Toll-like receptor 2 and palmitic acid cooperatively contribute to the development of nonalcoholic steatohepatitis through inflammasome activation in mice

Authors

  • Kouichi Miura,

    Corresponding author
    1. Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA
    2. Department of Gastroenterology, Akita University Graduate School of Medicine, Akita, Japan
    • Department of Gastroenterology, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita-shi, Akita, Japan 010-8543.
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  • Ling Yang,

    1. Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA
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  • Nico van Rooijen,

    1. Department of Molecular Cell Biology, Vrije Universiteit Medical Center, Amsterdam, Netherlands
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  • David A. Brenner,

    1. Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA
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  • Hirohide Ohnishi,

    1. Department of Gastroenterology, Akita University Graduate School of Medicine, Akita, Japan
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  • Ekihiro Seki

    Corresponding author
    1. Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA
    • Division of Gastroenterology, Department of Medicine, University of California, San Diego, School of Medicine, 9500 Gilman Drive, MC#0702, Leichtag Biomedical Research Building, Room #118B, La Jolla, CA 92093-0702.
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  • Potential conflict of interest: Nothing to report.

  • This study was supported by National Institutes of Health Grants R01AA02172 (to E. S.), R01DK085252 (to E. S.), R24DK090962 (to D. A. B.), and R01GM041804 (to D. A. B.); a pilot grant from the University of California, San Diego Digestive Diseases Research Development Center (DK080506) (to E. S.); the Takeda Science Foundation (K. M.); The Mochida Memorial Foundation for Medical and Pharmaceutical Research (K. M.); the Mishima Kaiun Memorial Foundation (K. M.); and a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (to K. M.).

Abstract

Innate immune signaling associated with Toll-like receptors (TLRs) is a key pathway involved in the progression of nonalcoholic steatohepatitis (NASH). Here we show that both TLR2 and palmitic acid are required for activation of the inflammasome, interleukin (IL)-1α, and IL-1β, resulting in the progression of NASH. Wild-type (WT) and TLR2−/− mice were fed a choline-deficient amino acid–defined (CDAA) diet for 22 weeks to induce NASH. Bone marrow–transplanted TLR2 chimeric mice were generated after the recipient mice were lethally irradiated. Kupffer cells and hepatic stellate cells (HSCs) were isolated from WT mice and stimulated with TLR2 ligand and/or palmitic acid. WT mice on the CDAA diet developed profound steatohepatitis and liver fibrosis. In contrast, TLR2−/− mice had suppressed progression of NASH. Although both Kupffer cells and HSCs respond to TLR2 ligand, TLR2 bone marrow chimeric mice demonstrated that Kupffer cells were relatively more important than HSCs in TLR2-mediated progression of NASH. In vitro, palmitic acid alone did not increase TLR2 signaling-target genes, including cytokines and inflammasome components in Kupffer cells and HSCs. The TLR2 ligand increased Nod-like receptor protein 3, an inflammasome component, in Kupffer cells but not in HSCs. In the presence of TLR2 ligand, palmitic acid did induce caspase-1 activation and release of IL-1α and IL-1β in Kupffer cells; however, these effects were not observed in HSCs. In vivo, WT mice on the CDAA diet showed increased caspase-1 activation in the liver and elevated serum levels of IL-1α and IL-1β levels, which were suppressed in TLR2−/− mice. Conclusion: TLR2 and palmitic acid cooperatively activate the inflammasome in Kupffer cells and/or macrophages in the development of NASH. (HEPATOLOGY 2013;)

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