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Steatosis-induced proteins adducts with lipid peroxidation products and nuclear electrophilic stress in hepatocytes.

ABSTRACT: Accumulating evidence suggests that fatty livers are particularly more susceptible to several pathological conditions, including hepatic inflammation, cirrhosis and liver cancer. However the exact mechanism of such susceptibility is still largely obscure. The current study aimed to elucidate the effect of hepatocytes lipid accumulation on the nuclear electrophilic stress. Accumulation of intracellular lipids was significantly increased in HepG2 cells incubated with fatty acid (FA) complex (1mM, 2:1 oleic and palmitic acids). In FA-treated cells, lipid droplets were localized around the nucleus and seemed to induce mechanical force, leading to the disruption of the nucleus morphology. Level of reactive oxygen species (ROS) was significantly increased in FA-loaded cells and was further augmented by treatment with moderate stressor (CoCl2). Increased ROS resulted in formation of reactive carbonyls (aldehydes and ketones, derived from lipid peroxidation) with a strong perinuclear accumulation. Mass-spectroscopy analysis indicated that lipid accumulation per-se can results in modification of nuclear protein by reactive lipid peroxidation products (oxoLPP). 235 Modified proteins involved in transcription regulation, splicing, protein synthesis and degradation, DNA repair and lipid metabolism were identified uniquely in FA-treated cells. These findings suggest that steatosis can affect nuclear redox state, and induce modifications of nuclear proteins by reactive oxoLPP accumulated in the perinuclear space upon FA-treatment.

SUBMITTER: Anavi S

PROVIDER: S-EPMC4309854 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Steatosis-induced proteins adducts with lipid peroxidation products and nuclear electrophilic stress in hepatocytes.

Anavi Sarit S Ni Zhixu Z Tirosh Oren O Fedorova Maria M

Redox biology 20141224

Accumulating evidence suggests that fatty livers are particularly more susceptible to several pathological conditions, including hepatic inflammation, cirrhosis and liver cancer. However the exact mechanism of such susceptibility is still largely obscure. The current study aimed to elucidate the effect of hepatocytes lipid accumulation on the nuclear electrophilic stress. Accumulation of intracellular lipids was significantly increased in HepG2 cells incubated with fatty acid (FA) complex (1mM, ...[more]

PMID: 25560244

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Project description:The incidence of obesity and its related morbidities has rapidly increased over the past twenty years. One consequence of this is the increased probability of having to treat obese individuals for breast cancer. An important co-morbidity associated with obesity are the spectrum of fatty liver diseases. As such, an important question is how treatment of breast cancer with standard therapeutic agents may alter in individuals with fatty liver disease. Such impacts could result in an enhanced adverse effect profile over both acute (e.g. increased cytotoxicity against non-malignant tissues) or chronic (e.g. increased progression through the fatty liver disease spectrum) time periods. In this work we examine if lipid loading in human hepatocytes, leading to a steatotic phenotype, results in an altered toxic liability for the cancer therapeutic doxorubicin. We demonstrate that there is a synergistic impact on cytotoxicity, due to increased oxidative stress. Array analysis reveals the cellular changes associated with hepatocyte adaptation to lipid loading or doxorubicin treatment alone, and how these profiles are significantly altered during doxorubicin treatment of lipid-loaded hepatocytes. Such alterations, we believe, not only underlie the enhanced sensitivity of obese individuals to the acute adverse effects of doxorubicin, but may also potentiate transition along the fatty liver disease spectrum.Experimental design: Huh7 cells were exposed to lipid and/or doxorubicin as required. Huh7 cells were treated with vehicle control or 300 μM FFA mixture for 24 h in T25 culture flasks. The following day, the cells were treated with either 300 μM FFA mixture, 0.1 μM or 3.6 μM DOX and incubated for 4 hrs or 12 hrs. By the end of incubation time, Total RNA was extracted from cells using the RNeasy Plus Mini Kit (QIAGEN-UK) according to the instructions of manufacturer. RNA samples were sent to the Central Biotechnology Services (Cardiff University, UK), for quality control, synthesis of biotin-labeled cRNA, and hybridisation against Illumina Human-HT12 (Illumina, Inc., Hayward, CA) chips. Washed chips were scanned with Bead Station 500x (Illumina) and the signal intensities quantified with BeadStudio (Illumina). To ensure high quality results from the microarray data, RNA samples were extracted from three independent treatments, giving a biological n = 3 per treatment which gives statistical power to increase the confidence of the results/conclusions generated from the microarray experiment.

Project description:Reactive electrophiles generated by lipid peroxidation are thought to contribute to cardiovascular disease and other oxidative stress-related pathologies by covalently modifying proteins and affecting critical protein functions. The difficulty of capturing and analyzing the relatively small fraction of modified proteins complicates identification of the protein targets of lipid electrophiles. We recently synthesized a biotin-modified linoleoylglycerylphosphatidylcholine probe called PLPBSO ( Tallman et al. Chem. Res. Toxicol. 2007, 20, 227-234 ), which forms typical linoleate oxidation products and covalent adducts with model peptides and proteins. Supplementation of human plasma with PLPBSO followed by free radical oxidation resulted in covalent adduction of PLPBSO to plasma proteins, which were isolated with streptavidin and identified by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Among the most highly modified proteins was apolipoprotein A1 (ApoA1), which is the core component of high density lipoprotein (HDL). ApoA1 phospholipid adduct sites were mapped by LC-MS-MS of tryptic peptides following mild base hydrolysis to release esterified phospholipid adducts. Several carboxylated adducts formed from phospholipid-esterified 9,12-dioxo-10( E)-dodecenoic acid (KODA), 9-hydroxy, 12-oxo-10( E)-dodecenoic acid (HODA), 7-oxoheptanoic acid, 8-oxooctanoic acid, and 9-oxononanoic acid were identified. Free radical oxidations of isolated HDL also generated adducts with 4-hydroxynonenal (HNE) and other noncarboxylated electrophiles, but these were only sporadically identified in the PLPBSO-adducted ApoA1, suggesting a low stoichiometry of modification in the phospholipid-adducted protein. Both phospholipid electrophiles and HNE adducted His162, which resides in an ApoA1 domain involved in the activation of Lecithin-cholesterol acyltransferase and maturation of the HDL particle. ApoA1 lipid electrophile adducts may affect protein functions and provide useful biomarkers for oxidative stress.

Dataset Information

Steatosis-induced proteins adducts with lipid peroxidation products and nuclear electrophilic stress in hepatocytes.

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Steatosis-induced proteins adducts with lipid peroxidation products and nuclear electrophilic stress in hepatocytes.

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