101. Estragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cells
- Author
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Dieter Schrenk, Adam D. Thomas, Ruth Schulte-Hubbert, and Jan-Heiner Küpper
- Subjects
0301 basic medicine ,Male ,Allylbenzene Derivatives ,Anisoles ,Toxicology ,medicine.disease_cause ,Adduct ,Hydroxylation ,03 medical and health sciences ,chemistry.chemical_compound ,DNA Adducts ,0302 clinical medicine ,Cytochrome P-450 CYP1A2 ,DNA adduct ,medicine ,carcinogenicity ,Animals ,Humans ,Rats, Wistar ,Carcinogen ,Cells, Cultured ,Estragole ,Micronucleus Tests ,genotoxicity ,CYP1A2 ,hepatoma ,Molecular biology ,030104 developmental biology ,chemistry ,Micronucleus test ,Carcinogens ,Hepatocytes ,liver cells ,030217 neurology & neurosurgery ,Genotoxicity - Abstract
Estragole is a natural constituent in herbs and spices and in products thereof such as essential oils or herbal teas. After cytochrome P450-catalyzed hydroxylation and subsequent sulfation, estragole acts as a genotoxic hepatocarcinogen forming DNA adducts in rodent liver. Because of the genotoxic mode of action and the widespread occurrence in food and phytomedicines a refined risk assessment for estragole is needed. We analyzed the time- and concentration-dependent levels of the DNA adducts N2-(isoestragole-3'-yl)-2'-desoxyguanosine (E3'N2dG) and N6-(isoestragole-3'-yl)-desoxyadenosine (E3'N6dA), reported to be the major adducts formed in rat liver, in rat hepatocytes (pRH) in primary culture after incubation with estragole. DNA adduct levels were measured via UHPLC-ESI-MS/MS using stable isotope dilution analysis. Both adducts were formed in pRH and could already be quantified after an incubation time of 1 h (E3'N6dA at 10 μM, E3'N2dG at 1μM estragole). E3'N2dG, the main adduct at all incubation times and concentrations, could be detected at estragole concentrations < 0.1 μM after 24 h and < 0.5 μM after 48 h. Adduct levels were highest after 6 h and showed a downward trend at later time-points, possibly due to DNA repair and/or apoptosis. While the concentration-response characteristics of adduct formation were apparently linear over the whole concentration range, strong indication for marked hypo-linearity was obtained when the modeling was based on concentrations < 1 μM only. In the micronucleus assay no mutagenic potential of estragole was found in HepG2 cells whereas in HepG2-CYP1A2 cells 1 μM estragole led to a 3.2 fold and 300 μM to a 7.1 fold increase in micronuclei counts. Our findings suggest the existence of a 'practical threshold' dose for DNA adduct formation as an initiating key event of the carcinogenicity of estragole indicating that the default assumption of concentration-response-linearity is questionable, at least for the two major adducts studied here.
- Published
- 2020