89 research outputs found
Approche d'immunothérapie dans un modÚle murin de pathologie Tau
Tau pathology is a common lesion observed in more than twenty neurological disorders, refered to as Tauopathies. It corresponds to the aggregation of the microtubule associated protein Tau hyper and abnormally phosphorylated into neurofibrillary tangles. In Alzheimer's disease (AD), the most common age-related dementia, the distribution and progression of Tau pathology have been reported to be well-correlated to the cognitive decline. Currently, treatments remain essentially symptomatic. However, several therapeutic approaches, including immunotherapy, are being developed to treat Tau pathology. The work presented in this thesis aim to investigate the effects of both active and passive Tau immunotherapy in a transgenic mouse model of Alzheimerâs disease-like Tau pathology. THY-Tau22 mice overexpress a double-mutated isoform of the human Tau protein, whose expression is under the control of a neuronal promoter. Several lines of evidence suggest that this transgenic mouse model is reproducing early stages of AD. Indeed, at three month old, the THY-Tau22 mouse model presents a progressive impairment of learning and memory without major neuronal loss, in parallel to Tau accumulation in the hippocampus. Moreover, Tau is hyper and abnormally phosphorylated at different sites including Ser422. Noteworthy, the pSer422 epitope is a single abnormal site of phosphorylation present only in pathological conditions, rendering it of particular interest for immunotherapy. In this present thesis work, we showed that early vaccination against the phosphorylated Ser422 Tau protein reduced spatial memory impairment as measured by the Y-maze test. Interestingly, this is associated with the decrease of the abnormal phosphorylation of Tau in the hippocampus and with a significant reduction of insoluble Tau species. Based on these results, we generated a new monoclonal antibody raised against pSer422 (2H9) to evaluate the effects of passive immunotherapy. The antibody was injected every week, intraperitoneally (5mg/kg and 10mg/kg of 2H9 or saline buffer) in the THY-Tau22 mice. We show that this approach can prevent the appearance of spatial memory deficits as measured by the Y maze and the Morris water maze tests. Immunohistochemical analysis also revealed a reduction of abnormally phosphorylated Tau proteins in the hippocampus. To investigate the mechanisms underlying Tau immunotherapy, we performed stereotaxic injections of anti-phosphoTau antibodies in the hippocampus of THY-Tau22 mice. We showed that, once in the brain, anti-phosphoTau antibodies were located inside the neurons in contrast to the isotype control. Several recent studies of immunotherapy, suggest an involvement of macroautophagy in the antibody-mediated degradation. We showed that internalized antibodies colocalized with different markers of the lysosomal pathway (NPC1, Lamp2) confirming this hypothesis of a lysosomal-mediated degradation. However, since the blood-brain barrier is highly selective, the antibodies may more likely act in the periphery. Indeed, we showed that peripheral administration of 250μg of the 2H9 generates a significant increase of Tau proteins levels in plasma, suggesting a peripheral sink mechanism as for Aβ immunotherapy. Vaccination, which generates a polyclonal response, leads to a greater increase of plasmatic Tau that confirms the peripheral degradation of Tau. Overall, the results of this PhD work confirmed the promising potential of Tau immunotherapy for Alzheimer\\\\\\\'s disease and other Tauopathies treatment. Moreover, it address a new hypothesis suggesting