A CD18/ICAM-1-dependent pathway mediates eosinophil adhesion to human bronchial epithelial cells

Methyl P-Coumarate Ameliorates the Inflammatory Response in Activated-Airway Epithelial Cells and Mice with Allergic Asthma

Methyl p-coumarate (methyl p-hydroxycinnamate) (MH) is a natural compound found in a variety of plants. In the present study, we evaluated the ameliorative effects of MH on airway inflammation in an experimental model of allergic asthma (AA). In this in vitro study, MH was found to exert anti-inflammatory activity on PMA-stimulated A549 airway epithelial cells by suppressing the secretion of IL-6, IL-8, MCP-1, and ICAM-1. In addition, MH exerted an inhibitory effect not only on NF-κB (p-NF-κB and p-IκB) and AP-1 (p-c-Fos and p-c-Jun) activation but also on A549 cell and EOL-1 cell (eosinophil cell lines) adhesion. In LPS-stimulated RAW264.7 macrophages, MH had an inhibitory effect on TNF-α, IL-1β, IL-6, and MCP-1. The results from in vivo study revealed that the increases in eosinophils/Th2 cytokines/MCP-1 in the bronchoalveolar lavage fluid (BALF) and IgE in the serum of OVA-induced mice with AA were effectively inhibited by MH administration. MH also exerted a reductive effect on the immune cell influx, mucus secretion, and iNOS/COX-2 expression in the lungs of mice with AA. The effects of MH were accompanied by the inactivation of NF-κB. Collectively, the findings of the present study indicated that MH attenuates airway inflammation in mice with AA, suggesting its potential as an adjuvant in asthma therapy.

Plasmin Cascade Mediates Thrombotic Events in SARS-CoV-2 Infection via Complement and Platelet-Activating Systems

Objective: Recently emerged beta-coronavirus SARS-CoV-2, has resulted in the current pandemic designated COVID-19. COVID-19 manifests as severe illness exhibiting systemic inflammatory response syndrome, acute respiratory distress syndrome (ARDS), thrombotic events, and shock, exacerbated further by co-morbidities and age. Recent clinical evidence suggests that the development of ARDS and subsequent pulmonary failure result from a complex interplay between cell types (endothelial, epithelial and immune) within the lung promoting inflammatory infiltration and a pro-coagulative state. How the complex molecular events mediated by SARS-CoV-2 in infected lung epithelial cells lead to thrombosis and pulmonary failure, is yet to be fully understood. Methods: We address these questions here, using publicly available transcriptomic data in the context of lung epithelia affected by SARS-CoV-2 and other respiratory infections, in vitro. We then extend our results to the understanding of in vivo lung, using a publicly available COVID-19 lung transcriptomic study. Results and Conclusions: Our analysis indicates that there exists a complex interplay between the fibrinolytic system particularly plasmin, and the complement and platelet-activating systems upon SARS-CoV-2 infection, with a potential for therapeutic intervention.

Blockade of Eosinophil-Induced Bronchial Epithelial-Mesenchymal Transition with a Geranyl Acetophenone in a Coculture Model

Epithelial-mesenchymal transition (EMT) is currently recognized as the main cellular event that contributes to airway remodeling. Eosinophils can induce EMT in airway epithelial cells via increased transforming growth factor (TGF)-β production. We assessed the effect of synthetic 2,4,6-trihydroxy-3-geranyl acetophenone (tHGA) upon eosinophil-induced EMT in a cellular model. The human eosinophil cell line EoL-1 was used to induce EMT in BEAS-2B human bronchial epithelial cells. The induction of EMT was dose-dependently suppressed following tHGA treatment in which the epithelial morphology and E-cadherin expression were not altered. Protein and mRNA expression of vimentin, collagen I and fibronectin in eosinophil-induced epithelial cells were also significantly suppressed by tHGA treatment. Following pathway analysis, we showed that tHGA suppressed eosinophil-induced activator protein-1-mediated TGF-β production by targeting c-Jun N-terminal kinase and phosphoinositide 3-kinase signaling pathways. These findings corroborated previous findings on the ability of tHGA to inhibit experimental murine airway remodeling.

Complement-Mediated Enhancement of Monocyte Adhesion to Endothelial Cells by HLA Antibodies, and Blockade by a Specific Inhibitor of the Classical Complement Cascade, TNT003

Background

Antibody-mediated rejection (AMR) of most solid organs is characterized by evidence of complement activation and/or intragraft macrophages (C4d + and CD68+ biopsies). We previously demonstrated that crosslinking of HLA I by antibodies triggered endothelial activation and monocyte adhesion. We hypothesized that activation of the classical complement pathway at the endothelial cell surface by HLA antibodies would enhance monocyte adhesion through soluble split product generation, in parallel with direct endothelial activation downstream of HLA signaling.

Methods

Primary human aortic endothelial cells (HAEC) were stimulated with HLA class I antibodies in the presence of intact human serum complement. C3a and C5a generation, endothelial P-selectin expression, and adhesion of human primary and immortalized monocytes (Mono Mac 6) were measured. Alternatively, HAEC or monocytes were directly stimulated with purified C3a or C5a. Classical complement activation was inhibited by pretreatment of complement with an anti-C1s antibody (TNT003).

Results

Treatment of HAEC with HLA antibody and human complement increased the formation of C3a and C5a. Monocyte recruitment by human HLA antibodies was enhanced in the presence of intact human serum complement or purified C3a or C5a. Specific inhibition of the classical complement pathway using TNT003 or C1q-depleted serum significantly reduced adhesion of monocytes in the presence of human complement.

Conclusions

Despite persistent endothelial viability in the presence of HLA antibodies and complement, upstream complement anaphylatoxin production exacerbates endothelial exocytosis and leukocyte recruitment. Upstream inhibition of classical complement may be therapeutic to dampen mononuclear cell recruitment and endothelial activation characteristic of microvascular inflammation during AMR.

Valenzuela et al show that HLA antibody binding to human endothelial cells in vitro, triggered complement C3a and C5a deposition that mediated monocyte recruitment, and the salutary effects of inhibiting the classical complement pathway with an anti-C1s antibody. Supplemental digital content is available in the text.

