Heterozygous germline mutations in BMPR2, encoding a TGF-beta receptor, cause familial primary pulmonary hypertension

United States Pulmonary Hypertension Scientific Registry (USPHSR): rationale, design, and clinical implications

Diagnostic World Health Organization (WHO) Group 1 pulmonary arterial hypertension (PAH) and Diagnostic Group 1' pulmonary veno-occlusive disease (PVOD) and/or pulmonary capillary hemangiomatosis (PCH) are progressive and fatal disorders. Past registries provided important insights into these disorders, but did not include hormonal exposures or genomic data. The United States Pulmonary Hypertension Scientific Registry (USPHSR) will provide demographic, physiologic, anorexigen and hormone exposure, genomic, and survival data in the current therapeutic era for 499 patients diagnosed with PAH, PVOD, or PCH. The USPHSR also will explore the relationship between pharmacologic, non-pharmacologic, and dietary hormonal exposures and the increased risk for women to develop idiopathic or heritable PAH.

miR-27a promotes endothelial-mesenchymal transition in hypoxia-induced pulmonary arterial hypertension by suppressing BMP signaling

AIM

Growing evidence suggests that endothelial-mesenchymal transition (EndMT) play key roles in pulmonary arterial remodeling during pulmonary arterial hypertension (PAH), but the underlying mechanisms have yet to be fully understood. miR-27a has been shown to promote proliferation of pulmonary arterial cells during PAH, but its role in EndMT remains unexplored. This study was designed to investigate the role and underlying mechanism of miR-27a in EndMT during PAH.

MAIN METHODS

Rats were exposed in hypoxia (10% O₂) for 3 weeks to induce PAH, and human pulmonary artery endothelial cells (HPAECs) were exposed in hypoxia (1% O₂) for 48 h to induce EndMT. Immunohistochemistry, in situ hybridization, immunofluorescence, real-time PCR and Western blot were conducted to detect the expressions of RNAs and proteins, and luciferase assay was used to verify the putative binding site of miR-27a.

KEY FINDINGS

We found that hypoxia up-regulated miR-27a in the tunica intima of rat pulmonary arteries and HPAECs, and that inhibition of miR-27a suppressed hypoxia-induced EndMT. Furthermore, elevated expression of miR-27a suppressed bone morphogenetic protein (BMP) signaling by targeting Smad5, thereby lessening Id2-mediated repression of the 2 critical mediators of EndMT (Snail and Twist).

SIGNIFICANCE

Our data unveiled a novel role of miR-27a in EndMT during hypoxia-induced PAH. Thus, targeting of miR-27a-related pathway may be therapeutically harnessed to treat PAH.

A Potential Role for Exosomal Translationally Controlled Tumor Protein Export in Vascular Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by increased proliferation and resistance to apoptosis of pulmonary vascular cells. Increased expression of translationally controlled tumor protein (TCTP), a prosurvival and antiapoptotic mediator, has recently been demonstrated in patients with heritable PAH; however, its role in the pathobiology of PAH remains unclear. Silencing of TCTP in blood outgrowth endothelial cells (BOECs) isolated from control subjects led to significant changes in morphology, cytoskeletal organization, increased apoptosis, and decreased directionality during migration. Because TCTP is also localized in extracellular vesicles, we isolated BOEC-derived extracellular vesicles (exosomes and microparticles) by sequential ultracentrifugation. BOECs isolated from patients harboring BMPR2 mutations released more exosomes than those derived from control subjects in proapoptotic conditions. Furthermore, TCTP expression was significantly higher in exosomes than in microparticles, indicating that TCTP is mainly exported via exosomes. Coculture assays demonstrated that exosomes transferred TCTP from ECs to pulmonary artery smooth muscle cells, suggesting a role for endothelial-derived TCTP in conferring proliferation and apoptotic resistance. In an experimental model of PAH, rats treated with monocrotaline demonstrated increased concentrations of TCTP in the lung and plasma. Consistent with this finding, we observed increased circulating TCTP levels in patients with idiopathic PAH compared with control subjects. Therefore, our data suggest an important role for TCTP in regulating the critical vascular cell phenotypes that have been implicated in the pathobiology of PAH. In addition, this research implicates TCTP as a potential biomarker for the onset and development of PAH.

