Mast cells, mediators and asthma

Diagnosis of asthma - new theories

INTRODUCTION

Recent studies have shown a remarkably high frequency of poorly controlled asthma. Several reasons for this treatment failure have been discussed, however, the basic question of whether the diagnosis is always correct has not been considered. Follow-up studies have shown that in many patients asthma cannot be verified despite ongoing symptoms. Mechanisms other than bronchial obstruction may therefore be responsible. The current definition of asthma may also include symptoms that are related to mechanisms other than bronchial obstruction, the clinical hallmark of asthma.

AIM

Based on a review of the four cornerstones of asthma - inflammation, hyperresponsiveness, bronchial obstruction and symptoms - the aim was to present some new aspects and suggestions related to the diagnosis of adult non-allergic asthma.

CONCLUSION

Recent studies have indicated that "classic" asthma may sometimes be confused with asthma-like disorders such as airway sensory hyperreactivity, small airways disease, dysfunctional breathing, non-obstructive dyspnea, hyperventilation and vocal cord dysfunction. This confusion may be one explanation for the high proportion of misdiagnosis and treatment failure. The current diagnosis, focusing on bronchial obstruction, may be too "narrow". As there may be common mechanisms a broadening to include also non-obstructive disorders, forming an asthma syndrome, is suggested. Such broadening requires additional diagnostic steps, such as qualitative studies with analysis of reported symptoms, non-effort demanding methods for determining lung function, capsaicin test for revealing airway sensory hyperreactivity, careful evaluation of the therapeutic as well as diagnostic effect of corticosteroids and testing of suggested theories.

Role of mast cells in mucosal diseases: current concepts and strategies for treatment

Mast cells are well known for their role in type I hypersensitivity. However, their role in the immune system as well as their pathophysiological role in other diseases is underacknowledged. The role of mast cells in inflammatory bowel disease, allergic contact dermatitis and asthma is illustrated in this review. The contribution of mast cell activation in these diseases is controversial and two alternative means are proposed: activation via stress response pathways and immunoglobulin-free light chains. Activation of the mast cells leads to release of preformed mediators and to generation of other potent biological substances that have both physiological and pathophysiological effects. The role of these mediators in the aforementioned diseases is also outlined in this review. When the roles of mast cells are better understood, drugs specifically targeting mast cells may be developed to effectively treat a wide range of diseases.

Inhibitory effects of inhaled complex traditional Chinese medicine on early and late asthmatic responses induced by ovalbumin in sensitized guinea pigs

Background

Many formulae of traditional Chinese medicines (TCMs) have been used for antiasthma treatment dating back many centuries. There is evidence to suggest that TCMs are effective as a cure for this allergenic disease administered via gastric tubes in animal studies; however, their efficacy, safety and side effects as an asthmatic therapy are still unclear.

Methods

In this study, guinea pigs sensitized with ovalbumin (OVA) were used as an animal model for asthma challenge, and the sensitization of animals by bronchial reactivity to methacholine (Mch) and the IgE concentration in the serum after OVA challenge were estimated. Complex traditional Chinese herbs (CTCM) were administered to the animals by nebulization, and the leukocytes were evaluated from bronchoalveolar lavage fluid (BALF).

Results

The results showed that inhalation of CTCM could abolish the increased lung resistance (13-fold increase) induced by challenge with OVA in the early asthmatic response (EAR), reducing to as low as baseline (1-fold). Moreover, our results indicated higher IgE levels (range, 78-83 ng/ml) in the serum of sensitized guinea pigs than in the unsensitized controls (0.9 ± 0.256 ng/ml). In addition, increased total leukocytes and higher levels of eosinophils and neutrophils were seen 6 hours after challenge, and the increased inflammatory cells were reduced by treatment with CTCM inhalation. The interleukin-5 (IL-5) level in BALF was also reduced by CTCM.

Conclusion

Our findings indicate a novel method of administering traditional Chinese medicines for asthma treatment in an animal model that may be more effective than traditional methods.

