51
|
Umeda T, Tomiyama T, Kitajima E, Idomoto T, Nomura S, Lambert MP, Klein WL, Mori H. Hypercholesterolemia accelerates intraneuronal accumulation of Aβ oligomers resulting in memory impairment in Alzheimer's disease model mice. Life Sci 2012; 91:1169-76. [DOI: 10.1016/j.lfs.2011.12.022] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 12/12/2011] [Accepted: 12/21/2011] [Indexed: 01/07/2023]
|
52
|
Velasco PT, Heffern MC, Sebollela A, Popova IA, Lacor PN, Lee KB, Sun X, Tiano BN, Viola KL, Eckermann AL, Meade TJ, Klein WL. Synapse-binding subpopulations of Aβ oligomers sensitive to peptide assembly blockers and scFv antibodies. ACS Chem Neurosci 2012; 3:972-81. [PMID: 23173076 DOI: 10.1021/cn300122k] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 10/12/2012] [Indexed: 01/04/2023] Open
Abstract
Amyloid β42 self-assembly is complex, with multiple pathways leading to large insoluble fibrils or soluble oligomers. Oligomers are now regarded as most germane to Alzheimer's pathogenesis. We have investigated the hypothesis that oligomer formation itself occurs through alternative pathways, with some leading to synapse-binding toxins. Immediately after adding synthetic peptide to buffer, solutions of Aβ42 were separated by a 50 kDa filter and fractions assessed by SDS-PAGE silver stain, Western blot, immunoprecipitation, and capacity for synaptic binding. Aβ42 rapidly assembled into aqueous-stable oligomers, with similar protein abundance in small (<50 kDa) and large (>50 kDa) oligomer fractions. Initially, both fractions were SDS-labile and resolved into tetramers, trimers, and monomers by SDS-PAGE. Upon continued incubation, the larger oligomers developed a small population of SDS-stable 10-16mers, and the smaller oligomers generated gel-impermeant complexes. The two fractions associated differently with neurons, with prominent synaptic binding limited to larger oligomers. Even within the family of larger oligomers, synaptic binding was associated with only a subset of these species, as a new scFv antibody (NUsc1) immunoprecipitated only a small portion of the oligomers while eliminating synaptic binding. Interestingly, low doses of the peptide KLVFFA blocked assembly of the 10-16mers, and this result was associated with loss of the smaller clusters of oligomers observed at synaptic sites. What distinguishes these smaller clusters from the unaffected larger clusters is not yet known. Results indicate that distinct species of Aβ oligomers are generated by alternative assembly pathways and that synapse-binding subpopulations of Aβ oligomers could be specifically targeted for Alzheimer's therapeutics.
Collapse
|
53
|
Costa RO, Lacor PN, Ferreira IL, Resende R, Auberson YP, Klein WL, Oliveira CR, Rego AC, Pereira CMF. Endoplasmic reticulum stress occurs downstream of GluN2B subunit of N-methyl-d-aspartate receptor in mature hippocampal cultures treated with amyloid-β oligomers. Aging Cell 2012; 11:823-33. [PMID: 22708890 DOI: 10.1111/j.1474-9726.2012.00848.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting both the hippocampus and the cerebral cortex. Reduced synaptic density that occurs early in the disease process seems to be partially due to the overactivation of N-methyl-d-aspartate receptors (NMDARs) leading to excitotoxicity. Recently, we demonstrated that amyloid-beta oligomers (AβO), the species implicated in synaptic loss during the initial disease stages, induce endoplasmic reticulum (ER) stress in cultured neurons. Here, we investigated whether AβO trigger ER stress by an NMDAR-dependent mechanism leading to neuronal dysfunction and analyzed the contribution of GluN2A and GluN2B subunits of this glutamate receptor. Our data revealed that AβO induce ER stress in mature hippocampal cultures, activating ER stress-associated sensors and increasing the levels of the ER chaperone GRP78. We also showed that AβO induce NADPH oxidase (NOX)-mediated superoxide production downstream of GluN2B and impairs ER and cytosolic Ca2+ homeostasis. These events precede changes in cell viability and activation of the ER stress-mediated apoptotic pathway, which was associated with translocation of the transcription factor GADD153 / CHOP to the nucleus and occurred by a caspase-12-independent mechanism. Significantly, ER stress took place after AβO interaction with GluN2B subunits. In addition, AβO-induced ER stress and hippocampal dysfunction were prevented by ifenprodil, an antagonist of GluN2B subunits, while the GluN2A antagonist NVP-AAM077 only slightly attenuated AβO-induced neurotoxicity. Taken together, our results highlight the role of GluN2B subunit of NMDARs on ER stress-mediated hippocampal dysfunction caused by AβO suggesting that it might be a potential therapeutic target during the early stages of AD.
