Expression of SPLUNC1 protein in nasal polyp epithelial cells in air-liquid interface culture treated with IL-13

Phenotype overlap in the natural history of asthma

The heterogeneity of asthma makes it challenging to unravel the pathophysiologic mechanisms of the disease. Despite the wealth of research identifying diverse phenotypes, many gaps still remain in our knowledge of the disease's complexity. A crucial aspect is the impact of airborne factors over a lifetime, which often results in a complex overlap of phenotypes associated with type 2 (T2), non-T2 and mixed inflammation. Evidence now shows overlaps between the phenotypes associated with T2, non-T2 and mixed T2/non-T2 inflammation. These interconnections could be induced by different determinants such as recurrent infections, environmental factors, T-helper plasticity and comorbidities, collectively resulting in a complex network of distinct pathways generally considered as mutually exclusive. In this scenario, we need to abandon the concept of asthma as a disease characterised by distinct traits grouped into static segregated categories. It is now evident that there are multiple interplays between the various physiologic, cellular and molecular features of asthma, and the overlap of phenotypes cannot be ignored.

Expression of Oxidative Stress and Inflammation-Related Genes in Nasal Mucosa and Nasal Polyps from Patients with Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a prevalent, multifaceted inflammatory condition affecting the nasal cavity and the paranasal sinuses, frequently accompanied by formation of nasal polyps (CRSwNP). This apparently uniform clinical entity is preceded by heterogeneous changes in cellular and molecular patterns, suggesting the presence of multiple CRS endotypes and a diverse etiology. Alterations of the upper airway innate defense mechanisms, including antimicrobial and antioxidant capacity, have been implicated in CRSwNP etiology. The aim of this study was to investigate mRNA expression patterns of antioxidative enzymes, including superoxide dismutase (SOD) and peroxiredoxin-2 (PRDX2), and innate immune system defense players, namely the bactericidal/permeability-increasing fold-containing family A, member 1 (BPIFA1) and PACAP family members, particularly adenylate-cyclase-activating polypeptide receptor 1 (ADCYAP1) in nasal mucosa and nasal polyps from CRSwNP patients. Additional stratification based on age, sex, allergic comorbidity, and disease severity was applied. The results showed that ADCYAP1, BPIFA1, and PRDX2 transcripts are differentially expressed in nasal mucosa and scale with radiologically assessed disease severity in CRSwNP patients. Sinonasal transcriptome is not associated with age, sex, and smoking in CRSwNP. Surgical and postoperative corticosteroid (CS) therapy improves endoscopic appearance of the mucosa, but variably reverses target gene expression patterns in the nasal cavity of CRSwNP patients. Transcriptional cross-correlations analysis revealed an increased level of connectedness among differentially expressed genes under inflammatory conditions and restoration of basic network following CS treatment. Although results of the present study imply a possible engagement of ADCYAP1 and BPIFA1 as biomarkers for CRSwNP, a more profound study taking into account disease severity and CRSwNP endotypes prior to the treatment would provide additional information on their sensitivity.

The Multifunctional Roles of Short Palate, Lung, and Nasal Epithelium Clone 1 in Regulating Airway Surface Liquid and Participating in Airway Host Defense

Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) is a kind of secretory protein, and gets expressed abundantly in normal respiratory epithelium of humans. As a natural immune molecule, SPLUNC1 is proved to be involved in inflammatory response and airway host defense. This review focuses on summarizing and discussing the role of SPLUNC1 in regulating airway surface liquid (ASL) and participating in airway host defense. PubMed and MEDLINE were used for searching and identifying the data in this review. The domain of bactericidal/permeability-increasing protein in SPLUNC1 and the α-helix, α4, are essential for SPLUNC1 to exert biological activities. As a natural innate immune molecule, SPLUNC1 plays a significant role in inflammatory response and airway host defense. Its special expression patterns are not only observed in physiological conditions, but also in some respiratory diseases. The mechanisms of SPLUNC1 in airway host defense include modulating ASL volume, acting as a surfactant protein, inhibiting biofilm formation, as well as regulating ASL compositions, such as LL-37, mucins, Neutrophil elastase, and inflammatory cytokines. Besides, potential correlations are found among these different mechanisms, especially among different ASL compositions, which should be further explored in more systematical frameworks. In this review, we summarize the structural characteristics and expression patterns of SPLUNC1 briefly, and mainly discuss the mechanisms of SPLUNC1 exerted in host defense, aiming to provide a theoretical basis and a novel target for future studies and clinical treatments.

