Interleukin-35 Prevents Development of Autoimmune Diabetes Possibly by Maintaining the Phenotype of Regulatory B Cells.

The anti-inflammatory role of regulatory B cells (Breg cells) has been associated with IL-35 based on studies of experimental autoimmune uveitis and encephalitis. The role of Breg cells and IL-35+ Breg cells for type 1 diabetes (T1D) remains to be investigated. We studied PBMCs from T1D subjects and healthy controls (HC) and found lowered proportions of Breg cells and IL-35+ Breg cells in T1D. To elucidate the role of Breg cells, the lymphoid organs of two mouse models of T1D were examined. Lower proportions of Breg cells and IL-35+ Breg cells were found in the animal models of T1D compared with control mice. In addition, the systemic administration of recombinant mouse IL-35 prevented hyperglycemia after multiple low dose streptozotocin (MLDSTZ) injections and increased the proportions of Breg cells and IL-35+ Breg cells. A higher proportion of IFN-γ+ cells among Breg cells were found in the PBMCs of the T1D subjects. In the MLDSTZ mice, IL-35 administration decreased the proportions of IFN-γ+ cells among the Breg cells. Our data illustrate that Breg cells may play an important role in the development of T1D and that IL-35 treatment prevents the development of hyperglycemia by maintaining the phenotype of the Breg cells under an experimental T1D condition.

Assessing the effectiveness of Interleukin-2 therapy in experimental type 1 diabetes.

AIM: Much focus of immunotherapy for type 1 diabetes (T1D) has been devoted on selectively boosting regulatory T (Treg) cells using low dose IL-2 due to their constitutive expression of IL-2Rα, CD25. However, several clinical trials using a low dose of IL-2 only showed a limited improvement of metabolic control. It can therefore be hypothesized that further decreasing IL-2 dosage may increase the selective responsiveness of Treg cells. METHODS: We induced experimental T1D using multiple low dose streptozotocin (STZ) injections and treated the mice with an ultra-low dose IL-2 (uIL-2, approximately 7-fold lower than low dose). Immune response was studied using multicolor flow cytometry. RESULTS: We found that uIL-2 did not protect STZ mice from developing hyperglycemia. It did neither increase Treg cell proportions, nor did it correct the phenotypic shift of Treg cells seen in T1D. It only partially decreased the proportion of IFN-γ+ T cells. Likewise, uIL-2 also did not protect the dysfunction of regulatory B (Breg) cells. Strikingly, when administered in combination with an anti-inflammatory cytokine IL-35, uIL-2 abrogated IL-35's protective effect. Low dose IL-2, on the other hand, protected half of the STZ mice from developing hyperglycemia. No difference was found in the Treg and Breg response, and it only tended to decrease CD80 expression in macrophages and dendritic cells. CONCLUSION: In conclusion, further decreasing IL-2 dosage may not be a suitable approach for T1D therapy, and the limited success suggests that an alternative low dose IL-2 therapy strategy or other immunotherapies should be considered.

Administration of IL-1 trap prolongs survival of transplanted pancreatic islets to type 1 diabetic NOD mice.

We previously reported that IL-1 Trap (a hybrid molecule consisting of the extracellular domain of IL-1 receptor accessory protein and IL-1 receptor type 1 arranged inline and fused to the Fc-portion of IgG1) can protect rat pancreatic islets in vitro against noxious effects induced by IL-1ß. In this study we tested the effect of administration of a murine IL-1 Trap on the recurrence of disease (ROD) model in non-obese diabetic (NOD) mice. Spontaneously diabetic female NOD mice received implantation of a curative number (600) of syngeneic pancreatic islets beneath their left kidney capsule from young healthy NOD mouse donors. Once a day, the mice were injected subcutaneously with IL-1 Trap (30mg/kg bodyweight), or an equimolar dose Fc-control protein (8.4mg/kg bodyweight) or saline. The treatments were maintained until ROD (i.e. a blood glucose value ⩾11.1mM for 2 consecutive days) or until 5days after transplantation. 3 out of 11 mice treated with IL-1 Trap showed a significantly increased graft survival compared to all other mice, and analysis of relative cytokine mRNA levels in isolated spleen cells showed elevated IL-4 mRNA levels, but no differences in FoxP3 or iNOS staining of grafts, from mice treated with IL-1 Trap, at both endpoints, compared to both control groups. Administration of IL-1 Trap counteracts islet cell destruction in the NOD mouse model of type 1 diabetes. In part this could be due to a shift towards Th2 cytokine production seen in IL-1 Trap treated animals.

