Effects of dexamethasone on nasal allergic response and hyperresponsiveness induced by Japanese cedar pollen in mice

Abstract

In the present study, effects of dexamethasone (Dex) on allergic rhinitis (AR) induced by Japanese cedar pollen (JCP) were investigated. Mice were sensitized by i.p. injections with JCP+alum on days 0, 7 and 14. From day 21, the sensitized mice were challenged by intranasal (i.n.) administrations of JCP for 4 consecutive days. Animals were also treated with Dex (i.p.) 30 min before each JCP challenge. Frequency of sneezing was counted for 20 min after each nasal challenge. On days 18 and 25, the histamine (Hist, i.n.)-induced sneezing was also counted. In mice that were sensitized and repeatedly challenged with JCP, both serum levels of IgG and IgE specific for Cry J1, a major allergen of JCP, were significantly increased. In the JCP-sensitized mice, JCP challenge caused a significant increase in sneezing, indicating that nasal allergic response was induced. The i.n. application of Hist also caused an increase in sneezing. The Hist-induced sneezing was further increased significantly on day 25, indicating that nasal hyperresponsiveness (NHR) had occurred after the repeated JCP challenges. Both the nasal allergic response and NHR induced by JCP were inhibited by pretreatments with Dex. Thus, the murine AR model used might be useful for making clear the mechanisms of the AR pathogenesis and the action of corticosteroid effects.