Testicular Sertoli cells exert both protective and destructive effects on syngeneic islet grafts in non-obese diabetic mice

Abstract Aims/hypothesis. Testicular Sertoli cells protect allogeneic islet grafts from rejection after transplantation into animals with chemically induced diabetes. The aims of this study were to determine whether Sertoli cells can protect syngeneic islets from autoimmune destruction after transplantation into non-obese diabetic (NOD) mice and, if so, whether protection is due to Sertoli cell expression of Fas ligand (FasL), believed to be the mechanism that protects against allograft rejection.?Methods. We compared the survival of syngeneic islets transplanted under the renal capsule of non-obese diabetic mice, alone and together with purified Sertoli cells prepared from testes of newborn non-obese diabetic mice. Additionally, we examined the composition of the islet and Sertoli cell co-transplants by immunohistochemistry to determine whether islet graft survival correlated with Sertoli cell expression of Fas ligand.?Results. Sertoli cell doses of 1, 2 and 4 × 10⁶ cells produced a dose-dependent prolongation of median islet graft survival from 11 days (islets alone) to 32 days (islets + 4 × 10⁶ Sertoli cells); addition of 8 × 10⁶ Sertoli cells to the islet grafts decreased, however, median survival to 8 days. Immunohistochemical analysis of the islet and Sertoli cell co-transplants showed a correlation between Fas ligand expression by Sertoli cells and graft infiltration by neutrophilic leucocytes, leading to islet beta-cell destruction and diabetes recurrence.?Conclusion/interpretation. Sertoli cells exert opposing effects on survival of syngeneic islet grafts in non-obese diabetic mice: Fas ligand-dependent neutrophil infiltration and graft destruction, and Fas ligand-independent protection of the graft from autoimmune destruction. [Diabetologia (2000) 43: 474–480] Received: 13 December 1999 and in revised form: 20 January 2000     

Th1细胞在NOD小鼠糖尿病早期的应用

目的评价Th1细胞对NOD小鼠糖尿病早期变化的作用。方法选择4 w、8 w和16 w的雌性NOD小鼠,采用流式细胞术测定脾Th1细胞,采用免疫组化法检测胰腺内Th1细胞。结果随年龄增加,雌性NOD小鼠脾和胰腺内Th1细胞逐渐增加。结论 Th1细胞参与NOD小鼠糖尿病早期的病理过程。     

Combination therapy with low dose sirolimus and tacrolimus is synergistic in preventing spontaneous and recurrent autoimmune diabetes in non-obese diabetic mice

Aims/hypothesis: Sirolimus and tacrolimus are immunosuppressive drugs that prevent rejection of pancreatic islet allografts transplanted into patients with Type I (insulin-dependent) diabetes mellitus. This study aimed to determine whether sirolimus and tacrolimus can prevent autoimmune beta-cell destruction, and if so, what the mechanisms of action are. Methods: Sirolimus and tacrolimus were given separately and together to female non-obese diabetic (NOD) mice from age 12 to 35 weeks. Diabetes incidence was determined and pancreatic insulitis and insulin content were measured. Sirolimus and tacrolimus were also given separately and together to diabetic NOD mice from the time of syngeneic islet transplantation until the reappearance of hyperglycaemia. Islet grafts were examined by RT-PCR assay for expression of interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-10 and transforming growth factor (TGF)-β1. Results: Low doses of sirolimus (0.1 mg/kg) and tacrolimus (0.1 mg/kg) were synergistic in reducing insulitis, preserving pancreatic insulin content and preventing diabetes in female NOD mice (8 % diabetes incidence at 35 weeks vs 66 % in vehicle-treated mice). Also, the combination of sirolimus and tacrolimus prolonged syngeneic islet graft survival (median 34 days vs 13 days for vehicle-treated mice). Islet grafts from sirolimus plus tacrolimus-treated mice expressed significantly decreased mRNA contents of Th1-type cytokines (IFN-γ and IL-2) and the highest ratio of TGF-β1/IFN-γ mRNA. Conclusion/interpretation: These findings suggest that combination therapy with sirolimus and tacrolimus prevent autoimmune beta-cell destruction by upregulating expression of the immunoregulatory cytokine, TGF-β1 and reducing Th1 cytokines (IFN-γ and IL-2) expressed in the islets. Low-dose sirolimus and tacrolimus combination therapy could warrant consideration for prevention or early treatment of human Type I diabetes. [Diabetologia (2002) 45: 224–230] Received: 20 August 2001 and in revised form: 29 October 2001     

