Human Basophil Histamine Release Research Articles

Effects of ibrutinib on proliferation and histamine release in canine neoplastic mast cells.

The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib is effective in the treatment of human chronic lymphocytic leukaemia and mantle cell lymphoma. Recent data have shown that ibrutinib also blocks IgE‐dependent activation and histamine release in human basophils (BAs) and mast cells (MCs). The aim of this study was to investigate whether BTK serves as a novel therapeutic target in canine mast cell tumours (MCTs). We evaluated the effects of ibrutinib on two canine MC lines, C2 and NI‐1 and on primary MCs obtained from canine MCTs (n = 3). Using flow cytometry, we found that ibrutinib suppresses phosphorylation of BTK and of downstream STAT5 in both MC lines. In addition, ibrutinib decreased proliferation of neoplastic MCs, with IC50 values ranging between 0.1 and 1 μM in primary MCT cells and between 1 and 3 μM in C2 and NI‐1 cells. In C2 cells, the combination “ibrutinib + midostaurin” produced synergistic growth‐inhibitory effects. At higher concentrations, ibrutinib also induced apoptosis in both MC lines. Finally, ibrutinib was found to suppress IgE‐dependent histamine release in primary MCT cells, with IC50 values ranging from 0.05 to 0.1 μM in NI‐1 cells, and from 0.05 to 1 μM in primary MCT cells. In summary, ibrutinib exerts anti‐proliferative effects in canine neoplastic MCs and counteracts IgE‐dependent histamine release in these cells. Based on our data, ibrutinib may be considered as a novel therapeutic agent for the treatment of canine MCT. The value of BTK inhibition in canine MCT patients remains to be elucidated in clinical trials.

BTK inhibition is a potent approach to block IgE-mediated histamine release in human basophils.

BackgroundRecent data suggest that Bruton's tyrosine kinase (BTK) is an emerging therapeutic target in IgE receptor (IgER)‐cross‐linked basophils.MethodsWe examined the effects of four BTK inhibitors (ibrutinib, dasatinib, AVL‐292, and CNX‐774) on IgE‐dependent activation and histamine release in blood basophils obtained from allergic patients (n=11) and nonallergic donors (n=5). In addition, we examined the effects of these drugs on the growth of the human basophil cell line KU812 and the human mast cell line HMC‐1.ResultsAll four BTK blockers were found to inhibit anti‐IgE‐induced histamine release from basophils in nonallergic subjects and allergen‐induced histamine liberation from basophils in allergic donors. Drug effects on allergen‐induced histamine release were dose dependent, with IC 50 values ranging between 0.001 and 0.5 μmol/L, and the following rank order of potency: ibrutinib>AVL‐292>dasatinib>CNX‐774. The basophil‐targeting effect of ibrutinib was confirmed by demonstrating that IgE‐dependent histamine release in ex vivo blood basophils is largely suppressed in a leukemia patient treated with ibrutinib. Dasatinib and ibrutinib were also found to counteract anti‐IgE‐induced and allergen‐induced upregulation of CD13, CD63, CD164, and CD203c on basophils, whereas AVL‐292 and CNX‐774 showed no significant effects. Whereas dasatinib and CNX‐774 were found to inhibit the growth of HMC‐1 cells and KU812 cells, no substantial effects were seen with ibrutinib or AVL‐292.Conclusions BTK‐targeting drugs are potent inhibitors of IgE‐dependent histamine release in human basophils. The clinical value of BTK inhibition in the context of allergic diseases remains to be determined.

