Activation of the cystic fibrosis transmembrane conductance regulator by the flavonoid quercetin: potential use as a biomarker of ΔF508 cystic fibrosis transmembrane conductance regulator rescue

Fractional Exhalation Nitric Oxide (FeNO) changes in cystic fibrosis patients induced by compound honey syrup: a pretest-posttest clinical trial

OBJECTIVE

To evaluate the effect of Persian medicine Syrup 'compound honey syrup (CHS)' on fractional exhalation nitric oxide (FENO) changes in patients with cystic fibrosis (CF).

STUDY DESIGN

We conducted a before-after clinical trial on 70 CF patients. All patients received classical treatments for CF along with CHS (including honey, Ginger, cinnamon, saffron, cardamom and galangal), 5-10 cc (depending on the age and weight of patients) in 100 cc of warm boiled water twice a day, 30 min after meals. In this clinical trial, before and 12 weeks after the start of the CHS, FeNO test was evaluated.

RESULTS

From 70 patients were enrolled, 44 patients completed this 12-week course of treatment. At the end of the study, changes in FeNO was significantly different before and after treatment (P-value < 0.05). At the end of the study, no dangerous side effects of CHS was reported.

CONCLUSIONS

This study revealed that CHS can be effective as a complementary and safe drug in the medication of CF patients.

Therapeutic potential of phytochemicals for cystic fibrosis

The aim of this review was to review and discuss various phytochemicals that exhibit beneficial effects on mutated membrane channels, and hence, improve transmembrane conductance. These therapeutic phytochemicals may have the potential to decrease mortality and morbidity of CF patients. Four databases were searched using keywords. Relevant studies were identified, and related articles were separated. Google Scholar, as well as gray literature (i.e., information that is not produced by commercial publishers), were also checked for related articles to locate/identify additional studies. The relevant databases were searched a second time to ensure that recent studies were included. In conclusion, while curcumin, genistein, and resveratrol have demonstrated effectiveness in this regard, it should be emphasized that coumarins, quercetin, and other herbal medicines also have beneficial effects on transporter function, transmembrane conductivity, and overall channel activity. Additional in vitro and in vivo studies should be conducted on mutant CFTR to unequivocally define the mechanism by which phytochemicals alter transmembrane channel function/activity, since the results of the studies evaluated in this review have a high degree of heterogenicity and discrepancy. Finally, continued research be undertaken to clearly define the mechanism(s) of action and the therapeutic effects that therapeutic phytochemicals have on the symptoms observed in CF patients in an effort to reduce mortality and morbidity.

Advances in Cystic Fibrosis Research in Qatar: A Commentary

Cystic fibrosis is a genetic disorder caused by a Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene defect. Many across the globe suffer the debilitating symptoms. The aim of this commentary is to briefly cover various aspects related to the disease in the Arab world and then in Qatar.

Complementary Dual Approach for In Silico Target Identification of Potential Pharmaceutical Compounds in Cystic Fibrosis

Cystic fibrosis is a genetic disease caused by mutation of the CFTR gene, which encodes a chloride and bicarbonate transporter in epithelial cells. Due to the vast range of geno- and phenotypes, it is difficult to find causative treatments; however, small-molecule therapeutics have been clinically approved in the last decade. Still, the search for novel therapeutics is ongoing, and thousands of compounds are being tested in different assays, often leaving their mechanism of action unknown. Here, we bring together a CFTR-specific compound database (CandActCFTR) and systems biology model (CFTR Lifecycle Map) to identify the targets of the most promising compounds. We use a dual inverse screening approach, where we employ target- and ligand-based methods to suggest targets of 309 active compounds in the database amongst 90 protein targets from the systems biology model. Overall, we identified 1038 potential target–compound pairings and were able to suggest targets for all 309 active compounds in the database.

Virtual Drug Repositioning as a Tool to Identify Natural Small Molecules That Synergize with Lumacaftor in F508del-CFTR Binding and Rescuing

Cystic fibrosis is a hereditary disease mainly caused by the deletion of the Phe 508 (F508del) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein that is thus withheld in the endoplasmic reticulum and rapidly degraded by the ubiquitin/proteasome system. Cystic fibrosis remains a potentially fatal disease, but it has become treatable as a chronic condition due to some CFTR-rescuing drugs that, when used in combination, increase in their therapeutic effect due to a synergic action. Also, dietary supplementation of natural compounds in combination with approved drugs could represent a promising strategy to further alleviate cystic fibrosis symptoms. On these bases, we screened by in silico drug repositioning 846 small synthetic or natural compounds from the AIFA database to evaluate their capacity to interact with the highly druggable lumacaftor binding site of F508del-CFTR. Among the identified hits, nicotinamide (NAM) was predicted to accommodate into the lumacaftor binding region of F508del-CFTR without competing against the drug but rather stabilizing its binding. The effective capacity of NAM to bind F508del-CFTR in a lumacaftor-uncompetitive manner was then validated experimentally by surface plasmon resonance analysis. Finally, the capacity of NAM to synergize with lumacaftor increasing its CFTR-rescuing activity was demonstrated in cell-based assays. This study suggests the possible identification of natural small molecules devoid of side effects and endowed with the capacity to synergize with drugs currently employed for the treatment of cystic fibrosis, which hopefully will increase the therapeutic efficacy with lower doses.

Development and Characterization of a Spray-Dried Inhalable Ciprofloxacin-Quercetin Co-Amorphous System

Spray drying is an increasingly used particle engineering technique for the production of dry powders for inhalation. However, the amorphous nature of most spray-dried particles remains a big challenge affecting both the chemical and the physical stability of the dried particles. Here, we study the possibility of producing co-amorphous ciprofloxacin-quercetin inhalable particles with improved amorphous stability compared to the individual amorphous drugs. Ciprofloxacin (CIP), a broad-spectrum antibiotic, was co-spray dried with quercetin (QUE), a compound with antibiofilm properties, from an ethanol-water co-solvent system at 2:1, 1:1 and 1:2 molar ratios to investigate the formation of co-amorphous CIP-QUE particles. Differential scanning colorimetry (DSC) and X-ray powder diffraction (XRPD) were used for solid-state characterization; dynamic vapor sorption (DVS) was used for investigating the moisture sorption behaviour. The intermolecular interaction was studied via solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy; the miscibility of the drugs was predicted via free energy calculations based on the Flory-Huggins interaction parameter (χ). A next generation impactor (NGI) was used to study the in vitro aerosol performance of the spray-dried powders. The physicochemical characteristics such as particle size, density, morphology, cohesion, water content and saturation solubility of the spray-dried powders were also studied. The co-spray-dried CIP-QUE powders prepared at the three molar ratios were predominantly amorphous. However, differences were observed between sample types. It was found that at a molar ratio of 1:1, CIP and QUE form a single co-amorphous system. However, increasing the molar ratio of either drug results in the formation of an additional amorphous phase, formed from the excess of the corresponding drug. Despite these differences, DVS showed that elevated humidity had a much lower influence on all three co-amorphous systems compared with the individual amorphous drugs. In vitro aerosolization study showed co-deposition of the two drugs from CIP-QUE powders with a desirable aerosol performance (ED ∼ 72% - 94%; FPF ∼ 48% - 65%) whereas QUE-only amorphous powder had an ED of 36% and a FPF of 22%. In summary, spray-dried CIP-QUE combinations resulted in co-amorphous systems with boosted stability and improved aerosol performance with the 1:1 molar ratio exhibiting the greatest improvement.

