1
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Tzouanas CN, Sherman MS, Shay JE, Rubin AJ, Mead BE, Dao TT, Butzlaff T, Mana MD, Kolb KE, Walesky C, Pepe-Mooney BJ, Smith CJ, Prakadan SM, Ramseier ML, Tong EY, Joung J, Chi F, McMahon-Skates T, Winston CL, Jeong WJ, Aney KJ, Chen E, Nissim S, Zhang F, Deshpande V, Lauer GM, Yilmaz ÖH, Goessling W, Shalek AK. Chronic metabolic stress drives developmental programs and loss of tissue functions in non-transformed liver that mirror tumor states and stratify survival. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569407. [PMID: 38077056 PMCID: PMC10705501 DOI: 10.1101/2023.11.30.569407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Under chronic stress, cells must balance competing demands between cellular survival and tissue function. In metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD/NASH), hepatocytes cooperate with structural and immune cells to perform crucial metabolic, synthetic, and detoxification functions despite nutrient imbalances. While prior work has emphasized stress-induced drivers of cell death, the dynamic adaptations of surviving cells and their functional repercussions remain unclear. Namely, we do not know which pathways and programs define cellular responses, what regulatory factors mediate (mal)adaptations, and how this aberrant activity connects to tissue-scale dysfunction and long-term disease outcomes. Here, by applying longitudinal single-cell multi -omics to a mouse model of chronic metabolic stress and extending to human cohorts, we show that stress drives survival-linked tradeoffs and metabolic rewiring, manifesting as shifts towards development-associated states in non-transformed hepatocytes with accompanying decreases in their professional functionality. Diet-induced adaptations occur significantly prior to tumorigenesis but parallel tumorigenesis-induced phenotypes and predict worsened human cancer survival. Through the development of a multi -omic computational gene regulatory inference framework and human in vitro and mouse in vivo genetic perturbations, we validate transcriptional (RELB, SOX4) and metabolic (HMGCS2) mediators that co-regulate and couple the balance between developmental state and hepatocyte functional identity programming. Our work defines cellular features of liver adaptation to chronic stress as well as their links to long-term disease outcomes and cancer hallmarks, unifying diverse axes of cellular dysfunction around core causal mechanisms.
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Affiliation(s)
- Constantine N. Tzouanas
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
- These authors contributed equally
| | - Marc S. Sherman
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Division of Gastroenterology, Massachusetts General Hospital, Boston, Massachusetts, USA
- These authors contributed equally
| | - Jessica E.S. Shay
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Alcohol Liver Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- These authors contributed equally
| | - Adam J. Rubin
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Benjamin E. Mead
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tyler T. Dao
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Titus Butzlaff
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Miyeko D. Mana
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Kellie E. Kolb
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Chad Walesky
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Brian J. Pepe-Mooney
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Division of Gastroenterology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Colton J. Smith
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Sanjay M. Prakadan
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michelle L. Ramseier
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Evelyn Y. Tong
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Julia Joung
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Brain and Cognitive Science, MA, Cambridge, MA, USA
- McGovern Institute for Brain Research at MIT, Cambridge, MA, USA
- Howard Hughes Medical Institute, MIT, Cambridge, MA, USA
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Fangtao Chi
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
| | - Thomas McMahon-Skates
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Carolyn L. Winston
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Woo-Jeong Jeong
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
| | - Katherine J. Aney
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
| | - Ethan Chen
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
| | - Sahar Nissim
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
- Gastroenterology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Feng Zhang
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Brain and Cognitive Science, MA, Cambridge, MA, USA
- McGovern Institute for Brain Research at MIT, Cambridge, MA, USA
- Howard Hughes Medical Institute, MIT, Cambridge, MA, USA
| | - Vikram Deshpande
- Department of Pathology, Massachusetts General Hospital, Boston, MA
| | - Georg M. Lauer
- Division of Gastroenterology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Ömer H. Yilmaz
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Pathology, Massachusetts General Hospital, Boston, MA
- These senior authors contributed equally
| | - Wolfram Goessling
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Genetics Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Division of Gastroenterology, Massachusetts General Hospital, Boston, Massachusetts, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
- Harvard Stem Cell Institute, Cambridge, MA, USA
- Developmental and Regenerative Biology Program, Harvard Medical School, Boston, MA, USA
- These senior authors contributed equally
| | - Alex K. Shalek
- Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard-MIT Program in Health Sciences and Technology, Harvard Medical School, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
- These senior authors contributed equally
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Wong W, Crane ED, Zhang H, Li J, Day TA, Green AE, Menzies KJ, Crane JD. Pgc-1α controls epidermal stem cell fate and skin repair by sustaining NAD + homeostasis during aging. Mol Metab 2022; 65:101575. [PMID: 35987498 PMCID: PMC9463389 DOI: 10.1016/j.molmet.2022.101575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 07/30/2022] [Accepted: 08/11/2022] [Indexed: 10/31/2022] Open
Abstract
OBJECTIVE The epidermal barrier is renewed by the activation, proliferation, and differentiation of keratinocyte stem cells after injury and aging impedes this repair process through undefined mechanisms. We previously identified a gene signature of metabolic dysfunction in aged murine epidermis, but the precise regulators of epidermal repair and age-related growth defects are not well established. Aged mouse models as well as mice with conditional epidermal loss of the metabolic regulator, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (Pgc-1α) were used to explore the cellular pathways which control skin repair after injury and stress. METHODS Aged mice or those with epidermal Pgc-1α deletion (epiPgc-1α KO) and young or Pgc1afl/fl controls were subjected to wound injury, UVB exposure or the inflammatory agent TPA. In vivo and ex vivo analyses of wound closure, skin structure, cell growth and stem cell differentiation were used to understand changes in epidermal re-growth and repair resulting from aging or Pgc-1α loss. RESULTS Aging impairs epidermal re-growth during wound healing and results in lower expression of Pgc-1α. Mice with conditional deletion of epidermal Pgc-1α exhibit greater inflammation- and UVB-induced cell differentiation, reduced proliferation, and slower wound healing. epiPgc-1α KO mice also displayed reduced keratinocyte NAD+ levels, shorter telomeres, and greater poly ADP-ribosylation, resulting in enhanced stress-stimulated p53 and p21 signaling. When NAD+ was reduced by Pgc-1α loss or pharmacologic inhibition of NAD+ synthesis, there was reduced stress-induced proliferation, increased differentiation, and protection against DNA damage via enhanced epidermal shedding. Similarly, aged mice exhibit disrupted epidermal NAD+ homeostasis and enhanced p53 activation, resulting in p21 growth arrest after wounding. NAD+ precursor treatment restores epidermal growth from old skin to that of young. CONCLUSIONS Our studies identify a novel role for epidermal Pgc-1α in controlling epidermal repair via its regulation of cellular NAD+ and downstream effects on p53-driven growth arrest. We also establish that parallel mechanisms are evident in aged epidermis, showing that NAD+ signaling is an important controller of physiologic skin repair and that dysfunction of this pathway contributes to age-related wound repair defects.
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Affiliation(s)
- Wesley Wong
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Elizabeth D Crane
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Hui Zhang
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Jiahe Li
- Department of Bioengineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Tovah A Day
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Alex E Green
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Canada
| | - Keir J Menzies
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Canada
| | - Justin D Crane
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
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3
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Ferreira-Gonzalez S, Rodrigo-Torres D, Gadd VL, Forbes SJ. Cellular Senescence in Liver Disease and Regeneration. Semin Liver Dis 2021; 41:50-66. [PMID: 33764485 DOI: 10.1055/s-0040-1722262] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cellular senescence is an irreversible cell cycle arrest implemented by the cell as a result of stressful insults. Characterized by phenotypic alterations, including secretome changes and genomic instability, senescence is capable of exerting both detrimental and beneficial processes. Accumulating evidence has shown that cellular senescence plays a relevant role in the occurrence and development of liver disease, as a mechanism to contain damage and promote regeneration, but also characterizing the onset and correlating with the extent of damage. The evidence of senescent mechanisms acting on the cell populations of the liver will be described including the role of markers to detect cellular senescence. Overall, this review intends to summarize the role of senescence in liver homeostasis, injury, disease, and regeneration.
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Affiliation(s)
| | - Daniel Rodrigo-Torres
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Victoria L Gadd
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Stuart J Forbes
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, United Kingdom
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4
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Ritschka B, Knauer-Meyer T, Gonçalves DS, Mas A, Plassat JL, Durik M, Jacobs H, Pedone E, Di Vicino U, Cosma MP, Keyes WM. The senotherapeutic drug ABT-737 disrupts aberrant p21 expression to restore liver regeneration in adult mice. Genes Dev 2020; 34:489-494. [PMID: 32139422 PMCID: PMC7111259 DOI: 10.1101/gad.332643.119] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 02/04/2020] [Indexed: 12/15/2022]
Abstract
In this study, Ritschka et al. investigated whether cellular senescence might play a role in loss of regenerative capacity during liver regeneration. They show that following partial hepatectomy, the senescence-associated genes p21, p16Ink4a, and p19Arf become dynamically expressed in different cell types when regenerative capacity decreases, but without a full senescent response, and that treatment with a senescence-inhibiting drug improves regeneration through targeting aberrantly prolonged p21 expression. Young mammals possess a limited regenerative capacity in some tissues, which is lost upon maturation. We investigated whether cellular senescence might play a role in such loss during liver regeneration. We found that following partial hepatectomy, the senescence-associated genes p21, p16Ink4a, and p19Arf become dynamically expressed in different cell types when regenerative capacity decreases, but without a full senescent response. However, we show that treatment with a senescence-inhibiting drug improves regeneration, by disrupting aberrantly prolonged p21 expression. This work suggests that senescence may initially develop from heterogeneous cellular responses, and that senotherapeutic drugs might be useful in promoting organ regeneration.
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Affiliation(s)
- Birgit Ritschka
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France.,Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain
| | - Tania Knauer-Meyer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France
| | - Daniel Sampaio Gonçalves
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France
| | - Alba Mas
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France.,Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain
| | - Jean-Luc Plassat
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France
| | - Matej Durik
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France
| | - Hugues Jacobs
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France
| | - Elisa Pedone
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain
| | - Umberto Di Vicino
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain
| | - Maria Pia Cosma
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain.,Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain.,Institución Catalana de Investigación y Estudios Avanzados (ICREA), Barcelona 08010, Spain
| | - William M Keyes
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch 67404, France.,UMR7104, Centre National de la Recherche Scientifique (CNRS), Illkirch 67404, France.,U1258, Institut National de la Santé et de la Recherche Médicale (INSERM), Illkirch 67404, France.,Université de Strasbourg, Illkirch 67404, France.,Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain.,Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain
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5
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Schulze S, Stöß C, Lu M, Wang B, Laschinger M, Steiger K, Altmayr F, Friess H, Hartmann D, Holzmann B, Hüser N. Cytosolic nucleic acid sensors of the innate immune system promote liver regeneration after partial hepatectomy. Sci Rep 2018; 8:12271. [PMID: 30115978 PMCID: PMC6095902 DOI: 10.1038/s41598-018-29924-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 07/20/2018] [Indexed: 12/19/2022] Open
Abstract
Stimulation of cytosolic nucleic acid sensors of innate immunity by pathogen-derived nucleic acids is important for antimicrobial defence, but stimulation through self-derived nucleic acids may contribute to autoinflammation and cancer. DNA sensing in the cytosol requires the stimulator of interferon genes (STING), while cytosolic RNA sensors use mitochondrial antiviral-signalling protein (MAVS). In a murine model of two-thirds hepatectomy, combined deficiency of MAVS and STING resulted in strongly impaired hepatocyte proliferation and delayed recovery of liver mass. Whereas lack of MAVS and STING did not influence upregulation of the G1-phase cyclins D1 and E1, it substantially reduced the hyperphosphorylation of retinoblastoma protein, attenuated the activation of cyclin-dependent kinase (CDK)-2, delayed upregulation of CDK1 and cyclins A2 and B1, and impaired S-phase entry of hepatocytes. Mechanistically, lack of cytosolic nucleic acid sensors strongly upregulated the anti-proliferative mediators TGF-β2 and activin A, which was associated with an increased expression of the cell cycle inhibitors p15 and p21. Partial hepatectomy was followed by the release of exosomes with abundant nucleic acid cargo, which may provide ligands for the MAVS and STING pathways. Together, these findings identify a previously unrecognised function of cytosolic nucleic acid sensors of innate immunity for promoting liver regeneration.
