Djuric Z, Potter D W, Taffe B G, Strasburg G M
Barbara Ann Karmanos Cancer Institute, 110 East Warren, Detroit, MI, USA.
J Biochem Mol Toxicol. 2001;15(2):114-9. doi: 10.1002/jbt.7.
Lipid and DNA oxidation catalyzed by iron(II) were compared in HEPES and phosphate buffers. Lipid peroxidation was examined in a sensitive liposome system constructed with a fluorescent probe that allowed us to examine the effects of both low and high iron concentrations. With liposomes made from synthetic 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine or from rat liver microsomal lipid, lipid peroxidation increased with iron concentration up to the range of 10--20 microM iron(II), but then rates decreased with further increases in iron concentration. This may be due to the limited amount of lipid peroxides available in liposomes for oxidation of iron(II) to generate equimolar iron(III), which is thought to be important for the initation of lipid peroxidation. Addition of hydrogen peroxide to incubations with 1--10 microM iron(II) decreased rates of lipid peroxidation, whereas addition of hydrogen peroxide to incubations with higher iron concentrations increased rates of lipid peroxidation. Thus, in this liposome system, sufficient peroxide from either within the lipid or from exogenous sources must be present to generate equimolar iron(II) and iron(III). With iron-catalyzed DNA oxidation, hydrogen peroxide always stimulated product formation. Phosphate buffer, which chelates iron but still allows for generation of hydroxyl radicals, inhibited lipid peroxidation but not DNA oxidation. HEPES buffer, which scavenges hydroxyl radicals, inhibited DNA oxidation, whereas lipid peroxidation was unaffected since presumably iron(II) and iron(III) were still available for reaction with liposomes in HEPES buffer.
在HEPES缓冲液和磷酸盐缓冲液中比较了铁（II）催化的脂质和DNA氧化。在一个由荧光探针构建的敏感脂质体系统中检测脂质过氧化，这使我们能够研究低铁浓度和高铁浓度的影响。对于由合成的1-硬脂酰-2-亚油酰基-sn-甘油-3-磷酸胆碱或大鼠肝微粒体脂质制成的脂质体，脂质过氧化随着铁浓度的增加而增加，直至铁（II）浓度达到10-20 microM范围，但随后随着铁浓度的进一步增加，反应速率下降。这可能是由于脂质体中可用于将铁（II）氧化生成等摩尔铁（III）的脂质过氧化物数量有限，而铁（III）被认为对脂质过氧化的引发很重要。向含有1-10 microM铁（II）的孵育体系中添加过氧化氢会降低脂质过氧化速率，而向含有更高铁浓度的孵育体系中添加过氧化氢会增加脂质过氧化速率。因此，在这个脂质体系统中，必须存在来自脂质内部或外源的足够过氧化物，以生成等摩尔的铁（II）和铁（III）。对于铁催化的DNA氧化，过氧化氢总是会刺激产物形成。磷酸盐缓冲液能螯合铁，但仍能产生羟基自由基，它抑制脂质过氧化但不抑制DNA氧化。HEPES缓冲液能清除羟基自由基，它抑制DNA氧化，而脂质过氧化不受影响，因为推测在HEPES缓冲液中铁（II）和铁（III）仍可用于与脂质体反应。
