Erythropoietin does not attenuate renal dysfunction or inflammation in a porcine model of endotoxemia.

BACKGROUND: Erythropoietin (EPO) is a multifunctional cytokine with anti-apoptotic, anti-inflammatory, and organ protective effects. EPO protects against ischemia-reperfusion injuries, and recent reports suggest that EPO also prevents organ dysfunction in experimental sepsis. The aims of this study were to determine whether EPO prevents endotoxemia-induced organ dysfunction in a porcine model and to characterize the immunomodulatory and anti-apoptotic effects of EPO. METHODS: Twenty-eight pigs were randomly assigned to three groups: (1) endotoxemia treated with EPO 5000 IU/kg, (2) endotoxemia treated with placebo, and (3) a sham group anesthetized and submitted to sham operation without treatment. A laparotomy was performed, and a flow probe was placed around the left renal artery, which allowed renal blood flow (RBF) measurements. Endotoxemia was induced by an infusion of lipopolysaccharide. After 2 h, the infusion was reduced to a maintenance dose and the animals were fluid resuscitated. The glomerular filtration rate (GFR), RBF, renal oxygen consumption, and plasma cytokines [interleukin (IL)-1ß, IL-6, IL-8, IL-10, and tumor necrosis factor-alpha] were analyzed. Renal biopsies were analyzed for cytokine content and apoptosis. RESULTS: Endotoxemia elicited impaired renal function, estimated as GFR, and increased the levels of renal apoptotic cells, with no modifying effect of EPO. Furthermore, EPO had no effect on RBF, renal oxygen consumption, or the systemic hemodynamic response to endotoxemia. EPO did not modify the inflammatory response, measured as changes in cytokine levels in plasma and organs. CONCLUSION: EPO did not confer renal protection in this fluid-resuscitated porcine model of endotoxemia, and EPO did not modify the inflammatory response.

Erythropoietin administration is associated with short-term improvement in glomerular filtration rate after ischemia-reperfusion injury.

BACKGROUND: Erythropoietin (EPO) is a cytokine with organ-protective properties. We hypothesized that EPO could attenuate acute renal dysfunction and inflammation in a porcine model of ischemia-reperfusion (IR). Furthermore, we aimed to characterize the impact of EPO on systemic and renal hemodynamics, and renal oxygen consumption. METHODS: Twenty-four pigs were randomly assigned to three groups: (1) EPO (5000 IU/kg) administered intravenously before IR (n=9), (2) placebo administered before IR (n=9), or (3) sham group, anesthetized and operated on only (n=6). IR was induced by clamping the left renal artery for 45 min. Hemodynamics and renal blood flow (RBF) were analyzed continuously. Glomerular filtration rate (GFR), renal oxygen consumption, and plasma cytokines (IL-1ß, IL-6, IL-8, IL-10, and TNF-α) were analyzed hourly. Renal biopsies were analyzed for cytokine content and apoptosis. RESULTS: GFR was higher during reperfusion in the EPO group than in the placebo group (P<0.01). No differences between the IR groups were found in hemodynamics, RBF, oxygen consumption, or renal apoptosis. The levels of TNF-α in the plasma (P=0.036) and the levels of TNF-α and IL-10 in the renal cortex (P=0.04 and P=0.01, respectively) were lower in the EPO group compared with the sham group. CONCLUSION: EPO attenuated the renal dysfunction as estimated as GFR. This effect was not related to changes in the hemodynamics. The immunomodulatory effects of EPO were manifested as decreased levels of TNF-α and IL-10 in renal biopsies and TNF-α levels in plasma.

Renal cytokine profile in an endotoxemic porcine model.

