Systemic administration of IL-18 promotes diabetes development in young nonobese diabetic mice

Kinetics of IFNγ-Induced Cytokines and Development of Immune-Related Adverse Events in Patients Receiving PD-(L)1 Inhibitors

Immune checkpoint inhibitors (ICI) have the potential to trigger unpredictable immune-related adverse events (irAEs), which can be severe. The underlying mechanisms of these events are not fully understood. As PD-L1 is upregulated by IFN, the heightened immune activation resulting from PD-1/PD-L1 inhibition may enhance the IFN response, triggering the expression of IFN-inducible genes and contributing to irAE development and its severity. In this study, we investigated the interplay between irAEs and the expression of IFN-inducible chemokines and cytokines in 134 consecutive patients with solid tumours treated with PD-(L)1 inhibitors as monotherapy or in combination with chemotherapy or other immunotherapy agents. We compared the plasma levels of IFN-associated cytokines (CXCL9/10/11, IL-18, IL-10, IL-6 and TGFβ) at various time points (at baseline, at the onset of irAE and previous to irAE onset) in three patient groups categorized by irAE development and severity: patients with serious irAEs, mild irAEs and without irAEs after PD-(L)1 inhibitors. No differences were observed between groups at baseline. However, patients with serious irAEs exhibited significant increases in CXCL9/10/11, IL-18 and IL-10 levels at the onset of the irAE compared to baseline. A network analysis and correlation patterns highlighted a robust relationship among these chemokines and cytokines at serious-irAE onset. Combining all of the analysed proteins in a cluster analysis, we identified a subgroup of patients with a higher incidence of serious irAEs affecting different organs or systems. Finally, an ROC analysis and a decision tree model proposed IL-18 levels ≥ 807 pg/mL and TGFβ levels ≤ 114 pg/mL as predictors for serious irAEs in 90% of cases. In conclusion, our study elucidates the dynamic changes in cytokine profiles associated with serious irAE development during treatment with PD-(L)1 inhibitors. The study's findings offer valuable insights into the intricate IFN-induced immune responses associated with irAEs and propose potential predictive markers for their severity.

The trigger for pancreatic disease: NLRP3 inflammasome

NLRP3 inflammasome is a multiprotein complex expressed in a variety of cells to stimulate the production of inflammatory factors. Activation of NLRP3 inflammasome depends on a complex regulatory mechanism, and its pro-inflammatory function plays an important role in pancreatic diseases. In this literature review, we summarize the activation mechanism of NLRP3 and analyze its role in each of the four typical pancreatic diseases. Through this article, we provide a relatively comprehensive summary to the researchers in this field, and provide some targeted therapy routes.

An evaluation of the effects of mixed heavy metals on prediabetes and type 2 diabetes: epidemiological and toxicogenomic analysis

The link between mixed heavy metals (mercury, lead, and cadmium), prediabetes, and type 2 diabetes mellitus (T2DM), especially molecular mechanisms, is poorly understood. Thus, we aimed to identify the association between mixed heavy metals and T2DM and its components using a data set from the Korean National Health and Nutrition Examination Survey. We further analyzed the main molecular mechanisms implicated in T2DM development induced by mixed heavy metals using in-silico analysis. Our findings observed that serum mercury was associated with prediabetes, elevated glucose, and ln2-transformed glucose when using different statistical methods. "AGE-RAGE signaling pathway in diabetic complications", "non-alcoholic fatty liver disease", "metabolic Syndrome X", and three miRNAs (hsa-miR-98-5p, hsa-let-7a-5p, and hsa-miR-34a-5p) were listed as the most important molecular mechanisms related to T2DM development caused by mixed heavy metals. These miRNA sponge structures were created and examined, and they may be beneficial in the treatment of T2DM. The predicted cutoff values for three heavy metal levels linked to T2DM and its components were specifically identified. Our results imply that chronic exposure to heavy metals, particularly mercury, may contribute to the development of T2DM. To understand the changes in the pathophysiology of T2DM brought on by a combination of heavy metals, more research is required.

Inhibition of NLRP3 inflammasome activity by MCC950 leads to exacerbation of Sjӧgren's syndrome pathologies in non-obese diabetic mice

Sjӧgren's syndrome (SS) is an autoimmune inflammatory disease characterized by chronic inflammation and dysfunction of exocrine glands and causes dry mouth, dry eyes and various systemic health problems. The objective of this study is to define the in vivo actions of the endogenous NLRP3 inflammasome, a key initiator and mediator of various immune and inflammatory conditions, in newly established SS disease. MCC950, a highly specific small-molecule inhibitor of NLRP3 inflammasome formation and activation, was intraperitoneally administered to the female non-obese diabetic (NOD) mice aged 11 weeks, which have newly established SS-like hyposalivation and pathologies. The injection was conducted three times weekly for three consecutive weeks and mice were analysed for characteristic SS pathologies at the end of the treatments. MCC950 treatment resulted in a marked reduction in salivary secretion and an exacerbation of leukocyte infiltration of submandibular glands. The disease-worsening effect of MCC950 treatment was accompanied by increased T and B cell numbers, enhanced T helper 1 response and reduced aquaporin 5 expression in submandibular glands. Hence, ablation of endogenous NLRP3 inflammasome activity by MCC950 with established autoimmune exocrinopathy exacerbates salivary gland dysfunction and inflammation, indicating a disease-alleviating and inflammation-dampening action of the endogenous NLRP3 inflammasome activity during established SS disease in the non-obese diabetic mouse model.

Interleukin-18 cytokine in immunity, inflammation, and autoimmunity: Biological role in induction, regulation, and treatment

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine involved in host defense against infections and regulates the innate and acquired immune response. IL-18 is produced by both hematopoietic and non-hematopoietic cells, including monocytes, macrophages, keratinocytes and mesenchymal cell. IL-18 could potentially induce inflammatory and cytotoxic immune cell activities leading to autoimmunity. Its elevated levels have been reported in the blood of patients with some immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, atopic dermatitis, psoriasis, and inflammatory bowel disease. In the present review, we aimed to summarize the biological properties of IL-18 and its pathological role in different autoimmune diseases. We also reported some monoclonal antibodies and drugs targeting IL-18. Most of these monoclonal antibodies and drugs have only produced partial effectiveness or complete ineffectiveness in vitro, in vivo and human studies. The ineffectiveness of these drugs targeting IL-18 may be largely due to the loophole caused by the involvement of other cytokines and proteins in the signaling pathway of many inflammatory diseases besides the involvement of IL-18. Combination drug therapies, that focus on IL-18 inhibition, in addition to other cytokines, are highly recommended to be considered as an important area of research that needs to be explored.

Combination of anti-CD25 antibody and poly I:C treatment in pregnant NOD mice may be used as "pregnancy-related" type 1 diabetes model

Aims/Introduction

Some women develop type 1 diabetes during pregnancy or immediately after delivery. However, the underlying pathophysiology remains largely unknown, probably because of the lack of a suitable animal model. In this study, we administered pregnant NOD mice with an anti‐CD25 antibody to reduce regulatory T cells along with poly I:C and examined the onset of diabetes.

