RESUMO
Oculoleptomeningeal amyloidosis (OA) is a fatal and untreatable hereditary disease characterized by the accumulation of transthyretin (TTR) amyloid within the central nervous system. The mechanisms underlying the pathogenesis of OA, and in particular how amyloid triggers neuronal damage, are still unknown. Here, we show that amyloid fibrils formed by a mutant form of TTR, A25T, activate microglia, leading to the secretion of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and nitric oxide. Further, we found that A25T amyloid fibrils induce the activation of Akt, culminating in the translocation of NFκB to the nucleus of microglia. While A25T fibrils were not directly toxic to neurons, the exposure of neuronal cultures to media conditioned by fibril-activated microglia caused synapse loss that culminated in extensive neuronal death via apoptosis. Finally, intracerebroventricular (i.c.v.) injection of A25T fibrils caused microgliosis, increased brain TNF-α and IL-6 levels and cognitive deficits in mice, which could be prevented by minocycline treatment. These results indicate that A25T fibrils act as pro-inflammatory agents in OA, activating microglia and causing neuronal damage.
Assuntos
Neuropatias Amiloides Familiares/patologia , Transtornos da Memória/patologia , Memória de Curto Prazo , Microglia/patologia , Pré-Albumina/metabolismo , Sinapses/metabolismo , Amiloide , Neuropatias Amiloides Familiares/complicações , Neuropatias Amiloides Familiares/fisiopatologia , Animais , Encéfalo/metabolismo , Morte Celular/efeitos dos fármacos , Núcleo Celular/metabolismo , Células Cultivadas , Meios de Cultivo Condicionados/farmacologia , Modelos Animais de Doenças , Endocitose , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Mediadores da Inflamação/metabolismo , Interleucina-6/metabolismo , Transtornos da Memória/complicações , Transtornos da Memória/fisiopatologia , Memória de Curto Prazo/efeitos dos fármacos , Camundongos , Microglia/efeitos dos fármacos , Microglia/metabolismo , Minociclina/farmacologia , Mutação/genética , NF-kappa B/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação , Transporte Proteico , Proteínas Proto-Oncogênicas c-akt/metabolismo , Sinapses/efeitos dos fármacos , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Yeasts are unicellular organisms that are exposed to a highly variable environment, concerning the availability of nutrients, temperature, pH, radiation, access to oxygen and, specially, water activity. Evolution has selected yeasts to tolerate, to a certain extent, these environmental stresses. High hydrostatic pressure (HHP) exerts a broad effect upon yeast cells, interfering with the cell membranes, cellular architecture and in processes ofpolymerisation and denaturation of proteins. Gene expression patterns in response to HHP revealed a stress response profile. The majority of the upregulated genes were involved in stress defence and carbohydrate metabolism while most of the repressed ones were in cell cycle progression and protein synthesis categories. In addition, in the present work it was seen that mild pressure induced cell cycle arrest and protection against severe stresses, such as high temperature, high pressure and ultra cold shock. Nevertheless, this protection was only significant if the cells were incubated at atmospheric pressure after the HHP treatment. Expression of genes that were upregulated by HHP and are related to resistance to this stresses were also analyzed, and, for the majority of them, higher induction was attained after 15 min post-pressurization. Taken together, the results imply an interconnection among stresses.