Macrophage migration inhibitory factor (MIF) enhances palmitic acid- and glucose-induced murine beta cell dysfunction and destruction in vitro.

Although several reports suggest a potentially deleterious role of macrophage migration inhibitory factor (MIF) in type 2 diabetes (T2D) pathology, it is still unclear how this pro-inflammatory cytokine acts on pancreatic beta cells. The aim of the present study was to evaluate MIF effects on murine beta cells in the in vitro settings mimicking T2D-associated conditions. Results indicate that recombinant MIF further increased apoptosis of pancreatic islets or MIN6 cells upon exposure to palmitic acid or glucose. This was accompanied by upregulation of several pro-apoptotic molecules. Furthermore, MIF potentiated nutrient-induced islet cell dysfunction, as revealed by lower glucose oxidation rate, ATP content, and depolarized mitochondrial membrane. The final outcome was potentiation of mitochondrial apoptotic pathway. The observed upregulation of nutrient-induced islet cell dysfunction and apoptosis by MIF implicates that silencing MIF may be beneficial for maintaining integrity of endocrine pancreas in obesity-associated T2D.

Macrophage migration inhibitory factor deficiency protects pancreatic islets from palmitic acid-induced apoptosis.

As a result of chronic exposure to high levels of free fatty acids, glucose and inflammatory mediators ß-cell apoptosis occurs at the end stage of obesity-associated type 2 diabetes (T2D). One potentially deleterious molecule for ß-cell function associated with T2D and obesity in humans is macrophage migration inhibitory factor (MIF). Therefore, the aim of this study was to explore MIF expression in vivo during development of obesity and insulin resistance in high-fat diet (HFD)-fed C57BL/6 mice and whether MIF inhibition could affect ß-cell apoptosis and dysfunction induced by palmitic acid (PA) in vitro. Indeed, increase in systemic and locally produced MIF correlated well with the weight gain, triglyceride upregulation, glucose intolerance and insulin resistance, which developed in HFD-fed mice. In in vitro settings PA dose-dependently induced MIF secretion before apoptosis development in islets. Further, mif gene deletion, mRNA silencing or protein inhibition rescued ß-cells from PA-induced apoptosis as measured by MTT assay and histone-DNA enzyme linked immuno sorbent assay. Protection from induced apoptosis was mediated by altered activation of caspase pathway and correlated with changes in the level of Bcl-2 family members. Further, MIF inhibition conveyed a significant resistance to PA-induced downregulation of insulin and PDX-1 expression and ATP content. However, ß-cell function was not entirely preserved in the absence of MIF judging by low glucose oxidation and depolarized mitochondrial membrane. In conclusion, the observed considerable preservation of ß-cells from nutrient-induced apoptosis might implicate MIF as a potential therapeutic target in the later stage of obesity-associated T2D.

Medical education in Sweden.

Undergraduate medical education in Sweden has moved from nationally regulated, subject-based courses to programmes integrated either around organ systems or physiological and patho-physiological processes, or organised around basic medical science in conjunction with clinical specialities, with individual profiles at the seven medical schools. The national regulations are restricted to overall academic and professional outcomes. The 5½ year long university undergraduate curriculum is followed by a mandatory 18 months internship, delivered by the County Councils. While quality control and accreditation for the university curriculum is provided by the Swedish National Agency for Higher Education, no such formal control exists for the internship; undergraduate medical education is therefore in conflict with EU directives from 2005. The Government is expected to move towards 6 years long university undergraduate programmes, leading to licence, which will facilitate international mobility of both Swedish and foreign medical students and doctors. Ongoing academic development of undergraduate education is strengthened by the Bologna process. It includes outcome (competence)-based curricula, university Masters level complying with international standards, progression of competence throughout the curriculum, student directed learning, active participation and roles in practical clinical education and a national assessment model to assure professional competence. In the near future, the dimensioning of Swedish undergraduate education is likely to be decided more by international demands and aspects of quality than by national demands for doctors.

