Immunohistochemistry on resin sections: a comparison of resin embedding techniques for small mucosal biopsies

Acute airway inflammation following controlled biodiesel exhaust exposure in healthy subjects

BACKGROUND

Exposure to standard petrodiesel exhaust is linked to adverse health effects. Moreover, there is a mounting request to replace fossil-based fuels with renewable and sustainable alternatives and, therefore, rapeseed methyl ester (RME) and other biofuels have been introduced. However, recent toxicological research has indicated that biodiesel exhaust may also induce adverse health-related events.

AIM

To determine whether exposure to 100% RME biodiesel (BD100) exhaust would cause an acute airway neutrophilic recruitment in humans.

METHODS

Fourteen healthy subjects underwent exposure to diluted BD100 exhaust and filtered air for 1-h, in a blinded, random fashion. Bronchoscopy with endobronchial mucosal biopsies, bronchial wash (BW) and bronchoalveolar lavage (BAL) was performed six hours after exposure. Differential cell counts and inflammatory markers were determined in the supernatant and biopsies were stained immunohistochemically.

RESULTS

Compared with filtered air, BD100 exhaust exposure increased bronchial mucosal endothelial P-selectin adhesion molecule expression, as well as neutrophil, mast cell and CD68 + macrophage numbers. An increased influx of neutrophils and machrophages was also seen in BW.

CONCLUSION

Exposure to biodiesel exhaust was associated with an acute airway inflammation that appeared similar to preceding petrodiesel exposure studies. The present findings, together with the recently reported adverse cardiovascular effects after similar biodiesel exposure, indicate that biodiesel is not free of toxicity and may affect human health.

Human exposure to diesel exhaust induces CYP1A1 expression and AhR activation without a coordinated antioxidant response

BACKGROUND

Diesel exhaust (DE) induces neutrophilia and lymphocytosis in experimentally exposed humans. These responses occur in parallel to nuclear migration of NF-κB and c-Jun, activation of mitogen activated protein kinases and increased production of inflammatory mediators. There remains uncertainty regarding the impact of DE on endogenous antioxidant and xenobiotic defences, mediated by nuclear factor erythroid 2-related factor 2 (Nrf2) and the aryl hydrocarbon receptor (AhR) respectively, and the extent to which cellular antioxidant adaptations protect against the adverse effects of DE.

METHODS

Using immunohistochemistry we investigated the nuclear localization of Nrf2 and AhR in the epithelium of endobronchial mucosal biopsies from healthy subjects six-hours post exposure to DE (PM10, 300 µg/m3) versus post-filtered air in a randomized double blind study, as a marker of activation. Cytoplasmic expression of cytochrome P450s, family 1, subfamily A, polypeptide 1 (CYP1A1) and subfamily B, Polypeptide 1 (CYP1B1) were examined to confirm AhR activation; with the expression of aldo-keto reductases (AKR1A1, AKR1C1 and AKR1C3), epoxide hydrolase and NAD(P)H dehydrogenase quinone 1 (NQO1) also quantified. Inflammatory and oxidative stress markers were examined to contextualize the responses observed.

RESULTS

DE exposure caused an influx of neutrophils to the bronchial airway surface (p = 0.013), as well as increased bronchial submucosal neutrophil (p < 0.001), lymphocyte (p = 0.007) and mast cell (p = 0.002) numbers. In addition, DE exposure enhanced the nuclear translocation of the AhR and increased the CYP1A1 expression in the bronchial epithelium (p = 0.001 and p = 0.028, respectively). Nuclear translocation of AhR was also increased in the submucosal leukocytes (p < 0.001). Epithelial nuclear AhR expression was negatively associated with bronchial submucosal CD3 numbers post DE (r = -0.706, p = 0.002). In contrast, DE did not increase nuclear translocation of Nrf2 and was associated with decreased NQO1 in bronchial epithelial cells (p = 0.02), without affecting CYP1B1, aldo-keto reductases, or epoxide hydrolase protein expression.

CONCLUSION

These in vivo human data confirm earlier cell and animal-based observations of the induction of the AhR and CYP1A1 by diesel exhaust. The induction of phase I xenobiotic response occurred in the absence of the induction of antioxidant or phase II xenobiotic defences at the investigated time point 6 h post-exposures. This suggests DE-associated compounds, such as polycyclic aromatic hydrocarbons (PAHs), may induce acute inflammation and alter detoxification enzymes without concomitant protective cellular adaptations in human airways.

Identification of a new P450s gene (AccCYP4AV1) and its roles in abiotic stress resistance in the Apis cerana cerana Fabricius

Cytochrome P450 monooxygenases (P450s) play significant roles in protecting organisms from abiotic stress damage. Here, we report the sequence and characterization of a P450s gene (AccCYP4AV1), isolated from Apis cerana cerana Fabricius. The open reading frame of AccCYP4AV1 is 1506 base pairs long and encodes a predicted protein of 501 amino acids and 57.84 kDa, with an isoelectric point of 8.67. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis indicated that AccCYP4AV1 is more highly expressed in the midgut than in other tissues. In addition, the highest expression occurs in newly emerged adult workers, followed by the first instar of the larval stage. In addition, the expression of the AccCYP4AV1 was upregulated by low temperature (4 °C), ultraviolet radiation, hydrogen peroxide, paraquat, and dichlorvos treatments. In contrast, AccCYP4AV1 transcription was downregulated by other abiotic stress conditions: exposure to increased temperature (44 °C), deltamethrin, cadmium chloride, and mercury (II) chloride. Moreover, when AccCYP4AV1 was knocked-down by RNA interference, the results suggested that multiple antioxidant genes (AccsHSP22.6, AccSOD2, AccTpx1, and AccTpx4) were downregulated and antioxidant genes AccGSTO1 and AccTrx1 were upregulated. The activity levels of peroxidase and catalase were upregulated in the AccCYP4AV1-knocked-down samples, compared with those in the control groups. These findings suggest that the AccCYP4AV1 protein might be involved in the defense against abiotic stress damage.

Predominant DNMT and TET mediate effects of allergen on the human bronchial epithelium in a controlled air pollution exposure study

BACKGROUND

Epidemiological data show that traffic-related air pollution contributes to the increasing prevalence and severity of asthma. DNA methylation (DNAm) changes may elucidate adverse health effects of environmental exposures.

OBJECTIVES

We sought to assess the effects of allergen and diesel exhaust (DE) exposures on global DNAm and its regulation enzymes in human airway epithelium.

METHODS

A total of 11 participants, including 7 with and 4 without airway hyperresponsiveness, were recruited for a randomized, double-blind crossover study. Each participant had 3 exposures: filtered air + saline, filtered air + allergen, and DE + allergen. Forty-eight hours postexposure, endobronchial biopsies and bronchoalveolar lavages were collected. Levels of DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) enzymes, 5-methylcytosine, and 5-hydroxymethylcytosine were determined by immunohistochemistry. Cytokines and chemokines in bronchoalveolar lavages were measured by electrochemiluminescence multiplex assays.

RESULTS

Predominant DNMT (the most abundant among DNMT1, DNMT3A, and DNMT3B) and predominant TET (the most abundant among TET1, TET2, and TET3) were participant-dependent. 5-Methylcytosine and its regulation enzymes differed between participants with and without airway hyperresponsiveness at baseline (filtered air + saline) and in response to allergen challenge (regardless of DE exposure). Predominant DNMT and predominant TET correlated with lung function. Allergen challenge effect on IL-8 in bronchoalveolar lavages was modified by TET2 baseline levels in the epithelium.

CONCLUSIONS

Response to allergen challenge is associated with key DNAm regulation enzymes. This relationship is generally unaltered by DE coexposure but is rather dependent on airway hyperresponsiveness status. These enzymes therefore warranted further inquiry regarding their potential in diagnosis, prognosis, and treatment of asthma.

Staphylococcus aureus internalization in mast cells in nasal polyps: Characterization of interactions and potential mechanisms

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps is a common chronic condition. The exact cause of nasal polyps remains unknown. Recently, we made the novel observation of intracellular localization of Staphylococcus aureus within mast cells in nasal polyps.

OBJECTIVE

This follow-up study aimed to further characterize interactions between S aureus and mast cells in this setting and elucidate potential internalization mechanisms with particular emphasis on the role of staphylococcal enterotoxin B (SEB).

METHODS

A prospective study was performed using an explant tissue model with ex vivo inferior turbinate mucosa obtained from patients with chronic rhinosinusitis with nasal polyps (n = 7) and patients without CRS (n = 5). Immunohistochemistry was used to characterize S aureus uptake into mast cells and investigate the effects of SEB on this process. An in vitro cell-culture model was used to investigate mast cell-S aureus interactions by using a combination of fluorescent in situ hybridization, confocal laser scanning microscopy, scanning electron microscopy, transmission electron microscopy, and proliferation assays.

