The Experts below are selected from a list of 2235 Experts worldwide ranked by ideXlab platform
Manolis Pasparakis - One of the best experts on this subject based on the ideXlab platform.
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the p55tnfr IKK2 ripk3 axis orchestrates arthritis by regulating death and inflammatory pathways in synovial fibroblasts
Nature Communications, 2018Co-Authors: Marietta Armaka, Manolis Pasparakis, Caroline Ospelt, George KolliasAbstract:NFκB activation and regulated cell death are important in tissue homeostasis, inflammation and pathogenesis. Here we show the role of the p55TNFR–IKK2l–Ripk3 axis in the regulation of synovial fibroblast homeostasis and pathogenesis in TNF-mediated mouse models of arthritis. Mesenchymal-specific p55TNFR triggering is indispensable for arthritis in acute and chronic TNF-dependent models. IKK2 in joint mesenchymal cells is necessary for the development of cartilage destruction and bone erosion; however, in its absence synovitis still develops. IKK2 deletion affects arthritic and antiapoptotic gene expression leading to hypersensitization of synovial fibroblasts to TNF/Ripk1-mediated death via district mechanisms, depending on acute or chronic TNF signals. Moreover, Ripk3 is dispensable for TNF-mediated arthritis, yet it is required for synovitis in mice with mesenchymal-specific IKK2 deletion. These results demonstrate that p55TNFR–IKK2–Ripk3 signalling orchestrates arthritogenic and death responses in synovial fibroblasts, suggesting that therapeutic manipulation of this pathway in arthritis may require combinatorial blockade of both IKK2 and Ripk3 signals. TNF is a major therapeutic target for rheumatoid arthritis (RA) and synovial fibroblasts are central to the pathogenesis of RA. Here the authors dissect TNF-induced death and activation signalling in RA synovial fibroblasts and TNF-driven arthritis and indicate that a successful therapeutic strategy might be to target both IKK2 and RIPK3 at the same time.
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IKK2 inhibition attenuates laser induced choroidal neovascularization
PLOS ONE, 2014Co-Authors: Manolis Pasparakis, Huayi Lu, Qingxian Lu, Subhash Gaddipati, Ramesh Babu Kasetti, Wei Wang, Henry J Kaplan, Qiutang LiAbstract:Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-κB pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either IKK2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding IKK2−/flox mice with Nestin-Cre mice. Deletion of IKK2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-κB signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD.
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selective ablation of lung epithelial IKK2 impairs pulmonary th17 responses and delays the clearance of pneumocystis
Journal of Immunology, 2013Co-Authors: Nelissa Pereznazario, Manolis Pasparakis, Javier Rangelmoreno, Michael A Oreilly, Francis Gigliotti, Terry W WrightAbstract:Pneumocystis is an atypical fungal pathogen that causes severe, often fatal pneumonia in immunocompromised patients. Healthy humans and animals also encounter this pathogen, but they generate a protective CD4 + T cell–dependent immune response that clears the pathogen with little evidence of disease. Pneumocystis organisms attach tightly to respiratory epithelial cells, and in vitro studies have demonstrated that this interaction triggers NF-κB–dependent epithelial cell responses. However, the contribution of respiratory epithelial cells to the normal host response to Pneumocystis remains unknown. IκB kinase 2 (IKK2) is the upstream kinase that is critical for inducible NF-κB activation. To determine whether IKK2-dependent lung epithelial cell (LEC) responses contribute to the anti- Pneumocystis immune response in vivo, transgenic mice with LEC-specific deletion of IKK2 (IKK2 ΔLEC ) were generated. Compared to wild-type mice, IKK2 ΔLEC mice exhibited a delayed onset of Th17 and B cell responses in the lung and delayed fungal clearance. Importantly, delayed Pneumocystis clearance in IKK2 ΔLEC mice was associated with an exacerbated immune response, impaired pulmonary function, and altered lung histology. These data demonstrate that IKK2-dependent LEC responses are important regulators of pulmonary adaptive immune responses and are required for optimal host defense against Pneumocystis infection. LECs likely set the threshold for initiation of the pulmonary immune response and serve to prevent exacerbated lung inflammation by promoting the rapid control of respiratory fungal infection.
