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Sample records for amyloid beta peptides

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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 ...

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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,…

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  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. 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.

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  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. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  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. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. The effect of tachykinin neuropeptides on amyloid {beta} aggregation

    SciTech Connect

    Flashner, Efrat; Raviv, Uri; Friedler, Assaf

    2011-04-01

    Research highlights: {yields} Mechanistic explanation of how tachykinin neuropeptides reduce A{beta}-induced neurotoxicity. {yields} Biophysical studies suggest that tachykinins do not modulate the distribution of A{beta} oligomeric states, but rather may incorporate into the fibrils. {yields} A possible strategy to inhibit toxicity of amyloid fibrils. -- Abstract: A hallmark of Alzheimer's disease is production of amyloid {beta} peptides resulting from aberrant cleavage of the amyloid precursor protein. Amyloid {beta} assembles into fibrils under physiological conditions, through formation of neurotoxic intermediate oligomers. Tachykinin peptides are known to affect amyloid {beta} neurotoxicity in cells. To understand the mechanism of this effect, we studied how tachykinins affect A{beta}(1-40) aggregation in vitro. Fibrils grown in the presence of tachykinins exhibited reduced thioflavin T (ThT) fluorescence, while their morphology, observed in transmission electron microscopy (TEM), did not alter. Cross linking studies revealed that the distribution of low molecular weight species was not affected by tachykinins. Our results suggest that there may be a specific interaction between tachykinins and A{beta}(1-40) that allows them to co-assemble. This effect may explain the reduction of A{beta}(1-40) neurotoxicity in cells treated with tachykinins.

  13. 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).

  14. 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

  15. 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

  16. Laser-induced propagation and destruction of amyloid beta fibrils.

    PubMed

    Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

    2010-06-18

    The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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.

  4. Sulfonated dyes attenuate the toxic effects of beta-amyloid in a structure-specific fashion.

    PubMed

    Pollack, S J; Sadler, I I; Hawtin, S R; Tailor, V J; Shearman, M S

    1995-09-15

    We recently reported that several sulfate-containing glycosaminoglycans, a class of compounds associated with the beta-amyloid plaques of Alzheimer's disease, attenuate the toxic effects of beta-amyloid fragments beta 25-35 and beta 1-40. The amyloid-binding sulfonated dye Congo Red was shown to have a similar effect. Using two clonal cell lines, we now demonstrate that several sulfonated dyes attenuate beta-amyloid toxicity and that the protective effect appears specific for compounds whose sulfonate groups can interact with the beta-pleated structure of aggregated amyloid. These results suggest that by binding beta-amyloid these compounds may prevent toxic interactions of the peptide with cells.

  5. Copper abolishes the beta-sheet secondary structure of preformed amyloid fibrils of amyloid-beta(42).

    PubMed

    House, Emily; Mold, Matthew; Collingwood, Joanna; Baldwin, Alex; Goodwin, Steven; Exley, Christopher

    2009-01-01

    The observation of the co-deposition of metals and amyloid-beta(42) (Abeta(42)) in brain tissue in Alzheimer's disease prompted myriad investigations into the role played by metals in the precipitation of this peptide. Copper is bound by monomeric Abeta(12) and upon precipitation of the copper-peptide complex thereby prevents Abeta(42) from adopting a beta-sheet secondary structure. Copper is also bound by beta-sheet conformers of Abeta(42), and herein we have investigated how this interaction affects the conformation of the precipitated peptide. Copper significantly reduced the thioflavin T fluorescence of aged, fibrillar Abeta(42) with, for example, a 20-fold excess of the metal resulting in a ca 90% reduction in thioflavin T fluorescence. Transmission electron microscopy showed that copper significantly reduced the quantities of amyloid fibrils while Congo red staining and polarized light demonstrated a copper-induced abolition of apple-green birefringence. Microscopy under cross-polarized light also revealed the first observation of spherulites of Abeta(42). The size and appearance of these amyloid structures were found to be very similar to spherulites identified in Alzheimer's disease tissue. The combined results of these complementary methods strongly suggested that copper abolished the beta-sheet secondary structure of pre-formed, aged amyloid fibrils of Abeta(42). Copper may protect against the presence of beta-sheets of Abeta(42) in vivo, and its binding by fibrillar Abeta(42) could have implications for Alzheimer's disease therapy. PMID:19749401

  6. Amyloid-beta(29-42) dimer formations studied by a multicanonical-multioverlap molecular dynamics simulation.

    PubMed

    Itoh, Satoru G; Okamoto, Yuko

    2008-03-13

    Amyloid-beta peptides are known to form amyloid fibrils and are considered to play an important role in Alzheimer's disease. Amyloid-beta(29-42) is a fragment of the amyloid-beta peptide and also has a tendency to form amyloid fibrils. In order to study the mechanism of amyloidogenesis of this fragment, we applied one of the generalized-ensemble algorithms, the multicanonical-multioverlap algorithm, to amyloid-beta(29-42) dimer in aqueous solution. We obtained a detailed free-energy landscape of the dimer system. From the detailed free-energy landscape, we examined monomer and dimer formations of amyloid-beta(29-42) and deduced dimerization processes, which correspond to seeding processes in the amyloidogenesis of amyloid-beta(29-42).

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. Evidence for Novel [beta]-Sheet Structures in Iowa Mutant [beta]-Amyloid Fibrils

    SciTech Connect

    Tycko, Robert; Sciarretta, Kimberly L.; Orgel, Joseph P.R.O.; Meredith, Stephen C.

    2009-07-24

    Asp23-to-Asn mutation within the coding sequence of {beta}-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-A{beta}40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-A{beta}40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10{sup -3} min{sup -1} and 1.07 x 10{sup -4} min{sup -1} for D23N-A{beta}40 and the wild-type peptide WT-A{beta}40, respectively) and without a lag phase. Electron microscopy shows that D23N-A{beta}40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-{beta} pattern, with a sharp reflection at 4.7 {angstrom} and a broad reflection at 9.4 {angstrom}, which is notably smaller than the value for WT-A{beta}40 fibrils (10.4 {angstrom}). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-A{beta}40 fibrils containing the in-register, parallel {beta}-sheet structure commonly found in WT-A{beta}40 fibrils and most other amyloid fibrils. Antiparallel {beta}-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through 13C-13C and 15N-13C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-A{beta}40 fibrils and the unusual vasculotropic clinical picture in these patients.

  12. Ferulic acid destabilizes preformed {beta}-amyloid fibrils in vitro

    SciTech Connect

    Ono, Kenjiro; Hirohata, Mie; Yamada, Masahito . E-mail: m-yamada@med.kanazawa-u.ac.jp

    2005-10-21

    Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that curcumin (Cur) inhibits fA{beta} formation from A{beta} and destabilizes preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of ferulic acid (FA) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of FA with Cur, rifampicin, and tetracycline. Ferulic acid dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide, as well as their extension. Moreover, it destabilized preformed fA{beta}s. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.

  13. 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

  14. 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.

  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. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. Inhibition of beta-amyloid aggregation by fluorescent dye labels

    SciTech Connect

    Amaro, Mariana; Wellbrock, Thorben; Birch, David J. S.; Rolinski, Olaf J.

    2014-02-10

    The fluorescence decay of beta-amyloid's (Aβ) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled Aβ monomers and the results compared with previously studied oligomerization of the non-labelled Aβ peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.

  4. Inhibition of beta-amyloid aggregation by fluorescent dye labels

    NASA Astrophysics Data System (ADS)

    Amaro, Mariana; Wellbrock, Thorben; Birch, David J. S.; Rolinski, Olaf J.

    2014-02-01

    The fluorescence decay of beta-amyloid's (Aβ) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled Aβ monomers and the results compared with previously studied oligomerization of the non-labelled Aβ peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.

  5. Shear flow promotes amyloid-{beta} fibrilization.

    PubMed

    Dunstan, Dave E; Hamilton-Brown, Paul; Asimakis, Peter; Ducker, William; Bertolini, Joseph

    2009-12-01

    The rate of formation of amyloid fibrils in an aqueous solution of amyloid-beta (Abeta) is greatly increased when the solution is sheared. When Abeta solution is stirred with a magnetic stirrer bar at 37 degrees C, a rapid increase in thioflavin T fluorescence is observed. Atomic Force Microscopy (AFM) images show the formation of aggregates, the growth of fibrils and the intertwining of the fibrils with time. Circular dichroism (CD) spectroscopy of samples taken after stirring shows a transition from random coil to alpha-helix to beta-sheet secondary structure over 20 h at 37 degrees C. The fluorescence, AFM and CD measurements are all consistent with the formation of amyloid fibrils. Quiescent, non-stirred solutions incubated at 37 degrees C showed no evidence of amyloid formation over a period of 3 days. Couette flow was found to accelerate the formation of amyloid fibrils demonstrating that the primary effect of stirring is not mixing but shearing. Only very small shear forces are applied to individual molecules in our experiments. Simple calculation suggests that the force is too small to support a hypothesis that shearing promotes partial unfolding of the protein as is observed. PMID:19850675

  6. 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

  7. 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

  8. 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.

  9. Molecular basis for amyloid-[beta] polymorphism

    SciTech Connect

    Colletier, Jacques-Philippe; Laganowsky, Arthur; Landau, Meytal; Zhao, Minglei; Soriaga, Angela B.; Goldschmidt, Lukasz; Flot, David; Cascio, Duilio; Sawaya, Michael R.; Eisenberga, David

    2011-10-19

    Amyloid-beta (A{beta}) aggregates are the main constituent of senile plaques, the histological hallmark of Alzheimer's disease. A{beta} molecules form {beta}-sheet containing structures that assemble into a variety of polymorphic oligomers, protofibers, and fibers that exhibit a range of lifetimes and cellular toxicities. This polymorphic nature of A{beta} has frustrated its biophysical characterization, its structural determination, and our understanding of its pathological mechanism. To elucidate A{beta} polymorphism in atomic detail, we determined eight new microcrystal structures of fiber-forming segments of A{beta}. These structures, all of short, self-complementing pairs of {beta}-sheets termed steric zippers, reveal a variety of modes of self-association of A{beta}. Combining these atomic structures with previous NMR studies allows us to propose several fiber models, offering molecular models for some of the repertoire of polydisperse structures accessible to A{beta}. These structures and molecular models contribute fundamental information for understanding A{beta} polymorphic nature and pathogenesis.

  10. Interaction between Alzheimer's amyloid-beta and amyloid-beta-metal complexes with cell membranes.

    PubMed

    Suwalsky, Mario; Bolognin, Silvia; Zatta, Paolo

    2009-01-01

    A number of observations indicate that the primary target of amyloid-beta (Abeta) peptide is the cellular membrane of neurons. In the context of these observations we investigated, using X-ray diffraction techniques, whether Abeta-metal complexes were able to affect lipid bilayers as a model of cell membranes. The binding of Al to Abeta gave particular conformational properties to the peptide that led to a marked alteration of the lipid bilayer representing phospholipids located in the outer monolayer of cell membranes. This effect was peculiar, since in our experimental conditions Abeta alone did not affect the lipid architecture, whereas the Al salt did, but only at concentrations several orders of magnitude higher than those of the Abeta-Al complex. In accordance with the effects observed with lipid bilayers, studies with human neuroblastoma cells demonstrated an impairment of cell functioning only in the presence of Abeta-Al complex. Our findings imply that Al, compared to the other Abeta-metal complexes tested, could have a specifically relevant effect in enhancing Abeta toxicity. PMID:19494433

  11. 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

  12. Alzheimer's amyloid-beta rescues yeast from hydroxide toxicity.

    PubMed

    Dubey, Ashok K; Bharadwaj, Prashant R; Varghese, Joseph N; Macreadie, Ian G

    2009-01-01

    Amyloid-beta(Abeta42), which is known to be toxic to neuronal cells, protects yeast cells from severe sodium hydroxide toxicity. More than 85% cell death was caused by treatment with 1 mM NaOH and approximately 95% was observed at a 2 mM concentration. However, greater than 55% cells survived the treatment in the presence of Abeta42. A strong protective effect of the peptide was also evident from the differential staining of the treated culture with propidium iodide.

  13. Detection of Alzheimer's amyloid beta aggregation by capturing molecular trails of individual assemblies

    SciTech Connect

    Vestergaard, Mun'delanji Hamada, Tsutomu; Saito, Masato; Yajima, Yoshifumi; Kudou, Monotori; Tamiya, Eiichi; Takagi, Masahiro

    2008-12-12

    Assembly of Amyloid beta (A{beta}) peptides, in particular A{beta}-42 is central to the formation of the amyloid plaques associated with neuro-pathologies such as Alzheimer's disease (AD). Molecular assembly of individual A{beta}-42 species was observed using a simple fluorescence microscope. From the molecular movements (aka Brownian motion) of the individual peptide assemblies, we calculated a temporal evolution of the hydrodynamic radius (R{sub H}) of the peptide at physiological temperature and pH. The results clearly show a direct relationship between R{sub H} of A{beta}-42 and incubation period, corresponding to the previously reported peptide's aggregation kinetics. The data correlates highly with in solution-based label-free electrochemical detection of the peptide's aggregation, and A{beta}-42 deposited on a solid surface and analysed using atomic force microscopy (AFM). To the best of our knowledge, this is the first analysis and characterisation of A{beta} aggregation based on capturing molecular trails of individual assemblies. The technique enables both real-time observation and a semi-quantitative distribution profile of the various stages of A{beta} assembly, at microM peptide concentration. Our method is a promising candidate for real-time observation and analysis of the effect of other pathologically-relevant molecules such as metal ions on pathways to A{beta} oligomerisation and aggregation. The method is also a promising screening tool for AD therapeutics that target A{beta} assembly.

  14. 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

  15. 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.

  16. 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

  17. [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

  18. Evidence for novel beta-sheet structures in Iowa mutant beta-amyloid fibrils.

    PubMed

    Tycko, Robert; Sciarretta, Kimberly L; Orgel, Joseph P R O; Meredith, Stephen C

    2009-07-01

    Asp23-to-Asn mutation within the coding sequence of beta-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-Abeta40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-Abeta40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10(-3) min(-1) and 1.07 x 10(-4) min(-1) for D23N-Abeta40 and the wild-type peptide WT-Abeta40, respectively) and without a lag phase. Electron microscopy shows that D23N-Abeta40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-beta pattern, with a sharp reflection at 4.7 A and a broad reflection at 9.4 A, which is notably smaller than the value for WT-Abeta40 fibrils (10.4 A). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-Abeta40 fibrils containing the in-register, parallel beta-sheet structure commonly found in WT-Abeta40 fibrils and most other amyloid fibrils. Antiparallel beta-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through (13)C-(13)C and (15)N-(13)C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-Abeta40 fibrils and the unusual vasculotropic clinical picture in these patients.

  19. Dissociation of ERK and Akt signaling in endothelial cell angiogenic responses to {beta}-amyloid

    SciTech Connect

    Magrane, Jordi; Christensen, Rial A.; Rosen, Kenneth M.; Veereshwarayya, Vimal; Querfurth, Henry W. . E-mail: hquerf01@granite.tufts.edu

    2006-04-15

    Cerebrovascular deposits of {beta}-amyloid (A{beta}) peptides are found in Alzheimer's disease and cerebral amyloid angiopathy with stroke or dementia. Dysregulations of angiogenesis, the blood-brain barrier and other critical endothelial cell (EC) functions have been implicated in aggravating chronic hypoperfusion in AD brain. We have used cultured ECs to model the effects of {beta}-amyloid on the activated phosphorylation states of multifunctional serine/threonine kinases since these are differentially involved in the survival, proliferation and migration aspects of angiogenesis. Serum-starved EC cultures containing amyloid-{beta} peptides underwent a 2- to 3-fold increase in nuclear pyknosis. Under growth conditions with sublethal doses of {beta}-amyloid, loss of cell membrane integrity and inhibition of cell proliferation were observed. By contrast, cell migration was the most sensitive to A{beta} since inhibition was significant already at 1 {mu}M (P = 0.01, migration vs. proliferation). In previous work, intracellular A{beta} accumulation was shown toxic to ECs and Akt function. Here, extracellular A{beta} peptides do not alter Akt activation, resulting instead in proportionate decreases in the phosphorylations of the MAPKs: ERK1/2 and p38 (starting at 1 {mu}M). This inhibitory action occurs proximal to MEK1/2 activation, possibly through interference with growth factor receptor coupling. Levels of phospho-JNK remained unchanged. Addition of PD98059, but not LY294002, resulted in a similar decrease in activated ERK1/2 levels and inhibition of EC migration. Transfection of ERK1/2 into A{beta}-poisoned ECs functionally rescued migration. The marked effect of extracellular A{beta} on the migration component of angiogenesis is associated with inhibition of MAPK signaling, while Akt-dependent cell survival appears more affected by cellular A{beta}.

  20. Amyloid-beta Alzheimer targets - protein processing, lipid rafts, and amyloid-beta pores.

    PubMed

    Arbor, Sage C; LaFontaine, Mike; Cumbay, Medhane

    2016-03-01

    Amyloid beta (Aβ), the hallmark of Alzheimer's Disease (AD), now appears to be deleterious in its low number aggregate form as opposed to the macroscopic Aβ fibers historically seen postmortem. While Alzheimer targets, such as the tau protein, amyloid precursor protein (APP) processing, and immune system activation continue to be investigated, the recent discovery that amyloid beta aggregates at lipid rafts and likely forms neurotoxic pores has led to a new paradigm regarding why past therapeutics may have failed and how to design the next round of compounds for clinical trials. An atomic resolution understanding of Aβ aggregates, which appear to exist in multiple conformations, is most desirable for future therapeutic development. The investigative difficulties, structures of these small Aβ aggregates, and current therapeutics are summarized in this review. PMID:27505013

  1. Amyloid-beta Alzheimer targets — protein processing, lipid rafts, and amyloid-beta pores

    PubMed Central

    Arbor, Sage C.; LaFontaine, Mike; Cumbay, Medhane

    2016-01-01

    Amyloid beta (Aβ), the hallmark of Alzheimer’s Disease (AD), now appears to be deleterious in its low number aggregate form as opposed to the macroscopic Aβ fibers historically seen postmortem. While Alzheimer targets, such as the tau protein, amyloid precursor protein (APP) processing, and immune system activation continue to be investigated, the recent discovery that amyloid beta aggregates at lipid rafts and likely forms neurotoxic pores has led to a new paradigm regarding why past therapeutics may have failed and how to design the next round of compounds for clinical trials. An atomic resolution understanding of Aβ aggregates, which appear to exist in multiple conformations, is most desirable for future therapeutic development. The investigative difficulties, structures of these small Aβ aggregates, and current therapeutics are summarized in this review. PMID:27505013

  2. Disrupting beta-amyloid aggregation for Alzheimer disease treatment.

    PubMed

    Estrada, L D; Soto, C

    2007-01-01

    Alzheimer's disease is a devastating degenerative disorder for which there is no cure or effective treatment. Although the etiology of Alzheimer's disease is not fully understood, compelling evidence indicates that deposition of aggregates composed by a misfolded form of the amyloid beta peptide (Abeta) is the central event in the disease pathogenesis. Therefore, an attractive therapeutic strategy is to prevent or reverse Abeta misfolding and aggregation. Diverse strategies have been described to identify inhibitors of this process, including screening of libraries of small molecules chemical compounds, rational design of synthetic peptides, assessment of natural Abeta-binding proteins and stimulation of the immune system by vaccination. In this article we describe these different approaches, their principles and their potential strengths and weaknesses. Overall the available data suggest that the development of drugs to interfere with Abeta misfolding and aggregation is a feasible target that hold great promise for the treatment of Alzheimer's disease.

  3. Characteristics of Amyloid-Related Oligomers Revealed by Crystal Structures of Macrocyclic [beta]-Sheet Mimics

    SciTech Connect

    Liu, Cong; Sawaya, Michael R.; Cheng, Pin-Nan; Zheng, Jing; Nowick, James S.; Eisenberg, David

    2011-09-20

    Protein amyloid oligomers have been strongly linked to amyloid diseases and can be intermediates to amyloid fibers. {beta}-Sheets have been identified in amyloid oligomers. However, because of their transient and highly polymorphic properties, the details of their self-association remain elusive. Here we explore oligomer structure using a model system: macrocyclic peptides. Key amyloidogenic sequences from A{beta} and tau were incorporated into macrocycles, thereby restraining them to {beta}-strands, but limiting the growth of the oligomers so they may crystallize and cannot fibrillate. We determined the atomic structures for four such oligomers, and all four reveal tetrameric interfaces in which {beta}-sheet dimers pair together by highly complementary, dry interfaces, analogous to steric zippers found in fibers, suggesting a common structure for amyloid oligomers and fibers. In amyloid fibers, the axes of the paired sheets are either parallel or antiparallel, whereas the oligomeric interfaces display a variety of sheet-to-sheet pairing angles, offering a structural explanation for the heterogeneity of amyloid oligomers.

  4. Amyloid beta-protein induces the cerebrovascular cellular pathology of Alzheimer's disease and related disorders.

    PubMed

    Van Nostrand, W E; Davis-Salinas, J; Saporito-Irwin, S M

    1996-01-17

    One of the hallmark pathologic characteristics of Alzheimer's disease (AD) and related disorders is deposition of the 39-42 amino acid amyloid beta-protein (A beta) in the walls of cerebral blood vessels. The cerebrovascular A beta deposits in these disorders are associated with degenerating smooth muscle cells in the vessel wall which have been implicated in the expression of the amyloid beta-protein precursor (A beta PP) and formation of A beta. We have established primary cultures of human cerebrovascular smooth muscle cells as a model for investigating the cellular pathologic processes involved in the cerebral amyloid angiopathy of AD and related disorders. Recently, we have shown that A beta 1-42, the predominant pathologic cerebrovascular form of A beta, causes extensive cellular degeneration that is accompanied by a striking increase in the levels of cellular A beta PP, potentially amyloidogenic carboxyl terminal A beta PP fragments, and soluble A beta peptide in the cultured human cerebrovascular smooth muscle cells. Together, these studies provide evidence that A beta contributes to the onset and progression of the cerebrovascular pathology associated with AD and related disorders and suggests the mechanism involves a molecular cascade with a novel product-precursor relationship that results in the adverse production and accumulation of A beta.

  5. 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

  6. Propagating structure of alzheimer's {beta}-amyloid is parallel {beta}-sheet with residues in exact register.

    SciTech Connect

    Benzinger, T. L. S.; Gregory, D. M.; Burkoth, T. S.; Miller-Auer, H.; Lynn, D. G.; Botto, R. E.; Meredith, S. C.; Chemistry; Univ. of Chicago

    1998-11-10

    The pathognomonic plaques of Alzheimer's disease are composed primarily of the 39- to 43-aa {beta}-amyloid (A{beta}) peptide. Crosslinking of A{beta} peptides by tissue transglutaminase (tTg) indicates that Gln15 of one peptide is proximate to Lys16 of another in aggregated A{beta}. Here we report how the fibril structure is resolved by mapping interstrand distances in this core region of the A{beta} peptide chain with solid-state NMR. Isotopic substitution provides the source points for measuring distances in aggregated A{beta}. Peptides containing a single carbonyl 13C label at Gln15, Lys16, Leu17, or Val18 were synthesized and evaluated by NMR dipolar recoupling methods for the measurement of interpeptide distances to a resolution of 0.2 Angstrom. Analysis of these data establish that this central core of A{beta} consists of a parallel {beta}-sheet structure in which identical residues on adjacent chains are aligned directly, i.e., in register. Our data, in conjunction with existing structural data, establish that the A{beta} fibril is a hydrogen-bonded, parallel {beta}-sheet defining the long axis of the A{beta} fibril propagation.

  7. 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

  8. Binding of fullerenes to amyloid beta fibrils: size matters.

    PubMed

    Huy, Pham Dinh Quoc; Li, Mai Suan

    2014-10-01

    Binding affinity of fullerenes C20, C36, C60, C70 and C84 for amyloid beta fibrils is studied by docking and all-atom molecular dynamics simulations with the Amber force field and water model TIP3P. Using the molecular mechanic-Poisson Boltzmann surface area method one can demonstrate that the binding free energy linearly decreases with the number of carbon atoms of fullerene, i.e. the larger is the fullerene size, the higher is the binding affinity. Overall, fullerenes bind to Aβ9-40 fibrils stronger than to Aβ17-42. The number of water molecules trapped in the interior of 12Aβ9-40 fibrils was found to be lower than inside pentamer 5Aβ17-42. C60 destroys Aβ17-42 fibril structure to a greater extent compared to other fullerenes. Our study revealed that the van der Waals interaction dominates over the electrostatic interaction and non-polar residues of amyloid beta peptides play the significant role in interaction with fullerenes providing novel insight into the development of drug candidates against Alzheimer's disease.

  9. Atomic models of de novo designed cc beta-Met amyloid-like fibrils.

    PubMed

    Steinmetz, Michel O; Gattin, Zrinka; Verel, Rene; Ciani, Barbara; Stromer, Thusnelda; Green, Janelle M; Tittmann, Peter; Schulze-Briese, Clemens; Gross, Heinz; van Gunsteren, Wilfred F; Meier, Beat H; Serpell, Louise C; Müller, Shirley A; Kammerer, Richard A

    2008-02-22

    The common characteristics of amyloid and amyloid-like fibrils from disease- and non-disease-associated proteins offer the prospect that well-defined model systems can be used to systematically dissect the driving forces of amyloid formation. We recently reported the de novo designed cc beta peptide model system that forms a native-like coiled-coil structure at low temperatures and which can be switched to amyloid-like fibrils by increasing the temperature. Here, we report a detailed molecular description of the system in its fibrillar state by characterizing the cc beta-Met variant using several microscopic techniques, circular dichroism spectroscopy, X-ray fiber diffraction, solid-state nuclear magnetic resonance, and molecular dynamics calculations. We show that cc beta-Met forms amyloid-like fibrils of different morphologies on both the macroscopic and atomic levels, which can be controlled by variations of assembly conditions. Interestingly, heterogeneity is also observed along single fibrils. We propose atomic models of the cc beta-Met amyloid-like fibril, which are in good agreement with all experimental data. The models provide a rational explanation why oxidation of methionine residues completely abolishes cc beta-Met amyloid fibril formation, indicating that a small number of site-specific hydrophobic interactions can play a major role in the packing of polypeptide-chain segments within amyloid fibrils. The detailed structural information available for the cc beta model system provides a strong molecular basis for understanding the influence and relative contribution of hydrophobic interactions on native-state stability, kinetics of fibril formation, fibril packing, and polymorphism.

  10. Inhibition of Beta-Amyloid Fibrillation by Luminescent Iridium(III) Complex Probes

    PubMed Central

    Lu, Lihua; Zhong, Hai-Jing; Wang, Modi; Ho, See-Lok; Li, Hung-Wing; Leung, Chung-Hang; Ma, Dik-Lung

    2015-01-01

    We report herein the application of kinetically inert luminescent iridium(III) complexes as dual inhibitors and probes of beta-amyloid fibrillogenesis. These iridium(III) complexes inhibited Aβ1–40 peptide aggregation in vitro, and protected against Aβ-induced cytotoxicity in neuronal cells. Furthermore, the complexes differentiated between the aggregated and unaggregated forms of Aβ1–40 peptide on the basis of their emission response. PMID:26419607

  11. Solution structures of {beta}-amyloid{sub 10-35} and {beta}-amyloid{sub 10-35} PEG3000 aggregates.

    SciTech Connect

    Benzinger, T. L. S.; Burkoth, T. S.; Gordon, D.; Lynn, D. G.; Meredith, S. C.; Morgan, D. M.; Seifert, S.; Thiyagarajan, P.; Urban, V.

    1999-07-02

    Small angle neutron and x-ray scattering (SANS/SAXS) studies were conducted on the structure of the aggregates formed from both the truncated model peptide {beta}-Amyloid(10-35) (A{beta}{sub 10-35}) and a block copolymer {beta}-Amyloid (10-35)-PEG3000 (A{beta}{sub 10-35}-PEG) in D{sub 2}O at pHs from 3.0 to 7.0. These studies indicate that A{beta}{sub 10-35} aggregates into rod-like particles (fibril) and their radii are strongly dependent on the Pm of the solution. The fibril-fibril association in A{beta}{sub 10-35} solutions is less of pH < 5.6, but becomes larger at higher pH. A{beta}{sub 10-35}-PEG also assembles into rod-like particles whose radius is larger by about 30 {angstrom} than that for A{beta}{sub 10-35} fibril at pH 4.2, while it is about 23 {angstrom} larger at higher pH. Contrast matching SAXS/SANS experiments that eliminate the coherent scattering from PEG reveal that PEG moiety is located at the periphery of the fibril. Also, the mass per unit length of the peptide portion is similar for both A{beta}{sub 10-35} and A{beta}{sub 10-35}-PEG fibrils at pH 5.6. The mass per unit length of the rods from SANS provides key information on the packing of A{beta}{sub 10-35} peptides in the fibril.

  12. 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

  13. Early Treatment Critical: Bexarotene Reduces Amyloid-Beta Burden In Silico.

    PubMed

    Rosenthal, Joseph; Belfort, Georges; Isaacson, David

    2016-01-01

    Amyloid-beta peptides have long been implicated in the pathology of Alzheimer's disease. Bexarotene, a drug approved by the U.S. Food and Drug Administration for treating a class of non-Hodgkin's lymphoma, has been reported to facilitate the removal of amyloid-beta. We have developed a mathematical model to explore the efficacy of bexarotene treatment in reducing amyloid-beta load, and simulate amyloid-beta production throughout the lifespan of diseased mice. Both aspects of the model are based on and consistent with previous experimental results. Beyond what is known empirically, our model shows that low dosages of bexarotene are unable to reverse symptoms in diseased mice, but dosages at and above an age-dependent critical concentration can recover healthy brain cells. Further, early treatment was shown to have significantly improved efficacy versus treatment in older mice. Relevance with respect to bexarotene-based amyloid-beta-clearance mechanism and direct treatment for Alzheimer's disease is emphasized.

  14. Early Treatment Critical: Bexarotene Reduces Amyloid-Beta Burden In Silico

    PubMed Central

    Belfort, Georges; Isaacson, David

    2016-01-01

    Amyloid-beta peptides have long been implicated in the pathology of Alzheimer’s disease. Bexarotene, a drug approved by the U.S. Food and Drug Administration for treating a class of non-Hodgkin’s lymphoma, has been reported to facilitate the removal of amyloid-beta. We have developed a mathematical model to explore the efficacy of bexarotene treatment in reducing amyloid-beta load, and simulate amyloid-beta production throughout the lifespan of diseased mice. Both aspects of the model are based on and consistent with previous experimental results. Beyond what is known empirically, our model shows that low dosages of bexarotene are unable to reverse symptoms in diseased mice, but dosages at and above an age-dependent critical concentration can recover healthy brain cells. Further, early treatment was shown to have significantly improved efficacy versus treatment in older mice. Relevance with respect to bexarotene-based amyloid-beta-clearance mechanism and direct treatment for Alzheimer’s disease is emphasized. PMID:27073866

  15. 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.

  16. 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

  17. Rationally designed peptoids modulate aggregation of amyloid-beta 40.

    PubMed

    Turner, J Phillip; Lutz-Rechtin, Tammy; Moore, Kelly A; Rogers, Lauren; Bhave, Omkar; Moss, Melissa A; Servoss, Shannon L

    2014-07-16

    Alzheimer's disease (AD) is the most common form of dementia and the sixth leading cause of death in the United States. Plaques composed of aggregated amyloid-beta protein (Aβ) accumulate between the neural cells in the brain and are associated with dementia and cellular death. Many strategies have been investigated to prevent Aβ self-assembly into disease-associated β-sheet amyloid aggregates; however, a promising therapeutic has not yet been identified. In this study, a peptoid-based mimic of the peptide KLVFF (residues 16-20 of Aβ) was tested for its ability to modulate Aβ aggregation. Peptoid JPT1 includes chiral, aromatic side chains to induce formation of a stable helical secondary structure that allows for greater interaction between the aromatic side chains and the cross β-sheet of Aβ. JPT1 was found to modulate Aβ40 aggregation, specifically decreasing lag time to β-sheet aggregate formation as well as the total number of fibrillar, β-sheet structured aggregates formed. These results suggest that peptoids may be able to limit the formation of Aβ aggregates that are associated with AD. PMID:24689364

  18. Cerebrolysin decreases amyloid-beta production by regulating amyloid protein precursor maturation in a transgenic model of Alzheimer's disease.

    PubMed

    Rockenstein, Edward; Torrance, Magdalena; Mante, Michael; Adame, Anthony; Paulino, Amy; Rose, John B; Crews, Leslie; Moessler, Herbert; Masliah, Eliezer

    2006-05-15

    Cerebrolysin is a peptide mixture with neurotrophic effects that might reduce the neurodegenerative pathology in Alzheimer's disease (AD). We have previously shown in an amyloid protein precursor (APP) transgenic (tg) mouse model of AD-like neuropathology that Cerebrolysin ameliorates behavioral deficits, is neuroprotective, and decreases amyloid burden; however, the mechanisms involved are not completely clear. Cerebrolysin might reduce amyloid deposition by regulating amyloid-beta (Abeta) degradation or by modulating APP expression, maturation, or processing. To investigate these possibilities, APP tg mice were treated for 6 months with Cerebrolysin and analyzed in the water maze, followed by RNA, immunoblot, and confocal microscopy analysis of full-length (FL) APP and its fragments, beta-secretase (BACE1), and Abeta-degrading enzymes [neprilysin (Nep) and insulin-degrading enzyme (IDE)]. Consistent with previous studies, Cerebrolysin ameliorated the performance deficits in the spatial learning portion of the water maze and reduced the synaptic pathology and amyloid burden in the brains of APP tg mice. These effects were associated with reduced levels of FL APP and APP C-terminal fragments, but levels of BACE1, Notch1, Nep, and IDE were unchanged. In contrast, levels of active cyclin-dependent kinase-5 (CDK5) and glycogen synthase kinase-3beta [GSK-3beta; but not stress-activated protein kinase-1 (SAPK1)], kinases that phosphorylate APP, were reduced. Furthermore, Cerebrolysin reduced the levels of phosphorylated APP and the accumulation of APP in the neuritic processes. Taken together, these results suggest that Cerebrolysin might reduce AD-like pathology in the APP tg mice by regulating APP maturation and transport to sites where Abeta protein is generated. This study clarifies the mechanisms through which Cerebrolysin might reduce Abeta production and deposition in AD and further supports the importance of this compound in the potential treatment of early AD.

