Effect of Th2 type cytokines on hCLCA1 and mucus expression in cystic fibrosis airways

CLCA1 Regulates Airway Mucus Production and Ion Secretion Through TMEM16A

TMEM16A, a Ca²⁺-activated chloride channel (CaCC), and its regulator, CLCA1, are associated with inflammatory airway disease and goblet cell metaplasia. CLCA1 is a secreted protein with protease activity that was demonstrated to enhance membrane expression of TMEM16A. Expression of CLCA1 is particularly enhanced in goblet cell metaplasia and is associated with various lung diseases. However, mice lacking expression of CLCA1 showed the same degree of mucous cell metaplasia and airway hyperreactivity as asthmatic wild-type mice. To gain more insight into the role of CLCA1, we applied secreted N-CLCA1, produced in vitro, to mice in vivo using intratracheal instillation. We observed no obvious upregulation of TMEM16A membrane expression by CLCA1 and no differences in ATP-induced short circuit currents (Iscs). However, intraluminal mucus accumulation was observed by treatment with N-CLCA1 that was not seen in control animals. The effects of N-CLCA1 were augmented in ovalbumin-sensitized mice. Mucus production induced by N-CLCA1 in polarized BCi-NS1 human airway epithelial cells was dependent on TMEM16A expression. IL-13 upregulated expression of CLCA1 and enhanced mucus production, however, without enhancing purinergic activation of Isc. In contrast to polarized airway epithelial cells and mouse airways, which express very low levels of TMEM16A, nonpolarized airway cells express large amounts of TMEM16A protein and show strong CaCC. The present data show an only limited contribution of TMEM16A to airway ion secretion but suggest a significant role of both CLCA1 and TMEM16A for airway mucus secretion.

Kathon Induces Fibrotic Inflammation in Lungs: The First Animal Study Revealing a Causal Relationship between Humidifier Disinfectant Exposure and Eosinophil and Th2-Mediated Fibrosis Induction

Currently available toxicity data on humidifier disinfectants are primarily limited to polyhexamethylene guanidine phosphate-induced lung fibrosis. We, therefore, investigated whether the sterilizer component Kathon, which is a mixture of chloromethylisothiazolinone and methylisothiazolinone, induces fibrotic lung injury following direct lung exposure in an animal model. Mice were intratracheally instilled with either the vehicle or Kathon. Differential cell counts, cytokine analysis, and histological analysis of lung tissue were then performed to characterize the injury features, and we investigated whether Kathon altered fibrosis-related gene expression in lung tissues via RNA-Seq and bioinformatics. Cell counting showed that Kathon exposure increased the proportion of macrophages, eosinophils, and neutrophils. Moreover, T helper 2 (Th2) cytokine levels in the bronchoalveolar lavage were significantly increased in the Kathon groups. Histopathological analysis revealed increased perivascular/alveolar inflammation, eosinophilic cells, mucous cell hyperplasia, and pulmonary fibrosis following Kathon exposure. Additionally, Kathon exposure modulated the expression of genes related to fibrotic inflammation, including the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, extracellular signal regulated kinase (ERK)1 and ERK2 cascade, extracellular matrix (ECM)-receptor interaction pathway, transforming growth factor beta receptor signaling pathway, cellular response to tumor necrosis factor, and collagen fibril organization. Our results suggest that Kathon exposure is associated with fibrotic lung injury via a Th2-dependent pathway and is thus a possible risk factor for fibrosis.

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.

Von Willebrand Factor Type A domain of hCLCA1 is sufficient for U-937 macrophage activation

The human hCLCA1 gene is a member of the CLCA gene family that has a well-documented role in inflammatory airway diseases. Previously, we demonstrated that secreted hCLCA1 plays a role in regulating the innate immune response by activating airway macrophages. However, the mechanism of this regulation remains unclear. In this present study, recombinant proteins containing different hCLCA1 domains are expressed to determine the specific hCLCA1 domain(s) responsible for macrophage activation. Specifically, hCLCA1 constructs containing the hydrolase domain (HYD), the von Willebrand Factor Type A (VWA) domain, and the fibronectin type III (FN3) domain were heterologously expressed and affinity purified through fast protein liquid chromatography. Circular dichroism spectroscopy revealed that the purified hCLCA1 constructs exhibited secondary structure consistent with folded proteins. The VWA domain clearly demonstrated an ability to activate macrophages, inducing an increase in both IL-1β mRNA and protein expression. This activation was associated with the activation of MAPKs and NF-κB pathways, identifying potential mechanistic pathways by which hCLCA1's VWA domain exerts its signaling effect. Altogether, this work identifies a domain with signaling function within hCLCA1, providing a specific target to one of the most highly induced gene products of airway inflammatory disease.

