Abstract 257: Calreticulin Regulates Acetylation in Cardiac Cells During Endoplasmic Reticulum Stress

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Janet R Manning
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Cardiac Tissue ◽  
Stress Proteins ◽  
Cardiac Cells ◽  
Tunel Staining ◽  
Signaling Proteins ◽  
Cell Mortality ◽  
Simulated Hypoxia

Background: Myocardial infarction (MI) is exacerbated by endoplasmic reticulum (ER) stress, which contributes to apoptosis signaling and tissue death in cardiomyocytes. Although the calcium-handing protein calreticulin is upregulated during MI, the role of calreticulin in the progression of ER stress remains controversial. We hypothesized that calreticulin expression accelerates ER stress via regulation of the acetylation status of ER proteins, and knockdown reduces pro-apoptotic ER stress. Methods: We examined the expression of calreticulin in human cardiac cells in response to ischemia or thapsigargin-mediated ER stress. To test the effect of calreticulin modulation on cell mortality, we generated a stable partial calreticulin knockdown line in proliferating human cardiomyocyte-derived cells. We further examined the induction and acetylation of ER stress signaling proteins, including proteins in each of the three major pathways that account for ER-stress mediated cell death. Results and Conclusions: Calreticulin is upregulated in human ischemic heart failure cardiac tissue, as well as simulated hypoxia and reoxygenation and thapsigargin-mediated ER stress. It was found that partial knockdown protects against the expression of caspase 12, CHOP, and reduces thapsigargin-driven TUNEL staining. In addition, significant changes in the acetylation of ER stress proteins and the expression of the deacetylase SIRT1 were observed. These data shed light on the role that calreticulin plays in apoptosis signaling during ER stress in cardiac cells.

scholarly journals Activation of endoplasmic reticulum stress response during the development of ischemic heart disease

2006 ◽  
Vol 291 (3) ◽  
pp. H1411-H1420 ◽  
Author(s):  
Asim Azfer ◽  
Jianli Niu ◽  
Linda M. Rogers ◽  
Frances M. Adamski ◽  
Pappachan E. Kolattukudy
Keyword(s):  
Endoplasmic Reticulum ◽  
Heart Disease ◽  
Stress Response ◽  
Transgenic Mice ◽  
Ischemic Heart Disease ◽  
Er Stress ◽  
Stress Proteins ◽  
Gene Array ◽  
Ischemic Heart ◽  
Endoplasmic Reticulum Stress Response

Endoplasmic reticulum (ER) stress has been found to be associated with neurodegenerative diseases and diabetes mellitus. Whether ER stress is involved in the development of heart disease is not known. Cardiac-specific expression of monocyte chemoattractant protein-1 (MCP-1) in mice causes the development of ischemic heart disease. Here we report that microarray analysis of gene expression changes in the heart of these transgenic mice revealed that a cluster of ER stress-related genes was transcriptionally activated in the heart during the development of ischemic heart disease. The gene array results were verified by quantitative real-time PCR that showed highly elevated transcript levels of genes involved in unfolded protein response such as ER and cytoplasmic chaperones, oxidoreductases, protein disulfide isomerase (PDI) family, and ER-associated degradation system such as ubiquitin. Immunoblot analysis confirmed the expression of chaperones, PDI, and ubiquitin. Immunohistochemical analyses showed that ER stress proteins were associated mainly with the degenerating cardiomyocytes. A novel ubiquitin fold modifier (Ufm1) that has not been previously associated with ER stress and not found to be induced under any condition was also found to be upregulated in the hearts of MCP mice (transgenic mice that express MCP-1 specifically in the heart). The present results strongly suggest that activation of ER stress response is involved in the development of ischemic heart disease in this murine model.

c-Jun Inhibits Thapsigargin-Induced ER Stress Through Up-Regulation of DSCR1/Adapt78

