Lipoxin A4 (LXA4) is an endogenous anti-inflammatory lipid mediator which is reduced in Cystic Fibrosis (CF) airways1. The altered Cl- secretion and Na+ hyperabsorption in CF affects the Airway Surface Liquid (ASL) homeostasis and leads to a defective mucociliary clearance, chronic infection, inflammation and progressive lung destruction. In this study, the role of LXA4 in modulating ion transport and ASL height in CF and non-CF airway epithelia was investigated. CF (CuFi-1) and non-CF (NuLi-1) bronchial epithelial cell lines were grown into well-differentiated epithelia. LXA4 effects were explored using laser confocal fluorescence microscopy to measure ASL height, short-circuit current and whole-cell patch clamp to investigate ion transporters activity, intracellular calcium imaging and ATP assay to measure ATP release at the apical side of CF epithelia. Data are given as mean ± SEM. The spontaneous steady-state ASL height was significantly lower in CF (5.7±0.1 μm, P<0.001, n=36) than in non-CF (7.9±0.2 μm, n=27) epithelium. LXA4 (1nM) treatment for 15 minutes, increased ASL by 47.5±0.5 % in Nuli-1 epithelia (from 8.0±0.2 μm to 11.8±0.3 μm, P<0.001, n=18). LXA4 also had a marked stimulatory effect in CuFi-1 epithelia increasing ASL by 103.0±3.0 % (from 5.9±0.1 μm to 12.0±0.4 μm, P<0.001, n=19). The stimulatory effect of LXA4 on ASL height was sustained over 24 hours in the CF epithelia and was inhibited by Boc-2 (FPR2 antagonist), bumetanide (Cl- transport inhibitor), amiloride (Na+ channel inhibitor), reactive blue (P2Y2 receptor antagonist) and extracellular hexokinase (ATP hydrolysis). LXA4 stimulated an intracellular Ca2+ mobilization, activated Cl- secretion and inhibited Na+ absorption in the CF epithelia. In addition, LXA4 stimulated a Boc-2 sensitive release of ATP from cells into the ASL in CF epithelia. Our results provide evidence for a novel effect of LXA4 involving the FPR2 receptor, apical ATP release and purinoreceptor activation, inhibition of Na+ absorption and stimulation of Cl- secretion in CF and non-CF epithelia to finally increase ASL height. These novel effects of LXA4 open up a new therapeutic avenue in the treatment of Cystic fibrosis.