Double-stranded RNA and TGF-alpha promote MUC5AC induction in respiratory cells

Airway Remodeling Factors During Early-Life Rhinovirus Infection and the Effect of Premature Birth

Background: Early rhinovirus (RV) infection is a strong risk factor for asthma development. Airway remodeling factors play a key role in the progression of the asthmatic condition. We hypothesized that RV infection in young children elicits the secretion of growth factors implicated in airway remodeling and asthma progression. Methods: We examined the nasal airway production of remodeling factors in children ( ≤ 2 years old) hospitalized due to PCR-confirmed RV infection. Airway remodeling proteins included: MMP-1, MMP-2, MMP-7, MMP-9, MMP-10, TIMP-1, TIMP-2, EGF, Angiopoietin-2, G-CSF, BMP-9, Endoglin, Endothelin-1, Leptin, FGF-1, Follistatin, HGF, HB-EGF, PLGF, VEGF-A, VEGF-C, VEGF-D, FGF-2, TGF-β1, TGF-β2, TGF-β3, PDGF AA, PDGF BB, SPARC, Periostin, OPN, and TGF-α. Results: A total of 43 young children comprising RV cases (n = 26) and uninfected controls (n = 17) were included. Early RV infection was linked to (1) enhanced production of several remodeling factors (e.g., HGF, TGFα), (2) lower MMP-9/TIMP-2 and MMP-2/TIMP-2 ratios, and (3) increased MMP-10/TIMP-1 ratios. We also found that relative to term infants, severely premature children had reduced MMP-9/TIMP-2 ratios at baseline. Conclusion: RV infection in young children elicits the airway secretion of growth factors implicated in angiogenesis, fibrosis, and extracellular matrix deposition. Our results highlight the potential of investigating virus-induced airway remodeling growth factors during early infancy to monitor and potentially prevent chronic progression of respiratory disorders in all ages.

Characterizing smoking-induced transcriptional heterogeneity in the human bronchial epithelium at single-cell resolution

The human bronchial epithelium is composed of multiple distinct cell types that cooperate to defend against environmental insults. While studies have shown that smoking alters bronchial epithelial function and morphology, its precise effects on specific cell types and overall tissue composition are unclear. We used single-cell RNA sequencing to profile bronchial epithelial cells from six never and six current smokers. Unsupervised analyses led to the characterization of a set of toxin metabolism genes that localized to smoker ciliated cells, tissue remodeling associated with a loss of club cells and extensive goblet cell hyperplasia, and a previously unidentified peri-goblet epithelial subpopulation in smokers who expressed a marker of bronchial premalignant lesions. Our data demonstrate that smoke exposure drives a complex landscape of cellular alterations that may prime the human bronchial epithelium for disease.

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

BACKGROUND

Excessive mucin secretion in the airway is an important feature of airway inflammatory diseases. MUC5AC expression is regulated by a variety of stimuli such as cytokines. Little is known about the role of interferon (IFN)-γ in MUC5AC expression in human bronchial epithelial cells.

METHODS

Human pulmonary mucoepidermoid carcinoma cell line (NCI-H292) and normal human bronchial epithelial (NHBE) cells were used to assess the effects of IFN-γ on MUC5AC transcription.

RESULTS

Transforming growth factor (TGF)-α and double-stranded RNA (polyI:C)-induced MUC5AC mRNA and protein expression was repressed by IFN-γ in a concentration-dependent manner. IFN-γ showed limited effects on TGF-α and polyI:C-induced activation of epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK). A chromatin immunoprecipitation assay indicated that Sp1 bound to its cognate sequence located on the MUC5AC promoter. The Sp1 inhibitor mithramycin A inhibited MUC5AC mRNA expression, implying a critical role for Sp1 in MUC5AC induction. Importantly, IFN-γ impeded Sp1 binding to the MUC5AC promoter.

CONCLUSIONS

These results suggest that IFN-γ represses MUC5AC expression, disturbing binding of Sp1 to its target sequences.

