Antimicrobial activity of PLUNC protects against Pseudomonas aeruginosa infection

PLUNC inhibits invasion and metastasis in nasopharyngeal carcinoma by inhibiting NLRP3 inflammasome activation

Nasopharyngeal carcinoma (NPC) is a malignant tumor that occurs in the nasopharynx. Palate, lung, and nasal epithelium clone (PLUNC) has been identified as an early secreted protein that is specifically expressed in the nasopharynx. The aim of this study was to determine the role and mechanism of PLUNC in NPC. We used mRNA sequencing (seq) combined with ribosome-nascent chain complex (RNC)-seq to determine the biological role of PLUNC. The expression of epithelial-to-mesenchymal transition (EMT)-related molecules was detected by western blotting. Then, cell migration and invasion were detected by wound healing and Transwell chamber assays. NPC cells were injected into the tail vein of nude mice to explore the biological role of PLUNC in vivo. The sequencing results showed that PLUNC inhibited the progression of NPC and its expression was correlated with that of NOD-like receptors. Experiments confirmed that PLUNC inhibited the invasion and metastasis of NPC cells by promoting the ubiquitination degradation of NLRP3. PLUNC overexpression in combination with the treatment by MCC950, an inhibitor of NLRP3 inflammasome activation, was most effective in inhibiting NPC invasion and metastasis. In vivo experiments also confirmed that the combination of PLUNC overexpression and MCC950 treatment effectively inhibited the lung metastasis of NPC cells. In summary, our research suggested that PLUNC inhibited the invasion and metastasis of NPC by inhibiting NLRP3 inflammasome activation, and targeting the PLUNC-NLRP3 inflammasome axis could provide a new strategy for the diagnosis and treatment of NPC patients.

The roles of Braun Lipoprotein in inducing tolerance of bovine endometrium infected by Escherichia coli

Escherichia coli (E. coli), a Gram-negative bacterium, is the primary pathogen responsible for endometritis in dairy cattle. The outer membrane components of E. coli, namely lipopolysaccharide (LPS) and bacterial lipoprotein, have the capacity to trigger the host's innate immune response through pattern recognition receptors (PRRs). Tolerance to bacterial cell wall components, including LPS, may play a crucial role as an essential regulatory mechanism during bacterial infection. However, the precise role of Braun lipoprotein (BLP) tolerance in E. coli-induced endometritis in dairy cattle remains unclear. In this study, we aimed to investigate the impact of BLP on the regulation of E. coli infection-induced endometritis in dairy cattle. The presence of BLP was found to diminish the expression and release of proinflammatory cytokines (IL-8 and IL-6), while concurrently promoting the expression and release of the anti-inflammatory cytokine IL-10 in endometrial epithelial cells (EECs). Furthermore, BLP demonstrated the ability to impede the activation of MAPK (ERK and p38) and NF-κB (p65) signaling pathways, while simultaneously enhancing signaling through the STAT3 pathway in EECs. Notably, BLP exhibited a dual role, acting both as an activator of TLR2 and as a regulator of TLR2 activation in LPS- and E. coli-treated EECs. In E. coli-infected endometrial explants, the presence of BLP was noted to decrease the release of proinflammatory cytokines and the expression of HMGB1, while simultaneously enhancing the release of anti-inflammatory cytokines. Collectively, our findings provide evidence that the bacterial component BLP plays a protective role in E. coli-induced endometritis in dairy cattle.

Short Palate, Lung, and Nasal Epithelial Clone1 (SPLUNC1) level determines steroid-resistant airway inflammation in aging

Asthma and its heterogeneity change with age. Increased airspace neutrophil numbers contribute to severe steroid-resistant asthma exacerbation in the elderly, which correlates with the changes seen in adults with asthma. However, whether that resembles the same disease mechanism and pathophysiology in aged and adults is poorly understood. Here, we sought to address the underlying molecular mechanism of steroid-resistant airway inflammation development and response to corticosteroid (Dex) therapy in aged mice. To study the changes in inflammatory mechanism, we used a clinically relevant treatment model of house-dust mite (HDM)-induced allergic asthma and investigated lung adaptive immune response in adult (20–22 wk old) and aged (80–82 wk old) mice. Our result indicates an age-dependent increase in airway hyperresponsiveness (AHR), mixed granulomatous airway inflammation comprising eosinophils and neutrophils, and Th1/Th17 immune response with progressive decrease in frequencies and numbers of HDM-bearing dendritic cells (DC) accumulation in the draining lymph node (DLn) of aged mice as compared with adult mice. RNA-Seq experiments of the aged lung revealed short palate, lung, and nasal epithelial clone 1 (SPLUNC1) as one of the steroid-responsive genes, which progressively declined with age and further by HDM-induced inflammation. Moreover, we found increased glycolytic reprogramming, maturation/activation of DCs, the proliferation of OT-II cells, and Th2 cytokine secretion with recombinant SPLUNC1 (rSPLUNC1) treatment. Our results indicate a novel immunomodulatory role of SPLUNC1 regulating metabolic adaptation/maturation of DC. An age-dependent decline in the SPLUNC1 level may be involved in developing steroid-resistant airway inflammation and asthma heterogeneity.

Salivary BPIFA proteins are altered in patients undergoing hematopoietic cell transplantation

OBJECTIVE

The aim of this study was to evaluate the expression of BPIFA proteins in the saliva and salivary glands of hematopoietic cell transplant (HCT) patients.

MATERIAL AND METHODS

This longitudinal study included patients who had undergone autologous HCT (auto-HCT) and allogeneic HCT (allo-HCT), and unstimulated saliva was collected at three time points, with a fourth collection at oral chronic graft-versus-host disease (cGVHD) onset. BPIFA expression was analysed by Western blotting in saliva and immunostaining in the minor salivary glands of cGVHD patients.

RESULTS

Auto-HCT patients showed increased levels of BPIFA1 (p = .021) and BPIFA2 at D+7 (p = .040), whereas allo-HCT group demonstrated decreased expression of BPIFA2 at D+8 (p = .002) and at D+80 (p = .001) and a significant association between BPIFA2 low levels and hyposalivation was observed (p = .02). BPIFA2 was significantly lower in the cGVHD patients when compared to baseline (p = .04).

CONCLUSIONS

The results of this study show distinct pattern of expression of BPIF proteins in both auto-HCT and allo-HCT recipients with decreased levels of BPIFA2 during hyposalivation and cGVHD. Further studies are necessary to elucidate these proteins mechanisms and their clinical implications in these groups of patients.

A Rare Mutation in SPLUNC1 Affects Bacterial Adherence and Invasion in Meningococcal Disease

Background

Neisseria meningitidis (Nm) is a nasopharyngeal commensal carried by healthy individuals. However, invasive infections occurs in a minority of individuals, with devastating consequences. There is evidence that common polymorphisms are associated with invasive meningococcal disease (IMD), but the contributions of rare variants other than those in the complement system have not been determined.

Methods

We identified familial cases of IMD in the UK meningococcal disease study and the European Union Life-Threatening Infectious Disease Study. Candidate genetic variants were identified by whole-exome sequencing of 2 patients with familial IMD. Candidate variants were further validated by in vitro assays.

Results

Exomes of 2 siblings with IMD identified a novel heterozygous missense mutation in BPIFA1/SPLUNC1. Sequencing of 186 other nonfamilial cases identified another unrelated IMD patient with the same mutation. SPLUNC1 is an innate immune defense protein expressed in the nasopharyngeal epithelia; however, its role in invasive infections is unknown. In vitro assays demonstrated that recombinant SPLUNC1 protein inhibits biofilm formation by Nm, and impedes Nm adhesion and invasion of human airway cells. The dominant negative mutant recombinant SPLUNC1 (p.G22E) showed reduced antibiofilm activity, increased meningococcal adhesion, and increased invasion of cells, compared with wild-type SPLUNC1.

