Voltage-gated calcium (CaV) channels are ubiquitously expressed in various cell types throughout the body. In principle, the molecular identity, biophysical profile, and pharmacological property of CaV channels are independent of the cell type where they reside, whereas these channels execute unique functions in different cell types, such as muscle contraction, neurotransmitter release, and hormone secretion. At least six CaValpha1 subunits, including CaV1.2, CaV1.3, CaV2.1, CaV2.2, CaV2.3, and CaV3.1, have been identified in pancreatic beta-cells. These pore-forming subunits complex with certain auxiliary subunits to conduct L-, P/Q-, N-, R-, and T-type CaV currents, respectively. beta-Cell CaV channels take center stage in insulin secretion and play an important role in beta-cell physiology and pathophysiology. CaV3 channels become expressed in diabetes-prone mouse beta-cells. Point mutation in the human CaV1.2 gene results in excessive insulin secretion. Trinucleotide expansion in the human CaV1.3 and CaV2.1 gene is revealed in a subgroup of patients with type 2 diabetes. beta-Cell CaV channels are regulated by a wide range of mechanisms, either shared by other cell types or specific to beta-cells, to always guarantee a satisfactory concentration of Ca2+. Inappropriate regulation of beta-cell CaV channels causes beta-cell dysfunction and even death manifested in both type 1 and type 2 diabetes. This review summarizes current knowledge of CaV channels in beta-cell physiology and pathophysiology.

The Role of Voltage-Gated Calcium Channels in Pancreatic β-Cell Physiology and Pathophysiology

Stem Cell Therapies for Treating Diabetes: Progress and Remaining Challenges

For almost 30 years, the non-obese diabetic (NOD) mouse has served as the primary model for dissecting the genetic and pathogenic basis for T-lymphocyte-mediated autoimmune type 1 diabetes (T1D). However, while sharing many similarities, it is becoming increasingly appreciated that there are also some differences in the immunopathogenic basis of T1D development between humans and NOD mice. This review will focus on aspects of T1D development in NOD mice that are similar and different from that in humans.

Mouse models for the study of autoimmune type 1 diabetes: a NOD to similarities and differences to human disease.

The autoimmune type 1 diabetes (T1D) that arises spontaneously in NOD mice is considered to be a model of T1D in humans. It is characterized by the invasion of pancreatic islets by mononuclear cells (MNCs), which ultimately leads to destruction of insulin-producing β cells. Although T cell dependent, the molecular mechanisms triggering β cell death have not been fully elucidated. Here, we report that a glycosaminoglycan, heparan sulfate (HS), is expressed at extraordinarily high levels within mouse islets and is essential for β cell survival. In vitro, β cells rapidly lost their HS and died. β Cell death was prevented by HS replacement, a treatment that also rendered the β cells resistant to damage from ROS. In vivo, autoimmune destruction of islets in NOD mice was associated with production of catalytically active heparanase, an HS-degrading enzyme, by islet-infiltrating MNCs and loss of islet HS. Furthermore, in vivo treatment with the heparanase inhibitor PI-88 preserved intraislet HS and protected NOD mice from T1D. Our results identified HS as a critical molecular requirement for islet β cell survival and HS degradation as a mechanism for β cell destruction. Our findings suggest that preservation of islet HS could be a therapeutic strategy for preventing T1D.

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Heparan sulfate and heparanase play key roles in mouse β cell survival and autoimmune diabetes

Environmental triggers of autoimmune thyroiditis.

Publisher Summary This chapter discusses the origin of the nonobese diabetic (NOD) mouse, the pathogenesis of diabetes, and the role of the immune cells in pathogenesis and some of the important discoveries that have facilitated and expanded the understanding of both immunity and autoimmunity. With the development of spontaneous diabetes, the NOD mouse shares many pathological features with human type 1 diabetes (T1D) making it a valuable model for research. Disease is associated with specific major histocompatibility complex (MHC) alleles, anti-insulin autoantibodies precede diabetes, and β-cell–specific cellular responses are discussed. Some important advantages of the NOD mouse autoimmune model for diabetes include access to the pancreas at preclinical stages in the immunopathology, the ability to breed and genetically manipulate animals, and the capacity to employ intervention strategies at preclinical and postclinical disease stages. The NOD mouse model has provided researchers with an excellent opportunity to examine islets at various stages of the diabetes disease process.

The pathogenesis of diabetes in the NOD mouse.

