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 (IC50 ∼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 = α1-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 (ED50 = 3 μg/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.
Footnotes
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Some of the data presented here have appeared in abstract form as follows: Proceedings of the 2007 North American Cystic Fibrosis Conference; 2007 Apr 10; Anaheim, CA. 92A, p 232, Cystic Fibrosis Foundation, Bethesda, MD.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.108.148155.
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ABBREVIATIONS: CFTR, cystic fibrosis transmembrane conductance regulator; ENaC, epithelial sodium channel; CF, cystic fibrosis; MCC, mucociliary clearance; CAP, channel-activating protease; PRSS8, prostasin; HNE, human neutrophil elastase; LMW, low molecular weight; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate; amc, amino-4-methylcoumarin; SBTI, soya bean trypsin inhibitor; 4-GBCE, 4-guanidino-benzoic acid 4-carboxymethyl-phenyl ester; BEGM, bronchial epithelial growth media; PGBA, p-guanidinobenzoic acid; HBE, human bronchial epithelial cell; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; GPTEC, guinea pig tracheal epithelial cell; ISC, short-circuit current; ANOVA, analysis of variance; TPD, tracheal potential difference; 99mTc-SC, technetium-labeled sulfur colloid; 552-02, N-(3,5-diamino-6-chloropyrazine-2-carbonyl)-N′-4-[4-(2,3-dihydroxypropoxy)phenyl] butyl-guanidine; NVP-QAU145, camostat; FOY-305, camostat; HBC276, camostat; 4-GBCE, 4-guanidinobenzoic acid 4-carboxymethyl-phenyl ester.
- Received October 30, 2008.
- Accepted February 2, 2009.
- The American Society for Pharmacology and Experimental Therapeutics
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