Pancreatic Islet Inflammation Research Articles

Possible etiological role of impaired endogenous double strand RNA editing in β-cells in type 1 diabetes.

Proposed mechanisms by which disruption of endogenous dsRNA editing in β-cells leads to type 1 diabetes-like phenotypes in βAdarKO mice. Disruption of endogenous dsRNA editing in β-cells initiates IFN responses, thereby inducing pancreatic islet inflammation and β-cell dysfunction. Hyperglycemia induced by β-cell dysfunction further promotes islet inflammation, likely via increased dsRNA resulting from increased β-cell workload, thereby producing a vicious cycle. The mechanism by which impairment of dsRNA editing is integrated with autoimmune-mediated pathogenesis of type 1 diabetes remains to be clarified.

Intracellular C3 protects β-cells from IL-1β-driven cytotoxicity via interaction with Fyn-related kinase

One of the hallmarks of type 1 but also type 2 diabetes is pancreatic islet inflammation, associated with altered pancreatic islet function and structure, if unresolved. IL-1β is a proinflammatory cytokine which detrimentally affects β-cell function. In the course of diabetes, complement components, including the central complement protein C3, are deregulated. Previously, we reported high C3 expression in human pancreatic islets, with upregulation after IL-1β treatment. In the current investigation, using primary human and rodent material and CRISPR/Cas9 gene-edited β-cells deficient in C3, or producing only cytosolic C3 from a noncanonical in-frame start codon, we report a protective effect of C3 against IL-1β-induced β-cell death, that is attributed to the cytosolic fraction of C3. Further investigation revealed that intracellular C3 alleviates IL-1β-induced β-cell death, by interaction with and inhibition of Fyn-related kinase (FRK), which is involved in the response of β-cells to cytokines. Furthermore, these data were supported by increased β-cell death in vivo in a β-cell-specific C3 knockout mouse. Our data indicate that a functional, cytoprotective association exists between FRK and cytosolic C3.

Dectin-2 Deficiency Promotes Proinflammatory Cytokine Release From Macrophages and Impairs Insulin Secretion.

Pancreatic islet inflammation plays a crucial role in the etiology of type 2 diabetes (T2D). Macrophages residing in pancreatic islets have emerged as key players in islet inflammation. Macrophages express a plethora of innate immune receptors that bind to environmental and metabolic cues and integrate these signals to trigger an inflammatory response that contributes to the development of islet inflammation. One such receptor, Dectin-2, has been identified within pancreatic islets; however, its role in glucose metabolism remains largely unknown. Here we have demonstrated that mice lacking Dectin-2 exhibit local inflammation within islets, along with impaired insulin secretion and β-cell dysfunction. Our findings indicate that these effects are mediated by proinflammatory cytokines, such as interleukin (IL)-1α and IL-6, which are secreted by macrophages that have acquired an inflammatory phenotype because of the loss of Dectin-2. This study provides novel insights into the mechanisms underlying the role of Dectin-2 in the development of islet inflammation.

TFP5, a Peptide Derived from Cdk5 Activator p35, Protects Pancreatic β Cells from Glucose Toxicity.

We studied the effect of TFP5 on MIN6 cells (cultured mouse islet β cells) treated with different concentrations of glucose (5 or 25 mM). The results were verified in C57BL/6J mice (control; n=12) and db/db mice with type 2 diabetes mellitus (n=12). To synthesize TFP5, peptide p5 (a derivative of p35 protein, activator of cyclin-dependent kinase 5, Cdk5) was conjugated with a FITC tag at the N-terminus and an 11-amino acid TAT protein transduction domain at the C-terminus. TFP5 was employed to inhibit Cdk5 activity and then to evaluate its efficiency in treating experimental type 2 diabetes mellitus. TFP5 effectively inhibited the pathological hyperactivity of Cdk5, enhanced insulin secretion, and protected pancreatic β cells from apoptosis in vitro and in vivo. In addition, TFP5 inhibited inflammation in pancreatic islets by reducing the expression of inflammatory cytokines TGF-β1, TNFα, and IL-1β. These novel data indicates that TFP5 is a promising candidate for treatment of type 2 diabetes mellitus.