Loss of SMAD3 Promotes Vascular Remodeling in Pulmonary Arterial Hypertension via MRTF Disinhibition

RATIONALE

Vascular remodeling in pulmonary arterial hypertension (PAH) results from smooth muscle cell hypertrophy and proliferation of vascular cells. Loss of BMPR-II (bone morphogenetic protein receptor 2) signaling and increased signaling via TGF-β (transforming growth factor β) and its downstream mediators SMAD (small body size [a C. elegans protein] mothers against decapentaplegic [a Drosophila protein family])-2/3 has been proposed to drive lung vascular remodeling; yet, proteomic analyses indicate a loss of SMAD3 in PAH.

OBJECTIVES

We proposed that SMAD3 may be dysregulated in PAH and that loss of SMAD3 may present a pathophysiological master switch by disinhibiting its interaction partner, MRTF (myocardin-related transcription factor), which drives muscle protein expression.

METHODS

SMAD3 levels were measured in lungs from PAH patients, rats treated either with Sugen/hypoxia or monocrotaline (MCT), and in mice carrying a BMPR2 mutation. In vitro, effects of SMAD3 or BMPR2 silencing or SMAD3 overexpression on cell proliferation or smooth muscle hypertrophy were assessed. In vivo, the therapeutic and prophylactic potential of CCG1423, an inhibitor of MRTF, was investigated in Sugen/hypoxia rats.

MEASUREMENTS AND MAIN RESULTS

SMAD3 was downregulated in lungs of patients with PAH and in pulmonary arteries of three independent PAH animal models. TGF-β treatment replicated the loss of SMAD3 in human pulmonary artery smooth muscle cells (huPASMCs) and human pulmonary artery endothelial cells. SMAD3 silencing increased proliferation and migration in huPASMCs and human pulmonary artery endothelial cells. Coimmunoprecipitation revealed reduced interaction of MRTF with SMAD3 in TGF-β-treated huPASMCs and pulmonary arteries of PAH animal models. In huPASMCs, loss of SMAD3 or BMPR-II increased smooth muscle actin expression, which was attenuated by MRTF inhibition. Conversely, SMAD3 overexpression prevented TGF-β-induced activation of an MRTF reporter and reduced actin stress fibers in BMPR2-silenced huPASMCs. MRTF inhibition attenuated PAH and lung vascular remodeling in Sugen/hypoxia rats.

CONCLUSIONS

Loss of SMAD3 presents a novel pathomechanism in PAH that promotes vascular cell proliferation and-via MRTF disinhibition-hypertrophy of huPASMCs, thereby reconciling the parallel induction of a synthetic and contractile huPASMC phenotype.

Bone Morphogenetic Protein 9 Is a Mechanistic Biomarker of Portopulmonary Hypertension

RATIONALE

BMP9 (bone morphogenetic protein 9) is a circulating endothelial quiescence factor with protective effects in pulmonary arterial hypertension (PAH). Loss-of-function mutations in BMP9, its receptors, and downstream effectors have been reported in heritable PAH.

OBJECTIVES

To determine how an acquired deficiency of BMP9 signaling might contribute to PAH.

METHODS

Plasma levels of BMP9 and antagonist soluble endoglin were measured in group 1 PAH, group 2 and 3 pulmonary hypertension (PH), and in patients with severe liver disease without PAH.

MEASUREMENTS AND MAIN RESULTS

BMP9 levels were markedly lower in portopulmonary hypertension (PoPH) versus healthy control subjects, or other etiologies of PAH or PH; distinguished PoPH from patients with liver disease without PAH; and were an independent predictor of transplant-free survival. BMP9 levels were decreased in mice with PH associated with CCl₄-induced portal hypertension and liver cirrhosis, but were normal in other rodent models of PH. Administration of ALK1-Fc, a BMP9 ligand trap consisting of the activin receptor-like kinase-1 extracellular domain, exacerbated PH and pulmonary vascular remodeling in mice treated with hypoxia versus hypoxia alone.

CONCLUSIONS

BMP9 is a sensitive and specific biomarker of PoPH, predicting transplant-free survival and the presence of PAH in liver disease. In rodent models, acquired deficiency of BMP9 signaling can predispose to or exacerbate PH, providing a possible mechanistic link between PoPH and heritable PAH. These findings describe a novel experimental model of severe PH that provides insight into the synergy between pulmonary vascular injury and diminished BMP9 signaling in the pathogenesis of PAH.

