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      Liver Cholesterol Overload Aggravates Obstructive Cholestasis by Inducing Oxidative Stress and Premature Death in Mice

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          Abstract

          Nonalcoholic steatohepatitis is one of the leading causes of liver disease. Dietary factors determine the clinical presentation of steatohepatitis and can influence the progression of related diseases. Cholesterol has emerged as a critical player in the disease and hence consumption of cholesterol-enriched diets can lead to a progressive form of the disease. The aim was to investigate the impact of liver cholesterol overload on the progression of the obstructive cholestasis in mice subjected to bile duct ligation surgery. Mice were fed with a high cholesterol diet for two days and then were subjected to surgery procedure; histological, biochemical, and molecular analyses were conducted to address the effect of cholesterol in liver damage. Mice under the diet were more susceptible to damage. Results show that cholesterol fed mice exhibited increased apoptosis and oxidative stress as well as reduction in cell proliferation. Mortality following surgery was higher in HC fed mice. Liver cholesterol impairs the repair of liver during obstructive cholestasis and aggravates the disease with early fatal consequences; these effects were strongly associated with oxidative stress.

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          Most cited references26

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          Glutathione and mitochondria

          Glutathione (GSH) is the main non-protein thiol in cells whose functions are dependent on the redox-active thiol of its cysteine moiety that serves as a cofactor for a number of antioxidant and detoxifying enzymes. While synthesized exclusively in the cytosol from its constituent amino acids, GSH is distributed in different compartments, including mitochondria where its concentration in the matrix equals that of the cytosol. This feature and its negative charge at physiological pH imply the existence of specific carriers to import GSH from the cytosol to the mitochondrial matrix, where it plays a key role in defense against respiration-induced reactive oxygen species and in the detoxification of lipid hydroperoxides and electrophiles. Moreover, as mitochondria play a central strategic role in the activation and mode of cell death, mitochondrial GSH has been shown to critically regulate the level of sensitization to secondary hits that induce mitochondrial membrane permeabilization and release of proteins confined in the intermembrane space that once in the cytosol engage the molecular machinery of cell death. In this review, we summarize recent data on the regulation of mitochondrial GSH and its role in cell death and prevalent human diseases, such as cancer, fatty liver disease, and Alzheimer’s disease.
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            Mitochondrial free cholesterol loading sensitizes to TNF- and Fas-mediated steatohepatitis.

            The etiology of progression from steatosis to steatohepatitis (SH) remains unknown. Using nutritional and genetic models of hepatic steatosis, we show that free cholesterol (FC) loading, but not free fatty acids or triglycerides, sensitizes to TNF- and Fas-induced SH. FC distribution in endoplasmic reticulum (ER) and plasma membrane did not cause ER stress or alter TNF signaling. Rather, mitochondrial FC loading accounted for the hepatocellular sensitivity to TNF due to mitochondrial glutathione (mGSH) depletion. Selective mGSH depletion in primary hepatocytes recapitulated the susceptibility to TNF and Fas seen in FC-loaded hepatocytes; its repletion rescued FC-loaded livers from TNF-mediated SH. Moreover, hepatocytes from mice lacking NPC1, a late endosomal cholesterol trafficking protein, or from obese ob/ob mice, exhibited mitochondrial FC accumulation, mGSH depletion, and susceptibility to TNF. Thus, we propose a critical role for mitochondrial FC loading in precipitating SH, by sensitizing hepatocytes to TNF and Fas through mGSH depletion.
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              Cholesterol metabolism and the pathogenesis of non-alcoholic steatohepatitis.

