Caspase-3-dependent protein kinase C delta activity is required for the progression of Ginsenoside-Rh2-induced apoptosis in SK-HEP-1 cells

Ginsenoside-Rh2 (G-Rh2) has been shown to induce apoptosis in a variety of cell types. In this study, we show that G-Rh2-induced apoptosis is accompanied by the mitochondrial release of cytochrome c and activation of caspase-3 in the human hepatoma cell line, SK-HEP-1. Furthermore, protein kinase C delta (PKCδ) activity was markedly up-regulated in a lipid activator-independent manner with kinetics similar to those of PKCδ and PARP cleavages during the apoptotic progression. Pre-treatment of cells with the caspase-3 specific inhibitor (z-DEVD-fmk) effectively prevented the G-Rh2-induced proteolytic activation of PKCδ. Moreover, rottlerin, a specific PKCδ inhibitor blocked G-Rh2-induced proapoptotic effects on the cells including the release of cytochrome c, activation of caspase-3 activity, and proteolytic cleavage and activation of PKCδ. These results suggest that G-Rh2-induced apoptosis is functionally linked to mitochondrial dysfunction and caspase-3 activity is regulated by positive feedback with PKCδ via the mitochondrial pathway.