Biomedical subjects

T Mandrup-Poulsen

Publications and source records attributed to T Mandrup-Poulsen.

At least 37 records · Page 2Linked to original sources

PubMed2001

A choice of death--the signal-transduction of immune-mediated beta-cell apoptosis.

Apoptosis is likely to be the main form of beta-cell death in immune-mediated diabetes mellitus in rodents and possibly in humans. Clarification of the regulation of beta-cell death could indicate novel sites for therapeutic intervention in Type I (insulin-dependent) diabetes mellitus. We review the molecular effectors and signal transduction of immune-mediated beta-cell apoptosis. Data obtained on non-obese diabetic (NOD) mice suggest that macrophages and CD4+ T-cells are the main cellular effectors, whereas CD8+ T-cells are more important initiators of the immune process leading to beta-cell death. Perforin could be the effector molecule utilized by CD8+ T-cell initiation, whereas CD4+ mediated beta-cell destruction is mostly dependent on Fas/FasL and the cytokines IFNgamma and TNF-alpha. The macrophage cytokine IL-1beta in combination with IFN-gamma and TNF-alpha, plays an important role for beta-cell dysfunction and death. Signal transduction by these cytokines involves: (i) binding to specific receptors, (ii) signal transduction by cytosolic kinases (especially the so-called mitogen- and stress-activated protein kinases) and/or phosphatases, (iii) mobilization of diverse transcription factors - with nuclear factor kappaB (NF-kappaB), AP-1 and STAT-1 probably playing key roles for beta-cell apoptosis; (iv) up-regulation or down-regulation of gene transcription. Recent data obtained by microarray and proteomic analysis suggest that the process of beta-cell apoptosis depends on the parallel and/or sequential up-regulation and down-regulation of considerable numbers of genes, which can be grouped in gene modules or patterns according to their functions. A detailed characterization of these "gene modules", and of the signalling pathways and transcription factors regulating them could allow us to understand the ultimate mechanisms leading to beta-cell apoptosis.

Animals↗

PubMed2001

beta-cell apoptosis: stimuli and signaling.

Pancreatic beta-cells are sensitive to a number of proapoptotic stimuli. Thus, apoptosis is an important part of the physiological neonatal remodeling of the endocrine pancreas, and a number of pathological stimuli involved in type 1 and type 2 diabetes have been shown to elicit beta-cell apoptosis. Factors of relevance to type 1 diabetes include proinflammatory cytokines, nitric oxide, and reactive oxygen species as well as Fas ligand. Recent findings that free fatty acids, glucose, sulfonylurea, and amylin cause beta-cell apoptosis in vitro suggest that programmed cell death may also be involved in the pathogenesis of type 2 diabetes. Furthermore, there is evidence favoring a convergence in signaling pathways toward common effectors of beta-cell apoptosis elicited by stimuli implicated in the pathogenesis of type 1 and type 2 diabetes. Therefore, recent studies involving the stimuli and signaling pathways of beta-cell apoptosis-in particular, mitogen- and stress-activated protein kinases-will be reviewed. It is concluded that immunological, inflammatory, and metabolic signals cause beta-cell apoptosis, and the possibility that these signals converge toward a common beta-cell death signaling pathway should be investigated further.

Animals↗

PubMed2000

IDDM7 links to insulin-dependent diabetes mellitus in Danish multiplex families but linkage is not explained by novel polymorphisms in the candidate gene GALNT3. The Danish Study Group of Diabetes in Childhood and The Danish IDDM Epidemiology and Genetics Group.

