Determination of singlet oxygen-specific versus radical-mediated lipid peroxidation in photosensitized oxidation of lipid bilayers: Effect of beta-carotene and alpha-tocopherol
Determination of singlet oxygen-specific versus radical-mediated lipid peroxidation in photosensitized oxidation of lipid bilayers: Effect of beta-carotene and alpha-tocopherol
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DOI：
10.1021/bi9708646
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发表时间：
1997-10-21
期刊：
影响因子：
2.9
通讯作者：
Liebler, DC
中科院分区：
文献类型：
--
作者：
Stratton, SP;Liebler, DC
光敏氧化反应通过催化氧自由基和单线态氧的形成来损伤组织。假设β-胡萝卜素通过猝灭II型反应形成的单线态氧和通过清除I型反应形成的自由基而发挥光保护作用。β-胡萝卜素的抗氧化机制进行了研究，在磷脂膜模型的光氧化与新的同位素稀释气相色谱-质谱（GC-MS）分析，定量区分单线态氧介导的和自由基介导的脂质过氧化。本试验测量9-和10-羟基亚油酸甲酯，并用于生成光敏剂亚甲蓝、玫瑰红和四苯基卟啉的光氧化曲线。这些配置文件表明从II型到I型光氧化机制的转变，在光氧化的后期阶段。β-胡萝卜素（0.45摩尔%）抑制单线态氧介导的脂质过氧化反应的早期阶段的亚甲基蓝敏化的光氧化。自由基介导的产品的生产增加速度比单线态氧介导的产品在后期阶段。β-胡萝卜素-5，8-内过氧化物是溶液中β-胡萝卜素单线态氧氧化的特异性标志物，在孵育条件下不稳定，并且在该系统中未检测到。α-生育酚（0.45 mol %）在抑制光敏脂质过氧化方面无效，而4.5 mol % α-生育酚抑制几乎所有自由基介导的脂质过氧化以及早期单线态氧介导的脂质过氧化。氢过氧化枯烯刺激自由基介导的脂质过氧化反应，表明II型光氧化氢过氧化物的积累可能会增强I型反应。这些数据表明，单线态氧淬灭，而不是自由基清除反应，占β-胡萝卜素的光保护作用。
Photosensitized oxidation reactions damage tissue by catalyzing the formation of oxyradicals and singlet oxygen. beta-Carotene is hypothesized to exert photoprotective effects by quenching singlet oxygen formed by Type II reactions and by scavenging free radicals formed by Type I reactions. beta-Carotene antioxidant mechanisms were studied in a phospholipid membrane model of photooxidation with a new isotope dilution gas chromatography-mass spectrometry (GC-MS) assay that quantitatively distinguishes singlet oxygen-mediated and radical-mediated lipid peroxidation. This assay measures 9- and 10-hydroxylinoleate methyl esters and was used to generate photooxidation profiles for the photosensitizers methylene blue, Rose Bengal, and tetraphenylporphine. These profiles indicate a shift from Type II to Type I photooxidation mechanisms in later stages of photooxidation. beta-Carotene (0.45 mol %) inhibited singlet oxygen-mediated lipid peroxidation at early stages of methylene blue-sensitized photooxidation. Production of radical-mediated products increased faster than singlet oxygen-mediated products at later stages. beta-Carotene-5,8-endoperoxide, a specific marker for singlet oxygen oxidation of beta-carotene in solution, was unstable under the incubation conditions and was not detected in this system. alpha-Tocopherol (0.45 mol %) was ineffective in inhibiting photosensitized lipid peroxidation, whereas 4.5 mol % alpha-tocopherol inhibited almost all radical-mediated lipid peroxidation as well as early-stage singlet oxygen-mediated lipid peroxidation. Cumene hydroperoxide stimulated radical-mediated lipid peroxidation, indicating that accumulation of hydroperoxides from Type II photooxidation may enhance Type I reactions These data suggest that singlet oxygen quenching, rather than radical scavenging reactions, accounts for the photoprotective actions of beta-carotene.