Background: To assess the importance of the route of challenge in an existing mouse model of chemical-induced asthma, we replaced intranasal instillation by oropharyngeal aspiration. To our knowledge, oropharyngeal aspiration as a challenge route has not yet been investigated in a mouse model of chemical-induced asthma.
Methods: On days 1 and 8, mice were dermally sensitized with toluene diisocyanate (TDI) (0.3%) [or vehicle (acetone/olive oil)] and on day 15 they received a single challenge, via oropharyngeal aspiration, with TDI (0.01%) or vehicle. One day after challenge, airway reactivity to methacholine was measured by a forced oscillation technique (FlexiVent) and total and differential cell counts, as well as levels of KC, IL-5, IL-17 and TNF-alpha, were assessed in the bronchoalveolar lavage (BAL) fluid. Lymphocytes from the auricular and mediastinal lymph nodes were cultured to determine the concanavaline A-induced secretion of IL-2, IL-4, IL-10, IL-13, IL-17 and IFN-gamma. Total serum IgE was measured.
Results: In TDI-sensitized mice, a significant increase in airway reactivity was found after a single oropharyngeal challenge with TDI. BAL neutrophils and eosinophils were increased 7- and 5-fold, respectively. An upregulation of Th1 (IFN-gamma), Th2 (IL-4, IL-10, IL-13) and Th17 (IL-17) cytokines was found in the auricular lymph nodes, in the mediastinal lymph nodes only IL-4 was upregulated. The total serum IgE level in TDI-sensitized mice was significantly increased when compared to control mice.
Conclusion: We conclude that challenging mice via oropharyngeal aspiration mimics the characteristics of human asthma well, without the possible drawbacks of other techniques.