Fas and Fas ligand-mediated apoptosis and its role in autoimmune diabetes

The relationship between Fas-mediated apoptosis and Type 1 diabetes is currently under investigation. Fas/Fas ligand interaction could be involved both in the insulitis process and in β-cell death. Nevertheless, different mechanisms appear to be involved in human Type 1 diabetes and in NOD mice. In the present work, we review recent evidence of the role of the Fas/Fas ligand system in human and NOD mouse diabetes, describing possible hypotheses for its involvement in the pathogenesis of the disease, with possible implications for therapy and islet transplantation. Copyright © 1998 John Wiley & Sons, Ltd.     

Protection of islet allografts transplanted together with Fas ligand expressing testicular allografts

Summary Fas ligand (FasL) is highly expressed in testicular tissues and thought to be responsible for protection from allograft rejection by inducing apoptosis of anti-graft activated T cells. FasL-expressing islets have been shown to induce a granulocyte-mediated inflammatory reaction. We investigated whether a graft can be protected from alloimmune responses by manipulating the Fas/FasL-system. We transplanted allogeneic islets under the kidney capsule of streptozotocin-induced diabetic mice together with testicular tissue. Significant prolongation of survival of C3H islet allograft was observed in C57BL/6 (B6) recipients transplanted with C3H testicular tissue, but not in those transplanted with C3H-gld testicular tissue expressing non-functional FasL. No significant prolongation was observed in B6-lpr recipients expressing non-functional Fas. Immunohistochemical staining of C3H testicular tissue in the composite graft showed a high expression of FasL, but not that of the C3H-gld testicular tissue. In situ terminal deoxynucleotidyl transferase-mediated dUDP-biotin catalysed DNA nick-end labelling (TUNEL) staining of a composite graft of C3H islet and testicular tissue in B6 recipients demonstrated extensive apoptosis of infiltrating mononuclear cells around the graft. The protective effect of C3H testicular tissue was abrogated when anti-FasL monoclonal antibody was administered i. p. postoperatively. Our results suggest that FasL-positive testicular allografts protect composite islet allografts and indicate that manipulation of Fas/FasL mediated apoptosis is a suitable strategy for controlling rejection of islet allografts. [Diabetologia (1998) 41: 315–321] Received: 12 September 1997 and in revised form: 14 November 1997     

Streptococcal wall component OK432 restores sensitivity of non-obese diabetic (NOD) thymocytes to apoptotic signals