TMEM16A/ANO1: Current Strategies and Novel Drug Approaches for Cystic Fibrosis

Cystic fibrosis (CF) is the most common of rare hereditary diseases in Caucasians, and it is estimated to affect 75,000 patients globally. CF is a complex disease due to the multiplicity of mutations found in the CF transmembrane conductance regulator (CFTR) gene causing the CFTR protein to become dysfunctional. Correctors and potentiators have demonstrated good clinical outcomes for patients with specific gene mutations; however, there are still patients for whom those treatments are not suitable and require alternative CFTR-independent strategies. Although CFTR is the main chloride channel in the lungs, others could, e.g., anoctamin-1 (ANO1 or TMEM16A), compensate for the deficiency of CFTR. This review summarizes the current knowledge on calcium-activated chloride channel (CaCC) ANO1 and presents ANO1 as an exciting target in CF.

In silico drug repositioning on F508del-CFTR: A proof-of-concept study on the AIFA library

Computational drug repositioning is of growing interest to academia and industry, for its ability to rapidly screen a huge number of candidates in silico (exploiting comprehensive drug datasets) together with reduced development cost and time. The potential of drug repositioning has not been fully evaluated yet for cystic fibrosis (CF), a disease mainly caused by deletion of Phe 508 (F508del) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. F508del-CFTR is thus withheld in the endoplasmic reticulum and rapidly degraded by the ubiquitin/proteasome system. CF is still a fatal disease. Nowadays, it is treatable by some CFTR-rescuing drugs, but new-generation drugs with stronger therapeutic benefits and fewer side effects are still awaited. In this manuscript we report about the results of a pilot computational drug repositioning screening in search of F508del-CFTR-targeted drugs performed on AIFA library by means of a dedicated computational pipeline and surface plasmon resonance binding assay to experimentally validate the computational findings.

A Novel G542X CFTR Rat Model of Cystic Fibrosis Is Sensitive to Nonsense Mediated Decay

Nonsense mutations that lead to the insertion of a premature termination codon (PTC) in the cystic fibrosis transmembrane conductance regulator (CFTR) transcript affect 11% of patients with cystic fibrosis (CF) worldwide and are associated with severe disease phenotype. While CF rat models have contributed significantly to our understanding of CF disease pathogenesis, there are currently no rat models available for studying CF nonsense mutations. Here we created and characterized the first homozygous CF rat model that bears the CFTR G542X nonsense mutation in the endogenous locus using CRISPR/Cas9 gene editing. In addition to displaying severe CF manifestations and developmental defects such as reduced growth, abnormal tooth enamel, and intestinal obstruction, CFTR G542X knockin rats demonstrated an absence of CFTR function in tracheal and intestinal sections as assessed by nasal potential difference and transepithelial short-circuit current measurements. Reduced CFTR mRNA levels in the model further suggested sensitivity to nonsense-mediated decay, a pathway elicited by the presence of PTCs that degrades the PTC-bearing transcripts and thus further diminishes the level of CFTR protein. Although functional restoration of CFTR was observed in G542X rat tracheal epithelial cells in response to single readthrough agent therapy, therapeutic efficacy was not observed in G542X knockin rats in vivo. The G542X rat model provides an invaluable tool for the identification and in vivo validation of potential therapies for CFTR nonsense mutations.

Approaching two decades of cystic fibrosis research in Qatar: a historical perspective and future directions

Cystic fibrosis (CF) is a genetic disease caused by a defect of CF transmembrane conductance regulator (CFTR) gene. CF affects multiple systems, predominantly with respiratory involvement. In Qatar, researchers have been exploring various aspects of the disease for almost 20 years. PubMed and Google Scholar were reviewed for articles related to CF in Qatar. The first publication appeared in the year 2000. Since then, several studies have been conducted on CF patients in Qatar considering a variety of topics. The presence of the CFTR I1234V mutation in a certain Arab tribe stands out as a distinguishing characteristic of CF patients in Qatar when compared to the larger Arab region or even worldwide. We aim here to summarize the existing CF research conducted in Qatar over the years as well as to introduce topics for future research.

MicroRNA-145 Antagonism Reverses TGF-β Inhibition of F508del CFTR Correction in Airway Epithelia

RATIONALE

MicroRNAs (miRNAs) destabilize mRNA transcripts and inhibit protein translation. miR-145 is of particular interest in cystic fibrosis (CF) as it has a direct binding site in the 3'-untranslated region of CFTR (cystic fibrosis transmembrane conductance regulator) and is upregulated by the CF genetic modifier TGF (transforming growth factor)-β.

OBJECTIVES

To demonstrate that miR-145 mediates TGF-β inhibition of CFTR synthesis and function in airway epithelia.

METHODS

Primary human CF (F508del homozygous) and non-CF airway epithelial cells were grown to terminal differentiation at the air-liquid interface on permeable supports. TGF-β (5 ng/ml), a miR-145 mimic (20 nM), and a miR-145 antagonist (20 nM) were used to manipulate CFTR function. In CF cells, lumacaftor (3 μM) and ivacaftor (10 μM) corrected mutant F508del CFTR. Quantification of CFTR mRNA, protein, and function was done by standard techniques.

MEASUREMENTS AND MAIN RESULTS

miR-145 is increased fourfold in CF BAL fluid compared with non-CF (P < 0.01) and increased 10-fold in CF primary airway epithelial cells (P < 0.01). Exogenous TGF-β doubles miR-145 expression (P < 0.05), halves wild-type CFTR mRNA and protein levels (P < 0.01), and nullifies lumacaftor/ivacaftor F508del CFTR correction. miR-145 overexpression similarly decreases wild-type CFTR protein synthesis (P < 0.01) and function (P < 0.05), and eliminates F508del corrector benefit. miR-145 antagonism blocks TGF-β suppression of CFTR and enhances lumacaftor correction of F508del CFTR.

CONCLUSIONS

miR-145 mediates TGF-β inhibition of CFTR synthesis and function in airway epithelia. Specific antagonists to miR-145 interrupt TGF-β signaling to restore F508del CFTR modulation. miR-145 antagonism may offer a novel therapeutic opportunity to enhance therapeutic benefit of F508del CFTR correction in CF epithelia.