Therapeutic effects of recombinant SPLUNC1 on Mycoplasma ovipneumoniae-infected Argali hybrid sheep

Clinical therapeutic and immunoregulatory effects of recombinant SPLUNC1 protein (rSPLUNC1) were evaluated in Mycoplasma ovipneumoniae (Mo)-infected Argali hybrid sheep (AHS). Group A contained six Bashibai sheep (BS) and groups B-D contained six AHS each. All sheep were manually infected with Mo. Five days post-infection, rSPLUNC1 from BS and AHS was injected intratracheally into group C and D animals; physiological saline was administered to groups A and B. Serum IL-5, IL-6, and IL-9 were quantified by ELISA. After sacrificing the sheep, lung tissues were extracted for pathological examination. The qPCR was used to quantify Mo load in the lungs and evaluate therapeutic efficacy. Serum IL-5, IL-6, and IL-9 concentrations increased during early infection stages in all groups but were significantly lower in groups A, C, and D than in group B on days 14 and 21. On day 21, IL-5 concentrations were lower in group A than in groups C and D. IL-6 concentration in groups A, C, and D was significantly lower than that in group B, and that in groups C and D was significantly lower than that in group A. Mean mycoplasma pneumonia histopathology scores were significantly lower in groups C and D than in group B, and Mo load in group C and D lung tissue decreased significantly compared to that in group B. Intratracheal injection of rSPLUNC1 into Mo-infected sheep decreased the cytokine levels and alleviated clinical symptoms with no mortality. rSPLUNC1 had significant therapeutic effects on Mo-infected AHS and can regulate pro-inflammatory cytokines.

The effect of BPIFA1/SPLUNC1 genetic variation on its expression and function in asthmatic airway epithelium

Bacterial permeability family member A1 (BPIFA1), also known as short palate, lung, and nasal epithelium clone 1 (SPLUNC1), is a protein involved in the antiinflammatory response. The goal of this study was to determine whether BPIFA1 expression in asthmatic airways is regulated by genetic variations, altering epithelial responses to type 2 cytokines (e.g., IL-13). Nasal epithelial cells from patients with mild to severe asthma were collected from the National Heart, Lung, and Blood Institute Severe Asthma Research Program centers, genotyped for rs750064, and measured for BPIFA1. To determine the function of rs750064, cells were cultured at air-liquid interface and treated with IL-13 with or without recombinant human BPIFA1 (rhBPIFA1). Noncultured nasal cells with the rs750064 CC genotype had significantly less BPIFA1 mRNA expression than the CT and TT genotypes. Cultured CC versus CT and TT cells without stimulation maintained less BPIFA1 expression. With IL-13 treatment, CC genotype cells secreted more eotaxin-3 than CT and TT genotype cells. Also, rhBPIFA1 reduced IL-13-mediated eotaxin-3. BPIFA1 mRNA levels negatively correlated with serum IgE and fractional exhaled nitric oxide. Baseline FEV1% levels were lower in the asthma patients with the CC genotype (n = 1,016). Our data suggest that less BPIFA1 in asthma patients with the CC allele may predispose them to greater eosinophilic inflammation, which could be attenuated by rhBPIFA1 protein therapy.

The Role of BPIFA1 in Upper Airway Microbial Infections and Correlated Diseases

The mucosa is part of the first line of immune defense against pathogen exposure in humans and prevents viral and bacterial infection of the soft palate, lungs, uvula, and nasal cavity that comprise the ear-nose-throat (ENT) region. Bactericidal/permeability-increasing fold containing family A, member 1 (BPIFA1) is a secretory protein found in human upper aerodigestive tract mucosa. This innate material is secreted in mucosal fluid or found in submucosal tissue in the human soft palate, lung, uvula, and nasal cavity. BPIFA1 is a critical component of the innate immune response that prevents upper airway diseases. This review will provide a brief introduction of the roles of BPIFA1 in the upper airway (with a focus on the nasal cavity, sinus, and middle ear), specifically its history, identification, distribution in various human tissues, function, and diagnostic value in various upper airway infectious diseases.

Modelling upper respiratory tract diseases: getting grips on host-microbe interactions in chronic rhinosinusitis using in vitro technologies

Chronic rhinosinusitis (CRS) is a chronic inflammation of the mucosa of the nose and paranasal sinuses affecting approximately 11% of the adult population in Europe. Inadequate immune responses, as well as a dysbiosis of the sinonasal microbiota, have been put forward as aetiological factors of the disease. However, despite the prevalence of this disease, there is no consensus on the aetiology and mechanisms of pathogenesis of CRS. Further research requires in vitro models mimicking the healthy and diseased host environment along with the sinonasal microbiota. This review aims to provide an overview of CRS model systems and proposes in vitro modelling strategies to conduct mechanistic research in an ecological framework on the sinonasal microbiota and its interactions with the host in health and CRS.

