Signalisation intracellulaire dans la régulation des fonctions bactéricides chez les polynucléaires neutrophiles de souris

Since the creation of the transgenic mice, the study of the innate immunity of this animal has received renewed interest. To exploit this experimental model as well as possible, it was initially necessary to know its normal function in order to compare to our current knowledge of the human immune system. The aim is to apprehend and define the limits of the murine model. We isolated neutrophils from mouse blood and bone marrow and compared their bactericidal functions. We have shown that mouse bone marrow contains a large population of neutrophils which are morphologically and functionally as mature as blood neutrophils. In addition, the discovery of new molecules aiming at stimulating the microbicidal activity of neutrophils as well as the study of intracellular signalling pathways leading to either the activation of these cells, their survival or their accelerated death, allowed us to better understand their regulation.Depuis la création des souris transgéniques, l'étude de l'immunité innée de cet animal a connu un regain d'intérêt. Pour exploiter au mieux ce modèle expérimental, il fallait d'abord connaître son fonctionnement normal afin de comparer les connaissances ainsi acquises chez la souris aux données connues chez l'Homme. Ceci dans le but d'appréhender et de définir les limites du modèle murin. Nous avons isolé des neutrophiles du sang et de la moelle osseuse de souris et comparé leurs fonctions bactéricides. Nous avons montré que la moelle osseuse des souris contient une grande population de neutrophiles morphologiquement et fonctionnellement aussi matures que ceux issus du sang. D'autre part, la découverte de nouvelles molécules visant à stimuler l'activité microbicide des neutrophiles ainsi que l'étude des voies de signalisation intracellulaire aboutissant soit à l'activation de ces cellules, à leur survie ou à leur mort accélérée, nous ont permis de mieux comprendre leur fonctionnement

Signalisation intracellulaire dans la régulation des fonctions bactéricides chez les polynucléaires neutrophiles de souris

Depuis la création des souris transgéniques, l'étude de l'immunité innée de cet animal a connu un regain d'intérêt. Pour exploiter au mieux ce modèle expérimental, il fallait d'abord connaître son fonctionnement normal afin de comparer les connaissances ainsi acquises chez la souris aux données connues chez l'Homme. Ceci dans le but d'appréhender et de définir les limites du modèle murin. Nous avons isolé des neutrophiles du sang et de la moelle osseuse de souris et comparé leurs fonctions bactéricides. Nous avons montré que la moelle osseuse des souris contient une grande population de neutrophiles morphologiquement et fonctionnellement aussi matures que ceux issus du sang. D'autre part, la découverte de nouvelles molécules visant à stimuler l'activité microbicide des neutrophiles ainsi que l'étude des voies de signalisation intracellulaire aboutissant soit à l'activation de ces cellules, à leur survie ou à leur mort accélérée, nous ont permis de mieux comprendre leur fonctionnement.Since the creation of the transgenic mice, the study of the innate immunity of this animal has received renewed interest. To exploit this experimental model as well as possible, it was initially necessary to know its normal function in order to compare to our current knowledge of the human immune system. The aim is to apprehend and define the limits of the murine model. We isolated neutrophils from mouse blood and bone marrow and compared their bactericidal functions. We have shown that mouse bone marrow contains a large population of neutrophils which are morphologically and functionally as mature as blood neutrophils. In addition, the discovery of new molecules aiming at stimulating the microbicidal activity of neutrophils as well as the study of intracellular signalling pathways leading to either the activation of these cells, their survival or their accelerated death, allowed us to better understand their regulation.NANCY1-SCD Sciences & Techniques (545782101) / SudocSudocFranceF

Potent inhibition of store-operated Ca2+ influx and superoxide production in HL60 cells and polymorphonuclear neutrophils by the pyrazole derivative BTP2.: BTP2 inhibits calcium influx in neutrophils

