Quercetin Inhalation Inhibits the Asthmatic Responses by Exposure to Aerosolized-Ovalbumin in Conscious Guinea-pigs

Effects of quercetin inhalation on immediate (IAR), late-phase (LAR) and late late-phase (LLAR) asthmatic responses by exposure to aerosolized-ovalbumin (AOA) (2w/v% in saline, inhalation for 3 min) were studied in conscious guinea-pigs sensitized with AOA. We measured specific airway resistance (sRaw), and recruitment of leukocytes, histamine and protein contents and phospholipase $A_2\;(PLA_2)$ activity in bronchoalveolar lavage fluid (BALF). Effects of quercetin (10 mg/mL, inhalation for 2 min) compared with cromolyn sodium, salbutamol, and dexamethasone inhalations, respectively. Quercetin inhalation decreased sRaw by $57.15\;{\pm}\;3.82%$ in IAR, $57.72\;{\pm}\;7.28%$ in LAR, and $55.20\;{\pm}\;5.69%$ in LLAR compared with AOA-inhaled control. Salbutamol inhalation (5 mg/mL) significantly inhibited sRaw in IAR, but inhalations of cromolyn sodium (10 mg/mL) and dexamethasone (5 mg/mL) significantly inhibited sRaw in IAR, LAR and LLAR, respectively. Inhibitory activity of quercetin inhalation on sRaw was similar to effect of its oral administration (10 mg/kg) in asthmatic responses. Quercetin (10 mg/mL, inhalation for 2 min) significantly decreased histamine and protein contents, $PLA_2$ activity, and recruitments of leukocytes in BALF and also improved slightly infiltration of eosinophils and neutrophils in histopathological survey. Its anti-asthmatic activity was similar to cromolyn sodium and dexamethasone.