Deucravacitinib, a tyrosine kinase 2 pseudokinase inhibitor, protects human EndoC-βH1 β-cells against proinflammatory insults.

Type 1 diabetes is characterized by pancreatic islet inflammation and autoimmune-driven pancreatic β-cell destruction. Interferon-α (IFNα) is a key player in early human type 1 diabetes pathogenesis. IFNα activates the tyrosine kinase 2 (TYK2)-signal transducer and activator of transcription (STAT) pathway, leading to inflammation, HLA class I overexpression, endoplasmic reticulum (ER) stress, and β-cell apoptosis (in synergy with IL-1β). As TYK2 inhibition has raised as a potential therapeutic target for the prevention or treatment of type 1 diabetes, we investigated whether the selective TYK2 inhibitor deucravacitinib could protect β-cells from the effects of IFNα and other proinflammatory cytokines (i.e., IFNγ and IL-1β). All experiments were performed in the human EndoC-βH1 β-cell line. HLA class I expression, inflammation, and ER stress were evaluated by real-time PCR, immunoblotting, and/or immunofluorescence. Apoptosis was assessed by the DNA-binding dyes Hoechst 33342 and propidium iodide or caspase 3/7 activity. The promoter activity was assessed by luciferase assay. Deucravacitinib prevented IFNα effects, such as STAT1 and STAT2 activation and MHC class I hyperexpression, in a dose-dependent manner without affecting β-cell survival and function. A comparison between deucravacitinib and two Janus kinase inhibitors, ruxolitinib and baricitinib, showed that deucravacitinib blocked IFNα- but not IFNγ-induced signaling pathway. Deucravacitinib protected β-cells from the effects of two different combinations of cytokines: IFNα + IL-1β and IFNγ + IL-1β. Moreover, this TYK2 inhibitor could partially reduce apoptosis and inflammation in cells pre-treated with IFNα + IL-1β or IFNγ + IL-1β. Our findings suggest that, by protecting β-cells against the deleterious effects of proinflammatory cytokines without affecting β-cell function and survival, deucravacitinib could be repurposed for the prevention or treatment of early type 1 diabetes.

Sodium Selenite Modulates Global Activation of Proinflammatory M1-like Macrophages, Necroinflammation and M1-like/M2-like Dichotomy at the Onset of Human Type 1 Diabetes.

The study aims to show that sodium selenite (Ss) would have an immunomodulatory effect on the functional activity of proinflammatory macrophages (Mφs) during their extended extracellular activation at the onset of human type 1 diabetes (T1D). Exacerbated activation of proinflammatory "M1" macrophages (Mφs) can promote chronic local pancreatic islet inflammation and T1D development. We investigated the ex vivo effects of Ss on the immune modulation of global/extended activation of human proinflammatory M1-like Mφs. Experiments were carried out on primary monocytes-derived Mφs (MDMs). The levels of IL-1β, TNF-α, H2O2 and intracellular free calcium ions (ifCa2+), and the ratios of IL-1β-to-IL-10 and TNF-α-to-IL-10 were markedly increased in T1D Mφs than in healthy control Mφs. Conversely, both IL-10 production and arginase 1 (ARG1) activity were downregulated in T1D Mφs. Additionally, Ss treatment induced a marked downregulation of respiratory burst, ifCa2+ levels, M1-like Mφ-associated inducible nitric oxide (NO) synthase (iNOS) activity, cell necrosis and related necroinflammation biomarkers, including IL-1β and TNF-α, CD14 expression, and the ratios of iNOS-to-ARG1, IL-1β-to-IL-10, and TNF-α-to-IL-10. Moreover, Ss upregulated anti-inflammatory "M2-like" Mφ activity as demonstrated by ARG1 activity and IL-10 production, as well as phagocytosis capacity. Ss exerts a potent immunomodulatory role on functional activities of human proinflammatory T1D M1-like Mφs subjected to extended activation, as well as on the M1-like/M2-like dichotomy. Additionally, the current study provides a novel therapeutic approach using Ss to promote the anti-inflammatory function of Mφs at the onset of T1D.

