CD28/B7 regulation of autoimmune diabetes

A novel model of early type 1 diabetes mellitus: The chick embryo air sack model

Diabetes Mellitus (DM) is a metabolic disease characterized by hyperglycemia. Chronic hyperglycemia is associated with long-term dysfunction such as retinopathy, nephropathy, neuropathy and cardiovascular diseases. These complications increase rates of death and disability worldwide. Due to the negative effects of DM on the quality of life, the mechanism and treatments of the disease should be investigated in more detail. Most of the research in diabetes is performed in experimental animals. Experimental animal models contributed to the advancement of clinical research, the development of new therapeutic approaches, the discovery of insulin and the purification of insulin. There are many animal models of DM in the literature. But there are a few DM model studies created with chick embryos. In these studies, it was seen that there were differences in STZ doses and STZ administration techniques. The objective of this study was to create a more acceptable and easier DM model. 180 specific pathogen free (SPF) fertilized chicken eggs (White Leghorn chicken) were used in this study. STZ was administered to 160 SPF eggs for an induced DM model. The remaining 20 SPF eggs were separated as a control group. We used two different DM models (Air sack model (ASM) and Chorioallantoic membrane model (CAMM)) and blood sampling technique in our study. 160 SPF eggs were divided into two groups with 80 eggs in each group, according to the model in which STZ was administered. When the relationship between blood glucose and blood insulin levels were examined, it was determined that there was a significantly strong negative correlation in the control group and ASM 1 group; and a significantly very strong negative correlation was found in the ASM 2 group and ASM 3 group. Our data indicate that the optimal STZ dose to create a DM model was 0.45 mg/egg and the best DM model was ASM. The second technique to be the best blood sampling technique for determining blood glucose levels. We believe that ASM can be used in DM studies and anti-DM drug studies in terms of its easebly, applicability, reproducibility and low cost.

CD40-mediated signalling influences trafficking, T-cell receptor expression, and T-cell pathogenesis, in the NOD model of type 1 diabetes

CD40 plays a critical role in the pathogenesis of type 1 diabetes (T1D). The mechanism of action, however, is undetermined, probably because CD40 expression has been grossly underestimated. CD40 is expressed on numerous cell types that now include T cells and pancreatic β cells. CD40⁺ CD4⁺ cells [T helper type 40 (TH40)] prove highly pathogenic in NOD mice and in translational human T1D studies. We generated BDC2.5.CD40^-/- and re-derived NOD.CD154^-/- mice to better understand the CD40 mechanism of action. Fully functional CD40 expression is required not only for T1D development but also for insulitis. In NOD mice, TH40 cell expansion in pancreatic lymph nodes occurs before insulitis and demonstrates an activated phenotype compared with conventional CD4⁺ cells, apparently regardless of antigen specificity. TH40 T-cell receptor (TCR) usage demonstrates increases in several Vα and Vβ species, particularly Vα3.2⁺ that arise early and are sustained throughout disease development. TH40 cells isolated from diabetic pancreas demonstrate a relatively broad TCR repertoire rather than restricted clonal expansions. The expansion of the Vα/Vβ species associated with diabetes depends upon CD40 signalling; NOD.CD154^-/- mice do not expand the same TCR species. Finally, CD40-mediated signals significantly increase pro-inflammatory Th1- and Th17-associated cytokines whereas CD28 co-stimulus alternatively promotes regulatory cytokines.

Study of the pathogenesis and treatment of diabetes mellitus through animal models

Most research in diabetes mellitus (DM) has been conducted in animals, and their replacement is currently a chimera. As compared to when they started to be used by modern science in the 17th century, a very high number of animal models of diabetes is now available, and they provide new insights into almost every aspect of diabetes. Approaches combining human, in vitro, and animal studies are probably the best strategy to improve our understanding of the underlying mechanisms of diabetes, and the choice of the best model to achieve such objective is crucial. Traditionally classified based on pathogenesis as spontaneous or induced models, each has its own advantages and disadvantages. The most common animal models of diabetes are described, and in addition to non-obese diabetic mice, biobreeding diabetes-prone (BB-DP) rats, streptozotocin-induced models, or high-fat diet-induced diabetic C57Bl/6J mice, new valuable models, such as dogs and cats with spontaneous diabetes, are described.

