[The mechanism underlying the effects of tea polyphenol on epirubicin-induced autophagy and apoptosis in T24 bladder cancer cells].

Objective To investigate the mechanism by which epirubicin (EPI) induces autophagy and the mechanism by which tea polyphenol (TP) regulates EPI-induced autophagy and apoptosis in T24 bladder cancer cells. Methods T24 cells weredivided into control group, EPI group, TP group and TP plus EPI group. Eight hours after corresponding treatments in different groups, transmission electron microscopy (TEM) was used to observe the image of autophagosomes. The expressions of autophagy-related protein LC3II and p62 in the cells were detected by Western blotting. Apoptotic cells were evaluated after EPI-treatment for 24 hours by flow cytometry combined with annexin V-FITC/PI staining. Western blotting was performed to determine the levels of cleaved-caspase-3 (c-caspase-3) and cleaved-PARP (c-PARP). LC3II was again tested by Western blotting 8 hours after T24 cells were treated with EPI added with autophagy pathway inhibitor chloroquine and 3-methyladenine, and moreover, the levels of LC3II and p-JNK were detected by Western blotting after T24 cells were treated with EPI combined with TP or the JNK inhibitor SP for 8 hours. Results The amount of autophagosomes and the level of LC3IIin TP plus EPI group were much lower than those in EPI group. SP reduced the level of LC3II induced by EPI. EPI increased p-JNK in a time-dependent manner. TP combined with EPI reduced the activity of JNK pathway. The apoptosis rate and the levels of c-caspase-3 and c-PARP in TP plus EPI group were much higher than those in EPI group. Conclusion TP inhibits autophagy through JNK pathway to enhance EPI-induced apoptosis in T24 bladder cancer cell line.