Bayram, H; Fakili, F; Gogebakan, B; Bayraktar, R; Ekinci, E
RATIONALE: Epidemiological studies suggest that there is an association between increases in particulate air pollution and respiratory morbidity; however, the underlying mechanisms are unclear. We have previously demonstrated that diesel exhaust particles (DEP) induce human lung epithelial cell (A549) proliferation under serum free condition. However, it is not known whether DEP have any effects on viability of these cells in the presence of serum, a condition that may be seen in inflamed airways.
METHODS: We cultured A549 cells in 12 well culture plates, and incubated with 50, 100, 200, 400 and 1000μg/ml DEP under 0-10% fetal calf serum (FCS) condition in the presence and absence of N-acetylcysteine (NAC), an inhibitor of JNK (SP600125), an inhibitor of ERK (PD 98059) and NF-kB inhibitor (SN50) for 48hrs, and stained the cells with MTT to determine cell viability.
RESULTS: We have shown that 50μg/ml, 100μg/ml and 200μg/ml DEP significantly increased cell viability under serum free condition as compared to the control group (0μg/ml DEP) following 48hrs’ incubation, however, this was reversed, and the cell viability was decreased as 1-10% FCS was added to the culture medium. The marked effect was observed by 50μg/ml (optical density [OD]=1.8, p<0.01), 100μg/ml (OD=1.76, p<0.0001), 200μg/ml (OD=1.50, p<0.0001), 400μg/ml (OD=1.52, p<0.0001) and 1000μg/ml DEP (OD=0.92, p<0.0001) in the presence of 3.3% FCS as compared to the control cells (OD=2.01). NAC (3.3-33mM), and inhibitors of JNK (10 and 33μM), ERK (3.3-33μM) and NF-κB (3.3-33μM) significantly inhibited the viability of cells treated in culture medium containing 3.3% FCS. However, none of the drugs used reversed 200μg/ml DEP-induced decrease in A549 cell viability. In contrast, the highest concentrations of 33mM NAC and 33μM JNK inhibitor further decreased viability of A549 cells treated with 200μg/ml DEP in 3.3% FCS.
CONCLUSION: These findings suggest that DEP may play a role in the pathogenesis of inflammatory airway diseases such as asthma and chronic obstructive pulmonary diseases by decreasing airway epithelial cell viability; however, further studies are needed to elucidate the underlying mechanisms.