Conclusions

A mutation in SPLUNC1 affecting mucosal attachment, biofilm formation, and invasion of mucosal epithelial cells is a new genetic cause of meningococcal disease.

The SPLUNC1-βENaC complex prevents Burkholderia cenocepacia invasion in normal airway epithelia

Cystic fibrosis (CF) patients are extremely vulnerable to Burkholderia cepacia complex (Bcc) infections. However, the underlying etiology is poorly understood. We tested the hypothesis that short palate lung and nasal epithelial clone 1 (SPLUNC1)–epithelial sodium channel (ENaC) interactions at the plasma membrane are required to reduce Bcc burden in normal airways. To determine if SPLUNC1 was needed to reduce Bcc burden in the airways, SPLUNC1 knockout mice and their wild-type littermates were infected with B. cenocepacia strain J2315. SPLUNC1 knockout mice had increased bacterial burden in the lungs compared to wild-type littermate mice. SPLUNC1-knockdown primary human bronchial epithelia (HBECs) were incubated with J2315, which resulted in increased bacterial burden compared to non-transduced HBECs. We next determined the interaction of the SPLUNC1-ENaC complex during J2315 infection. SPLUNC1 remained at the apical plasma membrane of normal HBECs but less was present at the apical plasma membrane of CF HBECs. Additionally, SPLUNC1-βENaC complexes reduced intracellular J2315 burden. Our data indicate that (i) secreted SPLUNC1 is required to reduce J2315 burden in the airways and (ii) its interaction with ENaC prevents cellular invasion of J2315.

Bioinformatics Analysis and Identification of Underlying Biomarkers Potentially Linking Allergic Rhinitis and Asthma

Background

Rhinitis is the most common clinical manifestation of allergy, affecting more than 400 million people around the world. Rhinitis increases the risk of developing bronchial hyper-responsiveness and asthma. Previous studies have shown that rhinitis is closely related with the physiology, pathology, and pathogenesis of asthma. We analyzed co-expressed genes to explore the relationships between rhinitis and asthma and to find biomarkers of comorbid rhinitis and asthma.

Material/Methods

Asthma- and rhinitis-related differentially-expressed genes (DEGs) were identified by bioinformatic analysis of GSE104468 and GSE46171 datasets from the Gene Expression Omnibus (GEO) database. After assessment of Gene Ontology (GO) terms and pathway enrichment for DEGs, a protein–protein interaction (PPI) network was conducted via comprehensive target prediction and network analyses. We also evaluated co-expressed DEGs and corresponding predicted miRNAs involved in the developing process of rhinitis and asthma.

Results

We identified 687 and 1001 DEGs in bronchial and nasal epithelia samples of asthma patients, respectively. For patients with rhinitis, we found 245 DEGs. The hub-genes of PAX6, NMU, NTS, NMUR1, PMCH, and KRT6A may be associated with rhinitis, while CPA3, CTSG, POSTN, CLCA1, HDC, and MUC5B may be involved in asthma. The co-expressed DEGs of BPIFA1, CCL26, CPA3, and CST1, together with corresponding predicted miRNAs (e.g., miR-195-5p and miR-125a-3p) were found to be significantly correlated with rhinitis and asthma.

Conclusions

Rhinitis and asthma are related, and there are significant correlations of BPIFA1, CCL26, CPA3, and CST1 genes with novel biomarkers involved in the comorbidity of rhinitis and asthma.

LunX-CAR T Cells as a Targeted Therapy for Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) carries a high mortality, and efficacious therapy is lacking. Therapy using chimeric antigen receptor (CAR) T cells has been used efficaciously against hematologic malignancies, but the curative effect against solid tumors is not satisfactory. A lack of antigen targets is one of the main reasons for this limited efficacy. Previously, we showed that lung-specific X (LUNX; also known as BPIFA1, PLUNC, and SPLUNC1) is overexpressed in lung cancer cells. Here, we constructed a CAR-T-cell-based strategy to target LunX (CAR^LunX T cells). CAR T cells were developed so that, upon specific recognition of LunX, they secreted cytokines and killed LunX-positive NSCLC cells. In vitro, CAR^LunX T cells displayed enhanced toxicity toward NSCLC lines and production of cytokines and showed specific LunX-dependent recognition of NSCLC cells. Adoptive transfer of CAR^LunX T cells induced regression of established metastatic lung cancer xenografts and prolonged survival. CAR^LunX T cells could infiltrate into the tumor. Also, we constructed a patient-derived xenograft model of lung cancer. After therapy with CAR^LunX T cells, tumor growth was suppressed, and survival was prolonged significantly. Together, our findings offer preclinical evidence of the immunotherapeutic targeting of LunX as a strategy to treat NSCLC.

Mechanisms of Epithelial Immunity Evasion by Respiratory Bacterial Pathogens

Bacterial lung infections are major healthcare challenges killing millions of people worldwide and resulting in a huge economic burden. Both basic and clinical research have elucidated host mechanisms that contribute to the bacterial clearance where an indispensable role of immune cells has been established. However, the role of respiratory epithelial cells in bacterial clearance has garnered limited attention due to their weak inflammatory or phagocytic ability compared to immune cells such as macrophages and neutrophils. These studies often underappreciate the fact that epithelial cells are the most abundant cells in the lung, not only serving as building blocks but also providing immune protection throughout the lung. Epithelial cells function either independently to eradicate the pathogen or communicate with immune cells to orchestrate pathogen clearance. The epithelial cells have multiple mechanisms that include mucus production, antimicrobial peptide production, muco-ciliary clearance, and phagocytosis, all of which contribute to their direct antibacterial function. Secretion of cytokines to recruit immune cells and potentiate their antimicrobial activities is a pathway by which the epithelium contributes to bacterial clearance. Successful pathogens outsmart epithelial resistance and find a way to replicate in sufficient numbers to establish infections in the airway or lung epithelial surfaces. In this mini-review, we discuss evidences that establish important roles for epithelial host defense against invading respiratory bacterial pathogens and demonstrate how pathogens outsmart these epithelial immune mechanisms to successfully establish infection. Finally, we discuss briefly how to boost epithelial immunity to improve outcomes in bacterial lung infections.

Mechanisms of Epithelial Immunity Evasion by Respiratory Bacterial Pathogens

Bacterial lung infections are major healthcare challenges killing millions of people worldwide and resulting in a huge economic burden. Both basic and clinical research have elucidated host mechanisms that contribute to the bacterial clearance where an indispensable role of immune cells has been established. However, the role of respiratory epithelial cells in bacterial clearance has garnered limited attention due to their weak inflammatory or phagocytic ability compared to immune cells such as macrophages and neutrophils. These studies often underappreciate the fact that epithelial cells are the most abundant cells in the lung, not only serving as building blocks but also providing immune protection throughout the lung. Epithelial cells function either independently to eradicate the pathogen or communicate with immune cells to orchestrate pathogen clearance. The epithelial cells have multiple mechanisms that include mucus production, antimicrobial peptide production, muco-ciliary clearance, and phagocytosis, all of which contribute to their direct antibacterial function. Secretion of cytokines to recruit immune cells and potentiate their antimicrobial activities is a pathway by which the epithelium contributes to bacterial clearance. Successful pathogens outsmart epithelial resistance and find a way to replicate in sufficient numbers to establish infections in the airway or lung epithelial surfaces. In this mini-review, we discuss evidences that establish important roles for epithelial host defense against invading respiratory bacterial pathogens and demonstrate how pathogens outsmart these epithelial immune mechanisms to successfully establish infection. Finally, we discuss briefly how to boost epithelial immunity to improve outcomes in bacterial lung infections.

