Interleukin 12 mRNA expression in islets correlates with beta-cell destruction in NOD mice

Long-term inhibition of dipeptidyl-peptidase 4 reduces islet infiltration and downregulates IL-1β and IL-12 in NOD mice

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DPP-4 inhibition reduced CD4+T cells infiltration and ameliorated insulitis.

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DPP-4 inhibition downregulated serum IL-1β and IL-12.

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LPS increased CD11b+ cells to infiltrate into islets.

Dipeptidyl-peptidase 4 (DPP-4) inhibitor (sitagliptin) is a novel anti-hyperglycemia drug in the treatment of type 2 diabetes. However, its potential in type 1 diabetes is still unclear. Recent studies show that increased infection, especially respiratory tract infection, is significantly associated with DPP-4 inhibitors. In this study, we aimed to explore the effects of long-term inhibition of DPP- 4 on innate immunity in type 1 diabetes. Forty mice were randomly divided into 4 groups (n = 10 in each group): control group, lipopolysaccharide (LPS) group, sitagliptin group and sitagliptin + LPS group. The concentrations of IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, TNF-α and IFN-γ were measured with Mesco Scale Discovery multiplexed-assay kit. Immunohistochemistry staining of pancreases was performed and insulitis scores for each islet were determined. The results showed that DPP-4 inhibition has no effect on incident rate of diabetes and metabolic parameters in NOD mice. Long-term inhibition of DPP-4 reduced CD4+T cells to infiltrate into islets and ameliorated insulitis in NOD mice. DPP-4 inhibition downregulated serum interleukin IL-1β and IL-12 in NOD mice. However, it had no significant effect on LPS-induced IL-1β, IL-6, IL-10, IL-12, tumor necrosis factor (TNF)-α and interferon (IFN)-γ in NOD mice. In conclusion, Long-term inhibition of DPP-4 exists anti-inflammatory effect in type 1 diabetes probably by reducing CD4+T cells to infiltrate into islets and downregulating L-1β and IL-12 in serum.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

Interleukin-12 (IL-12)/STAT4 Axis Is an Important Element for β-Cell Dysfunction Induced by Inflammatory Cytokines

Pathology driving β-cell loss in diabetes is poorly defined. Chronic subclinical inflammation is associated with β-cell dysfunction. Acute in vitro exposure of islets and β-cells to an inflammatory cytokine cocktail (IL-1β/TNF-α/IFN-γ) results in loss of cell function and viability. The contribution of each cytokine alone or in combination has been evaluated in homogeneous mouse β-cell lines and primary mouse islets. Cytokine cooperation is required for β-cell apoptosis with the most potent combinations including IL-1β. Single cytokine exposure did not induce β-cell apoptosis. Expression of endogenous interleukin-12 in β-cells correlated with inflammatory cytokine combinations that induced β-cell apoptosis. Uncoupling of the IL-12 axis by a block of IL-12 production, inhibition of IL-12 receptor/ligand interaction or disruption of IL-12 receptor signaling conferred protection to β-cells from apoptosis induced by inflammatory cytokine stimulation. Signaling through STAT4 is indicated since disruption of IL-12 concomitantly reduced inflammatory cytokine stimulation of endogenous IFN-γ expression. Primary mouse islets isolated from mice deficient in STAT4 show resistance to inflammatory-cytokine-induced cell death when compared to islets isolated from wild type mice. Collectively, the data identify IL-12 as an important mediator of inflammation induced β-cell apoptosis. Modulation of IL-12/STAT4 signaling may be a valuable therapeutic strategy to preserve islet/β-cell viability in established diabetes.

Severe hypertriglyceridemia and hypercholesterolemia accelerating renal injury: a novel model of type 1 diabetic hamsters induced by short-term high-fat / high-cholesterol diet and low-dose streptozotocin

Background

Hyperlipidemia is thought to be a major risk factor for the progression of renal diseases in diabetes. Recent studies have shown that lipid profiles are commonly abnormal early on type 2 diabetes mellitus (T2DM) with diabetic nephropathy. However, the early effects of triglyceride and cholesterol abnormalities on renal injury in type 1 diabetes mellitus (T1DM) are not fully understood and require reliable animal models for exploration of the underlying mechanisms. Hamster models are important tools for studying lipid metabolism because of their similarity to humans in terms of lipid utilization and high susceptibility to dietary cholesterol and fat.

Methods

Twenty-four male Golden Syrian hamsters (100–110 g) were rendered diabetes by intraperitoneal injections of streptozotocin (STZ) on consecutive 3 days at dose of 30 mg/kg, Ten days after STZ injections, hamsters with a plasma Glu concentration more than 12 mmol/L were selected as insulin deficient ones and divided into four groups (D-C, D-HF, D-HC, and D-HFHC), and fed with commercially available standard rodent chow, high-fat diet, high-cholesterol diet, high-fat and cholesterol diet respectively, for a period of four weeks.

Results

After an induction phase, a stable model of renal injury was established with the aspects of early T1DM kidney disease, These aspects were severe hypertriglyceridemia, hypercholesterolemia, proteinuria with mesangial matrix accumulation, upgraded creatinine clearance, significant cholesterol and triglyceride deposition, and increasing glomerular surface area, thickness of basement membrane and mesangial expansion. The mRNA levels of sterol regulatory element binding protein-1c, transforming growth factors-β, plasminogen activator inhibitor-1, tumor necrosis factor-α and interleukin-6 in the D-HFHC group were significantly up-regulated compared with control groups.

Conclusions

This study presents a novel, non-transgenic, non-surgical method for induction of renal injury in hamsters, which is an important complement to existing diabetic models for pathophysiological studies in early acute and chronic kidney disease, especially hyperlipidemia. These data suggest that both severe hypertriglyceridemia and hypercholesterolemia can accelerate renal injury in the early development of T1DM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0041-5) contains supplementary material, which is available to authorized users.

