Human lung fibroblast-derived granulocyte-macrophage colony stimulating factor (GM-CSF) mediates eosinophil survival in vitro

Regulation of eosinophil recruitment and heterogeneity during allergic airway inflammation

Eosinophils represent a granulocyte cell type that is strongly associated with type 2 inflammatory conditions. During steady state conditions few eosinophils are found in lung tissue, though they may contribute to homeostasis. In allergic airway inflammation, eosinophils are strongly increased and associated to disease severity. The underlying type 2 immune response tightly regulates eosinophil development, recruitment, survival, and heterogeneity. Inflammatory eosinophils in the lung are unfavourable, as they can cause tissue damage, amplify type 2 immunity and induce bronchial obstruction by expelling granular proteins and cytokines. In this review we provide an overview about mechanisms regulating development of eosinophils in the bone marrow and their extravasation into the lung including recent findings on induction and diversity of eosinophilia in allergic airway inflammation.

An open microfluidic coculture model of fibroblasts and eosinophils to investigate mechanisms of airway inflammation

Interactions between fibroblasts and immune cells play an important role in tissue inflammation. Previous studies have found that eosinophils activated with interleukin-3 (IL-3) degranulate on aggregated immunoglobulin G (IgG) and release mediators that activate fibroblasts in the lung. However, these studies were done with eosinophil-conditioned media that have the capacity to investigate only one-way signaling from eosinophils to fibroblasts. Here, we demonstrate a coculture model of primary normal human lung fibroblasts (HLFs) and human blood eosinophils from patients with allergy and asthma using an open microfluidic coculture device. In our device, the two types of cells can communicate via two-way soluble factor signaling in the shared media while being physically separated by a half wall. Initially, we assessed the level of eosinophil degranulation by their release of eosinophil-derived neurotoxin (EDN). Next, we analyzed the inflammation-associated genes and soluble factors using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and multiplex immunoassays, respectively. Our results suggest an induction of a proinflammatory fibroblast phenotype of HLFs following the coculture with degranulating eosinophils, validating our previous findings. Additionally, we present a new result that indicate potential impacts of activated HLFs back on eosinophils. This open microfluidic coculture platform provides unique opportunities to investigate the intercellular signaling between the two cell types and their roles in airway inflammation and remodeling.

The Enhanced Adhesion of Eosinophils Is Associated with Their Prolonged Viability and Pro-Proliferative Effect in Asthma

Before eosinophils migrate into the bronchial lumen, they promote airway structural changes after contact with pulmonary cells and extracellular matrix components. We aimed to investigate the impact of eosinophil adhesion to their viability and pro-proliferative effect on airway smooth muscle (ASM) cells and pulmonary fibroblasts during different asthma phenotypes. A total of 39 individuals were included: 14 steroid-free non-severe allergic asthma (AA) patients, 10 severe non-allergic eosinophilic asthma (SNEA) patients, and 15 healthy control subjects (HS). For AA patients and HS groups, a bronchial allergen challenge with Dermatophagoides pteronysinnus was performed. Individual combined cells cultures were prepared between isolated peripheral blood eosinophils and ASM cells or pulmonary fibroblasts. Eosinophil adhesion was measured by evaluating their peroxidase activity, cell viability was performed by annexin V and propidium iodide staining, and proliferation by Alamar blue assay. We found that increased adhesion of eosinophils was associated with prolonged viability (p < 0.05) and an enhanced pro-proliferative effect on ASM cells and pulmonary fibroblasts in asthma (p < 0.05). However, eosinophils from SNEA patients demonstrated higher viability and inhibition of pulmonary structural cell apoptosis, compared to the AA group (p < 0.05), while their adhesive and pro-proliferative properties were similar. Finally, in the AA group, in vivo allergen-activated eosinophils demonstrated a higher adhesion, viability, and pro-proliferative effect on pulmonary structural cells compared to non-activated eosinophils (p < 0.05).

The Microenvironmental Differentiation Hypothesis of Airway Inflammation

We have observed clinically relevant increases and fluctuations in metachromatic cell and eosinophil progenitors in response to antigenic challenge in patients with upper and lower respiratory tract disease. Based on this we have developed in vitro models to assess cytokine and microenvironmental influences on nasal mucosal inflammation. Purified structural cells (nasal epithelial cells or fibroblasts) grown from nasal polyps and atopic or nonatopic inferior turbinate secrete known (GM-CSF, G-CSF, and IL-6) and possibly novel (basophil differentiation factor) hemopoietic cytokines capable of inducing neutrophil, monocyte-macrophage, eosinophil, and metachromatic cell differentiation, as well as influencing their activation and survival. Nasal polyp structural cells are phenotypically different from those derived from allergic rhinitis or normal control subjects, having increased proliferative potential and constitutively producing higher levels of cytokines and extracellular matrices capable of supporting cell growth. These studies emphasize the importance of microenvironmental influences on allergic and nonallergic airway inflammation, and point out potentially new approaches to the diagnosis and therapy of nasal polyposis, allergic rhinitis, and asthma.

Interstital lung disease in ANCA vasculitis

Anti-neutrophil cytoplasmic antibodies (ANCA) vasculitides are immune-mediated disorders that primarily affect small blood vessels of the airway and kidneys. Lung involvement, one of the hallmarks of microscopic polyangiitis and granulomatosis with polyangiitis, is associated with increased mortality and morbidity. In recent years, several retrospective series and case reports have described the association of interstitial lung disease (ILD) and ANCA vasculitis, particularly those positive for ANCA specific for myeloperoxidase. In the majority of these patients pulmonary fibrosis occurs concurrently or predates the diagnosis of ANCA vasculitis. More importantly, these studies have shown that ILD has an adverse impact on the long-term prognosis of ANCA vasculitis. This review focuses on the main clinical and radiologic features of pulmonary fibrosis associated with anti-neutrophil cytoplasmic antibodies. Major histopathology features, prognosis and therapeutic options are summarized.

Severe asthma: anti-IgE or anti-IL-5?

Severe asthma is a discrete clinical entity characterised by recurrent exacerbations, reduced quality of life and poor asthma control as ordinary treatment regimens remain inadequate. Difficulty in managing severe asthma derives partly from the multiple existing phenotypes and our inability to recognise them. Though the exact pathogenetic pathway of severe allergic asthma remains unclear, it is known that numerous inflammatory cells and cytokines are involved, and eosinophils represent a key inflammatory cell mediator. Anti-IgE (omalizumab) and anti-IL-5 (mepolizumab) antibodies are biological agents that interfere in different steps of the Th2 inflammatory cascade and are licensed in severe asthma. Both exhibit a favourable clinical outcome as they reduce exacerbation rate and improve asthma control and quality of life, while mepolizumab also induces an oral steroid sparing effect. Nevertheless, it is still questionable which agent is more suitable in the management of severe allergic asthma since no comparable studies have been conducted. Omalizumab's established effectiveness in clinical practice over a long period is complemented by a beneficial effect on airway remodelling process mediated mainly through its impact on eosinophils and other parameters strongly related to eosinophilic inflammation. However, it is possible that mepolizumab through nearly depleting eosinophils could have a similar effect on airway remodelling. Moreover, to date, markers indicative of the patient population responding to each treatment are unavailable although baseline eosinophils and exacerbation rate in the previous year demonstrate a predictive value regarding anti-IL-5 therapy effectiveness. On the other hand, a better therapeutic response for omalizumab has been observed when low forced expiratory volume in 1 sec, high-dose inhaled corticosteroids and increased IgE concentrations are present. Consequently, conclusions are not yet safe to be drawn based on existing knowledge, and additional research is necessary to unravel the remaining issues for the severe asthmatic population.

