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

Am J Physiol Lung Cell Mol Physiol. 2020 Feb 1;318(2):L356-L365. doi: 10.1152/ajplung.00449.2019. Epub 2019 Dec 4.

Abstract

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 A2B receptor. An alternative CFTR-independent mechanism of fluid secretion is regulated by ATP via the P2Y2 receptor (P2Y2R) that activates Ca2+-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 P2Y2R-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 [γ32P]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 [Co4(H2O)2(PW9O34)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.

Keywords: cystic fibrosis; ecto-ATPases; extracellular ATP; polyoxometalates; purinergic receptors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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

Substances

  • Enzyme Inhibitors
  • Tungsten Compounds
  • polyoxometalate I
  • Adenosine Triphosphate
  • Alkaline Phosphatase
  • Adenosine Triphosphatases
  • ectoATPase