Publications by authors named "Nadine Hövelmeyer"

30 Publications

  • Page 1 of 1

Active Akt signaling triggers CLL toward Richter transformation via overactivation of Notch1.

Blood 2021 Feb;137(5):646-660

Max Planck Institute for Metabolism Research, Cologne, Germany.

Richter's transformation (RT) is an aggressive lymphoma that occurs upon progression from chronic lymphocytic leukemia (CLL). Transformation has been associated with genetic aberrations in the CLL phase involving TP53, CDKN2A, MYC, and NOTCH1; however, a significant proportion of RT cases lack CLL phase-associated events. Here, we report that high levels of AKT phosphorylation occur both in high-risk CLL patients harboring TP53 and NOTCH1 mutations as well as in patients with RT. Genetic overactivation of Akt in the murine Eµ-TCL1 CLL mouse model resulted in CLL transformation to RT with significantly reduced survival and an aggressive lymphoma phenotype. In the absence of recurrent mutations, we identified a profile of genomic aberrations intermediate between CLL and diffuse large B-cell lymphoma. Multiomics assessment by phosphoproteomic/proteomic and single-cell transcriptomic profiles of this Akt-induced murine RT revealed an S100 protein-defined subcluster of highly aggressive lymphoma cells that developed from CLL cells, through activation of Notch via Notch ligand expressed by T cells. Constitutively active Notch1 similarly induced RT of murine CLL. We identify Akt activation as an initiator of CLL transformation toward aggressive lymphoma by inducing Notch signaling between RT cells and microenvironmental T cells.
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http://dx.doi.org/10.1182/blood.2020005734DOI Listing
February 2021

Endogenous CD83 Expression in CD4 Conventional T Cells Controls Inflammatory Immune Responses.

J Immunol 2020 06 27;204(12):3217-3226. Epub 2020 Apr 27.

Institute of Medical Microbiology, University Hospital Essen, University Duisburg-Essen, 45147 Essen, Germany;

The glycoprotein CD83 is known to be expressed by different immune cells including activated CD4Foxp3 regulatory T cells (Tregs) and CD4Foxp3 conventional T cells. However, the physiological function of endogenous CD83 in CD4 T cell subsets is still unclear. In this study, we have generated a new CD83 mouse line on BALB/c background, allowing for specific ablation of CD83 in T cells upon breeding with CD4-cre mice. Tregs from CD83/CD4-cre mice had similar suppressive activity as Tregs from CD83/CD4-cre wild-type littermates, suggesting that endogenous CD83 expression is dispensable for the inhibitory capacity of Tregs. However, CD83-deficient CD4 conventional T cells showed elevated proliferation and IFN-γ secretion as well as an enhanced capacity to differentiate into Th1 cells and Th17 cells upon stimulation in vitro. T cell-specific ablation of CD83 expression resulted in aggravated contact hypersensitivity reaction accompanied by enhanced CD4 T cell activation. Moreover, adoptive transfer of CD4CD45RB T cells from CD83/CD4-cre mice into Rag2-deficient mice elicited more severe colitis associated with increased serum concentrations of IL-12 and elevated CD40 expression on CD11c dendritic cells (DCs). Strikingly, DCs from BALB/c mice cocultured with CD83-deficient CD4 conventional T cells showed enhanced CD40 expression and IL-12 secretion compared with DCs cocultured with CD4 conventional T cells from CD83/CD4-cre wild-type mice. In summary, these results indicate that endogenous CD83 expression in CD4 conventional T cells plays a crucial role in controlling CD4 T cell responses, at least in part, by regulating the activity of CD11c DCs.
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http://dx.doi.org/10.4049/jimmunol.2000042DOI Listing
June 2020

Nuclear Translocation of RELB Is Increased in Diseased Human Liver and Promotes Ductular Reaction and Biliary Fibrosis in Mice.

Gastroenterology 2019 03 13;156(4):1190-1205.e14. Epub 2018 Nov 13.

Department of Medical Oncology, National Center for Tumor Diseases, University Hospital Heidelberg, Heidelberg, Germany; Liver Cancer Center Heidelberg, University Hospital Heidelberg, Heidelberg, Germany. Electronic address:

Background & Aims: Cholangiocyte proliferation and ductular reaction contribute to the onset and progression of liver diseases. Little is known about the role of the transcription factor nuclear factor-κB (NF-κB) in this process. We investigated the activities of the RELB proto-oncogene NF-κB subunit in human cholangiocytes and in mouse models of liver disease characterized by a ductular reaction.

Methods: We obtained liver tissue samples from patients with primary sclerosing cholangitis, primary biliary cholangitis, hepatitis B or C virus infection, autoimmune hepatitis, alcoholic liver disease, or without these diseases (controls) from a tissue bank in Germany. Tissues were analyzed by immunohistochemistry for levels of RELB and lymphotoxin β (LTB). We studied mice with liver parenchymal cell (LPC)-specific disruption of the cylindromatosis (CYLD) lysine 63 deubiquitinase gene (Cyld), with or without disruption of Relb (Cyld mice and Cyld/Relb mice) and compared them with C57BL/6 mice (controls). Mice were fed 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or standard chow diets to induce biliary injury or were given injections of CCl to induce non-cholestatic liver fibrosis. Liver tissues were analyzed by histology, immunohistochemistry, immunoblots, in situ hybridization, and quantitative real-time polymerase chain reaction. Cholangiocytes were isolated from normal human liver, incubated with LTB receptor agonist, and transfected with small interfering RNAs to knock down RELB.

Results: In liver tissues from patients with primary sclerosing cholangitis, primary biliary cholangitis, chronic infection with hepatitis B or C virus, autoimmune hepatitis, or alcoholic liver disease, we detected increased nuclear translocation of RELB and increased levels of LTB in cholangiocytes that formed reactive bile ducts compared with control liver tissues. Human cholangiocytes, but not those with RELB knockdown, proliferated with exposure to LTB. The phenotype of Cyld mice, which included ductular reaction, oval cell activation, and biliary fibrosis, was completely lost from Cyld/Relb mice. Compared with livers from control mice, livers from Cyld mice (but not Cyld/Relb mice) had increased levels of mRNAs encoding cytokines (LTB; CD40; and tumor necrosis factor superfamily [TNFSF] members TNFSF11 [RANKL], TNFSF13B [BAFF], and TNFSF14 [LIGHT]) produced by reactive cholangiocytes. However, these strains of mice developed similar levels of liver fibrosis in response to CCl exposure. Cyld mice and Cyld/Relb mice had improved liver function on the DDC diet compared with control mice fed the DDC diet.

