Membrane damage model of lipid peroxidation, using carboxyfluorescein enveloping liposome

为了研究脂质过氧化作用，提出了一种包裹羧基荧光素(CF)的脂质体作为生物膜的物理化学损伤模型。膜损伤的程度可以通过测量脂膜与自由基引发剂相互作用后从受损脂质体释放的CF的荧光强度来评估。同时进行硫代巴比妥酸反应物质(TBARS)检测，以生化方法证实脂质过氧化过程。将含多不饱和脂肪酸的大豆磷脂酰胆碱(SPC)、含饱和脂肪酸的二棕榈酰磷脂酰胆碱(DPPC)和大豆磷脂酰胆碱+α-生育酚三种类型的CF包膜脂质体暴露于已知的自由基引发剂--含有还原剂(半胱氨酸、还原型谷胱甘肽或抗坏血酸)的氮三乙酸铁。用荧光分光光度计法测定过氧化脂质体释放量。SPC脂质体有较高的CF释放量和较高的TBARS释放量，而DPPC脂质体和α-生育酚SPC脂质体则无此现象。这种脂质体模型优于传统的红细胞溶血模型，原因如下：(1)定义了膜的组成；(2)CF不是自由基引发剂，而血红蛋白是潜在的自由基引发剂；(3)根据实验目的，膜成分可以很容易地改变。

A Carboxyfluorescein (CF) -enveloping liposome is presented as a physicochemical damage model of the biomembrane for the study of lipid peroxidation. The degree of membrane damage may be assessed by measurement of the fluorescence intensity of CF released from damaged liposomes after the interaction between the liposomal membrane and a radical initiator. The process of lipid peroxidation was biochemically confirmed by the thiobarbituric acidreactive substances (TBARS) test done simultaneously. Three types of CF-enveloping liposomes, i.e., soybean phosphatidylcholine (SPC) containing polyunsaturated fatty acid, dipalmitoylphosphatidylcholine (DPPC) containing saturated fatty acid, and soybean phosphatidylcholine plus alpha-tocopherol, were exposed to a known radical initiator, ferric nitrilotriacetate with a reductant (either cysteine, reduced form glutathione, or ascorbic acid). The release of CF from the peroxidized liposome was measured with a fluorospectrophotometer. A high release of CF and a high level of TBARS were seen in the SPC liposomes, but not in the DPPC and alpha-tocopherol-inserted SPC liposomes. This liposome model is superior to the conventional red cell hemolysis model for several reasons : (1) the constituents of the membrane are defined ; (2) CF is not a radical initiator, whereas hemoglobin is a potential radical initiator ; and (3) the membrane components can be easily changed depending on the purpose of the experiment.