RESUMO
Progressive supranuclear palsy is a primary tauopathy affecting both neurons and glia and is responsible for both motor and cognitive symptoms. Recently, it has been suggested that progressive supranuclear palsy tauopathy may spread in the brain from cell to cell in a 'prion-like' manner. However, direct experimental evidence of this phenomenon, and its consequences on brain functions, is still lacking in primates. In this study, we first derived sarkosyl-insoluble tau fractions from post-mortem brains of patients with progressive supranuclear palsy. We also isolated the same fraction from age-matched control brains. Compared to control extracts, the in vitro characterization of progressive supranuclear palsy-tau fractions demonstrated a high seeding activity in P301S-tau expressing cells, displaying after incubation abnormally phosphorylated (AT8- and AT100-positivity), misfolded, filamentous (pentameric formyl thiophene acetic acid positive) and sarkosyl-insoluble tau. We bilaterally injected two male rhesus macaques in the supranigral area with this fraction of progressive supranuclear palsy-tau proteopathic seeds, and two other macaques with the control fraction. The quantitative analysis of kinematic features revealed that progressive supranuclear palsy-tau injected macaques exhibited symptoms suggestive of parkinsonism as early as 6 months after injection, remaining present until euthanasia at 18 months. An object retrieval task showed the progressive appearance of a significant dysexecutive syndrome in progressive supranuclear palsy-tau injected macaques compared to controls. We found AT8-positive staining and 4R-tau inclusions only in progressive supranuclear palsy-tau injected macaques. Characteristic pathological hallmarks of progressive supranuclear palsy, including globose and neurofibrillary tangles, tufted astrocytes and coiled bodies, were found close to the injection sites but also in connected brain regions that are known to be affected in progressive supranuclear palsy (striatum, pallidum, thalamus). Interestingly, while glial AT8-positive lesions were the most frequent near the injection site, we found mainly neuronal inclusions in the remote brain area, consistent with a neuronal transsynaptic spreading of the disease. Our results demonstrate that progressive supranuclear palsy patient-derived tau aggregates can induce motor and behavioural impairments in non-human primates related to the prion-like seeding and spreading of typical pathological progressive supranuclear palsy lesions. This pilot study paves the way for supporting progressive supranuclear palsy-tau injected macaque as a relevant animal model to accelerate drug development targeting this rare and fatal neurodegenerative disease.
Assuntos
Doenças Neurodegenerativas , Paralisia Supranuclear Progressiva , Tauopatias , Animais , Masculino , Paralisia Supranuclear Progressiva/patologia , Proteínas tau/metabolismo , Doenças Neurodegenerativas/patologia , Macaca mulatta/metabolismo , Projetos Piloto , Tauopatias/patologia , Encéfalo/patologiaRESUMO
INTRODUCTION: The "prion-like" features of Alzheimer's disease (AD) tauopathy and its relationship with amyloid-ß (Aß) have never been experimentally studied in primates phylogenetically close to humans. METHODS: We injected 17 macaques in the entorhinal cortex with nanograms of seeding-competent tau aggregates purified from AD brains or control extracts from aged-matched healthy brains, with or without intracerebroventricular co-injections of oligomeric-Aß. RESULTS: Pathological tau injection increased cerebrospinal fluid (CSF) p-tau181 concentration after 18 months. Tau pathology spreads from the entorhinal cortex to the hippocampal trisynaptic loop and the cingulate cortex, resuming the experimental progression of Braak stage I to IV. Many AD-related molecular networks were impacted by tau seeds injections regardless of Aß injections in proteomic analyses. However, we found mature neurofibrillary tangles, increased CSF total-tau concentration, and pre- and postsynaptic degeneration only in Aß co-injected macaques. DISCUSSION: Oligomeric-Aß mediates the maturation of tau pathology and its neuronal toxicity in macaques but not its initial spreading. HIGHLIGHTS: This study supports the "prion-like" properties of misfolded tau extracted from AD brains. This study empirically validates the Braak staging in an anthropomorphic brain. This study highlights the role of oligomeric Aß in driving the maturation and toxicity of tau pathology. This work establishes a novel animal model of early sporadic AD that is closer to the human pathology.