  19. beta-amyloid protein of Alzheimer's disease is found in cerebral and spinal cord vascular malformations.

    PubMed Central

    Hart, M. N.; Merz, P.; Bennett-Gray, J.; Menezes, A. H.; Goeken, J. A.; Schelper, R. L.; Wisniewski, H. M.

    1988-01-01

    Congo/Red deposition with birefringence to polarized light was demonstrated focally in cerebrovascular malformations removed surgically from 4 older patients (ages 85, 74, 74, and 63), and in a spinal cord vascular malformation in a 76-year-old patient. Lesser degrees of Congophilic change were observed in cerebrovascular malformations screened from 4 of 10 patients between the ages of 30 and 59. No Congophilic change was seen in 10 cerebrovascular malformations removed from patients under 30 years of age. Congophilic areas in all cases decorated with W-2 and 85/45 polyclonal antibodies raised to peptide sequences of cerebrovascular beta-amyloid and beta-amyloid of senile plaques from patients with Alzheimer's disease. Thus, the amyloid in these vascular malformations is immunologically related to beta-amyloid protein. This finding provides another indication that vascular beta-amyloid deposition is not specific for Alzheimer's disease and suggests that an existing abnormality of vessels may be a predisposing factor. Images Figure 1 Figure 2A Figure 2B Figure 3 Figure 4 PMID:3293463

  20. 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.

  1. 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.

  2. 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

  3. Preformed {beta}-amyloid fibrils are destabilized by coenzyme Q{sub 10} in vitro

    SciTech Connect

    Ono, Kenjiro; Hasegawa, Kazuhiro; Naiki, Hironobu; Yamada, Masahito . E-mail: m-yamada@med.kanazawa-u.ac.jp

    2005-04-29

    Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that nordihydroguaiaretic acid (NDGA) and wine-related polyphenol, myricetin (Myr), inhibit fA{beta} formation from A{beta} and destabilize preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of coenzyme Q{sub 10} (CoQ{sub 10}) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of CoQ{sub 10} with NDGA and Myr. CoQ{sub 10} dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide (A{beta}), as well as their extension. Moreover, it destabilized preformed fA{beta}s. The anti-amyloidogenic effects of CoQ{sub 10} were slightly weaker than those of NDGA and Myr. CoQ{sub 10} could be a key molecule for the development of therapeutics for AD.

  4. 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.

  5. On the biodegradation of beta-peptides.

    PubMed

    Schreiber, Jürg V; Frackenpohl, Jens; Moser, Frank; Fleischmann, Thomas; Kohler, Hans-Peter E; Seebach, Dieter

    2002-05-01

    A consortium of microorganisms was established that was able to grow with the beta-tripeptide H-beta-HVal-beta-HAla-beta-HLeu-OH, with the beta-dipeptide H-beta-HAla-beta-HLeu-OH, and with the beta-amino acids H-beta-HAla-OH, H-beta-HVal-OH, and H-beta-HLeu-OH as the sole carbon and energy sources. This growth was achieved after several incubation-transfer cycles with the beta-tripeptide as the substrate. During degradation of the beta-tripeptide H-beta-HVal-beta-HAla-beta-HLeu-OH, the temporary formation of a metabolite was observed. The metabolite was identified as the beta-dipeptide H-beta-HAla-beta-HLeu-OH by nuclear magnetic resonance spectroscopy and mass spectrometry. This result indicates that in the course of the degradation of the beta-tripeptide, the N-terminal beta-HVal residue was cleaved off by a not yet known mechanism. During the subsequent degradation of the beta-dipeptide, formation of additional metabolites could not be detected. The growth-yield coefficients Y(x/s) for growth on the beta-di- and beta-tripeptide both had a value of 0.45. When a 1:1 mixture of the beta-tripeptide and the corresponding alpha-tripeptide H-Val-Ala-Leu-OH was added to the enrichment culture, the alpha-peptide was completely utilized in six days and thereafter growth of the culture stopped. This result indicates that even in beta-peptide enrichment cultures, alpha-peptides are the preferred substrates. Our experiments clearly show for the first time that beta-peptides and beta-amino acids are amenable to biodegradation and that a microbial consortium was able to utilize these compounds as sole carbon and energy sources. Furthermore, the preparation of beta-amino acids, of derivatives thereof, and of beta-di- and beta-tripeptides is described.

  6. 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

  7. Catechol oxidase-like oxidation chemistry of the 1-20 and 1-16 fragments of Alzheimer's disease-related beta-amyloid peptide: their structure-activity correlation and the fate of hydrogen peroxide.

    PubMed

    da Silva, Giordano F Z; Tay, William M; Ming, Li-June

    2005-04-29

    The Cu2+ complexes of the 1-16 and the 1-20 fragments of the Alzheimer's disease-related beta-amyloid peptide (CuAbeta) show significant oxidative activities toward a catechol-like substrate trihydroxylbenzene and plasmid DNA cleavage. The latter reflects possible oxidative stress to biological macromolecules, yielding supporting data to the pathological role of these soluble Abeta fragments. The former exhibits enzyme-like kinetics and is dependent on [H2O2], exhibiting k(cat) of 0.066 s-1 (6000-fold higher than the reaction without CuAbeta) and k(cat)/Km of 37.2 m-1s-1 under saturating [H2O2] of approximately 0.24%. This kinetic profile is consistent with metal-centered redox chemistry for the action of CuAbeta. A mechanism is proposed by the use of the catalytic cycle of dinuclear catechol oxidase as a working model. Trihydroxylbenzene is also oxidized by CuAbeta aerobically without H2O2, affording rate constants of 6.50x10(-3) s-1 and 3.25 m-1s-1. This activity is also consistent with catechol oxidase action in the absence of H2O2, wherein the substrate binds and reduces the Cu2+ center first, followed by O2 binding to afford the mu-eta2:eta2-peroxo intermediate, which oxidizes a second substrate to complete the catalytic cycle. A tetragonally distorted octahedral metal coordination sphere with three coordinated His side chains and some specific H-bonding interactions is concluded from the electronic spectrum of CuAbeta, hyperfine-shifted 1H NMR spectrum of CoAbeta, and molecular mechanics calculations. The results presented here are expected to add further insight into the chemistry of metallo-Abeta, which may assist better understanding of the neuropathology of Alzheimer's disease. PMID:15699049

  8. Proteomic study of amyloid beta (25-35) peptide exposure to neuronal cells: Impact on APE1/Ref-1's protein-protein interaction.

    PubMed

    Mantha, Anil K; Dhiman, Monisha; Taglialatela, Giulio; Perez-Polo, Regino J; Mitra, Sankar

    2012-06-01

    The genotoxic, extracellular accumulation of amyloid β (Aβ) protein and subsequent neuronal cell death are associated with Alzheimer's disease (AD). APE1/Ref-1, the predominant apurinic/apyrimidinic (AP) endonuclease and essential in eukaryotic cells, plays a central role in the base excision repair (BER) pathway for repairing oxidized and alkylated bases and single-strand breaks (SSBs) in DNA. APE1/Ref-1 is also involved in the redox activation of several trans-acting factors (TFs) in various cell types, but little is known about its role in neuronal functions. There is emerging evidence for APE1/Ref-1's role in neuronal cells vulnerable in AD and other neurodegenerative disorders, as reflected in its nuclear accumulation in AD brains. An increase in APE1/Ref-1 has been shown to enhance neuronal survival after oxidative stress. To address whether APE1/Ref-1 level or its association with other proteins is responsible for this protective effect, we used 2-D proteomic analyses and identified cytoskeleton elements (i.e., tropomodulin 3, tropomyosin alpha-3 chain), enzymes involved in energy metabolism (i.e., pyruvate kinase M2, N-acetyl transferase, sulfotransferase 1c), proteins involved in stress response (i.e., leucine-rich and death domain, anti-NGF30), and heterogeneous nuclear ribonucleoprotien-H (hnRNP-H) as being associated with APE1/Ref-1 in Aβ(25-35)-treated rat pheochromocytoma PC12 and human neuroblastoma SH-SY5Y cell lines, two common neuronal precursor lines used in Aβ neurotoxicity studies. Because the levels of some of these proteins are affected in the brains of AD patients, our study suggests a neuroprotective role for APE1/Ref-1 via its association with those proteins and modulating their cellular functions during Aβ-mediated neurotoxicity.

  9. Antiaggregation Potential of Padina gymnospora against the Toxic Alzheimer’s Beta-Amyloid Peptide 25–35 and Cholinesterase Inhibitory Property of Its Bioactive Compounds

    PubMed Central

    Shanmuganathan, Balakrishnan; Sheeja Malar, Dicson; Sathya, Sethuraman; Pandima Devi, Kasi

    2015-01-01

    Inhibition of β-amyloid (Aβ) aggregation in the cerebral cortex of the brain is a promising therapeutic and defensive strategy in identification of disease modifying agents for Alzheimer’s disease (AD). Since natural products are considered as the current alternative trend for the discovery of AD drugs, the present study aims at the evaluation of anti-amyloidogenic potential of the marine seaweed Padina gymnospora. Prevention of aggregation and disaggregation of the mature fibril formation of Aβ 25–35 by acetone extracts of P. gymnospora (ACTPG) was evaluated in two phases by Thioflavin T assay. The results were further confirmed by confocal laser scanning microscopy (CLSM) analysis and Fourier transform infrared (FTIR) spectroscopic analysis. The results of antiaggregation and disaggregation assay showed that the increase in fluorescence intensity of aggregated Aβ and the co-treatment of ACTPG (250 μg/ml) with Aβ 25–35, an extensive decrease in the fluorescence intensity was observed in both phases, which suggests that ACTPG prevents the oligomers formation and disaggregation of mature fibrils. In addition, ACTPG was subjected to column chromatography and the bioactivity was screened based on the cholinesterase inhibitory activity. Finally, the active fraction was subjected to LC-MS/MS analysis for the identification of bioactive compounds. Overall, the results suggest that the bioactive compound alpha bisabolol present in the alga might be responsible for the observed cholinesterase inhibition with the IC50 value < 10 μg/ml for both AChE and BuChE when compared to standard drug donepezil (IC50 value < 6 μg/ml) and support its use for the treatment of neurological disorders. PMID:26536106

  10. Neurotrophin receptor p75 mediates the uptake of the amyloid beta (Aβ) peptide, guiding it to lysosomes for degradation in basal forebrain cholinergic neurons.

    PubMed

    Ovsepian, Saak V; Antyborzec, Inga; O'Leary, Valerie B; Zaborszky, Laszlo; Herms, Jochen; Oliver Dolly, J

    2014-09-01

    A fascinating yet perhaps overlooked trait of the p75 neurotrophin receptor (p75(NTR)) is its ability to bind ligands with no obvious neurotrophic function. Using cultured basal forebrain (BF) neurons, this study demonstrates selective internalization of amyloid β (Aβ) 1-42 in conjunction with p75(NTR) (labelled with IgG192-Cy3) by cholinergic cells. Active under resting conditions, this process was enhanced by high K(+) stimulation and was insensitive to inhibitors of regulated synaptic activity-tetrodotoxin or botulinum neurotoxins (BoNT type/A and/B). Blockade of sarco-endoplasmic reticulum (SERCA) Ca(2+) ATPase with thapsigargin and CPA or chelation of Ca(2+) with EGTA-AM strongly suppressed the endocytosis of p75(NTR), implicating the role of ER released Ca(2+). The uptake of IgG192-Cy3 was also reduced by T-type Ca(2+) channel blocker mibefradil but not Cd(2+), an indiscriminate blocker of high voltage-activated Ca(2+) currents. A strong co-localization of IgG192-Cy3 with late endosome (Rab7) or lysosome (Lamp1) qualifier proteins suggest these compartments as the primary destination for internalized IgG192 and Aβ. Selective uptake and labeling of BF cholinergic cells with IgG192-Cy3 injected into the prefrontal cortex was verified also in vivo. The significance of these findings in relation to Aβ clearance in the cerebral cortex and pathophysiology of Alzheimer's disease is discussed. PMID:23716278

  11. Combination of memantine and vitamin D prevents axon degeneration induced by amyloid-beta and glutamate.

    PubMed

    Annweiler, Cédric; Brugg, Bernard; Peyrin, Jean-Michel; Bartha, Robert; Beauchet, Olivier

    2014-02-01

    The currently available drugs for treatment of Alzheimer's disease are symptomatic and only temporarily slow down the natural history of the disease process. Recently, its has been proposed that the combination of memantine with vitamin D, a neurosteroid hormone, may prevent amyloid-beta and glutamate neurotoxicity. Here, our purpose was to examine the potential protective effects of memantine and vitamin D against amyloid-beta peptide and glutamate toxicity in cortical neuronal cultures. We provide the first evidence that cortical axons degenerate less after exposure to amyloid-beta peptide or glutamate in microfluidic neuronal cultures enriched with memantine plus vitamin D compared to control medium and cultures enriched with only memantine or only vitamin D. The reported synergistic neuroprotective effect of memantine plus vitamin D -the combination originating an effect stronger than the sum- corroborate previous clinical finding that Alzheimer's disease patients using this drug combination have improved cognition. This finding reinforces the pharmacological potential of a new drug combining memantine plus vitamin D for the treatment or the prevention of Alzheimer's disease.

  12. 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

  13. Beta-Amyloid Precursor Protein (βAPP) Processing in Alzheimer's Disease (AD) and Age-Related Macular Degeneration (AMD).

    PubMed

    Zhao, Yuhai; Bhattacharjee, Surjyadipta; Jones, Brandon M; Hill, James M; Clement, Christian; Sambamurti, Kumar; Dua, Prerna; Lukiw, Walter J

    2015-08-01

    Amyloid is a generic term for insoluble, often intensely hydrophobic, fibrous protein aggregates that arise from inappropriately folded versions of naturally-occurring polypeptides. The abnormal generation and accumulation of amyloid, often referred to as amyloidogenesis, has been associated with the immune and pro-inflammatory pathology of several progressive age-related diseases of the human central nervous system (CNS) including Alzheimer's disease (AD) and age-related macular degeneration (AMD). This 'research perspective' paper reviews some of the research history, biophysics, molecular-genetics and environmental factors concerning the contribution of amyloid beta (Aβ) peptides, derived from beta-amyloid precursor protein (βAPP), to AD and AMD that suggests an extensive similarity in immune and inflammatory degenerative mechanisms between these two CNS diseases.

  14. 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.

  15. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    SciTech Connect

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  16. Estrogen has anti-amyloidogenic effects on Alzheimer's {beta}-amyloid fibrils in vitro

    SciTech Connect

    Morinaga, Akiyoshi; Hirohata, Mie; Ono, Kenjiro; Yamada, Masahito . E-mail: m-yamada@med.kanazawa-u.ac.jp

    2007-08-03

    Inhibition of the assembly of amyloid {beta}-peptide (A{beta}) as well as the destabilization of preformed {beta}-amyloid fibrils (fA{beta}) in the central nervous system could be valuable therapeutics of patients with Alzheimer's disease (AD). Epidemiological studies have indicated that estrogen therapy reduced the risk of developing AD in women. Here, we examined the effects of estrogen (estrone (E1), estradiol (E2), and estriol (E3)) and related sexual steroids (androstenedione (AND) and testosterone (TES)) on the polymerization, extension and destabilization of fA{beta}(1-42) and fA{beta}(1-40) at pH 7.5 at 37 {sup o}C in vitro, using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies. E1, E2, and E3 dose-dependently inhibited the formation, as well as destabilization of fA{beta}s. The overall anti-amyloidogenic activity of these molecules was in the order of: E3 > E2 = E1 >>AND = TES. Estrogen could be a potential therapeutic agent to prevent or delay AD progression.

  17. 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

  18. 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.

  19. Giant multilevel cation channels formed by Alzheimer disease amyloid beta-protein [A beta P-(1-40)] in bilayer membranes.

    PubMed Central

    Arispe, N; Pollard, H B; Rojas, E

    1993-01-01

    We have recently shown that the Alzheimer disease 40-residue amyloid beta-protein [A beta P-(1-40)] can form cation-selective channels when incorporated into planar lipid bilayers by fusion of liposomes containing the peptide. Since A beta P-(1-40) comprises portions of the putative extracellular and membrane-spanning domains of the amyloid precursor protein (APP751), we suggested that the channel-forming property could be the underlying cause of amyloid neurotoxicity. The peptide has been proposed to occur in vivo in both membrane-bound and soluble forms, and we now report that soluble A beta P-(1-40) can also form similar channels in solvent-free lipid bilayers formed at the tip of a patch pipet, as well as in the planar lipid bilayer system. As in the case of liposome-mediated incorporation, the amyloid channel activity in the patch pipet exhibits multiple conductance levels between 40 and 400 pS, cation selectivity, and sensitivity to tromethamine (Tris). Further studies with A beta P channels incorporated into planar lipid bilayers from the liposome complex have also revealed that the channel activity can express spontaneous transitions to a much higher range of conductances between 400 and 4000 pS. Under these conditions, the amyloid channel continues to be cation selective. Amyloid channels were insensitive to nitrendipine at either conductance range. We calculate that if such channels were expressed in cells, the ensuing ion fluxes down their electrochemical potential gradients would be homeostatically dissipative. We therefore interpret these data as providing further support for the concept that cell death in Alzheimer disease may be due to amyloid ion-channel activity. PMID:7504270

  20. Structure of beta-crystallite assemblies formed by Alzheimer beta-amyloid protein analogues: analysis by x-ray diffraction.

    PubMed Central

    Inouye, H.; Fraser, P. E.; Kirschner, D. A.

    1993-01-01

    To elucidate the relation between amyloid fibril formation in Alzheimer disease and the primary structure of the beta/A4 protein, which is the major component of the amyloid, we have been investigating the ability of peptides sharing sequences with beta/A4 to form fibrils in vitro. In previous studies we focused on the macroscopic morphology of the assemblies formed by synthetic peptides corresponding in sequence to different regions of this protein. In the present study we analyze the x-ray diffraction patterns obtained from these assemblies. All specimens showed wide angle reflections that could be indexed by an orthogonal lattice of beta-crystallites having unit cell dimensions a = 9.4 A, b = 7 A, and c = 10 A, where a refers to hydrogen bonding direction, b to polypeptide chain direction, and c to intersheet direction. Given the amino acid sequence of beta/A4 as NH2-DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIAT-COOH, we found that, based on their orientation and assembly, the analogues could be classified into three groups: Group A, residues 19-28, 13-28, 12-28, 11-28, 9-28, 1-28, 1-38, 1-40, 6-25, 11-25 and 34-42; Group B, residues 18-28, 17-28, and 15-28; and Group C, residues 22-35 and 26-33. For Groups A and C, the sharpest reflections were (h00), indicating that the assemblies were fibrillar, i.e., elongated in a single direction. Lateral alignment of the crystallites in Group A account for its cross-beta pattern, in which the hydrogen bonding (H-bonding) direction is the fiber (rotation) axis. By comparison, the beta-crystallites of Group C had no preferential orientation, thus giving circular scattering. For Group B, the sharpest reflections were (h0l) on the meridian, indicating that the assemblies were plate-like, i.e., extended in two directions. A series of equatorial Bragg reflections having a 40 A period indicated regular stacking of the plates, and the rotation axis was normal to the surface of the plates. Of the Group A peptides, the analogues 11

  1. Distribution of precursor amyloid-. beta. -protein messenger RNA in human cerebral cortex: relationship to neurofibrillary tangles and neuritic plaques

    SciTech Connect

    Lewis, D.A.; Higgins, G.A.; Young, W.G.; Goldgaber, D.; Gajdusek, D.C.; Wilson, M.C.; Morrison, J.H.

    1988-03-01

    Neurofibrillary tangles (NFT) and neuritic plaques (NP), two neuropathological markers of Alzheimer disease, may both contain peptide fragments derived from the human amyloid ..beta.. protein. However, the nature of the relationship between NFT and NP and the source of the amyloid ..beta.. proteins found in each have remained unclear. The authors used in situ hybridization techniques to map the anatomical distribution of precursor amyloid-..beta..-protein mRNA in the neocortex of brains from three subjects with no known neurologic disease and from five patients with Alzheimer disease. In brains from control subjects, positively hybridizing neurons were present in cortical regions and layers that contain a high density of neuropathological markers in Alzheimer disease, as well as in those loci that contain NP but few NFT. Quantitative analyses of in situ hybridization patterns within layers III and V of the superior frontal cortex revealed that the presence of high numbers of NFT in Alzheimer-diseased brains was associated with a decrease in the number of positively hybridizing neurons compared to controls and Alzheimer-diseased brains with few NFT. These findings suggest that the expression of precursor amyloid-..beta..-protein mRNA may be a necessary but is clearly not a sufficient prerequisite for NFT formation. In addition, these results may indicate that the amyloid ..beta.. protein, present in NP in a given region or layer of cortex, is not derived from the resident neuronal cell bodies that express the mRNA for the precursor protein.

  2. The interaction of beta-amyloid protein fragment (12-28) with lipid environments.

    PubMed Central

    Fletcher, T. G.; Keire, D. A.

    1997-01-01

    The neurotoxicity of beta-amyloid protein (beta AP) fragments may be a result of their solution conformation, which is very sensitive to solution conditions. In this work we describe NMR and CD studies of the conformation of beta AP(12-28) in lipid (micelle) environments as a function of pH and lipid type. The interaction of beta AP(12-28) with zwitterionic dodecylphosphocholine (DPC) micelles is weak and alters the conformation when compared to water solution alone. By contrast, the interaction of the peptide with anionic sodium dodecylsulfate (SDS) micelles is strong: beta AP(12-28) is mostly bound, is alpha-helical from K16 to V24, and aggregates slowly. The pH-dependent conformation changes of beta AP(12-28) in solution occur in the pH range at which the side-chain groups of E22, D23, H13, and H14 are deprotonated (pKas ca. 4 and 6.5); the interaction of beta AP(12-28) with SDS micelles alters the pH-dependent conformational transitions of the peptide whereas the weak interaction with DPC micelles causes little change. PMID:9070449

  3. Arf6 controls beta-amyloid production by regulating macropinocytosis of the Amyloid Precursor Protein to lysosomes.

    PubMed

    Tang, Weihao; Tam, Joshua H K; Seah, Claudia; Chiu, Justin; Tyrer, Andrea; Cregan, Sean P; Meakin, Susan O; Pasternak, Stephen H

    2015-01-01

    Alzheimer's disease (AD) is characterized by the deposition of Beta-Amyloid (Aβ) peptides in the brain. Aβ peptides are generated by cleavage of the Amyloid Precursor Protein (APP) by the β - and γ - secretase enzymes. Although this process is tightly linked to the internalization of cell surface APP, the compartments responsible are not well defined. We have found that APP can be rapidly internalized from the cell surface to lysosomes, bypassing early and late endosomes. Here we show by confocal microscopy and electron microscopy that this pathway is mediated by macropinocytosis. APP internalization is enhanced by antibody binding/crosslinking of APP suggesting that APP may function as a receptor. Furthermore, a dominant negative mutant of Arf6 blocks direct transport of APP to lysosomes, but does not affect classical endocytosis to endosomes. Arf6 expression increases through the hippocampus with the development of Alzheimer's disease, being expressed mostly in the CA1 and CA2 regions in normal individuals but spreading through the CA3 and CA4 regions in individuals with pathologically diagnosed AD. Disruption of lysosomal transport of APP reduces both Aβ40 and Aβ42 production by more than 30 %. Our findings suggest that the lysosome is an important site for Aβ production and that altering APP trafficking represents a viable strategy to reduce Aβ production. PMID:26170135

  4. Gold Nanoparticles and Microwave Irradiation Inhibit Beta-Amyloid Amyloidogenesis

    PubMed Central

    2008-01-01

    Peptide-Gold nanoparticles selectively attached to β-amyloid protein (Aβ) amyloidogenic aggregates were irradiated with microwave. This treatment produces dramatic effects on the Aβ aggregates, inhibiting both the amyloidogenesis and the restoration of the amyloidogenic potential. This novel approach offers a new strategy to inhibit, locally and remotely, the amyloidogenic process, which could have application in Alzheimer’s disease therapy. We have studied the irradiation effect on the amyloidogenic process in the presence of conjugates peptide-nanoparticle by transmission electronic microscopy observations and by Thioflavine T assays to quantify the amount of fibrils in suspension. The amyloidogenic aggregates rather than the amyloid fibrils seem to be better targets for the treatment of the disease. Our results could contribute to the development of a new therapeutic strategy to inhibit the amyloidogenic process in Alzheimer’s disease.

  5. Gold Nanoparticles and Microwave Irradiation Inhibit Beta-Amyloid Amyloidogenesis

    NASA Astrophysics Data System (ADS)

    Araya, Eyleen; Olmedo, Ivonne; Bastus, Neus G.; Guerrero, Simón; Puntes, Víctor F.; Giralt, Ernest; Kogan, Marcelo J.

    2008-11-01

    Peptide-Gold nanoparticles selectively attached to β-amyloid protein (Aβ) amyloidogenic aggregates were irradiated with microwave. This treatment produces dramatic effects on the Aβ aggregates, inhibiting both the amyloidogenesis and the restoration of the amyloidogenic potential. This novel approach offers a new strategy to inhibit, locally and remotely, the amyloidogenic process, which could have application in Alzheimer’s disease therapy. We have studied the irradiation effect on the amyloidogenic process in the presence of conjugates peptide-nanoparticle by transmission electronic microscopy observations and by Thioflavine T assays to quantify the amount of fibrils in suspension. The amyloidogenic aggregates rather than the amyloid fibrils seem to be better targets for the treatment of the disease. Our results could contribute to the development of a new therapeutic strategy to inhibit the amyloidogenic process in Alzheimer’s disease.

  6. 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

  7. P-glycoprotein efflux and other factors limit brain amyloid beta reduction by beta-site amyloid precursor protein-cleaving enzyme 1 inhibitors in mice.

    PubMed

    Meredith, Jere E; Thompson, Lorin A; Toyn, Jeremy H; Marcin, Lawrence; Barten, Donna M; Marcinkeviciene, Jovita; Kopcho, Lisa; Kim, Young; Lin, Alan; Guss, Valerie; Burton, Catherine; Iben, Lawrence; Polson, Craig; Cantone, Joe; Ford, Michael; Drexler, Dieter; Fiedler, Tracey; Lentz, Kimberley A; Grace, James E; Kolb, Janet; Corsa, Jason; Pierdomenico, Maria; Jones, Kelli; Olson, Richard E; Macor, John E; Albright, Charles F

    2008-08-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disease. Amyloid beta (Abeta) peptides are hypothesized to cause the initiation and progression of AD based on pathologic data from AD patients, genetic analysis of mutations that cause early onset forms of AD, and preclinical studies. Based on this hypothesis, beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) inhibitors are an attractive therapeutic approach for AD because cleavage of the APP by BACE1 is required to form Abeta. In this study, three potent BACE1 inhibitors are characterized. All three inhibitors decrease Abeta formation in cultured cells with IC(50) values less than 10 nM. Analysis of APP C-terminal fragments by immunoblotting and Abeta peptides by mass spectrometry showed that these inhibitors decreased Abeta by inhibiting BACE1. An assay for Abeta1-40 in mice was developed and used to show that these BACE1 inhibitors decreased plasma Abeta1-40, but not brain Abeta1-40, in wild-type mice. Because these BACE1 inhibitors were substrates for P-glycoprotein (P-gp), a member of the ATP-binding cassette superfamily of efflux transporters, these inhibitors were administered to P-gp knockout (KO) mice. These studies showed that all three BACE1 inhibitors decreased brain Abeta1-40 in P-gp KO mice, demonstrating that P-gp is a major limitation for development of BACE1 inhibitors to test the amyloid hypothesis. A comparison of plasma Abeta1-40 and brain Abeta1-40 dose responses for these three compounds revealed differences in relative ED(50) values, indicating that factors other than P-gp can also contribute to poor brain activity by BACE1 inhibitors.

  8. Production and increased detection of amyloid beta protein and amyloidogenic fragments in brain microvessels, meningeal vessels and choroid plexus in Alzheimer's disease.

    PubMed

    Kalaria, R N; Premkumar, D R; Pax, A B; Cohen, D L; Lieberburg, I

    1996-01-01

    Recent advances indicate soluble amyloid beta (A beta) protein is produced constitutively during normal metabolism of the amyloid precursor protein (APP). This has not been directly examined in human brain vascular tissues. Using a panel of well-characterized antibodies, here we show that increased amounts of soluble A beta were found in isolated vascular tissues from AD subjects compared to age-matched controls without significant Alzheimer pathology. Immunocytochemical analyses of isolated vessel preparations showed characteristic transverse patterns of A beta deposits in large vessels with smooth muscle, however, fine A beta deposits were apparent even in capillaries. A proportion of such A beta protein and potentially amyloidogenic carboxyl terminal fragments were released by solubilization and disruption of the vascular basement membrane by collagenase treatments. We further demonstrated by in vitro metabolic labelling that soluble A beta or an A beta-like peptide is associated and produced by cerebral microvessels, meningeal vessels and the choroid plexus isolated postmortem from human as well as rat brain. Compared to those from young rats, cerebral microvessels from aging rats showed increased release of carboxyl terminal fragments of APP and A beta-like peptide. Our observations provide the first direct demonstration that human vascular tissues produce soluble A beta, a product of the secretory pathway in APP processing. Our findings also suggest that aging associated alterations in the basement membranes are a factor in A beta accumulation that results in vascular amyloid deposition, the principal feature of cerebral amyloid angiopathy.

  9. The beta-amyloid domain is essential for axonal sorting of amyloid precursor protein.

    PubMed Central

    Tienari, P J; De Strooper, B; Ikonen, E; Simons, M; Weidemann, A; Czech, C; Hartmann, T; Ida, N; Multhaup, G; Masters, C L; Van Leuven, F; Beyreuther, K; Dotti, C G

    1996-01-01

    We have analysed the axonal sorting signals of amyloid precursor protein (APP). Wild-type and mutant versions of human APP were expressed in hippocampal neurons using the Semliki forest virus system. We show that wild-type APP and mutations implicated in Alzheimer's disease and another brain beta-amyloidosis are sorted to the axon. By analysis of deletion mutants we found that the membrane-inserted APP ectodomain but not the cytoplasmic tail is required for axonal sorting. Systematic deletions of the APP ectodomain identified two regions required for axonal delivery: one encoded by exons 11-15 in the carbohydrate domain, the other encoded by exons 16-17 in the juxtamembraneous beta-amyloid domain. Treatment of the cells with the N-glycosylation inhibitor tunicamycin induced missorting of wild-type APP, supporting the importance of glycosylation in axonal sorting of APP. The data revealed a hierarchy of sorting signals on APP: the beta-amyloid-dependent membrane proximal signal was the major contributor to axonal sorting, while N-glycosylation had a weaker effect. Furthermore, recessive somatodendritic signals, most likely in the cytoplasmic tail, directed the protein to the dendrites when the ectodomain was deleted. Analysis of detergent solubility of APP and another axonally delivered protein, hemagglutinin, demonstrated that only hemagglutinin formed CHAPS-insoluble complexes, suggesting distinct mechanisms of axonal sorting for these two proteins. This study is the first delineation of sorting requirements of an axonally targeted protein in polarized neurons and indicates that the beta-amyloid domain plays a major role in axonal delivery of APP. Images PMID:8895567

  10. Neuroprotective approaches in experimental models of beta-amyloid neurotoxicity: relevance to Alzheimer's disease.

    PubMed

    Harkany, T; Hortobágyi, T; Sasvári, M; Kónya, C; Penke, B; Luiten, P G; Nyakas, C

    1999-08-01

    1. beta-Amyloid peptides (A beta s) accumulate abundantly in the Alzheimer's disease (AD) brain in areas subserving information acquisition and processing, and memory formation. A beta fragments are produced in a process of abnormal proteolytic cleavage of their precursor, the amyloid precursor protein (APP). While conflicting data exist in the literature on the roles of A beta s in the brain, and particularly in AD, recent studies have provided firm experimental evidence for the direct neurotoxic properties of A beta. 2. Sequence analysis of A beta s revealed a high degree of evolutionary conservation and inter-species homology of the A beta amino acid sequence. In contrast, synthetic A beta fragments, even if modified fluorescent or isotope-labeled derivatives, are pharmacological candidates for in vitro and in vivo modeling of their cellular actions. During the past decade, acute injection, prolonged mini-osmotic brain perfusion approaches or A beta infusions into the blood circulation were developed in order to investigate the effects of synthetic A beta s, whereas transgenic models provided insight into the distinct molecular steps of pathological APP cleavage. 3. The hippocampus, caudate putamen, amygdala and neocortex all formed primary targets of acute neurotoxicity screening, but functional consequences of A beta infusions were primarily demonstrated following either intracerebroventricular or basal forebrain (medial septum or magnocellular basal nucleus (MBN)) infusions of A beta fragments. 4. In vivo investigations confirmed that, while the active core of A beta is located within the beta(25-35) sequence, the flanking peptide regions influence not only the folding properties of the A beta fragments, but also their in vivo neurotoxic potentials. 5. It has recently been established that A beta administration deranges neuron-glia signaling, affects the glial glutamate uptake and thereby induces noxious glutamatergic stimulation of nerve cells. In fact, a

  11. Design and biological activity of {beta}-sheet breaker peptide conjugates

    SciTech Connect

    Rocha, Sandra Cardoso, Isabel; Boerner, Hans; Pereira, Maria Carmo; Saraiva, Maria Joao; Coelho, Manuel

    2009-03-06

    The sequence LPFFD (iA{beta}{sub 5}) prevents amyloid-{beta} peptide (A{beta}) fibrillogenesis and neurotoxicity, hallmarks of Alzheimer's disease (AD), as previously demonstrated. In this study iA{beta}{sub 5} was covalently linked to poly(ethylene glycol) (PEG) and the activity of conjugates was assessed and compared to the activity of the peptide alone by in vitro studies. The conjugates were characterized by MALDI-TOF. Competition binding assays established that conjugates retained the ability to bind A{beta} with similar strength as iA{beta}{sub 5}. Transmission electron microscopy analysis showed that iA{beta}{sub 5} conjugates inhibited amyloid fibril formation, which is in agreement with binding properties observed for the conjugates towards A{beta}. The conjugates were also able to prevent amyloid-induced cell death, as evaluated by activation of caspase 3. These results demonstrated that the biological activity of iA{beta}{sub 5} is not affected by the pegylation process.

