Accessory cell function of airway epithelial cells

Analysis of Nipah Virus Replication and Host Proteome Response Patterns in Differentiated Porcine Airway Epithelial Cells Cultured at the Air-Liquid Interface

Respiratory tract epithelium infection plays a primary role in Nipah virus (NiV) pathogenesis and transmission. Knowledge about infection dynamics and host responses to NiV infection in respiratory tract epithelia is scarce. Studies in non-differentiated primary respiratory tract cells or cell lines indicate insufficient interferon (IFN) responses. However, studies are lacking in the determination of complex host response patterns in differentiated respiratory tract epithelia for the understanding of NiV replication and spread in swine. Here we characterized infection and spread of NiV in differentiated primary porcine bronchial epithelial cells (PBEC) cultivated at the air-liquid interface (ALI). After the initial infection of only a few apical cells, lateral spread for 12 days with epithelium disruption was observed without releasing substantial amounts of infectious virus from the apical or basal sides. Deep time course proteomics revealed pronounced upregulation of genes related to type I/II IFN, immunoproteasomal subunits, transporter associated with antigen processing (TAP)-mediated peptide transport, and major histocompatibility complex (MHC) I antigen presentation. Spliceosomal factors were downregulated. We propose a model in which NiV replication in PBEC is slowed by a potent and broad type I/II IFN host response with conversion from 26S proteasomes to immunoproteasomal antigen processing and improved MHC I presentation for adaptive immunity priming. NiV induced cytopathic effects could reflect the focal release of cell-associated NiV, which may contribute to efficient airborne viral spread between pigs.

The role of ferroptosis-related genes in airway epithelial cells of asthmatic patients based on bioinformatics

It has been reported that airway epithelial cells and ferroptosis have certain effect on asthma. However, the action mechanism of ferroptosis-related genes in airway epithelial cells of asthmatic patients is still unclear. Firstly, the study downloaded the GSE43696 training set, GSE63142 validation set and GSE164119 (miRNA) dataset from the gene expression omnibus database. 342 ferroptosis-related genes were downloaded from the ferroptosis database. Moreover, differentially expressed genes (DEGs) between asthma and control samples in the GSE43696 dataset were screened by differential analysis. Consensus clustering analysis was performed on asthma patients to classify clusters, and differential analysis was performed on clusters to obtain inter-cluster DEGs. Asthma-related module was screened by weighted gene co-expression network analysis. Then, DEGs between asthma and control samples, inter-cluster DEGs and asthma-related module were subjected to venn analysis for obtaining candidate genes. The last absolute shrinkage and selection operator and support vector machines were respectively applied to the candidate genes to screen for feature genes, and functional enrichment analysis was performed. Finally, a competition endogenetic RNA network was constructed and drug sensitivity analysis was conducted. There were 438 DEGs (183 up-regulated and 255 down-regulated) between asthma and control samples. 359 inter-cluster DEGs (158 up-regulated and 201 down-regulated) were obtained by screening. Then, the black module was significantly and strongly correlated with asthma. The venn analysis yielded 88 candidate genes. 9 feature genes (NAV3, ITGA10, SYT4, NOX1, SNTG2, RNF182, UPK1B, POSTN, SHISA2) were screened and they were involved in proteasome, dopaminergic synapse etc. Besides, 4 mRNAs, 5 miRNAs, and 2 lncRNAs collectively formed competition endogenetic RNA regulatory network, which included RNF182-hsa-miR-455-3p-LINC00319 and so on. The predicted therapeutic drug network map contained NAV3-bisphenol A and other relationship pairs. The study investigated the potential molecular mechanisms of NAV3, ITGA10, SYT4, NOX1, SNTG2, RNF182, UPK1B, POSTN, SHISA2 in airway epithelial cells of asthmatic patients through bioinformatics analysis, providing a reference for the research of asthma and ferroptosis.

