| 1. |
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| 2. |
- Andersson, Annika K., 1974-
(författare)
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Role of Inducible Nitric Oxide Synthase and Melatonin in Regulation of β-cell Sensitivity to Cytokines
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mechanisms of β-cell destruction leading to type 1 diabetes are complex and not yet fully understood, but infiltration of the islets of Langerhans by autoreactive immune cells is believed to be important. Activated macrophages and T-cells may then secrete cytokines and free radicals, which could selectively damage the β-cells. Among the cytokines, IL-1β, IFN-γ and TNF-α can induce expression of inducible nitric synthase (iNOS) and cyclooxygenase-2. Subsequent nitric oxide (NO) and prostaglandin E2 (PGE2) formation may impair islet function.In the present study, the ability of melatonin (an antioxidative and immunoregulatory hormone) to protect against β-cell damage induced by streptozotocin (STZ; a diabetogenic and free radical generating substance) or IL-1β exposure was examined. In vitro, melatonin counteracted STZ- but not IL-1β-induced islet suppression, indicating that the protective effect of melatonin is related to interference with free radical generation and DNA damage, rather than NO synthesis. In vivo, non-immune mediated diabetes induced by a single dose of STZ was prevented by melatonin.Furthermore, the effects of proinflammatory cytokines were examined in islets obtained from mice with a targeted deletion of the iNOS gene (iNOS -/- mice) and wild-type controls. The in vitro data obtained show that exposure to IL-1β or (IL-1β + IFN-γ) induce disturbances in the insulin secretory pathway, which were independent of NO or PGE2 production and cell death. Initially after addition, in particular IL-1β seems to be stimulatory for the insulin secretory machinery of iNOS –/- islets, whereas IL-1β acts inhibitory after a prolonged period. Separate experiments suggest that the stimulatory effect of IL-1β involves an increased gene expression of phospholipase D1a/b. In addition, the formation of new insulin molecules appears to be affected, since IL-1β and (IL-1β + IFN-γ) suppressed mRNA expression of both insulin convertase enzymes and insulin itself.
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| 3. |
- Barbu, Andreea R., et al.
(författare)
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A perfusion protocol for highly efficient transduction of intact pancreatic islets of Langerhans
- 2006
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 49:10, s. 2388-2391
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Tidskriftsartikel (refereegranskat)abstract
- Successful gene transfer to pancreatic islets might be a powerful tool for dissecting the biological pathways involved in the functional impairment and destruction of beta cells in type 1 diabetes. In the long run, such an approach may also prove useful for promoting islet graft survival after transplantation in diabetic patients. However, efficient genetic modification of primary insulin-producing cells is limited by the specific compact structure of the pancreatic islet. We present here a whole-pancreas perfusion-based transduction procedure for genetic modification of intact pancreatic islets. We used flow cytometry analysis and confocal microscopy to evaluate the efficiency of in vitro and perfusion-based transduction protocols that use adenoviral and lentiviral vectors expressing green fluorescent protein. Islet cell viability was assessed by fluorescence microscopy and beta cell function was determined via glucose-stimulated insulin secretion. In intact rat and human pancreatic islets, adenoviral and lentiviral vectors mediated gene transfer to about 30% of cells, but they did not reach the inner cellular mass within the islet core. Using the whole-pancreas perfusion protocol, we demonstrate that at least in rodent models the centrally located insulin-producing cells can be transduced with high efficiency, while preserving the structural integrity of the islet. Moreover, islet cell viability and function are not impaired by this procedure. These results support the view that perfusion-based transduction protocols may significantly improve the yield of successfully engineered primary insulin-producing cells for diabetes research.
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| 4. |
- Hägerkvist, Robert, et al.
(författare)
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Consequences of Shb and c-Abl interactions for cell death in response to various stress stimuli
- 2007
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 313:2, s. 284-291
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Tidskriftsartikel (refereegranskat)abstract
- The adaptor protein Shb has previously been shown to regulate apoptosis in response to cytokines and inhibitors of angiogenesis although the mechanisms governing these effects have remained obscure. We currently demonstrate interactions between Shb and c-Abl and that Shb regulates c-Abl kinase activity. The data suggest that c-Abl binds to tyrosine phosphorylated Shb via a concerted effort involving both the c-Abl SH3 and SH2 domains. The biological significance of the Shb/c-Abl interaction was presently tested in overexpression experiments and was found to promote hydrogen peroxide-induced cell death. We also show by Shb knockdown experiments that Shb regulates c-Abl activity and modulates cell death in response to the genotoxic agent cisplatin and the endoplasmic reticulum stress-inducer tunicamycin. The findings are in agreement with the notion of Shb playing a pivotal role in modulating c-Abl pro-apoptotic signaling in response to various stress stimuli.
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| 5. |
- Mokhtari, Dariush, et al.
(författare)
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Increased Hsp70 expression attenuates cytokine-induced cell death in islets of Langerhans from Shb knockout mice
- 2009
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 387:3, s. 553-557
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Tidskriftsartikel (refereegranskat)abstract
- Type 1 diabetes may depend on cytokine-induced beta-cell death and therefore the current investigation was performed in order to elucidate this response in Shb-deficient islets. A combination of interleukin-1beta and interferon-gamma caused a diminished beta-cell death response in Shb null islets. Furthermore, the induction of an unfolded protein response (UPR) by adding cyclopiazonic acid did not increase cell death in Shb-deficient islets, despite simultaneous expression of UPR markers. The heat-shock protein Hsp70 was more efficiently induced in Shb knockout islets, providing an explanation for the decreased susceptibility of Shb-deficient islets to cytokines. It is concluded that islets deficient in the Shb protein are less susceptible to cytotoxic conditions, and that this partly depends on their increased ability to induce Hsp70 under such circumstances. Interference with Shb signaling may provide means to improve beta-cell viability under conditions of beta-cell stress.
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| 6. |
- Mokhtari, Dariush, 1977-
(författare)
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MEKK-1 and NF-κB Signaling in Pancreatic Islet Cell Death
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes is an autoimmune disease resulting in the selective destruction of the insulin producing β-cells in the pancreas. Pro-inflammatory cytokines and the free radical nitric oxide (NO) have been implicated in mediating the destruction of β-cells, possibly through activation of the mitogen activated protein kinases (MAPKs) JNK, ERK and p38. In addition to MAPKs, cytokine signaling also results in activation of the transcription factor nuclear factor-kappaB (NF-κB). The upstream signaling events leading to MAPK and NF-κB activation in β-cells are not well known. The work presented in this thesis therefore aims at characterizing the regulation of MAPKs and NF-κB in human islets, with emphasis on the role of the MAPK activator MAP/ERK kinase kinase-1 (MEKK-1) in islet cell death. It was found that MEKK-1 was phosphorylated in response to the nitric oxide donor DETA/NONOate (DETA/NO), the β-cell toxin streptozotocin (STZ) and pro-inflammatory cytokines and that MEKK-1 downstream signaling in response to the same treatments involved activation of JNK but not ERK and p38. MEKK-1 was also found to be essential for cytokine-induced NF-κB activation. MEKK-1 downregulation protected human islet cells from DETA/NO-, STZ, and cytokine-induced cell death. Furthermore, overexpression of the NF-κB subunit c-Rel protected human islet cells from STZ and hydrogen peroxide-induced cell death indicating that NF-κB activity protects against cell death in human islets. In summary, these results support an essential role for MEKK-1 in the activation of JNK and NF-κB, with important consequences for human islet cell death and that strategies preventing human islets death by inhibition of the JNK pathway instead of NF-κB might be suitable.
