Sophora Flavescens Suppresses Lung Eosinophilia By Inhibiting Both Eosinophil Hematopoiesis and Migration

Rationale:   A dried root of Sophora flavescens (S. flavescens) is a traditional Chinese herbal medicine used for the treatment of allergic diseases. Previous studies have demonstrated that S. flavescens possesses anti-inflammatory activities and suppresses allergic inflammation such as allergic rhinitis. However, the mechanism of anti-asthmatic effect of S. flavescens is not yet clarified.

Methods:   To clarify the effect of S. flavescens on asthma, we analyzed OVA-induced asthma mice treated with S. flavescens extract. We also conducted flow cytometry, cell count assay and gene expression analysis to evaluate the effect of S. flavescens on eosinophil hematopoiesis. To reveal the effect of S. flavescens on eosinophil chemotaxis, we performed transwell migration assay. 

Results:   Lung eosinophilic inflammation in OVA-induced asthma mice was suppressed by the treatment of S. flavescens. In addition, S. flavescens inhibited allergen-induced increment of eosinophil progenitors (EoPs) in the bone marrow. In vitro, S. flavescens suppressed IL-5-induced expansion of EoPs and eosinophil lineage specification directly. Moreover, IL-5 expression was suppressed in CD4⁺ T cells isolated from asthmatic mice treated with Sophora flavescens. In terms of eosinophil migration, S. flavescens suppressed eosinophil chemotaxis for eotaxin-1, one of the major chemokines for eosinophil migration.

Conclusions:   S. flavescens suppressed eosinophil accumulation in the lung of asthmatic mice by inhibiting both eosinophil hematopoiesis and migration. S. flavescens might be valuable for the treatment of eosinophil-related diseases such as asthma.