Collapse
|
54
|
Bomfim TR, Forny-Germano L, Sathler LB, Brito-Moreira J, Houzel JC, Decker H, Silverman MA, Kazi H, Melo HM, McClean PL, Holscher C, Arnold SE, Talbot K, Klein WL, Munoz DP, Ferreira ST, De Felice FG. An anti-diabetes agent protects the mouse brain from defective insulin signaling caused by Alzheimer's disease- associated Aβ oligomers. J Clin Invest 2012; 122:1339-53. [PMID: 22476196 DOI: 10.1172/jci57256] [Citation(s) in RCA: 644] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 01/05/2012] [Indexed: 02/06/2023] Open
Abstract
Defective brain insulin signaling has been suggested to contribute to the cognitive deficits in patients with Alzheimer's disease (AD). Although a connection between AD and diabetes has been suggested, a major unknown is the mechanism(s) by which insulin resistance in the brain arises in individuals with AD. Here, we show that serine phosphorylation of IRS-1 (IRS-1pSer) is common to both diseases. Brain tissue from humans with AD had elevated levels of IRS-1pSer and activated JNK, analogous to what occurs in peripheral tissue in patients with diabetes. We found that amyloid-β peptide (Aβ) oligomers, synaptotoxins that accumulate in the brains of AD patients, activated the JNK/TNF-α pathway, induced IRS-1 phosphorylation at multiple serine residues, and inhibited physiological IRS-1pTyr in mature cultured hippocampal neurons. Impaired IRS-1 signaling was also present in the hippocampi of Tg mice with a brain condition that models AD. Importantly, intracerebroventricular injection of Aβ oligomers triggered hippocampal IRS-1pSer and JNK activation in cynomolgus monkeys. The oligomer-induced neuronal pathologies observed in vitro, including impaired axonal transport, were prevented by exposure to exendin-4 (exenatide), an anti-diabetes agent. In Tg mice, exendin-4 decreased levels of hippocampal IRS-1pSer and activated JNK and improved behavioral measures of cognition. By establishing molecular links between the dysregulated insulin signaling in AD and diabetes, our results open avenues for the investigation of new therapeutics in AD.
Collapse
|
55
|
Ferretti MT, Bruno MA, Ducatenzeiler A, Klein WL, Cuello AC. Intracellular Aβ-oligomers and early inflammation in a model of Alzheimer's disease. Neurobiol Aging 2012; 33:1329-42. [DOI: 10.1016/j.neurobiolaging.2011.01.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 01/21/2011] [Accepted: 01/26/2011] [Indexed: 12/21/2022]
|
56
|
Nunes-Tavares N, Santos LE, Stutz B, Brito-Moreira J, Klein WL, Ferreira ST, de Mello FG. Inhibition of choline acetyltransferase as a mechanism for cholinergic dysfunction induced by amyloid-β peptide oligomers. J Biol Chem 2012; 287:19377-85. [PMID: 22505713 DOI: 10.1074/jbc.m111.321448] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Dysregulated cholinergic signaling is an early hallmark of Alzheimer disease (AD), usually ascribed to degeneration of cholinergic neurons induced by the amyloid-β peptide (Aβ). It is now generally accepted that neuronal dysfunction and memory deficits in the early stages of AD are caused by the neuronal impact of soluble Aβ oligomers (AβOs). AβOs build up in AD brain and specifically attach to excitatory synapses, leading to synapse dysfunction. Here, we have investigated the possibility that AβOs could impact cholinergic signaling. The activity of choline acetyltransferase (ChAT, the enzyme that carries out ACh production) was inhibited by ~50% in cultured cholinergic neurons exposed to low nanomolar concentrations of AβOs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction, lactate dehydrogenase release, and [(3)H]choline uptake assays showed no evidence of neuronal damage or loss of viability that could account for reduced ChAT activity under these conditions. Glutamate receptor antagonists fully blocked ChAT inhibition and oxidative stress induced by AβOs. Antioxidant polyunsaturated fatty acids had similar effects, indicating that oxidative damage may be involved in ChAT inhibition. Treatment with insulin, previously shown to down-regulate neuronal AβO binding sites, fully prevented AβO-induced inhibition of ChAT. Interestingly, we found that AβOs selectively bind to ~50% of cultured cholinergic neurons, suggesting that ChAT is fully inhibited in AβO-targeted neurons. Reduction in ChAT activity instigated by AβOs may thus be a relevant event in early stage AD pathology, preceding the loss of cholinergic neurons commonly observed in AD brains.
