BACKGROUND: Pulmonary Hypertension (PH) is a common form of high blood pressure in the lungs. It affects the pulmonary arteries, which normally allow blood to flow from the right heart to the lungs. Nitric Oxide (NO) is a potential mediator for establishing PH and decreasing its availability is implicated in the pathogenesis of PH. HYPOTHESIS: We tested the hypothesis that Fractional Exhaled Nitric Oxide (FeNO) is a good indicator to assess disease severity that may add to understanding the disease. METHODS: The aim of the study was to measure FeNO levels in consecutive PH patients and seek correlations with the 6 Minute walk distance (6MWD) within different World Health Organization (WHO) groups and New York Health Association Function Class (NYHA FC). Assignment to groups I or IV was done respecting the current guidelines. All values were taken at Tufts Medical Center PAH clinic visits. FeNO levels were measured utilizing the NIOX device. RESULTS: FeNO levels were highest in WHO Group 1 and lowest in WHO Group 5 patients. There was a strong inverse correlation between FeNO and 6MWD for each NYHA FC. (Pearson correlation of -0.986, p = 0.014). Within WHO Groups, we found significantly inverse correlations between FeNO and 6MWD in PH Group 4 (p= 0.012) and PH Group 5 (p=0.001). NYHA FC correlated with 6MWD across all WHO Groups (P=0.001). CONCLUSION: We report for the first time FeNO levels in all WHO Groups of PH. FeNO levels are low in early disease. FeNO levels correlate inversely with the severity of PH in WHO Group 4 and 5 patients. The increase in FeNO in more severe patients may reflect the degree of oxidative stress and inflammation in severe PH. Further studies to determine whether FeNO may be a biomarker in early disease, especially in PH Group 4 and 5 warrants further investigation.

No description available.

Yes / Pulmonary Arterial Hypertension (PAH) is a devastating cardiovascular disorder characterised by the remodelling of pre-capillary pulmonary arteries. The vascular remodelling observed in PAH patients results from excessive proliferation and apoptosis resistance of pulmonary arterial smooth muscle (PASMCs) and endothelial cells (PAECs). We have previously demonstrated that mutations in the type II receptor for bone morphogenetic protein (BMPRII) underlie the majority of the familial and inherited forms of the disease. We have further demonstrated that BMPRII deficiency promotes excessive proliferation and attenuates apoptosis in PASMCs, but the underlying mechanisms remain unclear. The major objective of this study is to investigate how BMPRII deficiency impairs apoptosis in PAH. Using multidisciplinary approaches, we demonstrate that deficiency in the expression of BMPRII impairs apoptosis by modulating the alternative splicing of the apoptotic regulator, Bcl-x (B-cell lymphoma X) transcripts: a finding observed in circulating leukocytes and lungs of PAH subjects, hypoxia-induced PAH rat lungs as well as in PASMCs and PAECs. BMPRII deficiency elicits cell specific effects: promoting the expression of Bcl-xL transcripts in PASMCs whilst inhibiting it in ECs, thus exerting differential apoptotic effects in these cells. The pro-survival effect of BMPRII receptor is mediated through the activin receptor like kinase 1 (ALK1) but not the ALK3 receptor. Finally, we show that BMPRII interacts with the ALK1 receptor and pathogenic mutations in the BMPR2 gene abolish this interaction. Taken together, dysfunctional BMPRII responsiveness impairs apoptosis via the BMPRII-ALK1-Bcl-xL pathway in PAH. We suggest Bcl-xL as a potential biomarker and druggable target. / This work was supported by a fellowship (awarded to MTN) from the Department of Health via the NIHR Comprehensive Biomedical Research Centre award to Guy’s & St Thomas’ NHS Foundation Trust in partnership with King’s College London, Heptagon Life Science Proof of Concept Fund (grant KCL24 to MTN), the Great Britain Sasakawa Foundation (grant B70 to MTN), the Royal Society (grant 43049 to MTN), the Medical Research Council (grant G900865 to RCT, MTN and NWM) and the University of Bradford (grants 003200, 66006/001NAS and DH005 to MTN). NS and MYB were supported by scholarships from the Commonwealth Scholarship Commission, UK and Scientific and Technological Research Council of Turkey (TUBITAK), respectively.

