Furan in food: a dietary risk factor for human cholangiocarcinoma? Characterization of functional changes an protein adducts in the hepatobliliary tract of rats exposed to turan

在最近的一项调查中，美国食品和药物管理局(FDA)在各种经过热处理的食品中发现了这种化学物质呋喃。呋喃对啮齿动物有很强的肝脏毒性和致癌作用。长期给大鼠灌胃呋喃，剂量低至2 mg/kg体重。导致胆管细胞癌的发病率非常高。尽管有关人类摄取呋喃的数据有限，但人类接触呋喃与导致啮齿动物肝脏肿瘤的剂量之间似乎存在相对较小的差距，这表明食物中呋喃的存在可能对人类健康构成潜在风险。然而，目前关于呋喃毒性的现有数据不足以进行风险评估，还需要更多关于呋喃致癌机制的研究。在使用14C标记呋喃的体内研究中，无法建立呋喃或其活性代谢物顺-2-丁烯-1，4-Dial与DNA的共价结合。相比之下，肝脏中80%的放射性被发现与蛋白质有关。已有研究表明，通过顺式-2-丁烯-1，4-Dial与关键靶蛋白结合而介导的呋喃细胞毒性引起的慢性炎症和胆管细胞增殖增强，可能在呋喃的致癌作用中起关键作用。这项拟议工作的目的是利用最先进的蛋白质组学方法鉴定呋喃反应中间体的目标蛋白质，包括给大鼠注射14C标记的呋喃，通过双向凝胶电泳分离肝脏中存在的未修饰和呋喃加成的蛋白质，放射自显影，以及通过现代MS技术鉴定蛋白质，并通过分析肝胆损伤、组织病理学改变和细胞增殖的标记物，以及蛋白质表达的变化来表征与蛋白质损伤相关的细胞和功能后果。在这个项目中将获得的知识，特别是与剂量-反应关系有关的知识，可以决定是否需要控制食品中的呋喃含量。

In a recent investigation, the U.S. Food and Drug Administration (FDA) identified the chemical furan in a variety of food items that undergo heat treatment. Furan is a potent hepatotoxicant and liver carcinogen in rodents. Chronic administration of furan to rats at doses as low as 2 mg/kg b.w. results in very high incidences of cholangiocarcinoma. Although data on human intake of furan are limited, it appears that there is a relatively narrow margin between human exposure and doses which cause liver tumors in rodents, suggesting that the presence of furan in food may present a potential risk to human health. However, the presently available data on furan toxicity is insufficient to perform a risk assessment and more research regarding the mechanism of furan carcinogenicity is needed. In an in vivo study using 14C-labeled furan, covalent binding of furan or its reactive metabolite cis-2-butene-1,4-dial to DNA could not be established. In contrast, 80% of the radioactivity present in livers was found to be associated with proteins. It has been suggested that chronic inflammation and enhanced biliary cell proliferation in response to furan cytotoxicity, mediated through binding of cis-2-butene-1,4-dial to critical target proteins, is likely to play a key role in furan carcinogenicity. The aim of the proposed work is to identify target proteins of furan reactive intermediates by employing state-of-the-art proteomics methods involving administration of 14C-labeled furan to rats, separation of unmodified and furan-adducted proteins present in liver by two-dimensional gel electrophoresis, autoradiography, and identification of proteins by modern MS techniques, and to characterize the cellular and functional consequences associated with protein damage by analyzing markers of hepatobiliary injury, histopathological alterations and cell proliferation, and changes in protein expression. With the knowledge to be gained in this project, particularly in relation to the dose-response relationships, decisions can be made as to whether furan levels in food need to be controlled.