Defective CFTR Research Articles

Current landscape of cystic fibrosis gene therapy.

Cystic fibrosis is a life-threatening disease that is caused by mutations in CFTR, a gene which encodes an ion channel that supports proper function of several epithelial tissues, most critically the lung. Without CFTR, airway barrier mechanisms are impaired, allowing for chronic, recurrent infections that result in airway remodeling and deterioration of lung structure and function. Small molecule modulators can rescue existing, defective CFTR protein; however, they still leave a subset of people with CF with no current disease modifying treatments, aside from lung transplantation. Gene therapy directed to the lung is a promising strategy to modify CF disease in the organ most associated with morbidity and mortality. It is accomplished through delivery of a CFTR transgene with an airway permissive vector. Despite more than threedecades of research in this area, a lung directed gene therapy has yet to be realized. There is hope that with improved delivery vectors, sufficient transduction of airway cells can achieve therapeutic levels of functional CFTR. In order to do this, preclinical programs need to meet a certain level of CFTR protein expression in vitro and in vivo through improved transduction, particularly in relevant airway cell types. Furthermore, clinical programs must be designed with sensitive methods to detect CFTR expression and function as well as methods to measure meaningful endpoints for lung structure, function and disease. Here, we discuss the current understanding of how much and where CFTR needs to be expressed, the most advanced vectors for CFTR delivery and clinical considerations for detecting CFTR protein and function in different patient subsets.

Evaluation of the Effectiveness of Using the CFTR Modulator Ivacaftor/Lumacaftor in Children with Cystic Fibrosis in the Sverdlovsk Region (Prospective Cohort Study)

Background. A modern achievement in the treatment of cystic fibrosis has been the discovery of small molecules that restore the processes of synthesis, transport to the membrane, and the work of the defective CFTR protein. Drugs whose action is aimed at restoring the function of the CFTR protein are called CFTR modulators. The aim of the study is the conduction of a comprehensive assessment of the effectiveness of CFTR modulator ivacaftor/lumacaftor therapy in children with cystic fibrosis based on the study of clinical, laboratory, and instrumental data. Methods. CFTR modulator ivacaftor/lumacaftor was received for 12 months by 23 children of the main group aged 2–17 years, who are homozygous carriers of the F508del mutation of the CFTR gene in the absence of the L467F complex allele. A control examination of the main group was conducted at the start of the study and then every 3 months for 12 months of drug administration. Results. The condition of the patients in the observation groups at the start of the study was assessed as moderate to severe, the bronchopulmonary process was in the stage of incomplete clinical remission. In the main group, the level of aspartate aminotransferase significantly decreased, in the control, on the contrary, there was a tendency for this indicator to increase. The level of alkaline phosphatase (alkaline phosphatase) decreased and reached normal in the main group; the relative risk of hyperphosphatasemia during treatment decreased by 5 times (0.187 (0.063–0.557)). The level of gamma-glutamyltranspeptidase (gamma-GTP) and the number of patients with elevated GGTP decreased (24.65 and 19.69 IU/l, respectively; 61 and 13%). In the control group, the level of gamma-GTP increased and the alkaline phosphatase did not normalize. The indicators of forced exhalation volume in the first second and forced vital capacity of the lungs were initially lower in the main group, after 12 months the differences remained. There was a tendency to decrease the frequency of severe pancreatic insufficiency in the main group by 17.3%, and no changes in the control group. Sweat chlorides tended to decrease in the main group in the absence of reaching the standard values. Conclusion. The usage of the CFTR modulator ivacaftor/lumacaftor showed a greater clinical effect in improving the functioning of the digestive organs: a decrease in the risk of hyperphosphatasemia and a significant decrease in the number of patients with high levels of gamma-GTP were established, a stable level of liver enzyme activity was noted, and a tendency to increase the activity of pancreatic elastase was revealed. The tendency to decrease the indicators of sweat chlorides is shown. There were no changes in the indicators of respiratory function.