2008 ◽  
Vol 233 (10) ◽  
pp. 1289-1300 ◽  
Author(s):  
Peng Zhao ◽  
Xiaoyan Xiao ◽  
Agnes S. Kim ◽  
M. Fatima Leite ◽  
Jinxia Xu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Wild Type Mouse ◽  
Mouse Fibroblast ◽  
Expression Levels ◽  
Mouse Fibroblasts ◽  
The Unfolded Protein Response ◽  
Calcineurin Activity

The endoplasmic reticulum (ER) is exquisitely sensitive to changes in its internal environment. Various conditions, collectively termed “ER stress”, can perturb ER function, leading to the activation of a complex response known as the unfolded protein response (UPR). Although c-Jun N-terminal kinase (JNK) activation is nearly always associated with cell death by various stimuli, the functional role of JNK in ER stress-induced cell death remains unclear. JNK regulates gene expression through the phosphorylation and activation of transcription factors, such as c-Jun. Here, we investigated the role of c-Jun in the regulation of ER stress-related genes. c-Jun expression levels determined the response of mouse fibroblasts to ER stress induced by thapsigargin (TG, an inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase). c-jun−/− mouse fibroblast cells were more sensitive to TG-induced cell death compared to wild-type mouse fibroblasts, while reconstitution of c-Jun expression in c-jun−/− cells (c-Jun Re) enhanced resistance to TG-induced cell death. The expression levels of ER chaperones Grp78 and Gadd153 induced by TG were lower in c-Jun Re than in c-jun−/− cells. Moreover, TG treatment significantly increased calcineurin activity in c-jun−/− cells, but not in c-Jun Re cells. In c-Jun Re cells, TG induced the expression of Adapt78, also known as the Down syndrome critical region 1 (DSCR1), which is known to block calcineurin activity. Taken together, our findings suggest that c-Jun, a transcription factor downstream of the JNK signaling pathway, up-regulates Adapt78 expression in response to TG-induced ER stress and contributes to protection against TG-induced cell death.

Abstract 276: SR-BI Suppresses Apoptosis by Reducing Endoplasmic Reticulum Stress and Promoting Akt Activity in Macrophages

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Huan Tao ◽  
Patricia G Yancey ◽  
Sean S Davies ◽  
L Jackson Roberts ◽  
John L Blakemore ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Apolipoprotein E ◽  
Er Stress ◽  
Cell Apoptosis ◽  
Free Cholesterol ◽  
Oxidized Ldl ◽  
Tunel Staining ◽  
Type I ◽  
Apoptotic Cells ◽  
Atherosclerotic Lesions

Objective: Macrophage apoptosis contributes to atherosclerotic plaque necrosis, inflammation, development and rupture. Scavenger receptor class B type I (SR-BI) is a key regulator of HDL metabolism and cellular cholesterol homeostasis. Here we examined the hypothesis that macrophage SR-BI modulates lipid-associated cellular stress and apoptosis. Methods and Results: In vitro cell apoptosis assays were performed in primary macrophages, and for in vivo evidence, we examined TUNEL staining of atherosclerotic lesions of LDLR -/- mice that were reconstituted with SR-BI -/- or WT bone marrow after 16 weeks on a Western diet. We found that SR-BI deficiency led to ~64.3% more apoptotic cells induced by oxidized LDL or free cholesterol in primary macrophages, and 6-fold more lesional apoptotic cells in SR-BI -/- →LDLR -/- mice compared to WT recipient mice. In macrophages, SR-BI deficiency caused significant accumulations of cellular free cholesterol and elevated markers of endoplasmic reticulum (ER) stress. These were exacerbated by feeding mice a high-cholesterol diet or inactivating the apolipoprotein E gene. Peroxidation of lipoproteins and cell membranes leads to modification of phosphatidylethanolamine by lipid aldehydes including isolevuglandins (IsoLG-PE). Treatment of macrophages with IsoLG-PE induced 52.6% more apoptotic cells in SR-BI -/- macrophages compared to WT. Transgenic expression of SR-BI by transfection of SR-BI -/- macrophages rescued oxidative stress-induced ER stress and cell apoptosis. SR-BI deficiency inhibited the Akt pathway compromising macrophage survival and increasing lesion necrosis. Moreover, Akt Activator was able to rescue SR-BI deficiency associated apoptosis in macrophages. Apolipoprotein E interacts with SR-BI in macrophages, co-operating for cellular lipid homeostasis and cell survival signaling. Conclusion: SR-BI protects against cell apoptosis induced by lipid stress in macrophages and atherosclerotic lesions. The underlying mechanisms are, at least in part, through reducing lipid-associated ER stress and promoting Akt activity in macrophages. Thus, we identify macrophage SR-BI-mediated apoptosis pathways as molecular targets for the prevention of atherosclerotic cardiovascular events.

