Hellebrigenin induces cell cycle arrest and apoptosis in human hepatocellular carcinoma HepG2 cells through inhibition of Akt.

Abstract

Hellebrigenin, one of bufadienolides belonging to cardioactive steroids, was found in skin secretions of toads and plants of Helleborus and Kalanchoe genera. In searching for natural constituents with anti-hepatoma activities, we found that hellebrigenin, isolated from traditional Chinese medicine Venenum Bufonis, potently reduced the viability and colony formation of human hepatocellular carcinoma cells HepG2, and went on to explore the underlying molecular mechanisms. Our results demonstrated that hellebrigenin triggered DNA damage through DNA double-stranded breaks and subsequently induced cell cycle G2/M arrest associated with up-regulation of p-ATM (Ser(1981)), p-Chk2 (Tyr(68)), p-CDK1 (Tyr(15)) and Cyclin B1, and down-regulation of p-CDC25C (Ser(216)). It was also found that hellebrigenin induced mitochondrial apoptosis, characterized by Bax translocation to mitochondria, disruption of mitochondrial membrane potential, release of cytochrome c into cytosol and sequential activation of caspases and PARP. In addition, Akt expression and phosphorylation were inhibited by hellebrigenin, whereas Akt silencing with siRNA significantly blocked cell cycle arrest but enhanced apoptosis induced by hellebrigenin. Activation of Akt by human insulin-like growth factor I (hIGF-I) could obviously attenuate hellebrigenin-induced cell death. In summary, our study is the first to report the efficacy of hellebrigenin against HepG2 and elucidated its molecular mechanisms including DNA damage, mitochondria collapse, cell cycle arrest and apoptosis, which will contribute to the development of hellebrigenin into a chemotherapeutic agent in the treatment of liver cancer.

• Authors: Li-Juan Deng, Li-Ping Hu, Qun-Long Peng, Xiao-Lin Yang, Liang-Liang Bai, Anita Yiu, Yong Li, Hai-Yan Tian, Wen-Cai Ye, Dong-Mei Zhang
• Journal: Chemico-biological interactions (Chem Biol Interact) Vol. 219 Pg. 184-94 (Aug 05 2014) ISSN: 1872-7786 [Electronic] Ireland
• PMID: 24954031 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Bufanolides
• CCNB1 protein, human
• Cyclin B1
• hellebrigenin
• Checkpoint Kinase 2
• CHEK2 protein, human
• Proto-Oncogene Proteins c-akt
• CDC2 Protein Kinase
• CDK1 protein, human
• Cyclin-Dependent Kinases
• CDC25C protein, human
• cdc25 Phosphatases

Topics

• Apoptosis (physiology)
• Blotting, Western
• Bufanolides (pharmacology, therapeutic use)
• CDC2 Protein Kinase
• Carcinoma, Hepatocellular (drug therapy, enzymology)
• Cell Cycle Checkpoints (physiology)
• Cell Survival (drug effects)
• Checkpoint Kinase 2 (metabolism)
• Comet Assay
• Cyclin B1 (metabolism)
• Cyclin-Dependent Kinases (metabolism)
• DNA Damage (physiology)
• Flow Cytometry
• Gene Expression Regulation, Neoplastic (physiology)
• Hep G2 Cells
• Humans
• Liver Neoplasms (drug therapy, enzymology)
• Membrane Potential, Mitochondrial (physiology)
• Proto-Oncogene Proteins c-akt (antagonists & inhibitors, metabolism)
• cdc25 Phosphatases (metabolism)