ovalbumin and bepafant

We have previously shown that the Platelet-Activating Factor Receptor (PAFR) engagement in murine macrophages and dendritic cells (DCs) promotes a tolerogenic phenotype reversed by PAFR-antagonists treatment in vitro. Here, we investigated whether a PAFR antagonist would modulate the immune response in vivo. Mice were subcutaneously injected with OVA or OVA with PAFR-antagonist WEB2170 on days 0 and 7. On day 14, OVA-specific IgG2a and IgG1 were measured in the serum. The presence of WEB2170 during immunization significantly increased IgG2a without affecting IgG1 levels. When WEB2170 was added to OVA in complete Freund's adjuvant, enhanced IgG2a but not IgG1 production was also observed, and CD4+ FoxP3+ T cell frequency in the spleen was reduced compared to mice immunized without the antagonist. Similar results were observed in PAFR-deficient mice, along with increased Tbet mRNA expression in the spleen. Additionally, bone marrow-derived DCs loaded with OVA were transferred into naïve mice and their splenocytes were co-cultured with fresh OVA-loaded DCs. CD4

Topics: Adaptive Immunity; Animals; Azepines; CD4-Positive T-Lymphocytes; Cells, Cultured; Dendritic Cells; Freund's Adjuvant; Immunization; Immunoglobulin G; Mice; Ovalbumin; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Receptors, G-Protein-Coupled; Spleen; Triazoles

The interference of the platelet-activating factor (PAF) receptor antagonist compound, WEB 2170, on death caused by antigen in boosted or unboosted immunized mice was investigated. Death was triggered by the i.v. injection of ovalbumin into animals actively sensitized 14 or 21 days before and that received (boosted) or did not receive (unboosted), a second immunization 14 days later. No significant difference in the response to PAF (50 micrograms/kg) or to ovalbumin (500 micrograms/kg) was noted in boosted or unboosted mice in terms of mortality. WEB 2170 was equieffective to prevent death by PAF in non-sensitized or sensitized boosted or unboosted mice. The i.p. treatment with WEB 2170 (8-16 mg/kg) 1 h before the antigenic challenge prevented death due to antigen in unboosted or in boosted mice. Our results suggest that PAF is involved in the anaphylactic shock in unboosted and boosted mice. In addition, different from the anaphylactic reaction developed in the mouse paw, the participation of PAF in the anaphylactic shock caused by antigen is not dependent on the delivery of a booster injection.

Topics: Anaphylaxis; Animals; Azepines; Immunization, Secondary; Immunoglobulin E; Immunoglobulin G; Male; Mice; Ovalbumin; Platelet Activating Factor; Triazoles; Vaccination

A new model of active anaphylactic reaction in mice was developed. The edematogenic reaction appeared 5 min after the intraplantar injection of ovalbumin, peaked at 30 min after the antigenic challenge, and decreased thereafter. Using the non-steroidal, anti-inflammatory agents indomethacin and aspirin, we found that cyclooxygenase products do not participate in the reaction. In contrast, vasoactive amines appear to be involved, because meclizine and methysergide reduced the edema. Dexamethasone, BW755C, LY 171883 and WEB 2170 effectively interfered with the edematogenic reaction, which suggests that lipid mediators such as leukotrienes and PAF play a role in the active anaphylactic response.

Topics: 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; Acetophenones; Anaphylaxis; Animals; Aspirin; Azepines; Cimetidine; Dexamethasone; Edema; Male; Meclizine; Methysergide; Mice; Ovalbumin; Platelet Activating Factor; Platelet Membrane Glycoproteins; Prednisolone; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Tetrazoles; Triazoles

The selective hetrazepinoic platelet-activating factor (PAF) antagonist WEB 2170 (Bepafant) was used to study the pathophysiological role of PAF in several models of anaphylaxis in mice and guinea pigs. In actively sensitized mice, the PAF antagonist WEB 2170 (1.0-10 mg/kg p.o.) protected mice from anaphylactic death in a dose-dependent manner when the anaphylactic response was potentiated by the beta-receptor antagonist propranolol. When active anaphylaxis in guinea pigs was induced intravenously by 100 mg/kg ovalbumin (OA) in the presence of small doses of the antihistamine mepyramine, additional treatment with oral or intravenous WEB 2170 protected the guinea pigs from anaphylactic death. Also, the remaining anaphylactic bronchoconstriction and blood pressure changes (including anaphylactic hypotension) were attenuated. When guinea pigs were passively sensitized with a heterologous antibody via the tracheal route and then challenged by ovalbumin (100 mg/kg i.v.) 24 hr after sensitization in the presence of 0.003 mg/kg i.v. mepyramine, additional treatment with tracheal WEB 2170 at 0.1-1 mg/kg protected the guinea pigs dose-dependently not only from anaphylactic death but also from a further decrease of respiratory flow and changes of blood pressure. Increased levels of PAF-like activity (20-50 ng PAF/whole lung) were detected in lungs removed from antigen-challenged animals. The results suggest a causative role for PAF in active and passive anaphylaxis.

Topics: Anaphylaxis; Animals; Azepines; Blood Pressure; Guinea Pigs; Lung; Male; Mice; Mice, Inbred Strains; Ovalbumin; Passive Cutaneous Anaphylaxis; Platelet Activating Factor; Propranolol; Pyrilamine; Respiration; Triazoles

The aim of this study was to examine the ability of the novel PAF (platelet-activating factor) antagonist WEB 2170 to inhibit active anaphylaxis in mice and guinea pigs. Previous studies with other PAF antagonists have given equivocal results. This study was designed to define conditions under which a clear and significant effect of the PAF antagonist would be shown. WEB 2170 could be shown active, at concentrations of between 1 and 10 mg/kg p.o. in a model of murine anaphylaxis, in which the mice were actively sensitized and also treated with the beta-adrenoceptor antagonist propranolol to potentiate the anaphylactic response. WEB 2170 was also active in guinea pig models of anaphylaxis (tested dose range: 5 mg/kg i.v. and 0.04-3 mg/kg p.o.), in which the guinea pigs were sensitized according to one of three specified immunization schedules and pretreated with low doses of mepyramine before antigen challenge. These results suggest that PAF has a role in active anaphylaxis in mice and guinea pigs. However, to demonstrate this effect in guinea pigs, models must be used in which the effects of histamine release are minimized.

Topics: Anaphylaxis; Animals; Azepines; Blood Pressure; Bronchoconstriction; Guinea Pigs; Immunization; Male; Mice; Ovalbumin; Platelet Activating Factor; Propranolol; Pulmonary Ventilation; Pyrilamine; Triazoles