RESUMO
Current research including the basic biology of Alzheimer's disease (AD) provides a foundation to explore whether our current state of knowledge is sufficient to initiate prevention studies and allow us to believe prevention of AD is possible. Current research and recently revised criteria for the diagnosis of AD by the National Institutes on Aging and the Alzheimer's Association suggest a continuum of disease from preclinical asymptomatic to symptomatic Alzheimer's dementia. In light of these revised criteria, the possibility of secondary prevention and even primary prevention is under discussion. The Alzheimer's Association Research Roundtable convened a meeting to discuss the rationale and feasibility of conducting secondary prevention trials in AD.
Assuntos
Doença de Alzheimer/prevenção & controle , Ensaios Clínicos como Assunto , Prevenção Secundária/métodos , HumanosRESUMO
Positron emission tomography (PET) of brain amyloid b is a technology that is becoming more available, but its clinical utility in medical practice requires careful definition. To provide guidance to dementia care practitioners, patients, and caregivers, the Alzheimer's Association and the Society of Nuclear Medicine and Molecular Imaging convened the Amyloid Imaging Taskforce (AIT). The AIT considered a broad range of specific clinical scenarios in which amyloid PET could potentially be used appropriately. Peer-reviewed, published literature was searched to ascertain available evidence relevant to these scenarios, and the AIT developed a consensus of expert opinion. Although empirical evidence of impact on clinical outcomes is not yet available, a set of specific appropriate use criteria (AUC) were agreed on that define the types of patients and clinical circumstances in which amyloid PET could be used. Both appropriate and inappropriate uses were considered and formulated,and are reported and discussed here. Because both dementia care and amyloid PET technology are in active development, these AUC will require periodic reassessment. Future research directions are also outlined, including diagnostic utility and patient-centered outcomes.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides , Encéfalo/diagnóstico por imagem , Humanos , Medicina Nuclear/normas , Tomografia por Emissão de PósitronsRESUMO
Amyloid PET imaging is a novel diagnostic test that can detect in living humans one of the two defining pathologic lesions of Alzheimer disease, amyloid-ß deposition in the brain. The Amyloid Imaging Task Force of the Alzheimer's Association and Society for Nuclear Medicine and Molecular Imaging previously published appropriate use criteria for amyloid PET as an important tool for increasing the certainty of a diagnosis of Alzheimer disease in specific patient populations. Here, the task force further clarifies and expands 3 topics discussed in the original paper: first, defining dementia experts and their use of proper documentation to demonstrate the medical necessity of an amyloid PET scan; second, identifying a specific subset of individuals with mild cognitive impairment for whom an amyloid PET scan is appropriate; and finally, developing educational programs to increase awareness of the amyloid PET appropriate use criteria and providing instructions on how this test should be used in the clinical decision-making process.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Disfunção Cognitiva/diagnóstico por imagem , Placa Amiloide/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/normas , Doença de Alzheimer/etiologia , Peptídeos beta-Amiloides/análise , Química Encefálica , Causalidade , Lista de Checagem , Disfunção Cognitiva/etiologia , Congressos como Assunto , Gerenciamento Clínico , Educação Médica Continuada , Medicina de Família e Comunidade/educação , Geriatria/educação , Humanos , Neurologia/educação , Educação de Pacientes como Assunto , Competência Profissional , Encaminhamento e Consulta/normas , Materiais de EnsinoRESUMO
The idea that qualities acquired from experience can be transmitted to future offspring has long been considered incompatible with current understanding of genetics. However, the recent documentation of non-Mendelian transgenerational inheritance makes such a "Lamarckian"-like phenomenon more plausible. Here, we demonstrate that exposure of 15-d-old mice to 2 weeks of an enriched environment (EE), that includes exposure to novel objects, elevated social interactions and voluntary exercise, enhances long-term potentiation (LTP) not only in these enriched mice but also in their future offspring through early adolescence, even if the offspring never experience EE. In both generations, LTP induction is augmented by a newly appearing cAMP/p38 MAP kinase-dependent signaling cascade. Strikingly, defective LTP and contextual fear conditioning memory normally associated with ras-grf knock-out mice are both masked in the offspring of enriched mutant parents. The transgenerational transmission of this effect occurs from the enriched mother to her offspring during embryogenesis. If a similar phenomenon occurs in humans, the effectiveness of one's memory during adolescence, particularly in those with defective cell signaling mechanisms that control memory, can be influenced by environmental stimulation experienced by one's mother during her youth.
