Effect of human recombinant interleukin-5 on in vitro responsiveness to PAF of lung from actively sensitized guinea-pigs

The effects of IL-5 on airway physiology and inflammation in rats

BACKGROUND

There is evidence that the cytokine IL-5 is a prominent feature of airway inflammation in asthma.

OBJECTIVE

The aim of this study was to determine whether exogenous IL-5 could cause changes in lung physiology, the early and late airway response after antigen challenge, and airway inflammation in rats that do not have a propensity to develop these changes after sensitization and challenge.

METHOD AND RESULTS

Intratracheal administration of IL-5 to ovalbumin sensitized Brown Norway SSN rats increased the airway responsiveness to methacholine (AHR) 20 hours after administration of IL-5 at the same time as an increase in neutrophils occurred in the lung lavage. This effect was dose dependent and was not caused by endotoxin. Concurrent intratracheal administration of 50 ng of anti-IL-5 monoclonal antibody with 10 microg of recombinant human IL-5 decreased the AHR and neutrophil influx. Pretreatment with 3 microg of IL-5 had no effect on the early and late airway response or on AHR after ovalbumin challenge. However, IL-5 increased lung re-sistance 20 hours after antigen challenge. Although total lung cells and differential counts did not differ significantly 8 hours after antigen challenge, the blood lymphocyte CD4/CD8 ratio decreased in IL-5 pretreated rats (P <.05). In addition, in situ hybridization showed a significant increase in cells within the airway wall expressing IL-4 and IL-5 mRNA in IL-5 treated/challenged rats compared to controls (P <.05).

CONCLUSION

The intratracheal administration of IL-5 causes only part of the physiologic changes that are associated with asthma. Other factors are necessary to obtain the complete asthma phenotype.

Modifications of experimental bronchopulmonary hyperresponsiveness

Bronchopulmonary hyperresponsiveness (BHR) is a hallmark of asthma and other inflammatory diseases of the airways. Animal models of BHR are available in which systemic or local immunizations, followed by acute allergenic provocations into the airways, augment responses to intravenous or intratracheal nonspecific bronchoconstrictor agents. Guinea-pig models are easy to manipulate but have serious handicaps: lack of proper genetics, lack of biomolecular tools, and frequent excess of eosinophils in the bronchoalveolar lavage fluid (BALF). Murine models have proper genetics and molecular tools, and they have the further advantage of being widely used for the study of other pathologies. In many of these studies, interleukin (IL)-5 appears as a major cytokine, produced by Th2 lymphocytes. Interleukin-5 promotes eosinophil differentiation and maturation, recruitment to the airways, and possibly activation. The presence of eosinophils in the airways and in the BALF may be necessary but is not sufficient to support BHR, since intense eosinophilia may be present in its absence. Bronchopulmonary hyperresponsiveness is also induced by the administration of lipopolysaccharide (LPS); in that case, eosinophils are not involved, and the role of neutrophils and of tumor necrosis factor-alpha, even though likely, has not been proven. Comparison of BHR induced by allergen (Th2- and largely eosinophil-dependent) and by LPS (probably macrophage-dependent) should allow for a better understanding of the mechanisms of BHR and for the development of important remedies.

Role for neurokinin-2 receptor in interleukin-5-induced airway hyperresponsiveness but not eosinophilia in guinea pigs

