Histamine release from bronchoalveolar lavage cells from asthmatic subjects after allergen challenge and relationship to the late asthmatic response

Regulation of mast cell responses in health and disease

Mast cells are multifunctional cells that initiate not only IgE-dependent allergic diseases but also play a fundamental role in innate and adaptive immune responses to microbial infection. They are also thought to play a role in angiogenesis, tissue remodeling, wound healing, and tumor repression or growth. The broad scope of these physiologic and pathologic roles illustrates the flexible nature of mast cells, which is enabled in part by their phenotypic adaptability to different tissue microenvironments and their ability to generate and release a diverse array of bioactive mediators in response to multiple types of cell-surface and cytosolic receptors. There is increasing evidence from studies in cell cultures that release of these mediators can be selectively modulated depending on the types or groups of receptors activated. The intent of this review is to foster interest in the interplay among mast cell receptors to help understand the underlying mechanisms for each of the immunological and non-immunological functions attributed to mast cells. The second intent of this review is to assess the pathophysiologic roles of mast cells and their products in health and disease. Although mast cells have a sufficient repertoire of bioactive mediators to mount effective innate and adaptive defense mechanisms against invading microorganisms, these same mediators can adversely affect surrounding tissues in the host, resulting in autoimmune disease as well as allergic disorders.

A new chemical tool (C0036E08) supports the role of adenosine A(2B) receptors in mediating human mast cell activation

Asthma is a chronic inflammatory disease of the airways that involves many cell types, amongst which mast cells are known to be important. Adenosine, a potent bronchoconstricting agent, exerts its ability to modulate adenosine receptors of mast cells thereby potentiating derived mediator release, histamine being one of the first mediators to be released. The heterogeneity of sources of mast cells and the lack of highly potent ligands selective for the different adenosine receptor subtypes have been important hurdles in this area of research. In the present study we describe compound C0036E08, a novel ligand that has high affinity (pK(i) 8.46) for adenosine A(2B) receptors, being 9 times, 1412 times and 3090 times more selective for A(2B) receptors than for A(1), A(2A) and A(3) receptors, respectively. Compound C0036E08 showed antagonist activity at recombinant and native adenosine receptors, and it was able to fully block NECA-induced histamine release in freshly isolated mast cells from human bronchoalveolar fluid. C0036E08 has been shown to be a valuable tool for the identification of adenosine A(2B) receptors as the adenosine receptors responsible for the NECA-induced response in human mast cells. Considering the increasing interest of A(2B) receptors as a therapeutic target in asthma, this chemical tool might provide a base for the development of new anti-asthmatic drugs.

The impact of comorbid atopic disease on asthma: clinical expression and treatment

Clinically, asthma and allergic rhinitis involve separate regions of the respiratory tract while representing a common underlying inflammatory syndrome. Much evidence supports an epidemiologic association between the diseases, paranasal sinus involvement in both conditions, and parallel relationship in severity and treatment outcomes. Pathophysiologic mechanisms, including immunoglobulin E (IgE)- mediated inflammation, are also shared. Blocking IgE with the recombinant humanized monoclonal antibody omalizumab demonstrated clinical efficacy in patients with upper and lower airway diseases. IgE blockade, leukotriene modulation, and B-cell depletion therapy have all exhibited success in chronic inflammation, reinforcing and expanding the beneficial role of immunomodulation of global mediators.

Airway inflammation in asthma and its consequences: implications for treatment in children and adults

The development and wide availability of novel research techniques such as bronchoscopy and induced sputum have enhanced our understanding of the pathophysiology of asthma. The appreciation of the inflammatory nature of asthma and the remodeling associated with chronic disease have undoubtedly led to improved disease management and a better understanding of how anti-asthma drugs work. Although extensive data about inflammation and its sequelae in children are lacking, both chronic inflammation and airway remodeling are more than likely to be involved in the development and progression of asthma in this young population. Indeed, evidence suggests that airway restructuring occurs early. The implications for treatment in any differences of inflammation and remodeling between children and adults, then, are likely to be important. Although corticosteroids are considered as first-line anti-inflammatory treatment, especially in chronic asthma, for many patients neither inhaled nor oral corticosteroid therapy can control inflammation adequately. In children, neither the addition of long-acting beta(2)-agonist therapy nor doubling of the corticosteroid dose has produced the same benefits seen in adults. A clearer understanding of the pathophysiologic mechanisms of asthma in adults and pediatric patients should provide new insights into different asthma phenotypes. Therefore, the development and application of relatively simple and safe methods for assessing markers of inflammation and alterations in the airways are vital, especially for children.

