Effet de l’hypoxie intermittente sur l’expression génique et le phénotype angiogénique des cellules endothéliales.

Intermittent hypoxia (IH), evidenced in solid tumours, positively influences the tumour growth by modulating the behaviour of cancer cells, but also of the endothelial cells (EC) from the tumour vasculature. The formation of the new tumour vasculature plays a critical role in tumour development and metastasis dissemination. However, the molecular mechanisms regulated by IH in these tumours, and more particularly in EC, remain still largely undetermined. In order to better understand the molecular mechanisms regulated by IH, we studied, during this thesis, the modifications of transcriptomic and proteomic expression in EC exposed to IH cycles in comparison to EC incubated under normoxia or continuous hypoxia. We showed that IH induces, in EC, the stabilization of HIF-1 alpha subunit as well as its phosphorylation, which is probably due, at least in part, to the Protein Kinase A (PKA) specifically activated by IH. The activity of the HIF-1 transcription factor is also increased under IH. This activity depends on the phosphorylation of HIF-1 alpha subunit by the PKA. We next evidenced, by a transcriptomic study, variations of the expression of gene known to favour angiogenic processes. This pro-angiogenic effect of IH was confirmed by the increase in EC migration. By the use of siRNA, we demonstrated the involvement of HIF-1 in the IH-induced increase in endothelial migration. Finally, we studied the changes induced by IH in the EC proteome. We identified some proteins, the expression of which varied under IH. Amongst these ones, we showed that NDRG1 and CRK-I/II are regulators of EC migration under IH. All these results show that IH favours angiogenic processes promoting EC activation and hence, the tumour vasculature and the tumour growth.L'hypoxie intermittente (HI) présente dans les tumeurs solides influence positivement la croissance tumorale en modulant le comportement des cellules cancéreuses, mais également celui des cellules endothéliales (CE) constituant le réseau vasculaire. La formation du réseau vasculaire tumoral au sein des tumeurs joue un rôle critique dans le développement des tumeurs et la dissémination des métastases. Cependant, les mécanismes moléculaires régulés par l'hypoxie intermittente dans ces tumeurs et plus particulièrement dans les CE restent encore largement indéterminés. Afin de mieux comprendre les mécanismes moléculaires régulés par l'hypoxie intermittente, nous avons étudié au cours de cette thèse, les modifications d'expression transcriptomique et protéomique dans des CE soumises à des cycles d'hypoxie intermittente par rapport à des CE incubées en normoxie ou en hypoxie chronique. Nous avons montré que l'hypoxie intermittente induit, dans les CE, la stabilisation de la sous-unité HIF-1 alpha ainsi que sa phosphorylation, qui serait due, tout au moins en partie, à la Protéine Kinase A (PKA) spécifiquement activée par l'hypoxie intermittente. L'activité transcriptionnelle du facteur de transcription HIF-1 est également augmentée en HI. Cette activité dépend de la phosphorylation de la sous-unité HIF-1 alpha par la PKA. Nous avons ensuite mis en évidence, par une étude transcriptomique, des variations d'expression génique en hypoxie intermittente qui seraient favorables aux processus angiogéniques. Cet effet proangiogénique de l'hypoxie intermittente fut confirmé par la mise en évidence de l'augmentation du potentiel migratoire des CE. Par l'utilisation de siRNA, nous avons démontré l'implication du facteur de transcription HIF-1 dans la mise en place de ces processus de migration endothéliale. Enfin, nous avons étudié les changements induits par l'hypoxie intermittente au niveau du protéome des CE. Nous avons identifié une série de protéines dont l'expression variait en HI. Parmi celles-ci, nous avons montré que NDRG1 et CRK-I/II étaient des régulateurs de la migration des CE en HI. L'ensemble de nos résultats montre que l'hypoxie intermittente favorise les processus de l'angiogenèse en promouvant l'activation des CE et ainsi le développement du réseau vasculaire tumoral et la croissance des tumeurs.(DOCSC03) -- FUNDP, 200

Intermittent hypoxia changes HIF-1α phosphorylation pattern in endothelial cells: Unravelling of a new PKA-dependent regulation of HIF-1α

AbstractVascularized tumors are exposed to intermittent hypoxia, that is, hypoxia followed by periods of reoxygenation. Abnormal structure and dysfunction of tumor blood vessels are responsible for these conditions. These repeated short periods of hypoxia concern tumor cells as well as endothelial cells. However, the effects of intermittent hypoxia are poorly understood. The aim of this study was to investigate the effects of intermittent hypoxia on endothelial cells and particularly on HIF-1α, a central actor in adaptive response to hypoxia. For that, endothelial cells were exposed to four repeated cycles of 1-h hypoxia followed by 30 min of reoxygenation. We showed that repeated cycles of hypoxia/reoxygenation induced a modification in HIF-lα phosphorylation pattern: a progressive increase in HIF-1α phosphorylated form was observed during the hypoxic periods. Activation of p42/p44, Akt and PKA was observed in parallel. PKA was shown to be involved in the phosphorylation of HIF-lα under intermittent hypoxia, while p42/p44 and Akt were not. As HIF-1 activity is often associated with enhanced cell survival, a better knowledge of the effects of intermittent hypoxia on endothelial cells and the highlight of particular mechanisms induced by intermittent hypoxia are essential to understand the behavior of endothelial cells during neo-angiogenesis

