Suppression of phospholipase Cγ1 phosphorylation by cinnamaldehyde inhibits antigen-induced extracellular calcium influx and degranulation in mucosal mast cells

Antigen-IgE-mediated mucosal mast-cell activation is critical in the development of food allergies. Cinnamaldehyde, a major constituent of Cinnamomi cortex, dose-dependently inhibited the antigen-IgE-induced degranulation of mucosal-type bone-marrow derived mast cells (mBMMCs) and RBL-2H3 cells. Cinnamaldehyde also suppressed the elevation of the intracellular Ca(2+) level that is induced by the extracellular Ca(2+) influx in antigen-IgE-stimulated mBMMCs. Furthermore, tyrosine phosphorylation of phospholipase C (PLC) γ1, which is a crucial activation switch for the intracellular Ca(2+) mobilization in mast cells, was attenuated by cinnamaldehyde. Together, our results demonstrated that cinnamaldehyde suppressed the intracellular Ca(2+) mobilization and the degranulation of mucosal mast cells by inhibiting the activity of the IgE receptor-PLCγ-Ca(2+) influx pathway. These findings suggest that cinnamaldehyde may have therapeutic potential in mucosal mast cell-related allergic diseases, such as food allergies.     

Adrenomedullin and proadrenomedullin N-terminal 20 peptide induce histamine release from rat peritoneal mast cell

Adrenomedullin (ADM)-induced histamine release from rat peritoneal mast cells was investigated. We compared the ability of full-length ADM to induce histamine release to the fragments ADM-(1-25) and ADM-(22-52), as well as proadrenomedullin N-terminal 20 peptide (PAMP). ADM (10(-8) to 10(-5) M) and PAMP (10(-8) to 10(-5) M) dose-dependently increased histamine release from peritoneal mast cell preparations. The effect of ADM-(1-25) was similar to ADM, whereas ADM-(22-52) did not show any effects. These data suggest the relative importance of the ADM C-terminal fragment, which contains a six-membered ring structure. Histamine release, induced by ADM, was significantly and dose-dependently inhibited by the addition of ADM-(22-52) (10(-5) M), Ca(2+) (0.5 to 2.0 mM), and benzalkonium chloride (3 to 7 microM), a selective inhibitor of Gi type G proteins. In contrast, PAMP (10(-5) M)-induced histamine release was not inhibited by Ca(2+). These results suggest that ADM induce histamine release via a putative ADM receptor in a manner sensitive to Gi-protein function and extracellular Ca(2+) concentration, and that PAMP might produce its effect by a different mechanism than ADM.     

Interleukin-4 (IL-4) enhances and soluble interleukin-4 receptor (sIL-4R) inhibits histamine release from peripheral blood basophils and mast cells in vitro and in vivo

The aim of the study was to analyse the effect of interleukin-4 (IL-4) on allergen and anti-IgE mediated histamine release from basophils and human skin mast cells and to assess whether soluble recombinant interleukin-4 receptor (sIL4R) can inhibit these effects. Anti-IgE stimulated histamine release from peripheral blood basophils and mast cells of atopic donors was enhanced after preincubation with IL-4, whereas after preincubation with sIL-4R it was inhibited. These effects were even more pronounced when samples were stimulated with a clinically relevant allergen. In IL-4 preincubated skin mast cells, there was a similar enhancement of anti-IgE stimulated histamine release, which could again be inhibited by sIL-4R. The effects of IL-4 and sIL4R were dose- and time-dependent. Mice sensitized to ovalbumin and treated with soluble recombinant murine sIL-4R showed significantly reduced immediate-type cutaneous hypersensitivity responses compared with untreated mice. These in vivo effects were IgE independent, since there were no significant differences in total and allergen specific IgE/IgG1 antibody titres between treated and untreated mice. This indicates that IL4 exerts priming effects on histamine release by effector cells of the allergic response and that these effects are potently antagonized by soluble IL-4R both in vitro and in vivo.     