Characterization of mast-cell tryptase-expressing peripheral blood cells as basophils

BACKGROUND

Mast-cell tryptase is a protease with proinflammatory activity, the expression of which by peripheral blood leukocytes (PBLs) has not been fully characterized.

OBJECTIVE

We examined tryptase expression in human PBLs to further characterize this tryptase-expressing cell population for lineage and disease association.

METHODS

PBLs were fixed, permeabilized, stained with antibodies to tryptase and a panel of mast cell- and basophil-specific markers, and analyzed by means of flow cytometry.

RESULTS

Tryptase expression was restricted to a population of cells that stained positive for IgE and negative for the panel of lineage markers (IgE(+), lin(-)). This IgE(+), lin(-) population did not stain for the mast-cell markers Kit or chymase but did stain for the basophil-specific granule proteins recognized by the 2D7 and BB1 mAbs. Per-cell tryptase expression demonstrated a greater than 100-fold range of expression among donors but did not correlate with disease status (asthma or mastocytosis), FEV(1), or serum tryptase concentration. Tryptase was released by purified basophils after anti-IgE activation.

CONCLUSIONS

The phenotype of tryptase-expressing PBLs and their lack of increase in patients with mastocytosis demonstrates that these cells are basophils. Per-cell basophil tryptase expression is highly variable between donors, with some donors expressing levels approaching those of mast cells. As such, anti-tryptase antibodies cannot be used to distinguish these 2 cell types from one another by means of flow cytometry. These results demonstrate that tryptase represents an additional mediator through which basophils may contribute to allergic inflammation.

Human eosinophils induce histamine release from antigen-activated rat peritoneal mast cells: a possible role for mast cells in late-phase allergic reactions

BACKGROUND

Mast cells and eosinophils are believed to interact during the late and the chronic stages of allergic inflammation.

OBJECTIVE

In this study we investigated whether eosinophils can cause activation and consequent histamine release of already challenged mast cells, a situation likely to take place during the allergic late-phase reaction.

METHODS

Rat peritoneal mast cells presensitized with IgE anti-dinitrophenol-human serum albumin and challenged by dinitrophenol-human serum albumin or compound 48/80 were incubated with either eosinophil sonicate or major basic protein (MBP). Eosinophils were purified from the peripheral (>98%) blood of mildly allergic patients. Heparin and pertussis toxin and different extracellular Ca(2+) concentrations were used to modulate mast cell reactivation by MBP. Histamine release was assessed as a marker of mast cell activation.

RESULTS

IgE-challenged mast cells were sensitive to reactivation induced by eosinophil sonicate and MBP. Reactivation was not cytotoxic for the mast cells. Mast cells previously challenged with compound 48/80 did not respond to subsequent MBP activation. Furthermore, heparin and pertussis toxin both inhibited mast cell reactivation induced by MBP. The ability of eosinophil sonicate and MBP to activate mast cells was not significantly affected at the different Ca(2+) concentrations.

CONCLUSIONS

In summary, we have shown a direct activating activity of eosinophils, partially due to MBP, toward IgE-challenged and immunologically desensitized mast cells. This suggests that in vivo mast cells can be reactivated during a late-phase reaction to release histamine by a non-IgE-dependent mechanism.