In vitro study of histamine and histamine receptor ligands influence on the adhesion of purified human eosinophils to endothelium

It is a well-known fact that histamine is involved in eosinophil-dependent inflammatory responses including cellular chemotaxis and migration. Nevertheless, the relative role of histamine receptors in the mechanisms of eosinophils adhesion to endothelial cells is not known. Therefore the aim of presented study was to examine the effect of selective histamine receptors ligands on eosinophils adhesion to endothelium. For that purpose the highly purified human eosinophils have been isolated from the peripheral blood. The viability and functional integrity of isolated eosinophils have been validated in several tests. Histamine as well as 4-methylhistamine (selective H4 agonist) in concentration-dependent manner significantly increased number of eosinophils that adhere to endothelium. Among the selective histamine receptors antagonist or H1 inverse agonist only JNJ7777120 (histamine H4 antagonist) and thioperamide (dual histamine H3/H4 antagonist) had direct effect on eosinophils adhesion to endothelial cells. Antagonists of H1 (diphenhydramine, mepyramine) H2 (ranitidine and famotidine) and H3 (pitolisant) histamine receptors were ineffective. To the best of our knowledge, this is the first study to demonstrate that histamine receptor H4 plays a dominant role in histamine-induced eosinophils adhesion to endothelium.

Effect of tumor necrosis factor family member LIGHT (TNFSF14) on the activation of basophils and eosinophils interacting with bronchial epithelial cells

Allergic asthma can cause airway structural remodeling, involving the accumulation of extracellular matrix and thickening of smooth muscle. Tumor necrosis factor (TNF) family ligand LIGHT (TNFSF14) is a cytokine that binds herpesvirus entry mediator (HVEM)/TNFRSF14 and lymphotoxin β receptor (LTβR). LIGHT induces asthmatic cytokine IL-13 and fibrogenic cytokine transforming growth factor-β release from allergic asthma-related eosinophils expressing HVEM and alveolar macrophages expressing LTβR, respectively, thereby playing crucial roles in asthmatic airway remodeling. In this study, we investigated the effects of LIGHT on the coculture of human basophils/eosinophils and bronchial epithelial BEAS-2B cells. The expression of adhesion molecules, cytokines/chemokines, and matrix metalloproteinases (MMP) was measured by flow cytometry, multiplex, assay or ELISA. Results showed that LIGHT could significantly promote intercellular adhesion, cell surface expression of intercellular adhesion molecule-1, release of airway remodeling-related IL-6, CXCL8, and MMP-9 from BEAS-2B cells upon interaction with basophils/eosinophils, probably via the intercellular interaction, cell surface receptors HVEM and LTβR on BEAS-2B cells, and extracellular signal-regulated kinase, p38 mitogen activated protein kinase, and NF-κB signaling pathways. The above results, therefore, enhance our understanding of the immunopathological roles of LIGHT in allergic asthma and shed light on the potential therapeutic targets for airway remodeling.

Airway epithelial regulation of pulmonary immune homeostasis and inflammation

Recent genetic, structural and functional studies have identified the airway and lung epithelium as a key orchestrator of the immune response. Further, there is now strong evidence that epithelium dysfunction is involved in the development of inflammatory disorders of the lung. Here we review the characteristic immune responses that are orchestrated by the epithelium in response to diverse triggers such as pollutants, cigarette smoke, bacterial peptides, and viruses. We focus in part on the role of epithelium-derived interleukin (IL)-25, IL-33 and thymic stromal lymphopoietin (TSLP), as well as CC family chemokines as critical regulators of the immune response. We cite examples of the function of the epithelium in host defense and the role of epithelium dysfunction in the development of inflammatory diseases.

NOD-like receptors mediated activation of eosinophils interacting with bronchial epithelial cells: a link between innate immunity and allergic asthma

Key intracytosolic pattern recognition receptors of innate immunity against bacterial infections are nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs). We elucidated the NOD1 and NOD2-mediated activation of human eosinophils, the principal effector cells for allergic inflammation, upon interacting with human bronchial epithelial BEAS-2B cells in allergic asthma. Eosinophils constitutively expressed NOD1,2 but exhibited nonsignificant responses to release chemokines upon the stimulation by NOD1 ligand γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) and NOD2 ligand muramyl dipeptide (MDP). However, iE-DAP and MDP could significantly upregulate cell surface expression of CD18 and intercellular adhesion molecule (ICAM)-1 on eosinophils and ICAM-1 on BEAS-2B cells, as well as induce chemokines CCL2 and CXCL8 release in the coculture system (all P<0.05). Both eosinophils and BEAS-2B cells were the main source for CXCL8 and CCL2 release in the coculture system upon iE-DAP or MDP stimulation. Direct interaction between eosinophils and BEAS-2B cells is responsible for CCL2 release, and soluble mediators are implicated in CXCL8 release. ERK and NF-κB play regulatory roles for the expression of adhesion molecules and chemokines in coculture. Treatment with NOD1,2 ligand could induce the subepithelial fibrosis and significantly enhance the serum concentration of total IgE, chemokine CCL5 for eosinophils and T helper type 2 (Th2) cells and asthma Th2 cytokine IL-13 in bronchoalveolar lavage fluid of ovalbumin-sensitized allergic asthmatic mice (all P<0.05). This study provides further evidence of bacterial infection-mediated activation of NOD1,2 in triggering allergic asthma via the activation of eosinophils interacting with bronchial epithelial cells at inflammatory airway.

Modulation by flunisolide of tumor necrosis factor-alpha-induced stimulation of airway epithelial cell activities related to eosinophil inflammation

BACKGROUND

Tumor necrosis factor (TNF)-alpha, a proinflammatory cytokine involved in the pathogenesis of asthma, displays multiple functions on a variety of cells, including bronchial epithelial cells (BECs).

OBJECTIVE

To characterize in vitro changes induced by TNF-alpha on the function of BECs that may be related to eosinophilic inflammation and to evaluate their modulation by an inhaled corticosteroid, flunisolide.

METHODS

A normal human bronchial epithelial cell line (BEAS-2B) was incubated with TNF-alpha (10 ng/ml) to evaluate (a) intercellular adhesion molecule (ICAM)-1 expression and granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-5 release by BEAS-2B; (b) eosinophil adhesion to BEAS-2B; and (c) the modulation of these activities by flunisolide (0.1 to 10 microM).

RESULTS

Stimulation of BEAS-2 with TNF-alpha generated an increase in ICAM-1 expression (p = .0012), in GM-CSF and IL-5 release (p < .01), and in eosinophil adhesion to BEAS-2B, but this latter effect did not reach statistical significance. Flunisolide at all the tested concentrations effectively inhibited ICAM-1 expression and GM-CSF and IL-5 release (p < .05). The percent inhibition induced by the highest flunisolide concentration (10 muM) for the various BEAS-2B functions was 30%, 60%, and 70%, respectively. The effect of flunisolide appeared to be related to an inhibition of "TNF-alpha-induced" ICAM-1 expression and cytokine release with little or no involvement of the "constitutive" expression and release.

CONCLUSION

An increase in ICAM-1 expression in BECs was found to be induced by TNF-alpha and associated with enhancement of the constitutive secretion of GM-CSF and IL-5, cytokines related to eosinophilic inflammation. The ability of flunisolide to modulate these BECs activities appears to be mostly related to the inhibition of the "TNF-alpha-induced" responses.

