The Chemokine Binding Protein M3 Prevents Diabetes Induced by Multiple Low Doses of Streptozotocin

Exosomal miR-25 from Mesenchymal stem cells inhibits T cells migration and Alleviates Type 1 diabetes mellitus by Targeting CXCR3 models

Mesenchymal stem cells (MSCs) have demonstrated promising therapeutic potential in the treatment of type 1 diabetes mellitus (T1DM); however, the underlying mechanism remains unclear. The primary pathological mechanism of T1DM involves activated T cells infiltrating the pancreas, leading to islet inflammation and the destruction of β-cells. However, the question of whether exosomes derived from MSCs can suppress the migration of T cells to the pancreas in the context of T1DM remains unresolved. In this study, we observed that miR-25 was highly expressed in MSCs exosomes and associated with signaling pathways related to cell migration. In vitro assay, we synthesized a miR-25 mimic and transiently transfected it into activated T cells, which revealed that miR-25 can effectively reduce the expression of CXCR3. Additionally, according to the in vivo T1DM mouse model, we found that there was a significant increase in miR-25 levels in T1DM mice treated with MSCs and the number of T cells decreased. Overall, our findings suggest that MSCs exosomes containing miR-25 can impede the infiltration of activated T cells into the pancreas in T1DM by repressing CXCR3 expression in these cells.

Epigallocatechin-3-gallate maintains Th1/Th2 response balance and mitigates type-1 autoimmune diabetes induced by streptozotocin through promoting the effect of bone-marrow-derived mesenchymal stem cells

Stem-cell-based therapy is one of the most promising therapeutic strategies owing to its regenerative and immunomodulatory properties. Epigallocatechin-3-gallate (EGCG), a known antioxidant and anti-inflammatory agent, has beneficial effects on cellular protection. We aimed to elucidate the feasibility of using EGCG, along with bone marrow-derived mesenchymal stem cells (BM-MSCs), to improve pancreatic damage through their immune regulatory functions in an experimental model of type 1 diabetes mellitus (T1DM) induced by multiple injections of streptozotocin (STZ). BM-MSCs were isolated from C57BL/6 mice and characterized. The diabetic groups were treated intraperitoneally with PBS, MSCs, EGCG, and a combination of MSCs and EGCG. Real-time PCR assays showed that MSCs with EGCG modulated T-bet and GATA-3 expression and upregulated the mRNA levels of Foxp-3 more efficiently. Analyses of spleen-isolated lymphocytes revealed that combinational treatment pronouncedly increased regulatory cytokines and decreased pro-inflammatory cytokines and splenocyte proliferation. The histopathological assessment demonstrated that co-treatment significantly reduced insulitis and recovered pancreatic islet morphology. Furthermore, the combination of MSCs and EGCG is associated with downregulated blood glucose and enhanced insulin levels. Therefore, combined therapy with EGCG and MSCs holds clinical potential for treating T1DM through synergetic effects in maintaining the Th1/Th2 response balance and promoting the regeneration of damaged pancreatic tissues.

Kinetin Ameliorates Cisplatin-Induced Hepatotoxicity and Lymphotoxicity via Attenuating Oxidative Damage, Cell Apoptosis and Inflammation in Rats

Though several previous studies reported the in vitro and in vivo antioxidant effect of kinetin (Kn), details on its action in cisplatin-induced toxicity are still scarce. In this study we evaluated, for the first time, the effects of kinetin in cisplatin (cp)- induced liver and lymphocyte toxicity in rats. Wistar male albino rats were divided into nine groups: (i) the control (C), (ii) groups 2,3 and 4, which received 0.25, 0.5 and 1 mg/kg kinetin for 10 days; (iii) the cisplatin (cp) group, which received a single intraperitoneal injection of CP (7.0 mg/kg); and (iv) groups 6, 7, 8 and 9, which received, for 10 days, 0.25, 0.5 and 1 mg/kg kinetin or 200 mg/kg vitamin C, respectively, and Cp on the fourth day. CP-injected rats showed a significant impairment in biochemical, oxidative stress and inflammatory parameters in hepatic tissue and lymphocytes. PCR showed a profound increase in caspase-3, and a significant decline in AKT gene expression. Intriguingly, Kn treatment restored the biochemical, redox status and inflammatory parameters. Hepatic AKT and caspase-3 expression as well as CD95 levels in lymphocytes were also restored. In conclusion, Kn mitigated oxidative imbalance, inflammation and apoptosis in CP-induced liver and lymphocyte toxicity; therefore, it can be considered as a promising therapy.

Fluorine MR Imaging Probes Dynamic Migratory Profiles of Perfluorocarbon-Loaded Dendritic Cells After Streptozotocin-Induced Inflammation

PURPOSE

The pathogenesis of type 1 diabetes (T1D) involves presentation of islet-specific self-antigens by dendritic cells (DCs) to autoreactive T cells, resulting in the destruction of insulin-producing pancreatic beta cells. We aimed to study the dynamic homing of diabetes-prone DCs to the pancreas and nearby organs with and without induction of pancreatic stress in a T1D susceptible model of repeated streptozotocin (STZ) injection.

PROCEDURES

In vitro labeling of activated bone marrow-derived DCs (BMDCs) from NOD (Nonobese diabetes) mice was performed using zonyl perfluoro-15-crown-5-ether nanoparticles (ZPFCE-NPs). Internalization of particles was confirmed by confocal microscopy. Two groups of NOD.SCID (nonobese diabetic/severe combined immunodeficiency) mice with (induced by low dose STZ administration) or without pancreatic stress were compared. Diabetogenic BMDCs loaded with BDC2.5 mimotope were pre-labeled with ZPFCE-NPs and adoptively transferred into mice. Longitudinal in vivo fluorine MRI (19F MRI) was performed 24 h, 36 h and 48 h after transfer of BMDCs. For ex vivo quantification of labeled cells, 19F NMR and flow cytometry were performed on dissected tissues to validate in vivo 19F MRI data.

RESULTS

In vitro flow cytometry and confocal microscopy confirmed high uptake of nanoparticles in BMDCs during the process of maturation. Migration/homing of activated and ZPFCE-NP- labeled BMDCs to different organs was monitored and quantified longitudinally, showing highest cell density in pancreas at 48-h time-point. Based on 19F MRI, STZ induced mild inflammation in the pancreatic region, as indicated by high accumulation of ZPFCE-NP-labeled BMDCs in the pancreas when compared to the vehicle group. Pancreatic draining lymph nodes showed elevated homing of labeled BMDCs in the vehicle groups in contrast to the STZ group after 72 h. The effect of STZ was confirmed by increased blood glucose levels.

