CFTR is required for zinc-mediated antibacterial defense in human macrophages.

Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion transporter required for epithelial homeostasis in the lung and other organs, with CFTR mutations leading to the autosomal recessive genetic disease CF. Apart from excessive mucus accumulation and dysregulated inflammation in the airways, people with CF (pwCF) exhibit defective innate immune responses and are susceptible to bacterial respiratory pathogens such as Pseudomonas aeruginosa. Here, we investigated the role of CFTR in macrophage antimicrobial responses, including the zinc toxicity response that is used by these innate immune cells against intracellular bacteria. Using both pharmacological approaches, as well as cells derived from pwCF, we show that CFTR is required for uptake and clearance of pathogenic Escherichia coli by CSF-1-derived primary human macrophages. CFTR was also required for E. coli-induced zinc accumulation and zinc vesicle formation in these cells, and E. coli residing in macrophages exhibited reduced zinc stress in the absence of CFTR function. Accordingly, CFTR was essential for reducing the intramacrophage survival of a zinc-sensitive E. coli mutant compared to wild-type E. coli. Ectopic expression of the zinc transporter SLC30A1 or treatment with exogenous zinc was sufficient to restore antimicrobial responses against E. coli in human macrophages. Zinc supplementation also restored bacterial killing in GM-CSF-derived primary human macrophages responding to P. aeruginosa, used as an in vitro macrophage model relevant to CF. Thus, restoration of the zinc toxicity response could be pursued as a therapeutic strategy to restore innate immune function and effective host defense in pwCF.

Evaluation of the efficiency of nanomicellar formulation of fat-soluble vitamins in patients with cystic fibrosis: the study protocol for a randomized controlled trial.

BACKGROUND: Cystic fibrosis is an inherited disease, which is caused by the CFTR protein defects due to mutations in the CFTR gene. Along with CFTR dysfunction, exocrine pancreatic insufficiency plays a key role in persistent fat malabsorption in CF patients; therefore, deficiency of fat-soluble vitamins (A, D, E, and K) is still a therapeutic challenge. Even with efficient pancreatic enzyme medication and CF-specific vitamins, many patients with CF have fat-soluble vitamins deficiency. The present study aims to evaluate the efficiency of nanomicelle formulation of fat-soluble vitamins in children with CF in order to achieve the appropriate serum levels of these vitamins. METHODS: This prospective, single-blind control trial will be conducted at the Akbar Children's Hospital in Mashhad, Iran. Patients with CF will be enrolled based on the eligibility criteria. The control group will receive the standard formulation of fat-soluble vitamins similar to the routine CF treatment, and for the intervention group, the nanomicelle formulation of fat-soluble vitamins will be administered for 3 months. The primary outcome of this study is the measurement of serum levels of fat-soluble vitamins. The secondary outcomes are clinical assessment by the Shwachman-Kulczycki score, anthropometrics, and quality of life. Outcomes will be assessed before and after 3 months. DISCUSSION: Due to persistent fat-soluble vitamin deficiency in CF disease, the nanomicelle formulation could be proposed as a new delivery method of fat-soluble vitamins in the treatment of cystic fibrosis. TRIAL REGISTRATION: Iranian Registry of Clinical Trials IRCT20220415054541N1. Registered on July 23, 2022.

A liposomal platform for the delivery of ion channel proteins for treatment of channelopathies - Application in therapy of cystic fibrosis.

Channelopathies arise from ion channel dysfunction. Successful treatment entails delivery of functional ion channels to replace dysfunctional ones. Glycine receptor (GlyR)-rich cell membrane fragments (CMF) were previously delivered to target cell membranes using fusogenic liposomes. Here, cystic fibrosis transmembrane conductance regulator (CFTR)-bearing CMF were similarly delivered to target cells. We studied the effect of lipid composition on liposomes' ability to incorporate CMF and fuse with target cell membranes to deliver functional CFTR. Four formulations were prepared using thin-film hydration out of different lecithin sources, egg and soy lecithin (EL and SL), in the presence and absence of cholesterol (CHOL): EL + CHOL, EL-CHOL, SL + CHOL, and SL-CHOL. EL liposomes incorporated more CMF than SL liposomes, with CHOL only increasing CMF incorporation in SL liposomes. SL + CHOL fused better with target cell membranes than EL + CHOL. SL + CHOL and EL + CHOL equally delivered CFTR to target cell membranes, owing to the former's superior fusogenic capacity and the latter's superior CMF-incorporation capacity. SL-CHOL and EL-CHOL delivered CFTR to a lesser extent, indicating the importance of CHOL for fusion. Patch-clamp electrophysiology and confocal laser scanning microscopy (CLSM) confirmed CFTR delivery to target cell membranes by SL + CHOL. Therefore, CMF-bearing fusogenic liposomes offer a promising universal platform for the treatment of channelopathies.

Changes in nutrition and growth status in young children in the first 12 weeks of ivacaftor therapy.

