Kurt Reifenberg

Universitätsklinikum Freiburg, Freiburg an der Elbe, Lower Saxony, Germany

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Publications (71)

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    Fei Cheng · Laura Twardowski · Kurt Reifenberg · [...] · Michael Torzewski
    [Show abstract] [Hide abstract] ABSTRACT: This study focused on the unique properties of both the Ldlr knockout defect (closely mimicking the human situation) and the BALB/c (C) inbred mouse strain (Th-2 slanted immune response). We generated two immunodeficient strains with severe combined B- and T-cell immunodeficiency with or without a complete lack of natural killer cells to revisit the role of adaptive immune responses on atherogenesis. C-Ldlr-/- Rag1-/- mice, which show severe combined B- and T-cell immunodeficiency and C-Ldlr-/- Rag1-/- Il2rg-/- mice, which combine the T- and B-cell defect with a complete lack of natural killer cells and inactivation of multiple cytokine signalling pathways were fed an atherogenic Western type diet (WTD). Both B6-Ldlr-/- and C-Ldlr-/- immunocompetent mice were used as controls. Body weights and serum cholesterol levels of both immunodeficient strains were significantly increased compared to C-Ldlr-/- controls, except for cholesterol levels of C-Ldlr-/- Rag1-/- double mutants after 12 weeks on the WTD. Quantification of the aortic sinus plaque area revealed that both strains of immunodeficient mice developed significantly more atherosclerosis compared to C-Ldlr-/- controls after 24 weeks on the WTD. Increased atherosclerotic lesion development in C-Ldlr-/- Rag1-/- Il2rg-/- triple mutants was associated with significantly increased numbers of macrophages and significantly decreased numbers of smooth muscle cells compared to both C-Ldlr-/- wild type and C-Ldlr-/- Rag1-/- double mutants pointing to a plaque destabilizing effect of NK cell loss. Collectively, the present study reveals a previously unappreciated complexity with regard to the impact of lymphocytes on lipoprotein metabolism and the role of lymphocyte subsets in plaque composition.
    Full-text Article · Aug 2016 · PLoS ONE
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    [Show abstract] [Hide abstract] ABSTRACT: Objective: The Hepatitis B virus genome persists in the nucleus of virus infected hepatocytes where it serves as template for viral mRNA synthesis. Epigenetic modifications, including methylation of the CpG islands contribute to the regulation of viral gene expression. The present study investigates the effects of spontaneous age dependent loss of hepatitis B surface protein- (HBs) expression due to HBV-genome specific methylation as well as its proximate positive effects in HBs transgenic mice. Methods: Liver and serum of HBs transgenic mice aged 5-33 weeks were analyzed by Western blot, immunohistochemistry, serum analysis, PCR, and qRT-PCR. Results: From the third month of age hepatic loss of HBs was observed in 20% of transgenic mice. The size of HBs-free area and the relative number of animals with these effects increased with age and struck about 55% of animals aged 33 weeks. Loss of HBs-expression was strongly correlated with amelioration of serum parameters ALT and AST. In addition lower HBs-expression went on with decreased ER-stress. The loss of surface protein expression started on transcriptional level and appeared to be regulated epigenetically by DNA methylation. The amount of the HBs-expression correlated negatively with methylation of HBV DNA in the mouse genome. Conclusions: Our data suggest that methylation of specific CpG sites controls gene expression even in HBs-transgenic mice with truncated HBV genome. More important, the loss of HBs expression and intracellular aggregation ameliorated cell stress and liver integrity. Thus, targeted modulation of HBs expression may offer new therapeutic approaches. Furthermore, HBs-transgenic mice depict a non-infectious mouse model to study one possible mechanism of HBs gene silencing by hypermethylation.
