Emodin regulates apoptotic pathway in human liver cancer cells.

Emodin, a natural anthraquinone, has been reported to possess antiproliferative effects in many cancer cell lines. However, anticancer mechanism against human liver cancer remains unclear. In this study, we observed that emodin induced apoptosis in HepG2 cells and caused a significant accumulation of cells in the G1 phase. Western blot data showed that emodin treatment caused the increasing of release of cytochrome c into cytosol from mitochondria and the activation of caspase-8 and caspase-9, which suggest that the intrinsic and extrinsic pathways could be involved. Emodin treatment also resulted in a dose-dependent accumulation of intracellular reactive oxygen species. Furthermore, emodin increased the protein level of p53 and decreased the protein level of NF-κB/p65 in HepG2 cells, which indicated these two regulators might play a role in emodin-induced apoptosis. Computational modeling showed that emodin could directly bind to the BH3 domain of Bcl-2 through forming one hydrogen bond with Ala146 residue in Bcl-2. From these examinations, emodin not only significantly downregulated expression of Bcl-2 but also inhibited the heterodimerization of Bcl-2 with Bax because of strong interaction between emodin and Bcl-2. These suggest that emodin induces apoptosis in liver cancer cell line through a multifaceted complex cascade of events.

Activation of apoptosis by ethyl acetate fraction of ethanol extract of Dianthus superbus in HepG2 cell line.

Dianthus superbus L. is commonly used as a traditional Chinese medicine. We recently showed that ethyl acetate fraction (EE-DS) from ethanol extract of D. superbus exhibited the strongest antioxidant and cytotoxic activities. In this study, we examined apoptosis of HepG2 cells induced by EE-DS, and the mechanism underlying apoptosis was also investigated. Treatment of HepG2 cells with EE-DS (20-80 µg/ml) for 48 h led to a significant dose-dependent increase in the percentage of cells in sub-G1 phase by analysis of the content of DNA in cells, and a large number of apoptotic bodies containing nuclear fragments were observed in cells treated with 80 µg/ml of EE-DS for 24 h by using Hoechst 33258 staining. These data show that EE-DS can induce apoptosis of HepG2 cells. Immunoblot analysis showed that EE-DS significantly suppressed the expressions of Bcl-2 and NF-κB. Treatment of cells with EE-DS (80 µg/ml) for 48 h resulted in significant increase of cytochrome c in the cytosol, which indicated cytochrome c release from mitochondria. Activation of caspase-9 and -3 were also determined when the cells treated with EE-DS. The results suggest that apoptosis of HepG2 cells induced by EE-DS could be through the mitochondrial intrinsic pathway. High performance liquid chromatography (HPLC) data showed that the composition of EE-DS is complicated. Further studies are needed to find the effective constituents of EE-DS.