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Potenciação de Longa Duração/genética , Comportamento Materno/fisiologia , Memória/fisiologia , Meio Social , Fatores Etários , Animais , Animais Recém-Nascidos , Efeito de Coortes , Condicionamento Psicológico/fisiologia , Potenciais Pós-Sinápticos Excitadores/genética , Feminino , Masculino , Comportamento Materno/psicologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Gravidez , Comportamento SocialRESUMO
Parkinson's disease (PD) is the second most common neurodegenerative disorder. Despite intense investigations, no effective therapy is available to stop its onset or halt its progression. The present study evaluates the ability of peptide corresponding to the NF-kappaB essential modifier-binding domain (NBD) of IkappaB kinase alpha (IKKalpha) or IKKbeta to prevent nigrostriatal degeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and establish a role for NF-kappaB in human parkinsonism. First, we found that NF-kappaB was activated within the substantia nigra pars compacta of PD patients and MPTP-intoxicated mice. However, i.p. injection of wild-type NBD peptide reduced nigral activation of NF-kappaB, suppressed nigral microglial activation, protected both the nigrostriatal axis and neurotransmitters, and improved motor functions in MPTP-intoxicated mice. These findings were specific because mutated NBD peptide had no effect. We conclude that selective inhibition of NF-kappaB activation by NBD peptide may be of therapeutic benefit for PD patients.
Assuntos
Dopamina/metabolismo , NF-kappa B/antagonistas & inibidores , NF-kappa B/metabolismo , Doença de Parkinson/metabolismo , 1-Metil-4-Fenil-1,2,3,6-Tetra-Hidropiridina/farmacologia , Animais , Sítios de Ligação , Modelos Animais de Doenças , Progressão da Doença , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Doença de Parkinson/patologia , Doença de Parkinson/fisiopatologia , Peptídeos/farmacologiaRESUMO
BACKGROUND: A challenge in biomedical research is to design experimental paradigms that reflect a natural setting. Even when freshly isolated tissues are used, they are almost always derived from animals housed in cages that poorly reflect the animal's native environment. This issue is highlighted by studies on brain function, where mice housed in a more natural "enriched environment" display enhanced learning and memory and delayed onset of symptoms of neurodegenerative diseases compared to mice housed conventionally. How the environment mediates its effects on brain function is poorly understood. RESULTS: We show that after exposure of adolescent mice to an "enriched environment," the induction of long-term potentiation (LTP), a form of synaptic plasticity that is thought to contribute to learning and memory, involves a novel signal transduction pathway that is nonfunctional in comparable mice housed conventionally. This environmentally gated signaling pathway, which rescues defective LTP induction in adolescent Ras-GRF knockout mice, consists of NMDA glutamate receptor activation of p38, a MAP kinase that does not contribute to LTP in mice housed conventionally. Interestingly, the same exposure to environmental enrichment does not have this effect in adult mice. CONCLUSIONS: This study reveals a new level of cell signaling control whereby environmental factors gate the efficacy of a specific signaling cascade to control how LTP is induced in adolescent animals. The suppression of this gating mechanism in mature animals represents a new form of age-dependent decline in brain plasticity.
