ADDUCT FORMATION IN THE TOXICITY OF DITHIOCARBAMATES

人类对二硫代氨基甲酸酯的接触源于其在农业、工业中的许多用途。和药品。虽然二硫代氨基甲酸酯的降解和代谢途径已经相当清楚，但目前对二硫代氨基甲酸酯观察到的生物学效应的分子靶点和机制知之甚少。该项目的长期目标是描述二硫代氨基甲酸酯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果的生物标志物的效用。先前的研究已经证明N，N-二乙基二硫代氨基甲酸盐能够产生cs2介导的中枢-外周远端轴索病，而其二硫，二硫仑则产生选择性雪旺细胞神经毒性。本研究基于以下假设：1)双硫代氨基甲酸亚砜对雪旺细胞具有生物活性，通过半胱氨酸残基共价修饰抑制髓磷脂合成；2)双硫仑通过氨基化活性位点半胱氨酸残基抑制低Km醛脱氢酶；3)硫氨基甲酸酯以及其他可代谢为硫氨基甲酸亚砜的化合物具有神经毒性，其机制与双（硫氨基甲酸酯）二硫化物相同。这些假设将通过利用改变Po和p75的表达，在体外和体内测定双（硫代氨基甲酸乙酯）二硫和硫代氨基甲酸酯的相对神经毒性来进行检验；确定二硫代氨基甲酸酯共价修饰的蛋白质在神经系统和肝脏中的身份和位置；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磷脂合成的影响。描述毒性机制，定义生物效应，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，以预测其他可能通过类似机制起作用的制剂。

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.