65 results on '"Gurzov EN"'
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2. Death protein 5 and p53-upregulated modulator of apoptosis mediate the endoplasmic reticulum stress-mitochondrial dialog triggering lipotoxic rodent and human β-cell apoptosis.
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Cunha DA, Igoillo-Esteve M, Gurzov EN, Germano CM, Naamane N, Marhfour I, Fukaya M, Vanderwinden JM, Gysemans C, Mathieu C, Marselli L, Marchetti P, Harding HP, Ron D, Eizirik DL, Cnop M, Cunha, Daniel A, Igoillo-Esteve, Mariana, Gurzov, Esteban N, and Germano, Carla M
- Abstract
Environmental factors such as diets rich in saturated fats contribute to dysfunction and death of pancreatic β-cells in diabetes. Endoplasmic reticulum (ER) stress is elicited in β-cells by saturated fatty acids. Here we show that palmitate-induced β-cell apoptosis is mediated by the intrinsic mitochondrial pathway. By microarray analysis, we identified a palmitate-triggered ER stress gene expression signature and the induction of the BH3-only proteins death protein 5 (DP5) and p53-upregulated modulator of apoptosis (PUMA). Knockdown of either protein reduced cytochrome c release, caspase-3 activation, and apoptosis in rat and human β-cells. DP5 induction depends on inositol-requiring enzyme 1 (IRE1)-dependent c-Jun NH₂-terminal kinase and PKR-like ER kinase (PERK)-induced activating transcription factor (ATF3) binding to its promoter. PUMA expression is also PERK/ATF3-dependent, through tribbles 3 (TRB3)-regulated AKT inhibition and FoxO3a activation. DP5(-/-) mice are protected from high fat diet-induced loss of glucose tolerance and have twofold greater pancreatic β-cell mass. This study elucidates the crosstalk between lipotoxic ER stress and the mitochondrial pathway of apoptosis that causes β-cell death in diabetes. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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3. PTPN2, a candidate gene for type 1 diabetes, modulates pancreatic β-cell apoptosis via regulation of the BH3-only protein Bim.
- Author
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Santin I, Moore F, Colli ML, Gurzov EN, Marselli L, Marchetti P, Eizirik DL, Santin, Izortze, Moore, Fabrice, Colli, Maikel L, Gurzov, Esteban N, Marselli, Lorella, Marchetti, Piero, and Eizirik, Decio L
- Abstract
Objective: Genome-wide association studies allowed the identification of several associations between specific loci and type 1 diabetes (T1D). However, the mechanisms by which most candidate genes predispose to T1D remain unclear. We presently evaluated the mechanisms by which PTPN2, a candidate gene for T1D, modulates β-cell apoptosis after exposure to type I and II interferons (IFNs), cytokines that contribute to β-cell loss in early T1D.Research Design and Methods: Small interfering RNAs were used to inhibit PTPN2, STAT1, Bim, and Jun NH(2)-terminal kinase 1 (JNK1) expression. Cell death was assessed by Hoechst and propidium iodide staining. BAX translocation, Bim phosphorylation, cytochrome c release, and caspases 9 and 3 activation were measured by Western blot or immunofluorescence.Results: PTPN2 knockdown exacerbated type I IFN-induced apoptosis in INS-1E, primary rat, and human β-cells. PTPN2 silencing and exposure to type I and II IFNs induced BAX translocation to the mitochondria, cytochrome c release, and caspase 3 activation. There was also an increase in Bim phosphorylation that was at least in part regulated by JNK1. Of note, both Bim and JNK1 knockdown protected β-cells against IFN-induced apoptosis in PTPN2-silenced cells.Conclusions: The present findings suggest that local IFN production may interact with a genetic factor (PTPN2) to induce aberrant proapoptotic activity of the BH3-only protein Bim, resulting in increased β-cell apoptosis via JNK activation and the intrinsic apoptotic pathway. This is the first indication of a direct interaction between a candidate gene for T1D and the activation of a specific downstream proapoptotic pathway in β-cells. [ABSTRACT FROM AUTHOR]- Published
- 2011
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4. Peripheral and islet interleukin-17 pathway activation characterizes human autoimmune diabetes and promotes cytokine-mediated β-cell death.
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Arif S, Moore F, Marks K, Bouckenooghe T, Dayan CM, Planas R, Vives-Pi M, Powrie J, Tree T, Marchetti P, Huang GC, Gurzov EN, Pujol-Borrell R, Eizirik DL, Peakman M, Arif, Sefina, Moore, Fabrice, Marks, Katherine, Bouckenooghe, Thomas, and Dayan, Colin M
- Subjects
ANIMAL experimentation ,APOPTOSIS ,CARRIER proteins ,CELLS ,CYTOKINES ,TYPE 1 diabetes ,INTERLEUKINS ,ISLANDS of Langerhans ,ISLANDS of Langerhans tumors ,PANCREATIC tumors ,PROTEINS ,RATS ,RESEARCH funding ,T cells ,TUMOR necrosis factors - Abstract
Objective: CD4 T-cells secreting interleukin (IL)-17 are implicated in several human autoimmune diseases, but their role in type 1 diabetes has not been defined. To address the relevance of such cells, we examined IL-17 secretion in response to β-cell autoantigens, IL-17A gene expression in islets, and the potential functional consequences of IL-17 release for β-cells.Research Design and Methods: Peripheral blood CD4 T-cell responses to β-cell autoantigens (proinsulin, insulinoma-associated protein, and GAD65 peptides) were measured by IL-17 enzyme-linked immunospot assay in patients with new-onset type 1 diabetes (n = 50). mRNA expression of IL-17A and IFNG pathway genes was studied by qRT-PCR using islets obtained from subjects who died 5 days and 10 years after diagnosis of disease, respectively, and from matched control subjects. IL-17 effects on the function of human islets, rat β-cells, and the rat insulinoma cell line INS-1E were examined.Results: A total of 27 patients (54%) showed IL-17 reactivity to one or more β-cell peptides versus 3 of 30 (10%) control subjects (P = 0.0001). In a single case examined close to diagnosis, islet expression of IL17A, RORC, and IL22 was detected. It is noteworthy that we show that IL-17 mediates significant and reproducible enhancement of IL-1β/interferon (IFN)-γ-induced and tumor necrosis factor (TNF)-α/IFN-γ-induced apoptosis in human islets, rat β-cells, and INS-1E cells, in association with significant upregulation of β-cell IL17RA expression via activation of the transcription factors STAT1 and nuclear factor (NF)-κB.Conclusions: Circulating IL-17(+) β-cell-specific autoreactive CD4 T-cells are a feature of type 1 diabetes diagnosis. We disclose a novel pathway to β-cell death involving IL-17 and STAT1 and NF-κB, rendering this cytokine a novel disease biomarker and potential therapeutic target. [ABSTRACT FROM AUTHOR]- Published
- 2011
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5. Glucagon-like peptide-1 agonists protect pancreatic beta-cells from lipotoxic endoplasmic reticulum stress through upregulation of BiP and JunB.
- Author
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Cunha DA, Ladrière L, Ortis F, Igoillo-Esteve M, Gurzov EN, Lupi R, Marchetti P, Eizirik DL, Cnop M, Cunha, Daniel A, Ladrière, Laurence, Ortis, Fernanda, Igoillo-Esteve, Mariana, Gurzov, Esteban N, Lupi, Roberto, Marchetti, Piero, Eizirik, Décio L, and Cnop, Miriam
- Abstract
Objective: Chronic exposure of pancreatic beta-cells to saturated free fatty acids (FFAs) causes endoplasmic reticulum (ER) stress and apoptosis and may contribute to beta-cell loss in type 2 diabetes. Here, we evaluated the molecular mechanisms involved in the protection of beta-cells from lipotoxic ER stress by glucagon-like peptide (GLP)-1 agonists utilized in the treatment of type 2 diabetes.Research Design and Methods: INS-1E or fluorescence-activated cell sorter-purified primary rat beta-cells were exposed to oleate or palmitate with or without the GLP-1 agonist exendin-4 or forskolin. Cyclopiazonic acid was used as a synthetic ER stressor, while the activating transcription factor 4-C/EBP homologous protein branch was selectively activated with salubrinal. The ER stress signaling pathways modulated by GLP-1 agonists were studied by real-time PCR and Western blot. Knockdown by RNA interference was used to identify mediators of the antiapoptotic GLP-1 effects in the ER stress response and downstream mitochondrial cell death mechanisms.Results: Exendin-4 and forskolin protected beta-cells against FFAs via the induction of the ER chaperone BiP and the antiapoptotic protein JunB that mediate beta-cell survival under lipotoxic conditions. On the other hand, exendin-4 and forskolin protected against synthetic ER stressors by inactivating caspase 12 and upregulating Bcl-2 and X-chromosome-linked inhibitor of apoptosis protein that inhibit mitochondrial apoptosis.Conclusions: These observations suggest that GLP-1 agonists increase in a context-dependent way the beta-cell defense mechanisms against different pathways involved in ER stress-induced apoptosis. The identification of the pathways modulated by GLP-1 agonists allows for targeted approaches to alleviate beta-cell ER stress in diabetes. [ABSTRACT FROM AUTHOR]- Published
- 2009
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6. HAMSAB diet ameliorates dysfunctional signaling in pancreatic islets in autoimmune diabetes.
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Vandenbempt V, Eski SE, Brahma MK, Li A, Negueruela J, Bruggeman Y, Demine S, Xiao P, Cardozo AK, Baeyens N, Martelotto LG, Singh SP, Mariño E, Gysemans C, and Gurzov EN
- Abstract
An altered gut microbiota is associated with type 1 diabetes (T1D), affecting the production of short-chain fatty acids (SCFA) and glucose homeostasis. We previously demonstrated that enhancing serum acetate and butyrate using a dietary supplement (HAMSAB) improved glycemia in non-obese diabetic (NOD) mice and patients with established T1D. The effects of SCFA on immune-infiltrated islet cells remain to be clarified. Here, we performed single-cell RNA sequencing on islet cells from NOD mice fed an HAMSAB or control diet. HAMSAB induced a regulatory gene expression profile in pancreas-infiltrated immune cells. Moreover, HAMSAB maintained the expression of β-cell functional genes and decreased cellular stress. HAMSAB-fed mice showed preserved pancreatic endocrine cell identity, evaluated by decreased numbers of poly-hormonal cells. Finally, SCFA increased insulin levels in human β-like cells and improved transplantation outcome in NOD/SCID mice. Our findings support the use of metabolite-based diet as attractive approach to improve glucose control in T1D., Competing Interests: E.M. is an inventor on a patent WO2018027274A1 submitted by Monash University that covers methods and compositions of metabolites for treatment and prevention of autoimmune disease related to this paper and stock ownership for ImmunoBiota Therapeutics Pty Ltd. E.N.G. declares that there are no other relationships or activities that might bias, or be perceived to bias, the present work., (© 2023 The Author(s).)
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- 2023
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7. Non-alcoholic fatty liver disease and diabetes mellitus as growing aetiologies of hepatocellular carcinoma.
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Talamantes S, Lisjak M, Gilglioni EH, Llamoza-Torres CJ, Ramos-Molina B, and Gurzov EN
- Abstract
Obesity-related complications such as non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D) are well-established risk factors for the development of hepatocellular carcinoma (HCC). This review provides insights into the molecular mechanisms that underlie the role of steatosis, hyperinsulinemia and hepatic inflammation in HCC development and progression. We focus on recent findings linking intracellular pathways and transcription factors that can trigger the reprogramming of hepatic cells. In addition, we highlight the role of enzymes in dysregulated metabolic activity and consequent dysfunctional signalling. Finally, we discuss the potential uses and challenges of novel therapeutic strategies to prevent and treat NAFLD/T2D-associated HCC., (© 2023 The Author(s).)
- Published
- 2023
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8. Inhibition of RIPK1 kinase does not affect diabetes development: β-Cells survive RIPK1 activation.