Assuntos
Meio Ambiente , Sistema de Sinalização das MAP Quinases/fisiologia , Plasticidade Neuronal , Sinapses/fisiologia , Fatores Etários , Animais , AMP Cíclico/fisiologia , Potenciação de Longa Duração , Depressão Sináptica de Longo Prazo , Camundongos , Camundongos Knockout , Receptores de N-Metil-D-Aspartato/fisiologia , Transdução de Sinais , Proteínas Quinases p38 Ativadas por Mitógeno/fisiologia , ras-GRF1/fisiologiaRESUMO
NMDA-type glutamate receptors (NMDARs) contribute to many forms of long-term potentiation (LTP) and long-term depression (LTD). NMDARs are heteromers containing calcium-permeating neuronal receptor 1 (NR1) subunits and a variety of NR2 subunits. Evidence suggests that, in the CA1 region of the hippocampus, NR2A-containing NMDARs promote LTP whereas NR2B-containing receptors promote LTD. However, the calcium sensors that distinguish between these signals to promote the appropriate form of synaptic plasticity are not known. Ras-guanine nucleotide-releasing factor 1 (Ras-GRF1) and Ras-GRF2 are highly similar calcium-stimulated exchange factors that activate Ras and Rac GTPases. Here, using a set of Ras-GRF knock-out mice, we show that Ras-GRF2 contributes predominantly to the induction of NMDAR-dependent LTP, whereas Ras-GRF1 contributes predominantly to the induction of NMDAR-dependent LTD in the CA1 region of the hippocampus of postpubescent mice (postnatal days 25-36). In contrast, neither Ras-GRF protein influences synaptic plasticity in prepubescent mice (postnatal days 14-18). Ras-GRF2 mediates signaling from (R)-[(S)-1-(4-bromo-phenyl)-ethylamino]-(2,3-dioxo-1,2,3,4-tetrahydroquinoxalin-5-yl)-methyl-phosphonic acid-sensitive (NVP-AAM077-sensitive) (NR2A-containing) NMDARs to the Ras effector extracellular signal-related protein kinase 1/2 (Erk1/2) mitogen-activated protein (MAP) kinase, a promoter of NMDAR-induced LTP at this site. In contrast, Ras-GRF1 mediates signaling from ifenprodil-sensitive (NR2B-containing) NMDARs to the Rac effector p38 MAP kinase, a promoter of LTD. These findings show that, despite their similar functional domain organization, Ras-GRF1 and Ras-GRF2 mediate opposing forms of synaptic plasticity by coupling different classes of NMDARs to distinct MAP kinase pathways. Moreover, the postnatal appearance of Ras-GRF-dependent LTP and LTD coincides with the emergence of hippocampal-dependent behavior, implying that Ras-GRF proteins contribute to forms of synaptic plasticity that are required specifically for mature hippocampal function.
Assuntos
Fator 2 de Liberação do Nucleotídeo Guanina/fisiologia , Potenciação de Longa Duração/fisiologia , Depressão Sináptica de Longo Prazo/fisiologia , ras-GRF1/fisiologia , Animais , Potenciais Pós-Sinápticos Excitadores , Fator 2 de Liberação do Nucleotídeo Guanina/deficiência , Fator 2 de Liberação do Nucleotídeo Guanina/genética , Hipocampo/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Camundongos , Camundongos Knockout , Plasticidade Neuronal/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , ras-GRF1/deficiência , ras-GRF1/genéticaRESUMO
Recent studies support the hypothesis that soluble oligomers of amyloid beta-peptide (Abeta) rather than mature amyloid fibrils are the earliest effectors of synaptic compromise in Alzheimer's disease. We took advantage of an amyloid precursor protein-overexpressing cell line that secretes SDS-stable Abeta oligomers to search for inhibitors of the pathobiological effects of natural human Abeta oligomers. Here, we identify small molecules that inhibit formation of soluble Abeta oligomers and thus abrogate their block of long-term potentiation (LTP). Furthermore, we show that cell-derived Abeta oligomers can be separated from monomers by size exclusion chromatography under nondenaturing conditions and that the isolated, soluble oligomers, but not monomers, block LTP. The identification of small molecules that inhibit early Abeta oligomer formation and rescue LTP inhibition offers a rational approach for therapeutic intervention in Alzheimer's disease and highlights the utility of our cell-culture paradigm as a useful secondary screen for compounds designed to inhibit early steps in Abeta oligomerization under biologically relevant conditions.