Defective CFTR modulates mechanosensitive channels TRPV4 and PIEZO1 and drives endothelial barrier failure

Cystic fibrosis (CF) is a genetic disease caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Despite reports of CFTR expression on endothelial cells, pulmonary vascular perturbations, and perfusion deficits in CF patients, the mechanism of pulmonary vascular disease in CF remains unclear. Here, our pilot study of 40 CF patients reveals a loss of small pulmonary blood vessels in patients with severe lung disease. Using a vessel-on-a-chip model, we establish a shear-stress-dependent mechanism of endothelial barrier failure in CF involving TRPV4, a mechanosensitive channel. Furthermore, we demonstrate that CFTR deficiency downregulates the function of PIEZO1, another mechanosensitive channel involved in angiogenesis and wound repair, and exacerbates loss of small pulmonary blood vessel. We also show that CFTR directly interacts with PIEZO1 and enhances its function. Our study identifies key cellular targets to mitigate loss of small pulmonary blood vessels in CF.

Evaluation of elexacaftor–tezacaftor–ivacaftor treatment in individuals with cystic fibrosis and CFTRN1303K in the USA: a prospective, multicentre, open-label, single-arm trial

CFTR modulators are approved for approximately 90% of people with cystic fibrosis in the USA and provide substantial clinical benefit. N1303K (Asn1303Lys), one of the most common class 2 CFTR defects, has not been approved for these therapies by any regulatory agency. Preclinical investigation by our laboratories showed N1303K CFTR activation with elexacaftor-tezacaftor-ivacaftor (ETI). In this trial, we evaluate whether ETI improves CFTR function, measured by sweat chloride and other clinical outcomes, in people with cystic fibrosis and CFTRN1303K. In this prospective, open-label, single-arm trial, participants aged 12 years or older with cystic fibrosis encoding at least one N1303K variant and at least one CFTRN1303K allele who were ineligible for modulator therapy by US Food and Drug Administration labelling were given ETI for 28 days followed by a 28-day washout period at two cystic fibrosis centres in the USA. Participants received two orally administered pills of 100 mg elexacaftor, 50 mg tezacaftor, and 75 mg ivacaftor once daily in the morning, and 150 mg ivacaftor once daily in the evening. The primary endpoint was mean change in sweat chloride from baseline up to day 28 compared with mixed-effects models. Secondary endpoints were changes in percentage of predicted FEV1 (ppFEV1), Cystic Fibrosis Questionnaire-Revised (CFQ-R) respiratory domain, BMI, and weight after ETI therapy. Safety was assessed in all participants who received at least one dose of the study drug and primary and secondary analyses were performed in all participants who took the study drug per protocol. The trial was registered at ClinicalTrials.gov (NCT03506061) and remains open for reporting purposes. Between June 7, 2022, and Oct 20, 2023, 20 participants (ten male and ten female) were enrolled and received ETI treatment. One participant was lost to follow-up but was included in intention-to-treat analyses. At 28 days, the mean sweat chloride reduction was -1·1 mmol/L (95% CI -5·3 to 3·1; p=0·61) with only one participant showing a sweat chloride decrease greater than 15 mmol/L. There was a mean increase in ppFEV1 from baseline at day 28 of 9·5 percentage points (6·7-12·3; p<0·0001) with 15 (75%) participants showing at least a 5% increase in ppFEV1. Improvements were also identified in mean CFQ-R respiratory domain score (20·8 increase [95% CI 11·9-29·8]; p<0·0001), BMI (0·4 kg/m2 increase [0·2-0·7]; p=0·0017), and weight (1·0 kg increase [0·4-1·7]; p=0·0020) after 28 days of ETI treatment. 14 (70%) of 20 participants had adverse events (12 [60%] mild, one [5%] moderate), with one (5%) serious adverse event of hospitalisation attributed to pneumonia. No deaths were recorded in the study. Individuals with CFTRN1303K showed no change in sweat chloride after 28 days of treatment with ETI. However, there were improvements in secondary clinical endpoints, which suggest clinical efficacy. Our approach provides support for the use of in vitro model systems to inform clinical trials for rare CFTR variants. The Cystic Fibrosis Foundation and the US National Institutes of Health.

An ex vivo rat trachea model reveals abnormal airway physiology and a gland secretion defect in cystic fibrosis.