The insulin-dependent diabetes mellitus (IDDM) susceptibility locus IDDM7 on 2q31 links to IDDM in some but not other populations. Linkage of D2S152, the marker for IDDM7, has hitherto not been demonstrated in Danish patients. GALNT3 that encodes the UDP-GalNAc: polypeptide N-acetyl-galactosaminyltransferase-T3 (GalNAc-T3), was recently identified and mapped to a region 5-25 cM from D2S152. The GalNAc transferases may play a role in immune mediated diseases by glycosylating autoantigens. Hence, the aims of the present study were to investigate by means of extended transmission disequilibrium testing (ETDT) and transmission disequilibrium testing (TDT) of the marker for IDDM7, D2S152, the marker for GALNT3, D2S2363, and novel polymorphisms identified through mutation screening of the entire GALNT3 for linkage with IDDM in 241 Danish IDDM multiplex families. ETDT analysis demonstrated linkage between IDDM and D2S152 (P(ETDT)=0.034). A prevalent T-->A polymorphism, T284A, was found in the GALNT3 3'UTR. Analysis of the D2S2363 and the T284A GALNT3 transmission patterns did not show linkage to IDDM in Danish patients (P(ETDT)=0.15 and P(TDT)=0.76, respectively). In conclusion, IDDM7 (D2S152) links to IDDM in Danish patients, but D2S2363 and the identified T284A polymorphism in the GALNT3 3'UTR did not. Hence, it is unlikely that the GALNT3 is an IDDM susceptibility gene.

Adult↗

PubMed2000

Linkage disequilibrium testing of four interleukin-1 gene-cluster polymorphisms in Danish multiplex families with insulin-dependent diabetes mellitus.

The molecules of the interleukin 1 (IL-1) system have been suggested to play a role in the pathogenesis of insulin-dependent diabetes mellitus (IDDM), and polymorphisms in the genes encoding IL-1beta (IL1B), the IL-1 Type 1 receptor (IL1RTI) and the IL-1 receptor antagonist (IL1RN) molecules have been associated with IDDM in case-control studies. It can be difficult to exclude selection biases in case-control studies leading to spurious association. This risk is eliminated when using the transmission disequilibrium test (TDT). Hence, by means of the TDT we have investigated four intragenic IL-1 gene-cluster polymorphisms, the IL1B AvaI, the IL1B TaqI, the IL1RTI PstI and the IL1RN 2(nd)intron polymorphisms, for linkage and intra-familial association with IDDM in Danish IDDM multiplex family material comprising 245 families. We found no evidence for overall linkage or intra-familial association between any of the polymorphisms and IDDM. In addition, we did not find linkage between any of the polymorphisms and IDDM in HLA-DR3/4 heterozygous or HLA-non-DR3/4 heterozygous IDDM subjects, respectively. In conclusion, by means of intra-familial TDT analysis we found no linkage or intra-familial association between IDDM and the four IL-1 gene-cluster polymorphisms in Danish IDDM multiplex family material.

Denmark↗

PubMed2000

Glutathione depletion inhibits IL-1 beta-stimulated nitric oxide production by reducing inducible nitric oxide synthase gene expression.

L-buthionine-S,R-sulfoximine (BSO), an inhibitor of GSH synthesis, decreased IL-1 beta-induced nitrite release in rat islets and purified rat beta cells, nitrite formation and iNOS gene promoter activity in insulinoma cells, and iNOS mRNA expression in rat islets. The thiol depletor diethyl maleate (DEM) and an inhibitor of glutathione reductase 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) reduced IL-1 beta-stimulated nitrite release in islets. We conclude that GSH regulates IL-1 beta-induced NO production in islets, purified beta cells and insulinoma cells by modulation of iNOS gene expression.

Animals↗

PubMed2000

Complete molecular scanning of the human Fas gene: mutational analysis and linkage studies in families with type I diabetes mellitus. The Danish Study Group of Diabetes in Childhood and The Danish IDDM Epidemiology and Genetics Group.

