Roflumilast reverses CFTR-mediated ion transport dysfunction in cigarette smoke-exposed mice

S Vamsee Raju,Lawrence Rasmussen,Emily Falk Libby,Peter A Sloane,Li Ping Tang,Steven M Rowe

doi:10.1186/s12931-017-0656-0

S Vamsee Raju, Lawrence Rasmussen + Show 4 more

Open Access

https://doi.org/10.1186/s12931-017-0656-0

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Journal: Respiratory research	Publication Date: Sep 18, 2017
Citations: 25	License type: open-access

Affiliation: University of Alabama at Birmingham

Abstract

BackgroundDysfunction in cystic fibrosis transmembrane conductance regulator (CFTR) can be elicited by cigarette smoke and is observed in patients with chronic bronchitis. We have previously demonstrated in human airway epithelial cell monolayers that roflumilast, a clinically approved phosphodiesterase 4 inhibitor that reduces the risk of exacerbations in chronic obstructive pulmonary disease patients with chronic bronchitis and a history of exacerbations, activates CFTR-dependent chloride secretion via a cAMP-mediated pathway, partially restores the detrimental effects of cigarette smoke on CFTR-mediated ion transport, and increases CFTR-dependent gastrointestinal fluid secretion in isolated murine intestine segments. Based on these findings, we hypothesized that roflumilast could improve CFTR-mediated chloride transport and induce secretory diarrhea in mice exhibiting cigarette smoke-induced CFTR dysfunction.MethodsA/J mice expressing wild type CFTR (+/+) were exposed to cigarette smoke or air with or without roflumilast and the effect of treatment on CFTR-dependent chloride transport was quantified using nasal potential difference (NPD) measurements in vivo and short-circuit current (Isc) analysis of trachea ex vivo. Stool specimen were collected and the wet/dry ratio measured to assess the effect of roflumilast on secretory diarrhea.ResultsAcute roflumilast treatment increased CFTR-dependent chloride transport in both smoke- and air-exposed mice (smoke, −2.0 ± 0.4 mV, 131.3 ± 29.3 μA/cm2, P < 0.01 and air, 3.9 ± 0.8 mV, 147.7 ± 38.0 μA/cm2, P < 0.01 vs. vehicle −0.3 ± 0.7 mV, 10.4 ± 7.0 μA/cm2). Oral administration of roflumilast over five weeks completely reversed the deleterious effects of cigarette smoke on CFTR function in smoke-exposed animals, in which CFTR-dependent chloride transport was 64% that of air controls (roflumilast, −15.22 ± 2.7 mV vs. air, −14.45 ± 1.4 mV, P < 0.05). Smoke exposure increased the wet/dry ratio of stool specimen to a level beyond which roflumilast had little additional effect.ConclusionsRoflumilast effectively rescues CFTR-mediated chloride transport in vivo, further implicating CFTR activation as a mechanism through which roflumilast benefits patients with bronchitis.

Highlights

Dysfunction in cystic fibrosis transmembrane conductance regulator (CFTR) can be elicited by cigarette smoke and is observed in patients with chronic bronchitis
We found in primary human bronchial epithelial monolayers that roflumilast activated CFTRdependent chloride secretion via cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)-dependent phosphorylation of the Cystic fibrosis transmembrane conductance regulator (CFTR) regulatory domain, and was able to partially restore the detrimental effects of cigarette smoke on CFTR-mediated ion transport
Roflumilast increases CFTR activity in the nasal airways in vivo and tracheal segments ex vivo To verify prior studies in airway monolayers and tissues that implicated CFTR activation as a mechanism mediating the clinical benefit of roflumilast [20], we evaluated whether roflumilast alters CFTR function on the surface of the respiratory epithelium in healthy, wild-type mice, the anticipated CFTR genotype in the majority of chronic obstructive pulmonary disease (COPD)

Summary

Introduction

Dysfunction in cystic fibrosis transmembrane conductance regulator (CFTR) can be elicited by cigarette smoke and is observed in patients with chronic bronchitis. We have previously demonstrated in human airway epithelial cell monolayers that roflumilast, a clinically approved phosphodiesterase 4 inhibitor that reduces the risk of exacerbations in chronic obstructive pulmonary disease patients with chronic bronchitis and a history of exacerbations, activates CFTR-dependent chloride secretion via a cAMP-mediated pathway, partially restores the detrimental effects of cigarette smoke on CFTR-mediated ion transport, and increases CFTR-dependent gastrointestinal fluid secretion in isolated murine intestine segments. Based on these findings, we hypothesized that roflumilast could improve CFTR-mediated chloride transport and induce secretory diarrhea in mice exhibiting cigarette smoke-induced CFTR dysfunction. Restoration of impaired CFTR function may represent an important approach in COPD therapeutics, as underscored by investigations exhibiting that the CFTR potentiator ivacaftor rescues CFTR ion transport and epithelial function in smoke-exposed human airway cells [10] as well as improves CFTR activity in current and former smokers with chronic bronchitis [19]

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