Genetic linkage analysis of a large family identifies FIGN as a candidate modulator of reduced penetrance in heritable pulmonary arterial hypertension

BACKGROUND

Mapping the genetic component of molecular mechanisms responsible for the reduced penetrance (RP) of rare disorders constitutes one of the most challenging problems in human genetics. Heritable pulmonary arterial hypertension (PAH) is one such disorder characterised by rare mutations mostly occurring in the bone morphogenetic protein receptor type 2 (BMPR2) gene and a wide heterogeneity of penetrance modifier mechanisms. Here, we analyse 32 genotyped individuals from a large Iberian family of 65 members, including 22 carriers of the pathogenic BMPR2 mutation c.1472G>A (p.Arg491Gln), 8 of them diagnosed with PAH by right-heart catheterisation, leading to an RP rate of 36.4%.

METHODS

We performed a linkage analysis on the genotyping data to search for genetic modifiers of penetrance. Using functional genomics data, we characterised the candidate region identified by linkage analysis. We also predicted the haplotype segregation within the family.

RESULTS

We identified a candidate chromosome region in 2q24.3, 38 Mb upstream from BMPR2, with significant linkage (LOD=4.09) under a PAH susceptibility model. This region contains common variants associated with vascular aetiology and shows functional evidence that the putative genetic modifier is located in the upstream distal promoter of the fidgetin (FIGN) gene.

CONCLUSION

Our results suggest that the genetic modifier acts through FIGN transcriptional regulation, whose expression variability would contribute to modulating heritable PAH. This finding may help to advance our understanding of RP in PAH across families sharing the p.Arg491Gln pathogenic mutation in BMPR2.

Widening the landscape of heritable pulmonary hypertension mutations in paediatric and adult cases

BACKGROUND

Heritable forms of pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease/pulmonary capillary haemangiomatosis (PVOD/PCH) diverge by lung histopathological lesions, clinical and para-clinical presentation, their responsible genes, and mode of transmission. Since the identification of the BMPR2 gene in families affected by PAH, mutations in several other genes have been discovered for both forms. The mutation landscape in these new genes is not yet well known.

METHODS

We set up a next-generation sequencing-based targeted sequencing gene panel allowing known genes for PAH and PVOD/PCH to be analysed simultaneously. Genetic analysis was prospectively performed on 263 PAH and PVOD/PCH patients (adult and paediatric cases).

RESULTS

Pathogenic mutations were identified in 19.5% of sporadic PAH patients (n=180), 54.5% of familial PAH patients and 13.3% of PVOD/PCH patients. BMPR2 was the most frequently mutated gene, followed by TBX4 in both paediatric and adult PAH. BMP9 mutations were identified in 1.2% of adult PAH cases. EIF2AK4 biallelic mutations were restricted to PVOD/PCH. A truncating mutation and a predicted loss-of-function variant were also identified in BMP10 in two severely affected sporadic PAH female patients.

CONCLUSION

Our results confirm that mutations are found in genes beyond BMPR2 in heritable PAH, emphasise the role of TBX4 and BMP9, and designate BMP10 as a new PAH gene.

Germline BMP9 mutation causes idiopathic pulmonary arterial hypertension

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a rare disease with high heritability. Although several predisposing genes have been linked to IPAH, the genetic aetiology remains unknown for a large number of IPAH cases.

METHODS

We conducted an exome-wide gene-based burden analysis on two independent case-control studies, including a total of 331 IPAH cases and 10 508 controls. Functional assessments were conducted to analyse the effects of genetic mutations on protein biosynthesis and function.

RESULTS

The gene encoding human bone morphogenetic protein 9 (BMP9) was identified as a novel genetic locus displaying exome-wide association with IPAH in the discovery cohort (OR 18.8; p=1.9×10^-11). This association was authenticated in the independent replication cohort (p=1.0×10^-5). Collectively, the rare coding mutations in BMP9 occurred in 6.7% of cases, ranking this gene second to BMPR2, comprising a combined significance of 2.7×10^-19 (OR 21.2). Intriguingly, the patients with BMP9 mutations had lower plasma levels of BMP9 than those without. Functional studies showed that the BMP9 mutations led to reduced BMP9 secretion and impaired anti-apoptosis ability in pulmonary arterial endothelial cells.

