Mediator Release Activity Research Articles

Glutathione-S-transferase: a minor allergen in birch pollen due to limited release from hydrated pollen.

BackgroundRecently, a protein homologous to glutathione-S-transferases (GST) was detected in prominent amounts in birch pollen by proteomic profiling. As members of the GST family are relevant allergens in mites, cockroach and fungi we investigated the allergenic relevance of GST from birch (bGST).MethodologybGST was expressed in Escherichia coli, purified and characterized by mass spectrometry. Sera from 217 birch pollen-allergic patients were tested for IgE-reactivity to bGST by ELISA. The mediator-releasing activity of bGST was analysed with IgE-loaded rat basophil leukaemia cells (RBL) expressing human FcεRI. BALB/c mice were immunized with bGST or Bet v 1. Antibody and T cell responses to either protein were assessed. IgE-cross-reactivity between bGST with GST from house dust mite, Der p 8, was studied with murine and human sera in ELISA. The release kinetics of bGST and Bet v 1 from birch pollen were assessed in water, simulated lung fluid, 0.9% NaCl and PBS. Eluted proteins were quantified by ELISA and analysed by immunoblotting.Principle findingsOnly 13% of 217 birch pollen-allergic patients showed IgE-reactivity to bGST. In RBL assays bGST induced mediator release. Immunization of mice with bGST induced specific IgE and a Th2-dominated cellular immune response comparably to immunization with Bet v 1. bGST did not cross-react with Der p 8. In contrast to Bet v 1, only low amounts of bGST were released from pollen grains upon incubation in water and the different physiological solutions.Conclusion/SignificanceAlthough bGST is abundant in birch pollen, immunogenic in mice and able to induce mediator release from effector cells passively loaded with specific IgE, it is a minor allergen for birch pollen-allergic patients. We refer this discrepancy to its limited release from hydrated pollen. Hence, bGST is an example demonstrating that allergenicity depends mainly on rapid elution from airborne particles.

Natural Self-Assembly of Allergen-S-Layer Fusion Proteins Is No Prerequisite for Reduced Allergenicity and T Cell Stimulatory Capacity

Background: Recombinant allergen-S-layer fusion proteins display a strongly reduced IgE-binding activity and promote the induction of allergen-specific Th0/1 cells and regulatory T cells. Such fusion proteins show a natural capacity to self-assemble into mono- or double-layer sheets reaching particle-like dimensions of 0.5–2 μm. We were interested in finding out whether self-assembly was crucial for the immunological characteristics of allergen-S-layer fusion proteins. Methods: The IgE-binding and mediator-releasing capacities of nonassembled and self-assembled rSbpA-Bet v 1, consisting of the major birch pollen allergen Bet v 1 and the S-layer protein SbpA, were compared in inhibition ELISA and basophil activation assays using sera from patients allergic to birch pollen. T cell stimulation was evaluated using Bet v 1-specific T cell clones reactive to distinct epitopes of Bet v 1. Autologous B lymphocytes, monocytes and monocyte-derived dendritic cells were employed to evaluate potential differences in uptake and processing by different antigen-presenting cells. Results: Both rSbpA-Bet v 1 variants showed significantly less IgE-binding and mediator-releasing activity than Bet v 1. However, self-assembly further minimized the reduced allergenicity of nonassembled rSbpA-Bet v 1. Both rSbpA-Bet v 1 variants induced comparable proliferation in Bet v 1-specific T cell clones. B cells inappropriately presented either variant of rSbpA-Bet v 1. Self-assembly amplified the T cell stimulatory capacity of monocytes and dendritic cells. Conclusions: The promising characteristics of allergen-S-layer fusion proteins regarding their potential use for allergy treatment do not depend on the formation of particle-like structures.

