calcimycin and oxatomide

Eosinophils are prominent inflammatory cells which play a critical role in the pathogenesis of allergic diseases and bronchial asthma. The aim of this experiment was to examine the effects of oxatomide (CAS 60607-34-3, KW-4354), an antiallergic agent, on oxygen-radical generation and peptide-leukotriene (p-LT) release from guinea pig eosinophils. Ketotifen (CAS 345080-13-7) and epinastine (CAS 80012-43-7) were used as reference drugs. Eosinophils were isolated from the peritoneal exudate of guinea pigs, in which peritoneal eosinophilia had been induced by injection of horse serum. Oxygen-radicals were measured with luminol-dependent chemiluminescence and p-LT release was measured with enzyme immunoassay. When eosinophils were stimulated with phorbol miristate acetate, oxatomide and ketotifen inhibited the oxygen-radical generation with a concentration required for 50% inhibition (IC50) of 11.7 mumol/l and 28.4 mumol/l. Oxatomide, ketotifen or epinastine showed an inhibition of oxygen-radical generation induced by calcium ionophore A-23187 and the IC50 value was 11.3 mumol/l for oxatomide, 15.1 mumol/l for ketotifen and 27.3 mumol/l for epinastine, suggesting that oxatomide is a more potent inhibitor of oxygen-radical generation than ketotifen and epinastine. Oxatomide also inhibited p-LT release induced by calcium ionophore A-23187 (IC50, 9.83 mumol/l). Ketotifen and epinastine only weakly inhibited p-LT release. These results suggest that oxatomide may regulate inflammatory diseases, such as bronchial asthma, through suppression of eosinophil function.

Topics: Animals; Anti-Allergic Agents; Calcimycin; Dibenzazepines; Eosinophils; Free Radicals; Guinea Pigs; Histamine H1 Antagonists; Imidazoles; In Vitro Techniques; Ketotifen; Leukotrienes; Luminescent Measurements; Male; Oxygen Consumption; Piperazines

A series of benzimidazolone and benzimidazole analogues of the antiallergic drug oxatomide (1-¿3-[4-(diphenylmethyl)-1-piperazinyl]propyl¿-1,3-dihydro-2H- benzimidazol-2-one, CAS 60607-34-3) [formula: see text], was evaluated for inhibiting the release of the performed mediator beta-hexosaminidase from the rat basophilic leukemia (RBL-2H3) cell line. Activation of the cells was induced by antigen, or by the calcium ionophore A23187 (calcimycin) in combination with or without the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). For the active compounds, inhibition of exocytosis was found with all triggers, with the antigen trigger being somewhat more sensitive. This indicates that the compounds influence several steps in the signal transduction route leading to exocytosis. The activity of the compounds is not totally aspecific as small structural changes strongly affect the inhibiting activity. Introduction of a chlorine substituent at the 6-position of the benzimidazolone group results in loss of activity. There does not seem to be a significant activity difference between the benzimidazolone and benzimidazole analogues. Analogues with n < 3, n > 5 or a branched alkyl chain between the piperazinyl and the benzimidazol(on)e moiety lose inhibitory activity. Secretion of the newly formed mediator arachidonic acid and its metabolites was affected by the compounds comparable to the effect on the release of beta-hexosaminidase. The anti-allergic activity did not correlate with the histamine H1-receptor antagonistic activity.

Topics: Animals; Anti-Allergic Agents; Arachidonic Acid; beta-N-Acetylhexosaminidases; Calcimycin; Cells, Cultured; Exocytosis; Histamine H1 Antagonists; Histamine Release; Ionophores; L-Lactate Dehydrogenase; Mast Cells; Piperazines; Rats; Signal Transduction; Structure-Activity Relationship; Tetradecanoylphorbol Acetate

In a mast cell model, oxatomide displays inhibition of mediator release which is not related to its histamine H1 receptor antagonistic activity. From a previous study it appeared that especially early steps in the signal transduction leading to exocytosis were influenced by oxatomide. We now studied effects of oxatomide on those early steps in more detail. The antigen- and thapsigargin-mediated exocytosis in rat basophilic leukemia (RBL-2H3) cells were both inhibited by oxatomide. After aggregation of high affinity receptors for immunoglobulin E (Fc epsilon RI), protein tyrosine phosphorylation is induced. Oxatomide caused remarkable changes in the tyrosine phosphorylation pattern in resting cells. Also after antigen and thapsigargin activation, changes in the tyrosine phosphorylation of cellular proteins are observed. In addition, Ca2+ fluxes were studied by means of the net influx of 45Ca2+ and by measuring intracellular free Ca2+ concentrations ([Ca2+]) with the fluorescent probe fura-2. Oxatomide inhibited the 45Ca2+ influx and the increase in [Ca2+]i upon antigen and thapsigargin activation of the cells. Neither the release of Ca2+ from internal stores nor the efflux of Ca2+ over the plasma membrane seems to be affected. The effect of oxatomide on Ca2+ influx was further characterized by studying Ba2+ influx in the absence of extracellular free Ca2+. We conclude that inhibition of mediator release is mainly caused by inhibition of influx of extracellular Ca2+, via plasma membrane Ca2+ channels that are activated by depletion of intracellular Ca2+ stores. The molecular mechanism with which oxatomide might interfere with these channels is discussed.