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hepatocyte IKK2 protects mdr2 mice from chronic liver failure
PLOS ONE, 2011Co-Authors: Hanno Ehlken, Jan Heinrichsdorff, Tania Roskams, Vangelis Kondylis, Laura Ochoacallejero, Manolis PasparakisAbstract:Mice lacking the Abc4 protein encoded by the multidrug resistance-2 gene (Mdr2−/−) develop chronic periductular inflammation and cholestatic liver disease resulting in the development of hepatocellular carcinoma (HCC). Inhibition of NF-κB by expression of an IκBα super-repressor (IκBαSR) transgene in hepatocytes was shown to prevent HCC development in Mdr2−/− mice, suggesting that NF-κB acts as a tumour promoter in this model of inflammation-associated carcinogenesis. On the other hand, inhibition of NF-κB by hepatocyte specific ablation of IKK2 resulted in increased liver tumour development induced by the chemical carcinogen DEN. To address the role of IKK2-mediated NF-κB activation in hepatocytes in the pathogenesis of liver disease and HCC in Mdr2−/− mice, we generated Mdr2-deficient animals lacking IKK2 specifically in hepatocytes using the Cre-loxP system. Mdr2−/− mice lacking IKK2 in hepatocytes developed spontaneously a severe liver disease characterized by cholestasis, major hyperbilirubinemia and severe to end-stage fibrosis, which caused muscle wasting, loss of body weight, lethargy and early spontaneous death. Cell culture experiments showed that primary hepatocytes lacking IKK2 were more sensitive to bile acid induced death, suggesting that hepatocyte-specific IKK2 deficiency sensitized hepatocytes to the toxicity of bile acids under conditions of cholestasis resulting in greatly exacerbated liver damage. Mdr2−/−IKK2Hep-KO mice remarkably recapitulate chronic liver failure in humans and might be of special importance for the study of the mechanisms contributing to the pathogenesis of end-stage chronic liver disease or its implications on other organs. Conclusion: IKK2-mediated signaling in hepatocytes protects the liver from damage under conditions of chronic inflammatory cholestasis and prevents the development of severe fibrosis and liver failure.
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ikk1 and IKK2 cooperate to maintain bile duct integrity in the liver
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Tom Luedde, Jan Heinrichsdorff, Rossana De Lorenzi, Tania Roskams, Manolis PasparakisAbstract:Inflammatory destruction of intrahepatic bile ducts is a common cause of vanishing bile duct syndrome and cholestasis, often progressing to biliary cirrhosis and liver failure. However, the molecular mechanisms underlying the pathogenesis of inflammatory biliary disease are poorly understood. Here, we show that the two IκB kinases, IKK1/IKKα and IKK2/IKKβ, display distinct collaborative and specific functions that are essential to protect the liver from cytokine toxicity and bile duct disease. Combined conditional ablation of IKK1 and IKK2, but not of each kinase alone, sensitized the liver to in vivo LPS challenge, uncovering a redundant function of the two IκB kinases in mediating canonical NF-κB signaling in hepatocytes and protecting the liver from TNF-induced failure. Unexpectedly, mice with combined ablation of IKK1 and IKK2 or IKK1 and NEMO spontaneously developed severe jaundice and fatal cholangitis characterized by inflammatory destruction of small portal bile ducts. This bile duct disease was caused by the combined impairment of canonical NF-κB signaling together with inhibition of IKK1-specific functions affecting the bile–blood barrier. These results reveal a novel function of the two IκB kinases in cooperatively regulating liver immune homeostasis and bile duct integrity and suggest that IKK signaling may be implicated in human biliary diseases.
Qiutang Li - One of the best experts on this subject based on the ideXlab platform.