Role of calcium in histamine release from rat mast cells activated by various secretagogues; intracellular calcium mobilization correlates with histamine release

Anti-IgE, con A or antigen caused an increase in the intracellular calcium concentration, [Ca2+]i, of mast cells. The increase occurred in two stages: a rapid initial rise caused by Ca-mobilization from intracellular Ca-stores and a second sustained rise caused by an influx of extracellular calcium (White, J.R., Pluznik, D.V., Ishizaka, K. & Ishizaka, T. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 8193-8197). The rapid initial rise was followed by a release of histamine, which seemed to coincide with the second rise. A23187 and compound 48/80 induced a rapid initial rise in [Ca2+]i, followed by a gradual decrease in [Ca2+]i, GMCHA-OPhBut, a specific pH 7 tryptase inhibitor (Muramatu, M., Ito, T., Takei, M. & Endo, K. (1988) Biol. Chem. Hoppe-Seyler 369, 617-625), strongly inhibited both the initial and second rises of [Ca2+]i, as well as histamine release by these secretagogues, and its effects on the initial rise were closely correlated with those on histamine release. Addition of GMCHA-OPhBut immediately after the initial rise strongly inhibited the second rise, thereby decreasing the final [Ca2+]i. These results strongly suggested a possible involvement of pH 7 tryptase, not only in Ca-mobilization leading to the initial rise in [Ca2+]i, but also in the second rise. Trapping of extracellular calcium by 3mM EGTA decreased both the initial rise in [Ca2+]i and histamine secretion induced by anti-IgE or con A; the magnitude of this effect depended on the time between induction and EGTA addition. Histamine release was closely correlated with the initial rise in [Ca2+]i. Similar results were obtained with A23187, but even 5 min after the addition of EGTA an initial rise of [Ca2+]i could still be induced, and histamine (30% of total histamine) was still released. However, A23187 did not induce a rise in [Ca2+]i in mast cells which had been exhaustively washed with Tyrode/Hepes solution containing 3mM EGTA, followed by suspension in the same solution. Even at 20 min after depletion of the extracellular calcium, compound 48/80 still caused an initial rise in [Ca2+]i to above half the maximal value, and histamine secretion was even less affected. The above results indicated that the initial rise in [Ca2+]i, due to Ca-mobilization, correlates with the histamine release promoted by the secretagogues described. On the other hand, isoproterenol strongly induced histamine secretion with no change of [Ca2+]i, while EGTA treatment prior to isoproterenol stimulation had no effect on histamine release, indicating a different secretion mechanism.     

Characterization of the anti-inflammatory effect of FK-506 on human mast cells.

We have examined the effects of FK-506 and of the struturally related macrolide rapamycin, which bind with high affinity to a specific binding protein (FKBP), to evaluate the involvement of this protein in the release of preformed (histamine) and de novo synthesized inflammatory mediators (sulfidopeptide leukotriene C4 and prostaglandin D2) from mast cells isolated from human lung parenchyma. FK-506 (0.1 to 300 nM) concentration dependently inhibited histamine release from lung parenchymal mast cells activated by anti-IgE. FK-506 was more potent in lung mast cells than in basophils (IC50 = 1.13 +/- 0.46 nM vs 5.28 +/- 0.88 nM; p less than 0.001), whereas the maximal inhibitory effect was higher in basophils than in lung mast cells (88.4 +/- 2.5% vs 76.4 +/- 3.8%; p less than 0.01). FK-506 had little or no inhibitory effect on histamine release from lung mast cells challenged with compound A23187, whereas it completely suppressed A23187-induced histamine release from basophils. FK-506 also inhibited the de novo synthesis of 5-lipoxygenase (sulfidopeptide leukotriene C4) and cyclo-oxygenase (prostaglandin D2) metabolites of arachidonic acid from mast cells challenged with anti-IgE. Unlike in basophils, Il-3 (3 to 30 ng/ml) did not modify anti-IgE- or A23187-induced histamine release from lung mast cells nor did it reverse the inhibitory effect of FK-506. Rapamycin (3 to 300 nM) had little or no effect on the release of histamine from lung mast cells, but it was a competitive antagonist of the inhibitory effect of FK-506 on anti-IgE-induced histamine release from human mast cells with a dissociation constant of about 12 nM. These data indicate that FK-506 is a potent anti-inflammatory agent that acts on human lung mast cells presumably by binding to a receptor site (i.e., FKBP).     