No description available.

Introdução: Vários genes, particularmente os envolvidos na via de transcrição Transforming Growth Factor beta, estão claramente associados ao risco de desenvolvimento de hipertensão arterial pulmonar. Entretanto, pouco ou quase nada se sabe sobre a existência de fatores genéticos que possam estar associados a uma das formas mais prevalentes de hipertensão arterial pulmonar no mundo, a hipertensão arterial pulmonar associada a esquistossomose (HAP-Sch). O objetivo deste estudo foi avaliar a associação dos genes já descritos na hipertensão arterial pulmonar idiopática (HAPI) com a HAP-Sch. Método: Estudo transversal, comparando amostras de pacientes seguidos no ambulatório de Circulação Pulmonar no Instituto do Coração do HCFMUSP, com diagnóstico de HAP-Sch ou HAPI. Foram avaliadas as características genéticas nestes grupos quanto à presença de variantes patogênicas dos genes:BMPR2, ACVRL1, KCNK3, KCNK5, CAV-1, CBLN2, ENG, andSMAD9. Resultados: Foram incluídos 69 pacientes com HAP-Sch e 74 pacientes com HAPI. O grupo HAP-Sch apresentou idade mais avançada (52.1 ± 11.8 vs 41.5 ± 15.0; p = < 0,001) e débito cardíaco mais preservado ao diagnóstico (4.7 ± 1.9 vs 4.0 ± 1.4 p = 0.019). Cerca de 24% dos pacientes com HAPI apresentaram resposta aguda durante o teste de vasorreatividade, enquanto nenhum paciente com HAP-Sch apresentou resposta (p =< 0.001). Pacientes com HAP-Sch apresentaram 7% de variantes patogênicas, comparado com11% dos HAPI(p=0,782). Em ambos os grupos, pacientes portadores de variantes patogênicas possuíam características clínicas e hemodinâmicas semelhantes aos demais pacientes. No grupo HAP-Sch, a sobrevida dos portadores de variantes patogênicas foi significativamente menor (p=0.035). Conclusão: A prevalência de variantes patogênicas na HAP-Sch é semelhante à encontrada na HAPI e, da mesma forma, sua presença está associada a pior prognóstico / Background: Several genes, mainly those involved with the Transforming Growth Factor ? transcription pathway, are well-defined as risk factors for developing pulmonary arterial hypertension. Nevertheless, little is known about the existence of a genetic background associated with one of the most prevalent forms of pulmonary arterial hypertension worldwide, which is schistosomiasis associated pulmonary arterial hypertension (Sch-PAH). The aim of this study was to evaluate the association of genes already described in idiopathic pulmonary arterial hypertension (IPAH) with Sch-PAH. Method: A cross-sectional study comparing samples from patients followed at the Pulmonary Circulation clinic at the Heart Institute of HCFMUSP, diagnosed as Sch-PAH or IPAH. Genetic characteristics in these groups were evaluated for the presence of pathogenic variants of the genes: BMPR2, ACVRL1, KCNK3, KCNK5, CAV-1, CBLN2, ENG, and SMAD9.Results: A total of 69 patients with Sch-PAH and 74 patients with IPAH were included. The Sch-PAH group presented older age (52.1 ± 11.8 vs 41.5 ± 15.0, p =< 0.001) and higher cardiac output at diagnosis (4.7 ± 1.9 vs 4.0 ± 1.4 p = 0.019). About 24% of patients with IPAH presented acute response during the vasoreactivity test, whereas no Sch-PAH patient presented response (p = < 0.001). Patients with PAH-Sch had 7% prevalence of pathogenic variants, compared to 11% in IPAH (p = 0.782). In both groups, patients with pathogenic variants had clinical and hemodynamic characteristics similar to the other patients. In the Sch-PAH group, the survival of patients with pathogenic variants was significantly lower (p = 0.035). Conclusion: The prevalence of pathogenic variants in Sch-PAH is similar to that found in IPAH and, likewise, its presence is associated with worse prognosis