Histidine Decarboxylase Deficiency Prevents Autoimmune Diabetes in NOD Mice

Recent evidence has highlighted the role of histamine in inflammation. Since this monoamine has also been strongly implicated in the pathogenesis of type-1 diabetes, we assessed its effect in the nonobese diabetic (NOD) mouse model. To this end, we used mice (inactivated) knocked out for the gene encoding histidine decarboxylase, the unique histamine-forming enzyme, backcrossed on a NOD genetic background. We found that the lack of endogenous histamine in NOD HDC(-/-) mice decreased the incidence of diabetes in relation to their wild-type counterpart. Whereas the proportion of regulatory T and myeloid-derived suppressive cells was similar in both strains, histamine deficiency was associated with increased levels of immature macrophages, as compared with wild-type NOD mice. Concerning the cytokine pattern, we found a decrease in circulating IL-12 and IFN-γ in HDC(-/-) mice, while IL-6 or leptin remained unchanged, suggesting that histamine primarily modulates the inflammatory environment. Paradoxically, exogenous histamine given to NOD HDC(-/-) mice provided also protection against T1D. Our study supports the notion that histamine is involved in the pathogenesis of diabetes, thus providing additional evidence for its role in the regulation of the immune response.

Production and function of IL-12 in islets and beta cells

AIMS/HYPOTHESIS

IL-12 is an important cytokine in early inflammatory responses and is implicated in the immune-mediated pathogenesis of pancreatic islets in diabetes. However, little is known about the direct effects of IL-12 on islets and beta cells.

METHODS

In this study, beta cell function, gene expression and protein production were assessed in primary human donor islets and murine beta cell lines in response to stimulation with IL-12 or a pro-inflammatory cytokine cocktail (TNF-α, IL-1β and IFN-γ).

RESULTS

The pro-inflammatory cytokine cocktail induced islet dysfunction and potently increased the expression and production of IL-12 ligand and IL-12 receptor in human islets. In human islets, the receptor for IL-12 co-localised to the cell surface of insulin-producing cells. Both IL-12 ligand and IL-12 receptor are expressed in the homogeneous beta cell line INS-1. IL-12 induced changes in gene expression, including a dose-dependent upregulation of IFNγ (also known as IFNG), in INS-1 cells. A neutralising antibody to IL-12 directly inhibited IFNγ gene expression in human donor islets induced by either IL-12 or pro-inflammatory cytokine stimulation. Functionally, IL-12 impaired glucose-stimulated insulin secretion (GSIS) in INS-1 cells and human donor islets. A neutralising antibody to IL-12 reversed the beta cell dysfunction (uncoupling of GSIS or induction of caspase-3 activity) induced by pro-inflammatory cytokines.

CONCLUSIONS/INTERPRETATION

These data identify beta cells as a local source of IL-12 ligand and suggest a direct role of IL-12 in mediating beta cell pathology.

Ultrathin polymeric coatings based on hydrogen-bonded polyphenol for protection of pancreatic islet cells

Though transplantation of pancreatic islet cells has emerged as a promising treatment for Type 1 diabetes its clinical application remains limited due to a number of limitations including both pathogenic innate and adaptive immune responses. We report here on a novel type of multifunctional cytoprotective material applied to coat living pancreatic islets. The coating utilizes hydrogen-bonded interactions of a natural polyphenol (tannic acid) with poly(N-vinylpyrrolidone) deposited on the islet surface via non-ionic layer-by-layer assembly. We demonstrate that the coating is conformal over the surface of mammalian islets including those derived from rat, non-human primate (NHP), and human. In contrast to unmodified controls, the coated islets maintain their viability and β-cell functionality for at least 96 hours in vitro. We also determine that the coating demonstrates immunomodulatory cytoprotective properties suppressing pro-inflammatory cytokine synthesis in stimulated bone marrow-derived macrophages and diabetogenic BDC-2.5 T cells. The coating material combines high chemical stability under physiologically relevant conditions with capability of suppressing cytokine synthesis, crucial parameters for prolonged islet integrity, viability, and function in vivo. Our study offers new opportunities in the area of advanced multifunctional materials to be used for a cell-based transplantation therapy.

Young patients with both type 1 diabetes mellitus and asthma have a unique IL-12 and IL-18 secretory pattern

BACKGROUND

The expression of the regulatory cytokines interleukin (IL)-12 and IL-18 in patients with both Th1- and Th2-mediated diseases, type 1 diabetes mellitus (T1DM) and asthma, is unknown.

OBJECTIVE

To investigate the in vivo and in vitro IL-12 and IL-18 secretion patterns in patients with both T1DM and asthma.

METHODS

Peripheral blood mononuclear cells (PBMC) were collected from 44 patients. Mean age 19.4 ± 4.7 yr (10.5-28 yr), divided into four paired groups: T1DM and asthma, asthma only, T1DM only, and healthy controls. T-cell proliferative response was assessed. IL-12 and IL-18 serum levels and expression by PBMC following in vitro stimulation by lipopolysaccharide (LPS) were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Patients with T1DM and asthma had higher serum levels of both IL-12 and IL-18 compared to controls: 146.2 ± 69.2 and 109.7 ± 34.6 pg/mL, p = 0.038 and 436.1 ± 117.9, 320.2 ± 99.1 pg/mL, p = 0.028, respectively. Stimulated IL-12 secretion was significantly lower in these patients compared to those with one disease only: 809 ± 426.4, 2111.6 ± 2214.3, 3188.1 ± 2692.9 pg/mL and after 48 h: 956.3 ± 489.3, 2429.8 ± 2394.6, 3874.5 ± 2820.3 pg/mL, respectively, p < 0.03 for all. The IL-18/IL-12 serum ratio was also significantly higher in patients with both diseases compared to those with asthma only, p = 0.017.

