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

Unveiling the systemic impact of airborne microplastics: Integrating breathomics and machine learning with dual-tissue transcriptomics

Airborne microplastics (MPs) pose significant respiratory and systemic health risks upon inhalation; however, current assessment methods remain inadequate. This study integrates breathomics and transcriptomics to establish a non-invasive approach for evaluating MP-induced damage to the lungs and heart. C57BL/6 mice were exposed to polystyrene MPs (0.1 μm, 2 μm, and 10 μm), and their exhaled volatile organic compounds (VOCs) were analyzed using photoinduced associative ionization time-of-flight mass spectrometry. Machine learning algorithms identified hydrogen sulfide, acetone, acrolein, propionitrile, and butyronitrile as key VOC biomarkers, linking MP exposure to oxidative stress and metabolic dysregulation. Transcriptomic analysis further revealed significant gene expression alterations in pulmonary and cardiac tissues, implicating immune dysregulation, metabolic disturbance, and cardiac dysfunction. Pathway enrichment analysis, supported by histological and immunohistochemical validation, confirmed pulmonary inflammation and cardiac injury. By integrating exhaled biomarker profiling with transcriptomic insights, this study advances non-invasive detection strategies for MP-related health effects, offering valuable prospects for public health monitoring and early diagnosis.

SPLUNC1 as a biomarker of pulmonary exacerbations in children with cystic fibrosis

BACKGROUND

Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) is an innate defence protein that acts as an anti-microbial agent and regulates airway surface liquid volume through inhibition of the epithelial sodium channel (ENaC). SPLUNC1 levels were found to be reduced in airway secretions of adults with cystic fibrosis (CF). The potential of SPLUNC1 as a biomarker in children with CF is unknown.

METHODS

We quantified SPLUNC1, interleukin-8 (IL-8) and neutrophil elastase (NE) in sputum of CF children treated with either intravenous antibiotics or oral antibiotics for a pulmonary exacerbation (PEx)s, and in participants of a prospective cohort of CF children with preserved lung function on spirometry, followed over a period of two years.

RESULTS

Sputum SPLUNC1 levels were significantly lower before compared to after intravenous and oral antibiotic therapy for PEx. In the longitudinal cohort, SPLUNC1 levels were found to be decreased at PEx visits compared to both previous and subsequent stable visits. Higher SPLUNC1 levels at stable visits were associated with longer PEx-free time (hazard ratio 0.85, p = 0.04). SPLUNC1 at PEx visits did not correlate with IL-8 or NE levels in sputum or forced expiratory volume in one second (FEV1) but did correlate with the lung clearance index (LCI) (r=-0.53, p < 0.001).

CONCLUSION

SPLUNC1 demonstrates promising clinometric properties as a biomarker of PEx in children with CF.

CC16 drives VLA-2-dependent SPLUNC1 expression

Rationale

CC16 (Club Cell Secretory Protein) is a protein produced by club cells and other non-ciliated epithelial cells within the lungs. CC16 has been shown to protect against the development of obstructive lung diseases and attenuate pulmonary pathogen burden. Despite recent advances in understanding CC16 effects in circulation, the biological mechanisms of CC16 in pulmonary epithelial responses have not been elucidated.

Objectives

We sought to determine if CC16 deficiency impairs epithelial-driven host responses and identify novel receptors expressed within the pulmonary epithelium through which CC16 imparts activity.

Methods

We utilized mass spectrometry and quantitative proteomics to investigate how CC16 deficiency impacts apically secreted pulmonary epithelial proteins. Mouse tracheal epithelial cells (MTECS), human nasal epithelial cells (HNECs) and mice were studied in naïve conditions and after Mp challenge.

Measurements and main results

We identified 8 antimicrobial proteins significantly decreased by CC16-/- MTECS, 6 of which were validated by mRNA expression in Severe Asthma Research Program (SARP) cohorts. Short Palate Lung and Nasal Epithelial Clone 1 (SPLUNC1) was the most differentially expressed protein (66-fold) and was the focus of this study. Using a combination of MTECs and HNECs, we found that CC16 enhances pulmonary epithelial-driven SPLUNC1 expression via signaling through the receptor complex Very Late Antigen-2 (VLA-2) and that rCC16 given to mice enhances pulmonary SPLUNC1 production and decreases Mycoplasma pneumoniae (Mp) burden. Likewise, rSPLUNC1 results in decreased Mp burden in mice lacking CC16 mice. The VLA-2 integrin binding site within rCC16 is necessary for induction of SPLUNC1 and the reduction in Mp burden.

