L'endothéline-1 (ET-1) et l'angiotensine II (Ang II) jouent un rôle important dans le maintien de la pression artérielle et l'homéostasie vasculaire. Une activité accrue de ces peptides vasoactifs est présumée contribuer au développement de pathologies vasculaires, telles que l'hypertension, l'athérosclérose, l'hypertrophie et la resténose. Ceci est causé par une activation excessive de plusieurs voies de signalisation hypertrophiques et prolifératives, qui incluent des membres de la famille des Mitogen Activated Protein Kinases (MAPK), ainsi que la famille phosphatidylinositol 3-kinase (PI3-K) / protéine kinase B (PKB). Bien que l'activation de ces voies de signalisation soit bien élucidée, les éléments en amont responsables de l'activation des MAPK et de la PKB, induite par l'ET-1 et Ang II, demeurent mal compris. Durant les dernières années, le concept de la transactivation de récepteurs et/ou non-récepteurs protéines tyrosine kinases (PTK) dans le déclenchement des événements de signalisation induits par les peptides vasoactifs a gagné beaucoup de reconnaissance. Nous avons récemment démontré que la PTK Insulin-like Growth Factor type-1 Receptor (IGF-1R) joue un rôle dans la transduction des signaux induits par l‟H2O2, menant à la phosphorylation de la PKB. Étant donné que les peptides vasoactifs génèrent des espèces réactives d'oxygène, telles que l‟H2O2 lors de leur signalisation, nous avons examiné le rôle de d‟IGF-1R dans la phosphorylation de la PKB et les réponses hypertrophiques dans les cellules muscle lisse vasculaires (CMLV) induites par l'ET-1 et Ang II. AG-1024, un inhibiteur spécifique de l'IGF-1R, a atténué la phosphorylation de la PKB induite à la fois par l'ET-1 et Ang II. Le traitement des CMLVs avec l‟ET-1 et Ang II a également induit une phosphorylation des résidus tyrosine dans les sites d'autophosphorylation d'IGF-1R, celle-ci a été bloquée par l‟AG-1024. En outre, l‟ET-1 et l‟Ang II on tous les deux provoqué la phosphorylation de c-Src, une PTK non-récepteur, bloqué par PP-2, inhibiteur spécifique de la famille Src. La PP-2 a également inhibé la phosphorylation de PKB et d‟IGF-1R induite par l‟ET-1 et l‟Ang II. De plus, la synthèse de protéines ainsi que d‟ADN, marqueurs de la prolifération cellulaire et de l'hypertrophie, ont également été atténuée par l‟AG-1024 et le PP-2. Bien que ce travail démontre le rôle de c-Src dans la phosphorylation PKB induite par l'ET-1 et Ang II, son rôle dans l'activation des MAPK induit par l'ET-1 dans les CMLVs reste controversé. Par conséquent, nous avons examiné l'implication de c-Src dans l'activation de ERK 1/2, JNK et p38MAPK, par l'ET-1 et Ang II, ainsi que leur capacité à régulariser l'expression du facteur de transcription Early growth transcription factor-1 « Egr-1 ». ET-1 et Ang II ont induit la phosphorylation de ERK 1/2, JNK et p38 MAPK, et ont amplifié l'expression d'Egr-1 dans les CMLVs. Cette augmentation de la phosphorylation des MAPK a été diminuée par la PP-2, qui a aussi atténué l'expression d'Egr-1 induite par l'ET-1 et l'Ang II. Une preuve supplémentaire du rôle de c-Src dans ce processus a été obtenue en utilisant des fibroblastes embryonnaires de souris déficientes en c-Src (Src -/- MEF). L'expression d'Egr-1, ainsi que l'activation des trois MAPKs par l'ET-1 ont été atténuées dans les cellules Src -/- par rapport au MEF exprimant des taux normaux Src. En résumé, ces données suggèrent que l'IGF-1R et c-Src PTK jouent un rôle essentiel dans la régulation de la phosphorylation de PKB et des MAPK dans l‟expression d'Egr-1, ainsi que dans les réponses hypertrophiques et prolifératives induites par l'ET-1 et Ang II dans les CMLVs. / Endothelin-1 (ET-1) and angiotensin II (Ang II) play important roles in maintaining blood pressure and vascular homeostasis, and a heightened activity of these vasoactive peptides is thought to contribute to the development of vascular pathologies, such as hypertension, atherosclerosis, hypertrophy and restenosis. This is caused by an excessive activation of several growth and proliferative signaling pathways, which include members of the mitogen-activated protein kinase (MAPK) family, as well as the phosphatidylinositol 3-kinase (PI3-K)/protein kinase B (PKB) pathway. While the activation of these signaling pathways is well elucidated, the upstream elements responsible for ET-1 and Ang II-induced MAPK and PI3-K/PKB activation remain poorly understood. During the last several years, the concept of transactivation of receptor and/or non-receptor protein tyrosine kinases (PTK) in triggering vasoactive peptide-induced signaling events has gained much recognition. We have recently demonstrated that insulin-like growth factor-1 receptor (IGF-1R) plays a role in tranducing the effect of H2O2, leading to PKB phosphorylation. Since vasoactive peptides elicit their responses through generation of reactive oxygen species, including H2O2, we investigated whether IGF-1R transactivation plays a similar role in ET-1 and Ang II-induced PKB phosphorylation and hypertrophic responses in VSMC. AG-1024, a specific inhibitor of IGF-1R, attenuated both ET-1 and Ang II-induced PKB phosphorylation in a dose-dependent manner. ET-1 and Ang II treatment also induced the phosphorylation of tyrosine residues in the autophosphorylation sites of IGF-1R, which was blocked by AG-1024. In addition, both ET-1 and Ang II evoked tyrosine phosphorylation of c-Src, a non-receptor PTK, and pharmacological inhibition of c-Src PTK activity by PP-2, a specific inhibitor of Src-family tyrosine kinase, significantly reduced PKB phosphorylation as well as tyrosine phosphorylation of IGF-1R induced by the two vasoactive peptides. Furthermore, protein and DNA synthesis, markers of cell growth and proliferation, enhanced by ET-1 and Ang II were also attenuated by AG-1024 and PP-2. While this work demonstrates the role of c-Src in ET-1 and Ang II-induced PKB phosphorylation, its role in ET-1-induced MAPK signaling and regulation of transcription factors, such as early growth response factor-1 (Egr-1), which was recently shown to be expressed in atherosclerotic plaque, remains controversial in VSMC. Therefore, we have also investigated the involvement of c-Src in ET-1 and Ang II-induced ERK 1/2, JNK and p38mapk activation, as well as Egr-1 regulation. ET-1 and Ang II-induced the phosphorylation of ERK 1/2, JNK and p38mapk, and enhanced the expression of Egr-1 in aortic VSMC. This increased phosphorylation was decreased by PP-2. Further proof for the role of c-Src in this process was obtained by using mouse embryonic fibroblasts (MEF) deficient in c-Src (Src -/- MEF). ET-1-induced Egr-1 expression, as well as MAPK activation, were found to be downregulated in Src -/- MEF, as compared to MEF expressing normal Src levels. In summary, these data demonstrate that IGF-1R and c-Src PTK play a critical role in mediating both PKB and MAPK phosphorylation and Egr-1 expression, as well as hypertrophic and proliferative responses induced by ET-1 and Ang II in VSMC.