Distribution of major basic protein on human airway following in vitro eosinophil incubation

Major basic protein (MBP) released from activated eosinophils may influence airway hyperresponsiveness (AHR) by either direct effects on airway myocytes or by an indirect effect. In this study, human bronchi, freshly isolated human eosinophils, or MBP purified from human eosinophil granules were incubated for studying eosinophil infiltration and MBP localization. Eosinophils immediately adhered to intact human airway as well as to cultured human airway myocytes and epithelium. Following incubation 18-24 h, eosinophils migrated into the airway media, including the smooth muscle layer, but had no specific recruitment to airway neurons. Eosinophils released significant amounts of MBP within the airway media, including areas comprising the smooth muscle layer. Most deposits of MBP were focally discrete and restricted by immunologic detection to a maximum volume of approximately 300 microm(3) about the eosinophil. Native MBP applied exogenously was immediately deposited on the surface of the airway, but required at least 1 h to become detected within the media of the airway wall. Tissue MBP infiltration and deposition increased in a time- and concentration-dependent manner. Taken together, these findings suggest that eosinophil-derived cationic proteins may alter airway hyperresponsiveness (AHR) in vivo by an effect that is not limited to the bronchial epithelium.

Intracellular signaling mechanisms regulating the activation of human eosinophils by the novel Th2 cytokine IL-33: implications for allergic inflammation

The novel interleukin (IL)-1 family cytokine IL-33 has been shown to activate T helper 2 (Th2) lymphocytes, mast cells and basophils to produce an array of proinflammatory cytokines, as well as to mediate blood eosinophilia, IgE secretion and hypertrophy of airway epithelium in mice. In the present study, we characterized the activation of human eosinophils by IL-33, and investigated the underlying intracellular signaling mechanisms. IL-33 markedly enhanced eosinophil survival and upregulated cell surface expression of the adhesion molecule intercellular adhesion molecule (ICAM)-1 on eosinophils, but it suppressed that of ICAM-3 and L-selectin. In addition, IL-33 mediates significant release of the proinflammatory cytokine IL-6 and the chemokines CXCL8 and CCL2. We found that IL-33-mediated enhancement of survival, induction of adhesion molecules, and release of cytokines and chemokines were differentially regulated by activation of the nuclear factor (NF)-kappaB, p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) pathways. Furthermore, we compared the above IL-33 activities with two structurally and functionally related cytokines, IL-1beta and IL-18. IL-1beta, but not IL-18, markedly upregulated cell surface expression of ICAM-1. IL-1beta and IL-18 also significantly enhanced eosinophil survival, and induced the release of IL-6 and chemokines CXCL8 and CCL2 via the activation of the NF-kappaB, p38 MAPK and ERK pathways. Synergistic effects on the release of IL-6 were also observed in combined treatment with IL-1beta, IL-18 and IL-33. Taken together, our findings provide insight into IL-33-mediated activation of eosinophils via differential intracellular signaling cascades in the immunopathogenesis of allergic inflammation.

Breakdown in epithelial barrier function in patients with asthma: identification of novel therapeutic approaches

The bronchial epithelium is pivotally involved in the provision of chemical, physical, and immunologic barriers to the inhaled environment. These barriers serve to maintain normal homeostasis, but when compromised, the immunologic barrier becomes activated to protect the internal milieu of the lung. We discuss what is currently understood about abnormalities in these barrier functions in patients with asthma and consider novel therapeutic opportunities that target this key structure.

Human antibodies targeting cell surface antigens overexpressed by the hormone refractory metastatic prostate cancer cells: ICAM-1 is a tumor antigen that mediates prostate cancer cell invasion

Transition from hormone-sensitive to hormone-refractory metastatic tumor types poses a major challenge for prostate cancer treatment. Tumor antigens that are differentially expressed during this transition are likely to play important roles in imparting prostate cancer cells with the ability to grow in a hormone-deprived environment and to metastasize to distal sites such as the bone and thus, are likely targets for therapeutic intervention. To identify those molecules and particularly cell surface antigens that accompany this transition, we studied the changes in cell surface antigenic profiles between a hormone-sensitive prostate cancer line LNCaP and its hormone-refractory derivative C4-2B, using an antibody library-based affinity proteomic approach. We selected a naïve phage antibody display library to identify human single-chain antibodies that bind specifically to C4-2B but not LNCaP. Using mass spectrometry, we identified one of the antibody-targeted antigens as the ICAM-1/CD54/human rhinovirus receptor. Recombinant IgG1 derived from this single-chain antibody binds to a neutralizing epitope of ICAM-1 and blocks C4-2B cell invasion through extracellular matrix in vitro. ICAM-1 is thus differentially expressed during the transition of the hormone-sensitive prostate cancer cell line LNCaP to its hormone-refractory derivative C4-2B, plays an important role in imparting the C4-2B line with the ability to invade, and may therefore be a target for therapeutic intervention.

Signalling mechanisms regulating the activation of human eosinophils by mast-cell-derived chymase: implications for mast cell-eosinophil interaction in allergic inflammation

Allergic diseases such as asthma and allergic dermatitis are associated with the degranulation of mast cells. Chymase, a mast-cell-specific protease, is the major component in mast cell granules that can induce eosinophil infiltration into inflammatory sites. We examined the immunopathological mechanisms for the activation of eosinophils by chymase in allergic inflammation. Cytokines were measured by cytometric bead array Flex Sets multiplex assay using flow cytometry and enzyme-linked immunosorbent assay. Adhesion molecules, migration and intracellular signalling pathways were assessed by flow cytometry, Boyden chamber assay and Western blot, respectively. Chymase suppressed the apoptosis of eosinophils and induce the release of the cytokine interleukin-6 (IL-6) and chemokines CXCL8, CCL2 and CXCL1 by eosinophils dose-dependently. It also up-regulated the surface expression of adhesion molecule CD18 and stimulated the chemokinetic migration of eosinophils. The expressions of adhesion molecules, cytokines and chemokines, and chemokinetic migration were differentially regulated by the activation of extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, Akt, Janus-activated kinase and nuclear factor-kappaB pathways. Chymase therefore plays a pivotal immunological role in the interaction between mast cells and eosinophils in allergic diseases such as allergic dermatitis by inducing adhesion molecule-mediated chemokinetic migration and inflammatory cytokines and chemokines of eosinophils, through multiple intracellular signalling molecules and transcription factor. Our results therefore provide a further biochemical basis for the pathogenesis of allergic inflammation consequent on the interaction between mast cells and eosinophils, and give insight for the development of new therapies.