BACKGROUND: Highly effective CFTR modulators improve nutritional status and are of particular importance among younger children experiencing rapid growth. This study was designed to examine CFTR modulator associated changes in nutritional and other extrapulmonary outcomes in children 4-24 months of age with ivacaftor treatment over 12 weeks. METHODS: Children 4-24 months were recruited from US and Canadian CF Centers. Eligible children were ivacaftor naïve and approved to start therapy. Anthropometrics, diet, sleeping energy expenditure (SEE), nutrition biomarkers, pancreatic status, serum and fecal calprotectin, serum bile acids, plasma fatty acids were measured. Changes from baseline at 6 and 12 weeks were examined using mixed effects linear regression modeling. RESULTS: Fifteen participants enrolled (40% male). Weight-for-age z-scores increased at 6 (p = 0.03) and 12 weeks ivacaftor therapy (p<0.001) compared to baseline. Plasma docosatetraenoic acid (DTA), total saturated fatty acids increased at 6 weeks (p = 0.02) and 12 weeks (p = 0.009). At 12 weeks, serum CO2 concentration decreased (p = 0.002), serum urea nitrogen increased (p = 0.01) and fecal elastase increased (p = 0.02) compared to baseline. Bile acids, deoxycholic acid increased (p = 0.03) and ursodeoxycholic acid decreased (p = 0.02) after 12 weeks. Plasma total fatty acids, palmitic acid, mead, and docosatetraenoic acid (DTA) increased after 12 weeks (p = 0.02, p = 0.002 and p = 0.04, respectively). Plasma total saturated fatty acids increased at 6 weeks (p = 0.02) and 12 weeks (p = 0.009). Dietary intake (p = 0.04) and percent kcal from protein (p = 0.04) increased after 12 weeks compared to baseline. CONCLUSIONS: Overall, younger children experienced favorable changes in nutritional and growth status in the first 12 weeks of ivacaftor therapy.

Olive Leaf Extract (OLE) as a Novel Antioxidant That Ameliorates the Inflammatory Response in Cystic Fibrosis.

The deletion of phenylalanine at position 508 (F508del) produces a misfolded CFTR protein that is retained in the ER and degraded. The lack of normal CFTR channel activity is associated with chronic infection and inflammation which are the primary causes of declining lung function in Cystic Fibrosis (CF) patients. Moreover, LPS-dependent oxidative stress downregulates CFTR function in airway epithelial cells. Olive leaf extract (OLE) is used in traditional medicine for its effects, including anti-oxidant and anti-inflammatory ones. We found that OLE decreased the intracellular ROS levels in a dose-response manner in CFBE cells. Moreover, OLE attenuates the inflammatory response to LPS or IL-1ß/TNFα stimulation, mimicking the infection and inflammatory status of CF patients, in CFBE and primary nasal epithelial (HNE) cells. Furthermore, we demonstrated that OLE restored the LPS-mediated decrease of TrikfaftaTM-dependent F508del-CFTR function in CFBE and HNE cultures. These findings provide strong evidence of OLE to prevent redox imbalance and inflammation that can cause chronic lung damage by enhancing the antioxidant activity and attenuating inflammation in CF airway epithelial cells. Additionally, OLE might be used in combination with CFTR modulators therapy to improve their efficacy in CF patients.

FDA-approved drug screening in patient-derived organoids demonstrates potential of drug repurposing for rare cystic fibrosis genotypes.

BACKGROUND: Preclinical cell-based assays that recapitulate human disease play an important role in drug repurposing. We previously developed a functional forskolin induced swelling (FIS) assay using patient-derived intestinal organoids (PDIOs), allowing functional characterization of CFTR, the gene mutated in people with cystic fibrosis (pwCF). CFTR function-increasing pharmacotherapies have revolutionized treatment for approximately 85% of people with CF who carry the most prevalent F508del-CFTR mutation, but a large unmet need remains to identify new treatments for all pwCF. METHODS: We used 76 PDIOs not homozygous for F508del-CFTR to test the efficacy of 1400 FDA-approved drugs on improving CFTR function, as measured in FIS assays. The most promising hits were verified in a secondary FIS screen. Based on the results of this secondary screen, we further investigated CFTR elevating function of PDE4 inhibitors and currently existing CFTR modulators. RESULTS: In the primary screen, 30 hits were characterized that elevated CFTR function. In the secondary validation screen, 19 hits were confirmed and categorized in three main drug families: CFTR modulators, PDE4 inhibitors and tyrosine kinase inhibitors. We show that PDE4 inhibitors are potent CFTR function inducers in PDIOs where residual CFTR function is either present, or created by additional compound exposure. Additionally, upon CFTR modulator treatment we show rescue of CF genotypes that are currently not eligible for this therapy. CONCLUSION: This study exemplifies the feasibility of high-throughput compound screening using PDIOs. We show the potential of repurposing drugs for pwCF carrying non-F508del genotypes that are currently not eligible for therapies. ONE-SENTENCE SUMMARY: We screened 1400 FDA-approved drugs in CF patient-derived intestinal organoids using the previously established functional FIS assay, and show the potential of repurposing PDE4 inhibitors and CFTR modulators for rare CF genotypes.

