We have investigated the action of oxidative stress in arsenite-induced apoptosis of human gastric cancer MGC-803 cells. Cells exhibited obvious characteristic of apoptosis following the treatment with 1.0 microM arsenite for 24 h. During the process, low concentration of arsenite significantly increased superoxide formation and lipid peroxidation, which was dose-dependent and was related to cell apoptosis induced by arsenite. The oxidant-dependent increase in intracellular [Ca(2+)] level and p53 gene expression were also observed at the same time. A phospholipase C inhibitor, 1-[6-([(17 beta)-3-methoxyestra-1,3,5,(10)-trien-17-yl]-amino)hexyl]-2,5-dione (U73122), could block the rapid transient increase in intracellular Ca(2+) levels, as well as the subsequent fragmentation of nuclear DNA. Addition of alpha-tocopherol before arsenite treatment abolished the transient increase in superoxide formation, lipid peroxidation, intracellular [Ca(2+)] levels and p53 gene expression, and furthermore could significantly inhibited the arsenite-induced apoptosis of MGC-803 cells. These results indicate that arsenite-induced oxidative stress, which stimulate cellular signaling systems, are involved in apoptosis of MGC-803 cells.
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