151
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Rutkowski DT. Liver function and dysfunction - a unique window into the physiological reach of ER stress and the unfolded protein response. FEBS J 2018; 286:356-378. [PMID: 29360258 DOI: 10.1111/febs.14389] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 01/08/2018] [Accepted: 01/17/2018] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) improves endoplasmic reticulum (ER) protein folding in order to alleviate stress. Yet it is becoming increasingly clear that the UPR regulates processes well beyond those directly involved in protein folding, in some cases by mechanisms that fall outside the realm of canonical UPR signaling. These pathways are highly specific from one cell type to another, implying that ER stress signaling affects each tissue in a unique way. Perhaps nowhere is this more evident than in the liver, which-beyond being a highly secretory tissue-is a key regulator of peripheral metabolism and a uniquely proliferative organ upon damage. The liver provides a powerful model system for exploring how and why the UPR extends its reach into physiological processes that occur outside the ER, and how ER stress contributes to the many systemic diseases that involve liver dysfunction. This review will highlight the ways in which the study of ER stress in the liver has expanded the view of the UPR to a response that is a key guardian of cellular homeostasis outside of just the narrow realm of ER protein folding.
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Affiliation(s)
- D Thomas Rutkowski
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, IA, USA.,Department of Internal Medicine, University of Iowa Carver College of Medicine, IA, USA
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152
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Qiu X, Li J, Lv S, Yu J, Jiang J, Yao J, Xiao Y, Xu B, He H, Guo F, Zhang ZN, Zhang C, Luan B. HDAC5 integrates ER stress and fasting signals to regulate hepatic fatty acid oxidation. J Lipid Res 2018; 59:330-338. [PMID: 29229738 PMCID: PMC5794426 DOI: 10.1194/jlr.m080382] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/27/2017] [Indexed: 01/23/2023] Open
Abstract
Disregulation of fatty acid oxidation, one of the major mechanisms for maintaining hepatic lipid homeostasis under fasting conditions, leads to hepatic steatosis. Although obesity and type 2 diabetes-induced endoplasmic reticulum (ER) stress contribute to hepatic steatosis, it is largely unknown how ER stress regulates fatty acid oxidation. Here we show that fasting glucagon stimulates the dephosphorylation and nuclear translocation of histone deacetylase 5 (HDAC5), where it interacts with PPARα and promotes transcriptional activity of PPARα. As a result, overexpression of HDAC5 but not PPARα binding-deficient HDAC5 in liver improves lipid homeostasis, whereas RNAi-mediated knockdown of HDAC5 deteriorates hepatic steatosis. ER stress inhibits fatty acid oxidation gene expression via calcium/calmodulin-dependent protein kinase II-mediated phosphorylation of HDAC5. Most important, hepatic overexpression of a phosphorylation-deficient mutant HDAC5 2SA promotes hepatic fatty acid oxidation gene expression and protects against hepatic steatosis in mice fed a high-fat diet. We have identified HDAC5 as a novel mediator of hepatic fatty acid oxidation by fasting and ER stress signals, and strategies to promote HDAC5 dephosphorylation could serve as new tools for the treatment of obesity-associated hepatic steatosis.
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Affiliation(s)
- Xinchen Qiu
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Jian Li
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Sihan Lv
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Jiamin Yu
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Junkun Jiang
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Jindong Yao
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Yang Xiao
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Bingxin Xu
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Haiyan He
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Fangfei Guo
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Zhen-Ning Zhang
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Chao Zhang
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, China
| | - Bing Luan
- Department of Endocrinology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
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153
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Zhang M, Sun W, Qian J, Tang Y. Fasting exacerbates hepatic growth differentiation factor 15 to promote fatty acid β-oxidation and ketogenesis via activating XBP1 signaling in liver. Redox Biol 2018; 16:87-96. [PMID: 29482168 PMCID: PMC5952356 DOI: 10.1016/j.redox.2018.01.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 01/17/2018] [Accepted: 01/29/2018] [Indexed: 02/05/2023] Open
Abstract
Liver coordinates a series of metabolic adaptations to maintain systemic energy balance and provide adequate nutrients for critical organs, tissues and cells during starvation. However, the mediator(s) implicated in orchestrating these fasting-induced adaptive responses and the underlying molecular mechanisms are still obscure. Here we show that hepatic growth differentiation factor 15 (GDF15) is regulated by IRE1α-XBP1s branch and promotes hepatic fatty acids β-oxidation and ketogenesis upon fasting. GDF15 expression was exacerbated in liver of mice subjected to long-term fasted or ketogenic diet feeding. Abrogation of hepatic Gdf15 dramatically attenuated hepatic β-oxidation and ketogenesis in fasted mice or mice with STZ-initiated type I diabetes. Further study revealed that XBP1s activated Gdf15 transcription via binding to its promoter. Elevated GDF15 in liver reduced lipid accumulation and impaired NALFD development in obese mice through enhancing fatty acids oxidation in liver. Therefore, our results demonstrate a novel and critical role of hepatic GDF15 activated by IRE1α-XBP1s branch in regulating adaptive responses of liver upon starvation stress. GDF15 is augmented in livers of mice subjected to fasting or ketogenic diet feeding. XBP1s activates the transcription of Gdf15 via binding to its promoter. Abrogation of hepatic Gdf15 impairs fatty acid β-oxidation and ketogenesis. Inhibition of hepatic Gdf15 attenuates ketoacidosis of diabetic mice. Ectopic expression of hepatic GDF15 alleviates obese-induced NAFLD development.
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Affiliation(s)
- Meiyuan Zhang
- Emergency Intensive Care Unit, Qingpu Branch of Zhongshan Hospital, Fudan University, Shanghai 201700, China
| | - Weilan Sun
- Emergency Intensive Care Unit, Qingpu Branch of Zhongshan Hospital, Fudan University, Shanghai 201700, China
| | - Jin Qian
- Emergency Intensive Care Unit, Qingpu Branch of Zhongshan Hospital, Fudan University, Shanghai 201700, China
| | - Yan Tang
- Emergency Intensive Care Unit, Qingpu Branch of Zhongshan Hospital, Fudan University, Shanghai 201700, China.
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154
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Namkoong S, Cho CS, Semple I, Lee JH. Autophagy Dysregulation and Obesity-Associated Pathologies. Mol Cells 2018; 41:3-10. [PMID: 29370691 PMCID: PMC5792710 DOI: 10.14348/molcells.2018.2213] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/02/2017] [Accepted: 10/10/2017] [Indexed: 12/20/2022] Open
Abstract
Autophagy is one of the major degradative mechanisms that can eliminate excessive nutrients, toxic protein aggregates, damaged organelles and invading microorganisms. In response to obesity and obesity-associated lipotoxic, proteotoxic and oxidative stresses, autophagy plays an essential role in maintaining physiological homeostasis. However, obesity and its associated stress insults can often interfere with the autophagic process through various mechanisms, which result in further aggravation of obesity-related metabolic pathologies in multiple metabolic organs. Paradoxically, inhibition of autophagy, within specific contexts, indirectly produces beneficial effects that can alleviate several detrimental consequences of obesity. In this minireview, we will provide a brief discussion about our current understanding of the impact of obesity on autophagy and the role of autophagy dysregulation in modulating obesity-associated pathological outcomes.
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Affiliation(s)
- Sim Namkoong
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-2200,
USA
| | - Chun-Seok Cho
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-2200,
USA
| | - Ian Semple
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-2200,
USA
| | - Jun Hee Lee
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-2200,
USA
- Institute of Gerontology, University of Michigan, Ann Arbor, Michigan 48109-2200,
USA
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155
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156
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Balachander GJ, Subramanian S, Ilango K. Rosmarinic acid attenuates hepatic steatosis by modulating ER stress and autophagy in oleic acid-induced HepG2 cells. RSC Adv 2018; 8:26656-26663. [PMID: 35547559 PMCID: PMC9087887 DOI: 10.1039/c8ra02849d] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 06/23/2018] [Indexed: 12/13/2022] Open
Abstract
Non-alcoholic fatty acid disease (NAFLD) has become an emerging entity of liver disorders worldwide. Oxidative stress and deranged autophagy-induced endoplasmic reticulum (ER) stress has recently been recognized as one of the prime factors involved in the pathological mechanism underlying NAFLD and progressive non-alcoholic steato-hepatitis (NASH). Epidemiological and experimental data reveal the potency of dietary polyphenols in averting NAFLD. In this line, to analyse and address the underlying pathogenic mechanisms, in the present study, oleic acid-induced HepG2 cells were treated with rosmarinic acid (RA), a dietary polyphenol with well-established cytoprotective properties. Treatment with rosmarinic acid (20 μg) was found to potently counter the elevated levels of total cholesterol (TC) and triglycerides (TG). Additionally, exposure of oleic acid-induced HepG2 cells to rosmarinic acid showed reduced levels of ROS and increased activity of enzymic and non-enzymic antioxidants. The steatotic HepG2 cells presented a pronounced increase in the expression of key ER stress markers such as p-PERK, p-IRE-1, ATF-6, p-eIF-α and CHOP, which was considerably reduced upon treatment with rosmarinic acid. Moreover, exposure to rosmarinic acid altered the deranged autophagic mechanism in oleic acid-induced HepG2 cells, which was observed via the protein expression of Beclin 1, LC31, ATG5 and ATG7. This study demonstrates that rosmarinic acid abrogates NAFLD via diminishing ER stress by nullifying oxidative stress and restoring deranged autophagy and can be used as a potent adjunct in the treatment of NAFLD, thus illustrating the valuable application of polyphenols in combating NAFLD. Non-alcoholic fatty acid disease (NAFLD) has become an emerging entity of liver disorders worldwide.![]()
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Affiliation(s)
- Govindaraj Jayanthy Balachander
- Molecular Biology Division
- Interdisciplinary Institute of Indian System of Medicine (IIISM)
- SRM Institute of Science and Technology
- Kattankulathur
- India
| | | | - Kaliappan Ilango
- Molecular Biology Division
- Interdisciplinary Institute of Indian System of Medicine (IIISM)
- SRM Institute of Science and Technology
- Kattankulathur
- India
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157
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Oubaha M, Miloudi K, Dejda A, Guber V, Mawambo G, Germain MA, Bourdel G, Popovic N, Rezende FA, Kaufman RJ, Mallette FA, Sapieha P. Senescence-associated secretory phenotype contributes to pathological angiogenesis in retinopathy. Sci Transl Med 2017; 8:362ra144. [PMID: 27797960 DOI: 10.1126/scitranslmed.aaf9440] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2016] [Accepted: 06/17/2016] [Indexed: 12/13/2022]
Abstract
Pathological angiogenesis is the hallmark of diseases such as cancer and retinopathies. Although tissue hypoxia and inflammation are recognized as central drivers of vessel growth, relatively little is known about the process that bridges the two. In a mouse model of ischemic retinopathy, we found that hypoxic regions of the retina showed only modest rates of apoptosis despite severely compromised metabolic supply. Using transcriptomic analysis and inducible loss-of-function genetics, we demonstrated that ischemic retinal cells instead engage the endoplasmic reticulum stress inositol-requiring enzyme 1α (IRE1α) pathway that, through its endoribonuclease activity, induces a state of senescence in which cells adopt a senescence-associated secretory phenotype (SASP). We also detected SASP-associated cytokines (plasminogen activator inhibitor 1, interleukin-6, interleukin-8, and vascular endothelial growth factor) in the vitreous humor of patients suffering from proliferative diabetic retinopathy. Therapeutic inhibition of the SASP through intravitreal delivery of metformin or interference with effectors of senescence (semaphorin 3A or IRE1α) in mice reduced destructive retinal neovascularization in vivo. We conclude that the SASP contributes to pathological vessel growth, with ischemic retinal cells becoming prematurely senescent and secreting inflammatory cytokines that drive paracrine senescence, exacerbate destructive angiogenesis, and hinder reparative vascular regeneration. Reversal of this process may be therapeutically beneficial.
