Cystic fibrosis transmembrane conductance regulator activation by roflumilast contributes to therapeutic benefit in chronic bronchitis.

Cigarette smoking causes acquired cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction and is associated with delayed mucociliary clearance and chronic bronchitis. Roflumilast is a clinically approved phosphodiesterase 4 inhibitor that improves lung function in patients with chronic bronchitis. We hypothesized that its therapeutic benefit was related in part to activation of CFTR. Primary human bronchial epithelial (HBE) cells, Calu-3, and T84 monolayers were exposed to whole cigarette smoke (WCS) or air with or without roflumilast treatment. CFTR-dependent ion transport was measured in modified Ussing chambers. Airway surface liquid (ASL) was determined by confocal microscopy. Intestinal fluid secretion of ligated murine intestine was monitored ex vivo. Roflumilast activated CFTR-dependent anion transport in normal HBE cells with a half maximal effective concentration of 2.9 nM. Roflumilast partially restored CFTR activity in WCS-exposed HBE cells (5.3 ± 1.1 µA/cm(2) vs. 1.2 ± 0.2 µA/cm(2) [control]; P < 0.05) and was additive with ivacaftor, a specific CFTR potentiator approved for the treatment of CF. Roflumilast improved the depleted ASL depth of HBE monolayers exposed to WCS (9.0 ± 3.1 µm vs. 5.6 ± 2.0 µm [control]; P < 0.05), achieving 79% of that observed in air controls. CFTR activation by roflumilast also induced CFTR-dependent fluid secretion in murine intestine, increasing the wet:dry ratio and the diameter of ligated murine segments. Roflumilast activates CFTR-mediated anion transport in airway and intestinal epithelia via a cyclic adenosine monophosphate-dependent pathway and partially reverses the deleterious effects of WCS, resulting in augmented ASL depth. Roflumilast may benefit patients with chronic obstructive pulmonary disease with chronic bronchitis by activating CFTR, which may also underlie noninfectious diarrhea caused by roflumilast.

Acquired defects in CFTR-dependent ß-adrenergic sweat secretion in chronic obstructive pulmonary disease.

RATIONALE: Smoking-induced chronic obstructive pulmonary disease (COPD) is associated with acquired systemic cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. Recently, sweat evaporimetry has been shown to efficiently measure ß-adrenergic sweat rate and specifically quantify CFTR function in the secretory coil of the sweat gland. OBJECTIVES: To evaluate the presence and severity of systemic CFTR dysfunction in smoking-related lung disease using sweat evaporimetry to determine CFTR-dependent sweat rate. METHODS: We recruited a cohort of patients consisting of healthy never smokers (N = 18), healthy smokers (12), COPD smokers (25), and COPD former smokers (12) and measured ß-adrenergic sweat secretion rate with evaporative water loss, sweat chloride, and clinical data (spirometry and symptom questionnaires). MEASUREMENTS AND MAIN RESULTS: ß-adrenergic sweat rate was reduced in COPD smokers (41.9 ± 3.4, P < 0.05, ± SEM) and COPD former smokers (39.0 ± 5.4, P < 0.05) compared to healthy controls (53.6 ± 3.4). Similarly, sweat chloride was significantly greater in COPD smokers (32.8 ± 3.3, P < 0.01) and COPD former smokers (37.8 ± 6.0, P < 0.01) vs. healthy controls (19.1 ± 2.5). Univariate analysis revealed a significant association between ß-adrenergic sweat rate and female gender (ß = 0.26), age (-0.28), FEV1% (0.35), dyspnea (-0.3), and history of smoking (-0.27; each P < 0.05). Stepwise multivariate regression included gender (0.39) and COPD (-0.43) in the final model (R()2 = 0.266, P < 0.0001). CONCLUSIONS: ß-adrenergic sweat rate was significantly reduced in COPD patients, regardless of smoking status, reflecting acquired CFTR dysfunction and abnormal gland secretion in the skin that can persist despite smoking cessation. ß-adrenergic sweat rate and sweat chloride are associated with COPD severity and clinical symptoms, supporting the hypothesis that CFTR decrements have a causative role in COPD pathogenesis.

Cigarette smoke induces systemic defects in cystic fibrosis transmembrane conductance regulator function.

RATIONALE: Several extrapulmonary disorders have been linked to cigarette smoking. Smoking is reported to cause cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction in the airway, and is also associated with pancreatitis, male infertility, and cachexia, features characteristic of cystic fibrosis and suggestive of an etiological role for CFTR. OBJECTIVES: To study the effect of cigarette smoke on extrapulmonary CFTR function. METHODS: Demographics, spirometry, exercise tolerance, symptom questionnaires, CFTR genetics, and sweat chloride analysis were obtained in smokers with and without chronic obstructive pulmonary disease (COPD). CFTR activity was measured by nasal potential difference in mice and by Ussing chamber electrophysiology in vitro. Serum acrolein levels were estimated with mass spectroscopy. MEASUREMENTS AND MAIN RESULTS: Healthy smokers (29.45 ± 13.90 mEq), smokers with COPD (31.89 ± 13.9 mEq), and former smokers with COPD (25.07 ± 10.92 mEq) had elevated sweat chloride levels compared with normal control subjects (14.5 ± 7.77 mEq), indicating reduced CFTR activity in a nonrespiratory organ. Intestinal current measurements also demonstrated a 65% decrease in CFTR function in smokers compared with never smokers. CFTR activity was decreased by 68% in normal human bronchial epithelial cells exposed to plasma from smokers, suggesting that one or more circulating agents could confer CFTR dysfunction. Cigarette smoke-exposed mice had decreased CFTR activity in intestinal epithelium (84.3 and 45%, after 5 and 17 wk, respectively). Acrolein, a component of cigarette smoke, was higher in smokers, blocked CFTR by inhibiting channel gating, and was attenuated by antioxidant N-acetylcysteine, a known scavenger of acrolein. CONCLUSIONS: Smoking causes systemic CFTR dysfunction. Acrolein present in cigarette smoke mediates CFTR defects in extrapulmonary tissues in smokers.