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Background: Right ventricular (RV) function is the major determinant for both functional capacity and survival in patients with pulmonary arterial hypertension (PAH). Despite the recognized clinical importance of preserving RV function, the subcellular mechanisms that govern the transition from a compensated to a decompensated state remain poorly understood and as a consequence there are no clinically established treatments for RV failure and a paucity of clinically useful biomarkers. Accumulating evidence indicates that long noncoding RNAs are powerful regulators of cardiac development and disease. Nonetheless, their implication in adverse RV remodeling in PAH is unknown., Methods: Expression of the long noncoding RNA H19 was assessed by quantitative PCR in plasma and RV from patients categorized as control RV, compensated RV or decompensated RV based on clinical history and cardiac index. The impact of H19 suppression using GapmeR was explored in 2 rat models mimicking RV failure, namely the monocrotaline and pulmonary artery banding. Echocardiographic, hemodynamic, histological, and biochemical analyses were conducted. In vitro gain- and loss-of-function experiments were performed in rat cardiomyocytes., Results: We demonstrated that H19 is upregulated in decompensated RV from PAH patients and correlates with RV hypertrophy and fibrosis. Similar findings were observed in monocrotaline and pulmonary artery banding rats. We found that silencing H19 limits pathological RV hypertrophy, fibrosis and capillary rarefaction, thus preserving RV function in monocrotaline and pulmonary artery banding rats without affecting pulmonary vascular remodeling. This cardioprotective effect was accompanied by E2F transcription factor 1-mediated upregulation of enhancer of zeste homolog 2. In vitro, knockdown of H19 suppressed cardiomyocyte hypertrophy induced by phenylephrine, while its overexpression has the opposite effect. Finally, we demonstrated that circulating H19 levels in plasma discriminate PAH patients from controls, correlate with RV function and predict long-term survival in 2 independent idiopathic PAH cohorts. Moreover, H19 levels delineate subgroups of patients with differentiated prognosis when combined with the NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels or the risk score proposed by both REVEAL (Registry to Evaluate Early and Long-Term PAH Disease Management) and the 2015 European Pulmonary Hypertension Guidelines., Conclusions: Our findings identify H19 as a new therapeutic target to impede the development of maladaptive RV remodeling and a promising biomarker of PAH severity and prognosis.

Background: Excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells (PASMCs) are key mechanisms of pulmonary arterial hypertension (PAH). Despite the multiple combination therapy, a considerable number of patients develop severe pulmonary hypertension (PH) because of the lack of diagnostic biomarker and antiproliferative therapies for PASMCs., Methods: Microarray analyses were used to identify a novel therapeutic target for PAH. In vitro experiments, including lung and serum samples from patients with PAH, cultured PAH-PASMCs, and high-throughput screening of 3336 low-molecular-weight compounds, were used for mechanistic study and exploring a novel therapeutic agent. Five genetically modified mouse strains, including PASMC-specific selenoprotein P (SeP) knockout mice and PH model rats, were used to study the role of SeP and therapeutic capacity of the compounds for the development of PH in vivo., Results: Microarray analysis revealed a 32-fold increase in SeP in PAH-PASMCs compared with control PASMCs. SeP is a widely expressed extracellular protein maintaining cellular metabolism. Immunoreactivity of SeP was enhanced in the thickened media of pulmonary arteries in PAH. Serum SeP levels were also elevated in patients with PH compared with controls, and high serum SeP predicted poor outcome. SeP-knockout mice ( SeP -/- ) exposed to chronic hypoxia showed significantly reduced right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary artery remodeling compared with controls. In contrast, systemic SeP-overexpressing mice showed exacerbation of hypoxia-induced PH. Furthermore, PASMC-specific SeP -/- mice showed reduced hypoxia-induced PH compared with controls, whereas neither liver-specific SeP knockout nor liver-specific SeP-overexpressing mice showed significant differences with controls. Altogether, protein levels of SeP in the lungs were associated with the development of PH. Mechanistic experiments demonstrated that SeP promotes PASMC proliferation and resistance to apoptosis through increased oxidative stress and mitochondrial dysfunction, which were associated with activated hypoxia-inducible factor-1α and dysregulated glutathione metabolism. It is important to note that the high-throughput screening of 3336 compounds identified that sanguinarine, a plant alkaloid with antiproliferative effects, reduced SeP expression and proliferation in PASMCs and ameliorated PH in mice and rats., Conclusions: These results indicate that SeP promotes the development of PH, suggesting that it is a novel biomarker and therapeutic target of the disorder.

