Effects of dexamethasone on TNF-alpha-induced release of cytokines from purified human blood eosinophils

BACKGROUND

TNF-alpha is an important mediator in allergy also for its effects on eosinophils.

METHODS

The effect of dexamethasone on TNF-alpha induced eosinophils survival, degranulation (ECP), cytokines release (IL-8, GM-CSF) and adhesion to VCAM-1, ICAM-1 and IgG coated wells (EPO release) were evaluated.

RESULTS

The drug inhibited IL-8 and GM-CSF production, but not viability, degranulation or adhesion in human peripheral blood eosinophils.

CONCLUSION

These results indicate that part of the activity of glucocorticosteroids on eosinophils may be mediated by their ability to inhibit cytokine secretion that in turn is important for the perpetuation of the allergic inflammation.

2B4 (CD244) is expressed and functional on human eosinophils

Eosinophils are present in parasitic, allergic, various immunological, and malignant disorders as well as in a variety of idiopathic hypereosinophilic syndromes. However, their exact role in some of these conditions remains elusive. They can be activated both in vivo and in vitro by various agonists, such as Igs, lipid mediators, and cytokines. By phenotyping the surface of the eosinophils, it may be possible to better define their function(s) in different pathophysiological settings. In the present work we screened eosinophils with a panel of Abs recognizing CD2 subfamily receptors usually present on a number of hemopoietic cells. We have demonstrated that human peripheral blood eosinophils, but not basophils or neutrophils, express NTB-A. In addition eosinophils express 2B4, CD84, CD58, and CD48, but not signaling lymphocytic activation molecule or CD2, on their surface (FACS). Cross-linking of 2B4 on eosinophils elicited a significant release of eosinophil peroxidase (30 min), IFN-gamma, and IL-4 (18 h). Moreover, activation of eosinophils via 2B4 induced eosinophil-mediated cytotoxicity toward two malignant cell lines, i.e., mouse mastocytoma P815 and EBV-infected 721.221 B cell lines. Cross-linking of 2B4 on the surface of eosinophils or pervenadate treatment elicited ERK and tyrosine phosphorylation, respectively. Furthermore, we showed that eosinophils express slam-associated protein. The demonstration that human eosinophils express a functional 2B4 receptor indicates a broader role for these cells in health and disease.

Nerve growth factor involvement in the visual system: implications in allergic and neurodegenerative diseases

The purpose of this review is to outline the main role of nerve growth factor (NGF) in the visual system and particularly in the ocular surface in physiological and pathological conditions. The present review of experimental and clinical studies will highlight old and recent strategies for treating ocular surface and tear disorders with NGF.

Reduced eosinophil pro-fibrogenic effect in severe childhood asthma compared to mild disease: an effect of corticosteroids?

Eosinophils play an important role in inflammation and probably in airway remodeling in asthma. We previously demonstrated that eosinophils from atopic subjects display pro-fibrogenic properties towards lung fibroblasts partially by preformed transforming growth factor-beta (TGF-beta). We hypothesized that the pro-fibrogenic potential of eosinophils is increased in children with life-threatening asthma (LTA). Six children with atopic LTA clinically well-controlled by inhaled corticosteroids (ICS) and 5 children with atopic mild asthma (MA) treated only with inhaled beta(2)-agonists were investigated. The effects of their peripheral blood eosinophils on fibroblast proliferation and lattice contraction were investigated. In addition, TGF-beta(1) and IL-6 eosinophil content were also evaluated. Unexpectedly, eosinophils from LTA increased fibroblast proliferation (5.4-fold) and gel contraction (1.1-fold) significantly less than those from MA. TGF-beta(1) but not IL-6 eosinophil content in LTA was significantly lower than that in MA (2.7-fold). In vitro, addition of dexamethasone on eosinophils stimulated by mast cells resulted in a marked decrease in their TGF-beta(1) content by 1.6-fold. In conclusion, eosinophils from children with ICS-treated LTA displayed significantly less pro-fibrogenic properties than those from MA treated only with beta(2)-agonists. Our data suggest that the pro-fibrogenic effect of eosinophils might be influenced by treatment with ICS in childhood asthma.