High-protein-induced glomerular hyperfiltration is independent of the tubuloglomerular feedback mechanism and nitric oxide synthases.

A high protein intake is associated with increased glomerular filtration rate (GFR), which has been suggested to be mediated by reduced signaling of the tubuloglomerular feedback (TGF) mechanism. Nitric oxide (NO) has been shown to contribute to high protein-induced glomerular hyperfiltration, but the specific NO synthase (NOS) isoform responsible is not clear. In this study, a model for high-protein-induced hyperfiltration in conscious mice was developed. Using this model, we investigated the role of TGF using adenosine A(1)-receptor knockout mice lacking the TGF mechanism. Furthermore, the role of the different NOS isoforms was studied using neuronal-, inducible-, and endothelial-NOS knockout mice, and furthermore, wild-type mice acutely administered with the unspecific NOS inhibitor N(ω)-nitro-l-arginine methyl ester (100 mg/kg). GFR was measured consecutively in mice given a low-protein diet (8% casein) for 10 days, followed by a high-protein diet (50% casein) for 10 days. All mice developed high protein-induced hyperfiltration to a similar degree. These results demonstrate that high protein-induced glomerular hyperfiltration is independent of the TGF mechanism and NOS isoforms.

Significance of host heparanase in promoting tumor growth and metastasis.

Heparanase, the sole heparan sulfate degrading endoglycosidase, regulates multiple biological activities that enhance tumor growth, angiogenesis and metastasis. Much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth and metastasis. We have utilized mice over-expressing (Hpa-tg) heparanase to reveal the role of host heparanase in tumor initiation, growth and metastasis. While in wild type mice tumor development in response to DMBA carcinogenesis was restricted to the mammary gland, Hpa-tg mice developed tumors also in their lungs and liver, associating with reduced survival of the tumor-bearing mice. Consistently, xenograft tumors (lymphoma, melanoma, lung carcinoma, pancreatic carcinoma) transplanted in Hpa-tg mice exhibited accelerated tumor growth and shorter survival of the tumor-bearing mice compared with wild type mice. Hpa-tg mice were also more prone to the development of metastases following intravenous or subcutaneous injection of tumor cells. In some models, the growth advantage was associated with infiltration of heparanase-high host cells into the tumors. However, in other models, heparanase-high host cells were not detected in the primary tumor, implying that the growth advantage in Hpa-tg mice is due to systemic factors. Indeed, we found that plasma from Hpa-tg mice enhanced tumor cell migration and invasion attributed to increased levels of pro-tumorigenic factors (i.e., RANKL, SPARC, MIP-2) in the plasma of Hpa-Tg vs. wild type mice. Furthermore, tumor aggressiveness and short survival time were demonstrated in wild type mice transplanted with bone marrow derived from Hpa-tg but not wild type mice. These results were attributed, among other factors, to upregulation of pro-tumorigenic (i.e., IL35+) and downregulation of anti-tumorigenic (i.e., IFN-γ+) T-cell subpopulations in the spleen, lymph nodes and blood of Hpa-tg vs. wild type mice and their increased infiltration into the primary tumor. Collectively, our results emphasize the significance of host heparanase in mediating the pro-tumorigenic and pro-metastatic interactions between the tumor cells and the host tumor microenvironment, immune cells and systemic factors.

The protective effect of simvastatin against low dose streptozotocin induced type 1 diabetes in mice is independent of inhibition of HMG-CoA reductase.

Besides a cholesterol-lowering effect, simvastatin possesses anti-inflammatory properties attributed to inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and/or direct binding to, and inhibition of, the integrin lymphocyte function associated antigen-1 (LFA-1). We have shown that simvastatin protects against multiple low dose streptozotocin (MLDS) induced type 1 diabetes in mice. Presently, we examined if this effect could be abolished by co-administration of mevalonic acid, thus determining if the protective effect is dependent or independent of inhibition of HMG-CoA reductase. Mevalonic acid did not affect the protective effect of simvastatin against MLDS diabetes. Moreover, spleens from these mice did not show any signs of toxic side-effects, thus excluding the possibility that the protective effect is secondary to a general inflammatory response. We suggest that simvastatin's protective effect mainly is independent of HMG-CoA reductase inhibition. This implies that inhibition of LFA-1 activation is important for the protective effect exerted by simvastatin.

