Inhibition of airway remodeling and inflammatory response by Icariin in asthma

Background: Icariin (ICA) is the major active ingredient extracted from Chinese herbal medicine Epimedium, which has the effects of improving cardiovascular function, inducing tumor cell differentiation and increasing bone formation. It is still rarely reported that ICA can exert its therapeutic potential in asthma via anti-airway remodeling. The point of the study was to estimate the role of ICA in anti-. airway remodeling and its possible mechanism of action in a mouse ovalbumin. (OVA)-induced asthma model. Methods: Hematoxylin and Eosin Staining were performed for measuring airway remodeling related indicators. ELISA, Western blot and Immunohistochemistr-. y (IHC) were used for analyzing the level of protein. RT-PCR was used for analyzing the level of mRNA. Results: On days 1 and 8, mice were sensitized to OVA by intraperitoneal injection. From day 16 to day 43, previously sensitized mice were exposed to OVA once daily by nebulizer. Interventions were performed orally with ICA (ICA low, medium and high dose groups) or dexamethasone 1 h prior to each OVA exposure. ICA improves pulmonary function, attenuates pulmonary inflammation and airway remodeling in mice exposed to OVA. Histological and Western blot analysis of the lungs show that ICA suppressed transforming growth factor beta 1 and vascular endothelial growth factor expression. Increase in interleukin 13 and endothelin-1 in serum and bronchoalveolar lavage fluid in OVA-induced asthmatic mice are also decreased by ICA. ICA attenuates airway smooth muscle cell proliferation, as well as key factors in the MAPK/Erk pathway. Conclusions: The fact that ICA can alleviate OVA-induced asthma at least partly through inhibition of ASMC proliferation via MAPK/Erk pathway provides a solid theoretical basis for ICA as a replacement therapy for asthma. These data reveal the underlying reasons of the use of ICA-rich herbs in Traditional Chinese Medicine to achieve good results in treating asthma.