Immunomodulatory function of the cystic fibrosis modifier gene BPIFA1

BACKGROUND

Cystic fibrosis (CF) is characterized by a progressive decline in lung function due to airway obstruction, infection, and inflammation. CF patients are particularly susceptible to respiratory infection by a variety of pathogens, and the inflammatory response in CF is dysregulated and prolonged. BPI fold containing family A, member 1 (BPIFA1) and BPIFB1 are proteins expressed in the upper airways that may have innate immune activity. We previously identified polymorphisms in the BPIFA1/BPIFB1 region associated with CF lung disease severity.

METHODS

We evaluated whether the BPIFA1/BPIFB1 associations with lung disease severity replicated in individuals with CF participating in the International CF Gene Modifier Consortium (n = 6,365). Furthermore, we investigated mechanisms by which the BPIFA1 and BPIFB1 proteins may modify lung disease in CF.

RESULTS

The association of the G allele of rs1078761 with reduced lung function was replicated in an independent cohort of CF patients (p = 0.001, n = 2,921) and in a meta-analysis of the full consortium (p = 2.39x10-5, n = 6,365). Furthermore, we found that rs1078761G which is associated with reduced lung function was also associated with reduced BPIFA1, but not BPIFB1, protein levels in saliva from CF patients. Functional assays indicated that BPIFA1 and BPIFB1 do not have an anti-bacterial role against P. aeruginosa but may have an immunomodulatory function in CF airway epithelial cells. Gene expression profiling using RNAseq identified Rho GTPase signaling pathways to be altered in CF airway epithelial cells in response to treatment with recombinant BPIFA1 and BPIFB1 proteins.

CONCLUSIONS

BPIFA1 and BPIFB1 have immunomodulatory activity and genetic variation associated with low levels of these proteins may increase CF lung disease severity.

Using Bronchoalveolar Lavage to Evaluate Changes in Pulmonary Diseases

Bronchoalveolar lavage (BAL) is a procedure that can be used to collect samples from human and animal lungs to efficiently evaluate the immune response and the potentially pathological changes by examining both the compositions of cells and fluid from lavage. There are observable changes including inflammatory response in human and animal lungs exposed to environmental exposures such as toxic chemicals and microorganisms, or under pathophysiological conditions in respiratory system. The profile of inflammatory cells in BAL provides a qualitative description of inflammatory response, and the secretion in BAL fluid contains secreted proteins of inflammatory mediators and albumin as a quantitative measurement of inflammation and tissue injury in the lungs. Mouse is the most common model system being used for pulmonary disease-related research. A consistent experimental approach on how to lavage mouse lungs and collect samples from mouse lungs is important for a reproducible evaluation of pathological and physiological changes in mouse lung especially for the analysis of inflammation.

Diverse phenotypes and endotypes of fungus balls caused by mixed bacterial colonization in chronic rhinosinusitis

BACKGROUND

The pathogenic roles of fungus and bacteria in chronic rhinosinusitis (CRS) remain unclear. Recently, we described the bacterial ball, which is distinct from the fungus ball, as an unusual phenotype of bacterial infection. In this study, we investigated the clinical, histopathologic, and immunologic characteristics of sinonasal microorganic materials, including fungus ball and bacterial ball.

METHODS

In this study, we enrolled 80 CRS patients with sinonasal microorganic materials and 10 control subjects who underwent skull base surgery or endoscopic dacryocystorhinostomy and had no signs or symptoms of nasal inflammation. All specimens were stained with hematoxylin-eosin, Gomori-methenamine-silver, and Gram stain to identify fungal organisms and Gram-positive/negative bacterial colonies. The expression of tumor necrosis factor (TNF)-α; interleukin (IL)-1β; S100A7; S100A8/A9; and short, palate, lung, and nasal epithelial clone 1 (SPLUNC1) were evaluated by enzyme-linked immunosorbent assay using sinus lavage fluid.

RESULTS

We histologically classified sinonasal microorganic materials into the following 4 groups: fungus ball (n = 45); bacterial ball (n = 6); mixed ball (formed by a mixture of fungus and bacteria, n = 27); and double ball (formed by separate fungal and bacterial balls, n = 2). Compared with the fungus ball, the mixed ball was more frequently detected in immunocompromised patients (p < 0.0001). In addition, TNF-α expression was significantly higher in fungus and mixed balls than in control, whereas the mixed ball showed higher expression of IL-1β compared with the fungus ball. Moreover, the expression of S100A7 and S100A8/A9 protein in the mixed ball was significantly decreased when compared with the fungus ball, whereas there was no significant difference in SPLUNC1 expression between fungus and mixed balls.

CONCLUSION

Our findings suggest that fungal and bacterial interactions are diverse in CRS. Specifically, the mixed ball is prevalent in CRS with an immunocompromised state and it may decrease epithelial barrier function.

Tobacco exposure inhibits SPLUNC1-dependent antimicrobial activity

Background

Tobacco smoke exposure impairs the lung’s innate immune response, leading to an increased risk of chronic infections. SPLUNC1 is a secreted, multifunctional innate defense protein that has antimicrobial activity against Gram negative organisms. We hypothesize that tobacco smoke-induced SPLUNC1 dysfunction contributes to the observed defect in innate immunity in tobacco smokers and that this dysfunction can be used as a potential biomarker of harm.

Methods

We collected sputum from never-smokers and otherwise healthy smokers. We performed Western blotting to determine SPLUNC1 levels and determined antimicrobial activity against nontypeable Haemophilus influenzae. An in vitro exposure model was utilized to measure the effect of tobacco exposure on human bronchial epithelial culture (HBEC) antimicrobial activity against H. influenzae. The direct effects of cigarette and little cigar smoke exposure on SPLUNC1 function was determined using 24 h growth measurements and LPS binding assays.

Results

H. influenzae growth in cigarette smoker’s sputum was significantly greater compared to never-smokers sputum over 24 h. HBEC supernatants and lysates contained significantly higher numbers of H. influenzae following chronic cigarette and little cigar smoke exposure compared to air-exposed controls. Furthermore, SPLUNC1’s antimicrobial activity and LPS-binding capability against both H. influenzae and P. aeruginosa was attenuated following cigarette and little cigar exposure.

Conclusions

These data suggest that cigarette and little cigar exposure impairs SPLUNC1’s antimicrobial ability and that this inhibition may serve as a novel biomarker of harm that can be used to assess the toxicity of commercial tobacco products.

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.

Sex influences susceptibility to methamphetamine cardiomyopathy in mice

In this study, we created a mouse model of methamphetamine cardiomyopathy that reproduces the chronic, progressive dosing commonly encountered in addicted subjects. We gradually increased the quantity of methamphetamine given to C57Bl/6 mice from 5 to 40 mg/kg over 2 or 5 months during two study periods. At the fifth month, heart weight was increased, echocardiograms showed a dilated cardiomyopathy and survival was lower in males, with less effect in females. Interestingly, these findings correspond to previous observations in human patients, suggesting greater male susceptibility to the effects of methamphetamine on the heart. Transcriptional analysis showed changes in genes dysregulated in previous methamphetamine neurological studies as well as many that likely play a role in cardiac response to this toxic stress. We expect that a deeper understanding of the molecular biology of methamphetamine exposure in the heart will provide insights into the mechanism of cardiomyopathy in addicts and potential routes to more effective treatment.