CONCLUSION

We showed the potential of 19F MRI for the non-invasive visualization and quantification of migrating immune cells in models for pancreatic inflammation after STZ administration. Without any intrinsic background signal, 19F MRI serves as a highly specific imaging tool to study the migration of diabetic-prone BMDCs in T1D models in vivo. This approach could particularly be of interest for the longitudinal assessment of established or novel anti-inflammatory therapeutic approaches in preclinical models.

Multiwalled carbon nanotubes functionalized bacterial cellulose as an efficient healing material for diabetic wounds

The unique pool of features makes bacterial cellulose (BC) a robust platform to tailor its functionalities. Herein, the BC matrix was reinforced with multiwalled carbon nanotubes (MWCNT) to control infection and accelerate the healing process of diabetic wounds. The prepared BC-MWCNT composite film was characterized and antibacterial activity was assessed. Further, the in-vivo wound healing activity was performed and temporal expression of interleukin (IL-1α), tumor necrosis factor (TNF-α), vascular endothelial growth factor (VEGF) and platelets derived growth factor (PDGF) was quantitatively measured by real-time PCR. The characterization results confirmed the reinforcement of the BC matrix with MWCNT. The composite film showed antibacterial activity against all the tested strains. Moreover, the macroscopic analysis of the wound demonstrated faster closure of the diabetic wound in BC-MWCNT group (99% healing) as compared to negative control (77%) in 21 days. Histological studies further supported the results where complete reepithelization of the epidermis and healthy granulation tissue were observed in BC-MWCNT treated group. Molecular studies revealed that BC-MWCNT group showed relatively lesser expression of pro-inflammatory cytokines IL-1α and TNF-α and higher expression of VEGF than control that may have favored the faster healing. This study suggested that the tailorable properties of BC can be exploited to develop composites with potential applications in diabetic wound healing.

Resveratrol Inhibited ADAM10 Mediated CXCL16-Cleavage and T-Cells Recruitment to Pancreatic β-Cells in Type 1 Diabetes Mellitus in Mice

Background: CXCL16 attracts T-cells to the site of inflammation after cleaving by A Disintegrin and Metalloproteinase (ADAM10). Aim: The current study explored the role of ADAM10/CXCL16/T-cell/NF-κB in the initiation of type 1 diabetes (T1D) with special reference to the potential protecting role of resveratrol (RES). Methods: Four sets of Balb/c mice were created: a diabetes mellitus (DM) group (streptozotocin (STZ) 55 mg/kg, i.p.], a control group administered buffer, a RES group [RES, 50 mg/kg, i.p.), and a DM + RES group (RES (50 mg/kg, i.p.) and STZ (55 mg/kg, i.p.) administered daily for 12 days commencing from the fourth day of STZ injection). Histopathological changes, fasting blood insulin (FBI), glucose (FBG), serum and pancreatic ADAM10, CXCL16, NF-κB, T-cells pancreatic expression, inflammatory, and apoptotic markers were analyzed. Results: FBG, inflammatory and apoptotic markers, serum TNF-α, cellular CXCL16 and ADAM10 protein expression, pancreatic T-cell migration and NF-κB were significantly increased in diabetic mice compared to normal mice. RES significantly improved the biochemical and inflammatory parameters distorted in STZ-treated mice. Conclusions: ADAM10 promotes the cleaved form of CXCL16 driving T-cells into the islets of the pancreatic in T1D. RES successfully prevented the deleterious effect caused by STZ. ADAM10 and CXCL16 may serve as novel therapeutic targets for T1D.

Simvastatin mitigates streptozotocin-induced type 1 diabetes in mice through downregulation of ADAM10 and ADAM17

BACKGROUND

T cell mediates immune response in type 1 diabetes mellitus (T1DM) through its trafficking into pancreatic islets. The role of A Disintigrin And Metalloproteinase 10 (ADAM10) and 17 (ADAM17) in pancreatic T-cells recruitment into the pancreatic islets during T1DM is not known.

AIM

Explore the role of ADAM10 and ADAM17 in the processing of CXCL16 in T1DM and possible protective effect of simvastatin (SIM) in streptozotocin (STZ)-induced T1DM.

MAIN METHODS

Balb/c mice were classified into 4 groups, 10 each. Control group received buffer while SIM group received 50 mg/kg, i.p daily for 12 days starting from day 4 of the experiment. Diabetic group; received STZ (55 mg/kg, i.p.) for 5 consecutive days starting from day 1 of the experiment. SIM + STZ group; received SIM (50 mg/kg, i.p.) daily for 12 days and STZ (55 mg/kg, i.p.) for 5 consecutive days. Biochemical, inflammatory and apoptotic markers as well as expression of CXCL16, ADAM10, NF-κB and pancreatic T-cells expression were analyzed.

KEY FINDINGS

Significant increase in biochemical, inflammatory, apoptotic parameters, expression of ADAM10, ADAM17, CXCL16, NF-κB, and infiltrated T-cells to the pancreatic islets were found in STZ group. SIM treatment in the presence of STZ improved biochemical and inflammatory parameters as well as it reduced the expression of CXCL16, ADAM10, ADAM17, NF-κΒ, T-cells migration and apoptosis in the pancreatic islets.

SIGNIFICANCE

SIM mitigated pancreatic β-cell death induced by STZ through down regulation of ADAM10, ADAM17and CXCL16. Therefore, ADAM10/ADAM17 and CXCL16 may serve as novel therapeutic targets for T1DM.

The binding and specificity of chemokine binding proteins, through the lens of experiment and computation

Chemokines are small proteins that are critical for immune function, being primarily responsible for the activation and chemotaxis of leukocytes. As such, many viruses, as well as parasitic arthropods, have evolved systems to counteract chemokine function in order to maintain virulence, such as binding chemokines, mimicking chemokines, or producing analogs of transmembrane chemokine receptors that strongly bind their targets. The focus of this review is the large group of chemokine binding proteins (CBP) with an emphasis on those produced by mammalian viruses. Because many chemokines mediate inflammation, these CBP could possibly be used pharmaceutically as anti-inflammatory agents. In this review, we summarize the structural properties of a diverse set of CBP and describe in detail the chemokine binding properties of the poxvirus-encoded CBP called vCCI (viral CC Chemokine Inhibitor). Finally, we describe the current and emerging capabilities of combining computational simulation, structural analysis, and biochemical/biophysical experimentation to understand, and possibly re-engineer, protein–protein interactions.