INTRODUCTION: In animals exposed to acute endotoxemia with lipopolysaccharide (LPS), high levels of cytokines are found in the kidney. The objective of this study is to determine whether the high renal content of TNF-alpha, IL-1beta, IL-10 and IL-1 receptor antagonist (IL-1ra) is due to glomerular filtration and reabsorption, or whether the cytokines are produced locally in the kidney. METHODS: Eighteen anesthetized and mechanically ventilated pigs (35-43 kg) were randomized into two groups: Group 1 (n=12) LPS infusion for 360 min and Group 2 (n=6) control pigs, no treatment. At 360 min, the pigs were euthanized and tissue samples from the kidneys were obtained. Localization of the cytokines was determined by immunohistochemistry and double immunofluorescence (dIF). RESULTS: Pigs exposed to endotoxemia showed increased accumulation of leukocytes and increased protein expression of TNF-alpha and IL-1beta when compared with controls. dIF showed that TNF-alpha-positive cells co-localized with both endothelial and mesangial cells in the glomeruli. Furthermore, the endothelial cells of the cortical arterioles were positive for IL-1beta. TNF-alpha and IL-1beta staining were absent in renal tubular cells. A positive signal for IL-10 was detected at the tubular brush border while IL-1ra was detected in the glomerulus and in the tubular cells. CONCLUSION: LPS-induced endotoxemia increased TNF-alpha and IL-1beta protein expression and leukocyte accumulation in the kidneys. The results indicate that the increased levels of the pro-inflammatory cytokines TNF-alpha and IL-1beta are caused by a local production in the kidneys while the anti-inflammatory cytokines IL-10 and IL-1ra are filtrated and reabsorbed in the tubuli.

Does brain death induce a pro-inflammatory response at the organ level in a porcine model?

BACKGROUND: Organs from brain-dead donors have a poorer prognosis after transplantation than organs from living donors. A possible explanation for this is that brain death might initiate a systemic inflammatory response, elicited by a metabolic stress response or brain ischemia. The aim of this study was to investigate the effect of brain death on the cytokine content in the heart, liver, and kidney. In addition, the metabolic and hemodynamic response caused by brain death was carefully registered. METHODS: Fourteen pigs (35-40 kg) were randomized into two groups (1) eight brain-dead pigs and (2) six pigs only sham operated. Brain death was induced by inflation of an epidurally placed balloon. Blood samples for insulin, glucose, catecholamine, free fatty acids (FAA), and glucagon were obtained during the experimental period of 360 min. At the conclusion of the experiment, biopsies were taken from the heart, liver, and kidney and were analyzed for cytokine mRNA and proteins [tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and IL-10). RESULTS: We found a dramatic response to brain death on plasma levels of epinephrine (P=0.004), norepinephrine (P=0.02), FAA (P=0.0001), and glucagon (P=0.0003) compared with the sham group. There was no difference in cytokine content in any organ between the groups. CONCLUSION: In this porcine model, brain death induced a severe metabolic response in peripheral blood. At the organ level, however, there was no difference in the cytokine response between the groups.

Insulin alters cytokine content in two pivotal organs after brain death: a porcine model.

BACKGROUND: To optimize the quantity and quality of organs available for transplantation, it is crucial to gain further insight into the treatment of brain dead organ donors. In the current study we hypothesized that insulin treatment after brain death alters cytokine content in the heart, liver, and kidney. METHODS: Sixteen brain dead pigs (35-40 kg) were treated with either (1) no insulin [brain dead without insulin treatment treatment (BD)], or (2) insulin infusion intravenously (i.v.) at a constant rate of 0.6 mU/kg/min during 360 min [brain dead with insulin treatment (BD+I)]. Blood glucose was clamped at 4.5 mmol/l by infusion of 20% glucose. Blood samples for insulin, glucose, catecholamines, free fatty acids, and glucagon were obtained during the experimental period. Six hours after brain death biopsies were taken from the heart, liver, and kidney. These were analyzed for cytokine mRNA and proteins [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, and IL-10]. RESULTS: The BD+I compared with the BD animals had lower IL-6 concentrations in the right ventricle of the heart (P=0.001), in the renal cortex (P=0.04) and in the renal medulla (P=0.05), and lower IL-6 mRNA in the renal medulla (P=0.0002). Furthermore, the BD+I animals had lower concentrations in the renal medulla of IL-10 (P=0.01), and tended to have lower TNF-alpha in the renal cortex (P=0.06) than the BD animals. In the right ventricle of the heart TNF-alpha mRNA and IL-10 mRNA were higher in the BD+I than in the BD group (P=0.002 and 0.004). CONCLUSION: Insulin has anti-inflammatory effects on cytokine concentration in the heart and kidney after brain death.

Real-time PCR: housekeeping genes in the INS-1E beta-cell line.

Investigation of gene expression is a developing area with several methods available. One method is quantitative PCR. A major pitfall in quantitative PCR is the normalisation procedure of the gene expression. Many experiments include a housekeeping gene, some use RNA concentration, and others use a geometric mean of several internal, stably expressed genes. This study demonstrates that real-time-PCR results differ with varying housekeeping genes and analysis protocols when applied to insulin-secreting INS-1E cells derived from the pancreas and stimulated by DEDTC (diethyldithiocarbamate, a zinc chelator) and GLP-1.