Aims/hypothesis. The streptococcal wall component, OK432, prevents diabetes in NOD mice and BB rats by elimination of effector cells. Based on the knowledge of a link between autoimmunity and resistance of immune cells to elimination by apoptosis, we investigated whether OK432 treatment restored the sensitivity of NOD lymphocytes to apoptotic signals centrally (thymus) or peripherally (spleen) or both and we examined the pathways for the enhanced apoptosis rate.¶Methods. We treated NOD mice with OK432 (0.1 mg/kg i. p. weekly from 21 to 70 days). Apoptosis was measured by TUNEL 16 h after cyclophosphamide (70 mg/kg) and 24 h after dexamethasone (0.2 mg/mouse). Real time quantitative RT-PCR was used to investigate changes in gene expression.¶Results. Thymocyte apoptosis levels after cyclophosphamide were restored by OK432 treatment to levels observed in C57BL/6 mice: in NOD males apoptosis increased from 8 ± 1 % to 18 ± 5 % (p < 0.05) compared with 20 ± 4 % in C57BL/6 males, and in NOD females from 6 ± 2 % to 11 ± 2 % (p < 0.05) compared with 12 ± 2 % in C57BL/6 females. The dexamethasone-induced thymocyte apoptosis rate was equally restored by OK432 treatment (58 ± 4 % vs 41 ± 3 % in control males (p < 0.0005) and 39 ± 5 % vs 26 ± 3 % in control females (p < 0.05)]. No change in apoptosis levels was on the contrary observed in splenocytes after OK432 treatment. By RT-PCR analysis of a panel of apoptosis-related genes in thymocytes we showed a down-regulation of anti-apoptotic Bcl-xL and c-myc by OK432 treatment.¶Conclusions/interpretation. Our data suggest that OK432 prevents diabetes in NOD mice by better elimination of effector cells through increased sensitivity to apoptotic signals centrally in the thymus. [Diabetologia (2000) 43: 1302–1308]     

Prospective prediction of spontaneous but not recurrent autoimmune diabetes in the non-obese diabetic mouse

Aims/hypothesis Type 1 diabetes is a T cell-mediated autoimmune disease with a clinically silent prodrome, during which prediction and treatment of disease are theoretically possible. Using retrospective analysis, spontaneous disease in the non-obese diabetic (NOD) mouse has been correlated with islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)-reactive CD8⁺ T cells in the peripheral blood. In this study, we determined prospectively whether IGRP-reactive T cells in peripheral blood could predict disease occurrence. Since recurrent autoimmunity is an important contributor to transplant failure, we also determined whether failure of islet grafts (syngeneic and allogeneic) could be predicted by the presence of circulating autoreactive T cells. Materials and methods Peripheral blood samples were taken weekly from female NOD mice between the ages of 8 and 30 weeks and from NOD mice transplanted with NODscid islets. Peripheral blood cells and islet grafts were analysed for the presence of IGRP-reactive CD8⁺ T cells by flow cytometry. Results Prospective analysis of peripheral blood IGRP-reactive T cells in the prediabetic period predicted disease development with a sensitivity of 100% and a specificity of 60%, resulting in positive and negative predictive values of 85 and 100%, respectively. Significant proportions of IGRP-reactive T cells were found in the grafts, but not in peripheral blood of NOD mice undergoing syngeneic and allogeneic rejection. Conclusions/interpretation The occurrence of spontaneous diabetes can be predicted prospectively by measuring peripheral blood autoreactive T cells. Rejection of syngeneic or allogeneic islets is associated with large populations of autoreactive CD8⁺ T cells within islets, suggesting that immunodominant autoreactive T cells during the prediabetic period are also responsible for autoimmune graft rejection.     

Fas and Fas ligand expression in inflamed islets in pancreas sections of patients with recent-onset Type I diabetes mellitus

Abstract Aims/hypothesis. Type I (insulin-dependent) diabetes results mainly from T-cell-mediated autoimmune destruction of pancreatic beta cells. Cytotoxic T lymphocytes destroy target cells via a perforin-based or Fas-based mechanism. Our previous study indicated that the Fas-Fas ligand (FasL) pathway is required for the development of autoimmune diabetes in the NOD mouse. We now investigated whether or not the Fas-FasL system is involved in the beta-cell destruction in human Type I diabetes. Methods. We immunohistochemically analysed pancreas biopsy specimens of 13 recent-onset patients. Results. Pancreatic islets were identified but showed various degrees of reduction in beta-cell volume in all patients. Out of 13 patients 6 had insulitis. In these 6 patients Fas was expressed in both the islets and infiltrating cells but not in either cell type in the 7 other patients without insulitis. Double immunostaining showed that Fas was positive in 92.2 to 97.7 % of beta cells but only in 17.6 to 46.7 % of alpha cells in Fas-positive, insulin-remaining islets. We found FasL was expressed exclusively in islet-infiltrating cells in patients with insulitis. Double immunostaining revealed that the most prevalent phenotype of FasL-positive cells was CD8, which was followed by macrophages and CD4. Conclusion/interpretation. The interaction between Fas on beta cells and FasL on infiltrating cells might trigger selective apoptotic beta-cell death in inflamed islets, leading to immune-mediated Type I diabetes. [Diabetologia (1999) 42: 1332–1340] Received: 3 March 1999 and in final revised form: 9 July 1999     

