A Carboxyfluorescein-Enveloping liposome as a Physicochemical Damage Model of the Biomembrane for the Study of Lipid Peroxidation.

Abstract

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 acid-reactive 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 α-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 α-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.