Identification of the Syk kinase inhibitor R112 by a human mast cell screen

BACKGROUND: Activation of the IgE receptor, FcvarepsilonRI, in mast cells is the key mechanism initiating and propagating pathophysiological responses in allergic rhinitis. OBJECTIVE: Identify and characterize a small molecule inhibitor of IgE-dependent mast cell activation for the treatment of allergic diseases. METHODS: A cell-based high-throughput screen for small molecules that block IgE signaling was performed in cultured human mast cells. A potent inhibitor, referred to as R112, was selected and characterized by using biochemical and cell-based assays. R112 effects on IgE-dependent degranulation and cytokine production was measured in mast cells and basophils and compared with other mast cell inhibitors. RESULTS: R112 inhibited degranulation induced by anti-IgE cross-linking in mast cells (tryptase release, effective concentration for 50% inhibition [EC(50)] = 353 nmol/L) or basophils (histamine release, EC(50) = 280 nmol/L), and by allergen (dust mite) in basophils (histamine release, EC(50) = 490 nmol/L). R112 also blocked leukotriene C4 production and all proinflammatory cytokines tested. Subsequent molecular characterization indicated that R112 is an ATP-competitive spleen tyrosine kinase (Syk) inhibitor (inhibitory constant [K(i)] = 96 nmol/L). Its onset of action was immediate, and the inhibition was reversible. Incubation of mast cells with R112 showed that cytokine production in mast cells was dependent on sustained activation of the FcvarepsilonRI-Lyn-spleen tyrosine kinase pathway. Unlike other mast cell inhibitors, R112 was able to completely inhibit all three IgE-induced mast cell functions: degranulation, lipid mediator production, and cytokine production. CONCLUSION: R112 potently, completely, and rapidly abrogated all mast cell activation cascades triggered by IgE receptor cross-linking. CLINICAL IMPLICATIONS: R112 and its analogues offer a new modality in the treatment of allergic rhinitis.     

Inhibition of allergic histamine release by azelastine and selected antiallergic drugs from rabbit leukocytes

The ability of azelastine to inhibit allergic histamine release from rabbit mixed leukocytes was studied and compared with selected antiallergic drugs. Azelastine, ketotifen, diphenhydramine, theophylline and disodium cromoglycate (DSCG) produced concentration-dependent inhibition of allergic histamine release from rabbit basophils. The concentrations inhibiting histamine release by 50% (IC50; microM) were as follows: azelastine = 4.5; ketotifen = 9.5; diphenhydramine = 18.9; theophylline = 56.9; DSCG = greater than 1,000. DSCG was added to the cells immediately prior to antigen challenge. All other drugs were preincubated for a period of 10 min prior to antigen challenge. At the IC50 level, azelastine is about 2, 4, 13 and greater than 200 times as effective as ketotifen, diphenhydramine, theophylline and DSCG, respectively. The IC50 of azelastine following 0, 10 and 30 min preincubation were 2.4, 1.9 and 3.5 microM, respectively. These observations showed: (1) azelastine is capable of acting rapidly on basophils and of inhibiting allergic histamine secretion, and (2) the prolongation of the preincubation time of azelastine up to 30 min with rabbit leukocytes did not exhibit any sign of tachyphylaxis (loss of activity). In conclusion, azelastine is a potent inhibitor of allergic histamine secretion from the leukocytes of ragweed-sensitized rabbits.     

Ambroxol inhibits the release of histamine, leukotrienes and cytokines from human leukocytes and mast cells

