Antibody to interleukin-5 inhibits virus-induced airway hyperresponsiveness to histamine in guinea pigs

In humans, respiratory viral infections lead to increased airway responsiveness and exacerbations of asthma. In the present study, the role of interleukin-5 (IL-5) in virus-induced airway hyperresponsiveness and inflammation was examined in guinea pigs. In animals treated with control antibody, parainfluenza-3 virus significantly potentiated (219%) the histamine-induced increase in lung resistance compared with vehicle treatment. In addition, viral infection significantly increased (130 to 450%) the responsiveness of isolated tracheal segments to histamine in animals treated with control antibody. In guinea pigs treated with control antibody, the numbers of eosinophils (226%), neutrophils (1,380%), and monocytes (626%) in bronchoalveolar lavage fluid were significantly increased after viral infection. The level of major basic protein in bronchoalveolar lavage fluid was not altered after viral infection. In addition, electron microscopic examination of eosinophils in airway tissue and alveolar lumen did not point to increased degranulation after viral infection. In guinea pigs treated with antibody to IL-5 the virus-induced airway hyperresponsiveness to histamine both in vivo and in vitro was almost completely inhibited. In guinea pigs treated with anti-IL-5, viral infection significantly increased the numbers of eosinophils (234%), neutrophils (1,255%), and monocytes (617%) in bronchoalveolar lavage fluid. These data suggest that IL-5 plays an important role in airway hyperresponsiveness to histamine but not in the infiltration of eosinophils after respiratory viral infection

Bronchoconstriction and airway hyperresponsiveness after ovalbumin inhalation in sensitized mice

To investigate the mechanisms underlying airway hyperresponsiveness a murine model was developed with several important characteristics of human allergic asthma. Mice were intraperitoneally sensitized with ovalbumin and after 4 weeks challenge via an ovalbumin aerosol. After aerosol, lung function was evaluated with a non-invasive forced oscillation technique. The amount of mucosal exudation into the airway lumen and the presence of mast cell degranulation was determined. Tracheal responsiveness was measured at several time points after challenge. At these time points also bronchoalveolar lavage and histology were performed. Sensitization induced high antigen-specific IgE levels in serum. Inhalation of ovalbumin in sensitized mice induced an immediate but no late bronchoconstrictive response. During this immediate phase, respiratory resistance was increased (54%). Within the first hour after ovalbumin inhalation increased mucosal exudation and mast cell degranulation were observed. At 12 and 24 h after ovalbumin challenge, mice showed tracheal hyperresponsiveness (29% and 34%, respectively). However, no apparent inflammation was found in the lungs or bronchoalveolar lavage. From these results it can be concluded that hyperresponsiveness can develop via mechanisms independent of an inflammatory infiltrate. Since mast cell degranulation occurred after ovalbumin exposure, we hypothesize that mast cells are involved in the induction of airway hyperresponsiveness in this model

Partial cell fusion: A newly recognized type of communication between dedifferentiating cardiomyocytes and fibroblasts

Objective: Fibroblasts have been shown to couple to neonatal cardiomyocytes in heterocellular cultures through functional gap junctions. Our objective was to provide evidence for an additional type of heterocellular communication between fibroblasts and adult cardiomyocytes in vitro and in vivo. Methods: The contact areas in heterocellular co-cultures were evaluated by specific labeling and the intercellular communication was studied using preloading of fibroblasts with tracer molecules. Heterocellular fibroblast-cardiomyocyte contacts present in the in vitro setting and in the border zone of a rabbit myocardial infarction in vivo were further examined by electron microscopy. Results: Addition of fibroblasts preloaded with the fluorescent low molecular weight tracer calcein-AM to cultured myocytes indicated early dye transfer via connexin 43 functional gap junctions. At a later time-period after co-culturing, dye transfer of fibroblasts preloaded with the high molecular weight tracer dextran 10,000 suggested partial cell fusion. The membrane continuity giving rise to this partial cell fusion was confirmed by electron microscopy, clearly showing areas of intercytoplasmic contacts between fibroblasts and phenotypically adapted (dedifferentiated) cardiomyocytes. Fluorescein-labeled annexin V affinity studies revealed transient exposure of phosphatidylserine at the contact sites, suggesting that phosphatidylserine mediates the fusion process. Close contacts between cardiac fibroblasts and dedifferentiated cardiomyocytes accompanied by disruption of the basal lamina were observed in the border zone of a rabbit myocardial infarction in vivo. Conclusion: Our results suggest that the partial cell fusion-type of heterocellular communication in our co-culture model and the contacts observed in vivo may lead to new insights in cardiovascular disease