The NOD mouse: a model of immune dysregulation

Blood leukocytes recapitulate diabetogenic peptide-MHC-II complexes displayed in the pancreatic islets

Assessing the self-peptides presented by susceptible major histocompatibility complex (MHC) molecules is crucial for evaluating the pathogenesis and therapeutics of tissue-specific autoimmune diseases. However, direct examination of such MHC-bound peptides displayed in the target organ remains largely impractical. Here, we demonstrate that the blood leukocytes from the nonobese diabetic (NOD) mice presented peptide epitopes to autoreactive CD4 T cells. These peptides were bound to the autoimmune class II MHC molecule (MHC-II) I-A^g7 and originated from insulin B-chain and C-peptide. The presentation required a glucose challenge, which stimulated the release of the insulin peptides from the pancreatic islets. The circulating leukocytes, especially the B cells, promptly captured and presented these peptides. Mass spectrometry analysis of the leukocyte MHC-II peptidome revealed a series of β cell–derived peptides, with identical sequences to those previously identified in the islet MHC-II peptidome. Thus, the blood leukocyte peptidome echoes that found in islets and serves to identify immunogenic peptides in an otherwise inaccessible tissue.

Natural Protection From Type 1 Diabetes in NOD Mice Is Characterized by a Unique Pancreatic Islet Phenotype

The NOD mouse develops spontaneous type 1 diabetes, with some features of disease that are very similar to the human disease. However, a proportion of NOD mice are naturally protected from developing diabetes, and currently, studies characterizing this cohort are very limited. Here, using both immunofluorescence and multiparameter flow cytometry, we focus on the pancreatic islet morphology and immune infiltrate observed in naturally protected NOD mice. We show that naturally protected NOD mice are characterized by an increased frequency of insulin-containing, smaller-sized, pancreatic islets. Although mice remain diabetes free, florid immune infiltrate remains. However, this immune infiltrate is skewed toward a regulatory phenotype in both T- and B-cell compartments. Pancreatic islets have an increased frequency of IL-10-producing B cells and associated cell surface markers. Resident memory CD69⁺CD8⁺ T cells show a significant shift toward reduced CD103 expression, while CD4⁺ T cells have increased FoxP3⁺CTLA4⁺ expression. These data indicate that naturally protected NOD mice have a unique islet signature and provide new insight into regulatory mechanisms within pancreatic islets.

NOD Mice Recapitulate the Cardiac Disturbances Observed in Type 1 Diabetes

This work aimed at testing the hypothesis that NOD/ShiLtJ mice (NOD) recapitulate the cardiac disturbances observed on type 1 diabetes (T1D). NOD mice were studied 4 weeks after the onset of hyperglycemia, and NOR/Lt mice matched as control. Cardiac function was evaluated by echocardiography and electrocardiography (ECG). Action potentials (AP) and Ca2+ transients were evaluated at whole heart level. Heart mitochondrial function was evaluated by high-resolution respirometry and H2O2 release. NOD mice presented a reduction in hearth weight. Mitochondrial oxygen fluxes and H2O2 release were similar between NOD and NOR mice. ECG revealed a QJ interval prolongation in NOD mice. Furthermore, AP duration at 30% of repolarization was increased, and it depicted slower Ca2+ transient kinetics. NOD mice presented greater number/severity of ventricular arrhythmias both in vivo and in vitro. In conclusion, NOD mice evoked cardiac electrical and calcium handling disturbances similar to the observed in T1D. Graphical Abstract .

Evidence of genetic epistasis in autoimmune diabetes susceptibility revealed by mouse congenic sublines

Susceptibility to autoimmune diabetes is a complex genetic trait. Linkage analyses exploiting the NOD mouse, which spontaneously develops autoimmune diabetes, have proved to be a useful tool for the characterization of some of these traits. In a linkage analysis using 3A9 TCR transgenic mice on both B10.BR and NOD.H2^k backgrounds, we previously determined that both the Idd2 and Idd13 loci were linked to the proportion of immunoregulatory CD4^-CD8^- double negative (DN) T cells. In addition to Idd2 and Idd13, five other loci showed weak linkage to the proportion of DN T cells. Of interest, in an interim analysis, a locus on chromosome 12 is linked to DN T cell proportion in both the spleen and the lymph nodes. To determine the impact of this locus on DN T cells, we generated two congenic sublines, which we named Chr12P and Chr12D for proximal and distal, respectively. While 3A9 TCR:insHEL NOD.H2^k-Chr12D mice were protected from diabetes, 3A9 TCR:insHEL NOD.H2^k-Chr12P showed an increase in diabetes incidence. Yet, the proportion of DN T cells was similar to the parental 3A9 TCR NOD.H2^k strain for both of these congenic sublines. A genome-wide two dimensional LOD score analysis reveals genetic epistasis between chromosome 12 and the Idd13 locus. Altogether, this study identified further complex genetic interactions in defining the proportion of DN T cells, along with evidence of genetic epistasis within a locus on chromosome 12 influencing autoimmune susceptibility.

CD5 levels reveal distinct basal T-cell receptor signals in T cells from non-obese diabetic mice

Type 1 diabetes in non-obese diabetic (NOD) mice occurs when autoreactive T cells eliminate insulin producing pancreatic β cells. While extensively studied in T-cell receptor (TCR) transgenic mice, the contribution of alterations in thymic selection to the polyclonal T-cell pool in NOD mice is not yet resolved. The magnitude of signals downstream of TCR engagement with self-peptide directs the development of a functional T-cell pool, in part by ensuring tolerance to self. TCR interactions with self-peptide are also necessary for T-cell homeostasis in the peripheral lymphoid organs. To identify differences in TCR signal strength that accompany thymic selection and peripheral T-cell maintenance, we compared CD5 levels, a marker of basal TCR signal strength, on immature and mature T cells from autoimmune diabetes-prone NOD and -resistant B6 mice. The data suggest that there is no preferential selection of NOD thymocytes that perceive stronger TCR signals from self-peptide engagement. Instead, NOD mice have an MHC-dependent increase in CD4⁺ thymocytes and mature T cells that express lower levels of CD5. In contrast, T cell-intrinsic mechanisms lead to higher levels of CD5 on peripheral CD8⁺ T cells from NOD relative to B6 mice, suggesting that peripheral CD8⁺ T cells with higher basal TCR signals may have survival advantages in NOD mice. These differences in the T-cell pool in NOD mice may contribute to the development or progression of autoimmune diabetes.

Evolving Antibody Therapies for the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is widely considered to be a T cell driven autoimmune disease resulting in reduced insulin production due to dysfunction/destruction of pancreatic β cells. Currently, there continues to be a need for immunotherapies that selectively reestablish persistent β cell-specific self-tolerance for the prevention and remission of T1D in the clinic. The utilization of monoclonal antibodies (mAb) is one strategy to target specific immune cell populations inducing autoimmune-driven pathology. Several mAb have proven to be clinically safe and exhibit varying degrees of efficacy in modulating autoimmunity, including T1D. Traditionally, mAb therapies have been used to deplete a targeted cell population regardless of antigenic specificity. However, this treatment strategy can prove detrimental resulting in the loss of acquired protective immunity. Nondepleting mAb have also been applied to modulate the function of immune effector cells. Recent studies have begun to define novel mechanisms associated with mAb-based immunotherapy that alter the function of targeted effector cell pools. These results suggest short course mAb therapies may have persistent effects for regaining and maintaining self-tolerance. Furthermore, the flexibility to manipulate mAb properties permits the development of novel strategies to target multiple antigens and/or deliver therapeutic drugs by a single mAb molecule. Here, we discuss current and potential future therapeutic mAb treatment strategies for T1D, and T cell-mediated autoimmunity.