OBJECTIVES AND DESIGN: The effects of the mucolytic agents ambroxol and N-acetylcystein (NAC) were studied on the release of histamine, leukotrienes, cytokines and superoxide anions from a variety of cells involved in the pathogenesis of allergic inflammation. SUBJECTS: Mast cells were isolated from human adenoids and skin (n = 5-6). Basophils, monocytes and granulocytes were obtained from Buffy-coat blood obtained from healthy blood donors (n = 4-7) and enriched by density centrifugation. TREATMENT AND METHODS: Ambroxol or NAC were added to the cells for different periods before stimulation with various immunological and non-immunological secretagogues. Histamine release from mast cells, basophils and monocytes was assayed either by radioimmunoassay or spectrofluorometrically. LTC4 (basophils), LTB4 (neutrophil/eosinophil granulocytes or monocytes), IL-4 and IL-13 (basophils) were measured by ELISA. RESULTS: Ambroxol inhibited histamine release by more than 50% from human adenoidal mast cells (1000 microM ambroxol) and skin mast cells (100 microM ambroxol) stimulated by Con A and compound 48/80, respectively. Ambroxol (100 microM) strikingly inhibited anti-IgE induced release of both histamine, LTC4, IL-4 and IL-13 from basophils and reduced both histamine and LTB4 release induced by C5a or Zymosan in monocytes. The drug also reduced LTB4 and superoxide anion production in granulocytes stimulated by zymosan or fMLP. In all cell types studied, ambroxol was more efficacious following a short preincubation (5-15 min) of the drug with the cells before stimulation. In contrast, NAC produced no clear effects on any of the different cell types studied, regardless of the preincubation period, the concentration or the stimulus employed. CONCLUSIONS: Unlike NAC, ambroxol is able to not only inhibit acute mediator release from mast cells and leukocytes but also reduce immunomodulatory cytokine generation from basophils and may have beneficial effects in the treatment of allergic respiratory diseases.     

Differential modulation of mediator release from human basophils and mast cells by mizolastine

BACKGROUND: Basophils and mast cells play a major role in the pathogenesis of allergic disorders by releasing several proinflammatory mediators. Some histamine H1 receptor antagonists exert anti-inflammatory activities by modulating mediator release from basophils and mast cells. OBJECTIVE: To study the in vitro effects of mizolastine, an H1 receptor antagonist, on the release of eicosanoids, histamine and IL-4 from human basophils and lung mast cells. METHODS AND RESULTS: Mizolastine (10(-7)-10(-5) M) concentration-dependently inhibited the release of cysteinyl leukotriene C4 from anti-IgE-stimulated basophils (IC(50): 3.85+/-0.28 microM) and mast cells (IC(50): 3.92+/-0.41 microM). The same concentrations of mizolastine did not affect anti-IgE-induced prostaglandin D2 release from lung mast cells. In contrast, mizolastine enhanced up to 80% IgE-mediated histamine release (EC(50): 4.63+/-0.14 microM) from basophils, but not from mast cells and it significantly potentiated IL-4 release from basophils induced by anti-IgE. Mizolastine did not affect histamine release from basophils induced by formyl peptide, whereas it inhibited cysteinyl leukotriene C4 release (IC(50): 1.86+/-0.24 microM). Blockade of cytosolic phospholipase A2 and arachidonic acid mobilization by pyrrolidine-1 did not alter the effect of mizolastine on histamine release from basophils, thereby excluding accumulation of arachidonic acid metabolic intermediates as the cause of this effect. Mizolastine did not influence anti-IgE-induced activation of extracellular signal-regulated kinase-1 and -2 (ERK-1 and -2) in human basophils. CONCLUSIONS: Mizolastine efficiently inhibits LTC4 synthesis in human basophils and mast cells presumably by interfering with 5-lipoxygenase. In contrast, it enhances histamine and IL-4 release only from anti-IgE-stimulated basophils. Therefore, mizolastine differentially regulates the production of mediators from basophils and mast cells in a cell- and stimulus-specific fashion.     

