Un microarn au coeur de l'hypertension artérielle pulmonaire

L’hypertension artérielle pulmonaire (HTAP) est caractérisée par l’obstruction des artères pulmonaires, principalement due au phénotype pro-prolifératif/anti-apoptotique des cellules musculaires lisses de la paroi des artères pulmonaires (CMLAP). L’augmentation progressive des résistances vasculaires pulmonaires aboutit à une élévation de la pression pulmonaire qui va induire rapidement une insuffisance cardiaque droite et conduire au décès des patients à moyen terme. Plusieurs études ont démontré l’implication du facteur de transcription NFAT (nuclear factor of activated T cell) dans le maintien du phénotype pro-prolifératif/anti-apoptotique des CMLAP-HTAP. Cependant les voies de signalisation responsables de l’activation constitutive d’NFAT restent peu connues. Durant mon doctorat, j’ai étudié les mécanismes responsables de l’activation d’NFAT dans l’HTAP. Nous nous sommes intéressés au rôle des microARN et notamment à miR-204. Ainsi, les facteurs circulants augmentés dans HTAP, diminue l’expression de miR-204 via l’activation du facteur de transcription STAT3. Par un mécanisme de rétro-action positive, la diminution de miR-204 induit une suractivation de STAT3 aboutissant au phénotype pathologique. Ainsi, l’augmentation exogène de miR-204 permettrait de soigner l’HTAP in vitro et in vivo. Nous avons montré que miR-204 va également moduler l’expression de Runx2, facteur de transcription connu pour être impliqué dans la calcification. Dans les CMLAP-HTAP, la diminution de miR-204 est associée à une augmentation de l’expression de Runx2, connu comme un régulateur positif de l’activation du facteur de transcription HIF-1 impliqué dans l’HTAP. Ainsi la modulation de miR-204 affecte la prolifération et l’apoptose des CMLAP-HTAP par plusieurs axes de signalisation. Enfin, nous avons démontré l’implication du facteur de transcription Krüppel Like Factor 5 (KLF5) dans l’HTAP. La surexpression de KLF5 dans l’HTAP est secondaire à l’activation de STAT3, tandis que son inhibition diminue la prolifération et favorise l’apoptose des CMLAP-HTAP. In vivo, l’administration de siKLF5 renverse l’HTAP en diminuant les pressions pulmonaires, l’hypertrophie ventriculaire droite, la prolifération et augmentant l’apoptose des CMLAP des artères pulmonaires distales. Finalement, j’ai étudié différents aspects du développement de l’HTAP et notamment de l’activation de l’axe STAT3/NFAT. Nous avons pu mettre en évidence que cibler cette voie de signalisation par différents moyens (mimic miR-204, siRunx2, siSTAT3, siKLF5) semble une bonne stratégie pour traiter l’HTAP. Mots clés : l’hypertension artérielle pulmonaire, thérapeutique, prolifération, apoptose, microARN, facteur de transcription, réparation à l’ADN.Pulmonary arterial hypertension (PAH) is characterized by the obstruction of the pulmonary arteries, mainly due to the pro-proliferative and anti-apoptotic phenotype of the pulmonary artery smooth muscle cells (PASMC). The progressive increase of pulmonary vascular resistance first leads to an increase of pulmonary pressure and then leads to a right heart failure, which generates patient’s death within few years. Many studies demonstrated the implication of the transcription factor NFAT (nuclear factor of activated T cell), which maintains the pro-proliferative and anti-apoptotic phenotype in PAH-PASMC. However, pathways that lead to the constitutive NFAT activation remain unclear. During my doctorate, I studied mechanisms responsible for the activiation of NFAT in HTAP. We study the role of the microRNA and more exactly to miR-204. Thus, the circulating factors, which are increased in PAH and which decreased miR-204 expression in PAH, via the transcription factor STAT3 activation. Through a positive regulation loop mechanism, the decrease of miR-204 induces an overactivation sustain of STAT3 leading to the pathologique phenotype. Thus, the exogenous increase of miR-204 could treat PAH in vitro as well as in vivo. We demonstrated that miR-204 is able to modulate the expression of the transcription factor Runx2 known to be implicated in calcification. In PAH-PASMC, the decrease of miR-204 is associated to an increase of Runx2 expression, known as positive regulator of the HIF-1 activation implicated in PAH. Thus miR-204 modulations affected the proliferation and apoptosis of PAH-PASMC through many molecular axes. Finaly we reveal the implication of the transcription factor Kruppel Like Factor 5 (KLF5) in PAH. The KLF5 overexpressed in PAH is associated to the STAT3 activation, wherease its inhibition decreased the proliferation and promoted apoptosis in PAH-PASMC. In vivo, si KLF5 reversed PAH by decreasing pulmonary pressures, right ventricular hypertrophy, proliferation and increasing apoptosis in PASMC from distal PA. Finally, I studied many aspects implicated in PAH development and especially the STAT3/NFAT axis activation. We showed that targeting this pathway using many technics (mimic miR-204, siRunx2, siSTAT3, siKLF5) seem to be an interesting strategy to treat PAH. Key words: Pulmonary arterial hypertension, therapeutic, proliferation, apoptosis, microRNA, and transcription factor

