Junghans A, Sies H, Stahl W
Institut für Physiologische Chemie I and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine-Universität Düsseldorf, Germany.
Free Radic Res. 2000 Dec;33(6):801-8. doi: 10.1080/10715760000301321.
Unilamellar liposomes are used as a simple two-compartment model to study the interaction of antioxidants. The vesicle membrane can be loaded with lipophilic compounds such as carotenoids or tocopherols, and the aqueous core space with hydrophilic substances like glutathione (GSH) ascorbate, mimicking the interphase between an aqueous compartment of a cell and its surrounding membrane. Unilamellar liposomes were used to investigate the interaction of GSH with the carotenoids lutein, beta-carotene and lycopene in preventing lipid peroxidation. Lipid peroxidation was initiated with 2,2'-azobis-[2,4-dimethylvaleronitrile] (AMVN). Malondialdehyde (MDA) formation was measured as an indicator of oxidation; additionally, the loss of GSH was followed. In liposomes without added antioxidant, MDA levels of 119 +/- 6 nmol/mg phospholipid were detected after incubation with AMVN for 2 h at 37 degrees C. Considerably lower levels of 57 +/- 8 nmol MDA/mg phospholipid were found when the liposomal vesicles had been loaded with GSH. Upon incorporation of beta-carotene, lycopene or lutein, the resistance of unilamellar liposomes towards lipid peroxidation was further modified. An optimal further protection was observed with 0.02 nmol beta-carotene/mg phospholipid or 0.06 nmol lycopene/mg phospholipid. At higher levels both these carotenoids exhibited prooxidant effects. Lutein inhibited lipid peroxidation in a dose-dependent manner between 0.02 and 2.6 nmol/mg phospholipid. With increasing levels of lycopene and lutein the consumption of encapsulated GSH decreased moderately, and high levels of beta-carotene led to a more pronounced loss of GSH. The data demonstrate that interactions between GSH and carotenoids may improve resistance of biological membranes towards lipid peroxidation. Different carotenoids exhibit specific properties, and the level for optimal protection varies between the carotenoids.
单层脂质体被用作一个简单的双室模型来研究抗氧化剂之间的相互作用。囊泡膜可以装载亲脂性化合物，如类胡萝卜素或生育酚，而水相核心空间则装载亲水性物质，如谷胱甘肽（GSH）、抗坏血酸盐，模拟细胞水相区室与其周围膜之间的界面。单层脂质体被用于研究GSH与类胡萝卜素叶黄素、β-胡萝卜素和番茄红素在预防脂质过氧化方面的相互作用。脂质过氧化反应由2,2'-偶氮二-[2,4-二甲基戊腈]（AMVN）引发。丙二醛（MDA）的形成作为氧化的指标进行测定；此外，还监测了GSH的损失。在未添加抗氧化剂的脂质体中，在37℃与AMVN孵育2小时后，检测到MDA水平为119±6 nmol/mg磷脂。当脂质体囊泡装载有GSH时，发现MDA水平显著降低至57±8 nmol MDA/mg磷脂。加入β-胡萝卜素、番茄红素或叶黄素后，单层脂质体对脂质过氧化的抗性进一步改变。观察到0.02 nmol β-胡萝卜素/mg磷脂或0.06 nmol番茄红素/mg磷脂时具有最佳的进一步保护作用。在较高水平时，这两种类胡萝卜素均表现出促氧化作用。叶黄素在0.02至2.6 nmol/mg磷脂之间以剂量依赖方式抑制脂质过氧化。随着番茄红素和叶黄素水平的增加，包封的GSH消耗适度减少，而高水平的β-胡萝卜素导致GSH损失更为明显。数据表明，GSH与类胡萝卜素之间的相互作用可能会提高生物膜对脂质过氧化的抗性。不同的类胡萝卜素表现出特定的性质，最佳保护水平在类胡萝卜素之间有所不同。
