Abstract: AIM: To investigate the effects and the molecular mechanisms of Naja atra L-amino acid oxidase (NA-LAAO) on the proliferation and cell apoptosis of human stomach cancer MGC-803 cells.METHODS: MGC-803 cells were exposed to different concentrations of NA-LAAO and the cytotoxicity was measured using a CCK-8 kit. The apoptosis-inducing activities of NA-LAAO were examined by propidium iodide staining and Annexin V/PI assay in flow cytometry. The enzyme activity of caspase-3 was measured by a colorimetric assay. The cleavage of PARP-1 was analyzed by Western-blot.RESULTS: NA-LAAO exhibited cytotoxicity on MGC-803 in a dose- and time-dependent manner. The half maximal inhibitory concentration (IC₅₀) values of NA-LAAO were (2.48±0.41), (1.74±0.27) and (0.83±0.19) mg/L in MGC-803 cells at 6 h, 12 h and 24 h, respectively. NA-LAAO induced apoptosis accompanied DNA hypodiploidy, phosphatidylserine exposure, activation of caspase-3, and PARP cleavage.CONCLUSION: NA-LAAO inhibited cell proliferation by inducing a caspase-mediated cell apoptosis.

Key words: Snake venoms, Naja atra, L-amino acid oxidase, Cell proliferation, Apoptosis