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IKK2 inhibition using tpca 1 loaded plga microparticles attenuates laser induced choroidal neovascularization and macrophage recruitment
PLOS ONE, 2015Co-Authors: Subhash Gaddipati, Qingxian Lu, Ramesh Babu Kasetti, Henry J Kaplan, Clarke M Miller, Qingjun Lu, John O Trent, Qiutang LiAbstract:The inhibition of NF-κB by genetic deletion or pharmacological inhibition of IKK2 significantly reduces laser-induced choroid neovascularization (CNV). To achieve a sustained and controlled intraocular release of a selective and potent IKK2 inhibitor, 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1) (MW: 279.29), we developed a biodegradable poly-lactide-co-glycolide (PLGA) polymer-delivery system to further investigate the anti-neovascularization effects of IKK2 inhibition and in vivo biosafety using laser-induced CNV mouse model. The solvent-evaporation method produced spherical TPCA-1-loaded PLGA microparticles characterized with a mean diameter of 2.4 ¼m and loading efficiency of 80%. Retrobulbar administration of the TPCA-1-loaded PLGA microparticles maintained a sustained drug level in the retina during the study period. No detectable TPCA-1 level was observed in the untreated contralateral eye. The anti-CNV effect of retrobulbarly administrated TPCA-1-loaded PLGA microparticles was assessed by retinal fluorescein leakage and isolectin staining methods, showing significantly reduced CNV development on day 7 after laser injury. Macrophage infiltration into the laser lesion was attenuated as assayed by choroid/RPE flat-mount staining with anti-F4/80 antibody. Consistently, laser induced expressions of Vegfa and Ccl2 were inhibited by the TPCA-1-loaded PLGA treatment. This TPCA-1 delivery system did not cause any noticeable cellular or functional toxicity to the treated eyes as evaluated by histology and optokinetic reflex (OKR) tests; and no systemic toxicity was observed. We conclude that retrobulbar injection of the small-molecule IKK2 inhibitor TPCA-1, delivered by biodegradable PLGA microparticles, can achieve a sustained and controllable drug release into choroid/retina and attenuate laser-induced CNV development without causing apparent systemic toxicity. Our results suggest a potential clinical application of TPCA-1 delivered by microparticles in treatment of CNV in the patients with age-related macular degeneration and other retinal neovascularization diseases.
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IKK2 inhibition attenuates laser induced choroidal neovascularization
PLOS ONE, 2014Co-Authors: Manolis Pasparakis, Huayi Lu, Qingxian Lu, Subhash Gaddipati, Ramesh Babu Kasetti, Wei Wang, Henry J Kaplan, Qiutang LiAbstract:Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-κB pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either IKK2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding IKK2−/flox mice with Nestin-Cre mice. Deletion of IKK2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-κB signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD.
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complete lack of nf κb activity in ikk1 and IKK2 double deficient mice additional defect in neurulation
Genes & Development, 2000Co-Authors: Qiutang Li, Alain Israël, Gabriela Estepa, Sylvie Memet, Inder M. VermaAbstract:NF-κB activity is induced by cytokines, stress, and pathogens. IKK1 and IKK2 are critical IκB kinases in NF-κB activation. In this study mice lacking IKK1 and IKK2 died at E12. Additional defect in neurulation associated with enhanced apoptosis in the neuroepithelium was also observed. MEF cells from IKK1−/−/IKK2−/− embryos did not respond to NF-κB inducers. Upon crossing with κB–lacZ transgenic mice, double-deficient embryos also lost lacZ transgene expression in vascular endothelial cells during development. Our data suggest that IKK1 and IKK2 are essential for NF-κB activation in vivo and have an important role in protecting neurons against excessive apoptosis during development.
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Severe Liver Degeneration in Mice Lacking the IκB Kinase 2 Gene
Science, 1999Co-Authors: Qiutang Li, Daniel Van Antwerp, Frank Mercurio, Inder M. VermaAbstract:Phosphorylation of inhibitor of kappa B (IκB) proteins is an important step in the activation of the transcription nuclear factor kappa B (NF-κB) and requires two IκB kinases, IKK1 (IKKα) and IKK2 (IKKβ). Mice that are devoid of the IKK2 gene had extensive liver damage from apoptosis and died as embryos, but these mice could be rescued by the inactivation of the gene encoding tumor necrosis factor receptor 1. Mouse embryonic fibroblast cells that were isolated from IKK2–/– embryos showed a marked reduction in tumor necrosis factor–α (TNF-α)– and interleukin-1α–induced NF-κB activity and an enhanced apoptosis in response to TNF-α. IKK1 associated with NF-κB essential modulator (IKKγ/IKKAP1), another component of the IKK complex. These results show that IKK2 is essential for mouse development and cannot be substituted with IKK1.
Huayi Lu - One of the best experts on this subject based on the ideXlab platform.
