Therapeutic Target For Pulmonary Arterial Hypertension Research Articles

Serum uric acid and pulmonary arterial hypertension: A two-sample Mendelian randomization study

BackgroundObservational studies have suggested a correlation between hyperuricemia and pulmonary arterial hypertension (PAH), yet the causal relationship remains uncertain. We aimed to establish this link using Mendelian Randomization (MR) methods. ObjectivesBased on publicly accessible data, our study employs MR to determine the causal relationship between uric acid (UA) and PAH. MethodMR analysis was conducted among individuals of European descent. Genetic instruments linked to UA (p-value < 5 × 10–8) were extracted from the Chronic Kidney Disease Genetic Consortium and genome-wide association study databases. PAH risk genetic associations were sourced separately. We employed four MR methods (MR-Egger, weighted median, inverse variance weighted, and weighted mode) with selected instrumental variables to assess the causal association between UA and PAH. MR-PRESSO was used to evaluate pleiotropy and outlier Single Nucleotide Polymorphisms (SNPs), while Cochran's Q test and funnel plot assessed SNP heterogeneity. Leave-one-out analysis examined SNP impacts on causal assessment. ResultTwo-sample MR analysis revealed a positive, causal relationship between UA levels and PAH. ConclusionOur MR analysis provides robust evidence of a causal link between serum UA and PAH, suggesting UA's potential as a biomarker and therapeutic target for PAH.

Inhibition of DLL4/Notch Signaling Pathway Promotes M2 Polarization and Cell Proliferation in Pulmonary Arterial Hypertension.

In this study, we conducted a comprehensive analysis to identify key genes and pathways associated with pulmonary arterial hypertension (PAH) and investigated the role of delta-like ligand 4 (DLL4) in PAH pathogenesis. Through integrated analysis of multiple data sets, we identified 6 candidate differentially expressed genes (DEGs), notably DLL4, which showed the highest distinguishing efficiency between PAH and control samples. Functional and pathway enrichment analyses revealed the involvement of DLL4 in critical biological processes and pathways related to PAH, including notch signaling, immune cell function, and inflammatory responses. Further investigation demonstrated that decreased DLL4 expression correlated with increased M2 macrophage polarization, suggesting a potential role for DLL4 in preventing M2 differentiation. Additionally, the DLL4/Notch1 axis was found to influence the Notch profile and regulate signaling mediators during M2 differentiation. These findings highlight DLL4 as a promising biomarker and therapeutic target for PAH, shedding light on the underlying molecular mechanisms and providing insights for the development of novel treatment strategies.

Novel Drp1 GTPase Inhibitor, Drpitor1a: Efficacy in Pulmonary Hypertension.

Drp1 (dynamin-related protein 1), a large GTPase, mediates the increased mitochondrial fission, which contributes to hyperproliferation of pulmonary artery smooth muscle cells in pulmonary arterial hypertension (PAH). We developed a potent Drp1 GTPase inhibitor, Drpitor1a, but its specificity, pharmacokinetics, and efficacy in PAH are unknown. Drpitor1a's ability to inhibit recombinant and endogenous Drp1 GTPase was assessed. Drpitor1a's effects on fission were studied in control and PAH human pulmonary artery smooth muscle cells (hPASMC) and blood outgrowth endothelial cells (BOEC). Cell proliferation and apoptosis were studied in hPASMC. Pharmacokinetics and tissue concentrations were measured following intravenous and oral drug administration. Drpitor1a's efficacy in regressing monocrotaline-PAH was assessed in rats. In a pilot study, Drpitor1a reduced PA remodeling only in females. Subsequently, we compared Drpitor1a to vehicles in control and monocrotaline-PAH females. Drp1 GTPase activity was increased in PAH hPASMC. Drpitor1a inhibited the GTPase activity of recombinant and endogenous Drp1 and reversed the increased fission, seen in PAH hPASMC and PAH BOEC. Drpitor1a inhibited proliferation and induced apoptosis in PAH hPASMC without affecting electron transport chain activity, respiration, fission/fusion mediator expression, or mitochondrial Drp1 translocation. Drpitor1a did not inhibit proliferation or alter mitochondrial dynamics in normal hPASMC. Drpitor1a regressed monocrotaline-PAH without systemic vascular effects or toxicity. Drpitor1a is a specific Drp1 GTPase inhibitor that reduces mitochondrial fission in PAH hPASMC and PAH BOEC. Drpitor1a reduces proliferation and induces apoptosis in PAH hPASMC and regresses monocrotaline-PAH. Drp1 is a therapeutic target in PAH, and Drpitor1a is a potential therapy with an interesting therapeutic sexual dimorphism.

The TREK-1 potassium channel is a potential pharmacological target for vasorelaxation in pulmonary hypertension.

