Bioactivation of Halogenated Hydrocarbons

描述（由申请人提供）：烷基和乙烯基卤化物因其高产量、广泛的人类暴露和已知的遗传毒性和致癌性而引起关注。继续的研究是针对这类双功能亲电试剂（包括氧化产物）和相关的化合物二氧化丁二烯，这是另一种商品化学品（1,3-丁二烯）的氧化产物。目前的研究主要集中在1,2-二溴乙烷（二溴乙烯）和二氧化丁二烯的硫醇依赖性激活机制，特别是谷胱甘肽（GSH）转移酶（GSTs）和DNA修复蛋白o6 -烷基鸟嘌呤DNA-烷基转移酶（AGT）。第一个特异性目标涉及1,2-二溴乙烷和二氧化丁二烯衍生的DNA-AGT交联突变机制的表征。除n7 -鸟腈交联外，还将对其他交联进行进一步的表征，一个主要的假设是，从AGT衍生的肽是致突变加合物。第二个特定目的涉及二氧化二丁二烯的谷胱甘肽缀合物，并假设这是一个突出的亲电物种，参与DNA烷基化和二氧化二丁二烯的遗传毒性（而不是解毒产物）。我们还提出了一种方法来评估这些化学物质在啮齿动物体内的AGT和GST途径。第三个特异性目的是利用一种新的化学方法合成具有不稳定糖苷键的DNA加合物，包括一些来自烷基和乙烯基卤化物，特别是N7-（2-氧乙基）-鸟嘌呤，S-[N7-（2-鸟酰乙基）]谷胱甘肽和N2,3-乙二(5)鸟嘌呤。我们的假设是这些加合物编码错误。这些和其他不稳定加合物的错误编码潜力将用几种微生物和人类DNA聚合酶进行评估，并进行比较。总的来说，这些研究应该为这些加合物的毒性和致癌性提供新的机制见解，并提供可能改变风险评估范式的重要信息。

DESCRIPTION (provided by applicant): Alkyl and vinyl halides are of interest because of their high volumes of production, extensive human exposure, and known genotoxicity and carcinogenicity. Continuing studies are directed toward bifunctional electrophiles in this group (including oxidation products) and the related compound butadiene diepoxide, an oxidation product of another commodity chemical (1,3-butadiene). The proposed studies are focused on thiol- dependent activation mechanisms of 1,2-dibromoethane (ethylene dibromide) and butadiene diepoxide, particularly by glutathione (GSH) transferases (GSTs) and the DNA repair protein O6-alkylguanine DNA- alkyltransferase (AGT). The first Specific Aim involves the characterization of mechanisms of mutation of DNA-AGT crosslinks derived from 1,2-dibromoethane and butadiene diepoxide. Further characterization of crosslinks other than the N7-guanyl ones will be done, and a major hypothesis is that peptides derived from AGT are the mutagenic adducts. The second Specific Aim involves the GSH conjugate of butadiene diepoxide and the hypothesis that this is a prominent electrophilic species involved in DNA alkylation and genotoxicity of butadiene diepoxide (as opposed to a detoxication product). An approach is also proposed to evaluate the AGT and GST pathways for these chemicals in rodents in vivo. The third Specific Aim utilizes a new chemical approach to the synthesis of DNA adducts with unstable glycosidic bonds, including several derived from alkyl and vinyl halides, especially N7-(2-oxoethyl)-guanine, S-[N7-(2-guanylethyl)]glutathione, and N2,3-etheno(5)guanine. Our hypothesis is that these adducts are miscoding. The miscoding potentials of these and other unstable adducts will be evaluated with several microbial and human DNA polymerases, and comparisons will be made. Collectively these studies should provide new mechanistic insight into the toxicity and carcinogenicity of these adducts and important information that may alter paradigms in risk assessment.