scholarly journals The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis

2015 ◽  
Vol 290 (34) ◽  
pp. 20687-20699 ◽  
Author(s):  
Cong Yu ◽  
Shang Cui ◽  
Chen Zong ◽  
Weina Gao ◽  
Tongfu Xu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Survivin Promoter ◽  
Min6 Cells ◽  
Chop Expression ◽  
Mouse Islets

The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (−1872 bp to −1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as “positive and negative regulation.”

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 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 γ-Oryzanol Protects Pancreatic β-Cells Against Endoplasmic Reticulum Stress in Male Mice

Endocrinology ◽  
2015 ◽  
Vol 156 (4) ◽  
pp. 1242-1250 ◽  
Author(s):  
Chisayo Kozuka ◽  
Sumito Sunagawa ◽  
Rei Ueda ◽  
Moritake Higa ◽  
Hideaki Tanaka ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Insulin Secretion ◽  
Er Stress ◽  
High Fat Diet ◽  
Diabetic Mice ◽  
High Fat ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Glucose Stimulated Insulin Secretion

Abstract Endoplasmic reticulum (ER) stress is profoundly involved in dysfunction of β-cells under high-fat diet and hyperglycemia. Our recent study in mice showed that γ-oryzanol, a unique component of brown rice, acts as a chemical chaperone in the hypothalamus and improves feeding behavior and diet-induced dysmetabolism. However, the entire mechanism whereby γ-oryzanol improves glucose metabolism throughout the body still remains unclear. In this context, we tested whether γ-oryzanol reduces ER stress and improves function and survival of pancreatic β-cells using murine β-cell line MIN6. In MIN6 cells with augmented ER stress by tunicamycin, γ-oryzanol decreased exaggerated expression of ER stress-related genes and phosphorylation of eukaryotic initiation factor-2α, resulting in restoration of glucose-stimulated insulin secretion and prevention of apoptosis. In islets from high-fat diet-fed diabetic mice, oral administration of γ-oryzanol improved glucose-stimulated insulin secretion on following reduction of exaggerated ER stress and apoptosis. Furthermore, we examined the impact of γ-oryzanol on low-dose streptozotocin-induced diabetic mice, where exaggerated ER stress and resultant apoptosis in β-cells were observed. Also in this model, γ-oryzanol attenuated mRNA level of genes involved in ER stress and apoptotic signaling in islets, leading to amelioration of glucose dysmetabolism. Taken together, our findings demonstrate that γ-oryzanol directly ameliorates ER stress-induced β-cell dysfunction and subsequent apoptosis, highlighting usefulness of γ-oryzanol for the treatment of diabetes mellitus.

scholarly journals AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells

2020 ◽  
Vol 40 (11) ◽  
Author(s):  
Zhechu Peng ◽  
Richa Aggarwal ◽  
Ni Zeng ◽  
Lina He ◽  
Eileen X. Stiles ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Adaptive Response ◽  
Metabolic Stress ◽  
Cell Phenotype ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Α Subunit ◽  
Growth And Survival

ABSTRACT Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.

scholarly journals Endoplasmic reticulum stress induces Wfs1 gene expression in pancreatic β-cells via transcriptional activation

2005 ◽  
Vol 153 (1) ◽  
pp. 167-176 ◽  
Author(s):  
Kohei Ueda ◽  
June Kawano ◽  
Komei Takeda ◽  
Toshiaki Yujiri ◽  
Katsuya Tanabe ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Stress Responses ◽  
Gene Promoter ◽  
Luciferase Reporter ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Min6 Cells ◽  
Insulinoma Cells

