Human Cytochrome P450 Enzyme Specificity for Bioactivation of Safrole to the Proximate Carcinogen 1‘-Hydroxysafrole

Abstract

In the present study, the cytochrome P450 mediated bioactivation of safrole to its proximate carcinogenic metabolite, 1'-hydroxysafrole, has been investigated for the purpose of identifying the human P450 enzymes involved. The 1'-hydroxylation of safrole was characterized in a variety of in vitro test systems, including Supersomes, expressing individual human P450 enzymes to a high level, and microsomes derived from cell lines expressing individual human P450 enzymes to a lower, average human liver level. Additionally, a correlation study was performed, in which safrole was incubated with a series of 15 human liver microsomes, and the 1'-hydroxylation rates obtained were correlated with the activities of these microsomes toward specific substrates for nine different isoenzymes. To complete the study, a final experiment was performed in which pooled human liver microsomes were incubated with safrole in the presence and absence of coumarin, a selective P450 2A6 substrate. On the basis of the results of these experiments, important roles for P450 2C9*1, P450 2A6, P450 2D6*1, and P450 2E1 were elucidated. The possible consequences of these results for the effects of genetic polymorphisms and life style factors on the bioactivation of safrole are discussed. Polymorphisms in P450 2C9, P450 2A6, and P450 2D6, leading to poor metabolizer phenotypes, may reduce the relative risk on the harmful effects of safrole, whereas life style factors, such as the use of alcohol, an inducer of P450 2E1, and barbiturates, inducers of P450 2C9, and polymorphisms in P450 2D6 and P450 2A6, leading to ultraextensive metabolizer phenotypes, may increase the relative risk.

DNA adducts from alkoxyallylbenzene herb and spice constituents in cultured human (HepG2) cells

“…For safrole, CYP2A6 is the most efficient human enzyme involved in 1 0 -hydroxylation at physiologically relevant concentrations [Jeurissen et al, 2004[Jeurissen et al, , 2007. In a recent study, Jeurissen et al [2007] identified CYP1A2 and CYP2A6 as the most important enzymes in estragole 1 0 -hydroxylation, while CYP1A2 has been identified by this group [2006] as the major enzyme catalyzing the 1 0 -hydroxylation of methyleugenol.…”

Molecular mechanisms of toxicity of important food-borne phytotoxins

“…The CYP enzymes involved in the bioactivation of safrole to its proximate carcinogen 19-hydroxysafrole in man were identified to be CYP2C9, CYP2A6, CYP2D6, and CYP2E1 [94,95]. Data from Gentest microsomes in which the activities towards enzyme-selective substrates are considered to be in the same order as the mean activities found in human liver microsomes, reveal CYP2A6 to contribute about two times more than the other CYPs that are active in safrole 19-hydroxylation [94].…”

Joint FAO/WHO Expert Committee on Food Additives (JECFA)

“…Human CYP enzymes involved in the formation of the 1 -hydroxy metabolite of estragole, methyl eugenol and safrole were evaluated (Jeurissen et al, 2004(Jeurissen et al, , 2005(Jeurissen et al, , 2007. Safrole was incubated either with Supersomes (baculovirus-infected insect cell microsomes that express individual human CYP enzymes to a high level) or with microsomes derived from cell lines that express individual human CYP enzymes to a lower, more typical human liver level.…”

“…Based on research performed since the late 1990s (Gardner et al, 1997a(Gardner et al, , 1997bWakazono et al, 1998;Jeurissen et al, 2004Jeurissen et al, , 2005Jeurissen et al, , 2007Ueng et al, 2004), significant induction of the CYP activation pathway is expected to successively convert alkoxy-substituted allylbenzenes into their 1 -hydroxy metabolites and sulfate conjugates. This is especially prevalent at higher dose levels in rodents.…”