Adam W, Mielke K, Saha-Möller C R, Möller M, Stopper H, Hutterer R, Schneider F W, Ballmaier D, Epe B, Gasparro F F, Chen X, Kagan J
Institute of Organic Chemistry, University of Würzburg, Germany.
Photochem Photobiol. 1997 Jul;66(1):46-54. doi: 10.1111/j.1751-1097.1997.tb03137.x.
Photobiological activities of the benzo-spaced psoralen analog furonaphthopyranone 3 have been investigated in cell-free and cellular DNA. The molecular geometry parameters of 3 suggest that it should not form interstrand crosslinks with DNA. With cell-free DNA no evidence for crosslinking but also not for monoadduct formation was obtained; rather, the unnatural furocoumarin 3 induces oxidative DNA modifications under near-UVA irradiation. The enzymatic assay of the photosensitized damage in cell-free PM2 DNA revealed the significant formation of lesions sensitive to formamidopyrimidine DNA glycosylase (Fpg protein). In the photooxidation of calf thymus DNA by the furonaphthopyranone 3, 0.29 +/- 0.02% 8-oxo-7,8-dihydroguanine (8-oxoGua) was observed. With 2'-deoxyguanosine (dGuo), the guanidine-releasing photooxidation products oxazolone and oxoimidazolidine were formed predominately, while 8-oxodGuo and 4-HO-8-oxodGuo were obtained in minor amounts. The lack of a significant D2O effect in the photooxidation of DNA and dGuo reveals that singlet oxygen (type II process) plays a minor role; control experiments with tert-butanol and mannitol confirm the absence of hydroxyl radicals as oxidizing species. The furonaphthopyranone 3 (Ered = -1.93 +/- 0.03V) should act in its singlet-excited state as electron acceptor for the photooxidation of dGuo (delta GET ca -6 kcal/mol), which corroborates photoinduced electron transfer (type I) as a major DNA-oxidizing mechanism. A comet assay in Chinese hamster ovary (CHO) AS52 cells demonstrated that the psoralen analog 3 damages cellular DNA upon near-UVA irradiation; however, no photosensitized mutagenicity was observed in CHO AS52 cell cultures.
已在无细胞和细胞DNA中研究了苯并间隔补骨脂素类似物呋喃萘并吡喃酮3的光生物学活性。3的分子几何参数表明它不应与DNA形成链间交联。对于无细胞DNA，未获得交联的证据，但也未获得单加合物形成的证据；相反，非天然呋喃香豆素3在近UVA照射下诱导DNA氧化修饰。无细胞PM2 DNA中光敏损伤的酶促测定显示，对甲酰胺嘧啶DNA糖基化酶（Fpg蛋白）敏感的损伤大量形成。在呋喃萘并吡喃酮3对小牛胸腺DNA的光氧化中，观察到0.29±0.02%的8-氧代-7,8-二氢鸟嘌呤（8-氧代鸟嘌呤）。对于2'-脱氧鸟苷（dGuo），主要形成释放胍的光氧化产物恶唑酮和氧代咪唑烷，而8-氧代dGuo和4-HO-8-氧代dGuo的产量较少。DNA和dGuo光氧化中缺乏显著的重水效应表明单线态氧（II型过程）起次要作用；用叔丁醇和甘露醇进行的对照实验证实不存在作为氧化物种的羟基自由基。呋喃萘并吡喃酮3（Ered = -1.93±0.03V）在其单重激发态应作为dGuo光氧化的电子受体（ΔGET约为-6 kcal/mol），这证实了光诱导电子转移（I型）是主要的DNA氧化机制。中国仓鼠卵巢（CHO）AS52细胞中的彗星试验表明，补骨脂素类似物3在近UVA照射下会损伤细胞DNA；然而，在CHO AS52细胞培养物中未观察到光敏致突变性。