252-LB: Dectin-2 Deficiency Promotes Proinflammatory Cytokine Release from Macrophages and Impairs Glucose-Stimulated Insulin Secretion

Pancreatic islet inflammation plays an important role in the pathogenesis of diabetes mellitus. Islet macrophages, which have emerged as a key player in islet inflammation, express Dectin-2 (D2), one of the C-type lectin receptors recognizing α-mannans, while endocrine cells such as α-cells and β-cells lack the expression of D2. To elucidate the role of D2 in glucose metabolism and β-cell function, we analyzed the phenotype of D2 knockout (D2KO) mice. D2KO mice exhibited significantly impaired glucose tolerance compared to wild-type (WT) mice, although there were no significant differences in insulin sensitivity. Glucose-stimulated insulin secretion (GSIS) was significantly reduced in isolated islets from D2KO mice compared to WT mice. Comprehensive analysis of RNA-seq in isolated islets from D2KO and WT mice revealed that D2 deficiency induced immune cell infiltration and inflammation in pancreatic islets. Furthermore, RNA-seq analysis in peritoneal macrophages from D2KO and WT mice showed that macrophages from D2KO mice acquired an inflammatory phenotype and exhibited enhanced NF-κB signaling compared to those from WT mice. Next, to determine whether humoral factors secreted from macrophages affect GSIS, we examined GSIS using the culture supernatants of macrophages from D2KO and WT mice. The culture supernatants of macrophages from D2KO mice suppressed GSIS compared to WT mice. Furthermore, the multiplex cytokine assay revealed that IL-1α and IL-6 were significantly increased in the culture supernatants from macrophages of D2KO mice. Finally, we found that the stimulation of IL-1α and IL-6 reduced GSIS in β-cells. These findings suggest that macrophages from D2KO mice suppress GSIS by increasing IL-1α and IL-6 production. This study provides new insights into the mechanism by which D2 is involved in the pathogenesis of pancreatic islet inflammation. Disclosure M. Fujita: None. T. Miyazawa: None. K. Uchida: None. N. Uchida: None. T. Hatayama: None. S. Nakamura: None. Y. Takeichi: None. Y. Miyachi: None. Y. Ogawa: None.

Extracellular Vesicles Derived from Three-Dimensional-Cultured Human Umbilical Cord Blood Mesenchymal Stem Cells Prevent Inflammation and Dedifferentiation in Pancreatic Islets.

It is unclear whether extracellular vesicles (EVs) from mesenchymal stem cells (MSCs) have a direct protective effect on pancreatic islets. In addition, whether culturing MSCs in three dimensions (3D) instead of a monolayer (2D) can induce changes in the cargo of EVs that facilitate the polarization of macrophages into an M2 phenotype has not been investigated. We sought to determine whether EVs from MSCs cultured in 3D can prevent inflammation and dedifferentiation in pancreatic islets and, if so, whether the protective effect is superior to that of EVs from 2D MSCs. Human umbilical cord blood- (hUCB-) MSCs cultured in 3D were optimized according to cell density, exposure to hypoxia, and cytokine treatment based on the ability of the hUCB-MSC-derived EVs to induce the M2 polarization of macrophages. Islets isolated from human islet amyloid polypeptide (hIAPP) heterozygote transgenic mice were cultured in serum-deprived conditions with hUCB-MSC-derived EVs. EVs derived from 3D hUCB-MSCs had more abundant microRNAs involved in M2 polarization of macrophages and had an enhanced M2 polarization ability on macrophages, which was optimized when the 3D culture condition was 2.5 × 104 cells per spheroid without preconditioning with hypoxia and cytokine exposure. When islets isolated from hIAPP heterozygote transgenic mice were cultured in serum-deprived conditions with hUCB-MSC-derived EVs, the EVs derived from 3D hUCB-MSCs suppressed the expression of proinflammatory cytokines and caspase-1 in pancreatic islets and increased the proportion of M2-polarized islet-resident macrophages. They improved glucose-stimulated insulin secretion, reduced the expression of Oct4 and NGN3, and induced the expression of Pdx1 and FoxO1. The greater suppression of IL-1β, NLRP3 inflammasome, caspase-1, and Oct4 and induction of Pdx1 and FoxO1 were found in islets cultured with the EVs derived from 3D hUCB-MSCs. In conclusion, EVs derived from 3D hUCB-MSCs optimized for M2 polarization attenuated nonspecific inflammation and preserved β-cell identity of pancreatic islets.

