RESUMO
<p><b>OBJECTIVE</b>To study the effects of dexamethasone on intracellular expression of Th17 cytokine interleukin 17 and the mechanisms in asthmatic mice.</p><p><b>METHODS</b>Experimental asthma was induced by ovalbumin (OVA) sensitization in 20 in female Balb/c mice with (dexamethasone group, n=10) or without dexamethasone treatment (model group, n=10), with another 10 serving as the control group. The levels of IL-17 in the bronchoalveolar lavage fluid (BALF) and serum of the mice were measured by enzyme-linked immunosorbent assay (ELISA), and the airway inflammation was evaluated by HE staining. The expressions of IL-17 and RORgammat mRNA were measured by reverse transcription-polymerase chain reaction (RT-PCR), and the expression of RORgammat protein was measured by immunohistochemical staining.</p><p><b>RESULTS</b>The levels of RORgammat and IL-17 mRNA and protein in the asthmatic model group were significantly higher than those in the control group (P<0.01), and the increased expressions of RORgammat and IL-17 mRNA and protein in the asthmatic mice were significantly reduced by dexamethasone treatment (P<0.05).</p><p><b>CONCLUSION</b>Dexamethasone can inhibit the release of IL-17 probably by inhibiting RORgammat expression and blocking Th17 differentiation in asthmatic mice.</p>