scholarly journals Modulation of Apoptosis Pathways by Oxidative Stress and Autophagy in β Cells

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Maorong Wang ◽  
Mia Crager ◽  
Subbiah Pugazhenthi
Keyword(s):  
Oxidative Stress ◽  
Promoter Activity ◽  
Human Islets ◽  
Β Cells ◽  
Β Cell ◽  
Multiple Stresses ◽  
Apoptosis Pathway ◽  
Min6 Cells ◽  
Beta Cell Line ◽  
Induced Apoptosis

Human islets isolated for transplantation are exposed to multiple stresses including oxidative stress and hypoxia resulting in significant loss of functional β cell mass. In this study we examined the modulation of apoptosis pathway genes in islets exposed to hydrogen peroxide, peroxynitrite, hypoxia, and cytokines. We observed parallel induction of pro- and antiapoptotic pathways and identified several novel genes including BFAR, CARD8, BNIP3, and CIDE-A. As BNIP3 is an inducer of autophagy, we examined this pathway in MIN6 cells, a mouse beta cell line and in human islets. Culture of MIN6 cells under low serum conditions increased the levels of several proteins in autophagy pathway, including ATG4, Beclin 1, LAMP-2, and UVRAG. Amino acid deprivation led to induction of autophagy in human islets. Preconditioning of islets with inducers of autophagy protected them from hypoxia-induced apoptosis. However, induction of autophagy during hypoxia exacerbated apoptotic cell death. ER stress led to induction of autophagy and apoptosis in β cells. Overexpression of MnSOD, an enzyme that scavenges free radicals, resulted in protection of MIN6 cells from cytokine-induced apoptosis. Ceramide, a mediator of cytokine-induced injury, reduced the active phosphorylated form of Akt and downregulated the promoter activity of the antiapoptotic gene bcl-2. Furthermore, cytokine-stimulated JNK pathway downregulated the bcl-2 promoter activity which was reversed by preincubation with SP600125, a JNK inhibitor. Our findings suggest that β cell apoptosis by multiple stresses in islets isolated for transplantation is the result of orchestrated gene expression in apoptosis pathway.

Differential activation of ER stress and apoptosis in response to chronically elevated free fatty acids in pancreatic β-cells

2008 ◽  
Vol 294 (3) ◽  
pp. E540-E550 ◽  
Author(s):  
Elida Lai ◽  
George Bikopoulos ◽  
Michael B. Wheeler ◽  
Maria Rozakis-Adcock ◽  
Allen Volchuk
Keyword(s):  
Er Stress ◽  
Cell Lines ◽  
Cell Apoptosis ◽  
Human Islets ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Min6 Cells ◽  
Relative Contribution ◽  
Induced Apoptosis

Chronic exposure to elevated saturated free fatty acid (FFA) levels has been shown to induce endoplasmic reticulum (ER) stress that may contribute to promoting pancreatic β-cell apoptosis. Here, we compared the effects of FFAs on apoptosis and ER stress in human islets and two pancreatic β-cell lines, rat INS-1 and mouse MIN6 cells. Isolated human islets cultured in vitro underwent apoptosis, and markers of ER stress pathways were elevated by chronic palmitate exposure. Palmitate also induced apoptosis in MIN6 and INS-1 cells, although the former were more resistant to both apoptosis and ER stress. MIN6 cells were found to express significantly higher levels of ER chaperone proteins than INS-1 cells, which likely accounts for the ER stress resistance. We attempted to determine the relative contribution that ER stress plays in palmitate-induced β-cell apoptosis. Although overexpressing GRP78 in INS-1 cells partially reduced susceptibility to thapsigargin, this failed to reduce palmitate-induced ER stress or apoptosis. In INS-1 cells, palmitate induced apoptosis at concentrations that did not result in significant ER stress. Finally, MIN6 cells depleted of GRP78 were more susceptible to tunicamycin-induced apoptosis but not to palmitate-induced apoptosis compared with control cells. These results suggest that ER stress is likely not the main mechanism involved in palmitate-induced apoptosis in β-cell lines. Human islets and MIN6 cells were found to express high levels of stearoyl-CoA desaturase-1 compared with INS-1 cells, which may account for the decreased susceptibility of these cells to the cytotoxic effects of palmitate.

scholarly journals Enhancer of Zeste Homolog 2 (EZH2) Mediates Glucolipotoxicity-Induced Apoptosis in β-Cells