Materials and Methods

Anti‐CD25 antibody and poly I:C were intraperitoneally administered to mated female NOD mice. Mice delivered within 3 weeks after the treatment, and the onset of diabetes during pregnancy or within 6 weeks after delivery was examined. Some mice were killed 1 week after treatment, and their spleen and pancreas were excised to examine the expression levels of cytokines and for histological examination.

Results

Half of the mice treated with anti‐CD25 antibody plus poly I:C developed diabetes, as compared with none of the poly I:C‐injected mice (P < 0.05). The ratios of interleukin‐18/forkhead box P3 and granzyme B/forkhead box P3 were higher in the pancreas of anti‐CD25 antibody plus poly I:C‐treated mice than in the pancreas of control mice. The insulitis score decreased in the pancreas of anti‐CD25 antibody plus poly I:C‐injected pregnant NOD mice.

Conclusions

We describe the use of anti‐CD25 antibody to reduce regulatory T cells and poly I:C as a Toll‐like receptor 3 stimulator to mimic viral infection in a pregnant NOD mouse, which can be used as a model of ‘pregnancy‐related’ type 1 diabetes.

Interleukin-18 in metabolism: From mice physiology to human diseases

Interleukin-18 (IL-18) is a classical member of the IL-1 superfamily of cytokines. As IL-1β, IL-18 precursor is processed by inflammasome/caspase-1 into a mature and biologically active form. IL-18 binds to its specific receptor composed of two chains (IL-18Rα and IL-18Rβ) to trigger a similar intracellular signaling pathway as IL-1, ultimately leading to activation of NF-κB and inflammatory processes. Independently of this IL-1-like signaling, IL-18 also specifically induces IFN-γ production, driving the Th1 immune response. In circulation, IL-18 binds to the IL-18 binding protein (IL-18BP) with high affinity, letting only a small fraction of free IL-18 able to trigger receptor-mediated signaling. In contrast to other IL-1 family members, IL-18 is produced constitutively by different cell types, suggesting implications in normal physiology. If the roles of IL-18 in inflammatory processes and infectious diseases are well described, recent experimental studies in mice have highlighted the action of IL-18 signaling in the control of energy homeostasis, pancreatic islet immunity and liver integrity during nutritional stress. At the same time, clinical observations implicate IL-18 in various metabolic diseases including obesity, type 1 and 2 diabetes and nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). In the present review, we summarize and discuss both the physiological actions of IL-18 in metabolism and its potential roles in pathophysiological mechanisms leading to the most common human metabolic disorders, such as obesity, diabetes and NAFLD/NASH.

Neutrophils and their role in the aetiopathogenesis of type 1 and type 2 diabetes

Multiple and complex aetiological processes underlie diabetes mellitus, which invariably result in the development of hyperglycaemia. Although there are two prevalent distinct forms of the disease, that is, type 1 and type 2 diabetes, accumulating evidence indicates that these syndromes share more aetiopathological mechanisms than originally thought. This compels a rethinking of the approaches to prevent and treat the different manifestations of what eventually becomes a hyperglycaemic state. This review aims to address the involvement of neutrophils, the most abundant type of granulocytes involved in the initiation of the acute phase of inflammation, in the aetiopathogenesis of diabetes mellitus, with a focus on type 1 and type 2 diabetes. We review the evidence that neutrophils are the first leucocytes to react to and accumulate inside target tissues of diabetes, such as the pancreas and insulin-sensitive tissues. We then review available data on the role of neutrophils and their functional alteration, with a focus on NETosis, in the progression towards clinical disease. Finally, we review potential approaches as secondary and adjunctive treatments to limit neutrophil-mediated damage in the prevention of the progression of subclinical disease to clinical hyperglycaemia.

NLRP3 inflammasome is involved in ambient PM2.5-related metabolic disorders in diabetic model mice but not in wild-type mice

AIMS

To explore the role of nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome in ambient fine particulate matter (PM_2.5)-related metabolic disorders.

METHODS

In this study, the C57BL/6 and db/db mice were exposed to concentrated PM_2.5 or filtered air (FA) using Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) for 12 weeks. Indices of lipid metabolism, glucose metabolism, insulin sensitivity, and protein expression of NLRP3 inflammasome in visceral adipose tissue (VAT) were measured, respectively.

RESULTS

The results showed that PM_2.5 exposure increased circulatory insulin, triglycerides (TG), and total cholesterol (TC), and decreased high-density lipoprotein (HDL) in both C57BL/6 and db/db mice. The levels of NLRP3-related circulatory inflammatory cytokines including both interleukin (IL)-18 and IL-1β in serum were increased in the PM_2.5-exposed mice and accompanied by the elevation in fasting blood glucose and insulin. The results also showed that exposure to PM_2.5 promoted the activation of NLRP3, pro-caspase-1, caspase-1, and apoptosis-associated speck-like protein containing CARD (ASC), simultaneously accompanied by the increase of IL-18 and IL-1β expression in VAT, but the statistically significant difference only found in the db/db mice, not in C57BL/6 mice.

CONCLUSION

The activation of NLRP3 inflammasome might be not the main mechanism of PM_2.5-related metabolic disorders in wide type mice but it partly mediated the exacerbation of metabolic disorders in diabetic model mice.

Possible involvement of autoimmunity in fulminant type 1 diabetes

Fulminant type 1 diabetes (FT1D) is characterized by a relatively low HbA1c level at the onset, despite the abrupt occurrence of marked hyperglycemia with ketosis or ketoacidosis. The initial symptoms/findings are flu-like, absence of islet-associated autoantibodies, and a drastic decrease in β-cells and α-cells, which strongly suggest the involvement of a viral infection. In fact, we successfully demonstrated that a FT1D-like phenotype can be reproduced in encephalomyocarditis virus-induced diabetes murine model. However, there is a discussion on the possible involvement of autoimmunity rather than viral infection as the underlying cause of FT1D. For example, HLA-DRB1*04:05, a susceptible antigen of type 1A diabetes, is reportedly associated with FT1D in Japan. Moreover, anti-glutamic acid decarboxylase antibody is reportedly detected in ~ 5% of the patients. Additionally, half of the patients with anti-programmed cell death-1 therapy-related type 1 diabetes fulfilled the criteria of the disease. These findings suggest that islet-associated autoimmunity can partially contribute to the development of FT1D. Furthermore, using nonobese diabetic mice with reduced regulatory T-cell (Treg) numbers, we found that a human FT1D-like phenotype can be induced by islet-associated autoimmunity through collaboration between innate immunity (macrophages and/or natural killer cells) and acquired immunity (predominantly cytotoxic CD8⁺ T cells) in genetically predisposed individuals of autoimmune type 1 diabetes with low Tregs or Treg dysfunction. To clarify greater details regarding the association of autoimmunity in the pathogenesis of FT1D, further studies using suitable animal models and accumulation of the relevant patients are required.

Increased interleukin 18 activity in adolescents with early-onset psychosis is associated with cortisol and depressive symptoms

OBJECTIVE

Evidence indicates that the pathophysiology of adult psychosis involves immune dysregulation, but its associations with stress are often not considered. The inflammatory cytokine interleukin (IL)-18, which is elevated in adult schizophrenia, is suggested to be sensitive to stress. We compared the associations of IL-18 with cortisol and clinical variables in adolescents with early-onset psychosis (EOP) aged 12-18 years and age-matched healthy controls (HC).

