Photochemical and photobiological studies of a furonaphthopyranone as a benzo-spaced psoralen analog in cell-free and cellular DNA.
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.
Adam
W
W
Institute of Organic Chemistry, University of Würzburg, Germany. adam@chemie.uni-wuerzburg.de
Mielke
K
K
Saha-Möller
C R
CR
Möller
M
M
Stopper
H
H
Hutterer
R
R
Schneider
F W
FW
Ballmaier
D
D
Epe
B
B
Gasparro
F F
FF
Chen
X
X
Kagan
J
J
D000818:Animals; D016466:CHO Cells; D002417:Cattle; D002474:Cell-Free System; D006224:Cricetinae; D004247:DNA / Q000737:chemistry / Q000187:drug effects* / Q000528:radiation effects; D004249:DNA Damage; D004279:DNA, Viral / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000737:chemistry; D005363:Ficusin / Q000737:chemistry / Q000633:toxicity; D011564:Furocoumarins; D008730:Methoxsalen / Q000633:toxicity; D008968:Molecular Conformation; D015394:Molecular Structure; D009152:Mutagenicity Tests; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry / Q000633:toxicity*; D014466:Ultraviolet Rays
D004279:DNA, Viral; D011564:Furocoumarins; D017319:Photosensitizing Agents; C107447:furonaphthopyranone; D004247:DNA; D003849:Deoxyguanosine; D005363:Ficusin; D008730:Methoxsalen