Effect of diesel exhaust particles and house dust mite allergens on airway epithelium cells

Epidemiological studies demonstrate an association between particulate air pollution and chronic airway diseases including asthma and chronic obstructive pulmonary diseases (COPD). Indoor allergens such as house dust mite (HDM) are reported to have important roles in the pathogenesis of allergic airway diseases. Animal studies of diesel exhaust particles (DEP), which make an important fraction of particulate air pollution, have reported that HDM allergens can interact with these particles and potentiate their effects. However, the role of air way epithelial cells and underlying mechanisms are not adequately known. In my studies, I have investigated the effects of DEP (0, 30, 100, 300µg/ml) on trans-epithelial electrical resistance (TED), cell viability and synthesis of inflammatory mediators in the absence and presence of HDM. TER was measured at t0, t2, t4, t6, and t24 hours, whereas cell viability and protein, and mRNA levels of interleukin (IL)-8, granulocyte macrophage-colony stimulating factor (GM-CSF), RANTES and soluble intercellular adhesion molecule (sICAM)-1 were assessed at t24 hours and t4 hours, respectively. The highest concentration of DEP (300µg/ml) decreased TER of cultures, whereas both 100 and 300µg/ml DEP decreased TER, when HDM added. In the presence of HDM and IL-1ß, both 100 and 300µg/ml DEP supressed TER at all time points studied (t2-t24 hours). All concentrations of DEP studied (30-300µg/ml) attenuated release of IL-8, while only 100 and 300µg/ml DEP supressed IL-8 release in the presence of HDM. Although low concentrations of 30 and 100µg/ml DEP induced GM-CSF release, 300µg/ml showed an inhibitory effect. On addition of HDM, GM-CSF release was significantly decreased comparing to HDM-untreated cells. DEP with and without HDM decreased RANTES release, whereas, HDM itself decreased the release of this cytokine. DEP (300µg/ml) suppressed sICAM release both in the absence and presence of HDM. RT-PCR analysis has shown that DEP (100µg/ml) induce gene expression for IL-8 and GM-CSF under only HDM condition, and that in all cultures treated with HDM, both IL-8 and GM-CSF mRNA expression was significantly higher comparing to cells un-treated with HDM. RANTES mRNA expression was, however, attenuated in only cell treated with 100µg/ml DEP + HDM. DEP significantly induced sICAM-1 mRNA expression under HDM condition. Our findings have demonstrated that DEP, at high concentrations, can induce permeability of BEAS-2B cultures, while decreasing cell viability, and that HDM can potentiate this effect. Furthermore, DEP can modify protein and gene expression of inflammatory mediators and this may be affected by HDM.