Role of Quercetin in Modulating Chloride Transport in the Intestine

Epithelial chloride channels provide the pathways for fluid secretion in the intestine. Cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride channels (CaCCs) are the main chloride channels in the luminal membrane of enterocytes. These transmembrane proteins play important roles in many physiological processes. In this study, we have identified a flavonoid quercetin as a modulator of CaCC chloride channel activity. Fluorescence quenching assay showed that quercetin activated Cl⁻ transport in a dose-dependent manner, with EC₅₀ ~37 μM. Short-circuit current analysis confirmed that quercetin activated CaCC-mediated Cl⁻ currents in HT-29 cells that can be abolished by CaCC_inh-A01. Ex vivo studies indicated that application of quercetin to mouse ileum and colon on serosal side resulted in activation of CFTR and CaCC-mediated Cl⁻ currents. Notably, we found that quercetin exhibited inhibitory effect against ANO1 chloride channel activity in ANO1-expressing FRT cells and decreased mouse intestinal motility. Quercetin-stimulated short-circuit currents in mouse ileum was multi-component, which included elevation of Ca²⁺ concentration through L-type calcium channel and activation of basolateral NKCC, Na⁺/K⁺-ATPase, and K⁺ channels. In vivo studies further revealed that quercetin promoted fluid secretion in mouse ileum. The modulatory effect of quercetin on CaCC chloirde channels may therefore represent a potential therapeutic strategy for treating CaCC-related diseases like constipation, secretory diarrhea and hypertension. The inverse effects of quercetin on CaCCs provided evidence that ANO1 and intestinal epithelial CaCCs are different calcium-activated chloride channels.

CFTR Modulators: Shedding Light on Precision Medicine for Cystic Fibrosis

Cystic fibrosis (CF) is the most common life-threatening monogenic disease afflicting Caucasian people. It affects the respiratory, gastrointestinal, glandular and reproductive systems. The major cause of morbidity and mortality in CF is the respiratory disorder caused by a vicious cycle of obstruction of the airways, inflammation and infection that leads to epithelial damage, tissue remodeling and end-stage lung disease. Over the past decades, life expectancy of CF patients has increased due to early diagnosis and improved treatments; however, these patients still present limited quality of life. Many attempts have been made to rescue CF transmembrane conductance regulator (CFTR) expression, function and stability, thereby overcoming the molecular basis of CF. Gene and protein variances caused by CFTR mutants lead to different CF phenotypes, which then require different treatments to quell the patients' debilitating symptoms. In order to seek better approaches to treat CF patients and maximize therapeutic effects, CFTR mutants have been stratified into six groups (although several of these mutations present pleiotropic defects). The research with CFTR modulators (read-through agents, correctors, potentiators, stabilizers and amplifiers) has achieved remarkable progress, and these drugs are translating into pharmaceuticals and personalized treatments for CF patients. This review summarizes the main molecular and clinical features of CF, emphasizes the latest clinical trials using CFTR modulators, sheds light on the molecular mechanisms underlying these new and emerging treatments, and discusses the major breakthroughs and challenges to treating all CF patients.

Chlorogenic Acid Activates CFTR-Mediated Cl- Secretion in Mice and Humans: Therapeutic Implications for Chronic Rhinosinusitis

OBJECTIVES

Salubrious effects of the green coffee bean are purportedly secondary to high concentrations of chlorogenic acid. Chlorogenic acid has a molecular structure similar to bioflavonoids that activate transepithelial Cl(-) transport in sinonasal epithelia. In contrast to flavonoids, the drug is freely soluble in water. The objective of this study is to evaluate the Cl(-) secretory capability of chlorogenic acid and its potential as a therapeutic activator of mucus clearance in sinus disease.

STUDY DESIGN

Basic research.

SETTING

Laboratory.

SUBJECTS AND METHODS

Chlorogenic acid was tested on primary murine nasal septal epithelial (MNSE) (CFTR(+/+) and transgenic CFTR(-/-)) and human sinonasal epithelial (HSNE) (CFTR(+/+) and F508del/F508del) cultures under pharmacologic conditions in Ussing chambers to evaluate effects on transepithelial Cl(-) transport. Cellular cyclic adenosine monophosphate (cAMP), phosphorylation of the CFTR regulatory domain (R-D), and CFTR mRNA transcription were also measured.

RESULTS

Chlorogenic acid stimulated transepithelial Cl(-) secretion (change in short-circuit current [ΔISC = µA/cm(2)]) in MNSE (13.1 ± 0.9 vs 0.1 ± 0.1; P < .05) and HSNE (34.3 ± 0.9 vs 0.0 ± 0.1; P < .05). The drug had a long duration until peak effect at 15 to 30 minutes after application. Significant inhibition with INH-172 as well as absent stimulation in cultures lacking functional CFTR suggest effects are dependent on CFTR-mediated pathways. However, the absence of elevated cellular cAMP and phosphorylation the CFTR R-D indicates chlorogenic acid does not work through a PKA-dependent mechanism.

CONCLUSION

Chlorogenic acid is a water-soluble agent that promotes CFTR-mediated Cl(-) transport in mouse and human sinonasal epithelium. Translating activators of mucociliary transport to clinical use provides a new therapeutic approach to sinus disease. Further in vivo evaluation is planned.

Resveratrol ameliorates abnormalities of fluid and electrolyte secretion in a hypoxia-Induced model of acquired CFTR deficiency

OBJECTIVE/HYPOTHESIS

Ineffective mucociliary clearance (MCC) is a common pathophysiologic process that underlies airway inflammation and infection. A dominant fluid and electrolyte secretory pathway in the nasal airways is governed by the cystic fibrosis transmembrane conductance regulator (CFTR). Decreased transepithelial Cl(-) transport secondary to an acquired CFTR deficiency may exacerbate respiratory epithelial dysfunction by diminishing MCC and increasing mucus viscosity. The objectives of the present study are to 1) develop a model of acquired CFTR deficiency in sinonasal epithelium using hypoxia, 2) investigate whether the polyphenol resveratrol promotes CFTR-mediated anion transport, 3) explore resveratrol mechanism of action and determine therapeutic suitability for overcoming acquired CFTR defects, and 4) test the drug in the hypoxic model of acquired CFTR deficiency in preparation for a clinical trial in human sinus disease. We hypothesize that hypoxia will induce depletion of airway surface liquid (ASL) secondary to acquired CFTR deficiency and that resveratrol will restore transepithelial Cl(-) secretion and recover ASL hydration.

STUDY DESIGN

Basic science.

