ADDUCT FORMATION IN THE TOXICITY OF DITHIOCARBAMATES

人类接触二硫代氨基甲酸酯是由于其在农业、工业和环境中的许多用途。和医药虽然二硫代氨基甲酸酯的降解和代谢途径已相当清楚，但目前对二硫代氨基甲酸酯所观察到的生物学效应的分子靶点和机制知之甚少。本项目的长期目标是描述二硫代氨基甲酸盐及其代谢物在生物系统中的相互作用，并确定这些相互作用作为毒性机制的相关性以及这些相互作用作为暴露和效应生物标志物的实用性。先前的研究已经证明了N，N-二乙基二硫代氨基甲酸酯产生CS2介导的中心-外周远端轴突病的能力，而其二硫化物双硫仑产生选择性许旺细胞神经毒性。本申请中的研究由以下工作假设指导：（硫代氨基甲酰基）二硫化物通过半胱氨酸残基的共价修饰从能够抑制髓磷脂合成的硫代氨基甲酸酯亚砜代谢物的生物活化发挥许旺细胞毒性; 2）双硫仑通过活性位点半胱氨酸残基的氨甲酰化抑制低Km醛脱氢酶; 3）硫代氨基甲酸酯以及可代谢为硫代氨基甲酸酯亚砜的其他化合物通过与双（硫代氨基甲酰基）二硫化物相同的机制具有神经毒性。这些假设将通过确定bis的相对神经毒性效力来检验。（硫代氨基甲酰基）二硫化物和硫代氨基甲酸酯在体外和体内使用改变的Po和p75的表达;确定在神经系统和肝脏内被二硫代氨基甲酸酯共价修饰的蛋白质的身份和位置;确定年龄、暴露途径和酸稳定性对二硫代氨基甲酸酯诱导的神经毒性的影响;以及测定双硫仑对雪旺细胞内髓鞘合成的影响。描述毒性机制，定义生物效应，并确定二硫代氨基甲酸酯的易感人群将有助于制定基于机制的暴露建议，并制定结构活性关系，用于预测可能通过类似机制起作用的其他药剂。

Human exposure to dithiocarbamates derives from their many uses in agriculture, industry. and medicine. Although the degradative and metabolic pathways of dithiocarbamates are fairly well understood, there is currently little knowledge regarding the molecular targets and mechanisms underlying the observed biological effects of dithiocarbamates. The long range objectives of this project are to delineate the interactions of dithiocarbamates and their metabolites within biological systems, and to determine both the relevance of these interactions as mechanisms of toxicity and the utility of these interactions as biomarkers of exposure and effect. Previous investigations have demonstrated the ability of N,N-diethyldithiocarbamate to produce a CS2-mediated central-peripheral distal axonopathy whereas its disulfide, disulfiram, produces a selective Schwann cell neurotoxicity. The investigations in this application are guided by the following working hypotheses: 1)bis(thiocarbamoyl) disulfides exert Schwann cell toxicity from bioactivation to a thiocarbamate sulfoxide metabolite capable of inhibiting myelin synthesis via covalent modification of cysteine residues; 2)disulfiram inhibits low Km aldehyde dehydrogenase by carbamylation of an active site cysteine residue; 3)thiocarbamate esters as well as other compounds that can be metabolized to thiocarbamate sulfoxides are neurotoxic through a mechanism identical to bis(thiocarbamoyl) disulfides. These hypotheses will be tested through determining the relative neurotoxic potencies of bis(thiocarbamoyl)disulfide and thiocarbamate esters in vitro and in vivo using altered expressions of Po and p75; determining the identity and location of proteins covalently modified by dithiocarbamates within the nervous system and liver; determining the influence of age, route of exposure and acid stability on dithiocarbamate induced neurotoxicity; and determining the effects of disulfiram upon myelin synthesis within Schwann cells. Delineating the mechanisms of toxicity, defining the biological effects, and identifying susceptible populations for dithiocarbamates will aid in developing mechanistically based exposure recommendations and formulating structure activity relationships for predicting other agents that may act through a similar mechanism.