Cholinergic Insecticide Toxicology

胆碱能杀虫剂毒理学

• 批准号: 6929823
• 负责人: JOHN E CASIDA
• 金额: $ 26.6万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6929823
• 关键词: X ray crystallography; acetylcholine; affinity chromatography; analog; conformation; environmental exposure; environmental toxicology; insecticide biological effect; insecticides; laboratory mouse; laboratory rabbit; nicotine; nicotinic receptors; nuclear magnetic resonance spectroscopy; receptor binding; tissue /cell culture

DESCRIPTION (provided by applicant): Neonicotinoids are the most important new class of insecticides of the last three decades, already accounting for about 10% of the world insecticide market and with major human exposure. They have the same nicotinic acetylcholine receptor (nAChR) target as nicotine but are much more potent and selective for insects. The long term objective is to define the mechanisms of selective toxicity for the major neonicotinoids, imidacloprid, thiacloprid, thiamethoxam and acetamiprid. The first specific aim is to establish the unique neonicotinoid and nicotinoid structural features for nAChR specificity and selective toxicity. The negatively-charged tip is proposed to confer potency and selectivity for insect nAChRs, prompting us to synthesize structural probes with this feature. The preferred conformation and configuration will be determined by X-ray crystallography and NMR and related to potency. Quantum mechanics studies will establish the electrostatic potential surface, molecular charge distribution and binding energy. The same approaches will be used to characterize the analogous nicotinoids selective for mammalian nAChRs. The second aim is to characterize nAChR subtypes, subunits and subsites that determine selective action. One goal is to establish the role(s) of alpha4beta2, alpha3beta2(and/or beta4) alpha5, or alpha7 and alpha1Gamma alpha1deltabeta1 subtypes in binding neonicotinoids and their metabolites relative to functional assays and selective toxicity. Drosophila nAChR and vertebrate nAChR subtypes are solubilized, purified by neonicotinoid- or nicotinoid-affinity chromatography, and labeled with potent azidoneonicotinoid and azidonicotinoid photoaffinity probes designed in this laboratory. The labeled subunits will be identified with particular attention to the proposed cationic subsite(s) in insects and pi-electron-rich subsite(s) in vertebrates. Molecular modeling of the detailed binding site architecture will then relate the structure of the Drosophila D-alpha subunits and the acetylcholine binding protein to the findings on photoaffinity labeling. The third aim is to define neonicotinoid metabolic activation and detoxification relative to selective toxicity. Metabolites of imidacloprid, thiacloprid, thiamethoxam and acetamiprid will be characterized and synthesized for receptor, toxicity and functional assays to clarify selective metabolic activation versus detoxification. Toxicokinetic studies with mice will relate the brain levels of neonicotinoids and their desnitro and descyano metabolites (toxic iminium derivatives) to the poisoning signs. Continuing investigations will define human cytochrome P450 isozyme specificity in metabolism of neonicotinoids and characterize human microsomal "neonicotinoid nitroimine reductase" that generates unique hydrazone and triazolone derivatives of imidacloprid.

描述（由申请人提供）：新烟碱类动物是过去三十年中最重要的新型杀虫剂，已经占世界杀虫剂市场的10％，并进行了主要的人类暴露。它们具有相同的烟碱乙酰胆碱受体（NACHR）靶标与尼古丁的靶标，但对昆虫的效力更大和有选择性。长期目标是定义主要的新烟碱，吡啶藻，硫克罗里德，硫甲酰胺和乙酰氨基甲酰胺的选择性毒性的机制。第一个具体目的是建立用于NACHR特异性和选择性毒性的独特新烟碱和烟素结构特征。提出了带负电荷的尖端以赋予昆虫NACHR的效力和选择性，促使我们与此特征合成结构探针。首选的构象和配置将由X射线晶体学和NMR确定，并且与效力有关。量子力学研究将建立静电势表面，分子电荷分布和结合能。将使用相同的方法来表征针对哺乳动物NACHR的类似烟碱类似。第二个目的是表征确定选择性作用的NACHR亚型，亚基和亚场。一个目标是确定alpha4beta2，alpha3beta2（和/或beta4）alpha5或alpha77和alpha1gamma alpha1deltabeta1子类型在结合新辅助素及其相对于功能分析和选择性的毒性中的作用。果蝇NACHR和脊椎动物NACHR亚型被溶解化，由新烟碱或烟素 - 亲和力色谱法纯化，并用有效的副偶氮蛋白素和副偶氮计素光探针标记，并在该实验室设计。标记的亚基将特别注意脊椎动物中昆虫和富含Pi电子的亚铁矿中所提出的阳离子亚基。然后，详细结合位点结构的分子模型将将果蝇D-α亚基的结构与乙酰胆碱结合蛋白与光致授原性标记的发现联系起来。第三个目的是相对于选择性毒性定义新烟碱代谢激活和解毒。将对受体，毒性和功能测定法进行表征和合成，以阐明选择性代谢激活与排毒。小鼠的毒性研究将将新烟碱的大脑水平及其脱核和脱氧代谢物（有毒的伊米尼衍生物）与中毒体征联系起来。继续进行的研究将定义人类细胞色素P450的新烟碱代谢中的同工酶特异性，并表征人类微粒细胞“新二他二胺还原二亚胺还原酶”，从而产生独特的hirdarzone和trize酮衍生物。