Inhibitory effect of traxanox sodium on IgE-mediated histamine release from passively-sensitized mast cells of the rat in vitro

Traxanox sodium, a benzopyranopyridine derivative showing a potent oral antiallergic activity in the rat, was compared with disodium cromoglycate (DSCG) for ability to block the release of histamine from the rat mast cell in vitro. Traxanox sodium showed dose-, antigen- and time-dependent inhibiton of the IgE-mediated release of histamine. The 50% inhibitory concentration was 0.04 microM for traxanox sodium, 1 microM for DSCG and 660 microM for theophylline. All these drugs blocked the release of histamine potentiated by preincubation of the mast cell with 10 micro M adenosine at lower concentrations than those which could inhibit the IgE-mediated histamine release. In addition, traxanox sodium at concentration of 1-100 microM inhibited the histamine release caused by 0.25 microgram/ml compound 48/80 in the presence and absence of calcium, and the drug at 100 micro M slightly inhibited the release caused by 0.2 microgram/ml ionophore A23187. These results suggest that traxanox sodium is a more potent inhibitor than DSCG on the histamine release from the mast cells of the rat, and a part of its antiallergic action is due to a selective inhibition of the immunological release of allergic mediators from the mast cell.     

Antiallergic activity profiles in vitro of RHC 3164 and related compounds. II. Comparison of RHC 3164 with disodium cromoglycate

RHC 3164 has been investigated for its antiallergic activities in 3 in vitro models of anaphylaxis. RHC 3164 was 6 times more potent than DSCG as an inhibitor of antigen-induced release of histamine (AIR) from rat mast cells (RMC) and had an activity profile identical to that of DSCG in the following respects: loss of inhibitory activity with increasing preincubation time, tachyphylactic properties, cross-tachyphylaxis to DSCG, and inability to inhibit nonimmunologic release of histamine. Neither RHC 3164 nor DSCG had any effect on immunologic release of histamine from human basophils or guinea pig lung slices. We conclude that RHC 3164 is a potent inhibitor of immunologic release of histamine from RMC with a mechanism of action similar to that of DSCG.     

A modulation of the anaphylactic basophil histamine release by selective H2 histamine agonists

Two selective H₂-histamine agonists, dimaprit and impromidine, have been tested for their action on histamine release from human basophils and rat mast cells.IgE-mediated basophil histamine release was inhibited by stimulation of histamine H₂-receptors. However, differences between the actions of both dimaprit and impromidine were noticed. Both impromidine and dimaprit had no specific effect on 48/80-induced histamine release from rat mast cells, although the latter in higher concentrations either slightly increased spontaneous histamine release or non-specifically inhibited compound 48/80-induced release.The results are consistent with the view that activation of adenylate cyclase via H₂-histamine receptors might be an important regulatory mechanism of histamine release from human basophils but not from rat mast cells.     

Antiallergic activity of nylidrin hydrochloride (RHC 3432-A). I. Effect on release of histamine in vitro from rat peritoneal mast cells, guinea pig lung slices and human basophils

Nylidrin (RHC 3432-A) has been investigated for its antiallergic activity in three in vitro models. Nylidrin was an effective inhibitor of IgE-mediated release of histamine from passively sensitized rat peritoneal mast cells and human basophils, and of IgG1-mediated release of histamine from passively sensitized guinea pig lung slices. The inhibition of the release of histamine by nylidrin in all three models was not antagonized by propranolol, indicating that nylidrin does not inhibit histamine release via stimulation of beta-adrenergic receptors. Isoproterenol and epinephrine were effective as inhibitors of the release of histamine only from guinea pig lung while salbutamol and terbutaline had no effect on immunologic release of histamine in all three models. Detailed comparative studies with disodium cromoglycate (DSCG) indicated that the mechanism of action of nylidrin in the rat mast cell model is different from that of DSCG.     

Effects of Angelica acutiloba on mast cell-mediated allergic reactions in vitro and in vivo