Pulmonary arterial hypertension (PAH) is a progressive disease in which chronic membrane potential (Em) depolarisation of the pulmonary arterial smooth muscle cells (PASMCs) causes calcium overload, a key pathological alteration. Under resting conditions, the negative Em is mainly set by two pore domain potassium (K2P) channels, of which the TASK-1 has been extensively investigated. Ion channel currents and membrane potential of primary cultured human(h) PASMCs were measured using the voltage- and current clamp methods. Intracellular [Ca2+] was monitored using fluorescent microscopy. Pulmonary BP and vascular tone measurements were also performed ex vivo using a rat PAH model. TREK-1 was the most abundantly expressed K2P in hPASMCs of healthy donors and idiopathic(I) PAH patients. Background K+-current was similar in hPASMCs for both groups and significantly enhanced by the TREK activator ML-335. In donor hPASMCs, siRNA silencing or pharmacological inhibition of TREK-1 caused depolarisation, reminiscent of the electrophysiological phenotype of idiopathic PAH. ML-335 hyperpolarised donor hPASMCs and normalised the Em of IPAH hPASMCs. A close link was found between TREK-1 activity and intracellular Ca2+-signalling using a channel activator, ML-335, and an inhibitor, spadin. In the rat, ML-335 relaxed isolated pre-constricted pulmonary arteries and significantly decreased pulmonary arterial pressure in the isolated perfused lung. These data suggest that TREK-1is a key factor in Em setting and Ca2+ homeostasis of hPASMC, and therefore, essential for maintenance of a low resting pulmonary vascular tone. Thus TREK-1 may represent a new therapeutic target for PAH.

Medical Management of Pulmonary Arterial Hypertension: Current Approaches and Investigational Drugs.

Pulmonary arterial hypertension (PAH) is a malignant pulmonary vascular syndrome characterized by a progressive increase in pulmonary vascular resistance and pulmonary arterial pressure, which eventually leads to right heart failure and even death. Although the exact mechanism of PAH is not fully understood, pulmonary vasoconstriction, vascular remodeling, immune and inflammatory responses, and thrombosis are thought to be involved in the development and progression of PAH. In the era of non-targeted agents, PAH had a very dismal prognosis with a median survival time of only 2.8 years. With the deep understanding of the pathophysiological mechanism of PAH as well as advances in drug research, PAH-specific therapeutic drugs have developed rapidly in the past 30 years, but they primarily focus on the three classical signaling pathways, namely the endothelin pathway, nitric oxide pathway, and prostacyclin pathway. These drugs dramatically improved pulmonary hemodynamics, cardiac function, exercise tolerance, quality of life, and prognosis in PAH patients, but could only reduce pulmonary arterial pressure and right ventricular afterload to a limited extent. Current targeted agents delay the progression of PAH but cannot fundamentally reverse pulmonary vascular remodeling. Through unremitting efforts, new therapeutic drugs such as sotatercept have emerged, injecting new vitality into this field. This review comprehensively summarizes the general treatments for PAH, including inotropes and vasopressors, diuretics, anticoagulants, general vasodilators, and anemia management. Additionally, this review elaborates the pharmacological properties and recent research progress of twelve specific drugs targeting three classical signaling pathways, as well as dual-, sequential triple-, and initial triple-therapy strategies based on the aforementioned targeted agents. More crucially, the search for novel therapeutic targets for PAH has never stopped, with great progress in recent years, and this review outlines the potential PAH therapeutic agents currently in the exploratory stage to provide new directions for the treatment of PAH and improve the long-term prognosis of PAH patients.

FUT8-Mediated Core Fucosylation Promotes the Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a progressive cardiopulmonary disease with unclear underlying molecular mechanisms and limited therapeutic options. This study aimed to explore the role of core fucosylation and the only glycosyltransferase FUT8 in PAH. We observed increased core fucosylation in a monocrotaline (MCT)-induced PAH rat model and isolated rat pulmonary artery smooth muscle cells (PASMCs) treated with platelet-derived growth factor-BB (PDGF-BB). We found that 2-fluorofucose (2FF), a drug used to inhibit core fucosylation, improved hemodynamics and pulmonary vascular remodeling in MCT-induced PAH rats. In vitro, 2FF effectively restrains the proliferation, migration, and phenotypic switching of PASMCs and promotes apoptosis. Compared with controls, serum FUT8 concentration in PAH patients and MCT-induced rats was significantly elevated. FUT8 expression appeared increased in the lung tissues of PAH rats, and the co-localization of FUT8 with α-SMA was also observed. SiRNA was used to knockdown FUT8 in PASMCs (siFUT8). After effectively silencing FUT8 expression, phenotypic changes induced in PASMCs by PDGF-BB stimulation were alleviated. FUT8 activated the AKT pathway, while the admission of AKT activator SC79 could partially counteract the negative effect of siFUT8 on the proliferation, apoptotic resistance, and phenotypic switching of PASMCs, which may be involved in the core fucosylation of vascular endothelial growth factor receptor (VEGFR). Our research confirmed the critical role of FUT8 and its mediated core fucosylation in pulmonary vascular remodeling in PAH, providing a potential novel therapeutic target for PAH.