[Chinese experts consensus statement: diagnosis and treatment of cystic fibrosis (2023)].

Cystic fibrosis (CF) is one of the most common autosomal recessive genetic diseases in Caucasians, but CF patients in China are rare, and it was listed as the first batch of rare diseases in China in 2018. In recent years, CF has been gradually recognized in China, and the number of CF patients reported in China in the past 10 years is more than 2.5 times the total number in the previous 30 years, and the total number of CF patients is estimated to be more than 20 000. The research progress of CF gene modification has led to the innovation of CF treatment. However, the sweat test as an important test for the diagnosis of CF has not been widely implemented in China. At present, the diagnosis and treatment of CF in China still lacks standardized recommendations. In view of these updates, the Chinese Experts Cystic Fibrosis Consensus Committee has formed "the Chinese experts consensus statement: diagnosis and treatment of cystic fibrosis" based on extensive opinion gathering, literatures review, multiple meetings and discussions. This consensus collects 38 core issues related to CF, including pathogenesis, epidemiology, clinical characteristics, diagnosis, treatment, rehabilitation, and patient management. Finally, 32 recommendations were formulated. The consensus used the modified GRADE methodology to grade the evidence evaluation and recommendations. This is the current state of CF consensus in China, and we hope to improve the diagnosis and treatment of CF in China in the future.Summary of recommendationsQuestion 1: How can CF be identified?CF should be suspected if there is: (1) a family history of CF; (2) delayed meconium expulsion or meconium ileus; (3) pancreatic exocrine insufficiency, mainly characterized by long-standing steatorrhea and malnutrition; (4) recurrent lower respiratory tract infections of infantile onset, especially Pseudomonas aeruginosa (PA), Staphylococcus aureus infections of respiratory aetiology; (5) chronic sinusitis, especially when combined with juvenile presentation of nasal polyps; (6) chest CT abnormalities such as the presence of air trapping, bronchiectasis (upper lobe predominant); (7) pseudo-Bartter syndrome; (8) absence of vas deferens in males; (9) clubbing in young bronchiectasis patients(1C).Question 2: What are the diagnostic criteria for CF?1.1 Presence of one or more of the characteristic clinical manifestations or family history consistent with CF, and meeting at least one of the following definite diagnostic criteria in 1.2 or 1.3.1.2 Sweat chloride testing:(1) Concentrations of more than 60 mmol/L are diagnostic; (2) concentrations between 30-59 mmol/L are intermediate, and genetic variation must be considered to confirm the diagnosis; (3) concentrations less than 30 mmol/L are considered normal.1.3 Genetic testing:(1) Detection of two disease-causing CFTR(cystic fibrosis transmembrane conductance regulator) mutations on biallelic alleles; (2) The CFTR variants are of undetermined significance, but tests such as sweat chloride concentration, intestinal current measurement, or nasal mucosal potential difference suggest abnormal CFTR function, then CF is diagnostic(1C).Question 3: What is the diagnostic process for CF arranged?Sweat chloride testing and CFTR gene analysis are recommended in all patients suspected of CF(1D).Question 4: What is the value of sweat chloride testing in the diagnosis of CF?Sweat chloride testing is the gold standard for the clinical diagnosis of CF(1C).Question 5: What is the value of CFTR genetic testing in Chinese CF diagnosis?Biallelic pathogenic variants of CFTR are a definitive diagnosis of CF(1D).Question 6: What is the diagnostic value of imaging for CF?Chest CT is a sensitive test for early stages of lung disease in patients with CF and is appropriate in younger patients and to assess disease progression. The imaging findings of abdominal visceral involvement in CF lack specificity(2C).Question 7: How to evaluate the pancreatic function of CF patients?Fecal elastase may be used as the first indicator to assess pancreatic exocrine function in patients with CF (2C).Question 8: How to diagnose hepatic abnormality of CF?CF related liver disease was diagnosed when CF was confirmed and 2 of the following 4 criteria were met: (1) hepatomegaly and/or splenomegaly confirmed by ultrasound; (2) ALT, AST, and GGT on three consecutive occasions above the upper limit of normal on three consecutive occasions for more than 12 months and excluding other causes; (3) had evidence of liver involvement, portal hypertension, or bile duct dilatation by ultrasound; (4) liver biopsy confirmation (focal biliary cirrhosis or multilobular cirrhosis) may be indicated if the diagnosis is suspected(2D).Question 9: How to identify pulmonary exacerbations in patients with CF?Pulmonary exacerbations are indicated when any 4 of the following 12 signs or symptoms are met: increased sputum; new onset haemoptysis or increased haemoptysis; exacerbation of cough; increased dyspnea; malaise, fatigue, or somnolence; body temperature above 38 ℃; anorexia or weight loss; sinus pain or tenderness; increased sinus secretions; new chest signs; FEV1≥10% decline from previous; imaging changes suggestive of pulmonary infection(2D).Question 10: How to diagnose CF related diabetes?Diagnostic criteria for CF related diabetes are the same as those for diabetes in the population(1D).Question 11: How to evaluate the nutritional status of CF patients?Anthropometric parameters reflecting nutritional status should be assessed regularly. And the goal of nutritional assessment is to evaluate and monitor whether pediatric patients are achieving normal standards of growth and development or whether adult patients are maintaining adequate nutritional status(1C).Question 12: Does CF require pathological examination as a diagnostic basis?Pathohistological biopsy