The use of transgenic animals in the study of diabetic kidney disease.

Diabetic nephropathy is one of the most common diseases leading to fibrosis and end-stage renal disease (ESRD) world wide. Under normal conditions, a delicate equilibrium exists between synthesis, composition, and removal of extracellular matrix (ECM). If this is disturbed, ECM accumulation and fibrosis may result. The fragile balance between synthesis and removal of ECM is crucial for the prognosis of glomerular as well as interstitial pathological processes. Some features may favor ECM accumulation and progression to ESRD (dialysis and transplantation), whereas other elements may favor ECM removal and resolution (recovery). Pathogenetic mechanisms and the cellular sources of ECM in the glomerular basement membrane as well as in the tubulointerstitial space are still under investigation. Among several growth factors, transforming growth factor beta1 (TGF-beta1) plays a major role. We consider the use of living animals necessary for our understanding of the complex biological processes that occur during the development of ESRD. The present review will discuss the glomerular as well as interstitial accumulation of ECM and the use of transgenic animals in studying the pathogenetic mechanisms with special emphasis on diabetic kidney disease and TGF-beta1.

High plasma concentrations of prorenin in a transgenic animal model of nephropathy with overexpression of transforming growth factor-beta1 in the kidneys.

1. Plasma concentrations of prorenin were determined in a transgenic animal model of nephropathy induced by overexpression of transforming growth factor (TGF)-beta1 in the juxtaglomerular apparatus. 2. In both female and male mice, plasma concentrations of prorenin were higher in transgenic than in non-transgenic animals. In sexually mature mice, plasma prorenin concentrations were higher in males than in females in both transgenic and non-transgenic animals in accordance with a sexual dimorphism of the plasma concentration of prorenin. 3. The results indicate that TGF-beta1-like androgens increase prorenin secretion in the kidneys and may explain the increased plasma prorenin concentrations in patients with diabetic nephropathy.

TGF-beta1-induced glomerular disorder is associated with impaired concentrating ability mimicking primary glomerular disease with renal failure in man.

Transforming growth factor-beta1 (TGF-beta1) may play a major role in the pathogenesis of glomerulopathy and end-stage renal disease (ESRD). The aim of this study was to explore the functional consequences of localized overproduction of TGF-beta1 in relation to glomerular ultrastructure and the composition of the extracellular matrix (ECM) in the inner medulla. We used a transgenic mouse with overexpression of TGF-beta1 targeted to the juxtaglomerular apparatus (JGA) by the Ren-1c promoter. The kidney function was evaluated using urine production and metabolite excretion over a 24-hour period, glomerular filtration rate (GFR), and concentrating ability. The glomerular structure was analyzed in terms of volume, ie, the volume of the mesangium per glomerulus (Vv[mes/glom]) and the volume of the matrix per glomerulus (Vv[matrix/glom]), ECM per glomerulus, the area of the filtration surface, and the thickness of the peripheral basement membrane (PBM). Immunohistochemistry or in situ hybridization was used to examine the expression of aquaporin 2 (AQP2), plasminogen activator inhibitor-1 (PAI-1), and the composition of the ECM in the inner medulla. The mice exhibited polyuria, reduced concentrating ability, decreased GFR, and albuminuria paralleled by increased glomerular volume, with increased volume of ECM, decreased filtration surface, and thickening of the PBM being detectable between 1 and 2 months of age. The deposition of glomerular ECM was accompanied by increased levels of PAI-1. As estimated by excretion of Clara cell protein-1 (CC16) and lysozyme, tubular damage occurred only in older mice. Collagen Type I was deposited in the inner medulla in the presence of normal AQP2-expression in the collecting ducts. This study reached the following conclusions: (a) TGF-beta1 reduces the GFR and the glomerular filtration surface, (b) TGF-beta1 induces albuminuria in association with widening of the PBM, (c) expansion of the mesangial volume seems to precede the widening of the PBM, (d) TGF-beta1-induced accumulation of glomerular ECM is partly explained by increased PAI-1 expression, (e) Decreased concentrating ability and polyuria caused by accumulation of ECM in the inner medulla may be an early marker of glomerular diseases associated with increased expression of TGF-beta1 in man.

