Effets cellulaires et voies de signalisation activés par le facteur anticoagulant, la protéine S, sur les cellules endothéliales (implication lors de l'angiogenèse)

L'angiogenèse est un processus physiologique qui correspond à la formation de nouveaux vaisseaux sanguins à partir d'un réseau vasculaire préexistant et est régulée par l'équilibre entre les facteurs endogènes pro- et anti-angiogéniques. La rupture de cet équilibre est associée à de nombreuses pathologies dont l'ischémie, la rétinopathie ou encore la progression tumorale. Etant donné que les cellules endothéliales, principal type cellulaire composant les vaisseaux sanguins expriment les récepteurs à activité tyrosine kinase du facteur anticoagulant, la protéine S, Tyro3, Axl et Mer et produisent de la protéine S, l'objectif de ce travail est d'étudier le rôle, de la protéine S dans l'angiogenèse. Dans la première partie de ce travail, nous avons montré in vivo que la protéine S inhibe l'angiogenèse induite par les facteurs pro-angiogéniques (VEGFA et FGF2). Parallèlement, nous avons observé in vitro une inhibition par la protéine S de la prolifération et de la migration des cellules endothéliales induites par le VEGFA. Cet effet est corrélé à l'inhibition par la protéine S des voies de signalisation des MAP-Kinases et de la phosphatidylinositol 3-kinase (PIK3) induites par le VEGFA. Nous avons ensuite mis en évidence, par l'utilisation d'inhibiteurs pharmacologiques et de petits ARNs interférents, que la protéine S inhibe, via l'activation du récepteur Mer et le recrutement de la protéine phosphatase SHP2, l'activation du VEGFR2, le principal récepteur du VEGFA. Dans la deuxième partie, nous avons montré de manière intéressante que le rôle joué par la protéine S lors de l'angiogenèse est plus complexe, puisqu'elle est capable d'activer directement la voie de signalisatioAngiogenesis is a physiological process that leads to new blood vessel formation and is regulated by a balance between pro-and anti-angiogenic endogenous factors. Disruption of this balance leads to many pathologies such as ischemia, retinopathies or tumor growth. Because endothelial cells, the main cellular type composing blood vessels, produce the anticoagulant factor, protein S and express its tyrosine kinase receptors Tyro3, Axl and Mer, we investigated the implication of protein S in angiogenesis. In the first part of this work, we demonstrated that protein S inhibits pro-angiogenic factors (VEGFA and FGF2)-induced angiogenesis in vivo. We also observed an inhibition of VEGFA-dependent endothelial cell proliferation and migration induced by protein S. These effects were correlated with protein S induced inhibition of VEGFA-dependent MAP-Kinases (Erk1, Erk2) and phosphatidylinositol 3-kinase (PIK3) activation. Furthermore, we demonstrated, using pharmacological inhibitors and small interfering RNAs, that protein S inhibits VEGFA-induced VEGFR-2 activation through Mer receptor activation and SHP2 protein phosphatase recruitment. In the second part, we demonstrated that, protein S on its own, is able to induce MAP-kinases pathway activation and endothelial cells proliferation. These cellular and molecular effects involved Mer receptor and SHP2 protein activation and required protein kinase SRC recruitment. Our results describe for the first time that protein S is an endogenous regulator for angiogenesis both in vitro and in vivo and may form the framework for the use of protein S as part of an anti-angiogenic treatment.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Contribution a l'etude du transforming growth factor beta, mise en evidence. Effet sur la croissance cellulaire et approche du mecanisme d'action

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 82116 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

An endogenous vitamin K-dependent mechanism regulates cell proliferation in the brain subventricular stem cell niche