Single-cell RNA sequencing of murine islets shows high cellular complexity at all stages of autoimmune diabetes

Tissue-specific autoimmune diseases are driven by activation of diverse immune cells in the target organs. However, the molecular signatures of immune cell populations over time in an autoimmune process remain poorly defined. Using single-cell RNA sequencing, we performed an unbiased examination of diverse islet-infiltrating cells during autoimmune diabetes in the nonobese diabetic mouse. The data revealed a landscape of transcriptional heterogeneity across the lymphoid and myeloid compartments. Memory CD4 and cytotoxic CD8 T cells appeared early in islets, accompanied by regulatory cells with distinct phenotypes. Surprisingly, we observed a dramatic remodeling in the islet microenvironment, in which the resident macrophages underwent a stepwise activation program. This process resulted in polarization of the macrophage subpopulations into a terminal proinflammatory state. This study provides a single-cell atlas defining the staging of autoimmune diabetes and reveals that diabetic autoimmunity is driven by transcriptionally distinct cell populations specialized in divergent biological functions.

Continuous stimulation of dual-function peptide PGLP-1-VP inhibits the morbidity and mortality of NOD mice through anti-inflammation and immunoregulation

Multiple animal and human studies have shown that administration of GLP-1RA can enhance β-cell recovery, reduce insulin dosage, reduce HbA1c content in the blood, reduce the risk of hypoglycemia and reduce inflammation. In the NOD mouse model, peptide VP treatment can prevent and treat type 1 diabetes through immunomodulation. Therefore, we designed a new dual-functional PGLP-1-VP, which is expected to combine the anti-inflammatory effect of PGLP-1 and the immunomodulatory effect of VP peptide. In streptozotocin-induced hyperglycemic mice model, we demonstrated that PGLP-1-VP can act as a GLP-1R agonist to improve hyperglycemia and increase insulin sensitivity. In the NOD mouse model, PGLP-1-VP treatment reduced morbidity, mortality, and pancreatic inflammation, and showed superior effect to PGLP-1 or VP treatment alone, confirming that PGLP-1-VP may act as a dual-function peptide. PGLP-1-VP provided immunomodulatory effect through increasing Th2 cell percentage and balancing the ratio of Th2/Th1 in spleen and PLN, similar to P277 and VP. Additionally, PGLP-1-VP and PGLP-1 act the anti-inflammation by increasing Treg cells and TGF-β1 content like DPP-IV inhibitor. Taken together, our data shows that the dual-functional PGLP-1-VP reduces morbidity and mortality in the NOD model, suggesting a potential role in preventing and treating type 1 diabetes.

CDK11 Promotes Cytokine-Induced Apoptosis in Pancreatic Beta Cells Independently of Glucose Concentration and Is Regulated by Inflammation in the NOD Mouse Model

Background

Pancreatic islets are exposed to strong pro-apoptotic stimuli: inflammation and hyperglycemia, during the progression of the autoimmune diabetes (T1D). We found that the Cdk11(Cyclin Dependent Kinase 11) is downregulated by inflammation in the T1D prone NOD (non-obese diabetic) mouse model. The aim of this study is to determine the role of CDK11 in the pathogenesis of T1D and to assess the hierarchical relationship between CDK11 and Cyclin D3 in beta cell viability, since Cyclin D3, a natural ligand for CDK11, promotes beta cell viability and fitness in front of glucose.

Methods

We studied T1D pathogenesis in NOD mice hemideficient for CDK11 (N-HTZ), and, in N-HTZ deficient for Cyclin D3 (K11HTZ-D3KO), in comparison to their respective controls (N-WT and K11WT-D3KO). Moreover, we exposed pancreatic islets to either pro-inflammatory cytokines in the presence of increasing glucose concentrations, or Thapsigargin, an Endoplasmic Reticulum (ER)-stress inducing agent, and assessed apoptotic events. The expression of key ER-stress markers (Chop, Atf4 and Bip) was also determined.

Results

N-HTZ mice were significantly protected against T1D, and NS-HTZ pancreatic islets exhibited an impaired sensitivity to cytokine-induced apoptosis, regardless of glucose concentration. However, thapsigargin-induced apoptosis was not altered. Furthermore, CDK11 hemideficiency did not attenuate the exacerbation of T1D caused by Cyclin D3 deficiency.

Conclusions

This study is the first to report that CDK11 is repressed in T1D as a protection mechanism against inflammation-induced apoptosis and suggests that CDK11 lies upstream Cyclin D3 signaling. We unveil the CDK11/Cyclin D3 tandem as a new potential intervention target in T1D.

Auto-antigen and Immunomodulatory Agent-Based Approaches for Antigen-Specific Tolerance in NOD Mice

PURPOSE OF REVIEW

Type 1 diabetes (T1D) can be managed by insulin replacement, but it is still associated with an increased risk of microvascular/cardiovascular complications. There is considerable interest in antigen-specific approaches for treating T1D due to their potential for a favorable risk-benefit ratio relative to non-specific immune-based treatments. Here we review recent antigen-specific tolerance approaches using auto-antigen and/or immunomodulatory agents in NOD mice and provide insight into seemingly contradictory findings.

RECENT FINDINGS

Although delivery of auto-antigen alone can prevent T1D in NOD mice, this approach may be prone to inconsistent results and has not demonstrated an ability to reverse established T1D. Conversely, several approaches that promote presentation of auto-antigen in a tolerogenic context through cell/tissue targeting, delivery system properties, or the delivery of immunomodulatory agents have had success in reversing recent-onset T1D in NOD mice. While initial auto-antigen based approaches were unable to substantially influence T1D progression clinically, recent antigen-specific approaches have promising potential.

The Role of T Cell Receptor Signaling in the Development of Type 1 Diabetes

T cell receptor (TCR) signaling influences multiple aspects of CD4⁺ and CD8⁺ T cell immunobiology including thymic development, peripheral homeostasis, effector subset differentiation/function, and memory formation. Additional T cell signaling cues triggered by co-stimulatory molecules and cytokines also affect TCR signaling duration, as well as accessory pathways that further shape a T cell response. Type 1 diabetes (T1D) is a T cell-driven autoimmune disease targeting the insulin producing β cells in the pancreas. Evidence indicates that dysregulated TCR signaling events in T1D impact the efficacy of central and peripheral tolerance-inducing mechanisms. In this review, we will discuss how the strength and nature of TCR signaling events influence the development of self-reactive T cells and drive the progression of T1D through effects on T cell gene expression, lineage commitment, and maintenance of pathogenic anti-self T cell effector function.

Recombinant Lactococcus lactis Carrying IL-4 and IL-10 Coding Vectors Protects against Type 1 Diabetes in NOD Mice and Attenuates Insulitis in the STZ-Induced Model

Type 1 diabetes (T1D) is an autoimmune disease that culminates in beta cell destruction in the pancreas and, subsequently, deficiency in insulin production. Cytokines play a crucial role in the development of diabetes, orchestrating the recruitment and action of immune cells, to not only destroy insulin-producing cells but also preserve them. Therefore, the aim of this study was to investigate the effect of orally administered Lactococcus lactis MG1363 FnBPA+ strains carrying plasmids encoding IL-4 and IL-10 in the streptozotocin- (STZ-) induced diabetes model and in nonobese diabetic (NOD) mice. The STZ-induced mice that were treated with combined bacterial strains carrying plasmids encoding IL-4 and IL-10 showed lower incidence of diabetes and more preserved pancreatic islets than the mice that received the individual bacterial strains. Combined administration of L. lactis MG1363 FnBPA+ (pValac::dts::IL-4) and L. lactis MG1363 FnBPA+ (pValac::IL-10) resulted in protection against diabetes in NOD mice. It was shown that the combined treatment with recombinant bacterial by oral route prevented hyperglycemia and reduced the pancreatic islets-destruction in NOD mice. In addition, increased levels of IL-4 and IL-10 in serum and pancreatic tissue revealed a systemic effect of the treatment and also favored an anti-inflammatory microenvironment. Reduced concentrations of IL-12 in pancreas were essential to the regulation of inflammation, resulting in no incidence of diabetes in treated NOD mice. Normal levels of intestinal sIgA after long-term treatment with the L. lactis strains carrying plasmids encoding IL-4 and IL-10 indicate the development of oral tolerance and corroborate the use of this potent tool of mucosal delivery. For the first time, L. lactis MG1363 FnBPA+ strains carrying eukaryotic expression vectors encoding IL-4 and IL-10 are tested in STZ-induced and NOD mouse models. Therefore, our study demonstrates this innovative strategy provides immunomodulatory potential for further investigations in T1D and other autoimmune diseases.

