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1.
J Nucl Med ; 60(1): 93-99, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29777006

RESUMO

Tau PET imaging has potential for elucidating changes in the deposition of neuropathological tau aggregates that are occurring during the progression of Alzheimer disease (AD). This work investigates in vivo kinetics, quantification strategies, and imaging characteristics of a novel tau PET radioligand 18F-MK-6240 in humans. Methods: Fifty-one individuals ranging from cognitively normal young controls to persons with dementia underwent T1-weighted MRI as well as 11C-PiB and 18F-MK-6240 PET imaging. PET data were coregistered to the MRI, and time-activity curves were extracted from regions of interest to assess 18F-MK-6240 kinetics. The pons and inferior cerebellum were investigated as potential reference regions. Reference tissue methods (Logan graphical analysis [LGA] and multilinear reference tissue method [MRTM2]) were investigated for quantification of 18F-MK-6240 distribution volume ratios (DVRs) in a subset of 19 participants. Stability of DVR methods was evaluated using truncated scan durations. SUV ratio (SUVR) estimates were compared with DVR estimates to determine the optimal timing window for SUVR analysis. Parametric SUVR images were used to identify regions of potential off-target binding and to compare binding patterns with neurofibrillary tau staging established in neuropathology literature. Results: SUVs in the pons and the inferior cerebellum indicated consistent clearance across all 51 subjects. LGA and MRTM2 DVR estimates were similar, with LGA slightly underestimating DVR compared with MRTM2. DVR estimates remained stable when truncating the scan duration to 60 min. SUVR determined 70-90 min after injection of 18F-MK-6240 indicated linearity near unity when compared with DVR estimates and minimized potential spill-in from uptake outside the brain. 18F-MK-6240 binding patterns in target regions were consistent with neuropathological neurofibrillary tau staging. Off-target binding regions included the ethmoid sinus, clivus, meninges, substantia nigra, but not the basal ganglia or choroid plexus. Conclusion: 18F-MK-6240 is a promising PET radioligand for in vivo imaging of neurofibrillary tau aggregates in AD with minimal off-target binding in the human brain.


Assuntos
Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/metabolismo , Radioisótopos de Flúor , Isoquinolinas/metabolismo , Neurofibrilas/metabolismo , Tomografia por Emissão de Pósitrons , Proteínas tau/metabolismo , Adulto , Idoso , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Estudos de Casos e Controles , Cognição , Feminino , Humanos , Ligantes , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade
2.
Exp Neurol ; 299(Pt A): 172-196, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29056362

RESUMO

Lewy body disorders are characterized by the emergence of α-synucleinopathy in many parts of the central and peripheral nervous systems, including in the telencephalon. Dense α-synuclein+ pathology appears in regio inferior of the hippocampus in both Parkinson's disease and dementia with Lewy bodies and may disturb cognitive function. The preformed α-synuclein fibril model of Parkinson's disease is growing in use, given its potential for seeding the self-propagating spread of α-synucleinopathy throughout the mammalian brain. Although it is often assumed that the spread occurs through neuroanatomical connections, this is generally not examined vis-à-vis the uptake and transport of tract-tracers infused at precisely the same stereotaxic coordinates. As the neuronal connections of the hippocampus are historically well defined, we examined the first-order spread of α-synucleinopathy three months following fibril infusions centered in the mouse regio inferior (CA2+CA3), and contrasted this to retrograde and anterograde transport of the established tract-tracers FluoroGold and biotinylated dextran amines (BDA). Massive hippocampal α-synucleinopathy was insufficient to elicit memory deficits or loss of cells and synaptic markers in this model of early disease processes. However, dense α-synuclein+ inclusions in the fascia dentata were negatively correlated with memory capacity. A modest compensatory increase in synaptophysin was evident in the stratum radiatum of cornu Ammonis in fibril-infused animals, and synaptophysin expression correlated inversely with memory function in fibril but not PBS-infused mice. No changes in synapsin I/II expression were observed. The spread of α-synucleinopathy was somewhat, but not entirely consistent with FluoroGold and BDA axonal transport, suggesting that variables other than innervation density also contribute to the materialization of α-synucleinopathy. For example, layer II entorhinal neurons of the perforant pathway exhibited somal α-synuclein+ inclusions as well as retrogradely labeled FluoroGold+ somata. However, some afferent brain regions displayed dense retrograde FluoroGold label and no α-synuclein+ inclusions (e.g. medial septum/diagonal band), supporting the selective vulnerability hypothesis. The pattern of inclusions on the contralateral side was consistent with specific spread through commissural connections (e.g. stratum pyramidale of CA3), but again, not all commissural projections exhibited α-synucleinopathy (e.g. hilar mossy cells). The topographical extent of inclusions is displayed here in high-resolution images that afford viewers a rich opportunity to dissect the potential spread of pathology through neural circuitry. Finally, the results of this expository study were leveraged to highlight the challenges and limitations of working with preformed α-synuclein fibrils.