Tissue remodeling in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized, immune-mediated disease characterized clinically by symptoms of esophageal dysfunction and histologically by eosinophil-predominant inflammation. The chronic esophageal eosinophilia of EoE is associated with tissue remodeling that includes epithelial hyperplasia, subepithelial fibrosis, and hypertrophy of esophageal smooth muscle. This remodeling causes the esophageal rings and strictures that frequently complicate EoE and underlies the mucosal fragility that predisposes to painful mucosal tears in the EoE esophagus. The pathogenesis of tissue remodeling in EoE is not completely understood, but emerging studies suggest that secretory products of eosinophils and mast cells, as well as cytokines produced by other inflammatory cells, epithelial cells, and stromal cells in the esophagus, all contribute to the process. Interleukin (IL)-4 and IL-13, Th2 cytokines overproduced in allergic disorders, have direct profibrotic and remodeling effects in EoE. The EoE esophagus exhibits increased expression of transforming growth factor (TGF)-β1, which is a potent activator of fibroblasts and a strong inducer of epithelial-mesenchymal transition. In addition, IL-4, IL-13, and TGF-β all have a role in regulating periostin, an extracellular matrix protein that might influence remodeling by acting as a ligand for integrins, by its effects on eosinophils or by activating fibrogenic genes in the esophagus. Presently, few treatments have been shown to affect the tissue remodeling that causes EoE complications. This report reviews the potential roles of fibroblasts, eosinophils, mast cells, and profibrotic cytokines in esophageal remodeling in EoE and identifies potential targets for future therapies that might prevent EoE complications.

Non-allergic Eosinophilic Inflammation

Much is known about the eosinophilic processes associated with antigens, tumors, and infection, yet data on other causes of eosinophilic inflammation are scarce. This paper investigates the locations and causes of other nonrespiratory eosinophilic inflammation. Although eosinophilic inflammation can involve locomotor, urinary, cardiovascular, nervous, gastrointestinal, and other mucosal surfaces, such inflammation also can accompany tissue trauma, foreign-body reactions, and necrotic or granulomatous processes. Despite their cytolytic/histolytic effects, eosinophil leukocytes are a component of tissue remodeling, can be antigen-presenting cells, and have a role in the reproductive system and in blood coagulation. The study of various types of eosinophilic inflammation may increase our understanding of the biological responses of eosinophil leukocytes to different inflammatory stimuli.

Mycoplasma fermentans and TNF-beta interact to amplify immune-modulating cytokines in human lung fibroblasts

Mycoplasma can establish latent infections and are associated with arthritis, leukemia, and chronic lung disease. We developed an experimental model in which lung cells are deliberately infected with Mycoplasma fermentans. Human lung fibroblasts (HLF) were exposed to live M. fermentans and immune-modulating cytokine release was assessed with and without known inducers of cytokine production. M. fermentans increased IL-6, IL-8/CXCL8, MCP-1/CCL2, and Gro-alpha/CXCL1 production. M. fermentans interacted with TNF-beta to release more IL-6, CXCL8, and CXCL1 than predicted by the responses to either stimulus alone. The effects of live infection were recapitulated by exposure to M. fermentans-derived macrophage-activating lipopeptide-2 (MALP-2), a Toll-like receptor-2- and receptor-6-specific ligand. The synergistic effect of combined stimuli was more pronounced with prolonged incubations. Preexposure to TNF-beta sensitized the cells to subsequent MALP-2 challenge, but preexposure to MALP-2 did not alter the IL-6 response to TNF-beta. Exposure to M. fermentans or MALP-2 did not enhance nuclear localization, DNA binding, or transcriptional activity of NF-kappaB and did not modulate early NF-kappaB activation in response to TNF-beta. Application of specific inhibitors of various MAPKs suggested that p38 and JNK/stress-activated protein kinase were involved in early IL-6 release after exposure to TNF-beta and M. fermentans, respectively. The combined response to M. fermentans and TNF-beta, however, was uniquely sensitive to delayed application of SP-600125, suggesting that JNK/stress-activated protein kinase contributes to the amplification of IL-6 release. Thus M. fermentans interacts with stimuli such as TNF-beta to amplify lung cell production of immune-modulating cytokines. The mechanisms accounting for this interaction can now be dissected with the use of this in vitro model.

Stimulus-dependent glucocorticoid-resistance of GM-CSF production in human cultured airway smooth muscle

For a subpopulation of asthmatics, symptoms persist even with high doses of glucocorticoids. Glucocorticoids reduce the levels of the proinflammatory and fibrogenic cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by human cultured airway smooth muscle (ASM). We have contrasted the effects of a synthetic glucocorticoid, dexamethasone, on thrombin- and IL-1alpha-stimulated GM-CSF production in human ASM cells. Although IL-1alpha stimulated three-fold higher levels of GM-CSF mRNA and protein compared to thrombin, dexamethasone concentration-dependently reduced IL-1alpha-stimulated GM-CSF more potently and to a greater extent than the response to thrombin. This pattern of glucocorticoid regulation was also observed at the GM-CSF mRNA level and was reproduced with other glucocorticoids such as fluticasone propionate. IL-1alpha and thrombin stimulated NF-kappa B-dependent luciferase expression equally. Dexamethasone treatment reduced luciferase expression stimulated by both IL-1alpha and thrombin. The GM-CSF mRNA half life was markedly prolonged by IL-1alpha compared to thrombin. This IL-1alpha-induced GM-CSF mRNA stability was prevented by either dexamethasone or the p38(MAPK) inhibitor, SB203580, neither of which influenced GM-CSF mRNA stability in thrombin-treated cells. Dexamethasone inhibited p38(MAPK) phosphorylation in IL-1alpha-stimulated ASM, whereas thrombin does not stimulate p38(MAPK) phosphorylation. These data suggest that the mechanism underlying the greater potency and efficacy of glucocorticoids in reducing GM-CSF synthesis stimulated by IL-1alpha depends on inhibition of the involvement of p38(MAPK)-induced increases in GM-CSF message stability.

GM-CSF induction in human lung fibroblasts by IL-1beta, TNF-alpha, and macrophage contact

Fibroblast-derived cytokines may play crucial roles in airway inflammation. In this study, we analyzed expression of the inflammatory cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF), a major eosinophilopoietin, by normal human lung fibroblast (NHLF) cells and its regulation by monokines and macrophage contact. NHLFs were stimulated with interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) and were cocultured with the U937 myelomonocytic cell line. The expression of GM-CSF transcripts was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), and GM-CSF protein was detected by ELISA. Nuclear translocation of nuclear factor-kappaB (NF-kappaB), an important transcription factor for inflammatory gene expression, was assessed by electrophoretic mobility shift assay (EMSA). Both IL-1beta and TNF-alpha significantly enhanced the production of GM-CSF by NHLF. Coculturing of peripheral blood mononuclear cells (PBMC) with NHLF induced GM-CSF expression. This phenomenon was also seen on coculturing U937 cells or membranes derived from U937 with NHLF but was inhibited when the two types of cells were separated, suggesting a need for cell-cell contact. U937 membranes, as well as IL-1beta and TNF-alpha, induced nuclear translocation of NF-kappaB. These data support a prominent role for macrophage-fibroblast interactions in airway inflammation and fibrosis.

