scholarly journals Inhibition of Nuclear Factor-κB or Bax Prevents Endoplasmic Reticulum Stress- But Not Nitric Oxide-Mediated Apoptosis in INS-1E Cells

Endocrinology ◽  
2009 ◽  
Vol 150 (9) ◽  
pp. 4094-4103 ◽  
Author(s):  
Morten F. Tonnesen ◽  
Lars G. Grunnet ◽  
Josefine Friberg ◽  
Alessandra K. Cardozo ◽  
Nils Billestrup ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Transcription Factor ◽  
Er Stress ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Β Cell ◽  
No Donor ◽  
Homologous Protein ◽  
Enhancer Binding Protein

Abstract Accumulating evidence suggests that endoplasmic reticulum (ER) stress by mechanisms that include ER Ca2+ depletion via NO-dependent down-regulation of sarcoendoplasmic reticulum Ca2+ ATPase 2b (SERCA2b) contributes to β-cell death in type 1 diabetes. To clarify whether the molecular pathways elicited by NO and ER Ca2+ depletion differ, we here compare the direct effects of NO, in the form of the NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP), with the effects of SERCA2 inhibitor thapsigargin (TG) on MAPK, nuclear factor κB (NFκB), Bcl-2 proteins, ER stress, and apoptosis. Exposure of INS-1E cells to TG or SNAP caused caspase-3 cleavage and apoptosis. Both TG and SNAP induced activation of the proapoptotic transcription factor CCAAT/enhancer-binding protein homologous protein (CHOP). However, other classical ER stress-induced markers such as up-regulation of ER chaperone Bip and alternative splicing of the transcription factor Xbp-1 were exclusively activated by TG. TG exposure caused NFκB activation, as assessed by IκB degradation and NFκB DNA binding. Inhibition of NFκB or the Bcl-2 family member Bax pathways protected β-cells against TG- but not SNAP-induced β-cell death. These data suggest that NO generation and direct SERCA2 inhibition cause two quantitative and qualitative different forms of ER stress. In contrast to NO, direct ER stress induced by SERCA inhibition causes activation of ER stress signaling pathways and elicit proapoptotic signaling via NFκB and Bax.

scholarly journals Endoplasmic reticulum and oxidant stress mediate nuclear factor-κB activation in the subfornical organ during angiotensin II hypertension

2015 ◽  
Vol 308 (10) ◽  
pp. C803-C812 ◽  
Author(s):  
Colin N. Young ◽  
Anfei Li ◽  
Frederick N. Dong ◽  
Julie A. Horwath ◽  
Catharine G. Clark ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Angiotensin Ii ◽  
Er Stress ◽  
Bioluminescence Imaging ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Ang Ii ◽  
Arterial Blood

Endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation in the brain circumventricular subfornical organ (SFO) mediate the central hypertensive actions of Angiotensin II (ANG II). However, the downstream signaling events remain unclear. Here we tested the hypothesis that angiotensin type 1a receptors (AT1aR), ER stress, and ROS induce activation of the transcription factor nuclear factor-κB (NF-κB) during ANG II-dependent hypertension. To spatiotemporally track NF-κB activity in the SFO throughout the development of ANG II-dependent hypertension, we used SFO-targeted adenoviral delivery and longitudinal bioluminescence imaging in mice. During low-dose infusion of ANG II, bioluminescence imaging revealed a prehypertensive surge in NF-κB activity in the SFO at a time point prior to a significant rise in arterial blood pressure. SFO-targeted ablation of AT1aR, inhibition of ER stress, or adenoviral scavenging of ROS in the SFO prevented the ANG II-induced increase in SFO NF-κB. These findings highlight the utility of bioluminescence imaging to longitudinally track transcription factor activation during the development of ANG II-dependent hypertension and reveal an AT1aR-, ER stress-, and ROS-dependent prehypertensive surge in NF-κB activity in the SFO. Furthermore, the increase in NF-κB activity before a rise in arterial blood pressure suggests a causal role for SFO NF-κB in the development of ANG II-dependent hypertension.

scholarly journals Free Fatty Acids and Cytokines Induce Pancreatic β-Cell Apoptosis by Different Mechanisms: Role of Nuclear Factor-κB and Endoplasmic Reticulum Stress

