RESUMO
Amyloid ß protein (Aß) and tau, the two main proteins implicated in causing Alzheimer's disease (AD), are posited to trigger synaptic dysfunction long before significant synaptic loss occurs in vulnerable circuits. Whereas soluble Aß aggregates from AD brain are well recognized potent synaptotoxins, less is known about the synaptotoxicity of soluble tau from AD or other tauopathy patient brains. Minimally manipulated patient-derived aqueous brain extracts contain the more diffusible native forms of these proteins. Here, we explore how intracerebral injection of Aß and tau present in such aqueous extracts of patient brain contribute to disruption of synaptic plasticity in the CA1 area of the male rat hippocampus. Aqueous extracts of certain AD brains acutely inhibited long-term potentiation (LTP) of synaptic transmission in a manner that required both Aß and tau. Tau-containing aqueous extracts of a brain from a patient with Pick's disease (PiD) also impaired LTP, and diffusible tau from either AD or PiD brain lowered the threshold for AD brain Aß to inhibit LTP. Remarkably, the disruption of LTP persisted for at least 2 weeks after a single injection. These findings support a critical role for diffusible tau in causing rapid onset, persistent synaptic plasticity deficits, and promoting Aß-mediated synaptic dysfunction.SIGNIFICANCE STATEMENT The microtubule-associated protein tau forms relatively insoluble fibrillar deposits in the brains of people with neurodegenerative diseases including Alzheimer's and Pick's diseases. More soluble aggregates of disease-associated tau may diffuse between cells and could cause damage to synapses in vulnerable circuits. We prepared aqueous extracts of diseased cerebral cortex and tested their ability to interfere with synaptic function in the brains of live rats. Tau in these extracts rapidly and persistently disrupted synaptic plasticity and facilitated impairments caused by amyloid ß protein, the other major pathologic protein in Alzheimer's disease. These findings show that certain diffusible forms of tau can mediate synaptic dysfunction and may be a target for therapy.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Masculino , Ratos , Animais , Peptídeos beta-Amiloides/metabolismo , Potenciação de Longa Duração , Doença de Alzheimer/metabolismo , Proteínas tau/metabolismo , Plasticidade Neuronal , Sinapses/metabolismo , Hipocampo/metabolismo , Encéfalo/metabolismoRESUMO
Neurodegenerative diseases are an enormous public health problem, affecting tens of millions of people worldwide. Nearly all of these diseases are characterized by oligomerization and fibrillization of neuronal proteins, and there is great interest in therapeutic targeting of these aggregates. Here, we show that soluble aggregates of α-synuclein and tau bind to plate-immobilized PrP in vitro and on mouse cortical neurons, and that this binding requires at least one of the same N-terminal sites at which soluble Aß aggregates bind. Moreover, soluble aggregates of tau, α-synuclein and Aß cause both functional (impairment of LTP) and structural (neuritic dystrophy) compromise and these deficits are absent when PrP is ablated, knocked-down, or when neurons are pre-treated with anti-PrP blocking antibodies. Using an all-human experimental paradigm involving: (1) isogenic iPSC-derived neurons expressing or lacking PRNP, and (2) aqueous extracts from brains of individuals who died with Alzheimer's disease, dementia with Lewy bodies, and Pick's disease, we demonstrate that Aß, α-synuclein and tau are toxic to neurons in a manner that requires PrPC. These results indicate that PrP is likely to play an important role in a variety of late-life neurodegenerative diseases and that therapeutic targeting of PrP, rather than individual disease proteins, may have more benefit for conditions which involve the aggregation of more than one protein.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Doenças Neurodegenerativas/metabolismo , Neurônios/metabolismo , Príons/metabolismo , alfa-Sinucleína/metabolismo , Proteínas tau/metabolismo , Animais , Encéfalo/metabolismo , Humanos , Camundongos , Ligação ProteicaRESUMO
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 , RatosRESUMO
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/farmacologiaRESUMO