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IKK2 inhibition attenuates laser induced choroidal neovascularization
PLOS ONE, 2014Co-Authors: Manolis Pasparakis, Huayi Lu, Qingxian Lu, Subhash Gaddipati, Ramesh Babu Kasetti, Wei Wang, Henry J Kaplan, Qiutang LiAbstract:Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-κB pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either IKK2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding IKK2−/flox mice with Nestin-Cre mice. Deletion of IKK2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-κB signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD.
Thomas Wirth - One of the best experts on this subject based on the ideXlab platform.
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transient IKK2 activation in astrocytes initiates selective non cell autonomous neurodegeneration
Molecular Neurodegeneration, 2017Co-Authors: Michael Lattke, Stephanie N Reichel, Alexander Magnutzki, Alireza Abaei, Volker Rasche, Paul Walther, Dinis P Calado, Boris Ferger, Thomas WirthAbstract:Neuroinflammation is associated with a wide range of neurodegenerative disorders, however the specific contribution to individual disease pathogenesis and selective neuronal cell death is not well understood. Inflammatory cerebellar ataxias are neurodegenerative diseases occurring in various autoimmune/inflammatory conditions, e.g. paraneoplastic syndromes. However, how inflammatory insults can cause selective cerebellar neurodegeneration in the context of these diseases remains open, and appropriate animal models are lacking. A key regulator of neuroinflammatory processes is the NF-κB signalling pathway, which is activated by the IκB kinase 2 (IKK2) in response to various pathological conditions. Importantly, its activation is sufficient to initiate neuroinflammation on its own. To investigate the contribution of IKK/NF-κB-mediated neuroinflammation to neurodegeneration, we established conditional mouse models of cerebellar neuroinflammation, which depend either on the tetracycline-regulated expression of IKK2 in astrocytes or Cre-recombination based IKK2 activation in Bergmann glia. We demonstrate that IKK2 activation for a limited time interval in astrocytes is sufficient to induce neuroinflammation, astrogliosis and loss of Purkinje neurons, resembling the pathogenesis of inflammatory cerebellar ataxias. We identified IKK2-driven irreversible dysfunction of Bergmann glia as critical pathogenic event resulting in Purkinje cell loss. This was independent of Lipocalin 2, an acute phase protein secreted by reactive astrocytes and well known to mediate neurotoxicity. Instead, downregulation of the glutamate transporters EAAT1 and EAAT2 and ultrastructural alterations suggest an excitotoxic mechanism of Purkinje cell degeneration. Our results suggest a novel pathogenic mechanism how diverse inflammatory insults can cause inflammation/autoimmune-associated cerebellar ataxias. Disease-mediated elevation of danger signals like TLR ligands and inflammatory cytokines in the cerebellum activates IKK2/NF-κB signalling in astrocytes, which as a consequence triggers astrogliosis-like activation of Bergmann glia and subsequent non-cell-autonomous Purkinje cell degeneration. Notably, the identified hit and run mechanism indicates only an early window for therapeutic interventions.
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long term IKK2 nf κb signaling in pancreatic β cells induces immune mediated diabetes
Diabetes, 2014Co-Authors: Martin Wagner, Heba Salem, Bernadette Trojanowski, Katja Fiedler, Harald J Maier, Reinhold Schirmbeck, Bernhard O Boehm, Thomas WirthAbstract:Type 1 diabetes is a multifactorial inflammatory disease in genetically susceptible individuals characterized by progressive autoimmune destruction of pancreatic β-cells initiated by yet unknown factors. Although animal models of type 1 diabetes have substantially increased our understanding of disease pathogenesis, heterogeneity seen in human patients cannot be reflected by a single model and calls for additional models covering different aspects of human pathophysiology. Inhibitor of κB kinase (IKK)/nuclear factor-κB (NF-κB) signaling is a master regulator of inflammation; however, its role in diabetes pathogenesis is controversially discussed by studies using different inhibition approaches. To investigate the potential diabetogenic effects of NF-κB in β-cells, we generated a gain-of-function model allowing conditional IKK2/NF-κB activation in β-cells. A transgenic mouse model that expresses a constitutively active mutant of human IKK2 dependent on Pdx-1 promoter activity (IKK2-CA Pdx-1 ) spontaneously develops full-blown immune-mediated diabetes with insulitis, hyperglycemia, and hypoinsulinemia. Disease development involves a gene expression program mimicking virus-induced diabetes and allergic inflammatory responses as well as increased major histocompatibility complex class I/II expression by β-cells that could collectively promote diabetes development. Potential novel diabetes candidate genes were also identified. Interestingly, animals successfully recovered from diabetes upon transgene inactivation. Our data give the first direct evidence that β-cell–specific IKK2/NF-κB activation is a potential trigger of immune-mediated diabetes. Moreover, IKK2-CA Pdx-1 mice provide a novel tool for studying critical checkpoints in diabetes pathogenesis and mechanisms governing β-cell degeneration/regeneration.