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| 7. |
- Wang, Xuan, 1984-
(författare)
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Study of the Proliferation, Function and Death of Insulin-Producing Beta-Cells in vitro: Role of the Transcription Factor ZBED6
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A thorough understanding of beta-cell proliferation, function, death and regeneration under normal condition as well as in the progression of diabetes is crucial to the conquest of this disease. The work presented in this thesis aimed to investigate the expression and role of a novel transcription factor, Zinc finger BED domain-containing protein 6 (ZBED6), in beta-cells.ZBED6 was present in mouse βTC-6 cells and human islets as a double nuclear band at 115/120 kDa and as a single cytoplasmic band at 95-100 kDa, which lacked N-terminal nuclear localization signals. Lentiviral shRNA-mediated stable silencing of ZBED6 in βTC-6 cells resulted in altered morphology, decreased proliferation, a partial S/G2 cell cycle arrest, increased expression of beta-cell specific genes, and higher rates of apoptosis. ChIP sequencing of human islets showed that ZBED6 binding was preferentially to genes that control transcription, macromolecule biosynthesis and apoptosis. We proposed that ZBED6 supported proliferation and survival of beta-cells, possibly at the expense of specialized beta-cell function, i.e. insulin production.To further investigate the role of ZBED6 in beta-cells, ChIP sequencing and whole transcriptome analysis were performed using MIN6 cells. More than 4000 putative target genes of ZBED6 were identified, including Pdx1, MafA and Nkx6.1. ZBED6-silencing resulted in differential expression of more than 700 genes, which was paralleled by an increase in the content and release of insulin in response to a high glucose concentration. Altered morphology/growth patterns as indicated by increased cell clustering were observed in ZBED6 silenced cells. We found also that ZBED6 decreased the ratio between N- and E-cadherin. A lower N- to E-cadherin ratio may hamper the formation of three-dimensional beta-cell clusters and cell-to-cell junctions with neural crest stem cells, and instead promote efficient attachment to a laminin support and monolayer growth. Thus, by controlling beta-cell adhesion and cell-to-cell junctions, ZBED6 might play an important role in beta-cell differentiation, proliferation and survival.
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| 8. |
- Welsh, Michael, et al.
(författare)
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Transgeneic mice expressing the Shb adaptor protein under the control of rat insulin promoter exhibit altered viability of pancreatic islet cells
- 1999
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Ingår i: Molecular Medicine. - 1076-1551. ; 5:3, s. 169-180
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUNDThe Src-homology 2 domain-containing adaptor protein Shb was recently cloned as a serum-inducible gene in the insulin-producing beta-TC1 cell line. Subsequent studies have revealed an involvement of Shb for apoptosis in NIH3T3 fibroblasts and differentiation in the neuronal PC12 cells. To assess a role of Shb for beta-cell function, transgenic mice utilizing the rat insulin promoter to drive expression of Shb were generated.MATERIALS AND METHODSA gene construct allowing the Shb cDNA to be expressed from the rat insulin 2 promoter was microinjected into fertilized mouse oocytes and implanted into pseudopregnant mice. Mice containing a low copy number of this transgene were bred and used for further experimentation. Shb expression was determined by Western blot analysis. The insulin-positive area of whole pancreas, insulin secretion of isolated islets and islet cell apoptosis, glucose tolerance tests, and in vivo sensitivity to multiple injections of the beta-cell toxin streptozotocin were determined in control CBA and Shb-transgenic mice.RESULTSWestern blot analysis revealed elevated islet content of the Shb protein. Shb-transgenic mice displayed enhanced glucose-disappearance rates in response to an intravenous glucose injection. The relative pancreatic beta-cell area neonatally and at 6 months of age were increased in the Shb-transgenic mice. Islets isolated from Shb-transgenic mice showed enhanced insulin secretion in response to glucose and increased insulin and DNA content. Apoptosis was increased in islets isolated from Shb-transgenic mice compared with control islets both under basal conditions and after incubation with IL-1 beta + IFN-gamma. Rat insulinoma RINm5F cells overexpressing Shb displayed decreased viability during culture in 0.1% serum and after exposure to a cytotoxic dose of nicotinamide. Shb-transgenic mice injected with multiple doses of streptozotocin showed increased blood glucose values compared with the corresponding controls, suggesting increased in vivo susceptibility to this toxin.CONCLUSIONThe results suggest that Shb has dual effects on beta-cell growth: whereas Shb increases beta-cell formation during late embryonal stages, Shb also enhances beta-cell death under certain stressful conditions and may thus contribute to beta-cell destruction in type 1 diabetes.
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| 9. |
- Welsh, Nils, et al.
(författare)
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Overexpression of the Shb SH2 domain-protein in insulin-producing cells leads to altered signaling through the IRS-1 and IRS-2 proteins
- 2002
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Ingår i: Molecular Medicine. ; 8:11, s. 695-704
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundOverexpression of the Src homology 2 domain protein Shb in _-cells of transgenic mice has been shown to promote an increased _-cell mass. To investigate the mechanisms by which Shb controls the _-cell mass, we have presently studied the effects of Shb overexpression on the IRS-1–induced signaling pathway in mouse islet _-cells and in insulin-producing RINm5F cells and correlated these effects to growth and death patterns.Materials and MethodsShb overexpression was achieved in RINm5F cells by selection of stable clones or by FACS purification of transiently transfected cells. For Shb overexpression in primary mouse islet cells, a Shb-transgene mouse was used. Cell proliferation and death rates were determined using flow cytometry. Serum-, insulin-, and IGF-1-stimulated signaling events were studied by immunoblot, immunoprecipitation, and in vitro kinase procedures.ResultsTransient Shb overexpression in RINm5F cells resulted in increased proliferation. Both Shb-overexpressing RINm5F cells and islet cells from transgenic mice (islet Shb) exhibited increased basal tyrosine phosphorylation of IRS-1. Shb overexpression resulted also in the assembly and activation of a multiunit complex consisting of at least Shb, IRS-1, IRS-2, FAK, and PI3K. Consequently, the phosphorylation of Akt was enhanced under basal conditions in Shb overexpressing cells. Finally, Shb overexpression did not affect insulin-induced phosphorylation of the PI3K-antagonist PTEN.ConclusionIt is concluded that the Shb-induced alterations in the IRS-1/PI3K/Akt pathway may be relevant to the understanding of growth and death patterns of insulin-producing cells.
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| 10. |
- Allagnat, F., et al.
(författare)
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C/EBP homologous protein contributes to cytokine-induced pro-inflammatory responses and apoptosis in beta-cells
- 2012
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Ingår i: Cell Death and Differentiation. - : Springer Science and Business Media LLC. - 1350-9047 .- 1476-5403. ; 19:11, s. 1836-1846
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Tidskriftsartikel (refereegranskat)abstract
- Induction of the C/EBP homologous protein (CHOP) is considered a key event for endoplasmic reticulum (ER) stress-mediated apoptosis. Type 1 diabetes (T1D) is characterized by an autoimmune destruction of the pancreatic beta-cells. Pro-inflammatory cytokines are early mediators of beta-cell death in T1D. Cytokines induce ER stress and CHOP overexpression in beta-cells, but the role for CHOP overexpression in cytokine-induced beta-cell apoptosis remains controversial. We presently observed that CHOP knockdown (KD) prevents cytokine-mediated degradation of the anti-apoptotic proteins B-cell lymphoma 2 (Bcl-2) and myeloid cell leukemia sequence 1 (Mcl-1), thereby decreasing the cleavage of executioner caspases 9 and 3, and apoptosis. Nuclear factor-kappa B (NF-kappa B) is a crucial transcription factor regulating beta-cell apoptosis and inflammation. CHOP KD resulted in reduced cytokine-induced NF-kappa B activity and expression of key NF-kappa B target genes involved in apoptosis and inflammation, including iNOS, FAS, IRF-7, IL-15, CCL5 and CXCL10. This was due to decreased I kappa B degradation and p65 translocation to the nucleus. The present data suggest that CHOP has a dual role in promoting beta-cell death: (1) CHOP directly contributes to cytokine-induced beta-cell apoptosis by promoting cytokine-induced mitochondrial pathways of apoptosis; and (2) by supporting the NF-kappa B activation and subsequent cytokine/chemokine expression, CHOP may contribute to apoptosis and the chemo attraction of mononuclear cells to the islets during insulitis. Cell Death and Differentiation (2012) 19, 1836-1846; doi:10.1038/cdd.2012.67; published online 1 June 2012
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| 11. |
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| 12. |
- Anvari, Ebrahim, et al.