Endocrinology ◽  
2004 ◽  
Vol 145 (11) ◽  
pp. 5087-5096 ◽  
Author(s):  
Ilham Kharroubi ◽  
Laurence Ladrière ◽  
Alessandra K. Cardozo ◽  
Zeynep Dogusan ◽  
Miriam Cnop ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Fatty Acids ◽  
Cell Death ◽  
Er Stress ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Β Cells ◽  
Β Cell ◽  
Er Stress Response ◽  
Activating Transcription Factor

Abstract Apoptosis is probably the main form of β-cell death in both type 1 diabetes mellitus (T1DM) and T2DM. In T1DM, cytokines contribute to β-cell destruction through nuclear factor-κB (NF-κB) activation. Previous studies suggested that in T2DM high glucose and free fatty acids (FFAs) are β-cell toxic also via NF-κB activation. The aims of this study were to clarify whether common mechanisms are involved in FFA- and cytokine-induced β-cell apoptosis and determine whether TNFα, an adipocyte-derived cytokine, potentiates FFA toxicity through enhanced NF-κB activation. Apoptosis was induced in insulinoma (INS)-1E cells, rat islets, and fluorescence-activated cell sorting-purified β-cells by oleate, palmitate, and/or cytokines (IL-1β, interferon-γ, TNFα). Palmitate and IL-1β induced a similar percentage of apoptosis in INS-1E cells, whereas oleate was less toxic. TNFα did not potentiate FFA toxicity in primary β-cells. The NF-κB-dependent genes inducible nitric oxide synthase and monocyte chemoattractant protein-1 were induced by IL-1β but not by FFAs. Cytokines activated NF-κB in INS-1E and β-cells, but FFAs did not. Moreover, FFAs did not enhance NF-κB activation by TNFα. Palmitate and oleate induced C/EBP homologous protein, activating transcription factor-4, and immunoglobulin heavy chain binding protein mRNAs, X-box binding protein-1 alternative splicing, and activation of the activating transcription factor-6 promoter in INS-1E cells, suggesting that FFAs trigger an endoplasmic reticulum (ER) stress response. We conclude that apoptosis is the main mode of FFA- and cytokine-induced β-cell death but the mechanisms involved are different. Whereas cytokines induce NF-κB activation and ER stress (secondary to nitric oxide formation), FFAs activate an ER stress response via an NF-κB- and nitric oxide-independent mechanism. Our results argue against a unifying hypothesis for the mechanisms of β-cell death in T1DM and T2DM.

scholarly journals Unification of Opposites between Two Antioxidant Transcription Factors Nrf1 and Nrf2 in Mediating Distinct Cellular Responses to the Endoplasmic Reticulum Stressor Tunicamycin

Antioxidants ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 4 ◽  
Author(s):  
Yu-ping Zhu ◽  
Ze Zheng ◽  
Shaofan Hu ◽  
Xufang Ru ◽  
Zhuo Fan ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Er Stress ◽  
Target Genes ◽  
Cellular Responses ◽  
Water Soluble ◽  
Heme Oxygenase 1 ◽  
Nuclear Factor ◽  
Activating Transcription Factor

