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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A possible role for oxygen free radicals in mediating the cytotoxic effects of cytokines in islets was sought by the use of agents that scavenge free radicals. Rat islet cell monolayer cultures were incubated for 6 days with t-butylhydroperoxide, alloxan, streptozotocin, or the cytokines, interleukin 1, tumour necrosis factor, and interferon gamma, without and together with the oxygen free radical scavenger combination of dimethylthiourea and citiolone, and islet cell lysis was measured in a 51chromium cytotoxicity assay. The free radical scavengers significantly inhibited the islet cell cytotoxic effects of t-butylhydroperoxide and alloxan, but not streptozotocin. Similarly, the cytotoxic effects of the cytokine combinations of interleukin 1 plus tumour necrosis factor, interferon gamma plus tumour necrosis factor, and interferon gamma plus interleukin 1 were significantly inhibited by the free radical scavenger combination of dimethylthiourea and citiolone. These results suggest that the cytokine products of macrophages and lymphocytes infiltrating islets in Type 1 (insulin-dependent) diabetes may contribute to B-cell damage by inducing the production of oxygen free radicals in the islet cells.
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PMID:Oxygen free radical scavengers protect rat islet cells from damage by cytokines. 248 Feb 59

Recombinant human interleukin 1 alpha (IL-1) has been found to induce prostaglandin E2 (PGE2) accumulation by isolated rat islets of Langerhans at concentrations similar to those at which the cytokine inhibits glucose-induced insulin secretion and islet glucose oxidation. Maximal stimulation of PGE2 accumulation (5 times control value) occurred at 200 pM IL-1, and half-maximal stimulation occurred at 25 pM IL-1. Significant augmentation of PGE2 accumulation by IL-1 required 10-18 h of exposure to the cytokine. Islets that had been pretreated with IL-1 for 18 h showed elevated rates of PGE2 production at basal (3-mM) and stimulatory (16.5-mM) glucose concentrations and converted exogenous arachidonic acid to PGE2 at twice the maximal rate of control islets. Exogenous PGE2 did not mimic the inhibitory effects of IL-1 on glucose-induced insulin secretion or glucose oxidation. To rule out the possibility that endogenous PGE2 is involved in the inhibitory effects of IL-1, the effect of a cyclooxygenase inhibitor on IL-1-treated islets was examined. Pharmacological blockade of PGE2 biosynthesis by 10 microM indomethacin did not influence the inhibitory effects of IL-1 on glucose-induced insulin secretion or glucose oxidation. Thus, exogenous PGE2 does not mimic the effects of IL-1 on islets, and inhibition of endogenous PGE2 biosynthesis does not suppress the effects of IL-1 on islets. These results suggest that PGE2 is not a principal mediator of the inhibitory effects of IL-1 on glucose-induced insulin secretion or glucose oxidation.
Diabetes 1989 Oct
PMID:Interleukin 1-induced prostaglandin E2 accumulation by isolated pancreatic islets. 250 77

Polypeptide products of mononuclear cells of the immune system (cytokines) have been reported to be cytotoxic to the insulin-producing pancreatic islet beta-cells. The objective of this study was to distinguish between reversible effects of cytokines on insulin secretion and irreversible cytotoxic effects on the islet beta-cells. When tested as single agents or added together at very low concentrations, interleukin 1 (IL-1), tumor necrosis factor (TNF), and interferon gamma (IFN-gamma) inhibited insulin release from rat islet cell monolayer cultures during 4 day incubations; however, this secretory function improved after the cytokines were removed. In contrast, combinations of slightly higher concentrations of IL-1, TNF, and IFN-gamma produced irreversible inhibition of insulin release, as well as decreased cell insulin content and proportional increase in cell lysis, measured as release of 51Cr from labeled islet cell cultures. These findings suggest that cytokine products of T lymphocytes (IFN-gamma) and macrophage/monocytic cells (IL-1, TNF) infiltrating pancreatic islets in "autoimmune" diabetes may interact synergistically to produce functional inhibition or lethal cytocidal effects on islet beta-cells, possibly accounting for reversible and irreversible stages of insulin-dependent diabetes.
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PMID:Effects of cytokines on rat pancreatic islet cell monolayer cultures: distinction between functional and cytotoxic effects on islet beta-cells. 251 61

