Effects of dexamethasone on the expression of transforming growth factor-beta in the mouse model of allergic rhinitis.

Objectives/hypothesis: This study aimed to evaluate the effect of dexamethasone on the expression of transforming growth factor (TGF)-beta in the mouse model of allergic rhinitis.
Study Design: Female BALB/c mice were randomly assigned to four groups, including two control groups and two treatment groups.
Methods: General sensitization and local challenge were performed with ovalbumin (OVA). In the treatment groups, dexamethasone was injected intraperitoneally 3 hours before general sensitization or local challenge. Symptom score, eosinophil infiltration, and immunostaining for TGF-beta1 and CD4 in nasal mucosa, and TGF-beta1 and OVA-specific immunoglobulin E (IgE) in sera were analyzed.
Results: Dexamethasone administration before general sensitization reduced the symptom score, OVA-specific IgE, and eosinophil infiltration and increased the serum level of TGF-beta1 significantly. Dexamethasone administration before local challenge reduced only the eosinophil infiltration significantly. Immunoreactivity of TGF-beta1 and CD4 was lower in both treatment groups.
Conclusion: These results suggest that dexamethasone may play an important role in the regulation of allergic reactions by at least two mechanisms; one by suppressing allergic sensitization through decrease of CD4+ T cells and increase of TGF-beta, and the other by suppressing late allergic reactions through the inhibition of proliferation and chemotaxis of inflammatory cells such as eosinophils.