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Takiishi T, Xiao P, Franchimont M, Gilglioni EH, Arroba EN, Gurzov EN, Bertrand MJ, and Cardozo AK
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- Mice, Animals, Humans, Inflammation metabolism, Serine, Obesity, Receptor-Interacting Protein Serine-Threonine Kinases, Protein Kinases metabolism, Diabetes Mellitus, Type 1
- Abstract
Objectives: Type 1 diabetes (T1D) is caused by progressive immune-mediated loss of insulin-producing β-cells. Inflammation is detrimental to β-cell function and survival, moreover, both apoptosis and necrosis have been implicated as mechanisms of β-cell loss in T1D. The receptor interacting serine/threonine protein kinase 1 (RIPK1) promotes inflammation by serving as a scaffold for NF-κB and MAPK activation, or by acting as a kinase that triggers apoptosis or necroptosis. It is unclear whether RIPK1 kinase activity is involved in T1D pathology. In the present study, we investigated if absence of RIPK1 activation would affect the susceptibility to immune-mediated diabetes or diet induced obesity (DIO)., Methods: The RIPK1 knockin mouse line carrying a mutation mimicking serine 25 phosphorylation (Ripk1
S25D/S25D ), which abrogates RIPK1 kinase activity, was utilized to assess the in vivo role of RIPK1 in immune-mediated diabetes or diet induced obesity (DIO). In vitro, β-cell death and RIPK1 kinase activity was analysed in conditions known to induce RIPK1-dependent apoptosis/necroptosis., Results: We demonstrate that Ripk1S25D/S25D mice presented normal glucose metabolism and β-cell function. Furthermore, immune-mediated diabetes and DIO were not different between Ripk1S25D/S25D and Ripk1+/+ mice. Despite strong activation of RIPK1 kinase and other necroptosis effectors (RIPK3 and MLKL) by TNF+BV6+zVAD, no cell death was observed in mouse islets nor human β-cells., Conclusion: Our results contrast recent literature showing that most cell types undergo necroptosis following RIPK1 kinase activation. This peculiarity may reflect an adaptation to the inability of β-cells to proliferate and self-renewal., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)- Published
- 2023
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9. Nova1 or Bim Deficiency in Pancreatic β-Cells Does Not Alter Multiple Low-Dose Streptozotocin-Induced Diabetes and Diet-Induced Obesity in Mice.
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Brahma MK, Xiao P, Popa M, Negueruela J, Vandenbempt V, Demine S, Cardozo AK, and Gurzov EN
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- Animals, Blood Glucose metabolism, Cytokines metabolism, Diet, High-Fat, Glucose metabolism, Humans, Insulin, Mice, Neuro-Oncological Ventral Antigen, Obesity etiology, Obesity metabolism, RNA-Binding Proteins metabolism, Streptozocin, Bcl-2-Like Protein 11 metabolism, Diabetes Mellitus, Experimental metabolism, Diabetes Mellitus, Type 2 metabolism, Insulin-Secreting Cells metabolism
- Abstract
The loss of functional pancreatic β-cell mass is an important hallmark of both type 1 and type 2 diabetes. The RNA-binding protein NOVA1 is expressed in human and rodent pancreatic β-cells. Previous in vitro studies indicated that NOVA1 is necessary for glucose-stimulated insulin secretion and its deficiency-enhanced cytokine-induced apoptosis. Moreover, Bim, a proapoptotic protein, is differentially spliced and potentiates apoptosis in NOVA1-deficient β-cells in culture. We generated two novel mouse models by Cre-Lox technology lacking Nova1 (βNova1
-/- ) or Bim (βBim-/- ) in β-cells. To test the impact of Nova1 or Bim deletion on β-cell function, mice were subjected to multiple low-dose streptozotocin (MLD-STZ)-induced diabetes or high-fat diet-induced insulin resistance. β-cell-specific Nova1 or Bim deficiency failed to affect diabetes development in response to MLD-STZ-induced β-cell dysfunction and death evidenced by unaltered blood glucose levels and pancreatic insulin content. In addition, body composition, glucose and insulin tolerance test, and pancreatic insulin content were indistinguishable between control and βNova1-/- or βBim-/- mice on a high fat diet. Thus, Nova1 or Bim deletion in β-cells does not impact on glucose homeostasis or diabetes development in mice. Together, these data argue against an in vivo role for the Nova1-Bim axis in β-cells.- Published
- 2022
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10. NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes.
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Xiao P, Takiishi T, Violato NM, Licata G, Dotta F, Sebastiani G, Marselli L, Singh SP, Sze M, Van Loo G, Dejardin E, Gurzov EN, and Cardozo AK
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- Animals, Mice, NF-kappa B metabolism, Protein Serine-Threonine Kinases genetics, Signal Transduction physiology, NF-kappaB-Inducing Kinase, Diabetes Mellitus pathology, Insulin-Secreting Cells metabolism
- Abstract
The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice. Therefore, NIK has been proposed as a potential target for diabetes therapy. However, no clear studies showed whether inhibition of NIK improves diabetes development. Here we show that genetic silencing of NIK in pancreatic β-cells neither modifies diabetes incidence nor inflammatory responses in a mouse model of immune-mediated diabetes. Moreover, NIK silencing in DIO mice did not influence body weight gain, nor glucose metabolism. In vitro studies corroborated the in vivo findings in terms of β-cell survival, function, and downstream gene regulation. Taken together, our data suggest that NIK activation is dispensable for the development of diabetes., (© 2022. The Author(s).)
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- 2022
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11. PTPN2 Regulates the Interferon Signaling and Endoplasmic Reticulum Stress Response in Pancreatic β-Cells in Autoimmune Diabetes.
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Elvira B, Vandenbempt V, Bauzá-Martinez J, Crutzen R, Negueruela J, Ibrahim H, Winder ML, Brahma MK, Vekeriotaite B, Martens PJ, Singh SP, Rossello F, Lybaert P, Otonkoski T, Gysemans C, Wu W, and Gurzov EN
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- Animals, Apoptosis genetics, Endoplasmic Reticulum Stress physiology, Humans, Interferon-gamma pharmacology, Mice, Mice, Inbred NOD, Protein Tyrosine Phosphatase, Non-Receptor Type 2 genetics, Diabetes Mellitus, Type 1 metabolism, Insulin-Secreting Cells metabolism, Protein Tyrosine Phosphatase, Non-Receptor Type 2 metabolism
- Abstract
Type 1 diabetes (T1D) results from autoimmune destruction of β-cells in the pancreas. Protein tyrosine phosphatases (PTPs) are candidate genes for T1D and play a key role in autoimmune disease development and β-cell dysfunction. Here, we assessed the global protein and individual PTP profiles in the pancreas from nonobese mice with early-onset diabetes (NOD) mice treated with an anti-CD3 monoclonal antibody and interleukin-1 receptor antagonist. The treatment reversed hyperglycemia, and we observed enhanced expression of PTPN2, a PTP family member and T1D candidate gene, and endoplasmic reticulum (ER) chaperones in the pancreatic islets. To address the functional role of PTPN2 in β-cells, we generated PTPN2-deficient human stem cell-derived β-like and EndoC-βH1 cells. Mechanistically, we demonstrated that PTPN2 inactivation in β-cells exacerbates type I and type II interferon signaling networks and the potential progression toward autoimmunity. Moreover, we established the capacity of PTPN2 to positively modulate the Ca2+-dependent unfolded protein response and ER stress outcome in β-cells. Adenovirus-induced overexpression of PTPN2 partially protected from ER stress-induced β-cell death. Our results postulate PTPN2 as a key protective factor in β-cells during inflammation and ER stress in autoimmune diabetes., (© 2022 by the American Diabetes Association.)
- Published
- 2022
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12. Metabolite-based dietary supplementation in human type 1 diabetes is associated with microbiota and immune modulation.
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Bell KJ, Saad S, Tillett BJ, McGuire HM, Bordbar S, Yap YA, Nguyen LT, Wilkins MR, Corley S, Brodie S, Duong S, Wright CJ, Twigg S, de St Groth BF, Harrison LC, Mackay CR, Gurzov EN, Hamilton-Williams EE, and Mariño E
- Subjects
- Animals, Dietary Supplements, Fatty Acids, Volatile, Humans, Mice, Diabetes Mellitus, Type 1, Diabetes Mellitus, Type 2 microbiology, Gastrointestinal Microbiome, Microbiota
- Abstract
Background: Short-chain fatty acids (SCFAs) produced by the gut microbiota have beneficial anti-inflammatory and gut homeostasis effects and prevent type 1 diabetes (T1D) in mice. Reduced SCFA production indicates a loss of beneficial bacteria, commonly associated with chronic autoimmune and inflammatory diseases, including T1D and type 2 diabetes. Here, we addressed whether a metabolite-based dietary supplement has an impact on humans with T1D. We conducted a single-arm pilot-and-feasibility trial with high-amylose maize-resistant starch modified with acetate and butyrate (HAMSAB) to assess safety, while monitoring changes in the gut microbiota in alignment with modulation of the immune system status., Results: HAMSAB supplement was administered for 6 weeks with follow-up at 12 weeks in adults with long-standing T1D. Increased concentrations of SCFA acetate, propionate, and butyrate in stools and plasma were in concert with a shift in the composition and function of the gut microbiota. While glucose control and insulin requirements did not change, subjects with the highest SCFA concentrations exhibited the best glycemic control. Bifidobacterium longum, Bifidobacterium adolescentis, and vitamin B7 production correlated with lower HbA1c and basal insulin requirements. Circulating B and T cells developed a more regulatory phenotype post-intervention., Conclusion: Changes in gut microbiota composition, function, and immune profile following 6 weeks of HAMSAB supplementation were associated with increased SCFAs in stools and plasma. The persistence of these effects suggests that targeting dietary SCFAs may be a mechanism to alter immune profiles, promote immune tolerance, and improve glycemic control for the treatment of T1D., Trial Registration: ACTRN12618001391268. Registered 20 August 2018, https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375792 Video Abstract., (© 2022. The Author(s).)
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- 2022
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13. Insulin-Binding Peptide Probes Provide a Novel Strategy for Pancreatic β-Cell Imaging.
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Eriksson M, Litwak SA, Yun Y, Stanley WJ, Thorn P, Ahlgren U, and Gurzov EN
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- Animals, Cells, Cultured, Humans, Insulin analysis, Mice, Mice, Inbred C57BL, Microscopy, Confocal, Staining and Labeling, Diabetes Mellitus, Type 1 diagnostic imaging, Insulin-Secreting Cells metabolism, Intracellular Signaling Peptides and Proteins metabolism
- Abstract
Type 1 diabetes develops in childhood and adolescence, with peak incidence in the early teenage years. There is an urgent need for an accurate method to detect insulin-producing β-cells in patients that is not affected by alterations in β-cell function. As part of our research program to design specific probes to measure β-cell mass, we recently developed a novel insulin-binding peptide probe (IBPP) for the detection of β-cells in vivo. Here, we applied our innovative method to show specific labeling of this IBPP to human and mouse fixed β-cells in pancreatic islets. Importantly, we showed staining of human and mouse islets in culture without any negative functional or cell viability impact. Moreover, the IBPP-stained mouse islets after tail vein injection in vivo, albeit with batch differences in staining efficiency. In conclusion, we provide evidence showing that the IBPP can be used for future accurate detection of β-cell mass in a variety of preclinical models of diabetes.
- Published
- 2021
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14. STAT3 Regulates Mitochondrial Gene Expression in Pancreatic β-Cells and Its Deficiency Induces Glucose Intolerance in Obesity.
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Schaschkow A, Pang L, Vandenbempt V, Elvira B, Litwak SA, Vekeriotaite B, Maillard E, Vermeersch M, Paula FMM, Pinget M, Perez-Morga D, Gough DJ, and Gurzov EN
- Subjects
- Animals, Blood Glucose metabolism, Diet, High-Fat, Genes, Mitochondrial, Glucose Intolerance genetics, Humans, Insulin metabolism, Mice, Mice, Knockout, Mitochondria genetics, Obesity genetics, STAT3 Transcription Factor genetics, Glucose Intolerance metabolism, Insulin-Secreting Cells metabolism, Mitochondria metabolism, Obesity metabolism, STAT3 Transcription Factor metabolism
- Abstract
Most obese and insulin-resistant individuals do not develop diabetes. This is the result of the capacity of β-cells to adapt and produce enough insulin to cover the needs of the organism. The underlying mechanism of β-cell adaptation in obesity, however, remains unclear. Previous studies have suggested a role for STAT3 in mediating β-cell development and human glucose homeostasis, but little is known about STAT3 in β-cells in obesity. We observed enhanced cytoplasmic expression of STAT3 in severely obese subjects with diabetes. To address the functional role of STAT3 in adult β-cells, we generated mice with tamoxifen-inducible partial or full deletion of STAT3 in β-cells and fed them a high-fat diet before analysis. Interestingly, β-cell heterozygous and homozygous STAT3-deficient mice showed glucose intolerance when fed a high-fat diet. Gene expression analysis with RNA sequencing showed that reduced expression of mitochondrial genes in STAT3 knocked down human EndoC-β
1 H cells, confirmed in FACS-purified β-cells from obese STAT3-deficient mice. Moreover, silencing of STAT3 impaired mitochondria activity in EndoC-β1 H cells and human islets, suggesting a mechanism for STAT3-modulated β-cell function. Our study postulates STAT3 as a novel regulator of β-cell function in obesity., (© 2021 by the American Diabetes Association.)- Published
- 2021
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15. Oxidative stress in obesity-associated hepatocellular carcinoma: sources, signaling and therapeutic challenges.