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Affiliation(s)
- Malika Oubaha
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4 Canada
| | - Khalil Miloudi
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4 Canada
| | - Agnieszka Dejda
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Vera Guber
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Gaëlle Mawambo
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Marie-Anne Germain
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada.,Department of Medicine, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Guillaume Bourdel
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Natalija Popovic
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Flavio A Rezende
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Frédérick A Mallette
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada. .,Department of Medicine, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
| | - Przemyslaw Sapieha
- Department of Biochemistry, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada. .,Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4 Canada.,Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
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158
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Insulin Resistance, Obesity and Lipotoxicity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 960:277-304. [PMID: 28585204 DOI: 10.1007/978-3-319-48382-5_12] [Citation(s) in RCA: 273] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Lipotoxicity , originally used to describe the destructive effects of excess fat accumulation on glucose metabolism, causes functional impairments in several metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. Lipotoxicity has roles in insulin resistance and pancreatic beta cell dysfunction. Increased circulating levels of lipids and the metabolic alterations in fatty acid utilization and intracellular signaling, have been related to insulin resistance in muscle and liver. Different pathways, like novel protein kinase c pathways and the JNK-1 pathway are involved as the mechanisms of how lipotoxicity leads to insulin resistance in nonadipose tissue organs, such as liver and muscle. Mitochondrial dysfunction plays a role in the pathogenesis of insulin resistance. Endoplasmic reticulum stress, through mainly increased oxidative stress, also plays important role in the etiology of insulin resistance, especially seen in non-alcoholic fatty liver disease. Visceral adiposity and insulin resistance both increase the cardiometabolic risk and lipotoxicity seems to play a crucial role in the pathophysiology of these associations.
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159
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Hong F, Liu B, Wu BX, Morreall J, Roth B, Davies C, Sun S, Diehl JA, Li Z. CNPY2 is a key initiator of the PERK-CHOP pathway of the unfolded protein response. Nat Struct Mol Biol 2017; 24:834-839. [PMID: 28869608 PMCID: PMC6102046 DOI: 10.1038/nsmb.3458] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 08/08/2017] [Indexed: 12/15/2022]
Abstract
The unfolded protein response (UPR) in the endoplasmic reticulum (ER) is a highly conserved protein quality control mechanism critical for cells to make survival-or-death decisions under ER stress conditions. However, how UPR sensors are activated remains unclear. Here, we report that ER luminal protein canopy homolog 2 (CNPY2) is released from grp78 upon ER stress. Free CNPY2 then engages protein kinase R-like ER kinase (PERK) to induce expression of the transcription factor C/EBP homologous protein (CHOP), thereby initiating the UPR. Indeed, deletion of CNPY2 blocked the PERK-CHOP pathway and protected mice from UPR-induced liver damage and steatosis. Additionally, CNPY2 is transcriptionally upregulated by CHOP in a forward-feed loop to further enhance the UPR signaling. These findings demonstrate the critical roles of CNPY2 in ER stress, and suggest that CNPY2 is a potential new therapeutic target for UPR-related diseases such as metabolic disorders, inflammation and cancer.
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Affiliation(s)
- Feng Hong
- Department of Microbiology &Immunology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Bei Liu
- Department of Microbiology &Immunology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Bill X Wu
- Department of Microbiology &Immunology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Jordan Morreall
- Department of Microbiology &Immunology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Brady Roth
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Christopher Davies
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Shaoli Sun
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina, USA
| | - J Alan Diehl
- Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA.,Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Zihai Li
- Department of Microbiology &Immunology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA.,First Affiliated Hospital, Zhengzhou University School of Medicine, Zhengzhou, China
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160
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Yang Z, Kim H, Ali A, Zheng Z, Zhang K. Interaction between stress responses and circadian metabolism in metabolic disease. LIVER RESEARCH 2017; 1:156-162. [PMID: 29430321 PMCID: PMC5805151 DOI: 10.1016/j.livres.2017.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Circadian rhythms play crucial roles in orchestrating diverse physiological processes that are critical for health and disease. Dysregulated circadian rhythms are closely associated with various human metabolic diseases, including type 2 diabetes, cardiovascular disease, and non-alcoholic fatty liver disease. Modern lifestyles are frequently associated with an irregular circadian rhythm, which poses a significant risk to public health. While the central clock has a set periodicity, circadian oscillators in peripheral organs, particularly in the liver, can be entrained by metabolic alterations or stress cues. At the molecular level, the signal transduction pathways that mediate stress responses interact with, and are often integrated with, the key determinants of circadian oscillation, to maintain metabolic homeostasis under physiological or pathological conditions. In the liver, a number of nuclear receptors or transcriptional regulators, which are regulated by metabolites, hormones, the circadian clock, or environmental stressors, serve as direct links between stress responses and circadian metabolism. In this review, we summarize recent advances in the understanding of the interactions between stress responses (the endoplasmic reticulum (ER) stress response, the oxidative stress response, and the inflammatory response) and circadian metabolism, and the role of these interactions in the development of metabolic diseases.
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Affiliation(s)
- Zhao Yang
- Center for Molecular Medicine and Genetics, Wayne State University, MI, USA
| | - Hyunbae Kim
- Center for Molecular Medicine and Genetics, Wayne State University, MI, USA
| | - Arushana Ali
- Center for Molecular Medicine and Genetics, Wayne State University, MI, USA
| | - Ze Zheng
- Center for Molecular Medicine and Genetics, Wayne State University, MI, USA
| | - Kezhong Zhang
- Center for Molecular Medicine and Genetics, Wayne State University, MI, USA,Department of Microbiology, Immunology, and Biochemistry, Wayne State University, MI, USA,Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA,Corresponding author. Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA. (K. Zhang)
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161
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Choi WG, Han J, Kim JH, Kim MJ, Park JW, Song B, Cha HJ, Choi HS, Chung HT, Lee IK, Park TS, Hatzoglou M, Choi HS, Yoo HJ, Kaufman RJ, Back SH. eIF2α phosphorylation is required to prevent hepatocyte death and liver fibrosis in mice challenged with a high fructose diet. Nutr Metab (Lond) 2017; 14:48. [PMID: 28781602 PMCID: PMC5537942 DOI: 10.1186/s12986-017-0202-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/28/2017] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Dietary fructose can rapidly cause fatty liver in animals through de novo lipogenesis (DNL) and contribute to the development and severity of nonalcoholic fatty liver disease (NAFLD). In response to diverse cellular insults including endoplasmic reticulum (ER) and oxidative stress, phosphorylation of the eukaryotic translation initiation factor 2 alpha subunit (eIF2α) attenuates general translation initiation, allowing cells to conserve resources and initiate adaptive gene expression to restore homeostasis. The present study aimed to investigate the role of eIF2α phosphorylation in protecting against NAFLD induced by high fructose ingestion in a hepatocyte-specific eIF2α-phosphorylation-deficient mouse model. METHODS Hepatocyte-specific non-phosphorylatable (S51A) eIF2α knock-in (A/A;fTg/0;CreHep/0, A/AHep ) mice were generated by crossing A/A;fTg/fTg mice with the floxed WT eIF2α transgene (fTg) with Alfp-Cre recombinase transgenic S/A;CreHep/0 (S/A-CreHep ) mice. Hepatocyte-specific eIF2α-phosphorylation-deficient 3-month-old mice or 12-month-old mice were fed a 60% high fructose diet (HFrD) for 16 or 5 wks, and the effects of eIF2α-phosphorylation deficiency on NADP/NADPH and GSSG/GSH levels, ROS-defense gene expression, oxidative damage, cell death, and fibrosis were observed. RESULTS Prolonged fructose feeding to mice caused dysregulation of the unfolded protein response (UPR) sensor activation and UPR gene expression, and then led to decreased expression of several ROS defense genes including glutathione biogenesis genes. Nonetheless, these changes were not sufficient to induce the death of eIF2α phosphorylation-sufficient hepatocytes. However, there was a substantial increase in hepatocyte death and liver fibrosis in fructose-fed middle-aged mice deficient in hepatocyte-specific eIF2α phosphorylation because of diminished antioxidant capacity due to reduced expression of antioxidant enzymes (GPX1 and HO-1) and lower NADPH and glutathione levels, as well as a possible increase in ROS-induced damage from infiltrating NOX2-expressing leukocytes; all this led to a vicious cycle of hepatocyte death and leukocyte infiltration. CONCLUSION Our findings suggest that eIF2α phosphorylation maintains NADPH and GSH levels and controls the expression of ROS-defense genes, thereby protecting hepatocytes from oxidative stresses induced by fructose metabolism.
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Affiliation(s)
- Woo-Gyun Choi
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
| | - Jaeseok Han
- Soonchunhyang Institute of Med-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Choongchungnam-do, 31151 Republic of Korea.,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037 USA
| | - Ji-Hyeon Kim
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea.,Biomedical Research Center, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, 05505 Republic of Korea
| | - Mi-Jeong Kim
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
| | - Jae-Woo Park
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
| | - Benbo Song
- NGM Biopharmaceuticals, Inc., 333 Oyster Point Blvd, South San Francisco, CA 94080 USA
| | - Hee-Jeong Cha
- Department of Pathology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, 44043 Republic of Korea
| | - Hye-Seon Choi
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
| | - Hun-Taeg Chung
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
| | - In-Kyu Lee
- Department of Internal Medicine and Biochemistry and Cell Biology, Kyungpook National University School of Medicine, Daegu, 41944 Republic of Korea
| | - Tae-Sik Park
- Department of Life Science, Gachon University, Seongnam, Republic of Korea
| | - Maria Hatzoglou
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106 USA
| | - Hueng-Sik Choi
- School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Hyun Ju Yoo
- Biomedical Research Center, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, 05505 Republic of Korea
| | - Randal J Kaufman
- Soonchunhyang Institute of Med-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Choongchungnam-do, 31151 Republic of Korea
| | - Sung Hoon Back
- School of Biological Sciences, University of Ulsan, Ulsan, 44610 Republic of Korea
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162
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Chen X, Bisschops MMM, Agarwal NR, Ji B, Shanmugavel KP, Petranovic D. Interplay of Energetics and ER Stress Exacerbates Alzheimer's Amyloid-β (Aβ) Toxicity in Yeast. Front Mol Neurosci 2017; 10:232. [PMID: 28798664 PMCID: PMC5529408 DOI: 10.3389/fnmol.2017.00232] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 07/06/2017] [Indexed: 12/21/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegeneration. Oligomers of amyloid-β peptides (Aβ) are thought to play a pivotal role in AD pathogenesis, yet the mechanisms involved remain unclear. Two major isoforms of Aβ associated with AD are Aβ40 and Aβ42, the latter being more toxic and prone to form oligomers. Here, we took a systems biology approach to study two humanized yeast AD models which expressed either Aβ40 or Aβ42 in bioreactor cultures. Strict control of oxygen availability and culture pH, strongly affected chronological lifespan and reduced variations during cell growth. Reduced growth rates and biomass yields were observed upon Aβ42 expression, indicating a redirection of energy from growth to maintenance. Quantitative physiology analyses furthermore revealed reduced mitochondrial functionality and ATP generation in Aβ42 expressing cells, which matched with observed aberrant mitochondrial structures. Genome-wide expression level analysis showed that Aβ42 expression triggered strong ER stress and unfolded protein responses. Equivalent expression of Aβ40, however, induced only mild ER stress, which resulted in hardly affected physiology. Using AD yeast models in well-controlled cultures strengthened our understanding on how cells translate different Aβ toxicity signals into particular cell fate programs, and further enhance their potential as a discovery platform to identify possible therapies.
