK9, a nine-residue peptide of the extra membrane C-terminal tail of the SARS corona virus envelope, and its variants were characterized through biophysical, spectroscopic, and simulated studies, and it was confirmed that the structure of these peptides influences their aggregation propensity, hence, mimicking amyloid proteins. TK9, which forms a beta-sheet rich fibril, contains a key sequence motif that may be critical for beta-sheet formation, thus making it an interesting system to study amyloid fibrillation. TK9 aggregates were further examined through simulations to evaluate the possible intra- and interpeptide interactions at the molecular level. These self-assembly peptides can also serve as amyloid inhibitors through hydrophobic and electrophilic recognition interactions. Our results show that TK9 inhibits the fibrillation of hIAPP, a 37 amino acid peptide implicated in the pathology of type-II diabetes. Thus, biophysical and NMR experimental results have revealed a molecular level understanding of peptide folding events, as well as the inhibition of amyloid-protein aggregation are reported.

  8. Green tea aroma fraction reduces β-amyloid peptide-induced toxicity in Caenorhabditis elegans transfected with human β-amyloid minigene.

    PubMed

    Takahashi, Atsushi; Watanabe, Tatsuro; Fujita, Takashi; Hasegawa, Toshio; Saito, Michio; Suganuma, Masami

    2014-01-01

    Green tea is a popular world-wide beverage with health benefits that include preventive effects on cancer as well as cardiovascular, liver and Alzheimer's diseases (AD). This study will examine the preventive effects on AD of a unique aroma of Japanese green tea. First, a transgenic Caenorhabditis elegans (C. elegans) CL4176 expressing human β-amyloid peptide (Aβ) was used as a model of AD. A hexane extract of processed green tea was further fractionated into volatile and non-volatile fractions, named roasty aroma and green tea aroma fractions depending on their aroma, by microscale distillation. Both hexane extract and green tea aroma fraction were found to inhibit Aβ-induced paralysis, while only green tea aroma fraction extended lifespan in CL4176. We also found that green tea aroma fraction has antioxidant activity. This paper indicates that the green tea aroma fraction is an additional component for prevention of AD. PMID:25229860

  9. How the amyloidpeptide and membranes affect each other: an extensive simulation study.

    PubMed

    Poojari, Chetan; Kukol, Andreas; Strodel, Birgit

    2013-02-01

    The etiology of Alzheimer's disease is thought to be linked to interactions between amyloid-β (Aβ) and neural cell membranes, causing membrane disruption and increased ion conductance. The effects of Aβ on lipid behavior have been characterized experimentally, but structural and causal details are lacking. We used atomistic molecular dynamics simulations totaling over 6 μs in simulation time to investigate the behavior of Aβ(42) in zwitterionic and anionic lipid bilayers. We simulated transmembrane β-sheets (monomer and tetramer) resulting from a global optimization study and a helical structure obtained from an NMR study. In all simulations Aβ(42) remained embedded in the bilayer. It was found that the surface charge and the lipid tail type are determinants for transmembrane stability of Aβ(42) with zwitterionic surfaces and unsaturated lipids promoting stability. From the considered structures, the β-sheet tetramer is most stable as a result of interpeptide interactions. We performed an in-depth analysis of the translocation of water in the Aβ(42)-bilayer systems. We observed that this process is generally fast (within a few nanoseconds) yet generally slower than in the peptide-free bilayers. It is mainly governed by the lipid type, simulation temperature and Aβ(42) conformation. The rate limiting step is the permeation through the hydrophobic core, where interactions between Aβ(42) and permeating H(2)O molecules slow the translocation process. The β-sheet tetramer allows more water molecules to pass through the bilayer compared to monomeric Aβ, allowing us to conclude that the experimentally observed permeabilization of membranes must be due to membrane-bound Aβ oligomers, and not monomers.

  10. Amyloidpeptide induces temporal membrane biphasic changes in astrocytes through cytosolic phospholipase A2

    PubMed Central

    Hicks, Jacob B.; Lai, Yinzhi; Sheng, Wenwen; Yang, Xiaoguang; Zhu, Donghui; Sun, Grace Y.; Lee, James C-M

    2008-01-01

    Oligomeric amyloidpeptide (Aβ) is known to induce cytotoxic effects and to damage cell functions in Alzheimer’s disease. However, mechanisms underlying the effects of Aβ on cell membranes have yet to be fully elucidated. In this study, Aβ 1–42 (Aβ42) was shown to cause a temporal biphasic change in membranes of astrocytic DITNC cells using fluorescence microscopy of Laurdan. Aβ42 made astrocyte cell membranes became more molecularly-disordered within the first 30 minutes to 1 hour, but gradually changed to more molecularly-ordered after 3 hours. However, Aβ42 caused artificial membranes of vesicles made of rat whole brain lipid extract to become more disordered only. The trend for more molecularly-ordered membranes in astrocytes induced by Aβ42 was abrogated by either an NADPH oxidase inhibitor, apocynin, or an inhibitor of cytosolic phospholipase A2 (cPLA2), but not by an inhibitor of calcium-independent PLA2 (iPLA2). Apocynin also suppressed the increased production of superoxide anions (O2.−) and phosphorylation of cPLA2 induced by Aβ42. In addition, hydrolyzed products of cPLA2, arachidonic acid (AA), but not lysophosphatidylcholine (LPC) caused astrocyte membranes to become more molecularly-ordered. These results suggest (1) a direct interaction of Aβ42 with cell membranes making them more molecularly-disordered, and (2) Aβ42 also indirectly makes membranes become more molecularly-ordered by triggering the signaling pathway involving NADPH oxidase and cPLA2 in astrocytes. PMID:18725190

  11. Amyloidpeptide fibrils induce nitro-oxidative stress in neuronal cells.

    PubMed

    Ill-Raga, Gerard; Ramos-Fernández, Eva; Guix, Francesc X; Tajes, Marta; Bosch-Morató, Mónica; Palomer, Ernest; Godoy, Juan; Belmar, Sebastián; Cerpa, Waldo; Simpkins, James W; Inestrosa And, Nibaldo C; Muñoz, Francisco J

    2010-01-01

    Different mechanisms including oxidative stress are proposed for amyloidpeptide (Aβ) neurotoxicity, and here we contribute to demonstrate that nitro-oxidative stress is playing a key role. Yeasts are a well-known model for H2O2 toxicity. Interestingly, yeast cell wall prevents interaction of Aβ fibrils with membrane receptors or calcium channels and we found a significant viability reduction in yeasts when challenged with Aβ fibrils. Furthermore, iron and copper chelators, as well as the antioxidants glutathione and trolox, were neuroprotective on neuroblastoma cells and mouse hippocampal neurons challenged with Aβ fibrils. Glutathione prevents the oxidation, glycation and nitrotyrosination of cell proteins induced by Aβ. Trolox protected neurons in cell viability studies, maintaining the vesicular transport integrity and preventing the trigger of apoptotic mechanisms. Interestingly, we have also found that brain derived neuronal factor (BDNF) and neurotrophin-3 (NT-3) were able to protect mouse hippocampal and cortical neurons against H2O2 and Aβ fibrils. Considering that superoxide anion, produced by Aβ cell damage, and nitric oxide, whose production is altered in AD, react to form the highly reactive peroxynitrite anion, we studied the role of trolox to ameliorate the peroxynitrite cell damage. Finally, one of the major proteins to be nitrotyrosinated in AD, the triose phosphate isomerase (TPI) was assayed searching for a denitrase activity that could reverse intracellular nitrotyrosination. We have found that human neuroblastoma SH-SY5Y cells express a constitutive denitrase activity that partially denitrated nitro-TPI. Altogether, our results support a key role of nitro-oxidative stress in the neuronal damage induced by Aβ fibrils. PMID:20858976

  12. Apolipoprotein E, especially apolipoprotein E4, increases the oligomerization of amyloid β peptide.

    PubMed

    Hashimoto, Tadafumi; Serrano-Pozo, Alberto; Hori, Yukiko; Adams, Kenneth W; Takeda, Shuko; Banerji, Adrian Olaf; Mitani, Akinori; Joyner, Daniel; Thyssen, Diana H; Bacskai, Brian J; Frosch, Matthew P; Spires-Jones, Tara L; Finn, Mary Beth; Holtzman, David M; Hyman, Bradley T

    2012-10-24

    Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder causing dementia. Massive deposition of amyloid β peptide (Aβ) as senile plaques in the brain is the pathological hallmark of AD, but oligomeric, soluble forms of Aβ have been implicated as the synaptotoxic component. The apolipoprotein E ε 4 (apoE ε4) allele is known to be a genetic risk factor for developing AD. However, it is still unknown how apoE impacts the process of Aβ oligomerization. Here, we found that the level of Aβ oligomers in APOE ε4/ε4 AD patient brains is 2.7 times higher than those in APOE ε3/ε3 AD patient brains, matched for total plaque burden, suggesting that apoE4 impacts the metabolism of Aβ oligomers. To test this hypothesis, we examined the effect of apoE on Aβ oligomer formation. Using both synthetic Aβ and a split-luciferase method for monitoring Aβ oligomers, we observed that apoE increased the level of Aβ oligomers in an isoform-dependent manner (E2 < E3 < E4). This effect appears to be dependent on the ApoE C-terminal domain. Moreover, these results were confirmed using endogenous apoE isolated from the TBS-soluble fraction of human brain, which increased the formation of Aβ oligomers. Together, these data show that lipidated apoE, especially apoE4, increases Aβ oligomers in the brain. Higher levels of Aβ oligomers in the brains of APOE ε4/ε4 carriers compared with APOE ε3/ε3 carriers may increase the loss of dendritic spines and accelerate memory impairments, leading to earlier cognitive decline in AD.

  13. Investigation of the effect of erythrosine B on amyloid beta peptide using molecular modeling.

    PubMed

    Lee, Juho; Kwon, Inchan; Jang, Seung Soon; Cho, Art E

    2016-04-01

    Neurotoxic plaques composed of 39 to 42 residue-long amyloid beta peptides (Aβs) are copiously present in the brains of patients with Alzheimer's disease (AD). Erythrosine B (ER), a xanthene food dye, inhibits the formation of Aβ fibrils and Aβ-associated cytotoxicity in vitro. Here, in an attempt to elucidate the inhibition mechanism, we performed molecular dynamics (MD) simulations to demonstrate the conformational change of Aβ40 induced by ER molecules in atomistic detail. During the simulation, the ER bound to the surfaces of both N-terminus and C-terminus regions of Aβ40. Our result shows that ER interacts with the aromatic side chains at the N-terminus region resulting in destabilization of the inter-chain stacking of Aβ40. Moreover, the stablility of the helical structures at the residues from 13 to 16 suggests that ER disturbs conformational transition of Aβ40. At the C-terminus region, the bound ER blocks water molecules and stabilizes the α-helical structure. Regardless of the number of ER molecules used, the interruption of the formation of the salt-bridge between aspartic acid 23 and lysine 28 occurred. To further validate our analysis, binding free energies of ER at each binding site were evaluated. The finding of stronger binding energy at the N-terminus region supports an inhibition mechanism induced by stacking interaction between ER and phenylalanine. These findings could aid present and future treatment studies for AD by clarifying the inhibition mechanism of ER on the conformational transition of Aβ40 at the molecular level. PMID:27021211

  14. Molecular dynamics simulation and molecular docking studies of Angiotensin converting enzyme with inhibitor lisinopril and amyloid Beta Peptide.

    PubMed

    Jalkute, Chidambar Balbhim; Barage, Sagar Hindurao; Dhanavade, Maruti Jayram; Sonawane, Kailas Dasharath

    2013-06-01

    Angiotensin converting enzyme (ACE) cleaves amyloid beta peptide. So far this cleavage mechanism has not been studied in detail at atomic level. Keeping this view in mind, we performed molecular dynamics simulation of crystal structure complex of testis truncated version of ACE (tACE) and its inhibitor lisinopril along with Zn(2+) to understand the dynamic behavior of active site residues of tACE. Root mean square deviation results revealed the stability of tACE throughout simulation. The residues Ala 354, Glu 376, Asp 377, Glu 384, His 513, Tyr 520 and Tyr 523 of tACE stabilized lisinopril by hydrogen bonding interactions. Using this information in subsequent part of study, molecular docking of tACE crystal structure with Aβ-peptide has been made to investigate the interactions of Aβ-peptide with enzyme tACE. The residues Asp 7 and Ser 8 of Aβ-peptide were found in close contact with Glu 384 of tACE along with Zn(2+). This study has demonstrated that the residue Glu 384 of tACE might play key role in the degradation of Aβ-peptide by cleaving peptide bond between Asp 7 and Ser 8 residues. Molecular basis generated by this attempt could provide valuable information towards designing of new therapies to control Aβ concentration in Alzheimer's patient.

  15. Structural, thermodynamical, and dynamical properties of oligomers formed by the amyloid NNQQ peptide: Insights from coarse-grained simulations

    NASA Astrophysics Data System (ADS)

    Lu, Yan; Wei, Guanghong; Derreumaux, Philippe

    2012-07-01

    Characterizing the early formed oligomeric intermediates of amyloid peptides is of particular interest due to their links with neurodegenerative diseases. Here we study the NNQQ peptide, known to display parallel β-strands in amyloid fibrils by x-ray microcrystallography, and investigate the structural, thermodynamical, and dynamical properties of 20 NNQQ peptides using molecular dynamics and replica exchange molecular dynamics simulations coupled to a coarse-grained force field. All simulations are initiated from randomized and fully dispersed monomeric conformations. Our simulations reveal that the phase transition is characterized by a change in the oligomer and β-sheet size distributions and the percentage of mixed parallel/antiparallel β-strands when the sheets are formed. At all temperatures, however, the fraction of parallel β-strands remains low, though there are many association/fragmentation events. This work and a growing body of computational studies provide strong evidence that the critical nucleus goes beyond 20 chains and reordering of the β-strands occurs in larger oligomers.

  16. Probing amyloid beta-induced cell death using a fluorescence-peptide conjugate in Alzheimer's disease mouse model.

    PubMed

    Lee, Jong Kil; Wang, Kai; Park, Min Hee; Kim, Namoh; Lee, Ju Youn; Jin, Hee Kyung; Kim, In-San; Lee, Byung-Heon; Bae, Jae-Sung

    2016-09-01

    With the increasing worldwide incidence of Alzheimer's disease (AD), there is a critical need for the discovery of more effective diagnostic methods. However, development of diagnostic tools in AD has been hindered by obstacles such as the absence of exact biomarkers. Apoptosis caused by amyloid-β (Aβ) plays an important role in AD pathology; therefore, provides an attractive biological target for the diagnosis of AD. The present study aimed to evaluate the potential of small peptide, named ApoPep-1 (Apoptosis-targeting peptide-1) as a new apoptosis imaging agent in AD. The fluorescein-conjugated ApoPep-1, but not the control peptide, targeted apoptotic cells in the brain of amyloid precursor protein (APP)/presenilin 1 (PS1) mice. We also observed fluorescence signals during in vivo imaging of apoptotic cells using ApoPep-1, and fluorescence levels increased in an age-dependent manner in APP/PS1 mice. Ex vivo imaging of isolated brains in APP/PS1 mice further confirmed the targeting of ApoPep-1 to apoptotic cells. The fluorescein-labeled ApoPep-1 co-localized with brain cells such as neurons, astrocytes, and microglia, all of which undergo apoptosis in the APP/PS1 mice brain. These findings demonstrate that ApoPep-1 can target apoptotic brain cells, and be used for experimental investigations relevant to apoptosis in AD. PMID:27369450

  17. Enhanced antidepressant effect of sigma(1) (sigma(1)) receptor agonists in beta(25-35)-amyloid peptide-treated mice.

    PubMed

    Urani, Alexandre; Romieu, Pascal; Roman, François J; Maurice, Tangui

    2002-08-21

    This study examined the antidepressant efficacy of the selective sigma(1) receptor agonists igmesine or PRE-084 in mice injected intracerebroventricularly (i.c.v.) with beta(25-35)-amyloid peptide and submitted to the forced swim test. Beta(25-35) peptide-injected animals developed memory deficits after 8 days contrarily to controls injected with scrambled beta(25-35) peptide or vehicle solution. In the forced swim test, the i.c.v. treatment failed to affect the immobility duration, but the antidepressant effect of the sigma(1) agonists was facilitated in beta(25-35) animals. Igmesine reduced immobility duration at 30 versus 60 mg/kg in control groups. PRE-084 decreased immobility duration at 30 and 60 mg/kg only in beta(25-35) animals. Desipramine reduced the immobility duration similarly among groups and fluoxetine appeared less potent in beta(25-35) animals. The beta(25-35) animals exhibited decreased progesterone levels in the hippocampus (-47%). The behavioural efficacy of sigma(1) agonists is known to depend on neuro(active)steroids levels synthesised by glial cells and neurones, which are affected by the beta-amyloid toxicity. This behavioural study suggests that sigma(1) agonists, due to their enhanced efficacy, may allow to alleviate the depressive symptoms associated with Alzheimer's disease.

  18. Proteolytically inactive insulin-degrading enzyme inhibits amyloid formation yielding non-neurotoxic aβ peptide aggregates.

    PubMed

    de Tullio, Matias B; Castelletto, Valeria; Hamley, Ian W; Martino Adami, Pamela V; Morelli, Laura; Castaño, Eduardo M

    2013-01-01

    Insulin-degrading enzyme (IDE) is a neutral Zn(2+) peptidase that degrades short peptides based on substrate conformation, size and charge. Some of these substrates, including amyloid β (Aβ) are capable of self-assembling into cytotoxic oligomers. Based on IDE recognition mechanism and our previous report of the formation of a stable complex between IDE and intact Aβ in vitro and in vivo, we analyzed the possibility of a chaperone-like function of IDE. A proteolytically inactive recombinant IDE with Glu111 replaced by Gln (IDEQ) was used. IDEQ blocked the amyloidogenic pathway of Aβ yielding non-fibrillar structures as assessed by electron microscopy. Measurements of the kinetics of Aβ aggregation by light scattering showed that 1) IDEQ effect was promoted by ATP independent of its hydrolysis, 2) end products of Aβ-IDEQ co-incubation were incapable of "seeding" the assembly of monomeric Aβ and 3) IDEQ was ineffective in reversing Aβ aggregation. Moreover, Aβ aggregates formed in the presence of IDEQ were non-neurotoxic. IDEQ had no conformational effects upon insulin (a non-amyloidogenic protein under physiological conditions) and did not disturb insulin receptor activation in cultured cells. Our results suggest that IDE has a chaperone-like activity upon amyloid-forming peptides. It remains to be explored whether other highly conserved metallopeptidases have a dual protease-chaperone function to prevent the formation of toxic peptide oligomers from bacteria to mammals. PMID:23593132

  19. Transmissible amyloid.

    PubMed

    Tjernberg, L O; Rising, A; Johansson, J; Jaudzems, K; Westermark, P

    2016-08-01

    There are around 30 human diseases associated with protein misfolding and amyloid formation, each one caused by a certain protein or peptide. Many of these diseases are lethal and together they pose an enormous burden to society. The prion protein has attracted particular interest as being shown to be the pathogenic agent in transmissible diseases such as kuru, Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. Whether similar transmission could occur also in other amyloidoses such as Alzheimer's disease, Parkinson's disease and serum amyloid A amyloidosis is a matter of intense research and debate. Furthermore, it has been suggested that novel biomaterials such as artificial spider silk are potentially amyloidogenic. Here, we provide a brief introduction to amyloid, prions and other proteins involved in amyloid disease and review recent evidence for their potential transmission. We discuss the similarities and differences between amyloid and silk, as well as the potential hazards associated with protein-based biomaterials. PMID:27002185

  20. High-resolution molecular structure of a peptide in an amyloid fibril determined by magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Jaroniec, Christopher P.; Macphee, Cait E.; Bajaj, Vikram S.; McMahon, Michael T.; Dobson, Christopher M.; Griffin, Robert G.

    2004-01-01

    Amyloid fibrils are self-assembled filamentous structures associated with protein deposition conditions including Alzheimer's disease and the transmissible spongiform encephalopathies. Despite the immense medical importance of amyloid fibrils, no atomic-resolution structures are available for these materials, because the intact fibrils are insoluble and do not form diffraction-quality 3D crystals. Here we report the high-resolution structure of a peptide fragment of the amyloidogenic protein transthyretin, TTR(105-115), in its fibrillar form, determined by magic angle spinning NMR spectroscopy. The structure resolves not only the backbone fold but also the precise conformation of the side chains. Nearly complete 13C and 15N resonance assignments for TTR(105-115) formed the basis for the extraction of a set of distance and dihedral angle restraints. A total of 76 self-consistent experimental measurements, including 41 restraints on 19 backbone dihedral angles and 35 13C-15N distances between 3 and 6 Å were obtained from 2D and 3D NMR spectra recorded on three fibril samples uniformly 13C, 15N-labeled in consecutive stretches of four amino acids and used to calculate an ensemble of peptide structures. Our results indicate that TTR(105-115) adopts an extended -strand conformation in the amyloid fibrils such that both the main- and side-chain torsion angles are close to their optimal values. Moreover, the structure of this peptide in the fibrillar form has a degree of long-range order that is generally associated only with crystalline materials. These findings provide an explanation of the unusual stability and characteristic properties of this form of polypeptide assembly.

  1. Effect of curcumin and Cu 2+/Zn 2+ ions on the fibrillar aggregates formed by the amyloid peptide and other peptides at the organic-aqueous interface

    NASA Astrophysics Data System (ADS)

    Sanghamitra, Nusrat J. M.; Varghese, Neenu; Rao, C. N. R.

    2010-08-01

    Characteristic features of a perilous neuro-degenerative disease such as the Alzhiemer's disease is fibrillar plaque formation by the amyloid (Aβ) peptide. We have modelled the formation and disintegration of fibrils by studying the aggregate structures formed by Aβ structural motif diphenylalanine as well as insulin and bovine serum albumin at the organic-aqueous interface. Even small concentrations of curcumin in the organic medium or Cu 2+ and Zn 2+ ions in the aqueous medium are found to break down the fibrillar structures.

  2. Hydrogen peroxide is generated during the very early stages of aggregation of the amyloid peptides implicated in Alzheimer disease and familial British dementia.

    PubMed

    Tabner, Brian J; El-Agnaf, Omar M A; Turnbull, Stuart; German, Matthew J; Paleologou, Katerina E; Hayashi, Yoshihito; Cooper, Leanne J; Fullwood, Nigel J; Allsop, David

    2005-10-28

    Alzheimer disease and familial British dementia are neurodegenerative diseases that are characterized by the presence of numerous amyloid plaques in the brain. These lesions contain fibrillar deposits of the beta-amyloid peptide (Abeta) and the British dementia peptide (ABri), respectively. Both peptides are toxic to cells in culture, and there is increasing evidence that early "soluble oligomers" are the toxic entity rather than mature amyloid fibrils. The molecular mechanisms responsible for this toxicity are not clear, but in the case of Abeta, one prominent hypothesis is that the peptide can induce oxidative damage via the formation of hydrogen peroxide. We have developed a reliable method, employing electron spin resonance spectroscopy in conjunction with the spin-trapping technique, to detect any hydrogen peroxide generated during the incubation of Abeta and other amyloidogenic peptides. Here, we monitored levels of hydrogen peroxide accumulation during different stages of aggregation of Abeta-(1-40) and ABri and found that in both cases it was generated as a short "burst" early on in the aggregation process. Ultrastructural studies with both peptides revealed that structures resembling "soluble oligomers" or "protofibrils" were present during this early phase of hydrogen peroxide formation. Mature amyloid fibrils derived from Abeta-(1-40) did not generate hydrogen peroxide. We conclude that hydrogen peroxide formation during the early stages of protein aggregation may be a common mechanism of cell death in these (and possibly other) neurodegenerative diseases.

  3. Multiscale MD Simulations of Folding Dynamics and Mobility of Beta-Amyloid Peptide on Lipid Bilayer Surfaces

    NASA Astrophysics Data System (ADS)

    van Tilburg, Scott; Cheng, Kelvin

    2013-03-01

    Early interaction events of beta-amyloid peptides with the neuronal membranes play a key role in the pathogenesis of Alzheimer's disease. We have used multiscale Molecular Dynamics (MD) simulations to study the protein folding dynamics and lateral mobility of beta-amyloid protein on the cholesterol-enriched and -depleted lipid nano-domains. Several independent simulation replicates of all-atom and coarse-grained MD simulations of beta-amyloid on different lipid bilayer nano-domains have been generated. Using Define Secondary Structure of Proteins (DSSP) algorithm and mean-square-distance (MSD) analysis, the protein conformation and the lateral diffusion coefficients of protein, as well as the lipid and water, were calculated as a function of simulation time up to 200 nanoseconds for atomistic and 2 microseconds for coarse-grained simulations per replicate in different bilayer systems. Subtle differences in the conformation and mobility of the protein were observed in lipid bilayers with and without cholesterol. The structural dynamics information obtained from this work will provide useful insights into understanding the role of protein/lipid interactions in the membrane-associated aggregation of protein on neuronal membranes. HHMI-Trinity University and NIH RC1-GM090897-02

  4. Synthetic Curcumin Analogs as Inhibitors of β -Amyloid Peptide Aggregation: Potential Therapeutic and Diagnostic Agents for Alzheimer's Disease.

    PubMed

    Bukhari, Syed Nasir Abbas; Jantan, Ibrahim

    2015-01-01

    There is a crucial need to develop new effective drugs for Alzheimer's disease (AD) as the currently available AD treatments provide only momentary and incomplete symptomatic relief. Amongst natural products, curcumin, a major constituent of turmeric, has been intensively investigated for its neuroprotective effect against β-amyloid (Aβ)-induced toxicity in cultured neuronal cells. The ability of curcumin to attach to Aβ peptide and prevent its accumulation is attributed to its three structural characteristics such as the presence of two aromatic end groups and their co-planarity, the length and rigidity of the linker region and the substitution conformation of these aromatics. However, curcumin failed to reach adequate brain levels after oral absorption in AD clinical trials due to its low water solubility and poor oral bioavailability. A number of new curcumin analogs that mimic the active site of the compound along with analogs that mimic the curcumin anti-amyloid effect combined with anticholinesterase effect have been developed to enhance the bioavailability, pharmacokinetics, water solubility, stability at physiological conditions and delivery of curcumin. In this article, we have summarized all reported synthetic analogs of curcumin showing effects on β-amyloid and discussed their potential as therapeutic and diagnostic agents for AD.

  5. The architecture of amyloid-like peptide fibrils revealed by X-ray scattering, diffraction and electron microscopy.

    PubMed

    Langkilde, Annette E; Morris, Kyle L; Serpell, Louise C; Svergun, Dmitri I; Vestergaard, Bente

    2015-04-01

    Structural analysis of protein fibrillation is inherently challenging. Given the crucial role of fibrils in amyloid diseases, method advancement is urgently needed. A hybrid modelling approach is presented enabling detailed analysis of a highly ordered and hierarchically organized fibril of the GNNQQNY peptide fragment of a yeast prion protein. Data from small-angle X-ray solution scattering, fibre diffraction and electron microscopy are combined with existing high-resolution X-ray crystallographic structures to investigate the fibrillation process and the hierarchical fibril structure of the peptide fragment. The elongation of these fibrils proceeds without the accumulation of any detectable amount of intermediate oligomeric species, as is otherwise reported for, for example, glucagon, insulin and α-synuclein. Ribbons constituted of linearly arranged protofilaments are formed. An additional hierarchical layer is generated via the pairing of ribbons during fibril maturation. Based on the complementary data, a quasi-atomic resolution model of the protofilament peptide arrangement is suggested. The peptide structure appears in a β-sheet arrangement reminiscent of the β-zipper structures evident from high-resolution crystal structures, with specific differences in the relative peptide orientation. The complexity of protein fibrillation and structure emphasizes the need to use multiple complementary methods. PMID:25849399

  6. Dual Effect of (LK)nL Peptides on the Onset of Insulin Amyloid Fiber Formation at Hydrophobic Surfaces.

    PubMed

    Chouchane, Karim; Vendrely, Charlotte; Amari, Myriam; Moreaux, Katie; Bruckert, Franz; Weidenhaupt, Marianne

    2015-08-20

    Soluble proteins are constantly in contact with material or cellular surfaces, which can trigger their aggregation and therefore have a serious impact on the development of stable therapeutic proteins. In contact with hydrophobic material surfaces, human insulin aggregates readily into amyloid fibers. The kinetics of this aggregation can be accelerated by small peptides, forming stable beta-sheets on hydrophobic surfaces. Using a series of (LK)nL peptides with varying length, we show that these peptides, at low, substoichiometric concentrations, have a positive, cooperative effect on insulin aggregation. This effect is based on a cooperative adsorption of (LK)nL peptides at hydrophobic surfaces, where they form complexes that help the formation of aggregation nuclei. At higher concentrations, they interfere with the formation of an aggregative nucleus. These effects are strictly dependent on the their adsorption on hydrophobic material surfaces and highlight the importance of the impact of materials on protein stability. (LK)nL peptides prove to be valuable tools to investigate the mechanism of HI aggregation nuclei formation on hydrophobic surfaces.

  7. Genetic background modulates outcome of therapeutic amyloid peptides in treatment of neuroinflammation.

    PubMed

    Kraus, Allison; Race, Brent; Phillips, Katie; Winkler, Clayton; Saturday, Greg; Kurnellas, Michael; Rothbard, Jonathan B; Groveman, Bradley R; Steinman, Lawrence; Caughey, Byron

    2016-09-15

    Amyloid hexapeptide molecules are effective in the treatment of the murine model of neuroinflammation, known as experimental autoimmune encephalomyelitis (EAE). Efficacy however differs between two inbred mouse strains, C57BL/6J (B6) and C57BL/10SnJ (B10). Amyloid hexapeptide treatments improved the clinical outcomes of B6, but not B10 mice, indicating that genetic background influences therapeutic efficacy. Moreover, although previous studies indicated that prion protein deficiency results in more severe EAE in B6 mice, we observed no such effect in B10 mice. In addition, we found that amyloid hexapeptide treatments of B10 and B6 mice elicited differential IL4 responses. Thus, the modulatory potential of prion protein and related treatments with other amyloid hexapeptides in EAE depends on mouse strain. PMID:27609274

  8. Evaluation of β-Amyloid Peptides Fibrillation Induced by Nanomaterials Based on Molecular Dynamics and Surface Plasmon Resonance.

    PubMed

    Hou, Yafei; Li, Pengfei; Zhou, Hongjian; Zhu, Xiaoli; Chen, Haifeng; Lee, Jaebeom; Koh, Kwangnak; Shen, Zhongming; Chen, Hongxia

    2015-02-01

    This report investigated the effect of carbon nanomaterials, single-wall carbon nanotube (SWCNT) and graphene oxide, on fibrillation of β-amyloid 40 (Aβ40) based on surface plasmon resonance (SPR) and molecular dynamics (MD). MD simulations are carried out in order to reveal the molecular mechanisms of the interaction between nanomaterials and Aβ40. The strong interaction between Aβ40 and nanomaterials is related to Van der Waals forces and the Coulomb force, inducing delicate manipulation of the main bonding energy for fibrillation of Aβ40. The interaction energy between the Aβ peptide and graphene is higher than that of SWCNT. Experimental results show both carbon nanomaterials enhance the appearance of a critical nucleus for nucleation of peptide fibrils. Graphene is more beneficial to assist the nucleation process than SWCNT. Combination of SPR and molecular dynamics could be a high-throughput method to screen protein fibrillation.

  9. Molecular dynamics simulation and computational two-dimensional infrared spectroscopic study of model amyloid β-peptide oligomers.

    PubMed

    Xu, Jun; Zhang, John Z H; Xiang, Yun

    2013-07-25

    Molecular dynamics simulations were carried out to study the structure stability of model amyloid β40 (Aβ40) peptide oligomers, from monomer to hexamer, in aqueous solution at room temperature. The initial oligomer models were built by using the parallel in-register β-sheet fibril structure and then allowed to relax in the simulations. Our simulation results indicated that the stable Aβ40 monomer was a random coil, while the oligomer structures became more fibril-like with the increase of the peptide strands. Linear absorption and two-dimensional infrared spectra of the isotope-labeled oligomers were calculated and analyzed in detail, which revealed the differential secondary structural features characteristic of Aβ40 aggregation. A quantitative relation was established to make connection between the calculated spectra and experimental ensemble measurements.

  10. Plasma AmyloidPeptides and Homocysteine in Depression in the Homebound Elderly

    PubMed Central

    Qiu, Wei Qiao; Sun, Xiaoyan; Mwamburi, D. Mkaya; Haker, Jacqueline; Lisle, David; Rizal, Abishek; Lin, Yu-min; Qiao, Liyan; Summergrad, Paul; Folstein, Marshal; Rosenberg, Irwin

    2011-01-01

    Objectives Both plasma amyloidpeptide 40 (Aβ40) and homocysteine (tHcy) are linked to vascular disease, which is related to depression in the elderly. We sought to study whether the relationship between tHcy and plasma Aβ40 differs in those with and without depression. Study Design and Methods In a cross-sectional study of 1058 homebound elders, vascular depression was defined as a score ≥ 16 on the Center for Epidemiological Studies Depression scale (CES-D) along with self-reported cardiovascular disease (CVD). Plasma Aβ40 and Aβ42, and serum tHcy and creatinine were measured. Results Elders with high tHcy had higher concentrations of plasma Aβ40 (median: 147.5 vs. 123.1 pg/ml, P < 0.0001) and Aβ42 (median: 20.2 vs. 16.6 pg/ml, P < 0.0001) than those with low tHcy. In elders with depression, the relationship between logarithm of plasma Aβ40 (LogAβ40), but not LogAβ42, and tHcy was significant (β = +0.010, SE = 0.004, P = 0.007); in contrast, this relationship was not observed in those without depression. Subjects with vascular depression had the highest concentration of tHcy (mean ± SD: 12.8 ± 4.6 vs. 11.7 ± 4.5 vs. 11.9 + 5.5, P = 0.008) compared to those without CVD and those without depression. Depressed subjects without CVD had the lowest concentration of plasma Aβ42 (median: 15.5 vs. 19.1 vs. 18.7, P = 0.01) compared to those with CVD and those without depression. Conclusions Vascular depression, which is associated with tHcy and Aβ40 in blood, appears to be different from depression that is associated with low plasma Aβ42. This suggests that reducing tHcy and Aβ40 may be an adjunct treatment for vascular depression. PMID:23766866

  11. Differential modulation of Alzheimer's disease amyloid beta-peptide accumulation by diverse classes of metal ligands.

    PubMed

    Caragounis, Aphrodite; Du, Tai; Filiz, Gulay; Laughton, Katrina M; Volitakis, Irene; Sharples, Robyn A; Cherny, Robert A; Masters, Colin L; Drew, Simon C; Hill, Andrew F; Li, Qiao-Xin; Crouch, Peter J; Barnham, Kevin J; White, Anthony R

    2007-11-01

    Biometals have an important role in AD (Alzheimer's disease) and metal ligands have been investigated as potential therapeutic agents for treatment of AD. In recent studies the 8HQ (8-hydroxyquinoline) derivative CQ (clioquinol) has shown promising results in animal models and small clinical trials; however, the actual mode of action in vivo is still being investigated. We previously reported that CQ-metal complexes up-regulated MMP (matrix metalloprotease) activity in vitro by activating PI3K (phosphoinositide 3-kinase) and JNK (c-jun N-terminal kinase), and that the increased MMP activity resulted in enhanced degradation of secreted Abeta (amyloid beta) peptide. In the present study, we have further investigated the biochemical mechanisms by which metal ligands affect Abeta metabolism. To achieve this, we measured the effects of diverse metal ligands on cellular metal uptake and secreted Abeta levels in cell culture. We report that different classes of metal ligands including 8HQ and phenanthroline derivatives and the sulfur compound PDTC (pyrrolidine dithiocarbamate) elevated cellular metal levels (copper and zinc), and resulted in substantial loss of secreted Abeta. Generally, the ability to inhibit Abeta levels correlated with a higher lipid solubility of the ligands and their capacity to increase metal uptake. However, we also identified several ligands that potently inhibited Abeta levels while only inducing minimal change to cellular metal levels. Metal ligands that inhibited Abeta levels [e.g. CQ, 8HQ, NC (neocuproine), 1,10-phenanthroline and PDTC] induced metal-dependent activation of PI3K and JNK, resulting in JNK-mediated up-regulation of metalloprotease activity and subsequent loss of secreted Abeta. The findings in the present study show that diverse metal ligands with high lipid solubility can elevate cellular metal levels resulting in metalloprotease-dependent inhibition of Abeta. Given that a structurally diverse array of ligands was assessed, the

  12. Assembly of amyloid β peptides in the presence of fibril seeds: one-pot coarse-grained molecular dynamics simulations.

    PubMed

    Xu, Liang; Chen, Yonggang; Wang, Xiaojuan

    2014-08-01

    The identification of a secondary nucleation pathway in the early aggregation of amyloid peptides suggests that the generation of toxic oligomers involves both monomers and preformed fibril seeds. To elucidate the underlying molecular mechanism, a set of one-pot coarse-grained molecular dynamics simulations was performed to investigate the self-assembly of amyloid β peptides in the presence of fibril seeds. It was observed that fibril seeds alone randomly assemble into an elongated protofibril, whereas monomers alone form an elongated globular oligomer with various morphologies. In the mixture of monomers and fibril seeds, both the self-assembly of monomers into small oligomers and the association of monomers and oligomers on the surface of fibril seeds are primarily driven by hydrophobic interactions. The cooperativity of conformational selection and competition leads to different binding propensity of two hydrophobic surfaces of fibril seeds. The molecular architecture of the final aggregate shows that the fibril seeds establish the elongated framework, and oligomers cover them. Oligomers exposed to the solvent are less compact and unstable and can be disassociated from the fibril seeds, providing an origin for oligomers generated from the secondary nucleation pathway.

  13. First and second generation γ-secretase modulators (GSMs) modulate amyloid-β (Aβ) peptide production through different mechanisms.

    PubMed

    Borgegard, Tomas; Juréus, Anders; Olsson, Fredrik; Rosqvist, Susanne; Sabirsh, Alan; Rotticci, Didier; Paulsen, Kim; Klintenberg, Rebecka; Yan, Hongmei; Waldman, Magnus; Stromberg, Kia; Nord, Johan; Johansson, Jonas; Regner, Anna; Parpal, Santiago; Malinowsky, David; Radesater, Ann-Cathrin; Li, Tingsheng; Singh, Rajeshwar; Eriksson, Hakan; Lundkvist, Johan

    2012-04-01

    γ-Secretase-mediated cleavage of amyloid precursor protein (APP) results in the production of Alzheimer disease-related amyloid-β (Aβ) peptides. The Aβ42 peptide in particular plays a pivotal role in Alzheimer disease pathogenesis and represents a major drug target. Several γ-secretase modulators (GSMs), such as the nonsteroidal anti-inflammatory drugs (R)-flurbiprofen and sulindac sulfide, have been suggested to modulate the Alzheimer-related Aβ production by targeting the APP. Here, we describe novel GSMs that are selective for Aβ modulation and do not impair processing of Notch, EphB2, or EphA4. The GSMs modulate Aβ both in cell and cell-free systems as well as lower amyloidogenic Aβ42 levels in the mouse brain. Both radioligand binding and cellular cross-competition experiments reveal a competitive relationship between the AstraZeneca (AZ) GSMs and the established second generation GSM, E2012, but a noncompetitive interaction between AZ GSMs and the first generation GSMs (R)-flurbiprofen and sulindac sulfide. The binding of a (3)H-labeled AZ GSM analog does not co-localize with APP but overlaps anatomically with a γ-secretase targeting inhibitor in rodent brains. Combined, these data provide compelling evidence of a growing class of in vivo active GSMs, which are selective for Aβ modulation and have a different mechanism of action compared with the original class of GSMs described.

  14. First and Second Generation γ-Secretase Modulators (GSMs) Modulate Amyloid-β (Aβ) Peptide Production through Different Mechanisms

    PubMed Central

    Borgegard, Tomas; Juréus, Anders; Olsson, Fredrik; Rosqvist, Susanne; Sabirsh, Alan; Rotticci, Didier; Paulsen, Kim; Klintenberg, Rebecka; Yan, Hongmei; Waldman, Magnus; Stromberg, Kia; Nord, Johan; Johansson, Jonas; Regner, Anna; Parpal, Santiago; Malinowsky, David; Radesater, Ann-Cathrin; Li, Tingsheng; Singh, Rajeshwar; Eriksson, Hakan; Lundkvist, Johan

    2012-01-01

    γ-Secretase-mediated cleavage of amyloid precursor protein (APP) results in the production of Alzheimer disease-related amyloid-β (Aβ) peptides. The Aβ42 peptide in particular plays a pivotal role in Alzheimer disease pathogenesis and represents a major drug target. Several γ-secretase modulators (GSMs), such as the nonsteroidal anti-inflammatory drugs (R)-flurbiprofen and sulindac sulfide, have been suggested to modulate the Alzheimer-related Aβ production by targeting the APP. Here, we describe novel GSMs that are selective for Aβ modulation and do not impair processing of Notch, EphB2, or EphA4. The GSMs modulate Aβ both in cell and cell-free systems as well as lower amyloidogenic Aβ42 levels in the mouse brain. Both radioligand binding and cellular cross-competition experiments reveal a competitive relationship between the AstraZeneca (AZ) GSMs and the established second generation GSM, E2012, but a noncompetitive interaction between AZ GSMs and the first generation GSMs (R)-flurbiprofen and sulindac sulfide. The binding of a 3H-labeled AZ GSM analog does not co-localize with APP but overlaps anatomically with a γ-secretase targeting inhibitor in rodent brains. Combined, these data provide compelling evidence of a growing class of in vivo active GSMs, which are selective for Aβ modulation and have a different mechanism of action compared with the original class of GSMs described. PMID:22334705

  15. Probing the Efficacy of Peptide-Based Inhibitors against Acid- and Zinc-Promoted Oligomerization of AmyloidPeptide via Single-Oligomer Spectroscopy

    PubMed Central

    Powell, Lyndsey R.; Dukes, Kyle D.; Lammi, Robin K.

    2011-01-01

    One avenue for prevention and treatment of Alzheimer's disease involves inhibiting the aggregation of amyloidpeptide (Aβ). Given the deleterious effects reported for Aβ dimers and trimers, it is important to investigate inhibition of the earliest association steps. We have employed quantized photobleaching of dye-labeled Aβ peptides to characterize four peptide-based inhibitors of fibrillogenesis and/or cytotoxicity, assessing their ability to inhibit association in the smallest oligomers (n = 2–5). Inhibitors were tested at acidic pH and in the presence of zinc, conditions that may promote oligomerization in vivo. Distributions of peptide species were constructed by examining dozens of surface-tethered monomers and oligomers, one at a time. Results show that all four inhibitors shift the distribution of Aβ species toward monomers; however, efficacies vary for each compound and sample environment. Collectively, these studies highlight promising design strategies for future oligomerization inhibitors, affording insight into oligomer structures and inhibition mechanisms in two physiologically significant environments. PMID:21945664

  16. 1–42 β-Amyloid peptide requires PDK1/nPKC/Rac 1 pathway to induce neuronal death

    PubMed Central

    Manterola, L; Hernando-Rodríguez, M; Ruiz, A; Apraiz, A; Arrizabalaga, O; Vellón, L; Alberdi, E; Cavaliere, F; Lacerda, H M; Jimenez, S; Parada, L A; Matute, C; Zugaza, J L

    2013-01-01

    1–42 β-Amyloid (Aβ1–42) peptide is a key molecule involved in the development of Alzheimer's disease. Some of its effects are manifested at the neuronal morphological level. These morphological changes involve loss of neurites due to cytoskeleton alterations. However, the mechanism of Aβ1–42 peptide activation of the neurodegenerative program is still poorly understood. Here, Aβ1–42 peptide-induced transduction of cellular death signals through the phosphatidylinositol 3-kinase (PI3K)/phosphoinositol-dependent kinase (PDK)/novel protein kinase C (nPKC)/Rac 1 axis is described. Furthermore, pharmacological inhibition of PDK1 and nPKC activities blocks Rac 1 activation and neuronal cell death. Our results provide insights into an unsuspected connection between PDK1, nPKCs and Rac 1 in the same signal-transduction pathway and points out nPKCs and Rac 1 as potential therapeutic targets to block the toxic effects of Aβ1–42 peptide in neurons. PMID:23340502

  17. 1-42 β-amyloid peptide requires PDK1/nPKC/Rac 1 pathway to induce neuronal death.

    PubMed

    Manterola, L; Hernando-Rodríguez, M; Ruiz, A; Apraiz, A; Arrizabalaga, O; Vellón, L; Alberdi, E; Cavaliere, F; Lacerda, H M; Jimenez, S; Parada, L A; Matute, C; Zugaza, J L

    2013-01-22

    1-42 β-Amyloid (Aβ(1-42)) peptide is a key molecule involved in the development of Alzheimer's disease. Some of its effects are manifested at the neuronal morphological level. These morphological changes involve loss of neurites due to cytoskeleton alterations. However, the mechanism of Aβ(1-42) peptide activation of the neurodegenerative program is still poorly understood. Here, Aβ(1-42) peptide-induced transduction of cellular death signals through the phosphatidylinositol 3-kinase (PI3K)/phosphoinositol-dependent kinase (PDK)/novel protein kinase C (nPKC)/Rac 1 axis is described. Furthermore, pharmacological inhibition of PDK1 and nPKC activities blocks Rac 1 activation and neuronal cell death. Our results provide insights into an unsuspected connection between PDK1, nPKCs and Rac 1 in the same signal-transduction pathway and points out nPKCs and Rac 1 as potential therapeutic targets to block the toxic effects of Aβ(1-42) peptide in neurons.

  18. Structural Studies of Copper(I) Complexes of Amyloid-Beta Peptide Fragments: Formation of Two-Coordinate Bis(Histidine) Complexes

    SciTech Connect

    Himes, R.A.; Park, G.Young.; Siluvai, G.Sutha.; Blackburn, N.J.; Karlin, K.D.

    2009-05-18

    The beta bind: Copper(I) binds to amyloid {beta}-peptide fragments (see structure) as a stable bis(histidine), two-coordinate, near-linear complex, even in the presence of potential additional ligands. As has been proposed or assumed in other studies, the copper(I)-peptide complexes react with dioxygen to form the reactive oxygen species H{sub 2}O{sub 2}, without the need for a third histidine ligand to promote the chemistry.

  19. High-affinity Anticalins with aggregation-blocking activity directed against the Alzheimer β-amyloid peptide

    PubMed Central

    Rauth, Sabine; Hinz, Dominik; Börger, Michael; Uhrig, Markus; Mayhaus, Manuel; Riemenschneider, Matthias; Skerra, Arne

    2016-01-01

    Amyloid beta (Aβ) peptides, in particular Aβ42 and Aβ40, exert neurotoxic effects and their overproduction leads to amyloid deposits in the brain, thus constituting an important biomolecular target for treatments of Alzheimer's disease (AD). We describe the engineering of cognate Anticalins as a novel type of neutralizing protein reagent based on the human lipocalin scaffold. Phage display selection from a genetic random library comprising variants of the human lipocalin 2 (Lcn2) with mutations targeted at 20 exposed amino acid positions in the four loops that form the natural binding site was performed using both recombinant and synthetic target peptides and resulted in three different Anticalins. Biochemical characterization of the purified proteins produced by periplasmic secretion in Escherichia coli revealed high folding stability in a monomeric state, with Tm values ranging from 53.4°C to 74.5°C, as well as high affinities for Aβ40, between 95 pM and 563 pM, as measured by real-time surface plasmon resonance analysis. The central linear VFFAED epitope within the Aβ sequence was mapped using a synthetic peptide array on membranes and was shared by all three Anticalins, despite up to 13 mutual amino acid differences in their binding sites. All Anticalins had the ability–with varying extent–to inhibit Aβ aggregation in vitro according to the thioflavin-T fluorescence assay and, furthermore, they abolished Aβ42-mediated toxicity in neuronal cell culture. Thus, these Anticalins provide not only useful protein reagents to study the molecular pathology of AD but they also show potential as alternative drug candidates compared with antibodies. PMID:27029347

  20. Inhibition of amyloid fibril formation of human amylin by N-alkylated amino acid and alpha-hydroxy acid residue containing peptides.

