OBJECTIVE: Modified Guomin Decoction (MGD) is an effective Chinese herbal medicine for treatment of various allergic diseases, especially allergic asthma. Its water decoction is conventionally used for treatment of allergic bronchitis in China. Up to date, the underlying mechanisms of this herbal combination have not been fully investigated yet.
METHODS: In the in vivo study, the mice were treated with Chicken egg ovalbumin (OVA) and aluminum hydroxide gel as the classic allergic asthma animal model. After treatment with MGD, the lung tissues were examined by Histological assessment. The flow cytometric analysis was used to classify the CD4+ T-cell subsets. RT-PCR, Real time fluorescence quota PCR and Western blotting were used to analyze the gene expression of IL-4, IL-5, IFN-γ T-bet/GAIA-3 and Foxp3 in lung tissues.
RESULTS: MGD significantly reduced ovalbumin-specific IgE production in mouse serum and suppressed inflammatory cell infiltration, thus, improved the asthma symptoms. The mechanistic studies indicated that MGD treatment mainly modified the differentiation of CD4+ T-cell subsets and improved their functions. These included that MGD enhanced the proportion of Th1-cell, reduced Th2-cell subsets to CD4+ cell and balanced Treg/Th17 cell populations in the asthmatic mice spleen tissues. For Th1-cells, MGD upregulated the gene expression of their cytokine IFN-γ and its transcription factor T-bet while it downregulated the gene expression of their cytokines of IL-4 and IL-5. For Th2-cells, MGD mainly downregulated its transcription factor GATA-3 in lung tissues of asthmatic mice. MGD suppressed the Th17-cell subsets in CD4+ cells and upregulated the expression of Foxp3, a specific transcription factor of Treg-cell.