Induction of apoptosis by hinokitiol, a potent iron chelator, in teratocarcinoma F9 cells is mediated through the activation of caspase-3

Hinokitiol, a potent iron chelator, has been reported to induce differentia tion in teratocarcinoma F9 cells with a reduction of viable cells. In this study, we examined the steps leading to eventual cell death by hinokitiol d uring differentiation. Hinokitiol induced DNA fragmentation of F9 cells in a concentration- and time-dependent manner. This effect was also observed i n a cell-free system using the nuclei from intact cells and the cytosols fr om hinokitiol-treated cells. In contrast, hinokitiol methyl ether and hinok itiol-Fe (III) complex, which are deficient in iron-chelating activity, sho wed no DNA fragmentation activity in both cell culture and cell-free system s. These results suggest that iron deprivation by hinokitiol may be involve d in the induction of apoptosis of F9 cells. Caspase-3, one of the key enzy mes in the apoptotic cascade, was specifically activated by hinokitiol trea tment, but not by the other two derivatives. In addition, its specific inhi bitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, strongly blocked hinokitiol-induced DNA fragmentation. These results indicate that iron depr ivation by hinokitiol can induce apoptosis of F9 cells through the activati on of caspase-3.