The root of Angelica acutiloba is a widely used herbal medicine which has been used as a typical therapeutic for allergic diseases in traditional medicine. This study was aimed to investigate the effects of A. acutiloba on allergic reactions in in vitro and in vivo models and its mechanism of action. A. acutiloba was extracted by maceration with 80% ethanol (AAE) and standardized by high-performance liquid chromatography. We investigated the effect of AAE on phorbol-12-myristate-13-acetate plus calcium ionophore A23187 (PMACI)-induced cytokine release; phosphorylation of JNK, ERK, and p38 in human mast cell-1 (HMC-1); and compound 48/80-induced release of histamine in rat peritoneal mast cells (RPMCs). We also investigated the effects on Evans blue (EB) extravasation induced by anti-DNP IgE in rats. Treatment with 1, 10 and 100 μg/ml AAE concentration-dependently inhibited the release of cytokines (tumor necrosis factor-α, interleukin (IL) -6, and IL-8) and phosphorylation of ERK and JNK induced by PMACI in HMC-1 cells, but it did not inhibit the phosphorylation of p38. It also inhibited compound 48/80-induced histamine release in RPMCs. Oral administration of 271?mg/kg AAE inhibited EB extravasation in a passive cutaneous anaphylaxis rat model. In conclusion, AAE inhibited mast cell-derived allergic reactions by inhibiting the release of histamine, the production of pro-inflammatory cytokines, and the phosphorylation of ERK and JNK.     

Effect of chinese herbal medicines and disodium cromoglycate on IgE-dependent histamine release from mouse cultured mast cells

We examined the effect of anti-allergic Chinese herbal medicines such as Ma-Xing-Gan-Shi-Tang (MXGST) and Xiao-Feng-San (XFS), and a mast cell stabilizer, disodium cromoglycate (DSCG) on histamine release from mouse cultured mast cells. The mast cells (ILMCMC) were obtained by culturing mouse bone marrow cells for 3–6 weeks in the presence of IL-3. Some of the cells (FMCMC) were further cultured with a fibroblast cell line, 3T3 for 3 weeks. FMCMC had safranin-positive granules and released histamine in response to compound 48/80, whereas ILMCMC failed to do so. MXGST and XFS at 4–40 μg/ml inhibited IgE-dependent histamine release from ILMCMC but not from FMCMC. On the contrary, DSCG at 10−4 M inhibited histamine release from FMCMC but not from ILMCMC. Chinese herbal medicines and DSCG may act on different types of mast cells.     

Anomalous effects of disodium cromoglycate. A study on two secretory systems

The effects of disodium cromoglycate (DSCG) on in vitro histamine release from peritoneal and pleural mast cells, and a possible interference with adrenergic mechanisms was studied. Parallel to this study, the effects of DSCG on the well-established adrenoceptor-mediated amylase release from parotid glands were investigated. It was found that DSCG in low concentrations potentiates histamine release from peritoneal mast cells. Further more, this potentiation is enhanced by alpha-adrenoceptor blockade and diminished by beta-adrenoceptor antagonists. Histamine release from pleural mast cells is affected inversely to peritoneal cells, that is, the secretion is inhibited by DSCG at a high concentration but not at a low one. The inhibition is unaffected by alpha-blockers but totally abolished by the beta-antagonist propranolol. The amylase release induced by norepinephrine, mediated via beta1-adrenoceptor, is depressed by DSCG. The beta-antagonist-sensitive amylase release induced by phentolamine is also inhibited by DSCG. Finally, DSCG alone induces amylase release from the parotid gland. These results would seem to indicate that DSCG exerts some alpha-adrenoceptor activity. However, it is not possible, at present, to state whether this activity is of agonistic nature. DSCG has effects which with respect to pattern, correspond well to the action of beta-adrenoceptor agonists.     

Chemical constituents of diesel exhaust particles induce IL-4 production and histamine release by human basophils

