Objective:To explore the effect and mechanism of grape seed proanthocyanidin extract(GSPE) on airway inflammation and hyperresponsiveness in a murine model of allergic asthma. Methods:BALB/c mice(n=32; aged 8 weeks) were randomly and averagely divided into 4 groups: control group, asthma group, budesonide group and GSPE group. The mice were sensitized and challenged with ovalbumin(OVA) to produce a murine model of asthma. The GSEP group mice were intraperitoneally injected with GSPE[50 mg/(kg·d)]. Mice in the budesonide group were treated with aerosolized budesonide. The airway responsiveness of mice in each group to acetylcholine chloride (Ach) was evaluated. HE staining and PAS staining were used to observe airway inflammation in lung tissue and airway mucus secretion, respectively. Quantification of cytokines in bronchoalveolar lavage fluid(BALF) and total serum immunoglobulin E(IgE) were detected by ELISA. The protein expression of inducible nitric oxide synthase(iNOS) in lung tissue was evaluated by Western blot analysis. Results:As compared with the control group, the asthma group showed significant increase of airway resistance, total inflammatory cell and eosinophil counts and interleukin(IL)-4 level in BALF, total IgE level in serum, as well as iNOS expression, while the level of interferon (IFN)-γ in BALF decreased (P < 0.05). Remarkable reduction was observed in all the above items except IFN-γ level, which increased, in the GSEP group and the budesonide group(P < 0.05). Conclusion:GSPE decreases the progression of airway inflammation and hyperresponsiveness by downregulating the iNOS expression, promising to be a potential drug in the treatment of allergic asthma.