MicroRNAs in pulmonary arterial remodeling

Pulmonary arterial remodeling is a presently irreversible pathologic hallmark of pulmonary arterial hypertension (PAH). This complex disease involves pathogenic dysregulation of all cell types within the small pulmonary arteries contributing to vascular remodeling leading to intimal lesions, resulting in elevated pulmonary vascular resistance and right heart dysfunction. Mutations within the bone morphogenetic protein receptor 2 gene, leading to dysregulated proliferation of pulmonary artery smooth muscle cells, have been identified as being responsible for heritable PAH. Indeed, the disease is characterized by excessive cellular proliferation and resistance to apoptosis of smooth muscle and endothelial cells. Significant gene dysregulation at the transcriptional and signaling level has been identified. MicroRNAs are small non-coding RNA molecules that negatively regulate gene expression and have the ability to target numerous genes, therefore potentially controlling a host of gene regulatory and signaling pathways. The major role of miRNAs in pulmonary arterial remodeling is still relatively unknown although research data is emerging apace. Modulation of miRNAs represents a possible therapeutic target for altering the remodeling phenotype in the pulmonary vasculature. This review will focus on the role of miRNAs in regulating smooth muscle and endothelial cell phenotypes and their influence on pulmonary remodeling in the setting of PAH

MEF2C-MYOCD and Leiomodin1 Suppression by miRNA-214 Promotes Smooth Muscle Cell Phenotype Switching in Pulmonary Arterial Hypertension.

BACKGROUND: Vascular hyperproliferative disorders are characterized by excessive smooth muscle cell (SMC) proliferation leading to vessel remodeling and occlusion. In pulmonary arterial hypertension (PAH), SMC phenotype switching from a terminally differentiated contractile to synthetic state is gaining traction as our understanding of the disease progression improves. While maintenance of SMC contractile phenotype is reportedly orchestrated by a MEF2C-myocardin (MYOCD) interplay, little is known regarding molecular control at this nexus. Moreover, the burgeoning interest in microRNAs (miRs) provides the basis for exploring their modulation of MEF2C-MYOCD signaling, and in turn, a pro-proliferative, synthetic SMC phenotype. We hypothesized that suppression of SMC contractile phenotype in pulmonary hypertension is mediated by miR-214 via repression of the MEF2C-MYOCD-leiomodin1 (LMOD1) signaling axis. METHODS AND RESULTS: In SMCs isolated from a PAH patient cohort and commercially obtained hPASMCs exposed to hypoxia, miR-214 expression was monitored by qRT-PCR. miR-214 was upregulated in PAH- vs. control subject hPASMCs as well as in commercially obtained hPASMCs exposed to hypoxia. These increases in miR-214 were paralleled by MEF2C, MYOCD and SMC contractile protein downregulation. Of these, LMOD1 and MEF2C were directly targeted by the miR. Mir-214 overexpression mimicked the PAH profile, downregulating MEF2C and LMOD1. AntagomiR-214 abrogated hypoxia-induced suppression of the contractile phenotype and its attendant proliferation. Anti-miR-214 also restored PAH-PASMCs to a contractile phenotype seen during vascular homeostasis. CONCLUSIONS: Our findings illustrate a key role for miR-214 in modulation of MEF2C-MYOCD-LMOD1 signaling and suggest that an antagonist of miR-214 could mitigate SMC phenotype changes and proliferation in vascular hyperproliferative disorders including PAH