Lipophilic Allergens, Different Modes of Allergen-Lipid Interaction and Their Impact on Asthma and Allergy

Molecular allergology research has provided valuable information on the structure and function of single allergenic molecules. There are several allergens in food and inhalant allergen sources that are able to interact with lipid ligands via different structural features: hydrophobic pockets, hydrophobic cavities, or specialized domains. For only a few of these allergens information on their associated ligands is already available. Several of the allergens are clinically relevant, so that it is highly probable that the individual structural features with which they interact with lipids have a direct effect on their allergenic potential, and thus on allergy development. There is some evidence for a protective effect of lipids delaying the enzymatic digestion of the peanut (Arachis hypogaea) allergen Ara h 8 (hydrophobic pocket), probably allowing this molecule to get to the intestinal immune system intact (sensitization). Oleosins from different food allergen sources are part of lipid storage organelles and potential marker allergens for the severity of the allergic reaction. House dust mite (HDM), is more often associated with allergic asthma than other sources of inhalant allergens. In particular, lipid-associated allergens from Dermatophagoides pteronyssinus which are Der p 2, Der p 5, Der p 7, Der p 13, Der p 14, and Der p 21 have been reported to be associated with severe allergic reactions and respiratory symptoms such as asthma. The exact mechanism of interaction of these allergens with lipids still has to be elucidated. Apart from single allergens glycolipids have been shown to directly induce allergic inflammation. Several-in parts conflicting-data exist on the lipid (and allergen) and toll-like receptor interactions. For only few single allergens mechanistic studies were performed on their interaction with the air-liquid interface of the lungs, in particular with the surfactant components SP-A and SP-D. The increasing knowledge on protein-lipid-interaction for lipophilic and hydrophobic food and inhalant allergens on the basis of their particular structure, of their capacity to be integral part of membranes (like the oleosins), and their ability to interact with membranes, surfactant components, and transport lipids (like the lipid transfer proteins) are essential to eventually clarify allergy and asthma development.

Pseudomonas aeruginosa quorum-sensing metabolite induces host immune cell death through cell surface lipid domain dissolution

Bacterial quorum-sensing autoinducers are small chemicals released to control microbial community behaviours. N-(3-oxo-dodecanoyl) homoserine lactone, the autoinducer of the Pseudomonas aeruginosa LasI-LasR circuitry, triggers significant cell death in lymphocytes. We found that this molecule is incorporated into the mammalian plasma membrane and induces dissolution of eukaryotic lipid domains. This event expels tumour necrosis factor receptor 1 into the disordered lipid phase for its spontaneous trimerization without its ligand and drives caspase 3-caspase 8-mediated apoptosis. In vivo, P. aeruginosa releases N-(3-oxo-dodecanoyl) homoserine lactone to suppress host immunity for its own better survival; conversely, blockage of caspases strongly reduces the severity of the infection. This work reveals an unknown communication method between microorganisms and the mammalian host and suggests interventions of bacterial infections by intercepting quorum-sensing signalling.

BPIFA1 regulates lung neutrophil recruitment and interferon signaling during acute inflammation

Bpifa1 (BPI fold-containing group A member 1) is an airway host-protective protein with immunomodulatory properties that binds to LPS and is regulated by infectious and inflammatory signals. Differential expression of Bpifa1 has been widely reported in lung disease, yet the biological significance of this observation is unclear. We sought to understand the role of Bpifa1 fluctuations in modulating lung inflammation. We treated wild-type (WT) and Bpifa1^-/- mice with intranasal LPS and performed immunological and transcriptomic analyses of lung tissue to determine the immune effects of Bpifa1 deficiency. We show that neutrophil (polymorphonuclear cells, PMNs) lung recruitment and transmigration to the airways in response to LPS is impaired in Bpifa1^-/- mice. Transcriptomic analysis revealed a signature of 379 genes that differentiated Bpifa1^-/- from WT mice. During acute lung inflammation, the most downregulated genes in Bpifa1^-/- mice were Cxcl9 and Cxcl10. Bpifa1^-/- mice had lower bronchoalveolar lavage concentrations of C-X-C motif chemokine ligand 10 (Cxcl10) and Cxcl9, interferon-inducible PMN chemokines. This was consistent with lower expression of IFNγ, IFNλ, downstream IFN-stimulated genes, and IFN-regulatory factors, which are important for the innate immune response. Administration of Cxcl10 before LPS treatment restored the inflammatory response in Bpifa1^-/- mice. Our results identify a novel role for Bpifa1 in the regulation of Cxcl10-mediated PMN recruitment to the lungs via IFNγ and -λ signaling during acute inflammation.

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.

Enhanced efficacy of the engineered antimicrobial peptide WLBU2 via direct airway delivery in a murine model of Pseudomonas aeruginosa pneumonia

OBJECTIVES

Pseudomonas aeruginosa is a common cause of pneumonia in patients with cystic fibrosis with the property to generate multidrug resistance against clinically used antibiotics. Antimicrobial peptides (AMPs) are a diverse group of effector molecules of the innate immune system that protect the host against pathogens. However, the lack of activity in common biological matrices has hampered efforts towards clinical development. In this study, we evaluated the therapeutic potential of the engineered AMP WLBU2 via direct airway delivery in a murine model of P. aeruginosa infection.

METHODS

The human AMPs LL37 and WLBU2 were compared for (i) antibiofilm activity using P. aeruginosa on polarized human bronchial epithelial cells, and (ii) efficacy in P. aeruginosa pneumonia in mice using intratracheal instillation of bacteria and AMPs.

RESULTS

WLBU2 (16 μM) prevents biofilm formation by up to 3-log compared with 1-log reduction by LL37. With a single dose of 1 μg (0.05 mg/kg) delivered intratracheally, the initial effect of LL37 was moderate and transitory, as bacterial load and inflammatory cytokines increased at 24 h with observed signs of disease such as lethargy and hypothermia, consistent with moribund state requiring euthanasia. In sharp contrast, WLBU2 reduced bacterial burden (by 2 logs) and bacteria-induced inflammation (leucocytic infiltrates, cytokine and chemokine gene expression) at 6 h and 24 h post-exposure, with no observed signs of disease or host toxicity.

CONCLUSION

These promising results now establish a much lower minimum therapeutic dose of WLBU2 (a net gain of 80-fold) compared with the previously reported 4 mg/kg systemic minimum therapeutic dose, with significant implications for clinical development.

In vivo therapeutic efficacy of frog skin-derived peptides against Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa is an opportunistic and frequently drug-resistant pulmonary pathogen especially in cystic fibrosis sufferers. Recently, the frog skin-derived antimicrobial peptide (AMP) Esc(1-21) and its diastereomer Esc(1-21)-1c were found to possess potent in vitro antipseudomonal activity. Here, they were first shown to preserve the barrier integrity of airway epithelial cells better than the human AMP LL-37. Furthermore, Esc(1-21)-1c was more efficacious than Esc(1-21) and LL-37 in protecting host from pulmonary bacterial infection after a single intra-tracheal instillation at a very low dosage of 0.1 mg/kg. The protection was evidenced by 2-log reduction of lung bacterial burden and was accompanied by less leukocytes recruitment and attenuated inflammatory response. In addition, the diastereomer was more efficient in reducing the systemic dissemination of bacterial cells. Importantly, in contrast to what reported for other AMPs, the peptide was administered at 2 hours after bacterial challenge to better reflect the real life infectious conditions. To the best of our knowledge, this is also the first study investigating the effect of AMPs on airway-epithelia associated genes upon administration to infected lungs. Overall, our data highly support advanced preclinical studies for the development of Esc(1-21)-1c as an efficacious therapeutic alternative against pulmonary P. aeruginosa infections.

