Role of tyrosine kinases in IgE-mediated signal transduction in human lung mast cells and basophils.

Recent evidence suggests that tyrosine kinases play an important role in signal transduction mechanisms utilized by a range of different agonists in many cell types. We have investigated the effects of four different inhibitors of tyrosine kinases on IgE-dependent histamine release from human lung mast cells and basophils. Genistein inhibited the anti-IgE-induced histamine release from human basophils (at 10 microM genistein, inhibition = 55 +/- 5%, n = 17, P < 0.005) with an IC50 of 8 microM, but was much less effective in the human lung mast cell (at 10 microM, inhibition = 18 +/- 6%, n = 11, P < 0.05). Two inactive analogs of genistein, genistin and diadzein, failed to affect anti-IgE-induced histamine release significantly in either mast cells or basophils. A second inhibitor of tyrosine kinases, tyrphostin 25, inhibited IgE-dependent release from basophils (at 10 microM, inhibition = 25 +/- 7%, n = 6, P < 0.05) though it was less effective than genistein and failed to affect IgE-induced histamine release from human lung mast cells (at 10 microM, inhibition = 22 +/- 16%, n = 5, P = NS). In contrast, methyl 2,5 dihydroxycinnamate (MDC) failed to inhibit anti-IgE-dependent histamine release in human basophils (at 10 microM, inhibition = 3 +/- 3%, n = 5, P = NS) but proved to be an effective inhibitor of anti-IgE-induced degranulation in human lung mast cells (at 10 microM, inhibition = 53 +/- 16%, n = 5, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

CI-959, a new, potential antiallergic drug, inhibits mediator release from lung and contractions of human airways in vitro.

Many symptoms of the immediate allergic response can be attributed to the synthesis/release and subsequent actions of histamine and metabolic products of arachidonic acid oxidation. CI-959 [5-methoxy-3-(1-methylethoxy)-N-1H-tetrazole-5-yl-benzo(b) thiophene-2-carboxamide], a new, potential antiallergic drug, inhibited the release of histamine, immunoreactive sulfidopeptide leukotrienes C4, D4 and E4 and immunoreactive thromboxane B2 from immunologically activated guinea-pig and human lung cells in vitro. The IC50s of CI-959 using guinea-pig lung were: histamine, 0.8 +/- 1.4 microM; leukotriene, 0.7 +/- 1.6 microM and thromboxane, 9.6 +/- 3.3 microM. Using human lung the IC50s were: 2.3 +/- 1.3 microM for histamine; 0.3 +/- 5.1 microM for leukotriene, and 0.3 +/- 2.6 microM for thromboxane. CI-959 caused a concentration-dependent inhibition of anti-IgE-induced contractions of human bronchial muscle. Mean percent inhibitions were 45, 65 and 96 at 1, 3 and 10 microM, respectively. Cromolyn, 10 microM, inhibited bronchial contractions only 42%. The ability of CI-959 to inhibit these immunologically induced contractions indicates that the release of all mediators responsible for bronchoconstriction was effectively inhibited. These data suggest that CI-959 may be effective in preventing the development of symptoms directly related to inflammatory mediator release in a variety of allergic and inflammatory states.     

Inhibition of human basophil leukotriene release by antiinflammatory steroids

We have previously shown that 24-hour culture of human basophils with the antiinflammatory steroid dexamethasone produces an inhibition of the IgE-dependent release of histamine. In contrast, similar treatment of purified human lung mast cells does not inhibit the subsequent release of either histamine, prostaglandin D2, or leukotriene (LT) C4. We now show that incubation of mixed leukocytes for 24 h with 10(-7) M dexamethasone produces an inhibition of anti-IgE-induced basophil LTC4 release as detected by radioimmunoassay. In three experiments, control (CON) and dexamethasone (10(-7) M; DEX)-treated cells were challenged with 0.01, 0.03 and 0.1 micrograms/ml of anti-IgE, and histamine and LTC4 were monitored. LTC4 release (ng LTC4/micrograms total cell histamine) from cells stimulated with anti-IgE was: 0.01 micrograms/ml anti-IgE, 6.9 +/- 4, 0.3 +/- 0.1 (CON, DEX); 0.03 micrograms/ml anti-IgE, 13.8 +/- 4.7, 0.9 +/- 0.5; 0.1 micrograms/ml anti-IgE, 19.5 +/- 2.3, 4.9 +/- 1.2. Histamine release was inhibited by 50-75% by treatment with DEX in these experiments. Dose-response studies (n = 4) indicate that the inhibitory actions of DEX on LTC4 release occur in the range of 10(-10) to 10(-7) M. The concentration of DEX at which LTC4 release was inhibited by 50% (IC50) was approximately 2 X 10(-9) M. Another glucocorticoid (betamethasone) inhibited LTC4 release, while the nonglucocorticoids tetrahydrocortisone and beta-estradiol were inactive. High performance liquid chromatography (HPLC) analysis (coupled with RIA) indicated that the relative proportions of LTC4, LTD4, and LTE4 did not differ in supernatants from CON- and DEX-treated, anti-IgE-challenged cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mouse IL-3 induces histamine release from mouse peritoneal mast cells.