Using gold nanoparticles for enhanced intradermal delivery of poorly soluble auto-antigenic peptides

Ultra-small 1-2 nm gold nanoparticles (NP) were conjugated with a poorly-soluble peptide auto-antigen, associated with type 1 diabetes, to modify the peptide pharmacokinetics, following its intradermal delivery. Peptide distribution was characterized, in vivo, after delivery using either conventional intradermal injection or a hollow microneedle device. The poorly-soluble peptide was effectively presented in distant lymph nodes (LN), spleen and draining LN when conjugated to the nanoparticles, whereas peptide alone was only presented in the draining LN. By contrast, nanoparticle conjugation to a highly-soluble peptide did not enhance in vivo distribution. Transfer of both free peptide and peptide-NPs from the skin to LN was reduced in mice lacking lymphoid homing receptor CCR7, suggesting that both are actively transported by migrating dendritic cells to LN. Collectively, these data demonstrate that intradermally administered ultra-small gold nanoparticles can widen the distribution of poorly-soluble auto-antigenic peptides to multiple lymphoid organs, thus enhancing their use as potential therapeutics.

Macrophage inflammatory state in Type 1 diabetes: triggered by NLRP3/iNOS pathway and attenuated by docosahexaenoic acid

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by insulin-producing pancreatic β-cell destruction and hyperglycemia. While monocytes and NOD-like receptor family-pyrin domain containing 3 (NLRP3) are associated with T1D onset and development, the specific receptors and factors involved in NLRP3 inflammasome activation remain unknown. Herein, we evaluated the inflammatory state of resident peritoneal macrophages (PMs) from genetically modified non-obese diabetic (NOD), NLRP3-KO, wild-type (WT) mice and in peripheral blood mononuclear cells (PBMCs) from human T1D patients. We also assessed the effect of docosahexaenoic acid (DHA) on the inflammatory status. Macrophages from STZ-induced T1D mice exhibited increased inflammatory cytokine/chemokine levels, nitric oxide (NO) secretion, NLRP3 and iNOS protein levels, and augmented glycolytic activity compared to control animals. In PMs from NOD and STZ-induced T1D mice, DHA reduced NO production and attenuated the inflammatory state. Furthermore, iNOS and IL-1β protein expression levels and NO production were lower in the PMs from diabetic NLRP3-KO mice than from WT mice. We also observed increased IL-1β secretion in PBMCs from T1D patients and immortalized murine macrophages treated with advanced glycation end products and palmitic acid. The present study demonstrated that the resident PMs are in a proinflammatory state characterized by increased NLRP3/iNOS pathway-mediated NO production, up-regulated proinflammatory cytokine/chemokine receptor expression and altered glycolytic activity. Notably, ex vivo treatment with DHA reverted the diabetes-induced changes and attenuated the macrophage inflammatory state. It is plausible that DHA supplementation could be employed as adjuvant therapy for treating individuals with T1D.

Pancreas Optical Clearing and 3-D Microscopy in Health and Diabetes

Although first described over a hundred years ago, tissue optical clearing is undergoing renewed interest due to numerous advances in optical clearing methods, microscopy systems, and three-dimensional (3-D) image analysis programs. These advances are advantageous for intact mouse tissues or pieces of human tissues because samples sized several millimeters can be studied. Optical clearing methods are particularly useful for studies of the neuroanatomy of the central and peripheral nervous systems and tissue vasculature or lymphatic system. Using examples from solvent- and aqueous-based optical clearing methods, the mouse and human pancreatic structures and networks will be reviewed in 3-D for neuro-insular complexes, parasympathetic ganglia, and adipocyte infiltration as well as lymphatics in diabetes. Optical clearing with multiplex immunofluorescence microscopy provides new opportunities to examine the role of the nervous and circulatory systems in pancreatic and islet functions by defining their neurovascular anatomy in health and diabetes.

Mouse Models of Sjögren's Syndrome with Ocular Surface Disease

Sjögren’s syndrome (SS) is a systemic rheumatic disease that predominantly affects salivary and lacrimal glands resulting in oral and ocular dryness, respectively, referred to as sicca symptoms. The clinical presentation of ocular dryness includes keratoconjunctivitis sicca (KCS), resulting from the inflammatory damage to the ocular surface tissues of cornea and conjunctiva. The diagnostic evaluation of KCS is a critical component of the classification criteria used by clinicians worldwide to confirm SS diagnosis. Therapeutic management of SS requires both topical and systemic treatments. Several mouse models of SS have contributed to our current understanding of immunopathologic mechanisms underlying the disease. This information also helps develop novel therapeutic interventions. Although these models address glandular aspects of SS pathology, their impact on ocular surface tissues is addressed only in a few models such as thrombospondin (TSP)-1 deficient, C57BL/6.NOD.Aec1Aec2, NOD.H2^b, NOD.Aire KO, and IL-2Rα (CD25) KO mice. While corneal and/or conjunctival damage is reported in most of these models, the characteristic SS specific autoantibodies are only reported in the TSP-1 deficient mouse model, which is also validated as a preclinical model. This review summarizes valuable insights provided by investigations on the ocular spectrum of the SS pathology in these models.

Obesity-associated microbiota contributes to mucus layer defects in genetically obese mice

The intestinal mucus layer is a physical barrier separating the tremendous number of gut bacteria from the host epithelium. Defects in the mucus layer have been linked to metabolic diseases, but previous studies predominantly investigated mucus function during high-caloric/low-fiber dietary interventions, thus making it difficult to separate effects mediated directly through diet quality from potential obesity-dependent effects. As such, we decided to examine mucus function in mouse models with metabolic disease to distinguish these factors. Here we show that, in contrast to their lean littermates, genetically obese (ob/ob) mice have a defective inner colonic mucus layer that is characterized by increased penetrability and a reduced mucus growth rate. Exploiting the coprophagic behavior of mice, we next co-housed ob/ob and lean mice to investigate if the gut microbiota contributed to these phenotypes. Co-housing rescued the defect of the mucus growth rate, whereas mucus penetrability displayed an intermediate phenotype in both mouse groups. Of note, non-obese diabetic mice with high blood glucose levels displayed a healthy colonic mucus barrier, indicating that the mucus defect is obesity- rather than glucose-mediated. Thus, our data suggest that the gut microbiota community of obesity-prone mice may regulate obesity-associated defects in the colonic mucosal barrier, even in the presence of dietary fiber.

A biomimetic five-module chimeric antigen receptor (5MCAR) designed to target and eliminate antigen-specific T cells

T cells express clonotypic T cell receptors (TCRs) that recognize peptide antigens in the context of class I or II MHC molecules (pMHCI/II). These receptor modules associate with three signaling modules (CD3γε, δε, and ζζ) and work in concert with a coreceptor module (either CD8 or CD4) to drive T cell activation in response to pMHCI/II. Here, we describe a first-generation biomimetic five-module chimeric antigen receptor (^5MCAR). We show that 1) chimeric receptor modules built with the ectodomains of pMHCII assemble with CD3 signaling modules into complexes that redirect cytotoxic T lymphocyte (CTL) specificity and function in response to the clonotypic TCRs of pMHCII-specific CD4⁺ T cells, and 2) surrogate coreceptor modules enhance the function of these complexes. Furthermore, we demonstrate that adoptively transferred ^5MCAR-CTLs can mitigate type I diabetes by targeting autoimmune CD4⁺ T cells in NOD mice. This work provides a framework for the construction of biomimetic ^5MCARs that can be used as tools to study the impact of particular antigen-specific T cells in immune responses, and may hold potential for ameliorating diseases mediated by pathogenic T cells.