CONCLUSION

Patients with both T1DM and asthma display a different pattern of IL-12 and IL-18 expression compared to patients with one disease only and controls.

Identification of T helper type 1-like, Foxp3+ regulatory T cells in human autoimmune disease

CD4(+)CD25(high)CD127(low/-) forkhead box p3 (Foxp3)(+) regulatory T cells (T(reg) cells) possess functional plasticity. Here we describe a higher frequency of T helper type 1 (T(H)1)-like, interferon-γ (IFN-γ)-secreting Foxp3(+) T cells in untreated subjects with relapsing remitting multiple sclerosis (RRMS) as compared to healthy control individuals. In subjects treated with IFN-β, the frequency of IFN-γ(+)Foxp3(+) T cells is similar to that in healthy control subjects. In vitro, human T(reg) cells from healthy subjects acquire a T(H)1-like phenotype when cultured in the presence of interleukin-12 (IL-12). T(H)1-like T(reg) cells show reduced suppressive activity in vitro, which can partially be reversed by IFN-γ-specific antibodies or by removal of IL-12.

Attenuation of Th1 response through galectin-9 and T-cell Ig mucin 3 interaction inhibits autoimmune diabetes in NOD mice

Galectin-9 (gal-9), widely expressed in many tissues, regulates Th1 cells and induces their apoptosis through its receptor, T-cell Ig mucin 3, which is mainly expressed on terminally differentiated Th1 cells. Type 1 diabetes is a Th1-dominant autoimmune disease that specifically destroys insulin-producing beta cells. To suppress the Th1 immune response in the development of autoimmune diabetes, we overexpressed gal-9 in NOD mice by injection of a plasmid encoding gal-9. Mice treated with gal-9 plasmid were significantly protected from diabetes and showed less severe insulitis compared with controls. Flow cytometric analyses in NOD-T1/2 double transgenic mice showed that Th1-cell population in spleen, pancreatic lymph node and pancreas was markedly decreased in gal-9 plasmid-treated mice, indicating a negative regulatory role of gal-9 in the development of pathogenic Th1 cells. Splenocytes from gal-9 plasmid-treated mice were less responsive to mitogenic stimulation than splenocytes from the control group. However, adoptive transfer of splenocytes from gal-9-treated or control mice caused diabetes in NOD/SCID recipients with similar kinetics, suggesting that gal-9 treatment does not induce active tolerance in NOD mice. We conclude that gal-9 may downregulate Th1 immune response in NOD mice and could be used as a therapeutic target in autoimmune diabetes.

Immunology and genetics of type 1 diabetes

Type 1 diabetes is one of the most well-characterized autoimmune diseases. Type 1 diabetes compromises an individual's insulin production through the autoimmune destruction of pancreatic beta-cells. Although much is understood about the mechanisms of this disease, multiple potential contributing factors are thought to play distinct parts in triggering type 1 diabetes. The immunological diagnosis of type 1 diabetes relies primarily on the detection of autoantibodies against islet antigens in the serum of type 1 diabetes mellitus patients. Genetic analyses of type 1 diabetes have linked human leukocyte antigen, specifically class II alleles, to susceptibility to disease onset. Environmental catalysts include various possible factors, such as viral infections, although the evidence linking infections with type 1 diabetes remains inconclusive. Imbalances within the immune system's system of checks and balances may promote immune activation, while undermining immune regulation. A lack of proper regulation and overactive pathogenic responses provide a framework for the development of autoimmune abnormalities. Type 1 diabetes is a predictable and potentially treatable disease that still requires much research to fully understand and pinpoint the exact triggering events leading to autoimmune activation. In silico research can aid the comprehension of the etiology of complex disease pathways, including Type I diabetes, in order to and help predict the outcome of therapeutic strategies aimed at preserving beta-cell function.

The novel inosine analogue, INO-2002, protects against diabetes development in multiple low-dose streptozotocin and non-obese diabetic mouse models of type I diabetes

Endogenous purines including inosine have been shown to exert immunomodulatory and anti-inflammatory effects in a variety of disease models. The dosage of inosine required for protection is very high because of the rapid metabolism of inosine in vivo. The aim of this study was to determine whether a metabolic-resistant purine analogue, INO-2002, exerts anti-inflammatory effects in two animal models of type I diabetes. Type I diabetes was induced chemically with streptozotocin or genetically using the non-obese diabetic (NOD) female mouse model. Mice were treated with INO-2002 or inosine as required at 30, 100, or 200 mg/kg per day, while blood glucose and diabetes incidence were monitored. The effect of INO-2002 on the pancreatic cytokine profile was also determined. INO-2002 reduced both the hyperglycaemia and incidence of diabetes in both streptozotocin-induced and spontaneous diabetes in NOD mice. INO-2002 proved to be more effective in protecting against diabetes than the naturally occurring purine, inosine, when administered at the same dose. INO-2002 treatment decreased pancreatic levels of interleukin (IL)-12 and tumour necrosis factor-alpha, while increasing levels of IL-4 and IL-10. INO-2002 also reduced pancreatic levels of the chemokine MIP-1 alpha. The inosine analogue, INO-2002, was protected more effectively than the naturally occurring purine, inosine, against development of diabetes in two separate animal models. INO-2002 exerts protective effects by changing the pancreatic cytokine expression from a destructive Th1 to a protective Th2 profile. The use of analogues of inosine such as INO-2002 should be considered as a potential preventative therapy in individuals susceptible to developing type I diabetes.