Le système endothéline (ET) est activé en condition d’hypertension pulmonaire (HTP). L’efficacité des antagonistes des récepteurs à l’ET a clairement été démontrée et a menée à l’approbation clinique de tels antagonistes dans le traitement de l’hypertension artérielle pulmonaire (HTAP). Toutefois, il existe présentement un important débat opposant l’utilisation d’un antagoniste sélectif des récepteur ETA à l’utilisation d’un antagoniste double ETA/ETB dans le traitement de cette pathologie. Bien que nous sachions que le système ET est activé et contribue à l’HTAP, les modifications locales de ce système induites par la pathologie, particulièrement au niveau des artères de résistance pulmonaires, demeurent inconnues. De plus, l’impact de ces modifications sur la réponse pharmacologique aux divers antagonistes des récepteurs à l’ET (sélectifs versus double) est d’une importance capitale. Ainsi, le but de la première étude de cette thèse était d’évaluer les modifications potentielles de la pharmacologie du système ET au niveau des artères de résistance pulmonaires induites par l’HTAP. Dans cette étude, nous avons démontré qu’en condition contrôle l’antagoniste sélectif ETA et l’antagoniste double n’ont eu aucun effet sur la réponse vasoconstrictrice à l’ET-1. Toutefois, en condition d’HTAP, les antagonistes sélectif et double ont tous deux été en mesure de réduire la vasoconstriction pulmonaire induite par l’ET-1. Une diminution importante de l’expression génique du récepteur ETB pourrait être à l’origine de cette modification du profil pharmacologique des antagonistes. Une meilleure compréhension des rôles joués par les récepteurs ETA et ETB au niveau des artères de résistance pulmonaires pourrait permettre l’optimisation des traitements de l’HTAP. Ainsi, le but de la deuxième étude était d’évaluer les effets d’un traitement antisens ex vivo dirigé contre l’ARNm des récepteurs ETA et ETB dans la vasoconstriction des artères de résistance pulmonaires induite par l’ET-1. Dans cette étude, nous avons démontré dans un premier temps que les récepteurs ETA et ETB pouvaient former des dimères au niveau des artères de résistance pulmonaires. De plus, nous avons observé qu’une réduction de l’expression protéique du R-ETA entraînait une potentialisation de la vasoconstriction ETB dépendante suggérant ainsi qu’en condition contrôle, le récepteur ETA aurait un effet inhibiteur sur la vasoconstriction pulmonaire induite par la stimulation du récepteur ETB. Les effets délétères de l’ET-1 sur la circulation pulmonaire sont bien connus, toutefois seules quelques études ont porté leur attention sur l’implication de l’ET-3 dans l’HTAP. Ainsi, le but de la troisième étude était d’évaluer l’implication potentielle de l’ET-3 dans l’HTAP. Dans cette étude, nous avons démontré qu’il était nécessaire en condition contrôle de bloquer simultanément les récepteurs ETA et ETB afin de réduire la réponse vasoconstrictrice pulmonaire à l’ET-3. En condition d’HTAP, nous avons observé une augmentation non-significative des concentrations plasmatiques d’ET-3 ainsi qu’une modification du profil pharmacologique des antagonistes des récepteurs à l’ET. En effet, l’utilisation de l’antagoniste sélectif ETA ou de l’antagoniste double était dans les deux cas en mesure de réduire la vasoconstriction pulmonaire à l’ET-3. Les résultats de ces trois études suggèrent qu’il est préférable d’utiliser un antagoniste double dans le traitement de l’HTAP. En effet, (1) en condition d’HTAP, l’utilisation d’un antagoniste double est aussi efficace que l’utilisation d’un antagoniste sélectif ETA; (2) les récepteurs ETA et ETB peuvent former des dimères au niveau des artères de résistance pulmonaires et (3) le récepteur ETB joue un rôle prédominant dans la vasoconstriction pulmonaire, il semble donc essentiel de bloquer simultanément les récepteurs ETA et ETB afin d’inhiber la réponse vasoconstrictrice induite par l’ET. Mots-clés: endothéline-1, endothéline-3, artère de résistance pulmonaire, récepteur vasculaire, antagoniste des récepteurs à l’ET, dimérisation, phosphorothioate, hypertension artérielle pulmonaire / The endothelin (ET) system is activated in pulmonary arterial hypertension (PAH); indeed, increased plasma levels of ET-1 were detected in patients with various forms of PAH and in various experimental models. The therapeutic value of pharmacological blockade of ET receptors has been demonstrated in various animal models and led to the current approval and continued development of these drugs for the therapy of human PAH. Whether the net effect of either selective ETA receptor blockade or combined ETA/ETB receptor blockade provides greater therapeutic benefit remains a subject of debate. Although the ET system contributes to PAH, we currently incompletely comprehend which local modifications of this system occur as a consequence of PAH, particularly in small resistance arteries, and how this could affect the pharmacological response to ET receptor antagonists. The purpose of the first study was therefore to evaluate potential modifications of the pharmacology of the ET system in rat pulmonary resistance arteries from monocrotaline-induced PAH. Our results reveal striking changes in pulmonary vasculature