Combination Treatment with Antigen-Specific Dual-Sized Microparticle System Plus Anti-CD3 Immunotherapy Fails to Synergize to Improve Late-Stage Type 1 Diabetes Prevention in Nonobese Diabetic Mice

Type 1 diabetes (T1D) pathophysiology, while incompletely understood, has in part been attributed to aberrant presentation of self-antigen plus proinflammatory costimulation by professional antigen-presenting cells (APCs). Therapies targeting dendritic cells (DCs) offer an avenue to restore antigen-specific tolerance by promoting presentation of self-antigen in an anti-inflammatory or suppressive context. Here, we describe a subcutaneously administered, dual-sized biodegradable microparticle (MP) platform that includes phagocytosable (∼1 μm) and nonphagocytosable (∼30 μm) MPs to deliver pro-tolerogenic factors both intra- and extracellularly, as well as the T1D-associated autoantigen, insulin, to DCs for amelioration of autoimmunity. This MP platform resulted in increased recruitment of DCs, suppressive skewing of DC phenotype with diminished expression of CD86 and MHC-II, increased regulatory T cell (Treg) frequency, and upregulated expression of the checkpoint inhibitor programmed cell death protein 1 (PD-1) on T cells. When administered concomitantly with anti-CD3 antibody, which provides transient T cell depletion while preserving Treg populations, in 12-week-old nonobese diabetic (NOD) mice, regulatory immune populations persisted out to 20 weeks of age; however, combination anti-CD3 and dual-sized MP (dMP) therapy failed to synergistically inhibit diabetes onset.

Investigation of type 1 diabetes in NOD mice knockout for the osteopontin gene

OBJECTIVE

Type 1 diabetes onset is preceded by a pre-inflammatory stage leading to insulitis and followed by targeted destruction of the insulin-producing beta cells of the pancreas. Osteopontin (OPN) is a secreted phosphoprotein with cytokine properties, implicated in many physiological and pathological processes, including infection and autoimmunity. We have previously identified up-regulated osteopontin transcripts in the pancreatic lymph nodes of the NOD (Non-Obese Diabetic) mouse at the pre-diabetic stages. Investigating the underlined disease initiating mechanisms may well contribute to the development of novel preventive therapies. Our aim was to construct opn null mice in a NOD autoimmune-prone genetic background and address the pathogenic or protective role of the osteopontin molecule in the early stages of type 1 diabetes.

METHODS

We generated opn null mutant mice in a NOD genetic background by serial backcrossing to the existing C57BL/6 opn knockout strain. The presence of opn wild type or null alleles in the congenic lines was evaluated by PCR amplification. We used NOD opn-null mice to assess the phenotypic evolution of type 1 diabetes. The presence of OPN in the serum was evaluated by ELISA and by immunostaining on the mouse tissues. The primary gene structure of the NOD opn encoding gene and protein sequences were compared to the known alleles of other mouse strains. Evaluation of Single Nucleotide Polymorphisms (SNPs) variation between opn alleles of the opn gene is reported.

RESULTS

In the absence of OPN, type 1 diabetes is accelerated, suggesting a protective role of this cytokine on the insulin-producing cells of the pancreatic islets. Conversely, in the presence of the opn gene, an increase of the OPN protein in the serum of young NOD mice indicates that this molecule might be involved in the immune regulatory events taking place at early stages, prior to disease onset. Our data support that OPN acts as a positive regulator of the early islet autoimmune damage, possibly by a shift of the steady-state of T1D pathogenesis. We report that the OPN protein structure of the NOD/ShiLtJ strain corresponds to the a-type allele of the osteopontin gene. Comparative analysis of the single nucleotide polymorphisms between the a-type and b-type alleles indicates that the majority of variations are within the non-coding regions of the gene.

CONCLUSIONS

The construction of opn null mice in an autoimmune genetic background (NOD.B6.Cg-spp1^-/-) provides important tools for the study of the implication of the OPN in type 1 diabetes, offering the possibility to address the significance of this molecule as an early marker of the disease and as a therapeutic agent in preclinical studies.

ICOS+ Tregs: A Functional Subset of Tregs in Immune Diseases

Recent studies have reported the pathological effect of ICOS⁺ T cells, but ICOS signals also widely participate in anti-inflammatory responses, particularly ICOS⁺ regulatory T (Treg) cells. The ICOS signaling pathway endows Tregs with increased generation, proliferation, and survival abilities. Furthermore, there is enough evidence to suggest a superior capacity of ICOS⁺ Tregs, which is partly attributable to IL-10 induced by ICOS, yet the associated mechanism needs further investigation. In this review, we discuss the complicated role of ICOS⁺ Tregs in several classical autoimmune diseases, allergic diseases, and cancers and investigate the related therapeutic applications in these diseases. Moreover, we identify ICOS as a potential biomarker for disease treatment and prognostic prediction. In addition, we believe that anti-ICOS/ICOSL monoclonal antibodies exhibit excellent clinical application potential. A thorough understanding of the effect of ICOS⁺ Tregs and the holistic role of ICOS toward the immune system will help to improve the therapeutic schedule of diseases.

Lipid mediators and biomarkers associated with type 1 diabetes development

Type 1 diabetes (T1D) is a consequence of autoimmune β cell destruction, but the role of lipids in this process is unknown. We previously reported that activation of Ca2+-independent phospholipase A2β (iPLA2β) modulates polarization of macrophages (MΦ). Hydrolysis of the sn-2 substituent of glycerophospholipids by iPLA2β can lead to the generation of oxidized lipids (eicosanoids), pro- and antiinflammatory, which can initiate and amplify immune responses triggering β cell death. As MΦ are early triggers of immune responses in islets, we examined the impact of iPLA2β-derived lipids (iDLs) in spontaneous-T1D prone nonobese diabetic mice (NOD), in the context of MΦ production and plasma abundances of eicosanoids and sphingolipids. We find that (a) MΦNOD exhibit a proinflammatory lipid landscape during the prediabetic phase; (b) early inhibition or genetic reduction of iPLA2β reduces production of select proinflammatory lipids, promotes antiinflammatory MΦ phenotype, and reduces T1D incidence; (c) such lipid changes are reflected in NOD plasma during the prediabetic phase and at T1D onset; and (d) importantly, similar lipid signatures are evidenced in plasma of human subjects at high risk for developing T1D. These findings suggest that iDLs contribute to T1D onset and identify select lipids that could be targeted for therapeutics and, in conjunction with autoantibodies, serve as early biomarkers of pre-T1D.

Premature Activation of Immune Transcription Programs in Autoimmune-Predisposed Mouse Embryonic Stem Cells and Blastocysts

Autoimmune diabetes is a complex multifactorial disease with genetic and environmental factors playing pivotal roles. While many genes associated with the risk of diabetes have been identified to date, the mechanisms by which external triggers contribute to the genetic predisposition remain unclear. Here, we derived embryonic stem (ES) cell lines from diabetes-prone non-obese diabetic (NOD) and healthy C57BL/6 (B6) mice. While overall pluripotency markers were indistinguishable between newly derived NOD and B6 ES cells, we discovered several differentially expressed genes that normally are not expressed in ES cells. Several genes that reside in previously identified insulin-dependent diabetics (Idd) genomic regions were up-regulated in NOD ES cells. Gene set enrichment analysis showed that different groups of genes associated with immune functions are differentially expressed in NOD. Transcriptomic analysis of NOD blastocysts validated several differentially overexpressed Idd genes compared to B6. Genome-wide mapping of active histone modifications using ChIP-Seq supports active expression as the promoters and enhancers of activated genes are also marked by active histone modifications. We have also found that NOD ES cells secrete more inflammatory cytokines. Our data suggest that the known genetic predisposition of NOD to autoimmune diabetes leads to epigenetic instability of several Idd regions.

Dextran Sulfate Protects Pancreatic β-Cells, Reduces Autoimmunity, and Ameliorates Type 1 Diabetes

A failure in self-tolerance leads to autoimmune destruction of pancreatic β-cells and type 1 diabetes (T1D). Low-molecular-weight dextran sulfate (DS) is a sulfated semisynthetic polysaccharide with demonstrated cytoprotective and immunomodulatory properties in vitro. However, whether DS can protect pancreatic β-cells, reduce autoimmunity, and ameliorate T1D is unknown. In this study, we report that DS, but not dextran, protects human β-cells against cytokine-mediated cytotoxicity in vitro. DS also protects mitochondrial function and glucose-stimulated insulin secretion and reduces chemokine expression in human islets in a proinflammatory environment. Interestingly, daily treatment with DS significantly reduces diabetes incidence in prediabetic NOD mice and, most importantly, reverses diabetes in early-onset diabetic NOD mice. DS decreases β-cell death, enhances islet heparan sulfate (HS)/HS proteoglycan expression, and preserves β-cell mass and plasma insulin in these mice. DS administration also increases the expression of the inhibitory costimulatory molecule programmed death-1 (PD-1) in T cells, reduces interferon-γ⁺CD4⁺ and CD8⁺ T cells, and enhances the number of FoxP3⁺ cells. Collectively, these studies demonstrate that the action of one single molecule, DS, on β-cell protection, extracellular matrix preservation, and immunomodulation can reverse diabetes in NOD mice, highlighting its therapeutic potential for the treatment of T1D.

