Influence of (−)-epigallocatechin-3-gallate on the expression of connexin43 and gap junction intercellular communication of the bladder cancer cell lines BIU-87 in vitro

Abstract

Objective

The aim of our study was to investigate the effects of (−)-epigallocatechin-3-gallate (EGCG, the major phytochemistry component in green tea) on the expression of connexin43 (Cx43) gene and detect the intercellular communication of the human bladder cancer cell lines BIU-87, and explore its possible mechanisms of prevention and cure for the bladder tumor.

Methods

The methyl thiazolyl tetrazolium and Annexin-V/PI double-labeled flow cytometry methods were used to observe the growth inhibitory rate (IR) and apoptosis rate (AR) of BIU-87 cells treated by EGCG at different concentrations (0, 5, 10 and 20 mg/L), respectively. The reverse transcription-polymerase chain reaction (RT-PCR) and Western Blotting analysis were employed to detect the relative expression levels of the Cx43 mRNA and its protein. The scrape-loading fluorescence dye transfer method was used to assess the gap junction intercellular communication (GJIC) under fluorescence microscope.

Results

EGCG at concentrations (10 and 20 mg/L) both could significantly inhibit the proliferation and induce the apoptosis of BIU-87 cells. The IR and AR were (15.67 ± 1.15)%, (18.33 ± 1.53)% and (42.00 ± 4.34)%, (27.33 ± 3.21)%, respectively. And compared with the control groups of 0 mg/L and 5 mg/L (P<0.05), EGCG could significantly up-regulate the expression of Cx43 mRNA and its protein and enhance the function of BIU-87 cells. The effects had the significant correlation with the dose-dependent of EGCG.

Conclusion

EGCG (10, 20 mg/L) could effectively up-regulate Cx43 expression and enhance the GJIC of BIU-87 cells. The results may indicate the effects of EGCG inducing bladder tumor cells apoptosis and inhibiting its growth which provides the experimental evidence for further demonstrating the mechanism of chemical prevention and cure for the bladder tumor by EGCG.