Induction of Apoptosis in the Human HepG2 Hepatoma Cell Line Through the Extrinsic Pathway by Delphinium Alkaloid A

Hai-Mei Guo, Zhi-Feng Zhao, Yu-Qin Che and Jian-Hua Fan

Background and Objective: Hepatocellular carcinoma (HCC) is a primary malignant neoplasm derived from hepatocytes and HCC is currently the second most common cause of cancer-related death worldwide, HCC causes large numbers of deaths around the world each year. Delphinium alkaloid A is a novel C19-diterpenoid alkaloid that has been identified from Delphinium giraldii Diels (D. giraldii). In this study, a novel natural product from D. giraldii was used to explore its antitumor effect on death receptor pathway-mediated apoptosis in HepG2 cells as well as the underlying mechanism. Materials and Methods: The cytotoxicity of delphinium alkaloid A in HepG2 cells was analyzed by the MTT method. The morphology of HepG2 cells stained with Hoechst 33258 was assessed by fluorescence microscopy. Flow cytometry was used to analyze the cell cycle progression. The expression levels and activities of proteins related to the extrinsic pathway of apoptosis were subsequently analyzed. Results: The IC₅₀ value of Delphinium alkaloid A in HepG2 cells was 48.67 μg mL^–1. After treatment with delphinium alkaloid A (25, 50 and 100 μg mL^–1), HepG2 cells exhibited an obvious apoptotic morphology, which included cell protuberance, concentrated cytoplasm and apoptotic bodies. Moreover, the cell cycle was altered and apoptosis peaked. The expression of FasL, Fas, TRAIL, TRAIL-R1, TRAIL-R2 and FADD in HepG2 cells was unregulated, while the expression of Pro-Caspase-8 and Pro-Caspase-3 was down regulated. Moreover, the activities of Caspase-8 and Caspase-3 were increased. Conclusion: Delphinium alkaloid A could induce HepG2 apoptosis via a death receptor-mediated pathway.

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