Effects of Ding-Chuan-Tang on bronchoconstriction and airway leucocyte infiltration in sensitized guinea pigs

Ding-Chuan-Tang (DCT), a traditional Chinese medicine, has been used in treatment of the bronchial asthma for several centuries. However, the therapeutic mechanism of these Chinese medicine are still far from clear. To understand the mechanism of antiasthmatic property of DCT. A guinea pig model of allergic asthma was used to investigate the effects of DCT on ovalbumin-induced early and late asthmatic responses and airway inflammation, particularly the extent of eosinophil infiltration, and examine it direct beta2-adrenoceptor agonist activity in guinea-pig isolated trachea. We had used three different protocals in ovalbumin sensitized guinea pigs by administrating 10 g/kg of DCT extracts to sensitized guinea pigs 30 min before antigen challenge (group I), 5 hr after antigen challenge (group II) and 2.5 g/kg once daily from the day of sensitization to the day of challenge. Our result showed that administration of DCT singificantly inhibited the antigen induced immediate asthmatic responses (IAR) in group I and inhibited both IRA and late asthmatic responses (LAR) in actively sensitized guinea pig in group III. DCT caused concentration-dependent relaxations in strips of guinea pig trachea contracted with carbachol, however ICI-118551, a selective beta2-adrenoceptor antagonist, didn't significantly competitively inhibit the relaxations caused by DCT. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that DCT significantly inhibited the increase in percent of eosinophils in the airway after antigen challenge in three group. Histopathologic examination showed DCT suppressed the eosinophil infiltration into lung tissue. These results suggest that the antiasthmatic effect of DCT is mainly due to its bronchodilatation effect and its ability to inhibit the eosinophil into the airway and there is prophylactic effect of DCT on allergen-induced airway inflammation.

The role of the mast cell in asthma: induction of airway hyperresponsiveness by interaction with smooth muscle?

In a recent study, the difference between asthma and eosinophilic bronchitis (a condition characterized by cough but not airway hyperresponsiveness or airflow obstruction) was infiltration of airway smooth muscle (ASM) by mast cells. Mast cells produce a variety of lipid mediators, chemokines, cytokines, and enzymes that may interact with ASM cells to cause hyperreactivity to constrictive stimuli and proliferation, and activated ASM can produce stem cell factor and other chemokines, cytokines, and growth factors that may act in recruitment, differentiation, and retention of mast cells. Mast cell infiltration of the airways in asthma is T-cell-dependent, and TH2 cytokines from T cells and other sources act in mast cell expansion from circulating and tissue precursors. The recent data on interactions of mast cells and ASM suggest that this could be an important contributor to airway hyperresponsiveness in asthma. Why this occurs in asthma and how it is sustained remain to be established.

TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], an anti-asthmatic agent, inhibits leukotriene production induced by IgE receptor stimulation in RBL-2H3 cells

A novel quinolinone derivative, TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], has been shown to inhibit antigen-induced asthmatic responses including the early-phase bronchoconstriction in actively sensitized guinea pigs. Here we characterized the action mechanisms of TA-270 in cellular level in vitro. In RBL-2H3 mast cells sensitized with dinitrophenol (DNP)-specific IgE, the antigen exhibited several mast cell functions, including hexosaminidase release as a marker of degranulation, production of tumor necrosis factor-alpha, and production of immunologically detective leukotrienes. These antigen-induced actions were associated with the activation of several early signaling events, including inositol phosphate production reflecting phospholipase C activation and extracellular signal-regulated kinase activation. When the cells were treated with TA-270, the antigen-induced leukotriene production was almost completely suppressed, but other antigen-induced actions listed above were hardly affected. This drug also failed to affect the antigen-induced phospholipase A2 activation as evaluated by the total release of arachidonic acid and its metabolites from the cells prelabeled with radioactive arachidonic acid. However, TA-270 clearly changed the arachidonic acid metabolic pathway. It suppressed the accumulation of 5-lipoxygenase products, including leukotrienes, but hardly affected the accumulation of cyclooxygenase products. The inhibitory action of TA-270 on leukotriene production was also observed in human neutrophils and eosinophils. We conclude that TA-270 inhibits 5-lipoxygenase activity and, thereby, suppresses the antigen-induced leukotriene production.

Effects of xiao-qing-long-tang (XQLT) on bronchoconstriction and airway eosinophil infiltration in ovalbumin-sensitized guinea pigs: in vivo and in vitro studies

BACKGROUND

Xiao-qing-long-tang (XQLT sho-seiru-to), a traditional Chinese medicine, has been used to treat patients with bronchial asthma in Oriental countries for several centuries. However, the therapeutic mechanisms of this Chinese medicine remain a matter of considerable debate. Therefore, a series of experiments using ovalbumin-sensitized guinea pigs was performed to elucidate the possible antiasthmatic effect of XQLT.