is not recommended as a first-line diagnostic method in patients with a suspected diagnosis of CF(1D).Question 13: Do CF patients need long-term macrolides?At least 6 months of azithromycin treatment is recommended for CF patients with chronic PA infection(2A).Question 14: Do CF patients need long-term inhalation of hypertonic saline?Long term treatment with hypertonic saline is recommended for patients with CF(1A).Question 15: Do CF patients need long-term inhalation of Dornase alfa(DNase)?Long term use of DNase is recommended in patients with CF aged 6 years and older(1A).Question 16: Do CF patients need inhalation of mannitol?Inhaled mannitol therapy is recommended for more than 6 months in patients with CF aged 18 years and older when other inhaled treatments are unavailable or intolerable(2A).Question 17: How to deal with PA found in the sputum culture of CF patients?When sputum cultures from patients with CF are positive for PA, it needs to determine the characteristics of the infection first. The purpose for acute infection is to eradicate PA. Chronic colonization does not need to be eradicated, and the main purpose is to reduce the bacterial load and improve symptoms(1A).Question 18: Do CF patients need inhalation of antibiotics?Inhaled antibiotic therapy is recommended for CF patients with PA infection(1A).Question 19: Do CF patients need inhaled or systemic corticosteroids?In patients with CF without asthma or ABPA, routine inhaled or systemic glucocorticoids are not recommended (2A).Question 20: Do CF patients need to inhale bronchodilators?Bronchodilators can be used in the short term to improve symptoms in patients with CF in the presence of airway obstruction, but the long-term benefit is insufficient (2B).Question 21: Do CF patients need expectorant medicine?Patients with CF can take acetylcysteine orally or aerosolized(2A).Question 22: How to deal with acute pulmonary exacerbation in CF patients?Intensive implementation of non-antimicrobial therapy is recommended during pulmonary exacerbations in patients with CF. Antimicrobials with activity against PA were selected for empirical treatment, and the treatment was adjusted according to the results of bacterial culture and drug susceptibility testing. A 21-day long course of anti-infective therapy is not recommended(1B).Question 23: How to treat CF patients with ABPA?Medical therapy is recommended for CF patients with ABPA who meet any of the following criteria: patients with elevated immunoglobulin E levels and concomitant worsening of pulmonary function and/or pulmonary symptoms, or imaging suggesting new infiltrative foci in the chest(1D).Glucocorticoids are recommended for ABPA exacerbations in CF patients without contraindications(2D).Itraconazole should be added if the patient presents with poor response to corticosteroids, recurrence of ABPA, corticosteroid dependence, or corticosteroid toxicity(2D).Question 24: Is lung transplantation recommended for patients with CF? When is it recommended?Patients with CF may be evaluated for lung transplantation when they meet the following criteria after optimal medical therapy: (1) FEV1<30% predicted; (2) FEV1<40% predicted (<50% predicted in children) with the following: 6-minute walk distance<400 meters; PaCO2>50 mmHg(1 mmHg=0.133 kPa); hypoxia at rest or after activity; pulmonary artery pressure measured by cardiotocography>50 mmHg or right heart dysfunction; continued deterioration despite aggressive supplementation of nutritional support; two exacerbations requiring intravenous antibiotic therapy per year; massive hemoptysis (>240 ml) requiring pulmonary artery embolization; presented with pneumothorax; (3) FEV1<50% predicted and rapid decline in lung function or rapid worsening of symptoms; (4) Presented with an acute exacerbation requiring positive pressure mechanical ventilation(2C).Question 25: How to deal with pancreatic disease in CF patients?Pancreatic enzyme replacement therapy is recommended in patients with CF pancreatic disease(1A).Question 26: How to deal with hepatobiliary disease in CF patients?Ursodeoxycholic acid is not recommended in asymptomatic patients with CF hepatobiliary disease(2B).Question 27: How to deal with gastrointestinal problems such as acid regurgitation in CF patients?Acid suppression is recommended for CF patients with gastrointestinal symptoms such as acid regurgitation (2B).Question 28: How to deal with CF related diabetes?Insulin therapy is recommended in CF related diabetes(1B).Question 29: How should nutritional support be given to patients with CF?Energy intake in patients with CF is recommended to be 110%-200% of the energy requirement of a healthy person under equivalent physiological conditions. And maintaining adequate protein, appropriate intake of fats, electrolytes, and fat-soluble vitamins are recommanded(1A).Question 30: How should respiratory rehabilitation be performed in patients with CF?Airway clearance therapy and appropriate exercise are recommended for patients with CF(1A).Question 31: What is included in the follow-up of CF patient?Patients with CF should have regular follow-up. Adult patients are recommended to be followed every 3-6 months, and children should be followed more frequently(2A).Question 32: How should CF patients avoid infections?Inpatients and outpatients are recommended to be separated according to microbiota carriage status(1D).Good hand hygiene is recommended for the patients with CF and their contacts(1D).It is recommended that CF patients wear masks in healthcare settings. This may reduce the release of potentially infectious aerosols during coughing (1D).Annual influenza vaccination is recommended for patients with CF>6 months of age and for all family members of patients with CF and all healthcare workers caring for these patients(2D).Palivizumab may be considered for the prevention of respiratory syncytial virus infection in patients with CF under two years of age(2A).