Identification of JPX-RABEP1 Pair as an Immune-Related Biomarker and Therapeutic Target in Pulmonary Arterial Hypertension by Bioinformatics and Experimental Analyses

Pulmonary arterial hypertension (PAH) is a pulmonary vascular disease characterized by pulmonary vascular remodeling and right heart enlargement the pathogenesis of PAH is complicated; no biologic-based therapy is available for the treatment of PAH, but recent studies suggest that inflammatory response and abnormal proliferation of pulmonary artery smooth muscle cells are the main pathogenic mechanism, while the role of immune-related long non-coding RNAs (lncRNAs) remains unclear. The aim of this study was to systematically analyze immune-related lncRNAs in PAH. Here, we downloaded a publicly available microarray data from PAH and control patients (GSE113439). A total of 243 up-regulated and 203 down-regulated differentially expressed genes (DEGs) were screened, and immune-related DEGs were further obtained from ImmPort. The immune-related lncRNAs were obtained by co-expression analysis of immune-related mRNAs. Then, immune-related lncRNAs-mRNAs network including 2 lncRNAs and 6 mRNAs was constructed which share regulatory miRNAs and have significant correlation. Among the lncRNA-mRNA pairs, one pair (JPX-RABEP1) was verified in the validating dataset GSE53408 and PAH mouse model. Furthermore, the immune cell infiltration analysis of the GSE113439 dataset revealed that the JPX-RABEP1 pair may participate in the occurrence and development of PAH through immune cell infiltration. Together, our findings reveal that the lncRNA-mRNA pair JPX-RABEP1 may be a novel biomarker and therapeutic target for PAH.

Abstract 15069: The Rna M 6 A Demethylase, Fto, Regulates Vascular Remodeling in the Pathogenesis of Pulmonary Arterial Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a devastating disease characterized by obliterative pulmonary vascular remodeling and progressive elevation of pulmonary vascular resistance that leads to right heart failure and premature death. RNA modifications such as N6-methyladenosine (m 6 A) has have recently been discovered as essential regulators of gene expression but its function in regulating the development of PAH remain unclear. Hypothesis: Fat mass and obesity-associated protein (FTO), as a major m 6 A eraser, acts as a key regulator of endothelial cell (EC) dysfunction and pulmonary vascular remodeling and, thus, is a novel therapeutic target for PAH. Methods: To determine the FTO expression on the idiopathic PAH (IPAH) patients, we performed Western blotting and immunofluorescence on lung tissue from IPAH patients. A novel mouse model with Tie2-Cre-mediated deletion of Fto in endothelial cells was generated and treated with hypoxia for 3 weeks to induce experimental PAH. Measurement of right ventricular systolic pressure (RVSP) and weight ratio of right ventricular versus left ventricular plus septum (RV/LV+S), an indicator of RV hypertrophy were determined. To evaluate the translational potential of targeting FTO in PAH, rats were exposed to monocrotaline to induce pulmonary hypertension and then were treated with FTO inhibitor FB23-2. RVSP, RV/(LV+S) ratio and histology assessment were measured subsequently. Results: FTO expression level is markedly elevated in the endothelial cells of IPAH patients. The Tie2-Cre-Fto (CKO) mice exhibited inhibited PAH under hypoxia treatment as evident by reduced RVSP and lower RV/(LV+S) ratio. Histological and immunofluorescent staining showed that media layer of pulmonary arteries had less cell proliferation and reduced pulmonary vascular remodeling. Moreover, preclinical MCT-rat PAH model showed attenuated PAH phenotype as well as pulmonary vascular remodeling with pharmacological inhibition of FTO. Conclusions: These studies demonstrate that FTO expression markedly elevates in the EC of IPAH patients. Tie2-Cre mediated loss of FTO protects mice from hypoxia-induced PAH. Thus, targeting FTO is a promising therapeutic strategy for PAH.

HNRNPA2B1: RNA-Binding Protein That Orchestrates Smooth Muscle Cell Phenotype in Pulmonary Arterial Hypertension.