Cystic fibrosis (CF) is a genetic disease hallmarked by aberrant ion transport that results in delayed mucus clearance, chronic infection, and progressive lung function decline. Several animal models have been developed to study the airway anatomy and mucus physiology in CF, but they are costly and difficult to maintain, making them less accessible for many applications. A more available CFTR-/- rat model has been developed and characterized to develop CF airway abnormalities, but consistent dosing of pharmacologic agents and longitudinal evaluation remain a challenge. In this study, we report the development and characterization of a novel ex vivo trachea model that utilizes both wild type (WT) and CFTR-/- rat tracheae cultured on a porcine gelatin matrix. Here we show that the ex vivo tracheae remain viable for weeks, maintain a CF disease phenotype that can be readily quantified, and respond to stimulation of mucus and fluid secretion by cholinergic stimulation. Furthermore, we show that ex vivo tracheae may be used for well-controlled pharmacological treatments, which are difficult to perform on freshly excised trachea or in vivo models with this degree of scrutiny. With improved interrogation possible with a durable trachea, we also established firm evidence of a gland secretion defect in CFTR-/- rat tracheae compared to WT controls. Finally, we demonstrate that the ex vivo tracheae can be used to generate high mucus protein yields for subsequent studies, which are currently limited by in vivo mucus collection techniques. Overall, this study suggests that the ex vivo trachea model is an effective, easy to set up culture model to study airway and mucus physiology.

The revolution of personalized pharmacotherapies for cystic fibrosis: what does the future hold?

ABSTRACT Introduction Cystic fibrosis (CF), a potentially fatal genetic disease, is caused by loss-of-function mutations in the gene encoding for the CFTR chloride/bicarbonate channel. Modulator drugs rescuing mutant CFTR traffic and function are now in the clinic, providing unprecedented breakthrough therapies for people with CF (PwCF) carrying specific genotypes. However, several CFTR variants are unresponsive to these therapies. Area covered We discussed several therapeutic approaches that are under development to tackle the fundamental cause of CF, including strategies targeting defective CFTR mRNA and/or protein expression and function. Alternatively, defective chloride secretion and dehydration in CF epithelia could be restored by exploiting pharmacological modulation of alternative targets, i.e., ion channels/transporters that concur with CFTR to maintain the airway surface liquid homeostasis (e.g., ENaC, TMEM16A, SLC26A4, SLC26A9, and ATP12A). Finally, we assessed progress and challenges in the development of gene-based therapies to replace or correct the mutant CFTR gene. Expert opinion CFTR modulators are benefiting many PwCF responsive to these drugs, yielding substantial improvements in various clinical outcomes. Meanwhile, the CF therapy development pipeline continues to expand with the development of novel CFTR modulators and alternative therapeutic strategies with the ultimate goal of providing effective therapies for all PwCF in the foreseeable future.

WS17.03 An alternative mutation agnostic therapy for cystic fibrosis with oligonucleotide antisense

Objectives: CFTR modulators have significantly changed the course of the disease in patients carrying drug-sensitive mutations. Unfortunately, those drugs cannot treat people with CF-carrying CFTR nonsense mutations. Hence, there is a growing interest in finding alternative strategies to treat all CF patients regardless of their mutations. An exciting alternative is to develop “mutation-agnostic” therapies by activating other anion channels. TMEM16A is one of the most promising alternative channels that could compensate for defective CFTR. However, previous studies demonstrated that miRNA-9 downregulates TMEM16A expression by binding to its 3′ UTR mRNA. To restore TMEM16A expression, our team has developed an oligonucleotide antisense (TMEM16A ASO) that binds to the TMEM16A 3’ UTR and prevents miRNA-9 binding, therefore, re-establishing TMEM16A expression and activity. Here we determine the effectiveness of the TMEM16A ASO on CF-dysregulated parameters and evaluate its toxicity and specificity.

