In type 2 diabetes, hyperglycemia is present when an increased demand for insulin, typically due to insulin resistance, is not met as a result of progressive pancreatic beta cell dysfunction. This defect in beta cell activity is typically characterized by impaired insulin biosynthesis and secretion, usually accompanied by oxidative and endoplasmic reticulum (ER) stress. We demonstrate that multiple inflammatory cytokines elevated in diabetic pancreatic islets induce beta cell oxidative and ER stress, with interleukin-23 (IL-23), IL-24 and IL-33 being the most potent. Conversely, we show that islet-endogenous and exogenous IL-22, by regulating oxidative stress pathways, suppresses oxidative and ER stress caused by cytokines or glucolipotoxicity in mouse and human beta cells. In obese mice, antibody neutralization of IL-23 or IL-24 partially reduced beta cell ER stress and improved glucose tolerance, whereas IL-22 administration modulated oxidative stress regulatory genes in islets, suppressed ER stress and inflammation, promoted secretion of high-quality efficacious insulin and fully restored glucose homeostasis followed by restitution of insulin sensitivity. Thus, therapeutic manipulation of immune regulators of beta cell stress reverses the hyperglycemia central to diabetes pathology.

Mouse dendritic cells (DC) have been extensively studied in various tissues, especially spleen, and they comprise subsets with distinct developmental origins, surface phenotypes, and functions. Considerably less is known about human DC due to their rarity in blood and inaccessibility of other human tissues. The study of DC in human blood has revealed four subsets distinct in phenotype and function. In this study, we describe four equivalent DC subsets in human spleen obtained from deceased organ donors. We identify three conventional DC subsets characterized by surface expression of CD1b/c, CD141, and CD16, and one plasmacytoid DC subset characterized by CD304 expression. Human DC subsets in spleen were very similar to those in human blood with respect to surface phenotype, TLR and transcription factor expression, capacity to stimulate T cells, cytokine secretion, and cross-presentation of exogenous Ag. However, organ donor health status, in particular treatment with corticosteroid methylprednisolone and brain death, may affect DC phenotype and function. DC T cell stimulatory capacity was reduced but DC were qualitatively unchanged in methylprednisolone-treated deceased organ donor spleen compared with healthy donor blood. Overall, our findings indicate that human blood DC closely resemble human spleen DC. Furthermore, we confirm parallels between human and mouse DC subsets in phenotype and function, but also identify differences in transcription factor and TLR expression as well as functional properties. In particular, the hallmark functions of mouse CD8α+ DC subsets, that is, IL-12p70 secretion and cross-presentation, are not confined to the equivalent human CD141+ DC but are shared by CD1b/c+ and CD16+ DC subsets.

Type 1 diabetes (T1D) develops when insulin-secreting b-cells, found in the pancreatic islets of Langerhans, are destroyed by infiltrating T cells. How human T cells recognize b-cell-derived antigens remains unclear. Genetic studies have shown that HLA and insulin alleles are the most strongly associated with risk of T1D. These longstanding observations implicate CD4 + T-cell responses against (pro)insulin in the pathogenesis of T1D. To dissect the autoimmune T-cell response against human b-cells, we isolated and characterized 53 CD4 + T-cell clones from within the residual pancreatic islets of a deceased organ donor who had T1D. These 53 clones expressed 47 unique clonotypes, 8 of which encoded proinsulin-specific T-cell receptors. On an individual clone basis, 14 of 53 CD4 + T-cell clones (26%) recognized 6 distinct but overlapping epitopes in the C-peptide of proinsulin. These clones recognized C-peptide epitopes presented by HLA-DQ8 and, notably, HLA-DQ8 transdimers that form in HLA-DQ2/-DQ8 heterozygous individuals. Responses to these epitopes were detected in the peripheral blood mononuclear cells of some people with recent-onset T1D but not in HLAmatched control subjects. Hence, proinsulin-specific, HLA-DQ8, and HLA-DQ8-transdimer-restricted CD4 + T cells are strongly implicated in the autoimmune pathogenesis of human T1D.Type 1 diabetes (T1D) is an autoimmune disease caused by the CD4 + and CD8 + T-cell-mediated destruction of pancreatic insulin-producing b-cells (1). b-Cell destruction leads to primary insulin deficiency, which is treated by exogenous insulin therapy, and currently there is no cure. The pathogenesis of T1D has been well characterized using the NOD mouse model, but the immune basis of T1D in humans is less clear.Genetic association studies have provided powerful insights into the etiology of human T1D (2,3). The HLA class II region has the strongest impact on risk of T1D. Some HLA alleles-DQB1*06:02 for example-dominantly protect against T1D (4). In contrast, of all alleles, HLA-DQ2

Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that regulates cellular stress responses. While the levels of HIF-1α protein are tightly regulated, recent studies suggest that it can be active under normoxic conditions. We hypothesized that HIF-1α is required for normal β cell function and reserve and that dysregulation may contribute to the pathogenesis of type 2 diabetes (T2D). Here we show that HIF-1α protein is present at low levels in mouse and human normoxic β cells and islets. Decreased levels of HIF-1α impaired glucosestimulated ATP generation and β cell function. C57BL/6 mice with β cell-specific Hif1a disruption (referred to herein as β-Hif1a-null mice) exhibited glucose intolerance, β cell dysfunction, and developed severe glucose intolerance on a high-fat diet. Increasing HIF-1α levels by inhibiting its degradation through iron chelation markedly improved insulin secretion and glucose tolerance in control mice fed a high-fat diet but not in β-Hif1a-null mice. Increasing HIF-1α levels markedly increased expression of ARNT and other genes in human T2D islets and improved their function. Further analysis indicated that HIF-1α was bound to the Arnt promoter in a mouse β cell line, suggesting direct regulation. Taken together, these findings suggest an important role for HIF-1α in β cell reserve and regulation of ARNT expression and demonstrate that HIF-1α is a potential therapeutic target for the β cell dysfunction of T2D. IntroductionThe transcription factor HIF-1α is important for a range of functions, including cellular responses to hypoxia and other stressors, angiogenesis, and fetal development (1-6). It has strong antiapoptotic effects (7-11) and is implicated in the pathogenesis of cardiovascular diseases and some cancers (12)(13)(14)(15)(16)(17)(18)(19)(20).HIF-1α is a member of the bHLH-PAS family (reviewed in refs. 2, 18, 21) and functions as an obligate dimer with other family members, including aryl hydrocarbon receptor (AhR) nuclear translocator (ARNT). We previously reported that ARNT was decreased in islets isolated from patients with type 2 diabetes (T2D) and that decreasing ARNT in Min6 cells or disrupting it in mouse β cells caused changes in gene expression and glucose-stimulated insulin secretion (GSIS) similar to those seen in islets isolated from humans with T2D (22). Recently, we reported a loss of ARNT expression in the livers of people with T2D, affecting dysregulation of gluconeogenesis (23). Though the specific ARNT partner which is important for its actions in β cells (or liver) is not known, candidates include AhR, HIF-1α, HIF-2α, HIF-3α, and circadian rhythm molecules, e.g., BMAL.

In the context of islet transplantation, experimental models show that induction of islet intrinsic NF-kBdependent proinflammatory genes can contribute to islet graft rejection. Isolation of human islets triggers activation of the NF-kB and mitogen-activated kinase (MAPK) stress response pathways. However, the downstream NF-kB target genes induced in human islets during the isolation process are poorly described. Therefore, in this study, using microarray, bioinformatic, and RTqPCR approaches, we determined the pattern of genes expressed by a set of 14 human islet preparations. We found that isolated human islets express a panel of genes reminiscent of cells undergoing a marked NF-kB-dependent proinflammatory response. Expressed genes included matrix metallopeptidase 1 (MMP1) and fibronectin 1 (FN1), factors involved in tissue remodeling, adhesion, and cell migration; inflammatory cytokines IL-1b and IL-8; genes regulating cell survival including A20 and ATF3; and notably high expression of a set of chemokines that would favor neutrophil and monocyte recruitment including CXCL2, CCL2, CXCL12, CXCL1, CXCL6, and CCL28. Of note, the inflammatory profile of isolated human islets was maintained after transplantation into RAG -/recipients. Thus, human islets can provide a reservoir of NF-kB-dependent inflammatory factors that have the potential to contribute to the antiislet-graft immune response. To test this hypothesis, we extracted rodent islets under optimal conditions, forced activation of NF-kB, and transplanted them into allogenic recipients. These NF-kB activated islets not only expressed the same chemokine profile observed in human islets but also struggled to maintain normoglycemia posttransplantation. Further, NF-kB-activated islets were rejected with a faster tempo as compared to non-NF-kB-activated rodent islets. Thus, isolated human islets can make cell autonomous contributions to the ensuing allograft response by elaborating inflammatory factors that contribute to their own demise. These data highlight the potential importance of islet intrinsic proinflammatory responses as targets for therapeutic intervention.