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Stancill JS, Hansen PA, Mathison AJ, Schmidt EE, Corbett JA. Deletion of Thioredoxin Reductase Disrupts Redox Homeostasis and Impairs β-Cell Function. FUNCTION (OXFORD, ENGLAND) 2022; 3:zqac034. [PMID: 35873655 PMCID: PMC9301323 DOI: 10.1093/function/zqac034] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/17/2022] [Accepted: 06/27/2022] [Indexed: 01/07/2023]
Abstract
Reactive oxygen species (ROS) have been implicated as mediators of pancreatic β-cell damage. While β-cells are thought to be vulnerable to oxidative damage, we have shown, using inhibitors and acute depletion, that thioredoxin reductase, thioredoxin, and peroxiredoxins are the primary mediators of antioxidant defense in β-cells. However, the role of this antioxidant cycle in maintaining redox homeostasis and β-cell survival in vivo remains unclear. Here, we generated mice with a β-cell specific knockout of thioredoxin reductase 1 (Txnrd1fl/fl; Ins1Cre/+ , βKO). Despite blunted glucose-stimulated insulin secretion, knockout mice maintain normal whole-body glucose homeostasis. Unlike pancreatic islets with acute Txnrd1 inhibition, βKO islets do not demonstrate increased sensitivity to ROS. RNA-sequencing analysis revealed that Txnrd1-deficient β-cells have increased expression of nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated genes, and altered expression of genes involved in heme and glutathione metabolism, suggesting an adaptive response. Txnrd1-deficient β-cells also have decreased expression of factors controlling β-cell function and identity which may explain the mild functional impairment. Together, these results suggest that Txnrd1-knockout β-cells compensate for loss of this essential antioxidant pathway by increasing expression of Nrf2-regulated antioxidant genes, allowing for protection from excess ROS at the expense of normal β-cell function and identity.
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Affiliation(s)
| | - Polly A Hansen
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, 53226, USA
| | - Angela J Mathison
- Genomic Sciences and Precision Medicine Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA,Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Edward E Schmidt
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MN 59717, USA,Redox Biology Laboratory, University of Veterinary Medicine, Budapest 1078, Hungary
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Oxidative stress and impaired insulin secretion in cystic fibrosis pig pancreas. ADVANCES IN REDOX RESEARCH 2022; 5. [PMID: 35903252 PMCID: PMC9328447 DOI: 10.1016/j.arres.2022.100040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cystic fibrosis-related diabetes (CFRD) is one the most common comorbidities in cystic fibrosis (CF). Pancreatic oxidative stress has been postulated in the pathogenesis of CFRD, but no studies have been done to show an association. The main obstacle is the lack of suitable animal models and no immediate availability of pancreas tissue in humans. In the CF porcine model, we found increased pancreatic total glutathione (GSH), glutathione disulfide (GSSG), 3-nitrotyrosine- and 4-hydroxynonenal-modified proteins, and decreased copper zinc superoxide dismutase (CuZnSOD) activity, all indicative of oxidative stress. CF pig pancreas demonstrated increased DHE oxidation (as a surrogate marker of superoxide) in situ compared to non-CF and this was inhibited by a SOD-mimetic (GC4401). Catalase and glutathione peroxidase activities were not different between CF and non-CF pancreas. Isolated CF pig islets had significantly increased DHE oxidation, peroxide production, reduced insulin secretion in response to high glucose and diminished secretory index compared to non-CF islets. Acute treatment with apocynin or an SOD mimetic failed to restore insulin secretion. These results are consistent with the hypothesis that CF pig pancreas is under significant oxidative stress as a result of increased O2●− and peroxides combined with reduced antioxidant defenses against reactive oxygen species (ROS). We speculate that insulin secretory defects in CF may be due to oxidative stress.