High Dietary Iron in Western Diet-Fed Male Rats Causes Pancreatic Islet Injury and Acute Pancreatitis

BackgroundHigh dietary iron has been linked to an increased type 2 diabetes risk. We have previously shown that intrauterine growth restriction (IUGR) and feeding a Western diet (WD) to male Sprague-Dawley rats independently, as well as together, cause pancreatic islet inflammation, fibrosis, and hemosiderosis. ObjectivesTo investigate whether iron has a role in the pathogenesis of this inflammatory islet injury caused by IUGR and WD intake. MethodsMale Sprague-Dawley offspring of bilateral uterine artery ligated (IUGR) and sham-operated (Sham) dams, fostered to nonoperated dams, were fed a WD [45% sucrose, 19.4% protein and 23% fat (w/w)] containing low iron (LI, 20 mg/kg) or high iron (HI, 500 mg/kg) from weaning. Four groups were studied: Sham-LI, Sham-HI, IUGR-LI, and IUGR-HI. Serial measurements of rat body weight, blood glucose, lipids and insulin, an intraperitoneal glucose tolerance test (age 13 wk), and histological analysis of pancreas and liver (age 14 wk) were recorded. The effects of iron, IUGR, and their interaction, on these measurements have been analyzed. ResultsWD with HI compared with LI caused an 11% greater weight gain by age 14 wk (P < 0.001), impaired glucose tolerance [AUC for glucose (G-AUC) 17% higher; P < 0.001), acute pancreatitis (17/18, HI; 6/17, LI; P < 0.001), pancreas-associated fat necrosis and saponification (7/18, HI; 0/17 LI; P < 0.01), and a trend to islet fibrotic injury (7/18, HI; 1/17 LI; P = 0.051). Although pancreatic and hepatic steatosis was evident in almost all WD-fed rats, pancreatic and hepatic iron accumulation was prevalent only in HI-fed rats (P < 0.0001 for both), being only mild in the livers. IUGR, independent of dietary iron, also caused impairment in glucose tolerance (G-AUC: 17% higher; P < 0.05). ConclusionsA postweaning WD containing HI, independent of IUGR, causes acute pancreatitis and islet injury in Sprague-Dawley rats suggesting a role of dietary iron in the development of steatopancreatitis.

N-terminal BET bromodomain inhibitors disrupt a BRD4-p65 interaction and reduce inducible nitric oxide synthase transcription in pancreatic β-cells.

Chronic inflammation of pancreatic islets is a key driver of β-cell damage that can lead to autoreactivity and the eventual onset of autoimmune diabetes (T1D). In the islet, elevated levels of proinflammatory cytokines induce the transcription of the inducible nitric oxide synthase (iNOS) gene, NOS2, ultimately resulting in increased nitric oxide (NO). Excessive or prolonged exposure to NO causes β-cell dysfunction and failure associated with defects in mitochondrial respiration. Recent studies showed that inhibition of the bromodomain and extraterminal domain (BET) family of proteins, a druggable class of epigenetic reader proteins, prevents the onset and progression of T1D in the non-obese diabetic mouse model. We hypothesized that BET proteins co-activate transcription of cytokine-induced inflammatory gene targets in β-cells and that selective, chemotherapeutic inhibition of BET bromodomains could reduce such transcription. Here, we investigated the ability of BET bromodomain small molecule inhibitors to reduce the β-cell response to the proinflammatory cytokine interleukin 1 beta (IL-1β). BET bromodomain inhibition attenuated IL-1β-induced transcription of the inflammatory mediator NOS2 and consequent iNOS protein and NO production. Reduced NOS2 transcription is consistent with inhibition of NF-κB facilitated by disrupting the interaction of a single BET family member, BRD4, with the NF-κB subunit, p65. Using recently reported selective inhibitors of the first and second BET bromodomains, inhibition of only the first bromodomain was necessary to reduce the interaction of BRD4 with p65 in β-cells. Moreover, inhibition of the first bromodomain was sufficient to mitigate IL-1β-driven decreases in mitochondrial oxygen consumption rates and β-cell viability. By identifying a role for the interaction between BRD4 and p65 in controlling the response of β-cells to proinflammatory cytokines, we provide mechanistic information on how BET bromodomain inhibition can decrease inflammation. These studies also support the potential therapeutic application of more selective BET bromodomain inhibitors in attenuating β-cell inflammation.