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Affiliation(s)
- Xin Chen
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
| | - Markus M. M. Bisschops
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
| | - Nisha R. Agarwal
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
| | - Boyang Ji
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
| | - Kumaravel P. Shanmugavel
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
| | - Dina Petranovic
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of TechnologyGothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of TechnologyGothenburg, Sweden
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163
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Abstract
Numerous environmental, physiological, and pathological insults disrupt protein-folding homeostasis in the endoplasmic reticulum (ER), referred to as ER stress. Eukaryotic cells evolved a set of intracellular signaling pathways, collectively termed the unfolded protein response (UPR), to maintain a productive ER protein-folding environment through reprogramming gene transcription and mRNA translation. The UPR is largely dependent on transcription factors (TFs) that modulate expression of genes involved in many physiological and pathological conditions, including development, metabolism, inflammation, neurodegenerative diseases, and cancer. Here we summarize the current knowledge about these mechanisms, their impact on physiological/pathological processes, and potential therapeutic applications.
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Affiliation(s)
- Jaeseok Han
- Soonchunhyang Institute of Medi-Bio Science (SIMS), Soonchunhyang University, Cheonan-si, Choongchungnam-do 31151, Republic of Korea
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, 92307 USA
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164
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Hepatic ZIP14-mediated zinc transport is required for adaptation to endoplasmic reticulum stress. Proc Natl Acad Sci U S A 2017; 114:E5805-E5814. [PMID: 28673968 DOI: 10.1073/pnas.1704012114] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Extensive endoplasmic reticulum (ER) stress damages the liver, causing apoptosis and steatosis despite the activation of the unfolded protein response (UPR). Restriction of zinc from cells can induce ER stress, indicating that zinc is essential to maintain normal ER function. However, a role for zinc during hepatic ER stress is largely unknown despite important roles in metabolic disorders, including obesity and nonalcoholic liver disease. We have explored a role for the metal transporter ZIP14 during pharmacologically and high-fat diet-induced ER stress using Zip14-/- (KO) mice, which exhibit impaired hepatic zinc uptake. Here, we report that ZIP14-mediated hepatic zinc uptake is critical for adaptation to ER stress, preventing sustained apoptosis and steatosis. Impaired hepatic zinc uptake in Zip14 KO mice during ER stress coincides with greater expression of proapoptotic proteins. ER stress-induced Zip14 KO mice show greater levels of hepatic steatosis due to higher expression of genes involved in de novo fatty acid synthesis, which are suppressed in ER stress-induced WT mice. During ER stress, the UPR-activated transcription factors ATF4 and ATF6α transcriptionally up-regulate Zip14 expression. We propose ZIP14 mediates zinc transport into hepatocytes to inhibit protein-tyrosine phosphatase 1B (PTP1B) activity, which acts to suppress apoptosis and steatosis associated with hepatic ER stress. Zip14 KO mice showed greater hepatic PTP1B activity during ER stress. These results show the importance of zinc trafficking and functional ZIP14 transporter activity for adaptation to ER stress associated with chronic metabolic disorders.
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165
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Tsai TH, Chen E, Li L, Saha P, Lee HJ, Huang LS, Shelness GS, Chan L, Chang BHJ. The constitutive lipid droplet protein PLIN2 regulates autophagy in liver. Autophagy 2017; 13:1130-1144. [PMID: 28548876 DOI: 10.1080/15548627.2017.1319544] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Excess triglyceride (TG) accumulation in the liver underlies fatty liver disease, a highly prevalent ailment. TG occurs in the liver sequestered in lipid droplets, the major lipid storage organelle. Lipid droplets are home to the lipid droplet proteins, the most abundant of which are the perilipins (PLINs), encoded by 5 different genes, Plin1 to Plin5. Of the corresponding gene products, PLIN2 is the only constitutive and ubiquitously expressed lipid droplet protein that has been used as a protein marker for lipid droplets. We and others reported that plin2-/- mice have an ∼60% reduction in TG content, and are protected against fatty liver disease. Here we show that PLIN2 overexpression protects lipid droplets against macroautophagy/autophagy, whereas PLIN2 deficiency enhances autophagy and depletes hepatic TG. The enhanced autophagy in plin2-/- mice protects against severe ER stress-induced hepatosteatosis and hepatocyte apoptosis. In contrast, hepatic TG depletion resulting from other genetic and pharmacological manipulations has no effect on autophagy. Importantly, PLIN2 deficiency lowers cellular TG content in wild-type mouse embryonic fibroblasts (MEFs) via enhanced autophagy, but does not affect cellular TG content in atg7-/- MEFs that are devoid of autophagic function. Conversely, adenovirus-shAtg7-mediated hepatic Atg7 knockdown per se does not alter the hepatic TG level, suggesting a more complex regulation in vivo. In sum, PLIN2 guards its own house, the lipid droplet. PLIN2 overexpression protects against autophagy, and its downregulation stimulates TG catabolism via autophagy.
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Affiliation(s)
- Tsung-Huang Tsai
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA
| | - Elaine Chen
- b Molecular and Cellular Biology , Baylor College of Medicine , Houston , TX , USA
| | - Lan Li
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA
| | - Pradip Saha
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA.,b Molecular and Cellular Biology , Baylor College of Medicine , Houston , TX , USA
| | - Hsiao-Ju Lee
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA
| | - Li-Shin Huang
- c Department of Medicine , Columbia University , New York , NY , USA
| | - Gregory S Shelness
- d Department of Internal Medicine , Section on Molecular Medicine, Wake Forest School of Medicine , Winston-Salem , NC , USA
| | - Lawrence Chan
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA.,b Molecular and Cellular Biology , Baylor College of Medicine , Houston , TX , USA
| | - Benny Hung-Junn Chang
- a Departments of Medicine, Baylor College of Medicine , Houston , TX , USA.,b Molecular and Cellular Biology , Baylor College of Medicine , Houston , TX , USA
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166
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Hepatic p63 regulates steatosis via IKKβ/ER stress. Nat Commun 2017; 8:15111. [PMID: 28480888 PMCID: PMC5424198 DOI: 10.1038/ncomms15111] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 03/01/2017] [Indexed: 12/28/2022] Open
Abstract
p53 family members control several metabolic and cellular functions. The p53 ortholog p63 modulates cellular adaptations to stress and has a major role in cell maintenance and proliferation. Here we show that p63 regulates hepatic lipid metabolism. Mice with liver-specific p53 deletion develop steatosis and show increased levels of p63. Down-regulation of p63 attenuates liver steatosis in p53 knockout mice and in diet-induced obese mice, whereas the activation of p63 induces lipid accumulation. Hepatic overexpression of N-terminal transactivation domain TAp63 induces liver steatosis through IKKβ activation and the induction of ER stress, the inhibition of which rescues the liver functions. Expression of TAp63, IKKβ and XBP1s is also increased in livers of obese patients with NAFLD. In cultured human hepatocytes, TAp63 inhibition protects against oleic acid-induced lipid accumulation, whereas TAp63 overexpression promotes lipid storage, an effect reversible by IKKβ silencing. Our findings indicate an unexpected role of the p63/IKKβ/ER stress pathway in lipid metabolism and liver disease.
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167
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Rashid HO, Kim HK, Junjappa R, Kim HR, Chae HJ. Endoplasmic reticulum stress in the regulation of liver diseases: Involvement of Regulated IRE1α and β-dependent decay and miRNA. J Gastroenterol Hepatol 2017; 32:981-991. [PMID: 27774654 DOI: 10.1111/jgh.13619] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/24/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022]
Abstract
Compromised protein folding capacity in the endoplasmic reticulum (ER) leads to a protein traffic jam that produces a toxic environment called ER stress. However, the ER smartly handles such a critical situation by activating a cascade of proteins responsible for sensing and responding to the noxious stimuli of accumulated proteins. The ER protein load is higher in secretory cells, such as liver hepatocytes, which are thus prone to stress-mediated toxicity and various diseases, including alcohol-induced liver injury, fatty liver disease, and viral hepatitis. Therefore, we discuss the molecular cues that connect ER stress to hepatic diseases. Moreover, we review the literature on ER stress-regulated miRNA in the pathogenesis of liver diseases to give a comprehensive overview of mechanistic insights connecting ER stress and miRNA in the context of liver diseases. We also discuss currently discovered regulated IRE1 dependent decay in regulation of hepatic diseases.
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Affiliation(s)
- Harun-Or Rashid
- Department of Pharmacology and New Drug Development Institute, Medical School, Chonbuk National University, Jeonju, Korea
| | - Hyun-Kyoung Kim
- Department of Pharmacology and New Drug Development Institute, Medical School, Chonbuk National University, Jeonju, Korea
| | - Raghupatil Junjappa
- Department of Pharmacology and New Drug Development Institute, Medical School, Chonbuk National University, Jeonju, Korea
| | - Hyung-Ryong Kim
- Graduate School and Institute of Science and Technology, DGIST, Daegu, Republic of Korea
| | - Han-Jung Chae
- Department of Pharmacology and New Drug Development Institute, Medical School, Chonbuk National University, Jeonju, Korea
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168
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Doultsinos D, Avril T, Lhomond S, Dejeans N, Guédat P, Chevet E. Control of the Unfolded Protein Response in Health and Disease. SLAS DISCOVERY 2017; 22:787-800. [PMID: 28453376 DOI: 10.1177/2472555217701685] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The unfolded protein response (UPR) is an integrated, adaptive biochemical process that is inextricably linked with cell homeostasis and paramount to maintenance of normal physiological function. Prolonged accumulation of improperly folded proteins in the endoplasmic reticulum (ER) leads to stress. This is the driving stimulus behind the UPR. As such, prolonged ER stress can push the UPR past beneficial functions such as reduced protein production and increased folding and clearance to apoptotic signaling. The UPR is thus contributory to the commencement, maintenance, and exacerbation of a multitude of disease states, making it an attractive global target to tackle conditions sorely in need of novel therapeutic intervention. The accumulation of information of screening tools, readily available therapies, and potential pathways to drug development is the cornerstone of informed clinical research and clinical trial design. Here, we review the UPR's involvement in health and disease and, beyond providing an in-depth description of the molecules found to target the three UPR arms, we compile all the tools available to screen for and develop novel therapeutic agents that modulate the UPR with the scope of future disease intervention.
