The Inhibition of the Membrane-Bound Transcription Factor Site-1 Protease (MBTP1) Alleviates the p.Phe508del-Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Defects in Cystic Fibrosis Cells

Cystic Fibrosis (CF) is present due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, the most frequent variant being p.phe508del. The CFTR protein is a chloride (Cl-) channel which is defective and almost absent of cell membranes when the p.Phe508del mutation is present. The p.Phe508del-CFTR protein is retained in the endoplasmic reticulum (ER) and together with inflammation and infection triggers the Unfolded Protein Response (UPR). During the UPR, the Activating Transcription Factor 6 (ATF6) is activated with cleavage and then decreases the expression of p.Phe508del-CFTR. We have previously shown that the inhibition of the activation of ATF6 alleviates the p.Phe508del-CFTR defects in cells overexpressing the mutated protein. In the present paper, our aim was to inhibit the cleavage of ATF6, and thus its activation in a human bronchial cell line with endogenous p.Phe508del-CFTR expression and in bronchial cells from patients, to be more relevant to CF. This was achieved by inhibiting the protease MBTP1 which is responsible for the cleavage of ATF6. We show here that this inhibition leads to increased mRNA and p.Phe508del-CFTR expression and, consequently, to increased Cl-efflux. We also explain the mechanisms linked to these increases with the modulation of genes when MBTP1 is inhibited. Indeed, RT-qPCR assays show that genes such as HSPA1B, CEBPB, VIMP, PFND2, MAPK8, XBP1, INSIG1, and CALR are modulated. In conclusion, we show that the inhibition of MBTP1 has a beneficial effect in relevant models to CF and that this is due to the modulation of genes involved in the disease.

IL-20 Cytokines Are Involved in the Repair of Airway Epithelial Barrier: Implication in Exposure to Cigarette Smoke and in COPD Pathology

BACKGROUND

Dysregulated inflammation as seen in chronic obstructive pulmonary disease (COPD) is associated with impaired wound healing. IL-20 cytokines are known to be involved in wound healing processes. The purpose of this study was to use ex vivo and in vitro approaches mimicking COPD to evaluate the potential modulatory role of interleukin-20 (IL-20) on the inflammatory and healing responses to epithelial wounding.

METHODS

The expression of IL-20 cytokines and their receptors was investigated in lung-derived samples collected from non-COPD and COPD patients, from mice chronically exposed to cigarette smoke and from airway epithelial cells from humans and mice exposed in vitro to cigarette smoke. To investigate the role of IL-20 cytokines in wound healing, experiments were performed using a blocking anti-IL-20Rb antibody.

RESULTS

Of interest, IL-20 cytokines and their receptors were expressed in bronchial mucosa, especially on airway epithelial cells. Their expression correlated with the disease severity. Blocking these cytokines in a COPD context improved the repair processes after a lesion induced by scratching the epithelial layer.

CONCLUSIONS

Collectively, this study highlights the implication of IL-20 cytokines in the repair of the airway epithelium and in the pathology of COPD. IL-20 subfamily cytokines might provide therapeutic benefit for patients with COPD to improve epithelial healing.

[Involvement of inorganic phosphate starvation in Pseudomonas aeruginosa bacterial virulence]

Pseudomonas aeruginosa is a bacterium causing a wide spectrum of nosocomial and opportunistic respiratory infections. As an element essential for bacterial metabolism , phosphorus is incorporated as an inorganic phosphate and regulated by a two-component PhoB-PhoR system. Recently, it has been shown that as a result of overexpression of virulence factors, including the PhoB transcription factor, P. aeruginosa exhibited increased virulence in phosphate-deficient conditions. Exploration of the relationship between phosphate homeostasis and P. aeruginosa virulence could effectively contribute to the development of new, simple and innovative therapeutic strategies.

Current concepts on Pseudomonas aeruginosa interaction with human airway epithelium

Pseudomonas aeruginosa is a major, but opportunistic, respiratory pathogen, which rarely infects healthy individuals, mainly due to the barrier effect of the human airway epithelium (HAE). This review explores the interaction of P. aeruginosa with HAE and the progression of the infection. The basolateral part of the epithelium, which includes the basolateral membrane of the epithelial cells and the basement membrane, is inaccessible in normal tight epithelia with intact junctions. We highlight how P. aeruginosa exploits weaknesses in the HAE barrier to gain access to the basolateral part of the epithelium. This access is crucial to initiate respiratory infection and is mainly observed in the injured epithelium, in repairing or chronically remodeled epithelium, and during extrusion of senescent cells or cell multiplication during normal epithelium renewal. The subsequent adhesion of the bacteria and cytotoxic action of virulence factors, including the toxins delivered by the type 3 secretion system (T3SS), lead to retractions and cell death. Eventually, P. aeruginosa progressively reaches the basement membrane and propagates radially through the basal part of the epithelium to disseminate using twitching and flagellar motility.