Eosinophil major basic protein: first identified natural heparanase-inhibiting protein

BACKGROUND

Heparanase and eosinophils are involved in several diseases, including inflammation, cancer, and angiogenesis.

OBJECTIVE

We sought to determine whether eosinophils produce active heparanase.

METHODS

Human peripheral blood eosinophils were isolated by immunoselection and tested for heparanase protein (immunocytochemistry, Western blot), mRNA (RT-PCR) and activity (Na(2)[(35)S]O(4)-labeled extracellular matrix degradation) before and after activation. Heparanase intracellular localization (confocal laser microscopy) and ability to bind to eosinophil major basic protein (MBP) were also evaluated (immunoprecipitation). A model of allergic peritonitis resulting in eosinophilia was induced in TNF knockout and wild-type mice for in vivo studies.

RESULTS

Eosinophils synthesized heparanase mRNA and contained heparanase in the active (50-kd) and latent (65-kd) forms. Heparanase partially co-localized with and was bound to MBP. No heparanase enzymatic activity was detected in eosinophils resting or activated with various agonists, including GM-CSF/C5a. Eosinophil lysates and MBP inhibited recombinant heparanase activity in a concentration-dependent manner (100%, 2 x 10(-7) mol/L). Eosinophil peroxidase and eosinophil cationic protein, but not myelin basic protein or compound 48/80, partially inhibited heparanase activity. Poly-l-arginine at very high concentrations caused an almost complete inhibition. In allergic peritonitis, heparanase activity in the peritoneal fluid inversely correlated with eosinophil number.

CONCLUSIONS

MBP is the first identified natural heparanase-inhibiting protein. Its presence in the eosinophil granules might indicate a protective function of these cells in diseases associated with inflammation and cancer progression.

Mast cells and eosinophils have a potential profibrogenic role in Crohn disease

BACKGROUND

Mast cells and eosinophils have an important role in allergic inflammation and probably also in chronic inflammatory diseases resulting in fibrosis, such as Crohn disease where fibrosis is present as strictures. The involvement of mast cells and eosinophils in Crohn disease fibrosis was investigated.

METHODS

Biopsies from diseased foci were stained for mast cells, eosinophils, anti-collagen type IV and VIII, laminin and alpha-smooth muscle actin (alpha-SMA) (IHC). Fibroblasts outgrown from the biopsies and a normal fetal intestinal fibroblast line were cultured in the presence of the human mast cell line HMC-1, or of human peripheral blood eosinophil (MACS, purity > 98%) sonicates, or of selected mediators. Fibroblast proliferation (3H-thymidine), collagen synthesis ([3H]-proline) and collagen gel contraction were evaluated.

RESULTS

Mast cells were present in all the biopsies and only faintly positive for extra cellular matrix (ECM) products. Pronounced eosinophilia was detected in only two cases. Mast cell sonicates increased both Crohn disease (alpha-SMA positive) and control fibroblast proliferation, decreased collagen production and increased collagen gel contraction. Eosinophil sonicates increased fibroblast proliferation, gel contraction and collagen production. TNF-alpha decreased collagen production. Histamine, tryptase and chymase had no influence.

CONCLUSIONS

These in vitro data show that mast cells and eosinophils could be involved in modulating Crohn disease fibrosis by directly influencing intestinal fibroblast properties.

Substance P and other neuropeptides do not induce mediator release in isolated human intestinal mast cells

Neuropeptides such as substance P (SP) and related peptides are supposed to act as mast cell agonists, and thus as mediators of neuroimmune interactions. The data supporting this hypothesis were obtained mostly from rodent experiments. Here, we studied for the first time the effect of SP and other peptides on mediator release in human intestinal mast cells, either unpurified or enriched to 85-99% purity. We found that SP at 0.1-100 micromol L(-1), or other peptides including neurokinin A and B, calcitonin gene-related peptide, vasoactive intestinal peptide and serotonin at 1 micromol L(-1) do not induce release of mediators such as histamine, sulphidoleukotrienes, and tumour necrosis factor alpha. The peptides also failed to cause mediator release in mast cells isolated from inflamed tissue derived from Crohn's disease. Using reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry, we could show that human intestinal mast cells do not express the tachykinin receptors NK-1, NK-2, or NK-3 under basal conditions. However, upon stimulation by immunoglobulin E (IgE) receptor-crosslinking, which induces an extensive mediator release reaction, a subpopulation of mast cells clearly expressed NK-1, the SP receptor. In conclusion, our data show that SP and other neuropeptides do not act as secretagogues in human intestinal mast cells that have not been pre-activated by IgE receptor-crosslinking.