Assuntos
Doença de Alzheimer , Príons , Animais , Humanos , Idoso , Doença de Alzheimer/patologia , Macaca/metabolismo , Proteômica , Proteínas tau/metabolismo , Peptídeos beta-Amiloides/metabolismo , Encéfalo/patologiaRESUMO
Hyperphosphorylation and aggregation of the protein tau play key roles in the development of Alzheimer's disease (AD). While the molecular structure of the filamentous tau aggregates has been determined to atomic resolution, there is far less information available about the smaller, soluble aggregates, which are believed to be more toxic. Traditional techniques are limited to bulk measures and struggle to identify individual aggregates in complex biological samples. To address this, we developed a novel single-molecule pull-down-based assay (MAPTau) to detect and characterize individual tau aggregates in AD and control post-mortem brain and biofluids. Using MAPTau, we report the quantity, as well as the size and circularity of tau aggregates measured using super-resolution microscopy, revealing AD-specific differences in tau aggregate morphology. By adapting MAPTau to detect multiple phosphorylation markers in individual aggregates using two-color coincidence detection, we derived compositional profiles of the individual aggregates. We find an AD-specific phosphorylation profile of tau aggregates with more than 80 % containing multiple phosphorylations, compared to 5 % in age-matched non-AD controls. Our results show that MAPTau is able to identify disease-specific subpopulations of tau aggregates phosphorylated at different sites, that are invisible to other methods and enable the study of disease mechanisms and diagnosis.
Assuntos
Doença de Alzheimer , Agregados Proteicos , Proteínas tau , Humanos , Doença de Alzheimer/metabolismo , Doença de Alzheimer/diagnóstico , Proteínas tau/metabolismo , Proteínas tau/química , Proteínas tau/análise , Fosforilação , Imagem Individual de Molécula/métodos , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagem , Encéfalo/patologiaRESUMO
The accumulation of amyloid Tau aggregates is implicated in Alzheimer's disease (AD) and other tauopathies. Molecular chaperones are known to maintain protein homeostasis. Here, we show that an ATP-dependent human chaperone system disassembles Tau fibrils in vitro We found that this function is mediated by the core chaperone HSC70, assisted by specific cochaperones, in particular class B J-domain proteins and a heat shock protein 110 (Hsp110)-type nucleotide exchange factor (NEF). The Hsp70 disaggregation machinery processed recombinant fibrils assembled from all six Tau isoforms as well as Sarkosyl-resistant Tau aggregates extracted from cell cultures and human AD brain tissues, demonstrating the ability of the Hsp70 machinery to recognize a broad range of Tau aggregates. However, the chaperone activity released monomeric and small oligomeric Tau species, which induced the aggregation of self-propagating Tau conformers in a Tau cell culture model. We conclude that the activity of the Hsp70 disaggregation machinery is a double-edged sword, as it eliminates Tau amyloids at the cost of generating new seeds.
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Doença de Alzheimer , Amiloide , Encéfalo , Proteínas de Choque Térmico HSP70 , Proteínas tau , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Amiloide/química , Amiloide/genética , Amiloide/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Células HEK293 , Proteínas de Choque Térmico HSP70/química , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico HSP70/metabolismo , Humanos , Proteínas tau/química , Proteínas tau/genética , Proteínas tau/metabolismoRESUMO
Endocytic processes are facilitated by both curvature-generating BAR-domain proteins and the coordinated polymerization of actin filaments. Under physiological conditions, the N-BAR protein Bin1 has been shown to sense and curve membranes in a variety of cellular processes. Recent studies have identified Bin1 as a risk factor for Alzheimer's disease, although its possible pathological function in neurodegeneration is currently unknown. Here, we report that Bin1 not only shapes membranes, but is also directly involved in actin binding through its BAR domain. We observed a moderate actin bundling activity by human Bin1 and describe its ability to stabilize actin filaments against depolymerization. Moreover, Bin1 is also involved in stabilizing tau-induced actin bundles, which are neuropathological hallmarks of Alzheimer's disease. We also provide evidence for this effect in vivo, where we observed that downregulation of Bin1 in a Drosophila model of tauopathy significantly reduces the appearance of tau-induced actin inclusions. Together, these findings reveal the ability of Bin1 to modify actin dynamics and provide a possible mechanistic connection between Bin1 and tau-induced pathobiological changes of the actin cytoskeleton.