(författare)
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The H-1-Receptor Antagonist Cetirizine Protects Partially Against Cytokine- and Hydrogen Peroxide-Induced beta-TC6 Cell Death In Vitro
- 2014
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Ingår i: Pancreas. - 0885-3177 .- 1536-4828. ; 43:4, s. 624-629
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Tidskriftsartikel (refereegranskat)abstract
- Objective It has been proposed that the histamine 1 (H-1) receptor not only promotes allergic reactions but also modulates autoimmune diseases, such as type 1 diabetes. In line with this, it has recently been reported that the H-1-receptor antagonist cetirizine can counteract the activation of signals/factors pertinent to the pathogenesis of type 1 diabetes and cytokine-induced beta-cell destruction. Therefore, the overall aim of this study was to determine whether H-1-receptor antagonists affect cytokine-induced beta-cell death and signaling in vitro. Methods The insulin-producing cell line beta-TC6 was exposed to the proinflammatory cytokines interleukin 1 beta(+) interferon gamma, or hydrogen peroxide. The H-1-receptor antagonists desloratadine and cetirizine were added to the cell cultures and cell viability; macrophage inhibitory factor levels, c-Jun N-terminal kinase phosphorylation, c-Jun expression, and beta-catenin levels were analyzed by flow cytometry, real-time polymerase chain reaction, and immunoblotting. Results Cetirizine protected partially against both cytokine- and hydrogen peroxide-induced cell death. This effect was paralleled by an inhibition of cytokine-induced c-Jun N-terminal kinase phosphorylation, c-Jun induction, and a restoration of macrophage inhibitory factor contents. Cetirizine also increased the beta-TC6 cell contents of beta-catenin at basal conditions. Conclusions Our results indicate a protective effect of a specific H-1-receptor antagonist.
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| 13. |
- Anvari, Ebrahim, et al.
(författare)
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The H1-receptor antagonist cetirizine ameliorates high-fat diet-induced glucose intolerance in male C57BL/6 mice, but not diabetes outcome in female non-obese diabetic (NOD) mice
- 2015
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Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 120:1, s. 40-46
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Tidskriftsartikel (refereegranskat)abstract
- Background. It has been proposed that the histamine 1-receptor (H1-receptor) not only promotes allergic reactions, but also modulates innate immunity and autoimmune reactions. In line with this, we have recently reported that the H1-receptor antagonist cetirizine partially counteracts cytokine-induced beta-cell signaling and destruction. Therefore, the aim of this study was to determine whether cetirizine affects diabetes in NOD mice, a model for human type 1 diabetes, and glucose intolerance in high-fat diet C57BL/6 mice, a model for human glucose intolerance. Methods. Female NOD mice were treated with cetirizine in the drinking water (25 mg/kg body weight) from 9 until 30 weeks of age during which precipitation of diabetes was followed. Male C57BL/6 mice were given a high-fat diet from 5 weeks of age. When the mice were 12 weeks of age cetirizine was given for 2 weeks in the drinking water. The effects of cetirizine were analyzed by blood glucose determinations, glucose tolerance tests, and insulin sensitivity tests. Results. Cetirizine did not affect diabetes development in NOD mice. On the other hand, cetirizine treatment for 1 week protected against high-fat diet-induced hyperglycemia. The glucose tolerance after 2 weeks of cetirizine treatment was improved in high-fat diet mice. We observed no effect of cetirizine on the insulin sensitivity of high-fat diet mice. Conclusion. Our results suggest a protective effect of cetirizine against high-fat diet-induced beta-cell dysfunction, but not against autoimmune beta-cell destruction.
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| 14. |
- Anvari, Ebrahim, et al.
(författare)
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The novel NADPH oxidase 4 inhibitor GLX351322 counteracts glucose intolerance in high-fat diet-treated C57BL/6 mice
- 2015
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Ingår i: Free radical research. - : Informa UK Limited. - 1071-5762 .- 1029-2470. ; 49:11, s. 1308-1318
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Tidskriftsartikel (refereegranskat)abstract
- In type 2 diabetes, it has been proposed that pancreatic beta-cell dysfunction is promoted by oxidative stress caused by NADPH oxidase (NOX) overactivity. Five different NOX enzymes (NOX1-5) have been characterized, among which NOX1 and NOX2 have been proposed to negatively affect beta-cells, but the putative role of NOX4 in type 2 diabetes-associated beta-cell dysfunction and glucose intolerance is largely unknown. Therefore, we presently investigated the importance of NOX4 for high-fat diet or HFD-induced glucose intolerance using male C57BL/6 mice using the new NOX4 inhibitor GLX351322, which has relative NOX4 selectivity over NOX2. In HFD-treated male C57BL/6 mice a two-week treatment with GLX351322 counteracted non-fasting hyperglycemia and impaired glucose tolerance. This effect occurred without any change in peripheral insulin sensitivity. To ascertain that NOX4 also plays a role for the function of human beta-cells, we observed that glucose- and sodium palmitate-induced insulin release from human islets in vitro was increased in response to NOX4 inhibitors. In long-term experiments (1-3 days), high-glucose-induced human islet cell reactive oxygen species (ROS) production and death were prevented by GLX351322. We propose that while short-term NOX4-generated ROS production is a physiological requirement for beta-cell function, persistent NOX4 activity, for example, during conditions of high-fat feeding, promotes ROS-mediated beta-cell dysfunction. Thus, selective NOX inhibition may be a therapeutic strategy in type 2 diabetes.
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| 15. |
- Barbu, Andreea, et al.
(författare)
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Diabetes Mellitus: Gene Therapy
- 2007
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Ingår i: ENCYCLOPEDIA OF LIFE SCIENCES. - : John Wiley & Sons.
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Bokkapitel (populärvet., debatt m.m.)abstract
- Gene therapy in diabetes mellitus can be defined as transfer of DNA to somatic cells in order to understand, treat or prevent the disease. For many gene therapy strategies in the treatment of diabetes, successful transduction of insulin producing cells is a prerequisite. Therefore, much effort is currently directed in developing efficient and non-toxic vectors for gene transfer in pancreatic insulin producing beta-cell. If available, these gene therapy tools could prevent the autoimmune beta-cell destruction in type 1 diabetes by protecting the remaining beta-cell mass in newly diagnosed diabetics or in prediabetic individuals at a high risk of becoming diabetic. Such an approach may also prove useful for promoting islet graft survival after transplantation in diabetic patients. Alternatively, attempts are being made to genetically engineer cells to become artificial beta-cells. Such cells could conceivably compensate for the lost endogenous beta-cell mass and restore a regulated insulin secretion.
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| 16. |
- Barbu, Andreea, et al.