Eosinophils: 'new' roles for 'old' cells

Prominent blood and tissue eosinophilia is manifested in a number of inflammatory states, particularly in allergic diseases. Eosinophils are a source of numerous cytokines and growth factors, thus in principle they can display both pro-inflammatory and anti-inflammatory activities as well as immunoregulatory ones. In this review, we will discuss the cross-talk between eosinophils and other cell types that they come in contact with in the inflammatory milieu, such as mast cells, fibroblasts and endothelial cells. 'New' roles for eosinophils in cancer and novel activatory signals will also be described.

Fibrosis in ocular allergic inflammation: recent concepts in the pathogenesis of ocular allergy

PURPOSE OF REVIEW

Mast cells and eosinophils are the main effector cells in allergic inflammation, but there is now compelling evidence that fibroblasts are also important players in the inflammatory response. In fact, they respond to different stimuli and release several mediators that modulate mast-cell and eosinophil functionality. In several allergic conditions such as vernal keratoconjunctivitis, asthma and atopic dermatitis the chronic presence of the inflammatory process has been associated with fibrosis and tissue remodeling, which in turn could cause irreversible alterations in the organ anatomy and functions. This review will discuss current advances in mast cell, eosinophil and fibroblast interactions in terms of their importance in the perpetuation of allergic inflammation and in contributing to the fibrosis and/or remodeling process in ocular allergy. As a main example of allergic ocular diseases associated with fibrosis, vernal keratoconjunctivitis is discussed in the light of recent findings.

RECENT FINDINGS

Several studies have recently shown that fibroblasts can modulate the functions of mast cells and eosinophils through the membrane form of stem cell factor and granulocyte-macrophage colony-stimulating factor, respectively. On the other hand, fibroblasts can be affected by inflammatory mediators derived from mast cells and eosinophils, such as transforming growth factor beta and nerve growth factor and by the T helper type 2 cytokines, IL-4 and IL-13, and vernal keratoconjunctivitis-derived fibroblasts display altered functions.

SUMMARY

Considerable useful information has been gained about the role of mast cells, eosinophils and fibroblasts in the perpetuation of allergic inflammation and tissue fibrosis and/or remodeling in general, and specifically in ocular allergy.

Human Intestinal Fibroblasts Prevent Apoptosis in Human Intestinal Mast Cells by a Mechanism Independent of Stem Cell Factor, IL-3, IL-4, and Nerve Growth Factor

In rodents, fibroblasts (FBs) mediate stem cell factor (SCF)-dependent growth of mast cells (MCs). In humans, SCF is mandatory for MC differentiation and survival. Other factors such as IL-3, IL-4, and nerve growth factor (NGF) act in synergism with SCF, thus enhancing proliferation and/or preventing apoptosis in MCs. In this study, we studied in vitro interactions between human MCs and human FBs, both isolated from the intestine and purified to homogeneity. In coculture with FBs, MCs survived for up to 3 wk, whereas purified MCs cultured alone died within a few days. TNF-alpha and IL-1beta, which both did not affect MC survival directly, enhanced FB-dependent MC growth. We provide evidence that FB-derived MC growth factors are soluble, heat-sensitive molecules which down-regulate MC apoptosis without enhancing MC proliferation. However, only low amounts of SCF were measured in FB-conditioned medium (<0.2 ng/ml). Moreover, blocking of SCF/c-kit interaction by anti-SCF or anti-c-kit Abs and neutralization of IL-3, IL-4, and NGF did not affect MC survival in the coculture system. In conclusion, our data indicate that human FBs promote survival of human MCs by mechanisms independent of SCF, IL-3, IL-4, and NGF. Such interactions between MCs and FBs may explain why MCs accumulate at sites of inflammatory bowel disease and intestinal fibrosis.

