Exogenous Lipoxin A4 attenuates IL4-induced Mucin Expression in Human Airway Epithelial Cells

Introduction: The proinflammatory cytokine interleukin-4 (IL-4) induces mucus hypersecretion by human airway epithelial cells and the MAP kinase signalling pathway may be important in terms of IL-4-induced MUC5AC gene expression. Lipoxin A₄ (LXA₄) is an arachidonic acid-derived mediator that promotes inflammation by binding to the anti-inflammatory receptors (ALXs) or the formyl-peptide receptor like-1 (FPRL1) protein expressed by airway epithelial cells. Here, we explore the effects of LXA4 on IL-4-induced mucin gene expression in, and secretion from, human airway epithelial cells. Methods: We co-treated cells with IL-4 (20 ng/mL) and LXA₄ (1 nM) and measured the expression levels of mRNAs encoding MUC5AC and 5B via real-time polymerase chain reaction; protein expression levels were determined by Western blotting and immunocytofluorescence. The ability of IL-4 and LXA₄ to suppress protein expression was determined by Western blotting. Results: IL-4 increased MUC5AC and 5B gene and protein expression. LXA₄ suppressed IL-4-induced MUC5AC and 5B gene and protein expression by interacting with the IL4 receptor and mitogen-activated protein kinase (MAPK) pathway, including both phospho-p38 MAPK and phospho-extracellular signal-regulated kinase (phospho-ERK). IL-4 and LXA₄ increased and decreased, respectively, the number of cells that stained with anti-MUC5AC and 5B antibodies. Conclusions: LXA₄ may regulate mucus hypersecretion induced by IL4 in human airway epithelial cells.