Suppression of MUC5AC expression in human bronchial epithelial cells by interferon-γ

Characteristics of mucin hypersecretion in different inflammatory patterns based on endotypes of chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is usually accompanied by mucin hypersecretion that can lead to mucus accumulation and impair nasal mucociliary clearance, thus exacerbating airway inflammation. Abnormal mucin hypersecretion is regulated by different T helper (Th) cytokines, which are associated with different endotype-driven inflammatory responses. Therefore, it is of great significance to understand how these factors regulate mucin hypersecretion to provide precise treatment strategies for different endotypes of CRS. BODY: Thus far, the most common endotypes of CRS are classified as type 1, type 2, or type 3 immune responses based on innate and adaptive cell-mediated effector immunity, and the representative Th cytokines in these immune responses, such as IFN-γ, TNF-α, IL-4, IL-5, IL-13, IL-10, IL-17, and IL-22, play an important regulatory role in mucin secretion. We reviewed all the related literature in the PubMed database to determine the expression of these Th cytokines in CRS and the role they play in the regulation of mucin secretion.

CONCLUSION

We believe that the main Th cytokines involved in specific endotypes of CRS play a key role in regulating abnormal mucin secretion, which contributes to better understanding of the pathogenesis of CRS and provides therapeutic targets for airway inflammatory diseases associated with mucin hypersecretion.

Knockdown of Transmembrane Protein 150A (TMEM150A) Results in Increased Production of Multiple Cytokines

Lipopolysaccharide (LPS)-induced signaling through Toll-like receptor 4 (TLR4) is mediated by the plasma membrane lipid, phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P₂] and its derivatives diacylglycerol and inositol trisphosphate. Levels of PI(4,5)P₂ are controlled enzymatically and fluctuate in LPS-stimulated cells. Recently, transmembrane protein 150A (TMEM150A/TM6P1/damage-regulated autophagy modulator 5) has been shown to regulate PI(4,5)P₂ production at the plasma membrane by modifying the composition of the phosphatidylinositol 4-kinase enzyme complex. To determine if TMEM150A function impacts TLR4 signaling, TMEM150A was knocked down in TLR4-expressing epithelial cells and cytokine expression quantified after LPS stimulation. In general, decreased expression of TMEM150A led to increased levels of LPS-induced cytokine secretion and transcript levels. Unexpectedly, knockdown of TMEM150A in a lung epithelial cell line (H292) also led to increased cytokine levels in the unstimulated conditions suggesting TMEM150A plays an important role in cellular homeostasis. Future studies will investigate if TMEM150A plays a similar role for other TLR agonists and in other cell lineages.

Human Neutrophil Elastase Mediates MUC5AC Hypersecretion via the Tumour Necrosis Factor-α Converting Enzyme-Epidermal Growth Factor Receptor Signalling Pathway in vivo

OBJECTIVES

The objective of this study is to examine the role of the tumour necrosis factor-α converting enzyme-epidermal growth factor receptor (TACE-EGFR) pathway in human neutrophil elastase (HNE)-induced MUC5AC mucin expression in mice.

METHOD

Four groups of mice, treated with HNE alone (HNE group), HNE plus TACE inhibitor (HNE + TAPI-2 group), HNE plus EGFR inhibitor (HNE + AG1478 group), and untreated (control group), were used in the experiment. Histopathological changes were monitored by haematoxylin-eosin (HE) and periodic acid-Schiff (PAS) staining. TACE, EGFR, and MUC5AC expression in the nasal mucosa were determined using immunohistochemistry. The expression of p-EGFR, EGFR, and TACE protein was analysed on Western blots, and MUC5AC protein levels were assessed via ELISA. TACE, EGFR, and MUC5AC expression in the nasal mucosa were determined using real-time quantitative PCR.

