Lynn Opare-Addo

Inflammatory cytokines are involved in autoimmune diabetes: among the most prominent is interleukin (IL)-1β. We postulated that blockade of IL-1β would modulate the effects of anti-CD3 monoclonal antibody (mAb) in treating diabetes in NOD mice. To test this, we treated hyperglycemic NOD mice with F(ab')(2) fragments of anti-CD3 mAb with or without IL-1 receptor antagonist (IL-1RA), or anti-IL-1β mAb. We studied the reversal of diabetes and effects of treatment on the immune system. Mice that received a combination of anti-CD3 mAb with IL-1RA showed a more rapid rate of remission of diabetes than mice treated with anti-CD3 mAb or IL-1RA alone. Combination-treated mice had increased IL-5, IL-4, and interferon (IFN)-γ levels in circulation. There were reduced pathogenic NOD-relevant V7 peptide-V7(+) T cells in the pancreatic lymph nodes. Their splenocytes secreted more IL-10, had increased arginase expression in macrophages and dendritic cells, and had delayed adoptive transfer of diabetes. After 1 month, there were increased concentrations of IgG1 isotype antibodies and reduced intrapancreatic expression of IFN-γ, IL-6, and IL-17 despite normal splenocyte cytokine secretion. These studies indicate that the combination of anti-CD3 mAb with IL-1RA is synergistic in reversal of diabetes through a combination of mechanisms. The combination causes persistent remission from islet inflammation.

OBJECTIVE: β-Cell and islet endothelial cell destruction occurs during the progression of type 1 diabetes, but, paradoxically, β-cell proliferation is increased during this period. Altered glucose tolerance may affect β-cell mass and its association with endothelial cells. Our objective was to study the effects of glucose and inflammation on islet vascularity and on β function, mass, and insulin in immunologically tolerant anti-CD3 monoclonal antibody (mAb)-treated and prediabetic NOD mice. RESEARCH DESIGN AND METHODS: The effects of phloridzin or glucose injections on β-cells and endothelial cells were tested in prediabetic and previously diabetic NOD mice treated with anti-CD3 mAbs. Glucose tolerance, immunofluorescence staining, and examination of islet cultures ex vivo were evaluated. RESULTS: Islet endothelial cell density decreased in NOD mice and failed to recover after anti-CD3 mAb treatment despite baseline euglycemia. Glucose treatment of anti-CD3 mAb-treated mice showed increased islet vascular density and increased insulin content, which was associated with improved glucose tolerance. The increase in the vascular area was dependent on islet inflammation. Increased islet endothelial cell density was associated with increased production of vascular endothelial growth factor (VEGF) by islets from NOD mice. This response was recapitulated ex vivo by the transfer of supernatants from NOD islets cultured in high-glucose levels. CONCLUSIONS: Our results demonstrate a novel role for glucose and inflammation in the control of islet vasculature and insulin content of β-cells in prediabetic and anti-CD3-treated NOD mice. VEGF production by the islets is affected by glucose levels and is imparted by soluble factors released by inflamed islets.

It is thought that differentiation of beta-cell precursors into mature cells is largely autonomous, but under certain conditions differentiation can be modified by external factors. The factors that modify beta-cell differentiation have not been identified. In this study, we tested whether adult islet cells can affect the differentiation process in mouse and human pancreatic anlage cells. We assessed beta-cell proliferation and differentiation in mouse and human pancreatic anlage cells cocultured with adult islet cells or betaTC3 cells using cellular, molecular, and immunohistochemical methods. Differentiation of murine anlage cells into beta-cells was induced by mature islet cells. It was specific for beta-cells and not a general feature of endodermal derived cells. beta-Cell differentiation required cell-cell contact. The induced cells acquired features of mature beta-cells including increased expression of beta-cell transcription factors and surface expression of receptor for stromal cell-derived factor 1 and glucose transporter-2 (GLUT-2). They secreted insulin in response to glucose and could correct hyperglycemia in vivo when cotransplanted with vascular cells. Human pancreatic anlage cells responded in a similar manner and showed increased expression of pancreatic duodenal homeobox 1 and v-maf musculoaponeurotic fibrosarcoma oncogene homolog A and increased production of proinsulin when cocultured with adult islets. We conclude that mature beta-cells can modify the differentiation of precursor cells and suggest a mechanism whereby changes in differentiation of beta-cells can be affected by other beta-cells.

The capacity of pancreatic β cells to maintain glucose homeostasis during chronic physiologic and immunologic stress is important for cellular and metabolic homeostasis. Insulin receptor substrate 2 (IRS2) is a regulated adapter protein that links the insulin and IGF1 receptors to downstream signaling cascades. Since strategies to maintain or increase IRS2 expression can promote β cell growth, function, and survival, we conducted a screen to find small molecules that can increase IRS2 mRNA in isolated human pancreatic islets. We identified 77 compounds, including 15 that contained a tricyclic core. To establish the efficacy of our approach, one of the tricyclic compounds, trimeprazine tartrate, was investigated in isolated human islets and in mouse models. Trimeprazine is a first-generation antihistamine that acts as a partial agonist against the histamine H1 receptor (H1R) and other GPCRs, some of which are expressed on human islets. Trimeprazine promoted CREB phosphorylation and increased the concentration of IRS2 in islets. IRS2 was required for trimeprazine to increase nuclear Pdx1, islet mass, β cell replication and function, and glucose tolerance in mice. Moreover, trimeprazine synergized with anti-CD3 Abs to reduce the progression of diabetes in NOD mice. Finally, it increased the function of human islet transplants in streptozotocin-induced (STZ-induced) diabetic mice. Thus, trimeprazine, its analogs, or possibly other compounds that increase IRS2 in islets and β cells without adverse systemic effects might provide mechanism-based strategies to prevent the progression of diabetes.