Effect of NMDA receptor ligands on mast cell histamine release, a reappraisal

Natural polyamines have been proposed to induce histamine release from mast cells through a direct interaction with G proteins. Alternatively, the polyamine binding site of ionotropic N-methyl-d-aspartate (NMDA) receptors has been suggested as a target for spermine on mast cells. We reexamined both hypotheses. Incubation of rat peritoneal mast cells with spermine resulted in a concentration-dependent histamine release (EC₅₀ 270 μM). Incubation with NMDA receptor agonists, glutamate or NMDA, associated to the co-agonist glycine, did not induce secretion. Western blot experiments did not reveal NMDA R1, R2a, R2b or R2c subunit expression in rat peritoneal mast cell membranes. The NMDA receptor antagonist at the glycine site, L-689,560, did not modify, at relevant concentrations, the spermine-induced secretion. The NMDA receptor antagonists, ifenprodil and LY 235959, and the NMDA channel blocker, MK801, slightly inhibited, at high concentrations, the secretory effect of spermine. The polyamine arcaine, an antagonist of the NMDA receptor polyamine binding site, induced histamine secretion (EC₅₀ 350 μM). Both spermine- and arcaine-induced effects were independent upon extracellular calcium and were largely inhibited by treatment of mast cells with pertussis toxin or benzalkonium chloride. The response to spermine and arcaine was prevented by the hydrolysis of sialic acid residues of the cell surface by neuraminidase, and was restored by permeabilization of the plasma membrane with streptolysine-O, indicating that polyamines act intracellularly. These results confirm the involvement of pertussis toxin-sensitive G proteins in the secretory effect of polyamines and demonstrate the absence of NMDA receptors on rat peritoneal mast cells. Nonselective effects of some NMDA receptor ligands on mast cells cannot be excluded. Received: 28 December 1998 / Accepted: 19 March 1999     

Characterization of the prostaglandin E receptor expressed on a cultured mast cell line,BNu-2c13

Interleukin 3-dependent BNu-2c13 mast cells, mucosal type-like mast cells, exhibited a specific high-affinity binding site for [³H]prostaglandin (PG) E₂. The binding was completely displaced by M&B 28767, an EP₃-selective agonist, but not by EP₁- or EP₂-selective ligands, indicating that the PGE₂ binding site is of the EP₃ subtype PGE receptor. Whereas the EP₃ subtype is presumed to be coupled to inhibition of adenylate cyclase in various tissues and cells, in BNu-2c13 cells PGE₂ had no ability to inhibit adenylate cyclase activity, while it induced concentration-dependent stimulation of phosphoinositide metabolism and caused an increase in the intracellular free Ca²⁺ concentration in a pertussis toxin-sensitive manner. PGE₂ by itself did not evoke histamine release from the cells, but it markedly stimulated histamine release in concert with ionomycin, a Ca²⁺ ionophore. The PGE₂-stimulated release was also comletely blocked by pertussis toxin. Thus, the PGE receptor expressed on BNu-2c13 mast cells is of the EP₃ subtype and is linked to phosphoinositide metabolism via a pertussis toxin-sensitive G protein, and this activation leads to histamine release.     

A pertussis toxin-sensitive G protein is required to induce histamine release from rat peritoneal mast cells by bradykinin.

Bradykinin, kallidin (Lys-bradykinin) and [Thi 5,8, D-Phe7]-bradykinin, a functional B2 antagonist, induce histamine release from rat peritoneal mast cells. The histamine release is dependent upon added calcium when mast cells are placed in calcium-free medium 30 min before being triggered with the kinins. Histamine release was dose-dependently inhibited by pertussis toxin (1-100 ng/ml) and by benzalkonium chloride (0.1-3 micrograms/ml). The efficiency of ionophore A23187 on histamine release was affected neither by pertussis toxin nor by benzalkonium chloride. The parallel response of rat peritoneal mast cells to kinins and to substance P suggest that these peptides have the same mechanisms of action i.e. activation of a pertussis toxin-sensitive G protein and of phospholipase C defining a peptidergic triggering pathway of mast cells.     

Inhibition of GTPase activity of Gi proteins and decreased agonist affinity at M2 muscarinic acetylcholine receptors by spermine and methoctramine.

