Biomedical subjects

B B Vargaftig

Publications and source records attributed to B B Vargaftig.

At least 19 recordsLinked to original sources

PubMed1992

Activation and damage of cultured airway epithelial cells by human elastase and cathepsin G.

Accumulation of polymorphonuclear neutrophils (PMN) and epithelium damage have often been described during airway inflammation. We studied the effects of two PMN-derived proteinases, namely elastase and cathepsin G, on guinea-pig tracheal epithelial cells in culture. Both proteinases activated tracheal epithelial cells in terms of prostaglandin (PG) E2 production. A concentration- and time-dependent effect was observed with 10 micrograms/ml and 6 h as the optimal conditions for both enzymes. Optical microscopic studies confirmed an effect on tracheal epithelial cells as intercellular gaps were observed upon incubation of the monolayers with proteinases. A small cytotoxic effect was observed after 1 h incubation but remained stable up to 6 h. This cytotoxic effect, more pronounced with elastase than with cathepsin G, was dissociated from PGE2 formation.

Animals↗

PubMed1992

Suppression by cetirizine of pleurisy triggered by antigen in actively sensitized rats.

The efficacy of cetirizine in comparison with meclizine, another piperazine H1 receptor antagonist, in rat pleurisy caused by allergen or autacoid was investigated. Sensitization was achieved by subcutaneous injection of a mixture of ovalbumin and aluminium hydroxide. Fourteen days later, the animals were challenged with an intrathoracic injection of ovalbumin (12 micrograms/cavity), which caused drastic mast cell degranulation, followed by pleural oedema and leucocyte influx. Cetirizine and meclizine (2.5-30 mg/kg i.p.), 1 h before challenge, inhibited the exudatory response evoked by antigen, under conditions where neutrophil and eosinophil accumulation was affected only by the former. When administered intrathoracically 22 h after allergen, i.e. using a curative approach, cetirizine (15 micrograms/cavity) drastically reduced the pleural eosinophilia noted 24 h post-challenge, indicating that this drug can reverse an already established eosinophilia. Cetirizine (15 mg/kg i.p.) also restored, to about 39% (P < 0.001), the number of uninjured mast cells recovered from the pleural cavity following allergen stimulation. In normal rats, cetirizine (5-15 micrograms/cavity) completely inhibited the pleural exudation elicited by histamine and only partially the exudation caused by 5-hydroxytryptamine or bradykinin, but was quite inactive against platelet-activating factor. We conclude that the pleural exudation triggered by allergen, vasoactive amines or bradykinin is clearly sensitive to cetirizine. In addition, the ability of the drug to interfere with pleural neutrophil or eosinophil mobilization and mast cell degranulation seems not to be associated with its ability to block the histamine H1 receptor.

Animals↗

PubMed1992

Inhibition of phospholipase A2 activity in guinea pig eosinophils by human recombinant IL-1 beta.

The effect of human rIL-1 beta on the release of arachidonic acid (AA) and on the phospholipase A2 (PLA2) activity in guinea pig eosinophils was investigated. Stimulation of [3H]AA-labeled eosinophils with the ionophore A23187 resulted in a time and concentration-dependent release of AA in parallel to hydrolysis of endogenous phosphatidylcholine (PC). Both events were abrogated by the chelation of intracellular free calcium, but not by its depletion from the medium, suggesting that the ionophore-induced AA release involves a PLA2 activity dependent on the mobilization of intracellular calcium. Addition of human rIL-1 beta (0.01 to 100 ng/ml) to eosinophils for 15 min had no effect on the release of AA induced by the ionophore. However, prolonged incubation with human rIL-1 beta (30 to 180 min) inhibited in a concentration- and time-dependent manner the release of AA and the hydrolysis of phosphatidylcholine in ionophore-stimulated eosinophils. Our results also showed that eosinophil homogenates contain a calcium-dependent PLA2 whose activity was markedly reduced when eosinophils were pretreated with human rIL-1 beta. The inhibition was time and concentration dependent and was observed in the presence of calcium and phospholipid excess. Finally, studies with Fura-2-loaded eosinophils showed that the ionophore A23187 stimulated an increase in intracellular calcium concentration that was not altered by pretreating the eosinophils with human rIL-1 beta. These results suggest that human rIL-1 beta inhibits the release of AA by eosinophils via the inhibition of a PLA2 activity and through a calcium-independent mechanism. Inhibition by human rIL-1 beta required a prolonged incubation (30 to 180 min) and was observed after its removal from the medium, suggesting that human rIL-1 beta did not interact directly with the PLA2 itself, but with a metabolic process involved with the regulation of its activity in eosinophils.