Collapse
|
57
|
Zhou Y, Klein WL. Aβ oligomers-induced toxicity is attenuated in cells cultured with NbActiv4™ medium. Neurotox Res 2012; 22:335-44. [PMID: 22441766 DOI: 10.1007/s12640-012-9318-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 02/28/2012] [Accepted: 03/08/2012] [Indexed: 01/09/2023]
Abstract
Pathogenic Aβ-derived diffusible ligands (ADDLs) bind to post-synaptic targets, induce excessive reactive oxygen species (ROS) and stimulate tau hyperphosphorylation in cultured neurons. Recently, NbActiv4™ medium was reported to increase neuron synapse densities in cultured hippocampal neurons. We aimed to investigate the effect of this novel medium on ADDL-induced toxicity. We found that ADDL-induced ROS was attenuated in cells cultured with NbActiv4™. ADDL binding assay was performed in neurons cultured by different feeding conditions with NbActiv4™. Feeding cells with 30 % medium once a week, ADDL binding sites were abundant at days in vitro (DIV) 18. However, changing 50 % medium once a week decreased ADDL binding about 80 %. NbActiv4™ produced about 40 % more glial fibrillary acidic protein (GFAP) positive astrocytes than the widely used hippocampal culture medium, neurobasal supplemented with B27 (neurobasal/B27). Astrocytes are reported to produce kinds of trophic factors including insulin-like growth factor 1 (IGF-1). Consistently, when cultured with NbActiv4™, neurons were sensitive to inhibitors of insulin/IGF-1 signaling in response to ADDL attack. Overall, this study supports the important role of astrocytes in neuroprotection and indicates that targeting astrocytes dysfunction may lead to new therapeutic strategies for Alzheimer's disease.
Collapse
|
58
|
Ferreira ST, Klein WL. The Aβ oligomer hypothesis for synapse failure and memory loss in Alzheimer's disease. Neurobiol Learn Mem 2011; 96:529-43. [PMID: 21914486 PMCID: PMC4390395 DOI: 10.1016/j.nlm.2011.08.003] [Citation(s) in RCA: 341] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 07/15/2011] [Accepted: 08/17/2011] [Indexed: 01/08/2023]
Abstract
Alzheimer's disease (AD) is the 3rd most costly disease and the leading cause of dementia. It can linger for many years, but ultimately is fatal, the 6th leading cause of death. Alzheimer's disease (AD) is fatal and affected individuals can sometimes linger many years. Current treatments are palliative and transient, not disease modifying. This article reviews progress in the search to identify the primary AD-causing toxins. We summarize the shift from an initial focus on amyloid plaques to the contemporary concept that AD memory failure is caused by small soluble oligomers of the Aβ peptide, toxins that target and disrupt particular synapses. Evidence is presented that links Aβ oligomers to pathogenesis in animal models and humans, with reference to seminal discoveries from cell biology and new ideas concerning pathogenic mechanisms, including relationships to diabetes and Fragile X. These findings have established the oligomer hypothesis as a new molecular basis for the cause, diagnosis, and treatment of AD.
