Photochemical and Photobiological Studies of a Furonaphthopyranone as a Benzo-spaced Psoralen Analog in Cell-free and Cellular DNA |
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| Authors: | Waldemar Adam Karsten Mielke Chantu R Saha-Möller Marianne Möller Helga Stopper Rudolf Hutterer Friedemann W Schneider Daniel Ballmaier Bernd Epe Francis F Gasparro Xinsheng Chen Jacques Kagan |
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| Institution: | 1nstitute of Organic Chemistry;department of Toxicology;institute of Physical Chemistry, University of Würzburg, Würzburg, Germany;Institute of Pharmacy, University of Mainz, Mainz, Germany;Department of Dermatology &Cutaneous Biology, Thomas Jefferson University, Philadelphia, PA, USA;Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA |
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| Abstract: | Abstract— 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 glyco-sylase (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 (δGET ca – 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 |
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