Effects of diesel exhasust particles (DEP) on human airway epithelial cell viability under serum condition

Although there is a close association between particular air pollution and respiratory diseases, the underlying mechanisms are unclear. It has been reported that diesel exhaust particles (DEP) induce epithelial cell proliferation under serum-free condition; however, it is not known whether these particles have any effect on the proliferation of airway epithelial cells in the presence of serum, a condition that can be seen in inflamed airways. The aim of my studies was to investigate effects of DEP on viability of A549 cells under serum condition (FCS), and the underlying mechanisms.We cultured A549 cells in 12 well culture plates, and incubated these with N-acetyl cysteine (NAC), and inhibitors of c-jun N-terminal kinase (JNK), extra regulated kinase (ERK) and nuclear factor (NF)-?B in the presence and absence of DEP (0-1000 ?g/ml) under 0-10% FCS condition, and assessed cell viability using MTT staining. Cells cultured in flasks under 3.3% FCS media incubated with 200?g/ml DEP, and analysed for apoptosis by flow cytometry (FACS). Cells obtained in similar flasks were also analysed for p21, P27 and p53 mRNA expression by means of real-time polymerase chain reaction (RT-PCR).Although DEP (50-200?g/ml) increased cell viability under serum free condition, this was not observed in the presence of 1% FCS. DEP (50-1000?g/ml) decreased cell viability under 3.3% FCS, however; when 10% FCS added this effect disappeared. NAC (3.3-33mM) and inhibitors of JNK (10-33?M), ERK (3.3-33?M) and NF-?B (3.3-33?M) decreased cell viability under 3.3% FCS condition, whereas only 33mM NAC and 33?M JNK inhibitor further reduced cell viability in the presence of 200?g/ml DEP under the same condition. While DEP did not show any effect on cell apoptosis in FACS studies, these particles tended to increase p21 mRNA expression. However, because of technical problems, the mRNA expression of p21, p27 and p53 could not be statistically evaluated.These findings suggest that DEP may play a role in the pathogenesis of airway diseases such as asthma and COPD by decreasing airway epithelial cell viability in airways with oedema. However, further studies are needed to investigate the underlying mechanisms.