Lipid mediator Leukotriene D4-induces airway epithelial cells proliferation through EGFR/ERK1/2 pathway

Background: Cysteinyl leukotrienes (CysLTs), the potent lipid inflammatory mediators, are elevated in many pathological conditions and implicated in various inflammatory diseases including asthma, however their role in airway epithelial cells modulation is not clearly understood. We have investigated the effects of a CysLT, Leukotriene D-4 (LTD4) on human airway epithelial cells, and assessed its role and mode of action in these cells. Methodology: Human small airway epithelial cells (SAECs) and A549 cells were incubated with different concentrations of LTD4 for different time intervals. Subsequently trypan blue dye exclusion assay, MTT assay, Western blotting, RT-PCR and immunofluorescence experiments were performed to examine the effects of LTD4 on proliferation and related molecular changes in the airway epithelial cells. Results: The treatment of human airway epithelial cells with LTD4 resulted in a significant increase in cell proliferation and modulation in the expression of receptors, CysLT(1)R and CysLT(2)R in SAECs as well as A549 cells. In both types of cells, LTD4 increased the expression levels of PCNA and c-myc, and trans-activated EGF receptor and increased the activation of ERK1/2. When treated along with epidermal growth factor (EGF), LTD4 showed a marginal additive effect in ERK1/2 and EGFR phosphorylation compared to LTD4 alone in both types of airway epithelial cells. Conclusion: In conclusion, these results suggest that sustained presence of lipid inflammatory mediator LTD4 could induce human airway epithelial cell proliferation through ERK1/2 phosphorylation, either directly via CysLT(1) receptor or by transactivating EGFR.