Collapse
|
59
|
Ferretti MT, Partridge V, Leon WC, Canneva F, Allard S, Arvanitis DN, Vercauteren F, Houle D, Ducatenzeiler A, Klein WL, Glabe CG, Szyf M, Cuello AC. Transgenic mice as a model of pre-clinical Alzheimer's disease. Curr Alzheimer Res 2011; 8:4-23. [PMID: 21143159 DOI: 10.2174/156720511794604561] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 07/07/2010] [Indexed: 11/22/2022]
Abstract
At diagnosis, Alzheimer's disease (AD) brains are extensively burdened with plaques and tangles and display a degree of synaptic failure most likely beyond therapeutic treatment. It is therefore crucial to identify early pathological events in the progression of the disease. While it is not currently feasible to identify and study early, pre-clinical stages of AD, transgenic (Tg) models offer a valuable tool in this regard. Here we investigated cognitive, structural and biochemical CNS alterations occurring in our newly developed McGill-Thyl-APP Tg mice (over-expressing the human amyloid precursor protein with the Swedish and Indiana mutations) prior to extracellular plaque deposition. Pre-plaque, 3-month old Tg mice already displayed cognitive deficits concomitant with reorganization of cortical cholinergic pre-synaptic terminals. Conformational specific antibodies revealed the early appearance of intracellular amyloid β (Aβ)-oligomers and fibrillar oligomers in pyramidal neurons of cerebral cortex and hippocampus. At the same age, the cortical levels of insulin degrading enzyme -a well established Aβ-peptidase, were found to be significantly down-regulated. Our results suggest that, in the McGill-Thy1-APP Tg model, functional, structural and biochemical alterations are already present in the CNS at early, pre-plaque stages of the pathology. Accumulation of intraneuronal neurotoxic Aβ-oligomers (possibly caused by a failure in the clearance machinery) is likely to be the culprit of such early, pre-plaque pathology. Similar neuronal alterations might occur prior to clinical diagnosis in AD, during a yet undefined 'latent' stage. A better understanding of such pre-clinical AD might yield novel therapeutic targets and or diagnostic tools.
Collapse
|
60
|
Bao F, Wicklund L, Lacor PN, Klein WL, Nordberg A, Marutle A. Different β-amyloid oligomer assemblies in Alzheimer brains correlate with age of disease onset and impaired cholinergic activity. Neurobiol Aging 2011; 33:825.e1-13. [PMID: 21683475 DOI: 10.1016/j.neurobiolaging.2011.05.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 04/20/2011] [Accepted: 05/06/2011] [Indexed: 01/06/2023]
Abstract
In this study, we examined the relationship between various β-amyloid (Aβ) oligomer assemblies in autopsy brain with the levels of fibrillar Aβ and cholinergic synaptic function. Brain tissues obtained from the frontal cortex of 14 Alzheimer's disease (AD) patients grouped into early-onset AD (EOAD) and late-onset AD (LOAD) and 12 age-matched control subjects were used to extract and quantify Aβ oligomers in soluble (TBS), detergent soluble (TBST), and insoluble (GuHCl) fractions. The predominant oligomeric Aβ assemblies detected were dodecamers, decamers, and pentamers, and different patterns of expression were observed between EOAD and LOAD patients. There was no association between any of the detected Aβ oligomer assemblies and fibrillar Aβ levels measured by N-methyl[(3)H] 2-(40-methylaminophenyl)-6-hydroxy-benzothiazole ([(3)H]PIB) binding. Levels of pentamers in the soluble fraction significantly correlated with a reduction in choline acetyltransferase activity in AD patients. The number of nicotinic acetylcholine receptors negatively correlated with the total amount of Aβ oligomers in the insoluble fraction in EOAD patients, and with decamers in the soluble fraction in LOAD patients. These novel findings suggest that distinct Aβ oligomers induce impairment of cholinergic neurotransmission in AD pathogenesis.
Collapse
|
61
|
Wilcox KC, Lacor PN, Pitt J, Klein WL. Aβ oligomer-induced synapse degeneration in Alzheimer's disease. Cell Mol Neurobiol 2011; 31:939-48. [PMID: 21538118 DOI: 10.1007/s10571-011-9691-4] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Accepted: 04/07/2011] [Indexed: 12/12/2022]
Abstract
Aβ oligomers cause a collection of molecular events associated with memory loss in Alzheimer's disease, centering on disrupting the maintenance of synapse structure and function. In this brief review of the synaptotoxic effects of Aβ oligomers, we focus on the neuronal properties governing oligomer targeting and toxicity-especially with respect to binding sites and mechanisms of binding. We also discuss ways in which mechanistic insights from other diseases offer clues in the pursuit of the molecular basis of Alzheimer's disease.