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Affiliation(s)
- Sarah Schulze
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Christian Stöß
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Miao Lu
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Baocai Wang
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Melanie Laschinger
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Katja Steiger
- Technical University of Munich, School of Medicine, Comparative Experimental Pathology, Institute of Pathology, Trogerstr. 18, 81675, Munich, Germany
| | - Felicitas Altmayr
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Helmut Friess
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Daniel Hartmann
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
| | - Bernhard Holzmann
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany.
| | - Norbert Hüser
- Technical University of Munich, School of Medicine, Department of Surgery, Ismaninger Str. 22, 81675, Munich, Germany
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6
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Heber-Katz E. Oxygen, Metabolism, and Regeneration: Lessons from Mice. Trends Mol Med 2017; 23:1024-1036. [PMID: 28988849 DOI: 10.1016/j.molmed.2017.08.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/05/2017] [Accepted: 08/20/2017] [Indexed: 12/12/2022]
Abstract
The discovery that the Murphy Roths Large (MRL) mouse strain is a fully competent, epimorphic tissue regenerator, proved that the machinery of regeneration was preserved through evolution from hydra, to salamanders, to mammals. Such concepts have allowed translation of the biology of amphibians, and their ability to regenerate, to a mammalian context. We identified the ancient hypoxia-inducible factor (HIF)-1α pathway, operating through prolyl hydroxylase domain proteins (PHDs), as a central player in mouse regeneration. Thus, the possibility of targeting PHDs or other HIF-1α modifiers to effectively recreate the amphibian regenerative state has emerged. We posit that these regenerative pathways are critical in mammals. Moreover, the current approved use of PHD inhibitors in the clinic should allow fast-track translation from mouse studies to drug-based regenerative therapy in humans.
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Affiliation(s)
- Ellen Heber-Katz
- Laboratory of Regenerative Medicine, Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA.
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7
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Liu M, Chen P. Proliferation‑inhibiting pathways in liver regeneration (Review). Mol Med Rep 2017; 16:23-35. [PMID: 28534998 DOI: 10.3892/mmr.2017.6613] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 03/13/2017] [Indexed: 12/14/2022] Open
Abstract
Liver regeneration, an orchestrated process, is the primary compensatory mechanism following liver injury caused by various factors. The process of liver regeneration consists of three stages: Initiation, proliferation and termination. Proliferation‑promoting factors, which stimulate the recovery of mitosis in quiescent hepatocytes, are essential in the initiation and proliferation steps of liver regeneration. Proliferation‑promoting factors act as the 'motor' of liver regeneration, whereas proliferation inhibitors arrest cell proliferation when the remnant liver reaches a suitable size. Certain proliferation inhibitors are also expressed and activated in the first two steps of liver regeneration. Anti‑proliferation factors, acting as a 'brake', control the speed of proliferation and determine the terminal point of liver regeneration. Furthermore, anti‑proliferation factors function as a 'steering‑wheel', ensuring that the regeneration process proceeds in the right direction by preventing proliferation in the wrong direction, as occurs in oncogenesis. Therefore, proliferation inhibitors to ensure safe and stable liver regeneration are as important as proliferation‑promoting factors. Cytokines, including transforming growth factor‑β and interleukin‑1, and tumor suppressor genes, including p53 and p21, are important members of the proliferation inhibitor family in liver regeneration. Certain anti‑proliferation factors are involved in the process of gene expression and protein modification. The suppression of liver regeneration led by metabolism, hormone activity and pathological performance have been reviewed previously. However, less is known regarding the proliferation inhibitors of liver regeneration and further investigations are required. Detailed information regarding the majority of known anti‑proliferation signaling pathways also remains fragmented. The present review aimed to understand the signalling pathways that inhbit proliferation in the process of liver regeneration.
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Affiliation(s)
- Menggang Liu
- Department of Hepatobiliary Surgery, Daping Hospital, The Third Military Medical University, Chongqing 400042, P.R. China
| | - Ping Chen
- Department of Hepatobiliary Surgery, Daping Hospital, The Third Military Medical University, Chongqing 400042, P.R. China
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8
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Dadhania VP, Bhushan B, Apte U, Mehendale HM. Wnt/β-Catenin Signaling Drives Thioacetamide-Mediated Heteroprotection Against Acetaminophen-Induced Lethal Liver Injury. Dose Response 2017; 15:1559325817690287. [PMID: 28210203 PMCID: PMC5302098 DOI: 10.1177/1559325817690287] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Preplacement of compensatory tissue repair (CTR) by exposure to a nonlethal dose of a toxicant protects animals against a lethal dose of another toxicant. Although CTR is known to heteroprotect, the underlying molecular mechanisms are not completely known. Here, we investigated the mechanisms of heteroprotection using thioacetamide (TA): acetaminophen (APAP) heteroprotection model. Male Swiss Webster mice received a low dose of TA or distilled water (DW) vehicle 24 hours prior to a lethal dose of APAP. Liver injury, tissue repair, and promitogenic signaling were studied over a time course of 24 hours after APAP overdose to the TA- and DW-primed mice (TA + APAP and DW + APAP, respectively). Thioacetamide pretreatment afforded 100% protection against APAP overdose compared to 100% lethality in the DW + APAP-treated mice. Although hepatic Cyp2e1 was similar at the time of APAP administration, immediate activation of hepatic c-Jun N-terminal kinases (JNK) was observed in the TA + APAP-treated mice compared to its delayed activation in the DW + APAP group. In contrast to the DW + APAP group, the TA + APAP-treated mice exhibited extensive CTR, which was secondary to the timely activation of Wnt/β-catenin pathway. Our data indicate that rapid activation and appropriate termination of Wnt/β-catenin signaling and modulation of JNK activity underlie TA + APAP heteroprotection.
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Affiliation(s)
- Vivekkumar P Dadhania
- Department of Toxicology, College of Health & Pharmaceutical Sciences, The University of Louisiana at Monroe (ULM), Monroe, LA, USA
| | - Bharat Bhushan
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center (KUMC), Kansas City, KS, USA
| | - Udayan Apte
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center (KUMC), Kansas City, KS, USA
| | - Harihara M Mehendale
- Department of Toxicology, College of Health & Pharmaceutical Sciences, The University of Louisiana at Monroe (ULM), Monroe, LA, USA
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9
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Charni M, Aloni-Grinstein R, Molchadsky A, Rotter V. p53 on the crossroad between regeneration and cancer. Cell Death Differ 2016; 24:8-14. [PMID: 27768121 PMCID: PMC5260496 DOI: 10.1038/cdd.2016.117] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 09/18/2016] [Accepted: 09/19/2016] [Indexed: 12/19/2022] Open
Abstract
Regeneration and tumorigenesis share common molecular pathways, nevertheless the outcome of regeneration is life, whereas tumorigenesis leads to death. Although the process of regeneration is strictly controlled, malignant transformation is unrestrained. In this review, we discuss the involvement of TP53, the major tumor-suppressor gene, in the regeneration process. We point to the role of p53 as coordinator assuring that regeneration will not shift to carcinogenesis. The fluctuation in p53 activity during the regeneration process permits a tight control. On one hand, its inhibition at the initial stages allows massive proliferation, on the other its induction at advanced steps of regeneration is essential for preservation of robustness and fidelity of the regeneration process. A better understanding of the role of p53 in regulation of regeneration may open new opportunities for implementation of TP53-based therapies, currently available for cancer patients, in regenerative medicine.
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Affiliation(s)
- Meital Charni
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Ronit Aloni-Grinstein
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Alina Molchadsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Varda Rotter
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
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10
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Chen JL, Walton KL, Qian H, Colgan TD, Hagg A, Watt MJ, Harrison CA, Gregorevic P. Differential Effects of IL6 and Activin A in the Development of Cancer-Associated Cachexia. Cancer Res 2016; 76:5372-82. [PMID: 27328730 DOI: 10.1158/0008-5472.can-15-3152] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 06/13/2016] [Indexed: 11/16/2022]
Abstract
Cachexia is a life-threatening wasting syndrome lacking effective treatment, which arises in many cancer patients. Although ostensibly induced by multiple tumor-produced cytokines (tumorkines), their functional contribution to initiation and progression of this syndrome has proven difficult to determine. In this study, we used adeno-associated viral vectors to elevate circulating levels of the tumorkines IL6 and/or activin A in animals in the absence of tumors as a tactic to evaluate hypothesized roles in cachexia development. Mice with elevated levels of IL6 exhibited 8.1% weight loss after 9 weeks, whereas mice with elevated levels of activin A lost 11% of their body weight. Co-elevation of both tumorkines to levels approximating those observed in cancer cachexia models induced a more rapid and profound body weight loss of 15.4%. Analysis of body composition revealed that activin A primarily triggered loss of lean mass, whereas IL6 was a major mediator of fat loss. Histologic and transcriptional analysis of affected organs/tissues (skeletal muscle, fat, and liver) identified interactions between the activin A and IL6 signaling pathways. For example, IL6 exacerbated the detrimental effects of activin A in skeletal muscle, whereas activin A curbed the IL6-induced acute-phase response in liver. This study presents a useful model to deconstruct cachexia, opening a pathway to determining which tumorkines are best targeted to slow/reverse this devastating condition in cancer patients. Cancer Res; 76(18); 5372-82. ©2016 AACR.
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Affiliation(s)
- Justin L Chen
- Hudson Institute of Medical Research, Clayton, Australia. Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Kelly L Walton
- Hudson Institute of Medical Research, Clayton, Australia
| | - Hongwei Qian
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Timothy D Colgan
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia. Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Adam Hagg
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Matthew J Watt
- The Obesity and Metabolism Program of the Biomedicine Discovery Institute, Monash University, Clayton, Australia. Department of Physiology, Monash University, Clayton, Australia
| | - Craig A Harrison
- Hudson Institute of Medical Research, Clayton, Australia. Department of Physiology, Monash University, Clayton, Australia. Department of Molecular and Translational Sciences, Monash University, Clayton, Australia
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia. Department of Physiology, The University of Melbourne, Melbourne, Australia. Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia. Department of Neurology, The University of Washington School of Medicine, Seattle, Washington.
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11
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Jackson DP, Li H, Mitchell KA, Joshi AD, Elferink CJ. Ah receptor-mediated suppression of liver regeneration through NC-XRE-driven p21Cip1 expression. Mol Pharmacol 2014; 85:533-41. [PMID: 24431146 DOI: 10.1124/mol.113.089730] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies in hepatocyte-derived cell lines and the whole liver established that the aryl hydrocarbon receptor (AhR) can disrupt G1-phase cell cycle progression following exposure to persistent AhR agonists, such as TCDD (dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin). Growth arrest was attributed to inhibition of G1-phase cyclin-dependent kinase 2 (CDK2) activity. The present study examined the effect of TCDD exposure on liver regeneration following 70% partial hepatectomy in mice lacking the Cip/Kip inhibitors p21(Cip1) or p27(Kip1) responsible for regulating CDK2 activity. Assessment of the regenerative process in wild-type, p21(Cip1) knockout, and p27(Kip1) knockout mice confirmed that TCDD-induced inhibition of liver regeneration is entirely dependent on p21(Cip1) expression. Compared with wild-type mice, the absence of p21(Cip1) expression completely abrogated the TCDD inhibition, and accelerated hepatocyte progression through G1 phase during the regenerative process. Analysis of the transcriptional response determined that increased p21(Cip1) expression during liver regeneration involved an AhR-dependent mechanism. Chromatin immunoprecipitation studies revealed that p21(Cip1) induction required AhR binding to the newly characterized nonconsensus xenobiotic response element, in conjunction with the tumor suppressor protein Kruppel-like factor 6 functioning as an AhR binding partner. The evidence also suggests that AhR functionality following partial hepatectomy is dependent on a p21(Cip1)-regulated signaling process, intimately linking AhR biology to the G1-phase cell cycle program.