2020 ◽  
Vol 21 (21) ◽  
pp. 8016
Author(s):  
Tina Dahlby ◽  
Christian Simon ◽  
Marie Balslev Backe ◽  
Mattias Salling Dahllöf ◽  
Edward Holson ◽  
...  
Keyword(s):  
Er Stress ◽  
Molecular Mechanisms ◽  
Selective Inhibition ◽  
Human Islets ◽  
Β Cells ◽  
Β Cell ◽  
Enhancer Of Zeste ◽  
Cell Gene Expression ◽  
Nfκb Pathway ◽  
Induced Apoptosis

Selective inhibition of histone deacetylase 3 (HDAC3) prevents glucolipotoxicity-induced β-cell dysfunction and apoptosis by alleviation of proapoptotic endoplasmic reticulum (ER) stress-signaling, but the precise molecular mechanisms of alleviation are unexplored. By unbiased microarray analysis of the β-cell gene expression profile of insulin-producing cells exposed to glucolipotoxicity in the presence or absence of a selective HDAC3 inhibitor, we identified Enhancer of zeste homolog 2 (EZH2) as the sole target candidate. β-Cells were protected against glucolipotoxicity-induced ER stress and apoptosis by EZH2 attenuation. Small molecule inhibitors of EZH2 histone methyltransferase activity rescued human islets from glucolipotoxicity-induced apoptosis. Moreover, EZH2 knockdown cells were protected against glucolipotoxicity-induced downregulation of the protective non-canonical Nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB) pathway. We conclude that EZH2 deficiency protects from glucolipotoxicity-induced ER stress, apoptosis and downregulation of the non-canonical NFκB pathway, but not from insulin secretory dysfunction. The mechanism likely involves transcriptional regulation via EZH2 functioning as a methyltransferase and/or as a methylation-dependent transcription factor.

scholarly journals Hepatocyte growth factor protects rat RINm5F cell line against free fatty acid-induced apoptosis by counteracting oxidative stress

2007 ◽  
Vol 38 (1) ◽  
pp. 147-158 ◽  
Author(s):  
Carmela Santangelo ◽  
Paola Matarrese ◽  
Roberta Masella ◽  
Maria Chiara Di Carlo ◽  
Angela Di Lillo ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Protective Effect ◽  
Chronic Exposure ◽  
Β Cells ◽  
Β Cell ◽  
Rinm5f Cell ◽  
Induced Apoptosis ◽  
Hepatocyte Growth

Type 2 diabetes is characterized by peripheral insulin resistance, pancreatic β-cells dysfunction, and decreased β-cell mass with increased rate of apoptosis. Chronic exposure to high levels of free fatty acids (FFAs) has detrimental effects on β-cell function and survival. FFAs have adverse effects on mitochondrial function, with a consequent increase in the production of reactive oxygen species. Hepatocyte growth factor (HGF) plays a critical role in promoting β-cell survival. In the present study, we investigated whether HGF was capable of protecting β-cells from death induced by prolonged exposure to FFAs. RINm5F cell line was cultured in the presence of FFAs (oleate:palmitate 2:1) for 72 h in order to induce apoptosis. Simultaneous administration of HGF and FFAs significantly suppressed the impaired insulin secretion and FFA-induced apoptosis. Specifically, HGF exerted its protective effect by counteracting: (i) the overproduction of either hydrogen peroxide and superoxide anion, (ii) the reduction of intracellular γ-glutamylcysteinylglycine level, and (iii) the depolarization of mitochondrial membrane, induced by prolonged FFAs exposure. These effects appear to be mediated by bcl-2 and phosphatidylinositol 3 kinase (PI3K)/Akt pathways. Indeed, HGF increased mRNA and protein expression of bcl-2 downregulated by FFAs-treatment; moreover, pre-treatment with the specific PI3-kinase inhibitor LY294002, significantly abolished the protective effect of HGF. In conclusion, in rat insulin-producing RINm5F cells, HGF exerts its prosurvival effect by counteracting the increased intracellular oxidative stress and, consequently, by inhibiting apoptosis induced by chronic exposure to FFAs.

scholarly journals Inhibition of the Keap1/Nrf2 Signaling Pathway Significantly Promotes the Progression of Type 1 Diabetes Mellitus

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Yanmei Lou ◽  
Muyan Kong ◽  
Leyan Li ◽  
Yu Hu ◽  
Wenjun Zhai ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Signaling Pathway ◽  
Cell Damage ◽  
Pancreatic Β Cell ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Min6 Cells ◽  
Nrf2 Signaling Pathway