IL-13 regulates human nasal epithelial cell differentiation via H3K4me3 modification

Introduction

Epigenetic regulation has been shown to play an important role in the development of inflammatory diseases, including chronic rhinosinusitis and nasal polyps. The latter are characterized by epithelial mis-differentiation and infiltration of inflammatory cytokines. H3K4me3 has been shown to be involved in regulating lineage commitment. However, the underlying mechanisms, especially in human nasal epithelial cells (HNEpC), remain underexplored. The objective of this study was to investigate the role of H3K4me3 in HNEpC differentiation treated with the Th2 cytokine IL-13.

Patients and methods

The expression levels of mRNA and proteins were investigated using reverse transcription-polymerase chain reaction (RT-PCR) assays and Western blot in nasal polyp tissues and human nasal epithelial cells respectively. We measured these levels of H3K4me3, MLL1 and targeted genes compared with control subjects.

Results

We demonstrate that expression of H3K4me3 and its methyltransferase MLL1 was significantly upregulated in IL-13-treated HNEpC. This elevation was also observed in nasal polyps. Expression of cilia-related transcription factors FOXJ1 and DNAI2 decreased, while goblet cell-derived genes CLCA1 and MUC5a increased upon IL-13 treatment. Mechanistically, knockdown of MLL1 restored expression of these four genes induced by IL-13.

Conclusion

These findings suggest that H3K4me3 is a critical regulator in control of nasal epithelial cell differentiation. MLL1 may be a potential therapeutic target for nasal inflammatory diseases.

Differential short palate, lung, and nasal epithelial clone 1 suppression in eosinophilic and noneosinophilic chronic rhinosinusitis with nasal polyps: implications for pathogenesis and treatment

PURPOSE OF REVIEW

Short palate, lung, and nasal epithelial clone 1 (SPLUNC1) is an epithelium-secreted protein that is involved in innate immunity. A protective role for SPLUNC1 in lower respiratory inflammation and chronic rhinosinusitis (CRS) has recently been recognized.

RECENT FINDINGS

An impaired epithelial immune barrier has been proposed to play a critical role in the pathogenesis of CRS. Recent research has demonstrated that SPLUNC1 is profoundly reduced in polyp tissues of CRS with nasal polyps (CRSwNP) compared with control tissues. Studies investigating the differential expression of SPLUNC1 in eosinophilic and noneosinophilic CRSwNP have been published. Nasal SPLUNC1 expression was inhibited by Th2 cytokines (IL-4 and IL-13) but was stimulated by toll-like receptor (TLR) agonists and glucocorticoids. Decreased SPLUNC1 expression in the sinus mucosa is associated with positive Pseudomonas aeruginosa bacterial colonization and poor surgical outcomes in CRS patients.

SUMMARY

These studies identify the role of SPLUNC1 in sinonasal innate immunity and the pathogenesis of CRS. Defective expression of SPLUNC1 in CRSwNP patients may lead to insufficient maintenance of the epithelial barrier function and enhanced bacterial colonization. The use of SPLUNC1 as a therapeutic target for CRSwNP remains to be determined.

Interleukin-13 Inhibits Lipopolysaccharide-Induced BPIFA1 Expression in Nasal Epithelial Cells

Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) protein is expressed in human nasopharyngeal and respiratory epithelium and has demonstrated antimicrobial activity. SPLUNC1 is now referred to as bactericidal/permeability-increasing fold containing family A, member 1 (BPIFA1). Reduced BPIFA1 expression is associated with bacterial colonization in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). Interleukin 13 (IL-13), predominately secreted by T helper 2 (T_H2) cells, has been found to contribute to airway allergies and suppress BPIFA1 expression in nasal epithelial cells. However, the molecular mechanism of IL-13 perturbation of bacterial infection and BPIFA1 expression in host airways remains unclear. In this study, we found that lipopolysaccharide (LPS)-induced BPIFA1 expression in nasal epithelial cells was mediated through the JNK/c-Jun signaling pathway and AP-1 activation. We further demonstrated that IL-13 downregulated the LPS-induced activation of phosphorylated JNK and c-Jun, followed by attenuation of BPIFA1 expression. Moreover, the immunohistochemical analysis showed that IL-13 prominently suppressed BPIFA1 expression in eosinophilic CRSwNP patients with bacterial infection. Taken together, these results suggest that IL-13 plays a critical role in attenuation of bacteria-induced BPIFA1 expression that may result in eosinophilic CRSwNP.