Increased expression of BPI fold-containing family A member 1 is associated with metastasis and poor prognosis in human colorectal carcinoma

Bactericidal or permeability-increasing protein fold-containing family A member 1 (BPIFA1) has been demonstrated to be involved in inflammatory responses in the upper airway and the progression of non-small cell lung cancer. However, the expression levels of BPIFA1 and its clinical prognostic significance in colorectal carcinoma (CRC) has not yet been elucidated. Reverse transcription-polymerase chain reaction and immunohistochemistry were used to analyze the expression levels of BPIFA1 in CRC and normal mucosal tissues. The associations between BPIFA1 expression levels and clinicopathological characteristics, and its predictive value for prognosis in CRC, were statistically evaluated as appropriate. The expression levels of BPIFA1 were revealed to be upregulated at the transcriptional and translational levels in CRC tissues, compared with in normal mucosal tissues. A high expression level of BPIFA1 is significantly associated with invasion depth (P=0.040), lymph node metastasis (P=0.035) and distant metastasis (P=0.010). Furthermore, Kaplan-Meier analysis indicated that BIPFA1 overexpression is associated with short survival time, and the Cox proportional hazards model of risk analysis indicated that BPIFA1 is an independent prognostic factor for patients with CRC. The results of the present study suggested that BPIFA1 expression is upregulated in CRC tissues, and that an increased expression level of BPIFA1 is associated with tumor invasion, metastasis and poor prognosis, indicating that BPIFA1 may be a potential clinical prognostic predictor and therapeutic target for patients with CRC.

Antimicrobial peptides alter early immune response to influenza A virus infection in C57BL/6 mice

Influenza is a disease of the respiratory system caused by single stranded RNA viruses with varying genotypes. Immunopathogenesis to influenza viruses differs based on virus strain, dose, and mouse strain used in laboratory models. Although effective mucosal immune defenses are important in early host defense against influenza, information on the kinetics of these immune defense mechanisms during the course of influenza infection is limited. We investigated changes to antimicrobial peptides and primary innate immune cells at early time points after infection and compared these variables between two prominent H1N1 influenza A virus (IAV) strains, A/CA/04/2009 and A/PR/08/1934 in C57BL/6 mice. Alveolar and parenchymal macrophage ratios were altered after IAV infection and pro-inflammatory cytokine production in macrophages was induced after IAV infection. Genes encoding antimicrobial peptides, β-defensin (Defb4), bactericidal-permeability increasing protein (Bpifa1), and cathelicidin antimicrobial peptide (Camp), were differentially regulated after IAV infection and the kinetics of Defb4 expression differed in response to each virus strain. Beta-defensin reduced infectivity of A/CA/04/2009 virus but not A/PR/08/1934. Beta defensins also changed the innate immune cell profile wherein mice pre-treated with β-defensin had increased alveolar macrophages and CD103(+) dendritic cells, and reduced CD11b(+) dendritic cells and neutrophils. In addition to highlighting that immune responses may vary based on influenza virus strain used, our data suggest an important role for antimicrobial peptides in host defense against influenza virus.

Structural Features Essential to the Antimicrobial Functions of Human SPLUNC1

SPLUNC1 is an abundantly secreted innate immune protein in the mammalian respiratory tract that exerts bacteriostatic and antibiofilm effects, binds to lipopolysaccharide (LPS), and acts as a fluid-spreading surfactant. Here, we unravel the structural elements essential for the surfactant and antimicrobial functions of human SPLUNC1 (short palate lung nasal epithelial clone 1). A unique α-helix (α4) that extends from the body of SPLUNC1 is required for the bacteriostatic, surfactant, and LPS binding activities of this protein. Indeed, we find that mutation of just four leucine residues within this helical motif to alanine is sufficient to significantly inhibit the fluid spreading abilities of SPLUNC1, as well as its bacteriostatic actions against Gram-negative pathogens Burkholderia cenocepacia and Pseudomonas aeruginosa. Conformational flexibility in the body of SPLUNC1 is also involved in the bacteriostatic, surfactant, and LPS binding functions of the protein as revealed by disulfide mutants introduced into SPLUNC1. In addition, SPLUNC1 exerts antibiofilm effects against Gram-negative bacteria, although α4 is not involved in this activity. Interestingly, though, the introduction of surface electrostatic mutations away from α4 based on the unique dolphin SPLUNC1 sequence, and confirmed by crystal structure, is shown to impart antibiofilm activity against Staphylococcus aureus, the first SPLUNC1-dependent effect against a Gram-positive bacterium reported to date. Together, these data pinpoint SPLUNC1 structural motifs required for the antimicrobial and surfactant actions of this protective human protein.

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.

Bactericidal/Permeability-increasing protein fold-containing family member A1 in airway host protection and respiratory disease

Bactericidal/permeability-increasing protein fold-containing family member A1 (BPIFA1), formerly known as SPLUNC1, is one of the most abundant proteins in respiratory secretions and has been identified with increasing frequency in studies of pulmonary disease. Its expression is largely restricted to the respiratory tract, being highly concentrated in the upper airways and proximal trachea. BPIFA1 is highly responsive to airborne pathogens, allergens, and irritants. BPIFA1 actively participates in host protection through antimicrobial, surfactant, airway surface liquid regulation, and immunomodulatory properties. Its expression is modulated in multiple lung diseases, including cystic fibrosis, chronic obstructive pulmonary disease, respiratory malignancies, and idiopathic pulmonary fibrosis. However, the role of BPIFA1 in pulmonary pathogenesis remains to be elucidated. This review highlights the versatile properties of BPIFA1 in antimicrobial protection and its roles as a sensor of environmental exposure and regulator of immune cell function. A greater understanding of the contribution of BPIFA1 to disease pathogenesis and activity may clarify if BPIFA1 is a biomarker and potential drug target in pulmonary disease.

Influenza-induced type I interferon enhances susceptibility to gram-negative and gram-positive bacterial pneumonia in mice

Suppression of type 17 immunity by type I interferon (IFN) during influenza A infection has been shown to enhance susceptibility to secondary bacterial pneumonia. Although this mechanism has been described in coinfection with gram-positive bacteria, it is unclear whether similar mechanisms may impair lung defense against gram-negative infections. Furthermore, precise delineation of the duration of type I IFN-associated susceptibility to bacterial infection remains underexplored. Therefore, we investigated the effects of preceding influenza A virus infection on subsequent challenge with the gram-negative bacteria Escherichia coli or Pseudomonas aeruginosa and the temporal association between IFN expression with susceptibility to Staphylococcus aureus challenge in a mouse model of influenza and bacterial coinfection. Here we demonstrate that preceding influenza A virus led to increased lung E. coli and P. aeruginosa bacterial burden, which was associated with suppression of type 17 immunity and attenuation of antimicrobial peptide expression. Enhanced susceptibility to S. aureus coinfection ceased at day 14 of influenza infection, when influenza-associated type I IFN levels had returned to baseline levels, further suggesting a key role for type I IFN in coinfection pathogenesis. These findings further implicate type I IFN-associated suppression of type 17 immunity and antimicrobial peptide production as a conserved mechanism for enhanced susceptibility to both gram-positive and gram-negative bacterial coinfection during influenza infection.

Early pulmonary inflammation and lung damage in children with cystic fibrosis

Individuals with cystic fibrosis (CF) suffer progressive airway inflammation, infection and lung damage. Airway inflammation and infection are present from early in life, often before children are symptomatic. CF gene mutations cause changes in the CF transmembrane regulator protein that result in an aberrant airway microenvironment including airway surface liquid (ASL) dehydration, reduced ASL acidity, altered airway mucin and a dysregulated inflammatory response. This review discusses how an altered microenvironment drives CF lung disease before overt airway infection, the response of the CF airway to early infection, and methods to prevent inflammation and early lung disease.