sensitivity to ET receptor antagonism in PAH that may be related to a reduction in ETB receptor expression. A better understanding of the exact role played by both ETA and ETB receptors on pulmonary resistance arteries might contribute to optimization of PAH treatments. Therefore the aim of the second study was to clarify the role played by both ETA and ETB receptors in ET-1 induced pulmonary vasoconstriction using an antisense (AS) oligonucleotide ex vivo treatment. In this study we have demonstrated that ETA and ETB receptors can form heterodimers in pulmonary resistance arteries. Furthermore, suppression of ETA receptors potentiated the response to ET-1 suggesting that in control condition the ETA receptor has an inhibitory action on the ET-1 induced pulmonary vasoconstriction induced by the stimulation of the ETB receptor. Although the deleterious effects of ET-1 on the pulmonary circulation are well established, only a few studies have focused on ET-3 in PAH. Therefore, the purpose of the last study was to evaluate the potential implication of ET-3 in MCT-induced PAH and evaluate the roles of ETA and ETB receptors on ET-3-induced pulmonary vascular reactivity. In control condition, the use of a combination of both ETA and ETB receptor antagonists is necessary to reduce the ET-3 induced pulmonary vasoconstriction. In PAH, we found an increased ET-3 plasma levels and a modification of the pharmacological profile of ET receptor antagonists. Indeed, the use of either the ETA receptor antagonist or the dual antagonist was able to reduce the ET-3 response. The results from these three studies suggest that it is preferable to use a dual antagonist in the treatment of PAH. Indeed, (1) in PAH the use of a dual antagonist is as effective as the use of a selective ETA receptor antagonist (2) ETA and ETB receptors can form heterodimers in pulmonary resistance arteries and (3) ETB receptor plays an important role in the ET-1 induced pulmonary vasoconstriction, suggesting that it is necessary to block both receptors to reduce the ET-1 induced pulmonary vasoconstriction. Keywords: endothelin-1, endothelin-3, pulmonary resistance artery, receptor, endothelin receptor antagonist, dimerisation, phosphorothioate pulmonary arterial hypertension

INTRODUÇÂO: A morte encefálica (ME) induz instabilidade hemodinâmica com hipoperfusão microcirculatória, desencadeando inflamação e disfunção de órgãos. OBJETIVO: Este estudo teve como objetivo investigar os efeitos da solução salina hipertônica (SH) 7,5% na evolução da resposta inflamatória no tecido mesentérico de ratos submetidos à ME. MÉTODOS: Ratos Wistar machos foram anestesiados e ventilados mecanicamente. A ME foi induzida pela insuflação rápida de um balão posicionado na cavidade intracraniana (Fogart 4F). Os ratos foram divididos aleatoriamente em: 1) Falso-operado, ratos submetidos aos procedimentos cirúrgicos e trepanação (FO, n=17); 2) Controle, ratos tratados com solução salina isotônica (NaCl 0,9%, 4 mL/kg) imediatamente após ME (CO, n=17); 3) Solução hipertônica 1, ratos tratados com solução hipertônica (NaCl 7,5%, 4 mL/kg) imediatamente após ME (SH1, n=17); 4) Solução hipertônica 60, ratos tratados com solução hipertônica 60 min após ME (SH60, n=17). Três horas após a indução da ME ou o término do procedimento cirúrgico para os animais do grupo FO, foram coletados os seguintes dados: (a) perfusão mesentérica, fluxo sanguíneo e interações leucócito-endotélio no mesentério, pela técnica de microscopia intravital; (b) expressão de proteínas de óxido nítrico sintase endotelial (eNOS), endotelina-1, P-selectina e molécula de adesão intercelular (ICAM)-1, por imunohistoquímica; (c) expressão gênica de eNOS e endotelina-1, por reação em cadeia da polimerase em tempo real (PCR); (d) concentrações séricas de citocinas, quimiocinas e corticosterona por meio de enzimaimunoensaio (ELISA). RESULTADOS: Todos os grupos submetidos a ME apresentaram um comportamento semelhante da pressão arterial, sendo observado um pico hipertensivo, seguido de período de hipotensão, logo após a insuflação do cateter intra-craniano. A proporção de pequenos vasos perfundidos foi diminuída no grupo CO (46%) em comparação com FO (74%, p=0,0039). A SH foi capaz de restaurar a proporção de vasos perfundidos (SH1=71%, p=0,0018). Não houve diferenças no fluxo sanguíneo mesentérico entre os grupos. A expressão proteica de eNOS aumentou significativamente em ratos com SH (SH1 e SH60, p=0,0002) em comparação ao grupo CO. Resultados semelhantes foram observados em relação à endotelina-1 (p < 0,0001). Não houve diferenças na expressão gênica de eNOS e endotelina-1. O aumento no número de leucócitos \"rollers\" (p=0,0015) e migrados (p=0,0063) foi observado no grupo CO em comparação com FO. Ratos com SH demonstraram redução significativa em todos os parâmetros da interação leucócito-endotélio. Com relação às moléculas de adesão, a expressão de ICAM-1 estava elevada no grupo CO em comparação com o FO, enquanto que o tratamento com SH diminuiu a expressão de ICAM-1 (SH1 e SH60, p=0,0002). CONCLUSÕES: O emprego da solução salina hipertônica melhorou a perfusão mesentérica, influenciou positivamente o metabolismo do óxido nítrico e reduziu a inflamação no