International audienceStore-operated calcium entry (SOCE) is a key regulator in the activation of leukocytes. 3,5-Bistrifluoromethyl pyrazole (BTP) derivatives have been identified recently as inhibitors of T lymphocyte activation. The inhibitory effect of one of these compounds, N-(4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP2), appears to be a result of inhibition of SOC influx. Polymorphonuclear neutrophils provide effective protection against bacterial infection, but they are also involved in tissue damage during chronic inflammation. As for T lymphocytes, their activation relies on SOCE. We therefore investigated the effect of BTP2 on calcium homeostasis and functional responses of human neutrophils. BTP2 significantly inhibited the calcium influx after stimulation with thapsigargin or fMLF. This inhibition was seen after 5 min of incubation with 10 microM BTP2 and after 24 h with lower concentrations. With 24 h incubation, the effect appeared irreversible, as the removal of BTP2 3 h before the experiment did not reduce this inhibition in granulocyte-differentiated HL60 cells. In human neutrophils, BTP2 reduced superoxide anion production by 82% after 24 h of incubation. On the contrary, phagocytosis, intraphagosomal radical production, and bacterial killing by neutrophils were not reduced significantly, even after 24 h treatment with 10 microM BTP2. This work suggests that BTP2 could become an important tool to characterize calcium signaling in neutrophils. Furthermore, BTP2 or related compounds could constitute a new approach to the down-regulation of neutrophils in chronic inflammatory disease without compromising antibacterial host defense

Neutrophil elastase cleaves epithelial cadherin in acutely injured lung epithelium

International audienceAbstractBackgroundIn acutely injured lungs, massively recruited polymorphonuclear neutrophils (PMNs) secrete abnormally neutrophil elastase (NE). Active NE creates a localized proteolytic environment where various host molecules are degraded leading to impairment of tissue homeostasis. Among the hallmarks of neutrophil-rich pathologies is a disrupted epithelium characterized by the loss of cell-cell adhesion and integrity. Epithelial-cadherin (E-cad) represents one of the most important intercellular junction proteins. E-cad exhibits various functions including its role in maintenance of tissue integrity. While much interest has focused on the expression and role of E-cad in different physio- and physiopathological states, proteolytic degradation of this structural molecule and ensuing potential consequences on host lung tissue injury are not completely understood.MethodsNE capacity to cleave E-cad was determined in cell-free and lung epithelial cell culture systems. The impact of such cleavage on epithelial monolayer integrity was then investigated. Using mice deficient in NE in a clinically relevant experimental model of acute pneumonia, we examined whether degraded E-cad is associated with lung inflammation and injury and whether NE contributes to E-cad cleavage. Finally, we checked for the presence of both degraded E-cad and NE in bronchoalveolar lavage samples obtained from patients with exacerbated COPD, a clinical manifestation characterised by a neutrophilic inflammatory response.ResultsWe show that NE is capable of degrading E-cad in vitro and in cultured cells. NE-mediated degradation of E-cad was accompanied with loss of epithelial monolayer integrity. Our in vivo findings provide evidence that NE contributes to E-cad cleavage that is concomitant with lung inflammation and injury. Importantly, we observed that the presence of degraded E-cad coincided with the detection of NE in diseased human lungs.ConclusionsActive NE has the capacity to cleave E-cad and interfere with its cell-cell adhesion function. These data suggest a mechanism by which unchecked NE participates potentially to the pathogenesis of neutrophil-rich lung inflammatory and tissue-destructive diseases

Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data

The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data were the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high-resolution two-dimensional (2-D) airgun, sweep frequency SYSIF, and three-dimensional (3-D) p-cable seismic reflection data were acquired at the south-eastern part of the ridge between 2011 and 2013. The CSEM and seismic data contain profiles across and along the ridge, passing several active and inactive pockmarks. Joint interpretation of resistivity models obtained from CSEM and seismic reflection data provides new information regarding the fluid composition beneath the pockmarks. There is considerable variation in transverse resistance and seismic reflection characteristics of the gas hydrate stability zone (GHSZ) between the ridge flanks and chimneys beneath pockmarks. Layered seismic reflectors on the flanks are associated with around 300 Ωm2 transverse resistance, whereas the seismic reflectors within the chimneys exhibit amplitude blanking and chaotic patterns. The transverse resistance of the GHSZ within the chimneys vary between 400 and 1200 Ωm2. Variance attributes obtained from the 3-D p-cable data also highlight faults and chimneys, which coincide with the resistivity anomalies. Based on the joint data interpretation, widespread gas hydrate presence is likely at the ridge, with both hydrates and free gas contained within the faults and chimneys. However, at the active chimneys the effect of gas likely dominates the resistive anomalies