Differential release of MIP-1alpha and eotaxin during infection of mice by Histoplasma capsulatum or inoculation of beta-glucan.

OBJECTIVE: In the present study, we evaluated the levels of MIP-1alpha and eotaxin and in vivo migration in the peritoneal cavity model, in mice inoculated with live yeast forms of Histoplasma capsulatum or the beta-glucan cell wall component of this fungus, and the influence of a leukotriene biosynthesis inhibitor, MK886, on the release of these chemokines in relation to cell recruitment. MATERIALS: Female outbred Swiss mice (N = 4-5 per group, 3-4 wk, were used. Mice were injected i.p. with 1 ml of the 6 x 10(5) live yeast form of the fungus or with 10 microg of beta-glucan from the cell wall fraction, and treated daily with MK886 (1 mg kg(-1), p.o.) or vehicle. RESULTS: The fungus induced rapid generation of high levels of MIP-1alpha, which remained elevated from 4-48 h whereas very little eotaxin was detected at any time point (Fig. 1A and B). In contrast, the beta-glucan induced a little MIP-1alpha but considerably higher concentrations of eotaxin within the first four hours; however, the level of neither chemokine was sustained (Fig. 2A and B). Treatment of animals with MK886 was effective in reducing the numbers of neutrophils, eosinophils and, to a lesser degree, mononuclear cells accumulating in the peritoneal cavity in response to both the live fungus (Fig. 1C-E) and the cell wall beta-glucan (Fig. 2C-E). CONCLUSIONS: The results suggest that chemokines and leukotrienes may play key roles in the inflammatory cell influx to H. capsulatum infection or to the inoculation of the beta-glucan cell wall component of this fungus

The role of the eosinophil-selective chemokine, eotaxin, in allergic and non-allergic airways inflammation.

Blood eosinophilia and tissue infiltration by eosinophils are frequently observed in allergic inflammation and parasitic infections. This selective accumulation of eosinophils suggested the existence of endogenous eosinophil-selective chemoattractants. We have discovered a novel eosinophil-selective chemoattractant which we called eotaxin in an animal model of allergic airways disease. Eotaxin is generated in both allergic and non-allergic bronchopulmonary inflammation. The early increase in eotaxin paralleled eosinophil infiltration in the lung tissue in both models. An antibody to IL-5 suppressed lung eosinophilia, correlating with an inhibition of eosinophil release from bone marrow, without affecting eotaxin generation. This suggests that endogenous IL-5 is important for eosinophil migration but does not appear to be a stimulus for eotaxin production. Constitutive levels of eotaxin observed in guinea-pig lung may be responsible for the basal lung eosinophilia observed in this species. Allergen-induced eotaxin was present mainly in the epithelium and alveolar macrophages, as detected by immunostaining. In contrast there was no upregulation of eotaxin by the epithelial cells following the injection of sephadex beads and the alveolar macrophage and mononuclear cells surrounding the granuloma were the predominant positive staining cells. Eotaxin and related chemokines acting through the CCR3 receptor may play a major role in eosinophil recruitment in allergic inflammation and parasitic diseases and thus offer and attractive target for therapeutic intervention.

Reduction of Sephadex-induced lung inflammation and bronchial hyperreactivity by rapamycin.

Rapamycin is a macrolide antibiotic whose potent immunosuppressor activity was recently described in vivo and in vitro. The aim of the present work was to determine if rapamycin could affect an established inflammatory response. Conscious pathogen-free Dunkin-Hartley guinea pigs (300-400 g) were injected intravenously with Sephadex beads (G50, superfine, 10 to 40 microns, 24 mg/kg) to induce lung inflammation and bronchial hyperreactivity. Bronchoalveolar lavage (BAL) fluid was collected 2, 12 and 24 h after Sephadex administration and the cells were counted. Bronchial tissue was used to construct dose-response (contraction, g) curves to histamine and acetylcholine 24 h after the Sephadex injection, using a cascade system. Results are presented as area under the log dose-response curves. Test animals were injected with rapamycin (5 mg/kg) or its vehicle by the intramuscular route either 2 or 12 h after Sephadex injection and BAL fluid collected 24 h after Sephadex administration. Rapamycin administration 2 h after Sephadex reduced eosinophil and lymphocyte numbers in BAL by 52 and 55%, respectively, but not ex vivo bronchial hyperreactivity induced by Sephadex injection. However, rapamycin administration 12 h after Sephadex reduced BAL eosinophil and lymphocyte numbers (55 and 62%, respectively) and bronchial hyperreactivity. The increase in neutrophil numbers in BAL induced by Sephadex injection was not modified by rapamycin. Since lymphocyte numbers in BAL were significantly increased in Sephadex-treated animals at 12 h but not at 2 h after Sephadex injection, the present results suggest that the inhibition of bronchial hyperreactivity by rapamycin may be dependent on the presence of lymphocytes elicited into the airways by Sephadex injection.

Reduction of Sephadex-induced lung inflammation and bronchial hyperreactivity by rapamycin

Rapamycin is a macrolide antibiotic whose potent immunosuppressor activity was recently described in vivo and in vitro. The aim of the present work was to determine if rapamycin could affect an established inflammatory response. Conscious pathogen-free Dunkin-Hartley guinea pigs (300-400 g) were injected intravenously with Sephadex beads (G50, superfine, 10 to 40 microns, 24 mg/kg) to induce lung inflammation and bronchial hyperreactivity. Bronchoalveolar lavage (BAL) fluid was collected 2, 12 and 24 h after Sephadex administration and the cells were counted. Bronchial tissue was used to construct dose-response (contraction, g) curves to histamine and acetylcholine 24 h after the Sephadex injection, using a cascade system. Results are presented as area under the log dose-response curves. Test animals were injected with rapamycin (5 mg/kg) or its vehicle by the intramuscular route either 2 or 12 h after Sephadex injection and BAL fluid collected 24 h after Sephadex administration. Rapamycin administration 2 h after Sephadex reduced eosinophil and lymphocyte numbers in BAL by 52 and 55 per cent , respectively, but not ex vivo bronchial hyperreactivity induced by Sephadex injection. However, rapamycin administration 12 h after Sephadex reduced BAL eosinophil and lymphocyte numbers (55 and 62 per cent , respectively) and bronchial hyperreactivity. The increase in neutrophil numbers in BAL induced by Sephadex injection was not modified by rapamycin. Since lymphocyte numbers in BAL were significantly increased in Sephadex-treated animals at 12 h but not at 2 h after Sephadex injection, the present results suggest that the inhibition of bronchial hyperreactivity by rapamycin may be dependent on the presence of lymphocytes elicited into the airways by Sephadex injection