Estabelecimento de um modelo de Doença de Huntington induzido por ácido-3-nitropropiônico em peixe-zebra : avaliação de parâmetros comportamentais

• Main Author: Wiprich, Melissa Talita
• Publication Date: 2019
• Format: Master thesis
• Language: por
• Source: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Download full: http://tede2.pucrs.br/tede2/handle/tede/8724
• topic: Locomoção; Ácido-3-nitropropiônico; Doença de Huntington; Memória; Peixe-zebra; Locomotion; 3-nitropropionic Acid; Huntington Disease; Memory; Zebrafish; CIENCIAS DA SAUDE::MEDICINA

Huntington’s disease (HD) is a neurodegenerative genetic inheritance condition caused by an abnormal expansion of the CAG trinucleotide resulting in a mutation of the huntingtin protein. It is characterized by a triad of symptoms with progressive alterations of motor, cognitive and psychiatric functions. The first symptoms usually appear in the adult phase, but they can also appear in the juvenile age, around the 20 years old, being denominated juvenile HD. The disease becomes fatal 15 to 20 years after the onset of the first symptoms. In addition, the age of onset and intensity of symptoms are related to the number of CAG repeats, i.e. the more CAG repeats, the earlier the pathology develops and the greater the intensity of symptoms. The main neuropathological characteristic of HD is the remarkable neurodegeneration of the midline striatal neurons, altering different neurotransmitter systems, such as GABAergic, glutamatergic, dopaminergic, and adenosinergic. Currently, animal models of HD usually use rodents and non-human primates and are classified into genetic and pharmacological models. Among the pharmacological agents, the most commonly tested is the mitochondrial toxin model with the use of 3-nitropropionic acid (3-NPA), that inhibits the mitochondrial complex II-III and is able to reproduce the motor and biochemical alterations occurred in HD. In this context, zebrafish has become an excellent animal model for the study and development of neurodegenerative disease models. In this study, we performed a behavior screening in larval and adult zebrafish to establish the 3-NPA induced HD model. In the larval stage, the treatment consisted of exposure to 3-NPA at concentrations of 0.01, 0.05, 0.1, 0.2 and 0.5 mM for 7 days post-fertilization (dpf). From the 7th dpf to 14th dpf the animals remained only in the water. For the treatment of adult animals, the doses used were 10, 20, and 60 mg/kg and saline for the control group. The treatment consisted of 7 intraperitoneal injections performed every 96 hours.The locomotor and anxiety behavior was assessed 24 hours after each injection and the social interaction, aggression and memory at the end of the 29 days of the treatment. In the larval stage, the exposure to 3-NPA at concentrations of 0.1, 0.2 and 0.5 mM increased the heart rate at 2 and 5 dpf, caused a morphological alteration at the concentration of 0.05 mM and did not alter the locomotor behavior at the ages of 7, 10 and 14 dpf. In the adult stage, the exposure to 3-NPA in the doses at 10, 20, and 60 mg/kg induced a decrease in locomotor activity whereas it had no effect on anxiety and social interaction of the animals. However, the dose of 60 mg/kg caused a decrease in aggressive behavior and a memory impairment in the inhibitory avoidance task. These data suggest that zebrafish in the larval stage is a viable model for studying the characteristics of the pre-manifestation phase of HD and, in the adult stage, we identified through the long-term treatment with 3-NPA a new animal model to study the phenotypic characteristics of the late stage of HD.