  12. Development and characterization of a TAPIR-like mouse monoclonal antibody to amyloid-beta.

    PubMed

    Wang, Jun; Hara, Hideo; Makifuchi, Takao; Tabira, Takeshi

    2008-06-01

    Tissue amyloid plaque immuno-reactive (TAPIR) antibody was better related to the effect of immunotherapy in Alzheimer's disease (AD) than ELISA antibody. Here we used a hybridoma technique to develop a TAPIR-like anti-human amyloid-beta (Abeta) mouse monoclonal antibody. The obtained monoclonal antibody, 3.4A10, was an IgG2b isotype and recognized N-terminal portion of Abeta1-42 without binding denatured or native amyloid-beta protein precursor. It had higher affinity to Abeta1-42 than to Abeta1-40 by Biacore affinity analysis and stained preferably the peripheral part of senile plaques and recognized the plaque core less than 4G8. It inhibited the Abeta1-42 fibril formation as well as degraded pre-aggregated Abeta1-42 peptide in a thioflavin T fluorescence spectrophotometry assay. The in vivo studies showed that 3.4A10 treatment decreased amyloid burden compared to the control group and significantly reduced Abeta42 levels rather than Abeta40 levels in brain lysates as well as the Abeta*56 oligomer (12mer) in TBS fraction of the brain lysates. 3.4A10 entered brain and decorated some plaques, which is surrounded by more Iba1-positive microglia. 3.4A10 therapy did not induce lymphocytic infiltration and obvious increase in microhemorrhage. We conclude that 3.4A10 is a TAPIR-like anti-human amyloid monoclonal antibody, and has a potential of therapeutic application for AD. PMID:18560128

  13. Development and characterization of a TAPIR-like mouse monoclonal antibody to amyloid-beta.

    PubMed

    Wang, Jun; Hara, Hideo; Makifuchi, Takao; Tabira, Takeshi

    2008-06-01

    Tissue amyloid plaque immuno-reactive (TAPIR) antibody was better related to the effect of immunotherapy in Alzheimer's disease (AD) than ELISA antibody. Here we used a hybridoma technique to develop a TAPIR-like anti-human amyloid-beta (Abeta) mouse monoclonal antibody. The obtained monoclonal antibody, 3.4A10, was an IgG2b isotype and recognized N-terminal portion of Abeta1-42 without binding denatured or native amyloid-beta protein precursor. It had higher affinity to Abeta1-42 than to Abeta1-40 by Biacore affinity analysis and stained preferably the peripheral part of senile plaques and recognized the plaque core less than 4G8. It inhibited the Abeta1-42 fibril formation as well as degraded pre-aggregated Abeta1-42 peptide in a thioflavin T fluorescence spectrophotometry assay. The in vivo studies showed that 3.4A10 treatment decreased amyloid burden compared to the control group and significantly reduced Abeta42 levels rather than Abeta40 levels in brain lysates as well as the Abeta*56 oligomer (12mer) in TBS fraction of the brain lysates. 3.4A10 entered brain and decorated some plaques, which is surrounded by more Iba1-positive microglia. 3.4A10 therapy did not induce lymphocytic infiltration and obvious increase in microhemorrhage. We conclude that 3.4A10 is a TAPIR-like anti-human amyloid monoclonal antibody, and has a potential of therapeutic application for AD.

  14. Cannabidiol promotes amyloid precursor protein ubiquitination and reduction of beta amyloid expression in SHSY5YAPP+ cells through PPARγ involvement.

    PubMed

    Scuderi, Caterina; Steardo, Luca; Esposito, Giuseppe

    2014-07-01

    The amyloidogenic cascade is regarded as a key factor at the basis of Alzheimer's disease (AD) pathogenesis. The aberrant cleavage of amyloid precursor protein (APP) induces an increased production and a subsequent aggregation of beta amyloid (Aβ) peptide in limbic and association cortices. As a result, altered neuronal homeostasis and oxidative injury provoke tangle formation with consequent neuronal loss. Cannabidiol (CBD), a Cannabis derivative devoid of psychotropic effects, has attracted much attention because it may beneficially interfere with several Aβ-triggered neurodegenerative pathways, even though the mechanism responsible for such actions remains unknown. In the present research, the role of CBD was investigated as a possible modulating compound of APP processing in SHSY5Y(APP+) neurons. In addition, the putative involvement of peroxisome proliferator-activated receptor-γ (PPARγ) was explored as a candidate molecular site responsible for CBD actions. Results indicated the CBD capability to induce the ubiquitination of APP protein which led to a substantial decrease in APP full length protein levels in SHSY5Y(APP+) with the consequent decrease in Aβ production. Moreover, CBD promoted an increased survival of SHSY5Y(APP+) neurons, by reducing their long-term apoptotic rate. Obtained results also showed that all, here observed, CBD effects were dependent on the selective activation of PPARγ.

  15. Insulin-degrading enzyme in brain microvessels: proteolysis of amyloid {beta} vasculotropic variants and reduced activity in cerebral amyloid angiopathy.

    PubMed

    Morelli, Laura; Llovera, Ramiro E; Mathov, Irina; Lue, Lih-Fen; Frangione, Blas; Ghiso, Jorge; Castaño, Eduardo M

    2004-12-31

    The accumulation of amyloid beta (Abeta) in the walls of small vessels in the cerebral cortex is associated with diseases characterized by dementia or stroke. These include Alzheimer's disease, Down syndrome, and sporadic and hereditary cerebral amyloid angiopathies (CAAs) related to mutations within the Abeta sequence. A higher tendency of Abeta to aggregate, a defective clearance to the systemic circulation, and insufficient proteolytic removal have been proposed as mechanisms that lead to Abeta accumulation in the brain. By using immunoprecipitation and mass spectrometry, we show that insulin-degrading enzyme (IDE) from isolated human brain microvessels was capable of degrading (125)I-insulin and cleaved Abeta-(1-40) wild type and the genetic variants Abeta A21G (Flemish), Abeta E22Q (Dutch), and Abeta E22K (Italian) at the predicted sites. In microvessels from Alzheimer's disease cases with CAA, IDE protein levels showed a 44% increase as determined by sandwich enzyme-linked immunosorbent assay and Western blot. However, the activity of IDE upon radiolabeled insulin was significantly reduced in CAA as compared with age-matched controls. These results support the notion that a defect in Abeta proteolysis by IDE contributes to the accumulation of this peptide in the cortical microvasculature. Moreover they raise the possibility that IDE inhibition or inactivation is a pathogenic mechanism that may open novel strategies for the treatment of cerebrovascular Abeta amyloidoses. PMID:15489232

  16. 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.

  17. Expression of the alternative oxidase mitigates beta-amyloid production and toxicity in model systems.

    PubMed

    El-Khoury, Riyad; Kaulio, Eveliina; Lassila, Katariina A; Crowther, Damian C; Jacobs, Howard T; Rustin, Pierre

    2016-07-01

    Mitochondrial dysfunction has been widely associated with the pathology of Alzheimer's disease, but there is no consensus on whether it is a cause or consequence of disease, nor on the precise mechanism(s). We addressed these issues by testing the effects of expressing the alternative oxidase AOX from Ciona intestinalis, in different models of AD pathology. AOX can restore respiratory electron flow when the cytochrome segment of the mitochondrial respiratory chain is inhibited, supporting ATP synthesis, maintaining cellular redox homeostasis and mitigating excess superoxide production at respiratory complexes I and III. In human HEK293-derived cells, AOX expression decreased the production of beta-amyloid peptide resulting from antimycin inhibition of respiratory complex III. Because hydrogen peroxide was neither a direct product nor substrate of AOX, the ability of AOX to mimic antioxidants in this assay must be indirect. In addition, AOX expression was able to partially alleviate the short lifespan of Drosophila models neuronally expressing human beta-amyloid peptides, whilst abrogating the induction of markers of oxidative stress. Our findings support the idea of respiratory chain dysfunction and excess ROS production as both an early step and as a pathologically meaningful target in Alzheimer's disease pathogenesis, supporting the concept of a mitochondrial vicious cycle underlying the disease.

  18. Imaging of dialysis-related amyloid (AB-amyloid) deposits with sup 131 I-beta 2-microglobulin

    SciTech Connect

    Floege, J.; Burchert, W.; Brandis, A.; Gielow, P.; Nonnast-Daniel, B.; Spindler, E.; Hundeshagen, H.; Shaldon, S.; Koch, K.M. )

    1990-12-01

    The diagnosis of dialysis-related amyloid (AB-amyloid) has been based usually on clinical and radiological criteria. Following the discovery that beta 2-microglobulin was the major protein of this amyloid, we isolated and radiolabelled uremic plasma beta 2-microglobulin. After intravenous injection, gamma-camera images of selected joint areas were obtained from 42 patients who were on regular hemodialysis therapy. Positive scans involving the shoulder, hip, knee and carpal regions were found in 13 of 14 patients treated for more than 10 years and 10 of 16 patients treated for 5 to 10 years. Patients treated for less time had negative scans. Specificity was indicated by negative scans in non-amyloid inflammatory lesions in control hemodialysis patients. Up to 48-fold tracer enrichment was detected in excised AB-amyloid containing tissue as compared to amyloid-free tissue. These findings suggest that circulating radiolabelled beta 2-microglobulin is taken up by the amyloid deposits. This method may non-invasively detect tissue infiltrates of amyloid. It may also permit prospective evaluation of the efficacy of prophylactic dialysis strategies which are designed to prevent or delay the onset of this complication of long-term dialysis.

  19. 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.

  20. Pin1 promotes production of Alzheimer's amyloid {beta} from {beta}-cleaved amyloid precursor protein

    SciTech Connect

    Akiyama, Hirotada; Shin, Ryong-Woon; Uchida, Chiyoko; Kitamoto, Tetsuyuki; Uchida, Takafumi . E-mail: uchidat@cir.tohoku.ac.jp

    2005-10-21

    Here we show that prolyl isomerase Pin1 is involved in the A{beta} production central to the pathogenesis of Alzheimer's disease. Enzyme immunoassay of brains of the Pin1-deficient mice revealed that production of A{beta}40 and A{beta}42 was lower than that of the wild-type mice, indicating that Pin1 promotes A{beta} production in the brain. GST-Pin1 pull-down and immunoprecipitation assay revealed that Pin1 binds phosphorylated Thr668-Pro of C99. In the Pin1 {sup -/-} MEF transfected with C99, Pin1 co-transfection enhanced the levels of A{beta}40 and A{beta}42 compared to that without Pin1 co-transfection. In COS7 cells transfected with C99, Pin1 co-transfection enhanced the generation of A{beta}40 and A{beta}42, and reduced the expression level of C99, facilitating the C99 turnover. Thus, Pin1 interacts with C99 and promotes its {gamma}-cleavage, generating A{beta}40 and A{beta}42. Further, GSK3 inhibitor lithium blocked Pin1 binding to C99 by decreasing Thr668 phosphorylation and attenuated A{beta} generation, explaining the inhibitory effect of lithium on A{beta} generation.

  1. ToF-SIMS analysis of amyloid beta aggregation on different lipid membranes.

    PubMed

    Yokoyama, Yuta; Aoyagi, Satoka; Shimanouchi, Toshinori; Iwamura, Miki; Iwai, Hideo

    2016-06-28

    Amyloid beta (Aβ) peptides are considered to be strongly related to Alzheimer's disease. Aβ peptides form a β-sheet structure on hard lipid membranes and it would aggregate to form amyloid fibrils, which are toxic to cells. However, the aggregation mechanism of Aβ is not fully understood. To evaluate the influence of the lipid membrane condition for Aβ aggregation, the adsorption forms of Aβ (1-40) on mixture membranes of lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and cholesterol β-d-glucoside (β-CG) were investigated by time-of-flight secondary ion mass spectrometry. As a result, Aβ adsorbed along the localized DMPC lipid on the mixture lipid membranes, whereas it was adsorbed homogeneously on the pure DMPC and β-CG membranes. Moreover, amino acid fragments that mainly existed in the n-terminal of Aβ (1-40) peptide were strongly detected on the localized DMPC region. These results suggested that the Aβ was adsorbed along the localized DMPC lipid with a characteristic orientation. These findings suggest that the hardness of the membrane is very sensitive to coexisting materials and that surface hardness is important for aggregation of Aβ.

  2. Amyloid beta-degrading cryptidases: insulin degrading enzyme, presequence peptidase, and neprilysin.

    PubMed

    Malito, E; Hulse, R E; Tang, W-J

    2008-08-01

    The accumulation of aggregates of amyloidogenic peptides is associated with numerous human diseases. One well studied example is the association between deposition of amyloid beta (Abeta) and Alzheimer's disease. Insulin degrading enzyme and neprilysin are involved in the clearance of Abeta, and presequence peptidase is suggested to play a role in the degradation of mitochondrial Abeta. Recent structural analyses reveal that these three peptidases contain a catalytic chamber (crypt) that selectively encapsulates and cleaves amyloidogenic peptides, hence the name cryptidase. The substrate selectivity of these cryptidases is determined by the size and charge distribution of their crypt as well as the conformational flexibility of substrates. The interaction of Abeta with the catalytic core of these cryptidases is controlled by conformational changes that make the catalytic chambers accessible for Abeta binding. These new structural and biochemical insights into cryptidases provide potential therapeutic strategies for the control of Abeta clearance.

  3. 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.

  4. Curcumin Binding to Beta Amyloid: A Computational Study.

    PubMed

    Rao, Praveen P N; Mohamed, Tarek; Teckwani, Karan; Tin, Gary

    2015-10-01

    Curcumin, a chemical constituent present in the spice turmeric, is known to prevent the aggregation of amyloid peptide implicated in the pathophysiology of Alzheimer's disease. While curcumin is known to bind directly to various amyloid aggregates, no systematic investigations have been carried out to understand its ability to bind to the amyloid aggregates including oligomers and fibrils. In this study, we constructed computational models of (i) Aβ hexapeptide (16) KLVFFA(21) octamer steric-zipper β-sheet assembly and (ii) full-length Aβ fibril β-sheet assembly. Curcumin binding in these models was evaluated by molecular docking and molecular dynamics (MD) simulation studies. In both the models, curcumin was oriented in a linear extended conformation parallel to fiber axis and exhibited better stability in the Aβ hexapeptide (16) KLVFFA(21) octamer steric-zipper model (Ebinding  = -10.05 kcal/mol) compared to full-length Aβ fibril model (Ebinding  = -3.47 kcal/mol). Analysis of MD trajectories of curcumin bound to full-length Aβ fibril shows good stability with minimum Cα-atom RMSD shifts. Interestingly, curcumin binding led to marked fluctuations in the (14) HQKLVFFA(21) region that constitute the fibril spine with RMSF values ranging from 1.4 to 3.6 Å. These results show that curcumin binding to Aβ shifts the equilibrium in the aggregation pathway by promoting the formation of non-toxic aggregates.

  5. Beta-amyloid deposition and the aging brain.

    PubMed

    Rodrigue, Karen M; Kennedy, Kristen M; Park, Denise C

    2009-12-01

    A central issue in cognitive neuroscience of aging research is pinpointing precise neural mechanisms that determine cognitive outcome in late adulthood as well as identifying early markers of less successful cognitive aging. One promising biomarker is beta amyloid (Abeta) deposition. Several new radiotracers have been developed that bind to fibrillar Abeta providing sensitive estimates of amyloid deposition in various brain regions. Abeta imaging has been primarily used to study patients with Alzheimer's Disease (AD) and individuals with Mild Cognitive Impairment (MCI); however, there is now building data on Abeta deposition in healthy controls that suggest at least 20% and perhaps as much as a third of healthy older adults show significant deposition. Considerable evidence suggests amyloid deposition precedes declines in cognition and may be the initiator in a cascade of events that indirectly leads to age-related cognitive decline. We review studies of Abeta deposition imaging in AD, MCI, and normal adults, its cognitive consequences, and the role of genetic risk and cognitive reserve.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Novel amyloid-beta specific scFv and VH antibody fragments from human and mouse phage display antibody libraries.

    PubMed

    Medecigo, M; Manoutcharian, K; Vasilevko, V; Govezensky, T; Munguia, M E; Becerril, B; Luz-Madrigal, A; Vaca, L; Cribbs, D H; Gevorkian, G

    2010-06-01

    Anti-amyloid immunotherapy has been proposed as an appropriate therapeutic approach for Alzheimer's disease (AD). Significant efforts have been made towards the generation and assessment of antibody-based reagents capable of preventing and clearing amyloid aggregates as well as preventing their synaptotoxic effects. In this study, we selected a novel set of human anti-amyloid-beta peptide 1-42 (Abeta1-42) recombinant monoclonal antibodies in a single chain fragment variable (scFv) and a single-domain (VH) format. We demonstrated that these antibody fragments recognize in a specific manner amyloid-beta deposits in APP/Tg mouse brains, inhibit toxicity of oligomeric Abeta1-42 in neuroblastoma cell cultures in a concentration-dependent manner and reduced amyloid deposits in APP/Tg2576 mice after intracranial administration. These antibody fragments recognize epitopes in the middle/C-terminus region of Abeta, which makes them strong therapeutic candidates due to the fact that most of the Abeta species found in the brains of AD patients display extensive N-terminus truncations/modifications.

  11. NOVEL AMYLOID-BETA SPECIFIC scFv and VH ANTIBODY FRAGMENTS FROM HUMAN AND MOUSE PHAGE DISPLAY ANTIBODY LIBRARIES

    PubMed Central

    Medecigo, M.; Manoutcharian, K.; Vasilevko, V.; Govezensky, T.; Munguia, M. E.; Becerril, B.; Luz-Madrigal, A.; Vaca, L.; Cribbs, D. H.; Gevorkian, G.

    2010-01-01

    Anti-amyloid immunotherapy has been proposed as an appropriate therapeutic approach for Alzheimer’s disease (AD). Significant efforts have been made towards the generation and assessment of antibody-based reagents capable of preventing and clearing amyloid aggregates as well as preventing their synaptotoxic effects. In this study, we selected a novel set of human anti-amyloid-beta peptide 1-42 (Aβ1-42) recombinant monoclonal antibodies in a single chain fragment variable (scFv) and a single domain (VH) formats. We demonstrated that these antibody fragments recognize in a specific manner amyloid beta deposits in APP/Tg mouse brains, inhibit toxicity of oligomeric Aβ1-42 in neuroblastoma cell cultures in a concentration-dependently manner and reduced amyloid deposits in APP/Tg2576 mice after intracranial administration. These antibody fragments recognize epitopes in the middle/C-terminus region of Aβ, which makes them strong therapeutic candidates due to the fact that most of the Aβ species found in the brains of AD patients display extensive N-terminus truncations/modifications. PMID:20451261

  12. 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.

  13. Structural model of the amyloid fibril formed by beta(2)-microglobulin #21-31 fragment based on vibrational spectroscopy.

    PubMed

    Hiramatsu, Hirotsugu; Goto, Yuji; Naiki, Hironobu; Kitagawa, Teizo

    2005-06-01

    A structural model of amyloid fibril formed by the #21-31 fragment of beta2-microglobulin is proposed from microscope IR measurements on specifically 13C-labeled peptide fibrils and Raman spectra of the dispersed fibril solution. The 13C-shifted amide frequency indicated the secondary structure of the labeled residues. The IR spectra have demonstrated that the region between F22 and V27 forms the core part with the extended beta-sheet structure. Raman spectra indicated the formation of a dimer with a disulfide bridge between C25 residues.

  14. 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.

  15. 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

  16. 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

  17. Alzheimer's disease amyloid beta-protein forms Zn(2+)-sensitive, cation-selective channels across excised membrane patches from hypothalamic neurons.

    PubMed Central

    Kawahara, M; Arispe, N; Kuroda, Y; Rojas, E

    1997-01-01

    We have previously shown that the 40-residue peptide termed amyloid beta-protein (A beta P[1-40]) in solution forms cation-selective channels across artificial phospholipid bilayer membranes. To determine whether A beta P[1-40] also forms channels across natural membranes, we used electrically silent excised membrane patches from a cell line derived from hypothalamic gonadotrophin-releasing hormone GnRH neurons. We found that exposing either the internal or the external side of excised membrane patches to A beta P[1-40] leads to the spontaneous formation of cation-selective channels. With Cs+ as the main cation in both the external as well as the internal saline, the amplitude of the A beta P[1-40] channel currents was found to follow the Cs+ gradient and to exhibit spontaneous conductance changes over a wide range (50-500 pS). We also found that free zinc (Zn2+), reported to bind to amyloid beta-protein in solution, can block the flow of Cs+ through the A beta P[1-40] channel. Because the Zn2+ chelator o-phenanthroline can reverse this blockade, we conclude that the underlying mechanism involves a direct interaction between the transition element Zn2+ and sites in the A beta P[1-40] channel pore. These properties of the A beta P[1-40] channel are rather similar to those observed in the artificial bilayer system. We also show here, by immunocytochemical confocal microscopy, that amyloid beta-protein molecules form deposits closely associated with the plasma membrane of a substantial fraction of the GnRH neurons. Taken together, these results suggest that the interactions between amyloid beta-protein and neuronal membranes also occur in vivo, lending further support to the idea that A beta P[1-40] channel formation might be a mechanism of amyloid beta-protein neurotoxicity. Images FIGURE 5 PMID:9199772

  18. Effect of initial stagger selection on the handedness of Amyloid beta helical fibrils

    SciTech Connect

    Ghattyvenkatakrishna, Pavan K; Cheng, Xiaolin; Uberbacher, Edward C

    2013-01-01

    Various structural models for Amyloid $\\beta$ fibrils derived from a variety of experimental techniques are currently available. However, this data cannot differentiate between the relative position of the two arms of the $\\beta$ hairpin called the stagger. Amyloid fibrils of various heirarchical levels form left--handed helices composed of $\\beta$ sheets. However it is unclear if positive, negative and neutral staggers all form the macroscopic left--handed helices. Studying this is important since the success of computational approaches to develop drugs for amyloidic diseases will depend on selecting the physiologically relevant structure of the sheets. To address this issue we have conducted extensive molecular dynamics simulations of Amyloid$\\beta$ sheets of various staggers and show that only negative staggers generate the experimentally observed left--handed helices while positive staggers generate the incorrect right--handed helices. The implications of this result extend in to all amyloidic--aggregation type diseases.

  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. Naturally occurring and experimentally induced beta-amyloid deposits in the brains of marmosets (Callithrix jacchus).

    PubMed

    Maclean, C J; Baker, H F; Ridley, R M; Mori, H

    2000-01-01

    Cerebral beta-amyloid occurs in elderly animals of some species and in Alzheimer's disease. Previously, we injected 3 young marmosets intracerebrally with brain tissue from a patient with Alzheimer's disease. Six years later, when the monkeys were middle aged, we found moderate numbers of intracerebral plaques and cerebrovascular deposits containing beta-amyloid. We have re-examined these brains and those of 10 other marmosets injected with brain homogenate containing beta-amyloid, and have found some beta-amyloid in animals injected more than 4 years previously. We have found beta-amyloid in 4 of 26 elderly control marmosets, but not in 9 young to middle-aged control marmosets. The beta-amyloid found in middle aged marmosets injected with Alzheimer brain tissue was, therefore, not a consequence of their age. Deposits in large cerebral vessels in elderly marmosets, and in marmosets previously injected with brain tissue containing beta-amyloid, reacted with antibodies to Abeta and Abeta1-40; plaques and microvessel deposits reacted with antibodies to Abeta and Abeta1-42.

  1. Luteinizing hormone, a reproductive regulator that modulates the processing of amyloid-beta precursor protein and amyloid-beta deposition.

    PubMed

    Bowen, Richard L; Verdile, Giuseppe; Liu, Tianbing; Parlow, Albert F; Perry, George; Smith, Mark A; Martins, Ralph N; Atwood, Craig S

    2004-05-01

    Hormonal changes associated with the dysregulation of the hypothalamic-pituitary-gonadal (HPG) axis following menopause/andropause have been implicated in the pathogenesis of Alzheimer's disease (AD). Experimental support for this has come from studies demonstrating an increase in amyloid-beta (Abeta) deposition following ovariectomy/castration. Because sex steroids and gonadotropins are both part of the HPG feedback loop, any loss in sex steroids results in a proportionate increase in gonadotropins. To assess whether Abeta generation was due to the loss of serum 17beta-estradiol or to the up-regulation of serum gonadotropins, we treated C57Bl/6J mice with the anti-gonadotropin leuprolide acetate, which suppresses both sex steroids and gonadotropins. Leuprolide acetate treatment resulted in a 3.5-fold (p < 0.0001) and a 1.5-fold (p < 0.024) reduction in total brain Abeta1-42 and Abeta1-40 concentrations, respectively, after 8 weeks of treatment. To further explore the role of gonadotropins in promoting amyloidogenesis, M17 neuroblastoma cells were treated with the gonadotropin luteinizing hormone (LH) at concentrations equivalent to early adulthood (10 mIU/ml) or post-menopause/andropause (30 mIU/ml). LH did not alter amyloid-beta precursor protein (AbetaPP) expression but did alter AbetaPP processing toward the amyloidogenic pathway as evidenced by increased secretion and insolubility of Abeta, decreased alphaAbetaPP secretion, and increased AbetaPP-C99 levels. These results suggest the marked increases in serum LH following menopause/andropause as a physiologically relevant signal that could promote Abeta secretion and deposition in the aging brain. Suppression of the age-related increase in serum gonadotropins using anti-gonadotropin agents may represent a novel therapeutic strategy for AD.

  2. Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

    PubMed Central

    Jean, Ying Y.; Baleriola, Jimena; Fà, Mauro; Hengst, Ulrich; Troy, Carol M.

    2015-01-01

    Alzheimer’s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the over-production of amyloid-beta and the deposition of amyloid-beta plaques in brain regions of the afflicted individuals. Throughout the years scientists have generated numerous Alzheimer’s disease mouse models that attempt to replicate the amyloid-beta pathology. Unfortunately, the mouse models only selectively mimic the disease features. Neuronal death, a prominent effect in the brains of Alzheimer’s disease patients, is noticeably lacking in these mice. Hence, we and others have employed a method of directly infusing soluble oligomeric species of amyloid-beta - forms of amyloid-beta that have been proven to be most toxic to neurons - stereotaxically into the brain. In this report we utilize male C57BL/6J mice to document this surgical technique of increasing amyloid-beta levels in a select brain region. The infusion target is the dentate gyrus of the hippocampus because this brain structure, along with the basal forebrain that is connected by the cholinergic circuit, represents one of the areas of degeneration in the disease. The results of elevating amyloid-beta in the dentate gyrus via stereotaxic infusion reveal increases in neuron loss in the dentate gyrus within 1 week, while there is a concomitant increase in cell death and cholinergic neuron loss in the vertical limb of the diagonal band of Broca of the basal forebrain. These effects are observed up to 2 weeks. Our data suggests that the current amyloid-beta infusion model provides an alternative mouse model to address region specific neuron death in a short-term basis. The advantage of this model is that amyloid-beta can be elevated in a spatial and temporal manner. PMID:26132278

  3. Beta-amyloid protein-containing inclusions in skeletal muscle of apolipoprotein-E-deficient mice.

    PubMed Central

    Robertson, T. A.; Dutton, N. S.; Martins, R. N.; Roses, A. D.; Kakulas, B. A.; Papadimitriou, J. M.

    1997-01-01

    The tibialis anterior muscle and soleus muscle of apolipoprotein-E-deficient mice were examined by light and electron microscopy. By light microscopy, sarcoplasmic inclusions were seen in tibialis anterior muscle and 40% of type 2 myofibers were affected in all animals over 8 months of age. These inclusions reacted for nonspecific esterase, cytochrome oxidase, and myoadenylate deaminase and were also periodic acid Schiff positive and stained basophilic with hematoxylin. Moreover, they reacted immunocytochemically with an antibody specific to fragment 17 to 24 of the published sequence of Alzheimer's cerebrovascular amyloid peptide. Immunoreactivity was lost when the antibody was adsorbed with the appropriate synthetic peptide. Ultrastructurally, the inclusions consisted of tubular arrays and were similar to those observed in human muscle in several pathological conditions. In type 1 myofibers of both tibialis anterior and soleus muscle, however, mitochondrial abnormalities including an increase in their number and size were detected, but tubular aggregates were not seen. These large mitochondria possessed an electron-dense inner chamber with an increased number of tightly packed cristae. The results obtained suggest that in these mice there is a disturbed lipid metabolism in skeletal muscle fibers that manifests itself with an accumulation of phospholipid in the form of sarcoplasmic reticulum tubules in the type 2 fibers and enlarged mitochondria with tightly packed cristae in the type 1 fibers. In addition, beta-amyloid protein was closely associated with the accumulated tubules and vesicles of sarcoplasmic reticulum and may represent dysregulation of amyloid precursor protein metabolism. Images Figure 1 Figure 2 Figure 3 PMID:9033257

  4. Mechanisms of enzymatic degradation of amyloid Beta microfibrils generating nanofilaments and nanospheres related to cytotoxicity.

    PubMed

    Numata, Keiji; Kaplan, David L

    2010-04-20

    Amyloid beta (Abeta) fibrils are found in the brain tissue of persons with Alzheimer's disease (AD), where they accumulate as plaques. One way to reduce the level of accumulation of Abeta in the brain and potentially treat AD is with Abeta-degrading enzymes such as neprilysin (NEP) and insulin-degrading enzyme (IDE). However, enzymatic responses and degradation mechanisms of Abeta fibrils (crystalline-state Abeta) have not been investigated, particularly with respect to how to avoid cytotoxicity of the degradation products to neuronal cells. Thus, insight into mechanisms of enzymatic degradation of Abeta fibrils would be instructive as a route to elucidating different structural features related to degradation and to cytotoxicity. We report mechanisms of enzymatic degradation of Abeta with cross-beta structures and show the series of steps involved in the digestion of Abeta microfibrils to nanospheres or nanofilaments by protease XIV or alpha-chymotrypsin, respectively. These degradation products, which contained almost the same secondary structures, exhibited different cytotoxicities, indicating that relationships between nanoassembled structures and cytotoxicity of Abeta peptides are more significant than the beta-sheet content. In addition, the enzymatic digestion at the Lys28 loop region linking the two beta-sheets in Abeta fibrils is suggested as a key target related to cytotoxicity, a feature that can be selectively targeted on the basis of the choice of protease.

  5. Identification of distinct physiochemical properties of toxic prefibrillar species formed by A{beta} peptide variants

    SciTech Connect

    Goeransson, Anna-Lena; Nilsson, K. Peter R.; Kagedal, Katarina; Brorsson, Ann-Christin

    2012-04-20

    Highlights: Black-Right-Pointing-Pointer Identification of toxic prefibrillar A{beta} species. Black-Right-Pointing-Pointer Fluorescence measurements using a combined set of fluorophores. Black-Right-Pointing-Pointer Morphology studies using transmission electron microscopy. -- Abstract: The formation of amyloid-{beta} peptide (A{beta}) aggregates at an early stage during the self-assembly process is an important factor in the development of Alzheimer's disease. The toxic effect is believed to be exerted by prefibrillar species of A{beta}. It is therefore important to identify which prefibrillar species are toxic and characterize their distinct properties. In the present study, we investigated the in vitro aggregation behavior of A{beta}-derived peptides possessing different levels of neurotoxic activity, using fluorescence spectroscopy in combination with transmission electron microscopy. The toxicity of various A{beta} aggregates was assessed by using cultures of human neuroblastoma cells. Through combined use of the fluorescence probe 8-anilino-1-napthalenesulfonate (ANS) and the novel luminescent probe pentamer formyl thiophene acetic acid (p-FTAA), we were able to identify those A{beta} peptide-derived prefibrillar species which exhibited cellular toxicity. In particular, species, which formed early during the aggregation process and showed strong p-FTAA and ANS fluorescence, were the species that possessed toxic activities. Moreover, by manipulating the aggregation conditions, it was possible to change the capacity of the A{beta} peptide to form nontoxic versus toxic species.

  6. 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.

  7. Degeneration of beta-amyloid-associated cholinergic structures in transgenic APP SW mice.

    PubMed

    Lüth, Hans-Joachim; Apelt, Jenny; Ihunwo, Amadi O; Arendt, Thomas; Schliebs, Reinhard

    2003-07-01

    Cholinergic dysfunction is a consistent feature of Alzheimer's disease, and the interrelationship between beta-amyloid deposits, inflammation and early cholinergic cell loss is still not fully understood. To characterize the mechanisms by which beta-amyloid and pro-inflammatory cytokines may exert specific degenerating actions on cholinergic cells ultrastructural investigations by electron microscopy were performed in brain sections from transgenic Tg2576 mice that express the Swedish double mutation of the human amyloid precursor protein and progressively develop beta-amyloid plaques during aging. Both light and electron microscopical investigations of the cerebral cortex of 19-month-old transgenic mice revealed a number of pathological tissue responses in close proximity of beta-amyloid plaques, such as activated microglia, astroglial proliferation, increased number of fibrous astrocytes, brain edema, degeneration of nerve cells, dendrites and axon terminals. Ultrastructural detection of choline acetyl transferase (ChAT)-immunostaining in cerebral cortical sections of transgenic mice clearly demonstrated degeneration of ChAT-immunoreactive fibres in the environment of beta-amyloid plaques and activated glial cells suggesting a role of beta-amyloid and/or inflammation in specific degeneration of cholinergic synaptic structures. PMID:12788508

  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. Modulatory activity of soluble beta amyloid on HPA axis function in rats.