B-cell isotype control in atopy and asthma assessed with cDNA array technology

B-cell isotype switching and the production of IgE is regulated by a variety of gene products through different mechanisms. A better understanding of these processes has the potential to identify markers of disease and new therapeutic targets. The aim of the study was to investigate human B-cell isotype control and IgE production in atopy and asthma with cDNA array technology. Eighteen atopic asthmatic, eight atopic nonasthmatic, and fourteen healthy control subjects were included. Peripheral blood mononuclear cells were separated by gradient centrifugation, mRNA was purified, and the reverse-transcribed probes were hybridized to cDNA membranes. Group differences were assessed with the Mann-Whitney U-test. Twenty-three of seventy-eight tested IgE-related genes had significantly altered expression in atopy and asthma compared with that in the healthy subjects. The differentially expressed genes include surface molecules involved in T- and B-cell interaction and activation, cytokines, intracellular signaling products, and transcription factors. In conclusion, both atopic nonasthmatic and atopic asthmatic individuals had activated proinflammatory pathways, a minimal requirement for B-cell isotype switching, and a clear net pro-IgE cytokine climate.

The pathology of chronic asthma

Our understanding of the pathophysiology of asthma has undergone great advances in the past decade, particularly with the recognition of cytokines and the roles they may take in orchestrating the local immune response. With this information, it has been possible to target new therapeutic entities such as cytokine or chemokine receptors. Eosinophils and T lymphocytes have a special place in the inflammatory and structural alterations contributing to the asthmatic diathesis. It is possible that phenotype subsets of these cells exist and they hold the key to perpetuation of immunologic and physiologic abnormalities in asthma.

Influence of bronchial allergen challenge on histamine release by human basophils

BACKGROUND

Basophils can be primed by cytokines such as interleukin (IL) -3, IL-5 or granulocyte macrophage-colony stimulating factor (GM-CSF). It has been described that the concentrations of these cytokines are enhanced at sites of allergic inflammation as well as systemic in allergic asthma.

OBJECTIVE

To investigate the priming status of basophils as detected by thapsigargin-induced histamine release during bronchial allergen challenge.

METHODS

Ten subjects allergic to house dust mite were challenged via an aerosol delivery system. Spontaneous leucocyte histamine release as well as histamine release induced by various stimuli was measured in vitro at several time points. In addition, lung function parameters, serum IL-5 and blood eosinophil counts were evaluated.

RESULTS

We found no effect of bronchial allergen challenge upon spontaneous leucocyte histamine release, nor upon histamine release induced by anti-immunoglobulin (Ig) E, house dust mite extract, C5a, fMLP, IL-3, PMA+ thapsigargin or IL-3+ thapsigargin. However, the priming status of basophils as measured by thapsigargin-induced histamine release was enhanced at 24 h after bronchial allergen challenge. Analysis of the individual data showed a heterogeneous initial response (30 min, 6 h) followed by a predominant increase at 24 h after allergen challenge. This increase in the thapsigargin-induced histamine release correlated with the increase in serum IL-5 levels at 24 h after allergen challenge.

CONCLUSION

The priming status of human basophils as measured by thapsigargin-induced histamine release is enhanced 24 h after allergen challenge.

Sensory neuropeptides induce histamine release from bronchoalveolar lavage cells in both nonasthmatic coughers and cough variant asthmatics

BACKGROUND

Sensory neuropeptides have been suggested to play a role in the pathogenesis of a number of respiratory diseases including asthma and chronic non-productive cough.

OBJECTIVES

To investigate the action of sensory neuropeptides on airway mast cells obtained by bronchoalveolar lavage (BAL).

METHODS

BAL was performed on 23 nonasthmatic patients with cough (NAC), 11 patients with cough variant asthma (CVA) and 10 nonatopic controls. Washed lavage cells were stimulated (20 min, 37 degrees C) with calcitonin gene-related peptide (CGRP), neurokinin A (NKA) and substance P (25 and 50 micromol/L).

RESULTS

The neuropeptides tested induced histamine release in all groups studied. Only CGRP (50 micromol/L) induced significantly more histamine release from both NAC and CVA patients compared with control subjects (P = 0.038 and 0.045, respectively).

CONCLUSION

Regardless of aetiology, mast cells from patients with chronic cough appear to have an increased responsiveness to CGRP compared with controls. The results of the present study suggest that the role of CGRP in chronic cough should be further investigated.