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.