Gastroenterology

Gastroenterology

Volume 130, Issue 2, February 2006, Pages 435-452
Gastroenterology

Basic–liver, pancreas, and biliary tract
Natural Killer Cells Ameliorate Liver Fibrosis by Killing Activated Stellate Cells in NKG2D-Dependent and Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand–Dependent Manners

https://doi.org/10.1053/j.gastro.2005.10.055Get rights and content

Background & Aims: Viral hepatitis infection, which is a major cause of liver fibrosis, is associated with activation of innate immunity. However, the role of innate immunity in liver fibrosis remains obscure. Methods: Liver fibrosis was induced either by feeding mice with the 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet or by injecting them with carbon tetrachloride. The Toll-like receptor 3 ligand, polyinosinic-polycytidylic acid, was used to activate innate immunity cells and mediators, including natural killer cells and interferon γ. Results: In the mouse model of DDC-induced liver fibrosis, natural killer cell activation by polyinosinic-polycytidylic acid induced cell death to activated hepatic stellate cells and attenuated the severity of liver fibrosis. Polyinosinic-polycytidylic acid treatment also ameliorated liver fibrosis induced by carbon tetrachloride. The observed protective effect of polyinosinic-polycytidylic acid on liver fibrosis was diminished through either depletion of natural killer cells or by disruption of the interferon γ gene. Expression of retinoic acid early inducible 1, the NKG2D ligand, was undetectable on quiescent hepatic stellate cells, whereas high levels were found on activated hepatic stellate cells, which correlated with the resistance and susceptibility of quiescent hepatic stellate cells and activated hepatic stellate cells to natural killer cell lysis, respectively. Moreover, treatment with polyinosinic-polycytidylic acid or interferon γ enhanced the cytotoxicity of natural killer cells against activated hepatic stellate cells and increased the expression of NKG2D and tumor necrosis factor–related apoptosis-inducing ligand on liver natural killer cells. Blocking NKG2D or tumor necrosis factor–related apoptosis-inducing ligand with neutralizing antibodies markedly diminished the cytotoxicity of polyinosinic-polycytidylic acid–activated natural killer cells against activated hepatic stellate cells. Conclusions: Our findings suggest that natural killer cells kill activated hepatic stellate cells via retinoic acid early inducible 1/NKG2D-dependent and tumor necrosis factor–related apoptosis-inducing ligand–dependent mechanisms, thereby ameliorating liver fibrosis.

Section snippets

Materials

Poly I:C, Gey’s balanced salt solution, and OptiPrep were purchased from Sigma (St Louis, MO). Pronase E and collagenase D were obtained from Roche (Indianapolis, IN).

Mice

Eight- to 10-week old male C57BL/6J, IFN-γ−/− mice (C57BL/6J background), perforin−/− mice (C57BL/6J background), and Fas ligand (FasL)−/− mice (C57BL/6Smn background) were purchased from the Jackson Laboratory (Bar Harbor, ME). CD1d−/− mice (natural killer T cell [NKT] deficient) on a BALB/c background were originally purchased

Polyinosinic-Polycytidylic Acid Treatment Attenuates Liver Fibrosis Induced by DDC Diet or Carbon Tetrachloride Injection

Feeding mice with a diet containing DDC induced liver injury as evidenced by elevation of serum alanine aminotransferase levels and necrosis in the liver (Figure 1A). Fibrosis was also induced, as shown by collagen deposition (blue staining by Masson trichrome) and HSC activation (α-SMA–positive staining; Figure 1B and C). To investigate the effect of NK cell activation on liver fibrosis, mice were fed the DDC diet and cotreated with poly I:C, which activates NK cells and induces accumulation

Discussion

In this article, we show (1) that NK cells are able to kill activated HSCs, central mediators in the development of liver fibrosis, thereby ameliorating liver fibrosis; (2) that NK cell cytotoxicity against activated HSCs is mediated via NKG2D/RAE1- and TRAIL-dependent mechanisms; and (3) that IFN-γ and the TLR3 ligand poly I:C inhibit liver fibrosis by enhancing NK cell cytotoxicity against activated HSCs.

Conclusions

In our investigation, we show in a mouse model of DDC-induced fibrosis that NK cells kill activated HSCs via RAE1/NKG2D- and TRAIL-dependent mechanisms, thereby controlling liver fibrosis. Clinical evidence suggests that HCV-infected patients with suppressed immune functions and low NK cell activity have accelerated progression of liver fibrosis.43, 44, 45 For example, progression of liver fibrosis is much faster in HCV patients who are coinfected with human immunodeficiency virus44 or who have

References (76)

  • F. Oakley et al.