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Affiliation(s)
- Daniel P Jackson
- Department of Pharmacology and Toxicology (D.P.J., A.D.J., C.J.E.) and Department of Pediatrics (H.L.), University of Texas Medical Branch, Galveston, Texas; and Department of Biological Sciences, Boise State University, Boise, Idaho (K.A.M.)
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12
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The Complex Relationship between Liver Cancer and the Cell Cycle: A Story of Multiple Regulations. Cancers (Basel) 2014; 6:79-111. [PMID: 24419005 PMCID: PMC3980619 DOI: 10.3390/cancers6010079] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 12/24/2013] [Accepted: 01/03/2014] [Indexed: 12/14/2022] Open
Abstract
The liver acts as a hub for metabolic reactions to keep a homeostatic balance during development and growth. The process of liver cancer development, although poorly understood, is related to different etiologic factors like toxins, alcohol, or viral infection. At the molecular level, liver cancer is characterized by a disruption of cell cycle regulation through many molecular mechanisms. In this review, we focus on the mechanisms underlying the lack of regulation of the cell cycle during liver cancer, focusing mainly on hepatocellular carcinoma (HCC). We also provide a brief summary of novel therapies connected to cell cycle regulation.
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13
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Inoue Y, Tomiya T, Nishikawa T, Ohtomo N, Tanoue Y, Ikeda H, Koike K. Induction of p53-dependent p21 limits proliferative activity of rat hepatocytes in the presence of hepatocyte growth factor. PLoS One 2013; 8:e78346. [PMID: 24223793 PMCID: PMC3817248 DOI: 10.1371/journal.pone.0078346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/20/2013] [Indexed: 12/26/2022] Open
Abstract
Background Hepatocyte growth factor (HGF), a potent mitogen for hepatocytes, enhances hepatocyte function without stimulating proliferation, depending on the physiological conditions. p53, a transcription factor, suppresses the cell proliferation by expressing p21WAF1/CIP1 in various tissues. Aim To investigate the mechanism through which the hepatocytes maintain mitotically quiescent even in the presence of HGF. Methods We studied the relationship between p53 and p21 expression and the effect of p53-p21 axis on hepatocyte proliferation in primary cultured rat hepatocytes stimulated by HGF. Hepatic p21 levels are determined serially after partial hepatectomy or sham operation in rats. Results DNA synthesis was markedly increased by HGF addition in rat hepatocytes cultured at low density but not at high density. Cellular p53 levels increased in the hepatocytes cultured at both the densities. p21 levels were increased and correlated with cellular p53 levels in hepatocytes cultured at high density but not at low density. When the activity of p53 was suppressed by a chemical inhibitor for p53, cellular p21 levels were reduced, and DNA synthesis was increased. Similarly, p21 antisense oligonucleotide increased the DNA synthesis. In rats after partial hepatectomy, transient elevation of hepatic p21 levels was observed. In contrast, in sham-operated rats, hepatic p21 levels were increased on sustained time scales. Conclusion p53-related induction of p21 may suppress hepatocyte proliferation in the presence of HGF in the setting that mitogenic activity of HGF is not elicitable.
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Affiliation(s)
- Yukiko Inoue
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tomoaki Tomiya
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- * E-mail:
| | - Takako Nishikawa
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Natsuko Ohtomo
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yasushi Tanoue
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hitoshi Ikeda
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kazuhiko Koike
- Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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14
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Corlu A, Loyer P. Regulation of the g1/s transition in hepatocytes: involvement of the cyclin-dependent kinase cdk1 in the DNA replication. Int J Hepatol 2012; 2012:689324. [PMID: 23091735 PMCID: PMC3471441 DOI: 10.1155/2012/689324] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 08/29/2012] [Indexed: 12/16/2022] Open
Abstract
A singular feature of adult differentiated hepatocytes is their capacity to proliferate allowing liver regeneration. This review emphasizes the literature published over the last 20 years that established the most important pathways regulating the hepatocyte cell cycle. Our article also aimed at illustrating that many discoveries in this field benefited from the combined use of in vivo models of liver regeneration and in vitro models of primary cultures of human and rodent hepatocytes. Using these models, our laboratory has contributed to decipher the different steps of the progression into the G1 phase and the commitment to S phase of proliferating hepatocytes. We identified the mitogen dependent restriction point located at the two-thirds of the G1 phase and the concomitant expression and activation of both Cdk1 and Cdk2 at the G1/S transition. Furthermore, we demonstrated that these two Cdks contribute to the DNA replication. Finally, we provided strong evidences that Cdk1 expression and activation is correlated to extracellular matrix degradation upon stimulation by the pro-inflammatory cytokine TNFα leading to the identification of a new signaling pathway regulating Cdk1 expression at the G1/S transition. It also further confirms the well-orchestrated regulation of liver regeneration via multiple extracellular signals and pathways.
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Affiliation(s)
- Anne Corlu
- Inserm UMR S 991, Foie Métabolismes et Cancer, Université de Rennes 1, Hôpital Pontchaillou, 35033 Rennes Cedex, France
| | - Pascal Loyer
- Inserm UMR S 991, Foie Métabolismes et Cancer, Université de Rennes 1, Hôpital Pontchaillou, 35033 Rennes Cedex, France
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15
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Pan C, Chen H, Wang L, Yang S, Fu H, Zheng Y, Miao M, Jiao B. Down-regulation of MiR-127 facilitates hepatocyte proliferation during rat liver regeneration. PLoS One 2012; 7:e39151. [PMID: 22720056 PMCID: PMC3376093 DOI: 10.1371/journal.pone.0039151] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 05/16/2012] [Indexed: 01/27/2023] Open
Abstract
Liver regeneration (LR) after partial hepatectomy (PH) involves the proliferation and apoptosis of hepatocytes, and microRNAs have been shown to post-transcriptionally regulate genes involved in the regulation of these processes. To explore the role of miR-127 during LR, the expression patterns of miR-127 and its related proteins were investigated. MiR-127 was introduced into a rat liver cell line to examine its effects on the potential target genes Bcl6 and Setd8, and functional studies were undertaken. We discovered that miR-127 was down-regulated and inversely correlated with the expression of Bcl6 and Setd8 at 24 hours after PH, a time at which hypermethylation of the promoter region of the miR-127 gene was detected. Furthermore, in BRL-3A rat liver cells, we observed that overexpression of miR-127 significantly suppressed cell growth and directly inhibited the expression of Bcl6 and Setd8. The results suggest that down-regulation of miR-127 may be due to the rapid methylation of its promoter during the first 24 h after PH, and this event facilitates hepatocyte proliferation by releasing Bcl6 and Setd8. These findings support a miRNA-mediated negative regulation pattern in LR and implicate an anti-proliferative role for miR-127 in liver cells.
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Affiliation(s)
- Chuanyong Pan
- Department of Biochemistry and Molecular Biology, Second Military Medical University, Shanghai, China
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16
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Hayashi H, Sakai K, Baba H, Sakai T. Thrombospondin-1 is a novel negative regulator of liver regeneration after partial hepatectomy through transforming growth factor-beta1 activation in mice. Hepatology 2012; 55:1562-73. [PMID: 22105716 PMCID: PMC3295913 DOI: 10.1002/hep.24800] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 11/01/2011] [Indexed: 01/17/2023]
Abstract
UNLABELLED The matricellular protein, thrombospondin-1 (TSP-1), is prominently expressed during tissue repair. TSP-1 binds to matrix components, proteases, cytokines, and growth factors and activates intracellular signals through its multiple domains. TSP-1 converts latent transforming growth factor-beta1 (TGF-β1) complexes into their biologically active form. TGF-β plays significant roles in cell-cycle regulation, modulation of differentiation, and induction of apoptosis. Although TGF-β1 is a major inhibitor of proliferation in cultured hepatocytes, the functional requirement of TGF-β1 during liver regeneration remains to be defined in vivo. We generated a TSP-1-deficient mouse model of a partial hepatectomy (PH) and explored TSP-1 induction, progression of liver regeneration, and TGF-β-mediated signaling during the repair process after hepatectomy. We show here that TSP-1-mediated TGF-β1 activation plays an important role in suppressing hepatocyte proliferation. TSP-1 expression was induced in endothelial cells (ECs) as an immediate early gene in response to PH. TSP-1 deficiency resulted in significantly reduced TGF-β/Smad signaling and accelerated hepatocyte proliferation through down-regulation of p21 protein expression. TSP-1 induced in ECs by reactive oxygen species (ROS) modulated TGF-β/Smad signaling and proliferation in hepatocytes in vitro, suggesting that the immediately and transiently produced ROS in the regenerating liver were the responsible factor for TSP-1 induction. CONCLUSIONS We have identified TSP-1 as an inhibitory element in regulating liver regeneration by TGF-β1 activation. Our work defines TSP-1 as a novel immediate early gene that could be a potential therapeutic target to accelerate liver regeneration.
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Affiliation(s)
- Hiromitsu Hayashi
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Keiko Sakai
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Hideo Baba
- Department of Gastroenterological Surgery, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Takao Sakai
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
- Orthopaedic and Rheumatologic Research Center, Cleveland Clinic, Cleveland, Ohio 44195, USA
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17
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Bugyik E, Dezso K, Turányi E, Szurián K, Paku S, Nagy P. 1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene induces substantial hyperplasia in fibrotic mouse liver. Int J Exp Pathol 2012; 93:125-9. [PMID: 22243368 DOI: 10.1111/j.1365-2613.2011.00803.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The proliferative response of hepatocytes in vivo can be induced by two mechanisms: severe damage to hepatic tissue results in regenerative growth and so-called primary hepatocyte mitogens can initiate liver cell proliferation without preceding loss of parenchyma. The regulation of the two responses is quite different. The decreased regenerative response of cirrhotic/fibrotic liver is well known, and is a severe obstacle to surgery of the diseased liver. In the present experiments we investigated the efficiency of a primary hepatocyte mitogen 1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOB) on two different liver cirrhosis/fibrosis models in mice induced by chronic administration of CCl(4) and thioacetamide respectively. BrdU incorporation and cyclin A expression established clearly that there is a reduced but still powerful mitogenic response of the fibrotic livers. Therefore, primary hepatocyte mitogens appear to be suitable to be used to rescue the regenerative response of cirrhotic livers.
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Affiliation(s)
- Edina Bugyik
- First Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
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18
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Leinicke JA, Longshore S, Wakeman D, Guo J, Warner BW. Regulation of retinoblastoma protein (Rb) by p21 is critical for adaptation to massive small bowel resection. J Gastrointest Surg 2012; 16:148-55; discussion 155. [PMID: 22042567 PMCID: PMC3779625 DOI: 10.1007/s11605-011-1747-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 10/13/2011] [Indexed: 01/31/2023]
Abstract
BACKGROUND Adaptation following massive intestinal loss is characterized by increased villus height and crypt depth. Previously, we demonstrated that p21-null mice do not adapt after small bowel resection (SBR). As retinoblastoma protein (Rb) levels are elevated in p21-null crypt cells, we first sought to determine whether Rb is required for normal adaptation. Next, we tested whether Rb expression is responsible for blocked adaptation in p21-nulls. METHODS Genetically manipulated mice and wild-type (WT) littermates underwent either 50% SBR or sham operation. The intestine was harvested at 3, 7, or 28 days later and intestinal adaptation was evaluated. Enterocytes were isolated and protein levels evaluated by Western blot and quantified by optical density. RESULTS Rb-null mice demonstrated increased villus height, crypt depth, and proliferative rate at baseline, but there was no further increase following SBR. Deletion of one Rb allele lowered Rb expression and restored resection-induced adaptation responses in p21-null mice. CONCLUSION Rb is specifically required for resection-induced adaptation. Restoration of adaptation in p21-null mice by lowering Rb expression suggests a crucial mechanistic role for Rb in the regulation of intestinal adaptation by p21.