TLR3 activation increases chemokine expression in human fetal airway smooth muscle cells

Viral infections, such as respiratory syncytial virus and rhinovirus, adversely affect neonatal and pediatric populations, resulting in significant lung morbidity, including acute asthma exacerbation. Studies in adults have demonstrated that human airway smooth muscle (ASM) cells modulate inflammation through their ability to secrete inflammatory cytokines and chemokines. The role of ASM in the developing airway during infection remains undefined. In our study, we used human fetal ASM cells as an in vitro model to examine the effect of Toll-like receptor (TLR) agonists on chemokine secretion. We found that fetal ASM express multiple TLRs, including TLR3 and TLR4, which are implicated in the pathogenesis of respiratory syncytial virus and rhinovirus infection. Cells were treated with TLR agonists, polyinosinic-polycytidylic acid [poly(I:C)] (TLR3 agonist), lipopolysaccharide (TLR4 agonist), or R848 (TLR7/8 agonist), and IL-8 and chemokine (C-C motif) ligand 5 (CCL5) secretion were evaluated. Interestingly, poly(I:C), but neither lipopolysaccharide nor R848, increased IL-8 and chemokine (C-C motif) ligand 5 secretion. Examination of signaling pathways suggested that the poly(I:C) effects in fetal ASM involve TLR and ERK signaling, in addition to another major inflammatory pathway, NF-κB. Moreover, there are variations between fetal and adult ASM with respect to poly(I:C) effects on signaling pathways. Pharmacological inhibition suggested that ERK pathways mediate poly(I:C) effects. Overall, our data show that poly(I:C) initiates activation of proinflammatory pathways in developing ASM, which may contribute to immune responses to infection and exacerbation of asthma.

Cigarette smoke augments MUC5AC production via the TLR3-EGFR pathway in airway epithelial cells

BACKGROUND

Viral infections are a major cause of chronic obstructive pulmonary disease (COPD) exacerbations. Toll-like receptor 3 (TLR3) reacts with double-stranded RNA (dsRNA) and participates in the immune response after viral infection. In the present study, we examined whether cigarette smoke, which is involved in the pathogenesis of COPD, enhances mucin production via the TLR3-epidermal growth factor receptor (EGFR) pathway in airway epithelial cells.

METHODS

We studied the effects of cigarette smoke extract (CSE) on signal transduction and the production of mucin 5AC (MUC5AC) in NCI-H292 cells and differentiated primary human bronchial epithelial cells stimulated with a synthetic dsRNA analogue, polyinosinic-polycytidylic acid [poly(I:C)], used as a TLR3 ligand.

RESULTS

CSE significantly potentiated the production of MUC5AC in epithelial cells stimulated with poly(I:C). Antibodies to EGFR or EGFR ligands inhibited CSE-augmented MUC5AC release in poly(I:C)-treated cells. Treatment with poly(I:C) or CSE alone increased the phosphorylation of EGFR and extracellular signal-regulated kinase (ERK). However, after poly(I:C) stimulation, CSE did not enhance EGFR phosphorylation, but did augment ERK phosphorylation. EGFR inhibitors and an ERK inhibitor inhibited the augmented release of MUC5AC. In addition, treatment with N-acetylcysteine, an antioxidant, inhibited the CSE-augmented phosphorylation of ERK and MUC5AC.

CONCLUSIONS

These data show that cigarette smoke increases TLR3-stimulated MUC5AC production in airway epithelial cells, mainly via ERK signaling. The effect might be mediated in part by oxidative stress. Modulation of this pathway might be a therapeutic target for viral-induced mucin overproduction in COPD exacerbation.