Compelling genetic evidence links the amyloid precursor protein (APP) to Alzheimer's disease (AD) and several theories have been advanced to explain the relationship. A leading hypothesis proposes that a small amphipathic fragment of APP, the amyloid ß-protein (Aß), self-associates to form soluble aggregates that impair synaptic and network activity. Here, we used the most disease-relevant form of Aß, protein isolated from AD brain. Using this material, we show that the synaptotoxic effects of Aß depend on expression of APP and that the Aß-mediated impairment of synaptic plasticity is accompanied by presynaptic effects that disrupt the excitatory/inhibitory (E/I) balance. The net increase in the E/I ratio and inhibition of plasticity are associated with Aß localizing to synapses and binding of soluble Aß aggregates to synapses requires the expression of APP. Our findings indicate a role for APP in AD pathogenesis beyond the generation of Aß and suggest modulation of APP expression as a therapy for AD.SIGNIFICANCE STATEMENT Here, we report on the plasticity-disrupting effects of amyloid ß-protein (Aß) isolated from Alzheimer's disease (AD) brain and the requirement of amyloid precursor protein (APP) for these effects. We show that Aß-containing AD brain extracts block hippocampal LTP, augment glutamate release probability, and disrupt the excitatory/inhibitory balance. These effects are associated with Aß localizing to synapses and genetic ablation of APP prevents both Aß binding and Aß-mediated synaptic dysfunctions. Our results emphasize the importance of APP in AD and should stimulate new studies to elucidate APP-related targets suitable for pharmacological manipulation.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/biossíntese , Encéfalo/metabolismo , Plasticidade Neuronal/fisiologia , Fragmentos de Peptídeos/metabolismo , Sinapses/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Precursor de Proteína beta-Amiloide/deficiência , Animais , Encéfalo/patologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pessoa de Meia-Idade , Técnicas de Cultura de Órgãos , Ligação Proteica/fisiologia , Sinapses/patologiaRESUMO
Voltage-gated ion channels are critical for neuronal integration. Some of these channels, however, are misregulated in several neurological disorders, causing both gain- and loss-of-function channelopathies in neurons. Using several transgenic mouse models of Alzheimer's disease (AD), we find that sub-threshold voltage signals strongly influenced by hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels progressively deteriorate over chronological aging in hippocampal CA1 pyramidal neurons. The degraded signaling via HCN channels in the transgenic mice is accompanied by an age-related global loss of their non-uniform dendritic expression. Both the aberrant signaling via HCN channels and their mislocalization could be restored using a variety of pharmacological agents that target the endoplasmic reticulum (ER). Our rescue of the HCN channelopathy helps provide molecular details into the favorable outcomes of ER-targeting drugs on the pathogenesis and synaptic/cognitive deficits in AD mouse models, and implies that they might have beneficial effects on neurological disorders linked to HCN channelopathies.
Assuntos
Doença de Alzheimer/fisiopatologia , Região CA1 Hipocampal/fisiologia , Canalopatias/fisiopatologia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/fisiologia , Plasticidade Neuronal , Células Piramidais/fisiologia , Potenciais de Ação , Envelhecimento , Animais , Região CA1 Hipocampal/ultraestrutura , Modelos Animais de Doenças , Retículo Endoplasmático/fisiologia , Feminino , Masculino , Camundongos Transgênicos , Células Piramidais/ultraestruturaRESUMO
Amyloid precursor protein (APP) derivative ß-amyloid (Aß) plays an important role in the pathogenesis of Alzheimer's disease (AD). Sequential proteolysis of APP by ß-secretase and γ-secretase generates Aß. Conversely, the α-secretase "a disintegrin and metalloproteinase" 10 (ADAM10) cleaves APP within the eventual Aß sequence and precludes Aß generation. Therefore, up-regulation of ADAM10 represents a plausible therapeutic strategy to combat overproduction of neurotoxic Aß. Peroxisome proliferator-activated receptor α (PPARα) is a transcription factor that regulates genes involved in fatty acid metabolism. Here, we determined that the Adam10 promoter harbors PPAR response elements; that knockdown of PPARα, but not PPARß or PPARγ, decreases the expression of Adam10; and that lentiviral overexpression of PPARα restored ADAM10 expression in Ppara(-/-) neurons. Gemfibrozil, an agonist of PPARα, induced the recruitment of PPARα:retinoid x receptor α, but not PPARγ coactivator 1α (PGC1α), to the Adam10 promoter in wild-type mouse hippocampal neurons and shifted APP processing toward the α-secretase, as determined by augmented soluble APPα and decreased Aß production. Accordingly, Ppara(-/-) mice displayed elevated SDS-stable, endogenous Aß and Aß1-42 relative to wild-type littermates, whereas 5XFAD mice null for PPARα (5X/α(-/-)) exhibited greater cerebral Aß load relative to 5XFAD littermates. These results identify PPARα as an important factor regulating neuronal ADAM10 expression and, thus, α-secretase proteolysis of APP.
