Interaction of cigarette smoke and house dust mite allergens on inflammatory mediator release from primary cultures of human bronchial epithelial cells

Background Several studies have shown that exposure to cigarette smoke and/ or house dust mite (HDM) can lead to increased airway inflammation in susce ptible individuals. The underlying mechanisms, however, are not defined. Objective To investigate the interaction between cigarette smoke and HDM al lergen on mediator release from primary cultures of human bronchial epithel ial cells. Methods Confluent human bronchial epithelial cell cultures were exposed to cigarette smoke in the absence or presence of HDM allergen and investigated for the release of IL-8, IL-1 beta, and sICAM-1. Damage to the epithelial cells themselves was assessed by release of Cr-51. On separate occasions, w e investigated the effect of PTL11028, a highly patent and selective Der p1 inhibitor, on HDM allergen-induced release of IL-8, following activation o f HDM allergen by incubation with cysteine. The effect of cigarette smoke e xposure on the stability of these released mediators in prepared solutions in the absence/presence of reduced glutathione was also studied. Results Both HDM allergens and short-term (20 min) cigarette smoke exposure led to a significantly increased release of IL-8, IL-1 beta and sICAM-1 fr om the epithelial cell cultures. Longer exposure (1-6 h) to cigarette smoke led to a dramatic decrease in the amount of these mediators detected in th e culture medium. Whilst incubation of epithelial cultures with HDM allerge n did not cause any significant change in the release of Cr-51 from pre-loa ded cells, cigarette smoke on its own led to a marked, exposure and incubat ion-time dependent increase in the release of Cr-51. Incubation with HDM al lergen led to a significant, dose and time-dependent increase in the releas e of IL-8, which was further enhanced when the allergen extract was pre-act ivated with cysteine. This effect was completely abrogated by PTL11028, a n ovel Der p1 inhibitor. Prepared solutions of various concentrations of IL-8 , IL-1 beta and sICAM-1 exposed to cigarette smoke demonstrated a dramatic exposure time-dependent decrease in the detectable amount of these mediator s, an effect which was abrogated by GSH. Conclusions HDM-induced airway inflammation may include DET p-mediated rele ase of inflammatory mediators from epithelial cells. Additionally, short-te rm cigarette smoke exposure may induce airway inflammation by release of in flammatory mediators from these cells, an effect which may be potentiated b y Der p allergens. Longer term cigarette smoke exposure may cause damage to epithelial cells and changes in the structure of inflammatory mediators.