Pharmacotoxicology of Trichloroethylene Metabolites

描述（由申请人提供）：本资助最初的特定目标1是在成年患者接受开放式手术切除良性肝脏病变（如囊肿、腺瘤）之前，对其进行为期2天的口服DCA暴露，覆盖环境（2.5¿g/kg/d）-临床（25 mg/kg/d）剂量范围。切除病变的邻近健康组织，分析谷胱甘肽转移酶（GSTz1）的ζ -1家族异构体，该酶将DCA生物转化为乙醛酸盐。GSTz1与酪氨酸分解代谢的倒数第二酶——马来酰乙酰乙酸异构酶（MAAI）相同。由于DCA抑制动物肝脏中的这种酶，我们假设它也会在人类肝脏中起作用，导致潜在毒性酪氨酸代谢物在血浆中积累。然而，去年UF外科医生对这些患者采用的标准治疗方法从开放切口改为经皮囊肿引流和经皮切除大多数腺瘤，从而基本上取消了我们的受试者招募。因此，本次ES014617竞争性修订的目的是通过应用由PI及其同事在授予该R01之前和之后开发的最先进的稳定同位素动力学和动力学建模技术来纠正这一缺陷，以实现以下目标：具体目标4：量化DCA对人体酪氨酸代谢的影响以及与剂量和基因型相关的自身生物转化。本研究旨在验证DCA抑制GSTz1/MAAI在环境和临床暴露水平下改变健康成人13c -酪氨酸动力学的假设，从而导致潜在毒性酪氨酸代谢物的积累。我们进一步假设，在DCA显示高Km的GSTz1/MAAI KRT变体中，酪氨酸代谢的抑制将是最大的。还将确定全身蛋白质周转，以帮助解释酪氨酸动力学数据。

DESCRIPTION (provided by applicant): The original Specific Aim 1 of this grant was to conduct a 2-day exposure of oral DCA covering the environmental (2.5 ¿g/kg/d)-clinical (25 mg/kg/d) dose range in adult patients just prior to them undergoing open surgical removal of a benign liver lesion (e.g., cyst, adenoma). Adjacent healthy tissue excised with the lesion would be taken for analysis of the zeta-1 family isoform of glutathione transferase (GSTz1), which biotransforms DCA to glyoxylate. GSTz1 is identical to the penultimate enzyme in tyrosine catabolism, maleylacetoacetate isomerase (MAAI). Because DCA inhibits this enzyme in animal livers, we postulated it would also do so in human livers, leading to the plasma accumulation of potentially toxic tyrosine metabolites. However, last year the standard-of-care approach applied by UF surgeons to these patients changed from open incisions to percutaneous drainage of cysts and percutaneous removal of most adenomas, thereby essentially eliminating our recruitment of subjects for this Aim. Accordingly, the purpose of this Competitive Revision of ES014617 is to redress this deficiency by applying state-of-the-art stable isotope kinetics and kinetic modeling techniques developed by the PI and his colleagues prior to and since the awarding of this R01 to accomplish the following aim: Specific Aim 4: Quantify the effects of DCA on human tyrosine metabolism and on its own biotransformation in relation to dose and genotype. This aim tests the postulate that inhibition of GSTz1/MAAI by DCA alters 13C-tyrosine kinetics in healthy adults at both environmental and clinical exposure levels, resulting in accumulation of potentially toxic tyrosine metabolites. We further postulate that inhibition of tyrosine metabolism will be greatest in subjects who harbor the KRT variant for GSTz1/MAAI for which DCA exhibits a high Km. Whole body protein turnover will also be determined to aid in the interpretation of the tyrosine kinetic data. PUBLIC HEALTH RELEVANCE: Dichloroacetate (DCA) occupies a unique place in biomedicine because of its significance as both a potential environmental toxin and a therapeutic agent. DCA is believed to inhibit human tyrosine metabolism and this it thought to be genetically influenced and related to its potential environmental and clinical toxicology. This application seeks to determine the quantitative impact of DCA, administered at both environmentally and clinically relevant doses, on tyrosine metabolism in human in relation to genotype, thereby elucidating the relevant risk of human populations to different DCA exposure levels.