RESULTS

S aureus was captured by extracellular traps and entered mast cells through phagocytosis. Proliferating intracellular S aureus led to the expansion and eventual rupture of mast cells, resulting in release of viable S aureus into the extracellular space. The presence of SEB appeared to promote internalization of S aureus into mast cells.

CONCLUSION

This study provides new insights into the interactions between S aureus and mast cells, including the internalization process, and demonstrates a prominent role for SEB in promoting uptake of the bacteria into these cells.

Allergenic proteases cleave the chemokine CX3CL1 directly from the surface of airway epithelium and augment the effect of rhinovirus

CX3CL1 has been implicated in allergen-induced airway CD4⁺ T-lymphocyte recruitment in asthma. As epidemiological evidence supports a viral infection-allergen synergy in asthma exacerbations, we postulated that rhinovirus (RV) infection in the presence of allergen augments epithelial CX3CL1 release. Fully differentiated primary bronchial epithelial cultures were pretreated apically with house dust mite (HDM) extract and infected with rhinovirus-16 (RV16). CX3CL1 was measured by enzyme-linked immunosorbent assay and western blotting, and shedding mechanisms assessed using inhibitors, protease-activated receptor-2 (PAR-2) agonist, and recombinant CX3CL1-expressing HEK293T cells. Basolateral CX3CL1 release was unaffected by HDM but stimulated by RV16; inhibition by fluticasone or GM6001 implicated nuclear factor-κB and ADAM (A Disintegrin and Metalloproteinase) sheddases. Conversely, apical CX3CL1 shedding was stimulated by HDM and augmented by RV16. Although fluticasone or GM6001 reduced RV16+HDM-induced apical CX3CL1 release, heat inactivation or cysteine protease inhibition completely blocked CX3CL1 shedding. The HDM effect was via enzymatic cleavage of CX3CL1, not PAR-2 activation, yielding a product mitogenic for smooth muscle cells. Extracts of Alternaria fungus caused similar CX3CL1 shedding. We have identified a novel mechanism whereby allergenic proteases cleave CX3CL1 from the apical epithelial surface to yield a biologically active product. RV16 infection augmented HDM-induced CX3CL1 shedding-this may contribute to synergy between allergen exposure and RV infection in triggering asthma exacerbations and airway remodeling.

Human hantavirus infection elicits pronounced redistribution of mononuclear phagocytes in peripheral blood and airways

Hantaviruses infect humans via inhalation of virus-contaminated rodent excreta. Infection can cause severe disease with up to 40% mortality depending on the viral strain. The virus primarily targets the vascular endothelium without direct cytopathic effects. Instead, exaggerated immune responses may inadvertently contribute to disease development. Mononuclear phagocytes (MNPs), including monocytes and dendritic cells (DCs), orchestrate the adaptive immune responses. Since hantaviruses are transmitted via inhalation, studying immunological events in the airways is of importance to understand the processes leading to immunopathogenesis. Here, we studied 17 patients infected with Puumala virus that causes a mild form of hemorrhagic fever with renal syndrome (HFRS). Bronchial biopsies as well as longitudinal blood draws were obtained from the patients. During the acute stage of disease, a significant influx of MNPs expressing HLA-DR, CD11c or CD123 was detected in the patients’ bronchial tissue. In parallel, absolute numbers of MNPs were dramatically reduced in peripheral blood, coinciding with viremia. Expression of CCR7 on the remaining MNPs in blood suggested migration to peripheral and/or lymphoid tissues. Numbers of MNPs in blood subsequently normalized during the convalescent phase of the disease when viral RNA was no longer detectable in plasma. Finally, we exposed blood MNPs in vitro to Puumala virus, and demonstrated an induction of CCR7 expression on MNPs. In conclusion, the present study shows a marked redistribution of blood MNPs to the airways during acute hantavirus disease, a process that may underlie the local immune activation and contribute to immunopathogenesis in hantavirus-infected patients.

Inhalation of hantavirus-infected rodent droppings can cause a wide range of disease ranging from mild symptoms to deaths in humans. Central to hantavirus disease is vascular leakage that can manifest in different organs, including the lungs. Although the virus can infect endothelial cells lining the blood vessels, it does not cause cell death. Instead, activation of the immune system in response to viral infection has been implicated in causing vascular leakage. In this study, we investigated how monocytes and dendritic cells (DCs) are involved in hantavirus disease, given their capacity to activate other immune cells. We obtained unique clinical material from 17 Puumala virus-infected patients including mucosal biopsies from the airways as well as multiple blood draws over the course of disease. In the airways of these patients, we observed an infiltration of monocytes and DCs. In parallel, there was a dramatic depletion in peripheral blood—more than ten-fold—of monocytes and DCs that was sustained throughout the first two weeks of disease. Taken together, this study provides novel insights into immune mediated processes underlying human hantavirus pathogenesis.

Human Adenovirus Type 37 Uses αVβ1 and α3β1 Integrins for Infection of Human Corneal Cells

Epidemic keratoconjunctivitis (EKC) is a severe, contagious ocular disease that affects 20 to 40 million individuals worldwide every year. EKC is mainly caused by six types of human adenovirus (HAdV): HAdV-8, -19, -37, -53, -54, and -56. Of these, HAdV-8, -19, and -37 use sialic acid-containing glycans as cellular receptors. αVβ3, αVβ5, and a few additional integrins facilitate entry and endosomal release of other HAdVs. With the exception of a few biochemical analyses indicating that HAdV-37 can interact physically with αVβ5, little is known about the integrins used by EKC-causing HAdVs. Here, we investigated the overall integrin expression on human corneal cells and found expression of α2, α3, α6, αV, β1, and β4 subunits in human corneal in situ epithelium and/or in a human corneal epithelial (HCE) cell line but no or less accessible expression of α4, α5, β3, or β5. We also identified the integrins used by HAdV-37 through a series of binding and infection competition experiments and different biochemical approaches. Together, our data suggest that HAdV-37 uses αVβ1 and α3β1 integrins for infection of human corneal epithelial cells. Furthermore, to confirm the relevance of these integrins in the HAdV-37 life cycle, we developed a corneal multilayer tissue system and found that HAdV-37 infection correlated well with the patterns of αV, α3, and β1 integrin expression. These results provide further insight into the tropism and pathogenesis of EKC-causing HAdVs and may be of importance for future development of new antiviral drugs.

IMPORTANCE Keratitis is a hallmark of EKC, which is caused by six HAdV types (HAdV-8, -19, -37, -53, -54, and -56). HAdV-37 and some other HAdV types interact with integrin αVβ5 in order to enter nonocular human cells. In this study, we found that αVβ5 is not expressed on human corneal epithelial cells, thus proposing other host factors mediate corneal infection. Here, we first characterized integrin expression patterns on corneal tissue and corneal cells. Among the integrins identified, competition binding and infection experiments and biochemical assays pointed out αVβ1 and α3β1 to be of importance for HAdV-37 infection of corneal tissue. In the absence of a good animal model for EKC-causing HAdVs, we also developed an in vitro system with multilayer HCE cells and confirmed the relevance of the suggested integrins during HAdV-37 infection.

Human Lung Dendritic Cells: Spatial Distribution and Phenotypic Identification in Endobronchial Biopsies Using Immunohistochemistry and Flow Cytometry

The lungs are constantly exposed to the external environment, which in addition to harmless particles, also contains pathogens, allergens, and toxins. In order to maintain tolerance or to induce an immune response, the immune system must appropriately handle inhaled antigens. Lung dendritic cells (DCs) are essential in maintaining a delicate balance to initiate immunity when required without causing collateral damage to the lungs due to an exaggerated inflammatory response. While there is a detailed understanding of the phenotype and function of immune cells such as DCs in human blood, the knowledge of these cells in less accessible tissues, such as the lungs, is much more limited, since studies of human lung tissue samples, especially from healthy individuals, are scarce. This work presents a strategy to generate detailed spatial and phenotypic characterization of lung tissue resident DCs in healthy humans that undergo a bronchoscopy for the sampling of endobronchial biopsies. Several small biopsies can be collected from each individual and can be subsequently embedded for ultrafine sectioning or enzymatically digested for advanced flow cytometric analysis. The outlined protocols have been optimized to yield maximum information from small tissue samples that, under steady-state conditions, contain only a low frequency of DCs. While the present work focuses on DCs, the methods described can directly be expanded to include other (immune) cells of interest found in mucosal lung tissue. Furthermore, the protocols are also directly applicable to samples obtained from patients suffering from pulmonary diseases where bronchoscopy is part of establishing the diagnosis, such as chronic obstructive pulmonary disease (COPD), sarcoidosis, or lung cancer.