Assuntos
Actinas/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas de Transporte/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas Nucleares/genética , Tauopatias/genética , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor/genética , Proteínas tau/genética , Citoesqueleto de Actina/genética , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Sítios de Ligação , Proteínas de Transporte/metabolismo , Clonagem Molecular , Modelos Animais de Doenças , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Regulação da Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Proteínas Nucleares/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Tauopatias/metabolismo , Tauopatias/patologia , Fatores de Transcrição/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Proteínas tau/metabolismoRESUMO
OBJECTIVE: Easy common bile duct (CBD) cannulation is associated with low complication rate. This study aimed to investigate the potential impact of nitroglycerin and glucagon administration on selective CBD cannulation and prevention of post-ERCP pancreatitis. METHODS: A prospective single center, double-blind randomized study in which a total of 455 patients were randomly assigned to CBD cannulation by receiving 6 puffs (2.4 mg) sublingual nitroglycerin and glucagon 1 mg intravenously (n = 227, group A) or 6 puffs sterile water and 20 mg hyoscine-n-butyl bromide intravenously (n = 228, group B). After ERCP, patients were followed for the development of drugs' side-effects and post-ERCP complications. RESULTS: There were no statistically significant differences between the two groups regarding demographic data and ERCP findings. Success rate of selective CΒD cannulation was 95.15% in group A versus 82.29% in group B (p < .001). Time required for CBD cannulation was 2.82 ± 2.31 min in group A versus 4.27 ± 3.84 min in group B (p = .021). Needle-knife papillotomy was used in 11 (4.85%) patients of group A and 39 (17.11%) patients of group B (p = .001). The frequency of post-ERCP pancreatitis was significantly lower in group A than in group B (3.08% versus 7.46%, p = .037). No difference was observed between the two groups with regard to the occurrence of post-procedure hemorrhage. There was no procedure-related mortality; no adverse event related to the combination regimen was observed. CONCLUSIONS: Combined nitroglycerin and glucagon administration achieves a high selective CBC cannulation rates with concomitant reduction of post-ERCP pancreatitis incidence. However, further relative large-scale studies are needed to confirm our findings before definite conclusions can be drawn (Clinical trial registration number: NT: 4321).
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Cateterismo/efeitos adversos , Colangiopancreatografia Retrógrada Endoscópica/efeitos adversos , Ducto Colédoco/cirurgia , Glucagon/administração & dosagem , Nitroglicerina/administração & dosagem , Pancreatite/prevenção & controle , Idoso , Idoso de 80 Anos ou mais , Método Duplo-Cego , Feminino , Grécia , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/prevenção & controle , Estudos ProspectivosAssuntos
Doença de Alzheimer , Demência , Helicobacter pylori , Síndrome Metabólica , Humanos , Incidência , Inquéritos e QuestionáriosRESUMO
Filaments made of residues 120-254 of transmembrane protein 106B (TMEM106B) form in an age-dependent manner and can be extracted from the brains of neurologically normal individuals and those of subjects with a variety of neurodegenerative diseases. TMEM106B filament formation requires cleavage at residue 120 of the 274 amino acid protein; at present, it is not known if residues 255-274 form the fuzzy coat of TMEM106B filaments. Here we show that a second cleavage appears likely, based on staining with an antibody raised against residues 263-274 of TMEM106B. We also show that besides the brain TMEM106B inclusions form in dorsal root ganglia and spinal cord, where they were mostly found in non-neuronal cells. We confirm that in the brain, inclusions were most abundant in astrocytes. No inclusions were detected in heart, liver, spleen or hilar lymph nodes. Based on their staining with luminescent conjugated oligothiophenes, we confirm that TMEM106B inclusions are amyloids. By in situ immunoelectron microscopy, TMEM106B assemblies were often found in structures resembling endosomes and lysosomes.