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Affiliation(s)
- Jennifer A. Leinicke
- Division of Pediatric Surgery, St. Louis Children’s Hospital, Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Shannon Longshore
- Division of Pediatric Surgery, St. Louis Children’s Hospital, Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Derek Wakeman
- Division of Pediatric Surgery, St. Louis Children’s Hospital, Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Jun Guo
- Division of Pediatric Surgery, St. Louis Children’s Hospital, Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Brad W. Warner
- Division of Pediatric Surgery, St. Louis Children’s Hospital, Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, USA. Division of Pediatric Surgery, St. Louis Children’s Hospital, One Children’s Place, Suite 5s40, St. Louis, MO 63110, USA
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19
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Kim RD, Kim JS, Watanabe G, Mohuczy D, Behrns KE. Liver regeneration and the atrophy-hypertrophy complex. Semin Intervent Radiol 2011; 25:92-103. [PMID: 21326550 DOI: 10.1055/s-2008-1076679] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The atrophy-hypertrophy complex (AHC) refers to the controlled restoration of liver parenchyma following hepatocyte loss. Different types of injury (e.g., toxins, ischemia/reperfusion, biliary obstruction, and resection) elicit the same hypertrophic response in the remnant liver. The AHC involves complex anatomical, histological, cellular, and molecular processes. The signals responsible for these processes are both intrinsic and extrinsic to the liver and involve both physical and molecular events. In patients in whom resection of large liver malignancies would result in an inadequate functional liver remnant, preoperative portal vein embolization may increase the remnant liver sufficiently to permit aggressive resections. Through continued basic science research, the cellular mechanisms of the AHC may be maximized to permit curative resections in patients with potentially prohibitive liver function.
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Affiliation(s)
- Robin D Kim
- Department of Surgery, Division of General and GI Surgery, University of Florida, Gainesville, Florida
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20
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Abstract
The MRL (Murphy Roths Large) mouse has provided a unique model of adult mammalian regeneration as multiple tissues show this important phenotype. Furthermore, the healing employs a blastema-like structure similar to that seen in amphibian regenerating tissue. Cells from the MRL mouse display DNA damage, cell cycle G2/M arrest, and a reduced level of p21CIP1/WAF. A functional role for p21 was confirmed when tissue injury in an adult p21-/- mouse showed a healing phenotype that matched the MRL mouse, with the replacement of tissues, including cartilage, and with hair follicle formation and a lack of scarring. Since the major canonical function of p21 is part of the p53/p21 axis, we explored the consequences of p53 deletion. A regenerative response was not seen in a p53-/- mouse and the elimination of p53 from the MRL background had no negative effect on the regeneration of the MRL.p53-/- mouse. An exploration of other knockout mice to identify p21-dependent, p53-independent regulatory pathways involved in the regenerative response revealed another significant finding showing that elimination of transforming growth factor-β1 displayed a healing response as well. These results are discussed in terms of their effect on senescence and differentiation.
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21
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The balance between rRNA and ribosomal protein synthesis up- and downregulates the tumour suppressor p53 in mammalian cells. Oncogene 2011; 30:3274-88. [PMID: 21399665 DOI: 10.1038/onc.2011.48] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Data on the relationship between ribosome biogenesis and p53 function indicate that the tumour suppressor can be activated by either nucleolar disruption or ribosomal protein defects. However, there is increasing evidence that the induction of p53 does not always require these severe cellular changes, and data are still lacking on a possible role of ribosome biogenesis in the downregulation of p53. Here, we studied the effect of the up- and downregulation of the rRNA transcription rate on p53 induction in mammalian cells. We found that a downregulation of rRNA synthesis, induced by silencing the POLR1A gene coding for the RNA polymerase I catalytic subunit, stabilised p53 without altering the nucleolar integrity in human cancer cells. p53 stabilisation was due to the inactivation of the MDM2-mediated p53 degradation by the binding of ribosomal proteins no longer used for ribosome building. p53 stabilisation did not occur when rRNA synthesis downregulation was associated with a contemporary reduction of protein synthesis. Furthermore, we demonstrated that in three different experimental models characterised by an upregulation of rRNA synthesis, cancer cells treated with insulin or exposed to the insulin-like growth factor 1, rat liver stimulated by cortisol and regenerating rat liver after partial hepatectomy, the p53 protein level was reduced due to a lowered ribosomal protein availability for MDM2 binding. It is worth noting that the upregulation of rRNA synthesis was responsible for a decreased p53-mediated response to cytotoxic stresses. These findings demonstrated that the balance between rRNA and ribosomal protein synthesis controls the function of p53 in mammalian cells, that p53 can be induced without the occurrence of severe changes of the cellular components controlling ribosome biogenesis, and that conditions characterised by an upregulated rRNA synthesis are associated with a reduced p53 response.
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22
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Kurinna S, Stratton SA, Tsai WW, Akdemir KC, Gu W, Singh P, Goode T, Darlington GJ, Barton MC. Direct activation of forkhead box O3 by tumor suppressors p53 and p73 is disrupted during liver regeneration in mice. Hepatology 2010; 52:1023-32. [PMID: 20564353 PMCID: PMC3741038 DOI: 10.1002/hep.23746] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED The p53 family of proteins regulates the expression of target genes that promote cell cycle arrest and apoptosis, which may be linked to cellular growth control as well as tumor suppression. Within the p53 family, p53 and the transactivating p73 isoform (TA-p73) have hepatic-specific functions in development and tumor suppression. Here, we determined TA-p73 interactions with chromatin in the adult mouse liver and found forkhead box O3 (Foxo3) to be one of 158 gene targets. Global profiling of hepatic gene expression in the regenerating liver versus the quiescent liver revealed specific, functional categories of genes regulated over the time of regeneration. Foxo3 is the most responsive gene among transcription factors with altered expression during regenerative cellular proliferation. p53 and TA-p73 bind a Foxo3 p53 response element (p53RE) and maintain active expression in the quiescent liver. During regeneration of the liver, the binding of p53 and TA-p73, the recruitment of acetyltransferase p300, and the active chromatin structure of Foxo3 are disrupted along with a loss of Foxo3 expression. In agreement with the loss of Foxo3 transcriptional activation, a decrease in histone activation marks (dimethylated histone H3 at lysine 4, acetylated histone H3 at lysine 14, and acetylated H4) at the Foxo3 p53RE was detected after partial hepatectomy in mice. These parameters of Foxo3 regulation are reestablished with the completion of liver growth and regeneration and support a temporary suspension of p53 and TA-p73 regulatory functions in normal cells during tissue regeneration. p53-dependent and TA-p73-dependent activation of Foxo3 was also observed in mouse embryonic fibroblasts and in mouse hepatoma cells overexpressing p53, TA-p73alpha, and TA-p73beta isoforms. CONCLUSION p53 and p73 directly bind and activate the expression of the Foxo3 gene in the adult mouse liver and murine cell lines. p53, TA-p73, and p300 binding and Foxo3 expression decrease during liver regeneration, and this suggests a critical growth control mechanism mediated by these transcription factors in vivo.
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Affiliation(s)
- Svitlana Kurinna
- Graduate program in Genes and Development, University of Texas Graduate School of Biomedical Sciences, Houston, TX,Department of Biochemistry and Molecular Biology, Center for Stem Cell and Developmental Biology
| | - Sabrina A. Stratton
- Department of Biochemistry and Molecular Biology, Center for Stem Cell and Developmental Biology
| | - Wen-Wei Tsai
- Department of Biochemistry and Molecular Biology, Center for Stem Cell and Developmental Biology
| | - Kadir C. Akdemir
- Department of Biostatistics and Bioinformatics, UT MD Anderson Cancer Center, Houston, TX
| | | | - Pallavi Singh
- Columbia University College of Physicians and Surgeons, New York, NY
| | - Triona Goode
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX
| | | | - Michelle Craig Barton
- Graduate program in Genes and Development, University of Texas Graduate School of Biomedical Sciences, Houston, TX,Department of Biochemistry and Molecular Biology, Center for Stem Cell and Developmental Biology
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23
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Pewzner-Jung Y, Brenner O, Braun S, Laviad EL, Ben-Dor S, Feldmesser E, Horn-Saban S, Amann-Zalcenstein D, Raanan C, Berkutzki T, Erez-Roman R, Ben-David O, Levy M, Holzman D, Park H, Nyska A, Merrill AH, Futerman AH. A critical role for ceramide synthase 2 in liver homeostasis: II. insights into molecular changes leading to hepatopathy. J Biol Chem 2010; 285:10911-23. [PMID: 20110366 PMCID: PMC2856297 DOI: 10.1074/jbc.m109.077610] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 01/05/2010] [Indexed: 01/26/2023] Open
Abstract
We have generated a mouse that cannot synthesize very long acyl chain (C22-C24) ceramides (Pewzner-Jung, Y., Park, H., Laviad, E. L., Silva, L. C., Lahiri, S., Stiban, J., Erez-Roman, R., Brugger, B., Sachsenheimer, T., Wieland, F. T., Prieto, M., Merrill, A. H., and Futerman, A. H. (2010) J. Biol. Chem. 285, 10902-10910) due to ablation of ceramide synthase 2 (CerS2). As a result, significant changes were observed in the sphingolipid profile of livers from these mice, including elevated C16-ceramide and sphinganine levels. We now examine the functional consequences of these changes. CerS2 null mice develop severe nonzonal hepatopathy from about 30 days of age, the age at which CerS2 expression peaks in wild type mice, and display increased rates of hepatocyte apoptosis and proliferation. In older mice there is extensive and pronounced hepatocellular anisocytosis with widespread formation of nodules of regenerative hepatocellular hyperplasia. Progressive hepatomegaly and noninvasive hepatocellular carcinoma are also seen from approximately 10 months of age. Even though CerS2 is found at equally high mRNA levels in kidney and liver, there are no changes in renal function and no pathological changes in the kidney. High throughput analysis of RNA expression in liver revealed up-regulation of genes associated with cell cycle regulation, protein transport, cell-cell interactions and apoptosis, and down-regulation of genes associated with intermediary metabolism, such as lipid and steroid metabolism, adipocyte signaling, and amino acid metabolism. In addition, levels of the cell cycle regulator, the cyclin dependent-kinase inhibitor p21(WAF1/CIP1), were highly elevated, which occurs by at least two mechanisms, one of which may involve p53. We propose a functional rationale for the synthesis of sphingolipids with very long acyl chains in liver homeostasis and in cell physiology.