Assuntos
Proteínas ADAM/metabolismo , Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Membrana/metabolismo , PPAR alfa/metabolismo , Proteínas ADAM/genética , Proteína ADAM10 , Doença de Alzheimer/genética , Secretases da Proteína Precursora do Amiloide/genética , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Células Cultivadas , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Immunoblotting , Estimativa de Kaplan-Meier , Masculino , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Microscopia de Fluorescência , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , PPAR alfa/agonistas , PPAR alfa/genética , Proteólise , Pirimidinas/farmacologia , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Progressive cerebral accumulation of tau aggregates is a defining feature of Alzheimer's disease (AD). A popular theory that seeks to explain the apparent spread of neurofibrillary tangle pathology proposes that aggregated tau is passed from neuron to neuron. Such a templated seeding process requires that the transferred tau contains the microtubule binding repeat domains that are necessary for aggregation. While it is not clear how a protein such as tau can move from cell to cell, previous reports have suggested that this may involve extracellular vesicles (EVs). Thus, measurement of tau in EVs may both provide insights on the molecular pathology of AD and facilitate biomarker development. Here, we report the use of sensitive immunoassays specific for full-length (FL) tau and mid-region tau, which we applied to analyze EVs from human induced pluripotent stem cell (iPSC)-derived neuron (iN) conditioned media, cerebrospinal fluid (CSF), and plasma. In each case, most tau was free-floating with a small component inside EVs. The majority of free-floating tau detected by the mid-region assay was not detected by our FL assays, indicating that most free-floating tau is truncated. Inside EVs, the mid-region assay also detected more tau than the FL assay, but the ratio of FL-positive to mid-region-positive tau was higher inside exosomes than in free solution. These studies demonstrate the presence of minute amounts of free-floating and exosome-contained FL tau in human biofluids. Given the potential for FL tau to aggregate, we conclude that further investigation of these pools of extracellular tau and how they change during disease is merited.
Assuntos
Vesículas Extracelulares/metabolismo , Neurônios/metabolismo , Agregados Proteicos , Agregação Patológica de Proteínas , Proteínas tau/metabolismo , Idoso , Idoso de 80 Anos ou mais , Alelos , Doença de Alzheimer/sangue , Doença de Alzheimer/líquido cefalorraquidiano , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Apolipoproteínas E/genética , Biomarcadores/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Estudos de Casos e Controles , Diferenciação Celular , Disfunção Cognitiva/sangue , Disfunção Cognitiva/líquido cefalorraquidiano , Disfunção Cognitiva/metabolismo , Exossomos/metabolismo , Feminino , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Masculino , Neurônios/citologia , Proteínas tau/líquido cefalorraquidianoRESUMO