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Affiliation(s)
- Dimitrios Doultsinos
- 1 Inserm U1242, Chemistry, Oncogenesis, Stress & Signaling, University of Rennes 1, Rennes, France.,2 Centre de Lutte contre le Cancer Eugène Marquis, Rennes, France
| | - Tony Avril
- 1 Inserm U1242, Chemistry, Oncogenesis, Stress & Signaling, University of Rennes 1, Rennes, France.,2 Centre de Lutte contre le Cancer Eugène Marquis, Rennes, France
| | | | | | | | - Eric Chevet
- 1 Inserm U1242, Chemistry, Oncogenesis, Stress & Signaling, University of Rennes 1, Rennes, France.,2 Centre de Lutte contre le Cancer Eugène Marquis, Rennes, France.,3 BMYscreen, Bergonié Cancer Institute, Bordeaux, France
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169
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Yao T, Deng Z, Gao Y, Sun J, Kong X, Huang Y, He Z, Xu Y, Chang Y, Yu KJ, Findley BG, Berglund ED, Wang RT, Guo H, Chen H, Li X, Kaufman RJ, Yan J, Liu T, Williams KW. Ire1α in Pomc Neurons Is Required for Thermogenesis and Glycemia. Diabetes 2017; 66:663-673. [PMID: 28028078 PMCID: PMC5319716 DOI: 10.2337/db16-0533] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 12/16/2016] [Indexed: 12/18/2022]
Abstract
Whether neuronal inositol-requiring enzyme 1 (Ire1) is required for the proper regulation of energy balance and glucose homeostasis is unclear. We found that pro-opiomelanocortin (Pomc)-specific deficiency of Ire1α accelerated diet-induced obesity concomitant with a decrease in energy expenditure. This hypometabolic phenotype included deficits in thermogenic responses to diet and cold exposure as well as "beiging" of white adipose tissue. We also demonstrate that loss of Ire1α in Pomc neurons impaired whole-body glucose and insulin tolerance as well as hepatic insulin sensitivity. At the cellular level, deletion of Ire1α in Pomc neurons elevated hypothalamic endoplasmic reticulum (ER) stress and predisposed Pomc neurons to leptin and insulin resistance. Together, the current studies extend and confirm conclusions that Ire1α-Xbp1s and associated molecular targets link ER stress in arcuate Pomc neurons to aspects of normal energy and glucose homeostasis.
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Affiliation(s)
- Ting Yao
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi, China
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Zhuo Deng
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Department of Gynecology, Shaanxi Provincial People's Hospital, Shaanxi, China
| | - Yong Gao
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jia Sun
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Xingxing Kong
- Division of Endocrinology, Beth Israel Deaconess Medical Center and Harvard Medical School, Harvard University, Boston, MA
| | - Yiru Huang
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Zhenyan He
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Yanchao Xu
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Yongsheng Chang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Kai-Jiang Yu
- Department of Intensive Care Unit, Third Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Brianna G Findley
- Division of Metabolic Mechanisms of Disease, Advanced Imaging Research Center and Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Eric D Berglund
- Division of Metabolic Mechanisms of Disease, Advanced Imaging Research Center and Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Rui-Tao Wang
- Department of Intensive Care Unit, Third Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Hongbo Guo
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Hong Chen
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Xu Li
- Department of Obstetrics and Gynecology, First Affiliated Hospital, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi, China
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
| | - Jianqun Yan
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi, China
| | - Tiemin Liu
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Department of Intensive Care Unit, Third Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Kevin W Williams
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
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170
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Kang M, Kim J, An HT, Ko J. Human leucine zipper protein promotes hepatic steatosis via induction of apolipoprotein A-IV. FASEB J 2017; 31:2548-2561. [PMID: 28246167 DOI: 10.1096/fj.201601227r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 02/07/2017] [Indexed: 12/13/2022]
Abstract
The molecular mechanism of stress-induced hepatic steatosis is not well known. Human leucine zipper protein (LZIP) regulates the expression of genes involved in inflammation, cell migration, and stress response. The aim of this study was to determine the regulatory role of LZIP in stress-induced hepatic steatosis. We used a microarray analysis to identify LZIP-induced genes involved in hepatic lipid metabolism. LZIP increased the expression of apolipoprotein A-IV (APOA4) mRNA. In the presence of stress inducer, APOA4 promoter analysis was performed, and LZIP-induced lipid accumulation was monitored in mouse primary cells and human tissues. Under Golgi stress conditions, LZIP underwent proteolytic cleavage and was phosphorylated by AKT to protect against proteasome degradation. The stabilized N-terminal LZIP was translocated to the nucleus, where it directly bound to the APOA4 promoter, leading to APOA4 induction. LZIP-induced APOA4 expression resulted in increased absorption of surrounding free fatty acids. LZIP also promoted hepatic steatosis in mouse liver. Both LZIP and APOA4 were highly expressed in human steatosis samples. Our findings indicate that LZIP is a novel modulator of APOA4 expression and hepatic lipid metabolism. LZIP might be a therapeutic target for developing treatment strategies for hepatic steatosis and related metabolic diseases.-Kang, M., Kim, J., An, H.-T., Ko, J. Human leucine zipper protein promotes hepatic steatosis via induction of apolipoprotein A-IV.
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Affiliation(s)
| | | | | | - Jesang Ko
- Division of Life Sciences, Korea University, Seoul, South Korea
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171
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A critical role of DDRGK1 in endoplasmic reticulum homoeostasis via regulation of IRE1α stability. Nat Commun 2017; 8:14186. [PMID: 28128204 PMCID: PMC5290148 DOI: 10.1038/ncomms14186] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 12/07/2016] [Indexed: 12/30/2022] Open
Abstract
Disturbance of endoplasmic reticulum (ER) homoeostasis induces ER stress and leads to activation of the unfolded protein response (UPR), which is an adaptive reaction that promotes cell survival or triggers apoptosis, when homoeostasis is not restored. DDRGK1 is an ER membrane protein and a critical component of the ubiquitin-fold modifier 1 (Ufm1) system. However, the functions and mechanisms of DDRGK1 in ER homoeostasis are largely unknown. Here, we show that depletion of DDRGK1 induces ER stress and enhances ER stress-induced apoptosis in both cancer cells and hematopoietic stem cells (HSCs). Depletion of DDRGK1 represses IRE1α-XBP1 signalling and activates the PERK-eIF2α-CHOP apoptotic pathway by targeting the ER-stress sensor IRE1α. We further demonstrate that DDRGK1 regulates IRE1α protein stability via its interaction with the kinase domain of IRE1α, which is dependent on its ufmylation modification. Altogether, our results provide evidence that DDRGK1 is essential for ER homoeostasis regulation. DDRGK1 is an ER membrane protein that is subject to Ufm1 modification, but its function in ER homeostasis is unknown. Here, the authors show that ufmylated DDRGK1 interacts with and stabilizes the ER-stress sensor protein IRE1a, in turn repressing ER stress and apoptosis.
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172
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Wang JM, Qiu Y, Yang ZQ, Li L, Zhang K. Inositol-Requiring Enzyme 1 Facilitates Diabetic Wound Healing Through Modulating MicroRNAs. Diabetes 2017; 66:177-192. [PMID: 27634225 PMCID: PMC5204310 DOI: 10.2337/db16-0052] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 09/09/2016] [Indexed: 12/12/2022]
Abstract
Diabetic skin ulcers represent a challenging clinical problem with mechanisms not fully understood. In this study, we investigated the role and mechanism for the primary unfolded protein response (UPR) transducer inositol-requiring enzyme 1 (IRE1α) in diabetic wound healing. Bone marrow-derived progenitor cells (BMPCs) were isolated from adult male type 2 diabetic and their littermate control mice. In diabetic BMPCs, IRE1α protein expression and phosphorylation were repressed. The impaired diabetic BMPC angiogenic function was rescued by adenovirus-mediated expression of IRE1α but not by the RNase-inactive IRE1α or the activated X-box binding protein 1 (XBP1), the canonical IRE1α target. In fact, IRE1α RNase processes a subset of microRNAs (miRs), including miR-466 and miR-200 families, through which IRE1α plays an important role in maintaining BMPC function under the diabetic condition. IRE1α attenuated maturation of miR-466 and miR-200 family members at precursor miR levels through the regulated IRE1α-dependent decay (RIDD) independent of XBP1. IRE1α deficiency in diabetes resulted in a burst of functional miRs from miR-466 and miR-200 families, which directly target and repress the mRNA encoding the angiogenic factor angiopoietin 1 (ANGPT1), leading to decreased ANGPT1 expression and disrupted angiogenesis. Importantly, cell therapies using IRE1α-expressing BMPCs or direct IRE1α gene transfer significantly accelerated cutaneous wound healing in diabetic mice through facilitating angiogenesis. In conclusion, our studies revealed a novel mechanistic basis for rescuing angiogenesis and tissue repair in diabetic wound treatments.
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Affiliation(s)
- Jie-Mei Wang
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI
| | - Yining Qiu
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI
| | - Zeng-Quan Yang
- Karmanos Cancer Institute, Wayne State University, Detroit, MI
| | - Li Li
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI
- Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI
| | - Kezhong Zhang
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI
- Karmanos Cancer Institute, Wayne State University, Detroit, MI
- Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI
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173
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Chandrahas VK, Han J, Kaufman RJ. Coordinating Organismal Metabolism During Protein Misfolding in the ER Through the Unfolded Protein Response. Curr Top Microbiol Immunol 2017; 414:103-130. [PMID: 28900680 DOI: 10.1007/82_2017_41] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The endoplasmic reticulum (ER) is a cellular organelle responsible for folding of secretory and membrane proteins. Perturbance in ER homeostasis caused by various intrinsic/extrinsic stimuli challenges the protein-folding capacity of the ER, leading to an ER dysfunction, called ER stress. Cells have developed a defensive response to adapt and/or survive in the face of ER stress that may be detrimental to cell function and survival. When exposed to ER stress, the cell activates a complex and elaborate signaling network that includes translational modulation and transcriptional induction of genes. In addition to these autonomous responses, recent studies suggest that the stressed tissue secretes peptides or unknown factors that transfer the signal to other cells in the same or different organs, leading the organism as a whole to cope with challenges in a non-autonomous manner. In this review, we discuss the mechanisms by which cells adapt to ER stress challenges autonomously and transfer the stress signal to non-stressed cells in different organs.
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Affiliation(s)
- Vishwanatha K Chandrahas
- Degenerative Diseases Program, Sanford_Burnham_Prebys Medical Discovery Institute, 92037, La Jolla, CA, USA
| | - Jaeseok Han
- Soonchunhyang Institute of Med-bio Science (SIMS), Soonchunhyang University, 31151, Cheonan-si, Chungcheongnam-do, Republic of Korea.
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford_Burnham_Prebys Medical Discovery Institute, 92037, La Jolla, CA, USA.
