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377 Publications visible to you, out of a total of 377
Balance between macrophage migration inhibitory factor and sCD74 predicts outcome in patients with acute decompensation of cirrhosis

Abstract

Not specified

Authors: Theresa H. Wirtz, Philipp A. Reuken, Christian Jansen, Petra Fischer, Irina Bergmann, Christina Backhaus, Christoph Emontzpohl, Johanna Reißing, Elisa F. Brandt, M. Teresa Koenen, Kai M. Schneider, Robert Schierwagen, Maximilian J. Brol, Johannes Chang, Henning W. Zimmermann, Nilay Köse-Vogel, Thomas Eggermann, Ingo Kurth, Christian Stoppe, Richard Bucala, Jürgen Bernhagen, Michael Praktiknjo, Andreas Stallmach, Christian Trautwein, Jonel Trebicka, Tony Bruns, Marie-Luise Berres

Date Published: 1st Dec 2020

Publication Type: Journal

Basal MET phosphorylation is an indicator of hepatocyte dysregulation in liver disease

Abstract (Expand)

Abstract Chronic liver diseases are worldwide on the rise. Due to the rapidly increasing incidence, in particular in Western countries, metabolic dysfunction-associated steatotic liver disease (MASLD) …otic liver disease (MASLD) is gaining importance as the disease can develop into hepatocellular carcinoma. Lipid accumulation in hepatocytes has been identified as the characteristic structural change in MASLD development, but molecular mechanisms responsible for disease progression remained unresolved. Here, we uncover in primary hepatocytes from a preclinical model fed with a Western diet (WD) an increased basal MET phosphorylation and a strong downregulation of the PI3K-AKT pathway. Dynamic pathway modeling of hepatocyte growth factor (HGF) signal transduction combined with global proteomics identifies that an elevated basal MET phosphorylation rate is the main driver of altered signaling leading to increased proliferation of WD-hepatocytes. Model-adaptation to patient-derived hepatocytes reveal patient-specific variability in basal MET phosphorylation, which correlates with patient outcome after liver surgery. Thus, dysregulated basal MET phosphorylation could be an indicator for the health status of the liver and thereby inform on the risk of a patient to suffer from liver failure after surgery.

Authors: Sebastian Burbano de Lara, Svenja Kemmer, Ina Biermayer, Svenja Feiler, Artyom Vlasov, Lorenza A D’Alessandro, Barbara Helm, Christina Mölders, Yannik Dieter, Ahmed Ghallab, Jan G Hengstler, Christiane Körner, Madlen Matz-Soja, Christina Götz, Georg Damm, Katrin Hoffmann, Daniel Seehofer, Thomas Berg, Marcel Schilling, Jens Timmer, Ursula Klingmüller

Date Published: 12th Jan 2024

Publication Type: Journal

Basal MET Phosphorylation is an Indicator of Hepatocyte Dysregulation in Liver Disease (preprint)

Abstract (Expand)

Chronic liver diseases are worldwide on the rise. Due to the rapidly increasing incidence, in particular in Western countries, Non-alcoholic fatty liver disease (NAFLD) is gaining importance as the … disease can develop into hepatocellular carcinoma. Lipid accumulation in hepatocytes has been identified as the characteristic structural change in NAFLD development, but molecular mechanisms responsible for disease progression remained unresolved. Here, we uncover in primary hepatocytes from a preclinical model fed with a Western diet (WD) a strong downregulation of the PI3K-AKT pathway and an upregulation of the MAPK pathway. Dynamic pathway modeling of hepatocyte growth factor (HGF) signal transduction combined with global proteomics identifies that an elevated basal MET phosphorylation rate is the main driver of altered signaling leading to increased proliferation of WD-hepatocytes. Model-adaptation to patient-derived hepatocytes reveal patient-specific variability in basal MET phosphorylation, which correlates with patient outcome after liver surgery. Thus, dysregulated basal MET phosphorylation could be an indicator for the health status of the liver and thereby inform on the risk of a patient to suffer from liver failure after surgery.