BACKGROUND: An epidemiologic relationship between airway allergic diseases and exposure to atmospheric pollutants has been demonstrated and suggested to be one factor in the increasing prevalence of asthma. Diesel exhaust particles (DEPs) have been shown to participate in the development of allergic airway inflammation, in which the targets include macrophages, B and T cells, epithelial cells, and mast cells. In addition to the adjuvant effect of DEPs on total and allergen-specific IgE production, DEPs also act to induce chemokines and cytokines and may play a key role in primary sensitization. OBJECTIVE: DEPs have been shown to increase local IL-4-containing Kit(+) cells soon after in vivo nasal challenge. The aim of this study was to examine the effects of DEPs on human basophils, a key source of IL-4. METHODS: Peripheral blood leukocytes from allergic and control subjects were cultured in the presence of organic extracts of DEP (DEPex) with or without allergen. The cultures were analyzed for IL-4-containing cells by using multiparameter flow cytometry, IL-4 secretion with ELISA, and histamine release. RESULTS: Basophils, when exposed in vitro to DEPex, expressed IL-4 and released histamine significantly (P <.01) more than with antigen activation. DEPex did not synergize with allergen in cytokine production and histamine release. DEPex-induced basophil IL-4 expression peaked at 2 hours and persisted through 20 hours, in contrast to allergen-induced IL-4, which was transient. The effect of DEPex on basophil cytokine expression and histamine release was dose dependent and occurred with cells from both allergic and nonallergic subjects. DEPex induced IL-4 expression and histamine release in highly enriched basophil populations, suggesting it acts directly on basophils. Other peripheral blood leukocytes, including T cells, did not contribute to this cytokine expression. Preincubation with N-acetylcysteine completely abrogated DEPex-driven basophil IL-4 expression. CONCLUSIONS: Basophils are a direct target for DEPex, inducing IL-4 expression and histamine release in an IgE-allergen independent fashion. N-acetylcysteine inhibition of DEPex-driven IL-4 expression provides evidence that generation of reactive oxygen species is required for the effects observed. The capability of DEPex to activate basophils in both allergic and nonallergic subjects suggests a potential role of this pollutant in the increasing prevalence of allergic diseases.     

Calcineurin antagonists differentially affect mediator secretion, p38 mitogen-activated protein kinase and extracellular signal-regulated kinases from immunologically activated human basophils

BACKGROUND: Basophils participate in allergic diseases by invading affected tissues and secreting histamine, leukotriene (LT)C4, IL-4 and IL-13 following FcepsilonRI cross-linking. A reduction of basophil mediator production is therefore of considerable therapeutical interest. Macrolactam derivatives, which inhibit calcineurin activation, may be candidates for antiallergic therapy as they reduce both symptoms of inflammatory skin disease in animal models and mast cell degranulation. OBJECTIVE: To investigate the effects of the calcineurin antagonists ascomycin and cyclosporin A on IgE-dependent mediator release from human basophils. METHODS: Basophils were purified by Ficoll density centrifugation, elutriation and negative selection. Histamine release was measured spectrofluorometrically; LTC4, IL-4 and IL-13 secretions were assayed by enzyme-linked immunosorbent assay (ELISA). Lysed cells were subjected to Western blotting using specific antibodies to phospho-p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)-1 and -2. RESULTS: Ascomycin (0.01 nm to 1 micro m) and cyclosporin A (0.1 nm to 10 micro m) strikingly inhibited (maximally 100%) anti-IgE-induced histamine and cytokine release from basophils, and these actions were unaffected by IL-3 priming. Ascomycin, however, was less potent at blocking LTC4 secretion, whereas cyclosporin A was unable to block production of this mediator. In immunoblotting studies, ascomycin and cyclosporin A reduced IgE-dependent p38 MAPK activation but were less potent at reducing ERK phosphorylation in basophils. CONCLUSION: Calcineurin antagonists like ascomycin and cyclosporin A block IgE-dependent basophil degranulation and cytokine synthesis. Calcineurin may target p38 MAPK activation, but seems to have less activity on ERK phosphorylation. This is paralleled by a reduced or even absent effect of calcineurin antagonists on eicosanoid production.     