Autoantigen-specific protection of non-obese diabetic mice from cyclophosphamide-accelerated diabetes by vaccination with dendritic cells

Aims/hypothesis Dendritic cells (DCs) are professional antigen presenting cells involved in the initiation of primary immune responses and the preservation of peripheral tolerance. The aim of this study was to develop a DC vaccine for autoantigen-specific prevention of autoimmune diabetes.Methods Splenocytes from diabetes-prone NOD mice were cultured in conditioned media to obtain a homogeneous DC sub-population for vaccination experiments. These cells were used to modulate autoimmune responses in NOD mice after synchronization of diabetes with cyclophosphamide. After immunisation with insulin-pulsed DCs the incidence of diabetes, the insulitis grade and the cytokine production was examined.Results The long-term culture of splenocytes resulted in the generation of a cell line, termed NOD-DC1, which have a phenotype of myeloid DCs (CD11c, CD11b, DEC-205), express MHC class II and co-stimulatory molecules (CD40, CD80, CD86). The NOD-DC1 cells have preserved functional activity shown by the detection of a high antigen uptake capacity, the induction of a mixed lymphocyte reaction and stimuli-dependent IL-6 and TNF- secretion. Vaccination with insulin-pulsed NOD-DC1 cells results in an antigen-specific prevention of diabetes. This was mediated by a reduction of the severity of insulitis and a decrease of T helper 1 effector cells.Conclusion/interpretation We describe the generation of a DC line which confers protection from diabetes in an antigen-specific way. Our data shows that autoantigen-loaded DCs can induce strong immunoregulatory effects supporting the hypothesis that DCs are promising candidates to develop novel vaccines for the prevention of autoimmune diabetes.Abbreviations APC antigen-presenting cells - CY cyclophosphamide - DCs, dendritic cells - LPS lipopolysaccharide - mAb monoclonal antibodies - NOD non-obese diabetic - Th T-helper cells     

Dissecting autoimmune diabetes through genetic manipulation of non-obese diabetic mice

Type 1 diabetes results from a genetically and immunologically complex autoimmune process that is specifically directed against the pancreatic beta cells. Non-obese diabetic mice spontaneously develop a form of autoimmune diabetes closely resembling the disease in humans. This happens because, like human diabetic patients, non-obese diabetic mice have an unfortunate combination of apparently normal alleles at numerous loci associated with Type 1 diabetes. In isolation, each of these allelic variants affords a small degree of susceptibility to diabetes. In combination, however, they set in motion a series of immunological events that lead to islet inflammation and overt diabetes. Type 1 diabetes is associated with defects in self-tolerance and immunoregulation. It involves presentation of beta cell antigens to autoreactive T lymphocytes by professional antigen-presenting cells, the recruitment of antigen-activated T cells into pancreatic islets, and the differentiation of these antigen-activated lymphocytes into beta cell killers. Understanding the precise sequence of events in the pathogenesis of Type 1 diabetes has been, and remains, a challenging task. Much of our understanding of the immunology of the disease stems from studies of genetically engineered, non-obese diabetic mice. These mice provide reductionist systems, with which the contribution of individual cellular elements, molecules or genes to the disease process can be dissected. This review focuses on the lessons that have been learned through studies of these mice.Abbreviations APCs, antigen-presenting cells - 2m, beta-2 microglobulin - CD62L, L-selectin - CDR3, complementarity-determining region 3 - CTL, cytotoxic T lymphocyte - DC, dendritic cell - IA-2, insulinoma-associated protein 2 - ICA69, islet cell antigen 69 KDa - ICAM-1, intercellular adhesion molecule-1 - IFN-, interferon- - LFA-1, leucocyte function-associated antigen-1 - mAb, monoclonal antibody - NK, natural killer - MIP-1, macrophage inflammatory protein 1 - NOD, non-obese diabetic - 8.3-NOD, 8.3-TCR-transgenic NOD mice - PLN, pancreatic lymph node - rag, recombination-activating gene - RAG-2, recombination-activating gene 2 - RIP, rat insulin promoter - TCR, T cell receptor     

