Polystyrene nanoplastics exposure induces cognitive impairment in mice via induction of oxidative stress and ERK/MAPK-mediated neuronal cuproptosis.

Background: Recent studies emphasize the significance of copper dyshomeostasis in neurodegenerative diseases, such as Alzheimer's and Parkinson's, thereby highlighting the role of copper in neurotoxicity. Cuproptosis, a novel mechanism of copper-dependent cell death, remains underexplored, particularly concerning environmental pollutants like polystyrene nanoplastics (PS-NPs). While PS-NPs are recognized for inducing neurotoxicity through various forms of cell death, including apoptosis and ferroptosis, their potential to trigger neuronal cuproptosis has not yet been investigated. This study aims to determine whether exposure to PS-NPs induces neurotoxicity via cuproptosis and to explore the preliminary molecular mechanisms involved, thereby addressing this significant knowledge gap.

Methods: Seven-week-old male C57BL/6 mice were exposed to PS-NPs at dose of 12.5 mg/kg, and were co-treated with the antioxidant N-acetylcysteine (NAC). Complementary in vitro experiments were conducted using SH-SY5Y neuronal cells exposed to PS-NPs at a concentration of 0.75 mg/mL, with interventions that included the copper chelator tetrathiomolybdate (TTM), NAC, and the MAPK inhibitor PD98059.

Results: Exposure to PS-NPs significantly increased cerebral copper accumulation (P < 0.05) and induced cuproptosis, characterized by lipid-acylated DLAT oligomerization, dysregulation of cuproptosis regulators (FDX1, LIAS, HSP70), and mitochondrial damage. In murine models, PS-NPs elicited neurotoxicity, as evidenced by neuronal loss, decreased Nissl body density, impaired synaptic plasticity, and suppressed oxidative stress markers (GSH, SOD, Nrf2), alongside activation of the ERK-MAPK pathway, ultimately resulting in deficits in learning and memory. Treatment with NAC alleviated these adverse effects. In SH-SY5Y cells, exposure to PS-NPs resulted in reduced cell viability (p < 0.01), an effect that was mitigated by TTM. Furthermore, NAC and PD98059 were found to reverse elevated copper levels, cuproptosis markers, and mitochondrial anomalies (p < 0.05).

Conclusion: This study presents preliminary evidence indicating that PS-NPs may induce neuronal cuproptosis, potentially through the oxidative stress-mediated activation of the ERK-MAPK pathway, which contributes to cognitive dysfunction in mice. These findings provide insights into the potential mechanisms underlying PS-NPs neurotoxicity and highlight possible therapeutic targets, such as copper chelation or MAPK inhibition, for mitigating the neurological risks associated with nanoplastic exposure, pending further validation in human-relevant models.