Complexity and redundancy in the pathogenesis of asthma: reassessing the roles of mast cells and T cells

Elevated serum polyclonal immunoglobulin free light chains in patients with severe asthma

Background: Inflammation plays a pivotal role in the pathophysiology of asthma. Free light chains (FLC) can cause inflammation by mast cell antigen-activation. Serum immunoglobulin (Ig) FLC κ, but not λ, were shown elevated in adult males with asthma. We sought to investigate if serum Ig FLC concentrations are affected by asthma severity and their relationships with inflammatory outcomes. Methods: By using immunoassays, we measured serum κ and λ Ig FLCs in 24 severe persistent asthma patients, 15 patients with moderate persistent asthma, 15 steroid-naïve mild persistent asthma patients and 20 healthy control subjects in a cross-sectional observational study. Total and specific serum IgE concentrations, fractional exhaled nitric oxide (F_ENO), lung function, peripheral blood eosinophils and neutrophils, and C reactive protein (CRP) were also measured. Results: Serum κ FLC concentrations were elevated in severe asthma patients compared mild asthma patients (p < 0.05) and healthy subjects (p < 0.05). Serum λ FLCs were higher in severe asthma patients than in healthy subjects (p < 0.05) and correlated with blood eosinophil counts (percentage, κ: r = 0.51, p = 2.9678^-6; λ: r = 0.42, p = 1.7377^-4; absolute values, κ: r = 0.45, p = 6.1284^-5; λ: r = 0.38, p = 7.8261^-4), but not with total or specific serum IgE. In severe asthma patients, serum Ig FLC correlated with serum CRP (κ: r = 0.33; p = 0.003; λ: r = 0.38, p = 8.8305^-4) and blood neutrophil cell counts (percentage, κ: r = 0.31; p = 0.008; λ: r = 0.29, p = 0.01; absolute values, κ: r = 0.40; p = 3.9176^-4; λ: r = 0.40, p = 4.5479^-4), were elevated in subjects with blood eosinophilia (≥300 cells/µL) (n = 13) compared with non-eosinophilic subjects (n = 10) (κ: 19.2 ± 1.2 mg/L versus 12.1 ± 1.3 mg/L, p < 0.001; λ: 27.2 ± 2.6 mg/L versus 16.8 ± 2.5 mg/L, p < 0.01), but were similar in atopic (n = 15) versus nonatopic subjects (n = 9) (κ: p = 0.20; λ: p = 0.80). Serum FLC were negatively correlated with lung function tests, including forced expiratory volume in one second (FEV1) (κ: r = -0.33; p = 0.0034; λ: r = -0.33; p = 0.0035), and FEV₁/forced vital capacity ratio (κ: r = -0.33; p = 0.0034; λ: r = -0.33; p = 0.0036). Conclusion: Serum Ig FLCs are elevated in severe asthma adults and might represent new surrogate markers of inflammation. The pathophysiological implications of these findings require further research. This study was approved by the ethics committee of the University Hospital Agostino Gemelli Foundation and Catholic University of the Sacred Heart (approval number P/1034/CE2012).

Establishment and characterization of murine models of asthma and subcutaneous immunotherapy for Humulus pollen allergy

Introduction

Humulus pollen is an important cause of allergic asthma in East Asia. There have been some murine models for Humulus pollen allergy established by intraperitoneal (IP) sensitization and nasal drip stimulation, but they were not comprehensive enough. Here, we used atomized inhalation for challenge and compared the subcutaneous (SC) and IP sensitization routes to determine the optimal method to establish a model of asthma induced by Humulus pollen. Subsequently, we tried to develop a rapid subcutaneous immunotherapy (SCIT) model for Humulus allergy.

Methods

BALB/c Mice were sensitized through the SC or IP route, with respective reference to previously established sensitization methods and allergen dosing, and challenged with nebulized Humulus pollen extract to induce asthma. To compare the two sensitization methods, airway hyperresponsiveness (AHR), inflammatory cell infiltration, allergen‐specific serum immunoglobulin (Ig)E (sIgE) levels, cytokine levels, and lung histopathology were assessed. The effects of SCIT (once every other day for 16 days) on airway inflammation, AHR, sIgE, and allergen‐specific serum IgG2a (sIgG2a) levels were evaluated by using the model established in this study.

Results

Although mice sensitized by the SC or IP routes both showed AHR and airway inflammation, the SC route elicited significantly higher levels of sIgE, eosinophil inflammation, and T helper type 2 cytokines, compared with the IP route. SCIT in the treatment group significantly reduced the titers of sIgE, enhanced the titers of sIgG2a, and effectively alleviated pulmonary inflammation and AHR, compared with the vehicle group.

Conclusions

The SC route can be used to establish a murine model of Humulus pollen allergy that recapitulates the characteristics of clinical allergic asthma. Short‐term SCIT can significantly improve symptoms and pathophysiology in asthmatic mice.

Characterization of mast cell-derived rRNA-containing microvesicles and their inflammatory impact on endothelial cells

Tissue-resident mast cells (MCs) are well known for their role in inflammatory responses and allergic and anaphylactic reactions, but they also contribute to processes of arterial remodeling. Although ribosomes and cytosolic RNAs are located around secretory granules in mature MCs, their functional role in MC responses remains unexplored. Previous studies by our group characterized extracellular RNA (eRNA) as an inflammatory and pathogenetic factor in vitro and in vivo. In the present study, RNA-containing MCs and eRNA were located in close proximity to growing collateral arteries in vivo. In vitro, various agonists were found to induce the degranulation of MCs and the concomitant release of eRNA in association with microvesicles (MVs). The liberation of eRNA from MCs was abolished by MC stabilizers or by preventing the increase of intracellular Ca²⁺ in MCs. eRNA was found to be mainly contained inside MVs, as demonstrated by electron microscopy and immunocytochemistry. The exposure to and the uptake of MC-released MVs by cultured endothelial cells increased their expression of cytokines, such as monocyte chemoattractant protein or IL-6, in a dose- and time-dependent manner. These results indicate that RNA-containing MC-derived MVs are likely to be involved in inflammatory responses, relevant, for example, to processes of vascular remodeling.-Elsemüller, A.-K., Tomalla, V., Gärtner, U., Troidl, K., Jeratsch, S., Graumann, J., Baal, N., Hackstein, H., Lasch, M., Deindl, E., Preissner, K. T., Fischer, S. Characterization of mast cell-derived rRNA-containing microvesicles and their inflammatory impact on endothelial cells.