Lower threshold to NFκB activity sensitizes murine β-cells to streptozotocin

The β-cell response to injury may be as critical for the development of diabetes as the specific insult. In the current study, we used streptozotocin (STZ) to injure the β-cell in order to study the response with a focus on NFκB. MIN6 cells were exposed to STZ (0.5-8 mM, 0-24h) ±TNFα (100 ng/mL) and ±IκBβ siRNA to lower the threshold to NFκB activation. Cell viability was determined by trypan blue exclusion. NFκB activation was determined by the expression of the target genes Nos2 and Cxcl10, localization of the NFκB proteins p65 and p50, and expression and localization of the NFκB inhibitors, IκBβ and IκBα. There was no NFκB activation in MIN6 cell exposed to STZ (2 mM) alone. However, knocking down IκBβ expression using siRNA resulted in STZ-induced expression of NFκB target genes and increased cell death, while co-incubation with STZ and TNFα enhanced cell death compared to either exposure alone. Adult male IκBβ-/- and WT mice were exposed to STZ and monitored for diabetes. The IκBβ-/- mice developed hyperglycemia and diabetes more frequently than controls following STZ exposure. Based on these results we conclude that STZ exposure alone does not induce NFκB activity. However, lowering the threshold to NFκB activation by co-incubation with TNFα or lowering IκBβ levels by siRNA sensitizes the NFκB response to STZ and results in a higher likelihood of developing diabetes in vivo. Therefore, increasing the threshold to NFκB activation through stabilizing NFκB inhibitory proteins may prevent β-cell injury and the development of diabetes.

Resveratrol mitigates pancreatic TF activation and autophagy-mediated beta cell death via inhibition of CXCL16/ox-LDL pathway: A novel protective mechanism against type 1 diabetes mellitus in mice

The role of CXC chemokine ligand 16 (CXCL16), oxidized LDL (ox-LDL), tissue factor (TF) and autophagy-induced beta cell death in type 1 diabetes mellitus (T1DM) pathogenesis is still unclear. We examined the therapeutic potential and mechanism of resveratrol (RES) against T1DM. Diabetes was induced in Balb/c mice by i. p. injection of 55 mg/kg streptozotocin (STZ) for five consecutive days. The control group received vehicles. RES or (RES + STZ) groups received RES (50 mg/kg, i. p.) daily for 12 days starting from the fourth day of buffer or STZ injections, respectively. Blood glucose, serum insulin, beta cell mass, serum lipid profiles, histological changes, oxidative stress biomarkers were determined. Moreover, CXCL16, TF, ox-LDL, P62 and LC3 tissue expression were also analyzed. Diabetic mice showed a marked deterioration in biochemical, physical and oxidative stress parameters. Interestingly, immunofluorescence analysis showed a remarkable elevation in CXCL16 (12 folds), ox-LDL (9 folds), TF (8.3 folds) in pancreatic B-cells. Moreover, western blotting revealed a profound increase in ox-LDL (2.6 folds), TF (3.2 folds), while a significant decline in P62 (0.34) and LC3 (0.25) when compared to control. RES mitigated biochemical, physical, oxidative imbalance and distorted pancreatic architecture in T1DM mice. Intriguingly, CXCL16, ox-LDL, TF and autophagic markers were also restored after RES treatment. Our data give the first direct evidence that beta cell-specific CXCL16/ox-LDL pathway activation is a potential trigger of TF activation and autophagic beta cell death in T1DM. Moreover, RES may have potential therapeutic applications for prevention of T1DM mainly via ameliorating this pathway.

Resveratrol inhibits macrophage infiltration of pancreatic islets in streptozotocin-induced type 1 diabetic mice via attenuation of the CXCL16/NF-κΒ p65 signaling pathway

AIM

Despite CXC chemokine ligand 16 (CXCL16) contributes to the pathogenesis of many inflammatory disorders, the mechanism by which CXCL16 is involved in T1DM remains unclear. In this study, we examined the role of the CXCL16/NF-κΒ p65 signaling pathway in the progression of this disease and the possible protective effect of resveratrol (RES) on streptozotocin (STZ)-induced T1DM.

MAIN METHODS

Mice were classified into four groups of 10 animals each. The control group received citrate buffer. The RES group received 50 mg/kg i.p. RES for 12 days beginning on day 4 of citrate buffer. The STZ group received 55 mg/kg i.p. STZ once a day for 5 consecutive days. The fourth group injected with RES (50 mg/kg) for 12 days starting on day 4 of STZ injection. Biochemical, physical and oxidative stress parameters were measured in all groups. Moreover, expression of CXCL16 and CD45 was measured in pancreatic islets and spleen. Additionally, NF-κΒ p65 was investigated in isolated islets.

KEY FINDINGS

Our results showed a significant elevation of CXCL16, NF-κΒ p65 and CD45 in islets of diabetic (DM) mice. Intriguingly, RES significantly restored distorted biochemical, physical and oxidative stress parameters after STZ treatment as well as inhibited the expression of CXCL16/NF-κΒ p65 in pancreatic islets. Moreover, RES normalized CXCL16 and CD45 expression in islets and spleen.

SIGNIFICANCE

This study demonstrates first evidence that CXCL16/NF-κΒ p65 signaling pathway is associated with macrophage infiltration to pancreatic islet in T1DM and that RES successfully improved T1DM may be at least via inhibiting this pathway.

Impact of coxsackievirus-B4E2 combined with a single low dose of streptozotocin on pancreas of outbred mice: investigation of viral load, pathology and inflammation

Coxsackieviruses B (CV-B) belong to the EV-B species. CV-B and particularly CV-B4 are thought to be involved in the development of chronic diseases like type 1 diabetes (T1D). The mechanisms of the enteroviral pathogenesis of T1D are not well known, yet. The in vitro studies are rich with information but in vivo infection models are needed to investigate the impact of viruses onto organs. Our objective was to study the impact of CV-B4E2 combined with a single sub-diabetogenic dose of streptozotocin (STZ) on the pancreas of mice. The infection with CV-B4E2 of CD1 outbred mice treated with a sub-diabetogenic dose of STZ induced hyperglycemia and hypoinsulinemia. Along with the chemokine IP-10, viral RNA and infectious particles were detected in the pancreas. The pancreas of these animals was also marked with insulitis and other histological alterations. The model combining STZ and CV-B4E2 opens the door to new perspectives to better understand the interactions between virus and host, and the role of environmental factors capable, like STZ, to predispose the host to the diabetogenic effects of enteroviruses.