Increased expression of glucagon-like peptide-1 and cystic fibrosis transmembrane conductance regulator in the ileum and colon in mouse treated with metformin.

Metformin, an oral medication, is prescribed to patients with type 2 diabetes mellitus. Although the efficacy, safety, and low economic burden of metformin on patients have long been recognized, approximately 5% of the patients treated with this drug develop severe diarrhea and discontinue the treatment. We previously reported that 1,000 mg·kg-1·day-1 of metformin induced diarrhea in diabetic obese (db/db) mice and wood creosote (traditional medication for diarrhea) ameliorated the symptoms. In this study, we attempted to elucidate the molecular mechanisms by which metformin induces diarrhea. Cystic fibrosis transmembrane conductance regulator (CFTR) is a key ion (chloride) channel in cyclic adenosine monophosphate (cAMP)-induced diarrhea. Metformin treatment increased bile flow (bile acids and bilirubin) in the ileum of mice. In addition, the treatment was accompanied by an increase in mRNA and protein levels of CFTR in the mucosa of the ileum and colon in both wild-type (C57BL/6J) and db/db mice. Glucagon-like peptide-1 (GLP-1), as well as cholic acid, induces CFTR mRNA expression in human colon carcinoma Caco-2 cells through cAMP signaling. Although wood creosote (10 mg/kg) ameliorated diarrhea symptoms, it did not alter the mRNA levels of Glp-1 or Cftr. Similar to overeating, metformin upregulated GLP-1 and CFTR expression, which may have contributed to diarrhea symptoms in mice. Although we could not identify db/db mouse-specific factors associated with metformin-induced diarrhea, these factors may modulate colon function. Wood creosote may not interact with these factors but ameliorates diarrhea symptoms.

Impact of highly effective CFTR modulator therapy on digital clubbing in patients with cystic fibrosis.

BACKGROUND: The association of certain disease processes with digital clubbing is well documented. Digital clubbing is often reversible after successful treatment of the underlying pathology, for example, after lung transplantation in patients with cystic fibrosis (CF). We examined the effect of highly effective Cystic Fibrosis Transmembrane Regulator (CFTR) modulators, defined for the purposes of this study as ivacaftor or the combination of ivacaftor, tezacaftor, and elexacaftor (ETI), on digital clubbing. MATERIALS AND METHODS: Clubbing index was measured on plaster of Paris casts of right index fingers obtained from 15 patients with cystic fibrosis, before and after initiation of CFTR modulator therapy. Similar measurements were made on casts for 9 cystic fibrosis patients who underwent lung transplantation. Measurements were made on the most recent casts available before treatment and the first cast available at least 3 months after initiation of treatment. The Wilcoxon signed-rank text was used to detect any significant difference in the pre- and post-treatment casts for each individual. RESULTS: A significant decrease in the clubbing index was found after both lung transplantation and treatment with highly effective CFTR modulator therapy. CONCLUSIONS: These results add to the body of evidence demonstrating the efficacy of highly effective CFTR modulator therapy, the first agents that act directly at the dysfunctional chloride channel responsible for CF. By demonstrating that CFTR modulator therapy is capable of reversing digital clubbing, this study suggests a beneficial effect on lung pathology aside from air flow and gas transfer.

Impact of elexacaftor/tezacaftor/ivacaftor on vitamin D absorption in cystic fibrosis patients.

BACKGROUND: Cystic fibrosis (CF) is a multisystem disorder that results in the buildup of mucus in various organs. Ninety percent of CF patients are classified as pancreatic insufficient, leading to malabsorption of nutrients and fat-soluble vitamins without the assistance of exogenous pancreatic enzymes. This study was designed to determine if serum 25-hydroxyvitamin D concentrations were impacted by initiation of elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA). METHODS: Serum 25-hydroxyvitamin D concentrations were measured before and 1 year post-ELX/TEZ/IVA initiation. A Wilcoxon signed-rank test was used to compare values. RESULTS: Seventy-six patients were included in the final analysis. The average age of our population was 25.8 years (SD = 13.2 years) with a majority being male, homozygous F508del, pancreatic insufficient, and not modulator-naive. The median increase of serum vitamin D concentration after initiating ELX/TEZ/IVA was 5 ng/ml (interquartile range = -4, 13; p = .0035). CONCLUSIONS: We suggest that ELX/TEZ/IVA may improve fat-soluble vitamin absorption, specifically serum 25-hydroxyvitamin D. These results may lead to adjustments in vitamin supplementation in patients receiving cystic fibrosis transmembrane conductance regulator modulator therapy.