Cannabidiol arrests onset of autoimmune diabetes in NOD mice

We have previously reported that cannabidiol (CBD) lowers the incidence of diabetes in young non-obese diabetes-prone (NOD) female mice. In the present study we show that administration of CBD to 11-14 week old female NOD mice, which are either in a latent diabetes stage or with initial symptoms of diabetes, ameliorates the manifestations of the disease. Diabetes was diagnosed in only 32% of the mice in the CBD-treated group, compared to 86% and 100% in the emulsifier-treated and untreated groups, respectively. In addition, the level of the proinflammatory cytokine IL-12 produced by splenocytes was significantly reduced, whereas the level of the anti-inflammatory IL-10 was significantly elevated following CBD-treatment. Histological examination of the pancreata of CBD-treated mice revealed more intact islets than in the controls. Our data strengthen our previous assumption that CBD, known to be safe in man, can possibly be used as a therapeutic agent for treatment of type 1 diabetes.

IL-12p40 is not required for islet allograft rejection

AIM

To investigate whether IL-12p40 plays a crucial role in regulating islet allograft rejection in a streptozotocin (STZ)-induced diabetes mouse model.

METHODS

C57BL/6 and IL-12p40 gene knockout mice were selected as recipient mice, to which the diabetes was induced with a treatment of STZ (150-200 mg/kg) by a single ip injection. BALB/c mice were selected as donor mice and islet cells were isolated from the mice. The 500 islets were transplanted into recipient mice beneath the capsule of the left kidney. Following the islet transplantation the glucose from the mice sera was monitored and the rejection rate of islets was analyzed.

RESULTS

STZ could induce diabetes in the recipient mice within 1 week. After transplantation of allograft islets, the increased glucose in wild-type (WT) mice returned to normal level and was maintained for 10 d. Unexpectedly, the rejection rate of islet allograft between IL-12p40-deficient mice and WT mice was similar.

CONCLUSION

The results suggested that, although islet allograft rejection is believed to be Th1-cell predominant, the Th1 response inducer, IL-12 and IL-23 are not essential to induce islet allograft rejection.

Immunopathogenic role of TH1 cells in autoimmune diabetes: Evidence from a T1 and T2 doubly transgenic non-obese diabetic mouse model

To improve the feasibility of in vivo monitoring of autoreactive T cells in the diabetogenic process, we generated T1 and T2 doubly transgenic non-obese diabetic (NOD) mice in which transgenic human CD90 (hCD90) is simultaneously expressed on IFN-gamma-producing cells or murine CD90.1 (mCD90.1) is expressed on IL-4-producing cells. These transgenic NOD mice develop diabetes with the same kinetics and incidence as wild type NOD mice, permitting the physiological characterization of CD4(+)hCD90(+) cells, which represent T(H)1 cells in lymphoid organs and at the site of insulitis. CD4(+)hCD90(+) cells had a higher capacity to secret IFN-gamma than CD4(+)hCD90(-) cells in an autoantigen-specific manner. Transgenic mice treated with GAD65 plasmid were protected from autoimmune diabetes, and had a lower number of CD4(+)hCD90(+) cells, confirming the pathogenic role of CD4(+)hCD90(+) cells in autoimmune diabetes. To further investigate the effect of IL-12 on the development of T(H)1 cells in autoimmune diabetes, we crossed these doubly transgenic mice to IL-12p35-deficient NOD mice. Despite severe disturbance of diabetes in p35(-/-) mice, the frequency of T(H)1 cells in these mice was slightly lower than in wild type mice. These data support the pathological role of IL-12 in autoimmune diabetes and suggest the existence an IL-12-independent pathway of T(H)1 development.

IL-12 administration accelerates autoimmune diabetes in both wild-type and IFN-gamma-deficient nonobese diabetic mice, revealing pathogenic and protective effects of IL-12-induced IFN-gamma

IL-12 administration to nonobese diabetic (NOD) mice induces IFN-gamma-secreting type 1 T cells and high circulating IFN-gamma levels and accelerates insulin-dependent diabetes mellitus (IDDM). Here we show that IL-12-induced IFN-gamma production is dispensable for diabetes acceleration, because exogenous IL-12 could enhance IDDM development in IFN-gamma-deficient as well as in IFN-gamma-sufficient NOD mice. Both in IFN-gamma(+/-) and IFN-gamma(-/-) NOD mice, IL-12 administration generates a massive and destructive insulitis characterized by T cells, macrophages, and CD11c(+) dendritic cells, and increases the number of pancreatic CD4(+) cells secreting IL-2 and TNF-alpha. Surprisingly, IL-12-induced IFN-gamma hinders pancreatic B cell infiltration and inhibits the capacity of APCs to activate T cells. Although pancreatic CD4(+) T cells from IL-12-treated IFN-gamma(-/-) mice fail to up-regulate the P-selectin ligand, suggesting that their entry into the pancreas may be impaired, T cell expansion is favored in these mice compared with IL-12-treated IFN-gamma(+/-) mice because IL-12 administration in the absence of IFN-gamma leads to enhanced cell proliferation and reduced T cell apoptosis. NO, an effector molecule in beta cell destruction, is produced ex vivo in high quantity by pancreas-infiltrating cells through a mechanism involving IL-12-induced IFN-gamma. Conversely, in IL-12-treated IFN-gamma-deficient mice, other pathways of beta cell death appear to be increased, as indicated by the up-regulated expression of Fas ligand on Th1 cells in the absence of IFN-gamma. These data demonstrate that IFN-gamma has a dual role, pathogenic and protective, in IDDM development, and its deletion allows IL-12 to establish alternative pathways leading to diabetes acceleration.