Animals↗

PubMed1992

Interference of antihistamines and anti-allergic drugs with antigen-induced paw edema in boosted and unboosted mice.

The protective effects of two antihistamines and two anti-allergic drugs against anaphylactic paw edema were studied in immunized animals that had or had not received a booster injection of antigen. The injection of 1 or 10 micrograms/paw ovalbumin induced acute paw edema of similar intensity in both groups. The antihistamine meclizine and the mixed anti histamine/anti-5-HT antagonist cyproheptadine reduced the anaphylactic reaction by 55 and 84% respectively, in non-boosted animals and were less effective against edema induced by 1 microgram antigen in boosted animals. The effectiveness of these drugs was also reduced when boosted mice were challenged with 10 micrograms antigen, where meclizine and cyproheptadine inhibited edema by 31 and 59%, respectively. The anti-allergic compounds ketotifen and azelastine, although effective against allergic inflammation in non-boosted mice, had a reduced or no effect in boosted mice. Our results suggest that allergic edema is less sensitive to antihistamine and anti-allergic drugs in boosted mice, which may be accounted for by an increased role of other mediators.

Analysis of Variance↗

PubMed1992

Inhibition by azelastine of the effects of platelet-activating factor in lungs from actively sensitised guinea-pigs.

The effect of azelastine on platelet-activating factor (PAF)-induced bronchoconstriction and mediator release in isolated lungs from actively sensitised guinea-pigs was investigated. Guinea-pigs were actively sensitised with two s.c. injections of 10 micrograms ovalbumin in 1 mg Al (OH)3 at a 2-week interval. One week after the second injection, the lungs were removed and challenged intra-arterially with PAF or arachidonic acid. In some experiments lungs from non-immunised guinea-pigs were injected with PAF or histamine. Bronchoconstriction, the release of thromboxane (TX)B2 or leukotriene (LT)-like material and the histamine content of the effluent were evaluated. Azelastine was given s.c. at 10 or 100 micrograms/kg, 4 h before lung removal. Azelastine (100 micrograms/kg) did not inhibit PAF-induced bronchoconstriction and mediator release from lungs from non-immunised guinea-pigs. In contrast, the hyperresponsiveness to 1 ng PAF observed in lungs from actively sensitised animals was dose dependently inhibited by azelastine. Azelastine did not reduce the histamine-induced bronchoconstriction and consequent TXB2 release from lungs from immunised guinea-pigs, indicating that the protective effect exerted against hyperresponsiveness to PAF was not due to histamine antagonism. Azelastine also reduced arachidonic acid-induced bronchoconstriction and LT-like material release from sensitised lungs, regardless of the presence of indomethacin. These results suggest that inhibition of lung hyperresponsiveness to PAF by azelastine may result from an interference with leukotriene synthesis.

Animals↗

PubMed1992

Interference of azelastine with anaphylaxis induced by ovalbumin challenge in actively sensitized rats.

The inhibition of the haematological alterations and prevention of death due to systemic anaphylaxis after antigen challenge were investigated in rats after various drug treatments. The i.v. injection of ovalbumin (250 micrograms/kg) into actively sensitized rats induced marked thrombocytopenia and haemoconcentration within 5 min and significant leukocytosis within 30 min, lasting for 2 h after the challenge. Pretreatment with meclizine or terfenadine (15-30 mg/kg i.p.) inhibited antigen-induced haemoconcentration, whereas WEB 2086 (2-10 mg/kg i.p.) and PCA 4248 (5-10 mg/kg p.o.), two platelet-activating factor (PAF) antagonists, interfered with thrombocytopenia only. Azelastine (1-20 mg/kg p.o.) dose dependently inhibited antigen-induced haemoconcentration and thrombocytopenia but failed to block leukocytosis. Azelastine also inhibited the thrombocytopenia observed after the i.v. administration of PAF (4 micrograms/kg). Administration of ovalbumin at a dose of 1.5 mg/kg resulted in a lethal anaphylactic reaction in about 85% of the rats. Pretreatment with WEB 2086 (10 mg/kg i.p.), meclizine (30 mg/kg i.p.) or both increased the survival rate from 15 to 57, 68 and 87%, respectively. Azelastine alone (20 mg/kg p.o.) completely blocked the lethal reaction. It was concluded that the ability of azelastine to antagonize histamine and PAF is important for its effectiveness against anaphylactic shock.

