Induction of apoptosis by penta-O-galloyl-beta-D-glucose through activation of caspase-3 in human leukemia HL-60 cells

Penta-O-galloyl-beta-D-glucose is structurally related to (-)-epigallocatec hin gallate and is isolated from hydrolyzed tannin. Penta-O-galloyl-beta-D- glucose can inhibit tumor promotion by teleocidin. We investigated the effe cts of penta-O-galloyl-beta-D-glucose and various tea polyphenols on cell v iability in human leukemia HL-60 cells. In this study, we demonstrated that penta-O-galloyl-beta-D-glucose was able to induce apoptosis in a concentra tion- and time-dependent manner; however, other polyphenols were less effec tive. We further investigated the molecular mechanisms of penta-O-galloyl-b eta-D-glucose-induced apoptosis. Treatment with penta-O-galloyl-beta-D-gluc ose caused induction of caspase-3/CPP32 activity in dose- and time-dependen t manner, but not caspase-1 activity, and induced the degradation of poly-( ADP-ribose) polymerase. Pretreatment with acetyl-Asp-Glu-Val-Asp-aldehyde ( Ac-DEVD-CHO) and Z-Val-Ala-Asp-fluoromethyl-ketone (Z-VAD-FMK) inhibited pe nta-O-galloyl-beta-D-glucose-induced DNA fragmentation. Furthermore, treatm ent with penta-O-galloyl-beta-D-glucose (50 mu M) caused a rapid loss of mi tochondrial transmembrane potential, release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 processing. Our resu lts indicate that penta-O-galloyl-beta-D-glucose allows caspase-activated d eoxyribonuclease to enter the nucleus and degrade chromosomal DNA, and indu ces DFF-45 (DNA fragmentation factor) degradation. These results lead to a working hypothesis that penta-O-galloyl-beta-D-glucose-induced apoptosis is triggered by the release of cytochrome c into the cytosol, procaspase-9 pr ocessing, activation of caspase-3, degradation of poly-(ADP-ribose) polymer ase, and DNA fragmentation caused by the caspase-activated deoxyribonucleas e through the digestion of DFF-45. The induction of apoptosis by penta-O-ga lloyl-beta-D-glucose may provide a pivotal mechanism for its cancer chemopr eventive action. (C) 1999 Elsevier Science B.V. All rights reserved.