Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC186
The lipoxin A4 increases ASL height in normal and cystic fibrosis bronchial epithelium.
V. Verriere2, G. Higgins3, M. Al Alawi2, R. Costello2, R. Chiron1, B. Harvey2, V. Urbach1,3
1. INSERM, Montpellier, France. 2. Royal College of Surgeons, Dublin, Ireland. 3. National Children Research center, Dublin, Ireland.
Mutations of the Cystic Fibrosis (CF) gene result in defective Cl- secretion and Na+ hyperabsorption. This contributes to a reduction of the airway surface liquid layer (ASL) height and impairs mucociliary clearance, thus promoting bacterial colonization and chronical inflammation. Identification of agents that promote hydration of the ASL is likely to be of therapeutic benefit to patients with CF. Lipoxins are bioactive lipid mediator produced at inflammatory sites from the interaction of lipoxygenase activities of several cell types including neutrophils, platelets and epithelium. This lipid mediator is one member of the newly identify molecules playing a role in ending/resolving the inflammatory process by modulating neutrophilic inflammation, clearing apoptotic PMN and inhibiting pro-inflammatory cytokines production. The levels of LXA4 have been reported to be decreased in the airways of patients with CF. We have discovered a pro-secretory effect of the endogenous LXA4 in human bronchial epithelium. Human bronchus epithelial (HBE) cell primary cultures and CF(CuFi-1) and non-CF(NuLi-1) bronchial epithelial cell lines were grown under an air-liquid interface into well-differentiated epithelia. LXA4(1nM) treatment significantly increased ASL height in non-CF and CF HBE. This effect was sustained over 24 hours in the CF HBE and was inhibited by Boc-2, the antagonist of the ALX/FPR2 receptor that we found to be expressed in the apical membrane of HBE. We investigated the contribution of Na+ absorption (via ENaC) and of Cl- secretion in the ASL height regulation by LXA4. LXA4 pre-treatment reduced the amiloride-sensitive short-circuit current in CuFi-1 epithelium indicating that LXA4 inhibits ENaC activity. LXA4 and amiloride produced additive stimulating effects on the ASL height. LXA4 increased the whole-cell currents of non-CF and CF HBE and this effect was inhibited by BAPTA-AM (chelator of intracellular Ca2+) and NPPB (non selective inhibitor of Ca2+- activated Cl- channels) but not by the CFTRinh-172 (CFTR inhibitor). Bumetanide abolished the ASL height increase induced by LXA4. In addition, LXA4 stimulated an apical ATP release. Hexokinase (ATP hydrolysis), reactive-blue-2 (P2Y purinoreceptor antagonist) and NF340 (P2Y 11 purinoreceptor antagonist) abolished the LXA4 effect on ASL height. Taken together, our results provide evidence for a novel effect of LXA4 involving the FPR2 receptor in the apical membrane, luminal ATP secretion and P2Y receptor(s) activation inhibition of Na+ absorption and stimulation of Cl- secretion in CF and non-CF epithelia to finally increase ASL height. These novel pro-resolving effects of LXA4 reveal a cross-talk between an endogenous anti-inflammatory mediator decrease and the ion transport defect in CF and open up a new therapeutic avenue in the treatment of CF.
Where applicable, experiments conform with Society ethical requirements