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1.
Front Neurosci ; 13: 861, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474823

RESUMO

How endogenously produced soluble amyloid ß-protein (Aß) affects synaptic plasticity in vulnerable circuits should provide insight into early Alzheimer's disease pathophysiology. McGill-R-Thy1-APP transgenic rats, modeling Alzheimer's disease amyloidosis, exhibit an age-dependent soluble Aß-mediated impairment of the induction of long-term potentiation (LTP) by 200 Hz conditioning stimulation at apical CA3-to-CA1 synapses. Here, we investigated if synaptic weakening at these synapses in the form of activity-dependent persistent reversal (depotentiation) of LTP is also altered in pre-plaque rats in vivo. In freely behaving transgenic rats strong, 400 Hz, conditioning stimulation induced stable LTP that was NMDA receptor- and voltage-gated Ca2+ channel-dependent. Surprisingly, the ability of novelty exploration to induce depotentiation of 400 Hz-induced LTP was impaired in an Aß-dependent manner in the freely behaving transgenic rats. Moreover, at apical synapses, low frequency conditioning stimulation (1 Hz) did not trigger depotentiation in anaesthetized transgenic rats, with an age-dependence similar to the LTP deficit. In contrast, at basal synapses neither LTP, induced by 100 or 200 Hz, nor novelty exploration-induced depotentiation was impaired in the freely behaving transgenic rats. These findings indicate that activity-dependent weakening, as well as strengthening, is impaired in a synapse- and age-dependent manner in this model of early Alzheimer's disease amyloidosis.

2.
Neurobiol Dis ; 127: 582-590, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30910746

RESUMO

Soluble synaptotoxic aggregates of the main pathological proteins of Alzheimer's disease, amyloid ß-protein (Aß) and tau, have rapid and potent inhibitory effects on long-term potentiation (LTP). Although the promotion of synaptic weakening mechanisms, including long-term depression (LTD), is posited to mediate LTP inhibition by Aß, little is known regarding the action of exogenous tau on LTD. The present study examined the ability of different assemblies of full-length human tau to affect LTD in the dorsal hippocampus of the anaesthetized rat. Unlike Aß, intracerebroventricular injection of soluble aggregates of tau (SτAs), but not monomers or fibrils, potently increased the threshold for LTD induction in a manner that required cellular prion protein. However, MTEP, an antagonist of the putative prion protein coreceptor metabotropic glutamate receptor 5, did not prevent the disruption of synaptic plasticity by SτAs. In contrast, systemic treatment with Ro 25-6981, a selective antagonist at GluN2B subunit-containing NMDA receptors, reduced SτA-mediated inhibition of LTD, but not LTP. Intriguingly, SτAs completely blocked Aß-facilitated LTD, whereas a subthreshold dose of SτAs facilitated Aß-mediated inhibition of LTP. Overall, these findings support the importance of cellular prion protein in mediating a range of, sometimes opposing, actions of soluble Aß and tau aggregates with different effector mechanisms on synaptic plasticity.


Assuntos
Peptídeos beta-Amiloides/farmacologia , Hipocampo/efeitos dos fármacos , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Agregados Proteicos/fisiologia , Proteínas tau/metabolismo , Animais , Hipocampo/metabolismo , Depressão Sináptica de Longo Prazo/fisiologia , Masculino , Piridinas/farmacologia , Ratos , Receptor de Glutamato Metabotrópico 5/agonistas , Sinapses/efeitos dos fármacos , Sinapses/fisiologia , Tiazóis/farmacologia
3.
J Neurosci ; 38(50): 10595-10606, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30355631

RESUMO

Intracellular neurofibrillary tangles (NFTs) composed of tau protein are a neuropathological hallmark of several neurodegenerative diseases, the most common of which is Alzheimer's disease (AD). For some time NFTs were considered the primary cause of synaptic dysfunction and neuronal death, however, more recent evidence suggests that soluble aggregates of tau are key drivers of disease. Here we investigated the effect of different tau species on synaptic plasticity in the male rat hippocampus in vivo Intracerebroventricular injection of soluble aggregates formed from either wild-type or P301S human recombinant tau potently inhibited hippocampal long-term potentiation (LTP) at CA3-to-CA1 synapses. In contrast, tau monomers and fibrils appeared inactive. Neither baseline synaptic transmission, paired-pulse facilitation nor burst response during high-frequency conditioning stimulation was affected by the soluble tau aggregates. Similarly, certain AD brain soluble extracts inhibited LTP in a tau-dependent manner that was abrogated by either immunodepletion with, or coinjection of, a mid-region anti-tau monoclonal antibody (mAb), Tau5. Importantly, this tau-mediated block of LTP was prevented by administration of mAbs selective for the prion protein (PrP). Specifically, mAbs to both the mid-region (6D11) and N-terminus (MI-0131) of PrP prevented inhibition of LTP by both recombinant and brain-derived tau. These findings indicate that PrP is a mediator of tau-induced synaptic dysfunction.SIGNIFICANCE STATEMENT Here we report that certain soluble forms of tau selectively disrupt synaptic plasticity in the live rat hippocampus. Further, we show that monoclonal antibodies to cellular prion protein abrogate the impairment of long-term potentiation caused both by recombinant and Alzheimer's disease brain-derived soluble tau. These findings support a critical role for cellular prion protein in the deleterious synaptic actions of extracellular soluble tau in tauopathies, including Alzheimer's disease. Thus, approaches targeting cellular prion protein, or downstream pathways, might provide an effective strategy for developing therapeutics.


