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Hepatic protein Carbonylation profiles induced by lipid accumulation and oxidative stress for investigating cellular response to non-alcoholic fatty liver disease in vitro.

ABSTRACT: Background:Non-alcoholic fatty liver disease (NAFLD) is caused by excessive accumulation of fat within the liver, leading to further severe conditions such as non-alcoholic steatohepatitis (NASH). Progression of healthy liver to steatosis and NASH is not yet fully understood in terms of process and response. Hepatic oxidative stress is believed to be one of the factors driving steatosis to NASH. Oxidative protein modification is the major cause of protein functional impairment in which alteration of key hepatic enzymes is likely to be a crucial factor for NAFLD biology. In the present study, we aimed to discover carbonylated protein profiles involving in NAFLD biology in vitro. Methods:Hepatocyte cell line was used to induce steatosis with fatty acids (FA) in the presence and absence of menadione (oxidative stress inducer). Two-dimensional gel electrophoresis-based proteomics and dinitrophenyl hydrazine derivatization technique were used to identify carbonylated proteins. Sequentially, in order to view changes in protein carbonylation pathway, enrichment using Funrich algorithm was performed. The selected carbonylated proteins were validated with western blot and carbonylated sites were further identified by high-resolution LC-MS/MS. Results:Proteomic results and pathway analysis revealed that carbonylated proteins are involved in NASH pathogenesis pathways in which most of them play important roles in energy metabolisms. Particularly, carbonylation level of ATP synthase subunit ? (ATP5A), a key protein in cellular respiration, was reduced after FA and FA with oxidative stress treatment, whereas its expression was not altered. Carbonylated sites on this protein were identified and it was revealed that these sites are located in nucleotide binding region. Modification of these sites may, therefore, disturb ATP5A activity. As a consequence, the lower carbonylation level on ATP5A after FA treatment solely or with oxidative stress can increase ATP production. Conclusions:The reduction in carbonylated level of ATP5A might occur to generate more energy in response to pathological conditions, in our case, fat accumulation and oxidative stress in hepatocytes. This would imply the association between protein carbonylation and molecular response to development of steatosis and NASH.

SUBMITTER: Chienwichai P

PROVIDER: S-EPMC6438040 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Project description:Chronic alcohol intake leads to alcoholic fatty liver. The pathogenesis of alcoholic fatty liver is related to abnormal lipid accumulation, oxidative stress, endotoxins, and cytokines. Solanum muricatum Ait. (Pepino) is a plant food commonly cultivated in the Penghu island, Taiwan. Previous studies indicated that the aqueous extract of pepino was able to attenuate diabetic progression via its antioxidative and anti-inflammatory effects. However, the mechanisms of the antioxidative and anti-inflammatory effects of pepino leaf in preventing alcoholic fatty liver remain unknown. In this study, Lieber?DeCarli ethanol-containing liquid diet was used to induce alcoholic hepatic injury in C57BL/6 mice. The hepatoprotective effects and the related mechanisms of aqueous extract of pepino leaf (AEPL) were examined. Our results showed that 2% AEPL treatments protected the liver from ethanol-induced injury through reducing serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol (TC) and triglyceride (TG) (all p < 0.05). AEPL had the effects in improving the ethanol-induced lipid accumulation in mice under histological examination. Molecular data indicated that the anti-lipid accumulation effect of AEPL might be mediated via inducing hepatic levels of phospho-adenosine monophosphate-activated kinase (p-AMPK) and peroxisome proliferator-activated receptor (PPAR)-?, and reducing the expressions of hepatic lipogenic enzymes, including sterol regulatory element-binding protein (SREBP)-1c, acetyl-CoA carboxylase (ACC), and fatty acid synthase (FAS) (all p < 0.05). AEPL also decreased hepatic levels of thiobarbituric acid relative substances (TBARS), tumor necrosis factor (TNF)-?, and interleukin (IL)-6, as well as the expression of nuclear factor kappa B (NF-?B) (all p < 0.05). Moreover, AEPL significantly elevated the activities of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx), and glutathione (GSH) content compared to the ethanol-fed group (all p < 0.05). Our present study suggests that AEPL could protect the liver against ethanol-induced oxidative injury and lipid accumulation.

Project description:Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver-related morbidity and mortality. Oxidative stress and release of pro-inflammatory cytokines, such as tumor necrosis factor α (TNFα), are major consequences of hepatic lipid overload, which can contribute to progression of NAFLD to non-alcoholic steatohepatitis (NASH). Also, mitochondria are involved in the NAFLD pathogenesis for their role in hepatic lipid metabolism. Definitive treatments for NAFLD/NASH are lacking so far. Silybin, the extract of the milk thistle seeds, has previously shown beneficial effects in NAFLD. Sequential exposure of hepatocytes to high concentrations of fatty acids (FAs) and TNFα resulted in fat overload and oxidative stress, which mimic in vitro the progression of NAFLD from simple steatosis (SS) to steatohepatitis (SH). The exposure to 50 µM silybin for 24 h reduced fat accumulation in the model of NAFLD progression. The in vitro progression of NAFLD from SS to SH resulted in reduced hepatocyte viability, increased apoptosis and oxidative stress, reduction in lipid droplet size, and up-regulation of IκB kinase β-interacting protein and adipose triglyceride lipase expressions. The direct action of silybin on SS or SH cells and the underlying mechanisms were assessed. Beneficial action of silybin was sustained by changes in expression/activity of peroxisome proliferator-activated receptors and enzymes for FA oxidation. Moreover, silybin counteracted the FA-induced mitochondrial damage by acting on complementary pathways: (i) increased the mitochondrial size and improved the mitochondrial cristae organization; (ii) stimulated mitochondrial FA oxidation; (iii) reduced basal and maximal respiration and ATP production in SH cells; (iv) stimulated ATP production in SS cells; and (v) rescued the FA-induced apoptotic signals and oxidative stress in SH cells. We provide new insights about the direct protective effects of the nutraceutic silybin on hepatocytes mimicking in vitro NAFLD progression.

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Hepatic protein Carbonylation profiles induced by lipid accumulation and oxidative stress for investigating cellular response to non-alcoholic fatty liver disease in vitro.

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