Anti-allergic activities of 5,7-dimethoxy-3,4'-dihydroxyflavone via inhalation in rat allergic models

Various studies have shown that flavones have several pharmacological activities including anti-allergy activities. However, the bioavailability of oral flavones is very low, and whether inhaled administration can improve efficacy in respiratory disease models is unclear. In the present study, the anti-allergic activities of inhaling 5,7-dimethoxy-3,4'-dihydroxyflavone (MHF), a synthetic flavonoid, was investigated by comparison with disodium cromoglycate (DSCG) and nedocromil sodium (NS) in rat allergic models. In an anti-DNP-IgE-induced asthmatic model, inhaled MHF dose-dependently inhibited the increase in airway resistance after antigen challenge. In an ovalbumin (OVA)-induced asthmatic model, inhaled MHF showed significant suppression of airway hyperresponsiveness; a decrease in eosinophil and neutrophil counts, IL-4, IL-5 and leukotriene D₄ in bronchoalveolar lavage fluid; a reduction in total IgE and OVA-specific IgE levels in serum; and suppression of eosinophil infiltration in lung tissue after antigen challenge. The efficacy of inhaled MHF was comparable to that of NS and DSCG. In conclusion, based on these findings, the report for the first time that that inhaled MHF may be a potential drug for the treatment of allergic asthma.