Increased susceptibility to otitis media in a Splunc1-deficient mouse model

Otitis media (inflammation of the middle ear) is one of the most common diseases of early childhood. Susceptibility to otitis is influenced by a number of factors, including the actions of innate immune molecules secreted by the epithelia lining the nasopharynx, middle ear and Eustachian tube. The SPLUNC1 (short palate, lung, nasal epithelial clone 1) protein is a highly abundant secretory product of the mammalian nasal, oral and respiratory mucosa that is thought to play a multifunctional role in host defense. In this study we investigated Splunc1 expression in the ear of the mouse, and examined whether this protein contributes to overall host defense in the middle ear and/or Eustachian tube. We found that Splunc1 is highly expressed in both the surface epithelium and in submucosal glands in these regions in wild-type mice. In mice lacking Splunc1, we noted histologically an increased frequency of otitis media, characterized by the accumulation of leukocytes (neutrophils with scattered macrophages), proteinaceous fluid and mucus in the middle ear lumens. Furthermore, many of these mice had extensive remodeling of the middle ear wall, suggesting a chronic course of disease. From these observations, we conclude that loss of Splunc1 predisposes mice to the development of otitis media. The Splunc1^−/− mouse model should help investigators to better understand both the biological role of Splunc1 as well as host defense mechanisms in the middle ear.

Summary: We document expression of the innate immune factor Splunc1 in the murine middle ear and Eustachian tube, and describe spontaneous development of otitis media in mice lacking functional Splunc1.

Structural characterization of the pulmonary innate immune protein SPLUNC1 and identification of lipid ligands

The short palate, lung and nasal epithelial clone 1 (SPLUNC1) protein is a member of the palate, lung, and nasal epithelium clone (PLUNC) family, also known as bactericidal/permeability-increasing (BPI) fold-containing protein, family A, member 1 (BPIFA1). SPLUNC1 is an abundant protein in human airways, but its function remains poorly understood. The lipid ligands of SPLUNC1 as well as other PLUNC family members are largely unknown, although some reports provide evidence that lipopolysaccharide (LPS) could be a lipid ligand. Unlike previous hypotheses, we found significant structural differences between SPLUNC1 and BPI. Recombinant SPLUNC1 produced in HEK 293 cells harbored several molecular species of sphingomyelin and phosphatidylcholine as its ligands. Significantly, in vitro lipid-binding studies failed to demonstrate interactions between SPLUNC1 and LPS, lipoteichoic acid, or polymyxin B. Instead, one of the major and most important pulmonary surfactant phospholipids, dipalmitoylphosphatidylcholine (DPPC), bound to SPLUNC1 with high affinity and specificity. We found that SPLUNC1 could be the first protein receptor for DPPC. These discoveries provide insight into the specific determinants governing the interaction between SPLUNC1 and lipids and also shed light on novel functions that SPLUNC1 and other PLUNC family members perform in host defense.

PLUNC proteins positivity in patients with chronic rhinosinusitis: a case-control study

Introduction. Innate immunity is the first protection against microorganisms. Nowadays, there is a growing interest in innate immune molecule known as palate, lung, nasal epithelial clone (PLUNC). PLUNC is a specific product of the airways, of approximately 25 kDa, encoded by adjacent genes found within a 300 kb region of chromosome 20; these proteins must be detected predominantly in the upper respiratory tract. Materials and Methods. We performed a case-control study to investigate the presence of this protein in nasal tissue of patients affected by chronic rhinosinusitis. 59 patients were enrolled (44 cases, 15 controls). We have examined the correlation between the presence of pathology and the PLUNC proteins positivity. Results. 100% of controls have a +++ rated PLUNC proteins positivity, while cases have a lower percentage of positivity. We used χ² statistical test to analyze the results of the study and there is a difference statistically significant between cases and controls in PLUNC proteins positivity. Conclusions. These observations suggest that, in response to agents or chemical factors, nasal mucosal epithelium will react and produce PLUNC proteins. So PLUNC proteins have a protective function on upper airways mucosa, as we can see by evaluating the high positivity in control group.

The effects of physical exercise and smoking habits on the expression of SPLUNC1 in nasal lavage fluids from allergic rhinitis subjects

OBJECTIVE

Palate lung nasal epithelial clone (PLUNC) is a family of proteins, which are proposed to participate in the innate immune defense against infections in the upper aero-digestive tract. The aim of this study was to investigate the expression of SPLUNC1 in allergic rhinitis subjects with considerations taken to the mucosal function and smoking habits.

METHODS

The participants, recruited from a cohort followed from infancy, were re-examined at the age of 18 years regarding allergy development. Based on medical histories and skin prick tests the participants were classified into groups with persistent allergic rhinitis (n=18), intermittent allergic rhinitis (n = 8) and healthy controls (n = 13). Seven subjects (3, 2 and 2 in each group, respectively) reported smoking habits. The SPLUNC1 levels in nasal lavage fluids were analyzed by Western blot. Changes in the volume of the proper nasal cavity before and after physical exercise (Vol2(increase)) were analyzed by acoustic rhinometry.

RESULTS

Compared to the control group the SPLUNC1 level was significantly lower in the persistent allergy group (3.8 ± 3.4 OD vs. 1.3 ± 1.5 OD; p = 0.02), but not in the intermittent allergy group without current exposure to allergens (3.6 ± 4.7 OD). No differences were found in Vol2(increase) between any of the allergy groups and controls. In smokers Vol2(increase) was significantly reduced (p < 0.01) and the SPLUNC1 levels were lower compared to non-smokers. A significant correlation was found between SPLUNC1 and Vol2(increase) (p < 0.01; r = 0.53) in non-smokers.

CONCLUSIONS

Current allergen exposure has an impact on SPLUNC1 expression in nasal lavage fluid, why allergy ought to be considered in study populations where analyses of SPLUNC1 levels are included in the reports. The normal nasal decongestion after exercise was not affected by allergy in contrast to smoking habits. The correlation between SPLUNC1 levels and Vol2(increase) in non-smokers may indicate involvement of SPLUNC1in the regulation of the normal function of the nasal mucosa. Complementary studies are needed to confirm the smoke-related reduction of SPLUNC1 expression and to analyze the possible participation of SPLUNC1 in the nasal mucosa regulation.

Assessment of pathological and physiological changes in mouse lung through bronchoalveolar lavage

In animals, environmental exposure such as toxic chemicals and microorganisms or pathophysiological conditions in respiratory system could result in inflammatory response in their lungs. Bronchoalveolar lavage (BAL) is a procedure that can be used to collect samples from animal lungs to efficiently evaluate the immune response by examining both the compositions of cells and fluid from lavage. The profile of inflammatory cells in BAL provides a qualitative description of inflammatory response and the secretion in BAL fluid contains proteins of inflammatory mediators and albumin as a quantitative measurement of inflammation and tissue injury in the lungs. A consistent experimental approach on how to lavage mouse lungs and collect samples is important for a reproducible evaluation of pathological and physiological changes in mouse lung especially for the analysis of inflammation.

Ovocalyxin-36 is a pattern recognition protein in chicken eggshell membranes

The avian eggshell membranes are essential elements in the fabrication of the calcified shell as a defense against bacterial penetration. Ovocalyxin-36 (OCX-36) is an abundant avian eggshell membrane protein, which shares protein sequence homology to bactericidal permeability-increasing protein (BPI), lipopolysaccharide-binding protein (LBP) and palate, lung and nasal epithelium clone (PLUNC) proteins. We have developed an efficient method to extract OCX-36 from chicken eggshell membranes for purification with cation and anion exchange chromatographies. Purified OCX-36 protein exhibited lipopolysaccharide (LPS) binding activity and bound lipopolysaccharide (LPS) from Escherichia coli O111:B4 in a dose-dependent manner. OCX-36 showed inhibitory activity against growth of Staphylococcus aureus ATCC 6538. OCX-36 single nucleotide polymorphisms (SNPs) were verified at cDNA 211 position and the corresponding proteins proline-71 (Pro-71) or serine-71 (Ser-71) were purified from eggs collected from genotyped hens. A significant difference between Pro-71 and Ser-71 OCX-36 for S. aureus lipoteichoic acid (LTA) binding activity was detected. The current study is a starting point to understand the innate immune role that OCX-36 may play in protection against bacterial invasion of both embryonated eggs (relevant to avian reproductive success) and unfertilized table eggs (relevant to food safety).