Collapse
|
62
|
Umeda T, Tomiyama T, Sakama N, Tanaka S, Lambert MP, Klein WL, Mori H. Intraneuronal amyloid β oligomers cause cell death via endoplasmic reticulum stress, endosomal/lysosomal leakage, and mitochondrial dysfunction in vivo. J Neurosci Res 2011; 89:1031-42. [PMID: 21488093 DOI: 10.1002/jnr.22640] [Citation(s) in RCA: 202] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 02/04/2011] [Accepted: 02/08/2011] [Indexed: 12/22/2022]
Abstract
Intraneuronal accumulation of amyloid β (Aβ) is an early pathological change in Alzheimer's disease. Previously, we showed that the E693Δ mutation (referred to as the "Osaka" mutation) of amyloid precursor protein (APP) caused intracellular accumulation of Aβ oligomers and apoptosis in transfected COS-7 cells. We also showed that transgenic mice expressing APP(E693Δ) (APP(OSK) ) displayed both an age-dependent accumulation of intraneuronal Aβ oligomers from 8 months of age and apparent neuronal loss in the hippocampus at 24 months of age. These findings indicate that intraneuronal Aβ oligomers cause cell death, but the mechanism of this process remains unclear. Accordingly, here we investigated the subcellular localization and toxicity of intraneuronal Aβ oligomers in APP(OSK) -transgenic mice. We found Aβ oligomer accumulation in the endoplasmic reticulum (ER), endosomes/lysosomes, and mitochondria in hippocampal neurons of 22-month-old mice. We also detected up-regulation of Grp78 and HRD1 (an E3 ubiquitin ligase), leakage of cathepsin D from endosomes/lysosomes into cytoplasm, cytochrome c release from mitochondria, and activation of caspase-3 in the hippocampi of 18-month-old mice. Collectively, our findings suggest that intraneuronal Aβ oligomers cause cell death by inducing ER stress, endosomal/lysosomal leakage, and mitochondrial dysfunction in vivo. © 2011 Wiley-Liss, Inc.
Collapse
|
63
|
Saraiva LM, Seixas da Silva GS, Galina A, da-Silva WS, Klein WL, Ferreira ST, De Felice FG. Amyloid-β triggers the release of neuronal hexokinase 1 from mitochondria. PLoS One 2010; 5:e15230. [PMID: 21179577 PMCID: PMC3002973 DOI: 10.1371/journal.pone.0015230] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 10/29/2010] [Indexed: 01/30/2023] Open
Abstract
Brain accumulation of the amyloid-β peptide (Aβ) and oxidative stress underlie neuronal dysfunction and memory loss in Alzheimer's disease (AD). Hexokinase (HK), a key glycolytic enzyme, plays important pro-survival roles, reducing mitochondrial reactive oxygen species (ROS) generation and preventing apoptosis in neurons and other cell types. Brain isozyme HKI is mainly associated with mitochondria and HK release from mitochondria causes a significant decrease in enzyme activity and triggers oxidative damage. We here investigated the relationship between Aβ-induced oxidative stress and HK activity. We found that Aβ triggered HKI detachment from mitochondria decreasing HKI activity in cortical neurons. Aβ oligomers further impair energy metabolism by decreasing neuronal ATP levels. Aβ-induced HKI cellular redistribution was accompanied by excessive ROS generation and neuronal death. 2-deoxyglucose blocked Aβ-induced oxidative stress and neuronal death. Results suggest that Aβ-induced cellular redistribution and inactivation of neuronal HKI play important roles in oxidative stress and neurodegeneration in AD.