Factors influencing the regulation of cytokine balance during islet transplantation in mice.

Many experimental islet studies compare the effect of allogeneic transplantations with either syngeneically transplanted or sham-operated animals. Presently we examined multiple "control" treatments to be able to distinguish effects by the operating procedures themselves versus reactions induced by islet graft rejection. Herein, we have studied untreated, sham-operated, syngeneically or allogeneically (C57BL/6) islet transplanted BALB/c mice, and subsequently examined cytokine production (TNFalpha, IFNgamma, IL-4, IL-10, IL-17 and TGF-beta) in vitro by RT-PCR and ELISA in spleen cells and transplants. To investigate if the strain of the recipient mice influences cytokine production we also performed allogeneic islet transplantations in the reverse direction. So-called control treatments such as sham operations and syngeneic transplantations had a distinct effect on cytokines in spleen cells, possibly induced by surgery and/or anaesthesia. This seems to decrease the regulatory T cells, thereby leading to increased cytokine expression. Furthermore, spleen cells from surgically manipulated animals seem to have a decreased responsive capacity to con A stimulation in culture. Cytokine generation, FoxP3 mRNA expression and COX-2 mRNA expression in the two investigated mouse strains were sometimes altered in opposite directions by the treatments. In conclusion, the genetic background of both the islet donor and recipient has a major impact on both the magnitude and skewing of a cytokine response. Moreover, factors not directly related to allorejection influences systemic cytokine production in connection to islet transplantation.

Kinetics of immune cell responses in the multiple low-dose streptozotocin mouse model of type 1 diabetes.

In type 1 diabetes (T1D), the insulin-producing ß cells are destructed by immune mechanisms. It has been hypothesized that the very first immune response in T1D onset comes from innate immune cells, which further activates the adaptive immune cells to attack the islets. Despite intensive research on characterization of islet-infiltrating immune cells, the kinetics of different immune cells in multiple low-dose streptozotocin (MLDSTZ)-induced T1D mouse model is still much unclear. Therefore, we investigated the proportions of innate immune cells such as neutrophils, dendritic cells (DCs), plasmacytoid dendritic cells (pDCs), macrophages, natural killer (NK) cells, and adaptive immune cells (T and B lymphocytes) in thymi, pancreatic-draining lymph nodes, and spleens of MLDSTZ mice on days 3, 7, 10, and 21 after the first injection of STZ by flow cytometry. The proportions of DCs and B cells were increased from day 3, while the proportions of B-1a lymphocytes and interferon-γ+ cells among NK cells were increased, but NK cells were decreased on day 10 in MLDSTZ-treated mice, illustrating that the initial immune response is induced by DCs and B cells. Later, the proportions of T helper 1 and cytotoxic T cells were increased from day 7, suggesting that the innate immune cells precede adaptive immune cell response in MLDSTZ mice. Altogether, our data demonstrate a possible sequence of events regarding the involvement of DCs, pDCs, NK cells, B-1a lymphocytes, B, and T cells at the early stage of T1D development.

Amelioration of diabetes by imatinib mesylate (Gleevec): role of beta-cell NF-kappaB activation and anti-apoptotic preconditioning.