METHOD

We measured serum IL-18, IL-18 binding protein (IL-18BP), IL-18 receptor accessory protein (IL-18RAP), IL-18 receptor 1 (IL-18R1) and cortisol, and calculated the IL-18/IL-18BP ratio in patients (n = 31) and HC (n = 60). Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale and depressive symptoms by the Mood and Feelings Questionnaire-Child version (MFQ-C). Bivariate correlation analysis was used to explore relationships between IL-18/IL-18BP ratio and cortisol, depression and other clinical characteristics. Hierarchical multiple linear regression analysis was used to assess their individual contributions to the variance of the IL-18/IL-18BP ratio.

RESULTS

Patients had significantly higher IL-18 levels and IL-18/IL-18BP ratios than HC, but similar IL-18BP, IL-18RAP and IL-18R1. Both cortisol (R² change = 0.05) and the MFQ-C score (R² change = 0.09) contributed significantly to the variance in IL-18/IL-18BP ratios after controlling for confounders.

CONCLUSION

We found increased IL-18 system activity in adolescents with EOP. Cortisol and depressive symptoms each contributed to the variance in the IL-18/IL-18BP ratio. Our findings support activation of inflammatory pathways in adolescent psychosis and suggest interactions between stress, inflammation and depressive symptoms in EOP.

Hepatitis B vaccine non response: A predictor of latent autoimmunity?

Unresponsiveness to Hepatitis B virus (HBV) vaccine has been associated with interleukins involved with Th1 functioning including Interleukin-8 (IL-18) and Interferon-γ (IFN-γ). IL-18 and IFN-γ have also been implicated in the onset of different types of immune-mediate inflammatory conditions such as Type 1 Diabetes (T1D), Celiac disease (CD), rheumatoid arthritis (RA), obesity and systemic lupus erythematosus (SLE). Taking into account that HBV vaccination is provided in the 1st year of life worldwide, I propose that all babies should be tested for anti-HBs response after completion of the vaccine series. And I suggest that children with undetectable anti-HBs titers after recommended immunization schedule as well as the additional booster doses should be followed up over time because they may be at risk of developing a number of autoimmune disorders. In this light, the non-responsiveness to HBV vaccine might be a predictor of latent autoimmunity. For that reason, research studies are needed in order to verify the existence of potential IL-18 and IFN-γ gene polymorphisms to utilize as biomarkers of latent autoimmunity. As a final point, administration of neutralizing antibodies against IFN-γ and/or IL-18 might represent a future target for immune-modulatory therapeutic approach to halt or even reverse autoimmune phenomena.

Systemic Elevation of Proinflammatory Interleukin 18 in HIV/HCV Coinfection versus HIV or HCV Monoinfection

BACKGROUND

HIV/HCV coinfection and elevated interleukin (IL)-18 levels are both associated with enhanced progression of hepatic inflammation and increased risk of diabetes, kidney disease, and cardiovascular disease. IL-18 is a proinflammatory cytokine made upon activation of the inflammasome, an innate sensing system. We assessed whether increased IL-18 could explain the increased incidence and progression of inflammatory conditions seen with HIV/HCV coinfection.

METHODS

Serum from 559 subjects with HIV monoinfection, HCV monoinfection, HIV/HCV coinfection, or people who inject drugs with neither infection was tested for IL-18 by ELISA and for 16 other analytes by electrochemiluminescence immunoassay. IL-18 levels were measured in 14 additional chronically HCV infected subjects who developed incident HIV infection to determine if IL-18 increases with coinfection.

RESULTS

IL-18 was significantly elevated in coinfected individuals versus both monoinfections (p<0.0001) independent of age, sex, and race. IL-18 levels were significantly higher in HIV monoinfection than in HCV monoinfection. High IL-18 levels were correlated with detectable HIV viremia and inversely with CD4 count (p<0.0001), consistent with HIV activation of the inflammasome resulting in CD4 T cell depletion. Incident HIV infection of chronically HCV infected subjects resulted in increased IL-18 (p<0.001), while HIV suppression was associated with normal IL-18 levels. Four additional analytes (IP-10, IL-12/23p40, IFNy, IL-15) were found to be elevated in HIV/HCV coinfection when compared to both monoinfections.

CONCLUSIONS

HIV/HCV coinfection results in significantly elevated serum IL-18. The elevated levels of this proinflammatory cytokine may explain the increased incidence and progression of inflammatory illnesses seen in coinfected individuals.

Imbalanced production of IL-18 and its antagonist in human diseases, and its implications for HIV-1 infection

IL-18 is a pleiotropic and multifunctional cytokine that belongs to the IL-1 family. It is produced as a biologically inactive precursor, which is cleaved into its active mature form mainly by caspase-1. The caspase becomes active from its inactive precursor (procaspase-1) upon assembly of an inflammasome. Because of IL-18's potential pro-inflammatory and tissue destructive effects, its biological activities are tightly controlled in the body by its naturally occurring antagonist called IL-18BP. The antagonist is produced in the body both constitutively and in response to an increased production of IL-18 as a negative feedback mechanism. Under physiological conditions, most of IL-18 in the circulation is bound with IL-18BP and is inactive. However, an imbalance in the production of IL-18 and its antagonist (an increase in the production of IL-18 with a decrease, no increase or an insufficient increase in the production of IL-18BP) has been described in many chronic inflammatory diseases in humans. The imbalance results in an increase in the concentrations of free IL-18 (unbound with its antagonist) resulting in increased biological activities of the cytokine that contribute towards pathogenesis of the disease. In this article, we provide an overview of the current biology of IL-18 and its antagonist, discuss how the imbalance occurs in HIV infections and how it contributes towards development of AIDS and other non-AIDS-associated clinical conditions occurring in HIV-infected individuals undergoing combination anti-retroviral therapy (cART). Finally, we discuss challenges facing immunotherapeutic strategies aimed at restoring balance between IL-18 and its antagonist in these patients.

NLRP3 deficiency protects from type 1 diabetes through the regulation of chemotaxis into the pancreatic islets

Studies in animal models and human subjects have shown that both innate and adaptive immunity contribute to the pathogenesis of type 1 diabetes (T1D). Whereas the role of TLR signaling pathways in T1D has been extensively studied, the contribution of the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing protein (NLRP) 3 inflammasome pathway remains to be explored. In this study, we report that NLRP3 plays an important role in the development of T1D in the nonobese diabetic (NOD) mouse model. NLRP3 deficiency not only affected T-cell activation and Th1 differentiation, but also modulated pathogenic T-cell migration to the pancreatic islet. The presence of NLRP3 is critical for the expression of the chemokine receptors CCR5 and CXCR3 on T cells. More importantly, NLRP3 ablation reduced the expression of chemokine genes CCL5 and CXCL10 on pancreatic islet cells in an IRF-1-dependent manner. Our results suggest that molecules involved in chemotaxis, accompanied by the activation of the NLRP3 inflammasome, may be effective targets for the treatment of T1D.

