Biomedical subjects

J Lefort

Publications and source records attributed to J Lefort.

At least 19 recordsLinked to original sources

PubMed1998

Systemic administration of endotoxin induces bronchopulmonary hyperreactivity dissociated from TNF-alpha formation and neutrophil sequestration into the murine lungs.

Bronchopulmonary hyperreactivity (BHR), an increased responsiveness to nonspecific bronchoconstrictor agents, is a well-known characteristic of bronchial asthma. It has been recently suggested that the severity of this disease is related to the endotoxin content of house dust. In the present report, it is shown that the i.p. administration of bacterial LPS to mice is followed by a marked early dose-dependent BHR in response to methacholine. The microscopic examination showed no ultrastructural lesions of the lungs or of the airways, but a marked neutrophil accumulation in the capillaries, as confirmed by an increase of the lung content in the neutrophil enzyme marker myeloperoxidase. In parallel, high levels of TNF-alpha were found in plasma as well as its transcripts in the lung tissues. Using immunologic (anti-TNF-alpha and anti-granulocyte Abs), and pharmacologic (dexamethasone and vinblastine) tools, it is demonstrated that BHR is apparently neither related to the presence of neutrophils in the pulmonary microvasculature nor to the synthesis of TNF-alpha.

Aerosols↗

PubMed1997

Inhibition by the immunosuppressive agent FK-506 of antigen-induced airways eosinophilia and bronchial hyperreactivity in mice.

1. The effect of the immunosuppressive agent, FK-506, an allergen-induced airways eosinophilia and bronchial hyperreactivity (BHR) in hyper IgE mice (BP2 selection) was investigated. 2. Administration of FK-506 at 2 mg kg-1 s.c., 1 h before and 5 h after the first four ovalbumin challenges, reduced the recruitment of eosinophils into the bronchoalveolar lavage fluid (BALF) from 1.36 +/- 0.22 x 10(5) to 0.53 +/- 0.24 x 10(5) cells ml-1 (n = 5-6, P < 0.05; 60% inhibition), inhibited by 80% BHR in response to i.v. 5-HT and practically suppressed BHR in response to inhaled methacholine. 3. The antigen-induced interleukin (IL)-5 formation in the BALF and serum was inhibited by FK-506 by 75% in both instances. 4. FK-506 failed to modify the bronchoconstriction in BP2 mice, suggesting that different mechanisms are involved in acute bronchoconstriction and BHR. 5. The increased number of CD4+, CD8+, CD3+ T lymphocytes in the BALF to antigen-challenged mice was unaffected by FK-506. 6. These findings indicate that antigen-induced in vivo IL-5 release and eosinophil, but not T-cell, infiltration into the bronchial lumen of sensitized BP2 mice are targets for the anti-allergic activities of FK-506.

Animals↗

PubMed1996

Germinal center formation and local immunoglobulin E (IgE) production in the lung after an airway antigenic challenge.

Airway inflammation plays a central role in the pathogenesis of asthma. However, the precise contribution of all cell types in the development and maintenance of airway hyperreactivity and histopathology during allergic inflammation remains unclear. After sensitization of mice in the periphery, challenge by multiple intratracheal (i.t.) instillations of ovalbumin (OVA) results in eosinophilia, mononuclear cell infiltration, and airway epithelial changes analogous to that seen in asthma (Blyth, D.I., M.S. Pedrick, T.J. Savage, E.M. Hessel, and D. Fattah. 1996. Am. J. Respir. Cell Mol. Biol. 14:425-438). To investigate further the nature of the cellular infiltrate, lungs from OVA-versus saline-treated mice were processed for histology and immunohistochemistry. One of the most striking features observed was the formation of germinal centers within the parenchyma of the inflamed lungs. In addition, follicular dendritic cells (FDCs) bearing OVA on their plasma membranes appeared and, adjacent to these sites, OVA-specific IgG1-, IgE-, and IgA-producing plasma cells emerged. To confirm that antigen-specific immunoglobulins (Ig) were being produced within the parenchyma, plasma cell number and antibody production were quantitated in vitro after isolation of cells from the lung. These assays confirmed that the isotypes observed in situ were a secreted product. As IgE-dependent mechanisms have been implicated as being central to the pathogenesis of bronchial asthma, airway hyperresponsiveness was evaluated. The mice undergoing lung inflammation were hyperresponsive, while the control group remained at baseline. These data demonstrate that antigen-driven differentiation of B cells via induction of an FDC network and germinal centers occurs in the parenchyma of inflamed lungs. These germinal centers would then provide a local source of IgE-secreting plasma cells that contribute to the release of factors mediating inflammatory processes in the lung.