Ciliogenesis is intrinsically altered in COPD small airways

COPD is characterised by a progressive and irreversible airflow limitation due to airway obstruction and emphysema [1]. We and others showed that bronchial epithelial remodelling in COPD is characterised by alteration of ciliogenesis and cilia function [2, 3], as well as a dysregulation of non-motile primary cilia (PC) [4]. In COPD, the main site of obstruction is in the small airways [5]. Considering that COPD is foremost a small airway disease (SAD) [6–8], we investigated the differentiation of bronchiolar epithelium in COPD, focusing on motile and primary ciliogenesis.

An alteration of primary and motile ciliogenesis is detected in mild/moderate COPD small airways and could be at the origin of the initiation of epithelial remodelling http://bit.ly/3Tz3JDj

The rescue of F508del-CFTR by elexacaftor/tezacaftor/ivacaftor (Trikafta) in human airway epithelial cells is underestimated due to the presence of ivacaftor

Trikafta, currently the leading therapeutic in Cystic Fibrosis (CF), has demonstrated a real clinical benefit. This treatment is the triple combination therapy of two folding correctors elexacaftor/tezacaftor (VX445/VX661) plus the gating potentiator ivacaftor (VX770). In this study, our aim was to compare the properties of F508del-CFTR in cells treated with either lumacaftor (VX809), tezacaftor, elexacaftor, elexacaftor/tezacaftor with or without ivacaftor. We studied F508del-CFTR function, maturation and membrane localisation by Ussing chamber and whole-cell patch clamp recordings, Western blot and immunolocalization experiments. With human primary airway epithelial cells and the cell lines CFBE and BHK expressing F508del, we found that, whereas the combination elexacaftor/tezacaftor/ivacaftor was efficient in rescuing F508del-CFTR abnormal maturation, apical membrane location and function, the presence of ivacaftor limits these effects. The basal F508del-CFTR short-circuit current was significantly increased by elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor compared to other correctors and non-treated cells, an effect dependent on ivacaftor and cAMP. These results suggest that the level of the basal F508del-CFTR current might be a marker for correction efficacy in CF cells. When cells were treated with ivacaftor combined to any correctors, the F508del-CFTR current was unresponsive to the subsequently acute addition of ivacaftor unlike the CFTR potentiators genistein and Cact-A1 which increased elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor-corrected F508del-CFTR currents. These findings show that ivacaftor reduces the correction efficacy of Trikafta. Thus, combining elexacaftor/tezacaftor with a different potentiator might improve the therapeutic efficacy for treating CF patients.

Involvement of the Prion Protein in the Protection of the Human Bronchial Epithelial Barrier Against Oxidative Stress

Aim: Bronchial epithelium acts as a defensive barrier against inhaled pollutants and microorganisms. This barrier is often compromised in inflammatory airway diseases that are characterized by excessive oxidative stress responses, leading to bronchial epithelial shedding, barrier failure, and increased bronchial epithelium permeability. Among proteins expressed in the junctional barrier and participating to the regulation of the response to oxidative and to environmental stresses is the cellular prion protein (PrP^C). However, the role of PrP^C is still unknown in the bronchial epithelium. Herein, we investigated the cellular mechanisms by which PrP^C protein participates into the junctional complexes formation, regulation, and oxidative protection in human bronchial epithelium. Results: Both PrP^C messenger RNA and mature protein were expressed in human epithelial bronchial cells. PrP^C was localized in the apical domain and became lateral, at high degree of cell polarization, where it colocalized and interacted with adherens (E-cadherin/γ-catenin) and desmosomal (desmoglein/desmoplakin) junctional proteins. No interaction was detected with tight junction proteins. Disruption of such interactions induced the loss of the epithelial barrier. Moreover, we demonstrated that PrP^C protection against copper-associated oxidative stress was involved in multiple processes, including the stability of adherens and desmosomal junctional proteins. Innovation: PrP^C is a pivotal protein in the protection against oxidative stress that is associated with the degradation of adherens and desmosomal junctional proteins. Conclusion: Altogether, these results demonstrate that the loss of the integrity of the epithelial barrier by oxidative stress is attenuated by the activation of PrP^C expression, where deregulation might be associated with respiratory diseases.

