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

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.

SUBMITTER: Nuno-Lambarri N

PROVIDER: S-EPMC5011220 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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

Nuño-Lámbarri Natalia N Domínguez-Pérez Mayra M Baulies-Domenech Anna A Monte Maria J MJ Marin Jose J G JJ Rosales-Cruz Patricia P Souza Verónica V Miranda Roxana U RU Bucio Leticia L Montalvo-Jave Eduardo E EE Concepción Gutiérrez-Ruiz María M García-Ruiz Carmen C Fernández-Checa José C JC Fernández-Checa José C JC Gomez-Quiroz Luis Enrique LE

Oxidative medicine and cellular longevity 20160821

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 ...[more]

PMID: 27635189

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Project description:Background: Genetic elimination of c-Met signaling in the liver has been shown to impact many cellular pathways involved in repair, regeneration, lipid homeostasis and redox balance. In this study, we analyzed a nutritional model of hepatic steatosis in Met fl/fl ; Alb-Cre +/- (MetKO) mice in a 129SV/C57BL/6 background fed a high cholesterol diet for 30 days. Methods: Liver injury was determined by histopathology and plasma enzymes, transcriptomic changes were examined using gene expression microarrays, and evaluation of key molecules involved in liver damage and lipid homestasis were evaluated by Western blot analysis. Results: We observed that in comparison with wild type mice subjected to the same diet, MetKO mice developed a strong liver lipid deposition, inflammatory infiltration and increment in total bile acids synthesis and liver damage markers. Global transcriptomic changes analysis confirmed the steatosis and cholestasis induced by the high cholesterol diet. In addition, we found affected pathways related to amino acids, glutathione and lipid metabolism, oxidative stress and mitochondria dysfunction. Oxidative stress exacerbation was corroborated by lipid and protein oxidation in liver tissue. To address further, Western blot studies revealed downregulation on Erk, NF-kB and Nrf2 survival pathways and target genes (cyclin D1, SOD1, gamma-GCS), an increment in proapoptotic proteins (p53, caspase 3) and changes in nuclear receptors such as RAR and RXR, which were increased, and CAR, FXR and PPAR alfa, which were decreased, in the MetKO diet. These results are in agreement with the steatosis and cholestasis phenotype. Conclusion: Our data provide evidence of c-Met signaling involvement in lipid metabolism, and bile acids synthesis and excretion. Disruption of these pathways leads to liver dysfunction, improper metabolism and hepatocellular damage. Global transcriptome changes between WT mice vs. c-Met KO mice fed a 2% cholesterol and 0.5% sodium cholate diet (high cholesterol) or a Chow regular diet (Chow) as control. Mice were fed a high cholesterol or chow regular diet for 30 days. Liver tissue was obtained, and RNA was extracted and subjected to Illumina microarray analysis.

Project description:Background: Vitamin A is an essential nutrient that mammals obtain from dietary carotenoids and retinyl esters. Bile salts aid in the intestinal absorption of vitamin A, after which it is stored in the stellate cells of the liver. Vitamin A-metabolites, such as retinoic acids, are important for cell differentiation, proliferation and immunological processes, and act mostly by activating the nuclear receptors Retinoic Acid Receptor (RAR) and Retinoid Xreceptor (RXR). These receptors also perform key functions in the liver by regulating bile salt, lipid and glucose homeostasisas well is the intrahepatic immune response. Chronic liver diseases are characterized by hepatic vitamin A loss often leading to vitamin A deficiency (VAD). We found that VAD strongly aggravates liver damage in bile duct ligated (BDL) rats and in biliary atresia patients. Here, we performed a transcriptome analysis to characterize the cell biological processes in the rat liver that are disturbed in obstructive cholestasis under VADconditions. Methods: Rats were made VAD by omitting vitamin A from the diet for 16 weeks, followed by ligation of the common bile duct (BDL). 7 days later, the animals were sacrificed. During the 7 days of BDL, half of the animals received daily IP injections with retinyl-palmitate (vitamin A therapy). Bile salt concentrations and liver damage markers (AST/ALT) were determined in serum. Whole genome gene expression in liver tissue was analyzed with the Illumina platform RatRef-12 beadchip. False discovery rate (FDR) was set at a stringent 1%. Data were confirmed by quantitative real time PCR, Western blotting and/or histochemistry. Results: BDL induced dramatic liver damage in VAD rats with serum liver damage markers (AST/ALT)approximately 10-fold increased compared to BDL rats receiving a vitamin A-sufficient (VAS) diet. Only 20 genes were differentially expressed between sham-treated VAS and VAD rats and clustered in the vitamin A metabolism, immune response, carbohydrate and lipid homeostasis. In contrast, 1583 genes were differentially expressed between the BDL-treated VAS and VAD rats. The strongest effects were observed in genes from the vitamin A metabolism, immune response, collagen production and oxidative stress response. Importantly, all the liver damage markers were efficiently reversed by retinyl-palmitate therapy, which was mirrored by an almost complete normalisation of the transcript profile in VAS-BDL rats. Conclusions: We conclude that vitamin A deficiency dramatically aggravates liver damage caused by obstructive cholestasis. The transcriptome analysis suggests that a disturbed immune response may be the predominant causative factor.

