Mitochondrial double-stranded RNA in exosome promotes interleukin-17 production through toll-like receptor 3 in alcoholic liver injury

Mitochondrial double-stranded RNA (mtdsRNA) and its innate immune responses have been reported previously; however, mtdsRNA generation and its effects on alcoholic liver disease (ALD) remain unclear. Here, we report that hepatic mtdsRNA stimulates toll-like receptor 3 (TLR3) in Kupffer cells through the exosome to enhance IL-17A production in ALD. Following binge ethanol 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 ethanol consumption. These were not observed in TLR3 KO or Kupffer cell-depleted WT mice. The expression of PNPase, an mtdsRNA restricting enzyme, was significantly decreased in ethanol-exposed livers and hepatocytes of WT mice. Immunostaining revealed that mtdsRNA co-localized with the mitochondria in ethanol-treated hepatocytes from WT mice and healthy humans. Bioanalyzer analysis revealed that small-sized RNAs were enriched in ethanol-treated exosomes (EtOH-Exo) rather than EtOH-treated microvesicles in hepatocytes of WT mice and humans. qPCR and RNA sequencing analyses indicated that mRNA expression of mitochondrial genes encoded by heavy and light strands was robustly increased in EtOH-Exo from mice and humans. After direct treatment with EtOH-Exo, 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.