Upper airways are lined with a pseudostratified mucociliary epithelium maintained by basal cells. To investigate functional and phenotypic heterogeneity within the human basal cell compartment, we used a combination of limiting dilution assays and surface marker profiling on primary cultures of basal cells with verified progenitor activity. The limiting dilution assay suggested functional heterogeneity in the ability of basal cells to repopulate a filter and maintain a barrier at ALI. The frequency of cells with this activity varied between patient strains and ranged from 0.08%-1% of basal cells. Validation of large-scale comprehensive surface marker profiling on basal cells led to identification of 74 antigens demarking consistent subpopulations. Preliminary functional analyses suggest differences in differentiation potential of some subpopulations. This work supports the idea that the basal cell compartment may be functionally heterogeneous, and provides new molecular tools for interrogation of human basal cells.

Upper airways are lined with a pseudostratified mucociliary epithelium maintained by basal cells. To investigate functional and phenotypic heterogeneity within the human basal cell compartment, we used a combination of limiting dilution assays and surface marker profiling on primary cultures of basal cells with verified progenitor activity. The limiting dilution assay suggested functional heterogeneity in the ability of basal cells to repopulate a filter and maintain a barrier at ALI. The frequency of cells with this activity varied between patient strains and ranged from 0.08%-1% of basal cells. Validation of large-scale comprehensive surface marker profiling on basal cells led to identification of 74 antigens demarking consistent subpopulations. Preliminary functional analyses suggest differences in differentiation potential of some subpopulations. This work supports the idea that the basal cell compartment may be functionally heterogeneous, and provides new molecular tools for interrogation of human basal cells.

Allergen proteases from a number sources including the filamentous fungus A. fumigatus, are thought to be important in the development of severe asthma through protease dependent interactions with the respiratory epithelium. The first aim of the thesis was to determine the effect of a variety of growth substrates on the secretion of proteases from different strains of A. fumigatus. The second aim was to investigate the effects of recombinant allergen proteases Asp f 5 and Asp f 13 expressed in the P. pastoris protein expression system and crude A. fumigatus culture supernatants on airway epithelial cells and determine whether protease induced interleukin 8 (IL-8) release from airway epithelial cells was dependent on the activation of protease activated receptor 2 (PAR-2).Results demonstrated that the AF293 strain of A. fumigatus secreted serine proteases during growth on pig lung homogenate medium and metalloproteases during growth on a casein based medium but suppressed protease secretion in Vogel's minimal medium. Analysis of the secretion and RNA levels of proteases in A. fumigatus showed that the matrix metalloprotease, Asp f 5 and the serine protease, Asp f 13 were up-regulated and secreted during growth in pig lung medium and that the matrix metalloprotease, Lap1 was up-regulated and secreted along with Asp f 5 and Asp f 13 in casein medium. This finding was confirmed using protease inhibitors and by using strains of A. fumigatus in which Asp f 5 and Asp f 13 genes were disrupted. These results suggest that A. fumigatus was able to detect different complex proteins available as substrates in its environment and regulate protease secretion accordingly. Furthermore, in several strains of A. fumigatus, protease activity was not suppressed by growth in Vogel's medium, suggesting differences in the regulation of protease secretion between strains. Both A. fumigatus culture supernatants and recombinant Asp f 5 and Asp f 13 produced in P. pastoris caused epithelial airway cell desquamination, and IL-8 release in a protease and dose-dependent manner. In addition, both recombinant Asp f 5 and Asp f 13 were both shown to cleave PAR-2 at a site that resulted in receptor activation.In conclusion, differences in the secretion of proteases between A. fumigatus strains and during growth of A. fumigatus on different media suggests a requirement for the standardisation of the preparation of A. fumigatus allergen extracts used both in clinical diagnosis of A. fumigatus allergy and in vitro and in vivo research studies. Furthermore, it is proposed that allergen proteases secreted by A. fumigatus may interact with a variety of host proteins including, matrix molecules, enzymes and receptors which may exacerbate allergic airway diseases.

