Fortini P, Rosa S, Zijno A, Calcagnile A, Bignami M, Dogliotti E
Laboratory of Comparative Toxicology and Ecotoxicology, Istituto Superiore di Sanita, Rome, Italy.
Carcinogenesis. 1992 Jan;13(1):87-93. doi: 10.1093/carcin/13.1.87.
The biological effects of the interaction of methoxyamine (MX) with apurinic/apyrimidinic (AP) sites produced in CHO cells by treatment with alkylating agents were examined. A decrease in cytotoxicity was observed after a 10 min treatment with the SN1 alkylating agents ethylnitrosourea (ENU), N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) and N-methyl-nitrosourea when MX was present in the culture medium. Furthermore MX reduced the number of mutations to 6-thioguanine resistance induced by ENU and ENNG and the number of sister chromatid exchanges induced by ENU. In contrast, no protective effect of MX on survival was observed after a 10 min treatment with the SN2 alkylating agents diethylsulfate (DES), ethyl methane sulfonate and methyl methane sulfonate. A 3 h exposure to MX abolished the protective effect of MX on ENU-induced cytotoxicity and increased the cytotoxicity of DES. In vitro studies with synthetic oligonucleotides containing a single AP site opposite a normal guanine or O6-methylguanine showed that MX inhibits the cleavage of AP sites by the CHO AP endonuclease(s). A model is proposed in which different DNA lesions are involved in AP site formation after treatment with SN2 or SN2 alkylating agents. The involvement of specific alkylation products in cytotoxicity and mutagenesis is also discussed.
研究了甲氧基胺（MX）与经烷基化剂处理的CHO细胞中产生的无嘌呤/无嘧啶（AP）位点相互作用的生物学效应。当培养基中存在MX时，用SN1烷基化剂乙基亚硝基脲（ENU）、N-乙基-N'-硝基-N-亚硝基胍（ENNG）和N-甲基亚硝基脲处理10分钟后，观察到细胞毒性降低。此外，MX减少了ENU和ENNG诱导的对6-硫代鸟嘌呤抗性的突变数量以及ENU诱导的姐妹染色单体交换数量。相比之下，用SN2烷基化剂硫酸二乙酯（DES）、甲基磺酸乙酯和甲基磺酸甲酯处理10分钟后，未观察到MX对细胞存活的保护作用。暴露于MX 3小时消除了MX对ENU诱导的细胞毒性的保护作用，并增加了DES的细胞毒性。对含有与正常鸟嘌呤或O6-甲基鸟嘌呤相对的单个AP位点的合成寡核苷酸进行的体外研究表明，MX抑制CHO AP核酸内切酶对AP位点的切割。提出了一个模型，其中在用SN2或SN2烷基化剂处理后，不同的DNA损伤参与了AP位点的形成。还讨论了特定烷基化产物在细胞毒性和诱变中的作用。
