Biomarkers of Organophosphorus Pesticide-Induced Neurotoxicity

描述(申请人提供)：有机磷农药(OP)是美国和世界范围内最常用的杀虫剂。来自人类和动物研究的证据清楚地表明，神经毒性是令人担忧的主要终点。然而，由于以下原因：1)OP剂量与人类神经行为缺陷之间的关系尚未建立；2)没有可靠地预测OP诱导的神经行为缺陷的生物标志物；3)遗传变异改变暴露敏感性的可能性尚未得到彻底的研究，因此很难预测反复低剂量OP暴露给人类带来的风险。拟议的研究将检验以下假设：OP诱导的神经行为缺陷与剂量相关，氧化应激和炎症的测量比胆碱酯酶抑制更好地预测神经行为缺陷。这些假说将通过研究埃及梅努菲亚省的一群农药应用工人来验证，此前有报道称，这些工人在接触OP后表现出最广泛的神经行为缺陷。这一埃及队列特别适合于这些研究，因为与大多数农药暴露不同，暴露是简单的(单一的有机磷，毒死蜱)，在工作类别内是一致的，但工作类别之间有很大差异。在目标1中，将使用从255名埃及工人在应用周期中收集的尿液OP代谢物数据的PBPK/PD模型来估计OP剂量。这些工人还将对OP代谢中涉及的关键酶(CYP2B6、CYP2C19和PON1)的多态性进行基因分型，以评估改变内部剂量的遗传变异的可能性。在目标2中，行为缺陷将在表现出一系列OP暴露的工人子集中确定。来自AIMS 1和AIMS 2的数据将被整合以确定OP剂量和神经行为缺陷之间的关系。大鼠研究将平行进行(目标3)，以测试候选生物标记物作为OP诱导的神经行为缺陷的预测因子。将被检测的特定生物标记物包括胆碱酯酶抑制，作为氧化应激指标的尿异前列腺素，以及作为炎症指标的血清C反应蛋白和炎症细胞因子水平。在目标4中，将测试那些预测OP诱导的大鼠神经行为缺陷的生物标记物，以确定它们是否类似地预测埃及农药工人的行为表现缺陷。拟议的研究将提供开发有效的OP暴露、生物反应和遗传易感性生物标记物所需的关键数据。这类生物标志物的提供将有助于识别高危个人以及测试干预和治疗策略，有证据表明人类广泛接触有机磷农药，以及有机磷农药作为恐怖主义化学毒剂构成的可信威胁，突显了制定这些战略的必要性。项目摘要/摘要-相关性拟议研究的目标是确定暴露和影响的生物标志物，这些生物标志物可以预测暴露在有机磷农药(OP)下的人类的神经行为缺陷。此外，我们将研究影响OP新陈代谢的酶CYP2B6和CYP2C19的人类遗传变异，不仅为OP暴露数据的解释提供信息，还提供对调节OP神经毒性反应的遗传易感性的见解。这些研究将提供识别高危个人至关重要的数据，并将提供工具，以促进干预和治疗策略的开发和评估，这些策略不仅适用于OP杀虫剂，也适用于被认为是可信的恐怖主义威胁的神经毒剂。OP杀虫剂是美国和世界范围内最常用的杀虫剂。

DESCRIPTION (provided by applicant): Organophosphorus pesticides (OPs) are the most commonly used pesticides in the U.S. and worldwide. Evidence from human and animal studies clearly identifies neurotoxicity as the primary endpoint of concern. However, it has been difficult to predict the risk that repeated low-dose exposure to OPs pose to humans because: 1) a relationship between OP dose and neurobehavioral deficits has yet to be established in humans; 2) biomarkers that reliably predict OP-induced neurobehavioral deficits are not available: and 3) the potential for genetic variation to modify exposure sensitivity has not been thoroughly investigated. The proposed studies will test the hypotheses that OP-induced neurobehavioral deficits are dose-related and that measures of oxidative stress and inflammation are better predictors of neurobehavioral deficit than cholinesterase inhibition. These hypotheses will be tested by studying a cohort of pesticide application workers in Egypt's Menoufia Governorate previously reported to exhibit the broadest range of neurobehavioral deficits in humans following OP exposure. This Egyptian cohort is uniquely suited for these studies because, unlike most pesticide exposures, the exposure is simple (a single OP, chlorpyrifos) and consistent within job categories, but with substantial differences between job categories. In aim 1, OP doses will be estimated using PBPK/PD modeling of urinary OP metabolite data collected from 255 Egyptian workers over the application cycle. These workers will also be genotyped for polymorphisms of key enzymes involved in OP metabolism (CYP2B6, CYP2C19 and PON1) to evaluate the potential for genetic variation to modify internal dose. In aim 2, behavioral deficits will be determined in a subset of workers exhibiting a range of OP exposures. Data from aims 1 and 2 will be integrated to determine the relationship between OP dose and neurobehavioral deficits. Rat studies will be conducted in parallel (aim 3) to test candidate biomarkers as predictors of OP-induced neurobehavioral deficits. The specific biomarkers that will be examined include cholinesterase inhibition, urinary isoprostanes as a measure of oxidative stress, and serum levels of C-reactive protein and inflammatory cytokines as measures of inflammation. In aim 4, those biomarkers that predict OP-induced neurobehavioral deficits in rats will be tested to determine if they similarly predict deficits in behavioral performance in Egyptian pesticide workers. The proposed studies will provide critical data needed to develop effective biomarkers of OP exposure, biological response and genetic susceptibility. The availability of such biomarkers would facilitate the identification of at-risk individuals as well as the testing of intervention and treatment strategies, and the need to develop these strategies is underscored by evidence of widespread human exposure to OPs and the credible threat of OPs as chemical agents of terrorism. Project Summary/Abstract - Relevance The goal of the proposed studies is to identify biomarkers of exposure and effect that are predictive of neurobehavioral deficits in humans exposed to organophosphorus pesticides (OPs). In addition, we will examine human genetic variants of the enzymes CYP2B6 and CYP2C19 that influence OP metabolism to not only inform interpretation of OP exposure data, but also provide insights into genetic susceptibilities that modulate neurotoxic responses to OPs. These studies will provide data critically needed to identify at-risk individuals and will provide tools to facilitate the development and evaluation of intervention and treatment strategies for exposure to not only OP pesticides, which are the most commonly used pesticides in the U.S. and worldwide, but also to nerve agents that are considered a credible terrorist threat.