Selective eosinophil adhesion to fibroblast via IFN-gamma-induced galectin-9

Among galectin family members, galectin-9 was first described as a potent eosinophil chemoattractant derived from Ag-stimulated T cells. In the present study a role of galectin-9 in the interaction between eosinophils and fibroblasts was investigated using a human lung fibroblast cell line, HFL-1. RT-PCR, real-time PCR, and Western blot analyses revealed that both galectin-9 mRNA and protein in HFL-1 cells were up-regulated by IFN-gamma stimulation. On the one hand, IL-4, known as a Th2 cytokine, did not affect the galectin-9 expression in HFL-1 cells. We further confirmed that IFN-gamma up-regulated the expression of galectin-9 in primary human dermal fibroblasts. Flow cytometric analysis revealed that IFN-gamma up-regulated surface galectin-9 expression on HFL-1 cells. Stimulation of HFL-1 cells with IFN-gamma up-regulated adhesion of eosinophils, but not neutrophils, to HFL-1 cells. This adherence of eosinophils to HFL-1 cells was inhibited by both lactose and anti-galectin-9 Ab. These findings demonstrate that IFN-gamma-induced galectin-9 expression in fibroblasts mediates eosinophil adhesion to the cells, suggesting a crucial role of galectin-9 in IFN-gamma-stimulated fibroblasts as a physiological modulator at the inflammatory sites.

Characterization of YM-90709 as a novel antagonist which inhibits the binding of interleukin-5 to interleukin-5 receptor

Interleukin-5 (IL-5) plays an important role in the activation of eosinophils in allergic inflammation including asthma and atopic dermatitis. A newly synthesized compound, YM-90709, 2,3-dimethoxy-6,6-dimethyl-5,6-dihydrobenzo[7,8]indolizino [2,3-b]quinoxaline, is reported here to inhibit the binding of IL-5 to its receptor on peripheral human eosinophils and butyric acid-treated eosinophilic HL-60 clone 15 cells, with IC50 values of 1.0 and 0.57 microM, respectively. In contrast, YM-90709 did not affect the binding of granulocyte-macrophage colony-stimulating factor (GM-CSF) to its receptor on eosinophils and eosinophilic HL-60 clone 15 cells. In functional assays, YM-90709 inhibited IL-5-prolonged eosinophil survival with an IC50 value of 0.45 microM and did not affect the GM-CSF-prolonged eosinophil survival. Furthermore, YM-90709 inhibited the IL-5-induced but not GM-CSF-induced tyrosine phosphorylation of Janus kinase 2 (JAK2) in eosinophilic HL-60 clone 15 cells. These results indicate that YM-90709 is a novel IL-5 inhibitor which selectively blocks the binding of IL-5 to the IL-5 receptor (IL-5R).

GM-CSF expression by human lung microvascular endothelial cells: in vitro and in vivo findings

Recently, many findings indicate that granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the pathogenesis of acute and chronic lung diseases. In the present paper, the production of this cytokine in human pulmonary microvascular endothelial cells (HPMEC) is investigated. In an in vitro study, quiescent HPMEC did not express GM-CSF, either at the transcriptional or at the protein level. After activation for 4 h with tumor necrosis factor (TNF)-alpha (30/300 U/ml), lipopolysaccharide (LPS; 0.1/1 microg/ml), or interleukin (IL)-1 beta (100 U/ml), a significant release of GM-CSF was measured by enzyme-linked immunosorbent assay, with a time-dependent increase over 72 h. IL-8 (4, 16, or 64 ng/ml) or IL-1 beta at a concentration of 10 U/ml did not induce the release of GM-CSF. Human umbilical vein endothelial cells (HUVEC) and the angiosarcoma cell line HAEND served as reference cell lines. GM-CSF release in HPMEC was significantly (P < 0.025-0.05) less inducible by IL-1 beta than in HUVEC. A constitutive expression of GM-CSF by HAEND was observed. Additionally, GM-CSF expression in vivo by the lung microvasculature was confirmed by immunohistochemistry in lung tissue. To our knowledge, this is the first report of the ability of human pulmonary endothelial cells to synthesize and release GM-CSF. These results support the hypothesis that the lung microvasculature via the production of GM-CSF is a potential contributor to the cytokine network in lung diseases. This could be of particular importance in the pathogenesis of the acute respiratory distress syndrome in which endothelial dysfunction plays a central pathogenetic role.

Normal human lung fibroblasts differently modulate interleukin-10 and interleukin-12 production by monocytes: implications for an altered immune response in pulmonary chronic inflammation

The ability of lung fibroblasts to modulate the immune response has been evaluated by analyzing the synthesis and release of interleukin (IL)-10 and IL-12 by lipopolysaccharide (LPS)-stimulated peripheral blood monocytes exposed to pulmonary fibroblast conditioned medium (FCM). IL-10 and IL-12 contents and gene expression were markedly modified by treatment with FCM as measured by ELISA (+97.5 +/- 12.8% and -68 +/- 7.3% for IL-10 and IL-12, respectively), immunocytochemistry, and reverse transcriptase-polymerase chain reaction (RT-PCR). These effects appeared to be mediated by prostaglandin E(2) (PGE(2)) as the modified release of both cytokines was reduced by treatment with indomethacin and mimicked by addition of exogenous PGE(2.) As a result of the enhanced production of IL-10, exposure of LPS/interferon (IFN)-gamma-activated monocytes to FCM was also able to reduce the expression of the class II major histocompatibility complex (MHC) molecule, human leukocyte-associated antigen-DR (HLA-DR) (-51.8 +/- 8.7%) and of the costimulatory molecule, CD40 (-53.9 +/- 11.7%). The expression of both molecules was completely restored when monocytes were pretreated with a neutralizing anti-IL-10 monoclonal antibody. The FCM obtained from fibrotic lung fibroblasts was instead less efficacious in potentiating LPS-stimulated IL-10 release and, consequently, in reducing HLA-DR and CD40 expression, suggesting that an impairment of the immune regulation operated by fibroblasts may be involved in the maintenance of chronic pulmonary inflammation.

Effects of crocidolite asbestos on human bronchoepithelial-dependent fibroblast stimulation in coculture: the role of IL-6 and GM-CSF

Cocultures of human pulmonary epithelial cells (BEAS-2B) and lung fibroblasts (WISTAR-38), representing two cell types of central regulatory potential in (chronic) lung disease, were used as an in vitro model to study the role of interleukin 6 (IL-6) and of granulocyte macrophage-colony stimulating factor (GM-CSF) in early fibrogenesis. For this purpose, epithelial cells were pre-exposed to UICC crocidolite asbestos fibers or titanium dioxide (TiO2) particles for 96 h and subsequently cocultured with fibroblasts for additional 72 h. Gene expression of IL-6 or GM-CSF in both cell types as well as of alpha1 procollagens types I and III in fibroblasts was determined by RT-PCR. Synthesis of IL-6, GM-CSF or collagen I was quantified using IL-6 bioassay or ELISA tests, respectively. Both mediators were directly induced in bronchoepithelial cells by crocidolite but not by TiO2. Likewise, steady-state mRNA levels of procollagens as well as collagen synthesis were upregulated in cocultured fibroblasts. As a result of coculture, cytokine concentrations were synergistically enhanced and further increased by crocidolite in a dose-dependent manner. Suppression of cytokine induction by corresponding neutralizing antibodies consistently abrogated collagen enhancement. Direct stimulation of fibroblast monocultures with recombinant human IL-6 or GM-CSF significantly increased collagen synthesis and transcription in a dose-dependent manner. Thus, our results demonstrate that crocidolite selectively stimulated production of IL-6 and GM-CSF in bronchoepithelial cells. In epithelial-fibroblast interactions, these mediators appear to play a key role in regulating fibroblast activity, indicating a close correlation between these cytokines and the fibrogenic potential of particulates.