CONCLUSION

We identify BMP9 as an IPAH culprit gene.

Molecular Research in Chronic Thromboembolic Pulmonary Hypertension

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) is a debilitating disease, for which the underlying pathophysiological mechanisms have yet to be fully elucidated. Occurrence of a pulmonary embolism (PE) is a major risk factor for the development of CTEPH, with non-resolution of the thrombus being considered the main cause of CTEPH. Polymorphisms in the α-chain of fibrinogen have been linked to resistance to fibrinolysis in CTEPH patients, and could be responsible for development and disease progression. However, it is likely that additional genetic predisposition, as well as genetic and molecular alterations occurring as a consequence of tissue remodeling in the pulmonary arteries following a persistent PE, also play an important role in CTEPH. This review summarises the current knowledge regarding genetic differences between CTEPH patients and controls (with or without pulmonary hypertension). Mutations in BMPR2, differential gene and microRNA expression, and the transcription factor FoxO1 have been suggested to be involved in the processes underlying the development of CTEPH. While these studies provide the first indications regarding important dysregulated pathways in CTEPH (e.g., TGF-β and PI3K signaling), additional in-depth investigations are required to fully understand the complex processes leading to CTEPH.

Role of BRCA1-associated protein (BRAP) variant in childhood pulmonary arterial hypertension

Although mutations in several genes have been reported in pulmonary arterial hypertension (PAH), most of PAH cases do not carry these mutations. This study aimed to identify a novel cause of PAH. To determine the disease-causing variants, direct sequencing and multiplex ligation-dependent probe amplification were performed to analyze 18 families with multiple affected family members with PAH. In one of the 18 families with PAH, no disease-causing variants were found in any of BMPR2, ACVRL1, ENG, SMAD1/4/8, BMPR1B, NOTCH3, CAV1, or KCNK3. In this family, a female proband and her paternal aunt developed PAH in their childhood. Whole-exome next-generation sequencing was performed in the 2 PAH patients and the proband’s healthy mother, and a BRCA1-associated protein (BRAP) gene variant, p.Arg554Leu, was identified in the 2 family members with PAH, but not in the proband’s mother without PAH. Functional analyses were performed using human pulmonary arterial smooth muscle cells (hPASMCs). Knockdown of BRAP via small interfering RNA in hPASMCs induced p53 signaling pathway activation and decreased cell proliferation. Overexpression of either wild-type BRAP or p.Arg554Leu-BRAP cDNA constructs caused cell death confounding these studies, however we observed higher levels of p53 signaling inactivation and hPASMC proliferation in cells expressing p.Arg554Leu-BRAP compared to wild-type BRAP. In addition, p.Arg554Leu-BRAP induced decreased apoptosis of hPASMCs compared with wild-type BRAP. In conclusion, we have identified a novel variant of BRAP in a Japanese family with PAH and our results suggest it could have a gain-of-function. This study sheds light on new mechanism of PAH pathogenesis.

Genetics and genomics of pulmonary arterial hypertension

Since 2000 there have been major advances in our understanding of the genetic and genomics of pulmonary arterial hypertension (PAH), although there remains much to discover. Based on existing knowledge, around 25-30% of patients diagnosed with idiopathic PAH have an underlying Mendelian genetic cause for their condition and should be classified as heritable PAH (HPAH). Here, we summarise the known genetic and genomic drivers of PAH, the insights these provide into pathobiology, and the opportunities afforded for development of novel therapeutic approaches. In addition, factors determining the incomplete penetrance observed in HPAH are discussed. The currently available approaches to genetic testing and counselling, and the impact of a genetic diagnosis on clinical management of the patient with PAH, are presented. Advances in DNA sequencing technology are rapidly expanding our ability to undertake genomic studies at scale in large cohorts. In the future, such studies will provide a more complete picture of the genetic contribution to PAH and, potentially, a molecular classification of this disease.

