Objective      To investigate apoptotic effects of cinobufacini on human neuroblastoma SH-SY5Y cells and its  relevant mechanism.       Methods      Effects of cinobufacini on SH-SY5Y cell proliferation were tested by SRB assay. Cell apoptosis of SH-SY5Y was measured by flow cytometry. The levels of reactive oxygen species (ROS) in the cells were analyzed by ROS-sensitive fluorometric probe DCFH-DA assay and mitochondria transmembrane potential was revealed by rhodamine123 staining. The expression of cyto

solic Cyt-C was analyzed by Western blotting. Caspase-3 and caspase-9 activities were detected by ELISA.       Results      Cinobufacini inhibited the proliferation of SH-SY5Y cells in a dose- and time-dependent manner. Flow cytometry results showed that the apoptotic rates in the control group and the cinobufacini-treated groups (cinobufacini concentration 0.125

0.25

and 0.5 μg/mL) were (3.12±0.91)%

(17.65±4.28)%

(29.14±6.72)%

and (50.01±9.26)%

respectively. Compared with the control group

the cinobufacini-treated cells showed increased apoptotic rate (

P

0.01). Cinobufacini

in a dose-dependent manner

increased the ROS levels (

P

0.01)

decreased mitochondria transmembrane potential (

P

0.01)

enhanced cytosolic Cyt-C expression (

P

0.01) in SH-SY5Y cells

and increased caspase-3 and caspase-9 activities.       Conclusion      Cinobufacini can inhibit the proliferation of SH-SY5Y cells by inducing cell apoptosis

which may involves the stimulation of mitochondrial apoptotic pathway.