Under control of the Ren-1c promoter, locally produced transforming growth factor-beta1 induces accumulation of glomerular extracellular matrix in transgenic mice.

Our purpose was to elucidate the hypothesis that paracrine-produced transforming growth factor (TGF)-beta1 regulates the accumulation of extracellular matrix (ECM) in renal glomeruli, a hallmark of diabetic nephropathy. To produce TGF-beta1 from the juxtaglomerular apparatus in mouse kidneys, we cloned a mouse Ren-1c promoter fragment (-4.100 to +6 base pairs) upstream of porcine TGF-beta1 (pTGF-beta1) cDNA, mutated to ensure secretion of biologically active TGF-beta beta1. The resulting transgenic mice had significantly more TGF-beta1 in their kidneys than was in those of nontransgenic controls, as confirmed by immunohistochemistry, and the production of TGF-beta1 was enhanced in vivo by captopril-induced stimulation of the Ren-1c promoter. Overproduction of pTGF-beta1 close to the glomerulus resulted in a local accumulation of ECM, composed partly of collagen type IV and laminin, and thickening of the basement membrane, characteristic features of diabetic nephropathy. Interstitial accumulation of ECM and signs of tubular atrophy were present only in older mice (>5 months of age). Results from in situ hybridization and immunohistochemistry suggest that pTGF-beta1 stimulated the production of endogenous TGF-beta1 along collecting ducts and connecting tubules. The increased amount of biologically active TGF-beta1, transgenic as well as endogenous, was corroborated by heightened proteoglycan synthesis from incubated kidney slices. This transgenic model demonstrates that sustained local expression of TGF-beta1 leads to glomerulopathy. We conclude that autocrine- or paracrine-produced TGF-beta1 may play a role in the development of glomerular diseases, such as diabetic nephropathy.

Myasthenia gravis-like syndrome induced by expression of interferon gamma in the neuromuscular junction.

Abnormal humoral responses toward motor end plate constituents in muscle induce myasthenia gravis (MG). To study the etiology of this disease, and whether it could be induced by host defense molecules, we examined the consequences of interferon (IFN) gamma production within the neuromuscular junction of transgenic mice. The transgenic mice exhibited gradually increasing muscular weakness, flaccid paralysis, and functional disruption of the neuromuscular junction that was reversed after administration of an inhibitor of acetylcholinesterase, features which are strikingly similar to human MG. Furthermore, histological examination revealed infiltration of mononuclear cells and autoantibody deposition at motor end plates. Immunoprecipitation analysis indicated that a previously unidentified 87-kD target antigen was recognized by sera from transgenic mice and also by sera from the majority of human MG patients studied. These results suggest that expression of IFN-gamma at motor end plates provokes an autoimmune humoral response, similar to human MG, thus linking the expression of this factor with development of this disease.

Circulating interleukin-1 receptor antagonist concentrations are increased in adult patients with thermal injury.

OBJECTIVE: To investigate the balance between circulating concentrations of interleukin (IL)-1 and its natural inhibitor interleukin-1 receptor antagonist (IL-1Ra) in human inflammation. DESIGN: Prospective case-control study. SETTING: University hospital burn care unit. PATIENTS: Fifteen patients with second- or third-degree thermal injuries of 7% to 78% of total body surface and 15 healthy age- and sex-matched control subjects. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Median plasma IL-1Ra, but not IL-1 beta or tumor necrosis factor-alpha (TNF-alpha) concentrations were markedly increased on the day of admission in patients with thermal injuries compared with controls (1615 [range 426 to 23,800] vs. 494 [range 196 to 1093] pg/mL; p < .001). In survivors, the median IL-1Ra concentration normalized 12 to 21 days after admission. The concentration of IL-1Ra on the day of admission was weakly positively correlated to the extent and degree of thermal injury (r2 = .46; p < .05). IL-1Ra on days 1 to 3 was highest in three nonsurvivors with inhalation injuries compared with survivors (2166 [range 1362 to 36,624] vs. 1344 [range 665 to 13,085] pg/mL; p < .05). IL-1Ra increased significantly after debridement and skin transplantation (preoperatively 742 [range 488 to 1506] vs. postoperatively 1431 [range 1286 to 2107] pg/mL; p < .01). In nonsurvivors, median IL-1Ra was 3.6-fold higher than IL-1 beta on days 1 to 2 and 36-fold higher than IL-1 beta in three patients with bacteremia. IL-1Ra was studied for its relationship to previously reported parameters of the acute-phase response determined in the same samples from these patients. The increased concentrations of IL-1Ra coincided with a decrease in serum albumin concentration and increases in rectal temperature. However, IL-1Ra did not correlate with rectal temperature, plasma concentrations of endotoxin, IL-1 beta, or TNF-alpha either at admission or in follow-up samples. CONCLUSIONS: Thermal injury causes an increase of circulating IL-1Ra, especially in patients with inhalation injuries. With the current plasma assays for IL-1 beta, IL-1Ra may be a more sensitive marker of human inflammation than IL-1 beta or TNF-alpha.