Conclusion: Reactive bile ducts in patients with chronic liver diseases have increased levels of LTB and nuclear translocation of RELB. RELB is required for the ductular reaction and development of biliary fibrosis in Cyld mice. Deletion of RELB and CYLD from LPCs protects mice from DDC-induced cholestatic liver fibrosis.
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http://dx.doi.org/10.1053/j.gastro.2018.11.018DOI Listing
March 2019

Alternative Splice Forms of CYLD Mediate Ubiquitination of SMAD7 to Prevent TGFB Signaling and Promote Colitis.

Gastroenterology 2019 02 10;156(3):692-707.e7. Epub 2018 Oct 10.

Institute for Molecular Medicine, University Medical Centre, Johannes Gutenberg University of Mainz, Mainz, Germany. Electronic address:

Background & Aims: The CYLD lysine 63 deubiquitinase gene (CYLD) encodes tumor suppressor protein that is mutated in familial cylindromatosus, and variants have been associated with Crohn disease (CD). Splice forms of CYLD that lack exons 7 and 8 regulate transcription factors and functions of immune cells. We examined the expression of splice forms of CYLD in colon tissues from patients with CD and their effects in mice.

Methods: We performed immunohistochemical analyses of colon tissues from patients with untreated CD and patients without inflammatory bowel diseases (controls). We obtained mice that expressed splice forms of CYLD (sCYLD mice) without or with SMAD7 (sCYLD/SMAD7 mice) from transgenes and CYLD-knockout mice (with or without transgenic expression of SMAD7) and performed endoscopic analyses. Colitis was induced in Rag1 mice by transfer of CD4 CD62L T cells from C57/Bl6 or transgenic mice. T cells were isolated from mice and analyzed by flow cytometry and quantitative real-time polymerase chain reaction and intestinal tissues were analyzed by histology and immunohistochemistry. CYLD forms were expressed in mouse embryonic fibroblasts, primary T cells, and HEK293T cells, which were analyzed by immunoblot, mobility shift, and immunoprecipitation assays.

Results: The colonic lamina propria from patients with CD was infiltrated by T cells and had higher levels of sCYLD (but not full-length CYLD) and SMAD7 than tissues from controls. Incubation of mouse embryonic fibroblasts and T cells with transforming growth factor β increased their production of sCYLD and decreased full-length CYLD. Transgenic expression of sCYLD and SMAD7 in T cells prevented the differentiation of regulatory T cells and T-helper type 17 cells and increased the differentiation of T-helper type 1 cells. The same effects were observed in colon tissues from sCYLD/SMAD7 mice but not in those from CYLD-knockout SMAD7 mice. The sCYLD mice had significant increases in the numbers of T-helper type 1 cells and CD44 CD62L memory-effector CD4 T cells in the spleen and mesenteric lymph nodes compared with wild-type mice; sCYLD/SMAD7 mice had even larger increases. The sCYLD/SMAD7 mice spontaneously developed severe colitis, with infiltration of the colon by dendritic cells, neutrophils, macrophages, and CD4 T cells and increased levels of Ifng, Il6, Il12a, Il23a, and Tnf mRNAs. Co-transfer of regulatory T cells from wild-type, but not from sCYLD/SMAD7, mice prevented the induction of colitis in Rag1 mice by CD4 T cells. We found increased levels of poly-ubiquitinated SMAD7 in sCYLD CD4 T cells. CYLD formed a nuclear complex with SMAD3, whereas sCYLD recruited SMAD7 to the nucleus, which inhibited the expression of genes regulated by SMAD3 and SMAD4. We found that sCYLD mediated lysine 63-linked ubiquitination of SMAD7. The sCYLD-SMAD7 complex inhibited transforming growth factor β signaling in CD4 T cells.

Conclusions: Levels of the spliced form of CYLD are increased in colon tissues from patients with CD. sCYLD mediates ubiquitination and nuclear translocation of SMAD7 and thereby decreases transforming growth factor β signaling in T cells. This prevents immune regulatory mechanisms and leads to colitis in mice.
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http://dx.doi.org/10.1053/j.gastro.2018.10.023DOI Listing
February 2019

mTORC1 activation in B cells confers impairment of marginal zone microarchitecture by exaggerating cathepsin activity.

Immunology 2018 12 16;155(4):505-518. Epub 2018 Sep 16.

Institute for Drug Research, The School of Pharmacy, The Hebrew University, Jerusalem, Israel.

Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of cell metabolism and lymphocyte proliferation. It is inhibited by the tuberous sclerosis complex (TSC), a heterodimer of TSC1 and TSC2. Deletion of either gene results in robust activation of mTORC1. Mature B cells reside in the spleen at two major anatomical locations, the marginal zone (MZ) and follicles. The MZ constitutes the first line of humoral response against blood-borne pathogens and undergoes atrophy in chronic inflammation. In previous work, we showed that mice deleted for TSC1 in their B cells (TSC1 ) have almost no MZ B cells, whereas follicular B cells are minimally affected. To explore potential underlying mechanisms for MZ B-cell loss, we have analysed the spleen MZ architecture of TSC1 mice and found it to be severely impaired. Examination of lymphotoxins (LTα and LTβ) and lymphotoxin receptor (LTβR) expression indicated that LTβR levels in spleen stroma were reduced by TSC1 deletion in the B cells. Furthermore, LTα transcripts in B cells were reduced. Because LTβR is sensitive to proteolysis, we analysed cathepsin activity in TSC1 . A higher cathepsin activity, particularly of cathepsin B, was observed, which was reduced by mTORC1 inhibition with rapamycin in vivo. Remarkably, in vivo administration of a pan-cathepsin inhibitor restored LTβR expression, LTα mRNA levels and the MZ architecture. Our data identify a novel connection, although not elucidated at the molecular level, between mTORC1 and cathepsin activity in a manner relevant to MZ dynamics.
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http://dx.doi.org/10.1111/imm.12996DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231019PMC
December 2018

Obesity exacerbates colitis-associated cancer via IL-6-regulated macrophage polarisation and CCL-20/CCR-6-mediated lymphocyte recruitment.

Nat Commun 2018 04 25;9(1):1646. Epub 2018 Apr 25.

Max Planck Institute for Metabolism Research Cologne, Institute for Genetics, University of Cologne, Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC), Center for Endocrinology, Diabetes and Preventive Medicine (CEDP) Cologne, 50931, Cologne, Germany.