Assessment of immunotoxicity induced by chemicals in human precision-cut lung slices (PCLS)

Occupational asthma can be induced by a number of chemicals at the workplace. Risk assessment of potential sensitizers is mostly performed in animal experiments. With increasing public demand for alternative methods, human precision-cut lung slices (PCLS) have been developed as an ex vivo model. Human PCLS were exposed to increasing concentrations of 20 industrial chemicals including 4 respiratory allergens, 11 contact allergens, and 5 non-sensitizing irritants. Local respiratory irritation was characterized and expressed as 75% (EC25) and 50% (EC50) cell viability with respect to controls. Dose-response curves of all chemicals except for phenol were generated. Local respiratory inflammation was quantified by measuring the production of cytokines and chemokines. TNF-α and IL-1α were increased significantly in human PCLS after exposure to the respiratory sensitizers trimellitic anhydride (TMA) and ammonium hexachloroplatinate (HClPt) at subtoxic concentrations, while contact sensitizers and non-sensitizing irritants failed to induce the release of these cytokines to the same extent. Interestingly, significant increases in T(H)1/T(H)2 cytokines could be detected only after exposure to HClPt at a subtoxic concentration. In conclusion, allergen-induced cytokines were observed but not considered as biomarkers for the differentiation between respiratory and contact sensitizers. Our preliminary results show an ex vivo model which might be used for prediction of chemical-induced toxicity, but is due to its complex three-dimensional structure not applicable for a simple screening of functional and behavior changes of certain cell populations such as dendritic cells and T-cells in response to allergens.

Marine macro- and microalgae as potential agents for the prevention of asthma: hyperresponsiveness and inflammatory subjects

Asthma is a variable disease and various factors are affected to increase the asthmatic symptoms and level of asthma control. It is believed that the cause for this disease is a combination of genetic and environmental factors. Numerous medications are available at present to treat this disease but it has been failed to control number of incidences successfully. Hence, recently many researchers have paid their interest to identify potential drugs from marine-based resources such as marine algae. In vitro and in vivo experiments have been conducted with extracts or compounds from algae and found that they showed significant activities against asthma. Accordingly, many marine macro- and microalgae have been reported to have potential to ameliorate the effect of asthma. However, detailed studies are needed in relation to identify the molecular mechanism of this disease to apply those marine resources against asthma effectively. In this chapter, an attempt has been taken to discuss the potential antiasthmatic activity of marine macro- and microalgae.

Association of 5-lipoxygenase gene polymorphisms with bronchial asthma

Leukotrienes are important pro-inflammatory mediators in bronchial asthma (BA) and are derived from arachidonic acid by the action of 5-lipoxygenase (5-LO). We investigated the association of 5-LO gene polymorphisms with BA. Thirty-six single-nucleotide polymorphisms (SNPs) of the 5-LO gene, as referenced in the dbSNP gene bank, were analyzed with sequencing and allele-specific PCR (AS-PCR) in genomic DNA from individuals with BA and controls. Of these 36 SNPs, 4 were identified in our study. The c.760 G>A (E254K) (rs2228065) was detected in 15 out of 215 BA patients and 6 out of 212 controls (P<0.05). There were no differences in the frequencies of the other three silent polymorphisms, rs2228064 (c.270 G>A), rs116961353 (c.780G>A) and rs2229136 (c.1728 A>G) between individuals with BA and controls (P>0.05). With our designed primers for AS-PCR, the detection of the 5-LO gene E254K polymorphism was clear and accurate, and the genotype was directly distinguished. Our findings contribute to the evaluation of one of the genetic risk factors for BA and we report an accurate and simple method to rapidly detect the 5-LO E254K polymorphism. It is important to further study the correlation between drug response in BA patients using 5-LO inhibitors with the E254K polymorphism in the clinic.

Receptor signaling in immune cell development and function

Immune cell development and function must be tightly regulated through cell surface receptors to ensure proper responses to pathogen and tolerance to self. In T cells, the signal from the T-cell receptor is essential for T-cell maturation, homeostasis, and activation. In mast cells, the high-affinity receptor for IgE transduces signal that promotes mast cell survival and induces mast cell activation. In dendritic cells and macrophages, the toll-like receptors recognize microbial pathogens and play critical roles for both innate and adaptive immunity against pathogens. Our research explores how signaling from these receptors is transduced and regulated to better understand these immune cells. Our recent studies have revealed diacylglycerol kinases and TSC1/2-mTOR as critical signaling molecules/regulators in T cells, mast cells, dendritic cells, and macrophages.

A zinc chelator TPEN attenuates airway hyperresponsiveness and airway inflammation in mice in vivo

BACKGROUND

Zinc is an essential element required for the cell metabolism, including gene transcription, signal transduction, immunity, and apoptosis. The pathophysiological role of zinc in asthma, however, is not entirely clear. Mast cells have been implicated in atopic asthma, and zinc deprivation has been reported to reduce mast cell activation. Here, we investigate the effects of a zinc chelator, N,N,N',N'-tetrakis (2-pyridyl-methyl) ethylenediamine (TPEN), on asthmatic responses in mouse models of ovalbumin (OVA)-induced airway hyperresponsiveness and allergic airway inflammation.

METHODS

Mice were sensitized with OVA with or without the adjuvant aluminum hydroxide (alum) and subjected to OVA exposure with or without treatment of TPEN. Cell profiles and cytokine levels in bronchoalveolar lavage (BAL) fluids, airway responsiveness to inhaled acetylcholine, and goblet cell hyperplasia after allergen exposure were assessed.

RESULTS

In mice sensitized to OVA without alum, TPEN significantly suppressed airway hyperresponsiveness and eosinophilia in BAL fluids. TPEN also attenuated the upregulation of TNFα, IL-13 and IL-4 in BAL fluids and goblet cell hyperplasia after OVA exposure. By contrast, in mice sensitized to OVA with alum, TPEN suppressed eosinophilia in BAL fluids but not airway hyperresponsiveness and goblet cell hyperplasia.

CONCLUSIONS

In pulmonary allergic inflammation induced in mice immunized with antigen without alum, zinc chelator inhibits airway inflammation and hyperresponsiveness. These findings suggest that zinc may be a therapeutic target of allergic asthma.

Modulation of mast cell adhesion, proliferation, and cytokine secretion on electrospun bioresorbable vascular grafts

Mast cells synthesize several potent angiogenic factors and can also stimulate fibroblasts, endothelial cells, and macrophages. An understanding of how they participate in wound healing and angiogenesis is important to further our knowledge about in situ vascular prosthetic regeneration. The adhesion, proliferation, and cytokine secretion of bone marrow-derived murine mast cells (BMMC) on electrospun polydioxanone, polycaprolactone, and silk scaffolds, as well as tissue culture plastic, has been investigated in the presence or absence of IL-3, stem cell factor, IgE and IgE with a crosslinking antigen, dinitrophenol-conjugated albumin (DNP). It was previously believed that only activated BMMCs exhibit adhesion and cytokine secretion. However, this study shows nonactivated BMMC adhesion to electrospun scaffolds. Silk scaffold was not found to be conducive for mast cell adhesion and cytokine secretion. Activation by IgE and DNP significantly enhanced mast cell adhesion, proliferation, migration, and secretion of tumor necrosis factor alpha, macrophage inflammatory protein-1α, and IL-13. This indicates that mast cells might play a role in the process of biomaterial integration into the host tissue, regeneration, and possibly angiogenesis.