Neurotrophins, such as brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), are believed to be genuine molecular mediators of neuronal growth and homeostatic synapse activity. However, levels of these neurotrophic factors decrease in different brain regions of patients with Alzheimer disease (AD). Induction of astrocytic neurotrophin synthesis is a poorly understood phenomenon but represents a plausible therapeutic target because neuronal neurotrophin production is aberrant in AD and other neurodegenerative diseases. Here, we delineate that sodium phenylbutyrate (NaPB), a Food and Drug Administration-approved oral medication for hyperammonemia, induces astrocytic BDNF and NT-3 expression via the protein kinase C (PKC)-cAMP-response element-binding protein (CREB) pathway. NaPB treatment increased the direct association between PKC and CREB followed by phosphorylation of CREB (Ser(133)) and induction of DNA binding and transcriptional activation of CREB. Up-regulation of markers for synaptic function and plasticity in cultured hippocampal neurons by NaPB-treated astroglial supernatants and its abrogation by anti-TrkB blocking antibody suggest that NaPB-induced astroglial neurotrophins are functionally active. Moreover, oral administration of NaPB increased the levels of BDNF and NT-3 in the CNS and improved spatial learning and memory in a mouse model of AD. Our results highlight a novel neurotrophic property of NaPB that may be used to augment neurotrophins in the CNS and improve synaptic function in disease states such as AD.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Astrócitos/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Neurotrofina 3/metabolismo , Fenilbutiratos/farmacologia , Administração Oral , Doença de Alzheimer/metabolismo , Doença de Alzheimer/psicologia , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/fisiologia , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Forma Celular , Células Cultivadas , Formiatos/farmacologia , Proteína Glial Fibrilar Ácida/metabolismo , Hipocampo/patologia , Humanos , Masculino , Memória/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurotrofina 3/genética , Fenilbutiratos/administração & dosagem , Fosforilação , Cultura Primária de Células , Proteína Quinase C , Processamento de Proteína Pós-Traducional , Receptores de Fator de Crescimento Neural/genética , Receptores de Fator de Crescimento Neural/metabolismo , Regulação para Cima/efeitos dos fármacosRESUMO
Chronic inflammation is becoming a hallmark of several neurodegenerative disorders and accordingly, IL-1ß, a proinflammatory cytokine, is implicated in the pathogenesis of neurodegenerative diseases. Although IL-1ß binds to its high-affinity receptor, IL-1R, and upregulates proinflammatory signaling pathways, IL-1R antagonist (IL-1Ra) adheres to the same receptor and inhibits proinflammatory cell signaling. Therefore, upregulation of IL-1Ra is considered important in attenuating inflammation. The present study underlines a novel application of gemfibrozil (gem), a Food and Drug Administration-approved lipid-lowering drug, in increasing the expression of IL-1Ra in primary mouse and human neurons. Gem alone induced an early and pronounced increase in the expression of IL-1Ra in primary mouse cortical neurons. Activation of type IA p110α PI3K and Akt by gem and abrogation of gem-induced upregulation of IL-1Ra by inhibitors of PI3K and Akt indicate a role of the PI3K-Akt pathway in the upregulation of IL-1Ra. Gem also induced the activation of CREB via the PI3K-Akt pathway, and small interfering RNA attenuation of CREB abolished the gem-mediated increase in IL-1Ra. Furthermore, gem was able to protect neurons from IL-1ß insult. However, small interfering RNA knockdown of neuronal IL-1Ra abrogated the protective effect of gem against IL-1ß, suggesting that this drug increases the defense mechanism of cortical neurons via upregulation of IL-1Ra. Taken together, these results highlight the importance of the PI3K-Akt-CREB pathway in mediating gem-induced upregulation of IL-1Ra in neurons and suggest gem as a possible therapeutic treatment for propagating neuronal self-defense in neuroinflammatory and neurodegenerative disorders.