Colorectal cancer (CRC) is one of the most lethal cancers worldwide in which the vast majority of cases exhibit little genetic risk but are associated with a sedentary lifestyle and obesity. Although the mechanisms underlying CRC and colitis-associated colorectal cancer (CAC) remain unclear, we hypothesised that obesity-induced inflammation predisposes to CAC development. Here, we show that diet-induced obesity accelerates chemically-induced CAC in mice via increased inflammation and immune cell recruitment. Obesity-induced interleukin-6 (IL-6) shifts macrophage polarisation towards tumour-promoting macrophages that produce the chemokine CC-chemokine-ligand-20 (CCL-20) in the CAC microenvironment. CCL-20 promotes CAC progression by recruiting CC-chemokine-receptor-6 (CCR-6)-expressing B cells and γδ T cells via chemotaxis. Compromised cell recruitment as well as inhibition of B and γδ T cells protects against CAC progression. Collectively, our data reveal a function for IL-6 in the CAC microenvironment via lymphocyte recruitment through the CCL-20/CCR-6 axis, thereby implicating a potential therapeutic intervention for human patients.
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http://dx.doi.org/10.1038/s41467-018-03773-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5916940PMC
April 2018

Hepatocyte-specific deletion of IL1-RI attenuates liver injury by blocking IL-1 driven autoinflammation.

J Hepatol 2018 05 31;68(5):986-995. Epub 2018 Jan 31.

I. Department of Medicine, University Medical Center Mainz, Germany. Electronic address:

Background & Aims: Interleukin (IL)-1-type cytokines including IL-1α, IL-1β and interleukin-1 receptor antagonist (IL-1Ra) are among the most potent molecules of the innate immune system and exert biological activities through the ubiquitously expressed interleukin-1 receptor type 1 (IL-1R1). The role of IL-1R1 in hepatocytes during acute liver failure (ALF) remains undetermined.

Methods: The role of IL-1R1 during ALF was investigated using a novel transgenic mouse model exhibiting deletion of all signaling-capable IL-1R isoforms in hepatocytes (Il1r1).

Results: ALF induced by D-galactosamine (D-GalN) and lipopolysaccharide (LPS) was significantly attenuated in Il1r1 mice leading to reduced mortality. Conditional deletion of Il1r1 decreased activation of injurious c-Jun N-terminal kinases (JNK)/c-Jun signaling, activated nuclear factor-kappa B (NF-κB) p65, inhibited extracellular signal-regulated kinase (ERK) and prevented caspase 3-mediated apoptosis. Moreover, Il1r1 mice exhibited reduced local and systemic inflammatory cytokine and chemokine levels, especially TNF-α, IL-1α/β, IL-6, CC-chemokine ligand 2 (CCL2), C-X-C motif ligand 1 (CXCL-1) and CXCL-2, and a reduced neutrophil recruitment into the hepatic tissue in response to injury. NLRP3 inflammasome expression and caspase 1 activation were suppressed in the absence of the hepatocellular IL-1R1. Inhibition of IL-1R1 using IL-1ra (anakinra) attenuated the severity of liver injury, while IL-1α administration exaggerated it. These effects were lost ex vivo and at later time points, supporting a role of IL-1R1 in inflammatory signal amplification during acute liver injury.

Conclusion: IL-1R1 in hepatocytes plays a pivotal role in an IL-1-driven auto-amplification of cell death and inflammation in the onset of ALF.

Lay Summary: Acute liver injury which can cause lethal liver failure is medicated by a class of proteins called cytokines. Among these, interleukin-1 (IL-1) and the corresponding receptor IL-1R1 play a prominent role in the immune system, but their role in the liver is undetermined. In the current study, a novel mouse model with defective IL-1R1 in liver cells was studied. Mice lacking this receptor in liver cells were protected from cell death to a certain extent. This protection occurred only in the presence of other, neighboring cells, arguing for the involvement of proteins derived from these cells. This effect is called paracrine signaling and the current study has for the first time shown that the IL-1R1 receptor on hepatocytes is involved in acute liver failure in this context. The approved drug anakinra - which blocks IL-1R1 - had the same effect, supporting the proposed mechanism of action. The findings of this study suggest new treatment options for patients with acute liver failure by blocking defined signals of the immune system.
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http://dx.doi.org/10.1016/j.jhep.2018.01.008DOI Listing
May 2018

Balanced Bcl-3 expression in murine CD4 T cells is required for generation of encephalitogenic Th17 cells.

Eur J Immunol 2017 08 29;47(8):1335-1341. Epub 2017 Jun 29.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.

The function of NF-κB family members is controlled by multiple mechanisms including the transcriptional regulator Bcl-3, an atypical member of the IκB family. By using a murine model of conditional Bcl-3 overexpression specifically in T cells, we observed impairment in the development of Th2, Th1, and Th17 cells. High expression of Bcl-3 promoted CD4 T-cell survival, but at the same time suppressed proliferation in response to TCR stimulation, resulting in reduced CD4 T-cell expansion. As a consequence, T-cell-specific overexpression of Bcl-3 led to reduced inflammation in the small intestine of mice applied with anti-CD3 in a model of gut inflammation. Moreover, impaired Th17-cell development resulted in the resistance of Bcl-3 overexpressing mice to EAE, a mouse model of multiple sclerosis. Thus, we concluded that fine-tuning expression of Bcl-3 is needed for proper CD4 T-cell development and is required to sustain Th17-cell mediated pathology.
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http://dx.doi.org/10.1002/eji.201746933DOI Listing
August 2017

Elevated levels of Bcl-3 inhibits Treg development and function resulting in spontaneous colitis.

Nat Commun 2017 04 28;8:15069. Epub 2017 Apr 28.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg, University of Mainz, Obere Zahlbarer Str 67, 55131 Mainz, Germany.

Bcl-3 is an atypical NF-κB family member that regulates NF-κB-dependent gene expression in effector T cells, but a cell-intrinsic function in regulatory T (Treg) cells and colitis is not clear. Here we show that Bcl-3 expression levels in colonic T cells correlate with disease manifestation in patients with inflammatory bowel disease. Mice with T-cell-specific overexpression of Bcl-3 develop severe colitis that can be attributed to defective Treg cell development and function, leading to the infiltration of immune cells such as pro-inflammatory γδT cells, but not αβ T cells. In Treg cells, Bcl-3 associates directly with NF-κB p50 to inhibit DNA binding of p50/p50 and p50/p65 NF-κB dimers, thereby regulating NF-κB-mediated gene expression. This study thus reveals intrinsic functions of Bcl-3 in Treg cells, identifies Bcl-3 as a potential prognostic marker for colitis and illustrates the mechanism by which Bcl-3 regulates NF-κB activity in Tregs to prevent colitis.
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http://dx.doi.org/10.1038/ncomms15069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414353PMC
April 2017

Past, present and future of immunology in Mainz.