Decreased expression of surfactant Protein-C and CD74 in alveolar epithelial cells during influenza virus A(H1N1)pdm09 and H3N2 infection

The primary replication site of Influenza A virus (IAV) is type II alveolar epithelial cells (AECII), which are central to normal lung function and present important immune functions. Surfactant components are synthesized primarily by AECII, which play a crucial role in host defense against infection. The aim of this study was to analyze if the impact of influenza infection is differential between A(H1N1)pdm09 and A/Victoria/3/75 (H3N2) on costimulatory molecules and ProSP-C expression in AECII from BALB/c mice infected and A549 cell line infected with both strains. Pandemic A(H1N1)pdm09 and A/Victoria/3/75 (H3N2) were used to infect BALB/c mice and the A549 cell line. We evaluated the surface expression of co-stimulatory molecules (CD45/CD31/CD74/ProSP-C) in AECII and A549 cell lines. Our results showed a significant decrease in ProSP-C⁺ CD31^- CD45^- and CD74⁺ CD31^- CD45^- expression in AECII and A549 cell line with the virus strain A(H1N1)pdm09 versus A/Victoria/3/75 (H3N2) and controls (non-infection conditions). Our findings indicate that changes in the expression of ProSP-C in AECII and A549 cell lines in infection conditions could result in dysfunction leading to decreased lung compliance, increased work of breathing and increased susceptibility to injury.

Cathepsin S: investigating an old player in lung disease pathogenesis, comorbidities, and potential therapeutics

Dysregulated expression and activity of cathepsin S (CTSS), a lysosomal protease and a member of the cysteine cathepsin protease family, is linked to the pathogenesis of multiple diseases, including a number of conditions affecting the lungs. Extracellular CTSS has potent elastase activity and by processing cytokines and host defense proteins, it also plays a role in the regulation of inflammation. CTSS has also been linked to G-coupled protein receptor activation and possesses an important intracellular role in major histocompatibility complex class II antigen presentation. Modulated CTSS activity is also associated with pulmonary disease comorbidities, such as cancer, cardiovascular disease, and diabetes. CTSS is expressed in a wide variety of immune cells and is biologically active at neutral pH. Herein, we review the significance of CTSS signaling in pulmonary diseases and associated comorbidities. We also discuss CTSS as a plausible therapeutic target and describe recent and current clinical trials examining CTSS inhibition as a means for treatment.

Chronic E-Cigarette Use Increases Neutrophil Elastase and Matrix Metalloprotease Levels in the Lung

Rationale: Proteolysis is a key aspect of the lung's innate immune system. Proteases, including neutrophil elastase and MMPs (matrix metalloproteases), modulate cell signaling, inflammation, tissue remodeling, and leukocyte recruitment via cleavage of their target proteins. Excessive proteolysis occurs with chronic tobacco use and is causative for bronchiectasis and emphysema. The effect of e-cigarettes (vaping) on proteolysis is unknown.

Objectives: We used protease levels as biomarkers of harm to determine the impact of vaping on the lung.

Methods: We performed research bronchoscopies on healthy nonsmokers, cigarette smokers, and e-cigarette users (vapers), and determined protease levels in BAL. In parallel, we studied the effects of e-cigarette components on protease secretion in isolated human blood neutrophils and BAL-derived macrophages. We also analyzed the nicotine concentration in induced sputum and BAL.

Measurements and Main Results: Neutrophil elastase, MMP-2, and MMP-9 activities and protein levels were equally elevated in both vapers' and smokers' BAL relative to nonsmokers. In contrast, antiprotease levels were unchanged. We also found that exposure of isolated neutrophils and macrophages to nicotine elicited dose-dependent increases in protease release. After vaping, measurable levels of nicotine were detectable in sputum and BAL, which corresponded to the half-maximal effective concentration values for protease release seen in immune cells.

Conclusions: We conclude that vaping induces nicotine-dependent protease release from resident pulmonary immune cells. Thus, chronic vaping disrupts the protease-antiprotease balance by increasing proteolysis in lung, which may place vapers at risk of developing chronic lung disease. These data indicate that vaping may not be safer than tobacco smoking.

Calcitonin Gene-Related Peptide Regulates the Potential Antigen Uptake Ability of Human Bronchial Epithelial Cells

In this study we tried to explore whether calcitonin gene-related peptide (CGRP) regulates the potential antigen uptaking ability of human bronchial epithelial cells (HBECs) and promoting the differentiation of Th1/Th2. We found that CGRP increased the uptake of fluorescein isothiocyanate labeled ovalbumin (FITC-OVA) by HBECs using fluorescence microscopy and flow cytometry analysis. MTT assay showed that T cells proliferated in a dose-dependent manner in the presence of OVA-pretreated HBECs and CGRP inhibited the proliferation of T cells. CGRP decreased secretion of IFN-γ, while it had no influence on secretion of IL-4 by ELISA. Our data suggest that CGRP enhanced HBECs antigen uptake ability and inhibits HBECs induced T cells proliferation.

