The Mechanism of Elevated Toxicity in HepG2 Cells Due to Combined Exposure to Ethanol and Ionizing Radiation


Ethanol and ionizing radiation exposure are independently known to cause tissue damage through various mechanisms. The non-enzymatic and enzymatic metabolism of ethanol, the latter via the cytochrome P450 2E1 dependent pathway produces free radicals, which deplete cellular glutathione (GSH). Ionizing radiation exposure has been shown to induce lipid peroxidation, DNA damage, protein oxidation and GSH depletion. It was postulated that cells sensitized by ethanol will be susceptible to additional insult, such as by radiation through increased oxidative stress. In this investigation, cultured liver cells (HepG2, human hepatocellular liver carcinoma) were exposed to ethanol, followed by ionizing radiation. The antioxidant status of the cells was evaluated by an array of techniques. Levels of glutathione, cysteine (CYS), and malondialdehyde (MDA) were measured by HPLC. Activities of antioxidant enzymes, catalase and glutathione reductase (GR) were determined enzymatically. Apoptosis was evaluated by the caspases-3 assay and fluorescence microscopy. The data showed that combined treatment with ethanol and radiation resulted in the lowest levels of GSH, and highest MDA level compared with the control. The catalase activity was lower in the combined exposure groups, when compared with the single agent exposure groups, and the glutathione reductase activity was the highest in the combined exposure groups and lowest in the control. These findings suggest that a combination of ethanol and ionizing radiation results in greater toxicity in vitro through elevated oxidative stress.


Biological Sciences

Second Department



Matthews Foundation


This investigation was supported in part by a research grant from the Matthews Foundation.

Keywords and Phrases

Anti-Oxidant Enzymes; Cysteine; Ethanol; Free Radicals; Glutathione; HepG2; Liver; Malondialdehyde; Oxidative Stress; Radiation; DNA Damage; Ionizing Radiation

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





© 2008 John Wiley & Sons, All rights reserved.

Publication Date

01 Apr 2008

PubMed ID