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174
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Gomez JA, Rutkowski DT. Experimental reconstitution of chronic ER stress in the liver reveals feedback suppression of BiP mRNA expression. eLife 2016; 5. [PMID: 27938665 PMCID: PMC5179193 DOI: 10.7554/elife.20390] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/09/2016] [Indexed: 12/13/2022] Open
Abstract
Endoplasmic reticulum (ER) stress is implicated in many chronic diseases, but very little is known about how the unfolded protein response (UPR) responds to persistent ER stress in vivo. Here, we experimentally reconstituted chronic ER stress in the mouse liver, using repeated injection of a low dose of the ER stressor tunicamycin. Paradoxically, this treatment led to feedback-mediated suppression of a select group of mRNAs, including those encoding the ER chaperones BiP and GRP94. This suppression was due to both silencing of the ATF6α pathway of UPR-dependent transcription and enhancement of mRNA degradation, possibly via regulated IRE1-dependent decay (RIDD). The suppression of mRNA encoding BiP was phenocopied by ectopic overexpression of BiP protein, and was also observed in obese mice. Our findings suggest that persistent cycles of UPR activation and deactivation create an altered, quasi-stable setpoint for UPR-dependent transcriptional regulation—an outcome that could be relevant to conditions such as metabolic syndrome. DOI:http://dx.doi.org/10.7554/eLife.20390.001 Toxic chemicals, extreme temperatures and other abnormal environmental conditions can cause the cells in our bodies to become stressed. Several kinds of stresses overwhelm a compartment in the cell called the endoplasmic reticulum, which is critical for processing new proteins so that they can work correctly. Endoplasmic reticulum stress has been linked to long-term diseases such as diabetes, cancer and neurodegenerative diseases. Most of what is known about how cells sense and respond to endoplasmic reticulum stress comes from studies on isolated cells that were subjected to harsh conditions that cells cannot tolerate for longer than a day or two. By contrast, little is known about how cells within whole organisms respond to milder but longer-lasting endoplasmic reticulum stress, which is closer to what occurs during disease. To investigate this issue, Gomez and Rutkowski treated mice repeatedly with a chemical that causes mild endoplasmic reticulum stress in the liver. The cells exposed to this persistent stress responded differently to those exposed to severe short-term stress. Whereas short-term stress causes liver cells to turn on genes that help the endoplasmic reticulum to process proteins more efficiently, long-term stress causes cells to turn off some of those genes. Further investigation revealed that cells in the livers of obese mice show similar patterns of gene activity as cells exposed to long-term endoplasmic reticulum stress. The findings presented by Gomez and Rutkowski could therefore also help us to understand more about the liver problems that often occur during obesity and diabetes. Further studies are now needed to examine exactly how long-lasting stress can shut off the cells’ protective mechanisms. Future experiments could also investigate whether other types of cells and organs respond to long-term endoplasmic reticulum stress in the same way as cells in the liver. DOI:http://dx.doi.org/10.7554/eLife.20390.002
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Affiliation(s)
- Javier A Gomez
- Graduate Program in Molecular and Cellular Biology, University of Iowa Carver College of Medicine, Iowa City, United States
| | - D Thomas Rutkowski
- Departments of Anatomy and Cell Biology and Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, United States
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175
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Abstract
Hepatic steatosis, the first step in the progression of nonalcoholic fatty liver disease, is characterized by triglyceride accumulation in hepatocytes and is highly prevalent in people with obesity. Although initially asymptomatic, hepatic steatosis is an important risk factor for the development of hepatic insulin resistance and type 2 diabetes mellitus and can also progress to more severe pathologies such as nonalcoholic steatohepatitis, liver fibrosis and cirrhosis; hepatic steatosis has, therefore, received considerable research interest in the past 20 years. The lipid accumulation that defines hepatic steatosis disturbs the function of the endoplasmic reticulum (ER) in hepatocytes, thereby generating chronic ER stress that interferes with normal cellular function. Although ubiquitous stress response mechanisms (namely, ER-associated degradation, unfolded protein response and autophagy) are the main processes for restoring cellular proteostasis, these mechanisms are unable to alleviate ER stress in the context of the fatty liver. Furthermore, ER stress and ER stress responses can promote lipid accumulation in hepatocytes in a counter-productive manner and could, therefore, be the origin of a vicious pathological cycle.
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Affiliation(s)
- Andrei Baiceanu
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
- University of Medicine and Pharmacy Iuliu Hat¸ieganu, Faculty of Pharmacy, 8 Victor Babes Street, 400012 Cluj-Napoca, Romania
| | - Pierre Mesdom
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
| | - Marie Lagouge
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
| | - Fabienne Foufelle
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
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176
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Hepatic BSCL2 (Seipin) Deficiency Disrupts Lipid Droplet Homeostasis and Increases Lipid Metabolism via SCD1 Activity. Lipids 2016; 52:129-150. [DOI: 10.1007/s11745-016-4210-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 10/25/2016] [Indexed: 12/11/2022]
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177
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Baena M, Sangüesa G, Hutter N, Beltrán JM, Sánchez RM, Roglans N, Alegret M, Laguna JC. Liquid fructose in Western-diet-fed mice impairs liver insulin signaling and causes cholesterol and triglyceride loading without changing calorie intake and body weight. J Nutr Biochem 2016; 40:105-115. [PMID: 27883935 DOI: 10.1016/j.jnutbio.2016.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 10/24/2016] [Accepted: 10/27/2016] [Indexed: 01/17/2023]
Abstract
BACKGROUND/OBJECTIVES Liquid fructose associates with prevalence of type 2 diabetes mellitus and obesity. Intervention studies suggest that metabolically unfit individuals are more responsive than healthy individuals to liquid fructose. We determined whether mice consuming an obesogenic Western diet were more responsive than chow-fed mice to the alterations induced by liquid fructose supplementation (LFS). METHODS C57BL/6N mice were fed chow or Western diet±ad libitum 15% fructose solution for 12 weeks. Food and liquid intake and body weight were monitored. Plasma analytes and liver lipids, histology and the expression of genes related to lipid handling, endoplasmic reticulum stress, inflammation and insulin signaling were analyzed. RESULTS Western diet increased energy intake, visceral adipose tissue (vWAT), body weight, plasma and liver triglycerides and cholesterol, and inflammatory markers in vWAT vs. chow-fed mice. LFS did not change energy intake, vWAT or body weight. LFS significantly increased plasma and liver triglycerides and cholesterol levels only in Western-diet-fed mice. These changes associated with a potentiation of the increased liver expression of PPARγ and CD36 that was observed in Western-fed mice and related to the increased liver mTOR phosphorylation induced by LFS. Furthermore, LFS in Western-diet-fed mice induced the largest reduction in liver IRS2 protein and a significant decrease in whole-body insulin sensitivity. CONCLUSIONS LFS in mice, in a background of an unhealthy diet that already induces fatty liver visceral fat accretion and obesity, increases liver lipid burden, hinders hepatic insulin signaling and diminishes whole-body insulin sensitivity without changing energy intake.
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Affiliation(s)
- Miguel Baena
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain
| | - Gemma Sangüesa
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain
| | - Natalia Hutter
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain
| | - José María Beltrán
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain
| | - Rosa María Sánchez
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBERObn), Spain
| | - Núria Roglans
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBERObn), Spain
| | - Marta Alegret
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBERObn), Spain.
| | - Juan Carlos Laguna
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, School of Pharmacy and Food Science, University of Barcelona, Spain; Institute of Biomedicine University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBERObn), Spain.
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178
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Imbernon M, Sanchez‐Rebordelo E, Romero‐Picó A, Kalló I, Chee MJ, Porteiro B, Al‐Massadi O, Contreras C, Fernø J, Senra A, Gallego R, Folgueira C, Seoane LM, van Gestel M, Adan RA, Liposits Z, Dieguez C, López M, Nogueiras R. Hypothalamic kappa opioid receptor mediates both diet-induced and melanin concentrating hormone-induced liver damage through inflammation and endoplasmic reticulum stress. Hepatology 2016; 64:1086-104. [PMID: 27387967 PMCID: PMC5129461 DOI: 10.1002/hep.28716] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/05/2016] [Indexed: 12/14/2022]
Abstract
UNLABELLED The opioid system is widely known to modulate the brain reward system and thus affect the behavior of humans and other animals, including feeding. We hypothesized that the hypothalamic opioid system might also control energy metabolism in peripheral tissues. Mice lacking the kappa opioid receptor (κOR) and adenoviral vectors overexpressing or silencing κOR were stereotaxically delivered in the lateral hypothalamic area (LHA) of rats. Vagal denervation was performed to assess its effect on liver metabolism. Endoplasmic reticulum (ER) stress was inhibited by pharmacological (tauroursodeoxycholic acid) and genetic (overexpression of the chaperone glucose-regulated protein 78 kDa) approaches. The peripheral effects on lipid metabolism were assessed by histological techniques and western blot. We show that in the LHA κOR directly controls hepatic lipid metabolism through the parasympathetic nervous system, independent of changes in food intake and body weight. κOR colocalizes with melanin concentrating hormone receptor 1 (MCH-R1) in the LHA, and genetic disruption of κOR reduced melanin concentrating hormone-induced liver steatosis. The functional relevance of these findings was given by the fact that silencing of κOR in the LHA attenuated both methionine choline-deficient, diet-induced and choline-deficient, high-fat diet-induced ER stress, inflammation, steatohepatitis, and fibrosis, whereas overexpression of κOR in this area promoted liver steatosis. Overexpression of glucose-regulated protein 78 kDa in the liver abolished hypothalamic κOR-induced steatosis by reducing hepatic ER stress. CONCLUSIONS This study reveals a novel hypothalamic-parasympathetic circuit modulating hepatic function through inflammation and ER stress independent of changes in food intake or body weight; these findings might have implications for the clinical use of opioid receptor antagonists. (Hepatology 2016;64:1086-1104).
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Affiliation(s)
- Monica Imbernon
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Estrella Sanchez‐Rebordelo
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Amparo Romero‐Picó
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Imre Kalló
- Laboratory of Endocrine NeurobiologyInstitute of Experimental Medicine, Hungarian Academy of SciencesBudapestHungary
| | - Melissa J. Chee
- Division of Endocrinology, Department of MedicineBeth Israel Deaconess Medical Center, Harvard Medical SchoolBostonMA
| | - Begoña Porteiro
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Omar Al‐Massadi
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Cristina Contreras
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Johan Fernø
- Department of Clinical ScienceKG Jebsen Center for Diabetes Research, University of BergenBergenNorway
| | - Ana Senra
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Rosalia Gallego
- Department of Morphological Sciences, School of MedicineUniversity of Santiago de Compostela‐Instituto de Investigación Sanitaria
| | - Cintia Folgueira
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain,Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo, Hospitalario Universitario de Santiago (CHUS/SERGAS)Santiago de CompostelaSpain
| | - Luisa M. Seoane
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain,Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo, Hospitalario Universitario de Santiago (CHUS/SERGAS)Santiago de CompostelaSpain
| | - Margriet van Gestel
- Department of Neuroscience and PharmacologyRudolf Magnus Institute of Neuroscience, University Medical Center UtrechtUtrechtThe Netherlands
| | - Roger A. Adan
- Department of Neuroscience and PharmacologyRudolf Magnus Institute of Neuroscience, University Medical Center UtrechtUtrechtThe Netherlands
| | - Zsolt Liposits
- Laboratory of Endocrine NeurobiologyInstitute of Experimental Medicine, Hungarian Academy of SciencesBudapestHungary
| | - Carlos Dieguez
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Miguel López
- Department of PhysiologyCIMUS, University of Santiago de Compostela‐Instituto de Investigación Sanitaria,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn)Santiago de CompostelaSpain
| | - Ruben Nogueiras
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria. .,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain.