AIMS/HYPOTHESIS: The human Fas gene (FAS) on chromosome 10q24.1 encoding a cell surface receptor involved in apoptosis was evaluated as a candidate susceptibility gene for Type I (insulin-dependent) diabetes mellitus. Apoptosis mediated by Fas is important in maintaining peripheral self-tolerance and in down-regulating the immune response and could have a role in immune-mediated beta-cell destruction. METHODS: We did a molecular scan of the entire human FAS (promoter, exons 1-9 including exon-intron boundaries and the 3'UTR) using single strand conformational polymorphism-heteroduplex analysis. RESULTS: We identified 15 mutations, of which 11 are new. Of these a g-1194A-->T and a g-295Ains give rise to alterations of transcription-factor-binding consensus sequences for c-Myb, SP-1 and NF-kappa B, respectively. A total of 1068 people from a Danish family collection comprising 138 Type I diabetic sib-pair families (289 affected and 121 unaffected offspring) and 103 Type I diabetic parent-offspring multiplex families (103 affected and 112 unaffected offspring) were typed for the three most frequent polymorphisms with high heterozygosity indices and for a FAS microsatellite. Haplotypes were established and data analysed using the extended transmission disequilibrium test, ETDT. CONCLUSION/INTERPRETATION: We found no overall evidence for linkage of the FAS polymorphisms to Type I diabetes. We conclude that it is unlikely that the Fas gene does contribute to genetic susceptibility for Type I diabetes.

Adult↗

PubMed2000

TNFalpha and IFNgamma potentiate IL-1beta induced mitogen activated protein kinase activity in rat pancreatic islets of Langerhans.

AIMS/HYPOTHESIS: Interleukin-1 beta (IL-1beta) in synergy with tumour necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma) is cytotoxic to pancreatic beta cells. Mitogen-activated protein kinase (MAPK) activity that is induced by interleukin-1 beta has been suggested to signal nitric oxide-dependent as well as nitric oxide-independent beta-cell destructive pathways. The aim of this study was to investigate if TNFalpha and IFNgamma signal through mitogen-activated protein kinases in isolated rat islets of Langerhans and if they potentiate mitogen-activated protein kinase activity induced by IL-1beta. METHODS: Islets of Langerhans were isolated from 5- to 7-day-old Wistar rats and precultured for 7 days before stimulation with IL-1beta, TNFalpha and/or IFNgamma for 20 min followed by lysis. Kinase activity was measured with a whole cell lysate kinase assay and after immunoprecipitation of the kinase using immunocomplex kinase assay. RESULTS: Exposure to IL-1beta or TNFalpha significantly increased mitogen-activated protein kinase activity, whereas IFNgamma tended to decrease extracellular-signal-regulated kinase activity. Further, TNFalpha and IFNgamma were found to synergistically increase mitogen-activated protein kinase activity induced by IL-1beta. CONCLUSION/INTERPRETATION: We hypothesise that the synergistic effect of IL-1beta, TNFalpha and IFNgamma in the functional inhibition and induction of cell death in pancreatic beta cells is signalled through a synergistic activation of mitogen-activated protein kinase activity.

Activating Transcription Factor 2↗

PubMed2000

The intercellular adhesion molecule-1 K469E polymorphism in type 1 diabetes.

Type 1 (insulin-dependent) diabetes is a complex trait. The region harboring the ICAM1 gene on 19p13 links to type 1 diabetes, and a growing body of evidence indicates that intercellular adhesion molecule-1 (ICAM-1) could play a role in type 1 diabetes development. Recently, association studies of an ICAM-1 K469E polymorphism in type 1 diabetes populations have reported conflicting results. Hence, we performed a transmission disequilibrium test analysis of the ICAM-1 K469E variations in 253 Danish type 1 diabetes families. Linkage and association was not found between the ICAM-1 K469E variation and type 1 diabetes in Danish patients (P(tdt)> or =0.48), and our data did not indicate an interaction between ICAM1 and IDDM1 in predisposition to type 1 diabetes in Danes (P=0.78). We did not observe significant association with late-onset type 1 diabetes (P(tdt)> or =0.12) or differences in transmission patterns between groups of affected offspring stratified for age at onset (P> or =0.19), as suggested in Japanese patients. Combined analysis of the present and previously reported transmission data comprising 728 affected offspring of Romanian, Finnish, and Danish ancestry suggested association between the ICAM-1 E469 allele and type 1 diabetes (P(tdt)=0.013), but association was not found in the combined Scandinavian material. In conclusion, we found no association of the ICAM-1 K469E polymorphism with type 1 diabetes or its subsets stratified for age at onset and HLA risk in Danish patients. Analysis of ICAM-1 K469E transmissions reported in three populations suggested association to type 1 diabetes, but also demonstrated heterogeneity between populations.