    Full-text Article · Dec 2015 · PLoS ONE
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    Dataset: S1 Table
    [Show abstract] [Hide abstract] ABSTRACT: Primer and PCR conditions for qRT-PCR. HBs-mRNA and genomic DNA qRT-PCR was analysed by qRT-PCR using primer and PCR characteristics presented in STab 1. We used r18S as housekeeping gene control. AT = annealing temperature, bp = base pairs, LHB = large HBV surface protein, SHB = short HBV surface protein. (DOCX)
    Full-text Dataset · Dec 2015
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    [Show abstract] [Hide abstract] ABSTRACT: The link between the extensive usage of calcineurin (CN) inhibitors Cyclosporin A (CsA) and Tacrolimus (FK506) in transplantation medicine and the increasing rate of opportunistic infections within this segment of patients is alarming. Currently, how peritoneal infections are favored by these drugs, which impair the activity of several signalling pathways including the Ca(++) /CN/NFAT, Ca(++) /CN/cofilin, Ca(++) /CN/BAD and NF-κB networks, is unknown. Here, we show that Saccharomyces cerevisiae infection of peritoneal resident macrophages triggers the transient nuclear translocation of NFATc1β isoforms., resulting in a coordinated, CN-dependent induction of the Ccl2, Ccl7 and Ccl12 genes, all encoding CCR2 agonists. CN inhibitors block the CCR2-dependent recruitment of inflammatory monocytes (IM) to the peritoneal cavities of S. cerevisiae-infected mice. In myeloid cells, NFATc1/β proteins represent the most prominent NFATc1 isoforms. NFATc1/β ablation leads to a decrease of CCR2 chemokines, impaired mobilization of IMs and delayed clearance of infection. We show that, upon binding to a composite NFAT/BCL6 regulatory element within the Ccl2 promoter, NFATc1/β proteins release the BCL6-dependent repression of Ccl2 gene in macrophages. These findings suggest a novel CN-dependent cross talk between NFAT and BCL6 transcription factors, which may affect the outcome of opportunistic fungal infections in immunocompromised patients. This article is protected by copyright. All rights reserved.
    Full-text Article · Dec 2015 · European Journal of Immunology
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    [Show abstract] [Hide abstract] ABSTRACT: While the immune pathogenesis caused by hepatitis B virus (HBV) infection has been studied extensively, little is known about direct pathogenic effects of HBV surface proteins. Here, we have investigated pathological cellular effects of HBV surface protein expression in the liver of transgenic mice with different genetic background. The impact of HBV surface protein expression on the liver was studied in two mouse strains, BALB/c and C57BL/6. Histology and hydroxyproline assays were performed to investigate liver morphology and fibrosis. Gene expression and signaling were analyzed by microarray, qPCR and Western blotting. Expression of HBV surface proteins in the liver of transgenic mice induced activation of protein kinase-like endoplasmic reticulum kinase (PERK) and eukaryotic initiation factor 2α (eIF2α) phosphorylation. Phosphorylation of eIF2α resulted in activation of the ER stress markers glucose regulated protein (GRP) 78 and pro-apoptotic C/EBP homologous protein (CHOP) in transgenic mice on BALB/c genetic background leading to stronger liver injury and fibrosis in comparison with transgenic mice on C57BL/6 background. Hepatic stellate cells represented the main collagen-producing liver cells in HBV transgenic mice. The key regulators of hepatocyte proliferation, transcription factors c-Jun and STAT3 were activated in HBV transgenic mice. Tumour incidence in transgenic mice was strain- and sex-dependent. Extent of liver injury, fibrosis, and tumour development induced by hepatic HBV surface protein expression considerably depends on host genetic background.