scholarly journals RHBDL4 protects against endoplasmic reticulum stress by regulating the morphology and distribution of ER sheets

2021 ◽  
Author(s):  
Viorica Liebe Lastun ◽  
Matthew Freeman
Keyword(s):  
Cell Cycle ◽  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Er Stress ◽  
Liver Steatosis ◽  
Physiological Role ◽  
Cell Types ◽  
Rhomboid Protease ◽  
Rapid Changes

In metazoans, the architecture of the endoplasmic reticulum (ER) differs between cell types, and undergoes major changes through the cell cycle and according to physiological needs. Although much is known about how the different ER morphologies are generated and maintained, especially the ER tubules, how context dependent changes in ER shape and distribution are regulated and the factors involved are less characterized. Here, we show that RHBDL4, an ER-resident rhomboid protease, modulates the shape and distribution of the ER, especially under conditions that require rapid changes in the ER sheet distribution, including ER stress. RHBDL4 interacts with CLIMP-63, a protein involved in ER sheet stabilisation, and with the cytoskeleton. Mice lacking RHBDL4 are sensitive to ER stress and develop liver steatosis, a phenotype associated with unresolved ER stress. Our data introduce a new physiological role of RHBDL4 and also imply that this function does not require its enzymatic activity.

Abstract 357: Hepatic ERK2 Suppresses Endoplasmic Reticulum Stress, Leading to Protection from Oxidative Stress and Endothelial Dysfunction

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Takehiko Kujiraoka ◽  
Yasushi Satoh ◽  
Makoto Ayaori ◽  
Yasunaga Shiraishi ◽  
Yuko Arai-Nakaya ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Endoplasmic Reticulum ◽  
Fatty Acid ◽  
Endothelial Dysfunction ◽  
Er Stress ◽  
Vascular Complications ◽  
Metabolic Remodeling ◽  
And Oxidative Stress

Background Insulin signaling comprises 2 major cascades, the IRS/PI3K/Akt and Ras/Raf/MEK/ERK pathways. Many studies on the tissue-specific effects of the former pathway had been conducted, however, the role of the latter cascade in tissue-specific insulin resistance had not been investigated. High glucose/fatty acid toxicity, inflammation and oxidative stress, all of which are associated with insulin resistance, can activate ERK. Liver plays a central role of metabolism and hepatosteatosis (HST) is associated with vascular diseases. The aim of this study is to elucidate the role of hepatic ERK2 in HST, metabolic remodeling and endothelial dysfunction. Methods Serum biomarkers of vascular complications in human were compared between subjects with and without HST diagnosed by echography for regular medical checkup. Next, we created liver-specific ERK2 knockout mice (LE2KO) and fed them with a high-fat/high-sucrose diet (HFHSD) for 20 weeks. The histological analysis, the expression of hepatic sarco/endoplasmic reticulum (ER) Ca 2+ -ATPase 2 (SERCA2) and glucose-tolerance/insulin-sensitivity (GT/IS) were tested. Vascular superoxide production and endothelial function were evaluated with dihydroethidium staining and isometric tension measurement of aorta. Results The presence of HST significantly increased HOMA-IR, an indicator of insulin resistance or atherosclerotic index in human. HFHSD-fed LE2KO revealed a marked exacerbation in HST and metabolic remodeling represented by the impairment of GT/IS, elevated serum free fatty acid and hyperhomocysteinemia without changes in body weight, blood pressure and serum cholesterol/triglyceride levels. In the HFHSD-fed LE2KO, mRNA and protein expressions of hepatic SERCA2 were significantly decreased, which resulted in hepatic ER stress. Induction of vascular superoxide production and remarkable endothelial dysfunction were also observed in them. Conclusions Hepatic ERK2 revealed the suppression of hepatic ER stress and HST in vivo , which resulted in protection from vascular oxidative stress and endothelial dysfunction. HST with hepatic ER stress can be a prominent risk of vascular complications by metabolic remodeling and oxidative stress in obese-related diseases.