Residue Mutations in Murine Herpesvirus 68 Immunomodulatory Protein M3 Reveal Specific Modulation of Chemokine Binding

The M3 protein (M3) encoded by murine gammaherpesvirus 68 (MHV-68) is a unique viral immunomodulator with a high-affinity for a broad spectrum of chemokines, key mediators responsible for the migration of immune cells to sites of inflammation. M3 is currently being studied as a very attractive and desirable tool for blocking the chemokine signaling involved in some inflammatory diseases and cancers. In this study, we elucidated the role of M3 residues E70 and T272 in binding to chemokines by examining the effects of the E70A and T272G mutations on the ability of recombinant M3, prepared in Escherichia coli cells, to bind the human chemokines CCL5 and CXCL8. We found that the E70A mutation enhanced binding of M3 to CCL5 two-fold but had little effect on its binding to CXCL8. In contrast, the T272G mutation was found to be important for the thermal stability of M3 and significantly decreased M3's binding to both CCL5 (by about 4×) and CXCL8 (by about 5×). We also constructed in silico models of the wild-type M3-CCL5 and M3-CCL8 complexes and found substantial differences in their physical and chemical properties. M3 models with single mutation E70A and T272G suggested the role of E70 and T272 in binding M3 protein to chemokines. In sum, we have confirmed that site-directed mutagenesis could be an effective tool for modulating the blockade of particular chemokines by M3, as desired in therapeutic treatments for severe inflammatory illnesses arising from chemokine network dysregulation.

Immunomodulatory effects of mesenchymal stem cell-derived exosomes on experimental type-1 autoimmune diabetes

Exosomes derived from adipose tissue-derived mesenchymal stem cells (AD-MSCs) have immunomodulatory effects of T-cell inflammatory response and reduction of clinical symptoms on streptozotocin-induced of the type-1 diabetes mellitus (T1DM). Beside control group and untreated T1DM mice, a group of T1DM mice was treated with intraperitoneal injections of characterized exosomes derived from autologous AD-MSCs. Body weight and blood glucose levels were measured during the procedure. Histopathology and immunohistochemistry were used for evaluation of pancreatic islets using hemotoxylin and eosin (H&E) staining and anti-insulin antibody. Isolated splenic mononuclear cells (MNCs) were subjected to splenocytes proliferation assay using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, immunophenotyping of regulatory T cells and cytokines. A significant increase in the levels of interleukin-4 (IL-4), IL-10, and transforming growth factor-β, and a decrease in the levels of IL-17 and interferon-γ in concordance with the significant increase in the Treg cell ratio in splenic MNCs (P < 0.05) was shown in T1DM mice treated with AD-MSC's exosomes as compared to T1DM untreated mice. This amelioration of autoimmune reaction after treatment of T1DM mice with the AD-MSC exosomes was confirmed with a significant increase in islets using H&E staining and Immunohistochemistry analyses. As expected, body weight, blood glucose levels in a survival of T1DM mice treated with AD-MSC's exosomes were maintained stable in comparison to untreated T1DM mice. It can be concluded that AD-MSC's exosomes exert ameliorative effects on autoimmune T1DM through increasing regulatory T-cell population and their products without a change in the proliferation index of lymphocytes, which makes them more effective and practical candidates.

Pancreatic islet inflammation: an emerging role for chemokines

Both type 1 and type 2 diabetes exhibit features of inflammation associated with alterations in pancreatic islet function and mass. These immunological disruptions, if unresolved, contribute to the overall pathogenesis of disease onset. This review presents the emerging role of pancreatic islet chemokine production as a critical factor regulating immune cell entry into pancreatic tissue as well as an important facilitator of changes in tissue resident leukocyte activity. Signaling through two specific chemokine receptors (i.e., CXCR2 and CXCR3) is presented to illustrate key points regarding ligand-mediated regulation of innate and adaptive immune cell responses. The prospective roles of chemokine ligands and their corresponding chemokine receptors to influence the onset and progression of autoimmune- and obesity-associated forms of diabetes are discussed.

Extracted Triterpenes from Antrodia cinnamomea Reduce the Inflammation to Promote the Wound Healing via the STZ Inducing Hyperglycemia-Diabetes Mice Model

This research evaluated the effects of triterpenes on the regulation of STZ-induced hyperglycaemic diabetes through an anti-inflammatory response. Diabetic mice were orally administered various concentrations of triterpenes on a daily basis. Weight gain, volume of drinking water, and liver and spleen weight were recorded and evaluated. These evaluations presented a positive regulation to the abnormal metabolism appearance compared to the diabetic mice. In the diabetic mice, the detection of adiponectin production or elevated levels of inflammatory factors such as CCL1 and TPO expression were found to reduce hyperglycaemia and thereby induce an inflammatory response. Moreover, to the best of our knowledge, hyperglycaemia impairs the tissue healing associated with an increased and prolonged inflammatory response. An investigation of the anti-inflammatory response in wound healing as affected by the triterpenes verified the promotion of wound recovery.

Collagen I-induced dendritic cells activation is regulated by TNF-alpha production through down-regulation of IRF4

Previously we have shown that collagen I enhances the maturation and function of dendritic cells (DCs). Inflammatory mediators such as tumour necrosis factor (TNF)- alpha, interleukin (IL)-1 beta and lipopolysaccharide (LPS) are also known to activate DCs. Here we investigated the involvement of TNF-alpha on the collagen I-induced DCs activation. TNF-a neutralization inhibited collagen I-induced IL-12 secretions by DCs. Additionally, we observed suppression of collagen I-induced costimulatory molecules expression along with down-regulation of genes involved in DCs activation pathway. Furthermore, TNF- alpha inhibition upon collagen Istimulation up-regulated the expression of interferon regulatory transcription factor IRF4, when compared to collagen I only treated cells. Collectively, our data demonstrate that collagen I induce TNF- alpha production, which is crucial for the activation and function of DCs, through down-regulation of IRF4, and implicates the importance in development of anti- TNF-alpha therapeutics for several inflammatory diseases.