Postnatal anti-interferon-gamma treatment prevents pancreatic inflammation in transgenic mice with beta-cell expression of interferon-gamma.

beta-Cell-targeted expression of interferon-gamma (IFN-gamma) leads to pancreatitis and immune sensitization to beta-cells. This transgenic model is used to explore the possible role of locally produced IFN-gamma in loss of tolerance to beta-cell-specific antigens in insulin-dependent diabetes mellitus (IDDM). The aim of the present study was to test if postnatal treatment with antibodies against IFN-gamma could inhibit morphological changes in the IFN-gamma transgenic pancreas, even though the transgene is expressed during embryogenesis. Treatment with a monoclonal rat anti-mouse IFN-gamma antibody for 6 weeks, starting from 5 to 7 days of age, completely inhibited IFN-gamma-induced morphological changes in the pancreas, and only a modest inflammatory reaction emerged after prolonged treatment for 12 weeks. The lack of morphological changes may reflect the ability of nonterminally differentiated neonatal pancreatic cells to compensate for transgene-induced pathological alterations occurring in utero prior to the antibody treatment. We conclude that inflammation and altered pancreas morphology in the transgenic mice is the result of the biological actions of IFN-gamma and not by disrupted islet development due to transgene overexpression in the pancreatic beta-cells. Furthermore, our treatment schedule can serve as a model for future intervention studies in the transgenic mice, elaborating the role of IFN-gamma in localized inflammatory reactions, IDDM in particular.

Production of interleukin 10 by islet cells accelerates immune-mediated destruction of beta cells in nonobese diabetic mice.

The T helper type 2 (Th2) cell product interleukin 10 (IL-10) inhibits the proliferation and function of Th1 lymphocytes and macrophages (M phi). The nonobese diabetic mouse strain (NOD/Shi) develops a M phi and T cell-dependent autoimmune diabetes that closely resembles human insulin-dependent diabetes mellitus (IDDM). The objective of the present study was to explore the consequences of localized production of IL-10 on diabetes development in NOD/Shi mice. Surprisingly, local production of IL-10 accelerated the onset and increased the prevalence of diabetes, since diabetes developed at 5-10 wk of age in 92% of IL-10 positive I-A beta g7/g7, I-E- mice in first (N2) and second (N3) generation backcrosses between IL-10 transgenic BALB/c mice and (NOD/Shi) mice. None of the IL-10 negative major histocompatibility complex-identical littermates were diabetic at this age. Furthermore, diabetes developed in 33% of I-A beta g7/d, I-E+ N3 mice in the presence of IL-10 before the mice were 10 wk old. Our findings support the notion that IL-10 should not simply be regarded as an immunoinhibitory cytokine, since it possesses powerful, immunostimulatory properties as well. Furthermore, our observations suggest that beta cell destruction in NOD mice may be a Th2-mediated event.

Pancreatic islet production of murine interleukin-10 does not inhibit immune-mediated tissue destruction.

IL-10 inhibits macrophage-dependent antigen presentation, cytokine production, and generation of allospecific cells in vitro. These findings have lead to the widespread expectation that IL-10 may be a useful immunosuppressive agent to inhibit allograft rejection or autoimmunity in vivo. We used two experimental paradigms to study effects of murine IL-10 on in vivo immune responses. First, fetal pancreata or adult pancreatic islets from transgenic mice expressing IL-10 in pancreatic beta cells (Ins-IL-10 mice) were grafted across the MHC barrier to examine if IL-10 could inhibit allograft rejection. Second, Ins-IL-10 mice were crossed with transgenic mice expressing lymphocytic choriomeningitis virus (LCMV) antigens in pancreatic beta cells. These mice were infected with LCMV to elicit autoimmune diabetes, allowing us to ask if IL-10 protects islets from autoimmune destruction. We observed that allografts from IL-10-transgenic donors were rejected with comparable kinetics to the rejection of control nontransgenic allografts, indicating that IL-10 does not inhibit allograft rejection. After LCMV infection, IL-10 and LCMV antigen double transgenic mice developed diabetes earlier than LCMV antigen single transgenic littermates, suggesting that IL-10 does not inhibit islet antigen presentation or recognition. Our results contrast to in vitro observations and suggest that IL-10 cannot overcome immune-mediated tissue destruction within the pancreas.

