Icariin which is a
flavonoid glucoside isolated from Epimedium brevicornu Maxim, has been reported to have anti-osteoporotic, anti-inflammatory and anti-depressant-like activities. In this study, we observed the effect of
icariin on airway
inflammation of
ovalbumin (OVA)-induced murine
asthma model and the associated regulatory mode on T-helper (Th)17 and regulatory T (Treg) cell function. Our data revealed that chronic OVA inhalation induced a dramatic increase in airway resistance (RL) and decrease in the lung dynamic compliance (Cdyn), and
icariin and DEX treatment caused significant attenuation of such
airway hyperresponsiveness (AHR). BALF cell counts demonstrated that
icariin and DEX led to a prominent reduction in total leukocyte as well as lymphocyte, eosinophil, neutrophil, basophil and monocyte counts. Histological analysis results indicated that
icariin and DEX alleviated the inflammatory cells infiltrating into the peribronchial tissues and goblet cells
hyperplasia and mucus hyper-production. Flow cytometry test demonstrated that
icariin or DEX administration resulted in a significant percentage reduction in CD4+RORγt+ T cells and elevation of CD4+Foxp3+ T cells in BALF. Furthermore,
icariin or DEX caused a significant reduction in
IL-6,
IL-17 and TGF-β level in BALF. Unfortunately,
icariin had no effect on
IL-10 level in BALF. Western blot assay found that
icariin or DEX suppressed RORγt and promoted Foxp3 expression in the lung tissue. qPCR analysis revealed that
icariin and DEX resulted in a notable decrease in RORγt and increase in Foxp3
mRNA expression in isolated spleen CD4+ T cell. In conclusion, our results suggested that
icariin was effective in the attenuation of AHR and chronic airway inflammatory changes in OVA-induced murine
asthma model, and this effect was associated with regulation of Th17/Treg responses, which indicated that
icariin may be used as a potential therapeutic method to treat
asthma with Th17/Treg imbalance phenotype.