Amelioration of oxidative stress mediated inflammation and apoptosis in pancreatic islets by Lupeol in STZ-induced hyperglycaemic mice

BackgroundType 1 Diabetes mellitus initiates by loss of pancreatic activity which affects other major organs leading to multi-organ failure. Lupeol, a novel phytochemical, is emerging as a potent bioactive molecule. However, the effect of lupeol on hyperglycaemia is not clearly understood. This study delivers an elaborate vision towards the detailed molecular pathway of lupeol against STZ induced diabetic difficulties of the pancreas. MethodThe current experiments were designed to focus on the ameliorative effect of the triterpene in combating oxidative damage on the pancreas in a preclinical streptozotocin induced mouse model. After diabetic induction, the animals were subjected to administration with 75 mg kg−1 body weight of lupeol, thrice a week for 7 weeks. Histological measurements were done to investigate the anatomy of the pancreas as well as molecular mechanisms were explored. ResultsThe compound was found to regulate several hyperglycaemic and oxidative stress related markers. Lupeol treatment also reversed the expression levels of inflammatory cytokines (TNF-α and IL-1β) as well as attenuated the NF-κB mediated inflammatory and extrinsic apoptotic pathway. DiscussionThese findings in preclinical streptozotocin induced in vivo mouse model strongly suggest the discovery of novel properties of lupeol against oxidative stress in pancreatic β cells by regulating the NF-κB and extrinsic apoptotic pathway.

Carbonyl Posttranslational Modification Associated With Early-Onset Type 1 Diabetes Autoimmunity.

Inflammation and oxidative stress in pancreatic islets amplify the appearance of various posttranslational modifications to self-proteins. In this study, we identified a select group of carbonylated islet proteins arising before the onset of hyperglycemia in NOD mice. Of interest, we identified carbonyl modification of the prolyl-4-hydroxylase β subunit (P4Hb) that is responsible for proinsulin folding and trafficking as an autoantigen in both human and murine type 1 diabetes. We found that carbonylated P4Hb is amplified in stressed islets coincident with decreased glucose-stimulated insulin secretion and altered proinsulin-to-insulin ratios. Autoantibodies against P4Hb were detected in prediabetic NOD mice and in early human type 1 diabetes prior to the onset of anti-insulin autoimmunity. Moreover, we identify autoreactive CD4+ T-cell responses toward carbonyl-P4Hb epitopes in the circulation of patients with type 1 diabetes. Our studies provide mechanistic insight into the pathways of proinsulin metabolism and in creating autoantigenic forms of insulin in type 1 diabetes.

Artemisia dracunculus L. Ethanolic Extract and an Isolated Component, DMC2, Ameliorate Inflammatory Signaling in Pancreatic β-Cells via Inhibition of p38 MAPK

Non-resolving pancreatic islet inflammation is widely viewed as a contributor to decreases in β-cell mass and function that occur in both Type 1 and Type 2 diabetes. Therefore, strategies aimed at reducing or eliminating pathological inflammation would be useful to protect islet β-cells. Herein, we described the use of 2′,4′-dihydroxy-4-methoxydihydrochalcone (DMC2), a bioactive molecule isolated from an ethanolic extract of Artemisia dracunculus L., as a novel anti-inflammatory agent. The ethanolic extract, termed PMI 5011, reduced IL-1β-mediated NF-κB activity. DMC2 retained this ability, indicating this compound as the likely source of anti-inflammatory activity within the overall PMI 5011 extract. We further examined NF-κB activity using promoter-luciferase reporter constructs, Western blots, mRNA abundance, and protein secretion. Specifically, we found that PMI 5011 and DMC2 each reduced the ability of IL-1β to promote increases in the expression of the Ccl2 and Ccl20 genes. These genes encode proteins that promote immune cell recruitment and are secreted by β-cells in response to IL-1β. Phosphorylation of IκBα and the p65 subunit of NF-κB were not reduced by either PMI 5011 or DMC2; however, phosphorylation of p38 MAPK was blunted in the presence of DMC2. Finally, we observed that while PMI 5011 impaired glucose-stimulated insulin secretion, insulin output was preserved in the presence of DMC2. In conclusion, PMI 5011 and DMC2 reduced inflammation, but only DMC2 did so with the preservation of glucose-stimulated insulin secretion.

