1. Academic Validation
  2. The apical mucus layer alters the pharmacological properties of the airway epitheliumy

The apical mucus layer alters the pharmacological properties of the airway epitheliumy

  • J Physiol. 2025 Mar 6. doi: 10.1113/JP287891.
Daniela Guidone 1 Martina de Santis 1 Emanuela Pesce 2 Valeria Capurro 2 Nicoletta Pedemonte 2 Luis J V Galietta 1 3
Affiliations

Affiliations

  • 1 Telethon Institute of Genetics and Medicine, Pozzuoli, Italy.
  • 2 UOC Genetica Medica, Istituto Giannina Gaslini, Genova, Italy.
  • 3 Department of Translational Medical Sciences, University of Napoli 'Federico II', Naples, Italy.
Abstract

Electrogenic transepithelial ion transport can be measured with the short-circuit current technique. Such experiments are frequently used to evaluate the activity of the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated Chloride Channel that is defective in cystic fibrosis, one of the most frequent genetic diseases. Typically, CFTR activity is estimated from the effect of CFTRinh-172, a selective CFTR inhibitor. Unexpectedly, we found that CFTRinh-172, in addition to PPQ-102, another CFTR inhibitor, caused only partial inhibition of CFTR function, particularly in epithelia in pro-inflammatory conditions, which are characterized by abundant mucus secretion. We hypothesized that the mucus layer was responsible for the poor activity of CFTR inhibitors. Therefore, we treated the epithelial surface with the reducing agent dithiothreitol to remove mucus. Removal of mucus, confirmed by immunofluorescence, resulted in highly enhanced sensitivity of CFTR to pharmacological inhibition. Our results show that the mucus layer represents an important barrier whose presence limits the activity of pharmacological agents. This is particularly relevant for CFTR and the evaluation of therapeutic approaches for correction of the basic defect in cystic fibrosis. KEY POINTS: Activity of the cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR) Chloride Channel can be evaluated by measuring the inhibition elicited by the selective blockers CFTRinh-172 and PPQ-102. In short-circuit current recordings on human airway epithelia, CFTR inhibitors had only a partial effect on cAMP-dependent chloride secretion, suggesting the possible contribution of Other ion channels. The mucus layer covering the epithelial surface was removed with the reducing agent dithiothreitol. Treatment of epithelia with dithiothreitol markedly improved the efficacy of CFTR inhibitors. The partial effect of CFTR inhibitors might be explained by the presence of the mucus layer acting as a barrier.

Keywords

airway epithelium; channel blocker; chloride channel; cystic fibrosis transmembrane conductance regulator; mucus.

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