Conclusion

Our findings demonstrate a novel role for CC16 in epithelial-driven host defense by up-regulating antimicrobials and define a novel epithelial receptor for CC16, VLA-2, through which signaling is necessary for enhanced SPLUNC1 production.

Transcriptomic alterations in the olfactory bulb induced by exposure to air pollution: Identification of potential biomarkers and insights into olfactory system function

This study evaluated how exposure to the ubiquitous air pollution component, ultrafine particles (UFPs), alters the olfactory bulb (OB) transcriptome. The study utilised a whole-body inhalation chamber to simulate real-life conditions and focused on UFPs due to their high translocation and deposition ability in OBs as well as their prevalence in ambient air. Female C57BL/6J mice were exposed to clean air or to freshly generated combustion derived UFPs for two weeks, after which OBs were dissected and mRNA transcripts were investigated using RNA sequencing analysis. For the first time, transcriptomics was applied to determine changes in mRNA expression levels occurring after subacute exposure to UFPs in the OBs. We found forty-five newly described mRNAs to be involved in air pollution-induced responses, including genes involved in odorant binding, synaptic regulation, and myelination signalling pathway, providing new gene candidates for future research. This study provides new insights for the environmental science and neuroscience fields and nominates future research directions.

BPIFA1 is a secreted biomarker of differentiating human airway epithelium

In vitro culture and differentiation of human-derived airway basal cells under air-liquid interface (ALI) into a pseudostratified mucociliated mucosal barrier has proven to be a powerful preclinical tool to study pathophysiology of respiratory epithelium. As such, identifying differentiation stage-specific biomarkers can help investigators better characterize, standardize, and validate populations of regenerating epithelial cells prior to experimentation. Here, we applied longitudinal transcriptomic analysis and observed that the pattern and the magnitude of OMG, KRT14, STC1, BPIFA1, PLA2G7, TXNIP, S100A7 expression create a unique biosignature that robustly indicates the stage of epithelial cell differentiation. We then validated our findings by quantitative hemi-nested real-time PCR from in vitro cultures sourced from multiple donors. In addition, we demonstrated that at protein-level secretion of BPIFA1 accurately reflects the gene expression profile, with very low quantities present at the time of ALI induction but escalating levels were detectable as the epithelial cells terminally differentiated. Moreover, we observed that increase in BPIFA1 secretion closely correlates with emergence of secretory cells and an anti-inflammatory phenotype as airway epithelial cells undergo mucociliary differentiation under air-liquid interface in vitro.

SPLUNC1 is a negative regulator of the Orai1 Ca2+ channel

Orai1 is a ubiquitously-expressed plasma membrane Ca2+ channel that is involved in store-operated Ca2+ entry (SOCE): a fundamental biological process that regulates gene expression, the onset of inflammation, secretion, and the contraction of airway smooth muscle (ASM). During SOCE, Ca2+ leaves the endoplasmic reticulum, which then stimulates a second, amplifying wave of Ca2+ influx through Orai1 into the cytoplasm. Short Palate LUng and Nasal epithelial Clone 1 (SPLUNC1; gene name BPIFA1) is a multi-functional, innate defense protein that is highly abundant in the lung. We have previously reported that SPLUNC1 was secreted from epithelia, where it bound to and inhibited Orai1, leading to reduced SOCE and ASM relaxation. However, the underlying mechanism of action is unknown. Here, we probed the SPLUNC1-Orai1 interactions in ASM and HEK293T cells using biochemical and imaging techniques. We observed that SPLUNC1 caused a conformational change in Orai1, as measured using Forster resonance energy transfer (FRET). SPLUNC1 binding also led to Nedd4-2 dependent ubiquitination of Orai1. Moreover, SPLUNC1 internalized Orai1 to lysosomes, leading to Orai1 degradation. Thus, we conclude that SPLUNC1 is an allosteric regulator of Orai1. Our data indicate that SPLUNC1-mediated Orai1 inhibition could be utilized as a therapeutic strategy to reduce SOCE.

Short palate, lung, and nasal epithelial clone 1 (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.