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179
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The unfolded protein response is a negative regulator of scavenger receptor class B, type I (SR-BI) expression. Biochem Biophys Res Commun 2016; 479:557-562. [DOI: 10.1016/j.bbrc.2016.09.110] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 09/21/2016] [Indexed: 11/23/2022]
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180
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Zhang J, Zhang K, Li Z, Guo B. ER Stress-induced Inflammasome Activation Contributes to Hepatic Inflammation and Steatosis. ACTA ACUST UNITED AC 2016; 7. [PMID: 27942420 PMCID: PMC5146989 DOI: 10.4172/2155-9899.1000457] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Endoplasmic reticulum (ER) stress functions as a protein folding and quality control mechanism to maintain cell homeostasis. Emerging evidence indicates that ER stress is also involved in metabolic and inflammatory diseases. However, the link between ER stress and inflammation remains not well characterized. In this study, we have demonstrated that ER stress-induced inflammasome activation plays a critical role in the pathogenesis of hepatic steatosis. By utilizing genetic and pharmacological agent-induced hepatic steatosis animal models, we found that hepatic steatosis was associated with inflammasome activation and ER stress. Our results show that caspase-1 ablation alleviated liver inflammation and injury. Liver tissues from caspase-1 KO mice had significantly reduced production of IL-1β under ER stress conditions. We also found that ER stress promoted inflammasome activation and IL-1β processing in both hepatocytes and Kupffer cells/macrophages. Moreover, lack of caspase-1 ameliorated cell death or pyropoptosis of hepatocytes induced by ER stress. Taken together, our findings suggest that ER stress-induced inflammasome activation and IL-1β production generate a positive feedback loop to amplify inflammatory response, eventually leading to liver steatosis and injury.
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Affiliation(s)
- Jinyu Zhang
- Department of Microbiology and Immunology, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425-5040, USA; Hollings Cancer Center, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425, USA
| | - Kezhong Zhang
- Department of Immunology and Microbiology, Center for Molecular Medicine & Genetics, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Zihai Li
- Department of Microbiology and Immunology, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425-5040, USA; Hollings Cancer Center, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425, USA
| | - Beichu Guo
- Department of Microbiology and Immunology, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425-5040, USA; Hollings Cancer Center, Medical University of South Carolina (MUSC), Charleston, South Carolina 29425, USA
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181
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Alleviation of hepatic fat accumulation by betaine involves reduction of homocysteine via up-regulation of betaine-homocysteine methyltransferase (BHMT). Biochem Biophys Res Commun 2016; 477:440-7. [DOI: 10.1016/j.bbrc.2016.06.080] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 06/15/2016] [Indexed: 01/08/2023]
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182
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Bozaykut P, Sahin A, Karademir B, Ozer NK. Endoplasmic reticulum stress related molecular mechanisms in nonalcoholic steatohepatitis. Mech Ageing Dev 2016; 157:17-29. [DOI: 10.1016/j.mad.2016.07.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 06/23/2016] [Accepted: 07/02/2016] [Indexed: 12/18/2022]
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183
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Zhang L, Wang HH. The essential functions of endoplasmic reticulum chaperones in hepatic lipid metabolism. Dig Liver Dis 2016; 48:709-16. [PMID: 27133206 DOI: 10.1016/j.dld.2016.03.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 03/06/2016] [Accepted: 03/22/2016] [Indexed: 12/11/2022]
Abstract
The endoplasmic reticulum (ER) is an essential organelle for protein and lipid synthesis in hepatocytes. ER homeostasis is vital to maintain normal hepatocyte physiology. Perturbed ER functions causes ER stress associated with accumulation of unfolded protein in the ER that activates a series of adaptive signalling pathways, termed unfolded protein response (UPR). The UPR regulates ER chaperone levels to preserve ER protein-folding environment to protect the cell from ER stress. Recent findings reveal an array of ER chaperones that alter the protein-folding environment in the ER of hepatocytes and contribute to dysregulation of hepatocyte lipid metabolism and liver disease. In this review, we will discuss the specific functions of these chaperones in regulation of lipid metabolism, especially de novo lipogenesis and lipid transport and demonstrate their homeostatic role not only for ER-protein synthesis but also for lipid metabolism in hepatocyte.
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Affiliation(s)
- LiChun Zhang
- Department of Emergency, Shengjing Affiliated Hospital of China Medical University, Shenyang, Liaoning Province, China.
| | - Hong-Hui Wang
- College of Biology, Hunan University, Changsha, Hunan Province, China.
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184
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Grootjans J, Kaser A, Kaufman RJ, Blumberg RS. The unfolded protein response in immunity and inflammation. Nat Rev Immunol 2016; 16:469-84. [PMID: 27346803 DOI: 10.1038/nri.2016.62] [Citation(s) in RCA: 508] [Impact Index Per Article: 63.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) is a highly conserved pathway that allows the cell to manage endoplasmic reticulum (ER) stress that is imposed by the secretory demands associated with environmental forces. In this role, the UPR has increasingly been shown to have crucial functions in immunity and inflammation. In this Review, we discuss the importance of the UPR in the development, differentiation, function and survival of immune cells in meeting the needs of an immune response. In addition, we review current insights into how the UPR is involved in complex chronic inflammatory diseases and, through its role in immune regulation, antitumour responses.
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Affiliation(s)
- Joep Grootjans
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115, USA
| | - Arthur Kaser
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, USA
| | - Richard S Blumberg
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115, USA
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185
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Herrema H, Zhou Y, Zhang D, Lee J, Salazar Hernandez MA, Shulman GI, Ozcan U. XBP1s Is an Anti-lipogenic Protein. J Biol Chem 2016; 291:17394-404. [PMID: 27325692 DOI: 10.1074/jbc.m116.728949] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Indexed: 12/31/2022] Open
Abstract
Endoplasmic reticulum (ER) stress has been shown to contribute to various metabolic diseases, including non-alcoholic fatty liver disease and type 2 diabetes. Reduction of ER stress by treatment with chemical chaperones or overexpression of ER chaperone proteins alleviates hepatic steatosis. Nonetheless, X-box binding protein 1s (XBP1s), a key transcription factor that reduces ER stress, has been proposed as a lipogenic transcription factor. In this report, we document that XBP1s leads to suppression of lipogenic gene expression and reduction of hepatic triglyceride and diacylglycerol content in livers of diet-induced obese and genetically obese and insulin-resistant ob/ob mice. Furthermore, we also show that PKCϵ activity, which correlates with fatty liver and which causes insulin resistance, was significantly reduced in diet-induced obese mice. Finally, we have shown that XBP1s reduces the hepatic fatty acid synthesis rate and enhances macrolipophagy, an initiating step in lipolysis. Our results reveal that XBP1s reduces hepatic lipogenic gene expression and improves hepatosteatosis in mouse models of obesity and insulin resistance, which leads us to conclude that XBP1s has anti-lipogenic properties in the liver.
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Affiliation(s)
- Hilde Herrema
- From the Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115,
| | - Yingjiang Zhou
- From the Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Dongyan Zhang
- the Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06519, and
| | - Justin Lee
- From the Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | | | - Gerald I Shulman
- the Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06519, and Departments of Internal Medicine and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Umut Ozcan
- From the Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115,
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186
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Lee HY, Lee GH, Bhattarai KR, Park BH, Koo SH, Kim HR, Chae HJ. Bax Inhibitor-1 regulates hepatic lipid accumulation via ApoB secretion. Sci Rep 2016; 6:27799. [PMID: 27297735 PMCID: PMC4906294 DOI: 10.1038/srep27799] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 05/25/2016] [Indexed: 12/13/2022] Open
Abstract
In this study, we explored the effects of Bax Inhibitor-1 (BI-1) on ApoB aggregation in high-fat diet (HFD)-induced hepatic lipid accumulation. After 1 week on a HFD, triglycerides and cholesterol accumulated more in the liver and were not effectively secreted into the plasma, whereas after 8 weeks, lipids were highly accumulated in both the liver and plasma, with a greater effect in BI-1 KO mice compared with BI-1 WT mice. ApoB, a lipid transfer protein, was accumulated to a greater extent in the livers of HFD-BI-1 KO mice compared with HFD-BI-1 WT mice. Excessive post-translational oxidation of protein disulfide isomerase (PDI), intra-ER ROS accumulation and folding capacitance alteration were also observed in HFD-BI-1 KO mice. Higher levels of endoplasmic reticulum (ER) stress were consistently observed in KO mice compared with the WT mice. Adenovirus-mediated hepatic expression of BI-1 in the BI-1 KO mice rescued the above phenotypes. Our results suggest that BI-1-mediated enhancement of ApoB secretion regulates hepatic lipid accumulation, likely through regulation of ER stress and ROS accumulation.
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Affiliation(s)
- Hwa Young Lee
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju 560-182, Korea
| | - Geum-Hwa Lee
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju 560-182, Korea
| | - Kashi Raj Bhattarai
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju 560-182, Korea
| | - Byung-Hyun Park
- Department of Biochemistry, School of Medicine, Chonbuk National University, Jeonju 560-182, Korea
| | - Seung-Hoi Koo
- Division of Life Sciences, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul, 136-713, Korea
| | - Hyung-Ryong Kim
- Department of Dental Pharmacology, School of Dentistry, Wonkwang University, Iksan, 570-749, Korea
| | - Han Jung Chae
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju 560-182, Korea
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187
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Han J, Kaufman RJ. The role of ER stress in lipid metabolism and lipotoxicity. J Lipid Res 2016; 57:1329-38. [PMID: 27146479 DOI: 10.1194/jlr.r067595] [Citation(s) in RCA: 397] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Indexed: 12/23/2022] Open
Abstract
The endoplasmic reticulum (ER) is a cellular organelle important for regulating calcium homeostasis, lipid metabolism, protein synthesis, and posttranslational modification and trafficking. Numerous environmental, physiological, and pathological insults disturb ER homeostasis, referred to as ER stress, in which a collection of conserved intracellular signaling pathways, termed the unfolded protein response (UPR), are activated to maintain ER function for cell survival. However, excessive and/or prolonged UPR activation leads to initiation of self-destruction through apoptosis. Excessive accumulation of lipids and their intermediate products causes metabolic abnormalities and cell death, called lipotoxicity, in peripheral organs, including the pancreatic islets, liver, muscle, and heart. Because accumulating evidence links chronic ER stress and defects in UPR signaling to lipotoxicity in peripheral tissues, understanding the role of ER stress in cell physiology is a topic under intense investigation. In this review, we highlight recent findings that link ER stress and UPR signaling to the pathogenesis of peripheral organs due to lipotoxicity.
