Human neurons are susceptible to the internalization of small-sized nanoplastics

Environmental pollution caused by small plastics has become a social concern due to growing awareness of their adverse impacts on organisms, including humans. While the brain has been identified as a major site of small plastic accumulation, fundamental information about their impacts at the cellular level remains limited. In this study, we investigated the neuronal uptake and toxicity of nanoplastics using the human neurons (LUHMES). LUHMES cells internalized polystyrene (PS) nanoplastics with a preference for 50 nm particles, mainly through clathrin-mediated endocytosis and macropinocytosis. However, PS uptake by LUHMES cells was lower than that by other neural cell types. PS nanoparticles were predominantly localized in lysosomes and minimally in mitochondria. On the other hand, PS nanoparticles had no obvious effects on acute cytotoxicity, neurite outgrowth, and oxidative stress. This study provides essential data on the neuronal responses to nanoplastics and highlights the need for further evaluation of their neurodevelopmental impact.