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Brahma MK, Gilglioni EH, Zhou L, Trépo E, Chen P, and Gurzov EN
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- Humans, Animals, Carcinoma, Hepatocellular metabolism, Carcinoma, Hepatocellular etiology, Carcinoma, Hepatocellular pathology, Liver Neoplasms metabolism, Liver Neoplasms pathology, Liver Neoplasms etiology, Liver Neoplasms genetics, Obesity complications, Obesity metabolism, Oxidative Stress, Signal Transduction, Reactive Oxygen Species metabolism
- Abstract
Obesity affects more than 650 million individuals worldwide and is a well-established risk factor for the development of hepatocellular carcinoma (HCC). Oxidative stress can be considered as a bona fide tumor promoter, contributing to the initiation and progression of liver cancer. Indeed, one of the key events involved in HCC progression is excessive levels of reactive oxygen species (ROS) resulting from the fatty acid influx and chronic inflammation. This review provides insights into the different intracellular sources of obesity-induced ROS and molecular mechanisms responsible for hepatic tumorigenesis. In addition, we highlight recent findings pointing to the role of the dysregulated activity of BCL-2 proteins and protein tyrosine phosphatases (PTPs) in the generation of hepatic oxidative stress and ROS-mediated dysfunctional signaling, respectively. Finally, we discuss the potential and challenges of novel nanotechnology strategies to prevent ROS formation in obesity-associated HCC., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)
- Published
- 2021
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16. Novel Strategies to Protect and Visualize Pancreatic β Cells in Diabetes.
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Gurzov EN, Ke PC, Ahlgren U, Garcia Ribeiro RS, and Gotthardt M
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- Animals, Humans, Insulin-Secreting Cells physiology, Diabetes Mellitus, Type 1 physiopathology, Diabetes Mellitus, Type 2 physiopathology
- Abstract
A common feature in the pathophysiology of different types of diabetes is the reduction of β cell mass and/or impairment of β cell function. Diagnosis and treatment of type 1 and type 2 diabetes is currently hampered by a lack of reliable techniques to restore β cell survival, to improve insulin secretion, and to quantify β cell mass in patients. Current new approaches may allow us to precisely and specifically visualize β cells in vivo and provide viable therapeutic strategies to preserve, recover, and regenerate β cells. In this review, we discuss recent protective approaches for β cells and the advantages and limitations of current imaging probes in the field., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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17. Obesity Drives STAT-1-Dependent NASH and STAT-3-Dependent HCC.
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Grohmann M, Wiede F, Dodd GT, Gurzov EN, Ooi GJ, Butt T, Rasmiena AA, Kaur S, Gulati T, Goh PK, Treloar AE, Archer S, Brown WA, Muller M, Watt MJ, Ohara O, McLean CA, and Tiganis T
- Subjects
- Animals, CD8-Positive T-Lymphocytes immunology, CD8-Positive T-Lymphocytes metabolism, Carcinoma, Hepatocellular metabolism, Diet, High-Fat, Disease Models, Animal, Hepatocytes metabolism, Humans, Liver metabolism, Liver pathology, Liver Cirrhosis metabolism, Liver Cirrhosis pathology, Liver Neoplasms metabolism, Mice, Mice, Inbred C57BL, Mice, Knockout, Non-alcoholic Fatty Liver Disease metabolism, Obesity metabolism, Oxidative Stress, Protein Tyrosine Phosphatase, Non-Receptor Type 2 deficiency, Protein Tyrosine Phosphatase, Non-Receptor Type 2 genetics, Protein Tyrosine Phosphatase, Non-Receptor Type 2 metabolism, Signal Transduction, Carcinoma, Hepatocellular pathology, Liver Neoplasms pathology, Non-alcoholic Fatty Liver Disease pathology, Obesity pathology, STAT1 Transcription Factor metabolism, STAT3 Transcription Factor metabolism
- Abstract
Obesity is a major driver of cancer, especially hepatocellular carcinoma (HCC). The prevailing view is that non-alcoholic steatohepatitis (NASH) and fibrosis or cirrhosis are required for HCC in obesity. Here, we report that NASH and fibrosis and HCC in obesity can be dissociated. We show that the oxidative hepatic environment in obesity inactivates the STAT-1 and STAT-3 phosphatase T cell protein tyrosine phosphatase (TCPTP) and increases STAT-1 and STAT-3 signaling. TCPTP deletion in hepatocytes promoted T cell recruitment and ensuing NASH and fibrosis as well as HCC in obese C57BL/6 mice that normally do not develop NASH and fibrosis or HCC. Attenuating the enhanced STAT-1 signaling prevented T cell recruitment and NASH and fibrosis but did not prevent HCC. By contrast, correcting STAT-3 signaling prevented HCC without affecting NASH and fibrosis. TCPTP-deletion in hepatocytes also markedly accelerated HCC in mice treated with a chemical carcinogen that promotes HCC without NASH and fibrosis. Our studies reveal how obesity-associated hepatic oxidative stress can independently contribute to the pathogenesis of NASH, fibrosis, and HCC., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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18. Can GABA turn pancreatic α-cells into β-cells?
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Eizirik DL and Gurzov EN
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- Artesunate, Cell Transdifferentiation, Humans, gamma-Aminobutyric Acid, Glucagon-Secreting Cells, Insulin-Secreting Cells
- Published
- 2018
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19. Sweet Killing in Obesity and Diabetes: The Metabolic Role of the BH3-only Protein BIM.
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Miani M, Elvira B, and Gurzov EN
- Subjects
- Animals, Apoptosis, Autoimmunity, Bcl-2-Like Protein 11 antagonists & inhibitors, Bcl-2-Like Protein 11 chemistry, Diabetes Mellitus diagnosis, Diabetes Mellitus drug therapy, Hepatocytes metabolism, Humans, Insulin metabolism, Insulin Resistance, Insulin-Secreting Cells immunology, Insulin-Secreting Cells metabolism, Insulin-Secreting Cells pathology, Mitochondria metabolism, Molecular Targeted Therapy, Obesity drug therapy, Signal Transduction, Bcl-2-Like Protein 11 metabolism, Diabetes Mellitus etiology, Diabetes Mellitus metabolism, Obesity etiology, Obesity metabolism, Peptide Fragments chemistry, Protein Interaction Domains and Motifs, Proto-Oncogene Proteins chemistry
- Abstract
Diabetes is a metabolic disorder affecting more than 400 million individuals and their families worldwide. The major forms of diabetes (types 1 and 2) are characterized by pancreatic β-cell dysfunction and, in some cases, loss of β-cell mass causing hyperglycemia due to absolute or relative insulin deficiency. The BCL-2 homology 3 (BH3)-only protein BIM has a wide role in apoptosis induction in cells. In this review, we describe the apoptotic mechanisms mediated by BIM activation in β cells in obesity and both forms of diabetes. We focus on molecular pathways triggered by inflammation, saturated fats, and high levels of glucose. Besides its role in cell death, BIM has been implicated in the regulation of mitochondrial oxidative phosphorylation and cellular metabolism in hepatocytes. BIM is both a key mediator of pancreatic β-cell death and hepatic insulin resistance and is thus a potential therapeutic target for novel anti-diabetogenic drugs. We consider the implications and challenges of targeting BIM in the treatment of the disease., (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Published
- 2018
- Full Text
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20. Loss of BIM increases mitochondrial oxygen consumption and lipid oxidation, reduces adiposity and improves insulin sensitivity in mice.
- Author
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Wali JA, Galic S, Tan CY, Gurzov EN, Frazier AE, Connor T, Ge J, Pappas EG, Stroud D, Varanasi LC, Selck C, Ryan MT, Thorburn DR, Kemp BE, Krishnamurthy B, Kay TW, McGee SL, and Thomas HE
- Subjects
- Animals, Bcl-2-Like Protein 11 genetics, Electron Transport Complex IV metabolism, Energy Metabolism, Glucose metabolism, Hepatocytes metabolism, Insulin Resistance, Liver metabolism, Membrane Potential, Mitochondrial, Mice, Oxidation-Reduction, Oxygen Consumption, Weight Loss, Adiposity, Bcl-2-Like Protein 11 physiology, Lipid Metabolism, Mitochondria metabolism
- Abstract
BCL-2 proteins are known to engage each other to determine the fate of a cell after a death stimulus. However, their evolutionary conservation and the many other reported binding partners suggest an additional function not directly linked to apoptosis regulation. To identify such a function, we studied mice lacking the BH3-only protein BIM. BIM
-/- cells had a higher mitochondrial oxygen consumption rate that was associated with higher mitochondrial complex IV activity. The consequences of increased oxygen consumption in BIM-/- mice were significantly lower body weights, reduced adiposity and lower hepatic lipid content. Consistent with reduced adiposity, BIM-/- mice had lower fasting blood glucose, improved insulin sensitivity and hepatic insulin signalling. Lipid oxidation was increased in BIM-/- mice, suggesting a mechanism for their metabolic phenotype. Our data suggest a role for BIM in regulating mitochondrial bioenergetics and metabolism and support the idea that regulation of metabolism and cell death are connected.- Published
- 2018
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- View/download PDF
21. Star Polymers Reduce Islet Amyloid Polypeptide Toxicity via Accelerated Amyloid Aggregation.
- Author
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Pilkington EH, Lai M, Ge X, Stanley WJ, Wang B, Wang M, Kakinen A, Sani MA, Whittaker MR, Gurzov EN, Ding F, Quinn JF, Davis TP, and Ke PC
- Subjects
- Amyloidosis pathology, Animals, Cell Line, Diabetes Mellitus, Type 2 pathology, Male, Mice, Mice, Inbred C57BL, Molecular Dynamics Simulation, Nanoparticles chemistry, Amyloid chemistry, Amyloidogenic Proteins chemistry, Islet Amyloid Polypeptide chemistry, Polymers chemistry, Protein Aggregation, Pathological pathology
- Abstract
Protein aggregation into amyloid fibrils is a ubiquitous phenomenon across the spectrum of neurodegenerative disorders and type 2 diabetes. A common strategy against amyloidogenesis is to minimize the populations of toxic oligomers and protofibrils by inhibiting protein aggregation with small molecules or nanoparticles. However, melanin synthesis in nature is realized by accelerated protein fibrillation to circumvent accumulation of toxic intermediates. Accordingly, we designed and demonstrated the use of star-shaped poly(2-hydroxyethyl acrylate) (PHEA) nanostructures for promoting aggregation while ameliorating the toxicity of human islet amyloid polypeptide (IAPP), the peptide involved in glycemic control and the pathology of type 2 diabetes. The binding of PHEA elevated the β-sheet content in IAPP aggregates while rendering a new morphology of "stelliform" amyloids originating from the polymers. Atomistic molecular dynamics simulations revealed that the PHEA arms served as rodlike scaffolds for IAPP binding and subsequently accelerated IAPP aggregation by increased local peptide concentration. The tertiary structure of the star nanoparticles was found to be essential for driving the specific interactions required to impel the accelerated IAPP aggregation. This study sheds new light on the structure-toxicity relationship of IAPP and points to the potential of exploiting star polymers as a new class of therapeutic agents against amyloidogenesis.
- Published
- 2017
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22. JNK Activation of BIM Promotes Hepatic Oxidative Stress, Steatosis, and Insulin Resistance in Obesity.