Role of inflammation and oxidative stress in tissue damage associated with cystic fibrosis: CAPE as a future therapeutic strategy.

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, responsible for the synthesis of the CFTR protein, a chloride channel. The gene has approximately 2000 known mutations and all of them affect in some degree the protein function, which makes the pathophysiological manifestations to be multisystemic, mainly affecting the respiratory, gastrointestinal, endocrine, and reproductive tracts. Currently, the treatment of the disease is restricted to controlling symptoms and, more recently, a group of drugs that act directly on the defective protein, known as CFTR modulators, was developed. However, their high cost and difficult access mean that their use is still very restricted. It is important to search for safe and low-cost alternative therapies for CF and, in this context, natural compounds and, mainly, caffeic acid phenethyl ester (CAPE) appear as promising strategies to assist in the treatment of the disease. CAPE is a compound derived from propolis extracts that has antioxidant and anti-inflammatory activities, covering important aspects of the pathophysiology of CF, which points to the possible benefit of its use in the disease treatment. To date, no studies have effectively tested CAPE for CF and, therefore, we intend with this review to elucidate the role of inflammation and oxidative stress for tissue damage seen in CF, associating them with CAPE actions and its pharmacologically active derivatives. In this way, we offer a theoretical basis for conducting preclinical and clinical studies relating the use of this molecule to CF.

Might Routine Vitamin A Monitoring in Cystic Fibrosis Patients Reduce Virus-Mediated Lung Pathology?

Cystic fibrosis (CF) is an autosomal recessive gene disorder that affects tens of thousands of patients worldwide. Individuals with CF often succumb to progressive lung disease and respiratory failure following recurrent infections with bacteria. Viral infections can also damage the lungs and heighten the CF patient's susceptibility to bacterial infections and long-term sequelae. Vitamin A is a key nutrient important for immune health and epithelial cell integrity, but there is currently no consensus as to whether vitamin A should be monitored in CF patients. Here we evaluate previous literature and present results from a CF mouse model, showing that oral vitamin A supplements significantly reduce lung lesions that would otherwise persist for 5-6 weeks post-virus exposure. Based on these results, we encourage continued research and suggest that programs for the routine monitoring and regulation of vitamin A levels may help reduce virus-induced lung pathology in CF patients.

ß-Catenin-NF-κB-CFTR interactions in cholangiocytes regulate inflammation and fibrosis during ductular reaction.

Expansion of biliary epithelial cells (BECs) during ductular reaction (DR) is observed in liver diseases including cystic fibrosis (CF), and associated with inflammation and fibrosis, albeit without complete understanding of underlying mechanism. Using two different genetic mouse knockouts of ß-catenin, one with ß-catenin loss is hepatocytes and BECs (KO1), and another with loss in only hepatocytes (KO2), we demonstrate disparate long-term repair after an initial injury by 2-week choline-deficient ethionine-supplemented diet. KO2 show gradual liver repopulation with BEC-derived ß-catenin-positive hepatocytes and resolution of injury. KO1 showed persistent loss of ß-catenin, NF-κB activation in BECs, progressive DR and fibrosis, reminiscent of CF histology. We identify interactions of ß-catenin, NFκB, and CF transmembranous conductance regulator (CFTR) in BECs. Loss of CFTR or ß-catenin led to NF-κB activation, DR, and inflammation. Thus, we report a novel ß-catenin-NFκB-CFTR interactome in BECs, and its disruption may contribute to hepatic pathology of CF.

