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.