Marked Differences in the Signaling Requirements for Expression of CD203c and CD11b versus CD63 Expression and Histamine Release in Human Basophils

Many techniques are being used to examine the status of circulating human basophils including the enhanced expression of a variety of cell surface proteins. There is accumulating evidence that there are at least two compartments containing these activation marker proteins but there are only some indications for the signaling requirements for each of the compartments. This study began with published reports by other investigators who potentially dissociated CD63 expression from anaphylactic degranulation with the p38 inhibitor, SB203580, a possible falsification of a previously proposed hypothesis regarding CD63 expression. To explore the signaling requirements for CD63, a variety of pharmacological agents were used to inhibit or enhance 4 endpoints of basophil activation. First, it was found that inhibition of both histamine release and CD63 expression with SB203580 was concordant. But it was also found that this agent had no effect on increased expression of CD203c and CD11b. Actin polymerization inhibitors caused marked enhancement of CD63 expression (concordant with their effects on degranulation) with no effect on expression of CD203c and CD11b. The third generation syk inhibitor, NVP-QAB205, showed a 5-fold lower potency for inhibiting expression of CD203c and CD11b than for CD63. Finally, while desensitization of CD11b and CD203c expression occurs, it is slower than desensitization of the CD63 response. Taken together, these various observations demonstrate a marked difference in the early signaling requirements for the CD11b/CD203c compartment and CD63 degranulation and provide support for the hypothesis that CD11b and CD203c reside in a similar compartment.

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.

The effects of dasatinib on IgE receptor–dependent activation and histamine release in human basophils

AbstractDasatinib is a multitargeted drug that blocks several tyrosine kinases. Apart from its well-known antileukemic activity, the drug has attracted attention because of potential immunosuppressive and anti-inflammatory effects. We report that dasatinib at 1 μM completely blocks anti-IgE–induced histamine release in blood basophils in healthy donors, and allergen-induced release of histamine in sensitized individuals. In addition, dasatinib inhibited FcϵRI-mediated release of IL-4 and IgE-mediated up-regulation of CD13, CD63, CD164, and CD203c in basophils. The effects of dasatinib were dose-dependent (IC50: 50-500 nM) and specific for FcϵRI activation in that the drug failed to inhibit C5a-induced or Ca-ionophore–induced histamine release. Interestingly, at lower concentrations, dasatinib even promoted FcϵRI-dependent histamine release in basophils in allergic subjects. In consecutive studies, dasatinib was found to interact with and block several FcϵRI downstream targets in basophils, in-cluding Btk. Correspondingly, FcϵRI-mediated histamine secretion in basophils was markedly reduced in Btk knockout mice and in a patient with Btk deficiency. However, the remaining “low-level” mediator secretion in Btk-deficient cells was fully blocked down again by 1 μM dasatinib. Together, these data suggest that dasatinib inhibits FcϵRI-mediated activation of basophils through multiple signaling molecules including Btk. Dasatinib may be an interesting agent for immunologic disorders involving Btk-dependent responses or/and FcϵRI activation of basophils.

Distinct characteristics of signal transduction events by histamine-releasing factor/translationally controlled tumor protein (HRF/TCTP)–induced priming and activation of human basophils

We previously identified a negative correlation between histamine release to histamine releasing factor/translationally controlled tumor protein (HRF/TCTP) and protein levels of the Src homology 2 domain-containing inositol 5' phosphatase (SHIP) in basophils. We have also demonstrated that HRF/TCTP primes basophils to release mediators. The purpose of this study was to begin characterization of signal transduction events directly induced by HRF/TCTP and to investigate these events when HRF/TCTP is used as a priming agent for human basophil histamine release. Highly purified human basophils were examined for surface expression of bound HRF/TCTP, changes in calcium, and phosphorylation of Akt, mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase (ERK), Syk, and FcepsilonRIgamma. Results showed that basophils from all donors bound HRF/TCTP. There was a biphasic calcium response to HRF/TCTP, which corresponded to the magnitude of histamine release. Furthermore, those donors who have direct histamine release when exposed to HRF/TCTP (HRF/TCTP responder [HRF/TCTP-R] donors) have phosphorylation of Syk, Akt, MEK, and ERK. Remarkably, basophils from HRF/TCTP-nonresponder (HRF/TCTP-NR) donors do not show phosphorylation of these molecules. This finding is different from IL-3, which also primes basophils for histamine release, but does show phosphorylation of these events. We conclude that priming induced by HRF/TCTP is distinct from that induced by IL-3.