    PubMed

    Rijkers, Dirk T S; Höppener, Jo W M; Posthuma, George; Lips, Cornelis J M; Liskamp, Rob M J

    2002-09-16

    Amyloid deposits are formed as a result of uncontrolled aggregation of (poly)peptides or proteins. Today several diseases are known, for example Alzheimer's disease, Creutzfeldt-Jakob disease, mad cow disease, in which amyloid formation is involved. Amyloid fibrils are large aggregates of beta-pleated sheets and here a general method is described to introduce molecular mutations in order to achieve disruption of beta-sheet formation. Eight backbone-modified amylin derivatives, an amyloidogenic peptide involved in maturity onset diabetes, were synthesized. Their beta-sheet forming properties were studied by IR spectroscopy and electron microscopy. Modification of a crucial amide NH by an alkyl chain led to a complete loss of the beta-sheet forming capacity of amylin. The resulting molecular mutated amylin derivative could be used to break the beta-sheet thus retarding beta-sheet formation of unmodified amylin. Moreover, it was found that the replacement of this amide bond by an ester moiety suppressed fibrillogenesis significantly. Introduction of N-alkylated amino acids and/or ester functionalities-leading to depsipeptides-into amyloidogenic peptides opens new avenues towards novel peptidic beta-sheet breakers for inhibition of beta-amyloid aggregation. PMID:12298020

  1. The Structure of Intrinsically Disordered Peptides Implicated in Amyloid Diseases: Insights from Fully Atomistic Simulations

    NASA Astrophysics Data System (ADS)

    Wu, Chun; Shea, Joan-Emma

    Protein aggregation involves the self-assembly of proteins into large β-sheet-rich complexes. This process can be the result of aberrant protein folding and lead to "amyloidosis," a condition characterized by deposits of protein aggregates known as amyloids on various organs of the body [1]. Amyloid-related diseases include, among others, Alzheimer's disease, Parkinson's disease, Creutzfeldt-Jakob disease, and type II diabetes [2, 3, 4]. In other instances, however, protein aggregation is not a pathological process, but rather a functional one, with aggregates serving as structural scaffolds in a number of organisms [5].

  2. Genetic Variations in ABCA7 Can Increase Secreted Levels of Amyloid-β40 and Amyloid-β42 Peptides and ABCA7 Transcription in Cell Culture Models.

    PubMed

    Bamji-Mirza, Michelle; Li, Yan; Najem, Dema; Liu, Qing Yan; Walker, Douglas; Lue, Lih-Fen; Stupak, Jacek; Chan, Kenneth; Li, Jianjun; Ghani, Mahdi; Yang, Ze; Rogaeva, Ekaterina; Zhang, Wandong

    2016-06-13

    Alzheimer's disease (AD) is characterized by extracellular deposits of amyloid-β (Aβ) in the brain. ABCA7 is highly expressed in the brain and a susceptibility gene for late-onset AD (LOAD). The minor alleles at two ABCA7 single-nucleotide polymorphisms (SNPs), rs3764650 (T>G; intron13) and rs3752246 at a predicted myristoylation site (C>G; exon33; p.Gly1527Ala), are significantly associated with LOAD risk; however, the mechanism of this association is unknown. Functional consequences of both SNPs were examined in HEK293 and CHO cells stably expressing AβPPSwe. Luciferase reporter assays in HEK293 cells suggested that intron13 carrying rs3764650 major T-allele (int13-T) possessed promoter-enhancing capabilities. Co-transfection experiments with hABCA7 and int13-T resulted in significantly increased ABCA7 protein level relative to that with int13-G. Expression of hABCA7 carrying rs3752246 risk allele led to increases in secreted Aβ40 and Aβ42 and β-secretase activity in CHO- and HEK-AβPPSwe cells. Hydroxymyristic acid treatment of cells expressing hABCA7 carrying the rs3752246 major G allele resulted in increased β-secretase activity and levels of Aβ, suggesting that lack of myristoylation contributes to the observed cell-phenotypes. Molecular weight determination, by gel-electrophoresis and mass spectrometry, of hABCA7 peptides spanning position 1527 showed loss of post-translational modification in the risk-allele peptide. These results suggest that decreased expression, or impaired function, of ABCA7 may contribute to AD pathology. PMID:27314524

  3. Surface Plasmon Resonance Binding Kinetics of Alzheimer’s Disease Amyloid β Peptide Capturing- and Plaque Binding- Monoclonal Antibodies†

    PubMed Central

    Ramakrishnan, Muthu; Kandimalla, Karunya K.; Wengenack, Thomas M.; Howell, Kyle G.; Poduslo, Joseph F.

    2009-01-01

    Several different monoclonal antibodies (mAbs) have been actively developed in the field of Alzheimer’s disease (AD) for basic science and clinical applications; however, the binding kinetics of many of the mAbs with the β-amyloid peptides (Aβ) are poorly understood. A panel of mAbs with different Aβ recognition sites, including our plaque binding antibody (IgG4.1), a peptide capturing antibody (11A50), and two classical mAbs (6E10 and 4G8) used for immunohistochemistry, were chosen to characterize their binding kinetics to monomeric and fibrillar forms of Aβ40 using surface plasmon resonance and their amyloid plaque binding ability in AD mouse brain sections using immunohistochemistry. The plaque binding antibody (IgG4.1) with epitope specificity of Aβ(2-10) showed a weaker affinity (512 nM) to monomeric Aβ40 but higher affinity (1.5 nM) to Aβ40 fibrils and labeled dense core plaques better than 6E10 by immunohistochemistry. The peptide capturing antibody (11A50) showed preferential affinity (32.5 nM) to monomeric Aβ40, but did not bind to Aβ40 fibrils, whereas antibodies 6E10 and 4G8 had moderate affinity to monomeric Aβ40 (22.3 and 30.1 nM, respectively). 4G8, which labels diffuse plaques better than 6E10, had a higher association rate constant than 6E10 but showed similar association and dissociation kinetics compared to 11A50. Enzymatic digestion of IgG4.1 to the F(ab’)24.1 fragments or their polyamine-modified derivatives that enhance blood brain barrier permeability did not affect the kinetic properties of the antigen binding site. These differences in kinetic binding to monomeric and fibrillar Aβ among various antibodies could be utilized to distinguish mAbs that might be useful for immunotherapy or amyloid plaque imaging versus those that could be utilized for bioanalytical techniques. PMID:19775170

  4. Polymorphism of amyloid fibrils formed by a peptide from the yeast prion protein Sup35: AFM and Tip-Enhanced Raman Scattering studies.

    PubMed

    Krasnoslobodtsev, Alexey V; Deckert-Gaudig, Tanja; Zhang, Yuliang; Deckert, Volker; Lyubchenko, Yuri L

    2016-06-01

    Aggregation of prion proteins is the cause of various prion related diseases. The infectious form of prions, amyloid aggregates, exist as multiple strains. The strains are thought to represent structurally different prion protein molecules packed into amyloid aggregates, but the knowledge on the structure of different types of aggregates is limited. Here we report on the use of AFM (Atomic Force Microscopy) and TERS (Tip-Enhanced Raman Scattering) to study morphological heterogeneity and access underlying conformational features of individual amyloid aggregates. Using AFM we identified the morphology of amyloid fibrils formed by the peptide (CGNNQQNY) from the yeast prion protein Sup35 that is critically involved in the aggregation of the full protein. TERS results demonstrate that morphologically different amyloid fibrils are composed of a distinct set of conformations. Fibrils formed at pH 5.6 are composed of a mixture of peptide conformations (β-sheets, random coil and α-helix) while fibrils formed in pH~2 solution primarily have β-sheets. Additionally, peak positions in the amide III region of the TERS spectra suggested that peptides have parallel arrangement of β-sheets for pH~2 fibrils and antiparallel arrangement for fibrils formed at pH 5.6. We also developed a methodology for detailed analysis of the peptide secondary structure by correlating intensity changes of Raman bands in different regions of TERS spectra. Such correlation established that structural composition of peptides is highly localized with large contribution of unordered secondary structures on a fibrillar surface. PMID:27060278

  5. Zinc(II) Binding Site to the AmyloidPeptide: Insights from Spectroscopic Studies with a Wide Series of Modified Peptides

    PubMed Central

    2016-01-01

    The Zn(II) ion has been linked to Alzheimer’s disease (AD) due to its ability to modulate the aggregating properties of the amyloid-β (Aβ) peptide, where Aβ aggregation is a central event in the etiology of the disease. Delineating Zn(II) binding properties to Aβ is thus a prerequisite to better grasp its potential role in AD. Because of (i) the flexibility of the Aβ peptide, (ii) the multiplicity of anchoring sites, and (iii) the silent nature of the Zn(II) ion in most classical spectroscopies, this is a difficult task. To overcome these difficulties, we have investigated the impact of peptide alterations (mutations, N-terminal acetylation) on the Zn(Aβ) X-ray absorption spectroscopy fingerprint and on the Zn(II)-induced modifications of the Aβ peptides’ NMR signatures. We propose a tetrahedrally bound Zn(II) ion, in which the coordination sphere is made by two His residues and two carboxylate side chains. Equilibria between equivalent ligands for one Zn(II) binding position have also been observed, the predominant site being made by the side chains of His6, His13 or His14, Glu11, and Asp1 or Glu3 or Asp7, with a slight preference for Asp1. PMID:27665863

  6. Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

    SciTech Connect

    Altman, Robin; Ly, Sonny; Hilt, Silvia; Petrlova, Jitka; Maezawa, Izumi; Kálai, Tamás; Hideg, Kálmán; Jin, Lee-Way; Laurence, Ted A.; Voss, John C.

    2015-12-01

    Alzheimer’s disease is characterized by the presence of extracellular plaques comprised of amyloid beta (Aβ) peptides. Soluble oligomers of the Aβ peptide underlie a cascade of neuronal loss and dysfunction associated with Alzheimer's disease. Single particle analyses of Aβ oligomers in solution by fluorescence correlation spectroscopy (FCS) were used to provide real-time descriptions of how spin-labeled fluorenes (SLFs; bi-functional small molecules that block the toxicity of Aβ) prevent and disrupt oligomeric assemblies of Aβ in solution. The FCS results, combined with electron paramagnetic resonance spectroscopy and circular dichroism spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disrupt existing oligomers while retaining Aβ in a largely disordered state. Furthermore, while the ability of SLF to block Aβ toxicity correlates with a reduction in oligomer size, our results suggest the conformation of Aβ within the oligomer determines the toxicity of the species. Attenuation of Aβ toxicity, which has been associated primarily with the soluble oligomeric form, can be achieved through redistribution of the peptides into smaller oligomers and arrest of the fractional increase in beta secondary structure.

  7. Current and future implications of basic and translational research on amyloidpeptide production and removal pathways

    PubMed Central

    Bohm, C.; Chen, F.; Sevalle, J.; Qamar, S.; Dodd, R.; Li, Y.; Schmitt-Ulms, G.; Fraser, P.E.; St George-Hyslop, P.H.

    2015-01-01

    Inherited variants in multiple different genes are associated with increased risk for Alzheimer's disease (AD). In many of these genes, the inherited variants alter some aspect of the production or clearance of the neurotoxic amyloid β-peptide (Aβ). Thus missense, splice site or duplication mutants in the presenilin 1 (PS1), presenilin 2 (PS2) or the amyloid precursor protein (APP) genes, which alter the levels or shift the balance of Aβ produced, are associated with rare, highly penetrant autosomal dominant forms of Familial Alzheimer's Disease (FAD). Similarly, the more prevalent late-onset forms of AD are associated with both coding and non-coding variants in genes such as SORL1, PICALM and ABCA7 that affect the production and clearance of Aβ. This review summarises some of the recent molecular and structural work on the role of these genes and the proteins coded by them in the biology of Aβ. We also briefly outline how the emerging knowledge about the pathways involved in Aβ generation and clearance can be potentially targeted therapeutically. This article is part of Special Issue entitled "Neuronal Protein". PMID:25748120

  8. Amyloid-like fibrils from an 18-residue peptide analogue of a part of the central domain of the B-family of silkmoth chorion proteins.

    PubMed

    Iconomidou, V A; Chryssikos, G D; Gionis, V; Vriend, G; Hoenger, A; Hamodrakas, S J

    2001-06-22

    Chorion is the major component of silkmoth eggshell. More than 95% of its dry mass consists of the A and B families of low molecular weight structural proteins, which have remarkable mechanical and chemical properties, and protect the oocyte and the developing embryo from the environment. We present data from negative staining, Congo red binding, X-ray diffraction, Fourier transform-Raman, attenuated total reflectance infrared spectroscopy and modelling studies of a synthetic peptide analogue of a part of the central domain of the B family of silkmoth chorion proteins, indicating that this peptide folds and self-assembles, forming amyloid-like fibrils. These results support further our proposal, based on experimental data from a synthetic peptide analogue of the central domain of the A family of chorion proteins, that silkmoth chorion is a natural, protective amyloid [Iconomidou et al., FEBS Lett. 479 (2000) 141-145]. PMID:11423129

  9. Proposal for an inhibitor of Alzheimer's disease blocking aggregation of amyloidpeptides: ab initio molecular simulations

    NASA Astrophysics Data System (ADS)

    Okamoto, A.; Nomura, K.; Yano, A.; Higai, S.; Kondo, T.; Kamba, S.; Kurita, N.

    2013-04-01

    Aggregation of amyloid-β (Aβ) peptides is believed to play a key role in the mechanism of molecular pathogenesis of Alzheimer's disease (AD). To inhibit the aggregation and prevent AD, numerous compounds have been synthesized. A previous experimental study elucidated that a triazine derivative AA3E2 has anti-amyloidogenic ability, while a triazine derivative AA3D2 having a different substituent has no inhibitory effect. However, the reason for this remarkable difference in the ability cannot be explained by the chemical structures of these derivatives. In the present study, we present stable structures of the solvated complexes with Aβ and AA3E2/AA3D2 obtained by classical molecular mechanics method. The specific interactions between Aβ and AA3E2/AA3D2 in the complexes are investigated by ab initio fragment molecular orbital calculations. Based on the results obtained, we attempt to propose new potent inhibitors for the Aβ aggregation.

  10. Folic Acid Inhibits Amyloid β-Peptide Production through Modulating DNA Methyltransferase Activity in N2a-APP Cells.

    PubMed

    Li, Wen; Jiang, Mingyue; Zhao, Shijing; Liu, Huan; Zhang, Xumei; Wilson, John X; Huang, Guowei

    2015-10-20

    Alzheimer's disease (AD) is a common neurodegenerative disease resulting in progressive dementia, and is a principal cause of dementia among older adults. Folate acts through one-carbon metabolism to support the methylation of multiple substrates. We hypothesized that folic acid supplementation modulates DNA methyltransferase (DNMT) activity and may alter amyloid β-peptide (Aβ) production in AD. Mouse Neuro-2a cells expressing human APP695 were incubated with folic acid (2.8-40 μmol/L), and with or without zebularine (the DNMT inhibitor). DNMT activity, cell viability, Aβ and DNMTs expression were then examined. The results showed that folic acid stimulated DNMT gene and protein expression, and DNMT activity. Furthermore, folic acid decreased Aβ protein production, whereas inhibition of DNMT activity by zebularine increased Aβ production. The results indicate that folic acid induces methylation potential-dependent DNMT enzymes, thereby attenuating Aβ production.

  11. Molecular mechanisms linking diabetes mellitus and Alzheimer disease: beta-amyloid peptide, insulin signaling, and neuronal function.

    PubMed

    Takeda, Shuko; Sato, Naoyuki; Rakugi, Hiromi; Morishita, Ryuichi

    2011-06-01

    The incidence of Alzheimer disease (AD) and diabetes mellitus (DM) is increasing at an alarming rate and has become a major public health concern worldwide. Recent epidemiological studies have provided direct evidence that DM is a strong risk factor for AD; this finding is now attracting attention. However, the underlying mechanisms for this association remain largely unknown. Previous in vitro and in vivo studies reported that diabetic conditions could cause an increase in the beta-amyloid peptide (Aβ) levels, which exhibits neurotoxic properties and plays a causative role in AD. However, unexpectedly, recent clinicopathological studies have shown no evidence that the pathological hallmarks of AD, including amyloid plaque, were increased in the brains of diabetic patients, suggesting that DM could affect the pathogenesis of AD through mechanisms other than modulation of Aβ metabolism. One possible mechanism is the alteration in brain insulin signaling. It has been shown that insulin signaling is involved in a variety of neuronal functions, and that it also plays a significant role in the pathophysiology of AD. Thus, the modification of neuronal insulin signaling by diabetic conditions may contribute to AD progression. Another possible mechanism is cerebrovascular alteration, a common pathological change observed in both diseases. Accumulating evidence has suggested the importance of Aβ-induced cerebrovascular dysfunction in AD, and indicated that pathological interactions between the receptor for advanced glycation end products (RAGE) and Aβ peptides may play a role in this dysfunction. Our study has provided a further understanding of the potential underlying mechanisms linking DM and AD by establishing novel mouse models showing pathological manifestations of both diseases. The current review summarizes the results from recent studies on the pathological relationship between DM and AD while focusing on brain insulin signaling and cerebrovascular alteration

  12. Amyloid beta-peptide induces cell monolayer albumin permeability, impairs glucose transport, and induces apoptosis in vascular endothelial cells.

    PubMed

    Blanc, E M; Toborek, M; Mark, R J; Hennig, B; Mattson, M P

    1997-05-01

    Amyloid beta-peptide (A beta) is deposited as insoluble fibrils in the brain parenchyma and cerebral blood vessels in Alzheimer's disease (AD). In addition to neuronal degeneration, cerebral vascular alterations indicative of damage to vascular endothelial cells and disruption of the blood-brain barrier occur in AD. Here we report that A beta25-35 can impair regulatory functions of endothelial cells (ECs) from porcine pulmonary artery and induce their death. Subtoxic exposures to A beta25-35 induced albumin transfer across EC monolayers and impaired glucose transport into ECs. Cell death induced by A beta25-35 was of an apoptotic form, characterized by DNA condensation and fragmentation, and prevented by inhibitors of macromolecular synthesis and endonucleases. The effects of A beta25-35 were specific because A beta1-40 also induced apoptosis in ECs with the apoptotic cells localized to the microenvironment of A beta1-40 aggregates and because astrocytes did not undergo similar changes after exposure to A beta25-35. Damage and death of ECs induced by A beta25-35 were attenuated by antioxidants, a calcium channel blocker, and a chelator of intracellular calcium, indicating the involvement of free radicals and dysregulation of calcium homeostasis. The data show that A beta induces increased permeability of EC monolayers to macromolecules, impairs glucose transport, and induces apoptosis. If similar mechanisms are operative in vivo, then A beta and other amyloidogenic peptides may be directly involved in vascular EC damage documented in AD and other disorders that involve vascular amyloid accumulation. PMID:9109512

  13. Lysosomal dysfunction in a mouse model of Sandhoff disease leads to accumulation of ganglioside-bound amyloidpeptide.

    PubMed

    Keilani, Serene; Lun, Yi; Stevens, Anthony C; Williams, Hadis N; Sjoberg, Eric R; Khanna, Richie; Valenzano, Kenneth J; Checler, Frederic; Buxbaum, Joseph D; Yanagisawa, Katsuhiko; Lockhart, David J; Wustman, Brandon A; Gandy, Sam

    2012-04-11

    Alterations in the lipid composition of endosomal-lysosomal membranes may constitute an early event in Alzheimer's disease (AD) pathogenesis. In this study, we investigated the possibility that GM2 ganglioside accumulation in a mouse model of Sandhoff disease might be associated with the accumulation of intraneuronal and extracellular proteins commonly observed in AD. Our results show intraneuronal accumulation of amyloidpeptide (Aβ)-like, α-synuclein-like, and phospho-tau-like immunoreactivity in the brains of β-hexosaminidase knock-out (HEXB KO) mice. Biochemical and immunohistochemical analyses confirmed that at least some of the intraneuronal Aβ-like immunoreactivity (iAβ-LIR) represents amyloid precursor protein C-terminal fragments (APP-CTFs) and/or Aβ. In addition, we observed increased levels of Aβ40 and Aβ42 peptides in the lipid-associated fraction of HEXB KO mouse brains, and intraneuronal accumulation of ganglioside-bound Aβ (GAβ) immunoreactivity in a brain region-specific manner. Furthermore, α-synuclein and APP-CTFs and/or Aβ were found to accumulate in different regions of the substantia nigra, indicating different mechanisms of accumulation or turnover pathways. Based on the localization of the accumulated iAβ-LIR to endosomes, lysosomes, and autophagosomes, we conclude that a significant accumulation of iAβ-LIR may be associated with the lysosomal-autophagic turnover of Aβ and fragments of APP-containing Aβ epitopes. Importantly, intraneuronal GAβ immunoreactivity, a proposed prefibrillar aggregate found in AD, was found to accumulate throughout the frontal cortices of postmortem human GM1 gangliosidosis, Sandhoff disease, and Tay-Sachs disease brains. Together, these results establish an association between the accumulation of gangliosides, autophagic vacuoles, and the intraneuronal accumulation of proteins associated with AD. PMID:22496568

  14. Alpha7 nicotinic acetylcholine receptor expression by vascular smooth muscle cells facilitates the deposition of Abeta peptides and promotes cerebrovascular amyloid angiopathy.

    PubMed

    Clifford, Peter M; Siu, Gilbert; Kosciuk, Mary; Levin, Eli C; Venkataraman, Venkateswar; D'Andrea, Michael R; Nagele, Robert G

    2008-10-01

    Deposition of beta-amyloid (Abeta) peptides in the walls of brain blood vessels, cerebral amyloid angiopathy (CAA), is common in patients with Alzheimer's disease (AD). Previous studies have demonstrated Abeta peptide deposition among vascular smooth muscle cells (VSMCs), but the source of the Abeta and basis for its selective deposition in VSMCs are unknown. In the present study, we examined the deposition patterns of Abeta peptides, Abeta40 and Abeta42, within the cerebrovasculature of AD and control patients using single- and double-label immunohistochemistry. Abeta40 and Abeta42 were abundant in VSMCs, especially in leptomeningeal arteries and their initial cortical branches; in later-stage AD brains this pattern extended into the microvasculature. Abeta peptide deposition was linked to loss of VSMC viability. Perivascular leak clouds of Abeta-positive material were associated primarily with arterioles. By contrast, control brains possessed far fewer Abeta42- and Abeta40-immunopositive blood vessels, with perivascular leak clouds of Abeta-immunopositive material rarely observed. We also demonstrate that VSMCs in brain blood vessels express the alpha7 nicotinic acetylcholine receptor (alpha7nAChR), which has high binding affinity for Abeta peptides, especially Abeta42. These results suggest that the blood and blood-brain barrier permeability provide a major source of the Abeta peptides that gradually deposit in brain VSMCs, and the presence and abundance of the alpha7nAChR on VSMCs may facilitate the selective accumulation of Abeta peptides in these cells.

  15. Involvement of insulin-degrading enzyme in insulin- and atrial natriuretic peptide-sensitive internalization of amyloidpeptide in mouse brain capillary endothelial cells.

    PubMed

    Ito, Shingo; Ohtsuki, Sumio; Murata, Sho; Katsukura, Yuki; Suzuki, Hiroya; Funaki, Miho; Tachikawa, Masanori; Terasaki, Tetsuya

    2014-01-01

    Cerebral clearance of amyloidpeptide (Aβ), which is implicated in Alzheimer's disease, involves elimination across the blood-brain barrier (BBB), and we previously showed that an insulin-sensitive process is involved in the case of Aβ1-40. The purpose of this study was to clarify the molecular mechanism of the insulin-sensitive Aβ1-40 elimination across mouse BBB. An in vivo cerebral microinjection study demonstrated that [125I]hAβ1-40 elimination from mouse brain was inhibited by human natriuretic peptide (hANP), and [125I]hANP elimination was inhibited by hAβ1-40, suggesting that hAβ1-40 and hANP share a common elimination process. Internalization of [125I]hAβ1-40 into cultured mouse brain capillary endothelial cells (TM-BBB4) was significantly inhibited by either insulin, hANP, other natriuretic peptides or insulin-degrading enzyme (IDE) inhibitors, but was not inhibited by phosphoramidon or thiorphan. Although we have reported the involvement of natriuretic peptide receptor C (Npr-C) in hANP internalization, cells stably expressing Npr-C internalized [125I]hANP but not [125I]hAβ1-40, suggesting that there is no direct interaction between Npr-C and hAβ1-40. IDE was detected in plasma membrane of TM-BBB4 cells, and internalization of [125I]hAβ1-40 by TM-BBB4 cells was reduced by IDE-targeted siRNAs. We conclude that elimination of hAβ1-40 from mouse brain across the BBB involves an insulin- and ANP-sensitive process, mediated by IDE expressed in brain capillary endothelial cells.

  16. The inhibitory mechanism of a fullerene derivative against amyloidpeptide aggregation: an atomistic simulation study.

    PubMed

    Sun, Yunxiang; Qian, Zhenyu; Wei, Guanghong

    2016-05-14

    Alzheimer's disease (AD) is associated with the pathological self-assembly of amyloid-β (Aβ) peptides into β-sheet enriched fibrillar aggregates. Aβ dimers formed in the initial step of Aβ aggregation were reported to be the smallest toxic species. Inhibiting the formation of β-sheet-rich oligomers and fibrils is considered as the primary therapeutic strategy for AD. Previous studies reported that fullerene derivatives strongly inhibit Aβ fibrillation. However, the underlying inhibitory mechanism remains elusive. As a first step to understand fullerene-modulated full-length Aβ aggregation, we investigated the conformational ensemble of the Aβ1-42 dimer with and without 1,2-(dimethoxymethano)fullerene (DMF) - a more water-soluble fullerene derivative - by performing a 340 ns explicit-solvent replica exchange molecular dynamics simulation. Our simulations show that although disordered states are the most abundant conformations of the Aβ1-42 dimer, conformations containing diverse extended β-hairpins are also populated. The first most-populated β-hairpins involving residues L17-D23 and A30-V36 strongly resemble the engineered β-hairpin which is a building block of toxic Aβ oligomers. We find that the interaction of DMFs with Aβ peptides greatly impedes the formation of such β-hairpins and inter-peptide β-sheets. Binding energy analyses demonstrate that DMF preferentially binds not only to the central hydrophobic motif LVFFA of the Aβ peptide as suggested experimentally, but also to the aromatic residues including F4 and Y10 and the C-terminal hydrophobic region I31-V40. This study reveals a complete picture of the inhibitory mechanism of full-length Aβ1-42 aggregation by fullerenes, providing theoretical insights into the development of drug candidates against AD.

  17. Multi-layer Parallel Beta-Sheet Structure of Amyloid Beta peptide (1-40) aggregate observed by discrete molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Peng, Shouyong; Urbanc, Brigita; Ding, Feng; Cruz, Luis; Buldyrev, Sergey; Dokholyan, Nikolay; Stanley, H. E.

    2003-03-01

    New evidence shows that oligomeric forms of Amyloid-Beta are potent neurotoxins that play a major role in neurodegeneration of Alzheimer's disease. Detailed knowledge of the structure and assembly dynamics of Amyloid-Beta is important for the development of new therapeutic strategies. Here we apply a two-atom model with Go interactions to model aggregation of Amyloid-Beta (1-40) peptides using the discrete molecular dynamics simulation. At temperatures above the transition temperature from an alpha-helical to random coil, we obtain two types of parallel beta-sheet structures, (a) a helical beta-sheet structure at a lower temperature and (b) a parallel beta-sheet structure at a higher temperature, both with inter-sheet distance of 10 A and with free edges which possibly enable further fibrillar elongation.

  18. Accumulation of triosephosphate isomerase, with sequence homology to Beta amyloid peptides, in vessel walls of the newborn piglet hippocampus.

    PubMed

    Kusaka, Takashi; Ueno, Masaki; Miki, Takanori; Kanenishi, Kenji; Nagai, Yukiko; Huang, Cheng-Long; Okamoto, Yasuo; Ogawa, Takafumi; Onodera, Masayuki; Itoh, Susumu; Akiguchi, Ichiro; Sakamoto, Haruhiko

    2007-07-01

    We investigated whether beta-amyloid (Abeta)-like immunoreactivity was seen in the brains of newborn piglets. The immunoreactivity for Abeta(1-42) and Abeta(1-40) proteins, but not Abeta precursor protein, was present in CD68-positive perivascular cells of the hippocampus and in parts of the meninges. It was colocalized with immunoreactivity for receptor for advanced glycation end product and tumor necrosis factor-alpha. The protein with a molecular mass of 27 kDa, which was recognized by the Abeta antibodies, was identified as triosephosphate isomerase (TPI) with sequence homology to Abeta peptides by N-terminal amino acid sequencing, mass fingerprint analysis using matrix-associated laser desorption/ionization mass spectrometry, and Western blotting. Western blotting assay also revealed that detectable expression of Abeta proteins were not seen in the piglet brains. These findings indicate that TPI with sequence homology to Abeta peptides accumulates in perivascular cells of the microglia/macrophage lineage located around arterial vessels of the newborn piglet hippocampus.

  19. Large-scale production of soluble recombinant amyloidpeptide 1-42 using cold-inducible expression system.

    PubMed

    Kim, Eun-Kyung; Moon, Jeong Chan; Lee, Jeong Mi; Jeong, Min Seop; Oh, Choongseob; Ahn, Sung-Min; Yoo, Yung Joon; Jang, Ho Hee

    2012-11-01

    Amyloidpeptide 1-42 (Aβ(1-42)), the predominant form in senile plaques, plays important roles in the pathogenesis of Alzheimer's disease. Because Aβ(1-42) has aggregation-prone nature, it has been difficult to produce in a soluble state in bacterial expression systems. In this study, we modified our expression system to increase the soluble fraction of Aβ(1-42) in Escherichia coli (E. coli) cells. The expression level and solubility of recombinant Aβ(1-42) induced at the low temperature (16°C) is highly increased compared to that induced at 37°C. To optimize expression temperature, the coding region of Aβ(1-42) was constructed in a pCold vector, pCold-TF, which has a hexahistidine-tagged trigger factor (TF). Recombinant Aβ(1-42) was expressed primarily as a soluble protein using pCold vector system and purified with a nickel-chelating resin. When the toxic effect of recombinant Aβ(1-42) examined on human neuroblastoma SH-SY5Y cells, the purified Aβ(1-42) induced cell toxicity on SH-SY5Y cells. In conclusion, the system developed in this study will provide a useful method for the production of aggregation prone-peptide such as Aβ(1-42).

  20. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function

    PubMed Central

    Barucker, Christian; Bittner, Heiko J.; Chang, Philip K.-Y.; Cameron, Scott; Hancock, Mark A.; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M.; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P.; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W.; McKinney, R. Anne; Multhaup, Gerhard

    2015-01-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically “trapping” low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal. PMID:26510576

  1. The Structure of the Amyloid-[beta] Peptide High-Affinity Copper II Binding Site in Alzheimer Disease

    SciTech Connect

    Streltsov, Victor A.; Titmuss, Stephen J.; Epa, V. Chandana; Barnham, Kevin J.; Masters, Colin L.; Varghese, Joseph N.

    2008-11-03

    Neurodegeneration observed in Alzheimer disease (AD) is believed to be related to the toxicity from reactive oxygen species (ROS) produced in the brain by the amyloid-{beta} (A{beta}) protein bound primarily to copper ions. The evidence for an oxidative stress role of A{beta}-Cu redox chemistry is still incomplete. Details of the copper binding site in A{beta} may be critical to the etiology of AD. Here we present the structure determined by combining x-ray absorption spectroscopy (XAS) and density functional theory analysis of A{beta} peptides complexed with Cu{sup 2+} in solution under a range of buffer conditions. Phosphate-buffered saline buffer salt (NaCl) concentration does not affect the high-affinity copper binding mode but alters the second coordination sphere. The XAS spectra for truncated and full-length A{beta}-Cu{sup 2+} peptides are similar. The novel distorted six-coordinated (3N3O) geometry around copper in the A{beta}-Cu{sup 2+} complexes include three histidines: glutamic, or/and aspartic acid, and axial water. The structure of the high-affinity Cu{sup 2+} binding site is consistent with the hypothesis that the redox activity of the metal ion bound to A{beta} can lead to the formation of dityrosine-linked dimers found in AD.

  2. ESEEM Analysis of Multi-Histidine Cu(II)-Coordination in Model Complexes, Peptides, and Amyloid

    PubMed Central

    2015-01-01

    We validate the use of ESEEM to predict the number of 14N nuclei coupled to a Cu(II) ion by the use of model complexes and two small peptides with well-known Cu(II) coordination. We apply this method to gain new insight into less explored aspects of Cu(II) coordination in amyloid-β (Aβ). Aβ has two coordination modes of Cu(II) at physiological pH. A controversy has existed regarding the number of histidine residues coordinated to the Cu(II) ion in component II, which is dominant at high pH (∼8.7) values. Importantly, with an excess amount of Zn(II) ions, as is the case in brain tissues affected by Alzheimer’s disease, component II becomes the dominant coordination mode, as Zn(II) selectively substitutes component I bound to Cu(II). We confirm that component II only contains single histidine coordination, using ESEEM and set of model complexes. The ESEEM experiments carried out on systematically 15N-labeled peptides reveal that, in component II, His 13 and His 14 are more favored as equatorial ligands compared to His 6. Revealing molecular level details of subcomponents in metal ion coordination is critical in understanding the role of metal ions in Alzheimer’s disease etiology. PMID:25014537

  3. A new evidence for DNA nicking property of amyloid beta-peptide (1-42): relevance to Alzheimer's disease.

    PubMed

    Suram, A; Hegde, M L; Rao, K S J

    2007-07-15

    Alzheimer's disease (AD) is a complex neurodegenerative disorder with a progressive mental deterioration manifested by memory loss. No definite etiology has been established for AD to date. Amyloid beta (Abeta) protein plays a central role in the pathology of AD through multiple pathways like oxidative stress, apoptosis etc. Recently, our laboratory first time has evidenced localization of Abeta immunoreactivity in apoptotic nuclei of degenerating AD brain hippocampal neurons and also showed that Abeta (1-42) binds and alters the helicity of DNA. The present study provided fundamental data on DNA nicking induced by Abeta. The results showed that Abeta (1-42) has DNA nicking activity similar to nucleases. Further, magnesium ion (1mM) enhanced DNA nicking activity of Abeta. The data on Abeta solution stability on DNA nicking revealed that the oligomers of Abeta (1-42) peptides showed more DNA nicking activity compared to monomers and fibrillar forms. The nuclease specific inhibitor aurintricarboxylic acid prevented the DNA nicking property of Abeta. Transmission electron microscopy (TEM) studies revealed that Abeta causes open circular and linear forms in supercoiled DNA and also clearly evidenced the physical association of protein-DNA complex. The above data indicated that Abeta mimics endonuclease behavior. Our finding of DNA nicking activity of Abeta peptides has biological significance in terms of causing direct DNA damage.

  4. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function

    NASA Astrophysics Data System (ADS)

    Barucker, Christian; Bittner, Heiko J.; Chang, Philip K.-Y.; Cameron, Scott; Hancock, Mark A.; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M.; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P.; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W.; McKinney, R. Anne; Multhaup, Gerhard

    2015-10-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically “trapping” low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal.

  5. ESEEM analysis of multi-histidine Cu(II)-coordination in model complexes, peptides, and amyloid-β.

    PubMed

    Silva, K Ishara; Michael, Brian C; Geib, Steven J; Saxena, Sunil

    2014-07-31

    We validate the use of ESEEM to predict the number of (14)N nuclei coupled to a Cu(II) ion by the use of model complexes and two small peptides with well-known Cu(II) coordination. We apply this method to gain new insight into less explored aspects of Cu(II) coordination in amyloid-β (Aβ). Aβ has two coordination modes of Cu(II) at physiological pH. A controversy has existed regarding the number of histidine residues coordinated to the Cu(II) ion in component II, which is dominant at high pH (∼8.7) values. Importantly, with an excess amount of Zn(II) ions, as is the case in brain tissues affected by Alzheimer's disease, component II becomes the dominant coordination mode, as Zn(II) selectively substitutes component I bound to Cu(II). We confirm that component II only contains single histidine coordination, using ESEEM and set of model complexes. The ESEEM experiments carried out on systematically (15)N-labeled peptides reveal that, in component II, His 13 and His 14 are more favored as equatorial ligands compared to His 6. Revealing molecular level details of subcomponents in metal ion coordination is critical in understanding the role of metal ions in Alzheimer's disease etiology.

  6. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function.

    PubMed

    Barucker, Christian; Bittner, Heiko J; Chang, Philip K-Y; Cameron, Scott; Hancock, Mark A; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W; McKinney, R Anne; Multhaup, Gerhard

    2015-01-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically "trapping" low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal. PMID:26510576

  7. Binding of iron(III) to the single tyrosine residue of amyloid β-peptide probed by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Miura, Takashi; Suzuki, Kiyoko; Takeuchi, Hideo

    2001-10-01

    The Fe(III) ion binds to amyloid β-peptide (Aβ) and induces significant aggregation of the peptide. In addition to the Aβ aggregation, the redox activity of the Fe(III) ion bound to Aβ is considered to play a role in the pathogenesis of Alzheimer's disease. In order to understand the role of Fe(III) in Aβ aggregation and neurotoxicity, we have examined the Fe(III)-binding mode of human Aβ by Raman spectroscopy. The Raman spectra of Fe(III)-Aβ complexes excited at 514.5 nm are dominated by resonance Raman bands of metal-bound tyrosinate, evidencing that the Fe(III) ion primarily binds to Aβ via the phenolic oxygen of Tyr10. In addition, carboxylate groups of glutamate/aspartate side chains are also bound to Fe(III). On the other hand, histidine residues in the N-terminal hydrophilic region of Aβ do not bind to Fe(III). These results are in sharp contrast to the Zn(II)- or Cu(II)-induced aggregation of Aβ, in which histidine residues act as the primary metal binding sites. The Fe(III)-Tyr10 binding may play an important role in Aβ aggregation and in decreasing the reduction potential of the bound Fe(III) ion.

  8. The Peptide Vaccine Combined with Prior Immunization of a Conventional Diphtheria-Tetanus Toxoid Vaccine Induced Amyloid β Binding Antibodies on Cynomolgus Monkeys and Guinea Pigs

    PubMed Central

    Yano, Akira; Ito, Kaori; Miwa, Yoshikatsu; Kanazawa, Yoshito; Chiba, Akiko; Iigo, Yutaka; Kashimoto, Yoshinori; Kanda, Akira; Murata, Shinji; Makino, Mitsuhiro

    2015-01-01

    The reduction of brain amyloid beta (Aβ) peptides by anti-Aβ antibodies is one of the possible therapies for Alzheimer's disease. We previously reported that the Aβ peptide vaccine including the T-cell epitope of diphtheria-tetanus combined toxoid (DT) induced anti-Aβ antibodies, and the prior immunization with conventional DT vaccine enhanced the immunogenicity of the peptide. Cynomolgus monkeys were given the peptide vaccine subcutaneously in combination with the prior DT vaccination. Vaccination with a similar regimen was also performed on guinea pigs. The peptide vaccine induced anti-Aβ antibodies in cynomolgus monkeys and guinea pigs without chemical adjuvants, and excessive immune responses were not observed. Those antibodies could preferentially recognize Aβ40, and Aβ42 compared to Aβ fibrils. The levels of serum anti-Aβ antibodies and plasma Aβ peptides increased in both animals and decreased the brain Aβ40 level of guinea pigs. The peptide vaccine could induce a similar binding profile of anti-Aβ antibodies in cynomolgus monkeys and guinea pigs. The peptide vaccination could be expected to reduce the brain Aβ peptides and their toxic effects via clearance of Aβ peptides by generated antibodies. PMID:26539559

  9. Ab initio model studies of copper binding to peptides containing a His-His sequence: relevance to the beta-amyloid peptide of Alzheimer's disease.

    PubMed

    Raffa, Duilio F; Gómez-Balderas, Rodolfo; Brunelle, Patrick; Rickard, Gail A; Rauk, Arvi

    2005-12-01

    Two of the defining hallmarks of Alzheimer's disease (AD) are deposits of the beta-amyloid peptide, Abeta, and the generation of reactive oxygen species, both of which may be due to the Abeta peptide coordinating metal ions. The Cu2+ concentrations in cores of senile plaques are significantly elevated in AD patients. Experimental results indicate that Abeta1-42 in particular has a very high affinity for Cu2+, and that His13 and His14 are the two most firmly established ligands in the coordination sphere of the copper ion. Quantum chemical calculations using the unrestricted B3LYP hybrid density functional method with the 6-31G(d) basis set were performed for geometries, zero point energies and thermochemistry. The effects of solvation were accommodated using the CPCM method. The enthalpies were calculated with the 6-311+G(2df,2p) basis set. Calculations show that when Cu(H2O)(4)2+ combines with the model compound 1 (3-(1H-imidazol-5-yl)-N-[2-(1H-imidazol-5-yl)ethyl] propanamide) in the aqueous phase, the most stable binding site involves the Npi atoms of His13 and His14 as well as the carbonyl of the intervening backbone amide group. These structures are fairly rigid and the implications for conformational changes to the Abeta backbone are discussed. In solution at pH=7, Cu2+ promotes the deprotonation and involvement in the binding of the backbone amide nitrogen in a beta-sheet like structure. This geometry does not induce strain in the peptide backbone, making it the most likely representation of that portion of the Cu2+-Abeta complex monomer in aqueous solution. PMID:16267663

  10. Dry amyloid fibril assembly in a yeast prion peptide is mediated by long-lived structures containing water wires

    PubMed Central

    Reddy, Govardhan; Straub, John E.; Thirumalai, D.

    2010-01-01

    Amyloid-like fibrils from a number of small peptides that are unrelated by sequence adopt a cross-β-spine in which the two sheets fully interdigitate to create a dry interface. Formation of such a dry interface is usually associated with self-assembly of extended hydrophobic surfaces. Here we investigate how a dry interface is created in the process of protofilament formation in vastly different sequences using two amyloidogenic peptides, one a polar sequence from the N terminus of the yeast prion Sup35 and the other a predominantly hydrophobic sequence from the C terminus of Aβ-peptide. Using molecular dynamics simulations with three force fields we show that spontaneous formation of two ordered one-dimensional water wires in the pore between the two sheets of the Sup35 protofilaments results in long-lived structures, which are stabilized by a network of hydrogen bonds between the water molecules in the wires and the polar side chains in the β-sheet. Upon decreasing the stability of the metastable structures, water molecules are expelled resulting in a helically twisted protofilament in which side chains from a pair of β-strands in each sheet pack perfectly resulting in a dry interface. Although drying in hydrophobically dominated interfaces is abrupt, resembling a liquid to vapor transition, we find that discrete transitions between the liquid to one-dimensional ordered water in the nanopore enclosed by the two β-sheets to dry interface formation characterizes protofilament assembly in the yeast prions. Indeed, as the two sheets of the hydrophobic Aβ-sequence approach each other, fibril formation and expulsion of water molecules occur rapidly and nearly simultaneously. PMID:21098298

  11. Protective Effect of AmyloidPeptides Against Herpes Simplex Virus-1 Infection in a Neuronal Cell Culture Model.

    PubMed

    Bourgade, Karine; Le Page, Aurélie; Bocti, Christian; Witkowski, Jacek M; Dupuis, Gilles; Frost, Eric H; Fülöp, Tamás

    2016-01-01

    Senile amyloid plaques are one of the main hallmarks of Alzheimer's disease (AD). They correspond to insoluble deposits of amyloidpeptides (Aβ) and are responsible for the inflammatory response and neurodegeneration that lead to loss of memory. Recent data suggest that Aβ possess antimicrobial and anti-viral activity in vitro. Here, we have used cocultures of neuroglioma (H4) and glioblastoma (U118-MG) cells as a minimal in vitro model to investigate whether Aβ is produced by neuroglioma cells and whether this could result in protective anti-viral activity against HSV-1 infection. Results showed that H4 cells secreted Aβ42 in response to HSV-1 challenge and that U118-MG cells could rapidly internalize Aβ42. Production of pro-inflammatory cytokines TNFα and IL-1β by H4 and U118-MG cells occurred under basal conditions but infection of the cells with HSV-1 did not significantly upregulate production. Both cell lines produced low levels of IFNα. However, extraneous Aβ42 induced strong production of these cytokines. A combination of Aβ42 and HSV-1 induced production of pro-inflammatory cytokines TNFα and IL-1β, and IFNα in the cell lines. The reported anti-viral protection of Aβ42 was revealed in transfer experiments involving conditioned medium (CM) of HSV-1-infected H4 cells. CM conferred Aβ-dependent protection against HSV-1 replication in de novo cultures of H4 cells challenged with HSV-1. Type 1 interferons did not play a role in these assays. Our data established that H4 neuroglioma cells produced Aβ42 in response to HSV-1 infection thus inhibiting secondary replication. This mechanism may play a role in the etiology of AD. PMID:26836158

  12. Transducible P11-CNTF rescues the learning and memory impairments induced by amyloid-beta peptide in mice.

    PubMed

    Qu, Heng Yan; Zhang, Ting; Li, Xu Ling; Zhou, Jian Ping; Zhao, Bao Quan; Li, Qian; Sun, Man Ji

    2008-10-10

    Alzheimer's disease is a progressive brain disorder with the loss of memory and other intellectual abilities. Amyloid species and neurofibrillary tangles are the prime suspects in damaging and killing nerve cells. Abnormal accumulation of Amyloid-beta peptide (Abeta) may cause synaptic dysfunction and degeneration of neurons. Drugs that can prevent its formation and accumulation or stimulate its clearance might ultimately be of therapeutic benefit. Ciliary neurotrophic factor (CNTF), a neurotrophic cytokine, promotes the survival of various neurons in brain. However, the blood-brain barrier hinders the systemic delivery of CNTF to brain. Recently the 11-amino acid of protein transduction domain TAT has successfully assisted the delivery of many macromolecules to treat preclinical models of human disease. The present study aimed to evaluate whether P11-CNTF fusion protein (P11-CNTF) is protective against the Abeta25-35-induced dementia in mice. Immunofluorescence experiments showed that P11 effectively carried CNTF to the SH-SY5Y cells in vitro, and to the brains of mice in vivo. The learning and memory impairments of mice induced by Abeta were substantially rescued by supplement with the P11-CNTF. Furthermore, mRNAs of enzymes involved in the Abeta metabolism, e.g. neprilysin (NEP), endothelin-converting enzyme 1 (ECE-1) and insulin degrading enzyme (IDE), increased in the P11-CNTF treated dementia mice, accompanied by the proliferation of nestin- and choline acetyltransferase (ChAT)-positive cells in hippocampus. It implies that the delivery of P11-CNTF may be a novel treatment for Alzheimer's disease. PMID:18644361

  13. Exploring the Alzheimer amyloidpeptide conformational ensemble: A review of molecular dynamics approaches.

    PubMed

    Tran, Linh; Ha-Duong, Tâp

    2015-07-01

    Alzheimer's disease is one of the most common dementia among elderly worldwide. There is no therapeutic drugs until now to treat effectively this disease. One main reason is due to the poorly understood mechanism of Aβ peptide aggregation, which plays a crucial role in the development of Alzheimer's disease. It remains challenging to experimentally or theoretically characterize the secondary and tertiary structures of the Aβ monomer because of its high flexibility and aggregation propensity, and its conformations that lead to the aggregation are not fully identified. In this review, we highlight various structural ensembles of Aβ peptide revealed and characterized by computational approaches in order to find converging structures of Aβ monomer. Understanding how Aβ peptide forms transiently stable structures prior to aggregation will contribute to the design of new therapeutic molecules against the Alzheimer's disease.