that the antibodies mediated degradation of Tau proteins might be through a peripheral sink such as for Aβ.La pathologie Tau est une lĂ©sion commune Ă plus dâune vingtaine de maladies neurodĂ©gĂ©nĂ©ratives, regroupĂ©es sous le terme de Tauopathies. Elle correspond Ă lâaccumulation intracellulaire de matĂ©riel fibrillaire constituĂ© de protĂ©ines Tau hyper- et anormalement phosphorylĂ©es. Dans la maladie dâAlzheimer (MA), dĂ©mence la plus courante chez la personne ĂągĂ©e, la progression et la distribution topographique de ces agrĂ©gats Ă©voluent au cours du temps et sont corrĂ©lĂ©s aux dĂ©ficits cognitifs observĂ©s. A ce jour, les traitements sont principalement symptomatiques. Cependant, plusieurs stratĂ©gies thĂ©rapeutiques sont Ă©tudiĂ©es parmi lesquelles lâimmunothĂ©rapie. Les travaux prĂ©sentĂ©s dans cette thĂšse ont pour objectif dâĂ©tudier les effets de lâimmunothĂ©rapie Tau, active et passive, dans un modĂšle transgĂ©nique murin mimant la pathologie Tau de type Alzheimer. Les souris THY-Tau22, surexpriment une isoforme de Tau humaine mutĂ©e sur deux sites et sous contrĂŽle dâun promoteur neuronal. Ce modĂšle prĂ©sente dĂšs lâĂąge de trois mois des altĂ©rations progressives de lâapprentissage et de la mĂ©moire en parallĂšle dâune accumulation de protĂ©ine Tau principalement au niveau hippocampique, sans perte neuronale majeure, ce qui lui confĂšre les caractĂ©ristiques dâun stade prĂ©coce de MA. Au sein du modĂšle THY-Tau22, on retrouve la protĂ©ine Tau phosphorylĂ©e en Ser422, un Ă©pitope particuliĂšrement pertinent pour lâimmunothĂ©rapie. En effet, la pSer422 est un Ă©pitope de phosphorylation anormale unique, prĂ©sent dans la plupart des Tauopathies. Dans ces travaux de thĂšse, nous montrons que la vaccination prĂ©coce contre la Ser422 phosphorylĂ©e de la protĂ©ine Tau peut prĂ©venir l'altĂ©ration de mĂ©moire spatiale mesurĂ©e par le test du labyrinthe en Y. Cette diminution de l'atteinte cognitive est associĂ©e Ă une diminution de la phosphorylation anormale de Tau au niveau de l'hippocampe et Ă une rĂ©duction significative des espĂšces insolubles de Tau. Les rĂ©sultats de cette vaccination nous ont amenĂ©s Ă gĂ©nĂ©rer un anticorps monoclonal dirigĂ© contre la pSer422 (2H9) afin dâĂ©valuer les effets de lâimmunothĂ©rapie passive. Selon la mĂȘme cinĂ©tique dâĂąge, nous avons injectĂ©, chaque semaine, par voie intrapĂ©ritonĂ©ale, des souris THY-Tau22 avec 5mg/kg et 10mg/kg de 2H9 ou une solution saline. Cette approche prĂ©vient lâapparition de dĂ©ficits de mĂ©moire spatiale mesurĂ©e par les tests du labyrinthe en Y et de la piscine de Morris. Les analyses immunohistochimiques rĂ©vĂšlent Ă©galement une rĂ©duction des protĂ©ines Tau anormalement phosphorylĂ©es au niveau de lâhippocampe. Afin dâĂ©tudier les mĂ©canismes sous-jacents Ă lâimmunothĂ©rapie anti Tau, nous avons injectĂ© des anticorps anti-phosphoTau par stĂ©rĂ©otaxie au niveau de lâhippocampe de souris THY-Tau22. Nous montrons, quâune fois au sein du cerveau, ils sont capables dâentrer dans les neurones contrairement au contrĂŽle isotypique. Plusieurs Ă©tudes rĂ©centes dâimmunothĂ©rapie, suggĂšrent une implication de la macroautophagie dans la dĂ©gradation mĂ©diĂ©e par les anticorps. Nous montrons que les anticorps internalisĂ©s dans les neurones colocalisent avec diffĂ©rents marqueurs de la voie lysosomiale (NPC1, Lamp2) confirmant lâhypothĂšse dâune dĂ©gradation par le lysosome. Cependant, la barriĂšre hĂ©mato encĂ©phalique Ă©tant trĂšs sĂ©lective, il est fort probable que les anticorps gĂ©nĂ©rĂ©s restent en pĂ©riphĂ©rie. [...
Rebound pathway overactivation by cancer cells following discontinuation of PI3K or mTOR inhibition promotes cancer cell growth.