In utero undernutrition reduces diabetes incidence in non-obese diabetic mice

AIMS/HYPOTHESIS: Observational studies in humans suggest that low birthweight may decrease the risk of type 1 diabetes, but the mechanism is unknown. We hypothesised that antenatal undernutrition would decrease the incidence of type 1 diabetes in non-obese diabetic (NOD) mice. MATERIALS AND METHODS: A 40% restriction of energy intake was applied to pregnant NOD dams from day 12.5 to day 18.5 of gestation, resulting in intrauterine growth retardation of offspring. All mice were fed a standard diet after weaning. Control and undernourished female offspring were followed to assess diabetes incidence. Male NOD mice were treated with cyclophosphamide to accelerate development of diabetes. Glucose homeostasis, body composition and pancreatic histology were compared in control and undernourished offspring. RESULTS: Mean birthweight was lower in undernourished than in control mice (p = 0.00003). At 24 weeks of age, the cumulative incidence of spontaneous diabetes in female mice was 73% in control and 48% in undernourished mice (p = 0.003). In cyclophosphamide-treated male mice, antenatal undernutrition also tended to reduce the development of diabetes (p = 0.058). Maternal leptin levels were lower in undernourished dams on day 18.5 of pregnancy (p = 0.039), while postnatal leptin levels were significantly higher in undernourished offspring at 4, 20 and 27 weeks of life (p < 0.05). Beta cell mass was similar in both groups (control = 0.4 mg; undernourished = 0.54 mg; p = 0.24). Histological evidence of apoptosis at 20 weeks was greater in control than in undernourished mice (control = 6.3 +/- 1.4%; undernourished = 4.2 +/- 0.3%, p = 0.05). CONCLUSIONS/INTERPRETATION: Antenatal undernutrition reduces the incidence of diabetes in NOD mice, perhaps via alterations in apoptosis.     

Production of monoclonal antibodies to islet cell surface antigens using hybridization of spleen lymphocytes from non-obese diabetic mice

Summary Non-obese diabetic mice display a syndrome with dramatic clinical and pathological features similar to those of Type 1 (insulin-dependent) diabetes in man. Circulating autoantibodies to the surface of islet cells were demonstrated in some of these mice by a protein A radioligand assay. To produce monoclonal antibodies to islet cell surface antigens, therefore, we took the spleens of non-obese diabetic mice, transferred the spleen cells into non-immunized recipient mice, which were made immunologically incompetent by a large dose of X-irradiation, and then fused their lymphocytes with FO mouse myeloma cells. After screening the resultant hybrids, one stable hybridoma (3A4) that produced a monoclonal antibody (IgG1) specifically bound to the surface of islet cells was obtained. The purified monoclonal antibody was bound to the surface of transplantable Syrian golden hamster insulinoma cells sevenfold more than control antibody. Adsorption of the antibody on mouse spleen lymphocytes or thymocytes resulted in only a slight decrease in ¹²⁵I-protein A binding to insulinoma cells. This antibody also reacted with the surface of mouse and rat islet cells, but not with that of rat spleen cells or hepatocytes. A spectrophotometric assay for peroxidase activity demonstrated that six times more peroxidase bound to insulinoma cells incubated with the antibody than to cells treated with control antibody. Furthermore, this antibody could be visually detected in the immunoenzymatic labelling of the surface of insulinoma cells. In summary, we have developed a novel method of producing monoclonal antibodies to the surface of islet cells for probing into the pathogenesis of Type 1 diabetes.     