Inactivation of the interleukin-22 pathway in the airways of cystic fibrosis patients

Interleukin (IL)-22 plays a critical role in regulating the maintenance of the mucosal barrier. As airway epithelial regeneration is abnormal in cystic fibrosis (CF), we investigated IL-22 integrity in CF. We first demonstrated, using Il-22-/- mice, that IL-22 is important to prevent lung damage induced by the CF pathogen Pseudomonas aeruginosa. Next, IL-22 receptor was found normally expressed at the airway epithelial surfaces of CF patients. In wound-healing assays, IL-22-treated CF cultures had higher wound-closure rate than controls, suggesting that IL-22 signaling per se could be functional in a CF context. However, persistence of neutrophil-derived serine-proteases is a major feature of CF airways. Remarkably, IL-22 was found altered in this protease-rich inflammatory microenvironment; the serine protease-3 being the most prone to fully degrade IL-22. Consequently, we suspect an acquired deficiency of the IL-22 pathway in the lungs of CF patients due to IL-22 cleavage by the surrounding neutrophil serine-proteases.

Buserelin alleviates chloride transport defect in human cystic fibrosis nasal epithelial cells

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians caused by mutations in the gene encoding the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) chloride (Cl-) channel regulated by protein kinases, phosphatases, divalent cations and by protein-protein interactions. Among protein-protein interactions, we previously showed that Annexin A5 (AnxA5) binds to CFTR and is involved in the channel localization within membranes and in its Cl- channel function. The deletion of phenylalanine at position 508 (F508del) is the most common mutation in CF which leads to an altered protein (F508del-CFTR) folding with a nascent protein retained within the ER and is quickly degraded. We previously showed that AnxA5 binds to F508del-CFTR and that its increased expression due to a Gonadoliberin (GnRH) augments Cl- efflux in cells expressing F508del-CFTR. The aim of the present work was to use the GnRH analog buserelin which is already used in medicine. Human nasal epithelial cells from controls and CF patients (F508del/F508del) were treated with buserelin and we show here that the treatment alleviates Cl- channel defects in CF cells. Using proteomics we highlighted some proteins explaining this result. Finally, we propose that buserelin is a potential new pharmaceutical compound that can be used in CF and that bronchus can be targeted since we show here that they express GnRH-R.

In vitro and in vivo evidence for an inflammatory role of the calcium channel TRPV4 in lung epithelium: Potential involvement in cystic fibrosis

Cystic fibrosis (CF) is an inherited disease associated with chronic severe lung inflammation, leading to premature death. To develop innovative anti-inflammatory treatments, we need to characterize new cellular and molecular components contributing to the mechanisms of lung inflammation. Here, we focused on the potential role of "transient receptor potential vanilloid-4" (TRPV4), a nonselective calcium channel. We used both in vitro and in vivo approaches to demonstrate that TRPV4 expressed in airway epithelial cells triggers the secretion of major proinflammatory mediators such as chemokines and biologically active lipids, as well as a neutrophil recruitment in lung tissues. We characterized the contribution of cytosolic phospholipase A2, MAPKs, and NF-κB in TRPV4-dependent signaling. We also showed that 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids, i.e., four natural lipid-based TRPV4 agonists, are present in expectorations of CF patients. Also, TRPV4-induced calcium mobilization and inflammatory responses were enhanced in cystic fibrosis transmembrane conductance regulator-deficient cellular and animal models, suggesting that TRPV4 is a promising target for the development of new anti-inflammatory treatments for diseases such as CF.

Non-diluted seawater enhances nasal ciliary beat frequency and wound repair speed compared to diluted seawater and normal saline

Background

The regulation of mucociliary clearance is a key part of the defense mechanisms developed by the airway epithelium. If a high aggregate quality of evidence shows the clinical effectiveness of nasal irrigation, there is a lack of studies showing the intrinsic role of the different irrigation solutions allowing such results. This study investigated the impact of solutions with different pH and ionic compositions, eg, normal saline, non‐diluted seawater and diluted seawater, on nasal mucosa functional parameters.

Methods

For this randomized, controlled, blinded, in vitro study, we used airway epithelial cells obtained from 13 nasal polyps explants to measure ciliary beat frequency (CBF) and epithelial wound repair speed (WRS) in response to 3 isotonic nasal irrigation solutions: (1) normal saline 0.9%; (2) non‐diluted seawater (Physiomer®); and (3) 30% diluted seawater (Stérimar). The results were compared to control (cell culture medium).

Results

Non‐diluted seawater enhanced the CBF and the WRS when compared to diluted seawater and to normal saline. When compared to the control, it significantly enhanced CBF and slightly, though nonsignificantly, improved the WRS. Interestingly, normal saline markedly reduced the number of epithelial cells and ciliated cells when compared to the control condition.

Conclusion

Our results suggest that the physicochemical features of the nasal wash solution is important because it determines the optimal conditions to enhance CBF and epithelial WRS thus preserving the respiratory mucosa in pathological conditions. Non‐diluted seawater obtains the best results on CBF and WRS vs normal saline showing a deleterious effect on epithelial cell function.