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Eguchi N, Vaziri ND, Dafoe DC, Ichii H. The Role of Oxidative Stress in Pancreatic β Cell Dysfunction in Diabetes. Int J Mol Sci 2021; 22:ijms22041509. [PMID: 33546200 PMCID: PMC7913369 DOI: 10.3390/ijms22041509] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/29/2021] [Accepted: 01/30/2021] [Indexed: 02/07/2023] Open
Abstract
Diabetes is a chronic metabolic disorder characterized by inappropriately elevated glucose levels as a result of impaired pancreatic β cell function and insulin resistance. Extensive studies have been conducted to elucidate the mechanism involved in the development of β cell failure and death under diabetic conditions such as hyperglycemia, hyperlipidemia, and inflammation. Of the plethora of proposed mechanisms, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and oxidative stress have been shown to play a central role in promoting β cell dysfunction. It has become more evident in recent years that these 3 factors are closely interrelated and importantly aggravate each other. Oxidative stress in particular is of great interest to β cell health and survival as it has been shown that β cells exhibit lower antioxidative capacity. Therefore, this review will focus on discussing factors that contribute to the development of oxidative stress in pancreatic β cells and explore the downstream effects of oxidative stress on β cell function and health. Furthermore, antioxidative capacity of β cells to counteract these effects will be discussed along with new approaches focused on preserving β cells under oxidative conditions.
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Affiliation(s)
- Natsuki Eguchi
- Department of Surgery, University of California, Irvine, CA 92697, USA; (N.E.); (D.C.D.)
| | | | - Donald C. Dafoe
- Department of Surgery, University of California, Irvine, CA 92697, USA; (N.E.); (D.C.D.)
| | - Hirohito Ichii
- Department of Surgery, University of California, Irvine, CA 92697, USA; (N.E.); (D.C.D.)
- Correspondence: ; Tel.: +1-714-456-8590
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Stancill JS, Corbett JA. The Role of Thioredoxin/Peroxiredoxin in the β-Cell Defense Against Oxidative Damage. Front Endocrinol (Lausanne) 2021; 12:718235. [PMID: 34557160 PMCID: PMC8453158 DOI: 10.3389/fendo.2021.718235] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/19/2021] [Indexed: 02/02/2023] Open
Abstract
Oxidative stress is hypothesized to play a role in pancreatic β-cell damage, potentially contributing to β-cell dysfunction and death in both type 1 and type 2 diabetes. Oxidative stress arises when naturally occurring reactive oxygen species (ROS) are produced at levels that overwhelm the antioxidant capacity of the cell. ROS, including superoxide and hydrogen peroxide, are primarily produced by electron leak during mitochondrial oxidative metabolism. Additionally, peroxynitrite, an oxidant generated by the reaction of superoxide and nitric oxide, may also cause β-cell damage during autoimmune destruction of these cells. β-cells are thought to be susceptible to oxidative damage based on reports that they express low levels of antioxidant enzymes compared to other tissues. Furthermore, markers of oxidative damage are observed in islets from diabetic rodent models and human patients. However, recent studies have demonstrated high expression of various isoforms of peroxiredoxins, thioredoxin, and thioredoxin reductase in β-cells and have provided experimental evidence supporting a role for these enzymes in promoting β-cell function and survival in response to a variety of oxidative stressors. This mini-review will focus on the mechanism by which thioredoxins and peroxiredoxins detoxify ROS and on the protective roles of these enzymes in β-cells. Additionally, we speculate about the role of this antioxidant system in promoting insulin secretion.
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Stancill JS, Happ JT, Broniowska KA, Hogg N, Corbett JA. Peroxiredoxin 1 plays a primary role in protecting pancreatic β-cells from hydrogen peroxide and peroxynitrite. Am J Physiol Regul Integr Comp Physiol 2020; 318:R1004-R1013. [PMID: 32292063 DOI: 10.1152/ajpregu.00011.2020] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Both reactive nitrogen and oxygen species (RNS and ROS), such as nitric oxide, peroxynitrite, and hydrogen peroxide, have been implicated as mediators of pancreatic β-cell damage during the pathogenesis of autoimmune diabetes. While β-cells are thought to be vulnerable to oxidative damage due to reportedly low levels of antioxidant enzymes, such as catalase and glutathione peroxidase, we have shown that they use thioredoxin reductase to detoxify hydrogen peroxide. Thioredoxin reductase is an enzyme that participates in the peroxiredoxin antioxidant cycle. Peroxiredoxins are expressed in β-cells and, when overexpressed, protect against oxidative stress, but the endogenous roles of peroxiredoxins in the protection of β-cells from oxidative damage are unclear. Here, using either glucose oxidase or menadione to continuously deliver hydrogen peroxide, or the combination of dipropylenetriamine NONOate and menadione to continuously deliver peroxynitrite, we tested the hypothesis that β-cells use peroxiredoxins to detoxify both of these reactive species. Either pharmacological peroxiredoxin inhibition with conoidin A or specific depletion of cytoplasmic peroxiredoxin 1 (Prdx1) using siRNAs sensitizes INS 832/13 cells and rat islets to DNA damage and death induced by hydrogen peroxide or peroxynitrite. Interestingly, depletion of peroxiredoxin 2 (Prdx2) had no effect. Together, these results suggest that β-cells use cytoplasmic Prdx1 as a primary defense mechanism against both ROS and RNS.