Assuntos
Hipocampo/metabolismo , Hipocampo/patologia , Plasticidade Neuronal/fisiologia , Proteínas PrPC/metabolismo , Proteínas tau/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Inibidores da Angiogênese/farmacologia , Animais , Feminino , Hipocampo/efeitos dos fármacos , Humanos , Masculino , Plasticidade Neuronal/efeitos dos fármacos , Proteínas Priônicas/metabolismo , Ratos
4.
Cell Rep ; 23(7): 1932-1938, 2018 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-29768194

RESUMO

The early stages of Alzheimer's disease are associated with synaptic dysfunction prior to overt loss of neurons. To identify extracellular molecules that impair synaptic plasticity in the brain, we studied the secretomes of human iPSC-derived neuronal models of Alzheimer's disease. When introduced into the rat brain, secretomes from human neurons with either a presenilin-1 mutation, amyloid precursor protein duplication, or trisomy of chromosome 21 all strongly inhibit hippocampal long-term potentiation. Synaptic dysfunction caused by presenilin-1 mutant and amyloid precusor protein duplication secretomes is mediated by Aß peptides, whereas trisomy of chromosome 21 (trisomy 21) neuronal secretomes induce dysfunction through extracellular tau. In all cases, synaptotoxicity is relieved by antibody blockade of cellular prion protein. These data indicate that human models of Alzheimer's disease generate distinct proteins that converge at the level of cellular prion protein to induce synaptic dysfunction in vivo.


Assuntos
Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/metabolismo , Espaço Extracelular/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Modelos Biológicos , Plasticidade Neuronal , Proteínas tau/metabolismo , Doença de Alzheimer/metabolismo , Animais , Genótipo , Humanos , Potenciação de Longa Duração , Masculino , Neurônios/metabolismo , Presenilina-1/metabolismo , Ratos
5.
Sci Rep ; 8(1): 4391, 2018 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-29535352

RESUMO

Synaptic long-term depression (LTD) is believed to underlie critical mnemonic processes in the adult hippocampus. The roles of the metabotropic and ionotropic actions of glutamate in the induction of synaptic LTD by electrical low-frequency stimulation (LFS) in the living adult animal is poorly understood. Here we examined the requirement for metabotropic glutamate (mGlu) and NMDA receptors in LTD induction in anaesthetized adult rats. LTD induction was primarily dependent on NMDA receptors and required the involvement of both the ion channel function and GluN2B subunit of the receptor. Endogenous mGlu5 receptor activation necessitated the local application of relatively high doses of either competitive or non-competitive NMDA receptor antagonists to block LTD induction. Moreover, boosting endogenous glutamate activation of mGlu5 receptors with a positive allosteric modulator lowered the threshold for NMDA receptor-dependent LTD induction by weak LFS. The present data provide support in the living animal that NMDA receptor-dependent LTD is boosted by endogenously released glutamate activation of mGlu5 receptors. Given the predominant perisynaptic location of mGlu5 receptors, the present findings emphasize the need to further evaluate the contribution and mechanisms of these receptors in NMDA receptor-dependent synaptic plasticity in the adult hippocampus in vivo.


Assuntos
Hipocampo/fisiologia , Potenciação de Longa Duração , Receptor de Glutamato Metabotrópico 5/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Estimulação Elétrica , Ácido Glutâmico/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Ratos , Receptor de Glutamato Metabotrópico 5/antagonistas & inibidores , Receptor de Glutamato Metabotrópico 5/química , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Potenciais Sinápticos
6.
Neurobiol Dis ; 114: 24-30, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29477641