(författare)
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Lipofection of insulin-producing RINm5F cells : methodological improvements
- 2007
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Ingår i: Journal of liposome research. - : Informa UK Limited. - 0898-2104 .- 1532-2394. ; 17:2, s. 49-62
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Tidskriftsartikel (refereegranskat)abstract
- Cationic lipid/DNA-complexes have been widely used as gene transfer vectors because they are less toxic and immunogenic than viral vectors. The aim of the present study was to improve and characterize lipofection of an insulin-producing cell line. We compared the transfection efficiency of seven commercially available lipid formulations (Lipotaxi, SuperFect, Fugene, TransFast, Dosper, GenePORTER and LipofectAMINE) by flow cytometry analysis of GFP-expression. In addition, we have determined the influences of centrifugation, serum and a nuclear localization signal peptide on the lipofection efficiency. We observed that two lipid formulations, GenePORTER and LipofectAMINE, were able to promote efficient gene transfer in RINm5F cells. However, GenePORTER exhibited the important advantage of being able to transfect cells in the presence of serum and with less cytotoxicity than LipofectAMINE. LipofectAMINE-induced RINm5F cell death could partially be counteracted by TPA, forskolin or fumonisin β1. Finally, both centrifugation and a nuclear localization signal peptide increased transfection efficiency.
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| 17. |
- Barbu, Andreea R, et al.
(författare)
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Adenoviral-induced islet cell cytotoxicity is not counteracted by Bcl-2 overexpression
- 2002
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Ingår i: Molecular Medicine. - 1076-1551 .- 1528-3658. ; 8:11, s. 733-741
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The ability to transfer immunoregulatory, cytoprotective, or anti-apoptotic genes into pancreatic islet cells may allow enhanced resistance against the autoimmune destruction of these cells in type 1 diabetes. We describe here an inducible transduction system for expression of the anti-apoptotic bcl-2 gene in insulin-producing cells as a potential tool for protecting against beta-cell death.MATERIALS AND METHODS: Isolated pancreatic rat islet cells or rat insulinoma (RINm5F) cells were transduced using a progesterone antagonist (RU 486) inducible adenoviral vector system, expressing the bcl-2 gene. Bcl-2 overexpression was measured by Western blot assays and flow cytometry analysis. Following exposure to cytokines or to the mitochondrial uncoupler FCCP, cell survival was determined using fluorescence and electron microscopy, and a colorimetric assay (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]- 2H-tetrazolium-5-carboxanilide [XTT]-based) for cell viability. The mitochondrial membrane potential ((m)) was assessed using the lipophilic cationic membrane potential-sensitive dye JC-1.RESULTS: The adenoviral gene transfer system induced Bcl-2 expression in more than 70% of beta-cells and the protein expression levels were successfully regulated in response to varying concentrations of progesterone antagonist RU 486. Exposure of islet cells to proinflammatory cytokines IL-1beta, TNF-alpha, and IFN-gamma, or to the mitochondrial uncoupler FCCP resulted in disruption of the mitochondrial membrane potential ((m)) and beta-cell death. Bcl-2 overexpression stabilized (m) and prevented cell death in RINm5F cells but not in islet cells. In addition, prolonged in vitro culture revealed adenoviral-induced islet cell necrosis.CONCLUSIONS: The RU 486-regulated adenoviral system can achieve an efficient control of gene transfer at relatively low doses of the adenoviral vector. However, Bcl-2 overexpression in islet cells did not prevent adenoviral- or cytokine-induced toxicity, suggesting that the specific death pathway involved in adenoviral toxicity in beta-cells may bypass the mitochondrial permeability transition event.
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| 18. |
- Barbu, Andreea R, et al.
(författare)
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Adenoviral-mediated transduction of human pancreatic islets : importance of adenoviral genome for cell viability and association with a deficient antiviral response
- 2005
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 146:5, s. 2406-2414
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Tidskriftsartikel (refereegranskat)abstract
- As adenoviral vectors are extensively used for genetic manipulation of insulin-producing cells in vitro, there is an increasing need to evaluate their effects on the function, morphology, and viability of transduced pancreatic islets. In the present study we observed that specific adenoviral genotypes, carrying E4 and E1/E3 deletions, correlate with differential induction of necrosis in pancreatic islet cells. In particular, the adenovirus death protein encoded from the E3 region of the adenoviral genome was able to modulate the changes induced in the morphology and viability of the transduced cells. We also propose a putative role for the transcriptional regulator pIX. Although human islet cells showed an increased resistance in terms of viral concentrations required for the induction of cell toxicity, our results showed that they were unable to build up an efficient antiviral response after transduction and that their survival was dependent on the exogenous addition of alpha-interferon. An intact and fully functional beta-cell is crucial for the successful application of gene therapy approaches in type 1 diabetes, and therefore, the implications of our findings need to be considered when designing vectors for gene transfer into pancreatic beta-cells.
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| 19. |
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| 20. |
- Barbu, Andrea R, et al.
(författare)
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Gene Therapy
- 2010. - 4th edition
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Ingår i: Textbook of Diabetes. - Thousand Oaks, CA : Wiley-Blackwell. - 9781405191814 ; 25, s. 604-604
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 21. |
- Barbu, Andreea Roxana, 1973-
(författare)
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In vitro Studies of β-cell Death and Survival. Modulation by Adenoviral Vectors and Bcl-2 Overexpression
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes is a multifactorial disease resulting from the selective destruction of insulin-producing β-cells within the pancreatic islets of Langerhans. The mechanisms of β-cell death are not fully understood but cytokines are important mediators of this process. In the present study we found that the combination of IL-1β, TNF-α and IFN-γ induced a nitric oxide-dependent disruption of the mitochondrial membrane potential in rat insulin-producing RINm5F-cells, which seems to be a necessary event for both RINm5F-cell apoptosis and necrosis. The antiapoptotic protein Bcl-2 was able to prevent cellular death in RINm5F cells, most probably by counteracting the mitochondrial permeability transition. These results pointed out the potential of such antiapoptotic genes as gene therapy tools, to allow enhanced resistance against autoimmune destruction of β-cells in type 1 diabetes. For this purpose we used a progesterone-antagonist (RU 486)-inducible gene transfer system to achieve an efficient and controlled Bcl-2 overexpression in primary rat β-cells. However, in our experience, prolonged in vitro culture revealed adenoviral-induced islet cell necrosis, a process that was not prevented by Bcl-2 overexpression. Moreover, we observed that specific adenoviral genotypes correlate with differential induction of necrosis in both human and rat pancreatic islet cells. Although human islet cells showed an increased resistance in terms of viral concentrations required for the induction of cell-toxicity, our results showed that they were unable to build up an efficient antiviral response following infection and that their survival was dependent on the exogenous addition of α-interferon.In conclusion, adenoviral techniques for overexpression of antiapoptotic proteins in insulin-producing cells may provide useful tools against β-cell directed autoimmune destruction. However, understanding the specific interactions of the viral gene products with cellular proteins and how they are involved in β-cell death regulation is fundamental for an efficient and safe application of gene therapy approaches to type 1 diabetes.
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| 23. |
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| 24. |
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| 26. |
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| 27. |
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| 28. |
- Elksnis, Andris, et al.