Animals↗

PubMed1996

In vivo neutralization of eosinophil-derived major basic protein inhibits antigen-induced bronchial hyperreactivity in sensitized guinea pigs.

This study examines the effect of purified rabbit antiguinea pig eosinophil-derived major basic protein (MBP) Ig on antigen-induced bronchial hyperreactivity to inhaled acetylcholine in aerosol-sensitized guinea pigs. Ovalbumin inhalation by sensitized guinea pigs induced a rise in the numbers of eosinophils and in the levels of MBP in the bronchoalveolar lavage fluid, which peaked at 24 h and resolved at 72 h. Antigen-challenged animals exhibited bronchial hyperreactivity to inhale acetylcholine at 72 h, but not at 6 or 24 h. The intranasal administration of 200 microliter of purified rabbit anti-guinea pig MBP Ig, at 2.5 mg/ml, but not of the control preimmune rabbit Ig, 1 h before and 5 h after ovalbumin inhalation suppressed bronchial hyperreactivity to acetylcholine at 72 h without affecting the number of eosinophils accumulating in the bronchoalveolar lavage fluid. These findings indicate that antigen challenge in sensitized guinea pigs is followed by early eosinophil infiltration and activation within the airways and by late bronchial hyperreactivity. Neutralization of endogenously secreted MBP by a specific antiserum prevented antigen-induced bronchial hyperreactivity, suggesting that eosinophil degranulation plays an important role in the alterations of bronchopulmonary function in the guinea pig.

Acetylcholine↗

PubMed1996

Effect of antigen provocation of IL-5 transgenic mice on eosinophil mobilization and bronchial hyperresponsiveness.

We investigated whether allergen-induced eosinophil recruitment into mouse airways modifies the in vivo bronchopulmonary responses to standard agonists, and adaptation of a technique described for larger animals. Swiss, CBA, and IL-5 transgenic mice were immunized with ovalbumin and challenged intranasally after 14 days. Immunization alone was followed by increased eosinophil counts in bone marrow and blood, whereas antigenic challenge induced eosinophil infiltration in lungs and bronchoalveolar lavage fluid, which was suppressed by dexamethasone. Despite the high eosinophil counts, no bronchopulmonary hyperreactivity to methacholine or serotonin was detected 3 to 96 hours after antigenic provocation. Our results demonstrate that immunization augments the production of eosinophils by mice, which is further increased by antigenic challenge, but that eosinophil overproduction and lung infiltration, per se, are not sufficient to induce bronchopulmonary hyperreactivity, even in constitutively hypereosinophilic IL-5 transgenic mice.

Airway Resistance↗

PubMed1996

Effect of cyclo-oxygenase inhibitors and modulators of cyclic AMP formation on lipopolysaccharide-induced neutrophil infiltration in mouse lung.

