Inhibition of Th17 cells regulates autoimmune diabetes in NOD mice

Cytokines in type 1 diabetes: mechanisms of action and immunotherapeutic targets

Cytokines play crucial roles in orchestrating complex multicellular interactions between pancreatic β cells and immune cells in the development of type 1 diabetes (T1D) and are thus potential immunotherapeutic targets for this disorder. Cytokines that can induce regulatory functions-for example, IL-10, TGF-β and IL-33-are thought to restore immune tolerance and prevent β-cell damage. By contrast, cytokines such as IL-6, IL-17, IL-21 and TNF, which promote the differentiation and function of diabetogenic immune cells, are thought to lead to T1D onset and progression. However, targeting these dysregulated cytokine networks does not always result in consistent effects because anti-inflammatory or proinflammatory functions of cytokines, responsible for β-cell destruction, are context dependent. In this review, we summarise the current knowledge on the involvement of well-known cytokines in both the initiation and destruction phases of T1D and discuss advances in recently discovered roles of cytokines. Additionally, we emphasise the complexity and implications of cytokine modulation therapy and discuss the ways in which this strategy has been translated into clinical trials.

Salivary and serum interleukin-17A and interleukin-18 levels in patients with type 2 diabetes mellitus with and without periodontitis

OBJECTIVE

Interleukin (IL)-17A and IL-18 have been proposed to play important roles in periodontitis and type 2 diabetes mellitus (DM), but human data are conflicting. The present study aimed to investigate the roles of IL-17A and IL-18 in periodontitis and DM by measuring salivary and serum levels, respectively.

MATERIALS AND METHODS

A total of 49 participants with type 2 DM and 25 control subjects without type 2 DM were recruited. A periodontal screening and recording (PSR) index (0, 1-2, 3, and 4) was used to classify whether these subjects had periodontitis. Salivary and serum IL-17A and IL-18 levels were measured by enzyme-linked immunosorbent assay. Multiple linear regression analyses were used to evaluate the associations between these cytokines and clinical parameters.

RESULTS

Salivary IL-17A levels were not significantly different between patients with DM and controls, however, the levels were significantly higher in controls with periodontitis than those without periodontitis (p = 0.031). Salivary IL-17A levels were significantly associated with the PSR index (β = 0.369, p = 0.011). Multiple linear regression analyses revealed the association of salivary IL-18 levels and fasting plasma glucose (β = 0.270, p = 0.022) whereas serum IL-18 levels were associated with HbA1C (β = 0.293, p = 0.017). No correlation between salivary and serum levels of IL-17A and IL-18 was found.

CONCLUSION

Salivary IL-17A was strongly associated with periodontitis, whereas salivary IL-18 was associated with FPG and serum IL-18 was associated with HbA1C. These results suggest the role of these cytokines in periodontal inflammation and DM.

Could IL-17A Be a Novel Therapeutic Target in Diabetic Nephropathy?

Chronic kidney disease has become a major medical issue in recent years due to its high prevalence worldwide, its association with premature mortality, and its social and economic implications. A number of patients gradually progress to end-stage renal disease (ESRD), requiring then dialysis and kidney transplantation. Currently, approximately 40% of patients with diabetes develop kidney disease, making it the most prevalent cause of ESRD. Thus, more effective therapies for diabetic nephropathy are needed. In preclinical studies of diabetes, anti-inflammatory therapeutic strategies have been used to protect the kidneys. Recent evidence supports that immune cells play an active role in the pathogenesis of diabetic nephropathy. Th17 immune cells and their effector cytokine IL-17A have recently emerged as promising targets in several clinical conditions, including renal diseases. Here, we review current knowledge regarding the involvement of Th17/IL-17A in the genesis of diabetic renal injury, as well as the rationale behind targeting IL-17A as an additional therapy in patients with diabetic nephropathy.

Two to Tango: Dialogue between Adaptive and Innate Immunity in Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is a long-term and chronic autoimmune disorder, in which the immune system attacks the pancreatic β-cells. Both adaptive and innate immune systems are involved in T1DM development. Both B-cells and T-cells, including CD4 ⁺ and CD8 ⁺ T-cells, as well as other T-cell subsets, could affect onset of autoimmunity. Furthermore, cells involved in innate immunity, including the macrophages, dendritic cells, and natural killer (NK) cells, could also accelerate or decelerate T1DM development. In this review, the crosstalk and function of immune cells in the pathogenesis of T1DM, as well as the corresponding therapeutic interventions, are discussed.

Evaluating the Causal Role of Gut Microbiota in Type 1 Diabetes and Its Possible Pathogenic Mechanisms

Type 1 diabetes (T1D) is a multifactorial autoimmune disease mediated by genetic, epigenetic, and environmental factors. In recent years, the emergence of high-throughput sequencing has allowed us to investigate the role of gut microbiota in the development of T1D. Significant changes in the composition of gut microbiome, also termed dysbiosis, have been found in subjects with clinical or preclinical T1D. However, whether the dysbiosis is a cause or an effect of the disease remains unclear. Currently, increasing evidence has supported a causal link between intestine microflora and T1D development. The current review will focus on recent research regarding the associations between intestine microbiome and T1D progression with an intention to evaluate the causality. We will also discuss the possible mechanisms by which imbalanced gut microbiota leads to the development of T1D.

From Discrete to Continuous Modeling of Lymphocyte Development and Plasticity in Chronic Diseases

The molecular events leading to differentiation, development, and plasticity of lymphoid cells have been subject of intense research due to their key roles in multiple pathologies, such as lymphoproliferative disorders, tumor growth maintenance and chronic diseases. The emergent roles of lymphoid cells and the use of high-throughput technologies have led to an extensive accumulation of experimental data allowing the reconstruction of gene regulatory networks (GRN) by integrating biochemical signals provided by the microenvironment with transcriptional modules of lineage-specific genes. Computational modeling of GRN has been useful for the identification of molecular switches involved in lymphoid specification, prediction of microenvironment-dependent cell plasticity, and analyses of signaling events occurring downstream the activation of antigen recognition receptors. Among most common modeling strategies to analyze the dynamical behavior of GRN, discrete dynamic models are widely used for their capacity to capture molecular interactions when a limited knowledge of kinetic parameters is present. However, they are less powerful when modeling complex systems sensitive to biochemical gradients. To compensate it, discrete models may be transformed into regulatory networks that includes state variables and parameters varying within a continuous range. This approach is based on a system of differential equations dynamics with regulatory interactions described by fuzzy logic propositions. Here, we discuss the applicability of this method on modeling of development and plasticity processes of adaptive lymphocytes, and its potential implications in the study of pathological landscapes associated to chronic diseases.

Frontline Science: Abnormalities in the gut mucosa of non-obese diabetic mice precede the onset of type 1 diabetes

Alterations in the composition of the intestinal microbiota have been associated with development of type 1 diabetes (T1D), but little is known about changes in intestinal homeostasis that contribute to disease pathogenesis. Here, we analyzed oral tolerance induction, components of the intestinal barrier, fecal microbiota, and immune cell phenotypes in non-obese diabetic (NOD) mice during disease progression compared to non-obese diabetes resistant (NOR) mice. NOD mice failed to develop oral tolerance and had defective protective/regulatory mechanisms in the intestinal mucosa, including decreased numbers of goblet cells, diminished mucus production, and lower levels of total and bacteria-bound secretory IgA, as well as an altered IEL profile. These disturbances correlated with bacteria translocation to the pancreatic lymph node possibly contributing to T1D onset. The composition of the fecal microbiota was altered in pre-diabetic NOD mice, and cross-fostering of NOD mice by NOR mothers corrected their defect in mucus production, indicating a role for NOD microbiota in gut barrier dysfunction. NOD mice had a reduction of CD103⁺ dendritic cells (DCs) in the MLNs, together with an increase of effector Th17 cells and ILC3, as well as a decrease of Th2 cells, ILC2, and Treg cells in the small intestine. Importantly, most of these gut alterations precede the onset of insulitis. Disorders in the intestinal mucosa of NOD mice can potentially interfere with the development of T1D due the close relationship between the gut and the pancreas. Understanding these early alterations is important for the design of novel therapeutic strategies for T1D prevention.

