Beta-catenin–NF-κB interactions in murine hepatocytes: A complex to die for

Authors

  • Kari Nejak-Bowen,

    Corresponding author
    1. Departments of Pathology, University of Pittsburgh, Pittsburgh, PA
    • University of Pittsburgh, School of Medicine, 200 Lothrop Street, S433-BST, Pittsburgh, PA 15261
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    • fax: 412-648-1916;

  • Alexander Kikuchi,

    1. Departments of Pathology, University of Pittsburgh, Pittsburgh, PA
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  • Satdarshan P.S. Monga

    Corresponding author
    1. Departments of Pathology, University of Pittsburgh, Pittsburgh, PA
    2. Departments of Medicine, University of Pittsburgh, Pittsburgh, PA
    • University of Pittsburgh, School of Medicine, 200 Lothrop Street S-421 BST, Pittsburgh, PA 15261
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    • fax: 412-648-1916.


  • Potential conflict of interest: Dr. Monga consults for Bristol-Myers Squibb, Merck, and Phase Rx.

  • Supported by National Institutes of Health Grants 1R01DK62277 and 1R01CA124414 (to S. P. S. M.) and by Rango's Fund for the Enhancement of Pathology Research. This work was also supported in part by a Postdoctoral Research Fellowship from ALF/AASLD to KNB.

Abstract

Wnt/β-catenin signaling plays an important role in hepatic homeostasis, especially in liver development, regeneration, and cancer, and loss of β-catenin signaling is often associated with increased apoptosis. To elucidate how β-catenin may be regulating hepatocyte survival, we investigated the susceptibility of β-catenin conditional knockout (KO) mice and their wild-type (WT) littermates to Fas and tumor necrosis factor-α (TNF-α), two common pathways of hepatocyte apoptosis. While comparable detrimental effects from Fas activation were observed in WT and KO, a paradoxical survival benefit was observed in KO mice challenged with D-galactosamine/lipopolysaccharide. KO mice showed significantly lower morbidity and liver injury due to early, robust, and protracted activation of NF-κB in the absence of β-catenin. Enhanced NF-κB activation in KO mice was associated with increased basal inflammation and Toll-like receptor 4 expression and lack of the p65/β-catenin complex in hepatocytes. The p65/β-catenin complex in WT livers underwent temporal dissociation allowing for NF-κB activation to regulate hepatocyte survival following TNF-α-induced hepatic injury. Decrease of total β-catenin protein but not its inactivation induced p65 activity, whereas β-catenin stabilization either chemically or due to mutations repressed it in hepatomas in a dose-dependent manner, whereas β-catenin stabilization repressed it either chemically or due to mutations. Conclusion: The p65/β-catenin complex in hepatocytes undergoes dynamic changes during TNF-α–induced hepatic injury and plays a critical role in NF-κB activation and cell survival. Modulation of β-catenin levels is a unique mode of regulating NF-κB activity and thus may present novel opportunities in devising therapeutics in specific hepatic injuries. (HEPATOLOGY 2013)

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