Decreased Hepatocyte Autophagy Leads to Synergistic IL-1 beta and TNF Mouse Liver Injury and Inflammation

• Type of Material: Article
• Authors: Yang Shen, Emory University; Shoaib Ahmad Malik, Emory University; Muhammad Amir, Emory University; Pradeep Kumar, Emory University; Francesca Cingolani, Emory University; Jing Wen, Emory University; Yunshan Liu, Emory University; Enpeng Zhao, Icahn School of Medicine at Mount Sinai; Alton B Farris, Emory University; Reben Raeman, University of Pittsburgh; Mark Czaja, Emory University
• Language: English
• Date: 2020-06-23
• Publisher: WILEY
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2020 by the American Association for the Study of Liver Diseases.
• Final Published Version (URL): http://dx.doi.org/10.1002/hep.31209
• Title of Journal or Parent Work: HEPATOLOGY
• Volume: 72
• Issue: 2
• Start Page: 595
• End Page: 608
• Grant/Funding Information: Supported by National Institutes of Health grants R01DK044234, R01AA022601 (to M.J.C.), and T32DK108735 (to M.A.). Core resources were supported by G12MD007602.
• Keywords: IL-1 RECEPTOR ANTAGONIST; ALPHA; DISEASE; STEATOHEPATITIS; Science & Technology; ENERGY-METABOLISM; Gastroenterology & Hepatology; Life Sciences & Biomedicine; CELL-DEATH; TUMOR NECROSIS FACTOR; PROMOTES; INCREASES; LYSOSOMAL MEMBRANE PERMEABILIZATION

Abstract

Background and Aims: The proinflammatory cytokine IL-1β has been implicated in the pathophysiology of nonalcoholic and alcoholic steatohepatitis. How IL-1β promotes liver injury in these diseases is unclear, as no IL-1β receptor-linked death pathway has been identified. Autophagy functions in hepatocyte resistance to injury and death, and findings of decreased hepatic autophagy in many liver diseases suggest a role for impaired autophagy in disease pathogenesis. Recent findings that autophagy blocks mouse liver injury from lipopolysaccharide led to an examination of autophagy’s function in hepatotoxicity from proinflammatory cytokines. Approach and Results: AML12 cells with decreased autophagy from a lentiviral autophagy-related 5 (Atg5) knockdown were resistant to toxicity from TNF, but sensitized to death from IL-1β, which was markedly amplified by TNF co-treatment. IL-1β/TNF death was necrosis by trypan blue and propidium iodide positivity, absence of mitochondrial death pathway and caspase activation, and failure of a caspase inhibitor or necrostatin-1s to prevent death. IL-1β/TNF depleted autophagy-deficient cells of ATP, and ATP depletion and cell death were prevented by supplementation with the energy substrate pyruvate or oleate. Pharmacological inhibitors and genetic knockdown studies demonstrated that IL-1β/TNF-induced necrosis resulted from lysosomal permeabilization and release of cathepsins B and L in autophagy-deficient cells. Mice with a tamoxifen-inducible, hepatocyte-specific Atg5 knockout were similarly sensitized to cathepsin-dependent hepatocellular injury and death from IL-1β/TNF in combination, but neither IL-1β nor TNF alone. Knockout mice had increased hepatic inflammation, and IL-1β/TNF-treated, autophagy-deficient AML12 cells secreted exosomes with proinflammatory damage–associated molecular patterns. Conclusions: The findings delineate mechanisms by which decreased hepatocyte autophagy promotes IL-1β/TNF-induced necrosis from impaired energy homeostasis and lysosomal permeabilization and inflammation through the secretion of exosomal damage–associated molecular patterns.