It was recently reported that tyrosine kinase inhibitor imatinib mesylate (Gleevec) improves Type 2 diabetes, possibly by decreasing insulin resistance. However, as both Type 2 and Type 1 diabetes are characterized by beta-cell dysfunction and death, we investigated whether imatinib counteracts diabetes by maintaining beta-cell function. We observed that imatinib counteracted diabetes in two animal models, the streptozotocin-injected mouse and the nonobese diabetes mouse, and that this was paralleled by a partial preservation of the beta-cell mass. In addition, imatinib decreased the death of human beta-cells in vitro when exposed to NO, cytokines, and streptozotocin. The imatinib effect was mimicked by siRNA-mediated knockdown of c-Abl mRNA. Imatinib enhanced beta-cell survival by promoting a state similar to ischemic preconditioning, as evidenced by NF-kappaB activation, increased NO and reactive oxygen species production, and depolarization of the inner mitochondrial membrane. Imatinib did not suppress islet cell death in the presence of an NF-kappaB inhibitor, suggesting that NF-kappaB activation is a necessary step in the antiapoptotic action of imatinib. We conclude that imatinib mediates beta-cell survival and that this could contribute to the beneficial effects observed in diabetes.

Pro-tumoral immune cell alterations in wild type and Shb-deficient mice in response to 4T1 breast carcinomas.

To assess mechanisms responsible for breast carcinoma metastasis, 4T1 breast carcinomas were grown orthotopically in wild type or Shb knockout mice. Tumor growth, metastasis, vascular characteristics and immune cell properties were analyzed. Absence of Shb did not affect tumor growth although it increased lung metastasis. Shb knockout mouse tumors showed decreased redness and less developed vascular plexa located at the periphery of the tumors. No difference in overall tumor vascular density, leakage or pericyte coverage was noted between the genotypes although the average vessel size was smaller in the knockout. Tumors induced an increase of CD11b+ cells in spleen, lymph node, thymus, bone marrow and blood. Numbers of Shb knockout CD11b/CD8+ cells were decreased in lymph nodes and bone marrow of tumor bearing mice. Mice with tumors had reduced numbers of CD4+ lymphocytes in blood/lymphoid organs, whereas in most of these locations the proportion of CD4+ cells co-expressing FoxP3 was increased, suggesting a relative increase in Treg cells. This finding was reinforced by increased blood interleukin-35 (IL-35) in wild type tumor bearing mice. Shb knockout blood showed in addition an increased proportion of IL-35 expressing Treg cells, supporting the notion that absence of Shb further promotes tumor evasion from immune cell recognition. This could explain the increased number of lung metastases observed under these conditions. In conclusion, 4T1 tumors alter immune cell responses that promote tumor expansion, metastasis and escape from T cell recognition in an Shb dependent manner.

Complete protection against interleukin-1beta-induced functional suppression and cytokine-mediated cytotoxicity in rat pancreatic islets in vitro using an interleukin-1 cytokine trap.

Cytokines, particularly interleukin (IL)-1beta, have been postulated to cause beta-cell destruction in type 1 diabetes. We tested the efficacy of an IL-1 cytokine trap in counteraction of suppressive and toxic effects after exposure of rat pancreatic islets in vitro to IL-1beta. The IL-1 cytokine trap used herein comprised extracellular domains of the IL-1 receptor accessory protein and the human IL-1 receptor 1 arranged inline and fused to the Fc portion of human IgG1. Groups of isolated rat pancreatic islets were maintained in medium culture with or without IL-1beta (150 pmol/l) for 48 hours in the absence or presence of the IL-1 trap at 1-, 10-, or 100-fold excess the molar concentration of the cytokine. IL-1beta alone induced a strong inhibition of insulin secretion and glucose oxidation rate and a marked increase in medium nitrite accumulation as an indicator of nitric oxide generation. When the IL-1 trap was used at a ratio 10:1 or 100:1, a complete protection against these effects were observed. Moreover, the IL-1 trap (100:1) blocked the increased islet cell death seen in islets treated with a combination of IL-1beta + tumor necrosis factor-alpha + interferon-gamma as well as functional suppression induced by the cytokine combination. In conclusion, we show that addition of an IL-1 trap can protect rat pancreatic islets in vitro against noxious effects induced by IL-1beta. Exploring the IL-1 trap in relevant animal models of type 1 diabetes represents an interesting future intervention strategy.

The Increased Circulating Plasma Levels of Vascular Endothelial Growth Factor in Patients with Type 1 Diabetes Do Not Correlate to Metabolic Control.