RESUMO

Pro-inflammatory mechanisms have recently emerged as an important component of early Alzheimer's disease (AD) pathogenesis. A particularly attractive therapeutic strategy is to selectively prevent the disruptive effects of activation of the innate immune system in the brain at an early transitional stage by reducing the production or directly neutralizing pro-inflammatory cytokines, in particular IL-1ß and TNF-α. Here we tested their in vivo effects on synaptic plasticity deficits, which provide sensitive and robust measures of synaptic failure, in a rat model of AD amyloidosis. Using electrophysiological techniques we longitudinally studied the effects of the NLRP3 inflammasome inhibitor Mcc950, the IL-1 receptor antagonist (anakinra) and an anti-TNF-α agent (etanercept) in awake freely moving transgenic rats overexpressing AD associated ß-amyloid precursor protein at a pre-plaque stage of amyloidosis. Repeated treatment with Mcc950 reversibly abrogated the inhibition of long-term potentiation. The IL-1 receptor antagonist and etanercept also had a similar beneficial effect on the deficit in synaptic plasticity. Our findings support the clinical development of Mcc950 and clinically available IL-1- and TNF-α-neutralizing agents in early AD.


Assuntos
Doença de Alzheimer/fisiopatologia , Amiloidose/fisiopatologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/fisiologia , Plasticidade Neuronal/fisiologia , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/genética , Amiloidose/tratamento farmacológico , Amiloidose/genética , Animais , Anti-Inflamatórios não Esteroides/farmacologia , Anti-Inflamatórios não Esteroides/uso terapêutico , Etanercepte/farmacologia , Etanercepte/uso terapêutico , Humanos , Proteína Antagonista do Receptor de Interleucina 1/farmacologia , Proteína Antagonista do Receptor de Interleucina 1/uso terapêutico , Masculino , Proteína 3 que Contém Domínio de Pirina da Família NLR/agonistas , Proteína 3 que Contém Domínio de Pirina da Família NLR/antagonistas & inibidores , Plasticidade Neuronal/efeitos dos fármacos , Ratos , Ratos Transgênicos
7.
Cell Rep ; 22(8): 2053-2065, 2018 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-29466733

RESUMO

Promotion of long-term depression (LTD) mechanisms by synaptotoxic soluble oligomers of amyloid-ß (Aß) has been proposed to underlie synaptic dysfunction in Alzheimer's disease (AD). Previously, LTD was induced by relatively non-specific electrical stimulation. Exploiting optogenetics, we studied LTD using a more physiologically diffuse spatial pattern of selective pathway activation in the rat hippocampus in vivo. This relatively sparse synaptic LTD requires both the ion channel function and GluN2B subunit of the NMDA receptor but, in contrast to electrically induced LTD, is not facilitated by boosting endogenous muscarinic acetylcholine or metabotropic glutamate 5 receptor activation. Although in the absence of Aß, there is no evidence of hippocampal LTD asymmetry, in the presence of Aß, the induction of LTD is preferentially enhanced in the left hippocampus in an mGluR5-dependent manner. This circuit-selective disruption of synaptic plasticity by Aß provides a route to understanding the development of aberrant brain lateralization in AD.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Hipocampo/fisiopatologia , Depressão Sináptica de Longo Prazo , Sinapses/fisiologia , Doença de Alzheimer/metabolismo , Animais , Região CA1 Hipocampal/fisiopatologia , Região CA3 Hipocampal/fisiopatologia , Channelrhodopsins/metabolismo , Neurônios Colinérgicos/metabolismo , Estimulação Elétrica , Depressão Sináptica de Longo Prazo/fisiologia , Masculino , Ratos Wistar , Receptor de Glutamato Metabotrópico 5/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo
8.
Neuropharmacology ; 121: 231-246, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28390893

RESUMO

Alzheimer's disease amyloid-ß (Aß) oligomers are synaptotoxic, inappropriately increasing extracellular glutamate concentration and glutamate receptor activation to thereby rapidly disrupt synaptic plasticity. Thus, acutely promoting brain glutamate homeostasis with a blood-based scavenging system, glutamate-oxaloacetate transaminase (GOT), and blocking metabotropic glutamate 5 (mGlu5) receptor or its co-receptor cellular prion protein (PrP), prevent the acute inhibition of long-term potentiation (LTP) by exogenous Aß. Here, we evaluated the time course of the effects of such interventions in the persistent disruptive effects of Aß oligomers, either exogenously injected in wild type rats or endogenously generated in transgenic rats that model Alzheimer's disease amyloidosis. We report that repeated, but not acute, systemic administration of recombinant GOT type 1, with or without the glutamate co-substrate oxaloacetate, reversed the persistent deleterious effect of exogenous Aß on synaptic plasticity. Moreover, similar repetitive treatment reversibly abrogated the inhibition of LTP monitored longitudinally in freely behaving transgenic rats. Remarkably, brief repeated treatment with an mGlu5 receptor antagonist, basimglurant, or an antibody that prevents Aß oligomer binding to PrP, ICSM35, also had similar reversible ameliorative effects in the transgenic rat model. Overall, the present findings support the ongoing development of therapeutics for early Alzheimer's disease based on these complementary approaches.