METHODS

The effect of XQLT on ovalbumin-induced airway inflammation in a guinea pig model of allergic asthma was examined, and early and late asthmatic responses were measured in terms of airway resistance and extent of eosinophil infiltration. Furthermore, the bronchorelaxing effect of XQLT was measured in isolated guinea pig trachea.

RESULTS

XQLT significantly inhibited the antigen-induced immediate asthmatic response (IAR) and late asthmatic response (LAR) in actively sensitized guinea pigs. Cumulative administration of XQLT caused concentration-dependent relaxation of the carbachol-precontracted guinea pig trachea. The bronchorelaxing effect of XQLT was reversed by ICI-118551, a selective beta2-adrenoceptor antagonist. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that XQLT significantly suppressed the increase in eosinophils (24 h after antigen challenge) in the airway. In addition, XQLT significantly attenuated the increase in eosinophils at 1, 6, 24, 48, and 72 h after antigen challenge when it was administered once daily from the day of sensitization to the day of challenge. Histopathologic examination results showed that XQLT suppressed eosinophil infiltration into lung tissue.

CONCLUSIONS

These results demonstrate that the antiasthmatic effects of XQLT appear to be partly mediated by stimulation of beta2-adrenoceptors, leading to bronchorelaxation, and that XQLT inhibits the infiltration of eosinophils into the airway. Thus, XQLT may be useful for the prevention or treatment of asthma.

The effects of Ma-Xing-Gan-Shi-Tang on respiratory resistance and airway leukocyte infiltration in asthmatic guinea pigs

Ma-Xing-Gan-Shi-Tang (MXGST), a traditional Chinese medicine, has been used in treatment of the bronchial asthma for several centuries. However, the therapeutic mechanisms of this Chinese medicine are still far from clear. To understand the mechanism of anti-asthmatic property of MXGST, a guinea pig model of allergic asthma was used to investigate the effects of MXGST on Dermatophagoides pteronyssinus-induced early and late asthmatic responses and airway inflammation, and examine direct beta2-adrenoceptor agonist activity in guinea-pig isolated trachea. Administration of MXGST (10 g/kg) extracts significantly inhibited the antigen induced immediate asthmatic responses (IAR) in actively sensitized guinea pig. MXGST caused concentration-dependent relaxation in strips of guinea pig trachea contracted with carbachol, and ICI-118551, a selective beta2-adrenoceptor antagonist, significantly inhibit the relaxation caused by MXGST. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that MXGST significantly inhibited the increase in neutrophil in the airway at 1, 6 and 24 hr after antigen challenge. Histopathologic examination results showed that MXGST suppressed the neutrophil infiltration into lung tissue. In conclusion, we suggest that the anti-asthmatic effects of MXGST are mainly due to its stimulation of beta2-adrenoceptors on bronchial smooth muscle and its anti-inflammatory ability to inhibit the neutrophil into the airway. The precise mechanism of action of MXGST in asthma remains to be elucidated.

Inhibitory effect of a novel quinolinone derivative, TA-270, on asthmatic inflammatory responses in sensitized guinea pigs

TA-270 (4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)- quinolinone), a novel quinolinone derivative, was designed as an antioxidant to scavenge reactive oxygen species. Here, we investigated the effects of TA-270, in comparison with several antiasthmatic drugs, on asthmatic responses as induced by ovalbumin in sensitized guinea pigs. When orally administered 1 h before and 3 h after the antigen challenge, TA-270 at 10 mg/kg and higher doses significantly inhibited both immediate and late responses in airway resistance induced by the antigen. The inhibitory effects were comparable to or superior, at least under the present experimental conditions, to those of several clinically used antiasthmatic drugs. Furthermore, TA-270, in a dose-dependent manner, reduced accumulation of pulmonary inflammatory cells, especially eosinophils, and significantly reversed the airway hyperresponsiveness to acetylcholine 24 h after the antigen challenge. These results suggest that TA-270 may be of therapeutic use for bronchial asthma.

