Lipoxin A4 stimulates calcium-activated chloride secretion and increases airway surface liquid height in normal and cystic fibrosis airway epithelia
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Cystic Fibrosis (CF) is a genetic disease characterised by a deficit in epithelial Cl- secretion leading to airway dehydration and a reduced Airway Surface Liquid (ASL) height. The endogenous lipoxin LXA4 is a member of the newly identified eicosanoids playing a key role in ending the inflammatory process. Levels of LXA4 are decreased in the airways of patients with CF. We have previously shown that in normal human bronchial epithelial cells, LXA4 produced a rapid and transient intracellular Ca2+ increase. We have investigated here, the effect of LXA4 on Cl- secretion and the functional consequences on ASL height in bronchial epithelial cells obtained from CF and non-CF patient biopsies and in bronchial epithelial cell lines. We found that LXA4 stimulated a rapid intracellular Ca2+ increase in all of the different CF bronchial epithelial cells tested. In non-CF and CF bronchial epithelia, LXA4 stimulated whole-cell Cl- currents which were inhibited by NPPB (calcium-activated Cl- channel inhibitor), BAPTA-AM (chelator of intracellular Ca2+) but not by CFTRinh-172 (CFTR inhibitor). We found, using confocal imaging, that LXA4 increased the ASL height in non-CF and in CF airway bronchial epithelia. The LXA4 effect on ASL height was sensitive to bumetanide an inhibitor of transepithelial Cl- secretion. The effects of LXA4 on intracellular Ca2+, whole-cell Cl- currents, conductances and ASL height were inhibited by Boc-2 the antagonist of the ALX/FPR2 receptor. Our results provide, for the first time, evidence for a novel role of LXA4 in the stimulation of Ca2+ signalling, Ca2+-activated Cl- secretion and ASL height in non-CF and CF bronchial epithelia.