(författare)
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Imatinib protects against human beta-cell death via inhibition of mitochondrial respiration and activation of AMPK
- 2021
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Ingår i: Clinical Science. - : Portland Press. - 0143-5221 .- 1470-8736. ; 135:19, s. 2243-2263
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Tidskriftsartikel (refereegranskat)abstract
- The protein tyrosine kinase inhibitor imatinib is used in the treatment of various malignancies but may also promote beneficial effects in the treatment of diabetes. The aim of the present investigation was to characterize the mechanisms by which imatinib protects insulin producing cells. Treatment of non-obese diabetic (NOD) mice with imatinib resulted in increased beta-cell AMP-activated kinase (AMPK) phosphorylation. Imatinib activated AMPK also in vitro, resulting in decreased ribosomal protein S6 phosphorylation and protection against islet amyloid polypeptide (IAPP)-aggregation, thioredoxin interacting protein (TXNIP) up-regulation and beta-cell death. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) mimicked and compound C counteracted the effect of imatinib on beta-cell survival. Imatinib-induced AMPK activation was preceded by reduced glucose/pyruvate-dependent respiration, increased glycolysis rates, and a lowered ATP/AMP ratio. Imatinib augmented the fractional oxidation of fatty acids/malate, possibly via a direct interaction with the beta-oxidation enzyme enoyl coenzyme A hydratase, short chain, 1, mitochondrial (ECHS1). In non-beta cells, imatinib reduced respiratory chain complex I and II-mediated respiration and acyl-CoA carboxylase (ACC) phosphorylation, suggesting that mitochondrial effects of imatinib are not beta-cell specific. In conclusion, tyrosine kinase inhibitors modestly inhibit mitochondrial respiration, leading to AMPK activation and TXNIP down-regulation, which in turn protects against beta-cell death.
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| 29. |
- Elksnis, Andris, 1993-
(författare)
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Pharmaceutical Protection of Beta-Cells in Diabetes : Using Tyrosine Kinase Inhibition and NOX4 Inhibitors
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diabetes mellitus is a complex and heterogenous disease, with loss of beta-cell function and mass being a characteristic of not only type 1 diabetes (T1D), but also type 2 diabetes (T2D). In T1D, inappropriate inflammatory signaling is thought to participate in the autoimmune suppression and destruction of beta-cells. In T2D progressive insulin resistance with resulting glucolipotoxicity, increased inflammation and oxidative stress, drives islet amyloid formation and subsequent beta-cell exhaustion and failure. Even under best managed care, disease progression and eventual complications are unavoidable. New interventions that aim to improve beta-cell survival are highly needed. This thesis investigates two such possible interventions: the tyrosine kinase inhibitor Imatinib, and selective NADPH-oxidase inhibition.Imatinib mesylate, used in treatment of chronic myeloid leukemia and other malignancies, was soon after its introduction reported to possess anti-diabetic properties in both T1D and T2D patients undergoing treatment. Imatinib has been shown to prevent and reverse diabetes in NOD mice and improve glucose tolerance in high fat diet treated rats. In paper I, we aimed to characterize the mechanisms by which imatinib protects beta-cells. We found that imatinib inhibits complex I and II of the respiratory chain, leading to improved beta-cell survival through AMPK activation, reduced amyloid formation and protection against TXNIP upregulation.Oxidative stress may play a pivotal role in the development of beta-cell dysfunction and failure in T2D. The NADPH-oxidases are a family of 7 enzymes (NOX1-5 and DUOX 1-2), that produce reactive oxygen species that are important in various physiological processes but may, if excessively activated, also be a source for oxidative stress in T2D. In paper II, we evaluate novel selective NOX inhibitors as protective agents against in vitro induced human beta-cell stress. Selective NOX4 inhibition protected beta-cells against both cytokines and high-glucose + palmitate. In paper III we found that NOX4 inhibition increased mitochondrial membrane potential, mitochondrial reactive oxygen species and ATP/ADP ratio in a human beta-cell line, and this was paralleled with protection against human islet cell death when challenged with high-glucose and palmitate. Finally, in paper IV, we attempt to apply these findings in vivo, by transplanting athymic diabetic mice with human islets and treating them with a NOX4 inhibitor over a period of 4 weeks. Treated mice achieved lower blood glucose levels and water consumption throughout the treatment period, and apoptotic rates of insulin-positive human cells, measured as co-localization of insulin and cleaved caspase-3, were greatly reduced.
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| 30. |
- Elksnis, Andris, et al.
(författare)
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Pharmacological Inhibition of NOX4 Improves Mitochondrial Function and Survival in Human Beta-Cells
- 2021
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Ingår i: Biomedicines. - : MDPI. - 2227-9059. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have reported beneficial effects of NADPH oxidase 4 (NOX4) inhibition on beta-cell survival in vitro and in vivo. The mechanisms by which NOX4 inhibition protects insulin producing cells are, however, not known. The aim of the present study was to investigate the effects of a pharmacological NOX4 inhibitor (GLX7013114) on human islet and EndoC-beta H1 cell mitochondrial function, and to correlate such effects with survival in islets of different size, activity, and glucose-stimulated insulin release responsiveness. We found that maximal oxygen consumption rates, but not the rates of acidification and proton leak, were increased in islets after acute NOX4 inhibition. In EndoC-beta H1 cells, NOX4 inhibition increased the mitochondrial membrane potential, as estimated by JC-1 fluorescence; mitochondrial reactive oxygen species (ROS) production, as estimated by MitoSOX fluorescence; and the ATP/ADP ratio, as assessed by a bioluminescent assay. Moreover, the insulin release from EndoC-beta H1 cells at a high glucose concentration increased with NOX4 inhibition. These findings were paralleled by NOX4 inhibition-induced protection against human islet cell death when challenged with high glucose and sodium palmitate. The NOX4 inhibitor protected equally well islets of different size, activity, and glucose responsiveness. We conclude that pharmacological alleviation of NOX4-induced inhibition of beta-cell mitochondria leads to increased, and not decreased, mitochondrial ROS, and this was associated with protection against cell death occurring in different types of heterogeneous islets. Thus, NOX4 inhibition or modulation may be a therapeutic strategy in type 2 diabetes that targets all types of islets.
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| 31. |
- Elksnis, Andris, et al.
(författare)
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The selective NOX4 inhibitor GLX7013159 decreases blood glucose concentrations and human beta-cell apoptotic rates in diabetic NMRI nu/nu mice transplanted with human islets
- 2023
-
Ingår i: Free radical research. - : Taylor & Francis. - 1071-5762 .- 1029-2470. ; 57:6-12, s. 460-469
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Tidskriftsartikel (refereegranskat)abstract
- NADPH oxidase 4 (NOX4) inhibition has been reported to mitigate diabetes-induced beta-cell dysfunction and improve survival in vitro, as well as counteract high-fat diet-induced glucose intolerance in mice. We investigated the antidiabetic effects of the selective NOX4 inhibitor GLX7013159 in vivo in athymic diabetic mice transplanted with human islets over a period of 4 weeks. The GLX7013159-treated mice achieved lower blood glucose and water consumption throughout the treatment period. Furthermore, GLX7013159 treatment resulted in improved insulin and c-peptide levels, better insulin secretion capacity, as well as in greatly reduced apoptotic rates of the insulin-positive human cells, measured as colocalization of insulin and cleaved caspase-3. We conclude that the antidiabetic effects of NOX4 inhibition by GLX7013159 are observed also during a prolonged study period in vivo and are likely to be due to an improved survival and function of the human beta-cells.
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| 32. |
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| 33. |
- Fred, Rikard G, et al.