              Emerging experimental and human evidence has linked altered hepatic cholesterol homeostasis and free cholesterol (FC) accumulation to the pathogenesis of non-alcoholic steatohepatits (NASH). This review focuses on cellular mechanisms of cholesterol toxicity involved in liver injury and on alterations in cholesterol homeostasis promoting hepatic cholesterol overload in NASH. FC accumulation injures hepatocytes directly, by disrupting mitochondrial and endoplasmic reticulum (ER) membrane integrity, triggering mitochondrial oxidative injury and ER stress, and by promoting generation of toxic oxysterols, and indirectly, by inducing adipose tissue dysfunction. Accumulation of oxidized LDL particles may also activate Kupffer and hepatic stellate cells, promoting liver inflammation and fibrogenesis. Hepatic cholesterol accumulation is driven by a deeply deranged cellular cholesterol homeostasis, characterized by elevated cholesterol synthesis and uptake from circulating lipoproteins and by a reduced cholesterol excretion. Extensive dysregulation of cellular cholesterol homeostasis by nuclear transcription factors sterol regulatory binding protein (SREBP)-2, liver X-receptor (LXR)-α and farnesoid X receptor (FXR) plays a key role in hepatic cholesterol accumulation in NASH. The therapeutic implications and opportunities for normalizing cellular cholesterol homeostasis in these patients are also discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.
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                Author and article information

                Journal
                Oxid Med Cell Longev
                Oxid Med Cell Longev
                OMCL
                Oxidative Medicine and Cellular Longevity
                Hindawi Publishing Corporation
                1942-0900
                1942-0994
                2016
                21 August 2016
                : 2016
                : 9895176
                Affiliations
                1Postgraduate Program in Experimental Biology, DCBS, Universidad Autónoma Metropolitana Iztapalapa, 09340 Mexico City, DF, Mexico
                2Health Science Department, Universidad Autónoma Metropolitana Iztapalapa, 09340 Mexico City, DF, Mexico
                3Translational Research Unit, Medica Sur Clinic and Foundation, 14050 Mexico City, DF, Mexico
                4Department of Cell Death and Proliferation, Instituto Investigaciones Biomédicas de Barcelona, CSIC, Barcelona and Liver Unit-Hospital Clinic-IDIBAPS and Centro de Investigación Biomédica en Red (CIBERehd), 08036 Barcelona, Spain
                5Laboratory of Experimental Hepatology and Drug Targeting (HEVEFARM), University of Salamanca, Centro de Investigación Biomédica en Red (CIBERehd), Instituto de Investigación Biomédica de Salamanca (IBSAL), 37007 Salamanca, Spain
                6Red “Fisiopatología de Enfermedades Hepáticas” PRODEP-SEP, 09340 Mexico City, DF, Mexico
                7General Surgery Service 304, General Hospital of Mexico, UNAM School of Medicine, 06726 Mexico City, DF, Mexico
                8Research Center for Alcohol Liver and Pancreatic Diseases and Cirrhosis, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
                Author notes
                *José C. Fernández-Checa: checa229@ 123456yahoo.com and
                *Luis Enrique Gomez-Quiroz: legq@ 123456xanum.uam.mx

                Academic Editor: Ravirajsinh Jadeja

                Author information
                http://orcid.org/0000-0003-2278-7724
                http://orcid.org/0000-0002-5704-5985
                Article
                10.1155/2016/9895176
                5011220
                27635189
                0b7978b8-84b9-4c37-b00a-d881807b296c
                Copyright © 2016 Natalia Nuño-Lámbarri et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 2 May 2016
                : 13 July 2016
                Funding
                Funded by: Consejo Nacional de Ciencia y Tecnología
                Award ID: 252942
                Award ID: 236558
                Award ID: 166042
                Funded by: Asociación Mexicana de Hepatología
                Award ID: SEP-PRODEP-913026-1461211
                Funded by: Universidad Autónoma Metropolitana Iztapalapa
                Award ID: SAF-2011-23031
                Award ID: SAF-2012-34831
                Funded by: National Institute on Alcohol Abuse and Alcoholism
                Award ID: P50-AA-11999
                Funded by: Instituto Salud Carlos III
                Funded by: Fundació la Marató de TV3
                Award ID: PI11/0325
                Categories
                Research Article

                Molecular medicine
                Molecular medicine

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