SPLUNC1: a novel marker of cystic fibrosis exacerbations

Acute pulmonary Exacerbations (AE) are episodes of clinical worsening in cystic fibrosis (CF), often precipitated by infection. Timely detection is critical to minimise morbidity and lung function declines associated with acute inflammation during AE. Based on our previous observations that airway protein Short Palate Lung Nasal epithelium Clone 1 (SPLUNC1) is regulated by inflammatory signals, we investigated the use of SPLUNC1 fluctuations to diagnose and predict AE in CF.We enrolled CF participants from two independent cohorts to measure AE markers of inflammation in sputum and recorded clinical outcomes for a 1-year follow-up period.SPLUNC1 levels were high in healthy controls (n=9, 10.7 μg mL^-1), and significantly decreased in CF participants without AE (n=30, 5.7 μg mL^-1, p=0.016). SPLUNC1 levels were 71.9% lower during AE (n=14, 1.6 μg mL^-1, p=0.0034) regardless of age, sex, CF-causing mutation, or microbiology findings. Cytokines Il-1β and TNFα were also increased in AE, whereas lung function did not consistently decrease. Stable CF participants with lower SPLUNC1 levels were much more likely to have an AE at 60 days (HR: 11.49, Standard Error: 0.83, p=0.0033). Low-SPLUNC1 stable participants remained at higher AE risk even one year after sputum collection (HR: 3.21, Standard Error: 0.47, p=0.0125). SPLUNC1 was downregulated by inflammatory cytokines and proteases increased in sputum during AE.In acute CF care, low SPLUNC1 levels could support a decision to increase airway clearance or to initiate pharmacological interventions. In asymptomatic, stable patients, low SPLUNC1 levels could inform changes in clinical management to improve long-term disease control and clinical outcomes in CF.

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.

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.

An innate defense peptide BPIFA1/SPLUNC1 restricts influenza A virus infection

The airway epithelium secretes proteins that function in innate defense against infection. Bactericidal/permeability-increasing fold-containing family member A1 (BPIFA1) is secreted into airways and has a protective role during bacterial infections, but it is not known whether it also has an antiviral role. To determine a role in host defense against influenza A virus (IAV) infection and to find the underlying defense mechanism, we developed transgenic mouse models that are deficient in BPIFA1 and used these, in combination with in vitro three-dimensional mouse tracheal epithelial cell (mTEC) cultures, to investigate its antiviral properties. We show that BPIFA1 has a significant role in mucosal defense against IAV infection. BPIFA1 secretion was highly modulated after IAV infection. Mice deficient in BPIFA1 lost more weight after infection, supported a higher viral load and virus reached the peripheral lung earlier, indicative of a defect in the control of infection. Further analysis using mTEC cultures showed that BPIFA1-deficient cells bound more virus particles, displayed increased nuclear import of IAV ribonucleoprotein complexes, and supported higher levels of viral replication. Our results identify a critical role of BPIFA1 in the initial phase of infection by inhibiting the binding and entry of IAV into airway epithelial cells.

Association of innate defense proteins BPIFA1 and BPIFB1 with disease severity in COPD

Chronic obstructive pulmonary disease (COPD) is characterized by an abnormal inflammatory response in the lungs caused by the inhalation of noxious particles and gases. The airway epithelium has a protective function against these harmful agents by maintaining a physical barrier and by secreting defensive proteins, such as bactericidal/permeability-increasing fold-containing (BPIF) proteins, BPIFA1 and BPIFB1. However, inconsistent data regarding BPIFA1 expression in smokers and COPD patients have been reported to date. Therefore, we investigated the expression of BPIFA1 and BPIFB1 in a large cohort of never-smokers and smokers with and without COPD, both on the messenger RNA (mRNA) level in lung tissue and on the protein level in airway epithelium. Furthermore, we examined the correlation between BPIFA1 and BPIFB1 levels, goblet cell hyperplasia, and lung function measurements. BPIFA1 and BPIFB1 mRNA expressions were significantly increased in stage III-IV COPD patients compared with stage II COPD patients and subjects without COPD. In addition, protein levels in COPD patients were significantly increased in comparison with subjects without COPD. BPIFA1 and BPIFB1 levels were inversely correlated with measurements of airflow limitation and positively correlated with goblet cell hyperplasia. In addition, by the use of immunofluorescence double staining, we demonstrated the expression of BPIFB1 in goblet cells. In conclusion, we show that BPIFA1 and BPIFB1 levels are elevated in COPD patients and correlate with disease severity.

[Streptococcus pneumoniae induces SPLUNC1 and the regulatory effects of resveratrol]

OBJECTIVE

To investigate the host-defense role of short palate, lung, and nasal epithelium clone 1 (SPLUNC1) in Streptococcus pneumoniae (SP) infection and the effect of resveratrol (Res) on SPLUNC1 expression, and to provide new thoughts for the treatment of diseases caused by SP infection.