PD-L1 Expression on Circulating CD34＋ Hematopoietic Stem Cells Closely Correlated with T-cell Apoptosis in Chronic Hepatitis C Infected Patients

Background and Objectives

Lack of understanding of the interplay between hematopoietic stem cells (HSCs) and the immune system has severely hampered stem cell research. Programmed death-1 (PD-L1) has been reported on parenchymal cells in patients with chronically inflamed livers and found to play an essential role in T cell homeostasis regulation. However, the bidirectional interaction between HSCs and lymphocytes remains elusive. Here, we aimed to get more insight into circulating CD34+ HSCs PD-L1 expression and T cell apoptosis in chronic HCV infected patients.

Methods

CD34+ HSCs were isolated and purified by immunomagnetic separation. PD-L1 expression was analyzed by quantitative PCR and flow cytometry. Furthermore, co-culture experiments between CD34+ HSCs and T-lymphocytes were established. T-cell lymphocyte apoptosis in peripheral blood and in cultures was detected.

Results

CD34+ HSCs constitutively express low levels of PD-L1. Its expression is up-regulated in chronic HCV infected patients. Moreover, PD-L1 expression on circulating CD34+ HSCs enhanced T cell apoptosis in peripheral blood and co-culture.

Conclusion

Our results suggest novel bidirectional interplay between HSCs and lymphocytes mediated by PD-L1 expression on CD34+ HSCs. PD-L1 expression correlated with T-cell lymphocyte apoptosis. This may contribute to immunomodulatory properties of HSCs which improves its use for allogeneic transplantation.

ITGB4 is essential for containing HDM-induced airway inflammation and airway hyperresponsiveness

Airway epithelial cells play a significant role in the pathogenesis of asthma. Although the structural and functional defects of airway epithelial cells have been postulated to increase asthma susceptibility and exacerbate asthma severity, the mechanism and implication of these defects remain uncertain. Integrin β4 (ITGB4) is a structural adhesion molecule that is downregulated in the airway epithelium of asthma patients. In this study, we demonstrated that ITGB4 deficiency leads to severe allergy-induced airway inflammation and airway hyper-responsiveness (AHR) in mice. After house dust mite (HDM) challenge, epithelial cell-specific ITGB4-deleted mice showed increased lymphocyte, eosinophil, and neutrophil infiltration into lung compared with that of the wild-type mice. ITGB4 deficiency also resulted in increased expression of the Th2 cytokine IL-4, IL-13, and the Th17 cytokine IL-17A in the lung tissue and in the T cells after HDM challenge. The aggravated inflammation in ITGB4 defect mice was partly caused by enhanced disrupted epithelial barrier integrity after HDM stress, which induced the increased thymic stromal lymphopoietin secretion from airway epithelial cells. This study therefore demonstrates that ITGB4 plays a pivotal role in containing allergen-mediated lung inflammation and airway hyper-responsiveness in allergic asthma.

Nasal nanovaccines

Nasal administration of vaccines is convenient for the potential stimulation of mucosal and systemic immune protection. Moreover the easy accessibility of the intranasal route renders it optimal for pandemic vaccination. Nanoparticles have been identified as ideal delivery systems and adjuvants for vaccine application. Heterogeneous protocols have been used for animal studies. This complicates the understanding of the formulation influence on the immune response and the comparison of the different nanoparticles approaches developed. Moreover anatomical and immunological differences between rodents and humans provide an additional hurdle in the rational development of nasal nanovaccines. This review will give a comprehensive expertise of the state of the art in nasal nanovaccines in animals and humans focusing on the nanomaterial used.