In the guinea pig, interleukin-5 (IL-5) has been shown to induce airway hyperresponsiveness as well as eosinophilia, which are important symptoms in asthma. IL-5 seems to be a critical cytokine since it selectively affects eosinophil functions. The mechanism of action by which IL-5 leads to airway hyperresponsiveness may be important for our understanding of the pathogenesis of asthma. Neurogenic inflammation, which is mediated by nonadrenergic noncholinergic nerves (NANC), may play a role in the IL-5-induced effects in guinea pig airways. In this study, the role of neuropeptides in the IL-5-induced airway hyperresponsiveness and eosinophilia in the guinea pig was examined using selective neurokinin receptor antagonists. Intra-airway application of IL-5 (1 microgram, twice) induces a selective eosinophil migration (control: 12 [8-22] x 10(5) cells and IL-5: 90 [67-187] x 10(5) cells, p < 0.05) and activation (control: 6.3 +/- 0.9 ng eosinophil peroxidase [EPO]/ml bronchoalveolar lavage [BAL] fluid and IL-5: 29.3 +/- 4.9 ng EPO/ml BAL fluid, p < 0.05) and a pronounced airway hyperresponsiveness in vivo. The maximal responses to histamine are increased by 160 +/- 16% (p < 0.05) after IL-5. Treatment of guinea pigs with either the nonselective neurokinin (NK)-receptor antagonist, FK224, or the selective NK2-receptor antagonist, SR48968, results in a complete inhibition of the in vivo hyperresponsiveness found after application of IL-5. Vice versa, intra-airway administration of substance P (10 micrograms, twice) results in an airway hyperresponsiveness (increased maximal response after substance P: 166 +/- 15% [p < 0.05]) without inducing migration or activation of eosinophils. All examined NK-receptor antagonists do not influence the IL-5-induced eosinophil accumulation. In addition, no effect of the NK-receptor antagonists is observed on the IL-5-induced eosinophil activation, as determined by BAL fluid EPO levels. The release of NK2-receptor active tachykinins plays an important role in the development of IL-5-induced airway hyperresponsiveness. This feature appears to be a step following eosinophil infiltration and activation since there are no effects on eosinophil function by pretreatment of the used NK-receptor antagonists.

Role of interleukin-5 in enhanced migration of eosinophils from airways of immunized guinea-pigs

1. Platelet activating factor (PAF), leukotriene B4 (LTB4) and interleukin-5 (IL-5) are potent chemoattractants for guinea-pig eosinophils, which may be involved in eosinophil recruitment and up-regulation in allergic diseases. Eosinophils from the bronchoalveolar lavage fluid (BALF) of ovalbumin-sensitized guinea-pigs were collected 24 h after antigen provocation and migration induced by PAF, LTB4 and rhIL-5 was studied. 2. Total BALF content and distribution of eosinophils were greater in immunized, ovalbumin-challenged guinea-pigs (5.0 +/- 0.8 x 10(6)/guinea-pig; 12 +/- 1%) than in immunized, saline-challenged animals (3.0 +/- 0.7 x 10(6)/guinea-pig; 7 +/- 1%). 3. The chemoattraction of eosinophils isolated on a metrizamide gradient was studied in micro-Boyden chambers, results being expressed as the number of migrating cells (mean +/- s.e. mean). PAF and LTB4-induced migration of eosinophils from immunized and OA-challenged guinea-pigs were significantly enhanced, as compared to immunized and saline-challenged animals (170 +/- 36 vs 35 +/- 9 migrating eosinophils for 10 nM PAF; 271 +/- 60 vs 110 +/- 19 for 1 nM LTB4). 4. The IL-5 antibody TRFK-5, in vivo, reduced eosinophil recruitment in BALF of antigen-challenged immunized animals as well as the enhanced responsiveness of eosinophils from the challenged animals, suggesting a role for IL-5 in the priming of eosinophils in vivo. 5. In contrast to TRFK-5, nedocromil sodium reduced to a similar extent eosinophil, macrophage and lymphocyte recruitment into the BALF of antigen-challenged, but failed to down-regulate the enhanced responsiveness of eosinophils from the challenged animals. 6. The increased eosinophil content in lungs from antigen-challenged guinea-pigs is thus selectively reduced by the anti-IL-5 antibody, which also attenuates the concomitant enhancement of the eosinophil responsiveness, supporting the concept that IL-5 is essential for recruitment and priming of eosinophils in vivo. In contrast, nedocromil sodium reduced non-selectively the total cell recruitment to the airways,but failed to attenuate the enhanced responsiveness of those eosinophils which migrated, indicating that its effects involve a different target.