METHODS

According to the multiplicity of infection (MOI), BEAS-2B cells with SP infection were divided into control group, MOI20 SP group, and MOI50 SP group. According to the different concentrations of Res, the BEAS-2B cells with MOI20 SP infection pretreated by Res were divided into 12.5Res+SP group, 25Res+SP group, and 50Res+SP group (the final concentrations of Res were 12.5, 25, and 50 μmol/L, respectively). Cell Counting Kit-8 was used to measure cell activity and determine the optimal concentration and action time of SP and Res. In the formal experiment, the cells were divided into control group, Res group, SP group, and Res+SP group. Real-time PCR and ELISA were used to measure the mRNA and protein expression of SPLUNC1.

RESULTS

Over the time of SP infection, cell activity tended to decrease. Compared with the control group and the MOI20 SP group, the MOI50 SP group had a reduction in cell activity. Compared with the MOI20 SP group, the 25Res+SP group had increased cell activity and the 50Res+SP group had reduced cell activity (P<0.05). MOI20 SP bacterial suspension and 25 μmol/L Res were used for the formal experiment. Over the time of SP infection, the mRNA expression of SPLUNC1 in BEAS-2B cells firstly increased and then decreased in the SP group and the Res+SP group (P<0.05). Compared with the SP group, the Res+SP group had significant increases in the mRNA and protein expression of SPLUNC1 at all time points (P<0.05). Compared with the control group, the Res group had no significant changes in the mRNA and protein expression of SPLUNC1 (P>0.05).

CONCLUSIONS

SP infection can induce SPLUNC1 expression and the host-defense role of SPLUNC1. Res can upregulate SPLUNC1 expression during the development of infection and enhance cell protection in a concentration- and time-dependent manner.

Short Palate, Lung, and Nasal Epithelial Clone 1 Has Antimicrobial and Antibiofilm Activities against the Burkholderia cepacia Complex

The opportunistic bacteria of the Burkholderia cepacia complex (Bcc) are extremely pathogenic to cystic fibrosis (CF) patients, and acquisition of Bcc bacteria is associated with a significant increase in mortality. Treatment of Bcc infections is difficult because the bacteria are multidrug resistant and able to survive in biofilms. Short palate, lung, and nasal epithelial clone 1 (SPLUNC1) is an innate defense protein that is secreted by the upper airways and pharynx. While SPLUNC1 is known to have antimicrobial functions, its effects on Bcc strains are unclear. We therefore tested the hypothesis that SPLUNC1 is able to impair Bcc growth and biofilm formation. We found that SPLUNC1 exerted bacteriostatic effects against several Bcc clinical isolates, including B. cenocepacia strain J2315 (50% inhibitory concentration [IC50] = 0.28 μM), and reduced biofilm formation and attachment (IC50 = 0.11 μM). We then determined which domains of SPLUNC1 are responsible for its antimicrobial activity. Deletions of SPLUNC1's N terminus and α6 helix did not affect its function. However, deletion of the α4 helix attenuated antimicrobial activity, while the corresponding α4 peptide displayed antimicrobial activity. Chronic neutrophilia is a hallmark of CF lung disease, and neutrophil elastase (NE) cleaves SPLUNC1. However, we found that the ability of SPLUNC1 to disrupt biofilm formation was significantly potentiated by NE pretreatment. While the impact of CF on SPLUNC1-Bcc interactions is not currently known, our data suggest that understanding this interaction may have important implications for CF lung disease.

CFTR, bicarbonate, and the pathophysiology of cystic fibrosis

The gene that encodes for the cystic fibrosis transmembrane regulator protein (CFTR) was identified in 1989, yet major pathophysiologic questions remain unanswered. There is emerging evidence that CFTR is a bicarbonate channel, a driver of chloride-bicarbonate exchange and through its action on local pH, a regulator of other ion channels and of proteins that function optimally in a neutral environment. In both the respiratory and gastrointestinal (GI) tracts, bicarbonate drives ionic content and fluid on epithelial surfaces, allows mucins to unfold and become slippery, and contributes to innate immunity. In the GI tract bicarbonate neutralizes gastric acid to support digestion and absorption. When CFTR is dysfunctional, lack of bicarbonate secretion disrupts these normal processes and thus leads directly to the clinical symptoms and signs of CF. This article synthesizes evidence from cell, animal, and human investigations that support these concepts. Bicarbonate secretion does not seem to be the same in all tissues and varies with physiologic demand. Thus, tissue type and whether conditions are baseline or stimulated needs to be taken into account when evaluating the evidence concerning the role of bicarbonate in the pathophysiology of CF as a regulator of local pH. Basic and applied research that focuses on the role of CFTR-mediated bicarbonate secretion helps explain many of the diverse clinical manifestations that are CF.