Transcriptional regulation of chemokine genes: a link to pancreatic islet inflammation?

Enhanced expression of chemotactic cytokines (aka chemokines) within pancreatic islets likely contributes to islet inflammation by regulating the recruitment and activation of various leukocyte populations, including macrophages, neutrophils, and T-lymphocytes. Because of the powerful actions of these chemokines, precise transcriptional control is required. In this review, we highlight what is known about the signals and mechanisms that govern the transcription of genes encoding specific chemokine proteins in pancreatic islet β-cells, which include contributions from the NF-κB and STAT1 pathways. We further discuss increased chemokine expression in pancreatic islets during autoimmune-mediated and obesity-related development of diabetes.

Virtual screening of m3 protein antagonists for finding a model to study the gammaherpesvirus damaged immune system and chemokine related diseases

INTRODUCTION

M3 protein is a chemokine decoy receptor involved in pathogenesis of persistent infection with gammaherpesvirus and complications related to the latency of this pathogen. We proposed that antagonists of the M3 would provide a unique opportunity for studying new therapeutic strategies in disordered immune system, immune-deficient states and role of chemokines in pathogenesis development.

METHODS

Comparative modeling and fold recognition algorithms have been used for prediction of M3 protein 3-D model. Evaluation of the models using Q-mean and ProSA-web score, has led to choosing predicted model by fold recognition algorithm as the best model which was minimized regarding energy level using Molegro Virtual Docker 2011.4.3.0 (MVD) software. Pockets and active sites of model were recognized using MVD cavity detection, and MetaPocket algorithms. Ten thousand compounds accessible on KEGG database were screened; MVD was used for computer simulated docking study; MolDock SE was selected as docking scoring function and final results were evaluated based on MolDock and Re-rank score.

RESULTS

Docking data suggested that prilocaine, which is generally applied as a topical anesthetic, binds strongly to 3-D model of M3 protein.

CONCLUSION

This study proposes that prilocaine is a potential inhibitor of M3 protein and possibly has immune enhancing properties.

The biology of chemokines and their receptors

This article summarizes the work done by our laboratory and by our collaborators on the biological role of chemokines and their receptors. Using both gain-of-function and loss of function genetic approaches, we have demonstrated that chemokines are important for the homeostatic distribution of leukocytes in tissues and for their mobilization from the bone marrow. We have also shown that chemokines are important players in inflammation and autoimmunity and that they contribute to lymphoid organogenesis, angiogenesis, and immune regulation. Together, our results and those of the literature suggest an important role for chemokines in homeostasis and disease and characterize chemokines as important targets for therapeutic intervention.

Subversion of cytokine networks by virally encoded decoy receptors

During the course of evolution, viruses have captured or created a diverse array of open reading frames, which encode for proteins that serve to evade and sabotage the host innate and adaptive immune responses that would otherwise lead to their elimination. These viral genomes are some of the best textbooks of immunology ever written. The established arsenal of immunomodulatory proteins encoded by viruses is large and growing, and includes specificities for virtually all known inflammatory pathways and targets. The focus of this review is on herpes and poxvirus-encoded cytokine and chemokine-binding proteins that serve to undermine the coordination of host immune surveillance. Structural and mechanistic studies of these decoy receptors have provided a wealth of information, not only about viral pathogenesis but also about the inner workings of cytokine signaling networks.

Restoration of direct pathway glycogen synthesis flux in the STZ-diabetes rat model by insulin administration

Type 1 diabetes subjects are characterized by impaired direct pathway synthesis of hepatic glycogen that is unresponsive to insulin therapy. Since it is not known whether this is an irreversible defect of insulin-dependent diabetes, direct and indirect pathway glycogen fluxes were quantified in streptozotocin (STZ)-induced diabetic rats and compared with STZ rats that received subcutaneous or intraperitoneal insulin (I-SC or I-IP). Three groups of STZ rats were studied at 18 days post-STZ treatment. One group was administered I-SC and another I-IP as two daily injections of short-acting insulin at the start of each light and dark period for days 9-18. A third group did not receive any insulin, and a fourth group of nondiabetic rats was used as control. Glycogen synthesis via direct and indirect pathways, de novo lipogenesis, and gluconeogenesis were determined over the nocturnal feeding period using deuterated water. Direct pathway was residual in STZ rats, and glucokinase activity was also reduced significantly from control levels. Insulin administration restored both net glycogen synthesis via the direct pathway and glucokinase activity to nondiabetic control levels and improved the lipogenic pathway despite an inefficient normalization of the gluconeogenic pathway. We conclude that the reduced direct pathway flux is not an irreversible defect of insulin-dependent diabetes.

Immunoglobulin Fc fragment tagging allows strong activation of endogenous CD4 T cells to reshape the tumor milieu and enhance the antitumor effect of lentivector immunization

A major problem with current cancer vaccines is that the induction of CD8 immune responses is rarely associated with antitumor benefits, mainly owing to multiple immune suppressions in established tumor lesions. In this study, we investigated if and how activation of endogenous CD4 T cells could be achieved to influence the suppressive tumor milieu and antitumor effect. We engineered a lentivector (lv) to express a nominal fusion Ag composed of hepatitis B surface protein and IgG2a Fc fragment (HBS-Fc-lv) to increase the magnitude of CD8 response but, more importantly, to induce effective coactivation of CD4 T cells. We found that, remarkably, immunization with HBS-Fc-lv caused significant regression of established tumors. Immunologic analysis revealed that, compared with HBS-lv without Fc fragment, immunization with HBS-Fc-lv markedly increased the number of functional CD8 and CD4 T cells and the level of Th1/Tc1-like cytokines in the tumor while substantially decreasing the regulatory T cell ratio. The favorable immunologic changes in tumor lesions and the improvement of antitumor effects from HBS-Fc-lv immunization were dependent on the CD4 activation, which was Fc receptor mediated. Adoptive transfer of CD4 T cells from the HBS-Fc-lv-immunized mice could activate endogenous CD8 T cells in an IFN-γ-dependent manner. We conclude that endogenous CD4 T cells can be activated by lv expressing Fc-tagged Ag to provide another layer of help--that is, creating a Th1/Tc1-like proinflammatory milieu within the tumor lesion to boost the effector phase of immune responses in enhancing the antitumor effect.

