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Evidence of hippocampal astrogliosis and antioxidant imbalance after L-tyrosine chronic administration in rats

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Abstract

Tyrosinemia type II is a genetic disorder characterized by elevated blood levels of the amino acid tyrosine caused by the deficiency of tyrosine aminotransferase enzyme, resulting in neurologic and developmental difficulties in the patients. Although neurological sequelae are common in Tyrosinemia type II patients, the mechanisms involved are still poorly understood. The oxidative stress appears to be, at least in part, responsible for neurological complication in this inborn error metabolism. We observed that an acute injection of tyrosine in rats caused a massive oxidative stress in different brain structures. The glutathione system and superoxide dismutase enzyme are relevant antioxidant strategies of the cells and tissues, including in the brain. Other important point is the strong relation between oxidative damage and inflammatory events. Herein, we investigated the effects of chronic administration of tyrosine in the hippocampus of young rats, with emphasis in the activity of GSH related enzymes and superoxide dismutase enzyme, and the astrocytosis. We observed that rats exposed to high levels of tyrosine presented an increased content of tyrosine, which was associated with an increment in the activity of glutathione peroxidase and glutathione reductase as well as with a diminished activity of superoxide dismutase. This antioxidant imbalance was accompanied by enhanced glial fibrillary acidic protein immunoreactivity, a marker of astrocytes, in the brain area studied. In conclusion, hippocampus astrogliosis is also a characteristic of brain alteration in Tyrosinemia. In addition, the chronic exposition to high levels of tyrosine is associated with an alteration in the activity of fundamental antioxidant enzymes.

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Acknowledgements

Laboratory of Experimental Neurology (Brazil) is one of the centers of the National Institute for Molecular Medicine (INCT-MM) and one of the members of the Center of Excellence in Applied Neurosciences of Santa Catarina (NENASC).

Funding

This research was supported by grants from Universidade do Extremo Sul Catarinense (UNESC), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).

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Correspondence to Emilio L. Streck.

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The authors declare that they have no conflict of interest.

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All experimental procedures were carried out in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals, with the approval of the Ethics Committee of UNESC (protocols numbers 74/2014-01 and 14/2016-01).

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Carvalho-Silva, M., Gomes, L.M., de Prá, S.DT. et al. Evidence of hippocampal astrogliosis and antioxidant imbalance after L-tyrosine chronic administration in rats. Metab Brain Dis 35, 193–200 (2020). https://doi.org/10.1007/s11011-019-00511-3

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  • DOI: https://doi.org/10.1007/s11011-019-00511-3

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