Regulation pharmacologique de la concentration cytosolique d'ions calcium dans les erythrocytes et les myocytes et fibroblastes cardiaques en culture: application a l'hypertension primaire

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 78906 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Caractérisation électrochimique et spectrofluorimétrique du monoxyde d'azote et de ses métabolites (application au Corvasal®)

PARIS-BIUP (751062107) / SudocSudocFranceF

Mécanismes de régulation de la biodisponibilité du NO endothélial (influence de différents facteurs athérogènes)

PARIS-BIUP (751062107) / SudocSudocFranceF

Signalisation endothéliale des récepteurs thrombomoduline, PAR-1 et ErbB (rôle dans le remodelage vasculaire et auriculaire)

L a-thrombine est une sérine-protéase impliquées dans le maintien de la fonction vasculaire. Elle exerce des actions ambivalentes via ses récepteurs PAR-1 et thrombomoduline. La thrombomoduline possède des effets anti-inflammatoires et anti-prolifératif, par un mécanisme de signalisation qui reste à caractériser. J ai d abord démontré que la liaison de la thrombine à la thrombomoduline induit la libération de fragments solubles de thrombomoduline pour activer les récepteurs à tyrosine kinase EGFR et ErbB2. Par cette signalisation, la thrombomoduline inhibe l adhérence des monocytes à l endothélium et freine les signaux pro-inflammatoires du PAR-1. En utilisant des modèles de remodelage auriculaire et de resténose chez le rat, nous avons montré que la transcription de la thrombomoduline est dérégulée tandis que la signalisation du PAR-1 est activée. Un inhibiteur du PAR-1 inhibe la dilatation auriculaire en stimulant la voie de signalisation anti-apoptotique du récepteur ErbB2, mais sans restaurer la transcription de thrombomoduline. Il inhibe également la resténose post-angioplastie sans prévenir la diminution d expression des récepteurs thrombomoduline, EGFR et ErbB2. Ces observations démontrent l existence d une balance entre les voies de signalisation de la thrombomoduline et du PAR-1. Sa dérégulation participe aux processus inflammatoires et au remodelage tissulaire. Ainsi, les inhibiteurs du PAR-1 ont un intérêt thérapeutique potentiel et la thrombomoduline est une nouvelle cible thérapeutique pour les pathologies cardiovasculaires et prolifératives.PARIS-BIUP (751062107) / SudocSudocFranceF

Thiosulfinates modulate platelet activation by reaction with surface free sulfhydryls and internal thiol-containing proteins.

Thiosulfinates are characteristic flavors of Allium vegetables, with a highly reactive S-S=O group, that we previously showed to inhibit platelet aggregation through calpain-dependent mechanisms. With the aim to clarify the mode of action of these redox phytochemicals, we studied their effect on extracellular free sulfhydryls in relation to their effect on platelet responses (Ca(2+) signals, release reaction, and a(IIb)beta(3) integrin activation state). At the platelet surface, thiosulfinate dose-dependently increased the basal level of free sulfhydryls, independently of protein disulfide isomerase activity. This generation of new free sulfhydryls was associated with: (i) a three fold increase in labeling of resting platelets with an anti ligand-induced binding site antibody and (ii) marked inhibition of subsequent a(IIb)beta(3) activation by agonists. Thiosulfinates increased the basal intracellular Ca(2+) level of platelets. In activated platelets, they markedly inhibited the Ca(2+) mobilization independently of the external Ca(2+), the calpain-induced SNAP-23 cleavage and the granule release. In platelet free systems, thiosulfinates inhibited the activity of purified calpain and the free sulfhydryl of glutathione without any reducing properties on disulfides. The results demonstrate for the first time that thiosulfinates rapidly interact with sulfhydryls both at the platelet surface and inside the cell on intracellular cysteine-proteins, especially calpain. Inhibition of free cysteine and glutathione in whole blood may also contribute to their anti-aggregant properties. Such sulfur compounds are of interest for the development of a new class of antithrombotic agents

Mitochondrial arginase II modulates nitric-oxide synthesis through nonfreely exchangeable L-arginine pools in human endothelial cells

Reduced synthesis of nitric oxide ( NO) contributes to the endothelial dysfunction and may be related to limited availability of L-arginine, the common substrate of constitutive nitric-oxide synthase ( NOS) and cytosolic arginase I and mitochondrial arginase II. To determine whether arginases modulate the endothelial NO synthesis, we investigated the effects of the competitive arginase inhibitor N omega-hydroxy-nor-L-arginine (NorNOHA) on the activity of NOS, arginases, and L-arginine transporter and on NO release at surface of human umbilical vein endothelial cells (HUVECs). In unstimulated cells, Nor-NOHA dose-dependently reduced the arginase activity with maximal inhibition at 20 mu M. When HUVECs were stimulated by thrombin without extracellular L-arginine, Nor-NOHA dose-dependently increased the NOS activity and the NO release with maximal effects at 20 mu M. Extracellular L-arginine also dose-dependently increased NO release and arginase activity. When HUVECs were stimulated by thrombin in the presence of 100 mu M L- arginine, NOS activity and NO release were similar in untreated and Nor-NOHA-treated cells. However, despite activation of L- arginine uptake, the inhibition of arginase activity by Nor-NOHA was still significant. The depletion of freely exchangeable L- arginine pools with extracellular L- lysine did not prevent Nor-NOHA from increasing the NO release. This indicates the presence of pools, which are accessible to NOS and arginase, but not exchangeable. Interestingly, the mitochondrial arginase II was constitutively expressed, whereas the cytosolic arginase I was barely detectable in HUVECs. These data suggest that endothelial NO synthesis depends on the activity of arginase II in mitochondria and L-arginine carriers in cell membrane

Homocysteine induces oxidative stress by uncoupling of no synthase activity through reduction of tetrahydrobiopterin

International audienc