title: Gas6/Axl pathway is activated in chronic liver disease and its targeting reduces fibrosis via hepatic stellate cell inactivation.
abstract: OBJECTIVE
  Liver fibrosis, an important health concern associated to chronic liver injury that provides a permissive environment for cancer development, is characterized by accumulation of extracellular matrix components mainly derived from activated hepatic stellate cells (HSCs). Axl, a receptor tyrosine kinase and its ligand Gas6, are involved in cell differentiation, immune response and carcinogenesis.
  
  
  METHODS
  HSCs were obtained from WT and Axl(-/-) mice, treated with recombinant Gas6 protein (rGas6), Axl siRNAs or the Axl inhibitor BGB324, and analyzed by western blot and real-time PCR. Experimental fibrosis was studied in CCl4-treated WT and Axl(-/-) mice, and in combination with Axl inhibitor. Gas6 and Axl serum levels were measured in alcoholic liver disease (ALD) and hepatitis C virus (HCV) patients.
  
  
  RESULTS
  In primary mouse HSCs, Gas6 and Axl levels paralleled HSC activation. rGas6 phosphorylated Axl and AKT prior to HSC phenotypic changes, while Axl siRNA silencing reduced HSC activation. Moreover, BGB324 blocked Axl/AKT phosphorylation and diminished HSC activation. In addition, Axl(-/-) mice displayed decreased HSC activation in vitro and liver fibrogenesis after chronic damage by CCl4 administration. Similarly, BGB324 reduced collagen deposition and CCl4-induced liver fibrosis in mice. Importantly, Gas6 and Axl serum levels increased in ALD and HCV patients, inversely correlating with liver functionality.
  
  
  CONCLUSIONS
  The Gas6/Axl axis is required for full HSC activation. Gas6 and Axl serum levels increase in parallel to chronic liver disease progression. Axl targeting may be a therapeutic strategy for liver fibrosis management.
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bárcena
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Milica
authors.initials: M
authors.lastname: Stefanovic
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Tutusaus
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Leonel
authors.initials: L
authors.lastname: Joannas
authors.affiliation: Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Anghara
authors.initials: A
authors.lastname: Menéndez
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: García-Ruiz
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain.
authors.forename: Pau
authors.initials: P
authors.lastname: Sancho-Bru
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Marí
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Caballeria
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Carla V
authors.initials: CV
authors.lastname: Rothlin
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain; Research Center for Alcoholic Liver and Pancreatic Diseases, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA.
authors.forename: José C
authors.initials: JC
authors.lastname: Fernández-Checa
authors.affiliation: Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain. Electronic address: pablo.garcia@iibb.csic.es.
authors.forename: Pablo García
authors.initials: PG
authors.lastname: de Frutos
authors.affiliation: Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain. Electronic address: amorales@clinic.ub.es.
authors.forename: Albert
authors.initials: A
authors.lastname: Morales
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D002251:Carbon Tetrachloride; D049109:Cell Proliferation; D002478:Cells, Cultured; D002908:Chronic Disease; D055166:Hepatic Stellate Cells / Q000502:physiology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood / Q000502:physiology*; D008103:Liver Cirrhosis / Q000188:drug therapy / Q000209:etiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D016328:NF-kappa B / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D000076202:c-Mer Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D002251:Carbon Tetrachloride; D036341:Intercellular Signaling Peptides and Proteins; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6; C097072:MERTK protein, human
keywords: Chronic liver patients; Experimental fibrosis; Gas6/Axl serum levels; HSC activation; TAM receptors