Reactive Intermediates of Oxidative Lipid Fragmentation

描述(由申请人提供)：该项目的总体目标是为合理设计治疗措施提供一个基本的机械基础，以防止或改善脂质氧化的病理后果，例如通过阻止某些有毒产品的形成来损害视网膜，导致老年性黄斑变性。我们的直接目标是了解多不饱和脂肪酰基衍生物的氧化裂解反应，这些反应产生氧化截断的磷脂(OxPC)和脂类片段的复杂混合物。这些裂解产物表现出不同的、往往是病理性的生物活性。诱变的环氧烯烃和细胞毒性的羟基烯烃尤其令人感兴趣。了解参与其生成的活性中间体的化学知识对于了解环境或遗传因素如何促进它们的形成是重要的。我们最近的观察表明，暴露在强光下会在大鼠视网膜产生大量具有生物活性的oxPC，并证明oxPC可以通过涉及单线态氧的非自由基途径产生，即光激发的氧。尽管单线态氧的产生被怀疑具有病理意义，但对由此导致的视网膜病理的分子基础尚缺乏了解。 该项目重点研究在氧化裂解反应条件下不稳定的关键中间体。三个基本问题将被解决：(1)假定的中间体是否实际参与，如果是，(2)它们的分解产生什么产物，(3)它们是通过什么机制(S)分解的？在某些情况下，它们将被困为稳定的衍生品，以确认它们参与其中。为了提供大量的活性中间体，明确的全合成将被设计和执行。真实样品将被用作标准，用于建立检测和定量氧化反应产物混合物和体内中间体水平的方法。然后将对它们的产生和转化为有毒或无害的最终产品进行调查。我们将确定(1)环境，如那些在不同细胞器中发现的或与病理条件有关的环境，(2)辅助因子的水平，或(3)氧化启动系统和抑制剂，对活性中间体的产生以及对它们随后转化的各种途径的相对重要性的影响。

DESCRIPTION (provided by applicant): The overall objective of the project is to provide a fundamental mechanistic basis for the rational design of therapeutic measures to prevent or ameliorate the pathological consequences of lipid oxidation, for example, by blocking the formation of certain toxic products that damage the retina resulting in age-related macular degeneration. Our immediate goal is to understand oxidative fragmentation reactions of polyunsaturated fatty acyl derivatives that generate a complex mixture of oxidatively truncated phospholipids (oxPCs) and aliphatic lipid fragments. These fragmentation products exhibit diverse and often pathological biological activities. Mutagenic epoxyalkenals and cytotoxic hydroxyalkenals are of particular interest. Knowledge of the chemistry of the reactive intermediates involved in their generation is important for understanding how environmental or genetic factors can promote their formation. Our recent observations showed that exposure to intense light generates significant levels of biologically active oxPCs in rat retinas, and demonstrated that oxPCs can be produced through non free radical pathways that involve singlet, i.e., photoexcited, oxygen. Although the generation of singlet oxygen has been suspected of having pathological significance, an understanding of the molecular basis of the consequent retinal pathology is sorely lacking. The project focuses on studying key intermediates that are not stable under the oxidative fragmentation reaction conditions. Three basic questions will be addressed: (1) are the putative intermediates actually involved, and if so (2) what products are generated by their decomposition and (3) by what mechanism(s) do they fragment? In some cases, they will be trapped as stable derivatives to confirm their involvement. To provide ample quantities of some reactive intermediates, unambiguous total syntheses will be designed and executed. The authentic samples will be used as standards for establishing methods to detect and quantify levels of the intermediates in oxidation reaction product mixtures and in vivo. Their generation and conversion into toxic or innocuous end products will then be investigated. We will determine the influences of (1) environments such as those found in different organelles or associated with pathological conditions, (2) levels of cofactors, or (3) oxidation initiating systems and inhibitors, on the production of the reactive intermediates and on the relative importance of various pathways for their subsequent transformations.