Interleukin-1 beta (IL-1) does not reduce the diabetes incidence in diabetes-prone BB rats.

The cytokine interleukin 1 beta (IL-1) has been implicated as a pathogenetic factor in the initial events leading to insulin-dependent diabetes mellitus. Previous studies investigating the impact of IL-1 on diabetes incidence in spontaneously diabetic rodent models have been conflicting. IL-1 induces anorexia and previous studies are hampered by the lack of pair-fed controls to the IL-1 treated animals. We report that daily injections of 4.0 micrograms/kg/day of recombinant human IL-1 (rhIL-1) for 13 weeks from 25-30 days of age did not alter the incidence of diabetes in the diabetes-prone (DP) BB rats (75%) when compared to pair-fed, vehicle treated controls (55%, p = 0.18), or to unhandled DP BB rats (80%, p = 0.71). However, IL-1 induced significantly higher blood glucose concentrations in the prediabetic period (p < 0.00005) and at diabetes onset (p < 0.00005) in the DP BB rats and caused episodes of blood glucose concentrations > 11 mmol/l in the prediabetic period in 11/20 DP BB rats compared to 4/27 diabetes-resistant (DR) BB rats and 4/28 Wistar Furth (WF) rats (both p < 0.004), compared to DP BB). Further, rhIL-1 induced fever in 11 weeks in the DP BB rats compared to 3 weeks in the DR BB and 6 weeks in the WF rats. Using high performance size exclusion chromatography specific anti-rhIL-1-antibodies were demonstrated in DR BB and WF, but not in DP BB rats. These antibodies neutralized the inhibitory effect of rhIL-1 on insulin secretion from isolated islets of Langerhans in vitro. The reduced pyrogenic and endocrine effect of rhIL-1 in the DR BB and WF rats compared to the DP BB rats could be explained by the impaired ability of the DP BB rats to produce anti-rhIL-1-antibodies. In conclusion, administration of rhIL-1 modulated the prediabetic period, and produced higher blood glucose concentrations at diagnosis, but did not change the diabetes incidence in DP BB rats. The results are not in conflict with the hypothesis that IL-1 is a pathogenetic factor in IDDM, caused by high local concentrations of rat IL-1 in the islets during early insulitis. The results also show the necessity of pair-feeding of the control group to the rhIL-1 group when interpreting data from experiments investigating rhIL-1 effects on diabetes development in animal models.

Functional effects of transgenic expression of cholera toxin in pancreatic beta-cells.

Investigation of intracellular pathways of stimulus-secretion signaling in vivo is possible by transgenic expression of agents known to influence specific biochemical interactions in the cells. The objective of the present study was to establish an experimental model for analyzing signal transduction mechanisms in pancreatic beta-cells in vivo, by expressing the cholera toxin A1 subunit under control of the insulin promoter, intending a constant activation of the Gs-protein, and thereby constant generation of cAMP. Surprisingly, the transgenic mice demonstrated mild hyperglycemia and hypoinsulinemia in vivo, and diminished glucose-induced insulin release from the in vitro perfused pancreas, whereas the pancreatic insulin content was normal. These observations suggest a deficiency in either the insulin release mechanisms or glucose recognition. Although the translated cholera toxin A1 subunit was biologically active, there was no increase in the islet content of cAMP. We conclude that the observed phenotype in the cholera toxin transgenic mice may be caused by a deleterious effect of the transgene itself on beta-cell function, or that counter regulatory mechanisms may compensate for the transgene-induced changes in intracellular enzymatic pathways.

Leukocyte extravasation into the pancreatic tissue in transgenic mice expressing interleukin 10 in the islets of Langerhans.