In this study, we have attempted to determine whether mouse peritoneal mast cells released histamine in response to IL-3. Recombinant mouse (m)IL-3 induced histamine release from mouse peritoneal mast cells in a dose-dependent fashion. Histamine release did not occur in the absence of phosphatidyl serine (PS), and was dependent on PS concentrations. The release was 14.3 +/- 3.8 and 43.5 +/- 11.5% (mean +/- SEM, n = 5) at 1 nM IL-3 in the presence of 10 and 20 micrograms/ml of PS. Calcium was required for the response, and in the absence of calcium, significant histamine release was not observed. The kinetics were slower than those of anti-IgE-induced response. IL-3-induced histamine release reached a peak within 15 min, while that by anti-IgE reached 80% of the maximum in 3 min. Lower concentrations of IL-3, which failed to directly induce histamine release, did not enhance anti-IgE-induced histamine release. Other cytokines, including mIL-4, mIL-5, m-granulocyte-macrophage colony-stimulating factor, human (h)IL-1 alpha, hIL-1 beta and hIL-8, neither induced histamine release nor enhanced anti-IgE induced histamine release. IL-4 had no capacity to enhance IL-3-induced histamine release. These results suggest that locally produced IL-3 might modulate mast cell-related inflammation through histamine release from mast cells.     

Histamine releasability of basophils and skin mast cells in chronic urticaria

In order to clarify the pathogenetic role of basophils and mast cells in chronic urticaria, histamine and leukotrienes (LT) C₄ release was examined in washed mixed leukocytes (n=8) and skin mast cells (n=5) from patients with chronic urticaria and compared with the same cells from normal controls (n=9). Anti-IgE-stimulated basophil histamine release was significantly reduced in urticaria patients (median 2.9% vs 15.1% in normal controls), whereas histamine release to A23187, FMLP, and PAF, as well as anti-IgE-induced LTC₄ release, showed no differences in both groups. In contrast, anti-IgE-stimulated skin mast cells from urticaria patients reacted similarly to those of controls (median histamine release 11.4% vs 14.2% in normal controls). Pretreatment of the cells with interleukin (IL)-3 upregulated responsiveness of basophil histamine release to anti-IgE in urticaria patients (median histamine release 14.3%), but pretreatment with the H₂-antagonist cimetidine showed no effect. These data show that reduced basophil histamine releasability in chronic urticaria is not H₂ mediated. It is a stimulus-, mediator-, and cell type-restricted phenomenon that can, at least partially, be reversed in the presence of the cytokine IL-3.     

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.     

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.     