    PubMed

    Morgese, Maria Grazia; Tucci, Paolo; Colaianna, Marilena; Zotti, Margherita; Cuomo, Vincenzo; Schiavone, Stefania; Trabace, Luigia

    2014-01-01

    Despite the consolidation of the amyloid hypothesis, the main component of senile plaques in Alzheimer's disease (AD), recent findings have led to a conceptual shift opening new questions about the potential physiological role of this peptide. In addition, soluble beta amyloid (sBA), in transgenic AD model, resulted to be increased after chronic and acute stress and alterations in cortisol levels have been reported in AD. Impaired hypothalamic pituitary adrenal (HPA) axis has been linked to depressive state and, consistently, we have previously demonstrated that BA is able to provoke depressive-like profile in rats. Here we further analysed the effect of the peptide in behavioural paradigms used to study emotional and cognitive response, by using the passive avoidance task, for cognitive parameters, and the sucrose preference test (SPT), to evaluate anhedonia. Moreover, in order to correlate behavioural with neurochemical and neuroendocrinal data, we investigated the effects of the peptide on noradrenergic system in amygdala (AMY), prefrontal cortex (PFC) and hippocampus (HIPP) along with plasmatic corticosterone and hypothalamic corticotrophin releasing factor (CRF). We found that BA-treated animals showed an impaired memory consolidation of inhibitory avoidance training, while no effect was evident in SPT. These results lead us to hypothesize a different response to stress coping behaviour in BA treated rats. Moreover, BA caused a significant increase in noradrenaline (NA) in PFC and HIPP, while in AMY was decreased. Consistently, we found a significant decrease in plasma corticosterone concentrations in BA-treated rats. Taken together, our data suggest that BA exerts an inhibitory effect on HPA axis activation.

  15. 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

  16. 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

  17. Neurotoxic amyloid beta oligomeric assemblies recreated in microfluidic platform with interstitial level of slow flow

    PubMed Central

    Choi, Yoon Jung; Chae, Sukyung; Kim, Jeong Hun; Barald, Kate F.; Park, Joong Yull; Lee, Sang-Hoon

    2013-01-01

    Alzheimer's disease is accompanied by progressive, time-dependent changes of three moieties of amyloid beta. In vitro models therefore should provide same conditions for more physiologic studies. Here we observed changes in the number of fibrils over time and studied the correlation between amyloid beta moieties and neurotoxicity. Although the number of fibrils increased dramatically, the change in neurotoxicity with time was small, suggesting that fibrils make little contribution to neurotoxicity. To study the neurotoxicity of diffusible moieties by regulating microenvironments, we created a bio-mimetic microfluidic system generating spatial gradients of diffusible oligomeric assemblies and assessed their effects on cultured neurons. We found amyloid beta exposure produced an atrophy effect and observed neurite extension during the differentiation of neural progenitor cells increased when cells were cultured with continuous flow. The results demonstrate the potential neurotoxicity of oligomeric assemblies and establish a prospective microfluidic platform for studying the neurotoxicity of amyloid beta. PMID:23719665

  18. Brain beta-amyloid accumulation in transgenic mice expressing mutant superoxide dismutase 1.

    PubMed

    Turner, Bradley J; Li, Qiao-Xin; Laughton, Katrina M; Masters, Colin L; Lopes, Elizabeth C; Atkin, Julie D; Cheema, Surindar S

    2004-12-01

    Oxidative stress is implicated in both the deposition and pathogenesis of beta-amyloid (Abeta) protein in Alzheimer's disease (AD). Accordingly, overexpression of the antioxidant enzyme superoxide dismutase 1 (SOD1) in neuronal cells and transgenic AD mice reduces Abeta toxicity and accumulation. In contrast, mutations in SOD1 associated with amyotrophic lateral sclerosis (ALS) confer enhanced pro-oxidative enzyme activities. We therefore examined whether ALS-linked mutant SOD1 overexpression in motor neuronal cells or transgenic ALS mice modulates Abeta toxicity or its accumulation in the brain. Aggregated, but not freshly solubilised, substrate-bound Abeta peptides induced degenerative morphology and cytotoxicity in motor neuron-like NSC-34 cells. Transfection of NSC-34 cells with human wild-type SOD1 attenuated Abeta-induced toxicity, however this neuroprotective effect was also observed for ALS-linked mutant SOD1. Analysis of the cerebral cortex, brainstem, cerebellum and olfactory bulb from transgenic SOD1G93A mice using enzyme-linked immunosorbent assay of acid-guanidine extracts revealed age-dependent elevations in Abeta levels, although not significantly different from wild-type mouse brain. In addition, brain amyloid protein precursor (APP) levels remained unaltered as a consequence of mutant SOD1 expression. We therefore conclude that mutant SOD1 overexpression promotes neither Abeta toxicity nor brain accumulation in these ALS models.

  19. Intraneuronal amyloid beta accumulation and oxidative damage to nucleic acids in Alzheimer disease.

    PubMed

    Nunomura, Akihiko; Tamaoki, Toshio; Tanaka, Koich; Motohashi, Nobutaka; Nakamura, Masao; Hayashi, Takaaki; Yamaguchi, Haruyasu; Shimohama, Shun; Lee, Hyoung-gon; Zhu, Xiongwei; Smith, Mark A; Perry, George

    2010-03-01

    In an analysis of amyloid pathology in Alzheimer disease, we used an in situ approach to identify amyloid-beta (Abeta) accumulation and oxidative damage to nucleic acids in postmortem brain tissue of the hippocampal formation from subjects with Alzheimer disease. When carboxyl-terminal-specific antibodies directed against Abeta40 and Abeta42 were used for immunocytochemical analyses, Abeta42 was especially apparent within the neuronal cytoplasm, at sites not detected by the antibody specific to Abeta-oligomer. In comparison to the Abeta42-positive neurons, neurons bearing oxidative damage to nucleic acids were more widely distributed in the hippocampus. Comparative density measurements of the immunoreactivity revealed that levels of intraneuronal Abeta42 were inversely correlated with levels of intraneuronal 8-hydroxyguanosine, an oxidized nucleoside (r=- 0.61, p<0.02). Together with recent evidence that the Abeta peptide can act as an antioxidant, these results suggest that intraneuronal accumulation of non-oligomeric Abeta may be a compensatory response in neurons to oxidative stress in Alzheimer disease.

  20. The amyloid-beta forming tripeptide cleavage mechanism of γ-secretase.

    PubMed

    Bolduc, David M; Montagna, Daniel R; Seghers, Matthew C; Wolfe, Michael S; Selkoe, Dennis J

    2016-01-01

    γ-secretase is responsible for the proteolysis of amyloid precursor protein (APP) into short, aggregation-prone amyloid-beta (Aβ) peptides, which are centrally implicated in the pathogenesis of Alzheimer's disease (AD). Despite considerable interest in developing γ-secretase targeting therapeutics for the treatment of AD, the precise mechanism by which γ-secretase produces Aβ has remained elusive. Herein, we demonstrate that γ-secretase catalysis is driven by the stabilization of an enzyme-substrate scission complex via three distinct amino-acid-binding pockets in the enzyme's active site, providing the mechanism by which γ-secretase preferentially cleaves APP in three amino acid increments. Substrate occupancy of these three pockets occurs after initial substrate binding but precedes catalysis, suggesting a conformational change in substrate may be required for cleavage. We uncover and exploit substrate cleavage preferences dictated by these three pockets to investigate the mechanism by which familial Alzheimer's disease mutations within APP increase the production of pathogenic Aβ species. PMID:27580372

  1. Low-power laser irradiation inhibits amyloid beta-induced cell apoptosis

    NASA Astrophysics Data System (ADS)

    Zhang, Heng; Wu, Shengnan

    2011-03-01

    The deposition and accumulation of amyloid-β-peptide (Aβ) in the brain are considered a pathological hallmark of Alzheimer's disease(AD). Apoptosis is a contributing pathophysiological mechanism of AD. Low-power laser irradiation (LPLI), a non-damage physical therapy, which has been used clinically for decades of years, is shown to promote cell proliferation and prevent apoptosis. Recently, low-power laser irradiation (LPLI) has been applied to moderate AD. In this study, Rat pheochromocytoma (PC12) cells were treated with amyloid beta 25-35 (Aβ25-35) for induction of apoptosis before LPLI treatment. We measured cell viability with CCK-8 according to the manufacture's protocol, the cell viability assays show that low fluence of LPLI (2 J/cm2 ) could inhibit the cells apoptosis. Then using statistical analysis of proportion of apoptotic cells by flow cytometry based on Annexin V-FITC/PI, the assays also reveal that low fluence of LPLI (2 J/cm2 ) could inhibit the Aβ-induced cell apoptosis. Taken together, we demonstrated that low fluence of LPLI (2 J/cm2 ) could inhibit the Aβ-induced cell apoptosis, these results directly point to a therapeutic strategy for the treatment of AD through LPLI.

  2. Neurocytopathic effects of beta-amyloid-stimulated monocytes: a potential mechanism for central nervous system damage in Alzheimer disease.

    PubMed Central

    London, J A; Biegel, D; Pachter, J S

    1996-01-01

    Growing evidence indicates that cells of the mononuclear phagocyte lineage, which includes peripheral blood monocytes (PBM) and tissue macrophages, participate in a variety of neurodestructive events and may play a pivotal role in neurodegenerative conditions such as Alzheimer disease. The present study sought to determine whether exposure of PBM to beta-amyloid peptide (A beta), the major protein of the amyloid fibrils that accumulate in the brain in Alzheimer disease, could induce cytopathic activity in these cells upon their subsequent incubation with neural tissue. PBM were incubated with A beta for 3 days, centrifuged and washed to remove traces of cell-free A beta, and then applied to organotypic cultures of rat brain for varying periods of time. By using a cell-viability assay to quantitate neurocytopathic effect, an increase in the ratio of dead to live cells was detected in cultures containing A beta-stimulated PBM versus control PBM (stimulated with either bovine serum albumin or reverse A beta peptide) as early as 3 days after coculture. The ratio of dead to live cells increased further by 10 days of coculture. By 30 days of coculture, the dead to live cell ratio remained elevated, and the intensity of neurocytopathic effect was such that large areas of brain mass dissociated from the cultures. These results indicate that stimulation of PBM with A beta significantly heightens their neurocytopathic activity and highlight the possibility that inflammatory reactions in the brain play a role in the neurodegeneration that accompanies Alzheimer disease. Images Fig. 2 Fig. 3 Fig. 4 PMID:8633031

  3. 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.

  4. The Protective Role of Carnosic Acid against Beta-Amyloid Toxicity in Rats

    PubMed Central

    Rasoolijazi, H.; Azad, N.; Joghataei, M. T.; Kerdari, M.; Nikbakht, F.; Soleimani, M.

    2013-01-01

    Oxidative stress is one of the pathological mechanisms responsible for the beta- amyloid cascade associated with Alzheimer's disease (AD). Previous studies have demonstrated the role of carnosic acid (CA), an effective antioxidant, in combating oxidative stress. A progressive cognitive decline is one of the hallmarks of AD. Thus, we attempted to determine whether the administration of CA protects against memory deficit caused by beta-amyloid toxicity in rats. Beta-amyloid (1–40) was injected by stereotaxic surgery into the Ca1 region of the hippocampus of rats in the Amyloid beta (Aβ) groups. CA was delivered intraperitoneally, before and after surgery in animals in the CA groups. Passive avoidance learning and spontaneous alternation behavior were evaluated using the shuttle box and the Y-maze, respectively. The degenerating hippocampal neurons were detected by fluoro-jade b staining. We observed that beta-amyloid (1–40) can induce neurodegeneration in the Ca1 region of the hippocampus by using fluoro-jade b staining. Also, the behavioral tests revealed that CA may recover the passive avoidance learning and spontaneous alternation behavior scores in the Aβ + CA group, in comparison with the Aβ group. We found that CA may ameliorate the spatial and learning memory deficits induced by the toxicity of beta-amyloid in the rat hippocampus. PMID:24363627

  5. The protective role of carnosic acid against beta-amyloid toxicity in rats.

    PubMed

    Rasoolijazi, H; Azad, N; Joghataei, M T; Kerdari, M; Nikbakht, F; Soleimani, M

    2013-01-01

    Oxidative stress is one of the pathological mechanisms responsible for the beta- amyloid cascade associated with Alzheimer's disease (AD). Previous studies have demonstrated the role of carnosic acid (CA), an effective antioxidant, in combating oxidative stress. A progressive cognitive decline is one of the hallmarks of AD. Thus, we attempted to determine whether the administration of CA protects against memory deficit caused by beta-amyloid toxicity in rats. Beta-amyloid (1-40) was injected by stereotaxic surgery into the Ca1 region of the hippocampus of rats in the Amyloid beta (Aβ) groups. CA was delivered intraperitoneally, before and after surgery in animals in the CA groups. Passive avoidance learning and spontaneous alternation behavior were evaluated using the shuttle box and the Y-maze, respectively. The degenerating hippocampal neurons were detected by fluoro-jade b staining. We observed that beta-amyloid (1-40) can induce neurodegeneration in the Ca1 region of the hippocampus by using fluoro-jade b staining. Also, the behavioral tests revealed that CA may recover the passive avoidance learning and spontaneous alternation behavior scores in the Aβ + CA group, in comparison with the Aβ group. We found that CA may ameliorate the spatial and learning memory deficits induced by the toxicity of beta-amyloid in the rat hippocampus.

  6. Initial stages of beta-amyloid Aβ1-40 and Aβ1-42 oligomerization observed using fluorescence decay and molecular dynamics analyses of tyrosine

    NASA Astrophysics Data System (ADS)

    Amaro, Mariana; Kubiak-Ossowska, Karina; Birch, David J. S.; Rolinski, Olaf J.

    2013-03-01

    The development of Alzheimer’s disease is associated with the aggregation of the beta-amyloid peptides Aβ1-40 and Aβ1-42. It is believed that the small oligomers formed during the early stages of the aggregation are neurotoxic and involved in the process of neurodegeneration. In this paper we use fluorescence decay measurements of beta-amyloid intrinsic fluorophore tyrosine (Tyr) and molecular dynamics (MD) simulations to study the early stages of oligomer formation for the Aβ1-40 and Aβ1-42 peptides in vitro. We demonstrate that the lifetime distributions of the amyloid fluorescence decay efficiently describe changes in the complex Tyr photophysics during the peptide aggregation and highlight the differences in aggregation performance of the two amyloids. Tyr fluorescence decay is found to be a more sensitive sensor of Aβ1-40 aggregation than Aβ1-42 aggregation. The MD simulation of the peptide aggregation is compared with the experimental data and supports a four-rotamer model of Tyr.

  7. 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

  8. Is Alzheimer's disease a result of presynaptic failure? Synaptic dysfunctions induced by oligomeric beta-amyloid.

    PubMed

    Nimmrich, Volker; Ebert, Ulrich

    2009-01-01

    Since Alois Alzheimer first described morphological alterations associated with his patient's dementia more than 100 years ago, Alzheimer's disease (AD) was defined as neurodegenerative disease caused by extracellular deposits of misfolded proteins. These amyloid plaques and neurofibrillary tangles have been unambiguously considered as hallmarks of this ailment, accompanied by devastating brain atrophy and cell loss. When a 40-42 amino acid peptide, called beta-amyloid (Abeta), was identified as a main component of amyloid plaques and a few genetic cases of AD were linked to Abeta metabolism, the Abeta hypothesis of AD was proposed. It was initially thought that an increase in Abeta42 precipitates plaque formation, which causes the generation of neurofibrillary tangles and ultimately the death of neurons. However, during the last decade it became apparent that soluble rather than deposited Abeta is associated with dementia. Among the constituents of soluble Abeta, small oligomeric forms were increasingly associated with neuropathology. There is now ample evidence that Abeta oligomers do not affect neuronal viability in general, but interfere specifically with synaptic function. Long-term neurophysiological impairment ultimately causes degeneration of synapses, which becomes most apparent on the morphological level by retraction of dendritic spines. Loss of meaningful synaptic connections in the brain of patients with AD will shatter their capacity to encode and retrieve memories. The precise molecular mechanism of Abeta oligomer-induced impairment of synaptic transmission is not fully understood, but there are several independent observations that oligomers interfere with the vesicular release machinery at the presynaptic terminal. While this hypothesis offers a promising avenue to understand the underlying cause of cognition and memory deficits in the AD brain, it also opens a possibility to address new mechanisms for preventing and ultimately curing AD.

  9. 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.

  10. Atomistic MD simulations reveal the protective role of cholesterol in dimeric beta-amyloid induced disruptions in neuronal membrane mimics

    NASA Astrophysics Data System (ADS)

    Qiu, Liming; Buie, Creighton; Cheng, Sara; Chou, George; Vaughn, Mark; Cheng, K.

    2011-10-01

    Interactions of oligomeric beta-amyloid peptides with neuronal membranes have been linked to the pathogenesis of Alzheimer's disease (AD). The molecular details of the interactions of different lipid components, particularly cholesterol (CHOL), of the membranes with the peptides are not clear. Using an atomistic MD simulations approach, the water permeability barrier, structural geometry and order parameters of binary phosphatidylcholine (PC) and PC/CHOL lipid bilayers were examined from various 200 ns-simulation replicates. Our results suggest that the longer length dimer (2 x 42 residues) perturbs the membrane more than the shorter one (2 x 40 residues). In addition, we discovered a significant protective role of cholesterol in protein-induced disruptions of the membranes. The use of a new Monte-Carlo method in characterizing the structures of the conformal annular lipids in close proximity with the proteins will be introduced. We propose that the neurotoxicity of beta-amyloid peptide may be associated with the nanodomain or raft-like structures of the neuronal membranes in-vivo in the development of AD.

  11. Molecular organization of amyloid protofilament-like assembly of betabellin 15D: helical array of beta-sandwiches.

    PubMed Central

    Inouye, Hideyo; Bond, Jeremy E; Deverin, Sean P; Lim, Amareth; Costello, Catherine E; Kirschner, Daniel A

    2002-01-01

    Betabellin is a 32-residue peptide engineered to fold into a four-stranded antiparallel beta-sheet protein. Upon air oxidation, the betabellin peptides can fold and assemble into a disulfide-bridged homodimer, or beta-sandwich, of 64 residues. Recent biophysical and ultrastructural studies indicate that betabellin 15D (B15D) (a homodimer of HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, where p = DPro, k = DLys, and h = DHis) forms unbranched, 35-A wide assemblies that resemble the protofilaments of amyloid fibers. In the present study, we have analyzed in detail the X-ray diffraction patterns of B15D prepared from acetonitrile. The fiber diffraction analysis indicated that the B15D fibril was composed of a double helix defined by the selection rule l = n + 7m (where l is even, and n and m are any integers), and having a 199-A period and pitch, 28-A rise per unit, and 10-A radius. This helical model is equivalent to a reverse-handed, single helix with half the period and defined by the selection rule l = -3n + 7m (where l is any integer). The asymmetric unit is the single B15D beta-sandwich molecule. These results suggest that the betabellin assembly that models the protofilaments of amyloid fibers is made up of discrete subunits on a helical array. Multiple intersheet hydrogen bonds in the axial direction and intersandwich polar interactions in the lateral direction stabilize the array. PMID:12202394

  12. Amyloid Beta-Protein and Neural Network Dysfunction

    PubMed Central

    Peña-Ortega, Fernando

    2013-01-01

    Understanding the neural mechanisms underlying brain dysfunction induced by amyloid beta-protein (Aβ) represents one of the major challenges for Alzheimer's disease (AD) research. The most evident symptom of AD is a severe decline in cognition. Cognitive processes, as any other brain function, arise from the activity of specific cell assemblies of interconnected neurons that generate neural network dynamics based on their intrinsic and synaptic properties. Thus, the origin of Aβ-induced cognitive dysfunction, and possibly AD-related cognitive decline, must be found in specific alterations in properties of these cells and their consequences in neural network dynamics. The well-known relationship between AD and alterations in the activity of several neural networks is reflected in the slowing of the electroencephalographic (EEG) activity. Some features of the EEG slowing observed in AD, such as the diminished generation of different network oscillations, can be induced in vivo and in vitro upon Aβ application or by Aβ overproduction in transgenic models. This experimental approach offers the possibility to study the mechanisms involved in cognitive dysfunction produced by Aβ. This type of research may yield not only basic knowledge of neural network dysfunction associated with AD, but also novel options to treat this modern epidemic. PMID:26316994

  13. Amyloid beta protein levels in cerebrospinal fluid are elevated in early-onset Alzheimer's disease.

    PubMed

    Nakamura, T; Shoji, M; Harigaya, Y; Watanabe, M; Hosoda, K; Cheung, T T; Shaffer, L M; Golde, T E; Younkin, L H; Younkin, S G

    1994-12-01

    The 4-kd amyloid beta protein (A beta) deposited as amyloid in Alzheimer's disease (AD) is produced and released by normal proteolytic processing of the amyloid beta protein precursor (beta APP) and is readily detected in cerebrospinal fluid (CSF). Here, we present the levels of A beta in CSF from a total of 95 subjects, including 38 patients with AD, 14 with early-onset AD and 24 with late-onset AD, 25 normal control subjects, and 32 patients with other neurological diseases. The level of A beta decreased with normal aging, and there was a significant elevation in the level of A beta in the CSF of early-onset AD patients (4.14 +/- 1.37 pmol/ml, p < 0.01). Neither Mini-Mental State nor Functional Assessment Staging were correlated with the amount of A beta in the CSF. The A beta/secreted form of beta APP ratio was elevated, but the level of alpha 1-antichymotrypsin in the CSF did not correlate with the level of CSF A beta in early-onset AD patients. Thus, the level of A beta in the CSF is elevated in early-onset AD patients and is suggested to be correlated with the pathology in the brain that characterizes AD. PMID:7998778

  14. Microbiosensor for Alzheimer’s Disease Diagnostics: Detection of Amyloid Beta Biomarkers

    PubMed Central

    Prabhulkar, Shradha; Piatyszek, Rudolph; Cirrito, John R.; Wu, Ze-zhi; Li, Chen-Zhong

    2012-01-01

    Alzheimer’s disease (AD) affects about 35.6 million people worldwide, and if current trends continue with no medical advancement, 1 in 85 people will be affected by 2050. Thus, there is an urgent need to develop a cost effective, easy to use, sensor platform to diagnose and study AD. The measurement of peptide amyloid beta (Aβ) found in cerebrospinal fluid (CSF) has been assessed as an avenue to diagnose and study the disease. The quantification of the ratio of Aβ1-40/42 (or Aβ ratio) has been established as a reliable test to diagnose AD through human clinical trials. Therefore we have developed a multiplexed, implantable immunosensor to detect amyloid beta (Aβ) isoforms using triple barrel carbon fiber microelectrodes as the sensor platform. Antibodies act as the biorecognition element of the sensor and selectively capture and bind Aβ1-40 and Aβ1-42 to the electrode surface. Electrochemistry was used to measure the intrinsic oxidation signal of Aβ at 0.65 V (vs Ag/AgCl), originating from a single tyrosine (Tyr) residue found at position 10 in its amino acid sequence. Using the proposed immunosensor Aβ1-40 and Aβ1-42 could be specifically detected in CSF from mice within a detection range of 20 nM to 50 nM and 20 nM to 140 nM respectively. The immunosensor enables real-time, highly sensitive detection of Aβ and opens up the possibilities for diagnostic ex-vivo applications and research-based in-vivo studies. PMID:22372824

  15. 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.

  16. {alpha}-Lipoic acid exhibits anti-amyloidogenicity for {beta}-amyloid fibrils in vitro

    SciTech Connect

    Ono, Kenjiro; Hirohata, Mie; Yamada, Masahito . E-mail: m-yamada@med.kanazawa-u.ac.jp

    2006-03-24

    Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of {alpha}-lipoic acid (LA) and the metabolic product of LA, dihydrolipoic acid (DHLA), on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 {sup o}C in vitro. LA and DHLA dose-dependently inhibited fA{beta} formation from amyloid {beta}-protein, as well as their extension. Moreover, they destabilized preformed fA{beta}s. LA and DHLA could be key molecules for the development of therapeutics for AD.

  17. MD-simulations of Beta-Amyloid Protein Insertion Efficiency and Kinetics into Neuronal Membrane Mimics

    NASA Astrophysics Data System (ADS)

    Qiu, Liming; Buie, Creighton; Vaughn, Mark; Cheng, Kwan

    2011-03-01

    Early interaction events of beta-amyloid (A β) peptides with the neuronal membranes play a key role in the pathogenesis of Alzheimer's disease. We have used all-atom MD simulations to study the protein insertion efficiency and kinetics of monomeric A β40 and A β42 into phosphatidylcholine lipid bilayers (PC) with and without 40 mole% cholesterol (CHOL) that mimic the cholesterol-enriched and depleted lipid nanodomains of the neuronal plasma membranes. Independent replicates of 200-ns simulations of each protein pre-inserted in the upper lipid layer were generated. In PC bilayers, only 25% of A β40 and 50% of A β42 in the replicates showed complete insertion into the lower lipid layer, whereas the percentages increased to 50% and 100%, respectively, in PC/CHOL bilayers, providing evidence that cholesterol improves the protein insertion efficiency into the bilayers. The rate of protein insertion was proportional to the hydrophobic, transmembrane helix length of the inserted peptide and depended on the cholesterol content. We propose that the lysine snorkeling and C-terminus anchoring of A β to the PC headgroups at the upper and lower lipid/water interfaces represent the dual-transmembrane stabilization mechanisms of A β in the neuronal membrane domains.

  18. 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.

  19. In situ hybridization of nucleus basalis neurons shows increased. beta. -amyloid mRNA in Alzheimer disease

    SciTech Connect

    Cohen, M.L.; Golde, T.E.; Usiak, M.F.; Younkin, L.H.; Younkin, S.G.

    1988-02-01

    To determine which cells within the brain produce ..beta..-amyloid mRNA and to assess expression of the ..beta..-amyloid gene in Alzheimer disease, the authors analyzed brain tissue from Alzheimer and control patients by in situ hybridization. The results demonstrate that ..beta..-amyloid mRNA is produced by neurons in the nucleus basalis of Meynert and cerebral cortex and that nuclues basalis perikarya from Alzheimer patients consistently hybridize more ..beta..-amyloid probe than those from controls. These observations support the hypothesis that increased expression of the ..beta..-amyloid gene plays an important role in the deposition of amyloid in the brains of patients with Alzheimer disease.

  20. Solid-state NMR analysis of the {beta}-strand orientation of the protofibrils of amyloid {beta}-protein

    SciTech Connect

    Doi, Takashi; Masuda, Yuichi; Irie, Kazuhiro; Akagi, Ken-ichi; Monobe, Youko; Imazawa, Takayoshi; Takegoshi, K.

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer The supramolecular structure of A{beta}42 protofibrils was analyzed by solid-state NMR. Black-Right-Pointing-Pointer The Ala-21 residue in the A{beta}42 protofibrils is included in a slightly disordered {beta}-strand. Black-Right-Pointing-Pointer The A{beta}42 protofibrils do not form intermolecular in-register parallel {beta}-sheets. -- Abstract: Alzheimer's disease (AD) is caused by abnormal deposition (fibrillation) of a 42-residue amyloid {beta}-protein (A{beta}42) in the brain. During the process of fibrillation, the A{beta}42 takes the form of protofibrils with strong neurotoxicity, and is thus believed to play a crucial role in the pathogenesis of AD. To elucidate the supramolecular structure of the A{beta}42 protofibrils, the intermolecular proximity of the Ala-21 residues in the A{beta}42 protofibrils was analyzed by {sup 13}C-{sup 13}C rotational resonance experiments in the solid state. Unlike the A{beta}42 fibrils, an intermolecular {sup 13}C-{sup 13}C correlation was not found in the A{beta}42 protofibrils. This result suggests that the {beta}-strands of the A{beta}42 protofibrils are not in an in-register parallel orientation. A{beta}42 monomers would assemble to form protofibrils with the {beta}-strand conformation, then transform into fibrils by forming intermolecular parallel {beta}-sheets.

  1. The iA{beta}5p {beta}-breaker peptide regulates the A{beta}(25-35) interaction with lipid bilayers through a cholesterol-mediated mechanism

    SciTech Connect

    Vitiello, Giuseppe; Grimaldi, Manuela; D'Ursi, Anna Maria; D'Errico, Gerardino

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part of a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.

  2. Transthyretin Protects against A-Beta Peptide Toxicity by Proteolytic Cleavage of the Peptide: A Mechanism Sensitive to the Kunitz Protease Inhibitor

    PubMed Central

    Costa, Rita; Ferreira-da-Silva, Frederico; Saraiva, Maria J.; Cardoso, Isabel

    2008-01-01

    Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of amyloid β-peptide (A-Beta) in the brain. Transthyretin (TTR) is a tetrameric protein of about 55 kDa mainly produced in the liver and choroid plexus of the brain. The known physiological functions of TTR are the transport of thyroid hormone T4 and retinol, through binding to the retinol binding protein. TTR has also been established as a cryptic protease able to cleave ApoA-I in vitro. It has been described that TTR is involved in preventing A-Beta fibrilization, both by inhibiting and disrupting A-Beta fibrils, with consequent abrogation of toxicity. We further characterized the nature of the TTR/A-Beta interaction and found that TTR, both recombinant or isolated from human sera, was able to proteolytically process A-Beta, cleaving the peptide after aminoacid residues 1, 2, 3, 10, 13, 14,16, 19 and 27, as determined by mass spectrometry, and reversed phase chromatography followed by N-terminal sequencing. A-Beta peptides (1–14) and (15–42) showed lower amyloidogenic potential than the full length counterpart, as assessed by thioflavin binding assay and ultrastructural analysis by transmission electron microscopy. A-Beta cleavage by TTR was inhibited in the presence of an αAPP peptide containing the Kunitz Protease Inhibitor (KPI) domain but not in the presence of the secreted αAPP derived from the APP isoform 695 without the KPI domain. TTR was also able to degrade aggregated forms of A-Beta peptide. Our results confirmed TTR as a protective molecule in AD, and prompted A-Beta proteolysis by TTR as a protective mechanism in this disease. TTR may prove to be a useful therapeutic agent for preventing or retarding the cerebral amyloid plaque formation implicated in AD pathology. PMID:18682830

  3. 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.

  4. Luteinizing hormone modulates cognition and amyloid-beta deposition in Alzheimer APP transgenic mice.

    PubMed

    Casadesus, Gemma; Webber, Kate M; Atwood, Craig S; Pappolla, Miguel A; Perry, George; Bowen, Richard L; Smith, Mark A

    2006-04-01

    Until recently, the study of hormonal influences in Alzheimer disease was limited to the role of sex steroids. Despite numerous epidemiological studies supporting a protective role for estrogen in Alzheimer disease, recent studies show that estrogen administration in elderly women increases the risk of disease. Reconciling these contradictory reports, we previously hypothesized that other hormones of the hypothalamic-pituitary-gonadal axis, such as luteinizing hormone, may be involved in the onset and development of the disease. In this regard, luteinizing hormone is elevated in Alzheimer disease and is known to modulate amyloidogenic processing of amyloid-beta protein precursor. Therefore, in this study, to evaluate the therapeutic potential of luteinizing hormone ablation, we administered a gonadotropin-releasing hormone analogue, leuprolide acetate, to an aged transgenic mouse model of Alzheimer disease (Tg 2576) and measured cognitive Y-maze performance and amyloid-beta deposition after 3 months of treatment. Our data indicate that luteinizing hormone ablation significantly attenuated cognitive decline and decreased amyloid-beta deposition as compared to placebo-treated animals. Importantly, leuprolide acetate-mediated reduction of amyloid-beta correlated with improved cognition. Since both cognitive loss and amyloid-beta deposition are features of Alzheimer disease, leuprolide acetate treatment may prove to be a useful therapeutic strategy for this disease.

  5. 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.

  6. 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

  7. Design of peptidyl compounds that affect beta-amyloid aggregation: importance of surface tension and context.

    PubMed

    Gibson, Todd J; Murphy, Regina M

    2005-06-21

    Self-association of beta-amyloid (Abeta) peptide into cross-beta-sheet fibrils induces cellular toxicity in vitro and is linked with progression of Alzheimer's disease. Previously, we demonstrated that hybrid peptides, containing a recognition domain that binds to Abeta and a disrupting domain consisting of a chain of charged amino acids, inhibited Abeta-associated toxicity in vitro and increased the rate of Abeta aggregation. In this work we examine the design parameter space of the disrupting domain. Using KLVFFKKKKKK as a base case, we tested hybrid compounds with a branched rather than linear lysine oligomer, with l-lysine replaced by d-lysine, and with lysine replaced by diaminopropionic acid. We synthesized a compound with a novel anionic disrupting domain that contained cysteine thiols oxidized to sulfates, as well as other compounds in which alkyl or ether chains were appended to KLVFF. In all cases, the hybrid compound's ability to increase solvent surface tension was the strongest predictor of its effect on Abeta aggregation kinetics. Finally, we investigated the effects of arginine on Abeta aggregation. Arginine is a well-known chaotrope but increases surface tension of water. Arginine modestly decreased Abeta aggregation. In contrast, RRRRRR slightly, and KLVFFRRRRRR greatly, increased Abeta aggregation. Thus, the influence of arginine on Abeta aggregation depends strongly on the context in which it is presented. The effect of arginine, RRRRRR, and KLVFFRRRRRR on Abeta aggregation was examined in detail using laser light scattering, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, thioflavin T fluorescence, and transmission electron microscopy. PMID:15952797

  8. 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

  9. 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.

  10. The tissue plasminogen activator-plasminogen proteolytic cascade accelerates amyloid-beta (Abeta) degradation and inhibits Abeta-induced neurodegeneration.

    PubMed

    Melchor, Jerry P; Pawlak, Robert; Strickland, Sidney

    2003-10-01

    Accumulation of the amyloid-beta (Abeta) peptide depends on both its generation and clearance. To better define clearance pathways, we have evaluated the role of the tissue plasminogen activator (tPA)-plasmin system in Abeta degradation in vivo. In two different mouse models of Alzheimer's disease, chronically elevated Abeta peptide in the brain correlates with the upregulation of plasminogen activator inhibitor-1 (PAI-1) and inhibition of the tPA-plasmin system. In addition, Abeta injected into the hippocampus of mice lacking either tPA or plasminogen persists, inducing PAI-1 expression and causing activation of microglial cells and neuronal damage. Conversely, Abeta injected into wild-type mice is rapidly cleared and does not cause neuronal degeneration. Thus, the tPA-plasmin proteolytic cascade aids in the clearance of Abeta, and reduced activity of this system may contribute to the progression of Alzheimer's disease.

  11. 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).