Epithelial cells lining the upper airways are characterized by low sodium absorption and elevated chloride secretion. Together, the movement of these ions creates the osmotic drive to hydrate the airways. Recent studies indicate that influenza is capable of directly modulating the vectorial transport of sodium and chloride ions. However, the direct impact of influenza has not been studied with respect to potassium channels. This is significant because potassium conductance creates the driving force for chloride secretion. Disruptions to this process leads to edema formation in the lungs and can subsequently cause Acute Respiratory Distress Syndrome. Additionally, it has been demonstrated that the induction of pro-inflammatory cytokines in infected cells may contribute to altered ion channel function, further exacerbating edema formation. The purpose of this study was to assess the direct and indirect effects of influenza virus infection on potassium and chloride ion channel function in a secretory epithelial cell model. In order to assess the direct effects we exposed polarized epithelial cell monolayers to varying doses of H1N1 virus. Potassium and chloride channel function was measured by means of short-circuit current in an Ussing chamber. The immune response to viral infection was determined by RT-qPCR and Bioplex suspension array. Virus conditioned media (CM), and IL-8 were used to characterize the indirect effects on non-infected cells. We observed an increase in chloride secretion, consistent with edema formation, when 60% of the epithelium was infected, and after CM treatment. This observation correlated with increased potassium channel conductance through the calcium-activated (KCNN4) and cAMP-activated potassium channels (KCNQ1), which was ameliorated upon specific inhibition of these channels. The data suggest that the mixture of pro-inflammatory cytokines induced by viral infection directly up-regulate these potassium channels. However, treatment with IL-8 also appears to increase chloride secretion, although the underlying mechanism remains to be determined, as it is not mediated through KCNN4 and KCNQ1. We conclude that the strong induction of cytokines in infected cells act in a paracrine manner on non-infected cells to increase potassium channel conductance. This up-regulation of potassium channels subsequently drives an increase in chloride secretion, leading to fluid build-up in the lungs and edema formation.

Tracheal epithelium is organized along two axes: apicobasal, seen through apical ciliogenesis, and planar seen through organized ciliary beating, which moves mucus out of the airway. Diseased patients with affected ciliary motility have serious chronic respiratory infections. The standard method to construct epithelium is through air liquid interface culture which creates apicobasal polarization, not planar organization. Nanogrooved surface topography created in diffusible substrates for use in air liquid interface culture will induce planar organization of the cytoskeleton. We have created a nanogrooved gelatin device which allows basal nutrient diffusion. Multiple epithelial cells have been found to align in the direction of the nanogrooves in both sparse and confluent conditions. This device is also congruent with ALI culture as seen through formation of tight junctions and ciliogenesis. Thus, we have created nanogrooved surface topography in a diffusible substrate that induces planar alignment of epithelial cells and cytoskeleton.

Tracheal epithelium is organized along two axes: apicobasal, seen through apical ciliogenesis, and planar seen through organized ciliary beating, which moves mucus out of the airway. Diseased patients with affected ciliary motility have serious chronic respiratory infections. The standard method to construct epithelium is through air liquid interface culture which creates apicobasal polarization, not planar organization. Nanogrooved surface topography created in diffusible substrates for use in air liquid interface culture will induce planar organization of the cytoskeleton. We have created a nanogrooved gelatin device which allows basal nutrient diffusion. Multiple epithelial cells have been found to align in the direction of the nanogrooves in both sparse and confluent conditions. This device is also congruent with ALI culture as seen through formation of tight junctions and ciliogenesis. Thus, we have created nanogrooved surface topography in a diffusible substrate that induces planar alignment of epithelial cells and cytoskeleton.