Therapeutic efficacy of TBC3711 in monocrotaline-induced pulmonary hypertension

Background: Endothelin-1 signalling plays an important role in pathogenesis of pulmonary hypertension. Although different endothelin-A receptor antagonists are developed, a novel therapeutic option to cure the disease is still needed. This study aims to investigate the therapeutic efficacy of the selective endothelin-A receptor antagonist TBC3711 in monocrotaline-induced pulmonary hypertension in rats. Methods: Monocrotaline-injected male Sprague-Dawley rats were randomized and treated orally from day 21 to 35 either with TBC3711 (Dose: 30 mg/kg body weight/day) or placebo. Echocardiographic measurements of different hemodynamic and right-heart hypertrophy parameters were performed. After day 35, rats were sacrificed for invasive hemodynamic and right-heart hypertrophy measurements. Additionally, histologic assessment of pulmonary vascular and right-heart remodelling was performed. Results: The novel endothelin-A receptor antagonist TBC3711 significantly attenuated monocrotaline-induced pulmonary hypertension, as evident from improved hemodynamics and right-heart hypertrophy in comparison with placebo group. In addition, muscularization and medial wall thickness of distal pulmonary vessels were ameliorated. The histologic evaluation of the right ventricle showed a significant reduction in fibrosis and cardiomyocyte size, suggesting an improvement in right-heart remodelling. Conclusion: The results of this study suggest that the selective endothelin-A receptor antagonist TBC3711 demonstrates therapeutic benefit in rats with established pulmonary hypertension, thus representing a useful therapeutic approach for treatment of pulmonary hypertension

Role for miR-204 in human pulmonary arterial hypertension

Reduced miR-204 expression facilitates the excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells characteristic of human pulmonary arterial hypertension

MicroRNAs in Human Diseases: From Cancer to Cardiovascular Disease

The great discovery of microRNAs (miRNAs) has revolutionized current cell biology and medical science. miRNAs are small conserved non-coding RNA molecules that post-transcriptionally regulate gene expression by targeting the 3' untranslated region of specific messenger RNAs for degradation or translational repression. New members of the miRNA family are being discovered on a daily basis and emerging evidence has demonstrated that miRNAs play a major role in a wide range of developmental process including cell proliferation, cell cycle, cell differentiation, metabolism, apoptosis, developmental timing, neuronal cell fate, neuronal gene expression, brain morphogenesis, muscle differentiation and stem cell division. Moreover, a large number of studies have reported links between alterations of miRNA homeostasis and pathological conditions such as cancer, psychiatric and neurological diseases, cardiovascular disease, and autoimmune disease. Interestingly, in addition, miRNA deficiencies or excesses have been correlated with a number of clinically important diseases ranging from cancer to myocardial infarction. miRNAs can repress the gene translation of hundreds of their targets and are therefore well-positioned to target a multitude of cellular mechanisms. As a consequence of extensive participation in normal functions, it is quite logical to ask the question if abnormalities in miRNAs should have importance in human diseases. Great discoveries and rapid progress in the past few years on miRNAs provide the hope that miRNAs will in the near future have a great potential in the diagnosis and treatment of many diseases. Currently, an explosive literature has focussed on the role of miRNA in human cancer and cardiovascular disease. In this review, I briefly summarize the explosive current studies about involvement of miRNA in various human cancers and cardiovascular disease

Increasing pulmonary artery pulsatile flow improves hypoxic pulmonary hypertension in piglets

Pulmonary arterial hypertension (PAH) is a disease affecting distal pulmonary arteries (PA). These arteries are deformed, leading to right ventricular failure. Current treatments are limited. Physiologically, pulsatile blood flow is detrimental to the vasculature. In response to sustained pulsatile stress, vessels release nitric oxide (NO) to induce vasodilation for self-protection. Based on this observation, this study developed a protocol to assess whether an artificial pulmonary pulsatile blood flow could induce an NO-dependent decrease in pulmonary artery pressure. One group of piglets was exposed to chronic hypoxia for 3 weeks and compared to a control group of piglets. Once a week, the piglets underwent echocardiography to assess PAH severity. At the end of hypoxia exposure, the piglets were subjected to a pulsatile protocol using a pulsatile catheter. After being anesthetized and prepared for surgery, the jugular vein of the piglet was isolated and the catheter was introduced through the right atrium, the right ventricle and the pulmonary artery, under radioscopic control. Pulmonary artery pressure (PAP) was measured before (T0), immediately after (T1) and 30 min after (T2) the pulsatile protocol. It was demonstrated that this pulsatile protocol is a safe and efficient method of inducing a significant reduction in mean PAP via an NO-dependent mechanism. These data open up new avenues for the clinical management of PAH