New insights on the palate, lung, and nasal epithelium clone (PLUNC) proteins: Based on molecular and functional analysis of its homolog of YH1/SPLUNC1

The palate, lung, and nasal epithelium clone (PLUNC) proteins are intricate immune molecules and arisen questions from them are still unresolved. In order to identify the role of PLUNC family proteins, we had analyzed its homolog protein YH1/SPLUNC1, which highly expresses in nontumor nasopharyngeal epithelium while expresses weakly in nasopharyngeal carcinoma (NPC) tissues. It is found that YH1/SPLUNC1 protein expression level was higher in chronic normal nasopharynx inflammatory cells compared to NPC tissue cells. An approach to produce active YH1/SPLUNC1 protein had been established and recombinant YH1/SPLUNC1 protein could bind to all four Gram-positive and four Gram-negative bacteria we tested, and triggered the aggregation of those bacteria. Interestingly, YH1/SPLUNC1 protein has antimicrobial activity, and it can directly kill Escherichia coli and Acinetobacter haemolyticus. The microorganism cell showed morphological changes in cell wall such as cell damage and cytoplasmic leakage after exposure to YH1/SPLUNC1 protein, indicating that YH1/SPLUNC1 directly killed the microorganisms by cell wall permeabilization. All these results indicated that YH1/SPLUNC1 might be an important antimicrobial protein involved in innate immunity defense.

The distribution of human surfactant proteins within the oral cavity and their role during infectious diseases of the gingiva

The oral cavity with the teeth and the surrounding gingival epithelium, the periodontium, the salivary glands and other structures are open to the oral environment and thus exposed to multiple microbiological and pathogenic influences. To prevent permanent inflammatory processes such as gingivitis or periodontitis an efficient defense system is essential to ensure healthy and physiological function of the oral cavity and other interacting organic systems. Surfactant proteins (SPs), originally found in pulmonary tissue are important factors of the immune system and beyond this, support the stability and rheology of gas or fluid interfaces. This study aimed to analyze the distribution of surfactant proteins by means of Western blot and immunohistochemistry in salivary glands as well as in healthy and pathological saliva. The different expression patterns of SP-A, -B, -C and -D in healthy and pathological (periodontitis) saliva were determined using ELISA quantification. One further objective of the study was the first detection of two recent discovered proteins belonging to the surfactant protein family within human salivary glands and saliva. The results of the study reveal differences in protein expression of SP-A, -B, -C and -D within healthy and pathologic saliva. The concentration of the surfactant proteins SP-A, SP-C and SP-D is increased in saliva of people suffering from periodontal diseases, whereas by contrast, SP-B shows an opposite expression pattern. Furthermore, the results evidence the presence of SP-G and SP-H within saliva and salivary glands for the first time.

Advances in asthma drug discovery: evaluating the potential of nasal cell sampling and beyond

INTRODUCTION

Inhaled corticosteroid anti-inflammatory therapy is effective at controlling disease symptoms of asthma, but a subset of patients remains symptomatic despite optimal treatment, creating a clear unmet medical need. Moreover, none of the currently available drugs for asthma are really disease-modifying or curative. Although murine models of asthma, based on transgenic and knockout animals, may offer an integrated pathophysiological system for studying the characteristics of airway inflammation and hyperresponsiveness, these alterations are noteworthily different compared with those observed in asthmatic patients. Since a clear functional and inflammatory relationship between the nasal mucosa and bronchial tissue in patients suffering from asthma and allergic rhinitis has been recognized, using preclinical models based on human nasal cells sampling might support a prompt and effective anti-inflammatory drug discovery in asthma.

AREAS COVERED

The authors provide a review, which discusses the potential role of nasal cell sampling and its application in advanced drug discovery for asthma. The contents range from the similarities and differences between asthma and allergic rhinitis up to artificial airway models based on sophisticated human lung-on-a-chip devices.

EXPERT OPINION

Nasal cell sampling and processing have reached a great potential in asthma drug discovery. The authors believe that models of asthma, which are based on human nasal cells, can provide valuable indications of proof of pharmacological and potential therapeutic efficacy in both preclinical and early clinical settings.