Introdução: Vários genes, particularmente os envolvidos na via de transcrição Transforming Growth Factor beta, estão claramente associados ao risco de desenvolvimento de hipertensão arterial pulmonar. Entretanto, pouco ou quase nada se sabe sobre a existência de fatores genéticos que possam estar associados a uma das formas mais prevalentes de hipertensão arterial pulmonar no mundo, a hipertensão arterial pulmonar associada a esquistossomose (HAP-Sch). O objetivo deste estudo foi avaliar a associação dos genes já descritos na hipertensão arterial pulmonar idiopática (HAPI) com a HAP-Sch. Método: Estudo transversal, comparando amostras de pacientes seguidos no ambulatório de Circulação Pulmonar no Instituto do Coração do HCFMUSP, com diagnóstico de HAP-Sch ou HAPI. Foram avaliadas as características genéticas nestes grupos quanto à presença de variantes patogênicas dos genes:BMPR2, ACVRL1, KCNK3, KCNK5, CAV-1, CBLN2, ENG, andSMAD9. Resultados: Foram incluídos 69 pacientes com HAP-Sch e 74 pacientes com HAPI. O grupo HAP-Sch apresentou idade mais avançada (52.1 ± 11.8 vs 41.5 ± 15.0; p = < 0,001) e débito cardíaco mais preservado ao diagnóstico (4.7 ± 1.9 vs 4.0 ± 1.4 p = 0.019). Cerca de 24% dos pacientes com HAPI apresentaram resposta aguda durante o teste de vasorreatividade, enquanto nenhum paciente com HAP-Sch apresentou resposta (p =< 0.001). Pacientes com HAP-Sch apresentaram 7% de variantes patogênicas, comparado com11% dos HAPI(p=0,782). Em ambos os grupos, pacientes portadores de variantes patogênicas possuíam características clínicas e hemodinâmicas semelhantes aos demais pacientes. No grupo HAP-Sch, a sobrevida dos portadores de variantes patogênicas foi significativamente menor (p=0.035). Conclusão: A prevalência de variantes patogênicas na HAP-Sch é semelhante à encontrada na HAPI e, da mesma forma, sua presença está associada a pior prognóstico / Background: Several genes, mainly those involved with the Transforming Growth Factor ? transcription pathway, are well-defined as risk factors for developing pulmonary arterial hypertension. Nevertheless, little is known about the existence of a genetic background associated with one of the most prevalent forms of pulmonary arterial hypertension worldwide, which is schistosomiasis associated pulmonary arterial hypertension (Sch-PAH). The aim of this study was to evaluate the association of genes already described in idiopathic pulmonary arterial hypertension (IPAH) with Sch-PAH. Method: A cross-sectional study comparing samples from patients followed at the Pulmonary Circulation clinic at the Heart Institute of HCFMUSP, diagnosed as Sch-PAH or IPAH. Genetic characteristics in these groups were evaluated for the presence of pathogenic variants of the genes: BMPR2, ACVRL1, KCNK3, KCNK5, CAV-1, CBLN2, ENG, and SMAD9.Results: A total of 69 patients with Sch-PAH and 74 patients with IPAH were included. The Sch-PAH group presented older age (52.1 ± 11.8 vs 41.5 ± 15.0, p =< 0.001) and higher cardiac output at diagnosis (4.7 ± 1.9 vs 4.0 ± 1.4 p = 0.019). About 24% of patients with IPAH presented acute response during the vasoreactivity test, whereas no Sch-PAH patient presented response (p = < 0.001). Patients with PAH-Sch had 7% prevalence of pathogenic variants, compared to 11% in IPAH (p = 0.782). In both groups, patients with pathogenic variants had clinical and hemodynamic characteristics similar to the other patients. In the Sch-PAH group, the survival of patients with pathogenic variants was significantly lower (p = 0.035). Conclusion: The prevalence of pathogenic variants in Sch-PAH is similar to that found in IPAH and, likewise, its presence is associated with worse prognosis

L'hypertension artérielle pulmonaire (HTAP) est caractérisée par une atteinte progressive et chronique des vaisseaux pulmonaires entraînant une augmentation des résistances vasculaires pulmonaires. Mes travaux de doctorat ont eu pour but de comprendre l'implication des progéniteurs vasculaires dans le remodelage et dans la néomuscularisation des vaisseaux pulmonaires, caractéristique de l'HTAP. Une nouvelle population de cellules progénitrices positives pour le marqueur PW1, récemment identifiée dans les tissus adultes, a la capacité de se différencier en cellules musculaires lisses (CMLs). Notre hypothèse a donc été que cette population progénitrice pourrait être recrutée, se différencierait en CMLs et participerait ainsi au remodelage vasculaire au cours de l'HTAP. Nous avons mis en évidence la présence de trois populations progénitrices PW1+ dans le poumon de souris, capables de se différencier en CMLs vasculaires. Les cellules PW1+ sont résidentes et sont mobilisées dans 2 modèles d'HTAP; leur recrutement est précoce, dès 4j d'hypoxie chronique chez la souris ; le nombre de cellules PW1+ est augmenté chez le rat traité à la monocrotaline. Des résultats préliminaires suggèrent une implication des macrophages et de la voie CXCR4 