Emerging roles of T helper subsets in the pathogenesis of asthma

The cardinal features of asthma include pulmonary inflammation and airway hyperresponsiveness (AHR). Classically, asthma, specifically allergic asthma, has been attributed to a hyperactive Th2 cell immune response. However, the Th2 cell-mediated inflammation model has failed to adequately explain many of the clinical and molecular aspects of asthma. In addition, the outcomes of Th2-targeted therapeutic trials have been disappointing. Thus, asthma is now believed to be a complex and heterogeneous disorder, with several molecular mechanisms underlying the airway inflammation and AHR that is associated with asthma. The original classification of Th1 and Th2 pathways has recently been expanded to include additional effector Th cell subsets. These include Th17, Th9 and Treg cells. Emerging data highlight the involvement of these new Th cell subsets in the initiation and augmentation of airway inflammation and asthmatic responses. We now review the roles of these recently classified effector Th cell subsets in asthmatic inflammation and the insights they may provide in addition to the traditional Th2 paradigm. The hope is that a clearer understanding of the inflammatory pathways involved and the mediators of inflammation will yield better targeted therapeutics.

Janus kinase-3 dependent inflammatory responses in allergic asthma

Allergic asthma is a chronic inflammatory condition of the lung characterized by reversible airway obstruction, high serum immunoglobulin (Ig) E levels, and chronic airway inflammation. A number of cells including mast cells, T cells, macrophages and dendritic cells play a role in the pathogenesis of the disease. Janus kinase (JAK)-3, a non-receptor protein tyrosine kinase, traditionally known to mediate cytokine signaling, also regulates functional responses of these cells. In this review the role of JAK-3 in regulating various pathogenic processes in allergic asthma is discussed. We propose that targeting JAK-3 is a rationale approach to control the inflammatory responses of multiple cell types responsible for the pathogenesis of allergic asthma.

Mast cells in atopic dermatitis

Mast cells play as the major effector cells in immediate hypersensitivity through activation via the high-affinity IgE receptor, Fc epsilon RI, although many other functions have recently been discovered for this cell type. Given the broad array of proinflammatory mediators secreted from Fc epsilon RI-activated mast cells, as well as sensitization to allergens, IgE elevation, and increased mast cells in a majority of atopic dermatitis patients, mast cells are believed to be involved in the pathogenesis of atopic dermatitis. Numerous animal models have been used to study this epidemic disease. Here we review the recent progress to synthesize our current understanding of this disease and potential mechanisms for a mast cell's role in the disease.

TH17 cells mediate steroid-resistant airway inflammation and airway hyperresponsiveness in mice

Steroid-resistant asthma comprises an important source of morbidity in patient populations. T(H)17 cells represent a distinct population of CD4(+) Th cells that mediate neutrophilic inflammation and are characterized by the production of IL-17, IL-22, and IL-6. To investigate the function of T(H)17 cells in the context of Ag-induced airway inflammation, we polarized naive CD4(+) T cells from DO11.10 OVA-specific TCR-transgenic mice to a T(H)2 or T(H)17 phenotype by culturing in conditioned medium. In addition, we also tested the steroid responsiveness of T(H)2 and T(H)17 cells. In vitro, T(H)17 cytokine responses were not sensitive to dexamethasone (DEX) treatment despite immunocytochemistry confirming glucocorticoid receptor translocation to the nucleus following treatment. Transfer of T(H)2 cells to mice challenged with OVA protein resulted in lymphocyte and eosinophil emigration into the lung that was markedly reduced by DEX treatment, whereas T(H)17 transfer resulted in increased CXC chemokine secretion and neutrophil influx that was not attenuated by DEX. Transfer of T(H)17 or T(H)2 cells was sufficient to induce airway hyperresponsiveness (AHR) to methacholine. Interestingly, AHR was not attenuated by DEX in the T(H)17 group. These data demonstrate that polarized Ag-specific T cells result in specific lung pathologies. Both T(H)2 and T(H)17 cells are able to induce AHR, whereas T(H)17 cell-mediated airway inflammation and AHR are steroid resistant, indicating a potential role for T(H)17 cells in steroid-resistant asthma.

The Tec family kinase, IL-2-inducible T cell kinase, differentially controls mast cell responses

The Tec family tyrosine kinase, IL-2-inducible T cell kinase (Itk), is expressed in T cells and mast cells. Mice lacking Itk exhibit impaired Th2 cytokine secretion; however, they have increased circulating serum IgE, but exhibit few immunological symptoms of allergic airway responses. We have examined the role of Itk in mast cell function and FcepsilonRI signaling. We report in this study that Itk null mice have reduced allergen/IgE-induced histamine release, as well as early airway hyperresponsiveness in vivo. This is due to the increased levels of IgE in the serum of these mice, because the transfer of Itk null bone marrow-derived cultured mast cells into mast cell-deficient W/W(v) animals is able to fully rescue histamine release in the W/W(v) mice. Further analysis of Itk null bone marrow-derived cultured mast cells in vitro revealed that whereas they have normal degranulation responses, they secrete elevated levels of cytokines, including IL-13 and TNF-alpha, particularly in response to unliganded IgE. Analysis of biochemical events downstream of the FcepsilonRI revealed little difference in overall tyrosine phosphorylation of specific substrates or calcium responses; however, these cells express elevated levels of NFAT, which was largely nuclear. Our results suggest that the reduced mast cell response in vivo in Itk null mice is due to elevated levels of IgE in these mice. Our results also suggest that Itk differentially modulates mast cell degranulation and cytokine production in part by regulating expression and activation of NFAT proteins in these cells.

Mast cells can mediate vascular permeability through regulation of the PI3K-HIF-1alpha-VEGF axis

RATIONALE

Bronchial inflammation is usually accompanied by increased vascular permeability. Mast cells release a number of mediators that act directly on the vasculature, resulting in vasodilatation, increased permeability, and subsequent plasma protein extravasation. Vascular endothelial growth factor (VEGF) has been implicated to contribute to asthmatic tissue edema through its effect on vascular permeability. However, the effects of mast cells on VEGF-mediated signaling in allergic airway disease are not clearly understood.

OBJECTIVES

An aim of the present study was to investigate the role of mast cells on VEGF-mediated signal transduction in allergic airway disease.

METHODS

We used genetically mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-v) (W/W(v)) mice and the congenic normal WBB6F(1)(+/+) mouse model for allergic airway disease to investigate the role of mast cells on VEGF-mediated signal transduction in allergic airway disease, more specifically in vascular permeability.

MEASUREMENTS AND MAIN RESULTS

Our present study, with ovalbumin (OVA)-sensitized without adjuvant and OVA-challenged mice, revealed the following typical pathophysiologic features of allergic airway diseases: increased inflammatory cells of the airways, airway hyperresponsiveness, increased vascular permeability, and increased levels of VEGF. However, levels of VEGF and plasma exudation in W/W(v) mice after OVA inhalation were significantly lower than levels in WBB6F(1)(+/+) mice. Moreover, mast cell-reconstituted W/W(v) mice restored vascular permeability and VEGF levels similar to those of the WBB6F(1)(+/+) mice. Our data also showed that VEGF expression was regulated by hypoxia-inducible factor-1alpha (HIF-1alpha) activation through the phosphatidylinositol 3-kinase (PI3K)-HIF-1alpha pathway in allergic airway disease.

CONCLUSIONS

These results suggest that mast cells modulate vascular permeability by the regulation of the PI3K-HIF-1alpha-VEGF axis.