The role of beta-cell dysfunction in early type 1 diabetes

PURPOSE OF REVIEW

Emerging data have suggested that β-cell dysfunction may exacerbate the development and progression of type 1 diabetes (T1D). In this review, we highlight clinical and preclinical studies suggesting a role for β-cell dysfunction during the evolution of T1D and suggest agents that may promote β-cell health in T1D.

RECENT FINDINGS

Metabolic abnormalities exist years before development of hyperglycemia and exhibit a reproducible pattern reflecting progressive deterioration of β-cell function and increases in β-cell stress and death. Preclinical studies indicate that T1D may be prevented by modification of pathways impacting intrinsic β-cell stress and antigen presentation. Recent findings suggest that differences in metabolic phenotypes and β-cell stress may reflect differing endotypes of T1D. Multiple pathways representing potential drug targets have been identified, but most remain to be tested in human populations with preclinical disease.

SUMMARY

This cumulative body of work shows clear evidence that β-cell stress, dysfunction, and death are harbingers of impending T1D and likely contribute to progression of disease and insulin deficiency. Treatment with agents targeting β-cell health could augment interventions with immunomodulatory therapies but will need to be tested in intervention studies with endpoints carefully designed to capture changes in β-cell function and health.

Gut Microbiota Regulation of T Cells During Inflammation and Autoimmunity

The intestinal microbiota plays a crucial role in influencing the development of host immunity, and in turn the immune system also acts to regulate the microbiota through intestinal barrier maintenance and immune exclusion. Normally, these interactions are homeostatic, tightly controlled, and organized by both innate and adaptive immune responses. However, a combination of environmental exposures and genetic defects can result in a break in tolerance and intestinal homeostasis. The outcomes of these interactions at the mucosal interface have broad, systemic effects on host immunity and the development of chronic inflammatory or autoimmune disease. The underlying mechanisms and pathways the microbiota can utilize to regulate these diseases are just starting to emerge. Here, we discuss the recent evidence in this area describing the impact of microbiota-immune interactions during inflammation and autoimmunity, with a focus on barrier function and CD4⁺ T cell regulation.

Allograft inflammatory factor-1 in myeloid cells drives autoimmunity in type 1 diabetes

Allograft inflammatory factor-1 (AIF1) is a calcium-responsive cytoplasmic scaffold protein that directs hematopoiesis and immune responses within dendritic cells (DC) and macrophages. Although the role of AIF1 in transplant rejection and rheumatoid arthritis has been explored, little is known about its role in type 1 diabetes. Here, we show that in vivo silencing of AIF1 in NOD mice restrained infiltration of immune cells into the pancreas and inhibited diabetes incidence. Analyses of FACS-sorted CD45neg nonleukocyte populations from resected pancreatic islets showed markedly higher expression of insulin in the AIF1-silenced groups. Evaluation of CD45+ leukocytes revealed diminished infiltration of effector T cells and DC in the absence of AIF1. Transcriptional profiling further revealed a marked decrease in cDC1 DC-associated genes CD103, BATF3, and IRF8, which are required for orchestrating polarized type 1 immunity. Reduced T cell numbers within the islets were observed, with concomitant lower levels of IFN-γ and T-bet in AIF1-silenced cohorts. In turn, there was a reciprocal increase in functionally suppressive pancreas-resident CD25+Foxp3+CD4+ Tregs. Taken together, results show that AIF1 expression in myeloid cells plays a pivotal role in promoting type 1 diabetes and that its suppression restrains insulitis by shifting the immune microenvironment toward tolerance.

Immune checkpoint inhibitor diabetes mellitus: a novel form of autoimmune diabetes

Autoimmune diabetes mellitus is a rare but significant side effect of treatment with immune checkpoint inhibitors. Immune checkpoint inhibitor-induced diabetes mellitus (CPI-DM) is characterized by acute onset of dramatic hyperglycemia with severe insulin deficiency and occurrence following exposure to programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) inhibitors rather than cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) inhibitors. As a growing number of patients undergo immunotherapy, further understanding of the characteristics of CPI-DM patients is needed for improved prognostic and diagnostic application in order to reduce overall morbidity for this already at-risk population. Additionally, understanding of the features and mechanisms of CPI-DM may contribute to understanding mechanisms of spontaneous type I diabetes mellitus (T1DM). Here, we summarize the clinical features of CPI-DM and interrogate the genetic and cellular mechanisms that may contribute to the disease, as well as the clinical challenges for predicting and treating these patients as increasing cancer immunotherapies reach clinical utility.

miR-216a-targeting theranostic nanoparticles promote proliferation of insulin-secreting cells in type 1 diabetes animal model

Aberrant expression of miRNAs in pancreatic islets is closely related to the development of type 1 diabetes (T1D). The aim of this study was to identify key miRNAs dysregulated in pancreatic islets during T1D progression and to develop a theranostic approach to modify their expression using an MRI-based nanodrug consisting of iron oxide nanoparticles conjugated to miRNA-targeting oligonucleotides in a mouse model of T1D. Isolated pancreatic islets were derived from NOD mice of three distinct age groups (3, 8 and 18-week-old). Total RNA collected from cultured islets was purified and global miRNA profiling was performed with 3D-Gene global miRNA microarray mouse chips encompassing all mouse miRNAs available on the Sanger miRBase V16. Of the miRNAs that were found to be differentially expressed across three age groups, we identified one candidate (miR-216a) implicated in beta cell proliferation for subsequent validation by RT-PCR. Alterations in miR-216a expression within pancreatic beta cells were also examined using in situ hybridization on the frozen pancreatic sections. For in vitro studies, miR-216a mimics/inhibitors were conjugated to iron oxide nanoparticles and incubated with beta cell line, βTC-6. Cell proliferation marker Ki67 was evaluated. Expression of the phosphatase and tensin homolog (PTEN), which is one of the direct targets of miR-216a, was analyzed using western blot. For in vivo study, the miR-216a mimics/inhibitors conjugated to the nanoparticles were injected into 12-week-old female diabetic Balb/c mice via pancreatic duct. The delivery of the nanodrug was monitored by in vivo MRI. Blood glucose of the treated mice was monitored post injection. Ex vivo histological analysis of the pancreatic sections included staining for insulin, PTEN and Ki67. miRNA microarray demonstrated that the expression of miR-216a in the islets from NOD mice significantly changed during T1D progression. In vitro studies showed that treatment with a miR-216a inhibitor nanodrug suppressed proliferation of beta cells and increased the expression of PTEN, a miR-216a target. In contrast, introduction of a mimic nanodrug decreased PTEN expression and increased beta cell proliferation. Animals treated in vivo with a mimic nanodrug had higher insulin-producing functionality compared to controls. These observations were in line with downregulation of PTEN and increase in beta cell proliferation in that group. Our studies demonstrated that miR-216a could serve as a potential therapeutic target for the treatment of diabetes. miR-216a-targeting theranostic nanodrugs served as exploratory tools to define functionality of this miRNA in conjunction with in vivo MR imaging.