Secretion of cytokines,histamine and leukotrienes in chronic urticaria

BACKGROUND: Approximately 35-40% of patients with chronic urticaria have an IgG autoantibody to the IgE receptor which can activate basophils and mast cells so that they release histamine. In this study we assessed the cytokine profile present in chronic urticaria sera, and then measured cytokine and leukotriene release from basophils and mast cells upon incubation with chronic urticaria sera. Finally we assessed cytokine expression at the single-cell level and characterized the T cell subpopulations involved in their production. We chose IL-4 as representative of Th2 lymphocytes and IFN-gamma for Th1 lymphocytes. METHODS: We analyzed IL-4, IL-5 and IFN-gamma in 60 chronic urticaria sera versus 51 controls. Sera were incubated with purified human basophils and cutaneous mast cells and the release of histamine, IL-4 and leukotrienes (C(4), D(4), E(4)) was quantitated. Immunoblotting was performed to identify IgG antibody to FcepsilonRIalpha, alpha subunit. We measured intracellular cytokine production in peripheral blood mononuclear cells of 17 chronic urticaria patients compared to 50 healthy controls. RESULTS: We found higher IL-4 levels (p = 0.028) in the sera of chronic urticaria patients (1.03 pg/ml) versus healthy donors (0.20 pg/ml) but no difference between urticaria sera and atopic control sera (0.52 pg/ml). We did not detect IFN-gamma or IL-5 in any serum. However, sera that activated basophils so that they released histamine also produced leukotriene and IL-4, and leukotriene production by cutaneous mast cells and basophils was closely correlated. However, there was no correlation between immunoblotting and the functional ability to induce either histamine or IL-4. After stimulating with PMA-ionomycin we found significant differences in CD4+ lymphocyte production of IL-4 and IFN-gamma with no differences in CD8+ lymphocyte production of either cytokine. CONCLUSION: Our data support the presence of basophil and mast cell activators in the sera of patients with chronic urticaria which can lead to the production of leukotrienes and IL-4 in addition to the histamine. IL-4 levels are similar to those seen in atopic subjects. We found that CD4+ T cells from patients with chronic urticaria are activated and tend to produce higher cytokine levels than CD4+ T cells from healthy controls. There were no differences when cytokine production by CD8+ lymphocytes was similarly assessed. These results are consistent with the histology found in biopsies of chronic urticaria lesions, where a CD4+-predominant infiltrate is found with cytokine production suggesting either a Th0 response or a mixture of Th1 and Th2 lymphocytes.     

Comparison of intestinal mast cell and basophil histamine release in children with food allergic reactions

The in vitro histamine release response of human intestinal mast cells and basophils challenged with anti-IgE, Concanavalin A, ionophore A23187 and food extracts was compared with skin prick test, RAST analysis and open food challenge. It was not possible to perform food challenge in all patients; however, seven children underwent open food challenge and in five the clinical diagnosis of "true" food allergy was confirmed. The intestinal mast cells were pooled from enzymatically dispersed duodenal biopsies obtained by duodenoscopy from 15 selected children suspected of food allergy, and five age-matched controls. In nine of 10 patients classified as "food allergic" intestinal mast cells released histamine to various food extracts in a dose-dependent fashion. From the mast cells of the nine food-allergic patients compared with non-allergics, the anti-IgE mediated mast cell histamine release was increased. Additionally, at 1000 U/ml anti-IgE the mast cell histamine release was increased compared with their corresponding basophils. However, in non-allergic subjects the histamine release of basophils was increased compared with their corresponding mast cells. Histamine release from basophils was positively correlated to the test scores of the RAST analysis, skin prick test, and food challenge. No apparent correlation between tests scores obtained from histamine release of intestinal mast cell and the other tests was demonstrated, except in children with diarrhoea as only symptom. However, the study gives evidence that duodenal mast cells actually are sensitized with specific IgE and thus may play a pathophysiological role in food hypersensitivity. In addition, the study shows that the ability of different stimuli, including food extracts, to trigger basophil histamine release does not correlate with their potency to induce histamine release from mast cells.     

Substance P-induced histamine release from human basophils, skin and lung fragments: effect of nedocromil sodium and theophylline.

We compared histamine release induced by substance P with those obtained with classical secretagogues on human basophils, lung and skin fragments. We also tested the capacity of nedocromil sodium and theophylline to inhibit histamine release in these 3 experimental models. Substance P (10(-4) M) caused a noncytotoxic histamine release (about 10% of total) from basophils, lung and skin fragments. Substance P-induced histamine release was always smaller than that obtained with optimal doses of anti-IgE, formyl-methionine phenylalanine or compound 48/80. Nedocromil sodium did not prevent secretagogue-induced histamine release from basophils or sliced skin. In contrast, it significantly inhibited anti-IgE- or substance P-induced histamine release from human lung. Theophylline caused a dose-related inhibition on these 3 models. We conclude that substance P is a modest secretagogue for human basophils and mast cells, and that skin and lung mast cells are heterogeneous with respect to their response to nedocromil sodium.     

