Anorexigen-induced pulmonary hypertension and the serotonin (5-HT) hypothesis: lessons for the future in pathogenesis

Epidemiological studies have established that fenfluramine, D-fenfluramine, and aminorex, but not other appetite suppressants, increase the risk of primary pulmonary hypertension (PH). One current hypothesis suggests that fenfluramine-like medications may act through interactions with the serotonin (5-hydroxytryptamine [5-HT]) transporter (5-HTT) located on pulmonary artery smooth muscle cells and responsible for the mitogenic action of 5-HT. Anorexigens may contribute to PH by boosting 5-HT levels in the bloodstream, directly stimulating smooth muscle cell growth, or altering 5-HTT expression. We suggest that individuals with a high basal level of 5-HTT expression related to the presence of the long 5-HTT gene promoter variant may be particularly susceptible to one or more of these potential mechanisms of appetite-suppressant-related PH

Endothelin A receptor blockade improves regression of flow-induced pulmonary vasculopathy in piglets

ObjectivesIn patients with chronic thromboembolic pulmonary hypertension, high flow in unobstructed lung regions may induce small-vessel damage responsible for persistent pulmonary hypertension after pulmonary thromboendarterectomy. In piglets, closure of an experimental aortopulmonary shunt reverses the flow-induced vascular lesions and diminishes the elevated levels of messenger RNA (mRNA) expression for endothelin-1 and endothelin receptor A (ETA). We wanted to study the effect of the ETA antagonist TBC 3711 on reversal of flow-induced pulmonary vascular lesions.MethodsTwenty piglets were studied. In 15 piglets, pulmonary vasculopathy was induced by creating an aortopulmonary shunt. After 5 weeks of shunting, some animals were studied (n = 5); others underwent shunt closure for 1 week with (n = 5) or without (n = 5) TBC3711 treatment. Anti-ETA treatment started 1 week before and ended 1 week after the shunt closure. The controls were sham-operated animals (n = 5).ResultsHigh blood flow led to medial hypertrophy of the distal pulmonary arteries (54.9% ± 1.3% vs 35.3% ± 0.9%; P < .0001) by stimulating smooth muscle cell proliferation (proliferating cell nuclear antigen) and increased the expression of endothelin-1, ETA or endothelin receptor type A or endothelin receptor A, angiopoietin 1, and Tie2 (real-time polymerase chain reaction). One week after shunt closure, gene expression levels were normal and smooth muscle cells showed increased apoptosis (terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling) without proliferation. However, pulmonary artery wall thickness returned to control values only in the group given TBC3711 (33.2% ± 8% with and 50.3% ± 1.3% without; P < .05).ConclusionsAnti-ETA therapy accelerated the reversal of flow-induced pulmonary arterial disease after flow correction. In patients with chronic thromboembolic pulmonary hypertension and severe distal pulmonary vasculopathy, anti-ETA agents may prove useful for preventing persistent pulmonary hypertension after pulmonary thromboendarterectomy

Gene expression in lungs of mice lacking the 5-hydroxytryptamine transporter gene

<p>Abstract</p> <p>Background</p> <p>While modulation of the serotonin transporter (5HTT) has shown to be a risk factor for pulmonary arterial hypertension for almost 40 years, there is a lack of in vivo data about the broad molecular effects of pulmonary inhibition of 5HTT. Previous studies have suggested effects on inflammation, proliferation, and vasoconstriction. The goal of this study was to determine which of these were supported by alterations in gene expression in serotonin transporter knockout mice.</p> <p>Methods</p> <p>Eight week old normoxic mice with a 5-HTT knock-out (5HTT-/-) and their heterozygote(5HTT+/-) or wild-type(5HTT+/+) littermates had right ventricular systolic pressure(RVSP) assessed, lungs collected for RNA, pooled, and used in duplicate in Affymetrix array analysis. Representative genes were confirmed by quantitative RT-PCR and western blot.</p> <p>Results</p> <p>RVSP was normal in all groups. Only 124 genes were reliably changed between 5HTT-/- and 5HTT+/+ mice. More than half of these were either involved in inflammatory response or muscle function and organization; in addition, some matrix, heme oxygenase, developmental, and energy metabolism genes showed altered expression. Quantitative RT-PCR for examples from each major group confirmed changes seen by array, with an intermediate level in 5HTT +/- mice.</p> <p>Conclusion</p> <p>These results for the first time show the in vivo effects of 5HTT knockout in lungs, and show that many of the downstream mechanisms suggested by cell culture and ex vivo experiments are also operational in vivo. This suggests that the effect of 5HTT on pulmonary vascular function arises from its impact on several systems, including vasoreactivity, proliferation, and immune function.</p