Effect of San-Ao-Tang on immediate and late airway response and leukocyte infiltration in asthmatic guinea pigs

San-Ao-Tang (SAT), a traditional Chinese medicines, has been used to treat patients with the bronchial asthma for several centuries. However, the therapeutic mechanisms of this Chinese medicine are still far from clear. To understand the mechanism of antiasthmatic property of SAT, a guinea pig model of allergic asthma was used to investigate the effects of SAT on Dermatophagoides pteronyssinus-induced immediate and late asthmatic responses and airway inflammation. Our results showed that administration of SAT (10 g/kg) extracts significantly inhibited the antigen induced immediate asthmatic responses (IAR) in actively sensitized guinea pig. Examination of bronchoalveolar lavage fluid (BALF) revealed that SAT significantly inhibited the increase in neutrophil in the airway at 1, 2, 4, 6, 8 hr after antigen challenge. Histopathologic examination showed SAT suppressed the neutrophil infiltration into lung tissue. These results suggest that the antiasthmatic effect of SAT be mainly due to its bronchodilator effect and its ability to inhibit the neutrophil into the airway. The precise mechanism of action of SAT in asthma remains to be elucidated.

The role of mast cells in disc herniation inflammation

STUDY DESIGN

A study of herniated lumbar disc tissue samples and control disc material to determine the presence of mast cells in disc herniations.

OBJECTIVES

To analyze whether mast cells have any involvement in disc herniation pathophysiology and lumbar pain, because mast cells may have an important role in acute and chronic inflammatory responses.

SUMMARY OF BACKGROUND DATA

Studies of inflammatory cells, biochemical mediators of inflammation, and tissue degrading enzymes have suggested that these factors may be involved--and perhaps play an important role--in the pathophysiology of lumbar pain and radiculopathy. Mast cells are known to play an important role in acute and chronic inflammatory responses. It was therefore of interest to clarify their possible role in intervertebral disc herniation inflammation.

METHODS

Fifty herniated lumbar discs from 50 patients who had undergone disc surgery and three normal control discs were obtained. Sections from every disc then were examined histologically and immunocytochemically for mast cells by using monoclonal antibodies to either of two types of specific proteases of mast cells, tryptase and chymase.

RESULTS

By none of the methods could any mast cells be observed in any of the control disc samples. With toluidine blue staining, mast cells were observed in 9 of 50 (18%) of discs. Mast cells immunoreactive to either tryptase or chymase were observed in 10 of 50 disc samples (20%) and immunoreactive for tryptase and chymase simultaneously in 4 of 50 disc samples (8%). However, the majority of the samples studied (80%) demonstrated immunoreactivity to neither tryptase nor chymase. Among the samples studied were five disc protrusions that totally lacked mast cells.

CONCLUSIONS

A minority of disc herniations exhibited mast cells, as verified by toluidine blue staining and immunocytochemistry. The results may suggest a role of mast cells in intervertebral disc herniation inflammation, but only in a subset of these cases. Massive infiltration by mast cells never was observed.

The effect of cetirizine and loratadine on codeine-induced histamine release in human skin in vivo assessed by cutaneous microdialysis

OBJECTIVE AND DESIGN

To determine whether or not cetirizine and loratadine inhibit codeine- induced histamine release in human skin in vivo, we conducted a placebo-controlled double-blind trial in which histamine release was assessed by dermal microdialysis.

SUBJECTS

A group of ten normal volunteers were studied, each subject visiting the laboratory on three occasions with intervals of at least 2 weeks between visits.

TREATMENT

Cetirizine, loratadine (both 10 mg) or placebo was given orally 4 h before provocation of weal and flare responses in the skin by intradermal injection of 25 microliters of 3 or 10 mg/ml codeine 1 mm from the centre of individual 216 microns diameter microdialysis fibres inserted in the dermis.

METHODS

Dialysate was collected at 2 min intervals for 4 min before and 20 min after codeine injection and histamine assayed spectrofluorometrically. Weal and flare responses to codeine were assessed in the opposite arm.

RESULTS

Histamine concentrations in the microdialysis fibre outflow with 3 and 10 mg/ml codeine were maximal at 2-4 min when 910 +/- 156 and 1194 +/- 304 nM respectively were found in the placebo group. Cetirizine and loratadine did not modify either the kinetics or total histamine release while significantly (p < 0.01) inhibiting weal and flare responses.

CONCLUSIONS

Neither cetirizine nor loratadine inhibited codeine-induced histamine release or modified the time course of its release in human skin in vivo when given in clinically used doses which are sufficient to significantly reduce weal and flare responses.

