Nasal mucociliary transport and ciliary ultrastructure in cystic fibrosis. A comparative study with healthy volunteers

Comparison of a novel potentiator of CFTR channel activity to ivacaftor in ameliorating mucostasis caused by cigarette smoke in primary human bronchial airway epithelial cells

BACKGROUND

Cystic Fibrosis causing mutations in the gene CFTR, reduce the activity of the CFTR channel protein, and leads to mucus aggregation, airway obstruction and poor lung function. A role for CFTR in the pathogenesis of other muco-obstructive airway diseases such as Chronic Obstructive Pulmonary Disease (COPD) has been well established. The CFTR modulatory compound, Ivacaftor (VX-770), potentiates channel activity of CFTR and certain CF-causing mutations and has been shown to ameliorate mucus obstruction and improve lung function in people harbouring these CF-causing mutations. A pilot trial of Ivacaftor supported its potential efficacy for the treatment of mucus obstruction in COPD. These findings prompted the search for CFTR potentiators that are more effective in ameliorating cigarette-smoke (CS) induced mucostasis.

METHODS

Small molecule potentiators, previously identified in CFTR binding studies, were tested for activity in augmenting CFTR channel activity using patch clamp electrophysiology in HEK-293 cells, a fluorescence-based assay of membrane potential in Calu-3 cells and in Ussing chamber studies of primary bronchial epithelial cultures. Addition of cigarette smoke extract (CSE) to the solutions bathing the apical surface of Calu-3 cells and primary bronchial airway cultures was used to model COPD. Confocal studies of the velocity of fluorescent microsphere movement on the apical surface of CSE exposed airway epithelial cultures, were used to assess the effect of potentiators on CFTR-mediated mucociliary movement.

RESULTS

We showed that SK-POT1, like VX-770, was effective in augmenting the cyclic AMP-dependent channel activity of CFTR. SK-POT-1 enhanced CFTR channel activity in airway epithelial cells previously exposed to CSE and ameliorated mucostasis on the surface of primary airway cultures.

CONCLUSION

Together, this evidence supports the further development of SK-POT1 as an intervention in the treatment of COPD.

Comparison of a novel potentiator of CFTR channel activity to ivacaftor in ameliorating mucostasis caused by cigarette smoke in primary human bronchial airway epithelial cells

Background

Cystic Fibrosis causing mutations in the gene CFTR , reduce the activity of the CFTR channel protein, and leads to mucus aggregation, airway obstruction and poor lung function. A role for CFTR in the pathogenesis of other muco-obstructive airway diseases such as Chronic Obstructive Pulmonary Disease (COPD) has been well established. The CFTR modulatory compound, Ivacaftor (VX-770), potentiates channel activity of CFTR and certain CF-causing mutations and has been shown to ameliorate mucus obstruction and improve lung function in people harbouring these CF-causing mutations. A pilot trial of Ivacaftor supported its potential efficacy for the treatment of mucus obstruction in COPD. These findings prompted the search for CFTR potentiators that are more effective in ameliorating cigarette-smoke (CS) induced mucostasis.

Methods

A novel small molecule potentiator (SK-POT1), previously identified in CFTR binding studies, was tested for its activity in augmenting CFTR channel activity using patch clamp electrophysiology in HEK-293 cells, a fluorescence-based assay of membrane potential in Calu-3 cells and in Ussing chamber studies of primary bronchial epithelial cultures. Addition of cigarette smoke extract (CSE) to the solutions bathing the apical surface of Calu-3 cells and primary bronchial airway cultures was used to model COPD. Confocal studies of the velocity of fluorescent microsphere movement on the apical surface of CSE exposed airway epithelial cultures, were used to assess the effect of potentiators on CFTR-mediated mucociliary movement.

Results

We showed that SK-POT1, like VX-770, was effective in augmenting the cyclic AMP-dependent channel activity of CFTR. SK-POT-1 enhanced CFTR channel activity in airway epithelial cells previously exposed to CSE and ameliorated mucostasis on the surface of primary airway cultures.