Assuntos
Doença por Corpos de Lewy/patologia , Neurofibrilas , alfa-Sinucleína , Animais , Comportamento Animal , Modelos Animais de Doenças , Hipocampo/patologia , Corpos de Inclusão/patologia , Doença por Corpos de Lewy/psicologia , Sistema Límbico/patologia , Transtornos da Memória/patologia , Transtornos da Memória/psicologia , Camundongos , Camundongos Endogâmicos C57BL , Vias Neurais/patologia , Transmissão Sináptica , Telencéfalo/patologia
3.
PLoS One ; 12(11): e0187841, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29131828

RESUMO

Among therapeutic approaches for amyloid-related diseases, attention has recently turned to the use of natural products as effective anti-aggregation compounds. Although a wealth of in vitro and in vivo evidence indicates some common inhibitory activity of these compounds, they don't generally suggest the same mechanism of action. Here, we show that taxifolin, a ubiquitous bioactive constituent of foods and herbs, inhibits formation of HEWL amyloid fibrils and their related toxicity by causing formation of very large globular, chain-like aggregates. A range of amyloid-specific techniques were employed to characterize this process. We found that taxifolin exerts its effect by binding to HEWL prefibrillar species, rather than by stabilizing the molecule in its native-like state. Furthermore, it's binding results in diverting the amyloid pathway toward formation of very large globular, chain-like aggregates with low ß-sheet content and reduced solvent-exposed hydrophobic patches. ThT fluorescence measurements show that the binding capacity of taxifolin is significantly reduced, upon generation of large protofibrillar aggregates at the end of growth phase. We believe these results may help design promising inhibitors of protein aggregation for amyloid-related diseases.


Assuntos
Neurofibrilas/efeitos dos fármacos , Quercetina/análogos & derivados , Sítios de Ligação , Linhagem Celular , Dicroísmo Circular , Eletroforese em Gel de Poliacrilamida , Humanos , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Força Atômica , Simulação de Acoplamento Molecular , Neurofibrilas/metabolismo , Quercetina/metabolismo , Quercetina/farmacologia , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta
4.
Cytotherapy ; 17(9): 1200-12, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26276003

RESUMO

BACKGROUND AIMS: This study sought to identify correlations between vascular endothelial growth factor (VEGF) expression after tail-vein injection of rat-derived bone marrow stromal cells (BMSCs) and neurogenesis and angiogenesis in cerebral infarct of rats. METHODS: Rats with intraluminal middle cerebral artery occlusion were injected in a tail vein with Hoechst-labeled BMSCs. Functional recovery from cerebral infarction was observed through the use of a locomotion score. The brains of injected rats were sliced, and Hoechst-labeled BMSCs in the infarct and peri-infarct areas and subventricular zone (SVZ) were detected with the use of fluorescence microscopy. Ki-67 (as a cell proliferation marker) and VEGF expression were determined by means of immunohistochemistry. Neurofibril formation and angiogenesis were examined by means of Bielschowsky staining. RESULTS: Within 1 to 2 weeks after BMSC injection, rats showed significantly improved locomotion scores compared with rats without BMSC injection (P < 0.01). Viable BMSCs were found in the peri-infarct area. The numbers of Ki-67-positive and VEGF-positive cells in the peri-infarct area and SVZ of injected rats were significantly increased compared with the control group (P < 0.01). Numerous new vessels, neurofibrils and anastomosed vasculatures were present in the infarct area. These neurofibrils mainly surrounded the neovasculatures. CONCLUSIONS: These results indicate that BMSC-transplantation in rats through tail vein injection can increase neurogenesis, perhaps as the result of VEGF-mediated and/or Ki-67-mediated angiogenesis.


Assuntos
Infarto Cerebral/terapia , Transplante de Células-Tronco Mesenquimais/métodos , Células-Tronco Mesenquimais/metabolismo , Neovascularização Fisiológica/fisiologia , Neurogênese/fisiologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Animais , Encéfalo/irrigação sanguínea , Proliferação de Células , Terapia Baseada em Transplante de Células e Tecidos/métodos , Infarto Cerebral/patologia , Feminino , Masculino , Neurofibrilas/fisiologia , Ratos , Ratos Sprague-Dawley , Recuperação de Função Fisiológica , Cauda
5.
Eur J Nucl Med Mol Imaging ; 42(7): 1052-61, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25792456

RESUMO

PURPOSE: Visualization of the spatial distribution of neurofibrillary tangles would help in the diagnosis, prevention and treatment of dementia. The purpose of the study was to evaluate the clinical utility of [(18)F]THK-5117 as a highly selective tau imaging radiotracer. METHODS: We initially evaluated in vitro binding of [(3)H]THK-5117 in post-mortem brain tissues from patients with Alzheimer's disease (AD). In clinical PET studies, [(18)F]THK-5117 retention in eight patients with AD was compared with that in six healthy elderly controls. Ten subjects underwent an additional [(11)C]PiB PET scan within 2 weeks. RESULTS: In post-mortem brain samples, THK-5117 bound selectively to neurofibrillary deposits, which differed from the binding target of PiB. In clinical PET studies, [(18)F]THK-5117 binding in the temporal lobe clearly distinguished patients with AD from healthy elderly subjects. Compared with [(11)C]PiB, [(18)F]THK-5117 retention was higher in the medial temporal cortex. CONCLUSION: These findings suggest that [(18)F]THK-5117 provides regional information on neurofibrillary pathology in living subjects.