METHODS

Murine nasal septal (MNSE) and human sinonasal epithelial (HSNE) cultures were incubated under hypoxic conditions (1% O2 , 5% CO2 ) and transepithelial ion transport (change in short-circuit current = ΔISC ) evaluated in Ussing chambers. Resveratrol was tested using primary cells and HEK293 cells expressing human CFTR by Ussing chamber and patch clamp techniques under both phosphorylating and nonphosphorylating conditions. CFTR activation was evaluated in human explants and by murine in vivo (nasal potential difference) assessment. Cellular cyclic adenosine monophosphate (cAMP) (ELISA) and subsequent CFTR regulatory domain (R-D) phosphorylation (gel-shift assay) were also evaluated. Effects of hypoxia and resveratrol on ASL were tested using confocal laser scanning microscopy (CLSM) and micro-optical coherence tomography (µOCT).

RESULTS

Hypoxia significantly decreased ΔISC (in µA/cm(2) ) attributable to CFTR at 12 and 24 hours of exposure in both MNSE (13.55 ± 0.46 [12 hours]; 12.75 ± 0.07 [24 hours] vs. 19.23 ± 0.18 [control]; P < 0.05) and HSNE (19.55 ± 0.56 [12 hours]; 17.67 ± 1.13 [24 hours] vs. 25.49 ± 1.48 [control]; P < 0.05). We have shown that resveratrol (100 μM) enhanced CFTR-dependent Cl(-) secretion in HSNE to an extent comparable to the recently Food and Drug Administration-approved CFTR potentiator, ivacaftor. Cl(-) transport across human sinonasal explants (78.42 ± 1.75 vs. 1.75 ± 1.5 [control]; P < 0.05) and in vivo murine nasal epithelium (-4 ± 1.8 vs. -0.8 ± 1.7 mV [control]; P < 0.05) were also significantly increased by the drug. No increase in cAMP or CFTR R-D phosphorylation was detected. Inside-out patches showed increased CFTR open probability (NPo/N (N = channel number]) compared to controls in both MNSE (0.329 ± 0.116 vs. 0.119 ± 0.059 [control]; P < 0.05) and HEK293 cells (0.22 ± 0.048 vs. 0.125 ± 0.07 [control]; P < 0.05). ASL thickness was decreased under hypoxic conditions when measured by CLSM (4.19 ± 0.44 vs. 6.88 ± 0.67 [control]; P < 0.05). A 30-minute apical application of resveratrol increased ASL depth in normal epithelium (8.08 ± 1.68 vs. 6.11 ± 0.47 [control]; P < 0.05). Furthermore, hypoxia-induced abnormalities of fluid and electrolyte secretion in sinonasal epithelium were restored with resveratrol treatment (5.55 ± 0.74 vs. 3.13 ± 0.17 [control]; P < 0.05).

CONCLUSIONS

CFTR activation with a leading edge Cl(-) secretagogue such as resveratrol represents an innovative approach to overcoming acquired CFTR defects in sinus and nasal airway disease. This exciting new strategy bears further testing in non-CF individuals with chronic rhinosinusitis.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 125:S1-S13, 2015.

Cystic fibrosis transmembrane conductance regulator is involved in polyphenol-induced swelling of the endothelial glycocalyx

Previous studies show that polyphenol-rich compounds can induce a swelling of the endothelial glycocalyx (eGC). Our goal was to reveal the mechanism behind the eGC-swelling. As polyphenols are potent modulators of fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, the hypothesis was tested whether polyphenol-induced increase in CFTR activity is responsible for the eGC-swelling. The impact of the polyphenols resveratrol, (-)-epicatechin, and quercetin on nanomechanics of living endothelial GM7373 cells was monitored by AFM-nanoindentation. The tested polyphenols lead to eGC-swelling with a simultaneous decrease in cortical stiffness. EGC-swelling, but not the change in cortical stiffness, was prevented by the inhibition of CFTR. Polyphenol-induced eGC-swelling could be mimicked by cytochalasin D, an actin-depolymerizing agent. Thus, in the vascular endothelium, polyphenols induce eGC-swelling by softening cortical actin and activating CFTR. Our findings imply that CFTR plays an important role in the maintenance of vascular homeostasis and may explain the vasoprotective properties of polyphenols.

FROM THE CLINICAL EDITOR

Many vascular problems clinically can be attributed to a dysregulation of endothelial glycocalyx (eGC). The underlying mechanism however remains unclear. In this article, the authors used nanoindentation and showed that polyphenols could swell the endothelial glycocalyx and alter its function. This investigative method can lead to further mechanistic studies of other molecular pathways.

Second-hand cigarette smoke impairs bacterial phagocytosis in macrophages by modulating CFTR dependent lipid-rafts

Introduction

First/Second-hand cigarette-smoke (FHS/SHS) exposure weakens immune defenses inducing chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are not fully understood. Hence, we evaluated if SHS induced changes in membrane/lipid-raft (m-/r)-CFTR (cystic fibrosis transmembrane conductance regulator) expression/activity is a potential mechanism for impaired bacterial phagocytosis in COPD.

Methods

RAW264.7 murine macrophages were exposed to freshly prepared CS-extract (CSE) containing culture media and/or Pseudomonas-aeruginosa-PA01-GFP for phagocytosis (fluorescence-microscopy), bacterial survival (colony-forming-units-CFU), and immunoblotting assays. The CFTR-expression/activity and lipid-rafts were modulated by transient-transfection or inhibitors/inducers. Next, mice were exposed to acute/sub-chronic-SHS or room-air (5-days/3-weeks) and infected with PA01-GFP, followed by quantification of bacterial survival by CFU-assay.

Results

We investigated the effect of CSE treatment on RAW264.7 cells infected by PA01-GFP and observed that CSE treatment significantly (p<0.01) inhibits PA01-GFP phagocytosis as compared to the controls. We also verified this in murine model, exposed to acute/sub-chronic-SHS and found significant (p<0.05, p<0.02) increase in bacterial survival in the SHS-exposed lungs as compared to the room-air controls. Next, we examined the effect of impaired CFTR ion-channel-activity on PA01-GFP infection of RAW264.7 cells using CFTR172-inhibitor and found no significant change in phagocytosis. We also similarly evaluated the effect of a CFTR corrector-potentiator compound, VRT-532, and observed no significant rescue of CSE impaired PA01-GFP phagocytosis although it significantly (p<0.05) decreases CSE induced bacterial survival. Moreover, induction of CFTR expression in macrophages significantly (p<0.03) improves CSE impaired PA01-GFP phagocytosis as compared to the control. Next, we verified the link between m-/r-CFTR expression and phagocytosis using methyl-β-cyclodextran (CD), as it is known to deplete CFTR from membrane lipid-rafts. We observed that CD treatment significantly (p<0.01) inhibits bacterial phagocytosis in RAW264.7 cells and adding CSE further impairs phagocytosis suggesting synergistic effect on CFTR dependent lipid-rafts.

Conclusion

Our data suggest that SHS impairs bacterial phagocytosis by modulating CFTR dependent lipid-rafts.