Calcium requirement for the inhibition by theophylline of histamine release from mast cells

When added to Ca2+-free Hanks' solution, Ca2+ (0.1-2.5 mM) had no significant effect on antigen-induced histamine release from rat mast cells, but Sr2+ (1.0-3.0 mM) dose-dependently increased the release. Ba2+ (1.0 and 2.0 mM) also enhanced the release. Ca2+ and Ba2+ inhibited compound 40/80-induced histamine release, in a dose-dependent manner. In ordinary Hanks' medium, theophylline and 3-isobutyl-1-methylxanthine (IBMX) dose-dependently inhibited the antigen-induced histamine release but these drugs were ineffective in Ca2+-free medium. Theophylline (1.0 mM) also inhibited compound 48/80-induced histamine release in the presence but not absence of Ca2+. There was an optimal Ca2+ concentration for the theophylline effect. Sr2+ but not Ba2+ could substitute for Ca2+ in supporting the theophylline effect. Theophylline (1.0 mM) and IBMX (1.0 mM) increased mast cell cyclic AMP levels both in the presence and absence of Ca2+. These results suggest that Ca2+ is required in the interaction of theophylline and specific sites on mast cells or in the mast cell response to theophylline which probably does not involve the cyclic AMP increase and is linked to the inhibition of histamine release.     

Effects of valinomycin on calcium mobilization in vascular smooth muscle cells induced by angiotensin II

The effect of the specific potassium (K+) ionophore valinomycin on increase in intracellular calcium concentration [( Ca2+]i) was studied in vascular smooth muscle cells (VSMC). Valinomycin at more than 10(-9) M dose-dependently suppressed phasic increase in [Ca2+]i in VSMC induced by angiotensin II (AII) in both control and Ca2+-free solution, indicating that it suppressed the release of Ca2+ from intracellular Ca2+ stores. Nicorandil and cromakalim, which are both K+ channel openers, also suppressed the increases in [Ca2+]i induced by AII in the Ca2+ free solution. However, valinomycin did not suppress AII-induced production of inositol 1,4,5-trisphosphate (IP3), which is known to mediate the release of Ca2+. These results indicate that decrease of intracellular K+ induced by valinomycin suppressed the release of Ca2+ from intracellular Ca2+ stores induced by IP3.     

Effects of a time varying strong magnetic field on release of cytosolic free Ca2+ from intracellular stores in cultured bovine adrenal chromaffin cells

This study was made to explain the mechanisms for the effects of exposure to a time varying 1.51 T magnetic field on the intracellular Ca(2+) signaling pathway. The exposure inhibited an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in bovine chromaffin cells induced by addition of bradykinin (BK) to a Ca(2+) free medium. The exposure did not change BK induced production of inositol 1,4,5-trisphosphate (IP(3)). [Ca(2+)](i) was markedly increased in IP(3) loaded cells, and this increase was inhibited by the magnetic field exposure. A similar increase in [Ca(2+)](i) by other drugs, which stimulated Ca(2+) release from intracellular Ca(2+) stores, was again inhibited by the same exposure. However, transmembrane Ca(2+) fluxes caused in the presence of thapsigargin were not inhibited by the magnetic field exposure in a Ca(2+) containing medium. Inhibition of the BK induced increase in [Ca(2+)](i) by the exposure for 30 min was mostly recovered 1 h after exposure ended. Our results reveal that the magnetic field exposure inhibits Ca(2+) release from intracellular Ca(2+) stores, but that BK bindings to BK receptors of the cell membrane and intracellular inositol IP(3) production are not influenced.     

The human recombinant c-kit receptor ligand, rhSCF, induces mediator release from human cutaneous mast cells and enhances IgE-dependent mediator release from both skin mast cells and peripheral blood basophils.

