Both bone marrow-derived and non-bone marrow-derived cells contribute to AIM2 and NLRP3 inflammasome activation in a MyD88-dependent manner in dietary steatohepatitis

Liver Int. 2014 Oct;34(9):1402-13. doi: 10.1111/liv.12537. Epub 2014 Apr 17.

Abstract

Background & aims: Inflammation promotes the progression of non-alcoholic steatohepatitis (NASH). Toll-like receptor 4 (TLR4) and TLR9 activation through myeloid differentiation primary response gene 88 (MyD88) and production of mature interleukin-1β (IL-1β) via inflammasome activation contribute to steatohepatitis. Here, we investigated the inter-relationship between TLR signalling and inflammasome activation in dietary steatohepatitis.

Methods: Wild type (WT), TLR4- and MyD88-deficient (KO) mice received methionine-choline-deficient (MCD) or -supplemented (MCS) diets for 5 weeks and a subset was challenged with TLR9 ligand CpG-DNA.

Results: TLR4, TLR9, AIM2 (absent in melanoma 2) and NLRP3 (NLR family pyrin domain containing 3) inflammasome mRNA, and mature IL-1β protein levels were increased in MCD diet-induced steatohepatitis compared to MCS controls. TLR9 stimulation resulted in greater up-regulation of the DNA-sensing AIM2 expression and IL-1β production in livers of MCD compared to MCS diet-fed mice. High mobility group box 1 (HMGB1), a TLR9-activating danger molecule and phospho-HMGB1 protein levels were also increased in livers of MCD diet-fed mice. MyD88- but not TLR4-deficiency prevented up-regulation of AIM2, NLRP3 mRNA and IL-1β protein production in dietary steatohepatitis. Selective MyD88 deficiency either in bone marrow (BM)-derived or non-BM-derived cells attenuated hepatic up-regulation of inflammasome mRNA, caspase-1 activation and IL-1β protein production, but only BM-derived cell-specific MyD88-deficiency attenuated liver injury.

Conclusions: Our data demonstrate that both bone marrow-derived and non-BM-derived cells contribute to inflammasome activation in a MyD88-dependent manner in dietary steatohepatitis. We show that AIM2 inflammasome expression and activation are further augmented by TLR9 ligands in dietary steatohepatitis.

Keywords: AIM2; HMGB1; IL-1β; MyD88; NLRP3; TLR4; TLR9; caspase-1; inflammasome; non-alcoholic steatohepatitis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Blotting, Western
  • Bone Marrow Cells / metabolism
  • Carrier Proteins / metabolism*
  • Choline Deficiency
  • DNA-Binding Proteins / metabolism*
  • Diet
  • Gene Expression Regulation / physiology*
  • Immunoprecipitation
  • Inflammasomes / metabolism*
  • Methionine / deficiency
  • Mice
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism*
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Non-alcoholic Fatty Liver Disease / metabolism*
  • Real-Time Polymerase Chain Reaction
  • Signal Transduction / physiology*
  • Statistics, Nonparametric
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism
  • Toll-Like Receptor 9 / metabolism

Substances

  • Aim2 protein, mouse
  • Carrier Proteins
  • DNA-Binding Proteins
  • Inflammasomes
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Nlrp3 protein, mouse
  • Tlr4 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 4
  • Toll-Like Receptor 9
  • Methionine