Anaphylaxis↗

PubMed1992

Pertussis toxin induces bronchopulmonary hyperresponsiveness in guinea-pigs while antagonizing the effects of formyl-L-methionyl-L-leucyl-L-phenylalanine.

Pertussis toxin injected i.v. at 0.8-20 micrograms/kg markedly enhanced bronchoconstriction induced by the i.v. administration of histamine or serotonin (5-HT) (0.5-16 micrograms/kg) to propranolol-treated guinea-pigs, under conditions where propranolol or pertussis toxin alone were poorly effective. In contrast, bronchoconstriction and the accompanying leukopenia induced by the i.v. administration of the secretagogue formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) were suppressed by pertussis toxin. Bronchoconstriction induced by histamine or 5-HT was not enhanced when perfused lungs from pertussis toxin-treated guinea-pigs were studied in vitro, under conditions where bronchoconstriction and thromboxane A2 release evoked by fMLP were suppressed. Pertussis toxin negatively modifies signal transduction in cells involved in the lung responses to fMLP both in vivo and in vitro, but positively and only in vivo it modifies signal transduction in cells involved in the lung responses to the direct constricting agents histamine and 5-HT. As hyperresponsiveness to histamine and 5-HT were exclusively found in vivo, the target for pertussis toxin is probably not the adrenergic nor the cholinergic systems, since neither hexamethonium, isoprenaline, atropine nor vagotomy were effective. In addition, since dexamethasone and nedocromil sodium were inactive and enrichment of bronchoalveolar lavage with inflammatory cells was not noted, despite lung invasion by neutrophils and lymphocytes, acute inflammation does not account for pertussis toxin-induced hyperresponsiveness.

Animals↗

PubMed1992

Differential inhibition by the PAF receptor antagonist, WEB 2170, of allergic inflammation in single sensitized and boosted mice.

Interference of the PAF antagonist, WEB 2170, with the paw edema induced by antigen in boosted or unboosted sensitized mice was investigated. Edema was triggered by the intraplantar injection of ovalbumin to animals actively sensitized 21 days before and that received (boosted), or did not receive (unboosted), a second immunization after 14 days. There was no difference in the intensity of the response to antigen or to PAF (platelet-activating factor) in boosted or in unboosted animals. Intraperitoneal treatment with WEB 2170 1 h before challenge reduced dose dependently the edema in boosted mice but did not modify the reaction in unboosted mice. It is noteworthy that WEB 2170 was more effective against PAF-induced paw edema in unboosted than in boosted mice, the maximum inhibition of 84% being reached at 16 mg/kg. In addition, topical and selective desensitization to PAF inhibited the edema caused by antigen only in boosted animals. Our findings indicate that the booster injection during the immunization process shifts the anaphylactic mouse paw edema from a PAF-independent to a PAF-dependent reaction.

Animals↗

PubMed1992

Formation of LTB4 by fMLP-stimulated alveolar macrophages accounts for eosinophil migration in vitro.