Delay of airway epithelial wound repair in COPD is associated with airflow obstruction severity

BACKGROUND

Airway epithelium integrity is essential to maintain its role of mechanical and functional barrier. Recurrent epithelial injuries require a complex mechanism of repair to restore its integrity. In chronic obstructive pulmonary disease (COPD), an abnormal airway epithelial repair may participate in airway remodeling. The objective was to determine if airway epithelial wound repair of airway epithelium is abnormal in COPD.

METHODS

Patients scheduled for lung resection were prospectively recruited. Demographic, clinical data and pulmonary function tests results were recorded. Emphysema was visually scored and histological remodeling features were noted. Primary bronchial epithelial cells (BEC) were extracted and cultured for wound closure assay. We determined the mean speed of wound closure (MSWC) and cell proliferation index, matrix metalloprotease (MMP)-2, MMP-9 and cytokines levels in supernatants of BEC 18 hours after cell wounding. In a subset of patients, bronchiolar epithelial cells were also cultured for wound closure assay for MSWC analyze.

RESULTS

13 COPD and 7 non COPD patients were included. The severity of airflow obstruction and the severity of emphysema were associated with a lower MSWC in BEC (p = 0.01, 95% CI [0.15-0.80]; p = 0.04, 95% CI [-0.77;-0.03] respectively). Cell proliferation index was decreased in COPD patients (19 ± 6% in COPD vs 27 ± 3% in non COPD, p = 0.04). The severity of COPD was associated with a lower level of MMP-2 (7.8 ± 2 10(5) AU in COPD GOLD D vs 12.8 ± 0.13 10(5) AU in COPD GOLD A, p = 0.04) and a lower level of IL-4 (p = 0.03, 95% CI [0.09;0.87]). Moreover, higher levels of IL-4 and IL-2 were associated with a higher MSWC (p = 0.01, 95% CI [0.17;0.89] and p = 0.02, 95% CI [0.09;0.87] respectively). Clinical characteristics and smoking history were not associated with MSWC, cell proliferation index or MMP and cytokines levels. Finally, we showed an association of the MSWC of bronchial and corresponding bronchiolar epithelial cells obtained from the same patients (p = 0.02, 95% CI [0.12;0.89]).

CONCLUSION

Our results showed an abnormal bronchial epithelial wound closure process in severe COPD. Further studies are needed to elucidate the contribution and the regulation of this mechanism in the complex pathophysiology of COPD.

[Regeneration of airway epithelium]

INTRODUCTION

Epithelial regeneration is a complex process. It can lead to the remodeling of the airway epithelium as in asthma, COPD or cystic fibrosis.

BACKGROUND

The development of in vivo and in vitro models has allowed the analysis of remodeling mechanisms and showed the role of components of extracellular matrix, proteases, cytokines and growth factors. Airway epithelial progenitors and stems cells have been studied in these models. However, their identification remains difficult.

CONCLUSION

Identification and characterization of airway epithelial progenitor/stem-cells, and a better knowledge of the regeneration process may allow the development of new therapeutic strategies for airway epithelial reconstitution.

Modification of macroporous titanium tracheal implants with biodegradable structures: tracking in vivo integration for determination of optimal in situ epithelialization conditions

Previously, we showed that macroporous titanium implants, colonized in vivo together with an epithelial graft, are viable options for tracheal replacement in sheep. To decrease the number of operating steps, biomaterial-based replacements for epithelial graft and intramuscular implantation were developed in the present study. Hybrid microporous PLLA/titanium tracheal implants were designed to decrease initial stenosis and provide a surface for epithelialization. They have been implanted in New Zealand white rabbits as tracheal substitutes and compared to intramuscular implantation samples. Moreover, a basement membrane like coating of the implant surface was also designed by Layer-by-Layer (LbL) method with collagen and alginate. The results showed that the commencement of stenosis can be prevented by the microporous PLLA. For determination of the optimum time point of epithelialization after implantation, HPLC analysis of blood samples, C-reactive protein (CRP), and Chromogranin A (CGA) analyses and histology were carried out. Following 3 weeks the implant would be ready for epithelialization with respect to the amount of tissue integration. Calcein-AM labeled epithelial cell seeding showed that after 3 weeks implant surfaces were suitable for their attachment. CRP readings were steady after an initial rise in the first week. Cross-linked collagen/alginate structures show nanofibrillarity and they form uniform films over the implant surfaces without damaging the microporosity of the PLLA body. Human respiratory epithelial cells proliferated and migrated on these surfaces which provided a better alternative to PLLA film surface. In conclusion, collagen/alginate LbL coated hybrid PLLA/titanium implants are viable options for tracheal replacement, together with in situ epithelialization.