Systematic Profiling and Novel Targets of the Bcr-Abl Kinase Inhibitors Imatinib, Nilotinib and Dasatinib.

The BCR-ABL tyrosine kinase inhibitor imatinib represents the current frontline therapy in chronic myeloid leukemia (CML). Since imatinib resistance has become a major clinical problem in recent years, two second-generation drugs, nilotinib and dasatinib, displaying increased potency against BCR-ABL and targeting imatinib-resistant CML clones were developed. To predict potential side effects and novel medical uses we generated comprehensive drug-protein interaction profiles for all three drugs. We have used an unbiased chemical proteomics approach to detect drug-binding proteins directly from lysates of CML cells. Our studies yielded four major findings:a.The interaction profiles of the three drugs displayed strong differences and only a small overlap covering the ABL kinases.b.Dasatinib bound in excess of thirty Tyr− and Ser−/Thr−kinases, including major regulators of the immune system suggesting that dasatinib might have a particular impact on immune function.c.Despite the high specificity of nilotinib the receptor tyrosine kinase DDR1 was identified and validated as an additional major target.d.The oxidoreductase NQO2 was bound and inhibited by imatinib and nilotinib at physiologically relevant drug concentrations representing the first non-kinase target of these drugs.In addition, we have concentrated on the promiscuous binding profile of dasatinib: Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib in vitro and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to Ile and Thr-442 in Tec to Ile conferred resistance to dasatinib, while mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of pro-inflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer new therapeutic opportunities for inflammatory and immunological disorders.

The Btk tyrosine kinase is a major target of the Bcr-Abl inhibitor dasatinib

Dasatinib is a small-molecule kinase inhibitor used for the treatment of imatinib-resistant chronic myelogenous leukemia (CML). We have analyzed the kinases targeted by dasatinib by using an unbiased chemical proteomics approach to detect binding proteins directly from lysates of CML cells. Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib in vitro and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to Ile and Thr-442 in Tec to Ile conferred resistance to dasatinib, whereas mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of proinflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer therapeutic opportunities for inflammatory and immunological disorders.

Dasatinib (BMS354825) Inhibits IgE-Dependent Activation and Histamine Release in Human Blood Basophils.

Dasatinib (BMS354825) is a small molecule-type inhibitory drug that blocks several tyrosine kinases including PDGFR, KIT, BCR/ABL, and several src kinases. Dasatinib has recently been introduced as a new effective antileukemic drug in patients with imatinib-resistant chronic myeloid leukemia. However, because of the many targets of dasatinib and the broad range of potential target-cells in physiologic and pathologic tissues, dasatinib has recently been examined for its immunosuppressive and anti-inflammatory effects. We here report that dasatinib at 1 μM completely blocks the anti-IgE-induced release of histamine in human blood basophils in healthy subjects. The effects of dasatinib on histamine secretion in basophils were dose-dependent (IC50: 50–100 nM). Dasatinib was also found to block recombinant allergen-induced release of histamine from human basophils in sensitized individuals. In addition, as assessed by flow cytometry, dasatinib (1 μM) was found to inhibit the IgE-dependent upregulation of several activation-linked antigens, including aminopeptidase N (CD13), LAMP-3 (CD63), endolyn (CD164), and the basophil-specific ectoenzyme E-NPP3 (CD203c) on the cell surface of human basophils. The effects of dasatinib on upregulation of basophil differentiation antigens were found to be dose-dependent and were seen in normal subjects as well as in allergic individuals. Together, these data show that dasatinib blocks IgE-mediated activation and histamine release in human blood basophils. These anti-allergic effects of dasatinib may have clinical implications and may point to additional indications for this multifunctional drug.