Guinea pig alveolar macrophages obtained by bronchoalveolar lavage were isolated by adherence for 2 h and stimulated with 1 microM of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) for different time intervals. The supernatants then were tested for their chemotactic effect on guinea pig peritoneal normodense eosinophils and for release of thromboxane B2, leukotriene B4 (LTB4), and platelet activating factor (PAF). The supernatant from fMLP-stimulated alveolar macrophages induced a significant eosinophil attraction (96.0 +/- 11.9, number of migrating eosinophils [mean +/- SEM], n = 17) as compared to unstimulated macrophages (4.8 +/- 1.4, n = 15). This effect was not accounted for by fMLP carry-over to the macrophages because, in contrast to human eosinophils, fMLP has no chemotactic effect on guinea pig eosinophils. Pretreatment of eosinophils with BN 52021 (100 microM), a specific PAF antagonist, and with indomethacin (10 microM), a cyclooxygenase inhibitor, failed to inhibit migration of eosinophils induced by supernatants from either stimulated or unstimulated alveolar macrophages. In contrast, inhibition of the 5-lipoxygenase enzyme with N-(3-phenoxycinamyl)-acetohydroxamic acid (1 microM) suppressed eosinophil migration by alveolar macrophage supernatants (94.1 +/- 2.6% of inhibition, n = 6). Desensitization of eosinophils by and to LTB4 (10 nM) inhibited migration induced by supernatants from stimulated alveolar macrophages (87.5 +/- 5.4% of desensitization toward LTB4 and 83.1 +/- 5.4% of desensitization toward supernatants, n = 5). Under the present experimental conditions, LTB4 is the only agent implicated in eosinophil migration induced by supernatants from fMLP-stimulated alveolar macrophages.

Animals↗

PubMed1992

Azelastine potentiates the prostaglandin-induced increase of cyclic AMP content in human platelets and in guinea-pig alveolar macrophages.

The effect of azelastine on intracellular cyclic AMP concentration and on various indexes of cell activation was evaluated in guinea-pig alveolar macrophages and in human platelets. The effect of azelastine was further investigated on adenylate cyclase activity using membranes and homogenates from guinea-pig alveolar macrophages. Pretreatment of alveolar macrophages with azelastine prevented the activation induced by PAF-acether and by the chemotactic peptide fMLP as estimated by the reduced liberation of arachidonic acid metabolites formed by the cyclooxygenase and the lipoxygenase pathways. The effect of azelastine was concentration-dependent (50 to 500 microM) and reversible. Similarly, a short pretreatment with azelastine (100 microM) prevented arachidonic acid-induced platelet aggregation. This effect was also reversible after washing the platelets. In guinea-pig alveolar macrophages, azelastine induced a concentration-dependent (10 to 500 microM) increase in intracellular cyclic AMP and markedly potentiated the increase induced by PGE2. In human platelets, azelastine alone increased intracellular cyclic AMP concentration marginally only but, as in the case of macrophages, synergized with PGI2. Azelastine did not activate significantly adenylate cyclase unless a cytosolic factor was included within the membrane fraction. This effect of azelastine was not due to Ca2+ movements and was not modified by GTP. Our findings show that azelastine interferes with cell activation through a mechanism related to an increase in intracellular cyclic AMP concentration. The increase in cyclic AMP was induced by azelastine in intact cells and in homogenates but not in a crude membrane fraction. Those results indicate that azelastine modifies a cytosolic factor that may be phosphodiesterase. In addition, similarities between the effects of azelastine and those of reference phosphodiesterase inhibitors (theophylline, isobutyl-methyl-xanthine) are shown in this study, suggesting that azelastine might behave as a phosphodiesterase inhibitor.

1-Methyl-3-isobutylxanthine↗

PubMed1992

Guinea-pig treatment with pertussis toxin suppresses macrophage-dependent bronchoconstriction by fMLP and fails to inhibit the effects of PAF.

1. Bronchoconstriction and thromboxane B2 (TxB2) release following the intra-tracheal administration of the secretagogue N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) to lungs from pertussis toxin-treated guinea-pigs in vivo and in vitro were inhibited as compared to saline-treated animals, under conditions where the responses to PAF were modified less effectively. 2. The cell target accounting for bronchoconstriction by fMLP and for inhibition by pertussis toxin is located in the airways and is probably the alveolar macrophage. Indeed (a) fMLP-induced superoxide anions and TxB2 formation by alveolar macrophages were inhibited by pertussis toxin given in vivo; (b) Gi proteins of membranes from alveolar macrophages were ADP-ribosylated in vivo by pertussis toxin and (c) bronchoconstriction and TxB2 release in response to the intra-tracheal administration of fMLP to lungs from pertussis toxin-treated animals were restored when alveolar macrophages from control guinea-pigs were transferred into the airways of pertussis toxin-treated animals before lung isolation. 3. Pertussis toxin administered to guinea-pigs in vivo, reduced the subsequent TxB2 formation and superoxide anion release by alveolar macrophages stimulated with PAF, but failed to inhibit PAF-induced bronchoconstriction. 4. Formation of TxB2 by alveolar macrophages following the intra-tracheal administration of fMLP accounts for bronchoconstriction and requires pertussis toxin-sensitive Gi proteins. PAF operates via a different mechanism, which is independent of Gi-like protein and involves mediators other than TxB2 and superoxide anions.