Assuntos
Doença de Alzheimer/diagnóstico por imagem , Compostos de Anilina/farmacocinética , Neurofibrilas/diagnóstico por imagem , Tomografia por Emissão de Pósitrons , Quinolinas/farmacocinética , Compostos Radiofarmacêuticos , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Compostos de Anilina/farmacologia , Benzotiazóis , Estudos de Casos e Controles , Córtex Cerebral/diagnóstico por imagem , Córtex Cerebral/patologia , Feminino , Humanos , Masculino , Neurofibrilas/patologia , Quinolinas/farmacologia , Tiazóis
6.
Neurology ; 84(16): 1639-43, 2015 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-25809304

RESUMO

OBJECTIVE: We assessed CSF levels of the light chain subunit of neurofilaments (NfL) at baseline and after fingolimod therapy or placebo in patients with relapsing-remitting multiple sclerosis (RRMS). Changes in NfL levels were also correlated with relapse and MRI outcomes. METHODS: CSF samples were available, at baseline and 12 months after treatment initiation, from a subset of 36 patients with RRMS (fingolimod 0.5 mg: n = 9; fingolimod 1.25 mg: n = 15; placebo: n = 12) participating in the 2-year, phase 3 Fingolimod (FTY720) Research Evaluating Effects of Daily Oral Therapy in Multiple Sclerosis (FREEDOMS) study. NfL levels were determined in a blinded fashion using a commercial ELISA kit. RESULTS: Median NfL levels did not differ between treatment groups at baseline (0.5 mg: 644 pg/mL; 1.25 mg: 659 pg/mL; pooled 0.5/1.25 mg: 652 pg/mL, placebo: 886 pg/mL; p value [fingolimod vs placebo] = 0.619, 0.495, and 0.481, respectively). Following 12 months of treatment, median changes from baseline in NfL levels were lower than zero in the fingolimod groups (0.5 mg: -346 pg/mL, p = 0.039; 1.25 mg: -313 pg/mL, p = 0.035) and pooled 0.5/1.25 mg fingolimod group (-326 pg/mL, 83.3% with reduction, p = 0.002) but not in the placebo group (-214 pg/mL, 66.7% with reduction, p = 0.388). Reductions in NfL levels at month 12 correlated with an improvement in relapse and MRI outcomes. CONCLUSIONS: Our results suggest a beneficial effect of fingolimod on this marker of axonal injury and support the utility of NfL as a quantitative biomarker in multiple sclerosis.


Assuntos
Imunossupressores/farmacologia , Filamentos Intermediários , Esclerose Múltipla Recidivante-Remitente/líquido cefalorraquidiano , Esclerose Múltipla Recidivante-Remitente/tratamento farmacológico , Neurofibrilas , Propilenoglicóis/farmacologia , Esfingosina/análogos & derivados , Adulto , Axônios/patologia , Biomarcadores , Feminino , Cloridrato de Fingolimode , Humanos , Imunossupressores/administração & dosagem , Masculino , Placebos , Propilenoglicóis/administração & dosagem , Esfingosina/administração & dosagem , Esfingosina/farmacologia , Resultado do Tratamento
8.
Neurobiol Aging ; 36(3): 1590-9, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25573097

RESUMO

We have previously shown that amyotrophic lateral sclerosis with cognitive impairment can be characterized by pathologic inclusions of microtubule-associated protein tau (tau) phosphorylated at Thr(175) (pThr(175)) in association with GSK3ß activation. We have now examined whether pThr(175) induces GSK3ß activation and whether this leads to pathologic fibril formation through Thr(231) phosphorylation. Seventy-two hours after transfection of Neuro2A cells with pseudophosphorylated green fluorescent protein-tagged 2N4R tau (Thr(175)Asp), phosphorylated kinase glycogen synthase kinase 3 beta (active GSK3ß) levels were significantly increased as was pathologic fibril formation and cell death. Treatment with each of 4 GSK3ß inhibitors or small hairpin RNA knockdown of GSK3ß abolished fibril formation and prevented cell death. Inhibition of Thr(231) phosphorylation (Thr(231)Ala) prevented pathologic tau fibril formation, regardless of Thr(175) state, whereas Thr(231)Asp (pseudophosphorylated at Thr(231)) developed pathologic tau fibrils. Ser(235) mutations did not affect fibril formation, indicating an unprimed mechanism of Thr(231) phosphorylation. These findings suggest a mechanism of tau pathology by which pThr(175) induces GSK3ß phosphorylation of Thr(231) leading to fibril formation, indicating a potential therapeutic avenue for amyotrophic lateral sclerosis with cognitive impairment.