Bronchial epithelial innate and adaptive immunity signals are induced by polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons including Benzo[a]pyrene have been recognised as important pollutant chemicals with the potential to influence the respiratory system in disease. Airway epithelial cells are an integral component of how immune responses are directed as a consequence of exposure to inhaled material. It was aim of this study to examine how such cells respond to PAH exposure and to characterise the immune response. Human primary bronchial epithelial cells (HPBECs) were exposed to Benzo[a]pyrene, Benzo[e]pyrene, Fluoranthene and Benzo[b]fluoranthene for 24 h and a repeat exposure up to 7 days, and examined for global gene expression using RNA-Seq. In addition to increased expression of CYP1A1 and other AHR dependent changes, we identified significant increases in innate and adaptive immune signals including, IL-1A, IL-19, SERPINB2, STAT6, HLA-DMB and HLA-DRA. We also observed increased expression of HMOX1 and NQO1, genes involved in the response to oxidative stress. Immune system related gene expression was differentially induced by each compound with Benzo[a]pyrene and Benzo[b]fluoranthene demonstrating the most potent responses. Differential induction paralleled the level to which AHR dependent gene expression and oxidative stress markers were induced. We also observed similar levels of gene expression when cells were exposed to organic extracts from diesel exhaust particles. In conclusion, hazard characterisation of responses to PAH exposure in HPBECs highlights specific responses of both innate and adaptive immunity.

miR-31 dysregulation in cystic fibrosis airways contributes to increased pulmonary cathepsin S production

RATIONALE

Cathepsin S (CTSS) activity is increased in bronchoalveolar lavage (BAL) fluid from patients with cystic fibrosis (CF). This activity contributes to lung inflammation via degradation of antimicrobial proteins, such as lactoferrin and members of the β-defensin family.

OBJECTIVES

In this study, we investigated the hypothesis that airway epithelial cells are a source of CTSS, and mechanisms underlying CTSS expression in the CF lung.

METHODS

Protease activity was determined using fluorogenic activity assays. Protein and mRNA expression were analyzed by ELISA, Western blotting, and reverse-transcriptase polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

In contrast to neutrophil elastase, CTSS activity was detectable in 100% of CF BAL fluid samples from patients without Pseudomonas aeruginosa infection. In this study, we identified epithelial cells as a source of pulmonary CTSS activity with the demonstration that CF airway epithelial cells express and secrete significantly more CTSS than non-CF control cells in the absence of proinflammatory stimulation. Furthermore, levels of the transcription factor IRF-1 correlated with increased levels of its target gene CTSS. We discovered that miR-31, which is decreased in the CF airways, regulates IRF-1 in CF epithelial cells. Treating CF bronchial epithelial cells with a miR-31 mimic decreased IRF-1 protein levels with concomitant knockdown of CTSS expression and secretion.

CONCLUSIONS

The miR-31/IRF-1/CTSS pathway may play a functional role in the pathogenesis of CF lung disease and may open up new avenues for exploration in the search for an effective therapeutic target.

Role of major histocompatibility complex class II expression by non-hematopoietic cells in autoimmune and inflammatory disorders: facts and fiction

It is well established that interactions between CD4(+) T cells and major histocompatibility complex class II (MHCII) positive antigen-presenting cells (APCs) of hematopoietic origin play key roles in both the maintenance of tolerance and the initiation and development of autoimmune and inflammatory disorders. In sharp contrast, despite nearly three decades of intensive research, the functional relevance of MHCII expression by non-hematopoietic tissue-resident cells has remained obscure. The widespread assumption that MHCII expression by non-hematopoietic APCs has an impact on autoimmune and inflammatory diseases has in most instances neither been confirmed nor excluded by indisputable in vivo data. Here we review and put into perspective conflicting in vitro and in vivo results on the putative impact of MHCII expression by non-hematopoietic APCs--in both target organs and secondary lymphoid tissues--on the initiation and development of representative autoimmune and inflammatory disorders. Emphasis will be placed on the lacunar status of our knowledge in this field. We also discuss new mouse models--developed on the basis of our understanding of the molecular mechanisms that regulate MHCII expression--that constitute valuable tools for filling the severe gaps in our knowledge on the functions of non-hematopoietic APCs in inflammatory conditions.

