The mechanism of elevated toxicity in HepG2 cells due to combined exposure to ethanol and ionizing radiation

Abstract

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 P(450) 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.

Chronic ethanol treatment depletes glutathione regeneration capacity in hepatoma cell line HepG2

“…5). A similar moderate reduction of GSH stores by treatment of HepG2 cells with 30 mM ethanol for 48 hours was reported previously [23].…”

Potential in vitro Protective Effect of Quercetin, Catechin, Caffeic Acid and Phytic Acid against Ethanol-Induced Oxidative Stress in SK-Hep-1 Cells

“…In addition to acetaldehyde and acetate, ethanol metabolism generates ROS, which induces GSH depletion, damage to the cell membrane, protein oxidation, DNA damage, and alteration of antioxidant enzyme activity (Kurose et al ., 1996; Navasumrit et al ., 2000; Ogony et al ., 2008). Lipid hydroperoxide (LPO) is one of many lipid peroxidation substances induced in the cell membrane by oxidative stress.…”

Antroquinonol from ethanolic extract of mycelium of Antrodia cinnamomea protects hepatic cells from ethanol-induced oxidative stress through Nrf-2 activation

“…Ogny et al (2008) demonstrated that incubation of HepG2 cells with ethanol induces oxidative stress and leaves the cells vulnerable to further injury by ROS. Ethanol exposure also increased intracellular ROS accumulation in HepG2 cells in this study; however, pretreatment with antroquinonol or silymarin inhibited this ethanol-induced ROS generation.…”