Collapse
|
64
|
Decker H, Jürgensen S, Adrover MF, Brito-Moreira J, Bomfim TR, Klein WL, Epstein AL, De Felice FG, Jerusalinsky D, Ferreira ST. N-Methyl-d-aspartate receptors are required for synaptic targeting of Alzheimer’s toxic amyloid-β peptide oligomers. J Neurochem 2010; 115:1520-9. [DOI: 10.1111/j.1471-4159.2010.07058.x] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
65
|
Nogalska A, D'Agostino C, Engel WK, Klein WL, Askanas V. Novel demonstration of amyloid-β oligomers in sporadic inclusion-body myositis muscle fibers. Acta Neuropathol 2010; 120:661-6. [PMID: 20711838 DOI: 10.1007/s00401-010-0737-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 08/06/2010] [Accepted: 08/09/2010] [Indexed: 11/30/2022]
Abstract
Accumulation of amyloid-β (Aβ) within muscle fibers has been considered an upstream step in the development of the s-IBM pathologic phenotype. Aβ42, which is considered more cytotoxic than Aβ40 and has a higher propensity to oligomerize, is preferentially increased in s-IBM muscle fibers. In Alzheimer disease (AD), low-molecular weight Aβ oligomers and toxic oligomers, also referred to as "Aβ-Derived Diffusible Ligands" (ADDLs), are considered strongly cytotoxic and proposed to play an important pathogenic role. ADDLs have been shown to be increased in AD brain. We now report for the first time that in s-IBM muscle biopsies Aβ-dimer, -trimer, and -tetramer are identifiable by immunoblots. While all the s-IBM samples we studied had Aβ-oligomers, their molecular weights and intensity varied between the patient samples. None of the control muscle biopsies had Aβ oligomers. Dot-immunoblots using highly specific anti-ADDL monoclonal antibodies also showed highly increased ADDLs in all s-IBM biopsies studied, while controls were negative. By immunofluorescence, in some of the abnormal s-IBM muscle fibers ADDLs were accumulated in the form of plaque-like inclusions, and were often increased diffusely in very small fibers. Normal and disease-controls were negative. By gold-immuno-electron microscopy, ADDL-immunoreactivities were in close proximity to 6-10 nm amyloid-like fibrils, and also were immunodecorating amorphous and floccular material. In cultured human muscle fibers, we found that inhibition of autophagy led to the accumulation of Aβ oligomers. This novel demonstration of Aβ42 oligomers in s-IBM muscle biopsy provides additional evidence that intra-muscle fiber accumulation of Aβ42 oligomers in s-IBM may contribute importantly to s-IBM pathogenic cascade.
Collapse
|
66
|
Tchantchou F, Lacor PN, Cao Z, Lao L, Hou Y, Cui C, Klein WL, Luo Y. Stimulation of neurogenesis and synaptogenesis by bilobalide and quercetin via common final pathway in hippocampal neurons. J Alzheimers Dis 2010; 18:787-98. [PMID: 19661619 DOI: 10.3233/jad-2009-1189] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Loss of synapses has been correlated with dementia in Alzheimer's disease (AD) as an early event during the disease progression. Hence, synaptogenesis and neurogenesis in adulthood could serve as a therapeutic target for the prevention and treatment of AD. Recently, we have demonstrated enhanced hippocampal neurogenesis by oral administration of Ginkgo biloba extract (EGb 761) to a mouse model of AD. This study aims to identify the constituents that contribute to EGb 761-induced neurogenesis. Among the constituents tested, bilobalide and quercetin significantly increased cell proliferation in the hippocampal neurons in a dose-dependent manner. Bilobalide and quercetin also enhanced phosphorylation of cyclic-AMP Response Element Binding Protein (CREB) in these cells, and elevated the levels of pCREB and, brain-derived neurotrophic factor in mice brain. Immunofluorescence staining of synaptic markers shows remarkable dendritic processes in hippocampal neurons treated with either quercetin or bilobalide. Furthermore, both constituents restored amyloid-beta oligomers (also known as ADDL)-induced synaptic loss and phosphorylation of CREB. The present findings suggest that enhanced neurogenesis and synaptogenesis by bilobalide and quercetin may share a common final signaling pathway mediated by phosphorylation of CREB. Despite a recent report showing that EGb 761 was insufficient in prevent dementia, its constituents still warrant future investigation.