RNA-binding proteins are master orchestrators of gene expression regulation. They regulate hundreds of transcripts at once by recognizing specific motifs. Thus, characterizing RNA-binding proteins targets is critical to harvest their full therapeutic potential. However, such investigation has often been restricted to a few RNA-binding protein targets, limiting our understanding of their function. In cancer, the RNA-binding protein HNRNPA2B1 (heterogeneous nuclear ribonucleoprotein A2B1; A2B1) promotes the pro-proliferative/anti-apoptotic phenotype. The same phenotype in pulmonary arterial smooth muscle cells (PASMCs) is responsible for the development of pulmonary arterial hypertension (PAH). However, A2B1 function has never been investigated in PAH. Through the integration of computational and experimental biology, the authors investigated the role of A2B1 in human PAH-PASMC. Bioinformatics and RNA sequencing allowed them to investigate the transcriptome-wide function of A2B1, and RNA immunoprecipitation and A2B1 silencing experiments allowed them to decipher the intricate molecular mechanism at play. In addition, they performed a preclinical trial in the monocrotaline-induced pulmonary hypertension rat model to investigate the relevance of A2B1 inhibition in mitigating pulmonary hypertension severity. They found that A2B1 expression and its nuclear localization are increased in human PAH-PASMC. Using bioinformatics, they identified 3 known motifs of A2B1 and all mRNAs carrying them. In PAH-PASMC, they demonstrated the complementary nonredundant function of A2B1 motifs because all motifs are implicated in different aspects of the cell cycle. In addition, they showed that in PAH-PASMC, A2B1 promotes the expression of its targets. A2B1 silencing in PAH-PASMC led to a decrease of all tested mRNAs carrying an A2B1 motif and a concomitant decrease in proliferation and resistance to apoptosis. Last, in vivo A2B1 inhibition in the lungs rescued pulmonary hypertension in rats. Through the integration of computational and experimental biology, the study revealed the role of A2B1 as a master orchestrator of the PAH-PASMC phenotype and its relevance as a therapeutic target in PAH.

Weighted gene co-expression network analysis identifies dysregulated B-cell receptor signaling pathway and novel genes in pulmonary arterial hypertension.

BackgroundPulmonary arterial hypertension (PAH) is a devastating cardio-pulmonary vascular disease in which chronic elevated pulmonary arterial pressure and pulmonary vascular remodeling lead to right ventricular failure and premature death. However, the exact molecular mechanism causing PAH remains unclear.MethodsRNA sequencing was used to analyze the transcriptional profiling of controls and rats treated with monocrotaline (MCT) for 1, 2, 3, and 4 weeks. Weighted gene co-expression network analysis (WGCNA) was employed to identify the key modules associated with the severity of PAH. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to explore the potential biological processes and pathways of key modules. Real-time PCR and western blot analysis were used to validate the gene expression. The hub genes were validated by an independent dataset obtained from the Gene Expression Omnibus database.ResultsA total of 26 gene modules were identified by WGCNA. Of these modules, two modules showed the highest correlation with the severity of PAH and were recognized as the key modules. GO analysis of key modules showed the dysregulated inflammation and immunity, particularly B-cell-mediated humoral immunity in MCT-induced PAH. KEGG pathway analysis showed the significant enrichment of the B-cell receptor signaling pathway in the key modules. Pathview analysis revealed the dysregulation of the B-cell receptor signaling pathway in detail. Moreover, a series of humoral immune response-associated genes, such as BTK, BAFFR, and TNFSF4, were found to be differentially expressed in PAH. Additionally, five genes, including BANK1, FOXF1, TLE1, CLEC4A1, and CLEC4A3, were identified and validated as the hub genes.ConclusionThis study identified the dysregulated B-cell receptor signaling pathway, as well as novel genes associated with humoral immune response in MCT-induced PAH, thereby providing a novel insight into the molecular mechanisms underlying inflammation and immunity and therapeutic targets for PAH.

BMPR1A promotes ID2-ZEB1 interaction to suppress excessive endothelial to mesenchymal transition.

Components of bone morphogenetic protein (BMP) signalling have been implicated in both pathogenesis of pulmonary arterial hypertension (PAH) and endothelial-mesenchymal transition (EndoMT). In particular, the importance of BMP type 2 receptor in these processes has been extensively analysed. However, the contribution of BMP type 1 receptors (BMPR1s) to the onset of PAH and EndoMT remains poorly understood. BMPR1A, one of BMPR1s, was recently implicated in the pathogenesis of PAH, and was found to be down-regulated in the lungs of PAH patients, neither the downstream mechanism nor its contribution to EndoMT has been described. Therefore, we aim to delineate the role of endothelial BMPR1A in modulating EndoMT and pathogenesis of PAH. We find that BMPR1A knockdown in endothelial cells (ECs) induces hallmarks of EndoMT, and deletion of endothelial Bmpr1a in adult mice (Bmpr1aiECKO) leads to development of PAH-like symptoms due to excessive EndoMT. By lineage tracing, we show that endothelial-derived smooth muscle cells are increased in endothelial Bmpr1a-deleted mice. Mechanistically, we identify ZEB1 as a primary target for BMPR1A in this setting; upon BMPR1A activation, ID2 physically interacts and sequesters ZEB1 to attenuate transcription of Tgfbr2, which in turn lowers the responses of ECs towards transforming growth factor beta (TGFβ) stimulation and prevents excessive EndoMT. In Bmpr1aiECKO mice, administering endothelial targeting lipid nanoparticles containing siRNA against Tgfbr2 effectively ameliorate PAH, reiterating the importance of BMPR1A-ID2/ZEB1-TGFBR2 axis in modulating progression of EndoMT and pathogenesis of PAH. We demonstrate that BMPR1A is key to maintain endothelial identity and to prevent excessive EndoMT. We identify BMPR1A-induced interaction between ID2 and ZEB1 is the key regulatory step for onset of EndoMT and pathogenesis of PAH. Our findings indicate that BMPR1A-ID2/ZEB1-TGFBR2 signalling axis could serve as a potential novel therapeutic target for PAH and other EndoMT-related vascular disorders.