[Expression of adhesion molecule ICAM-1 in patients with nasal polyps]

INTRODUCTION

Nasal polyposis is a chronic inflammatory disease of the nasal mucosa. The prevalence of nasal polyps seems to vary between 1 and 4% of the population. The pathogenesis of nasal polyps is still not entirely known and has been debated for many years. The aim of the present study was to evaluate the expression of adhesion molecule ICAM-1 in patients with nasal polyps.

MATERIALS AND METHODS

53 patients with nasal polyposis were selected and divided into two groups--allergic and non-allergic. Patients with allergy were distinguished from those without allergy on the basis of positive allergy skin tests to dust and serum levels of IgE. Immunohistochemical studies with monoclonal antibody against ICAM-1 antigen (NCL-CD54, Novocastra) using immunoperoxidase method were performed to evaluate expression of ICAM-1.

RESULTS

Immunoexpression of ICAM-1 was present on some epithelial cells and on fibroblast, inflammatory cells and endothelium in the submucosa. The mean +/-SD values of the immunoexpression of ICAM-1 were significantly increased in dust-sensitive patients compared with dust-tolerant patients (1.93 +/- 0.83 vs 0.83 +/- 0.73 (p < 0.001).

CONCLUSIONS

This research suggests that ICAM-1 plays an important role in the pathogenesis of nasal polyps and the allergic mechanism may play a fundamental role in this process. However, further examinations to confirm this need to be undertaken.

Eosinophils and CCR3 regulate interleukin-13 transgene-induced pulmonary remodeling

Interleukin (IL)-13 transgene overexpression in the lung induces features of chronic inflammatory lung disorders, including an eosinophil-rich inflammatory cell infiltration, airway hyper-reactivity, and remodeling of the airway (eg, subepithelial fibrosis, goblet cell metaplasia, and smooth muscle hypertrophy and hyperplasia). Here, we aimed to define the role of eosinophils and eosinophil signaling molecules [eg, eotaxins and CC chemokine receptor (CCR) 3] in IL-13-mediated airway disease. To accomplish this, we mated IL-13-inducible lung transgenic mice with mice deficient in eosinophil chemoattractant molecules (eotaxin-1, eotaxin-2, and their receptor CCR3) and with mice genetically deficient in eosinophils (Deltadbl-GATA). We report that in the absence of eotaxin-2 or CCR3, there was a profound reduction in IL-13-induced eosinophil recruitment into the lung lumen. In contrast, in the absence of eotaxin-1, there was a fourfold increase in IL-13-mediated eosinophil recruitment into the airway. IL-13 transgenic mice deficient in CCR3 had a 98% reduction in lung eosinophils. Furthermore, the reduction in pulmonary eosinophils correlated with attenuation in IL-13-induced mucus cell metaplasia and collagen deposition. Mechanistic analysis identified alterations in pulmonary protease and transforming growth factor-beta1 expression in eosinophil-deficient mice. Taken together, these data definitively identify a functional contribution by eosinophils on the effects of chronic IL-13 expression in the lung.

Impact of Bronchial Epithelium on Dendritic Cell Migration and Function: Modulation by the Bacterial Motif KpOmpA

Mucosal immune response depends on the surveillance network established by dendritic cells (DC), APC localized within the epithelium. Bronchial epithelial cells (BEC) play a pivotal role both in the host defense and in the pathogenesis of inflammatory airway disorders. We previously showed that the outer membrane protein A from Klebsiella pneumoniae (KpOmpA), a pathogen-associated molecular pattern (PAMP) derived from Klebsiella pneumoniae, activates BEC. In this study, we evaluated the consequences of this activation on DC traffic and functions. KpOmpA significantly increased the production of CCL2, CCL5, CXCL10, and CCL20 by BEC. Stimulation of BEC increased their chemotactic activity for monocyte-derived DC (MDDC) precursors, through CCL5 and CXCL10 secretion. BEC/MDDC precursor coculture leads to an ICAM-1-dependent accelerated differentiation and enhanced maturation of MDDC. BEC/DC interactions did not affect the capacity of DC to induce T cell proliferation. However, DC preincubated with BEC increased significantly the IL-10 production by autologous T cells. Basolateral and intraepithelial DC differently enhance IL-4 and/or IL-10 synthesis according to the condition of stimulation. In vivo, intranasal injections of KpOmpA into BALB/c mice induced the recruitment of CD11c(+) and I-A(d+) myeloid DC associated with bronchial epithelium activation as evidenced by CCL20 expression. These data show that KpOmpA-exposed BEC participate in the homeostasis of myeloid DC network, and regulate the induction of local immune response.

Induction of adhesion molecules upon the interaction between eosinophils and bronchial epithelial cells: involvement of p38 MAPK and NF-kappaB

Eosinophils are principal effector cells of inflammation in allergic asthma, characterized by their infiltration and accumulation at inflammatory sites mediated by chemokine eotaxin, and interaction with adhesion molecules expressed on bronchial epithelial cells. In this study, tumor necrosis factor (TNF)-alpha and/or the interaction of eosinophils and bronchial epithelial BEAS-2B cells were found to up-regulate the cell surface expression of adhesion molecules intercellular adhesion molecule (ICAM)-1 and vascular adhesion molecule (VCAM)-1 on BEAS-2B cells, and ICAM-1 and leukocyte function-associated antigen-1 (LFA-1) on eosinophils. Interaction of eosinophils and BEAS-2B cells could induce the release of granulocyte macrophage colony-stimulating factor (GM-CSF) and activate both p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB activities in BEAS-2B cells but only NF-kappaB activity in eosinophils. Both proteasome inhibitor MG-132 and selective p38 MAPK inhibitor SB 203580 could significantly decrease the expression of ICAM-1 on BEAS-2B cells and CD18 on eosinophils upon co-culture with or without TNF-alpha treatment. However, the expression of VCAM-1 on BEAS-2B cells was only up-regulated by TNF-alpha-induced NF-kappaB activity. The interaction of eosinophils and bronchial epithelial cells therefore plays an important role in the up-regulation of adhesion molecules on eosinophils and epithelial cells via differential intracellular signalling pathways during allergic inflammation.