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by insulin deficiency due to pancreatic β-cell damage and leads to hyperglycemia. The precise molecular mechanisms of the etiology of T1DM are not completely understood. Oxidative stress and the antioxidant status of pancreatic β-cells play a vital role in the pathogenesis and progression of T1DM. The Keap1/Nrf2 signaling pathway plays a critical role in cellular resistance to oxidative stress. This study is aimed at investigating the role of the Keap1/Nrf2 signaling pathway in the progression of T1DM. An alloxan- (ALX-) stimulated T1DM animal model in wild-type (WT) and Nrf2 knockout (Nrf2-/-) C57BL/6J mice and a mouse pancreatic β-cell line (MIN6) were established. Compared with the tolerant (ALX exposure, nondiabetic) WT mice, the sensitive (ALX exposure, diabetic) WT mice exhibited higher blood glucose levels and lower plasma insulin levels. The Keap1/Nrf2 signaling pathway was significantly inhibited in the sensitive WT mice, which was reflected by overexpression of Keap1 and low expression of Nrf2, accompanied by a marked decrease in the expression of the antioxidative enzymes. Compared with WT mice, the Nrf2-/- mice had an increased incidence of T1DM and exhibited more severe pancreatic β-cell damage. The results of in vitro experiments showed that ALX significantly inhibited the viability and proliferation and promoted the apoptosis of MIN6 cells. ALX also markedly increased intracellular ROS production and caused DNA damage in MIN6 cells. In addition, the Keap1/Nrf2 signaling pathway was significantly inhibited in the damaged MIN6 cells. Moreover, Nrf2 silencing by transfection with Nrf2 siRNA markedly exacerbated ALX-induced MIN6 cell injury. Conclusively, this study demonstrates that inhibition of the Keap1/Nrf2 signaling pathway could significantly promote the incidence of T1DM. This study indicates that activation of Keap1/Nrf2 signaling in pancreatic β-cells may be a useful pharmacological strategy for the clinical prevention and treatment of T1DM.

scholarly journals Progesterone induces apoptosis of insulin-secreting cells: insights into the molecular mechanism

2014 ◽  
Vol 221 (2) ◽  
pp. 273-284 ◽  
Author(s):  
V A Nunes ◽  
E P Portioli-Sanches ◽  
M P Rosim ◽  
M S Araujo ◽  
P Praxedes-Garcia ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Dna Fragmentation ◽  
Islet Cells ◽  
Membrane Integrity ◽  
Reactive Species ◽  
Β Cells ◽  
Β Cell ◽  
Induced Apoptosis ◽  
Stress Dependent

Progesterone has been associated with the development of gestational diabetes (GD) due to the enhancement of insulin resistance. As β-cell apoptosis participates in type 1 and type 2 diabetes pathophysiology, we proposed the hypothesis that progesterone might contribute to the development of GD through a mechanism that also involves β-cell death. To address this question, RINm5F insulin-producing cells were incubated with progesterone (25–100 μM), in the presence or absence of α-tocopherol (40 μM). After 24 or 48 h, membrane integrity and DNA fragmentation were analyzed by flow cytometry. Caspase activity was used to identify the mode of cell death. The involvement of endoplasmic reticulum stress in the action of progesterone was investigated by western blotting. Oxidative stress was measured by 2',7'-dichlorofluorescein diacetate (DCFDA) oxidation. Isolated rat islets were used in similar experiments in order to confirm the effect of progesterone in primary β-cells. Incubation of RINm5F cells with progesterone increased the number of cells with loss of membrane integrity and DNA fragmentation. Progesterone induced generation of reactive species. Pre-incubation with α-tocopherol attenuated progesterone-induced apoptosis. Western blot analyses revealed increased expression of CREB2 and CHOP in progesterone-treated cells. Progesterone caused apoptotic death of rat islet cells and enhanced generation of reactive species. Our results show that progesterone can be toxic to pancreatic β-cells through an oxidative-stress-dependent mechanism that induces apoptosis. This effect may contribute to the development of GD during pregnancy, particularly under conditions that require administration of pharmacological doses of this hormone.

scholarly journals Antioxidant N-Acetylcysteine Protects Pancreatic β-Cells Against Aldosterone-Induced Oxidative Stress and Apoptosis in Female db/db Mice and Insulin-Producing MIN6 Cells