Transgenic expression of interleukin 10 (IL-10) in the islets of Langerhans leads to a pronounced pancreatic inflammation, without inflammation of the islets of Langerhans and without diabetes. A scattered infiltration of macrophages (M pi) precedes localized accumulations of CD4+ and CD8+ T lymphocytes, B lymphocytes, and M pi. This recruitment of inflammatory cells to the pancreas is somewhat surprising, since the biological activities of IL-10 in vitro indicate that IL-10 is a powerful immunosuppressive cytokine. Since endothelial cells play a major role in leukocyte extravasation, we examined if vascular changes and extralymphoid induction of peripheral and mucosal type vascular addressins contributed to IL-10-induced homing of mononuclear cells to the pancreas. The endothelium lining small vessels was highly activated in areas of inflammation, as the endothelial cells became cuboidal, and exhibited increased expression of major histocompatibility complex class II (Ia), intercellular adhesion molecule 1, and von Willebrand Factor. Furthermore, induction of vascular addressins simultaneously with accumulation of mononuclear cells around islets and vessels indicated that the endothelial cells take on the phenotype of differentiated endothelium specialized for leukocyte extravasation. In conclusion, pancreatic inflammation and vascular changes are prominent in IL-10 transgenic mice. We hypothesize that IL-10, in addition to its immuno-inhibitory properties, is a potent recruitment signal for leukocyte migration in vivo. These effects are relevant for in vivo therapeutic applications of IL-10.

Pancreatic beta-cell function and interleukin-1 beta in plasma during the acute phase response in patients with major burn injuries.

Animal experiments demonstrate that interleukin-1 beta (IL-1 beta) is beta-cell cytotoxic in vitro and inhibits insulin secretion in vivo. However, it is unknown if IL-1 beta affects beta-cell function in man. Since IL-1 beta and other cytokines are main mediators of the acute phase response, the objectives of the present study were to examine beta-cell function in patients with major burn injuries, and to test if changes in beta-cell function correlated to systemic levels of IL-1 beta and tumour necrosis factor alpha (TNF alpha). We established and validated an IL-1 beta assay measuring free and protein bound IL-1 beta; protein bound IL-1 beta was detached from the IL-1 beta specific binding protein by acidification, rendering it accessible for the employed antibody. The IL-1 beta specific binding protein (43-60 kDa) was found in serum and plasma from all tested patients and normal subjects. Survivors of burn injuries had a stimulated beta-cell function, whereas non-survivors had an impaired beta-cell function as indicated by an increased plasma concentration of proinsulin, and an increased proinsulin/insulin ratio. In addition, non-survivors had significantly increased plasma levels of IL-1 beta. However, we could not demonstrate any correlation between C-peptide, proinsulin, insulin or proinsulin/insulin ratio and plasma concentration of IL-1 beta. In conclusion, beta-cell function abnormalities are evident in patients with major burn injuries, and a high plasma level of IL-1 beta correlates with a fatal outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

A TaqI polymorphism in the human interleukin-1 beta (IL-1 beta) gene correlates with IL-1 beta secretion in vitro.

In the present study we searched for restriction fragment length polymorphisms (RFLP) in the human interleukin-1 beta (IL-1 beta) gene and for correlations to monocyte (Mo) function in non-related healthy donors and insulin-dependent diabetic patients. We demonstrated a diallelic polymorphism with the restriction enzyme TaqI consisting of fragments of 9.4 kb and 13.4 kb. No differences in allele or genotype frequencies of this RFLP were observed between randomly selected controls and randomly selected patients with insulin-dependent diabetes mellitus (IDDM). However, when analysing IDDM patients negative for HLA-DR3 and -DR4, our data demonstrate that the 13.4 kb allele is more frequent in this group compared to a matched control group. The functional impact of this RFLP was studied by analysing in vitro stimulated Mo IL-1 beta response. An IL-1 beta allele dosage effect on secretory capacity was observed after LPS-stimulation: 13.4/13.4 kb homozygous individuals secreted significantly more IL-1 beta than 9.4/13.4 kb heterozygous individuals, who secreted significantly more than 9.4/9.4 kb homozygous individuals. Analyses of supernatants from LPS-stimulated Mo cultures from individuals with each TaqI IL-1 beta genotype revealed no differences in the mouse thymocyte co-stimulatory assay when compared on a molar basis, indicating that the TaqI polymorphism gave rise only to quantitative differences in expression levels and probably not to a mutant IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)