Interleukin-3, -5, and granulocyte macrophage colony-stimulating factor induce adhesion and chemotaxis of human eosinophils via p38 mitogen-activated protein kinase and nuclear factor kappaB

Hematopoietic cytokines such as interleukin (IL)-3, IL-5, and granulocyte macrophage colony-stimulating factor (GM-CSF) play a fundamental role in eosinophil functions in allergic asthma. The intracellular signal transduction mechanisms of these cytokines regulating the activation of eosinophils have been potential therapeutic targets. We investigated the roles of p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-kappaB) in IL-3, IL-5, and GM-CSF-induced adhesion, morphological changes, and subsequence transmigration of human eosinophils. IL-3, IL-5, and GM-CSF could augment the phosphorylation of p38 MAPK and nucleus translocation of NF-kappaB in eosinophils. cDNA expression arrays demonstrated that the gene expression levels of several adhesion molecules including intercellular adhesion molecule-1 (ICAM-1), alpha6, beta2 integrin (CD18), and CD44 were upregulated by these cytokines. Results from functional assays showed that adhesion of eosinophils onto airway epithelial cells was enhanced after IL-3 and IL-5 but not GM-CSF stimulation. These cytokines could markedly induce shape change and augment the transmigration of eosinophils. Moreover, administration of either p38 MAPK inhibitor, SB 203580, or proteasome inhibitor, N-cbz-Leu-Leu-leucinal (MG-132), could inhibit the cytokine-induced adhesion, shape change, and transmigration of eosinophils. Together, our findings suggest that IL-3, IL-5, and GM-CSF regulated the adhesion and chemotaxis of human eosinophils through shared signaling pathways involving both p38 MAPK and NF-kappaB. Our results therefore shed light on the further development of more effective agents for allergic and inflammatory diseases.

Induction of IL-6 in co-culture of bronchial epithelial cells and eosinophils is regulated by p38 MAPK and NF-kappaB

BACKGROUND

Prominent infiltration of eosinophils into the airway mucosa and release of inflammatory mediators upon their adhesion onto airway epithelial cells are the immunopathogical mechanisms of allergic asthma.

OBJECTIVE

We investigated the effect of normal and paraformaldyhyde-fixed human eosinophils on BEAS-2B cells, a human bronchial epithelial cell line, for the release of inflammatory cytokine interleukin (IL)-6.

METHODS

Interleukin-6 in cell culture supernatant, protein amount of p38 mitogen-activated protein kinase (MAPK), and nuclear factor-kappaB (NF-kappaB) activity in BEAS-2B cells were analyzed by Western blot and enzyme-linked immunosorbent assay (ELISA). IL-6 gene expression was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), and p38 MAPK activity and inhibitor (I)kappaB-alpha induction were evaluated by Western blot.

RESULTS

Co-culture of BEAS-2B cells and eosinophils induced a significant elevation of IL-6 expression in BEAS-2B cells. Interaction of eosinophils and BEAS-2B cells led to a marked induction in phospho-p38 MAPK, phospho-IkappaB-alpha and activity of NF-kappaB in BEAS-2B cells. NF-kappaB inhibitor BAY 11-7082 and p38 MAPK inhibitor SB 203580 significantly decreased IL-6 release in a co-culture of BEAS-2B cells and eosinophils. Fixed human eosinophils were able to maintain their ability to induce IL-6 release in co-culture, activate p38 MAPK and NK-kappaB, and up-regulate IL-6 gene expression in BEAS-2B cells.

CONCLUSIONS

These data indicate that the interaction of eosinophils and bronchial epithelial cells plays an important role in airway inflammation, at least partly, via IL-6 induction.

Reversibility of airway inflammation and remodelling following cessation of antigenic challenge in a model of chronic asthma

BACKGROUND

Asthma is associated with recruitment of eosinophils, accumulation of chronic inflammatory cells in the airway walls, subepithelial fibrosis and other structural changes of airway wall remodelling. The role of ongoing exposure to allergens in their pathogenesis remains unclear.

OBJECTIVE

To examine whether changes of inflammation and remodelling were reversible following cessation of antigenic challenge in a mouse model of chronic asthma.

METHODS

BALB/c mice sensitized to ovalbumin (OVA) were chronically challenged by inhalation of a low mass concentration of antigen for 8 weeks, leading to development of acute-on-chronic airway inflammation, subepithelial fibrosis and other changes of airway wall remodelling. Epithelial injury was assessed by immunohistochemistry, while inflammation and remodelling were quantified by appropriate histomorphometric techniques. Regression of lesions was assessed in animals examined at 1, 2 and 4 weeks after exposure to OVA ceased.

RESULTS

We did not find evidence of airway epithelial injury in this model of low-level chronic inhalational exposure to antigen. Persistence of the recruitment of eosinophils and chronic inflammatory cells in the airway walls was dependent on continuing antigenic challenge, as was persistence of mucous cell hyperplasia/metaplasia. Subepithelial fibrosis and epithelial hypertrophy exhibited delayed reversibility following cessation of exposure to antigen, possibly related to matrix-associated accumulation of transforming growth factor-beta(1).

CONCLUSION

In chronic asthma, low-level antigenic challenge may be required to maintain the inflammatory response in the airway wall, but airway remodelling may persist in its absence.

Pharmacological targeting of anaphylatoxin receptors during the effector phase of allergic asthma suppresses airway hyperresponsiveness and airway inflammation

Airway hyperresponsiveness and airway inflammation are hallmarks of allergic asthma, the etiology of which is crucially linked to the presence of Th2 cytokines. A role for the complement anaphylatoxins C3a and C5a in allergic asthma was suggested, as deficiencies of the C3a receptor (C3aR) and of complement factor C5 modulate airway hyperresponsiveness, airway inflammation, and Th2 cytokine levels. However, such models do not allow differentiation of effects on the sensitization phase and the effector phase of the allergic response, respectively. In this study, we determined the role of the anaphylatoxins on the effector phase of asthma by pharmacological targeting of the anaphylatoxin receptors. C3aR and C5a receptor (C5aR) signaling was blocked using the nonpeptidic C3aR antagonist SB290157 and the neutralizing C5aR mAb 20/70 in a murine model of Aspergillus fumigatus extract induced pulmonary allergy. Airway hyperresponsiveness was substantially improved after C5aR blockade but not after C3aR blockade. Airway inflammation was significantly reduced in mice treated with the C3aR antagonist or the anti-C5aR mAb, as demonstrated by reduced numbers of neutrophils and eosinophils in bronchoalveolar lavage fluid. Of note, C5aR but not C3aR inhibition reduced lymphocyte numbers in bronchoalveolar lavage fluid. Cytokine levels of IL-5 and IL-13 in bronchoalveolar lavage fluid were not altered by C3aR or C5aR blockade. However, blockade of both anaphylatoxin receptors markedly reduced IL-4 levels. These data suggest an important and exclusive role for C5aR signaling on the development of airway hyperresponsiveness during pulmonary allergen challenge, whereas both anaphylatoxins contribute to airway inflammation and IL-4 production.