Th17 Cells and the IL-23/IL-17 Axis in the Pathogenesis of Periodontitis and Immune-Mediated Inflammatory Diseases

Innate immunity represents the semi-specific first line of defense and provides the initial host response to tissue injury, trauma, and pathogens. Innate immunity activates the adaptive immunity, and both act highly regulated together to establish and maintain tissue homeostasis. Any dysregulation of this interaction can result in chronic inflammation and autoimmunity and is thought to be a major underlying cause in the initiation and progression of highly prevalent immune-mediated inflammatory diseases (IMIDs) such as psoriasis, rheumatoid arthritis, inflammatory bowel diseases among others, and periodontitis. Th1 and Th2 cells of the adaptive immune system are the major players in the pathogenesis of IMIDs. In addition, Th17 cells, their key cytokine IL-17, and IL-23 seem to play pivotal roles. This review aims to provide an overview of the current knowledge about the differentiation of Th17 cells and the role of the IL-17/IL-23 axis in the pathogenesis of IMIDs. Moreover, it aims to review the association of these IMIDs with periodontitis and briefly discusses the therapeutic potential of agents that modulate the IL-17/IL-23 axis.

Tellurium Compounds Prevent and Reverse Type-1 Diabetes in NOD Mice by Modulating α4β7 Integrin Activity, IL-1β, and T Regulatory Cells

The study shows that treatment of NOD mice with either of two tellurium-based small molecules, AS101 [ammonium trichloro(dioxoethylene-o,o')tellurate] or SAS [octa-O-bis-(R,R)-tartarate ditellurane] could preserve β cells function and mass. These beneficial effects were reflected in decreased incidence of diabetes, improved glucose clearance, preservation of body weight, and increased survival. The normal glucose levels were associated with increased insulin levels, preservation of β cell mass and increased islet size. Importantly, this protective activity could be demonstrated when the compounds were administered either at the early pre-diabetic phase with no or initial insulitis, at the pre-diabetic stage with advanced insulitis, or even at the advanced, overtly diabetic stage. We further demonstrate that both tellurium compounds prevent migration of autoimmune lymphocytes to the pancreas, via inhibition of the α4β7 integrin activity. Indeed, the decreased migration resulted in diminished pancreatic islets damage both with respect to their size, β cell function, and caspase-3 activity, the hallmark of apoptosis. Most importantly, AS101 and SAS significantly elevated the number of T regulatory cells in the pancreas, thus potentially controlling the autoimmune process. We show that the compounds inhibit pancreatic caspase-1 activity followed by decreased levels of the inflammatory cytokines IL-1β and IL-17 in the pancreas. These properties enable the compounds to increase the proportion of Tregs in the pancreatic lymph nodes. AS101 and SAS have been previously shown to regulate specific integrins through a unique redox mechanism. Our current results suggest that amelioration of disease in NOD mice by this unique mechanism is due to decreased infiltration of pancreatic islets combined with increased immune regulation, leading to decreased inflammation within the islets. As these tellurium compounds show remarkable lack of toxicity in clinical trials (AS101) and pre-clinical studies (SAS), they may be suitable for the treatment of type-1 diabetes.

Metformin mitigates autoimmune insulitis by inhibiting Th1 and Th17 responses while promoting Treg production

Type 1 diabetes mellitus (T1DM) is still one of the major threats on global public health. This autoimmune condition is mainly caused by the imbalance of auto-reactive inflammatory effector T cells (Teffs) and protective regulatory T cells (Tregs). Therefore, inhibiting the development of Teffs and/or promoting Tregs provides a therapeutic strategy for preventing the development of T1DM. Pathways of energy metabolism have been shown to play a pivotal role in dictating the activation, differentiation and immune function of T cells. Studies have shown that inhibition of glycolysis suppresses the development of Th1 and Th17 cells, but promotes Treg production. AMP-activated protein kinase (AMPK) is a master sensor and regulator of cellular energy metabolism in mammals, which has also been demonstrated to interfere with T cell differentiation and effector function through inhibiting mammalian target of rapamycin (mTOR) and subsequent inhibition of glycolysis, and enhancement of lipid oxidation. In this study, we found that AMPK activator metformin suppresses T cell proliferation and inhibits the differentiation of Th1 and Th17 cells while promoting the development of Tregs in vitro in a dose-dependent manner. Treatment of NOD mice with metformin significantly mitigated autoimmune insulitis and substantially decreased the number of pro-inflammatory IFN-γ+ as well as IL17+ CD4 T cells in the spleens of NOD mice. However, a significantly increased percentage of regulatory IL-10+ and Foxp3+ CD4 T cells were seen. We provided a novel potential therapeutic method--by regulating T cell metabolism through targeting AMPK, to reduce the severity of autoimmune insulitis.

The Association between Depression and Type 1 Diabetes Mellitus: Inflammatory Cytokines as Ferrymen in between?

The depression incidence is much higher in patients with diabetes mellitus (DM), and the majority of these cases remain under-diagnosed. Type 1 diabetes mellitus (T1D) is now widely thought to be an organ-specific autoimmune disease. As a chronic autoimmune condition, T1D is characterized by T cell-mediated selective loss of insulin-producing β-cells. The age of onset of T1D is earlier than T2D, and T1D patients have an increased vulnerability to depression due to its diagnosis and treatment burden occurring in a period when the individuals are young. The literature has suggested that inflammatory cytokines play a wide role in both diseases. In this review, the mechanisms behind the initiation and propagation of the autoimmune response in T1D and depression are analyzed, and the contribution of cytokines to both conditions is discussed. This review outlines the immunological mechanism of T1D and depression, with a particular emphasis on the role of tumor necrosis factor-α (TNF-α), IL-1β, and interferon-γ (IFN-γ) cytokines and their signaling pathways. The purpose of this review is to highlight the possible pathways of the cytokines shared by these two diseases via deciphering their cytokine cascades. They may provide a basic groundwork for future study of the possible mechanism that links these two diseases and to develop new compounds that target the same pathway but can conquer two diseases.

Interleukin-17A blockade reduces albuminuria and kidney injury in an accelerated model of diabetic nephropathy

Diabetic nephropathy (DN) is one of the most common complications of diabetes, and currently the first end-stage renal disease worldwide. New strategies to treat DN using agents that target inflammatory pathways have attracted special interest. Recent pieces of evidences suggest a promising effect of IL-17A, the Th17 effector cytokine. Among experimental DN models, mouse strain BTBR ob/ob (leptin deficiency mutation) develops histological features similar to human DN, which means an opportunity to study mechanisms and novel therapies aimed at DN regression. We found that BTBR ob/ob mice presented renal activation of the factors controlling Th17 differentiation. The presence of IL-17A-expressing cells, mainly CD4⁺ and γδ lymphocytes, was associated with upregulation of proinflammatory factors, macrophage infiltration and the beginning of renal damage. To study IL-17A involvement in experimental DN pathogenesis, treatment with an IL-17A neutralizing antibody was carried out starting when the renal damage had already appeared. IL-17A blockade ameliorated renal dysfunction and disease progression in BTBR ob/ob mice. These beneficial effects correlated to podocyte number restoration and inhibition of NF-κB/proinflammatory factors linked to a decrease in renal inflammatory-cell infiltration. These data demonstrate that IL-17A takes part in diabetes-mediated renal damage and could be a promising therapeutic target to improve DN.

