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.

Pulmonary artery enlargement and cystic fibrosis pulmonary exacerbations: a cohort study.

BACKGROUND: Acute pulmonary exacerbations are associated with progressive lung function decline and increased mortality in cystic fibrosis. The role of pulmonary vascular disease in pulmonary exacerbations is unknown. We aimed to assess the association between pulmonary artery enlargement (defined as pulmonary artery diameter to ascending aorta diameter [PA:A] ratio >1), a marker of pulmonary vascular disease, and exacerbations. METHODS: In this cohort study, we used clinical, CT imaging, and prospective exacerbation data from a previous prospective clinical trial (derivation cohort) and from The Prince Charles Hospital (TPCH; Brisbane, QLD, Australia) cystic fibrosis registry (validation cohort). In our derivation cohort, we included adults aged 18 years or older with cystic fibrosis and at least one CFTR nonsense mutation, who were enrolled in the trial between Sept 8, 2009, and Nov 30, 2010, randomly assigned to receive placebo, and had baseline CT imaging. Our validation cohort included adult patients with cystic fibrosis who had CT imaging performed between Jan 1, 2002, and Dec 31, 2014. We measured the PA:A ratio at the level of the pulmonary artery bifurcation on CT scans. Patients in each cohort were separated into two groups on the basis of PA:A ratio (>1 or ≤1) and were followed up for 1 year in the derivation cohort and 2 years in the validation cohort. The primary endpoint was the development of one or more acute pulmonary exacerbations during follow-up. We used linear and logistic regression models to determine associations between clinical factors, the PA:A ratio, and pulmonary exacerbations. We used Cox regression to determine the time to first exacerbation in the validation cohort. FINDINGS: 37 (50%) of 74 patients in the derivation cohort and 89 (47%) of 190 patients in the validation cohort had enlarged pulmonary arteries (PA:A>1). 50 (68%) patients in the derivation cohort had one or more exacerbations at 1 year and 133 (70%) patients in the validation cohort had one or more exacerbations at 2 years. At baseline, patients with pulmonary artery enlargement were younger than those without enlargement in both cohorts and had elevated sweat chloride concentrations in the derivation cohort (100·5 mmol/L [SD 10·9] vs 90·4 mmol/L [19·9]; difference 10·1 mmol/L [95% CI 2·5-17·7], p=0·017). Pulmonary artery enlargement was associated with exacerbations in the derivation cohort (odds ratio 3·49 [95% CI 1·18-10·3], p=0·023) when adjusted for sex, body-mass index (BMI), forced expiratory volume in 1 s (FEV1), and PA:A greater than 1, and in the validation cohort (2·41 [1·06-5·52], p=0·037) when adjusted for sex, BMI, chronic Pseudomonas aeruginosa infection, FEV1/FVC (forced vital capacity), PA:A greater than 1, and previous exacerbation. The time to first exacerbation was shorter in patients with enlarged pulmonary arteries than in those with normal-sized pulmonary arteries in the validation cohort (hazard ratio 1·66 [95% CI 1·18-2·34], p=0·0038) in unadjusted analysis, but not when adjusted for sex, BMI, exacerbations within 1 year before index CT scan, FEV1/FVC, and chronic P aeruginosa infection (1·14 [0·80-1·62], p=0·82). INTERPRETATION: Pulmonary artery enlargement is prevalent in adult patients with cystic fibrosis and was associated with acute pulmonary exacerbation risk in two well characterised cohorts. The PA:A ratio could be a predictive marker in cystic fibrosis. FUNDING: US National Heart, Lung, and Blood Institute/National Institutes of Health, Cystic Fibrosis Foundation, the University of Alabama at Birmingham, and the Queensland Health Fellowship.