Mast cells in allergy and beyond

Mast cells (MC) are highly granulated tissue dwelling cells, widely distributed throughout the body in connective tissues and on mucosal surfaces. They are derived from bone marrow progenitors that migrate into the blood and subsequently into the tissues, where they undergo final maturation. Mast cell proliferation, differentiation, survival and activation are regulated by stem cell factor, the ligand for the c-kit tyrosine kinase receptor, expressed on the mast cell surface. They release a large number of pro-inflammatory and immunoregulatory mediators after activation induced by either immunoglobulin E-dependent or immunoglobulin E-independent mechanisms. Mast cells have been most widely studied in the context of allergic reactions and parasite infections, but there is now compelling evidences that they are important players in innate and acquired immunity, wound healing, fibrosis, tumors and autoimmune diseases. This review will discuss current advances in these fields.

What is the physiological function of mast cells?

Under physiological conditions, skin mast cells preferentially localize around nerves, blood vessels and hair follicles. This observation, which dates back to Paul Ehrlich, intuitively suggests that these enigmatic, multifacetted protagonists of natural immunity are functionally relevant to many more aspects of tissue physiology than just to the generation of inflammatory and vasodilatory responses to IgE-dependent environmental antigens. And yet, for decades, mainstream-mast cell research has been dominated by a focus on the -undisputedly prominent and important - mast cell functions in type I immune responses and in the pathogenesis and management of allergic diseases. Certainly, it is hard to believe that the very large and rather selectively distributed number of mast cells in normal, uninflamed, non-infected, non-traumatized mammalian skin or mucosal tissue simply hanging around there lazily day and night, just wait for the odd allergen or parasite-associated antigen to come by so the mast cell can finally swing into action. Indeed, the past decade has witnessed a renaissance of mast cell research 'beyond allergy', along with a more systematic exploration of the surprisingly wide range of physiological functions that mast cells may be involved in. The current debate sketches many exciting horizons that have recently come into our vision during this intriguing, ongoing search.

Tumor necrosis factors in a murine model of allergic peritonitis: effects on eosinophil accumulation and inflammatory mediators' release

In allergic disorders, the role of tumor necrosis factors (TNF) is not well established. We investigated the role of TNF in allergic peritonitis induced by ovalbumin (OVA) challenge in double TNF (TNF-alpha(-/-)/lymphotoxin-alpha(-/-)) knock out (TNF-KO) mice. In the peritoneal lavage of TNF-KO mice, mast cell number and histamine level (radioenzymatic assay) were similar to that in wild type (WT) mice. TNF-alpha (ELISA) and histamine were increased 1 h after challenge in WT mice. However, three days later eosinophil number and eosinophil peroxidase (EPO) levels (colorimetric-enzymatic assay) were found to be lower in TNF-KO mice. A second challenge three days after the first, increased EPO, histamine and IL-6 (ELISA) but did not alter eosinophil and mast cell numbers in both types of mice. On the other hand histamine and IL-6 were higher, while EPO was lower in TNF-KO mice. In conclusion, our findings show that TNF is involved in eosinophil accumulation and inflammatory mediators' release in a murine model of allergy.

New insights on the involvement of Nerve Growth Factor in allergic inflammation and fibrosis

Nerve Growth Factor (NGF), that was originally discovered for its properties of stimulating growth and differentiation of neurons, is now also considered responsible for several activities in the immune system and beyond. Mast cells and eosinophils, key cells of allergic inflammation, are a source of NGF and are influenced by it. These observations have prompted studies on NGF in allergy and tissue repair. Recent evidences link NGF and these two processes. While NGF is clearly a new tool in the management of untreatable ulcers, its role in allergic inflammation, although appearing to be pro-inflammatory, is still not clearly defined.

Food allergy as a risk factor for life-threatening asthma in childhood: a case-controlled study

BACKGROUND

No objective clinical risk factors exist for pediatric life-threatening asthma.