Assuntos
Proteínas de Membrana , Proteínas do Tecido Nervoso , Proteínas de Membrana/metabolismo , Humanos , Proteínas do Tecido Nervoso/metabolismo , Medula Espinal/metabolismo , Amiloide/metabolismo , Gânglios Espinais/metabolismo , Encéfalo/metabolismo , Masculino , Feminino , Sistema Nervoso Periférico/metabolismo , Idoso , AnimaisRESUMO
Alzheimer's disease is the most common cause of dementia in the elderly, prompting extensive efforts to pinpoint novel therapeutic targets for effective intervention. Among the hallmark features of Alzheimer's disease is the development of neurofibrillary tangles comprised of hyperphosphorylated tau protein, whose progressive spread throughout the brain is associated with neuronal death. Trans-synaptic propagation of tau has been observed in mouse models, and indirect evidence for tau spread via synapses has been observed in human Alzheimer's disease. Halting tau propagation is a promising therapeutic target for Alzheimer's disease; thus, a scalable model system to screen for modifiers of tau spread would be very useful for the field. To this end, we sought to emulate the trans-synaptic spread of human tau in Drosophila melanogaster. Employing the trans-Tango circuit mapping technique, we investigated whether tau spreads between synaptically connected neurons. Immunohistochemistry and confocal imaging were used to look for tau propagation. Examination of hundreds of flies expressing four different human tau constructs in two distinct neuronal populations reveals a robust resistance in Drosophila to the trans-synaptic spread of human tau. This resistance persisted in lines with concurrent expression of amyloid-ß, in lines with global human tau knock-in to provide a template for human tau in downstream neurons, and with manipulations of temperature. These negative data are important for the field as we establish that Drosophila expressing human tau in subsets of neurons are unlikely to be useful to perform screens to find mechanisms to reduce the trans-synaptic spread of tau. The inherent resistance observed in Drosophila may serve as a valuable clue, offering insights into strategies for impeding tau spread in future studies.
RESUMO
Tau is a soluble protein interacting with tubulin to stabilize microtubules. However, under pathological conditions, it becomes hyperphosphorylated and aggregates, a process that can be induced by treating cells with exogenously added tau fibrils. Here, we employ single-molecule localization microscopy to resolve the aggregate species formed in early stages of seeded tau aggregation. We report that entry of sufficient tau assemblies into the cytosol induces the self-replication of small tau aggregates, with a doubling time of 5 h inside HEK cells and 1 day in murine primary neurons, which then grow into fibrils. Seeding occurs in the vicinity of the microtubule cytoskeleton, is accelerated by the proteasome, and results in release of small assemblies into the media. In the absence of seeding, cells still spontaneously form small aggregates at lower levels. Overall, our work provides a quantitative picture of the early stages of templated seeded tau aggregation in cells.
Assuntos
Doença de Alzheimer , Proteínas tau , Camundongos , Animais , Proteínas tau/metabolismo , Microtúbulos/metabolismo , Tubulina (Proteína)/metabolismo , Citosol/metabolismo , Neurônios/metabolismo , Doença de Alzheimer/metabolismo , Agregados ProteicosRESUMO
Aggregates of the protein tau are proposed to drive pathogenesis in neurodegenerative diseases. Tau can be targeted by using passively transferred antibodies (Abs), but the mechanisms of Ab protection are incompletely understood. In this work, we used a variety of cell and animal model systems and showed that the cytosolic Ab receptor and E3 ligase TRIM21 (T21) could play a role in Ab protection against tau pathology. Tau-Ab complexes were internalized to the cytosol of neurons, which enabled T21 engagement and protection against seeded aggregation. Ab-mediated protection against tau pathology was lost in mice that lacked T21. Thus, the cytosolic compartment provides a site of immunotherapeutic protection, which may help in the design of Ab-based therapies in neurodegenerative disease.
Assuntos
Anticorpos Monoclonais , Imunização Passiva , Ribonucleoproteínas , Tauopatias , Proteínas com Motivo Tripartido , Ubiquitina-Proteína Ligases , Proteínas tau , Animais , Camundongos , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/uso terapêutico , Citosol/metabolismo , Modelos Animais de Doenças , Receptores Fc , Ribonucleoproteínas/genética , Ribonucleoproteínas/metabolismo , Proteínas tau/imunologia , Tauopatias/terapia , Proteínas com Motivo Tripartido/genética , Proteínas com Motivo Tripartido/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Assemblies of tau can transit between neurons, seeding aggregation in a prion-like manner. To accomplish this, tau must cross cell-limiting membranes, a process that is poorly understood. Here, we establish assays for the study of tau entry into the cytosol as a phenomenon distinct from uptake, in real time, and at physiological concentrations. The entry pathway of tau is cell type specific and, in neurons, highly sensitive to cholesterol. Depletion of the cholesterol transporter Niemann-Pick type C1 or extraction of membrane cholesterol renders neurons highly permissive to tau entry and potentiates seeding even at low levels of exogenous tau assemblies. Conversely, cholesterol supplementation reduces entry and almost completely blocks seeded aggregation. Our findings establish entry as a rate-limiting step to seeded aggregation and demonstrate that dysregulated cholesterol, a feature of several neurodegenerative diseases, potentiates tau aggregation by promoting entry of tau assemblies into the cell interior.