WS02.01 Decreased fertility in female cystic fibrosis patients: peering into the endometrial factor using cutting-edge organoid models

Female CF patients suffer from sub-to infertility, often facing problems to become pregnant. Underlying reasons remain understudied. In particular, it is largely unknown whether dysfunction of the endometrium is involved, the womb’s inner lining and key tissue for embryo implantation and development. This gap is mainly due to lack of appropriate study models. Therefore, we develop and apply tissue-mimicking organoid models to indetail decipher molecular and functional aberrations in fertility-deficient CF endometrium as compared to healthy (fertile) endometrium. First, we established endometrial organoids (EMO) from the Cftrtm1Eur mouse model. These organoids show a smaller lumen than wildtype (WT) EMO, and do not swell in the FIS assay, both validating the CFTR defect. Currently, we are comparing expression of endometrial functionality/fertility markers in CF versus WT EMO, as well as their responsiveness to estrogen (E2) and progesterone (P4), which in vivo regulate the estrous cycle. Second, we develop(ed) organoids from CF patient endometrium. Before, we have shown that EMO from healthy endometrium can reliably reproduce all menstrual cycle phases under defined E2/P4 exposure. Currently, we are deciphering whether and how menstrual cycle phases, including the receptivity stage, are different between CF and healthy EMO. We already observed dissimilarities in the proliferative (E2) and secretory (P4) phase, such as increased apoptosis and decreased fertility marker expression, respectively. Taken together, we establish(ed) organoid models from CF endometrium as novel and powerful tools to gain insight into the endometrial factor in CF fertility deficiency. Importantly, the organoids will be highly apt to explore the impact of new-era CFTR modulators on the endometrium, at present unknown. Moreover, our study has the potential to reveal paths toward restoring reproductive fitness in CF patients, which can be tested using the organoids as (drug) screening platform.

WS14.03 Combined therapeutic strategies for the restoration of airway epithelial integrity and function in cystic fibrosis

Background: In CF airways, dysfunctional Cl– secretion and mucociliary clearance favor bacterial infections contributing to progressive lung damage and respiratory failure, the first cause of morbidity and mortality. We thus devote our efforts to identify novel therapeutic strategies to promote CF lung repair. We previously discovered that the capability of CF airway epithelia to repair is less efficient, than in healthy controls, due to the CFTR defect and bacterial infections, in particular with P. aeruginosa (PA) and S. aureus (SA). Our work also unveiled that CFTR modulators enhance airway repair, but both CFTR rescue and repair improvement are dampened by infection.

Classic Cystic Fibrosis Presentation in Two Middle Eastern Siblings with a rare CFTR mutation (c.80G>T).

c.80G>T is a very rare CFTR missense mutation which has not been known to be a disease-causing alteration.The mutation causes an amino acid switch from glycine to valine at position 27 in exon 2, resulting in the production of defective CFTR protein.In the homozygous state, c.80G>T seems to be associated with the classic CF phenotype.

CFTR-beyond the airways: Recent findings on the role of the CFTR channel in the pancreas, the intestine and the kidneys

With increased longevity of patients suffering from cystic fibrosis, and widespread lung transplantation facilities, the sequelae of defective CFTR in other organs than the airways come to the fore. This minireview highlights recent scientific progress in the understanding of CFTR function in the pancreas, the intestine and the kidney, and explores potential therapeutic strategies to combat defective CFTR function in these organs.

Bicarbonate defective CFTR variants increase risk for chronic pancreatitis: A meta-analysis.

IntroductionCystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in pancreatic ductal fluid secretion by mediating Cl- and HCO3- ion transport across the apical membrane. Severe CFTR mutations that diminish chloride conductance cause cystic fibrosis (CF) if both alleles are affected, whereas heterozygous carrier status increases risk for chronic pancreatitis (CP). It has been proposed that a subset of CFTR variants characterized by a selective bicarbonate conductance defect (CFTRBD) may be associated with CP but not CF. However, a rigorous genetic analysis of the presumed association has been lacking.AimsTo investigate the role of heterozygous CFTRBD variants in CP by meta-analysis of published case-control studies.Materials and methodsA systematic search was conducted in the MEDLINE, Embase, Scopus, and CENTRAL databases for published studies that reported the CFTRBD variants p.R74Q, p.R75Q, p.R117H, p.R170H, p.L967S, p.L997F, p.D1152H, p.S1235R, and p.D1270N in CP patients and controls.ResultsTwenty-two studies were eligible for quantitative synthesis. Combined analysis of the 9 CFTRBD variants indicated enrichment in CP patients versus controls (OR = 2.31, 95% CI = 1.17–4.56). Individual analysis of CFTRBD variants revealed no association of p.R75Q with CP (OR = 1.12, 95% CI = 0.89–1.40), whereas variants p.R117H and p.L967S were significantly overrepresented in cases relative to controls (OR = 3.16, 95% CI = 1.94–5.14, and OR = 3.88, 95% CI = 1.32–11.47, respectively). The remaining 6 low-frequency variants gave inconclusive results when analyzed individually, however, their pooled analysis indicated association with CP (OR = 2.08, 95% CI = 1.38–3.13).ConclusionHeterozygous CFTRBD variants, with the exception of p.R75Q, increase CP risk about 2-4-fold.