Severe asthma exists despite suppressed tissue inflammation: findings of the U-BIOPRED study

The U-BIOPRED study is a multicentre European study aimed at a better understanding of severe asthma. It included three steroid-treated adult asthma groups (severe nonsmokers (SAn group), severe current/ex-smokers (SAs/ex group) and those with mild-moderate disease (MMA group)) and healthy controls (HC group). The aim of this cross-sectional, bronchoscopy substudy was to compare bronchial immunopathology between these groups.In 158 participants, bronchial biopsies and bronchial epithelial brushings were collected for immunopathologic and transcriptomic analysis. Immunohistochemical analysis of glycol methacrylate resin-embedded biopsies showed there were more mast cells in submucosa of the HC group (33.6 mm^-2) compared with both severe asthma groups (SAn: 17.4 mm^-2, p<0.001; SAs/ex: 22.2 mm^-2, p=0.01) and with the MMA group (21.2 mm^-2, p=0.01). The number of CD4⁺ lymphocytes was decreased in the SAs/ex group (4.7 mm^-2) compared with the SAn (11.6 mm^-2, p=0.002), MMA (10.1 mm^-2, p=0.008) and HC (10.6 mm^-2, p<0.001) groups. No other differences were observed.Affymetrix microarray analysis identified seven probe sets in the bronchial brushing samples that had a positive relationship with submucosal eosinophils. These mapped to COX-2 (cyclo-oxygenase-2), ADAM-7 (disintegrin and metalloproteinase domain-containing protein 7), SLCO1A2 (solute carrier organic anion transporter family member 1A2), TMEFF2 (transmembrane protein with epidermal growth factor like and two follistatin like domains 2) and TRPM-1 (transient receptor potential cation channel subfamily M member 1); the remaining two are unnamed.We conclude that in nonsmoking and smoking patients on currently recommended therapy, severe asthma exists despite suppressed tissue inflammation within the proximal airway wall.

Protocadherin-1 Localization and Cell-Adhesion Function in Airway Epithelial Cells in Asthma

Background

The asthma gene PCDH1 encodes Protocadherin-1, a putative adhesion molecule of unknown function expressed in the airway epithelium. Here, we characterize the localization, differential expression, homotypic adhesion specificity and function of PCDH1 in airway epithelial cells in asthma.

Methods

We performed confocal fluorescence microscopy to determine subcellular localization of PCDH1 in 16HBE cells and primary bronchial epithelial cells (PBECs) grown at air-liquid interface. Next, to compare PCDH1 expression and localization in asthma and controls we performed qRT-PCR and fluorescence microscopy in PBECs and immunohistochemistry on airway wall biopsies. We examined homotypic adhesion specificity of HEK293T clones overexpressing fluorescently tagged-PCDH1 isoforms. Finally, to evaluate the role for PCDH1 in epithelial barrier formation and repair, we performed siRNA knockdown-studies and measured epithelial resistance.

Results

PCDH1 localized to the cell membrane at cell-cell contact sites, baso-lateral to adherens junctions, with increasing expression during epithelial differentiation. No differences in gene expression or localization of PCDH1 isoforms expressing the extracellular domain were observed in either PBECs or airway wall biopsies between asthma patients and controls. Overexpression of PCDH1 mediated homotypic interaction, whereas downregulation of PCDH1 reduced epithelial barrier formation, and impaired repair after wounding.

Conclusions

In conclusion, PCDH1 is localized to the cell membrane of bronchial epithelial cells baso-lateral to the adherens junction. Expression of PCDH1 is not reduced nor delocalized in asthma even though PCDH1 contributes to homotypic adhesion, epithelial barrier formation and repair.

Impact of tobacco smoking on cytokine signaling via interleukin-17A in the peripheral airways

There is excessive accumulation of neutrophils in the airways in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms remain poorly understood. It is known that extracellular cytokine signaling via interleukin (IL)-17A contributes to neutrophil accumulation in the airways but nothing is known about the impact of tobacco smoking on extracellular signaling via IL-17A. Here, we characterized the impact of tobacco smoking on extracellular cytokine signaling via IL-17A in the peripheral airways in long-term smokers with and without COPD and in occasional smokers before and after short-term exposure to tobacco smoke. We quantified concentrations of IL-17A protein in cell-free bronchoalveolar lavage (BAL) fluid samples (Immuno-quantitative PCR) and cytotoxic T-cells (immunoreactivity for CD8⁺ and CD3⁺) in bronchial biopsies. Matrix metalloproteinase-8 and human beta defensin 2 proteins were also quantified (enzyme-linked immunosorbent assay) in the BAL samples. The concentrations of IL-17A in BAL fluid were higher in long-term smokers without COPD compared with nonsmoking healthy controls, whereas those with COPD did not differ significantly from either of the other groups. Short-term exposure to tobacco smoke did not induce sustained alterations in these concentrations in occasional smokers. Long-term smokers displayed higher concentrations of IL-17A than did occasional smokers. Moreover, these concentrations correlated with CD8⁺ and CD3⁺ cells in biopsies among long-term smokers with COPD. In healthy nonsmokers, BAL concentrations of matrix metalloproteinase-8 and IL-17A correlated, whereas this was not the case in the pooled group of long-term smokers with and without COPD. In contrast, BAL concentrations of human beta defensin 2 and IL-17A correlated in all study groups. This study implies that long-term but not short-term exposure to tobacco smoke increases extracellular cytokine signaling via IL-17A in the peripheral airways. In the smokers with COPD, this signaling may involve cytotoxic T-cells. Long-term exposure to tobacco smoke leads to a disturbed association of extracellular IL-17A signaling and matrix metalloproteinase-8, of potential importance for the coordination of antibacterial activity.

Soluble ADAM33 initiates airway remodeling to promote susceptibility for allergic asthma in early life

Asthma is a chronic inflammatory airways disease that usually begins in early life and involves gene-environment interactions. Although most asthma exhibits allergic inflammation, many allergic individuals do not have asthma. Here, we report how the asthma gene a disintegrin and metalloprotease 33 (ADAM33) acts as local tissue susceptibility gene that promotes allergic asthma. We show that enzymatically active soluble ADAM33 (sADAM33) is increased in asthmatic airways and plays a role in airway remodeling, independent of inflammation. Furthermore, remodeling and inflammation are both suppressed in Adam33-null mice after allergen challenge. When induced in utero or added ex vivo, sADAM33 causes structural remodeling of the airways, which enhances postnatal airway eosinophilia and bronchial hyperresponsiveness following subthreshold challenge with an aeroallergen. This substantial gene-environment interaction helps to explain the end-organ expression of allergic asthma in genetically susceptible individuals. Finally, we show that sADAM33-induced airway remodeling is reversible, highlighting the therapeutic potential of targeting ADAM33 in asthma.

Loss of ADAM33 suppresses airway remodeling and allergic inflammation in mice, suggesting the therapeutic potential of targeting ADAM33 in asthma.

The Demonstration of Immunohistochemical Biomarkers in Methyl Methacrylate-Embedded Plucked Human Hair Follicles

Plucked human hair follicles have been proposed as a potential surrogate for tumour tissue for measuring the effect of drugs on pharmacodynamic biomarkers in drug intervention studies. We describe a new technique of embedding plucked hair follicles in the acrylic resin, methyl methacrylate, and the immunohistochemical demonstration of six potential biomarkers (Ki67, EGFR, phospho-p27, phospho-histone H3, phospho-MAPK and phospho-Rb) in de-plasticised sections. The advantages of this technique over those that have been used in support of clinical drug trials, such as skin and tumour biopsies, whole blood and whole hair samples is discussed.

Dendritic Cells and Monocytes with Distinct Inflammatory Responses Reside in Lung Mucosa of Healthy Humans

Every breath we take contains potentially harmful pathogens or allergens. Dendritic cells (DCs), monocytes, and macrophages are essential in maintaining a delicate balance of initiating immunity without causing collateral damage to the lungs because of an exaggerated inflammatory response. To document the diversity of lung mononuclear phagocytes at steady-state, we performed bronchoscopies on 20 healthy subjects, sampling the proximal and distal airways (bronchial wash and bronchoalveolar lavage, respectively), as well as mucosal tissue (endobronchial biopsies). In addition to a substantial population of alveolar macrophages, we identified subpopulations of monocytes, myeloid DCs (MDCs), and plasmacytoid DCs in the lung mucosa. Intermediate monocytes and MDCs were highly frequent in the airways compared with peripheral blood. Strikingly, the density of mononuclear phagocytes increased upon descending the airways. Monocytes from blood and airways produced 10-fold more proinflammatory cytokines than MDCs upon ex vivo stimulation. However, airway monocytes were less inflammatory than blood monocytes, suggesting a more tolerant nature. The findings of this study establish how to identify human lung mononuclear phagocytes and how they function in normal conditions, so that dysregulations in patients with respiratory diseases can be detected to elucidate their contribution to immunity or pathogenesis.

