Tesoriere L, Bongiorno A, Pintaudi A M, D'Anna R, D'Arpa D, Livrea M A
Istituto di Farmacologia e Farmacognosia, Università di Palermo, Italy.
Arch Biochem Biophys. 1996 Feb 1;326(1):57-63. doi: 10.1006/abbi.1996.0046.
Interactions between alpha-tocopherol and all-trans retinol in suppressing lipid peroxidation were studied in a unilamellar liposomal system of phosphatidylcholine from either egg or soybean, in which peroxidation was initiated by the water-soluble azo initiator 2,2-azobis(2-amidino-propane)hydrochloride and peroxidation was measured as production of conjugated diene hydroperoxides. While all-trans retinol alone was poorly effective, the combination of all-trans retinol with alpha-tocopherol caused an inhibition period far beyond the sum of the inhibition periods observed with individual antioxidants, providing evidence of synergistic interactions. Furthermore, the inhibition rate calculated in the presence of both all-trans retinol and alpha-tocopherol, Rinh(E+A), was lower than Rinh(E) observed with alpha-tocopherol alone, suggesting that the extension of the inhibition time cannot be ascribed only to the antioxidant activity of alpha-tocopherol. The extent of synergism was linear with a molar ratio all-trans retinol/alpha-tocopherol ranging from 0.1 to 1.0, whereas a drop was observed at a ratio of 2.0. Synergistic antioxidant interactions between all-trans retinol and alpha-tocopherol were also evident when peroxidation was evaluated as production of malondialdehyde. A time course study, in which peroxidation of liposomes and depletion of antioxidants were concomitantly monitored, while showing that most of alpha-tocopherol was consumed to bring about the inhibition period, indicated that autooxidative reactions substantially contributed to the rapid depletion of all-trans retinol, when the antioxidants were allowed to act separately. On the other hand, when alpha-tocopherol and all-trans retinol were combined, the consumption of both antioxidants was significantly delayed, indicating reciprocal protection. Regeneration mechanisms cannot be accounted for by our results. The observed synergism between all-trans retinol and alpha-tocopherol does not appear as the result of specific structural interactions in the lipid bilayer. Combination of all-trans retinol with butylated hydroxytoluene, which reduced markedly all-trans retinol oxidation, resulted in a synergistic antioxidant activity greater than that observed with comparable amounts of alpha-tocopherol. In light of the known antioxidant mechanism of retinoids, the data suggest that by limiting autooxidation of all-trans retinol, alpha-tocopherol strongly promotes its antioxidant effectiveness. The concerted radical scavenging action in turn results in a synergistic protection of the lipid system against peroxidative stress and, ultimately, slows down the alpha-tocopherol consumption.
在由鸡蛋或大豆来源的磷脂酰胆碱构成的单层脂质体系统中，研究了α-生育酚与全反式视黄醇在抑制脂质过氧化方面的相互作用。在该系统中，通过水溶性偶氮引发剂2,2-偶氮双(2-脒基丙烷)盐酸盐引发过氧化反应，并以共轭二烯氢过氧化物的生成量来测定过氧化程度。单独的全反式视黄醇效果不佳，但全反式视黄醇与α-生育酚的组合导致抑制期远远超过单独使用每种抗氧化剂时观察到的抑制期之和，这提供了协同相互作用的证据。此外，在同时存在全反式视黄醇和α-生育酚时计算出的抑制率Rinh(E+A)，低于单独使用α-生育酚时观察到的Rinh(E)，这表明抑制时间的延长不能仅归因于α-生育酚的抗氧化活性。协同作用的程度与全反式视黄醇/α-生育酚的摩尔比在0.1至1.0范围内呈线性关系，而在比例为2.0时出现下降。当以丙二醛的生成量来评估过氧化时，全反式视黄醇与α-生育酚之间的协同抗氧化相互作用也很明显。一项时间进程研究同时监测了脂质体的过氧化和抗氧化剂的消耗情况，结果表明，虽然大部分α-生育酚被消耗以产生抑制期，但这表明当抗氧化剂单独作用时，自氧化反应在很大程度上导致了全反式视黄醇的快速消耗。另一方面，当α-生育酚和全反式视黄醇组合时，两种抗氧化剂的消耗都显著延迟，这表明存在相互保护作用。我们的结果无法解释再生机制。观察到的全反式视黄醇与α-生育酚之间的协同作用似乎并非脂质双层中特定结构相互作用的结果。全反式视黄醇与丁基羟基甲苯的组合显著降低了全反式视黄醇的氧化，其协同抗氧化活性大于使用等量α-生育酚时观察到的活性。鉴于类视黄醇已知的抗氧化机制，数据表明，通过限制全反式视黄醇的自氧化，α-生育酚强烈促进了其抗氧化效果。协同的自由基清除作用进而导致对脂质系统的协同保护，使其免受过氧化应激的影响，并最终减缓了α-生育酚的消耗。
