Changes in the proteome of human bronchial epithelial cells following stimulation with leucotriene E4 and transforming growth factor-β1

Background and objective: Activated bronchial epithelial cells exert considerable potential to maintain a microenvironment in the airway wall that promotes airway inflammation and remodelling. Cysteinyl leucotrienes (CysLT) and transforming growth factor‐β₁ (TGF‐β₁) are both increased in asthmatic airways and may influence the pathophysiology of disease. However, the consequences of activation of bronchial epithelial cells by these mediators are not fully understood. A proteomic‐based approach was used to characterize the inflammatory pathways in bronchial epithelial cells after stimulation with CysLT and TGF‐β₁. Methods: Human bronchial epithelial cells (BEAS‐2B) were stimulated with 1 ng/mL TGF‐β₁ and 50 nmol/L leucotriene E₄ (LTE₄) for 48 h and whole‐cell lysates were subjected to two‐dimensional gel electrophoresis. Proteins showing statistically significant differential expression were identified by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and database searching. Results: Stimulation with LTE₄ increased the expression of three proteins and five proteins showed decreased expression. Of the latter group, two were definitively identified as heat shock protein (Hsp90α) and stress‐70 protein. Hsp90α forms a heterocomplex with the glucocorticoid receptor (GR) and a significant decrease in GR following LTE₄ stimulation was confirmed. TGF‐β₁ downregulated 18 intracellular proteins, including lamin A/C, glyceraldehyde‐3‐phosphate dehydrogenase, protein DJ‐1, voltage‐dependent calcium channel gamma‐7 subunit, heterogeneous nuclear ribonucleoprotein A2/B1 and stress‐70 protein. Conclusions: The current findings suggest that by downregulating GR and Hsp90α, CysLT may interfere with the action of glucocorticoids. Overall, the results confirm the complex role of bronchial epithelium in aspects of airway inflammation and remodelling.