dans ce recrutement des progéniteurs PW1+. Chez le patient HTAP, les cellules PW1+ sont très nombreuses dans les lésions artérielles et nous avons commencé à les isoler par FACS. Cette meilleure compréhension des mécanismes de mobilisation des progéniteurs vasculaires permet d'identifier des pistes thérapeutiques potentielles, et d'encourager à poursuivre les recherches sur ce versant cellulaire encore peu exploité dans cette maladie. / Pulmonary arterial hypertension (PAH) is characterized by vascular remodeling and neomuscularization. PW1+ progenitor cells were identified in various adult tissues and can differentiate in smooth muscle cells (SMC) in vitro. Our hypothesis was that PW1+ progenitor cells are recruited to participate in the vascular remodeling during PAH. PW1+ cells are localized in the lung parenchyma and in the perivascular zone in rodent and human lungs. Three resident myogenic PW1+ populations were identified in the mouse lung. After 4 days of CH, two of these PW1+ populations were significantly increased. The number of pulmonary proliferating PW1+ cells and the proportion of vessel-associated SMC derived from PW1+ cells were also significantly increased, attesting a recruitment and a differentiation of PW1+ cells into pulmonary vascular SMC during early chronic hypoxia-induced neomuscularization. Moreover, in the MCT-injected rat lungs, a severe PH model, the number of PW1+ cells was also increased. Preliminary data suggest that macrophages and CXCR4 axis are involved in the mobilization of PW1+ progenitor cells. In the human PAH lung, PW1+ cells were observed in remodeled vascular structures and seem increased as compared to control lung. A better understanding of vascular progenitor cells mobilization mechanisms will help determining the pathological pathways involved in the disease and identifying new potential therapeutic avenues.

L'hypertension artérielle pulmonaire (HTAP) est une maladie rare caractérisée par une augmentation de la pression artérielle pulmonaire moyenne liée à un important remodelage de la paroi vasculaire obstruant progressivement les petites artères pulmonaires. Le récepteur NMDA (NMDAR) est un récepteur au glutamate jouant un rôle crucial dans la transmission synaptique neuronale. Il est aussi présent dans des cellules périphériques, notamment les cellules vasculaires aortiques et cérébrales, et participe à leur prolifération. De plus, le NMDAR contribue à la prolifération des cellules cancéreuses. Puisque dans l'HTAP, les cellules vasculaires pulmonaires présentent un phénotype cancer-like, hyperprolifératif et résistant à l'apoptose, nous avons émis l'hypothèse selon laquelle les NMDARs vasculaires pulmonaires pourraient contribuer au remodelage vasculaire et conduire à l'HTAP. Nous avons montré que les cellules vasculaires pulmonaires expriment physiologiquement les principaux éléments d'une communication glutamatergique fonctionnelle via le NMDAR. Dans l'HTAP, le glutamate s'accumule dans les vaisseaux remodelés et l'endothéline-1, un acteur majeur du remodelage vasculaire, induit la libération du glutamate par les cellules musculaires lisses. Le NMDAR est mobilisé dans les cellules vasculaires et sa fonction pourrait être altérée en raison d'un déséquilibre dans le ratio d'expression de ses sous-unités. L'activation du NMDAR contribue à la prolifération des cellules vasculaires pulmonaires et à l'angiogenèse, éléments clés de la physiopathologie de l'HTAP. Des études réalisées sur des souris n'exprimant pas les NMDARs vasculaires ou utilisant des antagonistes du NMDAR mettent en évidence le rôle du NMDAR dans l'hypertension pulmonaire expérimentale. Ces résultats suggèrent que le NMDAR est un nouvel acteur du remodelage vasculaire et qu'il représente une nouvelle cible thérapeutique de l'HTAP. Ils apportent également de nouveaux éléments alimentant l'analogie entre le système vasculaire et le système nerveux. / Pulmonary arterial hypertension (PAH) is a rare disease characterized by an increase in the mean pulmonary arterial pressure, due to a deep vascular remodeling leading to the progressive obstruction of the small pulmonary arteries. The NMDA receptor (NMDAR) is a glutamate receptor playing a crucial role in the neuronal synaptic communication. It is also present in peripheral cells, including aortic and