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Adverse effects of polystyrene nanoplastic and its binary mixtures with nonylphenol on zebrafish nervous system: From oxidative stress to impaired neurotransmitter system
Summary
Researchers investigated the individual and combined effects of polystyrene nanoplastics and the industrial chemical nonylphenol on the zebrafish nervous system over 45 days. Both substances induced oxidative stress and disrupted neurotransmitter systems, with combined exposure generally producing more severe effects on glutamate metabolism and brain tissue damage. The study suggests that the interaction between nanoplastics and co-occurring environmental pollutants can amplify neurotoxic effects in fish.
Micro(nano)plastics generally co-exist with other chemicals in the environment, resulting in inevitable interaction and combined toxic effects on biota. Nevertheless, little is known regarding the interaction of nanoplastics (NPs) with other co-occurring insults. Hereby, we investigated single and combined effects of chronic exposure (45 days) to polystyrene nanoplastic particulates (PS-NPs) and nonylphenol (4-NP) on zebrafish nervous system. Multiple biomarkers concerning with oxidative-stress [catalase (CAT) activity and reduced glutathione (GSH) level], cholinergic system [Acetylcholinesterase (AchE) activity], glutamatergic system [glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities], energy metabolism [a-ketoglutarate dehydrogenase (a-KGDH) activity], and histological alterations were assessed. Both single and binary exposure to PS-NPs and 4-NP induced oxidative stress through reducing CAT activity and GSH level, in which a more sever effect was noticed in combined exposure. The AchE activity was significantly inhibited only in single treatment groups demonstrating antagonistic interaction between PS-NPs and 4-NP. Effects on GS activity was also alleviated in binary exposure as compared with single exposure to each contaminant. In addition, an increase in GDH activity was noticed in PS-NPs at 10 and 100 μg/L, and simultaneous presence of PS-NPs and 4-NP with a greater response were observed in combined treatments. PS-NPs and 4-NP either in separate or binary mixtures disrupted energy metabolism by deficiency of α-KGDH activity; however, co-exposure to PS-NPs and 4-NP induced more intense adverse impacts on this parameter. Furthermore, histological analysis revealed that 4-NP and PS-NPs, alone or in combination, reduced neural cells. These findings provide new insight into the neurotoxic effects of binary exposure to PS-NPs and 4-NP at environmentally relevant concentrations. Overall, our findings raise concerns about the presence and toxicity of nano-scale plastic particulates and highlight the importance of investigating the interaction of Micro(nano)plastics with other environmental irritants.