Effect of cytokines on mediator release from human dispersed lung mast cells

To evaluate the contribution of human lung mast cells (HLMC) to allergic inflammation, we investigated whether or not cytokines, including stem-cell factor (SCF), monocyte chemotactic and activating factor (MCAF), and RANTES, activate HLMC. SCF induced histamine release from dispersed HLMC in a dose-dependent fashion (P<0.01). The release was 7.8 ± 1.0% at 500 ng/ml SCF (n= 9). This response was also observed in chopped lung tissue. HLMC from which surface IgE molecules had been removed by treatment with lactic acid responded to SCF, while these cells lost their response to anti-IgE. The process was relatively rapid and reached a maximum in 5 min. This response required extracellular calcium, and it was observed at 37°C, but not at 4°C or 20°. A brief preincubation (10 min) with lower concentrations of SCF, which were ineffective in releasing histamine, enhanced anti-IgE-induced histamine release (P<0.05), while its enhancing effect was lost by the longer preincubation (30 min). SCF did not prime basophils to enhance stimulated-histamine release. Interleukin (IL)-1α, IL-1β, IL-3, IL-4, IL-5, granulocyte/macrophage-colony stimulating factor (GM-CSF), MCAF, and RANTES neither induced histamine release nor enhanced the release stimulated by anti-IgE after a 10- or 30-min preincubation. The combination of IL-3 and IL-4 showed no effect on histamine release from HLMC. Leukotriene (LT)C₄/D₄/E₄ production by SCF was negligible, as compared with anti-IgE-induced LT production. SCF at 1.5 ng/ml augmented anti-IgE-induced LT generation significantly (536+ 117 pg/10⁵ mast cells and 1569 ± 258 pg/10⁵ mast cells; P<0.01). These results provide further evidence that numerous aspects of the phenotype of mast cells and basophils are heterogeneous, including structure, relevant secretagogues, and pharmacologic control.     

Effect of deuterium oxide on leukotriene C4 generation in immunologically stimulated human leukocytes

Addition of deuterium oxide (D2O), 6-36%, resulted in a dose-dependent increase in allergen- or anti-IgE-induced leukotriene C4 (LTC4) generation from human basophils. In the presence of 36% D2O, the enhancement was 260 +/- 135% for allergen stimulation and 480 +/- 152% for anti-IgE stimulation as compared with the control incubated in normal buffer. The increasing effect of D2O on LTC4 generation from basophils was completely reversed by washing the cells before incubation with allergen. Vinblastine as well as colchicine, at a concentration of 100 microM, counteracted the effect of D2O. The enhanced release of histamine and LTC4 from basophils challenged with allergen was suppressed by Dimaprit, a histamine H2 receptor agonist, at a concentration required to inhibit the release by 50% of 5 X 10(-5) M for histamine and 10(-5) M for LTC4. These observations suggest that microtubules may be involved in LTC4 generation from immunologically stimulated basophils.     

Cord blood basophil releasability: evaluation of histamine release and leukotriene C4 generation

This study was performed to evaluate mediator (histamine and leukotriene C4) release from cord blood and adult blood basophils, challenged with IgE-independent (calcium ionophore A23187) and IgE-mediated (anti-IgE) stimuli. IgE-independent mediator release was similar in adult blood and umbilical blood basophils. Conversely, the anti-IgE-induced histamine and immunoreactive leukotriene C4 (iLTC4) release was significantly reduced in cord blood basophils. Passive sensitization with an IgE-rich serum was followed by a significant increase in the number of eluted IgE molecules from cord blood basophils and by an increase in IgE-mediated histamine release. iLTC4 production was not affected by passive sensitization of umbilical blood basophils. The IgE-dependent mediator release from cord blood basophils was not correlated with the number of cell-bound IgE. In addition, histamine secretion and leukotriene C4 production from cord blood basophils seem to be independent events.     

Effect of AA-861, a 5-Lipoxygenase Inhibitor, on Leukotriene Synthesis in Human Polymorphonuclear Leukocytes and on Cyclooxygenase and 12-Lipoxygenase Activities in Human Platelets

AA-861, a selective inhibitor of 5-lipoxygenase of arachidonic acid, was tested for ability to inhibit leukotriene C4 and leukotriene B4 synthesis in human polymorphonuclear leukocytes after calcium ionophore stimulation. AA-861 dose-dependently inhibited leukotriene B4 and leukotriene C4 generation in human polymorphonuclear leukocytes; the concentration required to inhibit generation by 50% (IC50) was 3 X 10(-7) M for leukotriene B4 and 1 X 10(-8) M for leukotriene C4. BW-755C inhibited the generation of leukotriene C4 with an IC50 of about 10(-5) M, indicating that AA-861 is about 1,000 times more potent than BW-755C. AA-861 did not affect the activity of either cyclooxygenase or 12-lipoxygenase at a concentration up to 10(-5) M in human platelets. AA-861 did not inhibit histamine release from human basophils. These results indicate that AA-861 selectively inhibits 5-lipoxygenase but not cyclooxygenase or 12-lipoxygenase in human specimens.     