GABA-mediated inhibition of the anaphylactic response in the guinea-pig trachea

1. In sensitized guinea-pigs, the effects of gamma-aminobutyric acid (GABA) and GABAmimetic drugs have been investigated on tracheal segments contracted by cumulative application of an allergen (ovoalbumin, OA) and on serosal mast cells. The same drugs have also been tested on activation of alveolar macrophages isolated from unsensitized guinea-pigs. 2. Superfusion with GABA (1-1000 microM) reduced the contraction intensity of tracheal strips. The effect of GABA (100 microM) was not affected by the carrier blockers, nipecotic acid and beta-alanine (300 microM each). It was mimicked by the GABAB agonist (-)-baclofen (100 microM) but not 3-aminopropanephosphinic acid (100 microM, 3-APA). The GABAA agonist, isoguvacine (100 microM) did not exert any effect. GABA (10 microM)-induced inhibition of tracheal contractions was reduced by the GABAB antagonist, 2-hydroxysaclofen (100 microM, 2-HS), but not by the GABAA antagonist, bicuculline (30 microM). 3. The reduction in contraction intensity induced by GABA (100 microM) was prevented by a 40 min preincubation of tracheal strips with capsaicin (10 microM), but not tetrodotoxin (TTX, 0.3 microM). The effect of GABA (1000 microM) was absent after preincubation with indomethacin (2.8 microM) but unmodified when nordihydroguaiaretic acid (NDGA, 3.3 microM) was used. Finally, removal of the epithelium prevented the GABA effect. 4. Anaphylactic histamine release from serosal mast cells isolated from sensitized animals was not affected either by GABA (10-1000 microM) or the selective receptor agonists (-)-baclofen (0.1-1000 microM) and isoguvacine (10-1000 microM). The release of platelet-activating factor (PAF) from alveolar macrophages stimulated by formyl-Met-Leu-Phe (FMLP; 1 microM) was modified neither by GABA (100 microM)nor by (-)-baclofen (100microM).5. In conclusion, these data show that GABA can inhibit allergic phenomena in the guinea-pig airways through activation of GABAB receptors. An involvement of neuropeptidergic sensory structures is suggested but a role for epithelial cells and arachidonate metabolites is not definitely proved.

Assessment of inflammation in noninfectious chronic maxillary sinusitis

BACKGROUND AND AIM

Pathologic examination of the sinus mucosa and titration of inflammatory mediators in the sinus fluid were carried out to characterize inflammation in chronic sinusitis and determine whether patients with chronic allergic rhinitis (CAR) and sinusitis differ from patients with chronic nonallergic rhinitis (CNAR) and sinusitis.

METHODS

Nine control subjects (patients requiring ear, nose, and throat surgery not related to sinusitis), 12 patients with CAR and sinusitis, and 13 patients with CNAR and sinusitis were investigated. Eosinophil cationic protein, tryptase, myeloperoxidase, histamine, and prostaglandin D2 were measured in the sinus lavage fluids, and cells were enumerated. The cellular infiltrate was studied by immunohistochemistry with monoclonal antibodies against eosinophil cationic protein (eosinophils), tryptase (mast cells), neutrophil elastase (neutrophils), CD3 (lymphocytes), CD68 (macrophages), and proliferating cell nuclear antigens.

RESULTS

Neutrophils were not increased in sinusitis. In comparison with control subjects, patients with CAR and CNAR with sinusitis showed significant increases in eosinophils and macrophages in biopsy specimens and in eosinophil cationic protein in sinus lavage fluids. In comparison with patients with CNAR, patients with CAR had an increased number of intraepithelial mast cells and lymphocytes.

CONCLUSIONS

These findings suggest that patients with CNAR and sinusitis can be distinguished from patients with CAR and sinusitis, which resembles nonallergic rhinitis with eosinophilia syndrome.

Mechanism of airway inflammation in asthma

Airway inflammation has emerged as an important contributor to mechanisms of asthma. Furthermore, the presence of airway inflammation is present even in the absence of severe symptoms. To study the mechanisms by which bronchial inflammation can occur in asthma, a number of models have been developed including the airway response to antigen in allergic subjects. The pattern that has emerged from such studies indicates prompt pulmonary mast-cell activation and the apparent initiation of an inflammatory response. This inflammatory response develops over hours and is important in the later and more persistent development of bronchial obstruction. The eosinophil is an important cell in this process as are proinflammatory cytokines generated from activated lung mononuclear cells. The consequence of this multiple cell, multiple proinflammatory product interaction is the establishment of a self-perpetuating, redundant process by which asthma severity increases.

