Galangin induces apoptosis in hepatocellular carcinoma cells through the caspase 8/t-Bid mitochondrial pathway

Abstract

This study has investigated whether galangin, a flavonol derived from Alpinia officinarum Hance and used as food additives in southern China, induces apoptosis in hepatocellular carcinoma cells (HCCs) by activation of the caspase-8 and Bid pathway. The apoptosis of HCCs was evaluated by in situ uptake of propidium iodide and Hoechst 33258. Protein expressions were detected by Western blotting. Caspase-8 activity was measured using colorimetric method. To confirm the galangin-induced apoptotic pathway, inhibition of caspase-8 activity by Z-IETD-FMK, knockdown of Bid expression with siRNA, and overexpression of Bcl-2 in cells were carried out, respectively. The results show that galangin has significantly induced apoptosis in HCC lines. The caspase-8 is activated, and the cleavage of Bid results in the increase in tBid. The galangin-induced apoptosis is attenuated by Z-IETD-FMK, Bid siRNA, and Bcl-2 overexpression, respectively. However, Bcl-2 fails to suppress caspase-8 activation and the cleavage of Bid. This study has demonstrated that galangin induces apoptosis in HCCs by activating caspase 8/t-Bid mitochondrial pathway. Although Bcl-2 overexpression attenuates galangin-mediated apoptosis of HCCs, it is not mediated by the inhibition of tBid generation and caspase-8 activation.

Keywords:

• apoptosis
• Alpinia officinarum
• galangin
• caspase-8
• Bid
• hepatocellular carcinoma

Acknowledgments

This study was supported by the grants of Science and Technology Projects of Guangdong Province, China (No. 2011B031700057), Guangdong Natural Science Foundation (No. S2011010004076), and the Administration of Traditional Chinese Medicine of Guangdong Province (No. 2010190) and Science & Technology Innovation Fund of Guangdong Medical College (No. STIF201115).