    Full-text Article · Mar 2014 · PLoS ONE
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    Kurt Reifenberg · Fei Cheng · Laura Twardowski · [...] · Michael Torzewski
    [Show abstract] [Hide abstract] ABSTRACT: Clinical data have indicated a negative correlation between plasma TGFß1 concentrations and the extent of atherosclerosis and have thus led to the hypothesis that the pleiotropic cytokine may have anti-atherogenic properties. T-cells are currently discussed to significantly participate in atherogenesis, but the precise role of adaptive immunity in atherogenesis remains to be elucidated. TGFß1 is known to strongly modulate the function of T-cells, however, inhibition of TGFß1 signalling in T-cells of atherosclerosis-prone knock-out mice failed to unequivocally clarify the role of the cytokine for the development of atherosclerosis. In the present study, we thus tried to specify the role of TGFß1 in atherogenesis by using the murine CD2-TGFß1 transgenic strain which represents a well characterized model of T-cell specific TGFß1 overexpression. The CD2-TGFß1 transgenic mice were crossed to ApoE knock-out mice and quantity and quality of atherosclerosis regarding number of macrophages, smooth muscle cells, CD3 positive T-cells and collagen was analyzed in CD2-TGFß1 ApoE double mutants as well as non-transgenic ApoE controls on both normal and atherogenic diet of a duration of 8, 16 or 24 weeks, respectively. In all experimental groups investigated, we failed to detect any influence of TGFß1 overexpression on disease. Total number of CD3-positive T-lymphocytes was not significantly different in atherosclerotic lesions of CD2-TGFß1 ApoE(-/-) females and isogenic ApoE(-/-) controls, even after 24 weeks on the atherogenic diet. The synopsis of these data and our previous study on TGFß1 overexpressing macrophages suggests that potential effects of TGFß1 on atherosclerosis are most probably mediated by macrophages rather than T-cells.
    Full-text Article · Dec 2013 · PLoS ONE
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    Andreas Vlachos · Benno Ikenberg · Maximilian Lenz · [...] · Thomas Deller
    [Show abstract] [Hide abstract] ABSTRACT: Synaptopodin (SP) is a marker and essential component of the spine apparatus (SA), an enigmatic cellular organelle composed of stacked smooth endoplasmic reticulum that has been linked to synaptic plasticity. However, SP/SA-mediated synaptic plasticity remains incompletely understood. To study the role of SP/SA in homeostatic synaptic plasticity we here used denervation-induced synaptic scaling of mouse dentate granule cells as a model system. This form of plasticity is of considerable interest in the context of neurological diseases that are associated with the loss of neurons and subsequent denervation of connected brain regions. In entorhino-hippocampal slice cultures prepared from SP-deficient mice, which lack the SA, a compensatory increase in excitatory synaptic strength was not observed following partial deafferentation. In line with this finding, prolonged blockade of sodium channels with tetrodotoxin induced homeostatic synaptic scaling in wild-type, but not SP-deficient, slice cultures. By crossing SP-deficient mice with a newly generated transgenic mouse strain that expresses GFP-tagged SP under the control of the Thy1.2 promoter, the ability of dentate granule cells to form the SA and to homeostatically strengthen excitatory synapses was rescued. Interestingly, homeostatic synaptic strengthening was accompanied by a compensatory increase in SP cluster size/stability and SA stack number, suggesting that activity-dependent SP/SA remodeling could be part of a negative feedback mechanism that aims at adjusting the strength of excitatory synapses to persisting changes in network activity. Thus, our results disclose an important role for SP/SA in homeostatic synaptic plasticity.
    Full-text Article · Apr 2013 · Proceedings of the National Academy of Sciences
  • Y Churin · T Würger · M Roderfeld · [...] · E Roeb
    Article · Jan 2013 · Zeitschrift für Gastroenterologie
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    M Linke · A May · K Reifenberg · [...] · U Zechner
    [Show abstract] [Hide abstract] ABSTRACT: Ovarian stimulation with gonadotrophins is an integral part of assisted reproductive technologies in human subfertility/infertility treatment. Recent findings have associated ovarian stimulation with the increased incidence of imprinting disorders in humans as well as defects in genome-wide methylation reprogramming and, in particular, imprinting in mice. Here, we present the first study that determined the impact of ovarian stimulation on the expression of developmentally important reprogramming genes (Apex1, Lig1, Lig3, Mbd2, Mbd3, Mbd4, and Polb) in single early mouse morula embryos (16-cell stage). Using absolute quantification of mRNA by quantitative real-time PCR, we observed an association of ovarian stimulation with a downregulation of mRNAs encoding the base excision repair proteins APEX1 and POLB as well as the 5-methyl-CpG-binding domain protein MBD3 in individual morula embryos. Whole mount immunofluorescence staining of early and late morula embryos with an antibody against APEX1 revealed individual embryos with lower protein expression levels after ovarian stimulation and a correlation of mRNA expression with protein abundance. Our data argue for a negative impact of ovarian stimulation during female gametogenesis and/or early embryo development affecting the expression of candidate reprogramming factors.
