Particulate Matter Exacerbates the Death of Dopaminergic Neurons in Parkinson's Disease through an Inflammatory Response.

Particulate matter (PM), a component of air pollution, has been epidemiologically associated with a variety of diseases. Recent reports reveal that PM has detrimental effects on the brain. In this study, we aimed to investigate the biological effects of ambient particles on the neurodegenerative disease Parkinson's disease (PD). We exposed mice to coarse particles (PM: 2.5-10 μm) for short (5 days) and long (8 weeks) durations via intratracheal instillation. Long-term PM exposure exacerbated motor impairment and dopaminergic neuron death in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse models. Short-term PM exposure resulted in both pulmonary and systemic inflammatory responses in mice. We further investigated the mechanism underlying PM-induced neurotoxicity in cocultures of lung LA-4 epithelial cells and RAW264.7 macrophages. PM treatment elicited a dramatic increase in proinflammatory mediators in LA-4/RAW264.7 coculture. Treating BV2 microglial cells with PM-treated conditioned medium induced microglial activation. Furthermore, 1-methyl-4-phenylpyridinium (MPP) treatment caused notable cell death in N2A neurons cocultured with activated BV2 cells in PM-conditioned medium. Altogether, our results demonstrated that PM plays a role in the neurodegeneration associated with PD. Thus, the impact of PM on neurodegeneration could be related to detrimental air pollution-induced systemic effects on the brain.