Loperamide induces protective autophagy and apoptosis through the ROS/JNK signaling pathway in bladder cancer.

Bladder cancer is one of the most common carcinomas in the human urinary system worldwide. Loperamide, known as an antidiarrheal drug, exerts anti-tumor activities against various cancers. However, the effect of loperamide on bladder cancer cells remains unclear. Our study aimed to investigate the effect of loperamide on bladder cancer and explore the underlying mechanisms. We found that loperamide suppressed the proliferation of 5637 and T24 cells in a dose-dependent manner. Loperamide treatment showed both pro-apoptotic and pro-autophagic effects on bladder cancer cells. Moreover, it was revealed that loperamide induced reactive oxygen species (ROS) accumulation, leading to the activation of c-Jun N-terminal kinase (JNK) signaling pathway. Notably, ROS scavenger N-acetyl-L-cysteine (NAC) and JNK inhibitor SP600125 effectively attenuated the induction of autophagy and apoptosis triggered by loperamide. Finally, blocking autophagy with CQ could significantly enhance the anti-cancer effect of loperamide both in vitro and in vivo. Overall, these findings demonstrated that loperamide induced autophagy and apoptosis through the ROS-mediated JNK pathway in bladder cancer cells. Our results suggest that the strategy of combining loperamide with autophagy inhibitor CQ may provide a therapeutic option for the treatment of bladder cancer.