  14. Exploring the Alzheimer amyloidpeptide conformational ensemble: A review of molecular dynamics approaches.

    PubMed

    Tran, Linh; Ha-Duong, Tâp

    2015-07-01

    Alzheimer's disease is one of the most common dementia among elderly worldwide. There is no therapeutic drugs until now to treat effectively this disease. One main reason is due to the poorly understood mechanism of Aβ peptide aggregation, which plays a crucial role in the development of Alzheimer's disease. It remains challenging to experimentally or theoretically characterize the secondary and tertiary structures of the Aβ monomer because of its high flexibility and aggregation propensity, and its conformations that lead to the aggregation are not fully identified. In this review, we highlight various structural ensembles of Aβ peptide revealed and characterized by computational approaches in order to find converging structures of Aβ monomer. Understanding how Aβ peptide forms transiently stable structures prior to aggregation will contribute to the design of new therapeutic molecules against the Alzheimer's disease. PMID:25908410

  15. Association between amylin and amyloidpeptides in plasma in the context of apolipoprotein E4 allele.

    PubMed

    Qiu, Wei Qiao; Wallack, Max; Dean, Michael; Liebson, Elizabeth; Mwamburi, Mkaya; Zhu, Haihao

    2014-01-01

    Amylin, a pancreatic peptide that readily crosses the blood brain barrier (BBB), and amyloid-beta peptide (Aβ), the main component of amyloid plaques and a major component of Alzheimer's disease (AD) pathology in the brain, share several features. These include having similar β-sheet secondary structures, binding to the same receptor, and being degraded by the same protease. Thus, amylin may be associated with Aβ, but the nature of their relationship remains unclear. In this study, we used human samples to study the relationship between plasma amylin and Aβ in the context of the apolipoprotein E alleles (ApoE). We found that concentrations of Aβ1-42 (P<0.0001) and Aβ1-40 (P<0.0001) increased with each quartile increase of amylin. Using multivariate regression analysis, the study sample showed that plasma amylin was associated with Aβ1-42 (β = +0.149, SE = 0.025, P<0.0001) and Aβ1-40 (β = +0.034, SE = 0.016, P = 0.04) as an outcome after adjusting for age, gender, ethnicity, ApoE4, BMI, diabetes, stroke, kidney function and lipid profile. This positive association between amylin and Aβ1-42 in plasma was found regardless of the ApoE genotype. In contrast, the relationship between amylin and Aβ1-40 in plasma seen in ApoE4 non-carriers disappeared in the presence of ApoE4. Using AD mouse models, our recent study demonstrates that intraperitoneal (i.p.) injection of synthetic amylin enhances the removal of Aβ from the brain into blood, thus resulting in increased blood levels of both amylin and Aβ. The positive association between amylin and Aβ, especially Aβ1-42, in human blood samples is probably relevant to the findings in the AD mouse models. The presence of ApoE4 may attenuate amylin's capacity to remove Aβ, especially Aβ1-40, from the AD brain.

  16. Identification and quantification of amyloid beta-related peptides in human plasma using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

    PubMed Central

    KANEKO, Naoki; YAMAMOTO, Rie; SATO, Taka-Aki

    2014-01-01

    Proteolytic processing of the amyloid precursor protein (APP) by β-secretase and γ-secretase leads to the generation and deposition of amyloid β (Aβ) in Alzheimer’s disease (AD). N-terminally or C-terminally truncated Aβ variants have been found in human cerebrospinal fluid and cultured cell media using immunoprecipitation and mass spectrometry. Unfortunately, the profile of plasma Aβ variants has not been revealed due to the difficulty of isolating Aβ from plasma. We present here for the first time studies of Aβ and related peptides in human plasma. Twenty-two Aβ-related peptides including novel peptides truncated before the β-secretase site were detected in human plasma and 20 of the peptides were identified by tandem mass spectrometry. Using an internal standard, we developed a quantitative assay for the Aβ-related peptides and demonstrated plasma dilution linearity and the precision required for their quantitation. The present method should enhance the understanding of APP processing and clearance in AD progression. PMID:24621957

  17. Mutation-based structural modification and dynamics study of amyloid beta peptide (1-42): An in-silico-based analysis to cognize the mechanism of aggregation.

    PubMed

    Panda, Pritam Kumar; Patil, Abhaysinha Satish; Patel, Priyam; Panchal, Hetalkumar

    2016-03-01

    Alzheimer's disease is the prevalent cause of premature senility, a progressive mental disorder due to degeneration in brain and deposition of amyloid β peptide (1-42, a misfolded protein) in the form of aggregation that prevails for a prolonged time and obstructs every aspect of life. One of the primary hallmarks of the neuropathological disease is the accretion of amyloid β peptide in the brain that leads to Alzheimer's disease, but the mechanism is still a mystery. Several investigations have shown that mutations at specific positions have a significant impact in stability of the peptide as predicted from aggregation profiles. Here in our study, we have analyzed the mutations by substituting residues at position A22G, E22G, E22K, E22Q, D23N, L34V and molecular dynamics have been performed to check the deviation in stability and conformation of the peptide. The results validated that the mutations at specific positions lead to instability and the proline substitution at E22P and L34P stalled the aggregation of the peptide. PMID:26981406

  18. Mutation-based structural modification and dynamics study of amyloid beta peptide (1–42): An in-silico-based analysis to cognize the mechanism of aggregation

    PubMed Central

    Panda, Pritam Kumar; Patil, Abhaysinha Satish; Patel, Priyam; Panchal, Hetalkumar

    2016-01-01

    Alzheimer's disease is the prevalent cause of premature senility, a progressive mental disorder due to degeneration in brain and deposition of amyloid β peptide (1–42, a misfolded protein) in the form of aggregation that prevails for a prolonged time and obstructs every aspect of life. One of the primary hallmarks of the neuropathological disease is the accretion of amyloid β peptide in the brain that leads to Alzheimer's disease, but the mechanism is still a mystery. Several investigations have shown that mutations at specific positions have a significant impact in stability of the peptide as predicted from aggregation profiles. Here in our study, we have analyzed the mutations by substituting residues at position A22G, E22G, E22K, E22Q, D23N, L34V and molecular dynamics have been performed to check the deviation in stability and conformation of the peptide. The results validated that the mutations at specific positions lead to instability and the proline substitution at E22P and L34P stalled the aggregation of the peptide. PMID:26981406

  19. Amyloid Beta Mediates Memory Formation

    ERIC Educational Resources Information Center

    Garcia-Osta, Ana; Alberini, Cristina M.

    2009-01-01

    The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

  20. The Effects of Endogenous Non-Peptide Molecule Isatin and Hydrogen Peroxide on Proteomic Profiling of Rat Brain Amyloid-β Binding Proteins: Relevance to Alzheimer’s Disease?

    PubMed Central

    Medvedev, Alexei E.; Buneeva, Olga A.; Kopylov, Arthur T.; Gnedenko, Oksana V.; Medvedeva, Marina V.; Kozin, Sergey A.; Ivanov, Alexis S.; Zgoda, Victor G.; Makarov, Alexander A.

    2014-01-01

    The amyloidpeptide is considered as a key player in the development and progression of Alzheimer’s disease (AD). Although good evidence exists that amyloid-β accumulates inside cells, intracellular brain amyloid-binding proteins remain poorly characterized. Proteomic profiling of rat brain homogenates, performed in this study, resulted in identification of 89 individual intracellular amyloid-binding proteins, and approximately 25% of them were proteins that we had previously identified as specifically binding to isatin, an endogenous neuroprotector molecule. A significant proportion of the amyloid-binding proteins (more than 30%) are differentially expressed or altered/oxidatively modified in AD patients. Incubation of brain homogenates with 70 µM hydrogen peroxide significantly influenced the profile of amyloid-β binding proteins and 0.1 mM isatin decreased the number of identified amyloid-β binding proteins both in control and hydrogen peroxide treated brain homogenates. The effects of hydrogen peroxide and isatin have been confirmed in optical biosensor experiments with purified glyceraldehyde-3-phosphate dehydrogenase, one of the known crucial amyloid-β binding proteins (also identified in this study). Data obtained suggest that isatin protects crucial intracellular protein targets against amyloid binding, and possibly favors intracellular degradation of this protein via preventing formation of amyloid-β oligomers described in the literature for some isatin derivatives. PMID:25551598

  1. Exogenous β-amyloid peptide interferes with GLUT4 localization in neurons.

    PubMed

    Oliveira, Leandro T; Leon, Gabbriela V O; Provance, D William; de Mello, Fernando G; Sorenson, Martha M; Salerno, Verônica P

    2015-07-30

    Aging represents a major risk factor for numerous illnesses that are of increasing importance to society, including two of the most prevalent: diabetes and Alzheimer's disease. Studies have shown that diabetes is a risk factor for spontaneous Alzheimer's disease. While these studies suggest that diabetes can contribute to Alzheimer's disease, the implications of AD on diabetes are practically unexplored. The major mediator of the pathophysiological effects, the Aβ42 peptide, has been shown to enter neurons and lead to an alteration of the intracellular distribution of the molecular motor myosin Vb. Myosin Vb functions in memory and learning by participating in the strengthening of the long-term potentiation (LTP) of synaptic transmissions. It has also been implicated in the translocation of the glucose transporter, GLUT4, to the plasma membrane in response to insulin, a process that is defective in diabetes. Here, the effect on GLUT4 upon entry of the Aβ42 peptide into cultured chick retinal neurons was explored. The results suggest an alteration in distribution and a reduced level at the cell surface, as well as an increased colocalization with myosin Vb, which can partially explain the changes in glucose metabolism associated with AD. It is also shown that the presence of the Aβ40 peptide inhibits the internalization of the Aβ42 peptide in cultured cells. Together, the results provide additional targets for the development of therapeutics against the progression and effects of Alzheimer's disease.

  2. AmyloidPeptides and Tau Protein as Biomarkers in Cerebrospinal and Interstitial Fluid Following Traumatic Brain Injury: A Review of Experimental and Clinical Studies

    PubMed Central

    Tsitsopoulos, Parmenion P.; Marklund, Niklas

    2013-01-01

    Traumatic brain injury (TBI) survivors frequently suffer from life-long deficits in cognitive functions and a reduced quality of life. Axonal injury, observed in many severe TBI patients, results in accumulation of amyloid precursor protein (APP). Post-injury enzymatic cleavage of APP can generate amyloid-β (Aβ) peptides, a hallmark finding in Alzheimer’s disease (AD). At autopsy, brains of AD and a subset of TBI victims display some similarities including accumulation of Aβ peptides and neurofibrillary tangles of hyperphosphorylated tau proteins. Most epidemiological evidence suggests a link between TBI and AD, implying that TBI has neurodegenerative sequelae. Aβ peptides and tau may be used as biomarkers in interstitial fluid (ISF) using cerebral microdialysis and/or cerebrospinal fluid (CSF) following clinical TBI. In the present review, the available clinical and experimental literature on Aβ peptides and tau as potential biomarkers following TBI is comprehensively analyzed. Elevated CSF and ISF tau protein levels have been observed following severe TBI and suggested to correlate with clinical outcome. Although Aβ peptides are produced by normal neuronal metabolism, high levels of long and/or fibrillary Aβ peptides may be neurotoxic. Increased CSF and/or ISF Aβ levels post-injury may be related to neuronal activity and/or the presence of axonal injury. The heterogeneity of animal models, clinical cohorts, analytical techniques, and the complexity of TBI in the available studies make the clinical value of tau and Aβ as biomarkers uncertain at present. Additionally, the link between early post-injury changes in tau and Aβ peptides and the future risk of developing AD remains unclear. Future studies using methods such as rapid biomarker sampling combined with enhanced analytical techniques and/or novel pharmacological tools could provide additional information on the importance of Aβ peptides and tau protein in both the acute pathophysiology and long

  3. Intraperitoneal injection of the pancreatic peptide amylin potently reduces behavioral impairment and brain amyloid pathology in murine models of Alzheimer's disease.

    PubMed

    Zhu, H; Wang, X; Wallack, M; Li, H; Carreras, I; Dedeoglu, A; Hur, J-Y; Zheng, H; Li, H; Fine, R; Mwamburi, M; Sun, X; Kowall, N; Stern, R A; Qiu, W Q

    2015-02-01

    Amylin, a pancreatic peptide, and amyloid-beta peptides (Aβ), a major component of Alzheimer's disease (AD) brain, share similar β-sheet secondary structures, but it is not known whether pancreatic amylin affects amyloid pathogenesis in the AD brain. Using AD mouse models, we investigated the effects of amylin and its clinical analog, pramlintide, on AD pathogenesis. Surprisingly, chronic intraperitoneal (i.p.) injection of AD animals with either amylin or pramlintide reduces the amyloid burden as well as lowers the concentrations of Aβ in the brain. These treatments significantly improve their learning and memory assessed by two behavioral tests, Y maze and Morris water maze. Both amylin and pramlintide treatments increase the concentrations of Aβ1-42 in cerebral spinal fluid (CSF). A single i.p. injection of either peptide also induces a surge of Aβ in the serum, the magnitude of which is proportionate to the amount of Aβ in brain tissue. One intracerebroventricular injection of amylin induces a more significant surge in serum Aβ than one i.p. injection of the peptide. In 330 human plasma samples, a positive association between amylin and Aβ1-42 as well as Aβ1-40 is found only in patients with AD or amnestic mild cognitive impairment. As amylin readily crosses the blood-brain barrier, our study demonstrates that peripheral amylin's action on the central nervous system results in translocation of Aβ from the brain into the CSF and blood that could be an explanation for a positive relationship between amylin and Aβ in blood. As naturally occurring amylin may play a role in regulating Aβ in brain, amylin class peptides may provide a new avenue for both treatment and diagnosis of AD.

  4. The membrane-active amphibian peptide caerin 1.8 inhibits fibril formation of amyloid β1-42.

    PubMed

    Liu, Yanqin; Wang, Tianfang; Calabrese, Antonio N; Carver, John A; Cummins, Scott F; Bowie, John H

    2015-11-01

    The amphibian host-defense peptide caerin 1.8 [(1)GLFKVLGSV(10)AKHLLPHVVP(20)VIAEKL(NH2)] inhibits fibril formation of amyloid β 1-42 [(1)DAEFRHDSG(10)YEVHHQKLVF(20)FAEDVGSNKG(30)AIIGLMVGGV(40)VIA] [Aβ42] (the major precursor of the extracellular fibrillar deposits of Alzheimer's disease). Some truncated forms of caerin 1.8 also inhibit fibril formation of Aβ42. For example, caerin 1.8 (1-13) [(1)GLFKVLGSV(10)AKHL(NH2) and caerin 1.8 (22-25) [KVLGSV(10)AKHLLPHVVP(20)VIAEKL(NH2)] show 85% and 75% respectively of the inhibition activity of the parent caerin 1.8. The synthetic peptide KLVFFKKKKKK is a known inhibitor of Aβ42 fibril formation, and was used as a standard in this study. Caerin 1.8 is the more effective fibril inhibitor. IC50 values (± 15%) are caerin 1.8 (75 μM) and KLVFFKKKKKK (370 μM). MALDI mass spectrometry shows the presence of a small peak corresponding to a protonated 1:1 adduct [caerin 1.8/Aβ42]H(+). Molecular dynamics simulation suggests that both hydrogen bonding and hydrophobic interactions between Aβ42 and caerin 1.8 facilitate the formation of a 1:1 complex in water. Fibril formation from Aβ42 has been proposed to be based around the (16)KLVF(20)F region of Aβ42; this region in the 1:1 complex is partially blocked from attachment of a further molecule of Aβ42.

  5. Synthesis and evaluation of antineurotoxicity properties of an amyloidpeptide targeting ligand containing a triamino acid.

    PubMed

    Honcharenko, Dmytro; Bose, Partha Pratim; Maity, Jyotirmoy; Kurudenkandy, Firoz Roshan; Juneja, Alok; Flöistrup, Erik; Biverstål, Henrik; Johansson, Jan; Nilsson, Lennart; Fisahn, André; Strömberg, Roger

    2014-09-14

    Peptide-like compounds containing an arginine have been shown to bind and stabilize the central helix of the Alzheimer's disease related amyloidpeptide (Aβ) in an α-helical conformation, thereby delaying its aggregation into cytotoxic species. Here we study a novel Aβ targeting ligand AEDabDab containing the triamino acid, N(γ)-(2-aminoethyl)-2,4-diaminobutanoic (AEDab) acid. The new AEDab triamino acid carries an extra positive charge in the side chain and is designed to be incorporated into a ligand AEDabDab where the AEDab replaces an arginine moiety in a previously developed ligand Pep1b. This is done in order to increase the Aβ-ligand interaction, and molecular dynamics (MD) simulation of the stability of the Aβ central helix in the presence of the AEDabDab ligand shows further stabilization of the helical conformation of Aβ compared to the previously reported Pep1b as well as compared to the AEOrnDab ligand containing an N(δ)-(2-aminoethyl)-2,5-diaminopentanoic acid unit which has an additional methylene group. To evaluate the effect of the AEDabDab ligand on the Aβ neurotoxicity the AEDab triamino acid building block is synthesized by reductive alkylation of N-protected-glycinal with α-amino-protected diaminobutanoic acid, and the Aβ targeting ligand AEDabDab is prepared by solid-phase synthesis starting with attachment of glutarate to the Wang support. Replacement of the arginine residue by the AEDab triamino acid resulted in an improved capability of the ligand to prevent the Aβ1-42 induced reduction of gamma (γ) oscillations in hippocampal slice preparation.

  6. Translational, rotational and internal dynamics of amyloid β-peptides (Aβ40 and Aβ42) from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Bora, Ram Prasad; Prabhakar, Rajeev

    2009-10-01

    In this study, diffusion constants [translational (DT) and rotational (DR)], correlation times [rotational (τrot) and internal (τint)], and the intramolecular order parameters (S2) of the Alzheimer amyloidpeptides Aβ40 and Aβ42 have been calculated from 150 ns molecular dynamics simulations in aqueous solution. The computed parameters have been compared with the experimentally measured values. The calculated DT of 1.61×10-6 cm2/s and 1.43×10-6 cm2/s for Aβ40 and Aβ42, respectively, at 300 K was found to follow the correct trend defined by the Debye-Stokes-Einstein relation that its value should decrease with the increase in the molecular weight. The estimated DR for Aβ40 and Aβ42 at 300 K are 0.085 and 0.071 ns-1, respectively. The rotational (Crot(t)) and internal (Cint(t)) correlation functions of Aβ40 and Aβ42 were observed to decay at nano- and picosecond time scales, respectively. The significantly different time decays of these functions validate the factorization of the total correlation function (Ctot(t)) of Aβ peptides into Crot(t) and Cint(t). At both short and long time scales, the Clore-Szabo model that was used as Cint(t) provided the best behavior of Ctot(t) for both Aβ40 and Aβ42. In addition, an effective rotational correlation time of Aβ40 is also computed at 18 °C and the computed value (2.30 ns) is in close agreement with the experimental value of 2.45 ns. The computed S2 parameters for the central hydrophobic core, the loop region, and C-terminal domains of Aβ40 and Aβ42 are in accord with the previous studies.

  7. Intrinsic excitability changes induced by acute treatment of hippocampal CA1 pyramidal neurons with exogenous amyloid β peptide

    PubMed Central

    Scullion, Sarah; Brown, Jon T.; Randall, Andrew D.

    2015-01-01

    ABSTRACT Accumulation of beta‐amyloid (Aβ) peptides in the human brain is a canonical pathological hallmark of Alzheimer's disease (AD). Recent work in Aβ‐overexpressing transgenic mice indicates that increased brain Aβ levels can be associated with aberrant epileptiform activity. In line with this, such mice can also exhibit altered intrinsic excitability (IE) of cortical and hippocampal neurons: these observations may relate to the increased prevalence of seizures in AD patients. In this study, we examined what changes in IE are produced in hippocampal CA1 pyramidal cells after 2–5 h treatment with an oligomeric preparation of synthetic human Aβ 1–42 peptide. Whole cell current clamp recordings were compared between Aβ‐(500 nM) and vehicle‐(DMSO 0.05%) treated hippocampal slices obtained from mice. The soluble Aβ treatment did not produce alterations in sub‐threshold intrinsic properties, including membrane potential, input resistance, and hyperpolarization activated “sag”. Similarly, no changes were noted in the firing profile evoked by 500 ms square current supra‐threshold stimuli. However, Aβ 500 nM treatment resulted in the hyperpolarization of the action potential (AP) threshold. In addition, treatment with Aβ at 500 nM depressed the after‐hyperpolarization that followed both a single AP or 50 Hz trains of a number of APs between 5 and 25. These data suggest that acute exposure to soluble Aβ oligomers affects IE properties of CA1 pyramidal neurons differently from outcomes seen in transgenic models of amyloidopathy. However, in both chronic and acute models, the IE changes are toward hyperexcitability, reinforcing the idea that amyloidopathy and increased incidence in seizures might be causally related in AD patients. © 2014 The Authors Hippocampus Published by Wiley Periodicals, Inc. PMID:25515596

  8. Altered emotionality leads to increased pain tolerance in amyloid beta (Abeta1-40) peptide-treated mice.

    PubMed

    Pamplona, Fabrício A; Pandolfo, Pablo; Duarte, Filipe S; Takahashi, Reinaldo N; Prediger, Rui D S

    2010-09-01

    Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the decline in cognitive functions, but it is also related to emotional disturbances. Since pain experience results from a complex integration of sensory, cognitive and affective processes, it is not surprising that AD patients display a distinct pattern of pain responsivity. We evaluated whether mice treated with amyloid beta (Abeta) peptide-thought to be critical in the pathogenesis of AD-exhibit altered pain responses and its relation to altered emotionality. Mice received a single i.c.v. injection of vehicle (PBS) or Abeta fragment (1-40) (400pmol/mice) and after 30 days, they were evaluated in tests of pain (hotplate, footshock-sensitivity), learning/memory (water-maze), emotionality (elevated plus-maze, forced swim) and locomotion (open-field). Abeta(1-40)-treated mice presented similar latencies to the control group in the hotplate test and similar nociceptive flinch threshold in the footshock-sensitivity test. However, they presented an increased jump threshold in footshock-sensitivity, suggesting increased pain tolerance. Altered emotionality was observed in the elevated plus-maze (EPM) and forced-swim tests (FST), suggesting anxiogenic-like and depressive-like states, respectively. A multifactorial principal component analysis (PCA) revealed that jump threshold of the footshock-sensitivity test falls within 'Emotionality' and 'Pain', showing moderate correlation with each one of the components of behavior. Acute treatment with the antidepressant desipramine (10mg/kg, i.p.) reduced the jump threshold (i.e. pain tolerance) and time of immobility in FST (i.e. depressive-like state). Flinch threshold (i.e. pain sensitivity), locomotion and anxiety were not altered with desipramine treatment. These results suggest that Abeta(1-40) peptide increases pain tolerance, but not pain sensitivity in mice, which seems to be linked to alterations in cognitive/emotional components of pain

  9. Intrinsic excitability changes induced by acute treatment of hippocampal CA1 pyramidal neurons with exogenous amyloid β peptide.

    PubMed

    Tamagnini, Francesco; Scullion, Sarah; Brown, Jon T; Randall, Andrew D

    2015-07-01

    Accumulation of beta-amyloid (Aβ) peptides in the human brain is a canonical pathological hallmark of Alzheimer's disease (AD). Recent work in Aβ-overexpressing transgenic mice indicates that increased brain Aβ levels can be associated with aberrant epileptiform activity. In line with this, such mice can also exhibit altered intrinsic excitability (IE) of cortical and hippocampal neurons: these observations may relate to the increased prevalence of seizures in AD patients. In this study, we examined what changes in IE are produced in hippocampal CA1 pyramidal cells after 2-5 h treatment with an oligomeric preparation of synthetic human Aβ 1-42 peptide. Whole cell current clamp recordings were compared between Aβ-(500 nM) and vehicle-(DMSO 0.05%) treated hippocampal slices obtained from mice. The soluble Aβ treatment did not produce alterations in sub-threshold intrinsic properties, including membrane potential, input resistance, and hyperpolarization activated "sag". Similarly, no changes were noted in the firing profile evoked by 500 ms square current supra-threshold stimuli. However, Aβ 500 nM treatment resulted in the hyperpolarization of the action potential (AP) threshold. In addition, treatment with Aβ at 500 nM depressed the after-hyperpolarization that followed both a single AP or 50 Hz trains of a number of APs between 5 and 25. These data suggest that acute exposure to soluble Aβ oligomers affects IE properties of CA1 pyramidal neurons differently from outcomes seen in transgenic models of amyloidopathy. However, in both chronic and acute models, the IE changes are toward hyperexcitability, reinforcing the idea that amyloidopathy and increased incidence in seizures might be causally related in AD patients.

  10. Amyloid β Peptide Enhances RANKL-Induced Osteoclast Activation through NF-κB, ERK, and Calcium Oscillation Signaling

    PubMed Central

    Li, Shangfu; Yang, Bu; Teguh, Dian; Zhou, Lin; Xu, Jiake; Rong, Limin

    2016-01-01

    Osteoporosis and Alzheimer’s disease (AD) are common chronic degenerative disorders which are strongly associated with advanced age. We have previously demonstrated that amyloid beta peptide (Aβ), one of the pathological hallmarks of AD, accumulated abnormally in osteoporotic bone specimens in addition to having an activation effect on osteoclast (Bone 2014,61:164-75). However, the underlying molecular mechanisms remain unclear. Activation of NF-κB, extracellular signal-regulated kinase (ERK) phosphorylates, and calcium oscillation signaling pathways by receptor activator NF-κB ligand (RANKL) plays a pivotal role in osteoclast activation. Targeting this signaling to modulate osteoclast function has been a promising strategy for osteoclast-related diseases. In this study, we investigated the effects of Aβ on RANKL-induced osteoclast signaling pathways in vitro. In mouse bone marrow monocytes (BMMs), Aβ exerted no effect on RANKL-induced osteoclastogenesis but promoted osteoclastic bone resorption. In molecular levels, Aβ enhanced NF-κB activity and IκB-α degradation, activated ERK phosphorylation and stimulated calcium oscillation, thus leading to upregulation of NFAT-c1 expression during osteoclast activation. Taken together, our data demonstrate that Aβ enhances RANKL-induced osteoclast activation through IκB-α degradation, ERK phosphorylation, and calcium oscillation signaling pathways and that Aβ may be a promising agent in the treatment of osteoclast-related disease such as osteoporosis. PMID:27735865

  11. Non-fibrillar amyloid-{beta} peptide reduces NMDA-induced neurotoxicity, but not AMPA-induced neurotoxicity

    SciTech Connect

    Niidome, Tetsuhiro; Goto, Yasuaki; Kato, Masaru; Wang, Pi-Lin; Goh, Saori; Tanaka, Naoki; Akaike, Akinori; Kihara, Takeshi; Sugimoto, Hachiro

    2009-09-04

    Amyloid-{beta} peptide (A{beta}) is thought to be linked to the pathogenesis of Alzheimer's disease. Recent studies suggest that A{beta} has important physiological roles in addition to its pathological roles. We recently demonstrated that A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity, but the relationship between A{beta}42 assemblies and their neuroprotective effects remains largely unknown. In this study, we prepared non-fibrillar and fibrillar A{beta}42 based on the results of the thioflavin T assay, Western blot analysis, and atomic force microscopy, and examined the effects of non-fibrillar and fibrillar A{beta}42 on glutamate-induced neurotoxicity. Non-fibrillar A{beta}42, but not fibrillar A{beta}42, protected hippocampal neurons from glutamate-induced neurotoxicity. Furthermore, non-fibrillar A{beta}42 decreased both neurotoxicity and increases in the intracellular Ca{sup 2+} concentration induced by N-methyl-D-aspartate (NMDA), but not by {alpha}-amino-3-hydrozy-5-methyl-4-isoxazole propionic acid (AMPA). Our results suggest that non-fibrillar A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity through regulation of the NMDA receptor.

  12. Amyloid β peptide directly impairs pineal gland melatonin synthesis and melatonin receptor signaling through the ERK pathway.

    PubMed

    Cecon, Erika; Chen, Min; Marçola, Marina; Fernandes, Pedro A C; Jockers, Ralf; Markus, Regina P

    2015-06-01

    Melatonin is the hormone produced by the pineal gland known to regulate physiologic rhythms and to display immunomodulatory and neuroprotective properties. It has been reported that Alzheimer disease patients show impaired melatonin production and altered expression of the 2 G protein-coupled melatonin receptors (MTRs), MT₁ and MT₂, but the underlying mechanisms are not known. Here we evaluated whether this dysfunction of the melatonergic system is directly caused by amyloid β peptides (Aβ(1-40) and Aβ(1-42)). Aβ treatment of rat pineal glands elicited an inflammatory response within the gland, evidenced by the up-regulation of 52 inflammatory genes, and decreased the production of melatonin up to 75% compared to vehicle-treated glands. Blocking NF-κB activity prevented this effect. Exposure of HEK293 cells stably expressing recombinant MT₁ or MT₂ receptors to Aβ lead to a 40% reduction in [(125)I]iodomelatonin binding to MT₁. ERK1/2 activation triggered by MTRs, but not by the β₂-adrenergic receptor, was markedly impaired by Aβ in HEK293 transfected cells, as well as in primary rat endothelial cells expressing endogenous MTRs. Our data reveal the melatonergic system as a new target of Aβ, opening new perspectives to Alzheimer disease diagnosis and therapeutic intervention.

  13. Methylglyoxal produced by amyloidpeptide-induced nitrotyrosination of triosephosphate isomerase triggers neuronal death in Alzheimer's disease.

    PubMed

    Tajes, Marta; Eraso-Pichot, Abel; Rubio-Moscardó, Fanny; Guivernau, Biuse; Ramos-Fernández, Eva; Bosch-Morató, Mònica; Guix, Francesc Xavier; Clarimón, Jordi; Miscione, Gian Pietro; Boada, Mercé; Gil-Gómez, Gabriel; Suzuki, Toshiharu; Molina, Henrik; Villà-Freixa, Jordi; Vicente, Rubén; Muñoz, Francisco J

    2014-01-01

    Amyloidpeptide (Aβ) aggregates induce nitro-oxidative stress, contributing to the characteristic neurodegeneration found in Alzheimer's disease (AD). One of the most strongly nitrotyrosinated proteins in AD is the triosephosphate isomerase (TPI) enzyme which regulates glycolytic flow, and its efficiency decreased when it is nitrotyrosinated. The main aims of this study were to analyze the impact of TPI nitrotyrosination on cell viability and to identify the mechanism behind this effect. In human neuroblastoma cells (SH-SY5Y), we evaluated the effects of Aβ42 oligomers on TPI nitrotyrosination. We found an increased production of methylglyoxal (MG), a toxic byproduct of the inefficient nitro-TPI function. The proapoptotic effects of Aβ42 oligomers, such as decreasing the protective Bcl2 and increasing the proapoptotic caspase-3 and Bax, were prevented with a MG chelator. Moreover, we used a double mutant TPI (Y165F and Y209F) to mimic nitrosative modifications due to Aβ action. Neuroblastoma cells transfected with the double mutant TPI consistently triggered MG production and a decrease in cell viability due to apoptotic mechanisms. Our data show for the first time that MG is playing a key role in the neuronal death induced by Aβ oligomers. This occurs because of TPI nitrotyrosination, which affects both tyrosines associated with the catalytic center.

  14. Metabolic changes may precede proteostatic dysfunction in a Drosophila model of amyloid beta peptide toxicity

    PubMed Central

    Ott, Stanislav; Vishnivetskaya, Anastasia; Malmendal, Anders; Crowther, Damian C.

    2016-01-01

    Amyloid beta (Aβ) peptide aggregation is linked to the initiation of Alzheimer's disease; accordingly, aggregation-prone isoforms of Aβ, expressed in the brain, shorten the lifespan of Drosophila melanogaster. However, the lethal effects of Aβ are not apparent until after day 15. We used shibireTS flies that exhibit a temperature-sensitive paralysis phenotype as a reporter of proteostatic robustness. In this model, we found that increasing age but not Aβ expression lowered the flies' permissive temperature, suggesting that Aβ did not exert its lethal effects by proteostatic disruption. Instead, we observed that chemical challenges, in particular oxidative stressors, discriminated clearly between young (robust) and old (sensitive) flies. Using nuclear magnetic resonance spectroscopy in combination with multivariate analysis, we compared water-soluble metabolite profiles at various ages in flies expressing Aβ in their brains. We observed 2 genotype-linked metabolomic signals, the first reported the presence of any Aβ isoform and the second the effects of the lethal Arctic Aβ. Lethality was specifically associated with signs of oxidative respiration dysfunction and oxidative stress. PMID:27103517

  15. Posttranslational nitro-glycative modifications of albumin in Alzheimer's disease: implications in cytotoxicity and amyloidpeptide aggregation.

    PubMed

    Ramos-Fernández, Eva; Tajes, Marta; Palomer, Ernest; Ill-Raga, Gerard; Bosch-Morató, Mònica; Guivernau, Biuse; Román-Dégano, Irene; Eraso-Pichot, Abel; Alcolea, Daniel; Fortea, Juan; Nuñez, Laura; Paez, Antonio; Alameda, Francesc; Fernández-Busquets, Xavier; Lleó, Alberto; Elosúa, Roberto; Boada, Mercé; Valverde, Miguel A; Muñoz, Francisco J

    2014-01-01

    Glycation and nitrotyrosination are pathological posttranslational modifications that make proteins prone to losing their physiological properties. Since both modifications are increased in Alzheimer's disease (AD) due to amyloidpeptide (Aβ) accumulation, we have studied their effect on albumin, the most abundant protein in cerebrospinal fluid and blood. Brain and plasmatic levels of glycated and nitrated albumin were significantly higher in AD patients than in controls. In vitro turbidometry and electron microscopy analyses demonstrated that glycation and nitrotyrosination promote changes in albumin structure and biochemical properties. Glycated albumin was more resistant to proteolysis and less uptake by hepatoma cells occurred. Glycated albumin also reduced the osmolarity expected for a solution containing native albumin. Both glycation and nitrotyrosination turned albumin cytotoxic in a cell type-dependent manner for cerebral and vascular cells. Finally, of particular relevance to AD, these modified albumins were significantly less effective in avoiding Aβ aggregation than native albumin. In summary, nitrotyrosination and especially glycation alter albumin structural and biochemical properties, and these modifications might contribute for the progression of AD.

  16. Role of Notch-1 signaling pathway in PC12 cell apoptosis induced by amyloid beta-peptide (25–35)

    PubMed Central

    Liang, Huimin; Zhang, Yaozhou; Shi, Xiaoyan; Wei, Tianxiang; Lou, Jiyu

    2014-01-01

    Recent studies have demonstrated that Notch-1 expression is increased in the hippocampus of Alzheimer's disease patients. We speculate that Notch-1 signaling may be involved in PC12 cell apoptosis induced by amyloid beta-peptide (25–35) (Aβ25–35). In the present study, PC12 cells were cultured with different doses (0, 0.1, 1.0, 10 and 100 nmol/L) of N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, a Notch-1 signaling pathway inhibitor, for 30 minutes. Then cultured cells were induced with Aβ25–35 for 48 hours. Pretreatment of PC12 cells with high doses of N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (> 10 nmol/L) prolonged the survival of PC12 cells after Aβ25–35 induction, decreased the expression of apoptosis-related proteins caspase-3, -8, -9, increased the activity of oxidative stress-related superoxide dismutase and catalase, inhibited the production of active oxygen, and reduced nuclear factor kappa B expression. This study indicates that the Notch-1 signaling pathway plays a pivotal role in Aβ25–35-induced PC12 apoptosis. PMID:25221582

  17. Role of p75 Neurotrophin Receptor in the Neurotoxicity by β-amyloid Peptides and Synergistic Effect of Inflammatory Cytokines

    PubMed Central

    Perini, Giovanni; Della-Bianca, Vittorina; Politi, Valeria; Della Valle, Giuliano; Dal-Pra, Ilaria; Rossi, Filippo; Armato, Ubaldo

    2002-01-01

    The neurodegenerative changes in Alzheimer's disease (AD) are elicited by the accumulation of β-amyloid peptides (Aβ), which damage neurons either directly by interacting with components of the cell surface to trigger cell death signaling or indirectly by activating astrocytes and microglia to produce inflammatory mediators. It has been recently proposed that the p75 neurotrophin receptor (p75NTR) is responsible for neuronal damage by interacting with Aβ. By using neuroblastoma cell clones lacking the expression of all neurotrophin receptors or engineered to express full-length or various truncated forms of p75NTR, we could show that p75NTR is involved in the direct signaling of cell death by Aβ via the function of its death domain. This signaling leads to the activation of caspases-8 and -3, the production of reactive oxygen intermediates and the induction of an oxidative stress. We also found that the direct and indirect (inflammatory) mechanisms of neuronal damage by Aβ could act synergistically. In fact, TNF-α and IL-1β, cytokines produced by Aβ-activated microglia, could potentiate the neurotoxic action of Aβ mediated by p75NTR signaling. Together, our results indicate that neurons expressing p75NTR, mostly if expressing also proinflammatory cytokine receptors, might be preferential targets of the cytotoxic action of Aβ in AD. PMID:11927634

  18. Soluble Beta-Amyloid Peptides, but Not Insoluble Fibrils, Have Specific Effect on Neuronal MicroRNA Expression

    PubMed Central

    Li, Jing Jing; Dolios, Georgia; Wang, Rong; Liao, Francesca-Fang

    2014-01-01

    Recent studies indicate that soluble β-amyloid (sAβ) oligomers, rather than their fibrillar aggregates, contribute to the pathogenesis of Alzheimer's disease (AD), though the mechanisms of their neurotoxicity are still elusive. Here, we demonstrate that sAβ derived from 7PA2 cells exert a much stronger effect on the regulation of a set of functionally validated microRNAs (miRNAs) in primary cultured neurons than the synthetic insoluble Aβ fibrils (fAβ). Synthetic sAβ peptides at a higher concentration present comparable effect on these miRNAs in our neuronal model. Further, the sAβ-induced miR-134, miR-145 and miR-210 expressions are fully reversed by two selective N-methyl-d-aspartate (NMDA) receptor inhibitors, but are neither reversed by insulin nor by forskolin, suggesting an NMDA receptor-dependent, rather than PI3K/AKT or PKA/CREB signaling dependent regulatory mechanism. In addition, the repression of miR-107 expression by the sAβ containing 7PA2 CM is likely involved multiple mechanisms and multiple players including NMDA receptor, N-terminally truncated Aβ and reactive oxygen species (ROS). PMID:24595404

  19. Genetic Mechanisms of Coffee Extract Protection in a Caenorhabditis elegans Model of β-Amyloid Peptide Toxicity

    PubMed Central

    Dostal, Vishantie; Roberts, Christine M.; Link, Christopher D.

    2010-01-01

    Epidemiological studies have reported that coffee and/or caffeine consumption may reduce Alzheimer's disease (AD) risk. We found that coffee extracts can similarly protect against β-amyloid peptide (Aβ) toxicity in a transgenic Caenorhabditis elegans Alzheimer's disease model. The primary protective component(s) in this model is not caffeine, although caffeine by itself can show moderate protection. Coffee exposure did not decrease Aβ transgene expression and did not need to be present during Aβ induction to convey protection, suggesting that coffee exposure protection might act by activating a protective pathway. By screening the effects of coffee on a series of transgenic C. elegans stress reporter strains, we identified activation of the skn-1 (Nrf2 in mammals) transcription factor as a potential mechanism of coffee extract protection. Inactivation of skn-1 genetically or by RNAi strongly blocked the protective effects of coffee extract, indicating that activation of the skn-1 pathway was the primary mechanism of coffee protection. Coffee also protected against toxicity resulting from an aggregating form of green fluorescent protein (GFP) in a skn-1–dependent manner. These results suggest that the reported protective effects of coffee in multiple neurodegenerative diseases may result from a general activation of the Nrf2 phase II detoxification pathway. PMID:20805557

  20. L17A/F19A Substitutions Augment the α-Helicity of β-Amyloid Peptide Discordant Segment

    PubMed Central

    Wang, Chih-Ching; Chen, Yi-Ru; Chang, Chi-Fon; Shiao, Ming-Shi; Chen, Yi-Cheng; Lin, Ta-Hsien

    2016-01-01

    β-amyloid peptide (Aβ) aggregation has been thought to be associated with the pathogenesis of Alzheimer’s disease. Recently, we showed that L17A/F19A substitutions may increase the structural stability of wild-type and Arctic-type Aβ40 and decrease the rates of structural conversion and fibril formation. However, the underlying mechanism for the increase of structural stability as a result of the alanine substitutions remained elusive. In this study, we apply nuclear magnetic resonance and circular dichroism spectroscopies to characterize the Aβ40 structure, demonstrating that L17A/F19A substitutions can augment the α-helicity of the residues located in the α/β-discordant segment (resides 15 to 23) of both wild-type and Arctic-type Aβ40. These results provide a structural basis to link the α-helicity of the α/β-discordant segment with the conformational conversion propensity of Aβ. PMID:27104649

  1. Amyloidpeptide-specific DARPins as a novel class of potential therapeutics for Alzheimer disease.

    PubMed

    Hanenberg, Michael; McAfoose, Jordan; Kulic, Luka; Welt, Tobias; Wirth, Fabian; Parizek, Petra; Strobel, Lisa; Cattepoel, Susann; Späni, Claudia; Derungs, Rebecca; Maier, Marcel; Plückthun, Andreas; Nitsch, Roger M

    2014-09-26

    Passive immunization with anti-amyloidpeptide (Aβ) antibodies is effective in animal models of Alzheimer disease. With the advent of efficient in vitro selection technologies, the novel class of designed ankyrin repeat proteins (DARPins) presents an attractive alternative to the immunoglobulin scaffold. DARPins are small and highly stable proteins with a compact modular architecture ideal for high affinity protein-protein interactions. In this report, we describe the selection, binding profile, and epitope analysis of Aβ-specific DARPins. We further showed their ability to delay Aβ aggregation and prevent Aβ-mediated neurotoxicity in vitro. To demonstrate their therapeutic potential in vivo, mono- and trivalent Aβ-specific DARPins (D23 and 3×D23) were infused intracerebroventricularly into the brains of 11-month-old Tg2576 mice over 4 weeks. Both D23 and 3×D23 treatments were shown to result in improved cognitive performance and reduced soluble Aβ levels. These findings demonstrate the therapeutic potential of Aβ-specific DARPins for the treatment of Alzheimer disease.

  2. Methylglyoxal produced by amyloidpeptide-induced nitrotyrosination of triosephosphate isomerase triggers neuronal death in Alzheimer's disease.

    PubMed

    Tajes, Marta; Eraso-Pichot, Abel; Rubio-Moscardó, Fanny; Guivernau, Biuse; Ramos-Fernández, Eva; Bosch-Morató, Mònica; Guix, Francesc Xavier; Clarimón, Jordi; Miscione, Gian Pietro; Boada, Mercé; Gil-Gómez, Gabriel; Suzuki, Toshiharu; Molina, Henrik; Villà-Freixa, Jordi; Vicente, Rubén; Muñoz, Francisco J

    2014-01-01

    Amyloidpeptide (Aβ) aggregates induce nitro-oxidative stress, contributing to the characteristic neurodegeneration found in Alzheimer's disease (AD). One of the most strongly nitrotyrosinated proteins in AD is the triosephosphate isomerase (TPI) enzyme which regulates glycolytic flow, and its efficiency decreased when it is nitrotyrosinated. The main aims of this study were to analyze the impact of TPI nitrotyrosination on cell viability and to identify the mechanism behind this effect. In human neuroblastoma cells (SH-SY5Y), we evaluated the effects of Aβ42 oligomers on TPI nitrotyrosination. We found an increased production of methylglyoxal (MG), a toxic byproduct of the inefficient nitro-TPI function. The proapoptotic effects of Aβ42 oligomers, such as decreasing the protective Bcl2 and increasing the proapoptotic caspase-3 and Bax, were prevented with a MG chelator. Moreover, we used a double mutant TPI (Y165F and Y209F) to mimic nitrosative modifications due to Aβ action. Neuroblastoma cells transfected with the double mutant TPI consistently triggered MG production and a decrease in cell viability due to apoptotic mechanisms. Our data show for the first time that MG is playing a key role in the neuronal death induced by Aβ oligomers. This occurs because of TPI nitrotyrosination, which affects both tyrosines associated with the catalytic center. PMID:24614897

  3. Novel Nuclear Factor-KappaB Targeting Peptide Suppresses β-Amyloid Induced Inflammatory and Apoptotic Responses in Neuronal Cells

    PubMed Central

    Srinivasan, Mythily; Bayon, Baindu; Chopra, Nipun; Lahiri, Debomoy K.

    2016-01-01

    In the central nervous system (CNS), activation of the transcription factor nuclear factor-kappa B (NF-κβ) is associated with both neuronal survival and increased vulnerability to apoptosis. The mechanisms underlying these dichotomous effects are attributed to the composition of NF-κΒ dimers. In Alzheimer’s disease (AD), β-amyloid (Aβ) and other aggregates upregulate activation of p65:p50 dimers in CNS cells and enhance transactivation of pathological mediators that cause neuroinflammation and neurodegeneration. Hence selective targeting of activated p65 is an attractive therapeutic strategy for AD. Here we report the design, structural and functional characterization of peptide analogs of a p65 interacting protein, the glucocorticoid induced leucine zipper (GILZ). By virtue of binding the transactivation domain of p65 exposed after release from the inhibitory IκΒ proteins in activated cells, the GILZ analogs can act as highly selective inhibitors of activated p65 with minimal potential for off-target effects. PMID:27764084

  4. Preparation of fluorescently-labeled amyloid-beta peptide assemblies: the effect of fluorophore conjugation on structure and function

    PubMed Central

    Jungbauer, L. M.; Yu, C; Laxton, K. J.; LaDu, M. J.

    2009-01-01

    Recent research has focused on soluble oligomeric assemblies of the 42 amino acid isoform of the amyloid-beta peptide (Aβ42) as the proximal cause of neuronal injury, synaptic loss, and the eventual dementia associated with Alzheimer’s disease (AD). While neurotoxicity, neuroinflammation, and deficits in behavior and memory have all been attributed to oligomeric Aβ42, the specific roles for this assembly in the cellular neuropathology of AD remain poorly understood. In particular, lack of reliable and well-characterized forms of easily detectable Aβ42 oligomers has hindered study of the cellular trafficking of exogenous Aβ42 by neurons in vitro and in vivo. Therefore, the objective of this study is to fluorescently label soluble oligomeric Aβ42 without altering the structure or function of this assembly. Previous studies have demonstrated the advantages of using tapping mode atomic force microscopy (AFM) to characterize the structural assemblies formed by synthetic Aβ42 under specific solution conditions (e.g., oligomers, protofibrils, and fibrils). Here, we extend these methods to establish a strategy for fluorescent labeling of oligomeric Aβ42 assemblies that are structurally comparable to unlabeled oligomeric Aβ42. To compare function, we demon-strate that the uptake of labeled and unlabeled oligomeric Aβ42 by neurons in vitro is similar. AFM-characterized fluorophore-Aβ42 oligomers are an exciting new reagent for use in a variety of studies designed to elucidate critical cellular and molecular mechanisms underlying the functions of this Aβ42 assembly form in AD. PMID:19343729

  5. The Characterization of the Caenorhabditis elegans Mitochondrial Thioredoxin System Uncovers an Unexpected Protective Role of Thioredoxin Reductase 2 in β-Amyloid Peptide Toxicity

    PubMed Central

    Cacho-Valadez, Briseida; Muñoz-Lobato, Fernando; Pedrajas, José Rafael; Cabello, Juan; Fierro-González, Juan Carlos; Navas, Plácido; Swoboda, Peter; Link, Chris D.