Impaired regulation of PMCA activity by defective CFTR expression promotes epithelial cell damage in alcoholic pancreatitis and hepatitis.

Alcoholic pancreatitis and hepatitis are frequent, potentially lethal diseases with limited treatment options. Our previous study reported that the expression of CFTR Cl- channel is impaired by ethanol in pancreatic ductal cells leading to more severe alcohol-induced pancreatitis. In addition to determining epithelial ion secretion, CFTR has multiple interactions with other proteins, which may influence intracellular Ca2+ signaling. Thus, we aimed to investigate the impact of ethanol-mediated CFTR damage on intracellular Ca2+ homeostasis in pancreatic ductal epithelial cells and cholangiocytes. Human and mouse pancreas and liver samples and organoids were used to study ion secretion, intracellular signaling, protein expression and interaction. The effect of PMCA4 inhibition was analyzed in a mouse model of alcohol-induced pancreatitis. The decreased CFTR expression impaired PMCA function and resulted in sustained intracellular Ca2+ elevation in ethanol-treated and mouse and human pancreatic organoids. Liver samples derived from alcoholic hepatitis patients and ethanol-treated mouse liver organoids showed decreased CFTR expression and function, and impaired PMCA4 activity. PMCA4 co-localizes and physically interacts with CFTR on the apical membrane of polarized epithelial cells, where CFTR-dependent calmodulin recruitment determines PMCA4 activity. The sustained intracellular Ca2+ elevation in the absence of CFTR inhibited mitochondrial function and was accompanied with increased apoptosis in pancreatic epithelial cells and PMCA4 inhibition increased the severity of alcohol-induced AP in mice. Our results suggest that improving Ca2+ extrusion in epithelial cells may be a potential novel therapeutic approach to protect the exocrine pancreatic function in alcoholic pancreatitis and prevent the development of cholestasis in alcoholic hepatitis.

The use of targeted therapy lumacaftor/ivacaftor in patients with cystic fibrosis

Accepted, basic therapy of cystic fibrosis (CF), until recently, was symptomatic and aimed at slowing down pathological processes, mainly from the respiratory system and gastrointestinal tract, caused by a defect in the CFTR gene. New strategic opportunities have emerged since 2012 and are aimed at correcting a defect in a gene or its product. A mutation in the cystic fibrosis gene disrupts the function of the cystic fibrosis transmembrane conductance regulator protein (CFTR or CFTR in English transcription), which is located on the surface of the apical membrane of epithelial cells and functions as a chloride channel. The basic achievement for the new CF therapy was the discovery of small molecules that restore the processes of synthesis, transport to the membrane, or the functioning of the defective CFTR protein. The effectiveness of drugs that restore CFTR function is related to the ability of the molecules to deliver an adequate amount of the CFTR protein to the surface of the epithelial cell and/or improve its functional activity. Among them, correctors and potentiators for pharmacological modulation of ion transport are distinguished in clinical practice. Correctors are medicinal substances that allow the mutant CFTR protein to pass through the system of intracellular quality control and take the correct location on the apical membrane (with class II mutations). The action of potentiators is aimed at restoring (activating) the function of the ion channel formed by the mutant CFTR protein (class III–IV mutations). The purpose of this article is to analyze the literature sources, the results of clinical trials on the use of CFTR modulators, including combinations of a potentiator and a corrector. Their effectiveness and safety were evaluated. Literature sources (20) are used and own clinical observation is given. A positive assessment of the action of the modulator, the combination of a potentiator and a corrector, its safety and good tolerability is given. In conclusion, the place and indications for prescribing drugs of this class, the number of patients in the Russian Federation in need of such treatment are determined.