Pediatric allergy and immunology in Japan

The Japanese Society of Pediatric Allergy and Clinical Immunology (JSPACI) was started in 1966 and currently has 3613 members as of August 1, 2012. The number of pediatricians specializing in allergies who have been certified by the Japanese Society of Allergology is 817. Among these, there are 125 training directors and training facilities for allergy and clinical immunology. The JSPACI first published an asthma guideline specific for children in 2000, and this has been revised every 3 yrs, contributing to better control of pediatric asthma. Food allergy management guidelines were first developed in 2005, which have helped to improve the care of food allergy patients. Among 514 pediatric training programs by the Japanese Society of Pediatrics, there are 312 facilities routinely performing oral food challenges. Among these, there were already 53 facilities performing oral immunotherapy at the end of 2011, treating 1400 cases of food allergy. The prevalence of pediatric allergic diseases has increased in Japan over the past 50 yrs. A number of International Study of Asthma and Allergies in Childhood surveys have been conducted in the past at specific times. The prevalence of wheezing among children aged 13-14 yrs in 2002 was 13.0%. Multi-year surveys found a 1.5- to 2-fold increase every 10 yrs until 2002. However, according to the latest data in 2012, asthma prevalence seems to have slightly decreased in Japan. Food allergy mainly associated with infantile atopic eczema among infants younger than 1 yr of age is the most common form as with other developed countries. The estimated food allergy prevalence based on data from several surveys is 5-10% among infants (0-6 yrs) and 1-2% among schoolchildren (6-15 yrs). A variety of patients suffering from primary deficiency syndrome have been actively analyzed. Previously, antibody defects and well-defined syndromes with immunodeficiency were analyzed, but recent research is focusing on not only acquired immune disorders but also on innate immune disorders. In contrast to the widespread use of oral immunotherapy, one immediate issue is to develop and reassess subcutaneous and sublingual immunotherapies for mite and Japanese cedar pollen antigens that have been disused in Japan since the 1990s.

Glucocorticoids inhibit MUC5AC production induced by transforming growth factor-α in human respiratory cells

BACKGROUND

Mucus hypersecretion from airway epithelium is a characteristic feature of severe asthma. Glucocorticoids (GCs) may suppress mucus production and diminish the harmful airway obstruction. We investigated the ability of GCs to suppress mRNA expression and protein synthesis of a gene encoding mucin, MUC5AC, induced by transforming growth factor (TGF)-α in human mucoepidermoid carcinoma (NCI-H292) cells and the molecular mechanisms underlying the suppression.

METHODS

We determined if GCs such as dexamethasone (DEX), budesonide (BUD), and fluticasone (FP) could suppress MUC5AC production induced by a combination of TGF-α and double-strand RNA, polyinosinic-polycytidylic acid (polyI:C). MUC5AC mRNA expression and MUC5AC protein production were evaluated. The signaling pathways activated by TGF-α and their inhibition by GCs were tested using a phosphoprotein assay and MUC5AC promoter assay.

RESULTS

DEX significantly suppressed the expression of MUC5AC mRNA and MUC5AC protein induced by TGF-α. The activation of the MUC5AC promoter by TGF-α was significantly inhibited by DEX. DEX did not affect activation of downstream pathways of the EGF receptor or mRNA stability of MUC5AC transcripts. DEX, BUD, and FP suppressed MUC5AC protein expression induced by a combination of TGF-α and polyI:C in a dose-dependent manner.

CONCLUSIONS

GCs inhibited MUC5AC production induced by TGF-α alone or a combination of TGF-α and polyI:C; the repression may be mediated at the transcriptional but not post-transcriptional level.

Influenza A induces the major secreted airway mucin MUC5AC in a protease-EGFR-extracellular regulated kinase-Sp1-dependent pathway

