The preventive effects of dietary galacto-oligosaccharides in a house dust mite-induced asthma model in mice

Background: Allergic asthma is associated with the exposure to house dust mite (HDM). Characterised by a Th2 immune response, asthma leads to mucus hypersecretion, eosinophilic inflammation and airway hyperresponsiveness. Recently, there is an increased interest in using specific oligosaccharides as a novel strategy to prevent development or reduce symptoms in asthma. Aim: We examined the effects of galactooligosaccharides (GOS) compared to the corticosteroid, budesonide, on the development of allergic asthma. Method: BALB/c mice were intranasally (i.n.) sensitised with 1 lg HDM on day 0 and challenged i.n. with PBS or 10 lg HDM on days 7 till 11. From day -14 till 14 mice were fed a control diet or a diet containing 1% GOS. A separate group of mice were instilled oropharyngeally with budesonide (500 lg/kg) on day 7, 9, 11, and 13. On day 14 airway resistance was measured by applying increasing doses of methacholine in the airways of mice. Bronchoalveolar lavage (BAL) fluid and lungs were collected. Results: HDM allergy resulted in airway hyperresponsiveness and a significant increase of leukocytes in the BAL fluid. Dietary intervention with 1% GOS decreased the total number of leukocytes in the BAL fluid, represented by a significant decrease in macrophage and eosinophil subsets. Budesonide treatment resulted in a significant decrease in lymphocytes, neutrophils and eosinophils. The 1% GOS diet significantly decreased airway hyperresponsiveness, whereas budesonide did not. Moreover, HDM allergy resulted in significantly enhanced levels of IL-6, -13 and -33 in lung homogenates. Both IL-6 and -13 were significantly decreased after budesonide treatment. Dietary intervention with 1% GOS significantly decreased IL-13, but not IL-6 and -33 levels in lung homogenates. Conclusion: These findings show that 1% GOS has a preventive effect on the HDM induced influx of inflammatory cells and airway hyperresponsiveness, whereas budesonide only affects inflammatory cell numbers.