Regulation of metabolism by protein modifications in autoimmunity

Abstract In type 1 diabetes (T1D), inflammation and oxidative stress in pancreatic islets amplifies various post-translational modifications (PTMs) of self-proteins. The loss of immune tolerance to islet PTMs triggers an autoreactive T cell response and contributes to the destruction of insulin-producing beta cells in T1D. The major function of beta cells is to secret insulin in response to glucose uptake in order to maintain glucose homeostasis. In this study, we identify autoantibodies against to beta subunit of prolyl-4-hydroxylase (P4Hb; native and carbonylated form) and glucokinase (GK; native and citrullinated form) in both human T1D and murine models. Glucokinase serves as a glucose sensor to initiate glycolysis and insulin signaling in beta cells. P4Hb is required for the accurate folding of insulin. By mass spectrometry, six carbonyl residues and eleven citrulline residues were mapped in oxidative rhP4Hb and PAD-treated rhGK, respectively. Of interest, autoreactive CD4+ T cells to citrullinated GK epitopes are present in the circulation of T1D patients. In regards to glucose metabolism, the carbonylated-P4Hb is amplified in stressed human islets coincident with decreased glucose-stimulated insulin secretion and disturb (increase) proinsulin to insulin ratios. The citrullination alters GK biologic activity (Km) and suppresses glucose-stimulated insulin secretion. Moreover, PAD2/4 inhibitors can partially restore IFNg +IL-1b suppressed glucose stimulated insulin secretion in INS-1E beta cells. Our studies implicate the crucial enzymes, glucokinase and P4Hb, as the biomarkers, providing new insights into creating autoantigens and define the impact of metabolic PTMs on the aberrant beta cell functions of T1D. This research was supported by the Juvenile Diabetes Research Foundation (Innovative Grant to M.J.M., 2-SRA-2018-551-S-B to E.A.J.), and National Institutes of Health (DK104205-01 to K.H. and M.J.M.).

NAG-1/GDF15 protects against streptozotocin-induced type 1 diabetes by inhibiting apoptosis, preserving beta-cell function, and suppressing inflammation in pancreatic islets

The loss of functional insulin-producing β-cells is a hallmark of type 1 diabetes mellitus (T1DM). Previously, we reported that the non-steroidal anti-inflammatory drug activated gene-1, or growth differentiation factor-15 (NAG-1/GDF15) inhibits obesity and improves insulin sensitivity in both genetic and dietary-induced obese mice. However, the regulatory role of NAG-1/GDF15 in the structure and function of β-cells and the prevention of T1DM is largely unknown. In the current study, we reported that NAG-1/GDF15 transgenic (Tg) mice are resistant to diabetogenesis induced by multiple low-dose streptozotocin (MLD-STZ) treatment. NAG-1/GDF15 overexpression significantly reduced diabetes incidence, alleviated symptoms of T1DM, and improved MLD-STZ-induced glucose intolerance and insulin resistance. Both the mass and function of pancreatic β cells were preserved in the NAG-1/GDF15 Tg mice as evidenced by significantly increased islet area and insulin production. The mechanistic study revealed that NAG-1/GDF15 significantly inhibited STZ-induced apoptosis and preserved the reduction of proliferation in the islets of the Tg mice as compared to the wild-type (WT) mice upon MLD-STZ treatment. Additionally, NAG-1/GDF15 significantly reduced both the serum and islet levels of the inflammatory cytokines (IL-1β, IL-6, and TNFα), and reduced the expression of NF-κB expression and immune cells infiltration in the islets. Collectively, these results indicate that NAG-1/GDF15 is effective in improving STZ-induced glucose intolerance, probably was mediated via suppressing inflammation, inhibiting apoptosis, and preserving β-cell mass and function.