Whilst effects of anti-cancer drugs have been thoroughly explored, little is known about the repercussion of drug cessation. However, this has important clinical relevance since several clinical protocols such as intermittent drug scheduling lead to frequent drug discontinuation. In this study, we have thus investigated the consequences of withdrawal of agents that target the PI3K/AKT/mTOR signaling pathway in cancer cells. We report that washout of kinase inhibitors of mTOR or PI3K inhibitors led to a rapid and sustainable overactivation of AKT. Consequently, proliferation of tumor cells was significantly higher following drug washout in cancer cells that were pre-treated with mTOR or PI3K inhibitors compared to untreated cells. This effect was prevented by the addition of an AKT inhibitor following drug washout. Rebound AKT overactivation induced by mTOR or PI3K inhibitors discontinuation was mediated by IGF-1R, as demonstrated by its prevention in the presence of an IGF-1R inhibitor and by increased IGF-1R phosphorylation in treated cells versus control cells. Taken together, our results show that discontinuation of PI3K or mTOR inhibitors results in AKT overactivation that promotes tumor growth. They further highlight the benefit of adding an AKT inhibitor following cessation of PI3K or mTOR inhibitors
Analyse diachronique de lâefficience technique des systĂšmes de production bovin viande. Baisse de la productivitĂ© des facteurs variables sur 23 ans
De 1990 Ă 2012, les exploitations dâĂ©levage bovins viande françaises ont accru leur taille et leur productivitĂ© du travail de plus de 60 % grĂące, notamment, Ă une substitution travail/capital et Ă une simplification de certaines pratiques dâalimentation du troupeau, entre autres. Lâefficience technique des systĂšmes de production, mesurĂ©e par le ratio volume de production hors aides/volume des consommations intermĂ©diaires a baissĂ© de prĂšs de 20 %, alors que le revenu par travailleur sâest maintenu grĂące aux aides et aux gains de productivitĂ© physique du travail. Cette efficience technique est positivement corrĂ©lĂ©e Ă lâautonomie alimentaire des exploitations, elle-mĂȘme nĂ©gativement corrĂ©lĂ©e Ă la taille des exploitations et des troupeaux. Alors que le volume de production par hectare de surface agricole utilisĂ©e a stagnĂ©, lâautonomie alimentaire par les fourrages (la valorisation de lâherbe) a perdu 6 points. Les 23 annĂ©es de progrĂšs gĂ©nĂ©tique, technique, technologique et des connaissances ont accompagnĂ© lâaugmentation continue de la taille des exploitations et de la productivitĂ© du travail, et ont donc juste permis de compenser la diminution dâefficience des systĂšmes de production.Over the past 23 years (1990-2012) French beef-cattle farms had increased their size and labor productivity by more than 60%. These gains were possible thanks to a substitution work/capital and to a simplification of herd feeding practices. The efficiency of production systems is estimated by the ratio volume of agricultural production/volume of intermediate consumptions (inputs, services, capital consumption). This efficiency decreased by 20%, while income per worker remained stable thanks to aids and subsidies and to the gains in labor productivity. The efficiency of the beef-cattle farming systems is strongly positively correlated with the feed self-sufficiency, which is itself negatively correlated with the size of farms and herds. While the volume of agricultural products per hectare of agricultural area remained stable, the forage feed self-sufficient lost 6 points. 20 years of genetics, technical, technological and knowledge progress has thus helped offset lower efficiency strongly related to the continuous increase in the size of the farms
NMDA receptor dysfunction contributes to impaired brain-derived neurotrophic factor-induced facilitation of hippocampal synaptic transmission in a Tau transgenic model.
While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus-dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor-dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N-methyl-d-Aspartate receptors (NMDAR). Using THY-Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA-induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY-Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies
NPT088 reduces both amyloid-b and tau pathologies in transgenic mice
Introduction: Alzheimerâs disease (AD) is characterized by appearance of both extracellular senile plaques and intracellular neurofibrillary tangles, comprised of aggregates of misfolded amyloid-b (Ab) and hyper-phosphorylated tau, respectively. In a previous study, we demonstrated that g3p, a capsid protein from bacteriophage M13, binds to and remodels misfolded aggregates of proteins that assume an amyloid conformation. We engineered a fusion protein (âNPT088â) consisting of the active fragment of g3p and human-IgG1-Fc. Methods: Aged Tg2576 mice or rTg4510 mice received NPT088 weekly via IP injection. Cognitive and/or functional motor endpoints were monitored during dosing. Pathology was quantified biochemically and immunohistochemically. Results: NPT088-lowered Ab plaque and improved cognitive performance of aged Tg2576 mice. Moreover, NPT088 reduced phospho-tau pathology, reduced brain atrophy, and improved cognition in rTg4510 mice. Discussion: These observations establish NPT088 as a novel therapeutic approach and potential drug class that targets both Ab and tau, the hallmark pathologies of AD
