RESUMO
In Parkinson's disease (PD) patients, alpha-synuclein (α-syn) pathology advances in form of Lewy bodies and Lewy neurites throughout the brain. Clinically, PD is defined by motor symptoms that are predominantly attributed to the dopaminergic cell loss in the substantia nigra. However, motor deficits are frequently preceded by smell deficiency or neuropsychological symptoms, including increased anxiety and cognitive dysfunction. Accumulating evidence indicates that aggregation of α-syn impairs synaptic function and neurogenic capacity that may be associated with deficits in memory, learning and mood. Whether and how α-syn accumulation contributes to neuropathological events defining these earliest signs of PD is presently poorly understood. We used a tetracycline-suppressive (tet-off) transgenic mouse model that restricts overexpression of human A30P α-syn to neurons owing to usage of the neuron-specific CaMKIIα promoter. Abnormal accumulation of A30P correlated with a decreased survival of newly generated neurons in the hippocampus and olfactory bulb. Furthermore, when A30P α-syn expression was suppressed, we observed reduction of the human protein in neuronal soma. However, residual dox resistant A30P α-syn was detected in glial cells within the hippocampal neurogenic niche, concomitant with the failure to fully restore hippocampal neurogenesis. This finding is indicative to a potential spread of pathology from neuron to glia. In addition, mice expressing A30P α-syn show increased anxiety-related behavior that was reversed after dox treatment. This implies that glial A30P α-synucleinopathy within the dentate gyrus is part of a process leading to impaired hippocampal neuroplasticity, which is, however, not a sole critical event for circuits implicated in anxiety-related behavior.
Assuntos
Alanina/genética , Ansiedade , Neurogênese/genética , Neuroglia/patologia , Prolina/genética , alfa-Sinucleína/genética , Animais , Ansiedade/genética , Ansiedade/patologia , Ansiedade/fisiopatologia , Aprendizagem da Esquiva/efeitos dos fármacos , Aprendizagem da Esquiva/fisiologia , Contagem de Células , Modelos Animais de Doenças , Proteínas do Domínio Duplacortina , Doxiciclina/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Camundongos , Camundongos Transgênicos , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurogênese/efeitos dos fármacos , Neuroglia/efeitos dos fármacos , Neuropeptídeos/metabolismo , Bulbo Olfatório/metabolismo , Bulbo Olfatório/patologiaRESUMO
Dementias are a varied group of disorders typically associated with memory loss, impaired judgment and/or language and by symptoms affecting other cognitive and social abilities to a degree that interferes with daily functioning. Alzheimer's disease (AD) is the most common cause of a progressive dementia, followed by dementia with Lewy bodies (DLB), frontotemporal dementia (FTD), (VaD) and HIV-associated neurocognitive disorders (HAND). The pathogenesis of this group of disorders has been linked to the abnormal accumulation of proteins in the brains of affected individuals, which in turn has been related to deficits in protein clearance. Autophagy is a key cellular protein clearance pathway with proteolytic cleavage and degradation via the ubiquitin-proteasome pathway representing another important clearance mechanism. Alterations in the levels of autophagy and the proteins associated with the autophagocytic pathway have been reported in various types of dementias. This review will examine recent literature across these disorders and highlight a common theme of altered autophagy across the spectrum of the dementias.