The gene product of the steel locus of the mouse represents a growth factor for murine mast cells and a ligand for the c-kit proto-oncogene receptor, a member of the tyrosine kinase receptor class of oncogenes (for review, see O. N. Witte. 1990. Cell 63:5). We have studied the effect of the human recombinant c-kit receptor ligand stem cell factor (rhSCF) on the release of inflammatory mediators from human skin mast cells and peripheral blood basophils and compared its activity to that of rhIL-3, rhSCF (1 ng/ml to 1 microgram/ml) activated the release of histamine and PGD2 from mast cells isolated from human skin. Analysis by digital video microscopy indicated that purified human skin mast cells (84 +/- 5% pure) responded to rhSCF (0.1 to 1 microgram/ml) challenge with a rapid, sustained rise in intracellular Ca2+ levels that was accompanied by secretion of histamine. A brief preincubation (10 min) of mast cells with rhSCF (0.1 pg/ml to 1 ng/ml) significantly enhanced (100 +/- 35%) the release of histamine induced by anti-IgE (3 micrograms/ml), but was much less effective on IgE-mediated release of PGD2. In contrast, a short term incubation with rhSCF did not potentiate the secretion of histamine activated by substance P (5 microM). A 24-h incubation of mast cells with rhSCF did not affect the release of mediators induced by anti-IgE (3 micrograms/ml), probably due to receptor desensitization, rhSCF (1 ng/ml to 3 micrograms/ml) neither caused release of histamine or leukotriene C4 (LTC4) release from leukocytes of 14 donors, nor induced a rise in intracellular Ca2+ levels in purified (greater than 70%) basophils. Brief preincubation (10 min) of leukocytes with rhSCF (1 ng/ml to 3 micrograms/ml) caused an enhancement (69 +/- 11%) of anti-IgE-induced release of histamine that was significant at concentrations as low as 3 ng/ml (p less than 0.05), whereas it appeared less effective in potentiating IgE-mediated LTC4 release. In contrast, a prolonged incubation (24 h) with rhSCF (0.1 pg/ml to 100 ng/ml) did not enhance the release of histamine or LTC4 induced by anti-IgE (0.1 microgram/ml), whereas rhIL-3 (3 ng/ml) significantly potentiated the release of both mediators.(ABSTRACT TRUNCATED AT 400 WORDS)     

Differential effect of glycolytic intermediaries upon cyclic ADP-ribose-, inositol 1',4',5'-trisphosphate-, and nicotinate adenine dinucleotide phosphate-induced Ca(2+) release systems.

We investigated the effect of glycolytic pathway intermediaries upon Ca(2+) release induced by cyclic ADP-ribose (cADPR), inositol 1',4', 5-trisphosphate (IP(3)), and nicotinate adenine dinucleotide phosphate (NAADP) in sea urchin egg homogenate. Fructose 1,6, -diphosphate (FDP), at concentrations up to 8 mM, did not induce Ca(2+) release by itself in sea urchin egg homogenate. However, FDP potentiates Ca(2+) release mediated by agonists of the ryanodine channel, such as ryanodine, caffeine, and palmitoyl-CoA. Furthermore, glucose 6-phosphate had similar effects. FDP also potentiates activation of the ryanodine channel mediated by the endogenous nucleotide cADPR. The half-maximal concentration for cADPR-induced Ca(2+) release was decreased approximately 3.5 times by addition of 4 mM FDP. The reverse was also true: addition of subthreshold concentrations of cADPR sensitized the homogenates to FDP. The Ca(2+) release mediated by FDP in the presence of subthreshold concentrations of cADPR was inhibited by antagonists of the ryanodine channel, such as ruthenium red, and by the cADPR inhibitor 8-Br-cADPR. However, inhibition of Ca(2+) release induced by IP(3) or NAADP had no effect upon Ca(2+) release induced by FDP in the presence of low concentrations of cADPR. Furthermore, FDP had inhibitory effects upon Ca(2+) release induced by both IP(3) and NAADP. We propose that the state of cellular intermediary metabolism may regulate cellular Ca(2+) homeostases by switching preferential effects from one intracellular Ca(2+) release channel to another.     