Systemic aspects of allergic disease: bone marrow responses

In patients with allergic diseases, allergen provocation can activate a systemic response that provokes inflammatory cell production by the bone marrow. After release and differentiation of progenitor cells, eosinophils, basophils, and mast cells are typically recruited to tissues in atopic individuals. An understanding at the molecular level of the signaling process that leads to these systemic responses between the target organ, especially the airways, and the bone marrow may open up new avenues of therapy for allergic inflammatory disease. Studies that support the critical involvement of the bone marrow in the development of eosinophilic inflammation of the airways point out the systemic nature of these conditions and their potential for biologic intervention. Hemopoietic events that originate in the bone marrow are potential targets of long-term therapy for rhinitis and asthma. For example, the "beneficial" systemic activity of cortico-steroids through modulation of hemopoietic mechanisms and inflammatory cell recruitment to the airways is essential for the optimal treatment of both upper and lower airway inflammation.

Eosinophil granule-derived major basic protein induces IL-8 expression in human intestinal myofibroblasts

Eosinophil infiltration occurs in a variety of allergic and inflammatory diseases. The release of preformed mediators from eosinophils may contribute to inflammatory responses. We investigated the ability of eosinophil-derived major basic protein and eosinophil-derived neurotoxin to stimulate production of IL-8 from intestinal myofibroblasts. Intestinal myofibroblasts (18-Co cells) were incubated with major basic protein, eosinophil-derived neurotoxin, or a synthetic analogue of major basic protein, poly-L-arginine. Immunoreactive IL-8 was measured by ELISA and IL-8 mRNA levels were analysed by Northern blot or reverse transcription-polymerase chain assay. Major basic protein induced IL-8 mRNA production and release of significant levels of IL-8 immunoreactive protein. By contrast, eosinophil-derived neurotoxin stimulated little IL-8 release. The induction of IL-8 mRNA by poly-L-arginine was significantly inhibited by actinomycin D. These findings demonstrate a novel interaction between eosinophils and intestinal fibroblasts that may be involved in the pathogenesis of diseases associated with tissue eosinophilia.

Different expression of TNF-alpha receptors and prostaglandin E(2 )Production in normal and fibrotic lung fibroblasts: potential implications for the evolution of the inflammatory process

Normal human lung fibroblasts downregulate the production of tumor necrosis factor (TNF)-alpha by activated monocytes through the production of prostaglandin E(2) (PGE(2)), contributing to the local control of the inflammatory process. In this study, we provide evidence that fibroblasts derived from diseased tissue, such as fibrotic lung fibroblasts, exhibit different functional features compared with normal cells, with particular regard to their modulatory role. Indeed, fibrotic fibroblasts (FF) spontaneously produced less PGE(2) (3,300 +/- 410 pg/ml) compared with normal fibroblasts (NF) (7,500 +/- 270 pg/ml) and, as a consequence, they showed a reduced ability to downregulate the production of TNF-alpha by lipopolysaccharide (LPS)- activated monocytes. The percentage of inhibition induced by normal cells on the production of TNF-alpha by LPS-activated monocytes was 61 +/- 5.9%, whereas the inhibitory effect exerted by fibrotic cells was reduced to 32 +/- 4% (P < 0.01). We have also observed that the ability of TNF-alpha to induce PGE(2) was impaired in FF and was related to a reduced expression of cyclooxygenase 2. This was possibly due to the reduction of the expression of TNF receptors (TNFRs) in fibrotic cell lines compared with normal cell lines. Flow cytometry revealed that the mean fluorescence intensity (MFI) of both isoforms of TNFR was significantly lower in FF compared with NF. The MFI of TNFR1 was 3. 55 +/- 0.12 for NF and 1.78 +/- 0.35 for FF (P < 0.001). The MFI of TNFR2 was 1.95 +/- 0.27 for NF and 0.99 +/- 0.16 for FF (P < 0.01). The analysis of the effect of TNF-alpha on some functions associated with collagen metabolism in NF and FF showed an increase of the expression of the receptor for collagen type I (alpha(2)beta(1) integrin) in NF (42 +/- 10%) and an even larger increase in FF (102 +/- 23%) (P < 0.05). Interestingly, unlike NF, TNF-alpha failed to increase matrix metalloproteinase 1 levels in FF and did not cause any growth inhibition in these cells. The reduced capability of fibrotic cells to produce PGE(2) either spontaneously or after TNF-alpha treatment may lead to an unrestrained release of TNF-alpha from activated monocytes and, as a result of the reduced expression of TNFRs, to a different response of these cells to TNF-alpha. These changes may be important in the evolution of the inflammatory process, potentially contributing to its transformation into a chronic and self-perpetuating process.

Effects of Th2 Cytokines on Chemokine Expression in the Lung: IL-13 Potently Induces Eotaxin Expression by Airway Epithelial Cells

Airway inflammation associated with asthma is characterized by massive infiltration of eosinophils, mediated in part by specific chemoattractant factors produced in the lung. Allergen-specific Th2 cells appear to play a central role in asthma; for example, adoptively transferred Th2 cells induced lung eosinophilia associated with induction of specific chemokines. Interestingly, Th2 supernatant alone administered intranasally to naive mice induced eotaxin, RANTES, monocyte-chemotactic protein-1, and KC expression along with lung eosinophilia. We tested the major cytokines individually and found that IL-4 and IL-5 induced higher levels of macrophage-inflammatory protein-1α and KC; IL-4 also increased the production of monocyte-chemotactic protein-1; IL-13 and IL-4 induced eotaxin. IL-13 was by far the most potent inducer of eotaxin; indeed, a neutralizing anti-IL-13 Ab removed most of the eotaxin-inducing activity from Th2 supernatants, although it did not entirely block the recruitment of eosinophils. While TNF-α did not stimulate eotaxin production by itself, it markedly augmented eotaxin induction by IL-13. IL-13 was able to induce eotaxin in the lung of JAK3-deficient mice, suggesting that JAK3 is not required for IL-13 signaling in airway epithelial cells; however, eosinophilia was not induced in this situation, suggesting that JAK3 transduces other IL-13-mediated mechanisms critical for eosinophil recruitment. Our study suggests that IL-13 is an important mediator in the pathogenesis of asthma and therefore a potential target for asthma therapy.

Novel roles for chemokines and fibroblasts in interstitial fibrosis

BACKGROUND

Regardless of its involvement in either wound healing or excessive fibrosis, the interstitial fibroblast can now be considered an important early participant in inflammatory responses. Although it is recognized that certain immune cells and proinflammatory mediators are intricately linked to fibrotic disease, little is presently known about the manner in which these mediators and cells are orchestrated to a fibrotic finale. Experimental studies have shown that interstitial fibroblasts are capable of participating in an inflammatory response by promoting direct fibroblast-to-immune cell communication and/or modulating the release of soluble mediators that are mutually recognized by both types of cells.

