Highlights d Alcohol consumption increases xCT expression in HEPs d xCT-derived glutamate release increases expression of mGluR5 in HSCs d mGluR5 stimulates 2-AG production in HSC to influence lipogenesis of HEPs via CB 1 R d Inhibition of xCT and mGluR5 blocks alcoholic steatosis in liver

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.

Background and Aims The important roles of glutamate and metabotropic glutamate receptor 5 (mGluR5) in HSCs have recently been reported in various liver diseases; however, the mechanism linking the glutamine/glutamate metabolism and mGluR5 in liver fibrosis remains unclear. Here, we report that mGluR5 activation in natural killer (NK) cells attenuates liver fibrosis through increased cytotoxicity and interferon‐γ (IFN‐γ) production in both mice and humans. Approach and Results Following 2‐week injection of carbon tetrachloride (CCl4) or 5‐week methionine‐deficient and choline‐deficient diet, liver fibrosis was more aggravated in mGluR5 knockout mice with significantly decreased frequency of NK cells compared with wild‐type mice. Consistently, NK cell–specific mGluR5 knockout mice had aggravated CCl4‐induced liver fibrosis with decreased production of IFN‐γ. Conversely, in vitro activation of mGluR5 in NK cells significantly increased the expression of anti‐fibrosis‐related genes including Ifng, Prf1 (perforin), and Klrk1 (killer cell lectin like receptor K1) and the production of IFN‐γ through the mitogen‐activated extracellular signal‐regulated kinase/extracellular signal‐related kinase pathway, contributing to the increased cytotoxicity against activated HSCs. However, we found that the uptake of glutamate was increased in activated HSCs, resulting in shortage of extracellular glutamate and reduced stimulation of mGluR5 in NK cells. Consequently, this could enable HSCs to evade NK cell cytotoxicity in advanced liver fibrosis. In vivo, pharmacologic activation of mGluR5 accelerated CCl4‐induced liver fibrosis regression by restoring NK cell cytotoxicity. In humans, mGluR5 activation enhanced the cytotoxicity of NK cells isolated from healthy donors, but not from patients with cirrhosis with significantly reduced mGluR5 expression in NK cells. Conclusions mGluR5 plays important roles in attenuating liver fibrosis by augmenting NK cell cytotoxicity, which could be used as a potential therapeutic target for liver fibrosis.

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Background/Aims Our study aims to characterize esophageal motor function; evaluate the relationships among esophagogastroduodenoscopy (EGD), high-resolution manometry (HRM), and 24-hour esophageal multichannel intraluminal impedance monitoring combined with pHmetry (MII-pH); and elucidate the determinants of esophageal symptom perception in South Koreans with systemic sclerosis (SSc). Methods We reviewed prospectively collected HRM (n = 46), EGD (n = 41), and MII-pH (n = 37) data from 46 consecutive patients with SSc (42 females; mean age 50.1 years) who underwent esophageal tests between June 2013 and September 2018. Results The most common HRM diagnosis was normal (39.1%), followed by ineffective esophageal motility (23.9%) and absent contractility (21.7%). Erosive esophagitis was observed in 12.2% of total SSc patients, with a higher frequency in patients with absent contractility than those with normal motility (44.5% vs 0.0%, P = 0.01). Pathologic acid exposure was observed in 6 patients (20.0%) and positive symptom association in 18 patients (60.0%) in MII-pH tests of symptomatic patients. The proportion of SSc patients with esophageal symptoms not explained by reflux or mucosal or motor esophageal abnormalities was 33.0%. Conclusions Esophageal involvement among South Koreans with SSc was characterized by heterogeneous motility patterns, with a higher prevalence of normal motility and lower prevalence of erosive esophagitis. Reflux hypersensitivity or functional heartburn might be partly attributed to the perception of esophageal symptoms in SSc patients who have neither gastroesophageal reflux disease nor esophageal dysmotility.