Conclusion

Together, this evidence supports the further development of SK-POT1 as an intervention in the treatment of COPD.

Care for Patients with Type-2 Chronic Rhinosinusitis

In the last 20 years, growing interest in chronic rhinosinusitis (CRS) has become evident in medical literature; nevertheless, it is still difficult to identify the real prevalence of the disease. Epidemiological studies are few and focused on heterogeneous populations and diagnostic methods. Recent research has contributed to identifying CRS as a disease characterized by heterogeneous clinical scenarios, high impact on quality of life, and elevated social costs. Patient stratification with phenotypes and identification of the pathobiological mechanism at the origin of the disease (endotype) and its comorbidities are pivotal in the diagnostic process, and they should be addressed in order to properly tailor treatment. A multidisciplinary approach, shared diagnostic and therapeutic data, and follow-up processes are therefore necessary. Oncological multidisciplinary boards offer models to imitate in accordance with the principles of precision medicine: tracing a diagnostic pathway with the purpose of identifying the patient’s immunological profile, monitoring therapeutical processes, abstaining from having only a single specialist involved in treatment, and placing the patient at the center of the therapeutic plan. Awareness and participation from the patient’s perspective are fundamental steps to optimize the clinical course, improve quality of life, and reduce the socioeconomic burden.

Multi-scale spatial heterogeneity enhances particle clearance in airway ciliary arrays

Mucus clearance constitutes the primary defence of the respiratory system against viruses, bacteria and environmental insults [1]. This transport across the entire airway emerges from the integrated activity of thousands of multiciliated cells, each containing hundreds of cilia, which together must coordinate their spatial arrangement, alignment and motility [2, 3]. The mechanisms of fluid transport have been studied extensively at the level of an individual cilium [4, 5], collectively moving metachronal waves [6-10], and more generally the hydrodynamics of active matter [11, 12]. However, the connection between local cilia architecture and the topology of the flows they generate remains largely unexplored. Here, we image the mouse airway from the sub-cellular (nm) to the organ scales (mm), characterising quantitatively its ciliary arrangement and the generated flows. Locally we measure heterogeneity in both cilia organisation and flow structure, but across the trachea fluid transport is coherent. To examine this result, a hydrodynamic model was developed for a systematic exploration of different tissue architectures. Surprisingly, we find that disorder enhances particle clearance, whether it originates from fluctuations, heterogeneity in multiciliated cell arrangement or ciliary misalignment. This resembles elements of 'stochastic resonance' [13-15], in the sense that noise can improve the function of the system. Taken together, our results shed light on how the microstructure of an active carpet [16, 17] determines its emergent dynamics. Furthermore, this work is also directly applicable to human airway pathologies [1], which are the third leading cause of deaths worldwide [18].

What is the evidence for genetics in chronic rhinosinusitis?

PURPOSE OF REVIEW

To perform analysis of evidence in current literature on the topic of genetics and chronic rhinosinusitis (CRS), with a particular focus on recent findings in the cystic fibrosis transmembrane regulator (CFTR), genes associated with primary ciliary dyskinesia, and taste receptor T2R38. Other genes that have been found to have association with CRS are also presented and discussed.

RECENT FINDINGS

Recent studies in CFTR and CRS research have investigated possible CFTR-potentiators for treatment of refractory CRS. The T2R38 gene has been shown to be applicable in the clinical setting with a testable phenotype and may have a role in the prognosis and influencing management strategies of CRS patients. Many genes of the immune system have been studied, with genome-wide association studies and candidate-gene approaches identifying new associations that will need replication and further elucidation.

SUMMARY

CRS is a multifactorial disease, with strong evidence of a genetic component in its pathophysiology for some cases. Currently, there are over 70 genes that have been genetically associated with CRS in the past 15 years. Future investigations into genetic causes and predispositions of CRS may allow for improved prognostication and development of disease-prevention strategies as well as novel therapeutic targets.

