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Kaempferol and quercetin, essential ingredients in Ginkgo biloba extract, inhibit interleukin‐1β‐induced MUC5AC gene expression in human airway epithelial cells

According to our previous study, Ginkgo biloba extract (GBE) suppresses IL‐1β‐induced MUC5AC gene expression in NCI‐H292 cells via the ERK and p38 MAPK pathways. This study sought to identify which ingredients of GBE suppress IL‐1β‐induced MUC5AC gene expression in NCI‐H292 cells and to examine which MAPKs are related to MUC5AC gene suppression for each ingredient. After the cells were pretreated with each ingredient and treated with IL‐1β (10 ng/mL), MUC5AC mRNA expression was determined by RT‐PCR and real‐time PCR. The results showed that kaempferol (KP) and quercetin (QC) suppressed MUC5AC mRNA expression in a dose‐dependent manner, both with significant inhibition starting from 40 µm (equal concentration to about a twelfth or thirteenth dose of GBE). MAPK proteins were determined by western blot analysis after pretreatment with KP, QC and GBE. All three suppressed the phosphorylation of ERK and p38 kinases. In conclusion, the data suggested that KP and QC, essential ingredients in GBE, may overcome the dose problem of GBE and play a valuable role, clinically, in controlling mucin hypersecretion in airway inflammation. Copyright © 2009 John Wiley & Sons, Ltd.