title: A possible involvement of DNA topoisomerase I in "caffeine effect" after ultraviolet irradiation.
abstract: Caffeine has been known to enhance lethal and chromosome damaging effects of chemical and physical mutagens. In spite of numerous investigations, the mechanism is not fully elucidated. In this paper, we describe that 1) post-treatment with camptothecin (CPT), a specific inhibitor of DNA topoisomerase (topo) I, enhances SCE-induction by ultraviolet light (UV), as post-UV caffeine treatment does, 2) the lethal effect of UV is also enhanced but to a lesser degree than by post-UV caffeine treatment, and 3) caffeine, like CPT, inhibits calf thymus topo I activity, as determined by relaxation of pBR322 supercoiled DNA. These results suggest that the mechanism(s) of lethal and SCE enhancement involves the ability of caffeine to inhibit topo I.
authors.affiliation: Department of Pharmacology, Tohoku University, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tohda
authors.forename: J H
authors.initials: JH
authors.lastname: Zhao
authors.forename: A
authors.initials: A
authors.lastname: Oikawa
mesh_terms: D002110:Caffeine / Q000494:pharmacology*; D002460:Cell Line; D004264:DNA Topoisomerases, Type I / Q000502:physiology*; D006801:Humans; D012854:Sister Chromatid Exchange / Q000187:drug effects*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
chemical_list: D002110:Caffeine; D004264:DNA Topoisomerases, Type I