Background: Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterised by exuberant tissue remodelling and associated with high unmet medical needs. Outcomes are even worse when IPF results in secondary pulmonary hypertension (PH). Importantly, exaggerated resistance to cell death, excessive proliferation and enhanced synthetic capacity are key endophenotypes of both fibroblasts and pulmonary artery smooth muscle cells, suggesting shared molecular pathways. Under persistent injury, sustained activation of the DNA damage response (DDR) is integral to the preservation of cells survival and their capacity to proliferate. Checkpoint kinases 1 and 2 (CHK1/2) are key components of the DDR. The objective of this study was to assess the role of CHK1/2 in the development and progression of IPF and IPF+PH.Methods and Results: Increased expression of DNA damage markers and CHK1/2 were observed in lungs, remodelled pulmonary arteries and isolated fibroblasts from IPF patients and animal models. Blockade of CHK1/2 expression or activity-induced DNA damage overload and reverted the apoptosis-resistant and fibroproliferative phenotype of disease cells. Moreover, inhibition of CHK1/2 was sufficient to interfere with transforming growth factor beta 1-mediated fibroblast activation. Importantly, pharmacological inhibition of CHK1/2 using LY2606368 attenuated fibrosis and pulmonary vascular remodelling leading to improvement in respiratory mechanics and haemodynamic parameters in two animal models mimicking IPF and IPF+PH.Conclusion: This study identifies CHK1/2 as key regulators of lung fibrosis and provides a proof of principle for CHK1/2 inhibition as a potential novel therapeutic option for IPF and IPF+PH. [ABSTRACT FROM AUTHOR]

Abstract Pulmonary arterial hypertension (PAH) encompasses a group of clinical entities characterized by sustained vasoconstriction and progressive vascular remodeling that act in concert to elevate pulmonary vascular resistance. The current treatments for PAH are mainly dedicated to target the process of vasoconstriction and do not offer a cure. There is now accumulating evidence that expansion of pulmonary artery cells due to increased proliferation and apoptotic evasion is a key pathological component of vascular remodeling that occurs in PAH. Thus, vascular lesions seen in advanced PAH patients present some cancer-like characteristics offering important avenues for exploration and expanding treatment options. In this review article, we will discuss recent advances into mechanisms underlying disease progression, with a focus on pulmonary artery smooth muscle cells. [ABSTRACT FROM AUTHOR]

Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by a sustained elevation of pulmonary artery (PA) pressure, right ventricular failure, and premature death. Enhanced proliferation and resistance to apoptosis (as seen in cancer cells) of PA smooth muscle cells (PASMCs) is a major pathological hallmark contributing to pulmonary vascular remodeling in PAH, for which current therapies have only limited effects. Emerging evidence points toward a critical role for Enhancer of Zeste Homolog 2 (EZH2) in cancer cell proliferation and survival. However, its role in PAH remains largely unknown. The aim of this study was to determine whether EZH2 represents a new factor critically involved in the abnormal phenotype of PAH-PASMCs. We found that EZH2 is overexpressed in human lung tissues and isolated PASMCs from PAH patients compared to controls as well as in two animal models mimicking the disease. Through loss- and gain-of-function approaches, we showed that EZH2 promotes PAH-PASMC proliferation and survival. By combining quantitative transcriptomic and proteomic approaches in PAH-PASMCs subjected or not to EZH2 knockdown, we found that inhibition of EZH2 downregulates many factors involved in cell-cycle progression, including E2F targets, and contributes to maintain energy production. Notably, we found that EZH2 promotes expression of several nuclear-encoded components of the mitochondrial translation machinery and tricarboxylic acid cycle genes. Overall, this study provides evidence that, by overexpressing EZH2, PAH-PASMCs remove the physiological breaks that normally restrain their proliferation and susceptibility to apoptosis and suggests that EZH2 or downstream factors may serve as therapeutic targets to combat pulmonary vascular remodeling. [ABSTRACT FROM AUTHOR]

