Kawai Yoshichika, Uchida Koji, Osawa Toshihiko
Laboratory of Food and Biodynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Free Radic Biol Med. 2004 Mar 1;36(5):529-41. doi: 10.1016/j.freeradbiomed.2003.12.006.
Lipid peroxidation generates a variety of reactive products that covalently modify DNA, yielding several types of adducts with nucleobases. In the present study, we characterized the modification of nucleobases during peroxidation of linoleate and found that 2'-deoxycytidine (dC) could be a major target of the modification by lipid peroxidation reactions. Upon incubation with oxidized linoleate, dC and 2'-deoxyguanosine (dG) were significantly modified among four 2'-deoxynucleosides. The major product in dG/linoleate was identical to the 2-oxo-heptyl-substituted 1,N(2)-etheno-dG that had been previously identified as a 4-oxo-2-nonenal (ONE)-dG adduct. On the basis of spectroscopic and chemical characterization, we identified the major product in dC/linoleate as the 2-oxo-heptyl-substituted 3,N(4)-etheno-dC. The same adduct was also produced upon reaction of dC with ONE, suggesting that ONE might represent the major reactive species that modifies DNA during lipid peroxidation. Indeed, this proposition was supported by the observation that ONE was far more reactive with dC and dG than other genotoxic aldehydes, such as 4-hydroxy-2-nonenal. More strikingly, we found that, in contrast to the similar reactivity of ONE toward free nucleobases (dC and dG), ONE preferentially reacted with dC residues in double-stranded DNA. These results suggest that ONE and other 4-oxo-2-alkenals may possess by far the strongest electrophilic potential vs. dC and that the formation of 4-oxo-2-alkenal-adducted dC may thus serve as one mechanism for oxidative damage to DNA in vivo.
脂质过氧化作用会产生多种活性产物，这些产物会与DNA发生共价修饰，从而产生几种与核碱基的加合物。在本研究中，我们对亚油酸过氧化过程中核碱基的修饰进行了表征，发现2'-脱氧胞苷（dC）可能是脂质过氧化反应修饰的主要靶点。在与氧化亚油酸孵育后，四种2'-脱氧核苷中，dC和2'-脱氧鸟苷（dG）发生了显著修饰。dG/亚油酸中的主要产物与先前鉴定为4-氧代-2-壬烯醛（ONE）-dG加合物的2-氧代庚基取代的1,N(2)-乙烯基-dG相同。基于光谱和化学表征，我们确定dC/亚油酸中的主要产物为2-氧代庚基取代的3,N(4)-乙烯基-dC。dC与ONE反应时也会产生相同的加合物，这表明ONE可能是脂质过氧化过程中修饰DNA的主要反应性物种。事实上，这一观点得到了以下观察结果的支持：ONE与dC和dG的反应性远比其他遗传毒性醛类（如4-羟基-2-壬烯醛）高。更引人注目的是，我们发现，与ONE对游离核碱基（dC和dG）的相似反应性不同，ONE优先与双链DNA中的dC残基反应。这些结果表明，ONE和其他4-氧代-2-烯醛对dC的亲电潜力可能是迄今为止最强的，因此4-氧代-2-烯醛加合dC的形成可能是体内DNA氧化损伤的一种机制。