Butyrate Ameliorates Antibiotic-Driven Type 1 Diabetes in the Female Offspring of Nonobese Diabetic Mice

Maternal gut dysbiosis affects the development of the offspring immune system. Our previous study has indicated that microbial metabolite butyrate directly shapes pancreatic immune tolerance and dampens type 1 diabetes (T1D) progression. Therefore, maternal butyrate intervention may protect their offspring from maternal gut dysbiosis-accelerated T1D. To test this, pregnant nonobese diabetic (NOD) mice were treated with vancomycin in drinking water with or without a butyrate-supplemented diet during gestation and nursing (oral vancomycin is used to induce maternal gut dysbiosis). Three weeks after delivery, T1D-associated innate and adaptive immune cells were detected to investigate the effects of butyrate on the vancomycin-exacerbated pancreatic immune disorder in dams and pups. The results showed that butyrate inhibited maternal vancomycin-exacerbated secretion of proinflammation cytokines (interferon γ and interleukin-1β) and maternal vancomycin-exacerbated recruitment of interferon γ⁺ T cells (cytotoxic T lymphocytes 1 cells and T helper type 1 cells) in the pancreas of the female offspring, thus dampening T1D development. The protection may be due to butyrate inhibiting the activation of pancreatic dendritic cells (DCs). Our data thus demonstrate that maternal gut dysbiosis can exacerbate pancreatic-directed autoimmunity in the female offspring through T cell- and DC-associated mechanisms that are inhibited by butyrate.

Pancreatic islets seeded in a novel bioscaffold forms an organoid to rescue insulin production and reverse hyperglycemia in models of type 1 diabetes

Therapeutic approaches to combat type 1 diabetes (T1D) include donor pancreas transplantation, exogenous insulin administration and immunosuppressive therapies. However, these clinical applications are limited due to insufficient tissue compatible donors, side effects of exogenous insulin administration and/or increased onset of opportunistic infections attributable to induced global immunosuppression. An alternative approach to alleviate disease states is to utilize insulin-producing pancreatic islets seeded in a bioscaffold for implantation into diabetic recipients. The present studies now report that a newly developed cationic polymer biomaterial serves as an efficient bioscaffold for delivery of donor syngeneic pancreatic islet cells to reverse hyperglycemia in murine streptozotocin induced- or non-obese diabetic mouse models of T1D. Intraperitoneal implantation of pancreatic islets seeded within the copolymer bioscaffold supports long-term cell viability, response to extracellular signaling cues and ability to produce soluble factors into the microenvironment. Elevated insulin levels were measured in recipient diabetic mice upon implantation of the islet-seeded biomaterial coupled with reduced blood glucose levels, collectively resulting in increased survival and stabilization of metabolic indices. Importantly, the implanted islet-seeded biomaterial assembled into a solid organoid substructure that reorganized the extracellular matrix compartment and recruited endothelial progenitors for neovascularization. This allowed survival of the graft long-term in vivo and access to the blood for monitoring glucose levels. These results highlight the novelty, simplicity and effectiveness of this biomaterial for tissue regeneration and in vivo restoration of organ functions.

A Hybrid Insulin Epitope Maintains High 2D Affinity for Diabetogenic T Cells in the Periphery

β-Cell antigen recognition by autoreactive T cells is essential in type 1 diabetes (T1D) pathogenesis. Recently, insulin hybrid peptides (HIPs) were identified as strong agonists for CD4 diabetogenic T cells. Here, using BDC2.5 transgenic and NOD mice, we investigated T-cell recognition of the HIP2.5 epitope, which is a fusion of insulin C-peptide and chromogranin A (ChgA) fragments, and compared it with the WE14 and ChgA_{29 -42} epitopes. We measured in situ two-dimensional affinity on individual live T cells from thymus, spleen, pancreatic lymph nodes, and islets before and after diabetes. Although preselection BDC2.5 thymocytes possess higher affinity than splenic BDC2.5 T cells for all three epitopes, peripheral splenic T cells maintained high affinity only to the HIP2.5 epitope. In polyclonal NOD mice, a high frequency (∼40%) of HIP2.5-specific islet T cells were identified at both prediabetic and diabetic stages comprising two distinct high- and low-affinity populations that differed in affinity by 100-fold. This high frequency of high- and low-affinity HIP2.5 T cells in the islets potentially represents a major risk factor in diabetes pathogenesis.

Regulation of B cell homeostasis by Ptpn22 contributes to type 1 diabetes in NOD mice

PURPOSE

A coding variant in PTPN22 (C1858T) is one of the most important genetic risk factors in type 1 diabetes (T1D). The role of the PTPN22 risk allele in B cells is still incompletely understood and has not been investigated directly in T1D. This study aimed to explore the role of PTPN22 in the homeostasis of B cells and its influence in T1D.

METHODS

Wild-type (WT) and Ptpn22 inducible knockdown (KD) NOD mice were treated with 200 μg/ml doxycycline at the age of 10 weeks for 1-2 months. B cell compositions in the bone marrow, peritoneal cavity and spleen were examined. The pathogenicity of Ptpn22 KD B cells was explored by adoptive cell transfer.

RESULTS

Ptpn22 silencing increased the frequency of recirculating mature B cells in the bone marrow, decreased the frequency of B-1a cells in the peritoneal cavity and suppressed the formation of marginal zone B cells and plasma cells in the spleen. Changes in the composition of the peripheral B cell compartment caused by altered cell proliferation while rates of apoptosis were not affected. Significantly, co-transfer of Ptpn22 KD B cells with NY8.3 diabetogenic T cells diminished the frequency of diabetes in recipient NOD.scid mice compared with co-transfer of WT B cells.

CONCLUSIONS

Our study constitutes the first functional study of Ptpn22 in B cells in NOD mice. Our findings suggest that Ptpn22 variation contributes to T1D by modifying the B cell compartment and support a gain-of-function for the PTPN22 disease variant.

Genetic Variation in Type 1 Diabetes Reconfigures the 3D Chromatin Organization of T Cells and Alters Gene Expression

Genetics is a major determinant of susceptibility to autoimmune disorders. Here, we examined whether genome organization provides resilience or susceptibility to sequence variations, and how this would contribute to the molecular etiology of an autoimmune disease. We generated high-resolution maps of linear and 3D genome organization in thymocytes of NOD mice, a model of type 1 diabetes (T1D), and the diabetes-resistant C57BL/6 mice. Multi-enhancer interactions formed at genomic regions harboring genes with prominent roles in T cell development in both strains. However, diabetes risk-conferring loci coalesced enhancers and promoters in NOD, but not C57BL/6 thymocytes. 3D genome mapping of NODxC57BL/6 F1 thymocytes revealed that genomic misfolding in NOD mice is mediated in cis. Moreover, immune cells infiltrating the pancreas of humans with T1D exhibited increased expression of genes located on misfolded loci in mice. Thus, genetic variation leads to altered 3D chromatin architecture and associated changes in gene expression that may underlie autoimmune pathology.

Tissue-specific autoimmunity controlled by Aire in thymic and peripheral tolerance mechanisms

Tissue-specific autoimmune diseases are assumed to arise through malfunction of two checkpoints for immune tolerance: defective elimination of autoreactive T cells in the thymus and activation of these T cells by corresponding autoantigens in the periphery. However, evidence for this model and the outcome of such alterations in each or both of the tolerance mechanisms have not been sufficiently investigated. We studied these issues by expressing human AIRE (huAIRE) as a modifier of tolerance function in NOD mice wherein the defects of thymic and peripheral tolerance together cause type I diabetes (T1D). Additive huAIRE expression in the thymic stroma had no major impact on the production of diabetogenic T cells in the thymus. In contrast, huAIRE expression in peripheral antigen-presenting cells (APCs) rendered the mice resistant to T1D, while maintaining other tissue-specific autoimmune responses and antibody production against an exogenous protein antigen, because of the loss of Xcr1+ dendritic cells, an essential component for activating diabetogenic T cells in the periphery. These results contrast with our recent demonstration that huAIRE expression in both the thymic stroma and peripheral APCs resulted in the paradoxical development of muscle-specific autoimmunity. Our results reveal that tissue-specific autoimmunity is differentially controlled by a combination of thymic function and peripheral tolerance, which can be manipulated by expression of huAIRE/Aire in each or both of the tolerance mechanisms.