Assuntos
Córtex Cerebral/imunologia , Genfibrozila/uso terapêutico , Hipolipemiantes/uso terapêutico , Proteína Antagonista do Receptor de Interleucina 1/biossíntese , Doenças Neurodegenerativas/tratamento farmacológico , Neurônios/imunologia , Regulação para Cima/imunologia , Animais , Proteínas Reguladoras de Apoptose/antagonistas & inibidores , Proteínas Reguladoras de Apoptose/fisiologia , Proteínas Reguladoras de Apoptose/uso terapêutico , Células Cultivadas , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , Humanos , Mediadores da Inflamação/antagonistas & inibidores , Mediadores da Inflamação/fisiologia , Mediadores da Inflamação/uso terapêutico , Proteína Antagonista do Receptor de Interleucina 1/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Doenças Neurodegenerativas/imunologia , Doenças Neurodegenerativas/patologia , Neurônios/enzimologia , Neurônios/patologia , Fosfatidilinositol 3-Quinase/fisiologia , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-akt/fisiologia , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/imunologia , Regulação para Cima/efeitos dos fármacosRESUMO
The classical late infantile neuronal ceroid lipofuscinosis (LINCLs) is an autosomal recessive disease, where the defective gene is Cln2, encoding tripeptidyl-peptidase I (TPP1). At the molecular level, LINCL is caused by accumulation of autofluorescent storage materials in neurons and other cell types. Currently, there is no established treatment for this fatal disease. This study reveals a novel use of gemfibrozil and fenofibrate, Food and Drug Administration-approved lipid-lowering drugs, in up-regulating TPP1 in brain cells. Both gemfibrozil and fenofibrate up-regulated mRNA, protein, and enzymatic activity of TPP1 in primary mouse neurons and astrocytes as well as human astrocytes and neuronal cells. Because gemfibrozil and fenofibrate are known to activate peroxisome proliferator-activated receptor-α (PPARα), the role of PPARα in gemfibrozil- and fenofibrate-mediated up-regulation of TPP1 was investigated revealing that both drugs up-regulated TPP1 mRNA, protein, and enzymatic activity both in vitro and in vivo in wild type (WT) and PPARß(-/-), but not PPARα(-/-), mice. In an attempt to delineate the mechanism of TPP1 up-regulation, it was found that the effects of the fibrate drugs were abrogated in the absence of retinoid X receptor-α (RXRα), a molecule known to form a heterodimer with PPARα. Accordingly, all-trans-retinoic acid, alone or together with gemfibrozil, up-regulated TPP1. Co-immunoprecipitation and ChIP studies revealed the formation of a PPARα/RXRα heterodimer and binding of the heterodimer to an RXR-binding site on the Cln2 promoter. Together, this study demonstrates a unique mechanism for the up-regulation of TPP1 by fibrate drugs via PPARα/RXRα pathway.
Assuntos
Aminopeptidases/biossíntese , Encéfalo/efeitos dos fármacos , Dipeptidil Peptidases e Tripeptidil Peptidases/biossíntese , Fenofibrato/farmacologia , Genfibrozila/farmacologia , Lipofuscinoses Ceroides Neuronais/tratamento farmacológico , PPAR alfa/metabolismo , Serina Proteases/biossíntese , Regulação para Cima , Animais , Astrócitos/metabolismo , Encéfalo/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Hipolipemiantes/farmacologia , Lisossomos/metabolismo , Camundongos , Lipofuscinoses Ceroides Neuronais/metabolismo , Neurônios/metabolismo , Receptor X Retinoide alfa/metabolismo , Tripeptidil-Peptidase 1RESUMO
BACKGROUND: The prion protein (PrP) is known to bind certain soluble aggregates of the amyloid ß-protein (Aß), and two regions of PrP, one centered around residues 19-33, and the other around 87-112, are thought to be particularly important for this interaction. When either of these sequences are grafted into a human IgG the resulting antibodies react with disease-associated PrP conformers, whereas the parental b12 IgG does not. METHODS: Human antibodies containing grafts of PrP 19-33 or 87-112 were prepared as before (Solforosi et al., 2007) and tested for their ability to recognize synthetic and Alzheimer's disease (AD) brain-derived Aß. Since aqueous extracts of AD brain contain a complex mixture of active and inactive Aß species, we also assessed whether PrP-grafted antibodies could protect against neuritotoxicity mediated by AD brain-derived Aß. For these experiments, human iPSC-derived neurons were grown in 96-well plates at 5000 cells per well and on post-induction day 21, AD brain extracts were added +/- test antibodies. Neurons were imaged for 3â¯days using an IncuCyte live-cell imaging system, and neurite number and density quantified. RESULTS: Grafted antibodies bound a significant portion of aggregated Aß in aqueous AD extracts, but when these antibodies were co-incubated with neurons treated with brain extracts they did not reduce toxicity. By contrast, the PrP fragment N1 did protect against Aß. CONCLUSIONS: These results further demonstrate that not all Aß oligomers are toxic and suggest that PrP derivatives may allow development of agents that differentially recognize toxic and innocuous Aß aggregates.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/farmacologia , Anticorpos/farmacologia , Encéfalo/metabolismo , Proteínas Priônicas/farmacologia , Agregação Patológica de Proteínas/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Anticorpos/genética , Anticorpos/metabolismo , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Feminino , Humanos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Proteínas Priônicas/genética , Proteínas Priônicas/metabolismo , Ligação ProteicaRESUMO