Morphometric analysis of inflammation in bronchial biopsies following exposure to inhaled diesel exhaust and allergen challenge in atopic subjects

Background

Allergen exposure and air pollution are two risk factors for asthma development and airway inflammation that have been examined extensively in isolation. The impact of combined allergen and diesel exhaust exposure has received considerably less attention. Diesel exhaust (DE) is a major contributor to ambient particulate matter (PM) air pollution, which can act as an adjuvant to immune responses and augment allergic inflammation. We aimed to clarify whether DE increases allergen-induced inflammation and cellular immune response in the airways of atopic human subjects.

Methods

Twelve atopic subjects were exposed to DE 300 μg.m⁻³ or filtered air for 2 h in a blinded crossover study design with a four-week washout period between arms. One hour following either filtered air or DE exposure, subjects were exposed to allergen or saline (vehicle control) via segmental challenge. Forty-eight hours post-allergen or control exposure, bronchial biopsies were collected. The study design generated 4 different conditions: filtered air + saline (FAS), DE + saline (DES), filtered air + allergen (FAA) and DE + allergen (DEA). Biopsies sections were immunostained for tryptase, eosinophil cationic protein (ECP), neutrophil elastase (NE), CD138, CD4 and interleukin (IL)-4. The percent positivity of positive cells were quantified in the bronchial submucosa.

Results

The percent positivity for tryptase expression and ECP expression remained unchanged in the bronchial submucosa in all conditions. CD4 % positive staining in DEA (0.311 ± 0.060) was elevated relative to FAS (0.087 ± 0.018; p = 0.035). IL-4 % positive staining in DEA (0.548 ± 0.143) was elevated relative to FAS (0.127 ± 0.062; p = 0.034). CD138 % positive staining in DEA (0.120 ± 0.031) was elevated relative to FAS (0.017 ± 0.006; p = 0.015), DES (0.044 ± 0.024; p = 0.040), and FAA (0.044 ± 0.008; p = 0.037). CD138 % positive staining in FAA (0.044 ± 0.008) was elevated relative to FAS (0.017 ± 0.006; p = 0.049). NE percent positive staining in DEA (0.224 ± 0.047) was elevated relative to FAS (0.045 ± 0.014; p = 0.031).

Conclusions

In vivo allergen and DE co-exposure results in elevated CD4, IL-4, CD138 and NE in the respiratory submucosa of atopic subjects, while eosinophils and mast cells are not changed.

Trial registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01792232.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0114-z) contains supplementary material, which is available to authorized users.

Skeletal muscle morphology in sarcopenia defined using the EWGSOP criteria: findings from the Hertfordshire Sarcopenia Study (HSS)

Background

Sarcopenia is defined as the loss of muscle mass and function with age and is associated with decline in mobility, frailty, falls and mortality. There is considerable interest in understanding the underlying mechanisms. Our aim was to characterise muscle morphology changes associated with sarcopenia among community dwelling older men.

Methods

One hundred and five men aged 68–76 years were recruited to the Hertfordshire Sarcopenia Study (HSS) for detailed characterisation of muscle including measures of muscle mass, strength and function. Muscle tissue was obtained from a biopsy of the vastus lateralis for 99 men and was processed for immunohistochemical studies to determine myofibre distribution and area, capillarisation and satellite cell (SC) density.

Results

Six (6 %) men had sarcopenia as defined by the European Working Group on Sarcopenia in Older People (EWGSOP) criteria. These men had lower SC density (1.7 cells/mm² vs 3.8 cells/mm², p = 0.06) and lower SC/fibre ratio (0.02 vs 0.06, p = 0.06) than men without sarcopenia. Although men with sarcopenia tended to have smaller myofibres and lower capillary to fibre ratio, these relationships were not statistically significant.

Conclusion

We have shown that there may be altered muscle morphology parameters in older men with sarcopenia. These results have the potential to help identify cell and molecular targets for therapeutic intervention. This work now requires extension to larger studies which also include women.

Effects of controlled diesel exhaust exposure on apoptosis and proliferation markers in bronchial epithelium - an in vivo bronchoscopy study on asthmatics, rhinitics and healthy subjects

BACKGROUND

Epidemiological evidence demonstrates that exposure to traffic-derived pollution worsens respiratory symptoms in asthmatics, but controlled human exposure studies have failed to provide a mechanism for this effect. Here we investigated whether diesel exhaust (DE) would induce apoptosis or proliferation in the bronchial epithelium in vivo and thus contribute to respiratory symptoms.

METHODS

Moderate (n = 16) and mild (n = 16) asthmatics, atopic non-asthmatic controls (rhinitics) (n = 13) and healthy controls (n = 21) were exposed to filtered air or DE (100 μg/m(3)) for 2 h, on two separate occasions. Bronchial biopsies were taken 18 h post-exposure and immunohistochemically analysed for pro-apoptotic and anti-apoptotic proteins (Bad, Bak, p85 PARP, Fas, Bcl-2) and a marker of proliferation (Ki67). Positive staining was assessed within the epithelium using computerized image analysis.

RESULTS

No evidence of epithelial apoptosis or proliferation was observed in healthy, allergic or asthmatic airways following DE challenge.

CONCLUSION

In the present study, we investigated whether DE exposure would affect markers of proliferation and apoptosis in the bronchial epithelium of asthmatics, rhinitics and healthy controls, providing a mechanistic basis for the reported increased airway sensitivity in asthmatics to air pollutants. In this first in vivo exposure investigation, we found no evidence of diesel exhaust-induced effects on these processes in the subject groups investigated.

A novel lung explant model for the ex vivo study of efficacy and mechanisms of anti-influenza drugs

Influenza A virus causes considerable morbidity and mortality largely because of a lack of effective antiviral drugs. Viral neuraminidase inhibitors, which inhibit viral release from the infected cell, are currently the only approved drugs for influenza, but have recently been shown to be less effective than previously thought. Growing resistance to therapies that target viral proteins has led to increased urgency in the search for novel anti-influenza compounds. However, discovery and development of new drugs have been restricted because of differences in susceptibility to influenza between animal models and humans and a lack of translation between cell culture and in vivo measures of efficacy. To circumvent these limitations, we developed an experimental approach based on ex vivo infection of human bronchial tissue explants and optimized a method of flow cytometric analysis to directly quantify infection rates in bronchial epithelial tissues. This allowed testing of the effectiveness of TVB024, a vATPase inhibitor that inhibits viral replication rather than virus release, and to compare efficacy with the current frontline neuraminidase inhibitor, oseltamivir. The study showed that the vATPase inhibitor completely abrogated epithelial cell infection, virus shedding, and the associated induction of proinflammatory mediators, whereas oseltamivir was only partially effective at reducing these mediators and ineffective against innate responses. We propose, therefore, that this explant model could be used to predict the efficacy of novel anti-influenza compounds targeting diverse stages of the viral replication cycle, thereby complementing animal models and facilitating progression of new drugs into clinical trials.

Decreased maturation of dendritic cells in the central airways of COPD patients is associated with VEGF, TGF-β and vascularity

BACKGROUND

Dendritic cells (DCs) have a pivotal role in the onset and regulation of innate and adaptive immune responses. Moreover, DCs can interact with angiogenic modulators, resulting in modification of their biology and participation in angiogenesis.

OBJECTIVES

This study was designed to evaluate the relationship between the density of DCs, vascularity and expression of angiogenic factors [vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β and basic fibroblast growth factor (bFGF)] in the central airways of chronic obstructive pulmonary disease (COPD) patients.

METHODS

The study included 20 patients with moderate/severe COPD and 8 healthy control subjects. Bronchial biopsies were evaluated by immunohistochemistry. Specimens were examined for CD83 and CD207 to mark mature and immature DCs, respectively, for collagen IV to evaluate vascularity, and for VEGF, TGF-β and bFGF.

RESULTS

Compared to controls, COPD patients had a significant reduction of CD83+ cells and an increased CD207/CD83 ratio (p < 0.05). Vascularity, VEGF, TGF-β and bFGF were also significantly increased in COPD patients as compared to controls (p < 0.01). In COPD patients, CD83+ cells were inversely related to VEGF and TGF-β expression (p < 0.05). Moreover, the CD207/CD83 ratio was positively related to VEGF, TGF-β and vascularity (p < 0.05). Finally, CD207+ cells were inversely related to FEV1 (p < 0.05).

CONCLUSION

Our results show a reduced maturation of DCs in COPD that was related to airway vascularity and angiogenic factors (VEGF and TGF-β). Additionally, immature DCs were significantly related to disease severity. We propose that the interplay between airway vascular changes, on one hand, and DCs maturation on the other, may play a key role in the pathogenetic mechanisms of COPD.

TNF-α-mediated bronchial barrier disruption and regulation by src-family kinase activation

BACKGROUND

Because TNF-α is increased in severe asthma, we hypothesized that TNF-α contributes to barrier dysfunction and cell activation in bronchial epithelial cells. We further hypothesized that src-family kinase inhibition would improve barrier function in healthy cells in the presence of TNF-α and directly in cultures of severe asthmatic cells where the barrier is disrupted.

