title: Impaired mitochondrial function in HepG2 cells treated with hydroxy-cobalamin[c-lactam]: A cell model for idiosyncratic toxicity.
abstract: The vitamin B12 analog hydroxy-cobalamin[c-lactam] (HCCL) impairs mitochondrial protein synthesis and the function of the electron transport chain. Our goal was to establish an in vitro model for mitochondrial dysfunction in human hepatoma cells (HepG2), which can be used to investigate hepatotoxicity of idiosyncratic mitochondrial toxicants. For that, HepG2 cells were treated with HCCL, which inhibits the function of methylmalonyl-CoA mutase and impairs mitochondrial protein synthesis. Secondary, cells were incubated with propionate that served as source of propionyl-CoA, a percursor of methylmalonyl-CoA. Dose-finding experiments were conducted to evaluate the optimal dose and treatment time of HCCL and propionate for experiments on mitochondrial function. 50 μM HCCL was cytotoxic after exposure of HepG2 cells for 2d and 10 and 50 μM HCCL enhanced the cytotoxicity of 100 or 1000 μM propionate. Co-treatment with HCCL (10 μM) and propionate (1000 μM) dissipated the mitochondrial membrane potential and impaired the activity of enzyme complex IV of the electron transport chain. Treatment with HCCL decreased the mRNA content of mitochondrially encoded proteins, whereas the mtDNA content remained unchanged. We observed mitochondrial ROS accumulation and decreased mitochondrial SOD2 expression. Moreover, electron microscopy showed mitochondrial swelling. Finally, HepG2 cells pretreated with a non-cytotoxic combination of HCCL (10 μM) and propionate (100 μM) were more sensitive to the mitochondrial toxicants dronedarone, benzbromarone, and ketoconazole than untreated cells. In conclusion, we established and characterized a cell model, which could be used for testing drugs with idiosyncratic mitochondrial toxicity.
authors.affiliation: Division of Clinical Pharmacology & Toxicology, University Hospital, 4031 Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Haegler
authors.affiliation: Division of Clinical Pharmacology & Toxicology, University Hospital, 4031 Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Grünig
authors.affiliation: Division of Clinical Pharmacology & Toxicology, University Hospital, 4031 Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Berger
authors.affiliation: Division of Clinical Pharmacology & Toxicology, University Hospital, 4031 Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland; Swiss Centre of Applied Human Toxicology, SCAHT, Switzerland. Electronic address: kraehenbuehl@ubs.ch.
authors.forename: Stephan
authors.initials: S
authors.lastname: Krähenbühl
authors.affiliation: Division of Clinical Pharmacology & Toxicology, University Hospital, 4031 Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland; Swiss Centre of Applied Human Toxicology, SCAHT, Switzerland.
authors.forename: Jamal
authors.initials: J
authors.lastname: Bouitbir
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D004272:DNA, Mitochondrial / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport / Q000187:drug effects; D056945:Hep G2 Cells / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008765:Methylmalonyl-CoA Mutase / Q000037:antagonists & inhibitors / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000187:drug effects; D008954:Models, Biological; D060888:Real-Time Polymerase Chain Reaction; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; C071541:hydroxycobalamin(c-lactam); D000255:Adenosine Triphosphate; D008765:Methylmalonyl-CoA Mutase; D014805:Vitamin B 12
keywords: Hydroxy-cobalamin[c-lactam]; Idiosyncratic hepatotoxicity; Mitochondrial toxicity; Vitamin B12 deficiency