Inhibitory effect of xanthones isolated from the pericarp of Garcinia mangostana L. on rat basophilic leukemia RBL-2H3 cell degranulation

Mangostin, Garcinia mangostana L. is used as a traditional medicine in southeast Asia for inflammatory and septic ailments. Hitherto we indicated the anticancer activity induced by xanthones such as alpha-, beta-, and gamma-mangostin which were major constituents of the pericarp of mangosteen fruits. In this study, we examined the effect of xanthones on cell degranulation in rat basophilic leukemia RBL-2H3 cells. Antigen (Ag)-mediated stimulation of high affinity IgE receptor (FcepsilonRI) activates intracellular signal transductions resulting in the release of biologically active mediators such as histamine. The release of histamine and other inflammatory mediators from mast cell or basophils is the primary event in several allergic responses. These xanthones suppressed the release of histamine from IgE-sensitized RBL-2H3 cells. In order to reveal the inhibitory mechanism of degranulation by xanthones, we examined the activation of intracellular signaling molecules such as Lyn, Syk, and PLCgammas. All the xanthones tested significantly suppressed the signaling involving Syk and PLCgammas. In Ag-mediated activation of FcepsilonRI on mast cells, three major subfamilies of mitogen-activated protein kinases were activated. The xanthones decreased the level of phospho-ERKs. Furthermore, the levels of phospho-ERKs were observed to be regulated by Syk/LAT/Ras/ERK pathway rather than PKC/Raf/ERK pathway, suggesting that the inhibitory mechanism of xanthones was mainly due to suppression of the Syk/PLCgammas/PKC pathway. Although intracellular free Ca(2+) concentration ([Ca(2+)](i)) was elevated by FcepsilonRI activation, it was found that alpha- or gamma-mangostin treatment was reduced the [Ca(2+)](i) elevation by suppressed Ca(2+) influx.     

Modulatory effect of HCO3- on rat mast cell exocytosis: cross-talks between bicarbonate and calcium.

HCO-3 modulation of histamine release and its relationship with the Ca2+ signal were studied in serosal rat mast cells. Histamine release was induced by Ca2+ mobilizing stimuli, namely compound 48/80, thapsigargin, Ca2+ chelators, ionophore A23187, and PMA and ionophore A23187 in a HCO-3-buffered medium or a HCO-3-free medium. The presence of HCO-3 reduced histamine release by 48/80, Ca2+ chelators, A23187, and PMA/A23187, but increased histamine release induced by thapsigargin. Histamine release by PMA was significantly higher in a HCO-3-free medium than in a HCO-3-free medium, as it was the PMA potentiation of histamine release by A23187. [Ca2+]i changes induced by these drugs were measured in fura-2-loaded mast cells. In thapsigargin and EGTA or BAPTA preincubated mast cells [Ca2+]i increase was higher in a HCO-3-buffered medium than in a HCO-3-free medium in the presence of Ca2+. On the contrary, in compound 48/80 and PMA/A23187 activated mast cells the [Ca2+]i increase is the same both in the presence and in the absence of HCO-3. The effect of HCO-3 on histamine release in serosal rat mast cells depends on the stimulus, but it is not related to the presence of Cl-. In thapsigargin-stimulated mast cells the effect of HCO-3 on histamine release may be related to the Ca2+ signal, but in compound 48/80, EGTA, and PMA/A23187-activated mast cells there is no relationship between intracellular Ca2+ and the inhibitory effect of HCO-3 on histamine release. Additionally, the PKC pathway is implicated in the inhibitory effect of HCO-3 on histamine release, the higher the chelation of calcium rendering the higher the enhancement of the response after adding calcium in the absence of HCO-3.     

Amomum xanthiodes inhibits mast cell-mediated allergic reactions through the inhibition of histamine release and inflammatory cytokine production

In this study, we investigated the effect of Amomum xanthiodes (Zingiberaceae) extract (AXE) on the mast cell-mediated allergy model and studied the possible mechanism of action. We found that AXE inhibited compound 48/80-induced systemic reactions and plasma histamine release in mice. Additionally, AXE decreased immunoglobulin E (IgE)-mediated local allergic reactions and passive cutaneous anaphylaxis (PCA), and AXE dose-dependently attenuated the release of histamine from rat peritoneal mast cells (RPMC) activated by compound 48/80 or IgE. The amounts of AXE needed for inhibition of compound 48/80-induced plasma histamine release and PCA were similar to disodium cromoglycate, the known anti-allergic drug. We found that AXE increased the cAMP levels and decreased the compound 48/80-induced intracellular Ca2+. Furthermore, AXE attenuated the phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore (A23187)-stimulated tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 secretion in human mast cells. The inhibitory effect of AXE on the proinflammatory cytokines was nuclear factor-kappaB (NF-kappaB)-dependent. In addition, AXE decreased PMA plus A23187-induced degradation of IkappaBalphaand the nuclear translocation of NF-kappaB. Our findings provide evidence that AXE inhibits mast cell-derived immediate-type allergic reactions, and that cAMP, intracellular Ca2+, proinflammatory cytokines, and NF-kappaB are involved in these effects.     