Identification of Signal Pathways and Hub Genes of Pulmonary Arterial Hypertension by Bioinformatic Analysis.

Pulmonary arterial hypertension (PAH) is a progressive and complex pulmonary vascular disease with poor prognosis. The aim of this study was to provide a new understanding of the pathogenesis of disease and potential treatment targets for patients with PAH based on multiple-microarray analysis.Two microarray datasets (GSE53408 and GSE113439) downloaded from the Gene Expression Omnibus (GEO) database were analysed. All the raw data were processed by R, and differentially expressed genes (DEGs) were screened out by the “limma” package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed and visualized by R and Cytoscape software. Protein-protein interactions (PPI) of DEGs were analysed based on the NetworkAnalyst online tool. A total of 442 upregulated DEGs and 84 downregulated DEGs were identified. GO enrichment analysis showed that these DEGs were mainly enriched in mitotic nuclear division, organelle fission, chromosome segregation, nuclear division, and sister chromatid segregation. Significant KEGG pathway enrichment included ribosome biogenesis in eukaryotes, RNA transport, proteoglycans in cancer, dilated cardiomyopathy, rheumatoid arthritis, vascular smooth muscle contraction, focal adhesion, regulation of the actin cytoskeleton, and hypertrophic cardiomyopathy. The PPI network identified 10 hub genes including HSP90AA1, CDC5L, MDM2, LRRK2, CFTR, IQGAP1, CAND1, TOP2A, DDX21, and HIF1A. We elucidated potential biomarkers and therapeutic targets for PAH by bioinformatic analysis, which provides a theoretical basis for future study.

Abstract P3001: Hnrnpa2b1 An Rna-binding Protein That Orchestrates Smooth Muscle Cell Phenotype In Pulmonary Arterial Hypertension.

Background: RNA-binding proteins (RPBs) are master orchestrators of gene expression regulation. RBPs regulate hundreds of transcripts at once by recognizing specific motifs. Characterizing RBP targets is critical to harvest their full therapeutic potential. However, such investigation has often been restricted to a few RBP targets, limiting our understanding of their function. In cancer, the RBP HNRNPA2B1 (A2B1) promotes the pro-proliferative / anti-apoptotic phenotype. The same phenotype in pulmonary arterial smooth muscle cells (PASMC) is responsible for the development of pulmonary arterial hypertension (PAH). However, A2B1 function has never been investigated in PAH. Methods: Through the integration of computational and experimental biology, we investigated the role of A2B1 in human PAH-PASMC. Bioinformatics and RNA-sequencing allowed us to investigate the transcriptome-wide function of A2B1, while RNA immunoprecipitation and A2B1 silencing experiments in vitro allowed us to decipher the intricate molecular mechanism at play. In addition, we performed a pre-clinical trial in the monocrotaline-induced pulmonary hypertension rat model to investigate the relevance of A2B1 inhibition in mitigating pulmonary hypertension severity. Results: In the present study, we found that A2B1 is up-regulated in human PAH-PASMC. We also show that A2B1 localization shifts in PAH-PASMC from cytoplasmic to nuclear mainly due to significantly higher expression of B1 isoform compared to A2 isoform of A2B1. Using bio-informatics, we identified three known motifs of A2B1 and all mRNAs carrying them. In PAH-PASMC, we demonstrated the complementary non-redundant function of A2B1 motifs as all motifs are implicated in different aspect of the cell cycle. In addition, we showed that in PAH-PASMC, A2B1 promotes the expression of its targets. A2B1 silencing in PAH-PASMC lead to a decrease of all tested mRNAs carrying an A2B1 motif, and an according decrease in proliferation and resistance to apoptosis. Finally, in vivo A2B1 inhibition in the lungs rescued pulmonary hypertension in rats. Conclusion: Through the integration of computational and experimental biology, our study revealed the role of A2B1 as a master orchestrator of the PAH-PASMC phenotype and its relevance as a therapeutic target in PAH.