- Author
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Litwak SA, Pang L, Galic S, Igoillo-Esteve M, Stanley WJ, Turatsinze JV, Loh K, Thomas HE, Sharma A, Trepo E, Moreno C, Gough DJ, Eizirik DL, de Haan JB, and Gurzov EN
- Subjects
- Animals, Cells, Cultured, Enzyme Activation, Fatty Acids metabolism, Humans, Mice, Mice, Inbred C57BL, Reactive Oxygen Species metabolism, Bcl-2-Like Protein 11 physiology, Fatty Liver etiology, Insulin Resistance, JNK Mitogen-Activated Protein Kinases physiology, Liver metabolism, Obesity metabolism, Oxidative Stress
- Abstract
The members of the BCL-2 family are crucial regulators of the mitochondrial pathway of apoptosis in normal physiology and disease. Besides their role in cell death, BCL-2 proteins have been implicated in the regulation of mitochondrial oxidative phosphorylation and cellular metabolism. It remains unclear, however, whether these proteins have a physiological role in glucose homeostasis and metabolism in vivo. In this study, we report that fat accumulation in the liver increases c-Jun N-terminal kinase-dependent BCL-2 interacting mediator of cell death (BIM) expression in hepatocytes. To determine the consequences of hepatic BIM deficiency in diet-induced obesity, we generated liver-specific BIM-knockout (BLKO) mice. BLKO mice had lower hepatic lipid content, increased insulin signaling, and improved global glucose metabolism. Consistent with these findings, lipogenic and lipid uptake genes were downregulated and lipid oxidation enhanced in obese BLKO mice. Mechanistically, BIM deficiency improved mitochondrial function and decreased oxidative stress and oxidation of protein tyrosine phosphatases, and ameliorated activation of peroxisome proliferator-activated receptor γ/sterol regulatory element-binding protein 1/CD36 in hepatocytes from high fat-fed mice. Importantly, short-term knockdown of BIM rescued obese mice from insulin resistance, evidenced by reduced fat accumulation and improved insulin sensitivity. Our data indicate that BIM is an important regulator of liver dysfunction in obesity and a novel therapeutic target for restoring hepatocyte function., (© 2017 by the American Diabetes Association.)
- Published
- 2017
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23. Differential regulation of pro-inflammatory cytokine signalling by protein tyrosine phosphatases in pancreatic β-cells.
- Author
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Stanley WJ, Trivedi PM, Sutherland AP, Thomas HE, and Gurzov EN
- Subjects
- Animals, Cell Death genetics, Cell Death immunology, Gene Expression, Gene Knockout Techniques, Gene Targeting, Humans, JNK Mitogen-Activated Protein Kinases metabolism, Mice, Mice, Inbred NOD, Phosphorylation, Protein Tyrosine Phosphatase, Non-Receptor Type 1 genetics, Protein Tyrosine Phosphatase, Non-Receptor Type 1 metabolism, Protein Tyrosine Phosphatase, Non-Receptor Type 6 genetics, Protein Tyrosine Phosphatase, Non-Receptor Type 6 metabolism, Protein Tyrosine Phosphatases genetics, T-Lymphocytes immunology, T-Lymphocytes metabolism, Tumor Necrosis Factor-alpha metabolism, Cytokines metabolism, Inflammation Mediators metabolism, Insulin-Secreting Cells metabolism, Protein Tyrosine Phosphatases metabolism, Signal Transduction
- Abstract
Type 1 diabetes (T1D) is characterized by the destruction of insulin-producing β-cells by immune cells in the pancreas. Pro-inflammatory including TNF-α, IFN-γ and IL-1β are released in the islet during the autoimmune assault and signal in β-cells through phosphorylation cascades, resulting in pro-apoptotic gene expression and eventually β-cell death. Protein tyrosine phosphatases (PTPs) are a family of enzymes that regulate phosphorylative signalling and are associated with the development of T1D. Here, we observed expression of PTPN6 and PTPN1 in human islets and islets from non-obese diabetic (NOD) mice. To clarify the role of these PTPs in β-cells/islets, we took advantage of CRISPR/Cas9 technology and pharmacological approaches to inactivate both proteins. We identify PTPN6 as a negative regulator of TNF-α-induced β-cell death, through JNK-dependent BCL-2 protein degradation. In contrast, PTPN1 acts as a positive regulator of IFN-γ-induced STAT1-dependent gene expression, which enhanced autoimmune destruction of β-cells. Importantly, PTPN1 inactivation by pharmacological modulation protects β-cells and primary mouse islets from cytokine-mediated cell death. Thus, our data point to a non-redundant effect of PTP regulation of cytokine signalling in β-cells in autoimmune diabetes., (© 2017 Society for Endocrinology.)
- Published
- 2017
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24. Inhibition of Y1 receptor signaling improves islet transplant outcome.
- Author
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Loh K, Shi YC, Walters S, Bensellam M, Lee K, Dezaki K, Nakata M, Ip CK, Chan JY, Gurzov EN, Thomas HE, Waibel M, Cantley J, Kay TW, Yada T, Laybutt DR, Grey ST, and Herzog H
- Subjects
- Animals, Arginine analogs & derivatives, Arginine pharmacology, Cyclic AMP metabolism, Diabetes Mellitus, Experimental metabolism, Humans, Insulin metabolism, Insulin Secretion, Mice, Receptors, Neuropeptide Y antagonists & inhibitors, Receptors, Neuropeptide Y metabolism, Signal Transduction, Insulin-Secreting Cells metabolism, Islets of Langerhans metabolism, Islets of Langerhans Transplantation
- Abstract
Failure to secrete sufficient quantities of insulin is a pathological feature of type-1 and type-2 diabetes, and also reduces the success of islet cell transplantation. Here we demonstrate that Y1 receptor signaling inhibits insulin release in β-cells, and show that this can be pharmacologically exploited to boost insulin secretion. Transplanting islets with Y1 receptor deficiency accelerates the normalization of hyperglycemia in chemically induced diabetic recipient mice, which can also be achieved by short-term pharmacological blockade of Y1 receptors in transplanted mouse and human islets. Furthermore, treatment of non-obese diabetic mice with a Y1 receptor antagonist delays the onset of diabetes. Mechanistically, Y1 receptor signaling inhibits the production of cAMP in islets, which via CREB mediated pathways results in the down-regulation of several key enzymes in glycolysis and ATP production. Thus, manipulating Y1 receptor signaling in β-cells offers a unique therapeutic opportunity for correcting insulin deficiency as it occurs in the pathological state of type-1 diabetes as well as during islet transplantation.Islet transplantation is considered one of the potential treatments for T1DM but limited islet survival and their impaired function pose limitations to this approach. Here Loh et al. show that the Y1 receptor is expressed in β- cells and inhibition of its signalling, both genetic and pharmacological, improves mouse and human islet function.
- Published
- 2017
- Full Text
- View/download PDF
25. Zinc-coordination and C-peptide complexation: a potential mechanism for the endogenous inhibition of IAPP aggregation.
- Author
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Ge X, Kakinen A, Gurzov EN, Yang W, Pang L, Pilkington EH, Govindan-Nedumpully P, Chen P, Separovic F, Davis TP, Ke PC, and Ding F
- Abstract
Aggregation of the highly amyloidogenic IAPP is endogenously inhibited inside beta-cell granules at millimolar concentrations. Combining in vitro experiments and computer simulations, we demonstrated that the stabilization of IAPP upon the formation of zinc-coordinated ion molecular complex with C-peptide might be important for the endogenous inhibition of IAPP aggregation.
- Published
- 2017
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- View/download PDF
26. The JAK/STAT pathway in obesity and diabetes.
- Author
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Gurzov EN, Stanley WJ, Pappas EG, Thomas HE, and Gough DJ
- Subjects
- Adipose Tissue enzymology, Adipose Tissue metabolism, Animals, Brain enzymology, Brain metabolism, Diabetes Mellitus enzymology, Diabetes Mellitus therapy, Fatty Liver metabolism, Humans, Insulin-Secreting Cells enzymology, Insulin-Secreting Cells metabolism, Janus Kinases antagonists & inhibitors, Mice, Muscle, Skeletal enzymology, Muscle, Skeletal metabolism, Obesity enzymology, Obesity therapy, STAT Transcription Factors antagonists & inhibitors, Signal Transduction, Diabetes Mellitus metabolism, Janus Kinases metabolism, Obesity metabolism, STAT Transcription Factors metabolism
- Abstract
Diabetes mellitus are complex, multi-organ metabolic pathologies characterized by hyperglycemia. Emerging evidence shows that the highly conserved and potent JAK/STAT signaling pathway is required for normal homeostasis, and, when dysregulated, contributes to the development of obesity and diabetes. In this review, we analyze the role of JAK/STAT activation in the brain, liver, muscle, fat and pancreas, and how this affects the course of the disease. We also consider the therapeutic implications of targeting the JAK/STAT pathway in treatment of obesity and diabetes., (© 2016 Federation of European Biochemical Societies.)
- Published
- 2016
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27. Perinatal tolerance to proinsulin is sufficient to prevent autoimmune diabetes.
- Author
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Jhala G, Chee J, Trivedi PM, Selck C, Gurzov EN, Graham KL, Thomas HE, Kay TW, and Krishnamurthy B
- Subjects
- Animals, Antigen-Presenting Cells cytology, Autoantigens, CD8-Positive T-Lymphocytes cytology, Glucose-6-Phosphatase metabolism, Immune Tolerance, Mice, Mice, Inbred C57BL, Mice, Inbred NOD, Mice, Transgenic, Diabetes Mellitus, Type 1 drug therapy, Diabetes Mellitus, Type 1 prevention & control, Proinsulin therapeutic use
- Abstract
High-affinity self-reactive thymocytes are purged in the thymus, and residual self-reactive T cells, which are detectable in healthy subjects, are controlled by peripheral tolerance mechanisms. Breakdown in these mechanisms results in autoimmune disease, but antigen-specific therapy to augment natural mechanisms can prevent this. We aimed to determine when antigen-specific therapy is most effective. Islet autoantigens, proinsulin (PI), and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) were expressed in the antigen-presenting cells (APCs) of autoimmune diabetes-prone nonobese diabetic (NOD) mice in a temporally controlled manner. PI expression from gestation until weaning was sufficient to completely protect NOD mice from diabetes, insulitis, and development of insulin autoantibodies. Insulin-specific T cells were significantly diminished, were naive, and did not express IFN-γ when challenged. This long-lasting effect from a brief period of treatment suggests that autoreactive T cells are not produced subsequently. We tracked IGRP
206-214 -specific CD8+ T cells in NOD mice expressing IGRP in APCs. When IGRP was expressed only until weaning, IGRP206-214 -specific CD8+ T cells were not detected later in life. Thus, anti-islet autoimmunity is determined during early life, and autoreactive T cells are not generated in later life. Bolstering tolerance to islet antigens in the perinatal period is sufficient to impart lasting protection from diabetes.- Published
- 2016
- Full Text
- View/download PDF
28. p53-upregulated-modulator-of-apoptosis (PUMA) deficiency affects food intake but does not impact on body weight or glucose homeostasis in diet-induced obesity.
- Author
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Litwak SA, Loh K, Stanley WJ, Pappas EG, Wali JA, Selck C, Strasser A, Thomas HE, and Gurzov EN
- Subjects
- Adipose Tissue pathology, Animals, Apoptosis Regulatory Proteins genetics, Apoptosis Regulatory Proteins physiology, Diet, High-Fat adverse effects, Glucose Tolerance Test, Homeostasis physiology, Insulin pharmacology, Insulin Resistance, Leptin blood, Liver pathology, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Obesity pathology, Recombinant Proteins pharmacology, Tumor Suppressor Proteins genetics, Tumor Suppressor Proteins physiology, Apoptosis Regulatory Proteins deficiency, Body Weight physiology, Eating physiology, Glucose metabolism, Obesity physiopathology, Tumor Suppressor Proteins deficiency
- Abstract
BCL-2 proteins have been implicated in the control of glucose homeostasis and metabolism in different cell types. Thus, the aim of this study was to determine the role of the pro-apoptotic BH3-only protein, p53-upregulated-modulator-of-apoptosis (PUMA), in metabolic changes mediated by diet-induced obesity, using PUMA deficient mice. At 10 weeks of age, knockout and wild type mice either continued consuming a low fat chow diet (6% fat), or were fed with a high fat diet (23% fat) for 14-17 weeks. We measured body composition, glucose and insulin tolerance, insulin response in peripheral tissues, energy expenditure, oxygen consumption, and respiratory exchange ratio in vivo. All these parameters were indistinguishable between wild type and knockout mice on chow diet and were modified equally by diet-induced obesity. Interestingly, we observed decreased food intake and ambulatory capacity of PUMA knockout mice on high fat diet. This was associated with increased adipocyte size and fasted leptin concentration in the blood. Our findings suggest that although PUMA is dispensable for glucose homeostasis in lean and obese mice, it can affect leptin levels and food intake during obesity.