T cells and NKT cells in the pathogenesis of asthma

Asthma is an immunological disease with multiple inflammatory and clinical phenotypes, characterized by symptoms of wheezing, shortness of breath, and coughing due to airway hyperreactivity (AHR) and reversible airway obstruction. In allergic asthma, the most common form of asthma, airway inflammation is mediated by adaptive immune recognition of protein allergens by Th2 cells, resulting in airway eosinophilia. However, in other forms of asthma, inflammation is associated with immune responses to respiratory infections and airway neutrophilia. A central feature common to all forms of asthma is AHR, the heightened responsiveness of the airways to nonspecific stimuli. AHR has been shown recently in animal models of asthma to require the presence of CD1d-restricted, invariant T cell receptor-positive, natural killer T (iNKT) cells. Although allergen-specific Th2 cells and iNKT cells have many phenotypic similarities (e.g., expression of CD4 and production of Th2 cytokines), they have complementary activities, such as production of Th2 cytokines under different conditions, differential sensitivity to corticosteroids, and responsiveness to different classes of antigen (proteins versus glycolipids). We hypothesize that Th2 cells and iNKT cells interact synergistically to induce asthma but that different forms of asthma result from distinct roles of CD4(+) iNKT cells versus Th2 cells.

New insights on mast cell activation via the high affinity receptor for IgE

Mast cells are innate immune cells that function as regulatory or effector cells and serve to amplify adaptive immunity. In adaptive immunity these cells function primarily through cell surface Fc receptors that bind immunoglobulin antibodies. The dysregulation of their adaptive role makes them central players in allergy and asthma. Upon encountering an allergen (antigen), which is recognized by immunoglobulin E (IgE) antibodies bound to the high affinity IgE receptor (FcepsilonRI) expressed on their cell surface, mast cells secrete both preformed and newly synthesized mediators of the allergic response. Blocking of these responses is an objective in therapeutic intervention of allergic diseases. Thus, understanding the mechanisms by which antigens elicit mast cell activation (via FcepsilonRI) holds promise toward identifying therapeutic targets. Here we review the most recent advances in understanding antigen-dependent mast cell activation. Specifically, we focus on the requirements for FcepsilonRI activation, the regulation of calcium responses, co-stimulatory signals in FcepsilonRI-mediated mast cell activation and function, and how genetics influences mast cell signaling and responses. These recent discoveries open new avenues of investigation with therapeutic potential.

Lactate dehydrogenase-elevating virus infection at the sensitization and challenge phases reduces the development of delayed eosinophilic allergic rhinitis in BALB/c mice

The present study was conducted to determine whether lactate dehydrogenase-elevating virus (LDV) infection at the sensitization and challenge phases affect the development of delayed allergic eosinophilic rhinitis induced by ovalbumin (OVA) in BALB/c mice (DAR group). Compared to the DAR group, LDV infection at the priming (DAR/LDVs group) and immunizing (DAR/LDVc group) phases reduced the induction of eosinophils in the bone marrow (BM) and/or blood. However, the number of eosinophils in the BM was not affected in the DAR/LDVc group. In addition, total blood IgE values were reduced in the DAR/LDVs but not the DAR/LDVc groups. Compared to the production of cytokines from splenic cells and blood IgE values in the DAR group, OVA-specific IL-4 and IFN-gamma productions and IgE values were reduced in the DAR/LDVs, whereas OVA-specific IFN-gamma and IL-4 productions were increased and decreased, respectively in the DAR/LDVc,but not the DAR/LDVs groups. Both DAR/LDVs and DAR/LDVc groups reduced the development of eosinophilic rhinitis associated with reduced VCAM-1 expression on endothelium in blood vessels and ICAM-1 expression on nasal respiratory epithelium at inflamed areas. The present study suggests that LDV infection at the sensitization phase may reduce the development of T helper (Th) 1 and Th2 responses, whereas LDV infection at the challenge phase may inhibit the development of Th2 response by shifting to Th1 response. These may be responsible for the reduction of the development of DAR by LDV infection.

Systemic administration of olygodeoxynucleotides with CpG motifs at priming phase reduces local Th2 response and late allergic rhinitis in BALB/c mice

Oligodeoxynucleotides (ODN) with CpG motifs (CpG ODN) induce T helper (Th)1-type reaction. We aimed to evaluate the therapeutic effect of CpG ODN in the development of late allergic rhinitis induced by ovalbumin (OVA), which is one of Th2 diseaes, in BALB/c mice. Effects of a single dose of synthetic CpG-ODN (50 microg) intraperitoneally (i.p.) at the priming phase (on day 0) by OVA on the development of late eosinophilic rhinitis at respiratory areas were compared to the control mice treated with its vehicle (ODN without CpG motifs; 50 microg). Animals were again sensitized by OVA (on day 10) i.p., and 4 days after second sensitization animals were challenged by OVA intranasally (on day 14). Four days after challenge, eosinophilic reactions, nasal lesions and local cytokine values were examined. Compared to the control group, the CpG ODN-administration increased production of OVA-specific Th1 cytokine (interferon-gamma) and decreased productions of ovalubmin-specific Th2 cytokines [interleukin (IL)-5 and IL-13] in nasal cavity fluids, supernatants of splenocytes and/or sera. Also, eosinophilia and increased total IgE values were decreased in mice treated with the CpG ODN compared to the control group. Moreover, nasal lesions with infiltration of eosinophils were prominently reduced by the CpG ODN-treatment compared to the control mice. The present study suggests that the systemic administration of CpG ODN at the priming phase may reduce local OVA-specific Th2 responses, resulting in decreased nasal pathology in the late allergic eosinophilic rhinitis.

Src family kinases and lipid mediators in control of allergic inflammation

The Src family kinases Fyn and Lyn are important modulators of the molecular events initiated by engagement of the high-affinity IgE receptor (Fc epsilon RI). These kinases control many of the early signaling events and initiate the production of several lipid metabolites that have an important role in regulating mast cell responses. The intracellular level of phosphatidylinositol (3,4,5)-trisphosphate (PIP(3)), which is produced by phosphatidylinositol 3-OH kinase, plays an important role in determining the extent of a mast cells response to a stimulus. Enhanced levels lead to a hyperdegranulating phenotype (as seen in SHIP-1(-/-) and Lyn(-/-) mast cells), whereas decreased levels cause hypodegranulation (as seen in Fyn(-/-) mast cells). Downregulation of mast cell phosphatase and tensin homologue deleted on chromosone 10 expression, a phosphatase that reduces cellular levels of PIP(3), caused constitutive cytokine production, demonstrating that this response is particularly sensitive to PIP(3) levels. Lyn and Fyn are also intimately linked to other lipid kinases, like sphingosine kinases (SphK). By producing sphingosine-1-phosphate (S1P), SphKs contribute to mast cell chemotaxis and degranulation. In vivo studies now reveal that circulating S1P as well as that found within the mast cell is important in determining mast cell responsiveness. These studies demonstrate the connection between Src protein tyrosine kinases and lipid second messengers that control mast cell function and allergic responses.

