Library

Notes: 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 thromboxanc 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.

Notes: Background Matrix metalloproteinases (MMPs) are likely to be relevant mediators of the extracellular matrix (ECM) degradation and airway remodelling.〈section xml:id="abs1-1"〉〈title type="main"〉ObjectiveWe have compared the levels of MMPs, eotaxin and soluble interleukin 2 receptor (IL-2R) in the plasma of healthy subjects, atopic patients and asthmatic patients.Methods The asthmatic patients were separated into two groups, either well controlled on inhaled therapy or acute severe asthma. Patients with acute severe disease had all received systemic corticosteroids from 12 to 48 h before the blood was taken. Blood was recovered in EDTA tubes, incubated with either f MLP, PMA or vehicle for 10 min and centrifuged. MMP-9, TIMP-1, IL-2R and eotaxin levels were measured in the plasma by ELISA. Moreover, the activity of MMPs was also evaluated by zymography.Results An increased basal level of MMP-9 and IL2-R was observed in acute severe asthma. Following stimulation with f MLP and PMA there was an enhanced production of MMP-9 in the plasma of all groups of patients. However, the MMP-9 level was significantly enhanced in acute severe asthma, compared with the others. No difference was found for the TIMP-1 level between the patients. The eotaxin level in plasma was found to be significantly lower in acute severe asthmatics compared with the others groups. Zymography technique showed a significant increased activity of MMP-9 (92 kDa) but not MMP-2 (66 kDa) in the plasma of patients with acute asthma.Conclusion The increased in MMP-9 production and activity observed in the present study suggests a process of extracellular matrix degradation in acute severe asthmatic patients and proposes MMP-9 as a non-invasive systemic marker of inflammation and airway remodelling in asthma.

Notes: Background Selective type IV phosphodiesterase (PDE) inhibitors elicit anti-inflammatory and bronchodilatory activities in vitro and in vivo which suggest that these drugs could provide a new therapeutic approach for asthma treatment.Objective Regarding the role of IgE production in allergic and inflammatory reactions of the airways, we investigated the effect of selective PDE inhibitors on IL-4-driven IgE production by peripheral blood mononuclear cells (PBMC) or by purified B lymphocytes.Methods PBMC or purified B lymphocytes from non-allergic donors were stimulated for 13 days with IL-4 (100U/mL) in the presence or in the absence of selective PDE inhibitors. IgE production is evaluated by an ELISA technique.Results The selective PDE IV inhibitors, rolipram and Ro 20–1724 (10μM), inhibit lL-4-induced IgE production by PBMC. but not by purified B lymphocytes. No modification of the IgE production was noted with the selective PDE III inhibitors, milrinone and SK&F94-836, or the selective PDE V inhibitor, SK&F 96–231 (10 μM). Flow cytometry experiments showed that the effect of Rolipram could not be explained by the inhibition of the cell surface expression of the IL-4 receptor. Similarly, no significant effect of PDE IV inhibitors was observed on PHA-induced cell proliferation. The incubation of monocytes only with rolipram was sufficient to achieve a significant reduction of IgE production induced by IL-4.Conclusion Taken together, these results indicate that PDE IV inhibitors reduce lL-4-induced IgE production by PBMC and suggest that the inhibition of IgE production could be explained by a failure of monocytes to provide the necessary costimulatory signals.

Notes: 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 sensilization 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 lor 30 min. Fifteen to 20 days later, guinea-pigs were challenged by exposure to five successive aerosols ofincreasing concentrations of ovalbumin (OA) or respectively, 10 μg ml. KM) μ/ml, 1 mg/ml. 5 mg/ml and 10 mg/ml for 15 min each, orsaline 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 I-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 I hr before ovalbumin exposure with BN 52021 or BN 50730 (25 mg/kg, per ox), 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 hrafler 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 posl-ovalbumin challenge, under the pretreatment with BN 52021 or BN 50730. Pretrealment of guinea-pigs by BN 50730 or BN 52021 significantly reduced the PAF-induced (100μg/ml) increase in eosinophil number in the peribronchial area. By contrast, they did not inhibit the eosinophilia induced by aerosol administration of LTB4 (5 μg/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.

Notes: 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 aerosoli?.ed 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.

Notes: Background Chronic asthma is characterized by inflammatory cell infiltration and tissue remodelling leading to subepithelial fibrosis. Metalloproteinases (MMPs) are involved in degradation of extracellular matrix in most chronic inflammatory diseases.Objective The aim of this study was to investigate the expression of MMPs in the development of inflammatory processes associated or not with the concomitant development of subepithelial fibrosis in an experimental model of asthma.Methods Sensitized BP2 mice were challenged with ovalbumin (OA) every 2 weeks during 8 months. Several mice were removed once a month and bronchoalveolar lavages (BAL) or lung biopsies were performed.Results Lung sections stained with picrosirius and hydroxyproline measurements showed a significant collagen deposition after 16 weeks of OA challenge, demonstrating the development of subepithelial fibrosis. Pulmonary inflammation was present from the first OA challenge and was consistent throughout the 8 months of the study. Moreover, an up-regulation and activation of MMP-9 and, to a less extent, MMP-2 were observed in BAL fluid from challenged mice. The level of tissue inhibitor of metalloproteinases (TIMP)-1 increased after 12 weeks of OA challenge vs. control mice.Conclusion This study reveals that a decrease in the activation of the MMP-9 due to the increase in TIMP-1, could contribute to excessive collagen deposition following repeated antigen challenge in sensitized mice.

Notes: 1. Several observations suggest that tachykinins are involved in the pathogenesis of bronchopulmonary alterations. We have investigated the effect of antagonists for tachykinin NK1 (SR 140333), NK2 (SR 48968) or NK3 (SR 142801) receptors on inflammatory cell recruitment, tumour necrosis factor (TNF)-α and interleukin (IL)-6 release and matrix metalloproteinase (MMP)-9 activity in the bronchoalveolar lavage fluid (BALF) of mice exposed to lipopolysaccharide (LPS; 100 µg/mL aerosol for 30 min).2. Treatment of mice with a combination of SR 140333 and SR 48968 (10−6 mol/L, aerosol) significantly reduced the increase in the number of total cells and neutrophils and MMP-9 activity in the BALF of mice 2.5 h after LPS exposure. Treatment with the NK3 antagonist SR 142801 (10−6 mol/L, aerosol) did not inhibit the influx of neutrophils, but markedly reduced the increase in TNF-α and IL-6 levels at 2.5 h and MMP-9 activity at 20 h.3. These results show that the three tachykinin receptor antagonists may interfere with the development of airway inflammation, namely neutrophilia, TNF-α release or MMP-9 activity in the BALF of mice exposed to LPS and suggest that not only NK1 and NK2 receptors, but also NK3 receptors are involved in the modulation of the inflammatory response and airway remodelling.