Authors: Sebastian Burbano De Lara, Svenja Kemmer, Ina Biermayer, Svenja Feiler, Artyom Vlasov, Lorenza D'Alessandro, Barbara Helm, Yannik Dieter, Ahmed Ghallab, Jan Hengstler, Professor Dr. med. Katrin Hoffmann, Marcel Schilling, Jens Timmer, Ursula Klingmüller

Date Published: 4th Jul 2023

Publication Type: Journal

Basic Phenotypes of Endocytic System Recognized by Independent Phenotypes Analysis of a High-throughput Genomic Screen

Abstract (Expand)

High-content screens (HCS) using chemical and genomic interference based on light microscopy and quantitative image analysis yielded a large amount of multi-parametric (MP) phenotypic data. Such data-sets … hold great promise for the understanding of cellular mechanisms by systems biology. However, extracting functional information from data-sets, such as links between cellular processes and the functions of unknown genes, remains challenging. The limitation of HCS analysis lies in the complexity of cellular organization. Here, we assumed that cellular processes have a modular structure, and deconvolved the MP data into separate signals from different cellular modules by Blind Source Separation. We applied a combination of quantitative MP image analysis (QMPIA) and Independent Component Analysis (ICA) to an image-based HCS of endocytosis, the process whereby cells uptake molecules from the outside and distribute them to different sub-cellular organelles. We named our approach Independent Phenotypes Analysis (IPA). Phenotypic traits revealed by IPA are interpretable in terms of perturbation of specific endosomal populations (e.g. specific cargo, specific molecular markers) and of specific functional modules (early stages of endocytosis, recycling, cell cycle, etc.). The profile of perturbation of each gene in such basic phenotypic coordinates intrinsically suggest its possible mode of action.

Authors: Unknown, Kseniia Nikitina, Sandra Segeletz, Michael Kuhn, Yannis Kalaidzidis, Marino Zerial

Date Published: 2019

Publication Type: InProceedings

Benchmark and integration of resources for the estimation of human transcription factor activities

Abstract (Expand)

The prediction of transcription factor (TF) activities from the gene expression of their targets (i.e., TF regulon) is becoming a widely used approach to characterize the functional status of transcriptional … regulatory circuits. Several strategies and data sets have been proposed to link the target genes likely regulated by a TF, each one providing a different level of evidence. The most established ones are (1) manually curated repositories, (2) interactions derived from ChIP-seq binding data, (3) in silico prediction of TF binding on gene promoters, and (4) reverse-engineered regulons from large gene expression data sets. However, it is not known how these different sources of regulons affect the TF activity estimations and, thereby, downstream analysis and interpretation. Here we compared the accuracy and biases of these strategies to define human TF regulons by means of their ability to predict changes in TF activities in three reference benchmark data sets. We assembled a collection of TF–target interactions for 1541 human TFs and evaluated how different molecular and regulatory properties of the TFs, such as the DNA-binding domain, specificities, or mode of interaction with the chromatin, affect the predictions of TF activity. We assessed their coverage and found little overlap on the regulons derived from each strategy and better performance by literature-curated information followed by ChIP-seq data. We provide an integrated resource of all TF–target interactions derived through these strategies, with confidence scores, as a resource for enhanced prediction of TF activities.

Authors: Luz Garcia-Alonso, Christian H. Holland, Mahmoud M. Ibrahim, Denes Turei, Julio Saez-Rodriguez

Date Published: 1st Aug 2019

Publication Type: Not specified

beta-Catenin and Yes-Associated Protein 1 Cooperate in Hepatoblastoma Pathogenesis.

