Driessens Natacha, Versteyhe Soetkin, Ghaddhab Chiraz, Burniat Agnès, De Deken Xavier, Van Sande Jacqueline, Dumont Jacques-Emile, Miot Françoise, Corvilain Bernard
Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculty of Medicine, Université Libre de Bruxelles, Bat C Local C4.145, Campus Erasme, 808, Route de Lennik, B-1070 Brussels, Belgium.
Endocr Relat Cancer. 2009 Sep;16(3):845-56. doi: 10.1677/ERC-09-0020. Epub 2009 Jun 9.
DNA double-strand breaks (DSBs) are considered as one of the primary causes of cancer but their induction by hydrogen peroxide (H(2)O(2)) is still controversial. In this work, we studied whether the high levels of H(2)O(2) produced in the thyroid to oxidize iodide could induce DNA modifications. Scores of DNA damage, in terms of strand breaks, were obtained by comet assay (alkaline condition for single-strand breaks (SSBs) and neutral condition for DSBs). We demonstrated that in a rat thyroid cell line (PCCl3), non-lethal concentrations of H(2)O(2) (0.1-0.5 mmol/l) as well as irradiation (1-10 Gy) provoked a large number of SSBs ( approximately 2-3 times control DNA damage values) but also high levels of DSBs (1.2-2.3 times control DNA damage values). We confirmed the generation of DSBs in this cell line and also in human thyroid in primary culture and in pig thyroid slices by measuring phosphorylation of histone H2AX. L-Buthionine-sulfoximine, an agent that depletes cells of glutathione, decreased the threshold to observe H(2)O(2)-induced DNA damage. Moreover, we showed that DNA breaks induced by H(2)O(2) were more slowly repaired than those induced by irradiation. In conclusion, H(2)O(2) causes SSBs and DSBs in thyroid cells. DSBs are produced in amounts comparable with those observed after irradiation but with a slower repair. These data support the hypothesis that the generation of H(2)O(2) in thyroid could also play a role in mutagenesis particularly in the case of antioxidant defense deficiency.
DNA双链断裂（DSBs）被认为是癌症的主要病因之一，但其是否由过氧化氢（H₂O₂）诱导仍存在争议。在本研究中，我们探究了甲状腺中产生的用于氧化碘离子的高水平H₂O₂是否会诱导DNA修饰。通过彗星试验（单链断裂（SSBs）采用碱性条件，双链断裂采用中性条件）获得了DNA损伤评分（以链断裂数衡量）。我们证明，在大鼠甲状腺细胞系（PCCl3）中，非致死浓度的H₂O₂（0.1 - 0.5 mmol/L）以及辐射（1 - 10 Gy）会引发大量的SSBs（约为对照DNA损伤值的2 - 3倍），同时也会导致高水平的DSBs（为对照DNA损伤值的1.2 - 2.3倍）。我们通过检测组蛋白H2AX的磷酸化，证实了该细胞系、原代培养的人甲状腺以及猪甲状腺切片中均有DSBs产生。L - 丁硫氨酸 - 亚砜亚胺是一种消耗细胞内谷胱甘肽的试剂，它降低了观察H₂O₂诱导的DNA损伤的阈值。此外，我们还表明，H₂O₂诱导的DNA断裂修复速度比辐射诱导的更慢。总之，H₂O₂会导致甲状腺细胞中的SSBs和DSBs。DSBs的产生量与辐射后观察到的相当，但修复速度较慢。这些数据支持了以下假设：甲状腺中H₂O₂的产生在诱变过程中也可能起作用，尤其是在抗氧化防御缺乏的情况下。