Endocrinology ◽  
2013 ◽  
Vol 154 (11) ◽  
pp. 4068-4077 ◽  
Author(s):  
Hui Min Jin ◽  
Dong Chi Zhou ◽  
Hui Fang Gu ◽  
Qing Yan Qiao ◽  
Shun Kun Fu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mineralocorticoid Receptor ◽  
Oxidative Stress Marker ◽  
Oral Glucose ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Mineralocorticoid Receptor Antagonist ◽  
Min6 Cells ◽  
Cell Dysfunction

Previous studies have shown that primary aldosteronism is associated with glucose-related metabolic disorders. However, the mechanisms by which aldosterone (ALDO) triggers β-cell dysfunction remains unclear. This study aimed to investigate whether oxidative stress is involved in and whether the antioxidant N-acetylcysteine (NAC) or the mineralocorticoid receptor antagonist spironolactone (SPL) could prevent or delay β-cell damage in vivo and in vitro. As expected, 8 weeks after ALDO treatment, 12-week-old female diabetic db/db mice exhibited impaired oral glucose tolerance, decreased β-cell mass, and heightened levels of oxidative stress marker (urinary 8-hydroxy-2′-deoxyguanosine). NAC reversed these symptoms completely, whereas SPL treatment did so only partially. After exposure to ALDO, the mouse pancreatic β-cell line MIN6 exhibited decreased viability and increased caspase-3 activity, as well as reduced expression of Bcl-2/Bax and p-AKT, even if mineralocorticoid receptor was completely suppressed with small interfering RNA. NAC, but not SPL, suppressed oxidative stress in MIN6 cells, as revealed by the decrease in inducible NOS levels and expression of the proteins p22-phox and p67-phox. These findings suggest that oxidative stress may be involved in ALDO-induced β-cell dysfunction and that NAC, but not SPL, may protect pancreatic β-cells of mice from ALDO-induced oxidative stress and apoptosis in a manner independent of its receptor.

scholarly journals PDX1LOW MAFALOW β-cells contribute to islet function and insulin release

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Daniela Nasteska ◽  
Nicholas H. F. Fine ◽  
Fiona B. Ashford ◽  
Federica Cuozzo ◽  
Katrina Viloria ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Release ◽  
Metabolic Stress ◽  
Human Islets ◽  
Islet Function ◽  
Β Cells ◽  
Β Cell ◽  
Ionic Fluxes ◽  
Transcriptomic Level ◽  
Adult Islet

AbstractTranscriptionally mature and immature β-cells co-exist within the adult islet. How such diversity contributes to insulin release remains poorly understood. Here we show that subtle differences in β-cell maturity, defined using PDX1 and MAFA expression, contribute to islet operation. Functional mapping of rodent and human islets containing proportionally more PDX1HIGH and MAFAHIGH β-cells reveals defects in metabolism, ionic fluxes and insulin secretion. At the transcriptomic level, the presence of increased numbers of PDX1HIGH and MAFAHIGH β-cells leads to dysregulation of gene pathways involved in metabolic processes. Using a chemogenetic disruption strategy, differences in PDX1 and MAFA expression are shown to depend on islet Ca2+ signaling patterns. During metabolic stress, islet function can be restored by redressing the balance between PDX1 and MAFA levels across the β-cell population. Thus, preserving heterogeneity in PDX1 and MAFA expression, and more widely in β-cell maturity, might be important for the maintenance of islet function.

scholarly journals Furin controls β cell function via mTORC1 signaling

2020 ◽  
Author(s):  
Bas Brouwers ◽  
Ilaria Coppola ◽  
Katlijn Vints ◽  
Bastian Dislich ◽  
Nathalie Jouvet ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Cell Function ◽  
Mammalian Target Of Rapamycin ◽  
Human Islets ◽  
Β Cells ◽  
Β Cell ◽  
Differential Proteomics ◽  
Atpase Subunit ◽  
Proteolytic Activation ◽  
Mtorc1 Signaling

AbstractFurin is a proprotein convertase (PC) responsible for proteolytic activation of a wide array of precursor proteins within the secretory pathway. It maps to the PRC1 locus, a type 2 diabetes susceptibility locus, yet its specific role in pancreatic β cells is largely unknown. The aim of this study was to determine the role of furin in glucose homeostasis. We show that furin is highly expressed in human islets, while PCs that potentially could provide redundancy are expressed at considerably lower levels. β cell-specific furin knockout (βfurKO) mice are glucose intolerant, due to smaller islets with lower insulin content and abnormal dense core secretory granule morphology. RNA expression analysis and differential proteomics on βfurKO islets revealed activation of Activating Transcription Factor 4 (ATF4), which was mediated by mammalian target of rapamycin C1 (mTORC1). βfurKO cells show impaired cleavage of the essential V-ATPase subunit Ac45, and by blocking this pump in β cells the mTORC1 pathway is activated. Furthermore, βfurKO cells show lack of insulin receptor cleavage and impaired response to insulin. Taken together, these results suggest a model of mTORC1-ATF4 hyperactivation in β cells lacking furin, which causes β cell dysfunction.