Abstract (Expand)

Hepatoblastoma (HB), the most common pediatric primary liver neoplasm, shows nuclear localization of beta-catenin and yes-associated protein 1 (YAP1) in almost 80% of the cases. Co-expression of … constitutively active S127A-YAP1 and DeltaN90 deletion-mutant beta-catenin (YAP1-DeltaN90-beta-catenin) causes HB in mice. Because heterogeneity in downstream signaling is being identified owing to mutational differences even in the beta-catenin gene alone, we investigated if co-expression of point mutants of beta-catenin (S33Y or S45Y) with S127A-YAP1 led to similar tumors as YAP1-DeltaN90-beta-catenin. Co-expression of S33Y/S45Y-beta-catenin and S127A-YAP1 led to activation of Yap and Wnt signaling and development of HB, with 100% mortality by 13 to 14 weeks. Co-expression with YAP1-S45Y/S33Y-beta-catenin of the dominant-negative T-cell factor 4 or dominant-negative transcriptional enhanced associate domain 2, the respective surrogate transcription factors, prevented HB development. Although histologically similar, HB in YAP1-S45Y/S33Y-beta-catenin, unlike YAP1-DeltaN90-beta-catenin HB, was glutamine synthetase (GS) positive. However, both DeltaN90-beta-catenin and point-mutant beta-catenin comparably induced GS-luciferase reporter in vitro. Finally, using a previously reported 16-gene signature, it was shown that YAP1-DeltaN90-beta-catenin HB tumors exhibited genetic similarities with more proliferative, less differentiated, GS-negative HB patient tumors, whereas YAP1-S33Y/S45Y-beta-catenin HB exhibited heterogeneity and clustered with both well-differentiated GS-positive and proliferative GS-negative patient tumors. Thus, we demonstrate that beta-catenin point mutants can also collaborate with YAP1 in HB development, albeit with a distinct molecular profile from the deletion mutant, which may have implications in both biology and therapy.

Authors: Q. Min, L. Molina, J. Li, A. O. Adebayo Michael, J. O. Russell, M. E. Preziosi, S. Singh, M. Poddar, M. Matz-Soja, S. Ranganathan, A. W. Bell, R. Gebhardt, F. Gaunitz, J. Yu, J. Tao, S. P. Monga

Date Published: 23rd Feb 2019

Publication Type: Not specified

Bile canaliculi remodeling activates YAP via the actin cytoskeleton during liver regeneration

Abstract (Expand)

The mechanisms of organ size control remain poorly understood. A key question is how cells collectively sense the overall status of a tissue. We addressed this problem focusing on mouse liver regeneration. … Using digital tissue reconstruction and quantitative image analysis, we found that the apical surface of hepatocytes forming the bile canalicular network expands concomitant with an increase in F‐actin and phospho‐myosin, to compensate an overload of bile acids. These changes are sensed by the Hippo transcriptional co‐activator YAP, which localizes to apical F‐actin‐rich regions and translocates to the nucleus in dependence of the integrity of the actin cytoskeleton. This mechanism tolerates moderate bile acid fluctuations under tissue homeostasis, but activates YAP in response to sustained bile acid overload. Using an integrated biophysical–biochemical model of bile pressure and Hippo signaling, we explained this behavior by the existence of a mechano‐sensory mechanism that activates YAP in a switch‐like manner. We propose that the apical surface of hepatocytes acts as a self‐regulatory mechano‐sensory system that responds to critical levels of bile acids as readout of tissue status.

Authors: Kirstin Meyer, Hernan Morales‐Navarrete, Sarah Seifert, Michaela Wilsch‐Braeuninger, Uta Dahmen, Elly M Tanaka, Lutz Brusch, Yannis Kalaidzidis, Marino Zerial

Date Published: 24th Feb 2020

Publication Type: Not specified

Bile canaliculi remodeling activates YAP via the actin cytoskeleton during liver regeneration.

