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Biomedical subjects

V Lagente

Publications and source records attributed to V Lagente.

At least 73 records · Page 4Linked to original sources
PubMed1994

Inhibitory effect of cyclosporin A on eosinophil infiltration in the guinea-pig lung induced by antigen, platelet-activating factor and leukotriene B4.

The effect of the immunosuppressive compound, cyclosporin A, and the corticosteroid, betamethasone, was investigated on eosinophil accumulation in guinea-pig lung tissue induced by antigen, platelet-activating factor (PAF) and leukotriene B4 (LTB4). The accumulation of eosinophils in the peribronchial area was evaluated on histological preparations. The lung sections were stained with Luna's reagent specific for eosinophil granule content. Oral treatment of the guinea-pigs with cyclosporin, 10 mg.kg-1 three times a day for two days, and 10 mg.kg-1 1 h before antigen challenge, significantly reduced the accumulation of eosinophils observed at 4 and 24 h, in the peribronchial area of sensitized guinea-pig lung. Betamethasone (3 mg.kg-1), administered orally 24 h and 1 h before antigen challenge elicited a moderate but significant reduction of antigen-induced eosinophil accumulation. Pretreatment of the guinea-pigs with cyclosporin or betamethasone elicited a marked inhibition of the accumulation of eosinophils in the peribronchial area induced by aerosolized PAF (100 micrograms.ml-1) or LTB4 (5 micrograms.ml-1). Since cyclosporin and betamethasone significantly inhibit the antigen-induced eosinophil accumulation, these results suggest that antigen-induced lung eosinophilia is dependent of T-lymphocytes. However, cyclosporin and betamethasone may also reduce the chemotactic activity of PAF and LTB4 on guinea-pig eosinophils.

Animals↗
PubMed1993

Phosphoramidon potentiates the bronchoconstriction induced by inhaled bombesin in guinea pigs.

The effect of the neutral endopeptidase inhibitor, phosphoramidon, on the bronchoconstriction induced by aerosolized bombesin in the guinea pig was investigated. Administered by aerosol for 1 min, bombesin (0.01 or 0.1 mg/ml) induced a dose-dependent increase in pulmonary inflation pressure. Pretreatment of the guinea-pigs with phosphoramidon (0.1 mM), administered by aerosol for 15 min, 15 min prior to challenge, markedly potentiated the increase in pulmonary inflation pressure induced by bombesin (0.01 mg/ml) and substance P (0.1 mg/ml). This result suggests a local hydrolysis of bombesin by airway neutral endopeptidase reducing the activity of this peptide on smooth muscle.

Administration, Inhalation↗
PubMed1993

Inhaled substance P induces activation of alveolar macrophages and increases airway responses in the guinea-pig.

Guinea-pigs pretreated with phosphoramidon or saline were treated with an aerosol of substance P (SP) or saline. 24 h later, the pulmonary inflation pressure (PIP) to substance P or to cumulative doses of acetylcholine or of histamine was recorded. The PIP response to SP itself was significantly enhanced in animals treated with phosphoramidon+SP as compared with phosphoramidon+saline (2.5-fold increase 1 min after the end of the inhalation, P < 0.001). The response to acetylcholine and to histamine was also significantly enhanced in phosphoramidon+substance P-treated as compared with phosphoramidon+saline-treated guinea-pigs (PC200 = 38.9 and 1.6 as compared with 77.6 and 3.9 micrograms/ml, P < 0.01 and P < 0.05 respectively). The production of superoxide anions by alveolar macrophages in response to f-MLP was also enhanced after treatment with phosphoramidon+SP as compared with phosphoramidon+saline (6.4 +/- 0.7 and 3.8 +/- 0.3 cpm, P < 0.001 respectively). In animals treated with saline+SP or saline+saline, the PIP responses and the production of superoxide anion were similar. Altogether these results suggest that SP contributes to the bronchial hyper-responsiveness in asthma and this probably through activation of alveolar macrophages.

Acetylcholine↗
PubMed1993

Effects of the platelet activating factor antagonists BN 52021 and BN 50730 on antigen-induced bronchial hyperresponsiveness and eosinophil infiltration in lung from sensitized guinea-pigs.