- Published
- 2016
- Full Text
- View/download PDF
29. Inhibition of hIAPP Amyloid Aggregation and Pancreatic β-Cell Toxicity by OH-Terminated PAMAM Dendrimer.
- Author
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Gurzov EN, Wang B, Pilkington EH, Chen P, Kakinen A, Stanley WJ, Litwak SA, Hanssen EG, Davis TP, Ding F, and Ke PC
- Subjects
- Benzothiazoles, Cell Death drug effects, Cytoprotection drug effects, Humans, Hydroxylation, Insulin-Secreting Cells drug effects, Models, Molecular, Protein Multimerization drug effects, Thiazoles metabolism, Amyloid metabolism, Dendrimers toxicity, Insulin-Secreting Cells pathology, Islet Amyloid Polypeptide metabolism, Protein Aggregates drug effects
- Abstract
Human islet amyloid polypeptide (hIAPP, or amylin) forms amyloid deposits in the islets of Langerhans, a phenomenon that is associated with type-2 diabetes impacting millions of people worldwide. Accordingly, strategies against hIAPP aggregation are essential for the prevention and eventual treatment of the disease. Here, it is shown that generation-3 OH-terminated poly(amidoamine) dendrimer, a polymeric nanoparticle, can effectively halt the aggregation of hIAPP and shut down hIAPP toxicity in pancreatic MIN6 and NIT-1 cells as well as in mouse islets. This finding is supported by high-throughput dynamic light scattering experiment and thioflavin T assay, where the rapid evolution of hIAPP nucleation and elongation processes is halted by the addition of the dendrimer up to 8 h. Discrete molecular dynamics simulations further reveal that hIAPP residues bound strongly with the dendrimer near the c-terminal portion of the peptide, where the amyloidogenic sequence (residues 22-29) locates. Furthermore, simulations of hIAPP dimerization reveal that binding with the dendrimer significantly reduces formation of interpeptide contacts and hydrogen bonds, thereby prohibiting peptide self-association and amyloidosis. This study points to a promising nanomedicinal strategy for combating type-2 diabetes and may have broader implications for targeting neurological disorders whose distinct hallmark is also amyloid fibrillation., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2016
- Full Text
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30. Pancreatic β-Cell Membrane Fluidity and Toxicity Induced by Human Islet Amyloid Polypeptide Species.
- Author
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Pilkington EH, Gurzov EN, Kakinen A, Litwak SA, Stanley WJ, Davis TP, and Ke PC
- Subjects
- Cell Line, Cell Survival drug effects, Humans, Reactive Oxygen Species metabolism, Cell Membrane drug effects, Cell Membrane metabolism, Insulin-Secreting Cells drug effects, Insulin-Secreting Cells metabolism, Islet Amyloid Polypeptide pharmacology, Membrane Fluidity drug effects
- Abstract
Aggregation of human islet amyloid polypeptide (hIAPP) into fibrils and plaques is associated with pancreatic β-cell loss in type 2 diabetes (T2D). However, due to the rapidness of hIAPP conversion in aqueous phase, exactly which hIAPP species is responsible for the observed toxicity and through what mechanisms remains ambiguous. In light of the importance of understanding hIAPP toxicity for T2D here we show a biophysical scheme based on the use of a lipophilic Laurdan dye for examining MIN6 cell membranes upon exposure to fresh and oligomeric hIAPP as well as mature amyloid. It has been found that all three hIAPP species, especially fresh hIAPP, enhanced membrane fluidity and caused losses in cell viability. The cell generation of reactive oxygen species (ROS), however, was the most pronounced with mature amyloid hIAPP. The correlation between changes in membrane fluidity and cell viability and their lack of correlation with ROS production suggest hIAPP toxicity is elicited through both physical and biochemical means. This study offers a new insight into β-cell toxicity induced by controlled hIAPP species, as well as new biophysical methodologies that may prove beneficial for the studies of T2D as well as neurological disorders.
- Published
- 2016
- Full Text
- View/download PDF
31. Graphene oxide inhibits hIAPP amyloid fibrillation and toxicity in insulin-producing NIT-1 cells.
- Author
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Nedumpully-Govindan P, Gurzov EN, Chen P, Pilkington EH, Stanley WJ, Litwak SA, Davis TP, Ke PC, and Ding F
- Subjects
- Cell Line, Graphite chemistry, Humans, Insulin-Secreting Cells metabolism, Molecular Dynamics Simulation, Oxides chemistry, Graphite pharmacology, Insulin biosynthesis, Insulin-Secreting Cells drug effects, Islet Amyloid Polypeptide antagonists & inhibitors, Islet Amyloid Polypeptide metabolism, Oxides pharmacology, Protein Aggregates drug effects
- Abstract
Human islet amyloid polypeptide (hIAPP or amylin) aggregation is directly associated with pancreatic β-cell death and subsequent insulin deficiency in type 2 diabetes (T2D). Since no cure is currently available for T2D, it is of great benefit to devise new anti-aggregation molecules, which protect β-cells against hIAPP aggregation-induced toxicity. Engineered nanoparticles have been recently exploited as anti-aggregation nanomedicines. In this work, we studied graphene oxide (GO) nanosheets for their potential for hIAPP aggregation inhibition by combining computational modeling, biophysical characterization and cell toxicity measurements. Using discrete molecular dynamics (DMD) simulations and in vitro studies, we showed that GO exhibited an inhibitory effect on hIAPP aggregation. DMD simulations indicated that the strong binding of hIAPP to GO nanosheets was driven by hydrogen bonding and aromatic stacking and that the strong peptide-GO binding efficiently inhibited hIAPP self-association and aggregation on the nanosheet surface. Secondary structural changes of hIAPP upon GO binding derived from DMD simulations were consistent with circular dichroism (CD) spectroscopy measurements. Transmission electron microscopy (TEM) images confirmed the reduction of hIAPP aggregation in the presence of GO. Furthermore, we carried out a cell toxicity assay and found that these nanosheets protected insulin-secreting NIT-1 pancreatic β-cells against hIAPP-induced toxicity. Our multidisciplinary study suggests that GO nanosheets have the potential to be utilized as an anti-aggregation nanomedicine itself in addition to a biosensor or delivery vehicle for the mitigation of T2D progression.
- Published
- 2016
- Full Text
- View/download PDF
32. BIM Deficiency Protects NOD Mice From Diabetes by Diverting Thymocytes to Regulatory T Cells.
- Author
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Krishnamurthy B, Chee J, Jhala G, Trivedi P, Catterall T, Selck C, Gurzov EN, Brodnicki TC, Graham KL, Wali JA, Zhan Y, Gray D, Strasser A, Allison J, Thomas HE, and Kay TW
- Subjects
- Animals, Apoptosis Regulatory Proteins immunology, Bcl-2-Like Protein 11, CD5 Antigens metabolism, Clonal Deletion immunology, Diabetes Mellitus, Type 1 immunology, Disease Models, Animal, Glucocorticoid-Induced TNFR-Related Protein metabolism, I-kappa B Proteins metabolism, Membrane Proteins immunology, Mice, Mice, Inbred NOD, NF-KappaB Inhibitor alpha, Nuclear Receptor Subfamily 4, Group A, Member 1 metabolism, Phosphorylation, Proto-Oncogene Proteins immunology, Thymocytes metabolism, Apoptosis Regulatory Proteins genetics, Clonal Deletion genetics, Diabetes Mellitus, Type 1 genetics, Membrane Proteins genetics, Proto-Oncogene Proteins genetics, T-Lymphocytes, Regulatory immunology, Thymocytes immunology
- Abstract
Because regulatory T-cell (Treg) development can be induced by the same agonist self-antigens that induce negative selection, perturbation of apoptosis will affect both negative selection and Treg development. But how the processes of thymocyte deletion versus Treg differentiation bifurcate and their relative importance for tolerance have not been studied in spontaneous organ-specific autoimmune disease. We addressed these questions by removing a critical mediator of thymocyte deletion, BIM, in the NOD mouse model of autoimmune diabetes. Despite substantial defects in the deletion of autoreactive thymocytes, BIM-deficient NOD (NODBim(-/-)) mice developed less insulitis and were protected from diabetes. BIM deficiency did not impair effector T-cell function; however, NODBim(-/-) mice had increased numbers of Tregs, including those specific for proinsulin, in the thymus and peripheral lymphoid tissues. Increased levels of Nur77, CD5, GITR, and phosphorylated IκB-α in thymocytes from NODBim(-/-) mice suggest that autoreactive cells receiving strong T-cell receptor signals that would normally delete them escape apoptosis and are diverted into the Treg pathway. Paradoxically, in the NOD model, reduced thymic deletion ameliorates autoimmune diabetes by increasing Tregs. Thus, modulating apoptosis may be one of the ways to increase antigen-specific Tregs and prevent autoimmune disease., (© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)
- Published
- 2015
- Full Text
- View/download PDF
33. Inactivation of Protein Tyrosine Phosphatases Enhances Interferon Signaling in Pancreatic Islets.
- Author
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Stanley WJ, Litwak SA, Quah HS, Tan SM, Kay TW, Tiganis T, de Haan JB, Thomas HE, and Gurzov EN
- Subjects
- Aged, Animals, Cells, Cultured, Female, Humans, Mice, Mice, Inbred NOD, Middle Aged, Reactive Oxygen Species metabolism, STAT1 Transcription Factor physiology, Interferon-gamma pharmacology, Islets of Langerhans metabolism, Protein Tyrosine Phosphatases physiology, Signal Transduction physiology
- Abstract
Type 1 diabetes (T1D) is the result of an autoimmune assault against the insulin-producing pancreatic β-cells, where chronic local inflammation (insulitis) leads to β-cell destruction. T cells and macrophages infiltrate into islets early in T1D pathogenesis. These immune cells secrete cytokines that lead to the production of reactive oxygen species (ROS) and T-cell invasion and activation. Cytokine-signaling pathways are very tightly regulated by protein tyrosine phosphatases (PTPs) to prevent excessive activation. Here, we demonstrate that pancreata from NOD mice with islet infiltration have enhanced oxidation/inactivation of PTPs and STAT1 signaling compared with NOD mice that do not have insulitis. Inactivation of PTPs with sodium orthovanadate in human and rodent islets and β-cells leads to increased activation of interferon signaling and chemokine production mediated by STAT1 phosphorylation. Furthermore, this exacerbated STAT1 activation-induced cell death in islets was prevented by overexpression of the suppressor of cytokine signaling-1 or inactivation of the BH3-only protein Bim. Together our data provide a mechanism by which PTP inactivation induces signaling in pancreatic islets that results in increased expression of inflammatory genes and exacerbated insulitis., (© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)
- Published
- 2015
- Full Text
- View/download PDF
34. Protein tyrosine phosphatases: molecular switches in metabolism and diabetes.
- Author
-
Gurzov EN, Stanley WJ, Brodnicki TC, and Thomas HE
- Subjects
- Animals, Diabetes Mellitus, Type 1 immunology, Diabetes Mellitus, Type 1 metabolism, Diabetes Mellitus, Type 2 metabolism, Energy Metabolism genetics, Humans, Immunity, Cellular genetics, Insulin-Secreting Cells metabolism, Models, Molecular, Polymorphism, Genetic, Protein Tyrosine Phosphatases genetics, Diabetes Mellitus, Type 1 genetics, Diabetes Mellitus, Type 2 genetics, Genes, Switch physiology, Metabolism genetics, Protein Tyrosine Phosphatases physiology
- Abstract
Protein tyrosine phosphatases (PTPs) are a large family of enzymes that generally oppose the actions of protein tyrosine kinases (PTKs). Genetic polymorphisms for particular PTPs are associated with altered risk of both type 1 diabetes (T1D) and type 2 diabetes (T2D). Moreover, recent evidence suggests that PTPs play crucial roles in metabolism. They can act as regulators of liver homeostasis, food intake, or immune-mediated pancreatic b cell death. In this review we describe the mechanisms by which different members of the non-receptor PTP (PTPN) family influence metabolic physiology. This 'metabolic job' of PTPs is discussed in depth and the role of these proteins in different cell types compared. Understanding the pathways regulated by PTPs will provide novel therapeutic strategies for the treatment of diabetes.