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MESH Headings
- Animals
- Biomarkers, Tumor/genetics
- Biomarkers, Tumor/metabolism
- Blotting, Western
- Carcinoma, Hepatocellular/enzymology
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/pathology
- Female
- Gene Expression Profiling
- Gene Expression Regulation, Developmental
- Hepatocytes/cytology
- Hepatocytes/enzymology
- Hepatomegaly/enzymology
- Hepatomegaly/pathology
- Homeostasis
- Lipids/analysis
- Liver/metabolism
- Liver/pathology
- Liver Function Tests
- Liver Neoplasms, Experimental/enzymology
- Liver Neoplasms, Experimental/genetics
- Liver Neoplasms, Experimental/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Oligonucleotide Array Sequence Analysis
- Oxidoreductases/antagonists & inhibitors
- Oxidoreductases/physiology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
| | | | | | | | - Shifra Ben-Dor
- Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ester Feldmesser
- Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Shirley Horn-Saban
- Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | | | | | | | | - Michal Levy
- From the Departments of Biological Chemistry
| | | | - Hyejung Park
- the School of Biology and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0230
| | - Abraham Nyska
- the Timrat and Sackler School of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel, and
| | - Alfred H. Merrill
- the School of Biology and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0230
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24
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Zhang MF, Zhang ZY, Fu J, Yang YF, Yun JP. Correlation between expression of p53, p21/WAF1, and MDM2 proteins and their prognostic significance in primary hepatocellular carcinoma. J Transl Med 2009; 7:110. [PMID: 20025780 PMCID: PMC2809055 DOI: 10.1186/1479-5876-7-110] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 12/22/2009] [Indexed: 02/07/2023] Open
Abstract
Background Tumor Protein p53 (p53), cyclin-dependent kinase inhibitor 1A (p21/WAF1), and murine double minute 2 (MDM2) participate in the regulation of cell growth. Altered expression of these gene products has been found in malignant tumors and has been associated with poor prognosis. Our aim was to investigate the expression of the 3 proteins in hepatocellular carcinoma (HCC) and their prognostic significance. Methods We examined p53, p21/WAF1, and MDM2 expression in 181 pairs of HCC tissues and the adjacent hepatic tissues by performing immunohistochemistry and examined the expression of the 3 proteins in 7 pairs of HCC tissues and the adjacent hepatic tissues by using western blot analysis. Results The expression of p53, p21/WAF1, and MDM2 in the HCC tissues was significantly higher than those in the adjacent hepatic tissues (P < 0.05). A statistical correlation was observed between p53 and p21/WAF1 expression in HCC tissues (R = 0.195, P = 0.008). A statistical correlation was observed between expression of p53 and p21/WAF1 (R = 0.380, P = 0.000), p53 and MDM2 (R = 0.299, P = 0.000), p21/WAF1 and MDM2 (R = 0.285, P = 0.000) in 181 liver tissues adjacent to the tumor. Patients with a low pathologic grade HCC (I+II) had a higher tendency to express p53 on tumor cells than the patients with high pathologic grade HCC (III+IV) (P = 0.007). Survival analysis showed that positive p21/WAF1 expression or/and negative MDM2 expression in HCC was a predictor of better survival of patients after tumor resection (P < 0.05). Conclusions The proteins p53, p21/WAF1, and MDM2 were overexpressed in all the HCC cases in this study, and p53 and p21/WAF1 overexpression were positively correlated. The expression of p21/WAF1 and MDM2 can be considered as 2 useful indicators for predicting the prognosis of HCC.
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Affiliation(s)
- Mei-Fang Zhang
- State Key Laboratory of Oncology in Southern China, Cancer Center of Sun Yat-Sen University, Guangzhou, China.
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25
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Olazabal IM, Muñoz JA, Rodríguez-Navas C, Alvarez L, Delgado-Baeza E, García-Ruiz JP. Prolactin's role in the early stages of liver regeneration in rats. J Cell Physiol 2009; 219:626-33. [PMID: 19170064 DOI: 10.1002/jcp.21707] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Liver regeneration after partial hepatectomy (PHx) is a complex process that is regulated by hemodynamic changes, the modulation of cytokines and growth factors, and the activation of immediate early transcription factors that lead to a round of hepatocyte mitosis. Among the factors involved, the pituitary hormone prolactin (PRL) has been shown to induce a hepatotrophic response after partial hepatectomy similar to that caused by phorbol esters; and in isolated hepatocytes PRL triggers a mitogenic response. However, it is becoming clear that PRL exerts a dual role acting in proliferation and differentiation processes. In this work, we have assessed the role of PRL in the early stages of liver regeneration in rats. To this end, three groups of rats were compared: Sham operated, regenerant and regenerant with PRL i.p. administration. Results show that PRL administration prior to partial hepatectomy caused an increase in the binding activity of several transcription factors involved in cell proliferation: AP-1, c-Jun and STAT-3, and in liver-specific differentiation and maintenance of energetic metabolism: CEBPalpha, HNF-1, HNF-4 at early time points and at later time points HNF-3. Hepatic sections show that PRL administration increases the number of proliferating cells within 5 h post-partial hepatectomy. The mRNA of the angiogenic and survival factors VEGF and HIF-1alpha, was also induced by PRL treatment. Data indicate that PRL triggers, either directly or indirectly, an acceleration of liver regeneration, preserving liver function and fulfilling a hepatoprotective role. J. Cell. Physiol. 219: 626-633, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Isabel M Olazabal
- Departamento de Biología Molecular, Facultad de Ciencias C-V, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
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26
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A detailed methodology of partial hepatectomy in the mouse. Lab Anim (NY) 2008; 37:529-32. [DOI: 10.1038/laban1108-529] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 05/28/2008] [Indexed: 01/09/2023]
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27
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Wong CH, Chan SKP, Chan HLY, Tsui SKW, Feitelson M. The Molecular Diagnosis of Hepatitis B Virus-Associated Hepatocellular Carcinoma. Crit Rev Clin Lab Sci 2008; 43:69-101. [PMID: 16531275 DOI: 10.1080/10408360500410407] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hepatitis B virus (HBV) infection is the major cause of hepatocellular carcinoma (HCC) worldwide. The pathogenesis of HBV-associated HCC has been studied extensively, and molecular changes during malignant transformation have been identified. It has been proposed that the insertion of HBV DNA into the human genome results in chromosomal instability and inactivation of tumor suppressor genes. Transactivation of oncogenes, inactivation of tumor suppressor genes, and alteration of the cell cycle by HBV proteins are also involved in the progression of hepatocellular carcinogenesis. Traditional clinical examinations of HCC, such as biopsy, computer tomography, ultrasonic imaging, and detection of such biomarkers as a-fetoprotein, are currently the "gold standard" in diagnosis. These tests diagnose HCC only in the late stages of disease. This limitation has greatly reduced the chance of survival of HCC patients. To resolve this problem, new biomarkers that can diagnose HCC in earlier stages are necessary. Based on recent molecular studies of the effects of HBV on cellular transformation, differentially expressed biomarkers of HBV infection have been elucidated. With the analyses of the HBV replication profile, the viral load (HBV DNA levels) of patients, and the viral protein expression, the severity of hepatitis in the preneoplastic stages can be assessed. In the future, with the molecular profiles identified by genomic and proteomic approaches, stage-specific biomarkers should be identified to monitor the progression and prognosis of HCC.
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Affiliation(s)
- Chi-Hang Wong
- Center for Emerging Infectious Diseases, The Chinese University, Hong Kong, Shatin, N.T., Hong Kong SAR, China
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28
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Murata H, Yagi T, Iwagaki H, Ogino T, Sadamori H, Matsukawa H, Umeda Y, Haga S, Takaka N, Ozaki M. Mechanism of impaired regeneration of fatty liver in mouse partial hepatectomy model. J Gastroenterol Hepatol 2007; 22:2173-80. [PMID: 18031377 DOI: 10.1111/j.1440-1746.2006.04798.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND AND AIM The mechanism of injury in steatotic liver under pathological conditions been extensively examined. However, the mechanism of an impaired regeneration is still not well understood. The aim of this study was to analyze the mechanism of impaired regeneration of steatotic liver after partial hepatectomy (PH). METHODS db/db fatty mice and lean littermates were used for the experiments. Following 70% PH, the survival rate and recovery of liver mass were examined. Liver tissue was histologically examined and analyzed by western blotting and RT-PCR. RESULTS Of 35 db/db mice, 25 died within 48 h of PH, while all of the control mice survived. Liver regeneration of surviving db/db mice was largely impaired. In db/db mice, mitosis of hepatocytes after PH was disturbed, even though proliferating cell nuclear antigen (PCNA) expression (G1 to S phase marker) in hepatocytes was equally observed in both mice groups. Interestingly, phosphorylation of Cdc2 in db/db mice was suppressed by reduced expression of Wee1 and Myt1, which phosphorylate Cdc2 in S to G2 phase. CONCLUSIONS In steatotic liver, cell-cycle-related proliferative disorders occurred at mid-S phase after PCNA expression. Reduced expression of Wee1 and Myt1 kinases may therefore maintain Cdc2 in an unphosphorylated state and block cell cycle progression in mid-S phase. These kinases may be critical factors involved in the impaired liver regeneration in fatty liver.
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Affiliation(s)
- Hiroshi Murata
- Department of Gastroenterological Surgery, Transplant and Surgical Oncology, Okayama University Graduate School of Medicine and Dentistry, Shikata, Okayama, Japan
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29
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Satyanarayana A, Hilton MB, Kaldis P. p21 Inhibits Cdk1 in the absence of Cdk2 to maintain the G1/S phase DNA damage checkpoint. Mol Biol Cell 2007; 19:65-77. [PMID: 17942597 DOI: 10.1091/mbc.e07-06-0525] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Cdk1 was proposed to compensate for the loss of Cdk2. Here we present evidence that this is possible due to premature translocation of Cdk1 from the cytoplasm to the nucleus in the absence of Cdk2. We also investigated the consequence of loss of Cdk2 on the maintenance of the G1/S DNA damage checkpoint. Cdk2(-/-) mouse embryonic fibroblasts in vitro as well as regenerating liver cells after partial hepatectomy (PH) in Cdk2(-/-) mice, arrest promptly at the G1/S checkpoint in response to gamma-irradiation due to activation of p53 and p21 inhibiting Cdk1. Furthermore re-entry into S phase after irradiation was delayed in Cdk2(-/-) cells due to prolonged and impaired DNA repair activity. In addition, Cdk2(-/-) mice were more sensitive to lethal irradiation compared to wild-type and displayed delayed resumption of DNA replication in regenerating liver cells. Our results suggest that the G1/S DNA damage checkpoint is intact in the absence of Cdk2, but Cdk2 is important for proper repair of the damaged DNA.
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Affiliation(s)
- Ande Satyanarayana
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
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30
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Mullany LK, Nelsen CJ, Hanse EA, Goggin MM, Anttila CK, Peterson M, Bitterman PB, Raghavan A, Crary GS, Albrecht JH. Akt-mediated liver growth promotes induction of cyclin E through a novel translational mechanism and a p21-mediated cell cycle arrest. J Biol Chem 2007; 282:21244-52. [PMID: 17517888 DOI: 10.1074/jbc.m702110200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The control of hepatocyte growth is relevant to the processes of liver regeneration, development, metabolic homeostasis, and cancer. A key component of growth control is the protein kinase Akt, which acts downstream of mitogens and nutrients to affect protein translation and cell cycle progression. In this study, we found that transient transfection of activated Akt triggered a 3-4-fold increase in liver size within days but only minimal hepatocyte proliferation. Akt-induced liver growth was associated with marked up-regulation of cyclin E but not cyclin D1. Analysis of liver polyribosomes demonstrated that the post-transcriptional induction of cyclin E was associated with increased translational efficiency of this mRNA, suggesting that cell growth promotes expression of this protein through a translational mechanism that is distinct from the cyclin D-E2F pathway. Treatment of Akt-transfected mice with rapamycin only partially inhibited liver growth and did not prevent the induction of cyclin E protein, indicating that target of rapamycin activity is not necessary for this response. In the enlarged livers, cyclin E-Cdk2 complexes were present in high abundance but were inactive due to increased binding of p21 to these complexes. Akt transfection of p21(-/-) mice promoted liver growth, activation of Cdk2, and enhanced hepatocyte proliferation. In conclusion, growth promotes cyclin E expression through a novel translational mechanism in the liver, suggesting a new link between cell growth and the cell cycle machinery. Furthermore, p21 suppresses proliferation in the overgrown livers and may play a role in preventing cell cycle progression in response to organ size homeostatic mechanisms.