    2012-01-01

    Abstract Aim: Functional in vivo studies on the mitochondrial thioredoxin system are hampered by the embryonic or larval lethal phenotypes displayed by murine or Drosophila knock-out models. Thus, the access to alternative metazoan knock-out models for the mitochondrial thioredoxin system is of critical importance. Results: We report here the characterization of the mitochondrial thioredoxin system of Caenorhabditis elegans that is composed of the genes trx-2 and trxr-2. We demonstrate that the proteins thioredoxin 2 (TRX-2) and thioredoxin reductase 2 (TRXR-2) localize to the mitochondria of several cells and tissues of the nematode and that trx-2 and trxr-2 are upregulated upon induction of the mitochondrial unfolded protein response. Surprisingly, C. elegans trx-2 (lof ) and trxr-2 (null) single and double mutants are viable and display similar growth rates as wild-type controls. Moreover, the lack of the mitochondrial thioredoxin system does not affect longevity, reactive oxygen species production or the apoptotic program. Interestingly, we found a protective role of TRXR-2 in a transgenic nematode model of Alzheimer's disease (AD) that expresses human β-amyloid peptide and causes an age-dependent progressive paralysis. Hence, trxr-2 downregulation enhanced the paralysis phenotype, while a strong decrease of β-amyloid peptide and amyloid deposits occurred when TRXR-2 was overexpressed. Innovation: C. elegans provides the first viable metazoan knock-out model for the mitochondrial thioredoxin system and identifies a novel role of this system in β-amyloid peptide toxicity and AD. Conclusion: The nematode strains characterized in this work make C. elegans an ideal model organism to study the pathophysiology of the mitochondrial thioredoxin system at the level of a complete organism. Antioxid. Redox Signal. 16, 1384–1400. PMID:22220943

  6. The AmyloidPeptide of Alzheimer’s Disease Binds CuI in a Linear Bis-His Coordination Environment: Insight into a Possible Neuroprotective Mechanism for the AmyloidPeptide

    SciTech Connect

    Shearer, J.; Szalai, V

    2008-01-01

    Oxidative stress has been suggested to contribute to neuronal apoptosis associated with Alzheimer's disease (AD). Copper may participate in oxidative stress through redox-cycling between its +2 and +1 oxidation states to generate reactive oxygen species (ROS). In vitro, copper binds to the amyloid-? peptide of AD, and in vivo, copper is associated with amyloid plaques characteristic of AD. As a result, the A?CuI complex may be a critical reactant involved in ROS associated with AD etiology. To characterize the A?CuI complex, we have pursued X-ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopy of A?CuII and A?CuI (produced by ascorbate reduction of A?CuII). The A?CuII complex Cu K-edge XAS spectrum is indicative of a square-planar CuII center with mixed N/O ligation. Multiple scattering analysis of the extended X-ray absorption fine structure (EXAFS) data for A?CuII indicates that two of the ligands are imidazole groups of histidine ligands, indicating a (NIm)2(N/O)2 CuII ligation sphere for A?CuII. After reduction of the A?CuII complex with ascorbate, the edge region decreases in energy by 4 eV. The X-ray absorption near-edge spectrum region of A?CuI displays an intense pre-edge feature at 8984.1(2) eV. EXAFS data fitting yielded a two-coordinate geometry, with two imidazole ligands coordinated to CuI at 1.877(2) A in a linear geometry. Ascorbate reduction of A?CuII under inert atmosphere and subsequent air oxidation of A?CuI to regenerate A?CuII was monitored by low-temperature EPR spectroscopy. Slow reappearance of the A?CuII EPR signal indicates that O2 oxidation of the A?CuI complex is kinetically sluggish and A? damage is occurring following reoxidation of A?CuI by O2. Together, these results lead us to hypothesize that CuI is ligated by His13 and His14 in a linear coordination environment in ??, that A? may be playing a neuroprotective role, and that metal-mediated oxidative damage of A? occurs over multiple redox cycles.

  7. The amyloidpeptide of Alzheimer's disease binds CuI in a linear bis-His coordination environment: Insight into a possible neuroprotective mechanism for the amyloidpeptide

    PubMed Central

    2010-01-01

    Oxidative stress has been suggested to contribute to neuronal apoptosis associated with Alzheimer's disease (AD). Copper may participate in oxidative stress through redox-cycling between its +2 and +1 oxidation states to generate reactive oxygen species (ROS). In vitro, copper binds to the amyloidpeptide of AD and in vivo, copper is associated with amyloid plaques characteristic of AD. As a result, the AβCuI complex may be a critical reactant involved in ROS associated with AD etiology. To characterize the AβCuI complex, we have pursued X-ray absorption (XAS) and EPR spectroscopy of AβCuII and AβCuI (produced by ascorbate reduction of AβCuII). The AβCuII complex Cu K-edge X-ray absorption spectrum is indicative of a square-planar CuII center with mixed N/O ligation. Multiple scattering analysis of the extended X-ray absorption fine structure (EXAFS) data for AβCuII indicate that two of the ligands are imidazole groups of histidine ligands, indicating a (NIm)2(N/O)2 CuII ligation sphere for AβCuII. After reduction of the AβCuII complex with ascorbate, the edge region decreases by ∼4 eV in energy. The X-ray absorption near-edge spectrum (XANES) region of AβCuI displays an intense pre-edge feature at 8984.1(2) eV. EXAFS data fitting yielded a two coordinate geometry with two imidazole ligands coordinated to CuI at 1.877(2) Å in a linear geometry. Ascorbate reduction of AβCuII under inert atmosphere and subsequent air oxidation of AβCuI to regenerate AβCuII was monitored by low-temperature EPR spectroscopy. Slow re-appearance of the AβCuII EPR signal indicates that O2 oxidation of the AβCuI complex is kinetically sluggish, and Aβ damage is occurring following reoxidation of AβCuI by O2. Together, these results lead us to hypothesize that CuI is ligated by His13 and His14 in a linear coordination environment in Aβ, that Aβ may be playing a neuroprotective role, and that metal-mediated oxidative damage of Aβ occurs over multiple redox

  8. Heme prevents amyloid beta peptide aggregation through hydrophobic interaction based on molecular dynamics simulation.

    PubMed

    Zhao, Li Na; Mu, Yuguang; Chew, Lock Yue

    2013-09-01

    Heme, which is abundant in hemoglobin and many other hemoproteins, is known to play an important role in electron transfer, oxygen transport, regulation of gene expression, and many other biological functions. With the belief that the aggregation of Aβ peptides forming higher order oligomers is one of the central pathological pathways in Alzheimer's disease, the formation of the Aβ-heme complex is essential as it inhibits Aβ aggregation and protects the neurons from degradation. In our studies, conventional molecular dynamics simulations were performed on the 1 Aβ + 1 heme and 2 Aβ + 4 hemes system, respectively, with the identification of several dominant binding motifs. We found that hydrophobic residues of the Aβ peptide have a high affinity to interact with heme instead of the histidine residue. We conclude that hydrophobic interaction plays a dominant role in the Aβ-heme complex formation which indirectly serves to physically prevent Aβ aggregation.

  9. Scorpion Venom Heat-Resistant Peptide Protects Transgenic Caenorhabditis elegans from β-Amyloid Toxicity

    PubMed Central

    Zhang, Xiao-Gang; Wang, Xi; Zhou, Ting-Ting; Wu, Xue-Fei; Peng, Yan; Zhang, Wan-Qin; Li, Shao; Zhao, Jie

    2016-01-01

    Scorpion venom heat-resistant peptide (SVHRP) is a component purified from Buthus martensii Karsch scorpion venom. Our previous studies found SVHRP could enhance neurogenesis and inhibit microglia-mediated neuroinflammation in vivo. Here, we use the transgenic CL4176, CL2006, and CL2355 strains of Caenorhabditis elegans which express the human Aβ1-42 to investigate the effects and the possible mechanisms of SVHRP mediated protection against Aβ toxicity in vivo. The results showed that SVHRP-fed worms displayed remarkably decreased paralysis, less abundant toxic Aβ oligomers, reduced Aβ plaque deposition with respect to untreated animals. SVHRP also suppressed neuronal Aβ expression-induced defects in chemotaxis behavior and attenuated levels of ROS in the transgenic C. elegans. Taken together, these results suggest SVHRP could protect against Aβ-induced toxicity in C. elegans. Further studies need to be conducted in murine models and humans to analyze the effectiveness of the peptide. PMID:27507947

  10. Scorpion Venom Heat-Resistant Peptide Protects Transgenic Caenorhabditis elegans from β-Amyloid Toxicity.

    PubMed

    Zhang, Xiao-Gang; Wang, Xi; Zhou, Ting-Ting; Wu, Xue-Fei; Peng, Yan; Zhang, Wan-Qin; Li, Shao; Zhao, Jie

    2016-01-01

    Scorpion venom heat-resistant peptide (SVHRP) is a component purified from Buthus martensii Karsch scorpion venom. Our previous studies found SVHRP could enhance neurogenesis and inhibit microglia-mediated neuroinflammation in vivo. Here, we use the transgenic CL4176, CL2006, and CL2355 strains of Caenorhabditis elegans which express the human Aβ1-42 to investigate the effects and the possible mechanisms of SVHRP mediated protection against Aβ toxicity in vivo. The results showed that SVHRP-fed worms displayed remarkably decreased paralysis, less abundant toxic Aβ oligomers, reduced Aβ plaque deposition with respect to untreated animals. SVHRP also suppressed neuronal Aβ expression-induced defects in chemotaxis behavior and attenuated levels of ROS in the transgenic C. elegans. Taken together, these results suggest SVHRP could protect against Aβ-induced toxicity in C. elegans. Further studies need to be conducted in murine models and humans to analyze the effectiveness of the peptide. PMID:27507947

  11. Amorphous Aggregation of Amyloid Beta 1-40 Peptide in Confined Space.

    PubMed

    Foschi, Giulia; Albonetti, Cristiano; Liscio, Fabiola; Milita, Silvia; Greco, Pierpaolo; Biscarini, Fabio

    2015-11-16

    The amorphous aggregation of Aβ1-40 peptide is addressed by using micromolding in capillaries. Both the morphology and the size of the aggregates are modulated by changing the contact angle of the sub-micrometric channel walls. Upon decreasing the hydrophilicity of the channels, the aggregates change their morphology from small aligned drops to discontinuous lines, thereby keeping their amorphous structure. Aβ1-40 fibrils are observed at high contact angles.

  12. Alpha 7-type nicotinic acetylcholine receptor and prodynorphin mRNA expression after administration of (-)-nicotine and U-50,488H in beta-amyloid peptide (25-35)-treated mice.

    PubMed

    Hiramatsu, M; Watanabe, M; Baba, S; Kojima, R; Nabeshima, T

    2004-10-01

    We previously reported that (-)-nicotine and kappa-opioid receptor agonists lessened impairment of learning and/or memory in several animal models. Furthermore, these drugs prevented neurodegenerative damage induced by ischemia or beta-amyloid peptide (25-35). In the present study, we tested whether (-)-nicotine and U-50,488H prevent delayed-memory impairment induced by beta-amyloid peptide (25-35), and changes of expression of alpha7-type nicotinic acetylcholine receptor mRNA and prodynorphin mRNA. Seven days after treatment with beta-amyloid peptide (25-35) (9 nmol/mouse, i.c.v.), memory impairment was observed in the Y-maze test. Memory impairment was prevented when (-)-nicotine (6.16 micromol/kg, s.c.) or U-50,488H (21 micromol/kg, s.c.) was administered 1 h before, but not 1 h after, beta-amyloid peptide (25-35) treatment. There was no change in prodynorphin mRNA or alpha7-type nicotinic acetylcholine receptor mRNA expression in the hippocampus 10 days after beta-amyloid peptide (25-35) treatment alone. Of interest, mRNA expression of not only prodynorphin, but also the alpha7-type nicotinic acetylcholine receptor, was significantly decreased when U-50,488H was administered 1 h before, but not 1 h after, treatment with beta-amyloid peptide (25-35). However, these changes were not observed after the administration of (-)-nicotine. These results suggest that activation of the kappa-opioid system, but not beta7-type nicotinic receptors has a neuroprotective effect on beta-amyloid peptide (25-35)-induced memory impairment, and may be involved in the long-lasting changes in the expression of these mRNAs.

  13. Transcriptional Regulation of Insulin-degrading Enzyme Modulates Mitochondrial Amyloid β (Aβ) Peptide Catabolism and Functionality*

    PubMed Central

    Leal, María C.; Magnani, Natalia; Villordo, Sergio; Buslje, Cristina Marino; Evelson, Pablo; Castaño, Eduardo M.; Morelli, Laura

    2013-01-01

    Studies of post-mortem brains from Alzheimer disease patients suggest that oxidative damage induced by mitochondrial amyloid β (mitAβ) accumulation is associated with mitochondrial dysfunction. However, the regulation of mitAβ metabolism is unknown. One of the proteases involved in mitAβ catabolism is the long insulin-degrading enzyme (IDE) isoform (IDE-Met1). However, the mechanisms of its expression are unknown, and its presence in brain is uncertain. We detected IDE-Met1 in brain and showed that its expression is regulated by the mitochondrial biogenesis pathway (PGC-1α/NRF-1). A strong positive correlation between PGC-1α or NRF-1 and long IDE isoform transcripts was found in non-demented brains. This correlation was weaker in Alzheimer disease. In vitro inhibition of IDE increased mitAβ and impaired mitochondrial respiration. These changes were restored by inhibition of γ-secretase or promotion of mitochondrial biogenesis. Our results suggest that IDE-Met1 links the mitochondrial biogenesis pathway with mitAβ levels and organelle functionality. PMID:23525105

  14. The β-amyloid peptide compromises Reelin signaling in Alzheimer’s disease

    PubMed Central

    Cuchillo-Ibañez, Inmaculada; Mata-Balaguer, Trinidad; Balmaceda, Valeria; Arranz, Juan José; Nimpf, Johannes; Sáez-Valero, Javier

    2016-01-01

    Reelin is a signaling protein that plays a crucial role in synaptic function, which expression is influenced by β-amyloid (Aβ). We show that Reelin and Aβ oligomers co-immunoprecipitated in human brain extracts and were present in the same size-exclusion chromatography fractions. Aβ treatment of cells led to increase expression of Reelin, but secreted Reelin results trapped together with Aβ aggregates. In frontal cortex extracts an increase in Reelin mRNA, and in soluble and insoluble (guanidine-extractable) Reelin protein, was associated with late Braak stages of Alzheimer’s disease (AD), while expression of its receptor, ApoER2, did not change. However, Reelin-dependent induction of Dab1 phosphorylation appeared reduced in AD. In cells, Aβ reduced the capacity of Reelin to induce internalization of biotinylated ApoER2 and ApoER2 processing. Soluble proteolytic fragments of ApoER2 generated after Reelin binding can be detected in cerebrospinal fluid (CSF). Quantification of these soluble fragments in CSF could be a tool to evaluate the efficiency of Reelin signaling in the brain. These CSF-ApoER2 fragments correlated with Reelin levels only in control subjects, not in AD, where these fragments diminished. We conclude that while Reelin expression is enhanced in the Alzheimer’s brain, the interaction of Reelin with Aβ hinders its biological activity. PMID:27531658

  15. Is interaction of amyloid β-peptides with metals involved in cognitive activity?

    PubMed

    Tamano, Haruna; Takeda, Atsushi

    2015-08-01

    Metal ions, i.e., Zn(2+) and Cu(2+), are released from neuron terminals in the hippocampus, which plays important roles in spatial and declarative memory, and may serve as a signal factor. Synaptic homeostasis of metal ions is critical for cognitive activity in the hippocampus. Amyloid-β (Aβ) is a causative candidate for the pathogenesis of Alzheimer's disease (AD) and Aβ-induced synapse dysfunction is easy to emerge along with normal aging and leads to the cognitive decline and memory loss in the pre-dementia stage of AD. Because Aβ interacts with Zn(2+) and Cu(2+), it is likely that these metal ions are involved in the Aβ-induced modification of the synaptic function. There is evidence to indicate that the inhibition of the interaction of Aβ with Zn(2+) and Cu(2+) may ameliorate the pathophysiology of AD. Interaction of extracellular Zn(2+) with Aβ in the hippocampus is involved in transiently Aβ-induced cognition deficits, while the interaction of extracellular Cu(2+) reduces bioavailability of intracellular Cu(2+), followed by an increase in oxidative stress, which may lead to cognitive deficits. It is likely that Zn(2+) and Cu(2+) play as a key-mediating factor in pathophysiology of the synaptic dysfunction in which Aβ is involved. Based on the idea that understating Aβ-induced changes in synaptic plasticity is important to prevent AD, the present paper summarizes the interaction of Aβ with metal ions in cognition. PMID:25959547

  16. Monomeric Amyloid Beta Peptide in Hexafluoroisopropanol Detected by Small Angle Neutron Scattering

    PubMed Central

    Zhang-Haagen, Bo; Biehl, Ralf; Nagel-Steger, Luitgard; Radulescu, Aurel; Richter, Dieter; Willbold, Dieter

    2016-01-01

    Small proteins like amyloid beta (Aβ) monomers are related to neurodegenerative disorders by aggregation to insoluble fibrils. Small angle neutron scattering (SANS) is a nondestructive method to observe the aggregation process in solution. We show that SANS is able to resolve monomers of small molecular weight like Aβ for aggregation studies. We examine Aβ monomers after prolonged storing in d-hexafluoroisopropanol (dHFIP) by using SANS and dynamic light scattering (DLS). We determined the radius of gyration from SANS as 1.0±0.1 nm for Aβ1–40 and 1.6±0.1 nm for Aβ1–42 in agreement with 3D NMR structures in similar solvents suggesting a solvent surface layer with 5% increased density. After initial dissolution in dHFIP Aβ aggregates sediment with a major component of pure monomers showing a hydrodynamic radius of 1.8±0.3 nm for Aβ1–40 and 3.2±0.4 nm for Aβ1–42 including a surface layer of dHFIP solvent molecules. PMID:26919121

  17. The β-amyloid peptide compromises Reelin signaling in Alzheimer's disease.

    PubMed

    Cuchillo-Ibañez, Inmaculada; Mata-Balaguer, Trinidad; Balmaceda, Valeria; Arranz, Juan José; Nimpf, Johannes; Sáez-Valero, Javier

    2016-01-01

    Reelin is a signaling protein that plays a crucial role in synaptic function, which expression is influenced by β-amyloid (Aβ). We show that Reelin and Aβ oligomers co-immunoprecipitated in human brain extracts and were present in the same size-exclusion chromatography fractions. Aβ treatment of cells led to increase expression of Reelin, but secreted Reelin results trapped together with Aβ aggregates. In frontal cortex extracts an increase in Reelin mRNA, and in soluble and insoluble (guanidine-extractable) Reelin protein, was associated with late Braak stages of Alzheimer's disease (AD), while expression of its receptor, ApoER2, did not change. However, Reelin-dependent induction of Dab1 phosphorylation appeared reduced in AD. In cells, Aβ reduced the capacity of Reelin to induce internalization of biotinylated ApoER2 and ApoER2 processing. Soluble proteolytic fragments of ApoER2 generated after Reelin binding can be detected in cerebrospinal fluid (CSF). Quantification of these soluble fragments in CSF could be a tool to evaluate the efficiency of Reelin signaling in the brain. These CSF-ApoER2 fragments correlated with Reelin levels only in control subjects, not in AD, where these fragments diminished. We conclude that while Reelin expression is enhanced in the Alzheimer's brain, the interaction of Reelin with Aβ hinders its biological activity. PMID:27531658

  18. Antagonizing beta-amyloid peptide neurotoxicity of the anti-aging fungus Ganoderma lucidum.

    PubMed

    Lai, Cora Sau-Wan; Yu, Man-Shan; Yuen, Wai-Hung; So, Kwok-Fai; Zee, Sze-Yong; Chang, Raymond Chuen-Chung

    2008-01-23

    Ganoderma lucidum (Leyss. ex Fr.) Karst. (Lingzhi) is a medicinal fungus used clinically in many Asian countries to promote health and longevity. Synaptic degeneration is another key mode of neurodegeneration in Alzheimer's disease (AD). Recent studies have shown the loss of synaptic density proteins in each individual neuron during the progression of AD. It was recently reported that beta-amyloid (Abeta) could cause synaptic dysfunction and contribute to AD pathology. In this study, we reported that aqueous extract of G. lucidum significantly attenuated Abeta-induced synaptotoxicity by preserving the synaptic density protein, synaptophysin. In addition, G. lucidum aqueous extract antagonized Abeta-triggered DEVD cleavage activities in a dose-dependent manner. Further studies elucidated that phosphorylation of c-Jun N-terminal kinase, c-Jun, and p38 MAP kinase was attenuated by G. lucidum in Abeta-stressed neurons. Taken together, the results prove a hypothesis that anti-aging G. lucidum can prevent harmful effects of the exterminating toxin Abeta in AD. PMID:18083148

  19. Development of a Small D-Enantiomeric Alzheimer’s Amyloid-β Binding Peptide Ligand for Future In Vivo Imaging Applications

    PubMed Central

    Funke, Susanne Aileen; Bartnik, Dirk; Glück, Julian Marius; Piorkowska, Kasia; Wiesehan, Katja; Weber, Urs; Gulyas, Balazs; Halldin, Christer; Pfeifer, Andrea; Spenger, Christian; Muhs, Andreas; Willbold, Dieter

    2012-01-01

    Alzheimer’s disease (AD) is a devastating disease affecting predominantly the aging population. One of the characteristic pathological hallmarks of AD are neuritic plaques, consisting of amyloidpeptide (Aβ). While there has been some advancement in diagnostic classification of AD patients according to their clinical severity, no fully reliable method for pre-symptomatic diagnosis of AD is available. To enable such early diagnosis, which will allow the initiation of treatments early in the disease progress, neuroimaging tools are under development, making use of Aβ-binding ligands that can visualize amyloid plaques in the living brain. Here we investigate the properties of a newly designed series of D-enantiomeric peptides which are derivatives of ACI-80, formerly called D1, which was developed to specifically bind aggregated Aβ1–42. We describe ACI-80 derivatives with increased stability and Aβ binding properties, which were characterized using surface plasmon resonance and enzyme-linked immunosorbent assays. The specific interactions of the lead compounds with amyloid plaques were validated by ex vivo immunochemistry in transgenic mouse models of AD. The novel compounds showed increased binding affinity and are promising candidates for further development into in vivo imaging compounds. PMID:22848501

  20. [Heat-shock protein HSP70 protects neuroblastoma cells SK-N-SH from the neurotoxic effects hydrogen peroxide and the β-amyloid peptide].

    PubMed

    Yurinskaya, M M; Mit'kevich, V A; Barykin, E P; Garbuz, D G; Evgen'ev, M B; Makarov, A A; Vinokurov, M G

    2015-01-01

    Neuronal cell death in Alzheimer's disease is associated with the development of oxidative stress caused by the reactive oxygen species (ROS), which can be generated as a result of the effect of beta-amyloid peptides. One of the sources of ROS is hydrogen peroxide, inducing the apoptosis and necrosis of neural tissue cells. The mechanism of hydrogen peroxide apoptotic action includes launching signaling pathways that involve protein kinases PI3K, p38MAPK, JNK and ERK. Oxidative stress leads to increased synthesis of heat-shock proteins in the cells including HSP70. It was shown that the exogenous HSP70 could reduce generation of ROS in cells. In this study, we determined how HSP70 affected apoptosis and necrosis in human neuroblastoma cells SK-N-SH, induced by hydrogen peroxide and β-amyloid peptide Aβ(1-42). It was shown that HSP70 reduces the cytotoxic effects of hydrogen peroxide and beta-amyloid, and protein kinases PI3K and JNK play an important role in the mechanism of HSP70 protective effect on the peroxide induced apoptosis in SK-N-SH cells.

  1. Three histidine residues of amyloid-beta peptide control the redox activity of copper and iron.

    PubMed

    Nakamura, M; Shishido, N; Nunomura, Akihiko; Smith, Mark A; Perry, George; Hayashi, Y; Nakayama, K; Hayashi, T

    2007-11-01

    Zinc, iron and copper are concentrated in senile plaques of Alzheimer disease. Copper and iron catalyze the Fenton-Haber-Weiss reaction, which likely contributes to oxidative stress in neuronal cells. In this study, we found that ascorbate oxidase activity and the intensity of ascorbate radicals measured using ESR spectroscopy, generated by free Cu(II), was decreased in the presence of amyloid-beta (Abeta), the major component of senile plaques. Specifically, the ascorbate oxidase activity was strongly inhibited (85% decrease) in the presence of Abeta1-16 or Abeta1-42, whereas it was only slightly inhibited in the presence of Abeta1-12 or Abeta25-35 (<20% inhibition). Ascorbate-dependent hydroxyl radical generation by free Cu(II) decreased in the presence of Abeta in the identical order of Abeta1-42, Abeta1-16 > Abeta1-12 and was abolished in the presence of 2-fold molar excess glycylhystidyllysine (GHK). Ascorbate oxidase activity and ascorbate-dependent hydroxyl radical generation by free Fe(III) were inhibited by Abeta1-42, Abeta1-16, and Abeta1-12. Although Cu(II)-Abeta shows a significant SOD-like activity, the rate constant for the reaction of superoxide with Cu(II)-Abeta was much slower than that with SOD. Overall, our results suggest that His6, His13, and His14 residues of Abeta1-42 control the redox activity of transition metals present in senile plaques. PMID:17929832

  2. Binding, conformational transition and dimerization of amyloidpeptide on GM1-containing ternary membrane: insights from molecular dynamics simulation.

    PubMed

    Manna, Moutusi; Mukhopadhyay, Chaitali

    2013-01-01

    Interactions of amyloid-β (Aβ) with neuronal membrane are associated with the progression of Alzheimer's disease (AD). Ganglioside GM1 has been shown to promote the structural conversion of Aβ and increase the rate of peptide aggregation; but the exact nature of interaction driving theses processes remains to be explored. In this work, we have carried out atomistic-scale computer simulations (totaling 2.65 µs) to investigate the behavior of Aβ monomer and dimers in GM1-containing raft-like membrane. The oligosaccharide head-group of GM1 was observed to act as scaffold for Aβ-binding through sugar-specific interactions. Starting from the initial helical peptide conformation, a β-hairpin motif was formed at the C-terminus of the GM1-bound Aβ-monomer; that didn't appear in absence of GM1 (both in fluid POPC and liquid-ordered cholesterol/POPC bilayers and also in aqueous medium) within the simulation time span. For Aβ-dimers, the β-structure was further enhanced by peptide-peptide interactions, which might influence the propensity of Aβ to aggregate into higher-ordered structures. The salt-bridges and inter-peptide hydrogen bonds were found to account for dimer stability. We observed spontaneous formation of intra-peptide D(23)-K(28) salt-bridge and a turn at V(24)GSN(27) region - long been accepted as characteristic structural-motifs for amyloid self-assembly. Altogether, our results provide atomistic details of Aβ-GM1 and Aβ-Aβ interactions and demonstrate their importance in the early-stages of GM1-mediated Aβ-oligomerisation on membrane surface.

  3. Gas-Phase Structure of Amyloid-β (12 - 28) Peptide Investigated by Infrared Spectroscopy, Electron Capture Dissociation and Ion Mobility Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Le, Thi Nga; Poully, Jean Christophe; Lecomte, Frédéric; Nieuwjaer, Nicolas; Manil, Bruno; Desfrançois, Charles; Chirot, Fabien; Lemoine, Jerome; Dugourd, Philippe; van der Rest, Guillaume; Grégoire, Gilles

    2013-12-01

    The gas-phase structures of doubly and triply protonated Amyloid-β12-28 peptides have been investigated through the combination of ion mobility (IM), electron capture dissociation (ECD) mass spectrometry, and infrared multi-photon dissociation (IRMPD) spectroscopy together with theoretical modeling. Replica-exchange molecular dynamics simulations were conducted to explore the conformational space of these protonated peptides, from which several classes of structures were found. Among the low-lying conformers, those with predicted diffusion cross-sections consistent with the ion mobility experiment were further selected and their IR spectra simulated using a hybrid quantum mechanical/semiempirical method at the ONIOM DFT/B3LYP/6-31 g(d)/AM1 level. In ECD mass spectrometry, the c/z product ion abundance (PIA) has been analyzed for the two charge states and revealed drastic differences. For the doubly protonated species, N - Cα bond cleavage occurs only on the N and C terminal parts, while a periodic distribution of PIA is clearly observed for the triply charged peptides. These PIA distributions have been rationalized by comparison with the inverse of the distances from the protonated sites to the carbonyl oxygens for the conformations suggested from IR and IM experiments. Structural assignment for the amyloid peptide is then made possible by the combination of these three experimental techniques that provide complementary information on the possible secondary structure adopted by peptides. Although globular conformations are favored for the doubly protonated peptide, incrementing the charge state leads to a conformational transition towards extended structures with 310- and α-helix motifs.

  4. Inhibition of amyloid fiber assembly by both BiP and its target peptide.

    SciTech Connect

    Davis, D. P.; Raffen, R.; Vogen, S.; Williamson, E.; Stevens, F. J.; Argon, Y.; Biosciences Division; Univ. of Chicago

    2000-10-01

    Immunoglobulin light chain (LC) normally is a soluble, secreted protein, but some LC assemble into ordered fibrils whose deposition in tissues results in amyloidosis and organ failure. Here we reconstitute fibril formation in vitro and show that preformed fibrils can nucleate polymerization of soluble LC. This prion-like behavior has important physiological implications, since somatic mutations generate multiple related LC sequences. Furthermore, we demonstrate that fibril formation in vitro and aggregation of whole LC within cells are inhibited by BiP and by a synthetic peptide that is identical to a major LC binding site for BiP. We propose that LC form fibrils via an interprotein loop swap and that the underlying conformational change should be amenable to drug therapy.

  5. Exendin-4, a glucagon-like peptide 1 receptor agonist, protects against amyloidpeptide-induced impairment of spatial learning and memory in rats.

    PubMed

    Jia, Xiao-Tao; Ye-Tian; Yuan-Li; Zhang, Ge-Juan; Liu, Zhi-Qin; Di, Zheng-Li; Ying, Xiao-Ping; Fang, Yan; Song, Er-Fei; Qi, Jin-Shun; Pan, Yan-Fang

    2016-05-15

    Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share specific molecular mechanisms, and agents with proven efficacy in one may be useful against the other. The glucagon-like peptide-1 (GLP-1) receptor agonist exendin-4 has similar properties to GLP-1 and is currently in clinical use for T2DM treatment. Thus, this study was designed to characterize the effects of exendin-4 on the impairment of learning and memory induced by amyloid protein (Aβ) and its probable molecular underlying mechanisms. The results showed that (1) intracerebroventricular (i.c.v.) injection of Aβ1-42 resulted in a significant decline of spatial learning and memory of rats in water maze tests; (2) pretreatment with exendin-4 effectively and dose-dependently protected against the Aβ1-42-induced impairment of spatial learning and memory; (3) exendin-4 treatment significantly decreased the expression of Bax and cleaved caspase-3 and increased the expression of Bcl2 in Aβ1-42-induced Alzheimer's rats. The vision and swimming speed of the rats among all groups in the visible platform tests did not show any difference. These findings indicate that systemic pretreatment with exendin-4 can effectively prevent the behavioral impairment induced by neurotoxic Aβ1-42, and the underlying protective mechanism of exendin-4 may be involved in the Bcl2, Bax and caspase-3 pathways. Thus, the application of exendin-4 or the activation of its signaling pathways may be a promising strategy to ameliorate the degenerative processes observed in AD. PMID:26992957

  6. Cilostazol Upregulates Autophagy via SIRT1 Activation: Reducing AmyloidPeptide and APP-CTFβ Levels in Neuronal Cells.

    PubMed

    Lee, Hye Rin; Shin, Hwa Kyoung; Park, So Youn; Kim, Hye Young; Bae, Sun Sik; Lee, Won Suk; Rhim, Byung Yong; Hong, Ki Whan; Kim, Chi Dae

    2015-01-01

    Autophagy is a vital pathway for the removal of β-amyloid peptide (Aβ) and the aggregated proteins that cause Alzheimer's disease (AD). We previously found that cilostazol induced SIRT1 expression and its activity in neuronal cells, and thus, we hypothesized that cilostazol might stimulate clearances of Aβ and C-terminal APP fragment β subunit (APP-CTFβ) by up-regulating autophagy.When N2a cells were exposed to soluble Aβ1-42, protein levels of beclin-1, autophagy-related protein5 (Atg5), and SIRT1 decreased significantly. Pretreatment with cilostazol (10-30 μM) or resveratrol (20 μM) prevented these Aβ1-42 evoked suppressions. LC3-II (a marker of mammalian autophagy) levels were significantly increased by cilostazol, and this increase was reduced by 3-methyladenine. To evoke endogenous Aβ overproduction, N2aSwe cells (N2a cells stably expressing human APP containing the Swedish mutation) were cultured in medium with or without tetracycline (Tet+ for 48 h and then placed in Tet- condition). Aβ and APP-CTFβ expressions were increased after 12~24 h in Tet- condition, and these increased expressions were significantly reduced by pretreating cilostazol. Cilostazol-induced reductions in the expressions of Aβ and APP-CTFβ were blocked by bafilomycin A1 (a blocker of autophagosome to lysosome fusion). After knockdown of the SIRT1 gene (to ~40% in SIRT1 protein), cilostazol failed to elevate the expressions of beclin-1, Atg5, and LC3-II, indicating that cilostazol increases these expressions by up-regulating SIRT1. Further, decreased cell viability induced by Aβ was prevented by cilostazol, and this inhibition was reversed by 3-methyladenine, indicating that the protective effect of cilostazol against Aβ induced neurotoxicity is, in part, ascribable to the induction of autophagy. In conclusion, cilostazol modulates autophagy by increasing the activation of SIRT1, and thereby enhances Aβ clearance and increases cell viability.

  7. Amyloidpeptide on sialyl-Lewis(X)-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface.

    PubMed

    Askarova, Sholpan; Sun, Zhe; Sun, Grace Y; Meininger, Gerald A; Lee, James C-M

    2013-01-01

    Increased deposition of amyloidpeptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewis(x) (sLe(x)) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLe(x) and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf ), and produced a bimodal population of Fmtf , suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf . In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB.

  8. Amyloid beta-peptide impairs glucose transport in hippocampal and cortical neurons: involvement of membrane lipid peroxidation.

    PubMed

    Mark, R J; Pang, Z; Geddes, J W; Uchida, K; Mattson, M P

    1997-02-01

    A deficit in glucose uptake and a deposition of amyloid beta-peptide (A beta) each occur in vulnerable brain regions in Alzheimer's disease (AD). It is not known whether mechanistic links exist between A beta deposition and impaired glucose transport. We now report that A beta impairs glucose transport in cultured rat hippocampal and cortical neurons by a mechanism involving membrane lipid peroxidation. A beta impaired 3H-deoxy-glucose transport in a concentration-dependent manner and with a time course preceding neurodegeneration. The decrease in glucose transport was followed by a decrease in cellular ATP levels. Impairment of glucose transport, ATP depletion, and cell death were each prevented in cultures pretreated with antioxidants. Exposure to FeSO4, an established inducer of lipid peroxidation, also impaired glucose transport. Immunoprecipitation and Western blot analyses showed that exposure of cultures to A beta induced conjugation of 4-hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, to the neuronal glucose transport protein GLUT3. HNE induced a concentration-dependent impairment of glucose transport and subsequent ATP depletion. Impaired glucose transport was not caused by a decreased energy demand in the neurons, because ouabain, which inhibits Na+/K(+)-ATPase activity and thereby reduces neuronal ATP hydrolysis rate, had little or no effect on glucose transport. Collectively, the data demonstrate that lipid peroxidation mediates A beta-induced impairment of glucose transport in neurons and suggest that this action of A beta may contribute to decreased glucose uptake and neuronal degeneration in AD. PMID:8994059

  9. AmyloidPeptide on Sialyl-LewisX-Selectin-Mediated Membrane Tether Mechanics at the Cerebral Endothelial Cell Surface

    PubMed Central

    Askarova, Sholpan; Sun, Zhe; Sun, Grace Y.; Meininger, Gerald A.; Lee, James C-M.

    2013-01-01

    Increased deposition of amyloidpeptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewisx (sLex) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLex and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf), and produced a bimodal population of Fmtf, suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf. In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB. PMID:23593361

  10. Amyloidpeptide on sialyl-Lewis(X)-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface.

    PubMed

    Askarova, Sholpan; Sun, Zhe; Sun, Grace Y; Meininger, Gerald A; Lee, James C-M

    2013-01-01

    Increased deposition of amyloidpeptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewis(x) (sLe(x)) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLe(x) and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf ), and produced a bimodal population of Fmtf , suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf . In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB. PMID:23593361

  11. Astrocytic adenosine A2A receptors control the amyloidpeptide-induced decrease of glutamate uptake.

    PubMed

    Matos, Marco; Augusto, Elisabete; Machado, Nuno J; dos Santos-Rodrigues, Alexandre; Cunha, Rodrigo A; Agostinho, Paula

    2012-01-01

    Alzheimer's disease (AD) is characterized by a progressive cognitive impairment tightly correlated with the accumulation of amyloid-β (Aβ) peptides (mainly Aβ(1-42)). There is a precocious disruption of glutamatergic synapses in AD, in line with an ability of Aβ to decrease astrocytic glutamate uptake. Accumulating evidence indicates that caffeine prevents the burden of AD, likely through the antagonism of A(2A) receptors (A(2A)R) which attenuates Aβ-induced memory impairment and synaptotoxicity. Since A(2A)R also modulate astrocytic glutamate uptake, we now tested if A(2A)R blockade could prevent the decrease of astrocytic glutamate uptake caused by Aβ. In cultured astrocytes, Aβ(1-42). (1 μM for 24 hours) triggered an astrogliosis typified by an increased density of GFAP, which was mimicked by the A(2A)R agonist, CGS 26180 (30 nM), and prevented by the A(2A)R antagonist, SCH 58261 (100 nM). Aβ1-42 also decreased D-aspartate uptake by 28 ± 4%, an effect abrogated upon genetic inactivation or pharmacological blockade of A(2A)R. In accordance with the long term control of glutamate transporter expression by A(2A)R, Aβ(1-42). enhanced the expression and density of astrocytic A(2A)R and decreased GLAST and GLT-I expression in astrocytes from wild type, but not from A(2A)R knockout mice. This impact of Aβ(1-42). on glutamate transporters and uptake, dependent on A(2A)R function, was also confirmed in an ex vivo astrocyte preparation (gliosomes) from rats intracerebroventricularly (icv) injected with Aβ(1-42). . These results provide the first demonstration for a direct key role of astrocytic A(2A)R in the ability of Aβ-induced impairment of glutamate uptake, which may underlie glutamatergic synaptic dysfunction and excitotoxicity in AD.

  12. Magneto-immunocapture with on-bead fluorescent labeling of amyloidpeptides: towards a microfluidized-bed-based operation.

    PubMed

    Mai, Thanh Duc; Pereiro, Iago; Hiraoui, Mohamed; Viovy, Jean-Louis; Descroix, Stéphanie; Taverna, Myriam; Smadja, Claire

    2015-09-01

    A new sample treatment approach for sensitive determination of three amyloidpeptides (Aβ 1-42, Aβ 1-40 and Aβ 1-38) with capillary electrophoresis coupled with laser induced fluorescent detection is reported herein. These Aβ peptides are considered an important family of biomarkers in the cerebrospinal fluid (CSF) for early diagnosis of Alzheimer's disease (AD). Due to their extremely low abundance in CSF (down to sub nM ranges), batch-wise preconcentration via magneto-immunocapture with enrichment factors up to 100 was implemented. The Aβ peptides were first captured onto magnetic micro-beads. Then, on-beads fluorescent labeling of the captured Aβ peptides were carried out to avoid the unwanted presence of extra fluorescent dye in the eluent as in the case of in-solution labeling. Finally thermal elution was performed and eluted labeled peptides were analyzed off line with CE-LIF. The Aβ-capturing efficiencies of different commercially available antibodies grafted onto magnetic beads were tested. Aβ peptides in CSF samples collected from AD's patients and healthy persons (used as controls) were measured and evaluated. As a proof of concept, the developed strategy was adapted into a miniaturized fluidized bed configuration that has the potential for coupling with a microchip separation system. PMID:26206107

  13. Low molecular weight oligomers of amyloid peptides display β-barrel conformations: A replica exchange molecular dynamics study in explicit solvent

    NASA Astrophysics Data System (ADS)

    De Simone, Alfonso; Derreumaux, Philippe

    2010-04-01

    The self-assembly of proteins and peptides into amyloid fibrils is connected to over 40 pathological conditions including neurodegenerative diseases and systemic amyloidosis. Diffusible, low molecular weight protein and peptide oligomers that form in the early steps of aggregation appear to be the harmful cytotoxic species in the molecular etiology of these diseases. So far, the structural characterization of these oligomers has remained elusive owing to their transient and dynamic features. We here address, by means of full atomistic replica exchange molecular dynamics simulations, the energy landscape of heptamers of the amyloidogenic peptide NHVTLSQ from the beta-2 microglobulin protein. The simulations totaling 5 μs show that low molecular weight oligomers in explicit solvent consist of β-barrels in equilibrium with amorphous states and fibril-like assemblies. The results, also accounting for the influence of the pH on the conformational properties, provide a strong evidence of the formation of transient β-barrel assemblies in the early aggregation steps of amyloid-forming systems. Our findings are discussed in terms of oligomers cytotoxicity.

  14. Atomistic mechanism of polyphenol amyloid aggregation inhibitors: molecular dynamics study of Curcumin, Exifone, and Myricetin interaction with the segment of tau peptide oligomer.

    PubMed

    Berhanu, Workalemahu M; Masunov, Artëm E

    2015-01-01

    Amyloid fibrils are highly ordered protein aggregates associated with many diseases affecting millions of people worldwide. Polyphenols such as Curcumin, Exifone, and Myricetin exhibit modest inhibition toward fibril formation of tau peptide which is associated with Alzheimer's disease. However, the molecular mechanisms of this inhibition remain elusive. We investigated the binding of three polyphenol molecules to the protofibrils of an amyloidogenic fragment VQIVYK of tau peptide by molecular dynamics simulations in explicit solvent. We find that polyphenols induce conformational changes in the oligomer aggregate. These changes disrupt the amyloid H bonding, perturbing the aggregate. While the structural evolution of the control oligomer with no ligand is limited to the twisting of the β-sheets without their disassembly, the presence of polyphenol molecule pushes the β-sheets apart, and leads to a loosely packed structure where two of four β-sheets dissociate in each of the three cases considered here. The H-bonding capacity of polyphenols is responsible for the observed behavior. The calculated binding free energies and its individual components enabled better understanding of the binding. Results indicated that the contribution from Van der Waals interactions is more significant than electrostatic contribution to the binding. The findings from this study are expected to assist in the development of aggregation inhibitors. Significant binding between polyphenols and aggregate oligomer identified in our simulations confirms the previous experimental observations in which polyphenols refold the tau peptide without forming covalent bonds. PMID:25093402

  15. Nuclear magnetic resonance evidence for the dimer formation of beta amyloid peptide 1-42 in 1,1,1,3,3,3-hexafluoro-2-propanol.

    PubMed

    Shigemitsu, Yoshiki; Iwaya, Naoko; Goda, Natsuko; Matsuzaki, Mizuki; Tenno, Takeshi; Narita, Akihiro; Hoshi, Minako; Hiroaki, Hidekazu

    2016-04-01

    Alzheimer's disease involves accumulation of senile plaques in which filamentous aggregates of amyloid beta (Aβ) peptides are deposited. Recent studies demonstrate that oligomerization pathways of Aβ peptides may be complicated. To understand the mechanisms of Aβ(1-42) oligomer formation in more detail, we have established a method to produce (15)N-labeled Aβ(1-42) suited for nuclear magnetic resonance (NMR) studies. For physicochemical studies, the starting protein material should be solely monomeric and all Aβ aggregates must be removed. Here, we succeeded in fractionating a "precipitation-resistant" fraction of Aβ(1-42) from an "aggregation-prone" fraction by high-performance liquid chromatography (HPLC), even from bacterially overexpressed Aβ(1-42). However, both Aβ(1-42) fractions after 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) treatment formed amyloid fibrils. This indicates that the "aggregation seed" was not completely monomerized during HFIP treatment. In addition, Aβ(1-42) dissolved in HFIP was found to display a monomer-dimer equilibrium, as shown by two-dimensional (1)H-(15)N NMR. We demonstrated that the initial concentration of Aβ during the HFIP pretreatment altered the kinetic profiles of Aβ fibril formation in a thioflavin T fluorescence assay. The findings described here should ensure reproducible results when studying the Aβ(1-42) peptide. PMID:26772162

  16. Microscopic factors that control beta-sheet registry in amyloid fibrils formed by fragment 11-25 of amyloid beta peptide: insights from computer simulations.

    PubMed

    Negureanu, Lacramioara; Baumketner, Andrij

    2009-06-26

    Short fragments of amyloidogenic proteins are widely used as model systems in studies of amyloid formation. Fragment 11-25 of the amyloid beta protein involved in Alzheimer's disease (Abeta11-25) was recently shown to form amyloid fibrils composed of anti-parallel beta-sheets. Interestingly, fibrils grown under neutral and acidic conditions were seen to possess different registries of their inter-beta-strand hydrogen bonds. In an effort to explain the microscopic origin of this pH dependence, we studied Abeta11-25 fibrils using methods of theoretical modeling. Several structural models were built for fibrils at low and neutral pH levels and these were examined in short molecular dynamics simulations in explicit water. The models that displayed the lowest free energy, as estimated using an implicit solvent model, were selected as representative of the true fibrillar structure. It was shown that the registry of these models agrees well with the experimental results. At neutral pH, the main contribution to the free energy difference between the two registries comes from the electrostatic interactions. The charge group of the carboxy terminus makes a large contribution to these interactions and thus appears to have a critical role in determining the registry.

  17. Glucocorticoids facilitate astrocytic amyloidpeptide deposition by increasing the expression of APP and BACE1 and decreasing the expression of amyloid-β-degrading proteases.

    PubMed

    Wang, Yanyan; Li, Maoquan; Tang, Jun; Song, Min; Xu, Xueqing; Xiong, Jiaxiang; Li, Junxia; Bai, Yun

    2011-07-01

    In most cases, the molecular mechanism underlying the pathogenesis of sporadic Alzheimer's disease (AD) is unknown. Elevated basal cortisol levels in AD patients suggest that glucocorticoids (GC) may contribute to the development and/or maintenance of AD. Amyloid plaques are the hallmark of AD, and they are considered to play an early role in the AD process. However, little is known about how their formation is regulated by stress and GC. Astrocyte accumulation is one of the earliest neuropathological changes in AD. Here, we report that GC elevated amyloid-β (Aβ) production in primary cultures of astrocytes by increasing amyloid precursor protein (APP) and β-site APP-cleaving enzyme 1 gene expression. Notably, GC administered to normal, middle-aged mice promoted the expression of APP and β-site APP-cleaving enzyme 1 in astrocytes, as determined by double immunofluorescence. Additionally, confocal microscopy and ELISA revealed that GC markedly reduced Aβ degradation and clearance by astrocytes in vitro, indicating a decreased neuroprotective capacity of the astrocytes. This may have been due to the decrease of several Aβ-degrading proteases, such as insulin-degrading enzyme and matrix metalloproteinase-9. These effects occurred through the activation of GC receptors. Taken together, our results demonstrate that GC can enhance the production of Aβ, reduce its degradation in astrocytes, and provide a molecular mechanism linking stress factors to AD. Our study suggests that GC can facilitate AD pathogenesis and that reducing GC in the elderly and early AD patients would be beneficial.

  18. Development of a novel radioimmunoassay to detect autoantibodies to amyloid beta peptides in the presence of a cross-reactive therapeutic antibody.

    PubMed

    Sloan, John H; Ackermann, Bradley J; O'Dell, Mark; Bowsher, Ronald R; Dean, Robert A; Konrad, Robert J

    2011-12-15

    An increasing need in the development of biotherapeutic agents is the ability to monitor a potential autoimmune response to the therapeutic target of interest. Unfortunately, the presence of high concentrations of therapeutic antibody can hinder such detection, because there is competition for binding in cases where epitopes are not structurally distinct. This situation was encountered in the development of LY2062430, a therapeutic mid-domain monoclonal anti-amyloid beta peptide (Aβ) antibody undergoing clinical trials for the treatment of Alzheimer's disease. This communication reports the development and validation of a novel radioimmunoassay used to measure potential patient immune responses to Aβ in the presence of LY2062430. This assay employs a radioiodinated analog of the human amyloid beta 1-40 peptide (Aβ1-40) in which a single amino acid substitution of alanine for phenylalanine at position 19 (F19A) effectively eliminates binding by LY2062430. In contrast, F19A binding by monoclonal antibodies specific for the N- and C-termini of the human Aβ1-40 peptide was shown to be unaltered. Additional experiments involving a polyclonal rabbit antibody raised against the midregion of Aβ1-40 (residues 15-30) resulted in only a slight reduction in binding to the F19A tracer, suggesting that the modification does not affect distal epitopes in Aβ1-40 and supporting the notion that this conservative substitution produces only subtle change in the overall peptide structure. The assay is therefore believed to detect most, if not all, patient antibodies to native Aβ peptides. The assay was validated for use in clinical trials allowing detection of antibodies to Aβ in human serum in the presence of therapeutic concentrations of LY2062430. PMID:21868184

  19. CD147 is a regulatory subunit of the gamma-secretase complex inAlzheimer's disease amyloid beta-peptide production

    SciTech Connect

    Zhou, Shuxia; Zhou, Hua; Walian, Peter J.; Jap, Bing K.

