Ferguson E, Singh R J, Hogg N, Kalyanaraman B
Biophysics Research Institute, Medical College of Wisconsin, Milwaukee 53226, USA.
Arch Biochem Biophys. 1997 May 15;341(2):287-94. doi: 10.1006/abbi.1997.9975.
Oxidation of low-density lipoprotein (LDL) is recognized to be a key step in atherogenesis. Previous studies show that LDL contains low-molecular-weight antioxidants such as vitamin E, beta-carotene, and ubiquinol, which can retard oxidative modification. In this report, we have evaluated the antioxidant potential of apolipoprotein B-100 (apo-B) thiols during LDL oxidation. Both apo-B thiols and vitamin E were depleted concomitantly during the lag phase of Cu(2+)-mediated LDL oxidation. The rate of thiol depletion was significantly inhibited by the lipophilic spin trap N-tert-butyl-alpha-phenylnitrone (PBN) but not by the water-soluble spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Blocking apo-B thiols with sulfhydryl modifying agents increased the oxidizability of LDL. As with Cu2+, peroxynitrite also caused depletion of apo-B thiols, and again thiol depletion was inhibited by PBN but not by POBN. A PBN/lipid-derived radical adduct was observed by the electron spin resonance technique during oxidation of LDL with peroxynitrite. We conclude that apo-B thiol depletion is mediated by lipid peroxidation, prior to the onset of the propagation phase of LDL oxidation. The implications of apo-B thiols an intrinsic antioxidants of LDL are discussed.
低密度脂蛋白（LDL）的氧化被认为是动脉粥样硬化形成的关键步骤。先前的研究表明，LDL含有低分子量抗氧化剂，如维生素E、β-胡萝卜素和泛醇，它们可以延缓氧化修饰。在本报告中，我们评估了载脂蛋白B-100（apo-B）硫醇在LDL氧化过程中的抗氧化潜力。在铜（2+）介导的LDL氧化的延迟期，apo-B硫醇和维生素E同时被消耗。硫醇消耗的速率被亲脂性自旋捕获剂N-叔丁基-α-苯基硝酮（PBN）显著抑制，但不被水溶性自旋捕获剂α-（4-吡啶基-1-氧化物）-N-叔丁基硝酮（POBN）抑制。用巯基修饰剂封闭apo-B硫醇会增加LDL的氧化能力。与铜离子一样，过氧亚硝酸盐也会导致apo-B硫醇的消耗，并且硫醇消耗再次被PBN抑制，而不是被POBN抑制。在用过氧亚硝酸盐氧化LDL的过程中，通过电子自旋共振技术观察到了PBN/脂质衍生的自由基加合物。我们得出结论，在LDL氧化的传播阶段开始之前，apo-B硫醇的消耗是由脂质过氧化介导的。讨论了apo-B硫醇作为LDL内在抗氧化剂的意义。