Inhibitory effect of diethylstilbestrol on histamine release by rat mast cells and its relation to the cellular ATP content

The effect of diethylstilbestrol, a synthetic estrogen, on mast cell secretion was investigated. The results showed that 50 microM diethylstilbestrol inhibited histamine release from rat peritoneal mast cells in the presence and absence of glucose, but did not affect 45Ca uptake stimulated by concanavalin A. Diethylstilbestrol also inhibited histamine release induced by compound 48/80, exogenous ATP, or ionophore A23187. Since estradiol benzoate, hexestrol and daidzein were not inhibitory, the inhibitory action of diethylstilbestrol must be independent of its estrogenic activity. The ATP content of mast cells decreased to less than 0.1 nmol/10(6) cells on treatment with 50 microM diethylstilbestrol at 37 degrees C for 15 min. This effect of diethylstilbestrol in decreasing the ATP content of mast cells correlated well with its inhibitory effect on histamine release. Diethylstilbestrol at 50 microM depleted the cells of ATP at 37 degrees C, but not at 0 degrees C, whereas [3H]diethylstilbestrol ( [monoethyl-3H]diethylstilbestrol) binding to rat mast cells was the same at 0 and 37 degrees C. It is concluded that diethylstilbestrol reduced the ATP content of rat mast cells by inhibiting metabolism of the cells, and consequently inhibited degranulation.     

Effects of membrane depolarization and divalent cations on anaphylactic histamine secretion

The effects of membrane depolarization and divalent cations on histamine release have been studied in sensitized mast cells. Membrane potential of these cells has been measured with intracellular microelectrodes. Our results show that mast cells have a large resting potential (-61 +/- 12 mV) however they do not generate active membrane electrical responses when are depolarized by passing current through the recording microelectrode. High external K+ does not increase histamine release. Histamine secretion is supported by alkali-earth divalent cations (Ca2+ greater than Sr2+ greater than Ba2+) but strongly inhibited by transition metals. Ca2+ concentrations above 1 mM inhibit histamine release, however, this effect is not mimicked by Sr2+ and Ba2+.     

Mechanisms of mouse mast cell activation and inactivation for IgE-mediated histamine release.

The IgE-mediated histamine release from mouse mast cells requires Ca++, is optimal at 37 degrees C, and is enhanced by phosphatidylserine. The rate of release is relatively slow. The mast cells can be activated to release histamine by either anti-IgE or anti-Fab antibodies and, in the case of cells from sensitized mice, by the immunizing antigen. The incubation of mast cells with antigen in the absence of Ca++ or phosphatidylserine fails to release histamine. Such cells are desensitized to the further addition under optimal conditions of the same antigen. Desensitization is antigen specific, requires optimal levels of antigen, and occurs at both 30 degrees and 37 degrees C. In contrast, anti-IgE desensitizes all IgE-mediated histamine release reactions.     

Role of cyclic AMP during histamine release. Histamine release is not directly related to increase in cyclic AMP levels in rat mast cells activated by concanavalin A, anti-IgE, antigen, prostaglandin D2 and isoproterenol

