Cytotoxicity and oxidative stress in human liver carcinoma cells exposed to arsenic trioxide (HepG(2)).

Arsenic is a trace element that occurs naturally in the earth's crust. It has been found to be a major contaminant in groundwater supply in several countries of the world. Whether ingested or inhaled, arsenic induces both systemic (skin disorders, cardiovascular diseases, anemia, peripheral neuropathy, liver and kidney damage) and carcinogenic (skin, lung, bladder and liver neoplasms) effects. However, its molecular mechanisms of toxicity are not completely understood. In this research, we used HepG(2) cells as a model to study the cytotoxicity and oxidative stress associated with exposure to arsenic trioxide. We hypothesized that oxidative stress plays a role in arsenic trioxide induced cytotoxicity. To test this hypothesis, we performed both MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay and trypan blue exclusion test for cell viability and the thiobarbituric acid test for lipid peroxidation. Data obtained from the MTT assay indicated that arsenic trioxide significantly reduced the viability of HepG(2) cells, showing a LD(50) value of about 23 mug/mL upon 24 h of exposure, indicating a dose-dependent response. Similar trend was obtained with the trypan blue exclusion test. Data generated from the thiobarbituric acid test showed a significant increase (p </= 0.05) in MDA levels in arsenic trioxide-treated HepG(2) cells compared to control cells. Arsenic trioxide treatment significantly increased cellular content of reactive oxygen species (ROS), as evidenced by the increase in lipid peroxidation by-products. Taken together, these results indicate that arsenic trioxide is cytotoxic to HepG(2) cells. This cytotoxicity is mediated by oxidative stress, a biomarker of cellular injury.