Homoserine Lactone Stimulates Cftr-Dependent Cl- Secretion In Human Airway Epithelial Cells: Roles For Ca2+ And Camp

When cystic fibrosis (CF) patients become colonized with P. aeruginosa , the bacteria secrete quorum‐sensing molecules, including N‐(3‐oxo‐dodecanoyl)‐S‐homoserine lactone (3O‐C12) to regulate bacterial gene expression. 10–50 μM 3O‐C12 increased Cl − secretion (I Cl , transepithelial electrophysiology) in CFTR‐expressing airway epithelial cell lines (50% of I Cl stimulated by forskolin], but not in a CF line. Thus, 3O‐C12‐stimulated I Cl required CFTR. 3O‐C12 increased cytosolic [Ca 2+ ] (Ca i , fura‐2 imaging) similarly in Ca 2+ ‐containing and Ca 2+ ‐free solutions. 3O‐C12 had small effects to increase I Cl and Ca i in the presence of thapsigargin (inhibits Ca 2+ ‐ATPase and releases ER Ca 2+ ). 3O‐C12 increased cAMP (Epac H30 FRET imaging) to a level 25% of maximal stimulation with forskolin + isobutylmethylxanthine (IBMX, phosphodiesterase inhibitor). 3O‐C12‐stimulated I Cl was inhibited by cAMP antagonist RpBrcAMPS and increased by IBMX. It is concluded that 3O‐C12 stimulation of I Cl requires release of Ca 2+ from the ER and, importantly, increases in cAMP. In CF, 3O‐C12‐triggered increases of both Ca i and cAMP will not increase Cl − and fluid secretion by airway epithelia but will instead cause effects (mucus secretion, apoptosis) that increase bacterial retention or persistence in the airways.