(författare)
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High glucose suppresses human islet insulin biosynthesis by inducing miR-133a leading to decreased polypyrimidine tract binding protein-expression
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:5, s. e10843-
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Prolonged periods of high glucose exposure results in human islet dysfunction in vitro. The underlying mechanisms behind this effect of high glucose are, however, unknown. The polypyrimidine tract binding protein (PTB) is required for stabilization of insulin mRNA and the PTB mRNA 3'-UTR contains binding sites for the microRNA molecules miR-133a, miR-124a and miR-146. The aim of this study was therefore to investigate whether high glucose increased the levels of these three miRNAs in association with lower PTB levels and lower insulin biosynthesis rates.METHODOLOGY/PRINCIPAL FINDINGS:Human islets were cultured for 24 hours in the presence of low (5.6 mM) or high glucose (20 mM). Islets were also exposed to sodium palmitate or the proinflammatory cytokines IL-1beta and IFN-gamma, since saturated free fatty acids and cytokines also cause islet dysfunction. RNA was then isolated for real-time RT-PCR analysis of miR-133a, miR-124a, miR-146, insulin mRNA and PTB mRNA contents. Insulin biosynthesis rates were determined by radioactive labeling and immunoprecipitation. Synthetic miR-133a precursor and inhibitor were delivered to dispersed islet cells by lipofection, and PTB was analyzed by immunoblotting following culture at low or high glucose. Culture in high glucose resulted in increased islet contents of miR-133a and reduced contents of miR-146. Cytokines increased the contents of miR-146. The insulin and PTB mRNA contents were unaffected by high glucose. However, both PTB protein levels and insulin biosynthesis rates were decreased in response to high glucose. The miR-133a inhibitor prevented the high glucose-induced decrease in PTB and insulin biosynthesis, and the miR-133a precursor decreased PTB levels and insulin biosynthesis similarly to high glucose.CONCLUSION:Prolonged high-glucose exposure down-regulates PTB levels and insulin biosynthesis rates in human islets by increasing miR-133a levels. We propose that this mechanism contributes to hyperglycemia-induced beta-cell dysfunction.
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| 34. |
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| 35. |
- Fred, Rikard G., et al.
(författare)
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Imatinib mesylate stimulates low-density lipoprotein receptor-related protein 1-mediated ERK phosphorylation in insulin-producing cells
- 2015
-
Ingår i: Clinical Science. - 0143-5221 .- 1470-8736. ; 128:1, s. 17-28
-
Tidskriftsartikel (refereegranskat)abstract
- Low-density lipoprotein receptor-related protein 1 (LRP1) is an endocytic and multi-functional type I cell surface membrane protein, which is known to be phosphorylated by the activated platelet-derived growth factor receptor (PDGFR). The tyrosine kinase inhibitor imatinib, which inhibits PDGFR and c-Abl, and which has previously been reported to counteract beta-cell death and diabetes, has been suggested to reduce atherosclerosis by inhibiting PDGFR-induced LRP1 phosphorylation. The aim of the present study was to study LRP1 function in beta-cells and to what extent imatinib modulates LRP1 activity. LRP1 and c-Abl gene knockdown was performed by RNAi using rat INS-1 832/13 and human EndoC1-beta H1 cells. LRP1 was also antagonized by treatment with the antagonist low-density lipoprotein receptor-related protein associated protein 1 (LRPAP1). We have used PDGF-BB, a PDGFR agonist, and apolipoprotein E (ApoE), an LRP1 agonist, to stimulate the activities of PDGFR and LRP1 respectively. Knockdown or inhibition of LRP1 resulted in increased hydrogen peroxide (H2O2)(-) or cytokine-induced cell death, and glucose-induced insulin release was lowered in LRP1-silenced cells. These results indicate that LRP1 function is necessary for beta-cell function and that LRP1 is adversely affected by challenges to beta-cell health. PDGF-BB, or the combination of PDGF-BB+ApoE, induced phosphorylation of extracellular-signal-regulated kinase (ERK), Akt and LRP1. LRP1 silencing blocked this event. Imatinib blocked phosphorylation of LRP1 by PDGFR activation but induced phosphorylation of ERK. LRP1 silencing blocked imatinib-induced phosphorylation of ERK. Sunitinib also blocked LRP1 phosphorylation in response to PDGF-BB and induced phosphorylation of ERK, but this latter event was not affected by LRP1 knockdown. siRNA-mediated knockdown of the imatinib target c-Abl resulted in an increased ERK phosphorylation at basal conditions, with no further increase in response to imatinib. Imatinib-induced cell survival of tunicamycin-treated cells was partially mediated by ERK activation. We have concluded that imatinib promotes LRP1-dependent ERK activation, possibly via inhibition of c-Abl, and that this could contribute to the pro-survival effects of imatinib on beta-cells.
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| 36. |
- Fred, Rikard G, et al.
(författare)
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Increased expression of polypyrimidine tract binding protein results in higher insulin mRNA levels
- 2005
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 328:1, s. 38-42
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to further elucidate the role of the polypyrimidine tract binding protein (PTB) in the control of insulin mRNA stability. We observed that the glucose- or interleukin-1β-induced increase in insulin mRNA was paralleled by an increase in PTB mRNA. To further test the hypothesis that PTB controls insulin gene expression, βTC-6 cells were treated with a PTB-specific siRNA to modify the β-cell content of PTB. Surprisingly, we observed an increase in PTB mRNA and PTB protein levels in response to the siRNA treatment. In addition, the PTB-siRNA treatment also increased insulin mRNA. We conclude that expression of the PTB gene controls insulin production.
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| 37. |
- Fred, Rikard G, et al.
(författare)
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PTB and TIAR binding to insulin mRNA 3'- and 5'UTRs; implications for insulin biosynthesis and messenger stability.
- 2016
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 2:9
-
Tidskriftsartikel (refereegranskat)abstract
- ObjectivesInsulin expression is highly controlled on the posttranscriptional level. The RNA binding proteins (RBPs) responsible for this result are still largely unknown.Methods and resultsTo identify RBPs that bind to insulin mRNA we performed mass spectrometry analysis on proteins that bound synthetic oligonucloetides mimicing the 5′- and the 3′-untranslated regions (UTRs) of rat and human insulin mRNA in vitro. We observed that the RBPs heterogeneous nuclear ribonucleoprotein (hnRNP) U, polypyrimidine tract binding protein (PTB), hnRNP L and T-cell restricted intracellular antigen 1-related protein (TIA-1-related protein; TIAR) bind to insulin mRNA sequences, and that the in vitro binding affinity of these RBPs changed when INS-1 cells were exposed to glucose, 3-isobutyl-1-methylxanthine (IBMX) or nitric oxide. High glucose exposure resulted in a modest increase in PTB and TIAR binding to an insulin mRNA sequence. The inducer of nitrosative stress DETAnonoate increased markedly hnRNP U and TIAR mRNA binding. An increased PTB to TIAR binding ratio in vitro correlated with higher insulin mRNA levels and insulin biosynthesis rates in INS-1 cells. To further investigate the importance of RNA-binding proteins for insulin mRNA stability, we decreased INS-1 and EndoC-βH1 cell levels of PTB and TIAR by RNAi. In both cell lines, decreased levels of PTB resulted in lowered insulin mRNA levels while decreased levels of TIAR resulted in increased insulin mRNA levels. Thapsigargin-induced stress granule formation was associated with a redistribution of TIAR from the cytosol to stress granules.ConclusionsThese experiments indicate that alterations in insulin mRNA stability and translation correlate with differential RBP binding. We propose that the balance between PTB on one hand and TIAR on the other participates in the control of insulin mRNA stability and utilization for insulin biosynthesis.
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| 38. |
- Fred, Rikard G., et al.
(författare)
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Role of the AMP kinase in cytokine-induced human EndoC-beta H1 cell death
- 2015
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 414:C, s. 53-63
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present investigation was to delineate cytokine-induced signaling and death using the EndoC-beta H1 cells as a model for primary human beta-cells. The cytokines IL-1 beta and IFN-gamma induced a rapid and transient activation of NF-kappa B, STAT-1, ERK, JNK and eIF-2 alpha signaling. The EndoC-beta H1 cells died rapidly when exposed to IL-1 beta + IFN-gamma, and this occurred also in the presence of the actinomycin D. Inhibition of NF-kappa B and STAT-1 did not protect against cell death, nor did the cytokines activate iNOS expression. Instead, cytokines promoted a rapid decrease in EndoC-beta H1 cell respiration and ATP levels, and we observed protection by the AMPK activator AICAR against cytokine-induced cell death. It is concluded that EndoC-beta H1 cell death can be prevented by AMPK activation, which suggests a role for ATP depletion in cytokine-induced human beta-cell death.