1. The effects of spermine and methoctramine, a selective M2 muscarinic receptor antagonist, were studied on the high-affinity GTPase activity of G proteins, and on ligand binding to M2 muscarinic receptors in pig heart sarcolemma. 2. The spontaneous GTP hydrolysis by pig heart sarcolemma and its stimulation by mastoparan or carbachol were prevented by pertussis toxin and inhibited by methoctramine (IC50s: 21, 13 and 0.005 microM, respectively), and spermine (IC50s: 967, 278 and 11 microM). Spermine and methoctramine also inhibited spontaneous GTP hydrolysis by rat peritoneal mast cell membranes which do not respond to carbachol. 3. The neutral muscarinic antagonists, AF-DX 116 and atropine, did not modify the inhibitory effect of high concentrations of methoctramine, indicating that this effect was not related to the antagonist binding site of muscarinic receptors. We suggest that methoctramine behaves as a receptor antagonist at nanomolar concentrations and interacts with G proteins at micromolar concentrations. 4. Spermine did not modify the binding of the tritiated muscarinic antagonist [3H]-NMS, but decreased the binding of the agonist [3H]-Oxo-M. Spermine elicited a rightward shift of the carbachol/[3H]-NMS binding isotherm with a decrease in the proportion of sites with high-affinity for carbachol, suggesting that polyamines uncouple Gi proteins from receptors. 5. The inhibition of GTPase activity by polyamines, preventing the re-association of alpha and betagamma subunits of Gi proteins, might sustain the regulatory effect of Gi subunits on downstream effectors. The level of intracellular polyamines might be important for the control of the transduction of extracellular signals through Gi protein-coupled receptors.     

Lysophosphatidic acid (LPA) induces plasma exudation and histamine release in mice via LPA receptors

Lysophosphatidic acid (LPA), the simplest of the water-soluble phospholipids, can evoke various biological responses. The present study examined the activity of LPA to induce plasma exudation and histamine release in mice. Plasma exudation was assessed by extravasation of Evans blue. Subcutaneous administration of LPA (1 - 100 microg/site) led to increased plasma exudation in the skin. The LPA-induced plasma exudation was inhibited by ketotifen, a histamine H1-receptor antagonist, and diacylglycerol pyrophosphate (DGPP), a LPA1/LPA3-receptor antagonist. Moreover, pretreatment with pertussis toxin and DGPP inhibited the histamine release from peritoneal mast cells induced by LPA. These findings indicate that plasma exudation induced by LPA is mediated by histamine release from mast cells via LPA receptor(s), presumably LPA1 and/or LPA3, coupled to G(i/o) proteins. Moreover, these findings point to a role of LPA in the pathomechanisms of various allergic disorders.     

Neurotensin stimulation of mast cell secretion is receptor-mediated, pertussis-toxin sensitive and requires activation of phospholipase C

Pretreatment of isolated rat serosal mast cells with U-73122, an aminosteroid inhibitor of phospholipase C, inhibited histamine secretion in response to neurotensin (NT). This inhibition reached a maximum after 1 h of pretreatment at 37 degrees C and was dependent upon the concentration of U-73122 (IC50 approximately 0.2 microM). The inactive analog, U-73343, had no effect on the secretory response to NT. Pretreatment of mast cells with U-73122 also blocked histamine secretion in response to substance P (SP), mastoparan (MP), compound 48/80, or amidated NT (NT-NH2). Stimulation of mast cells by NT was accompanied by a rise in the level of intracellular free calcium and a rapid (within seconds) increase in the level of inositol trisphosphate (IP3) which was inhibited by pretreatment of the cells with U-73122. Pretreatment of isolated mast cells with pertussis toxin (PTx) blocked histamine release in response to NT as well as to all peptides tested. PTx had no effect on histamine secretion elicited by anti-IgE stimulation of sensitized mast cells. Pretreatment of mast cells with SR 48692, a NT-receptor antagonist, had no effect on histamine release induced by MP. At a high concentration (100 nM) SR 48692 partially inhibited the response to NT-NH2. These results, together with our earlier findings with SR 48692, indicate that the signal transduction pathway in mast cells activated by NT requires a specific NT-receptor, the activation of phospholipase C, and the involvement of a PTx sensitive G protein. The peptides SP and MP, and compound 48/80, while also requiring the activation of PLC and a PTx sensitive G protein, are not inhibited by the NT-R antagonist, SR 48692, suggesting that they exert their actions either via a different mast cell receptor or via a receptor-independent mechanism.     