cerebral vascular cells, and promotes their proliferation. Moreover, NMDAR contributes to proliferation of cancer cells. As pulmonary vascular cells exhibit a cancer-like hyperproliferative and apoptotic-resistant phenotype in PAH, we hypothesized that the activation of pulmonary vascular NMDARs may contribute to the vascular remodeling leading to PAH. We found that pulmonary vascular cells express the main features of a functional synaptic-like glutamatergic communication through NMDARs. In PAH, glutamate accumulates in pulmonary arteries, and endothelin-1, a major actor of the PAH-associated vascular remodeling, triggers glutamate release from smooth muscle cells. Furthermore, the NMDAR is mobilized and its function may be altered due to an unbalanced expression ratio of the NMDAR subunits. Moreover, NMDAR activation contributes to vascular cell proliferation and angiogenesis, key features of PAH pathophysiology. Finally, studies with NMDAR antagonists and vascular NMDAR-knockout mice showed that vascular NMDARs are involved in pulmonary hypertension. These results suggest that NMDAR is a new actor of the vascular remodeling and could represent a new therapeutic target in PAH. They also bring new pieces to the vascular/nervous parallels.

L’hypertension artérielle pulmonaire (HTAP) est une maladie mortelle caractérisée par un important remodelage vasculaire, principalement dû à l’hyperprolifération et à la résistance à l’apoptose des cellules du muscle lisse de l’artère pulmonaire (CML-AP). Récemment il a été montré que les CML-AP présentent un remodelage du métabolisme énergétique, avec une régulation négative de l’oxidation phosphorylante associée à une activation de la voie glycolytique, qui semble contribuer à leur phénotype particulier. La désacétylase sirtuine1 (SIRT1) est un important modulateur du métabolisme énergétique, notamment via son activation de peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), régulateur clé de la biogenèse mitochondriale. Dans cette étude, nous montrons pour la première fois que la prolifération des CML-AP de rat et humaines est caractérisée par une réduction de l’activité de SIRT1, et est augmentée suite à l’inhibition pharmacologique ou la sous-expression spécifique de SIRT1. De plus, suite à hypoxie chronique, des souris génétiquement déficientes en SIRT1 présentent un remodelage vasculaire plus important que celui observé chez les souris contrôles, ce qui est associé à une augmentation accentuée de l’hypertrophie et de la pression systolique du ventricule droit. Au contraire, l’activation pharmacologique de SIRT1 inhibe fortement la prolifération des CML-AP, et est associée à l’activation de la biogenèse mitochondriale. L’ensemble de ces résultats suggère que l'inactivation de SIRT1 joue un rôle causal dans l’hyperprolifération des CML-AP et cette enzyme pourrait être une nouvelle cible thérapeutique prometteuse pour le traitement de l’HTAP. / Pulmonary arterial hypertension (PAH) is a lethal disease characterized by an intensive vascular remodelling, mainly due to hyper-proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs). Recently it has been found that PASMCs, similarly to cancer cells, demonstrate a shift in energy metabolism from oxidative phosphorylation towards glycolysis thus contributing to their particular phenotype. The deacetylase sirtuin1 (SIRT1) is an important modulator of energy metabolism, particularly via its activation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), the master regulator of mitochondrial biogenesis. Here we show for the first time that rat and human PASMC proliferation is characterised by a diminution of SIRT1 activity, and is potentiated by SIRT1 pharmacological inhibition or specific downregulation. Moreover, after chronic hypoxia exposure, SIRT1 KO mice display a more intense vascular remodelling compared to their control littermates and this is associated with an exacerbated increase in right ventricle systolic pressure and hypertrophy. Conversely, pharmacological SIRT1 activation strongly inhibits PASMC proliferation, and is associated with the activation of mitochondrial biogenesis. In general, the data obtained show that SIRT1 inactivation plays a causative role in PASMC proliferation and this enzyme could be a promising therapeutic target for PAH treatment.