The multi-faceted role of allergen exposure to the local airway mucosa

Airway epithelial cells are the first to encounter aeroallergens and therefore have recently become an interesting target of many studies investigating their involvement in the modulation of allergic inflammatory responses. Disruption of a passive structural barrier composed of epithelial cells by intrinsic proteolytic activity of allergens may facilitate allergen penetration into local tissues and additionally affect chronic and ongoing inflammatory processes in respiratory tissues. Furthermore, the ability of rhinoviruses to disrupt and interfere with epithelial tight junctions may alter the barrier integrity and enable a passive passage of inhaled allergens through the airway epithelium. On the other hand, epithelial cells are no longer considered to act only as a physical barrier toward inhaled allergens, but also to actively contribute to airway inflammation by detecting and responding to environmental factors. Epithelial cells can produce mediators, which may affect the recruitment and activation of more specialized immune cells to the local tissue and also create a microenvironment in which these activated immune cells may function and propagate the inflammatory processes. This review presents the dual role of epithelium acting as a passive and active barrier when encountering an inhaled allergen and how this double role contributes to the start of local immune responses.

Downregulation of integrin β4 decreases the ability of airway epithelial cells to present antigens

Airway epithelial cells have been demonstrated to be accessory antigen presentation cells (APC) capable of activating T cells and may play an important role in the development of allergic airway inflammation of asthma. In asthmatic airways, loss of expression of the adhesion molecule integrin β4 (ITGB4) and an increase in Th2 inflammation bias has been observed in our previous study. Given that ITGB4 is engaged in multiple signaling pathways, we studied whether disruption of ITGB4-mediated cell adhesion may contribute to the adaptive immune response of epithelial cells, including their ability to present antigens, induce the activate and differentiate of T cells. We silenced ITGB4 expression in bronchial epithelial cells with an effective siRNA vector and studied the effects of ITGB4 silencing on the antigen presentation ability of airway epithelial cells. T cell proliferation and cytokine production was investigated after co-culturing with ITGB4-silenced epithelial cells. Surface expression of B7 homologs and the major histocompatibility complex (MHC) class II was also detected after ITGB4 was silenced. Our results demonstrated that silencing of ITGB4 resulted in impaired antigen presentation processes and suppressed T cell proliferation. Meanwhile, decrease in Th1 cytokine production and increase in Th17 cytokine production was induced after co-culturing with ITGB4-silenced epithelial cells. Moreover, HLA-DR was decreased and the B7 homologs expression was different after ITGB4 silencing. Overall, this study suggested that downregulation of ITGB4 expression in airway epithelial cells could impair the antigen presentation ability of these cells, which further regulate airway inflammation reaction in allergic asthma.

Timothy grass pollen extract-induced gene expression and signalling pathways in airway epithelial cells

BACKGROUND

Grass pollen allergy is one of the most common allergies worldwide and airborne allergens are the major cause of allergic rhinitis. Airway epithelial cells (AECs) are the first to encounter and respond to aeroallergens and are therefore interesting targets for the development of new therapeutics. Our understanding of the epithelial contribution to immune responses is limited as most studies focus on only a few individual genes or proteins.

OBJECTIVE

To describe in detail the Timothy grass pollen extract (GPE)-induced gene expression in AECs.

METHODS

NCI-H292 cells were exposed to GPE for 24 h, and isolated RNA and cell culture supernatants were used for microarray analysis and multiplex ELISA, respectively.

RESULTS

Eleven thousand and seven hundred fifty-eight transcripts were affected after exposure to GPE, with 141 genes up-regulated and 121 genes down-regulated by more than threefold. The gene ontology group cell communication was among the most prominent categories. Network analysis revealed that a substantial part of regulated genes are related to the cytokines IL-6, IL-8, IL-1A, and the transcription factor FOS. After analysing significantly regulated signalling pathways, we found, among others, epidermal growth factor receptor 1, IL-1, Notch-, and Wnt-related signalling members. Unexpectedly, we found Jagged to be down-regulated and an increased release of IL-12, in line with a more Th1-biased response induced by GPE.

CONCLUSION AND CLINICAL RELEVANCE

Our data show that the stimulation of AECs with GPE results in the induction of a broad response on RNA and protein level by which they are able to affect the initiation and regulation of local immune responses. Detailed understanding of GPE-induced genes and signalling pathways will allow us to better define the pathogenesis of the allergic response and to identify new targets for treatment.