Effects of ATP on Phosphoinositide Hydrolysis and Prostaglandin E2 Generation in Rabbit Astrocytes

Extracellular ATP secreted from stimulated nerves plays a role in neurotransmission. This study examined the effects of extracellular ATP on phospholipase A₂ and C signalling pathways in rabbit astrocytes. ATP caused prostaglandin E₂ (PGE₂) generation and phosphoinositide hydrolysis in a time- and concentration-dependent manner. A P_2y purinoceptor-selective agonist, 2-methylthio-ATP also caused phosphoinositide hydrolysis, but not PGE₂ generation. A P_2x purinoceptor-selective agonist, α,β-methylene-ATP did not cause either phosphoinositide hydrolysis or PGE₂ generation. Although pertussis toxin had no effect on 2-methylthio-ATP-induced phosphoinositide hydrolysis, it markedly decreased ATP-induced PGE₂ generation, with significant inhibition of phosphoinositide hydrolysis. Dexamethasone and indomethacin which potently inhibited ATP-induced PGE₂ generation, caused partial inhibition of phosphoinositide hydrolysis, suggesting that pertussis toxin-sensitive component of ATP-induced phospholipase C activation is mediated by cyclo-oxygenase metabolites of arachidonic acid. These results suggest that a stimulation of P_2y receptor results in phospholipase C activation in a pertussis toxin-insensitive manner, and that a P₂ receptor other than the P_2y or P_2x subtypes is involved in ATP-induced phospholipase A₂ activation via a pertussis toxin-sensitive G protein.     

Mechanism of histamine release induced by levofloxacin, a fluoroquinolone antibacterial agent

The present study was designed to clarify the mechanism of histamine release caused by levofloxacin, a fluoroquinolone antibacterial agent, using rat peritoneal mast cells. Levofloxacin induced a concentration-dependent histamine secretion from 300 microg/ml without lactate dehydrogenase leakage, and the release was rapidly completed within 30 s. This action was dependent on temperature, energy, pH and intracellular Ca(2+), similarly to the effect of compound 48/80, a basic compound. Unlike that with the calcium ionophore A23187, histamine secretion due to levofloxacin or compound 48/80 was prevented by pretreatment with either pertussis toxin or benzalkonium chloride, a selective inhibitor of G proteins of G(i) subtypes. Moreover, the histamine release elicited by levofloxacin or compound 48/80 was suppressed by hydrolysis of sialic acid residues on the cell surface brought about by neuraminidase. These results demonstrate that the mechanism by which levofloxacin exerts histamine release may be closely linked to activation of pertussis toxin-sensitive G proteins.     

Inhibition by calcium antagonists of histamine release and calcium influx of rat mast cells: Difference between induction of histamine release by concanavalin A and compound 48/80

The relation between calcium influx and histamine release from rat mast cells was investigated. When purified mast cells pretreated with a calcium antagonist (MnCl₂ or methoxyverapamil (D-600)) were exposed to concanavalin A or compound 48/80 in Tyrode solution (pH 7.4) at 37°C, the calcium antagonists inhibited the extracellular calcium-dependent component of concanavalin A-induced histamine release. MnCl₂ also inhibited the extracellular calcium-dependent component of compound 48/80-induced histamine release, whereas D-600 did not inhibit the release. D-600 inhibited the ⁴⁵Ca uptake induced by concanavalin A, but did not inhibit the ⁴⁵Ca uptake induced by compound 48/80. It was found that the inhibitory action of calcium antagonists depended on the uptake of extracellular calcium. These observations suggest that concanavalin A and compound 48/80 stimulate different mechanisms of calcium influx. Studies on inactivation of the mechanisms of calcium influx showed that calcium influx into cells activated by concavalin A stopped when concanavalin A was washed out, whereas the influxactivated by compound 48/80 was still operative after compound 48/80 had been washed out.     

Evidence for the interaction of mast cell-degranulating peptide with pertussis toxin-sensitive G proteins in mast cells.

