Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical School, Georgetown University Medical Center, LL level, S-122 3800 Reservoir Road, NW, Washington, DC, 20057, USA.
Mol Cell Biochem. 2014 Mar;388(1-2):185-93. doi: 10.1007/s11010-013-1909-y. Epub 2013 Dec 15.
The Long-Evans Cinnamon (LEC) rat is an animal model for Wilson's disease. This animal is genetically predisposed to copper accumulation in the liver, increased oxidative stress, accumulation of DNA damage, and the spontaneous development of hepatocellular carcinoma. Thus, this animal model is useful for studying the relationship of endogenous DNA damage to spontaneous carcinogenesis. In this study, we have investigated the apurinic/apyrimidinic endonuclease 1 (APE1)-mediated excision repair of endogenous DNA damage, apurinic/apyrimidinic (AP)-sites, which is highly mutagenic and implicated in human cancer. We found that the activity was reduced in the liver extracts from the acute hepatitis period of LEC rats as compared with extracts from the age-matched Long-Evans Agouti rats. The acute hepatitis period had also a heightened oxidative stress condition as assessed by an increase in oxidized glutathione level and loss of enzyme activity of glyceraldehyde 3-phosphate dehydrogenase, a key redox-sensitive protein in cells. Interestingly, the activity reduction was not due to changes in protein expression but apparently by reversible protein oxidation as the addition of reducing agents to extracts of the liver from acute hepatitis period reactivated APE1 activity and thus, confirmed the oxidation-mediated loss of APE1 activity under increased oxidative stress. These findings show for the first time in an animal model that the repair mechanism of AP-sites is impaired by increased oxidative stress in acute hepatitis via redox regulation which contributed to the increased accumulation of mutagenic AP-sites in liver DNA.
长爪沙鼠（LEC）是威尔逊病的动物模型。这种动物易发生肝脏内铜蓄积、氧化应激增加、DNA 损伤蓄积和肝细胞癌的自发发展。因此，这种动物模型可用于研究内源性 DNA 损伤与自发性癌变的关系。在本研究中，我们研究了参与自发性致癌作用的内源性 DNA 损伤修复的脱嘌呤/脱嘧啶内切核酸酶 1（APE1）介导的修复，脱嘌呤/脱嘧啶（AP）位点具有高度致突变性，与人类癌症有关。我们发现，与年龄匹配的长爪沙鼠相比，LEC 大鼠急性肝炎期的肝提取物中 APE1 活性降低。急性肝炎期还伴有氧化应激升高，表现为氧化型谷胱甘肽水平升高和甘油醛 3-磷酸脱氢酶（细胞中关键的氧化还原敏感蛋白）的酶活性丧失。有趣的是，活性降低不是由于蛋白质表达的变化，而是由于蛋白质的可逆氧化，因为向急性肝炎期肝提取物中加入还原剂可恢复 APE1 活性，从而证实了在氧化应激增加的情况下，APE1 活性的降低是由氧化介导的。这些发现首次在动物模型中表明，AP 位点的修复机制在急性肝炎中通过氧化还原调节而受到损害，这导致肝 DNA 中致突变性 AP 位点的积累增加。