Impaired Regulatory Volume Decrease and Characterization of Underlying Volume-Activated Currents in Cystic Fibrosis Human Cholangiocyte Cell Line.

The volume-activated chloride channel (VACC) serves vital cellular functions in secretion and cell volume regulation via regulatory volume decrease (RVD) in various epithelia. Previously, we have shown that RVD in primary CF mouse cholangiocytes is impaired. Thus, the effect of CFTR defect on VACC and RVD in CF human immortalized cholangiocyte cell (HBDC) was examined in comparison with those in normal HBDC by using cell volume measurement and whole-cell patch clamp techniques, respectively. The CF HBDC had an impaired RVD, which was not further inhibited by removing the extracellular calcium or administering BAPTA-AM, NPPB, or DIDS. When exposed to a hypotonic solution, CF HBDC exhibited large, outwardly rectified currents with time-dependent inactivation at a positive potential. The amplitude of the outward currents was about three times that of the inward currents. The amplitude and reversal potential of VACC was dependent on chloride concentration. The VACC was significantly inhibited by replacing chloride with gluconate, glutamate, sucrose, or acetate in the hypotonic solution as well as by an administration of NPPB or tamoxifen, classical VACC inhibitors. Surprisingly, the VACC amplitude is greater in CF HBDC than in normal HBDC, suggesting that the channel density or open probability of VACC is increased, thus CFTR may have inhibitory effects on VACC. On the contrary, the amplitude of the volume-activated potassium current is lower in CF HBDC, suggesting the potassium channel density or open probability is decreased in CF cholangiocytes and/or CFTR may have regulatory effects on volume-activated potassium current. In conclusion, RVD is impaired in CF human cholangiocytes. The VACC of CF human cholangiocytes has similar electrophysiological characteristics as that of normal cholangiocytes but its activity is augmented in CF cholangiocytes, while volume-activated potassium current is decreased in CF human cholangiocytes, providing a fundamental underlying pathophysiologic mechanism for the impaired RVD in CF cholangiocytes.

Impact of Airway Inflammation on the Efficacy of CFTR Modulators.

Defective CFTR biogenesis and activity in cystic fibrosis airways leads to airway dehydration and impaired mucociliary clearance, resulting in chronic airway infection and inflammation. Most cystic fibrosis patients have at least one copy of the F508del CFTR mutation, which results in a protein retained in the endoplasmic reticulum and degraded by the proteosomal pathway. CFTR modulators, e.g., correctors, promote the transfer of F508del to the apical membrane, while potentiators increase CFTR activity. Corrector and potentiator double therapies modestly improve lung function, whereas triple therapies with two correctors and one potentiator indicate improved outcomes. Enhanced F508del rescue by CFTR modulators is achieved by exposing F508del/F508del primary cultures of human bronchial epithelia to relevant inflammatory stimuli, i.e., supernatant from mucopurulent material or bronchoalveolar lavage fluid from human cystic fibrosis airways. Inflammation enhances the biochemical and functional rescue of F508del by double or triple CFTR modulator therapy and overcomes abrogation of CFTR correction by chronic VX-770 treatment in vitro. Furthermore, the impact of inflammation on clinical outcomes linked to CFTR rescue has been recently suggested. This review discusses these data and possible mechanisms for airway inflammation-enhanced F508del rescue. Expanding the understanding of how airway inflammation improves CFTR rescue may benefit cystic fibrosis patients.

The Impact of Highly Effective CFTR Modulators on Growth and Nutrition Status.