Identification of the inflammasome Nlrp1b as the candidate gene conferring diabetes risk at the Idd4.1 locus in the nonobese diabetic mouse

Type 1 diabetes in the NOD mouse model has been linked to >30 insulin-dependent diabetes (Idd) susceptibility loci. Idd4 on chromosome 11 consists of two subloci, Idd4.1 and Idd4.2. Using congenic analysis of alleles in NOD and NOD-resistant (NOR) mice, we previously defined Idd4.1 as an interval containing >50 genes that controlled expression of genes in the type 1 IFN pathway. In this study, we report refined mapping of Idd4.1 to a 1.1-Mb chromosomal region and provide genomic sequence analysis and mechanistic evidence supporting its role in innate immune regulation of islet-directed autoimmunity. Genetic variation at Idd4.1 was mediated by radiation-sensitive hematopoietic cells, and type 1 diabetes protection conferred by the NOR allele was abrogated in mice treated with exogenous type 1 IFN-β. Next generation sequence analysis of the full Idd4.1 genomic interval in NOD and NOR strains supported Nlrp1b as a strong candidate gene for Idd4.1. Nlrp1b belongs to the Nod-like receptor (NLR) gene family and contributes to inflammasome assembly, caspase-1 recruitment, and release of IL-1β. The Nlrp1b of NOR was expressed as an alternative spliced isoform that skips exon 9, resulting in a premature stop codon predicted to encode a truncated protein. Functional analysis of the truncated NOR Nlrp1b protein demonstrated that it was unable to recruit caspase-1 and process IL-1β. Our data suggest that Idd4.1-dependent protection from islet autoimmunity is mediated by differences in type 1 IFN- and IL-1β-dependent immune responses resulting from genetic variation in Nlrp1b.

IL-18 in inflammatory and autoimmune disease

Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.

The autoimmune disease-associated SNP rs917997 of IL18RAP controls IFNγ production by PBMC

Type 1 Diabetes (T1D) is an autoimmune disorder characterized by aberrant T cell responses. Innate immune activation defects may facilitate a T helper 1 (Th1) phenotype. The cytokine IL-18 synergizes with IL-12 to induce IFNγ production and Th1 differentiation. The IL-18R subunit (IL18RAP) SNP rs917997 has been linked to decreased IL18RAP gene expression. Prior reports link rs917997 allele A with protection from T1D, and conversely with susceptibility to Celiac disease. However, few studies have investigated the IL-18 pathway in T1D. In this study, we analyzed responsiveness to IL-18 in T1D, and the effect of rs917997 genotype on IL18RAP gene expression post-activation. Upon IL-12 and IL-18 treatment, peripheral blood mononuclear cells from subjects carrying susceptibility alleles at rs917997 produced higher levels of IFNγ than those with protective genotypes. Additionally, the SNP modified IL18RAP surface protein expression by NK cells and gene expression in activated T cells. Taken together, these data suggest that the disease-associated rs917997 allele G permits hyperresponsiveness to IL-18, providing a novel target for therapeutic intervention in T1D.

Potential biomarkers of insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease

Type 2 diabetes mellitus patients with coronary artery disease have become a major public health concern. The occurrence of insulin resistance accompanied with endothelial dysfunction worsens the state of atherosclerosis in type 2 diabetes mellitus patients. The combination of insulin resistance and endothelial dysfunction leads to coronary artery disease and ischemic heart disease complications. A recognized biological marker, high-sensitivity C-reactive protein, has been used widely to assess the progression of atherosclerosis and inflammation. Along with coronary arterial damage and inflammatory processes, high-sensitivity C-reactive protein is considered as an essential atherosclerosis marker in patients with cardiovascular disease, but not as an insulin resistance marker in type 2 diabetes mellitus patients. A new biological marker that can act as a reliable indicator of both the exact state of insulin resistance and atherosclerosis is required to facilitate optimal health management of diabetic patients. Malfunctioning of insulin mechanism and endothelial dysfunction leads to innate immune activation and released several biological markers into circulation. This review examines potential biological markers, YKL-40, alpha-hydroxybutyrate, soluble CD36, leptin, resistin, interleukin-18, retinol binding protein-4, and chemerin, as they may play significant roles in insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease.

Identification of novel type 1 diabetes candidate genes by integrating genome-wide association data, protein-protein interactions, and human pancreatic islet gene expression

Genome-wide association studies (GWAS) have heralded a new era in susceptibility locus discovery in complex diseases. For type 1 diabetes, >40 susceptibility loci have been discovered. However, GWAS do not inevitably lead to identification of the gene or genes in a given locus associated with disease, and they do not typically inform the broader context in which the disease genes operate. Here, we integrated type 1 diabetes GWAS data with protein-protein interactions to construct biological networks of relevance for disease. A total of 17 networks were identified. To prioritize and substantiate these networks, we performed expressional profiling in human pancreatic islets exposed to proinflammatory cytokines. Three networks were significantly enriched for cytokine-regulated genes and, thus, likely to play an important role for type 1 diabetes in pancreatic islets. Eight of the regulated genes (CD83, IFNGR1, IL17RD, TRAF3IP2, IL27RA, PLCG2, MYO1B, and CXCR7) in these networks also harbored single nucleotide polymorphisms nominally associated with type 1 diabetes. Finally, the expression and cytokine regulation of these new candidate genes were confirmed in insulin-secreting INS-1 β-cells. Our results provide novel insight to the mechanisms behind type 1 diabetes pathogenesis and, thus, may provide the basis for the design of novel treatment strategies.

A mimic of viral double-stranded RNA triggers fulminant type 1 diabetes-like syndrome in regulatory T cell-deficient autoimmune diabetic mouse

Human fulminant type 1 diabetes (FT1D) is an extremely aggressive disease. The delay of proper diagnosis results in high mortality. However, the pathophysiology of this disease remains unclear. We took advantage of CD28-deficient NOD (CD28(-/-) NOD) mice, which have limited numbers of regulatory T cells and develop aggressive autoimmune diabetes, to create a FT1D model that mimicked the disease in humans. Young CD28(-/-) NOD mice were injected with polyinosinic-polycytidylic acid to activate innate immunity in an effort to induce diabetes onset. In this model, innate immune cell activation precedes the onset of diabetes similar to ∼70% of FT1D patients. Eighty-three percent of CD28(-/-) NOD mice developed diabetes within 1-6 d after injection of polyinosinic-polycytidylic acid. Moreover, T cells infiltrated the pancreatic exocrine tissue and destroyed α cells, an observation characteristic of human FT1D. We conclude that an FT1D-like phenotype can be induced in the background of autoimmune diabetes by a mimic of viral dsRNA, and this model is useful for understanding human FT1D.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

IL-18 is required for self-reactive T cell expansion in NOD mice

IL-18 has a well-established role in pro-inflammatory responses in the islets in type 1 diabetes. Here, we identify a distinctive role for IL-18 in expanding pathogenic T cells in the periphery of NOD mice. Well in advance of disease onset, the periphery of IL-18-deficient mice exhibits reduced T cell turnover, an increased prevalence of naïve and quiescent T cells, emergence of fewer effector T cells, and disease protection. Islet-reactive T cells fail to become activated in the lymphoid organs of mice lacking IL-18 and their rapid expansion is inhibited. IL-18 secretion by antigen presenting cells increases with advancing disease and is required for expression of its receptor on T cells. Our results demonstrate that induction of the IL-18 receptor reflects a critical stage of autoreactive T cell activation and expansion on the pathway toward effector T cell differentiation. This study therefore assigns a novel role to IL-18 for expanding the pool of islet-destructive T cells during pre-diabetes. This report highlights a new basic mechanism in type 1 diabetes pathogenesis and suggests that targeting the IL-18 pathway should be explored as a potential treatment strategy.

Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies

Type 1 diabetes (T1D) is a chronic autoimmune disease in which destruction or damaging of the beta-cells in the islets of Langerhans results in insulin deficiency and hyperglycemia. We only know for sure that autoimmunity is the predominant effector mechanism of T1D, but may not be its primary cause. T1D precipitates in genetically susceptible individuals, very likely as a result of an environmental trigger. Current genetic data point towards the following genes as susceptibility genes: HLA, insulin, PTPN22, IL2Ra, and CTLA4. Epidemiological and other studies suggest a triggering role for enteroviruses, while other microorganisms might provide protection. Efficacious prevention of T1D will require detection of the earliest events in the process. So far, autoantibodies are most widely used as serum biomarker, but T-cell readouts and metabolome studies might strengthen and bring forward diagnosis. Current preventive clinical trials mostly focus on environmental triggers. Therapeutic trials test the efficacy of antigen-specific and antigen-nonspecific immune interventions, but also include restoration of the affected beta-cell mass by islet transplantation, neogenesis and regeneration, and combinations thereof. In this comprehensive review, we explain the genetic, environmental, and immunological data underlying the prevention and intervention strategies to constrain T1D.

T Cell-Associated Cytokines in the Pathogenesis of Sjögren's Syndrome

Sjögren's syndrome (SjS) is a systemic autoimmune disease that primarily targets salivary and lacrimal glands. SjS affects 2-4 million people in the US alone and greatly affects the life quality of the afflicted individuals. Autoreactive effector T cells are central executors and orchestrators in the pathogenic processes of SjS by mediating target organ inflammation and destruction and by facilitating B cell responses and autoantibody production. A variety of cytokines that are produced by effector T cells or capable of directly affecting effector T cells are elevated in the target organs and circulations of SjS patients. The recent advancement in the understanding about the functions of these cytokines, achieved by using both human samples and mouse disease models, has generated great insights into the cytokine control of autoimmune responses in the SjS disease setting. In this review, we summarized the recent findings on the expression and functions of cytokines in this disease, with specific focus on those derived from T cells and/or directly affecting T cell responses.

Intramuscular delivery of a naked DNA plasmid encoding proinsulin and pancreatic regenerating III protein ameliorates type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by inflammation of pancreatic islets and destruction of β cells. Up to now, there is still no cure for this devastating disease and alternative approach should be developed. To explore a novel gene therapy strategy combining immunotherapy and β cell regeneration, we constructed a non-viral plasmid encoding proinsulin (PI) and pancreatic regenerating (Reg) III protein (pReg/PI). Therapeutic potentials of this plasmid for T1DM were investigated. Intramuscular delivery of pReg/PI resulted in a significant reduction in hyperglycemia and diabetes incidence, with an increased insulin contents in the serum of T1DM mice model induced by STZ. Treatment with pReg/PI also restored the balance of Th1/Th2 cytokines and expanded CD4(+)CD25(+)Foxp3(+) T regulatory cells, which may attribute to the establishment of self-immune tolerance. Additionally, in comparison to the mice treated with empty vector pBudCE4.1 (pBud), attenuated insulitis and apoptosis achieved by inhibiting activation of NF-κB in the pancreas of pReg/PI treated mice were observed. In summary, these results indicate that intramuscular delivery of pReg/PI distinctly ameliorated STZ-induced T1DM by reconstructing the immunological self-tolerance and promoting the regeneration of β cells, which might be served as a promising candidate for the gene therapy of T1DM.

Thyrocyte interleukin-18 expression is up-regulated by interferon-γ and may contribute to thyroid destruction in Hashimoto's thyroiditis

Interferon-γ (IFN-γ) has a direct role in thyroid destruction in autoimmune thyroiditis. Interleukin-18 (IL-18), a pro-inflammatory cytokine with potent IFN-γ inducing activities, may play an important role in Th1-mediated autoimmune diseases. The purpose of this study was to characterize the expression and localization of IL-18 in the thyroid tissues of Hashimoto's thyroiditis (HT) and to investigate the effect of IFN-γ on IL-18 expression in isolated human thyroid follicular cells (TFCs). Thyroid tissues obtained from six euthyroid patients with HT and six control subjects were used to detect IL-18 expression by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical staining. Human TFCs were isolated and incubated for 48 h with or without IFN-γ, tumour necrosis factor-α (TNF-α) or IL-1β. IL-18 expression was analysed by RT-PCR, immunofluorescent double staining and western blot. We found that IL-18 expression was increased in the thyroid tissues of HT compared with control thyroid tissues. TFCs were major cell types expressing IL-18 in the thyroid tissues of HT. IL-18 was constitutively expressed in isolated human TFCs, and the expression was significantly up-regulated by IFN-γ rather than TNF-α or IL-1β. Western bolt revealed that a 24-kDa band corresponding to pro-IL-18 was broadened in the lysates of IFN-γ-treated TFCs. Our results demonstrated that IL-18 expression is up-regulated in the TFCs of HT patients and in primary human TFCs exposed to IFN-γ. Therefore, intrathyroidal interaction between IL-18 and IFN-γ may have a role in promoting the local immune response, which contributes to the thyroid destruction seen in HT.

CXC chemokine ligand 10 DNA vaccination plus Complete Freund's Adjuvant reverses hyperglycemia in non-obese diabetic mice

OBJECTIVE

Complete Freund's Adjuvant (CFA) is known to arrest autoimmune diabetes development in non-obese diabetic (NOD) mice. However, CFA alone cannot induce effective remission in diabetic NOD mice. Previously, we reported that anti-CXC chemokine ligand 10 (CXCL10) antibody can promote beta-cell proliferation in NOD mice. In the present study, we aimed to examine whether anti-CXCL10 plus CFA treatment can effectively reverse autoimmune diabetes development.

METHODS

Systemic supply of anti-CXCL10 antibody by CXCL10 DNA vaccination in combination with CFA injection was performed in new-onset diabetic NOD mice. Remission rate of diabetes, histological characteristics of residual insulitis lesions, residual beta-cell mass, and regulatory T cell population in local pancreas were examined.

RESULTS

A high frequency of diabetes reversal was observed after combination treatment with anti-CXCL10 plus CFA. In mice showing diabetes reversal, residual beta-cell mass was significantly increased, and some beta-cells were in a proliferative state. Although systemic cytokine profiles were unaffected, the frequency of "hybrid regulatory T cells", i.e. regulatory T cells expressing CXCR3, was significantly increased in local pancreatic lesions. This was possibly associated with the regulation of anti-islet autoimmunity.

CONCLUSIONS

Anti-CXCL10 plus appropriate immune adjuvant therapy arrested, and reversed, type 1 diabetes development.

Association of polymorphisms in the IL-18 and IL-12 genes with susceptibility to Type 1 diabetes in Turkish patients

BACKGROUND

Recent studies have indicated that polymorphisms of the interleukin-18 (IL-18) and interleukin- 12 (IL-12) genes are associated with the development of Type 1 diabetes mellitus (T1DM) in some populations, but not all.