Cell Immunol 2016 10;308:1-6

Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University, Mainz, Germany; Institute for Immunology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.

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http://dx.doi.org/10.1016/j.cellimm.2016.09.001DOI Listing
October 2016

Hepatic B cell leukemia-3 promotes hepatic steatosis and inflammation through insulin-sensitive metabolic transcription factors.

J Hepatol 2016 12 9;65(6):1188-1197. Epub 2016 Jul 9.

I. Department of Medicine, University Medical Center Mainz, Germany. Electronic address:

Background & Aims: The pathomechanisms underlying non-alcoholic fatty liver disease (NAFLD) and the involved molecular regulators are incompletely explored. The nuclear factor-kappa B (NF-κB)-cofactor gene B cell leukemia-3 (Bcl-3) plays a critical role in altering the transcriptional capacity of NF-κB - a key inducer of inflammation - but also of genes involved in cellular energy metabolism.

Methods: To define the role of Bcl-3 in non-alcoholic steatohepatitis (NASH), we developed a novel transgenic mouse model with hepatocyte-specific overexpression of Bcl-3 (Bcl-3) and employed a high-fat, high-carbohydrate dietary feeding model. To characterize the transgenic model, deep RNA sequencing was performed. The relevance of the findings was confirmed in human liver samples.

Results: Hepatocyte-specific overexpression of Bcl-3 led to pronounced metabolic derangement, characterized by enhanced hepatic steatosis from increased de novo lipogenesis and uptake, as well as decreased hydrolysis and export of fatty acids. Steatosis in Bcl-3 mice was accompanied by an augmented inflammatory milieu and liver cell injury. Moreover, Bcl-3 expression decreased insulin sensitivity and resulted in compensatory regulation of insulin-signaling pathways. Based on in vivo and in vitro studies we identified the transcription factors PPARα, PPARγ and PGC-1α as critical regulators of hepatic metabolism and inflammation downstream of Bcl-3. Metformin treatment improved the metabolic and inflammatory phenotype in Bcl-3 mice through modulation of PPARα and PGC-1α. Remarkably, these findings were recapitulated in human NASH, which exhibited increased expression and nuclear localization of Bcl-3.

Conclusions: In summary, Bcl-3 emerges as a novel regulator of hepatic steatosis, insulin sensitivity and inflammation in NASH.

Lay Summary: Non-alcoholic fatty liver disease (NAFLD) is considered the most prevalent liver disease worldwide. Patients can develop end-stage liver disease resulting in liver cirrhosis or hepatocellular carcinoma, but also develop complications unrelated to liver disease, e.g., cardiovascular disease. Still there is no full understanding of the mechanisms that cause NAFLD. In this study, genetically engineered mice were employed to examine the role of a specific protein in the liver that is involved in inflammation and the metabolism, namely Bcl-3. By this approach, a better understanding of the mechanisms contributing to disease progression was established. This can help to develop novel therapeutic and diagnostic options for patients with NAFLD.
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http://dx.doi.org/10.1016/j.jhep.2016.06.026DOI Listing
December 2016

IL-6 Signaling in Myelomonocytic Cells Is Not Crucial for the Development of IMQ-Induced Psoriasis.

PLoS One 2016 21;11(3):e0151913. Epub 2016 Mar 21.

Institute for Molecular Medicine, University Medical Center of the Johannes-Gutenberg University of Mainz, Mainz, Germany.

Psoriasis is an autoimmune skin disease that is associated with aberrant activity of immune cells and keratinocytes. In mice, topical application of TLR7/8 agonist IMQ leads to a skin disorder resembling human psoriasis. Recently, it was shown that the IL-23/ IL-17 axis plays a deciding role in the pathogenesis of human psoriasis, as well as in the mouse model of IMQ-induced psoriasis-like skin disease. A consequence of IL-17A production in the skin includes increased expression and production of IL-6, resulting in the recruitment of neutrophils and other myelomonocytic cells to the site of inflammation. To further investigate and characterize the exact role of IL-6 signaling in myelomonocytic cells during experimental psoriasis, we generated mice lacking the IL-6 receptor alpha specifically in myelomonocytic cells (IL-6RαΔmyel). Surprisingly, disease susceptibility of these mice was not affected in this model. Our study shows that classical IL-6 signaling in myelomonocytic cells does not play an essential role for disease development of IMQ-induced psoriasis-like skin disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151913PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4801375PMC
July 2016

NF-κB-inducing kinase is essential for B-cell maintenance in mice.

Eur J Immunol 2016 Mar 9;46(3):732-41. Epub 2015 Dec 9.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg University of Mainz, Mainz, Germany.

NF-κB-inducing kinase (NIK) is a key mediator of the noncanonical NF-κB signaling pathway, which is critical for normal B-cell development and function. It is well established that the complete deletion of NIK in mice results in defective B cells and impaired secondary lymphoid organogenesis. To address the role of NIK deficiency specifically in B cells, we generated a new mouse strain for the conditional deletion of this kinase. Deletion of NIK during B-cell development results in a drastic reduction of mature B cells from the transitional 2 stage on, while B-1 B cells are less affected. Moreover, deletion of NIK in the germinal centers decreases the numbers of germinal center B cells and impairs the ability of NIK-deficient B cells to develop into class-switched cells in vivo. This new mouse strain will be helpful for studying the role of NIK in different cell types of the body.
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http://dx.doi.org/10.1002/eji.201546081DOI Listing
March 2016

IL17A-Mediated Endothelial Breach Promotes Metastasis Formation.

Cancer Immunol Res 2016 Jan 19;4(1):26-32. Epub 2015 Nov 19.

Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland.