Assuntos
Quinase 3 da Glicogênio Sintase/metabolismo , Neurofibrilas/patologia , Proteínas tau/metabolismo , Motivos de Aminoácidos , Esclerose Amiotrófica Lateral/genética , Esclerose Amiotrófica Lateral/patologia , Esclerose Amiotrófica Lateral/terapia , Morte Celular/genética , Células Cultivadas , Biologia Computacional , Técnicas de Silenciamento de Genes , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Glicogênio Sintase Quinase 3 beta , Células HEK293 , Humanos , Fosforilação , RNA Interferente Pequeno/genética , Tauopatias/genética , Tauopatias/patologia , Tauopatias/terapia , Treonina/metabolismo , Proteínas tau/química
9.
Neurobiol Aging ; 36(2): 1221.e15-28, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25281018

RESUMO

In this study, we have assessed the expression and splicing status of genes involved in the pathogenesis or affecting the risk of Alzheimer's disease (AD) in the postmortem inferior temporal cortex samples obtained from 60 subjects with varying degree of AD-related neurofibrillary pathology. These subjects were grouped based on neurofibrillary pathology into 3 groups: Braak stages 0-II, Braak stages III-IV, and Braak stages V-VI. We also examined the right frontal cortical biopsies obtained during life from 22 patients with idiopathic shunt-responding normal pressure hydrocephalus, a disease that displays similar pathologic alterations as seen in AD. These 22 patients were categorized according to dichotomized amyloid-ß positive or negative pathology in the biopsies. We observed that the expression of FRMD4A significantly decreased, and the expression of MS4A6A significantly increased in relation to increasing AD-related neurofibrillary pathology. Moreover, the expression of 2 exons in both CLU and TREM2 significantly increased with increase in AD-related neurofibrillary pathology. However, a similar trend toward increased expression in CLU and TREM2 was observed with most of the studied exons, suggesting a global change in the expression rather than altered splicing. Correlation of gene expression with well-established AD-related factors, such as α-, ß-, and γ-secretase activities, brain amyloid-ß42 levels, and cerebrospinal fluid biomarkers, revealed a positive correlation between ß-secretase activity and the expression of TREM2 and BIN1. In expression quantitative trait loci analysis, we did not detect significant effects of the risk alleles on gene expression or splicing. Analysis of the normal pressure hydrocephalus biopsies revealed no differences in the expression or splicing profiles of the studied genes between amyloid-ß positive and negative patients. Using the protein-protein interaction-based in vitro pathway analysis tools, we found that downregulation of FRMD4A associated with increased APP-ß-secretase interaction, increased amyloid-ß40 secretion, and altered phosphorylation of tau. Taken together, our results suggest that the expression of FRMD4A, MS4A6A, CLU, and TREM2 is altered in relation to increasing AD-related neurofibrillary pathology, and that FRMD4A may play a role in amyloidogenic and tau-related pathways in AD. Therefore, investigation of gene expression changes in the brain and effects of the identified genes on disease-associated pathways in vitro may provide mechanistic insights on how alterations in these genes may contribute to AD pathogenesis.


Assuntos
Doença de Alzheimer/genética , Encéfalo/metabolismo , Perfilação da Expressão Gênica , Predisposição Genética para Doença/genética , Transcriptoma/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Encéfalo/patologia , Feminino , Expressão Gênica , Humanos , Técnicas In Vitro , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Neurofibrilas/patologia , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fosforilação , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo , Risco , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismo
10.
J Hist Neurosci ; 24(3): 229-43, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25513740

RESUMO

Neurofibrils, identified after staining with Cajal's reduced silver nitrate, for example, were thought by many senior histologists in the nineteenth and early-twentieth centuries to conduct action potentials. There was no basis for this popular idea, although it was the impetus for intense study of the "neurofibrillar network" within neurons by Golgi, Cajal, Freud, and many others. Here, I trace the way in which this "excitable neurofibrillary" hypothesis led to major problems in the attempt by histologists to identify the central excitatory synapse, postulated by Sherrington on functional grounds and eventually described by Berkley.


Assuntos
Neurofibrilas/ultraestrutura , Sinapses/ultraestrutura , Potenciais de Ação/fisiologia , Animais , Dendritos/fisiologia , Dendritos/ultraestrutura , Histologia/história , História do Século XIX , História do Século XX , Humanos , Neurofibrilas/fisiologia , Neurociências/história , Sinapses/fisiologia
11.
Endocrinology ; 155(5): 1944-55, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24605826