mesentério, com diminuição da adesão e migração leucocitária, em ratos submetidos a ME / BACKGROUND: Brain death (BD) induces hemodynamic instability with microcirculatory hypoperfusion leading to increased organ inflammation and dysfunction. OBJETIVE: To investigate the effects of 7.5% hypertonic saline solution (HS) on the course of the inflammatory response in rats submitted to BD. METHODS: Male Wistar rats were anesthetized and mechanically ventilated. BD was induced by rapid inflation of intracranial balloon catheter (Fogart 4F). Rats were randomly divided in: 1) Sham-operated, rats submitted only to trepanation (SH, n=17); 2) Control, rats treated with normal saline solution (NaCl 0.9%, 4 mL/kg) immediately after BD (CO, n=17); 3) Hypertonic solution 1, rats treated with hypertonic solution (NaCl 7.5%, 4 mL/kg) immediately after BD (HS1, n=17); 4) Hypertonic solution 60, rats treated with hypertonic solution 60 min after BD (HS60, n=17). Hundred eighty minutes thereafter the following experiments were performed: (a) mesenteric perfusion, blood flow, and leukocyte-endothelial interactions, by intravital microscopy; (b) protein expression of endothelial nitric oxide synthase (eNOS), endothelin-1, P-selectin, and intercellular cell adhesion molecule (ICAM)-1, by immunohistochemistry; (c) gene expression of eNOS, and endothelin-1, by real-time polymerase chain reaction (PCR); (d) serum concentrations of cytokines, chemokines and corticosterone by enzyme-linked immunosorbent assay (ELISA). RESULTS: All BD groups presented similar hypertensive peak followed by hypotension. The proportion of perfused small vessels was decreased in CO group (46%) compared to SH (74%, p=0.0039). HS was able to restore the proportion of perfused vessels (HS1=71%, p=0.0018). There were no differences in mesenteric blood flow between groups. eNOS protein expression significantly increased in rats given HS (HS1, and HS60, p=0.0002). Similar results were observed regarding endothelin-1 (p < 0.0001). There were no differences in eNOS and endothelin-1 gene expression. Increased numbers of rolling (p=0.0015) and migrated (p=0.0063) leukocytes were observed in CO group compared to SH. Rats given HS demonstrated an overall reduction in leukocyte-endothelial interactions. Levels of ICAM-1 increased in CO group compared to SH, and decreased in HS-treated groups (p=0.0002). CONCLUSIONS: Hypertonic saline improves mesenteric perfusion, increased eNOS and endothelin-1 protein expression, and reduced inflammation by decreasing leukocyte adhesion and migration in BD rats

Vasomotor tone is largely maintained by sympathetic nerves, myogenic reactivity and key local and circulating hormones. Acting together, these factors ensure moment-to-moment adjustments of net vascular tone required to maintain hemodynamic stability. In rat mesenteric small veins (MSV) and arteries (MSA), we investigated the contribution of the endothelium, L-type voltage operated calcium channels (L-VOCCs), PKC and Rho kinase to myogenic reactivity. The interaction of myogenic reactivity with norepinephrine (NE), endothelin-1 (ET-1), and sympathetic nerve activation was also investigated under conditions of changing transmural distending pressure. We also evaluated the relative contribution of alpha adrenergic (α-A) and endothelinergic receptors to NE and ET-1 contractile responses, respectively. Additionally, the effects of changing transmural pressure on endothelial dilator function of MSV were examined. Myogenic reactivity was not altered by nitric oxide synthase (NOS) inhibition or endothelium removal in both vessels. L-VOCCs blockade completely abolished arterial tone, while only partially reducing venous tone. PKC and Rho kinase inhibitors largely abolished venous and arterial myogenic reactivity. Increasing transmural pressure did not alter NE, ET-1, and bradykinin responses, but it significantly reduced neurogenic contractions. MSV were more sensitive to NE, ET-1 and sympathetic nerve activation compared with corresponding arteries. α-A and ET-1 receptor agonist and antagonist application revealed the participation of α1-A and ETA receptors in NE and ET-1 contractile responses, respectively. α2-A and ETB receptors appeared to mediate NE and ET-1 responses in MSV, respectively. Bradykinin induced-vasodilation was mainly reduced by NOS inhibition, and BKCa and SkCa blockade. These results suggest that myogenic factors are important contributors to net venous tone in MSV; PKC and Rho kinase activation are important to myogenic reactivity in both vessels, while L-VOCCs play a limited role in the veins versus the arteries; mesenteric veins maintain an enhanced sensitivity to NE, ET-1 and sympathetic nerve activation compared to the arteries with neurogenic contractions being affected by transmural pressure elevations; α1-ARs and ETA are the predominant receptors mediating contractile responses to NE and ET-1, respectively, with functional evidence indicating the presence of α2-ARs and ETB receptors in MSV; and venous endothelial dilator function is not affected by an elevation of transmural pressure. / Natural Sciences and Engineering Research Council of Canada (NSERC). Libyan Ministry of Education and Scientific Research.