    Inhibition of inhibitor of kappaB kinases stimulates hepatic stellate cell apoptosis and accelerated recovery from rat liver fibrosis

    Gastroenterology

    (2005)
  • D.M. Bissell et al.

    Transforming growth factor beta and the liver

    Hepatology

    (2001)
  • B. Schnabl et al.

    The role of Smad3 in mediating mouse hepatic stellate cell activation

    Hepatology

    (2001)
  • S. Dooley et al.

    Smad7 prevents activation of hepatic stellate cells and liver fibrosis in rats

    Gastroenterology

    (2003)
  • M.J. Smyth et al.

    Activation of NK cell cytotoxicity

    Mol Immunol

    (2005)
  • Y. Benhamou et al.

    Factors affecting liver fibrosis in human immunodeficiency virus- and hepatitis C virus-coinfected patientsimpact of protease inhibitor therapy

    Hepatology

    (2001)
  • M. Berenguer et al.

    HCV-related fibrosis progression following liver transplantationincrease in recent years

    J Hepatol

    (2000)
  • R. Safadi et al.

    Immune stimulation of hepatic fibrogenesis by CD8 cells and attenuation by transgenic interleukin-10 from hepatocytes

    Gastroenterology

    (2004)
  • R. Fischer et al.

    Caspase 9-dependent killing of hepatic stellate cells by activated Kupffer cells

    Gastroenterology

    (2002)
  • C.A. Biron et al.

    NK cells and NKT cells in innate defense against viral infections

    Curr Opin Immunol

    (2001)
  • C. Asseman et al.

    Schistosoma mansoni-infected mice show augmented hepatic fibrosis and selective inhibition of liver cytokine production after treatment with anti-NK1.1 antibodies

    Immunol Lett

    (1996)
  • M. Nomura et al.

    Isolation and characterization of retinoic acid-inducible cDNA clones in F9 cellsone of the early inducible clones encodes a novel protein sharing several highly homologous regions with a Drosophila polyhomeotic protein

    Differentiation

    (1994)
  • A. Cerwenka et al.

    Retinoic acid early inducible genes define a ligand family for the activating NKG2D receptor in mice

    Immunity

    (2000)
  • N. Kawarabayashi et al.

    Decrease of CD56(+)T cells and natural killer cells in cirrhotic livers with hepatitis C may be involved in their susceptibility to hepatocellular carcinoma

    Hepatology

    (2000)
  • C.A. Biron

    Interferons alpha and beta as immune regulators—a new look

    Immunity

    (2001)
  • B. Gao

    Alcohol and hepatitis virus interactions in liver pathology

  • T.J. Liang et al.

    Pathogenesis, natural history, treatment, and prevention of hepatitis C

    Ann Intern Med

    (2000)
  • S.K. Fung et al.

    Update on viral hepatitis in 2004

    Curr Opin Gastroenterol

    (2005)
  • B. Rehermann et al.

    Immunology of hepatitis B virus and hepatitis C virus infection

    Nat Rev Immunol

    (2005)
  • A. Ahmad et al.

    Role of NK and NKT cells in the immunopathogenesis of HCV-induced hepatitis

    J Leukoc Biol

    (2004)
  • Y. Chen et al.

    Activation and function of hepatic NK cells in hepatitis B infectionan underinvestigated innate immune response

    J Viral Hepat

    (2005)
  • G. Ahlenstiel et al.

    Hepatitis C virus and the threshold of natural killer cell inhibition

    Hepatology

    (2005)
  • S.I. Khakoo et al.

    HLA and NK cell inhibitory receptor genes in resolving hepatitis C virus infection

    Science

    (2004)
  • Z.X. Liu et al.

    NK cells cause liver injury and facilitate the induction of T cell-mediated immunity to a viral liver infection

    J Immunol

    (2000)
  • K.A. Muhlen et al.

    NK cells, but not NKT cells, are involved in Pseudomonas aeruginosa exotoxin A-induced hepatotoxicity in mice

    J Immunol

    (2004)
  • R. Bataller et al.

    Liver fibrosis

    J Clin Invest

    (2005)
  • S.L. Friedman

    Liver fibrosis—from bench to bedside

    J Hepatol

    (2003)
  • Z. Shi et al.

    Strain-specific differences in mouse hepatic wound healing are mediated by divergent T helper cytokine responses

    Proc Natl Acad Sci U S A

    (1997)

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