Matricellular protein CCN1/CYR61: a new player in inflammation and leukocyte trafficking

Cystein-rich protein 61 (CYR61/CCN1) is a component of the extracellular matrix, which is produced and secreted by several cell types including endothelial cells, fibroblasts and smooth muscle cells. CCN1 has been implicated in leukocyte migration and the inflammatory process, but it is also involved in cardiovascular development and carcinogenesis. It exerts its functions through binding to multiple integrins present in many different cell types. This multiplicity in function is now known to contribute to the diverse array of cellular processes it can regulate. The expression of CCN1 is tightly regulated by cytokines and growth factors. However, CCN1 can directly modulate cell adhesion and migratory processes whilst simultaneously regulating the production of other cytokines and chemokines through paracrine and autocrine feedback loops. This complex functionality of CCN1 has highlighted the pivotal role this molecule can play in regulating the immunosurveillance process. Furthermore, CCN1 has now emerged as an important partner when targeting components of the infectious or chronic inflammatory disease processes such as atherosclerosis or rheumatoid arthritis. This review will focus on CYR61/CCN1 and its ability to control the migration of leukocytes, the production of cytokines and cell proliferation or senescence at the site of inflammation

Influence de la protéine découplante mitochondriale UCP2 sur la signalisation et le métabolisme des macrophages

Uncoupling Protein UCP2 belogns to the familly of carrier proteins of the inner mitochondrial membrane. UCP2 protein expression is restricted to some tissues such as spleen, stomac or intestine. At cellular level, UCP2 is mostly present in macrophages where it controls the production of reactive oxygen species (ROS). Analysis of Ucp2-KO mice showed their better resistance to an infection by Toxoplasma gondii than wil-type animals thanks to higly active macrophages in terms of ROS production. In a murine model of human atherosclerosis, Ucp2-KO mice developed increased atherosclerotic lesions. Plaques in Ucp2-KO animals contained much more macrophages et nitric oxide (NO)-induced damage. My thesis work was mainly focused on the mechanisms involved in the modulation of immune responses by UCP2. We demonstrated that the quick downregulation of UCP2 in response to LPS potentiates MAPK activation in macrophages. Mictochondria through UCP2 is in the heart of a signal amplification loop involving mitochondrial ROS. As a consequence, signaling and activation of Ucp2-KO macrophages is accelerated, leading to increased production of NO and cytokines.The relevance of these data was next investigated in vivo in the framework of infection and autoimmunity. Mice infection with Listeria monocytogenes revealed a better resistance of Ucp2-KO mice. Higher production of pro-inflammatory cytokines in Ucp2-KO mice and increased recrutement of phagocytes in spleen highlight the regulatory function of UCP2 on innate immunity. Regarding autoimmunity, the developement of experimental type 1 diabetes is strongly accelerated in Ucp2-KO mice. Ucp2-KO macrophages played a the crucial rôle in pathogenesis due to their higher capacity to produce NO and cytokines.The biochemcal activity of UCP2, ie its transport activity, was also studied. Glutamine specifically induced the expression of UCP2. As a consequence, comparison of glutamine metabolism in Ucp2-KO and Ucp2-WT macrophages revealed that UCP2 is required to accurate oxidation of glutamine.Finally, the availability of whole genomes of several species allowed the realization of a phylogenomic study in order to understand the evolution of UCPs.My work showed for the first time a role for UCP2 as a key component of a signal amplification loop involving mitochondria. More importantly it highlighted UCP2 as a new player in the framework of type 1 diabetes. Future research on the development of strategies to induce UCP2 or to inhibit its downregulation in immune cells may be promising in the context of autoimmunity.La protéine UCP2 (UnCoupling Protein 2) appartient à la famille des transporteurs de la membrane interne de la mitochondrie. Son expression est restreinte à certains tissus comme la rate, l'estomac ou l'intestin. Au niveau cellulaire, UCP2 est particulièrement présente dans les macrophages où elle régule la production de radicaux libres (ROS). L'analyse des souris Ucp2-KO a montré qu'elles survivent mieux à une infection par le parasite Toxoplasma gondii que les animaux sauvages grâce à des macrophages superactifs en terme de production de ROS. Par ailleurs, dans le modèle murin de l'athérosclérose humaine, les souris Ucp2-KO développent des plaques athéromateuses plus instables et plus larges, présentant une forte accumulation de macrophages et des dégats importants liés au monoxyde d'azote (NO). Au cours de ma thèse, nous avons cherché à approfondir les connaissances sur le rôle physiologique d'UCP2 ainsi que sur son activité biochimique.Nous avons démontré que la diminution rapide d'UCP2 en réponse au LPS potentialise l'activation des MAPK dans les macrophages. La mitochondrie via UCP2 est ainsi au coeur d'une boucle d'amplification du signal impliquant la modulation des ROS mitochondriaux. Par conséquent, la signalisation et la vitesse d'activation des macrophages Ucp2-KO est accélérée, conduisant à une production accrue de NO et de cytokines.La pertinance de ces résultats a ensuite été testée in vivo avec un volet infection et un volet auto-immunité. L'infection des souris par la bactérie Listeria monocytogenes a révélé une meilleure résistance des souris Ucp2-KO. Une production accrue de cytokines pro-inflammatoires chez les souris Ucp2-KO ainsi qu'un recrutement plus important de phagocytes au niveau de leur rate soulignent le rôle régulateur d'UCP2 sur l'immunité innée. En ce qui concerne, l'auto-immunité, l'induction expérimentale d'un diabète de type 1 est nettement accélérée chez les souris Ucp2-KO. L'analyse de ces souris montrent un rôle capital des macrophages dans le développement de la maladie grâce à leur forte capacité de production de cytokines et de NO.L'activité biochimique d'UCP2, c'est-à-dire son activité de transport, a également été abordée. La glutamine est un inducteur spécifique de l'expression d'UCP2. Par conséquent, la comparaison du métabolisme de la glutamine dans les macrophages Ucp2-KO et Ucp2-WT a démontré que l'expression d'UCP2 est requise pour une oxydation correcte de la glutamine.Enfin, grâce à la disponibilité de génomes complets de nombreuses espèces, l'étude phylogénomique des UCP a permis de tracer une histoire de l'évolution des UCP de mammifères et aviaire.Nos études ont mis en évidence la participation d'UCP2 au métabolisme des macrophages. L'altération de celui-ci influe sur la signalisation et l'activité des cellules. Une meilleure compréhension de la fonction d'UCP2 et du métabolisme des cellules immunitaires pourrait ouvrir de nouvelles perspectives thérapeutiques