    2005-04-06

    {gamma}-secretase is a membrane protein complex that cleaves the {beta}-amyloid precursor protein (APP) within the transmembrane region, following prior processing by {beta}-secretase, producing amyloid {beta}-peptides (A{beta}{sub 40} and A{beta}{sub 42}). Errant production of A{beta}-peptides that substantially increases A{beta}{sub 42} production has been associated with the formation of amyloid plaques in Alzheimer's disease patients. Biophysical and genetic studies indicate that presenilin-1 (Psn-1), which contains the proteolytic active site, and three other membrane proteins, nicastrin (Nct), APH-1, and PEN-2 are required to form the core of the active {gamma}-secretase complex. Here, we report the purification of the native {gamma}-secretase complexes from HeLa cell membranes and the identification of an additional {gamma}-secretase complex subunit, CD147, a transmembrane glycoprotein with two immunoglobulin-like domains. The presence of this subunit as an integral part of the complex itself was confirmed through co-immunoprecipitation studies of the purified protein from HeLa cells and solubilized complexes from other cell lines such as neural cell HCN-1A and HEK293. Depletion of CD147 by RNA interference was found to increase the production of A{beta} peptides without changing the expression level of the other {gamma}-secretase components or APP substrates while CD147 overexpression had no statistically significant effect on amyloid {beta}-peptide production, other {gamma}-secretase components or APP substrates, indicating that the presence of the CD147 subunit within the {gamma}-secretase complex directly down-modulates the production of A{beta}-peptides. {gamma}-secretase was first recognized through its role in the production of the A{beta} peptides that are pathogenic in Alzheimer's disease (AD) (1). {gamma}-secretase is a membrane protein complex with unusual aspartyl protease activity that cleaves a variety of type I membrane proteins, such as APP

  20. Aromaticity and amyloid formation: effect of π-electron distribution and aryl substituent geometry on the self-assembly of peptides derived from hIAPP(22-29).

    PubMed

    Profit, Adam A; Vedad, Jayson; Saleh, Mohamad; Desamero, Ruel Z B

    2015-02-01

    A comprehensive investigation of peptides derived from the 22-29 region of human islet amyloid polypeptide (hIAPP) that contain phenylalanine analogs at position 23 with a variety of electron donating and withdrawing groups, along with heteroaromatic surrogates, has been employed to interrogate how π-electron distribution effects amyloid formation. Kinetic aggregation studies using turbidity measurements indicate that electron rich aromatic ring systems consistently abolish the amyloidogenic propensity of hIAPP(22-29). Electron poor systems modulate the rate of aggregation. Raman and Fourier transform infrared spectroscopy confirm the parallel β-sheet secondary structure of aggregates derived from peptides containing electron poor phenylalanine analogs and provide direct evidence of ring stacking. Transmission electron microscopy confirms the presence of amyloid fibrils. The effect of aryl substituent geometry on peptide self-assembly reveals that the electronic nature of substituents and not their steric profile is responsible for failure of the electron donating group peptides to aggregate. Non-aggregating hIAPP(22-29) peptides were found to inhibit the self-assembly of full-length hIAPP(1-37). The most potent inhibitory peptides contain phenylalanine with the p-amino and p-formamido functionalities. These novel peptides may serve as leads for the development of future aggregation inhibitors. A potential mechanism for inhibition of amylin self-assembly by electron rich (-29) peptides is proposed.

  1. A facile method for expression and purification of (15)N isotope-labeled human Alzheimer's β-amyloid peptides from E. coli for NMR-based structural analysis.

    PubMed

    Sharma, Sudhir C; Armand, Tara; Ball, K Aurelia; Chen, Anna; Pelton, Jeffrey G; Wemmer, David E; Head-Gordon, Teresa

    2015-12-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disease affecting millions of people worldwide. AD is characterized by the presence of extracellular plaques composed of aggregated/oligomerized β-amyloid peptides with Aβ42 peptide representing a major isoform in the senile plaques. Given the pathological significance of Aβ42 in the progression of AD, there is considerable interest in understanding the structural ensembles for soluble monomer and oligomeric forms of Aβ42. This report describes an efficient method to express and purify high quality (15)N isotope-labeled Aβ42 for structural studies by NMR. The protocol involves utilization of an auto induction system with (15)N isotope labeled medium, for high-level expression of Aβ42 as a fusion with IFABP. After the over-expression of the (15)N isotope-labeled IFABP-Aβ42 fusion protein in the inclusion bodies, pure (15)N isotope-labeled Aβ42 peptide is obtained following a purification method that is streamlined and improved from the method originally developed for the isolation of unlabeled Aβ42 peptide (Garai et al., 2009). We obtain a final yield of ∼ 6 mg/L culture for (15)N isotope-labeled Aβ42 peptide. Mass spectrometry and (1)H-(15)N HSQC spectra of monomeric Aβ42 peptide validate the uniform incorporation of the isotopic label. The method described here is equally applicable for the uniform isotope labeling with (15)N and (13)C in Aβ42 peptide as well as its other variants including any Aβ42 peptide mutants.

  2. Lipophilicity of amyloid β-peptide 12-28 and 25-35 to unravel their ability to promote hydrophobic and electrostatic interactions.

    PubMed

    Ermondi, G; Catalano, F; Vallaro, M; Ermondi, I; Camacho Leal, M P; Rinaldi, L; Visentin, S; Caron, G

    2015-11-10

    The growing interest for peptide therapeutics calls for new strategies to determine the physico-chemical properties responsible for the interactions of peptides with the environment. This study reports about the lipophilicity of two fragments of the amyloid β-peptide, Aβ 25-35 and Aβ 12-28. Firstly, computational studies showed the limits of log D(7.4)oct in describing the lipophilicity of medium-sized peptides. Chromatographic lipophilicity indexes (expressed as log k', the logarithm of the retention factor) were then measured in three different systems to highlight the different skills of Aβ 25-35 and Aβ 12-28 in giving interactions with polar and apolar environments. CD studies were also performed to validate chromatographic experimental conditions. Results show that Aβ 12-28 has a larger skill in promoting hydrophobic and electrostatic interactions than Aβ 25-35. This finding proposes a strategy to determine the lipophilicity of peptides for drug discovery purposes but also gives insights in unraveling the debate about the aminoacidic region of Aβ responsible for its neurotoxicity.

  3. Peptide nanotubes.

    PubMed

    Hamley, Ian W

    2014-07-01

    The self-assembly of different classes of peptide, including cyclic peptides, amyloid peptides and surfactant-like peptides into nanotube structures is reviewed. The modes of self-assembly are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.

  4. Serum amyloid A-derived peptides, present in human rheumatic synovial fluids, induce the secretion of interferon-gamma by human CD(4)(+) T-lymphocytes.

    PubMed

    Yavin, E J; Preciado-Patt, L; Rosen, O; Yaron, M; Suessmuth, R D; Levartowsky, D; Jung, G; Lider, O; Fridkin, M

    2000-04-28

    Serum amyloid A (SAA) is a major acute-phase protein whose biochemical functions remain largely obscure. Human rheumatic synovial fluids were screened by high performance liquid chromatography mass spectrometry for SAA-derived peptides, specifically the sequence AGLPEKY (SAA(98-104)) which was previously shown to modulate various leukocyte functions. Two such fluids were found to contain a truncated version of SAA(98-104). Synthetic SAA(98-104) and several of its analogs were shown capable of binding isolated human CD(4)(+) T-lymphocytes and stimulating them to produce interferon-gamma. Given the high acute-phase serum level of SAA and its massive proteolysis by inflammatory related enzymes, SAA-derived peptides may be involved in host defense mechanisms. PMID:10788622

  5. Peptide-cleaving agents for human islet amyloid polypeptide containing substrate recognition site based on quinoxaline: cleavage efficiency enhanced by lowering substrate concentration.

    PubMed

    Chei, Woosuk; Ju, Heeyeon; Suh, Junghun

    2012-02-15

    Oligomers of human islet amyloid polypeptide (h-IAPP) are believed to be the pathogenic species for type 2 diabetes mellitus. Peptide-cleaving agents selective for oligomers of h-IAPP were synthesized by using quinoxaline derivatives as recognition sites attached to the Co(III) complex of cyclen in this study. When the initial concentration of h-IAPP was lowered from 4.0 to 0.20 μM, cleavage yield of the new agents was enhanced by 3 times reaching 16-22 mol%. This shows that the agents would have significant activities at subnano molar concentrations if the concentration of h-IAPP is lowered to the in vivo values. This further indicates that the peptide-cleaving agents prepared previously in this laboratory possess sufficiently high activity for application as a new therapeutic option for Alzheimer's disease, type 2 diabetes mellitus, and Parkinson's disease.

  6. Monodisperse carboxyl-functionalized poly(ethylene glycol)-coated magnetic poly(glycidyl methacrylate) microspheres: application to the immunocapture of β-amyloid peptides.

    PubMed

    Horák, Daniel; Hlídková, Helena; Hiraoui, Mohamed; Taverna, Myriam; Proks, Vladimír; Mázl Chánová, Eliška; Smadja, Claire; Kučerová, Zdenka

    2014-11-01

    Identification and evaluation of small changes in β-amyloid peptide (Aβ) levels in cerebrospinal fluid is of crucial importance for early detection of Alzheimer's disease. Microfluidic detection methods enable effective preconcentration of Aβ using magnetic microparticles coated with Aβ antibodies. Poly(glycidyl methacrylate) microspheres are coated with α-amino-ω-methoxy-PEG5000 /α-amino-ω-Boc-NH-PEG5000 Boc groups deprotected and NH2 succinylated to introduce carboxyl groups. Capillary electrophoresis with laser-induced fluorescence detection confirms the efficient capture of Aβ 1-40 peptides on the microspheres with immobilized monoclonal anti-Aβ 6E10. The capture specificity is confirmed by comparing Aβ 1-40 levels on the anti-IgG-immobilized particles used as a control. PMID:25142028

  7. Monodisperse carboxyl-functionalized poly(ethylene glycol)-coated magnetic poly(glycidyl methacrylate) microspheres: application to the immunocapture of β-amyloid peptides.

    PubMed

    Horák, Daniel; Hlídková, Helena; Hiraoui, Mohamed; Taverna, Myriam; Proks, Vladimír; Mázl Chánová, Eliška; Smadja, Claire; Kučerová, Zdenka

    2014-11-01

    Identification and evaluation of small changes in β-amyloid peptide (Aβ) levels in cerebrospinal fluid is of crucial importance for early detection of Alzheimer's disease. Microfluidic detection methods enable effective preconcentration of Aβ using magnetic microparticles coated with Aβ antibodies. Poly(glycidyl methacrylate) microspheres are coated with α-amino-ω-methoxy-PEG5000 /α-amino-ω-Boc-NH-PEG5000 Boc groups deprotected and NH2 succinylated to introduce carboxyl groups. Capillary electrophoresis with laser-induced fluorescence detection confirms the efficient capture of Aβ 1-40 peptides on the microspheres with immobilized monoclonal anti-Aβ 6E10. The capture specificity is confirmed by comparing Aβ 1-40 levels on the anti-IgG-immobilized particles used as a control.

  8. Zn(II)- and Cu(II)-induced non-fibrillar aggregates of amyloid-beta (1-42) peptide are transformed to amyloid fibrils, both spontaneously and under the influence of metal chelators.

    PubMed

    Tõugu, Vello; Karafin, Ann; Zovo, Kairit; Chung, Roger S; Howells, Claire; West, Adrian K; Palumaa, Peep

    2009-09-01

    Aggregation of amyloid-beta (Abeta) peptides is a central phenomenon in Alzheimer's disease. Zn(II) and Cu(II) have profound effects on Abeta aggregation; however, their impact on amyloidogenesis is unclear. Here we show that Zn(II) and Cu(II) inhibit Abeta(42) fibrillization and initiate formation of non-fibrillar Abeta(42) aggregates, and that the inhibitory effect of Zn(II) (IC(50) = 1.8 micromol/L) is three times stronger than that of Cu(II). Medium and high-affinity metal chelators including metallothioneins prevented metal-induced Abeta(42) aggregation. Moreover, their addition to preformed aggregates initiated fast Abeta(42) fibrillization. Upon prolonged incubation the metal-induced aggregates also transformed spontaneously into fibrils, that appear to represent the most stable state of Abeta(42). H13A and H14A mutations in Abeta(42) reduced the inhibitory effect of metal ions, whereas an H6A mutation had no significant impact. We suggest that metal binding by H13 and H14 prevents the formation of a cross-beta core structure within region 10-23 of the amyloid fibril. Cu(II)-Abeta(42) aggregates were neurotoxic to neurons in vitro only in the presence of ascorbate, whereas monomers and Zn(II)-Abeta(42) aggregates were non-toxic. Disturbed metal homeostasis in the vicinity of zinc-enriched neurons might pre-dispose formation of metal-induced Abeta aggregates, subsequent fibrillization of which can lead to amyloid formation. The molecular background underlying metal-chelating therapies for Alzheimer's disease is discussed in this light. PMID:19619132

  9. Beta-amyloid peptides enhance the proliferative response of activated CD4CD28 lymphocytes from Alzheimer disease patients and from healthy elderly.

    PubMed

    Jóźwik, Agnieszka; Landowski, Jerzy; Bidzan, Leszek; Fülop, Tamas; Bryl, Ewa; Witkowski, Jacek M

    2012-01-01

    Alzheimer's disease (AD) is the most frequent form of dementia among elderly. Despite the vast amount of literature on non-specific immune mechanisms in AD there is still little information about the potential antigen-specific immune response in this pathology. It is known that early stages of AD include β-amyloid (Aβ)- reactive antibodies production and inflammatory response. Despite some evidence gathered proving cellular immune response background in AD pathology, the specific reactions of CD4(+) and CD8(+) cells remain unknown as the previous investigations yielded conflicting results. Here we investigated the CD4(+)CD28(+) population of human peripheral blood T cells and showed that soluble β-amyloids alone were unable to stimulate these cells to proliferate significantly, resulting only in minor, probably antigen-specific, proliferative response. On the other hand, the exposure of in vitro pre-stimulated lymphocytes to soluble Aβ peptides significantly enhanced the proliferative response of these cells which had also lead to increased levels of TNF, IL-10 and IL-6. We also proved that Aβ peptide-enhanced proliferative response of CD4(+)CD28(+) cells is autonomous and independent from disease status while being associated with the initial, ex vivo activation status of the CD4(+) cells. In conclusion, we suggest that the effect of Aβ peptides on the immune system of AD patients does not depend on the specific reactivity to Aβ epitope(s), but is rather a consequence of an unspecific modulation of the cell cycle dynamics and cytokine production by T cells, occurring simultaneously in a huge proportion of Aβ peptide-exposed T lymphocytes and affecting the immune system performance. PMID:22428008

  10. Beta-Amyloid Peptides Enhance the Proliferative Response of Activated CD4+CD28+ Lymphocytes from Alzheimer Disease Patients and from Healthy Elderly

    PubMed Central

    Jóźwik, Agnieszka; Landowski, Jerzy; Bidzan, Leszek; Fülop, Tamas; Bryl, Ewa; Witkowski, Jacek M.

    2012-01-01

    Alzheimer's disease (AD) is the most frequent form of dementia among elderly. Despite the vast amount of literature on non-specific immune mechanisms in AD there is still little information about the potential antigen-specific immune response in this pathology. It is known that early stages of AD include β-amyloid (Aβ)- reactive antibodies production and inflammatory response. Despite some evidence gathered proving cellular immune response background in AD pathology, the specific reactions of CD4+ and CD8+ cells remain unknown as the previous investigations yielded conflicting results. Here we investigated the CD4+CD28+ population of human peripheral blood T cells and showed that soluble β-amyloids alone were unable to stimulate these cells to proliferate significantly, resulting only in minor, probably antigen-specific, proliferative response. On the other hand, the exposure of in vitro pre-stimulated lymphocytes to soluble Aβ peptides significantly enhanced the proliferative response of these cells which had also lead to increased levels of TNF, IL-10 and IL-6. We also proved that Aβ peptide-enhanced proliferative response of CD4+CD28+ cells is autonomous and independent from disease status while being associated with the initial, ex vivo activation status of the CD4+ cells. In conclusion, we suggest that the effect of Aβ peptides on the immune system of AD patients does not depend on the specific reactivity to Aβ epitope(s), but is rather a consequence of an unspecific modulation of the cell cycle dynamics and cytokine production by T cells, occurring simultaneously in a huge proportion of Aβ peptide-exposed T lymphocytes and affecting the immune system performance. PMID:22428008

  11. Beta-amyloid peptides enhance the proliferative response of activated CD4CD28 lymphocytes from Alzheimer disease patients and from healthy elderly.

    PubMed

    Jóźwik, Agnieszka; Landowski, Jerzy; Bidzan, Leszek; Fülop, Tamas; Bryl, Ewa; Witkowski, Jacek M

    2012-01-01

    Alzheimer's disease (AD) is the most frequent form of dementia among elderly. Despite the vast amount of literature on non-specific immune mechanisms in AD there is still little information about the potential antigen-specific immune response in this pathology. It is known that early stages of AD include β-amyloid (Aβ)- reactive antibodies production and inflammatory response. Despite some evidence gathered proving cellular immune response background in AD pathology, the specific reactions of CD4(+) and CD8(+) cells remain unknown as the previous investigations yielded conflicting results. Here we investigated the CD4(+)CD28(+) population of human peripheral blood T cells and showed that soluble β-amyloids alone were unable to stimulate these cells to proliferate significantly, resulting only in minor, probably antigen-specific, proliferative response. On the other hand, the exposure of in vitro pre-stimulated lymphocytes to soluble Aβ peptides significantly enhanced the proliferative response of these cells which had also lead to increased levels of TNF, IL-10 and IL-6. We also proved that Aβ peptide-enhanced proliferative response of CD4(+)CD28(+) cells is autonomous and independent from disease status while being associated with the initial, ex vivo activation status of the CD4(+) cells. In conclusion, we suggest that the effect of Aβ peptides on the immune system of AD patients does not depend on the specific reactivity to Aβ epitope(s), but is rather a consequence of an unspecific modulation of the cell cycle dynamics and cytokine production by T cells, occurring simultaneously in a huge proportion of Aβ peptide-exposed T lymphocytes and affecting the immune system performance.

  12. Cilostazol Modulates Autophagic Degradation of β-Amyloid Peptide via SIRT1-Coupled LKB1/AMPKα Signaling in Neuronal Cells.

    PubMed

    Park, So Youn; Lee, Hye Rin; Lee, Won Suk; Shin, Hwa Kyoung; Kim, Hye Young; Hong, Ki Whan; Kim, Chi Dae

    2016-01-01

    A neuroprotective role of autophagy mediates the degradation of β-amyloid peptide (Aβ) in Alzheimer's disease (AD). The previous study showed cilostazol modulates autophagy by increasing beclin1, Atg5 and LC3-II expressions, and depletes intracellular Aβ accumulation. This study elucidated the mechanisms through which cilostazol modulates the autophagic degradation of Aβ in neurons. In N2a cells, cilostazol (10-30 μM), significantly increased the expression of P-AMPKα (Thr 172) and downstream P-ACC (acetyl-CoA carboxylase) (Ser 79) as did resveratrol (SIRT1 activator), or AICAR (AMPK activator), which were blocked by KT5720, compound C (AMPK inhibitor), or sirtinol. Furthermore, phosphorylated-mTOR (Ser 2448) and phosphorylated-P70S6K (Thr 389) expressions were suppressed, and LC3-II levels were elevated in association with decreased P62/Sqstm1 by cilostazol. Cilostazol increased cathepsin B activity and decreased p62/SQSTM 1, consequently decreased accumulation of Aβ1-42 in the activated N2aSwe cells, and these results were blocked by sirtinol, compound C and bafilomycin A1 (autophagosome blocker), suggesting enhanced autophagosome formation by cilostazol. In SIRT1 gene-silenced N2a cells, cilostazol failed to increase the expressions of P-LKB1 (Ser 428) and P-AMPKα, which contrasted with its effect in negative control cells transfected with scrambled siRNA duplex. Further, N2a cells transfected with expression vectors encoding pcDNA SIRT1 showed increased P-AMPKα expression, which mimicked the effect of cilostazol in N2a cells; suggesting cilostazol-stimulated expressions of P-LKB1 and P-AMPKα were SIRT1-dependent. Unlike their effects in N2a cells, in HeLa cells, which lack LKB1, cilostazol and resveratrol did not elevate SIRT1 or P-AMPKα expression, indicating cilostazol and resveratrol-stimulated expressions of SIRT1 and P-AMPKα are LKB1-dependent. In conclusion, cilostazol upregulates autophagy by activating SIRT1-coupled P-LKB1/P-AMPKα and

  13. Cilostazol Modulates Autophagic Degradation of β-Amyloid Peptide via SIRT1-Coupled LKB1/AMPKα Signaling in Neuronal Cells

    PubMed Central

    Lee, Won Suk; Shin, Hwa Kyoung; Kim, Hye Young; Hong, Ki Whan; Kim, Chi Dae

    2016-01-01

    A neuroprotective role of autophagy mediates the degradation of β-amyloid peptide (Aβ) in Alzheimer’s disease (AD). The previous study showed cilostazol modulates autophagy by increasing beclin1, Atg5 and LC3-II expressions, and depletes intracellular Aβ accumulation. This study elucidated the mechanisms through which cilostazol modulates the autophagic degradation of Aβ in neurons. In N2a cells, cilostazol (10–30 μM), significantly increased the expression of P-AMPKα (Thr 172) and downstream P-ACC (acetyl-CoA carboxylase) (Ser 79) as did resveratrol (SIRT1 activator), or AICAR (AMPK activator), which were blocked by KT5720, compound C (AMPK inhibitor), or sirtinol. Furthermore, phosphorylated-mTOR (Ser 2448) and phosphorylated-P70S6K (Thr 389) expressions were suppressed, and LC3-II levels were elevated in association with decreased P62/Sqstm1 by cilostazol. Cilostazol increased cathepsin B activity and decreased p62/SQSTM 1, consequently decreased accumulation of Aβ1–42 in the activated N2aSwe cells, and these results were blocked by sirtinol, compound C and bafilomycin A1 (autophagosome blocker), suggesting enhanced autophagosome formation by cilostazol. In SIRT1 gene-silenced N2a cells, cilostazol failed to increase the expressions of P-LKB1 (Ser 428) and P-AMPKα, which contrasted with its effect in negative control cells transfected with scrambled siRNA duplex. Further, N2a cells transfected with expression vectors encoding pcDNA SIRT1 showed increased P-AMPKα expression, which mimicked the effect of cilostazol in N2a cells; suggesting cilostazol-stimulated expressions of P-LKB1 and P-AMPKα were SIRT1-dependent. Unlike their effects in N2a cells, in HeLa cells, which lack LKB1, cilostazol and resveratrol did not elevate SIRT1 or P-AMPKα expression, indicating cilostazol and resveratrol-stimulated expressions of SIRT1 and P-AMPKα are LKB1-dependent. In conclusion, cilostazol upregulates autophagy by activating SIRT1-coupled P-LKB1/P-AMPKα and

  14. Serum amyloid A and pairing formyl peptide receptor 2 are expressed in corneas and involved in inflammation-mediated neovascularization

    PubMed Central

    Ren, Sheng-Wei; Qi, Xia; Jia, Chang-Kai; Wang, Yi-Qiang

    2014-01-01

    AIM To solidify the involvement of Saa-related pathway in corneal neovascularization (CorNV). The pathogenesis of inflammatory CorNV is not fully understood yet, and our previous study implicated that serum amyloid A (Saa) 1 (Saa1) and Saa3 were among the genes up-regulated upon CorNV induction in mice. METHODS Microarray data obtained during our profiling project on CorNV were analyzed for the genes encoding the four SAA family members (Saa1-4), six reported SAA receptors (formyl peptide receptor 2, Tlr2, Tlr4, Cd36, Scarb1, P2rx7) and seven matrix metallopeptidases (Mmp) 1a, 1b, 2, 3, 9, 10, 13 reportedly to be expressed upon SAA pathway activation. The baseline expression or changes of interested genes were further confirmed in animals with CorNV using molecular or histological methods. CorNV was induced in Balb/c and C57BL/6 mice by placing either three interrupted 10-0 sutures or a 2 mm filter paper soaked with sodium hydroxide in the central area of the cornea. At desired time points, the corneas were harvested for histology examination or for extraction of mRNA and protein. The mRNA levels of Saa1, Saa3, Fpr2, Mmp2 and Mmp3 in corneas were detected using quantitative reverse transcription-PCR, and SAA3 protein in tissues detected using immunohistochemistry or western blotting. RESULTS Microarray data analysis revealed that Saa1, Saa3, Fpr2, Mmp2, Mmp3 messengers were readily detected in normal corneas and significantly up-regulated upon CorNV induction. The changes of these five genes were confirmed with real-time PCR assay. On the contrary, other SAA members (Saa2, Saa4), other SAA receptors (Tlr2, Tlr4, Cd36, P2rx7, etc), or other Mmps (Mmp1a, Mmp1b, Mmp9, Mmp10, Mmp13) did not show consistent changes. Immunohistochemistry study and western blotting further confirmed the expression of SAA3 products in normal corneas as well as their up-regulation in corneas with CorNV. CONCLUSION SAA-FPR2 pathway composing genes were expressed in normal murine corneas and

  15. The involvement of sigma1 receptors in donepezil-induced rescue of hippocampal LTP impaired by beta-amyloid peptide.

    PubMed

    Solntseva, E I; Kapai, N A; Popova, O V; Rogozin, P D; Skrebitsky, V G

    2014-07-01

    Donepezil is a potent acetylcholinesterase inhibitor used for the treatment of Alzheimer's disease (AD). Additional therapeutically relevant target for donepezil is sigma1 receptor (Sig1-R). Beta-amyloid peptide (Aβ) is believed to contribute to the pathogenesis of AD. In our previous work (Kapai et al., 2012), we have shown that donepezil antagonizes the suppressive action of Aβ(1-42) on long-term potentiation (LTP) in rat hippocampal slices. The purpose of the present study was to determine whether Sig1-R is involved into the mechanisms of donepezil action. For this purpose, we have tested whether agonist of Sig1-R PRE-084 mimics, and antagonist of Sig1-R haloperidol abolishes the effect of donepezil. Population spikes (PSs) were recorded from the pyramidal layer of the CA1 region of rat hippocampal slices. Drugs were applied by addition to the perfusate starting 15 min before and ending 5 min after the tetanus. In the control group, the amplitude of PS 30 min post-tetanus reached 153±10%. Aβ (200 nM) markedly suppressed the LTP magnitude or even caused the suppression of baseline PS (82±8%, P<0.001). This suppression of LTP could be markedly prevented when 1 μM donepezil was co-administered with Aβ (136±11%, P<0.05). Further, we co-administered three substances: Aβ, donepezil and 0.5 μM haloperidol and have found that haloperidol antagonized the stimulating effect of donepezil on LTP (92±6%, P<0.05). Agonist of Sig1-R PRE-084 (0.1-10 μM) enhanced control LTP and abolished the inhibitory effect of Aβ on LTP in a concentration-dependent manner. The amplitude of PS 30 min post-tetanus reached 183±7% (P<0.01) for 10 μM PRE-084. The results suggest that activation of Sig1-R is involved into the mechanisms of donepezil-induced rescue of hippocampal LTP impaired by Aβ.

  16. Cilostazol Upregulates Autophagy via SIRT1 Activation: Reducing AmyloidPeptide and APP-CTFβ Levels in Neuronal Cells

    PubMed Central

    Lee, Hye Rin; Shin, Hwa Kyoung; Park, So Youn; Kim, Hye Young; Bae, Sun Sik; Lee, Won Suk; Rhim, Byung Yong; Hong, Ki Whan; Kim, Chi Dae

    2015-01-01

    Autophagy is a vital pathway for the removal of β-amyloid peptide (Aβ) and the aggregated proteins that cause Alzheimer’s disease (AD). We previously found that cilostazol induced SIRT1 expression and its activity in neuronal cells, and thus, we hypothesized that cilostazol might stimulate clearances of Aβ and C-terminal APP fragment β subunit (APP-CTFβ) by up-regulating autophagy.When N2a cells were exposed to soluble Aβ1–42, protein levels of beclin-1, autophagy-related protein5 (Atg5), and SIRT1 decreased significantly. Pretreatment with cilostazol (10–30 μM) or resveratrol (20 μM) prevented these Aβ1–42 evoked suppressions. LC3-II (a marker of mammalian autophagy) levels were significantly increased by cilostazol, and this increase was reduced by 3-methyladenine. To evoke endogenous Aβ overproduction, N2aSwe cells (N2a cells stably expressing human APP containing the Swedish mutation) were cultured in medium with or without tetracycline (Tet+ for 48 h and then placed in Tet- condition). Aβ and APP-CTFβ expressions were increased after 12~24 h in Tet- condition, and these increased expressions were significantly reduced by pretreating cilostazol. Cilostazol-induced reductions in the expressions of Aβ and APP-CTFβ were blocked by bafilomycin A1 (a blocker of autophagosome to lysosome fusion). After knockdown of the SIRT1 gene (to ~40% in SIRT1 protein), cilostazol failed to elevate the expressions of beclin-1, Atg5, and LC3-II, indicating that cilostazol increases these expressions by up-regulating SIRT1. Further, decreased cell viability induced by Aβ was prevented by cilostazol, and this inhibition was reversed by 3-methyladenine, indicating that the protective effect of cilostazol against Aβ induced neurotoxicity is, in part, ascribable to the induction of autophagy. In conclusion, cilostazol modulates autophagy by increasing the activation of SIRT1, and thereby enhances Aβ clearance and increases cell viability. PMID:26244661

  17. Structural exploration and Förster theory modeling for the interpretation of gas-phase FRET measurements: Chromophore-grafted amyloidpeptides

    NASA Astrophysics Data System (ADS)

    Kulesza, Alexander; Daly, Steven; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2015-07-01

    The distance-dependence of excitation energy transfer, e.g., being described by Förster theory (Förster resonance energy transfer (FRET)), allows the use of optical techniques for the direct observation of structural properties. Recently, this technique has been successfully applied in the gas phase. The detailed interpretation of the experimental FRET results, however, relies on the comparison with structural modeling. We therefore present a complete first-principles modeling approach that explores the gas-phase structure of chromophore-grafted peptides and achieves accurate predictions of FRET efficiencies. We apply the approach to amyloid-β 12-28 fragments, known to be involved in amyloid plaque formation connected to Alzheimer's disease. We sample structures of the peptides that are grafted with 5-carboxyrhodamine 575 (Rh575) and QSY-7 chromophores by means of replica-exchange molecular dynamics simulations upon an Amber-type forcefield parametrization as a function of the charge state. The generated ensembles provide chromophore-distance and -orientation distributions which are used with the spectral parameters of the Rh575/QSY-7 chromophores to model FRET-efficiencies for the systems. The theoretical values agree with the experimental average "action"-FRET efficiencies and motivate to use the herein reported parametrization, sampling, and FRET-modeling technique in future studies on the structural properties and aggregation-behavior of related systems.

  18. Structure−Activity Relationships in Peptide Modulators of β-Amyloid Protein Aggregation: Variation in α,α-Disubstitution Results in Altered Aggregate Size and Morphology

    PubMed Central

    2010-01-01

    Neuronal cytotoxicity observed in Alzheimer’s disease (AD) is linked to the aggregation of β-amyloid peptide (Aβ) into toxic forms. Increasing evidence points to oligomeric materials as the neurotoxic species, not Aβ fibrils; disruption or inhibition of Aβ self-assembly into oligomeric or fibrillar forms remains a viable therapeutic strategy to reduce Aβ neurotoxicity. We describe the synthesis and characterization of amyloid aggregation mitigating peptides (AAMPs) whose structure is based on the Aβ “hydrophobic core” Aβ17−20, with α,α-disubstituted amino acids (ααAAs) added into this core as potential disrupting agents of fibril self-assembly. The number, positional distribution, and side-chain functionality of ααAAs incorporated into the AAMP sequence were found to influence the resultant aggregate morphology as indicated by ex situ experiments using atomic force microscopy (AFM) and transmission electron microscopy (TEM). For instance, AAMP-5, incorporating a sterically hindered ααAA with a diisobutyl side chain in the core sequence, disrupted Aβ1−40 fibril formation. However, AAMP-6, with a less sterically hindered ααAA with a dipropyl side chain, altered fibril morphology, producing shorter and larger sized fibrils (compared with those of Aβ1−40). Remarkably, ααAA-AAMPs caused disassembly of existing Aβ fibrils to produce either spherical aggregates or protofibrillar structures, suggesting the existence of equilibrium between fibrils and prefibrillar structures. PMID:22778850

  19. Structural exploration and Förster theory modeling for the interpretation of gas-phase FRET measurements: Chromophore-grafted amyloidpeptides.

    PubMed

    Kulesza, Alexander; Daly, Steven; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2015-07-14

    The distance-dependence of excitation energy transfer, e.g., being described by Förster theory (Förster resonance energy transfer (FRET)), allows the use of optical techniques for the direct observation of structural properties. Recently, this technique has been successfully applied in the gas phase. The detailed interpretation of the experimental FRET results, however, relies on the comparison with structural modeling. We therefore present a complete first-principles modeling approach that explores the gas-phase structure of chromophore-grafted peptides and achieves accurate predictions of FRET efficiencies. We apply the approach to amyloid-β 12-28 fragments, known to be involved in amyloid plaque formation connected to Alzheimer's disease. We sample structures of the peptides that are grafted with 5-carboxyrhodamine 575 (Rh575) and QSY-7 chromophores by means of replica-exchange molecular dynamics simulations upon an Amber-type forcefield parametrization as a function of the charge state. The generated ensembles provide chromophore-distance and -orientation distributions which are used with the spectral parameters of the Rh575/QSY-7 chromophores to model FRET-efficiencies for the systems. The theoretical values agree with the experimental average "action"-FRET efficiencies and motivate to use the herein reported parametrization, sampling, and FRET-modeling technique in future studies on the structural properties and aggregation-behavior of related systems. PMID:26178129

  20. Candidate genes for Alzheimer's disease are associated with individual differences in plasma levels of beta amyloid peptides in adults with Down syndrome.

    PubMed

    Schupf, Nicole; Lee, Annie; Park, Naeun; Dang, Lam-Ha; Pang, Deborah; Yale, Alexander; Oh, David Kyung-Taek; Krinsky-McHale, Sharon J; Jenkins, Edmund C; Luchsinger, José A; Zigman, Warren B; Silverman, Wayne; Tycko, Benjamin; Kisselev, Sergey; Clark, Lorraine; Lee, Joseph H

    2015-10-01

    We examined the contribution of candidates genes for Alzheimer's disease (AD) to individual differences in levels of beta amyloid peptides in adults with Down syndrom, a population at high risk for AD. Participants were 254 non-demented adults with Down syndrome, 30-78 years of age. Genomic deoxyribonucleic acid was genotyped using an Illumina GoldenGate custom array. We used linear regression to examine differences in levels of Aβ peptides associated with the number of risk alleles, adjusting for age, sex, level of intellectual disability, race and/or ethnicity, and the presence of the APOE ε4 allele. For Aβ42 levels, the strongest gene-wise association was found for a single nucleotide polymorphism (SNP) on CAHLM1; for Aβ40 levels, the strongest gene-wise associations were found for SNPs in IDE and SOD1, while the strongest gene-wise associations with levels of the Aβ42/Aβ40 ratio were found for SNPs in SORCS1. Broadly classified, variants in these genes may influence amyloid precursor protein processing (CALHM1, IDE), vesicular trafficking (SORCS1), and response to oxidative stress (SOD1).

  1. Development of gold nanoparticle based colorimetric method for quantitatively studying the inhibitors of Cu(2+)/Zn(2+) induced β-amyloid peptide assembly.

    PubMed

    Wang, Chengke; Wang, Kun; Wang, Zhenxin

    2015-02-01

    In this paper, a kind of gold nanoparticle (GNP)-based colorimetric assay has been developed for studying the reversible interaction of β-amyloid peptide (Aβ) with Cu(2+) and Zn(2+), and quantitatively analyzing four inhibitors (i.e., EDTA, EGTA, histidine and clioquinol) of Cu(2+)/Zn(2+) induced Aβ assembly. The inhibition efficiencies (e.g., half maximal inhibitory concentration, IC50 value) of these inhibitors could be measured in this work. As far as we know, these IC50 values were reported at the first time. In this assay, the streptavidin conjugated GNPs (SA-GNPs) were employed as indicators to monitor the Cu(2+)/Zn(2+) induced aggregating/disaggregating behaviors of biotin modified β-amyloid 1-16 peptides (Aβ1-16(biotin)). Because of high affinity of streptavidin (SA) with biotin, the aggregating/disaggregating of Aβ1-16(biotin) results in the significant color change of SA-GNPs. Furthermore, we demonstrate that the assay can be used as an effective tool for designing anti-dementia drugs through quantitative analysis of the interactions of four representative inhibitors with Cu(2+)/Zn(2+) induced Aβ assembly. PMID:25597800

  2. Candidate genes for Alzheimer's disease are associated with individual differences in plasma levels of beta amyloid peptides in adults with Down syndrome.

    PubMed

    Schupf, Nicole; Lee, Annie; Park, Naeun; Dang, Lam-Ha; Pang, Deborah; Yale, Alexander; Oh, David Kyung-Taek; Krinsky-McHale, Sharon J; Jenkins, Edmund C; Luchsinger, José A; Zigman, Warren B; Silverman, Wayne; Tycko, Benjamin; Kisselev, Sergey; Clark, Lorraine; Lee, Joseph H

    2015-10-01

    We examined the contribution of candidates genes for Alzheimer's disease (AD) to individual differences in levels of beta amyloid peptides in adults with Down syndrom, a population at high risk for AD. Participants were 254 non-demented adults with Down syndrome, 30-78 years of age. Genomic deoxyribonucleic acid was genotyped using an Illumina GoldenGate custom array. We used linear regression to examine differences in levels of Aβ peptides associated with the number of risk alleles, adjusting for age, sex, level of intellectual disability, race and/or ethnicity, and the presence of the APOE ε4 allele. For Aβ42 levels, the strongest gene-wise association was found for a single nucleotide polymorphism (SNP) on CAHLM1; for Aβ40 levels, the strongest gene-wise associations were found for SNPs in IDE and SOD1, while the strongest gene-wise associations with levels of the Aβ42/Aβ40 ratio were found for SNPs in SORCS1. Broadly classified, variants in these genes may influence amyloid precursor protein processing (CALHM1, IDE), vesicular trafficking (SORCS1), and response to oxidative stress (SOD1). PMID:26166206

  3. Development of gold nanoparticle based colorimetric method for quantitatively studying the inhibitors of Cu(2+)/Zn(2+) induced β-amyloid peptide assembly.

    PubMed

    Wang, Chengke; Wang, Kun; Wang, Zhenxin

    2015-02-01

    In this paper, a kind of gold nanoparticle (GNP)-based colorimetric assay has been developed for studying the reversible interaction of β-amyloid peptide (Aβ) with Cu(2+) and Zn(2+), and quantitatively analyzing four inhibitors (i.e., EDTA, EGTA, histidine and clioquinol) of Cu(2+)/Zn(2+) induced Aβ assembly. The inhibition efficiencies (e.g., half maximal inhibitory concentration, IC50 value) of these inhibitors could be measured in this work. As far as we know, these IC50 values were reported at the first time. In this assay, the streptavidin conjugated GNPs (SA-GNPs) were employed as indicators to monitor the Cu(2+)/Zn(2+) induced aggregating/disaggregating behaviors of biotin modified β-amyloid 1-16 peptides (Aβ1-16(biotin)). Because of high affinity of streptavidin (SA) with biotin, the aggregating/disaggregating of Aβ1-16(biotin) results in the significant color change of SA-GNPs. Furthermore, we demonstrate that the assay can be used as an effective tool for designing anti-dementia drugs through quantitative analysis of the interactions of four representative inhibitors with Cu(2+)/Zn(2+) induced Aβ assembly.

  4. Copper(II)-bis-histidine coordination structure in a fibrillar amyloid β-peptide fragment and model complexes revealed by electron spin echo envelope modulation spectroscopy.

    PubMed

    Hernández-Guzmán, Jessica; Sun, Li; Mehta, Anil K; Dong, Jijun; Lynn, David G; Warncke, Kurt

    2013-09-23

    Truncated and mutated amyloid-β (Aβ) peptides are models for systematic study-in homogeneous preparations-of the molecular origins of metal ion effects on Aβ aggregation rates, types of aggregate structures formed, and cytotoxicity. The 3D geometry of bis-histidine imidazole coordination of Cu(II) in fibrils of the nonapetide acetyl-Aβ(13-21)H14A has been determined by powder (14) N electron spin echo envelope modulation (ESEEM) spectroscopy. The method of simulation of the anisotropic combination modulation is described and benchmarked for a Cu(II) -bis-cis-imidazole complex of known structure. The revealed bis-cis coordination mode, and the mutual orientation of the imidazole rings, for Cu(II) in Ac-Aβ(13-21)H14A fibrils are consistent with the proposed β-sheet structural model and pairwise peptide interaction with Cu(II) , with an alternating [-metal-vacancy-]n pattern, along the N-terminal edge. Metal coordination does not significantly distort the intra-β-strand peptide interactions, which provides a possible explanation for the acceleration of Ac-Aβ(13-21)H14A fibrillization by Cu(II) , through stabilization of the associated state and low-reorganization integration of β-strand peptide pair precursors.

  5. Phosphorylation of Alzheimer disease amyloid precursor peptide by protein kinase C and Ca sup 2+ /calmodulin-dependent protein kinase II

    SciTech Connect

    Gandy, S.; Czernik, A.J.; Greengard, P. )

    1988-08-01

    The amino acid sequence of the Alzheimer disease amyloid precursor (ADAP) has been deduced from the corresponding cDNA, and hydropathy analysis of the sequence suggest a receptor-like structure with a single transmembrane domain. The putative cytoplasmic domain of ADAP contains potential sites for serine and threonine phosphorylation. In the present study, synthetic peptides derived from this domain were used as model substrates for various purified protein kinases. Protein kinase C rapidly catalyzed the phosphorylation of a peptide corresponding to amino acid residues 645-661 of ADAP. Ca{sup 2+}/calmodulin-dependent protein kinase II phosphorylated ADAP peptide (645-661) on Thr-654 and Ser-655. Using rat cerebral cortex synaptosomes prelabeled with {sup 32}P{sub i}, a {sup 32}P-labeled phosphoprotein of {approx}135 kDa was immunoprecipitated by using antisera prepared against ADAP peptide(597-624), consistent with the possibility that the holoform of ADAP in rat brain is a phosphoprotein. Based on analogy with the effect of phosphorylation by protein kinase C of juxtamembrane residues in the cytoplasmic domain of the epidermal growth factor receptor and the interleukin 2 receptor, phosphorylation of ADAP may target it for internalization.

  6. Rational design and identification of a non-peptidic aggregation inhibitor of amyloid-β based on a pharmacophore motif obtained from cyclo[-Lys-Leu-Val-Phe-Phe-].

    PubMed

    Arai, Tadamasa; Araya, Takushi; Sasaki, Daisuke; Taniguchi, Atsuhiko; Sato, Takeshi; Sohma, Youhei; Kanai, Motomu

    2014-07-28

    Inhibition of pathogenic protein aggregation may be an important and straightforward therapeutic strategy for curing amyloid diseases. Small-molecule aggregation inhibitors of Alzheimer's amyloid-β (Aβ) are extremely scarce, however, and are mainly restricted to dye- and polyphenol-type compounds that lack drug-likeness. Based on the structure-activity relationship of cyclic Aβ16-20 (cyclo-[KLVFF]), we identified unique pharmacophore motifs comprising side-chains of Leu(2), Val(3), Phe(4), and Phe(5) residues without involvement of the backbone amide bonds to inhibit Aβ aggregation. This finding allowed us to design non-peptidic, small-molecule aggregation inhibitors that possess potent activity. These molecules are the first successful non-peptidic, small-molecule aggregation inhibitors of amyloids based on rational molecular design.

  7. Structural evolution and membrane interaction of the 40-residue β amyloid peptides: differences in the initial proximity between peptides and the membrane bilayer studied by solid-state nuclear magnetic resonance spectroscopy.

    PubMed

    Qiang, Wei; Akinlolu, Rumonat D; Nam, Mimi; Shu, Nicolas

    2014-12-01

    Interactions between the β amyloid (Aβ) peptides and cellular membranes have severe consequences such as neuronal cell disruption and therefore may play important roles in Alzheimer's disease. Understanding the structural basis behind such interactions, however, is hindered by the complexity of the Aβ-membrane systems. In particular, because the Aβ peptides are partially incorporated in the membrane bilayer after enzymatic cleavage, there are multiple possibilities in terms of the initial proximity between the peptides and membranes. Structural studies using in vitro model systems with either externally added or preincorporated Aβ in membrane bilayers resulted in distinct evolution pathways. Previous work has shown that the externally added Aβ formed long and mature filaments, while preincorporated Aβ generated short and curvy fibrils. In this study, we perform detailed characterizations on the structural evolution and membrane interaction for these two pathways, using a combination of solid-state nuclear magnetic resonance spectroscopy and other techniques. For the externally added Aβ, we determined the residue-specific structural evolution during the fibrillation process. While the entire fibrillation process for the externally added Aβ was slow, the preincorporated Aβ generated Aβ-lipid complexes rapidly. Specific interactions between the lipids and peptides were observed, suggesting the colocalization of lipids and peptides within the complex. Formation of such a complex induced molecular-level changes in the lipid bilayer, which may serve as a possible mechanism of membrane disruption. PMID:25397729

  8. Amyloid-β-induced action potential desynchronization and degradation of hippocampal gamma oscillations is prevented by interference with peptide conformation change and aggregation.

    PubMed

    Kurudenkandy, Firoz Roshan; Zilberter, Misha; Biverstål, Henrik; Presto, Jenny; Honcharenko, Dmytro; Strömberg, Roger; Johansson, Jan; Winblad, Bengt; Fisahn, André

    2014-08-20

    The amyloid-β hypothesis of Alzheimer's Disease (AD) focuses on accumulation of amyloidpeptide (Aβ) as the main culprit for the myriad physiological changes seen during development and progression of AD including desynchronization of neuronal action potentials, consequent development of aberrant brain rhythms relevant for cognition, and final emergence of cognitive deficits. The aim of this study was to elucidate the cellular and synaptic mechanisms underlying the Aβ-induced degradation of gamma oscillations in AD, to identify aggregation state(s) of Aβ that mediate the peptides neurotoxicity, and to test ways to prevent the neurotoxic Aβ effect. We show that Aβ(1-42) in physiological concentrations acutely degrades mouse hippocampal gamma oscillations in a concentration- and time-dependent manner. The underlying cause is an Aβ-induced desynchronization of action potential generation in pyramidal cells and a shift of the excitatory/inhibitory equilibrium in the hippocampal network. Using purified preparations containing different aggregation states of Aβ, as well as a designed ligand and a BRICHOS chaperone domain, we provide evidence that the severity of Aβ neurotoxicity increases with increasing concentration of fibrillar over monomeric Aβ forms, and that Aβ-induced degradation of gamma oscillations and excitatory/inhibitory equilibrium is prevented by compounds that interfere with Aβ aggregation. Our study provides correlative evidence for a link between Aβ-induced effects on synaptic currents and AD-relevant neuronal network oscillations, identifies the responsible aggregation state of Aβ and proofs that strategies preventing peptide aggregation are able to prevent the deleterious action of Aβ on the excitatory/inhibitory equilibrium and on the gamma rhythm. PMID:25143621

  9. Silibinin attenuates amyloid beta(25-35) peptide-induced memory impairments: implication of inducible nitric-oxide synthase and tumor necrosis factor-alpha in mice.

