Exposure to Nanoplastics Disrupts Neurotransmitter Release in Rat Hippocampal Neurons

Plastics are used broadly for various applications, and their degradation and fragmentation have led to widespread accumulation of nanoplastics in the environment. Although nanoplastics are ubiquitous and intractable in the environment and in organisms, their potential health impacts remain unclear. Emerging evidence showed that nanoplastics can cross the blood–brain barrier and accumulate in the brain. However, the effects of nanoplastics on neuronal health and functions in the brain are poorly understood. Here, we examined the effects of nanoplastic exposure on neurotransmitter release by measuring FM 4-64 (a lipophilic styryl dye) release from synaptic vesicles during electrical stimulation after exposing rat hippocampal neurons to 1–10 μg/mL of fluorescent polystyrene nanoplastics with an average diameter of 42 nm. We found that nanoplastics accumulated in the presynaptic terminal of hippocampal neurons and reduced stimulation-induced FM 4-64 release in a dose-dependent manner. Furthermore, nanoplastics decreased Ca2+ elevation in the presynaptic terminal of hippocampal neurons during electrical stimulation. Our results suggest that accumulated nanoplastics in the brain can impair neuronal functions by disrupting neurotransmitter release and Ca2+ dynamics in the presynaptic terminal of neurons, which could eventually lead to neurodegeneration.