Evaluation of the effects of chronic exposure to fluoxetine on zebrafish: a three-dimensional approach

• Autor(a) principal: Pinto, Bruno José Gonçalves
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36575
• topic: Depression; Antidepressants; Fluoxetine; Aquatic contamination; Zebrafish; Biochemical biomarkers; Fatty acids; Lipids; Lipidomics

Major depressive disorder (MDD) is a serious illness that affects the quality of life of patients and has a high incidence worldwide. Its diagnosis is very subjective due to the absence of specific biomarkers. Lipids have been studied in an attempt to find biomarkers for this pathology, and changes in the lipid profile have already been reported in animal models of MDD (brain and plasma/serum) or in patients with MDD (plasma/serum), as well as after antidepressant therapy. An increase in some classes of phospholipids and ceramides has been reported in cases of MDD, which may be involved in inflammation and cellular apoptosis. After treatment, studies have shown that antidepressants appear to reverse the observed changes in the disease. These results suggest that certain altered lipid profiles may allow the discovery of new biomarkers for the diagnosis and assessment of the progression of this pathology or for the monitoring of therapy. The increase in the incidence of depression leads to a consequent increase in the consumption of antidepressants, which, due to the limited efficiency of wastewater treatment plants, have been reported as contaminants of the aquatic environment. Fluoxetine, one of the most consumed antidepressants in the world, is a selective serotonin reuptake inhibitor found in the aquatic environment. This drug may have a toxic effect on certain aquatic organisms upon chronic exposure, which may cause physiological and behavioral changes, according to studies reported in zebrafish. This animal model has been increasingly used not only in toxicological studies but also in biomedicine. Thus, this work aimed to evaluate the effect produced by chronic exposure to fluoxetine, at environmentally relevant concentrations (1, 10, 100, and 1000 ng/L), using zebrafish as an animal model. In order to evaluate possible toxicological effects on zebrafish, namely on the head and body, a three-dimensional approach was carried out: behavioral, biochemical and molecular. Firstly, behavioral tests were performed, namely locomotion tests, but changes triggered by fluoxetine at different concentrations were not observed. Subsequently, the analysis of biochemical biomarkers was carried out, whose results showed an increase in catalase activity and a decrease in lactate dehydrogenase and glutathione S-transferase activities, indicative of decreased defense against oxidative stress and altered energy metabolism. In addition, an analysis of the fatty acid profile was performed, in which a decrease in omega-3 fatty acids and an increase in omega-6 fatty acids was observed, suggesting a state of inflammation associated with oxidative stress. However, these changes were more evident at the highest concentration of fluoxetine tested. Considering the vital role of lipids in various cellular mechanisms, the analysis of the polar lipid profile in zebrafish after exposure to the highest concentration of fluoxetine was performed using a lipidomics approach. Variations were observed in both phospholipids and sphingolipids, and as these appear to be associated with pro-inflammatory and cellular apoptosis processes, respectively, they reflect increased oxidative stress and a chronic inflammatory state. Thus, the results obtained in this work indicate that chronic exposure to fluoxetine causes changes, both at the level of biochemical biomarkers and at the molecular level (fatty acid and lipid profiles), in zebrafish as an animal model of other aquatic organisms. The importance of an analysis in different dimensions is also highlighted, as well as the relevance of molecular studies that may allow the early detection of the presence of antidepressants in aquatic organisms, even before behavioral changes are detected. However, this study has some limitations that encourage further work, namely the study of individualized organs (for example, the brain), as well as other antidepressants.