Environmental pollutants as risk factos for developing cognitive dysfunctions and Alzheimer’s disease

Abstract

Increasing lines of evidence have shown that environmental pollutants have significant impact in cognitive functions for young children, elderly and patients with Alzheimer’s disease (AD). While particular matters PM2.5 in the air pollutant have received much attention, silica nanoparticles are also important components that can damage neurons. Silica nanoparticles (SiO2-NPs) are typical and major components of mineral dust and many other airborne pollutants in the ambient air. In the current study, we employed fluorescein isothiocyanate-tagged SiO2-NPs (FITC-SiO2-NPs) to investigate the effects of SiO2-NPs on cognition and mood in animal model and primary culture of cortical neurons. By using cell culture of cortical neurons, we are able to demonstrate that SiO2-NPs can markedly affect synaptic functions by inhibiting exocytosis. In laboratory animal, we performed intranasal instillation of SiO2-NPs because the major route of infiltration of silica nanoparticles is via inhalation. After two months of daily instillation, laboratory mice rendered clear impairment of short-term and spatial memory assessed by novel object recognition test and Morris water maze test. The locomotor and motor functions examined by open field test and rotarod test were preserved. Our animal experiment confirmed that the synaptic functions were impaired by SiO2-NPs. Furthermore, increased tau protein phosphorylation was observed. Taken together, the results indicate that silica nanoparticles attribute to cognitive dysfunctions, which are most likely mediated via impairment of synaptic functions. Moreover, AD-like pathology such as tau protein phosphorylation is gradually developed. Therefore, environmental pollutants can be a risk factor for developing cognitive dysfunctions and even AD.