ACTIVATION OF ENDOGENOUS DELTA-F508 CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR BY PHOSPHODIESTERASE INHIBITION

Many heterologously expressed mutants of the cystic fibrosis transmemb rane conductance regulator (CFTR) exhibit residual chloride channel ac tivity that can be stimulated by agonists of the adenylate cyclase/pro tein kinase A pathway. Because of clinical implications for cystic fib rosis of activating mutants in vivo, we are investigating whether Delt a F508, the most common disease-associated CFTR mutation, can be activ ated in airway epithelial cells. Wr have found that Cl-36(-) efflux ca n be stimulated 19-61% above baseline by beta-adrenoreceptor agonists and cGI-phosphodiesterase inhibitors in transformed nasal polyp (CF-T4 3) cells homozygous for the Delta F508 mutation. The increase in Cl-36 (-) permeability is diminished by protein kinase A inhibitors and is n ot mediated by an increase in intracellular calcium concentrations. Pr eincubation of CF-T43 cells with CFTR antisense oligonucleotides preve nted an increase in Cl-36(-) efflux in response to beta-agonist and ph osphodiesterase inhibitor. Primary cells isolated from CF nasal polyps gave similar results. These data indicate that endogenous levels of D elta F508 protein can be stimulated to increase Cl-36(-) permeability in airway epithelial cells.