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Affiliation(s)
- Jennifer S Stancill
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - John T Happ
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | | | - Neil Hogg
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - John A Corbett
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
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Good AL, Stoffers DA. Stress-Induced Translational Regulation Mediated by RNA Binding Proteins: Key Links to β-Cell Failure in Diabetes. Diabetes 2020; 69:499-507. [PMID: 32198193 PMCID: PMC7085242 DOI: 10.2337/dbi18-0068] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 01/16/2020] [Indexed: 12/21/2022]
Abstract
In type 2 diabetes, β-cells endure various forms of cellular stress, including oxidative stress and endoplasmic reticulum stress, secondary to increased demand for insulin production and extracellular perturbations, including hyperglycemia. Chronic exposure to stress causes impaired insulin secretion, apoptosis, and loss of cell identity, and a combination of these processes leads to β-cell failure and severe hyperglycemia. Therefore, a better understanding of the molecular mechanisms underlying stress responses in β-cells promises to reveal new therapeutic opportunities for type 2 diabetes. In this perspective, we discuss posttranscriptional control of gene expression as a critical, but underappreciated, layer of regulation with broad importance during stress responses. Specifically, regulation of mRNA translation occurs pervasively during stress to activate gene expression programs; however, the convenience of RNA sequencing has caused translational regulation to be overlooked compared with transcriptional controls. We highlight the role of RNA binding proteins in shaping selective translational regulation during stress and the mechanisms underlying this level of regulation. A growing body of evidence indicates that RNA binding proteins control an array of processes in β-cells, including the synthesis and secretion of insulin. Therefore, systematic evaluations of translational regulation and the upstream factors shaping this level of regulation are critical areas of investigation to expand our understanding of β-cell failure in type 2 diabetes.
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Affiliation(s)
- Austin L Good
- Institute for Diabetes, Obesity, and Metabolism and Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Doris A Stoffers
- Institute for Diabetes, Obesity, and Metabolism and Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
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Oleson BJ, Corbett JA. Can insulin secreting pancreatic β-cells provide novel insights into the metabolic regulation of the DNA damage response? Biochem Pharmacol 2020; 176:113907. [PMID: 32171728 DOI: 10.1016/j.bcp.2020.113907] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/06/2020] [Indexed: 12/18/2022]
Abstract
Insulin, produced by pancreatic β-cells, is responsible for the control of whole-body glucose metabolism. Insulin is secreted by pancreatic β-cells in a tightly regulated process that is controlled by the serum level of glucose, glucose sensing and glucose oxidative metabolism. The regulation of intermediary metabolism in β-cells is unique as these cells oxidize glucose to CO2 on substrate supply while mitochondrial oxidative metabolism occurs on demand, for the production of intermediates or energy production, in most cell types. This review discusses recent findings that the regulation of intermediary metabolism by nitric oxide attenuates the DNA damage response (DDR) and DNA damage-dependent apoptosis in a β-cell selective manner. Specific focus is placed on the mechanisms by which iNOS derived nitric oxide (low micromolar levels) regulates DDR activation via the inhibition of intermediary metabolism. The physiological significance of the association of metabolism, nitric oxide and DDR signaling for cancer biology and diabetes is discussed.
