The Effect of Aerosolized and Intravenously Administered Clenbuterol and Aerosolized Fluticasone Propionate on Horses Challenged with Aspergillus fumigatus Antigen

β-Agonists have been shown to display anti-inflammatory properties in several experimental models. The aim of this study was to investigate the anti-inflammatory properties of clenbuterol (CB), administered either intravenously or by aerosol, in comparison with fluticasone propionate (FP) in recurrent airway obstruction (RAO)-susceptible horses. Eight horses, of which five were known to be susceptible to RAO, underwent an inhalation challenge with Aspergillus fumigatus (AF) antigen and were treated with CB intravenously, CB by aerosol, or FP by aerosol. Twenty-four hours after the challenge, bronchoalveolar lavage was performed, the total and differential cell counts were assessed, and cytokines were measured in isolated alveolar macrophages. After challenge with AF, RAO-susceptible horses showed an increase in total cell count, based on an increase in macrophages and lymphocytes, which was inhibited by treatment with intravenous CB, aerosolized CB and aerosolized FP. Neutrophil ratios were decreased when treated with aerosolized CB and FP. Expression of interleukin (IL)-1β and IL −8 was significantly increased after AF challenge .Interleukin −1β was significantly decreased following treatment with intravenous CB, aerosolized CB and aerosolized FP, whereas only FP decreased the expression of IL-8. These data suggest that the anti-inflammatory property of CB provide new opportunities in the therapeutic intervention of early inflammation in RAO.