Potentiation of beta-adrenergic function by saiboku-to and bakumondo-to in canine bronchial smooth muscle

To determine the effects of the Kampo drugs Saiboku-to, Bakumondo-to and Orengedoku-to on beta-adrenergic function in airway smooth muscle, we studied isolated canine bronchial segments under isometric conditions in vitro. Incubation of tissues with these drugs did not alter the contractile responses to acetylcholine and histamine. The relaxation of tissues precontracted with acetylcholine induced by isoproterenol was augmented by Saiboku-to and Bakumondo-to, so that the concentration of isoproterenol required to produce a half-maximal effect (IC50) was decreased from 4.6 +/- 0.5 x 10(-8) M to 1.9 +/- 1.0 x 10(-8) M (P < 0.05) and to 1.0 +/- 0.8 x 10(-8) M (P < 0.01), respectively, whereas Orengedoku-to had no effect. These effects were concentration-dependent with the threshold concentrations being 0.3 mg/ml for Saiboku-to and 0.1 mg/ml for Bakumondo-to. Saiboku-to and Bakumondo-to did not affect cyclic AMP levels in airway smooth muscle per se but potentiated the isoproterenol-induced cyclic AMP accumulation. These results suggest that Saiboku-to and Bakumondo-to but not Orengedoku-to potentiate beta-adrenergic function in airway smooth muscle, which may reflect the efficacy of these drugs on airway hyperresponsiveness and asthma.

Neutrophil-induced human bronchial hyperresponsiveness in vitro--pharmacological modulation

Although it has been postulated that inflammatory cells cause the bronchial hyperresponsiveness which is diagnostic of asthma, until recently there has been little direct evidence of such a link. We have recently shown that calcium ionophore-activated human neutrophils and eosinophils can induce a state of human airway hyperresponsiveness in vitro. In this study we have shown that the anti-inflammatory agent nedocromil sodium, 10(-7) M, inhibited the hyperresponsiveness induced by products released from ionophore activated neutrophils but did not inhibit the release of leukotriene B4 from the same cells. Neutrophil-induced bronchial hyperresponsiveness was also inhibited by pre-treatment of the bronchial tissues with a thromboxane A2 and prostaglandin receptor antagonist, GR32191, 10(-7) M. These findings indicate that cyclooxygenase products are involved in bronchial hyperresponsiveness induced by inflammatory cell products in vitro and that their release can be inhibited by nedocromil sodium.

Heparin inhibits the immediate response to antigen in the skin and lungs of allergic subjects

Although heparin is used as an anticoagulant, its biologic function remains unclear. Substantial evidence exists that suggests it may modulate many aspects of immune function and inflammation. We demonstrated, in a double-blind, placebo-controlled, crossover study involving 10 allergic subjects, that a small dose of heparin (25 U/kg) administered intravenously 10 min before challenge reduced the acute cutaneous reaction to 10 allergens and histamine from a group-average sum of mean (+/- SD) wheal diameters at a baseline of 29.9 +/- 10 mm and after normal saline placebo (29.5 +/- 10.7 mm) to after heparin (14.4 +/- 10.4 mm) (p < 0.02, Wilcoxon's signed rank test). In 15 subjects with asthma and dust mite allergy, nebulized heparin 20,000 units administered in a double-blind, placebo-controlled, crossover fashion 10 min before challenge inhibited the bronchospasm induced by inhaled dust mite extract. Log2 of the provocative dose of mite extract causing a 20% fall in FEV1 at baseline was 4.1 +/- 1.5 protein nitrogen units (PNU); after normal saline it was 4.5 +/- 2.0 PNU, and after heparin it was 5.1 +/- 2.5 PNU (p = 0.04). These data suggest heparin may have an inhibitory role in acute mast-cell-mediated allergic inflammation.

Is asthma curable?

