Increased human Ca²⁺-activated Cl⁻ channel 1 expression and mucus overproduction in airway epithelia of smokers and chronic obstructive pulmonary disease patients

Application of text mining to develop AOP-based mucus hypersecretion genesets and confirmation with in vitro and clinical samples

Mucus hypersecretion contributes to lung function impairment observed in COPD (chronic obstructive pulmonary disease), a tobacco smoking-related disease. A detailed mucus hypersecretion adverse outcome pathway (AOP) has been constructed from literature reviews, experimental and clinical data, mapping key events (KEs) across biological organisational hierarchy leading to an adverse outcome. AOPs can guide the development of biomarkers that are potentially predictive of diseases and support the assessment frameworks of nicotine products including electronic cigarettes. Here, we describe a method employing manual literature curation supported by a focused automated text mining approach to identify genes involved in 5 KEs contributing to decreased lung function observed in tobacco-related COPD. KE genesets were subsequently confirmed by unsupervised clustering against 3 different transcriptomic datasets including (1) in vitro acute cigarette smoke and e-cigarette aerosol exposure, (2) in vitro repeated incubation with IL-13, and (3) lung biopsies from COPD and healthy patients. The 5 KE genesets were demonstrated to be predictive of cigarette smoke exposure and mucus hypersecretion in vitro, and less conclusively predict the COPD status of lung biopsies. In conclusion, using a focused automated text mining and curation approach with experimental and clinical data supports the development of risk assessment strategies utilising AOPs.

Effects of cannabis oil extract on immune response gene expression in human small airway epithelial cells (HSAEpC): implications for chronic obstructive pulmonary disease (COPD)

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is commonly associated with both a pro-inflammatory and a T-helper 1 (Th1) immune response. It was hypothesized that cannabis oil extract can alleviate COPD symptoms by eliciting an anti-inflammatory Th2 immune response. Accordingly, the effects of cannabis oil extract on the expression of 84 Th2 and related immune response genes in human small airways epithelial cells (HSAEpC) were investigated.

METHODS

HSAEpC from a single donor were treated with three dilutions of a standardized cannabis oil extract (1:400, 1:800 and 1:1600) along with a solvent control (0.25% [2.5 ul/ml] ethanol) for 24 h. There were four replicates per treatment dilution, and six for the control. RNA isolated from cells were employed in pathway-focused quantitative polymerase chain reaction (qPCR) microarray assays.

RESULTS

The extract induced significant (P < 0.05) changes in expression of 37 tested genes. Six genes (CSF2, IL1RL1, IL4, IL13RA2, IL17A and PPARG) were up-regulated at all three dilutions. Another two (CCL22 and TSLP) were up-regulated while six (CLCA1, CMA1, EPX, LTB4R, MAF and PMCH) were down-regulated at the 1:400 and 1:800 dilutions. The relationship of differentially-expressed genes of interest to biologic pathways was explored using the Database for Annotation, Visualization and Integrated Discovery (DAVID).

CONCLUSIONS

This exploratory investigation indicates that cannabis oil extract may affect expression of specific airway epithelial cell genes that could modulate pro-inflammatory or Th1 processes in COPD. These results provide a basis for further investigations and have prompted in vivo studies of the effects of cannabis oil extract on pulmonary function.

TRIAL REGISTRATION

NONE (all in vitro experiments).

Calcium-activated chloride channel regulator 1 (CLCA1): More than a regulator of chloride transport and mucus production

CLCA1 is a member of the CLCA (calcium-activated chloride channel regulator) family and plays an essential role in goblet cell mucus production from the respiratory tract epithelium. CLCA1 also regulates Ca²⁺-dependent Cl^- transport that involves the channel protein transmembrane protein 16A (TMEM16A) and its accessary molecules. CLCA1 modulates epithelial cell chloride current and participates in the pathogenesis of mucus hypersecretory-associated respiratory and gastrointestinal diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, pneumonia, colon colitis, cystic fibrosis intestinal mucous disease, ulcerative colitis, and gastrointestinal parasitic infection. Most studies have been focused on the expression regulation of CLCA1 in human specimens. Limited studies used the CLCA1-deficient mice and CLCA1 blocking agents and yielded inconsistent conclusions regarding its role in these diseases. CLCA1 not only regulates mucin expression, but also participates in innate immune responses by binding to yet unidentified molecules on inflammatory cells for cytokine and chemokine production. CLCA1 also targets lymphatic endothelial cells and cancer cells by regulating lymphatic cell proliferation and lymphatic sinus growth in the lymphatic organs and controlling cancer cell differentiation, proliferation, and apoptosis, all which depend on the location of the lymphatic vessels, the type of cancers, the presence of Th2 cytokines, and possibly the availability and type of CLCA1-binding proteins. Here we summarize available studies related to these different activities of CLCA1 to assist our understanding of how this secreted modifier of calcium-activated chloride channels (CaCCs) affects mucus production and innate immunity during the pathogenesis of respiratory, gastrointestinal, and malignant diseases.