Inhibition of rBet v 1‐induced basophil histamine release with specific immunotherapy ‐induced serum immunoglobulin G: no evidence that FcγRIIB signalling is important

Human basophils and mast cells express the low-affinity immunoglobulin (Ig)G receptor FcgammaRIIB. It has previously been shown in artificial model systems that cross-linking of the high-affinity IgE receptor FcepsilonRI and FcgammaRIIB leads to inhibition of FcepsilonRI signalling. The aim of the present study was to investigate whether cross-linking of FcepsilonRI and FcgammaRIIB contributes to IgG-mediated inhibition of histamine release in human basophils in a system using the sera from specific immunotherapy (SIT) patients and the major allergen from birch pollen, Bet v 1. As IgG4 furthermore has been proposed to have special blocking properties, we investigated the significance of IgG subclass specificity for this inhibition. Binding of recombinant Bet v 1-IgG complexes to FcgammaRII and IgG-binding activities in the sera from 25 birch pollen-allergic patients treated with SIT were measured using (125)I-rBet v 1. Inhibition of basophil histamine release was assessed by incubating washed leucocytes with complexes of rBet v 1-IgG with or without blocking of FcgammaRII. We observed low binding of rBet v 1-IgG complexes to FcgammaRII, which was negatively correlated with the relative IgG4-binding activities. Blocking of FcgammaRII did not reverse the SIT-IgG-induced inhibition of basophil histamine release. However, IgG-binding activities correlated significantly with the ability of the SIT sera to inhibit basophil histamine release. We suggest that at least in birch pollen SIT, the contribution of FcgammaRIIB-mediated inhibitory signalling to SIT-IgG-induced inhibition of human basophil histamine release is of minor importance. The main contributor to the inhibitory effect of SIT-induced IgG seems to be blocking of the allergen-IgE interaction.

Biologic activity of RANTES in apheresis PLT concentrates and its involvement in nonhemolytic transfusion reactions.

RANTES, one of the PLT-derived biologic response modifiers, accumulates in PLT concentrates (PCs) during storage and may play a causative role in nonhemolytic transfusion reactions (NHTRs) after PC transfusion. To investigate the association of RANTES with NHTRs, the biologic activity of RANTES in the supernatant of stored PC at the intravascular concentration expected after PC transfusion was assessed by examining chemotaxis and histamine release in human basophils. In addition, the levels of RANTES in PCs involved in NHTRs were compared with those in PCs causing no transfusion reactions. The supernatant of PC diluted to contain 1 nM RANTES significantly increased the migration of and release of histamine from basophils. Neutralizing antibody to RANTES suppressed the PC-triggered migration, but not histamine release. The levels of RANTES in PCs involved in NHTRs after PC transfusion were comparable to those in PCs that did not cause any transfusion reactions. RANTES that accumulated in PCs during storage was biologically active in a basophil chemotaxis assay at the intravascular concentration expected after PC transfusion. However, the NHTRs after PC transfusion were not simply related to the RANTES level in PCs.

Environmental polycyclic aromatic hydrocarbons, benzo(a) pyrene (BaP) and BaP-quinones, enhance IgE-mediated histamine release and IL-4 production in human basophils

Polycyclic aromatic hydrocarbons (PAHs) are major components of diesel exhaust particles found in pollutant respirable particles. There is growing evidence that these fossil fuel combustion products exacerbate allergic inflammation. Basophils contribute to allergic inflammation through the release of preformed and granule-derived mediators. To determine whether allergens and PAHs interact, we incubated human basophils with PAHs and measured the release of histamine and IL-4 with and without added antigen. None of the PAHs induced mediator release by itself and none affected total cellular histamine levels. However, several PAHs enhanced histamine release and IL-4 production in response to crosslinking the high-affinity IgE receptor, FcεRI. The enhancement seen with 1,6-BaP-quinone involved an increase in tyrosine phosphorylation in several different substrates, including the FcεRI-associated tyrosine kinase, Lyn, and elevated reactive oxygen species (ROS) levels detected by dichlorofluorescein fluorescence and flow cytometry. The PAH-induced enhancement of mediator release and ROS production could be inhibited with the antioxidant N-acetylcysteine. These data provide further evidence that environmental pollutants can influence allergic inflammation through enhanced FcεRI-coupled mediator release from human basophils.

