The non-transcriptional activity of IRF3 modulates hepatic immune cell populations in acute-on-chronic ethanol administration in mice

• Published in: Journal of hepatology Vol. 70; no. 5; pp. 974 - 984
• Main Authors: Sanz-Garcia, Carlos, Poulsen, Kyle L., Bellos, Damien, Wang, Han, McMullen, Megan R., Li, Xiaoxia, Chattopadhyay, Saurabh, Sen, Ganes, Nagy, Laura E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-05-2019; Elsevier Science Ltd
• Subjects: Alanine; Alcohol; Alcoholic liver disease; Animal models; Animals; Apoptosis; Aspartate aminotransferase; Bax protein; Cell activation; Cell death; Disease Models, Animal; Endoplasmic reticulum; Endoplasmic Reticulum Stress; ER stress; Ethanol; Genotypes; Hepatitis; Hepatitis, Alcoholic - etiology; Hepatitis, Alcoholic - immunology; Humans; Immune response; Immunity, Innate; Inflammation; Innate immunity; Interferon; Interferon regulatory factor; Interferon regulatory factor 3; Interferon Regulatory Factor-3 - physiology; IRF3; Liver - immunology; Liver - pathology; Liver diseases; Macrophage Activation; Macrophages; Mice; Mice, Inbred C57BL; Mitochondria; Monocytes - physiology; Neutrophils; Neutrophils - physiology; NF-κB protein; Polyinosinic:polycytidylic acid; Restorative monocytes; Steatosis; Transcription, Genetic; ER stress; Restorative monocytes; IRF3; Neutrophils; Alcoholic liver disease; Apoptosis
• ISSN: 0168-8278; 1600-0641
• DOI: 10.1016/j.jhep.2019.01.021

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•Interferon regulatory factor 3 (IRF3) has both transcriptional and non-transcriptional activity.•Gao-binge ethanol exposure increases both the phosphorylation and ubiquitination of IRF3.•Irf3−/− are protected from ethanol-induced liver injury but mice expressing non-transcriptional IRF3 activity are not.•The non-transcriptional activity of IRF3 modulates the innate immune environment of the liver.
Interferon regulatory factor 3 (IRF3) is a transcription factor mediating antiviral responses, yet recent evidence indicates that IRF3 also has critical non-transcriptional functions, including activating RIG-I-like receptors-induced IRF-3-mediated pathway of apoptosis (RIPA) and restricting activity of NF-κB. Using a novel murine model expressing only non-transcriptional IRF3 activity (Irf3S1/S1), we tested the hypothesis that non-transcriptional functions of IRF3 modulate innate immune responses in the Gao-binge (acute-on-chronic) model of alcohol-related liver disease.
IRF3 and IRF3-mediated signals were analysed in liver samples from 5 patients transplanted for alcoholic hepatitis and 5 healthy controls. C57BL/6, Irf3−/− and Irf3S1/S1 mice were exposed to Gao-binge ethanol-induced liver injury. IRF3-mediated RIPA was investigated in cultured macrophages.
Phospho-IRF3 and IRF3-mediated signals were elevated in livers of patients with alcoholic hepatitis. In C57BL/6 mice, Gao-binge ethanol exposure activated IRF3 signaling and resulted in hepatocellular injury. Indicators of liver injury were differentially impacted by Irf3 genotype. Irf3−/−, but not Irf3S1/S1, mice were protected from steatosis, elevated alanine/aspartate aminotransferase levels and inflammatory cytokine expression. In contrast, neutrophil accumulation and endoplasmic reticulum stress were independent of genotype. Protection from Gao-binge injury in Irf3−/− mice was associated with an increased ratio of Ly6Clow (restorative) to Ly6Chigh (inflammatory) cells compared to C57BL/6 and Irf3S1/S1 mice. Reduced ratios of Ly6Clow/Ly6Chigh in C57BL/6 and Irf3S1/S1 mice were associated with increased apoptosis in the Ly6Clow population in response to Gao-binge. Activation of primary macrophage cultures with Poly (I:C) induced translocation of IRF3 to the mitochondria, where it associated with Bax and activated caspases 3 and 9, processes indicative of activation of the RIPA pathway.
Taken together, these data identify that the non-transcriptional function of IRF3 plays an important role in modulating the innate immune environment in response to Gao-binge ethanol exposure, via regulation of immune cell apoptosis.
Activation of the innate immune system contributes to inflammation in the progression of alcohol-related liver disease, as well as to the resolution of injury. Here we show that the protein IRF3 modulates the innate immune environment of the liver in a mouse model of alcoholic hepatitis. It does this by increasing the apoptotic cell death of immune cells that promote the resolution of injury.