Molecular mechanism of icariin on rat asthmatic model.

BACKGROUND: Effects of icariin on airway inflammation in asthmatic rats and the intervention of LPS induced inflammation are interfered with the machanism of icariin. Our study aimed to observe the effect of icariin on ovalbumin-induced imbalance of Th1/Th2 cytokine expression and its mechanism.

METHODS: Sixty male SD rats were randomly divided into control group (PBS), asthma group (ovalbumin (OVA)-induced), dexamethasone group, and OVA+icariin low, medium and high dose groups (5, 10, 20 mg/kg, respectively). Each group had ten rats. The model of OVA sensitization was a rat asthma model. Enzyme-linked immunosorbent assay (ELISA) method was used to observe the effects of icariin on interleukin-4 (IL-4) and inerferon γ (IFN-γ) in rats' lung tissue. Immunohistochemical staining was applied to detect the intervention effects of icariin on T cells (T-bet) and gatabinding protein 3 (GATA-3) in rat pulmonary tissue. Realtime RT-PCR was used to observe the intervention effects of icariin on T-bet and GATA-3 mRNA expression in rat pulmonary tissue and spleen lymphocytes. Western blotting was used to observe the icariin intervention effects on T-bet, GATA-3 and nuclear factor-Kappa B (NF-κB) p65 protein expressions in rat pulmonary tissue.

RESULTS: The ELISA results from pulmonary tissue showed that IL-4 expression was significantly reduced (P < 0.05), while the IFN-γ expression increased but not significantly when we compared OVA+icariin medium and high dose groups with the asthma group. Immunohistochemical staining of pulmonary tissue showed that the GATA-3 decreased significantly while the T-bet staining did not change in the OVA+icariin high dose group. In pulmonary tissue and spleen lymphocytes T-bet and GATA-3 mRNA expressions were significantly reduced (P < 0.05) in icariin treatment groups compared with the asthma model group. GATA-3 and T-bet mRNA in rat spleen lymphocytes in the asthma group were higher than in the control group. GATA-3 mRNA expression in pulmonary tissue significantly decreased (P < 0.05) while T-bet mRNA expression decreased but not significantly in the icariin treatment group compared with the asthma group. T-bet and GATA-3 protein expressions in pulmonary tissue increased significantly compared with the asthma group, which meant that icariin could inhibit the increase of GATA-3 protein, but not of T-bet. The bronchus, blood vessels and periphery pulmonary tissue had infiltration of inflammatory cells in the OVA+icariin high dose group while NF-κB p65 cells were reduced, and expression of NF-κB p65 in this group was less than in the asthma group. The expression of total p65 protein decreased with icariin treatment while the expression of cytoplasmic p65 protein increased.

CONCLUSIONS: Icariin could regulate the imbalance of Th1/Th2 cytokines in asthmatic rat pulmonary tissue. Icariin could regulate the imbalance of Th1/Th2 associated transcription factors T-bet and GATA-3 in asthmatic rat pulmonary tissue and spleen lymphocytes. Icariin could inhibit the activation of NF-κB p65 protein in asthmatic rat pulmonary tissue.