ICAM-1 PROMOTES THE ABNORMAL ENDOTHELIAL CELLPHENOTYPE IN CHRONIC THROMBOEMBOLIC PULMONARYHYPERTENSION

International audienceBACKGROUND - Pulmonary endothelial cells play a key role in the pathogenesis of ChronicThromboembolic Pulmonary Hypertension (CTEPH). Increased synthesis and/or release ofIntercellular Adhesion Molecule 1 (ICAM-1) by pulmonary endothelial cells of patients withCTEPH has been recently reported, suggesting a potential role for ICAM-1 in CTEPH.METHODS - We studied pulmonary endarterectomy specimens from 172 patients with CTEPHand pulmonary artery specimens from 97 controls undergoing lobectomy for low-stage cancerwithout metastasis.RESULTS - ICAM-1 was overexpressed in vitro in isolated and cultured endothelial cells fromendarterectomy specimens. Endothelial cell (EC) growth and apoptosis resistance weresignificantly higher in CTEPH specimens than in controls (P<0.001). Both abnormalities wereabolished by pharmacological inhibition of ICAM-1 synthesis or activity. Overexpression ofICAM-1 contributed to the acquisition and maintenance of abnormal EC growth and apoptosisresistance via phosphorylation of SRC, p38 and ERK1/2 and overproduction of Survivin.Regarding the ICAM-1 E469K polymorphism, the KE heterozygote genotype was significantlymore frequent in CTEPH than in controls, but was not associated with disease severity amongpatients with CTEPH.CONCLUSIONS - ICAM-1 contributes to maintaining the abnormal endothelial cell phenotypein CTEPH

Physiopathologie de l'hypertension artérielle pulmonaire expérimentale et humaine