Soluble mucus component CLCA1 modulates expression of leukotactic cytokines and BPIFA1 in murine alveolar macrophages but not in bone marrow-derived macrophages

The secreted airway mucus cell protein chloride channel regulator, calcium-activated 1, CLCA1, plays a role in inflammatory respiratory diseases via as yet unidentified pathways. For example, deficiency of CLCA1 in a mouse model of acute pneumonia resulted in reduced cytokine expression with less leukocyte recruitment and the human CLCA1 was shown to be capable of activating macrophages in vitro. Translation of experimental data between human and mouse models has proven problematic due to several CLCA species-specific differences. We therefore characterized activation of macrophages by CLCA1 in detail in solely murine ex vivo and in vitro models. Only alveolar but not bone marrow-derived macrophages freshly isolated from C57BL6/J mice increased their expression levels of several pro-inflammatory and leukotactic cytokines upon CLCA1 stimulation. Among the most strongly regulated genes, we identified the host-protective and immunomodulatory airway mucus component BPIFA1, previously unknown to be expressed by airway macrophages. Furthermore, evidence from an in vivo Staphylococcus aureus pneumonia mouse model suggests that CLCA1 may also modify BPIFA1 expression in airway epithelial cells. Our data underscore and specify the role of mouse CLCA1 in inflammatory airway disease to activate airway macrophages. In addition to its ability to upregulate cytokine expression which explains previous observations in the Clca1-deficient S. aureus pneumonia mouse model, modulation of BPIFA1 expression expands the role of CLCA1 in airway disease to involvement in more complex downstream pathways, possibly including liquid homeostasis, airway protection, and antimicrobial defense.

Reduction of Asthmatic Parameters by Sea Hare Hydrolysates in a Mouse Model of Allergic Asthma

Sea hare has a variety of biological activities. However, little is known regarding the anti-asthmatic effects of sea hare. This study was performed to identify the effect of sea hare hydrolysates (SHH) on an ovalbumin (OVA)-induced allergic asthma model. The experimental asthma model was sensitized and challenged with OVA. We found that a high-dose of SHH (HSHH) significantly inhibited OVA-induced airway inflammation and mucus production around the airway in lung sections, while low- and medium-dose SHH showed an insignificant effect. In addition, HSHH highly reduced OVA-induced production of interleukin-4, -5, -13, leukotriene D4, E4, and histamine in bronchoalveolar lavage fluid. HSHH decreased the histamine-induced increase in the intracellular Ca²⁺ level and contractions in asthmatic smooth muscle cells. Furthermore, HSHH did not affect the weights of the spleen nor thymus, whereas dexamethasone (DEX), a steroidal anti-inflammatory drug, reduced them. Taken together, these results showed that HSHH reduced asthmatic parameters in a mouse model of allergic asthma, and suggest that SHH could be used as a potential therapeutic agent for 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.

mCLCA3 modulates IL-17 and CXCL-1 induction and leukocyte recruitment in murine Staphylococcus aureus pneumonia

The human hCLCA1 and its murine ortholog mCLCA3 (calcium-activated chloride channel regulators) are exclusively expressed in mucus cells and linked to inflammatory airway diseases with increased mucus production, such as asthma, cystic fibrosis and chronic obstructive pulmonary disease. Both proteins have a known impact on the mucus cell metaplasia trait in these diseases. However, growing evidence points towards an additional role in innate immune responses. In the current study, we analyzed Staphylococcus aureus pneumonia, an established model to study pulmonary innate immunity, in mCLCA3-deficient and wild-type mice, focusing on the cellular and cytokine-driven innate inflammatory response. We compared clinical signs, bacterial clearance, leukocyte immigration and cytokine responses in the bronchoalveolar compartment, as well as pulmonary vascular permeability, histopathology, mucus cell number and mRNA expression levels of selected genes (mClca1 to 7, Muc5ac, Muc5b, Muc2, Cxcl-1, Cxcl-2, Il-17). Deficiency of mCLCA3 resulted in decreased neutrophilic infiltration into the bronchoalveolar space during bacterial infection. Only the cytokines IL-17 and the murine CXCL-8 homolog CXCL-1 were decreased on mRNA and protein levels during bacterial infection in mCLCA3-deficient mice compared to wild-type controls. However, no differences in clinical outcome, histopathology or mucus cell metaplasia were observed. We did not find evidence for regulation of any other CLCA homolog that would putatively compensate for the lack of mCLCA3. In conclusion, mCLCA3 appears to modulate leukocyte response via IL-17 and murine CXCL-8 homologs in acute Staphylococcus aureus pneumonia which is well in line with the proposed function of hCLCA1 as a signaling molecule acting on alveolar macrophages.

