Neuro- and hepato-toxicity of polystyrene nanoplastics and polybrominated diphenyl ethers on early life stages of zebrafish

Nanoplastics (NPs) are good carriers of persistent organic pollutants (POPs) such as polybrominated diphenyl ethers (PBDEs) and can modify their bioavailability and toxicity to aquatic organisms. This study highlights the single and combined toxic effects of polystyrene nanoplastics (PS-NPs) and 2,2 ',4,4 '-tetrabromodiphenyl ether (BDE-47, one of the major PBDE congeners) on zebrafish embryos after an exposure of up to 120 hpf. Our results showed that PS -NPs and BDE-47 formed larger particle aggregates during co-exposure, which attached to the surface of the yolk mem-brane and even changed its structure, and these particles also bioaccumulated in the intestine of zebrafish larvae, com-pared with the PS-NPs single exposure. Further, the co-exposure significantly increased mortality, accelerated voluntary movements, enhanced hatching rate, and decreased heart rate. Hepatoxicity analyses revealed that the mix-ture exposure induced a darker/browner liver colour, atrophied liver and greater hepatotoxicity in zebrafish larvae. In addition to increased ROS accumulation, the reduced expression of the antioxidant gpx1a gene and increased expres-sion of cyp1a1 were found after co-treatment. Moreover, ache and chrn7 alpha genes associated with neurocentral develop-ment, were significantly downregulated, mainly in the co-exposure group. In conclusion, simultaneous exposure to PS -NPs and BDE-47 exacerbated oxidative stress, developmental impacts, hepatotoxicity, and neurodevelopmental toxic-ity in zebrafish larvae. Therefore, neurotoxic effects of complex chemical interactions between PS-NPs and persistent organic pollutants in freshwater environments should be paid more attention.

Automated summary

This study focuses on the single and combined toxic effects of polystyrene nanoplastics (PS-NPs) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on zebrafish embryos. The results show that the co-exposure exacerbates oxidative stress, developmental impacts, hepatotoxicity, and neurodevelopmental toxicity in zebrafish larvae.