DETECTION OF ENDOG AND EXOGEN DERIVED ETHYLENE OXIDE DNA ADDUCTS BY 3H & 14C AM

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 环氧乙烷是化学工业中广泛使用的中间体，也是由正常生理过程中产生的乙烯代谢氧化内源性形成的。虽然环氧乙烷被归类为人类致癌物，但流行病学研究提供了关于其诱发人类癌症能力的相互矛盾的证据。因此，有必要评估与低剂量职业接触这种化学品有关的风险。环氧乙烷与DNA反应，主要形成N7-（2-羟乙基）-2 <$-脱氧鸟苷加合物（7 HEG），可用作暴露和潜在癌症风险的生物标志物。本项目的最终目标是确定内源性加合物形成的来源，并确定低剂量环氧乙烷暴露对体内形成的7 HEG加合物总体水平的相对贡献。这将通过给予乙烯（不饱和脂肪酸和甲硫氨酸）和[14 C]-环氧乙烷的[3 H]-标记生物前体，结合加速器质谱分析来实现。 具体而言，该项目将首先确定通过口服[3 H]标记的不饱和脂肪酸或蛋氨酸在大鼠组织中形成的内源性7 HEG加合物的来源和水平。还将在平行研究中测定在一定剂量范围内（包括职业暴露水平）急性给予[14 C]-环氧乙烷后大鼠组织中形成的外源性7 HEG加合物水平。为了确定内源性和外源性加合物的相对贡献，将[3 H]-标记脂肪酸或[3 H]-蛋氨酸与[14 C]-环氧乙烷联合给药。使用双同位素AMS形成的DNA加合物的分析将证明通过不同途径形成的加合物是否是相加的，以及环氧乙烷是否能够影响内源性加合物水平。 通过这项工作，我们将确定内源性7 HEG加合物形成的来源，并量化职业水平的环氧乙烷对加合物形成的影响，这将有助于评估人类暴露于这种化学品的风险。此外，开发的方法可以应用于其他化学致癌物的研究，能够产生DNA加合物也形成内源性。这将导致更好地了解DNA加合物形成的内源性和外源性途径的相对作用以及与接触工业化学品相关的风险。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ethylene oxide is a widely used intermediate in the chemical industry and is also formed endogenously from the metabolic oxidation of ethylene, which is generated during normal physiological processes. Although ethylene oxide is classed as a human carcinogen, epidemiological studies provide conflicting evidence regarding its ability to induce human cancers. Consequently, there is a need to assess the risks associated with low dose occupational exposures to this chemical. Ethylene oxide reacts with DNA, primarily forming N7-(2-hydroxyethyl)-2¿-deoxyguanosine adducts (7HEG), which can be used as a biomarker of exposure and potential cancer risk. The ultimate goal of this project is to identify sources of endogenous adduct formation and determine the relative contribution of low dose ethylene oxide exposures to the overall level of 7HEG adducts formed in vivo. This will be achieved through the administration of [3H]-labeled biological precursors of ethylene (unsaturated fatty acids and methionine) and [14C]-ethylene oxide, coupled with accelerator mass spectrometry analysis. Specifically, this project will involve first establishing the sources and level of endogenous 7HEG adducts formed in rat tissues through oral administration of [3H]-labeled unsaturated fatty acids or methionine. The level of exogenously derived 7HEG adducts formed in rat tissues following acute administration of [14C]-ethylene oxide over a range of doses, including occupational exposure levels will also be determined in parallel studies. In order to determine the relative contribution of adducts from endogenous and exogenous sources, a [3H]-labeled fatty acid or [3H]-methionine will be co-administered with [14C]-ethylene oxide. Analysis of the DNA adducts formed using dual-isotope AMS will demonstrate whether adduct formation by different routes is additive and whether ethylene oxide is able to influence endogenous adduct levels. Through this work we will identify sources of endogenous 7HEG adduct formation and quantify the effect of occupational levels of ethylene oxide on adduct formation, which will aid in assessing the risk to humans exposed to this chemical. Furthermore, the methods developed could be applied to the study of other chemical carcinogens capable of generating DNA adducts also formed endogenously. This will lead to a better appreciation of the relative roles of endogenous and exogenous pathways of DNA adduct formation and the risks associated with exposure to industrial chemicals.