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Loss of C/EBP? enhances IR-induced cell death by promoting oxidative stress and mitochondrial dysfunction.

ABSTRACT: Exposure of cells to ionizing radiation (IR) generates reactive oxygen species (ROS). This results in increased oxidative stress and DNA double strand breaks (DSBs) which are the two underlying mechanisms by which IR causes cell/tissue injury. Cells that are deficient or impaired in the cellular antioxidant response are susceptible to IR-induced apoptosis. The transcription factor CCAAT enhancer binding protein delta (Cebpd, C/EBP?) has been implicated in the regulation of oxidative stress, DNA damage response, genomic stability and inflammation. We previously reported that Cebpd-deficient mice are sensitive to IR and display intestinal and hematopoietic injury, however the underlying mechanism is not known. In this study, we investigated whether an impaired ability to detoxify IR-induced ROS was the underlying cause of the increased radiosensitivity of Cebpd-deficient cells. We found that Cebpd-knockout (KO) mouse embryonic fibroblasts (MEFs) expressed elevated levels of ROS, both at basal levels and after exposure to gamma radiation which correlated with increased apoptosis, and decreased clonogenic survival. Pre-treatment of wild type (WT) and KO MEFs with polyethylene glycol-conjugated Cu-Zn superoxide dismutase (PEG-SOD) and catalase (PEG-CAT) combination prior to irradiation showed a partial rescue of clonogenic survival, thus demonstrating a role for increased intracellular oxidants in promoting IR-induced cell death. Analysis of mitochondrial bioenergetics revealed that irradiated KO MEFs showed significant reductions in basal, adenosine triphosphate (ATP)-linked, maximal respiration and reserved respiratory capacity and decrease in intracellular ATP levels compared to WT MEFs indicating they display mitochondrial dysfunction. KO MEFs expressed significantly lower levels of the cellular antioxidant glutathione (GSH) and its precursor- cysteine as well as methionine. In addition to its antioxidant function, GSH plays an important role in detoxification of lipid peroxidation products such as 4-hydroxynonenal (4-HNE). The reduced GSH levels observed in KO MEFs correlated with elevated levels of 4-HNE protein adducts in irradiated KO MEFs compared to respective WT MEFs. We further showed that pre-treatment with the GSH precursor, N-acetyl L-cysteine (NAC) prior to irradiation showed a significant reduction of IR-induced cell death and increases in GSH levels, which contributed to the overall increase in clonogenic survival of KO MEFs. In contrast, pre-treatment with the GSH synthesis inhibitor- buthionine sulfoximine (BSO) further reduced the clonogenic survival of irradiated KO MEFs. This study demonstrates a novel role for C/EBP? in protection from basal as well as IR-induced oxidative stress and mitochondrial dysfunction thus promoting post-radiation survival.

SUBMITTER: Banerjee S

PROVIDER: S-EPMC5673253 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Loss of C/EBPδ enhances IR-induced cell death by promoting oxidative stress and mitochondrial dysfunction.

Banerjee Sudip S Aykin-Burns Nukhet N Krager Kimberly J KJ Shah Sumit K SK Melnyk Stepan B SB Hauer-Jensen Martin M Pawar Snehalata A SA

Free radical biology & medicine 20160820

Exposure of cells to ionizing radiation (IR) generates reactive oxygen species (ROS). This results in increased oxidative stress and DNA double strand breaks (DSBs) which are the two underlying mechanisms by which IR causes cell/tissue injury. Cells that are deficient or impaired in the cellular antioxidant response are susceptible to IR-induced apoptosis. The transcription factor CCAAT enhancer binding protein delta (Cebpd, C/EBPδ) has been implicated in the regulation of oxidative stress, DNA ...[more]

PMID: 27554969

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Project description:Glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein that also mediates cell death under oxidative stress. We reported previously that the active-site cysteine (Cys-152) of GAPDH plays an essential role in oxidative stress-induced aggregation of GAPDH associated with cell death, and a C152A-GAPDH mutant rescues nitric oxide (NO)-induced cell death by interfering with the aggregation of wild type (WT)-GAPDH. However, the detailed mechanism underlying GAPDH aggregate-induced cell death remains elusive. Here we report that NO-induced GAPDH aggregation specifically causes mitochondrial dysfunction. First, we observed a correlation between NO-induced GAPDH aggregation and mitochondrial dysfunction, when GAPDH aggregation occurred at mitochondria in SH-SY5Y cells. In isolated mitochondria, aggregates of WT-GAPDH directly induced mitochondrial swelling and depolarization, whereas mixtures containing aggregates of C152A-GAPDH reduced mitochondrial dysfunction. Additionally, treatment with cyclosporin A improved WT-GAPDH aggregate-induced swelling and depolarization. In doxycycline-inducible SH-SY5Y cells, overexpression of WT-GAPDH augmented NO-induced mitochondrial dysfunction and increased mitochondrial GAPDH aggregation, whereas induced overexpression of C152A-GAPDH significantly suppressed mitochondrial impairment. Further, NO-induced cytochrome c release into the cytosol and nuclear translocation of apoptosis-inducing factor from mitochondria were both augmented in cells overexpressing WT-GAPDH but ameliorated in C152A-GAPDH-overexpressing cells. Interestingly, GAPDH aggregates induced necrotic cell death via a permeability transition pore (PTP) opening. The expression of either WT- or C152A-GAPDH did not affect other cell death pathways associated with protein aggregation, such as proteasome inhibition, gene expression induced by endoplasmic reticulum stress, or autophagy. Collectively, these results suggest that NO-induced GAPDH aggregation specifically induces mitochondrial dysfunction via PTP opening, leading to cell death.

Project description:BackgroundPregnancy is a complicated physiological process. The multifaceted regulation of maternal-fetal interface is of great importance for maintaining normal pregnancy and avoiding fetal rejection and secondary abortion. Previous studies have focused on the clinical features or pathological biomarkers of fetal rejection and abortion. However, no significant breakthrough has been made. Therefore, it is important to understand the molecular mechanisms of recurrent pregnancy loss (RPL) to identify potential therapeutic strategies. The aim of this study was to investigate the pathogenesis of RPL.MethodsIn this study, Relative and absolute quantitation (iTRAQ) technology integrated with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was used to identify differentially expressed proteins in decidual from RPL patients and matched normal controls. Further, Molecules NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 3 (ndufb3) and cyclooxygenase-2 (COX-2) were validated by immunohistochemistry (IHC), Western blotting, CCK8 and mitochondrial red fluorescent probe (Mito-Tracker Red CMXRos).ResultsA total of 456 proteins reached the threshold of a 1.5-fold change were identified for further bioinformatics analysis. Upon mapping the differentially expressed proteins using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways database, iTRAQ results were confirmed by assessing NDUFB3 and COX-2 protein levels in specimens of decidual tissue by Western blotting. Our study indicates that the level of COX-2 and NDUFB3 were significantly increased in decidual cell from RPL patients. Overexpression of NDUFB3 inhibited cell vitality and oxidative stress of decimal cell. Further, our found that overexpression NDUFBD3 in decidual cell decreased the mitochondrial membrane potential expression levels. These results suggest that NDUFB3 might play an important role in promote the pathological process of RPL.ConclusionsThis comprehensive analysis of RPL proteomics reveals novel candidate: NDUFB3, which could be further investigated for explanation of the pathological mechanism of RPL.

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Loss of C/EBP? enhances IR-induced cell death by promoting oxidative stress and mitochondrial dysfunction.

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Loss of C/EBPδ enhances IR-induced cell death by promoting oxidative stress and mitochondrial dysfunction.

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