The water-soluble Nrf2 (nuclear factor, erythroid 2-like 2, also called Nfe2l2) is accepted as a master regulator of antioxidant responses to cellular stress, and it was also identified as a direct target of the endoplasmic reticulum (ER)-anchored PERK (protein kinase RNA-like endoplasmic reticulum kinase). However, the membrane-bound Nrf1 (nuclear factor, erythroid 2-like 1, also called Nfe2l1) response to ER stress remains elusive. Herein, we report a unity of opposites between these two antioxidant transcription factors, Nrf1 and Nrf2, in coordinating distinct cellular responses to the ER stressor tunicamycin (TU). The TU-inducible transcription of Nrf1 and Nrf2, as well as GCLM (glutamate cysteine ligase modifier subunit) and HO-1 (heme oxygenase 1), was accompanied by activation of ER stress signaling networks. Notably, the unfolded protein response (UPR) mediated by ATF6 (activating transcription factor 6), IRE1 (inositol requiring enzyme 1) and PERK was significantly suppressed by Nrf1α-specific knockout, but hyper-expression of Nrf2 and its target genes GCLM and HO-1 has retained in Nrf1α−/− cells. By contrast, Nrf2−/−ΔTA cells with genomic deletion of its transactivation (TA) domain resulted in significant decreases of GCLM, HO-1 and Nrf1; this was accompanied by partial decreases of IRE1 and ATF6, rather than PERK, but with an increase of ATF4 (activating transcription factor 4). Interestingly, Nrf1 glycosylation and its trans-activity to mediate the transcriptional expression of the 26S proteasomal subunits, were repressed by TU. This inhibitory effect was enhanced by Nrf1α−/− and Nrf2−/−ΔTA, but not by a constitutive activator caNrf2ΔN (that increased abundances of the non-glycosylated and processed Nrf1). Furthermore, caNrf2ΔN also enhanced induction of PERK and IRE1 by TU, but reduced expression of ATF4 and HO-1. Thus, it is inferred that such distinct roles of Nrf1 and Nrf2 are unified to maintain cell homeostasis by a series of coordinated ER-to-nuclear signaling responses to TU. Nrf1α (i.e., a full-length form) acts in a cell-autonomous manner to determine the transcription of most of UPR-target genes, albeit Nrf2 is also partially involved in this process. Consistently, transactivation of ARE (antioxidant response element)-driven BIP (binding immunoglobulin protein)-, PERK- and XBP1 (X-box binding protein 1)-Luc reporter genes was mediated directly by Nrf1 and/or Nrf2. Interestingly, Nrf1α is more potent than Nrf2 at mediating the cytoprotective responses against the cytotoxicity of TU alone or plus tBHQ (tert-butylhydroquinone). This is also further supported by the evidence that the intracellular reactive oxygen species (ROS) levels are increased in Nrf1α−/− cells, but rather are, to our surprise, decreased in Nrf2−/−ΔTA cells.

scholarly journals Research Resource: Monitoring Endoplasmic Reticulum Membrane Integrity in β-Cells at the Single-Cell Level

2015 ◽  
Vol 29 (3) ◽  
pp. 473-480 ◽  
Author(s):  
Kohsuke Kanekura ◽  
Jianhong Ou ◽  
Takashi Hara ◽  
Lihua J. Zhu ◽  
Fumihiko Urano
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Single Cell ◽  
Membrane Integrity ◽  
Membrane Permeabilization ◽  
Single Cell Level ◽  
Cell Level ◽  
Β Cell ◽  
Er Membrane

Abstract Endoplasmic reticulum (ER) membrane integrity is an emerging target for human chronic diseases associated with ER stress. Despite the underlying importance of compromised ER membrane integrity in disease states, the entire process leading to ER membrane permeabilization and cell death is still not clear due to technical limitations. Here we describe a novel method for monitoring ER membrane integrity at the single-cell level in real time. Using a β-cell line expressing ER-targeted redox sensitive green fluorescent protein, we could identify a β-cell population undergoing ER membrane permeabilization induced by palmitate and could monitor cell fate and ER stress of these cells at the single-cell level. Our method could be used to develop a novel therapeutic modality targeting the ER membrane for ER-associated disorders, including β-cell death in diabetes, neurodegeneration, and Wolfram syndrome.

scholarly journals A Novel Transcription Factor, ERD15 (Early Responsive to Dehydration 15), Connects Endoplasmic Reticulum Stress with an Osmotic Stress-induced Cell Death Signal

2011 ◽  
Vol 286 (22) ◽  
pp. 20020-20030 ◽  
Author(s):  
Murilo S. Alves ◽  
Pedro A. B. Reis ◽  
Silvana P. Dadalto ◽  
Jerusa A. Q. A. Faria ◽  
Elizabeth P. B. Fontes ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Transcription Factor ◽  
Osmotic Stress ◽  
Er Stress ◽  
Unfolded Protein ◽  
Eukaryotic Organisms ◽  
Protein Response

As in all other eukaryotic organisms, endoplasmic reticulum (ER) stress triggers the evolutionarily conserved unfolded protein response in soybean, but it also communicates with other adaptive signaling responses, such as osmotic stress-induced and ER stress-induced programmed cell death. These two signaling pathways converge at the level of gene transcription to activate an integrated cascade that is mediated by N-rich proteins (NRPs). Here, we describe a novel transcription factor, GmERD15 (Glycine max Early Responsive to Dehydration 15), which is induced by ER stress and osmotic stress to activate the expression of NRP genes. GmERD15 was isolated because of its capacity to stably associate with the NRP-B promoter in yeast. It specifically binds to a 187-bp fragment of the NRP-B promoter in vitro and activates the transcription of a reporter gene in yeast. Furthermore, GmERD15 was found in both the cytoplasm and the nucleus, and a ChIP assay revealed that it binds to the NRP-B promoter in vivo. Expression of GmERD15 in soybean protoplasts activated the NRP-B promoter and induced expression of the NRP-B gene. Collectively, these results support the interpretation that GmERD15 functions as an upstream component of stress-induced NRP-B-mediated signaling to connect stress in the ER to an osmotic stress-induced cell death signal.