Le système endothéline (ET) est activé en condition d’hypertension pulmonaire (HTP). L’efficacité des antagonistes des récepteurs à l’ET a clairement été démontrée et a menée à l’approbation clinique de tels antagonistes dans le traitement de l’hypertension artérielle pulmonaire (HTAP). Toutefois, il existe présentement un important débat opposant l’utilisation d’un antagoniste sélectif des récepteur ETA à l’utilisation d’un antagoniste double ETA/ETB dans le traitement de cette pathologie. Bien que nous sachions que le système ET est activé et contribue à l’HTAP, les modifications locales de ce système induites par la pathologie, particulièrement au niveau des artères de résistance pulmonaires, demeurent inconnues. De plus, l’impact de ces modifications sur la réponse pharmacologique aux divers antagonistes des récepteurs à l’ET (sélectifs versus double) est d’une importance capitale. Ainsi, le but de la première étude de cette thèse était d’évaluer les modifications potentielles de la pharmacologie du système ET au niveau des artères de résistance pulmonaires induites par l’HTAP. Dans cette étude, nous avons démontré qu’en condition contrôle l’antagoniste sélectif ETA et l’antagoniste double n’ont eu aucun effet sur la réponse vasoconstrictrice à l’ET-1. Toutefois, en condition d’HTAP, les antagonistes sélectif et double ont tous deux été en mesure de réduire la vasoconstriction pulmonaire induite par l’ET-1. Une diminution importante de l’expression génique du récepteur ETB pourrait être à l’origine de cette modification du profil pharmacologique des antagonistes. Une meilleure compréhension des rôles joués par les récepteurs ETA et ETB au niveau des artères de résistance pulmonaires pourrait permettre l’optimisation des traitements de l’HTAP. Ainsi, le but de la deuxième étude était d’évaluer les effets d’un traitement antisens ex vivo dirigé contre l’ARNm des récepteurs ETA et ETB dans la vasoconstriction des artères de résistance pulmonaires induite par l’ET-1. Dans cette étude, nous avons démontré dans un premier temps que les récepteurs ETA et ETB pouvaient former des dimères au niveau des artères de résistance pulmonaires. De plus, nous avons observé qu’une réduction de l’expression protéique du R-ETA entraînait une potentialisation de la vasoconstriction ETB dépendante suggérant ainsi qu’en condition contrôle, le récepteur ETA aurait un effet inhibiteur sur la vasoconstriction pulmonaire induite par la stimulation du récepteur ETB. Les effets délétères de l’ET-1 sur la circulation pulmonaire sont bien connus, toutefois seules quelques études ont porté leur attention sur l’implication de l’ET-3 dans l’HTAP. Ainsi, le but de la troisième étude était d’évaluer l’implication potentielle de l’ET-3 dans l’HTAP. Dans cette étude, nous avons démontré qu’il était nécessaire en condition contrôle de bloquer simultanément les récepteurs ETA et ETB afin de réduire la réponse vasoconstrictrice pulmonaire à l’ET-3. En condition d’HTAP, nous avons observé une augmentation non-significative des concentrations plasmatiques d’ET-3 ainsi qu’une modification du profil pharmacologique des antagonistes des récepteurs à l’ET. En effet, l’utilisation de l’antagoniste sélectif ETA ou de l’antagoniste double était dans les deux cas en mesure de réduire la vasoconstriction pulmonaire à l’ET-3. Les résultats de ces trois études suggèrent qu’il est préférable d’utiliser un antagoniste double dans le traitement de l’HTAP. En effet, (1) en condition d’HTAP, l’utilisation d’un antagoniste double est aussi efficace que l’utilisation d’un antagoniste sélectif ETA; (2) les récepteurs ETA et ETB peuvent former des dimères au niveau des artères de résistance pulmonaires et (3) le récepteur ETB joue un rôle prédominant dans la vasoconstriction pulmonaire, il semble donc essentiel de bloquer simultanément les récepteurs ETA et ETB afin d’inhiber la réponse vasoconstrictrice induite par l’ET. Mots-clés: endothéline-1, endothéline-3, artère de résistance pulmonaire, récepteur vasculaire, antagoniste des récepteurs à l’ET, dimérisation, phosphorothioate, hypertension artérielle pulmonaire / The endothelin (ET) system is activated in pulmonary arterial hypertension (PAH); indeed, increased plasma levels of ET-1 were detected in patients with various forms of PAH and in various experimental models. The therapeutic value of pharmacological blockade of ET receptors has been demonstrated in various animal models and led to the current approval and continued development of these drugs for the therapy of human PAH. Whether the net effect of either selective ETA receptor blockade or combined ETA/ETB receptor blockade provides greater therapeutic benefit remains a subject of debate. Although the ET system contributes to PAH, we currently incompletely comprehend which local modifications of this system occur as a consequence of PAH, particularly in small resistance arteries, and how this could affect the pharmacological response to ET receptor antagonists. The purpose of the first study was therefore to evaluate potential modifications of the pharmacology of the ET system in rat pulmonary resistance arteries from monocrotaline-induced PAH. Our results reveal striking changes in pulmonary vasculature sensitivity to ET receptor antagonism in PAH that may be related to a reduction in ETB receptor expression. A better understanding of the exact role played by both ETA and ETB receptors on pulmonary resistance arteries might contribute to optimization of PAH treatments. Therefore the aim of the second study was to clarify the role played by both ETA and ETB receptors in ET-1 induced pulmonary vasoconstriction using an antisense (AS) oligonucleotide ex vivo treatment. In this study we have demonstrated that ETA and ETB receptors can form heterodimers in pulmonary resistance arteries. Furthermore, suppression of ETA receptors potentiated the response to ET-1 suggesting that in control condition the ETA receptor has an inhibitory action on the ET-1 induced pulmonary vasoconstriction induced by the stimulation of the ETB receptor. Although the deleterious effects of ET-1 on the pulmonary circulation are well established, only a few studies have focused