Development of an in vitro diesel exposure model for human bronchial epithelial cells

The adverse effects of diesel engine emissions on human health have been amply established. However, further investigations are needed to clarify the biological mechanisms underneath these effects. As most of the previous mechanistic studies were based on the use of aged diesel exhaust particles ( DEPs ) and cell lines, our aim was to develop a new model of in vitro exposure using well characterized whole diesel exhaust ( DE ) and completely differentiated primary bronchial epithelial cells ( PBECs ) cultured at the air-liquid interface ( ALI ). DE was produced on site by a diesel engine and directed onto the apical surface of ALI-PBEC using VITROCELL© exposure modules. Three serial DE-dilutions with humidified medical air were tested during 1h exposure using air-exposed cells as control. Already at 6h after the exposure, we observed a dose-dependent increase in hmox1 mRNA expression (with 4∼f.i. in the highest DE dose compared to controls) suggesting an oxidative stress response; inflammation and cytotoxicity effects occurred at the highest DE dose at 6h as shown by a decrease in resistance ( TEER ), and an increase in IL-8 release. At 24h, these effects persisted and LDH release was increased, whereas TEER values were restored. These results describe the feasibility of in vitro exposure of fully differentiated airway epithelial cells to whole DE, which better reflects real-life exposure than aged DEPs. Use of this model will allow comparisons of differential susceptibility of PBECs from different patient populations, as well as exploring the effect of exposure dose and exposure duration on the cellular response. This study was supported by the Netherlands Asthma Foundation (grant# 3.2.11.009).