K(+)-channel blocker properties have been reported for mast cell-degranulating peptide (MCD) in the central nervous system, but its action mechanism in mast cells remains unknown. We studied the effect of MCD on the membrane potential of rat peritoneal mast cells using the fluorescent probe bis-oxonol. Unexpectedly, MCD induced a decrease in bis-oxonol fluorescence, in a rapid and then a slower phase, suggesting hyperpolarization of mast cells. Other K(+)-channel blockers, tetraethylammonium and 4-aminopyridine, did not significantly modify the bis-oxonol fluorescence and did not alter the effect of MCD. The late phase of bis-oxonol fluorescence decrease was inhibited by ouabain and by potassium deprivation, whereas histamine release was not affected. The first phase of putative hyperpolarization induced by MCD coincided with histamine release and with the generation of inositol polyphosphates. Prior treatment of the cells with pertussis toxin inhibited these effects of MCD. MCD stimulated the GTPase activity of purified G proteins (G0/Gi) in a concentration-dependent manner. These results indicate that the effect of MCD on mast cells is unrelated to K+ channels but that it is relevant to the activation of pertussis toxin-sensitive G proteins leading to the activation of phospholipase C. A direct interaction of MCD with G proteins is proposed, which, unlike mastoparan, does not require positive cooperativity.     

Identification of G protein-coupled receptors potently stimulating migration of human transitional-cell carcinoma cells

The expression of G protein-coupled receptors inducing calcium mobilization and stimulating cell migration was examined in human transitional-cell carcinoma (J82) cells. Measurements of cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) and phospholipase C activity indicated that these cells express several calcium-mobilizing receptors, including those for lysophosphatidic acid (LPA), thrombin, bradykinin, bombesin and histamine, of which only the LPA response was sensitive (∼ 50%) to pertussis toxin (PTX). Migration of J82 cells was strongly stimulated by LPA and thrombin, by 5- to 20-fold, whereas bradykinin, bombesin and histamine were ineffective. Migration induced by either LPA or thrombin was inhibited by the actin cytoskeleton-disrupting agent, cytochalasin B, by the Rho protein-inactivating Clostridium difficile toxin B, by preventing [Ca²⁺]_i transients with an intracellular calcium-chelating agent, and by the phorbol ester, phorbol 12-myristate 13-acetate, which also blocked the LPA- and thrombin-induced [Ca²⁺]_i increases. On the other hand, ADP-ribosylation of G_i type G proteins by PTX abrogated the migratory response to LPA, without affecting the thrombin effect. Similarly, raising cAMP levels inhibited, by about 50%, the LPA- but not the thrombin-induced J82 cell migration. In conclusion, human transitional-cell carcinoma (J82) cells express various G protein-coupled, calcium-mobilizing receptors, out of which only those for LPA and thrombin stimulate cell migration, indicating that phospholipase C-derived second messengers per se are not sufficient for initiating this response. The complex signal transduction processes leading to LPA- and thrombin-stimulated motility of these human carcinoma cells apparently involve several common, essential factors, such as [Ca²⁺]_i changes and Rho protein-regulated reorganization of the cytoskeleton, as well as some distinct components, most notably distinct subtypes of heterotrimeric G proteins and apparently also distinct cAMP-sensitive targets. Received: 25 June 1997 / 8 August 1997     

G Proteins endogenously expressed in Sf 9 cells: interactions with mammalian histamine receptors

Expression of functionally active mammalian histamine H₁- and H₂-receptors was recently demonstrated in Sf9 cells. Either receptor elicited phosphoinositide degradation leading to an increased cytoplasmic calcium concentration. In the present study we focussed on identifying the Sf9 guanine nucleotide-binding proteins (G proteins) involved. Immunodetection of Sf9 membranes showed expression of Gα isoforms belonging to all four G protein subfamilies. During prolonged baculovirus infection of Sf9 cells, binding of guanosine 5’-o-(3-thiotriphosphate) as well as the intensities of G protein immunoreactivity, pertussis toxin-mediated ADP-ribosylation, GTP azidoanilide labelling of Gα, and phosphate-labelling of Gβ declined in cell membranes. Some 48h after infection with mammalian histamine receptor-encoding viruses virtually no functional coupling of ligand-activated receptors to insect G proteins was observed despite a high level of expressed receptors. In contrast, Sf9 cells infected only for 28h allowed studies on histamine-induced G protein coupling. In membranes obtained from H₁-receptor-expressing cells, histamine increased incorporation of GTP azidoanilide into G _q/11-like proteins whereas in membranes containing H₂-receptors histamine enhanced GTP azidoanilide-labelling of G _q/11-like and G_s-like proteins. In fura-loaded H₁- and H₂-receptor-expressing cells histamine induced the release of calcium from intracellular stores. This study shows firstly that Sf9 G proteins couple to mammalian histamine receptors and secondly that H₁-receptors activate only G_q/11, whereas H₂-receptors activate G_q/11 and G_s, but neither receptor couples to G_i/o or G₁₂. Finally, the time following baculovirus infection is critical for studying the functional coupling between recombinantly expressed and endogenous signal transduction components. Received: 24 January 1997 /Accepted: 14 April 1997     