Aim. To characterize the plasma levels of vascular endothelial growth factor (VEGF) in type 1 diabetes mellitus (T1D) and its relation to both present and historical metabolic control and microvascular complications. Methods. Plasma levels of VEGF and routine clinical parameters were analyzed in 115 patients with long-standing T1D and 45 healthy controls (HC). All patients were under clinical routine diabetes treatment at Uppsala University Hospital. Results. The plasma levels of VEGF were increased by 37% in patients with T1D when compared to HC (18.2 ± 0.8 versus 13.2 ± 1.0 pg/ml, p < 0.001). The levels of VEGF correlated to insulin needs and BMI but not to present or historical metabolic control. The levels of VEGF were similar in patients with T1D and microvascular complications (microalbuminuria and retinopathy) when compared with patients without microvascular complications. Historical HbA1c levels were found to be the best predictor for present metabolic control. Conclusion. Circulating plasma levels of VEGF do not correlate to present or historical metabolic control in long-standing T1D and the levels are not affected by the presence of microvascular complications.

Increased Interleukin-35 Levels in Patients With Type 1 Diabetes With Remaining C-Peptide.

OBJECTIVE: Many patients with long-standing type 1 diabetes have remaining functional ß-cells. This study investigated immunological differences between patients with or without measurable remaining endogenous insulin production after ≥10 years duration of disease. RESEARCH DESIGN AND METHODS: Patients (n = 113; ≥18 years of age) with type 1 diabetes and with disease duration of ≥10 years were recruited at Uppsala University Hospital. Residual ß-cell function was determined with an ultrasensitive C-peptide ELISA. Circulating cytokines, including interleukin-35 (IL-35), were determined in plasma. Additional blood samples were collected from 14 of the identified C-peptide-positive patients and 12 of the C-peptide-negative patients, as well as from 15 healthy control subjects, and were used for immediate investigation of peripheral blood mononuclear cells. RESULTS: The blood concentration of the cytokine IL-35 was markedly lower in C-peptide-negative patients, and this was associated with a simultaneous decrease in the proportion of IL-35+ regulatory T cells (Tregs), IL-35+ regulatory B cells, and IL-35-producing CD8+Foxp3+ cells. IL-35 has previously been shown to maintain the phenotype of Tregs, block the differentiation of T-helper 17 cells, and thereby dampen immune assaults to ß-cells. We found that the proportions of IL-17a+ cells among the Tregs, CD4+ T cells, and CD8+ T cells were lower in the C-peptide-positive patients. CONCLUSIONS: Patients with remaining endogenous ß-cell function after >10 years duration of type 1 diabetes differ immunologically from other patients with long-standing type 1 diabetes. In particular, they have a much higher IL-35 production.

Overexpression of heparanase enhances T lymphocyte activities and intensifies the inflammatory response in a model of murine rheumatoid arthritis.

Heparanase is an endo-glucuronidase that degrades heparan sulfate chains. The enzyme is expressed at a low level in normal organs; however, elevated expression of heparanase has been detected in several inflammatory conditions, e.g. in the synovial joints of rheumatoid arthritis (RA) patients. Herein, we have applied the model of collagen-induced arthritis (CIA) to transgenic mice overexpressing human heparanase (Hpa-tg) along with wildtype (WT) mice. About 50% of the induced animals developed clinical symptoms, i.e. swelling of joints, and there were no differences between the Hpa-tg and WT mice in the incidence of disease. However, Hpa-tg mice displayed an earlier response and developed more severe symptoms. Examination of cells from thymus, spleen and lymph nodes revealed increased innate and adaptive immune responses of the Hpa-tg mice, reflected by increased proportions of macrophages, antigen presenting cells and plasmacytoid dendritic cells as well as Helios-positive CD4+ and CD8+ T cells. Furthermore, splenic lymphocytes from Hpa-tg mice showed higher proliferation activity. Our results suggest that elevated expression of heparanase augmented both the innate and adaptive immune system and propagated inflammatory reactions in the murine RA model.

Prolactin regulation of the expression of TNF-alpha, IFN-gamma and IL-10 by splenocytes in murine multiple low dose streptozotocin diabetes.