A novel secretagogin/ATF4 pathway is involved in oxidized LDL-induced endoplasmic reticulum stress and islet β-cell apoptosis

2020 ◽  
Author(s):  
Li Wu ◽  
Yuncheng Lv ◽  
Ying Lv ◽  
Sunmin Xiang ◽  
Zhibo Zhao ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Er Stress ◽  
Cell Apoptosis ◽  
Initiation Factor ◽  
Β Cells ◽  
Β Cell ◽  
Immunoprecipitation Assay ◽  
Min6 Cells ◽  
Stress Markers

Abstract Excessive accumulation of cholesterol in β cells initiates endoplasmic reticulum (ER) stress and associated apoptosis. We have reported that excessive uptake of cholesterol by MIN6 cells decreases the expression of secretagogin (SCGN) and then attenuates insulin secretion. Here, we aimed to determine whether cholesterol-induced SCGN decrease is involved in the modulation of ER stress and apoptosis in pancreatic β cells. In this study, MIN6 cells were treated with oxidized low-density lipoprotein (ox-LDL) for 24 h, and then intracellular lipid droplets and cell apoptosis were quantified, and SCGN and ER stress markers were identified by western blot analysis. Furthermore, small interfer RNA (siRNA)-mediated SCGN knockdown and recombinant plasmid-mediated SCGN restoration experiments were performed to confirm the role of SCGN in ER stress and associated cell apoptosis. Finally, the interaction of SCGN with ATF4 was computationally predicted and then validated by a co-immunoprecipitation assay. We found that ox-LDL treatment increased the levels of ER stress markers, such as phosphorylated protein kinase-like endoplasmic reticulum kinase, phosphorylated eukaryotic initiation factor 2 alpha, activating transcription factor 4 (ATF4), and transcription factor CCAAT-enhancer-binding protein homologous protein, and promoted MIN6 cell apoptosis; in addition, the expression of SCGN was downregulated. siRNA-mediated SCGN knockdown exacerbated β-cell ER stress by increasing ATF4 expression. Pretreatment of MIN6 cells with the recombinant SCGN partly antagonized ox-LDL-induced ER stress and apoptosis. Furthermore, a co-immunoprecipitation assay revealed an interaction between SCGN and ATF4 in MIN6 cells. Taken together, these results demonstrated that pancreatic β-cell apoptosis induced by ox-LDL treatment can be attributed, in part, to an SCGN/ATF4-dependent ER stress response.

scholarly journals Regulation of podocyte survival and endoplasmic reticulum stress by fatty acids

2010 ◽  
Vol 299 (4) ◽  
pp. F821-F829 ◽  
Author(s):  
Jonas Sieber ◽  
Maja Tamara Lindenmeyer ◽  
Kapil Kampe ◽  
Kirk Nicholas Campbell ◽  
Clemens David Cohen ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Oleic Acid ◽  
Palmitic Acid ◽  
Er Stress ◽  
Unfolded Protein ◽  
Homologous Protein ◽  
Protein Response ◽  
Apoptosis And Necrosis

Apoptosis of podocytes is considered critical in the pathogenesis of diabetic nephropathy (DN). Free fatty acids (FFAs) are critically involved in the pathogenesis of diabetes mellitus type 2, in particular the regulation of pancreatic β cell survival. The objectives of this study were to elucidate the role of palmitic acid, palmitoleic, and oleic acid in the regulation of podocyte cell death and endoplasmic reticulum (ER) stress. We show that palmitic acid increases podocyte cell death, both apoptosis and necrosis of podocytes, in a dose and time-dependent fashion. Palmitic acid induces podocyte ER stress, leading to an unfolded protein response as reflected by the induction of the ER chaperone immunoglobulin heavy chain binding protein (BiP) and proapoptotic C/EBP homologous protein (CHOP) transcription factor. Of note, the monounsaturated palmitoleic and oleic acid can attenuate the palmitic acid-induced upregulation of CHOP, thereby preventing cell death. Similarly, gene silencing of CHOP protects against palmitic acid-induced podocyte apoptosis. Our results offer a rationale for interventional studies aimed at testing whether dietary shifting of the FFA balance toward unsaturated FFAs can delay the progression of DN.