Focus sur les associations graminées-légumineuses en Ardenne belge

L’intérêt des légumineuses fourragères dans la composition des prairies est largement documenté (Pierre et al., 2016). Pourtant, certains freins identifiés par le passé subsistent toujours à l’heure actuelle alors que leurs utilisations devraient au contraire se généraliser au maximum pour mieux faire face aux aléas climatiques, pour gagner en autonomie fourragère et protéique, pour limiter les coûts des engrais de synthèse... L’intérêt des légumineuses est également réel dans les mélanges de céréales et de protéagineux récoltés en immatures (MCPI) (Crémer et al., 2018). Depuis plusieurs années, le Centre de Michamps étudie les légumineuses en Ardenne en collaboration avec le Centre pilote Fourrages Mieux. (I) Les potentiels de rendements quantitatifs et qualitatifs, tant en culture pure qu’en association, sont comparés pour différentes espèces (pérennes et annuelles) de même que leur résilience face aux changements climatiques (Lambert et al., 2020). Les pratiques de fertilisation sont adaptées en lien, notamment, avec la persistance des espèces. (II) Des pistes alternatives au désherbage chimique sont également proposées (Crémer et al., 2019). Ces avancées techniques devraient lever les freins existants et généraliser l’usage des légumineuses dans les ressources fourragères

NDRG1 and CRK-I/II are regulators of endothelial cell migration under intermittent hypoxia

Intermittent Hypoxia (IH) that develops in neovascularized solid tumours has been described to positively influence the tumour growth by modulating the behaviour of cancer cells as well as of endothelial cells. However, the molecular mechanisms regulated by IH still remain poorly understood. In this work, the effects of IH were investigated on endothelial cells by a proteomic approach. Protein abundance variations were studied using fluorescent 2D-Differential in Gel Electrophoresis (2D-DIGE). Amongst the proteins of which the abundance varied under IH, NDRG1 and CRK-I/II were identified by mass spectrometry. These proteins have already been described to influence cancer cell migration as well as the angiogenic processes in solid tumours. Since an increase in endothelial cell migration under IH was evidenced in our previous work, the involvement of NDRG1 and CRK-I/II proteins in endothelial cell migration under IH was determined by silencing the expression of both proteins using siRNA. The results revealed that NDRG1 and CRK-I/II are indeed regulators of endothelial cell migration under intermittent hypoxia: silencing of CRK-I/II resulted in an increase in endothelial cell migration, whereas the invalidation of NDRG1 decreased it. These results give news insight regarding the effects of IH on endothelial cell migration and hence on neoangiogenesis

Chromothripsis in an early recurrent chordoid meningioma.

INTRODUCTION : Meningiomas are the most frequent primary intracranial tumors and are generally considered benign, although they may harbor an aggressive clinical behavior [1]. While genetic criteria were introduced in the updated 2016 WHO classification for gliomas, stratification of meningiomas remains based on pure histological aspect [2]. Chordoid meningioma (CM), which represents only 1% of meningiomas, is a rare subtype characterized by cords of eosinophilic cells in an abundant myxoïd matrix with a chordoma-like appearance. It is classified as grade WHO 2 due to a high rate of early recurrence. In the last decade, genetic alterations of meningiomas were extensively studied. Monosomy 22 and inactivating mutations of neurofibromin 2 gene (NF2) are the most frequently encountered [3]. More recently, mutations in TERT promoter, TRAF7, AKT1, KLF4, SMO, and PIK3CA were detected by next-generation sequencing [4,5]. A DNA methylation-based classification was also proposed [6]. [...

Phylogeography and postglacial recolonization of Europe by Rhinolophus hipposideros: evidence from multiple genetic markers

The demographic history of Rhinolophus hipposideros (lesser horseshoe bat) was recon- structed across its European, North African and Middle-Eastern distribution prior to, during and following the most recent glaciations by generating and analysing a multi- marker data set. This data set consisted of an X-linked nuclear intron (Bgn; 543 bp), mitochondrial DNA(cytb-tRNA-control region; 1630 bp) and eight variable microsatel- lite loci for up to 373 individuals from 86 localities. Using this data set of diverse markers, it was possible to determine the species’ demography at three temporal stages. Nuclear intron data revealed early colonization into Europe from the east, which pre-dates the Quaternary glaciations. The mtDNA data supported multiple glacial refugia across the Mediterranean, the largest of which were found in the Ibero- Maghreb region and an eastern location (Anatolia/Middle East)–that were used by R. hipposideros during the most recent glacial cycles. Finally, microsatellites provided the most recent information on these species’ movements since the Last Glacial Maxi- mumand suggested that lineages that had diverged into glacial refugia, such as in the Ibero-Maghreb region, have remained isolated. These findings should be used to inform future conservation management strategies for R. hipposideros and show the power of using a multimarker data set for phylogeographic studies.Peer reviewe