VDR-dependent regulation of mast cell maturation mediated by 1,25-dihydroxyvitamin D3

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] is a secosteroid hormone that regulates bone metabolism, controls calcium homeostasis, and possesses immunomodulatory properties. We show here that 1,25(OH)2D3 contributes to the regulation of development and function of mast cells, which play a critical role in several inflammatory disorders. 1,25(OH)2D3 promotes apoptosis and inhibits maturation of mouse bone marrow-derived mast cell precursors. Dose-dependent inhibition of mast cell differentiation by 1,25(OH)2D3 is observed at discrete, intermediate stages of mast cell development, identified by expression of c-kit, FcepsilonRI, and IL-3 receptor-alpha chain, and depends on the expression of the vitamin D receptor (VDR). It is important that mast cell progenitors obtained from VDR-ablated mice undergo an accelerated maturation in vitro and give rise to more responsive mast cells than wild-type. Furthermore, histological analysis of mast cell density in peripheral tissues reveals a moderate increase in the number of mast cells in the skin of VDR-deficient mice compared with wild-type animals. These data support the hypothesis of a physiological role of 1,25(OH)2D3 in mast cell development and suggest novel, therapeutic uses of 1,25(OH)2D3 analogs.

Genome-wide gene expression profiling of human mast cells stimulated by IgE or FcepsilonRI-aggregation reveals a complex network of genes involved in inflammatory responses

Background

Mast cells are well established effectors of IgE-triggered allergic reactions and immune responses to parasitic infections. Recent studies indicate that mast cells may play roles in adaptive and innate immunity, suggesting an innovative view of the regulation of immune responses. Here, we profiled the transcriptome of human mast cells sensitized with IgE alone, or stimulated by FcεRI aggregation.

Results

Our data show that among 8,793 genes examined, 559 genes are differentially regulated in stimulated mast cells when compared with resting/unstimulated mast cells. The major functional categories of upregulated genes include cytokines, chemokines, and other genes involved in innate and adaptive immune-responses. We observed the increased expression of over 63 gene-transcripts following IgE-sensitization alone. Our data was validated using Real-Time-PCR; ELISA and western blot. We confirmed that IgE alone does not trigger mast cell-immediate responses, such as calcium signals, degranulation or protein-phosphorylation.

Conclusion

This report represents a substantial advance in our understanding of the genome wide effects triggered by "passive sensitization" or active stimulation of human mast cells, supporting mast cells' potential involvement in a wide range of inflammatory responses.

Mast cells can promote the development of multiple features of chronic asthma in mice

Bronchial asthma, the most prevalent cause of significant respiratory morbidity in the developed world, typically is a chronic disorder associated with long-term changes in the airways. We developed a mouse model of chronic asthma that results in markedly increased numbers of airway mast cells, enhanced airway responses to methacholine or antigen, chronic inflammation including infiltration with eosinophils and lymphocytes, airway epithelial goblet cell hyperplasia, enhanced expression of the mucin genes Muc5ac and Muc5b, and increased levels of lung collagen. Using mast cell-deficient (Kit(W-sh/W-sh) and/or Kit(W/W-v)) mice engrafted with FcRgamma+/+ or FcRgamma-/- mast cells, we found that mast cells were required for the full development of each of these features of the model. However, some features also were expressed, although usually at less than wild-type levels, in mice whose mast cells lacked FcRgamma and therefore could not be activated by either antigen- and IgE-dependent aggregation of Fc epsilonRI or the binding of antigen-IgG1 immune complexes to Fc gammaRIII. These findings demonstrate that mast cells can contribute to the development of multiple features of chronic asthma in mice and identify both Fc Rgamma-dependent and Fc Rgamma-independent pathways of mast cell activation as important for the expression of key features of this asthma model.

Free immunoglobulin light chains as target in the treatment of chronic inflammatory diseases

Immunoglobulin free light chains were long considered irrelevant bystander products of immunoglobulin synthesis by B lymphocytes. To date, different studies suggest that free light chains may have important functional activities. For instance, it has been shown that immunoglobulin free light chains can elicit mast cell-driven hypersensitivity responses leading to asthma and contact sensitivity. Free light chains also show other biologic actions such as anti-angiogenic and proteolytic activities or can be used as specific targeting vehicles. Levels of free light chain levels in body fluids increase markedly in diseases such as multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. In this review, we will focus on the unexpected biological activities of immunoglobulin free light chains with special attention to its possible role in the induction of chronic inflammatory diseases.

Rapidly changing perspectives about mast cells at mucosal surfaces

Mast cells (MCs) are major effector cells of immunoglobulin E (IgE)-mediated allergic inflammation. However, it has become increasingly clear that they also play important roles in diverse physiological and pathological processes. Recent advances have focused on the importance of MCs in both innate and adaptive immune responses and have fostered studies of MCs beyond the myopic focus on allergic reactions. MCs possess a variety of surface receptors and may be activated by inflammatory mediators, IgE, IgG, light chains, complement fragments, proteases, hormones, neuropeptides, and microbial products. Following activation, they produce a plethora of pro-inflammatory mediators and participate in inflammatory reactions in many organs. This review focuses on the role of MCs in inflammatory reactions in mucosal surfaces with particular emphasis on their role in respiratory and gastrointestinal inflammatory conditions.

Mast cells as "tunable" effector and immunoregulatory cells: recent advances

This review focuses on recent progress in our understanding of how mast cells can contribute to the initiation, development, expression, and regulation of acquired immune responses, both those associated with IgE and those that are apparently expressed independently of this class of Ig. We emphasize findings derived from in vivo studies in mice, particularly those employing genetic approaches to influence mast cell numbers and/or to alter or delete components of pathways that can regulate mast cell development, signaling, or function. We advance the hypothesis that mast cells not only can function as proinflammatory effector cells and drivers of tissue remodeling in established acquired immune responses, but also may contribute to the initiation and regulation of such responses. That is, we propose that mast cells can also function as immunoregulatory cells. Finally, we show that the notion that mast cells have primarily two functional configurations, off (or resting) or on (or activated for extensive mediator release), markedly oversimplifies reality. Instead, we propose that mast cells are "tunable," by both genetic and environmental factors, such that, depending on the circumstances, the cell can be positioned phenotypically to express a wide spectrum of variation in the types, kinetics, and/or magnitude of its secretory functions.

A Key Role for Mast Cell Chymase in the Activation of Pro-matrix Metalloprotease-9 and Pro-matrix Metalloprotease-2

Chymases, serine proteases exclusively expressed by mast cells, have been implicated in various pathological conditions. However, the basis for these activities is not known, i.e. the in vivo substrate(s) for mast cell chymase has not been identified. In this study we show that mice lacking the chymase mouse mast cell protease 4 (mMCP-4) fail to process pro-matrix metalloprotease 9 (pro-MMP-9) to its active form in vivo, whereas both the pro and active form of MMP-9 was found in tissues of wild type mice. Moreover, the processing of pro-MMP-2 into active enzyme was markedly defective in mMCP-4 null animals. Histological analysis revealed an increase in collagen in the ear tissue of mMCP-4-deficient animals accompanied by increased ear thickness and a higher content of hydroxyproline. Furthermore, both lung and ear tissue from the knock-out animals showed a markedly increased staining for fibronectin. MMP-9 and MMP-2 are known to have a range of important activities, but the mechanisms for their activation in vivo have not been clarified previously. The present study thus indicates a key role for mast cell chymase in the regulation of pro-MMP-2 and -9 activities. Moreover, the results suggest an important role for mast cell chymase in regulating connective tissue homeostasis.

