Expression and significance of Caspase-3 in hepatocellular carcinoma cells induced by high frequency square wave electric pulse with different intensities

Abstract

Objective To investigate the expression level of Caspase-3and the damage effect in hepatoma cells under different intensity pulses. Methods The pulses were divided into 10 groups according to the electric field intensity. After pulsed discharge of Hep-G2 hepatoma cells cultured in vitro. The damage effect was judged by detecting the activity of Caspase-3, proliferation activity, apoptotic rate and the expression levels of cytochrome C (Cyt C), Cleaved-Caspase-3 and cysteine protease-activated DNA enzymes (CAD). Results High expression of Caspase-3 was found in hepatoma cells treated with electric pulse. The expression level of 750-1 750 V/cm increased with the increase of field intensity (P 0.05). Then the field strength continued to rise, the expression level gradually decreased. The electric pulse could inhibit the proliferation of hepatoma cells, and its inhibition ability was positively correlated with the field intensity. When the electric field intensity was 2 250-2 750 V/cm, the proliferative activity decreased to the lowest level (P>0.05). The effect of pulsed electric field on cells injury included induction of apoptosis and necrosis. The apoptosis effect reached the peak at the field strength of 1 750-2 000 V/cm (P>0.05). The necrosis effect increased significantly when the field strength was higher than that of 2 000 V/cm, and reached the highest at 2 750 V/cm. Western blotting suggests that pulsed electric field can induce the up-regulation of Cyt C, Cleaved-Caspase-3 and CAD protein expression, which leads to apoptosis (P<0.05). Conclusion High frequency square wave electric pulse can induce the increase of Caspase-3 expression in hepatoma cells, and activate Cyt C signaling pathway to induce apoptosis. The apoptotic effect was the most obvious when the filed strength was set on 1 750-2 000 V/cm. Key words: High frequency square wave; Electric pulse; Electric intensity; Damage effect; Apoptpsis