The effect of hyaluronan on airway mucus transport and airway epithelial barrier integrity: potential application to the cytoprotection of airway tissue

The lubricating abilities and the protective functions of hyaluronan, a structural component of interstitial and connective tissues, were assessed in in vitro models of airway mucus transport and epithelial barrier. We found that hyaluronan enhanced the transport of airway mucus by cilia and by cough: the lower the hyaluronan molecular weight, the higher the increase. By immunofluorescence and western blot, we observed a significant dose-dependent (0.1, 1, 5 and 10 mg/ml) increase by low molecular weight hyaluronan (40 kDa) in the expression of tight junction proteins such as ZO-1, as well as an increase in the trans-epithelial resistance. Incubation of airway epithelial cells with hyaluronan 40 kDa also significantly increased the gap junction functionality. Finally, we demonstrated that hyaluronan 40 kDa protects the airway epithelium against injury induced by bacterial products during infection. These results demonstrate that the expression and functionality of intercellular adhesion molecules are increased by hyaluronan which can also act as a lubricant at the airway epithelium surface and suggest that hyaluronan may play a therapeutic role in a variety of respiratory diseases.

Impact of microRNA in normal and pathological respiratory epithelia

Extensive sequencing efforts, combined with ad hoc bioinformatics developments, have now led to the identification of 1222 distinct miRNAs in human (derived from 1368 distinct genomic loci) and of many miRNAs in other multicellular organisms. The present chapter is aimed at describing a general experimental strategy to identify specific miRNA expression profiles and to highlight the functional networks operating between them and their mRNA targets, including several miRNAs deregulated in cystic fibrosis and during differentiation of airway epithelial cells.

Long acting beta2-agonist and corticosteroid restore airway glandular cell function altered by bacterial supernatant

BACKGROUND

Staphylococcus aureus releases virulence factors (VF) that may impair the innate protective functions of airway cells. The aim of this study was to determine whether a long-acting beta2 adrenergic receptor agonist (salmeterol hydroxynaphthoate, Sal) combined with a corticosteroid (fluticasone propionate, FP) was able to regulate ion content and cytokine expression by airway glandular cells after exposure to S. aureus supernatant.

METHODS

A human airway glandular cell line was incubated with S. aureus supernatant for 1 h and then treated with the combination Sal/FP for 4 h. The expression of actin and CFTR proteins was analyzed by immunofluorescence. Videomicroscopy was used to evaluate chloride secretion and X-ray microanalysis to measure the intracellular ion and water content. The pro-inflammatory cytokine expression was assessed by RT-PCR and ELISA.

RESULTS

When the cells were incubated with S. aureus supernatant and then with Sal/FP, the cellular localisation of CFTR was apical compared to the cytoplasmic localisation in cells incubated with S. aureus supernatant alone. The incubation of airway epithelial cells with S. aureus supernatant reduced by 66% the chloride efflux that was fully restored by Sal/FP treatment. We also observed that Sal/FP treatment induced the restoration of ion (Cl and S) and water content within the intracellular secretory granules of airway glandular cells and reduced the bacterial supernatant-dependent increase of pro-inflammatory cytokines IL8 and TNFalpha.

CONCLUSIONS

Our results demonstrate that treatment with the combination of a corticosteroid and a long-acting beta2 adrenergic receptor agonist after bacterial infection restores the airway glandular cell function. Abnormal mucus induced by defective ion transport during pulmonary infection could benefit from treatment with a combination of beta2 adrenergic receptor agonist and glucocorticoid.

{alpha}7 nicotinic acetylcholine receptor regulates airway epithelium differentiation by controlling basal cell proliferation

Airway epithelial basal cells are known to be critical for regenerating injured epithelium and maintaining tissue homeostasis. Recent evidence suggests that the alpha7 nicotinic acetylcholine receptor (nAChR), which is highly permeable to Ca(2+), is involved in lung morphogenesis. Here, we have investigated the potential role of the alpha7 nAChR in the regulation of airway epithelial basal cell proliferation and the differentiation of the human airway epithelium. In vivo during fetal development and in vitro during the regeneration of the human airway epithelium, alpha7 nAChR expression coincides with epithelium differentiation. Inactivating alpha7 nAChR function in vitro increases cell proliferation during the initial steps of the epithelium regeneration, leading to epithelial alterations such as basal cell hyperplasia and squamous metaplasia, remodeling observed in many bronchopulmonary diseases. The regeneration of the airway epithelium after injury in alpha7(-/-) mice is delayed and characterized by a transient hyperplasia of basal cells. Moreover, 1-year-old alpha7(-/-) mice more frequently present basal cells hyperplasia. Modulating nAChR function or expression shows that only alpha7 nAChR, as opposed to heteropentameric alpha(x)beta(y) nAChRs, controls the proliferation of human airway epithelial basal cells. These findings suggest that alpha7 nAChR is a key regulator of the plasticity of the human airway epithelium by controlling basal cell proliferation and differentiation pathway and is involved in airway remodeling during bronchopulmonary diseases.