Adenosine Diphosphate Ribose↗

PubMed1992

Interference of cetirizine with the late eosinophil accumulation induced by either PAF or compound 48/80.

1. The effect of topical or systemic treatment with the histamine H1-receptor antagonist, cetirizine, on the rat pleural eosinophil accumulation induced by PAF or compound 48/80 was investigated. The number of pleural resident eosinophils increased 6 h after the intrathoracic (i.t.) injection of PAF (1 microgram/cavity), peaked within 24 h and persisted significantly augmented for at least 96 h. Compound 48/80 (25 micrograms/cavity) also produced a long lasting pleural eosinophilia but this was first noted only 24 h after stimulation. 2. Intraperitoneal pretreatment with cetirizine inhibited eosinophilia induced by either PAF (ED50 = 19 mg kg-1) or compound 48/80 (ED50 = 14 mg kg-1) whereas meclizine, another histamine H1-receptor antagonist, was inactive. 3. Administered locally, cetirizine (5 and 15 micrograms/cavity) also dose-dependently inhibited both PAF- and compound 48/80-induced eosinophilia, providing evidence that its inhibitory effect is not due to any action upon circulating eosinophils. Consistent with this result, incubation of isolated peritoneal eosinophils with cetirizine failed to modify in vitro eosinophil migration caused by PAF. 4. Since the late eosinophilia induced by PAF may depend on the synthesis of a transferable protein mediator, cetirizine was administered to donor or recipient rats in order to determine whether it interferes with the generation or with the expression of this protein. We showed that only the treatment of recipient rats abolished the transfer of the eosinophilotactic activity, indicating that cetirizine does not modify the generation but inhibits the expression of this activity. 5. Our findings indicate that cetirizine is able to inhibit eosinophil accumulation by acting locally. The mechanism is neither related to its recognized ability to antagonize histamine H,-receptors nor to a direct action upon circulating eosinophils.

Administration, Topical↗

PubMed1992

Nedocromil sodium prevents in vivo generation of the eosinophilotactic substance induced by PAF but fails to antagonize its effects.

1 The intrathoracic injection of platelet activating factor (PAF) into rats induced a decrease in the pleural leucocyte numbers within 15 min, accompanied by a marked exudation, maximal 1 h later. After 6 h, concomitantly with the reduction of exudation, a marked increase in the number of mononuclear cells, neutrophils and eosinophils was observed. Within 24 h, the pleural eosinophil accumulation peaked and persisted up to 96 h. 2 Topical treatment with nedocromil sodium affected pleural exudation by PAF under conditions where systemic meclizine was ineffective. Nedocromil sodium blocked, dose-dependently, the increase in the pleural content of mononuclear cells, neutrophils and eosinophils, observed 6 h after PAF administration, as well as the eosinophilia 24 h later. Moreover, the co-incubation of peritoneal eosinophils with nedocromil sodium did not interfere with the migration triggered by PAF. 3 The transfer of the 6 h-PAF pleural washings from donor to recipient rats caused a selective pleural eosinophilia, which was clearly inhibited when nedocromil sodium was administered to donor, but not to recipient animals, showing that this drug interferes with the generation rather than with the expression of the eosinophilotactic activity(ies). 4 These findings indicate that the nedocromil sodium interferes with PAF-induced exudation and leucocyte accumulation, by a mechanism other than its ability to reduce the local effects of histamine and which may relate to suppression of the eosinophilotactic principle generation.

Animals↗

PubMed1992

Effect of human recombinant interleukin-5 on in vitro responsiveness to PAF of lung from actively sensitized guinea-pigs.