The role of the IL23/IL17A axis in tumor-immune interactions is a matter of controversy. Although some suggest that IL17A-producing T cells (TH17) can suppress tumor growth, others report that IL17A and IL23 accelerate tumor growth. Here, we systematically assessed the impact of IL17A-secreting lymphocytes in several murine models of tumor lung metastasis. Genetic fate mapping revealed that IL17A was secreted within lung metastases predominantly by γδ T cells, whereas TH17 cells were virtually absent. Using different tumor models, we found Il17a(-/-) mice to consistently develop fewer pulmonary tumor colonies. IL17A specifically increased blood vessel permeability and the expression of E-selectin and VCAM-1 by lung endothelial cells in vivo. In transgenic mice, specific targeting of IL17A to the endothelium increased the number of tumor foci. Moreover, the direct impact of IL17A on lung endothelial cells resulted in impaired endothelial barrier integrity, showing that IL17A promotes the formation of lung metastases through tumor-endothelial transmigration.
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http://dx.doi.org/10.1158/2326-6066.CIR-15-0154DOI Listing
January 2016

The deubiquitinating enzyme CYLD regulates the differentiation and maturation of thymic medullary epithelial cells.

Immunol Cell Biol 2015 Jul 20;93(6):558-66. Epub 2015 Jan 20.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany.

The cross talk between thymocytes and the thymic epithelium is critical for T-cell development and the establishment of central tolerance. Medullary thymic epithelial cells (mTECs) are located in the thymic medulla and mediate the elimination of self-reactive thymocytes, thereby preventing the onset of autoimmunity. Previous studies identified the deubiquitinating enzyme CYLD as a critical regulator of T-cell development by activating proximal T-cell receptor signaling during the transition of double-positive to single-positive thymocytes. Here we evaluated the impact of the naturally occurring short-splice variant of the cyld gene (sCYLD) on the development and maturation of mTECs. We found that thymi of CYLD(ex7/8) mice, solely expressing sCYLD, displayed a reduced number of mature mTECs caused by a developmental block during the transition of immature to mature mTECs. Further, we could demonstrate an impaired negative selection of thymocytes in these mice. Our data demonstrate that inefficient negative selection in the thymus of CYLD(ex7/8) mice result from a defect in mTEC maturation.
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http://dx.doi.org/10.1038/icb.2014.122DOI Listing
July 2015

CYLD deletion triggers nuclear factor-κB-signaling and increases cell death resistance in murine hepatocytes.

World J Gastroenterol 2014 Dec;20(45):17049-64

Toni Urbanik, Bruno Christian Koehler, Laura Wolpert, Christin Elßner, Anna-Lena Scherr, Nicole Kautz, Stefan Welte, Dirk Jäger, Henning Schulze-Bergkamen, National Center for Tumor Diseases, Department of Medical Oncology, University Clinic of Heidelberg, 69120 Heidelberg, Baden-Wuerrtemberg, Germany.

Aim: To analyze the role of CYLD for receptor-mediated cell death of murine hepatocytes in acute liver injury models.

Methods: Hepatocyte cell death in CYLD knockout mice (CYLD(-/-) ) was analyzed by application of liver injury models for CD95- (Jo2) and tumor necrosis factor (TNF)-α- [D-GalN/lipopolysaccharide (LPS)] induced apoptosis. Liver injury was assessed by measurement of serum transaminases and histological analysis. Apoptosis induction was quantified by cleaved PARP staining and Western blotting of activated caspases. Nuclear factor (NF)-κB, ERK, Akt and jun amino-terminal kinases signaling were assessed. Primary Hepatocytes were isolated by two step-collagenase perfusion and treated with recombinant TNF-α and with the CD95-ligand Jo2. Cell viability was analyzed by MTT-assay.

Results: Livers of CYLD(-/-) mice showed increased anti-apoptotic NF-κB signaling. In both applied liver injury models CYLD(-/-) mice showed a significantly reduced apoptosis sensitivity. After D-GalN/LPS treatment CYLD(-/-) mice exhibited significantly lower levels of alanine aminotransferase (ALT) (295 U/L vs 859 U/L, P < 0.05) and aspartate aminotransferase (AST) (560 U/L vs 1025 U/L, P < 0.01). After Jo injection CYLD(-/-) mice showed 2-fold lower ALT (50 U/L vs 110 U/L, P < 0.01) and lower AST (250 U/L vs 435 U/L, P < 0.01) serum-levels compared to WT mice. In addition, isolated CYLD(-/-) primary murine hepatocytes (PMH) were less sensitive towards death receptor-mediated apoptosis and showed increased levels of Bcl-2, XIAP, cIAP1/2, survivin and c-FLIP expression upon TNF- and CD95-receptor triggering, respectively. Inhibition of NF-κB activation by the inhibitor of NF-κB phosphorylation inhibitor BAY 11-7085 inhibited the expression of anti-apoptotic proteins and re-sensitized CYLD(-/-) PMH towards TNF- and CD95-receptor mediated cell death.

Conclusion: CYLD is a central regulator of apoptotic cell death in murine hepatocytes by controlling NF-κB dependent anti-apoptotic signaling.
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http://dx.doi.org/10.3748/wjg.v20.i45.17049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4258573PMC
December 2014

Isolation of T cells from the gut.

Methods Mol Biol 2014 ;1193:21-5

Institute for Molecular Medicine, University Medical Center, Johannes Gutenberg-University, Obere Zahlbacher Str. 67, 55131, Mainz, Germany,

The lymphocytes of epithelial and lamina proprial compartments of the intestine are phenotypically and functionally distinct and serve a wide range of functions in the intestinal mucosa like regulating intestinal homeostasis, maintaining epithelial barrier function as well as regulating adaptive and innate immune responses. To analyze the role of these cells in different disease states, it is necessary to isolate pure cell populations of the intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) of the gut. In this protocol we describe a method to isolate T cells from IEL and LPL, which can be used for further investigations like comparative studies of mRNA expression, cell proliferation assay, or protein analysis.
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http://dx.doi.org/10.1007/978-1-4939-1212-4_3DOI Listing
April 2015

Overexpression of Bcl-3 inhibits the development of marginal zone B cells.

Eur J Immunol 2014 Feb 18;44(2):545-52. Epub 2013 Nov 18.

Institute for Molecular Medicine, Johannes Gutenberg-University of Mainz, Mainz, Germany.