AIM

The present study was designed to examine the roles of polymorphisms in the IL-18 promoter and IL-12p40 with respect to susceptibility to T1DM in Turkish patients.

SUBJECTS AND METHODS

Ninety-one patients with T1DM and 87 unrelated healthy subjects were included in the study. The IL-18 polymorphisms at positions -607 and -137 were detected by a sequence-specific PCR method. The single nucleotide polymorphism in the IL-12p40 3' untranslated region (3'-UTR) at position +1188 was analyzed by the PCR-restriction fragment length polymorphism (RFPL) method.

RESULTS

The allelic and genotypic frequencies of the IL-18 and IL-12p40 polymorphisms did not differ significantly between subjects with T1DM and the controls (p>0.05). However, diabetic patients with the -137 (CC) genotype showed a younger onset age compared to patients with the -137 (GG) genotype (p=0.02). In addition, patients with the -607 (CC) genotype had higher levels of glycated hemoglobin (HbA1c) than patients with the -607 (AC) genotype (p=0.004). Furthermore, patients with the IL-12p40 (AC) genotype had higher HbA(1c) levels than patients with the IL-12p40 (AA) genotype (p=0.01).

CONCLUSIONS

The results of the present study show that the IL- 18 and IL-12p40 polymorphisms may have some effect on the onset age and deterioration of glycemic control in Turkish patients with T1DM.

Transfusion of nonobese diabetic mice with allogeneic newborn blood ameliorates autoimmune diabetes and modifies the expression of selected immune response genes

Although allogeneic bone marrow transplantation has been shown to prevent autoimmune diabetes in heavily irradiated nonobese diabetic (NOD) mice, a similar procedure is not suitable for the treatment of patients with type 1 diabetes because of associated severe side effects. Therefore, we evaluated whether mouse newborn blood (NBB), equivalent to human umbilical cord blood, could be used for diabetes prevention without recipient preconditioning. To test this hypothesis, unconditioned, prediabetic female NOD mice were given a single injection of whole NBB derived from the allogeneic diabetes-resistant mouse strain C57BL/6. Transfusion of allogeneic NBB but not adult blood prevented diabetes incidence in a majority of treated mice for a prolonged period of time. This was accompanied by the release of insulin in response to a challenge with glucose. Invasive cellular infiltration of islets was also substantially reduced in these mice. Although NBB transfusion induced a low level of hematopoietic microchimerism, it did not strictly correlate with amelioration of diabetes. Induction of genes implicated in diabetes, such as Il18, Tnfa, and Inos but not Il4, Il17 or Ifng, was repressed in splenocytes derived from protected mice. Notably, expression of the transcription factor Tbet/Tbx21 but not Gata3 or Rorgt was upregulated in protected mice. These data indicate that allogeneic NBB transfusion can prevent diabetes in NOD mice associated with modulation of selected cytokine genes implicated in diabetes manifestation. The data presented in this study provide the proof of principle for the utility of allogeneic umbilical cord blood transfusion to treat patients with autoimmune diabetes.

Role of macrophages in the development of pancreatic islet injury in spontaneously diabetic torii rats

Spontaneously diabetic Torii (SDT) rats were established from Sprague-Dawley (SD) rat and are used as an animal model of type 2 diabetes mellitus. In the present study, the mechanism of the development of injury in the pancreas of these rats was examined focusing on the role of monocytes/macrophages. The number of lymphocytes and monocytes in the circulation of SDT rats increased with age, reaching a plateau at around 9 weeks of age and remaining at that level thereafter. The number of leukocytes in SDT rats was almost twice that of wild-type SD rats. Serum IL-18 levels began to increase at 8 weeks of age, forming a prominent peak at 9 weeks of age. In parallel with this, serum levels of NO2/NO3 showed an abrupt rise and decline. Spleen cells prepared from 9-week-old SDT rats expressed high levels of IFN-gamma in response to IL-18, while those from 9-week-old wild-type SD rats did not. Immunohistochemical analysis revealed marked infiltration of CD68+ cells in the islets of SDT rats. Treatment of SDT rats with Cl2MDP-liposomes reduced the number of monocytes as well as levels of NO2/NO3 in the circulation. Consistent with this, the number of infiltrated CD68+ cells in the islets was reduced in SDT rats treated with Cl2MDP-liposomes. These results suggest that macrophages are involved in pancreatic islet injury in SDT rats through excess production of NO induced by IL-18 which increases transitorily at around 9 weeks of age.

The role of the CXCL10/CXCR3 system in type 1 diabetes

Despite intervention with insulin, type 1 diabetes gradually deteriorates the patients' quality of life. The disease is characterized by an immune-mediated destruction of pancreatic beta-cells. Its etiology, however, remains controversial. Some studies argue that glutamic acid decarboxylase (GAD) antigen and GAD-reactive T cells are critical players in the development of diabetes by affecting the Th cell balance. A T-helper 1 (Th1)-dominant immune response is considered to be important in beta-cell failure in both human and animal models of type 1 diabetes. The Th1-type chemokine, CXCL10, and its receptor, CXCR3, are involved not only in the immune response, but also in the suppression of beta-cell proliferation. Thus, understanding the CXCL10/CXCR3 system may be important for finding a cure. In this short review, we discuss the role of the CXCL10/CXCR3 system in type 1 diabetes and propose relevant treatment options.

IL-18 overexpression promotes vascular inflammation and remodeling in a rat model of metabolic syndrome

Although considerable evidence implicates the cytokine interlukin-18 (IL-18) in metabolic syndrome (MetS), the direct effect of IL-18 on vascular changes of MetS remains unknown. We investigated the chronic in vivo effect of IL-18 on development of MetS and vascular inflammation and remodeling by overexpressing IL-18 protein in fructose-fed rats (FFR), a model of MetS using intravenous administration of an adenovirus encoding rat IL-18. Increased serum IL-18 and vascular inflammatory response were found in FFR. Overexpression of IL-18 aggravated insulin resistance and enhance vascular inflammation and remodeling, which can be reflected by increased aortic expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and enhanced infiltration of macrophages and increased aortic wall thickness and wall-to-lumen ratio. Interestingly, the levels of interleukin-1 receptor-associated kinase 1 (IRAK1) and the activity of nucleus factor-kappaB (NF-kappaB) were also significantly increased. Together, these results indicated that chronic elevated IL-18 levels at a supraphsiological concentration aggravated insulin resistance, enhanced vascular inflammation and remodeling, probably by increasing the level of IRAK1 and the activity of NF-kappaB. Targeting expression of IL-18 or its specific downstream mediators may retard the progression of MetS and its complications.

Interleukin-18, the Metabolic Syndrome, and Subclinical Atherosclerosis

OBJECTIVE

Although IL-18 promotes atherogenesis in animal studies and predicts cardiovascular risk in humans, it is unknown whether elevated IL-18 levels are associated with coronary atherosclerosis in the general population.