Anti-Inflammatory and Pro-Autophagy Effects of the Cannabinoid Receptor CB2R: Possibility of Modulation in Type 1 Diabetes.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease resulting from loss of insulin-secreting β-cells in islets of Langerhans. The loss of β-cells is initiated when self-tolerance to β-cell-derived contents breaks down, which leads to T cell-mediated β-cell damage and, ultimately, β-cell apoptosis. Many investigations have demonstrated the positive effects of antagonizing cannabinoid receptor 1 (CB1R) in metabolic diseases such as fatty liver disease, obesity, and diabetes mellitus, but the role of cannabinoid receptor 2 (CB2R) in such diseases is relatively unknown. Activation of CB2R is known for its immunosuppressive roles in multiple sclerosis, rheumatoid arthritis, Crohn’s, celiac, and lupus diseases, and since autoimmune diseases can share common environmental and genetic factors, we propose CB2R specific agonists may also serve as disease modifiers in diabetes mellitus. The CNR2 gene, which encodes CB2R protein, is the result of a gene duplication of CNR1, which encodes CB1R protein. This ortholog evolved rapidly after transitioning from invertebrates to vertebrate hundreds of million years ago. Human specific CNR2 isoforms are induced by inflammation in pancreatic islets, and a CNR2 nonsynonymous SNP (Q63R) is associated with autoimmune diseases. We collected evidence from the literature and from our own studies demonstrating that CB2R is involved in regulating the inflammasome and especially release of the cytokine interleukin 1B (IL-1β). Furthermore, CB2R activation controls intracellular autophagy and may regulate secretion of extracellular vesicles from adipocytes that participate in recycling of lipid droplets, dysregulation of which induces chronic inflammation and obesity. CB2R activation may play a similar role in islets of Langerhans. Here, we will discuss future strategies to unravel what roles, if any, CB2R modifiers potentially play in T1DM.

The Role of Proteases and Serpin Protease Inhibitors in β-Cell Biology and Diabetes.

Regulation of the equilibrium between proteases and their inhibitors is fundamental to health maintenance. Consequently, developing a means of targeting protease activity to promote tissue regeneration and inhibit inflammation may offer a new strategy in therapy development for diabetes and other diseases. Specifically, recent efforts have focused on serine protease inhibitors, known as serpins, as potential therapeutic targets. The serpin protein family comprises a broad range of protease inhibitors, which are categorized into 16 clades that are all extracellular, with the exception of Clade B, which controls mostly intracellular proteases, including both serine- and papain-like cysteine proteases. This review discusses the most salient, and sometimes opposing, views that either inhibition or augmentation of protease activity can bring about positive outcomes in pancreatic islet biology and inflammation. These potential discrepancies can be reconciled at the molecular level as specific proteases and serpins regulate distinct signaling pathways, thereby playing equally distinct roles in health and disease development.

Immunotherapy: Building a bridge to a cure for type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease in which T cells attack and destroy the insulin-producing β cells in the pancreatic islets. Genetic and environmental factors increase T1D risk by compromising immune homeostasis. Although the discovery and use of insulin have transformed T1D treatment, insulin therapy does not change the underlying disease or fully prevent complications. Over the past two decades, research has identified multiple immune cell types and soluble factors that destroy insulin-producing β cells. These insights into disease pathogenesis have enabled the development of therapies to prevent and modify T1D. In this review, we highlight the key events that initiate and sustain pancreatic islet inflammation in T1D, the current state of the immunological therapies, and their advantages for the treatment of T1D.