OBJECTIVES

We assessed the effect of TNF-α, with or without src-family kinase inhibitor SU6656, on barrier properties and cytokine release in differentiated human bronchial epithelial cultures. Further, we tested the effect of SU6656 on differentiated primary cultures from severe asthma.

METHODS

Barrier properties of differentiated human bronchial epithelial air-liquid interface cultures from healthy subjects and subjects with severe asthma were assessed with transepithelial electrical resistance and fluorescent dextran passage. Proteins were detected by immunostaining or Western blot analysis and cytokines by immunoassay. Mechanisms were investigated with src kinase and other inhibitors.

RESULTS

TNF-α lowered transepithelial electrical resistance and increased fluorescent dextran permeability, caused loss of occludin and claudins from tight junctions with redistribution of p120 catenin and E-cadherin from adherens junctions, and also increased endogenous TNF-α, IL-6, IL-1β, IL-8, thymic stromal lymphoprotein, and pro-matrix metalloprotease 9 release. SU6656 reduced TNF-α-mediated paracellular permeability changes, restored occludin, p120, and E-cadherin and lowered autocrine TNF-α release. Importantly, SU6656 improved the barrier properties of severe asthmatic air-liquid interface cultures. Redistribution of E-cadherin and p120 was observed in bronchial biopsies from severe asthmatic airways.

CONCLUSIONS

Inhibiting TNF-α or src kinases may be a therapeutic option to normalize barrier integrity and cytokine release in airway diseases associated with barrier dysfunction.

Airway inflammatory responses to diesel exhaust in allergic rhinitics

CONTEXT

Proximity to traffic, particularly to diesel-powered vehicles, has been associated with inducing and enhancing allergies. To investigate the basis for this association, we performed controlled exposures of allergic rhinitics to diesel exhaust (DE) at a dose known to be pro-inflammatory in healthy individuals.

OBJECTIVE

We hypothesized that diesel-exhaust exposure would augment lower airway inflammation in allergic rhinitics.

MATERIALS AND METHODS

Fourteen allergic rhinitics were exposed in a double-blinded, randomized trial to DE (100 μg/m³ PM₁₀) and filtered air for 2 h on separate occasions. Bronchoscopy with endobronchial mucosal biopsies and airway lavage was performed 18 h post-exposure, and inflammatory markers were assessed.

RESULTS

No evidence of neutrophilic airway inflammation was observed post-diesel, however, a small increase in myeloperoxidase was found in bronchoalveolar lavage (p = 0.032). We found no increases in allergic inflammatory cells. Reduced mast cell immunoreactivity for tryptase was observed in the epithelium (p = 0.013) parallel to a small decrease in bronchial wash stem cell factor (p = 0.033).

DISCUSSION AND CONCLUSION

DE, at a dose previously shown to cause neutrophilic inflammation in healthy individuals, induced no neutrophilic inflammation in the lower airways of allergic rhinitics, consistent with previous reports in asthmatics. Although there was no increase in allergic inflammatory cell numbers, the reduction in tryptase in the epithelium may indicate mast cell degranulation. However, this occurred in the absence of allergic symptoms. These data do not provide a simplistic explanation of the sensitivity in rhinitics to traffic-related air pollution. The role of mast cells requires further investigation.

Adhesion molecules in subjects with COPD and healthy non-smokers: a cross sectional parallel group study

Background

The aim of the study was to investigate how the expression of adhesion molecules changes as neutrophils migrate from the circulation to the lung and if these changes differ between non-smoking subjects and smokers with and without COPD.

Methods

Non-smoking healthy subjects (n=22), smokers without (n=21) and with COPD (n=18) were included. Neutrophils from peripheral blood, sputum and bronchial biopsies were analysed for cell surface expression of adhesion molecules (CD11b, CD62L, CD162). Serum, sputum supernatant and BAL-fluid were analysed for soluble adhesion molecules (ICAM-1, -3, E-selectin, P-selectin, VCAM-1, PECAM-1).

Results

Expression of CD11b was increased on circulating neutrophils from smokers with COPD. It was also increased on sputum neutrophils in both smokers groups, but not in non-smokers, as compared to circulating neutrophils.

Serum ICAM-1 was higher in the COPD group compared to the other two groups (p<0.05) and PECAM-1 was lower in smokers without COPD than in non-smoking controls and the COPD group (p<0.05). In BAL-fluid ICAM-1 was lower in the COPD group than in the other groups (p<0.05).

Conclusions

Thus, our data strongly support the involvement of a systemic component in COPD and demonstrate that in smokers neutrophils are activated to a greater extent at the point of transition from the circulation into the lungs than in non-smokers.

Tissue factor-bearing exosome secretion from human mechanically stimulated bronchial epithelial cells in vitro and in vivo

BACKGROUND

Tissue factor (TF), a primary initiator of blood coagulation, also plays a pivotal role in angiogenesis. TF expression in the airways is associated with asthma, a disease characterized in part by subepithelial angiogenesis.

OBJECTIVES

To determine potential sources of TF and the mechanisms of its availability in the lung microenvironment.

METHODS

Normal human bronchial epithelial cells grown in air-liquid interface culture were subjected to a compressive stress of 30 cm H(2)O; this is comparable to that generated in the airway epithelium during bronchoconstriction in asthma. Conditioned media and cells were harvested to measure TF mRNA and TF protein. We also tested bronchoalveolar lavage fluid and airway biopsies from asthmatic patients and healthy controls for TF.

RESULTS

TF mRNA was upregulated 2.2-fold after 3 hours of stress compared with unstressed cells. Intracellular and secreted TF proteins were enhanced 1.6-fold and more than 50-fold, respectively, compared with those of control cells after the onset of compression. The amount of TF in the bronchoalveolar lavage fluid from patients with asthma was found at mean concentrations that were 5 times greater than those of healthy controls. Immunohistochemical staining of endobronchial biopsies identified epithelial localization of TF with increased expression in asthma. Exosomes isolated from the conditioned media of normal human bronchial epithelial cells and the bronchoalveolar lavage fluid of asthmatic subjects by ultracentrifugation contained TF.

CONCLUSIONS

Our in vitro and in vivo studies show that mechanically stressed bronchial epithelial cells are a source of secreted TF and that exosomes are potentially a key carrier of the TF signal.

Increased expression of the 5-lipoxygenase pathway and its cellular localization in Barrett's adenocarcinoma

AIMS

Up-regulation of the 5-lipoxygenase (5-LOX) leukotriene pathway is evident in numerous tumour types, and has been linked to the promotion of cancer cell growth. The aim of this study was to evaluate the immunohistochemical expression of 5-LOX pathway proteins in oesophageal adenocarcinoma and its premalignant lesion, Barrett's metaplasia.

METHODS AND RESULTS

Tissue samples were collected at endoscopy from 16 patients with Barrett's metaplasia and from seven with oesophageal adenocarcinoma; five proximal squamous oesophagus samples were used as controls. Immunohistochemical analyses were performed on stromal and epithelial areas with optimized concentrations of primary antibodies for 5-LOX, 5-LOX-activating protein (FLAP), and the distal enzymes leukotriene (LT) A(4) hydrolase (LTA(4) H) and LTC(4) synthase (LTC(4) S). the diagnosis was histologically confirmed from adjacent sections by a gastrointestinal pathologist. Striking increases in the stromal immunoexpression of 5-LOX (P = 0.041), FLAP (P = 0.038), LTA(4) H (P = 0.0008) and LTC(4) S (P = 0.036) were seen in adenocarcinoma tissue. Stromal FLAP and LTA(4) H immunostaining correlated with elevated neutrophil counts (P < 0.001). LTC(4) S was also notably overexpressed within epithelial cells in both Barrett's metaplasia (P < 0.001) and adenocarcinoma (P < 0.01) tissue.

CONCLUSIONS

Key biosynthetic enzymes of the LTB(4) and LTC(4) biosynthetic pathways are incrementally expressed across the spectrum of squamous, Barrett's metaplasia and oesophageal adenocarcinoma tissues, suggesting, for the first time, a role for both LT subfamilies in disease progression.

Increased hypoxia-inducible factor 1α expression in lung cells of horses with recurrent airway obstruction

Background

Recurrent airway obstruction (RAO, also known as equine heaves) is an inflammatory condition caused by exposure of susceptible horses to organic dusts in hay. The immunological processes responsible for the development and the persistence of airway inflammation are still largely unknown. Hypoxia-inducible factor (Hif) is mainly known as a major regulator of energy homeostasis and cellular adaptation to hypoxia. More recently however, Hif also emerged as an essential regulator of innate immune responses. Here, we aimed at investigating the potential involvement of Hif1-α in myeloid cells in horse with recurrent airway obstruction.