The transcription factor Bcl-3 functions as a proto-oncogene via regulation of cell proliferation and apoptosis. Bcl-3 is an atypical member of the IκB family and plays a central role in the immune response through interactions with the NF-κB subunits p50 and p52. To investigate the impact of Bcl-3 on B-cell maturation and regulation, we generated mice that overexpress Bcl-3 specifically in B cells. Interestingly, these mice lack marginal zone B cells and exhibit a significant reduction in the number of B-1 B cells. Further, B cells from these mice are impaired in their proliferative capacity. Our data demonstrate that the overexpression of the transcription factor Bcl-3 inhibits germinal center formation, marginal zone B-cell development, and affects the B-1 B-cell compartment.
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http://dx.doi.org/10.1002/eji.201343655DOI Listing
February 2014

Mechanisms of chronic JAK-STAT3-SOCS3 signaling in obesity.

JAKSTAT 2013 Apr;2(2):e23878

Max Planck Institute for Neurological Research; Institute for Genetics; University of Cologne and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center of Molecular Medicine Cologne (CMMC); Cologne, Germany.

Janus kinase (JAK)-signal transducers and activators of transcription (STAT) signaling pathways are critical for the maintenance of homeostatic and developmental processes; however, deregulation and chronic activation of JAK-STAT3 results in numerous diseases. Among others, obesity is currently being intensively studied. In obesity, chronic JAK-STAT3 is activated by the CNS by increased circulating leptin levels leading to the development of leptin resistance, whereas in the peripheral organs chronic IL-6-induced JAK-STAT3 impairs insulin action. We report the consequences of chronic JAK-STAT3 induced signaling as present under obese conditions in the main metabolic organs.
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http://dx.doi.org/10.4161/jkst.23878DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3710326PMC
April 2013

The tumor suppressor CYLD controls the function of murine regulatory T cells.

J Immunol 2012 Nov 12;189(10):4770-6. Epub 2012 Oct 12.

Institute for Molecular Medicine, Johannes Gutenberg-University of Mainz, 55131 Mainz, Germany.

CYLD was originally identified as a tumor suppressor gene mutated in familial cylindromatosis, an autosomal dominant predisposition to multiple benign neoplasms of the skin known as cylindromas. The CYLD protein is a deubiquitinating enzyme that acts as a negative regulator of NF-κB and JNK signaling through its interaction with NEMO and TNFR-associated factor 2. We have previously described a novel mouse strain that expresses solely and excessively a naturally occurring splice variant of CYLD (CYLD(ex7/8)). In this study, we demonstrate that CYLD plays a critical role in Treg development and function. T cells of CYLD(ex7/8) mice had a hyperactive phenotype manifested by increased production of inflammatory cytokines and constitutive activation of the NF-κB pathway. Furthermore, the amount of Foxp3(+) regulatory T cells in these mice was markedly enhanced in thymus and peripheral organs. Importantly, these regulatory T cells displayed decreased expression levels of CD25 and CTLA-4 associated with impaired suppressive capacity. Hence, our data emphasize an essential role of CYLD in maintaining T cell homeostasis as well as normal T regulatory cell function, thereby controlling abnormal T cell responses.
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http://dx.doi.org/10.4049/jimmunol.1201993DOI Listing
November 2012

Liver specific deletion of CYLDexon7/8 induces severe biliary damage, fibrosis and increases hepatocarcinogenesis in mice.

J Hepatol 2012 Nov 21;57(5):995-1003. Epub 2012 Jun 21.

National Center for Tumor Diseases, Department of Medical Oncology, University Clinic of Heidelberg, Heidelberg, Germany.

Background & Aims: CYLD is a tumor suppressor gene that is mutated in familial cylindromatosis, an autosomal dominant predisposition to tumors of skin appendages. Reduced CYLD expression has been observed in other tumor entities, including hepatocellular carcinoma. In the present study, we analyzed the role of CYLD in liver homeostasis and hepatocarcinogenesis in vivo.

Methods: Mice with liver-specific deletion of CYLDexon7/8 (CYLD(FF)xAlbCre) were generated. Liver tissues were histologically analyzed and oval cell activation was investigated. Hepatocarcinogenesis was induced by diethylnitrosamine/phenobarbital (DEN/PB). Microarray expression profiling of livers was performed in untreated as well as DEN/PB-treated mice. NF-κB signaling was assessed by ELISA, quantitative real-time PCR, and Western blotting.

Results: CYLD(FF)xAlbCre hepatocytes and cholangiocytes did not express full-length CYLD (FL-CYLD) protein but showed increased expression of the naturally occurring short-CYLD splice variant (s-CYLD). CYLD(FF)xAlbCre mice exhibited a prominent biliary phenotype with ductular reaction and biliary-type fibrosis. In addition, CYLD(FF)xAlbCre mice showed a significantly increased sensitivity towards DEN/PB-induced hepatocarcinogenesis. Moreover, we could observe the development of cholangiocellular carcinoma, in line with enhanced oval cell activity. NF-κB-signaling was increased in livers of CYLD(FF)xAlbCre mice and likely contributed to the inflammatory and fibrotic response.

Conclusions: The deletion of exon7/8 of the CYLD gene activates oval cells, leads to a biliary phenotype, and increases the susceptibility towards carcinogenesis in the liver. Thus, our study presents a novel model of biliary damage and liver fibrosis, followed by cancer development.
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http://dx.doi.org/10.1016/j.jhep.2012.06.017DOI Listing
November 2012

A20 deficiency in B cells enhances B-cell proliferation and results in the development of autoantibodies.

Eur J Immunol 2011 Mar 10;41(3):595-601. Epub 2011 Feb 10.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University of Mainz, Mainz, Germany.

A20/TNFAIP3 is an ubiquitin-editing enzyme, important for the regulation of the NF-κB pathway. Mutations in the TNFAIP3 gene have been linked to different human autoimmune disorders. In human B-cell lymphomas, the inactivation of A20 results in constitutive NF-κB activation. Recent studies demonstrate that in mice the germline inactivation of A20 leads to early lethality, due to inflammation in multiple organs of the body. In this report, we describe a new mouse strain allowing for the tissue-specific deletion of A20. We show that B-cell-specific deletion of A20 results in a dramatic reduction in marginal zone B cells. Furthermore, A20-deficient B cells display a hyperactive phenotype represented by enhanced proliferation upon activation. Finally, these mice develop higher levels of serum immunoglobulins, resulting in an excessive production of self-reactive autoantibodies.
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http://dx.doi.org/10.1002/eji.201041313DOI Listing
March 2011

Down-regulation of CYLD as a trigger for NF-κB activation and a mechanism of apoptotic resistance in hepatocellular carcinoma cells.

Int J Oncol 2011 Jan;38(1):121-31

First Department of Medicine, Johannes Gutenberg University, Mainz, Germany.