The involvement of platelet activating factor (PAF) in antigen-induced bronchial hyperresponsiveness was investigated by the use of the PAF antagonists BN 52021 and BN 50730, in a guinea-pig model where sensitization and challenge were performed by aerosol. Male Hartley guinea-pigs were sensitized by two aerosol exposures at 48 hr intervals to a 0.9% NaCl solution (saline) containing 2 mg/ml ovalbumin for 30 min. Fifteen to 20 days later, guinea-pigs were challenged by exposure to five successive aerosols of increasing concentrations of ovalbumin (OA) or respectively, 10 microg/ml, 100 microg/ml, 1 mg/ml, 5 mg/ml and 10 mg/ml for 15 min each, or saline alone. Three to four hr and 18-24 hr after the aerosol challenge the guinea-pigs were prepared for recording of bronchopulmonary response and aerosol administrations were then generated with an ultrasonic nebulizer. The bronchopulmonary responses induced by successive 1-min aerosol bursts of acetylcholine (ACh) was assessed. As compared with saline-challenged guinea-pigs, an enhanced bronchopulmonary response to aerosol administration of cumulative doses of ACh was observed, 3-4 hr and 18-24 hr post-ovalbumin challenge. When the sensitized guinea-pigs were pretreated 1 hr before ovalbumin exposure with BN 52021 or BN 50730 (25 mg/kg, per os), a significant inhibition of the increase in the bronchopulmonary response to ACh was observed, both at 3-4 hr and 18-24 hr. Furthermore, when guinea-pigs were treated 3-4 hr after the ovalbumin exposure with BN 52021 or BN 50730, a significant inhibition of the hyperresponsiveness to ACh was recorded at 18-24 hr. A marked accumulation of eosinophils in the peribronchial regions was observed on histological preparations of lung specimens collected 4 hr or 24 hr after ovalbumin exposure. Pretreatment of the guinea-pigs by BN 50730 or BN 52021 did not modify the eosinophil accumulation in the peribronchial area. No significant difference in the number of eosinophils collected in the bronchoalveolar lavage fluid is observed, 24 hr post-ovalbumin challenge, under the pretreatment with BN 52021 or BN 50730. Pretreatment of guinea-pigs by BN 50730 or BN 52021 significantly reduced the PAF-induced (100 microg/ml) increase in eosinophil number in the peribronchial area. By contrast, they did not inhibit the eosinophilia induced by aerosol administration of LTB4 (5 microg/ml). These results suggest that the bronchial hyperresponsiveness observed in this study is associated with eosinophil accumulation in the lung. The potent inhibition of the bronchial hyperresponsiveness by the two unrelated antagonists of PAF suggests that the lipid mediator is involved in its triggering and duration, but not in the eosinophil infiltration.

Acetylcholine↗
PubMed1993

Bronchopulmonary responses to endothelin-1 in sensitized and challenged guinea-pigs: role of cyclooxygenase metabolites and platelet-activating factor.

The effect of phosphoramidon on the increase in pulmonary inflation pressure (PIP) induced by endothelin-1 (ET-1) administered by aerosol in ovalbumin (OA)-sensitized and challenged guinea-pigs was investigated after pretreatment or not of the animals with the neutral endopeptidase inhibitor, phosphoramidon, the cyclooxygenase inhibitor, indomethacin or the platelet activating factor (PAF) antagonist, BN 50730. When guinea-pigs were pretreated by phosphoramidon (0.1 mM, aerosol for 15 min), a significant enhancement of PIP was observed after administration of ET-1 (1 or 3 micrograms ml-1, aerosol for 2 min), whereas these doses of the peptide were only slightly active in control animals. In sensitized and unchallenged guinea-pigs, ET-1 (1 or 3 micrograms.ml-1, aerosol for 2 min) induced, as in controls, a moderate increase in PIP. In contrast, aerosol exposure of OA in sensitized guinea-pigs developed an increased PIP following ET-1 (1 and 3 micrograms.ml-1, aerosol for 2 min) administration, that was non significantly affected by pretreatment of the animals with phosphoramidon after the dose of 3 micrograms ml-1 ET-1. Guinea-pigs exposed to phorphoramidon and treated with indomethacin (10 mg kg-1, i.v.) or BN 50730 (25 mg kg-1, per os) significantly reduced the increase in PIP upon administration of ET-1 (3 micrograms.ml-1, aerosol for 2 min). No inhibitory effect of indomethacin was noted when ET-1 (3 micrograms.ml-1, aerosol for 2 min) was administered to sensitized and OA-exposed guinea-pigs, pretreated or not with phosphoramidon. In contrast, BN 50730 significantly reduced the increase in PIP induced by ET-1 observed in sensitized and OA-exposed guinea-pigs. Moreover, this drug was moderately active in reducing the increase in PIP induced by ET-1, when the animals were pretreated by phosphoramidon. These results suggest that a phosphoramidon-sensitive endopeptidase-like enzyme, present in the airway tissue modulates the effect of ET-1. Furthermore, the increase in PIP to ET-1 observed in aerosol-sensitized and antigen-exposed guinea-pigs appears to be mediated by PAF rather than cyclooxygenase metabolites, even though the participation of other mediators in this process is open.