Assuntos
Doença de Alzheimer , Príons , Doença de Alzheimer/metabolismo , Colesterol/metabolismo , Citosol/metabolismo , Humanos , Neurônios/metabolismo , Príons/metabolismo , Proteínas tau/metabolismoRESUMO
OBJECTIVE: This study assessed the diagnostic yield of capsule endoscopy (CE) and its impact on patients with obscure gastrointestinal bleeding (OGIB). SUBJECTS AND METHODS: Between May 2007 and May 2009, 63 patients with OGIB (overt bleeding: 25, and occult blood loss with chronic ferropenic anemia: 38) and normal upper and lower endoscopy were studied by CE. Demographic characteristics, prior diagnostic tests, CE findings, therapeutic interventions, medical treatment and clinical outcomes following CE were evaluated. RESULTS: The overall diagnostic yield was 44.44% of patients and included findings of angiectasia in 11 (17.46%) patients, nonsteroidal anti-inflammatory drugs enteropathy in 6 (9.52%) patients, celiac disease in 3 (4.76%) patients, tumors in 2 (3.17%) patients, and a variety of other diagnoses ranging from varices to ulcers (due to congenital afibrinogenemia and amyloidosis). The diagnostic yield was notably higher in overt bleeders (15/25, 60%) compared to occult bleeders (13/38, 34.21%; p = 0.044), and in patients with overt bleeding who had CE within the first 10 days (14/16, 87.5%) after the bleeding episode in comparison to overt bleeders who underwent CE >10 days after the bleeding episode (2/16, 11.1%; p < 0.0001). During follow-up (11.8 ± 7 months), CE findings led to specific therapy that resolved the underlying disease or improved the clinical condition in 45 of 63 patients, thus having a positive clinical impact of 71.43%. CONCLUSION: CE has a high diagnostic yield and a positive influence on clinical management in a significant proportion of patients with OGIB. These data further support the role of CE in routine clinical practice.
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Cápsulas Endoscópicas , Endoscopia/métodos , Hemorragia Gastrointestinal/diagnóstico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anti-Inflamatórios não Esteroides/efeitos adversos , Cápsulas Endoscópicas/normas , Endoscopia/normas , Feminino , Gastroenteropatias/complicações , Gastroenteropatias/diagnóstico , Gastroenteropatias/epidemiologia , Hemorragia Gastrointestinal/complicações , Hemorragia Gastrointestinal/terapia , Grécia , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento , Adulto JovemRESUMO
The deposition of tau aggregates throughout the brain is a pathological characteristic within a group of neurodegenerative diseases collectively termed tauopathies, which includes Alzheimer's disease. While recent findings suggest the involvement of unconventional secretory pathways driving tau into the extracellular space and mediating the propagation of the disease-associated pathology, many of the mechanistic details governing this process remain elusive. In the current study, we provide an in-depth characterization of the unconventional secretory pathway of tau and identify novel molecular determinants that are required for this process. Here, using Drosophila models of tauopathy, we correlate the hyperphosphorylation and aggregation state of tau with the disease-related neurotoxicity. These newly established systems recapitulate all the previously identified hallmarks of tau secretion, including the contribution of tau hyperphosphorylation as well as the requirement for PI(4,5)P2 triggering the direct translocation of tau. Using a series of cellular assays, we demonstrate that both the sulfated proteoglycans on the cell surface and the correct orientation of the protein at the inner plasma membrane leaflet are critical determinants of this process. Finally, we identify two cysteine residues within the microtubule binding repeat domain as novel cis-elements that are important for both unconventional secretion and trans-cellular propagation of tau.
