RESUMO
Autism spectrum disorders comprise a range of neurodevelopmental disorders characterized by deficits in social interaction and communication, and by repetitive behaviour. Mutations in synaptic proteins such as neuroligins, neurexins, GKAPs/SAPAPs and ProSAPs/Shanks were identified in patients with autism spectrum disorder, but the causative mechanisms remain largely unknown. ProSAPs/Shanks build large homo- and heteromeric protein complexes at excitatory synapses and organize the complex protein machinery of the postsynaptic density in a laminar fashion. Here we demonstrate that genetic deletion of ProSAP1/Shank2 results in an early, brain-region-specific upregulation of ionotropic glutamate receptors at the synapse and increased levels of ProSAP2/Shank3. Moreover, ProSAP1/Shank2(-/-) mutants exhibit fewer dendritic spines and show reduced basal synaptic transmission, a reduced frequency of miniature excitatory postsynaptic currents and enhanced N-methyl-d-aspartate receptor-mediated excitatory currents at the physiological level. Mutants are extremely hyperactive and display profound autistic-like behavioural alterations including repetitive grooming as well as abnormalities in vocal and social behaviours. By comparing the data on ProSAP1/Shank2(-/-) mutants with ProSAP2/Shank3αß(-/-) mice, we show that different abnormalities in synaptic glutamate receptor expression can cause alterations in social interactions and communication. Accordingly, we propose that appropriate therapies for autism spectrum disorders are to be carefully matched to the underlying synaptopathic phenotype.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Transtorno Autístico/genética , Comportamento Animal/fisiologia , Proteínas do Tecido Nervoso/genética , Agitação Psicomotora/genética , Animais , Transtorno Autístico/patologia , Espinhas Dendríticas/genética , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Agitação Psicomotora/patologia , Receptores Ionotrópicos de Glutamato/metabolismo , Sinapses/metabolismo , Regulação para Cima , Vocalização Animal/fisiologiaRESUMO
Proton magnetic resonance spectroscopy ((1)H MRS) is a valuable tool in Alzheimer's disease research, investigating the functional integrity of the brain. The present longitudinal study set out to characterize the neurochemical profile of the hippocampus, measured by single voxel (1)H MRS at 7 Tesla, in the brains of AßPPSswe-PS1dE9 and wild-type mice at 8 and 12 months of age. Furthermore, we wanted to determine whether alterations in hippocampal metabolite levels coincided with behavioral changes, cognitive decline and neuropathological features, to gain a better understanding of the underlying neurodegenerative processes. Moreover, correlation analyses were performed in the 12-month-old AßPP-PS1 animals with the hippocampal amyloid-ß deposition, TBS-T soluble Aß levels and high-molecular weight Aß aggregate levels to gain a better understanding of the possible involvement of Aß in neurochemical and behavioral changes, cognitive decline and neuropathological features in AßPP-PS1 transgenic mice. Our results show that at 8 months of age AßPPswe-PS1dE9 mice display behavioral and cognitive changes compared to age-matched wild-type mice, as determined in the open field and the (reverse) Morris water maze. However, there were no variations in hippocampal metabolite levels at this age. AßPP-PS1 mice at 12 months of age display more severe behavioral and cognitive impairment, which coincided with alterations in hippocampal metabolite levels that suggest reduced neuronal integrity. Furthermore, correlation analyses suggest a possible role of Aß in inflammatory processes, synaptic dysfunction and impaired neurogenesis.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Cognição/fisiologia , Hipocampo/patologia , Neurônios/patologia , Sinapses/patologia , Envelhecimento , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Transtornos Cognitivos/metabolismo , Transtornos Cognitivos/patologia , Modelos Animais de Doenças , Hipocampo/metabolismo , Estudos Longitudinais , Espectroscopia de Ressonância Magnética/métodos , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/metabolismo , Sinapses/metabolismoRESUMO
Research into the development of Alzheimer's disease (AD) provides increasing evidence that vascular risk factors, including high serum cholesterol, might influence the progression of cognitive impairment and neural degeneration. In this study, we investigated the effects of high dietary cholesterol intake and the cholesterol-lowering liver X receptor-agonist T0901317 on capillary density, amyloid-ß deposition, and presynaptic boutons in the hippocampus of adult (8 months) and aged (15 months) AßPPswe-PS1dE9 and wild-type mice to elucidate how cholesterol may affect neurodegenerative processes in aging and AD. Our results show increased number of presynaptic boutons in 15-month-old AßPP-PS1 mice compared to age-matched wild-type animals, but no difference at 8 months of age. High cholesterol intake accelerated this response by increasing the amount of presynaptic boutons at 8 and 15 months of age, while T0901317 intake decreased the amount of presynaptic boutons in 15-month-old AßPP-PS1 mice. These findings suggest a synaptic compensatory response to maintain connectivity during aging. We hypothesize that high cholesterol intake may cause impaired cerebral blood flow inducing ischemia, fortifying the above mentioned hypothesis of a compensatory mechanism. Contrarily, cholesterol-lowering agents may positively influence cerebral circulation, thereby diminishing aggravation of AD-like pathology.