Motile Ciliary Disorders in Chronic Airway Inflammatory Diseases: Critical Target for Interventions

PURPOSE OF REVIEW

Impaired mucociliary clearance has been implicated in chronic upper and lower airway inflammatory diseases (i.e., allergic and non-allergic rhinitis, chronic rhinosinusitis with or without nasal polyps and asthma). How motile ciliary disorders (impaired ciliogenesis, ciliary beating and ultrastructural defects) are implicated in chronic airway inflammatory diseases is not fully understood. Elaboration of the role of motile ciliary disorders may serve as therapeutic targets for improving mucociliary clearance, thereby complementing contemporary disease management.

RECENT FINDINGS

We have summarized the manifestations of motile ciliary disorders and addressed the underlying associations with chronic airway inflammatory diseases. A panel of established and novel diagnostic tests and therapeutic interventions are outlined. Physicians should be vigilant in screening for motile ciliary disorders, particularly in patients with co-existing upper and lower airway inflammatory diseases. Proper assessment and treatment of motile ciliary disorders may have added value to the management and prevention of chronic airway inflammatory diseases.

Single nucleotide polymorphisms related to cystic fibrosis in chronic rhinositus-a pilot study

BACKGROUND

The clinical association between cystic fibrosis (CF) and chronic rhinosinusitis (CRS) is well known. Studies have identified several non-CF transmembrane conductance regulator single nucleotide polymorphisms (SNPs) associated with disease severity in CF patients. We hypothesized that prevalence of these SNPs would be different between CRS patients and age/gender-matched non-CRS controls.

METHODS

This is a targeted SNP study of 1231 CRS patients identified through a large university hospital database who were compared with 8796 age- and gender-matched controls without a history of rhinitis, sinusitis, allergies, or asthma. Prevalence of 5 relevant SNPs was compared between groups, with p < 0.05 considered significant. Stratification by race and gender was performed among groups when statistically appropriate.

RESULTS

CRS patients exhibited a statistically significant (p = 0.036) lower prevalence of rs12883884 (associated with an ion transporter) compared with controls. This association was lost when patients were stratified by race. CRS patients manifested a greater prevalence of rs1403543 (chromosome 23) in both Caucasian and African American subgroups (p = 0.036 and p = 0.026, respectively). Statistical significance disappeared among Caucasians when stratified by gender, but persisted among African American women (p = 0.047). rs12188164 and rs12793173 were both more prevalent in African Americans with CRS than controls (p = 0.042 and p = 0.020, respectively). A trend was also observed for decreased prevalence of rs12883884 in CRS patients compared with controls in the African American subgroup (p = 0.086).

CONCLUSION

The identified SNPs were differentially prevalent in CRS compared with control groups, with some variability as a function of race and gender. Further research is required to confirm these findings and elucidate clinical significance.

Chronic Pseudomonas aeruginosa infection in cystic fibrosis airway disease: metabolic changes that unravel novel drug targets

The cystic fibrosis (CF) airways have an incompletely characterized defect in innate defense that eventually leads to bacterial infection and airway inflammation. Persistent Pseudomonas aerugionsa infection resulting from defective innate immunity and a bacterial phenotypic switch to a more intractable mucoid form inside the airway are now well established as important components of CF pathogenesis. Broad-based factors leading to chronic infection will be discussed with respect to: bacterial virulence in the context of biofilm formation, quorum sensing machinery and alginate overproduction, and failure of innate lung immunity in CF airways. In addition, a controversial question as to whether inflammation or infection comes first during CF airway disease will be addressed. Finally, a new hypothesis, that P. aeruginosa thrives as biofilms within the thickened anaerobic mucus layers, will be developed.

Genetics of chronic rhinosinusitis: state of the field and directions forward

The cause of chronic rhinosinusitis (CRS) remains unclear. Study of the genetic susceptibility to CRS might be a valuable strategy to understand the pathogenesis of this burdensome disorder. The purpose of this review is to critically evaluate the current literature regarding the genetics of CRS in a comprehensive fashion. The most promising findings from candidate gene studies include the cystic fibrosis transmembrane conductance regulator gene (CFTR), as well as genes involved in antigen presentation, innate and adaptive immune responses, tissue remodeling, and arachidonic acid metabolism. We also review the few hypothesis-independent genetic studies of CRS (ie, linkage analysis and pooling-based genome-wide association studies). Interpretation of the current literature is limited by challenges with study design, sparse replication, few functional correlates of associated polymorphisms, and inadequate examination of linkage disequilibrium or expression quantitative trait loci for reported associations. Given the relationship of CRS to other airway disorders with well-characterized genetic components (eg, asthma), study of the genetics of CRS deserves increased attention and investment, including the organization of large, detailed, and collaborative studies to advance knowledge of the mechanisms that underlie this disorder.