Short palate, lung, and nasal epithelial clone-1 is a tightly regulated airway sensor in innate and adaptive immunity

Short palate, lung, and nasal epithelial clone-1 (SPLUNC1) is a protein abundantly expressed by the respiratory epithelium of the proximal lower respiratory tract, a site of great environmental exposure. Previous studies showed that SPLUNC1 exerts antimicrobial effects, regulates airway surface liquid and mucociliary clearance, and suppresses allergic airway inflammation. We studied SPLUNC1 to gain insights into its role in host defense. In the lower respiratory tract, concentrations of SPLUNC1 are high under basal conditions. In models of pneumonia caused by common respiratory pathogens, and in Th1-induced and Th2-induced airway inflammation, SPLUNC1 secretion is markedly reduced. Pathogen-associated molecular patterns and IFN-γ act directly on airway epithelial cells to inhibit SPLUNC1 mRNA expression. Thus, SPLUNC1 is quickly suppressed during infection, in response to an insult on the epithelial surface. These experiments highlight the finely tuned fluctuations of SPLUNC1 in response to exposures in the respiratory tract, and suggest that the loss of SPLUNC1 is a crucial feature of host defense across air-breathing animal species.

Decreased PLUNC expression in nasal polyps is associated with multibacterial colonization in chronic rhinosinusitis patients

PLUNC (palate, lung, and nasal epithelium clone) is an epithelium-secreted protein that plays a crucial role in the host's defense against bacterial infection. The function of PLUNC in the sinus remains poorly understood. To examine whether the expression levels of PLUNC could serve as a predictive outcome biomarker for patients with CRSwNP and bacterial colonization, we investigated the association of PLUNC expression levels with bacterial colonization in the sinuses. A total of 174 patients who underwent sinus surgery for chronic rhinosinusitis with nasal polyps (CRSwNP) were enrolled in this study. The tissue samples obtained from patients were examined using preoperative sinus computed tomography (CT) scans, postoperative bacterial cultures, and nasal polyp examinations. PLUNC mRNA and protein expression were quantified using RT-PCR and immunohistochemistry. We identified that decreased PLUNC expression is associated with multibacterial colonization (P = 0.0001), specifically those mediated by Staphyloccocus aureus (P = 0.037) and Pseudomonas aeruginosa (P = 0.002). The patients who required repeated sinus surgeries for recurrent or persistent sinusitis also presented much lower PLUNC expression than those who did not require repeated sinus surgery (P = 0.001). However, gender, age, and CT scores were not associated with PLUNC expression. These results suggest that reduced PLUNC expression is associated with bacterial colonization as well as treatment outcome in CRSwNP patients. Investigation of the association between PLUNC expressions and chronic rhinosinusitis may lead to the development of a novel biomarker for treatment outcome in CRSwNP patients.

Interleukin 13 exposure enhances vitamin D-mediated expression of the human cathelicidin antimicrobial peptide 18/LL-37 in bronchial epithelial cells

Vitamin D is an important regulator of the expression of antimicrobial peptides, and vitamin D deficiency is associated with respiratory infections. Regulating expression of antimicrobial peptides, such as the human cathelicidin antimicrobial peptide 18 (hCAP18)/LL-37, by vitamin D in bronchial epithelial cells requires local conversion of 25(OH)-vitamin D(3) (25D(3)) into its bioactive metabolite, 1,25(OH)(2)-vitamin D(3) (1,25D(3)), by CYP27B1. Low circulating vitamin D levels in childhood asthma are associated with more-severe exacerbations, which are often associated with infections. Atopic asthma is accompanied by Th2-driven inflammation mediated by cytokines such as interleukin 4 (IL-4) and IL-13, and the effect of these cytokines on vitamin D metabolism and hCAP18/LL-37 expression is unknown. Therefore, we investigated this with well-differentiated bronchial epithelial cells. To this end, cells were treated with IL-13 with and without 25D(3), and expression of hCAP18/LL-37, CYP27B1, the 1,25D(3)-inactivating enzyme CYP24A1, and vitamin D receptor was assessed by quantitative PCR. We show that IL-13 enhances the ability of 25D(3) to increase expression of hCAP18/LL-37 and CYP24A1. In addition, exposure to IL-13 resulted in increased CYP27B1 expression, whereas vitamin D receptor (VDR) expression was not significantly affected. The enhancing effect of IL-13 on 25D(3)-mediated expression of hCAP18/LL-37 was further confirmed using SDS-PAGE Western blotting and immunofluorescence staining. In conclusion, we demonstrate that IL-13 induces vitamin D-dependent hCAP18/LL-37 expression, most likely by increasing CYP27B1. These data suggest that Th2 cytokines regulate the vitamin D metabolic pathway in bronchial epithelial cells.