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Affiliation(s)
- Bryndon J Oleson
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - John A Corbett
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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The Role of Metabolic Flexibility in the Regulation of the DNA Damage Response by Nitric Oxide. Mol Cell Biol 2019; 39:MCB.00153-19. [PMID: 31235477 DOI: 10.1128/mcb.00153-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 06/18/2019] [Indexed: 12/24/2022] Open
Abstract
In this report, we show that nitric oxide suppresses DNA damage response (DDR) signaling in the pancreatic β-cell line INS 832/13 and rat islets by inhibiting intermediary metabolism. Nitric oxide is known to inhibit complex IV of the electron transport chain and aconitase of the Krebs cycle. Non-β cells compensate by increasing glycolytic metabolism to maintain ATP levels; however, β cells lack this metabolic flexibility, resulting in a nitric oxide-dependent decrease in ATP and NAD+ Like nitric oxide, mitochondrial toxins inhibit DDR signaling in β cells by a mechanism that is associated with a decrease in ATP. Non-β cells compensate for the effects of mitochondrial toxins with an adaptive shift to glycolytic ATP generation that allows for DDR signaling. Forcing non-β cells to derive ATP via mitochondrial respiration (replacing glucose with galactose in the medium) and glucose deprivation sensitizes these cells to nitric oxide-mediated inhibition of DDR signaling. These findings indicate that metabolic flexibility is necessary to maintain DDR signaling under conditions in which mitochondrial oxidative metabolism is inhibited and support the inhibition of oxidative metabolism (decreased ATP) as one protective mechanism by which nitric oxide attenuates DDR-dependent β-cell apoptosis.
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Newsholme P, Keane KN, Carlessi R, Cruzat V. Oxidative stress pathways in pancreatic β-cells and insulin-sensitive cells and tissues: importance to cell metabolism, function, and dysfunction. Am J Physiol Cell Physiol 2019; 317:C420-C433. [PMID: 31216193 DOI: 10.1152/ajpcell.00141.2019] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It is now accepted that nutrient abundance in the blood, especially glucose, leads to the generation of reactive oxygen species (ROS), ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensatory response from antioxidant mechanisms, the cell, or indeed the tissue, becomes overwhelmed by oxidative stress, leading to the activation of intracellular stress-associated pathways. Activation of the same or similar pathways also appears to play a role in mediating insulin resistance, impaired insulin secretion, and late diabetic complications. The ability of antioxidants to protect against the oxidative stress induced by hyperglycemia and elevated free fatty acid (FFA) levels in vitro suggests a causative role of oxidative stress in mediating the latter clinical conditions. In this review, we describe common biochemical processes associated with oxidative stress driven by hyperglycemia and/or elevated FFA and the resulting clinical outcomes: β-cell dysfunction and peripheral tissue insulin resistance.
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Affiliation(s)
- Philip Newsholme
- School of Pharmacy and Biomedical Sciences, and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Kevin N Keane
- School of Pharmacy and Biomedical Sciences, and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Rodrigo Carlessi
- School of Pharmacy and Biomedical Sciences, and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Vinicius Cruzat
- Faculty of Health, Torrens University Australia, Melbourne, Victoria, Australia
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Stancill JS, Broniowska KA, Oleson BJ, Naatz A, Corbett JA. Pancreatic β-cells detoxify H 2O 2 through the peroxiredoxin/thioredoxin antioxidant system. J Biol Chem 2019; 294:4843-4853. [PMID: 30659092 DOI: 10.1074/jbc.ra118.006219] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 01/15/2019] [Indexed: 01/07/2023] Open
Abstract
Oxidative stress is thought to promote pancreatic β-cell dysfunction and contribute to both type 1 and type 2 diabetes. Reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, are mediators of oxidative stress that arise largely from electron leakage during oxidative phosphorylation. Reports that β-cells express low levels of antioxidant enzymes, including catalase and GSH peroxidases, have supported a model in which β-cells are ill-equipped to detoxify ROS. This hypothesis seems at odds with the essential role of β-cells in the control of metabolic homeostasis and organismal survival through exquisite coupling of oxidative phosphorylation, a prominent ROS-producing pathway, to insulin secretion. Using glucose oxidase to deliver H2O2 continuously over time and Amplex Red to measure extracellular H2O2 concentration, we found here that β-cells can remove micromolar levels of this oxidant. This detoxification pathway utilizes the peroxiredoxin/thioredoxin antioxidant system, as selective chemical inhibition or siRNA-mediated depletion of thioredoxin reductase sensitized β-cells to continuously generated H2O2 In contrast, when delivered as a bolus, H2O2 induced the DNA damage response, depleted cellular energy stores, and decreased β-cell viability independently of thioredoxin reductase inhibition. These findings show that β-cells have the capacity to detoxify micromolar levels of H2O2 through a thioredoxin reductase-dependent mechanism and are not as sensitive to oxidative damage as previously thought.