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 , RatosRESUMO
Induction of TLR2 activation depends on its association with the adapter protein MyD88. We have found that TLR2 and MyD88 levels are elevated in the hippocampus and cortex of patients with Alzheimer's disease (AD) and in a 5XFAD mouse model of AD. Since there is no specific inhibitor of TLR2, to target induced TLR2 from a therapeutic angle, we engineered a peptide corresponding to the TLR2-interacting domain of MyD88 (TIDM) that binds to the BB loop of only TLR2, and not other TLRs. Interestingly, WT TIDM peptide inhibited microglial activation induced by fibrillar Aß1-42 and lipoteichoic acid, but not 1-methyl-4-phenylpyridinium, dsRNA, bacterial lipopolysaccharide, flagellin, or CpG DNA. After intranasal administration, WT TIDM peptide reached the hippocampus, reduced hippocampal glial activation, lowered Aß burden, attenuated neuronal apoptosis, and improved memory and learning in 5XFAD mice. However, WT TIDM peptide was not effective in 5XFAD mice lacking TLR2. In addition to its effects in 5XFAD mice, WT TIDM peptide also suppressed the disease process in mice with experimental allergic encephalomyelitis and collagen-induced arthritis. Therefore, selective targeting of the activated status of 1 component of the innate immune system by WT TIDM peptide may be beneficial in AD as well as other disorders in which TLR2/MyD88 signaling plays a role in disease pathogenesis.
Assuntos
Doença de Alzheimer , Hipocampo/metabolismo , Fator 88 de Diferenciação Mieloide/metabolismo , Peptídeos/farmacologia , Receptor 2 Toll-Like/metabolismo , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides , Animais , Modelos Animais de Doenças , Feminino , Hipocampo/patologia , Humanos , Inflamação/genética , Inflamação/metabolismo , Inflamação/patologia , Masculino , Camundongos , Camundongos Transgênicos , Fator 88 de Diferenciação Mieloide/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Receptor 2 Toll-Like/genéticaRESUMO
A major challenge for clinical application of pluripotent stem cell therapy for Parkinson's disease (PD) is large-scale manufacturing and cryopreservation of neurons that can be efficiently prepared with minimal manipulation. To address this obstacle, midbrain dopamine neurons were derived from human induced pluripotent stem cells (iPSC-mDA) and cryopreserved in large production lots for biochemical and transplantation studies. Cryopreserved, post-mitotic iPSC-mDA neurons retained high viability with gene, protein, and electrophysiological signatures consistent with midbrain floor-plate lineage. To test therapeutic efficacy, cryopreserved iPSC-mDA neurons were transplanted without subculturing into the 6-OHDA-lesioned rat and MPTP-lesioned non-human-primate models of PD. Grafted neurons retained midbrain lineage with extensive fiber innervation in both rodents and monkeys. Behavioral assessment in 6-OHDA-lesioned rats demonstrated significant reversal in functional deficits up to 6 months post transplantation with reinnervation of the host striatum and no aberrant growth, supporting the translational development of pluripotent cell-based therapies in PD.
Assuntos
Criopreservação , Neurônios Dopaminérgicos/citologia , Neurônios Dopaminérgicos/transplante , Células-Tronco Pluripotentes Induzidas/citologia , Doença de Parkinson/terapia , Animais , Linhagem Celular , Corpo Estriado/citologia , Corpo Estriado/patologia , Criopreservação/métodos , Modelos Animais de Doenças , Dopamina/metabolismo , Neurônios Dopaminérgicos/metabolismo , Haplorrinos , Humanos , Mesencéfalo/citologia , Mesencéfalo/patologia , Neurogênese , Doença de Parkinson/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Neurotrophins are important for neuronal health and function. Here, statins, inhibitors of HMG-CoA reductase and cholesterol lowering drugs, were found to stimulate expression of neurotrophins in brain cells independent of the mevalonate pathway. Time-resolved fluorescence resonance energy transfer (FRET) analyses, computer-derived simulation, site-directed mutagenesis, thermal shift assay, and de novo binding followed by electrospray ionization tandem mass spectrometry (ESI-MS) demonstrates that statins serve as ligands of PPARα and that Leu331 and Tyr 334 residues of PPARα are important for statin binding. Upon binding, statins upregulate neurotrophins via PPARα-mediated transcriptional activation of cAMP-response element binding protein (CREB). Accordingly, simvastatin increases CREB and brain-derived neurotrophic factor (BDNF) in the hippocampus of Ppara null mice receiving full-length lentiviral PPARα, but not L331M/Y334D statin-binding domain-mutated lentiviral PPARα. This study identifies statins as ligands of PPARα, describes neurotrophic function of statins via the PPARα-CREB pathway, and analyzes the importance of PPARα in the therapeutic success of simvastatin in an animal model of Alzheimer's disease.
