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Oxidative stress, apoptosis and serotonergic system changes in zebrafish (Danio rerio) gills after long-term exposure to microplastics and copper
Summary
Researchers exposed adult zebrafish to microplastics and copper for 30 days and examined the effects on their gill tissue. They found that the combination caused greater oxidative stress, increased cell death, and disrupted the serotonin signaling system in gills more than either pollutant alone. The study demonstrates that microplastics can amplify the toxic effects of heavy metals on fish respiratory organs.
Fish gills are in direct contact with the surrounding pollutants, and thus, potentially more vulnerable to microplastics (MPs) and heavy metals. The present study aimed to evaluate the long-term exposure effects of MPs and copper (Cu) in the gills of adult zebrafish (Danio rerio). To this end, zebrafish were exposed to MPs (2 mg/L), Cu (Cu25, 25 μg/L) and their mixture (Cu25 + MPs) for 30 days, and then oxidative stress, detoxification, antioxidant, metabolic and neurotoxicity enzymes/genes, as well serotonergic system and apoptosis genes, were evaluated in gills. In the mixture group, ROS levels were increased, while CAT and GPx activities were inhibited, indicating the induction of oxidative stress in zebrafish gills. This was followed by an increase of LPO levels and potential oxidative damage in zebrafish gills. The tryptophan hydroxylase 1a (tph1a) and caspase-3 (casp3) genes were significantly upregulated in Cu25 + MPs group, indicating a potential dysregulation of serotonin synthesis and apoptosis pathways, respectively. Overall, the present study contributes to improving the knowledge about the response of aquatic organisms to MPs and the potential ecological risk that these particles represent to the ecosystems.