Salmeterol restores secretory functions in cystic fibrosis airway submucosal gland serous cells

The activity of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) can be mediated by surface G protein-coupled receptors such as the beta(2)-adrenergic receptor. In this study, we explored the effect of a long-acting beta(2)-adrenergic agonist, salmeterol, on the CFTR-dependent secretory capacity of a human CF tracheal gland serous cell line (CF-KM4), homozygous for the delF508 mutation. We showed that, compared with the untreated CF serous cells, a 24-hour pre-incubation period with 200 nM salmeterol induced an 83% increase in delF508-CFTR-mediated chloride efflux. The restoration of the bioelectric properties is associated with increased apical surface pool of delF508-CFTR. Salmeterol induced a decrease in ion concentration and an increase in the level of hydration of the mucus packaged inside the CF secretory granules. The effects of salmeterol are not associated with a persistent production of cAMP. Western blotting on isolated secretory granules demonstrated immunoreactivity for CFTR and lysozyme. In parallel, we measured by atomic force microscopy an increased size of secretory granules isolated from CF serous cells compared with non-CF serous cells (MM39 cell line) and showed that salmeterol was able to restore a CF cell granule size similar to that of non-CF cells. To demonstrate that the salmeterol effect was a CFTR-dependent mechanism, we showed that the incubation of salmeterol-treated CF serous cells with CFTR-inh172 suppressed the restoration of normal secretory functions. The capacity of salmeterol to restore the secretory capacity of glandular serous cells suggests that it could also improve the airway mucociliary clearance in patients with CF.

Video-microscopic imaging of cell spatio-temporal dispersion and migration

Live-cell imaging has become a powerful analytical tool in most cell biology laboratories. The scope of this paper is to give an overview of the environmental considerations for maintaining living cells on the microscope stage and the technical advances permitting multi-parameter imaging. The paper will then focus on two-dimensional and three-dimensional analysis of cell dispersion and migration and finally give a brief insight on computational modeling of the cell behavior.

Feasibility of nasal epithelial brushing for the study of airway epithelial functions in CF infants

BACKGROUND

For a better understanding of the early stages of cystic fibrosis (CF), it is of major interest to study respiratory epithelial cells obtained as early as possible. Although bronchoalveolar lavage has been proposed for this purpose, nasal brushing, which is a much less invasive technique, has seldom been used in CF infants. The aim of the present study was to examine in a few infants the feasibility of a nasal brushing technique for studies of airway epithelial functions in very young CF infants.

METHODS

In 5 CF (median age 12, range 1-18 months) and 10 control infants (median age 5, range 1-17 months), a nasal brushing was performed by means of a soft sterile cytology brush, after premedication with oral paracetamol (15 mg/kg body weight) and rectal midazolam (0.2 mg/kg body weight). Samples were used for microbiological, cytological and functional studies.

RESULTS

The procedure was well tolerated. Number of cells collected was similar in CF and non-CF patients (CF: median 230x10(3), range 42x10(3)-900x10(3); non-CF: median 340x10(3), range 140x10(3)-900x10(3)). Median number of viable cells was 67% (range 31-84%). Freshly obtained samples were successfully used for studies of ciliary beating frequency and cAMP-dependent chloride efflux. In 7 out of 17 cell cultures, confluence was obtained (CF: 2 out of 7; non-CF: 5 out of 10). The feasibility of studying protein release and mRNA expression of IL-8, IL-6 and TNF-alpha, under basal conditions and after stimulation by Pseudomonas aeruginosa, was demonstrated.

CONCLUSIONS

By means of a simple nasal brushing technique easily performed and well tolerated, it is feasible, in infants, to harvest respiratory cells in sufficient amounts to study the airway epithelium using a broad range of techniques including cell culture.

Human airway surface epithelial regeneration is delayed and abnormal in cystic fibrosis

Cystic fibrosis (CF) at an advanced stage of the disease is characterized by airway epithelial injury and remodelling. Whether CF remodelling is related to infection and inflammation or due to an abnormal regenerative process is still undecided. We have recently established the expression and secretion profiles of interleukin (IL)-8, matrix metalloproteinase (MMP)-7, MMP-9, and tissue inhibitor of metalloproteinase (TIMP)-1 during non-CF airway epithelial regeneration in a humanized nude mouse xenograft model. To enhance our understanding of CF remodelling, we compared the regeneration process of non-infected human CF and non-CF nasal epithelia. In both CF and non-CF situations, epithelial regeneration was characterized by successive steps of cell adhesion and migration, proliferation, pseudostratification, and terminal differentiation. However, histological examination of the grafts showed a delay in differentiation of the CF airway epithelium. Cell proliferation was higher in the regenerating CF epithelium, and the differentiated CF epithelium exhibited a pronounced height increase and basal cell hyperplasia in comparison with non-CF epithelium. In addition, while the number of goblet cells expressing MUC5AC was similar in CF and non-CF regenerated epithelia, the number of MUC5B-immunopositive goblet cells was lower in CF grafts. The expression of human IL-8, MMP-7, MMP-9, and TIMP-1 was enhanced in CF epithelium, especially early in the regenerative process. Together, our data strongly suggest that the regeneration of human CF airway surface epithelium is characterized by remodelling, delayed differentiation, and altered pro-inflammatory and MMP responses.