Assuntos
Amiloidose/patologia , Amiloidose/fisiopatologia , Região CA1 Hipocampal/fisiologia , Potenciação de Longa Duração/efeitos dos fármacos , Proteínas Priônicas/metabolismo , Receptor de Glutamato Metabotrópico 5/metabolismo , Peptídeos beta-Amiloides/imunologia , Peptídeos beta-Amiloides/farmacologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Amiloidose/sangue , Amiloidose/genética , Animais , Anticorpos/farmacologia , Aspartato Aminotransferase Citoplasmática/farmacologia , Região CA1 Hipocampal/efeitos dos fármacos , Modelos Animais de Doenças , Humanos , Imidazóis/farmacologia , Potenciação de Longa Duração/genética , Masculino , Mutação/genética , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/farmacologia , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/genética , Piridinas/farmacologia , Ratos , Ratos Transgênicos , Receptor de Glutamato Metabotrópico 5/antagonistas & inibidores , Vigília
9.
Cereb Cortex ; 27(7): 3724-3735, 2017 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27390019

RESUMO

Dysregulation of glutamate homeostasis in the interstitial fluid of the brain is strongly implicated in causing synaptic dysfunction in many neurological and psychiatric illnesses. In the case of Alzheimer's disease (AD), amyloid ß (Aß)-mediated disruption of synaptic plasticity and memory can be alleviated by interventions that directly remove glutamate or block certain glutamate receptors. An alternative strategy is to facilitate the removal of excess glutamate from the nervous system by activating peripheral glutamate clearance systems. One such blood-based system, glutamate oxaloacetate transaminase (GOT), is activated by oxaloacetate, which acts as a co-substrate. We report here that synthetic and AD brain-derived Aß-mediated inhibition of synaptic long-term potentiation in the hippocampus is alleviated by oxaloacetate. Moreover the effect of oxaloacetate was GOT-dependent. The disruptive effects of a general inhibitor of excitatory amino acid transport or TNFα, a pro-inflammatory mediator of Aß action, were also reversed by oxaloacetate. Furthermore, another intervention that increases peripheral glutamate clearance, peritoneal dialysis, mimicked the beneficial effect of oxaloacetate. These findings lend support to the promotion of the peripheral clearance of glutamate as a means to alleviate synaptic dysfunction that is caused by impaired glutamate homeostasis in the brain.


Assuntos
Peptídeos beta-Amiloides/farmacologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Ácido Glutâmico/sangue , Hipocampo/metabolismo , Homeostase/fisiologia , Sinapses/efeitos dos fármacos , Fator de Necrose Tumoral alfa/farmacologia , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Aspartato Aminotransferase Citoplasmática/farmacologia , Ácido Aspártico/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Hipocampo/efeitos dos fármacos , Homeostase/efeitos dos fármacos , Humanos , Injeções Intraperitoneais , Masculino , Ácido Oxaloacético/farmacologia , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Wistar , Sinapses/fisiologia , Fatores de Tempo , Fator de Necrose Tumoral alfa/metabolismo
10.
Hippocampus ; 26(12): 1655-1665, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27701797

RESUMO

Aggregated amyloid ß-protein (Aß) is pathognomonic of Alzheimer's disease and certain assemblies of Aß are synaptotoxic. Excess glutamate or diminished glutathione reserve are both implicated in mediating or modulating Aß-induced disruption of synaptic plasticity. The system xc- antiporter promotes Na+ -independent exchange of cystine with glutamate thereby providing a major source of extracellular glutamate and intracellular glutathione concentrations. Here we probed the ability of two drugs with opposite effects on system xc-, the inhibitor sulfasalazine and facilitator N-acetylcysteine, to modulate the ability of Aß1-42 to inhibit long-term potentiation (LTP) in the CA1 area of the anaesthetized rat. Whereas acute systemic treatment with sulfasalazine lowered the threshold for Aß to interfere with synaptic plasticity, N-acetylcysteine prevented the inhibition of LTP by Aß alone or in combination with sulfasalazine. Moreover acute N-acetylcysteine also prevented the inhibition of LTP by TNFα, a putative mediator of Aß actions, and repeated systemic N-acetylcysteine treatment for 7 days reversed the delayed deleterious effect of Aß on LTP. Since both of these drugs are widely used clinically, further evaluation of their potential beneficial and deleterious actions in early Alzheimer's disease seems warranted. © 2016 Wiley Periodicals, Inc.