Transforming growth factor-β1 and cigarette smoke inhibit the ability of β2-agonists to enhance epithelial permeability

Chronic bronchitis, caused by cigarette smoke exposure, is characterized by mucus hypersecretion and reduced mucociliary clearance (MCC). Effective MCC depends, in part, on adequate airway surface liquid. Cystic fibrosis transmembrane conductance regulator (CFTR) provides the necessary osmotic gradient for serosal to mucosal fluid transport through its ability to both secrete Cl(-) and regulate paracellular permeability, but CFTR activity is attenuated in chronic bronchitis and in smokers. β2-adrenergic receptor (β2-AR) agonists are widely used for managing chronic obstructive pulmonary disease, and can activate CFTR, stimulate ciliary beat frequency, and increase epithelial permeability, thereby stimulating MCC. Patients with chronic airway diseases and cigarette smokers demonstrate increased transforming growth factor (TGF)-β1 signaling, which suppresses β2-agonist-mediated CFTR activation and epithelial permeability increases. Restoring CFTR function in these diseases can restore the ability of β2-agonists to enhance epithelial permeability. Human bronchial epithelial cells, fully redifferentiated at the air-liquid interface, were used for (14)C mannitol flux measurements, Ussing chamber experiments, and quantitative RT-PCR. β2-agonists enhance epithelial permeability by activating CFTR via the β2-AR/adenylyl cyclase/cAMP/protein kinase A pathway. TGF-β1 inhibits β2-agonist-mediated CFTR activation and epithelial permeability enhancement. Although TGF-β1 down-regulates both β2-AR and CFTR mRNA, functionally it only decreases CFTR activity. Cigarette smoke exposure inhibits β2-agonist-mediated epithelial permeability increases, an effect reversed by blocking TGF-β signaling. β2-agonists enhance epithelial permeability via CFTR activation. TGF-β1 signaling inhibits β2-agonist-mediated CFTR activation and subsequent increased epithelial permeability, potentially limiting the ability of β2-agonists to facilitate paracellular transport in disease states unless TGF-β1 signaling is inhibited.

Sinupret activates CFTR and TMEM16A-dependent transepithelial chloride transport and improves indicators of mucociliary clearance

Introduction

We have previously demonstrated that Sinupret, an established treatment prescribed widely in Europe for respiratory ailments including rhinosinusitis, promotes transepithelial chloride (Cl⁻) secretion in vitro and in vivo. The present study was designed to evaluate other indicators of mucociliary clearance (MCC) including ciliary beat frequency (CBF) and airway surface liquid (ASL) depth, but also investigate the mechanisms that underlie activity of this bioflavonoid.

Methods

Primary murine nasal septal epithelial (MNSE) [wild type (WT) and transgenic CFTR^−/−], human sinonasal epithelial (HSNE), WT CFTR-expressing CFBE and TMEM16A-expressing HEK cultures were utilized for the present experiments. CBF and ASL depth measurements were performed. Mechanisms underlying transepithelial Cl⁻ transport were determined using pharmacologic manipulation in Ussing chambers, Fura-2 intracellular calcium [Ca²⁺]_i imaging, cAMP signaling, regulatory domain (R-D) phosphorylation of CFTR, and excised inside out and whole cell patch clamp analysis.

Results

Sinupret-mediated Cl⁻ secretion [ΔI_SC(µA/cm²)] was pronounced in WT MNSE (20.7+/−0.9 vs. 5.6+/−0.9(control), p<0.05), CFTR^−/− MNSE (10.1+/−1.0 vs. 0.9+/−0.3(control), p<0.05) and HSNE (20.7+/−0.3 vs. 6.4+/−0.9(control), p<0.05). The formulation activated Ca²⁺ signaling and TMEM16A channels, but also increased CFTR channel open probability (Po) without stimulating PKA-dependent pathways responsible for phosphorylation of the CFTR R-domain and resultant Cl⁻ secretion. Sinupret also enhanced CBF and ASL depth.

Conclusion

Sinupret stimulates CBF, promotes transepithelial Cl⁻ secretion, and increases ASL depth in a manner likely to enhance MCC. Our findings suggest that direct stimulation of CFTR, together with activation of Ca²⁺-dependent TMEM16A secretion account for the majority of anion transport attributable to Sinupret. These studies provide further rationale for using robust Cl⁻ secretagogue based therapies as an emerging treatment modality for common respiratory diseases of MCC including acute and chronic bronchitis and CRS.

Characterization of defects in ion transport and tissue development in cystic fibrosis transmembrane conductance regulator (CFTR)-knockout rats

Animal models for cystic fibrosis (CF) have contributed significantly to our understanding of disease pathogenesis. Here we describe development and characterization of the first cystic fibrosis rat, in which the cystic fibrosis transmembrane conductance regulator gene (CFTR) was knocked out using a pair of zinc finger endonucleases (ZFN). The disrupted Cftr gene carries a 16 base pair deletion in exon 3, resulting in loss of CFTR protein expression. Breeding of heterozygous (CFTR^+/−) rats resulted in Mendelian distribution of wild-type, heterozygous, and homozygous (CFTR^−/−) pups. Nasal potential difference and transepithelial short circuit current measurements established a robust CF bioelectric phenotype, similar in many respects to that seen in CF patients. Young CFTR^−/− rats exhibited histological abnormalities in the ileum and increased intracellular mucus in the proximal nasal septa. By six weeks of age, CFTR^−/− males lacked the vas deferens bilaterally. Airway surface liquid and periciliary liquid depth were reduced, and submucosal gland size was abnormal in CFTR^−/− animals. Use of ZFN based gene disruption successfully generated a CF animal model that recapitulates many aspects of human disease, and may be useful for modeling other CF genotypes, including CFTR processing defects, premature truncation alleles, and channel gating abnormalities.

Acquired cystic fibrosis transmembrane conductance regulator dysfunction in the lower airways in COPD

BACKGROUND

Cigarette smoke and smoking-induced inflammation decrease cystic fibrosis transmembrane conductance regulator (CFTR) activity and mucociliary transport in the nasal airway and cultured bronchial epithelial cells. This raises the possibility that lower airway CFTR dysfunction may contribute to the pathophysiology of COPD. We compared lower airway CFTR activity in current and former smokers with COPD, current smokers without COPD, and lifelong nonsmokers to examine the relationships between clinical characteristics and CFTR expression and function.

METHODS

Demographic, spirometry, and symptom questionnaire data were collected. CFTR activity was determined by nasal potential difference (NPD) and lower airway potential difference (LAPD) assays. The primary measure of CFTR function was the total change in chloride transport (Δchloride-free isoproterenol). CFTR protein expression in endobronchial biopsy specimens was measured by Western blot.

