Cadenas E, Sies H
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, USA.
Free Radic Res. 1998 Jun;28(6):601-9. doi: 10.3109/10715769809065816.
Peroxidation of lipids in membranes and lipoproteins proceeds through the classical free radical sequence encompassing initiation, propagation, and termination phases which are expressed by a lag phase in which little oxidation occurs, followed by a rapid increase in autocatalysis by chain-propagating intermediates and, finally, a decrease in the rate of oxidation. The lag phase is lengthened by preventive or chain-breaking antioxidants, which scavenge the initiation reaction or intercept the chain-carrying species. Hence, the lag phase in lipid peroxidation processes reflects the antioxidant status of membranes and lipoproteins and, as a corollary, their resistance to oxidation. A large number of lipid peroxidation studies with different membranes attest to the complex free radical network underlying this process. The type of initiator and the steady-state level of oxygen are important factors that affect differently the rates of the individual steps of peroxidation. Equally complex are the factors that influence the lag phase preceding the oxidation of LDL. Lipid peroxyl radicals play a key role in the dynamics of lipid peroxidation: on the one hand, the lag phase is best defined for chain-breaking compounds able to reduce peroxyl radicals; on the other hand, the overall time course of lipid peroxidation is largely influenced by the rate constants for propagation reactions and termination involving peroxyl radical recombination.
膜和脂蛋白中的脂质过氧化通过经典的自由基序列进行，包括引发、传播和终止阶段，这些阶段由一个几乎不发生氧化的滞后期表示，随后由链传播中间体进行的自动催化迅速增加，最后氧化速率降低。预防性或断链抗氧化剂会延长滞后期，这些抗氧化剂会清除引发反应或拦截链携带物种。因此，脂质过氧化过程中的滞后期反映了膜和脂蛋白的抗氧化状态，以及它们对氧化的抵抗力。大量针对不同膜的脂质过氧化研究证明了这一过程背后复杂的自由基网络。引发剂的类型和氧的稳态水平是不同地影响过氧化各个步骤速率的重要因素。影响低密度脂蛋白氧化之前滞后期的因素同样复杂。脂质过氧自由基在脂质过氧化动力学中起关键作用：一方面，对于能够还原过氧自由基的断链化合物，滞后期最容易确定；另一方面，脂质过氧化的总体时间进程在很大程度上受涉及过氧自由基重组的传播反应和终止反应的速率常数影响。