on ET-3 in PAH. Therefore, the purpose of the last study was to evaluate the potential implication of ET-3 in MCT-induced PAH and evaluate the roles of ETA and ETB receptors on ET-3-induced pulmonary vascular reactivity. In control condition, the use of a combination of both ETA and ETB receptor antagonists is necessary to reduce the ET-3 induced pulmonary vasoconstriction. In PAH, we found an increased ET-3 plasma levels and a modification of the pharmacological profile of ET receptor antagonists. Indeed, the use of either the ETA receptor antagonist or the dual antagonist was able to reduce the ET-3 response. The results from these three studies suggest that it is preferable to use a dual antagonist in the treatment of PAH. Indeed, (1) in PAH the use of a dual antagonist is as effective as the use of a selective ETA receptor antagonist (2) ETA and ETB receptors can form heterodimers in pulmonary resistance arteries and (3) ETB receptor plays an important role in the ET-1 induced pulmonary vasoconstriction, suggesting that it is necessary to block both receptors to reduce the ET-1 induced pulmonary vasoconstriction. Keywords: endothelin-1, endothelin-3, pulmonary resistance artery, receptor, endothelin receptor antagonist, dimerisation, phosphorothioate pulmonary arterial hypertension

One major reason of CNS pharmacotherapy's impediment is the existence of "barriers" between blood and CNS, especially the Blood-Brain Barrier (BBB), a neurovascular structure localized at the level of brain microvasculature. Main factors responsible for this barrier function are drug efflux transporters type ABC (ATP-Binding Cassette) and SLC (SoLute Carrier) expressed at BBB level and known to be at the origin of multi-drug resistance phenomenon. Recent researches aim at unraveling the signaling mechanisms regulating these transporters in order to modulate their activity and improve pharmacotherapy in brain diseases. For years, these transporters have been studied in adult organism. But, there is a wide spread belief that the BBB in embryo, fetus, new born and infant is "immature", implying caution in giving drugs to infants. However, current knowledge on the functional status of the BBB in immature organism remains very limited.This study was performed in the aim of understanding: 1) The ontogenesis of ABC and SLC transporters during brain maturation, 2) the functional role of four BBB drug efflux transporters (P-glycoprotein (P-gp), Breast Cancer Resistance Protein (bcrp), Organic Anion Transporter 3 (oat3), and Transporting Peptide 1a4 (oatp1a4) transporters) in children's brain, and 3) the mechanisms that regulate their functional expression under normal and pathological conditions, mostly under inflammatory conditions, because indeed alterations in structural and functional components of the BBB have been reported in a long list of CNS pathologies in adults. Our results showed changing properties of the BBB during ontogenesis, as well as an age-related differential regulation of BBB drug efflux transporters under normal and inflammatory conditions.These findings highlight the importance of considering an age-related response of CNS to drugs and of taking into account the specific properties of juvenile BBB during definition of therapeutic strategies designed to treat childhood brain diseases, and this in the clinical perspective of developing new drugs with enhanced efficacy in children's CNS.

INTRODUÇÂO: A morte encefálica (ME) induz instabilidade hemodinâmica com hipoperfusão microcirculatória, desencadeando inflamação e disfunção de órgãos. OBJETIVO: Este estudo teve como objetivo investigar os efeitos da solução salina hipertônica (SH) 7,5% na evolução da resposta inflamatória no tecido mesentérico de ratos submetidos à ME. MÉTODOS: Ratos Wistar machos foram anestesiados e ventilados mecanicamente. A ME foi induzida pela insuflação rápida de um balão posicionado na cavidade intracraniana (Fogart 4F). Os ratos foram divididos aleatoriamente em: 1) Falso-operado, ratos submetidos aos procedimentos cirúrgicos e trepanação (FO, n=17); 2) Controle, ratos tratados com solução salina isotônica (NaCl 0,9%, 4 mL/kg) imediatamente após ME (CO, n=17); 3) Solução hipertônica 1, ratos tratados com solução hipertônica (NaCl 7,5%, 4 mL/kg) imediatamente após ME (SH1, n=17); 4) Solução hipertônica 60, ratos tratados com solução hipertônica 60 min após ME (SH60, n=17). Três horas após a indução da ME ou o término do procedimento cirúrgico para os animais do grupo FO, foram coletados os seguintes dados: (a) perfusão mesentérica, fluxo sanguíneo e interações leucócito-endotélio no mesentério, pela técnica de microscopia intravital; (b) expressão de proteínas de óxido nítrico sintase endotelial (eNOS), endotelina-1, P-selectina e molécula de adesão intercelular (ICAM)-1, por imunohistoquímica; (c) expressão gênica de eNOS e endotelina-1, por reação em cadeia da polimerase em tempo real (PCR); (d) concentrações séricas de citocinas, quimiocinas e corticosterona por meio de enzimaimunoensaio (ELISA). RESULTADOS: Todos os grupos submetidos a ME apresentaram um comportamento semelhante da pressão arterial, sendo observado um pico hipertensivo, seguido de período de hipotensão, logo após a insuflação do cateter intra-craniano. A proporção de pequenos vasos perfundidos foi diminuída no grupo CO (46%) em comparação com FO (74%, p=0,0039). A SH foi capaz de restaurar a proporção de vasos perfundidos (SH1=71%, p=0,0018). Não houve diferenças no fluxo sanguíneo mesentérico entre os grupos. A expressão proteica de eNOS aumentou significativamente em ratos com SH (SH1 e SH60, p=0,0002) em comparação ao grupo CO. Resultados semelhantes foram observados em relação à endotelina-1 (p < 0,0001). Não houve diferenças na expressão gênica de eNOS e endotelina-1. O aumento no número de leucócitos \"rollers\" (p=0,0015) e migrados (p=0,0063) foi observado no grupo CO em comparação com FO. Ratos com SH demonstraram redução significativa em todos os parâmetros da interação leucócito-endotélio. Com relação às moléculas de adesão, a expressão de ICAM-1 estava elevada no grupo CO em comparação com o FO, enquanto que o tratamento com SH diminuiu a