Pinchuk I, Gal S, Lichtenberg D
Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel.
Free Radic Res. 2001 Apr;34(4):349-62. doi: 10.1080/10715760100300301.
Copper-induced peroxidation of lipoproteins involves continuous production of free radicals via a redox cycle of copper. Formation of Cu(I) during Cu(II)-induced peroxidation of LDL was previously demonstrated by accumulation of the colored complexes of Cu(I) in the presence of one of the Cu(I)-specific chelators bathocuproine (BC) or neocuproine (NC). All the studies conducted thus far employed high concentrations of these chelators (chelator/Cu(II) > 10). Under these conditions, at low copper concentrations the chelators prolonged the lag preceding oxidation, whereas at high copper concentrations the chelators shortened the lag. In an attempt to gain understanding of these non-monotonic effects, we have studied systematically the peroxidation of LDL (0.1 microM, 50 microg protein/mL) at varying concentrations of NC or BC over a wide range of concentrations of the chelators and copper. These studies revealed that: (i) At copper concentrations of 5 microM and below, NC prolonged the lag in a monotonic, dose-dependent fashion typical for other complexing agents. However, unlike with other chelators, the maximal rate of oxidation was only slightly reduced (if at all). (ii) At copper concentrations of 15 microM and above, the addition of about 20 microM NC or BC resulted in prolongation of the lag, but this effect became smaller at higher concentrations of the chelators, and at yet higher concentrations the lag became much shorter than that observed in the absence of chelators. Throughout the whole range of NC concentrations, the maximal rate of peroxidation increased monotonically upon increasing the NC concentration. (iii) Unlike in the absence of chelators, the prooxidative effect of copper did not exhibit saturation with respect to copper, up to copper concentrations of 30 microM. Based on these results we conclude that the copper-chelates can partition into the hydrophobic core of LDL particles and induce peroxidation by forming free radicals within the core. This may be significant with respect to the understanding of the possible mechanisms of peroxidation by chelated transition metals in vivo.
铜诱导的脂蛋白过氧化作用涉及通过铜的氧化还原循环持续产生自由基。先前通过在铜（I）特异性螯合剂浴铜灵（BC）或新铜灵（NC）之一存在下铜（I）有色络合物的积累，证明了在铜（II）诱导的低密度脂蛋白（LDL）过氧化过程中铜（I）的形成。迄今为止进行的所有研究都使用了高浓度的这些螯合剂（螯合剂/铜（II）> 10）。在这些条件下，在低铜浓度下，螯合剂延长了氧化之前的延迟期，而在高铜浓度下，螯合剂缩短了延迟期。为了试图理解这些非单调效应，我们系统地研究了在广泛的螯合剂和铜浓度范围内，不同浓度的NC或BC存在下低密度脂蛋白（0.1微摩尔/升，50微克蛋白质/毫升）的过氧化作用。这些研究表明：（i）在铜浓度为5微摩尔/升及以下时，NC以其他络合剂典型的单调、剂量依赖性方式延长延迟期。然而，与其他螯合剂不同的是，最大氧化速率仅略有降低（如果有降低的话）。（ii）在铜浓度为15微摩尔/升及以上时，添加约20微摩尔的NC或BC会导致延迟期延长，但在更高浓度的螯合剂下这种效应会变小，而在更高浓度下延迟期变得比不添加螯合剂时短得多。在整个NC浓度范围内，过氧化的最大速率随NC浓度的增加而单调增加。（iii）与不添加螯合剂的情况不同，铜的促氧化作用在高达30微摩尔/升的铜浓度下对铜不表现出饱和现象。基于这些结果，我们得出结论，铜螯合物可以分配到LDL颗粒的疏水核心中，并通过在核心内形成自由基来诱导过氧化。这对于理解体内螯合过渡金属过氧化的可能机制可能具有重要意义。