scholarly journals Lipotoxicity and β-Cell Failure in Type 2 Diabetes: Oxidative Stress Linked to NADPH Oxidase and ER Stress

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3328
Author(s):  
Eloisa Aparecida Vilas-Boas ◽  
Davidson Correa Almeida ◽  
Leticia Prates Roma ◽  
Fernanda Ortis ◽  
Angelo Rafael Carpinelli
Keyword(s):  
Oxidative Stress ◽  
Type 2 Diabetes ◽  
Nadph Oxidase ◽  
Er Stress ◽  
Cell Function ◽  
Caloric Intake ◽  
Β Cells ◽  
Β Cell ◽  
Β Cell Function

A high caloric intake, rich in saturated fats, greatly contributes to the development of obesity, which is the leading risk factor for type 2 diabetes (T2D). A persistent caloric surplus increases plasma levels of fatty acids (FAs), especially saturated ones, which were shown to negatively impact pancreatic β-cell function and survival in a process called lipotoxicity. Lipotoxicity in β-cells activates different stress pathways, culminating in β-cells dysfunction and death. Among all stresses, endoplasmic reticulum (ER) stress and oxidative stress have been shown to be strongly correlated. One main source of oxidative stress in pancreatic β-cells appears to be the reactive oxygen species producer NADPH oxidase (NOX) enzyme, which has a role in the glucose-stimulated insulin secretion and in the β-cell demise during both T1 and T2D. In this review, we focus on the acute and chronic effects of FAs and the lipotoxicity-induced β-cell failure during T2D development, with special emphasis on the oxidative stress induced by NOX, the ER stress, and the crosstalk between NOX and ER stress.

scholarly journals Human EndoC-βH1 β-cells form pseudoislets with improved glucose sensitivity and enhanced GLP-1 signaling in the presence of islet-derived endothelial cells

2018 ◽  
Vol 314 (5) ◽  
pp. E512-E521 ◽  
Author(s):  
Michael G. Spelios ◽  
Lauren A. Afinowicz ◽  
Regine C. Tipon ◽  
Eitan M. Akirav
Keyword(s):  
Endothelial Cells ◽  
Insulin Secretion ◽  
Cell Biology ◽  
Three Dimensional ◽  
Cell Types ◽  
Human Islets ◽  
Glucose Sensing ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Levels

Three-dimensional (3D) pseudoislets (PIs) can be used for the study of insulin-producing β-cells in free-floating islet-like structures similar to that of primary islets. Previously, we demonstrated the ability of islet-derived endothelial cells (iECs) to induce PIs using murine insulinomas, where PI formation enhanced insulin production and glucose responsiveness. In this report, we examined the ability of iECs to spontaneously induce the formation of free-floating 3D PIs using the EndoC-βH1 human β-cell line murine MS1 iEC. Within 14 days, the coculturing of both cell types produced fully humanized EndoC-βH1 PIs with little to no contaminating murine iECs. The size and shape of these PIs were similar to primary human islets. iEC-induced PIs demonstrated reduced dysregulated insulin release under low glucose levels and higher insulin secretion in response to high glucose and exendin-4 [a glucagon-like peptide-1 (GLP-1) analog] compared with monolayer cells cultured alone. Interestingly, iEC-PIs were also better at glucose sensing in the presence of extendin-4 compared with PIs generated on a low-adhesion surface plate in the absence of iECs and showed an overall improvement in cell viability. iEC-induced PIs exhibited increased expression of key genes involved in glucose transport, glucose sensing, β-cell differentiation, and insulin processing, with a concomitant decrease in glucagon mRNA expression. The enhanced responsiveness to exendin-4 was associated with increased protein expression of GLP-1 receptor and phosphokinase A. This rapid coculture system provides an unlimited number of human PIs with improved insulin secretion and GLP-1 responsiveness for the study of β-cell biology.

Sign in / Sign up

Export Citation Format

Share Document