Exposure of the Human HepaRG Liver Cell Line to Pyrrolizidine Alkaloids Results in a Gene Expression Profile Characteristic for Genotoxic Carcinogens

Samenvatting

Pyrrolizidine alkaloids (PAs) are secondary metabolites found in many
plant species and can be present as contaminants in food, herbal teas,
plant food supplements, and animal feed. A large number of PAs are toxic
not only to livestock and wildlife but also to humans. Hepatotoxicity,
genotoxicity, and carcinogenicity are the main toxicities observed in
experimental animals treated with PAs. However, there is little direct
evidence for mutagenicity and carcinogenicity of PAs in humans and epidemiological data are lacking. The present study aimed to contribute to
a better evaluation of the genotoxic and carcinogenic risks of PAs for humans.
To that end, the human hepatoma cell line HepaRG was exposed
in vitro for 72 hours to six PAs (riddelliine, retrorsine, echimidine, monocrotaline, lasiocarpine, senkirkine), and the genotoxic carcinogen benzo[
a]pyrene, the non-genotoxic carcinogen bis(2-ethylhexyl) phthalate,
and the non-carcinogen mannitol as controls. Upon exposure, RNA was
isolated and effects on whole genome mRNA expression were analysed
using DNA microarrays. Pathway analysis showed that several processes
involved in genotoxicity, including DNA damage response, p53 pathway
and cell cycle checkpoints, were modulated by the PAs. Comparison of
the array data with transcriptome data obtained by others upon exposure
of HepaRG to various model hepatocarcinogens showed that each
of the PAs used in the present study generated a gene expression profile
that is characteristic for genotoxic carcinogens.