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Sensitization of Human Liver Cells Toward Fas‐Mediated Apoptosis by the Metabolically Activated Pyrrolizidine Alkaloid Lasiocarpine
Author(s) -
Ebmeyer Johanna,
Franz Luise,
Lim Ramonique,
Niemann Birgit,
Glatt Hansruedi,
Braeuning Albert,
Lampen Alfonso,
HesselPras Stefanie
Publication year - 2019
Publication title -
molecular nutrition and food research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.495
H-Index - 131
eISSN - 1613-4133
pISSN - 1613-4125
DOI - 10.1002/mnfr.201801206
Subject(s) - apoptosis , fas ligand , biology , fas receptor , pyrrolizidine , microbiology and biotechnology , cell culture , viability assay , flow cytometry , receptor , cell , biochemistry , programmed cell death , chemistry , botany , genetics
Scope Pyrrolizidine alkaloids (PAs) are common phytotoxins. Intoxication can lead to liver damage. Previous studies showed PA‐induced apoptosis in liver cells. However, the exact role of the extrinsic apoptotic pathway has not been investigated yet. This study aims to analyze whether the PA representative lasiocarpine sensitizes human liver cells toward extrinsic Fas‐mediated apoptosis. Methods and results HepG2 cells with limited xenobiotic metabolic activity are used to analyze metabolism‐dependent effects. External in vitro metabolism is simulated using rat or human liver enzymes. Additionally, metabolically competent HepaRG cells are used to confirm the observed effects in a human liver cell system with internal xenobiotic metabolism. Metabolized lasiocarpine decreases cell viability and induces Fas receptor gene expression in both cell lines. Increased Fas receptor protein expression on the cell surface is demonstrated by flow cytometry. The addition of a Fas ligand–simulating antibody induces apoptosis. Induction of extrinsic Fas‐mediated apoptosis is verified by Western blotting for cleaved caspase 8, the initiator caspase of extrinsic apoptosis. All effects are dependent on lasiocarpine metabolism. Conclusion The results demonstrate that metabolically metabolized lasiocarpine sensitizes human liver cells toward Fas‐mediated apoptosis. They broaden our knowledge on the hepatotoxic molecular mechanisms of PA as widely distributed food contaminants.