Melatonin prolongs islet graft survival in diabetic NOD mice

Abstract:  Islet transplantation has been established as a potential therapy for type 1 diabetes. However, inflammation, allorejection, and on-going autoimmune damage contribute to early graft loss and failure of islet transplantation. Melatonin is the major secretory product of the pineal gland during the dark period of each day and displays multifunctional properties including the regulation of circadian and seasonal rhythms, antioxidation reactions and immune modulation. Based on the immunosuppressive properties of melatonin, we investigated whether melatonin treatment prolonged the survival of islet grafts in non-obese diabetic (NOD) mice. The mean islet graft survival time was 7.33 ± 1.51 and 7.75 ± 2.66 days in untreated controls and in the solvent-treated animals, respectively. Strikingly, the mean survival time of islet grafts in recipients treated with melatonin (200 mg/kg/bw) was 17 ± 7.76 days. Moreover, melatonin treatment reduced the proliferation of splenocytes in NOD mice. Using a T1 and T2 double transgenic mouse model, we found that T helper 1 (Th1) cells in mice treated with melatonin were significantly decreased. The reduction of Th1 cells and T cell proliferation may result from an increase in the immunosuppressive cytokine IL-10. Our results indicate that melatonin treatment suppresses autoimmune recurrence by inhibiting the proliferation of Th1 cells in NOD mice and thus prolongs the survival of syngeneic islet grafts.     

Ontogeny of islet cell antibodies,insulin autoantibodies and insulitis in the non-obese diabetic mouse

Summary The predictive value of insulitis, islet cell cytoplasmic antibodies and insulin autoantibodies for insulin-dependent diabetes was studied in young female non-obese diabetic mice. The ontogeny of the three markers was examined cross-sectionally at days 15, 25, 40 and 90 while islet cell antibodies and insulin autoantibodies were studied longitudinally from day 35 or day 144–168 until approximately day 250. Insulitis was first observed at day 40 (50%) and subsequently at day 90 (70%). Islet cell antibodies and insulin autoantibodies were present at day 15 in 46% and 54% of the animals respectively. The rate of islet cell antibodies was slightly higher at day 25 (60%) than at day 40 (40%) and day 90 (54%) whereas antibodies to insulin were present in all samples from day 25–90. At day 40 and day 90 insulitis and insulin autoantibodies were present together in 42% and 70% of the animals, respectively, while insulitis and islet cell antibodies had a lower rate of concordance (17% and 42%, respectively; diabetes rate, 30%). The concordance rates for islet cell antibodies and insulin autoantibodies were 42% at day 40 and 54% at day 90. Concordance for all three markers was first observed at day 40 (17%) which increased to 38% at day 90. In longitudinal studies, islet cell antibodies and insulin autoantibodies were often present together whether or not diabetes supervened. In the islet cell antibody procedure, immunoreactive cells were shown immunohistochemically to correspond with insulin and/or glucagon cells. However, this staining was not suppressible with insulin- or glucagon- absorbed sera, implying the presence of non-hormonal autoantigens. We conclude that the three markers investigated are expressed early after birth and well before clinical symptoms appear in this animal model. Both islet cell antibodies and insulin autoantibodies preceded insulitis but the prevalence rate for each marker or their degree of concordance was different from the anticipated rate of diabetes in our colony. Consequently, the early expression of the three markers alone is not predictive of diabetes although concordance for the two, or all three markers may be of some value. However, no animal developed diabetes without the prior appearance of both islet cell antibodies and insulin autoantibodies.     

