Fecapentaene-12 (FP-12), a fecal unsaturated, ether-linked lipid excre
ted by most human individuals in Western populations, has been found t
o be a potent genotoxin in mammalian cells. Its mechanism of genotoxic
ity may be mediated by oxygen radical-induced DNA damage or by direct
DNA alkylation, of which the relative importance remains to be determi
ned. In the present study, induction of oxidative genetic damage by FP
-12 has been investigated, in combination with the biological inactiva
tion 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'-d
eoxyguanosine (dG). It was demonstrated by application of radical scav
engers that production of both the superoxide anion and singlet oxygen
mag 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 formati
on, was found to increase the hydroxylation ratio in dG, an effect whi
ch was less pronounced in single-stranded DNA and even absent in doubl
e-stranded DNA. No induction of 8-oxodG was observed after exposure of
human skin fibroblasts to 60 mu M FP-12 for 3 h in vitro. It was conc
luded that the induction of 8-oxodG by FP-12 is determined by the acce
ssibility of the guanine molecule rather than the rate of oxygen radic
al formation. Although free radical formation is known to be stimulate
d by enzymatic peroxidation of FP-12, the inactivation of phi X-174 DN
A spontaneously induced by FP-12 was found to be reduced by applicatio
n of peroxidases. This furthermore demonstrates that the increased for
mation of reactive oxygen species by enzymatic peroxidation of FP-12 d
oes not directly relate to increased induction of genotoxic effects. T
he fact that addition of radical scavengers shows limited effects on t
he inactivation of phi X-174 DNA suggests that the contribution of oxi
dative DNA damage to the genotoxic potential of FP-12 is only of minor
importance.