Abstract: AIM: To study the effects of macrocalyxin A (MA) on proliferation inhibition and apoptosis in HL-60 human leukemia cell line and explore its mechanisms.METHODS: Different concentrations of MA and different times of cultivation were used to treat HL-60 cell.The proliferation inhibition was analyzed by MTT assay.The cell apoptosis was analyzed by cell morphology, DNA agarose gel electrophoresis, DNA content and cell cycle analyzation, Annexin-V/PI and Hoechst 33258 fluorescence staining.The expressions of Bcl-2, Bax, Fas P53 and mitochondrial membrane protein were analyzed by flow cytometry, while the mitochondrial transmembrancepotential (ΔΨm) was labeled by dihydrorhodamin 123.RT-PCR method was used to study the Bcl-2, Bax, P53 and caspase-3 mRNA levels.RESULTS: MA could inhibit HL-60 cell proliferation viability within a certain range of treating time and dose, with a 24 h IC₅₀ of 8.76 μg/mL, 48 h of 7.17 μg/mL and 72 h of 7.14 μg/mL.A majority of HL-60 cells were arrested in G₀/G₁ phase.The HL-60 cells apoptosis was confirmed by type cell morphology, DNA fragment, sub-G₁ phase and Annexin-Ⅴ PI labeling method with a time and dose related manner. The expression of Bax was increased, and Bcl-2, P53 and fas were unchanged by the treatment of MA.MA could increase the expression of mitochondrial membrane protein and caspase-3 in a dose-dependent manner while the ΔΨm was reduced.CONCLUSION: MA can inhibit the proliferation and induce the apoptosis of HL-60 cells.The mechanisms associate with its up-regulation of Bax and the ratio of Bax/Bcl-2, decreasing the mitochondrial membrane potential, opening the mitochondrial membrane pore and activating caspase-3.

Key words: macrocalyxin A, leukemia, apoptosis, mitochondria