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Affiliation(s)
- Jaeseok Han
- Soonchunhyang Institute of Med-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Choongchungnam-do, 31151, Republic of Korea
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307
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188
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Unfolded protein response induced by Brefeldin A increases collagen type I levels in hepatic stellate cells through an IRE1α, p38 MAPK and Smad-dependent pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2115-23. [PMID: 27155082 DOI: 10.1016/j.bbamcr.2016.05.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 04/16/2016] [Accepted: 05/03/2016] [Indexed: 01/04/2023]
Abstract
Unfolded protein response (UPR) triggered as a consequence of ER stress has been shown to be involved in the development of different pathologies, including fibrotic disorders. In the present paper we explore the role played by UPR on a key fibrogenic parameter in the liver: collagen type I levels in activated hepatic stellate cells (HSC). Using Brefeldin A (BFA) as an ER stress inducer we found that UPR correlated with enhanced mRNA and protein levels of collagen type I in a cell line of immortalized non-tumoral rat HSC. Analysis of the three branches of UPR revealed the activation of IRE1α, PERK and ATF6 in response to BFA, although PERK activation was shown not to be involved in the fibrogenic action of BFA. BFA also activated p38 MAPK in an IRE1α-dependent way and the p38 MAPK inhibitor SB203580 prevented the increase in collagen type I mRNA and protein levels caused by BFA, suggesting the involvement of this kinase on this effect. Analysis of Smad activation showed that phosphorylated nuclear levels of Smad2 and 3 were increased in response to BFA treatment. Inhibition of Smad3 phosphorylation by SIS3 prevented the enhancement of collagen type I levels caused by BFA. Pretreatment with IRE1α and p38 MAPK inhibitors also prevented the increased p-Smad3 accumulation in the nucleus, suggesting an IRE1α-p38 MAPK-Smad pathway to be responsible for the fibrogenic action of BFA on HSC.
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189
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Wang M, Kaufman RJ. Protein misfolding in the endoplasmic reticulum as a conduit to human disease. Nature 2016; 529:326-35. [PMID: 26791723 DOI: 10.1038/nature17041] [Citation(s) in RCA: 1043] [Impact Index Per Article: 130.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/11/2015] [Indexed: 12/18/2022]
Abstract
In eukaryotic cells, the endoplasmic reticulum is essential for the folding and trafficking of proteins that enter the secretory pathway. Environmental insults or increased protein synthesis often lead to protein misfolding in the organelle, the accumulation of misfolded or unfolded proteins - known as endoplasmic reticulum stress - and the activation of the adaptive unfolded protein response to restore homeostasis. If protein misfolding is not resolved, cells die. Endoplasmic reticulum stress and activation of the unfolded protein response help to determine cell fate and function. Furthermore, endoplasmic reticulum stress contributes to the aetiology of many human diseases.
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Affiliation(s)
- Miao Wang
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
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190
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Kim HM, Han JW, Chan JY. Nuclear Factor Erythroid-2 Like 1 (NFE2L1): Structure, function and regulation. Gene 2016; 584:17-25. [PMID: 26947393 DOI: 10.1016/j.gene.2016.03.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 02/18/2016] [Accepted: 03/01/2016] [Indexed: 02/06/2023]
Abstract
Nrf1 (also referred to as NFE2L1) is a member of the CNC-bZIP family of transcription factors that are characterized by a highly conserved CNC-domain, and a basic-leucine zipper domain required for dimerization and DNA binding. Nrf1 is ubiquitously expressed across tissue and cell types as various isoforms, and is induced by stress signals from a broad spectrum of stimuli. Evidence indicates that Nrf1 plays an important role in regulating a range of cellular functions including oxidative stress response, differentiation, inflammatory response, metabolism, and maintaining proteostasis. Thus, Nrf1 has been implicated in the pathogenesis of various disease processes including cancer development, and degenerative and metabolic disorders. This review summarizes our current understanding of Nrf1 and the molecular mechanism underlying its regulation and action in different cellular functions.
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Affiliation(s)
- Hyun Min Kim
- Department of Laboratory Medicine and Pathology, University of California, Irvine, D440 Medical Sciences, Irvine, CA 92697, USA
| | - Jeong Woo Han
- Department of Laboratory Medicine and Pathology, University of California, Irvine, D440 Medical Sciences, Irvine, CA 92697, USA
| | - Jefferson Y Chan
- Department of Laboratory Medicine and Pathology, University of California, Irvine, D440 Medical Sciences, Irvine, CA 92697, USA.
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191
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Foufelle F, Fromenty B. Role of endoplasmic reticulum stress in drug-induced toxicity. Pharmacol Res Perspect 2016; 4:e00211. [PMID: 26977301 PMCID: PMC4777263 DOI: 10.1002/prp2.211] [Citation(s) in RCA: 163] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 12/14/2015] [Indexed: 12/13/2022] Open
Abstract
Drug‐induced toxicity is a key issue for public health because some side effects can be severe and life‐threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug‐induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug‐induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug‐induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models.
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192
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Jung TW, Choi KM. Pharmacological Modulators of Endoplasmic Reticulum Stress in Metabolic Diseases. Int J Mol Sci 2016; 17:ijms17020192. [PMID: 26840310 PMCID: PMC4783926 DOI: 10.3390/ijms17020192] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 01/20/2016] [Accepted: 01/27/2016] [Indexed: 01/23/2023] Open
Abstract
The endoplasmic reticulum (ER) is the principal organelle responsible for correct protein folding, a step in protein synthesis that is critical for the functional conformation of proteins. ER stress is a primary feature of secretory cells and is involved in the pathogenesis of numerous human diseases, such as certain neurodegenerative and cardiometabolic disorders. The unfolded protein response (UPR) is a defense mechanism to attenuate ER stress and maintain the homeostasis of the organism. Two major degradation systems, including the proteasome and autophagy, are involved in this defense system. If ER stress overwhelms the capacity of the cell's defense mechanisms, apoptotic death may result. This review is focused on the various pharmacological modulators that can protect cells from damage induced by ER stress. The possible mechanisms for cytoprotection are also discussed.
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Affiliation(s)
- Tae Woo Jung
- Division of Endocrinology and Metabolism, Department of Internal Medicine, College of Medicine, Korea University, Seoul 152-703, Korea.
| | - Kyung Mook Choi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, College of Medicine, Korea University, Seoul 152-703, Korea.
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193
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Zheng J, Peng C, Ai Y, Wang H, Xiao X, Li J. Docosahexaenoic Acid Ameliorates Fructose-Induced Hepatic Steatosis Involving ER Stress Response in Primary Mouse Hepatocytes. Nutrients 2016; 8:nu8010055. [PMID: 26805874 PMCID: PMC4728666 DOI: 10.3390/nu8010055] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 01/13/2016] [Accepted: 01/14/2016] [Indexed: 12/11/2022] Open
Abstract
The increase in fructose consumption is considered to be a risk factor for developing nonalcoholic fatty liver disease (NAFLD). We investigated the effects of docosahexaenoic acid (DHA) on hepatic lipid metabolism in fructose-treated primary mouse hepatocytes, and the changes of Endoplasmic reticulum (ER) stress pathways in response to DHA treatment. The hepatocytes were treated with fructose, DHA, fructose plus DHA, tunicamycin (TM) or fructose plus 4-phenylbutyric acid (PBA) for 24 h. Intracellular triglyceride (TG) accumulation was assessed by Oil Red O staining. The mRNA expression levels and protein levels related to lipid metabolism and ER stress response were determined by real-time PCR and Western blot. Fructose treatment led to obvious TG accumulation in primary hepatocytes through increasing expression of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC), two key enzymes in hepatic de novo lipogenesis. DHA ameliorates fructose-induced TG accumulation by upregulating the expression of carnitine palmitoyltransferase 1A (CPT-1α) and acyl-CoA oxidase 1 (ACOX1). DHA treatment or pretreatment with the ER stress inhibitor PBA significantly decreased TG accumulation and reduced the expression of glucose-regulated protein 78 (GRP78), total inositol-requiring kinase 1 (IRE1α) and p-IRE1α. The present results suggest that DHA protects against high fructose-induced hepatocellular lipid accumulation. The current findings also suggest that alleviating the ER stress response seems to play a role in the prevention of fructose-induced hepatic steatosis by DHA.
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Affiliation(s)
- Jinying Zheng
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China.
| | - Chuan Peng
- Laboratory of Lipid & Glucose Metabolism, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
| | - Yanbiao Ai
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China.
| | - Heng Wang
- Laboratory of Lipid & Glucose Metabolism, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
| | - Xiaoqiu Xiao
- Laboratory of Lipid & Glucose Metabolism, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
| | - Jibin Li
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China.
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194
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Xu Z, Chikka MR, Xia H, Ready DF. Ire1 supports normal ER differentiation in developing Drosophila photoreceptors. J Cell Sci 2016; 129:921-9. [PMID: 26787744 PMCID: PMC4813318 DOI: 10.1242/jcs.180406] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 01/12/2016] [Indexed: 01/09/2023] Open
Abstract
The endoplasmic reticulum (ER) serves virtually all aspects of cell physiology and, by pathways that are incompletely understood, is dynamically remodeled to meet changing cell needs. Inositol-requiring enzyme 1 (Ire1), a conserved core protein of the unfolded protein response (UPR), participates in ER remodeling and is particularly required during the differentiation of cells devoted to intense secretory activity, so-called 'professional' secretory cells. Here, we characterize the role of Ire1 in ER differentiation in the developing Drosophila compound eye photoreceptors (R cells). As part of normal development, R cells take a turn as professional secretory cells with a massive secretory effort that builds the photosensitive membrane organelle, the rhabdomere. We find rough ER sheets proliferate as rhabdomere biogenesis culminates, and Ire1 is required for normal ER differentiation. Ire1 is active early in R cell development and is required in anticipation of peak biosynthesis. Without Ire1, the amount of rough ER sheets is strongly reduced and the extensive cortical ER network at the rhabdomere base, the subrhabdomere cisterna (SRC), fails. Instead, ER proliferates in persistent and ribosome-poor tubular tangles. A phase of Ire1 activity early in R cell development thus shapes dynamic ER.
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Affiliation(s)
- Zuyuan Xu
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | | | - Hongai Xia
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Donald F Ready
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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195
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Oxidative Stress in the Healthy and Wounded Hepatocyte: A Cellular Organelles Perspective. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2016:8327410. [PMID: 26788252 PMCID: PMC4691634 DOI: 10.1155/2016/8327410] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 09/10/2015] [Indexed: 02/06/2023]
Abstract
Accurate control of the cell redox state is mandatory for maintaining the structural integrity and physiological functions. This control is achieved both by a fine-tuned balance between prooxidant and anti-oxidant molecules and by spatial and temporal confinement of the oxidative species. The diverse cellular compartments each, although structurally and functionally related, actively maintain their own redox balance, which is necessary to fulfill specialized tasks. Many fundamental cellular processes such as insulin signaling, cell proliferation and differentiation and cell migration and adhesion, rely on localized changes in the redox state of signal transducers, which is mainly mediated by hydrogen peroxide (H2O2). Therefore, oxidative stress can also occur long before direct structural damage to cellular components, by disruption of the redox circuits that regulate the cellular organelles homeostasis. The hepatocyte is a systemic hub integrating the whole body metabolic demand, iron homeostasis and detoxification processes, all of which are redox-regulated processes. Imbalance of the hepatocyte's organelles redox homeostasis underlies virtually any liver disease and is a field of intense research activity. This review recapitulates the evolving concept of oxidative stress in the diverse cellular compartments, highlighting the principle mechanisms of oxidative stress occurring in the healthy and wounded hepatocyte.
