Low levels of clustered oxidative DNA damage induced at low and high LET irradiation in mammalian cells
Low levels of clustered oxidative DNA damage induced at low and high LET irradiation in mammalian cells
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DOI：
10.1007/s00411-006-0070-3
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发表时间：
2006-11-01
影响因子：
1.7
通讯作者：
Averbeck, Dietrich
中科院分区：
文献类型：
--
作者：
Boucher, Didier;Testard, Isabelle;Averbeck, Dietrich
电离辐射（IR）诱导的DNA双链断裂（DSB）和局部多重损伤位点（LMDS）被认为对哺乳动物细胞具有很强的遗传毒性。LMDS由两个或多个成簇的DNA损伤组成，包括局部能量沉积后由单个辐射轨迹在一个或两个螺旋圈内局部形成的氧化损伤。它们被认为是由IR而不是由正常的氧化代谢引起的。在哺乳动物细胞中，LMDS是在特定的酶处理后检测到的，这些酶处理将这些病变转化为可以通过脉冲场凝胶电泳（PFGE）显示的额外的DSB。在这里，我们研究了辐射诱导的中国仓鼠卵巢细胞（CHO-K1）的DSB和LMDS。加入铁螯合剂去铁胺（DFO）或抗氧化剂谷胱甘肽（GSH）的细胞裂解液后，我们观察到减少自发DNA断裂和辐射诱导的DSB的剂量依赖性增加。然而，LMDS诱导接近背景水平，与剂量、剂量率、温度和辐射质量（低和高LET）无关。在这些实验条件下，细胞裂解过程中的人为氧化DNA损伤不再与LMDS混淆。因此，我们表明，辐射诱导的LMDS氧化嘌呤或嘧啶组成的频率比迄今报道的要低得多，并建议他们可能是次要的辐射反应比DSBs。我们推测具有氧化末端的复杂DSB可能构成辐射诱导的簇状病变的主要部分。然而，这需要进一步研究。
DNA double-strand breaks (DSBs) and locally multiply damaged sites (LMDS) induced by ionizing radiation (IR) are considered to be very genotoxic in mammalian cells. LMDS consist of two or more clustered DNA lesions including oxidative damage locally formed within one or two helical turns by single radiation tracks following local energy deposition. They are thought to be frequently induced by IR but not by normal oxidative metabolism. In mammalian cells, LMDS are detected after specific enzymatic treatments transforming these lesions into additional DSBs that can be revealed by pulsed-field gel electrophoresis (PFGE). Here, we studied radiation-induced DSBs and LMDS in Chinese hamster ovary cells (CHO-K1). After addition of the iron chelator deferoxamine (DFO) or the antioxidant glutathione (GSH) to the cell lysis solution, we observed reduced spontaneous DNA fragmentation and a clear dose-dependent increase of radiation-induced DSBs. LMDS induction, however, was close to background levels, independently of dose, dose rate, temperature and radiation quality (low and high LET). Under these experimental conditions, artefactual oxidative DNA damage during cell lysis could not anymore be confounded with LMDS. We thus show that radiation-induced LMDS composed of oxidized purines or pyrimidines are much less frequent than hitherto reported, and suggest that they may be of minor importance in the radiation response than DSBs. We speculate that complex DSBs with oxidized ends may constitute the main part of radiation-induced clustered lesions. However, this needs further studies.