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Exacerbation of C1q dysregulation, synaptic loss and memory deficits in tau pathology linked to neuronal adenosine A2A receptor.

ABSTRACT: Accumulating data support the role of tau pathology in cognitive decline in ageing and Alzheimer's disease, but underlying mechanisms remain ill-defined. Interestingly, ageing and Alzheimer's disease have been associated with an abnormal upregulation of adenosine A2A receptor (A2AR), a fine tuner of synaptic plasticity. However, the link between A2AR signalling and tau pathology has remained largely unexplored. In the present study, we report for the first time a significant upregulation of A2AR in patients suffering from frontotemporal lobar degeneration with the MAPT P301L mutation. To model these alterations, we induced neuronal A2AR upregulation in a tauopathy mouse model (THY-Tau22) using a new conditional strain allowing forebrain overexpression of the receptor. We found that neuronal A2AR upregulation increases tau hyperphosphorylation, potentiating the onset of tau-induced memory deficits. This detrimental effect was linked to a singular microglial signature as revealed by RNA sequencing analysis. In particular, we found that A2AR overexpression in THY-Tau22 mice led to the hippocampal upregulation of C1q complement protein-also observed in patients with frontotemporal lobar degeneration-and correlated with the loss of glutamatergic synapses, likely underlying the observed memory deficits. These data reveal a key impact of overactive neuronal A2AR in the onset of synaptic loss in tauopathies, paving the way for new therapeutic approaches.

SUBMITTER: Carvalho K

PROVIDER: S-EPMC6821333 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Exacerbation of C1q dysregulation, synaptic loss and memory deficits in tau pathology linked to neuronal adenosine A2A receptor.

Carvalho Kevin K Faivre Emilie E Pietrowski Marie J MJ Marques Xavier X Gomez-Murcia Victoria V Deleau Aude A Huin Vincent V Hansen Jan N JN Kozlov Stanislav S Danis Clément C Temido-Ferreira Mariana M Coelho Joana E JE Mériaux Céline C Eddarkaoui Sabiha S Gras Stéphanie Le SL Dumoulin Mélanie M Cellai Lucrezia L Landrieu Isabelle I Chern Yijuang Y Hamdane Malika M Buée Luc L Boutillier Anne-Laurence AL Levi Sabine S Halle Annett A Lopes Luisa V LV Blum David D

Brain : a journal of neurology 20191101 11

Accumulating data support the role of tau pathology in cognitive decline in ageing and Alzheimer's disease, but underlying mechanisms remain ill-defined. Interestingly, ageing and Alzheimer's disease have been associated with an abnormal upregulation of adenosine A2A receptor (A2AR), a fine tuner of synaptic plasticity. However, the link between A2AR signalling and tau pathology has remained largely unexplored. In the present study, we report for the first time a significant upregulation of A2AR ...[more]

PMID: 31599329

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Project description:Alzheimer's disease (AD) is defined by the presence of intraneuronal neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau aggregates as well as extracellular amyloid-beta plaques. The presence and spread of tau pathology through the brain is classified by Braak stages and thought to correlate with the progression of AD. Several in vitro and in vivo studies have examined the ability of tau pathology to move from one neuron to the next, suggesting a "prion-like" spread of tau aggregates may be an underlying cause of Braak tau staging in AD. Using the HEK293 TauRD-P301S-CFP/YFP expressing biosensor cells as a highly sensitive and specific tool to identify the presence of seed competent aggregated tau in brain lysate-i.e., tau aggregates that are capable of recruiting and misfolding monomeric tau-, we detected substantial tau seeding levels in the entorhinal cortex from human cases with only very rare NFTs, suggesting that soluble tau aggregates can exist prior to the development of overt tau pathology. We next looked at tau seeding levels in human brains of varying Braak stages along six regions of the Braak Tau Pathway. Tau seeding levels were detected not only in the brain regions impacted by pathology, but also in the subsequent non-pathology containing region along the Braak pathway. These data imply that pathogenic tau aggregates precede overt tau pathology in a manner that is consistent with transneuronal spread of tau aggregates. We then detected tau seeding in frontal white matter tracts and the optic nerve, two brain regions comprised of axons that contain little to no neuronal cell bodies, implying that tau aggregates can indeed traverse along axons. Finally, we isolated cytosolic and synaptosome fractions along the Braak Tau Pathway from brains of varying Braak stages. Phosphorylated and seed competent tau was significantly enriched in the synaptic fraction of brain regions that did not have extensive cellular tau pathology, further suggesting that aggregated tau seeds move through the human brain along synaptically connected neurons. Together, these data provide further evidence that the spread of tau aggregates through the human brain along synaptically connected networks results in the pathogenesis of human Alzheimer's disease.

Project description:Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by a progressive cognitive decline. Epidemiological studies have suggested a protective role of caffeine consumption against age-related cognitive impairments and the risk of developing AD. Effects of caffeine have been particularly ascribed to its ability to block adenosine A2A receptors (A2ARs). Early pathological upregulation of these receptors by neurons is thought to be involved in the development of synaptic and memory deficits in AD but this remains ill-defined. To tackle this question, we employed a novel transgenic mouse model allowing to promote a neuronal upregulation of A2AR in the hippocampus of APP/PS1 mice, developing AD-like amyloidogenesis. This new model was used to determine the impact of an early upregulation of A2AR on the progression of neuropathological lesions, associated behavior and underlying mechanisms in APP/PS1 mice. Our findings revealed that the early upregulation of A2AR in the presence of an ongoing amyloid pathology exacerbates memory impairments of APP/PS1 mice. These behavioral changes were not linked to major change in the development of amyloid pathology but rather associate with an increased p-tau at neuritic plaques. Moreover, proteomic and transcriptomic analysis coupled to quantitative immunofluorescence studies indicated that neuronal impairment of the receptor promoted both neuronal- and non-neuronal autonomous alterations i.e. loss of excitatory synapses and neuroinflammatory response, respectively, both presumably accounting for the detrimental effect on memory. Overall, our results provide compelling evidence that neuronal A2AR dysfunction as seen in the brain of patients contributes to AD pathogenesis, favoring synaptic deficits promoted by both amyloid (this study) and tau lesions (our previous study). In addition to provide new insights into the complex pathophysiology of AD, the present findings underscore the potential of A2AR as a relevant therapeutic target for mitigating early synaptic loss in this neurodegenerative disorder.

Dataset Information

Exacerbation of C1q dysregulation, synaptic loss and memory deficits in tau pathology linked to neuronal adenosine A2A receptor.

Publications

Exacerbation of C1q dysregulation, synaptic loss and memory deficits in tau pathology linked to neuronal adenosine A2A receptor.

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