- Published
- 2015
- Full Text
- View/download PDF
35. Lipotoxic Stress Induces Pancreatic β-Cell Apoptosis through Modulation of Bcl-2 Proteins by the Ubiquitin-Proteasome System.
- Author
-
Litwak SA, Wali JA, Pappas EG, Saadi H, Stanley WJ, Varanasi LC, Kay TW, Thomas HE, and Gurzov EN
- Subjects
- Animals, Cell Line, Cell Survival drug effects, Endoplasmic Reticulum Stress drug effects, Humans, Insulin-Secreting Cells drug effects, Leupeptins pharmacology, Mice, Ubiquitination drug effects, Apoptosis drug effects, Insulin-Secreting Cells metabolism, Palmitic Acid pharmacology, Proteasome Endopeptidase Complex metabolism, Proto-Oncogene Proteins c-bcl-2 metabolism, Ubiquitin metabolism
- Abstract
Pancreatic β-cell loss induced by saturated free fatty acids (FFAs) is believed to contribute to type 2 diabetes. Previous studies have shown induction of endoplasmic reticulum (ER) stress, increased ubiquitinated proteins, and deregulation of the Bcl-2 family in the pancreas of type 2 diabetic patients. However, the precise mechanism of β-cell death remains unknown. In the present study we demonstrate that the FFA palmitate blocks the ubiquitin-proteasome system (UPS) and causes apoptosis through induction of ER stress and deregulation of Bcl-2 proteins. We found that palmitate and the proteasome inhibitor MG132 induced ER stress in β-cells, resulting in decreased expression of the prosurvival proteins Bcl-2, Mcl-1, and Bcl-XL, and upregulation of the prodeath BH3-only protein PUMA. On the other hand, pharmacological activation of the UPS by sulforaphane ameliorated ER stress, upregulated prosurvival Bcl-2 proteins, and protected β-cells from FFA-induced cell death. Furthermore, transgenic overexpression of Bcl-2 protected islets from FFA-induced cell death in vitro and improved glucose-induced insulin secretion in vivo. Together our results suggest that targeting the UPS and Bcl-2 protein expression may be a valuable strategy to prevent β-cell demise in type 2 diabetes.
- Published
- 2015
- Full Text
- View/download PDF
36. Activation of the NLRP3 inflammasome complex is not required for stress-induced death of pancreatic islets.
- Author
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Wali JA, Gurzov EN, Fynch S, Elkerbout L, Kay TW, Masters SL, and Thomas HE
- Subjects
- Analysis of Variance, Animals, Blotting, Western, DNA Primers genetics, Enzyme-Linked Immunosorbent Assay, Genotype, Islets of Langerhans metabolism, Mice, NLR Family, Pyrin Domain-Containing 3 Protein, Polymerase Chain Reaction, Apoptosis physiology, Carrier Proteins metabolism, Diabetes Mellitus, Type 2 metabolism, Endoplasmic Reticulum Stress physiology, Islets of Langerhans physiopathology
- Abstract
Loss of pancreatic beta cells is a feature of type-2 diabetes. High glucose concentrations induce endoplasmic reticulum (ER) and oxidative stress-mediated apoptosis of islet cells in vitro. ER stress, oxidative stress and high glucose concentrations may also activate the NLRP3 inflammasome leading to interleukin (IL)-1β production and caspase-1 dependent pyroptosis. However, whether IL-1β or intrinsic NLRP3 inflammasome activation contributes to beta cell death is controversial. This possibility was examined in mouse islets. Exposure of islets lacking functional NLRP3 or caspase-1 to H2O2, rotenone or thapsigargin induced similar cell death as in wild-type islets. This suggests that oxidative or ER stress do not cause inflammasome-mediated cell death. Similarly, deficiency of NLRP3 inflammasome components did not provide any protection from glucose, ribose or gluco-lipotoxicity. Finally, genetic activation of NLRP3 specifically in beta cells did not increase IL-1β production or cell death, even in response to glucolipotoxicity. Overall, our results show that glucose-, ER stress- or oxidative stress-induced cell death in islet cells is not dependent on intrinsic activation of the NLRP3 inflammasome.
- Published
- 2014
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37. JunB protects β-cells from lipotoxicity via the XBP1-AKT pathway.
- Author
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Cunha DA, Gurzov EN, Naamane N, Ortis F, Cardozo AK, Bugliani M, Marchetti P, Eizirik DL, and Cnop M
- Subjects
- Animals, DNA-Binding Proteins genetics, Diabetes Mellitus, Type 2 enzymology, Diabetes Mellitus, Type 2 genetics, Diabetes Mellitus, Type 2 metabolism, Female, Humans, Insulin-Secreting Cells enzymology, Male, Middle Aged, Phosphorylation, Proto-Oncogene Proteins c-akt metabolism, Rats, Regulatory Factor X Transcription Factors, Signal Transduction, Transcription Factors genetics, X-Box Binding Protein 1, DNA-Binding Proteins metabolism, Insulin-Secreting Cells metabolism, Transcription Factors metabolism
- Abstract
Diets rich in saturated fats may contribute to the loss of pancreatic β-cells in type 2 diabetes. JunB, a member of the activating protein 1 (AP-1) transcription factor family, promotes β-cell survival and mediates part of the beneficial effects of GLP-1 agonists. In this study we interrogated the molecular mechanisms involved in JunB-mediated β-cell protection from lipotoxicity. The saturated fatty acid palmitate decreased JunB expression, and this loss may contribute to β-cell apoptosis, as overexpression of JunB protected cells from lipotoxicity. Array analysis of JunB-deficient β-cells identified a gene expression signature of a downregulated endoplasmic reticulum (ER) stress response and inhibited AKT signaling. JunB stimulates XBP1 expression via the transcription factor c/EBPδ during ER stress, and forced expression of XBP1s rescued the viability of JunB-deficient cells, constituting an important antiapoptotic mechanism. JunB silencing inhibited AKT activation and activated the proapoptotic Bcl-2 protein BAD via its dephosphorylation. BAD knockdown reversed lipotoxic β-cell death potentiated by JunB siRNA. Interestingly, XBP1s links JunB and AKT signaling as XBP1 knockdown also reduced AKT phosphorylation. GLP-1 agonists induced cAMP-dependent AKT phosphorylation leading to β-cell protection against palmitate-induced apoptosis. JunB and XBP1 knockdown or IRE1 inhibition decreased AKT activation by cAMP, leading to β-cell apoptosis. In conclusion, JunB modulates the β-cell ER stress response and AKT signaling via the induction of XBP1s. The activation of the JunB gene network and the crosstalk between the ER stress and AKT pathway constitute a crucial defense mechanism by which GLP-1 agonists protect against lipotoxic β-cell death. These findings elucidate novel β-cell-protective signal transduction in type 2 diabetes.
- Published
- 2014
- Full Text
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38. Hepatic oxidative stress promotes insulin-STAT-5 signaling and obesity by inactivating protein tyrosine phosphatase N2.
- Author
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Gurzov EN, Tran M, Fernandez-Rojo MA, Merry TL, Zhang X, Xu Y, Fukushima A, Waters MJ, Watt MJ, Andrikopoulos S, Neel BG, and Tiganis T
- Subjects
- Animals, Cells, Cultured, Diet, High-Fat, Female, Glutathione Peroxidase deficiency, Glutathione Peroxidase genetics, Glutathione Peroxidase metabolism, Growth Hormone metabolism, Hepatocytes cytology, Hepatocytes metabolism, Insulin pharmacology, Insulin-Like Growth Factor I metabolism, Liver enzymology, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Obesity metabolism, Obesity pathology, Protein Tyrosine Phosphatase, Non-Receptor Type 2 deficiency, Protein Tyrosine Phosphatase, Non-Receptor Type 2 genetics, Reactive Oxygen Species metabolism, STAT1 Transcription Factor metabolism, STAT3 Transcription Factor metabolism, STAT5 Transcription Factor genetics, Signal Transduction drug effects, Glutathione Peroxidase GPX1, Insulin metabolism, Liver metabolism, Oxidative Stress, Protein Tyrosine Phosphatase, Non-Receptor Type 2 metabolism, STAT5 Transcription Factor metabolism
- Abstract
Hepatic insulin resistance is a key contributor to the pathogenesis of obesity and type 2 diabetes (T2D). Paradoxically, the development of insulin resistance in the liver is not universal, but pathway selective, such that insulin fails to suppress gluconeogenesis but promotes lipogenesis, contributing to the hyperglycemia, steatosis, and hypertriglyceridemia that underpin the deteriorating glucose control and microvascular complications in T2D. The molecular basis for the pathway-specific insulin resistance remains unknown. Here we report that oxidative stress accompanying obesity inactivates protein-tyrosine phosphatases (PTPs) in the liver to activate select signaling pathways that exacerbate disease progression. In obese mice, hepatic PTPN2 (TCPTP) inactivation promoted lipogenesis and steatosis and insulin-STAT-5 signaling. The enhanced STAT-5 signaling increased hepatic IGF-1 production, which suppressed central growth hormone release and exacerbated the development of obesity and T2D. Our studies define a mechanism for the development of selective insulin resistance with wide-ranging implications for diseases characterized by oxidative stress., (Copyright © 2014 Elsevier Inc. All rights reserved.)
- Published
- 2014
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39. The proapoptotic BH3-only proteins Bim and Puma are downstream of endoplasmic reticulum and mitochondrial oxidative stress in pancreatic islets in response to glucotoxicity.
- Author
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Wali JA, Rondas D, McKenzie MD, Zhao Y, Elkerbout L, Fynch S, Gurzov EN, Akira S, Mathieu C, Kay TW, Overbergh L, Strasser A, and Thomas HE
- Subjects
- Animals, Antioxidants pharmacology, Apoptosis Regulatory Proteins deficiency, Apoptosis Regulatory Proteins genetics, Bcl-2-Like Protein 11, Cell Line, Diabetes Mellitus, Type 2 metabolism, Diabetes Mellitus, Type 2 pathology, Endoplasmic Reticulum drug effects, Endoplasmic Reticulum pathology, Humans, Insulin-Secreting Cells metabolism, Insulin-Secreting Cells pathology, Islets of Langerhans drug effects, Islets of Langerhans pathology, Membrane Proteins deficiency, Membrane Proteins genetics, Mice, Mice, 129 Strain, Mice, Inbred C57BL, Mice, Knockout, Mitochondria drug effects, Mitochondria pathology, Oxidants pharmacology, Proto-Oncogene Proteins deficiency, Proto-Oncogene Proteins genetics, RNA, Messenger metabolism, Ribose metabolism, Tissue Culture Techniques, Transcription Factor CHOP deficiency, Transcription Factor CHOP genetics, Tumor Suppressor Proteins deficiency, Tumor Suppressor Proteins genetics, Apoptosis drug effects, Apoptosis Regulatory Proteins metabolism, Endoplasmic Reticulum metabolism, Endoplasmic Reticulum Stress drug effects, Glucose metabolism, Islets of Langerhans metabolism, Membrane Proteins metabolism, Mitochondria metabolism, Oxidative Stress drug effects, Proto-Oncogene Proteins metabolism, Tumor Suppressor Proteins metabolism
- Abstract
Apoptosis of pancreatic beta cells is a feature of type 2 diabetes and its prevention may have therapeutic benefit. High glucose concentrations induce apoptosis of islet cells, and this requires the proapoptotic Bcl-2 homology domain 3 (BH3)-only proteins Bim and Puma. We studied the stress pathways induced by glucotoxicity in beta cells that result in apoptosis. High concentrations of glucose or ribose increased expression of the transcription factor CHOP (C/EBP homologous protein) but not endoplasmic reticulum (ER) chaperones, indicating activation of proapoptotic ER stress signaling. Inhibition of ER stress prevented ribose-induced upregulation of Chop and Puma mRNA, and partially protected islets from glucotoxicity. Loss of Bim or Puma partially protected islets from the canonical ER stressor thapsigargin. The antioxidant N-acetyl-cysteine also partially protected islets from glucotoxicity. Islets deficient in both Bim and Puma, but not Bim or Puma alone, were significantly protected from killing induced by the mitochondrial reactive oxygen species donor rotenone. Our data demonstrate that high concentrations of glucose induce ER and oxidative stress, which causes cell death mediated by Bim and Puma. We observed significantly higher Bim and Puma mRNA in islets of human donors with type 2 diabetes. This indicates that inhibition of Bim and Puma, or their inducers, may prevent beta-cell destruction in type 2 diabetes.
