Photooxidative Damage in Cell Membranes

在含有光敏色素的照射下，细胞膜容易受到结构和功能的破坏。这种损伤的一个突出形式是脂质过氧化，它可以导致流动性改变、通透性增加和其他影响。生物系统中的光敏性脂质过氧化在反应途径、细胞毒作用和保护/修复机制方面还没有得到很好的研究。这项研究的总体目标是提高我们对这些区域中的膜脂质过氧化的了解。计划了一个全面和多样化的工作计划，首先使用模型系统(脂质体、红细胞膜)，然后使用培养细胞(小鼠L1210细胞)。感兴趣的增敏剂是非结合的尿卟啉，以及膜结合的原卟啉和血卟啉衍生物(HPD)。模型研究：(A)计划开展广泛的工作，将胆固醇(CH)作为I型(自由基)和II型(单线态氧)脂质过氧化途径的原位探针。(B)将从面向系统的角度研究抗坏血酸对光引发的脂质过氧化的放大作用，例如过氧化氢和氧自由基的影响。(C)将首次研究长程过氧化(在不同的膜室中使用增敏剂和靶标脂质)。(D)将使用谷胱甘肽还原酶/过氧化物酶系统研究光过氧化物酶的还原代谢(解毒)。细胞研究：(A)在活细胞中利用CH作为机械探针的第一次实验将使用(14C-CH)在HPD敏化的L1210细胞中进行。(B)光过氧化和细胞毒性之间的关系将通过(I)比较脂质过氧化含量和存活率，以及(Ii)确定谷胱甘肽或谷胱甘肽过氧化物酶的耗竭如何影响光敏性来研究。脂质过氧化的生化机制及其对生物膜完整性和功能的影响具有十分重要的基础性意义。从这项研究中获得的信息将有助于加强我们对不同领域的基本知识，如光与光感受器相互作用的机制，白细胞杀死细菌的机制，以及培养细胞在光学显微镜下研究一段时间后，其行为可能与生物体中的细胞不同的原因。

Cell membranes are subject to structural and functional damage when irradiated in the presence of photosensitizing pigments. A prominent form of such damage is lipid peroxidation, which can result in altered fluidity, increased permeability, and other effects. Photosensitized lipid peroxidation in biological systems has not been well studied in terms of reaction pathways, cytotoxic effects, and protective/repair mechanisms. The overall objective of this research is to improve our understanding of membrane lipid peroxidation in each of these areas. A comprehensive and diversified program of work is planned, using model systems initially (liposomes, erythrocyte membranes) and then cultured cells (murine L1210 cells). The sensitizers of interest are non-bound uroporphyrin, and membrane-bound protoporphyrin and hematoporphyrin derivative (HPD). Model Studies: (a) Extensive work is planned involving cholesterol (Ch) as an in situ probe of Type I (free radical) vs Type II (singlet oxygen) pathways of lipid peroxidation. (b) Amplification of photoinitiated lipid peroxidation by ascorbate will be investigated from a system-oriented perspective, e.g. effects of hydrogen peroxide and oxyradicals. (c) Long-range peroxidation (with sensitizer and target lipid in separate membrane compartments) will be studied for the first time. (d) Reductive metabolism (detoxification) of photoperoxides will be examined, using the glutathione reductase/peroxidase system. Cell Studies: (a) The first experiments to exploit Ch as a mechanistic probe in living cells will be carried out using (14C- Ch in HPD-sensitized L1210 cells. (b) The relationship between photoperoxidation and cytolethality will be investigated by (i) comparing lipid peroxide content and survivability, and (ii) determining how depletion of glutathione or glutathione peroxidase affects photosensitivity. The biochemical mechanisms and effects of lipid peroxidation on the integrity and function of biological membranes is of very great fundamental importance. Information that will be derived from this research will have implications in enhancing our basic knowledge of such diverse areas as the mechanisms by which light interacts with photoreceptors, the mechanisms by which leukocytes kill bacteria, and the reasons that cultured cells, when studied under the light microscope for periods of time, may behave differently from cells in the organism.