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| 39. |
- Fred, Rikard G., et al.
(författare)
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The human insulin mRNA is partly translated via a cap- and eIF4A-independent mechanism
- 2011
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 412:4, s. 693-698
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate whether cap-independent insulin mRNA translation occurs in human pancreatic islets at basal conditions, during stimulation at a high glucose concentration and at conditions of nitrosative stress. We also aimed at correlating cap-independent insulin mRNA translation with binding of the IRES trans-acting factor polypyrimidine tract binding protein (FTB) to the 5'-UTR of insulin mRNA. For this purpose, human islets were incubated for 2 h in the presence of low (1.67 mM) or high glucose (16.7 mM). Nitrosative stress was induced by addition of 1 mM DETA/NO and cap-dependent mRNA translation was inhibited with hippuristanol. Insulin biosynthesis rates were determined by radioactive labeling and immunoprecipitation. PTB affinity to insulin mRNA 5'-UTR was assessed by a magnetic micro bead pull-down procedure. We observed that in the presence of 1.67 mM glucose, approximately 70% of the insulin mRNA translation was inhibited by hippuristanol. Corresponding value from islets incubated at 16.7 mM glucose was 93%. DETA/NO treatment significantly decreased the translation of insulin by 85% in high glucose incubated islets, and by 50% at a low glucose concentration. The lowered insulin biosynthesis rates of DETA/NO-exposed islets were further suppressed by hippuristanol with 55% at 16.7 mM glucose but not at 1.67 mM glucose. Thus, hippuristanol-induced inhibition of insulin biosynthesis was less pronounced in DETA/NO-treated islets as compared to control islets. We observed also that PTB bound specifically to the insulin mRNA 5'-UTR in vitro, and that this binding corresponded well with rates of cap-independent insulin biosynthesis at the different conditions. In conclusion, our studies show that insulin biosynthesis is mainly cap-dependent at a high glucose concentration, but that the cap-independent biosynthesis of insulin can constitute as much as 40-100% of all insulin biosynthesis during conditions of nitrosative stress. These data suggest that the pancreatic beta-cell is able to uphold basal insulin synthesis at conditions of starvation and stress via a cap- and eIF4A-independent mechanism, possibly mediated by the binding of FIB to the 5'-UTR of the human insulin mRNA.
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| 40. |
- Fred, Rikard G., et al.
(författare)
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The importance of RNA binding proteins in preproinsulin mRNA stability
- 2009
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 297:1-2, s. 28-33
-
Forskningsöversikt (refereegranskat)abstract
- A dynamic production of insulin is necessary for proper glucose homeostasis. In order to generate enough insulin available for exocytosis in response to the demands of the organism, the level of preproinsulin mRNA in the pancreatic beta-cell needs to fluctuate. In animal models for type 2 diabetes the contents of preproinsulin mRNA are lowered, which might suggest that an impaired metabolism of preproinsulin mRNA contributes to the development of glucose intolerance and diabetes. Thus, it is of importance to understand the mechanisms by which preproinsulin mRNA levels are regulated. Although extensively studied, there are aspects of the regulation of insulin gene expression that still remain enigmatic. Our understanding of insulin gene transcription has improved considerably the last 20 years, but less effort has been invested into the control of preproinsulin mRNA stability. The preproinsulin mRNA has a long half-life and changes in preproinsulin mRNA stability, induced by glucose, are likely to be regulated through specific mechanisms. Recent findings indicate that the polypyrimidine tract-binding protein (PTB), also named hnRNP I, by binding to the 3'-UTR (untranslated region) of the preproinsulin mRNA molecule, stabilizes the messenger, thereby participating in the glucose-induced increase in preproinsulin mRNA. This review will focus both on recent findings pertinent to PTB function in general, and on the specific role of PTB on the production of insulin in beta-cells. We will also discuss the putative co-operativity between PTB and other proteins in the control of preproinsulin mRNA stability, and review beta-cell signaling events that may control the mRNA stabilizing effect of PTB.
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| 41. |
- Fred, Rikard G.
(författare)
-
The Role of RNA Binding Proteins in Insulin Messenger Stability and Translation
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although the reason for insufficient release of insulin in diabetes mellitus may vary depending on the type and stage of the disease, it is of vital importance that an amplified insulin biosynthesis can meet the increased need during periods of hyperglycemia. The insulin mRNA is highly abundant in beta cells and changes in insulin mRNA levels are, at least in part, controlled by altered rates of mRNA degradation. Since the mechanisms behind the control of insulin messenger stability and translation are still largely obscure, the work presented in this thesis therefore aimed to further investigate the role of insulin mRNA binding proteins in the control of insulin mRNA break-down and utilization for insulin biosynthesis. To clarify how glucose regulates insulin mRNA stability and translation we studied the correlation between polypyrimidine tract binding protein (PTB) gene expression and insulin mRNA levels. It was found that an increase in PTB mRNA and protein levels is paralleled by an increase in insulin mRNA levels. It was also found that PTB binds to the 5’-untranslated region of the insulin mRNA and that insulin mRNA can be translated through a cap-independent mechanism in human islets of Langerhans, possibly due to the interaction with PTB. Further it was discovered that the suppressed insulin biosynthesis in human islets during glucotoxicity is partly due to an induction of the microRNA miR-133a. This induction leads to decreased levels of PTB and insulin biosynthesis rates in human islets. Finally, we were able to identify two proteins, hnRNP U and TIAR, that bind specifically to the insulin mRNA in vitro, and show that the stability and translation of insulin mRNA is oppositely affected by these proteins. In conclusion, insulin producing cells seem to be able to regulate insulin messenger stability and translation by a control mechanism in which the binding of specific proteins to the insulin messenger dictates the outcome. A better understanding of the events leading to insulin production may in the future aid in optimal diagnosis and treatment of type 2 diabetes.
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| 42. |
- Hindlycke, Henrietta, et al.
(författare)
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Cytokine-induced human islet cell death in vitro correlateswith a persistently high phosphorylation of STAT-1, but not with NF-κB activation
- 2012
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 418:4, s. 845-850
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Tidskriftsartikel (refereegranskat)abstract
- Studies of insulin producing β-cells have reported conflicting responses to NF-κB activation,encompassing both pro- and anti-apoptotic effects, possibly reflecting the use of β-cells fromdifferent species. Therefore, the aim of this study was to compare the temporal activation of NF-κB in rat and human insulin producing cells and relate this to the dynamics of cell death, STAT-1activation and the production of nitric oxide (NO). Rat RIN5AH and human islet cells wereexposed to the cytokines IL-1β and IFN-γ and the NOS inhibitor aminoguanidine. Cell death, NOproduction, ΙκΒα phosphorylation, p65 methylation, STAT-1 phosphorylation and cIAP-2 levelswere analyzed at different time-points. Cytokine-induced RIN5AH cell death occurred on day 1,and this was paralleled by NF-κB activation, STAT-1 phosphorylation and production of NO. Onthe other hand, the human islet cells instead died by an NO-independent mechanism on day 3and 5. This later occurring cell death was associated with a gradual decrease in ΙκΒα phosphorylation and p65 methylation, and a lowered expression of the NF-κB target genes ΙκΒα and cIAP-2. STAT-1 phosphorylation was persistently high during the entire cytokine exposureperiod in human islet cells. The results favor a pro-survival role of NF-κB and a pro-apoptoticrole of STAT-1 in human islet cells. Thus, rodent insulin producing cells may not be suitable asmodels for human β-cells in the context of cytokine-induced damage.