RESUMO

Gonadotropin-inhibitory hormone (GnIH) neurons project to GnRH neurons to negatively regulate reproductive function. To fully explore the projections of the GnIH neurons, we created transgenic rats carrying an enhanced green fluorescent protein (EGFP) tagged to the GnIH promoter. With these animals, we show that EGFP-GnIH neurons are localized mainly in the dorsomedial hypothalamic nucleus (DMN) and project to the hypothalamus, telencephalon, and diencephalic thalamus, which parallels and confirms immunocytochemical and gene expression studies. We observed an age-related reduction in c-Fos-positive GnIH cell numbers in female rats. Furthermore, GnIH fiber appositions to GnRH neurons in the preoptic area were lessened in middle-aged females (70 weeks old) compared with their younger counterparts (9-12 weeks old). The fiber density in other brain areas was also reduced in middle-aged female rats. The expression of estrogen and progesterone receptors mRNA in subsets of EGFP-GnIH neurons was shown in laser-dissected single EGFP-GnIH neurons. We then examined estradiol-17ß and progesterone regulation of GnIH neurons, using c-Fos presence as a marker. Estradiol-17ß treatment reduced c-Fos labeling in EGFP-GnIH neurons in the DMN of young ovariectomized adult females but had no effect in middle-aged females. Progesterone had no effect on the number of GnIH cells positive for c-Fos. We conclude that there is an age-related decline in GnIH neuron number and GnIH inputs to GnRH neurons. We also conclude that the response of GnIH neurons to estrogen diminishes with reproductive aging.


Assuntos
Envelhecimento , Núcleo Hipotalâmico Dorsomedial/metabolismo , Regulação para Baixo , Hormônios Hipotalâmicos/metabolismo , Neurônios/metabolismo , Regiões Promotoras Genéticas , Animais , Biomarcadores/metabolismo , Extensões da Superfície Celular/metabolismo , Diencéfalo/citologia , Diencéfalo/crescimento & desenvolvimento , Diencéfalo/metabolismo , Núcleo Hipotalâmico Dorsomedial/citologia , Núcleo Hipotalâmico Dorsomedial/crescimento & desenvolvimento , Estradiol/metabolismo , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Hormônios Hipotalâmicos/genética , Hipotálamo/citologia , Hipotálamo/crescimento & desenvolvimento , Hipotálamo/metabolismo , Neurofibrilas/metabolismo , Neurônios/citologia , Ratos , Ratos Transgênicos , Ratos Wistar , Proteínas Recombinantes de Fusão/metabolismo , Telencéfalo/citologia , Telencéfalo/crescimento & desenvolvimento , Telencéfalo/metabolismo
12.
J Neuropathol Exp Neurol ; 72(12): 1145-61, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24226268

RESUMO

Truncated tau protein at Asp(421) is associated with neurofibrillary pathology in Alzheimer disease (AD); however, little is known about its presence in the form of nonfibrillary aggregates. Here, we report immunohistochemical staining of the Tau-C3 antibody, which recognizes Asp(421)-truncated tau, in a group of AD cases with different extents of cognitive impairment. In the hippocampus, we found distinct nonfibrillary aggregates of Asp(421)-truncated tau. Unlike Asp(421)-composed neurofibrillary tangles, however, these nonfibrillary pathologies did not increase significantly with respect to the Braak staging and, therefore, make no significant contribution to cognitive impairment. On the other hand, despite in vitro evidence that caspase-3 cleaves monomeric tau at Asp(421), to date, this truncation has not been demonstrated to be executed by this protease in polymeric tau entities. We determined that Asp(421) truncation can be produced by caspase-3 in oligomeric and multimeric complexes of recombinant full-length tau in isolated native tau filaments in vitro and in situ in neurofibrillary tangles analyzed in fresh brain slices from AD cases. Our data suggest that generation of this pathologic Asp(421) truncation of tau in long-lasting fibrillary structures may produce further permanent toxicity for neurons in the brains of patients with AD.


Assuntos
Doença de Alzheimer/patologia , Encéfalo/metabolismo , Caspase 3/farmacologia , Proteínas tau/efeitos dos fármacos , Proteínas tau/metabolismo , Idoso de 80 Anos ou mais , Clorometilcetonas de Aminoácidos/farmacologia , Ácido Aspártico/metabolismo , Encéfalo/patologia , Encéfalo/ultraestrutura , Caspase 3/metabolismo , Feminino , Humanos , Masculino , Microscopia Eletrônica , Peso Molecular , Emaranhados Neurofibrilares/metabolismo , Emaranhados Neurofibrilares/patologia , Emaranhados Neurofibrilares/ultraestrutura , Neurofibrilas/metabolismo , Neurofibrilas/patologia , Neurofibrilas/ultraestrutura , Fármacos Neuroprotetores/farmacologia , Oligopeptídeos/farmacologia , Proteínas tau/ultraestrutura
13.
Prog Brain Res ; 203: 115-60, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24041279

RESUMO

Available records indicate that the human body has always been conceived, in different periods and cultures, as spanned by multiple channels for internal communication and coherent functioning as a unit-"meridians" in treatises of Chinese medicine, metu in Egyptian papyri, srotas in Ayurvedic Indian texts, and neura in the Western scientific heritage from ancient Greece. Unfortunately, the earliest extant figurative depictions of such pathways of general control, complementary to the blood vessels, are late medieval copies of old crude sketches that attempted to show the main anatomico-physiological systems. The scarcity of adequate illustrations was more than compensated in the Renaissance, when the efforts of both artists and anatomists for the first time produced basically correct renditions of the human nervous system and many other bodily structures. As attention was next focused on microscopic structure as a requisite to understand physiological mechanisms, during the Enlightenment the nerves were revealed to consist of numerous thin tubes or fibers aligned in parallel. Improved microscopy techniques in the nineteenth century led to discovering and delineating still finer fibrils coursing along the cores of the nerve fibers themselves. Electron microscopy, developed throughout the twentieth century, recognized some of these fibrils within nerve fibers as being also tubular. All the progressive stages in understanding nerve construction, at increasingly more detailed scales, have been accompanied by technological advances and by debate about the structure and function relationship. And every step has been a source of amazing imagery.