Activation of mast cells by bridging of IgE-receptors or concanavalin A (Con A) results in a rapid initial rise and fall in cyclic AMP (cAMP) levels followed by a second rise in cAMP levels and histamine release (Sullivan, T. et al. (1976) J. Immunol. 117, 713-716; Lewis, R.A. et al. (1979) J. Immunol. 123, 1663-1668; Ishizaka, T. et al. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 6812-6816). trans-4-Guanidinomethylcyclohexanecarboxylic acid 4-tert-butylphenyl ester (GMCHA-OPhBut), a strong trypsin inhibitor and an anti-allergic agent (Muramatu, M. et al. (1982) Hoppe-Seyler's Z. Physiol. Chem. 363, 203-211; Takei, M. et al. Agents Actions, in press), strongly and dose-dependently inhibited the initial and second rises in cAMP levels, and release of histamine from rat mast cells by Con A, anti-IgE and antigen. Addition of GMCHA-OPhBut after the initial rise in cAMP inhibited the second rise in cAMP and histamine release. These results suggested a possible participation of a trypsin-like proteinase, probably pH 7 tryptase present in rat mast cells, in the activation of adenylate cyclase by the above secretagogues, and the initial rise in cAMP was not directly related to the latter events. The second rise in cAMP is induced by prostaglandin D2 (PGD2), a metabolic product of arachidonic acid. PGD2 elevated the cAMP levels in mast cells whereas no histamine was secreted. GMCHA-OPhBut did not inhibit the increase in cAMP by PGD2. Therefore, the strong inhibitory effect of GMCHA-OPhBut on the second rise in cAMP might depend on the inhibition of an earlier process than the activation of adenylate cyclase by PGD2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of disodium cromoglycate on mast cell-mediated immediate-type allergic reactions

We investigated the effect of disodium cromoglycate (DSCG) on mast cell-mediated immediate-type hypersensitivity. DSCG inhibited systemic allergic reaction induced by compound 48/80 dose-dependently. Passive cutaneous anaphylaxis was inhibited by 71.6% by oral administration of DSCG (1 g/kg). When DSCG was pretreated at concentration rang from 0.01-1000 g/kg, the serum histamine levels were reduced in a dose dependent manner. DSCG also significantly inhibited histamine release from rat peritoneal mast cell (RPMC) by compound 48/80. We confirmed that DSCG inhibited compound 48/80-induced degranulation of RPMC by alcian blue/nuclear fast red staining. In addition, DSCG showed a significant inhibitory effect on anti-dinitrophenyl IgE-mediated tumor necrosis factor-alpha production. These results indicate that DSCG inhibits mast cell-mediated immediate-type allergic reaction.     

Differential calcium effects on prostaglandin D2 generation and histamine release from isolated rat peritoneal mast cells

We examined the role of Ca2+ mobilization in prostaglandin (PG) D2 generation and histamine release induced by A23187 from rat peritoneal mast cells. Both PGD2 generation and histamine release accompanied with 45Ca uptake were observed above 0.1 microM A23187. Although an increase of PGD2 generation was not exactly correlated with that of Ca2+ uptake, histamine release occurred in proportion to Ca2+ uptake. In contrast to PGD2 generation, below 0.1 microM A23187, about 20% of the total histamine was released without Ca2+ uptake and this response was inhibited by 10 microM 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), which is an intracellular Ca2+ antagonist. However, TMB-8 had no effect on PGD2 generation. These results suggest that Ca2+ dependency of histamine release is clearly different from that of PGD2 generation, and that histamine release is induced by not only Ca2+ uptake but also intracellular Ca2+ mobilization.     

Amplification of Ca2+ signaling by diacylglycerol-mediated inositol 1,4,5-trisphosphate production

Stimulation of various cell surface receptors leads to the production of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) through phospholipase C (PLC) activation, and the IP3 and DAG in turn trigger Ca2+ release through IP3 receptors and protein kinase C activation, respectively. The amount of IP(3) produced is particularly critical to determining the spatio-temporally coordinated Ca(2+)-signaling patterns. In this paper, we report a novel signal cross-talk between DAG and the IP3-mediated Ca(2+)-signaling pathway. We found that a DAG derivative, 1-oleoyl-2-acyl-sn-glycerol (OAG), induces Ca2+ oscillation in various types of cells independently of protein kinase C activity and extracellular Ca2+. The OAG-induced Ca2+ oscillation was completely abolished by depletion of Ca2+ stores or inhibition of PLC and IP3 receptors, indicating that OAG stimulates IP3 production through PLC activation and thereby induces IP3-induced Ca2+ release. Furthermore, intracellular accumulation of endogenous DAG by a DAG-lipase inhibitor greatly increased the number of cells responding to agonist stimulation at low doses. These results suggest a novel physiological function of DAG, i.e. amplification of Ca2+ signaling by enhancing IP3 production via its positive feedback effect on PLC activity.