Project description:Oxidative stress has been shown to induce cell death in a wide range of human diseases including cardiac ischemia/reperfusion injury, drug induced cardiotoxicity, and heart failure. However, the mechanism of cell death induced by oxidative stress remains incompletely understood. Here we provide new evidence that oxidative stress primarily induces ferroptosis, but not apoptosis, necroptosis, or mitochondria-mediated necrosis, in cardiomyocytes. Intriguingly, oxidative stress induced by organic oxidants such as tert-butyl hydroperoxide (tBHP) and cumene hydroperoxide (CHP), but not hydrogen peroxide (H2O2), promoted glutathione depletion and glutathione peroxidase 4 (GPX4) degradation in cardiomyocytes, leading to increased lipid peroxidation. Moreover, elevated oxidative stress is also linked to labile iron overload through downregulation of the transcription suppressor BTB and CNC homology 1 (Bach1), upregulation of heme oxygenase 1 (HO-1) expression, and enhanced iron release via heme degradation. Strikingly, oxidative stress also promoted HO-1 translocation to mitochondria, leading to mitochondrial iron overload and lipid reactive oxygen species (ROS) accumulation. Targeted inhibition of mitochondrial iron overload or ROS accumulation, by overexpressing mitochondrial ferritin (FTMT) or mitochondrial catalase (mCAT), respectively, markedly inhibited oxidative stress-induced ferroptosis. The levels of mitochondrial iron and lipid peroxides were also markedly increased in cardiomyocytes subjected to simulated ischemia and reperfusion (sI/R) or the chemotherapeutic agent doxorubicin (DOX). Overexpressing FTMT or mCAT effectively prevented cardiomyocyte death induced by sI/R or DOX. Taken together, oxidative stress induced by organic oxidants but not H2O2 primarily triggers ferroptotic cell death in cardiomyocyte through GPX4 and Bach1/HO-1 dependent mechanisms. Our results also reveal mitochondrial iron overload via HO-1 mitochondrial translocation as a key mechanism as well as a potential molecular target for oxidative stress-induced ferroptosis in cardiomyocytes.

Project description:Background & aimsNon-absorbable inhibitors of the apical sodium-dependent bile acid transporter (ASBT; also called ileal bile acid transporter [IBAT]) are recently approved or in clinical development for multiple cholestatic liver disorders and lead to a reduction in pruritus and (markers for) liver injury. Unfortunately, non-absorbable ASBT inhibitors (ASBTi) can induce diarrhoea or may be ineffective if cholestasis is extensive and largely precludes intestinal excretion of bile acids. Systemically acting ASBTi that divert bile salts towards renal excretion may alleviate these issues.MethodsBile duct ligation (BDL) was performed in ASBT-deficient (ASBT knockout [KO]) mice as a model for chronic systemic ASBT inhibition in obstructive cholestasis. Co-infusion of radiolabelled taurocholate and inulin was used to quantify renal bile salt excretion after BDL. In a second (wild-type) mouse model, a combination of obeticholic acid (OCA) and intestine-restricted ASBT inhibition was used to lower the bile salt pool size before BDL.ResultsAfter BDL, ASBT KO mice had reduced plasma bilirubin and alkaline phosphatase compared with wild-type mice with BDL and showed a marked reduction in liver necrotic areas at histopathological analysis, suggesting decreased BDL-induced liver damage. Furthermore, ASBT KO mice had reduced bile salt pool size, lower plasma taurine-conjugated polyhydroxylated bile salt, and increased urinary bile salt excretion. Pretreatment with OCA + ASBTi in wild-type mice reduced the pool size and greatly improved liver injury markers and liver histology.ConclusionsA reduced bile salt pool at the onset of cholestasis effectively lowers cholestatic liver injury in mice. Systemic ASBT inhibition may be valuable as treatment for cholestatic liver disease by lowering the pool size and increasing renal bile salt output even under conditions of minimal faecal bile salt secretion.Lay summaryNovel treatment approaches against cholestatic liver disease (resulting in reduced or blocked flow of bile) involve non-absorbable inhibitors of the bile acid transport protein ASBT, but these are not always effective and/or can cause unwanted side effects. In this study, we demonstrate that systemic inhibition/inactivation of ASBT protects mice against developing severe cholestatic liver injury after bile duct ligation, by reducing bile salt pool size and increasing renal bile salt excretion.

Project description:RationalePossible beneficial effects of GDF11 (growth differentiation factor 11) on the normal, diseased, and aging heart have been reported, including reversing aging-induced hypertrophy. These effects have not been well validated. High levels of GDF11 have also been shown to cause cardiac and skeletal muscle wasting. These controversies could be resolved if dose-dependent effects of GDF11 were defined in normal and aged animals as well as in pressure overload-induced pathological hypertrophy.ObjectiveTo determine dose-dependent effects of GDF11 on normal hearts and those with pressure overload-induced cardiac hypertrophy.Methods and resultsTwelve- to 13-week-old C57BL/6 mice underwent transverse aortic constriction (TAC) surgery. One-week post-TAC, these mice received rGDF11 (recombinant GDF11) at 1 of 3 doses: 0.5, 1.0, or 5.0 mg/kg for up to 14 days. Treatment with GDF11 increased plasma concentrations of GDF11 and p-SMAD2 in the heart. There were no significant differences in the peak pressure gradients across the aortic constriction between treatment groups at 1 week post-TAC. Two weeks of GDF11 treatment caused dose-dependent decreases in cardiac hypertrophy as measured by heart weight/tibia length ratio, myocyte cross-sectional area, and left ventricular mass. GDF11 improved cardiac pump function while preventing TAC-induced ventricular dilation and caused a dose-dependent decrease in interstitial fibrosis (in vivo), despite increasing markers of fibroblast activation and myofibroblast transdifferentiation (in vitro). Treatment with the highest dose (5.0 mg/kg) of GDF11 caused severe body weight loss, with significant decreases in both muscle and organ weights and death in both sham and TAC mice.ConclusionsAlthough GDF11 treatment can reduce pathological cardiac hypertrophy and associated fibrosis while improving cardiac pump function in pressure overload, high doses of GDF11 cause severe cachexia and death. Use of GDF11 as a therapy could have potentially devastating actions on the heart and other tissues.

Dataset Information

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

Publications

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

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