Size matters: zebrafish (Danio rerio) as a model to study toxicity of nanoplastics from cells to the whole organism

13 pages, 3 figures, 1 table

The contamination of the aquatic environment by plastic nanoparticles is becoming a major concern due to their potential adverse effects in aquatic biota. Therefore, in-depth knowledge of their uptake, trafficking and effects at cellular and systemic levels is essential to understand their potential impacts for aquatic species. In this work, zebrafish (Danio rerio) was used as a model and our aims were: i) to determine the distribution, uptake, trafficking, degradation and genotoxicity of polystyrene (PS) NPs of different sizes in a zebrafish cell line; ii) to study PS NPs accumulation, migration of immune cells and genotoxicity in larvae exposed to PS NPs; and iii) to assess how PS NPs condition the survival of zebrafish larvae exposed to a pathogen and/or how they impact the resistance of an immunodeficient zebrafish. Our results revealed that the cellular distribution differed depending on the particle size: the 50 nm PS NPs were more homogeneously distributed in the cytoplasm and the 1 μM PS NPs more agglomerated. The main endocytic mechanisms for the uptake of NPs were dynamin-dependent internalization for the 50 nm NPs and phagocytosis for the 1 μm nanoparticles. In both cases, degradation in lysosomes was the main fate of the PS NPs, which generated alkalinisation and modified cathepsin genes expression. These effects at cellular level agree with the results in vivo, since lysosomal alkalization increases oxidative stress and vice versa. Nanoparticles mainly accumulated in the gut, where they triggered reactive oxygen species, decreased expression of the antioxidant gene catalase and induced migration of immune cells. Finally, although PS NPs did not induce mortality in wild-type larvae, immunodeficient and infected larvae had decreased survival upon exposure to PS NPs. This fact could be explained by the mechanical disruption and/or the oxidative damage caused by these NPs that increase their susceptibility to pathogens.

This work was conducted with the support of the projects BIO2017-82851-C3-1R from the Spanish Ministerio de Ciencia, Innovación y Universidades and CEIJ-C06.1 and CEIJ-C06.2 from CEI·MAR. P. Pereiro and M. Sendra wish to thank the Axencia Galega de Innovación (GAIN, Xunta de Galicia) and Ministerio de Ciencia, Innovación y Universidades, respectively, for their postdoctoral contracts (IN606B-2018/010; TJFI-2017-32493). Our laboratory is funded by EU Feder Programa Interreg España-Portugal 0474_BLUEBIOLAB and IN607B 2019/01 from Consellería de Economía, Emprego e Industria (GAIN), Xunta de Galicia

Peer reviewed