- Published
- 2014
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40. TCPTP regulates SFK and STAT3 signaling and is lost in triple-negative breast cancers.
- Author
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Shields BJ, Wiede F, Gurzov EN, Wee K, Hauser C, Zhu HJ, Molloy TJ, O'Toole SA, Daly RJ, Sutherland RL, Mitchell CA, McLean CA, and Tiganis T
- Subjects
- Animals, Breast metabolism, Breast pathology, Breast Neoplasms genetics, Breast Neoplasms pathology, Cell Line, Tumor, Cell Proliferation, Female, Gene Expression Regulation, Neoplastic, Gene Knockdown Techniques, Humans, Mice, Mice, Inbred C57BL, Protein Tyrosine Phosphatase, Non-Receptor Type 2 genetics, Signal Transduction, Breast Neoplasms metabolism, Protein Tyrosine Phosphatase, Non-Receptor Type 2 metabolism, STAT3 Transcription Factor metabolism, src-Family Kinases metabolism
- Abstract
Tyrosine phosphorylation-dependent signaling, as mediated by members of the epidermal growth factor receptor (EGFR) family (ErbB1 to -4) of protein tyrosine kinases (PTKs), Src family PTKs (SFKs), and cytokines such as interleukin-6 (IL-6) that signal via signal transducer and activator of transcription 3 (STAT3), is critical to the development and progression of many human breast cancers. EGFR, SFKs, and STAT3 can serve as substrates for the protein tyrosine phosphatase TCPTP (PTPN2). Here we report that TCPTP protein levels are decreased in a subset of breast cancer cell lines in vitro and that TCPTP protein is absent in a large proportion of "triple-negative" primary human breast cancers. Homozygous TCPTP deficiency in murine mammary fat pads in vivo is associated with elevated SFK and STAT3 signaling, whereas TCPTP deficiency in human breast cancer cell lines enhances SFK and STAT3 signaling. On the other hand, TCPTP reconstitution in human breast cancer cell lines severely impaired cell proliferation and suppressed anchorage-independent growth in vitro and xenograft growth in vivo. These studies establish TCPTP's potential to serve as a tumor suppressor in human breast cancer.
- Published
- 2013
- Full Text
- View/download PDF
41. Differential usage of NF-κB activating signals by IL-1β and TNF-α in pancreatic beta cells.
- Author
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Ortis F, Miani M, Colli ML, Cunha DA, Gurzov EN, Allagnat F, Chariot A, and Eizirik DL
- Subjects
- Animals, Cell Line, Cells, Cultured, Diabetes Mellitus, Type 1 drug therapy, Gene Silencing, Humans, I-kappa B Kinase antagonists & inhibitors, I-kappa B Kinase genetics, Insulin-Secreting Cells cytology, Insulin-Secreting Cells drug effects, Mice, Molecular Targeted Therapy, Protease Inhibitors pharmacology, Proteasome Inhibitors, Protein Kinase Inhibitors pharmacology, Protein Subunits antagonists & inhibitors, Protein Subunits genetics, Protein Subunits metabolism, Proteolysis drug effects, Rats, Rats, Wistar, Recombinant Proteins metabolism, Tumor Necrosis Factor-alpha genetics, I-kappa B Kinase metabolism, Insulin-Secreting Cells metabolism, Interleukin-1beta metabolism, NF-kappa B metabolism, Proteasome Endopeptidase Complex metabolism, Signal Transduction drug effects, Tumor Necrosis Factor-alpha metabolism
- Abstract
The cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α induce β-cell death in type 1 diabetes via NF-κB activation. IL-1β induces a more marked NF-κB activation than TNF-α, with higher expression of genes involved in β-cell dysfunction and death. We show here a differential usage of the IKK complex by IL-1β and TNF-α in β-cells. While TNF-α uses IKK complexes containing both IKKα and IKKβ, IL-1β induces complexes with IKKα only; this effect is achieved by induction of IKKβ degradation via the proteasome. Both IKKγ and activation of the TRAF6-TAK1-JNK pathway are involved in IL-1β-induced IKKβ degradation., (Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
42. Pancreatic β-cells activate a JunB/ATF3-dependent survival pathway during inflammation.
- Author
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Gurzov EN, Barthson J, Marhfour I, Ortis F, Naamane N, Igoillo-Esteve M, Gysemans C, Mathieu C, Kitajima S, Marchetti P, Ørntoft TF, Bakiri L, Wagner EF, and Eizirik DL
- Subjects
- Animals, Gene Knockdown Techniques, Humans, Mice, Mice, Inbred NOD, Mice, Transgenic, Proto-Oncogene Proteins c-jun genetics, Signal Transduction, Tumor Necrosis Factor-alpha pharmacology, Activating Transcription Factor 3 metabolism, Diabetes Mellitus, Type 1 metabolism, Inflammation metabolism, Insulin-Secreting Cells metabolism, Proto-Oncogene Proteins c-jun metabolism
- Abstract
Destruction of insulin-producing pancreatic β-cells by local autoimmune inflammation is a hallmark of type 1 diabetes. Histochemical analysis of pancreases from non-obese diabetic mice indicated activation of the transcription factor JunB/AP-1 (activator protein-1) after autoimmune infiltration of the islets. In vitro studies demonstrated that the cytokines tumor necrosis factor (TNF)-α and interferon (IFN)-γ induce JunB expression as a protective mechanism against apoptosis in both human and rodent β-cells. The gene network affected was studied by microarray analysis showing that JunB regulates nearly 20% of the cytokine-modified β-cell genes, including the transcription factor ATF3. Direct transcriptional induction of ATF3 by JunB is a key event for β-cell survival after TNF-α+IFN-γ treatment. Moreover, pharmacological upregulation of JunB/ATF3 via increased cAMP protected rodent primary β-cells and human islet cells against pro-inflammatory mediators. These results were confirmed in genetically modified islets derived from Ubi-JunB transgenic mice. Our findings identify ATF3 as a novel downstream target of JunB in the survival mechanism of β-cells under inflammatory stress.
- Published
- 2012
- Full Text
- View/download PDF
43. The transcription factor C/EBP delta has anti-apoptotic and anti-inflammatory roles in pancreatic beta cells.
- Author
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Moore F, Santin I, Nogueira TC, Gurzov EN, Marselli L, Marchetti P, and Eizirik DL
- Subjects
- Animals, Cell Line, Cytokines biosynthesis, Humans, Inflammation, Insulin-Secreting Cells drug effects, Insulinoma, Interferon Regulatory Factor-1, Rats, STAT1 Transcription Factor, Apoptosis, CCAAT-Enhancer-Binding Protein-delta physiology, Insulin-Secreting Cells pathology
- Abstract
In the course of Type 1 diabetes pro-inflammatory cytokines (e.g., IL-1β, IFN-γ and TNF-α) produced by islet-infiltrating immune cells modify expression of key gene networks in β-cells, leading to local inflammation and β-cell apoptosis. Most known cytokine-induced transcription factors have pro-apoptotic effects, and little is known regarding "protective" transcription factors. To this end, we presently evaluated the role of the transcription factor CCAAT/enhancer binding protein delta (C/EBPδ) on β-cell apoptosis and production of inflammatory mediators in the rat insulinoma INS-1E cells, in purified primary rat β-cells and in human islets. C/EBPδ is expressed and up-regulated in response to the cytokines IL-1β and IFN-γ in rat β-cells and human islets. Small interfering RNA-mediated C/EBPδ silencing exacerbated IL-1β+IFN-γ-induced caspase 9 and 3 cleavage and apoptosis in these cells. C/EBPδ deficiency increased the up-regulation of the transcription factor CHOP in response to cytokines, enhancing expression of the pro-apoptotic Bcl-2 family member BIM. Interfering with C/EBPδ and CHOP or C/EBPδ and BIM in double knockdown approaches abrogated the exacerbating effects of C/EBPδ deficiency on cytokine-induced β-cell apoptosis, while C/EBPδ overexpression inhibited BIM expression and partially protected β-cells against IL-1β+IFN-γ-induced apoptosis. Furthermore, C/EBPδ silencing boosted cytokine-induced production of the chemokines CXCL1, 9, 10 and CCL20 in β-cells by hampering IRF-1 up-regulation and increasing STAT1 activation in response to cytokines. These observations identify a novel function of C/EBPδ as a modulatory transcription factor that inhibits the pro-apoptotic and pro-inflammatory gene networks activated by cytokines in pancreatic β-cells.
- Published
- 2012
- Full Text
- View/download PDF
44. Cytokines tumor necrosis factor-α and interferon-γ induce pancreatic β-cell apoptosis through STAT1-mediated Bim protein activation.
- Author
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Barthson J, Germano CM, Moore F, Maida A, Drucker DJ, Marchetti P, Gysemans C, Mathieu C, Nuñez G, Jurisicova A, Eizirik DL, and Gurzov EN
- Subjects
- Adult, Aged, Animals, Antiviral Agents metabolism, Antiviral Agents pharmacology, Apoptosis drug effects, Apoptosis Regulatory Proteins genetics, Bcl-2-Like Protein 11, Cells, Cultured, Female, Gene Expression Regulation drug effects, Gene Expression Regulation physiology, Gene Silencing, Humans, Interferon-gamma genetics, Interferon-gamma pharmacology, Male, Membrane Proteins genetics, Mice, Mice, Knockout, Middle Aged, Neuropeptides genetics, Neuropeptides metabolism, Proto-Oncogene Proteins genetics, STAT1 Transcription Factor genetics, Tumor Necrosis Factor-alpha genetics, Tumor Necrosis Factor-alpha pharmacology, Tumor Suppressor Protein p53 genetics, Tumor Suppressor Protein p53 metabolism, Apoptosis physiology, Apoptosis Regulatory Proteins metabolism, Insulin-Secreting Cells metabolism, Interferon-gamma metabolism, Membrane Proteins metabolism, Proto-Oncogene Proteins metabolism, STAT1 Transcription Factor metabolism, Tumor Necrosis Factor-alpha metabolism
- Abstract
Type 1 diabetes is characterized by local inflammation (insulitis) in the pancreatic islets causing β-cell loss. The mitochondrial pathway of apoptosis is regulated by the balance and interaction between Bcl-2 members. Here we clarify the molecular mechanism of β-cell death triggered by the pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interferon (IFN)-γ. The combination of TNF-α + IFN-γ induced DP5, p53 up-regulated modulator of apoptosis (PUMA), and Bim expression in human islets and rodent β-cells. DP5 and PUMA inactivation by RNA interference partially protected against TNF-α + IFN-γ-induced β-cell apoptosis. DP5 knock-out mice had increased β-cell area, and isolated islets from these mice were resistant to cytokine exposure. Bim expression was transcriptionally regulated by STAT1, and its activation triggered cleavage of caspases. Silencing of Bim protected rodent and human β-cells to a large extent against TNF-α + IFN-γ, indicating a major role of this BH3-only activator protein in the mechanism of apoptosis. Our data support a highly regulated and context-dependent modulation of specific Bcl-2 members controlling the mitochondrial pathway of β-cell apoptosis during insulitis.
- Published
- 2011
- Full Text
- View/download PDF
45. Exposure to the viral by-product dsRNA or Coxsackievirus B5 triggers pancreatic beta cell apoptosis via a Bim / Mcl-1 imbalance.