NOD小鼠口服胰岛素对胰岛Fas及其配体表达的影响

目的观察口服胰岛素对ＮＯＤ小鼠糖尿病和胰岛炎发生情况的影响以及观察口服免疫耐受后胰岛Ｆａｓ和Ｆａｓ配体（ＦａｓＬ）表达的改变情况。方法将雌性ＮＯＤ小鼠６４只,随机分为两组：一组（３０只）给予磷酸缓冲液（ＰＢＳ）５００μｌ,另一组（３４只）给予胰岛素１ｍｇ加ＰＢＳ５００μｌ,５周龄开始给药,第１周两次,以后每周一次至３０周。采用免疫组化染色法观察了口服免疫耐受治疗后ＮＯＤ小鼠胰岛组织Ｆａｓ和ＦａｓＬ的改变情况。结果口服胰岛素能明显减少胰岛炎和糖尿病的发生,对照组１４周龄即出现糖尿病而胰岛素组２６周龄才出现糖尿病,２６周龄时两组的发病率分别为１１％和７９％（Ｐ＜０．００１）,Ｆａｓ出现在糖尿病小鼠而ＦａｓＬ出现在胰岛素喂饲后的小鼠。结论口服胰岛素能明显减少胰岛炎和糖尿病的发生,口服胰岛素诱导的ＦａｓＬ表达在胰岛素阻止糖尿病和胰岛炎的发生机制中起一定的作用     

Cell-mediated cytotoxic islet cell surface antibodies to human pancreatic beta cells

Summary Sera containing islet cell surface antibodies show a complement-dependent cytotoxic reaction against islet cells, but it has not yet been clarified whether islet cell surface antibodies exhibit cell-mediated cytotoxicity to these cells. By ⁵¹Cr release assay we investigated whether islet cell surface antibodies showed a cytotoxic reaction to human pancreatic B cells (JHPI-1 clone) in the presence of normal human lymphocytes. The sera from 14 islet cell surface antibody-positive, 16 islet cell surface antibody-negative Type 1 (insulin-dependent) diabetic patients and 18 islet cell surface antibody-negative healthy subjects were studied. Four sera containing islet cell surface antibodies showed specific cytotoxicity above the mean +3SD value of healthy subjects, and the mean specific cytotoxicity of islet cell surface antibody-positive sera differed significantly from that of both islet cell surface antibody-negative groups. These results suggest that this cell-mediated cytotoxic mechanism may play an important role in the pathogenesis of Type 1 diabetes.     

Apoptosis and remodelling of beta cells by paracrine interferon-γ without insulitis in transgenic mice

Abstract Aims/hypothesis. To examine whether interferon-γ destroys islet beta cells directly or indirectly through lymphocyte activation, or whether direct action of interferon-γ on beta cells by itself induces diabetes without insulitis. Methods. To avoid possible nonspecific breakdown of beta cells by transgenic overexpression of interferon-γ by the insulin promoter, we generated transgenic mice expressing interferon-γ under the control of rat glucagon promoter (RGP-IFN-γ-Tg mice). Results. The absence of insulitis in RGP-IFN-γ-Tg mice enabled us to investigate the direct effects of paracrine interferon-γ. In RGP-IFN-γ-Tg mice, serum concentrations of interferon-γ and tumour necrosis factor-α (TNF-α) were 50 and 6 times higher than those in their littermates, respectively, and glucose-responsive insulin secretion decreased to one-half the level of that in the littermates. Transgenic interferon-γ induced remodelling of beta cells where apoptosis of many beta cells was compensated by their vigorous regeneration and diabetes did not occur in most of the RGP-IFN-γ-Tg mice. Conclusion/interpretation. Interferon-γ alone is insufficient for the complete destruction of beta cells in vivo, and factors other than interferon-γ including activated lymphocytes or other cytokines, are necessary in addition to interferon-γ for the development of Type I (insulin-dependent) diabetes mellitus. [Diabetologia (1999) 42: 566–573] Received: 16 November 1998 and in final revised form: 11 January 1999     