Previously, the hormone prolactin (PRL) has been found to protect against development of type 1 diabetes induced by multiple injections of streptozotocin (STZ) in mice. To further investigate this effect of PRL, C57BL/Ks mice were injected intraperitoneally with STZ (40 mg/kg body weight) or NaCl for 5 days and PRL (4 mg/kg body weight) or NaCl for 14 days. On day 15, splenocytes were isolated from the in vivo treated mice. Spleen cell preparations depleted in erythrocytes and macrophages were stained for cytoplasmic TNF-alpha, IFN-gamma and IL-10 and analyzed with flow cytometry. Isolated spleen cells were also cultured (RPMI 1640+10% fetal bovine serum) for 24 h. Thereafter, cytokine mRNA expression by the spleen cells was measured by real-time PCR and cytokine secretion determined by enzyme linked immunosorbent assay (ELISA). Freshly isolated spleen cell preparations from PRL and STZ+PRL treated animals seemed to have an increased frequency of IL-10 positive cells compared to controls. In cultured spleen cells isolated from STZ treated mice, IFN-gamma and IL-10 mRNA expression was up-regulated. PRL treatment down-regulated the mRNA expression of these cytokines and also TNF-alpha in the splenocytes obtained from animals treated with STZ. The accumulation of these cytokines in the cultures of the explanted splenocytes showed only minor differences between the experimental groups. Overall, the data seems to favor the view that PRL enhanced a Th2 response, which may reflect the preventive effect of PRL against development of multiple low dose STZ diabetes in mice.

Survival of an islet allograft deficient in iNOS after implantation into diabetic NOD mice.

Proinflammatory cytokines play a major role in rejection of pancreatic islet allografts and in type 1 diabetes (T1D). In rodent islets, exposure to IL-1beta alone or combined with IFN-gamma induces expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS or a deletion of the iNOS gene has been shown to be protective in animal models of T1D. In the present study we tested the hypothesis that transplantation of pancreatic islets deficient in iNOS (iNOS-/-) would permit increased graft survival. Pancreatic islets isolated from wild-type (wt) mice and iNOS-/- mice were allogeneically transplanted beneath the kidney capsule of spontaneously diabetic NOD mice. When blood glucose increased above 12.0 mM after preceding normalization of hyperglycemia, animals were sacrificed. Histological examinations of grafts were performed and graft gene expression was analyzed by real-time PCR. Transplantations of the two types of islets could reverse hyperglycemia and the grafts functioned for on average 1 week posttransplantation. Morphological examination of both types of islet grafts showed immune cell infiltration around and within the grafts. Remaining endocrine cells could be observed in wt and iNOS-/- islet grafts. In the removed grafts iNOS-/- islet tissue contained higher mRNA levels of insulin, proinsulin convertases (PC-1 and PC-2), and IL-1beta compared to transplanted wt islets. The assessments of insulin, PC-1 and PC-2 mRNAs of the grafts suggest that the iNOS-/- islets may be more resistant to destruction in the transplantation model used; however, this was not sufficient to prolong the period of normoglycemia posttransplantation.

K(ATP) channels and pancreatic islet blood flow in anesthetized rats: increased blood flow induced by potassium channel openers.

K(ATP) channels are important for insulin secretion and depolarization of vascular smooth muscle. In view of the importance of drugs affecting K(ATP) channels in the treatment of diabetes, we investigated the effects of these channels on splanchnic blood perfusion in general and pancreatic islet blood flow in particular. We treated anesthetized Sprague-Dawley rats with the K(ATP) channel openers diazoxide or NNC 55-0118 or the K(ATP) channel closer glipizide. Both diazoxide and NNC 55-0118 dose-dependently increased total pancreatic and islet blood flow in the presence of moderate hyperglycemia, but had no effects on the blood perfusion of other splanchnic organs. Diazoxide markedly lowered the mean arterial blood pressure and thus increased vascular conductance in all organs studied. NNC 55-0118 had much smaller effects on the blood pressure. Glipizide did not affect total pancreatic blood flow, but decreased islet blood flow by 50% in the presence of hypoglycemia. We conclude that K(ATP) channels actively participate in the blood flow regulation of the pancreatic islets and that substances affecting such channels may also influence islet blood flow.