Pancreatic autoantibodies and CD14+CD16+ monocytes subset are associated with the impairment of ß-cell function after simultaneous pancreas-kidney transplantation

Pancreatic autoantibodies (AAb) has been associated with a worse pancreas graft survival after simultaneous pancreas-kidney transplantation (SPK). However, due to the variable time for AAb to become positive and the lack of early biomarkers suggesting such autoimmune activation, the mechanisms leading ß-cell destruction remain uncertain. The present study aimed to evaluate the association between post-transplant AAb and the functional impairment of the pancreatic ß-cell and also the association of such AAb with inflammation after SPK. In a longitudinal study, we analyzed the impact of post-transplant glutamic acid decarboxylase (GAD-65) and the insulinoma-associated autoantigen 2 (IA-2) AAb on pancreas graft function. Serum Hb1Ac and C-peptide (C-pep) were longitudinally compared between a group with positive posttransplant AAb (AAb+; n = 40) and another matched group with negative AAb (AAb-; n = 40) until the fifth year following seroconversion. In the cross-sectional analysis, we further evaluated the systemic signatures of inflammation by measuring pro-inflammatory CD14⁺CD16⁺ monocytes by flow-cytometry and interleukin 17-A serum levels in 38 SPK recipients and ten healthy controls. In the longitudinal study, patients with AAb+ showed higher levels of Hb1Ac (p<0.001) and lower C-pep levels (p<0.001) compared to those who remained AAb- throughout the follow-up. In the cross-sectional study, AAb+ patients showed a higher percentage of CD14⁺CD16⁺ monocytes compared with those with AAb- and the healthy controls (6.70±4.19% versus 4.0±1.84% and 3.44±0.93%; p = 0.026 and 0.009 respectively). Also, CD14⁺CD16⁺ monocytes correlated with Hb1Ac and C-pep serum levels. Multivariate logistic regression showed that posttransplant AAb+ was independently associated with a higher percentage of pro-inflammatory monocytes (adjusted-OR 1.59, 95%CI 1.05–2.40, p = 0.027). The group of patients with positive AAb also showed higher levels of IL17A as compared with the other groups (either healthy control or the negative AAb subjects). In conclusion, pancreatic AAb+ after SPK were not only associated with higher Hb1Ac and lower c-peptide serum levels but also with an increased percentage of CD14⁺CD16⁺ monocytes and higher levels of circulating IL17-A.

Interleukin 17A promotes diabetic kidney injury

The role of the pro-inflammatory cytokine IL-17 in the pathogenesis of numerous inflammatory disorders is well-documented, but conflicting results are reported for its role in diabetic nephropathy. Here we examined the role of IL-17 signalling in a model of streptozotocin-induced diabetic nephropathy through IL-17 knockout mice, administration of neutralising monoclonal anti-IL-17 antibody and in vitro examination of gene expression of renal tubular cells and podocytes under high glucose conditions with or without recombinant IL-17. IL-17 deficient mice were protected against progression of diabetic nephropathy, exhibiting reduced albuminuria, glomerular damage, macrophage accumulation and renal fibrosis at 12 weeks and 24 weeks. Administration of anti-IL-17 monoclonal antibody to diabetic wild-type mice was similarly protective. IL-17 deficiency also attenuated up-regulation of pro-inflammatory and pro-fibrotic genes including IL-6, TNF-α, CCL2, CXCL10 and TGF-β in diabetic kidneys. In vitro co-stimulation with recombinant IL-17 and high glucose were synergistic in increasing the expression of pro-inflammatory genes in both cultured renal tubular cells and podocytes. We conclude that absence of IL-17 signalling is protective against streptozotocin-induced diabetic nephropathy, thus implying a pro-inflammatory role of IL-17 in its pathogenesis. Targeting the IL-17 axis may represent a novel therapeutic approach in the treatment of this disorder.

Type 1 Diabetes in STAT Protein Family Mutations: Regulating the Th17/Treg Equilibrium and Beyond

Improvements in the immunological, molecular, and genetic technologies such as next-generation sequencing have led to an exponential increase in the number of monogenic immune dysregulatory syndromes diagnosed, where type 1 diabetes (T1D) forms part of the autoimmune manifestations. Here, we reviewed the mutations in the signal transducer and activator of transcription (STAT) protein family, namely gain-of-function (GOF) mutations in STAT1 and STAT3 as well as STAT5b deficiency, that show strong association to T1D susceptibility. The equilibrium of T-helper 17 (Th17) and regulatory T cells (Tregs) is often found altered in patients affected by STAT GOF mutations. While the increased number of Th17 cells and the concomitant decrease in Treg cells may explain T1D in STAT3 GOF patients, the reduced number of Th17 cells found in those carrying STAT1 GOF mutations added a new level of complexity on the exact role of Th17 in the pathogenesis of T1D. Here, we describe the possible mechanisms through which STAT3 and STAT1 GOF mutations may perturb the fate and function of Th17 and Tregs and explore how this may lead to the development of T1D. We propose that the study of monogenic diseases, and in particular STAT mutations, may not only improve our understanding of the function of the human immune system but also shed light onto the pathogenic mechanisms of T1D and the genetic variants that confer predisposition to the disease.

IL-17 in Rheumatoid Arthritis and Precision Medicine: From Synovitis Expression to Circulating Bioactive Levels

Interleukin (IL)-17A has a direct contribution in early induction and late chronic stages of various inflammatory diseases. In vitro and in vivo experiments have first characterized its local effects on different cell types and then its systemic effects. For instance, IL-17 axis is now identified as a key driver of psoriasis through its effects on keratinocytes. Similar observations apply for rheumatoid arthritis (RA) where IL-17A triggers changes in the synovium that lead to synovitis and maintain local inflammation. These results have prompted the development of biologics to target this cytokine. However, while convincing studies are reported on the efficacy of IL-17 inhibitors in psoriasis, there are conflicting results in RA. Patient heterogeneity but also the involvement of mediators that regulate IL-17 function may explain these results. Therefore, new tools and concepts are required to identify patients that could benefit from these IL-17 targeted therapies in RA and the development of predictive biomarkers of response has started with the emergence of various bioassays. Current strategies are also focusing on synovial biopsies that may be used to stratify patients. From local to systemic levels, new approaches are developing and move the field of RA management into the era of precision medicine.

A complex auxiliary: IL-17/Th17 signaling during type 1 diabetes progression

Type 1 diabetes (T1D) is an autoimmune disease centered around the loss of the beta cells of the islets of Langerhans, and consequent inability of the islets to produce the insulin necessary to maintain glycemic control. While most therapeutic approaches have been centered on insulin replacement, newer approaches to target the underlying immune response have become an area of focus. However, the immune landscape in T1D is extremely complex, and the roles played by individual cytokines during disease progression are incompletely understood, making the development of immunotherapies very difficult. In this review, we discuss the complex auxiliary role played by IL-17, both around the islet and in peripheral tissues such as the gut and kidney, which might influence T1D progression. Through our re-analysis of the key factors involved IL-17 signaling in recently published single-cell sequencing and sorted-cell bulk sequencing datasets, we find supporting evidence for the general existence of the signaling apparatus in islet endocrine cells. We also explore the emerging evidence of IL-17 serving as an influential factor in diabetic complications that affect distal tissues. While anti-IL-17 therapies are emerging as an option for psoriasis and other autoimmune disorders, we highlight here a number of questions that would need to be addressed before their potential applicability to treating T1D can be fully evaluated.

