NORMALIZATION OF RAISED SODIUM-ABSORPTION AND RAISED CALCIUM-MEDIATEDCHLORIDE SECRETION BY ADENOVIRUS-MEDIATED EXPRESSION OF CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR IN PRIMARY HUMAN CYSTIC-FIBROSIS AIRWAY EPITHELIAL-CELLS

Cystic fibrosis airway epithelia exhibit a spectrum of ion transport p roperties that differ from normal, including not only defective cAMP-m ediated Cl- secretion, but also increased Na+ absorption and increased Ca2+-mediated Cl- secretion. In the present study, we examined whethe r adenovirus-mediated (Ad5) transduction of CFTR can correct all of th ese CF ion transport abnormalities. Polarized primary cultures of huma n CF and normal nasal epithelial cells were infected with Ad5-CBCFTR a t an moi (10(4)) which transduced virtually all cells or Ad5-CMV lacZ as a control. Consistent with previous reports, Ad5-CBCFTR, but not Ad 5-CMV lacZ, corrected defective CF cAMP-mediated Cl- secretion. Basal Na+ transport rates (basal I-eq) in CF airway epithelial sheets (-78.5 +/- 9.8 mu A/cm(2)) were reduced to levels measured in normal epithel ial sheets (-30.0+/-2.0 mu A/cm(2)) by Ad5-CBCFTR (-36.9 +/- 4.8 mu A/ cm(2)), but not Ad5-CMV lacZ (-65.8 +/- 6.1 mu A/cm(2)). Surprisingly, a significant reduction in Delta I-eq in response to ionomycin, a mea sure of Ca2+-mediated Cl- secretion, was observed in CFTR-expressing ( corrected) CF epithelial sheets (-6.9 +/- 11.8 mu A/ cm(2)) when compa red to uninfected CF epithelial sheets (-76.2 +/- 15.1 mu A/cm(2)). Do se response effects of Ad5-CBCFTR on basal Na+ transport rates and Ca2 +-mediated Cl- secretion suggest that the mechanism of regulation of t hese two ion transport functions by CFTR may be different. In conclusi on, efficient transduction of CFTR corrects hyperabsorption of Na+ in primary CF airway epithelial cells and restores Ca2+-mediated Cl- secr etion to levels observed in normal airway epithelial cells. Moreover, assessment of these ion transport abnormalities may represent importan t endpoints for testing the efficacy of gene therapy for cystic fibros is.