Adolescent↗

PubMed2000

Characterization of new polymorphisms in the 5' UTR of the human interleukin-1 receptor type 1 (IL1R1) gene: linkage to type 1 diabetes and correlation to IL-1RI plasma level.

The human interleukin-1 type I receptor (IL-1RI) is the signal transducing receptor for IL-1, a principal proinflammatory cytokine, which is cytotoxic to pancreatic islet beta cells. The IL-1RI gene, IL1R1, maps to chromosome 2q12. We have previously examined part of the IL1R1 promoter region and in the present study we further characterized the promoter region demarcating exon 1B and 1C by sequencing and mutation scanning. New sequence was obtained 1762 bp upstream and 1609 bp downstream the known region. Within this sequence, we identified four frequent single nucleotide polymorphisms (SNPs). PCR-based RFLP assays were established and three of the polymorphisms were typed in a Danish Type 1 (insulin-dependent) diabetes mellitus (T1DM) family collection comprising 103 simplex and 150 sib-pair affected families. Linkage was evaluated by the sib-TDT (transmission disequilibrium test). One of the polymorphisms, defined by a Hinfl RFLP assay, demonstrated linkage to T1DM, P(sTDT) = 0.026. Random transmission was observed to unaffected offspring from heterozygous parents, P = 0.87. No evidence for positive linkage was seen for the other tested polymorphisms, P = 0.14 and P = 0.21, respectively. To evaluate the possible functional significance of the Hinfl polymorphism, we measured circulating IL-1RI plasma level in 30 T1DM patients and in 30 control subjects--10 with each genotype in both groups. Significant differences in plasma levels in relation to genotype--independent of disease status--were found (P = 0.04). In both diabetic and non-diabetic subjects, the wt/wt genotype correlated with the highest IL-1RI plasma level, whereas the plasma levels were lowest for the mt/mt genotype.

5' Untranslated Regions↗

PubMed2000

Functional rest through intensive treatment with insulin and potassium channel openers preserves residual beta-cell function and mass in acutely diabetic BB rats.

Diazoxide and the diazoxide-analogue, NNC 55-0118, are potassium channel openers that interfere with insulin secretion from beta-cells. In vitro, we show that these two drugs inhibit insulin release from diabetes-resistant BB rat islets cultured at either low or high glucose concentration and cause an intracellular accumulation of insulin with high glucose. Preservation of beta-cells was investigated in newly diabetic BB rats treated with insulin implants from day 0-8 under oral diazoxide, NNC 55-0118 or solvent gavage once a day from day 0-7. Three of eight rats (37.5%) treated with diazoxide and three of ten (30%) treated with NNC 55-0118 retained near normal C-peptide responses when challenged with glucose/arginine on day 9, whereas none of eight (0%) solvent-treated rats showed a C-peptide response. Immunohistochemical staining for insulin and glucagon showed that all the C-peptide responding rats had insulin-positive cells in their islets. In contrast, islets from non-responding rats displayed marked inflammation or end-stage lesions. Furthermore, rats with C-peptide response and treated with NNC 55-0118 exhibited only minimal signs of islet inflammation, whereas C-peptide responding diazoxide-treated rats had low level islet inflammation. These results imply that it is conceivable to preserve residual beta-cells at diabetes onset by induction of target cell rest with potassium channel openers and continuous insulin treatment.

Animals↗

PubMed2000

Interferon-gamma induces interleukin-1 converting enzyme expression in pancreatic islets by an interferon regulatory factor-1-dependent mechanism.