Assuntos
Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/metabolismo , Amiloide/metabolismo , Potenciação de Longa Duração/fisiologia , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/metabolismo , Peptídeos beta-Amiloides/síntese química , Animais , Células CHO , Cricetinae , Diaminas/farmacologia , Feminino , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Camundongos , Fragmentos de Peptídeos/síntese química , Piridazinas/farmacologiaRESUMO
INTRODUCTION: The AARR task force on suicidal ideation and behavior (SI/SB) in dementia conducted an online survey on the extent of SI/SB in individuals diagnosed with mild cognitive impairment (MCI) or dementia who were participating in clinical trials. METHODS: Investigators with experience in conducting SI/SB assessments in clinical trial subjects with MCI or dementia were invited to complete a global 19-item online survey. RESULTS: A total of 204 evaluable responses were collected with the majority from North America and Europe (83.4%) and the remainder from Asia, Latin America, and Mideast/Africa. The mean (SD) number of subjects personally assessed by the respondents in the past year with MCI, mild-moderate dementia, or severe dementia was 12.8 (26.2), 31.2 (39.6), and 10.1 (34.7), respectively. The mean number of subjects in each diagnostic group with suicidal ideation (SI), suicidal behavior (SB), or completed suicide (CS) was on average quite low (0.3 to 1.1 for SI, 0.1 to 0.2 for SB, and 0.0 to 0.2 for CS). Confidence in subject self-reports of SI/SB over different time periods declined with increasing severity of cognitive impairment and with increasing duration of the recall time period assessed. Of respondents, 56% and 75% had low confidence in self-ratings of SI/SB from subjects with severe dementia over the past 24 hours and the past week to 1 month, respectively. Ratings of the reliability of information collected on SI/SB also decreased with increasing severity of cognitive impairment. Approximately 70% of respondents rated the reliability of the information they obtained from all sources (patient, caregiver, and others) for subjects with MCI as high, but only about half (42.0% to 55.3%) and less than a quarter (17.4% to 24.3%) rated the reliability of information obtained for subjects with mild to moderate dementia or severe dementia as high, respectively. DISCUSSION: These results support the usefulness of prospective SI/SB assessments in MCI and mild dementia, raise questions about the reliability of assessments in moderate dementia, and confirm their lack of clinical utility in severe dementia. The results highlight the need for development of validated assessment instruments adapted to the stage of cognitive decline of the patients under study and may be the most effective in the earliest stages of the disease.
RESUMO
INTRODUCTION: Better understanding of suicide risk and its management in older adults with cognitive impairment and/or dementia remain significant unmet public health needs. Urgency to address them derives from concern that CNS treatments for dementia may impact suicide risk. Regulatory guidances requiring assessment of emergent suicidal ideation and behavior (SI/SB) at every clinical trial visit emphasize the need for understanding their prevalence. METHODS: The literature regarding SI/SB in older persons with cognitive impairment or dementia was reviewed by an Alzheimer's Association Taskforce with emphasis on epidemiology, classification, assessment, and regulatory requirements. RESULTS: Gaps in our knowledge were identified, challenges discussed and recommendations for future work provided. DISCUSSION: Currently available SI/SB data from geriatric persons with dementia do not provide adequate understanding of its epidemiology, identification, assessment, or management. The growing public health burden of this population requires greater attention from clinicians and researchers on tactics and assessment tools to meet these needs.
RESUMO
Although APP mutations associated with inherited forms of Alzheimer's disease (AD) are relatively rare, detailed studies of these mutations may prove critical for gaining important insights into the mechanism(s) and etiology of AD. Here, we present a detailed biophysical characterization of the structural properties of protofibrils formed by the Arctic variant (E22G) of amyloid-beta protein (Abeta40(ARC)) as well as the effect of Abeta40(WT) on the distribution of the protofibrillar species formed by Abeta40(ARC) by characterizing biologically relevant mixtures of both proteins that may mimic the situation in the heterozygous patients. These studies revealed that the Arctic mutation accelerates both Abeta oligomerization and fibrillogenesis in vitro. In addition, Abeta40(ARC) was observed to affect both the morphology and the size distribution of Abeta protofibrils. Electron microscopy examination of the protofibrils formed by Abeta40(ARC) revealed several morphologies, including: (1) relatively compact spherical particles roughly 4-5 nm in diameter; (2) annular pore-like protofibrils; (3) large spherical particles 18-25 nm in diameter; and (4) short filaments with chain-like morphology. Conversion of Abeta40(ARC) protofibrils to fibrils occurred more rapidly than protofibrils formed in mixed solutions of Abeta40(WT)/Abeta40(ARC), suggesting that co-incubation of Abeta40(ARC) with Abeta40(WT) leads to kinetic stabilization of Abeta40(ARC) protofibrils. An increase in the ratio of Abeta(WT)/Abeta(MUT(Arctic)), therefore, may result in the accumulation of potential neurotoxic protofibrils and acceleration of disease progression in familial Alzheimer's disease mutation carriers.