METHODS AND RESULTS

IL-18 plasma levels were determined by ELISA in 2231 subjects from the Dallas Heart Study. In univariable analysis, IL-18 levels associated with traditional cardiovascular risk factors and particularly with components of the metabolic syndrome (MS, P<0.01 for trend across the number of MS components); IL-18 also associated with coronary artery calcium (CAC) scores measured by electron beam computed tomography and aortic plaque measured by MRI (P<0.01 for each). In multivariable analyses, IL-18 remained associated with multiple components of the MS but not with CAC or aortic plaque.

CONCLUSIONS

In a large population-based sample, elevated IL-18 plasma levels associated with risk factors for atherosclerosis and with the metabolic syndrome. The association between IL-18 and atherosclerosis diminished after accounting for traditional cardiovascular risk factors. These data suggest that IL-18 does not add independently to detection of atherosclerotic burden in asymptomatic individuals.

IL-18 gene promoter ?137C/G and ?607C/A polymorphisms in Chinese Han children with type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a heterogeneous autoimmune disease, and both environmental and genetic factors play a role in its pathogenesis. Interleukin (IL)-18 is a potent pro-inflammatory cytokine capable of inducing interferon-gamma production that is associated with the development of T1DM. The gene for IL-18 is located on chromosome 11q22.2-q22.3 and has been reported to be associated with a susceptibility to T1DM. To test the putative involvement between IL-18 gene polymorphism and predisposition to T1DM, we conducted a case-control study in Chinese Han children. The single nucleotide polymorphisms at position -607(C/A) and -137(C/G) in the promoter region of the IL-18 gene were analysed by sequence-specific primers-polymerase chain reaction in 118 patients with T1DM and 150 healthy controls. (1) The allele frequency of -607A was 41.2% and 53.0%, respectively, in patients and in control subjects (P = 0.01), but the allele frequency of -137C/G was not statistically significant (P = 0.37). (2) The distribution of CC genotype at position -607 was significantly different between patients and normal controls (P = 0.03), while the distribution of AA genotype in patients was significantly lower than that in the controls (P = 0.03). (3) Furthermore, there was a significant increase in haplotype (-137C/-607G) and genotype combination (-137GG/ -607CC) in patients compared with controls (P = 0.03 and P = 0.04, respectively). The results of this study show that IL-18 gene promoter polymorphisms confer susceptibility to T1DM in Chinese Han children. Moreover, subjects carrying AA genotype at position -607 of the promoter of IL-18 gene may be a low risk of T1DM development.

Moving towards efficient therapies in type 1 diabetes: to combine or not to combine?

Every year, thirty thousand people worldwide are diagnosed with type 1 diabetes mellitus (T1DM). T1DM, also called autoimmune diabetes, is a multifactorial disease affecting predisposed individuals and involving genetic susceptibilities, environmental triggers, as well as unbalanced immune responses. Auto-reactive T cells, produced during the pathogenesis, play an important role by specifically destroying the pancreatic insulin-producing beta-cells in the islets of Langerhans. Numerous therapeutic interventions have been tested, mostly in animal models, but also in humans. To date, only three phase II/III clinical trials have demonstrated safety and efficacy: anti-CD3 antibody, DiaPep277, and GAD65 (in patients with latent autoimmune diabetes in adults). Unfortunately, a significant number of patients did not respond positively and remained insulin-dependent after completion of therapy. Several reasons account for this. Firstly, the severity of the disease as well as the auto-aggressive T cell repertoire vary from patient to patient leading to a broad range of therapeutic efficacies, and secondly at the time of the treatment the number of remaining beta-cells will directly impact the level of insulin production post-treatment. In this review, we will provide some clues to enhance efficacy of future immuno-interventions in patients with T1DM. We suggest that combination therapies might be the best approach.

Acute onset of type 1 diabetes accompanied by acute hepatitis C: the potential role of proinflammatory cytokine in the pathogenesis of autoimmune diabetes

A 22-year-old Japanese woman presented with general fatigue. Five days later, she demonstrated a body temperature of 39 degrees C and a loss in weight of 5kg. She thereafter became unconscious and was taken to Tomakomai City General Hospital. Urinary ketone body was positive, and plasma glucose was 1063mg/dl. The serum asparate aminotransferase and alanine aminotransferase levels were 158 and 1220IU/l, respectively. An arterial blood gas analysis showed metabolic acidosis. Glycated hemoglobin was 10.9%. Urinary C-peptide immnoreactivity was 11microg/day. Anti-glutamic acid decarboxylase antibody was 12.4U/ml. In general, islet-associated autoantibodies are detectable several years before the development of overt autoimmune diabetes, thus suggesting that an autoimmune reaction against beta-cells had already started in this case. On viral examinations, hepatitis C virus (HCV) antibody was negative, while HCV-RNA was positive. Based on these findings, she was diagnosed to have autoimmune diabetes and acute hepatitis C. In addition, her serum interleukin-18 level was elevated to 506pg/ml. The duration of diabetic characteristic symptoms before diagnosis is usually several weeks in most cases of autoimmune diabetes. However, it was extremely short in this case. Taken together, these findings suggested that the progression of autoimmune diabetes might have been accelerated due to the infection of HCV.

Adipose tissue interleukin-18 mRNA and plasma interleukin-18: effect of obesity and exercise

OBJECTIVES

Obesity and a physically inactive lifestyle are associated with increased risk of developing insulin resistance. The hypothesis that obesity is associated with increased adipose tissue (AT) interleukin (IL)-18 mRNA expression and that AT IL-18 mRNA expression is related to insulin resistance was tested. Furthermore, we speculated that acute exercise and exercise training would regulate AT IL-18 mRNA expression.

RESEARCH METHODS AND PROCEDURES

Non-obese subjects with BMI < 30 kg/m(2) (women: n = 18; men; n = 11) and obese subjects with BMI >30 kg/m(2) (women: n = 6; men: n = 7) participated in the study. Blood samples and abdominal subcutaneous AT biopsies were obtained at rest, immediately after an acute exercise bout, and at 2 hours or 10 hours of recovery. After 8 weeks of exercise training of the obese group, sampling was repeated 48 hours after the last training session.

RESULTS

AT IL-18 mRNA content and plasma IL-18 concentration were higher (p < 0.05) in the obese group than in the non-obese group. AT IL-18 mRNA content and plasma IL-18 concentration was positively correlated (p < 0.05) with insulin resistance. While acute exercise did not affect IL-18 mRNA expression at the studied time-points, exercise training reduced AT IL-18 mRNA content by 20% in both sexes.

DISCUSSION

Because obesity and insulin resistance were associated with elevated AT IL-18 mRNA and plasma IL-18 levels, the training-induced lowering of AT IL-18 mRNA content may contribute to the beneficial effects of regular physical activity with improved insulin sensitivity.