Interleukin-13 interferes with CFTR and AQP5 expression and localization during human airway epithelial cell differentiation

Interleukin-13 (IL-13) is a central regulator of Th2-dominated respiratory disorders such as asthma. Lesions of the airway epithelial barrier frequently observed in chronic respiratory inflammatory diseases are repaired through proliferation, migration and differentiation of epithelial cells. Our work is focused on the effects of IL-13 in human cellular models of airway epithelial cell regeneration. We have previously shown that IL-13 altered epithelial cell polarity during mucociliary differentiation of human nasal epithelial cells. In particular, the cytokine inhibited ezrin expression and interfered with its apical localization during epithelial cell differentiation in vitro. Here we show that CFTR expression is enhanced in the presence of the cytokine, that two additional CFTR protein isoforms are expressed in IL-13-treated cells and that part of the protein is retained within the endoplasmic reticulum. We further show that aquaporin 5 expression, a water channel localized within the apical membrane of epithelial cells, is completely abolished in the presence of the cytokine. These results show that IL-13 interferes with ion and water channel expression and localization during epithelial regeneration and may thereby influence mucus composition and hydration.

Airway Epithelial Repair, Regeneration, and Remodeling after Injury in Chronic Obstructive Pulmonary Disease

In chronic obstructive pulmonary disease (COPD), exacerbations are generally associated with several causes, including pollutants, viruses, bacteria that are responsible for an excess of inflammatory mediators, and proinflammatory cytokines released by activated epithelial and inflammatory cells. The normal response of the airway surface epithelium to injury includes a succession of cellular events, varying from the loss of the surface epithelium integrity to partial shedding of the epithelium or even complete denudation of the basement membrane. The epithelium then has to repair and regenerate to restore its functions, through several mechanisms, including basal cell spreading and migration, followed by proliferation and differentiation of epithelial cells. In COPD, the remodeling of the airway epithelium, such as squamous metaplasia and mucous hyperplasia that occur during injury, may considerably disturb the innate immune functions of the airway epithelium. In vitro and in vivo models of airway epithelial wound repair and regeneration allow the study of the spatiotemporal modulation of cellular and molecular interaction factors-namely, the proinflammatory cytokines, the matrix metalloproteinases and their inhibitors, and the intercellular adhesion molecules. These factors may be markedly altered during exacerbation periods of COPD and their dysregulation may induce remodeling of the airway mucosa and a leakiness of the airway surface epithelium. More knowledge of the mechanisms involved in airway epithelium regeneration may pave the way to cytoprotective and regenerative therapeutics, allowing the reconstitution of a functional, well-differentiated airway epithelium in COPD.

Trefoil factor family 3 peptide promotes human airway epithelial ciliated cell differentiation

Human airway surface epithelium is frequently damaged by inhaled factors (viruses, bacteria, xenobiotic substances) as well as by inflammatory mediators that contribute to the shedding of surface epithelial cells. To regain its protective function, the epithelium must rapidly repair and redifferentiate. The Trefoil Factor Family (TFF) peptides are secretory products of many mucous cells. TFF3, the major TFF in the airways, is able to enhance airway epithelial cell migration, but the role of this protein in differentiation has not been defined. To identify the specific role of TFF3 in the differentiation of the human airway surface epithelium, we analyzed the temporal expression pattern of TFF3, MUC5AC, and MUC5B mucins (goblet cells) and ciliated cell markers beta-tubulin (cilia) and FOXJ1 (ciliogenesis) during human airway epithelial regeneration using in vivo humanized airway xenograft and in vitro air-liquid interface (ALI) culture models. We observed that TFF3, MUC5AC, MUC5B, and ciliated cell markers were expressed in well-differentiated airway epithelium. The addition of exogenous recombinant human TFF3 to epithelial cell cultures before the initiation of differentiation resulted in no change in MUC5AC or cytokeratin 13 (CK13, basal cell marker)-positive cells, but induced an increase in the number of FOXJ1-positive cells and in the number of beta-tubulin-positive ciliated cells (P < 0.05). Furthermore, this effect on ciliated cell differentiation could be reversed by specific epidermal growth factor (EGF) receptor (EGF-R) inhibition. These results indicate that TFF3 is able to induce ciliogenesis and to promote airway epithelial ciliated cell differentiation, in part through an EGF-R-dependent pathway.