Assuntos
Peptídeos beta-Amiloides/química , Mutação , Fragmentos de Peptídeos/química , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/ultraestrutura , Animais , Humanos , Peso Molecular , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/ultraestrutura , Peptídeos/química , Peptídeos/genética , Peptídeos/metabolismo , Estrutura Quaternária de Proteína , UltracentrifugaçãoRESUMO
Alzheimer's disease (AD) is a progressive neurodegenerative disease, however, the underlying mechanism driving this condition is unknown. Unexplored is the possibility that the time-dependent generation of different Abeta assemblies may underlie the pathogenic cascade with biophysically distinct structures interacting with unique biological targets. Thus, the presence of subtle alterations in synaptic function during the earliest clinical phase of AD may be mediated by diffusible assemblies of the amyloid beta-protein (Abeta). Using primary neocortical cultures, here we compare the synaptic responses induced by two different Abeta assemblies, protofibrils (PFs) and fibrils (FBs), and demonstrate for the first time that neuronal activation was selectively dependent on the assembly state of Abeta. PF-induced activity was specifically attenuated by the N-methyl-D-aspartate (NMDA) receptor antagonist, D-APV. In contrast, the non-NMDA glutamate receptor antagonist, NBQX, preferentially reduced FB-induced activity. In support, removal of Mg(2+) from the medium, which enhances NMDA channels, increased both PF- or FB-induced activation, but D-APV was more effective in attenuating PF-induced excitatory activity. These findings suggest that PFs may activate neurons differently than fibrils and lend support to the hypothesis that pre-fibrillar assemblies of Abeta may play an important role in the development of AD-type synaptic deficits.
Assuntos
Peptídeos beta-Amiloides/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Valina/análogos & derivados , Animais , Células Cultivadas , Interações Medicamentosas , Embrião de Mamíferos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Imuno-Histoquímica/métodos , Técnicas In Vitro , Potenciais da Membrana/efeitos dos fármacos , Proteínas Associadas aos Microtúbulos/metabolismo , Neocórtex/citologia , Neurônios/classificação , Técnicas de Patch-Clamp/métodos , Conformação Proteica , Quinoxalinas/farmacologia , Ratos , Receptores de N-Metil-D-Aspartato/agonistas , Valina/farmacologiaRESUMO
Positron emission tomography (PET) of brain amyloid ß is a technology that is becoming more available, but its clinical utility in medical practice requires careful definition. To provide guidance to dementia care practitioners, patients, and caregivers, the Alzheimer's Association and the Society of Nuclear Medicine and Molecular Imaging convened the Amyloid Imaging Taskforce (AIT). The AIT considered a broad range of specific clinical scenarios in which amyloid PET could potentially be used appropriately. Peer-reviewed, published literature was searched to ascertain available evidence relevant to these scenarios, and the AIT developed a consensus of expert opinion. Although empirical evidence of impact on clinical outcomes is not yet available, a set of specific appropriate use criteria (AUC) were agreed on that define the types of patients and clinical circumstances in which amyloid PET could be used. Both appropriate and inappropriate uses were considered and formulated, and are reported and discussed here. Because both dementia care and amyloid PET technology are in active development, these AUC will require periodic reassessment. Future research directions are also outlined, including diagnostic utility and patient-centered outcomes.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Comitês Consultivos , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/metabolismo , Radioisótopos de Carbono , Disfunção Cognitiva/diagnóstico por imagem , Disfunção Cognitiva/metabolismo , Medicina Baseada em Evidências , Humanos , Medicina Nuclear , Compostos Radiofarmacêuticos , Sociedades MédicasRESUMO
Amyloid PET imaging is a novel diagnostic test that can detect in living humans one of the two defining pathologic lesions of Alzheimer disease, amyloid-ß deposition in the brain. The Amyloid Imaging Task Force of the Alzheimer's Association and Society for Nuclear Medicine and Molecular Imaging previously published appropriate use criteria for amyloid PET as an important tool for increasing the certainty of a diagnosis of Alzheimer disease in specific patient populations. Here, the task force further clarifies and expands 3 topics discussed in the original paper: first, defining dementia experts and their use of proper documentation to demonstrate the medical necessity of an amyloid PET scan; second, identifying a specific subset of individuals with mild cognitive impairment for whom an amyloid PET scan is appropriate; and finally, developing educational programs to increase awareness of the amyloid PET appropriate use criteria and providing instructions on how this test should be used in the clinical decision-making process.