The reactivity of dispersed human lung mast cells and peripheral blood basophils to acetylcholine]

To clarify the relation between human lung mast cells and parasympathetic nerve function as well as IgE mediated allergic reactions, highly purified dispersed human lung mast cells were obtained by using the techniques of scissors dispersion, enzymatic treatment, percoll centrifugation and exclusion of adherent cells. The reactivity to acetylcholine was examined by observing the histamine release of purified mast cells. Moreover, peripheral blood basophils, which have many functional similarities with mast cells, were also examined in the same manner. The following results were obtained; 1) Histamine was significantly released from dispersed human lung mast cells at a final concentration of 10(-5) M acetylcholine (p less than 0.05); the peak of histamine release was 10(-4) M of acetylcholine. Acetylcholine had the additional effect of releasing histamine in response to anti-IgE. Histamine release was partially inhibited by 10(-5) M atropine. 2) Basophils had no response to acetylcholine. These results suggest that human lung mast cells play an important role in the defensive mechanism as an effector cell of acetylcholine-mediated autonomic nerve system as well as IgE-mediated allergic reaction.     

RHC 3024: antiallergic activity in vitro and comparison with disodium cromoglycate and other antiallergic agents

RHC 3024 has been investigated for its antiallergic activity in three in vitro models of anaphylaxis. We have also compared its activity profile in these models with that of disodium cromoglycate (DSCG) and other antiallergic agents. As an inhibitor of antigen-induced release of histamine from rat mast cells RHC 3024 was 4 times more potent than DSCG. In the same model the activity profile of RHC 3024 was identical to that of DSCG in the following respects: loss of inhibitory activity with increasing preincubation time, reversibility of the inhibition, tachyphylaxis and cross-tachyphylaxis to each other and inability to inhibit histamine release stimulated by Ca++ ionophore, dextran/phosphatidyl serine and compound 48/80. Both drugs had no effect in the other two models, IgG1-mediated histamine release from guinea pig lung and anti-IgE-induced histamine release from human basophils. We conclude: (1) RHC 3024 is a potent inhibitor of mediator release with a mechanism of action similar to that of DSCG, M&B 22,948, PRD-92-Ea and AH-7725 and (2) the in vitro activity profiles of proxicromil, doxantrazole, ICI 74,917 and WY-16,922 are different from DSCG and RHC 3024.     

Actions and cross-reactivity of antiallergic agents and a calcium channel antagonist on rat peritoneal mast cells. Difference in the action mechanisms and cross-reactivity among the agents

The actions of the antiallergic agents, disodium chromoglycate (DSCG), tranilast and ketotifen, and of a calcium channel antagonist, nicardipine, and cross-reactivity among the agents were examined by observing the inhibition of⁴⁵Ca uptake and histamine release in rat mast cells stimulated by antigen and compound 48/80 (comp. 48/80).

1. All agents inhibited⁴⁵Ca uptake and histamine release in mast cells stimulated by antigen. The inhibition of⁴⁵Ca uptake by the antiallergic agents paralleled the inhibition of histamine release, while nicardipine inhibition of⁴⁵Ca uptake was stronger than its inhibition of histamine release.
2. The action of DSCG on⁴⁵Ca uptake and histamine release was significantly decreased in cells stimulated with antigen and phosphatidylserine (PS), while tranilast inhibition of histamine release was not affected by the addition of PS despite a significant decrease in the inhibition of⁴⁵Ca uptake.
3. The inhibitory effect of DSCG and tranilast was significantly lower in mast cells stimulated by comp. 48/80 than in the cells stimulated by antigen.
4. Tachyphylaxis was observed in cells re-exposed to DSCG and tranilast following previous exposure to the agents.
5. Cross-reactivity was found between DSCG and tranilast.