Immunopathologic alterations in the bronchi of immunized guinea pigs

Isolated lungs from guinea pigs actively sensitized to ovalbumin and boosted 2 wk later display an enhanced bronchoconstriction and release larger amounts of secondary mediators as compared with lungs from nonimmunized animals when stimulated by platelet-activating factor or other agonists. We have investigated changes in T lymphocytes and eosinophils found in the bronchial wall of immunized and nonimmunized guinea pigs. The animals received two injections of 10 micrograms ovalbumin in Al(OH)3, at a 2-wk interval. Two studies were performed: (1) the animals were killed 7 days after the booster injection of antigen, (2) they were challenged with ovalbumin at this same day and killed after 2 or 24 h. Lungs were resected and frozen, and cryostat sections stained using monoclonal antibodies that recognize T cells, T cell subsets, or other relevant epitopes. Cyanide-resistant peroxidase activity was used to identify eosinophils. A large number of T cells, mainly of the CD4+ subset, and eosinophils were recruited into the bronchi 7 days after the booster injection of the antigen, compared with nonimmunized or nonboosted animals. In antigen-challenged animals, the numbers of T cells did not change but eosinophils were further increased in number at the 24 h time point. Also at this time point, a population of cells with a dendritic appearance was seen in the bronchial wall, which did not express macrophage markers but was strongly class II positive. Class II positivity was also noted in the bronchial epithelium and on many cells infiltrating the mucosa. These findings suggest that activated T cells and/or their products play an important role in the bronchopulmonary immunopathology associated with this model and possibly with the development of bronchial hyperreactivity.

Recombinant interleukin-5 induces in vivo airway hyperresponsiveness to histamine in guinea pigs

Interleukin-5-producing CV-1 cells were encapsulated in alginate and injected i.p. in guinea pigs (4 x 10(6)/animal). These cells produced approximately 8 ng interleukin-5 per 4 x 10(6) cells per day. Airway hyperresponsiveness to histamine in vivo was observed 3 and 7 days after administration. The increase in lung resistance after intravenous administration of histamine to guinea pigs was significantly potentiated, by approximately 70 to 90% in interleukin-5-treated animals. In animals treated with antibody to interleukin-5, the administration of interleukin-5-producing CV-1 cells did not induce hyperresponsiveness. The percentage of eosinophils in broncho-alveolar lavage fluid was increased by 100% at 7 days but not at 3 days after administration of interleukin-5-producing CV-1 cells. Antibody to interleukin-5 prevented the broncho-alveolar lavage eosinophilia at 7 days after interleukin-5 administration. It can be concluded that interleukin-5 induces broncho-alveolar lavage eosinophilia and airway hyperresponsiveness and that these phenomena do not occur simultaneously. These data suggest a role for interleukin-5 in the development of airway hyperresponsiveness in bronchial asthma.

Priming with murine recombinant interleukin-5 resulted in the augmentation of PAF-induced airway hyperresponsiveness to histamine in guinea pigs

The effects of pretreatment with murine recombinant interleukin 5 (mrIL-5) on platelet activating factor (PAF)-induced bronchoconstriction and airway hyperreactivity were investigated in guinea pigs. The intratracheal administration of mrIL-5 (2.5-10 micrograms) augmented platelet activating factor (PAF; 50 ng/kg)-induced bronchoconstriction in guinea pigs. When IL-5 (2.5 micrograms) was injected intratracheally, PAF (25 ng/kg)-induced bronchoconstriction was not affected, but PAF-induced airway hyperresponsiveness to histamine was exacerbated. Airway inflammation, in terms of increased capillary permeability and the accumulation of leukocytes in bronchoalveolar lavage fluid, was not produced by pretreatment with PAF (25 ng/kg), mrIL-5 (2.5 micrograms), or by a combination of these agents. This mrIL-5-induced augmentation of airway hyperreactivity by PAF was clearly inhibited by the phosphodiesterase-type III inhibitors, SDZ-MKS-492 and AH 21-132, but not by aminophylline.