Airway symptoms and biological markers in nasal lavage fluid in subjects exposed to metalworking fluids

BACKGROUNDS

Occurrence of airway irritation among industrial metal workers was investigated. The aims were to study the association between exposures from water-based metal working fluids (MWF) and the health outcome among the personnel, to assess potential effects on the proteome in nasal mucous membranes, and evaluate preventive actions.

METHODS

The prevalence of airway symptoms related to work were examined among 271 metalworkers exposed to MWF and 24 metal workers not exposed to MWF at the same factory. At the same time, air levels of potentially harmful substances (oil mist, morpholine, monoethanolamine, formaldehyde) generated from MWF was measured. Nasal lavage fluid was collected from 13 workers and 15 controls and protein profiles were determined by a proteomic approach.

RESULTS

Airway symptoms were reported in 39% of the workers exposed to MWF although the measured levels of MWF substances in the work place air were low. Highest prevalence was found among workers handling the MWF machines but also those working in the same hall were affected. Improvement of the ventilation to reduce MWF exposure lowered the prevalence of airway problems. Protein profiling showed significantly higher levels of S100-A9 and lower levels of SPLUNC1, cystatin SN, Ig J and β2-microglobulin among workers with airway symptoms.

CONCLUSIONS

This study confirms that upper airway symptoms among metal workers are a common problem and despite low levels of MWF-generated substances, effects on airway immune proteins are found. Further studies to clarify the role of specific MWF components in connection to airway inflammation and the identified biological markers are warranted.

Dual acute proinflammatory and antifibrotic pulmonary effects of short palate, lung, and nasal epithelium clone-1 after exposure to carbon nanotubes

Carbon nanotubes (CNTs; allotropes of carbon with a cylindrical nanostructure) have emerged as one of the most commonly used types of nanomaterials, with numerous applications in industry and biomedicine. However, the inhalation of CNTs has been shown to elicit pulmonary toxicity, accompanied by a robust inflammatory response with an early-onset fibrotic phase. Epithelial host-defense proteins represent an important component of the pulmonary innate immune response to foreign inhalants such as particles and bacteria. The short palate, lung, and nasal epithelium clone-1 (SPLUNC1) protein, a member of the bactericidal/permeability-increasing-fold (BPIF)-containing protein family, is a 25-kD secretory protein that is expressed in nasal, oropharyngeal, and lung epithelia, and has been shown to have multiple functions, including antimicrobial and chemotactic activities, as well as surfactant properties. This study sought to assess the importance of SPLUNC1-mediated pulmonary responses in airway epithelial secretions, and to explore the biological relevance of SPLUNC1 to inhaled particles in a single-walled carbon nanotube (SWCNT) model. Using Scgb1a1-hSPLUNC1 transgenic mice, we observed that SPLUNC1 significantly modified host inflammatory responses by increasing leukocyte recruitment and enhancing phagocytic activity. Furthermore, we found that transgenic mice were more susceptible to SWCNT exposure at the acute phase, but showed resistance against lung fibrogenesis through pathological changes in the long term. The binding of SPLUNC1 also attenuated SWCNT-induced TNF-α secretion by RAW 264.7 macrophages. Taken together, our data indicate that SPLUNC1 is an important component of mucosal innate immune defense against pulmonary inhaled particles.

α1-Antitrypsin promotes SPLUNC1-mediated lung defense against Pseudomonas aeruginosa infection in mice

Background

Pseudomonas aeruginosa (PA) infection is involved in various lung diseases such as cystic fibrosis and chronic obstructive pulmonary disease. However, treatment of PA infection is not very effective in part due to antibiotic resistance. α1-antitrypsin (A1AT) has been shown to reduce PA infection in humans and animals, but the underlying mechanisms remain unclear. The goal of our study is to test whether a novel endogenous host defense protein, short palate, lung, and nasal epithelium clone 1 (SPLUNC1), is involved in the therapeutic effect of A1AT during lung PA infection.

Method

SPLUNC1 knockout (KO) and littermate wild-type (WT) mice on the C57BL/6 background were intranasally infected with PA to determine the therapeutic effects of A1AT. A1AT was aerosolized to mice 2 hrs after the PA infection, and mice were sacrificed 24 hrs later. PA load and inflammation were quantified in the lung, and SPLUNC1 protein in bronchoalveolar lavage (BAL) fluid was examined by Western blot.

Results

In WT mice, PA infection significantly increased neutrophil elastase (NE) activity, but reduced SPLUNC1 protein in BAL fluid. Notably, PA-infected mice treated with A1AT versus bovine serum albumin (BSA) demonstrated higher levels of SPLUNC1 protein expression, which are accompanied by lower levels of NE activity, lung bacterial load, and pro-inflammatory cytokine production. To determine whether A1AT therapeutic effects are dependent on SPLUNC1, lung PA load in A1AT- or BSA-treated SPLUNC1 KO mice was examined. Unlike the WT mice, A1AT treatment in SPLUNC1 KO mice had no significant impact on lung PA load and pro-inflammatory cytokine production.

Conclusion

A1AT reduces lung bacterial infection in mice in part by preventing NE-mediated SPLUNC1 degradation.

Anti-BPIFA1/SPLUNC1: a new autoantibody prevalent in patients with endstage cystic fibrosis

BACKGROUND

Bactericidal/permeability increasing protein fold containing family A (BPIFA) 1, is a secreted protein of the upper airways that shares structural homology with BPI and exhibits comparable antimicrobial capacities. We hypothesized that CF patients have circulating IgG or IgA anti-BPIFA1 autoantibodies, similarly as reported for BPI autoantibodies.

METHODS

We analyzed pre- and post-transplantation sera from 67 endstage lung disease patients who underwent lung transplantation (LTx) because of COPD (n=27), CF (n=25), and ILD (n=15).

RESULTS

Anti-BPIFA1 (48%) and anti-BPI (92%) were elevated in CF patients compared to healthy controls, with anti-BPIFA1 IgG isotype being most prevalent, whereas anti-BPI is of the IgA isotype. Levels of anti-BPI autoantibodies significantly declined post-LTx, whereas anti-BPIFA1 did not. No relation was found between autoantibodies against BPIFA1 and BPI.

CONCLUSION

Our results indicate that BPIFA1 is a novel target for autoantibodies in CF. The function of these autoantibodies needed to be investigated in future studies.

Increased susceptibility to pulmonary Pseudomonas infection in Splunc1 knockout mice

The airway epithelium is the first line of host defense against pathogens. The short palate, lung, and nasal epithelium clone (SPLUNC)1 protein is secreted in respiratory tracts and is a member of the bacterial/permeability increasing (BPI) fold-containing protein family, which shares structural similarities with BPI-like proteins. On the basis of its homology with BPIs and restricted expression of SPLUNC1 in serous cells of submucosal glands and surface epithelial cells of the upper respiratory tract, SPLUNC1 is thought to possess antimicrobial activity in host defense. SPLUNC1 is also reported to have surfactant properties, which may contribute to anti-biofilm defenses. The objective of this study was to determine the in vivo functions of SPLUNC1 following Pseudomonas aeruginosa infection and to elucidate the underlying mechanism by using a knockout (KO) mouse model with a genetic ablation of Splunc1. Splunc1 KO mice showed accelerated mortality and increased susceptibility to P. aeruginosa infection with significantly decreased survival rates, increased bacterial burdens, exaggerated tissue injuries, and elevated proinflammatory cytokine levels as compared with those of their wild-type littermates. Increased neutrophil infiltration in Splunc1 KO mice was accompanied by elevated chemokine levels, including Cxcl1, Cxcl2, and Ccl20. Furthermore, the expression of several epithelial secretory proteins and antimicrobial molecules was considerably suppressed in the lungs of Splunc1 KO mice. The deficiency of Splunc1 in mouse airway epithelium also results in increased biofilm formation of P. aeruginosa. Taken together, our results support that the ablation of Splunc1 in mouse airways affects the mucociliary clearance, resulting in decreased innate immune response during Pseudomonas-induced respiratory infection.

