title: Human keratin 8 variants promote mouse acetaminophen hepatotoxicity coupled with c-jun amino-terminal kinase activation and protein adduct formation.
abstract: Keratins 8 and 18 (K8/K18) are the intermediate filaments proteins of simple-type digestive epithelia and provide important cytoprotective function. K8/K18 variants predispose humans to chronic liver disease progression and poor outcomes in acute acetaminophen (APAP)-related liver failure. Given that K8 G62C and R341H/R341C are common K8 variants in European and North American populations, we studied their biological significance using transgenic mice. Mice that overexpress the human K8 variants, R341H or R341C, were generated and used together with previously described mice that overexpress wild-type K8 or K8 G62C. Mice were injected with 600 mg/kg of APAP or underwent bile duct ligation (BDL). Livers were evaluated by microarray analysis, quantitative real-time polymerase chain reaction, immunoblotting, histological and immunological staining, and biochemical assays. Under basal conditions, the K8 G62C/R341H/R341C variant-expressing mice did not show an obvious liver phenotype or altered keratin filament distribution, whereas K8 G62C/R341C animals had aberrant disulphide cross-linked keratins. Animals carrying the K8 variants displayed limited gene expression changes, but had lower nicotinamide N-methyl transferase (NNMT) levels and were predisposed to APAP-induced hepatotoxicity. NNMT represents a novel K8/K18-associated protein that becomes up-regulated after K8/K18 transfection. The more pronounced liver damage was accompanied by increased and prolonged JNK activation; elevated APAP protein adducts; K8 hyperphosphorylation at S74/S432 with enhanced keratin solubility; and prominent pericentral keratin network disruption. No differences in APAP serum levels, glutathione, or adenosine triphosphate levels were noted. BDL resulted in similar liver injury and biliary fibrosis in all mouse genotypes.
  
  
  CONCLUSIONS
  Expression of human K8 variants G62C, R341H, or R341C in mice predisposes to acute APAP hepatotoxicity, thereby providing direct evidence for the importance of these variants in human acute liver failure.
authors.affiliation: IZKF and Department of Internal Medicine III, University Hospital Aachen, Aachen, Germany.|Department of Internal Medicine I, University Hospital Ulm, Ulm, Germany.
authors.forename: Nurdan
authors.initials: N
authors.lastname: Guldiken
authors.affiliation: Department of Medicine, Palo Alto VA Medical Center, Palo Alto, CA.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Department of Internal Medicine I, University Hospital Ulm, Ulm, Germany.
authors.forename: Ozlem
authors.initials: O
authors.lastname: Kucukoglu
authors.affiliation: Department of Internal Medicine I, University Hospital Ulm, Ulm, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Rehm
authors.affiliation: IZKF and Department of Internal Medicine III, University Hospital Aachen, Aachen, Germany.
authors.forename: Kateryna
authors.initials: K
authors.lastname: Levada
authors.affiliation: IZKF and Department of Internal Medicine III, University Hospital Aachen, Aachen, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Gross
authors.affiliation: Department of Molecular & Integrative Physiology, University of Michigan Medical School, and the VA Ann Arbor Health Care System, Ann Arbor, MI.
authors.forename: Raymond
authors.initials: R
authors.lastname: Kwan
authors.affiliation: Arkansas Children's Hospital Research Institute and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR.
authors.forename: Laura P
authors.initials: LP
authors.lastname: James
authors.affiliation: IZKF and Department of Internal Medicine III, University Hospital Aachen, Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Trautwein
authors.affiliation: Department of Molecular & Integrative Physiology, University of Michigan Medical School, and the VA Ann Arbor Health Care System, Ann Arbor, MI.
authors.forename: M Bishr
authors.initials: MB
authors.lastname: Omary
authors.affiliation: IZKF and Department of Internal Medicine III, University Hospital Aachen, Aachen, Germany.|Department of Internal Medicine I, University Hospital Ulm, Ulm, Germany.
authors.forename: Pavel
authors.initials: P
authors.lastname: Strnad
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D005786:Gene Expression Regulation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D053533:Keratin-8 / Q000235:genetics*; D017114:Liver Failure, Acute / Q000139:chemically induced*; D051379:Mice; D008822:Mice, Transgenic; D014176:Protein Biosynthesis; D060888:Real-Time Polymerase Chain Reaction; D012680:Sensitivity and Specificity
chemical_list: C426203:KRT8 protein, human; D053533:Keratin-8; D000082:Acetaminophen; D048031:JNK Mitogen-Activated Protein Kinases