Pre, peri and posttransplant diabetes mellitus

PURPOSE OF REVIEW

The leading cause of death in both chronic kidney disease (CKD) and renal transplant patients is cardiovascular events. Post-transplant diabetes mellitus (PTx-DM), which is a major cardiovascular risk factor, is a metabolic disorder that affects 5.5-60.2% of renal allograft recipients by 1-year posttransplant (PTx). PTx-DM has been associated with a negative impact on patient and graft outcomes and survival.

RECENT FINDINGS

Individuals who develop PTx-DM are usually prone to this condition prior to and/or after developing CKD. Genetic factors, obesity, inflammation, medications and CKD all are risk factors for PTx-diabetes mellitus. The path to development of disease continues PTx frequently augmented by the use of diabetogenic maintenance immunosuppressive and some nonimmunosuppressive medications. These risk factors are usually associated with an increase in insulin resistance, a decrease in insulin gene expression and/or β-cell dysfunction and apoptosis.

SUMMARY

Some new anti-diabetes mellitus medications may help to improve the overall outcome; however, there is a real need for developing a preventive strategy. Identifying and targeting PTx-DM risk factors may help to guide the development of an effective programme. This could include the adoption of nondiabetogenic immunosuppressive protocols for high-risk patients.

Targeting inflammation in diabetic nephropathy: a tale of hope

INTRODUCTION

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Beyond the new anti-diabetic drugs that possess markedly cardiovascular and renal protective effects, no novel direct therapies for DN have become available on the market in the last twenty years. Recently well-designed clinical trials for the treatment of DN, with attractive pathogenetic rationale, e.g. bardoxolone and atrasentan, were canceled or stopped because of safety concerns or lack of reaching the end points, respectively.

AREAS COVERED

In this review, we focus on the involvement of inflammation in the pathogenesis of DN. We update information from recent experimental and clinical studies that reported beneficial effects of several agents targeting chemokines, cytokines, transcription factors and kinases as well as several compounds with anti-inflammatory properties on DN.

EXPERT OPINION

Inflammation plays a key role in the DN progression. Preclinical studies have identified several anti-inflammatory molecules that effective decrease albuminuria and/or proteinuria. However, limited clinical trials in humans have been performed to confirm these results. Inhibitors of CCL2/CCR2, IL-1β and JAK/STAT pathways, and Nrf2 inducers are promising therapeutic options to improve the renal outcome of patients with DN, but appropriate clinical trials are necessary.

Ethylenecarbodiimide-fixed splenocytes carrying whole islet antigens decrease the incidence of diabetes in NOD mice via down-regulation of effector memory T cells and autoantibodies

Type 1 diabetes mellitus (T1DM) is a syndrome of loss of glucose homeostasis caused by the loss of β cell chronic autoimmunity against islet cells. Islet-specific epitopes coupled antigen presenting cells by Ethylenecarbodiimide (ECDI) is a promising strategy to induce antigen-specific tolerance. However, single epitope induced tolerance is insufficient to prevent the onset of T1DM. The aim of this study is to evaluate the efficacy of whole islet antigens in preventing the onset and progression of T1DM and identify the underlying immune mechanism in NOD mice. In this study, the whole islet antigens, derived from islet lysate isolated from BALB/c mice, were coupled to splenocytes of BALB/c mice by ECDI fixation (SP-Islet lysate), and then intravenously administrated to NOD mice. The results showed that, compared with control group, SP-Islet lysate group significantly decreased T1DM incidence and improved the survival of NOD mice. SP-Islet lysate treated mice had reduced insulitis score and autoantibody levels, and improved glucose tolerance and insulin/glucagon production. Furthermore, the effector memory T cells (T_EMs) were downregulated and regulatory T cells (Tregs) were upregulated by the SP-Islet lysate treatment, with reduced populations of Th1&Th17 cells. In conclusion, ECDI-fixed splenocytes carrying whole islet antigens effectively prevented the onset of T1DM in NOD mice, via suppressing the production of autoantibodies and inducing anergy of autoreactive T cells.

Therapies to Suppress β Cell Autoimmunity in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is generally considered to be T cell-driven. Accordingly, most strategies of immunotherapy for T1D prevention and treatment in the clinic have targeted the T cell compartment. To date, however, immunotherapy has had only limited clinical success. Although certain immunotherapies have promoted a protective effect, efficacy is often short-term and acquired immunity may be impacted. This has led to the consideration of combining different approaches with the goal of achieving a synergistic therapeutic response. In this review, we will discuss the status of various T1D therapeutic strategies tested in the clinic, as well as possible combinatorial approaches to restore β cell tolerance.

Immune cell and cytokine patterns in children with type 1 diabetes mellitus undergoing a remission phase: A longitudinal study

OBJECTIVE

Type 1 diabetes (T1D) develops in distinct stages, before and after disease onset. Whether the natural course translates into different immunologic patterns is still uncertain. This study aimed at identifying peripheral immune patterns at key time-points, in T1D children undergoing remission phase.

METHODS

Children with new-onset T1D and healthy age and gender-matched controls were recruited at a pediatric hospital. Peripheral blood samples were evaluated by flow cytometry at 3 longitudinal time-points: onset (T1), remission phase (T2) and established disease (T3). Cytokine levels were quantified by multiplex assay. Fasting C-peptide, HbA1c, and 25OHD were also measured.

RESULTS

T1D children (n = 28; 10.0 ± 2.6 years) showed significant differences from controls in circulating neutrophils, T helper (Th)17 and natural killer (NK) cells, with relevant variations during disease progression. At onset, neutrophils, NK, Th17 and T cytotoxic (Tc)17 cells were decreased. As disease progressed, neutrophil counts recovered whereas NK counts remained low. Th17 and Tc17 cells behavior followed the neutrophil variation pattern. B-cells were lowest in the remission phase and regulatory T-cells significantly declined after remission. Two cytokine response profiles were identified. Low cytokine-responders showed higher circulating fasting C-peptide levels at onset and longer remission periods. C-peptide inversely correlated with pro-inflammatory and cytotoxic cells.

CONCLUSIONS

Our data suggest an association between immune cells, cytokine patterns and metabolic counterparts. The dynamic changes of circulating immune cells during disease progression involve key innate and acquired immune cell types. This longitudinal picture of T1D progression may enable disease staging and patient stratification, essential for individualized treatment.

Distinct gene expression pathways in islets from individuals with short- and long-duration type 1 diabetes

AIMS

Our current understanding of the pathogenesis of type 1 diabetes (T1D) arose, in large part, from studies using the non-obese diabetic (NOD) mouse model. In the present study, we chose a human-focused method to investigate T1D disease mechanisms and potential targets for therapeutic intervention by directly analysing human donor pancreatic islets from individuals with T1D.

MATERIALS AND METHODS

We obtained islets from a young individual with T1D for 3 years and from an older individual with T1D for 27 years and performed unbiased functional genomic analysis by high-depth RNA sequencing; the T1D islets were compared with islets isolated from 3 non-diabetic donors.