Elicitation of allergic asthma by immunoglobulin free light chains

The observation that only 50% of patients with adult asthma manifest atopy indicates that other inflammatory mechanisms are likely involved in producing the characteristic features of this disorder; namely reversible airway obstruction, hyperresponsiveness, and pulmonary inflammation. Our recent discovery that antigen-specific Ig free light chains (LCs) mediate hypersensitivity-like responses suggests that these molecules may be of import in the pathophysiology of asthma. Using a murine experimental model of nonatopic asthma, we now have shown that an LC antagonist, the 9-mer peptide F991, can abrogate the development of airway obstruction, hyperresponsiveness, and pulmonary inflammation. Further, passive immunization with antigen-specific LCs and subsequent airway challenge can elicit a mast cell-dependent reaction leading to acute bronchoconstriction. These findings, and the demonstration that the concentration of free kappa LCs in the sera of patients with adult asthma were significantly increased (as compared with age-matched nonasthmatic individuals), provide previously undescribed insight into the pathogenesis of asthma. In addition, the ability to inhibit pharmacologically LC-induced mast cell activation provides a therapeutic means to prevent or ameliorate the adverse bronchopulmonary manifestations of this incapacitating disorder.

Histidines are critical for heparin-dependent activation of mast cell tryptase

Mast cell tryptase is a tetrameric serine protease that is stored in complex with negatively charged heparin proteoglycans in the secretory granule. Tryptase has potent proinflammatory properties and has been implicated in diverse pathological conditions such as asthma and fibrosis. Previous studies have shown that tryptase binds tightly to heparin, and that heparin is required in the assembly of the tryptase tetramer as well as for stabilization of the active tetramer. Because the interaction of tryptase with heparin is optimal at acidic pH, we investigated in this study whether His residues are of importance for the heparin binding, tetramerization, and activation of the tryptase mouse mast cell protease 6. Molecular modeling of mouse mast cell protease 6 identified four His residues, H35, H106, H108, and H238, that are conserved among pH-dependent tryptases and are exposed on the molecular surface, and these four His residues were mutated to Ala. In addition, combinations of different mutations were prepared. Generally, the single His-Ala mutations did not cause any major defects in heparin binding, activation, or tetramerization, although some effect of the H106A mutation was observed. However, when several mutations were combined, large defects in all of these parameters were observed. Of the mutants, the triple mutant H106A/H108A/H238A was the most affected with an almost complete inability to bind to heparin and to form active tryptase tetramers. Taken together, this study shows that surface-exposed histidines mediate the interaction of mast cell tryptase with heparin and are of critical importance in the formation of active tryptase tetramers.

Induction of mast cell interactions with blood vessel wall components by direct contact with intact T cells or T cell membranes in vitro

BACKGROUND

Mast cells exert profound pleiotropic effects on immune cell reactions at inflammatory sites, where they are most likely influenced not only by the extracellular matrix (ECM) and inflammatory mediators but also by the proximity of activated T lymphocytes. We recently reported that activated T cells induce mast cell degranulation with the release of TNF-alpha, and that this activation pathway is mediated by lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) binding.

OBJECTIVE

To determine how this contact between the two cell types can modulate mast cell behaviour in an inflammatory milieu by examining the adhesion of mast cells to endothelial cells and ECM ligands in an integrin-dependent manner.

METHODS

Human mast cells (HMC-1) were co-cultured with resting or activated T cells followed by testing their adhesion to endothelial cell and ECM ligands, stromal derived factor-1alpha (SDF-1alpha)-induced migration, and western blotting.

RESULTS

Co-culturing HMC-1 with activated, but not with resting T cells resulted in marked stimulation of mast cell adhesion to vascular cell adhesion molecule-1 and ICAM-1 in a very late antigen-4- and LFA-1-dependent fashion. In addition, activated T cells or T cell membranes promoted HMC-1 adhesion to fibronectin (FN) and laminin. This effect was accompanied by the phosphorylation of extracellular regulated kinase and p38, but not of c-Jun N-terminal kinase. Importantly, the adhesive property of mast cells depended exclusively on the direct contact between the two cell types, since neither supernatants from activated T cells nor separation of the two cell populations with a porous membrane affected mast cell adhesion to FN. Furthermore, similar results were obtained when mast cells were incubated with purified membranes from activated T cells. These results suggest that, in addition to stimulating mast cell degranulation, the proximity of activated T lymphocytes to mast cells can mediate the adhesion of mast cell precursors to the endothelial ligands and ECM. Activated T cells also stimulated SDF-1alpha-induced mast cell migration.

CONCLUSION

This symbiotic relationship between the two types of immune cells may serve to direct mast cells to specific sites of inflammation where their effector functions are required.

Platelet-activating factor receptor develops airway hyperresponsiveness independently of airway inflammation in a murine asthma model

Lipid mediators play an important role in modulating inflammatory responses. Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with eosinophil chemotactic activity in vitro and in vivo. We show in this study that mice deficient in PAF receptor exhibited significantly reduced airway hyperresponsiveness to muscarinic cholinergic stimulation in an asthma model. However, PAF receptor-deficient mice developed an eosinophilic inflammatory response at a comparable level to that of wild-type mice. These results indicate an important role for PAF receptor, downstream of the eosinophilic inflammatory cascade, in regulating airway responsiveness after sensitization and aeroallergen challenge.

Staging the Initiation of Autoantibody-Induced Arthritis: A Critical Role for Immune Complexes

In the K/BxN mouse model of arthritis, autoantibodies against glucose-6-phosphate isomerase cause joint-specific inflammation and destruction. We have shown using micro-positron emission tomography that these glucose-6-phosphate isomerase-specific autoantibodies rapidly localize to distal joints of mice. In this study we used micro-positron emission tomography to delineate the stages involved in the development of arthritis. Localization of Abs to the joints depended upon mast cells, neutrophils, and FcRs, but not on C5. Surprisingly, anti-type II collagen Abs alone did not accumulate in the distal joints, but could be induced to do so by coinjection of irrelevant preformed immune complexes. Control Abs localized to the joint in a similar manner. Thus, immune complexes are essential initiators of arthritis by sequential activation of neutrophils and mast cells to allow Abs access to the joints, where they must bind a target Ag to initiate inflammation. Our findings support a four-stage model for the development of arthritis and identify checkpoints where the disease is reversible.

Ultrastructure of goblet-cell metaplasia from Clara cell in the allergic asthmatic airway inflammation in a mouse model of asthma in vivo

Mucus overproduction from goblet cells, a characteristic feature of the allergic asthmatic inflammation induced by ovalbumin (OVA) in mice, was examined morphologically. In OVA-untreated (normal) mice, there were no goblet cells in intrapulmonary bronchus and bronchiole. However, goblet cells with or without hyperplasia in the mucosa of inflamed bronchus-bronchiole were recognized in the allergic asthmatic mice. The non-ciliated epithelium containing electron lucent granules (mucus) showed many similarities to Clara cells, which have characteristic secretory granules and many mitochondria, except for the less-developed smooth endoplasmic reticulum seen in normal mice. Ciliated Clara cells with or without mucus were rarely recognized. In addition, mucus was found in neither ciliated nor basal epithelium. The present study suggests that goblet-cell metaplasia in the bronchus and bronchiole of inflamed mucosa may be derived, at least in part, from Clara cells.