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.

Gammaherpesvirus infection modulates the temporal and spatial expression of SCGB1A1 (CCSP) and BPIFA1 (SPLUNC1) in the respiratory tract

Murine γ-herpesvirus 68 (MHV-68) infection of Mus musculus-derived strains of mice is an established model of γ-herpesvirus infection. We have previously developed an alternative system using a natural host, the wood mouse (Apodemus sylvaticus), and shown that the MHV-68 M3 chemokine-binding protein contributes significantly to MHV-68 pathogenesis. Here we demonstrate in A. sylvaticus using high-density micro-arrays that M3 influences the expression of genes involved in the host response including Scgb1a1 and Bpifa1 that encode potential innate defense proteins secreted into the respiratory tract. Further analysis of MHV-68-infected animals showed that the levels of both protein and RNA for SCGB1A1 and BPIFA1 were decreased at day 7 post infection (p.i.) but increased at day 14 p.i. as compared with M3-deficient and mock-infected animals. The modulation of expression was most pronounced in bronchioles but was also present in the bronchi and trachea. Double staining using RNA in situ hybridization and immunohistology demonstrated that much of the BPIFA1 expression occurs in club cells along with SCGB1A1 and that BPIFA1 is stored within granules in these cells. The increase in SCGB1A1 and BPIFA1 expression at day 14 p.i. was associated with the differentiation of club cells into mucus-secreting cells. Our data highlight the role of club cells and the potential of SCGB1A1 and BPIFA1 as innate defense mediators during respiratory virus infection.

EGFR activation suppresses respiratory virus-induced IRF1-dependent CXCL10 production

Airway epithelial cells are the primary cell type involved in respiratory viral infection. Upon infection, airway epithelium plays a critical role in host defense against viral infection by contributing to innate and adaptive immune responses. Influenza A virus, rhinovirus, and respiratory syncytial virus (RSV) represent a broad range of human viral pathogens that cause viral pneumonia and induce exacerbations of asthma and chronic obstructive pulmonary disease. These respiratory viruses induce airway epithelial production of IL-8, which involves epidermal growth factor receptor (EGFR) activation. EGFR activation involves an integrated signaling pathway that includes NADPH oxidase activation of metalloproteinase, and EGFR proligand release that activates EGFR. Because respiratory viruses have been shown to activate EGFR via this signaling pathway in airway epithelium, we investigated the effect of virus-induced EGFR activation on airway epithelial antiviral responses. CXCL10, a chemokine produced by airway epithelial cells in response to respiratory viral infection, contributes to the recruitment of lymphocytes to target and kill virus-infected cells. While respiratory viruses activate EGFR, the interaction between CXCL10 and EGFR signaling pathways is unclear, and the potential for EGFR signaling to suppress CXCL10 has not been explored. Here, we report that respiratory virus-induced EGFR activation suppresses CXCL10 production. We found that influenza virus-, rhinovirus-, and RSV-induced EGFR activation suppressed IFN regulatory factor (IRF) 1-dependent CXCL10 production. In addition, inhibition of EGFR during viral infection augmented IRF1 and CXCL10. These findings describe a novel mechanism that viruses use to suppress endogenous antiviral defenses, and provide potential targets for future therapies.

Investigation of anti-infection mechanism of lactoferricin and splunc-1

The innate immune system is the first line in the defense system and prevents the body from further bacteria, virus, or fungal infections. Most of the innate immune system is relevant to mucosa immunity. Lactotransferrin is secreted from the human mammal breast duct epithelial tissue and strengthens infant immunity to defense with regard to outward pathogens. Splunc-1 is also an innate material secreted from the soft palate, lung, nasal cavity epithelium, and mucosa. It helps with mucosa defense against bacterial, virus, and even fungus. LPS is the main etiology of Gram-negative bacilla infection source. And studies of lactoferricin and slpunc-1 both can combine with LPS and subsequently cause insults to the mucosa. Although, we know that both of them partake in an important role in innate immunity, we do not know the effects when they work together. In this study, we just overview silicon stimulation to examine the combination of Lactoferricin and Splunc-1 and the effect with regard to LPS.