La physiopathologie de l'hypertension artérielle pulmonaire (HTAP) implique de multiples mécanismes. Elle est caractérisée, entre autres, par la réduction de la production des facteurs vasodilatateurs, l'augmentation exagérée des facteurs vasoconstricteurs et des facteurs de croissance qui conduisent à la vasoconstruction, la prolifération et le remodelage vasculaire pulmonaire. Les cellules endothéliales pulmonaires secrètent des facteurs paracrines qui contribuent à l'hyperplasie des cellules musculaires lisses pendant la progression de l'hypertension artérielle pulmonaire. Le FGF2 produit par les cellules endothéliales et stocké dans la matrice extracellulaire, est l'un de ces facteurs très bien documenté pour entraîner une prolifération des CML. Cette étude montre que l'inhibition de l'expression pulmonaire du bFGF par l'injection répétée du SiRNA chez les rats traités à la MCT, est corrélée à l'amélioration des paramètres hémodynamiques, du remodelage vasculaire et de l'hypertrophie cardiaque droite, en traitement préventif et curatif. Chez les sujets atteints d'hypertension pulmonaire le niveau de la sérotonine circulant est très élevé. La biosynthèse de la sérotonine dépend de la tryptophane hydroxylase. Nous avons étudié l'impact des variations génétiques de la Tph1 et de la Tph2 sur le développement de l'HTAP chez les souris. Cette étude a montré que la déficience en Tph1 (Tph périphérique) protège les souris contre l'hypoxie alors que les souches de souris porteuses du polymorphisme C1473G au niveau du gène Tph2 (Tph centrale) montrent des phénotypes d'HTAP différents pendant l'hypoxie. En plus de l'importance de la TPH, l'expression du 5-HTT est aussi déterminant dans l'HTAP. Les souris SM22 surexprimant le 5-HTT dans les CML à un niveau proche de celui des CML des patients atteints d'hypertension artérielle pulmonaire développent spontanément une HTAP qui s'aggrave avec l'âge. Du fait de la baisse considérable de l'activité de ces deux enzymes, le NO synthase et la prostacycline synthase, au niveau des cellules endothéliales chez les patients HTAP, le taux de l'AMPc et du GMPc baisse. Les PDEs hydrolysent les deux messagers des agents vasodilatateurs prostacycline et oxyde nitrique, et l'utilisation des inhibiteurs de phosphodiestérases augmentent la concentration intracellulaire de GMPc et AMPc et causent la vasodilatation pulmonaire. Le traitements des rats HTAP avec l'inhibiteur du PDE4 (Roflumilast) avec deux doses 1,5 et 0,5mg/Kg/jour, a montré une régression de l'HTAP, baisse de l'hypertrophie cardiaque et du remodelage vasculaire des rats traités à la monocrotaline ou mises en hypoxie aigüe (10% O2), chez qui un traitement préventif et curatif a été effectué.The physiopatholy of pulmonary arterial hypertension (PAH) implies multiple mechanisms. It is characterized by the reduction of the production of vasodilatators factors, the overproduction of vasoconstrictor factors and growth factors which lead to the pulmonary vasoconstriction, and the pulmonary vascular remodeling. The pulmonary endothelial cells release paracrine factors which contribute to the hyperplasy of the smooth muscule cells (SMC) during the progression of PAH. The FGF2 produced by the endothelial cells and stored in the extracellular matrix is reproted to be involved in the SMC proliferation. This study shows that inhibition of the pulmonary expression of FGF2 by the repeated injection of SiRNA in the rats treated with monocrotaline (MCT), is correlated with the improvment of the hemodynamic parameters, vascular remodeling and right ventricular hypertrophy, in both, a preventive and a curative treatment. In pateints with PAH, it has been shown that the circulating level of serotonin is very high as compared to control patients. The biosynthesis of serotonin depends on tryptophan hydroxylase. Therefore, we studied the impact of the genetic variations of Tph1 and Tph2 on the development of PAH in mice. This study showed that deficiency in Tph1 (peripheral Tph) protects mice against the hypoxia-induced PAH severity during hypoxia. In addition to the importance of the Tph, the serotonin transporter (5-HTT) expression is also a determining factor in the development of PAH. Mice overexpressing 5-HTT (SM22-5-HTT+ mice) specifically in SMC develop spontaneously PAH in normoxia, which worsens with age. We observed a significant decrease int he rate of cAMP and cGMP produced in the endothelial cells from patients with PAH, which has been reported to be due to low activities of NO synthase and prostacyclin synthase. Phosphodiesterases (PDE)hydrolize the two messengers (cAMP and cGMP), and the use of specific inhibitors of PDE increases the intracellular concentration of cGMP and cAMP and causes pulmonary vasodilatation. A daily oral administration of Roflumilast (1,5 and 0,5 mg/kg/day) a specific inhibitor of PDE4, was effective in preventing and in reversin the PAH in both experimental model of PAH, the MCT and chronic hypoxia (10%O2,2 weeks)PARIS-EST-Université (770839901) / SudocSudocFranceF

Anorexigen-induced pulmonary hypertension and the serotonin (5-HT) hypothesis: lessons for the future in pathogenesis

<p>Abstract</p> <p>Epidemiological studies have established that fenfluramine, D-fenfluramine, and aminorex, but not other appetite suppressants, increase the risk of primary pulmonary hypertension (PH). One current hypothesis suggests that fenfluramine-like medications may act through interactions with the serotonin (5-hydroxytryptamine [5-HT]) transporter (5-HTT) located on pulmonary artery smooth muscle cells and responsible for the mitogenic action of 5-HT. Anorexigens may contribute to PH by boosting 5-HT levels in the bloodstream, directly stimulating smooth muscle cell growth, or altering 5-HTT expression. We suggest that individuals with a high basal level of 5-HTT expression related to the presence of the long 5-HTT gene promoter variant may be particularly susceptible to one or more of these potential mechanisms of appetite-suppressant-related PH.</p

Physiopathologie de l'hypertension artérielle pulmonaire (rôle des facteurs vaso-actifs et de l'inflammation)