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Affiliation(s)
- Jennifer S Stancill
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Katarzyna A Broniowska
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Bryndon J Oleson
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Aaron Naatz
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - John A Corbett
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Oleson BJ, Corbett JA. Dual Role of Nitric Oxide in Regulating the Response of β Cells to DNA Damage. Antioxid Redox Signal 2018; 29:1432-1445. [PMID: 28978225 PMCID: PMC6166691 DOI: 10.1089/ars.2017.7351] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 09/09/2017] [Indexed: 01/09/2023]
Abstract
SIGNIFICANCE Cytokines released in and around pancreatic islets during islet inflammation are believed to contribute to impaired β cell function and β cell death during the development of diabetes. Nitric oxide, produced by β cells in response to cytokine exposure, controls many of the responses of β cells during islet inflammation. Recent Advances: Although nitric oxide has been shown to inhibit insulin secretion and oxidative metabolism and induce DNA damage in β cells, it also activates protective pathways that promote recovery of insulin secretion and oxidative metabolism and repair of damaged DNA. Recent studies have identified a novel role for nitric oxide in selectively regulating the DNA damage response in β cells. CRITICAL ISSUES Does nitric oxide mediate cytokine-induced β cell damage, or is nitric oxide produced by β cells in response to cytokines to protect β cells from damage? FUTURE DIRECTIONS β cells appear to be the only islet endocrine cell type capable of responding to proinflammatory cytokines with the production of nitric oxide, and these terminally differentiated cells have a limited capacity to regenerate. It is likely that there is a physiological purpose for this response, and understanding this could open new areas of study regarding the loss of functional β cell mass during diabetes development.
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Affiliation(s)
- Bryndon J. Oleson
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - John A. Corbett
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
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Barlow J, Solomon TPJ, Affourtit C. Pro-inflammatory cytokines attenuate glucose-stimulated insulin secretion from INS-1E insulinoma cells by restricting mitochondrial pyruvate oxidation capacity - Novel mechanistic insight from real-time analysis of oxidative phosphorylation. PLoS One 2018; 13:e0199505. [PMID: 29953508 PMCID: PMC6023166 DOI: 10.1371/journal.pone.0199505] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 06/10/2018] [Indexed: 11/30/2022] Open
Abstract
Pro-inflammatory cytokines cause pancreatic beta cell failure during the development of type 2 diabetes. This beta cell failure associates with mitochondrial dysfunction, but the precise effects of cytokines on mitochondrial respiration remain unclear. To test the hypothesis that pro-inflammatory cytokines impair glucose-stimulated insulin secretion (GSIS) by inhibiting oxidative ATP synthesis, we probed insulin release and real-time mitochondrial respiration in rat INS-1E insulinoma cells that were exposed to a combination of 2 ng/mL interleukin-1-beta and 50 ng/mL interferon-gamma. We show that 24-h exposure to these cytokines dampens both glucose- and pyruvate-stimulated insulin secretion (P < 0.0001 and P < 0.05, respectively), but does not affect KCl-induced insulin release. Mirroring secretory defects, glucose- and pyruvate-stimulated mitochondrial respiration are lowered after cytokine exposure (P < 0.01). Further analysis confirms that cytokine-induced mitochondrial respiratory defects occur irrespective of whether fuel oxidation is coupled to, or uncoupled from, ATP synthesis. These observations demonstrate that pro-inflammatory cytokines attenuate GSIS by restricting mitochondrial pyruvate oxidation capacity. Interleukin-1-beta and interferon-gamma also increase mitochondrial superoxide levels (P < 0.05), which may reinforce the inhibition of pyruvate oxidation, and cause a modest (20%) but significant (P < 0.01) loss of INS-1E cells. Cytokine-induced INS-1E cell failure is insensitive to palmitoleate and linoleate, which is at odds with the cytoprotection offered by unsaturated fatty acids against harm caused by nutrient excess. Our data disclose a mitochondrial mechanism for cytokine-impaired GSIS in INS-1E cells, and suggest that inflammatory and nutrient-related beta cell failure emerge, at least partly, through distinct paths.