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| 43. |
- Hägerkvist, Robert, et al.
(författare)
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Amelioration of diabetes by imatinib mesylate (Gleevec) : role of beta-cell NF-kappaB activation and anti-apoptotic preconditioning
- 2007
-
Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 21:2, s. 618-628
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Tidskriftsartikel (refereegranskat)abstract
- It was recently reported that tyrosine kinase inhibitor imatinib mesylate (Gleevec) improves Type 2 diabetes, possibly by decreasing insulin resistance. However, as both Type 2 and Type 1 diabetes are characterized by beta-cell dysfunction and death, we investigated whether imatinib counteracts diabetes by maintaining beta-cell function. We observed that imatinib counteracted diabetes in two animal models, the streptozotocin-injected mouse and the nonobese diabetes mouse, and that this was paralleled by a partial preservation of the beta-cell mass. In addition, imatinib decreased the death of human beta-cells in vitro when exposed to NO, cytokines, and streptozotocin. The imatinib effect was mimicked by siRNA-mediated knockdown of c-Abl mRNA. Imatinib enhanced beta-cell survival by promoting a state similar to ischemic preconditioning, as evidenced by NF-kappaB activation, increased NO and reactive oxygen species production, and depolarization of the inner mitochondrial membrane. Imatinib did not suppress islet cell death in the presence of an NF-kappaB inhibitor, suggesting that NF-kappaB activation is a necessary step in the antiapoptotic action of imatinib. We conclude that imatinib mediates beta-cell survival and that this could contribute to the beneficial effects observed in diabetes.
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| 44. |
- Hägerkvist, Robert, 1976-
(författare)
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Anti-Diabetic and Beta-Cell Protective Actions of Imatinib Mesylate
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes is a disease resulting from the progressive immune-mediated destruction of insulin producing β-cells. In order to understand more about diabetes we need to understand the mechanisms governing β-cell death.The leukemia drug Gleevec is a tyrosine kinase inhibitor that targets c-Abl. Surprisingly, Gleevec also counteracts Type 2 diabetes and acts as a cell death inhibiting agent, via inhibition c-Abl. Since both Type 1 and Type 2 diabetes are characterized by an increased β-cell death, and the role of c-Abl is unknown in β-cells, we wanted to investigate the following:1.Does Gleevec act via inhibition of c-Abl in β-cells?2.Can Gleevec treatment prevent beta-cell death and diabetes? 3.Which downstream signaling pathways are affected by Gleevec?In paper I, in order to determine whether Gleevec acts by inhibiting c-Abl, we used RNA-interference. Interestingly, siRNA against c-Abl produced by recombinant Dicer mediate almost complete and non-toxic silencing of c-Abl mRNA in dispersed islet cells and conferred protection from streptozotocin and cytokines.In paper II we show that Gleevec protects β-cells from nitric oxide, pro-inflammatory cytokines and streptozotocin in vitro and that Gleevec can prevent diabetes development in the NOD mouse and the streptozotocin-injected mouse. We also present the hypothesis that Gleevec induces a state resembling ischemic preconditioning.Paper III presents an additional mechanism by which Gleevec might improve β-cell survival, i.e. via the inhibition of the downstream stress-activated protein kinase c-Jun N-terminal kinase (JNK), the activity of which has been implicated in β-cell death signaling pathways. In paper IV we explore the interactions between the adaptor protein Shb and c-Abl. We presently show an association between Shb-c-Abl and that Shb is a substrate for the c-Abl kinase that might regulate stress-induced c-Abl activity.
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| 45. |
- Hägerkvist, Robert, et al.
(författare)
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Imatinib mesylate (Gleevec) protects against streptozotocin-induced diabetes and islet cell death in vitro
- 2006
-
Ingår i: Cell Biology International. - : Wiley. - 1065-6995 .- 1095-8355. ; 30:12, s. 1013-1017
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Tidskriftsartikel (refereegranskat)abstract
- The tyrosine kinase inhibitor imatinib mesylate (Gleevec) has been demonstrated to protect various cell types from death by inhibition of Abelson tyrosine kinase (c-Abl). The aim of the present study was to establish whether imatinib protects the insulin producing β-cell from the different apoptosis promoting agents in vitro and whether imatinib counteracts streptozotocin-induced diabetes in NMRI mice. We observe that imatinib attenuated the actions of several different death promoting substances. In addition, mice injected with streptozotocin did not develop diabetes when given imatinib. The beneficial effects of imatinib may be related to inhibition of the pro-apoptotic MAP kinase JNK. We conclude that imatinib protects against β-cell death and that this may contribute to the previously reported anti-diabetic actions of imatinib.
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| 46. |
- Hägerkvist, Robert, et al.
(författare)
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Imatinib mesylate improves insulin sensitivity and glucose disposal rates in rats fed a high-fat diet
- 2008
-
Ingår i: Clinical Science. - 0143-5221 .- 1470-8736. ; 114:1, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate whether imatinib affects insulin sensitivity and glucose disposal in HF (high-fat)-fed rats. Sprague-Dawley rats were fed either a standard pelleted rat food (low-fat diet) or an HF diet (60% fat) for 8 weeks. During the last 10 days of the HF diet regime, rats received saline alone or imatinib (50 or 100 mg/kg of body weight) daily by gavage. The higher dose of imatinib resulted in a decreased psoas fat pad weight in the HF-treated rats. Under euglycaemic hyperinsulinaemic clamp conditions, HF-fed rats exhibited increased insulin concentrations and decreased glucose disposal. The lower (50 mg/kg of body weight), but not the higher (100 mg/kg of body weight), dose of imatinib normalized insulin sensitivity and glucose disposal without affecting glucose metabolism in low-fat-fed rats. Hepatic glucose production at both fasting and hyperinsulinaemic conditions was only weakly affected by imatinib. We conclude that a moderate dose of imatinib efficiently counteracts HF-induced peripheral insulin resistance, and that further studies on the mechanisms by which imatinib increases insulin action in muscle and fat tissues might generate novel strategies for the treatment of Type 2 diabetes.
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| 47. |
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| 48. |
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| 49. |
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| 50. |
- Jiang, Lin, et al.
(författare)
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Stable silencing of ZBED6 affects morphology, gene expression and insulin release in insulin-producing islet cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Zbed6 has evolved from a domesticated DNA transposon and encodes a novel transcription factor unique to placental mammals. Here we have investigated the function of ZBED6 in insulin-producing beta cells based on whole transcriptome analysis of MIN6 cells with lentiviral shRNA-mediated stable silencing of either Zbed6 (shZbed6) or mock mRNA (shMock). Zbed6-silencing was associated with altered cell morphology as the shZbed6 cells showed increased neuron-like protrusions compared with shMock cells. ZBED6 appeared as an important transcriptional regulator in islet cells since more than 700 genes showed differential expression in shZbed6 cells when compared with control cells. The most significantly enriched GO categories among differentially expressed genes were neuronal differentiation and cell adhesion, which is consistent with the changes in morphology in the silenced cells. A ChIP-seq analysis identified more than 4,000 putative binding sites in the genome of MIN6 cells and there was a significant overrepresentation of genes with ZBED6 sites among the differentially expressed genes after silencing. This suggests that ZBED6 acts as a transcriptional regulator for many genes in MIN6 cells. The genes showing differential expression included Pdx1, Mafa and Nkx6-1, three crucial transcription factors in beta-cell maturation, which were all up-regulated after Zbed6-silencing. Finally, in shZbed6 MIN6 cells the content and release of insulin was increased. We conclude that ZBED6 is expressed in insulin-producing islet cells and has a significant role for the modulation of cellular functions in this cell type.
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