Ramifications of secreted mucin MUC5AC in malignant journey: a holistic view

Heavily glycosylated secreted mucin MUC5AC, by the virtue of its cysteine-rich repeats, can form inter- and intramolecular disulfide linkages resulting in complex polymers, which in turn craft the framework of the polymeric mucus gel on epithelial cell surfaces. MUC5AC is a molecule with versatile functional implications including barrier functions to epithelial cells, host-pathogen interaction, immune cell attraction to sites of premalignant or malignant lesions and tumor progression in a context-dependent manner. Differential expression, glycosylation and localization of MUC5AC have been associated with a plethora of benign and malignant pathologies. In this era of robust technologies, overexpression strategies and genetically engineered mouse models, MUC5AC is emerging as a potential diagnostic, prognostic and therapeutic target for various malignancies. Considering the clinical relevance of MUC5AC, this review holistically encompasses its genomic organization, domain structure, glycosylation patterns, regulation, functional and molecular connotation from benign to malignant pathologies. Furthermore, we have here explored the incipient and significant experimental tools that are being developed to study this structurally complex and evolutionary conserved gel-forming mucin.

Cigarette smoke differentially affects IL-13-induced gene expression in human airway epithelial cells

Allergic airways inflammation in asthma is characterized by an airway epithelial gene signature composed of POSTN, CLCA1, and SERPINB2 This Th2 gene signature is proposed as a tool to classify patients with asthma into Th2-high and Th2-low phenotypes. However, many asthmatics smoke and the effects of cigarette smoke exposure on the epithelial Th2 gene signature are largely unknown. Therefore, we investigated the combined effect of IL-13 and whole cigarette smoke (CS) on the Th2 gene signature and the mucin-related genes MUC5AC and SPDEF in air-liquid interface differentiated human bronchial (ALI-PBEC) and tracheal epithelial cells (ALI-PTEC). Cultures were exposed to IL-13 for 14 days followed by 5 days of IL-13 with CS exposure. Alternatively, cultures were exposed once daily to CS for 14 days, followed by 5 days CS with IL-13. POSTN, SERPINB2, and CLCA1 expression were measured 24 h after the last exposure to CS and IL-13. In both models POSTN, SERPINB2, and CLCA1 expression were increased by IL-13. CS markedly affected the IL-13-induced Th2 gene signature as indicated by a reduced POSTN, CLCA1, and MUC5AC expression in both models. In contrast, IL-13-induced SERPINB2 expression remained unaffected by CS, whereas SPDEF expression was additively increased. Importantly, cessation of CS exposure failed to restore IL-13-induced POSTN and CLCA1 expression. We show for the first time that CS differentially affects the IL-13-induced gene signature for Th2-high asthma. These findings provide novel insights into the interaction between Th2 inflammation and cigarette smoke that is important for asthma pathogenesis and biomarker-guided therapy in asthma.

Increased expression of hCLCA1 in chronic rhinosinusitis and its contribution to produce MUC5AC

OBJECTIVES/HYPOTHESIS

Mucus hypersecretion is a hallmarks of chronic rhinosinusitis. The expression of MUC5AC, a major respiratory mucin gene, is increased in chronic rhinosinusitis. The mechanisms inducing mucus hypersecretion have not been fully evaluated in chronic rhinosinusitis. Human Ca²⁺ -activated Cl- channel 1 (hCLCA1) is implicated in the regulation of mucus production, airway fluid, and electrolyte transport. The present study objectives was to investigate the expression of hCLCA1 in chronic rhinosinusitis and evaluate whether its level is altered by stimulation with type 1 T helper (Th1) and Th2 cytokines, and to determine the possible role of hCLCA1 on the regulation of mucin 5AC (MUC5AC) production.

STUDY DESIGN

Controlled prospective study.

METHODS

The expression of hCLCA1 and MUC5AC in normal and inflammatory ethmoid mucosa was determined by real-time polymerase chain reaction, immunohistochemistry, and Western blot. In cultured cells, the expression of hCLCA1 and MUC5AC was measured after stimulation with Th1 and Th2 cytokines. In a supernatant, the MUC5AC level was analyzed using enzyme-linked immunosorbent assay after treatment with niflumic acid.