Increased programmed death-ligand-1 expression in human gastric epithelial cells in Helicobacter pylori infection

B7-H1 [programmed death-ligand-1 (PD-L1)] is a B7-family member that binds to programmed death-1 (PD-1). Recently, deficiency of PD-L1 has been demonstrated to result in accelerated gastric epithelial cell damage in gastritis, and PD-L1 is suggested to play a critical role in regulating T cell homeostasis. Here, we aimed to gain more insight into gastric PD-L1 expression, regulation and function during Helicobacter pylori infection. PD-L1 expression in human gastric epithelial cells was analysed using Western blotting, quantitative polymerase chain reaction and fluorescence activated cell sorter analysis. Furthermore, co-culture experiments of human gastric epithelial cells with primary human T cells or Jurkat T cells were conducted. PD-L1 expression in primary human gastric epithelial cells was strongly enhanced by H. pylori infection and activated T cells, and augmented markedly by further stimulation with interferon-γ or tumour necrosis factor-α. Moreover, PD-L1 expression in gastric epithelial cells significantly induced apoptosis of T cells. Our results indicate that a novel bidirectional interaction between human gastric epithelial cells and lymphocytes modulates PD-L1 expression in human gastric epithelial cells, contributing to the unique immunological properties of the stomach.

Phenotypic characteristics of human type II alveolar epithelial cells suitable for antigen presentation to T lymphocytes

Background

Type II alveolar epithelial cells (AECII) are well known for their role in the innate immune system. More recently, it was proposed that they could play a role in the antigen presentation to T lymphocytes but contradictory results have been published both concerning their surface expressed molecules and the T lymphocyte responses in mixed lymphocyte cultures. The use of either AECII cell line or fresh cells could explain the observed discrepancies. Thus, this study aimed at defining the most relevant model of accessory antigen presenting cells by carefully comparing the two models for their expression of surface molecules necessary for efficient antigen presentation.

Methods

We have compared by flow cytometry the surface expression of the major markers involved in the immunological synapse on the A549 cell line, the most popular model of type II alveolar epithelial cells, and freshly isolated cells. HLA-DR, CD80, CD86, ICOS-L, CD54, CD58 surface expression were studied in resting conditions as well as after IFN-γ/TNF-α treatment, two inflammatory cytokines, known to modulate some of these markers.

Results

The major difference found between the two cells types was the very low surface expression of HLA-DR on the A549 cell line compared to its constitutive expression on freshly isolated AECII. The surface expression of co-stimulatory molecules from the B7 family was very low for the CD86 (B7-2) and ICOS-L (B7-H2) and absent for CD80 (B7-1) on both freshly isolated cells and A549 cell line. Neither IFN-γ nor TNF-α could increase the expression of these classical co-stimulatory molecules. However CD54 (ICAM-1) and CD58 (LFA-3) adhesion molecules, known to be implicated in B7 independent co-stimulatory signals, were well expressed on the two cell types.

Conclusions

Constitutive expression of MHC class I and II molecules as well as alternative co-stimulatory molecules by freshly isolated AECII render these cells a good model to study antigen presentation.

Cytokine induced expression of programmed death ligands in human neutrophils

Recent evidence indicates that human neutrophils can serve as non-professional antigen presenting cells (APC). Although expression of MHC class II and co-stimulatory molecules on human neutrophils is limited, these molecules can be significantly induced following in vitro exposure to the cytokines IFNgamma and GM-CSF. Since professional APCs such as dendritic cells express both co-stimulatory and co-inhibitory molecules for activation and regulation of adaptive immunity, we determined whether cytokines induce increased expression of specific co-signaling molecules on human neutrophils. We report here that circulating human neutrophils express co-inhibitory molecules such as immunoglobulin-like transcript (ILT) 4 and 5, and also comparatively low and highly variable levels of ILT2 and ILT3, but the expression of these ILTs was not significantly changed by cytokine treatment. In contrast, we demonstrate for the first time that human peripheral blood neutrophils, although do not express the co-inhibitory molecule, programmed death ligand (PD-L) 1 on their surface, can express this molecule at moderate levels following cytokine exposure. Although moderate PD-L1 levels on healthy volunteers' neutrophils were not inhibitory to T cells, our findings do not exclude a possible robust increase in neutrophil PD-L1 expression in pathological conditions with immunosuppressive functions. These results suggest a possible immunoregulatory role for human neutrophils in adaptive immunity.