Inosine protects against the development of diabetes in multiple-low-dose streptozotocin and nonobese diabetic mouse models of type 1 diabetes

Inosine, a naturally occurring purine, was long considered to be an inactive metabolite of adenosine. However, recently inosine has been shown to be an immunomodulator and anti-inflammatory agent. The aim of this study was to determine whether inosine influences anti-inflammatory effects and affects the development of type 1 diabetes in murine models. Type 1 diabetes was induced either chemically by streptozotocin or genetically using the nonobese diabetic mouse (NOD) model. Mice were treated with inosine (100 or 200 mg kg(-1)d(-1)d) and diabetes incidence was monitored. The effect of inosine on pancreas immune cell infiltration, oxidative stress, and cytokine profile also was determined. For the transplantation model islets were placed under the renal capsule of NOD mice and inosine (200 mg kg(-1)d d(-1)d) treatment started the day of islet transplantation. Graft rejection was diagnosed by return of hyperglycemia accompanied by glucosuria and ketonuria. Inosine reduced the incidence of diabetes in both streptozotocin-induced diabetes and spontaneous diabetes in NOD mice. Inosine decreased pancreatic leukocyte infiltration and oxidative stress in addition to switching the cytokine profile from a Th1 to a Th2 profile. Inosine prolonged pancreatic islet graft survival, increased the number of surviving beta cells, and reduced the number of infiltrating leukocytes. Inosine protects against both the development of diabetes and against the rejection of transplanted islets. The purine exerts anti-inflammatory effects in the pancreas, which is its likely mode of action. The use of inosine should be considered as a potential preventative therapy in humans susceptible to developing Type 1 diabetes and as a possible antirejection therapy for islet transplant recipients.

IL-12p40 is associated with type 1 diabetes in Caucasian-American families

The IL-12p40 locus has recently been shown to be associated with type 1 diabetes (1). Here, we report the identification of novel microsatellite and single-nucleotide polymorphisms (SNPs) within the IL-12p40 gene and a significant association between a (ATT)n repeat marker and type 1 diabetes in 364 U.S. Caucasian sib-pair families (P < 0.006). Haplotype analysis using the (ATT)n repeat (D5S2941) and the C1159A SNP at the 3' untranslated region of IL-12p40 showed a significant association (P = 0.02). Expression studies in individuals heterozygous for the C1159A SNP indicated that the expression of the 1159A allele is approximately 50% higher than that of the 1159C allele. These results provide genetic and functional evidence for IL-12p40 as a type 1 diabetes susceptibility gene.

Treatment of autoimmune diabetes recurrence in non-obese diabetic mice by mouse interferon-beta in combination with an analogue of 1alpha,25-dihydroxyvitamin-D3

Autoimmune diabetes recurrence is in part responsible for islet graft destruction in type 1 diabetic individuals. The aim of the present study was to design treatment modalities able to prevent autoimmune diabetes recurrence after islet transplantation in spontaneously diabetic NOD mice. In order to avoid confusion between autoimmune diabetes recurrence and allograft rejection, we performed syngeneic islet transplantations in spontaneously diabetic NOD mice. Mice were treated with mouse interferon-beta (IFN-beta, 1 x 105 IU/day), a new 14-epi-1,25-(OH)2D3-analogue (TX 527, 5 microg/kg/day) and cyclosporin A (CsA, 7.5 mg/kg/day) as single substances and in combinations. Treatment was stopped either 20 days (IFN-beta and CsA) or 30 days (TX 527) after transplantation. Autoimmune diabetes recurred in 100% of control mice (MST 11 days). None of the mono-therapies significantly prolonged islet graft survival. Combining CsA with TX 527 maintained graft function in 67% of recipients as long as treatment was given (MST 31 days, P < 0.01 versus controls). Interestingly, 100% of the IFN-beta plus TX 527-treated mice had normal blood glucose levels during treatment, and even had a more pronounced prolongation of graft survival (MST 62 days, P < 0.005 versus controls). Cytokine mRNA analysis of the grafts 6 days after transplantation revealed a significant decrease in IL-2, IFN-gamma and IL-12 messages in both IFN-beta plus TX 527- and CsA plus TX 527-treated mice, while only in the IFN-beta with TX 527 group were higher levels of IL-10 transcripts observed. Therefore, we conclude that a combination of IFN-beta and TX 527 delays autoimmune diabetes recurrence in islet grafts in spontaneously diabetic NOD mice.

Differential response of the murine IL-12 p35 gene to lipopolysaccharide compared with interferon-gamma and CD40 ligation

Expression of the heterodimeric cytokine interleukin-(IL-)12 is induced by pattern recognition receptors responding to microbial stimuli such as lipopolysaccharide (LPS) and products of the immune system such as interferon-gamma (IFN-gamma) and CD40L. The formation of bioactive IL-12 requires equimolar synthesis of p35 and p40 subunits. However, p35 expression limits the amount of IL-12 formed. Transcription of the gene for the p35 subunit of IL-12 initiates within the first exon, an alternate first exon (exon 1a), or second exon. Here we show that LPS and IFN-gamma/CD40 ligation increase the amount of total p35 mRNA in splenic adherent cells (SAC) to a similar extent. However, the exon 1 transcript was a smaller fraction of total p35 mRNA in IFN-gamma/CD40-stimulated cells than in unstimulated or LPS-stimulated cells. Despite comparable levels of total p35 mRNA, LPS-induced p35 exon 1 transcripts led to significantly more bioactive IL-12 from SAC than IFN-gamma/CD40-induced exon 1a/exon 2 transcripts as measured by ELISA. The data suggest that LPS-inducible p35 synthesis from exon 1 p35 transcripts leads to greater amount of bioactive IL-12 than IFN-gamma/CD40-induced p35 expression from alternate p35 exon 1a/exon 2 transcripts.