THERAPEUTIC EFFECTS OF NEBULIZATION- BASED DELIVERY OF ANTI-MIR-146A IN EXPERIMENTAL PULMONARY ARTERIAL HYPERTENSION

Objective: Pulmonary arterial hypertension (PAH), is a chronic disorder characterized by excessive pulmonary vascular remodelling, resulting in elevated pulmonary vascular resistance and right ventricle (RV) overload and failure. PAH remains incurable, and new therapeutic approaches are required. The microRNA-146a (miR-146a) promotes vascular smooth muscle cell proliferation and vascular neointimal hyperplasia, both important hallmarks of PAH. This study aimed to investigate the role of miR-146a in the pathophysiology of PAH and in the progression to RV hypertrophy and failure. Design and method: Sprague Dawley rats received a subcutaneous injection of monocrotaline (MCT group) or vehicle (CTRL group) and, after fourteen days they were treated, by intratracheal nebulization, with an anti-miR-146a, forming four distinct groups: CTRL-treated; CTRL-untreated, MCT-treated, and MCT-untreated. Twenty-seven days after MCT injection, echocardiographic and invasive hemodynamic evaluations were performed in all animal groups. Also, wild-type (WT) and miR-146a knock-out (KO) (miR-146a-/-) mice were submitted to either 3 weeks of chronic hypoxia-induced PAH with weekly Sugen 5416 administration (SuHx). Results: Compared to MCT-untreated rats, the MCT-treated rats showed decreased RV hypertrophy, (as measured by the Fulton index), decreased RV end-diastolic diameter/left ventricle end-diastolic diameter (RVEDD/LVEDD) ratio, and decreased in RV diastolic pressures. KO-SuHx group, when compared to WT-SuHx group, showed decreased RV hypertrophy (as measured by the Fulton index), and decreased RV systolic pressures and dilation, as well as lower RV end end-diastolic diameter (RVEDDi) and right atria area (RAAi). Conclusions: Our findings show that miR-146a pharmacological or genetic inhibition reduces RV remodelling and improves cardiac function. Thus, miR-146a represents a promising therapeutic target in PAH.

VPO1/HOCl/ERK pathway mediates the right ventricular remodeling in rats with hypoxic pulmonary hypertension

Right ventricular (RV) remodeling is a major feature of pulmonary arterial hypertension (PAH). Vascular peroxidase 1 (VPO1) is reported to participate in the process of PAH. This study aims to explore whether VPO1 contributes to hypoxia-induced cardiac hypertrophy and the underlying mechanisms. SD rats were exposure to continuous hypoxia (10% O2) for 3 weeks, which showed RV hypertrophy (increases in the ratio of RV weight to tibia length, cardiac cell size and hypertrophic markers), concomitant with upregulation of VPO1, elevation in hypochlorous acid (HOCl) production and ERK phosphorylation. In hypoxia (3% O2)-induced hypertrophic H9c2 cells, similar characteristics of cardiac hypertrophy to that of hypoxia-treated rats were observed. Administration of VPO1 siRNA or NaHS (the HOCl inhibitor) suppressed HOCl production, ERK phosphorylation, and cardiac hypertrophy. Replacement of hypoxia with NaClO (exogenous HOCl) could also induce cardiac cell hypertrophy and activate ERK signaling pathway. In addition, hypoxia-induced cardiac hypertrophy could be blocked by PD98059 (the ERK-specific inhibitor). Based on these observations, we conclude that VPO1 promotes RV remodeling in PAH rats through catalyzing HOCl production, leading to the activation of ERK signaling. Thus, VPO1 may have the potential as a therapeutic target for PAH.

Involvement of Orai1 Ca2+ channel in the pathogenesis of pulmonary arterial hypertension. Orai1 as a new potential therapeutic target?

The pathobiology of pulmonary arterial hypertension (PAH) involves pulmonary arterial smooth muscle cells (PASMCs) dysfunction leading to abnormal proliferation, apoptosis resistance and vasoconstriction. Store-operated Ca 2+ entry (SOCE) strongly contributes to Ca 2+ homeostasis in PASMCs, however, the role of SOCE archetype Orai1 Ca 2+ channel in PAH pathogenesis was unclear. To understand the role of Orai1, we used a combination of Ca 2+ imaging, molecular biology, in vitro, ex vivo and in vivo approaches. We also analyzed the consequence of in vivo pharmacological inhibition of Orai1 in two experimental PH models. We demonstrated that SOCE is increased in human PASMCs from patients with idiopathic PAH (iPAH). Pharmacological inhibition of Orai1 or Orai1 knockdown by siRNA reduced SOCE as well as aberrant proliferation, apoptosis resistance phenotype, exacerbated cell migration and exacerbated calcineurin activity in iPAH-PASMCs. We showed that pharmacological inhibition of Orai1 reduced the capacity of isolated human pulmonary arteries to constrict. In PH rat models induced by Monocrotaline (MCT) or Chronic-Hypoxia (CH) exposure, we found an overexpression of Orai1 in lung and isolated pulmonary arteries. Finally, we found that the in vivo pharmacological inhibition of Orai1 by three different blockers reduced experimental-PH (MCT and CH). Altogether our results provide proof of concept that Orai1 should be considered as a new therapeutic target in PAH.

