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化学呋喃。呋喃是啮齿类动物的一种强肝毒性和肝致癌物。以低至2 mg/kg b.w.的剂量对大鼠长期给予呋喃。导致胆管癌的发病率非常高。虽然有关人类摄入呋喃的数据有限，但人类摄入量与导致啮齿动物肝脏肿瘤的剂量之间的差距似乎相对较小，表明食物中存在的呋喃可能对人类健康构成潜在风险。然而，目前关于呋喃毒性的可用数据不足以进行风险评估，需要对呋喃致癌性的机制进行更多的研究。在一项使用1, 4C标记呋喃的体内研究中，无法确定呋喃或其反应性代谢产物顺式-2-丁烯-1，4-二醛与DNA的共价结合。相比之下，发现肝脏中80%的放射性与蛋白质有关。已经表明，慢性炎症和增强的胆管细胞增殖响应呋喃细胞毒性，通过结合的顺式-2-丁烯-1，4-二醛的关键靶蛋白介导的，很可能在呋喃致癌性中发挥关键作用。拟议工作的目的是通过采用最先进的蛋白质组学方法来鉴定呋喃反应中间体的靶蛋白，包括向大鼠给予14 C标记的呋喃，通过二维凝胶分离肝脏中存在的未修饰和呋喃加合的蛋白质电泳、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志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。通过本项目获得的知识，特别是关于剂量-反应关系的知识，可以决定是否需要控制食品中的呋喃水平。

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.