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）：新烟碱类杀虫剂是过去三十年中最重要的新型杀虫剂，已占世界杀虫剂市场的约 10%，并且人类大量接触新烟碱类杀虫剂。它们具有与尼古丁相同的烟碱乙酰胆碱受体 (nAChR) 靶标，但对昆虫更有效且更具选择性。长期目标是确定主要新烟碱类、吡虫啉、噻虫啉、噻虫嗪和啶虫脒的选择性毒性机制。第一个具体目标是建立 nAChR 特异性和选择性毒性的独特新烟碱类和烟碱类结构特征。带负电荷的尖端被认为可以赋予昆虫 nAChR 的效力和选择性，促使我们合成具有此特征的结构探针。优选的构象和构型将通过X射线晶体学和NMR确定并与效力相关。量子力学研究将建立静电势表面、分子电荷分布和结合能。相同的方法将用于表征对哺乳动物 nAChR 具有选择性的类似烟碱类化合物。第二个目标是表征决定选择性作用的 nAChR 亚型、亚基和亚位点。一个目标是确定 alpha4beta2、alpha3beta2（和/或 beta4）alpha5 或 alpha7 和 alpha1Gamma alpha1deltabeta1 亚型在结合新烟碱类及其代谢物中相对于功能测定和选择性毒性的作用。果蝇 nAChR 和脊椎动物 nAChR 亚型通过新烟碱类或烟碱类亲和层析进行溶解和纯化，并用本实验室设计的有效叠氮酮烟碱和叠氮酮烟碱光亲和探针进行标记。将特别注意昆虫中拟议的阳离子亚位点和脊椎动物中富含π电子的亚位点来识别标记的亚基。然后，详细结合位点结构的分子模型将果蝇 D-α 亚基和乙酰胆碱结合蛋白的结构与光亲和标记的发现联系起来。第三个目标是定义与选择性毒性相关的新烟碱代谢激活和解毒。吡虫啉、噻虫啉、噻虫嗪和啶虫脒的代谢物将被表征和合成，用于受体、毒性和功能测定，以阐明选择性代谢激活与解毒。对小鼠进行的毒代动力学研究将新烟碱类及其去硝基和去氰基代谢物（有毒亚胺衍生物）的脑水平与中毒症状联系起来。持续的研究将确定新烟碱类杀虫剂代谢中的人细胞色素 P450 同工酶特异性，并表征产生独特的吡虫啉腙和三唑酮衍生物的人微粒体“新烟碱类硝基亚胺还原酶”。