Caspase-4/11-Mediated Pulmonary Artery Endothelial Cell Pyroptosis Contributes to Pulmonary Arterial Hypertension.

Endothelial dysfunction enhances vascular inflammation, which initiates pulmonary arterial hypertension (PAH) pathogenesis, further induces vascular remodeling and right ventricular failure. Activation of inflammatory caspases is an important initial event at the onset of pyroptosis. Studies have shown that caspase-1-mediated pyroptosis has played a crucial role in the pathogenesis of PAH. However, the role of caspase-11, another inflammatory caspase, remains to be elucidated. Therefore, the purpose of this study was to clarify the role of caspase-11 in the development of PAH and its mechanism on endothelial cell function. The role of caspase-11 in the progression of PAH and vascular remodeling was assessed in vivo. In vitro, the effect of caspase-4 silencing on the human pulmonary arterial endothelial cells pyroptosis was determined. We confirmed that caspase-11 and its human homolog caspase-4 were activated in PAH animal models and TNF (tumor necrosis factor)-α-induced human pulmonary arterial endothelial cells. Caspase-11-/- relieved right ventricular systolic pressure, right ventricle hypertrophy, and vascular remodeling in Sugen-5416 combined with chronic hypoxia mice model. Meanwhile, pharmacological inhibition of caspase-11 with wedelolactone exhibited alleviated development of PAH on the monocrotaline-induced rat model. Moreover, knockdown of caspase-4 repressed the onset of TNF-α-induced pyroptosis in human pulmonary arterial endothelial cells and inhibited the activation of pyroptosis effector GSDMD (gasdermin D) and GSDME (gasdermin E). These observations identified the critical role of caspase-4/11 in the pyroptosis pathway to modulate pulmonary vascular dysfunction and accelerate the progression of PAH. Our findings provide a potential diagnostic and therapeutic target in PAH.

Abstract 12681: Implication of Aurora Kinase B in Pulmonary Arterial Hypertension

Objective: Pulmonary arterial hypertension (PAH) is a vascular disease characterized by a progressive remodelling of pulmonary arteries (PAs). This leads to an elevation in PA pressure and resistance, leading to right heart failure and death. Nowadays, it is recognized that PA smooth muscle cells (PASMCs) are key actors in the histopathological changes in PAH. As seen in cancer cells, PASMCs exhibit a pro-proliferative and anti-apoptotic cancer-like phenotype, sustained by an important metabolic switch known as Warburg effect. Aurora kinase B (AURKB) is strongly involved in cell proliferation, apoptosis and metabolism by controlling cell cycle activation and mitochondrial functions. Previous research has shown that AURKB is overexpressed in various human cancers and its inhibition repressed tumor progression both in vivo and in vitro, suggesting that it could be a novel therapeutic target in PAH. We thus hypothesized that AURKB is upregulated in PAH and contributes to PAH-PASMCs proliferation and resistance to apoptosis, inhibition of which may reverse PA remodeling. Methods/Results: Using Western blot (WB), we demonstrated a FOXM1-dependent upregulation of AURKB in PASMCs isolated from PAH patients compared to controls (p&lt;0.05 ; n=8-14). Similar results were found in the monocrotaline (MCT) and sugen-hypoxia (Su/Hx) rat models (p&lt;0.05 ; n=11-22). In vitro, we found that pharmacological inhibition of AURKB significantly decreases PAH-PASMC proliferation (EdU incorporation, Ki67 labeling) as well as resistance to apoptosis (Annexin V assay) (p&lt;0.05 ; n=6). We also demonstrated that inhibition of AURKB decreases pro-survival factors such as Survivin and PLK1 and increases apoptosis and cell cycle arrest factors including P21, P27, and P53 (WB; p&lt;0.05 ; n=6). As expected, inhibition of AURKB in PAH-PASMCs was associated with a dose-dependent decrease of phosphohistone H3 expression, a well-known target of AURKB (p&lt;0.05 ; n=6). The therapeutic potential of Barasertib, a clinically available and specific AURKB inhibitor, is currently investigated in both MCT and Su/Hx models. Conclusion: Our preliminary data suggests the contribution of AURKB in PA remodeling and the great potential of using AURKB inhibitors to reverse PAH development.