Aerosols↗
PubMed1992

Involvement of a phosphoramidon-sensitive endopeptidase in the processing of big endothelin-1 in the guinea-pig.

In anaesthetized and ventilated guinea-pigs, i.v. injection of 1 nmol/kg big endothelin-1 (big ET-1) did not evoke significant changes in pulmonary inflation pressure (PIP) and mean arterial blood pressure (MBP), whereas injection of the same dose of endothelin-1 (ET-1) induced marked and rapid bronchoconstrictor and pressor responses. Administered at the dose of 10 nmol/kg, big ET-1 provoked significant increases in PIP and MBP, which developed slowly and were long-lasting as compared to those evoked by ET-1. When big ET-1 was incubated for 45 min at 37 degrees C with alpha-chymotrypsin (2 mU/nmol) or pepsin (1 microgram/nmol) and then injected into guinea-pigs at the dose of 1 nmol/kg, marked bronchoconstrictor and pressor responses were observed, with kinetics similar to those noted after administration of the same dose of ET-1. The magnitude of the alpha-chymotrypsin- or pepsin-treated big ET-1 responses was similar to that induced by ET-1, incubated or not with the enzymes. Injected i.v. at the dose of 5 mg/kg, 5 min before the challenge, phosphoramidon almost totally inhibited the bronchoconstrictor and pressor responses induced by 10 nmol/kg big ET-1, whereas thiorphan (5 mg/kg) partially reduced the increase in PIP and exerted a minimal effect on the changes in MBP. Administered at the dose of 20 mg/kg per os, 1 h before i.v. administration of 10 nmol/kg big ET-1, enalapril maleate and captopril did not significantly alter the bronchoconstriction and the hypertensive response evoked by the peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Contractile activity of big endothelin-1 on the human isolated bronchus.

1. We have studied the contractile activity of the 39 amino acid precursor of endothelin-1 (ET-1), big endothelin-1 (big ET-1), on human isolated bronchi. The contribution of the metalloproteases, neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE), in the presence or absence of the epithelium lining, by use of specific inhibitors, was also evaluated on the effects of big ET-1. 2. Big ET-1 elicited a potent contraction of human isolated bronchus. The -log EC50 value for big ET-1 was 7.53 +/- 0.08 (n = 11) and Emax 78.5 +/- 3.8% (% of ACh 3mM). 3. Incubation of human isolated bronchi with the NEP inhibitor phosphoramidon (10(-5) M) induced a rightward shift of the concentration-response curve induced by big ET-1 (10(-9) M to 3 x 10(-7) M). Similar results were observed when human bronchi were incubated with thiorphan (10(-5) M), but the shift to the right was significantly less (P less than 0.01) than that observed in the case of phosphoramidon (-0.35 +/- 0.05 vs -0.67 +/- 0.07 log unit). 4. The two inhibitors of angiotensin I converting enzyme (ACE), captopril or enalapril diacid, did not affect the concentration-response curve for contraction induced by big ET-1. 5. When the epithelium was removed, a leftward shift of the concentration-response curve of big ET-1 (10(-9) M to 3 x 10(-7) M) was observed. Incubation of human isolated bronchi with phosphoramidon or thiorphan (10-5M) or with enalapril diacid or captopril did not modify the leftward shift of the concentration-response curve for big ET-1 after epithelium removal.6. These results suggest that big ET-1 elicits potent contractile activity in the human isolated bronchus and that its effect is the consequence of the conversion to ET-1 by a phosphoramidon-sensitive metalloprotease which, although different from NEP and ACE, appears to be similar to the endothelinconverting enzyme (ECE) described in other studies in animals.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

Activation of guinea pig alveolar macrophages by endothelin-1.