Assuntos
Encéfalo/metabolismo , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Memória/efeitos dos fármacos , Fatores de Crescimento Neural/biossíntese , PPAR alfa/metabolismo , Sinvastatina/farmacologia , Regulação para Cima/efeitos dos fármacos , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Encéfalo/patologia , Humanos , Camundongos , Camundongos Mutantes , Fatores de Crescimento Neural/genética , Neurônios/metabolismo , Neurônios/patologia , PPAR alfa/genéticaRESUMO
Alzheimer's disease (AD) is the most common form of dementia. Despite intense investigations, no effective therapy is available to halt its progression. We found that NF-κB was activated within the hippocampus and cortex of AD subjects and that activated forms of NF-κB negatively correlated with cognitive function monitored by Mini-Mental State Examination and global cognitive z score. Accordingly, NF-κB activation was also observed in the hippocampus of a transgenic (5XFAD) mouse model of AD. It has been shown that peptides corresponding to the NF-κB essential modifier (NEMO)-binding domain (NBD) of IκB kinase α (IKKα) or IκB kinase ß (IKKß) specifically inhibit the induction of NF-κB activation without inhibiting the basal NF-κB activity. Interestingly, after intranasal administration, wild-type NBD peptide entered into the hippocampus, reduced hippocampal activation of NF-κB, suppressed hippocampal microglial activation, lowered the burden of Aß in the hippocampus, attenuated apoptosis of hippocampal neurons, protected plasticity-related molecules, and improved memory and learning in 5XFAD mice. Mutated NBD peptide had no such protective effect, indicating the specificity of our finding. These results suggest that selective targeting of NF-κB activation by intranasal administration of NBD peptide may be of therapeutic benefit for AD patients.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Hipocampo/efeitos dos fármacos , Transtornos da Memória/prevenção & controle , Nootrópicos/administração & dosagem , Peptídeos/administração & dosagem , Administração Intranasal , Adulto , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Animais , Disfunção Cognitiva/tratamento farmacológico , Disfunção Cognitiva/patologia , Disfunção Cognitiva/fisiopatologia , Modelos Animais de Doenças , Feminino , Hipocampo/patologia , Hipocampo/fisiopatologia , Humanos , Masculino , Transtornos da Memória/patologia , Transtornos da Memória/fisiopatologia , Camundongos Transgênicos , Pessoa de Meia-IdadeRESUMO
Peroxisome proliferator-activated receptor α (PPARα) is a transcription factor that regulates genes involved in fatty acid catabolism. Here, we provide evidence that PPARα is constitutively expressed in nuclei of hippocampal neurons and, surprisingly, controls calcium influx and the expression of various plasticity-related genes via direct transcriptional regulation of cyclic AMP response element binding (CREB). Accordingly, Pparα-null, but not Pparß-null, mice are deficient in CREB and memory-associated proteins and have decreased spatial learning and memory. Small hairpin RNA knockdown of PPARα in the hippocampus suppressed CREB and NR2A, rendering wild-type animals markedly poor in consolidating spatial memory, whereas introduction of PPARα to the hippocampus of Pparα-null mice increased hippocampal CREB and NR2A and improved spatial learning and memory. Through detailed analyses of CREB and NR2A activity, as well as spatial learning and memory in bone marrow chimeric animals lacking PPARα in the CNS, we uncover a mechanism for transcriptional control of Creb and associated plasticity genes by PPARα.