Role of p38 MAPK and NF-kB for chemokine release in coculture of human eosinophils and bronchial epithelial cells

Eosinophils are principal effector cells of inflammation in allergic asthma, characterized by their accumulation and infiltration at inflammatory sites mediated by the chemokine eotaxin and their interaction with adhesion molecules expressed on bronchial epithelial cells. We investigated the modulation of nuclear factor-kappaB (NF-kappaB) and the mitogen-activated protein kinase (MAPK) pathway on the in vitro release of chemokines including regulated upon activation normal T cell expressed and secreted (RANTES), monokine induced by interferon-gamma (MIG), monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-8, and interferon-inducible protein-10 (IP-10) upon the interaction of human bronchial epithelial BEAS-2B cells and eosinophils. Gene expression of chemokines was evaluated by RT-PCR and the induction amount of chemokines quantified by cytometric bead array. NF-kappaB and p38 MAPK activities were assessed by electrophoretic mobility shift assay and Western blot, respectively. The interaction of eosinophils and BEAS-2B cells was found to up-regulate the gene expression of the chemokines IL-8, MCP-1, MIG, RANTES and IP-10 expression in BEAS-2B cells, and to significantly elevate the release of the aforementioned chemokines except RANTES in a coculture of BEAS-2B cells and eosinophils. IkappaB-alpha phosphorylation inhibitor, BAY 11-7082, and p38 MAPK inhibitor, SB 203580 could decrease the release of IL-8, IP-10 and MCP-1 in the coculture. Together, the above results show that the induction of the release of chemokines in a coculture of epithelial cells and eosinophils are regulated by p38 MAPK and NF-kappaB activities of BEAS-2B cells, at least partly, through intercellular contact. Our findings therefore shed light on the future development of more effective agents for allergic and inflammatory diseases.

Smoke and C5a induce airway epithelial intercellular adhesion molecule-1 and cell adhesion

The human bronchial epithelial cell is one of the first cell types to be exposed to the irritants and toxins present in inhaled cigarette smoke. The ability of the bronchial epithelium to modulate inflammatory and immune events in response to cigarette smoke is important in the pathogenesis of smoke-induced airway injury. We have shown that cigarette smoke extract and the complement anaphylatoxin C5a both independently induce increased expression of intercellular adhesion molecule (ICAM)-1 on airway epithelial monolayers compared with unstimulated cells in vitro. This enhanced ICAM-1 expression is associated with a greater capacity of the airway epithelial cells to bind mononuclear cells, a process that appears to require the proinflammatory cytokine tumor necrosis factor-alpha and protein kinase C intracellular signaling. Exposure of epithelial monolayers to the combination of cigarette smoke followed by C5a results in an additive response for ICAM-1 expression and mononuclear cell adhesion compared with smoke or C5a challenge alone. Inhibiting C5a receptor expression can attenuate these responses. These findings suggest that smoke exposure in some way enhances the functional responsiveness of the C5a receptor expressed on these airway epithelial cells for subsequent C5a-mediated increases in ICAM-1 expression and mononuclear cell adhesion. Our results may help explain the initiation and propagation of inflammatory events in vivo induced by chronic airway exposure to cigarette smoke.

Cellular adhesion is required for effector functions of human eosinophils via G-protein coupled receptors

BACKGROUND

Eosinophils play an important role in the pathogenesis of allergic diseases. Chemoattractants, including platelet-activating factor (PAF) and complement component 5a (C5a), induce eosinophil infiltration and promote eosinophil effector functions.

OBJECTIVE

To compare eosinophil degranulation and superoxide anion (O2-) generation induced by various chemoattractants, and to elucidate the role of cellular adhesion on these effector functions.

METHODS

Human eosinophils were stimulated with PAF, C5a, eotaxin, or leukotriene B4 (LTB4). O2- generation was assayed by a chemiluminescence method using a Cypridina luciferin analog as the amplifier. Degranulation and adhesion were measured by quantitating eosinophil protein X by radioimmunoassay. Expression of CD11b on eosinophils was measured by flow cytometry.

RESULTS

PAF and C5a induced significant degranulation and O2- generation from eosinophils. In contrast, the potency of eotaxin or LTB4 for these functions was much less. PAF and C5a also significantly enhanced eosinophil adhesion, whereas eotaxin and LTB4 did not. CD11b expression on eosinophils was enhanced by all four stimulants, and the order of potency to induce CD11b expression was C5a > PAF > eotaxin > LTB4.

CONCLUSIONS

The potency of PAF and C5a for inducing effector function in eosinophils was greater than that of eotaxin or LTB4. The magnitude of the effector function was consistent with the degree of eosinophil adherence induced by each stimulant. These results suggest that effector functions of eosinophils which are mediated through G-protein coupled receptors are dependent on cellular adhesion.

Role of TNF-alpha and its 55 and 75 kDa receptors in bronchial hyperreactivity

The pathophysiological role of the tumour necrosis factor (TNF) system was studied in adults (n=37) and children (n=43) non asthmatic offspring of asthmatic parents with and without bronchial hyperreactivity proved by methacholine airway challenge test. SerumTNFalpha and its soluble receptors (sTNF-R1 and R2) were determined by enzyme-linked immunosorbent assay (ELISA). Significantly elevated TNFalpha (adults: mean +/- SD=5.18 +/- 0.87 pg ml(-1), children: 5.08 +/- 1.78) vs. non-hyperreactives (adults: 4.12 +/- 0.43, P < 0.0001, children: 3.75 +/- 0.68, P=0.0084), sTNF-R1 (adults: 144 +/- 0.31 ng ml(-1), children: 1.30 +/- 0 25 vs. adults: 1.21 +/- 0.14, P=0.0305, children: 1.13+/-0.11 ng ml(-1), P=0.0042) and sTNF-R2 (adults: 0.85 +/- 0.40ng ml(-1), children: 0.70 +/- 0.46 vs. adults: 0.56 +/- 0.56 P=0.0084, children: 0.33 +/- 0.17, P=0.0048) and decreased sTNF-R1/R2 ratio (adults: mean +/- SD=0.96 +/- 0.73, children: 2.85 +/- 2.06 vs. adults: 4.82+/-3.40, P=0.0272, children: 4 42 +/- 2 30, P=0.0167) were measured in patients with bronchial hyperreactivityThe provocation doses of methacholine causing a 20% reduction (PD20) in forced expiratory volume in 1 sec (FEV1) were found to be in a significant negative linear correlation with TNFalpha sTNF-R1 and R2 levels in hyperreactive adults and with TNFalpha, sTNF-R2 in hyperreactive children. TNFalpha correlated significantly with its receptors both in hyperreactive adults and children and with the body mass index (BMI) values of adults. The TNF system may contribute to the pathophysiology of bronchial hyperreactivity Altered shedding of sTNF-R1 seems to occur in hyperreactive patients.