1. The intra-tracheal (i.t.) administration of human recombinant interleukin-5 (rhIL-5; 100 or 300 ng) to isolated perfused lungs from guinea-pigs actively sensitized to ovalbumin induced an increased bronchoconstriction and release of thromboxane A2 (TXA2) and histamine into the lung effluent following the subsequent (10 min) intra-arterial injection of platelet-activating factor (PAF). Lung responses to 5-hydroxytryptamine were unaffected by rhIL-5. 2. Hyperresponsiveness to PAF was observed when the lungs were obtained from guinea-pigs used 2 or 7 days after a booster injection of the antigen and, to a lower extent, when they were from animals sensitized by a single antigen administration. By contrast, rhIL-5 did not modify the responses to PAF of lungs from passively sensitized or from adjuvant-treated guinea-pigs, suggesting that immunological stimulation is required to allow the expression of synergism between rhIL-5 and PAF. 3. Guinea-pigs killed 2 and 7 days after the booster injection of the antigen exhibited a marked increase in the number of eosinophils in the bronchoalveolar lavage fluid (BAL), as compared to non-sensitized animals. 4. Our results demonstrate that rhIL-5 and PAF act synergistically to induce enhanced bronchoconstriction and mediator release exclusively when lungs are obtained from guinea-pigs sensitized once to ovalbumin and then boosted. Since recruitment of eosinophils into the airways and the development of hyperresponsiveness to PAF are concomitant, it is suggested that eosinophils are the target cells for interaction between rhIL-5 and PAF.

Animals↗

PubMed1992

Modulation of arachidonic acid metabolism and cyclic AMP content of human alveolar macrophages.

The exposure of human alveolar macrophages to inflammatory mediators such as PAF (1 microM), fMLP (1 microM) or the calcium ionophore A23187 (1 microM) induced a rapid decrease in their intracellular concentration of cAMP. Inhibition of TXA2 synthesis by the specific thromboxane synthase inhibitor ridogrel (1-10 microM) or by non-specific inhibitors as indomethacin (1-10 microM), the cyclooxygenase inhibitor, or BW A4C (1-10 microM), the 5-lipoxygenase inhibitor, partially prevented the decrease in cAMP induced by the different inflammatory stimuli. Evidence for an indirect control of cAMP levels in human alveolar macrophages by inflammatory mediators through the production of arachidonic acid derivatives from the cyclooxygenase pathway is supported by this study.

Adult↗

PubMed1992

Thromboxane A2 accounts for bronchoconstriction but not for platelet sequestration and microvascular albumin exchanges induced by fMLP in the guinea pig lung.

When injected i.v. to guinea pigs, the granulocyte secretagog N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) induces bronchoconstriction (BC), lung platelet sequestration and increased transendothelial albumin exchanges in lungs. We evaluated BC and the variations of the lung contents in radiolabeled platelets, erythrocytes and extravascular albumin, as measurements of platelet lung entrapment, reduction of lung blood volume and increase of transendothelial albumin exchanges, respectively. Trimetoquinol, a thromboxane A2 (TXA2)-endoperoxide receptor antagonist, inhibited BC and platelet entrapment by lungs induced by fMLP, but protection was nonspecific because it also suppressed BC by histamine. The specific TXA2 synthetase inhibitor/endoperoxide receptor antagonist ridogrel suppressed BC and reduced lung platelet entrapment, but failed to prevent the increase of extravascular albumin and the decrease of erythrocyte lung contents due to fMLP. Consequently, the fMLP-induced increase of vascular albumin exchanges and reduction of lung blood volume are TXA2-independent. Aspirin prevented BC, but failed to suppress lung platelet entrapment by fMLP, indicating that in vivo platelet activation is not TXA2-dependent, even though the levels of circulating TXB2, the stable metabolite of TXA2, were increased after fMLP concomitantly with that of 6-keto-prostaglandin (PG)F1 alpha, the stable metabolite of PGI2. The ridogrel-treated animals showed reduced blood level of TXB2 and increased levels of 6-keto-PGF1 alpha after fMLP challenge. Blocking the cyclooxygenase pathway with aspirin prevented ridogrel-induced protection against lung platelet sequestration after fMLP, supporting the concept that rechanneling of arachidonate metabolism toward protective prostaglandins accounts for protection by ridogrel.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1991

Activation of guinea pig eosinophils by human recombinant IL-5. Selective priming to platelet-activating factor-acether and interference of its antagonists.