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Affiliation(s)
- Lisa K Mullany
- Division of Gastroenterology, Hennepin County Medical Center, Minneapolis, Minnesota 55415, USA
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31
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Stepniak E, Ricci R, Eferl R, Sumara G, Sumara I, Rath M, Hui L, Wagner EF. c-Jun/AP-1 controls liver regeneration by repressing p53/p21 and p38 MAPK activity. Genes Dev 2006; 20:2306-14. [PMID: 16912279 PMCID: PMC1553212 DOI: 10.1101/gad.390506] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The AP-1 transcription factor c-Jun is a key regulator of hepatocyte proliferation. Mice lacking c-Jun in the liver (c-jun (Deltali*)) display impaired liver regeneration after partial hepatectomy (PH). This phenotype correlates with increased protein levels of the cdk-inhibitor p21 in the liver. We performed PH experiments in several double-knockout mouse models to genetically identify the signaling events regulated by c-Jun. Inactivation of p53 in c-jun (Deltali*) mice abrogated both hepatocyte cell cycle block and increased p21 protein expression. Consistently, liver regeneration was rescued in c-jun (Deltali*) p21 (-/-) double-mutant mice. This indicated that c-Jun controls hepatocyte proliferation by a p53/p21-dependent mechanism. Analyses of p21 mRNA and protein expression in livers of c-jun (Deltali*) mice after PH revealed that the accumulation of p21 protein is due to a post-transcriptional/post-translational mechanism. We have investigated several candidate pathways implicated in the regulation of p21 expression, and observed increased activity of the stress kinase p38 in regenerating livers of c-jun (Deltali*) mice. Importantly, conditional deletion of p38alpha in livers of c-jun (Deltali*) mice fully restored hepatocyte proliferation and attenuated increased p21 protein levels after PH. These data demonstrate that c-Jun/AP-1 regulates liver regeneration through a novel molecular pathway that involves p53, p21, and the stress kinase p38alpha.
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Affiliation(s)
- Ewa Stepniak
- Research Institute of Molecular Pathology (IMP), A-1030 Vienna, Austria
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32
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Fiedler N, Quant E, Fink L, Sun J, Schuster R, Gerlich WH, Schaefer S. Differential effects on apoptosis induction in hepatocyte lines by stable expression of hepatitis B virus X protein. World J Gastroenterol 2006; 12:4673-82. [PMID: 16937438 PMCID: PMC4087832 DOI: 10.3748/wjg.v12.i29.4673] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: Hepatitis B virus protein X (HBx) has been shown to be weakly oncogenic in vitro. The transforming activities of HBx have been linked with the inhibition of several functions of the tumor suppressor p53. We have studied whether HBx may have different effects on p53 depending on the cell type.
METHODS: We used the human hepatoma cell line HepG2 and the immortalized murine hepatocyte line AML12 and analyzed stably transfected clones which expressed physiological amounts of HBx. P53 was induced by UV irradiation.
RESULTS: The p53 induction by UV irradiation was unaffected by stable expression of HBx. However, the expression of the cyclin kinase inhibitor p21waf/cip/sdi which gets activated by p53 was affected in the HBx transformed cell line AML12-HBx9, but not in HepG2. In AML-HBx9 cells, p21waf/cip/sdi-protein expression and p21waf/cip/sdi transcription were deregulated. Furthermore, the process of apoptosis was affected in opposite ways in the two cell lines investigated. While stable expression of HBx enhanced apoptosis induced by UV irradiation in HepG2-cells, apoptosis was decreased in HBx transformed AML12-HBx9. P53 repressed transcription from the HBV enhancer I, when expressed from expression vectors or after induction of endogenous p53 by UV irradiation. Repression by endogenous p53 was partially reversible by stably expressed HBx in both cell lines.
CONCLUSION: Stable expression of HBx leads to deregulation of apoptosis induced by UV irradiation depending on the cell line used. In an immortalized hepatocyte line HBx acted anti-apoptotic whereas expression in a carcinoma derived hepatocyte line HBx enhanced apoptosis.
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Affiliation(s)
- Nicola Fiedler
- Abt. Virologie, Institut fur Medizinische Mikrobiologie, Schillingallee 70, Universitat Rostock, D-18055 Rostock, Germany
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33
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Stehr W, Bernal NP, Erwin CR, Bernabe KQ, Guo J, Warner BW. Roles for p21waf1/cip1 and p27kip1 during the adaptation response to massive intestinal resection. Am J Physiol Gastrointest Liver Physiol 2006; 290:G933-41. [PMID: 16322092 DOI: 10.1152/ajpgi.00235.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The magnitude of gut adaptation is a decisive factor in determining whether patients are able to live independent of parenteral nutrition after massive small bowel loss. We previously established that the cyclin-dependent kinase inhibitor (CDKI) p21(waf1/cip1) is necessary for enterocyte proliferation and a normal adaptation response. In the present study, we have further elucidated the role of this CDKI in the context of p27(kip1), another member of the Cip/Kip CDKI family. Small bowel resections (SBRs) or sham operations were performed in control (C57/BL6), p21(waf1/cip1)-null, p27(kip1)-null, and p21(waf1/cip1)/p27(kip1) double-null mice. Morphological (villus height/crypt depth) alterations in the mucosa, the kinetics of enterocyte turnover (rates of enterocyte proliferation and apoptosis), and the protein expression of various cell cycle-regulatory proteins were recorded at various postoperative times. Enterocyte compartment-specific mRNA expression was investigated using laser capture microdissection. Resection-induced adaptation in control mice coincided with increased protein expression of p21(waf1/cip1) and decreased p27(kip1) within 3 days postoperatively. Identical changes in mRNA expression were detected in crypt but not in villus enterocytes. Adaptation occurred normally in control and p27(kip1)-null mice; however, mice deficient in both p21(waf1/cip1) and p27(kip1) failed to increase baseline rates of enterocyte proliferation and adaptation. The expression of p21(waf1/cip1) protein and mRNA in the proliferative crypt compartment is necessary for resection-induced enterocyte proliferation and adaptation. The finding that deficient expression of p27(kip1) does not affect adaptation suggests that these similar CDKI family members display distinctive cellular functions during the complex process of intestinal adaptation.
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Affiliation(s)
- Wolfgang Stehr
- Division of Pediatric General and Thoracic Surgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
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Cheng YB, Wang YJ, Zhang SC, Liu J, Chen Z, Li JJ. Response of porcine hepatocytes in primary culture to plasma from severe viral hepatitis patients. World J Gastroenterol 2006; 11:7585-90. [PMID: 16437682 PMCID: PMC4727237 DOI: 10.3748/wjg.v11.i48.7585] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To observe the effects of plasma from patients with severe viral hepatitis (SVHP) on the growth and metabolism of porcine hepatocytes and the clinical efficiency of bioartificial liver device. METHODS Hepatocytes were isolated from male porcines by collagenase perfusion. The synthesis of DNA and total protein, leakages of AST and LDH, changes in glutathione (GSH), catalase and morphology of porcine hepatocytes exposed to SVHP were investigated to indicate the effect of plasma from patients with severe hepatitis on the growth, injury, detoxification, and morphology of porcine hepatocytes. RESULTS The synthesis of DNA and protein was inhibited in the medium containing 100% SVHP compared to the controls. The leakages of LDH and AST increased in porcine hepatocytes following exposure to 100% SVHP for 5 h. The difference between 100% SVHP and 10% newborn calf serum (NCS) was significant in t-test (LDH: t = 24.552, P = 0.001; AST: t = 4.169, P = 0.014). After exposure to SVHP for 24 h, alterations in GSH status were significant (F = 2.746, P<0.05) between porcine hepatocytes in 100% SVHP and 10% NCS, but no alteration occurred in the culture medium after 48 h (F = 4.378, P<0.05). A similar profile was observed in catalase activity. Many round vacuoles were observed in porcine hepatocytes cultured in SVHP. The membranes of these cells became indistinct and almost all the cells died on d 5. CONCLUSION Plasma from patients with severe hepatitis inhibits the growth, injures membrane, disturbs GSH homeostasis and induces morphological changes of porcine hepatocytes. It is suggested that SVHP should be pretreated to reduce the toxin load and improve the performance of porcine hepatocytes in extracorporeal liver-support devices.
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Affiliation(s)
- Yong-Bo Cheng
- Institute of Infectious Diseases, Southwest Hospital, Third Military Medical University, Chongqing 400038, China
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35
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Barone M, Ladisa R, Di Leo A, Spano D, Francioso D, Aglio V, Amoruso A, Francavilla A, Iolascon A. Estrogen-induced proliferation in cultured hepatocytes involves cyclin D1, p21(Cip1) and p27(Kip1). Dig Dis Sci 2006; 51:580-6. [PMID: 16614970 DOI: 10.1007/s10620-006-3173-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 07/12/2005] [Indexed: 02/07/2023]
Abstract
The purpose of this study was to establish if estrogen-induced hepatocyte proliferation in vitro involves the cell cycle regulators cyclin D1, p21(Cip1), and p27(Kip1). Male rat hepatocytes were cultured in presence of 17-beta-estradiol (E2) +/- ICI-182780, a pure estrogen antagonist, and [3H]-thymidine, as required. DNA synthesis as well as p21(Cip1), p27(Kip1), and cyclin D1mRNA and protein levels were evaluated at different times (12, 24, 36, and 48 hours) of incubation. E2-increased DNA synthesis was correlated with cyclin D1 and p21(Cip1) (mRNA and protein) variations that were reversed by the addition of ICI-182780. p27(Kip1) protein levels progressively increased regardless of the presence of E2 or ICI-182780. Our data confirm that estrogens' stimulatory effect is related to their ability to increase cyclin D1 levels. The increase of p21(Cip1) is probably related to the reentry of hepatocytes in the quiescent state. p27(Kip1) protein is not able to arrest hepatocyte proliferation.
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Affiliation(s)
- M Barone
- Section of Gastroenterology, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
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36
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Yang S, Leow CK, Tan TMC. Expression patterns of cytokine, growth factor and cell cycle-related genes after partial hepatectomy in rats with thioacetamide-induced cirrhosis. World J Gastroenterol 2006; 12:1063-70. [PMID: 16534847 PMCID: PMC4087898 DOI: 10.3748/wjg.v12.i7.1070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To examine the differences in the responses of normal and cirrhotic livers to partial hepatectomy in relation to the factors influencing liver regeneration.
METHODS: Cirrhosis was induced in rats by admini-stration of thioacetamide. Untreated rats were used as controls. The control rats as well as the cirrhotic rats were subjected to 70% partial hepatectomy. At different time points after hepatectomy, the livers were collected and the levels of cytokines, growth factors and cell cycle proteins were analyzed.
RESULTS: After hepatectomy, the cirrhotic remnant expressed significantly lower levels of cyclin D1, its kinase partner, cdk4, and cyclin E as compared to the controls up to 72 h post hepatectomy. Significantly lower levels of cyclin A and cdk2 were also observed while the cdk inhibitor, p27 was significantly higher. In addition, the cirrhotic group had lower IL-6 levels than the control group at all time points up to 72 h following resection.
CONCLUSION: The data from our study shows that impaired liver regeneration in cirrhotic remnants is associated with low expression of cyclins and cdks. This might be the consequence of the low IL-6 levels in cirrhotic liver remnant which would in turn influence the actions of transcription factors that regulate genes involved in cell proliferation and metabolic homeostasis during the regeneration process.