Patients with cystic fibrosis (CF) are at increased risk of malnutrition and growth failure due to multiple factors as a result of suboptimal or absent function of the CFTR chloride channel protein. Dysfunctional CFTR contributes to increased energy expenditure, exocrine pancreatic insufficiency causing impaired dietary macronutrient digestion and absorption, intestinal dysbiosis, and impaired bile acid homeostasis. Poor nutritional status as a result of these mechanisms is associated with decreased lung function, worse clinical outcomes, and ultimately, increased mortality. Nutritional interventions addressing these mechanisms, such as pancreatic enzyme-replacement therapy and enteral caloric supplementation, have improved nutritional status and, by association, clinical outcomes. In the last decade, the advent of medications targeting defective CFTR proteins has revolutionized the care of patients with CF by reducing the overall impact of CFTR dysfunction. Below, we summarize the effects of highly effective CFTR modulators on nutritional status overall as well as specific factors including bile acid metabolism, pancreatic function, energy expenditure, and intestinal dysbiosis. The future of CF nutrition care will require a paradigm shift away from focusing on methods addressing CFTR dysfunction such as excess calorie provision and toward an individualized, holistic approach in the context of specific mutations and CFTR-directed therapy.

Bicarbonate defective CFTR variants in chronic pancreatitis: A meta-analysis

Bicarbonate defective CFTR variants in chronic pancreatitis: A meta-analysis

Functional CFTR channel is essential for effective antimicrobial activities of neutrophils

Abstract Patients with Cystic Fibrosis (CF) are highly susceptible to infections caused by opportunistic pathogens including Burkholderia cenocepacia. In response to infection, CF neutrophils are deficient in clearing bacteria and release inflammatory molecules that contributes to aggravated lung-tissue damage in people with CF (PWCF). Although CF has no cure, novel therapeutic drugs have emerged targeting defective CFTR channel (CFTR modulators). However, it is unknown whether CFTR modulators may restore the basic antimicrobial functions of phagocytes in PWCF. Here, we first evaluated the expression and subcellular localization of CFTR. Neutrophils from PWCF and non-CF donors were treated in vitro with CF modulators, before infection with B. cenocepacia, and then, CFTR cellular localization was evaluated by confocal microscopy followed by the analysis of antimicrobial killing, and the production of Neutrophil Extracellular Traps (NETs). Furthermore, CFTR-mediated currents were measured by patch-clamp in non-CF and CF neutrophils after treatment with the CFTR modulators. We found that CFTR modulators increased the expression of functional CFTR channel at the plasma membrane, and also potentiated CFTR-mediated channel activity in CF and non-CF neutrophils, as recorded by whole-cell patch clamp. The production of NETs was also increased in both CF and non-CF neutrophils treated with CFTR modulators, those changes were comparable to cells stimulated with B. cenocepacia or PMA. Finally, CF neutrophils treated with the CFTR modulators restored their antimicrobial killing against B. cenocepacia. Together, these data indicate that functional CFTR channel is essential for regulating the antimicrobial mechanisms of neutrophils.

Update on Calcium Signaling in Cystic Fibrosis Lung Disease

Cystic fibrosis (CF) is an autosomal recessive disorder characterized by mutations in the cystic fibrosis transmembrane conductance regulator gene, which causes multifunctional defects that preferentially affect the airways. Abnormal viscosity of mucus secretions, persistent pathogen infections, hyperinflammation, and lung tissue damage compose the classical pathological manifestation referred to as CF lung disease. Among the multifunctional defects associated with defective CFTR, increasing evidence supports the relevant role of perturbed calcium (Ca2+) signaling in the pathophysiology of CF lung disease. The Ca2+ ion is a critical player in cell functioning and survival. Its intracellular homeostasis is maintained by a fine balance between channels, transporters, and exchangers, mediating the influx and efflux of the ion across the plasma membrane and the intracellular organelles. An abnormal Ca2+ profile has been observed in CF cells, including airway epithelial and immune cells, with heavy repercussions on cell function, viability, and susceptibility to pathogens, contributing to proinflammatory overstimulation, organelle dysfunction, oxidative stress, and excessive cytokines release in CF lung. This review discusses the role of Ca2+ signaling in CF and how its dysregulation in airway epithelial and immune cells contributes to hyperinflammation in the CF lung. Finally, we provide an outlook on the therapeutic options that target the Ca2+ signaling to treat the CF lung disease.