IntroductionLipoxin A4(LXA4) is a biologically active eicosanoids produced in airway and showing anti-inflammatory proper-ties. In the airway of cystic fibrosis (CF) and severe asthmatic patients, LXA4production is decreased. In both diseases, the quality of the airway lumen content clearance is depending on water and Cl^-transport. In addition, one of the consequences of the airway inflammation is the tight junctions (TJ) disruption. Since intracellular Ca²⁺plays a central role in epithelial secretion, we investigated the effects of LXA4on intracellular Ca²⁺, on Ca²⁺-activated Cl^-secretion, on tight junction formation and 118 production.MethodsAirway epithelial cell lines and primary cultures from patients biopsy have been used. The Ca²⁺imaging System and short circuit techniques were used to explore the regulation of [Ca²⁺]iand transpithelial ion transport respectively. Using immunofluorescence and transepithelial resistance (TER) measurements we studied the tight junction formation. ELISA techniques were used to measure Ilg production by epithelial cells.ResultsLXA4stimulated a rapid and transient [Ca²⁺]iincrease in bronchial epithelial cells expressing the receptor to LXA4(ALX) but not in A549 cells. The [Ca²⁺]; increase was dose-dependant, not affected by removal of external Ca²⁺but was inhibited by thap-sigargin (SER Ca²⁺-pump inhibitor). Pre-treatment with either MDL hydrochloride (adenylate cyclase inhibitor) or Rp-cAMP (cAMP dependent protein kinase inhibitor) inhibited the Ca response to LXA4. LXA4stimulated a transepithelial short-circuit current increase which was inhibited by removal of external Cl^-, by Cl^-channel inhibitors (NPPB, DPC) and by chelating Ca2+iusing BAPTA-AM. LXA410^-7M increased zonula occludens (ZO-1) expression at the plasma-membrane and the TER of airway epithelial monolayers. The LXA4effect on ZO-1 expression was decreased by BAPTA-AM, and by inhibition of PKC and PKA activities. Finally, LXA4inhibited Il8production by airway epithelial cells, whereas the Ca ionophore (A23187) stimulated it.ConclusionOur results provided evidence for the stimulation of Ca²⁺-activated Cl^-secretion and Ca²⁺dependant TJ formation by LXA4through the stimulation of the ALX receptor, a PKA signal-ling pathway and the Ca²⁺release from intracellular stores in airway epithelial cells. LXA4inhibited Il8production by airway epithelial cell, where the intracellular Ca²⁺signal is playing the role of negative feed-back.