L'hypertension artérielle pulmonaire (HTAP) est caractérisée par un intense remodelage de la microcirculation pulmonaire affectant principalement les artérioles pulmonaires musculaires. Lorsqu'elle survient en l'absence de condition associée, l'HTAP est considérée comme idiopathique (HTAPi). L'HTAP représente une pan-vasculopathie au cours de laquelle chaque type cellulaire (cellules endothéliale, musculaire lisse, fibroblaste) constituant la paroi vasculaire joue un rôle spécifique dans la réponse à l'agression. Les buts de ce travail étaient d'explorer l'implication de différentes voies de signalisation dans l'initiation ou la progression de la maladie. Les différentes études ont été réalisées à partir de cultures de cellules musculaires lisses (CML) d'artère pulmonaire et de cellules endothéliales (CE) pulmonaires obtenues à partir de prélèvements pulmonaires humains obtenus lors de transplantation chez des patients souffrant d'HTAP réfractaire.Des études antérieures avaient souligné le rôle majeur de la sérotonine au cours de l'HTAP idiopathique. Dans une première étude, nous avons étudié le rôle respectif de la sérotonine (5-HT), de son transporteur (5-HTT) ou de ses récepteurs (5-HT1B, 5-HT2A et 5-HT2B) dans le remodelage vasculaire pulmonaire mis en évidence dans l'HTP associée à diverses conditions. Les résultats de cette première étude montraient qu'une surexpression du 5-HTT dans les CML d'artère pulmonaire est une voie physiopathologique commune impliquée dans le remodelage vasculaire pulmonaire observé dans l'HTAP idiopathique, la maladie veino-occlusive et l'HTAP associée à différentes pathologies.Des mécanismes inflammatoires jouent probablement un rôle important dans la physiopathologie du remodelage microvasculaire pulmonaire. En effet, des infiltrats composés de cellules inflammatoires mononucléées (macrophages, lymphocytes T et B et cellules dendritiques) sont fréquemment mis en évidence autour des lésions vasculaires pulmonaires de patients présentant une HTAP idiopathique. Les mécanismes impliqués dans le recrutement de ces cellules mononucléées demeurent mal compris et nous avons étudié le rôle d'une chimiokine, CC chemokine ligand 2 (CCL2). Les résultats de cette seconde étude montraient que CCL2 était surexprimée au cours de l'HTAP idiopathique. La source de cette surexpression semblait provenir des cellules endothéliales pulmonaires. CCL2 agissait non seulement sur le recrutement des monocytes mais également sur les cellules musculaires lisses vasculaires pulmonaires en stimulant leur prolifération et leur migration.Des mutations germinales de gènes codant pour des membres de la famille des récepteurs du TGF tels que BMPR2 (Bone Morphogenic Protein Receptor type 2) sont retrouvées dans près de 70% des cas d'HTAP familiale mais également chez 10 à 30 % des cas d'HTAPi apparemment non familiales. Ces patients sont regroupés sous le terme d'HTAP héritable (HTAPh). Nous avons, dans une troisième étude, évalué si la dysfonction des voies de signalisation secondaires aux mutations de BMPR2 pouvait avoir des conséquences sur la voie de l'endothéline 1 (ET-1) qui représente l'une des cibles thérapeutiques de choix au cours de l'HTAP. Les résultats de cette troisième étude montraient que l'ET-1 était surexprimée au cours de l'HTAP avec ou sans mutation de BMPR2. En revanche, une surexpression des récepteurs ET-A dans les CML était mise en évidence au cours de l'HTAPh et était associée à une augmentation de l'effet pro-proliférant de l'ET-1 sur les CML.Ces résultats révèlent que des facteurs vaso-actifs (ET-1, 5-HT) et inflammatoires jouent un rôle déterminant dans la physiopathologie de l'HTAP et pourraient représenter de nouvelles cibles thérapeutiques.Pulmonary arterial hypertension (PAH) is characterized by intense pulmonary vascular remodelling affecting mainly the muscular pulmonary arteries and leading to increased pulmonary vascular resistance. When it occurs in the absence of associated conditions, PAH is regarded as idiopathic (iPAH). PAH represents a panvasculopathy in which each cell type constituting the vascular wall (endothelial cells, smooth muscle cells, fibroblast) plays a specific role. The aims of this work were to explore the implication of various pathways in the initiation or the progression of the disease. The various studies were carried out using pulmonary artery smooth muscle cells (PASMC) and pulmonary endothelial cells (PEC) obtained during lung transplantation from patients with refractory PAH.Former studies have emphasized the major role of serotonin (5-HT) in the process of pulmonary vascular remodelling in iPAH. In a first study, we studied the respective role of 5-HT, the 5-HT transporter (5-HTT) and several 5-HT receptors (5-HT1B, 5-HT2A and 5-HT2B) on PASMC proliferation in cells from patients with PH associated with various conditions. The results of this first study showed that 5-HTT overexpression in PASMC is a common pathogenic mechanism in various forms of PH.Inflammatory cytokines may affect pulmonary vascular remodelling in iPAH. Indeed, iPAH frequently reveals inflammatory infiltrates corresponding to macrophages, lymphocytes and dendritic cells in the range of plexiform lesions as well as in other vascular lesions. The mechanisms underlying pulmonary vessel infiltration by monocytes / macrophages are unclear and the role for inflammatory cells in pulmonary vascular remodeling remains to be elucidated. This second study showed that iPAH is associated with an overexpression of CCL2. PEC are a major source of CCL2, which behaves as chemoattractant for circulating inflammatory cells and as growth factor for PASMC.Germline mutations of bone morphogenetic protein (BMP) receptor type 2 (BMPR-2), a member of the transforming growth factor (TGF)-b receptor family, have been reported in nearly 70% of patients with the heritable form of the disease (hPAH), and in 10 30% of patients with sporadic iPAH. In a third study, we evaluated the functional consequences of BMPR-2 mutations on the endothelin 1 (ET-1) pathway which represents one of the therapeutic targets on PAH. The results of this third study showed that iPAH and hPAH were associated with a similar overexpression of ET-1. In contrast, ETA receptor mRNA levels which were increased in PASMC from patients with iPAH and hPAH compared to controls were much higher in hPAH than in iPAH cells. Consequently, the growth promoting effect of ET1 on PASMC was higher in PASMC from patients with iPAH, and was markedly elevated in PASMC from patients with hPAH. No changes in ETB receptor mRNA levels could be detected in PASMC from patients with iPAH or hPAH in comparison with controls.These results reveal that vasoactive factors (ET-1, 5-HT) and inflammatory factors play a determining role in the pathophysiology of PAH and could represent new therapeutic targets.PARIS-EST-Université (770839901) / SudocSudocFranceF