Advances in the therapy of Alzheimer's disease: Targeting amyloid beta and tau and perspectives for the future
Worldwide multidisciplinary translational research has led to a growing knowledge of the genetics and molecular pathogenesis of Alzheimer's disease (AD) indicating that pathophysiological brain alterations occur decades before clinical signs and symptoms of cognitive decline can be diagnosed. Consequently, therapeutic concepts and targets have been increasingly focused on early-stage illness before the onset of dementia; and distinct classes of compounds are now being tested in clinical trials. At present, there is a growing consensus that therapeutic progress in AD delaying disease progression would significantly decrease the expanding global burden. The evolving hypothesis- and evidence-based generation of new diagnostic research criteria for early-stage AD has positively impacted the development of clinical trial designs and the characterization of earlier and more specific target populations for trials in prodromal as well as in pre- and asymptomatic at-risk stages of AD
Tau filament self-assembly and structure: tau as a therapeutic target
Tau plays an important pathological role in a group of neurodegenerative diseases called tauopathies, including Alzheimer's disease, Pick's disease, chronic traumatic encephalopathy and corticobasal degeneration. In each disease, tau self-assembles abnormally to form filaments that deposit in the brain. Tau is a natively unfolded protein that can adopt distinct structures in different pathological disorders. Cryo-electron microscopy has recently provided a series of structures for the core of the filaments purified from brain tissue from patients with different tauopathies and revealed that they share a common core region, while differing in their specific conformation. This structurally resolvable part of the core is contained within a proteolytically stable core region from the repeat domain initially isolated from AD tau filaments. Tau has recently become an important target for therapy. Recent work has suggested that the prevention of tau self-assembly may be effective in slowing the progression of Alzheimer's disease and other tauopathies. Here we review the work that explores the importance of tau filament structures and tau self-assembly mechanisms, as well as examining model systems that permit the exploration of the mode of action of potential inhibitors
Immunotherapy approach in a mouse model of tau pathology
La pathologie Tau est une lĂ©sion commune Ă plus dâune vingtaine de maladies neurodĂ©gĂ©nĂ©ratives, regroupĂ©es sous le terme de Tauopathies. Elle correspond Ă lâaccumulation intracellulaire de matĂ©riel fibrillaire constituĂ© de protĂ©ines Tau hyper- et anormalement phosphorylĂ©es. Dans la maladie dâAlzheimer (MA), dĂ©mence la plus courante chez la personne ĂągĂ©e, la progression et la distribution topographique de ces agrĂ©gats Ă©voluent au cours du temps et sont corrĂ©lĂ©s aux dĂ©ficits cognitifs observĂ©s. A ce jour, les traitements sont principalement symptomatiques. Cependant, plusieurs stratĂ©gies thĂ©rapeutiques sont Ă©tudiĂ©es parmi lesquelles lâimmunothĂ©rapie. Les travaux prĂ©sentĂ©s dans cette thĂšse ont pour objectif dâĂ©tudier les effets de lâimmunothĂ©rapie Tau, active et passive, dans un modĂšle transgĂ©nique murin mimant la pathologie Tau de type Alzheimer. Les souris THY-Tau22, surexpriment une isoforme de Tau humaine mutĂ©e sur deux sites et sous contrĂŽle dâun promoteur neuronal. Ce modĂšle prĂ©sente dĂšs lâĂąge de trois mois des altĂ©rations progressives de lâapprentissage et de la mĂ©moire en parallĂšle dâune accumulation de protĂ©ine Tau principalement au niveau hippocampique, sans perte neuronale majeure, ce qui lui confĂšre les caractĂ©ristiques dâun stade prĂ©coce de MA. Au sein du modĂšle THY-Tau22, on retrouve la protĂ©ine Tau phosphorylĂ©e en Ser422, un Ă©pitope particuliĂšrement pertinent pour lâimmunothĂ©rapie. En effet, la pSer422 est un Ă©pitope de phosphorylation anormale unique, prĂ©sent dans la plupart des Tauopathies. Dans ces travaux de thĂšse, nous montrons que la vaccination prĂ©coce contre la Ser422 phosphorylĂ©e de la protĂ©ine Tau peut prĂ©venir l'altĂ©ration de mĂ©moire spatiale mesurĂ©e par le test du labyrinthe en Y. Cette diminution de l'atteinte cognitive est associĂ©e Ă une diminution de la phosphorylation anormale de Tau au niveau de l'hippocampe et Ă une rĂ©duction significative des espĂšces insolubles de Tau. Les rĂ©sultats de cette vaccination nous ont amenĂ©s Ă gĂ©nĂ©rer un anticorps monoclonal dirigĂ© contre la