Modulation of chemokine activity by viruses

Viruses encode a variety of mechanisms to evade host immune pathways. Large DNA viruses (herpesviruses and poxviruses) encode proteins that mimic chemokines and chemokine receptors. Also, some viruses encode secreted proteins that bind chemokines and have structure unrelated to host proteins. Recent research in this area has led to the identification of new viral proteins that modulate the chemokine system, has provided information on the molecular mechanisms leading to interference of chemokine signaling, and has shed light into the function of these proteins in the context of infection. The therapeutic value of these viral proteins to inhibit immune responses that cause pathology has been explored further. Finally, a new family of chemokine binding proteins identified in ticks expands this strategy of immune modulation beyond the virus world.

Analysis of mutations from SCID and Omenn syndrome patients reveals the central role of the Rag2 PHD domain in regulating V(D)J recombination

Rag2 plays an essential role in the generation of antigen receptors. Mutations that impair Rag2 function can lead to severe combined immunodeficiency (SCID), a condition characterized by complete absence of T and B cells, or Omenn syndrome (OS), a form of SCID characterized by the virtual absence of B cells and the presence of oligoclonal autoreactive T cells. Here, we present a comparative study of a panel of mutations that were identified in the noncanonical plant homeodomain (PHD) of Rag2 in patients with SCID or OS. We show that PHD mutant mouse Rag2 proteins that correspond to those found in these patients greatly impaired endogenous recombination of Ig gene segments in a Rag2-deficient pro-B cell line and that this correlated with decreased protein stability, impaired nuclear localization, and/or loss of the interaction between Rag2 and core histones. Our results demonstrate that point mutations in the PHD of Rag2 compromise the functionality of the entire protein, thus explaining why the phenotype of cells expressing PHD point mutants differs from those expressing core Rag2 protein that lacks the entire C-terminal region and is therefore devoid of the regulation imposed by the PHD. Together, our findings reveal the various deleterious effects of PHD Rag2 mutations and demonstrate the crucial role of this domain in regulating antigen receptor gene assembly. We believe these results reveal new mechanisms of immunodeficiency in SCID and OS.

Expression of the chemokine binding protein M3 promotes marked changes in the accumulation of specific leukocytes subsets within the intestine

BACKGROUND & AIMS

Chemokines are small proteins that direct leukocyte trafficking under homeostatic and inflammatory conditions. We analyzed the differential expression of chemokines in distinct segments of the intestine and investigated the importance of chemokines for the distribution of leukocytes in the intestine during homeostatic and inflammatory conditions.

METHODS

We analyzed messenger RNA for all known chemokines in different segments of the gut by quantitative polymerase chain reaction. To study the effect of multiple-chemokine blockade in the gut, we generated transgenic mice that expressed the chemokine binding protein M3 in the intestine (V-M3 mice). We used flow cytometry to evaluate the changes in the numbers of leukocytes.

RESULTS

We observed distinct chemokine expression profiles in the 6 segments of the gut. Some chemokines were expressed throughout the intestine (CCL28, CCL6, CXCL16, and CX3CL1), whereas others were expressed preferentially in the small (CCL25 and CCL5) or large intestine (CCL19, CCL21, and CXCL5). Expression of the chemokine blocker M3 in intestinal epithelial cells resulted in reduced numbers of B and T cells in Peyer's patches, reduced numbers of intraepithelial CD8alphabeta(+)/TCRalphabeta(+) and CD8alphaalpha(+)/TCRalphabeta(+) T cells, and reduced numbers of lamina propria CD8(+) T cells. Strikingly, M3 expression markedly reduced the number of eosinophils and macrophages in the small and large intestines. Dextran sulfate sodium treatment of control mice led to marked changes in the expression of chemokines and in the number of myeloid cells in the colon. These cellular changes were significantly attenuated in the presence of M3.

CONCLUSIONS

Our study reveals a complex pattern of chemokine expression in the intestine and indicates that chemokines are critical for leukocyte accumulation in the intestine during homeostasis and inflammation.

High beta-cell mass prevents streptozotocin-induced diabetes in thioredoxin-interacting protein-deficient mice

Thioredoxin-interacting protein (TxNIP) is an endogenous inhibitor of thioredoxin, a ubiquitous thiol oxidoreductase, that regulates cellular redox status. Diabetic mice exhibit increased expression of TxNIP in pancreatic islets, and recent studies suggest that TxNIP is a proapoptotic factor in beta-cells that may contribute to the development of diabetes. Here, we examined the role of TxNIP deficiency in vivo in the development of insulin-deficient diabetes and whether it impacted on pancreatic beta-cell mass and/or insulin secretion. TxNIP-deficient (Hcb-19/TxNIP(-/-)) mice had lower baseline glycemia, higher circulating insulin concentrations, and higher total pancreatic insulin content and beta-cell mass than control mice (C3H). Hcb-19/TxNIP(-/-) did not develop hyperglycemia when injected with standard multiple low doses of streptozotocin (STZ), in contrast to C3H controls. Surprisingly, although beta-cell mass remained higher in Hcb-19/TxNIP(-/-) mice compared with C3H after STZ exposure, the relative decrease induced by STZ was as great or even greater in the TxNIP-deficient animals. Consistently, cultured pancreatic INS-1 cells transfected with small-interfering RNA against TxNIP were more sensitive to cell death induced by direct exposure to STZ or to the combination of inflammatory cytokines interleukin-1beta, interferon-gamma, and tumor necrosis factor-alpha. Furthermore, when corrected for insulin content, isolated pancreatic islets from TxNIP(-/-) mice exhibited reduced glucose-induced insulin secretion. These data indicate that TxNIP functions as a regulator of beta-cell mass and influences insulin secretion. In conclusion, the relative resistance of TxNIP-deficient mice to STZ-induced diabetes appears to be because of an increase in beta-cell mass. However, TxNIP deficiency is associated with sensitization to STZ- and cytokine-induced beta-cell death, indicating complex regulatory roles of TxNIP under different physiological and pathological conditions.

The chemokine-binding protein M3 as a tool to understand the chemokine network in vivo

Murine herpesvirus 68 (MHV-68) codes for a secreted chemokine-binding protein, termed M3, which interacts with a broad range of chemokines with very high affinity, inhibiting chemokine function both in vitro and in vivo. Here we describe the transgenic methodology used to study the role of M3 as an immune modulator in vivo.