    Full-text Article · Nov 2012 · Cytogenetic and Genome Research
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    [Show abstract] [Hide abstract] ABSTRACT: Cytomegalovirus (CMV) disease with multiple organ manifestations is the most feared viral complication limiting the success of hematopoietic cell transplantation as a therapy of hematopoietic malignancies. A timely endogenous reconstitution of CD8 T cells controls CMV infection, and adoptive transfer of antiviral CD8 T cells is a therapeutic option to prevent CMV disease by bridging the gap between an early CMV reactivation and delayed endogenous reconstitution of protective immunity. Preclinical research in murine models has provided 'proof of concept' for CD8 T-cell therapy of CMV disease. Protection by CD8 T cells appears to be in conflict with the finding that CMVs encode proteins that inhibit antigen presentation to CD8 T cells by interfering with the constitutive trafficking of peptide-loaded MHC class I molecules (pMHC-I complexes) to the cell surface. Here, we have systematically explored antigen presentation in the presence of the three currently noted immune evasion proteins of murine CMV in all possible combinations and its modulation by pre-treatment of cells with interferon-gamma (IFN-γ). The data reveal improvement in antigen processing by pre-treatment with IFN-γ can almost overrule the inhibitory function of immune evasion molecules in terms of pMHC-I expression levels capable of triggering most of the specific CD8 T cells, though the intensity of stimulation did not retrieve their full functional capacity. Notably, an in vivo conditioning of host tissue cells with IFN-γ in adoptive cell transfer recipients constitutively overexpressing IFN-γ (B6-SAP-IFN-γ mice) enhanced the antiviral efficiency of CD8 T cells in this transgenic cytoimmunotherapy model.
    Full-text Article · Sep 2012 · Medical Microbiology and Immunology
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    Kurt Reifenberg · Fei Cheng · Carolin Orning · [...] · Michael Torzewski
    [Show abstract] [Hide abstract] ABSTRACT: Although macrophages represent the hallmark of both human and murine atherosclerotic lesions and have been shown to express TGF-ß1 (transforming growth factor β1) and its receptors, it has so far not been experimentally addressed whether the pleiotropic cytokine TGF-ß1 may influence atherogenesis by a macrophage specific mechanism. We developed transgenic mice with macrophage specific TGF-ß1 overexpression, crossed the transgenics to the atherosclerotic ApoE (apolipoprotein E) knock-out strain and quantitatively analyzed both atherosclerotic lesion development and composition of the resulting double mutants. Compared with control ApoE(-/-) mice, animals with macrophage specific TGF-ß1 overexpression developed significantly less atherosclerosis after 24 weeks on the WTD (Western type diet) as indicated by aortic plaque area en face (p<0.05). Reduced atherosclerotic lesion development was associated with significantly less macrophages (p<0.05 after both 8 and 24 weeks on the WTD), significantly more smooth muscle cells (SMCs; p<0.01 after 24 weeks on the WTD), significantly more collagen (p<0.01 and p<0.05 after 16 and 24 weeks on the WTD, respectively) without significant differences of inner aortic arch intima thickness or the number of total macrophages in the mice pointing to a plaque stabilizing effect of macrophage-specific TGF-ß1 overexpression. Our data shows that macrophage specific TGF-ß1 overexpression reduces and stabilizes atherosclerotic plaques in ApoE-deficient mice.
    Full-text Article · Jul 2012 · PLoS ONE
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    [Show abstract] [Hide abstract] ABSTRACT: Different murine models have been used as basis for Proteinase 3 (PR3)-associated vasculitis models, but sufficient reproduction of the human clinical manifestation has failed to this date. As a reliable animal model is needed to further elucidate the pathological value of PR3-ANCA, we developed a PR3-humanized transgenic mouse model, in order to induce a glomerulonephritis. Our huPR3-transgenic mice were injected i.v. with our monoclonal antibodies, either unlabeled or directly labeled by fluorescein isothiocyanate. For a period of 5 days, proteinuria and erythrocyte count were measured with urine dip sticks. None of the mice exhibited proteinuria and/or an abnormal number of erythrocytes in the urine. Five days after antibody treatment, the mice were killed and different organs were fixed and immunohistochemically assessed. In the case of the kidney, we could detect a glomerulonephritis. Our study is able to show that although a direct renal target was given in transgenic human PR3 mice, no renal pathology was detectable. Multifactorial mechanisms for PR3-ANCA involvement in the development of Wegener's granulomatosis must be hypothesized.