Collapse
|
67
|
Krafft GA, Klein WL. ADDLs and the signaling web that leads to Alzheimer’s disease. Neuropharmacology 2010; 59:230-42. [DOI: 10.1016/j.neuropharm.2010.07.012] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 07/13/2010] [Indexed: 12/29/2022]
|
68
|
Renner M, Lacor PN, Velasco PT, Xu J, Contractor A, Klein WL, Triller A. Deleterious effects of amyloid beta oligomers acting as an extracellular scaffold for mGluR5. Neuron 2010; 66:739-54. [PMID: 20547131 DOI: 10.1016/j.neuron.2010.04.029] [Citation(s) in RCA: 355] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2010] [Indexed: 12/18/2022]
Abstract
Soluble oligomers of amyloid beta (Abeta) play a role in the memory impairment characteristic of Alzheimer's disease. Acting as pathogenic ligands, Abeta oligomers bind to particular synapses and perturb their function, morphology, and maintenance. Events that occur shortly after oligomer binding have been investigated here in live hippocampal neurons by single particle tracking of quantum dot-labeled oligomers and synaptic proteins. Membrane-attached oligomers initially move freely, but their diffusion is hindered markedly upon accumulation at synapses. Concomitantly, individual metabotropic glutamate receptors (mGluR5) manifest strikingly reduced lateral diffusion as they become aberrantly clustered. This clustering of mGluR5 elevates intracellular calcium and causes synapse deterioration, responses prevented by an mGluR5 antagonist. As expected, clustering by artificial crosslinking also promotes synaptotoxicity. These results reveal a mechanism whereby Abeta oligomers induce the abnormal accumulation and overstabilization of a glutamate receptor, thus providing a mechanistic and molecular basis for Abeta oligomer-induced early synaptic failure.
Collapse
|
69
|
De Felice FG, Bonfim TR, Klein WL, Ferreira ST. P2‐327: Aβ oligomers impair neuronal insulin signaling. Alzheimers Dement 2010. [DOI: 10.1016/j.jalz.2010.05.1378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
70
|
Tomiyama T, Umeda T, Sakama N, Lambert MP, Klein WL, Mori H. O4‐05‐01: Intraneuronal accumulation of Aβ oligomers causes abnormal tau phosphorylation, glial activation and neuronal loss in transgenic mice with APP E693Δ mutation. Alzheimers Dement 2010. [DOI: 10.1016/j.jalz.2010.05.488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
71
|
Shekhawat GS, Lambert MP, Sharma S, Velasco PT, Viola KL, Klein WL, Dravid VP. Soluble state high resolution atomic force microscopy study of Alzheimer's beta-amyloid oligomers. APPLIED PHYSICS LETTERS 2009; 95:183701. [PMID: 19997583 PMCID: PMC2789110 DOI: 10.1063/1.3251779] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 09/29/2009] [Indexed: 05/20/2023]
Abstract
We report here the direct observation of high resolution structures of assemblies of Alzheimer beta-amyloid oligomers and monomers using liquid atomic force microscopy (AFM). Visualization of nanoscale features of Abeta oligomers (also known as ADDLs) was carried out in tapping mode AFM in F12 solution. Our results indicate that ADDL preparations exist in solution primarily as a mixture of monomeric peptides and higher molecular mass oligomers. Our study clearly reveals that the size and shape of these oligomer aggregates exhibit a pronounced dependence on concentration. These studies show that wet AFM enables direct assessment of oligomers in physiological fluids and suggests that this method may be developed to visualize Abeta oligomers from human fluids.
Collapse
|
72
|
Pitt J, Roth W, Lacor P, Smith AB, Blankenship M, Velasco P, De Felice F, Breslin P, Klein WL. Alzheimer's-associated Abeta oligomers show altered structure, immunoreactivity and synaptotoxicity with low doses of oleocanthal. Toxicol Appl Pharmacol 2009; 240:189-97. [PMID: 19631677 DOI: 10.1016/j.taap.2009.07.018] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 07/14/2009] [Accepted: 07/14/2009] [Indexed: 12/28/2022]
Abstract
It now appears likely that soluble oligomers of amyloid-beta1-42 peptide, rather than insoluble fibrils, act as the primary neurotoxin in Alzheimer's disease (AD). Consequently, compounds capable of altering the assembly state of these oligomers (referred to as ADDLs) may have potential for AD therapeutics. Phenolic compounds are of particular interest for their ability to disrupt Abeta oligomerization and reduce pathogenicity. This study has focused on oleocanthal (OC), a naturally-occurring phenolic compound found in extra-virgin olive oil. OC increased the immunoreactivity of soluble Abeta species, when assayed with both sequence- and conformation-specific Abeta antibodies, indicating changes in oligomer structure. Analysis of oligomers in the presence of OC showed an upward shift in MW and a ladder-like distribution of SDS-stable ADDL subspecies. In comparison with control ADDLs, oligomers formed in the presence of OC (Abeta-OC) showed equivalent colocalization at synapses but exhibited greater immunofluorescence as a result of increased antibody recognition. The enhanced signal at synapses was not due to increased synaptic binding, as direct detection of fluorescently-labeled ADDLs showed an overall reduction in ADDL signal in the presence of OC. Decreased binding to synapses was accompanied by significantly less synaptic deterioration assayed by drebrin loss. Additionally, treatment with OC improved antibody clearance of ADDLs. These results indicate oleocanthal is capable of altering the oligomerization state of ADDLs while protecting neurons from the synaptopathological effects of ADDLs and suggest OC as a lead compound for development in AD therapeutics.