Chemokine binding proteins encoded by pathogens

Chemokines are chemoattractant cytokines that play an important role in immunity. The role of chemokines against invading pathogens is emphasized by the expression of chemokine inhibitors by many pathogens. A mechanims employed by poxviruses and herpesviruses is the secretion of chemokine bindingproteins unrelated to host receptors that bind chemokines with high affinity and block their activity. Soluble chemokine binding proteins have also been identified in the human parasite Schistosoma mansoni and in ticks. The binding specificity of these inhibitors of cell migration point at chemokines that contribute to host defense mechanisms against various pathogens. Chemokine binding proteins modulate the immune response and may lead to new therapeutic approaches to treat inflamatory diseases.

The novel inosine analogue, INO-2002, protects against diabetes development in multiple low-dose streptozotocin and non-obese diabetic mouse models of type I diabetes

Endogenous purines including inosine have been shown to exert immunomodulatory and anti-inflammatory effects in a variety of disease models. The dosage of inosine required for protection is very high because of the rapid metabolism of inosine in vivo. The aim of this study was to determine whether a metabolic-resistant purine analogue, INO-2002, exerts anti-inflammatory effects in two animal models of type I diabetes. Type I diabetes was induced chemically with streptozotocin or genetically using the non-obese diabetic (NOD) female mouse model. Mice were treated with INO-2002 or inosine as required at 30, 100, or 200 mg/kg per day, while blood glucose and diabetes incidence were monitored. The effect of INO-2002 on the pancreatic cytokine profile was also determined. INO-2002 reduced both the hyperglycaemia and incidence of diabetes in both streptozotocin-induced and spontaneous diabetes in NOD mice. INO-2002 proved to be more effective in protecting against diabetes than the naturally occurring purine, inosine, when administered at the same dose. INO-2002 treatment decreased pancreatic levels of interleukin (IL)-12 and tumour necrosis factor-alpha, while increasing levels of IL-4 and IL-10. INO-2002 also reduced pancreatic levels of the chemokine MIP-1 alpha. The inosine analogue, INO-2002, was protected more effectively than the naturally occurring purine, inosine, against development of diabetes in two separate animal models. INO-2002 exerts protective effects by changing the pancreatic cytokine expression from a destructive Th1 to a protective Th2 profile. The use of analogues of inosine such as INO-2002 should be considered as a potential preventative therapy in individuals susceptible to developing type I diabetes.

Toll-like receptor signaling in small intestinal epithelium promotes B-cell recruitment and IgA production in lamina propria

BACKGROUND & AIMS

Several lines of evidence support a role for Toll-like receptor (TLR) signaling to protect the intestine from pathogenic infection. We hypothesized that TLR signaling at the level of the intestinal epithelium is critical for mucosal immune responses.

METHODS

We generated transgenic mice that express a constitutively active form of TLR4 in the intestinal epithelium (V-TLR4 mice). Lamina propria cellularity was evaluated by immunostaining and flow cytometry. Immunoglobulin (Ig) A levels in the stool and serum were measured by enzyme-linked immunosorbent assay. Chemokine and cytokine expression were analyzed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

V-TLR4 transgenic mice reproduced normally and had a normal life span. Constitutive activity of TLR4 in the intestinal epithelium promoted recruitment of B cells and an increase in fecal IgA levels. Intestinal epithelial cells of V-TLR4 mice expressed higher levels of CCL20 and CCL28, chemokines known to be involved in B-cell recruitment, and of a proliferation-inducing ligand (APRIL), a cytokine that promotes T-cell-independent class switching of B cells to IgA. The changes in B-cell numbers and IgA levels were blocked by simultaneous expression in intestinal epithelial cells of M3, a herpes virus protein that binds and inhibits multiple chemokines.

CONCLUSIONS

TLR signaling in the intestinal epithelial cells significantly elevated the production of IgA in the intestine. This effect was mediated by TLR-induced expression of a specific set of chemokines and cytokines that promoted both recruitment of B cells into the lamina propria and IgA class switching of B cells.

Mouse vanin-1 is cytoprotective for islet beta cells and regulates the development of type 1 diabetes

AIMS/HYPOTHESIS

Islet cell death is a key initiating and perpetuating event in type 1 diabetes and involves both immune-mediated and endogenous mechanisms. The epithelial pantetheinase vanin-1 is proinflammatory and cytoprotective via cysteamine release in some tissues. We investigated the impact of a vanin-1 deficiency on islet death and type 1 diabetes incidence.

METHODS

Vanin-1-deficient mice were produced and tested in drug-induced and autoimmune diabetes models. The contribution of vanin-1 to islet survival versus immune responses was evaluated using lymphocyte transfer and islet culture experiments.

RESULTS

The vanin-1/cysteamine pathway contributes to the protection of islet beta cells from streptozotocin-induced death in vitro and in vivo. Furthermore, vanin-1-deficient NOD mice showed a significant aggravation of diabetes, which depended upon loss of vanin-1 expression by host tissues. This increased islet fragility was accompanied by greater CD4+ insulitis without impairment of regulatory cells. Addition of cystamine, the product of pantetheinase activity, protected islets in vitro and compensated for vanin-1 deficiency in vivo.

CONCLUSIONS/INTERPRETATION

This study unravels a major cytoprotective role of cysteamine for islet cells and suggests that modulation of pantetheinase activity may offer alternative strategies to maintain islet cell homeostasis.

Islet expression of M3 uncovers a key role for chemokines in the development and recruitment of diabetogenic cells in NOD mice

OBJECTIVE

Type 1 diabetes is an autoimmune disease characterized by a local inflammatory reaction in and around islets followed by selective destruction of insulin-secreting beta-cells. We tested the hypothesis that chemokines affect different mechanisms responsible for the development of diabetes in NOD mice.

RESEARCH DESIGN AND METHODS

We examined chemokine expression in islets of NOD mice and tested their functional relevance to development of diabetes using transgenic mice expressing the mouse herpesvirus 68-encoded chemokine decoy receptor M3 (NOD-M3 mice) in insulin-secreting beta-cells.

RESULTS

Multiple chemokines were expressed in pancreatic islets of NOD mice before development of diabetes. Islet-specific expression of the pan-chemokine inhibitor M3 dramatically reduced leukocyte infiltration and islet destruction and completely blocked development of diabetes in NOD-M3 mice. M3 blocked diabetes by inhibiting the priming of diabetogenic cells in the pancreatic lymph nodes and their recruitment into the islets. This effect was specific to the pancreatic islets because M3 expression did not affect other ongoing autoimmune processes.

