Oxidant Mechanisms in Drug-Induced Hepatic Necrosis

描述（由申请人提供）：化学反应性中间体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促进许多人类疾病的发病。特定的活性氧和活性氮、自由基、自由基和其他氧化物质表现出不同的性质和反应性，为了预防或治疗氧化挑战的不利影响，我们需要了解活性中间体的性质及其作用机制。本研究的主要目的是阐明这些机制。先前的研究暗示了氧化损伤机制中蛋白质硫醇的损失，但我们一直没有在毒理学相关模型中观察到蛋白质硫醇状态的显著变化，特别是在体内。在氧化细胞死亡的几个模型中，数据表明，氧化还原活性铁螯合物催化的氧化特性与组织损伤的关系比硫醇/二硫化物氧化还原转移更密切。最近的初步数据表明，在我们研究的主要模型中，活性氮物种可能对损伤机制有重要作用，这些机制的相对贡献需要进一步研究。特异性目的1是验证一种假设，即除了二硫化物之外，肝脏蛋白质氧化的特定产物将提供体内氧化介导的肝坏死分子机制的生物标志物（化学家定义的分子）。尽管在氧化性组织损伤的相关模型中缺乏蛋白质硫醇的整体耗竭，但有几条证据表明，对蛋白质硫醇的影响是致命细胞损伤的重要决定因素，特异性目标2中描述的研究旨在验证隔区化和分子选择性硫醇/二硫转移和相关变化对氧化损伤有重要贡献的假设。我们采用的主要模型是基于地奎特、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。对乙酰氨基酚和呋塞米的治疗用途广泛，而双菊酯和百草枯是广泛使用的除草剂。虽然大多数公认的人体毒性是由急性接触或过量（通常是有意的）引起的，但新出现的证据表明，慢性低剂量接触这些物质可能造成比目前认识到的更大的不良影响。然而，我们对这些毒物影响研究的主要兴趣是了解药物诱导体内细胞死亡的基本原理和概念，主要关注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.