Proapoptotic effects of long-chain vitamin E metabolites in HepG2 cells are mediated by oxidative stress.
Although the metabolism of vitamin E has been extensively studied in cell culture, animals, and humans, biochemical analyses of intermediate metabolites are scarce. We here describe the synthesis and proapoptotic properties of long-chain metabolites of α- and δ-tocopherol. Several long-chain vitamin E metabolites, namely 13'-hydroxy- and 13'-carboxychromanols, were synthesized from garcinoic acid, a δ-tocotrienol derivative extracted from the African bitter nut Garcinia kola. Both α- and δ-13'-carboxychromanol induced cell death in HepG2 cells at EC(50) of 13.5 and 6.5 μM, respectively. Apoptosis was quantified by annexin V/7-AAD staining and flow cytometry analysis. By immunoblot analyses, we observed activation of both caspase-3 and caspase-9 as well as PARP-1 cleavage. Parameters of mitochondrial dysfunction including reduced mitochondrial membrane potential and increased intracellular and intramitochondrial reactive oxygen species formation were observed after metabolite treatment. Last, long-chain hydroxychromanols were readily metabolized to the corresponding carboxychromanols in HepG2 cells. Taken together, these results indicate that long-chain metabolites may be responsible for antiproliferative properties of vitamin E vitamers.
Birringer
Marc
M
Department of Human Nutrition, Institute of Nutrition, Friedrich-Schiller-University of Jena, Jena, Germany. marc.birringer@uni-jena.de
Lington
Dennis
D
Vertuani
Silvia
S
Manfredini
Stefano
S
Scharlau
Daniel
D
Glei
Michael
M
Ristow
Michael
M
D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000138:chemical synthesis / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D029763:Garcinia kola / Q000378:metabolism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012639:Seeds; D014810:Vitamin E / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*
D001578:Benzopyrans; D017382:Reactive Oxygen Species; C473370:garcinoic acid; D014810:Vitamin E; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D053453:Caspase 9