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196
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Kakazu E, Mauer AS, Yin M, Malhi H. Hepatocytes release ceramide-enriched pro-inflammatory extracellular vesicles in an IRE1α-dependent manner. J Lipid Res 2015; 57:233-45. [PMID: 26621917 DOI: 10.1194/jlr.m063412] [Citation(s) in RCA: 210] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Indexed: 12/16/2022] Open
Abstract
Nonalcoholic steatohepatitis (NASH) is a lipotoxic disease wherein activation of endoplasmic reticulum (ER) stress response and macrophage-mediated hepatic inflammation are key pathogenic features. However, the lipid mediators linking these two observations remain elusive. We postulated that ER stress-regulated release of pro-inflammatory extracellular vesicles (EVs) from lipotoxic hepatocytes may be this link. EVs were isolated from cell culture supernatants of hepatocytes treated with palmitate (PA) to induce lipotoxic ER stress, characterized by immunofluorescence, Western blotting, electron microscopy, and nanoparticle tracking analysis. Sphingolipids were measured by tandem mass spectrometry. EVs were employed in macrophage chemotaxis assays. PA induced significant EV release. Because PA activates ER stress, we used KO hepatocytes to demonstrate that PA-induced EV release was mediated by inositol requiring enzyme 1α (IRE1α)/X-box binding protein-1. PA-induced EVs were enriched in C16:0 ceramide in an IRE1α-dependent manner, and activated macrophage chemotaxis via formation of sphingosine-1-phosphate (S1P) from C16:0 ceramide. This chemotaxis was blocked by sphingosine kinase inhibitors and S1P receptor inhibitors. Lastly, elevated circulating EVs in experimental and human NASH demonstrated increased C16:0 ceramide. PA induces C16:0 ceramide-enriched EV release in an IRE1α-dependent manner. The ceramide metabolite, S1P, activates macrophage chemotaxis, a potential mechanism for the recruitment of macrophages to the liver under lipotoxic conditions.
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Affiliation(s)
- Eiji Kakazu
- Division of Gastroenterology and Hepatology Mayo Clinic, Rochester, MN 55905 Department of Community Medical Supports, Tohoku Medical Megabank Organization, Tohoku University, Aobaku, Sendai, 980-8573 Japan
| | - Amy S Mauer
- Division of Gastroenterology and Hepatology Mayo Clinic, Rochester, MN 55905
| | - Meng Yin
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | - Harmeet Malhi
- Division of Gastroenterology and Hepatology Mayo Clinic, Rochester, MN 55905
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197
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Hassler JR, Scheuner DL, Wang S, Han J, Kodali VK, Li P, Nguyen J, George JS, Davis C, Wu SP, Bai Y, Sartor M, Cavalcoli J, Malhi H, Baudouin G, Zhang Y, Yates III JR, Itkin-Ansari P, Volkmann N, Kaufman RJ. The IRE1α/XBP1s Pathway Is Essential for the Glucose Response and Protection of β Cells. PLoS Biol 2015; 13:e1002277. [PMID: 26469762 PMCID: PMC4607427 DOI: 10.1371/journal.pbio.1002277] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/08/2015] [Indexed: 12/11/2022] Open
Abstract
Although glucose uniquely stimulates proinsulin biosynthesis in β cells, surprisingly little is known of the underlying mechanism(s). Here, we demonstrate that glucose activates the unfolded protein response transducer inositol-requiring enzyme 1 alpha (IRE1α) to initiate X-box-binding protein 1 (Xbp1) mRNA splicing in adult primary β cells. Using mRNA sequencing (mRNA-Seq), we show that unconventional Xbp1 mRNA splicing is required to increase and decrease the expression of several hundred mRNAs encoding functions that expand the protein secretory capacity for increased insulin production and protect from oxidative damage, respectively. At 2 wk after tamoxifen-mediated Ire1α deletion, mice develop hyperglycemia and hypoinsulinemia, due to defective β cell function that was exacerbated upon feeding and glucose stimulation. Although previous reports suggest IRE1α degrades insulin mRNAs, Ire1α deletion did not alter insulin mRNA expression either in the presence or absence of glucose stimulation. Instead, β cell failure upon Ire1α deletion was primarily due to reduced proinsulin mRNA translation primarily because of defective glucose-stimulated induction of a dozen genes required for the signal recognition particle (SRP), SRP receptors, the translocon, the signal peptidase complex, and over 100 other genes with many other intracellular functions. In contrast, Ire1α deletion in β cells increased the expression of over 300 mRNAs encoding functions that cause inflammation and oxidative stress, yet only a few of these accumulated during high glucose. Antioxidant treatment significantly reduced glucose intolerance and markers of inflammation and oxidative stress in mice with β cell-specific Ire1α deletion. The results demonstrate that glucose activates IRE1α-mediated Xbp1 splicing to expand the secretory capacity of the β cell for increased proinsulin synthesis and to limit oxidative stress that leads to β cell failure.
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Affiliation(s)
- Justin R. Hassler
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Donalyn L. Scheuner
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- Lilly Research Laboratories, Eli Lilly & Company, Lilly Corporate Center, Indianapolis, Indiana, United States of America
| | - Shiyu Wang
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Jaeseok Han
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Vamsi K. Kodali
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Philip Li
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Julie Nguyen
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Jenny S. George
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Cory Davis
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Shengyang P. Wu
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Yongsheng Bai
- NCIBI Department of Bioinformatics, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- Department of Biology, Indiana State University, Terre Haute, Indiana, United States of America
| | - Maureen Sartor
- NCIBI Department of Bioinformatics, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - James Cavalcoli
- NCIBI Department of Bioinformatics, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Harmeet Malhi
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Gregory Baudouin
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Yaoyang Zhang
- Department of Chemical Physiology and Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - John R. Yates III
- Department of Chemical Physiology and Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Pamela Itkin-Ansari
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Niels Volkmann
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, United States of America
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- * E-mail:
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198
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Babayev E, Lalioti MD, Favero F, Seli E. Cross-Talk Between FSH and Endoplasmic Reticulum Stress: A Mutually Suppressive Relationship. Reprod Sci 2015; 23:352-64. [PMID: 26342052 DOI: 10.1177/1933719115602770] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Suboptimal cellular conditions result in the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and trigger ER stress. In this study, we investigated the effects of follicle stimulating hormone (FSH) on ER stress in granulosa cells (GCs) obtained from 3-week-old female C57BL6 mice 24 or 48 hours after intraperitoneal injection of 5 IU pregnant mare's serum gonadotropin (PMSG), and in primary mouse GCs in culture treated with FSH (10-100 mIU/mL) for 24 or 48 hours. Moreover, mouse GCs in culture were treated with tunicamycin (Tm) or thapsigargin (Tp), which induce ER stress by inhibiting N-glycosylation of ER proteins and ER calcium adenosine triphosphatase, respectively, and their response to FSH was evaluated. We found that FSH attenuated ER stress in mouse GCs in vivo and in vitro; messenger RNA levels of ER stress-associated genes Xbp1s, Atf6, Chop, and Casp12 were decreased upon exposure to FSH/PMSG. Activating transcription factor 4 protein levels also demonstrated consistent decrease following FSH stimulation. Both Tm and Tp treatments inhibited FSH response, ER stress-induced cells did not show any change in estradiol levels in response to FSH, whereas in untreated GCs, estradiol production increased 3-fold after incubation with FSH for 60 hours. Furthermore, ER stress-induced cells failed to demonstrate aromatase (Cyp19a1) expression upon exposure to FSH. Importantly, under high-ER stress conditions FSH stimulation was unable to downregulate the expression of ER stress-associated genes. Our findings suggest that FSH decreases ER stress in GCs under physiologic conditions. However, under conditions that cause a significant increase in ER stress, FSH response is attenuated.
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Affiliation(s)
- Elnur Babayev
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA
| | - Maria D Lalioti
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA Biogen Idec, Cambridge, MA, USA
| | - Federico Favero
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA
| | - Emre Seli
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA
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199
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Ashraf NU, Sheikh TA. Endoplasmic reticulum stress and Oxidative stress in the pathogenesis of Non-alcoholic fatty liver disease. Free Radic Res 2015. [PMID: 26223319 DOI: 10.3109/10715762.2015.1078461] [Citation(s) in RCA: 208] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome. The underlying causes of the disease progression in NAFLD are unclear. Recent evidences suggest endoplasmic reticulum stress in the development of lipid droplets (steatosis) and subsequent generation of reactive oxygen species (ROS) in the progression to non-alcoholic steatohepatitis (NASH). The signalling pathway activated by disruption of endoplasmic reticulum (ER) homoeostasis, called as unfolded protein response, is linked with membrane biosynthesis, insulin action, inflammation and apoptosis. ROS are important mediators of inflammation. Protein folding in ER is linked to ROS. Therefore understanding the basic mechanisms that lead to ER stress and ROS in NAFLD have become the topics of immense interest. The present review focuses on the role of ER stress and ROS in the pathogenesis of NAFLD. We also highlight the cross talk between ER stress and oxidative stress which suggest and encourage the development of therapeutics for NAFLD. Further we have reviewed various strategies used for the management of NAFLD/NASH and limitations of such strategies. Our review therefore highlights the need for newer strategies with regards to ER stress and oxidative stress.
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Affiliation(s)
- N U Ashraf
- a Academy of Scientific and Innovative Research (AcSIR) , New Delhi , India.,b PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine , Canal Road, Jammu Tawi , Jammu and Kashmir , India
| | - T A Sheikh
- a Academy of Scientific and Innovative Research (AcSIR) , New Delhi , India.,b PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine , Canal Road, Jammu Tawi , Jammu and Kashmir , India
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200
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Protein kinase Snf1 is involved in the proper regulation of the unfolded protein response in Saccharomyces cerevisiae. Biochem J 2015; 468:33-47. [PMID: 25730376 DOI: 10.1042/bj20140734] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Glc7 is the only catalytic subunit of the protein phosphatase type 1 in the yeast S. cerevisiae and, together with its regulatory subunits, is involved in many essential processes. Analysis of the non-essential mutants in the regulatory subunits of Glc7 revealed that the lack of Reg1, and no other subunit, causes hypersensitivity to unfolded protein response (UPR)-inducers, which was concomitant with an augmented UPR element-dependent transcriptional response. The Glc7-Reg1 complex takes part in the regulation of the yeast AMP-activated serine/threonine protein kinase Snf1 in response to glucose. We demonstrate in the present study that the observed phenotypes of reg1 mutant cells are attributable to the inappropriate activation of Snf1. Indeed, growth in the presence of limited concentrations of glucose, where Snf1 is active, or expression of active forms of Snf1 in a wild-type strain increased the sensitivity to the UPR-inducer tunicamycin. Furthermore, reg1 mutant cells showed a sustained HAC1 mRNA splicing and KAR2 mRNA levels during the recovery phase of the UPR, and dysregulation of the Ire1-oligomeric equilibrium. Finally, overexpression of protein phosphatases Ptc2 and Ptc3 alleviated the growth defect of reg1 cells under endoplasmic reticulum (ER) stress conditions. Altogether, our results reveal that Snf1 plays an important role in the attenuation of the UPR, as well as identifying the protein kinase and its effectors as possible pharmacological targets for human diseases that are associated with insufficient UPR activation.
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