Cilia motility and structure in primary and secondary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is a clinically uniform entity, although cilia motility and structure can vary among patients, making diagnosis difficult. Chronic sinusitis, bronchiectasis, sinus hypoplasia, secretory otitis media, and low fertility are common in PCD patients. The aim of this work was to correlate nasal ciliary activity with clinical and structural abnormalities in PCD. A secondary aim was to evaluate the usefulness of high-resolution digital high-speed video (DHSV) in the diagnosis of PCD.

METHODS

We analyzed nasal mucociliary transport and cilia ultrastructure by electron microscopy and studied nasal ciliary beat frequency (CBF) and beat pattern using high-resolution DHSV imaging in 34 healthy volunteers, 25 individuals with PCD (including 11 with Kartagener's syndrome [KS]with situs inversus), and 27 with secondary ciliary dyskinesia (SCD).

RESULTS

Nasal mucociliary transport was defective in the PCD and SCD patients. Ciliary immotility was observed in only six KS patients and was correlated with the absence of dynein. We observed a correlation between partial dynein deficiency and an uncoordinated, stiffly vibrating ciliary beat. Cilia activity and structure were normal in the SCD patients.

CONCLUSION

Nasal mucociliary transport showed a sensitivity of 100% for the diagnosis of PCD but has low specificity. High-resolution DHSV imaging has high sensitivity and specificity for the diagnosis of PCD. Video analysis is probably more useful than the study of mucociliary transport and cilia ultrastructure in screening for PCD. The absence of dynein was correlated with ciliary immotility and was more common in KS patients.

Restoration of mucociliary transport in the fluid-depleted trachea by surface-active instillates

Severe impairment of mucociliary transport (MCT) is a hallmark of cystic fibrosis (CF) lung disease. Recent studies demonstrate that pharmacologic inhibition of anion and liquid secretion in pig tracheas models the MCT defect in CF through depletion of the periciliary fluid component of airway surface liquid. In the present study, the effectiveness of various aqueous instillates on rehydration of the airway surface and restoration of MCT was assessed in this model. Excised porcine tracheas were mounted in a chamber that permitted simultaneous measurement of MCT and adventitial exposure of the airways to Krebs solution. When anion and liquid secretion were inhibited by treatment with bumetanide and dimethylamiloride, MCT was greatly reduced. Luminal instillation of aqueous solutions containing surface-active substances (1% Tween80 or calfactant) transiently restored MCT to high rates in nearly all tissues. Mucosal treatment with only Krebs solution or hypertonic saline restored MCT in only one half of the tracheas. We conclude that aqueous salt solutions alone can hydrate airway surfaces and restore MCT in some tissues, but surface-active substances may provide additional benefit in restoring MCT in this model of mucociliary stasis. We speculate that administration of surface-active substances, by aerosol or lavage, might help to restore MCT in the airways of patients with CF.

Mucociliary clearance in cystic fibrosis

Abnormal mucociliary clearance (MCC) is one of the central hypotheses for the development of lung disease in patients with cystic fibrosis (CF). However, attempts to demonstrate this decrease of MCC in vivo have proved to be somewhat less definitive, with the evidence barely favoring impaired clearance. Any apparent disparities are most likely due to the variety of methodologies used by different laboratories to measure MCC. The limitations of the various methodologies are examined in this review, in an attempt to better facilitate comparison of results. A number of physical and pharmacological therapies have been developed to promote mucus clearance from the CF airway. A summary of the results of interventional studies utilizing the measurement of MCC as an outcome measure is presented.