Antibody to mCLCA3 suppresses symptoms in a mouse model of asthma

Background

Asthma is a complex and heterogeneous chronic inflammatory disorder that is associated with mucous cell metaplasia and mucus hypersecretion. Functional genomic analysis indicates that mucous cell metaplasia and mucus hypersecretion depend on members of the calcium-activated chloride channel (CLCA) gene family. It has been reported that the inhibition of CLCAs could relieve the symptoms of asthma. Thus, the mCLCA3 antibody may be a promising strategy to treat allergic diseases such as asthma.

Methods

We constructed asthmatic mouse models of OVA-induced chronic airway inflammatory disorder to study the function of the mCLCA3 antibody. Airway inflammation was measured by HE staining; goblet cell hyperplasia and mucus hypersecretion were detected by PAS staining; muc5ac, IL-13, IFN-γ levels in bronchoalveolar lavage fluid (BALF) were examined by ELISA; Goblet cell apoptosis was measured by TUNEL assay and alcian blue staining; mCLCA3, Bcl-2 and Bax expression were detected by RT-PCR, Western blotting and immunohistochemical analysis.

Results

In our study, mice treated with mCLCA3 antibody developed fewer pathological changes compared with control mice and asthmatic mice, including a remarkable reduction in airway inflammation, the number of goblet cells and mCLCA3 expression in lung tissue. The levels of muc5ac and IL-13 were significantly reduced in BALF. We also found that the rate of goblet cell apoptosis was increased after treatment with mCLCA3 antibody, which was accompanied by an increase in Bax levels and a decrease in Bcl-2 expression in goblet cells.

Conclusions

Taken together, our results indicate that mCLCA3 antibody may have the potential as an effective pharmacotherapy for asthma.

Safety and immunogenicity of a DNA vaccine encoding human calcium-activated chloride channel 1 (hCLCA1) in asthmatic mice

BACKGROUND

Calcium-activated chloride channels (CLCAs) have been found to be preferentially expressed on the secretory epithelium. They may play a pivotal role in mucous overproduction by bronchial goblet cells in asthma. It has been reported that the inhibition of CLCAs with niflumic acid could relieve the symptoms of asthma. However, niflumic acid has serious adverse effects. DNA vaccination is considered to be a promising strategy to treat allergic diseases such as asthma and dust mite allergy.

METHODS

We constructed a vaccine encoding human CLCA1 (hCLCA1) and evaluated its effects on promoting antibodies against hCLCA1 and the related preventive function in a mouse model of asthma.

RESULTS

Our results reveal that the induced hCLCA1 antibodies can be detected in the first 2 weeks after immunization with hCLCA1 plasmids (hCLCA1-p) by intramuscular injection and augmented gradually in the following several weeks. The autoantibodies against hCLCA1 induced by the DNA vaccine bound to three segments of the mouse CLCA3 (mCLCA3) protein, including the amino terminal (PepN), the carboxyl terminal (PepC) and the middle of the protein (PepM). In our study, mice immunized with hCLCA1-p developed fewer pathological changes compared with other control groups, including a remarkable reduction in the air pressure-time index of the trachea, the number of eosinophils and mast cells in the bronchoalveolar lavage fluid and the mRNA level of MUC5AC in goblet cells.

CONCLUSION

Taken together, our results suggest that a DNA vaccine encoding the CLCA protein may have potential as a useful pharmacotherapy for asthma in the future.

