Cystic Fibrosis Transmembrane Regulator Correction Attenuates Heart Failure-Induced Lung Inflammation

Background and Purpose: Heart failure (HF) affects 64 million people worldwide. Despite advancements in prevention and therapy, quality of life remains poor for many HF patients due to target organ damage. Pulmonary manifestations of HF are well-established. However, difficulties in the treatment of HF patients with chronic lung phenotypes remain, as standard therapies are often complicated by contraindications. Here, we verify the downregulation of the cystic fibrosis transmembrane regulator (CFTR) in the HF lung, a concept that may provide new mechanism-based therapies for HF patients with pulmonary complications. Experimental Approach: Ligation of the left anterior descending coronary artery in mice was used to induce myocardial infarction (MI). At 10 weeks post-MI, pharmacological CFTR corrector therapy (Lumacaftor (Lum)) was applied systemically or lung-specific for 2 weeks, and the lungs were analysed using histology, flow cytometry, Western blotting, and qPCR. Key Results: Experimental HF associated with an apparent lung phenotype characterized by reduction of pulmonary CFTR+ cells, vascular remodelling, and pronounced tissue inflammation as evidenced by infiltration of pro-inflammatory monocytes and elevation of classically-activated macrophages in the lung. PharmacologicalCFTR correction with Lum mitigated the HF-induced downregulation of pulmonary CFTR expression, increased the proportion of CFTR+ cells in the lung, and diminished the HF-associated elevation of classically-activated non-alveolar macrophages within the lungs with implication for vessel wall thickness. Conclusion and Implications: Collectively, our data suggest that pharmacological CFTR correction possesses the capacity to alleviate HF-induced inflammation in the lung and may emerge as treatment option for HF patients with chronic lung phenotypes.

Adenylate Cyclase 1 Links Calcium Signaling to CFTR-Dependent Cytosolic Chloride Elevations in Chick Amacrine Cells

The strength and sign of synapses involving ionotropic GABA and glycine receptors are dependent upon the Cl− gradient. We have shown that nitric oxide (NO) elicits the release of Cl− from internal acidic stores in retinal amacrine cells (ACs); temporarily altering the Cl− gradient and the strength or even sign of incoming GABAergic or glycinergic synapses. The underlying mechanism for this effect of NO requires the cystic fibrosis transmembrane regulator (CFTR) but the link between NO and CFTR activation has not been determined. Here, we test the hypothesis that NO-dependent Ca2+ elevations activate the Ca2+-dependent adenylate cyclase 1 (AdC1) leading to activation of protein kinase A (PKA) whose activity is known to open the CFTR channel. Using the reversal potential of GABA-gated currents to monitor cytosolic Cl−, we established the requirement for Ca2+ elevations. Inhibitors of AdC1 suppressed the NO-dependent increases in cytosolic Cl− whereas inhibitors of other AdC subtypes were ineffective suggesting that AdC1 is involved. Inhibition of PKA also suppressed the action of NO. To address the sufficiency of this pathway in linking NO to elevations in cytosolic Cl−, GABA-gated currents were measured under internal and external zero Cl− conditions to isolate the internal Cl− store. Activators of the cAMP pathway were less effective than NO in producing GABA-gated currents. However, coupling the cAMP pathway activators with the release of Ca2+ from stores produced GABA-gated currents indistinguishable from those stimulated with NO. Together, these results demonstrate that cytosolic Ca2+ links NO to the activation of CFTR and the elevation of cytosolic Cl−.

Extensive CFTR Gene Analysis Revealed a Higher Occurrence of Cystic Fibrosis Transmembrane Regulator-Related Disorders (CFTR-RD) among CF Carriers

Background: A wide range of cystic fibrosis (CF)-related conditions are reported in CF carriers, but no study has explored the possibility that such subjects may be affected by cystic fibrosis transmembrane regulator-related disorders (CFTR-RD). No data are available so far on the occurrence of CFTR-RD among CF carriers. Methods: We studied 706 CF carriers—first- and second-degree relatives of CF patients that carried the parental mutation; such subjects were divided in two groups: a first group (353 subjects, group A) performed at first only the analysis of the CFTR proband mutation; we retrospectively evaluated the number of cases that had been diagnosed as CFTR-RD based on subsequent symptoms; a second group (353 subjects, group B) performed extensive CFTR molecular analysis in absence of any reported symptoms, followed by a clinical evaluation in cases that carry a second CFTR mutation; we evaluated the number of cases that prospectively were diagnosed as CFTR-RD. Results: We found seven (2.0%) out of 353 subjects of group A and 24 (6.8%) out of 353 subjects of group B as affected by CFTR-RD (chi square, p = 0.002). Conclusions: A percentage of CF carriers are affected by undiagnosed CFTR-RD. Genetic tasting scanning analysis helps to identify CFTR-RD, some of which may benefit from follow-up and specific therapies improving their outcome.

Heterozygous Cystic Fibrosis Transmembrane Regulator Gene Missense Variants Are Associated With Worse Cardiac Function in Patients With Duchenne Muscular Dystrophy

Background Duchenne muscular dystrophy (DMD) is a neuromuscular disorder caused by mutations within the dystrophin gene. DMD is characterized by progressive skeletal muscle degeneration and atrophy and progressive cardiomyopathy. It has been observed the severity of cardiomyopathy varies in patients with DMD. Methods and Results A cohort of male patients with DMD and female DMD carriers underwent whole exome sequencing. Potential risk factor variants were identified according to their functional annotations and frequencies. Cardiac function of 15 male patients with DMD was assessed by cardiac magnetic resonance imaging, and various cardiac magnetic resonance imaging parameters and circulating biomarkers were compared between genotype groups. Five subjects carrying potential risk factor variants in the cystic fibrosis transmembrane regulator gene demonstrated lower left ventricular ejection fraction, larger left ventricular end‐diastolic volume, and higher NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) levels compared with 10 subjects who did not carry the potential risk factor variants ( P =0.023, 0.019 and 0.028, respectively). Conclusions This study revealed heterozygous cystic fibrosis transmembrane regulator gene missense variants were associated with worse cardiac function in patients with DMD. The cystic fibrosis transmembrane regulator gene may serve as a genetic modifier that accounts for more severe cardiomyopathy in patients with DMD, who would require more aggressive management of the cardiomyopathy.

Pancreatitis in A Patient with Cystic Fibrosis Taking Ivacaftor

Pancreatitis is rare in pancreatic insufficient cystic fibrosis patients. While pancreatic insufficiency has been considered irreversible until now, in the current era of new therapies with modulators of the Cystic Fibrosis Transmembrane Regulator CFTR channel, there are reports of improvement of pancreatic exocrine function. We describe the case of an adolescent with cystic fibrosis who developed pancreatitis after the partial recovery of pancreatic function while taking ivacaftor. This case adds to the limited body of evidence that CFTR modulators lead to the improvement of pancreatic exocrine function in cystic fibrosis.

Cystic fibrosis

Cystic fibrosis (CF) is a recessively inherited disease caused by mutations in the cystic fibrosis gene, located on the long arm of chromosome 7, which codes for a membrane protein—the cystic fibrosis transmembrane regulator protein—that is a chloride channel. More than 2,000 CF mutations have been identified, with the Δ‎F508 mutation being the most common of around 200 mutations that definitely cause disease (70% of CF chromosomes in the European population). Birth incidence varies with country of origin from 1 in 2,000 to 1 in 100,000. The most popular hypothesis is that mutant cystic fibrosis transmembrane regulator protein fails to transport chloride ions normally, and there is secondary impairment of sodium, bicarbonate, and water transport.