scholarly journals Protection of pancreatic β-cells by exendin-4 may involve the reduction of endoplasmic reticulum stress; in vivo and in vitro studies

2007 ◽  
Vol 193 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Shin Tsunekawa ◽  
Naoki Yamamoto ◽  
Katsura Tsukamoto ◽  
Yuji Itoh ◽  
Yukiko Kaneko ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Islet Cells ◽  
Binding Protein ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

The aim of this study was to investigate the in vivo and in vitro effects of exendin-4, a potent glucagon-like peptide 1 agonist, on the protection of the pancreatic β-cells against their cell death. In in vivo experiments, we used β-cell-specific calmodulin-overexpressing mice where massive apoptosis takes place in their β-cells, and we examined the effects of chronic treatment with exendin-4. Chronic and s.c. administration of exendin-4 reduced hyperglycemia. The treatment caused significant increases of the insulin contents of the pancreas and islets, and retained the insulin-positive area. Dispersed transgenic islet cells lived only shortly, and several endoplasmic reticulum (ER) stress-related molecules such as immunoglobulin-binding protein (Bip), inositol-requiring enzyme-1α, X-box-binding protein-1 (XBP-1), RNA-activated protein kinase-like endoplasmic reticulum kinase, activating transcription factor-4, and C/EBP-homologous protein (CHOP) were more expressed in the transgenic islets. We also found that the spliced form of XBP-1, a marker of ER stress, was also increased in β-cell-specific calmodulin-overexpressing transgenic islets. In the quantitative real-time PCR analyses, the expression levels of Bip and CHOP were reduced in the islets from the transgenic mice treated with exendin-4. These findings suggest that excess of ER stress occurs in the transgenic β-cells, and the suppression of ER stress and resultant protection against cell death may be involved in the anti-diabetic effects of exendin-4.

scholarly journals Linking endoplasmic reticulum stress to cell death in hepatocytes: roles of C/EBP homologous protein and chemical chaperones in palmitate-mediated cell death

2010 ◽  
Vol 298 (5) ◽  
pp. E1027-E1035 ◽  
Author(s):  
Kyle T. Pfaffenbach ◽  
Christopher L. Gentile ◽  
Angela M. Nivala ◽  
Dong Wang ◽  
Yuren Wei ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Liver Cells ◽  
Primary Hepatocytes ◽  
Deficient Diet ◽  
Chemical Chaperones ◽  
Homologous Protein ◽  
Jnk Activation

Prolonged endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) have been linked to apoptosis via several mechanisms, including increased expression of C/EBP homologous protein ( Chop). Increased long-chain fatty acids, in particular saturated fatty acids, induce ER stress, Chop expression, and apoptosis in liver cells. The first aim of the present study was to determine the role of Chop in lipid-induced hepatocyte cell death and liver injury induced by a methionine-choline-deficient diet. Albumin-bound palmitate increased Chop gene and protein expression in a dose-dependent fashion in H4IIE liver cells. siRNA-mediated silencing of Chop in H4IIE liver cells reduced thapsigargin-mediated cell death by ∼40% and delayed palmitate-mediated cell death, but only at high concentrations of palmitate (400–500 μM). Similar results were observed in primary hepatocytes isolated from Chop-knockout mice. Indices of liver injury were also not reduced in Chop-knockout mice provided a methionine-choline-deficient diet. To ascertain whether ER stress was linked to palmitate-induced cell death, primary hepatocytes were incubated in the absence or presence of the chemical chaperones taurine-conjugated ursodeoxycholic acid or 4-phenylbutyric acid. The presence of either of these chemical chaperones protected liver cells from palmitate-mediated ER stress and cell death, in part, via inhibition of JNK activation. These data suggest that ER stress is linked to palmitate-mediated cell death via mechanisms that include JNK activation.

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