Responses of IL-18- and IL-18 receptor-deficient pancreatic islets with convergence of positive and negative signals for the IL-18 receptor

Pancreatic islets contain cells that produce IL-18 and cells that express IL-18 receptors. In experimentally induced diabetes, islet failure correlates with IL-18 levels and diabetes is delayed with blockade of endogenous IL-18. We studied islet-derived IL-18 and responses to IL-18 in a mouse model of islet allograft transplantation. In vitro, IL-18-stimulated islets produced nitric oxide, which closely matched islet apoptosis. By neutralizing IL-18 activity with IL-18 binding protein (IL-18BP), we observed that islets produce bioactive IL-18. In vivo, transgenic mice overproducing IL-18BP (IL-18BP-Tg) exhibited delayed hyperglycemia induced by beta cell toxic streptozotocin. Similarly, cultured IL-18BP-Tg islets were protected from streptozotocin-induced apoptosis. In the transplant model, islets grafted from WT to IL-18BP-Tg mice achieved prolonged normoglycemia (P = 0.031). Improved graft function was also observed by using IL-18-deficient islets transplanted into WT recipients, demonstrating that endogenous, islet-derived IL-18 mediates IL-18-driven graft damage. Unexpectedly, islets from mice deficient in IL-18 receptor alpha chain (IL-18R) exhibited rapid graft failure (P = 0.024; IL-18- versus IL-18R-deficient grafts in WT recipients). In related studies, IL-18R-deficient splenocytes and macrophages produced 2- to 3-fold greater amounts of IL-18, TNFalpha, macrophage inflammatory protein 1, macrophage inflammatory protein 2, and IFNgamma upon stimulation with Con A, Toll-like receptor 2 agonist, or anti-CD3 antibodies. These data reveal a role for islet-derived IL-18 activity during inflammation-mediated islet injury. Importantly, discrepancies between IL-18- and IL-18R-deficient cells suggest that IL-18Ralpha chain is used by an inflammation-suppressing signal.

IL-18 bridges innate and adaptive immunity through IFN-gamma and the CD134 pathway

IL-18 induces inflammation resulting in either enhanced protection from pathogens or exacerbation of autoimmunity, and T cells are profoundly activated during these responses. How IL-18 influences T cell activation is unknown, but this study in mice shows that IL-18 boosted Ag-specific T cell clonal expansion of effector T cells and induced a subpopulation of IFN-gamma superproducing T cells. Commitment to IFN-gamma production through IL-18 was independent of NK cells and IL-12 but dependent on host-derived IFN-gamma. To determine how expansion of these effectors occurred, IL-18 was shown to induce OX40L on dendritic cells, whereas peptide stimulation induced CD134 (OX40) on specific T cells. CD134 blockade inhibited T cell effector expansion thereby reducing the number of IFN-gamma superproducers by 12-fold. Thus, independent of IL-12, IL-18 impacts T cell immunity throughout lymphoid and nonlymphoid tissue by bridging the innate and adaptive arms of the immune system through IFN-gamma and the CD134 costimulatory pathway.

Influence of TNF-alpha and IL-6 infusions on insulin sensitivity and expression of IL-18 in humans

Inflammation is associated with insulin resistance, and both tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 may affect glucose uptake. TNF induces insulin resistance, whereas the role of IL-6 is controversial. High plasma levels of IL-18 are associated with insulin resistance in epidemiological studies. We investigated the effects of TNF and IL-6 on IL-18 gene expression in skeletal muscle and adipose tissue. Nine human volunteers underwent three consecutive interventions, receiving an infusion of recombinant human (rh)IL-6, rhTNF, and saline. Insulin sensitivity was assessed by measurement of whole body glucose uptake with the stable isotope tracer method during a euglycemic hyperinsulinemic clamp (20 mU.min(-1).kg(-1)), which was initiated 1 h after the IL-6-TNF-saline infusion. Cytokine responses were measured in plasma, muscle, and fat biopsies. Plasma concentrations of TNF and IL-6 increased 10- and 38-fold, respectively, during the cytokine infusions. Whole body insulin-mediated glucose uptake was significantly reduced during TNF infusion but remained unchanged during IL-6 infusion. TNF induced IL-18 gene expression in muscle tissue, but not in adipose tissue, whereas IL-6 infusion had no effect on IL-18 gene expression in either tissue. We conclude that TNF-induced insulin resistance of whole body glucose uptake is associated with increased IL-18 gene expression in muscle tissue, indicating that TNF and IL-18 interact, and both may have important regulatory roles in the pathogenesis of insulin resistance.

Association of IL-18 promoter polymorphisms with predisposition to Type 1 diabetes

AIMS

IL-18, a potent IFN-gamma-inducing cytokine, is capable of polarizing the immune response to a Th1 phenotype. Recent studies have demonstrated an association between single-nucleotide polymorphisms located at positions -607 (A/C) and -137 (C/G) in the promoter region of IL-18 gene and Type 1 diabetes. The aim of the present study was to determine whether the same polymorphisms of the gene were associated with Type 1 diabetes in Iranians.

METHODS

In 112 patients with Type 1 diabetes and 194 non-diabetic control subjects, these two single-nucleotide polymorphisms were analysed by sequence-specific PCR.

RESULTS

Allele and genotype frequencies of the IL-18 gene polymorphisms were similar in the whole group of Type 1 diabetic patients and controls. However, categorizing patients according to age at onset of diabetes revealed a significant difference in distribution of the genotypes at position -137 between patients with older age at onset (> 15 years) (GG 49%, GC 34%, CC 17%) and control subjects (GG 57.7%, GC 36.6%, CC 5.7%) (P = 0.027). Frequency of the C allele at position -137 was significantly higher in these patients than in controls (P = 0.038). Moreover, there was an association between -607AA/-137CC genotype combination and susceptibility to Type 1 diabetes in this subgroup of patients (pc = 0.027).

CONCLUSIONS

The results of this study show that polymorphisms of IL-18 promoter confer susceptibility to Type 1 diabetes in Iranian individuals with onset at older ages. Further investigations are necessary to clarify the effect of IL-18 variants on immune regulation.

Significance of serum CXCL10/IP-10 level in type 1 diabetes

Although we have previously reported an elevated serum level of CXCL10/IP-10 (CXCL10), a Th1 chemokine, in type 1 diabetic patients, little is known about the origin of serum CXCL10 and its significance in type 1 diabetes. Therefore, we examined serum CXCL10 level in NOD mice in association with the expression level of CXCL10 in the pancreas, pancreatic lymph nodes (LN) and spleen. Serum CXCL10 level increased over time towards the onset of diabetes, and was significantly higher in the "diabetic" period (20 and 24 weeks of age and at onset of diabetes) than in the "pre-diabetic" period (4, 8 and 16 weeks of age). Moreover, serum CXCL10 level was associated with CXCL10 and CXCR3 mRNA level in pancreatic LN. Furthermore, it seemed that serum CXCL10 level increased just before (or at) the onset of overt diabetes. These results suggest that serum CXCL10 level may reflect accumulation of Th1 lymphocytes in pancreatic LN, and measurement of serum CXCL10 level may be useful to assess the pathophysiology of the disease course in type 1 diabetes.

The adrenal gland is a source of stress-induced circulating IL-18

The present study compared plasma IL-18 levels between sham-operated and adrenalectomized mice following stress to investigate whether the adrenal gland contributes to the elevation of circulating IL-18 during stress. Two hours of stress provoked a robust, stressor-dependent, elevation of IL-18 mRNA and peptide in the adrenal gland in sham-operated mice. Consistently, levels of circulating mature IL-18 increased during stress and remained elevated for up to 6 h after stress. The stress-induced increase in circulating IL-18 was abolished by adrenalectomy. These findings demonstrate that the adrenal gland is required to achieve elevation of circulating IL-18 during stress.