Topics: Animals; Anti-Allergic Agents; Calcimycin; Calcium; Inositol 1,4,5-Trisphosphate; Mast Cells; Phosphorylation; Piperazines; Rats; Signal Transduction; Tumor Cells, Cultured; Tyrosine

The effects of three histamine H1 receptor antagonists, epinastine (CAS 80012-43-7, WAL-801 CL), ketotifen (CAS 34580-13-7) and oxatomide (CAS 60607-34-3), on mediator release have been studied in human peripheral leukocytes. When leukocytes from asthmatic patients sensitive to mite were stimulated with the allergen, epinastine inhibited histamine release with a concentration required for 50% inhibition (IC50) of 3 x 10(-5) mol/l and leukotriene C4 generation. On the other hand, ketotifen or oxatomide showed little inhibiting effect on histamine release elicited with the allergen. When the cells were stimulated with calcium ionophore A23187, epinastine failed to inhibit histamine release and leukotriene C4 generation. Oxatomide caused a concentration related inhibition of calcium ionophore-induced histamine release with the IC50 value of 5 x 10(-5) mol/l. Ketotifen or oxatomide also showed an inhibition of leukotriene C4 generation induced by calcium ionophore in a dose-dependent manner and the IC50 value was 6 x 10(-6) mol/l for oxatomide and 8 x 10(-5) mol/l for ketotifen, suggesting that oxatomide is a more potent inhibitor of leukotriene C4 generation than ketotifen. These results indicate that epinastine inhibits IgE-mediated histamine release and LTC4 generation, and oxatomide has a capacity to inhibit calcium ionophore-induced mediator release from human leukocytes. Additionally, when platelet activating factor was quantitated by radioimmunoassay in the supernatant and the cell pellet after ionophore stimulation, epinastine inhibited the formation and the secretion in a dose-dependent manner.

Topics: Asthma; Calcimycin; Dibenzazepines; Histamine H1 Antagonists; Humans; Hypersensitivity; Imidazoles; Immunoglobulin E; In Vitro Techniques; Ketotifen; Leukocytes; Leukotriene C4; Neutrophils; Piperazines; Platelet Activating Factor

Azelastine, a newly synthesized antiallergic agent, strikingly inhibited the production of leukotriene B4 and C4 (LTB4 and LTC4) in murine peritoneal cells which had been stimulated by calcium ionophore A23187. The 50% inhibitory concentrations (IC50) of the agent were approximately 1.0 x 10(-5) M. In addition, azelastine significantly inhibited also 5-lipoxygenase activity in peritoneal cells with an IC50 of 1.0 x 10(-5) M, but not on LTC4 synthetase, LTA4 hydrolase or phospholipase A2 activity. Furthermore, azelastine showed little effect on either 12-lipoxygenase activity or thromboxane synthesis in human platelets. These results suggest that at least the drug's antiallergic effects can be attributed to its inhibiting action of 5-lipoxygenase in regard to arachidonate metabolism.

Topics: Animals; Blood Platelets; Calcimycin; Dose-Response Relationship, Drug; Epoxide Hydrolases; Glutathione Transferase; Hydroxyeicosatetraenoic Acids; Ketotifen; Leukotrienes; Lipoxygenase; Mice; ortho-Aminobenzoates; Peritoneal Cavity; Phospholipases A; Phospholipases A2; Phthalazines; Piperazines; Pyridazines; Thromboxanes

The effects of the H1-antihistamines astemizole, oxatomide and pyrilamine, of the calmodulin antagonists trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), on the ionophore A23187 (5 mumol/l)-induced release of cysteinyl-leukotrienes (LT) and thromboxane (TX) B2 from mixed human leukocytes were investigated in comparison to those of the cyclooxygenase inhibitor indomethacin and the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). In contrast to pyrilamine both astemizole and oxatomide inhibited the release of cysteinyl-LT and TXB2 with IC50 values between 4 and 23 mumol/l. Both astemizole and oxatomide were about twice as effective in inhibiting cysteinyl-LT release as compared to TXB2 release. Similar to astemizole and oxatomide the calmodulin antagonists trifluoperazine and W-7 inhibited the eicosanoid release. W-7 was, however, clearly less effective and in contrast to trifluoperazine no difference was observed in its potency to inhibit cysteinyl-LT or TXB2 release. The H1-antihistamines, astemizole and oxatomide as well as the calmodulin antagonists did not cause intracellular retention of the eicosanoids tested. The reference compounds indomethacin and NDGA proved to be the most potent inhibitors. The results demonstrate that the therapeutic antihistamines astemizole and oxatomide as well as the classical calmodulin antagonists trifluoperazine and W-7 are able to inhibit eicosanoid formation.