    PubMed

    Lu, P; Mamiya, T; Lu, L L; Mouri, A; Niwa, M; Hiramatsu, M; Zou, L B; Nagai, T; Ikejima, T; Nabeshima, T

    2009-10-01

    In Alzheimer's disease (AD), the deposition of amyloid peptides is invariably associated with oxidative stress and inflammatory responses. Silibinin (silybin), a flavonoid derived from the herb milk thistle, has potent anti-inflammatory and antioxidant activities. However, it remains unclear whether silibinin improves amyloid beta (Abeta) peptide-induced neurotoxicity. In this study, we examined the effect of silibinin on the fear-conditioning memory deficits, inflammatory response, and oxidative stress induced by the intracerebroventricular injection of Abeta peptide(25-35) (Abeta(25-35)) in mice. Mice were treated with silibinin (2, 20, and 200 mg/kg p.o., once a day for 8 days) from the day of the Abeta(25-35) injection (day 0). Memory function was evaluated in cued and contextual fear-conditioning tests (day 6). Nitrotyrosine levels in the hippocampus and amygdala were examined (day 8). The mRNA expression of inducible nitric-oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) in the hippocampus and amygdala was measured 2 h after the Abeta(25-35) injection. We found that silibinin significantly attenuated memory deficits caused by Abeta(25-35) in the cued and contextual fear-conditioning test. Silibinin significantly inhibited the increase in nitrotyrosine levels in the hippocampus and amygdala induced by Abeta(25-35). Nitrotyrosine levels in these regions were negatively correlated with memory performance. Moreover, real-time RT-PCR revealed that silibinin inhibited the overexpression of iNOS and TNF-alpha mRNA in the hippocampus and amygdala induced by Abeta(25-35). These findings suggest that silibinin (i) attenuates memory impairment through amelioration of oxidative stress and inflammatory response induced by Abeta(25-35) and (ii) may be a potential candidate for an AD medication. PMID:19638571

  10. Immunohistochemical analysis of transporters related to clearance of amyloidpeptides through blood-cerebrospinal fluid barrier in human brain.

    PubMed

    Matsumoto, Koichi; Chiba, Yoichi; Fujihara, Ryuji; Kubo, Hiroyuki; Sakamoto, Haruhiko; Ueno, Masaki

    2015-12-01

    A large number of previous reports have focused on the transport of amyloidpeptides through cerebral endothelial cells via the blood-brain barrier, while fewer reports have mentioned the transport through the choroid plexus epithelium via the blood-cerebrospinal fluid barrier. Concrete roles of these two pathways remain to be clarified. In this study, we immunohistochemically examined the expression of transporters/receptors that are supposed to be related to the clearance of amyloidpeptides in the choroid plexus epithelium, the ventricular ependymal cells and the brain microvessels, using seven autopsied human brains. In the choroid plexus epithelium, immunoreactivity for low-density lipoprotein receptor (LDLR), LDLR-related protein 1 (LRP1), LRP2, formylpeptide receptor-like 1 (FPRL1), ATP-binding cassette (ABC) transporter-A1 (ABCA1), ABCC1 and ABCG4 was seen in 7 of 7 brains, while that for ABCB1, ABCG2, RAGE and CD36 was seen in 0-2 brains. In the ventricular ependymal cells, immunoreactivity for CD36, LDLR, LRP1, LRP2, FPRL1, ABCA1, ABCC1 and ABCG4 was seen in 6-7 brains, while that for ABCB1, ABCG2 and RAGE was seen in 0-1 brain. Immunoreactivity for insulin-degrading enzyme (IDE) was seen in three and four brains in the choroid plexus epithelium and the ventricular ependymal cells, respectively. In addition, immunoreactivity for LDLR, ABCB1 and ABCG2 was seen in over 40 % of the microvessels (all seven brains), and that for FPRL1, ABCA1, ABCC1 and RAGE was seen in over 5 % of the microvessels (4-6 brains), while that for CD36, IDE, LRP1, LRP2 and ABCG4 was seen in less than 5 % of the microvessels (0-2 brains). These findings may suggest that these multiple transporters/receptors and IDE expressed on the choroid plexus epithelium, ventricular ependymal cells and brain microvessels complementarily or cooperatively contribute to the clearance of amyloidpeptides from the brain.

  11. Label-free detection of Alzheimer's disease through the ADP3 peptoid recognizing the serum amyloid-beta42 peptide.

    PubMed

    Zhao, Zijian; Zhu, Ling; Bu, Xiangli; Ma, Huailei; Yang, Shu; Yang, Yanlian; Hu, Zhiyuan

    2015-01-14

    The early diagnosis of Alzheimer's disease (AD) is challenging due to the lack of reliable methods for detecting its biomarkers in the noninvasive biopsies. We used surface plasmon resonance imaging to identify AD based on the detection of amyloid-beta42 in the serum by the ADP3 peptoid. PMID:25418132

  12. pH-dependence of the specific binding of Cu(II) and Zn(II) ions to the amyloid-{beta} peptide

    SciTech Connect

    Ghalebani, Leila; Wahlstroem, Anna; Danielsson, Jens; Waermlaender, Sebastian K.T.S.; Graeslund, Astrid

    2012-05-11

    Highlights: Black-Right-Pointing-Pointer Cu(II) and Zn(II) display pH-dependent binding to the A{beta}(1-40) peptide. Black-Right-Pointing-Pointer At pH 7.4 both metal ions display residue-specific binding to the A{beta} peptide. Black-Right-Pointing-Pointer At pH 5.5 the binding specificity is lost for Zn(II). Black-Right-Pointing-Pointer Differential Cu(II) and Zn(II) binding may help explain metal-induced AD toxicity. -- Abstract: Metal ions like Cu(II) and Zn(II) are accumulated in Alzheimer's disease amyloid plaques. The amyloid-{beta} (A{beta}) peptide involved in the disease interacts with these metal ions at neutral pH via ligands provided by the N-terminal histidines and the N-terminus. The present study uses high-resolution NMR spectroscopy to monitor the residue-specific interactions of Cu(II) and Zn(II) with {sup 15}N- and {sup 13}C,{sup 15}N-labeled A{beta}(1-40) peptides at varying pH levels. At pH 7.4 both ions bind to the specific ligands, competing with one another. At pH 5.5 Cu(II) retains its specific histidine ligands, while Zn(II) seems to lack residue-specific interactions. The low pH mimics acidosis which is linked to inflammatory processes in vivo. The results suggest that the cell toxic effects of redox active Cu(II) binding to A{beta} may be reversed by the protective activity of non-redox active Zn(II) binding to the same major binding site under non-acidic conditions. Under acidic conditions, the protective effect of Zn(II) may be decreased or changed, since Zn(II) is less able to compete with Cu(II) for the specific binding site on the A{beta} peptide under these conditions.

  13. Hippocampal Injections of Oligomeric Amyloid β-peptide (1–42) Induce Selective Working Memory Deficits and Long-lasting Alterations of ERK Signaling Pathway

    PubMed Central

    Faucher, Pierre; Mons, Nicole; Micheau, Jacques; Louis, Caroline; Beracochea, Daniel J.

    2016-01-01

    Increasing evidence suggests that abnormal brain accumulation of soluble rather than aggregated amyloid-β1–42 oligomers (Aβo(1–42)) plays a causal role in Alzheimer’s disease (AD). However, as yet, animal’s models of AD based on oligomeric amyloid-β1–42 injections in the brain have not investigated their long-lasting impacts on molecular and cognitive functions. In addition, the injections have been most often performed in ventricles, but not in the hippocampus, in spite of the fact that the hippocampus is importantly involved in memory processes and is strongly and precociously affected during the early stages of AD. Thus, in the present study, we investigated the long-lasting impacts of intra-hippocampal injections of oligomeric forms of Aβo(1–42) on working and spatial memory and on the related activation of ERK1/2. Indeed, the extracellular signal-regulated kinase (ERK) which is involved in memory function had been found to be activated by amyloid peptides. We found that repeated bilateral injections (1injection/day over 4 successive days) of oligomeric forms of Aβo(1–42) into the dorsal hippocampus lead to long-lasting impairments in two working memory tasks, these deficits being observed 7 days after the last injection, while spatial memory remained unaffected. Moreover, the working memory deficits were correlated with sustained impairments of ERK1/2 activation in the medial prefrontal cortex (mPFC) and the septum, two brain areas tightly connected with the hippocampus and involved in working memory. Thus, our study is first to evidence that sub-chronic injections of oligomeric forms of Aβo(1–42) into the dorsal hippocampus produces the main sign of cognitive impairments corresponding to the early stages of AD, via long-lasting alterations of an ERK/MAPK pathway in an interconnected brain networks. PMID:26793098

  14. Hippocampal Injections of Oligomeric Amyloid β-peptide (1-42) Induce Selective Working Memory Deficits and Long-lasting Alterations of ERK Signaling Pathway.

    PubMed

    Faucher, Pierre; Mons, Nicole; Micheau, Jacques; Louis, Caroline; Beracochea, Daniel J

    2015-01-01

    Increasing evidence suggests that abnormal brain accumulation of soluble rather than aggregated amyloid-β1-42 oligomers (Aβo(1-42)) plays a causal role in Alzheimer's disease (AD). However, as yet, animal's models of AD based on oligomeric amyloid-β1-42 injections in the brain have not investigated their long-lasting impacts on molecular and cognitive functions. In addition, the injections have been most often performed in ventricles, but not in the hippocampus, in spite of the fact that the hippocampus is importantly involved in memory processes and is strongly and precociously affected during the early stages of AD. Thus, in the present study, we investigated the long-lasting impacts of intra-hippocampal injections of oligomeric forms of Aβo(1-42) on working and spatial memory and on the related activation of ERK1/2. Indeed, the extracellular signal-regulated kinase (ERK) which is involved in memory function had been found to be activated by amyloid peptides. We found that repeated bilateral injections (1injection/day over 4 successive days) of oligomeric forms of Aβo(1-42) into the dorsal hippocampus lead to long-lasting impairments in two working memory tasks, these deficits being observed 7 days after the last injection, while spatial memory remained unaffected. Moreover, the working memory deficits were correlated with sustained impairments of ERK1/2 activation in the medial prefrontal cortex (mPFC) and the septum, two brain areas tightly connected with the hippocampus and involved in working memory. Thus, our study is first to evidence that sub-chronic injections of oligomeric forms of Aβo(1-42) into the dorsal hippocampus produces the main sign of cognitive impairments corresponding to the early stages of AD, via long-lasting alterations of an ERK/MAPK pathway in an interconnected brain networks. PMID:26793098

  15. Ferrous iron formation following the co-aggregation of ferric iron and the Alzheimer's disease peptide β-amyloid (1–42)

    PubMed Central

    Everett, J.; Céspedes, E.; Shelford, L. R.; Exley, C.; Collingwood, J. F.; Dobson, J.; van der Laan, G.; Jenkins, C. A.; Arenholz, E.; Telling, N. D.

    2014-01-01

    For decades, a link between increased levels of iron and areas of Alzheimer's disease (AD) pathology has been recognized, including AD lesions comprised of the peptide β-amyloid (Aβ). Despite many observations of this association, the relationship between Aβ and iron is poorly understood. Using X-ray microspectroscopy, X-ray absorption spectroscopy, electron microscopy and spectrophotometric iron(II) quantification techniques, we examine the interaction between Aβ(1–42) and synthetic iron(III), reminiscent of ferric iron stores in the brain. We report Aβ to be capable of accumulating iron(III) within amyloid aggregates, with this process resulting in Aβ-mediated reduction of iron(III) to a redox-active iron(II) phase. Additionally, we show that the presence of aluminium increases the reductive capacity of Aβ, enabling the redox cycling of the iron. These results demonstrate the ability of Aβ to accumulate iron, offering an explanation for previously observed local increases in iron concentration associated with AD lesions. Furthermore, the ability of iron to form redox-active iron phases from ferric precursors provides an origin both for the redox-active iron previously witnessed in AD tissue, and the increased levels of oxidative stress characteristic of AD. These interactions between Aβ and iron deliver valuable insights into the process of AD progression, which may ultimately provide targets for disease therapies. PMID:24671940

  16. Mycoplasma hyorhinis markedly degrades β-amyloid peptides in vitro and ex vivo: a novel biological approach for treating Alzheimer’s disease?

    PubMed Central

    Habib, Ahsan; Deng, Juan; Hou, Huayan; Zou, Qiang; Giunta, Brian; Wang, Yan-Jiang; Obregon, Demian; Sawmiller, Darrell; Li, Song; Mori, Takashi; Tan, Jun

    2013-01-01

    Accumulation of amyloid-β (Aβ) peptides (predominantly Aβ40, 42) and their aggregation into plaques in the brain are thought to be the one of the major causes of Alzheimer’s disease (AD). Originally discovered in our Chinese hamster ovary (CHO) cell line stably expressing human wild-type amyloid precursor protein (APP) (CHO/APPwt) cultures devoid of Aβ production, we found that Mycoplasma selectively degrades soluble Aβ in a time and dose (colony forming unit) dependent manner. Moreover, we fully characterized the Mycoplasma species as Mycoplasma hyorhinis (M. hyorhinis) by genetic and colony morphological analyses by light microscopy. Most interestingly, we attenuated the pathogenicity of M. hyorhinis by γ irradiation (3.5 Gy), and found that its ability to degrade Aβ was retained. On the other hand, heated and sonicated M. hyorhinis failed to retain this ability to degrade Aβ, suggesting that this degradation requires viable cells and likely a biologically active signaling pathway. In addition, we found that M. hyorhinis can degrade Aβ produced in AD model mice (PSAPP mice) ex vivo. Finally, we found that irradiated (non-pathogenic) M. hyorhinis also can degrade Aβ produced in PSAPP mice in vivo. These studies suggest that irradiated (non-pathogenic) M. hyorhinis can be a novel and alternative biological strategy for AD treatment. PMID:24093060

  17. Design, synthesis, and evaluation of Trolox-conjugated amyloid-β C-terminal peptides for therapeutic intervention in an in vitro model of Alzheimer's disease.

    PubMed

    Arai, Takuya; Ohno, Akiko; Kazunori, Mori; Kakizawa, Taeko; Kuwata, Hiroshi; Ozawa, Toshihiko; Shibanuma, Motoko; Hara, Shuntaro; Ishida, Seiichi; Kurihara, Masaaki; Miyata, Naoki; Nakagawa, Hidehiko; Fukuhara, Kiyoshi

    2016-09-15

    Two hallmarks of Alzheimer's disease (AD) observed in the brains of patients with the disease include oxidative injury and deposition of protein aggregates comprised of amyloid-β (Aβ) variants. To inhibit these toxic processes, we synthesized antioxidant-conjugated peptides comprised of Trolox and various C-terminal motifs of Aβ variants, TxAβx-n (x=34, 36, 38, 40; n=40, 42, 43). Most of these compounds were found to exhibit anti-aggregation activities. Among them, TxAβ36-42 significantly inhibited Aβ1-42 aggregation, showed potent antioxidant activity, and protected SH-SY5Y cells from Aβ1-42-induced cytotoxicity. Thus, this method represents a promising strategy for developing multifunctional AD therapeutic agents.

  18. Alzheimer’s Disease Peptide Epitope Vaccine Reduces Insoluble But Not Soluble/Oligomeric Aβ Species in Amyloid Precursor Protein Transgenic Mice

    PubMed Central

    Petrushina, Irina; Ghochikyan, Anahit; Mktrichyan, Mikayel; Mamikonyan, Gregory; Movsesyan, Nina; Davtyan, Hayk; Patel, Archita; Head, Elizabeth; Cribbs, David H.; Agadjanyan, Michael G.

    2008-01-01

    Active vaccination of elderly Alzheimer’s disease (AD) patients with fibrillar amyloidpeptide (Aβ42), even in the presence of a potent Th1 adjuvant, induced generally low titers of antibodies in a small fraction (~20% responders) of those that received the AN-1792 vaccine. To improve the immunogenicity and reduce the likelihood of inducing adverse autoreactive T-cells specific for Aβ42, we previously tested in wild-type mice an alternative approach for active immunization: an epitope vaccine that selectively initiate B cell responses toward an immunogenic self-epitope of Aβ in the absence of anti-Aβ T cell responses. Here, we describe a second generation epitope vaccine composed of two copies of Aβ1–11 fused with the promiscuous nonself T cell epitope, PADRE (pan human leukocyte antigen DR-binding peptide) that completely eliminates the autoreactive T cell responses and induces humoral immune responses in amyloid precursor protein transgenic 2576 mice with pre-existing AD-like pathology. Based on the titers of anti-Aβ1–11 antibody experimental mice were divided into low, moderate and high responders, and for the first time we report a positive correlation between the concentration of anti-Aβ1–11 antibody and a reduction of insoluble, cerebral Aβ plaques. The reduction of insoluble Aβ deposition was not associated with adverse events, such as CNS T cell or macrophage infiltration or microhemorrhages. Surprisingly, vaccination did not alter the levels of soluble Aβ. Alternatively, early protective immunization before substantial neuropathology, neuronal loss and cognitive deficits have become firmly established may be more beneficial and safer for potential patients, especially if they can be identified in a preclinical stage by the development of antecedent biomarkers of AD. PMID:18003852

  19. Rescue of amyloid-Beta-induced inhibition of nicotinic acetylcholine receptors by a peptide homologous to the nicotine binding domain of the alpha 7 subtype.

    PubMed

    Nery, Arthur A; Magdesian, Margaret H; Trujillo, Cleber A; Sathler, Luciana B; Juliano, Maria A; Juliano, Luiz; Ulrich, Henning; Ferreira, Sergio T

    2013-01-01

    Alzheimer's disease (AD) is characterized by brain accumulation of the neurotoxic amyloidpeptide (Aβ) and by loss of cholinergic neurons and nicotinic acetylcholine receptors (nAChRs). Recent evidence indicates that memory loss and cognitive decline in AD correlate better with the amount of soluble Aβ than with the extent of amyloid plaque deposits in affected brains. Inhibition of nAChRs by soluble Aβ40 is suggested to contribute to early cholinergic dysfunction in AD. Using phage display screening, we have previously identified a heptapeptide, termed IQ, homologous to most nAChR subtypes, binding with nanomolar affinity to soluble Aβ40 and blocking Aβ-induced inhibition of carbamylcholine-induced currents in PC12 cells expressing α7 nAChRs. Using alanine scanning mutagenesis and whole-cell current recording, we have now defined the amino acids in IQ essential for reversal of Aβ40 inhibition of carbamylcholine-induced responses in PC12 cells, mediated by α7 subtypes and other endogenously expressed nAChRs. We further investigated the effects of soluble Aβ, IQ and analogues of IQ on α3β4 nAChRs recombinantly expressed in HEK293 cells. Results show that nanomolar concentrations of soluble Aβ40 potently inhibit the function of α3β4 nAChRs, and that subsequent addition of IQ or its analogues does not reverse this effect. However, co-application of IQ makes the inhibition of α3β4 nAChRs by Aβ40 reversible. These findings indicate that Aβ40 inhibits different subtypes of nAChRs by interacting with specific receptor domains homologous to the IQ peptide, suggesting that IQ may be a lead for novel drugs to block the inhibition of cholinergic function in AD.

  20. Physical, morphological and functional differences between ph 5.8 and 7.4 aggregates of the Alzheimer's amyloid peptide Abeta.

    PubMed

    Wood, S J; Maleeff, B; Hart, T; Wetzel, R

    1996-03-15

    The Alzheimer's amyloid peptide Abeta(1-40) generates a turbid, Congo re-binding aggregation reaction product within minutes when incubated in the pH range 5 to 6. At pH 7.4, Abeta forms little or no aggregate in this time frame, requiring hours or days, rather than minutes, to complete fibril formation. The pH 5.8 aggregates are not amyloid fibrils, but rather appear in electron micrographs as a mixture of larger particles of different morphologies. These aggregates differ from classical fibrils by a number of other measures. Per mass of peptide aggregated, the pH 5.8 product binds less Congo red and thioflavin T than does aggregate grow in unstirred reactions at pH 7.4. Both the pH 5.8 and 7.4 aggregates exhibit light scattering at 90 degrees. However, while the pH 5.8 aggregate is visible in suspension by the light microscopy, and exhibits turbidity at 405 nm, the fibrils grown at pH 7.4 in an unstirred reaction are transparent. The two aggregate types do not interconvert in pH shift experiments. Most dramatically, and in contrast to fibrils grown at pH 7.4, the turbid aggregate generated at pH 5.8 is incapable of seeding fibril growth at pH 7.4. Although proteolytic processing of betaAPP to generate Abeta probably takes place in a low pH compartment of the cell, our results suggest that fibril formation is not likely to be initiated in such an environment.

  1. Transfer of Copper from an Amyloid to a Natural Copper-Carrier Peptide with a Specific Mediating Ligand.

    PubMed

    Nguyen, Michel; Bijani, Christian; Martins, Nathalie; Meunier, Bernard; Robert, Anne

    2015-11-16

    The oxidative stress that arises from the catalytic reduction of dioxygen by Cu(II/I)-loaded amyloids is the major pathway for neuron death that occurs in Alzheimer's disease. In this work, we show that bis-8(aminoquinoline) ligands, copper(II) specific chelators, are able to catalytically extract Cu(II) from Cu-Aβ1-16 and then completely release Cu(I) in the presence of glutathione to provide a Cu(I)-glutathione complex, a biological intermediate that is able to deliver copper to apo forms of copper-protein complexes. These data demonstrate that bis-8(aminoquinolines) can perform the transfer of copper ions from the pathological Cu-amyloid complexes to regular copper-protein complexes. These copper-specific ligands assist GSH to recycle Cu(I) in an AD brain and consequently slow down oxidative damage that is due to copper dysregulation in Alzheimer's disease. Under the same conditions, we have shown that the copper complex of PBT2, a mono(8-hydroxyquinoline) previously used as a drug candidate, does not efficiently release copper in the presence of GSH. In addition, we report that GSH itself was unable to fully abstract copper ions from Cu-β-amyloid complexes.

  2. Amyloid Aggregation and Membrane Disruption by Amyloid Proteins

    NASA Astrophysics Data System (ADS)

    Ramamoorthy, Ayyalusamy

    2013-03-01

    Amyloidogenesis has been the focus of intense basic and clinical research, as an increasing number of amyloidogenic proteins have been linked to common and incurable degenerative diseases including Alzheimer's, type II diabetes, and Parkinson's. Recent studies suggest that the cell toxicity is mainly due to intermediates generated during the assembly process of amyloid fibers, which have been proposed to attack cells in a variety of ways. Disruption of cell membranes is believed to be one of the key components of amyloid toxicity. However, the mechanism by which this occurs is not fully understood. Our research in this area is focused on the investigation of the early events in the aggregation and membrane disruption of amyloid proteins, Islet amyloid polypeptide protein (IAPP, also known as amylin) and amyloid-beta peptide, on the molecular level. Structural insights into the mechanisms of membrane disruption by these amyloid proteins and the role of membrane components on the membrane disruption will be presented.

  3. The amyloid precursor protein: beyond amyloid

    PubMed Central

    Zheng, Hui; Koo, Edward H

    2006-01-01

    The amyloid precursor protein (APP) takes a central position in Alzheimer's disease (AD) pathogenesis: APP processing generates the β-amyloid (Aβ) peptides, which are deposited as the amyloid plaques in brains of AD individuals; Point mutations and duplications of APP are causal for a subset of early onset of familial Alzheimer's disease (FAD). Not surprisingly, the production and pathogenic effect of Aβ has been the central focus in AD field. Nevertheless, the biological properties of APP have also been the subject of intense investigation since its identification nearly 20 years ago as it demonstrates a number of interesting putative physiological roles. Several attractive models of APP function have been put forward recently based on in vitro biochemical studies. Genetic analyses of gain- and loss-of-function mutants in Drosophila and mouse have also revealed important insights into its biological activities in vivo. This article will review the current understanding of APP physiological functions. PMID:16930452

  4. Simulations of monomeric amyloid β-peptide (1-40) with varying solution conditions and oxidation state of Met35: implications for aggregation.

    PubMed

    Brown, Anne M; Lemkul, Justin A; Schaum, Nicholas; Bevan, David R

    2014-03-01

    The amyloid β-peptide (Aβ) is a 40-42 residue peptide that is the principal toxic species in Alzheimer's disease (AD). The oxidation of methionine-35 (Met35) to the sulfoxide form (Met35(ox)) has been identified as potential modulator of Aβ aggregation. The role Met35(ox) plays in Aβ neurotoxicity differs among experimental studies, which may be due to inconsistent solution conditions (pH, buffer, temperature). We applied atomistic molecular dynamics (MD) simulations as a means to probe the dynamics of the monomeric 40-residue alloform of Aβ (Aβ40) containing Met35 or Met35(ox) in an effort to resolve the conflicting experimental results. We found that Met35 oxidation decreases the β-strand content of the C-terminal hydrophobic region (residues 29-40), with a specific effect on the secondary structure of residues 33-35, thus potentially impeding aggregation. Further, there is an important interplay between oxidation state and solution conditions, with pH and salt concentration augmenting the effects of oxidation. The results presented here serve to rationalize the conflicting results seen in experimental studies and provide a fundamental biophysical characterization of monomeric Aβ40 dynamics in both reduced and oxidized forms, providing insight into the biochemical mechanism of Aβ40 and oxidative stress related to AD.

  5. A novel inhibitor of amyloid β (Aβ) peptide aggregation: from high throughput screening to efficacy in an animal model of Alzheimer disease.

    PubMed

    McKoy, Angela Fortner; Chen, Jermont; Schupbach, Trudi; Hecht, Michael H

    2012-11-01

    Compelling evidence indicates that aggregation of the amyloid β (Aβ) peptide is a major underlying molecular culprit in Alzheimer disease. Specifically, soluble oligomers of the 42-residue peptide (Aβ42) lead to a series of events that cause cellular dysfunction and neuronal death. Therefore, inhibiting Aβ42 aggregation may be an effective strategy for the prevention and/or treatment of disease. We describe the implementation of a high throughput screen for inhibitors of Aβ42 aggregation on a collection of 65,000 small molecules. Among several novel inhibitors isolated by the screen, compound D737 was most effective in inhibiting Aβ42 aggregation and reducing Aβ42-induced toxicity in cell culture. The protective activity of D737 was most significant in reducing the toxicity of high molecular weight oligomers of Aβ42. The ability of D737 to prevent Aβ42 aggregation protects against cellular dysfunction and reduces the production/accumulation of reactive oxygen species. Most importantly, treatment with D737 increases the life span and locomotive ability of flies in a Drosophila melanogaster model of Alzheimer disease.

  6. Aging, gender and APOE isotype modulate metabolism of Alzheimer's Abeta peptides and F-isoprostanes in the absence of detectable amyloid deposits.

    PubMed

    Yao, Jun; Petanceska, Suzana S; Montine, Thomas J; Holtzman, David M; Schmidt, Stephen D; Parker, Carolyn A; Callahan, Michael J; Lipinski, William J; Bisgaier, Charles L; Turner, Brian A; Nixon, Ralph A; Martins, Ralph N; Ouimet, Charles; Smith, Jonathan D; Davies, Peter; Laska, Eugene; Ehrlich, Michelle E; Walker, Lary C; Mathews, Paul M; Gandy, Sam

    2004-08-01

    Aging and apolipoprotein E (APOE) isoform are among the most consistent risks for the development of Alzheimer's disease (AD). Metabolic factors that modulate risk have been elusive, though oxidative reactions and their by-products have been implicated in human AD and in transgenic mice with overt histological amyloidosis. We investigated the relationship between the levels of endogenous murine amyloid beta (Abeta) peptides and the levels of a marker of oxidation in mice that never develop histological amyloidosis [i.e. APOE knockout (KO) mice with or without transgenic human APOEepsilon3 or human APOEepsilon4 alleles]. Aging-, gender-, and APOE-genotype-dependent changes were observed for endogenous mouse brain Abeta40 and Abeta42 peptides. Levels of the oxidized lipid F2-isoprostane (F2-isoPs) in the brains of the same animals as those used for the Abeta analyses revealed aging- and gender-dependent changes in APOE KO and in human APOEepsilon4 transgenic KO mice. Human APOEepsilon3 transgenic KO mice did not exhibit aging- or gender-dependent increases in F2-isoPs. In general, the changes in the levels of brain F2-isoPs in mice according to age, gender, and APOE genotype mirrored the changes in brain Abeta levels, which, in turn, paralleled known trends in the risk for human AD. These data indicate that there exists an aging-dependent, APOE-genotype-sensitive rise in murine brain Abeta levels despite the apparent inability of the peptide to form histologically detectable amyloid. Human APOEepsilon3, but not human APOEepsilon4, can apparently prevent the aging-dependent rise in murine brain Abeta levels, consistent with the relative risk for AD associated with these genotypes. The fidelity of the brain Abeta/F2-isoP relationship across multiple relevant variables supports the hypothesis that oxidized lipids play a role in AD pathogenesis, as has been suggested by recent evidence that F2-isoPs can stimulate Abeta generation and aggregation.

  7. The recombinant C-terminal fragment of tetanus toxin protects against cholinotoxicity by intraseptal injection of β-amyloid peptide (25-35) in rats.

    PubMed

    Patricio-Martínez, A; Mendieta, L; Martínez, I; Aguilera, J; Limón, I D

    2016-02-19

    The recombinant C-terminal domain of tetanus toxin (Hc-TeTx) is a new non-toxic peptide of the tetanus toxin that exerts a protective action against glutamate excitotoxicity in motoneurons. Moreover, its efficacy as a neuroprotective agent has been demonstrated in several animal models of neurodegeneration. The eleven amino acids in the β amyloid peptide (Aβ25-35) mimic the toxic effects of the full β amyloid peptide (Aβ1-42), causing the impairment of the cholinergic system in the medial septum (MS) which, in turn, alters the septo-hippocampal pathway and leads to learning and memory impairments. The aim of this study was to examine the neuroprotective effects of the Hc-TeTx fragment against cholinotoxicity. The Hc-TeTx fragment (100 ng) was injected into the rats intercranially, with the Aβ(25-35) (2 μg) then injected into their MS. The animals were tested for spatial learning and memory in the eight-arm radial maze. The brains were removed to assess cholinergic markers, such as choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), and to explore neurodegeneration in the MS and hippocampus, using amino-cupric silver and H&E staining. Finally, capase-3, a marker of apoptosis, was examined in the MS. Our results clearly demonstrate that the application of Hc-TeTx prevents the loss of cholinergic markers (ChAT and AChE), the activation of capase-3, and neurodegeneration in the MS and the CA1 and CA3 subfields of the hippocampus. All these improvements were reflected in spatial learning and memory performance, and were significantly higher compared with animals treated with Aβ(25-35). Interestingly, the single administration of Hc-TeTx into the MS modified the ChAT and AChE expression that affect cognitive processes, without inducing neurodegeneration or an increase in capase-3 expression in the MS and hippocampus. In summary, our findings suggest that the recombinant Hc-TeTx fragment offers effective protection for the septo-hippocampal pathway

  8. Platinum nanostructures via self-assembly of an amyloid-like peptide: a novel electrocatalyst for the oxygen reduction

    NASA Astrophysics Data System (ADS)

    Zhou, Binbin; Sun, Zhifang; Li, Ding; Zhang, Ting; Deng, Liu; Liu, You-Nian

    2013-03-01

    An aniline-GGAAKLVFF peptide (AFP) was prepared by solid-phase synthesis. The peptide can readily self-assemble into fibrils. Platinum nanoparticles (Pt NPs) were directly immobilized on the surface of the AFP fibrils via electrostatic interaction. Compared to other currently available techniques for the fabrication of metal-peptide fibrils, the noncovalent functionalization strategy is able to deposit nanoparticles on peptide fibrils with different morphologies and high metal loading, which is important for applications in catalysis, electronic materials and other corresponding fields. The Pt-AFP fibrils were employed to modify the electrode, which exhibits high electrocatalytic activities towards oxygen reduction. Thus, the Pt-AFP fibrils hold great potential for polymer electrolyte fuel cells and other electrochemical applications.An aniline-GGAAKLVFF peptide (AFP) was prepared by solid-phase synthesis. The peptide can readily self-assemble into fibrils. Platinum nanoparticles (Pt NPs) were directly immobilized on the surface of the AFP fibrils via electrostatic interaction. Compared to other currently available techniques for the fabrication of metal-peptide fibrils, the noncovalent functionalization strategy is able to deposit nanoparticles on peptide fibrils with different morphologies and high metal loading, which is important for applications in catalysis, electronic materials and other corresponding fields. The Pt-AFP fibrils were employed to modify the electrode, which exhibits high electrocatalytic activities towards oxygen reduction. Thus, the Pt-AFP fibrils hold great potential for polymer electrolyte fuel cells and other electrochemical applications. Electronic supplementary information (ESI) available: Materials, apparatus, synthesis of AFP and Pt NPs, scheme of AFP and Fig. S1-S3. See DOI: 10.1039/c3nr33998j

  9. Aggregation of amyloid Abeta((1-40)) peptide in perdeuterated 2,2,2-trifluoroethanol caused by ultrasound sonication.

    PubMed

    Filippov, Andrei V; Gröbner, Gerhard; Antzutkin, Oleg N

    2010-06-01

    Ultrasound sonication of protein and peptide solutions is routinely used in biochemical, biophysical, pharmaceutical and medical sciences to facilitate and accelerate dissolution of macromolecules in both aqueous and organic solvents. However, the impact of ultrasound waves on folding/unfolding of treated proteins, in particular, on aggregation kinetics of amyloidogenic peptides and proteins is not understood. In this work, effects of ultrasound sonication on the misfolding and aggregation behavior of the Alzheimer's Abeta((1-40))-peptide is studied by pulsed-field gradient (PFG) spin-echo diffusion NMR and UV circular dichroism (CD) spectroscopy. Upon simple dissolution of Abeta((1-40)) in perdeuterated trifluoroethanol, CF(3)-CD(2)-OD (TFE-d(3)), the peptide is present in the solution as a stable monomer adopting alpha-helical secondary structural motifs. The self-diffusion coefficient of Abeta((1-40)) monomers in TFE-d(3) was measured as 1.35 x 10(-10) m(2) s(-1), reflecting its monomeric character. However, upon ultrasonic sonication for less than 5 min, considerable populations of Abeta molecules (ca 40%) form large aggregates as reflected in diffusion coefficients smaller than 4.0 x 10(-13) m(2) s(-1). Sonication for longer times (up to 40 min in total) effectively reduces the fraction of these aggregates in (1)H PFG NMR spectra to ca 25%. Additionally, absorption below 230 nm increased significantly upon sonication treatment, an observation, which also clearly confirms the ongoing aggregation process of Abeta((1-40)) in TFE-d(3). Surprisingly, upon ultrasound sonication only small changes in the peptide secondary structure were detected by CD: the peptide molecules mainly adopt alpha-helical motifs in both monomers and aggregates formed upon sonication. PMID:20474020

  10. Influence of the solvent on the self-assembly of a modified amyloid beta peptide fragment. II. NMR and computer simulation investigation.

    PubMed

    Hamley, I W; Nutt, D R; Brown, G D; Miravet, J F; Escuder, B; Rodríguez-Llansola, F

    2010-01-21

    The conformation of a model peptide AAKLVFF based on a fragment of the amyloid beta peptide Abeta16-20, KLVFF, is investigated in methanol and water via solution NMR experiments and molecular dynamics computer simulations. In previous work, we have shown that AAKLVFF forms peptide nanotubes in methanol and twisted fibrils in water. Chemical shift measurements were used to investigate the solubility of the peptide as a function of concentration in methanol and water. This enabled the determination of critical aggregation concentrations. The solubility was lower in water. In dilute solution, diffusion coefficients revealed the presence of intermediate aggregates in concentrated solution, coexisting with NMR-silent larger aggregates, presumed to be beta-sheets. In water, diffusion coefficients did not change appreciably with concentration, indicating the presence mainly of monomers, coexisting with larger aggregates in more concentrated solution. Concentration-dependent chemical shift measurements indicated a folded conformation for the monomers/intermediate aggregates in dilute methanol, with unfolding at higher concentration. In water, an antiparallel arrangement of strands was indicated by certain ROESY peak correlations. The temperature-dependent solubility of AAKLVFF in methanol was well described by a van't Hoff analysis, providing a solubilization enthalpy and entropy. This pointed to the importance of solvophobic interactions in the self-assembly process. Molecular dynamics simulations constrained by NOE values from NMR suggested disordered reverse turn structures for the monomer, with an antiparallel twisted conformation for dimers. To model the beta-sheet structures formed at higher concentration, possible model arrangements of strands into beta-sheets with parallel and antiparallel configurations and different stacking sequences were used as the basis for MD simulations; two particular arrangements of antiparallel beta-sheets were found to be stable, one

  11. Amyloid-beta induced CA1 pyramidal cell loss in young adult rats is alleviated by systemic treatment with FGL, a neural cell adhesion molecule-derived mimetic peptide.

    PubMed

    Corbett, Nicola J; Gabbott, Paul L; Klementiev, Boris; Davies, Heather A; Colyer, Frances M; Novikova, Tatiana; Stewart, Michael G

    2013-01-01

    Increased levels of neurotoxic amyloid-beta in the brain are a prominent feature of Alzheimer's disease. FG-Loop (FGL), a neural cell adhesion molecule-derived peptide that corresponds to its second fibronectin type III module, has been shown to provide neuroprotection against a range of cellular insults. In the present study impairments in social recognition memory were seen 24 days after a 5 mg/15 µl amyloid-beta(25-35) injection into the right lateral ventricle of the young adult rat brain. This impairment was prevented if the animal was given a systemic treatment of FGL. Unbiased stereology was used to investigate the ability of FGL to alleviate the deleterious effects on CA1 pyramidal cells of the amyloid-beta(25-35) injection. NeuN, a neuronal marker (for nuclear staining) was used to identify pyramidal cells, and immunocytochemistry was also used to identify inactive glycogen synthase kinase 3beta (GSK3β) and to determine the effects of amyloid-beta(25-35) and FGL on the activation state of GSK3β, since active GSK3β has been shown to cause a range of AD pathologies. The cognitive deficits were not due to hippocampal atrophy as volume estimations of the entire hippocampus and its regions showed no significant loss, but amyloid-beta caused a 40% loss of pyramidal cells in the dorsal CA1 which was alleviated partially by FGL. However, FGL treatment without amyloid-beta was also found to cause a 40% decrease in CA1 pyramidal cells. The action of FGL may be due to inactivation of GSK3β, as an increased proportion of CA1 pyramidal neurons contained inactive GSK3β after FGL treatment. These data suggest that FGL, although potentially disruptive in non-pathological conditions, can be neuroprotective in disease-like conditions.

  12. Dual effects of familial Alzheimer's disease mutations (D7H, D7N, and H6R) on amyloid β peptide: correlation dynamics and zinc binding.

    PubMed

    Xu, Liang; Chen, Yonggang; Wang, Xiaojuan

    2014-12-01

    Although the N-terminal region of Amyloid β (Aβ) peptides plays dual roles as metal-coordinating sites and conformational modulator, few studies have been performed to explore the effects of mutations at this region on the overall conformational ensemble of Aβ and the binding propensity of metal ions. In this work, we focus on how three familial Alzheimer's disease mutations (D7H, D7N, and H6R) alter the structural characteristics and thermodynamic stabilities of Aβ42 using molecular dynamics simulations. We observe that each mutation displays increased β-sheet structures in both N and C termini. In particular, both the N terminus and central hydrophobic region of D7H can form stable β-hairpin structures with its C terminus. The conserved turn structure at Val²⁴-Lys²⁸ in all peptides and Zn²⁺-bound Aβ42 is confirmed as the common structural motif to nucleate folding of Aβ. Each mutant can significantly increase the solvation free energy and thus enhance the aggregation of Aβ monomers. The correlation dynamics between Aβ(1-16) and Aβ(17-42) fragments are elucidated by linking the domain motions with the corresponding structured conformations. We characterize the different populations of correlated domain motions for each mutant from a more macroscopic perspective, and unexpectedly find that Zn²⁺-bound Aβ42 ensemble shares the same populations as Aβ42, indicating that the binding of Zn²⁺ to Aβ follows the conformational selection mechanism, and thus is independent of domain motions, even though the structures of Aβ have been modified at a residue level.

  13. Effects of Transmitters and Amyloid-Beta Peptide on Calcium Signals in Rat Cortical Astrocytes: Fura-2AM Measurements and Stochastic Model Simulations

    PubMed Central

    Toivari, Eeva; Manninen, Tiina; Nahata, Amit K.; Jalonen, Tuula O.; Linne, Marja-Leena

    2011-01-01

    Background To better understand the complex molecular level interactions seen in the pathogenesis of Alzheimer's disease, the results of the wet-lab and clinical studies can be complemented by mathematical models. Astrocytes are known to become reactive in Alzheimer's disease and their ionic equilibrium can be disturbed by interaction of the released and accumulated transmitters, such as serotonin, and peptides, including amyloid- peptides (A). We have here studied the effects of small amounts of A25–35 fragments on the transmitter-induced calcium signals in astrocytes by Fura-2AM fluorescence measurements and running simulations of the detected calcium signals. Methodology/Principal Findings Intracellular calcium signals were measured in cultured rat cortical astrocytes following additions of serotonin and glutamate, or either of these transmitters together with A25–35. A25–35 increased the number of astrocytes responding to glutamate and exceedingly increased the magnitude of the serotonin-induced calcium signals. In addition to A25–35-induced effects, the contribution of intracellular calcium stores to calcium signaling was tested. When using higher stimulus frequency, the subsequent calcium peaks after the initial peak were of lower amplitude. This may indicate inadequate filling of the intracellular calcium stores between the stimuli. In order to reproduce the experimental findings, a stochastic computational model was introduced. The model takes into account the major mechanisms known to be involved in calcium signaling in astrocytes. Model simulations confirm the principal experimental findings and show the variability typical for experimental measurements. Conclusions/Significance Nanomolar A25–35 alone does not cause persistent change in the basal level of calcium in astrocytes. However, even small amounts of A25–35, together with transmitters, can have substantial synergistic effects on intracellular calcium signals. Computational modeling

  14. Restricted V gene usage and VH/VL pairing of mouse humoral response against the N-terminal immunodominant epitope of the amyloid β peptide

    PubMed Central

    Robert, Remy; Lefranc, Marie-Paule; Ghochikyan, Anahit; Agadjanyan, Michael G.; Cribbs, David H.; Van Nostrand, William E.; Wark, Kim L.; Dolezal, Olan

    2011-01-01

    Over the last decade, the potential of antibodies as therapeutic strategies to treat Alzheimer’s disease (AD) has been growing, based on successful experimental and clinical trials in transgenic mice. Despite, undesirable side effects in humans using an active immunization approach, immunotherapy still remains one of the most promising treatments for AD. In this study, we analyzed the V genes of twelve independently isolated monoclonal antibodies raised against the N-terminal immunodominant epitope of the amyloid β peptide (Aβ or A beta). Surprisingly, we found a high and unusual level of restriction in the VH/VL pairing of these antibodies. Moreover, these antibodies mostly differ in their heavy chain complementary determining region 3 (HCDR3) and the residues in the antibodies which contact Aβ are already present in the germline V-genes. Based on these observations and or co-crystal structures of antibodies with Aβ, the aim of the current study was to better understand the role of antibody V-domains, HCDR3 regions, key contact residue (H58) and germline encoded residues in Aβ recognition. For that purpose, we designed and produced a range of recombinant Fab constructs. All the Fabs were tested and compared by surface plasmon resonance on Aβ1–16, Aβ1–42 high molecular weight and Aβ1–42 low molecular weight soluble oligomers. Although all the Fabs recognized the Aβ1–16 peptide and the Aβ1–42 high molecular weight soluble oligomers, they did not bind the Aβ1–42 low molecular weight soluble oligomers. Furthermore, we demonstrated that: (1) an aromatic residue at position H58 in the antibody is essential in the recognition of Aβ and (2) Fabs based on germline V-genes bind to Aβ monomers with a low affinity. These findings may have important implications in designing more effective therapeutic antibodies against Aβ. PMID:20970857

  15. Characterization of the internal dynamics and conformational space of zinc-bound amyloid β peptides by replica-exchange molecular dynamics simulations.

    PubMed

    Xu, Liang; Wang, Xiaojuan; Wang, Xicheng

    2013-07-01

    Amyloid β (Aβ) peptides and metal ions have been associated with the pathogenesis of Alzheimer's disease. The conformational space of Aβ fragments of different length with and without binding of metal ions has been extensively investigated by replica-exchange molecular dynamics (REMD) simulation. However, only trajectories extracted at relatively low temperatures have been used for this analysis. The capability of REMD simulations to characterize the internal dynamics of such intrinsically disordered proteins (IDPs) as Aβ has been overlooked. In this work, we use an approach recently developed by Xue and Skrynnikov (J Am Chem Soc 133:14614-14628, 2011) to calculate NMR observables, including (15)N relaxation rates and (15)N-(1)H nuclear Overhauser enhancement (NOE), from the high-temperature trajectory of REMD simulations for zinc-bound Aβ peptides. The time axis of the trajectory was rescaled to correct for the effect of the high temperature (408 K) compared with the experimental temperature (278 K). Near-quantitative agreement between simulated values and experimental results was obtained. When the structural properties and free-energy surfaces of zinc-bound Aβ(1-40) and Aβ(1-42) were compared at the physiological temperature 310 K it was found that zinc-bound Aβ(1-42) was more rigid than Aβ(1-40) at the C terminus, and its conformational transitions were also more preferred. The self-consistent results derived from trajectories at high and low temperatures demonstrate the capability of REMD simulations to capture the internal dynamics of IDPs.

  16. Cholesterol accelerates the binding of Alzheimer's β-amyloid peptide to ganglioside GM1 through a universal hydrogen-bond-dependent sterol tuning of glycolipid conformation

    PubMed Central

    Fantini, Jacques; Yahi, Nouara; Garmy, Nicolas

    2013-01-01

    Age-related alterations of membrane lipids in brain cell membranes together with high blood cholesterol are considered as major risk factors for Alzheimer's disease. Yet the molecular mechanisms by which these factors increase Alzheimer's risk are mostly unknown. In lipid raft domains of the plasma membrane, neurotoxic Alzheimer's beta-amyloid (Abeta) peptides interact with both cholesterol and ganglioside GM1. Recent data also suggested that cholesterol could stimulate the binding of Abeta to GM1 through conformational modulation of the ganglioside headgroup. Here we used a combination of physicochemical and molecular modeling approaches to decipher the mechanisms of cholesterol-assisted binding of Abeta to GM1. With the aim of decoupling the effect of cholesterol on GM1 from direct Abeta-cholesterol interactions, we designed a minimal peptide (Abeta5-16) containing the GM1-binding domain but lacking the amino acid residues involved in cholesterol recognition. Using the Langmuir technique, we showed that cholesterol (but not phosphatidylcholine or sphingomyelin) significantly accelerates the interaction of Abeta5-16 with GM1. Molecular dynamics simulations suggested that Abeta5-16 interacts with a cholesterol-stabilized dimer of GM1. The main structural effect of cholesterol is to establish a hydrogen-bond between its own OH group and the glycosidic-bond linking ceramide to the glycone part of GM1, thereby inducing a tilt in the glycolipid headgroup. This fine conformational tuning stabilizes the active conformation of the GM1 dimer whose headgroups, oriented in two opposite directions, form a chalice-shaped receptacle for Abeta. These data give new mechanistic insights into the stimulatory effect of cholesterol on Abeta/GM1 interactions. They also support the emerging concept that cholesterol is a universal modulator of protein-glycolipid interactions in the broader context of membrane recognition processes. PMID:23772214

  17. Solvent exposure of Tyr10 as a probe of structural differences between monomeric and aggregated forms of the amyloidpeptide

    PubMed Central

    Aran Terol, Pablo; Kumita, Janet R.; Hook, Sharon C.; Dobson, Christopher M.; Esbjörner, Elin K.

    2015-01-01

    Aggregation of amyloid-β (Aβ) peptides is a characteristic pathological feature of Alzheimer's disease. We have exploited the relationship between solvent exposure and intrinsic fluorescence of a single tyrosine residue, Tyr10, in the Aβ sequence to probe structural features of the monomeric, oligomeric and fibrillar forms of the 42-residue Aβ1-42. By monitoring the quenching of Tyr10 fluorescence upon addition of water-soluble acrylamide, we show that in Aβ1-42 oligomers this residue is solvent-exposed to a similar extent to that found in the unfolded monomer. By contrast, Tyr10 is significantly shielded from acrylamide quenching in Aβ1-42 fibrils, consistent with its proximity to the fibrillar cross-β core. Furthermore, circular dichroism measurements reveal that Aβ1-42 oligomers have a considerably lower β-sheet content than the Aβ1-42 fibrils, indicative of a less ordered molecular arrangement in the former. Taken together these findings suggest significant differences in the structural assembly of oligomers and fibrils that are consistent with differences in their biological effects. PMID:26551456

  18. Neutron Scattering Studies of the Interplay of Amyloid β Peptide(1-40) and An Anionic Lipid 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol.