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Affiliation(s)
- Jonathan Barlow
- School of Biomedical and Healthcare Sciences, University of Plymouth, Plymouth, United Kingdom
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Thomas P. J. Solomon
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
- Institute for Metabolism and Systems Research (IMSR), University of Birmingham, Birmingham, United Kingdom
| | - Charles Affourtit
- School of Biomedical and Healthcare Sciences, University of Plymouth, Plymouth, United Kingdom
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Oleson BJ, Naatz A, Proudfoot SC, Yeo CT, Corbett JA. Role of Protein Phosphatase 1 and Inhibitor of Protein Phosphatase 1 in Nitric Oxide-Dependent Inhibition of the DNA Damage Response in Pancreatic β-Cells. Diabetes 2018; 67:898-910. [PMID: 29444892 PMCID: PMC5909998 DOI: 10.2337/db17-1062] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 02/02/2018] [Indexed: 11/13/2022]
Abstract
Nitric oxide is produced at micromolar levels by pancreatic β-cells during exposure to proinflammatory cytokines. While classically viewed as damaging, nitric oxide also activates pathways that promote β-cell survival. We have shown that nitric oxide, in a cell type-selective manner, inhibits the DNA damage response (DDR) and, in doing so, protects β-cells from DNA damage-induced apoptosis. This study explores potential mechanisms by which nitric oxide inhibits DDR signaling. We show that inhibition of DDR signaling (measured by γH2AX formation and the phosphorylation of KAP1) is selective for nitric oxide, as other forms of reactive oxygen/nitrogen species do not impair DDR signaling. The kinetics and broad range of DDR substrates that are inhibited suggest that protein phosphatase activation may be one mechanism by which nitric oxide attenuates DDR signaling in β-cells. While protein phosphatase 1 (PP1) is a primary regulator of DDR signaling and an inhibitor of PP1 (IPP1) is selectively expressed only in β-cells, disruption of either IPP1 or PP1 does not modify the inhibitory actions of nitric oxide on DDR signaling in β-cells. These findings support a PP1-independent mechanism by which nitric oxide selectively impairs DDR signaling and protects β-cells from DNA damage-induced apoptosis.
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Affiliation(s)
- Bryndon J Oleson
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI
| | - Aaron Naatz
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI
| | - Sarah C Proudfoot
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI
| | - Chay Teng Yeo
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI
| | - John A Corbett
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI
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Xuan X, Gao F, Ma X, Huang C, Wang Y, Deng H, Wang S, Li W, Yuan L. Activation of ACE2/angiotensin (1-7) attenuates pancreatic β cell dedifferentiation in a high-fat-diet mouse model. Metabolism 2018; 81:83-96. [PMID: 29225087 DOI: 10.1016/j.metabol.2017.12.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 11/14/2017] [Accepted: 12/03/2017] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Angiotensin-converting enzyme 2 (ACE2) has been identified in pancreatic islets and can preserve β cells. In this study, we aimed to examine the possible role of ACE2 and its end product, angiotensin 1-7 (A1-7), in reducing β cell dedifferentiation during metabolic stress. METHODS First, a lineage-tracing experiment was performed to track β cells in mice fed a high-fat diet (HFD). Second, the ACE2/A1-7 axis was evaluated in the HFD mouse model. Intraperitoneal glucose tolerance tests (IPGTTs) and intraperitoneal insulin tolerance tests (IPITTs) were conducted. Phenotypic changes in β cells were detected by immunohistochemistry and quantitative real-time PCR. Pancreatic sections were immunostained for vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS). Finally, the effects of the ACE2/A1-7 axis were explored in isolated mouse islets exposed to different concentrations of glucose. Glucose-stimulated insulin release and levels of insulin mRNA and OCT4 mRNA were measured. RESULTS Pancreatic β cell dedifferentiation occurred both in vitro and in vivo in response to metabolic stress and was accompanied by ACE2 reduction. HFD-induced insulin resistance and glucose intolerance were exacerbated in ACE2-knockout (ACE2KO) mice but were alleviated by exogenous A1-7 