Comprehensive Proteomics Analysis of Stressed Human Islets Identifies GDF15 as a Target for Type 1 Diabetes Intervention

Type 1 diabetes (T1D) results from the progressive loss of β cells, a process propagated by pro-inflammatory cytokine signaling that disrupts the balance between pro- and anti-apoptotic proteins. To identify proteins involved in this process, we performed comprehensive proteomics of human pancreatic islets treated with interleukin-1β and interferon-γ, leading to the identification of 11,324 proteins, of which 387 were significantly regulated by treatment. We then tested the function of growth/differentiation factor 15 (GDF15), which was repressed by the treatment. We found that GDF15 translation was blocked during inflammation, and it was depleted in islets from individuals with T1D. The addition of exogenous GDF15 inhibited interleukin-1β+interferon-γ-induced apoptosis of human islets. Administration of GDF15 reduced by 53% the incidence of diabetes in NOD mice. Our approach provides a unique resource for the identification of the human islet proteins regulated by cytokines and was effective in discovering a potential target for T1D therapy.

Type 1 diabetes pathogenesis and the role of inhibitory receptors in islet tolerance

Type 1 diabetes (T1D) affects over a million Americans, and disease incidence is on the rise. Despite decades of research, there is still no cure for this disease. Exciting beta cell replacement strategies are being developed, but in order for such approaches to work, targeted immunotherapies must be designed. To selectively halt the autoimmune response, researchers must first understand how this response is regulated and which tolerance checkpoints fail during T1D development. Herein, we discuss the current understanding of T1D pathogenesis in humans, genetic and environmental risk factors, presumed roles of CD4+ and CD8+ T cells as well as B cells, and implicated autoantigens. We also highlight studies in non-obese diabetic mice that have demonstrated the requirement for CD4+ and CD8+ T cells and B cells in driving T1D pathology. We present an overview of central and peripheral tolerance mechanisms and comment on existing controversies in the field regarding central tolerance. Finally, we discuss T cell- and B cell-intrinsic tolerance mechanisms, with an emphasis on the roles of inhibitory receptors in maintaining islet tolerance in humans and in diabetes-prone mice, and strategies employed to date to harness inhibitory receptor signaling to prevent or reverse T1D.

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.

New Frontiers in the Treatment of Type 1 Diabetes

Type 1 diabetes is an autoimmune disease caused by the immune-mediated destruction of pancreatic β cells that results in lifelong absolute insulin deficiency. For nearly a century, insulin replacement has been the only therapy for most people living with this disease. Recent advances in technology and our understanding of β cell development, glucose metabolism, and the underlying immune pathogenesis of the disease have led to innovative therapeutic and preventative approaches. A paradigm shift in immunotherapy development toward the targeting of islet-specific immune pathways involved in tolerance has driven the development of therapies that may allow for the prevention or reversal of this disease while avoiding toxicities associated with historical approaches that were broadly immunosuppressive. In this review, we discuss successes, failures, and emerging pharmacological therapies for type 1 diabetes that are changing how we approach this disease, from improving glycemic control to developing the "holy grail" of disease prevention.

Mouse Models of Autoimmune Diabetes: The Nonobese Diabetic (NOD) Mouse

There are now a number of different mouse models for type 1 diabetes. The best known is the nonobese diabetic (NOD) mouse which has a genetic susceptibility to autoimmune diabetes with some features that are similar to human type 1 diabetes. The mice also have a propensity to other autoimmune diatheses, including autoimmune thyroid disease and sialadenitis. In addition, it is well known that environmental factors affect the incidence of disease in these mice. While there are other rodent models, including numerous transgenic and knockout models, as well as those that express human proteins, none of these develop spontaneous diabetes over a period of time, when the natural history can be studied. We focus here on the unmanipulated NOD mouse and discuss features of the husbandry and investigation of the mice that allow for use of these long-studied mice in the pathogenesis of an autoimmune type of diabetes.

Dendritic cells license regulatory B cells to produce IL-10 and mediate suppression of antigen-specific CD8 T cells

Regulatory B cells (Bregs) suppress and reduce autoimmune pathology. However, given the variety of Breg subsets, the role of Bregs in the pathogenesis of type 1 diabetes is still unclear. Here, we dissect this fundamental mechanism. We show that natural protection from type 1 diabetes in nonobese diabetic (NOD) mice is associated with increased numbers of IL-10-producing B cells, while development of type 1 diabetes in NOD mice occurs in animals with compromised IL-10 production by B cells. However, B cells from diabetic mice regain IL-10 function if activated by the innate immune receptor TLR4 and can suppress insulin-specific CD8 T cells in a dendritic cell (DC)-dependent, IL-10-mediated fashion. Suppression of CD8 T cells is reliant on B-cell contact with DCs. This cell contact results in deactivation of DCs, inducing a tolerogenic state, which in turn can regulate pathogenic CD8 T cells. Our findings emphasize the importance of DC-Breg interactions during the development of type 1 diabetes.

Soluble CD137 Ameliorates Acute Type 1 Diabetes by Inducing T Cell Anergy

We show here that soluble CD137 (sCD137), the alternately spliced gene product of Tnfsfr9, effectively treats acute type 1 diabetes (T1D) in nonobese diabetic (NOD) mice. sCD137 significantly delayed development of end-stage disease, preserved insulin+ islet beta cells, and prevented progression to end-stage T1D in some mice. We demonstrate that sCD137 induces CD4+ T cell anergy, suppressing antigen-specific T cell proliferation and IL-2/IFN-γ secretion. Exogenous IL-2 reversed the sCD137 anergy effect. sCD137 greatly reduces inflammatory cytokine production by CD8 effector memory T cells, critical mediators of beta cell damage. We demonstrate that human T1D patients have decreased serum sCD137 compared to age-matched controls (as do NOD mice compared to NOD congenic mice expressing a protective Tnfsfr9 allele), that human sCD137 is secreted by regulatory T cells (Tregs; as in mice), and that human sCD137 induces T cell suppression in human T cells. These findings provide a rationale for further investigation of sCD137 as a treatment for T1D and other T cell-mediated autoimmune diseases.

IL-21 regulates SOCS1 expression in autoreactive CD8+ T cells but is not required for acquisition of CTL activity in the islets of non-obese diabetic mice

In type 1 diabetes, maturation of activated autoreactive CD8⁺ T cells to fully armed effector cytotoxic T lymphocytes (CTL) occurs within the islet. At present the signals required for the maturation process are poorly defined. Cytokines could potentially provide the necessary "third signal" required to generate fully mature CTL capable of killing insulin-producing β-cells. To determine whether autoreactive CTL within islets respond to cytokines we generated non-obese diabetic (NOD) mice with a reporter for cytokine signalling. These mice express a reporter gene, hCD4, under the control of the endogenous regulatory elements for suppressor of cytokine signalling (SOCS)1, which is itself regulated by pro-inflammatory cytokines. In NOD mice, the hCD4 reporter was expressed in infiltrated islets and the expression level was positively correlated with the frequency of infiltrating CD45⁺ cells. SOCS1 reporter expression was induced in transferred β-cell-specific CD8⁺ 8.3T cells upon migration from pancreatic draining lymph nodes into islets. To determine which cytokines induced SOCS1 promoter activity in islets, we examined hCD4 reporter expression and CTL maturation in the absence of the cytokine receptors IFNAR1 or IL-21R. We show that IFNAR1 deficiency does not confer protection from diabetes in 8.3 TCR transgenic mice, nor is IFNAR1 signalling required for SOCS1 reporter upregulation or CTL maturation in islets. In contrast, IL-21R-deficient 8.3 mice have reduced diabetes incidence and reduced SOCS1 reporter activity in islet CTLs. However IL-21R deficiency did not affect islet CD8⁺ T cell proliferation or expression of granzyme B or IFNγ. Together these data indicate that autoreactive CD8⁺ T cells respond to IL-21 and not type I IFNs in the islets of NOD mice, but neither IFNAR1 nor IL-21R are required for islet intrinsic CTL maturation.