CONCLUSIONS

These results demonstrate that chemokines mediate afferent and efferent immunity in type 1 diabetes and suggest that broad chemokine blockade may represent a viable strategy to prevent insulitis and islet destruction.

An ectromelia virus protein that interacts with chemokines through their glycosaminoglycan binding domain

Poxviruses encode a number of secreted virulence factors that modulate the host immune response. The vaccinia virus A41 protein is an immunomodulatory protein with amino acid sequence similarity to the 35-kDa chemokine binding protein, but the host immune molecules targeted by A41 have not been identified. We report here that the vaccinia virus A41 ortholog encoded by ectromelia virus, a poxvirus pathogen of mice, named E163 in the ectromelia virus Naval strain, is a secreted 31-kDa glycoprotein that selectively binds a limited number of CC and CXC chemokines with high affinity. A detailed characterization of the interaction of ectromelia virus E163 with mutant forms of the chemokines CXCL10 and CXCL12alpha indicated that E163 binds to the glycosaminoglycan binding site of the chemokines. This suggests that E163 inhibits the interaction of chemokines with glycosaminoglycans and provides a mechanism by which E163 prevents chemokine-induced leukocyte migration to the sites of infection. In addition to interacting with chemokines, E163 can interact with high affinity with glycosaminoglycan molecules, enabling E163 to attach to cell surfaces and to remain in the vicinity of the sites of viral infection. These findings identify E163 as a new chemokine binding protein in poxviruses and provide a molecular mechanism for the immunomodulatory activity previously reported for the vaccinia virus A41 ortholog. The results reported here also suggest that the cell surface and extracellular matrix are important targeting sites for secreted poxvirus immune modulators.

Fractalkine deficiency markedly reduces macrophage accumulation and atherosclerotic lesion formation in CCR2-/- mice: evidence for independent chemokine functions in atherogenesis

BACKGROUND

Monocyte-derived foam cells are the hallmark of early atherosclerosis, and recent evidence indicates that chemokines play important roles in directing monocyte migration from the blood to the vessel wall. Genetic deletions of monocyte chemoattractant protein-1 (MCP-1, CCL2), fractalkine (CX3CL1), or their cognate receptors, CCR2 and CX3CR1, markedly reduce atherosclerotic lesion size in murine models of atherosclerosis. The aim of this study was to determine whether these 2 chemokines act independently or redundantly in promoting atherogenesis.

METHODS AND RESULTS

We crossed CX3CL1(-/-)ApoE(-/-) and CCR2(-/-)ApoE(-/-) mice to create CX3CL1(-/-)CCR2(-/-)ApoE(-/-) triple knockouts and performed a 4-arm atherosclerosis study. Here, we report that deletion of CX3CL1 in CCR2(-/-) mice dramatically reduced macrophage accumulation in the artery wall and the subsequent development of atherosclerosis. Deletion of CX3CL1 did not reduce the number of circulating monocytes in either "wild-type" ApoE(-/-) mice or CCR2(-/-)ApoE(-/-) mice, which suggests a role for CX3CL1 in the direct recruitment and/or capture of CCR2-deficient monocytes.

CONCLUSIONS

These data provide the first in vivo evidence for independent roles for CCR2 and CX3CL1 in macrophage accumulation and atherosclerotic lesion formation and suggest that successful therapeutic strategies may need to target multiple chemokines or chemokine receptors.

Dual GPCR and GAG mimicry by the M3 chemokine decoy receptor

Viruses have evolved a myriad of evasion strategies focused on undermining chemokine-mediated immune surveillance, exemplified by the mouse γ-herpesvirus 68 M3 decoy receptor. Crystal structures of M3 in complex with C chemokine ligand 1/lymphotactin and CC chemokine ligand 2/monocyte chemoattractant protein 1 reveal that invariant chemokine features associated with G protein–coupled receptor binding are primarily recognized by the decoy C-terminal domain, whereas the N-terminal domain (NTD) reconfigures to engage divergent basic residue clusters on the surface of chemokines. Favorable electrostatic forces dramatically enhance the association kinetics of chemokine binding by M3, with a primary role ascribed to acidic NTD regions that effectively mimic glycosaminoglycan interactions. Thus, M3 employs two distinct mechanisms of chemical imitation to potently sequester chemokines, thereby inhibiting chemokine receptor binding events as well as the formation of chemotactic gradients necessary for directed leukocyte trafficking.

Deletion of STAT-1 pancreatic islets protects against streptozotocin-induced diabetes and early graft failure but not against late rejection

OBJECTIVE

Exposure of beta-cells to inflammatory cytokines leads to apoptotic cell death through the activation of gene networks under the control of specific transcription factors, such as interferon-gamma-induced signal transducer and activator of transcription (STAT)-1. We previously demonstrated that beta-cells lacking STAT-1 are resistant to cytokine-induced cell death in vitro. The aim of this study was to investigate the effect of STAT-1 elimination on immune-mediated beta-cell destruction in vivo.

RESEARCH DESIGN AND METHODS

Multiple low-dose streptozotocin (STZ) was given to C57BL/6 mice after syngeneic STAT-1(-/-) or wild-type islet transplantation. STAT-1(-/-) and wild-type islets were also transplanted in alloxan-diabetic BALB/c and spontaneously diabetic nonobese diabetic (NOD) mice. Additionally, mice were treated with interleukin (IL)-1 blockade (IL-1 receptor antagonist [IL-1ra]) and low-dose T-cell suppression (cyclosporine A [CsA]).

RESULTS

When exposed to multiple low-dose STZ in an immune-competent host, STAT-1(-/-) islets were more resistant to destruction than wild-type islets (28 vs. 100% diabetes incidence, P < or = 0.05). STAT-1 deletion also protected allogeneic islet grafts against primary nonfunction in autoimmune NOD mice (0 vs. 17% using wild-type islets). However, no difference in survival time was observed. Additionally, treating recipients with IL-1ra and CsA prolonged graft survival in chemically diabetic BALB/c mice, whereas no difference was seen between STAT-1(-/-) and C57BL/6 grafts.

CONCLUSIONS

These data indicate that STAT-1 is a key player in immune-mediated early beta-cell dysfunction and death. When considering the many effector mechanisms contributing to beta-cell death following islet transplantation, multiple combined interventions will be needed for prolongation of beta-cell survival in the autoimmune context of type 1 diabetes.