    PubMed

    Rai, Durgesh K; Sharma, Veerendra K; Anunciado, Divina; O'Neill, Hugh; Mamontov, Eugene; Urban, Volker; Heller, William T; Qian, Shuo

    2016-01-01

    The interaction between lipid bilayers and Amyloid β peptide (Aβ) plays a critical role in proliferation of Alzheimer's disease (AD). AD is expected to affect one in every 85 humans by 2050, and therefore, deciphering the interplay of Aβ and lipid bilayers at the molecular level is of profound importance. In this work, we applied an array of neutron scattering methods to study the structure and dynamics of Aβ(1-40) interacting 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) bilayers. In the structural investigations of lipid bilayer's response to Aβ binding, Small Angle Neutron Scattering and Neutron Membrane Diffraction revealed that the Aβ anchors firmly to the highly charged DMPG bilayers in the interfacial region between water and hydrocarbon chain, and it doesn't penetrate deeply into the bilayer. This association mode is substantiated by the dynamics studies with high resolution Quasi-Elastic Neutron Scattering experiments, showing that the addition of Aβ mainly affects the slower lateral motion of lipid molecules, especially in the fluid phase, but not the faster internal motion. The results revealed that Aβ associates with the highly charged membrane in surface with limited impact on the structure, but the altered membrane dynamics could have more influence on other membrane processes. PMID:27503057

  19. Insights into the mechanism of methionine oxidation catalyzed by metal (Cu(2+), Zn(2+), and Fe(3+)) - amyloid beta (Abeta) peptide complexes: A computational study.

    PubMed

    Barman, Arghya; Taves, Woody; Prabhakar, Rajeev

    2009-07-15

    In this DFT study, a mechanism of the oxidation of methionine (Met) amino acid residue catalyzed by the metal (Cu(2+), Zn(2+), and Fe(3+)) bound amyloid beta (Abeta) peptide has been proposed. Based on experimental information, two different mechanisms: (1) stepwise and (2) concerted mechanisms for this important process have been investigated. The B3LYP calculations suggest that in the stepwise mechanism, the two separate pathways leading to the same sulfoxide product [Met(O)] go through prohibitively high barriers of 27.3 and 35.1 kcal/mol, therefore it is ruled out. In the concerted mechanism, the Cu(2+)-Abeta complex has been found to be the most efficient catalyst with the computed barrier of 14.3 kcal/mol. The substitutions of Cu(2+) by Zn(2+) and Fe(3+) increase barriers to 19.6 and 16.9 kcal/mol, respectively and make the reaction thermodynamically less favorable. It was also found that, in comparison with the cysteine (Cys) residue, Met is more susceptible toward oxidation. Its substitution with Cys slightly increased the barrier to 15.8 kcal/mol for the Cu(2+)-Abeta complex.

  20. Transcription factor NF-κB is activated in primary neurons by amyloid β peptides and in neurons surrounding early plaques from patients with Alzheimer disease

    PubMed Central

    Kaltschmidt, Barbara; Uherek, Martin; Volk, Benedikt; Baeuerle, Patrick A.; Kaltschmidt, Christian

    1997-01-01

    Amyloid β peptide (Aβ)-containing plaques are a hallmark of Alzheimer disease. Here, we show that the neurotoxic Aβ, a major plaque component, is a potent activator of the transcription factor NF-κB in primary neurons. This activation required reactive oxygen intermediates as messengers because an antioxidant prevented Aβ-induced NF-κB activation. Maximal activation of NF-κB was found with 0.1 μM Aβ-(1–40) and 0.1 μM Aβ-(25–35) fragments, making a role for NF-κB in neuroprotection feasible. Using an activity-specific mAb for the p65 NF-κB subunit, activation of NF-κB also was observed in neurons and astroglia of brain sections from Alzheimer disease patients. Activated NF-κB was restricted to cells in the close vicinity of early plaques. Our data suggest that the aberrant gene expression in diseased nervous tissue is at least in part due to Aβ-induced activation of NF-κB, a potent immediate–early transcriptional regulator of numerous proinflammatory genes. PMID:9122249

  1. Neutron Scattering Studies of the Interplay of Amyloid β Peptide(1–40) and An Anionic Lipid 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol

    DOE PAGESBeta

    Rai, Durgesh K.; Sharma, Veerendra K.; Anunciado, Divina; O’Neill, Hugh; Mamontov, Eugene; Urban, Volker; Heller, William T.; Qian, Shuo

    2016-08-09

    The interaction between lipid bilayers and Amyloid β peptide (Aβ) plays a critical role in proliferation of Alzheimer’s disease (AD). AD is expected to affect one in every 85 humans by 2050, and therefore, deciphering the interplay of Aβ and lipid bilayers at the molecular level is of profound importance. In this work, we applied an array of neutron scattering methods to study the structure and dynamics of Aβ(1–40) interacting 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) bilayers. In the structural investigations of lipid bilayer’s response to Aβ binding, Small Angle Neutron Scattering and Neutron Membrane Diffraction revealed that the Aβ anchors firmly to themore » highly charged DMPG bilayers in the interfacial region between water and hydrocarbon chain, and it doesn’t penetrate deeply into the bilayer. This association mode is substantiated by the dynamics studies with high resolution Quasi-Elastic Neutron Scattering experiments, showing that the addition of Aβ mainly affects the slower lateral motion of lipid molecules, especially in the fluid phase, but not the faster internal motion. The results revealed that Aβ associates with the highly charged membrane in surface with limited impact on the structure, but the altered membrane dynamics could have more influence on other membrane processes.« less

  2. Protection of SK-N-MC cells against β-amyloid peptide-induced degeneration using neuron growth factor-loaded liposomes with surface lactoferrin.

    PubMed

    Kuo, Yung-Chih; Wang, Cheng-Ting

    2014-07-01

    A liposomal system with surface lactoferrin (Lf) was developed for delivering neuron growth factor (NGF) across the blood-brain barrier (BBB) and improving the viability of neuron-like SK-N-MC cells with deposited β-amyloid peptide (Aβ). The Lf-grafted liposomes carrying NGF (Lf/NGF-liposomes) were applied to a monolayer of human brain-microvascular endothelial cells (HBMECs) regulated by human astrocytes (HAs) and to fibrillar Aβ1-42-insulted SK-N-MC cells. An increase in cholesterol mole percentage enhanced the particle size, absolute value of zeta potential, and physical stability, however, reduced the entrapment efficiency and release rate of NGF. In addition, an increase in Lf concentration increased the particle size, surface nitrogen percentage, NGF permeability across the BBB, and viability of HBMECs, HAs, and SK-N-MC cells, however, decreased the absolute value of zeta potential, surface phosphorus percentage, and loading efficiency of Lf. After treating with Lf/NGF-liposomes, a higher Aβ concentration yielded a lower survival of SK-N-MC cells. The current Lf/NGF-liposomes are efficacious drug carriers to target the BBB and inhibit the Aβ-induced neurotoxicity as potential pharmacotherapy for Alzheimer's disease. PMID:24746790

  3. A role for 4-hydroxynonenal, an aldehydic product of lipid peroxidation, in disruption of ion homeostasis and neuronal death induced by amyloid beta-peptide.

    PubMed

    Mark, R J; Lovell, M A; Markesbery, W R; Uchida, K; Mattson, M P

    1997-01-01

    Peroxidation of membrane lipids results in release of the aldehyde 4-hydroxynonenal (HNE), which is known to conjugate to specific amino acids of proteins and may alter their function. Because accumulating data indicate that free radicals mediate injury and death of neurons in Alzheimer's disease (AD) and because amyloid beta-peptide (A beta) can promote free radical production, we tested the hypothesis that HNE mediates A beta 25-35-induced disruption of neuronal ion homeostasis and cell death. A beta induced large increases in levels of free and protein-bound HNE in cultured hippocampal cells. HNE was neurotoxic in a time- and concentration-dependent manner, and this toxicity was specific in that other aldehydic lipid peroxidation products were not neurotoxic. HNE impaired Na+, K(+)-ATPase activity and induced an increase of neuronal intracellular free Ca2+ concentration. HNE increased neuronal vulnerability to glutamate toxicity, and HNE toxicity was partially attenuated by NMDA receptor antagonists, suggesting an excitotoxic component to HNE neurotoxicity. Glutathione, which was previously shown to play a key role in HNE metabolism in nonneuronal cells, attenuated the neurotoxicities of both A beta and HNE. The antioxidant propyl gallate protected neurons against A beta toxicity but was less effective in protecting against HNE toxicity. Collectively, the data suggest that HNE mediates A beta-induced oxidative damage to neuronal membrane proteins, which, in turn, leads to disruption of ion homeostasis and cell degeneration. PMID:8978733

  4. Carbon nanotube inhibits the formation of β-sheet-rich oligomers of the Alzheimer's amyloid-β(16-22) peptide.

    PubMed

    Li, Huiyu; Luo, Yin; Derreumaux, Philippe; Wei, Guanghong

    2011-11-01

    Alzheimer's disease is associated with the abnormal self-assembly of the amyloid-β (Aβ) peptide into toxic β-rich aggregates. Experimental studies have shown that hydrophobic nanoparticles retard Aβ fibrillation by slowing down the nucleation process; however, the effects of nanoparticles on Aβ oligomeric structures remain elusive. In this study, we investigate the conformations of Aβ(16-22) octamers in the absence and presence of a single-walled carbon nanotube (SWCNT) by performing extensive all-atom replica exchange molecular-dynamics simulations in explicit solvent. Our simulations starting from eight random chains demonstrate that the addition of SWCNT into Aβ(16-22) solution prevents β-sheet formation. Simulation starting from a prefibrillar β-sheet octamer shows that SWCNT destabilizes the β-sheet structure. A detailed analysis of the Aβ(16-22)/SWCNT/water interactions reveals that both the inhibition of β-sheet formation and the destabilization of prefibrillar β-sheets by SWCNT result from the same physical forces: hydrophobic and π-stacking interactions (with the latter playing a more important role). By analyzing the stacking patterns between the Phe aromatic rings and the SWCNT carbon rings, we find that short ring-centroid distances mostly favor parallel orientation, whereas large distances allow all other orientations to be populated. Overall, our computational study provides evidence that SWCNT is likely to inhibit Aβ(16-22) and full-length Aβ fibrillation.

  5. Neutron Scattering Studies of the Interplay of Amyloid β Peptide(1–40) and An Anionic Lipid 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol

    PubMed Central

    Rai, Durgesh K.; Sharma, Veerendra K.; Anunciado, Divina; O’Neill, Hugh; Mamontov, Eugene; Urban, Volker; Heller, William T.; Qian, Shuo

    2016-01-01

    The interaction between lipid bilayers and Amyloid β peptide (Aβ) plays a critical role in proliferation of Alzheimer’s disease (AD). AD is expected to affect one in every 85 humans by 2050, and therefore, deciphering the interplay of Aβ and lipid bilayers at the molecular level is of profound importance. In this work, we applied an array of neutron scattering methods to study the structure and dynamics of Aβ(1–40) interacting 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) bilayers. In the structural investigations of lipid bilayer’s response to Aβ binding, Small Angle Neutron Scattering and Neutron Membrane Diffraction revealed that the Aβ anchors firmly to the highly charged DMPG bilayers in the interfacial region between water and hydrocarbon chain, and it doesn’t penetrate deeply into the bilayer. This association mode is substantiated by the dynamics studies with high resolution Quasi-Elastic Neutron Scattering experiments, showing that the addition of Aβ mainly affects the slower lateral motion of lipid molecules, especially in the fluid phase, but not the faster internal motion. The results revealed that Aβ associates with the highly charged membrane in surface with limited impact on the structure, but the altered membrane dynamics could have more influence on other membrane processes. PMID:27503057

  6. Validation of a Commercial Chemiluminescence Immunoassay for the Simultaneous Measurement of Three Different AmyloidPeptides in Human Cerebrospinal Fluid and Application to a Clinical Cohort.

    PubMed

    Klafki, Hans-W; Hafermann, Henning; Bauer, Chris; Haussmann, Ute; Kraus, Inga; Schuchhardt, Johannes; Muck, Stephan; Scherbaum, Norbert; Wiltfang, Jens

    2016-09-01

    A comprehensive assay validation campaign of a commercially available chemiluminescence multiplex immunoassay for the simultaneous measurement of the amyloidpeptides Aβ38, Aβ40, and Aβ42 in human cerebrospinal fluid (CSF) is presented. The assay quality parameters we addressed included impact of sample dilution, parallelism, lower limits of detection, lower limits of quantification, intra- and inter-assay repeatability, analytical spike recoveries, and between laboratory reproducibility of the measurements. The assay performed well in our hands and fulfilled a number of predefined acceptance criteria. The CSF levels of Aβ40 and Aβ42 determined in a clinical cohort (n = 203) were statistically significantly correlated with available ELISA data of Aβ1-40 (n = 158) and Aβ1-42 (n = 179) from a different laboratory. However, Bland-Altman method comparison indicated systematic differences between the assays. The data presented here furthermore indicate that the CSF concentration of Aβ40 can surrogate total CSF Aβ and support the hypothesis that the Aβ42/Aβ40 ratio outperforms CSF Aβ42 alone as a biomarker for Alzheimer's disease due to a normalization to total Aβ levels. PMID:27567847

  7. Increased amyloid β-peptide uptake in skeletal muscle is induced by hyposialylation and may account for apoptosis in GNE myopathy

    PubMed Central

    Bosch-Morató, Mònica; Iriondo, Cinta; Guivernau, Biuse; Valls-Comamala, Victòria; Vidal, Noemí; Olivé, Montse; Querfurth, Henry; Muñoz, Francisco J.

    2016-01-01

    GNE myopathy is an autosomal recessive muscular disorder of young adults characterized by progressive skeletal muscle weakness and wasting. It is caused by a mutation in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, which encodes a key enzyme in sialic acid biosynthesis. The mutated hypofunctional GNE is associated with intracellular accumulation of amyloid β-peptide (Aβ) in patient muscles through as yet unknown mechanisms. We found here for the first time that an experimental reduction in sialic acid favors Aβ1-42 endocytosis in C2C12 myotubes, which is dependent on clathrin and heparan sulfate proteoglycan. Accordingly, Aβ1-42 internalization in myoblasts from a GNE myopathy patient was enhanced. Next, we investigated signal changes triggered by Aβ1-42 that may underlie toxicity. We observed that p-Akt levels are reduced in step with an increase in apoptotic markers in GNE myopathy myoblasts compared to control myoblasts. The same results were experimentally obtained when Aβ1-42 was overexpressed in myotubes. Hence, we propose a novel disease mechanism whereby hyposialylation favors Aβ1-42 internalization and the subsequent apoptosis in myotubes and in skeletal muscle from GNE myopathy patients. PMID:26968811

  8. Differential effects of "Advanced glycation endproducts" and beta-amyloid peptide on glucose utilization and ATP levels in the neuronal cell line SH-SY5Y.

    PubMed

    Kuhla, B; Loske, C; Garcia De Arriba, S; Schinzel, R; Huber, J; Münch, G

    2004-03-01

    Beta-amyloid peptide (Abeta) and "Advanced glycation endproducts" (AGEs) are components of the senile plaques in Alzheimer's disease patients. It has been proposed that both AGEs and Abeta exert many of their effects, which include the upregulation of pro-inflammatory cytokines, through RAGE ("receptor for advanced glycation endproducts"). To investigate whether Abeta and AGEs cause similar or identical effects on cell survival and energy metabolism, we have compared the effects of a model-AGE and Abeta on cell viability, ATP level, glucose consumption and lactate production in the neuroblastoma cell line SH-SY5Y. The results show that AGEs and Abeta increase glucose consumption and decrease ATP levels in a dose dependent manner. Furthermore, both compounds decrease mitochondrial activity measured by the MTT assay. However, only AGEs decrease the number of cells and significantly increase lactate production. These data indicate that both AGEs and Abeta can cause differential disturbances in neuronal metabolism, which may contribute to the pathophysiological findings in Alzheimer's disease. However, their signalling pathways are apparently quite distinct, a fact which should stimulate a more detailed investigation in this field, e.g. for the purpose of a rational design of potential "neuroprotective" RAGE antagonists. PMID:14991463

  9. On the Involvement of Copper Binding to the N-Terminus of the Amyloid Beta Peptide of Alzheimer's Disease: A Computational Study on Model Systems

    PubMed Central

    Azimi, Samira; Rauk, Arvi

    2011-01-01

    Density functional and second order Moller-Plesset perturbation theoretical methods, coupled with a polarizable continuum model of water, were applied to determine the structures, binding affinities, and reduction potentials of Cu(II) and Cu(I) bound to models of the Asp1, Ala2, His6, and His13His14 regions of the amyloid beta peptide of Alzheimer's disease. The results indicate that the N-terminal Asp binds to Cu(II) together with His6 and either His13 or His14 to form the lower pH Component I of Aβ. Component II of Aβ is the complex between Cu(II) and His6, His13, and His14, to which an amide O (of Ala2) is also coordinated. Asp1 does not bind to Cu(II) if three His residues are attached nor to any Cu(I) species to which one or more His residues are bound. The most stable Cu(I) species is one in which Cu(I) bridges the Nδ of His13 and His14 in a linear fashion. Cu(I) binds more strongly to Aβ than does Cu(II). The computed reduction potential that closely matches the experimental value for Cu(II)/Aβ corresponds to reduction of Component II (without Ala2) to the Cu(I) complex after endergonic attachment of His6. PMID:22191059

  10. Accumulation of Exogenous Amyloid-Beta Peptide in Hippocampal Mitochondria Causes Their Dysfunction: A Protective Role for Melatonin

    PubMed Central

    Rosales-Corral, Sergio; Acuna-Castroviejo, Dario; Tan, Dun Xian; López-Armas, Gabriela; Cruz-Ramos, José; Munoz, Rubén; Melnikov, Valery G.; Manchester, Lucien C.; Reiter, Russel J.

    2012-01-01

    Amyloid-beta (Aβ) pathology is related to mitochondrial dysfunction accompanied by energy reduction and an elevated production of reactive oxygen species (ROS). Monomers and oligomers of Aβ have been found inside mitochondria where they accumulate in a time-dependent manner as demonstrated in transgenic mice and in Alzheimer's disease (AD) brain. We hypothesize that the internalization of extracellular Aβ aggregates is the major cause of mitochondrial damage and here we report that following the injection of fibrillar Aβ into the hippocampus, there is severe axonal damage which is accompanied by the entrance of Aβ into the cell. Thereafter, Aβ appears in mitochondria where it is linked to alterations in the ionic gradient across the inner mitochondrial membrane. This effect is accompanied by disruption of subcellular structure, oxidative stress, and a significant reduction in both the respiratory control ratio and in the hydrolytic activity of ATPase. Orally administrated melatonin reduced oxidative stress, improved the mitochondrial respiratory control ratio, and ameliorated the energy imbalance. PMID:22666521

  11. The ability of apolipoprotein E fragments to promote intraneuronal accumulation of amyloid beta peptide 42 is both isoform and size-specific.

    PubMed

    Dafnis, Ioannis; Argyri, Letta; Sagnou, Marina; Tzinia, Athina; Tsilibary, Effie C; Stratikos, Efstratios; Chroni, Angeliki

    2016-01-01

    The apolipoprotein (apo) E4 isoform is the strongest risk factor for late-onset Alzheimer's disease (AD). ApoE4 is more susceptible to proteolysis than apoE2 and apoE3 isoforms and carboxyl-terminal truncated apoE4 forms have been found in AD patients' brain. We have previously shown that a specific apoE4 fragment, apoE4-165, promotes amyloid-peptide beta 42 (Aβ42) accumulation in human neuroblastoma SK-N-SH cells and increased intracellular reactive oxygen species formation, two events considered to occur early in AD pathogenesis. Here, we show that these effects are allele-dependent and absolutely require the apoE4 background. Furthermore, the exact length of the fragment is critical since longer or shorter length carboxyl-terminal truncated apoE4 forms do not elicit the same effects. Structural and thermodynamic analyses showed that apoE4-165 has a compact structure, in contrast to other carboxyl-terminal truncated apoE4 forms that are instead destabilized. Compared however to other allelic backgrounds, apoE4-165 is structurally distinct and less thermodynamically stable suggesting that the combination of a well-folded structure with structural plasticity is a unique characteristic of this fragment. Overall, our findings suggest that the ability of apoE fragments to promote Aβ42 intraneuronal accumulation is specific for both the apoE4 isoform and the particular structural and thermodynamic properties of the fragment. PMID:27476701

  12. Basic FGF attenuates amyloid beta-peptide-induced oxidative stress, mitochondrial dysfunction, and impairment of Na+/K+-ATPase activity in hippocampal neurons.

    PubMed

    Mark, R J; Keller, J N; Kruman, I; Mattson, M P

    1997-05-01

    Basic fibroblast growth factor (bFGF) exhibits trophic activity for many populations of neurons in the brain, and can protect those neurons against excitotoxic, metabolic and oxidative insults. In Alzheimer's disease (AD), amyloid beta-peptide (A beta) fibrils accumulate in plaques which are associated with degenerating neurons. A beta can be neurotoxic by a mechanism that appears to involve induction of oxidative stress and disruption of calcium homeostasis. Plaques in AD brain contain high levels of bFGF suggesting a possible modulatory role for bFGF in the neurodegenerative process. We now report that bFGF can protect cultured hippocampal neurons against A beta25-35 toxicity by a mechanism that involves suppression of reactive oxygen species (ROS) accumulation and maintenance of Na+/K+-ATPase activity. A beta25-35 induced lipid peroxidation, accumulation of H2O2, mitochondrial ROS accumulation, and a decrease in mitochondrial transmembrane potential; each of these effects of A beta25-35 was abrogated in cultures pre-treated with bFGF. Na+/K+-ATPase activity was significantly reduced following exposure to A beta25-35 in control cultures, but not in cultures pre-treated with bFGF. bFGF did not protect neurons from death induced by ouabain (a specific inhibitor of the Na+/K+-ATPase) or 4-hydroxynonenal (an aldehydic product of lipid peroxidation) consistent with a site of action of bFGF prior to induction of oxidative stress and impairment of ion-motive ATPases. By suppressing accumulation of oxyradicals, bFGF may slow A beta-induced neurodegenerative cascades. PMID:9187334

  13. HLA-DR alleles in amyloid beta-peptide autoimmunity: a highly immunogenic role for the DRB1*1501 allele.

    PubMed

    Zota, Victor; Nemirovsky, Anna; Baron, Rona; Fisher, Yair; Selkoe, Dennis J; Altmann, Daniel M; Weiner, Howard L; Monsonego, Alon

    2009-09-01

    Active amyloid beta-peptide (Abeta) immunization of patients with Alzheimer's disease (AD) caused meningoencephalitis in approximately 6% of immunized patients in a clinical trial. In addition, long-term studies of AD patients show varying degrees of Abeta Ab responses, which correlate with the extent of Abeta clearance from the brain. In this study, we examined the contribution of various HLA-DR alleles to these immune-response variations by assessing Abeta T cell reactivity, epitope specificity, and immunogenicity. Analysis of blood samples from 133 individuals disclosed that the abundant DR haplotypes DR15 (found in 36% of subjects), DR3 (in 18%), DR4 (12.5%), DR1 (11%), and DR13 (8%) were associated with Abeta-specific T cell responses elicited via distinct T cell epitopes within residues 15-42 of Abeta. Because the HLA-DRB1*1501 occurred most frequently, we examined the effect of Abeta challenge in humanized mice bearing this allele. The observed T cell response was remarkably strong, dominated by secretion of IFN-gamma and IL-17, and specific to the same T cell epitope as that observed in the HLA-DR15-bearing humans. Furthermore, following long-term therapeutic immunization of an AD mouse model bearing the DRB1*1501 allele, Abeta was effectively cleared from the brain parenchyma and brain microglial activation was reduced. The present study thus characterizes HLA-DR alleles directly associated with specific Abeta T cell epitopes and demonstrates the highly immunogenic properties of the abundant allele DRB1*1501 in a mouse model of AD. This new knowledge enables us to explore the basis for understanding the variations in naturally occurring Abeta-reactive T cells and Abeta immunogenicity among humans.

  14. Effects of Zn2+ Binding on the Structural and Dynamic Properties of Amyloid Β Peptide Associated with Alzheimer’s Disease: Asp1 or Glu11?

    PubMed Central

    2013-01-01

    Extensive experimental and computational studies have suggested that multiple Zn2+ binding modes in amyloid β (Aβ) peptides could exist simultaneously. However, consistent results have not been obtained for the effects of Zn2+ binding on Aβ structure, dynamics, and kinetics in particular. Some key questions such as why it is so difficult to distinguish the polymorphic states of metal ions binding to Aβ and what the underlying rationale is, necessitate elucidation. In this work, two 3N1O Zn2+ binding modes were constructed with three histidines (His6, His13, and His14), and Asp1/Glu11 of Aβ40 coordinated to Zn2+. Results from molecular dynamics simulations reveal that the conformational ensembles of different Zn2+-Aβ40 complexes are nonoverlapping. The formation of turn structure and, especially, the salt bridge between Glu22/Asp23 and Lys28 is dependent on specific Zn2+ binding mode. Agreement with available NMR observations of secondary and tertiary structures could be better achieved if the two simulation results are considered together. The free energy landscape constructed by combining both conformations of Aβ40 indicates that transitions between distinct Aβ40 conformations thar are ready for Zn2+ binding could be possible in aqueous solution. Markov state model analyses reveal the complex network of conformational space of Aβ40 modeulated by Zn2+ binding, suggesting various misfolding pathways. The binding free energies evaluated using a combination of quantum mechanics calculations and the MM/3D-RISM method suggest that Glu11 is the preferred oxygen ligand of Zn2+. However, such preference is dependent on the relative populations of different conformations with specific Zn2+ binding modes, and therefore could be shifted when experimental or simulation conditions are altered. PMID:23947440

  15. The ability of apolipoprotein E fragments to promote intraneuronal accumulation of amyloid beta peptide 42 is both isoform and size-specific

    PubMed Central

    Dafnis, Ioannis; Argyri, Letta; Sagnou, Marina; Tzinia, Athina; Tsilibary, Effie C.; Stratikos, Efstratios; Chroni, Angeliki

    2016-01-01

    The apolipoprotein (apo) E4 isoform is the strongest risk factor for late-onset Alzheimer’s disease (AD). ApoE4 is more susceptible to proteolysis than apoE2 and apoE3 isoforms and carboxyl-terminal truncated apoE4 forms have been found in AD patients’ brain. We have previously shown that a specific apoE4 fragment, apoE4-165, promotes amyloid-peptide beta 42 (Aβ42) accumulation in human neuroblastoma SK-N-SH cells and increased intracellular reactive oxygen species formation, two events considered to occur early in AD pathogenesis. Here, we show that these effects are allele-dependent and absolutely require the apoE4 background. Furthermore, the exact length of the fragment is critical since longer or shorter length carboxyl-terminal truncated apoE4 forms do not elicit the same effects. Structural and thermodynamic analyses showed that apoE4-165 has a compact structure, in contrast to other carboxyl-terminal truncated apoE4 forms that are instead destabilized. Compared however to other allelic backgrounds, apoE4-165 is structurally distinct and less thermodynamically stable suggesting that the combination of a well-folded structure with structural plasticity is a unique characteristic of this fragment. Overall, our findings suggest that the ability of apoE fragments to promote Aβ42 intraneuronal accumulation is specific for both the apoE4 isoform and the particular structural and thermodynamic properties of the fragment. PMID:27476701

  16. Low energy laser light (632.8 nm) suppresses amyloidpeptide-induced oxidative and inflammatory responses in astrocytes.

    PubMed

    Yang, X; Askarova, S; Sheng, W; Chen, J K; Sun, A Y; Sun, G Y; Yao, G; Lee, J C-M

    2010-12-15

    Oxidative stress and inflammation are important processes in the progression of Alzheimer's disease (AD). Recent studies have implicated the role of amyloid β-peptides (Aβ) in mediating these processes. In astrocytes, oligomeric Aβ induces the assembly of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complexes resulting in its activation to produce anionic superoxide. Aβ also promotes production of pro-inflammatory factors in astrocytes. Since low energy laser has previously been reported to attenuate oxidative stress and inflammation in biological systems, the objective of this study was to examine whether this type of laser light was able to abrogate the oxidative and inflammatory responses induced by Aβ. Primary rat astrocytes were exposed to Helium-Neon laser (λ=632.8 nm), followed by the treatment with oligomeric Aβ. Primary rat astrocytes were used to measure Aβ-induced production of superoxide anions using fluorescence microscopy of dihydroethidium (DHE), assembly of NADPH oxidase subunits by the colocalization between the cytosolic p47(phox) subunit and the membrane gp91(phox) subunit using fluorescent confocal microscopy, phosphorylation of cytosolic phospholipase A(2) cPLA(2) and expressions of pro-inflammatory factors including interleukin-1β (IL-1β) and inducible nitric-oxide synthase (iNOS) using Western blot Analysis. Our data showed that laser light at 632.8 nm suppressed Aβ-induced superoxide production, colocalization between NADPH oxidase gp91(phox) and p47(phox) subunits, phosphorylation of cPLA(2,) and the expressions of IL-1β and iNOS in primary astrocytes. We demonstrated for the first time that 632.8 nm laser was capable of suppressing cellular pathways of oxidative stress and inflammatory responses critical in the pathogenesis in AD. This study should prove to provide the groundwork for further investigations for the potential use of laser therapy as a treatment for AD. PMID:20884337

  17. Development of a proteolytically stable retro-inverso peptide inhibitor of beta-amyloid oligomerization as a potential novel treatment for Alzheimer's disease.

    PubMed

    Taylor, Mark; Moore, Susan; Mayes, Jennifer; Parkin, Edward; Beeg, Marten; Canovi, Mara; Gobbi, Marco; Mann, David M A; Allsop, David

    2010-04-20

    The formation of beta-amyloid (Abeta) deposits in the brain is likely to be a seminal step in the development of Alzheimer's disease. Recent studies support the hypothesis that Abeta soluble oligomers are toxic to cells and have potent effects on memory and learning. Inhibiting the early stages of Abeta aggregation could, therefore, provide a novel approach to treating the underlying cause of AD. We have designed a retro-inverso peptide (RI-OR2, H(2)N-r<--G<--k<--l<--v<--f<--f<--G<--r-Ac), based on a previously described inhibitor of Abeta oligomer formation (OR2, H(2)N-R-G-K-L-V-F-F-G-R-NH(2)). Unlike OR2, RI-OR2 was highly stable to proteolysis and completely resisted breakdown in human plasma and brain extracts. RI-OR2 blocked the formation of Abeta oligomers and fibrils from extensively deseeded preparations of Abeta(1-40) and Abeta(1-42), as assessed by thioflavin T binding, an immunoassay method for Abeta oligomers, SDS-PAGE separation of stable oligomers, and atomic force microscopy, and was more effective against Abeta(1-42) than Abeta(1-40). In surface plasmon resonance experiments, RI-OR2 was shown to bind to immobilized Abeta(1-42) monomers and fibrils, with an apparent K(d) of 9-12 muM, and also acted as an inhibitor of Abeta(1-42) fibril extension. In two different cell toxicity assays, RI-OR2 significantly reversed the toxicity of Abeta(1-42) toward cultured SH-SY5Y neuroblastoma cells. Thus, RI-OR2 represents a strong candidate for further development as a novel treatment for Alzheimer's disease. PMID:20230062

  18. The ability of apolipoprotein E fragments to promote intraneuronal accumulation of amyloid beta peptide 42 is both isoform and size-specific.

    PubMed

    Dafnis, Ioannis; Argyri, Letta; Sagnou, Marina; Tzinia, Athina; Tsilibary, Effie C; Stratikos, Efstratios; Chroni, Angeliki

    2016-08-01

    The apolipoprotein (apo) E4 isoform is the strongest risk factor for late-onset Alzheimer's disease (AD). ApoE4 is more susceptible to proteolysis than apoE2 and apoE3 isoforms and carboxyl-terminal truncated apoE4 forms have been found in AD patients' brain. We have previously shown that a specific apoE4 fragment, apoE4-165, promotes amyloid-peptide beta 42 (Aβ42) accumulation in human neuroblastoma SK-N-SH cells and increased intracellular reactive oxygen species formation, two events considered to occur early in AD pathogenesis. Here, we show that these effects are allele-dependent and absolutely require the apoE4 background. Furthermore, the exact length of the fragment is critical since longer or shorter length carboxyl-terminal truncated apoE4 forms do not elicit the same effects. Structural and thermodynamic analyses showed that apoE4-165 has a compact structure, in contrast to other carboxyl-terminal truncated apoE4 forms that are instead destabilized. Compared however to other allelic backgrounds, apoE4-165 is structurally distinct and less thermodynamically stable suggesting that the combination of a well-folded structure with structural plasticity is a unique characteristic of this fragment. Overall, our findings suggest that the ability of apoE fragments to promote Aβ42 intraneuronal accumulation is specific for both the apoE4 isoform and the particular structural and thermodynamic properties of the fragment.

  19. Cell Adhesion on Amyloid Fibrils Lacking Integrin Recognition Motif.

    PubMed

    Jacob, Reeba S; George, Edna; Singh, Pradeep K; Salot, Shimul; Anoop, Arunagiri; Jha, Narendra Nath; Sen, Shamik; Maji, Samir K

    2016-03-01

    Amyloids are highly ordered, cross-β-sheet-rich protein/peptide aggregates associated with both human diseases and native functions. Given the well established ability of amyloids in interacting with cell membranes, we hypothesize that amyloids can serve as universal cell-adhesive substrates. Here, we show that, similar to the extracellular matrix protein collagen, amyloids of various proteins/peptides support attachment and spreading of cells via robust stimulation of integrin expression and formation of integrin-based focal adhesions. Additionally, amyloid fibrils are also capable of immobilizing non-adherent red blood cells through charge-based interactions. Together, our results indicate that both active and passive mechanisms contribute to adhesion on amyloid fibrils. The present data may delineate the functional aspect of cell adhesion on amyloids by various organisms and its involvement in human diseases. Our results also raise the exciting possibility that cell adhesivity might be a generic property of amyloids. PMID:26742841

  20. Template-directed deposition of amyloid

    NASA Astrophysics Data System (ADS)

    Ha, Chanki

    The formation of amyloid plaques in tissue is a pathological feature of many neurodegenerative diseases. Amyloid deposition, the process of amyloid plaque growth by the association of individual soluble amyloid molecules with a pre-existing amyloid template (i.e. plaque), is known to be critical for amyloid formation in vivo. In order to characterize amyloid deposition, we developed novel, synthetic amyloid templates like amyloid plaques in the human Alzheimer's brain by attaching amyloid seeds covalently onto an N-hydroxysuccinimide-activated surface. Amyloid plaques with a characteristic beta-sheet structure formed through a conformational rearrangement of soluble insulin or Abeta monomers upon interaction with the template. The amyloid deposition rate followed saturation kinetics with respect to insulin concentration in the solution. According to visualization of temporal evolution of Abeta plaque deposition on a template, it was found that mature amyloid plaques serve as a sink of soluble Abeta in a solution as well as a reservoir of small aggregates such as oligomers and protofibrils. Quantitative analysis of seeding efficiencies of three different Abeta species revealed that oligomeric forms of Abeta act more efficiently as seeds than monomers or fibrils do. Furthermore, studies on the interaction between Abeta40 and 42 showed an important role of Abeta42 in amyloid deposition. A slightly acidic condition was found to be unfavorable for amyloid plaque formation. Effects of metal ions on amyloid deposition indicated that Fe3+, but not Cu3 and Zn2+, is important for the deposition of amyloid plaques. The binding of Fe3+ to Abeta42 peptide was confirmed by using SIMS analysis. Zn2+ induced nonfibrillar amorphous aggregates, but the release of Zn2+ from Abeta42 deposits by Fe3+ triggered the formation of amyloid fibers. Effects or metal ion chelators such as ethylenediamine tetraacetic acid, deferoxamine, and clioquinol on amyloid deposition were tested to

  1. Intrafollicular amyloid in primary hyperparathyroidism

    PubMed Central

    Leedham, P. W.; Pollock, D. J.

    1970-01-01

    The histology of the parathyroids from 88 cases of primary hyperparathyroidism has been reviewed in a search for local amyloid deposits. Characteristic intrafollicular amyloid deposits of varying extent were found in nine cases. The case histories of these show that seven had suspected or proven pluriglandular adenomatosis but that the remainder had no such associations. The material studied shows no correlation with systemic primary or secondary amyloidosis. The significance of these findings is discussed in relation to the pluriglandular syndrome, peptide hormones, medullary carcinoma of the thyroid, and calcitonin secretion. It is suggested that amyloid in this context may be a `marker' for secretion of a peptide closely related to calcitonin. Images PMID:5504375

  2. Secondary structure propensity and chirality of the amyloidophilic peptide p5 and its analogues impacts ligand binding - In vitro characterization

    DOE PAGESBeta

    Wall, Jonathan S.; Williams, Angela; Wooliver, Craig; Martin, Emily B.; Cheng, Xiaolin; Heidel, R. Eric; Kennel, Stephen J.

    2016-08-11

    Here, polybasic helical peptides, such as peptide p5, bind human amyloid extracts and synthetic amyloid fibrils. When radio labeled, peptide p5 has been shown to specifically bind amyloid in vivo thereby allowing imaging of the disease. Structural requirements for heparin and amyloid binding have been studied using analogues of p5 that modify helicity and chirality.

  3. Amyloid fibrils

    PubMed Central

    Rambaran, Roma N

    2008-01-01

    Amyloid refers to the abnormal fibrous, extracellular, proteinaceous deposits found in organs and tissues. Amyloid is insoluble and is structurally dominated by β-sheet structure. Unlike other fibrous proteins it does not commonly have a structural, supportive or motility role but is associated with the pathology seen in a range of diseases known as the amyloidoses. These diseases include Alzheimer's, the spongiform encephalopathies and type II diabetes, all of which are progressive disorders with associated high morbidity and mortality. Not surprisingly, research into the physicochemical properties of amyloid and its formation is currently intensely pursued. In this chapter we will highlight the key scientific findings and discuss how the stability of amyloid fibrils impacts on bionanotechnology. PMID:19158505

  4. Amyloid beta-peptide impairs ion-motive ATPase activities: evidence for a role in loss of neuronal Ca2+ homeostasis and cell death.

    PubMed

    Mark, R J; Hensley, K; Butterfield, D A; Mattson, M P

    1995-09-01

    The amyloid beta-peptide (A beta) that accumulates as insoluble plaques in the brain in Alzheimer's disease can be directly neurotoxic and can increase neuronal vulnerability to excitotoxic insults. The mechanism of A beta toxicity is unclear but is believed to involve generation of reactive oxygen species (ROS) and loss of calcium homeostasis. We now report that exposure of cultured rat hippocampal neurons to A beta 1-40 or A beta 25-35 causes a selective reduction in Na+/K(+)-ATPase activity which precedes loss of calcium homeostasis and cell degeneration. Na+/K(+)-ATPase activity was reduced within 30 min of exposure to A beta 25-35 and declined to less than 40% of basal level by 3 hr. A beta did not impair other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. Experiments with ouabain, a specific inhibitor of the Na+/K(+)-ATPase, demonstrated that impairment of this enzyme was sufficient to induce an elevation of [Ca2+]i and neuronal injury. Impairment of Na+/K(+)-ATPase activity appeared to be causally involved in the elevation of [Ca2+]i and neurotoxicity since suppression of Na+ influx significantly reduced A beta- and ouabain-induced [Ca2+]i elevation and neuronal death. Neuronal degeneration induced by ouabain appeared to be of an apoptotic form as indicated by nuclear condensation and DNA fragmentation. The antioxidant free radical scavengers vitamin E and propylgallate significantly attenuated A beta-induced impairment of Na+/K(+)-ATPase activity, elevation of [Ca2+]i and neurotoxicity, suggesting a role for ROS. Finally, exposure of synaptosomes from postmortem human hippocampus to A beta resulted in a significant and specific reduction in Na+/K(+)-ATPase and Ca(2+)-ATPase activities, without affecting other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. These data suggest that impairment of ion-motive ATPases may play a role in the pathogenesis of neuronal injury in Alzheimer's disease. PMID:7666206

  5. The new β amyloid-derived peptide Aβ1-6A2V-TAT(D) prevents Aβ oligomer formation and protects transgenic C. elegans from Aβ toxicity.

    PubMed

    Diomede, Luisa; Romeo, Margherita; Cagnotto, Alfredo; Rossi, Alessandro; Beeg, Marten; Stravalaci, Matteo; Tagliavini, Fabrizio; Di Fede, Giuseppe; Gobbi, Marco; Salmona, Mario

    2016-04-01

    One attractive pharmacological strategy for Alzheimer's disease (AD) is to design small peptides to interact with amyloid-β (Aβ) protein reducing its aggregation and toxicity. Starting from clinical observations indicating that patients coding a mutated Aβ variant (AβA2V) in the heterozygous state do not develop AD, we developed AβA2V synthetic peptides, as well as a small peptide homologous to residues 1-6. These hindered the amyloidogenesis of Aβ and its neurotoxicity in vitro, suggesting a basis for the design of a new small peptide in D-isomeric form, linked to the arginine-rich TAT sequence [Aβ1-6A2V-TAT(D)], to allow translocation across biological membranes and the blood-brain barrier. Aβ1-6A2V-TAT(D) was resistant to protease degradation, stable in serum and specifically able to interfere with Aβ aggregation in vitro, reducing the appearance of toxic soluble species and protecting transgenic C. elegans from toxicity related to the muscular expression of human Aβ. These observations offer a proof of concept for future pharmacological studies in mouse models of AD, providing a foundation for the design of AβA2V-based peptidomimetic molecules for therapeutic purposes. PMID:26792398

  6. NMR WaterLOGSY Reveals Weak Binding of Bisphenol A with Amyloid Fibers of a Conserved 11 Residue Peptide from Androgen Receptor.

    PubMed

    Asencio-Hernández, Julia; Kieffer, Bruno; Delsuc, Marc-André

    2016-01-01

    There is growing evidence that bisphenol A (BPA), a molecule largely released in the environment, has detrimental effects on ecosystems and on human health. It acts as an endocrine disruptor targeting steroid hormone receptors, such as the estrogen receptor (ER), estrogen-related receptor (ERR) and androgen receptor (AR). BPA-derived molecules have recently been shown to interact with the AR N-terminal domain (AR-NTD), which is known to be largely intrinsically disordered. This N-terminal domain contains an 11 residue conserved domain that forms amyloid fibers upon oxidative dimerisation through its strictly conserved Cys240 residue. We investigate here the interaction of BPA, and other potential endocrine disruptors, with AR-NTD amyloid fibers using the WaterLOGSY NMR experiment. We observed a selective binding of these compounds to the amyloid fibers formed by the AR-NTD conserved region and glutamine homopolymers. This observation suggests that the high potency of endocrine disruptors may result, in part, from their ability to bind amyloid forms of nuclear receptors in addition to their cognate binding sites. This property may be exploited to design future therapeutic strategies targeting AR related diseases such as the spinal bulbar muscular atrophy or prostate cancer. The ability of NMR WaterLOGSY experiments to detect weak interactions between small ligands and amyloid fibers may prove to be of particular interest for identifying promising hit molecules. PMID:27583469

  7. NMR WaterLOGSY Reveals Weak Binding of Bisphenol A with Amyloid Fibers of a Conserved 11 Residue Peptide from Androgen Receptor.

    PubMed

    Asencio-Hernández, Julia; Kieffer, Bruno; Delsuc, Marc-André

    2016-01-01

    There is growing evidence that bisphenol A (BPA), a molecule largely released in the environment, has detrimental effects on ecosystems and on human health. It acts as an endocrine disruptor targeting steroid hormone receptors, such as the estrogen receptor (ER), estrogen-related receptor (ERR) and androgen receptor (AR). BPA-derived molecules have recently been shown to interact with the AR N-terminal domain (AR-NTD), which is known to be largely intrinsically disordered. This N-terminal domain contains an 11 residue conserved domain that forms amyloid fibers upon oxidative dimerisation through its strictly conserved Cys240 residue. We investigate here the interaction of BPA, and other potential endocrine disruptors, with AR-NTD amyloid fibers using the WaterLOGSY NMR experiment. We observed a selective binding of these compounds to the amyloid fibers formed by the AR-NTD conserved region and glutamine homopolymers. This observation suggests that the high potency of endocrine disruptors may result, in part, from their ability to bind amyloid forms of nuclear receptors in addition to their cognate binding sites. This property may be exploited to design future therapeutic strategies targeting AR related diseases such as the spinal bulbar muscular atrophy or prostate cancer. The ability of NMR WaterLOGSY experiments to detect weak interactions between small ligands and amyloid fibers may prove to be of particular interest for identifying promising hit molecules.

  8. NMR WaterLOGSY Reveals Weak Binding of Bisphenol A with Amyloid Fibers of a Conserved 11 Residue Peptide from Androgen Receptor

    PubMed Central

    Asencio-Hernández, Julia; Kieffer, Bruno

    2016-01-01

    There is growing evidence that bisphenol A (BPA), a molecule largely released in the environment, has detrimental effects on ecosystems and on human health. It acts as an endocrine disruptor targeting steroid hormone receptors, such as the estrogen receptor (ER), estrogen-related receptor (ERR) and androgen receptor (AR). BPA-derived molecules have recently been shown to interact with the AR N-terminal domain (AR-NTD), which is known to be largely intrinsically disordered. This N-terminal domain contains an 11 residue conserved domain that forms amyloid fibers upon oxidative dimerisation through its strictly conserved Cys240 residue. We investigate here the interaction of BPA, and other potential endocrine disruptors, with AR-NTD amyloid fibers using the WaterLOGSY NMR experiment. We observed a selective binding of these compounds to the amyloid fibers formed by the AR-NTD conserved region and glutamine homopolymers. This observation suggests that the high potency of endocrine disruptors may result, in part, from their ability to bind amyloid forms of nuclear receptors in addition to their cognate binding sites. This property may be exploited to design future therapeutic strategies targeting AR related diseases such as the spinal bulbar muscular atrophy or prostate cancer. The ability of NMR WaterLOGSY experiments to detect weak interactions between small ligands and amyloid fibers may prove to be of particular interest for identifying promising hit molecules. PMID:27583469

  9. Transgenic mice over-expressing human beta-amyloid have functional nicotinic alpha 7 receptors.

    PubMed

    Spencer, J P; Weil, A; Hill, K; Hussain, I; Richardson, J C; Cusdin, F S; Chen, Y H; Randall, A D

    2006-02-01

    A potentially major factor in the development of Alzheimer's disease is the enhanced production of soluble beta-amyloid peptide fragments amyloid beta peptide(1-40) and amyloid beta peptide(1-42). These amyloid peptides are generated by cleavage of the amyloid-precursor protein and aggregate spontaneously to form amyloid plaques, which are a classical pathological hallmark in Alzheimer's disease. Although the precise mechanisms are unknown, it is widely believed that amyloid peptides initiate the degenerative process, resulting in subsequent cognitive decline. One interaction of amyloid beta peptide that may contribute to an impairment of cognition is its high affinity binding to the alpha 7 nicotinic receptor; a receptor shown to be important for cognition in a number of studies. There is some controversy, however, whether amyloid beta peptide inhibits or activates this receptor. We have cloned and stably expressed the human alpha 7 receptor and investigated its interaction with amyloid beta peptide using patch clamp electrophysiology. Human alpha 7 was activated in a concentration-dependent fashion by nicotine, acetylcholine and choline and potently inhibited by methyllycaconitine citrate. The responses were inwardly rectifying and exhibited rapid activation, desensitization and deactivation. Amyloid beta peptide(1-42) antagonized human alpha7 responses in a partially reversible fashion; no agonist effects of amyloid beta peptide(1-42) were detected. A similar inhibition of mouse alpha 7 was also observed. In addition, we have assessed the function of native alpha 7 receptors in hippocampal slices prepared from transgenic mice that over-express human amyloid. Despite this clear inhibition of recombinant receptors, hippocampal GABAergic interneurones in slices from beta-amyloid over-expressing mice still possess alpha 7 receptor-mediated currents.

  10. Atomic force microscopy and MD simulations reveal pore-like structures of all-D-enantiomer of Alzheimer's β-amyloid peptide: relevance to the ion channel mechanism of AD pathology.