Assuntos
Acetilcisteína/farmacologia , Peptídeos beta-Amiloides/toxicidade , Fármacos do Sistema Nervoso Central/farmacologia , Hipocampo/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Fragmentos de Peptídeos/toxicidade , Sulfassalazina/farmacologia , Sistemas de Transporte de Aminoácidos Acídicos/antagonistas & inibidores , Sistemas de Transporte de Aminoácidos Acídicos/genética , Sistemas de Transporte de Aminoácidos Acídicos/metabolismo , Animais , Cateteres de Demora , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Glutationa/metabolismo , Hipocampo/metabolismo , Potenciação de Longa Duração/fisiologia , Masculino , Maleatos/farmacologia , Ratos Wistar , Fator de Necrose Tumoral alfa/metabolismo
11.
J Biol Chem ; 290(47): 28343-52, 2015 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-26221033

RESUMO

Despite significant advances, the molecular identity of the cytotoxic species populated during in vivo amyloid formation crucial for the understanding of neurodegenerative disorders is yet to be revealed. In this study lysozyme prefibrillar oligomers and fibrils in both mature and sonicated states have been isolated through an optimized ultrafiltration/ultracentrifugation method and characterized with various optical spectroscopic techniques, atomic force microscopy, and transmission electron microscopy. We examined their level and mode of toxicity on rat pheochromocytoma (PC12) cells in both differentiated and undifferentiated states. We find that oligomers and fibrils display cytotoxic capabilities toward cultured cells in vitro, with oligomers producing elevated levels of cellular injury toward undifferentiated PC12 cells (PC12(undiff)). Furthermore, dual flow cytometry staining experiments demonstrate that the oligomers and mature fibrils induce divergent cellular death pathways (apoptosis and secondary necrosis, respectively) in these PC12 cells. We have also shown that oligomers but not sonicated mature fibrils inhibit hippocampal long term potentiation, a form of synaptic plasticity implicated in learning and memory, in vivo. We conclude that our in vitro and in vivo findings confer a level of resistance toward amyloid fibrils, and that the PC 12-based comparative cytotoxicity assay can provide insights into toxicity differences between differently aggregated protein species.


Assuntos
Amiloide/metabolismo , Biopolímeros/metabolismo , Morte Celular , Amiloide/química , Animais , Biopolímeros/química , Células PC12 , Ratos
12.
Sci Rep ; 5: 10256, 2015 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-26194093

RESUMO

ß-amyloid (Aß) oligomers have been closely implicated in the pathogenesis of Alzheimer's disease (AD). We found, for the first time, that bis(heptyl)-cognitin, a novel dimeric acetylcholinesterase (AChE) inhibitor derived from tacrine, prevented Aß oligomers-induced inhibition of long-term potentiation (LTP) at concentrations that did not interfere with normal LTP. Bis(heptyl)-cognitin also prevented Aß oligomers-induced synaptotoxicity in primary hippocampal neurons. In contrast, tacrine and donepezil, typical AChE inhibitors, could not prevent synaptic impairments in these models, indicating that the modification of Aß oligomers toxicity by bis(heptyl)-cognitin might be attributed to a mechanism other than AChE inhibition. Studies by using dot blotting, immunoblotting, circular dichroism spectroscopy, and transmission electron microscopy have shown that bis(heptyl)-cognitin altered Aß assembly via directly inhibiting Aß oligomers formation and reducing the amount of preformed Aß oligomers. Molecular docking analysis further suggested that bis(heptyl)-cognitin presumably interacted with the hydrophobic pockets of Aß, which confers stabilizing powers and assembly alteration effects on Aß. Most importantly, bis(heptyl)-cognitin significantly reduced cognitive impairments induced by intra-hippocampal infusion of Aß oligomers in mice. These results clearly demonstrated how dimeric agents prevent Aß oligomers-induced synaptic and memory impairments, and offered a strong support for the beneficial therapeutic effects of bis(heptyl)-cognitin in the treatment of AD.


Assuntos
Peptídeos beta-Amiloides/toxicidade , Transtornos da Memória/induzido quimicamente , Transtornos da Memória/tratamento farmacológico , Fármacos Neuroprotetores/uso terapêutico , Sinapses/patologia , Tacrina/análogos & derivados , Tacrina/uso terapêutico , Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/ultraestrutura , Animais , Células Cultivadas , Inibidores da Colinesterase/farmacologia , Inibidores da Colinesterase/uso terapêutico , Estimulação Elétrica , Hipocampo/patologia , Interações Hidrofóbicas e Hidrofílicas , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Camundongos Endogâmicos ICR , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fármacos Neuroprotetores/farmacologia , Estrutura Secundária de Proteína , Ratos Sprague-Dawley , Ratos Wistar , Sinapses/efeitos dos fármacos , Tacrina/farmacologia , Receptor Nicotínico de Acetilcolina alfa7/metabolismo
13.
J Neurosci ; 35(16): 6265-76, 2015 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-25904780