  12. Beta-Amyloid Deposition and Alzheimer's Type Changes Induced by Borrelia Spirochetes

    SciTech Connect

    Miklossy,J.; Kis, A.; Radenovic, A.; Miller, L.; Forro, L.; Martins, R.; Reiss, K.; Darbinian, N.; Darekar, P.; et al.

    2006-01-01

    The pathological hallmarks of Alzheimer's disease (AD) consist of {beta}-amyloid plaques and neurofibrillary tangles in affected brain areas. The processes, which drive this host reaction are unknown. To determine whether an analogous host reaction to that occurring in AD could be induced by infectious agents, we exposed mammalian glial and neuronal cells in vitro to Borrelia burgdorferi spirochetes and to the inflammatory bacterial lipopolysaccharide (LPS). Morphological changes analogous to the amyloid deposits of AD brain were observed following 2-8 weeks of exposure to the spirochetes. Increased levels of {beta}-amyloid presursor protein (A{beta}PP) and hyperphosphorylated tau were also detected by Western blots of extracts of cultured cells that had been treated with spirochetes or LPS. These observations indicate that, by exposure to bacteria or to their toxic products, host responses similar in nature to those observed in AD may be induced.

  13. 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

  14. 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.

  15. 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.

  16. Driving force of binding of amyloid {beta}-protein to lipid bilayers

    SciTech Connect

    Ikeda, Keisuke; Matsuzaki, Katsumi

    2008-06-06

    Amyloid {beta}-protein (A{beta}) has been reported to interact with a variety of lipid species, although the thermodynamic driving force remains unclear. We investigated the binding of A{beta}s labeled with the dye diethylaminocoumarin (DAC-A{beta}s) to lipid bilayers under various conditions. DAC-A{beta}-(1-40) electrostatically bound to anionic and cationic lipids at acidic and alkaline interfacial pH, respectively. However, at neutral pH, electroneutral A{beta} did not bind to these lipids, indicating little hydrophobic interaction between A{beta}-(1-40) and the acyl chains of lipids. In contrast, DAC-A{beta} associated with glycolipids even under electroneutral conditions. These results suggested that hydrogen-bonding as well as hydrophobic interactions with sugar groups of glycolipids drive the membrane binding of A{beta}-(1-40)

  17. Phosphate and HEPES buffers potently affect the fibrillation and oligomerization mechanism of Alzheimer's A{beta} peptide

    SciTech Connect

    Garvey, Megan; Tepper, Katharina; Haupt, Caroline; Knuepfer, Uwe; Klement, Karolin; Meinhardt, Jessica; Horn, Uwe; Balbach, Jochen; Faendrich, Marcus

    2011-06-10

    Highlights: {yields} Sodium phosphate buffer accelerated A{beta}(1-40) nucleation relative to HEPES. {yields} A{beta}(1-40) fibrils formed in the two buffers show only minor structural differences. {yields} NMR revealed that A{beta}(1-40) histidine residues mediate buffer dependent changes. -- Abstract: The oligomerization of A{beta} peptide into amyloid fibrils is a hallmark of Alzheimer's disease. Due to its biological relevance, phosphate is the most commonly used buffer system for studying the formation of A{beta} and other amyloid fibrils. Investigation into the characteristics and formation of amyloid fibrils frequently relies upon material formed in vitro, predominantly in phosphate buffers. Herein, we examine the effects on the fibrillation and oligomerization mechanism of A{beta} peptide that occur due solely to the influence of phosphate buffer. We reveal that significant differences in amyloid fibrillation are observed due to fibrillation being initiated in phosphate or HEPES buffer (at physiological pH and temperature). Except for the differing buffer ions, all experimental parameters were kept constant. Fibril formation was assessed using fluorescently monitored kinetic studies, microscopy, X-ray fiber diffraction and infrared and nuclear magnetic resonance spectroscopies. Based on this set up, we herein reveal profound effects on the mechanism and speed of A{beta} fibrillation. The three histidine residues at positions 6, 13 and 14 of A{beta}(1-40) are instrumental in these mechanistic changes. We conclude that buffer plays a more significant role in fibril formation than has been generally acknowledged.

  18. Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

    SciTech Connect

    Miklossy, J.; Miller, L.; Qing, H.; Radenovic, A.; Kis, A.; Vileno, B.; Laszlo, F.; Martins, R.N.; Waeber, G.; Mooser, V.; Bosman, F.; Khalili, K.; Darbinian, N.; McGeer, P.L.

    2008-08-25

    Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.

  19. 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

  20. A Drosophila gene encoding a protein resembling the human. beta. -amyloid protein precursor

    SciTech Connect

    Rosen, D.R.; Martin-Morris, L.; Luo, L.; White, K. )

    1989-04-01

    The authors have isolated genomic and cDNA clones for a Drosophila gene resembling the human {beta}-amyloid precursor protein (APP). This gene produces a nervous system-enriched 6.5-kilobase transcript. Sequencing of cDNAs derived from the 6.5-kilobase transcript predicts an 886-amino acid polypeptide. This polypeptide contains a putative transmembrane domain and exhibits strong sequence similarity to cytoplasmic and extracellular regions of the human {beta}-amyloid precursor protein. There is a high probability that this Drosophila gene corresponds to the essential Drosophila locus vnd, a gene required for embryonic nervous system development.

  1. 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

  2. Compositions for labeling .beta.-amyloid plaques and neurofibrillary tangles

    DOEpatents

    Barrio, Jorge R.; Petric, Andrej; Satyamurthy, Nagichettiar; Small, Gary W.; Cole, Gregory M.; Huang, Sung-Cheng

    2008-03-11

    Compositions useful for labeling .beta.-amyloid plaques and neurofibrillary tangles are provided. The compositions comprises compounds of formula (I): ##STR00001## wherein R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2-alkyl, --C.dbd.C(CN).sub.2-alkylenyl-R.sub.4, ##STR00002## wherein R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5 is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 and --C(O)NH.sub.2; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S; and R.sub.2 is selected from the group consisting of alkyl and alkylenyl-R.sub.10 and R.sub.3 is alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal, and spiperone-3-yl, or R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl, and further wherein one or more of the hydrogen, halogen or carbon atoms are optionally replaced with a radiolabel.

  3. Methods for labeling .beta.-amyloid plaques and neurofibrillary tangles

    DOEpatents

    Barrio, Jorge R.; Petric, Andrej; Satyamurthy, Nagichettiar; Small, Gary W.; Cole, Gregory M.; Huang, Sung-Cheng

    2001-01-01

    A method for labeling .beta.-amyloid plaques and neurofibrillary tangles in vivo and in vitro, comprises contacting a compound of formula (I): ##STR1## with mammalian tissue. In formula (I), R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2 -alkyl, --C.dbd.C(CN).sub.2 -alkylenyl-R.sub.4 , ##STR2## R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5, is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4 ; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH , --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 ; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S. R.sub.2 and R.sub.3 are each independently selected from the group consisting of alkyl and alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal and spiperone-3-yl. Alternatively, R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkylenyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl. In the compounds of formula (I), one or more of the hydrogen, halogen or carbon atoms can, optionally, be replaced with a radiolabel.

  4. Methods for labeling .beta.-amyloid plaques and neurofibrillary tangles

    DOEpatents

    Barrio, Jorge R.; Petric, Andrej; Satyamurthy, Nagichettiar; Small, Gary W.; Cole, Gregory M.; Huang, Sung-Cheng

    2003-12-09

    A method for labeling .beta.-amyloid plaques and neurofibrillary tangles in vivo and in vitro, comprises contacting a compound of formula (I): ##STR1## with mammalian tissue. In formula (I), R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2 -alkyl, --C.dbd.C(CN).sub.2 -alkylenyl-R.sub.4, ##STR2## R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5 is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4 ; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH, --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 ; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S. R.sub.2 and R.sub.3 are each independently selected from the group consisting of alkyl and alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal and spiperone-3-yl. Alternatively, R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkylenyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl. In the compounds of formula (I), one or more of the hydrogen, halogen or carbon atoms can, optionally, be replaced with a radiolabel.

  5. Beta-amyloid fibrils of Alzheimer's disease: pathologically altered, basement membrane-associated microfibrils?

    PubMed

    Inoue, S; Kisilevsky, R

    2001-01-01

    Beta amyloid fibrils were examined in situ in the cerebral cortex of brains from patients with Alzheimer's disease using high resolution ultrastructural and immunohistochemical techniques. The main body of the fibril was identical with that of microfibrils and was made up of a core containing amyloid P component (AP), and a surface layer. Beta amyloid protein (Abeta) in the form of 1 nm wide flexible filaments was associated with the external surface of the microfibril. In cerebrovascular amyloid angiopathy the fibrils were formed at the outer surface of the vascular basement membrane. Overproduction of microfibrils has been reported at the basement membrane of "leaky" capillaries including the glomerular capillary in disease or leaky alveolar-capillary walls of normal lungs. Similarly, in Alzheimer's disease overproduction of microfibril-like beta amyloid fibrils in amyloid angiopathy coincided with breakdown of the blood-brain barrier of the cerebromicrovasculature. Thus, in the above three locations, the presence of abundant microfibrils, or microfibril-like structures, may be related to plasma which leaks out of the circulation into the adjoining vascular basement membrane. AP is an essential constituent of microfibrils and since the only site where AP is available in the cerebral cortex is in leaky microvasculature, a chronic, steady supply of AP into perivascular areas may be the cause of overproduction of microfibrils. Brain "microfibrils" may further be altered pathologically into beta amyloid fibrils by the addition of Abeta. The origin of the fibrils in senile plaques may also be the microvasculature since in the area of the plaques no source of AP is apparent.

  6. Beta-amyloid fibrils of Alzheimer's disease: pathologically altered, basement membrane-associated microfibrils?

    PubMed

    Inoue, S; Kisilevsky, R

    2001-01-01

    Beta amyloid fibrils were examined in situ in the cerebral cortex of brains from patients with Alzheimer's disease using high resolution ultrastructural and immunohistochemical techniques. The main body of the fibril was identical with that of microfibrils and was made up of a core containing amyloid P component (AP), and a surface layer. Beta amyloid protein (Abeta) in the form of 1 nm wide flexible filaments was associated with the external surface of the microfibril. In cerebrovascular amyloid angiopathy the fibrils were formed at the outer surface of the vascular basement membrane. Overproduction of microfibrils has been reported at the basement membrane of "leaky" capillaries including the glomerular capillary in disease or leaky alveolar-capillary walls of normal lungs. Similarly, in Alzheimer's disease overproduction of microfibril-like beta amyloid fibrils in amyloid angiopathy coincided with breakdown of the blood-brain barrier of the cerebromicrovasculature. Thus, in the above three locations, the presence of abundant microfibrils, or microfibril-like structures, may be related to plasma which leaks out of the circulation into the adjoining vascular basement membrane. AP is an essential constituent of microfibrils and since the only site where AP is available in the cerebral cortex is in leaky microvasculature, a chronic, steady supply of AP into perivascular areas may be the cause of overproduction of microfibrils. Brain "microfibrils" may further be altered pathologically into beta amyloid fibrils by the addition of Abeta. The origin of the fibrils in senile plaques may also be the microvasculature since in the area of the plaques no source of AP is apparent. PMID:11730002

  7. 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.

  8. Trafficking of cell surface beta-amyloid precursor protein: retrograde and transcytotic transport in cultured neurons

    PubMed Central

    1995-01-01

    Amyloid beta-protein (A beta), the principal constituent of senile plaques seen in Alzheimer's disease (AD), is derived by proteolysis from the beta-amyloid precursor protein (beta PP). The mechanism of A beta production in neurons, which are hypothesized to be a rich source of A beta in brain, remains to be defined. In this study, we describe a detailed localization of cell surface beta PP and its subsequent trafficking in primary cultured neurons. Full-length cell surface beta PP was present primarily on perikarya and axons, the latter with a characteristic discontinuous pattern. At growth cones, cell surface beta PP was inconsistently detected. By visualizing the distribution of beta PP monoclonal antibodies added to intact cultures, beta PP was shown to be internalized from distal axons or terminals and retrogradely transported back to perikarya in organelles which colocalized with fluid-phase endocytic markers. Retrograde transport of beta PP was shown in both hippocampal and peripheral sympathetic neurons, the latter using a compartment culture system that isolated cell bodies from distal axons and terminals. In addition, we demonstrated that beta PP from distal axons was transcytotically transported to the surface of perikarya from distal axons in sympathetic neurons. Indirect evidence of this transcytotic pathway was obtained in hippocampal neurons using antisense oligonucleotide to the kinesin heavy chain to inhibit anterograde beta PP transport. Taken together, these results demonstrate novel aspects of beta PP trafficking in neurons, including retrograde axonal transport and transcytosis. Moreover, the axonal predominance of cell surface beta PP is unexpected in view of the recent report of polarized sorting of beta PP to the basolateral domain of MDCK cells. PMID:7721945

  9. 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

  10. An investigation into the mechanisms mediating plasma lipoprotein-potentiated beta-amyloid fibrillogenesis.

    PubMed

    Stanyer, Lee; Betteridge, D John; Smith, Christopher C T

    2002-05-01

    The toxicity of the beta-amyloid (Abeta) peptide of Alzheimer's disease may relate to its polymerisation state (i.e. fibril content). We have shown previously that plasma lipoproteins, particularly when oxidised, greatly enhance Abeta polymerisation. In the present study the nature of the interactions between both native and oxidised lipoproteins and Abeta1-40 was investigated employing various chemical treatments. The addition of ascorbic acid or the vitamin E analogue, trolox, to lipoprotein/Abeta coincubations failed to inhibit Abeta fibrillogenesis, as did the treatment of lipoproteins with the aldehyde reductant, sodium borohydride. The putative lipid peroxide-derived aldehyde scavenger, aminoguanidine, however, inhibited Abeta-oxidised lipoprotein-potentiated polymerisation, but in a manner consistent with an antioxidant action for the drug. Lipoprotein treatment with the reactive aldehyde 4-hydroxy-2-trans-nonenal enhanced Abeta polymerisation in a concentration-dependent fashion. Incubation of Abeta with lipoprotein fractions from which the apoprotein components had been removed resulted in extents of polymerisation comparable to those observed with Abeta alone. These data indicate that the apoprotein components of plasma lipoproteins play a key role in promoting Abeta polymerisation, possibly via interactions with aldehydes.

  11. A mathematical model of the kinetics of beta-amyloid fibril growth from the denatured state.

    PubMed Central

    Pallitto, M M; Murphy, R M

    2001-01-01

    Spontaneous conversion of beta-amyloid peptide (Abeta) from soluble monomer to insoluble fibril may underlie the neurodegeneration associated with Alzheimer's disease. A complete description of Abeta self-association kinetics requires identification of the oligomeric species present and the pathway of association, as well as quantitation of rate constants and reaction order. Abeta was rendered monomeric and denatured by dissolution in 8 M urea, pH 10. "Refolding" and fibrillization were initiated by rapid dilution into phosphate-buffered saline, pH 7.4. The kinetics of growth were followed at three different concentrations, using size exclusion chromatography, dynamic light scattering, and static light scattering. A multi-step pathway for fibril formation and growth was postulated. This pathway included 1) rapid commitment to either stable monomer/dimer or unstable intermediate, 2) cooperative association of intermediate into a multimeric "nucleus," 3) elongation of the "nucleus" into filaments via addition of intermediate, 4) lateral aggregation of filaments into fibrils, and 5) fibril elongation via end-to-end association. Differential and algebraic equations describing this kinetic pathway were derived, and model parameters were determined by fitting the data. The utility of the model for identifying toxic Abeta oligomeric specie(s) is demonstrated. The model should prove useful for designing compounds that inhibit Abeta aggregation and/or toxicity. PMID:11509390

  12. Detection of Alzheimer’s disease amyloid-beta plaque deposition by deep brain impedance profiling

    NASA Astrophysics Data System (ADS)

    Béduer, Amélie; Joris, Pierre; Mosser, Sébastien; Fraering, Patrick C.; Renaud, Philippe

    2015-04-01

    Objective. Alzheimer disease (AD) is the most common form of neurodegenerative disease in elderly people. Toxic brain amyloid-beta (Aß) aggregates and ensuing cell death are believed to play a central role in the pathogenesis of the disease. In this study, we investigated if we could monitor the presence of these aggregates by performing in situ electrical impedance spectroscopy measurements in AD model mice brains. Approach. In this study, electrical impedance spectroscopy measurements were performed post-mortem in APPPS1 transgenic mice brains. This transgenic model is commonly used to study amyloidogenesis, a pathological hallmark of AD. We used flexible probes with embedded micrometric electrodes array to demonstrate the feasibility of detecting senile plaques composed of Aß peptides by localized impedance measurements. Main results. We particularly focused on deep brain structures, such as the hippocampus. Ex vivo experiments using brains from young and old APPPS1 mice lead us to show that impedance measurements clearly correlate with the percentage of Aβ plaque load in the brain tissues. We could monitor the effects of aging in the AD APPPS1 mice model. Significance. We demonstrated that a localized electrical impedance measurement constitutes a valuable technique to monitor the presence of Aβ-plaques, which is complementary with existing imaging techniques. This method does not require prior Aβ staining, precluding the risk of variations in tissue uptake of dyes or tracers, and consequently ensuring reproducible data collection.

  13. Amyloid Beta: Multiple Mechanisms of Toxicity and Only Some Protective Effects?

    PubMed Central

    Colín-Barenque, Laura

    2014-01-01

    Amyloid beta (Aβ) is a peptide of 39–43 amino acids found in large amounts and forming deposits in the brain tissue of patients with Alzheimer's disease (AD). For this reason, it has been implicated in the pathophysiology of damage observed in this type of dementia. However, the role of Aβ in the pathophysiology of AD is not yet precisely understood. Aβ has been experimentally shown to have a wide range of toxic mechanisms in vivo and in vitro, such as excitotoxicity, mitochondrial alterations, synaptic dysfunction, altered calcium homeostasis, oxidative stress, and so forth. In contrast, Aβ has also shown some interesting neuroprotective and physiological properties under certain experimental conditions, suggesting that both physiological and pathological roles of Aβ may depend on several factors. In this paper, we reviewed both toxic and protective mechanisms of Aβ to further explore what their potential roles could be in the pathophysiology of AD. The complete understanding of such apparently opposed effects will also be an important guide for the therapeutic efforts coming in the future. PMID:24683437

  14. Amyloid beta: multiple mechanisms of toxicity and only some protective effects?

    PubMed

    Carrillo-Mora, Paul; Luna, Rogelio; Colín-Barenque, Laura

    2014-01-01

    Amyloid beta (Aβ) is a peptide of 39-43 amino acids found in large amounts and forming deposits in the brain tissue of patients with Alzheimer's disease (AD). For this reason, it has been implicated in the pathophysiology of damage observed in this type of dementia. However, the role of Aβ in the pathophysiology of AD is not yet precisely understood. Aβ has been experimentally shown to have a wide range of toxic mechanisms in vivo and in vitro, such as excitotoxicity, mitochondrial alterations, synaptic dysfunction, altered calcium homeostasis, oxidative stress, and so forth. In contrast, Aβ has also shown some interesting neuroprotective and physiological properties under certain experimental conditions, suggesting that both physiological and pathological roles of Aβ may depend on several factors. In this paper, we reviewed both toxic and protective mechanisms of Aβ to further explore what their potential roles could be in the pathophysiology of AD. The complete understanding of such apparently opposed effects will also be an important guide for the therapeutic efforts coming in the future.

  15. Dementia of the eye: the role of amyloid beta in retinal degeneration.

    PubMed

    Ratnayaka, J A; Serpell, L C; Lotery, A J

    2015-08-01

    Age-related macular degeneration (AMD) is one of the most common causes of irreversible blindness affecting nearly 50 million individuals globally. The disease is characterised by progressive loss of central vision, which has significant implications for quality of life concerns in an increasingly ageing population. AMD pathology manifests in the macula, a specialised region of the retina, which is responsible for central vision and perception of fine details. The underlying pathology of this complex degenerative disease is incompletely understood but includes both genetic as well as epigenetic risk factors. The recent discovery that amyloid beta (Aβ), a highly toxic and aggregate-prone family of peptides, is elevated in the ageing retina and is associated with AMD has opened up new perspectives on the aetiology of this debilitating blinding disease. Multiple studies now link Aβ with key stages of AMD progression, which is both exciting and potentially insightful, as this identifies a well-established toxic agent that aggressively targets cells in degenerative brains. Here, we review the most recent findings supporting the hypothesis that Aβ may be a key factor in AMD pathology. We describe how multiple Aβ reservoirs, now reported in the ageing eye, may target the cellular physiology of the retina as well as associated layers, and propose a mechanistic pathway of Aβ-mediated degenerative change leading to AMD. PMID:26088679

  16. Nano-biosensors to detect beta-amyloid for Alzheimer's disease management.

    PubMed

    Kaushik, Ajeet; Jayant, Rahul Dev; Tiwari, Sneham; Vashist, Arti; Nair, Madhavan

    2016-06-15

    Beta-amyloid (β-A) peptides are potential biomarkers to monitor Alzheimer's diseases (AD) for diagnostic purposes. Increased β-A level is neurotoxic and induces oxidative stress in brain resulting in neurodegeneration and causes dementia. As of now, no sensitive and inexpensive method is available for β-A detection under physiological and pathological conditions. Although, available methods such as neuroimaging, enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) detect β-A, but they are not yet extended at point-of-care (POC) due to sophisticated equipments, need of high expertize, complicated operations, and challenge of low detection limit. Recently, β-A antibody based electrochemical immuno-sensing approach has been explored to detect β-A at pM levels within 30-40 min compared to 6-8h of ELISA test. The introduction of nano-enabling electrochemical sensing technology could enable rapid detection of β-A at POC and may facilitate fast personalized health care delivery. This review explores recent advancements in nano-enabling electrochemical β-A sensing technologies towards POC application to AD management. These analytical tools can serve as an analytical tool for AD management program to obtain bio-informatics needed to optimize therapeutics for neurodegenerative diseases diagnosis management.

  17. 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

  18. Positron emission tomography radiopharmaceuticals for imaging brain Beta-amyloid.

    PubMed

    Vallabhajosula, Shankar

    2011-07-01

    Alzheimer's disease (AD) is defined histologically by the presence of extracellular β-amyloid (Aβ) plaques and intraneuronal neurofibrillary tangles in the cerebral cortex. The diagnosis of dementia, along with the prediction of who will develop dementia, has been assisted by magnetic resonance imaging and positron emission tomography (PET) by using [(18)F]fluorodeoxyglucose (FDG). These techniques, however, are not specific for AD. Based on the chemistry of histologic staining dyes, several Aβ-specific positron-emitting radiotracers have been developed to image neuropathology of AD. Among these, [(11)C]PiB is the most studied Aβ-binding PET radiopharmaceutical in the world. The histologic and biochemical specificity of PiB binding across different regions of the AD brain was demonstrated by showing a direct correlation between Aβ-containing amyloid plaques and in vivo [(11)C]PiB retention measured by PET imaging. Because (11)C is not ideal for commercialization, several (18)F-labeled tracers have been developed. At this time, [(18)F]3'-F-PiB (Flutemetamol), (18)F-AV-45 (Florbetapir), and (18)F-AV-1 (Florbetaben) are undergoing extensive phase II and III clinical trials. This article provides a brief review of the amyloid biology and chemistry of Aβ-specific (11)C and (18)F-PET radiopharmaceuticals. Clinical trials have clearly documented that PET radiopharmaceuticals capable of assessing Aβ content in vivo in the brains of AD subjects and subjects with mild cognitive impairment will be important as diagnostic agents to detect in vivo amyloid brain pathology. In addition, PET amyloid imaging will also help test the amyloid cascade hypothesis of AD and as an aid to assess the efficacy of antiamyloid therapeutics currently under development in clinical trials.

  19. 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.

  20. Reduced beta-amyloid production and increased inflammatory responses in presenilin conditional knock-out mice.

    PubMed

    Beglopoulos, Vassilios; Sun, Xiaoyan; Saura, Carlos A; Lemere, Cynthia A; Kim, Richard D; Shen, Jie

    2004-11-01

    Mutations in presenilins (PS) 1 and 2 are the major cause of familial Alzheimer's disease. Conditional double knock-out mice lacking both presenilins in the postnatal forebrain (PS cDKO mice) exhibit memory and synaptic plasticity impairments followed by progressive neurodegeneration in the cerebral cortex. Here we further investigate the molecular events that may underlie the observed phenotypes and identify additional neuropathological markers in the PS cDKO brain. Enzyme-linked immunosorbent assay analysis showed reduced levels of the toxic beta-amyloid (Abeta) peptides in the cerebral cortex of PS cDKO mice. Interestingly, the reduction in Abeta40 and Abeta42 peptides is similar in PS1 conditional knock-out and PS cDKO mice. We further examined the gene expression profile by oligonucleotide microarrays in the PS cDKO cerebral cortex and found that a high number of genes are differentially expressed, most notably a group of up-regulated inflammatory genes. Quantitative real-time reverse transcription PCR and Western analyses confirmed the elevated levels of glial fibrillary acidic protein, complement component C1q, and cathepsin S, up-regulation of which has been associated with inflammatory responses in various neurodegenerative processes. Immunohistochemical analysis revealed that the increase in complement component C1q is confined to the hippocampal formation, whereas glial fibrillary acidic protein and cathepsin S are up-regulated throughout the entire neocortex and hippocampus. In addition, strong microglial activation occurs in the hippocampus and the deeper cortical layers of PS cDKO mice. These results indicate that the memory impairment and neurodegeneration in PS cDKO mice are not caused by Abeta accumulation and that loss of PS function leads to differential up-regulation of inflammatory markers in the cerebral cortex.

  1. Pioglitazone and exenatide enhance cognition and downregulate hippocampal beta amyloid oligomer and microglia expression in insulin-resistant rats.

    PubMed

    Gad, Enas S; Zaitone, Sawsan A; Moustafa, Yasser M

    2016-08-01

    Insulin resistance is known to be a risk factor for cognitive impairment, most likely linked to insulin signaling, microglia overactivation, and beta amyloid (Aβ) deposition in the brain. Exenatide, a long lasting glucagon-like peptide-1 (GLP-1) analogue, enhances insulin signaling and shows neuroprotective properties. Pioglitazone, a peroxisome proliferated-activated receptor-γ (PPAR-γ) agonist, was previously reported to enhance cognition through its effect on Aβ accumulation and clearance. In the present study, insulin resistance was induced in male rats by drinking fructose for 12 weeks. The effect of monotherapy with pioglitazone (10 mg·kg(-1)) and exenatide or their combination on memory dysfunction was determined and some of the probable underlying mechanisms were studied. The current results confirmed that (1) feeding male rats with fructose syrup for 12 weeks resulted in a decline of learning and memory registered in eight-arm radial maze test; (2) treatment with pioglitazone or exenatide enhanced cognition, reduced hippocampal neurodegeneration, and reduced hippocampal microglia expression and beta amyloid oligomer deposition in a manner that is equal to monotherapies. These results may give promise for the use of pioglitazone or exenatide for ameliorating the learning and memory deficits associated with insulin resistance in clinical setting. PMID:27389824

  2. 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.

  3. 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.

  4. 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

  5. Quantitation of amyloid beta-protein (A beta) in the cortex during aging and in Alzheimer's disease.

    PubMed Central

    Funato, H.; Yoshimura, M.; Kusui, K.; Tamaoka, A.; Ishikawa, K.; Ohkoshi, N.; Namekata, K.; Okeda, R.; Ihara, Y.

    1998-01-01

    In this study we sought to learn about when and how amyloid beta-protein (A beta) accumulates in the cortex of normal individuals and about the difference in the A beta accumulation between normal aged and Alzheimer's disease (AD) brains. From consecutive autopsy cases and AD cases, hippocampus CA1 and occipitotemporal cortex T4 were sampled for A beta quantitation by the well characterized two-site enzyme immunoassays (EIAs). There was a strong tendency toward A beta 42 accumulation between the ages of 50 and 70 years in T4 and a little later in CA1. The A beta 42 levels were consistently higher in T4 than those in CA1 in any given case. The levels of A beta 42 in AD brains were significantly higher than those in control brains, and the extent of A beta 42 amino-terminal modification was also much greater in AD brains than that in control brains. Even in cases in which no senile plaques were immunocytochemically detected, EIAs clearly showed that significant amounts of A beta 42 already had accumulated. In contrast to A beta 42, A beta 40 showed no apparent age-dependent accumulation, and its high levels were found to be associated with AD. PMID:9626067

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. Synchrotron-based Infrared and X-ray Imaging Shows Focalized Accumulation of Cu and Zn Co-localized With Beta-amyloid Deposits in Alzheimer's Disease

    SciTech Connect

    Miller,L.; Wang, Q.; Telivala, T.; Smith, R.; Lanzirotti, A.; Miklossy, J.

    2006-01-01

    Alzheimer's disease (AD) is characterized by the misfolding and plaque-like accumulation of a naturally occurring peptide in the brain called amyloid beta (Abeta). Recently, this process has been associated with the binding of metal ions such as iron (Fe), copper (Cu), and zinc (Zn). It is thought that metal dyshomeostasis is involved in protein misfolding and may lead to oxidative stress and neuronal damage. However, the exact role of the misfolded proteins and metal ions in the degenerative process of AD is not yet clear. In this study, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to image the in situ secondary structure of the amyloid plaques in brain tissue of AD patients. These results were spatially correlated with metal ion accumulation in the same tissue sample using synchrotron X-ray fluorescence (SXRF) microprobe. For both techniques, a spatial resolution of 5-10 microm was achieved. FTIRM results showed that the amyloid plaques have elevated beta-sheet content, as demonstrated by a strong amide I absorbance at 1625cm(-1). Using SXRF microprobe, we find that AD tissue also contains 'hot spots' of accumulated metal ions, specifically Cu and Zn, with a strong spatial correlation between these two ions. The 'hot spots' of accumulated Zn and Cu were co-localized with beta-amyloid plaques. Thus for the first time, a strong spatial correlation has been observed between elevated beta-sheet content in Abeta plaques and accumulated Cu and Zn ions, emphasizing an association of metal ions with amyloid formation in AD.

  11. Helix Bundle Quaternary Structure from [alpha]/[beta]-Peptide Foldamers

    SciTech Connect

    Horne, W. Seth; Price, Joshua L.; Keck, James L.; Gellman, Samuel H.

    2008-11-18

    The function of a protein generally depends on adoption of a specific folding pattern, which in turn is determined by the side chain sequence along the polypeptide backbone. Here we show that the sequence-encoded structural information in peptides derived from yeast transcriptional activator GCN4 can be used to prepare hybrid {alpha}/{beta}-peptide foldamers that adopt helix bundle quaternary structures. Crystal structures of two hybrid {alpha}/{beta}-peptides are reported along with detailed structural comparison to {alpha}-peptides of analogous side chain sequence. There is considerable homology between {alpha}- and {alpha}/{beta}-peptides at the level of helical secondary structure, with modest but significant differences in the association geometry of helices in the quaternary structure.

  12. Molecular simulations of beta-amyloid protein near hydrated lipids (PECASE).

    SciTech Connect

    Thompson, Aidan Patrick; Han, Kunwoo (Texas A&M University, College Station, TX); Ford, David M. (Texas A&M University, College Station, TX)

    2005-12-01

    We performed molecular dynamics simulations of beta-amyloid (A{beta}) protein and A{beta} fragment(31-42) in bulk water and near hydrated lipids to study the mechanism of neurotoxicity associated with the aggregation of the protein. We constructed full atomistic models using Cerius2 and ran simulations using LAMMPS. MD simulations with different conformations and positions of the protein fragment were performed. Thermodynamic properties were compared with previous literature and the results were analyzed. Longer simulations and data analyses based on the free energy profiles along the distance between the protein and the interface are ongoing.

  13. beta. amyloid gene duplication in Alzheimer's disease and karyotypically normal Down syndrome

    SciTech Connect

    Delabar, J.; Goldgaber, D.; Lamour, Y.; Nicole, A.; Huret, J.; De Groucy, J.; Brown, P.; Gajdusek, D.C.; Sinet, P.

    1987-03-13

    With the recently cloned complementary DNA probe, lambdaAm4 for the chromosome 21 gene encoding brain amyloid polypeptide (..beta.. amyloid protein) of Alzheimer's disease, leukocyte DNA from three patients with sporadic Alzheimer's disease and two patients with karyotypically normal Down syndrome was found to contain three copies of this bene. Because a small region of chromosome 21 containing the ets-2 gene is duplicated in patients with Alzheimer's disease, as well as in karyotypically normal Down syndrome, duplication of a subsection of the critical segment of chromosome 21 that is duplicated in Down syndrome may be the genetic defect in Alzeimer's disease.

  14. MMPBSA decomposition of the binding energy throughout a molecular dynamics simulation of amyloid-beta (Abeta(10-35)) aggregation.

    PubMed

    Campanera, Josep M; Pouplana, Ramon

    2010-04-15

    Recent experiments with amyloid-beta (Abeta) peptides indicate that the formation of toxic oligomers may be an important contribution to the onset of Alzheimer's disease. The toxicity of Abeta oligomers depend on their structure, which is governed by assembly dynamics. However, a detailed knowledge of the structure of at the atomic level has not been achieved yet due to limitations of current experimental techniques. In this study, replica exchange molecular dynamics simulations are used to identify the expected diversity of dimer conformations of Abeta(10-35) monomers. The most representative dimer conformation has been used to track the dimer formation process between both monomers. The process has been characterized by means of the evolution of the decomposition of the binding free energy, which provides an energetic profile of the interaction. Dimers undergo a process of reorganization driven basically by inter-chain hydrophobic and hydrophilic interactions and also solvation/desolvation processes.

