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      Interferon regulatory factor-1 activates autophagy to aggravate hepatic ischemia-reperfusion injury via the P38/P62 pathway in mice

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          Abstract

          Increasing evidence has linked autophagy to a detrimental role in hepatic ischemia- reperfusion (IR) injury (IRI). Here we focus on the role of interferon regulatory factor-1 (IRF-1) in regulating autophagy to aggravate hepatic IRI. We found that IRF-1 was up-regulated during hepatic IRI and was associated with an activation of the autophagic signaling. This increased IRF-1 expression, which was allied with high autophagic activity, amplified liver damage to IR, an effect which was abrogated by IRF-1 depletion. Moreover, IRF-1 contributed to P38 induced autophagic and apoptotic cell death, that can play a key role in liver dysfunction. The levels of P62 mRNA and protein were increased when P38 was activated and decreased when P38 was inhibited by SB203580. We conclude that IRF-1 functioned as a trigger to activate autophagy via P38 activation and that P62 was required for this P38-mediated autophagy. IRF-1 appears to exert a pivotal role in hepatic IRI, by predisposing hepatocytes to activate an autophagic pathway. Such an effect promotes autophagic cell death through the P38/P62 pathway. The identification of this novel pathway, that links expression levels of IRF-1 with autophagy, may provide new insights for the generation of novel protective therapies directed against hepatic IRI.

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          Most cited references35

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          ROS-dependent activation of the TRAF6-ASK1-p38 pathway is selectively required for TLR4-mediated innate immunity.

          Apoptosis signal-regulating kinase 1 (ASK1) is an evolutionarily conserved mitogen-activated protein 3-kinase that activates both Jnk and p38 mitogen-activated protein kinases. Here we used ASK1-deficient mice to show that ASK1 was selectively required for lipopolysaccharide-induced activation of p38 but not of Jnk or the transcription factor NF-kappaB. ASK1 was required for the induction of proinflammatory cytokines dependent on Toll-like receptor 4 (TLR4) but not TLR2 or other TLRs. Consistent with this, ASK1-deficient mice were resistant to lipopolysaccharide-induced septic shock. Lipopolysaccharide induced the production of intracellular reactive oxygen species, which was required for the formation of a complex of the adaptor molecule TRAF6 and ASK1 and subsequent activation of the ASK1-p38 pathway. Our data demonstrate that the reactive oxygen species-dependent TRAF6-ASK1-p38 axis is crucial for TLR4-mediated mammalian innate immunity.
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            Autophagy: regulation and role in development.

            Autophagy is an evolutionarily conserved cellular process through which long-lived proteins and damaged organelles are recycled to maintain energy homeostasis. These proteins and organelles are sequestered into a double-membrane structure, or autophagosome, which subsequently fuses with a lysosome in order to degrade the cargo. Although originally classified as a type of programmed cell death, autophagy is more widely viewed as a basic cell survival mechanism to combat environmental stressors. Autophagy genes were initially identified in yeast and were found to be necessary to circumvent nutrient stress and starvation. Subsequent elucidation of mammalian gene counterparts has highlighted the importance of this process to normal development. This review provides an overview of autophagy, the types of autophagy, its regulation and its known impact on development gleaned primarily from murine models.
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              Nrf2-mediated induction of p62 controls Toll-like receptor-4-driven aggresome-like induced structure formation and autophagic degradation.

              Toll-like receptors (TLRs) play a crucial role in several innate immune responses by regulating autophagy, but little is known about how TLR signaling controls autophagy. Here we demonstrate that p62/SQSTM1 is required for TLR4-mediated autophagy, which we show as selective autophagy of aggresome-like induced structures (ALIS). Treatment with LPS or Escherichia coli induced LC3(+) dot-like structures, and their assembly, but not lysosomal degradation, occurred independently of classic autophagic machinery. Microscopic and ultrastructural analyses showed that p62 is a component of the induced LC3(+) dots and these TLR4-induced p62(+) structures resemble ALIS. The levels of p62 mRNA and protein were increased in TLR4-activated cells and knockdown of p62 suppressed the ALIS formation and LC3-II conversion. The accumulation of p62 and ALIS required activation of Nrf2 by reactive oxygen species-p38 axis-dependent TLR4/MyD88 signaling, suggesting a link between innate immune and oxidative-stress responses. These findings indicate that TLR4-driven induction of p62 plays an essential role in the formation and the autophagic degradation of ALIS, which might be critical for regulating host defense.
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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                07 March 2017
                2017
                : 7
                : 43684
                Affiliations
                [1 ]First Central Clinical College, Tianjin Medical University , Tianjin 300192, China
                [2 ]Key Laboratory of Organ Transplantation of Tianjin , Tianjin 300071, China
                [3 ]Oriental Organ Transplant Center, Tianjin First Central Hospital , Tianjin 300192, China
                [4 ]Tianjin Nankai Hospital , Tianjin 300100, China
                [5 ]Affiliated Hospital of Logistics University of Chinese People’s Armed Police Forces , Tianjin 300162, China
                [6 ]Beijing Friendship Hospital, Capital Medical University , Beijing 100050, China
                [7 ]Department of Immunology and Inflammation, Tianjin Medical University , Tianjin 300070, China
                Author notes
                [*]

                These authors contributed equally to this work.

                Article
                srep43684
                10.1038/srep43684
                5339805
                28266555
                a16370dd-2d40-422b-ac9c-0282c89052f6
                Copyright © 2017, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 11 August 2016
                : 30 January 2017
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