Antiallergic activity profile in vitro of RHC 2963 and related compounds

RHC 2963 (7-methyl-pyrido (3',2':4,5)-thieno (3,2-d)-1,2,3 triazine-4(3H)-one and 20 related compounds have been investigated for their antiallergic activities in 3 in vitro models of anaphylaxis and for their effects on cyclic nucleotide phosphodiesterases (cNUC-PDE) from purified rat mast cells (RMC). Nine compounds were potent (I50 less than or equal to 80 microM) inhibitors of antigen-induced release of histamine (AIR) from RMC, 2 compounds inhibited anti-IgE-induced release of histamine from human basophils (I50 less than or equal to 60 microM) and one compound inhibited AIR from guinea pig lung slices (I50 = 55 microM). RHC 2963 was 18 times more potent than disodium cromoglycate (DSCG) as inhibitor of AIR from 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 and inability to inhibit non-immunologic release of histamine induced by compound 48/80. Neither RHC 2963 nor DSCG had any effect on anti-IgE-induced release of histamine from human basophils or IgG1-mediated release of histamine from guinea pig lung. Twelve of the compounds in this chemical series were more potent than theophylline as inhibitors of cyclic AMP and/or cyclic GMP phosphodiesterase (PDE) from RMC. Paired regression analysis of the I50 values for inhibition of AIR and cNUC-PDE from RMC revealed no statistically significant correlation between the inhibition of AIR and inhibition of cAMP- or cGMP-PDE. We conclude: (1) RHC 2963 and some of the related compounds are potent inhibitors of immunologic release of histamine from RMC with a mechanism of action similar to that of DSCG, and (2) inhibition of cAMP- or cGMP-PDE by these compounds is not the biochemical mechanism by which they inhibit AIR from RMC.     

The calcium antagonist, nicardipine, inhibits antigen-stimulated and anti-IgE-induced histamine release from basophilic leucocytes of atopic asthmatics

The inhibitory effect of nicardipine, a calcium antagonist, on the antigen- and anti-IgE-induced histamine release from basophilic leucocytes of patients with bronchial asthma was examined. The agent significantly inhibited both antigen-stimulated and anti-IgE-induced histamine release from basophils (the maximum percent inhibition was 57.8 +/- 7.2% and 56.0 +/- 8.8%, respectively). Pre-incubation of basophils with nicardipine for periods of up to 120 min did not alter the inhibitory effect. These results suggest that nicardipine modifies the histamine release from basophils which closely participate in an attack of bronchial asthma.     

Effects of the new 5-lipoxygenase inhibitor E6080 on leukotriene release in vitro.

Fundamental studies were conducted to examine the release of histamine and leukotriene (LT) C4 from lung fragments of guinea pigs and the effects of E6080 on the release of LTB4 and LTC4 from lung fragments or inflammatory cells. The release of histamine and LTs showed large interindividual variations and a marked dependence on experimental conditions. Addition of 10 mM L-cysteine significantly increased LTC4 release compared with that in its absence (about 1.7 times, in terms of mean value). E6080 inhibited antigen-stimulated LTB4 and LTC4 release from passively sensitized human (IC50: LTB4 0.08 microM, LTC4 0.2 microM) and guinea-pig lung fragments (IC50: LTC4 1.1 microM). The LTB4 and LTC4 releases from healthy human polymorphonuclear leukocytes (calcium ionophore A23187) and from allergic patients' leukocytes (basophils, antigen) were inhibited by E6080 with IC50 values of below 1.0 microM. Furthermore, the LTC4 release from rat alveolar macrophages (silica particles) was inhibited by E6080 with an IC50 of 0.2 microM. The potent inhibition by E6080 might be a result of the inhibition of 5-lipoxygenase, since 5-lipoxygenase in rat basophilic leukemia cell was inhibited by E6080 with an IC50 of 0.2 microM. The results confirm the potent inhibitory effects of E6080 on the release of LTs.     