1. The adult respiratory distress syndrome (ARDS) is an acute lung inflammation developed after direct or indirect contact with pathogenic agents. In the present study, a mouse model was developed to mimic this condition using aerosolized bacterial lipopolysaccharide (LPS) and to investigate the mechanisms involved in the lung inflammatory response. 2. Inhalation of LPS led to a time and dose-dependent increase in tumour necrosis factor-alpha (TNF-alpha) production and neutrophil recruitment into the bronchoalveolar lavage fluid (BALF) of Balb/c mice. Under the same conditions, neutrophil infiltration was also found in the BALF of the LPS-sensitive mouse strain C3H/HeN, but was absent in the LPS-resistant strain C3H/HeJ. Intranasal administration of murine recombinant TNF-alpha also triggered neutrophil recruitment. 3. One hour after inhalation of LPS, half of the maximal level of TNF-alpha was measured in the BALF, but only a few neutrophils were detected at this time. The peak TNF-alpha concentration was reached at 3 h, when the neutrophil amount started to increase. At 24 h, maximal neutrophil number was found in the BALF and TNF-alpha was no longer present. 4. Pretreatment of mice under different experimental conditions demonstrated that: (a) cycloheximide almost completely blocks both neutrophil recruitment and TNF-alpha production; (b) anti TNF-alpha antibodies block neutrophil recruitment; (c) indomethacin or aspirin enhance by two fold neutrophil recruitment; (d) indomethacin significantly increases TNF-alpha production 1 h after inhalation of LPS; (e) dibutyryl cyclic AMP and prostaglandin E2 (PGE2) block both neutrophil recruitment and TNF-alpha production. 5. It is concluded that aerosolized LPS in mice triggers an acute lung inflammation which can be used as a potential model of inhalational ARDS and that, strategies leading to the elevation of cyclic AMP levels in vivo can be effective in modulating LPS-induced TNF-alpha synthesis and neutrophil recruitment.

Administration, Inhalation↗

PubMed1996

Inhibition of airways inflammation by dexamethasone is followed by reduced bronchial hyperreactivity in BP2 mice.

BACKGROUND: Infiltration of inflammatory cells in the airways is a constant characteristic of asthma and is considered to result in bronchial hyperreactivity (BHR). We have recently developed a model of BHR using a selection of mice, named BP2, which display eosinophil-dependent BHR following antigen challenges. An anti-IL-5 antibody suppressed antigen-induced eosinophil recruitment to the airways and BHR in BP2 mice. OBJECTIVE: To investigate the implication of infiltrated inflammatory cells in the induction of BHR in mice. METHODS: The effects of glucocorticosteroid dexamethasone on airways eosinophilia and BHR were observed. RESULTS: Administration of dexamethasone at the dose of 1.25 mg/kg i.p. 1 h before each of four antigen provocations suppressed the airways eosinophilia and BHR in response to intravenous 5-HT and to aerosolized methacholine, as well as IL-5 production in the BALF and in the serum. By contrast, dexamethasone failed to reduce anaphylactic bronchoconstriction. CONCLUSIONS: These results suggest that dexamethasone exerts its inhibitory effects on antigen-induced airways eosinophilia in mice by inhibiting IL-5 production, but that it does not block the liberation of anaphylactic mediators in mice.

Anaphylaxis↗

PubMed1995

Eosinophil recruitment into the respiratory epithelium following antigenic challenge in hyper-IgE mice is accompanied by interleukin 5-dependent bronchial hyperresponsiveness.

A murine model for antigen-induced bronchial hyperreactivity (BHR) and airway eosinophilia, two hallmarks of asthma, was developed using ovalbumin-immunized mice, which produce large amounts of IgE (named BP2, "Bons Producteurs 2," for High Line of Selection 2). A single intranasal ovalbumin challenge failed to modify the bronchial responses, despite the intense eosinophil recruitment into the bronchoalveolar lavage fluid and airways. When mice were challenged twice a day for 2 days or once a day for 10 days, BHR in response to i.v. 5-hydroxytryptamine or to inhaled methacholine was induced in BP2 mice but not in BALB/c mice. Histological examination showed that eosinophils reached the respiratory epithelium after multiple ovalbumin challenges in BP2 mice but remained in the bronchial submucosa in BALB/c mice. Total IgE titers in serum were augmented significantly with immunization in both strains, but much more so in BP2 mice. Interleukin 5 (IL-5) titers in serum and bronchoalveolar lavage fluid of BP2 mice were augmented by the antigenic provocation, and a specific anti-IL5 neutralizing antibody suppressed altogether airway eosinophilia and BHR, indicating a participation of IL-5 in its development. Our results indicate that the recruitment of eosinophils to the airways alone does not induce BHR in mice and that the selective effect on BP2 mice is related to their increased IgE titers associated with antigen-driven eosinophil migration to the epithelium, following formation and secretion of IL-5.