The cylindromatosis gene (CYLD) was identified as a tumor suppressor gene, which is mutated in familial cylindromatosis (Brooke-Spiegler syndrome), an autosomal-dominant predisposition to multiple tumors of the skin appendages. CYLD is a deubiquitinating enzyme acting as a negative regulator of the nuclear factor κB (NF-κB) signaling pathway by removing lysine-63-linked polyubiquitin chains from NF-κB activating proteins. In order to investigate the role of CYLD in apoptotic signaling in human hepatocellular carcinoma (HCC) cells, we first studied the expression levels of CYLD in HCC tissues. CYLD expression was lower in HCC both at protein and mRNA levels compared to the surrounding non-malignant tissue. In order to further study the role of CYLD in the apoptotic sensitivity of HCC cells, CYLD was specifically down-regulated in HCC cell lines via RNA interference. The specific down-regulation of CYLD resulted in increased resistance towards treatment with doxorubicin, 5-fluorouracil and cisplatin. In addition, the down-regulation of CYLD in HCC cells decreased the sensitivity towards tumor necrosis factor-α-induced apoptosis. The CYLD knockdown also led to the degradation of the NF-κB inhibitor, IκB-α, resulting in enhanced NF-κB activity in HCC cells. Finally, we found that CYLD expression was triggered by the multikinase inhibitor, sorafenib, by the inhibition of Raf-1, as well as by the blockage of the pro-survival kinases, MEK (U0126) and the epidermal growth factor receptor (AG1478). In summary, we show that CYLD is down-regulated in human HCC and is involved in the apoptotic resistance of HCC cells. Our data identify the reconstitution of CYLD expression as an attractive approach for overcoming resistance to treatment in HCC.
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January 2011

Mutated cylindromatosis gene affects the functional state of dendritic cells.

Eur J Immunol 2010 Oct;40(10):2848-57

Clinical Research Unit Allergology, Department of Dermatology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany.

Cylindromatosis gene (CYLD) is a ubiquitously expressed deubiquitinating enzyme, which interacts with members of the NF-κB signaling pathway and attenuates NF-κB and JNK signaling. Here, we report that DC derived from transgenic mice, which solely express a naturally occurring CYLD isoform (CYLD(ex7/8)), display a higher content of nuclear RelB and express elevated levels of NF-κB family members as well as of known NF-κB-target genes comprising costimulatory molecules and pro-inflammatory cytokines, as compared with WT DC. Accordingly, unstimulated CYLD(ex7/8) DC exhibited a significantly higher primary allogenic T-cell stimulatory capacity than WT DC and exerted no tolerogenic activity. Transduction of unstimulated CYLD(ex7/8) DC with relB-specific shRNA reduced their T-cell stimulatory capacity. Treatment with the synthetic glucocorticoid dexamethasone known to inhibit NF-κB and AP-1 activity reverted the pro-immunogenic phenotype and function of CYLD(ex7/8) DC and re-established their tolerogenic function. DC derived from CYLD knockout mice showed no functional alterations compared with WT DC. Therefore, although complete loss of CYLD may be compensated for by other endogenous NF-κB inhibitors, CYLD(ex7/8) acts in a dominant negative manner. Our findings raise the question of whether genetic defects associated with increased NF-κB activity may result in disturbed maintenance of peripheral tolerance.
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http://dx.doi.org/10.1002/eji.200939285DOI Listing
October 2010

Smad7 in T cells drives T helper 1 responses in multiple sclerosis and experimental autoimmune encephalomyelitis.

Brain 2010 Apr 30;133(Pt 4):1067-81. Epub 2010 Mar 30.

Department of Neurology, University Medical Centre Regensburg, Universitätsstrasse 84, 93053 Regensburg, Germany.

Autoreactive CD4+ T lymphocytes play a vital role in the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis. Since the discovery of T helper 17 cells, there is an ongoing debate whether T helper 1, T helper 17 or both subtypes of T lymphocytes are important for the initiation of autoimmune neuroinflammation. We examined peripheral blood CD4+ cells from patients with active and stable relapsing-remitting multiple sclerosis, and used mice with conditional deletion or over-expression of the transforming growth factor-beta inhibitor Smad7, to delineate the role of Smad7 in T cell differentiation and autoimmune neuroinflammation. We found that Smad7 is up-regulated in peripheral CD4+ cells from patients with multiple sclerosis during relapse but not remission, and that expression of Smad7 strongly correlates with T-bet, a transcription factor defining T helper 1 responses. Concordantly, mice with transgenic over-expression of Smad7 in T cells developed an enhanced disease course during experimental autoimmune encephalomyelitis, accompanied by elevated infiltration of inflammatory cells and T helper 1 responses in the central nervous system. On the contrary, mice with a T cell-specific deletion of Smad7 had reduced disease and central nervous system inflammation. Lack of Smad7 in T cells blunted T cell proliferation and T helper 1 responses in the periphery but left T helper 17 responses unaltered. Furthermore, frequencies of regulatory T cells were increased in the central nervous system of mice with a T cell-specific deletion and reduced in mice with a T cell-specific over-expression of Smad7. Downstream effects of transforming growth factor-beta on in vitro differentiation of naïve T cells to T helper 1, T helper 17 and regulatory T cell phenotypes were enhanced in T cells lacking Smad7. Finally, Smad7 was induced during T helper 1 differentiation and inhibited during T helper 17 differentiation. Taken together, the level of Smad7 in T cells determines T helper 1 polarization and regulates inflammatory cellular responses. Since a Smad7 deletion in T cells leads to immunosuppression, Smad7 may be a potential new therapeutic target in multiple sclerosis.
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http://dx.doi.org/10.1093/brain/awq039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850583PMC
April 2010

Naturally occurring short splice variant of CYLD positively regulates dendritic cell function.

Blood 2009 Jun 2;113(23):5891-5. Epub 2009 Apr 2.

Institute for Immunology, Johannes Gutenberg University, Mainz, Germany.

