ObjectiveTo investigate the effects and mechanism of the combination of arsenic trioxide （ATO） and its dimethylarsinic acid （DMAV） metabolite on apoptosis of human acute promyelocytic leukemia NB4 cells by affecting the balance of metabolic reaction.MethodsThe rats were injected with the same amount of sterile normal saline， ATO（1.6 mg·kg^-1）， and DMAV（4， 8， 16， and 32 mg·kg^-1） combined with ATO（1.6 mg·kg^-1）， respectively， to obtain the corresponding drug-containing serum. The effect of drug-containing serum on the proliferation of NB4 cells was detected by the cell counting kit-8 （CCK-8 ）method. Apoptosis was detected by flow cytometry with Annexin-V-FITC/PI double staining. Intracellular reactive oxygen species （ROS） accumulation was detected by flow cytometry using fluorescent probe DCFH-DA. The changes of mitochondrial membrane potential （Δψm） were detected by the fluorescence probe JC-1. Western blot detected the expression of apoptosis-related proteins， namely B-cell lymphoma-2（Bcl-2）-associated X protein（Bax）/Bcl-2， Cytochrome C， cleaved Caspase-9， and cleaved Caspase-3， as well as c-Jun N-terminal kinase（JNK） phosphorylation levels.Results①The Combination of the two drugs had a higher proliferation inhibition rate and more apoptosis than ATO alone. ②The combination of two drugs can significantly increase the production of ROS compared with any single treatment group. ③The Δψm was significantly reduced in the two-drug combination group compared with any single treatment group. ④Compared with either group， the combination group significantly released Cytochrome C， significantly down-regulated the expression of Bcl-2， and up-regulated the expression of Bax， cleaved Caspase-3， and cleaved Caspase-9. ⑤The phosphorylation level of JNK was significantly up-regulated in the two-drug combination group compared with any single treatment group.ConclusionThe combination of DMAV and ATO may synergistically induce mitochondrial apoptosis through ROS-mediated oxidative stress， triggering Δψm dissipation and Cytochrome C release. By activating Caspase-9/Caspase-3 and the phosphorylation level of JNK， the Bcl-2 family protein （Bax/Bcl-2） was regulated to promote the apoptosis of NB4 cells.

dimethylarsinic acid;arsenic trioxide;oxidative stress;mitochondrial apoptosis