RESULTS

The levels of hCLCA1 and MUC5AC were increased in chronic rhinosinusitis, irrespective of nasal polyp presence, where they were distributed in superficial epithelial cells and submucosal glands. In cultured cells treated with interleukin (IL)-9, IL-4, IL-13, tumor necrosis factor-α, transforming growth factor-β, interferon-γ, and IL-1β, the expression of hCLCA1 and MUC5AC was increased. In cells treated with niflumic acid, the production of MUC5AC was inhibited.

CONCLUSIONS

The current findings indicate that the expression of hCLCA1 is increased in chronic rhinosinusitis and may be regulated by Th1 and Th2 cytokines, possibly contributing to the production of MUC5AC.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E347-E355, 2016.

Protein traffic disorders: an effective high-throughput fluorescence microscopy pipeline for drug discovery

Plasma membrane proteins are essential molecules in the cell which mediate interactions with the exterior milieu, thus representing key drug targets for present pharma. Not surprisingly, protein traffic disorders include a large range of diseases sharing the common mechanism of failure in the respective protein to reach the plasma membrane. However, specific therapies for these diseases are remarkably lacking. Herein, we report a robust platform for drug discovery applied to a paradigmatic genetic disorder affecting intracellular trafficking – Cystic Fibrosis. This platform includes (i) two original respiratory epithelial cellular models incorporating an inducible double-tagged traffic reporter; (ii) a plasma membrane protein traffic assay for high-throughput microscopy screening; and (iii) open-source image analysis software to quantify plasma membrane protein traffic. By allowing direct scoring of compounds rescuing the basic traffic defect, this platform enables an effective drug development pipeline, which can be promptly adapted to any traffic disorder-associated protein and leverage therapy development efforts.

TMEM16A-Mediated Mucin Secretion in IL-13-Induced Nasal Epithelial Cells From Chronic Rhinosinusitis Patients

Purpose

Chronic rhinosinusitis with nasal polyps (CRSwNP), a mainly Th2 cytokine-mediated disease, often involves mucus secretion. Recent evidence suggests that transmembrane protein 16A (TMEM16A), a calcium-activated Cl^- channel (CaCC), can regulate mucus secretion from airway epithelium by transepithelial electrolyte transport and hydration. However, the role of TMEM16A in mucin production/secretion in the airway epithelium is not clear. This study was conducted to determine the role of TMEM16A in mediating mucin secretion in human nasal polyp epithelial cells (HNPECs) induced by IL-13.

Methods

Human sinonasal mucosa tissue and dissociated sinonasal epithelium from control subjects and patients with CRSwNP were assessed for the expression of TMEM16A and the secretion of human mucin 5AC (MUC5AC) by immunohistochemistry, Western blot analysis, and enzyme-linked immuno-sorbent assay (ELISA). A model of the Th2 inflammatory environment was created by exposure of primary air-liquid interface (ALI)-cultured HNPECs to interleukin-13 (IL-13) for 14 days, with subsequent assessment of TMEM16A expression in cell lysates by Western blotting and MUC5AC secretion in apical washings of cells by ELISA.

Results

The expressions of TMEM16A and MUC5AC were increased in human nasal polyp tissue and dissociated nasal polyp epithelium. TMEM16A was detected in IL-13-treated HNPECs, specifically in MUC5AC-positive cells but not in ciliated cells. IL-13 treatment increased percentages of TMEM16A-positive cells, MUC5AC-positive cells, and cells coexpressing TMEM16A/MUC5AC, the expression of TMEM16A protein, and the secretion of MUC5AC. T16Ainh-A01, a TMEM16A inhibitor, attenuated these IL-13-induced effects.

Conclusions

The expression of TMEM16A and MUC5AC are increased in CRSwNP, which might be a direct effect of Th2 cytokines present in the sinonasal mucosa in CRSwNP. Down-regulation of TMEM16A expression and MUC5AC secretion in HNPECs by T16Ainh-A01 indicates that TMEM16A might play an important role in mucin secretion in upper airway inflammatory diseases.