CFTR, mucins, and mucus obstruction in cystic fibrosis

Mucus pathology in cystic fibrosis (CF) has been known for as long as the disease has been recognized and is sometimes called mucoviscidosis. The disease is marked by mucus hyperproduction and plugging in many organs, which are usually most fatal in the airways of CF patients, once the problem of meconium ileus at birth is resolved. After the CF gene, CFTR, was cloned and its protein product identified as a cAMP-regulated Cl(-) channel, causal mechanisms underlying the strong mucus phenotype of the disease became obscure. Here we focus on mucin genes and polymeric mucin glycoproteins, examining their regulation and potential relationships to a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR). Detailed examination of CFTR expression in organs and different cell types indicates that changes in CFTR expression do not always correlate with the severity of CF disease or mucus accumulation. Thus, the mucus hyperproduction that typifies CF does not appear to be a direct cause of a defective CFTR but, rather, to be a downstream consequence. In organs like the lung, up-regulation of mucin gene expression by inflammation results from chronic infection; however, in other instances and organs, the inflammation may have a non-infectious origin. The mucus plugging phenotype of the β-subunit of the epithelial Na(+) channel (βENaC)-overexpressing mouse is proving to be an archetypal example of this kind of inflammation, with a dehydrated airway surface/concentrated mucus gel apparently providing the inflammatory stimulus. Data indicate that the luminal HCO(3)(-) deficiency recently described for CF epithelia may also provide such a stimulus, perhaps by causing a mal-maturation of mucins as they are released onto luminal surfaces. In any event, the path between CFTR dysfunction and mucus hyperproduction has proven tortuous, and its unraveling continues to offer its own twists and turns, along with fascinating glimpses into biology.

Strain-dependent airway hyperresponsiveness and a chromosome 7 locus of elevated lymphocyte numbers in cystic fibrosis transmembrane conductance regulator-deficient mice

We previously observed the lungs of naive BALB/cJ Cftr(tm1UNC) mice to have greater numbers of lymphocytes, by immunohistochemical staining, than did BALB wild type littermates or C57BL/6J Cftr(tm1UNC) mice. In the present study, we initially investigated whether this mutation in Cftr alters the adaptive immunity phenotype by measuring the lymphocyte populations in the lungs and spleens by FACS and by evaluating CD3-stimulated cytokine secretion, proliferation, and apoptosis responses. Next, we assessed a potential influence of this lymphocyte phenotype on lung function through airway resistance measures. Finally, we mapped the phenotype of pulmonary lymphocyte counts in BALB × C57BL/6J F2 Cftr(tm1UNC) mice and reviewed positional candidate genes. By FACS analysis, both the lungs and spleens of BALB Cftr(tm1UNC) mice had more CD3(+) (both CD4(+) and CD8(+)) cells than did littermates or C57BL/6J Cftr(tm1UNC) mice. Cftr(tm1UNC) and littermate mice of either strain did not differ in anti-CD3-stimulated apoptosis or proliferation levels. Lymphocytes from BALB Cftr(tm1UNC) mice produced more IL-4 and IL-5 and reduced levels of IFN-γ than did littermates, whereas lymphocytes from C57BL/6J Cftr(tm1UNC) mice demonstrated increased Il-17 secretion. BALB Cftr(tm1UNC) mice presented an enhanced airway hyperresponsiveness to methacholine challenge compared with littermates and C57BL/6J Cftr(tm1UNC) mice. A chromosome 7 locus was identified to be linked to lymphocyte numbers, and genetic evaluation of the interval suggests Itgal and Il4ra as candidate genes for this trait. We conclude that the pulmonary phenotype of BALB Cftr(tm1UNC) mice includes airway hyperresponsiveness and increased lymphocyte numbers, with the latter trait being influenced by a chromosome 7 locus.

Epithelial microRNAs regulate gut mucosal immunity via epithelium-T cell crosstalk

Colonic homeostasis entails epithelium-lymphocyte cooperation, yet many participants in this process are unknown. We show here that epithelial microRNAs mediate the mucosa-immune system crosstalk necessary for mounting protective T helper type 2 (T(H)2) responses. Abolishing the induction of microRNA by gut-specific deletion of Dicer1 (Dicer1(Δgut)), which encodes an enzyme involved in microRNA biogenesis, deprived goblet cells of RELMβ, a key T(H)2 antiparasitic cytokine; this predisposed the host to parasite infection. Infection of Dicer1(Δgut) mice with helminths favored a futile T(H)1 response with hallmarks of inflammatory bowel disease. Interleukin 13 (IL-13) induced the microRNA miR-375, which regulates the expression of TSLP, a T(H)2-facilitating epithelial cytokine; this indicated a T(H)2-amplification loop. We found that miR-375 was required for RELMβ expression in vivo; miR-375-deficient mice had significantly less intestinal RELMβ, which possibly explains the greater susceptibility of Dicer1(Δgut) mice to parasites. Our findings indicate that epithelial microRNAs are key regulators of gut homeostasis and mucosal immunity.