Mitochondrial Double-Stranded RNA in Exosome Promotes Interleukin-17 Production Through Toll-Like Receptor 3 in Alcohol-associated Liver Injury

Hepatology. 2020 Aug;72(2):609-625. doi: 10.1002/hep.31041. Epub 2020 May 8.

Abstract

Background and aims: Mitochondrial double-stranded RNA (mtdsRNA) and its innate immune responses have been reported previously; however, mtdsRNA generation and its effects on alcohol-associated liver disease (ALD) remain unclear. Here, we report that hepatic mtdsRNA stimulates toll-like receptor 3 (TLR3) in Kupffer cells through the exosome (Exo) to enhance interleukin (IL)-17A (IL-17A) production in ALD.

Approach and results: Following binge ethanol (EtOH) drinking, IL-17A production primarily increased in γδ T cells of wild-type (WT) mice, whereas the production of IL-17A was mainly facilitated by CD4+ T cells in acute-on-chronic EtOH consumption. These were not observed in TLR3 knockout (KO) or Kupffer cell-depleted WT mice. The expression of polynucleotide phosphorylase, an mtdsRNA-restricting enzyme, was significantly decreased in EtOH-exposed livers and hepatocytes of WT mice. Immunostaining revealed that mtdsRNA colocalized with the mitochondria in EtOH-treated hepatocytes from WT mice and healthy humans. Bioanalyzer analysis revealed that small-sized RNAs were enriched in EtOH-treated Exos (EtOH-Exos) rather than EtOH-treated microvesicles in hepatocytes of WT mice and humans. Quantitative real-time PCR and RNA sequencing analyses indicated that mRNA expression of mitochondrial genes encoded by heavy and light strands was robustly increased in EtOH-Exos from mice and humans. After direct treatment with EtOH-Exos, IL-1β expression was significantly increased in WT Kupffer cells but not in TLR3 KO Kupffer cells, augmenting IL-17A production of γδ T cells in mice and humans.

Conclusions: EtOH-mediated generation of mtdsRNA contributes to TLR3 activation in Kupffer cells through exosomal delivery. Consequently, increased IL-1β expression in Kupffer cells triggers IL-17A production in γδ T cells at the early stage that may accelerate IL-17A expression in CD4+ T cells in the later stage of ALD. Therefore, mtdsRNA and TLR3 may function as therapeutic targets in ALD.

Publication types

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

MeSH terms

  • Animals
  • Exosomes / genetics*
  • Female
  • Interleukin-17 / biosynthesis*
  • Kupffer Cells / metabolism*
  • Liver Diseases, Alcoholic / genetics*
  • Liver Diseases, Alcoholic / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • RNA, Double-Stranded / physiology*
  • RNA, Mitochondrial / physiology*
  • Toll-Like Receptor 3 / physiology*

Substances

  • Il17a protein, mouse
  • Interleukin-17
  • RNA, Double-Stranded
  • RNA, Mitochondrial
  • Toll-Like Receptor 3