METHODS

Primary cultures of murine fibroblasts were recovered from either normal tissue or tissue undergoing a cell-mediated inflammatory response. These stromal cells were assessed for the expression of various cytokines and chemokines indicative of a type 1 or type 2 response. In addition, the fibroblasts were co-cultured with mononuclear cells to assess the cell-to-cell communication.

RESULTS

Fibroblasts recovered from different cell-mediated inflammatory responses demonstrated a dramatic alteration in their cytokine profile. Fibroblasts recovered from the type 2 immune response produced high levels of monocyte chemotactic protein-1 (MCP-1), as compared to the normal fibroblasts and fibroblasts recovered from the type 1 lesion. Mononuclear cells co-cultured with fibroblasts induced a contact-dependent expression of elevated levels of chemokines, especially the macrophage-derived MIP-1 alpha. Thus, both fibroblasts themselves and fibroblasts co-cultured with immune-inflammatory cells have the ability to participate in the maintenance of an inflammatory response via the expression of chemokines.

CONCLUSIONS

Our laboratory and others have addressed the role of chemotactic cytokines or chemokines in the fibrotic process, and have demonstrated that fibroblasts are capable of modulating the activation of various immune cells that have been implicated in fibrotic disease. In addition, the interstitial fibroblast is capable of regulating its own behavior within the interstitial environment via the expression of chemokines and chemokine receptors. Thus, novel strategies aimed at preventing fibrotic disease will likely need to address the early engagement of inflammatory cells by fibroblasts, and possibly modulate the ability of fibroblasts to generate and/or recognize profibrotic signals supplied by chemokines.

Cultured human airway smooth muscle cells stimulated by interleukin-1beta enhance eosinophil survival

Airway smooth muscle may be an important cellular source of proinflammatory mediators and cytokines and may participate directly in airway inflammation. In this study we have examined whether airway smooth muscle cells could contribute to mechanisms of eosinophil accumulation by prolonging their survival. To investigate this possibility, conditioned medium from human airway smooth muscle cells stimulated with interleukin (IL)-1beta was examined on the in vitro survival of highly purified human peripheral blood eosinophils. After 7 d, when cultured in control medium, less than 1 +/- 0.2% of the initial eosinophil population remained viable. In contrast, culture in medium conditioned for 96 h by human airway smooth muscle cells stimulated with IL-1beta (1 pg-100 ng/ml) resulted in a concentration-dependent increase in eosinophil survival. (The concentration that produced 50% of this effect was 0.03 ng/ml IL-1beta.) Maximum eosinophil survival occurred at 1 to 3 ng/ml IL-1beta. This effect was also time-dependent and was readily detected in airway smooth muscle cell-conditioned medium after just 3 h of stimulation with IL-1beta (1 ng/ml). It continued to increase before reaching a plateau around 24 h, with no decrease in activity for up to 120 h of stimulation. Conditioned medium from unstimulated airway smooth muscle cells did not enhance eosinophil survival. The survival-enhancing activity was completely inhibited (the concentration that inhibited 50% [IC50] was 6.9 microg/ml) by a polyclonal goat antihuman antibody to granulocyte-macrophage colony stimulating factor (GM-CSF) (0.3-100 microg/ml), but antibodies (10-100 microg/ml) to IL-3 and IL-5, and a normal goat immunoglobulin G control had no effect on the eosinophil survival-enhancing activity. GM-CSF levels in culture medium from smooth muscle cells were markedly increased by IL-1beta and were maximum at 30 ng/ml (0.037 ng/ml/10(6) cells versus 3.561 ng/ml/10(6) cells, unstimulated versus 30 ng/ml IL-1beta). The IL-1 receptor antagonist inhibited both the production of GM-CSF (IC50 19. 1 ng/ml) and the eosinophil survival-enhancing (IC50 53.7 ng/ml) activity stimulated by IL-1beta. Release of GM-CSF elicited by IL-1beta was inhibited by dexamethasone but not by indomethacin. These data indicate that cultured human airway smooth muscle cells stimulated with IL-1beta support eosinophil survival through production of GM-CSF and thus may contribute to the local control of inflammatory cell accumulation in the airways.

GM-CSF transgene expression in the airway allows aerosolized ovalbumin to induce allergic sensitization in mice

The purpose of this study was to explore whether repeated exposure to aerosolized ovalbumin (OVA) in the context of local expression of GM-CSF can initiate a Th2-driven, eosinophilic inflammation in the airways. On day -1, Balb/c mice were infected intranasally with an adenovirus construct expressing GM-CSF (Ad/GM-CSF). From day 0 to day 9 mice were exposed daily to an OVA aerosol. Mice exposed to OVA alone did not show any evidence of airway inflammation. Mice receiving both Ad/GM-CSF and aerosolized OVA exhibited marked airway inflammation characterized by eosinophilia and goblet cell hyperplasia. Migration of eosinophils into the airway was preceded by a rise in IL-5 and IL-4. Both IL-5 and class II MHC were critically required to generate airway eosinophilia. After resolution, airway eosinophilia was reconstituted after a single OVA exposure. Flow cytometric analysis of dispersed lung cells revealed an increase in macrophages and dendritic cells expressing B7.1 and B7.2, and expansion of activated (CD69-expressing) CD4 and CD8 T cells in mice exposed to OVA and Ad/GM-CSF. Our data indicate that expression of GM-CSF in the airway compartment increases local antigen presentation capacity, and concomitantly facilitates the development of an antigen-specific, eosinophilic inflammatory response to an otherwise innocuous antigen.

Changes in CD11b and L-selectin expression on eosinophils are mediated by human lung fibroblasts in vitro

Eosinophilic airway infiltration is a central feature in asthma. Eosinophils recovered from bronchoalveolar fluid show an activated phenotype, e.g., increased CD11b and decreased L-selectin expression. We investigated whether lung fibroblasts are able to activate eosinophils in vitro, and if so, which activating factor is most important. CD11b and L-selectin expression of isolated peripheral blood eosinophils were measured by flow cytometry after coculture with normal lung fibroblasts or their conditioned medium. We found that eosinophil CD11b expression increased (154% and 210%, p < 0.05) and L-selectin expression decreased (59% and 35.5%, p < 0.05) on eosinophils compared with baseline (100%) after 4 and 24 h of coculture with interleukin-1-beta (IL-1beta)-stimulated fibroblasts, respectively. Conditioned medium of stimulated fibroblasts also increased CD11b expression, but to a smaller extent (p < 0.05). L-selectin expression of eosinophils in cocultures was not different from that of eosinophils in conditioned medium. Only anti-granulocyte/macrophage colony-stimulating factor (anti-GM-CSF) reduced the activation of eosinophils in conditioned medium to almost basal levels (p < 0.05). An increase in CD11b expression is mediated by cytokines as well as direct cell contact, whereas a decrease in L-selectin expression is only mediated by cytokines. GM-CSF released by fibroblasts is an important factor in the modulation of both CD11b and L-selectin expression. These results show that lung fibroblasts can activate eosinophils by both adhesive interactions and by soluble factors.

