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.