RESULTS

Compared with healthy nonsmokers (n = 11), current smokers (n = 17) showed a significant reduction in LAPD CFTR activity (Δchloride-free isoproterenol, -8.70 mV vs -15.9 mV; P = .003). Similar reductions were observed in smokers with and without COPD. Former smokers with COPD (n = 7) showed a nonsignificant reduction in chloride conductance (-12.7 mV). A similar pattern was observed for CFTR protein expression. Univariate analysis demonstrated correlations between LAPD CFTR activity and current smoking, the presence of chronic bronchitis, and dyspnea scores.

CONCLUSIONS

Smokers with and without COPD have reduced lower airway CFTR activity compared with healthy nonsmokers, and this finding correlates with disease phenotype. Acquired CFTR dysfunction may contribute to COPD pathogenesis.

Comparison of cystic fibrosis transmembrane conductance regulator (CFTR) and ciliary beat frequency activation by the CFTR Modulators Genistein, VRT-532, and UCCF-152 in primary sinonasal epithelial cultures

IMPORTANCE

Pharmacologic activation of mucociliary clearance (MCC) represents an emerging therapeutic strategy for patients with chronic rhinosinusitis, even in the absence of congenital mutations of the CFTR gene. Drug discovery efforts have identified small molecules that activate the cystic fibrosis transmembrane conductance regulator (CFTR), including potentiators under development for treatment of cystic fibrosis.

OBJECTIVE

To evaluate the properties of CFTR modulators and their effects on ciliary beat frequency (CBF) in human sinonasal epithelium (HSNE).

DESIGN

Primary HSNE cultures (wild type and F508del/F508del) were used to compare stimulation of CFTR-mediated Cl- conductance and CBF by the CFTR modulators genistein, VRT-532, and UCCF-152.

MAIN OUTCOMES AND MEASURES

Increase in CFTR-dependent anion transport and CBF.

RESULTS

HSNE cultures were analyzed using pharmacologic manipulation of ion transport (change in short-circuit current [∆ISC]) and high-speed digital imaging (CBF). Activation of CFTR-dependent anion transport was significantly different among agonists (P < .001), with genistein exerting the greatest effect (mean [SD] ∆ISC, genistein, 23.1 [1.8] μA/cm2² > VRT-532, 8.1 [1.0] μA/cm² > UCCF-152, 3.4 [1.4] μA/cm² > control, 0.7 [0.2] μA/cm²; Tukey-Kramer P < .05) in the absence of forskolin. Genistein and UCCF-152 augmented CBF (under submerged conditions) significantly better (Tukey-Kramer P < .05) than cells treated with VRT-532 or dimethyl sulfoxide vehicle control (mean [SD] fold change over baseline, genistein, 1.63 [0.06]; UCCF-152, 1.56 [0.06]; VRT-532, 1.38 [0.08]; control, 1.27 [0.02]). Activation of CBF was blunted in F508del/F508del HSNE cultures.

CONCLUSIONS AND RELEVANCE

The degree of CBF stimulation was not dependent on the magnitude of Cl- secretion, suggesting that different mechanisms of action may underlie MCC activation by these small molecule potentiators. Agents that activate both CFTR-dependent ISC and CBF are particularly attractive as therapeutics because they may address 2 independent pathways that contribute to deficient MCC in chronic rhinosinusitis.

The Novel Dry Extract BNO 1011 Stimulates Chloride Transport and Ciliary Beat Frequency in Human Respiratory Epithelial Cultures

Background

Herbal remedies predate written history and continue to be used more frequently than conventional pharmaceutical medications. The novel dry extract BNO 1011 is based on a combination of five herbs that is used to treat acute and chronic rhinosinusitis. We evaluated the pharmacologic effects of the novel dry extract BNO 1011 on human respiratory epithelial cultures specifically addressing electrolyte transport and cilia beat frequency (CBF).

Methods

Well-differentiated human bronchial epithelial cultures grown at an air–liquid interface were treated on the apical or basolateral surface with varying concentrations of dry extract BNO 1011. Changes in transepithelial sodium and chloride transport were determined in Ussing chambers under voltage-clamped conditions. Changes in CBF were determined using the Sissons-Ammons Video Analysis system (Ammons Engineering, Mt. Morris, MI).

Results

When applied to the apical surface, dry extract BNO 1011 activated forskolin-stimulated chloride secretion and ciliary beat in a dose-dependent fashion. Basolateral application of dry extract BNO 1011 did not alter the measured physiological properties.

Conclusion

Apical application of dry extract BNO 1011 stimulates both chloride secretion and CBF and therefore may augment mucociliary clearance.

The effect of quercetin on human neutrophil elastase-induced mucin5AC expression in human airway epithelial cells

Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. Mucus hypersecretion is a common pathological change in chronic inflammatory diseases of the airway. We investigated the effect of quercetin on mucin 5AC (MUC5AC) expression induced by human neutrophil elastase (HNE) in airway epithelial cells and its molecular mechanisms. Human airway epithelial (HBE16) cells were pretreated with quercetin and were treated with HNE. We found that HNE induced a significant increase in the levels of MUC5AC and EGFR in cells treated only with HNE. Quercetin suppressed gene transcription and protein expression of MUC5AC in a dose-dependent manner, with significant inhibition from 40 μM. mRNA and protein expressions of EGFR decreased markedly when pretreated with quercetin. Among three MAPK proteins, only phosphorylated ERK1/2 protein expression increased significantly after treatment with HNE alone and decreased significantly after pretreatment with quercetin. HNE also activated phosphorylated PKC protein expression which was attenuated when pretreated with quercetin. These results suggest that quercetin can inhibit HNE-induced MUC5AC expression in human airway epithelial cells through PKC/EGFR/ERK signal transduction pathway. In the future, quercetin might be a valuable treatment for mucin hypersecretion in chronic inflammatory airway diseases in clinic.

Quercetin increases cystic fibrosis transmembrane conductance regulator-mediated chloride transport and ciliary beat frequency: therapeutic implications for chronic rhinosinusitis

BACKGROUND

Increasing epithelial chloride (Cl(-)) secretion in the upper airways represents a putative method for promoting mucociliary clearance through augmentation of airway surface liquid depth. Several naturally occurring flavonoid compounds, including quercetin, have shown the capacity to increase transepithelial Cl(-) transport. Quercetin exhibits well-known antioxidant and anti-inflammatory activity and is now recognized as a potent activator of the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel activity in a fashion largely independent of cyclic adenosine monophosphate signaling. The present study investigates whether this compound activates Cl(-) secretion and ciliary beat frequency (CBF) in well-characterized culture models of sinonasal epithelium.

METHODS

Cystic fibrosis and non-cystic fibrosis primary human sinonasal epithelial (HSNE) and murine nasal septal epithelial (MNSE) cultures were studied for transepithelial ion transport in Ussing chambers under voltage clamp conditions and CBF was performed using pharmacologic manipulation.