The use of nasal epithelial stem/progenitor cells to produce functioning ciliated cells in vitro

BACKGROUND

Although epithelial stem/progenitor cells have been isolated from many parts of the human airway epithelium such as lung and trachea, there is limited information in regard to stem cells in nasal epithelium. The aim of this study was to determine if (1) human nasal epithelial stem/progenitor cells (hNESPCs) can be isolated and propagated in vitro and (2) allogeneic adult primary human fibroblasts can serve as a feeder layer for hNESPCs expansion under serum-free conditions.

METHODS

Primary cells taken from inferior turbinate biopsy specimens (n = 3) were enzymically dissociated and plated on either allogeneic human fibroblasts or murine NIH 3T3 fibroblasts, in a chemical-defined medium supplemented with growth factors. Self-renewal, proliferation, and differentiation potential were compared.

RESULTS

The optimized media were capable of supporting the undifferentiated growth and expansion of hNESPCs on both feeder cells. The doubling time and cloning efficiency of hNESPCs cultured on a human feeder layer were comparable with that cultured on 3T3 feeders. Significantly, the hNESPCs on both feeder layers could be cultured for four passages, and they can differentiate into ciliated columnar cells and goblet cells at the air-liquid interface, resembling the in vivo mucociliary airway epithelium.

CONCLUSION

Our results showed the feasibility of expanding hNESPCs for clinical purpose by using human feeder layer, avoiding components of animal source, while preserving their self-renewal and differentiation potential. This study represents an early step toward a better understanding of hNESPCs, and serum -free media plus human feeder potentially would be an ideal method for making clinical grade hNESPCs on a large scale.

Oxidative stress induces unfolding protein response and inflammation in nasal polyposis

BACKGROUND

Nasal polyposis, a chronic inflammatory disease affecting the upper airways, is a valuable and accessible model to investigate the mechanisms underlying chronic inflammation. The main objective of this study was to investigate a potential involvement of the unfolded protein response (UPR) in the context of oxidative stress and inflammation in nasal epithelial cells from nasal polyps (NP).

METHODS

Epithelial cells from NP (n = 20) and normal mucosa (Controls, n = 15) in primary culture were analyzed by global proteomic approach and cell biology techniques for the glucose-regulated protein 78 (GRP78), the spliced X-box-binding protein 1 (sXBP-1), the glucose-regulated protein 94 (GRP94), and the calreticulin (immunoblot, mass spectrometry, immunocytochemistry).

RESULTS

Proteomics analysis of human nasal epithelial cells in culture revealed the activation of the unfolded protein response in NP. Systematic cell biology and biochemical analysis of two markers (GRP78, sXBP-1) in the presence and absence of oxidative stress in NP showed a susceptibility of the unfolded protein response to oxidative stress compared to controls at least partially linked to an abnormal redox state of the protein disulfide-isomerase 4. This unfolded protein response was correlated with mitochondrial depolarization and secretion of interleukin 8 (IL-8) and leukotriene B4 (LTB4) and was prevented by mitochondrial antioxidant.

CONCLUSIONS

We show the existence of UPR in nasal epithelial cells that is linked to oxidative stress leading to IL-8 and LTB4 secretions. These mechanisms may participate in chronic inflammation in nasal polyposis.

IL-13 dampens human airway epithelial innate immunity through induction of IL-1 receptor-associated kinase M

BACKGROUND

Impaired airway mucosal immunity can contribute to increased respiratory tract infections in asthmatic patients, but the involved molecular mechanisms have not been fully clarified. Airway epithelial cells serve as the first line of respiratory mucosal defense to eliminate inhaled pathogens through various mechanisms, including Toll-like receptor (TLR) pathways. Our previous studies suggest that impaired TLR2 function in T(H)2 cytokine-exposed airways might decrease immune responses to pathogens and subsequently exacerbate allergic inflammation. IL-1 receptor-associated kinase M (IRAK-M) negatively regulates TLR signaling. However, IRAK-M expression in airway epithelium from asthmatic patients and its functions under a T(H)2 cytokine milieu remain unclear.

OBJECTIVES

We sought to evaluate the role of IRAK-M in IL-13-inhibited TLR2 signaling in human airway epithelial cells.