Neural stem cells (NSC) persist in the adult mammalian brain, within the subventricular zone (SVZ). The endogenous mechanisms underpinning SVZ stem and progenitor cell proliferation are not fully elucidated. Vitamin K-dependent proteins (VKDPs) are mainly secreted factors that were initially discovered as major regulators of blood coagulation. Warfarin ((S(2)-3-acetonylbenzyl)-4- hydroxy-coumarin)), a widespread anticoagulant, is a vitamin K antagonist that inhibits the production of functional VKDP. We demonstrate that the suppression of functional VKDPs production, in vitro, by exposure of SVZ cell cultures to warfarin or, in vivo, by its intracerebroventricular injection to mice, leads to a substantial increase in SVZ cell proliferation. We identify the anticoagulant factors, protein S and its structural homolog Gas6, as the two only VKDPs produced by SVZ cells and describe the expression and activation pattern of their Tyro3, Axl, and Mer tyrosine kinase receptors. Both in vitro and in vivo loss of function studies consisting in either Gas6 gene invalidation or in endogenous protein S neutralization, provided evidence for an important novel regulatory role of these two VKDPs in the SVZ neurogenic niche. Specifically, we show that while a loss of Gas6 leads to a reduction in the numbers of stem-like cells and in olfactory bulb neurogenesis, endogenous protein S inhibits SVZ cell proliferation. Our study opens up new perspectives for investigating further the role of vitamin K, VKDPs, and anticoagulants in NSC biology in health and disease. © AlphaMed Press.This work was supported by La Ligue Contre le Cancer Grand Ouest (Comités de la Vienne, Deux-Sèvres, Charente, Loiret), Région Poitou-Charentes and Retina France. A.Gely holds a Ph.D. fellowship from the French Ministry for Education and Science and P. Garcia de Frutos work is supported by a grant from the Spanish Ministry of Science and Innovation BFU2007-61699/BFI.Peer Reviewe

Fonctions nouvelles de Gas-6 et de la protéine S

Les protéines vitamine K-dépendantes sont essentiellement connues pour leur implication dans la coagulation du sang. Récemment, deux protéines vitamine K-dépendantes, le facteur anticoagulant protéine S et son homologue structural Gas-6, ont été identifiés comme ligands des récepteurs à activité tyrosine kinase TAM (Tyro-3/Axl/Mer). L’analyse des phénotypes de souris transgéniques invalidées pour les gènes codant pour Gas-6 ou pour ses récepteurs a révélé que Gas-6 et la protéine S sont impliquées dans la régulation de la phagocytose des cellules apoptotiques, processus important dans la réponse immunitaire ainsi que dans les processus de différenciation cellulaire. Les nouvelles fonctions de ces protéines vitamine K-dépendantes ainsi que leur utilisation potentielle dans l’élaboration de traitements de pathologies associées à un déficit de phagocytose font l’objet de cet article

The vitamin K-dependent factor, protein S, regulates brain neural stem cell migration and phagocytic activities towards glioma cells

International audienceMalignant gliomas are the most common primary brain tumors. Due to both their invasive nature and resistance to multimodal treatments, these tumors have a very high percentage of recurrence leading in most cases to a rapid fatal outcome. Recent data demonstrated that neural stem/progenitor cells possess an inherent ability to migrate towards glioma cells, track them in the brain and reduce their growth. However, mechanisms involved in these processes have not been explored in-depth. In the present report, we investigated interactions between glioma cells and neural stem/progenitor cells derived from the subventricular zone, the major brain stem cell niche. Our data show that neural stem/pro-genitor cells are attracted by cultured glioma-derived factors. Using multiple approaches, we demonstrate for the first time that the vitamin K-dependent factor protein S produced by glioma cells is involved in tumor tropism through a mechanism involving the tyrosine kinase receptor Tyro3 that, in turn, is expressed by neural stem/ progenitor cells. Neural stem/progenitor cells decrease the growth of both glioma cell cultures and clonogenic population. Cultured neural stem/progenitor cells also engulf, by phagocytosis, apoptotic glioma cell-derived fragments and this mechanism depends on the exposure of phosphatidylserine eat-me signal and is stimulated by protein S. The disclosure of a role of protein S/Tyro3 axis in neural stem/progenitor cell tumor-tropism and the demonstration of a phagocytic activity of neural stem/progenitor cells towards dead glioma cells that is regulated by protein S open up new perspectives for both stem cell biology and brain physiopathology