Assuntos
Regulação da Expressão Gênica , Sequências Reguladoras de Ácido Nucleico , Proteínas tau/biossíntese , Proteínas tau/genética , Animais , Células CHO , Membrana Celular/metabolismo , Permeabilidade da Membrana Celular , Cromatografia Líquida , Cricetulus , Cisteína/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Imunofluorescência , Perfilação da Expressão Gênica , Fosforilação , Transporte Proteico , Proteínas Recombinantes , Retina/metabolismo , Espectrometria de Massas em TandemRESUMO
The microtubule-associated protein tau aggregates in multiple neurodegenerative diseases, causing inflammation and changing the inflammatory signature of microglia by unknown mechanisms. We have shown that microglia phagocytose live neurons containing tau aggregates cultured from P301S tau mice due to neuronal tau aggregate-induced exposure of the "eat me" signal phosphatidylserine. Here, we show that after phagocytosing tau aggregate-bearing neurons, microglia become hypophagocytic while releasing seed-competent insoluble tau aggregates. These microglia express a senescence-like phenotype, demonstrated by acidic ß-galactosidase activity, secretion of paracrine senescence-associated cytokines, and maturation of matrix remodeling enzymes, results that are corroborated in P301S mouse brains and ex vivo brain slices. In particular, the nuclear factor κBdependent activation of matrix metalloprotease 3 (MMP3/stromelysin1) was replicated in brains from patients with tauopathy. These data show that microglia that have been activated to ingest live tau aggregates-bearing neurons behave hormetically, becoming hypofunctional while acting as vectors of tau aggregate spreading.
RESUMO
A fundamental property of infectious agents is their particulate nature: infectivity arises from independently-acting particles rather than as a result of collective action. Assemblies of the protein tau can exhibit seeding behaviour, potentially underlying the apparent spread of tau aggregation in many neurodegenerative diseases. Here we ask whether tau assemblies share with classical pathogens the characteristic of particulate behaviour. We used organotypic hippocampal slice cultures from P301S tau transgenic mice in order to precisely control the concentration of extracellular tau assemblies in neural tissue. Whilst untreated slices displayed no overt signs of pathology, exposure to recombinant tau assemblies could result in the formation of intraneuronal, hyperphosphorylated tau structures. However, seeding ability of tau assemblies did not titrate in a one-hit manner in neural tissue. The results suggest that seeding behaviour of tau arises at high concentrations, with implications for the interpretation of high-dose intracranial challenge experiments and the possible contribution of seeded aggregation to human disease.
Assuntos
Príons/patogenicidade , Agregação Patológica de Proteínas/patologia , Agregação Patológica de Proteínas/fisiopatologia , Tauopatias/patologia , Tauopatias/fisiopatologia , Proteínas tau/metabolismo , Doença de Alzheimer , Animais , Modelos Animais de Doenças , Células HEK293 , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Técnicas In Vitro , Camundongos , Camundongos Transgênicos , Fosforilação , Agregação Patológica de Proteínas/metabolismo , Tauopatias/metabolismo , Técnicas de Cultura de Tecidos , Proteínas tau/genéticaRESUMO
Alzheimer's disease (AD) is a neurodegenerative disease and the main form of dementia, characterized by progressive cognitive decline and detrimental consequences in both personal-family and global level. Within this narrative review, we provide recent molecular aspects of Tau, a microtubule AD-associated protein, as well as amyloid beta, involved in AD pathophysiology. Moreover, we provide additional emerging data from basic research as well as clinical studies indicating an implicating role of gastrointestinal microbiota (GI-M), including Helicobacter pylori infection (Hp-I), in AD pathophysiology. Likewise, we identified through a molecular prism the current evidence of AD pathogenesis as well as its linkage with GI-M and emphasizing the role of Hp-I. All in all, additional large-scale studies are required for the further clarification of AD pathophysiology and its connection with GI-M and Hp-I, so as novel therapies on molecular basis become available.