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are fatal diseases; however, their pathogenesis still remains to be elucidated. We have recently screened novel pathogenic molecules and have performed drug discovery targeting those molecules. Pulmonary artery smooth muscle cells (PASMCs) in patients with PAH (PAH-PASMCs) have high proliferative properties like cancer cells, which leads to thickening and narrowing of distal pulmonary arteries. Thus, we conducted a comprehensive analysis of PAH-PASMCs and lung tissues to search for novel pathogenic proteins. We validated the pathogenic role of the selected proteins by using tissue-specific knockout mice. To confirm its clinical significance, we used patient-derived blood samples to evaluate the potential as a biomarker for diagnosis and prognosis. Finally, we conducted a high throughput screening and found inhibitors for the pathogenic proteins. [ABSTRACT FROM AUTHOR]

Background: Pulmonary arterial hypertension (PAH) is a vascular remodeling disease characterized by persistent elevation of pulmonary vascular resistance, which results in a striking increase in right ventricular (RV) afterload and subsequent failure. Pulmonary artery (PA) smooth muscle cells (PASMCs) from PAH patients exhibit a cancer-like phenotype with increased glycolysis (Hexokinase 2 activity) and reduced glucose oxidation (inhibition of pyruvate dehydrogenase (PDH)) promoting cell proliferation and apoptosis-resistant contributing to obliteration of the PA lumen. Emerging evidence have demonstrated a critical role for the histone methyltransferase EZH2 in cancer cell survival and several EZH2 inhibitors are now clinically investigated. However, its role in PAH remains unknown. We hypothesized that EZH2 expression is upregulated in PAH-PASMCs leading to PA remodeling. Methods and Results: Using Western blot (WB), we showed that EZH2 is upregulated in lungs, distal PAs and isolated PASMCs from PAH patients (p<0.01, n=10) compared to controls. Consistently, increased EZH2 expression was found in distal PAs from animal models mimicking PAH (monocrotaline and Sugen/Hypoxia). Using proteomic LC-MSMS approach followed by Maxquant/Andromeda analysis in PASMCs isolated from 4 PAH patients, we identified 139 proteins differentially expressed (27 up-regulated ≥ 1.2 or and 112 down-regulated ≤ 0.84; p ≤ 0.05) following EZH2 knockdown. Results of KEGG pathway analysis revealed that the tricarboxylic acid (TCA) cycle, carbon metabolism and metabolic pathways were the top significant pathways (FDR p-value <10-4). This suggests that EZH2 is important for regulating bioenergetic metabolism in PAH-PASMCs. In agreement with this, pharmacological (GSK126 or EPZ-6438) or molecular (siEZH2) inhibition of EZH2 leads to reduced expression (WB) of Hexokinase 2, pPDH and PDH. This was associated with a significant reduction in PAH-PASMC proliferation (Ki67 labeling and EdU assay, p<0.001) and resistance to apoptosis (Annexin V assay p<0.001). Conclusion: We provide evidence that EZH2 is overexpressed in human PAH and implicated in the pro-proliferative and anti-apoptotic phenotype of PAH-PASMCs. [ABSTRACT FROM AUTHOR]