RESULTS

The islets procured from these T1D donors represent a unique opportunity to identify gene expression changes in islets after significantly different disease duration. Data analysis identified several inflammatory pathways up-regulated in short-duration disease, which notably included many components of innate immunity. As proof of concept for translation, one of the pathways, governed by IL-23(p19), was selected for further study in NOD mice because of ongoing human trials of biologics against this target for different indications. A mouse monoclonal antibody directed against IL-23(p19) when administered to NOD mice resulted in a significant reduction in incidence of diabetes.

CONCLUSION

While the sample size for this study is small, our data demonstrate that the direct analysis of human islets provides a greater understanding of human disease. These data, together with the analysis of an expanded cohort to be obtained by future collaborative efforts, might result in the identification of promising novel targets for translation into effective therapeutic interventions for human T1D, with the added benefit of repurposing known biologicals for use in different indications.

Dipeptidyl peptidase-4(DPP-4) inhibitors: promising new agents for autoimmune diabetes

Dipeptidyl peptidase-4 (DPP-4) inhibitors constitute a novel class of anti-diabetic agents confirmed to improve glycemic control and preserve β-cell function in type 2 diabetes. Three major large-scale studies, EXAMINE, SAVOR-TIMI 53, and TECOS, have confirmed the cardiovascular safety profile of DPP-4 inhibitors. Based on these results, DPP-4 inhibitors have gained widespread use in type 2 diabetes treatment. It is currently unknown, however, whether DPP-4 inhibitors have similar therapeutic efficacy against autoimmune diabetes. Several in vitro and in vivo studies have addressed this issue, but the results remain controversial. In this review, we summarize experimental findings and preliminary clinical trial results, and identify potentially effective immune modulation targets of DPP-4 inhibitors for autoimmune diabetes.

miR-340 Alleviates Psoriasis in Mice through Direct Targeting of IL-17A

Th17 cell is a well-known lineage of CD4⁺ effector Th cells that selectively produce IL-17A and play critical roles during the pathogenesis of autoimmune disease. A microRNA (miRNA) is a small noncoding RNA molecule that functions in posttranscriptional regulation of gene expression. Recently, an increasing number of studies have demonstrated that multiple miRNAs are dysregulated in patients with various autoimmune diseases and mediate autoimmune disease pathologic condition at least in part through the regulation of Th17 response. However, among the few miRNAs identified so far that play possible roles in the differentiation of Th17 cells, they all regulate the Th17 response through targeting negative or positive regulators of Th17 differentiation. In the current study, we sought to identify new miRNAs that can directly regulate the expression of IL-17A, the most important cytokine produced by Th17 cells. Our results showed that the 3' untranslated region of mouse IL-17A can act as a negative regulatory element to downregulate gene expression. Further study revealed that miR-340 can specifically bind to the 3' untranslated region of mouse IL-17A and downregulate the expression of endogenous IL-17A. More importantly, we demonstrated that treatment with miR-340 alleviates the clinical severity of imiquimod-induced psoriasis in mice through the downregulation of IL-17A. These data indicate that miR-340 may be a useful therapeutic target for the treatment of psoriasis and other IL-17A-mediated autoimmune diseases.

Approaches in Immunotherapy, Regenerative Medicine, and Bioengineering for Type 1 Diabetes

Recent advances on using immune and stem cells as two-pronged approaches for type 1 diabetes mellitus (T1DM) treatment show promise for advancement into clinical practice. As T1DM is thought to arise from autoimmune attack destroying pancreatic β-cells, increasing treatments that use biologics and cells to manipulate the immune system are achieving better results in pre-clinical and clinical studies. Increasingly, focus has shifted from small molecule drugs that suppress the immune system nonspecifically to more complex biologics that show enhanced efficacy due to their selectivity for specific types of immune cells. Approaches that seek to inhibit only autoreactive effector T cells or enhance the suppressive regulatory T cell subset are showing remarkable promise. These modern immune interventions are also enabling the transplantation of pancreatic islets or β-like cells derived from stem cells. While complete immune tolerance and body acceptance of grafted islets and cells is still challenging, bioengineering approaches that shield the implanted cells are also advancing. Integrating immunotherapy, stem cell-mediated β-cell or islet production and bioengineering to interface with the patient is expected to lead to a durable cure or pave the way for a clinical solution for T1DM.

The role of infiltrating immune cells in dysfunctional adipose tissue

Adipose tissue (AT) dysfunction, characterized by loss of its homeostatic functions, is a hallmark of non-communicable diseases. It is characterized by chronic low-grade inflammation and is observed in obesity, metabolic disorders such as insulin resistance and diabetes. While classically it has been identified by increased cytokine or chemokine expression, such as increased MCP-1, RANTES, IL-6, interferon (IFN) gamma or TNFα, mechanistically, immune cell infiltration is a prominent feature of the dysfunctional AT. These immune cells include M1 and M2 macrophages, effector and memory T cells, IL-10 producing FoxP3+ T regulatory cells, natural killer and NKT cells and granulocytes. Immune composition varies, depending on the stage and the type of pathology. Infiltrating immune cells not only produce cytokines but also metalloproteinases, reactive oxygen species, and chemokines that participate in tissue remodelling, cell signalling, and regulation of immunity. The presence of inflammatory cells in AT affects adjacent tissues and organs. In blood vessels, perivascular AT inflammation leads to vascular remodelling, superoxide production, endothelial dysfunction with loss of nitric oxide (NO) bioavailability, contributing to vascular disease, atherosclerosis, and plaque instability. Dysfunctional AT also releases adipokines such as leptin, resistin, and visfatin that promote metabolic dysfunction, alter systemic homeostasis, sympathetic outflow, glucose handling, and insulin sensitivity. Anti-inflammatory and protective adiponectin is reduced. AT may also serve as an important reservoir and possible site of activation in autoimmune-mediated and inflammatory diseases. Thus, reciprocal regulation between immune cell infiltration and AT dysfunction is a promising future therapeutic target.

Insight Into Non-Pathogenic Th17 Cells in Autoimmune Diseases

Th17 cells are generally considered to be positive regulators of immune responses because they produce pro-inflammatory cytokines, including IL-17A, IL-17F, and IL-22. Cytokine production not only promotes accumulation of immune cells, such as macrophages, neutrophils and lymphocytes, at inflammatory sites but can also cause tissue pathologies. Conversely, certain Th17 cells can also negatively regulate immune responses by secreting immunosuppressive factors, such as IL-10; these cells are termed non-pathogenic Th17 cells. In this review, we summarize recent advances in the development and regulatory functions of non-pathogenic Th17 cells in autoimmune diseases.

Gluten-free diet during pregnancy alleviates signs of diabetes and celiac disease in NOD mouse offspring

BACKGROUND

Gluten-free (GF) diet during pregnancy ameliorates autoimmune diabetes in nonobese diabetic (NOD) mouse offspring. Due to comorbidity of celiac disease in type 1 diabetes, we hypothesized that GF diet in utero alleviates the humoral and histopathological signs of celiac disease in NOD mice. We aimed to establish the mechanisms behind the diabetes-protective effect of GF diet in utero.

METHODS

Breeding pairs of NOD mice were fed a GF or gluten-containing standard (STD) diet until parturition. The offspring were nursed by mothers on STD diet and continued on this diet until ages 4 and 13 weeks. Analyses of serum antitissue transglutaminase (anti-tTG) intestine and islet histology, islet transglutaminase (TG) activity, and cytokine expression in T cells from lymphoid organs were performed.

RESULTS

GF versus STD diet in utero led to reduced serum anti-tTG titre and increased villus-to-crypt ratio at both ages. Insulitis along with systemic and local inflammation were decreased, but islet TG activity was unchanged in 13-week-old GF mice. These mice had unchanged beta-cell volumes, but increased islet numbers throughout the prediabetic period.

