Adiponectin and heme oxygenase-1 suppress TLR4/MyD88-independent signaling in rat Kupffer cells and in mice after chronic ethanol exposure

J Immunol. 2010 Oct 15;185(8):4928-37. doi: 10.4049/jimmunol.1002060. Epub 2010 Sep 22.

Abstract

Alcoholic liver disease is mediated via activation of TLR4 signaling; MyD88-dependent and -independent signals are important contributors to injury in mouse models. Adiponectin, an anti-inflammatory adipokine, suppresses TLR4/MyD88-dependent responses via induction of heme oxygenase-1 (HO-1). Here we investigated the interactions between chronic ethanol, adiponectin, and HO-1 in regulation of TLR4/MyD88-independent signaling in macrophages and an in vivo mouse model. After chronic ethanol feeding, LPS-stimulated expression of IFN-β and CXCL10 mRNA was increased in primary cultures of Kupffer cells compared with pair-fed control mice. Treatment of Kupffer cells with globular adiponectin (gAcrp) normalized this response. LPS-stimulated IFN-β/CXCL10 mRNA and CXCL10 protein was also reduced in RAW 264.7 macrophages treated with gAcrp or full-length adiponectin. gAcrp and full-length adiponectin acted via adiponectin receptors 1 and 2, respectively. gAcrp decreased TLR4 expression in both Kupffer cells and RAW 264.7 macrophages. Small interfering RNA knockdown of HO-1 or inhibition of HO-1 activity with zinc protoporphyrin blocked these effects of gAcrp. C57BL/6 mice were exposed to chronic ethanol feeding, with or without treatment with cobalt protoporphyrin, to induce HO-1. After chronic ethanol feeding, mice were sensitized to in vivo challenge with LPS, expressing increased IFN-β/CXCL10 mRNA and CXCL10 protein in liver compared with control mice. Pretreatment with cobalt protoporphyrin 24 h before LPS challenge normalized this effect of ethanol. Adiponectin and induction of HO-1 potently suppressed TLR4-dependent/MyD88-independent cytokine expression in primary Kupffer cells from rats and in mouse liver after chronic ethanol exposure. These data suggest that induction of HO-1 may be a useful therapeutic strategy in alcoholic liver disease.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adiponectin / metabolism*
  • Animals
  • Blotting, Western
  • Cell Separation
  • Central Nervous System Agents / toxicity*
  • Enzyme-Linked Immunosorbent Assay
  • Ethanol / toxicity*
  • Female
  • Flow Cytometry
  • Heme Oxygenase-1 / drug effects
  • Heme Oxygenase-1 / metabolism*
  • Immunohistochemistry
  • Kupffer Cells / drug effects
  • Kupffer Cells / metabolism*
  • Liver Diseases, Alcoholic / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Myeloid Differentiation Factor 88 / drug effects
  • Myeloid Differentiation Factor 88 / metabolism*
  • Rats
  • Rats, Wistar
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Toll-Like Receptor 4 / drug effects
  • Toll-Like Receptor 4 / metabolism*

Substances

  • Adiponectin
  • Central Nervous System Agents
  • Myeloid Differentiation Factor 88
  • Toll-Like Receptor 4
  • Ethanol
  • Heme Oxygenase-1