Human epithelial cells of the respiratory tract and the skin differentially internalize grass pollen allergens

Epithelial cells of both the respiratory tract and the skin form a tight barrier against environmental harm. They represent the site of first contact for airborne allergen carriers. Consequently, in this study, we analyzed the uptake of grass pollen allergens by epithelial cells: Phl p 1 was selected as a glycosylated allergen containing disulfide bridges whereas Phl p 6 lacks post-translational modifications. Allergen uptake by the respiratory epithelial cell line A549 reached a plateau at 2 hours, and both allergens were localized intracellularly in non-acidic vesicles. In addition, in A549 cells allergens were exocytosed, suggesting a transcytosis mechanism in the passage of allergens over the respiratory epithelial barrier. In contrast, allergens were predominately localized in lysosomes in keratinocytes, and allergen uptake did not reach a plateau up to 24 hours. Notably, keratinocytes from atopic patients showed a significantly increased uptake of Phl p 1 as compared with healthy donors. Preincubation of epithelial cells with IL-4 and/or IFN-gamma to simulate inflammatory status led to an increased allergen uptake only in keratinocytes. This higher engulfment of allergens by inflammatory-type keratinocytes suggests a higher susceptibility of inflamed skin for the uptake of allergens and consequently a potentially higher risk for sensitization under natural exposure conditions, such as chronic atopic eczema.

Role of cathepsin S in ozone-induced airway hyperresponsiveness and inflammation

Ambient ozone has been linked to the worsening of symptoms of patients with obstructive diseases such as chronic obstructive pulmonary disease (COPD) and asthma. We investigated the role of cathepsin S on ozone-induced airway hyperresponsiveness (AHR) and inflammation, using the selective cathepsin S inhibitor, Compound A. Balb/c mice were exposed to ozone at a concentration of 3 ppm or air for 3 h, following administration by gavage of Compound A or vehicle. Bronchoalveolar lavage (BAL) was performed 3 h and 20-24 h following exposure, AHR was measured at 20-24 h only. Ozone exposure, compared to air exposure increased BAL cathepsin S levels, AHR and BAL inflammatory cells. Compound A (30 mg kg(-1) p.o.) dosing compared to vehicle dosing inhibited ozone-induced AHR (-logPC100 vehicle: -0.70+/-0.12, n=8 vs. cathepsin S inhibitor: -1.30+/-0.06, P<0.001, n=8) at 20-24 h and BAL neutrophilia at 3 h and 20-24 h (P<0.05, n=6). Ozone exposure increased levels of BAL cytokines IL-6, TNF-alpha and IFN-gamma. Compound A reduced IL-6 at 3 h and 20-24 h (P<0.05, n=5) and TNF-alpha, at 20-24 h (P<0.05, n=6). These data indicate an important role for cathepsin S in the regulation of ozone-induced AHR and neutrophil cell recruitment and suggest that cathepsin S may be a target in the treatment of oxidative stress-induced AHR and inflammation.

Extracellular nucleotides regulate CCL20 release from human primary airway epithelial cells, monocytes and monocyte-derived dendritic cells

Extracellular nucleotides regulate ion transport and mucociliary clearance in human airway epithelial cells (HAECs) via the activation of P2 receptors, especially P2Y(2). Therefore, P2Y(2) receptor agonists represent potential pharmacotherapeutic agents to treat cystic fibrosis (CF). Nucleotides also modulate inflammatory properties of immune cells like dendritic cells (DCs), which play an important role in mucosal immunity. Using DNA-microarray experiments, quantitative RT-PCR and cytokine measurements, we show here that UTP up-regulated approximately 2- to 3-fold the antimicrobial chemokine CCL20 expression and release in primary HAECs cultured on permeable supports at an air-liquid interface (ALI). Both P2Y(2) (ATPgammaS, UTP, INS365) and P2Y(6) (UDP, INS48823) agonists increased CCL20 release. UTP-induced CCL20 release was insensitive to NF-kappaB pathway inhibitors but sensitive to inhibitors of ERK1/2 and p38/MAPK pathways. Furthermore, UTP had no effect on interleukin-(IL)-8 release and reduced the release of both CCL20 and IL-8 induced by TNF-alpha and LPS. Accordingly, UTP reduced the capacity of basolateral supernatants of HAECs treated with TNF-alpha or LPS to induce the chemoattraction of both CD4(+) T lymphocytes and neutrophils. In addition, we show that, in monocyte-derived DCs, ATPgammaS, and UDP but not UTP/INS365-stimulated CCL20 release. Likewise, UDP but not ATPgammaS was also able to increase CCL20 release from monocytes. Pharmacological experiments suggested an involvement of P2Y(11) or P2Y(6) receptors through NF-kappaB, ERK1/2, and p38/MAPK pathways. Altogether, our data demonstrate that nucleotides may modulate chemokine release and leukocyte recruitment in inflamed airways by acting on both epithelial and immune cells. Our results could be relevant for further clinical investigations in CF.