L’hypertension artérielle pulmonaire (HTAP) est une maladie rare définie par une augmentation de la pression artérielle pulmonaire moyenne due à un remodelage progressif des artérioles pulmonaires, menant à une défaillance du ventricule cardiaque droit. Le remodelage vasculaire est la conséquence d’une dysfonction endothéliale conduisant à une hyperprolifération et à un défaut d’apoptose des cellules vasculaires pulmonaires. Le récepteur NMDA (NMDAR), un récepteur au glutamate connu pour son rôle dans la plasticité neuronale et la transmission synaptique, a été récemment identifié comme acteur de ce remodelage vasculaire. Cependant, le sous-type de NMDAR impliqué n’est pas connu. Le développement de traitements potentiels ciblant le NMDAR nécessite de mieux comprendre quelles sous-unités du récepteur sont mobilisées dans la maladie. Dans la mesure où la sous-unité GluN2A est impliquée dans la survie des neurones et la sous-unité GluN2B dans leur mort, nous avons fait l’hypothèse que la composition des NMDARs vasculaires pulmonaires devait être dérégulée dans l’HTAP. Par conséquent, cette thèse a pour objectifs i) d’étudier la composition du NMDAR dans l’HTAP, ii) d’en identifier les conséquences fonctionnelles, et iii) d’explorer son intégration au sein de la physiopathologie de l’HTAP.Nous avons montré que l’expression de la sous-unité GluN2B est réduite dans les artères pulmonaires des patients HTAP comparés à des sujets non-HTAP, malgré l’augmentation de l’expression de la sous-unité obligatoire GluN1, suggérant une commutation de l’expression des NMDARs de type GluN2B vers d’autres sous-types. Nous avons également montré que les NMDARs de type GluN2B sont rapidement et transitoirement recrutés à la membrane des cellules musculaires lisses (CMLs) en réponse à un facteur de croissance, le PDGF, par l’intermédiaire des Src family kinases (SFKs). En utilisant un inhibiteur spécifique des NMDARs de type GluN2B, nous avons observé qu’ils réduisaient la prolifération et la migration dépendantes du PDGF, indiquant une boucle de rétrocontrôle négatif. Ces résultats suggèrent une signalisation croisée entre le PDGFR-β, les SFKs et les NMDARs de type GluN2B. Ainsi le déficit en NMDARs de type GluN2B chez les patients HTAP pourrait potentialiser la réponse proliférative et migratoire au PDGF, une voie suractivée dans l’HTAP. De plus, nous avons montré que les NMDARs de type GluN2A sont recrutés de façon prolongée à la membrane des CMLs lors d’une stimulation par le PDGF. Néanmoins, le rôle précis des récepteurs de type GluN2A dans l’HTAP reste à découvrir. Pour approfondir le rôle du NMDAR dans la physiopathologie de l’HTAP, nous avons mené une étude bio-informatique complémentaire afin de modéliser les voies de signalisation impliquant le NMDAR dans l’HTAP. Nous avons construit et connecté en réseau les bases de connaissance sur les acteurs de l’HTAP d’une part, et les voies de signalisation impliquant le NMDAR dans le système nerveux central d’autre part. Nous avons montré que ces réseaux positionnent le NMDAR au cœur de nombreuses voies de signalisation caractéristiques de l’HTAP, dont celle du PDGFR-β.Ainsi, nous avons montré que l’expression membranaire des récepteurs de type GluN2A et GluN2B est dérégulée dans l’HTAP, orientant probablement la réponse au glutamate dépendante du PDGF vers les récepteurs de type GluN2A. Les conséquences d’un tel déséquilibre sont l’augmentation de la prolifération et de la migration des CMLs vasculaires pulmonaires. De plus le manque de récepteurs de type GluN2B est une caractéristique physiopathologique nouvelle dans l’HTAP et dans la compréhension du mode d’action des NMDARs périphériques en général. Enfin, le NMDAR semble être un acteur central dans la physiopathologie de l’HTAP, interagissant avec de nombreuses voies de signalisation impliquées dans la maladie, suggérant de nouvelles pistes pour avancer dans la compréhension des mécanismes physiopathologiques de l’HTAP. / Pulmonary