Induction of autophagy and apoptosis by the extract of Solanum nigrum Linn in HepG2 cells

Solanum nigrum L. (SN) has been used in traditional folk medicine to treat different cancers. It is also used as a hepatoprotective and anti-inflammatory agent. In this study, we demonstrated that the extract of SN (SNE) induced a strong cytotoxic effect toward HepG2 cells but much less to Chang liver and WRL-68 cells. The mechanisms of the cytotoxic effect were concentration-dependent. High doses of SNE (2 and 5 mg/mL) induced apoptotic cell death in HepG2 cells, as evidenced by increases in the expressions of p-JNK and Bax, mitochodrial release of cytochrome c, and caspase activation. On the other hand, cells treated with low concentrations of SNE (50-1000 mu g/mL) revealed morphological and ultrastructural changes of autophagocytic death under electron microscopic observation. Furthermore, these cells showed increased levels of autophagic vacuoles and LC3-I and LC3-II proteins, specific markers of autophagy. The levels of Bcl-2 and Akt that have been implicated in the down-regulation of autophagy were decreased upon SNE treatment. Taken together, these findings indicate that SNE induced cell death in hepatoma cells via two distinct antineoplastic activities of SNE, the ability to induce apoptosis and autophagocytosis, therefore suggesting that it may provide leverage to treat liver cancer.