Efeitos neurotóxicos da exposição ao óxido de grafeno em larvas de zebrafish (Danio rerio)

• Autor(a) principal: Soares, Jéssica Cavalheiro
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Texto Completo: http://tede2.pucrs.br/tede2/handle/tede/7519
• topic: Óxido de Grafeno; Neurotoxicologia; Nanotoxicologia; Larvas de Zebrafish; Dopamina; CIENCIAS BIOLOGICAS::BIOLOGIA GERAL

Recent studies have shown several applications of graphene oxide (GO) in neurology in the imaging area as a contrast agent for diagnostic purposes, for drug delivery of anticarcinogenic drugs, proteins and peptides and in the field of tissue engineering for applications in the regeneration of nervous lesions. Advances in GO applications research in neurology require addressing its potential toxic mechanisms of action. Zebrafish (Danio rerio) has been widely used in neurotoxicological trials due to the homology of biochemical processes and neural structures with vertebrates. To investigate the potential neurotoxic effects of GO exposure in different concentrations at development period, we evaluated in vivo parameters for initial toxicological screening. We found that GO did not induce changes in survival, hatching and spontaneous movement. However, an increase in heart rate at 48 hpf was found and a reduction in body length without altering the ocular area at 5 dpf. Additionally, molecular gene expression analyses of nervous system-related proteins were performed, showing synapsin IIa expression is increased and dopamine transporter (dat) gene expression is reduced, suggesting a potential compensatory mechanism. The evaluation of the locomotion behavior of animals exposed at GO showed an increase in the absolute turn angle. Based on these initial parameters, we performed biochemical analyzes to determination of the enzyme acetylcholinesterase (AChE) activity and dopamine levels. The exposure at GO did not change AChE activity and decreased dopamine levels. Additionally, the gene expression of B cell lymphoma 2 (bcl2) gene and caspase 3 (casp3) gene were evaluated for the group of larvae exposed to GO, demonstrating an increase of bcl2 and unchanged casp3 expression, suggesting no apoptosis involvement. The tissue and cellular structure of zebrafish larvae brain exposed at GO was evaluated by transmission electron microscopy (TEM) and cell dead by autophagosome formation with loss of cellular architecture was observed most likely due to exposure to the nanomaterial. Further studies are necessary to the complete understanding of the neurological changes observed in zebrafish by exposure to GO and the mechanisms involved in this process, are necessary.