Basal cells of the human adult airway surface epithelium retain transit-amplifying cell properties

In numerous airway diseases, such as cystic fibrosis, the epithelium is severely damaged and must regenerate to restore its defense functions. Although the human airway epithelial stem cells have not been identified yet, we have suggested recently that epithelial stem/progenitor cells exist among both human fetal basal and suprabasal cell subsets in the tracheal epithelium. In this study, we analyzed the capacity of human adult basal cells isolated from human adult airway tissues to restore a well-differentiated and functional airway epithelium. To this end, we used the human-specific basal cell markers tetraspanin CD151 and tissue factor (TF) to separate positive basal cells from negative columnar cells with a FACSAria cell sorter. Sorted epithelial cells were seeded into epithelium-denuded rat tracheae that were grafted subcutaneously in nude mice and on collagen-coated porous membranes, where they were grown at the air-liquid interface. Sorted basal and columnar populations were also analyzed for their telomerase activity, a specific transit-amplifying cell marker, by the telomeric repeat amplification protocol assay. After cell sorting, the pure and viable CD151/TF-positive basal cell population proliferated on plastic and adhered on epithelium-denuded rat tracheae, as well as on collagen-coated porous membranes, where it was able to restore a fully differentiated mucociliary and functional airway epithelium, whereas viable columnar negative cells did not. Telomerase activity was detected in the CD151/TF-positive basal cell population, but not in CD151/TF-negative columnar cells. These results demonstrate that human adult basal cells are at least airway surface transit-amplifying epithelial cells.

[Repair and regeneration of the airway epithelium]

Despite an efficient defence system, the airway surface epithelium, in permanent contact with the external milieu, is frequently injured by inhaled pollutants, microorganisms and viruses. The response of the airway surface epithelium to an acute injury includes a succession of cellular events varying from the loss of the surface epithelium integrity to partial shedding of the epithelium or even to complete denudation of the basement membrane. The epithelium has then to repair and regenerate to restore its functions, through several mechanisms including basal cell spreading and migration, followed by proliferation and differentiation of epithelial cells. The cellular and molecular factors involved in wound repair and epithelial regeneration are closely interacting and imply extracellular matrix proteins, matrix metalloproteinases (MMPs) and their inhibitors as well as cytokines and growth factors secreted by airway epithelial and mesenchymal cells. The development of in vitro and in vivo models of airway epithelium wound repair allowed the study of the spatio-temporal modulation of these factors during the different steps of epithelial repair and regeneration. In this context, several studies have demonstrated that the matrix and secretory environment are markedly involved in these mechanisms and that their dysregulation may induce remodelling of the airway mucosa. A better knowledge of the mechanisms involved in airway epithelium regeneration may pave the way to regenerative therapeutics allowing the reconstitution of a functional airway epithelium in numerous respiratory diseases such as asthma, chronic obstructive pulmonary diseases, cystic fibrosis and bronchiolitis.

alpha3alpha5beta2-Nicotinic acetylcholine receptor contributes to the wound repair of the respiratory epithelium by modulating intracellular calcium in migrating cells

Nicotinic acetylcholine receptors (nAChRs), present in human bronchial epithelial cells (HBECs), have been shown in vitro to modulate cell shape. Because cell spreading and migration are important mechanisms involved in the repair of the bronchial epithelium, we investigated the potential role of nAChRs in the wound repair of the bronchial epithelium. In vivo and in vitro, alpha3alpha5beta2-nAChRs accumulated in migrating HBECs involved in repairing a wound, whereas alpha7-nAChRs were predominantly observed in stationary confluent cells. Wound repair was improved in the presence of nAChR agonists, nicotine, and acetylcholine, and delayed in the presence of alpha3beta2 neuronal nAChR antagonists, mecamylamine, alpha-conotoxin MII, and kappa-bungarotoxin; alpha-bungarotoxin, an antagonist of alpha7-nAChR, had no effect. Addition of nicotine to a repairing wound resulted in a dose-dependent transient increase of intracellular calcium in migrating cells that line the wound edge. Mecamylamine and kappa-bungarotoxin inhibited both the cell-migration speed and the nicotine-induced intracellular calcium increase in wound-repairing migrating cells in vitro. On the contrary alpha-bungarotoxin had no significant effect on migrating cells. These results suggest that alpha3alpha5beta2-nAChRs actively contribute to the wound repair process of the respiratory epithelium by modulating intracellular calcium in wound-repairing migrating cells.