291-OR: GPR31 Appears to Mediate the Downstream Actions of 12-Lipoxygenase in the Setting of Diabetic Inflammation

Inflammation in macrophages and pancreatic islets is a hallmark of both type 1 diabetes (T1D) and type 2 diabetes (T2D). The enzyme 12-lipoxygenase (12-LOX) is expressed in macrophages and β cells, produces the eicosanoid 12(S)-HETE and promotes inflammation. GPR31 has recently been identified as the 12(S)-HETE receptor. To clarify the role of GPR31 in diabetic inflammation, we generated Gpr31b-/- mice on the C57BL/6J background. Gpr31-/- mice are viable, with normal body weight, glucose tolerance, and β-cell mass, similar to 12-LOX knockout mice. Upon low dose streptozotocin treatment to induce β-cell inflammation, Gpr31b-/- mice remained normoglycemic unlike wildtype littermates, and exhibited no reductions in β-cell mass. Isolated islets treated with the insulin receptor antagonist S961 to mimic insulin resistance showed the expected decrease in Ins1, Pdx1, and Gpx1 mRNA levels. By contrast, in Gpr31b-/- islets, these genes remained unaltered. Additionally, Gpr31b-/- islets showed a trend towards a decrease in ER stress markers Ddit3 and spliced-Xbp1 expression. To examine GPR31 in macrophage inflammation, we first interrogated its role in the generation of proinflammatory macrophages upon polarization in vitro to the M1 state; under these conditions, we found no differences between Gpr31b-/- and wildtype macrophages, suggesting that GPR31 does not play a role in macrophage polarization. To test a role for GPR31 in proinflammatory macrophage function, we leveraged a zebrafish tailfin injury model, in which macrophages migrate to the site of tailfin injury. Compared to control fish, fish harboring knockdown of GPR31 showed reduced numbers of macrophages at the site of injury. Taken together, our data support the notion that the effects of 12-LOX are mediated through GPR31, and that GPR31 appears to promote proinflammatory responses in both macrophages and pancreatic islets. Disclosure S. A. Tersey: None. M. Walsh: None. M. Hernandez-perez: None. J. Dowgielewicz: None. A. Kulkarni: None. R. Anderson: None. R. G. Mirmira: Advisory Panel; Self; Hibercell Inc., Sigilon Therapeutics, Inc., Veralox Therapeutics, Employee; Spouse/Partner; Beta Bionics, Inc. Funding National Center for Advancing Translational Sciences (R03TR003381)

1258-P: Il-1ß-Induced Transcription of Nf-kB Target Genes Is Repressed by Bet Bromodomain Inhibitors in Pancreatic ß-Cells

Autoimmune diabetes is characterized by chronic inflammation of pancreatic islets which ultimately destroys insulin-producing β-cells. In the islet, elevated proinflammatory cytokines lead to increased transcription of inducible nitric oxide synthase (iNOS) and its downstream product, nitric oxide (NO). Elevated levels of NO for prolonged periods lead to β-cell apoptosis. The exact causes of autoimmune diabetes are not well defined and, although genetic predisposition is a factor, low concordance rates of autoimmune diabetes among monozygotic twins indicates a role for epigenetic factors. Recent studies suggest that the bromodomain and extraterminal domain (BET) family of epigenetic regulatory proteins contribute to the onset and progression of autoimmune diabetes. BET proteins are epigenetic readers of sites of lysine acetylation found commonly on histones and have emerged as promising drug targets for a wide variety of diseases. We hypothesize that BET proteins increase proinflammatory cytokine-induced transcription in β-cells leading to β-cell damage and that selective inhibition of BET bromodomains with small molecules will prevent or reverse the progression of autoimmune diabetes. Here, we show that BET bromodomain inhibitors decrease the β-cell response to proinflammatory cytokines in an insulinoma β-cell line (INS832/13) and primary rat islets. BET inhibitors attenuated cytokine-induced transcription of inflammatory mediators, including iNOS. This decreased transcription is mediated through inhibition of the NF-κB signaling pathway by BET inhibitors. Using knockdown of individual BET proteins in a β-cell line, we identified the importance of individual BET family members in the altered transcriptional profile characteristic of autoimmune diabetes. This work uncovers important mechanisms of disease onset and progression of autoimmune diabetes, laying the groundwork for more targeted treatments with drug-like small molecules. Disclosure J. Nord: None. S. Wynia-smith: None. B. C. Smith: None. R. Jones lipinski: None. Funding American Diabetes Association (1-18-IBS-068 to B.C.S.); National Institutes of Health (R01DK119359, T32HL134643)