PD-L1 is induced in hepatocytes by viral infection and by interferon-alpha and -gamma and mediates T cell apoptosis

BACKGROUND/AIMS

B7-H1 (PD-L1) is a B7-family member that binds to programmed death-1 (PD-1). Recently, deficiency of PD-L1 has been demonstrated to result in accelerated hepatocyte damage in experimental autoimmune hepatitis, and PD-L1 was suggested to play a critical role in regulating T cell homeostasis. Absence of PD-1 enhanced proliferation of T cells in adenovirus-infected livers and resulted in a rapid clearance of the virus. Here, we aimed to get more insight into hepatic PD-L1 expression, regulation and function.

METHODS

PD-L1 expression was analyzed by quantitative PCR and FACS-analysis in primary human liver cells and hepatoma cells. Furthermore, coculture experiments with primary human T cells or Jurkat T cells were established.

RESULTS

In addition to nonparenchymal liver cells, also hepatocytes constitutively expressed low levels of PD-L1. PD-L1 expression in hepatocytes was strongly enhanced by activated T cells and viral infection, and markedly augmented by further stimulation with type I or type II interferons. Moreover, PD-L1 expression on hepatocytes induced apoptosis in T cells.

CONCLUSIONS

Our results suggest a novel bidirectional interaction between hepatocytes and lymphocytes modulated by PD-L1 expression in hepatocytes, which may contribute to the unique immunological properties of the liver.

Endosomal proteases in antigen presentation

Processing of cytoplasmic and endocytized foreign antigens were once thought to be completely separate pathways of peptide generation for MHC class I and class II peptide display. However, recent studies show actually that there is extensive overlap owing, in part, to the positioning of endosomal proteases at sites in which MHC class I and class II paths cross. The questions of how antigens access and persist at sites of endosomal processing are proving to be as important as those regarding the proteases themselves. However, individual proteases within the set of endosomal enzymes have emerged both as targets for microbial evasion from MHC-class-II-dependent immunity and as required elements in autoimmunity. Repeated implication of cathepsins in processing medically important antigens holds promise for therapeutic manipulation of proteases in diseases in which there is disordered adaptive immunity.

Nasal carriage of Staphylococcus aureus in house dust mite allergic patients and healthy controls

BACKGROUND

Staphylococcal colonization may influence the course of allergic diseases such as atopic dermatitis or allergic rhinitis. The frequency of Staphylococcus aureus (SA) nasal carriage and its possible influence on persistent allergic rhinitis was investigated.

METHODS

In nasal lavages from 22 patients with house dust mite allergy and 18 healthy controls, the number of SA colony forming units per ml were assessed and related to nasal symptom scores, the concentrations of three inflammatory cell activation markers, nasal total IgE and 17 cytokines in nasal secretions.

RESULTS

SA was found in 15/22 allergic patients and 4/18 controls (P < 0.01). Comparing allergic SA carriers with allergic noncarriers, nasal symptom scores tended to be higher (P < 0.1), and the cell activation markers ECP (10(2.23+/-0.33)vs 10(1.45+/-0.50) ng/ml; P < 0.05) and elastase (10(2.70+/-0.21)vs 10(2.12+/-0.34) ng/ml; P < 0.01), and nasal total IgE-levels (10(1.66+/-0.38)vs 10(1.2+/-0.28) kU/ml; P < 0.05) were significantly higher in allergic SA carriers. Nasal SA carriers had a higher nasal IL-13/IFN-gamma ratio (P < 0.01), and this was correlated with higher nasal total IgE in allergic patients (r = 0.6, P < 0.05).

CONCLUSION

Nasal SA carriage is frequent in patients with persistent allergic rhinitis. The data of this study suggest that they are not only secondary bystanders, but actively modulate the disease by promoting local IgE production.