RESULTS

Change in short circuit current (DeltaI(SC), expressed as microamperes per squared centimeter) in response to quercetin were significantly greater than controls in both MNSE (23.23 ± 5.44 versus 2.47 ± 1.62; p < 0.0001) and HSNE (-8.72 ± 1.88 versus -1.88 ± 0.66; p < 0.01) cultures. CBF was significantly increased in quercetin-treated cells (expressed as fold change over baseline) in wild type (1.65 ± 0.13 versus 1.23 ± 0.05 [control]; p < 0.01), but not CFTR(-/-) (1.65 ± 0.29 versus 1.48 ± 0.38; p = 0.23).

CONCLUSION

Quercetin significantly increased transepithelial Cl(-) transport and CBF in MNSE and HSNE cultures. Future studies investigating quercetin as a means to promote mucociliary transport in individuals with rhinosinusitis are warranted.

Quercetin-induced Growth Inhibition in Human Bladder Cancer Cells Is Associated with an Increase in Ca-activated K Channels

Quercetin (3,3',4',5,7-pentahydroxyflavone) is an attractive therapeutic flavonoid for cancer treatment because of its beneficial properties including apoptotic, antioxidant, and antiproliferative effects on cancer cells. However, the exact mechanism of action of quercetin on ion channel modulation is poorly understood in bladder cancer 253J cells. In this study, we demonstrated that large conductance Ca(2+)-activated K(+) (BK(Ca)) or MaxiK channels were functionally expressed in 253J cells, and quercetin increased BK(Ca) current in a concentration dependent and reversible manner using a whole cell patch configuration. The half maximal activation concentration (IC(50)) of quercetin was 45.5±7.2 µM. The quercetin-evoked BK(Ca) current was inhibited by tetraethylammonium (TEA; 5 mM) a non-specific BK(Ca) blocker and iberiotoxin (IBX; 100 nM) a BK(Ca)-specific blocker. Quercetin-induced membrane hyperpolarization was measured by fluorescence-activated cell sorting (FACS) with voltage sensitive dye, bis (1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC(4)(3); 100 nM). Quercetin-evoked hyperpolarization was prevented by TEA. Quercetin produced an antiproliferative effect (30.3±13.5%) which was recovered to 53.3±10.5% and 72.9±3.7% by TEA and IBX, respectively. Taken together our results indicate that activation of BK(Ca) channels may be considered an important target related to the action of quercetin on human bladder cancer cells.

Suppression of CFTR premature termination codons and rescue of CFTR protein and function by the synthetic aminoglycoside NB54

Certain aminoglycosides are capable of inducing "translational readthrough" of premature termination codons (PTCs). However, toxicity and relative lack of efficacy deter treatment with clinically available aminoglycosides for genetic diseases caused by PTCs, including cystic fibrosis (CF). Using a structure-based approach, the novel aminoglycoside NB54 was developed that exhibits reduced toxicity and enhanced suppression of PTCs in cell-based reporter assays relative to gentamicin. We examined whether NB54 administration rescued CFTR protein and function in clinically relevant CF models. In a fluorescence-based halide efflux assay, NB54 partially restored halide efflux in a CF bronchial epithelial cell line (CFTR genotype W1282X/F508del), but not in a CF epithelial cell line lacking a PTC (F508del/F508del). In polarized airway epithelial cells expressing either a CFTR-W1282X or -G542X cDNA, treatment with NB54 increased stimulated short-circuit current (I (SC)) with greater efficiency than gentamicin. NB54 and gentamicin induced comparable increases in forskolin-stimulated I (SC) in primary airway epithelial cells derived from a G542X/F508del CF donor. Systemic administration of NB54 to Cftr-/- mice expressing a human CFTR-G542X transgene restored 15-17% of the average stimulated transepithelial chloride currents observed in wild-type (Cftr+/+) mice, comparable to gentamicin. NB54 exhibited reduced cellular toxicity in vitro and was tolerated at higher concentrations than gentamicin in vivo. These results provide evidence that synthetic aminoglycosides are capable of PTC suppression in relevant human CF cells and a CF animal model and support further development of these compounds as a treatment modality for genetic diseases caused by PTCs.

Regulatory domain phosphorylation to distinguish the mechanistic basis underlying acute CFTR modulators

Modulator compounds intended to overcome disease-causing mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) show significant promise in clinical testing for cystic fibrosis. However, the mechanism(s) of action underlying these compounds are not fully understood. Activation of CFTR ion transport requires PKA-regulated phosphorylation of the regulatory domain (R-D) and dimerization of the nucleotide binding domains. Using a newly developed assay, we evaluated nine compounds including both CFTR potentatiators and activators discovered via various high-throughput screening strategies to acutely augment CFTR activity. We found considerable differences in the effects on R-D phosphorylation. Some (including UC(CF)-152) stimulated robust phosphorylation, and others had little effect (e.g., VRT-532 and VX-770). We then compared CFTR activation by UC(CF)-152 and VRT-532 in Ussing chamber studies using two epithelial models, CFBE41o(-) and Fischer rat thyroid cells, expressing various CFTR forms. UC(CF)-152 activated wild-type-, G551D-, and rescued F508del-CFTR currents but did not potentiate cAMP-mediated CFTR activation. In contrast, VRT-532 moderately activated CFTR short-circuit current and strongly potentiated forskolin-mediated current. Combined with the result that UC(CF)-152, but not VRT-532 or VX-770, acts by increasing CFTR R-D phosphorylation, these findings indicate that potentiation of endogenous cAMP-mediated activation of mutant CFTR is not due to a pathway involving augmented R-D phosphorylation. This study presents an assay useful to distinguish preclinical compounds by a crucial mechanism underlying CFTR activation, delineates two types of compound able to acutely augment CFTR activity (e.g., activators and potentiators), and demonstrates that a number of different mechanisms can be successfully employed to activate mutant CFTR.

Resveratrol has salutary effects on mucociliary transport and inflammation in sinonasal epithelium

OBJECTIVE/HYPOTHESIS

Therapeutic agents that enhance mucociliary transport (via stimulation of transepithelial Cl- secretion) and inhibit inflammation could provide considerable advantages over conventional treatments for chronic rhinosinusitis (CRS). The objectives of the present study were to investigate whether the polyphenolic compound resveratrol promotes transepithelial Cl- transport and inhibits KC/IL-8 secretion in sinonasal epithelium.

STUDY DESIGN

In vitro and in vivo study.

METHODS

Transepithelial Cl- transport was investigated in primary murine nasal septal (MNSE) and human sinonasal epithelial (HSNE) cultures. In vivo activity was also measured using the murine nasal potential difference assay. CFTR R-domain phosphorylation and cAMP levels were examined as a test of cAMP/PKA-dependent activation. In vitro LPS-induced KC/IL-8 secretion was quantified and compared to a panel of intranasal steroids.

