In the present study, we investigated the effects of the water extract of Euphorbiae humifusae (WEEH), an oriental medicinal herb, on the growth of Hep3B human hepatocarcinoma cells. We found that WEEH treatment resulted in a significant decrease in the cell viability of Hep3B cells depending on dosage. This decrease was revealed to be apoptosis, evidenced by chromatin condensation, DNA fragmentation and an accumulation of apoptotic fraction. WEEH induced the expression of death receptor-related proteins such as Fas, tumor necrosis factor-related apoptosis-inducing ligand, death receptor (DR) 4 and DR5, which further triggered caspase-8 activation and truncated Bid cleavage. Mitochondrial dysfunction, the catalytic activation of caspase-9, down-regulation of anti-apoptotic Bcl-2 and Bcl-xL expression, and up-regulation of the pro-apoptotic Bax protein were also observed in WEEH-treated cells. In addition, the increase in apoptosis induced by WEEH was correlated with caspase-3 activation and the concomitant degradation of poly (ADP-ribose) polymerase. However, the cytotoxic effects and apoptotic characteristics induced by WEEH were significantly inhibited by z-DEVD-fmk, a caspase-3 inhibitor. This demonstrates the important role played by caspase-3 in the process. Collectively, our data indicate that WEEH induces Hep3B cell apoptosis through a signaling cascade of death receptor-mediated extrinsic and mitochondria-mediated intrinsic caspase pathways.

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