Objective: The WFS1 gene encodes an endoplasmic reticulum (ER) membrane-embedded protein. Homozygous WFS1 gene mutations cause Wolfram syndrome, characterized by insulin-deficient diabetes mellitus and optic atropy. Pancreatic β-cells are selectively lost from the patient’s islets. ER localization suggests that WFS1 protein has physiological functions in membrane trafficking, secretion, processing and/or regulation of ER calcium homeostasis. Disturbances or overloading of these functions induces ER stress responses, including apoptosis. We speculated that WFS1 protein might be involved in these ER stress responses. Design and methods: Islet expression of the Wfs1 protein was analyzed immunohistochemically. Induction of Wfs1 upon ER stress was examined by Northern and Western blot analyses using three different models: human skin fibroblasts, mouse pancreatic β-cell-derived MIN6 cells, and Akita mouse-derived Ins2 96Y/Y insulinoma cells. The human WFS1 gene promoter-luciferase reporter analysis was also conducted. Result: Islet β-cells were the major site of Wfs1 expression. This expression was also found in δ-cells, but not in α-cells. WFS1 expression was transcriptionally up-regulated by ER stress-inducing chemical insults. Treatment of fibroblasts and MIN6 cells with thapsigargin or tunicamycin increased WFS1 mRNA. WFS1 protein also increased in response to thapsigargin treatment in these cells. WFS1 gene expression was also increased in Ins2 96Y/Y insulinoma cells. In these cells, ER stress was intrinsically induced by mutant insulin expression. The WFS1 gene promoter-luciferase reporter system revealed that the human WFS1 promoter was activated by chemically induced ER stress in MIN6 cells, and that the promoter was more active in Ins2 96Y/Y cells than Ins2 wild/wild cells. Conclusion: Wfs1 expression, which is localized to β- and δ-cells in pancreatic islets, increases in response to ER stress, suggesting a functional link between Wfs1 and ER stress.

scholarly journals Eukaryotic translation initiation factor 2A protects pancreatic beta cells during endoplasmic reticulum stress while rescuing translation inhibition

2021 ◽  
Author(s):  
Evgeniy Panzhinskiy ◽  
Søs Skovsø ◽  
Haoning Howard Cen ◽  
Kwan Yi Chu ◽  
Kate MacDonald ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Protein Translation ◽  
Human Islets ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Β Cell ◽  
Min6 Cells ◽  
Primary Mouse ◽  
Mouse Islets

ABSTRACTThe endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) helps decide β cell survival in diabetes. The alternative eukaryotic initiation factor 2A (EIF2A) has been proposed to mediate EIF2S1-independent translation during cellular stress and viral infection, but its role in β cells is unknown. EIF2A abundance is high in human and mouse islets relative to other tissues, and both thapsigargin and palmitate significantly increased EIF2A mRNA and EIF2A protein levels in MIN6 cells, mouse islets and human islets. Knockdowns of EIF2A, the related factor EIF2D, or both EIF2A and EIF2D, were not sufficient to cause apoptosis. On the other hand, transient or stable EIF2A over-expression protected MIN6 cells, primary mouse islets, and human islets from ER stress-induced, caspase-3-dependent apoptosis. Mechanistically, EIF2A overexpression decreased ERN1 (also known as IRE1α) expression in thapsigargin-treated MIN6 cells or human islets. In vivo, β cell specific EIF2A viral overexpression reduced ER stress, improved insulin secretion, and abrogated hyperglycemia in Ins2Akita/WT mice. EIF2A overexpression significantly increased expression of genes involved in protein translation and reduced expression of pro-apoptotic genes (e.g. ALDH1A3). Remarkably, the decrease in global protein synthesis during UPR was prevented by EIF2A, despite ER stress-induced EIF2S1 phosphorylation. The protective effects of EIF2A were additive to those of ISRIB, a drug that counteracts the effects of EIF2S1 phosphorylation. Cells overexpressing EIF2A showed higher expression of translation factor EIF2B5, which may contribute to the lack of translational inhibition in these cells. We conclude that EIF2A is a novel target for β cell protection and the circumvention of EIF2S1-mediated translational repression.

scholarly journals Pathological β-Cell Endoplasmic Reticulum Stress in Type 2 Diabetes: Current Evidence

2021 ◽  
Vol 12 ◽  
Author(s):  
Neha Shrestha ◽  
Elisa De Franco ◽  
Peter Arvan ◽  
Miriam Cnop
Keyword(s):  
Type 2 Diabetes ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Protein Misfolding ◽  
Cell Function ◽  
Current Evidence ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

The notion that in diabetes pancreatic β-cells express endoplasmic reticulum (ER) stress markers indicative of increased unfolded protein response (UPR) signaling is no longer in doubt. However, what remains controversial is whether this increase in ER stress response actually contributes importantly to the β-cell failure of type 2 diabetes (akin to ‘terminal UPR’), or whether it represents a coping mechanism that represents the best attempt of β-cells to adapt to changes in metabolic demands as presented by disease progression. Here an intercontinental group of experts review evidence for the role of ER stress in monogenic and type 2 diabetes in an attempt to reconcile these disparate views. Current evidence implies that pancreatic β-cells require a regulated UPR for their development, function and survival, as well as to maintain cellular homeostasis in response to protein misfolding stress. Prolonged ER stress signaling, however, can be detrimental to β-cells, highlighting the importance of “optimal” UPR for ER homeostasis, β-cell function and survival.