RESULTS

Resveratrol(100 μM) significantly increased CFTR-mediated Cl- transport (change in short-circuit current, ΔI(SC) ) in both MNSE (13.51 ± 0.77 vs. 4.4 ± 0.66 [control]; P < .05) and HSNE (12.28 ± 1.08 vs. 0.69 ± 0.32 [control]; P < .05). Cl- secretion across in vivo murine nasal epithelium was also enhanced (-4 ± 1.8 vs. -0.8 ± 1.7mV [control], P < .05). There was no increase in cellular cAMP or CFTR R-domain phosphorylation detected. Resveratrol also significantly inhibited KC/IL-8 secretion in a dose-dependent fashion (pg/mL) in MNSE (181 ± 39[100 μM) vs. 94 ± 16 [200 μM] vs. 16 ± 22 [500 μM] vs. 1195 ± 355 [LPS control]; P < .001). The compound robustly abrogated KC/IL-8 secretion when compared to ciclesonide (765 ± 139), triamcinolone (561 ± 124), and budesonide (742 ± 428), but had similar activity to fluticasone proprionate (65 ± 47). Similar effects were demonstrated in HSNE (975 ± 244 [100 μM] vs. 1825 ± 144 [LPS control]; P < .001) with inhibition comparable to fluticasone proprionate (785 ± 277).

CONCLUSIONS

These in vitro and in vivo findings indicate resveratrol is a potent Cl- secretagogue and anti-inflammatory agent. Future clinical trials for CRS are warranted.

Cystic fibrosis transmembrane conductance regulator protein repair as a therapeutic strategy in cystic fibrosis

PURPOSE OF REVIEW

Recent progress in understanding the production, processing, and function of the cystic fibrosis gene product, the cystic fibrosis transmembrane conductance regulator (CFTR), has revealed new therapeutic targets to repair the mutant protein. Classification of CFTR mutations and new treatment strategies to address each will be described here.

RECENT FINDINGS

High-throughput screening and other drug discovery efforts have identified small molecules that restore activity to mutant CFTR. Compounds such as VX-770 that potentiate CFTR have demonstrated exciting results in recent clinical trials and demonstrate robust effects across several CFTR mutation classes in the laboratory. A number of novel F508del CFTR processing correctors restore protein to the cell surface and improve ion channel function in vitro and are augmented by coadministration of CFTR potentiators. Ongoing discovery efforts that target protein folding, CFTR trafficking, and cell stress have also indicated promising results. Aminoglycosides and the novel small molecule ataluren induce translational readthrough of nonsense mutations in CFTR and other genetic diseases in vitro and in vivo and have shown activity in proof of concept trials, and ataluren is now being studied in confirmatory trials.

SUMMARY

An improved understanding of the molecular mechanisms underlying the basic genetic defect in cystic fibrosis have led to new treatment strategies to repair the mutant protein.

Hesperidin stimulates cystic fibrosis transmembrane conductance regulator-mediated chloride secretion and ciliary beat frequency in sinonasal epithelium

OBJECTIVE

Pharmacologic agents designed to promote mucociliary clearance (MCC) in chronic rhinosinusitis (CRS) represent a novel therapeutic strategy. The objectives of the present study were to investigate whether the natural bioflavonoid hesperidin 1) increases transepithelial chloride (Cl(-)) secretion in vitro and in vivo, 2) enhances ciliary beat frequency (CBF), and 3) exerts its mechanistic effects through cAMP/PKA-dependent pathways.

STUDY DESIGN

In vitro and in vivo study.

SETTING

Laboratory.

SUBJECTS AND METHODS

Transepithelial Cl(-) transport (Ussing chamber) and CBF were investigated in primary murine nasal septal (MNSE) and human sinonasal epithelial (HSNE) cultures. In vivo activity was measured using the murine nasal potential difference (NPD) assay, cystic fibrosis transmembrane conductance regulator (CFTR) R-domain phosphorylation, and cAMP levels were investigated to rule out a cAMP/PKA-dependent mechanism of activation.

RESULTS

Hesperidin significantly increased CFTR-mediated Cl(-) transport (change in short-circuit current, DeltaI(SC)) in both MNSE (13.51 +/- 0.77 vs 4.4 +/- 0.66 [control]; P < 0.05) and HSNE (12.28 +/- 1.08 vs 0.69 +/- 0.32 [control]; P < 0.05). Cl(-) transport across in vivo murine nasal epithelium was also significantly enhanced with hesperidin (-2.3 +/- 1.0 vs -0.8 +/- 0.8 mV [control], P < 0.05). There was no increase in cellular cAMP or phosphorylation of the CFTR R-domain. Hesperidin significantly increased CBF (ratio of pretreatment to post-treatment) with both basal (1.31 +/- 0.07 vs 0.93 +/- 0.06 [control]; P < 0.05), apical (1.72 +/- 0.09 vs 1.40 +/- 0.07 [control]; P < 0.05), and basal + apical delivery (2.26 +/- 0.18 vs 1.60 +/- 0.21, respectively; P < 0.05).

CONCLUSION

Our in vitro and in vivo investigations provide strong support for future testing of this robust Cl(-) secretagogue and CBF activator in human clinical trials for CRS.

DeltaF508 CFTR processing correction and activity in polarized airway and non-airway cell monolayers

We examined the activity of DeltaF508 cystic fibrosis transmembrane conductance regulator (CFTR) stably expressed in polarized cystic fibrosis bronchial epithelial cells (CFBE41o(-)) human airway cells and Fisher Rat Thyroid (FRT) cells following treatment with low temperature and a panel of small molecule correctors of DeltaF508 CFTR misprocessing. Corr-4a increased DeltaF508 CFTR-dependent Cl(-) conductance in both cell types, whereas treatment with VRT-325 or VRT-640 increased activity only in FRT cells. Total currents stimulated by forskolin and genistein demonstrated similar dose/response effects to Corr-4a treatment in each cell type. When examining the relative contribution of forskolin and genistein to total stimulated current, CFBE41o(-) cells had smaller forskolin-stimulated I(sc) following either low temperature or corr-4a treatment (10-30% of the total I(sc) produced by the combination of both CFTR agonists). In contrast, forskolin consistently contributed greater than 40% of total I(sc) in DeltaF508 CFTR-expressing FRT cells corrected with low temperature, and corr-4a treatment preferentially enhanced forskolin dependent currents only in FRT cells (60% of total I(sc)). DeltaF508 CFTR cDNA transcript levels, DeltaF508 CFTR C band levels, or cAMP signaling did not account for the reduced forskolin response in CFBE41o(-) cells. Treatment with non-specific inhibitors of phosphodiesterases (papaverine) or phosphatases (endothall) did not restore DeltaF508 CFTR activation by forskolin in CFBE41o(-) cells, indicating that the Cl(-) transport defect in airway cells is distal to cAMP or its metabolism. The results identify important differences in DeltaF508 CFTR activation in polarizing epithelial models of CF, and have important implications regarding detection of rescued of DeltaF508 CFTR in vivo.