It has been reported that the proinflammatory cytokine interleukin-1beta (IL-1beta) induces mucus hypersecretion in normal human nasal epithelial (NHNE) cells and that the MAP kinase pathway may be an important signal pathway in IL-1beta-induced MUC5AC gene expression. Green tea (Camellia sinensis) polyphenols are potent anti-inflammatory agents and have been shown to inhibit inflammation in tumor cell lines and cultured respiratory epithelial cells. In this study, we examined the effect of (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, on IL-1beta-induced MUC5AC gene expression and secretion in NHNE cells. After cells had been treated with IL-1beta (10 ng/ml) and pretreated with EGCG (10, 50 and 100 microM), mRNA expression of MUC5AC was determined by real-time polymerase chain reaction. The suppression of each signal pathway protein was determined by Western blot analysis after treatment with IL-1beta and EGCG, respectively. IL-1beta increased MUC5AC gene expression and MUC5AC secretion. EGCG markedly suppressed IL-1beta-induced MUC5AC gene expression and MUC5AC secretion via suppression of the phosphorylation of ERK MAP kinase, MSK1, and transcription factor, cAMP response element-binding protein. IL-1beta increased the number of cells staining positive with MUC5AC antibodies, and EGCG treatment decreased this number. Our data suggest that EGCG may be an effective inhibitor of IL-1beta-induced mucus hypersecretion.