Increased entry into the IFN-gamma effector pathway by CD4+ T cells selected by I-Ag7 on a nonobese diabetic versus C57BL/6 genetic background

IFN-gamma-mediated Th1 effects play a major role in the pathogenesis of autoimmune diabetes in nonobese diabetic (NOD) mice. We analyzed functional responses of CD4(+) T cells from NOD and B6.G7 MHC congenic mice, which share the H2(g7) MHC region but differ in their non-MHC genetic background. T cells from each strain proliferated equally to panstimulation with T cell lectins as well as to stimulation with glutamic acid decarboxylase 524-543 (self) and hen egg lysozyme 11-23 (foreign) I-A(g7)-binding peptide epitopes. Despite comparable proliferative responses, NOD CD4(+) T cells had significantly increased IFN-gamma intracellular/extracellular protein and mRNA responses compared with B6.G7 T cells as measured by intracellular cytokine analysis, time resolved fluorometry, and RNase protection assays. The increased IFN-gamma production was not due to an increase in the amount of IFN-gamma produced per cell but to an increase in the number of NOD CD4(+) T cells entering the IFN-gamma-producing pathway. The increased IFN-gamma response in NOD mice was not due to increased numbers of activated precursors as measured by activation/memory markers. B6.G7 lymphoid cells demonstrated an absolute decrease in IFN-gamma mRNA, an increase in IL-4 mRNA production, and a significantly decreased IFN-gamma:IL-4 mRNA transcript ratio compared with NOD cells. CD4(+) T cells from C57BL6 mice also showed significantly decreased IFN-gamma production compared with CD4(+) T cells from NOD.H2(b) MHC-congenic mice (which have an H2(b) MHC region introgressed onto an NOD non-MHC background). Therefore, the NOD non-MHC background predisposes to a quantitatively increased IFN-gamma response, independent of MHC class II-mediated T cell repertoire selection, even when compared with a prototypical Th1 strain.

Dual-label immunohistochemical study of interleukin-4-and interferon-gamma-expressing cells within the pancreas of the NOD mouse during disease acceleration with cyclophosphamide

Beta cell destruction has been shown to occur when rodent or human islets are exposed in vitro to inflammatory cytokines, such as interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). Other cytokines such as interleukin-4 (IL-4) or interleukin-10 (IL-10), when given to NOD mice, prevent insulin-dependent diabetes mellitus (IDDM). In this study, we have employed immunofluorescence histochemistry to study the expression of IFN-gamma and IL-4 in the pancreas of female NOD mice at various time-points (days 0, 4, 7, 11 and at onset of diabetes) following disease acceleration with cyclophosphamide (Cy). Dual-label confocal and light microscopy were employed to determine the precise cellular sources of the two cytokines. IL-4 immunolabelling was observed in a few immune cells at days 0, 4, and 7 within the pancreatic islets but in larger numbers at day 11 and at onset of diabetes. The cytokine was co-localized predominantly in CD4 cells, while only a small minority of CD8 cells and macrophages also expressed IL-4. At days 0, 4, 7 and 11, weak to moderate immunolabelling for IL-4 was also observed in beta cells. In contrast, immunolabelling for IFN-gamma within the islets was not observed until day 11 and this labelling persisted at onset of diabetes. It was immunolocalized in macrophages and to a lesser extent in CD4 cells. Only a few CD8 cells were immunopositive for IFN-gamma. At day 11, a proportion of beta cells showed weak immunolabelling for IFN-gamma. During the study period, immunolabelling for IFN-gamma was also observed in a proportion of endothelial cells located in the intra-islet and exocrine regions of Cy and diluent-treated mice. From day 11 onwards, both the cytokines were observed in some of the peri-vascular regions. Our results demonstrate that during Cy-induced diabetes, there is increasing expression of both IL-4 and IFN-gamma in specific immune cells within the inflamed islets in the late prediabetic stage and at onset of diabetes. Further studies are required to correlate our protein immunohistochemical findings with in situ cytokine gene expression and to determine whether there is a clear Th1 cytokine protein bias at clinical onset of diabetes and immediately preceding it.

Beta cell destruction in the development of autoimmune diabetes in the non-obese diabetic (NOD) mouse

In the non-obese diabetic (NOD) mouse model of Type 1 (insulin-dependent) diabetes, evidence suggests that pancreatic beta cells are destroyed in part by apoptotic mechanisms. The precise mechanisms of beta cell destruction leading to diabetes remain unclear. The NOD mouse has been studied to gain insight into the cellular and molecular mediators of beta cell death, which are discussed in this review. Perforin, secreted by CD8(+) T cells, remains one of the only molecules confirmed to be implicated in beta cell death in the NOD mouse. There are many other molecules, including Fas ligand and cytokines such as interferon-gamma, interleukin-1 and tumor necrosis factor-alpha, which may lead to beta cell destruction either directly or indirectly via regulation of toxic molecules such as nitric oxide. As beta cell death can occur in the absence of perforin, these other factors, in addition to other as yet unidentified factors, may be important in the development of diabetes. Effective protection of NOD mice from beta cell destruction may therefore require inhibition of multiple effector mechanisms.

Temporal relationship between immune cell influx and the expression of inducible nitric oxide synthase, interleukin-4 and interferon-gamma in pancreatic islets of NOD mice following adoptive transfer of diabetic spleen cells

Beta cell destruction in NOD mice can be accelerated by adoptive transfer of diabetic spleen cells into irradiated adult NOD mice. Here mice receiving diabetic spleen cells were examined at days 0, 7, 14, 21 and at onset of diabetes for the resulting insulitis and the number of intra-islet CD4 and CD8 cells and macrophages. The progression of insulitis and the number of intra-islet CD4 and CD8 cells and macrophages were correlated with the expression and co-localization of inducible nitric oxide synthase, interferon-gamma and interleukin-4 by dual-label light and confocal immunofluorescence microscopy. Diabetes developed in 7/8 mice by 27 days following cell transfer. The insulitis score increased slightly by day 7 but rose sharply at day 14 (p = 0.001) and was maintained until diabetes. The mean number of intra-islet CD4 and CD8 cells and macrophages showed a similar trend to the insulitis scores and were present in almost equal numbers within the islets. Immunolabelling for inducible nitric oxide synthase was observed at day 7 in only some cells of a few islets but increased sharply from day 14. It was restricted to islets with insulitis and was co-localized in selective macrophages. Weak intra-islet interleukin-4 labelling was observed at days 7 and 14 but became more pronounced at day 21 and at onset of diabetes, being present in selective CD4 cells. Intra-islet labelling for interferon-gamma was first observed at day 21, but became more intense at onset of diabetes and was co-localized in a proportion of macrophages. Both cytokines were expressed in islets with advanced insulitis. Interferon-gamma staining was also observed within endothelial cells located in the exocrine pancreas. We conclude that transfer of diabetic spleen cells results in a rapid influx of CD4 and CD8 cells and macrophages within the pancreas of recipient mice. During the period of heightened insulitis, selective immune cells begin to express inducible nitric oxide synthase and the opposing cytokines, interferon-gamma and interleukin-4. Expression of these molecules becomes more pronounced immediately prior to and during the onset of diabetes.