Diabetes susceptibility in non-obese diabetic (NOD) mice may entail faulty activation of immunoregulatory cells resulting from cytokine deficiencies. Depletion of T cells prevents disease onset in these mice. Since we had previously shown that IL-2 treatment in vivo restored the ability of NOD/Lt mice to produce self-restricted suppressor T cells (Ts) in a syngeneic mixed lymphocyte reaction (SMLR), we investigated the possibility that diabetes could be circumvented by treatment with immunostimulatory agents that increase cytokine production. By 20 weeks of age, 75% of vehicle-treated NOD/Lt female controls had become glycosuric, while glycosuria developed in only 17% of NOD/Lt females injected with human recombinant interleukin-2 (rIL-2, 250 U twice weekly) beginning at 6 weeks of age. Treatment of mice with Poly [I:C] alone [50 micrograms twice weekly, an inducer of Interferon (IFN) alpha/beta] or in conjunction with rIL-2 was even more effective, completely preventing glycosuria for 20 weeks. However, therapeutic effects required continuous administration of the immunostimulants since pancreatic insulin content declined and severity of insulitis increased following cessation of treatment. IL-2 treatment increased transcription of interleukin-1 (IL-1) mRNA in peritoneal macrophages and increased lipopolysaccharide (LPS)-stimulated IL-1 secretion in comparison to controls. In the presence of stimulators from IL-2-treated mice, T lymphocytes isolated from both controls and IL-2-treated NOD/Lt mice proliferated in a SMLR and acquired Ts function. Peritoneal macrophages from Poly [I:C]-treated mice exhibited increased IFN alpha gene transcription and LPS-stimulated IL-1 secretion. T cells isolated from Poly [I:C]-treated mice were capable of suppressing NOD-Lt T cell responses to alloantigens in a mixed lymphocyte culture without prior activation in a SMLR. Thus, Poly [I:C] treatment may recruit a different population of regulatory cells than those elicited by treatment with IL-2. However, the mechanisms by which autoreactive T-cell clones may be regulated by these two treatments in NOD/Lt mice may be synergistic. These results indicate that in addition to T-cell depletion protocols, diabetes in NOD mice can be prevented by treatment with immunostimulatory agents.
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PMID:Immunostimulation circumvents diabetes in NOD/Lt mice. 253 2

Interleukin 1 (IL-1), a cytokine released mainly by activated macrophages-monocytes, affects glucose homeostasis and may mediate some of the metabolic derangements observed during certain inflammatory and infectious processes. In this report, it is shown that IL-1 acts as a hypoglycemic agent not only in normal animals but also in mice at early stages of alloxan-induced diabetes and in genetically diabetic, insulin-resistant C57BL/Ks db/db mice and C57BL/6J ob/ob mice. In these animal models, a single injection of a low dose of human recombinant IL-1 normalized glucose blood levels for several hours. This effect was not mediated by possible insulin secretagogue actions of the cytokine. Furthermore, IL-1 markedly reduced the levels of triglycerides in blood of streptozotocin-induced diabetic mice at later stages of the disease. Although the final mechanism of action is at present unknown, the results showed that IL-1 is a hormone with powerful antidiabetic properties. Defective production of this cytokine associated with diabetes could contribute to aggravate the course of the disease during infectious and inflammatory processes.
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PMID:Antidiabetic effects of interleukin 1. 266 49

Nonobese diabetic (NOD) is an inbred mouse strain susceptible to development of T cell-mediated autoimmune diabetes. The strain is characterized by high percentages of T lymphocytes in lymphoid organs. The syngeneic mixed lymphocyte reaction (SMLR), a T cell response to self MHC class II Ag, is reportedly involved in the generation of a number of immunoregulatory cells, including suppressor inducers. A severely depressed SMLR characteristic of certain other autoimmune strains was found in NOD but not in nonautoimmune SWR/Bm mice. Moreover, IL-2 produced by NOD T cells at day 6 in an SMLR was at least one hundredfold reduced compared with SWR, and NOD T cells harvested from an SMLR at day 6 were functionally defective when tested for ability to induce suppression of an allogeneic MLR. However, functionally competent suppressor T cells were generated in NOD splenic leukocyte cultures in response to Con A, and IL-2 release from these was equivalent to that released by Con A-stimulated SWR splenocytes. A deficiency in cytokine release was not limited to IL-2, because peritoneal exudate cells from NOD exhibited a greatly diminished sensitivity to LPS-stimulated IL-1 release in comparison to SWR mice. IL-2 supplementation both in vitro and in vivo restored the ability of NOD T cells to respond in a SMLR, with production of cells capable of inducing suppression. Like SMLR-activated T cells from untreated SWR controls, SMLR blasts from IL-2-treated NOD mice were enriched for the L3T4 phenotype. IL-1 supplementation in vitro resulted in partial restoration of T suppressor activation in a SMLR. The depressed SMLR exhibited by NOD mice was apparently a stimulator cell dysfunction, because NOD stimulator cells failed to activate T cells from (SWR x NOD)F1 mice, whereas stimulators from SWR or F1 mice were capable of doing so. Collectively, these results suggest a defect in suppressor cell activation rather than an absence of this immunoregulatory cell population.
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PMID:Defective activation of T suppressor cell function in nonobese diabetic mice. Potential relation to cytokine deficiencies. 289 95