Endothelin-1 (ET-1) induced a concentration- and time-dependent increase in arachidonic acid release from guinea pig alveolar macrophages, a maximum being reached at 1 nM ET-1. Regarding the time-course study, maximal release of arachidonic acid was observed after 30 s of incubation with ET-1 and then followed by a marked decrease, suggesting a reuptake of free arachidonic acid. ET-1 (0.1-10 nM) induced a concentration- and time-dependent release of TXB2, the stable metabolite of TXA2, evaluated by an ELISA technique. Maximum release was also obtained with 1 nM ET-1 but only after a 1-min incubation period. By contrast, ET-1 (1 pM-1 microM) did not stimulate the release of superoxide anion at any time point of the kinetic study. These results suggests that ET-1 may activate guinea pig alveolar macrophages, probably through a mechanism involving the arachidonic acid pathway.

Animals↗
PubMed1991

Bronchopulmonary and pressor activities of endothelin-1 (ET-1), ET-2, ET-3, and big ET-1 in the guinea pig.

In anesthetized and ventilated guinea pigs, intravenous injection of ET-1, ET-2, or ET-3 induced similar rapid and dose-related increases in pulmonary inflation pressure (PIP) and mean arterial blood pressure (MABP). Indomethacin inhibited the increase in PIP evoked by ET-1, ET-2, or ET-3, whereas the changes in MABP following injection of the various ET isotypes were not significantly affected. Injection of ET-1, ET-2, or ET-3 via the pulmonary artery of isolated guinea pig lungs induced similar dose-dependent increases in PIP and pulmonary perfusion pressure (PPP), thromboxane B2 (TxB2) release, and formation of lung edema. Indomethacin (5 microM), added to the perfusion medium, significantly inhibited the alterations of PIP, PPP, TxB2 release, and lung edema formation evoked by the three ET isoforms. Intravenous injection of 1 nmol/kg of big ET-1 to guinea pigs did not induce significant changes in PIP and MABP. When administered at a dose of 10 nmol/kg, big ET-1 provoked marked slow-developing and sustained increases in PIP and MABP. When big ET-1 was incubated in vitro with either alpha-chymotrypsin or pepsin and injected into guinea pigs at a dose of 1 nmol/kg, marked rapid bronchoconstrictor and pressor responses were observed. The present results demonstrate that ET-1, ET-2, and ET-3 exert comparable bronchopulmonary and pressor activities in the guinea pig. On the contrary, big ET-1 exhibits moderate direct bronchoconstrictor and pressor effects and its hydrolysis by proteases appears to be essential for expression of its full activity.

Animals↗
PubMed1991

Endothelin-1 and bronchial hyperresponsiveness in the guinea pig.

Exposure of phosphoramidon-treated (0.1 mM solution by aerosol for 15 min) guinea pigs to an aerosol of endothelin-1 (ET-1) (10 micrograms/ml) for 30 min induced after 18-24 h an enhanced bronchopulmonary response (BR) to rechallenge with ET-1 (3 micrograms/ml) administered by aerosol. Compared with saline-exposed animals, aerosol exposure of guinea pigs to ET-1 (10 micrograms/ml) for 30 min did not alter the dose-related BR to acetylcholine (ACh) administered by aerosol 18-24 h following challenge with the peptide. In phosphoramidon-treated guinea pigs, ET-1 (5 micrograms/ml) exposure for 30 min evoked a slight but non-significant enhancement of the ACh-induced BR. Administered by aerosol in phosphoramidon-treated guinea pigs, ET-1 did not induce eosinophil accumulation in the lung, as demonstrated by examination of histological preparations and the assessment of the cell composition of bronchoalveolar lavages. The present data indicate that in spite of treatment of guinea pigs with phosphoramidon, ET-1 administration does not lead to the development of bronchial hyperresponsiveness.