Abstract (Expand)

The mechanisms of organ size control remain poorly understood. A key question is how cells collectively sense the overall status of a tissue. We addressed this problem focusing on mouse liver regeneration. … Using digital tissue reconstruction and quantitative image analysis, we found that the apical surface of hepatocytes forming the bile canalicular network expands concomitant with an increase in F-actin and phospho-myosin, to compensate an overload of bile acids. These changes are sensed by the Hippo transcriptional co-activator YAP, which localizes to apical F-actin-rich regions and translocates to the nucleus in dependence of the integrity of the actin cytoskeleton. This mechanism tolerates moderate bile acid fluctuations under tissue homeostasis, but activates YAP in response to sustained bile acid overload. Using an integrated biophysical-biochemical model of bile pressure and Hippo signaling, we explained this behavior by the existence of a mechano-sensory mechanism that activates YAP in a switch-like manner. We propose that the apical surface of hepatocytes acts as a self-regulatory mechano-sensory system that responds to critical levels of bile acids as readout of tissue status.

Authors: K. Meyer, H. Morales-Navarrete, S. Seifert, M. Wilsch-Braeuninger, U. Dahmen, E. M. Tanaka, L. Brusch, Y. Kalaidzidis, M. Zerial

Date Published: 25th Feb 2020

Publication Type: Journal

Bile micro-infarcts in cholestasis are initiated by rupture of the apical hepatocyte membrane and cause shunting of bile to sinusoidal blood

Abstract

Not specified

Authors: Ahmed Ghallab, Ute Hofmann, Selahaddin Sezgin, Nachiket Vartak, Reham Hassan, Ayham Zaza, Patricio Godoy, Kai Markus Schneider, Georgia Guenther, Yasser A Ahmed, Aya A Abbas, Verena Keitel, Lars Kuepfer, Steven Dooley, Frank Lammert, Christian Trautwein, Michael Spiteller, Dirk Drasdo, Alan F Hofmann, Peter L M Jansen, Jan G Hengstler, Raymond Reif

Date Published: 13th Aug 2018

Publication Type: Not specified

Bio-degradable highly fluorescent conjugated polymer nanoparticles for bio-medical imaging applications

Abstract (Expand)

Conjugated polymer nanoparticles exhibit strong fluorescence and have been applied for biological fluorescence imaging in cell culture and in small animals. However, conjugated polymer particles are … hydrophobic and often chemically inert materials with diameters ranging from below 50 nm to several microns. As such, conjugated polymer nanoparticles cannot be excreted through the renal system. This drawback has prevented their application for clinical bio-medical imaging. Here, we present fully conjugated polymer nanoparticles based on imidazole units. These nanoparticles can be bio-degraded by activated macrophages. Reactive oxygen species induce scission of the conjugated polymer backbone at the imidazole unit, leading to complete decomposition of the particles into soluble low molecular weight fragments. Furthermore, the nanoparticles can be surface functionalized for directed targeting. The approach opens a wide range of opportunities for conjugated polymer particles in the fields of medical imaging, drug-delivery, and theranostics.

Authors: Tatjana Repenko, Anne Rix, Simon Ludwanowski, Dennis Go, Fabian Kiessling, Wiltrud Lederle, Alexander J. C. Kuehne

Date Published: 1st Dec 2017

Publication Type: Not specified

BMP-9 interferes with liver regeneration and promotes liver fibrosis.

Abstract (Expand)

OBJECTIVE: Bone morphogenetic protein (BMP)-9, a member of the transforming growth factor-beta family of cytokines, is constitutively produced in the liver. Systemic levels act on many organs and tissues … including bone and endothelium, but little is known about its hepatic functions in health and disease. DESIGN: Levels of BMP-9 and its receptors were analysed in primary liver cells. Direct effects of BMP-9 on hepatic stellate cells (HSCs) and hepatocytes were studied in vitro, and the role of BMP-9 was examined in acute and chronic liver injury models in mice. RESULTS: Quiescent and activated HSCs were identified as major BMP-9 producing liver cell type. BMP-9 stimulation of cultured hepatocytes inhibited proliferation, epithelial to mesenchymal transition and preserved expression of important metabolic enzymes such as cytochrome P450. Acute liver injury caused by partial hepatectomy or single injections of carbon tetrachloride (CCl4) or lipopolysaccharide (LPS) into mice resulted in transient downregulation of hepatic BMP-9 mRNA expression. Correspondingly, LPS stimulation led to downregulation of BMP-9 expression in cultured HSCs. Application of BMP-9 after partial hepatectomy significantly enhanced liver damage and disturbed the proliferative response. Chronic liver damage in BMP-9-deficient mice or in mice adenovirally overexpressing the selective BMP-9 antagonist activin-like kinase 1-Fc resulted in reduced deposition of collagen and subsequent fibrosis. CONCLUSIONS: Constitutive expression of low levels of BMP-9 stabilises hepatocyte function in the healthy liver. Upon HSC activation, endogenous BMP-9 levels increase in vitro and in vivo and high levels of BMP-9 cause enhanced damage upon acute or chronic injury.