Assuntos
Proteínas Amiloidogênicas/metabolismo , Disfunção Cognitiva/metabolismo , Demência/diagnóstico por imagem , Imagem Molecular/normas , Medicina Nuclear/educação , Tomografia por Emissão de Pósitrons/normas , Guias de Prática Clínica como Assunto , Proteínas Amiloidogênicas/análise , Disfunção Cognitiva/complicações , Disfunção Cognitiva/diagnóstico por imagem , Demência/metabolismo , Humanos , Medicina Nuclear/normas , Estados UnidosRESUMO
BACKGROUND: The form(s) of amyloid-ß peptide (Aß) associated with the pathology characteristic of Alzheimer's disease (AD) remains unclear. In particular, the neurotoxicity of intraneuronal Aß accumulation is an issue of considerable controversy; even the existence of Aß deposits within neurons has recently been challenged by Winton and co-workers. These authors purport that it is actually intraneuronal APP that is being detected by antibodies thought to be specific for Aß. To further address this issue, an anti-Aß antibody was developed (MOAB-2) that specifically detects Aß, but not APP. This antibody allows for the further evaluation of the early accumulation of intraneuronal Aß in transgenic mice with increased levels of human Aß in 5xFAD and 3xTg mice. RESULTS: MOAB-2 (mouse IgG2b) is a pan-specific, high-titer antibody to Aß residues 1-4 as demonstrated by biochemical and immunohistochemical analyses (IHC), particularly compared to 6E10 (a commonly used commercial antibody to Aß residues 3-8). MOAB-2 did not detect APP or APP-CTFs in cell culture media/lysates (HEK-APPSwe or HEK-APPSwe/BACE1) or in brain homogenates from transgenic mice expressing 5 familial AD (FAD) mutation (5xFAD mice). Using IHC on 5xFAD brain tissue, MOAB-2 immunoreactivity co-localized with C-terminal antibodies specific for Aß40 and Aß42. MOAB-2 did not co-localize with either N- or C-terminal antibodies to APP. In addition, no MOAB-2-immunoreactivity was observed in the brains of 5xFAD/BACE-/- mice, although significant amounts of APP were detected by N- and C-terminal antibodies to APP, as well as by 6E10. In both 5xFAD and 3xTg mouse brain tissue, MOAB-2 co-localized with cathepsin-D, a marker for acidic organelles, further evidence for intraneuronal Aß, distinct from Aß associated with the cell membrane. MOAB-2 demonstrated strong intraneuronal and extra-cellular immunoreactivity in 5xFAD and 3xTg mouse brain tissues. CONCLUSIONS: Both intraneuronal Aß accumulation and extracellular Aß deposition was demonstrated in 5xFAD mice and 3xTg mice with MOAB-2, an antibody that will help differentiate intracellular Aß from APP. However, further investigation is required to determine whether a molecular mechanism links the presence of intraneuronal Aß with neurotoxicity. As well, understanding the relevance of these observations to human AD patients is critical.
Assuntos
Peptídeos beta-Amiloides/análise , Precursor de Proteína beta-Amiloide/análise , Anticorpos/análise , Imuno-Histoquímica/métodos , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/imunologia , Precursor de Proteína beta-Amiloide/imunologia , Animais , Anticorpos/imunologia , Especificidade de Anticorpos , Reações Antígeno-Anticorpo , Células Cultivadas , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Placa Amiloide/química , Placa Amiloide/patologiaRESUMO
Expression of the neuropeptide galanin is known to be upregulated in the brain of patients with Alzheimer's disease (AD). We and others have shown that galanin plays a neuroprotective role in a number of excitotoxic injury paradigms, mediated by activation of the second galanin receptor subtype (GAL2). In the present study, we investigated whether galanin/GAL2 plays a similar protective role against amyloid-ß(Aß) toxicity. Here we report that galanin or the GAL2/3-specific peptide agonist Gal2-11, both equally protect primary dispersed mouse wildtype (WT) neonatal hippocampal neurons from 250 nM Aß1-42 toxicity in a dose dependent manner. The amount of Aß1-42 induced cell death was significantly greater in mice with loss-of-function mutations in galanin (Gal-KO) or GAL2 (GAL2-MUT) compared to strain-matched WT controls. Conversely, cell death was significantly reduced in galanin over-expressing (Gal-OE) transgenic mice compared to strain-matched WT controls. Exogenous galanin or Gal2-11 rescued the deficits in the Gal-KO but not the GAL2-MUT cultures, confirming that the protective effects of endogenous or exogenous galanin are mediated by activation of GAL2. Despite the high levels of endogenous galanin in the Gal-OE cultures, the addition of exogenous 100 nM or 50 nM galanin or 100 nM Gal2-11 further significantly reduced cell death, implying that GAL2-mediated neuroprotection is not at maximum in the Gal-OE mice. These data further support the hypothesis that galanin over-expression in AD is a neuroprotective response and imply that the development of a drug-like GAL2 agonist might reduce the progression of symptoms in patients with AD.