  15. ETAS, an enzyme-treated asparagus extract, attenuates amyloid beta-induced cellular disorder in PC12 cells.

    PubMed

    Ogasawara, Junetsu; Ito, Tomohiro; Wakame, Koji; Kitadate, Kentaro; Sakurai, Takuya; Sato, Shogo; Ishibashi, Yoshinaga; Izawa, Tetsuya; Takahashi, Kazuto; Ishida, Hitoshi; Takabatake, Ichiro; Kizaki, Takako; Ohno, Hideki

    2014-04-01

    One of the pathological characterizations of Alzheimer's disease (AD) is the deposition of amyloid beta peptide (Abeta) in cerebral cortical cells. The deposition of Abeta in neuronal cells leads to an increase in the production of free radicals that are typified by reactive oxygen species (ROS), thereby inducing cell death. A growing body of evidence now suggests that several plant-derived food ingredients are capable of scavenging ROS in mammalian cells. The purpose of the present study was to investigate whether enzyme-treated asparagus extract (ETAS), which is rich in antioxidants, is one of these ingredients. The pre-incubation of differentiated PC 12 cells with ETAS significantly recovered Abeta-induced reduction of cell viability, which was accompanied by reduced levels of ROS. These results suggest that ETAS may be one of the functional food ingredients with anti-oxidative capacity to help prevent AD.

  16. Using optical profilometry to characterize cell membrane roughness influenced by amyloid-beta 42 aggregates and electric fields

    NASA Astrophysics Data System (ADS)

    Pan, Huei-Jyuan; Wang, Ruei-Lin; Xiao, Jian-Long; Chang, Yu-Jen; Cheng, Ji-Yen; Chen, Yun-Ru; Lee, Chau-Hwang

    2014-01-01

    The membrane roughness of Neuro-2a neroblastoma cells is measured by using noninterferometric wide-field optical profilometry. The cells are treated with the fibril and oligomer conformers of amyloid-beta (Aβ) 42, which is a peptide of 42 amino acids related to the development of Alzheimer's disease. We find that both the Aβ42 fibrils and Aβ42 oligomers reduced the cell membrane roughness, but the effect of Aβ42 oligomers was faster and stronger than that of the fibrils. We also apply direct-current electric field (dcEF) stimulations on the cells. A dcEF of 300 mV/mm can increase the membrane roughness under the treatment of Aβ42. These results suggest that Aβ42 can decrease the membrane compliance of live neuroblastoma cells, and dcEFs may counteract this effect.

  17. 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

  18. 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

  19. 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

  20. Intracerebral transplantation of bone marrow-derived mesenchymal stem cells reduces amyloid-beta deposition and rescues memory deficits in Alzheimer's disease mice by modulation of immune responses.

    PubMed

    Lee, Jong Kil; Jin, Hee Kyung; Endo, Shogo; Schuchman, Edward H; Carter, Janet E; Bae, Jae-Sung

    2010-02-01

    Alzheimer's disease (AD) is characterized by the deposition of amyloid-beta peptide (Abeta) and the formation of neurofibrillary tangles. Transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) has been suggested as a potential therapeutic approach to prevent various neurodegenerative disorders, including AD. However, the actual therapeutic impact of BM-MSCs and their mechanism of action in AD have not yet been ascertained. The aim of this study was therefore to evaluate the therapeutic effect of BM-MSC transplantation on the neuropathology and memory deficits in amyloid precursor protein (APP) and presenilin one (PS1) double-transgenic mice. Here we show that intracerebral transplantation of BM-MSCs into APP/PS1 mice significantly reduced amyloid beta-peptide (Abeta) deposition. Interestingly, these effects were associated with restoration of defective microglial function, as evidenced by increased Abeta-degrading factors, decreased inflammatory responses, and elevation of alternatively activated microglial markers. Furthermore, APP/PS1 mice treated with BM-MSCs had decreased tau hyperphosphorylation and improved cognitive function. In conclusion, BM-MSCs can modulate immune/inflammatory responses in AD mice, ameliorate their pathophysiology, and improve the cognitive decline associated with Abeta deposits. These results demonstrate that BM-MSCs are a potential new therapeutic agent for AD.

  1. 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.

  2. Rimmed vacuoles with beta-amyloid and tau protein deposits in the muscle of children with hereditary myopathy.

    PubMed

    Fidziańska, Anna; Glinka, Zofia

    2006-08-01

    We investigated whether beta-amyloid and tau protein are involved in the formation of inclusion body myositis (IBM)-like inclusions found in children with rimmed vacuoles and congenitally affected muscles. We immunostained muscle biopsy specimens from four children and one 18-year-old boy with congenital myopathy containing rimmed vacuoles and IBM-like inclusions with antibodies against beta-amyloid, tau protein and ubiquitin. Focal accumulations of both beta-amyloid and phosphorylated tau coexisted with tubulofilamentous structures in all cases. Our studies demonstrate for the first time that the full morphological phenotype of IBM including beta-amyloid and tau protein deposits may also develop in children, and that congenital, probably genetic, muscle defects may lead to abnormal protein aggregation in IBM-like inclusions.

  3. Differential regulation of amyloid-. beta. -protein mRNA expression within hippocampal neuronal subpopulations in Alzheimer disease

    SciTech Connect

    Higgins, G.A.; Lewis, D.A.; Bahmanyar, S.; Goldgaber, D.; Gajdusek, D.C.; Young, W.G.; Morrison, J.H.; Wilson, M.C.

    1988-02-01

    The authors have mapped the neuroanatomical distribution of amyloid-..beta..-protein mRNA within neuronal subpopulations of the hippocampal formation in the cynomolgus monkey (Macaca fascicularis), normal aged human, and patients with Alzheimer disease. Amyloid-..beta..-protein mRNA appears to be expressed in all hippocampal neurons, but at different levels of abundance. In the central nervous system of monkey and normal aged human, image analysis shows that neurons of the dentate gyrus and cornu Ammonis fields contain a 2.5-times-greater hybridization signal than is present in neurons of the subiculum and entorhinal cortex. In contrast, in the Alzheimer disease hippocampal formation, the levels of amyloid-..beta..-protein mRNA in the cornu Ammonis field 3 and parasubiculum are equivalent. These findings suggest that within certain neuronal subpopulations cell type-specific regulation of amyloid-..beta..-protein gene expression may be altered in Alzheimer disease.

  4. Design of beta-domain swapping, alpha/beta-protein, environmentally sensitive coiled coil and peptide functionalized titania materials

    NASA Astrophysics Data System (ADS)

    Nagarkar, Radhika P.

    2009-12-01

    The objective of this dissertation is to apply rational peptide design to fabricate nanomaterials via self-assembly. This has been demonstrated in structurally diverse systems with an aim of deciphering the underlying principles governing how sequence affects the peptide's ability to adopt a specific secondary structure and ultimate material properties that are realized from the association of these secondary structural elements. Several amyloidogenic proteins have been shown to self-assemble into fibrils using a mechanism known as domain swapping. Here, discreet units of secondary structure are exchanged among discreet proteins during self-assembly to form extended networks with precise three dimensional organization. The possibility of using these mechanisms to design peptides capable of controlled assembly and fibril formation leading to materials with targeted properties is explored. By altering the placement of a beta-turn sequence that varies the size and location of the exchanged strand, twisting, non-twisting and laminated fibrillar nanostructures are obtained. Hydrogels prepared from these strand swapping beta-hairpins have varied rheological properties due to differences in their fibrillar nanostructures. In a second distinct design, alpha/beta-proteins are used to prepare environmentally sensitive hydrogels. Here, multiple distinct motifs for structural integrity and dynamic response within a single self-assembling peptide allow the amyloid-like fibrils formed to controllably alter their nano-topography in response to an external stimulus such as temperature. The development of these self-assembling alpha/beta-protein motifs also necessitated the design of pH sensitive antiparallel coiled coils. Exploring the basic principles responsible for pH dependent conformational changes in coiled coils can lead to new insights in the control of protein structure and function. Lastly, this dissertation discusses the interface between biomolecules and inorganic

  5. 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

  6. 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

  7. Absence of amyloid-beta in lenses of Alzheimer patients: a confocal Raman microspectroscopic study.

    PubMed

    Michael, Ralph; Otto, Cees; Lenferink, Aufried; Gelpi, Ellen; Montenegro, Gustavo A; Rosandić, Jurja; Tresserra, Francisco; Barraquer, Rafael I; Vrensen, Gijs F J M

    2014-02-01

    We have compared the protein profiles in plaques and tangles in the hippocampus of post-mortem Alzheimer brains and in opaque and clear regions in the deep cortex of eye lenses of the same donors. From the 7 Alzheimer donors studied, 1 had pronounced bilateral cortical lens opacities, 1 moderate and 5 only minor or no cortical opacities. We focused on beta-sheet levels, a hallmarking property of amyloid-beta, the major protein of plaques and tau protein, the major protein of tangles in Alzheimer brains. Confocal Raman microspectroscopy and imaging was used in combination with hierarchical cluster analysis. Plaques and tangles show high levels of beta-sheets with a beta-sheet to protein ratio of 1.67. This ratio is 1.12 in unaffected brain tissue surrounding the plaques and tangles. In the lenses this ratio is 1.17 independently of the presence or absence of opacities. This major difference in beta-sheet conformation between hippocampus and lens is supported by Congo red and immunostaining of amyloid-beta and tau which were positive for plaques and tangles in the hippocampus but fully negative for the lens irrespective of the presence or absence of opacities. In line with a previous study (Michael et al., 2013) we conclude that cortical lens opacities are not typical for Alzheimer patients and are not hallmarked by accumulation of amyloid-beta, and can thus not be considered as predictors or indicators of Alzheimer disease as claimed by Goldstein et al. (2003).

  8. Novel roles of amyloid-beta precursor protein metabolites in fragile X syndrome and autism.

    PubMed

    Westmark, C J; Sokol, D K; Maloney, B; Lahiri, D K

    2016-10-01

    Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and is associated with up to 5% of autism cases. Several promising drugs are in preclinical testing for FXS; however, bench-to-bedside plans for the clinic are severely limited due to lack of validated biomarkers and outcome measures. Published work from our laboratories has demonstrated altered levels of amyloid-beta (Aβ) precursor protein (APP) and its metabolites in FXS and idiopathic autism. Westmark and colleagues have focused on β-secretase (amyloidogenic) processing and the accumulation of Aβ peptides in adult FXS models, whereas Lahiri and Sokol have studied α-secretase (non-amyloidogenic or anabolic) processing and altered levels of sAPPα and Aβ in pediatric autism and FXS. Thus, our groups have hypothesized a pivotal role for these Alzheimer's disease (AD)-related proteins in the neurodevelopmental disorders of FXS and autism. In this review, we discuss the contribution of APP metabolites to FXS and autism pathogenesis as well as the potential use of these metabolites as blood-based biomarkers and therapeutic targets. Our future focus is to identify key underlying mechanisms through which APP metabolites contribute to FXS and autism condition-to-disease pathology. Positive outcomes will support utilizing APP metabolites as blood-based biomarkers in clinical trials as well as testing drugs that modulate APP processing as potential disease therapeutics. Our studies to understand the role of APP metabolites in developmental conditions such as FXS and autism are a quantum leap for the neuroscience field, which has traditionally restricted any role of APP to AD and aging. PMID:27573877

  9. CCR5 deficiency accelerates lipopolysaccharide-induced astrogliosis, amyloid-beta deposit and impaired memory function.

    PubMed

    Hwang, Chul Ju; Park, Mi Hee; Hwang, Jae Yeon; Kim, Ju Hwan; Yun, Na Young; Oh, Sang Yeon; Song, Ju Kyung; Seo, Hyun Ok; Kim, Yun-Bae; Hwang, Dae Yeon; Oh, Ki-Wan; Han, Sang-Bae; Hong, Jin Tae

    2016-03-15

    Chemokine receptors are implicated in inflammation and immune responses. Neuro-inflammation is associated with activation of astrocyte and amyloid-beta (Aβ) generations that lead to pathogenesis of Alzheimer disease (AD). Previous our study showed that deficiency of CC chemokine receptor 5 (CCR5) results in activation of astrocytes and Aβ deposit, and thus memory dysfunction through increase of CC chemokine receptor 2 (CCR2) expression. CCR5 knockout mice were used as an animal model with memory dysfunction. For the purpose LPS was injected i.p. daily (0.25 mg/kg/day). The memory dysfunctions were much higher in LPS-injected CCR5 knockout mice compared to CCR5 wild type mice as well as non-injected CCR5 knockout mice. Associated with severe memory dysfuction in LPS injected CCR5 knockout mice, LPS injection significant increase expression of inflammatory proteins, astrocyte activation, expressions of β-secretase as well as Aβ deposition in the brain of CCR5 knockout mice as compared with that of CCR5 wild type mice. In CCR5 knockout mice, CCR2 expressions were high and co-localized with GFAP which was significantly elevated by LPS. Expression of monocyte chemoattractant protein-1 (MCP-1) which ligands of CCR2 also increased by LPS injection, and increment of MCP-1 expression is much higher in CCR5 knockout mice. BV-2 cells treated with CCR5 antagonist, D-ala-peptide T-amide (DAPTA) and cultured astrocytes isolated from CCR5 knockout mice treated with LPS (1 μg/ml) and CCR2 antagonist, decreased the NF-ĸB activation and Aβ level. These findings suggest that the deficiency of CCR5 enhances response of LPS, which accelerates to neuro-inflammation and memory impairment.

  10. A Novel Way of Amelioration of Amyloid Beta Induced Toxicity in Caenorhabditis elegans

    PubMed Central

    Saharia, Kopal; Kumar, Ranjeet; Gupta, Kuldeep; Mishra, Shrilekha; Subramaniam, Jamuna R.

    2016-01-01

    Background With an incidence of 1 in 85 persons above the age of 60 years succumbing to the disease, Alzheimer's disease (AD), has been predicted to create havoc globally. In spite of enormous efforts and exhaustive research, no cure is in sight. Hence, it is critical to unravel the mechanism of AD development/protection and identification of a cure soon. Purpose This study is aimed at investigating the mechanism of reserpine action, which alleviates the toxicity of amyloid beta (Aβ) (AD-causing peptide) in Caenorhabditis elegans [1, 2]. Methods Determination of alleviation of Aβ toxicity with reserpine manifested as reduction in progressive paralysis, in the background of GFP reporter driven by the promoter of the FMRFamide neuropeptide, FLP-11 (AD; Pflp-11::GFP) and acetylcholine contribution through aldicarb (which inhibits acetylcholine esterase) treatment. Results The most significant protection against Aβ toxicity was obtained in the background of Pflp-11::GFP. This protection had 2 components. The promoter of FLP-11 with the reporter GFP, Pflp-11::GFP, per se gave significant protection. Further reserpine treatment provided additional alleviation. Together they could almost eliminate Aβ toxicity. These 2 components of Aβ toxicity alleviation are dependent on acetylcholine levels, as an increase in acetylcholine by aldicarb treatment reduces the protective effect. Conclusion A unique way to alleviate Aβ toxicity is reserpine treatment in combination with Pflp-11::GFP. Reserpine should be evaluated as a potential drug in a pilot study in AD patients. Furthermore, identification of the mechanism of Pflp-11::GFP-mediated reduction in Aβ toxicity is a potential pathway to develop therapeutics for AD. PMID:27721583

  11. Novel roles of amyloid-beta precursor protein metabolites in fragile X syndrome and autism.

    PubMed

    Westmark, C J; Sokol, D K; Maloney, B; Lahiri, D K

    2016-10-01

    Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and is associated with up to 5% of autism cases. Several promising drugs are in preclinical testing for FXS; however, bench-to-bedside plans for the clinic are severely limited due to lack of validated biomarkers and outcome measures. Published work from our laboratories has demonstrated altered levels of amyloid-beta (Aβ) precursor protein (APP) and its metabolites in FXS and idiopathic autism. Westmark and colleagues have focused on β-secretase (amyloidogenic) processing and the accumulation of Aβ peptides in adult FXS models, whereas Lahiri and Sokol have studied α-secretase (non-amyloidogenic or anabolic) processing and altered levels of sAPPα and Aβ in pediatric autism and FXS. Thus, our groups have hypothesized a pivotal role for these Alzheimer's disease (AD)-related proteins in the neurodevelopmental disorders of FXS and autism. In this review, we discuss the contribution of APP metabolites to FXS and autism pathogenesis as well as the potential use of these metabolites as blood-based biomarkers and therapeutic targets. Our future focus is to identify key underlying mechanisms through which APP metabolites contribute to FXS and autism condition-to-disease pathology. Positive outcomes will support utilizing APP metabolites as blood-based biomarkers in clinical trials as well as testing drugs that modulate APP processing as potential disease therapeutics. Our studies to understand the role of APP metabolites in developmental conditions such as FXS and autism are a quantum leap for the neuroscience field, which has traditionally restricted any role of APP to AD and aging.

  12. [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.

  13. [beta subsccript 2]-microglobulin forms three-dimensional domain-swapped amyloid fibrils with disulfide linkages

    SciTech Connect

    Liu, Cong; Sawaya, Michael R.; Eisenberg, David

    2011-08-09

    {beta}{sub 2}-microglobulin ({beta}{sub 2}-m) is the light chain of the type I major histocompatibility complex. It deposits as amyloid fibrils within joints during long-term hemodialysis treatment. Despite the devastating effects of dialysis-related amyloidosis, full understanding of how fibrils form from soluble {beta}{sub 2}-m remains elusive. Here we show that {beta}{sub 2}-m can oligomerize and fibrillize via three-dimensional domain swapping. Isolating a covalently bound, domain-swapped dimer from {beta}{sub 2}-m oligomers on the pathway to fibrils, we were able to determine its crystal structure. The hinge loop that connects the swapped domain to the core domain includes the fibrillizing segment LSFSKD, whose atomic structure we also determined. The LSFSKD structure reveals a class 5 steric zipper, akin to other amyloid spines. The structures of the dimer and the zipper spine fit well into an atomic model for this fibrillar form of {beta}{sub 2}-m, which assembles slowly under physiological conditions.

  14. 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.

  15. 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.

  16. 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.

  17. Amyloid beta oligomers induce neuronal elasticity changes in age-dependent manner: a force spectroscopy study on living hippocampal neurons.

    PubMed

    Ungureanu, Andreea-Alexandra; Benilova, Iryna; Krylychkina, Olga; Braeken, Dries; De Strooper, Bart; Van Haesendonck, Chris; Dotti, Carlos G; Bartic, Carmen

    2016-01-01

    Small soluble species of amyloid-beta (Aβ) formed during early peptide aggregation stages are responsible for several neurotoxic mechanisms relevant to the pathology of Alzheimer's disease (AD), although their interaction with the neuronal membrane is not completely understood. This study quantifies the changes in the neuronal membrane elasticity induced by treatment with the two most common Aβ isoforms found in AD brains: Aβ40 and Aβ42. Using quantitative atomic force microscopy (AFM), we measured for the first time the static elastic modulus of living primary hippocampal neurons treated with pre-aggregated Aβ40 and Aβ42 soluble species. Our AFM results demonstrate changes in the elasticity of young, mature and aged neurons treated for a short time with the two Aβ species pre-aggregated for 2 hours. Neurons aging under stress conditions, showing aging hallmarks, are the most susceptible to amyloid binding and show the largest decrease in membrane stiffness upon Aβ treatment. Membrane stiffness defines the way in which cells respond to mechanical forces in their environment and has been shown to be important for processes such as gene expression, ion-channel gating and neurotransmitter vesicle transport. Thus, one can expect that changes in neuronal membrane elasticity might directly induce functional changes related to neurodegeneration.

  18. Amyloid beta oligomers induce neuronal elasticity changes in age-dependent manner: a force spectroscopy study on living hippocampal neurons

    PubMed Central

    Ungureanu, Andreea-Alexandra; Benilova, Iryna; Krylychkina, Olga; Braeken, Dries; De Strooper, Bart; Van Haesendonck, Chris; Dotti, Carlos G.; Bartic, Carmen

    2016-01-01

    Small soluble species of amyloid-beta (Aβ) formed during early peptide aggregation stages are responsible for several neurotoxic mechanisms relevant to the pathology of Alzheimer’s disease (AD), although their interaction with the neuronal membrane is not completely understood. This study quantifies the changes in the neuronal membrane elasticity induced by treatment with the two most common Aβ isoforms found in AD brains: Aβ40 and Aβ42. Using quantitative atomic force microscopy (AFM), we measured for the first time the static elastic modulus of living primary hippocampal neurons treated with pre-aggregated Aβ40 and Aβ42 soluble species. Our AFM results demonstrate changes in the elasticity of young, mature and aged neurons treated for a short time with the two Aβ species pre-aggregated for 2 hours. Neurons aging under stress conditions, showing aging hallmarks, are the most susceptible to amyloid binding and show the largest decrease in membrane stiffness upon Aβ treatment. Membrane stiffness defines the way in which cells respond to mechanical forces in their environment and has been shown to be important for processes such as gene expression, ion-channel gating and neurotransmitter vesicle transport. Thus, one can expect that changes in neuronal membrane elasticity might directly induce functional changes related to neurodegeneration. PMID:27173984

  19. Individual aggregates of amyloid beta induce temporary calcium influx through the cell membrane of neuronal cells

    PubMed Central

    Drews, Anna; Flint, Jennie; Shivji, Nadia; Jönsson, Peter; Wirthensohn, David; De Genst, Erwin; Vincke, Cécile; Muyldermans, Serge; Dobson, Chris; Klenerman, David

    2016-01-01

    Local delivery of amyloid beta oligomers from the tip of a nanopipette, controlled over the cell surface, has been used to deliver physiological picomolar oligomer concentrations to primary astrocytes or neurons. Calcium influx was observed when as few as 2000 oligomers were delivered to the cell surface. When the dosing of oligomers was stopped the intracellular calcium returned to basal levels or below. Calcium influx was prevented by the presence in the pipette of the extracellular chaperone clusterin, which is known to selectively bind oligomers, and by the presence a specific nanobody to amyloid beta. These data are consistent with individual oligomers larger than trimers inducing calcium entry as they cross the cell membrane, a result supported by imaging experiments in bilayers, and suggest that the initial molecular event that leads to neuronal damage does not involve any cellular receptors, in contrast to work performed at much higher oligomer concentrations. PMID:27553885

  20. Individual aggregates of amyloid beta induce temporary calcium influx through the cell membrane of neuronal cells.

    PubMed

    Drews, Anna; Flint, Jennie; Shivji, Nadia; Jönsson, Peter; Wirthensohn, David; De Genst, Erwin; Vincke, Cécile; Muyldermans, Serge; Dobson, Chris; Klenerman, David

    2016-01-01

    Local delivery of amyloid beta oligomers from the tip of a nanopipette, controlled over the cell surface, has been used to deliver physiological picomolar oligomer concentrations to primary astrocytes or neurons. Calcium influx was observed when as few as 2000 oligomers were delivered to the cell surface. When the dosing of oligomers was stopped the intracellular calcium returned to basal levels or below. Calcium influx was prevented by the presence in the pipette of the extracellular chaperone clusterin, which is known to selectively bind oligomers, and by the presence a specific nanobody to amyloid beta. These data are consistent with individual oligomers larger than trimers inducing calcium entry as they cross the cell membrane, a result supported by imaging experiments in bilayers, and suggest that the initial molecular event that leads to neuronal damage does not involve any cellular receptors, in contrast to work performed at much higher oligomer concentrations. PMID:27553885

  1. 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

  2. Effects of amyloid-beta on cholinergic and acetylcholinesterase-positive cells in cultured basal forebrain neurons of embryonic rat brain.

    PubMed

    Kasa, Peter; Papp, Henrietta; Kasa, Peter; Pakaski, Magdolna; Balaspiri, Lajos

    2004-02-13

    The neurotoxic effects of amyloid-beta(1-42) and amyloid-beta(25-35) (A beta) on cholinergic and acetylcholinesterase-positive neurons were investigated in primary cultures derived from embryonic 18-day-old rat basal forebrain. After various time intervals, the cultures were treated with 1, 5, 10 or 20 microM A beta for different time periods. The cholinergic neurons and their axon terminals were revealed by vesicular acetylcholine transporter immunohistochemistry and the cholinoceptive cells by acetylcholinesterase histochemical staining. To assess the toxic effects of these A beta peptides on the cholinergic neurons, image analysis was applied for quantitative determination of the numbers of axon varicosities/terminals and cells. The results demonstrate that, following treatment with 1 or 5 microM A beta for 5, 10, 30, 60 or 120 min, no changes in vesicular acetylcholine transporter immunohistochemical staining were observed. However, after treatment for 30 min with 10 or 20 microM A beta, the number of stained axon varicosities was reduced, and treatment for 2 h they had disappeared. In contrast, vesicular acetylcholine transporter-positivity could be seen in some of the neuronal perikarya even after 3 days after treatment. The acetylcholinesterase staining was homogeneously distributed in the control neurons. After A beta treatment, the histochemical reaction end-product was detected in some of the neuronal perikarya or in the dendritic processes near to the soma. It is concluded that the neurotoxic effects of A beta appear more rapidly in the cholinergic axon terminals than in the cholinergic and acetylcholinesterase-positive neuronal perikarya. PMID:14725970

  3. 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

  4. 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

  5. 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.

  6. Effect of pathogenic mutations on the structure and dynamics of Alzheimer's A beta 42-amyloid oligomers.

    PubMed

    Kassler, Kristin; Horn, Anselm H C; Sticht, Heinrich

    2010-05-01

    Converging lines of evidence suggest that soluble A beta-amyloid oligomers play a pivotal role in the pathogenesis of Alzheimer's disease, and present direct effectors of synaptic and cognitive dysfunction. Three pathological E22-A beta-amyloid point mutants (E22G, E22K, E22Q) and the deletion mutant E22 Delta exhibit an enhanced tendency to form prefibrillar aggregates. The present study assessed the effect of these four mutations using molecular dynamics simulations and subsequent structural and energetic analyses. Our data shows that E22 plays a unique role in wild type A beta, since it has a destabilising effect on the oligomer structure due to electrostatic repulsion between adjacent E22 side chains. Mutations in which E22 is replaced by an uncharged residue result in higher oligomer stability. This effect is also observed to a lesser extent for the E22K mutation and is consistent with its lower pathogenicity compared to other mutants. Interestingly, deletion of E22 does not destroy the amyloid fold but is compensated by local changes in the backbone geometry that allow the preservation of a structurally important salt bridge. The finding that all mutant oligomers investigated exhibit higher internal stability than the wild type offers an explanation for the experimentally observed enhanced oligomer formation and stability.

  7. Preferential Transport Theory for Beta-Amyloid Clearance from the Brain

    NASA Astrophysics Data System (ADS)

    Coloma, Mikhail; Schaffer, David; Chiarot, Paul; Huang, Peter

    2015-11-01

    The failure to clear beta-amyloid from the aging brain leads to its accumulation within the walls of arteries and to Alzheimer's disease. However, the transport mechanism for beta-amyloid clearance is not well understood. In this study, we propose a preferential transport theory for flow within the vascular walls in the cerebral arterial basement membrane. The flow conduit within the arterial basement membrane is modeled as an annulus between deformable concentric cylinders filled with an incompressible, single-phase Newtonian fluid. The transport is driven by arterial lumen deformation induced by heart pulsations superimposed with reflected boundary waves. Our theory predicts that while the overall arterial wave propagation is in the same direction as the blood flow toward the capillaries, a reverse flow in the basement membrane can be preferentially induced toward larger arteries. This has been suggested as a potential clearance pathway for beta-amyloid. We estimate the magnitude of the reverse transport through a control volume analysis which is corroborated by numerical solutions of the Navier-Stokes equations. Bench-top experiments to validate our computational models are presented.

  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. Interrelation of inflammation and APP in sIBM: IL-1 beta induces accumulation of beta-amyloid in skeletal muscle.

    PubMed

    Schmidt, Jens; Barthel, Konstanze; Wrede, Arne; Salajegheh, Mohammad; Bähr, Mathias; Dalakas, Marinos C

    2008-05-01

    Distinct interrelationships between inflammation and beta-amyloid-associated degeneration, the two major hallmarks of the skeletal muscle pathology in sporadic inclusion body myositis (sIBM), have remained elusive. Expression of markers relevant for these pathomechanisms were analysed in biopsies of sIBM, polymyositis (PM), dermatomyositis (DM), dystrophic and non-myopathic muscle as controls, and cultured human myotubes. By quantitative PCR, a higher upregulation was noted for the mRNA-expression of CXCL-9, CCL-3, CCL-4, IFN-gamma, TNF-alpha and IL-1 beta in sIBM muscle compared to PM, DM and controls. All inflammatory myopathies displayed overexpression of degeneration-associated markers, yet only in sIBM, expression of the mRNA of amyloid precursor protein (APP) significantly and consistently correlated with inflammation in the muscle and mRNA-levels of chemokines and IFN-gamma. Only in sIBM, immunohistochemical analysis revealed that inflammatory mediators including IL-1 beta co-localized to beta-amyloid depositions within myofibres. In human myotubes, exposure to IL-1 beta caused upregulation of APP with subsequent intracellular aggregation of beta-amyloid. Our data suggest that, in sIBM muscle, production of high amounts of pro-inflammatory mediators specifically induces beta-amyloid-associated degeneration. The observations may help to design targeted treatment strategies for chronic inflammatory disorders of the skeletal muscle.

  10. 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.

  11. Enzyme-catalyzed formation of beta-peptides: beta-peptidyl aminopeptidases BapA and DmpA acting as beta-peptide-synthesizing enzymes.

    PubMed

    Heck, Tobias; Kohler, Hans-Peter E; Limbach, Michael; Flögel, Oliver; Seebach, Dieter; Geueke, Birgit

    2007-09-01

    In recent studies, we discovered that the three beta-peptidyl aminopeptidases, BapA from Sphingosinicella xenopeptidilytica 3-2W4, BapA from S. microcystinivorans Y2, and DmpA from Ochrobactrum anthropi LMG7991, possess the unique feature of cleaving N-terminal beta-amino acid residues from beta- and alpha/beta-peptides. Herein, we investigated the use of the same three enzymes for the reverse reaction catalyzing the oligomerization of beta-amino acids and the synthesis of mixed peptides with N-terminal beta-amino acid residues. As substrates, we employed the beta-homoamino acid derivatives H-beta hGly-pNA, H-beta3 hAla-pNA, H-(R)-beta3 hAla-pNA, H-beta3 hPhe-pNA, H-(R)-beta3 hPhe-pNA, and H-beta3 hLeu-pNA. All three enzymes were capable of coupling the six beta-amino acids to oligomers with chain lengths of up to eight amino acid residues. With the enzyme DmpA as the catalyst, we observed very high conversion rates, which correspond to dimer yields of up to 76%. The beta-dipeptide H-beta3 hAla-beta3 hLeu-OH and the beta/alpha-dipeptide H-beta hGly-His-OH (carnosine) were formed with almost 50% conversion, when a five-fold excess of beta3-homoleucine or histidine was incubated with H-beta3 hAla-pNA and H-beta hGly-pNA, respectively, in the presence of the enzyme BapA from S. microcystinivorans Y2. BapA from S. xenopeptidilytica 3-2W4 turned out to be a versatile catalyst capable of coupling various beta-amino acid residues to the free N-termini of beta- and alpha-amino acids and even to an alpha-tripeptide. Thus, these aminopeptidases might be useful to introduce a beta-amino acid residue as an N-terminal protecting group into a 'natural' alpha-peptide, thereby stabilizing the peptide against degradation by other proteolytic enzymes. PMID:17886858

  12. Enzyme-catalyzed formation of beta-peptides: beta-peptidyl aminopeptidases BapA and DmpA acting as beta-peptide-synthesizing enzymes.

    PubMed

    Heck, Tobias; Kohler, Hans-Peter E; Limbach, Michael; Flögel, Oliver; Seebach, Dieter; Geueke, Birgit

    2007-09-01

    In recent studies, we discovered that the three beta-peptidyl aminopeptidases, BapA from Sphingosinicella xenopeptidilytica 3-2W4, BapA from S. microcystinivorans Y2, and DmpA from Ochrobactrum anthropi LMG7991, possess the unique feature of cleaving N-terminal beta-amino acid residues from beta- and alpha/beta-peptides. Herein, we investigated the use of the same three enzymes for the reverse reaction catalyzing the oligomerization of beta-amino acids and the synthesis of mixed peptides with N-terminal beta-amino acid residues. As substrates, we employed the beta-homoamino acid derivatives H-beta hGly-pNA, H-beta3 hAla-pNA, H-(R)-beta3 hAla-pNA, H-beta3 hPhe-pNA, H-(R)-beta3 hPhe-pNA, and H-beta3 hLeu-pNA. All three enzymes were capable of coupling the six beta-amino acids to oligomers with chain lengths of up to eight amino acid residues. With the enzyme DmpA as the catalyst, we observed very high conversion rates, which correspond to dimer yields of up to 76%. The beta-dipeptide H-beta3 hAla-beta3 hLeu-OH and the beta/alpha-dipeptide H-beta hGly-His-OH (carnosine) were formed with almost 50% conversion, when a five-fold excess of beta3-homoleucine or histidine was incubated with H-beta3 hAla-pNA and H-beta hGly-pNA, respectively, in the presence of the enzyme BapA from S. microcystinivorans Y2. BapA from S. xenopeptidilytica 3-2W4 turned out to be a versatile catalyst capable of coupling various beta-amino acid residues to the free N-termini of beta- and alpha-amino acids and even to an alpha-tripeptide. Thus, these aminopeptidases might be useful to introduce a beta-amino acid residue as an N-terminal protecting group into a 'natural' alpha-peptide, thereby stabilizing the peptide against degradation by other proteolytic enzymes.

  13. 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.

  14. 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.

  15. 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).