Physiopathologie de l'hypertension artérielle pulmonaire (rôles de la voie de signalisation TGF-b/ALK1/Endogline et de p53)

Mon projet porte d'une part sur le rôle de la voie TGF-b/Alk1 dans l hypertension artérielle (HTAP) humaine et expérimentale. Le but est d évaluer in vitro (i) l expression du TGF-b et de ses récepteurs ALK1/Endogline dans les cellules endothéliales d artères pulmonaires (CE-AP) de patients atteints d HTAP idiopathique (HTAPi), (ii) les conséquence de l activation de la voie TGF-b/ALK1 des CE-AP dans la synthèse de facteurs capables d induire la prolifération des cellules musculaires lisses d artères pulmonaires (CML-AP), (iii) identifier par une analyse protéomique différentielle la nature de ses facteurs paracrines, (iv) évaluer chez la souris la conséquence de la déficience en Endogline, co-récepteur de ALK1 sur le développement de l hypertension artérielle pulmonaire.My project relates to the role of the TGF-b/Alk1 pathway in human and experimental pulmobnary arterial hypertension (PAH). The goal is to evaluate in vitro (I) the expression of TGF-b and its receptors ALK1/Endoglin in pulmonary arterial endothelial (P-EC) of patients reached of idiopathic PAH (iPAH), (II) the consequence of the activation of the TGF-b/ALK1 pathway on the P-EC in the synthesis of factors able to induce the proliferation of the pulmonary arterial smooth muscle cell (PA-SMC), (III) to identify by a differential proteomic analysis the nature of its factors paracrines, (iv) to evaluate in the mouse the consequence of deficiency in Endoglin (co-receptor of ALK1) on the development of PAH.PARIS-EST-Université (770839901) / SudocSudocFranceF

Serotonin in pulmonary arterial hypertension.

CommentEditorialSCOPUS: ed.jinfo:eu-repo/semantics/publishe