Inhibition of ATP hydrolysis restores airway surface liquid production in cystic fibrosis airway epithelia

• Published in: American journal of physiology. Lung cellular and molecular physiology Vol. 318; no. 2; pp. L356 - L365
• Main Authors: van Heusden, Catharina, Button, Brian, Anderson, Wayne H., Ceppe, Agathe, Morton, Lisa C., O’Neal, Wanda K., Dang, Hong, Alexis, Neil E., Donaldson, Scott, Stephan, Holger, Boucher, Richard C., Lazarowski, Eduardo R.
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.02.2020
• Subjects: Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Alkaline Phosphatase - genetics; Alkaline Phosphatase - metabolism; Bronchi - pathology; Cystic Fibrosis - metabolism; Cystic Fibrosis - pathology; Enzyme Inhibitors - pharmacology; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Humans; Hydrolysis; Respiratory Mucosa - drug effects; Respiratory Mucosa - metabolism; Respiratory Mucosa - pathology; Sputum - enzymology; Tungsten Compounds - pharmacology; purinergic receptors; ecto-ATPases; cystic fibrosis; polyoxometalates; extracellular ATP
• ISSN: 1040-0605; 1522-1504; 1522-1504
• DOI: 10.1152/ajplung.00449.2019

Airway surface dehydration is a pathological feature of cystic fibrosis (CF) lung disease. CF is caused by mutations in the CF transmembrane conductance regulator (CFTR), a cyclic AMP-regulated Cl − channel controlled in part by the adenosine A 2B receptor. An alternative CFTR-independent mechanism of fluid secretion is regulated by ATP via the P2Y 2 receptor (P2Y 2 R) that activates Ca 2+ -regulated Cl − channels (CaCC/TMEM16) and inhibits Na + absorption. However, due to rapid ATP hydrolysis, steady-state ATP levels in CF airway surface liquid (ASL) are inadequate to maintain P2Y 2 R-mediated fluid secretion. Therefore, inhibiting airway epithelial ecto-ATPases to increase ASL ATP levels constitutes a strategy to restore airway surface hydration in CF. Using [γ 32 P]ATP as radiotracer, we assessed the effect of a series of ATPase inhibitory compounds on the stability of physiologically occurring ATP concentrations. We identified the polyoxometalate [Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] 10− (POM-5) as the most potent and effective ecto-ATPase inhibitor in CF airway epithelial cells. POM-5 caused long-lasting inhibition of ATP hydrolysis in airway epithelia, which was reversible upon removal of the inhibitor. Importantly, POM-5 markedly enhanced steady-state levels of released ATP, promoting increased ASL volume in CF cell surfaces. These results provide proof of concept for ecto-ATPase inhibitors as therapeutic agents to restore hydration of CF airway surfaces. As a test of this notion, cell-free sputum supernatants from CF subjects were studied and found to have abnormally elevated ATPase activity, which was markedly inhibited by POM-5.