    Full-text Article · Apr 2012 · Rheumatology International
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    [Show abstract] [Hide abstract] ABSTRACT: Severe Plasmodium falciparum malaria evolves through the interplay among capillary sequestration of parasitized erythrocytes, deregulated inflammatory responses, and hemostasis dysfunction. After rupture, each parasitized erythrocyte releases not only infective merozoites, but also the digestive vacuole (DV), a membrane-bounded organelle containing the malaria pigment hemozoin. In the present study, we report that the intact organelle, but not isolated hemozoin, dually activates the alternative complement and the intrinsic clotting pathway. Procoagulant activity is destroyed by phospholipase C treatment, indicating a critical role of phospholipid head groups exposed at the DV surface. Intravenous injection of DVs caused alternative pathway complement consumption and provoked apathy and reduced nociceptive responses in rats. Ultrasonication destroyed complement-activating and procoagulant properties in vitro and rendered the DVs biologically inactive in vivo. Low-molecular-weight dextran sulfate blocked activation of both complement and coagulation and protected animals from the harmful effects of DV infusion. We surmise that in chronic malaria, complement activation by and opsonization of the DV may serve a useful function in directing hemozoin to phagocytic cells for safe disposal. However, when the waste disposal system of the host is overburdened, DVs may transform into a trigger of pathology and therefore represent a potential therapeutic target in severe malaria.
    Full-text Article · Mar 2012 · Blood
  • Dasari P · Heber SD · Beisele M · [...] · Reiss K
    Article · Mar 2012
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    Michael Torzewski · Philip Wenzel · Hartmut Kleinert · [...] · Kurt Reifenberg
    [Show abstract] [Hide abstract] ABSTRACT: We recently described a model of inflammatory cardiomyopathy in interferon (IFN)-γ overexpressing transgenic mice stably circulating IFN-γ in the serum referred to as SAP--IFN-γ mice. SAP-IFN-γ transgenic mice show cardiac infiltration by mononuclear leukocytes, culminating in dilated cardiomyopathy characterized by an increase of left ventricular end diastolic diameter and reduction of fractional shortening. We hypothesized that the pathological mechanism underlying SAP-IFN-γ cardiomyopathy might be mediated by (auto)immune processes or tumor necrosis factor (TNF)-α synthesis from IFN-γ-activated macrophages. To verify these hypotheses, we crossed SAP-IFN-γ transgenic mice with immunodeficient Rag1(-/-) or TNF-α(-/-) knockout mice and analyzed the cardiac phenotype of the resulting double-mutant offspring. Immunodeficient Rag1(-/-) SAP-IFN-γ mice had a decreased impaired life span and intensive cardiac inflammatory reactions, showing that the cardiotoxic IFN-γ effect operative in SAP-IFN-γ mice was not mediated by an adaptive immune mechanism. SAP-IFN-γ TNF-α(-/-) hearts showed virtually no histopathological alterations, a significant reduction of cardiac infiltration by CD11c(+) dendritic cells and F4/80(+) macrophages, almost complete normalization of cardiac troponin T levels in serum and of left ventricular end diastolic diameter and fractional shortening, and a dramatic increase of life span, compared with SAP-IFN-γ transgenic controls. Thus, myocarditis and cardiomyopathy developing in IFN-γ-overexpressing transgenic mice is, to a significant degree, mediated by TNF-α. TNF-α-mediated cardiotoxicity in SAP-IFN-γ transgenic mice is independent of changes of apoptosis.