Deubiquitination of NF-kappaB members by CYLD is crucial in controlling the magnitude and nature of cell activation. The role of the naturally occurring CYLD splice variant in dendritic cell (DC) function was analyzed using CYLD(ex7/8) mice, which lack the full-length CYLD (flCYLD) transcript and overexpress the short splice variant (sCYLD). Bone marrow-derived DCs from CYLD(ex7/8) mice display a hyperactive phenotype in vitro and in vivo and have a defect in establishing tolerance with the use of DEC-205-mediated antigen targeting to resting DCs. The combination of sCYLD overexpression and lack of flCYLD in CYLD(ex7/8) DCs leads to enhanced NF-kappaB activity accompanied by an increased nuclear translocation of the IkappaB molecule Bcl-3, along with nuclear p50 and p65. This suggests that, in contrast to flCYLD, sCYLD is a positive regulator of NF-kappaB activity, and its overexpression induces a hyperactive phenotype in DCs.
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http://dx.doi.org/10.1182/blood-2008-08-175489DOI Listing
June 2009

Regulation of B cell homeostasis and activation by the tumor suppressor gene CYLD.

J Exp Med 2007 Oct 8;204(11):2615-27. Epub 2007 Oct 8.

I. Medical Department, Johannes Gutenberg-University Mainz, Verfügungsgebäude, 55131 Mainz, Germany.

B cell homeostasis is regulated by multiple signaling processes, including nuclear factor-kappaB (NF-kappaB), BAFF-, and B cell receptor signaling. Conditional disruption of genes involved in these pathways has shed light on the mechanisms governing signaling from the cell surface to the nucleus. We describe a novel mouse strain that expresses solely and excessively a naturally occurring splice variant of CYLD (CYLD(ex7/8) mice), which is a deubiquitinating enzyme that is integral to NF-kappaB signaling. This shorter CYLD protein lacks the TRAF2 and NEMO binding sites present in full-length CYLD. A dramatic expansion of mature B lymphocyte populations in all peripheral lymphoid organs occurs in this strain. The B lymphocytes themselves exhibit prolonged survival and manifest a variety of signaling disarrangements that do not occur in mice with a complete deletion of CYLD. Although both the full-length and the mutant CYLD are able to interact with Bcl-3, a predominant nuclear accumulation of Bcl-3 occurs in the CYLD mutant B cells. More dramatic, however, is the accumulation of the NF-kappaB proteins p100 and RelB in CYLD(ex7/8) B cells, which, presumably in combination with nuclear Bcl-3, results in increased levels of Bcl-2 expression. These findings suggest that CYLD can both positively and negatively regulate signal transduction and homeostasis of B cells in vivo, depending on the expression of CYLD splice variants.
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http://dx.doi.org/10.1084/jem.20070318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2118471PMC
October 2007

Apoptosis of oligodendrocytes via Fas and TNF-R1 is a key event in the induction of experimental autoimmune encephalomyelitis.

J Immunol 2005 Nov;175(9):5875-84

Laboratory for Molecular Immunology, Institute for Genetics, University of Cologne, Cologne, Germany.

In experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, immunization with myelin Ags leads to demyelination and paralysis. To investigate which molecules are crucial for the pathogenesis of EAE, we specifically assessed the roles of the death receptors Fas and TNF-R1. Mice lacking Fas expression in oligodendrocytes (ODCs) were generated and crossed to TNF-R1-deficient mice. To achieve specific deletion of a loxP-flanked fas allele in ODCs, we generated a new insertion transgene, expressing the Cre recombinase specifically in ODCs. Fas inactivation alone as well as the complete absence of TNF-R1 protected mice partially from EAE induced by the immunization with myelin ODC glycoprotein. The double-deficient mice, however, showed almost no clinical signs of EAE after immunization. Histological analysis revealed that demyelination was suppressed in CNS tissue and that lymphocyte infiltration was notably reduced. We conclude that the death receptors Fas and TNF-R1 are major initiators of ODC apoptosis in EAE. Although only moderate reduction of lymphocyte infiltration into CNS tissue was observed, the absence of these receptors appears to confer protection from demyelination and development of clinical disease.
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http://dx.doi.org/10.4049/jimmunol.175.9.5875DOI Listing
November 2005

Experimental autoimmune encephalomyelitis repressed by microglial paralysis.

Nat Med 2005 Feb 23;11(2):146-52. Epub 2005 Jan 23.

Institute of Neuropathology, University Hospital Zurich, CH-8091 Zurich, Switzerland.

Although microglial activation occurs in inflammatory, degenerative and neoplastic central nervous system (CNS) disorders, its role in pathogenesis is unclear. We studied this question by generating CD11b-HSVTK transgenic mice, which express herpes simplex thymidine kinase in macrophages and microglia. Ganciclovir treatment of organotypic brain slice cultures derived from CD11b-HSVTK mice abolished microglial release of nitrite, proinflammatory cytokines and chemokines. Systemic ganciclovir administration to CD11b-HSVTK mice elicited hematopoietic toxicity, which was prevented by transfer of wild-type bone marrow. In bone marrow chimeras, ganciclovir blocked microglial activation in the facial nucleus upon axotomy and repressed the development of experimental autoimmune encephalomyelitis. We conclude that microglial paralysis inhibits the development and maintenance of inflammatory CNS lesions. The microglial compartment thus provides a potential therapeutic target in inflammatory CNS disorders. These results validate CD11b-HSVTK mice as a tool to study the impact of microglial activation on CNS diseases in vivo.
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http://dx.doi.org/10.1038/nm1177DOI Listing
February 2005

The lack of annexin A7 affects functions of primary astrocytes.

Exp Cell Res 2003 Dec;291(2):406-14

Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Federal Republic of Germany.

Annexin A7 is a Ca(2+)- and phospholipid-binding protein, which is thought to function in membrane organization and Ca(2+)-dependent signaling processes. It localizes to different cellular compartments and exists in a 47- and 51-kDa isoform with the large isoform being expressed in brain, skeletal, and heart muscle. In human temporal brain annexin A7 was found exclusively in astroglial cells. As astrocytes are thought to play key roles in several processes of the brain we focused on Ca(2+)-dependent signaling processes and astrocyte proliferation. Primary astrocytes from an anxA7(-/-) mouse exhibited an increased velocity of mechanically induced astrocytic Ca(2+) waves as compared to wild type. We also observed a remarkably increased proliferation rate in cultured mutant astrocytes. A search for annexin A7 binding partners with advanced biochemical methods confirmed sorcin as the major binding protein. However, in vivo GFP-tagged annexin A7 and sorcin appeared to redistribute mainly independently from each other in wild type and in mutant astrocytes. Our results favor an involvement of annexin A7 in Ca(2+)-dependent signaling or Ca(2+) homeostasis in astrocytes.
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http://dx.doi.org/10.1016/j.yexcr.2003.07.012DOI Listing
December 2003