RESULTS

Compared to the control group, HE-stained tissues from the HNE group showed an irregular epithelium as well as goblet cell and submucosal glandular hyperplasia. In the nasal mucosa, strongly positive fuchsia granules were seen in PAS staining and significant increases in TACE, EGFR, MUC5AC mRNA, and protein expression were detected (p < 0.01). The HNE + TAPI-2 and HNE + AG1478 groups had significantly less goblet cell and submucosal gland hyperplasia as well as weaker PAS staining. Compared to mice treated with HNE alone, in HNE + TAPI-2-treated mice, the levels of TACE, EGFR, and MUC5AC mRNA and protein as well as p-EGFR protein were significantly reduced (p < 0.01). In HNE + AG1478-treated mice, EGFR and MUC5AC mRNA and protein levels and p-EGFR protein expression were reduced significantly (p < 0.01), but the difference in TACE mRNA and protein expression between the HNE + AG1478 and HNE groups was not significant (p > 0.05).

CONCLUSION

Using a newly developed, stable experimental model of nasal hypersecretion in mice, we showed that TAPI-2 or AG1478 inhibited HNE-induced MUC5AC production. This suggests that MUC5AC mucin expression in vivo is mediated by a cascade involving the HNE-TACE-EGFR signalling pathway.

Molecular mechanism underlying miR‑130b‑Sp1 transcriptional regulation in LPS‑induced upregulation of MUC5AC in the bile duct epithelium

Hepatolithiasis is a common disease that represents a serious health threat to the Chinese population. The pathological mechanism underlying hepatolithiasis is closely related to bacterial infections of the intrahepatic bile duct, followed by chronic inflammation and the overexpression of mucin 5AC (MUC5AC). However, the exact mechanism responsible for the lipopolysaccharide (LPS)-induced upregulation of MUC5AC has yet to be elucidated. Specificity protein 1 (Sp1) is a ubiquitous transcription factor that plays a vital role in the regulation of a number of genes that are responsible for normal cellular function. microRNA (miR/miRNA)-130b is a member of the miRNA family. miRNAs can bind to the 3′-untralsated region (3′-UTR) of a target gene and influence its expression levels. The present study found that LPS increases the expression of MUC5AC by influencing Sp1 secretion. Chromatin immunoprecipitation-quantitative PCR experiments further verified three Sp1 binding sites in the MUC5AC promoter sequence that can regulate the expression of MUC5AC. Further analysis demonstrated that Sp1 expression was regulated by miR-130b. Luciferase experiments identified one miR-130b binding site in the Sp1 3′-UTR region. In vivo experiments also confirmed the role of the miR-130b-Sp1-MUC5AC signaling pathway in the formation of biliary stones and indicated that this pathway may provide targeted therapeutic strategies for the treatment of intrahepatic bile duct stones.

Interferon Alpha Induces Multiple Cellular Proteins That Coordinately Suppress Hepadnaviral Covalently Closed Circular DNA Transcription

Covalently closed circular DNA (cccDNA) of hepadnaviruses exists as an episomal minichromosome in the nucleus of an infected hepatocyte and serves as the template for the transcription of viral mRNAs. It had been demonstrated by others and us that interferon alpha (IFN-α) treatment of hepatocytes induced a prolonged suppression of human and duck hepatitis B virus cccDNA transcription, which is associated with the reduction of cccDNA-associated histone modifications specifying active transcription (H3K9^ac or H3K27^ac), but not the histone modifications marking constitutive (H3K9^me3) or facultative (H3K27^me3) heterochromatin formation. In our efforts to identify IFN-induced cellular proteins that mediate the suppression of cccDNA transcription by the cytokine, we found that downregulating the expression of signal transducer and activator of transcription 1 (STAT1), structural maintenance of chromosomes flexible hinge domain containing 1 (SMCHD1), or promyelocytic leukemia (PML) protein increased basal level of cccDNA transcription activity and partially attenuated IFN-α suppression of cccDNA transcription. In contrast, ectopic expression of STAT1, SMCHD1, or PML significantly reduced cccDNA transcription activity. SMCHD1 is a noncanonical SMC family protein and implicated in epigenetic silencing of gene expression. PML is a component of nuclear domain 10 (ND10) and is involved in suppressing the replication of many DNA viruses. Mechanistic analyses demonstrated that STAT1, SMCHD1, and PML were recruited to cccDNA minichromosomes and phenocopied the IFN-α-induced posttranslational modifications of cccDNA-associated histones. We thus conclude that STAT1, SMCHD1, and PML may partly mediate the suppressive effect of IFN-α on hepadnaviral cccDNA transcription.IMPORTANCE Pegylated IFN-α is the only therapeutic regimen that can induce a functional cure of chronic hepatitis B in a small, but significant, fraction of treated patients. Understanding the mechanisms underlying the antiviral functions of IFN-α in hepadnaviral infection may reveal molecular targets for development of novel antiviral agents to improve the therapeutic efficacy of IFN-α. By a loss-of-function genetic screening of individual IFN-stimulated genes (ISGs) on hepadnaviral mRNAs transcribed from cccDNA, we found that downregulating the expression of STAT1, SMCHD1, or PML significantly increased the level of viral RNAs without altering the level of cccDNA. Mechanistic analyses indicated that those cellular proteins are recruited to cccDNA minichromosomes and induce the posttranslational modifications of cccDNA-associated histones similar to those induced by IFN-α treatment. We have thus identified three IFN-α-induced cellular proteins that suppress cccDNA transcription and may partly mediate IFN-α silencing of hepadnaviral cccDNA transcription.

