Trehalose Acts as a Mediator: Imbalance in Brain Proteostasis Induced by Polystyrene Nanoplastics via Gut Microbiota Dysbiosis during Early Life

As an emerging contaminant, nanoplastics have evolved into a global ecological issue. Studies have shown that nanoplastics induce neurotoxicity across species, however, the causal mechanism remains unknown. This study aimed to explore the mechanism underlying the neurotoxicity caused by polystyrene nanoplastics (PS-NPs) via microbiota–gut–brain axis in immature mice, which serve as a model of infants and young children who are at higher exposure risk to NPs. The results indicated that while only a minority of PS-NPs reached the brain after exposure, they still had significant neurotoxic effects, as reflected by abnormalities in behavior, biochemical marker levels and histopathology. Proteomics and quantification analyses revealed that a proteostasis imbalance mediated by lysosomal and proteasome dysfunction in the brain is the key reason for the induced neurotoxicity. Further, we confirmed the indirect role of gut microbiota in the neurotoxicity induced by PS-NPs through 16S rDNA analyses and fecal microbiota transplantation. Crucial bacterial species such as Eubacterium coprostanoligenes potentially act as indicators for gut dysbiosis after PS-NPs exposure. Notably, we first estimated the indirect effect of gut microbiota on neurotoxicity attributed to PS-NPs in immature mice as 39.20% by high-dimensional mediation analysis. Trehalose was identified as a mediator connecting the gut microbiota and the brain, and the crucial role of trehalose supplementation was highlighted in remodeling the brain proteostasis to alleviate the neurotoxicity in immature mice. These findings are expected to contribute to a deeper understanding of the risk assessment and health protection of the nervous system from exposure to PS-NPs early in life.