Animals↗

PubMed1994

Albumin exchange and inflammatory cell recruitment in lungs of antigen-challenged guinea pigs: role of histamine.

Microvascular albumin exchange and sequestration of inflammatory cells into the lungs of anesthetized guinea pigs immunized to ovalbumin were evaluated using radioactive tracers. Increased exchange of radiolabeled (*) albumin from airways to blood was noted in immunized and boosted animals under basal conditions. After the intratracheal injection of 300 micrograms of ovalbumin, an additional increase in exchange through epithelium occurred, since the rate of appearance of *albumin in blood was enhanced compared with control (140 +/- 30 vs. 54 +/- 20% in 1 h). The augmentation of lung content in extravascular *albumin compared with control (16.2 +/- 4.0 vs. 5.9 +/- 1.6%) indicates that transendothelial exchange was also facilitated. Concomitment with the sequestration of *platelets into the lungs of antigen-challenged sensitized animals (59.2 +/- 20% in 1 h), leukocytes (> 60% polymorphonuclear neutrophils) did not marginate. Histamine released during antigenic shock might promote leukocyte demargination from the vascular bed through its vasomotor effect and/or by inhibiting leukocyte activation and consequently may counteract the effects of other inflammatory mediators acting to sequester neutrophils. In confirmation, perfusion of histamine to the immunized animals induced demargination of lung leukocytes. Histamine antagonists prevented the increased exchange of *albumin through the epithelial and endothelial barriers and uncovered *leukocyte sequestration (100.7 +/- 28.9% in 1 h) in the lungs of antigen-challenged animals. Histamine antagonists may favor antigen-induced leukocyte sequestration in the lungs by preventing the effects of endogenous histamine on capillary recruitment and blood flow.

Animals↗

PubMed1994

Role of eosinophil activation in the bronchial reactivity of allergic guinea pigs.

Ovalbumin inhalation by sensitized guinea pigs induced a marked increase in the number of eosinophils (0.89 +/- 0.18 to 5.45 +/- 0.77 x 10(5)/ml, n = 10, p < 0.05) and elevations in the amounts of protein and eosinophil-derived major basic protein (MBP) (1,010.7 +/- 184.9 to 4,116.6 +/- 973.0 ng/ml, n = 10, p < 0.05) recovered by bronchoalveolar lavage (BAL). In contrast, no changes in the levels of eosinophil peroxidase (EPO) or in the sensitivity of the airways to bronchoconstriction induced by methacholine were detected. However, when ovalbumin-exposed guinea pigs received an intratracheal instillation of 1 microgram leukotriene (LT)B4 30 min prior to methacholine provocation, elevated levels of EPO and MBP in the BAL fluid and a marked bronchial hyperreactivity to methacholine were noted when compared with saline-challenged LTB4-injected animals (p < 0.05). In contrast, the intratracheal instillation of 1 or 3 micrograms platelet-activating factor (PAF) did not significantly modify the bronchial reactivity to methacholine or the levels of EPO and MBP. PAF and LTB4 induced similar enhancements in the amount of protein in BAL fluids from antigen-exposed guinea pigs, suggesting that increased endothelial/epithelial permeability does not account for hyperreactivity. A significant correlation between the levels of EPO or MBP and the intensity of the bronchial responsiveness to methacholine were shown in ovalbumin-challenged guinea pigs, irrespective of their subsequent treatment, i.e., either with PAF or with LTB4 or with their vehicle (r = 0.579, p = 0.0002 and r = 0.330, p = 0.049, n = 36 for EPO and MBP, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Compound PCA-4248 interferes with bronchopulmonary anaphylaxis and with in vitro hyperresponsiveness to platelet-activating factor.