Results

In vitro, we observed that Hif is expressed in equine myeloid cells after hay dust stimulation and regulates genes such as tumor necrosis factor alpha (TNF-α), interleukin-8 (IL-8) and vascular endothelial growth factor A (VEGF-A). We further showed in vivo that airway challenge with hay dust upregulated Hif1-α mRNA expression in myeloid cells from the bronchoalveolar lavage fluid (BALF) of healthy and RAO-affected horses, with a more pronounced effect in cells from RAO-affected horses. Finally, Hif1-α mRNA expression in BALF cells from challenged horses correlated positively with lung dysfunction.

Conclusion

Taken together, our results suggest an important role for Hif1-α in myeloid cells during hay dust-induced inflammation in horses with RAO. We therefore propose that future research aiming at functional inactivation of Hif1 in lung myeloid cells could open new therapeutic perspectives for RAO.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Salmon consumption by pregnant women reduces ex vivo umbilical cord endothelial cell activation

BACKGROUND

In vitro exposure of endothelial cells (ECs) to n-3 (omega-3) long-chain PUFAs (LCPUFAs) reduces cell adhesion molecule (CAM) expression. However, to our knowledge, no previous human studies have examined the influence of an altered diet on CAM expression.

OBJECTIVE

We assessed whether salmon (rich in n-3 LCPUFAs) consumption twice a week during pregnancy affected offspring umbilical vein EC CAM expression.

DESIGN

Women were randomly assigned to maintain their habitual diets or to consume 2 portions of salmon per week during pregnancy months 4-9. ECs were isolated from umbilical cord veins collected at birth and cultured. The cell surface expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) was assessed by flow cytometry after the culture of ECs in the presence and absence of bacterial LPS for 24 h. Cytokine and growth factor concentrations in culture supernatant fluid were measured by using a multiplex assay.

RESULTS

LPS increased the expression of VCAM-1 and the production of several cytokines and growth factors. The level of ICAM-1 expression per cell [ie, the median fluorescence intensity (MFI)] was increased by LPS stimulation in the control group (16.9 ± 2.4 compared with 135.3 ± 20.2; P < 0.001) and to a lesser extent in the salmon group (14.1 ± 3.8 compared with 65.8 ± 22.4; P = 0.037). The ICAM-1 MFI in the salmon group after LPS stimulation was lower than in the control group (P = 0.006).

CONCLUSION

Increased dietary salmon intake in pregnancy dampens offspring EC activation, which implicates a role for n-3 LCPUFAs in the suppression of inflammatory processes in humans. This trial was registered at clinicaltrials.gov as NCT00801502.

Airway inflammation in atopic patients: a comparison of the upper and lower airways

OBJECTIVE

The purpose of this study was to understand and assess the inflammatory response within the upper and lower airways in patients suffering from both asthma and allergic rhinitis. Study Design. Cross-sectional study. Setting. A laboratory-based study of patients with allergic rhinitis and asthma.

SUBJECTS AND METHODS

Glycol methacrylate resin-embedded specimens from 10 patients with allergic rhinitis and asthma taken from the nose and bronchi were assessed by immunohistochemistry. Monoclonal antibodies directed against specific cell markers for mast cells (AA1), eosinophils (EG2), neutrophils (NOE), and lymphocytes (CD3(+), CD4(+), CD8(+)) were studied. Cells were counted blind (as cells/mm(2)) in the submucosal matrix. Mann-Whitney U test was used for analyses. P values of .05 or lower were considered statistically significant.

RESULTS

There was a significant increase in CD4(+) (P = .05) and CD8(+) cell counts (P = .001) in the lower airway compared to the upper airway. There were no differences between the 2 groups in the number of neutrophils, mast cells, eosinophils, and the CD3(+) cell counts.

CONCLUSION

The upper and lower airways have parallel inflammation with possible bidirectional extension of inflammation in patients suffering from asthma and allergic rhinitis. There is increased lymphocytic infiltration in the lower airway, suggesting a possible preponderance for development and maintenance of allergic disease in the lower airway.

Defective epithelial barrier function in asthma

BACKGROUND

Asthma is a complex disease involving gene and environment interactions. Although atopy is a strong predisposing risk factor for asthma, local tissue susceptibilities are required for disease expression. The bronchial epithelium forms the interface with the external environment and is pivotally involved in controlling tissue homeostasis through provision of a physical barrier controlled by tight junction (TJ) complexes.

OBJECTIVES

To explain the link between environment exposures and airway vulnerability, we hypothesized that epithelial TJs are abnormal in asthma, leading to increased susceptibility to environmental agents.

METHODS

Localization of TJs in bronchial biopsies and differentiated epithelial cultures was assessed by electron microscopy or immunostaining. Baseline permeability and the effect of cigarette smoke and growth factor were assessed by measurement of transepithelial electrical resistance and passage of fluorescently labeled dextrans.

RESULTS

By using immunostaining, we found that bronchial biopsies from asthmatic subjects displayed patchy disruption of TJs. In differentiated bronchial epithelial cultures, TJ formation and transepithelial electrical resistance were significantly lower (P < .05) in cultures from asthmatic donors (n = 43) than from normal controls (n = 40) and inversely correlated with macromolecular permeability. Cultures from asthmatic donors were also more sensitive to disruption by cigarette smoke extract. Epidermal growth factor enhanced basal TJ formation in cultures from asthmatic subjects (P < .01) and protected against cigarette smoke-induced barrier disruption (P < .01).

CONCLUSIONS

Our results show that the bronchial epithelial barrier in asthma is compromised. This defect may facilitate the passage of allergens and other agents into the airway tissue, leading to immune activation and may thus contribute to the end organ expression of asthma.

Effect of bronchoconstriction on airway remodeling in asthma

BACKGROUND

Asthma is characterized pathologically by structural changes in the airway, termed airway remodeling. These changes are associated with worse long-term clinical outcomes and have been attributed to eosinophilic inflammation. In vitro studies indicate, however, that the compressive mechanical forces that arise during bronchoconstriction may induce remodeling independently of inflammation. We evaluated the influence of repeated experimentally induced bronchoconstriction on airway structural changes in patients with asthma.

METHODS

We randomly assigned 48 subjects with asthma to one of four inhalation challenge protocols involving a series of three challenges with one type of inhaled agent presented at 48-hour intervals. The two active challenges were with either a dust-mite allergen (which causes bronchoconstriction and eosinophilic inflammation) or methacholine (which causes bronchoconstriction without eosinophilic inflammation); the two control challenges (neither of which causes bronchoconstriction) were either saline alone or albuterol followed by methacholine (to control for nonbronchoconstrictor effects of methacholine). Bronchial-biopsy specimens were obtained before and 4 days after completion of the challenges.

RESULTS

Allergen and methacholine immediately induced similar levels of bronchoconstriction. Eosinophilic inflammation of the airways increased only in the allergen group, whereas both the allergen and the methacholine groups had significant airway remodeling not seen in the two control groups. Subepithelial collagen-band thickness increased by a median of 2.17 μm in the allergen group (interquartile range [IQR], 0.70 to 3.67) and 1.94 μm in the methacholine group (IQR, 0.37 to 3.24) (P<0.001 for the comparison of the two challenge groups with the two control groups); periodic acid-Schiff staining of epithelium (mucus glands) also increased, by a median of 2.17 percentage points in the allergen group (IQR, 1.03 to 4.77) and 2.13 percentage points in the methacholine group (IQR, 1.14 to 7.96) (P=0.003 for the comparison with controls). There were no significant differences between the allergen and methacholine groups.

CONCLUSIONS

Bronchoconstriction without additional inflammation induces airway remodeling in patients with asthma. These findings have potential implications for management.

Analysis of protein biomarkers in human clinical tumor samples: critical aspects to success from tissue acquisition to analysis

There has been increased interest in the analysis of protein biomarkers in clinical tumor tissues in recent years. Tissue-based biomarker assays can add value and aid decision-making at all stages of drug development, as well as being developed for use as predictive biomarkers and for patient stratification and prognostication in the clinic. However, there must be an awareness of the legal and ethical issues related to the sourcing of human tissue samples. This article also discusses the limits of scope and critical aspects on the successful use of the following tissue-based methods: immunohistochemistry, tissue microarrays and automated image analysis. Future advances in standardization of tissue biobanking methods, immunohistochemistry and quantitative image analysis techniques are also discussed.

Presence of activated airway T lymphocytes in human puumala hantavirus disease

BACKGROUND

Hantaviruses cause two clinical syndromes: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). The clinical spectrum in HFRS also often involves respiratory symptoms. As information about the pulmonary pathogenesis in HFRS is limited, we aimed to further study the local airway immune response in the lower airways.

METHODS

Bronchoscopy was performed in 15 hospitalized patients with HFRS, with sampling of endobronchial mucosal biopsies and BAL fluid. Biopsies were stained for leukocytes, lymphocyte subsets, and vascular endothelial adhesion molecules. BAL fluid and blood lymphocyte subsets were determined using flow cytometry. Fourteen healthy volunteers acted as a control group.