expressão de ICAM-1 (SH1 e SH60, p=0,0002). CONCLUSÕES: O emprego da solução salina hipertônica melhorou a perfusão mesentérica, influenciou positivamente o metabolismo do óxido nítrico e reduziu a inflamação no mesentério, com diminuição da adesão e migração leucocitária, em ratos submetidos a ME / BACKGROUND: Brain death (BD) induces hemodynamic instability with microcirculatory hypoperfusion leading to increased organ inflammation and dysfunction. OBJETIVE: To investigate the effects of 7.5% hypertonic saline solution (HS) on the course of the inflammatory response in rats submitted to BD. METHODS: Male Wistar rats were anesthetized and mechanically ventilated. BD was induced by rapid inflation of intracranial balloon catheter (Fogart 4F). Rats were randomly divided in: 1) Sham-operated, rats submitted only to trepanation (SH, n=17); 2) Control, rats treated with normal saline solution (NaCl 0.9%, 4 mL/kg) immediately after BD (CO, n=17); 3) Hypertonic solution 1, rats treated with hypertonic solution (NaCl 7.5%, 4 mL/kg) immediately after BD (HS1, n=17); 4) Hypertonic solution 60, rats treated with hypertonic solution 60 min after BD (HS60, n=17). Hundred eighty minutes thereafter the following experiments were performed: (a) mesenteric perfusion, blood flow, and leukocyte-endothelial interactions, by intravital microscopy; (b) protein expression of endothelial nitric oxide synthase (eNOS), endothelin-1, P-selectin, and intercellular cell adhesion molecule (ICAM)-1, by immunohistochemistry; (c) gene expression of eNOS, and endothelin-1, by real-time polymerase chain reaction (PCR); (d) serum concentrations of cytokines, chemokines and corticosterone by enzyme-linked immunosorbent assay (ELISA). RESULTS: All BD groups presented similar hypertensive peak followed by hypotension. The proportion of perfused small vessels was decreased in CO group (46%) compared to SH (74%, p=0.0039). HS was able to restore the proportion of perfused vessels (HS1=71%, p=0.0018). There were no differences in mesenteric blood flow between groups. eNOS protein expression significantly increased in rats given HS (HS1, and HS60, p=0.0002). Similar results were observed regarding endothelin-1 (p < 0.0001). There were no differences in eNOS and endothelin-1 gene expression. Increased numbers of rolling (p=0.0015) and migrated (p=0.0063) leukocytes were observed in CO group compared to SH. Rats given HS demonstrated an overall reduction in leukocyte-endothelial interactions. Levels of ICAM-1 increased in CO group compared to SH, and decreased in HS-treated groups (p=0.0002). CONCLUSIONS: Hypertonic saline improves mesenteric perfusion, increased eNOS and endothelin-1 protein expression, and reduced inflammation by decreasing leukocyte adhesion and migration in BD rats

Les récepteurs de type B de l'endothéline (ETB) sont présents sur l'enveloppe nucléaire des cardiomyocytes ventriculaires adultes (MVCAs). Il a été démontré que dans les MVCAs et les cellules endothéliales de rat, l’endocytose de l’endothéline marqué à la rhodamine colocalise avec le Lysotracker, un marqueur des lysosomes, mais n'est pas observée sur l’enveloppe nucléaire. Dans cette étude, nous avons caractérisé la localisation subcellulaire et la régulation de la biosynthèse de l’endothéline 1 dans les MVCAs et les fibroblastes cardiaques adultes de rat. Dans les deux types cellulaires les expériences d’immunocytofluorescence ont révélé une immunoréactivité de l’endothéline 1 correspondant à tous les stades de maturation du peptide, et détectable sur ou à proximité de la membrane nucléaire. L'enzyme de conversion d'endothéline 1(ECE1) est une métalloprotéase qui convertit la ̏ big˝ endothéline 1 en un peptide de 21 acides aminés biologiquement actif. L’immunoréactivité de l’ECE1 a été associée avec les tubules-T et les membranes nucléaires ou périnucléaires dans les MVCAs. Par contre, nous avons observé une immunoréactivité de l’ECE1 à la fois dans le noyau et le cytoplasme, mais pas sur la membrane plasmatique, dans les fibroblastes cardiaques à passage 3. L'ARNm de l’ET-1 a été détecté dans les deux types cellulaires. La régulation de la production de l'endothéline est principalement transcriptionnelle. L’application du facteur de croissance transformant ß1 (TGFß1) a augmenté l’ARNm de l’ET-1 dans les MVCAs et l'angiotensine II a stimulé l'augmentation de l’ARNm de l'ET-1 dans les fibroblastes. Dans les MVCAs, l'augmentation de l'ARNm ET-1 a été associée à une élévation du peptide intracellulaire ET-1 et du calcium nucléaire. Ces données suggèrent que l'endothéline endogène est disponible et serait capable d’activer le récepteur ETB nucléaire dans les MVCAs en réponse à des stimuli extracellulaires. / Type B endothelin receptors (ETB) are located in the nuclear envelope of adult ventricular cardiomyocytes (ACVMs). In both ACVMs and endothelial cells, endocytosed rhodamine endothelin colocalized with Lysotracker but was not observed at the nuclear membrane. In this study we have characterized the regulation and subcellular localization of endothelin biosynthesis in ACVMs and adult cardiac fibroblasts. In both cell types immunocytofluorescence experiments revealed endothelin-1 immunoreactivity, comprising all stages of peptide maturation, either on or near the nuclear membrane. Endothelin converting enzyme 1 (ECE1) is a metalloprotease that converts big endothelin to the biologically active 21-amino acid peptide. ECE1 immunoreactivity was associated with the T-tubules and nuclear or perinuclear membranes in ACVMs. In contrast, ECE1 immunoreactivity was observed both in the nucleus and the cytosol, but not at the plasma membrane, in passage 3 cardiac fibroblasts. Endothelin-1 mRNA was detected in both cell types. Regulation of endothelin production is primarily at the level of transcription. Application of TGFβ1 increased ET-1 mRNA in ACVMs whereas angiotensin II was effective in increasing ET-1 mRNA in fibroblasts. In AVCMs, the increase in ET-1 mRNA was associated with an increase of intracellular ET-1 peptide and nuclear calcium. These data suggest that endogenous endothelin is available and may activate nuclear ETB in ACVMs in response to extracellular stimuli.