- Author
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Colli ML, Nogueira TC, Allagnat F, Cunha DA, Gurzov EN, Cardozo AK, Roivainen M, Op de Beeck A, and Eizirik DL
- Subjects
- Animals, Bcl-2-Like Protein 11, Cell Line, Cell Survival, Coxsackievirus Infections pathology, Diabetes Mellitus, Type 1 etiology, Diabetes Mellitus, Type 1 metabolism, Diabetes Mellitus, Type 1 pathology, Diabetes Mellitus, Type 1 virology, Eukaryotic Initiation Factor-2 metabolism, Humans, Insulin-Secreting Cells pathology, Insulin-Secreting Cells virology, Male, Mitochondria metabolism, Myeloid Cell Leukemia Sequence 1 Protein, Phosphorylation, Rats, Rats, Wistar, Apoptosis, Apoptosis Regulatory Proteins metabolism, Coxsackievirus Infections metabolism, Enterovirus B, Human metabolism, Insulin-Secreting Cells metabolism, Membrane Proteins metabolism, Proto-Oncogene Proteins metabolism, Proto-Oncogene Proteins c-bcl-2 metabolism, RNA, Double-Stranded metabolism, RNA, Viral metabolism
- Abstract
The rise in type 1 diabetes (T1D) incidence in recent decades is probably related to modifications in environmental factors. Viruses are among the putative environmental triggers of T1D. The mechanisms regulating beta cell responses to viruses, however, remain to be defined. We have presently clarified the signaling pathways leading to beta cell apoptosis following exposure to the viral mimetic double-stranded RNA (dsRNA) and a diabetogenic enterovirus (Coxsackievirus B5). Internal dsRNA induces cell death via the intrinsic mitochondrial pathway. In this process, activation of the dsRNA-dependent protein kinase (PKR) promotes eIF2α phosphorylation and protein synthesis inhibition, leading to downregulation of the antiapoptotic Bcl-2 protein myeloid cell leukemia sequence 1 (Mcl-1). Mcl-1 decrease results in the release of the BH3-only protein Bim, which activates the mitochondrial pathway of apoptosis. Indeed, Bim knockdown prevented both dsRNA- and Coxsackievirus B5-induced beta cell death, and counteracted the proapoptotic effects of Mcl-1 silencing. These observations indicate that the balance between Mcl-1 and Bim is a key factor regulating beta cell survival during diabetogenic viral infections.
- Published
- 2011
- Full Text
- View/download PDF
46. Bcl-2 proteins in diabetes: mitochondrial pathways of β-cell death and dysfunction.
- Author
-
Gurzov EN and Eizirik DL
- Subjects
- Animals, Cell Death, Humans, Diabetes Mellitus metabolism, Diabetes Mellitus pathology, Insulin-Secreting Cells metabolism, Insulin-Secreting Cells pathology, Mitochondria metabolism, Proto-Oncogene Proteins c-bcl-2 metabolism
- Abstract
Diabetes is a metabolic disease affecting nearly 300 million individuals worldwide. Both types of diabetes (1 and 2) are characterized by loss of functional pancreatic β-cell mass causing different degrees of insulin deficiency. The Bcl-2 family has a double-edged effect in diabetes. These proteins are crucial controllers of the mitochondrial pathway of β-cell apoptosis induced by pro-inflammatory cytokines or lipotoxicity. In parallel, some Bcl-2 members also regulate glucose metabolism and β-cell function. In this review, we describe the role of Bcl-2 proteins in β-cell homeostasis and death. We focus on how these proteins interact, their contribution to the crosstalk between endoplasmic reticulum stress and mitochondrial permeabilization, their context-dependent usage following different pro-apoptotic stimuli, and their role in β-cell physiology., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
47. The transcription factor B-cell lymphoma (BCL)-6 modulates pancreatic {beta}-cell inflammatory responses.
- Author
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Igoillo-Esteve M, Gurzov EN, Eizirik DL, and Cnop M
- Subjects
- Animals, Apoptosis drug effects, Blotting, Western, Cell Line, Cell Survival drug effects, Cell Survival genetics, Colforsin pharmacology, Cytokines pharmacology, Exenatide, Fluorescent Antibody Technique, Insulin-Secreting Cells cytology, Insulin-Secreting Cells drug effects, Male, NF-kappa B genetics, Nitric Oxide Synthase Type II genetics, Peptides pharmacology, Polymerase Chain Reaction, Prolactin pharmacology, Proto-Oncogene Proteins c-bcl-6 genetics, Rats, Rats, Wistar, Venoms pharmacology, fas Receptor genetics, Insulin-Secreting Cells immunology, Insulin-Secreting Cells metabolism, Proto-Oncogene Proteins c-bcl-6 metabolism
- Abstract
Type 1 diabetes is a chronic autoimmune disease with a strong inflammatory component. We have previously shown that expression of the transcriptional repressor B-cell lymphoma (BCL)-6 is very low in pancreatic β-cells, which may favor prolonged proinflammatory responses after exposure to the cytokines IL-1β and interferon γ. Here we investigated whether cytokine-induced inflammation and apoptosis can be prevented in β-cells by BCL-6 expression using plasmid, prolactin, and adenoviral approaches. The induction of mild or abundant BCL-6 expression in β-cells by prolactin or an adenoviral BCL-6 expression construct, respectively, reduced cytokine-induced inflammatory responses in a dose-dependent manner through inhibition of nuclear factor-κB activation. BCL-6 decreased Fas and inducible nitric oxide synthase expression and nitric oxide production, but it inhibited the expression of the antiapoptotic proteins Bcl-2 and JunB while increasing the expression of the proapoptotic death protein 5. The net result of these opposite effects was an augmentation of β-cell apoptosis. In conclusion, BCL-6 expression tones down the unrestrained cytokine-induced proinflammatory response of β-cells but it also favors gene networks leading to apoptosis. This suggests that cytokine-induced proinflammatory and proapoptotic signals can be dissociated in β-cells. Further understanding of these pathways may open new possibilities to improve β-cell survival in early type 1 diabetes or after transplantation.
- Published
- 2011
- Full Text
- View/download PDF
48. STAT1 is a master regulator of pancreatic {beta}-cell apoptosis and islet inflammation.
- Author
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Moore F, Naamane N, Colli ML, Bouckenooghe T, Ortis F, Gurzov EN, Igoillo-Esteve M, Mathieu C, Bontempi G, Thykjaer T, Ørntoft TF, and Eizirik DL
- Subjects
- Animals, Apoptosis drug effects, Apoptosis Regulatory Proteins genetics, Apoptosis Regulatory Proteins immunology, Cell Differentiation immunology, Cells, Cultured, Feedback, Physiological physiology, Gene Knockdown Techniques, Interferon Regulatory Factor-1 immunology, Interferon Regulatory Factor-1 metabolism, Interferon-gamma immunology, Interferon-gamma metabolism, Interleukin-1beta pharmacology, Male, Neuropeptides genetics, Neuropeptides immunology, RNA, Small Interfering, Rats, Rats, Wistar, STAT1 Transcription Factor genetics, STAT1 Transcription Factor metabolism, Transcription, Genetic immunology, Apoptosis immunology, Insulin-Secreting Cells immunology, Insulin-Secreting Cells pathology, Pancreatitis immunology, Pancreatitis pathology, STAT1 Transcription Factor immunology
- Abstract
Cytokines produced by islet-infiltrating immune cells induce β-cell apoptosis in type 1 diabetes. The IFN-γ-regulated transcription factors STAT1/IRF-1 have apparently divergent effects on β-cells. Thus, STAT1 promotes apoptosis and inflammation, whereas IRF-1 down-regulates inflammatory mediators. To understand the molecular basis for these differential outcomes within a single signal transduction pathway, we presently characterized the gene networks regulated by STAT1 and IRF-1 in β-cells. This was done by using siRNA approaches coupled to microarray analysis of insulin-producing cells exposed or not to IL-1β and IFN-γ. Relevant microarray findings were further studied in INS-1E cells and primary rat β-cells. STAT1, but not IRF-1, mediates the cytokine-induced loss of the differentiated β-cell phenotype, as indicated by decreased insulin, Pdx1, MafA, and Glut2. Furthermore, STAT1 regulates cytokine-induced apoptosis via up-regulation of the proapoptotic protein DP5. STAT1 and IRF-1 have opposite effects on cytokine-induced chemokine production, with IRF-1 exerting negative feedback inhibition on STAT1 and downstream chemokine expression. The present study elucidates the transcriptional networks through which the IFN-γ/STAT1/IRF-1 axis controls β-cell function/differentiation, demise, and islet inflammation.
- Published
- 2011
- Full Text
- View/download PDF
49. p53 up-regulated modulator of apoptosis (PUMA) activation contributes to pancreatic beta-cell apoptosis induced by proinflammatory cytokines and endoplasmic reticulum stress.
- Author
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Gurzov EN, Germano CM, Cunha DA, Ortis F, Vanderwinden JM, Marchetti P, Zhang L, and Eizirik DL
- Subjects
- Animals, Apoptosis Regulatory Proteins genetics, Binding Sites genetics, Biphenyl Compounds pharmacology, Blotting, Western, Cell Line, Tumor, Cells, Cultured, Gene Expression drug effects, Humans, Insulin-Secreting Cells cytology, Insulin-Secreting Cells drug effects, Insulin-Secreting Cells metabolism, Interferon-gamma pharmacology, Interleukin-1beta pharmacology, Mutation, NF-kappa B metabolism, Nitrophenols pharmacology, Piperazines pharmacology, Proto-Oncogene Proteins genetics, RNA Interference, Rats, Rats, Wistar, Reverse Transcriptase Polymerase Chain Reaction, Sulfonamides pharmacology, bcl-X Protein genetics, bcl-X Protein metabolism, Apoptosis drug effects, Apoptosis Regulatory Proteins metabolism, Cytokines pharmacology, Endoplasmic Reticulum metabolism, Proto-Oncogene Proteins metabolism
- Abstract
Type 1 diabetes is an autoimmune disorder characterized by chronic inflammation and pancreatic beta-cell loss. Here, we demonstrate that the proinflammatory cytokine interleukin-1beta, combined with interferon-gamma, induces the expression of the Bcl-2 homology 3 (BH3)-only activator PUMA (p53 up-regulated modulator of apoptosis) in beta-cells. Transcriptional activation of PUMA is regulated by nuclear factor-kappaB and endoplasmic reticulum stress but is independent of p53. PUMA activation leads to mitochondrial Bax translocation, cytochrome c release, and caspase-3 cleavage resulting in beta-cell demise. The antiapoptotic Bcl-XL protein is localized mainly at the mitochondria of the beta-cells and antagonizes PUMA action, but Bcl-XL is inactivated by the BH3-only sensitizer DP5/Hrk in cytokine-exposed beta-cells. Moreover, a pharmacological mimic of the BH3-only sensitizer Bad, which inhibits Bcl-XL and Bcl-2, induces PUMA-dependent beta-cell death and potentiates cytokine-induced apoptosis. Our data support a hierarchical activation of BH3-only proteins controlling the intrinsic pathway of beta-cell apoptosis in the context of inflammation and type 1 diabetes.
- Published
- 2010
- Full Text
- View/download PDF
50. MDA5 and PTPN2, two candidate genes for type 1 diabetes, modify pancreatic beta-cell responses to the viral by-product double-stranded RNA.
- Author
-
Colli ML, Moore F, Gurzov EN, Ortis F, and Eizirik DL
- Subjects
- Animals, Apoptosis drug effects, Chemokines metabolism, Enzyme Activation drug effects, Insulin-Secreting Cells enzymology, Interferon-beta genetics, JNK Mitogen-Activated Protein Kinases metabolism, Male, NF-kappa B metabolism, Poly I-C pharmacology, Promoter Regions, Genetic genetics, RNA, Small Interfering metabolism, Rats, Rats, Wistar, DEAD-box RNA Helicases metabolism, Diabetes Mellitus, Type 1 enzymology, Diabetes Mellitus, Type 1 genetics, Insulin-Secreting Cells pathology, Protein Tyrosine Phosphatase, Non-Receptor Type 2 metabolism, RNA, Double-Stranded pharmacology, Viruses metabolism
- Abstract
beta-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a 'dialog' between beta-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects beta-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic beta-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat beta-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic-polycitidilic acid-PIC). Real-time RT-PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary beta-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify beta-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate beta-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic beta-cell level.
- Published
- 2010
- Full Text
- View/download PDF
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