Intradermal application of nociceptin increases vascular permeability in rats: the possible involvement of histamine release from mast cells

Intradermal application of nociceptin was used to investigate its in vivo effect on the inflammatory response in rats. Intradermal nociceptin (5 pmol/site-5 nmol/site) increased vascular permeability in a dose-dependent manner. The increased vascular permeability by nociceptin (5 nmol/site) was dose-dependently inhibited by the histamine H1 receptor antagonist pyrilamine (50 pmol/site-5 nmol/site). In rat peritoneal mast-cell preparation, nociceptin (10(-8)-10(-4) M) dose-dependently stimulated histamine release. The effect of nociceptin (10(-5) M) occurred rapidly (within 30 s) and was inhibited by pertussis toxin, Ca2+, but was not sensitive to naloxone, a classical opioid receptor antagonist. These characteristics are in agreement with features of the opioid-receptor-like 1 (ORL1) receptor, a non-classical opioid receptor linked to a pertussis toxin-sensitive G protein. Taken together, these data suggest that nociceptin, likely acting via the ORL1 receptor at the site of inflammation, might be critical for the enhancement of the inflammatory response by stimulating histamine release from mast cells.     

Stimulation of histamine H2- (and H1)-receptors activates Ca2+ influx in all-atrans-retinoic acid-differentiated HL-60 cells independently of phospholipase C or adenylyl cyclase

In human neutrophils, histamine H₂-receptors mediate activation of adenylyl cyclase (AC) and inhibition of N-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP)-induced superoxide anion (0 _inf2 ^sup– ) formation, and in HL-60 promyelocytes, H₂-receptors mediate parallel activation of AC, phospholipase C (PLC) and non-selective cation (NSC) channels. As all-trans-retinoic acid (RA) is successfully used in the differentiation therapy of acute promyelocytic leukaemia, we studied signal transduction in RA-differentiated HL-60 cells. Histamine and the H₂-receptor agonist, impromidine, induced both rises in cAMP levels and cytosolic Ca²⁺ ([Ca²⁺]_i). Substances acting at post-receptor sites to increase cAMP did not increase [Ca²⁺]_i. H₂-but not H₁-receptor antagonists inhibited histamine-induced cAMP accumulation and rises in [Ca²⁺]_i were more effectively inhibited by H₂- than by H₁-receptor antagonists. Histamine-induced rises in [Ca²⁺]_i were completely dependent on the presence of extracellular Ca²⁺ and were abolished by the blocker of NSC channels, Gd³⁺, but were resistant to inhibition by pertussis toxin. Unlike FMLP, histamine did not activate PLC. The effects of FMLP on [Ca²⁺]_i were less sensitive to blockade by Gd³⁺ than those of histamine, and there was no cross-desensitization between the two stimuli. FMLP, but not histamine, inhibited transiently thapsigargin-induced rises in [Ca²⁺]₁. Taken together, our results show that histamine activates AC-mediated cAMP accumulation in RA-differentiated HL-60 cells via H₂-receptors and NSC channel-mediated Ca²⁺ influx via H₂- (and H₁)-receptors. Histamine-induced NSC channel activation is not the consequence of AC- or PLC stimulation and occurs, directly or indirectly, via pertussis toxin-insensitive guanine nucleotide-binding proteins. FMLP and histamine activate Ca²⁺ influx by different mechanisms. There are similarities in H₂-receptor-mediated signal transduction between RA-differentiated HL-60 cells and HL-60 promyelocytes and differences between the former cells and neutrophils, indicating that RA-differentiated HL-60 cells must be considered as partially immature.     