Matricellular protein CCN1/CYR61: a new player in inflammation and leukocyte trafficking

Cystein-rich protein 61 (CYR61/CCN1) is a component of the extracellular matrix, which is produced and secreted by several cell types including endothelial cells, fibroblasts and smooth muscle cells. CCN1 has been implicated in leukocyte migration and the inflammatory process, but it is also involved in cardiovascular development and carcinogenesis. It exerts its functions through binding to multiple integrins present in many different cell types. This multiplicity in function is now known to contribute to the diverse array of cellular processes it can regulate. The expression of CCN1 is tightly regulated by cytokines and growth factors. However, CCN1 can directly modulate cell adhesion and migratory processes whilst simultaneously regulating the production of other cytokines and chemokines through paracrine and autocrine feedback loops. This complex functionality of CCN1 has highlighted the pivotal role this molecule can play in regulating the immunosurveillance process. Furthermore, CCN1 has now emerged as an important partner when targeting components of the infectious or chronic inflammatory disease processes such as atherosclerosis or rheumatoid arthritis. This review will focus on CYR61/CCN1 and its ability to control the migration of leukocytes, the production of cytokines and cell proliferation or senescence at the site of inflammation

Electromechanical association: a subtle electrocardiogram artifact

Artifacts on electrocardiogram (ECG) can simulate serious cardiac disorders. Although most common ECG artifacts can be easily recognized, in some exceptional situations, some patterns may hide pretty well even from experienced eyes. We recently reported an unusual ECG artifact caused by radial arterial impulse that closely imitates abnormal T wave. We now report 3 more examples and caught-in-the-act evidence of this subtle and dangerous artifact source. (C) 2012 Elsevier Inc. All rights reserved

Imaging Neutrophils and Monocytes in Mesenteric Veins by Intravital Microscopy on Anaesthetized Mice in Real Time

Efficient immune response is dependent on rapid mobilization of blood leukocytes to the site of infection or injury. Investigating leukocyte migration in vivo is crucial for understanding the molecular basis of leukocyte transendothelial migration and interaction with vascular endothelium. One powerful approach involves intravital microscopy on transgenic mice expressing fluorescent proteins in cells of interest. Here we present a protocol for imaging monocytes and neutrophils in the CX3CR1(gfp/wt) mouse i.v. injected with orange dye-labeled neutrophils with an inverted confocal microscope. Time-lapse movies gathered from 30 min to several hours of imaging allow the analysis of leukocyte behavior in mesenteric veins under both steady state and inflammatory conditions. We also describe the steps to locally induce blood vessel inflammation with TLR2/TLR1 agonist Pam3SK4 and monitor the subsequent recruitment of neutrophils and monocytes. The presented technique can also be used to monitor other populations of leukocytes and investigate molecules implicated in leukocyte recruitment or trafficking using other stimuli or transgenic mice