The liver has an incredible capacity to repair itself or 'regenerate' ­ that is, it has the ability to replace damaged tissue with new tissue. In order to do this, the organ relies on hepatocytes (the cells that form the liver) and bile duct cells (the cells that form the biliary ducts) dividing and transforming into each other to repair and replace damaged tissue, in case the insult is dire. During long-lasting or chronic liver injury, bile duct cells undergo a process called 'ductular reaction', which causes the cells to multiply and produce proteins that stimulate inflammation, and can lead to liver scarring (fibrosis). Ductular reaction is a hallmark of severe liver disease, and different diseases exhibit ductular reactions with distinct features. For example, in cystic fibrosis, a unique type of ductular reaction occurs at late stages, accompanied by both inflammation and fibrosis. Despite the role that ductular reaction plays in liver disease, it is not well understood how it works at the molecular level. Hu et al. set out to investigate how a protein called ß-catenin ­ which can cause many types of cells to proliferate ­ is involved in ductular reaction. They used three types of mice for their experiments: wild-type mice, which were not genetically modified; and two strains of genetically modified mice. One of these mutant mice did not produce ß-catenin in biliary duct cells, while the other lacked ß-catenin both in biliary duct cells and in hepatocytes. After a short liver injury ­ which Hu et al. caused by feeding the mice a specific diet ­ the wild-type mice were able to regenerate and repair the liver without exhibiting any ductular reaction. The mutant mice that lacked ß-catenin in hepatocytes showed a temporary ductular reaction, and ultimately repaired their livers by turning bile duct cells into hepatocytes. On the other hand, the mutant mice lacking ß-catenin in both hepatocytes and bile duct cells displayed sustained ductular reactions, inflammation and fibrosis, which looked like that seen in patients with liver disease associated to cystic fibrosis. Further probing showed that ß-catenin interacts with a protein called CTFR, which is involved in cystic fibrosis. When bile duct cells lack either of these proteins, another protein called NF-B gets activated, which causes the ductular reaction, leading to inflammation and fibrosis. The findings of Hu et al. shed light on the role of ß-catenin in ductular reaction. Further, the results show a previously unknown interaction between ß-catenin, CTFR and NF-B, which could lead to better treatments for cystic fibrosis in the future.

Discovery of Icenticaftor (QBW251), a Cystic Fibrosis Transmembrane Conductance Regulator Potentiator with Clinical Efficacy in Cystic Fibrosis and Chronic Obstructive Pulmonary Disease.

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel are established as the primary causative factor in the devastating lung disease cystic fibrosis (CF). More recently, cigarette smoke exposure has been shown to be associated with dysfunctional airway epithelial ion transport, suggesting a role for CFTR in the pathogenesis of chronic obstructive pulmonary disease (COPD). Here, the identification and characterization of a high throughput screening hit 6 as a potentiator of mutant human F508del and wild-type CFTR channels is reported. The design, synthesis, and biological evaluation of compounds 7-33 to establish structure-activity relationships of the scaffold are described, leading to the identification of clinical development compound icenticaftor (QBW251) 33, which has subsequently progressed to deliver two positive clinical proofs of concept in patients with CF and COPD and is now being further developed as a novel therapeutic approach for COPD patients.

Is the ENaC Dysregulation in CF an Effect of Protein-Lipid Interaction in the Membranes?

While approximately 2000 mutations have been discovered in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR), only a small amount (about 10%) is associated with clinical cystic fibrosis (CF) disease. The discovery of the association between CFTR and the hyperactive epithelial sodium channel (ENaC) has raised the question of the influence of ENaC on the clinical CF phenotype. ENaC disturbance contributes to the pathological secretion, and overexpression of one ENaC subunit, the ß-unit, can give a CF-like phenotype in mice with normal acting CFTR. The development of ENaC channel modulators is now in progress. Both CFTR and ENaC are located in the cell membrane and are influenced by its lipid configuration. Recent studies have emphasized the importance of the interaction of lipids and these proteins in the membranes. Linoleic acid deficiency is the most prevailing lipid abnormality in CF, and linoleic acid is an important constituent of membranes. The influence on sodium excretion by linoleic acid supplementation indicates that lipid-protein interaction is of importance for the clinical pathophysiology in CF. Further studies of this association can imply a simple clinical adjuvant in CF therapy.

Identification of Compounds That Promote Readthrough of Premature Termination Codons in the CFTR.

Cystic fibrosis (CF) is caused by a mutation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which disrupts an ion channel involved in hydration maintenance via anion homeostasis. Nearly 5% of CF patients possess one or more copies of the G542X allele, which results in a stop codon at residue 542, preventing full-length CFTR protein synthesis. Identifying small-molecule modulators of mutant CFTR biosynthesis that affect the readthrough of this and other premature termination codons to synthesize a fully functional CFTR protein represents a novel target area of drug discovery. We describe the implementation and integration for large-scale screening of a homogeneous, 1536-well functional G542X-CFTR readthrough assay. The assay uses HEK 293 cells engineered to overexpress the G542X-CFTR mutant, whose functional activity is monitored with a membrane potential dye. Cells are co-incubated with a CFTR amplifier and CFTR corrector to maximize mRNA levels and trafficking of CFTR to the cell surface. Compounds that allow translational readthrough and synthesis of functional CFTR chloride channels are reflected by changes in membrane potential in response to cAMP stimulation with forskolin and CFTR channel potentiation with genistein. Assay statistics yielded Z' values of 0.69 ± 0.06. As further evidence of its suitability for high-throughput screening, we completed automated screening of approximately 666,000 compounds, identifying 7761 initial hits. Following secondary and tertiary assays, we identified 188 confirmed hit compounds with low and submicromolar potencies. Thus, this approach takes advantage of a phenotypic screen with high-throughput scalability to identify new small-molecule G542X-CFTR readthrough modulators.

Emerging preclinical modulators developed for F508del-CFTR have the potential to be effective for ORKAMBI resistant processing mutants.