RESULTS

Compared with control subjects, endobronchial mucosal biopsies from patients with HFRS revealed increased numbers of CD8(+) T cells in both epithelium and submucosa (P ≤ .001), along with an increase in submucosal CD4(+) T cells (P = .001). In contrast, patients' submucosal neutrophil and eosinophil numbers were reduced (P < .001). The expression of vascular cell adhesion molecule-1 (VCAM-1) was enhanced in patients with HFRS (P < .001). In patients with HFRS, analyses of T-cell subsets in BAL fluid showed higher proportions of CD3(+) and CD8(+) T cells (P = .011 and P = .025) and natural killer cells (P < .001), together with an increased expression of activation markers human leukocyte antigen-DR (HLA-DR) and CD25 on T cells (P < .001 and P < .001).

CONCLUSIONS

The present findings indicate a local immune response in terms of activated T lymphocytes in the lungs of patients with HFRS. The elevated expression of activation markers and VCAM-1 further implies the importance of cytotoxic lymphocytes in the pathogenesis of pulmonary involvement in HFRS.

Enhanced immunohistochemical resolution of claudin proteins in glycolmethacrylate-embedded tissue biopsies

There are a number of disadvantages with conventional tissue immunohistochemistry for accurate -localisation of claudin proteins. Traditionally, tissue cryopreservation or formaldehyde fixation with wax embedding is utilised prior to sectioning and antibody localisation. Wax embedding gives better morphological preservation than frozen tissue, but the required use of chemical cross-linking fixatives renders many antigens inaccessible to antibody binding or results in subsequent disruption of antibody localisation patterns due to the use of harsh antigen retrieval methods. Use of frozen or wax-embedded tissue also requires the cutting of relatively thick>6-μm sections, making the interrogation of serial sections very limited. The use of glycolmethacrylate (GMA) tissue embedding with fixation in acetone is compatible with epitope preservation for many antibody reagents that are often destroyed by chemical cross-linking fixatives. GMA is a water-miscible embedding resin that maintains tissue hydration during processing, thus reducing tissue shrinkage, while embedding and cutting in the polymerised resin physically supports the tissue, thus improving morphology. This method also facilitates the cutting of 2-μm sequential sections for analysis of multiple antigens and maximises the information available from small tissue biopsies from human clinical sources.

Airway inflammatory response to diesel exhaust generated at urban cycle running conditions

CONTEXT

Diesel exhaust (DE) is an important component in traffic-related air pollution, associated with adverse health effects. DE generated at idling has been demonstrated to induce inflammation in human airways, in terms of inflammatory cell recruitment, enhanced expression of vascular endothelial adhesion molecules, cytokines, mitogen-activated protein kinases, and transcription factors in the bronchial epithelium.

OBJECTIVE

This study aimed to investigate airway inflammatory responses in healthy subjects exposed to DE generated during transient speed and engine load under the urban part of the European Transient Cycle.

METHODS

Fifteen healthy subjects were exposed to DE at an average particulate matter concentration of 270 µg/m(3) and filtered air for 1 h. Bronchoscopy with endobronchial mucosal biopsy sampling and airway lavage was performed 6 h postexposure.

RESULTS

Compared with filtered air, DE exposure caused an increased expression of the vascular endothelial adhesion molecules P-selectin and vascular cell adhesion molecule-1 (P  =  0.036 and P  =  0.030, respectively) in bronchial mucosal biopsies, together with increased numbers of bronchoalveolar lavage eosinophils (P  =  0.017).

CONCLUSIONS

DE generated under urban running conditions increased bronchial adhesion molecule expressions, together with the novel finding of bronchoalveolar eosinophilia, which has not been shown after exposure to DE at idling. Variations in airway inflammatory response to DE generated under diverse running condition may be related to differences in exhaust composition.

Cytotoxic T cells expressing the co-stimulatory receptor NKG2 D are increased in cigarette smoking and COPD

Background

A suggested role for T cells in COPD pathogenesis is based on associations between increased lung cytotoxic T lymphocyte (CD8⁺) numbers and airflow limitation. CD69 is an early T cell activation marker. Natural Killer cell group 2 D (NKG2D) receptors are co-stimulatory molecules induced on CD8⁺ T cells upon activation. The activating function of NKG2 D is triggered by binding to MHC class 1 chain-related (MIC) molecules A and B, expressed on surface of stressed epithelial cells. The aim of this study was to evaluate the expression of MIC A and B in the bronchial epithelium and NKG2 D and CD69 on BAL lymphocytes in subjects with COPD, compared to smokers with normal lung function and healthy never-smokers.

Methods

Bronchoscopy with airway lavages and endobronchial mucosal biopsy sampling was performed in 35 patients with COPD, 21 healthy never-smokers and 16 smokers with normal lung function. Biopsies were immunohistochemically stained and BAL lymphocyte subsets were determined using flow cytometry.

Results

Epithelial CD3⁺ lymphocytes in bronchial biopsies were increased in both smokers with normal lung function and in COPD patients, compared to never-smokers. Epithelial CD8⁺ lymphocyte numbers were higher in the COPD group compared to never-smoking controls. Among gated CD3⁺cells in BAL, the percentage of CD8⁺ NKG2D⁺ cells was enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. The percentage of CD8⁺ CD69⁺ cells and cell surface expression of CD69 were enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. No changes in the expression of MIC A or MIC B in the airway epithelium could be detected between the groups, whereas significantly decreased soluble MICB was detected in bronchial wash from smokers with normal lung function, compared to never-smokers.

Conclusions

In COPD, we found increased numbers of cytotoxic T cells in both bronchial epithelium and airway lumen. Further, the proportions of CD69- and NKG2D-expressing cytotoxic T cells in BAL fluid were enhanced in both subjects with COPD and smokers with normal lung function and increased expression of CD69 was found on CD8⁺ cells, indicating the cigarette smoke exposure-induced expansion of activated cytotoxic T cells, which potentially can respond to stressed epithelial cells.

Montelukast added to fluticasone propionate does not alter inflammation or outcomes

BACKGROUND

Airway inflammation is a key pathological feature of asthma which underlies its clinical presentation.

OBJECTIVES

To examine whether adding a leukotriene modifier to an inhaled corticosteroid produces further clinical and/or anti-inflammatory benefits in patients symptomatic on short-acting beta(2)-agonists.

METHODS

Patients uncontrolled on short-acting beta(2)-agonists were treated for 12 weeks with either fluticasone propionate (100mcg BD) or fluticasone propionate (100mcg BD) and montelukast (10mg QD) in a randomized, double-blind, parallel group study. Bronchoscopy with endobronchial biopsy and bronchoalveolar lavage (BAL) was performed before and after treatment to compare effects on airway inflammation.

RESULTS

Of 103 subjects enrolled, 89 subjects completed treatment and 82 subjects had matched pair biopsy samples. Submucosal eosinophil counts, the primary endpoint, and asthma control improved to similar extents after both treatments (p<or=0.008). Both treatments significantly reduced submucosal mast cell, CD3+, CD4+, CD8+ and CD25+ cell counts. Submucosal mast cell reduction was greater in the fluticasone propionate plus montelukast group. There were no differences between treatments in BAL markers of inflammation or thickness of sub-epithelial collagen.

CONCLUSIONS

Low-dose fluticasone propionate significantly improves clinical disease control and reduces airway inflammation in asthma patients uncontrolled with short-acting beta(2)-agonists without further improvement when montelukast is added to low-dose fluticasone propionate.

A panel of antibodies for identifying squamous metaplasia in endobronchial biopsies from smokers

Toxic injury can induce squamous metaplasia of respiratory epithelium, which normally is pseudostratified. Terminally differentiated squamous epithelial cells have a flattened, elongated appearance. During differentiation, they have an intermediate phenotype that is difficult to identify and distinguish from tangentially cut columnar cells in tissue sections from endobronchial biopsies, whose small size makes orientation difficult. The aim of our study was to develop a panel of antibodies that could be employed to distinguish normal epithelium from metaplastic epithelium and would be suitable for use on endobronchial biopsies. Nasal polyp tissue and tonsil tissue, which have pseudostratified and squamous epithelia, respectively, were collected from surgical cases and embedded in glycol methacrylate resin. Cut sections were stained immunohistochemically with a panel of antibodies to cytokeratins (CK), whose expression varies with epithelial type and stage of differentiation, and involucrin, a marker of terminal squamous differentiation. Squamous epithelium stained positively for CK5/6, CK13 and involucrin. In the pseudostratified epithelium, basal cells exhibited weak staining for CK13 and strong staining for CK5/6, and columnar cells exhibited strong immunoreactivity for CK7, CK8 and CK18. Application of this panel to endobronchial biopsies from smokers enabled areas of squamous metaplasia to be distinguished from tangentially sectioned epithelium.