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Affiliation(s)
- Shu Yang
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, MD7, 8 Medical Drive, S117597, Singapore
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37
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Eipel C, Schuett H, Glawe C, Bordel R, Menger MD, Vollmar B. Pifithrin-alpha induced p53 inhibition does not affect liver regeneration after partial hepatectomy in mice. J Hepatol 2005; 43:829-35. [PMID: 16087272 DOI: 10.1016/j.jhep.2005.04.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Revised: 03/30/2005] [Accepted: 04/20/2005] [Indexed: 01/22/2023]
Abstract
BACKGROUND/AIMS Beside its well-known function as tumour suppressor gene, p53 is supposed to positively regulate cell division and cell differentiation. Because hepatocyte proliferation has been reported to be reduced by blockade of p53 function in vitro, we examined in the present study the impact of p53 inhibition on hepatocyte proliferation in vivo. METHODS Mice treated with either pifithrin-alpha (PFT), a p53-inactivating agent, or the equivalent volume of vehicle, were subjected to 70% hepatectomy. In addition to assessment of liver mass restitution we examined p53 and p21 protein expression as well as PCNA expression and BrdU incorporation by using Western blot and immunohistochemical techniques. Extent of apoptosis was assessed by TUNEL assay. RESULTS PFT lowered nuclear but not cytoplasmic p53, and did not inhibit protein expression of regeneration-associated p21. PCNA protein expression as well as PCNA and BrdU immunohistochemistry did not differ between regenerating livers of either PFT- or vehicle-treated animals. Moreover, TUNEL analysis of regenerated liver tissue revealed comparable numbers of apoptotic cells in both groups. CONCLUSIONS Pharmacological inhibition of p53 did not impair liver regeneration in mice, implying that p53 is functionally redundant in that p53-independent pathways compensate for the blockade of p53 and sufficiently support the process of hepatocyte replication in liver regeneration.
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Affiliation(s)
- Christian Eipel
- Department of Experimental Surgery, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
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38
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Longo CR, Patel VI, Shrikhande GV, Scali ST, Csizmadia E, Daniel S, Sun DW, Grey ST, Arvelo MB, Ferran C. A20 protects mice from lethal radical hepatectomy by promoting hepatocyte proliferation via a p21waf1-dependent mechanism. Hepatology 2005; 42:156-64. [PMID: 15962316 DOI: 10.1002/hep.20741] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The liver has a remarkable regenerative capacity, allowing recovery following injury. Regeneration after injury is contingent on maintenance of healthy residual liver mass, otherwise fulminant hepatic failure (FHF) may arise. Understanding the protective mechanisms safeguarding hepatocytes and promoting their proliferation is critical for devising therapeutic strategies for FHF. We demonstrate that A20 is part of the physiological response of hepatocytes to injury. In particular, A20 is significantly upregulated in the liver following partial hepatectomy. A20 protects hepatocytes from apoptosis and ongoing inflammation by inhibiting NF-kappaB. Hepatic expression of A20 in BALB/c mice dramatically improves survival following extended and radical lethal hepatectomy. A20 expression in the liver limits hepatocellular damage hence maintains bilirubin clearance and the liver synthetic function. In addition, A20 confers a proliferative advantage to hepatocytes via decreased expression of the cyclin-dependent kinase inhibitor p21(waf1). In conclusion, A20 provides a proliferative advantage to hepatocytes. By combining anti-inflammatory, antiapoptotic and pro-proliferative functions, A20-based therapies could be beneficial in prevention and treatment of FHF.
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Affiliation(s)
- Christopher R Longo
- Immunobiology Research Center, Division of Vascular Surgery, and the Transplant Center, Department of Surgery, Harvard Medical School, Boston, MA 02215, USA
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39
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Lunz JG, Tsuji H, Nozaki I, Murase N, Demetris AJ. An inhibitor of cyclin-dependent kinase, stress-induced p21Waf-1/Cip-1, mediates hepatocyte mito-inhibition during the evolution of cirrhosis. Hepatology 2005; 41:1262-71. [PMID: 15880761 DOI: 10.1002/hep.20709] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
During the evolution of cirrhosis, there is a relative decrease in volume percentage of hepatocytes and a relative increase in biliary epithelial cells and myofibroblasts. This is recognized histopathologically as a ductular reaction and leads to gradual distortion of the normal hepatic architecture. The final or decompensated stage of cirrhosis is characterized by a further decline in hepatocyte proliferation and loss of functional liver mass that manifests clinically as ascites, encephalopathy, and other signs of liver failure. In this report, we tested the hypothesis that p21-mediated hepatocyte mito-inhibition accelerates the evolution of cirrhosis using an established mouse model of decompensated biliary cirrhosis, p21-deficient mice, and liver tissue from humans awaiting liver replacement. Despite the same insult of long-term (12-week) bile duct ligation, mice prone to decompensation showed significantly more oxidative stress and hepatocyte nuclear p21 expression, which resulted in less hepatocyte proliferation, an exaggerated ductular reaction, and more advanced disease compared with compensation-prone controls. Mice deficient in p21 were better able than wild-type controls to compensate for long-term bile duct ligation because of significantly greater hepatocyte proliferation, which led to a larger liver mass and less architectural distortion. Mito-inhibitory hepatocyte nuclear p21 expression in humans awaiting liver replacement directly correlated with pathological disease stage and model of end-stage liver disease scoring. In conclusion, stress-induced upregulation of hepatocyte p21 inhibits hepatocyte proliferation during the evolution of cirrhosis. These findings have implications for understanding the evolution of cirrhosis and associated carcinogenesis. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).
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Affiliation(s)
- John G Lunz
- Thomas E. Starzl Transplantation Institute, Division of Transplantation, University of Pittsburgh Medical Center, Pittsburgh, PA 15213-2582, USA
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40
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Wiemann SU, Satyanarayana A, Buer J, Kamino K, Manns MP, Rudolph KL. Contrasting effects of telomere shortening on organ homeostasis, tumor suppression, and survival during chronic liver damage. Oncogene 2005; 24:1501-9. [PMID: 15608677 DOI: 10.1038/sj.onc.1208308] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Telomere shortening limits the regenerative capacity of cells during aging and chronic disease but at the same time inhibits tumor progression, and it has yet to be determined which of these mechanisms is dominantly affecting organismal survival. Here we show that telomere shortening in telomerase knockout (mTERC-/-) mice in combination with chronic liver damage significantly reduced organismal survival even though telomere shortening strongly inhibited liver tumor formation. Decreased survival induced by telomere shortening correlated with an imbalance between liver cell proliferation and liver cell apoptosis. Specific changes in gene expression were associated with telomere shortening and chronic liver damage and these gene expression changes were partially reversed by adenovirus mediated telomerase gene delivery. This study gives experimental evidence that the negative impact of telomere shortening on organ homeostasis and organismal survival can surpass the beneficial effects of telomere shortening on suppression of tumor growth in the setting of chronic organ damage.
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Affiliation(s)
- Stefanie U Wiemann
- Department of Gastroenterology, Hepatology and Endocrinology, Medical School of Hannover, Carl-Neuberg-Str. 1, Germany
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41
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Pardali K, Kowanetz M, Heldin CH, Moustakas A. Smad pathway-specific transcriptional regulation of the cell cycle inhibitor p21WAF1/Cip1. J Cell Physiol 2005; 204:260-72. [PMID: 15690394 DOI: 10.1002/jcp.20304] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Transforming growth factor-beta (TGF-beta) inhibits epithelial cell growth, in part via transcriptional induction of the cell cycle inhibitor p21(WAF1/Cip1) (p21). We show that bone morphogenetic protein (BMP)-7 induces higher p21 expression than TGF-beta1 in various epithelial cells. Despite this, BMP-7 only weakly suppresses epithelial cell proliferation, as Id2, a cell cycle-promoting factor, becomes concomitantly induced by BMP-7. Signaling studies with all type I receptors of the TGF-beta superfamily show that BMP receptors induce higher p21 expression than TGF-beta/activin receptors. Smad4 is essential for p21 regulation by all receptor pathways. Based on the previously known ability of c-Myc to block p21 expression and epithelial growth arrest in response to TGF-beta1, we demonstrate that ectopic c-Myc expression can abrogate Smad-mediated p21 induction by all TGF-beta and BMP receptors. Furthermore, p21 induction by all receptor pathways can be blocked by the natural inhibitors of the TGF-beta superfamily. Smad7 inhibits all pathways whereas Smad6 selectively inhibits the BMP pathways. The observed pathway specificity reflects the efficiency by which BMP Smads, compared to TGF-beta Smads, transactivate the p21 promoter. In addition, BMP-specific Smads, Smad1, Smad5, and especially Smad8, induce endogenous p21 mRNA and protein levels, while they fail to induce epithelial growth inhibition when compared to TGF-beta receptor-phosphorylated Smads (R-Smads), Smad2 and Smad3. Thus, p21 is a common target of all TGF-beta superfamily pathways. However, the ability of TGF-beta superfamily members to induce cell growth arrest depends on the regulation of additional gene targets.
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42
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White P, Brestelli JE, Kaestner KH, Greenbaum LE. Identification of transcriptional networks during liver regeneration. J Biol Chem 2004; 280:3715-22. [PMID: 15546871 DOI: 10.1074/jbc.m410844200] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The molecular analysis of mammalian cellular proliferation in vivo is limited in most organ systems by the low turnover and/or the asynchronous nature of cell cycle progression. A notable exception is the partial hepatectomy model, in which quiescent hepatocytes reenter the cell cycle and progress in a synchronous fashion. Here we have exploited this model to identify regulatory networks operative in the mammalian cell cycle. We performed microarray-based expression profiling on livers 0-40 h post-hepatectomy corresponding to G0, G1, and S phases. Differentially expressed genes were identified using the statistical analysis program PaGE (Patterns from Gene Expression), which was highly accurate as confirmed by quantitative reverse transcription-PCR of randomly selected targets. A shift in the transcriptional program from genes involved in lipid and hormone biosynthesis in the quiescent liver to those contributing to cytoskeleton assembly and DNA synthesis in the proliferating liver was demonstrated by biological theme analysis. In a novel approach, we employed computational pathway analysis tools to identify specific regulatory networks operative at various stages of the cell cycle. This allowed us to identify a large cluster of genes controlling mitotic spindle assembly and checkpoint control at the 40-h time point as regulated at the mRNA level in vivo.
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Affiliation(s)
- Peter White
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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43
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Satyanarayana A, Greenberg RA, Schaetzlein S, Buer J, Masutomi K, Hahn WC, Zimmermann S, Martens U, Manns MP, Rudolph KL. Mitogen stimulation cooperates with telomere shortening to activate DNA damage responses and senescence signaling. Mol Cell Biol 2004; 24:5459-74. [PMID: 15169907 PMCID: PMC419883 DOI: 10.1128/mcb.24.12.5459-5474.2004] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Replicative senescence is induced by critical telomere shortening and limits the proliferation of primary cells to a finite number of divisions. To characterize the activity status of the replicative senescence program in the context of cell cycle activity, we analyzed the senescence phenotypes and signaling pathways in quiescent and growth-stimulated primary human fibroblasts in vitro and liver cells in vivo. This study shows that replicative senescence signaling operates at a low level in cells with shortened telomeres but becomes fully activated when cells are stimulated to enter the cell cycle. This study also shows that the dysfunctional telomeres and nontelomeric DNA lesions in senescent cells do not elicit a DNA damage signal unless the cells are induced to enter the cell cycle by mitogen stimulation. The amplification of senescence signaling and DNA damage responses by mitogen stimulation in cells with shortened telomeres is mediated in part through the MEK/mitogen-activated protein kinase pathway. These findings have implications for the further understanding of replicative senescence and analysis of its role in vivo.
