Mitochondrial-dependent caspase activation pathway is involved in baicalein-induced apoptosis in human hepatoma J5 cells

Baicalein has been reported to induce growth-inhibitory activity in vitro in human cancer cells; however, the molecular mechanism of action is not completely understood. A pharmacological dose (10-100 μM) of baicalein exerted a cytotoxic effect on human hepatoma J5 cells resulting in G2/M arrest and apoptosis. In addition to cytotoxicity in J5 cells, several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9 and -3 occurred. Baicalein induced AIF and Endo G release from mitochondria indicating that baicalein stimulates apoptosis through the caspase-independent pathway, while undergoing apoptosis, there was a remarkable accumulation of G2/M cells. Also, the ratio of Bax/Bcl-2 was increased leading to changes in mitochondria membrane potential (ΔΨ_m) and release of cytochrome c, whereas the baicalein-induced apoptosis was partially abrogated by pretreatment with the pan-caspase inhibitor z-VAD-fmk, the accumulation of G2/M cells remained. These results demonstrate that the cytotoxicity of baicalein in J5 cells is attributable to apoptosis mainly involving G2/M-arrest in an ER-dependent manner, via a mitochondria-dependent caspase pathway and as well as contributions of AIF and Endo G pathways.