Role of airway epithelial cells in the development of different asthma phenotypes

The term (bronchial) asthma describes a disorder syndrome that comprises several disease phenotypes, all characterized by chronic inflammation in the bronchial epithelium, with a variety of subsequent functional consequences. Thus, the epithelium in the conducting airways is the main localization of the complex pathological changes in the disease. In this regard, bronchial epithelial cells are not passively affected by inflammatory mechanisms induced by immunological processes but rather actively involved in all steps of disease development from initiation and perpetuation to chronification. In recent years it turned out that bronchial epithelial cells show a high level of structural and functional diversity and plasticity with epigenetic mechanisms playing a crucial role in the regulation of these processes. Thus, it is quite reasonable that differential functional activities of the bronchial epithelium are involved in the development of different asthma phenotypes and/or stages of disease. The current knowledge on this topic will be discussed in this review article.

Airway Mucus Restricts Neisseria meningitidis Away from Nasopharyngeal Epithelial Cells and Protects the Mucosa from Inflammation

N. meningitidis is transmitted from person to person by aerosol droplets produced by breathing, talking, or coughing or by direct contact with a contaminated fluid. The natural reservoir of N. meningitidis is the human nasopharynx mucosa, located at the back of the nose and above the oropharynx. The means by which meningococci cross the nasopharyngeal wall is still under debate, due to the lack of a convenient and relevant model mimicking the nasopharyngeal niche. Here, we took advantage of Calu-3 cells grown in air interface culture to study how meningococci colonize the nasopharyngeal niche. We report that the airway mucus is both a niche for meningococcal growth and a protective barrier against N. meningitidis infection. As such, N. meningitidis behaves like commensal bacteria and is unlikely to induce infection without an external trigger.

Neisseria meningitidis is an inhabitant of the nasopharynx, from which it is transmitted from person to person or disseminates in blood and becomes a harmful pathogen. In this work, we addressed colonization of the nasopharyngeal niche by focusing on the interplay between meningococci and the airway mucus that lines the mucosa of the host. Using Calu-3 cells grown in air interface culture (cells grown with the apical domain facing air), we studied meningococcal colonization of the mucus and the host response. Our results suggested that N. meningitidis behaved like commensal bacteria in mucus, without interacting with human cells or actively transmigrating through the cell layer. As a result, type IV pili do not play a role in this model, and meningococci did not trigger a strong innate immune response from the Calu-3 cells. Finally, we have shown that this model is suitable for studying interaction of N. meningitidis with other bacteria living in the nasopharynx and that Streptococcus mitis, but not Moraxella catarrhalis, can promote meningococcal growth in this model.

IMPORTANCEN. meningitidis is transmitted from person to person by aerosol droplets produced by breathing, talking, or coughing or by direct contact with a contaminated fluid. The natural reservoir of N. meningitidis is the human nasopharynx mucosa, located at the back of the nose and above the oropharynx. The means by which meningococci cross the nasopharyngeal wall is still under debate, due to the lack of a convenient and relevant model mimicking the nasopharyngeal niche. Here, we took advantage of Calu-3 cells grown in air interface culture to study how meningococci colonize the nasopharyngeal niche. We report that the airway mucus is both a niche for meningococcal growth and a protective barrier against N. meningitidis infection. As such, N. meningitidis behaves like commensal bacteria and is unlikely to induce infection without an external trigger.