The pathogenetic mechanisms leading to beta-cell destruction and insulin-dependent diabetes mellitus (IDDM) are major histocompatibility complex (MHC) nonrestricted and are MHC associated and beta-cell specific. The macrophage peptide hormone interleukin 1 (IL-1) may be the primary MHC-nonrestricted beta-cell-destructive molecule. Beta-Cell death most likely results from free radical induction by IL-1. Thus, islet cell-specific antibodies and cytotoxic T-lymphocytes are secondary in importance and time. The potentiation of IL-1 effects on beta-cells by tumor necrosis factor alpha (TNF), another macrophage hormone controlled by a gene in the HLA region on chromosome 6, may account for the MHC association of IDDM. In the experimental model of IDDM etiopathogenesis described, release of beta-cell antigen, processed and presented by macrophages to helper T-lymphocytes, initiates a self-perpetuating and self-limiting circuit of cytokine production of which IL-1 is beta-cell cytotoxic. As postulated, the IL-1 effect is potentiated by TNF, whereas IL-1 and/or TNF production is controlled in a quantitative way by HLA-D genes.
Diabetes Care
PMID:Mechanisms of pancreatic beta-cell destruction in type I diabetes. 306 87

Activated mononuclear cells appear to be important effector cells in autoimmune beta cell destruction leading to insulin-dependent (type 1) diabetes mellitus. Conditioned medium from activated mononuclear cells (from human blood) is cytotoxic to isolated rat and human islets of Langerhans. This cytotoxic activity was eliminated from crude cytokine preparations by adsorption with immobilized, purified antibody to interleukin-1 (IL-1). The islet-inhibitory activity and the IL-1 activity (determined by its comitogenic effect on thymocytes) were recovered by acid wash. Purified natural IL-1 and recombinant IL-1 derived from the predominant pI 7 form of human IL-1, consistently inhibited the insulin response. The pI 6 and pI 5 forms of natural IL-1 were ineffective. Natural and recombinant IL-1 exhibited similar dose responses in their islet-inhibitory effect and their thymocyte-stimulatory activity. Concentrations of IL-1 that inhibited islet activity were in the picomolar range. Hence, monocyte-derived pI 7 IL-1 may contribute to islet cell damage and therefore to the development of insulin-dependent diabetes mellitus.
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PMID:Cytotoxicity of human pI 7 interleukin-1 for pancreatic islets of Langerhans. 308 77

An assay was developed to detect the cytotoxic effects of cytokines on rat pancreatic islet cells in monolayer culture. Cell lysis was detected by a 51Cr-release assay after 4 days of incubation with various cytokines. When tested alone, murine (rat and mouse) interferon-gamma (mIFN-gamma) produced a small dose-dependent lysis of islet cells; human IFN-gamma, mouse IFN-alpha/beta, interleukins 1 and 2 (IL-1 and IL-2), tumor necrosis factor (TNF), and lymphotoxin (LT) were inactive. When added together, the following combinations of cytokines showed synergistic cytotoxic effects: TNF (or LT) plus IL-1, TNF (or LT) plus mIFN-gamma, and IL-1 plus mIFN-gamma. These results indicate that the cytokine products of mononuclear cells of the immune system, IFN-gamma, TNF, LT, and IL-1 have strong synergistic cytotoxic effects on islet cells and therefore may act as direct chemical mediators of islet beta-cell destruction in type I (insulin-dependent) diabetes.
Diabetes 1988 Jan
PMID:Destruction of rat islet cell monolayers by cytokines. Synergistic interactions of interferon-gamma, tumor necrosis factor, lymphotoxin, and interleukin 1. 312 15

We have previously reported that the cytokines IFN-gamma and TNF-alpha each upregulate the expression of class I MHC proteins and, in combination, induce the expression of class II MHC proteins on pancreatic islet cells. IFN-gamma and TNF-alpha are therefore implicated in the immunologic destruction of beta-cells in insulin-dependent diabetes mellitus. The objective of the present study was to define the effects of IFN-gamma and TNF-alpha on the function and viability of murine pancreatic islet beta-cells in vitro. Exposure of islets for 3 days to 200 U/ml of either IFN-gamma or TNF-alpha did not affect glucose-stimulated insulin release, but at higher concentrations (2000 U/ml) of either cytokine there was significant inhibition of glucose-stimulated insulin release. In combination, IFN-gamma and TNF-alpha each at 200 U/ml caused significant inhibition of glucose-stimulated insulin release; at 2000 U/ml glucose-stimulated insulin release was abolished. In time-course experiments, glucose-stimulated insulin release from islets exposed to IFN-gamma and TNF-alpha each at 1000 U/ml was significantly increased at 4-h (twofold increase compared with control islets), decreased back to control levels at 18 h, significantly inhibited by 24 h (threefold decrease compared with control islets), and completely abolished by 48 h. The progressive impairment of beta-cell function mediated by IFN-gamma plus TNF-alpha was associated with morphologic derangement of the islets that were almost totally disintegrated by day 6 of exposure to the cytokines. At day 6, insulin content of the islets was significantly reduced by exposure to TNF-alpha but not IFN-gamma. The combination of IFN-gamma and TNF-alpha resulted in a further dose-dependent depletion in insulin content compared with TNF-alpha alone. The synergistic functional and cytotoxic effects of IFN-gamma and TNF-alpha are consistent with a direct role for these cytokines in the destruction of beta-cells in insulin-dependent diabetes.
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PMID:IFN-gamma and tumor necrosis factor-alpha. Cytotoxicity to murine islets of Langerhans. 313 56


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