  16. Neuronal localization of amyloid beta protein precursor mRNA in normal human brain and in Alzheimer's disease.

    PubMed Central

    Goedert, M

    1987-01-01

    Clones for the amyloid beta protein precursor gene were isolated from a cDNA library prepared from the frontal cortex of a patient who had died with a histologically confirmed diagnosis of Alzheimer's disease; they were used to investigate the tissue and cellular distribution of amyloid beta protein precursor mRNA in brain tissues from control patients and from Alzheimer's disease patients. Amyloid beta protein precursor mRNA was expressed in similar amounts in all control human brain regions examined, but a reduction of the mRNA level was observed in the frontal cortex from patients with Alzheimer's disease. By in situ hybridization amyloid beta protein precursor mRNA was present in granule and pyramidal cell bodies in the hippocampal formation and in pyramidal cell bodies in the cerebral cortex. No specific labelling of glial cells or endothelial cells was found. The same qualitative distribution was observed in tissues from control patients and from patients with Alzheimer's disease. Senile plaque amyloid thus probably derives from neurones. The tissue distribution of amyloid beta protein precursor mRNA and its cellular localization demonstrate that its expression is not confined to the brain regions and cells that exhibit the selective neuronal death characteristic of Alzheimer's disease. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. PMID:3322812

  17. 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

  18. 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

  19. Amyloid beta modulation of neuronal network activity in vitro.

    PubMed

    Charkhkar, Hamid; Meyyappan, Susheela; Matveeva, Evgenia; Moll, Jonathan R; McHail, Daniel G; Peixoto, Nathalia; Cliff, Richard O; Pancrazio, Joseph J

    2015-12-10

    In vitro assays offer a means of screening potential therapeutics and accelerating the drug development process. Here, we utilized neuronal cultures on planar microelectrode arrays (MEA) as a functional assay to assess the neurotoxicity of amyloid-β 1-42 (Aβ42), a biomolecule implicated in the Alzheimer׳s disease (AD). In this approach, neurons harvested from embryonic mice were seeded on the substrate-integrated microelectrode arrays. The cultured neurons form a spontaneously active network, and the spiking activity as a functional endpoint could be detected via the MEA. Aβ42 oligomer, but not monomer, significantly reduced network spike rate. In addition, we demonstrated that the ionotropic glutamate receptors, NMDA and AMPA/kainate, play a role in the effects of Aβ42 on neuronal activity in vitro. To examine the utility of the MEA-based assay for AD drug discovery, we tested two model therapeutics for AD, methylene blue (MB) and memantine. Our results show an almost full recovery in the activity within 24h after administration of Aβ42 in the cultures pre-treated with either MB or memantine. Our findings suggest that cultured neuronal networks may be a useful platform in screening potential therapeutics for Aβ induced changes in neurological function.

  20. Amyloid beta modulation of neuronal network activity in vitro.

    PubMed

    Charkhkar, Hamid; Meyyappan, Susheela; Matveeva, Evgenia; Moll, Jonathan R; McHail, Daniel G; Peixoto, Nathalia; Cliff, Richard O; Pancrazio, Joseph J

    2015-12-10

    In vitro assays offer a means of screening potential therapeutics and accelerating the drug development process. Here, we utilized neuronal cultures on planar microelectrode arrays (MEA) as a functional assay to assess the neurotoxicity of amyloid-β 1-42 (Aβ42), a biomolecule implicated in the Alzheimer׳s disease (AD). In this approach, neurons harvested from embryonic mice were seeded on the substrate-integrated microelectrode arrays. The cultured neurons form a spontaneously active network, and the spiking activity as a functional endpoint could be detected via the MEA. Aβ42 oligomer, but not monomer, significantly reduced network spike rate. In addition, we demonstrated that the ionotropic glutamate receptors, NMDA and AMPA/kainate, play a role in the effects of Aβ42 on neuronal activity in vitro. To examine the utility of the MEA-based assay for AD drug discovery, we tested two model therapeutics for AD, methylene blue (MB) and memantine. Our results show an almost full recovery in the activity within 24h after administration of Aβ42 in the cultures pre-treated with either MB or memantine. Our findings suggest that cultured neuronal networks may be a useful platform in screening potential therapeutics for Aβ induced changes in neurological function. PMID:26453830

  1. 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.

  2. Chemokines, macrophage inflammatory protein-2 and stromal cell-derived factor-1{alpha}, suppress amyloid {beta}-induced neurotoxicity

    SciTech Connect

    Raman, Dayanidhi; Milatovic, Snjezana-Zaja; Milatovic, Dejan; Fan, Guo-Huang; Richmond, Ann

    2011-11-15

    Alzheimer's disease (AD) is characterized by a progressive cognitive decline and accumulation of neurotoxic oligomeric peptides amyloid-{beta} (A{beta}). Although the molecular events are not entirely known, it has become evident that inflammation, environmental and other risk factors may play a causal, disruptive and/or protective role in the development of AD. The present study investigated the ability of the chemokines, macrophage inflammatory protein-2 (MIP-2) and stromal cell-derived factor-1{alpha} (SDF-1{alpha}), the respective ligands for chemokine receptors CXCR2 and CXCR4, to suppress A{beta}-induced neurotoxicity in vitro and in vivo. Pretreatment with MIP-2 or SDF-1{alpha} significantly protected neurons from A{beta}-induced dendritic regression and apoptosis in vitro through activation of Akt, ERK1/2 and maintenance of metalloproteinase ADAM17 especially with SDF-1{alpha}. Intra-cerebroventricular (ICV) injection of A{beta} led to reduction in dendritic length and spine density of pyramidal neurons in the CA1 area of the hippocampus and increased oxidative damage 24 h following the exposure. The A{beta}-induced morphometric changes of neurons and increase in biomarkers of oxidative damage, F{sub 2}-isoprostanes, were significantly inhibited by pretreatment with the chemokines MIP-2 or SDF-1{alpha}. Additionally, MIP-2 or SDF-1{alpha} was able to suppress the aberrant mislocalization of p21-activated kinase (PAK), one of the proteins involved in the maintenance of dendritic spines. Furthermore, MIP-2 also protected neurons against A{beta} neurotoxicity in CXCR2-/- mice, potentially through observed up regulation of CXCR1 mRNA. Understanding the neuroprotective potential of chemokines is crucial in defining the role for their employment during the early stages of neurodegeneration. -- Research highlights: Black-Right-Pointing-Pointer Neuroprotective ability of the chemokines MIP2 and CXCL12 against A{beta} toxicity. Black-Right-Pointing-Pointer MIP-2 or

  3. Longitudinal assessment of tau and amyloid beta in cerebrospinal fluid of Parkinson disease.

    PubMed

    Zhang, Jing; Mattison, Hayley A; Liu, Changqin; Ginghina, Carmen; Auinger, Peggy; McDermott, Michael P; Stewart, Tessandra; Kang, Un Jung; Cain, Kevin C; Shi, Min

    2013-11-01

    Tau gene has been consistently associated with the risk of Parkinson disease in recent genome wide association studies. In addition, alterations of the levels of total tau, phosphorylated tau [181P], and amyloid beta 1-42 in cerebrospinal fluid have been reported in patients with sporadic Parkinson disease and asymptomatic carriers of leucine-rich repeat kinase 2 mutations, in patterns that clearly differ from those typically described for patients with Alzheimer disease. To further determine the potential roles of these molecules in Parkinson disease pathogenesis and/or in tracking the disease progression, especially at early stages, the current study assessed all three proteins in 403 Parkinson disease patients enrolled in the DATATOP (Deprenyl and tocopherol antioxidative therapy of parkinsonism) placebo-controlled clinical trial, the largest cohort to date with cerebrospinal fluid samples collected longitudinally. These initially drug-naive patients at early disease stages were clinically evaluated, and cerebrospinal fluid was collected at baseline and then at endpoint, defined as the time at which symptomatic anti-Parkinson disease medications were determined to be required. General linear models were used to test for associations between baseline cerebrospinal fluid biomarker levels or their rates of change and changes in the Unified Parkinson Disease Rating Scale (total or part III motor score) over time. Robust associations among candidate markers are readily noted. Baseline levels of amyloid beta were weakly but negatively correlated with baseline Unified Parkinson Disease Rating Scale total scores. Baseline phosphorylated tau/total tau and phosphorylated tau/amyloid beta were significantly and negatively correlated with the rates of the Unified Parkinson Disease Rating Scale change. While medications (deprenyl and/or tocopherol) did not appear to alter biomarkers appreciably, a weak but significant positive correlation between the rate of change in total

  4. Origin of life. Primordial genetics: Information transfer in a pre-RNA world based on self-replicating beta-sheet amyloid conformers.

    PubMed

    Maury, Carl Peter J

    2015-10-01

    The question of the origin of life on Earth can largely be reduced to the question of what was the first molecular replicator system that was able to replicate and evolve under the presumably very harsh conditions on the early Earth. It is unlikely that a functional RNA could have existed under such conditions and it is generally assumed that some other kind of information system preceded the RNA world. Here, I present an informational molecular system that is stable, self-replicative, environmentally responsive, and evolvable under conditions characterized by high temperatures, ultraviolet and cosmic radiation. This postulated pregenetic system is based on the amyloid fold, a functionally unique polypeptide fold characterized by a cross beta-sheet structure in which the beta strands are arranged perpendicular to the fiber axis. Beside an extraordinary structural robustness, the amyloid fold possesses a unique ability to transmit information by a three-dimensional templating mechanism. In amyloidogenesis short peptide monomers are added one by one to the growing end of the fiber. From the same monomeric subunits several structural variants of amyloid may be formed. Then, in a self-replicative mode, a specific amyloid conformer can act as a template and confer its spatially encoded information to daughter molecular entities in a repetitive way. In this process, the specific conformational information, the spatially changed organization, is transmitted; the coding element is the steric zipper structure, and recognition occurs by amino acid side chain complementarity. The amyloid information system fulfills several basic requirements of a primordial evolvable replicator system: (i) it is stable under the presumed primitive Earth conditions, (ii) the monomeric building blocks of the informational polymer can be formed from available prebiotic compounds, (iii) the system is self-assembling and self-replicative and (iv) it is adaptive to changes in the environment and

  5. 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

  6. 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.

  7. Spectral marker for Cα damage in beta peptides.

    PubMed

    Green, Mandy C; Stelzleni, Sarah; Francisco, Joseph S

    2013-01-24

    The work in this article describes a spectral signature for the detection of a C(α) radical damaged peptide, which should enable the use of infrared spectroscopic methods to directly monitor oxidative events. Spectra for radical damaged peptides are computed with ab initio methods. The amide bands A, I, II, and III are analyzed for trends in the damage site. The spectral signature is found in a region (i.e., 1700-1620 cm(-1)) normally void of vibrational absorption bands from stable undamaged beta peptides. An analysis of the vibrational motions of the spectral signature is described. The uniqueness of the spectral signature is explored by an examination and comparison with C(α) monoradicals and polyradicals, as well as with other bioradicals that could act as spectral interferences. The identification of unique infrared spectral features for C(α) damage could have important implications in diagnostics for beta conformational peptides damaged by oxidative stress processes. PMID:23301948

  8. Effect of D-amino acids at Asp{sup 23} and Ser{sup 26} residues on the conformational preference of A{beta}{sub 20-29} peptides

    SciTech Connect

    Shanmugam, Ganesh; Polavarapu, Prasad L. . E-mail: Prasad.L.Polavarapu@Vanderbilt.edu; Hallgas, Balazs; Majer, Zsuzsa

    2005-09-30

    The effects of D-amino acids at Asp{sup 23} and Ser{sup 26} residues on the conformational preference of {beta}-amyloid (A{beta}) peptide fragment (A{beta}{sub 20-29}) have been studied using different spectroscopic techniques, namely vibrational circular dichroism (VCD), vibrational absorption, and electronic circular dichroism. To study the structure of the A{beta}{sub 20-29}, [D-Asp{sup 23}]A{beta}{sub 20-29}, and [D-Ser{sup 26}]A{beta}{sub 20-29} peptides under different conditions, the spectra were measured in 10 mM acetate buffer (pH 3) and in 2,2,2-trifluoroethanol (TFE). The spectroscopic results indicated that at pH 3, A{beta}{sub 20-29} peptide takes random coil with {beta}-turn structure, while [D-Ser{sup 26}]A{beta}{sub 20-29} peptide adopts significant amount of polyproline II (PPII) type structure along with {beta}-turn contribution and D-Asp-substituted peptide ([D-Asp{sup 23}]A{beta}{sub 20-29}) adopts predominantly PPII type structure. The increased propensity for PPII conformation upon D-amino acid substitution, in acidic medium, has important biological implications. In TFE, A{beta}{sub 20-29}, [D-Asp{sup 23}]A{beta}{sub 20-29}, and [D-Ser{sup 26}]A{beta}{sub 20-29} peptides adopt 3{sub 10}-helix, {alpha}-helix, and random coil with some {beta}-turn structures, respectively. The VCD data obtained for the A{beta} peptide films suggested that the secondary structures for the peptide films are not the same as those for corresponding solution and are also different among the A{beta} peptides studied here. This observation suggests that dehydration can have a significant influence on the structural preferences of these peptides.

  9. 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

  10. 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.

  11. Intracellular production of beta A4 amyloid of Alzheimer's disease: modulation by phosphoramidon and lack of coupling to the secretion of the amyloid precursor protein.

    PubMed

    Fuller, S J; Storey, E; Li, Q X; Smith, A I; Beyreuther, K; Masters, C L

    1995-06-27

    The amyloid precursor protein (APP) undergoes abnormal metabolism in Alzheimer's disease, resulting in the accumulation of beta A4 amyloid in the brain. Normal APP metabolism includes the release of a truncated form (sAPP) which has been cleaved at the alpha-secretase site within the beta A4 amyloidogenic domain. However, intact forms of beta A4 protein may also be generated by the beta- and gamma-secretases. Soluble forms of beta A4 have been detected in various cell lines and in cerebrospinal fluid. Previous studies of protein kinase C activation have suggested a reciprocal relationship between sAPP secretion and beta A4 production and release. We find that phorbol ester activation of protein kinase C in untransfected SH-SY5Y neuroblastoma cells increases the release of sAPP without affecting beta A4 secretion. We provide further evidence for intracellular beta A4 production. Treatment of SY5Y cells with the protease inhibitor phosphoramidon results in a 2-fold increase in beta A4 secretion and an increase in the amount of beta A4 recovered from cell lysates, yet it does not affect sAPP secretion. The protease inhibitors thiorphan and N-[(RS)-2-carboxy-3-phenylpropanoyl]-L-leucine had no effect on beta A4 or sAPP secretion. The lysosomotropic agents chloroquine and NH4Cl decreased beta A4 secretion, providing additional evidence for the involvement of intracellular acidic compartments in the production of beta A4. Our results therefore demonstrate a double dissociation between the secretion of sAPP and beta A4 in the SH-SY5Y cell line. The effect of phosphoramidon supports previous studies which show that metalloproteases are involved in the biogenesis of beta A4.

  12. 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.

  13. Structure-based discovery of fiber-binding compounds that reduce the cytotoxicity of amyloid beta

    PubMed Central

    Jiang, Lin; Liu, Cong; Leibly, David; Landau, Meytal; Zhao, Minglei; Hughes, Michael P; Eisenberg, David S

    2013-01-01

    Amyloid protein aggregates are associated with dozens of devastating diseases including Alzheimer’s, Parkinson’s, ALS, and diabetes type 2. While structure-based discovery of compounds has been effective in combating numerous infectious and metabolic diseases, ignorance of amyloid structure has hindered similar approaches to amyloid disease. Here we show that knowledge of the atomic structure of one of the adhesive, steric-zipper segments of the amyloid-beta (Aβ) protein of Alzheimer’s disease, when coupled with computational methods, identifies eight diverse but mainly flat compounds and three compound derivatives that reduce Aβ cytotoxicity against mammalian cells by up to 90%. Although these compounds bind to Aβ fibers, they do not reduce fiber formation of Aβ. Structure-activity relationship studies of the fiber-binding compounds and their derivatives suggest that compound binding increases fiber stability and decreases fiber toxicity, perhaps by shifting the equilibrium of Aβ from oligomers to fibers. DOI: http://dx.doi.org/10.7554/eLife.00857.001 PMID:23878726

  14. Redox chemistry of copper-amyloid-beta: the generation of hydroxyl radical in the presence of ascorbate is linked to redox-potentials and aggregation state.

    PubMed

    Guilloreau, Luc; Combalbert, Sarah; Sournia-Saquet, Alix; Mazarguil, Honoré; Faller, Peter

    2007-07-23

    Aggregation of the beta-amyloid peptide (Abeta) to amyloid plaques is a key event in Alzheimer's disease. According to the amyloid-cascade hypothesis, Abeta aggregates are toxic to neurons through the production of reactive oxygen species (ROS). Copper ions play an important role, because they are able to bind to Abeta and influence its aggregation properties. Moreover, Cu-Abeta is supposed to be directly involved in ROS production. To get a better understanding of these reactions, we measured the production of HO(.) and the redox potential of Cu-Abeta. The results were compared to other biological copper-peptide complexes in order to get an insight into the biological relevance. Cu-Abeta produced more HO(.) than the complex of copper with Asp-Ala-His-Lys (Cu-DAHK), but less than with Gly-His-Lys (Cu-GHK). Cyclic voltammetry revealed that the order for reduction potential is Cu-GHK>Cu-Abeta>Cu-DAHK, but for the oxidation potential the order is reversed. Thus, easier copper redox cycling correlated to higher HO(.) production. The copper complex of the form Abeta1-42 showed a HO(.) production five-times higher than that of the form Abeta1-40. Time-dependence and aggregation studies suggest that an aggregation intermediate is responsible for this increased HO(.) production. PMID:17577900

  15. Amyloid-beta levels are significantly reduced and spatial memory defects are rescued in a novel neuroserpin-deficient Alzheimer's disease transgenic mouse model.

    PubMed

    Fabbro, Shay; Schaller, Kristin; Seeds, Nicholas W

    2011-09-01

    Amyloid-beta (Aβ) plaques are a hallmark of Alzheimer's disease. Several proteases including plasmin are thought to promote proteolytic cleavage and clearance of Aβ from brain. The activity of both plasmin and tissue plasminogen activator are reduced in Alzheimer's disease brain, while the tissue plasminogen activator inhibitor neuroserpin is up-regulated. Here, the relationship of tissue plasminogen activator and neuroserpin to Aβ levels is explored in mouse models. Aβ(1-42) peptide injected into the frontal cortex of tissue plasminogen activator knockout mice is slow to disappear compared to wildtype mice, whereas neuroserpin knockout mice show a rapid clearance of Aβ(1-42). The relationship of neuroserpin and tissue plasminogen activator to Aβ plaque formation was studied further by knocking-out neuroserpin in the human amyloid precursor protein-J20 transgenic mouse. Compared to the J20-transgenic mouse, the neuroserpin-deficient J20-transgenic mice have a dramatic reduction of Aβ peptides, fewer and smaller plaques, and more active tissue plasminogen activator associated with plaques. Furthermore, neuroserpin-deficient J20-transgenic mice have near normal performances in the Morris water maze, in contrast to the spatial memory defects seen in J20-transgenic mice. These results support the concept that neuroserpin inhibition of tissue plasminogen activator plays an important role both in the accumulation of brain amyloid plaques and loss of cognitive abilities.

  16. 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

  17. 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.

  18. Serum-derived immunoglobulins alter amyloid beta transport across a blood-brain barrier in vitro model.

    PubMed

    Poetsch, V; Bennani-Baiti, B; Neuhaus, W; Muchitsch, E M; Noe, C R

    2010-04-01

    Since passive immunization with serum-derived immunoglobulins (intravenous immunoglobulins) showed several positive effects in some patients with Alzheimer's disease (AD), intravenous immunoglobulins (IVIG) are discussed as a possible treatment option. IVIG, an antibody product derived from human plasma, contains natural antibodies against amyloid beta(Abeta) peptide. Until now it is not known, how IVIG interferes with pathogenesis in AD, but several proposed mechanisms are in discussion. Receptor types which are involved in transport processes at the BBB are LRP, RAGE and hFcRn. We were looking for an in vitro BBB model expressing these receptors and studied the alteration of transport of Abeta peptides across this model under the influence of immunoglobulins. Cell line ECV304 was found to be suitable for our experiments. We found evidence for involvement of an improved clearance of Abeta across the BBB as well as a decreased Abeta influx from blood to the brain probably following complex formation of immunoglobulins with free Abeta in the periphery. Furthermore, we were able to confirm the activity of IVIG preparations which acted the same way but showed slightly less efficacy in comparison to monoclonal anti-Abeta antibodies. Based on these results we suggest multiple mechanisms responsible for the efficacy of immunotherapy in Alzheimer's disease.

  19. 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.

  20. Membrane rafts in Alzheimer’s disease beta-amyloid production

    PubMed Central

    Thinakaran, Gopal

    2010-01-01

    Alzheimer’s disease (AD), the most common age-associated dementing disorder, is pathologically manifested by progressive cognitive dysfunction concomitant with the accumulation of senile plaques consisting of amyloid-β (Aβ) peptide aggregates in the brain of affected individuals. Aβ is derived from a type I transmembrane protein, amyloid precursor protein (APP), by the sequential proteolytic events mediated by β-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Multiple lines of evidence have implicated cholesterol and cholesterol-rich membrane microdomains, termed lipid rafts in the amyloidogenic processing of APP. In this review, we summarize the cell biology of APP, β- and γ-secretases and the data on their association with lipid rafts. Then, we will discuss potential raft targeting signals identified in the secretases and their importance on amyloidogenic processing of APP. PMID:20303415

  1. 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

  2. “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

  3. "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

  4. 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.

  5. 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

  6. Development of magnetic resonance imaging based detection methods for beta amyloids via sialic acid-functionalized magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kouyoumdjian, Hovig

    The development of a non-invasive method for the detection of Alzheimer's disease is of high current interest, which can be critical in early diagnosis and in guiding preventive treatment of the disease. The aggregates of beta amyloids are a pathological hallmark of Alzheimer's disease. Carbohydrates such as sialic acid terminated gangliosides have been shown to play significant roles in initiation of amyloid aggregation. Herein, we report a biomimetic approach using sialic acid coated iron oxide superparamagnetic nanoparticles for in vitro detection in addition to the assessment of the in vivo mouse-BBB (Blood brain barrier) crossing of the BSA (bovine serum albumin)-modified ones. The sialic acid functionalized dextran nanoparticles were shown to bind with beta amyloids through several techniques including ELISA (enzyme linked immunosorbent assay), MRI (magnetic resonance imaging), TEM (transmission electron microscopy), gel electrophoresis and tyrosine fluorescence assay. The superparamagnetic nature of the nanoparticles allowed easy detection of the beta amyloids in mouse brains in both in vitro and ex vivo model by magnetic resonance imaging. Furthermore, the sialic acid nanoparticles greatly reduced beta amyloid induced cytotoxicity to SH-SY5Y neuroblastoma cells, highlighting the potential of the glyconanoparticles for detection and imaging of beta amyloids. Sialic acid functionalized BSA (bovine serum albumin) nanoparticles also showed significant binding to beta amyloids, through ELISA and ex vivo mouse brain MRI experiments. Alternatively, the BBB crossing was demonstrated by several techniques such as confocal microscopy, endocytosis, exocytosis assays and were affirmed by nanoparticles transcytosis assays through bEnd.3 endothelial cells. Finally, the BBB crossing was confirmed by analyzing the MRI signal of nanoparticle-injected CD-1 mice.

  7. Concentration-dependent inhibitory effects of apolipoprotein E on Alzheimer's beta-amyloid fibril formation in vitro.

    PubMed

    Naiki, H; Gejyo, F; Nakakuki, K

    1997-05-20

    Recently, many research groups have examined the effect of apolipoprotein E (apoE) on beta-amyloid fibril (betaAf) formation in vitro. However, their data were somewhat controversial and no exact kinetic assessment of the role of apoE has thus far been available. We examined the effect of human apoE on betaAf formation in vitro, starting with various concentrations of freshly prepared beta-amyloid(1-40) (beta1-40) and using fluorescence spectroscopy with thioflavine T. When 50 microM of beta1-40 was incubated with a 1:1000 to 1:100 molar ratio of apoE, a dose-dependent inhibitory effect of apoE was observed. Both the nucleation and extension phases of betaAf formation in vitro were inhibited by apoE. On the other hand, when 300 microM of beta1-40 was incubated with a 1:100 molar ratio of apoE, the inhibitory effect of apoE was completely abolished. We then focused our study on the kinetics of the inhibitory effect of apoE on the extension phase of betaAf formation in vitro, utilizing the recently established first-order kinetic model of betaAf extension in vitro [Naiki, H., & Nakakuki, K. (1996) Lab. Invest. 74, 374-383]. The mathematical treatment of the data suggests that apoE inhibits the extension of betaAf in vitro, by making a complex with beta1-40, thus eliminating free beta1-40 from the reaction mixture. The equilibrium association constant with beta1-40 was practically the same among the three major recombinant apoE isoforms. These results indicate that the effects of apoE on betaAf formation in vitro is differential and could settle some of the controversy about beta-amyloid-apoE interaction in vitro.

  8. Agmatine protects against beta-amyloid25-35-induced memory impairments in the rat.

    PubMed

    Bergin, D H; Liu, P

    2010-08-25

    Amyloid beta fragment 25-35 (Abeta(25-35)) is the neurotoxic domain of the full-length Abeta(1-42) and causes memory impairments in rodents. Recent research suggests that agmatine, decarboxylated arginine, has a neuroprotective role. This study investigated the effects of a single bilateral i.c.v. infusion of aggregated Abeta(25-35) (30 nmol) in a battery of behavioural tests conducted during the period 4-6 (Experiment 1) and 4-14 (Experiment 2) weeks post-Abeta(25-35) infusion, and evaluated the protective effect of agmatine (40 mg/kg) administered i.p. 30 min prior to Abeta(25-35) infusion and once daily for a further nine consecutive days. In Experiment 1, Abeta(25-35) rats with saline treatment were not impaired in the elevated plus maze and open field and mildly impaired in the reference memory version of the water maze task, but performed poorly in the working memory version of the water maze task and the object recognition memory task, relative to the control rats that received the i.c.v. infusion of Abeta(35-25) (inactive peptide) and saline treatment. By contrast, Abeta(25-35) rats with agmatine treatment did not show performance impairments in the working memory version of the water maze task and the object recognition memory task. In Experiment 2, Abeta(25-35) rats with saline treatment were significantly impaired in the standard radial arm maze task, but only displayed no or very mild impairments in the delayed non-match to position and reference memory versions of the radial arm maze task, T-maze, object recognition memory task, both the reference and working memory versions of the water maze task, elevated plus maze and open field. By contrast, Abeta(25-35) rats with agmatine treatment were not impaired in the standard radial arm maze and performed even better than the controls in the reference memory version of the task. These results demonstrate that agmatine is able to protect against Abeta(25-35)-induced memory deficits.

  9. First selective dual inhibitors of tau phosphorylation and Beta-amyloid aggregation, two major pathogenic mechanisms in Alzheimer's disease.

    PubMed

    Mariano, Marica; Schmitt, Christian; Miralinaghi, Parisa; Catto, Marco; Hartmann, Rolf W; Carotti, Angelo; Engel, Matthias

    2014-12-17

    In Alzheimer's disease (AD), multiple factors account for the accumulation of neurocellular changes, which may begin several years before symptoms appear. The most important pathogenic brain changes that are contributing to the development of AD are the formation of the cytotoxic β-amyloid aggregates and of the neurofibrillary tangles, which originate from amyloidpeptides and hyperphosphorylated tau protein, respectively. New therapeutic agents that target both major pathogenic mechanisms may be particularly efficient. In this study, we introduce bis(hydroxyphenyl)-substituted thiophenes as a novel class of selective, dual inhibitors of the tau kinase Dyrk1A and of the amyloid-β aggregation. PMID:25247807

  10. 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

  11. Ab initio molecular simulations on specific interactions between amyloid beta and monosaccharides

    NASA Astrophysics Data System (ADS)

    Nomura, Kazuya; Okamoto, Akisumi; Yano, Atsushi; Higai, Shin'ichi; Kondo, Takashi; Kamba, Seiji; Kurita, Noriyuki

    2012-09-01

    Aggregation of amyloid β (Aβ) peptides, which is a key pathogenetic event in Alzheimer's disease, can be caused by cell-surface saccharides. We here investigated stable structures of the solvated complexes of Aβ with some types of monosaccharides using molecular simulations based on protein-ligand docking and classical molecular mechanics methods. Moreover, the specific interactions between Aβ and the monosaccharides were elucidated at an electronic level by ab initio fragment molecular orbital calculations. Based on the results, we proposed which type of monosaccharide prefers to have large binding affinity to Aβ and inhibit the Aβ aggregation.

  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. Oxidative stress induces increase in intracellular amyloid beta-protein production and selective activation of betaI and betaII PKCs in NT2 cells.

    PubMed

    Paola, D; Domenicotti, C; Nitti, M; Vitali, A; Borghi, R; Cottalasso, D; Zaccheo, D; Odetti, P; Strocchi, P; Marinari, U M; Tabaton, M; Pronzato, M A

    2000-02-16

    Amyloid beta-protein (Abeta) aggregation produces an oxidative stress in neuronal cells that, in turn, may induce an amyloidogenic shift of neuronal metabolism. To investigate this hypothesis, we analyzed intra- and extracellular Abeta content in NT2 differentiated cells incubated with 4-hydroxy-2,3-nonenal (HNE), a major product of lipid peroxidation. In parallel, we evaluated protein kinase C (PKC) isoenzymes activity, a signaling system suspected to modulate amyloid precursor protein (APP) processing. Low HNE concentrations (0.1-1 microM) induced a 2-6 fold increase of intracellular Abeta production that was concomitant with selective activation of betaI and betaII PKC isoforms, without affecting either cell viability or APP full-length expression. Selective activation of the same PKC isoforms was observed following NT2 differentiation. Our findings suggest that PKC beta isoenzymes are part of cellular mechanisms that regulate production of the intracellular Abeta pool. Moreover, they indicate that lipid peroxidation fosters intracellular Abeta accumulation, creating a vicious neurodegenerative loop. PMID:10679257

  16. 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

  17. Insight into the stability of cross-beta amyloid fibril from molecular dynamics simulation.

    PubMed

    Chen, Yue; He, Yong-Jie; Wu, Maoying; Yan, Guanwen; Li, Yixue; Zhang, Jian; Chen, Hai-Feng

    2010-06-01

    Amyloid fibrils are considered to play causal roles in the pathogenesis of amyloid-related degenerative diseases such as Alzheimer's disease, type II diabetes mellitus, the transmissible spongiform encephalopathies, and prion disease. The mechanism of fibril formation is still hotly debated and remains an important open question. In this study, we utilized molecular dynamics (MD) simulation to analyze the stability of hexamer for eight class peptides. The MD results suggest that VEALYL and MVGGVV-1 are the most stable ones, then SNQNNY, followed by LYQLEN, MVGGVV-2, VQIVYK, SSTSAA, and GGVVIA. The statistics result indicates that hydrophobic residues play a key role in stabilizing the zipper interface. Single point and two linkage mutants of MVGGVV-1 confirmed that both Met1 and Val2 are key hydrophobic residues. This is consistent with the statistics analysis. The stability results of oligomer for MVGGVV-1 suggest that the intermediate state should be trimer (3-0) and tetramer (2-2). These methods can be used in stabilization study of other amyloid fibril.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. Generation of soluble oligomeric beta-amyloid species via copper catalyzed oxidation with implications for Alzheimer's disease: a DFT study.

    PubMed

    Haeffner, Fredrik; Barnham, Kevin J; Bush, Ashley I; Brinck, Tore

    2010-06-01

    A mechanism for the oxidation of a dimeric beta-amyloid copper ion complex is proposed based on DFT calculations. It involves the Met35 residue, which is believed to be important in the neurotoxicity causing Alzheimer's disease. Oxidation of Met35 is found to proceed readily with dioxygen when two Met35 residues are close to each other and the copper ion. This indicates that oxidants, such as hydrogen peroxide, are not necessary for oxidation of beta-amyloid copper ion complexes. Understanding these processes could be pivotal in gaining more knowledge of this complex disease and for the development of therapeutic treatments.

  4. Effect of trichostatin A on gelsolin levels, proteolysis of amyloid precursor protein, and amyloid beta-protein load in the brain of transgenic mouse model of Alzheimer's disease.

    PubMed

    Yang, Wenzhong; Chauhan, Abha; Wegiel, Jerzy; Kuchna, Izabela; Gu, Feng; Chauhan, Ved

    2014-01-01

    In vivo and in vitro studies have shown that gelsolin is an anti-amyloidogenic protein. Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, promotes the expression of gelsolin. Fibrillized amyoid beta-protein (Aβ) is a key constituent of amyloid plaques in the brains of patients with Alzheimer's disease (AD). We studied the effects of TSA on the levels of gelsolin; amyloid precursor protein (APP); proteolytic enzymes (γ-secretase and β-secretase) responsible for the production of Aβ; Aβ-cleaving enzymes, i.e., neprilysin (NEP) and insulin-degrading enzyme (IDE); and amyloid load in the double transgenic (Tg) APPswe/PS1(δE9) mouse model of AD. Intraperitoneal injection of TSA for two months (9-11 months of age) resulted in decreased activity of HDAC, and increased levels of gelsolin in the hippocampus and cortex of the brain in AD Tg mice as compared to vehicle-treated mice. TSA also increased the levels of γ-secretase and β-secretase activity in the brain. However, TSA did not show any effect on the activities or the expression levels of NEP and IDE in the brain. Furthermore, TSA treatment of AD Tg mice showed no change in the amyloid load (percent of examined area occupied by amyloid plaques) in the hippocampus and cortex, suggesting that TSA treatment did not result in the reduction of amyloid load. Interestingly, TSA prevented the formation of new amyloid deposits but increased the size of existing plaques. TSA treatment did not cause any apoptosis in the brain. These results suggest that TSA increases gelsolin expression in the brain, but the pleiotropic effects of TSA negate the anti-amyloidogenic effect of gelsolin in AD Tg mice.

  5. Multiscale Molecular Dynamics Simulations of Beta-Amyloid Interactions with Neurons

    NASA Astrophysics Data System (ADS)

    Qiu, Liming; Vaughn, Mark; Cheng, Kelvin

    2012-10-01

    Early events of human beta-amyloid protein interactions with cholesterol-containing membranes are critical to understanding the pathogenesis of Alzheimer's disease (AD) and to exploring new therapeutic interventions of AD. Atomistic molecular dynamics (AMD) simulations have been extensively used to study the protein-lipid interaction at high atomic resolutions. However, traditional MD simulations are not efficient in sampling the phase space of complex lipid/protein systems with rugged free energy landscapes. Meanwhile, coarse-grained MD (CGD) simulations are efficient in the phase space sampling but suffered from low spatial resolutions and from the fact that the energy landscapes are not identical to those of the AMD. Here, a multiscale approach was employed to simulate the protein-lipid interactions of beta-amyloid upon its release from proteolysis residing in the neuronal membranes. We utilized a forward (AMD to CGD) and reverse (CGD-AMD) strategy to explore new transmembrane and surface protein configuration and evaluate the stabilization mechanisms by measuring the residue-specific protein-lipid or protein conformations. The detailed molecular interactions revealed in this multiscale MD approach will provide new insights into understanding the early molecular events leading to the pathogenesis of AD.