The potential role of platelet-activating factor (PAF)-acether and of IL-5 as an eosinophil-proliferating, activating, and/or recruiting mediator in asthma led us to study the effects of human (h) rIL-5 (hrIL-5) and PAF-acether, alone or combined, on isolated guinea pig eosinophils. Two populations of eosinophils were separated from peritoneal lavages of polymyxin B-treated guinea pigs upon a discontinuous metrizamide gradient: one of low density (between 20 and 22% of metrizamide, purity: 63 +/- 3%, n = 27) and another of normal density (between 22 and 24% of metrizamide, purity: 87 +/- 2%, n = 16). Chemotactic activity was evaluated on a micro-Boyden chamber, results being expressed as the number of migrating eosinophils (mean +/- SEM) at 40 microns through a cellulose nitrate filter (3 microns pore size) in the presence of the agonist or of the solvent alone. hrIL-5 dose-dependently stimulated normodense eosinophil chemotaxis, reaching a peak at 500 ng/ml (98 +/- 21 migrating eosinophils, n = 5, p less than 0.05). These eosinophils also responded to PAF-acether and to LTB4 and not to FMLP, hrTNF alpha, and LPS. Eosinophil preincubation with hrIL-5 increased significantly the migration by PAF-acether (173 +/- 23 migrating eosinophils with PAF-acether 10 nM after preincubation with hrIL-5 500 ng/ml vs 69 +/- 10 after preincubation with buffer alone, p less than 0.01) and failed to enhance migration by LTB4 or to uncover an activity for FMLP. Migration by PAF-acether was antagonized when the cells were preincubated with the antagonists BN 52021 and WEB 2086, which also inhibited migration by hrIL-5. Eosinophils were auto-desensitized by and to PAF-acether or LTB4, but were not cross-desensitized to each other. Eosinophils desensitized to PAF-acether failed to migrate with hrIL-5, but those desensitized to LTB4 responded to hrIL-5 as controls. hrIL-5 failed to induce the elevation of intracellular free calcium concentration and superoxide anion generation from basal values, whereas preincubation of eosinophils with hrIL-5 induced a significant increase in the rise in intracellular free calcium concentration and in superoxide anion generation by 10 nM PAF-acether but not by LTB4. In conclusion, the in vivo eosinophil migration in allergy may involve hrIL-5, particularly associated to PAF-acether.

Animals↗

PubMed1991

Effect of azelastine on platelet-activating factor and antigen-induced pleurisy in rats.

The interference of azelastine with pleurisy induced by antigen was investigated in actively sensitized rats. The antigenic challenge (ovalbumin, 12 micrograms/cavity) caused early plasma leakage, which peaked within 4 h, accompanied by intense neutrophil infiltration. Pleural exudate decayed 24 h after antigen provocation, when a long-lasting increase in the number of resident eosinophils was observed. Oral pretreatment with azelastine (1-10 mg/kg) dose dependently inhibited the vasopermeation (ED50 = 4.2 mg/kg) and reduced the pleural exudate (ED50 = 6.8 mg/kg) induced by the antigen. In contrast, azelastine (10 mg/kg) failed to modify the neutrophil influx observed at 4 h and the eosinophil accumulation detected at 24 h. Azelastine was also effective against rat pleurisy induced by either platelet-activating factor (PAF-acether), histamine or serotonin. It reduced exudation and the increase in the number of mononuclear cells, neutrophils and eosinophils observed 6 h after PAF-acether. Nevertheless, antagonism of PAF-acether may not be relevant to the inhibition observed in the present model of allergic pleurisy, as the inhibition was refractory to three distinct PAF-acether receptor antagonists. In contrast, like azelastine, the histamine H1 receptor antagonist meclizine and the dual histamine and serotonin receptor antagonist cyproheptadine blocked antigen-induced exudation and failed to interfere with cell influx. We conclude that the anti-exudatory activity of oral azelastine on antigen-induced pleurisy is consistent with it exerting direct effects against vasoactive amines, but is not related to an effect against leucocyte infiltration nor to its ability to inhibit PAF-acether.

Animals↗