Aspergillus fumigatus is a filamentous fungus and the main pathogen responsible for the often fatal respiratory condition, aspergillosis. Airway epithelial cells (AECs) are likely to be the first line of host defence that come into contact with the inhaled conidia of A. fumigatus. Recent evidence strongly suggests that the response of the airway epithelium to inhaled pathogens is pivotal in orchestrating immune responses by inducing phagocytic-like reactions and the secretion of inflammatory cytokines and antimicrobial peptides. However, the majority of previous work investigating A. fumigatus-host interactions has been performed using macrophages and neutrophils, thereby neglecting the epithelium. AECs have been shown to secrete inflammatory cytokines in response to A. fumigatus although these studies predominantly used transformed AEC lines that lack tight junctions and do not fully differentiate. Furthermore, most studies used culture filtrate or extract of A. fumigatus rather than live, whole organism and as a result, the direct interaction of the germinating fungus and the airway epithelium has been overlooked. During the early germination and growth period, the cell wall composition of A. fumigatus is dynamic, with various antigens exposed at different morphological stages. The aim of this thesis was to determine whether AECsare able to alter the germination and growth rate of A. fumigatus, and, conversely, if A. fumigatus affects AECs in terms of the secretion of inflammatory mediators. These studies used live, germinating A. fumigatus, and human primary differentiated AECs to obtain a more realistic in vitro model than those used in previous studies. Data showed that AECs are able to significantly inhibit the germination and growth of A. fumigatus, although this effect was less pronounced in differentiated primary AEC than in transformed AEC lines. A. fumigatus also significantly inducedthe expression and secretion of the inflammatory cytokines, IL-6 and IL-8, probably via the interaction of fungal cell wall β-glucans, and as of yet unidentified AEC receptor. The A1160pyrG+ strain of A. fumigatus secreted factors capable of inducing cytokine secretion whereas Af293 strain did not, highlighting diverse mechanisms of action for different strains. Upregulation of both cytokines was dependent on the stage of A. fumigatus growth with induction synchronous with germination. Despite being associated with fungal sensitisation in asthmatics, AEC-derived cytokines associated with this disease, namely TSLP, IL33 and IL25,did not appear to be upregulated by transformed AECs in response to A. fumigatus. Similarly, A. fumigatus did not seem to induce synthesis and secretion of the acute phase response protein, fibrinogen above baseline levels. The data presented in this thesis confirms the importance of the airway epithelium in directing anti-A. fumigatus immunity and the involvement of complex ligand-receptor interactions.

Thymic stromal lymphopoietin (TSLP) is a pleotropic cytokine highly implicated in the pathophysiology of asthma and allergic diseases. Although there are robust data regarding the associations of TSLP polymorphisms with the development of allergy and asthma, there is very little information on how these TSLP variants functionally affect downstream effector pathways and disease phenotype. The overall objective of this thesis was to investigate how TSLP polymorphisms are linked to alterations in TSLP secretion and subsequent downstream cellular events. Initially, we investigated the influence of innate and adaptive stimuli on epithelial-derived TSLP expression and secretion, including effects on dendritic cells (DC). We show that polyinosinic:polycytidylic acid (polyI:C) and allergen-specific T cells induced enhanced TSLP secretion from asthmatic bronchial epithelial cells (BEC) compared to non-asthmatic BEC. Furthermore, activated-BEC culture supernatants induced TSLP-dependent CCL17 production from monocyte-derived DC in relation to clinical asthmatic status (Chapter 2). Next, we examined effects of TSLP on hemopoietic progenitor eosinophil-basophil (Eo/B) differentiation, demonstrating enhanced TSLP-mediated hemopoiesis ex vivo in relation to clinical atopic status. We further demonstrated p38MAPK-dependent autocrine signaling by TNFα in TSLP-mediated human Eo/B differentiation ex vivo (Chapter 3). Lastly, to explore the potential functional consequences of a key variant of the TSLP gene, we investigated associations between the rs1837253 TSLP variant and ex vivo production of TSLP in nasal epithelial cells (NEC). We showed that NEC derived from individuals with the “protective” minor allele have diminished TSLP secretion, which suggests that this rs1837253 polymorphism may be directly involved in the regulation of TSLP secretion (Chapter 4). The novel work presented herein provides further evidence for TSLP regulation of distinct immunological pathways in allergic immune inflammatory airway responses initiated at the epithelial surface, and thus (by implication) of allergic disease. These observations support the concept that TSLP is potentially an important biomarker and therapeutic target for allergic diseases characterized by increased Th2 and/or eosinophilic-basophilic inflammation. Continued investigations into the functional mechanisms linking TSLP variants to allergic disease phenotype are of critical importance. / Dissertation / Doctor of Science (PhD)