CONCLUSIONS

Collectively, GF diet administered during pregnancy improves signs of celiac disease and autoimmune diabetes in the offspring. The diabetes-ameliorative effect of GF diet in utero is followed by dampening of inflammation, unchanged beta-cell volume, but increased islet numbers.

Interleukin 17 Family Cytokines: Signaling Mechanisms, Biological Activities, and Therapeutic Implications

The cytokines of the interleukin 17 (IL-17) family play a central role in the control of infections, especially extracellular fungi. Conversely, if unrestrained, these inflammatory cytokines contribute to the pathology of numerous autoimmune and chronic inflammatory conditions. Recent advances have led to the approval of IL-17A-blocking biologics for the treatment of moderate to severe plaque psoriasis, but much remains to be understood about the biological functions, regulation, and signaling pathways downstream of these factors. In this review, we outline the current knowledge of signal transduction and known physiological activities of IL-17 family cytokines. We will highlight in particular the current understanding of these cytokines in the context of skin manifestations of disease.

The potential pathogenic role of IL-17/Th17 cells in both type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) is a serious medical problem affecting millions of peoples worldwide, and has a great socio-economic impacts. Cytokines possess a pivotal role in modulation of immune reactions and disease pathogenesis. T-helper type 17 (Th17) cells, an important proinflammatory CD4⁺ T cell subset secreting interleukin 17 (IL-17), has been embroiled in development of DM. There are recent evidences supporting a definitive role of Th17 cells in the etiology of type 1 diabetes (T1D). In addition, IL-17 has been shown to play a crucial role in inflammation, insulin resistance, and type 2 diabetes (T2D). Recently, small molecules which have been specified to block Th17 cells differentiation are considered as potential therapeutics for the disease. Anti-IL-17 neutralizing antibodies and/or antibodies targeting Th17 cells have been investigated to protect individuals at risk from disease development. In this review we aimed to shed light on the potential role of IL-17 and Th17 cells in both T1D and T2D pathogenesis and future therapeutic strategies.

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.

Diabetes Mellitus and Sepsis: A Challenging Association

Sepsis is a life-threatening organ dysfunction caused by a deregulated host response to infection. This inappropriate response to micro-organism invasion is characterized by an overwhelmed systemic inflammatory response and cardiovascular collapse that culminate in high mortality and morbidity in critical care units. The occurrence of sepsis in diabetes mellitus (DM) patients has become more frequent, as the prevalence of DM has increased dramatically worldwide. These two important diseases represent a global public health concern and highlight the importance of increasing our knowledge of the key elements of the immune response related to both conditions. In this context, it is well established that the cells taking part in the innate and adaptive immune responses in diabetic patients have compromised function. These altered responses favor micro-organism growth, a process that contributes to sepsis progression. The present review provides an update on the characteristics of the immune system in diabetic and septic subjects. We also explore the beneficial effects of insulin on the immune response in a glycemic control-dependent and independent manner.

CD122 blockade restores immunological tolerance in autoimmune type 1 diabetes via multiple mechanisms

Signaling through IL-2/IL-15Rβ (CD122) is essential for the differentiation and function of T cells and NK cells. A mAb against CD122 has been implicated to suppress autoimmune type 1 diabetes (T1D) development in animal models. However, the mechanisms remain poorly understood. We find that in vivo administration of an anti-CD122 mAb (CD122 blockade) restores immune tolerance in nonobese diabetic (NOD) mice via multiple mechanisms. First, CD122 blockade selectively ablates pathogenic NK cells and memory phenotype CD8+ T cells from pancreatic islets. In contrast, islet CD4+Foxp3+ Tregs are only mildly affected. Second, CD122 blockade suppresses IFN-γ production in islet immune cells. Third, CD122 blockade inhibits the conversion of islet Th17 cells into diabetogenic Th1 cells. Furthermore, a combination of anti-CD122 mAb and Treg-trophic cytokines (IL-2 or IL-33) enhances the abundance and function of islet Tregs. In summary, these data provide crucial mechanistic insights into CD122 blockade-mediated immunoregulation and support therapeutic benefits of this combinational treatment in T1D.

MicroRNA-326 contributes to autoimmune thyroiditis by targeting the Ets-1 protein

PURPOSE

MicroRNA-326 (miR-326), as a member of the microRNA (miRNA) family, which includes endogenous single-stranded, conserved, noncoding small RNAs, has been reported to play important roles in autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus. However, few studies of the role of miR-326 in autoimmune thyroiditis (AIT) have been published. Here, we explored the roles of miR-326 and the involved pathway in iodine-induced AIT.

METHODS

NOD.H-2^h4 mice, which are a model of human AIT, were randomly divided into a normal water control group and a high-iodine group. Mice in the high-iodine group were administered 0.05% NaI (~1000 times the normal daily iodine intake), and mice in the control group received sterile water. Furthermore, we evaluated small interfering RNA (siRNA) interference in spleen mononuclear cell experiments in vitro.

RESULTS

In this study, we found that Th17 cells were significantly increased with a high expression of miR-326 in an iodine-induced thyroiditis NOD.H-2^h4 mouse model. In addition, the expression of Ets-1 protein, a negative regulator of Th17 differentiation, was significantly decreased. Intriguingly, our analysis showed that Ets-1 protein expression was negatively correlated with miR-326 levels in AIT mice (r = -0.814, p < 0.01). Our study indicated that miR-326 inhibited Ets-1 protein expression and promoted the differentiation of Th17 cells during the onset and development of AIT. The addition of a miR-326 inhibitor reversed Th17 cell production and Ets-1 protein expression, supporting this hypothesis.

CONCLUSIONS

The results of our study suggest that miR-326 may target the Ets-1 protein to contribute to iodide-induced thyroiditis, providing a new theoretical basis for the use of miRNA targeting therapy for the treatment of autoimmune diseases.

CRIg, a tissue-resident macrophage specific immune checkpoint molecule, promotes immunological tolerance in NOD mice, via a dual role in effector and regulatory T cells

How tissue-resident macrophages (TRM) impact adaptive immune responses remains poorly understood. We report novel mechanisms by which TRMs regulate T cell activities at tissue sites. These mechanisms are mediated by the complement receptor of immunoglobulin family (CRIg). Using animal models for autoimmune type 1 diabetes (T1D), we found that CRIg⁺ TRMs formed a protective barrier surrounding pancreatic islets. Genetic ablation of CRIg exacerbated islet inflammation and local T cell activation. CRIg exhibited a dual function of attenuating early T cell activation and promoting the differentiation of Foxp3⁺ regulatory (Treg) cells. More importantly, CRIg stabilized the expression of Foxp3 in Treg cells, by enhancing their responsiveness to interleukin-2. The expression of CRIg in TRMs was postnatally regulated by gut microbial signals and metabolites. Thus, environmental cues instruct TRMs to express CRIg, which functions as an immune checkpoint molecule to regulate adaptive immunity and promote immune tolerance.

Th17 pathway in recent-onset autoimmune diabetes

AIMS

Evaluate the participation of IL-17 pathway in T1D pathogenesis. T helper 17 cells are potent, highly inflammatory cells that produce interleukin 17A (IL-17A), considered a mediator of various immune disorders. However, their role in Type 1 diabetes (T1D) pathogenesis in humans is not totally elucidated.

METHODS

The expression of IL-17 Receptor A (IL-17RA) in peripheral T lymphocytes and IL-17A serum levels in recent-onset patients with T1D were compared with healthy controls. IL-17A gene variants were evaluated in a greater cohort.

