Environmentally relevant concentrations of polystyrene nanoplastics induce Parkinson’s-like neurotoxicity in C. elegans via oxidative stress

This study reveals that environmentally relevant polystyrene nanoplastics (PS-NPs) induces Parkinson's disease (PD)-like pathology in Caenorhabditis elegans (C. elegans) through oxidative stress. Wild-type and transgenic strains were exposed to PS-NPs at concentrations of 0.1-100 μg/L to assess behavioral toxicity, neuronal damage, and molecular mechanisms. Locomotor deficits (reduction in body bends and head thrashes) and disrupted PD-associated behaviors (impairment of food-induced basal slowing response; increased swimming paralysis rate) were observed at all concentrations, while developmental parameters remained unaffected. Although some behavioral endpoints didn't exhibit a strictly monotonic dose-response, Jonckheere-Terpstra trend analyses confirmed significant overall trends for multiple key parameters, underscoring the pervasive impact of PS-NP exposure. Selective degeneration of dopaminergic neurons and exacerbated α-synuclein aggregation confirmed neuropathological specificity. Transcriptomic analysis linked these phenotypes to oxidative stress, showing elevated reactive oxygen species (ROS) and upregulation of antioxidant enzymes (SOD-3, GST-4), alongside paradoxical suppression of the redox regulator skn-1. Genetic validation using trx-1 mutants prevented PS-NP-induced paralysis, whereas trx-4 deficiencies exacerbated toxicity, highlighting their distinct roles in redox defense. Co-treatment with N-acetylcysteine (NAC) attenuated PS-NP-induced paralysis, lowering the rate from 51.33 % to 29.47 %, though rescue failure in trx-4 mutants indicated mechanistic complexity and the indispensable role of endogenous defense systems. Critically, neurotoxicity occurred even at 0.1 μg/L PS-NPs, a level relevant to environmental contamination. These findings establish PS-NPs as potent inducers of PD-like neurodegeneration via complex oxidative stress cascades, validated by genetic and antioxidant interventions at environmentally realistic exposure levels, and highlight the urgency of monitoring nanoplastic pollution and developing antioxidant-based interventions.