Whereas nitric oxide (NO) production is associated with the toxic effect of cytokines on rodent pancreatic beta-cells, cytokine-induced apoptosis in human islets may occur independently of NO. The cysteine protease interleukin (IL)-1 converting enzyme (ICE) is a key proapoptotic caspase. Our aim was therefore to analyze the effect of cytokines on ICE expression in human, rat, and mouse islets and rat insulinoma cells. ICE messenger RNA (mRNA) expression was highly up-regulated after 6-, 24-, and 72-h exposure of human islets to interferon (IFN)gamma, tumor necrosis factor (TNF)alpha + IFNgamma or IL-1beta + TNFalpha + IFNgamma, paralleled by increased iNOS (the inducible form of NO synthase) expression and NO production after exposure to the combined cytokines but not to IFNgamma or TNFalpha + IFNgamma. Cytokine-induced NO-independent ICE transcription was confirmed using iNOS inhibitors. Exposure of rat and mouse islets, or rat insulinoma cells, for 24 h to IFNgamma alone or in combination with the two other cytokines also resulted in a highly significant ICE mRNA expression. ICE transcription was not inducible in islets from IFN regulatory factor-1 knock-out mice, suggesting a key-role of this transcription-factor in cytokine-mediated ICE expression in pancreatic islets. In conclusion, cytokines and IFNgamma in particular increase ICE mRNA expression in pancreatic islet cells and beta-cell lines, independently of NO synthesis, suggesting that ICE up-regulation may be involved in cytokine-induced NO-independent apoptosis of human islets.

Adult↗

PubMed2000

Cytokine- or chemically derived nitric oxide alters the expression of proteins detected by two-dimensional gel electrophoresis in neonatal rat islets of Langerhans.

Interleukin-1beta (IL-1beta) treatment of neonatal rat islets for 24 h induces changes in the expression of 105 of 2,200 proteins, as determined previously by two-dimensional (2D) gel electrophoresis. Nitric oxide (NO) has been implicated as one of the mediators of IL-1beta effects in insulin-containing cell lines and rat islets. The aims of this study were 1) to determine the involvement of NO in IL-1beta-induced alterations in protein expression and 2) to investigate the effects of chemically generated NO on protein expression by 2D gel electrophoresis of neonatal rat islet samples. IL-1beta-induced NO production was prevented by incubation of islets in arginine-free medium supplemented with the arginine analog NG-nitro-L-arginine. [35S]methionine-labeled islet proteins were separated using 2D gel electrophoresis and analyzed using the BioImage computer program. Analysis revealed that the expression levels of 23 protein spots of the 105 protein spots, altered by prior treatment with IL-1beta (60 U/ml) alone, were significantly affected (P < 0.01 [n = 4] and P < 0.05 [n = 19]) when NO production was prevented. The effects of chemically generated NO were investigated by exposing islets to the NO donor GSNO (100 micromol/l) for 24 h before labeling with [35S]methionine and 2D gel electrophoresis. Computer-based analysis identified alterations in the expression of 19 of a total of 1,600 detectable proteins in GSNO-treated islets (P < 0.01). We conclude 1) that the expression of up to 42 proteins is altered by cytokine-induced or chemically generated NO in the precise experimental conditions chosen and 2) that the majority of proteins altered by prior treatment with IL-1beta may be the result of NO-independent IL-1beta-mediated regulation of gene expression. This study demonstrates that the combination of 2D gel electrophoresis and mass spectrometry is a powerful tool in the identification of beta-cell proteins involved in the response to toxic mediators.

Animals↗

PubMed2000

The c-Jun amino-terminal kinase pathway is preferentially activated by interleukin-1 and controls apoptosis in differentiating pancreatic beta-cells.

