The potential cytotoxic effects of urban particle matter on olfaction

Background: Urban particulate matter (UPM) in ambient air is implicated in a variety of human health issues worldwide, however, few studies exist on the effect of UPM on the olfactory system. This study aimed to identify the factors affecting the destruction of the olfactory system in a mouse model following UPM exposure. Methods: Mice were divided into: control and four UPM-exposed groups (200 ㎍ UPM at 1 and 2 weeks, and 400 ㎍ UPM at 1 and 2 weeks [standard reference material 1649b; average particle diameter 10.5 ㎛]). The olfactory neuroepithelium was harvested for histologic examination, gene ontology, quantitative real-time polymerase chain reaction, and western blotting. Results: Compared to the control group, olfactory marker protein, Olfr1507, ADCY3, and GNAL mRNA levels were lower, and S-100, CNPase, NGFRAP1, BDNF, and TACR3 mRNA levels were higher in the olfactory neuroepithelium of the UPM groups. Moderately positive correlation was present between the 1- and 2-week groups. After analyzing the 200 and 400 UPM groups separately, the strength of the association between the 200 UPM 1- and 2-week groups was moderately positive. No differences was present in the neuroepithelial inflammatory marker levels between the UPM and control groups. Conclusions: UPM could have cytotoxic effects on the olfactory epithelium. The exposure time and particular concentration of UPM exposure could affect the degree of destruction of the olfactory neuroepithelium. The olfactory regeneration mechanism could be related to the neurotrophic factors, olfactory ensheathing cell stimulation, and trigeminal nerve support.