Hypoxic-ischemic insult is a most common form of perinatal brain damage that threatens a newborn's life and can leads to permanent neurological sequelae. However, detailed aspects of the cerebral ischemia in the immature brain stay unanswered. We decide to use the model of focal cerebral ischemia induced by intrahippocampal endothelin-1 (ET-1) in 12-days-old rats. The knowledge about consequences of ET-1 induced ischemia and the role of endothelin receptors (ETA and ETB) in ischemia-induced consequences in immature brain are poor at present. Agonists and selective antagonists of the ETA and ETB receptors were used to determine the role of these receptors in the development of ischemia, changes in regional blood flow and tissue oxygenation, local changes of biochemical parameters and acute neuronal death. Our results indicates, that activation of the ETA receptors causes a strong decrease of the blood flow, induced related hypoxia and subsequent neuronal degeneration, whereas activation of ETB receptors has likely modulatory role. Moreover, ischemia causes increase of excitatory amino acids concentration, whereas inhibitory amino acid, except taurine, decreased after ischemia. These facts provides new insights in a case of perinatal ischemia. This thesis demonstrates the wide range of different effects of...

Le stress oxydatif est impliqué dans l’expression du récepteur B1 des kinines (RB1) dans différents modèles de diabète et d'hypertension. Puisque l'angiotensine II (Ang II) et l'endothéline-1 (ET-1) sont des peptides prooxydants impliqués dans les maladies cardiovasculaires, leur contribution dans l'augmentation de l'expression du RB1 a été étudiée dans des cellules musculaires lisses vasculaires (CMLV). Le QRT-PCR et l’immunobuvardage de type Western ont été utilisés pour mesurer l’expression du RB1 dans des CMLV dérivées de la lignée A10 et de l’aorte de rats Sprague-Dawley. Cette étude montre que l’Ang II augmente l’expression du RB1 (ARNm et protéine) en fonction de la concentration et du temps (maximum 1 μM entre 3-6 h). Cette augmentation implique le récepteur AT1, la PI3K et le NF-κB, mais non le récepteur AT2 et ERK1/2. Aussi, le récepteur ETA de l’ET-1 est impliqué dans la réponse à l’Ang II à 6-8 h et non à 1-4 h. Par contre, l’ET-1 augmente l’expression du RB1 (maximum 2-4 h) via la stimulation des récepteurs ETA et ETB. L’augmentation du RB1 causée par l’Ang II et l’ET-1 est bloquée par les antioxydants (N-acétyl-cystéine et diphénylèneiodonium). Ces résultats suggèrent que l’Ang II induit le RB1 dans les CMLV par le récepteur AT1 dans la première phase, et par la libération d’ET-1 (majoritairement par ETA) dans la phase tardive, via le stress oxydatif et l’activation de la PI3K et du NF-κB. Ces résultats précisent le mécanisme impliqué dans la surexpression du RB1 ayant des effets néfastes dans le diabète et l'hypertension. / Oxidative stress is involved in the overexpression of kinin B1 receptor (B1R) in various models of diabetes and hypertension. Since angiotensin II (Ang II) and endothelin-1 (ET-1) are pro-oxidative peptides involved in cardiovascular diseases, their contribution in increasing the expression of B1R was examined in vascular smooth muscle cells (VSMC). QRT-PCR and Western blot analysis were used to measure the expression of B1R in VSMC derived from A10 cell line and the aorta of Sprague-Dawley rats. This study shows that Ang II increases the expression of B1R (mRNA and protein) in a concentration- and time-dependent manner (maximum 1 μM between 3-6 h). This increase involves AT1 receptor, PI3K and NF-κB, but not AT2 receptor and ERK1/2. Moreover, ETA receptor is involved in the effect of Ang II at 6-8 h but not at 1-4 h. However, ET-1 increases expression of B1R (maximum 2-4 h) via stimulation of ETA and ETB receptors. Ang II and ET-1-induced increase expression of B1R is blocked by antioxidants (N-acetyl-L-cysteine and diphenyleneiodonium). These results suggest that Ang II induces B1R in VSMC by AT1 receptor in the first phase and by releasing ET-1 (predominantly by ETA receptor) in the late phase, via oxidative stress and activation of PI3K and NF-κB. These results clarify the mechanism involved in the overexpression of B1R which has adverse effects in diabetes and hypertension.