Cantoni O, Murray D, Meyn R E
Biochim Biophys Acta. 1986 Jun 20;867(3):135-43. doi: 10.1016/0167-4781(86)90073-4.
The influence of the nuclear ADP-ribosyltransferase inhibitor 3-aminobenzamide on the DNA strand-break rejoining kinetics and cytotoxicity in Chinese hamster ovary cells following H2O2 treatment was investigated. For the DNA damage studies, cells were treated on ice with H2O2 (0-20 microM) for 1 h in serum-free medium, after which the H2O2 was removed and the cells were allowed to repair their damage in complete medium at 37 degrees C in the presence or absence of 3-aminobenzamide (5 mM) for periods up to 2 h. The DNA strand breaks remaining as a function of time were then estimated by alkaline elution. A linear relationship between the H2O2 concentration and the initial level of DNA single-strand breaks (zero time allowed for repair) was observed. No double-strand breaks or DNA-protein cross-links were detected at these doses. The rejoining of single-strand breaks after H2O2 (20 microM) alone was characterized by a single exponential process with a t1/2 of approx. 5 min. However, in the presence of 3-aminobenzamide, rejoining was much slower and biphasic, with t1/2 of approx. 10 and 36 min. The inhibitory action of 3-aminobenzamide was concentration-dependent and completely reversible in that, when the 3-aminobenzamide was removed from the treated cultures, the strand-break rejoining kinetics rapidly returned to the t1/2 of 5 min typical of H2O2 alone. Considerably higher concentrations of H2O2 (up to 600 microM) were required for cell killing compared to the DNA damage studies. Cell killing by H2O2 alone was characterized by a shoulderless, exponential survival curve (D0 = 880 microM). The cytotoxicity was potentiated when the cells were treated with 3-aminobenzamide (5 mM) for 1 h after the H2O2 treatment; the survival curve with 3-aminobenzamide also assumed a biphasic character (D0 of 212 microM and 520 microM). These results are consistent with the theory that OH.-induced single-strand breaks do not normally represent lethal lesions to the cell because of their rapid, efficient repair. However, interference with these repair processes (in this case by 3-aminobenzamide) can alter this relationship, possibly allowing lesion fixation.
研究了核ADP-核糖基转移酶抑制剂3-氨基苯甲酰胺对过氧化氢（H2O2）处理后的中国仓鼠卵巢细胞中DNA链断裂修复动力学和细胞毒性的影响。对于DNA损伤研究，细胞在无血清培养基中于冰上用H2O2（0 - 20微摩尔）处理1小时，之后去除H2O2，并使细胞在37℃的完全培养基中在存在或不存在3-氨基苯甲酰胺（5毫摩尔）的情况下修复损伤长达2小时。然后通过碱性洗脱估计随时间残留的DNA链断裂情况。观察到H2O2浓度与DNA单链断裂的初始水平（允许修复的零时间）之间存在线性关系。在这些剂量下未检测到双链断裂或DNA-蛋白质交联。单独用H2O2（20微摩尔）处理后单链断裂的修复以单指数过程为特征，半衰期约为5分钟。然而，在存在3-氨基苯甲酰胺的情况下，修复要慢得多且呈双相性，半衰期约为10分钟和36分钟。3-氨基苯甲酰胺的抑制作用是浓度依赖性的且完全可逆，即当从处理过的培养物中去除3-氨基苯甲酰胺时，链断裂修复动力学迅速恢复到单独用H2O2时典型的5分钟半衰期。与DNA损伤研究相比，细胞杀伤需要相当高浓度的H2O2（高达600微摩尔）。单独用H2O2进行细胞杀伤的特征是无肩的指数存活曲线（D0 = 880微摩尔）。在H2O2处理后用3-氨基苯甲酰胺（5毫摩尔）处理细胞1小时，细胞毒性增强；含3-氨基苯甲酰胺的存活曲线也呈现双相特征（D0为212微摩尔和520微摩尔）。这些结果与以下理论一致，即OH·诱导的单链断裂通常由于其快速、有效的修复而不代表细胞的致死性损伤。然而，对这些修复过程的干扰（在这种情况下是3-氨基苯甲酰胺）可以改变这种关系，可能导致损伤固定。