scholarly journals Extracellular Vesicles Derived from Human Umbilical Cord Mesenchymal Stromal Cells Protect Cardiac Cells Against Hypoxia/Reoxygenation Injury by Inhibiting Endoplasmic Reticulum Stress via Activation of the PI3K/Akt Pathway

2020 ◽  
Vol 29 ◽  
pp. 096368972094567
Author(s):  
Changyi Zhang ◽  
Hongwu Wang ◽  
Godfrey C.F. Chan ◽  
Yu Zhou ◽  
Xiulan Lai ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Umbilical Cord ◽  
Extracellular Vesicles ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Cardiac Cells ◽  
Akt Pathway ◽  
Human Umbilical Cord ◽  
Hypoxia Reoxygenation

Endoplasmic reticulum (ER) stress is implicated in the pathogenesis of many diseases, including myocardial ischemia/reperfusion injury. We hypothesized that human umbilical cord mesenchymal stromal cells derived extracellular vesicles (HuMSC-EVs) could protect cardiac cells against hyperactive ER stress induced by hypoxia/reoxygenation (H/R) injury. The H/R model was generated using the H9c2 cultured cardiac cell line. HuMSC-EVs were extracted using a commercially available exosome isolation reagent. Levels of apoptosis-related signaling molecules and the degree of ER stress were assessed by western blot. The role of the PI3K/Akt pathway was investigated using signaling inhibitors. Lactate dehydrogenase leakage and 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) analysis were used for evaluating the therapeutic effects of HuMSC-EVs in vitro. The results showed that ER stress and the rate of apoptosis were increased in the context of H/R injury. Treatment with HuMSC-EVs inhibited ER stress and increased survival in H9c2 cells exposed to H/R. Mechanistically, the PI3K/Akt pathway was activated by treatment with HuMSC-EVs after H/R. Inhibition of the PI3K/Akt pathway by a specific inhibitor, LY294002, partially reduced the protective effect of HuMSC-EVs. Our findings suggest that HuMSC-EVs could alleviate ER stress–induced apoptosis during H/R via activation of the PI3K/Akt pathway.

Role of O-GlcNAcylation and endoplasmic reticulum stress on obesity and insulin resistance

2019 ◽  
Vol 44 (5) ◽  
pp. 599-610 ◽  
Author(s):  
Benan Pelin Sermikli ◽  
Gulizar Aydogdu ◽  
Afsar Abbasi Taghidizaj ◽  
Erkan Yilmaz
Keyword(s):  
Insulin Resistance ◽  
Endoplasmic Reticulum ◽  
Western Blot ◽  
Er Stress ◽  
Insulin Receptor ◽  
Serine Phosphorylation ◽  
Wild Type ◽  
Adipose Tissues ◽  
Insulin Resistant

