Kwee J K, Armelin M S, Stefani H A, Augusto O
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Brazil.
Chem Biol Interact. 1998 Nov 6;116(1-2):61-77. doi: 10.1016/s0009-2797(98)00079-9.
The ability of C8-substituted guanine (Gua) ribonucleosides to induce B cell proliferation has been well documented in the literature. These compounds are analogues of adducts formed from free radical attack on ribonucleosides and RNA. Here we examined the proliferative properties of two of these radical adducts, 8-methylguanosine (8-MeG) and 8-oxo-7,8-dihydroguanosine (8-OxoG) and compared them with those of the well studied B cell mitogen, 8-bromoguanosine (8-BrG). 8-MeG and 8-OxoG were synthesized in the considerable yields of 28, and 55%, respectively, and were characterized by UV, NMR and CG-MS. Their effects upon [3H]thymidine uptake into DNA by Swiss mouse splenocytes, mouse embryo 3T3 fibroblasts (A31) and mouse B16F10 melanoma were examined. Both guanosine (G) radical adducts were shown to increase [3H]thymidine uptake by mouse splenocytes but displayed selectivity in respect to continuous cell lines. 8-MeG acted upon 3T3 fibroblasts whereas 8-OxoG acted upon B16F10 melanoma. The non-physiological analogue 8-BrG acted upon all tested cells. Parallel experiments of cell counting, cytotoxicity,and cell sorting indicated that DNA synthesis induced by the C8-substituted G's reflected cell growth. It is proposed that the compounds act intracellularly because their proliferative effects were blocked in the presence of a nucleoside transport inhibitor but were not inhibited by an antagonist of the A2 purine receptor. The present results, taken together with data from the literature, suggest that in the case of 3T3 fibroblasts and mouse splenocytes the proliferative effects of the compounds are not dependent on metabolism through purine salvage pathways. In the case of melanoma, however, the compounds are likely to become part of the purine nucleoside pool. The demonstration that adducts produced by free radical attack on ribonucleosides and RNA are able to induce cell proliferation opens new perspectives for the understanding of free radical mediated carcinogenesis.
文献中已充分证明C8取代鸟嘌呤（Gua）核糖核苷诱导B细胞增殖的能力。这些化合物是自由基攻击核糖核苷和RNA形成的加合物类似物。在此，我们研究了其中两种自由基加合物8-甲基鸟苷（8-MeG）和8-氧代-7,8-二氢鸟苷（8-OxoG）的增殖特性，并将它们与研究充分的B细胞有丝分裂原8-溴鸟苷（8-BrG）的增殖特性进行比较。8-MeG和8-OxoG的合成产率分别为可观的28%和55%，并通过紫外、核磁共振和气相色谱-质谱进行了表征。研究了它们对瑞士小鼠脾细胞、小鼠胚胎3T3成纤维细胞（A31）和小鼠B16F10黑色素瘤细胞摄取[3H]胸苷进入DNA的影响。两种鸟苷（G）自由基加合物均显示可增加小鼠脾细胞对[3H]胸苷的摄取，但对连续细胞系表现出选择性。8-MeG作用于3T3成纤维细胞，而8-OxoG作用于B16F10黑色素瘤细胞。非生理性类似物8-BrG作用于所有测试细胞。细胞计数、细胞毒性和细胞分选的平行实验表明，C8取代的G诱导的DNA合成反映了细胞生长。有人提出这些化合物在细胞内起作用，因为它们的增殖作用在核苷转运抑制剂存在时被阻断，但不受A2嘌呤受体拮抗剂的抑制。目前的结果与文献数据一起表明，对于3T3成纤维细胞和小鼠脾细胞，这些化合物的增殖作用不依赖于通过嘌呤补救途径的代谢。然而，对于黑色素瘤，这些化合物可能会成为嘌呤核苷池的一部分。自由基攻击核糖核苷和RNA产生的加合物能够诱导细胞增殖这一证明为理解自由基介导的致癌作用开辟了新的视角。
