The effects of morin (3,5,7,20,40-pentahydroxyflavone) on human leukemia HL-60 cells in vitro were investigated and the molecular mechanisms of morin-induced G2/M arrest and apoptosis in HL-60 cells were examined. Morin induced morphological changes and decreased the percentage of viable cells via induction of G2/M-phase arrest and apoptosis. Morin-induced G2/M-phase arrest was accompanied by the promotion of p21 and Wee1, and decreased levels of Cdc25c and cyclins A and B1 complex. Morin-induced apoptosis in HL-60 cells was also confirmed by flow cytometric assay, DNA gel electrophoresis for DNA fragmentation and DAPI staining. Morin induced apoptosis in time- and dose-dependent manners. Morin-induced apoptosis was associated with elevated intracellular reactive oxygen species (ROS) increased and Ca2+ production; decreased the levels of mitochondria membrane potential (ΔΨm) and increased caspase-3 activation. Collectively, these results suggest that the morin-induced apoptosis in HL-60 cells may result from the activation of caspase-3 and intracellular Ca2+ release, as well as the mitochondria membrane potential pathway.