Description of the sphingolipid content and subspecies in the diabetic cornea

PURPOSE

Diabetes mellitus (DM) is characterized by high blood sugar levels over a prolonged period. Long term complications include but not limited heart disease, stroke, kidney failure, and ocular damage. An estimated 382 million people are diagnosed with Type 2 DM accounting for 90% of the cases. Common corneal dysfunctions associated with DM result in impaired vision due to decreased wound healing, corneal edema, and altered epithelial basement membrane. Lipids play a fundamental role in tissue metabolism and disease states. We attempt to determine the role of sphingolipids (SPL) in human Type I and Type II diabetic corneas.

MATERIALS AND METHODS

Cadaver corneas from healthy (non-diabetic/no ocular trauma), Type I (T1DM), and Type II diabetic (T2DM) donors were obtained and processed for lipidomics using LC-MS/MS.

RESULTS

Our data show significant differences in the SPL composition between control, T1DM and T2DM corneas. Both T1DM and T2DM showed a 10-folddownregulation of sphingomyelin(SM), 5-fold up regulation of Ceramides (Cer) and 2-fold upregulation of monohexosylceramides (MHC). Differences were also seen in total amounts of SPL where Cer was increased by approximately 3 fold in both T1DM and T2DM where SM decreased by 50% in both T1DM and T2DM when compared to healthy controls. No differences were seen in MHC amounts.

CONCLUSIONS

Overall, our data indicate major differences in SPL distribution in human diabetic corneas. Information on the sphingolipids role in cornea, corneal cell physiology, and diseases are very limitedwhich highlights the importance of these findings.

Targeted immune interventions for type 1 diabetes: not as easy as it looks!

PURPOSE OF REVIEW

Although insulin is lifesaving and sustaining for those with type 1 diabetes (T1D), curing the disease will be much more complex than simple replacement of this hormone. T1D is an autoimmune disease orchestrated by T cells, and includes many arms of the immune response. Tremendous effort has gone into understanding its underlying immune, genetic, and environmental causes, and this progress has led to immunologically based clinical trials in T1D. This review will focus primarily on the clinical trials of the past decade that have attempted to translate these fundamental findings.

RECENT FINDINGS

It is known that powerful, nonspecific immune suppressants can temporarily slow the course of newly diagnosed T1D, yet are too toxic for long-term use, especially in children. Recent clinical trials to reverse T1D have used newly developed therapies that target specific components of the immune process believed to be involved with T1D. Although well justified and designed, no recent approach has resulted in clinical remission and few have had any effect on disease course.

SUMMARY

Advances in our fundamental understanding of how the human diabetes immune response is activated and regulated coupled with lessons that have been learnt from the most recent era of completed trials are guiding us toward the development of more effective, multipronged therapies to ablate diabetes autoimmunity, restore immune tolerance, preserve β cells, and, ultimately, improve the lives of patients with T1D.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

Animal models of diabetes mellitus

Animal models have been used extensively in diabetes research. Early studies used pancreatectomised dogs to confirm the central role of the pancreas in glucose homeostasis, culminating in the discovery and purification of insulin. Today, animal experimentation is contentious and subject to legal and ethical restrictions that vary throughout the world. Most experiments are carried out on rodents, although some studies are still performed on larger animals. Several toxins, including streptozotocin and alloxan, induce hyperglycaemia in rats and mice. Selective inbreeding has produced several strains of animal that are considered reasonable models of Type 1 diabetes, Type 2 diabetes and related phenotypes such as obesity and insulin resistance. Apart from their use in studying the pathogenesis of the disease and its complications, all new treatments for diabetes, including islet cell transplantation and preventative strategies, are initially investigated in animals. In recent years, molecular biological techniques have produced a large number of new animal models for the study of diabetes, including knock-in, generalized knock-out and tissue-specific knockout mice.

