Role of oxidative DNA damage in the mechanism of fecapentaene-12 genotoxicity.
Fecapentaene-12 (FP-12), a fecal unsaturated, ether-linked lipid excreted by most human individuals in Western populations, has been found to be a potent genotoxin in mammalian cells. Its mechanism of genotoxicity may be mediated by oxygen radical-induced DNA damage or by direct DNA alkylation, of which the relative importance remains to be determined. In the present study, induction of oxidative genetic damage by FP-12 has been investigated, in combination with the biological inactivation of single-stranded bacteriophage phi X-174 DNA. It was shown that formation of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG), a marker for oxidative DNA damage, is induced dose dependently by FP-12 in 2'-deoxyguanosine (dG). It was demonstrated by application of radical scavengers that production of both the superoxide anion and singlet oxygen may be involved in the induction of 8-oxodG. The effect of OH radical scavenging appeared to be less pronounced. Enzymatic peroxidation of FP-12, which has been demonstrated to stimulate oxygen radical formation, was found to increase the hydroxylation ratio in dG, an effect which was less pronounced in single-stranded DNA and even absent in double-stranded DNA. No induction of 8-oxodG was observed after exposure of human skin fibroblasts to 60 microM FP-12 for 3 h in vitro. It was concluded that the induction of 8-oxodG by FP-12 is determined by the accessibility of the guanine molecule rather than the rate of oxygen radical formation. Although free radical formation is known to be stimulated by enzymatic peroxidation of FP-12, the inactivation of phi X-174 DNA spontaneously induced by FP-12 was found to be reduced by application of peroxidases. This furthermore demonstrates that the increased formation of reactive oxygen species by enzymatic peroxidation of FP-12 does not directly relate to increased induction of genotoxic effects. The fact that addition of radical scavengers shows limited effects on the inactivation of phi X-174 DNA suggests that the contribution of oxidative DNA damage to the genotoxic potential of FP-12 is only of minor importance.
Department of Health Risk Analysis and Toxicology, University of Limburg, Maastricht, The Netherlands.
T M
TM
de Kok
D M
DM
Pachen
J M
JM
van Maanen
M V
MV
Lafleur
E J
EJ
Westmijze
F
F
ten Hoor
J C
JC
Kleinjans
D000818:Animals; D010584:Bacteriophage phi X 174 / Q000235:genetics; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000187:drug effects; D004279:DNA, Viral / Q000187:drug effects; D017665:Hydroxyl Radical; D009153:Mutagens / Q000633:toxicity*; D010084:Oxidation-Reduction; D011090:Polyenes / Q000633:toxicity*; D051381:Rats; D013482:Superoxide Dismutase / Q000494:pharmacology
D003497:Cyclic N-Oxides; D004277:DNA, Single-Stranded; D004279:DNA, Viral; D009153:Mutagens; D011090:Polyenes; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C037357:1-(1-glycero)dodeca-1,3,5,7,9-pentaene; D004247:DNA; D013482:Superoxide Dismutase