pSer422 (2H9) afin dâĂ©valuer les effets de lâimmunothĂ©rapie passive. Selon la mĂȘme cinĂ©tique dâĂąge, nous avons injectĂ©, chaque semaine, par voie intrapĂ©ritonĂ©ale, des souris THY-Tau22 avec 5mg/kg et 10mg/kg de 2H9 ou une solution saline. Cette approche prĂ©vient lâapparition de dĂ©ficits de mĂ©moire spatiale mesurĂ©e par les tests du labyrinthe en Y et de la piscine de Morris. Les analyses immunohistochimiques rĂ©vĂšlent Ă©galement une rĂ©duction des protĂ©ines Tau anormalement phosphorylĂ©es au niveau de lâhippocampe. Afin dâĂ©tudier les mĂ©canismes sous-jacents Ă lâimmunothĂ©rapie anti Tau, nous avons injectĂ© des anticorps anti-phosphoTau par stĂ©rĂ©otaxie au niveau de lâhippocampe de souris THY-Tau22. Nous montrons, quâune fois au sein du cerveau, ils sont capables dâentrer dans les neurones contrairement au contrĂŽle isotypique. Plusieurs Ă©tudes rĂ©centes dâimmunothĂ©rapie, suggĂšrent une implication de la macroautophagie dans la dĂ©gradation mĂ©diĂ©e par les anticorps. Nous montrons que les anticorps internalisĂ©s dans les neurones colocalisent avec diffĂ©rents marqueurs de la voie lysosomiale (NPC1, Lamp2) confirmant lâhypothĂšse dâune dĂ©gradation par le lysosome. Cependant, la barriĂšre hĂ©mato encĂ©phalique Ă©tant trĂšs sĂ©lective, il est fort probable que les anticorps gĂ©nĂ©rĂ©s restent en pĂ©riphĂ©rie. [...]Tau pathology is a common lesion observed in more than twenty neurological disorders, refered to as Tauopathies. It corresponds to the aggregation of the microtubule associated protein Tau hyper and abnormally phosphorylated into neurofibrillary tangles. In Alzheimer's disease (AD), the most common age-related dementia, the distribution and progression of Tau pathology have been reported to be well-correlated to the cognitive decline. Currently, treatments remain essentially symptomatic. However, several therapeutic approaches, including immunotherapy, are being developed to treat Tau pathology. The work presented in this thesis aim to investigate the effects of both active and passive Tau immunotherapy in a transgenic mouse model of Alzheimerâs disease-like Tau pathology. THY-Tau22 mice overexpress a double-mutated isoform of the human Tau protein, whose expression is under the control of a neuronal promoter. Several lines of evidence suggest that this transgenic mouse model is reproducing early stages of AD. Indeed, at three month old, the THY-Tau22 mouse model presents a progressive impairment of learning and memory without major neuronal loss, in parallel to Tau accumulation in the hippocampus. Moreover, Tau is hyper and abnormally phosphorylated at different sites including Ser422. Noteworthy, the pSer422 epitope is a single abnormal site of phosphorylation present only in pathological conditions, rendering it of particular interest for immunotherapy. In this present thesis work, we showed that early vaccination against the phosphorylated Ser422 Tau protein reduced spatial memory impairment as measured by the Y-maze test. Interestingly, this is associated with the decrease of the abnormal phosphorylation of Tau in the hippocampus and with a significant reduction of insoluble Tau species. Based on these results, we generated a new monoclonal antibody raised against pSer422 (2H9) to evaluate the effects of passive immunotherapy. The antibody was injected every week, intraperitoneally (5mg/kg and 10mg/kg of 2H9 or saline buffer) in the THY-Tau22 mice. We show that this approach can prevent the appearance of spatial memory deficits as measured by the Y maze and the Morris water maze tests. Immunohistochemical analysis also revealed a reduction of abnormally phosphorylated Tau proteins in the hippocampus. To investigate the mechanisms underlying Tau immunotherapy, we performed stereotaxic injections of anti-phosphoTau antibodies in the hippocampus of THY-Tau22 mice. We showed that, once in the brain, anti-phosphoTau antibodies were located inside the neurons in contrast to the isotype control. Several recent studies of immunotherapy, suggest an involvement of macroautophagy in the antibody-mediated degradation. We showed that internalized antibodies colocalized with different markers of the lysosomal pathway (NPC1, Lamp2) confirming this hypothesis of a lysosomal-mediated degradation. However, since the blood-brain barrier is highly selective, the antibodies may more likely act in the periphery. Indeed, we showed that peripheral administration of 250μg of the 2H9 generates a significant increase of Tau proteins levels in plasma, suggesting a peripheral sink mechanism as for Aβ immunotherapy. Vaccination, which generates a polyclonal response, leads to a greater increase of plasmatic Tau that confirms the peripheral degradation of Tau. Overall, the results of this PhD work confirmed the promising potential of Tau immunotherapy for Alzheimer\\\\\\\'s disease and other Tauopathies treatment. Moreover, it address a new hypothesis suggesting that the antibodies mediated degradation of Tau proteins might be through a peripheral sink such as for Aβ
- âŠ