    PubMed

    Connelly, Laura; Jang, Hyunbum; Arce, Fernando Teran; Capone, Ricardo; Kotler, Samuel A; Ramachandran, Srinivasan; Kagan, Bruce L; Nussinov, Ruth; Lal, Ratnesh

    2012-02-01

    Alzheimer's disease (AD) is a protein misfolding disease characterized by a buildup of β-amyloid (Aβ) peptide as senile plaques, uncontrolled neurodegeneration, and memory loss. AD pathology is linked to the destabilization of cellular ionic homeostasis and involves Aβ peptide-plasma membrane interactions. In principle, there are two possible ways through which disturbance of the ionic homeostasis can take place: directly, where the Aβ peptide either inserts into the membrane and creates ion-conductive pores or destabilizes the membrane organization, or, indirectly, where the Aβ peptide interacts with existing cell membrane receptors. To distinguish between these two possible types of Aβ-membrane interactions, we took advantage of the biochemical tenet that ligand-receptor interactions are stereospecific; L-amino acid peptides, but not their D-counterparts, bind to cell membrane receptors. However, with respect to the ion channel-mediated mechanism, like L-amino acids, D-amino acid peptides will also form ion channel-like structures. Using atomic force microscopy (AFM), we imaged the structures of both D- and L-enantiomers of the full length Aβ(1-42) when reconstituted in lipid bilayers. AFM imaging shows that both L- and D-Aβ isomers form similar channel-like structures. Molecular dynamics (MD) simulations support the AFM imaged 3D structures. Previously, we have shown that D-Aβ(1-42) channels conduct ions similarly to their L- counterparts. Taken together, our results support the direct mechanism of Aβ ion channel-mediated destabilization of ionic homeostasis rather than the indirect mechanism through Aβ interaction with membrane receptors.

  11. Effects of amyloid β-peptide fragment 31-35 on the BK channel-mediated K⁺ current and intracellular free Ca²⁺ concentration of hippocampal CA1 neurons.

    PubMed

    Zhang, Yu; Shi, Zhi-Gang; Wang, Zhi-Hua; Li, Jian-Guo; Chen, Jin-Yuan; Zhang, Ce

    2014-05-01

    The present study characterizes the effects of Aβ31-35, a short active fragment of amyloid β-peptide (Aβ), upon the BK channel-mediated K⁺ current and intracellular free Ca²⁺ concentration ([Ca²⁺]i) of freshly dissociated pyramidal cells from rat CA1 hippocampus by using whole-cell patch-clamp recording and single cell Ca²⁺ imaging techniques. The results show that: (1) in the presence of voltage- and ATP-gated K⁺ channel blockers application of 5.0 μM Aβ31-35 significantly diminished transient outward K⁺ current amplitudes at clamped voltages between 0 and 45mV; (2) under the same conditions [Ca²⁺]i was minimally affected by 5.0 μM but significantly increased by 12.5 μM and 25 μM Aβ31-35; and (3) when 25 μM of a larger fragment of the amyloid β-peptide, Aβ25-35, was applied, the results were similar to those obtained with the same concentration of Aβ31-35. These results indicate that Aβ31-35 is likely to be the shortest active fragment of the full Aβ sequence, and can be as effectively as the full-length Aβ peptide in suppressing BK-channel mediated K⁺ currents and significantly elevating [Ca²⁺]i in hippocampal CA1 neurons.

  12. Immunoprecipitation of Amyloid Fibrils by the Use of an Antibody that Recognizes a Generic Epitope Common to Amyloid Fibrils

    PubMed Central

    Greiner, Erin R.; Kelly, Jeffery W.; Palhano, Fernando L.

    2014-01-01

    Amyloid fibrils are associated with many maladies, including Alzheimer’s disease (AD). The isolation of amyloids from natural materials is very challenging because the extreme structural stability of amyloid fibrils makes it difficult to apply conventional protein science protocols to their purification. A protocol to isolate and detect amyloids is desired for the diagnosis of amyloid diseases and for the identification of new functional amyloids. Our aim was to develop a protocol to purify amyloid from organisms, based on the particular characteristics of the amyloid fold, such as its resistance to proteolysis and its capacity to be recognized by specific conformational antibodies. We used a two-step strategy with proteolytic digestion as the first step followed by immunoprecipitation using the amyloid conformational antibody LOC. We tested the efficacy of this method using as models amyloid fibrils produced in vitro, tissue extracts from C. elegans that overexpress Aβ peptide, and cerebrospinal fluid (CSF) from patients diagnosed with AD. We were able to immunoprecipitate Aβ1–40 amyloid fibrils, produced in vitro and then added to complex biological extracts, but not α-synuclein and gelsolin fibrils. This method was useful for isolating amyloid fibrils from tissue homogenates from a C. elegans AD model, especially from aged worms. Although we were able to capture picogram quantities of Aβ1–40 amyloid fibrils produced in vitro when added to complex biological solutions, we could not detect any Aβ amyloid aggregates in CSF from AD patients. Our results show that although immunoprecipitation using the LOC antibody is useful for isolating Aβ1–40 amyloid fibrils, it fails to capture fibrils of other amyloidogenic proteins, such as α-synuclein and gelsolin. Additional research might be needed to improve the affinity of these amyloid conformational antibodies for an array of amyloid fibrils without compromising their selectivity before application of this

  13. Contrasting effects of nanoparticle-protein attraction on amyloid aggregation

    PubMed Central

    Radic, Slaven; Davis, Thomas P; Ke, Pu Chun; Ding, Feng

    2015-01-01

    Nanoparticles (NPs) have been experimentally found to either promote or inhibit amyloid aggregation of proteins, but the molecular mechanisms for such complex behaviors remain unknown. Using coarse-grained molecular dynamics simulations, we investigated the effects of varying the strength of nonspecific NP-protein attraction on amyloid aggregation of a model protein, the amyloid-beta peptide implicated in Alzheimer's disease. Specifically, with increasing NP-peptide attraction, amyloid aggregation on the NP surface was initially promoted due to increased local protein concentration on the surface and destabilization of the folded state. However, further increase of NP-peptide attraction decreased the stability of amyloid fibrils and reduced their lateral diffusion on the NP surface necessary for peptide conformational changes and self-association, thus prohibiting amyloid aggregation. Moreover, we found that the relative concentration between protein and NPs also played an important role in amyloid aggregation. With a high NP/protein ratio, NPs that intrinsically promote protein aggregation may display an inhibitive effect by depleting the proteins in solution while having a low concentration of the proteins on each NP's surface. Our coarse-grained molecular dynamics simulation study offers a molecular mechanism for delineating the contrasting and seemingly conflicting effects of NP-protein attraction on amyloid aggregation and highlights the potential of tailoring anti-aggregation nanomedicine against amyloid diseases. PMID:26989481

  14. Amyloid Polymorphism: Structural Basis and Neurobiological Relevance

    PubMed Central

    Tycko, Robert

    2015-01-01

    Summary Our understanding of the molecular structures of amyloid fibrils that are associated with neurodegenerative diseases, of mechanisms by which disease-associated peptides and proteins aggregate into fibrils, and of structural properties of aggregation intermediates has advanced considerably in recent years. Detailed molecular structural models for certain fibrils and aggregation intermediates are now available. It is now well established that amyloid fibrils are generally polymorphic at the molecular level, with a given peptide or protein being capable of forming a variety of distinct, self-propagating fibril structures. Recent results from structural studies and from studies involving cell cultures, transgenic animals, and human tissue provide initial evidence that molecular structural variations in amyloid fibrils and related aggregates may correlate with or even produce variations in disease development. This article reviews our current knowledge of the structural and mechanistic aspects of amyloid formation, as well as current evidence for the biological relevance of structural variations. PMID:25950632

  15. Oral administration of a fusion protein between the cholera toxin B subunit and the 42-amino acid isoform of amyloidpeptide produced in silkworm pupae protects against Alzheimer's disease in mice.

    PubMed

    Li, Si; Wei, Zhen; Chen, Jian; Chen, Yanhong; Lv, Zhengbing; Yu, Wei; Meng, Qiaohong; Jin, Yongfeng

    2014-01-01

    A key molecule in the pathogenesis of Alzheimer's disease (AD) is a 42-amino acid isoform of the amyloidpeptide (Aβ42), which is the most toxic element of senile plaques. In this study, to develop an edible, safe, low-cost vaccine for AD, a cholera toxin B subunit (CTB)-Aβ42 fusion protein was successfully expressed in silkworm pupae. We tested the silkworm pupae-derived oral vaccination containing CTB-Aβ42 in a transgenic mouse model of AD. Anti-Aβ42 antibodies were induced in these mice, leading to a decreased Aβ deposition in the brain. We also found that the oral administration of the silk worm pupae vaccine improved the memory and cognition of mice, as assessed using a water maze test. These results suggest that the new edible CTB-Aβ42 silkworm pupae-derived vaccine has potential clinical application in the prevention of AD.

  16. A novel retro-inverso peptide inhibitor reduces amyloid deposition, oxidation and inflammation and stimulates neurogenesis in the APPswe/PS1ΔE9 mouse model of Alzheimer's disease.

    PubMed

    Parthsarathy, Vadivel; McClean, Paula L; Hölscher, Christian; Taylor, Mark; Tinker, Claire; Jones, Glynn; Kolosov, Oleg; Salvati, Elisa; Gregori, Maria; Masserini, Massimo; Allsop, David

    2013-01-01

    Previously, we have developed a retro-inverso peptide inhibitor (RI-OR2, rGffvlkGr) that blocks the in vitro formation and toxicity of the Aβ oligomers which are thought to be a cause of neurodegeneration and memory loss in Alzheimer's disease. We have now attached a retro-inverted version of the HIV protein transduction domain 'TAT' to RI-OR2 to target this new inhibitor (RI-OR2-TAT, Ac-rGffvlkGrrrrqrrkkrGy-NH(2)) into the brain. Following its peripheral injection, a fluorescein-labelled version of RI-OR2-TAT was found to cross the blood brain barrier and bind to the amyloid plaques and activated microglial cells present in the cerebral cortex of 17-months-old APPswe/PS1ΔE9 transgenic mice. Daily intraperitoneal injection of RI-OR2-TAT (at 100 nmol/kg) for 21 days into 10-months-old APPswe/PS1ΔE9 mice resulted in a 25% reduction (p<0.01) in the cerebral cortex of Aβ oligomer levels, a 32% reduction (p<0.0001) of β-amyloid plaque count, a 44% reduction (p<0.0001) in the numbers of activated microglial cells, and a 25% reduction (p<0.0001) in oxidative damage, while the number of young neurons in the dentate gyrus was increased by 210% (p<0.0001), all compared to control APPswe/PS1ΔE9 mice injected with vehicle (saline) alone. Our data suggest that oxidative damage, inflammation, and inhibition of neurogenesis are all a downstream consequence of Aβ aggregation, and identify a novel brain-penetrant retro-inverso peptide inhibitor of Aβ oligomer formation for further testing in humans as a potential disease-modifying treatment for Alzheimer's disease.

  17. Extension of the generic amyloid hypothesis to nonproteinaceous metabolite assemblies

    PubMed Central

    Shaham-Niv, Shira; Adler-Abramovich, Lihi; Schnaider, Lee; Gazit, Ehud

    2015-01-01

    The accumulation of amyloid fibrils is the hallmark of several major human diseases. Although the formation of these supramolecular entities has previously been associated with proteins and peptides, it was later demonstrated that even phenylalanine, a single amino acid, can form fibrils that have amyloid-like biophysical, biochemical, and cytotoxic properties. Moreover, the generation of antibodies against these assemblies in phenylketonuria patients and the correlating mice model suggested a pathological role for the assemblies. We determine that several other metabolites that accumulate in metabolic disorders form ordered amyloid-like ultrastructures, which induce apoptotic cell death, as observed for amyloid structures. The formation of amyloid-like assemblies by metabolites implies a general phenomenon of amyloid formation, not limited to proteins and peptides, and offers a new paradigm for metabolic diseases. PMID:26601224

  18. Amyloid β-sheet mimics that antagonize protein aggregation and reduce amyloid toxicity

    NASA Astrophysics Data System (ADS)

    Cheng, Pin-Nan; Liu, Cong; Zhao, Minglei; Eisenberg, David; Nowick, James S.

    2012-11-01

    The amyloid protein aggregation associated with diseases such as Alzheimer's, Parkinson's and type II diabetes (among many others) features a bewildering variety of β-sheet-rich structures in transition from native proteins to ordered oligomers and fibres. The variation in the amino-acid sequences of the β-structures presents a challenge to developing a model system of β-sheets for the study of various amyloid aggregates. Here, we introduce a family of robust β-sheet macrocycles that can serve as a platform to display a variety of heptapeptide sequences from different amyloid proteins. We have tailored these amyloid β-sheet mimics (ABSMs) to antagonize the aggregation of various amyloid proteins, thereby reducing the toxicity of amyloid aggregates. We describe the structures and inhibitory properties of ABSMs containing amyloidogenic peptides from the amyloidpeptide associated with Alzheimer's disease, β2-microglobulin associated with dialysis-related amyloidosis, α-synuclein associated with Parkinson's disease, islet amyloid polypeptide associated with type II diabetes, human and yeast prion proteins, and Tau, which forms neurofibrillary tangles.

  19. SOLID STATE NMR AS A PROBE OF AMYLOID STRUCTURE

    PubMed Central

    Tycko, Robert

    2005-01-01

    Solid state nuclear magnetic resonance (NMR) has developed into one of the most informative and direct experimental approaches to the characterization of the molecular structures of amyloid fibrils, including those associated with Alzheimer's disease. In this article, essential aspects of solid state NMR methods are described briefly and results obtained to date regarding the supramolecular organization of amyloid fibrils and the conformations of peptides within amyloid fibrils are reviewed. PMID:16515450

  20. [Amyloid goiter].

    PubMed

    Hrívó, A; Péter, I; Bánkúti, B; Péley, G; Baska, F; Besznyák, I

    1999-03-21

    Amyloid goitre is at an extremely rare occurrence. Authors review the origin of disease and its symptoms, diagnostic and therapeutic tools. The disease may be due to either primary or secondary systemic or local amyloidosis. Diagnosis may be made even before surgery on anamnestic data, on very rapid growth of thyroid glands, on diffuse appearance, on other symptoms of systemic amyloidosis, on findings of iconographic procedures and on detection of amyloid in aspirates. Final diagnosis is based on histology. Surgical therapy is aiming at avoidance of the existing and the threatening consequences of expanding mass. The outcome is independent from thyroid surgery, it is related to other manifestations of amyloidosis. Concerning with the present case the chronic superior vena cava syndrome and chylous pleural effusion as first described symptoms and asymptomatic hyperthyroxinaemia is emphasised. Neither other organ involvement, nor primary amyloidogenous molecula was found during the 18 months follow up, so patient has secondary and localised amyloidosis.

  1. Difference in aggregation between functional and toxic amyloids studied by atomistic simulations

    NASA Astrophysics Data System (ADS)

    Carballo Pacheco, Martin; Ismail, Ahmed E.; Strodel, Birgit

    Amyloids are highly structured protein aggregates, normally associated with neurodegenerative diseases such as Alzheimer's disease. In recent years, a number of nontoxic amyloids with physiologically normal functions, called functional amyloids, have been found. It is known that soluble small oligomers are more toxic than large fibrils. Thus, we study with atomistic explicit-solvent molecular dynamics simulations the oligomer formation of the amyloid- β peptide Aβ25 - 35, associated with Alzheimer's disease, and two functional amyloid-forming tachykinin peptides: kassinin and neuromedin K. Our simulations show that monomeric peptides in extended conformations aggregate faster than those in collapsed hairpin-like conformations. In addition, we observe faster aggregation by functional amyloids than toxic amyloids, which could explain their lack of toxicity.

  2. Neuritic Plaques and Cerebrovascular Amyloid in Alzheimer Disease are Antigenically Related

    NASA Astrophysics Data System (ADS)

    Wong, Caine W.; Quaranta, Vito; Glenner, George G.

    1985-12-01

    A synthetic peptide (Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr), homologous to the amino terminus of a protein purified from cerebrovascular amyloid (β protein), induced antibodies in BALB/c mice that were used immunohistochemically to stain not only amyloid-laden cerebral vessels but neuritic plaques as well. These findings suggest that the amyloid in neuritic plaques shares antigenic determinants with β protein of cerebral vessels. Since the amino acid compositions of plaque amyloid and cerebrovascular amyloid are similar, it is likely that plaque amyloid also consists of β protein. This possibility suggests a model for the pathogenesis of Alzheimer disease involving β protein.

  3. Cu(II)-Zn(II) Cross-Modulation in Amyloid-Beta Peptide Binding: an X-ray Absorption Spectroscopy Study

    PubMed Central

    De Santis, Emiliano; Minicozzi, Velia; Proux, Olivier; Rossi, Giancarlo; Silva, K. Ishara; Lawless, Matthew J.; Stellato, Francesco; Saxena, Sunil; Morante, Silvia

    2015-01-01

    In this work we analyze at a structural level the mechanism by which Cu(II) and Zn(II) ions compete for binding to the Aβ peptides that is involved in the etiology of Alzheimer’s disease. We collected X-ray Absorption Spectroscopy data on samples containing Aβ with Cu and Zn at different concentration ratios. We show that the order in which metals are added to the peptide solution matters and that, when Zn is added first, it prevents Cu from binding. On the contrary, when Cu is added first, it does not (completely) prevent Zn binding to Aβ peptides. Our analysis suggests that Cu and Zn ions are coordinated to different numbers of histidine residues depending on the [ion]:[peptide] concentration ratio. PMID:26646533

  4. Protective effects of testosterone on cognitive dysfunction in Alzheimer's disease model rats induced by oligomeric beta amyloid peptide 1-42.

    PubMed

    Huo, Dong-Sheng; Sun, Jian-Fang; Zhang, Baifeng; Yan, Xu-Sheng; Wang, He; Jia, Jian-Xin; Yang, Zhan-Jun

    2016-01-01

    Cognitive dysfunction is known to be influenced by circulating sex steroidal hormones. The aim of this study was to examine the protective effect and possible protective mechanism of testosterone (T) on cognitive performance in male rats induced by intrahippocampal injections of beta amyloid 1-42 oligomers (Aβ1-42). Treatment with T as evidenced by the Morris water maze (MWM) test significantly shortened escape latency and reduced path length to reach the platform compared to the control (C). During probe trials, the T group displayed a significantly greater percent of time in the target quadrant and improved the number of platform crossings compared with C, flutamide (F), an antiandrogen, and a combined F and T group. Flutamide markedly inhibited the influence of T on cognitive performance. Following Nissl staining, the number of intact pyramidal cells was significantly elevated in the T group, and the effect of T was blocked by F. Immunohistochemisty and Western blot analysis showed that the protein expression level of Aβ 1-42 was markedly decreased and expression levels of synaptophysin (SYN) significantly increased with T, while F inhibited all T-mediated effects. Our data suggest that the influence of T on cognitive performance was mediated via androgen receptors (AR) to remove beta amyloid, which leads to enhanced synaptic plasticity. PMID:27599231

  5. Curcumin Ameliorates the Reduction Effect of PGE2 on Fibrillar β-Amyloid Peptide (1-42)-Induced Microglial Phagocytosis through the Inhibition of EP2-PKA Signaling in N9 Microglial Cells

    PubMed Central

    Yang, Ju; Shen, Ting-ting; Chen, Yi; Yang, Xue-Sen

    2016-01-01

    Inflammatory activation of microglia and β amyloid (Aβ) deposition are considered to work both independently and synergistically to contribute to the increased risk of Alzheimer’s disease (AD). Recent studies indicate that long-term use of phenolic compounds provides protection against AD, primarily due to their anti-inflammatory actions. We previously suggested that phenolic compound curcumin ameliorated phagocytosis possibly through its anti-inflammatory effects rather than direct regulation of phagocytic function in electromagnetic field-exposed N9 microglial cells (N9 cells). Here, we explored the prostaglandin-E2 (PGE2)-related signaling pathway that involved in curcumin-mediated phagocytosis in fibrillar β-amyloid peptide (1–42) (fAβ42)-stimulated N9 cells. Treatment with fAβ42 increased phagocytosis of fluorescent-labeled latex beads in N9 cells. This increase was attenuated in a dose-dependent manner by endogenous and exogenous PGE2, as well as a selective EP2 or protein kinase A (PKA) agonist, but not by an EP4 agonist. We also found that an antagonist of EP2, but not EP4, abolished the reduction effect of PGE2 on fAβ42-induced microglial phagocytosis. Additionally, the increased expression of endogenous PGE2, EP2, and cyclic adenosine monophosphate (AMP), and activation of vasodilator-stimulated phosphoprotein, cyclic AMP responsive element-binding protein, and PKA were depressed by curcumin administration. This reduction led to the amelioration of the phagocytic abilities of PGE2-stimulated N9 cells. Taken together, these data suggested that curcumin restored the attenuating effect of PGE2 on fAβ42-induced microglial phagocytosis via a signaling mechanism involving EP2 and PKA. Moreover, due to its immune modulatory effects, curcumin may be a promising pharmacological candidate for neurodegenerative diseases. PMID:26824354

  6. Curcumin Ameliorates the Reduction Effect of PGE2 on Fibrillar β-Amyloid Peptide (1-42)-Induced Microglial Phagocytosis through the Inhibition of EP2-PKA Signaling in N9 Microglial Cells.

    PubMed

    He, Gen-Lin; Luo, Zhen; Yang, Ju; Shen, Ting-Ting; Chen, Yi; Yang, Xue-Sen

    2016-01-01

    Inflammatory activation of microglia and β amyloid (Aβ) deposition are considered to work both independently and synergistically to contribute to the increased risk of Alzheimer's disease (AD). Recent studies indicate that long-term use of phenolic compounds provides protection against AD, primarily due to their anti-inflammatory actions. We previously suggested that phenolic compound curcumin ameliorated phagocytosis possibly through its anti-inflammatory effects rather than direct regulation of phagocytic function in electromagnetic field-exposed N9 microglial cells (N9 cells). Here, we explored the prostaglandin-E2 (PGE2)-related signaling pathway that involved in curcumin-mediated phagocytosis in fibrillar β-amyloid peptide (1-42) (fAβ42)-stimulated N9 cells. Treatment with fAβ42 increased phagocytosis of fluorescent-labeled latex beads in N9 cells. This increase was attenuated in a dose-dependent manner by endogenous and exogenous PGE2, as well as a selective EP2 or protein kinase A (PKA) agonist, but not by an EP4 agonist. We also found that an antagonist of EP2, but not EP4, abolished the reduction effect of PGE2 on fAβ42-induced microglial phagocytosis. Additionally, the increased expression of endogenous PGE2, EP2, and cyclic adenosine monophosphate (AMP), and activation of vasodilator-stimulated phosphoprotein, cyclic AMP responsive element-binding protein, and PKA were depressed by curcumin administration. This reduction led to the amelioration of the phagocytic abilities of PGE2-stimulated N9 cells. Taken together, these data suggested that curcumin restored the attenuating effect of PGE2 on fAβ42-induced microglial phagocytosis via a signaling mechanism involving EP2 and PKA. Moreover, due to its immune modulatory effects, curcumin may be a promising pharmacological candidate for neurodegenerative diseases.

  7. Curcumin Ameliorates the Reduction Effect of PGE2 on Fibrillar β-Amyloid Peptide (1-42)-Induced Microglial Phagocytosis through the Inhibition of EP2-PKA Signaling in N9 Microglial Cells.

    PubMed

    He, Gen-Lin; Luo, Zhen; Yang, Ju; Shen, Ting-Ting; Chen, Yi; Yang, Xue-Sen

    2016-01-01

    Inflammatory activation of microglia and β amyloid (Aβ) deposition are considered to work both independently and synergistically to contribute to the increased risk of Alzheimer's disease (AD). Recent studies indicate that long-term use of phenolic compounds provides protection against AD, primarily due to their anti-inflammatory actions. We previously suggested that phenolic compound curcumin ameliorated phagocytosis possibly through its anti-inflammatory effects rather than direct regulation of phagocytic function in electromagnetic field-exposed N9 microglial cells (N9 cells). Here, we explored the prostaglandin-E2 (PGE2)-related signaling pathway that involved in curcumin-mediated phagocytosis in fibrillar β-amyloid peptide (1-42) (fAβ42)-stimulated N9 cells. Treatment with fAβ42 increased phagocytosis of fluorescent-labeled latex beads in N9 cells. This increase was attenuated in a dose-dependent manner by endogenous and exogenous PGE2, as well as a selective EP2 or protein kinase A (PKA) agonist, but not by an EP4 agonist. We also found that an antagonist of EP2, but not EP4, abolished the reduction effect of PGE2 on fAβ42-induced microglial phagocytosis. Additionally, the increased expression of endogenous PGE2, EP2, and cyclic adenosine monophosphate (AMP), and activation of vasodilator-stimulated phosphoprotein, cyclic AMP responsive element-binding protein, and PKA were depressed by curcumin administration. This reduction led to the amelioration of the phagocytic abilities of PGE2-stimulated N9 cells. Taken together, these data suggested that curcumin restored the attenuating effect of PGE2 on fAβ42-induced microglial phagocytosis via a signaling mechanism involving EP2 and PKA. Moreover, due to its immune modulatory effects, curcumin may be a promising pharmacological candidate for neurodegenerative diseases. PMID:26824354

  8. Alcadein Cleavages by Amyloid β-Precursor Protein (APP) α- and γ-Secretases Generate Small Peptides, p3-Alcs, Indicating Alzheimer Disease-related γ-Secretase Dysfunction*

    PubMed Central

    Hata, Saori; Fujishige, Sayaka; Araki, Yoichi; Kato, Naoko; Araseki, Masahiko; Nishimura, Masaki; Hartmann, Dieter; Saftig, Paul; Fahrenholz, Falk; Taniguchi, Miyako; Urakami, Katsuya; Akatsu, Hiroyasu; Martins, Ralph N.; Yamamoto, Kazuo; Maeda, Masahiro; Yamamoto, Tohru; Nakaya, Tadashi; Gandy, Sam; Suzuki, Toshiharu

    2009-01-01

    Alcadeins (Alcs) constitute a family of neuronal type I membrane proteins, designated Alcα, Alcβ, and Alcγ. The Alcs express in neurons dominantly and largely colocalize with the Alzheimer amyloid precursor protein (APP) in the brain. Alcs and APP show an identical function as a cargo receptor of kinesin-1. Moreover, proteolytic processing of Alc proteins appears highly similar to that of APP. We found that APP α-secretases ADAM 10 and ADAM 17 primarily cleave Alc proteins and trigger the subsequent secondary intramembranous cleavage of Alc C-terminal fragments by a presenilin-dependent γ-secretase complex, thereby generating “APP p3-like” and non-aggregative Alc peptides (p3-Alcs). We determined the complete amino acid sequence of p3-Alcα, p3-Alcβ, and p3-Alcγ, whose major species comprise 35, 37, and 31 amino acids, respectively, in human cerebrospinal fluid. We demonstrate here that variant p3-Alc C termini are modulated by FAD-linked presenilin 1 mutations increasing minor β-amyloid species Aβ42, and these mutations alter the level of minor p3-Alc species. However, the magnitudes of C-terminal alteration of p3-Alcα, p3-Alcβ, and p3-Alcγ were not equivalent, suggesting that one type of γ-secretase dysfunction does not appear in the phenotype equivalently in the cleavage of type I membrane proteins. Because these C-terminal alterations are detectable in human cerebrospinal fluid, the use of a substrate panel, including Alcs and APP, may be effective to detect γ-secretase dysfunction in the prepathogenic state of Alzheimer disease subjects. PMID:19864413

  9. Towards Prebiotic Catalytic Amyloids Using High Throughput Screening

    PubMed Central

    Friedmann, Michael P.; Torbeev, Vladimir; Zelenay, Viviane; Sobol, Alexander; Greenwald, Jason; Riek, Roland

    2015-01-01

    Enzymes are capable of directing complex stereospecific transformations and of accelerating reaction rates many orders of magnitude. As even the simplest known enzymes comprise thousands of atoms, the question arises as to how such exquisite catalysts evolved. A logical predecessor would be shorter peptides, but they lack the defined structure and size that are apparently necessary for enzyme functions. However, some very short peptides are able to assemble into amyloids, thereby forming a well-defined tertiary structure called the cross-β-sheet, which bestows unique properties upon the peptides. We have hypothesized that amyloids could have been the catalytically active precursor to modern enzymes. To test this hypothesis, we designed an amyloid peptide library that could be screened for catalytic activity. Our approach, amenable to high-throughput methodologies, allowed us to find several peptides and peptide mixtures that form amyloids with esterase activity. These results indicate that amyloids, with their stability in a wide range of conditions and their potential as catalysts with low sequence specificity, would indeed be fitting precursors to modern enzymes. Furthermore, our approach can be efficiently expanded upon in library size, screening conditions, and target activity to yield novel amyloid catalysts with potential applications in aqueous-organic mixtures, at high temperature and in other extreme conditions that could be advantageous for industrial applications. PMID:26650386

  10. Pathology of the vessels in cerebral amyloid angiopathy.

    PubMed

    Liberski, P P; Barcikowska, M

    1995-01-01

    We review here current data on congophilic amyloid angiopathy (congophilic angiopathy) or cerebral amyloid angiopathy in both transmissible and non-transmissible cerebral amyloidoses. A beta peptide is the amyloid in congophilic angiopathy of Alzheimer's disease, and in majority of cases of Creutzfeld-Jakob disease and Gerstmann-Sträussler-Scheinker disease. A variant of Cystatin C is the amyloid in hereditary cerebral hemorrhage with amyloidosis-Icelandic type. The only exception is a curious GSS-like family from Japan characterized by 145 stop codon at the PRNP gene. Both molecular pathology and neuropathology are covered by this review.

  11. Amyloid imaging in Alzheimer's disease: a literature review.

    PubMed

    Saidlitz, P; Voisin, T; Vellas, B; Payoux, P; Gabelle, A; Formaglio, M; Delrieu, J

    2014-07-01

    Therapies targeting amyloidpeptide currently represent approximately 50% of drugs now being developed for Alzheimer's disease. Some, including active and passive anti-Aβ immunotherapy, directly target the amyloid plaques. The new amyloid tracers are increasingly being included in the proposed updated diagnostic criteria, and may allow earlier diagnosis. Those targeting amyloidpeptide allow identification of amyloid plaques in vivo. We need to gain insight into all aspects of their application. As florbetapir (Amyvid™) and flutemetamol (Vizamyl™) have received marketing authorization, clinicians require deeper knowledge to be rationally used in diagnosis. In this paper, we review both completed and ongoing observational, longitudinal and interventional studies of these tracers, our main objective being to show the performance of the four most commonly used tracers and their validation. PMID:25226113

  12. Preparation of Amyloid Fibrils Seeded from Brain and Meninges.

    PubMed

    Scherpelz, Kathryn P; Lu, Jun-Xia; Tycko, Robert; Meredith, Stephen C

    2016-01-01

    Seeding of amyloid fibrils into fresh solutions of the same peptide or protein in disaggregated form leads to the formation of replicate fibrils, with close structural similarity or identity to the original fibrillar seeds. Here we describe procedures for isolating fibrils composed mainly of β-amyloid (Aβ) from human brain and from leptomeninges, a source of cerebral blood vessels, for investigating Alzheimer's disease and cerebral amyloid angiopathy. We also describe methods for seeding isotopically labeled, disaggregated Aβ peptide solutions for study using solid-state NMR and other techniques. These methods should be applicable to other types of amyloid fibrils, to Aβ fibrils from mice or other species, tissues other than brain, and to some non-fibrillar aggregates. These procedures allow for the examination of authentic amyloid fibrils and other protein aggregates from biological tissues without the need for labeling the tissue.

  13. Long-Term Treatment with Liraglutide, a Glucagon-Like Peptide-1 (GLP-1) Receptor Agonist, Has No Effect on β-Amyloid Plaque Load in Two Transgenic APP/PS1 Mouse Models of Alzheimer's Disease.

    PubMed

    Hansen, Henrik H; Fabricius, Katrine; Barkholt, Pernille; Kongsbak-Wismann, Pernille; Schlumberger, Chantal; Jelsing, Jacob; Terwel, Dick; Termont, Annelies; Pyke, Charles; Knudsen, Lotte Bjerre; Vrang, Niels

    2016-01-01

    One of the major histopathological hallmarks of Alzheimer's disease (AD) is cerebral deposits of extracellular β-amyloid peptides. Preclinical studies have pointed to glucagon-like peptide 1 (GLP-1) receptors as a potential novel target in the treatment of AD. GLP-1 receptor agonists, including exendin-4 and liraglutide, have been shown to promote plaque-lowering and mnemonic effects of in a number of experimental models of AD. Transgenic mouse models carrying genetic mutations of amyloid protein precursor (APP) and presenilin-1 (PS1) are commonly used to assess the pharmacodynamics of potential amyloidosis-lowering and pro-cognitive compounds. In this study, effects of long-term liraglutide treatment were therefore determined in two double APP/PS1 transgenic mouse models of Alzheimer's disease carrying different clinical APP/PS1 mutations, i.e. the 'London' (hAPPLon/PS1A246E) and 'Swedish' mutation variant (hAPPSwe/PS1ΔE9) of APP, with co-expression of distinct PS1 variants. Liraglutide was administered in 5 month-old hAPPLon/PS1A246E mice for 3 months (100 or 500 ng/kg/day, s.c.), or 7 month-old hAPPSwe/PS1ΔE9 mice for 5 months (500 ng/kg/day, s.c.). In both models, regional plaque load was quantified throughout the brain using stereological methods. Vehicle-dosed hAPPSwe/PS1ΔE9 mice exhibited considerably higher cerebral plaque load than hAPPLon/PS1A246E control mice. Compared to vehicle-dosed transgenic controls, liraglutide treatment had no effect on the plaque levels in hAPPLon/PS1A246E and hAPPSwe/PS1ΔE9 mice. In conclusion, long-term liraglutide treatment exhibited no effect on cerebral plaque load in two transgenic mouse models of low- and high-grade amyloidosis, which suggests differential sensitivity to long-term liraglutide treatment in various transgenic mouse models mimicking distinct pathological hallmarks of AD. PMID:27421117

  14. Long-Term Treatment with Liraglutide, a Glucagon-Like Peptide-1 (GLP-1) Receptor Agonist, Has No Effect on β-Amyloid Plaque Load in Two Transgenic APP/PS1 Mouse Models of Alzheimer’s Disease

    PubMed Central

    Barkholt, Pernille; Kongsbak-Wismann, Pernille; Schlumberger, Chantal; Jelsing, Jacob; Terwel, Dick; Termont, Annelies; Pyke, Charles; Knudsen, Lotte Bjerre; Vrang, Niels

    2016-01-01

    One of the major histopathological hallmarks of Alzheimer’s disease (AD) is cerebral deposits of extracellular β-amyloid peptides. Preclinical studies have pointed to glucagon-like peptide 1 (GLP-1) receptors as a potential novel target in the treatment of AD. GLP-1 receptor agonists, including exendin-4 and liraglutide, have been shown to promote plaque-lowering and mnemonic effects of in a number of experimental models of AD. Transgenic mouse models carrying genetic mutations of amyloid protein precursor (APP) and presenilin-1 (PS1) are commonly used to assess the pharmacodynamics of potential amyloidosis-lowering and pro-cognitive compounds. In this study, effects of long-term liraglutide treatment were therefore determined in two double APP/PS1 transgenic mouse models of Alzheimer’s disease carrying different clinical APP/PS1 mutations, i.e. the ‘London’ (hAPPLon/PS1A246E) and ‘Swedish’ mutation variant (hAPPSwe/PS1ΔE9) of APP, with co-expression of distinct PS1 variants. Liraglutide was administered in 5 month-old hAPPLon/PS1A246E mice for 3 months (100 or 500 ng/kg/day, s.c.), or 7 month-old hAPPSwe/PS1ΔE9 mice for 5 months (500 ng/kg/day, s.c.). In both models, regional plaque load was quantified throughout the brain using stereological methods. Vehicle-dosed hAPPSwe/PS1ΔE9 mice exhibited considerably higher cerebral plaque load than hAPPLon/PS1A246E control mice. Compared to vehicle-dosed transgenic controls, liraglutide treatment had no effect on the plaque levels in hAPPLon/PS1A246E and hAPPSwe/PS1ΔE9 mice. In conclusion, long-term liraglutide treatment exhibited no effect on cerebral plaque load in two transgenic mouse models of low- and high-grade amyloidosis, which suggests differential sensitivity to long-term liraglutide treatment in various transgenic mouse models mimicking distinct pathological hallmarks of AD. PMID:27421117

  15. Alzheimer's Disease Related Markers, Cellular Toxicity and Behavioral Deficits Induced Six Weeks after Oligomeric AmyloidPeptide Injection in Rats

    PubMed Central

    Zussy, Charleine; Brureau, Anthony; Keller, Emeline; Marchal, Stéphane; Blayo, Claire; Delair, Brice; Ixart, Guy; Maurice, Tangui; Givalois, Laurent

    2013-01-01

    Alzheimer’s disease (AD) is a neurodegenerative pathology associated with aging characterized by the presence of senile plaques and neurofibrillary tangles that finally result in synaptic and neuronal loss. The major component of senile plaques is an amyloid-β protein (Aβ). Recently, we characterized the effects of a single intracerebroventricular (icv) injection of Aβ fragment (25–35) oligomers (oAβ25–35) for up to 3 weeks in rats and established a clear parallel with numerous relevant signs of AD. To clarify the long-term effects of oAβ25–35 and its potential role in the pathogenesis of AD, we determined its physiological, behavioral, biochemical and morphological impacts 6 weeks after injection in rats. oAβ25–35 was still present in the brain after 6 weeks. oAβ25–35 injection did not affect general activity and temperature rhythms after 6 weeks, but decreased body weight, induced short- and long-term memory impairments, increased corticosterone plasma levels, brain oxidative (lipid peroxidation), mitochondrial (caspase-9 levels) and reticulum stress (caspase-12 levels), astroglial and microglial activation. It provoked cholinergic neuron loss and decreased brain-derived neurotrophic factor levels. It induced cell loss in the hippocampic CA subdivisions and decreased hippocampic neurogenesis. Moreover, oAβ25–35 injection resulted in increased APP expression, Aβ1–42 generation, and increased Tau phosphorylation. In conclusion, this in vivo study evidenced that the soluble oligomeric forms of short fragments of Aβ, endogenously identified in AD patient brains, not only provoked long-lasting pathological alterations comparable to the human disease, but may also directly contribute to the progressive increase in amyloid load and Tau pathology, involved in the AD physiopathology. PMID:23301030

  16. Analysis of serum β-amyloid peptides, α2-macroglobulin, complement factor H, and clusterin levels in APP/PS1 transgenic mice during progression of Alzheimer's disease.

    PubMed

    Wang, Dejiang; Di, Xiangjun; Fu, Lu; Li, Yingnan; Han, Xiao; Wu, Hui; Cai, Linjun; Meng, Xiangyu; Jiang, Chunlai; Kong, Wei; Su, Weiheng

    2016-10-19

    As a progressive age-related neurodegenerative disorder, Alzheimer's disease (AD) is a global health concern. Despite the availability of psychological testing, neuroimaging, genetic testing, and biochemical assays of cerebrospinal fluid, convenient and accurate blood biomarkers for the prediction, diagnosis, and preclinical studies of AD are still lacking. The present study aims to longitudinally evaluate the feasibility of β-amyloid proteins, α2-macroglobulin (α-2M), complement factor H (CFH), and clusterin as blood biomarkers of AD. Using APP/PS1 transgenic and wild-type mice, cognitive impairment and amyloid plaque counts in the brain were evaluated over a range of ages using the Morris water maze test and immunohistochemistry methods, respectively. Serum Aβ40, Aβ42, α-2M, CFH, and clusterin levels were measured by enzyme-linked immunosorbent assay and correlated with progression of AD. APP/PS1 transgenic mice presented progressive AD characteristics at the ages of 3, 6, 9, and 12 months. Serum Aβ42 levels and Aβ42/Aβ40 ratios increased significantly in transgenic 3- and 6-month-old mice compared with controls. Serum CFH levels decreased significantly in 3- and 6-month-old transgenic mice compared with controls. Meanwhile, serum clusterin levels increased significantly in 12-month-old transgenic mice compared with controls. The α-2M level was not significantly different between transgenic and wild-type mice. The APP/PS1 transgenic mouse is a model of familial AD. The present study indicated that the serum Aβ42 level, Aβ42/Aβ40 ratio, and CFH level are potential biomarkers in preclinical and early stages of AD, whereas serum clusterin level is a potential biomarker in the late stage of AD. PMID:27541273

  17. Suppressed Accumulation of Cerebral Amyloid β Peptides in Aged Transgenic Alzheimer’s Disease Mice by Transplantation with Wild-Type or Prostaglandin E2 Receptor Subtype 2-Null Bone Marrow

    PubMed Central

    Keene, C. Dirk; Chang, Rubens C.; Lopez-Yglesias, Americo H.; Shalloway, Bryan R.; Sokal, Izabella; Li, Xianwu; Reed, Patrick J.; Keene, Lisa M.; Montine, Kathleen S.; Breyer, Richard M.; Rockhill, Jason K.; Montine, Thomas J.

    2010-01-01

    A complex therapeutic challenge for Alzheimer’s disease (AD) is minimizing deleterious aspects of microglial activation while maximizing beneficial actions, including phagocytosis/clearance of amyloid β (Aβ) peptides. One potential target is selective suppression of microglial prostaglandin E2 receptor subtype 2 (EP2) function, which influences microglial phagocytosis and elaboration of neurotoxic cytokines. To test this hypothesis, we transplanted bone marrow cells derived from wild-type mice or mice homozygous deficient for EP2 (EP2−/−) into lethally irradiated 5-month-old wild-type or APPswe-PS1ΔE9 double transgenic AD mouse model recipients. We found that cerebral engraftment by bone marrow transplant (BMT)-derived wild-type or EP2−/− microglia was more efficient in APPswe-PS1ΔE9 than in wild-type mice, and APPswe-PS1ΔE9 mice that received EP2−/− BMT had increased cortical microglia compared with APPswe-PS1ΔE9 mice that received wild-type BMT. We found that myeloablative irradiation followed by bone marrow transplant-derived microglia engraftment, rather than cranial irradiation or BMT alone, was responsible for the approximate one-third reduction in both Aβ plaques and potentially more neurotoxic soluble Aβ species. An additional 25% reduction in cerebral cortical Aβ burden was achieved in mice that received EP2−/− BMT compared with mice that received wild-type BMT. Our results provide a foundation for an adult stem cell-based therapy to suppress soluble Aβ peptide and plaque accumulation in the cerebrum of patients with AD. PMID:20522650

  18. Method for measurement of the blood-brain barrier permeability in the perfused mouse brain: application to amyloid-beta peptide in wild type and Alzheimer's Tg2576 mice.

    PubMed

    LaRue, Barbra; Hogg, Elizabeth; Sagare, Abhay; Jovanovic, Suzana; Maness, Lawrence; Maurer, Calvin; Deane, Rashid; Zlokovic, Berislav V

    2004-09-30

    The role of transport exchanges of neuroactive solutes across the blood-brain barrier (BBB) is increasingly recognized. To take full advantage of genetically altered mouse models of neurodegenerative disorders for BBB transport studies, we adapted a brain perfusion technique to the mouse. During a carotid brain perfusion with a medium containing sheep red blood cells and mock plasma, the physiological parameters in the arterial inflow, regional cerebral blood flow (14C-iodoantipyrine autoradiography), ultrastructural integrity of the tissue, barrier to lanthanum, brain water content, energy metabolites and lactate levels remain unchanged. Amyloid-beta peptides (Abeta) were iodinated by lactoperoxidase method. Non-oxidized mono-iodinated Abeta monomers were separated by HPLC (as confirmed by MALDI-TOF spectrometry) and used in transport measurements. Transport of intact 125I-Abeta40 across the BBB was time- and concentration-dependent in contrast to negligible 14C-inulin uptake. In 5-6 months old Alzheimer's Tg2576 mice, Abeta40 BBB transport was increased by >eight-fold compared to age-matched littermate controls, and was mediated via the receptor for advanced glycation endproducts. We conclude the present arterial brain perfusion method provides strictly controlled environment in cerebral microcirculation suitable for examining transport of rapidly and slowly penetrating molecules across the BBB in normal and transgenic mice.

  19. Testing synthetic amyloid-β aggregation inhibitor using single molecule atomic force spectroscopy.

    PubMed

    Hane, Francis T; Lee, Brenda Y; Petoyan, Anahit; Rauk, Arvi; Leonenko, Zoya

    2014-04-15

    Alzheimer's disease is a neurodegenerative disease with no known cure and few effective treatment options. The principal neurotoxic agent is an oligomeric form of the amyloidpeptide and one of the treatment options currently being studied is the inhibition of amyloid aggregation. In this work, we test a novel pseudopeptidic aggregation inhibitor designated as SG1. SG1 has been designed to bind at the amyloid-β self-recognition site and prevent amyloid-β from misfolding into β sheet. We used atomic force spectroscopy, a nanoscale measurement technique, to quantify the binding forces between two single amyloid peptide molecules. For the first time, we demonstrate that single molecule atomic force spectroscopy can be used to assess the effectiveness of amyloid aggregation inhibitors by measuring the experimental yield of binding and can potentially be used as a screening technique for quick testing of efficacy of inhibitor drugs for amyloid aggregation.

  20. Protective effects of Borago officinalis extract on amyloid β-peptide(25-35)-induced memory impairment in male rats: a behavioral study.

    PubMed

    Ghahremanitamadon, Fatemeh; Shahidi, Siamak; Zargooshnia, Somayeh; Nikkhah, Ali; Ranjbar, Akram; Soleimani Asl, Sara

    2014-01-01

    Alzheimer's disease (AD) is a neurodegenerative disorder and most common form of dementia that leads to memory impairment. In the present study we have examined the protective effects of Borago officinalis (borage) extract on Amyloid β (A β)-Induced memory impairment. Wistar male rats received intrahippocampal (IHP) injection of the A β (25-35) and borage extract throughout gestation (100 mg/kg). Learning and memory functions in the rats were examined by the passive avoidance and the Morris water maze (MWM) tasks. Finally, the antioxidant capacity of hippocampus was measured using ferric ion reducing antioxidant power (FRAP) assay. The results showed that A β (25-35) impaired step-through latency and time in dark compartment in passive avoidance task. In the MWM, A β (25-35) significantly increased escape latency and traveled distance. Borage administration attenuated the A β-induced memory impairment in both the passive avoidance and the MWM tasks. A β induced a remarkable decrease in antioxidant power (FRAP value) of hippocampus and borage prevented the decrease of the hippocampal antioxidant status. This data suggests that borage could improve the learning impairment and oxidative damage in the hippocampal tissue following A β treatment and that borage consumption may lead to an improvement of AD-induced cognitive dysfunction. PMID:25013802

  1. The role of side-chain interactions in the early steps of aggregation: Molecular dynamics simulations of an amyloid-forming peptide from the yeast prion Sup35

    NASA Astrophysics Data System (ADS)

    Gsponer, Jörg; Haberthür, Urs; Caflisch, Amedeo

    2003-04-01

    Understanding the early steps of aggregation at atomic detail might be crucial for the rational design of therapeutics preventing diseases associated with amyloid deposits. In this paper, aggregation of the heptapeptide GNNQQNY, from the N-terminal prion-determining domain of the yeast protein Sup35, was studied by 20 molecular dynamics runs for a total simulation time of 20 μs. The simulations generate in-register parallel packing of GNNQQNY -strands that is consistent with x-ray diffraction and Fourier transform infrared data. The statistically preferred aggregation pathway does not correspond to a purely downhill profile of the energy surface because of the presence of enthalpic barriers that originate from out-of-register interactions. The parallel -sheet arrangement is favored over the antiparallel because of side-chain contacts; in particular, stacking interactions of the tyrosine rings and hydrogen bonds between amide groups. No ordered aggregation was found in control simulations with the mutant sequence SQNGNQQRG in accord with experimental data and the strong sequence dependence of aggregation.

  2. Protective effects of Borago officinalis extract on amyloid β-peptide(25-35)-induced memory impairment in male rats: a behavioral study.

    PubMed

    Ghahremanitamadon, Fatemeh; Shahidi, Siamak; Zargooshnia, Somayeh; Nikkhah, Ali; Ranjbar, Akram; Soleimani Asl, Sara

    2014-01-01

    Alzheimer's disease (AD) is a neurodegenerative disorder and most common form of dementia that leads to memory impairment. In the present study we have examined the protective effects of Borago officinalis (borage) extract on Amyloid β (A