The information reviewed here supports the concept that asthma is potentially curable. Reports of complete, durable remission of asthma can no longer be regarded as fortuitous occurrences, unrepresentative of asthma in general. Systematic studies of anti-inflammatory drug therapy designed to explore possible induction or remission of asthma clearly are warranted. Studies of aggressive anti-inflammatory drug therapy of asthma at the onset, to avoid establishment of chronic asthma, also are desirable. The current goals of therapy of asthma have been revised to include reduction of airway hyperreactivity with topical anti-inflammatory drugs, in addition to relief of current symptoms. This approach may provide valuable resistance to exacerbations in response to antigen exposures, infections, exercise, or irritants. Pathophysiologic mechanisms apparently essential to the establishment and perpetuation of chronic asthma have been identified. These processes may be vulnerable to eradication by combination therapy with existing pharmacologic agents such as cyclosporin A or FK-506 (to suppress cytokine production), gold, methotrexate, and other anti-inflammatory drugs, alone or in combination. Equally important, the vigorous anti-inflammatory therapy may be necessary only long enough to achieve a resolution of the chronic pulmonary inflammation. Systematic studies of the use of these agents to induce partial, or complete, stable remissions of asthma should be performed. In the past, remissions of asthma in children with neoplasia and the other patients presented herein were complete, durable, and welcome, but they were largely unexpected and unpredictable. For the future, there is increasing reason to believe that predictable pharmacologically induced remission of asthma will be feasible.

Mast cells in the labial salivary glands of patients with Sjögren's syndrome: a histochemical, immunohistochemical, and electron microscopical study

Mast cells in labial salivary glands obtained from patients with xerostomia with or without focal sialadenitis/Sjögren's syndrome were studied. There was no significant correlation between the intensity of local lymphocyte infiltration and the morphometrically analysed number of mast cells staining positive with toluidine blue. Histamine staining with heterologous 11C antiserum showed significantly fewer positive cells than staining with toluidine blue (mean (SD) 62 (10) v 138 (30)). This suggests heterogeneity of the mast cell population. Furthermore, there was a correlation between the focus score and the number of mast cells containing histamine. This suggests that the proliferation of mast cells containing histamine may be locally regulated by the immune inflammation, possibly through mediators from macrophages and fibroblasts. In contrast, the number of mast cells staining positive with toluidine blue could not be used as a marker of the degree of local inflammation. Although transmission electron microscopic analysis did not disclose signs of 'en masse' mast cell degranulation, mast cells may have a role in the local disease process.

The effect of inhaled fenoterol, administered during the late asthmatic reaction to house dust mite (Dermatophagoides pteronyssinus)

A double-blind, placebo-controlled crossover study was set up to investigate the effect of fenoterol (400 micrograms) during the late asthmatic reaction (LAR). Twenty young subjects with asthma (mean age, 11.8 years; range, 8.3 to 20.6 years) were selected on the basis that they developed an LAR after bronchial challenge with Dermatophagoides pteronyssinus. After the LAR occurred, a placebo and fenoterol were administered blindly by a metered-dose inhaler, with an interval of 15 minutes and in alternating, random sequence. At the start of the study, that is, a documented LAR, the two groups of subjects had the same severity of LAR, as expressed by the fall of the FEV1 (mean, -34.5% versus -33.5%). The mean FEV1 of the 10 patients who received placebo first changed only -1.1% (+/- 5.0), whereas after fenoterol, The FEV1 increased by 20.7% (+/- 10.8). In the 10 patients receiving fenoterol first, the mean FEV1 rose by 18.8% (+/- 8.0), whereas the placebo inhalation resulted in a supplementary increase of 3.1% (+/- 7.0). The paired Student's t test between these differences (placebo versus fenoterol) was highly significant (p less than 0.001). Although it was demonstrated in some studies that beta-agonists did not prevent the LAR, the present study demonstrates that the administration of fenoterol can reverse the FEV1 significantly, although it was not reversed completely, during an allergen-induced LAR.

Mast cell lines produce lymphokines in response to cross-linkage of Fc epsilon RI or to calcium ionophores

The cross-linkage of high affinity Fc epsilon receptors (Fc epsilon RI) on mast cells and basophils is central to the induction of allergic inflammatory responses. As a result of such cross-linkage, mast cells secrete a variety of preformed biologically active substances, such as histamine, and newly synthesized arachidonic acid metabolites. Here we show that cross-linkage of Fc epsilon RI on a series of nontransformed murine mast cell lines, or treatment of these cells with calcium ionophores, stimulates increased messenger RNA levels and secretion of a group of lymphokines classically produced by a subset of murine T cell lines (TH2 cells). These factors include interleukin-3 (a mast cell growth factor)s interleukin-4 (an IgE 'switch factor'), interleukin-5 (an eosinophil differentiation factor) and interleukin-6 (a factor controlling immunoglobulin secretion). The production of these polypeptide factors by mast cells may have great importance in the induction of allergic and anti-parasite inflammatory responses.

