Roy Béatrice, Guittet Olivier, Beuneu Claire, Lemaire Geneviève, Lepoivre Michel
UMR CNRS 8619, IBBMC, Université de Paris XI, F-91405 Orsay Cedex, France.
Free Radic Biol Med. 2004 Feb 15;36(4):507-16. doi: 10.1016/j.freeradbiomed.2003.11.028.
Nitric oxide displays pro- and anti-tumor activities, prompting further studies to better understand its precise role. Nitric oxide inhibits ribonucleotide reductase (RnR), the limiting enzyme for de novo dNTP synthesis. We report here the first detailed analysis of dNTP variations induced in tumor cells by NO. NO prodrugs induced a depletion in dNTP pools and an activation of the pyrimidine salvage pathway, as did hydroxyurea, the prototypic RnR inhibitor. In the presence of dipyridamole, which blocked salvaged dNTP synthesis, depletion of dNTP pools was also observed in tumor cells cocultured with macrophages expressing the high-output iNOS activity. This effect was rapid, reversible, blocked by NO scavengers, and cGMP independent. It was quantitatively correlated to iNOS activity. In the absence of dipyridamole, NO still induced a decrease in dATP concentration in tumor cells cocultured with macrophages, whereas surprisingly, concentrations of dCTP and dTTP expanded considerably, resulting in a strong imbalance in dNTP pools. NO prodrugs did not cause such an increase in pyrimidine dNTP, suggesting that pyrimidine nucleosides were released by NO-injured macrophages. Altered dNTP levels have been reported to promote mutagenesis and apoptosis. It is suggested that abnormal changes in dNTP pools in tumors might contribute to NO-dependent toxicity.
一氧化氮具有促肿瘤和抗肿瘤活性，这促使人们进一步开展研究以更好地了解其确切作用。一氧化氮可抑制核糖核苷酸还原酶（RnR），这是从头合成脱氧核苷酸三磷酸（dNTP）的限速酶。我们在此报告了对一氧化氮诱导肿瘤细胞中dNTP变化的首次详细分析。一氧化氮前药可导致dNTP池耗竭以及嘧啶补救途径的激活，典型的RnR抑制剂羟基脲也有此作用。在双嘧达莫存在的情况下，双嘧达莫可阻断补救性dNTP合成，在与表达高产量诱导型一氧化氮合酶（iNOS）活性的巨噬细胞共培养的肿瘤细胞中也观察到了dNTP池的耗竭。这种效应迅速、可逆，可被一氧化氮清除剂阻断，且不依赖环磷酸鸟苷（cGMP）。它与iNOS活性呈定量相关。在没有双嘧达莫的情况下，一氧化氮仍可导致与巨噬细胞共培养的肿瘤细胞中脱氧腺苷三磷酸（dATP）浓度降低，而令人惊讶的是，脱氧胞苷三磷酸（dCTP）和脱氧胸苷三磷酸（dTTP）的浓度大幅增加，导致dNTP池严重失衡。一氧化氮前药并未导致嘧啶dNTP如此增加，这表明嘧啶核苷是由一氧化氮损伤的巨噬细胞释放的。据报道，dNTP水平的改变会促进诱变和凋亡。有人认为，肿瘤中dNTP池的异常变化可能导致一氧化氮依赖性毒性。