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Doença de Alzheimer/genética , Infecções por Helicobacter/genética , Doenças Neurodegenerativas/genética , Proteínas tau/genética , Doença de Alzheimer/microbiologia , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/genética , Disfunção Cognitiva/genética , Disfunção Cognitiva/microbiologia , Disfunção Cognitiva/patologia , Microbioma Gastrointestinal/genética , Infecções por Helicobacter/microbiologia , Infecções por Helicobacter/patologia , Helicobacter pylori/patogenicidade , Humanos , Doenças Neurodegenerativas/microbiologiaRESUMO
Ordered assemblies of proteins are found in the postmortem brains of sufferers of several neurodegenerative diseases. The cytoplasmic microtubule associated protein tau and alpha-synuclein (αS) are found in an assembled state in Alzheimer's disease and Parkinson's disease, respectively. An accumulating body of evidence suggests a "prion-like" mechanism of spread of these assemblies through the diseased brain. Under this hypothesis, assembled variants of these proteins promote the conversion of native proteins to the assembled state. This likely inflicts pathology on cells of the brain through a toxic gain-of-function mechanism. Experiments in animal models of tau and αS pathology have demonstrated that the passive transfer of anti-tau or anti-αS antibodies induces a reduction in the levels of assembled proteins. This is further accompanied by improvements in neurological function and preservation of brain volume. Immunotherapy is therefore considered one of the brightest hopes as a therapeutic avenue in an area currently without disease-modifying therapy. Following a series of disappointing clinical trials targeting beta-amyloid, a peptide that accumulates in the extracellular spaces of the AD brain, attention is turning to active and passive immunotherapies that target tau and αS. However, there are several remaining uncertainties concerning the mechanism by which antibodies afford protection against self-propagating protein conformations. This review will discuss current understanding of how antibodies and their receptors can be brought to bear on proteins involved in neurodegeneration. Parallels will be made to antibody-mediated protection against classical viral infections. Common mechanisms that may contribute to protection against self-propagating protein conformations include blocking the entry of protein "seeds" to cells, clearance of immune complexes by microglia, and the intracellular protein degradation pathway initiated by cytoplasmic antibodies via the Fc receptor TRIM21. As with anti-viral immunity, protective mechanisms may be accompanied by the activation of immune signaling pathways and we will discuss the suitability of such activation in the neurological setting.
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Autoanticorpos/metabolismo , Encéfalo/metabolismo , Imunoterapia/métodos , Doenças Neurodegenerativas/imunologia , Vacinas/imunologia , alfa-Sinucleína/metabolismo , Proteínas tau/metabolismo , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Humanos , Doenças Neurodegenerativas/terapiaRESUMO
BACKGROUND: Observational studies have shown an increased risk of upper gastrointestinal bleeding in users of selective serotonin receptor inhibitors (SSRIs). We retrospectively investigated the impact of SSRIs, alone or combined with aspirin (ASA) or nonsteroidal anti-inflammatory drugs (NSAIDs), on the incidence of post-endoscopic sphincterotomy (post-ES) bleeding. METHODS: A total of 3058 patients were included. Of these, 457 patients received SSRIs, alone or plus ASA or NSAIDs, until the day of ES (SSRIs group), while 2659 patients (non SSRIs group) had never been on SSRIs (n=1925), though some had been on ASA (n=613) or NSAIDS (n=121). Patient assessment included indication for endoscopic retrograde cholangiopancreatography (ERCP), comorbid diseases, detailed drug history before and after ES, procedural details, and risk factors for post-ES bleeding. Primary outcome was defined as the incidence, type and severity of post-ES bleeding. RESULTS: There was no statistical difference in age, sex, indication for ERCP, comorbid diseases, technical characteristics or results of therapeutic ERCP between the 2 groups. The incidence of post-ES bleeding was 3.9% in the SSRIs group and 3% in the non SSRIs group, a difference not statistically significant (P=0.754). Likewise, there was no difference in type (P=0.145) or severity of bleeding (P=0.754) between the 2 groups. Multivariate analysis showed the precut technique as the only independent risk factor for post ES hemorrhage (odds ratio 2.56, 95% confidence interval 1.23-3.63; P=0.001). CONCLUSION: This study found that SSRIs, alone or combined with ASA or NSAIDs, had no influence on the incidence or the severity of post-ES bleeding.
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FGF2 is exported from cells by an unconventional secretory mechanism. Here, we directly visualized individual FGF2 membrane translocation events at the plasma membrane using live cell TIRF microscopy. This process was dependent on both PI(4,5)P2-mediated recruitment of FGF2 at the inner leaflet and heparan sulfates capturing FGF2 at the outer plasma membrane leaflet. By simultaneous imaging of both FGF2 membrane recruitment and the appearance of FGF2 at the cell surface, we revealed the kinetics of FGF2 membrane translocation in living cells with an average duration of â¼200 ms. Furthermore, we directly demonstrated FGF2 oligomers at the inner leaflet of living cells with a FGF2 dimer being the most prominent species. We propose this dimer to represent a key intermediate in the formation of higher FGF2 oligomers that form membrane pores and put forward a kinetic model explaining the mechanism by which membrane-inserted FGF2 oligomers serve as dynamic translocation intermediates during unconventional secretion of FGF2.