RESUMO

Alzheimer's disease (AD) and familial Danish dementia (FDD) are degenerative neurological diseases characterized by amyloid pathology. Normal human sera contain IgG antibodies that specifically bind diverse preamyloid and amyloid proteins and have shown therapeutic potential in vitro and in vivo. We cloned one of these antibodies, 3H3, from memory B cells of a healthy individual using a hybridoma method. 3H3 is an affinity-matured IgG that binds a pan-amyloid epitope, recognizing both Aß and λ Ig light chain (LC) amyloids, which are associated with AD and primary amyloidosis, respectively. The pan-amyloid-binding properties of 3H3 were demonstrated using ELISA, immunohistochemical studies, and competition binding assays. Functional studies showed that 3H3 inhibits both Aß and LC amyloid formation in vitro and abrogates disruption of hippocampal synaptic plasticity by AD-patient-derived soluble Aß in vivo. A 3H3 single-chain variable fragment (scFv) retained the binding specificity of the 3H3 IgG and, when expressed in the brains of transgenic mice using an adeno-associated virus (AAV) vector, decreased parenchymal Aß amyloid deposition in TgCRND8 mice and ADan (Danish Amyloid) cerebral amyloid angiopathy in the mouse model of FDD. These data indicate that naturally occurring human IgGs can recognize a conformational, amyloid-specific epitope and have potent anti-amyloid activities, providing a rationale to test their potential as antibody therapeutics for diverse neurological and other amyloid diseases.


Assuntos
Peptídeos beta-Amiloides/imunologia , Amiloide/metabolismo , Anticorpos Monoclonais/imunologia , Imunoglobulina G/imunologia , Amiloide/efeitos dos fármacos , Animais , Anticorpos Monoclonais/farmacologia , Encéfalo/metabolismo , Catarata/imunologia , Ataxia Cerebelar/imunologia , Angiopatia Amiloide Cerebral/imunologia , Surdez/imunologia , Demência/imunologia , Humanos , Imunoglobulina G/farmacologia , Masculino , Camundongos , Camundongos Transgênicos , Ratos
14.
Acta Neuropathol Commun ; 2: 175, 2014 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-25540024

RESUMO

Long before synaptic loss occurs in Alzheimer's disease significant harbingers of disease may be detected at the functional level. Here we examined if synaptic long-term potentiation is selectively disrupted prior to extracellular deposition of Aß in a very complete model of Alzheimer's disease amyloidosis, the McGill-R-Thy1-APP transgenic rat. Longitudinal studies in freely behaving animals revealed an age-dependent, relatively rapid-onset and persistent inhibition of long-term potentiation without a change in baseline synaptic transmission in the CA1 area of the hippocampus. Thus the ability of a standard 200 Hz conditioning protocol to induce significant NMDA receptor-dependent short- and long-term potentiation was lost at about 3.5 months of age and this deficit persisted for at least another 2-3 months, when plaques start to appear. Consistent with in vitro evidence for a causal role of a selective reduction in NMDA receptor-mediated synaptic currents, the deficit in synaptic plasticity in vivo was associated with a reduction in the synaptic burst response to the conditioning stimulation and was overcome using stronger 400 Hz stimulation. Moreover, intracerebroventricular treatment for 3 days with an N-terminally directed monoclonal anti- human Aß antibody, McSA1, transiently reversed the impairment of synaptic plasticity. Similar brief treatment with the BACE1 inhibitor LY2886721 or the γ-secretase inhibitor MRK-560 was found to have a comparable short-lived ameliorative effect when tracked in individual rats. These findings provide strong evidence that endogenously generated human Aß selectively disrupts the induction of long-term potentiation in a manner that enables potential therapeutic options to be assessed longitudinally at the pre-plaque stage of Alzheimer's disease amyloidosis.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Hipocampo/fisiopatologia , Potenciação de Longa Duração/fisiologia , Transmissão Sináptica/fisiologia , Fatores Etários , Doença de Alzheimer/fisiopatologia , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Peptídeos beta-Amiloides/imunologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/imunologia , Animais , Anticorpos/farmacologia , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Comportamento Animal/fisiologia , Modelos Animais de Doenças , Compostos Heterocíclicos com 2 Anéis/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Humanos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Ácidos Picolínicos/farmacologia , Ratos , Ratos Transgênicos , Ratos Wistar , Sulfonamidas/farmacologia , Transmissão Sináptica/efeitos dos fármacos
15.
Biochem J ; 461(3): 413-26, 2014 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-24785004