The role of the Annexin-A1/FPR2 system in the regulation of mast cell degranulation provoked by compound 48/80 and in the inhibitory action of nedocromil

• 1.We investigated the role of Annexin (ANX)-A1 and its receptor, ALX/FPR2, in the regulation of mast cell degranulation produced by compound 48/80.
• 2.Both human cord-blood derived mast cells (CBDMCs) and murine bone marrow derived mast cells (BMDMCs) release phosphorylated ANX-A1 during treatment with glucocorticoids or the mast cell ‘stabilising’ drugs ketotifen and nedocromil.
• 3.Compound 48/80 also stimulated ANX-A1 phosphorylation and release and this was also potentiated by nedocromil. Anti-ANX-A1 neutralising monoclonal antibodies (Mabs) enhanced the release of pro-inflammatory mediators in response to compound 48/80.
• 4.Nedocromil and ketotifen potently inhibited the release of histamine, PGD₂, tryptase and β-hexosaminidase from mast cells challenged with compound 48/80. Anti-ANX-A1 neutralising Mabs prevented the inhibitory effect of these drugs.
• 5.BMDMCs derived from Anx-A1^−/− mice were insensitive to the inhibitory effects of nedocromil or ketotifen but cells retained their sensitivity to the inhibitory action of hu-r-ANX-A1.
• 6.The fpr2/3 antagonist WRW4 blocked the action of nedocromil on PGD₂, but not histamine, release. BMDMCs derived from fpr2/3^−/− mice were insensitive to the inhibitory effects of nedocromil on PGD₂, but not histamine release.
• 7.Compound 48/80 stimulated both p38 and JNK phosphorylation in CBDMCs and this was inhibited by nedocromil. Inhibition of p38 phosphorylation was ANX-A1 dependent.
• 8.We conclude that ANX-A1 is an important regulator of mast cell reactivity to compound 48/80 exerting a negative feedback effect through a mechanism that depends at least partly on the FPR receptor.

     

Molecular basis for cellular effects of naturally occurring polyamines.

The naturally occurring polyamines, putrescine, spermidine and spermine, and the analogue cadaverine, induce a dose-dependent histamine release from rat peritoneal mast cells. Spermine was the most active among these polycationic metabolites, followed by spermidine and putrescine. The histamine release was inhibited by a 2 h pretreatment of the cells with pertussis toxin (100 ng/ml), demonstrating the involvement of a pertussis toxin-sensitive GTP-binding regulatory protein during the exocytotic process. Experiments performed with purified Go/Gi proteins reconstituted into phospholipid vesicles showed a direct stimulation of GTPase activity by the polyamines. This direct stimulation of G proteins and the consequent activation of the coupled effectors may represent a new mechanism of action for natural polyamines controlling receptor-dependent processes.     

Histamine inhibits activation of human neutrophils and HL-60 leukemic cells via H2-receptors

Summary The effects of prostaglandin E₁ (PGE₁) and histamine on activation of superoxide (O_22/su–) formation, exocytosis of -glucuronidase and aggregation in human neutrophils and HL-60 leukemic cells were studied. PGE₁, histamine and impromidine, a potent H₂-agonist, inhibited O₂ ^– formation in neutrophils induced by the chemotactic peptide, N-formyl-l,-methionyl-l-leucyl-l-phenylalanine (fMet-Leu-Phe) with IC₅₀ values of 0.5 µM, 8 µM and 2 µM, respectively. The full H₁-agonist and weak partial H₂-agonist, betahistine, was much less potent and effective than histamine. Dibutyryl cyclic AMP and forskolin mimicked the effects of histamine and PGE₁, on O₂ ^– formation. The H2-antagonist, famotidine, competitively reversed histamine-induced inhibition of O₂ ^– formation with a pA₂ value of 7.5. Histamine inhibited O₂ ^– formation when added prior to or after fMet-Leu-Phe. fMet-Leu-Phe-induced aggregation and release of -glucuronidase in neutrophils were less sensitive to inhibition by PGE₁, histamine, dibutyryl cyclic AMP and forskolin than_OZ formation. The inhibitor of cyclic AMP-specific phosphodiesterase, rac-4-(3-butoxy4-methoxybenzyl)-2-imidazolidinone (Ro 20-1724), additively enhanced the inhibitory effects of histamine and PGE₁, on the above cell functions. In HL-60 cells differentiated by dimethyl sulfoxide or dibutyryl cyclic AMP, histamine, impromidine and PGE₁, but not betahistine inhibited fMet-Leu-Phe-induced O₂ ^– formation as well. Our data suggest that histamine inhibits activation of neutrophils and HL-60 cells via H2-receptors through activation of adenylyl cyclase and increased formation of cyclic AMP. As stimulated basophils and mast cells release high quantities of histamine, this intercellular signal molecule may play an inhibitory role in the activation of cytotoxic functions of myeloid cells. Send offprint requests to R. Seifert at the above address     