To characterize the differentiation events that selectively target insulin-producing cells to interleukin (IL)-1beta-induced apoptosis, we studied IL-1beta signaling via mitogen-activated protein kinase (MAPK) and stress-activated protein kinase in 2 pancreatic endocrine cell lines. We studied the glucagon-secreting AN-glu cell line and the insulin and the islet amyloid polypeptide-producing beta-cell line (AN-ins cells), which is derived by stable transfection of AN-glu cells with the transcription factor pancreatic duodenal homeobox factor-1. AN-ins cells were more sensitive to the cytotoxic action of IL-1beta. This increased sensitivity was not associated with a more pronounced IL-l-induced nitric oxide production in AN-ins cells, but it correlated with a more marked activation of the 3 MAPKs extracellular signal-regulated kinases (ERKs)-1/2, c-Jun NH2-terminal kinase (JNK), and p38 MAPK (p38). This led to increased phosphorylation of the transcription factors c-Jun, Elk-1, and ATF2 and of heat shock protein 25. Inhibition of ERK-1/2 and p38 did not prevent but aggravated IL-1beta-induced cell death. In contrast, inhibition of JNK by transfection with the dominant negative inhibitor of the JNK-binding domain prevented apoptosis in both cell types. Cell death could be elicited by overexpressing the catalytic domain of MAPK kinase kinase 1, a specific activator of JNK and nuclear factor-kappaB, which does not recruit ERK-1/2 or p38. Coactivation of ERK-1/2 with JNK did not prevent apoptosis. In conclusion, increased MAPK signaling in response to IL-1beta may represent a novel molecular marker of beta-cell differentiation. JNK inhibition represents an effective means of preventing IL-1beta-activated beta-cell destruction.

Apoptosis↗

PubMed2000

Islet protein expression changes during diabetes development in islet syngrafts in BB-DP rats and during rejection of BB-DP islet allografts.

Interleukin 1beta (IL-1) is cytotoxic to rat pancreatic beta-cells in vitro, and increased expression of IL-1 mRNA is found in the islets of Langerhans during development of diabetes in BB/Wor/Mol-BB2 (BB-DP) rats and NOD mice. It has been proposed that IL-1 induces a race between protective and deleterious proteins in the beta-cells during development of diabetes, and that heat shock proteins 70 and 90, and manganese superoxide dismutase, all inducible by IL-1 are potentially protective proteins. We have established a database of approximately 2000 neonatal rat-islet proteins by two-dimensional gel (2-D gel) electrophoresis of [35S]-methionine labelled neonatal Wistar Furth rat islets. In these IL-1 was shown to up- or down-regulate the islet-expression level of 99, and to induce de novo synthesis of 6 proteins. The identity of most of the IL-1 induced proteins is unknown and under study. In this study we wished to investigate if changes in protein expression induced in vitro by IL-1 stimulation of islets are also seen in vivo during spontaneous development of diabetes in BB-DP rats, and during islet allograft rejection. Two-hundred neonatal BB-DP rat islets were grafted under the kidney capsule of either 30-day-old BB-DP rats killed at onset of diabetes or of 30-day-old Wistar Kyoto (WK) rats, killed 12 days after grafting. Proteins in excised islet-grafts and in vitro IL-1 exposed isolated neonatal BB-DP rat islets were labelled with [35S]-methionine, and processed for 2-D gel electrophoresis. Fluorographs of the gels were analysed by computer. A total of 1815 proteins were found in 3 of 3 12.5% polyacrylamide gels. Interleukin-1 was found to change expression level of 82 of these proteins (22 up- and 60 down-regulated) in neonatal BB-DP rat islets in vitro. Of these 82 proteins 33 (4 up- and 29 down-regulated) also changed level of expression during disease occurrence in syngeneic islet grafts from diabetic BB-DP rats, and 29 (4 up- and 25 down-regulated) during rejection of BB-DP islets grafted to WK rats. Changes in the expression level of 14 (3 up- and 11 down-regulated) of the 82 proteins altered by IL-1 in vitro were only found in syngeneic islet grafts in diabetic BB-DP rats, and changes in the expression level of 8 (2 up- and 6 down-regulated) of these 82 proteins expression were only found in BB-DP islet allografts in WK recipients. Identification of these proteins may be important in understanding the mechanisms of islet destruction during development of insulin-dependent diabetes mellitus and during islet allograft rejection.