Fungal colonization with Pneumocystis correlates to increasing chloride channel accessory 1 (hCLCA1) suggesting a pathway for up-regulation of airway mucus responses, in infant lungs

Fungal colonization with Pneumocystis is associated with increased airway mucus in infants during their primary Pneumocystis infection, and to severity of COPD in adults. The pathogenic mechanisms are under investigation. Interestingly, increased levels of hCLCA1 – a member of the calcium-sensitive chloride conductance family of proteins that drives mucus hypersecretion – have been associated with increased mucus production in patients diagnosed with COPD and in immunocompetent rodents with Pneumocystis infection. Pneumocystis is highly prevalent in infants; therefore, the contribution of Pneumocystis to hCLCA1 expression was examined in autopsied infant lungs. Respiratory viruses that may potentially increase mucus, were also examined. hCLCA1 expression was measured using actin-normalized Western-blot, and the burden of Pneumocystis organisms was quantified by qPCR in 55 autopsied lungs from apparently healthy infants who died in the community. Respiratory viruses were diagnosed using RT-PCR for RSV, metapneumovirus, influenza, and parainfluenza viruses; and by PCR for adenovirus. hCLCA1 levels in virus positive samples were comparable to those in virus-negative samples. An association between Pneumocystis and increased hCLCA1 expression was documented (P=0.028). Additionally, increasing Pneumocystis burden correlated with increasing hCLCA1 protein expression levels (P=0.017). Results strengthen the evidence of Pneumocystis-associated up-regulation of mucus-related airway responses in infant lungs. Further characterization of this immunocompetent host-Pneumocystis-interaction, including assessment of potential clinical significance, is warranted.

Influence of sex and disease severity on gene expression profiles in individuals with idiopathic pulmonary fibrosis

Epidemiological studies suggest sex-specific trends in the prevalence and mortality of idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) that are distinct for each disease. While the expression of numerous immune and extracellular matrix (ECM) genes in the lung have been well characterized in these diseases, associations elucidating their sex-specific expression patterns by disease type and severity, and the evaluation of hormone-related genes, have not been well studied. Here we performed targeted transcriptional profiling of 48 genes was performed on lung tissue samples from males and females with mild or medium severity IPF or COPD. The genes assessed included those involved in inflammation, ECM remodeling and hormonal processes. Data for 36 lung tissue samples were obtained that were stratified by disease and sex. Expression levels revealed a subset of genes which show differential expression among sexes, disease type, and disease severity. The most significant observations were the increased expression primarily of ECM genes in medium severity IPF (CATHK, COL1A1, COL3, MMP1, MMP7, IL-1RN) compared to mild IPF and COPD. Two genes, CH3L1 and MMP7 showed a tendency of interaction between sex and disease in IPF severity. Surprisingly, there were no significant differences in any of the sex genes measured between the IPF groups; however, ESR1 and AR expression levels were higher and lower, respectively, compared to COPD samples. Overall, this work highlights two genes, CH3L1 and MMP7, that may contribute to gender trends observed for IPF and COPD and are potential targets for future research.

CLCAs - a family of metalloproteases of intriguing phylogenetic distribution and with cases of substituted catalytic sites

The zinc-dependent metalloproteases with His-Glu-x-x-His (HExxH) active site motif, zincins, are a broad group of proteins involved in many metabolic and regulatory functions, and found in all forms of life. Human genome contains more than 100 genes encoding proteins with known zincin-like domains. A survey of all proteins containing the HExxH motif shows that approximately 52% of HExxH occurrences fall within known protein structural domains (as defined in the Pfam database). Domain families with majority of members possessing a conserved HExxH motif include, not surprisingly, many known and putative metalloproteases. Furthermore, several HExxH-containing protein domains thus identified can be confidently predicted to be putative peptidases of zincin fold. Thus, we predict zincin-like fold for eight uncharacterised Pfam families. Besides the domains with the HExxH motif strictly conserved, and those with sporadic occurrences, intermediate families are identified that contain some members with a conserved HExxH motif, but also many homologues with substitutions at the conserved positions. Such substitutions can be evolutionarily conserved and non-random, yet functional roles of these inactive zincins are not known. The CLCAs are a novel zincin-like protease family with many cases of substituted active sites. We show that this allegedly metazoan family has a number of bacterial and archaeal members. An extremely patchy phylogenetic distribution of CLCAs in prokaryotes and their conserved protein domain composition strongly suggests an evolutionary scenario of horizontal gene transfer (HGT) from multicellular eukaryotes to bacteria, providing an example of eukaryote-derived xenologues in bacterial genomes. Additionally, in a protein family identified here as closely homologous to CLCA, the CLCA_X (CLCA-like) family, a number of proteins is found in phages and plasmids, supporting the HGT scenario.