Polycyclic aromatic hydrocarbons (PAHs) enhance IgE-mediated histamine release and IL-4 production in human basophils

Polycyclic aromatic hydrocarbons (PAHs) enhance IgE-mediated histamine release and IL-4 production in human basophils

Cerivastatin and atorvastatin inhibit IL-3-dependent differentiation and IgE-mediated histamine release in human basophils and downmodulate expression of the basophil-activation antigen CD203c/E-NPP3.

Recent data suggest that the statins, apart from their lipid-lowering activity, exhibit profound anti-inflammatory effects. Basophils are major proinflammatory effector cells in diverse pathologic reactions. We have examined the in vitro effects of five different statins on primary human basophils, their progenitors, and the basophil cell line KU-812. Preincubation of blood basophils with cerivastatin or atorvastatin (0.1-100 microM) for 24 h reduced their capacity to release histamine on immunoglobulin E (IgE)-dependent stimulation in a dose-dependent manner. These statins also inhibited IgE-dependent up-regulation of the basophil-activation antigen CD203c. Moreover, both statins suppressed interleukin-3-induced differentiation of basophils from their progenitors as well as (3)H-thymidine uptake in KU-812 cells. All inhibitory effects of cerivastatin and atorvastatin were reversed by mevalonic acid (200 microM). The other statins tested (lovastatin, simvastatin, pravastatin) did not show significant inhibitory effects on basophils. Together, these data identify cerivastatin and atorvastatin as novel inhibitors of growth and activation of human basophils.

Association of IgG Fc receptor II with tyrosine kinases in the human basophilic leukemia cell line KU812F

Background: We previously reported that crosslinking of IgG Fc receptor II (FcγRII) induces intracellular calcium mobilization, but not histamine release in human basophils. To clarify functional activities of FcγRII on human basophils, we analyzed the FcγRII-mediated signaling events in the human basophilic leukemia cell line KU812F. Methods: Flow cytometric methods were used to investigate the effect on intracellular calcium mobilization of cross-linking of FcγRII. KU812F cells were pre-incubated with anti-FcγRII monoclonal antibody (IV.3). After the addition of various concentrations of the tyrosine kinase inhibitor genistein or buffer alone, cells were stimulated with goat antimouse IgG F(ab') 2 (GAM) and analyzed with the flow cytometer. Next, in order to test the signaling events after cross-linking of FcγRII, we examined tyrosine kinase activity. The time-course of tyrosine phosphorylation after cross-linking of FcγRII and the effect of genistein on this tyrosine phosphorylation were tested by immunoblotting. Immunoprecipitation was also performed to identify the type of tyrosine kinase associated with signal transduction of FcγRII. Results: The tyrosine kinase inhibitor genistein inhibited intracellular calcium mobilization caused by cross-linking of FcγRII in a dose-dependent manner. Rapid tyrosine phosphorylation after FcγRII cross-linking was shown by immunoblot analysis and this phosphorylation was inhibited by genistein. Furthermore, tyrosine phosphorylation of Lyn and Syk was observed upon cross-linking of FcγRII. Conclusions: Tyrosine phosphorylation is necessary for the signaling pathway through FcγRII and tyrosine phosphorylation of Lyn and Syk, at least, is actively involved in this signal transduction.