Azelastine in the prophylactic treatment of bronchial asthma: an Italian multicentre comparison with ketotifen

The prophylactic effectiveness of the phthalazinone derivative, azelastine was compared with ketotifen. A total of 111 patients, aged 18-65 years, from 10 centres was entered into this randomized, double-blind study. All patients had reversible asthma. After 1 week on placebo, patients were allocated to either 8 mg/day azelastine once or twice daily, or to 1 mg ketotifen, twice daily, for a further 12 weeks. Azelastine was more effective in improving respiratory function (forced expiratory flow in 1 s and peak expiratory flow rate) when given in the once daily regimen, whereas clinical measures (number of weekly asthma attacks) were most improved by twice daily dosing. There was no significant difference between the effectiveness of azelastine and that of ketotifen. Treatments were equally well tolerated and a low incidence of side-effects was reported. In conclusion, 8 mg/day azelastine, in either a single or twice daily dosage regimen may be regarded as providing effective prophylaxis against bronchial asthma.

A comparative study of the effects of two different doses of nedocromil sodium and placebo given by pressurised aerosol in exercise-induced bronchoconstriction

Fourteen adult subjects with stable asthma were treated using a double-blind crossover, randomised protocol, with either nedocromil sodium (4 mg or 2 mg) or placebo. The agents were administered from matched pressurised aerosol inhalers 30 min before exposure to an exercise regimen which, on a previous screening day, resulted in a 24-53% (mean: 33.9%) decrease in peak expiratory flow (PEF). Both doses of nedocromil sodium were significantly superior to placebo in preventing the exercise-induced decrease in PEF and were without side effects. This study confirms and extends the results of earlier trials with nedocromil sodium and further supports the contention that this new agent may be of benefit in the treatment of reversible obstructive airways disease in the adult patient.

The effect of immunotherapy on bronchial hyperresponsiveness and eosinophil cationic protein in pollen-allergic patients

The effect of immunotherapy (IT) on bronchial response to histamine and on eosinophil cationic protein (ECP) in 40 birch pollen-allergic patients with a history of rhinoconjunctivitis and wheezing during the birch season was examined. Twenty patients started IT with birch extract (Pharmacia, Uppsala, Sweden) before the season. The other 20 patients were not treated with IT. Histamine-challenge tests were performed before, at the start, at pollen peak, at the end, and after the birch-pollen season. Blood samples for determination of ECP were collected at the same time. Skin prick tests and nasal provocation tests were also performed before and after the season. A significant increase in bronchial hyperresponsiveness was noted in the group treated with IT and in the untreated group during the season. The increase was greatest in the untreated group with the maximal difference between the two groups at the end of the pollen season (p less than 0.07). IT treatment was followed by significantly less medication and higher peak expiratory flow values. The levels of ECP increased during the season in untreated patients (p less than 0.05) but not in patients treated with IT. The ECP levels of patients from both groups correlated significantly with histamine sensitivity (p less than 0.001).

Bronchial asthma: pathophysiological mechanisms and corticosteroids

The clinical effects in asthma of corticosteroids can be ascribed to their strong anti-inflammatory action. The pathophysiology of asthma is complex. A diversity of mediators and interactions between mediators and between mediators and various cell types enhances and maintains the inflammatory process in the airways resulting in severe asthma. This is a vicious circle. Penetration through the airway epithelium of allergens and other insulting particles trigger release of inflammatory mediators and neurotransmitters, which, by chemotaxis and activation of inflammatory cells, results in enhanced and prolonged mediator release. Several of these mediators possess tissue-toxic properties enhancing the airway inflammation. The glucocorticoids have several points of action affecting both mediator release and accumulation and activation of inflammatory cells, which explains their favourable effect in asthma.

Mast cell pharyngitis as a cause of supraglottic edema

A 30-year-old nonatopic woman had experienced a 9-year history of persistent symptoms of supraglottic edema. She had previously undergone epiglottectomy and excision of redundant left arytenoid tissue to improve her breathing and dysphagia. Uvular tissue was removed surgically at our clinic for histopathological examination of the excised tissues. This revealed diffuse infiltration by mast cells, many of which appeared degranulated. Uvular tissue from control patients undergoing uvulopalatopharyngoplasty for obstructive sleep apnea contained significantly fewer mast cells per high power field. To our knowledge such a degree of mast cell infiltration into supraglottic tissues has not been reported previously or associated with clinical symptoms.