Abstract 12932: An Epigenetic Upregulation of Dynamin 2, a Regulator of Mitochondrial Fission, Promotes Human and Experimental Pulmonary Arterial Hypertension

Introduction: Increase in mitotic fission in pulmonary arterial smooth muscle cells (PASMC) contributes to the obstructive vasculopathy in pulmonary arterial hypertension (PAH). PAH’s fissogenic phenotype is due, in part, to excessive mitochondrial fission caused by activation of dynamin related protein-1 (Drp1). Recent observation suggests that to complete mitochondrial fission, Drp1 requires assistance from the GTPase dynamin 2 (DNM2). In this study we explore the role of DNM2 in the pathogenesis of PAH. Hypothesis: In PAH, increased expression of DNM2 increases mitochondrial fission and proliferation of PASMC. Methods: Immunoblot was used to quantify the expression of DNM2 in control (n=4) and PAH PASMC (n=5). Immunofluorescence was used to quantify the expression of DNM2 in the pulmonary arteries of monocrotaline (MCT) vs control rats. Flow cytometry was used to assess the effects of manipulating the expression of DNM2 on cell proliferation, cell cycle progression and rates of unstimulated apoptosis. Mitochondrial network structure was assessed using confocal imaging of cells infected with Adv-TOM20 mNeon green. Results: The expression of DNM2 was increased in human PAH PASMC vs control PASMC. Increase in the expression of DNM2 expression was also observed in the pulmonary arteries of MCT-PAH rats. Silencing DNM2 inhibited mitochondrial fission in PAH PASMC. Furthermore, silencing DNM2 inhibited proliferation in PAH PASMC by blocking the cell cycle at G1/G0. Conversely, augmenting DNM2 in normal PASMC induced mitochondrial fission and accelerated cell proliferation, recapitulating the PAH phenotype. In silico analysis identified miR-124-3p as a putative negative regulator of DNM2. Augmenting miR-124-3p decreased DNM2 expression, inhibited proliferation and induced apoptosis in PAH PASMC. Conclusion: DNM2 promotes mitochondrial fission and regulates cell proliferation in human PAH PASMC. Decreased miR-124-3p expression may contribute to upregulation of DNM2 in PAH. This work highlights the importance of DNM2 as partner with Drp1 in regulation of mitochondrial fission and shows that like Drp1, DNM2 is increased in human PAH. DNM2 may constitute new therapeutic target for PAH.

Abstract 9512: Involvement of Orai1 Ca 2+ Channel in the Pathogenesis of Pulmonary Arterial Hypertension. Orai1 as a New Potential Therapeutic Target?

Introduction: Pulmonary arterial hypertension (PAH) is a devastating disease, characterized by a progressive obstruction of distal pulmonary artery (PA) leading to right ventricular hypertrophy and failure. Exacerbated intracellular Ca 2+ signalling contributes to functional abnormalities in pulmonary arterial smooth muscle cells (PASMCs), including aberrant proliferation, apoptosis resistance, exacerbated migration and pulmonary artery contractility. The role of archetypal Store-Operated Ca 2+ entry (SOCE) Orai1 Ca 2+ channel in PAH pathogenesis is unclear. Methods: Using a combination of Ca 2+ imaging, molecular biology, in vitro , ex vivo and in vivo approaches, we decipher the role of Orai1 Ca 2+ channel in pulmonary artery remodelling in PAH. We also analyzed the consequence of in vivo pharmacological inhibition of Orai1 in experimental models of PH. Results: We demonstrated that SOCE is increased in human PASMCs (hPASMCs) from patients with idiopathic PAH (iPAH) associated with an increased expression of Orai1 at mRNA and protein levels. Moreover, in vitro in iPAH-hPASMCs the pharmacological inhibition of Orai1 (by two different inhibitors) or the knockdown of Orai1 by siRNA reduced the SOCE as well as aberrant proliferation, apoptosis resistance phenotype and exacerbated cell migration. In addition, Orai1 knockdown reduced the exacerbated calcineurin activity in iPAH-hPASMCs. Using myograph experiments on isolated human and rat PAs we showed that pharmacological inhibition of Orai1 channels reduced the capacity of PAs to constrict. In rat experimental PH induced by Monocrotaline (MCT)-exposure or by Chronic-Hypoxia (CH) we found an overexpression of Orai1. Finally, in vivo pharmacological inhibition of Orai1 by three different blockers (BTP2, JPIII and 5J4) reduced experimental-PH in these experimental PH-models. Conclusion: In human PAH and experimental PH, the expression of Orai1 is increased compared to controls. In vitro and in vivo inhibition of Orai1 normalize the PAH phenotype of cultured iPAH-hPASMCs and reduce experimental-PH (MCT and CH). These results provide proof of concept that Orai1 contributes to PAH pathogenesis and that pharmacological inhibition of Orai1 should be considered as a new therapeutic target in PAH.