Curcumol induced apoptosis of human acute myeloid leukemia KG-1a cells

Objective: To investigate the effect of curcumol on the apoptosis of human acute myeloid leukemia KG-1a cells and to explore possible mechanism of action. Methods: CCK-8 method was used to detect the cell viability of KG-1a cells treated by 10, 20, 40, 60, 80 uM curcumol, and that of KG-1a cells treated by 40 uM curcumol after different periods of time. Confocal microscopy was used to observe morphologic changes after cells were incubated with 40 uM curcumol for 24 h and 48 h, respectively. Further, morphologic changes of the nucleus were observed after cells were stained by Hochest 33258. Annexin V-FITC/PI staining was also conducted. Then, after Rhodamine 123 staining of mitochondrial membrane potential specific probe, the decreasing ratio of mitochondrial membrane potential was detected with a flow cytometer. Finally, after cells were pretreated by a broad-spectrum caspase inhibitor z-VAD-fmk, the effect of curcumol on cell viability was tested and the expression of caspase 8, 9 and 3 was also detected by Western blot. Results: The inhibitive effect of curcumol on the viability of KG-1a cells showed significant concentration and time-dependence. The viability of cells treated by 10, 20, 40, 60 and 80 uM curcumol were (91.6 +/- 3.1)%, (74.1 +/- 3.4)%, (57.1 +/- 1.9)%, (37.9 +/- 2.3)% and (32.6 +/- 2.5)%, respectively. For cells treated by 40 uM curcumol for 6, 12, 24 and 48 h, their viability was (75.3 +/- 2.102)%, (50.6 +/- 1.9)%, (41.6 +/- 2.6)%, (20.1 +/- 2.1)%, respectively. Compared with blank control, cells treated by 40 uM curcumol for 24 h partially changed to round in shape and some dead ones floated, which was more obvious for cells treated for 48 h. In addition, nuclear staining showed shrinkage of nucleus and the presence of apoptotic body after treatment for 24 h, which was also more significant after treatment for 48 h. Apoptosis was confirmed by flow cytometry. Moreover, it was found that the mitochondrial membrane potential of cells treated by 40 uM curcumol for 24 and 48 h decreased remarkably, which was (43.1 +/- 1.9)% and (78.9 +/- 2.1)%, respectively (P<0.01). At last, before and after pretreatment with broad-spectrum caspases inhibitor z-VAD-fmk, the viability of cells treated for 24 h and 48 h presented no obvious change. Western blot found that caspases 8, 9 and 3 were not involved in the apoptosis induced by curcumol. Conclusion: Curcumol can decrease the viability of KG-1a cells and induce apoptosis via a possible mechanism of caspases-independent cell apoptosis caused by mitochondrial membrane potential dropping.