# Polystyrene Nanoplastics Induce DNA Damage and Excitotoxicity in Whole-Brain Organoids: The Role of the TLR9/MyD88 Pathway

## TL;DR

Polystyrene nanoplastics harm brain development by causing DNA damage and excitotoxicity, which may be mitigated by melatonin.

## Contribution

The study introduces whole-brain organoids and neonatal rat models to reveal nanoplastic-induced neurotoxicity mechanisms.

## Key findings

- PS-NPs caused DNA damage and inflammation in brain organoids and neonatal rat brains.
- TLR9/MyD88 pathway activation mediates excitotoxicity from PS-NPs exposure.
- Melatonin treatment reduced PS-NPs-induced neuronal damage and DNA damage.

## Abstract

Polystyrene nanoplastics (PS-NPs) can cross the placenta and blood–brain barrier to accumulate in the fetal brain following inhalation or ingestion, raising concerns about PS-NPs-induced developmental neurotoxicity (DNT). However, current evidence regarding the mechanisms underlying PS-NPs-elicited DNT remains critically scarce. Given the inherent limitations of two-dimensional cell culture techniques, we employed a whole-brain organoid (WBO) model, which more faithfully recapitulates the dynamic changes and substantial alterations during the early development of the human nervous system, to investigate the PS-NPs-induced DNT. Developing WBOs were exposed to 50-nm PS-NPs at concentrations of 50 and 100 μg/mL. Additionally, we established an early developmental exposure model in neonatal rat for robust validation. The results revealed aberrant formation of the tissue architecture of neural epithelial buds in PS-NPs-exposed WBOs, accompanied by significant inflammatory responses and oxidative stress. Marked DNA damage and substantial activation of the TLR9/MyD88 pathway were observed in WBOs and in the cerebral cortex of neonatal rat, leading to significant upregulation of the excitotoxicity marker c-Fos and the excitatory synaptic marker NMDAR. In vitro assays revealed that melatonin treatment could efficiently counteract PS-NPs-mediated neuronal impairment, with both the reduced cell viability and excessive DNA damage induced by PS-NPs being restored to levels close to those of the control group. In conclusion, by establishing WBOs and early developmental exposure models in neonatal rat, we found that PS-NPs can induce DNA double-strand breaks, and activation of the TLR9 pathway mediates PS-NPs-induced excitotoxicity.