Acetylcholine↗
PubMed1991

Bronchial hyperresponsiveness and cellular infiltration in the lung of guinea-pigs sensitized and challenged by aerosol.

We have studied the development of airway hyperresponsiveness and the pulmonary cell infiltration in a guinea-pig model in which both initial sensitization and subsequent exposure to the antigen were performed by aerosol. Enhanced bronchopulmonary response to aerosol administration of acetylcholine (ACh) and 5-hydroxytryptamine (5-HT) was observed 3-4 hr and 18-24 hr after antigen exposure of sensitized animals. In contrast, when ACh and 5-HT were administered intravenously 3-4 hr after the challenge, no significant alteration of the dose-response curves was observed. However, 18-24 hr after antigen challenge, a marked leftward shift of the dose-response curve was observed on intravenous injection of ACh or 5-HT. The increased bronchial reactivity to aerosolized ACh in sensitized and challenged guinea-pigs reached a maximum by days 2-4, was still significantly increased at day 5 and returned to the basal value by day 8. No further alteration of the dose-related bronchopulmonary response to aerosol or intravenous administration of ACh was recorded 24 hr after a second antigen challenge, performed 8 days after the initial one. The analysis of bronchoalveolar lavage fluids showed a significant increase in the number of polymorphonuclear neutrophils 3-4 hr after the exposure of sensitized animals to the antigen, which was also associated with a significant eosinophilia at 18-24 hr. Histological examination of lung specimens obtained from animals 3-4 hr following challenge demonstrated eosinophil infiltration in the peribronchial regions and bronchial walls, as well as within the epithelium. Furthermore, as compared to time 3-4 hr, less eosinophils in the peribronchial area and submucosa were counted 24 hr after antigen challenge. However, a role of eosinophil-derived products in the development of bronchial hyperresponsivenss in this experimental model remains to be established.

Acetylcholine↗
PubMed1991

Comparison of the effects of intra-arterial and aerosol administration of endothelin-1 (ET-1) in the guinea-pig isolated lung.

1. Intra-arterial injection of endothelin-1 (ET-1, 400 pmol; 1 microgram) in guinea-pig isolated perfused lungs, induced increases in pulmonary inflation pressure (PIP) and perfusion pressure (PPP), associated with oedema formation and thromboxane B2 (TxB2) release but not with the generation of sulphidopeptide leukotrienes or release of histamine. In contrast, aerosol administration of ET-1 (3, 6, 10 micrograms ml-1, for 2 min) evoked a dose-dependent increase in PIP, without significant changes in PPP, oedema formation or TxB2 release. 2. Addition of indomethacin (5 microM) or BW 755C (10 or 100 microM), but not nordihydroguaiaretic acid (NDGA, 50 microM) or FPL 55712 (10 microM), to the perfusion medium led to a significant inhibition of the increases in PIP and PPP, TxB2 release and oedema formation evoked by intra-arterial injection of 400 pmol ET-1. In contrast, indomethacin (5 microM), BW 755C (100 microM) or FPL 55712 (10 microM), added to the perfusion medium 10 min prior to challenge, did not affect the increase in PIP induced by a 2-min aerosol of a solution of ET-1 10 micrograms ml-1. 3. In vivo aerosol administration of indomethacin (100 mg ml-1, for 20 min) to non-anaesthetized guinea-pigs, 15 min before lung removal, did not modify the bronchopulmonary response evoked in isolated perfused lungs by an aerosol of ET-1 10 micrograms ml-1. However, under the same experimental conditions, indomethacin significantly inhibited TxB2 release evoked by aerosolized arachidonic acid (2 mg ml-1). 4. In conclusion, the present study shows that when injected by the intra-arterial route, ET-1 effects are mediated primarily via the generation of cyclo-oxygenase metabolites of arachidonic acid, whereas when the aerosol route is used, the peptide appears to act on airway smooth muscle cells, through an indomethacin-insensitive process which may involve some other, as yet unidentified, mediator(s).

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1991

Beta-2-adrenoceptor agonists up-regulate the in vitro Fc epsilon receptor II/CD23 expression on, and release from, the promonocytic cell line U937 and human blood monocytes.