in C57BL/6J mice. Approximately 20% of β cells were dedifferentiated in ACE2KO mice fed a standard rodent chow diet (SD). A higher percentage of dedifferentiated β cells was detected in ACE2KO mice than in wild-type (WT) mice under HFD conditions. In contrast, the administration of A1-7 alleviated HFD-induced β cell dedifferentiation in C57BL/6J mice. Moreover, the exogenous injection of A1-7 improved microcirculation in islets and decreased the production of iNOS in islets of C57BL/6J mice fed an HFD. Additionally, ACE2 was found to be mainly expressed in α cells of mice, while Mas, the receptor of A1-7, was distributed in β cells. CONCLUSIONS Overall, this study is the first to demonstrate that the ACE2/A1-7/Mas axis may be one of the intra-islet paracrine mechanisms of communication between α and β cells. Enhancing the ACE2/A1-7 axis exerts a protective effect by ameliorating β cell dedifferentiation, and this effect might be partially mediated through improvements in islet microcirculation and suppression of islet iNOS.
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Affiliation(s)
- Xiuping Xuan
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Fei Gao
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Xiaoyi Ma
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Chenghu Huang
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Ying Wang
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Hongjun Deng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Shiqi Wang
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Wencun Li
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Li Yuan
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
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15
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Oleson BJ, Broniowska KA, Naatz A, Hogg N, Tarakanova VL, Corbett JA. Nitric Oxide Suppresses β-Cell Apoptosis by Inhibiting the DNA Damage Response. Mol Cell Biol 2016; 36:2067-77. [PMID: 27185882 PMCID: PMC4946431 DOI: 10.1128/mcb.00262-16] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 05/12/2016] [Indexed: 12/15/2022] Open
Abstract
Nitric oxide, produced in pancreatic β cells in response to proinflammatory cytokines, plays a dual role in the regulation of β-cell fate. While nitric oxide induces cellular damage and impairs β-cell function, it also promotes β-cell survival through activation of protective pathways that promote β-cell recovery. In this study, we identify a novel mechanism in which nitric oxide prevents β-cell apoptosis by attenuating the DNA damage response (DDR). Nitric oxide suppresses activation of the DDR (as measured by γH2AX formation and the phosphorylation of KAP1 and p53) in response to multiple genotoxic agents, including camptothecin, H2O2, and nitric oxide itself, despite the presence of DNA damage. While camptothecin and H2O2 both induce DDR activation, nitric oxide suppresses only camptothecin-induced apoptosis and not H2O2-induced necrosis. The ability of nitric oxide to suppress the DDR appears to be selective for pancreatic β cells, as nitric oxide fails to inhibit DDR signaling in macrophages, hepatocytes, and fibroblasts, three additional cell types examined. While originally described as the damaging agent responsible for cytokine-induced β-cell death, these studies identify a novel role for nitric oxide as a protective molecule that promotes β-cell survival by suppressing DDR signaling and attenuating DNA damage-induced apoptosis.
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Affiliation(s)
- Bryndon J Oleson
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | | | - Aaron Naatz
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Neil Hogg
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Vera L Tarakanova
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - John A Corbett
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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16
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Gurgul-Convey E, Lenzen S. Is nitric oxide really the primary mediator of pancreatic β-cell death in type 1 diabetes? J Biol Chem 2015; 290:10570. [PMID: 25888569 DOI: 10.1074/jbc.l115.648089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Ewa Gurgul-Convey
- Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany
| | - Sigurd Lenzen
- Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany
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