Topics: Astemizole; Benzimidazoles; Calcimycin; Calcium Channel Blockers; Eicosanoic Acids; Histamine H1 Antagonists; Humans; In Vitro Techniques; Indomethacin; Leukocytes; Masoprocol; Piperazines; Pyrilamine; Reference Values; Sulfonamides; Trifluoperazine

Topics: Astemizole; Benzimidazoles; Calcimycin; Calmodulin; Fatty Acids, Unsaturated; Histamine H1 Antagonists; Humans; In Vitro Techniques; Leukocytes; Piperazines; SRS-A; Thromboxane B2

The effect of oxatomide, an orally active antiallergic drug, on immunoreactive LTC4 (iLTC4) production has been studied in rat peritoneal exudate cells (PEC) and guinea-pig lung fragments using the calcium ionophore A23187 and specific antigen in vitro. Oxatomide (10(-5) M) inhibited iLTC4 release by 70% with A23187 from rat PEC, and by 48% with antigen from guinea-pig lung. Oxatomide is supposed to affect the biosynthesis pathway of leukotrienes, because oxatomide inhibits 5-lipoxygenase from guinea-pig peritoneal leukocytes with an IC50 17 microM. Oxatomide also depressed the release of PGD2 from rat peritoneal mast cells stimulated by A23187 (IC50 4.2 microM). The effects of oxatomide on iLTC4 and PGD2 release were more potent than other antiallergic drugs (DSCG, ketotifen, tranilast).

Topics: Animals; Arachidonate 5-Lipoxygenase; Calcimycin; Cromolyn Sodium; Guinea Pigs; Ketotifen; Lung; Mast Cells; ortho-Aminobenzoates; Piperazines; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Prostaglandins D; Rats; SRS-A

The present study was carried out to evaluate the inhibitory effect of oxatomide and disodium cromoglycate (DSCG) on the histamine release from rat PEC and lung slices induced by antigen-antibody reaction, concanavalin A, compound 48/80 and A-23187. Oxatomide in the range of 1 microM to 10 microM inhibited the allergic histamine release from rat PEC and lung slices induced by antigen-antibody reaction in the presence of phosphatidyl-L-serine (PS). Although the inhibitory action of oxatomide was significant even at a concentration of 1 microM, the action did not increase with an increase in concentration of the drug. DSCG showed a concentration-dependent inhibition on the allergic histamine release from rat PEC and lung slices in the range of 10 microM to 100 microM. The histamine release from rat PEC induced by the combined treatment of concanavalin A and PS was inhibited by oxatomide (0.1 to 10 microM) and DSCG (10 to 100 microM). Oxatomide (up to 10 microM) showed no effect on the histamine release induced by compound 48/80, while DSCG in the range of 10 microM to 100 microM showed a concentration dependent inhibition of the release. Oxatomide at a concentration of 10 microM showed a significant inhibition on the histamine release induced by the calcium ionophore A-23187. On the other hand, DSCG had no effect on this reaction. Oxatomide at high concentrations did not stimulate the histamine release by itself.

Topics: Animals; Ascitic Fluid; Calcimycin; Concanavalin A; Cromolyn Sodium; Histamine H1 Antagonists; Histamine Release; In Vitro Techniques; Lung; Male; Mast Cells; p-Methoxy-N-methylphenethylamine; Piperazines; Rats; Rats, Inbred Strains

Oxatomide inhibits the release of histamine from rat peritoneal mast cells in vitro induced by C 48/80, antigen, anti-IgE and ionophore A 23 187, without effect on non-specific release by n-decylamine. Its effect is concentration- and pH-dependent and decreases with increasing extracellular Ca2+-concentrations. Prolonged incubation does not enhance the inhibition, which is lost after one single wash-out. Aminophylline and isoproterenol are not potentiated by oxatomide. The present study points to an effect of oxatomide on a Ca2+-dependent process at the level of cell membrane common to antigen, C 48/80 and ionophore A 23 187.

Topics: Animals; Antibodies, Anti-Idiotypic; Antigens; Ascitic Fluid; Calcimycin; Calcium; Histamine Release; Immunoglobulin E; In Vitro Techniques; Male; Mast Cells; p-Methoxy-N-methylphenethylamine; Piperazines; Rats