In vitro inhibitory effect of rupatadine on histamine and TNF-a release from dispersed canine skin mast cells and the human mast cell line HMC-1

OBJECTIVE AND DESIGN: To examine the inhibitory potential of rupatadine, a new H1-antihistamine and anti-PAF agent, on histamine and TNF-alpha release. Comparison with an H1-antihistamine (loratadine) and a PAF-antagonist (SR-27417A). MATERIAL: Dispersed canine skin mast cells were used to assess the effect of the drugs tested on FcepsilonRI-dependent and -independent histamine release; the human HMC-1 cell line was used to study TNF-alpha release. TREATMENT AND METHODS: Before stimulation mast cell populations were treated with increasing concentrations of rupatadine, loratadine and SR-27417A. Histamine and TNF-alpha release were measured following 15-30 min and 3 h activation, respectively. RESULTS: The IC50 for rupatadine in A23187, concanavalin A and anti-IgE induced histamine release was 0.7+/-0.4 microM, 3.2+/-0.7 microM and 1.5+/-0.4 microM, respectively whereas for loratadine the IC50 was 2.1+/-0.9 microM, 4.0+/-1.3 M and 1.7+/-0.5 microM. SR-27417A exhibited no inhibitory effect. Rupatadine, loratadine and SR-27417A inhibited TNF-alpha release with IC50 2.0+/-0.9 microM, 2.1+/-1.1 M and 4.3+/-0.6 microM, respectively. CONCLUSIONS: Rupatadine and loratadine showed similar inhibitory effect on histamine and TNF-alpha release, whereas SR-27417A only exhibited inhibitory effect against TNF-alpha.     

Histamine-releasing factor/translationally controlled tumor protein (HRF/TCTP)-induced histamine release is enhanced with SHIP-1 knockdown in cultured human mast cell and basophil models

Previously, we demonstrated a negative correlation between histamine release to histamine-releasing factor/translationally controlled tumor protein (HRF/TCTP) and protein levels of SHIP-1 in human basophils. The present study was conducted to investigate whether suppressing SHIP-1 using small interfering (si)RNA technology would alter the releasability of culture-derived mast cells and basophils, as determined by HRF/TCTP histamine release. Frozen CD34+ cells were obtained from the Fred Hutchinson Cancer Research Center (Seattle, WA, USA). Cells were grown in StemPro-34 medium containing cytokines: mast cells with IL-6 and stem cell factor (100 ng/ml each) for 6-8 weeks and basophils with IL-3 (6.7 ng/ml) for 2-3 weeks. siRNA transfections were performed during Week 6 for mast cells and Week 2 for basophils with siRNA for SHIP-1 or a negative control siRNA. Changes in SHIP-1 expression were determined by Western blot. The functional knockdown was measured by HRF/TCTP-induced histamine release. siRNA knockdown of SHIP-1 in mast cells ranged from 31% to 82%, mean 65 +/- 12%, compared with control (n=4). Histamine release to HRF/TCTP was increased only slightly in two experiments. SHIP-1 knockdown in basophils ranged from 34% to 69%, mean 51.8 +/- 7% (n=4). Histamine release to HRF/TCTP in these basophils was dependent on the amount of SHIP knockdown. Mast cells and basophils derived from CD34+ precursor cells represent suitable models for transfection studies. Reducing SHIP-1 protein in cultured mast cells and in cultured basophils increases releasability of the cells.     

Effect of interleukin 2 on basophil histamine release

Accumulating evidence suggests a link between immediate hypersensitivity and cellular immunity. In this study, we examined the effect of interleukin 2 (IL-2) on basophil histamine release. Histamine-releasing activity of IL-2 was very weak with % histamine release of 2.9 +/- 1.3 (mean +/- SEM, n = 9) at 1:12 dilution. IL-2 at 1:1200 dilution slightly inhibited anti-IgE-induced histamine release by 22.4 +/- 18.6% (P greater than 0.05). There was a significant potentiation of release at 1:12 dilution of IL-2 with % enhancement of 78.7 +/- 42.2 (P less than 0.05). IL-2 enhanced the calcium ionophore A23187-induced histamine release in a dose-dependent fashion. IL-2 at 1:12 dilution significantly potentiated release by 28.8 +/- 6.3% (P less than 0.05). There was a slight suppression of formyl-methionyl-leucyl-phenylalanine (FMLP)-induced histamine release at 1:1200 dilution with % inhibition of 23.4 +/- 7.4 (P greater than 0.05). At 1:12 dilution, IL-2 significantly potentiated FMLP-induced release by 73.7 +/- 41.6% (P less than 0.05). Recombinant IL-2 (RIL-2) augmented anti-IgE-induced histamine release with a significant enhancement at 200 units/ml. Conventional IL-2 was more potent than RIL-2 in enhancing release. These results indicate that IL-2 enhances basophil histamine release and some part of the effect of IL-2 on basophils is derived from other factors contained in conventional IL-2.     

