title: Human hepatocytes support the hypertrophic but not the hyperplastic response to the murine nongenotoxic hepatocarcinogen sodium phenobarbital in an in vivo study using a chimeric mouse with humanized liver.
abstract: High doses of sodium phenobarbital (NaPB), a constitutive androstane receptor (CAR) activator, have been shown to produce hepatocellular tumors in rodents by a mitogenic mode of action (MOA) involving CAR activation. The effect of 1-week dietary treatment with NaPB on liver weight and histopathology, hepatic CYP2B enzyme activity and CYP2B/3A mRNA expression, replicative DNA synthesis and selected genes related to cell proliferation, and functional transcriptomic and metabolomic analyses was studied in male CD-1 mice, Wistar Hannover (WH) rats, and chimeric mice with human hepatocytes. The treatment of chimeric mice with 1000-1500-ppm NaPB resulted in plasma levels around 3-5-fold higher than those observed in human subjects given therapeutic doses of NaPB. NaPB produced dose-dependent increases in hepatic CYP2B activity and CYP2B/3A mRNA levels in all animal models. Integrated functional metabolomic and transcriptomic analyses demonstrated that the responses to NaPB in the human liver were clearly different from those in rodents. Although NaPB produced a dose-dependent increase in hepatocyte replicative DNA synthesis in CD-1 mice and WH rats, no increase in replicative DNA synthesis was observed in human hepatocyte-originated areas of chimeric mice. In addition, treatment with NaPB had no effect on Ki-67, PCNA, GADD45β, and MDM2 mRNA expression in chimeric mice, whereas significant increases were observed in CD-1 mice and/or WH rats. However, increases in hepatocyte replicative DNA synthesis were observed in chimeric mice both in vivo and in vitro after treatment epidermal growth factor. Thus, although NaPB could activate CAR in both rodent and human hepatocytes, NaPB did not increase replicative DNA synthesis in human hepatocytes of chimeric mice, whereas it was mitogenic to rat and mouse hepatocytes. As human hepatocytes are refractory to the mitogenic effects of NaPB, the MOA for NaPB-induced rodent liver tumor formation is thus not relevant for humans.
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan yamadat8@sc.sumitomo-chem.co.jp.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Okuda
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kushida
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Sumida
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Takeuchi
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Nagahori
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Fukuda
authors.affiliation: Centre for Toxicology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Lake
authors.affiliation: Department of Pathology and Microbiology, Havlik-Wall Professor of Oncology, University of Nebraska Medical Center, 983135 Nebraska Medical Center, Omaha, Nebraska 68198-3135, USA.
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Cohen
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kawamura
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002678:Chimera; D000090702:Constitutive Androstane Receptor; D065702:Cytochrome P-450 CYP2B6 / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D020869:Gene Expression Profiling; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced* / Q000201:enzymology / Q000473:pathology; D008297:Male; D008815:Mice, Inbred Strains; D009929:Organ Size / Q000187:drug effects; D010634:Phenobarbital / Q000493:pharmacokinetics / Q000633:toxicity*; D011919:Rats, Inbred Strains; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013045:Species Specificity; D059467:Transcriptome / Q000187:drug effects
chemical_list: D000090702:Constitutive Androstane Receptor; D018160:Receptors, Cytoplasmic and Nuclear; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D010634:Phenobarbital
keywords: cell proliferation; cytochrome P450; human risk assessment; humanized mice; liver tumors; mode of action; sodium phenobarbital