Toxicity evaluation of the combination of emerging pollutants with polyethylene microplastics in zebrafish: Perspective study of genotoxicity, mutagenicity, and redox unbalance

Despite the toxicity of microplastics (MPs) in freshwater fish has been demonstrated in previous studies, their effects when mixed with other pollutants (organic and inorganic) are poorly understood. Thus, we aimed to test the hypothesis that the association of polyethylene MPs (PE-MPs) to a mix of emerging pollutants induces more adverse genotoxic, mutagenic, and redox unbalance effects in adult zebrafish (Danio rerio), after 15 days of exposure. Although the accumulation of MPs in animals was greater in animals exposed to PE-MPs alone, erythrocyte DNA damage (comet assay) and the frequency of erythrocytic nuclear abnormalities (ENAs) evidenced in zebrafish exposed to PE-MPs alone were as pronounced as those observed in animals exposed to the mix of pollutant (alone or in combination with MPs), which constitutes the big picture of the current study. Moreover, we noticed that such effects were associated with an imbalance between pro-and antioxidant metabolism in animals, whose activity of superoxide dismutase (SOD) and catalase (CAT) was assessed in different organs which were not sufficient to counterbalance the production of reactive oxygen species [hydrogen peroxide (H2O2)] and nitrogen [nitric oxide (NO)] evaluated. The principal component analysis (PCA) also revealed that while the antioxidant activity was more pronounced in the brain and liver of animals, the highest production of H2O2 was perceived in the gills and muscles, suggesting that the biochemical response of the animals was organ-dependent. Thus, the present study did not demonstrate antagonistic, synergistic, or additive effects on animals exposed to the combination between PE-MPs and a mix of pollutants in the zebrafish, which reinforces the theory that interactions between pollutants in aquatic ecosystems may be as complex as their effects on freshwater ichthyofauna.