Enhanced expression of GM-CSF in differentiating eosinophils of atopic and atopic asthmatic subjects

Higher numbers of eosinophil/basophil colony-forming units (Eo/B CFU) are observed in blood of atopic individuals, and can be enhanced in atopic asthmatics by allergen-inhalation challenge. It is known that mature basophils and eosinophils synthesize cytokines relevant to allergic inflammation. To investigate the potential role of growth factors in allergic disease we examined the expression of the hemopoietic cytokines, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-5, in differentiating Eo/B colony cells from normal and atopic individuals, and from atopic asthmatics before and after allergen-inhalation challenge. Peripheral blood was collected from two normal and 12 atopic individuals, and also from 25 atopic asthmatics before and 24 h after allergen challenge. Nonadherent mononuclear cells were isolated and grown in semisolid growth medium. Eo/B colonies were selected and cytospins were prepared for immunocytochemical analysis of colony cells. Eo/B colonies, especially carbol chromotrope 2R+ cells, selected at Days 10, 14, and 18 from atopic donors contained messenger RNA for GM-CSF by combined in situ reverse transcription-polymerase chain reaction and cytochemistry, and demonstrated time-dependent expression of GM-CSF by immunocytochemistry (P = 0.007). Atopic individuals demonstrated a higher percentage of cells expressing GM-CSF than did normal subjects under all growth conditions when examined at Day 14 (P = 0. 04). Atopic asthmatics challenged with inhaled allergen who demonstrated a dual airway response, an increase in the number of blood eosinophils (P = 0.0001), and an increase in the number of Eo/B CFU (P = 0.02) also demonstrated a significant increase in the percentage of colony cells expressing immunostainable GM-CSF (P = 0. 0009), but only a variable effect on those expressing IL-5, 24 h after allergen. These results suggest that GM-CSF expression by differentiating Eo/Bs may provide an additional stimulus in vivo to enhance Eo/B progenitor differentiation in atopic and asthmatic individuals, especially after allergen challenge. The concept of microenvironmental differentiation, where blood progenitor cells may aid in their own differentiation, is supported by these ex vivo findings.

Transforming growth factor-beta expression in mucosal biopsies in asthma and chronic bronchitis

We assessed whether transforming growth factor-beta (TGF-beta), a fibrogenic growth factor, may be involved in remodeling of asthma and chronic bronchitis; its expression was compared with that of epidermal growth factor (EGF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in bronchial mucosal biopsies from 13 normal subjects, 24 asthmatics, and 19 patients with chronic bronchitis. TGF-beta immunoreactivity was highly increased in epithelium and submucosa of those with bronchitis and to a lesser extent in asthmatics. By comparison, with normal subjects, EGF immunoreactivity was significantly increased in the epithelium of bronchitic subjects and submucosa of asthmatics, and, GM-CSF immunoreactivity was increased in both epithelial and submucosal cells of asthmatics and to a lesser extent in submucosa of bronchitics. A significant correlation was found between the number of epithelial or submucosal cells expressing TGF-beta in both asthma and chronic bronchitis and basement membrane thickness and fibroblast number. No such correlation was found for EGF or GM-CSF. in situ hybridization for TGF-beta 1 mRNA confirmed the results obtained by immunohistochemistry. By combining in situ hybridization and immunohistochemistry, it was found that eosinophils and fibroblasts were synthetizing TGF-beta in asthma and bronchitis. These data suggest that TGF-beta, but not EGF or GM-CSF, is involved in airways remodeling in asthma and chronic bronchitis.

Mast cells, eosinophils and fibrosis

We have presented results that increase our understanding of the roles MC and EOS play in modulating fibrotic processes. In vitro studies have provided clear-cut evidence for the direct involvement of these two inflammatory cells in enhancing proliferation, and either enhancing or decreasing collagen synthesis in human fibroblasts isolated from different anatomical locations. In addition, we have shown that MC and EOS interactions can also take part in modulating fibrosis. In vivo studies in murine and human cGVHD showed that MC activation is detrimental, and that MC stabilization therapy may be helpful in treating the fibrotic outcome of this disease. Much is still obscure. It is, for example, important to define the MC and EOS mediators involved in the modulation of fibroblast properties, and their pattern of influence, keeping in mind the ultimate goal of defining new therapeutic targets for the treatment of fibrotic diseases.

Effect of cyclosporin A on the allergen-induced late asthmatic reaction

BACKGROUND

The allergen-induced late asthmatic reaction (LAR) is associated with mucosal inflammation involving several cell types including activated T lymphocytes and eosinophils. In contrast, the early asthmatic reaction (EAR) is considered to results from rapid allergen-induced release of bronchoconstrictor mediators from IgE sensitised mast cells. Cyclosporin A has efficacy in chronic severe corticosteroid-dependent asthma and is believed to act principally by inhibiting cytokine mRNA transcription in T lymphocytes. However, it has effects on other cell types in vitro, including the inhibition of exocytosis/degranulation events in mast cells. It was therefore hypothesised that cyclosporin A would attenuate both the EAR and LAR in subjects with mild asthma.

METHODS

Twelve sensitised atopic asthmatic subjects with documented dual asthmatic responses were studied in a double blind, placebo controlled, crossover trial. On two separate study visits subjects received two oral doses of either cyclosporin A or matched placebo before inhaled allergen challenges. The forced expiratory volume in one second (FEV1) was measured half hourly for eight hours and blood eosinophil counts were analysed three, six, and 24 hours after the challenge. Treatment effects on blood eosinophil counts as well as the EAR and LAR, respectively defined as the areas under the curve (AUC) of FEV1 changes from baseline between 0-1 and 4-8 hours after challenge, were compared by non-parametric crossover analysis.

RESULTS

Cyclosporin A reduced both the LAR (median AUC -41.9 1.h (interquartile range -82.7 to -12.4) for cyclosporin A and -84.5 1.h (-248.9 to -39.1) for placebo; p = 0.007) and the late increase in blood eosinophils (median 0.2 x 10(9)/1 (0.15 to 0.4) for cyclosporin A and 0.4 x 10(9)/1 (0.25 to 0.55) for placebo; p = 0.024) but had no effect on the EAR. The reduction of the LAR by cyclosporin A correlated significantly with prechallenge blood concentrations of cyclosporin A (r = 0.6, p = 0.028).

CONCLUSIONS

These data are consistent with the concept that cyclosporin A has anti-inflammatory actions in asthma resulting from inhibition of mRNA transcription of eosinophil-active cytokines, predominantly in T lymphocytes. Cyclosporin A, possibly in its inhaled form, or other agents which prevent cytokine gene transcription may therefore have potential in ameliorating the inflammatory component of asthma.

Eosinophil activation in patients with pulmonary fibrosis

The eosinophil count and concentrations of eosinophil cationic protein (ECP) were measured in bronchoalveolar lavage fluid (BALF) from patients with idiopathic pulmonary fibrosis (IPF), pulmonary fibrosis associated with a collagen vascular disorder (PF-CVD), sarcoidosis, and healthy controls. The patients with IPF and PF-CVD showed significant increased eosinophil count and ECP levels in BALF compared with the controls. When the patients with IPF and PF-CVD were subclassified into chronic stable, progressive, and acute progressive subgroups in accordance with the observed progression of pulmonary dysfunction during the preceding 3- to 6-month period, those in the acute progressive subgroup showed significantly elevated recovered eosinophil count and ECP level, as well as recovered lymphocyte count and total protein, albumin, and type III procollagen aminoterminal peptide-related antigens (pIIIp) in BALF, compared with either of the other two subgroups. Multivariate stepwise logistic regression analysis revealed that, among these variables, only ECP and pIIIp significantly contributed to discrimination among the three subgroups differing in disease activity. These findings suggest that eosinophils are involved in the inflammatory process in pulmonary fibrosis and that the released ECP and other cytotoxic eosinophil products may contribute to the lung injury and development of fibrosis.

