Nanoplastics induce SH-SY5Y cell damage through oxidative stress and disruption of amino acid metabolism

Abstract

With the pervasive environmental distribution of plastics, their fragmentation into nanoplastics (NPs) has raised growing concerns regarding potential biological toxicity, particularly in neuronal cells. This study investigated the toxic effects and underlying mechanisms of NPs on SH-SY5Y cells. Five types of NPs were first systematically characterized using scanning electron microscopy (SEM), hydrodynamic diameter measurement, and Zeta potential analysis. Cell internalisation of fluorescently labelled NPs was observed using confocal microscopy. Cell viability was assessed across different NP concentrations to determine the optimal exposure dose. In vitro exposure to the five types of nanoplastics (PE-NPs, PET-NPs, PMMA-NPs, PP-NPs, and PS-NPs) resulted in differential reductions in SH-SY5Y cell viability. Notably, the PE-NPs and PP-NPs treatment groups exhibited a more significant decrease in cell viability, whereas the PET-NPs and PMMA-NPs treatment groups showed a relatively mild reduction in cell viability. Oxidative stress indicators (ROS, MMP, LDH, MDA, GSH, and SOD) were measured, and apoptosis was evaluated by TUNEL and EdU assays. Transcriptome sequencing was performed on PE- and PP-exposed cells, followed by GO/KEGG enrichment analyses; differentially expressed genes were validated via RT-qPCR, Western blotting, and amino acid content detection. Characterisation results showed that NPs were uniformly spherical particles (∼200 nm) with high aqueous stability (zeta potential: –30 to –20 mV) and could be internalized by SH-SY5Y cells. NPs reduced cell viability in a concentration-dependent manner, with 400 μg/mL selected for subsequent experiments. NP exposure increased reactive oxygen species (ROS) levels, impaired mitochondrial function, induced apoptosis, and disrupted cell proliferation in SH-SY5Y cells. Transcriptomic and validation results revealed that NPs disrupted amino acid and one-carbon unit metabolism. Collectively, NPs induce SH-SY5Y cell damage through oxidative stress, apoptosis, and amino acid metabolism disorder. These findings provide insights into NP-induced neuronal toxicity, laying the groundwork for further studies on the health risks of NPs and the development of targeted protective strategies.