Assuntos
Peptídeos beta-Amiloides/toxicidade , Galanina/metabolismo , Hipocampo/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fragmentos de Peptídeos/toxicidade , Receptor Tipo 2 de Galanina/metabolismo , Análise de Variância , Animais , Animais Recém-Nascidos , Morte Celular/efeitos dos fármacos , Morte Celular/genética , Células Cultivadas , Relação Dose-Resposta a Droga , Galanina/genética , Galanina/farmacologia , Ácido Glutâmico/toxicidade , Camundongos , Camundongos Transgênicos , Fragmentos de Peptídeos/farmacologia , Receptor Tipo 2 de Galanina/deficiênciaRESUMO
The amyloid cascade hypothesis, supported by strong evidence from genetics, pathology and studies using animal models, implicates amyloid-beta (Abeta) oligomerization and fibrillogenesis as central causative events in the pathogenesis of Alzheimer's disease (AD). Today, significant efforts in academia, biotechnology and the pharmaceutical industry are devoted to identifying the mechanisms by which the process of Abeta aggregation contributes to neurodegeneration in AD and to the identity of the toxic Abeta species. In this paper, we describe methods and detailed protocols for reproducibly preparing Abeta aggregates of defined size distribution and morphology, including monomers, protofibrils and fibrils, using size exclusion chromatography. In addition, we describe detailed biophysical procedures for elucidating the structural features, aggregation kinetics and toxic properties of the different Abeta aggregation states, with special emphasis on protofibrillar intermediates. The information provided by this approach allows for consistent correlation between the properties of the aggregates and their toxicity toward primary neurons and/or cell lines. A better understanding of the molecular and structural basis of Abeta aggregation and toxicity is crucial for the development of effective strategies aimed at prevention and/or treatment of AD. Furthermore, the identification of specific aggregation states, which correlate with neurodegeneration in AD, could lead to the development of diagnostic tools to detect and monitor disease progression. The procedures described can be performed in as little as 1 day, or may take longer, depending on the exact toxicity assays used.
Assuntos
Doença de Alzheimer/etiologia , Peptídeos beta-Amiloides/isolamento & purificação , Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/toxicidade , Animais , Células Cultivadas , Córtex Cerebral/citologia , Feminino , Humanos , Técnicas In Vitro , Camundongos , Complexos Multiproteicos/química , Complexos Multiproteicos/isolamento & purificação , Complexos Multiproteicos/toxicidade , Neurônios/efeitos dos fármacos , Gravidez , Multimerização ProteicaRESUMO
An increasing body of evidence suggests that soluble assemblies of amyloid beta-protein (Abeta) play an important role in the initiation of Alzheimer disease (AD). In vitro studies have found that synthetic Abeta can form soluble aggregates through self-assembly, but this process requires Abeta concentrations 100- to 1000-fold greater than physiological levels. Tissue transglutaminase (TGase) has been implicated in neurodegeneration and can cross-link Abeta. Here we show that TGase induces rapid aggregation of Abeta within 0.5-30 min, which was not observed with chemical cross-linkers. Both Abeta40 and Abeta42 are good substrates for TGase but show different aggregation patterns. Guinea pig and human TGase induced similar Abeta aggregation patterns, and oligomerization was observed with Abeta40 concentrations as low as 50 nm. The formed Abeta40 species range from 5 to 6 nm spheres to curvilinear structures of the same width, but up to 100 nm in length, that resemble the previously described self-assembled Abeta protofibrils. TGase-induced Abeta40 assemblies are resistant to a 1-h incubation with either neprilysin or insulin degrading enzyme, whereas the monomer is rapidly degraded by both proteases. In support of these species being pathological, TGase-induced Abeta40 assemblies (100 nm) inhibited long term potentiation recorded in the CA1 region of mouse hippocampus slices. Our data suggest that TGase can contribute to AD by initiating Abeta oligomerization and aggregation at physiological levels, by reducing the clearance of Abeta due to the generation of protease-resistant Abeta species, and by forming Abeta assemblies that inhibit processes involved in memory and learning. Our data suggest that TGase might constitute a specific therapeutic target for slowing or blocking the progression of AD.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Potenciação de Longa Duração , Peptídeo Hidrolases/metabolismo , Transglutaminases/metabolismo , Doença de Alzheimer/metabolismo , Animais , Reagentes de Ligações Cruzadas/química , Reagentes de Ligações Cruzadas/farmacologia , Progressão da Doença , Cobaias , Hipocampo/metabolismo , Humanos , Insulisina/química , Camundongos , Neprilisina/química , Peptídeos/química , Proteína 2 Glutamina gama-GlutamiltransferaseRESUMO