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.

Human neutrophil elastase degrades SPLUNC1 and impairs airway epithelial defense against bacteria

Background

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a significant cause of mortality of COPD patients, and pose a huge burden on healthcare. One of the major causes of AECOPD is airway bacterial (e.g. nontypeable Haemophilus influenzae [NTHi]) infection. However, the mechanisms underlying bacterial infections during AECOPD remain poorly understood. As neutrophilic inflammation including increased release of human neutrophil elastase (HNE) is a salient feature of AECOPD, we hypothesized that HNE impairs airway epithelial defense against NTHi by degrading airway epithelial host defense proteins such as short palate, lung, and nasal epithelium clone 1 (SPLUNC1).

Methodology/Main Results

Recombinant human SPLUNC1 protein was incubated with HNE to confirm SPLUNC1 degradation by HNE. To determine if HNE-mediated impairment of host defense against NTHi was SPLUNC1-dependent, SPLUNC1 protein was added to HNE-treated primary normal human airway epithelial cells. The in vivo function of SPLUNC1 in NTHi defense was investigated by infecting SPLUNC1 knockout and wild-type mice intranasally with NTHi. We found that: (1) HNE directly increased NTHi load in human airway epithelial cells; (2) HNE degraded human SPLUNC1 protein; (3) Recombinant SPLUNC1 protein reduced NTHi levels in HNE-treated human airway epithelial cells; (4) NTHi levels in lungs of SPLUNC1 knockout mice were increased compared to wild-type mice; and (5) SPLUNC1 was reduced in lungs of COPD patients.

Conclusions

Our findings suggest that SPLUNC1 degradation by neutrophil elastase may increase airway susceptibility to bacterial infections. SPLUNC1 therapy likely attenuates bacterial infections during AECOPD.

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.

SPLUNC1/BPIFA1 contributes to pulmonary host defense against Klebsiella pneumoniae respiratory infection

Epithelial host defense proteins comprise a critical component of the pulmonary innate immune response to infection. The short palate, lung, nasal epithelium clone (PLUNC) 1 (SPLUNC1) protein is a member of the bactericidal/permeability-increasing (BPI) fold-containing (BPIF) protein family, sharing structural similarities with BPI-like proteins. SPLUNC1 is a 25 kDa secretory protein that is expressed in nasal, oropharyngeal, and lung epithelia, and has been implicated in airway host defense against Pseudomonas aeruginosa and other organisms. SPLUNC1 is reported to have surfactant properties, which may contribute to anti-biofilm defenses. The objective of this study was to assess the importance of SPLUNC1 surfactant activity in airway epithelial secretions and to explore its biological relevance in the context of a bacterial infection model. Using cultured airway epithelia, we confirmed that SPLUNC1 is critically important for maintenance of low surface tension in airway fluids. Furthermore, we demonstrated that recombinant SPLUNC1 (rSPLUNC1) significantly inhibited Klebsiella pneumoniae biofilm formation on airway epithelia. We subsequently found that Splunc1(-/-) mice were significantly more susceptible to infection with K. pneumoniae, confirming the likely in vivo relevance of this anti-biofilm effect. Our data indicate that SPLUNC1 is a crucial component of mucosal innate immune defense against pulmonary infection by a relevant airway pathogen, and provide further support for the novel hypothesis that SPLUNC1 protein prevents bacterial biofilm formation through its ability to modulate surface tension of airway fluids.

Decreased SPLUNC1 expression is associated with Pseudomonas infection in surgically treated chronic rhinosinusitis patients who may require repeated sinus surgery

OBJECTIVES/HYPOTHESIS

Chronic rhinosinusitis colonized with Pseudomonas aruginosa is difficult to treat and is related to biofilm formation. Repeated sinus surgery is often required for these patients. Short palate, lung, and nasal epithelial clone 1 (SPLUNC1) is an epithelium-secreted protein that is involved in innate immunity and has anti-Pseudomonas and antibiofilm functions. This study examined if SPLUNC1 expression was related to sinusitis with bacterial culture positive for Pseudomonas and the possibility of using SPLUNC1 to predict treatment outcomes for sinusitis.

STUDY DESIGN

Nonrandomized retrospective study.

METHODS

This was a retrospective study of patients at a tertiary referral center. Pseudomonas aruginosa infection was compared to clinical variables such as SPLUNC1 mRNA expression levels, immunohistochemical (IHC) stain intensity, Lund-Mackay sinus computed tomography scores, rapid recurrent sinusitis, requirement for repeat sinus surgery, Phadiatop test results, age, gender, nasal polyp(s), and patients' presence/absence of diabetes mellitus. Comparisons between groups were performed using the χ(2) test or Fisher exact test when one confronter was <5. The statistical analyses were carried out with SPSS version 13.

RESULTS

P. aeruginosa sinus infections were associated with lower sinus mucosa SPLUNC1 expression (P = .0018), weaker SPLUNC1 IHC staining intensity (P = .011), and poor postoperative outcome (i.e., need repeated sinus surgery) (P < .001). Other factors were not associated with Pseudomonas sinus infection.

CONCLUSIONS

Sinusitis with positive P. aeruginosa bacterial culture is associated with decreased SPLUNC1 sinus mucosa expression. Repeated sinus surgeries are more frequently needed for these patients.

Multifunctional role of human SPLUNC1 in Pseudomonas aeruginosa infection

The human short PLUNC1 (SPLUNC1) protein has been identified as a component of the pulmonary antimicrobial response based on its structural similarity to the bactericidal/permeability-increasing (BPI) protein. Using a genetically modified mouse model, we recently verified the antimicrobial activity of SPLUNC1 against Pseudomonas aeruginosa in vivo. To further define the mechanism of epithelial SPLUNC1-mediated antibacterial action, we carried out studies to determine how SPLUNC1 protects the host from acute respiratory infections. P. aeruginosa treated with recombinant human SPLUNC1 protein showed decreased growth in vitro. This antibacterial activity was due to growth inhibition, as a consequence of a SPLUNC1-induced increase in bacterial cell permeability. Removal of SPLUNC1 allowed the recovery of P. aeruginosa and suggested no permanent cell injury or direct killing of bacteria. Further investigation showed coating of bacterial cells by SPLUNC1. We suggest that this "bacterial cell coating" is necessary for the bacteriostatic function of SPLUNC1. Additionally, we demonstrated a novel role for SPLUNC1 as a chemoattractant that facilitated migration of macrophages and neutrophils. Taking the findings together, we propose synergistic roles for human SPLUNC1 as an antibacterial agent with bacteriostatic and chemotactic activities.

Bactericidal/permeability increasing protein: a multifaceted protein with functions beyond LPS neutralization

Bactericidal permeability increasing protein (BPI), a 55-60 kDa protein, first reported in 1975, has gone a long way as a protein with multifunctional roles. Its classical role in neutralizing endotoxin (LPS) raised high hopes among septic shock patients. Today, BPI is not just a LPS-neutralizing protein, but a protein with diverse functions. These functions can be as varied as inhibition of endothelial cell growth and inhibition of dendritic cell maturation, or as an anti-angiogenic, chemoattractant or opsonization agent. Though the literature available is extremely limited, it is fascinating to look into how BPI is gaining major importance as a signalling molecule. In this review, we briefly summarize the recent research focused on the multiple roles of BPI and its use as a therapeutic.