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astrocyte specific IKK2 activation in mice is sufficient to induce neuroinflammation but does not increase susceptibility to mptp
Neurobiology of Disease, 2012Co-Authors: Patrick Oeckl, Bernd Baumann, Thomas Wirth, Michael Lattke, Boris FergerAbstract:Abstract A key regulator of inflammatory gene expression is the transcription factor NF-κB that is controlled by the IκB proteins. We used a transgenic mouse model expressing a constitutively active IκB-kinase-2 (IKK2-CA) in astrocytes under control of the human glial fibrillary acidic protein promotor (IKK2-mice) to investigate neuroinflammation, proinflammatory cytokine expression, microglial activation and a potential enhanced susceptibility to the neurotoxin MPTP (4 × 10 mg/kg). Readouts included the determination of cytokines, striatal dopamine (DA), nigral tyrosine hydroxylase (TH) positive neurons, microglial activation and motor activity. IKK2-CA expression in astrocytes conditionally induced by the tet-off system resulted in a widespread neuroinflammation indicated by the increased expression of inflammatory cytokines and the presence of activated microglia and astrogliosis. Additionally, striatal DA concentrations but not nigral TH-positive neurons were reduced in IKK2-mice by 20%. Motor activity of IKK2-mice was not affected. Surprisingly, there was a similar reduction in striatal DA concentrations and the number of nigral TH-positive neurons in IKK2 and control mice after MPTP treatment. In conclusion, although naive IKK2-mice showed reduced striatal DA concentrations and an increase in inflammatory markers in the brain, a higher susceptibility to MPTP was not observed. This finding argues against a prominent role of astrocyte specific, IKK2-mediated neuroinflammation in MPTP-induced neurodegeneration.
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constitutive IKK2 activation in acinar cells is sufficient to induce pancreatitis in vivo
Journal of Clinical Investigation, 2007Co-Authors: Bernd Baumann, Martin Wagner, T Aleksic, Gotz Von Wichert, Christoph K Weber, Guido Adler, Thomas WirthAbstract:Activation of the inhibitor of NF-κB kinase/NF-κB (IKK/NF-κB) system and expression of proinflammatory mediators are major events in acute pancreatitis. However, the in vivo consequences of IKK activation on the onset and progression of acute pancreatitis remain unclear. Therefore, we modulated IKK activity conditionally in pancreatic acinar cells. Transgenic mice expressing the reverse tetracycline-responsive transactivator (rtTA) gene under the control of the rat elastase promoter were generated to mediate acinar cell–specific expression of IKK2 alleles. Expression of dominant-negative IKK2 ameliorated cerulein-induced pancreatitis but did not affect activation of trypsin, an initial event in experimental pancreatitis. Notably, expression of constitutively active IKK2 was sufficient to induce acute pancreatitis. This acinar cell–specific phenotype included edema, cellular infiltrates, necrosis, and elevation of serum lipase levels as well as pancreatic fibrosis. IKK2 activation caused increased expression of known NF-κB target genes, including mediators of the inflammatory response such as TNF-α and ICAM-1. Indeed, inhibition of TNF-α activity identified this cytokine as an important effector of IKK2-induced pancreatitis. Our data identify the IKK/NF-κB pathway in acinar cells as being key to the development of experimental pancreatitis and the major factor in the inflammatory response typical of this disease.
