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基本的机制基础，以预防或改善脂质氧化的病理后果，例如，通过阻断某些有毒物质的形成，这些有毒物质会损害视网膜，导致年龄相关性黄斑变性。我们的直接目标是了解产生氧化截断磷脂（oxPCs）和脂肪脂片段的复杂混合物的多不饱和脂肪酸酰衍生物的氧化断裂反应。这些碎片化产物表现出多种多样的病理生物学活性。致突变性环氧醛和细胞毒性羟基醛是特别感兴趣的。了解其生成过程中反应性中间体的化学知识对于理解环境或遗传因素如何促进其形成非常重要。我们最近的观察表明，暴露在强光下会在大鼠视网膜中产生显著水平的生物活性氧化氧化合物，并证明氧化氧化合物可以通过涉及单线态（即光激发氧）的非自由基途径产生。虽然单线态氧的产生被怀疑具有病理意义，但对由此引起的视网膜病理的分子基础的理解是非常缺乏的。

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.