Alzheimer's disease starts as an almost imperceptible malady, first observed clinically as a mild memory problem. Accumulating genetic and biochemical data have suggested that amyloid beta-protein (Abeta) plays an important role in this memory loss, and Abeta has been shown to suppress long-term potentiation (LTP), a cellular model for memory and learning. Here we show that a very brief (3 min) swimming, twice daily for 2 weeks, rescues LTP inhibition in the CA1 region of hippocampal slices caused by Abeta(42) or Abeta(40) carrying the Arctic mutation using a theta burst stimulation (TBS) protocol. Whereas the input-output curve was not affected, the paired-pulse ratio was reduced in mice receiving our repeated swimming protocol, suggesting a possible involvement of presynaptic facilitation. Similar to swimming, Abeta's inhibition of LTP could be rescued with the adenylyl cyclase, forskolin. Interestingly, this swimming protocol produced conditions in which a weak-TBS could invoke LTP not observed in naïve mice, which again was mimicked by forskolin. In contrast, the protein kinase A (PKA) inhibitor, H89, blocked both the forskolin and swimming potentiation of LTP; these data implicate cAMP/PKA signaling in the protective effect of swimming and mediating Abeta' detrimental effects. Our data add a new simple behavior paradigm that shows the importance of an environmental factor in reversing the pathophysiological effects of Abeta, and suggest new therapeutic avenues.
Assuntos
Peptídeos beta-Amiloides/farmacologia , Hipocampo/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Fragmentos de Peptídeos/farmacologia , Natação , Animais , Animais Recém-Nascidos , Comportamento Animal , Colforsina/farmacologia , Relação Dose-Resposta Imunológica , Estimulação Elétrica/métodos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciais Pós-Sinápticos Excitadores/efeitos da radiação , Feminino , Técnicas In Vitro , Isoquinolinas/farmacologia , Potenciação de Longa Duração/fisiologia , Potenciação de Longa Duração/efeitos da radiação , Masculino , Camundongos , Inibidores de Proteínas Quinases/farmacologia , Sulfonamidas/farmacologia , Fatores de TempoRESUMO
The present study underlines the importance of gemfibrozil, a lipid-lowering drug and an activator of peroxisome proliferator-activated receptor-alpha (PPAR-alpha), in inhibiting the disease process of adoptively transferred experimental allergic encephalomyelitis (EAE), an animal model of relapsing-remitting multiple sclerosis. Clinical symptoms of EAE, infiltration of mononuclear cells, and demyelination were significantly lower in SJL/J female mice receiving gemfibrozil through food chow than those without gemfibrozil. It is noteworthy that the drug was equally effective in treating EAE in PPAR-alpha wild-type as well as knockout mice. Gemfibrozil also inhibited the encephalitogenicity of MBP-primed T cells and switched the immune response from a Th1 to a Th2 profile independent of PPAR-alpha. Gemfibrozil consistently inhibited the expression and DNA-binding activity of T-bet, a key regulator of interferon-gamma (IFN-gamma) expression and stimulated the expression and DNA-binding activity of GATA3, a key regulator of IL-4. Gemfibrozil treatment decreased the number of T-bet-positive T cells and increased the number of GATA3-positive T cells in spleen of donor mice. The histological and immunohistochemical analyses also demonstrate the inhibitory effect of gemfibrozil on the invasion of T-bet-positive T cells into the spinal cord of EAE mice. Furthermore, we demonstrate that the differential effect of gemfibrozil on the expression of T-bet and GATA3 was due to its inhibitory effect on NO production. Although excess NO favored the expression of T-bet, scavenging of NO stimulated the expression of GATA-3. Taken together, our results suggest gemfibrozil, an approved drug for hyperlipidemia in humans, may find further therapeutic use in multiple sclerosis.