title: Induction of 8-hydroxydeoxyguanosine in isolated DNA and HeLa cells exposed to fecapentaene-12: evidence for the involvement of prostaglandin H synthase and iron.
abstract: The genotoxic/mutagenic mechanism(s) of action of fecapentaene-12 (fec-12) is complex but there is evidence to suggest that the generation of active oxygen species (AOS) may be involved. This has been assessed by measuring the formation of 8-hydroxydeoxyguanosine (8-OHdG) in isolated DNA and HeLa cells exposed in vitro to fec-12. The possibility that fec-12 may form AOS via peroxidative 'activation' by prostaglandin H synthase (PHS) has been investigated by measuring 8-OHdG in HeLa cells exposed to fec-12 in the absence or presence of PHS inhibitors. The role of iron as a catalyst in this pathway has also been investigated. A 4-fold increase in the level of 8-OHdG in isolated DNA was seen after exposure to fec-12 (1 mM) alone. This increase was enhanced synergistically by ferrous iron. Fec-12 exposure of HeLa cells at 50 and 100 microM induced 2- and 3-fold increases (P < 0.001) respectively in the level of 8-OHdG in cellular DNA. No increase was seen at 10 microM fec-12. The PHS inhibitors indomethacin and acetylsalicylate blocked the formation of 8-OHdG induced by fec-12 (50 microM) but did not inhibit the formation of 8-OHdG in these cells after exposure to H2O2 and Fe2+. Addition of the iron chelating agent o-phenanthroline to cells prior to fec-12 exposure blocked the increase in 8-OHdG induced by fec-12 (50 microM). Addition of the radical scavenging agent DMSO (10%) to cells prior to fec-12 exposure reduced the level of 8-OHdG to within 10% of control. Specific inhibition of fec-12 induced 8-OHdG formation in HeLa cells by PHS inhibitors suggests that this enzyme may be involved in 'activating' fec-12 to form AOS in cells. Inhibition of fec-12 induced 8-OHdG formation in cells by o-phenanthroline suggests a role for intracellular iron as a catalyst in this process.
authors.affiliation: Centre for Mechanisms of Human Toxicity, Leicester, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Plummer
authors.forename: S P
authors.initials: SP
authors.lastname: Faux
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D011090:Polyenes / Q000378:metabolism / Q000633:toxicity*; D012459:Salicylates / Q000494:pharmacology
chemical_list: D016861:Cyclooxygenase Inhibitors; D010618:Phenanthrolines; D011090:Polyenes; D012459:Salicylates; C037357:1-(1-glycero)dodeca-1,3,5,7,9-pentaene; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine; C025205:1,10-phenanthroline; D007213:Indomethacin