Ligand-activation of the adenosine A2a receptors inhibits IL-12 production by human monocytes

Adenosine (ADO) exerts potent anti-inflammatory and immunosuppressive effects. In this paper we address the possibility that these effects are partly mediated by inhibition of the secretion of IL-12, a proinflammatory cytokine and a major inducer of Th1 responses. We demonstrate that 5'-N-ethylcarboxamidoadenosine (NECA), a nonspecific ADO analogue, and 2-p-(2-carbonyl-ethyl)phenylethylamino-5'-N-ethylcarboxamidoadenos ine (CGS-21680), a specific A2a receptor agonist, dose-dependently inhibited, in whole blood ex vivo and monocyte cultures, the production of human IL-12 induced by LPS and Stapholococcus aureus Cowan strain 1. However, the A1 receptor agonist 2-Chloro-N6-cyclopentyladenosine and the A3 receptor agonists N6-Benzyl-NECA and 1-deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-N-methyl-be ta-d -ribofuranuronamide expressed only weak inhibitory effects. On the other hand, NECA and CGS-21680 dose-dependently potentiated the production of IL-10. The differential effect of these drugs on monocyte IL-12 and IL-10 production implies that these effects are mediated by A2a receptor signaling rather than by intracellular toxicity of ADO analogue's metabolites. Moreover, CGS-21680 inhibited IL-12 production independently of endogenous IL-10 induction, because anti-IL-10 Abs failed to prevent its effect. The selective A2a antagonist 8-(3-Chlorostyryl) caffeine prevented the inhibitory effect of CGS-21680 on IL-12 production. The phosphodiesterase inhibitor Ro 20-1724 dose-dependently potentiated the inhibitory effect of CGS-21680 and, furthermore, Rp-cAMPS, a protein kinase A inhibitor, reversed the inhibitory effect of CGS-21680, implicating a cAMP/protein kinase A pathway in its action. Thus, ligand activation of A2a receptors simultaneously inhibits IL-12 and stimulates IL-10 production by human monocytes. Through this mechanism, ADO released in excess during inflammatory and ischemic conditions, or tissue injury, may contribute to selective suppression of Th1 responses and cellular immunity.

The role of IL-12 in inflammatory activity of patients with rheumatoid arthritis (RA)

The aim of this study was to investigate the role of IL-12 in patients with RA. IL-12 (p70) and its associated cytokines were measured in sera and synovial fluid (SF) using an enzyme-linked immunosorbent method. Seven American College of Rheumatology (ACR) core set measures as well as IL-12 levels were sequentially monitored at the commencement and 4 months after treatment with a low-dose steroid and disease-modifying anti-rheumatic drugs (DMARDs). In sera, 64 (42.2%) of 152 RA patients had detectable concentrations of IL-12 (p70), whereas one (1.4%) of 69 osteoarthritis (OA) patients and five (10%) of 50 healthy controls had detectable IL-12 (P < 0.001). The median level of circulating IL-12 was also higher in RA patients (P < 0.001). In SF, the number of patients with detectable IL-12 and the median IL-12 levels were significantly higher in RA patients (n = 53) than in OA patients (n = 22). In paired samples (n = 53) of sera and SF from RA patients, IL-12 levels were higher in the SF than in sera (P < 0.001). Patients with detectable IL-12 (n = 51) in sera had higher tender joint scores (P = 0.003), swollen joint scores (P < 0.001) and C-reactive protein (CRP; P = 0.036), than those without (n = 55). Four months after treatment with DMARDs, the improved group showed a larger IL-12 decrease than the non-improved group (P = 0.017). The levels of IL-12 correlated positively with those of IL-2, interferon-gamma, IL-6, and tumour necrosis factor-alpha, but were correlated inversely with those of IL-10. Our results demonstrate that IL-12 levels reflect RA disease activity and that IL-12 is involved in the production of proinflammatory cytokines. An IL-12 blockade could be useful for the treatment of RA.

Failure of exogenously administered interferon-gamma or blockage of endogenous interleukin-4 with specific inhibitors to augment the incidence of autoimmune diabetes in male NOD mice

Interferon (IFN)-gamma and interleukin (IL)-4 are prototypic type 1 and type 2 cytokines which are known to play pathogenetic and protective roles, respectively, in NOD mouse IDDM. The capacity of male NOD mice to produce more IL-4 and less IFN-gamma within the insulitic lesions than females has been suggested to contribute to their lower incidence of diabetes. In this study we have tested the effects of prolonged prophylactic treatment of male NOD mice with rat IFN-gamma, mouse IFN-gamma, anti-IL-4 monoclonal antibody (mAb) and recombinant murine soluble IL-4 receptor (smIL-4R) on the diabetogenic events leading to insulitis and diabetes. None of these treatments influenced spontaneous and/or cyclophosphamide-induced autoimmune diabetogenesis in male NOD mice. Control mice exhibited comparable histological signs of insulitis and incidence of diabetes to those treated with either mouse/rat IFN-gamma or specific IL-4 inhibitors. On the contrary, both clinical and histological signs of diabetes were suppressed by prophylactic treatment with anti-IFN-gamma mAb. These findings indicate that the autoimmune diathesis of male NOD mice towards IDDM cannot be augmented by manipulation of endogenous IFN-gamma or IL-4.