METHODS

We examined IRAK-M protein expression in epithelia from asthmatic patients versus that in normal airway epithelia. Moreover, IRAK-M regulation and function in modulating innate immunity (eg, TLR2 signaling) were investigated in cultured human airway epithelial cells with or without IL-13 stimulation.

RESULTS

IRAK-M protein levels were increased in asthmatic airway epithelium. Furthermore, in primary human airway epithelial cells, IL-13 consistently upregulated IRAK-M expression, largely through activation of phosphoinositide 3-kinase pathway. Specifically, phosphoinositide 3-kinase activation led to c-Jun binding to human IRAK-M gene promoter and IRAK-M upregulation. Functionally, IL-13-induced IRAK-M suppressed airway epithelial TLR2 signaling activation (eg, TLR2 and human β-defensin 2), partly through inhibiting activation of nuclear factor κB.

CONCLUSIONS

Our data indicate that epithelial IRAK-M overexpression in T(H)2 cytokine-exposed airways inhibits TLR2 signaling, providing a novel mechanism for the increased susceptibility of infections in asthmatic patients.

Distribution of human PLUNC/BPI fold-containing (BPIF) proteins

Although gene expression studies have shown that human PLUNC (palate, lung and nasal epithelium clone) proteins are predominantly expressed in the upper airways, nose and mouth, and proteomic studies have indicated they are secreted into airway and nasal lining fluids and saliva, there is currently little information concerning the localization of human PLUNC proteins. Our studies have focused on the localization of three members of this protein family, namely SPLUNC1 (short PLUNC1), SPLUNC2 and LPLUNC1 (long PLUNC1). Western blotting has indicated that PLUNC proteins are highly glycosylated, whereas immunohistochemical analysis demonstrated distinct patterns of expression. For example, SPLUNC2 is expressed in serous cells of the major salivary glands and in minor mucosal glands, whereas SPLUNC1 is expressed in the mucous cells of these glands. LPLUNC1 is a product of a population of goblet cells in the airway epithelium and nasal passages and expressed in airway submucosal glands and minor glands of the oral and nasal cavities. SPLUNC1 is also found in the epithelium of the upper airways and nasal passages and in airway submucosal glands, but is not co-expressed with LPLUNC1. We suggest that this differential expression may be reflected in the function of individual PLUNC proteins.

Up-regulation of MUC18 in airway epithelial cells by IL-13: implications in bacterial adherence

Airway bacterial infections are a major problem in lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. Increased Th2 cytokines, such as IL-13, are observed in lung diseases and may contribute to bacterial infections. How Th2 cytokines affect bacterial infection remains unknown. MUC18, an adhesion molecule shown to be involved in the pathogenesis of malignant melanoma, has been recently identified in airway epithelial cells of patients with COPD. We investigated MUC18 regulation by IL-13 and the role of MUC18 in bacterial adherence to epithelial cells. Human airway tissues, brushed bronchial epithelial cells from normal subjects and subjects with asthma, and epithelial cell lines (e.g., HEK293 cells) were used to study the regulation of MUC18 by IL-13 and the involvement of MUC18 in bacterial (e.g., Mycoplasma pneumoniae [Mp] and nontypeable Haemophilus influenzae [NTHi]) adherence to epithelial cells. Asthmatic bronchial epithelium expressed higher levels of MUC18 than normal bronchial epithelium. IL-13 increased MUC18 in cultured bronchial epithelial cells from normal subjects and particularly from subjects with asthma. IL-13-induced MUC18 expression may be modulated in part through transcription factor specificity protein 1. Overexpression of human MUC18 in HEK293 cells increased cell-associated Mp and NTHi levels. Moreover, MUC18 was shown to directly interact with Mp and NTHi. These results for the first time show that an allergic airway milieu (e.g., IL-13) increases MUC18 expression, which may contribute to increased bacterial infection/colonization in asthma and other lung diseases.

SPLUNC1 regulation in airway epithelial cells: role of Toll-like receptor 2 signaling

Background

Respiratory infections including Mycoplasma pneumoniae (Mp) contribute to various chronic lung diseases. We have shown that mouse short palate, lung, and nasal epithelium clone 1 (SPLUNC1) protein was able to inhibit Mp growth. Further, airway epithelial cells increased SPLUNC1 expression upon Mp infection. However, the mechanisms underlying SPLUNC1 regulation remain unknown. In the current study, we investigated if SPLUNC1 production following Mp infection is regulated through Toll-like receptor 2 (TLR2) signaling.

