Polystyrene nanoplastics-induced intestinal barrier disruption via inflammation and apoptosis in zebrafish larvae (Danio Rerio)

Plastics are one of the most pervasive materials on Earth, to which humans are exposed daily. Polystyrene (PS) is a common plastic packaging material. However, the impact of PS on human health remains poorly understood. Therefore, this study aimed to identify intestinal damage induced by PS nanoplastics (PS-NPs) in zebrafish larvae which have a high homology with humans. Four days post fertilization (dpf), zebrafish larvae were exposed to 0-, 10-, and 50-ppm PS-NPs for 48 h Initially, to ascertain if 100 nm PS-NPs could accumulate in the gastrointestinal (GI) tract of zebrafish larvae, the larvae were exposed to red fluorescence-labeled PS-NPs, and at 6 dpf, the larvae were examined using a fluorescence microscope. Analysis of the fluorescence intensity revealed that the GI tract of larvae exposed to 50-ppm exhibited a significantly stronger fluorescence intensity than the other groups. Nonfluorescent PS-NPs were then used in further studies. Scanning electron microscopy (SEM) confirmed the spherical shape of the PS-NPs. Fourier-transform infrared spectroscopy (FT-IR) analysis revealed chemical alterations in the PS-NPs before and after exposure to larvae. The polydispersity index (PDI) value derived using a Zetasizer indicated a stable dispersion of PS-NPs in egg water. Whole-mount apoptotic signal analysis via TUNEL assay showed increased apoptosis in zebrafish larval intestines exposed to 50-ppm PS-NPs. Damage to the intestinal tissue was assessed by Alcian blue (AB) and hematoxylin and eosin (H&E) staining. AB staining revealed increased mucin levels in the zebrafish larval intestines. Thin larval intestinal walls with a decrease in the density of intestinal epithelial cells were revealed by H&E staining. The differentially expressed genes (DEGs) induced by PS-NPs were identified and analyzed. In conclusion, exposure to PS-NPs may damage the intestinal barrier of zebrafish larvae due to increased intestinal permeability, and the in vivo gene network may change in larvae exposed to PS-NPs.