The infiltration of monocytes represents an important early event in the development of autoimmune diabetes in NOD mice. Given that chemokines are key regulators of leukocyte trafficking, we examined the requirement for the chemokine receptors β(CC)-chemokine receptor-5 (CCR5) and β(CC)-chemokine receptor-2 (CCR2), which recruit monocytes, in disease development in the NOD mouse. Whereas the onset of diabetes was significantly delayed in CCR2-/-NOD mice (25% at 30 weeks) compared to NOD mice (50% at 28 weeks), the pathogenesis of diabetes was accelerated in CCR5-/-NOD mice (75% at 23 weeks). The rapid development of diabetes in CCR5-/-NOD mice was associated with aggressive destructive insulitis and was accompanied by altered leukocyte migration into islets. In contrast, CCR2-/- NOD mice exhibited delayed inflammatory cell recruitment. Nevertheless, total diabetogenic splenocytes from CCR2-/-NOD and CCR5-/-NOD showed similar capability to adoptively transfer diabetes into NOD.scid recipients. Importantly,...

CCR2 and CCR5 chemokine receptors differentially influence the development of autoimmune diabetes in the NOD mouse.

Background. The ability to block interferon signaling represents an important strategy in designing therapies to prevent beta-cell destruction during islet allograft rejection. Methods. The SOCS proteins regulate cytokine signaling by blocking activation of JAK/STAT proteins. Using islets isolated from SOCS-1 transgenic mice (SOCS-1-Tg; these mice express SOCS-1 under the control of the human insulin promoter and are on the C57BL6/J background), we investigated whether SOCS proteins can prevent the destruction pancreatic islet cells transplanted beneath the kidney capsule of major histocompatibility complex mismatched normal BALB/c and spontaneously-diabetic NOD mouse recipients. Results. Immunohistochemical staining for insulin confirmed the presence of donor SOCS-1-Tg islets in islet allografts harvested at 22 days posttransplant, whereas grafts of control non-Tg islets were destroyed by 14 days. In contrast, SOCS-1-Tg allogeneic islets were not protected from beta-cell destruction in clinically diabetic NOD mice. The islet allografts functioned for 1 week posttransplant; however, hyperglycemia returned after 2 weeks and the grafts were destroyed. Rejection of SOCS-1-Tg and non-Tg islets in autoimmune diabetic NOD mice was associated with an infiltrate of both CD4+ and CD8+ T cells and a T2-type cytokine response (IL-4) rather than the conventional Tl -type cytokine response observed during islet allograft rejection. Self-antigen upregulation in response to IFN-γ stimulation did not appear to be a factor in rejection of the islet allografts. Conclusions. These results demonstrate that expression of SOCS-1 in islets delays islet allograft rejection but cannot circumvent destruction of the islets by the recurrence of the tissue-specific autoimmune process of spontaneous diabetes.

Differences in suppressor of cytokine signaling-1 (SOCS-1) expressing islet allograft destruction in normal BALB/c and spontaneously-diabetic NOD recipient mice.

Type 1 diabetes occurs when self-reactive T lymphocytes destroy the insulin-producing islet β cells of the pancreas. The defects causing this disease have often been assumed to occur exclusively in the immune system. We present evidence that genetic variation at the Idd9 diabetes susceptibility locus determines the resilience of the targets of autoimmunity, the islets, to destruction. Susceptible islets exhibit hyper-responsiveness to inflammatory cytokines resulting in enhanced cell death and increased expression of the death receptor Fas. Fas upregulation in β cells is mediated by TNFR2, and colocalization of TNFR2 with the adaptor TRAF2 in NOD β cells is altered. TNFR2 lies within the candidate Idd9 interval and the diabetes-associated variant contains a mutation adjacent to the TRAF2 binding site. A component of diabetes susceptibility may therefore be determined by the target of the autoimmune response, and protective TNFR2 signaling in islets inhibit early cytokine-induced damage required for the development of destructive autoimmunity. This article was reviewed by Matthiasvon Herrath, HaraldVon Boehmer, and Ciriaco Piccirillo (nominated by Ethan Shevach).

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Resistance of the target islet tissue to autoimmune destruction contributes to genetic susceptibility in Type 1 diabetes

Beta-cell specific expression of suppressor of cytokine signaling-1 (SOCS-1) delays islet allograft rejection by down-regulating Interferon Regulatory Factor-1 (IRF-1) signaling.

Michelle Solomon

Papers

The pathogenesis of diabetes in the NOD mouse.

CCR2 and CCR5 chemokine receptors differentially influence the development of autoimmune diabetes in the NOD mouse.

Differences in suppressor of cytokine signaling-1 (SOCS-1) expressing islet allograft destruction in normal BALB/c and spontaneously-diabetic NOD recipient mice.

Resistance of the target islet tissue to autoimmune destruction contributes to genetic susceptibility in Type 1 diabetes

Beta-cell specific expression of suppressor of cytokine signaling-1 (SOCS-1) delays islet allograft rejection by down-regulating Interferon Regulatory Factor-1 (IRF-1) signaling.