Endogenous interleukin-12 only plays a key pathogenetic role in non-obese diabetic mouse diabetes during the very early stages of the disease

A rat monoclonal antibody (mAb) that neutralizes mouse interleukin-12 (IL-12) was administered to female non-obese diabetic (NOD) mice of different ages to dismantle the role of endogenous IL-12 in murine autoimmune diabetogenesis. This mAb was effective in preventing clinical, but not histological signs of spontaneous diabetes when treatment was started early in life at the age of 4 weeks and consecutively continued for 10 weeks. Delaying commencement of anti-IL-12 mAb prophylaxis until the age of 18 weeks, when NOD mice suffer from advanced insulitis, was ineffective. Anti-IL-12 mAb did not influence the course of the accelerated model of diabetes induced by cyclophosphamide. These data prove that the pathogenetic role of endogenous IL-12 in NOD mouse diabetes is restricted to the very early diabetogenic events presumably occurring prior to insulitis development.

Multidose streptozotocin induction of diabetes in BALB/cBy mice induces a T cell proliferation defect in thymocytes which is reversible by interleukin-4

Thymic T cell function in streptozotocin-treated (STZ) diabetic mice has been examined. STZ administration suppresses thymic T cell proliferation in response to mitogen stimulation in vitro. Secretion of IL-4 was dramatically reduced; however, secretion of IL-2 or IFN-gamma was not significantly inhibited. RT-PCR analysis of thymocyte RNA revealed that levels of IL-4 mRNA were dramatically decreased in STZ-treated mice. Levels of mRNA encoding IFN-gamma were similar, but the appearance was delayed in thymocytes derived from STZ-treated mice, implying differential regulation of IL-4 and IFN-gamma. Defective thymocyte proliferation was partially restored by exposure to IL-2 in vitro; however, IL-4 completely reversed the STZ-induced defect. Administration in vivo of IL-4 before STZ treatment reversed the STZ-induced thymocyte proliferation defect and prevented both pancreatic islet destruction and hyperglycemia. Thymocyte cell surface differentiation markers were not appreciably different from control mice. Collectively these experiments suggest that STZ treatment of mice reduces expression of IL-4 which is associated with development of autoimmune diabetes.

Local expression of immunoregulatory IL-12p40 gene prolonged syngeneic islet graft survival in diabetic NOD mice

Local production of immunosuppressive cytokines will be one of the most suitable therapeutic strategies against organ-specific autoimmune diabetes. To establish such a new therapy, we constructed recombinant adenoviral vectors with inserted mIL-12p40 (Ad.IL-12p40) and mIL-10 (Ad.IL-10). Sufficient amounts of IL-12p40 and IL-10 were secreted by relevant adenovirus-transfected nonobese diabetic (NOD) islets. Shortly after transfection, 400 NOD islets transfected with Ad.IL-12p40 or Ad.IL-10 were transplanted under the renal capsule of a newly diabetic NOD mouse. NOD mice with IL-12p40-producing islet grafts kept normoglycemia in all of 14 grafted mice for over 4 wk after transplantation. In contrast, NOD mice with IL-10-producing islet grafts became diabetic in all of six grafted mice within 2 wk af-ter transplantation. Reverse transcription-PCR analysis revealed that local production of IL-12p40 led to the decrease of interferon-gamma and the augmentation of transforming growth factor-beta at the graft site. These results suggest that IL-12 plays an important role in the destruction of islet cells at the inflamed site of autoimmunity. Such a local blockade of IL-12 would be a useful gene therapy for human autoimmune diabetes.

Autoimmune diabetes: the role of T cells, MHC molecules and autoantigens

Type 1 diabetes (IDDM) is a T cell mediated autoimmune disease which in part is determined genetically by its association with major histocompatibility complex (MHC) class II alleles. The major role of MHC molecules is the regulation of immune responses through the presentation of peptide epitopes of processed protein antigens to the immune system. Recently it has been demonstrated that MHC molecules associated with autoimmune diseases preferentially present peptides of other endogenous MHC proteins, that often mimic autoantigen-derived peptides. Hence, these MHC-derived peptides might represent potential targets for autoreactive T cells. It has consistently been shown that humoral autoimmunity to insulin predominantly occurs in early childhood. The cellular immune response to insulin is relatively low in the peripheral blood of patients with IDDM. Studies in NOD mice however have shown, that lymphocytes isolated from pancreatic islet infiltrates display a high reactivity to insulin and in particular to an insulin peptide B 9-23. Furthermore we have evidence that cellular autoimmunity to insulin is higher in young pre-diabetic individuals, whereas cellular reactivity to other autoantigens is equally distributed in younger and older subjects. This implicates that insulin, in human childhood IDDM and animal autoimmune diabetes, acts as an important early antigen which may target the autoimmune response to pancreatic beta cells. Moreover, we observed that in the vast majority of newly diagnosed diabetic patients or individuals at risk for IDDM, T cell reactivity to various autoantigens occurs simultaneously. In contrast, cellular reactivity to a single autoantigen is found with equal frequency in (pre)-type 1 diabetic individuals as well as in control subjects. Therefore the autoimmune response in the inductive phase of IDDM may be targeted to pancreatic islets by the cellular and humoral reactivity to one beta-cell specific autoantigen, but spreading to a set of different antigens may be a prerequisite for progression to destructive insulitis and clinical disease. Due to mimic epitopes shared by autoantigen(s), autologous MHC molecules and environmental antigens autoimmunity may spread, intramolecularly and intermolecularly and amplify upon repeated reexposure to mimic epitopes of environmental triggers.