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Cellular immune reaction in the pancreas is induced by constitutively active IκB kinase-2
Gut, 2006Co-Authors: T Aleksic, Bernd Baumann, Martin Wagner, Guido Adler, Thomas Wirth, Christoph K WeberAbstract:Background: Activation of the nuclear factor κB (NF-κB) system is a major event in acute and chronic inflammatory processes. NF-κB cascades are comprised of IκB kinases, IκBs and NF-κB dimers. Little is known of the individual roles of these proteins in organ specific inflammation. The aim of the present study was to analyse the consequences of ectopic IκB kinase-2 (IKK2) activation in the pancreas of mice. Methods: Transgenic mice were generated using an inducible genetic system (tet system) to conditionally overexpress a gain of function mutant of IKK2 (tetO-IKK2-EE) in the pancreas. To achieve transgene expression in the pancreas, these animals were crossed with CMV-rtTA mice that are known to express the rtTA protein in the pancreas. Results: In these double transgenic animals, doxycycline treatment induced expression of IKK2-EE (IKK2 CA ) in pancreatic acinar cells resulting in moderate activation of the IκB kinase complex, as measured by the immune complex kinase assay, and up to 200-fold activation of the transgene expression cassette, as detected by luciferase assay. IKK2 CA expression in the pancreas had a mosaic appearance. Ectopic IKK2 CA mostly activated the classical NF-κB pathway. The activation level of the NF-κB cascade induced by IKK2 CA was considerably lower compared with that observed after supramaximal caerulein stimulation but still led to the formation of leucocyte infiltrates first observed after 4 weeks of doxycycline stimulation with a maximum after 8–12 weeks. The infiltrates were mainly composed of B lymphocytes and macrophages. Increased mRNA levels of tumour necrosis factor α and RANTES were detected in pancreatic acinar cells. However, only minor damage to pancreatic tissue was observed. A combination of supramaximal caerulein stimulation with induction of IKK2 CA caused increased tissue damage compared with either IKK2 CA or caerulein alone. Conclusions: Our observations suggest that the role of IKK2 activation in pancreatic acini is to induce leucocyte infiltration, but at a moderate level of activation it is not sufficient to induce pancreatic damage in mice. The IKK2 CA induced infiltrations resemble those observed in autoimmune pancreatitis, indicating a role for IKK2/NF-κB in this disease. IKK2 CA in pancreatic acinar cells increases tissue damage of secretagogue induced experimental pancreatitis underlining the proinflammatory role of the IKK/NF-κB pathway in this disease.
Tom Luedde - One of the best experts on this subject based on the ideXlab platform.
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ikk1 and IKK2 cooperate to maintain bile duct integrity in the liver
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Tom Luedde, Jan Heinrichsdorff, Rossana De Lorenzi, Tania Roskams, Manolis PasparakisAbstract:Inflammatory destruction of intrahepatic bile ducts is a common cause of vanishing bile duct syndrome and cholestasis, often progressing to biliary cirrhosis and liver failure. However, the molecular mechanisms underlying the pathogenesis of inflammatory biliary disease are poorly understood. Here, we show that the two IκB kinases, IKK1/IKKα and IKK2/IKKβ, display distinct collaborative and specific functions that are essential to protect the liver from cytokine toxicity and bile duct disease. Combined conditional ablation of IKK1 and IKK2, but not of each kinase alone, sensitized the liver to in vivo LPS challenge, uncovering a redundant function of the two IκB kinases in mediating canonical NF-κB signaling in hepatocytes and protecting the liver from TNF-induced failure. Unexpectedly, mice with combined ablation of IKK1 and IKK2 or IKK1 and NEMO spontaneously developed severe jaundice and fatal cholangitis characterized by inflammatory destruction of small portal bile ducts. This bile duct disease was caused by the combined impairment of canonical NF-κB signaling together with inhibition of IKK1-specific functions affecting the bile–blood barrier. These results reveal a novel function of the two IκB kinases in cooperatively regulating liver immune homeostasis and bile duct integrity and suggest that IKK signaling may be implicated in human biliary diseases.