    Full-text Article · Oct 2011 · American Journal Of Pathology
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    [Show abstract] [Hide abstract] ABSTRACT: To detect rare epigenetic effects associated with assisted reproduction, it is necessary to monitor methylation patterns of developmentally important genes in a few germ cells and individual embryos. Bisulfite treatment degrades DNA and reduces its complexity, rendering methylation analysis from small amounts of DNA extremely challenging. Here we describe a simple approach that allows determining the parent-specific methylation patterns of multiple genes in individual early embryos. Limiting dilution (LD) of bisulfite-treated DNA is combined with independent multiplex PCRs of single DNA target molecules to avoid amplification bias. Using this approach, we compared the methylation status of three imprinted (H19, Snrpn and Igf2r) and one pluripotency-related gene (Oct4) in three different groups of single mouse two-cell embryos. Standard in vitro fertilization of superovulated oocytes and the use of in vitro matured oocytes were not associated with significantly increased rates of stochastic single CpG methylation errors and epimutations (allele methylation errors), when compared with the in vivo produced controls. Similarly, we compared the methylation patterns of two imprinted genes (H19 and Snrpn) in individual mouse 16-cell embryos produced in vivo from superovulated and non-superovulated oocytes and did not observe major between-group differences. Using bovine oocytes and polar bodies as a model, we demonstrate that LD even allows the methylation analysis of multiple genes in single cells.
    Full-text Article · Oct 2011 · Epigenetics: official journal of the DNA Methylation Society
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    [Show abstract] [Hide abstract] ABSTRACT: Diabetes is associated with vascular oxidative stress, activation of NADPH oxidase, and uncoupling of nitric oxide (NO) synthase (endothelial NO synthase [eNOS]). Pentaerithrityl tetranitrate (PETN) is an organic nitrate with potent antioxidant properties via induction of heme oxygenase-1 (HO-1). We tested whether treatment with PETN improves vascular dysfunction in the setting of experimental diabetes. After induction of hyperglycemia by streptozotocin (STZ) injection (60 mg/kg i.v.), PETN (15 mg/kg/day p.o.) or isosorbide-5-mononitrate (ISMN; 75 mg/kg/day p.o.) was fed to Wistar rats for 7 weeks. Oxidative stress was assessed by optical methods and oxidative protein modifications, vascular function was determined by isometric tension recordings, protein expression was measured by Western blotting, RNA expression was assessed by quantitative RT-PCR, and HO-1 promoter activity in stable transfected cells was determined by luciferase assays. PETN, but not ISMN, improved endothelial dysfunction. NADPH oxidase and serum xanthine oxidase activities were significantly reduced by PETN but not by ISMN. Both organic nitrates had minor effects on the expression of NADPH oxidase subunits, eNOS and dihydrofolate reductase (Western blotting). PETN, but not ISMN, normalized the expression of GTP cyclohydrolase-1, extracellular superoxide dismutase, and S-glutathionylation of eNOS, thereby preventing eNOS uncoupling. The expression of the antioxidant enzyme, HO-1, was increased by STZ treatment and further upregulated by PETN, but not ISMN, via activation of the transcription factor NRF2. In contrast to ISMN, the organic nitrate, PETN, improves endothelial dysfunction in diabetes by preventing eNOS uncoupling and NADPH oxidase activation, thereby reducing oxidative stress. Thus, PETN therapy may be suited to treat patients with cardiovascular complications of diabetes.
    Full-text Article · Aug 2011 · Diabetes
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    [Show abstract] [Hide abstract] ABSTRACT: Chronic liver inflammation is a critical component of hepatocarcinogenesis. Indeed, inflammatory mediators are believed to promote liver cancer by upholding compensatory proliferation of hepatocytes in response to tissue damage. However, inflammation can also mediate the depletion of malignant cells, but the difference between tumor-suppressive and tumor-promoting inflammation is not defined at the molecular level. Here, we analyzed the role of the major inflammatory mediator IFN-γ in chemical hepatocarcinogenesis of transgenic mice that overexpress IFN-γ in the liver; these mice manifest severe chronic inflammatory liver damage and lasting compensatory regeneration. We found that chronic exposure to IFN-γ suppressed chemical hepatocarcinogenesis, despite overt liver injury. Indeed, IFN-γ-transgenic mice had significantly fewer and significantly less advanced malignant lesions than nontransgenic mice. This tumor-suppressive effect of IFN-γ seemed to be mediated in part by its known immune activating function, indicated by infiltration of IFN-γ-transgenic livers with CD8 T cells, natural killer T cells, and natural killer cells. However, IFN-γ seemed to prevent carcinogenesis also by activating the cell-intrinsic p53 tumor suppressor pathway. Indeed, exposure to IFN-γ in vivo or in vitro was associated with accumulation of p53 in hepatocytes and the sensitization of hepatocytes to apoptosis induced by genotoxic stress. The IFN-γ-induced increase in apoptosis of hepatocytes seemed to be p53 dependent. Thus, chronic inflammation dominated by IFN-γ may prevent hepatocarcinogenesis, despite continued inflammatory liver injury and regeneration. Therefore, the carcinogenic potential of inflammation seems to be determined by type and composition of its mediators and manipulating the type of chronic inflammation may serve the prevention of cancer.