RESULTS

Patients with recent-onset T1D (less than 6 months of diagnosis) exhibited lower expression of IL-17RA in CD3+ T (% of cells = 31.3% × 43.6%; p = .041) and CD4+ T cells (11.1% × 25.2%; p = .0019) and lower number of IL-17RA in CD4+ T cells (MFI = 1.16 × 4.56; p = .03) than controls. IL-17RA expression in CD8+ T cells and IL-17A serum levels were similar in both groups. The coding regions and boundary intron sequences of IL17A were sequenced. Seventeen allelic variants, including three novel variants in exon 3 (3'UTR n) were identified, but no one was associated with T1D susceptibility, as well as the resulting haplotypes and diplotypes. The expression of IL-17RA was not correlated with metabolic variables (glucose and HbA1c levels) or pancreatic autoantibodies titers.

CONCLUSIONS

The lower expression of IL-17RA in CD3+ and CD4+ T cells suggests a reduced effect of IL-17A in immune response of recent-onset T1D patients, at least at peripheral tissues. IL-17A allelic variants were not related with T1D susceptibility.

Human Gingiva-Derived Mesenchymal Stem Cells Ameliorate Streptozoticin-induced T1DM in mice via Suppression of T effector cells and Up-regulating Treg Subsets

There is yet no cure for type 1 diabetes (T1DM) so far. A significant body of evidence has demonstrated that bone marrow-derived mesenchymal stem cells (BMSCs) showed great potential in controlling T1DM. But there exists much difficulty in using BMSCs as a clinical therapy. We here test whether a new population of mesenchymal stem cells from human gingiva (GMSCs), which has many advantages over BMSCs, can delay or prevent progress of T1DM. GMSCs were adoptively transferred to multiple low-dose streptozotocin (STZ)-induced T1DM. Blood glucose levels and disease severities were analyzed. T cells subsets in blood, spleen and lymph nodes were detected dynamically by flow cytometry. GMSC distribution was dynamically analyzed. We found that infusion of GMSCs but not fibroblast cells significantly controlled blood glucose levels, delayed diabetes onset, ameliorated pathology scores in pancreas, and down-regulated production of IL-17 and IFN-γ in CD4+ and CD8+ T cells in spleens, pancreatic lymph nodes (pLN) and other lymph nodes. GMSCs also up-regulated the levels of CD4+ Treg induced in the periphery. Mechanismly, GMSCs could migrate to pancreas and local lymph node and function through CD39/CD73 pathway to regulate effector T cells. Thus, GMSCs show a potential promise in treating T1DM in the clinic.

KLK5 induces shedding of DPP4 from circulatory Th17 cells in type 2 diabetes

OBJECTIVE

Increasing plasma levels and activity of dipeptidyl peptidase-4 (DPP4 or CD26) are associated with rapid progression of metabolic syndrome to overt type 2 diabetes mellitus (T2DM). While DPP4 inhibitors are increasingly used as anti-hyperglycemic agents, the reason for the increase in plasma DPP4 activity in T2DM patients remains elusive.

METHODS

We looked into the source of plasma DPP4 activity in a cohort of 135 treatment naive nonobese (BMI < 30) T2DM patients. A wide array of ex vivo, in vitro, and in silico methods were employed to study enzyme activity, gene expression, subcellular localization, protease identification, surface expression, and protein-protein interactions.

RESULTS

We show that circulating immune cells, particularly CD4+ T cells, served as an important source for the increase in plasma DPP4 activity in T2DM. Moreover, we found kallikrein-related peptidase 5 (KLK5) as the enzyme responsible for cleaving DPP4 from the cell surface by directly interacting with the extracellular loop. Expression and secretion of KLK5 is induced in CD4+ T cells of T2DM patients. In addition, KLK5 shed DPP4 from circulating CD4+ T helper (Th)17 cells and shed it into the plasma of T2DM patients. Similar cleavage and shedding activities were not seen in controls.

CONCLUSIONS

Our study provides mechanistic insights into the molecular interaction between KLK5 and DPP4 as well as CD4+ T cell derived KLK5 mediated enzymatic cleavage of DPP4 from cell surface. Thus, our study uncovers a hitherto unknown cellular source and mechanism behind enhanced plasma DPP4 activity in T2DM.

Clostridium butyricum CGMCC0313.1 Protects against Autoimmune Diabetes by Modulating Intestinal Immune Homeostasis and Inducing Pancreatic Regulatory T Cells

Recent evidence indicates that indigenous Clostridium species induce colonic regulatory T cells (Tregs), and gut lymphocytes are able to migrate to pancreatic islets in an inflammatory environment. Thus, we speculate that supplementation with the well-characterized probiotics Clostridium butyricum CGMCC0313.1 (CB0313.1) may induce pancreatic Tregs and consequently inhibit the diabetes incidence in non-obese diabetic (NOD) mice. CB0313.1 was administered daily to female NOD mice from 3 to 45 weeks of age. The control group received an equal volume of sterile water. Fasting glucose was measured twice a week. Pyrosequencing of the gut microbiota and flow cytometry of mesenteric lymph node (MLN), pancreatic lymph node (PLN), pancreatic and splenic immune cells were performed to investigate the effect of CB0313.1 treatment. Early oral administration of CB0313.1 mitigated insulitis, delayed the onset of diabetes, and improved energy metabolic dysfunction. Protection may involve increased Tregs, rebalanced Th1/Th2/Th17 cells and changes to a less proinflammatory immunological milieu in the gut, PLN, and pancreas. An increase of α4β7+ (the gut homing receptor) Tregs in the PLN suggests that the mechanism may involve increased migration of gut-primed Tregs to the pancreas. Furthermore, 16S rRNA gene sequencing revealed that CB0313.1 enhanced the Firmicutes/Bacteroidetes ratio, enriched Clostridium-subgroups and butyrate-producing bacteria subgroups. Our results provide the basis for future clinical investigations in preventing type 1 diabetes by oral CB0313.1 administration.

Characterization and expression analysis of six interleukin-17 receptor genes in grouper (Epinephelus coioides) after Cryptocaryon irritans infection

Interleukin-17 receptors (IL17Rs) mediate the activation of several downstream signal pathways to induce inflammatory response and contribute to the pathology of many autoimmune diseases. In this study, six IL17Rs (IL17RA1, RA2, RB, RC, RD and RE) were cloned and characterized from Epinephelus coioides, an orange-spotted grouper. Multiple sequence alignment and structural analysis revealed that all members of IL17Rs were low in sequence identity with each other. But their structures were conservative in grouper, which contain signal peptide, extracellular FNIII domain (IL17RA1/RA2/RB) or IL-17_R_N domain (IL17RC/RD/RE), transmembrane domain and SEFIR domain in their intracellular region. The analysis of tissue distribution showed these six genes were ubiquitously and differentially expressed in all major types of tissues. What's more, it is interesting to find their high expression in immune tissues (liver, gill, skin and thymus). IL17RA1 and IL17RA2 were significantly down-regulated at all time-points in gill and spleen after Cryptocaryon irritans infection, however, there was no significant change in other grouper IL17Rs. It suggests that the C. irritans may escape from the host immunity or the host prevents serious inflammation by inhibiting the expression of ILl7Rs.