OBJECTIVES

In this study, we address whether persistent food allergy and degree of atopy are risk factors for life-threatening asthma.

METHODS

By use of a case-controlled design, children (1-16 years) ventilated for an exacerbation of asthma were enrolled. Each case was matched by sex, age, and ethnicity, with 2 controls who had attended with a non-life-threatening exacerbation. All subjects were assessed by means of a questionnaire, spirometry, and skin prick or RAST testing. The data were analyzed by conditional logistic regression.

RESULTS

Nineteen cases and 38 controls were enrolled. Compared with controls, cases were found to have the following risk factors: food allergy (odds ratio, 8.58; 95% CI, 1.85-39.71), multiple allergic diagnoses (4.42; 1.17-16.71), early onset of asthma (6.48; 1.36-30.85), and frequent admissions (14.2; 1.77-113.59). After regression analysis, only frequent admission with asthma (9.85; 1.04-93.27) and food allergy (5.89; 1.06-32.61) were independently associated with life-threatening asthma. Half the cases had food allergy compared with only 10% of controls.

CONCLUSION

This study demonstrates that poorly controlled asthma and food allergy are significant risk factors for life-threatening asthma. More intensive management of this high-risk group of children might help to reduce future morbidity and mortality.

Tryptase, a novel link between allergic inflammation and fibrosis

Allergy is a complex inflammatory disease, the etiology of which is well defined. It has recently been proposed that eosinophil, mast-cell and fibroblast interactions contribute to allergy perpetuation. Moreover, mast-cell-derived tryptase might act as a link among these cells. This hypothesis is supported by two recent papers that show that tryptase, seemingly through the protease-activated receptor-2, mediates eosinophil infiltration in the airways and fibroblast proliferation that depends on both cyclooxygenase and prostaglandin synthesis.

Interleukin-2 primes eosinophil degranulation in hypereosinophilia and Wells' syndrome

Patients with hypereosinophilia frequently suffer from eosinophil-mediated damages of the heart, lungs, skin, and other organs, while some do not. The reason(s) for this difference is not known. We observed that eosinophils from most patients with hypereosinophilia express the alpha-chain of the IL-2 receptor (CD25), and that IL-2 enhances platelet-activating factor-stimulated release of eosinophil cationic protein from CD25-expressing but not from CD25-negative eosinophils. Such a "priming" effect has previously been described for eosinophil hematopoietins. These data suggest that patients with increased eosinophil surface CD25 expression are at higher risk of eosinophil degranulation and subsequent tissue damage when IL-2 is present at inflammatory sites.

Non-IgE-dependent activation of human lung- and cord blood-derived mast cells is induced by eosinophil major basic protein and modulated by the membrane form of stem cell factor

The allergic reaction begins with the antigen-induced aggregation of occupied high-affinity IgE receptors expressed on mast cell surface, their activation, and the release of proinflammatory mediators that cause the "early phase" of this process. In addition, mast cell activation induces the onset of a "late phase" reaction characterized by the tissue infiltration of inflammatory cells, mainly eosinophils. We have hypothesized that during the late phase mast cells interact with and are activated by eosinophils. Here we report that highly purified human lung mast cells became responsive to eosinophil major basic protein (MBP) when in coculture with human lung fibroblasts. In addition, cord blood-derived mast cells maintained in coculture with 3T3 fibroblasts released more histamine and prostaglandin D(2) (PGD(2)) compared with cells maintained in suspension. The fibroblast-derived membrane form of stem cell factor (SCF) was found to be involved in the mast cell increased responsiveness to MBP. In fact, cord blood-derived mast cells cocultured with 3T3 in the presence of antisense for SCF or cocultured with fibroblasts that do not express the membrane form of SCF were inhibited in their histamine-releasing activity toward MBP. In addition, this form of SCF induced the expression of a pertussis toxin-sensitive G(i) protein, G(i3) that interacts with MBP to trigger mast cell non-IgE-dependent activation in a manner similar to other cationic compounds such as compound 48/80. Mast cell responsiveness to eosinophil mediators is a potentially novel evidence for an alternative pathway of allergen-independent activation able to contribute to the perpetuation of allergy.