Assuntos
Anatomia Artística/história , Sistema Nervoso/anatomia & histologia , Animais , História do Século XV , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , História Antiga , História Medieval , Humanos , Microtúbulos/ultraestrutura , Fibras Nervosas/ultraestrutura , Neurofibrilas/ultraestrutura , Dor , Prazer/fisiologia , Desempenho Psicomotor/fisiologia
14.
FEBS Lett ; 587(15): 2325-31, 2013 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-23792159

RESUMO

Several classes of chemicals are able to bind to the thyroxine binding sites of transthyretin (TTR), stabilizing its native state and inhibiting in vitro the amyloidogenic process. The amyloidogenic I84S TTR variant undergoes a large conformational change at moderately acidic pH. Structural evidence has been obtained by X-ray analysis for the native state stabilization of I84S TTR by two chemically distinct fibrillogenesis inhibitors. In fact, they fully prevent the acidic pH-induced protein conformational change as a result of a long-range stabilizing effect. This study provides further support to the therapeutic strategy based on the use of TTR stabilizers as anti-amyloidogenic drugs.


Assuntos
Amiloide/química , Neurofibrilas/efeitos dos fármacos , Pré-Albumina/química , Cristalografia por Raios X , Concentração de Íons de Hidrogênio , Modelos Moleculares , Conformação Proteica
15.
Neurochem Int ; 62(1): 103-12, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23064431

RESUMO

In the last decades, a series of compounds, including quinones and polyphenols, has been described as having anti-fibrillogenic action on α-synuclein (α-syn) whose aggregation is associated to the pathogenesis of Parkinson's disease (PD). Most of these molecules act as promiscuous anti-amyloidogenic agents, interacting with the diverse amyloidogenic proteins (mostly unfolded) through non-specific hydrophobic interactions. Herein we investigated the effect of the vitamins K (phylloquinone, menaquinone and menadione), which are 1,4-naphthoquinone (1,4-NQ) derivatives, on α-syn aggregation, comparing them with other anti-fibrillogenic molecules such as quinones, polyphenols and lipophilic vitamins. Vitamins K delayed α-syn fibrillization in substoichiometric concentrations, leading to the formation of short, sheared fibrils and amorphous aggregates, which are less prone to produce leakage of synthetic vesicles. In seeding conditions, menadione and 1,4-NQ significantly inhibited fibrils elongation, which could be explained by their ability to destabilize preformed fibrils of α-syn. Bidimensional NMR experiments indicate that a specific site at the N-terminal α-syn (Gly31/Lys32) is involved in the interaction with vitamins K, which is corroborated by previous studies suggesting that Lys is a key residue in the interaction with quinones. Together, our data suggest that 1,4-NQ, recently showed up by our group as a potential scaffold for designing new monoamine oxidase inhibitors, is also capable to modulate α-syn fibrillization in vitro.


Assuntos
Antifibrinolíticos , Neurofibrilas/efeitos dos fármacos , Quinonas/farmacologia , Vitamina K/farmacologia , alfa-Sinucleína/metabolismo , Núcleo Celular/efeitos dos fármacos , Humanos , Espectroscopia de Ressonância Magnética , Microscopia de Força Atômica , Naftoquinonas/farmacologia , Vitamina K/análogos & derivados , Vitamina K/química , Vitamina K 1/farmacologia , Vitamina K 2/farmacologia , Vitamina K 3/farmacologia , alfa-Sinucleína/genética
16.
J Alzheimers Dis ; 33 Suppl 1: S123-39, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22710920

RESUMO

Microtubule associated protein tau is a phosphoprotein which potentially has 80 serine/threonine and 5 tyrosine phosphorylation sites. Normal brain tau contains 2-3 moles of phosphate per mole of the protein. In Alzheimer's disease brain, tau is abnormally hyperphosphorylated to a stoichiometry of at least three-fold greater than normal tau, and in this altered state it is aggregated into paired helical filaments forming neurofibrillary tangles, a histopathological hallmark of the disease. The abnormal hyperphosphorylation of tau is also a hallmark of several other related neurodegenerative disorders, called tauopathies. The density of neurofibrillary tangles in the neocortex correlates with dementia and, hence, is a rational therapeutic target and an area of increasing research interest. Development of rational tau-based therapeutic drugs requires understanding of the role of various phosphorylation sites, protein kinases and phosphatases, and post-translational modifications that regulate the phosphorylation of this protein at various sites, as well as the molecular mechanism by which the abnormally hyperphosphorylated tau leads to neurodegeneration and dementia. In this article we briefly review the progress made in these areas of research.


