Analysis of the human DNA damageby antioxidants for evaluation of safety in cancer chemoprevention

作为评估癌症化学预防安全性的方法，我们使用人类培养细胞和 32P 标记的人类 p53 肿瘤抑制基因和 c-Ha-ras-l 原癌基因的分离 DNA 片段，研究了抗氧化剂是否具有人类 DNA 损伤的能力。为了检测细胞DN.A损伤，用抗氧化剂处理人类培养的细胞，并通过脉冲场电泳方法进行检查。结果。通过维生素 A、视网膜、α-生育酚和槲皮素处理检测到细胞 DNA 损伤。此外。我们通过 HPLC-ECD 定量测量了 8-羟基脱氧鸟苷 (8-OH-dG) 的形成，这是氧化 DNA 损伤的指标。用维生素 A、视黄醛和 N-乙酰半胱氨酸处理的细胞中，细胞内 8-OH-dG 的形成显着增加。为了检测分离的 DNA 的损伤，将抗氧化剂与 32P 标记的 DNA 片段在金属离子存在下一起孵育，并获得放射自显影图。 α-生育酚、维生素 A、视黄醛、槲皮素和 N-乙酰半胱氨酸在 Cm(II) 存在下引起位点特异性 DN,A 损伤。过氧化氢酶和浴铜灵。 Cu(I) 特异性螯合剂。抑制 Co(II) 介导的 DNA 损伤，表明 H_2O_2 和 Curl 的参与。在 Cu(II) 存在的情况下，在胸腺嘧啶和胞嘧啶残基处观察到 DNA 裂解频率。所谓的“抗氧化剂”在某些情况下充当抗氧化剂，但在其他情况下也充当氧化剂。换句话说，在某些情况下，抗氧化剂变得具有破坏 DNA 的能力，尽管在其他情况下，抗氧化剂可以防止氧化应激。这些氧化性 DNA 损伤可能是引发和/或肿瘤促进多阶段癌发生的原因。在建议使用抗氧化剂进行癌症化学预防之前，应先评估其安全性和有效性。

As a method to evaluatesafety in cancer chemoprevention, we have investigated whether antioxidants have the ability of the human DNA damage, using human cultured cells and 32P-labeledisolated DNA fragnrents of the human p53 tumor suppressor gene and c-Ha-ras-l prctooncogene. For detection of ce1lularDN.A damage, human cultured celles were treated with antioxidants, and examined by the pulsed-field get electrophoresis method. As the result. celularDNA damage was detected by the treatment of vitamin A, retinal, alpha-tocopherol and quercetin. Furthermore. we measured 8-hydroxy deoxyguanosine (8-OH-dG) formation, which was an index to an oxidative DNA lesion, quaruitativelyby HPLC-ECD.lntracellu1ar8-OH-dG formation significantly increased in cells treated with vitamin A, retinal and N-acetylcysteine. For detection of damage to isolated DN.A, antioxidants were incubated with 32P-labled DNA fragment in the presence of metalions, and the autoradiogram was obtained. alpha-Tocopherol, vitamin A, retinal, quercetin and N-acetylcysceine caused site-specific DN,A-damage in the presence of Cm(II). Catalase and bathocuproine. a Cu(I)-specific chelaror. inhibited the Co(II)-mediated DNA damage, suggesting the involvement of H_2O_2 and Curl).The DNA cleavage was observed frequency at thymine and cytosine residues in the presence of Cu(II).So-called "antioxidants" act as antioxidants in some circumstances, but also act as prooxidants in other circumstances. In another word, antioxidants become to have ability of damaging DNA in some cases, although antioxidants protect from oxidative stress in other cases. These oxidative DNA damage could be responsible for initiation and/or tumor promotion the multi-stage of carcinogenesis. In is requested chat safety and efficacy should be estimated before recommending use of antioxidants for cancer chemopreventton.