Hertfordshire sarcopenia study: design and methods

BACKGROUND

Sarcopenia is defined as the loss of muscle mass and strength with age. Although a number of adult influences are recognised, there remains considerable unexplained variation in muscle mass and strength between older individuals. This has focused attention on influences operating earlier in life. Our objective for this study was to identify life course influences on muscle mass and strength in an established birth cohort and develop methodology for collection of muscle tissue suitable to investigate underlying cellular and molecular mechanisms.

METHODS

One hundred and five men from the Hertfordshire Cohort Study (HCS), born between 1931 and 1939 who have historical records of birth weight and weight at one year took part in the Hertfordshire Sarcopenia Study (HSS). Each participant consented for detailed characterisation of muscle mass, muscle function and aerobic capacity. In addition, a muscle biopsy of the vastus lateralis using a Weil-Blakesley conchotome was performed. Data on muscle mass, function and aerobic capacity was collected on all 105 participants. Muscle biopsy was successfully carried out in 102 participants with high rates of acceptability. No adverse incidents occurred during the study.

DISCUSSION

The novel approach of combining epidemiological and basic science characterisation of muscle in a well established birth cohort will allow the investigation of cellular and molecular mechanisms underlying life course influences on sarcopenia.

Expression of the T helper 17-associated cytokines IL-17A and IL-17F in asthma and COPD

Background:

Asthma and COPD are characterized by airway dysfunction and inflammation. Neutrophilic airway inflammation is a common feature of COPD and is recognized in asthma, particularly in severe disease. The T helper (Th) 17 cytokines IL-17A and IL-17F have been implicated in the development of neutrophilic airway inflammation, but their expression in asthma and COPD is uncertain.

Methods:

We assessed IL-17A and IL-17F expression in the bronchial submucosa from 30 subjects with asthma, 10 ex-smokers with mild to moderate COPD, and 27 nonsmoking and 14 smoking control subjects. Sputum IL-17 concentration was measured in 165 subjects with asthma and 27 with COPD.

Results:

The median (interquartile range) IL-17A cells/mm² submucosa was increased in mild to moderate asthma (2.1 [2.4]) compared with healthy control subjects (0.4 [2.8]) but not in severe asthma (P = .04). In COPD, IL-17A⁺ cells/mm² submucosa were increased (0.5 [3.7]) compared with nonsmoking control subjects (0 [0]) but not compared with smoking control subjects (P = .046). IL-17F⁺ cells/mm² submucosa were increased in severe asthma (2.7 [3.6]) and mild to moderate asthma (1.6 [1.0]) compared with healthy controls subjects (0.7 [1.4]) (P = .001) but was not increased in subjects with COPD. IL-17A and IL-17F were not associated with increased neutrophilic inflammation, but IL-17F was correlated with the submucosal eosinophil count (rs = 0.5, P = .005). The sputum IL-17 concentration in COPD was increased compared with asthma (2 [0-7] pg/mL vs 0 [0-2] pg/mL, P < .0001) and was correlated with post-bronchodilator FEV₁% predicted (r = −0.5, P = .008) and FEV₁/FVC (r = −0.4, P = .04).

Conclusions:

Our findings support a potential role for the Th17 cytokines IL-17A and IL-17F in asthma and COPD, but do not demonstrate a relationship with neutrophilic inflammation.

Airway wall expression of OX40/OX40L and interleukin-4 in asthma

BACKGROUND

The costimulatory molecule OX40 and its ligand, OX40L, mediate key aspects of allergic airway inflammation in animal models of asthma, including eosinophilic airway inflammation, airway hyperresponsiveness, and T helper 2 polarization. We sought to examine OX40/OX40L and interleukin (IL)-4 expression in asthma across severities.

METHODS

Bronchial biopsies were obtained from 27 subjects with asthma (mild Global Initiative for Asthma [GINA] 1 [n = 10], moderate GINA 2-3 [n = 7], and severe GINA 4-5 [n = 10]) and 13 healthy controls. The number of OX40(+), OX40L(+), IL-4(+), and IL-4 receptor alpha (IL-4Ralpha)(+) cells in the lamina propria and airway smooth muscle (ASM) bundle and the intensity of IL-4Ralpha(+) expression by the ASM were assessed.

RESULTS

The number of OX40(+), OX40L(+), and IL-4(+) cells in the lamina propria and OX40(+) and IL-4(+) cells in the ASM bundle was significantly increased in subjects with mild asthma, but not in those with moderate or severe asthma, compared with healthy controls. In the subjects with asthma, OX40/OX40L expression was positively correlated with the number of eosinophils and IL-4(+) cells in the lamina propria. The number of IL-4Ralpha(+) cells in the lamina propria was significantly increased in moderate-to-severe disease, but not in mild asthma, compared with controls. IL-4Ralpha expression by the ASM bundle was not different among groups.

CONCLUSIONS

OX40/OX40L expression is increased in the bronchial submucosa in mild asthma, but not in moderate-to-severe disease, and is related to the degree of tissue eosinophilia and IL-4 expression. Whether these costimulatory molecules have a role as targets for asthma requires further investigation.

Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Differential expression of claudin tight junction proteins in the human cortical nephron

Background. In renal tubules, paracellular permeability is tightly controlled to facilitate solute absorption and urinary concentration and is regulated by tight junctions, which incorporate claudin proteins. There is very limited information confirming the localization of these proteins in the human renal cortex. Most data is inferred from mouse, bovine and rabbit studies and differences exist between mouse and other species.

Methods. A survey of claudin staining was performed on human kidney cortex embedded in glycolmethacrylate resin to enhance tissue morphology and facilitate the cutting of 2 µm serial sections.

Results. Claudin-2, -10 and -11 antibodies labelled renal tubular epithelial cells, correlating with Lotus tetragonolobus and N-cadherin positive proximal tubules. Claudin-3, -10, -11 and -16 antibodies strongly stained a population of tubules that were positive for Tamm Horsfall protein on adjacent sections, confirming expression in the thick ascending limb of the Loop of Henle. Claudin-3, -4 and -8 antibodies reacted with tubules that correlated with the distal nephron markers, E-cadherin, epithelial membrane antigen and Dolichos biflorus and claudin-3, -4, -7 and -8 with the distal tubule marker, calbindin, and the collecting duct marker, aquaporin-2. Claudin-14 was localized in distal convoluted tubules, correlating positively with calbindin but negatively with aquaporin-2, whereas claudin-1 staining was identified in the parietal epithelium of Bowman's capsule, distal convoluted tubule and collecting duct. Cellular and tight junction localization of claudin staining in renal tubules was heterogeneous and is discussed.

Conclusions. Complex variation in the expression of human claudins likely determines paracellular permeability in the kidney. Altered claudin expression may influence pathologies involving abnormalities of absorption.

Identification of lipocalin and apolipoprotein A1 as biomarkers of chronic obstructive pulmonary disease

RATIONALE

Much effort is being made to discover noninvasive biomarkers of chronic airway disease that might enable better management, predict prognosis, and provide new therapeutic targets.

OBJECTIVES

To undertake a comprehensive, unbiased proteomic analysis of induced sputum and identify novel noninvasive biomarkers for chronic obstructive pulmonary disease (COPD).

METHODS

Induced sputum was obtained from patients with COPD with a spectrum of disease severity and from control subjects. Two-dimensional gel electrophoresis and mass spectrometric identification of differentially expressed proteins were first applied to induced sputum from patients with GOLD stage 2 COPD and healthy smoker control subjects. Initial results thus obtained were validated by a combination of immunoassays (Western blotting and ELISA) applied to a large subject cohort. The biomarkers were localized to bronchial mucosa by immunohistochemistry.

MEASUREMENTS AND MAIN RESULTS

Of 1,325 individual protein spots identified, 37 were quantitatively and 3 qualitatively different between the two groups (P < 0.05%). Forty protein spots were subjected to tandem mass spectrometry, which identified 15 separate protein species. Seven of these were further quantified in induced sputum from 97 individuals. Using this sequential approach, two of these potential biomarkers (apolipoprotein A1 and lipocalin-1) were found to be significantly reduced in patients with COPD when compared with healthy smokers. Their levels correlated with FEV(1)/FVC, indicating their relationship to disease severity.

CONCLUSIONS

A potential role for apolipoprotein A1 and lipocalin-1 in innate defense has been postulated previously; our discovery of their reduction in COPD indicates a deficient innate defense system in airway disease that could explain increased susceptibility to infectious exacerbations.

Resin technologies: construction and staining of resin TMA's

The traditional formaldehyde-fixed paraffin-embedded tissue, and therefore the tissue microarrays created from it, provide good morphology but with a compromised antigenicity when compared to frozen tissue. In contrast, while solving the issue of antigenicity, frozen tissue suffers from a lack of morphology. We have demonstrated that tissue microarrays constructed in glycol methacrylate resin, when combined with a cold acetone fixation step, have been able to combine the superior morphology of resin-embedded sections with the superior antigenicity of frozen tissue for prospectively collected material.