Deapioplatycodin D promotes cell senescence induced by P21 through the mediation of incomplete mitophagy via BNIP3L

Deapioplatycodin D (DPD) is a triterpenoid saponin extracted from the root of Platycodon grandiflorum, which is a common source of medicine and food. Platycodon grandiflorum saponins have anti-inflammatory, antioxidative, antitumor, and immunity-promoting effects. However, the effect of DPD on hepatocellular carcinoma (HCC) cells has not been reported. The purpose of this study was to explore the cytotoxic effects and molecular mechanisms of DPD on HCC cells. Our study revealed that DPD significantly inhibits the proliferation of HCC, as demonstrated by the CCK-8 assay, and then we analyzed the inhibitory effects and pathways of DPD on HCC cells by Western blot and immunofluorescence assay, and found that DPD could increase the changes of autophagy-related protein levels, but had no significant effect on the expression of apoptosis-related proteins, and induced cell senescence. Then, transcriptomics analysis revealed that differential genes were significantly enriched in cell senescence and autophagy pathways and significant expression of mitochondrial autophagy-related gene BNIP3L and senescence-related gene P21. Subsequently, autophagy and cell senescence were analyzed using gene silencing, and it was found that DPD caused mitochondrial damage and promoted reactive oxygen species production, leading to the inhibition of autophagic fluxes and mitophagy via BNIP3L, and that DPD also mediated cell senescence via P21. Here, we found that autophagy promoted cell senescence, resulting in the inhibition of HCC cell proliferation. Similar results were obtained in the tumor-bearing model in vivo. In conclusion, DPD induces incomplete mitophagy and cell senescence in HCC cells, thereby inhibiting HCC cell proliferation. DPD is a potential new strategy for treating HCC.