GENOTOXICITY OF CHROMIUM COMPOUNDS

铬化合物的遗传毒性

• 批准号: 6382216
• 负责人: Anatoly Zhitkovich
• 金额: $ 22.74万
• 依托单位: BROWN UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6382216
• 关键词: DNA damage; adduct; autoradiography; carcinogen testing; chemical carcinogen; chemical carcinogenesis; chromium; cysteine; glutamates; glutathione; histidine; human genetic material tag; hypoxanthine phosphoribosyltransferase; mutagen testing; mutagens; neoplasm /cancer genetics; nucleic acid sequence; polymerase chain reaction; tissue /cell culture; transfection /expression vector

DESCRIPTION: Exposure to hexavalent chromium compounds has been established to present a significant cancer risk to human respiratory system. Induction of DNA lesions and subsequently, mutations is generally considered to be responsible for the initiation of Cr(VI)-dependent carcinogenic process. Cr(VI) compounds have been shown to be mutagenic to bacterial and mammalian cells, however, the nature of underlying DNA modifications have not yet been characterized. Reductive conversion of Cr(VI) to Cr(III) accompanied by the formation of intermediate Cr(V/VI) forms and radical byproducts is required for the induction of genotoxic effects. Recent data showed that a major form of DNA adducts formed in Cr(VI)-exposed cells is represented by crosslinks composed of intracellular amino acids or glutathione bridged to DNA by Cr(III). Cysteine, histidine and glutamic acid were predominant amino acids found crosslinked to DNA. Subsequent in vitro studies demonstrated that these ternary adducts are formed by binding of Cr(III)-amino acid complexes to DNA. In preliminary experiments some amino acid-Cr(III) adducts exhibited mutagenic activity. On the basis of these data Dr. Zhitkovich hypothesized that a significant portion of Cr(VI) genotoxicity results from reactions of its final reductive metabolite, Cr(III). In order to obtain evidence supporting this hypothesis, a number of experiments aimed at studying formation of Cr(III) adducts and their mutagenic potential will be carried out. Mutagenicity of the in vitro formed Cr(III)- and amino acids/glutathione-Cr(III)-DNA adducts will be investigated in human cells using a shuttle vector approach. Involvement of Cr(III) in the DNA adduction in vivo will be studied in mammalian cells following their exposure to Cr(VI) or particulate Cr(III) compounds. In addition, the role of nucleotide excision repair in the removal of different Cr(III) adducts will also be analyzed. The results of the proposed work will help understand molecular mechanisms of Cr(VI) carcinogenicity by testing a Cr(III)-dependent pathway of DNA damage and mutagenicity of major adducts. Clarification of the genotoxic activity of intracellular Cr(III) may also have important public health implications considering the fact that human exposure frequently occurs to mixtures of Cr(VI) and Cr(III) forms while current risk assessment is based predominantly on the Cr(VI) levels.

描述：已确定接触六价铬化合物 对人类呼吸系统带来显着的癌症风险。 就职 DNA 损伤以及随后的突变通常被认为是 负责启动 Cr(VI) 依赖性致癌过程。 Cr(VI) 化合物已被证明对细菌和哺乳动物有诱变作用 然而，细胞中潜在的 DNA 修饰的性质尚未被阐明。 特点。 Cr(VI) 还原转化为 Cr(III) 并伴随 需要形成中间体 Cr(V/VI) 形式和自由基副产物 用于诱导遗传毒性作用。 最新数据显示，一个主要 Cr(VI) 暴露细胞中形成的 DNA 加合物的形式表示为 由细胞内氨基酸或谷胱甘肽桥接组成的交联 DNA 通过 Cr(III) 检测。 以半胱氨酸、组氨酸和谷氨酸为主 发现与 DNA 交联的氨基酸。 随后的体外研究 证明这些三元加合物是通过结合形成的 Cr(III)-氨基酸与 DNA 的复合物。 在初步实验中，一些氨基 酸-Cr(III) 加合物表现出诱变活性。 在这些基础上 数据 Dr.zhitkovich 假设 Cr(VI) 的很大一部分 遗传毒性是由其最终还原代谢物的反应引起的， Cr(III)。 为了获得支持这一假设的证据，一些 旨在研究 Cr(III) 加合物的形成及其作用的实验 将进行潜在的诱变。 体外致突变性 形成的 Cr(III)- 和氨基酸/谷胱甘肽-Cr(III)-DNA 加合物将 使用穿梭载体方法在人类细胞中进行研究。 参与 将在哺乳动物细胞中研究体内 DNA 加合中的 Cr(III) 接触 Cr(VI) 或颗粒 Cr(III) 化合物后。 在 此外，核苷酸切除修复在去除不同的 Cr(III) 加合物也将被分析。 拟议工作的结果 将有助于了解 Cr(VI) 致癌性的分子机制 测试主要 DNA 损伤和致突变性的 Cr(III) 依赖性途径 加合物。 细胞内 Cr(III) 基因毒性活性的澄清 考虑到以下事实，也可能对公共卫生产生重要影响： 人类经常接触 Cr(VI) 和 Cr(III) 形式的混合物 而目前的风险评估主要基于 Cr(VI) 水平。