Methods

Airway epithelial cell cultures were utilized to reveal the contribution of TLR2 signaling including NF-κB to SPLUNC1 production upon bacterial infection and TLR2 agonist stimulation.

Results

Mp and TLR2 agonist Pam3CSK4 increased SPLUNC1 expression in tracheal epithelial cells from wild type, but not TLR2^-/- BALB/c mice. RNA interference (short-hairpin RNA) of TLR2 in normal human bronchial epithelial cells under air-liquid interface cultures significantly reduced SPLUNC1 levels in Mp-infected or Pam3CSK4-treated cells. Inhibition and activation of NF-κB pathway decreased and increased SPLUNC1 production in airway epithelial cells, respectively.

Conclusions

Our data for the first time suggest that airway epithelial TLR2 signaling is pivotal in mycoplasma-induced SPLUNC1 production, thus improving our understanding of the aberrant SPLUNC1 expression in airways of patients suffering from chronic lung diseases with bacterial infections.

Staphylococcus aureus invades the epithelium in nasal polyposis and induces IL-6 in nasal epithelial cells in vitro

BACKGROUND

Staphylococcus aureus has been associated with chronic rhinosinusitis with nasal polyps (CRSwNP) pathogenesis but its role is still controversially discussed. Here, we demonstrate S. aureus detection in the mucosa of CRSwNP. In addition, intracellular residency of S. aureus in nasal polyp epithelial cells (NPECs) and its capability to induce TH-2 cytokines were analyzed in vitro.

METHODS

Staphylococcus aureus detection in CRSwNP (n = 25), CRS without polyps (CRSsNP, n = 5), and turbinate mucosa (TM, n = 10) was performed by peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) and microbial cultivation from tissue biopsies. Intracellular residency was examined by intracellular persistence assay and electron microscopy. IL-6 and IL-13 responses to S. aureus infection and supernatants were quantified by ELISA.

RESULTS

Peptide nucleic acid-fluorescence in situ hybridization positive bacterial cells were significantly increased in the epithelium of CRSwNP (17/25) compared to CRSsNP (0/5) and TM (1/10). Good concordance of PNA-FISH results and S. aureus cultivation was found applying Cohen's κ for CRSwNP (κ = 0.841) and TM (κ = 1.0). Intracellular persistence assay with S. aureus strain Newman and its corresponding small-colony variant mutant strain III33 demonstrated intracellular survival and replication of S. aureus within NPECs. Both S. aureus strains significantly induced IL-6 but not IL-13 in infected NPECs and in NPECs challenged with corresponding staphylococcal supernatants.

CONCLUSION

Invasion of the epithelium by S. aureus was a phenomenon seen predominantly in CRSwNP. Regardless of an intra- or extracellular localization in the epithelium, S. aureus is capable to induce IL-6 synthesis in vitro and thus may contribute to the TH-2 cytokine pattern in CRSwNP.

beta2-agonists promote host defense against bacterial infection in primary human bronchial epithelial cells

Background

Airway epithelial cells are critical in host defense against bacteria including Mycoplasma pneumoniae (Mp) in chronic obstructive pulmonary disease (COPD) and asthma. β2-agonists are mainstay of COPD and asthma therapy, but whether β2-agonists directly affect airway epithelial host defense functions is unclear.

Methods

Epithelial cells from bronchial brushings of normal (n = 8), asthma (n = 8) and COPD (n = 8) subjects were grown in air-liquid interface cultures, and treated with cigarette smoke extract (CSE) and/or Th2 cytokine IL-13, followed by Mp infection and treatment with β2-agonists albuterol and formoterol for up to seven days. Mp and host defense proteins short palate, lung, and nasal epithelial clone 1 (SPLUNC1) and β-defensin-2 were quantified. Expression of β2-adrenergic receptors was also measured by real-time quantitative RT-PCR.

Results

(R)- or racemic albuterol and (R,R)- or racemic formoterol significantly decreased Mp levels in normal and asthma epithelial cells. Normal cells treated with Mp and (R)- or racemic albuterol showed an increase in SPLUNC1, but not in β-defensin-2. COPD cells did not respond to drug treatment with a significant decrease in Mp or an increase in SPLUNC1. IL-13 attenuated drug effects on Mp, and markedly decreased SPLUNC1 and β2-adrenergic receptors.

Conclusions

These results for the first time show that β2-agonists enhance host defense functions of primary bronchial epithelial cells from normal and asthma subjects, which is attenuated by IL-13.