Prolonged survival in rat liver transplantation with mouse monoclonal antibody against an inducible costimulator (ICOS)

BACKGROUND

An inducible costimulator (ICOS), a recently identified costimulatory receptor with a close structural homology to CD28 and CTLA4, is expressed on activated T cells. Interaction with its ligand on antigen-presenting cells stimulates T-cell proliferation to produce a different spectrum of cytokine. The inhibition of ICOS-mediated signal transduction by an anti-ICOS antibody is considered to be capable of protecting against graft rejection in organ transplantation.

METHODS

An anti-rat ICOS antibody was intravenously administered into recipients of dark Agouti-to-Lewis liver transplantations. The recipient lymphocytes from mesenteric lymph nodes were harvested on day 7 after transplantation for fluorescence-activated cell sorting analysis, and tissue specimens from the grafts were removed for histologic evaluation. Antigen-specific T-cell proliferation responses were assessed in vitro with anti-ICOS antibody.

RESULTS

Monotherapy with the antibody significantly prolonged the graft survival time by inhibiting T-cell activation and its proliferation response. The graft-infiltrating cells, both CD4 and CD8 T cells, were not completely reduced even when rats were administered the antibody, whereas the expression of ICOS almost completely disappeared in these cells.

CONCLUSIONS

T-cell activation through the ICOS costimulatory pathway plays an important role in graft rejection, and manipulating its pathway is an effective method for modulating transplantation immunity.

T lymphocyte costimulatory molecules in host defense and immunologic diseases

BACKGROUND

Costimulation is an essential component for the optimal induction of T cell-mediated immune responses. Manipulation of the costimulatory pathway with antibodies or genetically-engineered fusion proteins is an important strategy to treat immune-related diseases including allergy, asthma, transplantation and cancer. Recent advances have revealed several new costimulatory molecules, and the functional characteristics of each costimulatory pathway are now becoming clearer.

LEARNING OBJECTIVES

In this review, we summarize basic outlines of the costimulatory systems in terms of molecular structure, expression kinetics and immunological function. We further discuss involvement and therapeutic manipulation of costimulation in several clinical diseases.

DATA SOURCE

The MEDLINE database was used to review the literature related to costimulation.

CONCLUSION

Costimulatory pathways play an essential role in the activation and regulation of T cell immune responses and the induction of T cell tolerance. Therapeutic manipulation of the costimulatory system demonstrates beneficial effects to treat immunological diseases in murine models as well as some clinical situations.

Rel B is an early marker of autoimmune islet inflammation in the biobreeding (BB) rat

Because the development of insulitis and diabetes is predictable in Lyp/Lyp congenic BB rats, we have characterized early islet inflammation in these rats to determine the cell subsets involved in the onset of autoimmune insulitis. Pancreas sections from prediabetic Lyp/Lyp, Lyp/+ and +/+ rats were analyzed by immunohistochemistry. We found W3/25+ cells in the exo- and endocrine tissue from all three genotypes, but intraislet insulitis was never found in Lyp/+ or +/+ rats. The onset of massive, intraislet B- and T-cell infiltration in Lyp/Lyp rats was preceded by Rel B+ cells in and around the islets, followed by ED1+ monocytes/macrophages. Rel B+ cells were more frequent in the parafollicular cortex of pancreatic lymph nodes from Lyp/Lyp than from Lyp/+ and +/+ rats. In the Lyp/Lyp thymus, we found significantly increased expression of IL-12p40 messenger RNA (mRNA; p<0.001), located in the Rel B-protein-rich corticomedullary junction. The NF-KB/Rel B complex specifically transactivates genes involved in antigen presentation in dendritic cells. Rel B+ cells in the islets may therefore mark the onset of autoimmune insulitis and antigen-specific activation of autoreactive T cells in the lymph nodes of diabetes prone Lyp/Lyp BB rats. In the thymus, Rel B+ cells may support the Lyp-dependent development of self-reactive thymocytes by activation of cytokine expression.