FROM COAL MINE DUST TO QUARTZ: Mechanisms of Pulmonary Pathogenicity

Exposure to coal mine dust or crystalline silica can result in the initiation and progression of interstitial lung disease. Pathogenesis is the consequence of damage to lung cells and resulting lung scarring associated with activation of fibrotic processes. This review presents the radiologic and histologic characteristics of simple and complicated coal workers' pneumoconiosis (CWP) as well as pathological indices of acute and chronic silicosis. This presentation also reviews the results of in vitro, animal, and human investigations that elucidate mechanisms involved in the development of these pneumoconioses. Results support the involvement of four basic mechanisms in the etiology of CWP and silicosis: 1. Direct cytotoxicity of coal dust or silica, resulting in lung cell damage, release of lipases and proteases, and eventual lung scarring. 2. Activation of oxidant production by pulmonary phagocytes, such as alveolar macrophages. When oxidant production exceeds antioxidant defenses, lipid peroxidation and protein nitrosation occur, resulting in tissue injury and consequent scarring. 3. Activation of mediator release from alveolar macrophages and alveolar epithelial cells. Chemokines recruit polymorphonuclear leukocytes and macrophages from the pulmonary capillaries into the air spaces. Once within the air spaces, these leukocytes are activated by proinflammatory cytokines to produce reactive species, which increase oxidant injury and lung scarring. 4. Secretion of growth factors from alveolar macrophages and alveolar epithelial cells. Release of such mediators stimulates fibroblast proliferation and induces fibrosis. In conclusion, results of in vitro and animal studies have provided the basis for proposing mechanisms that may lead to the initiation and progression of CWP and silicosis. Data obtained from exposed workers has lent support to these proposals. The mechanistic understanding obtained for the development of CWP and silicosis should be useful in elucidating the possible pathogenicity of other inhaled particles.

From Coal Mine Dust To Quartz: Mechanisms of Pulmonary Pathogenicity

Exposure to coal mine dust or crystalline silica can result in the initiation and progression of interstitial lung disease. Pathogenesis is the consequence of damage to lung cells and resulting lung scarring associated with activation of fibrotic processes. This review presents the radiologic and histologic characteristics of simple and complicated coal workers’ pneumoconiosis (CWP) as well as pathological indices of acute and chronic silicosis. This presentation also reviews the results of in vitro, animal, and human investigations that elucidate mechanisms involved in the development of these pneumoconioses. Results support the involvement of four basic mechanisms in the etiology of CWP and silicosis:1. Direct cytotoxicity of coal dust or silica, resulting in lung cell damage, release of lipases and proteases, and eventual lung scarring.2. Activation of oxidant production by pulmonary phagocytes, such as alveolar macrophages. When oxidant production exceeds antioxidant defenses, lipid peroxidation and protein nitrosation occur, resulting in tissue injury and consequent scarring.3. Activation of mediator release from alveolar macrophages and alveolar epithelial cells. Chemokines recruit polymorphonuclear leukocytes and macrophages from the pulmonary capillaries into the air spaces. Once within the air spaces, these leukocytes are activated by proinflammatory cytokines to produce reactive species, which increase oxidant injury and lung scarring.4. Secretion of growth factors from alveolar macrophages and alveolar epithelial cells. Release of such mediators stimulates fibroblast proliferation and induces fibrosis.In conclusion, results of in vitro and animal studies have provided the basis for proposing mechanisms that may lead to the initiation and progression of CWP and silicosis. Data obtained from exposed workers has lent support to these proposals. The mechanistic understanding obtained for the development of CWP and silicosis should be useful in elucidating the possible pathogenicity of other inhaled particles.

Inhibition by dietary tea polyphenols of chemical mediator release from rat peritoneal exudate cells.

Male Wistar rats were given purified diets containing safflower (SAF), perilla (PER), or palm (PAL) oils with or without 1% tea polyphenols (TP) for 3 weeks, and chemical mediator releasing activity from rat peritoneal exudate cells (PEC) was measured. Histamine releasing activity was not influenced by TP, while histamine release and intracellular histamine content were significantly increased in the PAL-fed group. On the contrary, leukotriene B4 (LTB4) release was significantly lower in rats fed PER than in those fed SAF and PAL, and TP significantly decreased the release in all fat groups. TP also significantly inhibited the release of LTB5, which was generated only in rats fed PER. TP significantly decreased the proportion of arachidonic acid (AA) in PEC in the SAF-fed group and that of eicosapentaenoic acid (EPA), the precursor of LTB5 in the PER-fed group, but did not influence that of AA in the PAL- and PER-fed group. These results suggest that ingestion of TP improves type I allergic symptom through the inhibition of LT release though the inhibition by TP could not be totally explained by the reduction of substrate fatty acid.

Effect of Nedocromil Sodium on Leukotrienes and Platelet-Activating Factor Release in Asthmatic Children