Role of interleukin-25 in development of spontaneous arthritis in interleukin-1 receptor antagonist-deficient mice

Interleukin (IL)-25, which is a member of the IL-17 family of cytokines, induces production of such Th2 cytokines as IL-4, IL-5, IL-9 and/or IL-13 by various types of cells, including Th2 cells, Th9 cells and group 2 innate lymphoid cells (ILC2). On the other hand, IL-25 can suppress Th1- and Th17-associated immune responses by enhancing Th2-type immune responses. Supporting this, IL-25 is known to suppress development of experimental autoimmune encephalitis, which is an IL-17-mediated autoimmune disease in mice. However, the role of IL-25 in development of IL-17-mediated arthritis is not fully understood. Therefore, we investigated this using IL-1 receptor antagonist-deficient (IL-1Ra^-/-) mice, which spontaneously develop IL-17-dependent arthritis. However, development of spontaneous arthritis (incidence rate, disease severity, proliferation of synovial cells, infiltration of PMNs, and bone erosion in joints) and differentiation of Th17 cells in draining lymph nodes in IL-25^-/- IL-1Ra^-/- mice were similar to in control IL-25^+/+ IL-1Ra^-/- mice. These observations indicate that IL-25 does not exert any inhibitory and/or pathogenic effect on development of IL-17-mediated spontaneous arthritis in IL-1Ra^-/- mice.

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IL-25 is known to inhibit Th17 cell differentiation.

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IL-25 is known to suppress Th17-mediated autoimmune diseases in mice.

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IL-25 does not play any inhibitory and/or pathogenic role in IL-17-mediated arthritis.

Early-Life Nutritional Factors and Mucosal Immunity in the Development of Autoimmune Diabetes

Type 1 diabetes (T1D) is an immune-mediated disease with a strong genetic basis but might be influenced by non-genetic factors such as microbiome development that “programs” the immune system during early life as well. Factors influencing pathogenesis, including a leaky intestinal mucosal barrier, an aberrant gut microbiota composition, and altered immune responsiveness, offer potential targets for prevention and/or treatment of T1D through nutritional or pharmacologic means. In this review, nutritional approaches during early life in order to protect against T1D development have been discussed. The critical role of tolerogenic dendritic cells in central and peripheral tolerance has been emphasized. In addition, since the gut microbiota affects the development of T1D through short-chain fatty acid (SCFA)-dependent mechanisms, we hypothesize that nutritional intervention boosting SCFA production may be used as a novel prevention strategy. Current retrospective evidence has suggested that exclusive and prolonged breastfeeding might play a protective role against the development of T1D. The beneficial properties of human milk are possibly attributed to its bioactive components such as unique immune-modulatory components human milk oligosaccharides and metabolites derived thereof, including SCFAs. These components might play a key role in healthy immune development and creating a fit and resilient immune system in early and later life.

Development and validation of an ultra-performance liquid chromatography-tandem mass spectrometry method for quantification of SR1001, an inverse agonist of retinoid-related orphan receptors, and its application to pharmacokinetic studies in streptozotocin-induced diabetic mice

Retinoic acid receptor-related orphan receptors (RORs) play critical roles in the onset and progression of type I diabetes, an autoimmune disease characterized by the destruction of pancreatic β-cells. SR1001, an ROR inverse agonist, has been proven to be an effective diabetes treatment in the non-obese diabetic (NOD) mouse model. However, optimization of this treatment is challenging because knowledge of SR1001 pharmacokinetic (PK) behaviors in type I diabetic animals is limited. The aim of our study was to develop and validate a specific and sensitive ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method to measure the concentrations of SR1001 in plasma and biological samples. Using the developed UPLC-MS/MS method, SR1001 linearity ranges in biological matrices were determined to be 5-1000ng/mL, with correlation coefficients of >0.99. The limit of detection (LOD) and limit of quantification (LOQ) values of SR1001 were 1 and 5ng/mL, respectively. And the intra-day and inter-day variances were less than 10%, and accuracy was within 90%-110%. The extraction recoveries of SR1001 were ≥80%, and no significant matrix effect was observed. Using the validated UPLC-MS/MS method, levels of SR1001 in plasma and six major organs (heart, liver, spleen, lung, kidney, and brain) were determined in streptozotocin (STZ) -induced diabetic mice. The PK parameters of SR1001 were also calculated. The SR1001 drug concentration-time curves for organs and plasma showed similar trends, and the elimination half-lives of SR1001 in diabetic mice were about 12h. SR1001 was highly bound to plasma protein, resulting in a much higher maximum concentration (C_max=144394ng/mL) and area under the concentration-time curve (AUC_0-t=2728258ng/mL*h), but a low tissue/plasma partition coefficient (K_p) value of <0.3.

Interleukin-25 Produced by Synoviocytes Has Anti-inflammatory Effects by Acting As a Receptor Antagonist for Interleukin-17A Function

The production and function of cytokines are highly regulated. One mechanism is the balance between pro- and anti-inflammatory cytokines. As interleukin (IL)-17A and IL-25 share the IL-17RA receptor chain, we hypothesize that IL-25 acts as an IL-17A receptor antagonist and limits its pro-inflammatory effects. The production and expression kinetics of IL-25 and its receptor chains IL-17RA and RB were analyzed in rheumatoid synoviocytes alone or in coculture with peripheral blood mononuclear cells (PBMCs). The effects of autocrine or exogenous IL-25 on synoviocytes were investigated in the presence or not of an anti-IL-25 antibody. To study the regulatory effects of IL-25, synoviocytes and/or PBMCs were exposed to IL-25 before being treated with IL-17A and tumor necrosis factor alpha (TNF-α) alone or combined. IL-25, IL-6, and bioactive IL-17A were quantified in rheumatoid arthritis (RA) patient plasma. Synoviocytes expressed and secreted IL-25, and expressed the two chains of its receptor IL-17RA and IL-17RB. IL-17RB expression was increased by TNF-α. IL-25 production occurred at a delayed time point (5 days) after stimulation with IL-17A and TNF-α. Synoviocytes pretreated with IL-25 were less responsive to IL-17A and TNF-α. PBMCs exposed to IL-25 showed a decreased production of pro-inflammatory mediators, including IL-17A with a 57% decrease; p = 0.002. IL-25 levels were elevated in the plasma of RA patients compared to healthy subjects (p = 0.03). However, these levels are not high enough to inhibit the function of circulating IL-17A. In conclusion, it was shown for the first time that synoviocytes produce IL-25, specifically at late time points and that IL-25 acts as a regulator of IL-17A-driven inflammation, as indicated by in vitro results and in vivo, in a long-term RA patient follow-up. These results may be important when considering IL-17A inhibition.

Microbiota in T-cell homeostasis and inflammatory diseases

The etiology of disease pathogenesis can be largely explained by genetic variations and several types of environmental factors. In genetically disease-susceptible individuals, subsequent environmental triggers may induce disease development. The human body is colonized by complex commensal microbes that have co-evolved with the host immune system. With the adaptation to modern lifestyles, its composition has changed depending on host genetics, changes in diet, overuse of antibiotics against infection and elimination of natural enemies through the strengthening of sanitation. In particular, commensal microbiota is necessary in the development, induction and function of T cells to maintain host immune homeostasis. Alterations in the compositional diversity and abundance levels of microbiota, known as dysbiosis, can trigger several types of autoimmune and inflammatory diseases through the imbalance of T-cell subpopulations, such as Th1, Th2, Th17 and Treg cells. Recently, emerging evidence has identified that dysbiosis is involved in the progression of rheumatoid arthritis, type 1 and 2 diabetic mellitus, and asthma, together with dysregulated T-cell subpopulations. In this review, we will focus on understanding the complicated microbiota-T-cell axis between homeostatic and pathogenic conditions and elucidate important insights for the development of novel targets for disease therapy.