Abstract
Carvedilol has been identified as a promising agent for the treatment of liver fibrosis. Meanwhile, autophagy and apoptosis have been reported to play key roles in the activation of hepatic stellate cells (HSCs), which can contribute to the progression of liver fibrosis. However, the effects of carvedilol on autophagy and apoptosis in HSCs remain unclear. Our study aimed to detect these effects and identify the underlying mechanisms by which carvedilol mediates HSC autophagy and apoptosis. For this purpose, the LX-2 cell line was used in this study, and the cells were exposed to various concentrations of carvedilol for specific times. First, we found that carvedilol increased autophagic marker levels, the number of GFP-LC3-containing puncta and LC3B-II levels in LX-2 cells. Interestingly, the addition of chloroquine (CQ) failed to enhance the effects on GFP-LC3 puncta and LC3B-II levels, and carvedilol treatment resulted in a significant increase in p62 protein levels. Moreover, carvedilol treatment led to the accumulation of yellow dots only in GFP-RFP-LC3-LX-2 cells, similar to the results following CQ treatment, indicating that carvedilol inhibited autophagic flux. Next, we found evidence that carvedilol inhibited autophagic flux by increasing lysosomal pH and not by impairing the fusion of autophagosomes with lysosomes. Moreover, carvedilol substantially reduced the viability of LX-2 cells and noticeably induced cell apoptosis, as observed by flow cytometry. In addition, increased levels of cleaved caspase-3, cleaved caspase-8 and cleaved PARP, increased Bax activity and decreased Bcl-2 expression were detected in LX-2 cells. Finally, the carvedilol treatment inhibited autophagy and subsequently induced apoptosis in vitro. In conclusion, carvedilol suppresses autophagy and promotes apoptosis in HSCs and the late-stage inhibition of autophagy preceded the induction of apoptosis.