The intravenous (i.v.) or oral administration of the platelet-activating factor (PAF) antagonist, PCA-4248, to guinea-pigs blocked selectively the bronchoconstriction induced by PAF, as well as the accompanying thrombocytopenia and leucopenia. In addition, PCA-4248 i.v. or intratracheal (i.t.) administration blocked the bronchoconstriction caused by the i.t. instillation of PAF. As in the case of other PAF antagonists, bronchoconstriction caused by the i.t. instillation of antigen was only inhibited by PCA-4248 in guinea-pigs that did not receive a booster injection of antigen during sensitization whereas the booster injection of antigen made anaphylactic bronchoconstriction resistant to the compound. In vitro, when lungs from non-sensitized guinea-pigs were perfused with Krebs-bovine serum albumin (BSA) solution supplemented with PCA-4248, bronchoconstriction and the formation of thromboxane A2 by PAF were blocked. In this in vitro model of perfused lungs, active sensitization with a booster injection of antigen leads to bronchopulmonary hyperresponsiveness to PAF and failure of other PAF antagonists to inhibit the effects of PAF itself. Surprisingly, in lungs isolated from actively sensitized and boosted guinea-pigs, PCA-4248 blocked the effects of PAF, indicating that this compound possesses additional original properties in this model.

Anaphylaxis↗

PubMed1993

Inhibition by nedocromil sodium of recombinant human interleukin-5-induced lung hyperresponsiveness to platelet-activating factor in actively sensitized guinea pigs.

BACKGROUND: The intratracheal instillation of recombinant human interleukin-5 (rhIL-5) into isolated lungs from sensitized and antigen-boosted guinea pigs is followed by enhanced responses to platelet-activating factor (PAF). METHODS: Modulation by nedocromil sodium of rhIL-5-dependent hyperresponsiveness to PAF was investigated. Perfused lungs from guinea pigs actively sensitized to ovalbumin were injected intratracheally with 300 ng rhIL-5 followed by PAF (10 and 100 ng intraarterially). RESULTS: No inhibition of rhIL-5-induced increased bronchoconstriction and release of thromboxane (TX)B2 and histamine by PAF was observed when nedocromil sodium (10 mumol/L) was perfused into the lungs. In contrast, when guinea pigs were treated for 2 days (30 mg/kg twice a day), eosinophil recruitment into the bronchoalveolar lavage fluid and hyperresponsiveness to PAF were markedly reduced (100% [p < 0.001]; around 70% [p < 0.05] and around 90% [p < 0.001] inhibition for bronchoconstriction, TXB2 and histamine release, respectively). CONCLUSION: Our results indicate that nedocromil sodium prevents the rhIL-5-induced lung hyperresponsiveness to PAF and the eosinophil migration into the airways only when it is administered in vivo. It is thus suggested that nedocromil sodium interferes with the development of airway inflammation by inhibiting the recruitment in the lung of a target on which PAF and IL-5 interact.

Animals↗

PubMed1993

Interference of a neutrophil recruitment inhibitory factor upon the accumulation of inflammatory cells and airway hyperreactivity in sensitized guinea-pigs after intranasal antigen challenge.

1. A neutrophil recruitment inhibitory factor (NRIF) recovered from the crude supernatant of lipopolysaccharide (LPS)-stimulated macrophages inhibited neutrophil migration following both intratracheal and intravenous administration of LPS, but did not alter the pattern of leukopenia/leucocytosis induced by intravenous LPS. 2. The correlation between airway infiltration by inflammatory cells and hyperreactivity in lungs from actively sensitized and challenged guinea-pigs was investigated by use of NRIF. 3. Increased eosinophil counts were found in the bronchoalveolar lavage fluid from guinea-pigs sensitized with 10 micrograms ovalbumin and challenged at day 14 by the intranasal administration of the antigen. The increase was evident 5 h after challenge and persisted at 24 h. Neutrophil numbers were also increased at this time. Pretreatment with NRIF suppressed the leucocyte increase in the bronchoalveolar lavage fluid. 4. Bronchoconstriction and histamine release induced by 3 ng PAF injected into the isolated lungs were increased in challenged guinea-pigs as compared to sensitized but unchallenged controls. Pretreatment of the animals with NRIF did not interfere with this response, but significantly reduced the bronchoconstriction induced by ovalbumin injection. 5. Even though the increased number of inflammatory cells in bronchoalveolar lavage and airway hyperresponsiveness were concomitant, NRIF inhibited cellular infiltration but failed to alter airway hyperreactivity to PAF, demonstrating that these events may occur independently. Conversely, the inhibition of antigen-induced bronchoconstriction by NRIF suggests that this response is dependent upon the emigration of granulocytes.

