calix(4)arene and Cystic-Fibrosis

Calcium-activated Cl(-) secretion is an important modulator of regulated ion transport in murine airway epithelium and is mediated by an unidentified Ca(2+)-stimulated Cl(-) channel. We have transfected immortalized murine tracheal epithelial cells with the cDNA encoding the permeabilizing P2X(7) purinoreceptor (P2X(7)-R) to selectively permeabilize the basolateral membrane and thereby isolate the apical membrane Ca(2+)-activated Cl(-) current. In P2X(7)-R-permeabilized cells, we have demonstrated that UTP stimulates a Cl(-) current across the apical membrane of CF and normal murine tracheal epithelial cells. The magnitude of the UTP-stimulated current was significantly greater in CF than in normal cells. Ion substitution studies demonstrated that the current exhibited a permselectivity sequence of Cl(-) > I(-) > Br(-) > gluconate(-). We have also determined a rank order of potency for putative Cl(-) channel blockers: niflumic acid > or = 5-nitro-2-(3-phenylpropylamino)benzoic acid > 4, 4'-diisothiocyanostilbene-2,2'-disulfonate > glybenclamide >> diphenlyamine-2-carboxylate, tamoxifen, and p-tetra-sulfonato-tetra-methoxy-calix[4]arene. Complete characterization of this current and the corresponding single channel properties could lead to the development of a new therapy to correct the defective airway surface liquid in cystic fibrosis patients.

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Animals; Bromine; Calcium; Calcium Channel Blockers; Calixarenes; Cell Line; Cell Membrane; Chelating Agents; Chlorides; Cystic Fibrosis; DNA, Complementary; Electrophysiology; Epithelium; Gluconates; Glyburide; Hypoglycemic Agents; Iodine; Ions; Mice; Niflumic Acid; Nitrobenzoates; ortho-Aminobenzoates; Phenols; Receptors, Purinergic P2; Receptors, Purinergic P2X7; Tamoxifen; Time Factors; Trachea; Uridine Triphosphate