Animals↗

PubMed2000

Interleukin-18 mRNA, but not interleukin-18 receptor mRNA, is constitutively expressed in islet beta-cells and up-regulated by interferon-gamma.

Interleukin-18 (IL-18) mRNA is expressed in islets of NOD mice during the early stages of insulitis and IL-18 has therefore been implicated as a contributing factor in immune-mediated beta-cell destruction. However, a recent study failed to show any effect of human IL-18 on the function of isolated rat islets. Since species differences have been shown between human and murine IL-18, the aims of this study were to investigate 1) if species homologous IL-18 alone or following IL-12 pre-exposure affected rat islet function, 2) if IL-18 dose-dependently modulated IL-1 beta or interferon-gamma (IFN-gamma) + tumor necrosis factor-alpha (TNF-alpha) actions on islet function, and 3) if IL-18 and IL-18 receptor (IL-18R) were expressed in rat islet beta-cells. Insulin release and nitric oxide (NO) production from isolated rat islets were measured after incubation with or without cytokines. RT-PCR was used to quantitate mRNA expression of IL-18 and the IL-18R signaling chain (IL-18R beta). There were no significant effects of 0.625-10 nM recombinant murine (rm) IL-18 alone on accumulated or glucose-challenged insulin release or NO production after 24 hours. Fifteen pg/ml of recombinant human (rh) IL-1 beta as well as 200 U/ml recombinant rat (rr) IFN-gamma + 250 U/ml rhTNF-alpha significantly increased islet NO production and inhibited both accumulated and glucose-challenged islet insulin release. However, rmIL-18 failed to modulate these effects of IL-1 beta or IFN-gamma + TNF-alpha. Although IL-12 induces IL-18R expression in Th1 and B lymphocytes, 24-hours rmIL-12 preincubation neither sensitized islets to effects of 10 nM of rm or rrIL-18 alone nor primed the islets to IL-1 beta actions on insulin release and NO production. IL-18R beta mRNA, which was expressed in human peripheral blood mononuclear cells (PBMC), was not expressed in rat insulinoma (RIN) cells or in isolated rat islets, even after exposure to IL-1 beta and/or IFN-gamma + TNF-alpha or IL-12. IL-18 mRNA was constitutively expressed in RIN cells, in FACS-purified rat beta-cells and in intact rat and mouse islets, and was up-regulated by IFN-gamma in an interferon regulatory factor-1- IRF-1) and NO - independent manner. However, IL-18 protein was undetectable in lysates and supernates of RIN cells by ECL, Western blotting and immunoprecipitation. In conclusion, we show for the first time that IL-18 but not IL-18R is expressed in rodent islet beta-cells. The physiological importance and pathological role of IL-18 originating from islet beta-cells deserve further investigation.

Animals↗

PubMed2000

Activation of extracellular signal-regulated kinase (ERK)1/2 contributes to cytokine-induced apoptosis in purified rat pancreatic beta-cells.