Administration, Intranasal↗

PubMed1993

Intratracheal E. coli lipopolysaccharide induces platelet-dependent bronchial hyperreactivity.

Bronchial hyperresponsiveness (BHR) characterizes asthma and accompanies respiratory infections. Because endotoxin [lipopolysaccharide (LPS)] induces either hyper- or hyporesponsiveness of the guinea pig airways and protects against bronchopulmonary anaphylaxis in sensitized guinea pigs, we compared the effects of the intratracheal administration of Escherichia coli LPS on bronchopulmonary responsiveness to intravenous serotonin or acetylcholine in sensitized and nonsensitized guinea pigs. LPS (1 mg) induced BHR within 1-2 h, with a threefold increase in the bronchial response after serotonin challenge in both groups (n = 6; P < 0.005) and a marked influx of neutrophils into the perivascular and peribronchial connective tissue and the bronchoalveolar lavage fluid. This BHR was not leukocyte dependent, since it was still observed in animals depleted of circulating leukocytes with vinblastine and was not modified by antineutrophil serum, unless platelet counts were < 100,000/mm3. This suggested that LPS-induced BHR involves platelets, and indeed antiplatelet serum, which depleted platelets, or prostacyclin, which inhibited platelets, was effective in suppressing BHR. Neither aspirin, mepyramine, nor the platelet-activating factor antagonist WEB 2170, administered before LPS instillation, prevented BHR, whereas the association of methysergide, mepyramine, and aspirin was effective, without modifying platelet and leukocyte counts. This association has been shown to prevent the release of ATP by ex vivo platelets. Our results suggest that platelets or a platelet-derived product mediates LPS-induced BHR.

Acetylcholine↗

PubMed1993

Effect of active sensitization on the bronchopulmonary responses to tachykinins in the guinea pig. Modulation by peptidase inhibitors.

The i.v. administration of substance P (SP, 0.25-16 micrograms/kg) or of the selective metabolic stable NK-1 agonist, [Glp6,Pro9]SP-(6-11) (septide, 0.03-0.25 microgram) to atropine-treated guinea pigs or to isolated perfused lungs triggered a dose-dependent bronchoconstriction, which was enhanced in animals actively sensitized to ovalbumin. In vivo, bronchial hyper-responsiveness was restricted to SP and to septide, inasmuch as neurokinin A (0.06-1 microgram/kg)- or capsaicin (0.5-32 micrograms/kg)-induced bronchoconstriction were not modified. In contrast, isolated lungs from sensitized guinea pigs exhibited an increased bronchoconstriction also in response to capsaicin (0.01-10 micrograms), which was inhibited by atropine in the medium. Pretreatment of actively sensitized guinea pigs either with indomethacin plus mepyramine, the lipoxygenase inhibitor BW A4C or with the platelet-activating factor antagonist SR 27417, did not modify bronchial hyper-reactivity to SP. Captopril (5 mg/kg i.v.), but not thiorphan (0.8 mg/kg i.v.), increased the SP-induced bronchoconstriction in actively sensitized animals, whereas both inhibitors were equally effective in nonsensitized guinea pigs. Thiorphan, however, did not modify the in vivo response to septide. Our results demonstrate that guinea pigs sensitized to ovalbumin exhibit bronchial hyperreactivity to SP, but not to neurokinin A, as compared to nonsensitized animals, suggesting a decrease in the neutral endopeptidase activity in the airways brought by the immunization. However, the results obtained by using septide indicate that other mechanisms may be involved in the bronchial hyper-reactivity to SP.

6-Ketoprostaglandin F1 alpha↗

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

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

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↗