Induction of apoptosis by esculetin in human leukemia cells

Esculetin, a coumarin compound, has been shown to exhibit antioxidant and a nti-inflammatory effects. In the present study, esculetin was found to inhi bit the survival of human promyelocytic leukemia HL-60 cells in a concentra tion-dependent and time-dependent manner. HL-60 cells underwent internucleo somal DNA fragmentation and morphological changes characteristic of apoptos is after a 24-h treatment with esculetin (100 muM). Flow cytometric analysi s showed that the hypodiploid nuclei of HL-60 cells were increased to 40.93 % after a 36-h treatment with esculetin (100 muM). Further investigation sh owed that esculetin induced the release of cytochrome c from mitochondria i nto cytosol in a time-dependent and concentration-dependent manner. Moreove r, esculetin application reduced Bcl-2 protein expression to 58% after 9 h as compared with that time at 0. Cysteine protease 32 kDa proenzyme (CPP32) , a caspase 3, was activated and its substrate, poly (adenosine diphosphate -ribose) polymerase, was cleaved after a 24-h treatment of HL-60 cells with esculetin. These data suggest that esculetin induces apoptosis in human le ukemia cells by increasing cytosolic translocation of cytochrome c and acti vation of CPP32. (C) 2001 Elsevier Science B.V. All rights reserved.