scholarly journals Verbascoside Protects Pancreatic β-Cells against ER-Stress

Biomedicines ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 582
Author(s):  
Alessandra Galli ◽  
Paola Marciani ◽  
Algerta Marku ◽  
Silvia Ghislanzoni ◽  
Federico Bertuzzi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Therapeutic Potential ◽  
Mitochondrial Dynamics ◽  
Imaging Techniques ◽  
Biological Properties ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
The Unfolded Protein Response

Substantial epidemiological evidence indicates that a diet rich in polyphenols protects against developing type 2 diabetes. The phenylethanoid glycoside verbascoside/acteoside, a widespread polyphenolic plant compound, has several biological properties including strong antioxidant, anti-inflammatory and neuroprotective activities. The aim of this research was to test the possible effects of verbascoside on pancreatic β-cells, a target never tested before. Mouse and human β-cells were incubated with verbascoside (0.8–16 µM) for up to five days and a combination of biochemical and imaging techniques were used to assess the β-cell survival and function under normal or endoplasmic reticulum (ER)-stress inducing conditions. We found a dose-dependent protective effect of verbascoside against oxidative stress in clonal and human β-cells. Mechanistic studies revealed that the polyphenol protects β-cells against ER-stress mediated dysfunctions, modulating the activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK) branch of the unfolded protein response and promoting mitochondrial dynamics. As a result, increased viability, mitochondrial function and insulin content were detected in these cells. These studies provide the evidence that verbascoside boosts the ability of β-cells to cope with ER-stress, an important contributor of β-cell dysfunction and failure in diabetic conditions and support the therapeutic potential of verbascoside in diabetes.

scholarly journals Role of Nitric Oxide in the Pathogenesis of Encephalomyocarditis Virus-Induced Diabetes in Mice

2009 ◽  
Vol 83 (16) ◽  
pp. 8004-8011 ◽  
Author(s):  
Young-Sun Lee ◽  
Na Li ◽  
Seungjin Shin ◽  
Hee-Sook Jun
Keyword(s):  
Virus Infection ◽  
Encephalomyocarditis Virus ◽  
Wild Type ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Diabetes In Mice ◽  
Tnf Α ◽  
Deficient Mice

ABSTRACT The D variant of encephalomyocarditis virus (EMC-D virus) causes diabetes in mice by destroying pancreatic β cells. In mice infected with a low dose of EMC-D virus, macrophages play an important role in β-cell destruction by producing soluble mediators such as interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and nitric oxide (NO). To investigate the role of NO and inducible NO synthase (iNOS) in the development of diabetes in EMC-D virus-infected mice, we infected iNOS-deficient DBA/2 mice with EMC-D virus (2 × 102 PFU/mouse). Mean blood glucose levels in EMC-D virus-infected iNOS-deficient mice and wild-type mice were 205.5 and 466.7 mg/dl, respectively. Insulitis and macrophage infiltration were reduced in islets of iNOS-deficient mice compared with wild-type mice at 3 days after EMC-D virus infection. Apoptosis of β cells was decreased in iNOS-deficient mice, as evidenced by reduced numbers of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cells. There were no differences in mRNA expression of antiapoptotic molecules Bcl-2, Bcl-xL, Bcl-w, Mcl-1, cIAP-1, and cIAP-2 between wild-type and iNOS-deficient mice, whereas expression of proapoptotic Bax and Bak mRNAs was significantly decreased in iNOS-deficient mice. Expression of IL-1β and TNF-α mRNAs was significantly decreased in both islets and macrophages of iNOS-deficient mice compared with wild-type mice after EMC-D virus infection. Nuclear factor κB was less activated in macrophages of iNOS-deficient mice after virus infection. We conclude that NO plays an important role in the activation of macrophages and apoptosis of pancreatic β cells in EMC-D virus-infected mice and that deficient iNOS gene expression inhibits macrophage activation and β-cell apoptosis, contributing to prevention of EMC-D virus-induced diabetes.

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