Regulation of human basophil activation; the role of Na+ and Ca2+ in IL-3-induced potentiation of IgE-mediated histamine release from human basophils.

The release of mediators from human basophils is strongly enhanced by IL-3. However, the signalling pathways of IL-3 are poorly defined in these cells. Since external Ca2+ and Na+ play important regulating roles in histamine release, the possibility that these cations could be involved in the potentiation by IL-3 of the anti-IgE-induced histamine release from human basophils was considered, and it was observed that: (i) IL-3 dramatically decreased the external Ca2+ requirement for IgE-mediated histamine release. However, histamine release from IL-3-treated basophils became only partially independent of external Ca2+, since addition of EGTA in the external medium abolished the effect of IL-3; (ii) decreasing Na+ influx by lowering external Na+ concentration in isosmotic medium inhibited the potentiating effect of IL-3 on IgE-mediated release; (iii) amiloride, an inhibitor of Na+/Ca2+ and Na+/H+ exchanges, and its derivative, benzamil, more specific for Na+/Ca2+ exchanges, inhibited the release potentiated by IL-3. In contrast, the amiloride derivative 5-(N,N-dimethyl)-amiloride, more specific for Na+/H+ exchanges, slightly increased the IL-3-enhanced release. Thus, the decreased requirement for external Ca2+ and the dependence on external Na+, taken with the effect of the Na+/Ca2+ exchange inhibitors, suggest that Na+/Ca2+ exchanges are involved in the IL-3-induced enhancement of IgE-mediated human basophil histamine release.     

Humoral and cellular responses to histamine and pollen allergen in a skin chamber model: effect of mizolastine.

BACKGROUND: Mizolastine is a new non-sedative antihistamine and antiallergic drug proven to be effective and safe in the treatment of allergic rhinitis and urticaria. OBJECTIVE: To quantitatively explore the time course of mediator release and cell recruitment during allergen challenge and the effects of mizolastine on the event, using the skin chamber model. METHODS: Twelve pollen-sensitive patients (23+/-6 years) were included in a double-blind crossover study. Patients received 10 mg mizolastine or placebo once daily in the first 4-day period and, after a 3-week washout period, vice-versa in the crossover period. On day 4 of each period, a non-invasive in vivo skin chamber technique was used to determine the alteration of vascular permeability, mast cell mediator release, the release of soluble intercellular adhesion molecule -1(sICAM-1) in skin sites challenged with exogenous histamine or grass pollen allergen extract, over an 8-hour period. RESULTS: Challenge with allergen-induced significant mast cell activation, as indicated by the release of histamine, tryptase and LTC4, in chamber fluids 2 hours after initiation of the allergic reaction and during the following 6 hours. Both exogenous histamine and allergen induced significant vasodilatation, which was sustained during the 8-hour challenge, as indicated by the accumulation of protein in the chamber fluids. Likewise, both histamine and allergen induced the release of significant amounts of ICAM-1 throughout the 8-hour period. Mizolastine significantly inhibited the histamine- and allergen-induced extravasation (after 2 hours, P = .003; after 8 hours, P = .009; after 2 hours, P = .044; after 8 hours, P = .003 respectively) and the histamine- and allergen-induced--ICAM-1 release (after 2 hours, P = .004; after 8 hours, P = .05; after 2 hours, P = .03 respectively). CONCLUSION: Mizolastine strongly inhibited the local response to histamine in this skin chamber model with, of interest, inhibition of the release of the soluble adhesion-molecule ICAM-1.     

The role of 5-lipoxygenase pathway activation in basophil histamine release

This study was performed to evaluate the role of products of the 5-lipoxygenase pathway in histamine release from human basophils. AA-861, a specific inhibitor of 5-lipoxygenase, did not inhibit anti-IgE-induced histamine release from human basophils with 6 +/- 11% inhibition at 10(-6)M. Neither was there a marked inhibition of histamine release induced by ionophore A23187 and formyl-L-methionyl-L-leucyl-L-phenylalanine with 16 +/- 10 and 11 +/- 6% inhibition respectively at 10(-6)M of AA-861. In contrast, AA-861 enhanced 12-0-tetradecanoyl-phorbol-13-acetate-induced histamine release with 20 +/- 3% at 10(-6)M. These results suggest that 5-lipoxygenase activation may not play a role in basophil histamine release.