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

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.

Sinus Microanatomy and Microbiota in a Rabbit Model of Rhinosinusitis

“…On week 2, a thick slow-moving mucus blanket was readily observed (MCT velocity = 0.18 ± 0.02 mm/min, p = 0.0044) accompanying the depleted PCL (Figure 5B ); CBF was not detectable due to the thickness of the PCL layer. By 14 weeks, the overlying thick mucus layer of the ASL had resolved (Figure 4C ), but PCL remained depleted 3.27 ± 0.06 μm, p < 0.0001), suggesting residual deficits on anion secretion may exist, as has been shown previously (Cho et al, 2009 , 2016b ; Cohen et al, 2009 ; Dransfield et al, 2013 ; Liu L. et al, 2013 ; Raju et al, 2013 , 2017a , b ; Illing et al, 2015 ; Woodworth, 2015 ; Cho and Woodworth, 2016 ; Tipirneni et al, 2017 ). Consequently, CBF was significantly diminished (control = 7.4 ± 0.34 Hz vs. Week 14 = 6.08 ± 0.02 Hz, p < 0.0001) (Figure 5C ); MCT was not detectable due to depleted ASL (no traceable mucus), although is likely impaired given the changes in CBF.…”

“…These findings clearly establish the mechanistic basis for abnormal mucociliary host defense and point out the extent to which these changes to the epithelium can persist, despite resolution of the airway obstruction. They further indicate that PCL depletion can be an important mechanism in chronic sinus disease, as has been shown in the airways (Woodworth, 2015 ; Raju et al, 2017a , b ; Tipirneni et al, 2017 ). Of note, PCL depletion can be a factor despite sufficient quantity of overlying mucus within the ASL.…”

Precision medicine in united airways disease: A “treatable traits” approach

“…Ivacaftor reverses the acute reduction of CFTR activity after exposure to cigarette smoke in human bronchoepithelial cells, and has been demonstrated to ameliorate chronic bronchitis symptoms and improve CFTR activity in a preliminary study . Roflumilast, a phosphodiesterase‐4 inhibitor, can stimulate CFTR by increasing cyclic adenosine monophosphate and reverses smoke‐induced inhibition of CFTR activity . Roflumilast is approved for reducing exacerbations in severe COPD associated with chronic bronchitis.…”

The EGFR-ADAM17 Axis in Chronic Obstructive Pulmonary Disease and Cystic Fibrosis Lung Pathology

“…Cigarette smoke decreases CFTR mRNA expression and reduces CFTR protein level through accelerated degradation, leading to impaired mucociliary clearance and depleted ASL in vitro and in vivo [ 82 – 84 ]. Mice treated with cigarette smoke show reduced CFTR activity that can be corrected by the cAMP agonist and phosphodiesterase inhibitor roflumilast, restoring CFTR activity [ 85 ]. Furthermore, macrophage phagocytosis and CFTR activity are impaired by cigarette smoke [ 86 ].…”