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Affiliation(s)
- A Satyanarayana
- Department of Gastroenterology, Hepatology, and Endocrinology, Medical School Hannover, Germany
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44
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Reynolds R, Witherspoon S, Fox T. The infant mouse as a in vivo model for the detection and study of DNA damage-induced changes in the liver. Mol Carcinog 2004; 40:62-72. [PMID: 15108330 DOI: 10.1002/mc.20017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The present work describes the use of the infant (4-wk-old) mouse as an animal model for the study of DNA damage-induced G(1) checkpoint response, changes in p53 protein levels, and multiple gene expression changes after DNA damage has been induced in the liver. Hepatocytes in the infant B6C3F1 mouse had a proliferation index that was 27 times greater than that of the 12-wk-old B6C3F1 mouse (57.4 vs. 2.1%, respectively). Eight hours after infant mice were exposed to the DNA damaging agents bleomycin (100 mg/kg, i.p.) or 10 Gy of whole body gamma irradiation, the G(1)/S ratio significantly increased from 21 (control) to 66 and 75, respectively, because of the induction of the G(1)/S checkpoint response. One hour after whole body irradiation of infant mice the levels of the p53 protein, phosphoserine 18-p53 and phosphoserine 23-p53 increased dramatically and tended to peak at 1 h in the liver, whereas the p21(WAF1) protein increased more slowly and tended to peak at 2 h after irradiation. The mRNA expression of the p53-response genes p21, murine double minute clone 2 (mdm2), and cyclin G was increased at 2 h after irradiation but was decreased by 8 h postirradiation, relative to the 2-h time-point. The expression of insulin-like growth factor binding protein-1 (IGFBP-1) and growth-regulated oncogene 1 (GRO1) increased at 2 and 8 h postirradiation. This work characterizes various parameters in the infant mouse, thus validating the use of this model to study in vivo DNA damage-induced cell-cycle-related changes.
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Affiliation(s)
- Randall Reynolds
- Department of Comparative Biomedical Sciences, North Carolina State University, Raleigh, North Carolina, USA
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45
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Ilyin GP, Glaise D, Gilot D, Baffet G, Guguen-Guillouzo C. Regulation and role of p21 and p27 cyclin-dependent kinase inhibitors during hepatocyte differentiation and growth. Am J Physiol Gastrointest Liver Physiol 2003; 285:G115-27. [PMID: 12646420 DOI: 10.1152/ajpgi.00309.2002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Unlike a large number of cell types that undergo terminal differentiation associated with permanent withdrawal from the cell cycle, mature quiescent hepatocytes retain high proliferative potential. We report here a specific behavior of members of the Cip/Kip family of cyclin-dependent kinase (Cdk) inhibitors during development of the rat liver and proliferation of normal hepatocytes. Expression of p21, p27, and p57 transcripts and proteins was downregulated during the differentiation process to low or undetectable levels in adult liver. In contrast to p27, p21 protein increased in a mitogen-dependent manner in isolated hepatocytes and its expression pattern correlated with that of cyclin D1. In proliferating hepatocytes, p21 was predominantly associated with cyclin D1, these proteins were colocalized in the nucleus and p21-associated retinoblastoma protein (pRb) kinase activity increased in parallel with that of cyclin D1. Overexpression of p21 in mitogen-stimulated hepatocytes reduced DNA synthesis. In contrast, inhibition of p21 expression by antisense or small interfering RNAs oligonucleotides accelerated S phase entry. Finally, expression of p21 and cyclin D1, but not p27 proteins was regulated by MAPK kinase/extracellular signal-regulated kinase and phosphatidylinositol 3-kinase-ferric-reducing ability power/mammalian target of rapamycin signal transduction pathways. In conclusion, these results demonstrate a specific and differential regulation of p21 and p27 during hepatocyte differentiation and proliferation that may contribute to the control of quiescent differentiated hepatic cell proliferating activity.
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Affiliation(s)
- Gennady P Ilyin
- Institut National de la Santé et de la Recherche Médicale U522, Avenue de la Bataille Flandre/Dunkerque, Hôpital Pontchaillou, 35033 Rennes Cedex, France.
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46
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Abstract
The ability of the liver to regenerate after resection has been known for many years. Two reports from Germany in the late 1800s probably mark the introduction of the phenomenon into the scientific literature, but in the early 1900s the first reviews of this subject had appeared in the English literature. Predating these early scientific reports the legends from the Greek mythology described the fate of Prometheus. As punishment for defying Zeus and revealing the secret of fire to man, Prometheus was chained to a rock and each day had part of his liver ripped out by an eagle which, returning the following day, repeated the torture because his liver regenerated itself overnight. Although the speed of regeneration in the Greek legend is somewhat greater than that observed either clinically or in the laboratory, the myth does serve to emphasise the remarkable ability of the liver to repeatedly regenerate following repeated resections. This review aims to summarise the more recent literature concerning the early molecular events accompanying liver regeneration and to integrate this with the existing knowledge of this subject.
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Affiliation(s)
- David Mangnall
- University Department of Surgical and Anaesthetic Sciences, K Floor, Royal Hallamshire Hospital, Glossop Road S10 2JF, UK.
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47
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Yang C, Sun M, Ilic Z, Friedrich TD, Sell S. Reduced expression of p27kip1 and increased hepatocyte proliferation in p53-deficient mice. Mol Carcinog 2003; 36:15-22. [PMID: 12503075 DOI: 10.1002/mc.10086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Livers from wild-type and p53-deficient mice were analyzed for the expression of cell-cycle regulatory proteins in an attempt to determine the mechanism for the increased proliferation of liver cells in p53-deficient mice associated with enhanced susceptibility to aflatoxin-induced liver cancer. The most striking difference found was a significant reduction of the cyclin-dependent kinase inhibitor p27(kip1) in the livers of 3-mo-old p53-/- mice, whereas only small changes were found in the expression of cyclins, cyclin-dependent kinases, and the inhibitors p21(cip1) and p16(ink4a). Relative to wild-type liver, the amounts of p27(kip1) mRNA were reduced at both 1 and 3 mo, whereas the levels of p27(kip1) protein were decreased only at 3 mo. These results identify an uncharacterized link between the expression of p53 and p27(kip1) that may involve both transcriptional and post-transcriptional regulation and allow hepatocytes to continue to proliferate after 3 wk of age. We postulate that this increased proliferation leads to increased susceptibility to aflatoxin-induced hepatocarcinogenesis.
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Affiliation(s)
- Chuanwei Yang
- Center for Immunology and Microbial Disease, Albany Medical College, New York, USA
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48
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Osawa Y, Nagaki M, Banno Y, Brenner DA, Asano T, Nozawa Y, Moriwaki H, Nakashima S. Tumor necrosis factor alpha-induced interleukin-8 production via NF-kappaB and phosphatidylinositol 3-kinase/Akt pathways inhibits cell apoptosis in human hepatocytes. Infect Immun 2002; 70:6294-301. [PMID: 12379708 PMCID: PMC130316 DOI: 10.1128/iai.70.11.6294-6301.2002] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2002] [Revised: 05/03/2002] [Accepted: 08/02/2002] [Indexed: 12/20/2022] Open
Abstract
Tumor necrosis factor alpha (TNF-alpha) not only induces apoptotic signals but also causes antiapoptotic and regenerative responses in the liver. However, the molecular mechanism(s) of the latter events remains unclear. In the present study, we examined TNF-alpha-induced genes in Hc human normal (unsensitized) hepatocytes by cDNA microarray analysis. Interleukin-8 (IL-8) induction was the most pronounced of the upregulated genes. The IL-8 protein level was also increased. IL-8 belongs to the ELR-CXC chemokine family and appears to exert mitogenic and antiapoptotic functions in other cell systems. IL-8 expression by TNF-alpha was inhibited when two survival signals, nuclear factor kappaB (NF-kappaB) and phosphatidylinositol 3-kinase (PI3K)/Akt, were inhibited by a mutant form of inhibitor of NF-kappaB (IkappaB); by dominant negative (kinase-dead) Akt; or by treatment with LY 294002, an inhibitor of PI3K. TNF-alpha induced apoptosis in Hc cells that were sensitized by inhibition of NF-kappaB and PI3K activation. IL-8 administration protected mice against concanavalin A-induced hepatitis in vivo. IL-8 also rescued the sensitized Hc cells, at least in part, from TNF-alpha-induced apoptosis in vitro. TNF-alpha inhibited DNA synthesis in unsensitized Hc cells in the absence of serum. Exogenous IL-8 reversed, though anti-IL-8 neutralization antibody enhanced, growth inhibition by TNF-alpha. These results indicate that IL-8, the production of which is stimulated by TNF-alpha, inhibits apoptosis of sensitized hepatocytes and releases normal (unsensitized) hepatocytes from growth inhibition induced by TNF-alpha.
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Affiliation(s)
- Yosuke Osawa
- First Department of Internal Medicine, Gifu University School of Medicine, Gifu 500-8705, Japan
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49
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Kwon YH, Jovanovic A, Serfas MS, Kiyokawa H, Tyner AL. P21 functions to maintain quiescence of p27-deficient hepatocytes. J Biol Chem 2002; 277:41417-22. [PMID: 12202477 DOI: 10.1074/jbc.m203388200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hepatocytes rarely proliferate in the healthy adult liver. We explored the roles of the cyclin kinase inhibitors p21 and p27 in maintaining hepatocyte quiescence. p27 is expressed throughout the wild-type liver, but the related protein p21 was not detected. However, p21 was detected in livers of p27-deficient mice. Increased p21 protein levels did not result from an increase in p21 mRNA expression, indicating that p21 expression is regulated post-transcriptionally. p21 protein levels increased in cultured primary hepatocytes treated with the proteasome inhibitor MG132 and cycloheximide, indicating that p21 expression is regulated at the level of protein stability in liver cells. Although increased expression of cyclin-dependent kinase (Cdk) 4, Cdk2, and proliferating cell nuclear antigen was detected in p27-deficient livers, increased hepatocyte proliferation was detected only in livers of mice deficient for both p21 and p27. In p27-deficient livers, p21 was found in complexes with Cdk2 and CdK4 and can compensate for the absence of p27. Our data indicate that cyclin kinase inhibitor activity is important for maintaining hepatocyte quiescence in the adult liver. Significant increases in p21 were detected in multiple tissues of mature p27-deficient mice compared with wild-type mice, suggesting that the ability of p21 to functionally substitute for p27 is not liver-specific.
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Affiliation(s)
- Young Hye Kwon
- Department of Molecular Genetics, University of Illinois, Chicago 60607, USA
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50
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Inoue Y, Tomiya T, Yanase M, Arai M, Ikeda H, Tejima K, Ogata I, Kimura S, Omata M, Fujiwara K. p53 May positively regulate hepatocyte proliferation in rats. Hepatology 2002; 36:336-44. [PMID: 12143041 DOI: 10.1053/jhep.2002.34942] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
p53, known as a tumor suppressor gene, is a transcription factor that regulates various cellular functions. Recently, several growth factor gene promoters, including that of transforming growth factor alpha (TGF-alpha), were shown to be direct targets of p53-mediated transcription. Hepatic p53 mRNA is up-regulated during liver regeneration in rats. The aim of this study is to examine the role of p53 in hepatocyte proliferation. p53 protein levels were examined in rat hepatocytes cultured in the medium containing hepatocyte growth factor (HGF). p53 levels began to increase after 6 hours of incubation, reached a maximum at 18 hours, and decreased thereafter. DNA synthesis increased at 12 hours and peaked at 30 hours. When hepatocytes were incubated with p53 antisense oligonucleotide in addition to HGF, increases of p53 and TGF-alpha levels were suppressed, and DNA synthesis was reduced. The increases of TGF-alpha levels and DNA synthesis were also suppressed by a chemical inhibitor of p53, pifithrin-alpha. In rats after two-thirds partial hepatectomy, hepatic p53 increased and reached maximal levels around 16 hours when hepatic HGF levels have been shown to reach a maximum followed by an increase in hepatic TGF-alpha levels or hepatocyte proliferation. In contrast, sham-operated rats showed minor elevations of hepatic p53 levels. In conclusion, p53 production is stimulated by HGF and may contribute to the proliferation of rat hepatocytes. Considering previous findings indicating the importance of endogenous TGF-alpha for the proliferation of hepatocytes stimulated by HGF, TGF-alpha might play a role in HGF-p53 mediated hepatocyte proliferation.
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Affiliation(s)
- Yukiko Inoue
- Department of Gastroenterology, Faculty of Medicine, University of Tokyo, Tokyo, Japan
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