Eotaxin expression by epithelial cells and plasma cells in chronic asthma

Chemoattractants such as eotaxin are believed to play an important role in the recruitment of eosinophils into the airways in asthma. We investigated expression of eotaxin in the airway wall in a model of chronic human asthma, in which systemically sensitized mice were exposed to low mass concentrations of aerosolized antigen for 6 weeks. In these animals, the number of intraepithelial eosinophils in the airways was significantly increased 3 hours after exposure and declined by 24 hours. In parallel, immunoreactivity for eotaxin was strikingly up-regulated in airway epithelial cells and in inflammatory cells in the lamina propria. The latter were identified as plasma cells by double immunofluorescent labeling. Increased expression of eotaxin by epithelial cells and plasma cells was also demonstrated in a case of fatal human asthma. In contrast, sensitized mice that received a single exposure to a high mass concentration of aerosolized antigen exhibited delayed eosinophil recruitment, which did not correlate with eotaxin expression. Furthermore, in sensitized chronically exposed interleukin-13-deficient mice there was virtually no recruitment of eosinophils into the airways, although eotaxin expression was greater than or equal to that in wild-type mice. These results indicate that there are striking differences between acute and chronic exposure models in the time course of eotaxin expression and eosinophil recruitment. Although high eotaxin levels alone are not sufficient to cause recruitment of eosinophils into the airways, recurrent exposure may generate or up-regulate additional signals required for eosinophil chemotaxis.

TNF-alpha potentiates C5a-stimulated eosinophil adhesion to human bronchial epithelial cells: a role for alpha 5 beta 1 integrin

Cooperative action of inflammatory mediators and adhesion molecules orchestrates eosinophil recruitment during allergic inflammation in the airways. This study investigated the mechanisms involved in increasing eosinophil adhesion to human bronchial epithelial cells (HBEC) following priming and activation of eosinophils with TNF-alpha and complement protein C5a, respectively. Under primed conditions, eosinophil adhesion increased 3-fold from basal (16%), and the effect was significantly greater (p < 0.05) than the increase following stimulation with C5a alone (2-fold). Eosinophil contact with HBEC was essential for priming. In contrast to C5a, adhesion of eotaxin-stimulated eosinophils to HBEC was not primed with TNF-alpha nor IL-5, a known eosinophil-priming agent. Priming caused activation of alpha(M)beta(2) integrin; mAb against either the common beta(2) integrin subunit or its ICAM-1 ligand reduced the primed component of adhesion. Using mAbs against beta(1) or alpha(5), but not alpha(4) integrin subunit, together with anti-beta(2) integrin mAb, reduced stimulated adhesion to basal levels. Cross-linking alpha(5)beta(1) integrin increased alpha(M)beta(2) integrin-dependent adhesion of eosinophils. There are no known adhesion molecule ligands of alpha(5)beta(1) integrin expressed on HBEC; however, fibronectin, the major matrix protein ligand for alpha(5)beta(1) integrin, was detected in association with HBEC monolayers. A mAb against fibronectin, in combination with anti-beta(2) integrin mAb, reduced adhesion to basal levels. In conclusion, alpha(5)beta(1) integrin may provide a contact-dependent costimulus for eosinophil priming that, together with TNF-alpha, potentiated C5a activation of alpha(M)beta(2) integrin and increased eosinophil adhesion to ICAM-1. Fibronectin, associated with HBEC, may act as a ligand for alpha(5)beta(1) integrin. Dual regulation of eosinophil priming may prevent inappropriate activation of eosinophils in the circulation.

Transient exposure of human bronchial epithelial cells to cytokines leads to persistent increased expression of ICAM-1

Effects of several cytokines on kinetics of Intercellular Adhesion Molecule-1 (ICAM-1) and Vascular Cell Adhesion Molecule-1 (VCAM-1) expression were studied on a bronchial epithelial cell line (BEAS-2B). VCAM-I was neither constitutively expressed on BEAS-2B cells nor induced by Interferon-gamma (IFN-gamma). Tumor Necrosis Factor-alpha (TNF-alpha), Interleukin-1beta (IL-1beta), IFN-alpha, IL-4, IL-6, IL-8 or Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF). ICAM-1 was constitutively expressed on BEAS-2B cells. IFN-gamma and TNF-alpha upregulated ICAM-1 expression on these cells. The functional importance of IFN-gamma plus TNF-a upregulation of ICAM-1 expression on BEAS-2B cells was demonstrated by neutrophil-BEAS-2B cell adhesion assays. Cytokines are rapidly released and cleared in animals. Therefore, transient cytokine(s) exposure might occur on the bronchial mucosa. Brief incubation of BEAS-2B cells with IFN-gamma plus TNF-alpha led initial upregulation of ICAM-1 expression followed by a protracted downregulation. Our findings stress the importance of studying the mechanism(s) controlling the persistent increased expression of ICAM-1 after brief cytokine(s) exposure.

Transepithelial migration of activated eosinophils induces a decrease of E-cadherin expression in cultured human nasal epithelial cells

BACKGROUND

The damage of respiratory epithelium in allergic diseases has a close correlation with the extent of eosinophil infiltration. It seems to be a good possibility that eosinophil infiltration could induce the changes in the expression of the epithelial cell adhesion molecules, which play a key role in the maintenance of structural and functional rigidity of epithelium.

OBJECTIVE

We observed the expression of E-cadherin in cultured human nasal epithelial cells (HNECs) to study whether could it be affected by transepithelial migration of inflammatory cells, especially eosinophils.

METHODS

In vitro study of the transmigration assay was designed using various types of inflammatory cells and HNEC monolayers. Various assays of each experimental group were done under the stimulation of interleukin-5 (IL-5) and/or platelet activating factor (PAF). Subsequently immunohistochemistry for E-cadherin was performed in the HNECs. The intensity of immunofluorescence of E-cadherin was quantified using confocal laser scanning microscopy (CLSM) system and compared before and after the transmigration.

RESULTS

The mean intensity of immunofluorescence for E-cadherin decreased significantly after the transmigration of any types of inflammatory cells. Above all, the migration of eosinophils treated with IL-5 and PAF had an eminent effect on the decrease, whereas the degranulation extracts derived from eosinophils activated by IL-5 and secretory IgA (sIgA) did not affect the intensity.

CONCLUSION

This work suggests that transepithelial migration of inflammatory cells can directly induce the decrease in epithelial E-cadherin expression. Furthermore, the most prominent change was induced by transmigration of activated eosinophils, which might be caused by some mechanisms independent of the eosinophil contents. The decrease in E-cadherin expression may trigger the damage of epithelial barrier, which contributes to the pathogenesis of allergic diseases.

Airway mast cells and eosinophils correlate with clinical severity and airway hyperresponsiveness in corticosteroid-treated asthma

BACKGROUND

The relationship between airway inflammation and asthma severity in corticosteroid-treated asthma is unclear.

OBJECTIVES

Our purpose was to characterize the inflammatory cell profile of the airway lumen and epithelium in corticosteroid-treated asthma and to relate these findings to clinical and physiologic markers of asthma severity.