Airway inflammation is the most important component of asthma. Leukotrienes (LTB4, LTB-C4, LTB-D4, LTB-E4) and platelet-activating factor (PAF) play an important role in this inflammation. The pulmonary and peripheral leukocytes of asthmatics have a high potency of mediator-releasing activity after specific stimuli, and plasma levels of these are higher than in healthy controls. Nedocromil sodium (NES) is an inhaled anti-inflammatory drug and its inhibitory effect on inflammatory or epithelial cells has been demonstrated. The aim of this study was to determine whether inhaled NES affects plasma levels and release of PAF and leukotrienes from peripheral leukocytes of asthmatic children that were stimulated by house dust mites (as a specific allergen). Twenty-eight children (9 to 15 years of age) with atopic bronchial asthma were included in the study. They consisted of two age- and sex-matched groups (14 patients in the treatment group [group I]; 14 patients in the control group [group II]). Group I patients received inhaled NES (12 mg/d) for 12 weeks. Blood samples were drawn in the pre- and post-treatment periods. The measurements of plasma levels and secreted mediators levels after stimulation by house dust mites were performed with highpressure liquid chromatography (HPLC) and radioimmunoassay (RIA) methods. There were no significant differences between pretreatment plasma levels and secreted leukotrienes and PAF values of both groups. At the end of the study, significant decreases in plasma and in vitro stimulated LTB4, LT-C4, LT-D4, LT-E4, and PAF levels in group I were observed. There were no changes in the group II values. These in vivo and in vitro results suggest that NES is an effective anti-inflammatory drug for controlling childhood asthma by decreasing the high levels of inflammatory mediator release and immune cell activation.

Role of mast cells, basophils and their mediators in adverse reactions to general anesthetics and radiocontrast media.

General anesthetics and radiocontrast media (RCM) can cause anaphylactic or anaphylactoid reactions. These are usually underdiagnosed and underreported, but their incidence is apparently rising. Their pathogenesis is complex and not completely understood, but the release of vasoactive mediators from basophils and mast cells plays a central role. The recent development of in vitro techniques to study the release of preformed (histamine and tryptase) and de novo synthesized mediators (PGD2, LTC4, and PAF) from purified basophils and mast cells has made it possible to quantify the mediator-releasing activity of anesthetics such as muscle relaxants, general anesthetics, opioids, and benzodiazepines and RCM on human basophils and mast cells isolated from lung, skin and heart tissues. The majority of general anesthetics and RCM tested induced only the release of preformed mediators (histamine and tryptase), not of the de novo synthesized eicosanoids. There was wide variability in the response of basophils and mast cells from different donors to the same drug or RCM, presumably due to the releasability parameter. Hyperosmolality is probably not the only factor responsible for basophil and mast cell activation by RCM. The in vitro release of histamine induced by anesthetic drugs and RCM was correlated with the release of tryptase. Given the longer half-life of tryptase than histamine in plasma, measurements of plasma tryptase may become a useful diagnostic tool for identifying adverse reactions to anesthetics and RCM.

In vitro Interaction between Human Basophils and Polymorphonuclear Granulocytes Effect of Airborne Particulate Matter.

The effects of extracts of airborne particulate matter (APM) on morphology and mediator release from enriched basophils (HBC) and from purified neutrophils of pollen-allergic and nonallergic individuals were investigated. APM was collected on glass fiber filter sheets using high volume samplers HVS150. After preparing an aqueous extract, in which allergens are absent, followed by extraction of organic substances, the mediator-releasing activity of the APM extracts was studied under defined and physiological in vitro conditions. The results indicate that APM potentiates anti-IgE-induced histamine release (HR) and that this enhancement is significantly higher in HBC samples from pollen allergic donors than from nonallergic individuals. Electronmicroscopy of APM-exposed HBC reveals basophil degranulation in addition to strong activation of platelets and neutrophils, the latter sticking onto the surface of HBC and forming clusters with them. Incubation of purified PMN with APM prior to zymosan stimulation showed that these substances also enhance the release of LTB4, LTC4, PGE2 and IL-8. The results show that substances adsorbed to APM interfere with mediator cells of the allergic inflammation and exhibit 'priming' effects on them. Therefore, exposure of individuals to high concentrations of APM can provoke enhancement in symptoms of allergy and continuation of allergic inflammation.

Use of the Cutaneous Anaphylactoid Test to Detect Differences in Mast Cell Mediator-Releasing Activity among LHRH Peptides

The cutaneous anaphylactoid test was evaluated as a screen for assessing mast cell mediator-releasing (MCMR) activity of luteinizing hormone-releasing hormone (LHRH) peptides. As expected, LHRH and D-Trp6-LHRH, an agonist of LHRH, were nonreactive at concentrations of antagonist which induced pronounced skin lesions. Differences between LHRH and antagonists were obvious, but it was difficult to detect differences among antagonists using arithmetic means. However, when the geometric means of the highest positive dilution were calculated, the MCMR activities of the antagonists differed and these differences appeared to be related to the hydrophobicities of their N-termini. Thus, it appears that the cutaneous anaphylactoid test is an appropriate screen to assess the MCMR activity of LHRH peptides and should assist in the development of clinically useful inhibitory analogs of LHRH.