Oxidant Mechanisms in Drug-Induced Hepatic Necrosis

描述(申请人提供)：化学活性中间体会引起许多药物和环境化学品的毒性，并通过生物分子的共价修饰导致许多人类疾病的发病机制。特定的活性氧和氮物种、自由基、自由基和其他氧化剂物种表现出不同的性质和反应活性，预防或治疗氧化剂挑战的不利影响要求我们了解活性中间体的性质和它们的作用机理。本申请中描述的研究的主要目标是阐明这些机制。以前的研究表明蛋白质硫醇的丢失与氧化损伤的机制有关，但我们一直没有在毒理学相关的模型中观察到蛋白质硫醇状态的显著变化，特别是在体内。在几种氧化剂细胞杀伤模型中，数据表明，氧化还原活性铁络合物催化的氧化特征与组织损伤的相关性比硫醇/二硫化物氧化还原位移更密切。最近的初步数据表明，在我们研究的主要模型中，活性氮物种可能对伤害机制有重要贡献，这些机制的相对贡献需要调查。具体目的1是验证一种假设，即肝脏蛋白质氧化的特定产物，而不是二硫键，将为体内氧化剂介导的肝坏死的分子(分子的化学定义)机制提供生物标志物。尽管在相关的氧化性组织损伤模型中没有蛋白质硫醇的整体耗尽，但有几条证据表明，对蛋白质硫醇的影响是致死性细胞损伤的重要决定因素，特定目的2中描述的研究旨在检验这一假说，即隔区化和分子选择性的硫醇/二硫键移动和相关变化显著地促进了氧化剂损伤。我们使用的主要模型是基于敌草净、对乙酰氨基酚和速尿在体内和体外的毒性，以及一组有限的模型氧化剂用于体外研究。扑热息痛和速尿的治疗用途广泛，敌草净和百草枯是广泛使用的除草剂。尽管大多数公认的人类毒性是由急性暴露或过量引起的，通常是故意的，但新出现的证据表明，长期、低剂量接触这些制剂可能会造成比目前认识到的更多的不良影响。然而，我们对这些毒物的影响的研究的主要兴趣是了解体内药物诱导细胞死亡的基本原理和概念，主要集中在氧化剂诱导的肝坏死。

DESCRIPTION (provided by applicant): Chemically reactive intermediates cause the toxicities of a number of drugs and environmental chemicals and contribute to the pathogeneses of many human diseases through covalent modifications of biological molecules. Specific reactive oxygen and nitrogen species, radicals, free radicals, and other oxidant species exhibit different properties and reactivities, and efforts to prevent or treat the adverse effects of oxidant challenges require that we understand the properties of the reactive intermediates and the mechanisms by which they act. The principal goal of the research described in the present application is to elucidate these mechanisms. Previous studies implicated the loss of protein thiols in mechanisms of oxidant injury, but we have consistently not observed marked shifts in protein thiol status in toxicologically relevant models, particularly in vivo. In several models of oxidant cell killing, the data suggest that oxidations characteristic of those catalyzed by redox-active iron chelates correlate more closely with tissue damage than do thiol/disulfide redox shifts. Recent preliminary data indicate that reactive nitrogen species may contribute significantly to the mechanisms of injury in the primary models we study, and the relative contributions of these mechanisms need to be investigated. Specific Aim 1 is to test the hypothesis that specific products of oxidation of hepatic proteins other than disulfides will provide biomarkers of the molecular (chemist definition of molecular) mechanisms responsible for oxidant-mediated hepatic necrosis in vivo. Despite the absence of global depletion of protein thiols in relevant models of oxidant tissue damage, several lines of evidence indicate that effects on protein thiols are important determinants of lethal cell injury, and the studies described in Specific Aim 2 are designed to test the hypothesis that compartmentalized and molecularly selective thiol/disulfide shifts and related changes contribute significantly to oxidant injury. The major models we employ are based on toxicities of diquat, acetaminophen, and furosemide in vivo and in vitro, and a limited set of model oxidants for studies in vitro. Therapeutic uses of acetaminophen and furosemide are extensive, and diquat and paraquat are widely used herbicides. Although most recognized human toxicities arise from acute exposures or overdoses, often intentional, emerging evidence suggests that chronic, low dose exposures to these agents may cause more adverse effects than are appreciated at the present time. However, our major interest in the study of the effects of these toxicants is to understand the fundamental principles and concepts of drug-induced cell death in vivo, with a primary focus on oxidant-induced hepatic necrosis.