  6. 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.

  7. 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.

  8. Aminoguanidine treatment ameliorates inflammatory responses and memory impairment induced by amyloid-beta 25-35 injection in rats.

    PubMed

    Díaz, Alfonso; Rojas, Karla; Espinosa, Blanca; Chávez, Raúl; Zenteno, Edgar; Limón, Daniel; Guevara, Jorge

    2014-06-01

    Alzheimer disease (AD) is a neurodegenerative disorder caused by accumulation of the amyloid-beta peptide (Aβ) in neuritic plaques. Its neurotoxic mechanisms are associated with inflammatory responses and nitrosative stress generation that promote expression of inducible nitric oxide synthase (iNOS) and increased nitric oxide causing neuronal death and memory impairment. Studies suggest that treatment with anti-inflammatory and anti-oxidant agents decreases the risk of developing AD. Aminoguanidine (AG) is an iNOS inhibitor with anti-inflammatory and anti-oxidant effects. In this study, we evaluated the effects of systemic administration of AG (100 mg/kg/day for 4 days) on spatial memory and inflammatory responses induced by an injection of Aβ(25-35) [100 μM] into the temporal cortex (TCx) of rats. A significant improvement of spatial memory was evident in the Aβ(25-35)-treated group at day 30 post-injection subjected to AG treatment; this effect was correlated with decreases in reactive gliosis, IL-1β, TNF-α, and nitrite levels, as well as a reduction in neurodegeneration in the TCx and hippocampus (Hp). These results suggest that AG treatment inhibited glia activation and cytokine release, which may help to counteract neurodegenerative events induced by the toxicity of Aβ.

  9. Protective effects of low molecular weight chondroitin sulfate on amyloid beta (Aβ)-induced damage in vitro and in vivo.

    PubMed

    Zhang, Q; Li, J; Liu, C; Song, C; Li, P; Yin, F; Xiao, Y; Li, J; Jiang, W; Zong, A; Zhang, X; Wang, F

    2015-10-01

    In the present study, we investigated the effects of low molecular weight chondroitin sulfate (LMWCS) on amyloid beta (Aβ)-induced neurotoxicity in vitro and in vivo. The in vitro results showed that LMWCS blocked Aβ25-35-induced cell viability loss and apoptosis, decreased intracellular calcium concentration, reactive oxygen species (ROS) levels, the mitochondrial membrane potential (MMP) depolarization, and the protein expression of Caspase-3. During in vivo experiments, LMWCS improved the cognitive impairment induced by Aβ1-40, increased the level of choline acetyltransferase (ChAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and decreased the level of malondialdehyde (MDA) and acetylcholinesterase (AChE) in the mouse brain. Moreover, LMWCS decreased the density of pyramidal cells of CA1 regions, and suppressed the protein expression of Bax/Bcl-2 and Caspase-3, -9 in the hippocampus of mice. In conclusion, LMWCS possessed neuroprotective properties against toxic effects induced by Aβ peptides both in vitro and in vivo, which might be related to anti-apoptotic activity. LMWCS might be a useful preventive and therapeutic compound for Alzheimer's disease.

  10. Novel antioxidants protect mitochondria from the effects of oligomeric amyloid beta and contribute to the maintenance of epigenome function.

    PubMed

    Mastroeni, Diego; Khdour, Omar M; Arce, Pablo M; Hecht, Sidney M; Coleman, Paul D

    2015-04-15

    Alzheimer's disease is associated with metabolic deficits and reduced mitochondrial function, with the latter due to the effects of oligomeric amyloid beta peptide (AβO) on the respiratory chain. Recent evidence has demonstrated reduction of epigenetic markers, such as DNA methylation, in Alzheimer's disease. Here we demonstrate a link between metabolic and epigenetic deficits via reduction of mitochondrial function which alters the expression of mediators of epigenetic modifications. AβO-induced loss of mitochondrial function in differentiated neuronal cells was reversed using two novel antioxidants (1 and 2); both have been shown to mitigate the effects of reactive oxygen species (ROS), and compound 1 also restores adenosine triphosphate (ATP) levels. While both compounds were effective in reducing ROS, restoration of ATP levels was associated with a more robust response to AβO treatment. Our in vitro system recapitulates key aspects of data from Alzheimer's brain samples, the expression of epigenetic genes in which are also shown to be normalized by the novel analogues.

  11. Increased levels of plasma amyloid-beta are related to cortical thinning and cognitive decline in cognitively normal elderly subjects.

    PubMed

    Llado-Saz, Sandra; Atienza, Mercedes; Cantero, Jose L

    2015-10-01

    Plasma levels of circulating amyloid-beta (Aβ) peptides are of particular interest in Alzheimer' disease, but little is known about cognitive and cortical correlates of peripheral Aβ levels in normal aging. Here, we compared cognitive functioning, vascular risk factors, and patterns of cortical thickness between cognitively intact elderly subjects with low (N = 60) and high (N = 60) plasma Aβ levels (cutoffs: 225 pg/mL and 23 pg/mL for Aβ1-40 and Aβ1-42, respectively). Overall, subjects with high Aβ levels showed lower cognitive performance and thinner cortex than those with low Aβ levels. More specifically, subjects with high Aβ1-40 showed bilateral thinning of the prefrontal cortex, poorer objective memory, slower processing speed, and lower nonverbal reasoning skills, whereas subjects with high Aβ1-42 had thinner temporal lobe, poorer everyday memory, and increased levels of homocysteine. Overall, these results suggest that high plasma Aβ levels in normal elderly subjects are associated with subclinical markers of vulnerable aging, which may be helpful at predicting different trajectories of aging in cognitively intact older adults. PMID:26182906

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

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

    DOE PAGES

    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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta25–35 via the Autophagy Pathway

    PubMed Central

    Xu, Pengjuan; Li, Zhigui; Wang, Hui; Zhang, Xiaochen; Yang, Zhuo

    2015-01-01

    Evidence shows that an abnormal deposition of amyloid beta-peptide25–35 (Aβ25–35) was the primary cause of the pathogenesis of Alzheimer’s disease (AD). And the elimination of Aβ25–35 is considered an important target for the treatment of AD. Triptolide (TP), isolated from Tripterygium wilfordii Hook.f. (TWHF), has been shown to possess a broad spectrum of biological profiles, including neurotrophic and neuroprotective effects. In our study investigating the effect and potential mechanism of triptolide on cytotoxicity of differentiated rat pheochromocytoma cell line (the PC12 cell line is often used as a neuronal developmental model) induced by Amyloid-Beta25–35 (Aβ25–35), we used 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay, flow cytometry, Western blot, and acridine orange staining to detect whether triptolide could inhibit Aβ25–35–induced cell apoptosis. We focused on the potential role of the autophagy pathway in Aβ25–35-treated differentiated PC12 cells. Our experiments show that cell viability is significantly decreased, and the apoptosis increased in Aβ25–35-treated differentiated PC12 cells. Meanwhile, Aβ25–35 treatment increased the expression of microtubule-associated protein light chain 3 II (LC3 II), which indicates an activation of autophagy. However, triptolide could protect differentiated PC12 cells against Aβ25–35-induced cytotoxicity and attenuate Aβ25–35-induced differentiated PC12 cell apoptosis. Triptolide could also suppress the level of autophagy. In order to assess the effect of autophagy on the protective effects of triptolide in differentiated PC12 cells treated with Aβ25–35, we used 3-Methyladenine (3-MA, an autophagy inhibitor) and rapamycin (an autophagy activator). MTT assay showed that 3-MA elevated cell viability compared with the Aβ25–35-treated group and rapamycin inhibits the protection of triptolide. These results suggest that triptolide will repair the

  4. 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

  5. Plasma levels of amyloid beta 40 and 42 are independent from ApoE genotype and mental retardation in Down syndrome.

    PubMed

    Cavani, S; Tamaoka, A; Moretti, A; Marinelli, L; Angelini, G; Di Stefano, S; Piombo, G; Cazzulo, V; Matsuno, S; Shoji, S; Furiya, Y; Zaccheo, D; Dagna-Bricarelli, F; Tabaton, M; Mori, H

    2000-11-27

    In Down syndrome (DS) brain an early, selective accumulation of amyloid beta (Abeta) peptides ending at residue 42 (Abeta42) occurs. Whether this event depends on an altered processing of amyloid beta precursor protein (APP) or on defective clearance is uncertain. To investigate this issue, we measured Abeta species 40 and 42 in plasma from 61 patients with DS, 77 age-matched normal controls, and 55 mentally retarded subjects without chromosomal abnormalities. The Abeta 40 and 42 plasma levels were then correlated with apolipoprotein E (apoE) genotypes in all groups of cases, and with I. Q. and Mini Mental Status Examination values in DS subjects. Both Abeta species were significantly elevated in DS compared to control groups, and the extent of their increase reflects that expected from APP gene overexpression. Plasma levels of Abeta 40 and 42 did not correlate with apoE genotypes in DS and control cases, and with the extent of mental retardation in DS subjects. The results indicate that accumulation and clearance of plasma and cerebral Abeta are regulated by different and independent factors. PMID:11102927

  6. 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

  7. 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

  8. Neurodegenerative mechanisms in Alzheimer disease. A role for oxidative damage in amyloid beta protein precursor-mediated cell death.

    PubMed

    Sopher, B L; Fukuchi, K; Kavanagh, T J; Furlong, C E; Martin, G M

    1996-01-01

    We have established a stably transformed human neuroblastoma cell line (MC65) that conditionally expresses a C-terminal derivative of the amyloid beta protein precursor (beta PP) termed S beta C (a fusion protein composed of the amino-17 and carboxyl-99 residues of beta PP). Conditional expression of S beta C (mediated by the withdrawal of tetracycline from the culture medium) induces pronounced nuclear DNA fragmentation and cytotoxicity in this cell line. These effects are enhanced by hyperoxygen and suppressed by hypooxygen and antioxidants. This cell line is relatively insensitive to the extracellular application of amyloid beta 25-35, and coculture experiments suggest that this cytotoxicity is mediated by an intracellular process. These findings suggest that the overexpression of the C-terminal domain of beta PP can disrupt normal cellular processes in these cells in such a way as to induce a directed (deoxyribonuclease-mediated) mechanism of cell death. This process appears to be modulated and/or mediated by a reactive oxygen specie(s) (ROS). Consistent with a role for ROS in the process of S beta C-mediated toxicity, we have found that the MC65 cell line is hypersensitive to oxidative stress and that it is this sensitivity that appears (at least in part) to underlie its susceptibility to S beta C.

  9. 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.

  10. Protein corona composition of gold nanoparticles/nanorods affects amyloid beta fibrillation process

    NASA Astrophysics Data System (ADS)

    Mirsadeghi, Somayeh; Dinarvand, Rassoul; Ghahremani, Mohammad Hossein; Hormozi-Nezhad, Mohammad Reza; Mahmoudi, Zohreh; Hajipour, Mohammad Javad; Atyabi, Fatemeh; Ghavami, Mahdi; Mahmoudi, Morteza

    2015-03-01

    Protein fibrillation process (e.g., from amyloid beta (Aβ) and α-synuclein) is the main cause of several catastrophic neurodegenerative diseases such as Alzheimer's and Parkinson diseases. During the past few decades, nanoparticles (NPs) were recognized as one of the most promising tools for inhibiting the progress of the disease by controlling the fibrillation kinetic process; for instance, gold NPs have a strong capability to inhibit Aβ fibrillations. It is now well understood that a layer of biomolecules would cover the surface of NPs (so called ``protein corona'') upon the interaction of NPs with protein sources. Due to the fact that the biological species (e.g., cells and amyloidal proteins) ``see'' the protein corona coated NPs rather than the pristine coated particles, one should monitor the fibrillation process of amyloidal proteins in the presence of corona coated NPs (and not pristine coated ones). Therefore, the previously obtained data on NPs effects on the fibrillation process should be modified to achieve a more reliable and predictable in vivo results. Herein, we probed the effects of various gold NPs (with different sizes and shapes) on the fibrillation process of Aβ in the presence and absence of protein sources (i.e., serum and plasma). We found that the protein corona formed a shell at the surface of gold NPs, regardless of their size and shape, reducing the access of Aβ to the gold inhibitory surface and, therefore, affecting the rate of Aβ fibril formation. More specifically, the anti-fibrillation potencies of various corona coated gold NPs were strongly dependent on the protein source and their concentrations (10% serum/plasma (simulation of an in vitro milieu) and 100% serum/plasma (simulation of an in vivo milieu)).Protein fibrillation process (e.g., from amyloid beta (Aβ) and α-synuclein) is the main cause of several catastrophic neurodegenerative diseases such as Alzheimer's and Parkinson diseases. During the past few decades

  11. Primary structure of water buffalo beta-casein tryptic and CNBr peptides.

    PubMed

    Petrilli, P; Addeo, F; Chianese, L

    1983-01-01

    The partial amino acid sequence (70%) of water buffalo beta-casein has been determined by aligning the sequences of tryptic and CNBr peptides along the polypeptide chain of bovine beta-casein. Only five amino acid substitutions are observed. Moreover, as in all the beta-caseins so far investigated, a morphine-like peptide is present.

  12. REDUCTION OF AMYLOID-BETA LEVELS IN MOUSE EYE TISSUES BY INTRA-VITREALLY DELIVERED NEPRILYSIN

    PubMed Central

    Parthasarathy, Rajni; Chow, K. Martin; Derafshi, Zahra; Fautsch, Michael P.; Hetling, John R.; Rodgers, David W.; Hersh, Louis B.; Pepperberg, David R.

    2015-01-01

    Amyloid-beta (Aβ) is a group of aggregation-prone, 38- to 43-amino acid peptides generated in the eye and other organs. Numerous studies suggest that the excessive build-up of low-molecular-weight soluble oligomers of Aβ plays a role in the progression of Alzheimer’s disease and other brain degenerative diseases. Recent studies raise the hypothesis that excessive Aβ levels may contribute also to certain retinal degenerative diseases. These findings, together with evidence that a major portion of Aβ is released as monomer into the extracellular space, raise the possibility that a technology enabling the enzymatic break-down of monomeric Aβ in the living eye under physiological conditions could prove useful for research on ocular Aβ physiology and, perhaps ultimately, for therapeutic applications. Neprilysin (NEP), an endopeptidase known to cleave Aβ monomer into inactive products, is a membrane-associated protein. However, sNEP, a recombinant form of the NEP catalytic domain, is soluble in aqueous medium. With the aim of determining the Aβ-cleaving activity of exogenous sNEP in the microenvironment of the intact eye, we analyzed the effect of intra-vitreally delivered sNEP on ocular Aβ levels in mice that exhibit readily measurable, aqueous buffer-extractable Aβ40 and Aβ42, two principal forms of Aβ. Anesthetized 10-month wild-type (C57BL/6J) and 2–3-month 5XFAD transgenic mice received intra-vitreal injections of sNEP (0.004 – 10 μg) in one eye and were sacrificed at defined post-treatment times (30 min – 12 weeks). Eye tissues (combined lens, vitreous, retina, RPE and choroid) were homogenized in phosphate-buffered saline, and analyzed for Aβ40 and Aβ42 (ELISA) and for total protein (Bradford assay). The fellow, untreated eye of each mouse served as control, and concentrations of Aβ (pmol/g protein) in the treated eye were normalized to that of the untreated control eye. In C57BL/6J mice, as measured at 2 hr after sNEP treatment, increasing

  13. 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

  14. 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.

  15. Environmental enrichment improves cognition in aged Alzheimer's transgenic mice despite stable beta-amyloid deposition.

    PubMed

    Arendash, Gary W; Garcia, Marcos F; Costa, David A; Cracchiolo, Jennifer R; Wefes, Inge M; Potter, H

    2004-08-01

    Environmental enrichment (EE) has been shown to improve cognitive performance and brain indices of cognition in normal mice and rats. Because the therapeutic potential of intensive, long-term EE to benefit patients with Alzheimer's disease (AD) has yet to be explored, the present study evaluated the effect of long-term EE on cognition in an animal model of AD, the APPsw transgenic mouse. Beginning at 16 months of age, APPsw mice were put into EE or standard housing for 4 months and then tested in four cognitive-based tasks (Morris maze, circular platform, platform recognition, and radial arm water maze) between 20 and 22 months of age. Our results indicate that long-term EE of aged APPsw mice results in global, overall improvement in cognitive function across these tasks without decreasing brain beta-amyloid (A beta) deposition. The results suggest that long-term EE/cognitive stimulation could provide cognitive stabilization or improvement to AD patients through mechanisms independent of A beta deposition and clearance.

  16. In vitro screening on amyloid beta modulation of aqueous extracts from plant seeds

    PubMed Central

    Okada, Yoshinori; Okada, Mizue

    2016-01-01

    Introduction: Glycation process might contribute to both extensive protein cross-linking and oxidative stress in Alzheimer's disease (AD). The amyloid-like aggregation of glycated bovine serum albumin induces apoptosis in the neuronal cell. Dietary supplementation of antioxidants, vitamins, and polyphenols are beneficial to AD, and consumption of fruits and vegetables reduce the risk of AD. We conducted a screening of 14 aqueous extracts from plant seeds (PSAE) for inhibitory activity on amyloid beta (Aβ). Materials and Methods: To examine the effects of PSAE on the Aβ (1–42) concentration, PSAE were analyzed by Aβ (1–42) enzyme-linked immunosorbent assay. Furthermore, we carried out an antiglycation experiment of PSAE and an antiaggregation experiment of PSAE to confirm the modification mechanism of PSAE. PSAE were added to buffer containing D-ribose and albumins. The solutions were incubated at 37°C for 10 days. After incubation, the products were assayed on a fluorophotometer. Results: PSAE associated differential reduction in the levels of Aβ (1–42) (lettuce; 98.7% ± 2.4%, bitter melon; 95.9% ± 2.6%, and corn; 93.9% ± 2.1%), demonstrating that treatment with lettuce seeds extracts (LSE) effectively decreases Aβ (1–42) concentration. Among the 14 PSAE, LSE exhibited the second greatest potential for antiglycation. Inhibition of aggregates was not recognized in LSE. Conclusion: These results suggest that LSE reduces the toxicity of Aβ by modifying Aβ. PMID:27134467

  17. Polarization properties of amyloid-beta plaques in Alzheimer's disease (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Baumann, Bernhard; Wöhrer, Adelheid; Ricken, Gerda; Pircher, Michael; Kovacs, Gabor G.; Hitzenberger, Christoph K.

    2016-03-01

    In histopathological practice, birefringence is used for the identification of amyloidosis in numerous tissues. Amyloid birefringence is caused by the parallel arrangement of fibrous protein aggregates. Since neurodegenerative processes in Alzheimer's disease (AD) are also linked to the formation of amyloid-beta (Aβ) plaques, optical methods sensitive to birefringence may act as non-invasive tools for Aβ identification. At last year's Photonics West, we demonstrated polarization-sensitive optical coherence tomography (PS-OCT) imaging of ex vivo cerebral tissue of advanced stage AD patients. PS-OCT provides volumetric, structural imaging based on both backscatter contrast and tissue polarization properties. In this presentation, we report on polarization-sensitive neuroimaging along with numerical simulations of three-dimensional Aβ plaques. High speed PS-OCT imaging was performed using a spectral domain approach based on polarization maintaining fiber optics. The sample beam was interfaced to a confocal scanning microscope arrangement. Formalin-fixed tissue samples as well as thin histological sections were imaged. For comparison to the PS-OCT results, ray propagation through plaques was modeled using Jones analysis and various illumination geometries and plaque sizes. Characteristic polarization patterns were found. The results of this study may not only help to understand PS-OCT imaging of neuritic Aβ plaques but may also have implications for polarization-sensitive imaging of other fibrillary structures.

  18. 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.

  19. 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.

  20. Structural characterization of adsorbed helical and beta-sheet peptides

    NASA Astrophysics Data System (ADS)

    Samuel, Newton Thangadurai

    Adsorbed peptides on surfaces have potential applications in the fields of biomaterials, tissue engineering, peptide microarrays and nanobiotechnology. The surface region, the "biomolecular interface" between a material and the biological environment, plays a crucial role in these applications. As a result, characterization of adsorbed peptide structure, especially with respect to identity, concentration, spatial distribution, conformation and orientation, is important. The present research employs NEXAFS (near-edge X-ray absorption fine structure spectroscopy) and SFG (sum frequency generation spectroscopy) to provide information about the adsorbed peptide structure. Soft X-ray NEXAFS is a synchrotron-based technique which typically utilizes polarized X-rays to interrogate surfaces under ultra-high vacuum conditions. SFG is a non-linear optical technique which utilizes a combination of a fixed visible and a tunable infrared laser beams to generate a surface-vibrational spectrum of surface species. SFG has the added advantage of being able to directly analyze the surface-structure at the solid-liquid interface. The main goals of the present research were twofold: characterize the structure of adsorbed peptides (1) ex situ using soft X-ray NEXAFS, and (2) in situ using non-linear laser spectroscopy (SFG). Achieving the former goal involved first developing a comprehensive characterization of the carbon, nitrogen and oxygen k-edge NEXAFS spectra for amino acids, and then using a series of helical and beta-sheet peptides to demonstrate the sensitivity of polarization-dependent NEXAFS to secondary structure of adsorbed peptides. Characterizing the structure of adsorbed peptides in situ using SFG involved developing a model system to probe the solid-liquid interface in situ; demonstrating the ability to probe the molecular interactions and adsorbed secondary structure; following the time-dependent ordering of the adsorbed peptides; and establishing the ability to obtain

  1. Indirubin-3′-monoxime suppresses amyloid-beta-induced apoptosis by inhibiting tau hyperphosphorylation

    PubMed Central

    Zhang, Shu-gang; Wang, Xiao-shan; Zhang, Ying-dong; Di, Qing; Shi, Jing-ping; Qian, Min; Xu, Li-gang; Lin, Xing-jian; Lu, Jie

    2016-01-01

    Indirubin-3′-monoxime is an effective inhibitor of cyclin-dependent protein kinases, and may play an obligate role in neuronal apoptosis in Alzheimer's disease. Here, we found that indirubin-3′-monoxime improved the morphology and increased the survival rate of SH-SY5Y cells exposed to amyloid-beta 25–35 (Aβ25–35), and also suppressed apoptosis by reducing tau phosphorylation at Ser199 and Thr205. Furthermore, indirubin-3′-monoxime inhibited phosphorylation of glycogen synthase kinase-3β (GSK-3β). Our results suggest that indirubin-3′-monoxime reduced Aβ25–35-induced apoptosis by suppressing tau hyperphosphorylation via a GSK-3β-mediated mechanism. Indirubin-3′-monoxime is a promising drug candidate for Alzheimer's disease. PMID:27482230

  2. S-nitrosylation of Drp1 mediates beta-amyloid-related mitochondrial fission and neuronal injury.

    PubMed

    Cho, Dong-Hyung; Nakamura, Tomohiro; Fang, Jianguo; Cieplak, Piotr; Godzik, Adam; Gu, Zezong; Lipton, Stuart A

    2009-04-01

    Mitochondria continuously undergo two opposing processes, fission and fusion. The disruption of this dynamic equilibrium may herald cell injury or death and may contribute to developmental and neurodegenerative disorders. Nitric oxide functions as a signaling molecule, but in excess it mediates neuronal injury, in part via mitochondrial fission or fragmentation. However, the underlying mechanism for nitric oxide-induced pathological fission remains unclear. We found that nitric oxide produced in response to beta-amyloid protein, thought to be a key mediator of Alzheimer's disease, triggered mitochondrial fission, synaptic loss, and neuronal damage, in part via S-nitrosylation of dynamin-related protein 1 (forming SNO-Drp1). Preventing nitrosylation of Drp1 by cysteine mutation abrogated these neurotoxic events. SNO-Drp1 is increased in brains of human Alzheimer's disease patients and may thus contribute to the pathogenesis of neurodegeneration.

  3. [Genetics of late-onset Alzheimer's disease: vascular risk and beta-amyloid metabolism].

    PubMed

    Panza, Francesco; Solfrizzi, Vincenzo; D'Introno, Alessia; Capurso, Cristiano; Colacicco, Anna Maria; Torres, Francesco; Altomare, Emanuele; Capurso, Antonio

    2002-09-01

    Progress in clinical and basic research of Alzheimer's disease (AD) suggested theoretical models of possible pathogenetic mechanisms, with a primary role of the genetic factors that have been implicated in AD. These can be divided into two main categories. First, the three genes in which mutations are known to result in early onset autosomal dominant familial AD (presenilins 1 and 2, and amyloid beta protein precursor [APP]): well characterized but that account for only a small proportion of AD cases. Secondly, late onset, sporadic AD is more common and evidence suggests that there is a genetic component to this type of disease. A number of genetic risk factors have been implicated that might increase the risk of developing sporadic disease: particularly, apolipoprotein E (apo E) polymorphism and many others suggested by linkage studies [alpha-macroglobulin, low density receptor protein (LRP1), bleomycin hydrolase], with a precise role in beta-amyloid metabolism and deposition. Many of these are controversial and studies have shown conflicting results, but apoE polymorphism seems to be only one of the possible genetic factors suggested to play a role in the multifactoral pathogenesis of AD. Regional and ethnic differences may affect the strength of association between apoE epsilon 4 allele and the disease, and we reported evidences of the decreasing frequency of epsilon 4 allele in AD patients and centenarians from Northern to Southern European regions. Finally, several genetic risk factors of vascular origin (angiotensin converting enzyme, methyltetrahydropholate-reductase, and NOS3 gene polymorphisms) have been implicated in the development of both vascular dementia and AD with conflicting results.

  4. Reversible redox modifications in the microglial proteome challenged by beta amyloid.

    PubMed

    Correani, Virginia; Di Francesco, Laura; Cera, Isabella; Mignogna, Giuseppina; Giorgi, Alessandra; Mazzanti, Michele; Fumagalli, Lorenzo; Fabrizi, Cinzia; Maras, Bruno; Schininà, M Eugenia

    2015-06-01

    Microglia are resident macrophages in the central nervous system, whose participation against exogenous injuries and infections is mainly marked by an immediate release of inflammatory cytokines along with a toxic efflux of superoxide radicals. Indeed, many lines of evidence indicate that persistent activation of these cells turns their neuroprotective phenotype into a neurotoxic one, which contributes to destroy neuronal activity and induces neuronal loss in several neurodegeneration processes, such as Alzheimer's disease. In this study we attempted to fill-in the gap in our knowledge about redox regulation of amyloid activated microglia. With this aim, we carried out a robust and comprehensive characterization of the reversibly redox modified proteome both at the level of resting and amyloid-activated BV2 cells, an immortalised cell line of murine microglia. The approach we used combined the selective enrichment of reversible redox modified proteins through a biotin bait with nanoscale liquid chromatography tandem mass spectrometry of their proteolytic peptides. By this reliable approach, we identified 60 proteins changing the redox status of their selective cysteine residues upon treatment with the amyloidogenic Aβ25-35 peptide. These results assessed that in microglia stimulated by amyloids, redox modifications of the proteome specifically target proteins involved in crucial cell processes, i.e. those involved in the protein synthesis. In particular, for peroxiredoxin-6 (Prdx6) and Ras-related C3 botulinum toxin substrate 1 (Rac1) we suggest mechanisms through which reversible redox modifications could affect the peculiar role of microglia in amyloidogenic injury, which at the same time reinforce the oxidative burst and resist toward it. Moreover, the redox modulation we observed on chloride intracellular channel protein 1 (CLIC1) strengthens the structural and functional relationship between the oxidative stress and the metamorphic transition of this protein

  5. 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

  6. An attenuated immune response is sufficient to enhance cognition in an Alzheimer's disease mouse model immunized with amyloid-beta derivatives.

    PubMed

    Sigurdsson, Einar M; Knudsen, Elin; Asuni, Ayodeji; Fitzer-Attas, Cheryl; Sage, Daniel; Quartermain, David; Goni, Fernando; Frangione, Blas; Wisniewski, Thomas

    2004-07-14

    Immunization with amyloid-beta (Abeta) 1-42 has been shown to reduce amyloid burden and improve cognition in Alzheimer's disease (AD) model mice. In a human trial, possible cognitive benefit was found but in association with significant toxicity in a minority of patients. We proposed that immunization with nonfibrillogenic Abeta derivatives is much less likely to produce toxicity and have previously shown that one such derivative (K6Abeta1-30) can reduce amyloid burden in mice to a similar extent as Abeta1-42. Here, we immunized AD model mice (Tg2576) with Abeta1-30[E18E19] or with K6Abeta1-30[E18E19]. These peptides were designed to be nontoxic and to produce less T-cell response, which has been linked to toxicity. K6Abeta1-30[E18E19] induced primarily an IgM response, whereas Abeta1-30[E18E19] induced an IgG titer that was lower than previously seen with K6Abeta1-30 or Abeta1-42. However, both treated animal groups performed better than Tg controls in the radial arm maze. Amyloid burden was similar in Abeta1-30[E18E19]-vaccinated mice and their Tg controls, whereas the number of medium and small sized plaques was reduced (29-34%) in K6Abeta1-30[E18E19]-immunized mice compared with Tg controls. Amyloid burden in these mice correlated inversely with plasma IgM levels. The cognitive benefit and amyloid reduction in the K6Abeta1-30[E18E19]-vaccinated mice are likely to be related to peripheral clearance of Abeta, because IgM does not cross the blood-brain barrier because of its large size. Our results indicate that these nontoxic Abeta derivatives produce an attenuated antibody response, which is less likely to be associated with negative side effects while having cognitive benefits.

  7. Amyloid beta-protein gene duplication is not common in Alzheimer's disease: analysis by polymorphic restriction fragments.

    PubMed

    Furuya, H; Sasaki, H; Goto, I; Wong, C W; Glenner, G G; Sakaki, Y

    1988-01-15

    The amyloid beta-protein(BP) is an important component of amyloid fibrils of both Alzheimer's disease(AD) and adult Down syndrome(DS). It has been hypothesized that sporadic AD may involve the duplication of a subregion of chromosome 21 containing the BP locus. However, an improved method for detection of the BP gene duplication using polymorphic Hind III fragments led us to a conclusion that BP gene duplication is rare, if any, in (Japanese) sporadic AD patients, indicating that the duplication of the BP gene itself is not the common underlying genetic defect in AD.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. Molecular Mechanism of Thioflavin-T Binding to the Surface of [beta]-Rich Peptide Self-Assemblies

    SciTech Connect

    Biancalana, Matthew; Makabe, Koki; Koide, Akiko; Koide, Shohei

    2009-07-22

    A number of small organic molecules have been developed that bind to amyloid fibrils, a subset of which also inhibit fibrillization. Among these, the benzothiol dye Thioflavin-T (ThT) has been used for decades in the diagnosis of protein-misfolding diseases and in kinetic studies of self-assembly (fibrillization). Despite its importance, efforts to characterize the ThT-binding mechanism at the atomic level have been hampered by the inherent insolubility and heterogeneity of peptide self-assemblies. To overcome these challenges, we have developed a minimalist approach to designing a ThT-binding site in a 'peptide self-assembly mimic' (PSAM) scaffold. PSAMs are engineered water-soluble proteins that mimic a segment of beta-rich peptide self-assembly, and they are amenable to standard biophysical techniques and systematic mutagenesis. The PSAM beta-sheet contains rows of repetitive amino acid patterns running perpendicular to the strands (cross-strand ladders) that represent a ubiquitous structural feature of fibril-like surfaces. We successfully designed a ThT-binding site that recapitulates the hallmarks of ThT-fibril interactions by constructing a cross-strand ladder consisting of contiguous tyrosines. The X-ray crystal structures suggest that ThT interacts with the beta-sheet by docking onto surfaces formed by a single tyrosine ladder, rather than in the space between adjacent ladders. Systematic mutagenesis further demonstrated that tyrosine surfaces across four or more beta-strands formed the minimal binding site for ThT. Our work thus provides structural insights into how this widely used dye recognizes a prominent subset of peptide self-assemblies, and proposes a strategy to elucidate the mechanisms of fibril-ligand interactions.

  17. Powerful beneficial effects of benfotiamine on cognitive impairment and beta-amyloid deposition in amyloid precursor protein/presenilin-1 transgenic mice.

    PubMed

    Pan, Xiaoli; Gong, Neng; Zhao, Jing; Yu, Zhe; Gu, Fenghua; Chen, Jia; Sun, Xiaojing; Zhao, Lei; Yu, Meijing; Xu, Zhiru; Dong, Wenxin; Qin, Yan; Fei, Guoqiang; Zhong, Chunjiu; Xu, Tian-Le

    2010-05-01

    Reduction of glucose metabolism in brain is one of the main features of Alzheimer's disease. Thiamine (vitamin B1)-dependent processes are critical in glucose metabolism and have been found to be impaired in brains from patients with Alzheimer's disease. However, thiamine treatment exerts little beneficial effect in these patients. Here, we tested the effect of benfotiamine, a thiamine derivative with better bioavailability than thiamine, on cognitive impairment and pathology alterations in a mouse model of Alzheimer's disease, the amyloid precursor protein/presenilin-1 transgenic mouse. We show that after a chronic 8 week treatment, benfotiamine dose-dependently enhanced the spatial memory of amyloid precursor protein/presenilin-1 mice in the Morris water maze test. Furthermore, benfotiamine effectively reduced both amyloid plaque numbers and phosphorylated tau levels in cortical areas of the transgenic mice brains. Unexpectedly, these effects were not mimicked by another lipophilic thiamine derivative, fursultiamine, although both benfotiamine and fursultiamine were effective in increasing the levels of free thiamine in the brain. Most notably, benfotiamine, but not fursultiamine, significantly elevated the phosphorylation level of glycogen synthase kinase-3alpha and -3beta, and reduced their enzymatic activities in the amyloid precursor protein/presenilin-1 transgenic brain. Therefore, in the animal Alzheimer's disease model, benfotiamine appears to improve the cognitive function and reduce amyloid deposition via thiamine-independent mechanisms, which are likely to include the suppression of glycogen synthase kinase-3 activities. These results suggest that, unlike many other thiamine-related drugs, benfotiamine may be beneficial for clinical Alzheimer's disease treatment.

  18. 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

  19. 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

  20. 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.

  1. 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