Collapse
|
73
|
Zhao WQ, Lacor PN, Chen H, Lambert MP, Quon MJ, Krafft GA, Klein WL. Insulin receptor dysfunction impairs cellular clearance of neurotoxic oligomeric a{beta}. J Biol Chem 2009; 284:18742-53. [PMID: 19406747 PMCID: PMC2707198 DOI: 10.1074/jbc.m109.011015] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 04/20/2009] [Indexed: 12/16/2022] Open
Abstract
Accumulation of amyloid beta (Abeta) oligomers in the brain is toxic to synapses and may play an important role in memory loss in Alzheimer disease. However, how these toxins are built up in the brain is not understood. In this study we investigate whether impairments of insulin and insulin-like growth factor-1 (IGF-1) receptors play a role in aggregation of Abeta. Using primary neuronal culture and immortal cell line models, we show that expression of normal insulin or IGF-1 receptors confers cells with abilities to reduce exogenously applied Abeta oligomers (also known as ADDLs) to monomers. In contrast, transfection of malfunctioning human insulin receptor mutants, identified originally from patient with insulin resistance syndrome, or inhibition of insulin and IGF-1 receptors via pharmacological reagents increases ADDL levels by exacerbating their aggregation. In healthy cells, activation of insulin and IGF-1 receptor reduces the extracellular ADDLs applied to cells via seemingly the insulin-degrading enzyme activity. Although insulin triggers ADDL internalization, IGF-1 appears to keep ADDLs on the cell surface. Nevertheless, both insulin and IGF-1 reduce ADDL binding, protect synapses from ADDL synaptotoxic effects, and prevent the ADDL-induced surface insulin receptor loss. Our results suggest that dysfunctions of brain insulin and IGF-1 receptors contribute to Abeta aggregation and subsequent synaptic loss.
Collapse
|
74
|
Kiyota T, Yamamoto M, Xiong H, Lambert MP, Klein WL, Gendelman HE, Ransohoff RM, Ikezu T. CCL2 accelerates microglia-mediated Abeta oligomer formation and progression of neurocognitive dysfunction. PLoS One 2009; 4:e6197. [PMID: 19593388 PMCID: PMC2703798 DOI: 10.1371/journal.pone.0006197] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 06/01/2009] [Indexed: 01/14/2023] Open
Abstract
Background The linkages between neuroinflammation and Alzheimer's disease (AD) pathogenesis are well established. What is not, however, is how specific immune pathways and proteins affect the disease. To this end, we previously demonstrated that transgenic over-expression of CCL2 enhanced microgliosis and induced diffuse amyloid plaque deposition in Tg2576 mice. This rodent model of AD expresses a Swedish β-amyloid (Aβ) precursor protein mutant. Methodology/Principal Findings We now report that CCL2 transgene expression accelerates deficits in spatial and working memory and hippocampal synaptic transmission in β-amyloid precursor protein (APP) mice as early as 2–3 months of age. This is followed by increased numbers of microglia that are seen surrounding Aβ oligomers. CCL2 does not suppress Aβ degradation. Rather, CCL2 and tumor necrosis factor-α directly facilitated Aβ uptake, intracellular Aβ oligomerization, and protein secretion. Conclusions/Significance We posit that CCL2 facilitates Aβ oligomer formation in microglia and propose that such events accelerate memory dysfunction by affecting Aβ seeding in the brain.
Collapse
|
75
|
Tomiyama T, Matsuyama S, Iso H, Takuma H, Umeda T, Ohnishi K, Teraoka R, Ishibashi K, Nishitsuji K, Ito K, Borchelt DR, Lambert MP, Klein WL, Mori H. O2‐06‐07: A transgenic mouse model of amyloid β oligomers: Pathological effects of the E693Δ mutation in amyloid precursor protein in vivo. Alzheimers Dement 2009. [DOI: 10.1016/j.jalz.2009.05.367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|