    Full-text Article · Jun 2011 · Cancer Research
  • [Show abstract] [Hide abstract] ABSTRACT: In previous studies we and others have shown that streptozotocin (STZ)-induced diabetes in rats is associated with vascular oxidative stress and dysfunction. In the present study, we sought to determine whether vascular dysfunction and oxidative stress strictly depend on insulin deficiency. The effects of insulin (2.5 U/day s.c., 2 weeks) therapy on vascular disorders in STZ-induced (60 mg/kg i.v., 8 weeks) diabetes mellitus (type I) were studied in Wistar rats. The contribution of NADPH oxidase to overall oxidative stress was investigated by in vivo (30 mg/kg/day s.c., 4 days) and in vitro treatment with apocynin. Insulin therapy completely normalized blood glucose, body weight, vascular dysfunction and oxidative stress as well as increased cardiac reactive oxygen and nitrogen species formation in diabetic rats, although diabetes was already established for 6 weeks before insulin therapy was started for the last 2 weeks of the total treatment interval. Apocynin normalized cardiac NADPH oxidase activity, and L-NAME effects suggest a role for uncoupled endothelial nitric oxide synthase in diabetic vascular complications. Our findings indicate that STZ-induced diabetes is a model of insulin-dependent diabetes (type 1) and that cardiovascular complications are probably not associated with systemic toxic side effects of STZ.
    Article · Jun 2011 · Journal of Vascular Research
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    [Show abstract] [Hide abstract] ABSTRACT: By studying mice in which the Nfatc1 gene was inactivated in bone marrow, spleen, or germinal center B cells, we show that NFATc1 supports the proliferation and suppresses the activation-induced cell death of splenic B cells upon B cell receptor (BCR) stimulation. BCR triggering leads to expression of NFATc1/αA, a short isoform of NFATc1, in splenic B cells. NFATc1 ablation impaired Ig class switch to IgG3 induced by T cell-independent type II antigens, as well as IgG3(+) plasmablast formation. Mice bearing NFATc1(-/-) B cells harbor twofold more interleukin 10-producing B cells. NFATc1(-/-) B cells suppress the synthesis of interferon-γ by T cells in vitro, and these mice exhibit a mild clinical course of experimental autoimmune encephalomyelitis. In large part, the defective functions of NFATc1(-/-) B cells are caused by decreased BCR-induced Ca(2+) flux and calcineurin (Cn) activation. By affecting CD22, Rcan1, CnA, and NFATc1/αA expression, NFATc1 controls the Ca(2+)-dependent Cn-NFAT signaling network and, thereby, the fate of splenic B cells upon BCR stimulation.
    Full-text Article · Apr 2011 · Journal of Experimental Medicine

Publication Stats

2k Citations


  • 2010
    • Universitätsklinikum Freiburg
      Freiburg an der Elbe, Lower Saxony, Germany
  • 2007
    • Case Western Reserve University
      • Department of Biochemistry
      Cleveland, Ohio, United States
  • 2002
    • University of Freiburg
      Freiburg, Baden-Württemberg, Germany
  • 1995
    • Universität Ulm
      • Institute of Medical Microbiology and Hygiene
      Ulm, Baden-Württemberg, Germany