AIM: To investigate the(-)-epigallocatechin-3-gallate(EGCG) binding to transforming growth factor-β(TGF-β) type Ⅱ receptor(TGFRⅡ).METHODS: The expression of α-smooth muscle actin(α-SMA) was used as a marker for fibrotic change inhuman lung fibroblast MRC-5 cells. The α-SMA expression level was determined by western blotting and immunohistological analysis. We examined whether the anti-fibrotic effects of EGCG on MRC-5 cells was dependent on antioxidant mechanism by using edaravone and N-acetylcysteine(NAC). The suppression effects of EGCG on Smad2/3 activation were studied by confocal fluorescence microscopy. The binding of EGCG to recombinant TGFRⅡ protein was analyzed by immunoprecipitation and affinity chromatography.RESULTS: When MRC-5 cells were treated with TGF-β, EGCG decreased the expression of α-SMA in a dose dependent manner, whereas catechin did not influence the α-SMA expression in the cells. Except for EGCG, antioxidant compounds(e.g., edaravone and NAC) had no effects on the TGF-β-induced α-SMA expression. Nuclear localization of phosphorylated Smad2/3 was observed after TGF-β treatment; however, EGCG treatment attenuated the nuclear transportation of Smad2/3 in the presence or absence of TGF-β. After a TGFRⅡ expression vector was introduced into COS-7 cells, cell lysates were untreated or treated with EGCG or catechin. The immunoprecipitation experiments using the lysates showed that EGCG dose-dependently bound to TGFRⅡ and that catechin did not at all. Affinity chromatography study indicated that EGCG would bind to TGFRⅡ.CONCLUSION: Our results demonstrate that EGCG interacts with TGFRⅡ and inhibits the expression of α-SMA via the TGF-β-Smad2/3 pathway in human lung fibroblast MRC-5 cells. AIM: To investigate the (-) - epigallocatechin-3-gallate (EGCG) binding to transforming growth factor-β type Ⅱ receptor (TGFRⅡ) .METHODS: The expression of α-smooth muscle actin ) was used as a marker for fibrotic change in human lung fibroblast MRC-5 cells. The α-SMA expression level was determined by western blotting and immunohistological analysis. We examined whether the anti-fibrotic effects of EGCG on MRC-5 cells was dependent on The inhibitory effects of EGCG on Smad2 / 3 activation were studied by confocal fluorescence microscopy. The binding of EGCG to recombinant TGFRII protein was analyzed by immunoprecipitation and affinity chromatography .RESULTS: When MRC -5 cells were treated with TGF-β, EGCG decreased the expression of α-SMA in a dose dependent manner, but catechin did not affect the α-SMA expression in the cells. Except for EGCG, antioxidant compounds (eg, edaravone and NAC had No effects on the TGF-β-induced α-SMA expression. Nuclear localization of phosphorylated Smad2 / 3 was observed after TGF-β treatment; however, EGCG treatment attenuated the nuclear transportation of Smad2 / 3 in the presence or absence of TGF- β After a TGFRII expression vector was introduced into COS-7 cells, cell lysates were untreated or treated with EGCG or catechin. The immunoprecipitation experiments using the lysates showed that EGCG dose-dependently bound to TGFRII and that catechin did not at all. Affinity chromatography study indicated that EGCG would bind to TGFR II. CONCLUSION: Our results demonstrate that EGCG interacts with TGFR II and inhibits the expression of α-SMA via the TGF-β-Smad2 / 3 pathway in human lung fibroblast MRC-5 cells.