arterial hypertension (PAH) is a rare disease defined by an increase in mean pulmonary arterial pressure due to progressive obstruction of the small pulmonary arteries, leading to right heart failure and death. The vascular remodeling is a consequence of complex and multiple patho-mechanisms, including endothelial cells dysfunction and hyperproliferation of smooth muscle cells in the pulmonary vascular wall. The N-methyl-D-aspartate receptor (NMDAR), a glutamate receptor, has been recently identified as playing an active role in this vascular remodeling. It has been shown that in pulmonary arteries of PAH patients, NMDAR is overexpressed and overactivated and is involved in the proliferation and resistance to apoptosis of pulmonary vascular cells. However, the NMDAR subtype involved in this process remains unknown. The development of potential treatments targeting the NMDAR requires a better understanding of its subunit involvement in the disease. Since the GluN2A subunit is involved in the survival of neurons and the GluN2B subunit in their death, we hypothesized that the pulmonary vascular NMDAR subunit composition could be dysregulated in PAH. Therefore, in this thesis study we aimed to: i) study the composition of NMDAR in PAH, ii) explore its functional consequences in the pathophysiology of PAH, and iii) uncover its integration in the pathophysiology of PAH.We showed that the expression of the GluN2B subunit is reduced in the pulmonary arteries of PAH patients compared to non-PAH subjects. This occurs despite the overall increased expression of the obligatory GluN1 subunit, suggesting a switch from GluN2B-type receptors to, at least, another GluN2-type receptor. We also showed that in the presence of PDGF-BB, there is an immediate increase in the levels of phosphorylated Src family kinases (SFKs), associated to an increase in phosphorylated GluN2B (the active form) that were relocated to the cell membrane, suggesting the cross-talk between PDGF, SFKs and NMDAR. To validate the pathway, we inhibited the activation of PDGFR-β or SFKs, and in both cases the phosphorylation of GluN2B after PDGF stimulation was aborted. To assess the functional importance of this pathway, proliferation and “wound healing” tests were performed. The results clearly showed that selective inhibition of GluN2B, in the presence of PDGF, significantly increased both migration and proliferation of PASMCs. These results suggest that the lack of GluN2B-type receptors in PAH may potentiate SMC proliferative and migratory response to PDGF, a well-known overactivated pathway in PAH. In addition, we showed that GluN2A-type NMDARs arerecruited to the SMC membrane following PDGF stimulation, but the precise role of GluN2A-type NMDARs in PAH remains elusive. To further explore the crosstalk between the NMDAR and the PDGF receptor (PDGFR) pathways, we conducted a complementary bioinformatics study. To provide a model of the NMDAR signaling pathways in PAH we constructed and connected comprehensive knowledge bases of the actors involved in PAH on one hand and the signaling pathways involving NMDAR within the central nervous system on the other hand. Within these networks the NMDAR was revealed as a central downstream effector of the hallmark signaling pathways of PAH, including that of PDGFR.These results indicate that the membrane expression of GluN2A-type and GluN2B-type receptors is dysregulated in PAH, presumably switching the PDGF-dependent glutamate response towards GluN2A-type receptors. The consequences of such imbalance are the increased proliferation and migration of pulmonary vascular SMCs. Moreover, the lack of GluN2B-type NMDARs is a new feature in the pathophysiology of PAH and in the understanding of peripheral NMDA receptors in general. Besides, the NMDAR seems to be a central effector in PAH, interacting with multiple hallmark pathways of the disease, suggesting new tracks to further understanding the pathophysiology of PAH.