Development of new small molecule targets for radiation protection

在引爆“脏弹”或一些不那么险恶但同样严重的核事故后，预计大多数随之而来的伤亡人员将接受相对较低的剂量暴露。因此，急救服务将不得不治疗大量的受害者(包括受影响的公众、急救人员和医务人员)，其中，由于“旁观者效应”造成的组织损伤是至关重要的。辐射后产生的活性氧和活性氮物种(ROS和RNS)是一种慢性现象，在接受剂量后几分钟内开始产生。我们最近从照射后的大鼠组织中获得了证据，证明在终止低水平剂量的几天后，超氧阴离子自由基持续产生。线粒体显然是超氧化物产生的场所，因为照射前组织中锰超氧化物歧化酶(MnSOD)的表达显著改善了这一效应。此外，在内源性一氧化氮合酶(NOS)的刺激下，辐射后组织中容易检测到过氧亚硝酸根阴离子的产生，这表明这种强大的氧化剂的二次生成是超氧化物水平升高的主要结果。在从未经辐射的动物身上提取的对照组织中，没有观察到这些影响。具体目标：1)确定最初产生超氧化物的线粒体位置(建议为mtNOS)在接下来的几个小时内 这些研究包括：1)确定辐射损伤(“早期过程”)；2)确定ROS/RNS(建议为复合体III)损伤的线粒体位点导致进一步(慢性)超氧化物生成(“后期过程”)的原因，并制定使这些中心失活的策略；3)确定过亚硝酸根和过氧化氢的产生在辐照后对电子传输链(ETC)损伤中的相对重要性。在这些具体目标的框架内，建议开发和测试推定的药物，旨在防止关键的ROS/RN在被确定为负责它们产生的线粒体部位形成。除了功效之外， 将评估这些化合物(在ETC水平上)的可能毒性，以促进随后在反复几轮合成和测试中生产的更多候选药物的特性的改进。

Following detonation of a "dirty bomb," or some less sinister but equally serious nuclear accident, the majority of the ensuing casualties can be anticipated to receive relatively low-dose exposures. Consequently, emergency services will have to treat large numbers of victims (including the affected public, emergency responders and medical staff) where developing tissue damage due to "bystander effects" is of paramount importance. Post-irradiation production of reactive oxygen and reactive nitrogen species (ROS and RNS) is a chronic phenomenon that starts within minutes of the dose being received. We have recently obtained evidence from post-irradiated rat tissue for sustained production of superoxide radical days after low-level doses have been terminated. The mitochondrion is clearly implicated as the site of superoxide production as manganese supeoxide dismutase (MnSOD) expression in the pre-irradiated tissue significantly ameliorates the effect. Furthermore, the readily detectable production of peroxynitrite anion in postirradiated tissue following the stimulation of endogenous nitric oxide synthase (NOS) indicates the secondary generation of this powerful oxidant to be a major consequence of the elevated superoxide level. None of these effects are observed in control tissue taken from unirradiated animals. Specific Aims: 1) Identify the mitochondrial site of the initial superoxide production (proposed to be mtNOS) in the first few hours following irradiation (the 'early process'); 2) Identify the mitochondrial sites damaged by ROS/RNS (proposed to be complex III) resulting in further (chronic) superoxide generation (the 'later process') and devise strategies for deactivating these centers; 3) Determine the relative importance of peroxynitrite and hydrogen peroxide production in post-irradiation damage to the electron-transport chain (ETC). Within the framework of these specific aims, it is proposed to develop and test putative drugs designed to prevent the formation of key ROS/RNS at the mitochondrial sites identified as responsible for their generation. In addition to efficacy, the possible toxicity of these compounds (at the level of the ETC) will be evaluated to facilitate improvements in the characteristics of further candidate drugs produced subsequently in iterative rounds of synthesis and testing.