METHODS

Adults (n = 20) with asthma received standardized high-dose inhaled corticosteroid therapy with beclomethasone 2000 microgram per day for 8 weeks. Airway responsiveness to methacholine and hypertonic (4.5%) saline solution was then assessed, followed by sputum induction and, 1 week later, bronchoscopy with bronchoalveolar lavage and bronchial brush biopsy to assess inflammatory cells.

RESULTS

Clinical asthma severity was associated with airway hyperresponsiveness. Metachromatic cells were the main granulocyte present in bronchial brush biopsy specimens and correlated with airway responsiveness to saline solution (r = -0.75), methacholine (r = -0.74), peak flow variability (r = 0.59), and clinical asthma severity (r = 0.57). Eosinophils were the main granulocyte present in sputum and correlated with airway responsiveness to saline solution (r = -0.63) but not with other clinical markers of asthma severity. Bronchoalveolar lavage cell counts were not related to clinical asthma severity.

CONCLUSIONS

In asthmatic patients treated with cortico-steroids, the dominant inflammatory effector cell in the epithelium is the metachromatic cell, and in sputum it is the eosinophil. These cells correlate with the degree of airway hyperresponsiveness. Clinical asthma severity correlates with airway responsiveness and epithelial metachromatic cells. Induced sputum eosinophils and airway responsiveness to hypertonic saline solution may be useful markers of airway inflammation for clinical practice.

Alveolar macrophages bind and phagocytose allergen-containing pollen starch granules via C-type lectin and integrin receptors: implications for airway inflammatory disease

Recent studies suggest that IgE-independent mechanisms of airway inflammation contribute significantly to the pathophysiology of allergic airway inflammatory diseases such as asthma. Such mechanisms may involve direct interactions between inhaled allergens and cells of the respiratory tract such as macrophages, dendritic cells, and epithelial cells. In this study, we investigated receptor-mediated interactions occurring between alveolar macrophages and allergen-containing pollen starch granules (PSG). We report here that PSG are released from a range of grass species and are rapidly bound and phagocytosed by alveolar macrophages. Human monocyte-derived dendritic cells also bound PSG but no internalization was observed. Phagocytosis of PSG was dependent on Mg2+ and Ca2+ and was inhibited by neo-glycoproteins such as galactose-BSA and N-acetylgalactose-BSA. Partial inhibition of phagocytosis was also seen with the Arg-Gly-Asp-Ser (RGDS) motif and with an anti-CD18 mAb (OX42). The combination of both neo-glycoprotein and anti-CD18 achieved the greatest degree of inhibition (>90%). Together, these data suggest a role for both C-type lectins and beta2-integrins in the binding and internalization of PSG. The consequences of this interaction included a rapid up-regulation of inducible NO synthase mRNA and subsequent release of NO by alveolar macrophages. Thus, receptor-mediated recognition of inhaled allergenic particles by alveolar macrophages may represent a potential mechanism for modulating the inflammatory response associated with allergic airway diseases such as asthma.

Interleukin-5 enhances eosinophil adhesion to bronchial epithelial cells

BACKGROUND

Eosinophil-bronchial epithelial cell interactions are thought to be central to the pathogenesis of asthma, both in terms of the epithelium as a source of pro-inflammatory mediators and as a target for eosinophil-mediated damage. We have therefore investigated adhesion interactions between these two cell types.

OBJECTIVES

To determine the role of eosinophil and epithelial activation on eosinophil adhesion to bronchial epithelium and to characterize the adhesion receptors mediating eosinophil adhesion.

METHODS

Eosinophils were purified from human peripheral blood by immunomagnetic selection and adhesion to confluent cultures of the airway epithelial cell lines A549 and BEAS-2B was studied.

RESULTS

Stimulation of A549 cells with TNFalpha, IFNgamma or a combination of 50 ng/mL of TNFalpha, IFNgamma and IL-1 (cytomix) did not effect eosinophil binding despite an increase in ICAM-1 expression. Similarly stimulation of eosinophils with PAF or IL-5 had no effect on eosinophil binding to medium- or cytokine-treated A549 cells. In contrast stimulation of BEAS-2B cells with cytomix caused a significant increase in eosinophil adhesion. This was associated with an increase in expression of ICAM-1 and induced expression of VCAM-1. Treatment of eosinophils with Mn2+ and IL-5 but not eotaxin, RANTES or PAF also significantly enhanced eosinophil adhesion to medium-treated BEAS-2B cells. Using blocking mAbs we were able to demonstrate that the increased adhesion resulting from stimulation of eosinophils or BEAS-2B cells was in both cases mediated by a combination of CD18 and alpha4 integrins.

CONCLUSIONS

This study demonstrates a selective role for IL-5 in mediating integrin-dependent eosinophil adhesion to airway epithelium and once again emphasizes the importance of this cytokine in controlling eosinophil activation in diseases such as asthma.

Human eosinophil-airway smooth muscle cell interactions

Eosinophils are present throughout the airway wall of asthmatics. The nature of the interaction between human airway smooth muscle cells (ASMC) and eosinophils was investigated in this study. We demonstrated, using light microscopy, that freshly isolated eosinophils from healthy donors rapidly attach to ASMC in vitro. Numbers of attached eosinophils were highest at 2 h, falling to 50% of maximum by 20 h. Eosinophil attachment at 2 h was reduced to 72% of control by anti-VCAM-1, and to 74% at 20 h by anti-ICAM-1. Pre-treatment of ASMC for 24h with TNF-alpha, 10 nM, significantly increased eosinophil adhesion to 149 and 157% of control after 2 and 20 h. These results provide evidence that eosinophil interactions with ASMC involve VCAM-1 and ICAM-1 and are modulated by TNF-alpha.

Eotaxin expression in Sephadex-induced lung injury in rats

The CC chemokine eotaxin is a potent and specific eosinophil chemoattractant. Eosinophil-dependent tissue injury has been shown to contribute to airway inflammation such as that in asthma. In the present study, We investigated eotaxin expression in a rat model of pulmonary inflammation (featuring accumulation of eosinophils) induced by intratracheal instillation of cross-linked dextran beads (Sephadex G200). Intratracheal instillation of 5 mg/kg Sephadex caused a time-dependent eosinophil infiltration into the lung, reaching a peak at 24 hours. Eotaxin mRNA in the lung paralleled the eosinophil influx. Eotaxin protein in bronchoalveolar (BAL) fluids and lung homogenates was shown by Western blot and immunostaining to be maximally expressed by 24 hours. Sephadex-induced lung injury, as measured by (125)I-labeled albumin leakage from the pulmonary vasculature, developed in a time-dependent manner. Intravenous injection of blocking antibody to eotaxin significantly decreased eosinophil infiltration and lung permeability. These data suggest that, in the Sephadex model of lung inflammation, eotaxin up-regulation mediates intrapulmonary accumulation of eosinophils and the development of lung injury.