RESUMO

Dimers of Aß (amyloid ß-protein) are believed to play an important role in Alzheimer's disease. In the absence of sufficient brain-derived dimers, we studied one of the only possible dimers that could be produced in vivo, [Aß](DiY) (dityrosine cross-linked Aß). For comparison, we used the Aß monomer and a design dimer cross-linked by replacement of Ser²6 with cystine [AßS26C]2. We showed that similar to monomers, unaggregated dimers lack appreciable structure and fail to alter long-term potentiation. Importantly, dimers exhibit subtly different structural propensities from monomers and each other, and can self-associate to form larger assemblies. Although [Aß](DiY) and [AßS26C]2 have distinct aggregation pathways, they both populate bioactive soluble assemblies for longer durations than Aß monomers. Our results indicate that the link between Aß dimers and Alzheimer's disease results from the ability of dimers to further assemble and form synaptotoxic assemblies that persist for long periods of time.


Assuntos
Doença de Alzheimer/induzido quimicamente , Peptídeos beta-Amiloides/toxicidade , Cerebelo/efeitos dos fármacos , Proteínas do Tecido Nervoso/toxicidade , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/toxicidade , Sinapses/efeitos dos fármacos , Doença de Alzheimer/metabolismo , Substituição de Aminoácidos , Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Animais , Cerebelo/metabolismo , Dimerização , Potenciais Evocados/efeitos dos fármacos , Humanos , Injeções Intraventriculares , Cinética , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Ressonância Magnética Nuclear Biomolecular , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Conformação Proteica , Multimerização Proteica , Ratos , Ratos Wistar , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/toxicidade , Solubilidade , Sinapses/metabolismo
16.
J Neurosci ; 34(18): 6140-5, 2014 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-24790184

RESUMO

Alzheimer's disease (AD) is associated with pathological assembly states of amyloid-ß protein (Aß). Aß-related synaptotoxicity can be blocked by anti-prion protein (PrP) antibodies, potentially allowing therapeutic targeting of this aspect of AD neuropathogenesis. Here, we show that intravascular administration of a high-affinity humanized anti-PrP antibody to rats can prevent the plasticity-disrupting effects induced by exposure to soluble AD brain extract. These results provide an in vivo proof of principle for such a therapeutic strategy.


Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/farmacologia , Anticorpos Monoclonais/administração & dosagem , Região CA1 Hipocampal/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Príons/imunologia , Idoso de 80 Anos ou mais , Análise de Variância , Animais , Biofísica , Vias de Administração de Medicamentos , Estimulação Elétrica , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Masculino , Príons/metabolismo , Ratos , Ratos Wistar , Lobo Temporal/química , Lobo Temporal/metabolismo
17.
Biochemistry ; 53(24): 3908-21, 2014 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-24840308

RESUMO

Evidence for a central role of amyloid ß-protein (Aß) in the genesis of Alzheimer's disease (AD) has led to advanced human trials of Aß-lowering agents. The "amyloid hypothesis" of AD postulates deleterious effects of small, soluble forms of Aß on synaptic form and function. Because selectively targeting synaptotoxic forms of soluble Aß could be therapeutically advantageous, it is important to understand the full range of soluble Aß derivatives. We previously described a Chinese hamster ovary (CHO) cell line (7PA2 cells) that stably expresses mutant human amyloid precursor protein (APP). Here, we extend this work by purifying an sodium dodecyl sulfate (SDS)-stable, ∼8 kDa Aß species from the 7PA2 medium. Mass spectrometry confirmed its identity as a noncovalently bonded Aß40 homodimer that impaired hippocampal long-term potentiation (LTP) in vivo. We further report the detection of Aß-containing fragments of APP in the 7PA2 medium that extend N-terminal from Asp1 of Aß. These N-terminally extended Aß-containing monomeric fragments are distinct from soluble Aß oligomers formed from Aß1-40/42 monomers and are bioactive synaptotoxins secreted by 7PA2 cells. Importantly, decreasing ß-secretase processing of APP elevated these alternative synaptotoxic APP fragments. We conclude that certain synaptotoxic Aß-containing species can arise from APP processing events N-terminal to the classical ß-secretase cleavage site.


