PM_2.5 produced during cooking triggers impairments in the olfactory system of mice

Decades of researches have shown that particulate matter (PM) in cooking oil fumes (COFs) have the capacity to induce neurological diseases, such as cognitive impairment and stroke through multiple pathways. Olfactory system serves as an important route for exogenous PM to invade the central nervous system. Nevertheless, the olfactory injuries caused by PM_2.5 and its mechanism have remained uncertain. In this study, 10-week-old C57BL/6 mice were exposed to COF generated from heating soybean oil via an exposure chamber for 4 weeks and the toxic effects and mechanisms of COF on the olfactory epithelium (OE) and olfactory bulb (OB) in mice were investigated. The results indicated that the COF exposure led to the apoptosis of olfactory epithelial cells and inflammatory responses in the mice OE, which resulted in the olfactory barrier damage. The transformation of microglia cells from a ramified morphology to an amoeboid morphology was observed in the OB, accompanied by the activation of TLR4-NFκB neuroinflammation signaling and the disruption of olfactory transduction signaling in the OB. Our study revealed the potential harm of COF to olfactory system and suggested a potential pathway for PM-induced neuroinflammation.