Assuntos
Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Degeneração Neural/metabolismo , Emaranhados Neurofibrilares/metabolismo , Proteínas tau/metabolismo , Doença de Alzheimer/patologia , Animais , Encéfalo/patologia , Humanos , Camundongos , Degeneração Neural/patologia , Emaranhados Neurofibrilares/patologia , Neurofibrilas/metabolismo , Neurofibrilas/patologia , Fosforilação
17.
Ann Neurol ; 72(4): 517-24, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23109146

RESUMO

OBJECTIVE: The lesions of Parkinson disease spread through the brain in a characteristic pattern that corresponds to axonal projections. Previous observations suggest that misfolded α-synuclein could behave as a prion, moving from neuron to neuron and causing endogenous α-synuclein to misfold. Here, we characterized and quantified the axonal transport of α-synuclein fibrils and showed that fibrils could be transferred from axons to second-order neurons following anterograde transport. METHODS: We grew primary cortical mouse neurons in microfluidic devices to separate somata from axonal projections in fluidically isolated microenvironments. We used live-cell imaging and immunofluorescence to characterize the transport of fluorescent α-synuclein fibrils and their transfer to second-order neurons. RESULTS: Fibrillar α-synuclein was internalized by primary neurons and transported in axons with kinetics consistent with slow component-b of axonal transport (fast axonal transport with saltatory movement). Fibrillar α-synuclein was readily observed in the cell bodies of second-order neurons following anterograde axonal transport. Axon-to-soma transfer appeared not to require synaptic contacts. INTERPRETATION: These results support the hypothesis that the progression of Parkinson disease can be caused by neuron-to-neuron spread of α-synuclein aggregates and that the anatomical pattern of progression of lesions between axonally connected areas results from the axonal transport of such aggregates. That the transfer did not appear to be trans-synaptic gives hope that α-synuclein fibrils could be intercepted by drugs during the extracellular phase of their journey.


Assuntos
Transporte Axonal/fisiologia , Neurofibrilas/fisiologia , Neurônios/fisiologia , Transmissão Sináptica/fisiologia , alfa-Sinucleína/fisiologia , Peptídeos beta-Amiloides/metabolismo , Animais , Corantes Fluorescentes , Imuno-Histoquímica , Maleimidas , Camundongos , Técnicas Analíticas Microfluídicas , Microscopia Confocal , Microscopia de Fluorescência , Neuroglia/fisiologia , Fragmentos de Peptídeos/metabolismo
18.
Neurobiol Dis ; 46(3): 663-72, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22449754

RESUMO

An increasing body of evidence indicates a role for oligomers of the amyloid-ß peptide (Aß) in the neurotoxicity of this peptide and the pathology of Alzheimer's disease (AD). Several neurotoxic oligomeric forms of Aß have been noted ranging from the larger Amyloid ß-Derived Diffusible Ligands (ADDLs) to smaller trimers and dimers of Aß. More recently a dodecameric form of Aß with a 56 kDa molecular weight, denoted Aß*56, was shown to cause memory impairment in AD model mice. Here, we present for the first time a potential therapeutic strategy for AD that targets the early stages in the formation of neurotoxic Aß*56 oligomers using a modified quinone-Tryptophan small molecule N-(3-chloro-1,4-dihydro-1,4-dioxo-2-naphthalenyl)-L-Tryptophan (Cl-NQTrp). Using NMR spectroscopy we show that this compound binds the aromatic recognition core of Aß and prevents the formation of oligomers. We assessed the effect of Cl-NQTrp in vivo in transgenic flies expressing Aß(1-42) in their nervous system. When these flies were fed with Cl-NQTrp a marked alleviation of their Aß-engendered reduced life span and defective locomotion was observed. Finally, intraperitoneal injection of Cl-NQTrp into an aggressive AD mouse model reduced the level of the Aß*56 species in their brain and reversed their cognitive defects. Further experiments should assess whether this is a direct effect of the drug in the brain or an indirect peripheral effect. This is the first demonstration that targeted reduction of Aß*56 results in amelioration of AD symptoms. This second generation of tryptophan-modified naphthoquinones could therefore serve as potent disease modifying therapeutic for AD.


Assuntos
Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/metabolismo , Cognição/efeitos dos fármacos , Naftalenos/farmacologia , Fármacos Neuroprotetores/farmacologia , Triptofano/análogos & derivados , Doença de Alzheimer/metabolismo , Doença de Alzheimer/psicologia , Animais , Animais Geneticamente Modificados , Benzotiazóis , Barreira Hematoencefálica/metabolismo , Química Encefálica/efeitos dos fármacos , Drosophila/metabolismo , Corantes Fluorescentes , Humanos , Longevidade/efeitos dos fármacos , Espectroscopia de Ressonância Magnética , Masculino , Camundongos , Camundongos Transgênicos , Microscopia Eletrônica de Transmissão , Modelos Moleculares , Atividade Motora/efeitos dos fármacos , Neurofibrilas/efeitos dos fármacos , Neurofibrilas/patologia , Desempenho Psicomotor/efeitos dos fármacos , Reconhecimento Psicológico/efeitos dos fármacos , Tiazóis , Triptofano/farmacologia
19.
J Neurochem ; 121(2): 228-38, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22353164