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targeted ablation of IKK2 improves skeletal muscle strength maintains mass and promotes regeneration
Journal of Clinical Investigation, 2006Co-Authors: Foteini Mourkioti, Manolis Pasparakis, Tom Luedde, Paschalis Kratsios, Yaohua Song, Patrick Delafontaine, Raffaella Adami, Valeria Parente, Roberto Bottinelli, Nadia RosenthalAbstract:NF-κB is a major pleiotropic transcription factor modulating immune, inflammatory, cell survival, and proliferative responses, yet the relevance of NF-κB signaling in muscle physiology and disease is less well documented. Here we show that muscle-restricted NF-κB inhibition in mice, through targeted deletion of the activating kinase inhibitor of NF-κB kinase 2 (IKK2), shifted muscle fiber distribution and improved muscle force. In response to denervation, IKK2 depletion protected against atrophy, maintaining fiber type, size, and strength, increasing protein synthesis, and decreasing protein degradation. IKK2-depleted mice with a muscle-specific transgene expressing a local Igf-1 isoform (mIgf-1) showed enhanced protection against muscle atrophy. In response to muscle damage, IKK2 depletion facilitated skeletal muscle regeneration through enhanced satellite cell activation and reduced fibrosis. Our results establish IKK2/NF-κB signaling as an important modulator of muscle homeostasis and suggest a combined role for IKK inhibitors and growth factors in the therapy of muscle diseases.
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deletion of IKK2 in hepatocytes does not sensitize these cells to tnf induced apoptosis but protects from ischemia reperfusion injury
Journal of Clinical Investigation, 2005Co-Authors: Tom Luedde, Klaus Rajewsky, Tania Roskams, Ulrike Assmus, Torsten Wustefeld, Andreas Meyer Zu Vilsendorf, Mark Schmidtsupprian, David A Brenner, Michael P Manns, Manolis PasparakisAbstract:The inhibitor of NF-κB (I-κB) kinase (IKK) complex consists of 3 subunits, IKK1, IKK2, and NF-κB essential modulator (NEMO), and is involved in the activation of NF-κB by various stimuli. IKK2 or NEMO constitutive knockout mice die during embryogenesis as a result of massive hepatic apoptosis. Therefore, we examined the role of IKK2 in TNF-induced apoptosis and ischemia/reperfusion (I/R) injury in the liver by using conditional knockout mice. Hepatocyte-specific ablation of IKK2 did not lead to impaired activation of NF-κB or increased apoptosis after TNF-α stimulation whereas conditional NEMO knockout resulted in complete block of NF-κB activation and massive hepatocyte apoptosis. In a model of partial hepatic I/R injury, mice lacking IKK2 in hepatocytes displayed significantly reduced liver necrosis and inflammation than wild-type mice. AS602868, a novel chemical inhibitor of IKK2, protected mice from liver injury due to I/R without sensitizing them toward TNF-induced apoptosis and could therefore emerge as a new pharmacological therapy for liver resection, hemorrhagic shock, or transplantation surgery.
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Deletion of IKK2 in hepatocytes does not sensitize these cells to TNF-induced apoptosis but protects from ischemia/reperfusion injury
Journal of Clinical Investigation, 2005Co-Authors: Tom Luedde, Klaus Rajewsky, Tania Roskams, Ulrike Assmus, Torsten Wustefeld, Andreas Meyer Zu Vilsendorf, David A Brenner, Michael P Manns, Mark Schmidt-supprian, Manolis PasparakisAbstract:The inhibitor of NF-κB (I-κB) kinase (IKK) complex consists of 3 subunits, IKK1, IKK2, and NF-κB essential modulator (NEMO), and is involved in the activation of NF-κB by various stimuli. IKK2 or NEMO constitutive knockout mice die during embryogenesis as a result of massive hepatic apoptosis. Therefore, we examined the role of IKK2 in TNF-induced apoptosis and ischemia/reperfusion (I/R) injury in the liver by using conditional knockout mice. Hepatocyte-specific ablation of IKK2 did not lead to impaired activation of NF-κB or increased apoptosis after TNF-α stimulation whereas conditional NEMO knockout resulted in complete block of NF-κB activation and massive hepatocyte apoptosis. In a model of partial hepatic I/R injury, mice lacking IKK2 in hepatocytes displayed significantly reduced liver necrosis and inflammation than wild-type mice. AS602868, a novel chemical inhibitor of IKK2, protected mice from liver injury due to I/R without sensitizing them toward TNF-induced apoptosis and could therefore emerge as a new pharmacological therapy for liver resection, hemorrhagic shock, or transplantation surgery.