Effect of triphenyltin chloride on the release of histamine from mast cells

The effects of triphenyltin chloride (TPTC) on the release of histamine from rat and mouse mast cells in vitro and in vivo were investigated. The results obtained are summarized as follows: (a) At doses between 1 and 3 mg/kg, TPTC inhibited the dye leakage due to passive cutaneous anaphylaxis mediated by IgE antibody in mouse ear. At the same doses, TPTC inhibited the swelling due to reversed cutaneous anaphylaxis mediated by IgG antibody in rat. However, TPTC did not affect dye leakage due to histamine, serotonin, and LTC₄ in rat skin; (b) Histamine release by antigen and IgE antibody in rat peritoneal cavity was inhibited by the administration of TPTC at doses between 0.3 and 3 mg/kg; (c) Histamine release by calcium ionophore A 23187 from purified rat peritoneal mast cells in vitro was inhibited by TPTC at concentrations between 10^–7 and 10^–6 M. At the same concentration, TPTC, itself, caused neither the release of histamine nor any change in cell viability which was supported by the activity of lactate dehydrogenase (LDH) from purified rat peritoneal mast cells. All this evidence suggests that TPTC has an inhibitory effect on the release of histamine from mast cells without direct cytotoxicity.     

PEI6, a new basic secretagogue in rat peritoneal mast cells: Characteristics of polyethylenimine PEI6 resemble those of compound 48/80

• 1.1. Polyethylenimine with a molecular weight of 600 (PEI₆) was the simplest and the most useful to investigate mast cell-activating mechanisms via pertussis toxin (IAP)-sensitive G protein pathway.
• 2.2. IAP, lidocaine, or dibutyryl cyclic AMP were inhibitors of the histamine release induced by PEI₆, but anti-allergic drug DSCG, the calcium antagonist, D-600, kinase inhibitors, H-7 and K252a, or the calmodulin inhibitor, W-7 were not.
• 3.3. The additive effects of compound 48/80 and PEI₆ suggested that the action sites for PEI₆ overlapped the binding sites of compound 48/80.
• 4.4. Mast cell activation induced by PEI₆ was sugar-specifically inhibited by N-acetylglucosamine(Glc-NAc)-specific lectins and/or by sialic acid (Sia)-specific lectins, suggesting that the action sites for PEI₆ were glycoproteins having G1cNAc and/or Sia residues.
• 5.5. Four glycoproteins seemed to be involved in histamine release, including the IAP-sensitive G-protein pathway.

     

Differential response of mast cells separated from various organs and basophils of dogs to the fluoroquinolone antimicrobial levofloxacin

Histamine releases induced by the fluoroquinolone antimicrobial levofloxacin (LVFX) were investigated using mast cells separated from various organs and peripheral basophils of dogs, being the most susceptible species to quinolone derivatives, in both in vivo and in vitro systems. An intravenous infusion of LVFX at 30 mg/kg over a 30-min period produced endogenous histamine release from 5 min, and a maximum at 30 min, in which the plasma LVFX concentration was approximately 50 microM. A close correlation (r = 0.87, n = 20) between histamine and LVFX concentrations in plasma during the infusion was observed. In the in vitro study, LVFX at 30 microM or more caused histamine release from mast cells separated from the liver and skin, but not from the gastric mucosa, lung, and peripheral basophils. More exactly, the liver mast cells were most susceptible to LVFX among the organs tested. On the other hand, compound 48/80, a prototype histamine liberator, elicited the histamine release from the liver or skin mast cells at 10 microg/ml, and the calcium ionophore A23187 at 1 microM exhibited the histamine release from the mast cells derived from all organs examined. Histochemical analysis revealed that the liver and skin mast cells had positive reaction for both alcian blue and safranin staining, but the gastric mucosa and lung mast cells were only positive for alcian blue staining, indicating that LVFX preferably activated the connective tissue-type mast cells rather than the mucosal-type mast cells. The degranulation of the liver and skin mast cells brought about by either LVFX or compound 48/80, unlike the calcium ionophore A23187, was blocked by pretreatment with pertussis toxin, suggesting the involvement of pertussis toxin-sensitive G proteins. The results obtained from the canine experiments strongly suggest that LVFX induces histamine release from the connective tissue-type mast cells distributed mainly in the liver, somewhat in the cutaneous tissue, through the activation of pertussis toxin-sensitive G proteins.