Cristóvão L, Lechner M C, Fidalgo P, Leitão C N, Mira F C, Rueff J
Department of Genetics, Faculty of Medical Sciences, New University of Lisbon, Portugal.
Br J Cancer. 1998 May;77(10):1628-32. doi: 10.1038/bjc.1998.266.
Poly(ADP-ribose)polymerase (PARP) has been implicated in DNA repair mechanisms and the associated activity shown to markedly increase after DNA damage in carcinogen-treated cells. A defective DNA repair has been associated to the aetiology of human cancers. In order to assess the potential role of this enzyme in cellular response to DNA damage by gamma-radiation, we studied the activity of PARP in patients with familial adenomatous polyposis (FAP). We compared poly(ADP-ribose)polymerase activity by the rate of incorporation of radioactivity from [3H]adenine-NAD+ into acid-insoluble material in permeabilized leucocytes from FAP patients and healthy volunteers. Concomitantly, the intracellular levels of NAD+--the substrate for the PARP--and the reduced counterpart NADH were determined using an enzymatic cycling assay 30 min after [60Co] gamma-ray cells irradiation. Our results demonstrate that a marked stimulation of PARP activity is produced upon radiation of the cells from healthy subjects but not in the FAP leucocytes, which concomitantly show a marked decrease in total NAD-/NADH content. Our observations point to a role of PARP in the repair of the gamma-radiation-induced DNA lesions through a mechanism that is impaired in the cells from FAP patients genetically predisposed to colon cancer. The differences observed in PARP activation by gamma-radiation in patients and healthy individuals could reflect the importance of PARP activity dependent on treatment with gamma-rays. The absence of this response in FAP patients would seem to suggest a possible defect in the role of PARP in radiation-induced DNA repair in this cancer-prone disease.
聚（ADP - 核糖）聚合酶（PARP）与DNA修复机制有关，并且在致癌物处理的细胞中，DNA损伤后其相关活性显著增加。DNA修复缺陷与人类癌症的病因有关。为了评估这种酶在细胞对γ射线引起的DNA损伤反应中的潜在作用，我们研究了家族性腺瘤性息肉病（FAP）患者中PARP的活性。我们通过[³H]腺嘌呤 - NAD⁺的放射性掺入酸不溶性物质的速率，比较了FAP患者和健康志愿者透化白细胞中聚（ADP - 核糖）聚合酶的活性。同时，在[⁶⁰Co]γ射线照射细胞30分钟后，使用酶循环测定法测定PARP的底物NAD⁺以及还原型NADH的细胞内水平。我们的结果表明，健康受试者的细胞受到辐射后PARP活性受到显著刺激，但FAP患者的白细胞中未出现这种情况，同时FAP患者白细胞中总NAD⁺/NADH含量显著降低。我们的观察结果表明，PARP通过一种机制参与γ射线诱导的DNA损伤修复，而在遗传易患结肠癌的FAP患者细胞中这种机制受损。在患者和健康个体中观察到的γ射线对PARP激活的差异可能反映了依赖γ射线治疗的PARP活性的重要性。FAP患者中缺乏这种反应似乎表明在这种易患癌症的疾病中，PARP在辐射诱导的DNA修复中的作用可能存在缺陷。