The chymase, mouse mast cell protease 4, constitutes the major chymotrypsin-like activity in peritoneum and ear tissue. A role for mouse mast cell protease 4 in thrombin regulation and fibronectin turnover

To gain insight into the biological role of mast cell chymase we have generated a mouse strain with a targeted deletion in the gene for mast cell protease 4 (mMCP-4), the mouse chymase that has the closest relationship to the human chymase in terms of tissue localization and functional properties. The inactivation of mMCP-4 did not affect the storage of other mast cell proteases and did not affect the number of mast cells or the mast cell morphology. However, mMCP-4 inactivation resulted in complete loss of chymotryptic activity in the peritoneum and in ear tissue, indicating that mMCP-4 is the main source of stored chymotrypsin-like protease activity at these sites. The mMCP-4 null cells showed markedly impaired ability to perform inactivating cleavages of thrombin, indicating a role for mMCP-4 in regulating the extravascular coagulation system. Further, a role for mMCP-4 in connective tissue remodeling was suggested by the inability of mMCP-4 null peritoneal cells to process endogenous fibronectin.

Role of immunoglobulin E and mast cells in murine models of asthma

Immunoglobulin E (IgE) and mast cells are believed to play important roles in allergic inflammation. However, their contributions to the pathogenesis of human asthma have not been clearly established. Significant progress has been made recently in our understanding of airway inflammation and airway hyperresponsiveness through studies of murine models of asthma and genetically engineered mice. Some of the studies have provided significant insights into the role of IgE and mast cells in the allergic airway response. In these models mice are immunized systemically with soluble protein antigens and then receive an antigen challenge through the airways. Bronchoalveolar lavage fluid from mice with allergic airway inflammation contains significant amounts of IgE. The IgE can capture the antigen presented to the airways and the immune complexes so formed can augment allergic airway response in a high-affinity IgE receptor (FcepsilonRI)-dependent manner. Previously, there were conflicting reports regarding the role of mast cells in murine models of asthma, based on studies of mast cell-deficient mice. More recent studies have suggested that the extent to which mast cells contribute to murine models of asthma depends on the experimental conditions employed to generate the airway response. This conclusion was further supported by studies using FcepsilonRI-deficient mice. Therefore, IgE-dependent activation of mast cells plays an important role in the development of allergic airway inflammation and airway hyperresponsiveness in mice under specific conditions. The murine models used should be of value for testing inhibitors of IgE or mast cells for the development of therapeutic agents for human asthma.

Less sensitivity for late airway inflammation in males than females in BALB/c mice

Several studies have investigated allergic airway inflammation, a T helper 2 (Th2)-type immune response, using a mouse model of asthma. At present, however, no reports have described sex differences in the sensitivity of late airway inflammation (LAI). The LAI induced by ovalbumin in adult BALB/c mice was compared in males and females or sham-operated males and castrated males. The males showed less severe bronchial-bronchiolar inflammation with infiltration of eosinophils and lymphocytes and lower content of such cells in bronchoalveolar fluid than the females. Moreover, interleukin-4 (IL-4) mRNA expression levels in splenic cells were lower in the males than in the females. Castrated males performed like the females. Moreover, when compared with the sham-operated males, the castrated males showed lower testosterone levels in the blood. The present results suggest that less sensitivity for LAI in the males may be because of the decreased Th2 cell responses compared with the females. Moreover the testosterone, at least in part, may be responsible for the decreased Th2 cell responses in males in vivo.

Elicitation of the allergic reaction in beta-lactoglobulin-sensitized Balb/c mice: biochemical and clinical manifestations differ according to the structure of the allergen used for challenge

BACKGROUND

Mouse models of allergy are used to study the mechanisms of induction and perpetuation of bronchopulmonary hyper-reactivity (BHR) as related to eosinophils and specific IgE.

OBJECTIVE

Our aim was to adapt the current model for the study of bovine beta-lactoglobulin (BLG), a major cow's milk allergen, and to further analyse the mechanisms of the acute and late allergic reaction.

METHODS

Female Balb/c mice were sensitized intraperitoneally with BLG and the influence of the adjuvant and of the BLG dose on the IgE response was analysed, IgE and IgG1 epitopes being characterized. Once optimized, this model was applied to the study of the active phase of allergy in the respiratory tract after a single airway challenge using native or denatured BLG, which contains only linear epitopes.

RESULTS

An immediate allergic reaction was characterized by the rapid release of histamine into the bronchoalveolar lavage fluids. Prostaglandin (PG)D2 was only present when the standard histamine-releasing agent compound 48/80 or denatured BLG were used as triggers, whereas native BLG induced leukotriene release. Twenty-four hours after challenge, BHR, eosinophil influx, IL-4 and IL-5 production, plasma exudation and mucus production were very much increased, differently depending on the allergen structure, and indicated the occurrence of the late allergic reaction. Our results show that the murine model can be used to study the mechanisms of allergy to clinically relevant antigens, such as those contained in cow's milk. The acute allergic reaction, which depends on the structural feature of the allergen, is composed of two distinct pathways characterized by peptido-leukotrienes or PGD2 production, which may result from distinct activation intensities of mast cells, leading to distinct late reactions.

CONCLUSION

This study thus demonstrates a clear link between the structural feature of a protein, and the physiopathology of the experimental asthmatic reaction.

Allergen-independent maternal transmission of asthma susceptibility

Maternal asthma is a risk factor for development of asthma in children, but mechanisms remain unclear. Offspring of asthmatic mother mice (sensitized and repeatedly exposed to OVA Ag) showed airway hyperresponsiveness and allergic pulmonary inflammation after an intentionally suboptimal OVA sensitization and exposure protocol that had little effect on normal offspring. Similar results were obtained when offspring of OVA-allergic mothers were exposed to an unrelated allergen, casein, indicating that the maternal effect is allergen independent and not transferred by OVA-specific Abs. Premating treatment with neutralizing anti-IL-4 Ab or reduction of maternal allergen exposure abrogated the maternal effect, showing a critical mechanistic role for IL-4 and suggesting an additional benefit of allergen avoidance.

Regulation of mast-cell and basophil function and survival by IgE

Mast cells and basophils are important effector cells in T helper 2 (T(H)2)-cell-dependent, immunoglobulin-E-associated allergic disorders and immune responses to parasites. The crosslinking of IgE that is bound to the high-affinity receptor Fc epsilon RI with multivalent antigen results in the aggregation of Fc epsilon RI and the secretion of products that can have effector, immunoregulatory or autocrine effects. This response can be enhanced markedly in cells that have been exposed to high levels of IgE, which results in the increased surface expression of Fc epsilon RI. Moreover, recent work indicates that monomeric IgE (in the absence of crosslinking) can render mast cells resistant to apoptosis induced by growth-factor deprivation in vitro and, under certain circumstances, can induce the release of cytokines. So, the binding of IgE to Fc epsilon RI might influence mast-cell and basophil survival directly or indirectly, and can also regulate cellular function.

