title: Differential toxic effects of azathioprine, 6-mercaptopurine and 6-thioguanine on human hepatocytes.
abstract: Thiopurines (azathioprine, 6-mercaptopurine and 6-thioguanine) are therapeutic compounds widely administered in the clinic for their multiple uses (autoimmune diseases, post-transplant immunosuppression and cancer). Despite these advantages, their therapeutic potential is limited by occasional adverse effects (myelotoxicity and hepatotoxicity) and by a relatively frequent lack of efficacy. Previous studies have demonstrated that azathioprine decreased the viability of rat hepatocytes. In order to investigate cytotoxic effects of thiopurines in human liver, we used primary human hepatocytes and a highly differentiated human hepatoma cell line, HepaRG, treated or not with azathioprine, 6-mercaptopurine and 6-thioguanine. In parallel, expression of the genes involved in the metabolism of thiopurines, glutathione synthesis and antioxidant defences was measured by quantitative PCR. We clearly demonstrate that human liver parenchymal cells were much less sensitive than rat hepatocytes to thiopurine treatments. The toxic effects appeared after 96 h of treatment while ATP depletion was observed after a 24 h incubation with azathioprine and 6-mercaptopurine. Toxic effects were more pronounced for azathioprine and 6-mercaptopurine, when compared to 6-thioguanine, and might explain glutathione synthesis and antioxidant enzyme induction only by these two drugs. Finally, we also demonstrate for the first time an up-regulation by azathioprine and 6-mercaptopurine of inosine monophosphate dehydrogenase which might have consequences on the de novo biosynthesis of guanine nucleotides and thiopurines metabolism.
authors.affiliation: INSERM U620, Université de Rennes 1, 2 Avenue du Professeur Leon Bernard, 35043 Rennes, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Petit
authors.forename: Sophie
authors.initials: S
authors.lastname: Langouet
authors.forename: Hanane
authors.initials: H
authors.lastname: Akhdar
authors.forename: Christophe
authors.initials: C
authors.lastname: Nicolas-Nicolaz
authors.forename: André
authors.initials: A
authors.lastname: Guillouzo
authors.forename: Fabrice
authors.initials: F
authors.lastname: Morel
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000633:toxicity*; D001379:Azathioprine / Q000633:toxicity*; D005434:Flow Cytometry; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007168:IMP Dehydrogenase / Q000378:metabolism; D015122:Mercaptopurine / Q000633:toxicity*; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013866:Thioguanine / Q000633:toxicity*
chemical_list: D000964:Antimetabolites, Antineoplastic; D012334:RNA, Neoplasm; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D015122:Mercaptopurine; D007168:IMP Dehydrogenase; D013866:Thioguanine; D001379:Azathioprine