Determination of the site on the human recombinant histamine releasing factor (HrHRF) responsible for human basophil histamine release (HR)

Determination of the site on the human recombinant histamine releasing factor (HrHRF) responsible for human basophil histamine release (HR)

Degranulation of human basophils bypicomolar concentrations of IL–3, IL–5, orgranulocyte-macrophage colony-stimulating factor

In most secretory cells, an increase in the cytosolic free Ca 2+ concentration ([Ca 2+] i) is associated with the exocytosis response. In this study we have evaluated the effect of thapsigargin on histamine release from purified (70% to 97% pure) human basophils of nonallergic donors. Thapsigargin (2 μmol/L), by inhibiting the uptake of Ca 2+ in the stores of the endoplasmic reticulum, leads within 1 minute to a gradual increase in [Ca 2+] i in human basophils. Incubation of basophils with thapsigargin by itself induced only a very small release of histamine (5.6% ± 1.8%). However, under suboptimal conditions of stimulation with other agonists, preincubation of basophils with thapsigargin significantly enhanced histamine release. Most strikingly, addition of thapsigargin made basophils extremely sensitive for histamine release induced by IL–3 (maximum histamine release, 71% ± 7%), IL–5 (maximum histamine release, 43% ± 8%), or granulocyte-macrophage colony-stimulating factor (GM-CSF) (maximum histamine release, 57% ± 10%). These cytokines by themselves did not induce histamine release in purified basophils. The effect of thapsigargin was mimicked to a limited extent by addition of platelet-activating factor. We conclude that depletion of the Ca 2+ stores may be a critical event in the activation of receptor-mediated histamine release in human basophils. (J Allergy Clin Immunol 1998;101:683-90.)

Inhibition of allergen-induced histamine release from human basophils by cyclosporine A and FK-506.

A number of structurally different allergens trigger the release of mediators from basophils by cross-linking of IgE receptors. In this study, we analyzed the effects of cyclosporine A (CSA) and FK-506 on allergen-induced histamine release in human blood basophils obtained from birch- or grass-pollen-allergic donors (n = 12). Preincubation of basophils with CSA (0.003-3 microg/ml) or FK-506 (0.003-3 microg/ml) led to inhibition of histamine release induced by purified recombinant tree pollen allergens (r Bet v 1, r Bet v 2) and timothy grass pollen allergens (r Ph1 p 1, r Ph1 p 2, r Ph1 p 5). The effects of CSA and FK-506 were dose dependent, with IC50 values ranging between 0.03 and 0.3 microg/ml for both CSA and FK-506. Cyclosporine H, an inactive CSA analog, did not show any effect on allergen-induced histamine secretion. IgE dependency of the reaction was demonstrated in passive transfer experiments using highly enriched human basophils (> 95% pure) and specific IgE from a patient allergic to Bet v 2. In summary, our data show that CSA and FK-506 inhibit recombinant-allergen-induced histamine release from peripheral blood basophils in allergic donors.

325 Integrin-dependent histamine release in human basophils: Relationship with disease status

325 Integrin-dependent histamine release in human basophils: Relationship with disease status

The effect of okadaic acid on histamine release, cell morphology and phosphorylation in rat basophilic leukemia (RBL-2H3) cells, human basophils and rat peritoneal mast cells.

To study the involvement of serine/threonine phosphatase in the signal transduction of mast cells, we examined the effects of okadaic acid (OA), an inhibitor of type-1 and -2A phosphatase on histamine release, cell morphology, calcium influx and protein phosphorylation of rat basophilic leukemia (RBL-2H3) cells, human basophils and rat peritoneal mast cells. OA inhibited IgE-mediated histamine release from RBL-2H3 cells and human basophils dose-dependently. There was a remarkable enhancement of IgE-mediated histamine release when rat peritoneal mast cells were suboptimally challenged. OA induced a marked change of cell features, detached RBL-2H3 cells from plastic well and kept the 18- and 68-kD proteins phosphorylated. These findings show that phosphatase may play a role in the modulation of secretion in mast cells.