Camostat attenuates airway epithelial sodium channel function in vivo through the inhibition of a channel-activating protease

J Pharmacol Exp Ther. 2009 May;329(2):764-74. doi: 10.1124/jpet.108.148155. Epub 2009 Feb 3.

Abstract

Inhibition of airway epithelial sodium channel (ENaC) function enhances mucociliary clearance (MCC). ENaC is positively regulated by channel-activating proteases (CAPs), and CAP inhibitors are therefore predicted to be beneficial in diseases associated with impaired MCC. The aims of the present study were to 1) identify low-molecular-weight inhibitors of airway CAPs and 2) to establish whether such CAP inhibitors would translate into a negative regulation of ENaC function in vivo, with a consequent enhancement of MCC. To this end, camostat, a trypsin-like protease inhibitor, provided a potent (IC(50) approximately 50 nM) and prolonged attenuation of ENaC function in human airway epithelial cell models that was reversible upon the addition of excess trypsin. In primary human bronchial epithelial cells, a potency order of placental bikunin > camostat > 4-guanidinobenzoic acid 4-carboxymethyl-phenyl ester > aprotinin >> soybean trypsin inhibitor = alpha1-antitrypsin, was largely consistent with that observed for inhibition of prostasin, a molecular candidate for the airway CAP. In vivo, topical airway administration of camostat induced a potent and prolonged attenuation of ENaC activity in the guinea pig trachea (ED(50) = 3 microg/kg). When administered by aerosol inhalation in conscious sheep, camostat enhanced MCC out to at least 5 h after inhaled dosing. In summary, camostat attenuates ENaC function and enhances MCC, providing an opportunity for this approach toward the negative regulation of ENaC function to be tested therapeutically.

MeSH terms

  • Animals
  • Bronchi / cytology
  • Bronchi / drug effects
  • Bronchi / enzymology
  • Bronchi / metabolism
  • Cells, Cultured
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology
  • Epithelial Cells / metabolism
  • Epithelial Sodium Channels / metabolism*
  • Gabexate / analogs & derivatives*
  • Gabexate / pharmacology
  • Guinea Pigs
  • Humans
  • Male
  • Membrane Potentials / drug effects
  • Mucociliary Clearance / drug effects
  • Peptide Hydrolases / metabolism*
  • Protease Inhibitors / pharmacology*
  • Respiratory Mucosa / drug effects*
  • Respiratory Mucosa / enzymology
  • Respiratory Mucosa / metabolism
  • Sheep
  • Trachea / cytology
  • Trachea / drug effects
  • Trachea / enzymology
  • Trachea / metabolism

Substances

  • Epithelial Sodium Channels
  • Protease Inhibitors
  • camostat
  • Gabexate
  • Peptide Hydrolases