Assuntos
Peptídeos beta-Amiloides/fisiologia , Precursor de Proteína beta-Amiloide/metabolismo , Plasticidade Neuronal , Sinapses/efeitos dos fármacos , Doença de Alzheimer/fisiopatologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/isolamento & purificação , Peptídeos beta-Amiloides/farmacologia , Peptídeos beta-Amiloides/toxicidade , Animais , Células CHO , Células Cultivadas , Cricetinae , Cricetulus , Meios de Cultivo Condicionados , Humanos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Camundongos , Plasticidade Neuronal/efeitos dos fármacos , Fragmentos de Peptídeos , Ratos
18.
Nat Commun ; 5: 3374, 2014 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-24594908

RESUMO

NMDA-type glutamate receptors (NMDARs) are currently regarded as paramount in the potent and selective disruption of synaptic plasticity by Alzheimer's disease amyloid ß-protein (Aß). Non-NMDAR mechanisms remain relatively unexplored. Here we describe how Aß facilitates NMDAR-independent long-term depression of synaptic transmission in the hippocampus in vivo. Synthetic Aß and Aß in soluble extracts of Alzheimer's disease brain usurp endogenous acetylcholine muscarinic receptor-dependent long-term depression, to enable long-term depression that required metabotropic glutamate-5 receptors (mGlu5Rs). We also find that mGlu5Rs are essential for Aß-mediated inhibition of NMDAR-dependent long-term potentiation in vivo. Blocking Aß binding to cellular prion protein with antibodies prevents the facilitation of long-term depression. Our findings uncover an overarching role for Aß-PrP(C)-mGlu5R interplay in mediating both LTD facilitation and LTP inhibition, encompassing NMDAR-mediated processes that were previously considered primary.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Depressão Sináptica de Longo Prazo/fisiologia , Receptor de Glutamato Metabotrópico 5/metabolismo , Animais , Hipocampo/metabolismo , Masculino , Príons/metabolismo , Ratos , Ratos Wistar , Receptor de Glutamato Metabotrópico 5/genética
19.
Philos Trans R Soc Lond B Biol Sci ; 369(1633): 20130147, 2014 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-24298149

RESUMO

Many endogenous factors influence the time course and extent of the detrimental effects of amyloid ß-protein (Aß) on synaptic function. Here, we assessed the impact of varying endogenous glutamatergic and cholinergic transmission by pharmacological means on the disruption of plasticity at hippocampal CA3-to-CA1 synapses in the anaesthetized rat. NMDA receptors (NMDARs) are considered critical in mediating Aß-induced inhibition of long-term potentiation (LTP). However, intracerebroventricular injection of Aß1-42 inhibited not only NMDAR-dependent LTP but also voltage-activated Ca(2+)-dependent LTP induced by strong conditioning stimulation during NMDAR blockade. On the other hand, another form of NMDAR-independent synaptic plasticity, endogenous acetylcholine-induced muscarinic receptor-dependent long-term enhancement, was not hindered by Aß1-42. Interestingly, augmenting endogenous acetylcholine activation of nicotinic receptors prior to the injection of Aß1-42 prevented the inhibition of NMDAR-dependent LTP, whereas the same intervention when introduced after the infusion of Aß was ineffective. We also examined the duration of action of Aß, including water soluble Aß from Alzheimer's disease (AD) brain. Remarkably, the inhibition of LTP induction caused by a single injection of sodium dodecyl sulfate-stable Aß dimer-containing AD brain extract persisted for at least a week. These findings highlight the need to increase our understanding of non-NMDAR mechanisms and of developing novel means of overcoming, rather than just preventing, the deleterious synaptic actions of Aß.


Assuntos
Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/metabolismo , Hipocampo/fisiologia , Potenciação de Longa Duração/fisiologia , Fragmentos de Peptídeos/metabolismo , Sinapses/fisiologia , Acetilcolina/metabolismo , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/farmacologia , Análise de Variância , Animais , Química Encefálica , Potenciais Pós-Sinápticos Excitadores/fisiologia , Líquido Extracelular/metabolismo , Humanos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores Nicotínicos/metabolismo , Sinapses/efeitos dos fármacos
20.
Mol Brain ; 6: 47, 2013 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-24284042

RESUMO

BACKGROUND: Exosomes, small extracellular vesicles of endosomal origin, have been suggested to be involved in both the metabolism and aggregation of Alzheimer's disease (AD)-associated amyloid ß-protein (Aß). Despite their ubiquitous presence and the inclusion of components which can potentially interact with Aß, the role of exosomes in regulating synaptic dysfunction induced by Aß has not been explored. RESULTS: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aß. Mechanistically, this effect involves sequestration of synaptotoxic Aß assemblies by exosomal surface proteins such as PrPC rather than Aß proteolysis. CONCLUSIONS: These data suggest that exosomes can counteract the inhibitory action of Aß, which contributes to perpetual capability for synaptic plasticity.


Assuntos
Peptídeos beta-Amiloides/toxicidade , Exossomos/metabolismo , Plasticidade Neuronal , Sinapses/metabolismo , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Líquido Cefalorraquidiano/metabolismo , Difusão , Exossomos/efeitos dos fármacos , Feminino , Humanos , Ligantes , Potenciação de Longa Duração , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Plasticidade Neuronal/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Proteínas PrPC/metabolismo , Ratos , Ratos Wistar , Sinapses/efeitos dos fármacos
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