BACKGROUND: F508del is prototypical of Class 2 CFTR mutations associated with protein misprocessing and reduced function. Corrector compounds like lumacaftor partially rescue the processing defect of F508del-CFTR whereas potentiators like ivacaftor, enhance its channel activity once trafficked to the cell surface. We asked if emerging modulators developed for F508del-CFTR can rescue Class 2 mutations previously shown to be poorly responsive to lumacaftor and ivacaftor. METHODS: Rescue of mutant CFTRs by the correctors: AC1, AC2-1 or AC2-2 and the potentiator, AP2, was studied in HEK-293 cells and in primary human nasal epithelial (HNE) cultures, using a membrane potential assay and Ussing chamber, respectively. RESULTS: In HEK-293 cells, we found that a particular combination of corrector molecules (AC1 plus AC2-1) and a potentiator (AP2) was effective in rescuing both the misprocessing and reduced function of M1101K and G85E respectively. These findings were recapitulated in patient-derived nasal cultures, although another corrector combination, AC1 plus AC2-2 also improved misprocessing in these primary tissues. Interestingly, while this corrector combination only led to a modest increase in the abundance of mature N1303K-CFTR it did enable its functional expression in the presence of the potentiator, AP2, in part, because the nominal corrector, AC2-2 also exhibits potentiator activity. CONCLUSIONS: Strategic combinations of novel modulators can potentially rescue Class 2 mutants thought to be relatively unresponsive to lumacaftor and ivacaftor.

Perinatal Reduced Blood Concentrations of Free Carnitine and Acylcarnitines in Infants with Cystic Fibrosis.

OBJECTIVE: Cystic fibrosis (CF) is a multisystemic inherited disease. The aim of this study was to determine free carnitine (FC) and acylcarnitine concentrations in CF newborns with various mutations of the CFTR gene perinatally. STUDY DESIGN: FC/acylcarnitines were determined in dried blood spots via liquid chromatography-tandem mass spectrometry (LC-MS/MS) on the third day of life of full-term normal (n = 50) and CF (n = 28) newborns. For infants with elevated immunoreactive trypsinogen values, FC/acylcarnitines were quantified again 48 hours later, followed by mutational analysis of CFTR gene via Sanger sequencing. RESULTS: Initial FC and sums of acylcarnitine concentrations were statistically significantly lower in CF patients than in controls and even lower 48 hours later. The mutations F508del and 621 + 1G > T were predominantly identified among CF patients. CONCLUSION: Low FC and acylcarnitine concentrations were measured perinatally in CF patients, for all CFTR mutations detected. Carnitine supplementation of breastfeeding mothers could be beneficial.

Pseudo-Bartter syndrome in Chinese children with cystic fibrosis: Clinical features and genotypic findings.

OBJECTIVES: To characterize the clinical and genotypic features of cystic fibrosis-associated pseudo-Bartter syndrome (CF-PBS) in Chinese children. METHODS: We recruited and characterized the clinical manifestations of 12 Chinese children with CF-PBS. Sweat test, blood and urinary analysis, sputum culture, chest and sinus computed tomography, and abdominal ultrasonography were obtained. Whole-exome sequencing, bioinformatics analysis, and Sanger sequencing validation were performed to define the genotypes. RESULTS: CF-PBS was accompanied by recurrent and/or persistent pneumonia (91.7%), pancreatitis (83.3%), vomiting and/or diarrhea (66.7%), failure to thrive and liver disease (58.3% respectively), among our patients. The predominant organisms found in the airways were Pseudomonas aeruginosa (83.3%) and Staphylococcus aureus (75.0%). The mean concentrations of blood gas and electrolytes were pH 7.58, bicarbonate 40.8 mmol/L, sodium 125.9 mmol/L, chloride 77.5 mmol/L, and potassium 2.6 mmol/L. A high recurrence rate (50.0%) of CF-PBS was observed despite continued electrolyte supplementation during follow-up. In all, 19 different variants of CFTR gene were identified, and 10 of these were found to be novel observations (c.262_266delTTATA[p.L88FfsX21], c.579+2insACAT, c.1210-3C>G, c.1733T>C[p.L578P], c.2236_2246delGAGGCGATACTinsAAAAATC[p.E746KfsX8], c.3068T>G [p.I1023R], c.3635delT[p.V1212AfsX16], c.3859delG[p.G1287EfsX2], c.3964-7A>G and ΔE23 [c.3718-?_3873+?del]). The c.2909G>A[p.G970D] was the most common variant, with an allele frequency of 16.6%. A homozygous genotype of c.1521_1523delCTT[p.F508del] was discovered for the first time in patients of Chinese origin. CONCLUSIONS: In China, CF-PBS usually presents early and recurs frequently in infancy, accompanied by multiple comorbidities. Recurrence of CF-PBS in school-going patients does occur but is rare. The p.G970D is the most frequent variant, with a significant ethnic tendency of Chinese origin.