RESUMO

Amyloid ß-protein (Aß) deposits in brains of Alzheimer's disease patients generate proinflammatory cytokines and chemokines that recruit microglial cells to phagocytose Aß. Nucleotides released from apoptotic cells activate P2Y(2) receptors (P2Y(2) Rs) in macrophages to promote clearance of dead cells. In this study, we investigated the role of P2Y(2) Rs in the phagocytosis and clearance of Aß. Treatment of mouse primary microglial cells with fibrillar (fAß(1-42) ) and oligomeric (oAß(1-42) ) Aß(1-42) aggregation solutions caused a rapid release of ATP (maximum after 10 min). Furthermore, fAß(1-42) and oAß(1-42) treatment for 24 h caused an increase in P2Y(2) R gene expression. Treatment with fAß(1-42) and oAß(1-42) aggregation solutions increased the motility of neighboring microglial cells, a response inhibited by pre-treatment with apyrase, an enzyme that hydrolyzes nucleotides. The P2Y(2) R agonists ATP and UTP caused significant uptake of Aß(1-42) by microglial cells within 30 min, which reached a maximum within 1 h, but did not increase Aß(1-42) uptake by primary microglial cells isolated from P2Y(2) R(-/-) mice. Inhibitors of α(v) integrins, Src and Rac decreased UTP-induced Aß(1-42) uptake, suggesting that these previously identified components of the P2Y(2) R signaling pathway play a role in Aß phagocytosis by microglial cells. Finally, we found that UTP treatment enhances Aß(1-42) degradation by microglial cells, but not in cells isolated from P2Y(2) R(-/-) mice. Taken together, our findings suggest that P2Y(2) Rs can activate microglial cells to enhance Aß clearance and highlight the P2Y(2) R as a therapeutic target in Alzheimer's disease.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/toxicidade , Movimento Celular/efeitos dos fármacos , Microglia/metabolismo , Nucleotídeos/metabolismo , Nucleotídeos/farmacologia , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/toxicidade , Agonistas do Receptor Purinérgico P2Y , Receptores Purinérgicos P2Y2/efeitos dos fármacos , Trifosfato de Adenosina/metabolismo , Animais , Western Blotting , Separação Celular , Ensaio de Imunoadsorção Enzimática , Feminino , Integrina alfa5/farmacologia , L-Lactato Desidrogenase/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microglia/efeitos dos fármacos , Microscopia Eletrônica de Transmissão , Neurofibrilas/metabolismo , Fagocitose/efeitos dos fármacos , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Uridina Trifosfato/farmacologia , Proteínas rac de Ligação ao GTP/fisiologia , Quinases da Família src/fisiologia
20.
J Neurochem ; 121(4): 619-28, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22260232

RESUMO

Type 2 diabetes mellitus is thought to be a significant risk factor for Alzheimer's disease. Insulin resistance also affects the central nervous system by regulating key processes, such as neuronal survival and longevity, learning and memory. However, the mechanisms underlying these effects remain uncertain. To investigate whether insulin resistance is associated with the assembly of amyloid ß-protein (Aß) at the cell surface of neurons, we inhibited insulin-signalling pathways of primary neurons. The treatments of insulin receptor (IR)-knockdown and a phosphatidylinositol 3-kinase inhibitor (LY294002), but not an extracellular signal-regulated kinase inhibitor, induced an increase in GM1 ganglioside (GM1) levels in detergent-resistant membrane microdomains of the neurons. The aged db/db mouse brain exhibited reduction in IR expression and phosphorylation of Akt, which later induced an increase in the high-density GM1-clusters on synaptosomes. Neurons treated with IR knockdown or LY294002, and synaptosomes of the aged db/db mouse brains markedly accelerated an assembly of Aßs. These results suggest that ageing and peripheral insulin resistance induce brain insulin resistance, which accelerates the assembly of Aßs by increasing and clustering of GM1 in detergent-resistant membrane microdomains of neuronal membranes.


Assuntos
Peptídeos beta-Amiloides/fisiologia , Química Encefálica/fisiologia , Gangliosídeo G(M1)/metabolismo , Resistência à Insulina/fisiologia , Neurofibrilas/efeitos dos fármacos , Receptores Pré-Sinápticos/metabolismo , Envelhecimento/fisiologia , Animais , Western Blotting , Separação Celular , Células Cultivadas , Colesterol/metabolismo , Cromonas/farmacologia , Diabetes Mellitus Tipo 2/patologia , Inibidores Enzimáticos/farmacologia , Corantes Fluorescentes , Camundongos , Morfolinas/farmacologia , Neurônios/efeitos dos fármacos , RNA Interferente Pequeno/farmacologia , Ratos , Ratos Sprague-Dawley , Receptor de Insulina/genética , Receptor de Insulina/fisiologia , Esfingomielinas/metabolismo , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismo
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