Influence de la protéine découplante mitochondriale UCP2 sur la signalisation et le métabolisme des macrophages

La protéine découplante UCP2 est un transporteur mitochondrial. Présente dans les macrophages, UCP2 y régule la production de radicaux libres (ROS). Au cours de ma thèse, nous avons démontré que la mitochondrie via UCP2 est au coeur d'une boucle d'amplification du signal impliquant la modulation des ROS mitochondriaux et affectant les MAPK dans les macrophages. In vivo, l'induction d'un diabète de type 1 est accélérée chez les souris Ucp2-KO. En fait, les macrophages jouent un rôle capital dans le développement de la maladie grâce à leur forte capacité de production de cytokines et de NO. Enfin, le métabolisme de la glutamine dans les macrophages Ucp2-KO est altéré. UCP2 est requise pour une oxydation correcte de la glutamine. Une meilleure compréhension de la fonction d'UCP2 et du métabolisme des cellules immunitaires pourrait ouvrir de nouvelles perspectives thérapeutiques.Uncoupling protein UCP2 is a mitochondrial carrier. UCP2 is expressed in macrophages where it regulates the production of reactive oxygen species (ROS). During my thesis, we showed that mitochondria is involved via UCP2 in a signal amplification loop that implicates the modulation of mitochondroal ROS and affects MAPK in macrophages. Experimental type 1 diabetes induction is accelerated in Ucp2-KO mice. Actually, macrophages play a crucial role in the development of the pathology due to their increased ability to produce NO and cytokines. Finally, the metabolism of glutamine in Ucp2-KO macrophages is altered. UCP2 induction is necessary to maximal glutamine oxidation. Future research on the development of strategies to induce UCP2 or to inhibit its downregulation in immune cells may be promising in the context of autoimmunity.PARIS5-BU Méd.Cochin (751142101) / SudocSudocFranceF

An example of apparently normal electrocardiogram originating from incorrect electrocardiographic acquisition in a patient with ST-segment elevation myocardial infarction

Electrocardiography (ECG) is proved to be an invaluable tool for diagnosis of ischemic heart disease for a long while. Importance of ECG in acute management decision makes it a crucial method that must be known in depth by every physician, and the clinicians should also be aware of the dangerous pitfalls of ECG. We present a patient with ST-segment elevation myocardial infarction in whom incorrect interpretation of an inaccurately taken ECG might have led to disastrous consequences. (C) 2010 Elsevier Inc. All rights reserved

Filtering electrocardiogram: Music, math, and ST-elevation myocardial infarction

Clinicians should have a basic understanding of the working principle of the instruments they use to avoid potential pitfalls caused by post-processing of the acquired biological signals. An electrocardiogram (ECG) is no exception; many different errors can arise during the acquisition or the processing of the ECG data, which may result in dangerous misdiagnoses. We present a case where the use of an inappropriate high-pass filter led to a false diagnosis of ST-elevation myocardial infarction. In addition, this report discusses the basic mechanisms of this frequently overlooked phenomenon and methods to avoid it

Liver Glutamate Dehydrogenase Controls Whole-Body Energy Partitioning Through Amino Acid-Derived Gluconeogenesis and Ammonia Homeostasis

Ammonia detoxification and gluconeogenesis are major hepatic functions mutually connected through amino acid metabolism. The liver is rich in glutamate dehydrogenase (GDH) that catalyzes the reversible oxidative deamination of glutamate to α-ketoglutarate and ammonia, thus bridging amino acid-to-glucose pathways. Here we generated inducible liver-specific GDH-knockout mice (HepGlud1-/- ) to explore the role of hepatic GDH on metabolic homeostasis. Investigation of nitrogen metabolism revealed altered ammonia homeostasis in HepGlud1-/- mice characterized by increased circulating ammonia associated with reduced detoxification process into urea. The abrogation of hepatic GDH also modified energy homeostasis. In the fasting state, HepGlud1-/- mice could barely produce glucose in response to alanine due to impaired liver gluconeogenesis. Compared with control mice, lipid consumption in HepGlud1-/- mice was favored over carbohydrates as a compensatory energy fuel. The changes in energy partitioning induced by the lack of liver GDH modified the circadian rhythm of food intake. Overall, this study demonstrates the central role of hepatic GDH as a major regulator for the maintenance of ammonia and whole-body energy homeostasis