Feasibility of Localized Metabolomics in the Study of Pancreatic Islets and Diabetes

(1) Background: Disruption of insulin production by native or transplanted pancreatic islets caused by auto/allo-immunity leads to hyperglycemia, a serious health condition and important therapeutic challenge due to the lifelong need for exogeneous insulin administration. Early metabolic biomarkers can prompt timely interventions to preserve islet function, but reliable biomarkers are currently lacking. We explored the feasibility of "localized metabolomics" where initial biomarker discovery is made in aqueous humor samples for further validation in the circulation. (2) Methods: We conducted non-targeted metabolomic studies in parallel aqueous humor and plasma samples from diabetic and nondiabetic mice. Metabolite levels and associated pathways were compared in both compartments as well as to an earlier longitudinal dataset in hyperglycemia-progressor versus non-progressor non-obese diabetic (NOD) mice. (3) Results: We confirmed that aqueous humor samples can be used to assess metabolite levels. About half of the identified metabolites had well-correlated levels in the aqueous humor and plasma. Several plasma metabolites were significantly different between diabetic and nondiabetic animals and between males and females, and many of them were correlated with the aqueous humor. (4) Conclusions: This study provides proof-of-concept evidence that aqueous humor samples enriched with islet-related metabolites and representative of the immediate islet microenvironment following intraocular islet transplant can be used to assess metabolic changes that could otherwise be overlooked in the general circulation. The findings support localized metabolomics, with and without intraocular islet transplant, to identify biomarkers associated with diabetes and islet allograft rejection.

Exacerbation of Type 1 Diabetes in Perinatally Genistein Exposed Female Non-Obese Diabetic (NOD) Mouse Is Associated With Alterations of Gut Microbiota and Immune Homeostasis

Despite various hypothesized benefits of dietary isoflavone genistein (GEN) from soy-based products, many questions surrounding GEN's immunotoxic effects, especially during perinatal exposure, have yet to be answered. The objective of the study was to determine if there existed a sex-specific effect of GEN on type 1 diabetes (T1D) following perinatal exposure. We exposed offspring of non-obese diabetic (NOD) mice to GEN per oral at a physiological dose (20 mg/kg body weight) from embryonic day 7 to postnatal day (PND) 21. In female offspring, perinatal GEN dosing significantly increased the incidence of T1D at early time points, and the exacerbation was associated with decreased serum levels of interleukin (IL)-10, IgG2a, and IgM. In male offspring dosed with GEN, a decrease in serum IgG1 was also observed. Flow cytometric analysis in females suggested an increased pro-inflammatory splenic CD5+CD24- and CD4-CD8+ cell counts, while both %T cells and %CD4+ T cells were significantly decreased in males, suggesting an anti-inflammatory effect. Gut microbiota (GMB) analysis indicated that fecal microbiota from PND 90 female offspring exhibited an increased level of Enterobacteriales (suggesting a pro-inflammatory response), while the similar changes were not found in PND 30 females. Moreover, RNA sequencing showed that intestinal α-defensin expression was down-regulated in GEN-treated females, supporting a pro-inflammatory response. However, perinatal GEN administration perturbed GMB toward an anti-inflammatory response in PND 90 males. Taken together, a strong sex-specific effect was found in the perinatal GEN exposure window, and the T1D exacerbation in NOD females was associated with GMB-related immunomodulatory mechanisms.

Kinetics of immune cell responses in the multiple low-dose streptozotocin mouse model of type 1 diabetes

In type 1 diabetes (T1D), the insulin-producing β cells are destructed by immune mechanisms. It has been hypothesized that the very first immune response in T1D onset comes from innate immune cells, which further activates the adaptive immune cells to attack the islets. Despite intensive research on characterization of islet-infiltrating immune cells, the kinetics of different immune cells in multiple low-dose streptozotocin (MLDSTZ)-induced T1D mouse model is still much unclear. Therefore, we investigated the proportions of innate immune cells such as neutrophils, dendritic cells (DCs), plasmacytoid dendritic cells (pDCs), macrophages, natural killer (NK) cells, and adaptive immune cells (T and B lymphocytes) in thymi, pancreatic-draining lymph nodes, and spleens of MLDSTZ mice on days 3, 7, 10, and 21 after the first injection of STZ by flow cytometry. The proportions of DCs and B cells were increased from day 3, while the proportions of B-1a lymphocytes and interferon-γ+ cells among NK cells were increased, but NK cells were decreased on day 10 in MLDSTZ-treated mice, illustrating that the initial immune response is induced by DCs and B cells. Later, the proportions of T helper 1 and cytotoxic T cells were increased from day 7, suggesting that the innate immune cells precede adaptive immune cell response in MLDSTZ mice. Altogether, our data demonstrate a possible sequence of events regarding the involvement of DCs, pDCs, NK cells, B-1a lymphocytes, B, and T cells at the early stage of T1D development.

Molecular Targeting of Immunosuppressants Using a Bifunctional Elastin-Like Polypeptide

Elastin-Like Polypeptides (ELP) are environmentally responsive protein polymers which are easy to engineer and biocompatible, making them ideal candidates as drug carriers. Our team has recently utilized ELPs fused to FKBP12 to carry Rapamycin (Rapa), a potent immunosuppressant. Through high affinity binding to Rapa, FKBP carriers can yield beneficial therapeutic effects and reduce the off-site toxicity of Rapa. Since ICAM-1 is significantly elevated at sites of inflammation in diverse diseases, we hypothesized that a molecularly targeted ELP carrier capable of binding ICAM-1 might have advantageous properties. Here we report on the design, characterization, pharmacokinetics, and biodistribution of a new ICAM-1-targeted ELP Rapa carrier (IBPAF) and its preliminary characterization in a murine model exhibiting elevated ICAM-1. Lacrimal glands (LG) of male NOD mice, a disease model recapitulating the autoimmune dacryoadenitis seen in Sjögren's Syndrome patients, were analyzed to confirm that ICAM-1 was significantly elevated in the LG relative to control male BALB/c mice (3.5-fold, p < 0.05, n = 6). In vitro studies showed that IBPAF had significantly higher binding to TNF-α-stimulated bEnd.3 cells which overexpress surface ICAM-1, relative to nontargeted control ELP (AF)(4.0-fold, p < 0.05). A pharmacokinetics study in male NOD mice showed no significant differences between AF and IBPAF for plasma half-life, clearance, and volume of distribution. However, both constructs maintained a higher level of Rapa in systemic circulation compared to free Rapa. Interestingly, in the male NOD mouse, the accumulation of IBPAF was significantly higher in homogenized LG extracts compared to AF at 2 h (8.6 ± 6.6% versus 1.3 ± 1.3%, respectively, n = 5, p < 0.05). This accumulation was transient with no differences detected at 8 or 24 h. This study describes the first ICAM-1 targeted protein-polymer carrier for Rapa that specifically binds to ICAM-1 in vitro and accumulates in ICAM-1 overexpressing tissue in vivo, which may be useful for molecular targeting in diverse inflammatory diseases where ICAM-1 is elevated.

Transplantation of MHC-mismatched mouse embryonic stem cell-derived thymic epithelial progenitors and MHC-matched bone marrow prevents autoimmune diabetes

Background

Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of insulin-secreting islet β cells by autoreactive T cells. Non-obese diabetic (NOD) mice are the widely used animal model for human T1D. Autoimmunity in NOD mice is associated with particular major histocompatibility complex (MHC) loci and impaired islet autoantigen expression and/or presentation in the thymus, which results in defects in both central and peripheral tolerance. It has been reported that induction of mixed chimerism with MHC-mismatched, but not MHC-matched donor bone marrow (BM) transplants prevents the development T1D in NOD mice. We have reported that mouse embryonic stem cells (mESCs) can be selectively induced in vitro to generate thymic epithelial progenitors (TEPs) that further develop into thymic epithelial cells (TECs) in vivo to support T cell development.

Methods

To determine whether transplantation of MHC-mismatched mESC-TEPs could prevent the development of insulitis and T1D, NOD mice were conditioned and injected with MHC-mismatched B6 mESC-TEPs and MHC-matched BM from H-2^g7 B6 mice. The mice were monitored for T1D development. The pancreas, spleen, BM, and thymus were then harvested from the mice for evaluation of T1D, insulitis, chimerism levels, and T cells.

Results

Transplantation of MHC-mismatched mESC-TEPs and MHC-matched donor BM prevented insulitis and T1D development in NOD mice. This was associated with higher expression of proinsulin 2, a key islet autoantigen in the mESC-TECs, and an increased number of regulatory T cells.

Conclusions

Our results suggest that embryonic stem cell-derived TEPs may offer a new approach to control T1D.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1347-1) contains supplementary material, which is available to authorized users.