Cytokines may contribute to beta-cell apoptosis in the early stages of type 1 diabetes mellitus. It has been reported recently that interleukin-1 beta (IL-1 beta) induces activation of the mitogen-activated protein kinases (MAPK) p38 and ERK1/2 in neonatal rat islets. Since these kinases may participate in cytokine-induced apoptosis, we evaluated whether cytokines induce activation of MAPKs in FACS-purified primary rat beta-cells, and whether blockers of p38 and/or ERK1/2 prevent beta-cell death. IL-1 beta, but not interferon-gamma (IFN-gamma), caused phosphorylation of the substrates Elk-1, ATF-2 and hsp25, and the phosphorylation of both Elk-1 and hsp25 were decreased by the p38 blocker SB203580 (p38i) and the MAPK/ERK blocker PD 098059 (MEKi). When added together, p38i and MEKi decreased IL-1 beta-induced nitrite production over 24 hours by 60%, but did not affect IL-1 beta-induced manganese superoxide dismutase (MnSOD) mRNA expression. To test the effects of MAPK inhibitors on beta-cell death by necrosis or apoptosis, these cells were exposed for 6 or 9 days to IL-1 beta + IFN-gamma. This treatment induced cell death, mostly by apoptosis. The MEKi, but not the p38i, significantly decreased cytokine-induced apoptosis, thus decreasing the total number of dead cells. This protection was only partial, suggesting that ERK1/2 activation is not the only mechanism by which cytokines induce beta-cell apoptosis. We conclude that IL-1 beta induces activation of both p38 and ERK1/2, and that ERK1/2 contributes to the pro-apoptotic effects of the cytokine in primary beta-cells.

Animals↗

PubMed1999

No linkage of P187S polymorphism in NAD(P)H: quinone oxidoreductase (NQO1/DIA4) and type 1 diabetes in the Danish population. DIEGG and DSGD. Danish IDDM Epidemiology and Genetics Group and The Danish Study Group of Diabetes in Childhood.

Recent genome screening studies have identified novel regions of possible interest for susceptibility to type 1 diabetes. One of these is a 30-35 cM region mapping to 16q22-q24 (D16S515-D16S520), where also the gene encoding NAD(P)H: quinone oxidoreductase (NQO1) maps. Data has suggested association of a polymorphism (P187S) in the NQO1 gene and type 1 diabetes. NQO1 is involved in protection against oxidative stress, which is likely to be involved in beta-cell destruction. By use of the transmission disequilibrium test (TDT), we analyzed the P187S polymorphism for association to type 1 diabetes in a population-based sample of 247 Danish nuclear type 1 diabetic families. Random transmission patterns were observed to all affected offspring (p(tdt) = 0.82), to index cases (P(tdt) = 0.77), as well as to unaffected offspring (P(tdt) = 0.93). Hence, the NQO1 polymorphism is not likely to be an etiological mutation underlying the reported linkage of the 16q22-q24 region.

Chromosomes, Human, Pair 16↗

PubMed1999

Absence of toxicity associated with adenoviral-mediated transfer of the beta-galactosidase reporter gene to neonatal rat islets in vitro.

Transfer of genes with potential therapeutic utility to the pancreatic islets of Langerhans may enhance graft survival after islet transplantation. The aim of this study was to determine the optimal conditions for adenoviral-mediated gene transfer to the islets of Langerhans in the absence of vector-induced toxicity. Neonatal rat islets were transduced in groups of 25 with an adenoviral vector encoding beta-galactosidase (AdbetaGal) at doses of MOI 0, 10, 100 and 1000 pfu per islet cell. All experiments were performed in triplicate. Efficiency of gene transfer was determined by gross inspection and estimation of the percentage of beta-galactosidase positive cells after islet dispersion at 1, 4, 7 and 10 days post-transduction. Islet toxicity was assessed by measuring accumulated insulin levels at each time-point and by assessing static incubation insulin release at 3 and 10 days. Efficient dose-dependent gene transfer to the islets was documented at 1, 4, 7 and 10 days post-transduction. Transgene expression was relatively stable for the duration of the experiment. Insulin accumulation did not differ between transduced and non-transduced islets at each timepoint. Likewise, the insulin secretory response to glucose, obtained by dividing the insulin response to high glucose incubation by the insulin response to low glucose incubation was similar in transduced and non-transduced islets at 3 and 10 days at all doses studied. In summary, adenoviral-mediated transduction of islets results in dose dependent efficient gene transfer with relatively stable transgene expression in the absence of toxicity. This technology may be useful in the study of islet biology and also in the future in gene therapy approaches to the treatment of diabetes mellitus.

Adenoviruses, Human↗