The possible regulatory role of beta 2-adrenoceptor agonists in the modulation of CD23 on the human promonocytic cell line U937 and on human monocytes was investigated. Incubation for 48 h in the presence of interleukin-4 (IL-4; 30 U/ml) induced optimal expression and release of CD23 on both U937 cells and human monocytes. When a beta 2-adrenoceptor agonist, either salbutamol or fenoterol, was added to U937 cells or monocytes both the IL-4-induced CD23 expression and release were markedly up-regulated. This effect was dose-dependent, starting at 10 nM and reaching a maximum at 1 microM final concentration of either salbutamol or fenoterol. The potentiating effect of salbutamol and fenoterol on CD23 expression and release was not observed when a beta-adrenoceptor antagonist, either D,L-propranolol (1 microM) or butoxamine (1 microM), was added to the incubation medium. The alpha-adrenoceptor agonist norepinephrine (1 microM) was ineffective in enhancing the IL-4-induced expression and release of CD23 from U937 cells or human monocytes, demonstrating the specificity of the beta 2-adrenoceptor-mediated effect. In the absence of IL-4, a moderate but significant increase in the CD23 expression on U937 cells and human monocytes by these drugs was observed, as compared to the basal values. These results indicate that, besides their bronchodilator effect, beta 2-adrenoceptor agonists may regulate IgE-dependent processes.

Adrenergic beta-Agonists↗
PubMed1991

Pharmacological modulation of the antigen-induced expression of the low-affinity IgE receptor (Fc epsilon RII/CD23) on rat alveolar macrophages.

Brown-Norway (BN) rats were sensitized by 3 aerosol exposures to ovalbumin (OA; 10 mg/ml) at days 1, 3 and 14. At day 21, the rats were challenged with the antigen or vehicle by aerosol. Alveolar macrophages (AM) were obtained by bronchoalveolar lavage and the expression of Fc epsilon RII/CD23 was assessed by flow cytometry after staining with the BB10 monoclonal antibody. A maximum of 74% of the AM from sensitized and challenged BN rats expressed FC epsilon RII/CD23 24 h after OA exposure, compared to 12% of the cells from rats exposed to vehicle. Sprague-Dawley rats were passively sensitized by intravenous injection of 0.1 or 0.05 ml/kg mouse ascitic fluid containing dinitrophenyl (DNP)-specific monoclonal IgE (2682-1) and after 24 h exposed to an aerosol of 5 mg/ml of DNP-bovine serum albumin for 30 min. In this case also, antigen exposure induced the expression of Fc epsilon RII/CD23 on 75% AM, compared to 17% AM from saline-challenged rats. Such an induction of Fc epsilon RII/CD23 on AM was, however, not observed when the animals were challenged with either histamine, serotonin or acetylcholine by aerosol. The antigen-induced expression of Fc epsilon RII/CD23 on AM was inhibited upon treatment of the rats with ketotifen or beclomethasone. In addition, oral or aerosol administration of respectively BN 50730 or BN 52021 (two structurally unrelated platelet-activating factor antagonists), inhibited the antigen-induced Fc epsilon RII/CD23 expression on AM, indicating the participation of this lipid mediator in this process.

Animals↗
PubMed1990

Antigen-dependent activation of alveolar macrophages from ovalbumin-sensitized guinea-pigs: relevance of the route of administration and the amount of antigen provided.

Alveolar macrophages from guinea-pigs sensitized by different amounts of ovalbumin, administered either by subcutaneous injection or aerosol exposure, liberate increased amounts of arachidonic acid and thromboxane B2 when challenged in vitro with ovalbumin. This antigen-dependent activation of macrophages was immunospecific. The comparison between different sensitization procedures showed that the aerosol exposure was the most efficient with respect to the activation of macrophages, as cells from guinea-pigs sensitized subcutaneously were poorly activated by the antigen unless high doses were used for sensitization. The antigen-dependent activation of macrophages was affected by acid and neutral washings, suggesting the involvement of a loosely bound antibody that could not be identified. These observations suggest that, as mast cells and basophils, alveolar macrophages from actively sensitized guinea-pigs contribute to the allergic reaction by an antibody-mediated mechanism.

Aerosols↗