Authors: K. Breitkopf-Heinlein, C. Meyer, C. Konig, H. Gaitantzi, A. Addante, M. Thomas, E. Wiercinska, C. Cai, Q. Li, F. Wan, C. Hellerbrand, N. A. Valous, M. Hahnel, C. Ehlting, J. G. Bode, S. Muller-Bohl, U. Klingmuller, J. Altenoder, I. Ilkavets, M. J. Goumans, L. J. Hawinkels, S. J. Lee, M. Wieland, C. Mogler, M. P. Ebert, B. Herrera, H. Augustin, A. Sanchez, S. Dooley, P. Ten Dijke

Date Published: 25th Mar 2017

Publication Type: Not specified

BMP-9 interferes with liver regeneration and promotes liver fibrosis.

Abstract (Expand)

OBJECTIVE: Bone morphogenetic protein (BMP)-9, a member of the transforming growth factor-beta family of cytokines, is constitutively produced in the liver. Systemic levels act on many organs and tissues … including bone and endothelium, but little is known about its hepatic functions in health and disease. DESIGN: Levels of BMP-9 and its receptors were analysed in primary liver cells. Direct effects of BMP-9 on hepatic stellate cells (HSCs) and hepatocytes were studied in vitro, and the role of BMP-9 was examined in acute and chronic liver injury models in mice. RESULTS: Quiescent and activated HSCs were identified as major BMP-9 producing liver cell type. BMP-9 stimulation of cultured hepatocytes inhibited proliferation, epithelial to mesenchymal transition and preserved expression of important metabolic enzymes such as cytochrome P450. Acute liver injury caused by partial hepatectomy or single injections of carbon tetrachloride (CCl4) or lipopolysaccharide (LPS) into mice resulted in transient downregulation of hepatic BMP-9 mRNA expression. Correspondingly, LPS stimulation led to downregulation of BMP-9 expression in cultured HSCs. Application of BMP-9 after partial hepatectomy significantly enhanced liver damage and disturbed the proliferative response. Chronic liver damage in BMP-9-deficient mice or in mice adenovirally overexpressing the selective BMP-9 antagonist activin-like kinase 1-Fc resulted in reduced deposition of collagen and subsequent fibrosis. CONCLUSIONS: Constitutive expression of low levels of BMP-9 stabilises hepatocyte function in the healthy liver. Upon HSC activation, endogenous BMP-9 levels increase in vitro and in vivo and high levels of BMP-9 cause enhanced damage upon acute or chronic injury.

Authors: K. Breitkopf-Heinlein, C. Meyer, C. Konig, H. Gaitantzi, A. Addante, M. Thomas, E. Wiercinska, C. Cai, Q. Li, F. Wan, C. Hellerbrand, N. A. Valous, M. Hahnel, C. Ehlting, J. G. Bode, S. Muller-Bohl, U. Klingmuller, J. Altenoder, I. Ilkavets, M. J. Goumans, L. J. Hawinkels, S. J. Lee, M. Wieland, C. Mogler, M. P. Ebert, B. Herrera, H. Augustin, A. Sanchez, S. Dooley, P. Ten Dijke

Date Published: 23rd Mar 2017

Publication Type: Not specified

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