IgE-dependent mast cell activation potentiates airway responses in murine asthma models

We have studied murine models of asthma using FcepsilonRIalpha-chain-deficient (FcepsilonRIalpha(-/-)) mice to investigate the role of IgE-dependent mast cell activation in these models. When mice were either 1) immunized once with OVA in alum i.p. and then challenged with OVA intranasally, or 2) repeatedly immunized with OVA in the absence of adjuvant and subsequently challenged with nebulized OVA, FcepsilonRalpha(-/-) mice had significantly fewer eosinophils and lower IL-4 levels in their bronchoalveolar lavage fluid compared with wild-type mice. When mice were given anti-IL-5 antibody before OVA challenge in protocol 1, eosinophilic infiltration into the airways was significantly suppressed in both genotypes, but only FcepsilonRIalpha(-/-) mice showed significantly reduced airway hyperresponsiveness (AHR). In addition, when mice immunized and challenged with OVA also received a late OVA provocation at a higher concentration and were then exposed to methacholine, only wild-type mice developed a substantial increase in AHR. Since FcepsilonRI is expressed mainly on mast cells in mouse airways, we conclude that IgE-dependent activation of this cell type plays an important role in the development of allergic airway inflammation and AHR in mice. The models used may be of value for testing inhibitors of IgE or mast cells for development of therapeutic agents for human asthma.

Products from human mast cell line cells enhance the production of interferon-gamma by CD8+ and CD4+ T cells

In patients with allergic asthma, T-cell cytokines are implicated in the regulation of the local inflammation in the airways. The ability of sensitized mast cells to release mediators and cytokines early upon allergen stimulation makes them important candidates for local immunoregulation. We have studied the effects of human mast cells on T cells with the use of the human mast cell line HMC-1. We showed that activated human mast cells or their soluble products induced and enhanced the interferon-gamma (IFN-gamma) production by T cells up to about 60-fold. The production of interleukin (IL)-4 was hardly affected and that of IL-5 was slightly enhanced. The enhancement of IFN-gamma production was induced both in polyclonal CD4+ and CD8+ T cells and in CD4+ and CD8+ T-cell clones. Further characterization of the factors involved demonstrated a molecular mass above 30 000. Our results implicate that by this mechanism mast cells may account for a negative feedback system locally down-regulating allergen-induced T helper 2 responses via IFN-gamma production by the T cells.

Interleukin-5 and eosinophils as therapeutic targets for asthma

Extensive clinical investigations have implicated eosinophils in the pathogenesis of asthma. In a recent clinical trial, humanized monoclonal antibody to interleukin (IL)-5 significantly limited eosinophil migration to the lung. However, treatment did not affect the development of the late-phase response or airways hyperresponsiveness in experimental asthma. Although IL-5 is a key regulator of eosinophilia and attenuation of its actions without signs of clinical improvement raises questions about the contribution of these cells to disease, further studies are warranted to define the effects of anti-IL-5 in the processes that lead to chronic asthma. Furthermore, eosinophil accumulation into allergic tissues should not be viewed as a process that is exclusively regulated by IL-5 but one in which IL-5 greatly contributes. Indeed, data on anti-IL-5 treatments (human and animal models) are confounded by the failure of this approach to completely resolve tissue eosinophilia and the belief that IL-5 alone is the critical molecular switch for eosinophil development and migration. The contribution of these IL-5-independent pathways should be considered when assessing the role of eosinophils in disease processes.

Systemic administration of interferon-gamma-expressing plasmid reduces late allergic bronchitis in a mouse model of asthma

Asthma might be caused by a helper T(Th)2 immune response. We hypothesized that the systemic administration of the Th1 cytokines may reduce the Th2 type late asthmatic response (LAR). We examined the effect of the intraperitoneal injection of interferon(IFN)-gamma-expressing plasmid, a Th1 cytokine, or interleukin(IL)-4-expressing plasmid, a Th2 cytokine, at the time of sensitization on a mouse model of asthma induced by ovalbumin in BALB/c mice. We demonstrated that the IFN-gamma-expressing plasmid reduced the LAR, whereas the IL-4-expressing plasmid enhanced the LAR as compared with the saline or plasmid-only treated group. The present study suggests that the systemic administration of IFN-gamma-expressing plasmid may have a modulating ability of Th1/Th2 balance to down-regulate Th2 response by a mutual inhibitory mechanism between Th1 and Th2 cells, leading to the reduction of the LAR.

Design, synthesis and pharmacological evaluation of novel pyrazolo[3,4-b]thieno[2,3-d]pyridine acid derivatives: a new class of anti-inflammatory and anti-platelet agents

A series of pyrazolo[3,4-b]thieno[2,3-d]pyridine alkanoic acid derivatives has been synthesized and evaluated as thromboxane synthetase inhibitors and leukotriene D(4) receptor antagonists. The glutaric acid derivative LASSBio341 (6) was shown to be active in arachidonic acid-induced platelet aggregation (IC(50)=0.14 microM) and inhibition of the contraction of guinea pig tracheal strip induced with LTD(4) (IC(50) = 43.7 microM), displaying still in vivo anti-inflammatory profile.

Effects of wortmannin on airways inflammation induced by allergen in actively sensitised Brown Norway rats

We have investigated the effect of wortmannin, a potent and selective inhibitor of phosphatidylinositol-3-kinase, on the immediate-type allergic response and the late phase pulmonary inflammation induced by allergen challenge in the ovalbumin-sensitised Brown Norway rat. Intratracheal (i.t.) instillation of ovalbumin induced dose-related bronchoconstrictor responses. Administration of wortmannin (1, 10 or 100 microg kg(-1) i.t., 1 h prior to challenge) induced a marked and dose-dependent inhibition of ovalbumin-induced bronchospasm (ED(50) ca. 5 microg kg(-1) i.t.). At similar doses, wortmannin also suppressed the bronchoconstrictor responses to 5-hydroxytryptamine and methacholine but the degree of blockade of these spasmogens (1.4-1.9-fold) was less than that of ovalbumin (>20-fold). Wortmannin, given intratracheally 1 h prior to allergen challenge, also suppressed the increases in bronchoalveolar lavage fluid leukocyte numbers and eosinophil peroxidase activity measured 24 h post challenge. However, relatively high doses were necessary (ED(50) ca. 100 microg kg(-1) i.t.). The potency of wortmannin was increased when dosed 1 h prior to and 24 h after allergen challenge and the readout was 48 h after challenge (ED(50) 3-5 microg kg(-1) i.t.). Thus, wortmannin is a potent inhibitor of the bronchoconstrictor response induced by allergen in the airways of actively sensitised Brown Norway rats. Inhibition of phosphatidylinositol-3-kinase, an obligatory step in mast cell activation in response to allergen, is the presumed mechanism of action. The fact that similar doses of wortmannin do not suppress the late response to allergen suggests a minimal role for the mast cell in generating the late response to allergen in this model. The striking increase in potency to inhibit the late response when dosed 1 h prior to and 24 h after allergen challenge with the readout taken at 48 h may represent an effect of wortmannin to suppress the migration of leukocytes.