Abstract Background Obesity is a global public health problem. Obesity closely associated with various metabolic diseases such as; insulin resistance, hypertension, dyslipidemia and cardiovascular diseases. Endoplasmic reticulum (ER) stress is a critical factor for insulin resistance. O-linked N-acetyl-glucosamine (O-GlcNAc); is the post-translational modification which is has a vital role in biological processes; including cell signaling, in response to nutrients, stress and other extracellular stimuli. Materials and methods In this study, we aimed to investigate the role of O-GlcNAc modification in the context of obesity and obesity-associated insulin resistance in adipose tissue. For this purpose, first, the visceral and epididymal adipose tissues of obese and insulin resistant C57BL/6 Lepob/Lepob and wild-type mice were used to determine the O-GlcNAc modification pattern by western blot. Secondly, the external stimulation of O-GlcNAc modification in wild-type mice achieved by intraperitoneal 5 mg/kg/day glucosamine injection every 24 h for 5 days. The effect of increased O-GlcNAc modification on insulin resistance and ER stress investigated in adipose tissues of glucosamine challenged wild-type mice through regulation of the insulin signaling pathway and unfolded protein response (UPR) elements by western blot. In addition to that, the O-GlcNAc status of the insulin receptor substrate-1 (IRS1) investigated in epididymal and visceral adipose tissues of ob/ob, wild-type and glucosamine challenged mice by immunoprecipitation. Results We found that reduced O-GlcNAc levels in visceral and epididymal adipose tissues of obese and insulin-resistant ob/ob mice, although interestingly we observed that increased O-GlcNAc modification in glucosamine challenged wild-type mice resulted in insulin resistance and ER stress. Furthermore, we demonstrated that the IRS1 was modified with O-GlcNAc in visceral and epididymal adipose tissues in both ob/ob mice and glucosamine-injected mice, and was compatible with the serine phosphorylation of this modification. Conclusion Our results suggest that O-GlcNAcylation of proteins is a crucial factor for intracellular trafficking regulates insulin receptor signaling and UPR depending on the cellular state of insulin resistance.

scholarly journals Transient Cerebral Ischemia Activates Processing of xbp1 Messenger RNA Indicative of Endoplasmic Reticulum Stress

2003 ◽  
Vol 23 (4) ◽  
pp. 449-461 ◽  
Author(s):  
Wulf Paschen ◽  
Christoph Aufenberg ◽  
Svenja Hotop ◽  
Thorsten Mengesdorf
Keyword(s):  
Endoplasmic Reticulum ◽  
Cerebral Ischemia ◽  
Er Stress ◽  
Messenger Rna ◽  
Stress Proteins ◽  
Focal Cerebral Ischemia ◽  
Signal Transduction Pathway ◽  
Transient Cerebral Ischemia ◽  
Mrna Levels ◽  
Xbp1 Mrna

Cells respond to conditions associated with endoplasmic reticulum (ER) dysfunction with activation of the unfolded protein response, characterized by a shutdown of translation and induction of the expression of genes coding for ER stress proteins. The genetic response is based on IRE1-induced processing of xbp1 messenger RNA (mRNA), resulting in synthesis of new XBP1proc protein that functions as a potent transcription factor for ER stress genes. xbp1 processing in models of transient global and focal cerebral ischemia was studied. A marked increase in processed xbp1 mRNA levels during reperfusion was observed, most pronounced (about 35-fold) after 1-h occlusion of the right middle cerebral artery. The rise in processed xbp1 mRNA was not paralleled by a similar increase in XBP1proc protein levels because transient ischemia induces severe suppression of translation. As a result, mRNA levels of genes coding for ER stress proteins were only slightly increased, whereas mRNA levels of heat-shock protein 70 rose about 550-fold. Under conditions associated with ER dysfunction, cells require activation of the entire ER stress-induced signal transduction pathway, to cope with this severe form of stress. After transient cerebral ischemia, however, the block of translation may prevent synthesis of new XBP1proc protein and thus hinder recovery from ischemia-induced ER dysfunction.

Role of Endoplasmic Reticulum Calcium Disequilibria in the Mechanism of Homocysteine-Induced ER Stress

2007 ◽  
Vol 9 (11) ◽  
pp. 1863-1874 ◽  
Author(s):  
Jeffrey G. Dickhout ◽  
Sudesh K. Sood ◽  
Richard C. Austin
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Endoplasmic Reticulum Calcium
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