Abstract
BackgroundLoss of the epithelial barrier is characterized by a reduction in E-cadherin expression and is a hallmark of asthma. Qi-xian decoction (QXT) is a Chinese medicinal formula that has been used to effectively treat asthma. This study aimed to investigate the effect of QXT on E-cadherin expression in human lung epithelial 16HBE cells and ovalbumin-challenged mice and to explore the underlying molecular mechanism.Material/MethodsOvalbumin (OVA)-induced mice were used as a model of asthma. Real-time PCR and Western blotting were utilized to examine mRNA and protein levels. Lung tissue reactive oxygen species (ROS) levels were evaluated using dichloro-dihydro-fluorescein diacetate (DCFH-DA). Serum superoxide dismutase (SOD) and the total antioxidant capacity (TAOC) were measured via enzyme-linked immunosorbent assay (ELISA)-based analyses. 16HBE cells were utilized to explore the effect of QXT or hydrogen peroxide (H2O2) on the expression of E-cadherin in vitro.ResultsWe found that QXT treatment increased E-cadherin expression and decreased extracellular-signal-regulated kinase (ERK) phosphorylation levels in the lung tissues of OVA-challenged mice. QXT also downregulated ROS levels and increased serum SOD and TAOC levels in OVA-challenged mice. In vitro studies demonstrated that increased ROS generation induced by H2O2 resulted in decreased E-cadherin expression levels in 16HBE cells, which was attenuated by inhibition of ERK signaling. Moreover, the H2O2-induced downregulation of E-cadherin expression, increased ROS generation, and ERK activation in 16HBE cells were restored by treatment with QXT water or ethanol extract.ConclusionsThese data demonstrate that one mechanism by which QXT protects against asthma is to restore E-cadherin expression in vivo and in vitro by inhibiting ROS-mediated ERK activation.
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