<p>The cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP activated chloride channel in the apical membrane of epithelial cells, is defective in patients with cystic fibrosis (CF). Research efforts are focused on chloride channel function in order to find a cure for the disease.</p><p>Genistein increased chloride transport in normal and delF508-CFTR cultured airway epithelial cells without cAMP stimulation. Prior pretreatment with phenylbutyrate did not affect the rate of the genistein-stimulated chloride efflux in these cells.</p><p>S-nitrosoglutathione is an endogenous bronchodilator, present in decreased amounts in the lungs of CF patients. We studied the effect of GSNO on chloride (Cl-) transport in primary nasal epithelial cells from CF patients homozygous for the delF508-CFTR mutation, as well as in two CF cell lines, using a fluorescent Cl- indicator and X-ray microanalysis. GSNO increased chloride efflux in the CF cell lines and in primary nasal epithelial cells from CF patients. This effect was partly mediated by CFTR. If the cells were exposed to GSNO in the presence of L-cysteine, Cl- transport was enhanced after 5 min, but not after 4 h. GSNO may be a candidate for pharmacological treatment of CF patients. </p><p>Chloride transport properties of cultured NCL-SG3 sweat gland cells were investigated. The CFTR protein was neither functional nor expressed in these cells. Ca2+-activated chloride conductance was confirmed and the putative Ca2+-activated chloride channel (CaCC) was further characterized in term of its pharmacological sensitivity.</p><p>Corticosteroids, the primary treatment for asthma, cause necrosis/apoptosis of airway epithelial cells. It was investigated whether a newer generation of drugs used in asthma, leukotriene receptor antagonists, had similar effects. Both montelukast and dexamethasone, but not beclomethasone or budesonide induced apoptosis/necrosis in superficial airway epithelial cells. Montelukast and corticosteroids also caused decreased expression of intercellular adhesion molecule -1 (ICAM-1) in epithelial but not endothelial cells.</p>

La Broncho-pneumopathie Chronique Obstructive (BPCO) est une maladie respiratoire grave caractérisée par une inflammation chronique entrainant des lésions irréversibles de l’épithélium respiratoire et du parenchyme pulmonaire. Le principal facteur de risque est le tabagisme mais des études d’association génétique pangénomiques ont montré que certains polymorphismes nucléotidiques simples (SNP) des récepteurs nicotiniques (nAChRs) sont associés à l’incidence de la BPCO. Un de ces polymorphisme est le variant rs16969968 dans le 5ème exon du gène CHRNA5 codant la sous-unité α5. Le but de ce travail a été d’évaluer in vivo l’implication du SNP α5 dans les lésions pulmonaires caractérisant la BPCO et d’étudier l’impact fonctionnel du polymorphisme sur les voies de signalisation mises en jeu en aval des nAChRs. A l’aide de différents modèles in vivo murins et humains, nous avons pu montrer qu’indépendamment du tabagisme, le SNPα5 est associé à une inflammation cellulaire plus marquée, une sécrétion de cytokines pro-inflammatoires, des lésions emphysémateuses, une hyperplasie des cellules mucipares et des cellules Club moins fréquentes par rapport au génotype sauvage. Le SNPα5 est associé à une altération de la perméabilité calcique des cellules épithéliales et une modulation de la voie de signalisation AC3-PKA/C. Cette étude apporte pour la première fois une explication biologique à l’association entre le SNPα5 et la BPCO décrite dans les études d’association génétique pangénomiques à travers un rôle pro-inflammatoire du SNPα5 au niveau pulmonaire. / Chronic Obstructive Pulmonary Disease (COPD) is a critical respiratory disease characterized by a chronic inflammation leading to irreversible epithelial and parenchymal injuries. The main risk factor is tobacco consumption but several genome-wide association studies (GWAS) described some single-associated polymorphisms (SNP) on nicotinic acetylcholine receptors (nACHR) genes associated with COPD incidence. One of these polymorphisms is the rs16969968 variant in the 5th exon of CHRNA5 gene coding the α5 subunit (SNP α5). The aim of this study was to determine in vivo the involvement of SNPα5 in COPD-associated lung injuries and to deciphere the functional impact of the polymorphism on nAChR signaling pathways. Thanks to several in vivo models (mouse and human), we describe here that the SNPα5 is associated, irrespective of the tobacco consumption, to an increased inflammation, pro-inflammatory cytokines secretion, emphysema, goblet cell hyperplasia, and Club cell diminution compared to the wild-type genotype. The SNPα5 is associated with a decreased calcium influx and a modulation of AC3-PKA/C pathway in airway epithelial cells. Our study describe for the first time a biological explanation for the association between SNPα5 and COPD shown in GWAS with a pro-inflammatory role of SNPα5 in the lung.