ATP DEPLETION INDUCES A LOSS OF RESPIRATORY EPITHELIUM FUNCTIONAL INTEGRITY AND DOWN-REGULATES CFTR (CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR) EXPRESSION

To mimic the effect of ischemia on the integrity of airway epithelium and expression of cystic fibrosis transmembrane conductance regulator (CFTR), we induced an ATP depletion of the respiratory epithelium from upper airway cells (nasal tissue) and human bronchial epithelial 16HB E14o(-) cell line. Histological analysis showed that 2 h of ATP deplet ion led to a loss of the epithelium integrity at the interface between basal cells and columnar cells. The expression of connexin 43 (Cx43, subunit of the gap junctions) and desmoplakins 1 and 2 (DPs 1 and 2, m ajor components of the desmosomes) proteins was inhibited. After 90 mi n of ATP depletion, a significant decrease of the transepithelial resi stance (25%) was observed but was reversible. Similar results were obt ained with the 16HBE14o(-) human bronchial epithelial cell line. ATP d epletion led to actin filaments depolymerization. The expression of th e mature CFTR (170 kDa) and fodrin proteins at the apical domain of th e ciliated cells was down-regulated. The steady-state levels of CFTR, Cx43, DPs 1 and 2 mRNAs, semiquantified by RT-polymerase chain reactio n kinetics, remained constant throughout ATP depletion in nasal tissue as in the homogeneous cell population of 16HBE14o(-) human bronchial epithelial cell line. This suggests that the down-regulation of these proteins might be posttranscriptional. The intercellular diffusion thr ough gap junctions of Lucifer dye was completely inhibited after 90 mi n of ATP depletion but was reversible. The volume-dependent and the cA MP-dependent chloride secretion were inhibited in a nonreversible way. Taken together, these results suggest that an ATP depletion in human airway epithelium, mimicking ischemia, may induce a marked alteration in the junctional complexes and cytoskeleton structure concomitantly w ith a loss of apical CFTR expression and chloride secretion function.