Mucins, the main glycoproteins present within mucus, modulate the rheologic properties of airways and participate in lung defense. They are thought to be able to trap and eliminate microorganisms from the lung. Among the mucins secreted in the lung, MUC5AC is the most prominent factor secreted by surface epithelial cells. Although much is known about the signaling pathways involved in the regulation of MUC5AC by host factors such as cytokines or proteases, less is known about the pathways triggered by microorganisms and, specifically, by influenza A virus (IAV). We therefore set up experiments to dissect the molecular mechanisms responsible for the potential modulation of MUC5AC by IAV. Using epithelial cells, C57/Bl6 mice, and IAV strains, we measured MUC5AC expression at the RNA and protein levels, specificity protein 1 (Sp1) activation, and protease activity. Intermediate molecular partners were confirmed using pharmacological inhibitors, blocking antibodies, and small interfering (si)RNAs. We showed in vitro and in vivo that IAV up-regulates epithelial cell-derived MUC5AC and Muc5ac expression in mice, both at transcriptional (through the induction of Sp1) and translational levels. In addition, we determined that this induction was dependent on a protease-epithelial growth factor receptor-extracellular regulated kinase-Sp1 signaling cascade, involving in particular the human airway trypsin. Our data point to MUC5AC as a potential modulatory mechanism by which the lung epithelia respond to IAV infection, and we dissect, for the first time to the best of our knowledge, the molecular partners involved. Future experiments using MUC5AC-targeted strategies should help further unravel the pathophysiological consequences of IAV-induced MUC5AC expression for lung homeostasis.

Molecular cloning of two novel mucin-like genes in the disease-susceptibility locus for diffuse panbronchiolitis

Diffuse panbronchiolitis (DPB) is a rare complex genetic disease affecting East Asians and is strongly associated with the class I human leukocyte antigens (HLA)-B54 in Japanese and HLA-A11 in Koreans. We recently showed that an HLA-associated major susceptibility gene for DPB is probably located within the 200 kb in the class I region 300 kb telomeric of the HLA-B locus on the chromosome 6p21.3. We cloned two novel mucin-like genes designated panbronchiolitis related mucin-like 1 and 2 (PBMUCL1 and PBMUCL2) in the candidate region, which form a mucin-like gene cluster together with two adjacent genes, MUC21 and DPCR1. PBMUCL1 gene expression was remarkably upregulated by polyinosine-polycytidylic acid [poly(I:C)] stimulation in normal human bronchial epithelial cells redifferentiated at the air-liquid interface. We found genetic polymorphisms in PBMUCL1 gene which were associated with DPB: the A-allele of the PBMUCL1 intron 2 single nucleotide polymorphism (SNP) was positively associated and variable numbers of tandem repeats (VNTR) polymorphism in exon 3 (1,890-base pair deletion) was negatively associated. Despite a strong association with HLA-B in the Japanese, the mucin-like gene PBMUCL1 is also one of the candidate genes of DPB susceptibility.

Tissue remodeling induced by hypersecreted epidermal growth factor and amphiregulin in the airway after an acute asthma attack

BACKGROUND

Epidermal growth factor receptor ligands, such as epidermal growth factor (EGF) and amphiregulin, may play key roles in tissue remodeling in asthma. However, the kinetics of EGF and amphiregulin secretion in the airway after an acute asthma attack and the effect of prolonged airway exposure to these ligands on airway remodeling are unknown.

OBJECTIVE

To measure the EGF and amphiregulin concentrations in sputa obtained from patients with asthma under various conditions, and to examine the effects of EGF and amphiregulin on the proliferation or differentiation of airway structural cells.

METHODS

Epidermal growth factor and amphiregulin levels were measured by ELISA in sputum specimens collected from 14 hospitalized children with asthma during an acute asthma attack, 13 stable outpatients with asthma, 8 healthy control children, and 7 children with respiratory tract infections. The effects of EGF and amphiregulin on the proliferation and/or differentiation of normal human bronchial epithelial cells (NHBE), bronchial smooth muscle cells (BSMC), and normal human lung fibroblasts (NHLF) were examined.

RESULTS

The sputum levels of EGF were significantly higher for about a week after an acute asthma attack compared with the levels in stable subjects with asthma and control subjects. In contrast, upregulation of amphiregulin in the sputa of patients with asthma was observed only during the acute attack. EGF caused proliferation of NHBE, BSMC, and NHLF, whereas amphiregulin induced proliferation of only NHBE. Prolonged exposure of NHBE to EGF and amphiregulin induced mucous cell metaplasia in an IL-13-independent manner.

CONCLUSION

Acute asthma attacks are associated with hypersecretion of EGF and amphiregulin in the airway. Recurrent acute attacks may aggravate airway remodeling.