Sinapic acid ameliorates airway inflammation in murine ovalbumin-induced allergic asthma by reducing Th2 cytokine production

Objective: Asthma is a chronic inflammatory airway disease associated with the airway narrowing and obstruction. Sinapic acid (SA), a hydroxycinnamic acid, possesses various pharmacological properties including anti-oxidant and anti-inflammatory activity. This research evaluated effects of different doses of SA on murine model of ovalbumin (OVA)-induced allergic asthma. Materials and methods: Allergic asthma induced by sensitizing mice on days 1 and 14 by intraperitoneal injection of OVA. After initial sensitization, between days 21 and 23, mice were challenged for 30 min with an aerosol of 1 % (wt/vol) OVA. Treatment with dexamethasone (3 mg/kg) or SA (25, 50 or 100 mg/kg) were done by oral gavage on days 15-23. Inflammatory cells infiltration and interferon-gamma (IFN-gamma), interlukin-4 (IL-4), IL-5 and IL-13 levels were evaluated in the bronchoalveolar lavage fluid (BALF). Serum total and OVA-specific immunoglobulin E (IgE) and lung tissue nitric oxide (NO) levels were measured. Histological changes in lung tissue were examined by staining with hematoxylin and eosin (H&E) for cell infiltration, periodic acid-Schiff (PAS) for mucus production and Masson's trichrome for collagen deposition. Results: Treatment with SA significantly inhibited inflammatory cell infiltration, enhanced IFN-gamma level and decreased IL-4, IL-5 and IL-13 levels in BALF. Serum total and OVA-specific IgE levels and NO level in lung tissue were significantly reduced by SA. Histological examination demonstrated that SA significantly attenuated inflammatory cell infiltration and mucus-producing cells in the lung. Conclusion: These data suggest that SA may be a new therapeutic potential to treat allergic asthma through suppressing T-helper 2 immune responses.