Ogony Joshua, Matthews Richard, Anni Helen, Shannon Katie, Ercal Nuran
Department of Chemistry, University of Missouri-Rolla, 870 Miner Circle, Rolla, MO 65409, USA.
J Appl Toxicol. 2008 Apr;28(3):345-55. doi: 10.1002/jat.1285.
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.
已知乙醇和电离辐射暴露可通过多种机制独立导致组织损伤。乙醇的非酶促和酶促代谢，后者通过细胞色素P(450) 2E1依赖性途径产生自由基，从而消耗细胞内的谷胱甘肽（GSH）。电离辐射暴露已被证明可诱导脂质过氧化、DNA损伤、蛋白质氧化和GSH消耗。据推测，经乙醇致敏的细胞将易受额外损伤，例如通过增加氧化应激而受到辐射损伤。在本研究中，将培养的肝细胞（HepG2，人肝细胞肝癌细胞）先暴露于乙醇，然后再进行电离辐射。通过一系列技术评估细胞的抗氧化状态。通过高效液相色谱法测量谷胱甘肽、半胱氨酸（CYS）和丙二醛（MDA）的水平。通过酶法测定抗氧化酶过氧化氢酶和谷胱甘肽还原酶（GR）的活性。通过半胱天冬酶-3检测和荧光显微镜评估细胞凋亡。数据显示，与对照组相比，乙醇和辐射联合处理导致GSH水平最低，MDA水平最高。与单一药物暴露组相比，联合暴露组的过氧化氢酶活性较低，而联合暴露组的谷胱甘肽还原酶活性最高，对照组最低。这些发现表明，乙醇和电离辐射联合作用通过升高氧化应激在体外导致更大的毒性。