Interleukin 10 inhibits lipopolysaccharide-induced survival and cytokine production by human peripheral blood eosinophils

In this study we have investigated the effects of interleukin 10 (IL-10) on human peripheral blood eosinophils stimulated with granulocyte/macrophage colony stimulating factor (GM-CSF) and lipopolysaccharide (LPS). We show that LPS was able to enhance eosinophil survival in a dose-dependent manner, as well as release of the cytokines GM-CSF, tumor necrosis factor alpha, and IL-8. LPS-induced eosinophil survival was largely inhibited by an anti-GM-CSF neutralizing antibody and completely blocked by polymyxin B, suggesting GM-CSF involvement in the survival enhancing mechanism and LPS specificity, respectively. IL-10 significantly inhibited survival of, and cytokine production from, eosinophils induced by LPS, but did not inhibit the survival induced by GM-CSF. These observations suggest a novel activation mechanism of eosinophils and, also, that IL-10 may participate in the regulation of diseases characterized by eosinophil infiltration.

Variable expression of platelet-derived growth factor family proteins in acute lung injury

During acute lung injury, there is an outpouring of growth factors into the alveolar space that drive local repair and fibrosis. During the remodeling that follows the instillation of bleomycin via the trachea into the adult rat, at least two platelet-derived growth factor (PDGF)-like peptides are released sequentially into lung lining fluid. Groups of four to five animals were killed at 3, 6, 15, and 26 days after exposure to bleomycin and lungs lavaged with isotonic saline. PDGF-like peptides in epithelial lining fluid (ELF) were partially purified by cation exchange chromatography and concentrated. Isolated peptides were analyzed by immunoblotting to determine their molecular weight and immunologic identity. Western blots were probed with polyclonal antibodies to PDGF-BB and PDGF-AA. PDGF-like peptides of two distinct size classes (38-40 kD and 29 kD) were present in alveolar fluid from all rats with lung injury induced by bleomycin. No PDGF-like peptides were found in comparably prepared ELF from control animals. The 38-40 kD peptide was detected only with anti-PDGF-BB antibody; the 29 kD peptide was detected only with anti-PDGF-AA antibody. The presence of these two peptides varied independently with time after exposure to bleomycin. The 38-40 kD peptide was at peak levels at 3 to 6 days. In contrast, the 29 kD peptide was present at all times following injury but with far less variation over time. In parallel with these immunoassays for PDGF-like molecules, there was abundant growth-promoting activity for fibroblasts present in concentrated ELF during the course of injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of two modified techniques for purifying blood eosinophils

As there is much heterogeneity in the morphology and function of blood eosinophils, comparison of their properties between groups of subjects requires recovering the majority of these cells. In two currently used techniques to isolate eosinophils, blood granulocytes are processed either on Percoll gradients after an incubation of granulocytes with 10(-8) M N-formyl-methionyl-leucyl-phenylalanine (fMLP) or on a magnetic cell sorter (MACS). In this study, these techniques were modified to increase the efficiency of eosinophil recovery. With the Percoll gradients, using 1.078 g/ml as the top gradient instead of 1.082 g/ml doubled the eosinophil recovery from 43 +/- 5.3% (mean +/- SEM) to 86.9 +/- 2.9%, without decreasing the purity (96.1 +/- 1.4% versus 96.2 +/- 0.9%). With a MACS, the neutrophils in granulocytes obtained on Ficoll-Paque (1.077 g/ml) instead of on Percoll gradient 1.082-1.094 g/ml, were tagged with anti-CD16 antibodies and eliminated by passing them through a magnetic field. When blood eosinophils of the same subjects were isolated using the two techniques, similar recovery and purity levels were obtained: Percoll gradients, 72.7 +/- 6.8% and 92.5 +/- 2.2%; MACS, 80.2 +/- 5.1% and 90.4 +/- 3.8%. Eosinophils isolated through the two techniques were also compared for their production of superoxide anion and leukotriene (LT) C4, with and without pre-incubation with cytokines interleukin-3, interleukin-5 and granulocyte-macrophage colony stimulating factor. The release of these products was similar between the two eosinophil preparations under all conditions tested except for interleukin-3 where eosinophils isolated with a MACS produced more LTC4. These results show that both techniques efficiently recover pure eosinophils. Furthermore, cell incubation with 10(-8) M fMLP did not enhance superoxide anion and LTC4 production nor modify the response to cytokines. The two modified techniques are therefore suitable for comparative studies of eosinophils from different groups of subjects.

Cytokines and pulmonary fibrosis

Chronically inflamed and fibrotic tissue of the respiratory tract can be shown to actively express the genes and products of a number of powerful growth and differentiating factors. The initial activation of lung inflammatory cells, including alveolar macrophages, is presumed to result in the release of early acting cytokines such as IL-1 and TNF. Subsequent activation and possible phenotype alteration of the structural cells results in release of other growth factors and accumulation of blood derived inflammatory cells. These cells, once they have entered the tissue and become further activated, may begin to release their own autocrine factors and "feed back" some of the similar signals to the tissue cells in a paracrine manner, further inducing differentiation and phenotype change. These internal tissue cell and cytokine cascades could account for the chronic nature of the inflammation. Therapeutic intervention must therefore take into account the inflammatory component as well as the nature of the cytokines and structural cells involved in the propagation of the disease.

Lipopolysaccharide induces expression of granulocyte/macrophage colony-stimulating factor, interleukin-8, and interleukin-6 in human nasal, but not lung, fibroblasts: evidence for heterogeneity within the respiratory tract

Fibroblasts play an indirect augmenting effector role in the inflammatory response by releasing growth and differentiation factors and other inflammatory mediators after activation by inflammatory cytokines such as interleukin (IL)-1, but whether direct activation occurs by exogenous agents such as endotoxin (lipopolysaccharide, LPS) remains controversial. Using a number of primary human airways tissue-derived fibroblast lines, we demonstrate that in contrast to IL-1 alpha, LPS significantly induced gene expression and production of granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-8, and IL-6 only in nasal but not bronchial or lung tissue-derived fibroblasts. Enhanced expression was dose- and time-dependent, and the minimal stimulatory dose was 10 ng LPS/ml. Polymyxin B entirely abrogated increased cytokine expression by LPS. Actinomycin D treatment largely inhibited expression, and LPS markedly increased an IL-6 gene promoter-driven luciferase reporter response in transfected nasal fibroblasts, suggesting enhanced expression may involve transcriptional regulation. Secondary protein or IL-1 synthesis requirement seemed unlikely since cycloheximide superinduced LPS-stimulated cytokine expression and anti-IL-1 alpha/beta antibodies failed to abrogate the response. Thus our data show that GM-CSF, IL-8, and IL-6 are directly inducible in nasal fibroblasts by LPS, and establish heterogeneous responsiveness to LPS by different fibroblast populations in the airways.

Effects of recombinant GM-CSF and IgA opsonisation on neutrophil phagocytosis of latex beads coated with P6 outer membrane protein from Haemophilus influenzae

BACKGROUND

IgA is the major antibody class in mucosal secretions, yet its biological functions remain poorly understood and its role as an opsonin for neutrophils has been the subject of controversy. It has been reported that treatment of neutrophils with granulocyte-macrophage colony stimulating factor (GM-CSF) induces the cells to phagocytose particles opsonised with IgA. A study was performed to investigate the effects of GM-CSF and IgA opsonisation on the ability of human neutrophils to recognise and phagocytose latex beads coated with the P6 outer membrane protein of Haemophilus influenzae.

