title: p21 ablation in liver enhances DNA damage, cholestasis, and carcinogenesis.
abstract: Genetic mouse studies suggest that the NF-κB pathway regulator NEMO (also known as IKKγ) controls chronic inflammation and carcinogenesis in the liver. However, the molecular mechanisms explaining the function of NEMO are not well defined. Here, we report that overexpression of the cell-cycle regulator p21 is a critical feature of liver inflammation and carcinogenesis caused by the loss of NEMO. NEMO(Δhepa) mice develop chronic hepatitis characterized by increased hepatocyte apoptosis and proliferation that causes the development of fibrosis and hepatocellular carcinoma (HCC), similar to the situation in human liver disease. Having identified p21 overexpression in this model, we evaluated its role in disease progression and LPS-mediated liver injury in double mutant NEMO(Δhepa)/p21(-/-) mice. Eight-week-old NEMO(Δhepa)/p21(-/-) animals displayed accelerated liver damage that was not associated with alterations in cell-cycle progression or the inflammatory response. However, livers from NEMO(Δhepa)/p21(-/-) mice displayed more severe DNA damage that was further characterized by LPS administration correlating with higher lethality of the animals. This phenotype was attenuated by genetic ablation of the TNF receptor TNF-R1 in NEMO(Δhepa)/p21(-/-) mice, demonstrating that DNA damage is induced via TNF. One-year-old NEMO(Δhepa)/p21(-/-) mice displayed greater numbers of HCC and severe cholestasis compared with NEMO(Δhepa) animals. Therefore, p21 overexpression in NEMO(Δhepa) animals protects against DNA damage, acceleration of hepatocarcinogenesis, and cholestasis. Taken together, our findings illustrate how loss of NEMO promotes chronic liver inflammation and carcinogenesis, and they identify a novel protective role for p21 against the generation of DNA damage.
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Haksier
authors.initials: H
authors.lastname: Ehedego
authors.affiliation: Nutrition, Metabolism and Genomics group, Division of Human Nutrition, Wageningen University, Wageningen, the Netherlands.
authors.forename: Mark V
authors.initials: MV
authors.lastname: Boekschoten
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.affiliation: Institute of Pathology, Medical University of Graz, Graz, Austria.
authors.forename: Carina
authors.initials: C
authors.lastname: Doler
authors.affiliation: Institute of Pathology, Medical University of Graz, Graz, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Haybaeck
authors.affiliation: Institute of Pathology, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Gaβler
authors.affiliation: Nutrition, Metabolism and Genomics group, Division of Human Nutrition, Wageningen University, Wageningen, the Netherlands.
authors.forename: Michael
authors.initials: M
authors.lastname: Müller
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Liedtke
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany. ctrautwein@ukaachen.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Trautwein
mesh_terms: D000818:Animals; D002779:Cholestasis / Q000209:etiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D004249:DNA Damage; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000378:metabolism; D053539:Keratin-19 / Q000032:analysis; D008070:Lipopolysaccharides / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D053539:Keratin-19; D008070:Lipopolysaccharides; C514981:NEMO protein, mouse