In vivo proliferation of differentiated pancreatic islet beta cells in transgenic mice expressing mutated cyclin-dependent kinase 4

Aims/hypothesis It has previously been hypothesised that highly differentiated endocrine cells do not proliferate or regenerate. However, recent studies have revealed that cyclin-dependent kinase 4 (CDK4) is necessary for the proliferation of pancreatic islet beta cells. The aim of this study was to determine whether activation of CDK4 can potentially be used as a radical treatment for diabetes without malignant transformation.Methods We generated transgenic mice expressing mutant CDK4 under the control of the insulin promoter to examine the effect of activated CDK4 overexpression in the postnatal development of pancreatic islets.Results In the transgenic mice, total CDK4 protein expression was increased by up to 5-fold, with a concomitant increase in CDK4 activity indicated by the detection of phosphorylated Rb protein in pancreatic islets. Histopathologically, many cells tested positive for proliferating cell nuclear antigen, and pancreatic islets displayed hyperplasia due to the extreme proliferation of beta cells containing a large number of insulin granules. Pancreatic islet alpha, delta and PP cells did not increase. Over an 18-month observation period, the transgenic mice did not develop insulinoma. Levels of expression of GLUT1 and c-myc were comparable to those in the littermates of the transgenic mice. GLUT2 expression was identified in the pancreatic islets of transgenic mice. No significant differences in telomerase activities were detected between transgenic mice and their littermates. Transgenic mice were superior to their littermates in terms of glucose tolerance and insulin secretion in response to the intraperitoneal injection of glucose, and hypoglycaemia was not observed.Conclusions/interpretation Activated CDK4 stimulates postnatal pancreatic beta cell proliferation, during which the highly differentiated phenotypes of pancreatic islet beta cells are preserved without malignant transformation.     

Inhibition of insulin-specific autoreactive T-cells by sulphatide which is variably expressed in beta cells

Abstract Aims/hypothesis. Sulphatide and insulin are present in the secretory granules and at the surface of beta cells in islets of Langerhans. Insulin autoantibodies and T-cell reactivity against insulin exist during the development of Type I (insulin-dependent) diabetes during which active beta cells may be more vulnerable than passive. Our aims were to examine the presence of sulphatide in active and passive beta cells and to clarify whether sulphatide influences the direct autoimmunity against insulin. Methods. We incubated rat islets in 2.8, 11.0 or 20.0 mmol/l glucose for 24 h and did an electron microscopic evaluation after labelling with a specific anti-sulphatide monoclonal antibody. The reactivity of an insulin-specific T-cell clone isolated from a patient with Type I diabetes, was examined using insulin or insulin B-chain (B11–27) peptide incubated together with sulphatide. Results. We detected lower amounts of sulphatide per insulin secretory granule in active compared with passive beta cells (p = 0.003). The presence of sulphatide in vitro at doses of 43–8.3 μmol/l resulted in greatly reduced proliferation (median 3.4 % of control value, p = 0.0004) of the insulin-specific T-cell clone. No inhibition was found using the precursor of sulphatide, galactosylceramide, or GM1. Sulphatide did not reduce non-aspecific proliferation (induced by phorbol myristate acetate plus anti-CD3) or specific proliferation induced by insulin peptide. Conclusion/interpretation. These results imply that sulphatide possibly affect processing of the insulin molecule. Sulphatide which has been reported to interfere with phagosome-lysosome fusion, conceivably interacts with insulin. We hypothesize a (patho)physiological role of sulphatide, variably expressed in beta cells, by reducing the antigenicity of insulin. [Diabetologia (1999) 42: 1212–1218] Received: 25 March 1999 and in revised form:1 June 1999