METHODS

Human neutrophils with and without preincubation with 100 pmol/l GM-CSF, were incubated with non-opsonised P6-coated latex beads or beads opsonised with IgA purified from the blood of a bronchiectatic patient with high titres of IgA anti-P6. Phagocytosis was measured by counting internalised beads during microscopic examination.

RESULTS

The phagocytosis of IgA opsonised beads by untreated neutrophils (mean (SE) 2.1 (0.43) beads/cell) was significantly greater than that of non-opsonised beads (mean (SE) 1.3 (0.30) beads/cell). Treatment of neutrophils with GM-CSF resulted in increased phagocytosis of non-opsonised beads (mean (SE) 2.1 (0.39) beads/cell) but opsonisation with IgA increased this further (mean (SE) 3.4 (0.53) beads/cell).

CONCLUSIONS

Human neutrophils recognise and phagocytose non-opsonised particles coated with bacterial antigen. Antibodies of the IgA isotype opsonise for neutrophil phagocytosis of particles coated with bacterial antigen but this behaviour is enhanced, in an additive fashion, by treatment of the cells with GM-CSF. The results suggest that IgA and GM-CSF are important cofactors for neutrophil recognition and elimination of bacterial pathogens.

Enhanced secretion of immune-modulating cytokines by human lung fibroblasts during in vitro infection with Mycoplasma fermentans

Fibroblasts may play an important role in the modulation of immune and inflammatory responses through elaboration of cytokines. To test this hypothesis, human lung fibroblasts were isolated from transbronchial biopsy specimens and assayed for production of interleukin-6 (IL-6) and granulocyte/macrophage colony-stimulating factor (GM-CSF). The sources of fibroblasts included lung allografts, recipient lungs obtained at time of transplant, and normal lung tissue removed during tumor resection. During the course of these studies, several early-passage fibroblasts from transplant recipients were observed to contain mycoplasma (MP)-like organisms as detected by extranuclear fluorescent staining with Hoechst 33258. Positive staining cultures were associated with isolation of Mycoplasma fermentans. IL-6 and GM-GSF as measured by ELISA were found to be elevated over 50-fold in conditioned medium from MP-infected fibroblasts as compared with noninfected lines. Treatment of cells with mycoplasma removal agent (MRA) eliminated extranuclear Hoechst fluorescence and significantly reduced the production of these cytokines. Tumor necrosis factor-beta (TNF-beta) induction of IL-6 and GM-CSF was amplified synergistically in infected cultures. No additional production of IL-6 or GM-CSF was observed in infected cultures treated with interferon-gamma (IFN-gamma) despite the ability of IFN-gamma to modestly induce IL-6 in uninfected cultures. Thus, in vitro infection of lung fibroblasts with MP represents a potent stimulus for the production of inflammatory cytokines and, therefore, necessitates rigorous control for these organisms in cell culture studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Auto-induction of transforming growth factor-beta in human lung fibroblasts

The type beta transforming growth factors (TGF-beta s) are a family of potent cytokines with diverse effects on proliferation, differentiation, turnover of extracellular matrix components, oncogene expression, and other aspects of cellular phenotype. Unlike lung fibroblasts of certain species, unstimulated human lung fibroblast lines produce little or no TGF-beta in culture. However, TGF-beta has been reported to autoregulate its own production in certain human tumor cells and in rodent cell lines. To test whether this phenomenon is operative in fibroblasts from normal human lung tissue, confluent cultures of IMR90 normal fetal lung fibroblasts were exposed to TGF-beta. Cultures were exposed briefly to purified TGF-beta 1 under serum-free conditions and secretion of newly synthesized TGF-beta over the ensuing 72 h was determined by immunoblotting and bioassays made specific with the use of neutralizing antibodies. Steady-state levels of mRNA for TGF-beta 1 were detected by Northern and slot blot hybridization analysis of total cellular RNA. The 2.5 kb TGF-beta 1 mRNA species rose within 1.5 h of exposure of IMR90 cells to TGF-beta 1 and reached maximal levels after 16 h. Increased levels of TGF-beta were detected in conditioned medium 9 h after the start of the exposure. Thereafter, TGF-beta continued to accumulate at an elevated rate (90 +/- 7 versus < or = 15 pg/10(6) cells/h in uninduced cells) for up to 72 h. As little as 1 ng/ml TGF-beta 1 auto-induced TGF-beta secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

New perspectives on basic mechanisms in lung disease. 1. Lung injury, inflammatory mediators, and fibroblast activation in fibrosing alveolitis

It is over 25 years since Scadding first defined the term fibrosing alveolitis. It has since been established that complex mechanisms underlie its pathogenesis, including epithelial and endothelial injury, vascular leakage, production of inflammatory cells and their mediators, and fibroblast activation. Only through a detailed knowledge of how these cellular and molecular events are interlinked will we learn how to combat this disease, which is notoriously resistant to present treatments. So far the only therapeutic advances have been refinements in immunosuppression, and even these treatments are frequently disappointing. We believe that future advances in treatment will come from the development of agents that protect endothelial and epithelial cells from further injury and agents that can inhibit release of inflammatory mediators. A better knowledge of the mechanisms of collagen gene activation and the biochemical pathways of collagen production may also allow the identification of vulnerable sites at which new treatments may be directed. A combined approach to modifying appropriate parts of both the inflammatory component and the fibroblast/collagen component should provide a new stimulus to research. Further epidemiological studies are also needed to identify the environmental causes of lung injury that initiate the cascade of events leading to interstitial fibrosis.

Bronchial epithelial cell-derived cytokines (G-CSF and GM-CSF) promote the survival of peripheral blood neutrophils in vitro

Neutrophil accumulation in the respiratory tract occurs in a variety of inflammatory disorders, particularly those associated with cigarette smoking. We examined whether bronchial epithelial cells could contribute to this accumulation through the production of factors that increased the survival of neutrophils. Pure primary cultures of human bronchial epithelial cells (HBEC) were used to generate conditioned medium (CM), and the effect of this CM on the survival of neutrophils in vitro was examined. When neutrophils were cultured in control medium, survival was 8.7 +/- 1.7% at 72 h. In contrast, culture of neutrophils in CM resulted in a dose-dependent increase in survival: 22.6 +/- 5.5, 43.6 +/- 4.2, and 64 +/- 3.8% in 1, 10, and 50% CM respectively (mean +/- SEM; P < 0.05). As evidenced by the examination of neutrophil DNA, this prolongation of survival was associated with suppression of apoptosis. Cytokines with known actions on neutrophil biology identified in the CM included granulocyte colony-stimulating factor (G-CSF), granulocyte/macrophage colony-stimulating factor (GM-CSF), and interleukin-8. Through the use of specific neutralizing antibodies, G-CSF and GM-CSF were identified as promoting neutrophil survival. Neutrophil survival was prolonged in the presence of either recombinant human (rh) G-CSF or rhGM-CSF alone in a dose-dependent fashion. In contrast to the response of eosinophils to HBEC-CM, steroid treatment did not prevent the increase in neutrophil survival induced by HBEC-CM. In summary, we show that bronchial epithelial cells markedly increase the survival of human neutrophils in vitro via the release of G-CSF and GM-CSF.(ABSTRACT TRUNCATED AT 250 WORDS)