A Combined Targeted and Whole Exome Sequencing Approach Identified Novel Candidate Genes Involved in Heritable Pulmonary Arterial Hypertension

The pathogenesis of idiopathic and heritable forms of pulmonary arterial hypertension is still not completely understood, even though several causative genes have been proposed, so that a third of patients remains genetically unresolved. Here we applied a multistep approach to extend identification of the genetic bases of such a disease by searching for novel candidate genes/pathways. Twenty-eight patients belonging to 18 families were screened for BMPR2 mutations and BMPR2-negative samples were tested for 12 additional candidate genes by means of a specific massive parallel sequencing-based assay. Finally, whole exome sequencing was performed on four patients showing no mutations at known disease genes, as well as on their unaffected parents. In addition to EIF2AK4, which has been already suggested to be associated with pulmonary veno-occlusive disease, we identified the novel candidate genes ATP13A3, CD248, EFCAB4B, involved in lung vascular remodeling that represent reliable drivers contributing to the disease according to their biological functions/inheritance patterns. Therefore, our results suggest that combining gene panel and whole exome sequencing provides new insights useful for the genetic diagnosis of familial and idiopathic pulmonary arterial hypertension, as well as for the identification of biological pathways that will be potentially targeted by new therapeutic strategies.

Inflammation induces endothelial-to-mesenchymal transition and promotes vascular calcification through downregulation of BMPR2

Endothelial‐to‐mesenchymal transition (EndMT) has been unveiled as a common cause for a multitude of human pathologies, including cancer and cardiovascular disease. Vascular calcification is a risk factor for ischemic vascular disorders and slowing calcification may reduce mortality in affected patients. The absence of early biomarkers hampers the identification of patients at risk. EndMT and vascular calcification are induced upon cooperation between distinct stimuli, including inflammatory cytokines and transforming growth factor beta (TGF‐β) family members. However, how these signaling pathways interplay to promote cell differentiation and eventually vascular calcification is not well understood. Using in vitro and ex vivo analysis in animal models and patient‐derived tissues, we have identified that the pro‐inflammatory cytokines tumor necrosis factor alpha (TNF‐α) and interleukin‐1 beta (IL‐1β) induce EndMT in human primary aortic endothelial cells, thereby sensitizing them for BMP‐9‐induced osteogenic differentiation. Downregulation of the BMP type II receptor BMPR2 is a key event in this process. Rather than compromising BMP canonical signal transduction, loss of BMPR2 results in decreased JNK signaling in ECs, thus enhancing BMP‐9‐induced mineralization. Altogether, our results point at the BMPR2–JNK signaling axis as a key pathway regulating inflammation‐induced EndMT and contributing to calcification. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

FHIT, a Novel Modifier Gene in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of pulmonary arteries, resulting in right heart failure and death. BMPR2 (bone morphogenetic protein receptor type 2) mutations account for most familial PAH forms whereas reduced BMPR2 is present in many idiopathic PAH forms, suggesting dysfunctional BMPR2 signaling to be a key feature of PAH. Modulating BMPR2 signaling is therapeutically promising, yet how BMPR2 is downregulated in PAH is unclear.

OBJECTIVES

We intended to identify and pharmaceutically target BMPR2 modifier genes to improve PAH.

METHODS

We combined siRNA high-throughput screening of >20,000 genes with a multicohort analysis of publicly available PAH RNA expression data to identify clinically relevant BMPR2 modifiers. After confirming gene dysregulation in tissue from patients with PAH, we determined the functional roles of BMPR2 modifiers in vitro and tested the repurposed drug enzastaurin for its propensity to improve experimental pulmonary hypertension (PH).

MEASUREMENTS AND MAIN RESULTS

We discovered FHIT (fragile histidine triad) as a novel BMPR2 modifier. BMPR2 and FHIT expression were reduced in patients with PAH. FHIT reductions were associated with endothelial and smooth muscle cell dysfunction, rescued by enzastaurin through a dual mechanism: upregulation of FHIT as well as miR17-5 repression. Fhit-/- mice had exaggerated hypoxic PH and failed to recover in normoxia. Enzastaurin reversed PH in the Sugen5416/hypoxia/normoxia rat model, by improving right ventricular systolic pressure, right ventricular hypertrophy, cardiac fibrosis, and vascular remodeling.

CONCLUSIONS

This study highlights the importance of the novel BMPR2 modifier FHIT in PH and the clinical value of the repurposed drug enzastaurin as a potential novel therapeutic strategy to improve PAH.

Drug abuse and HIV-related pulmonary hypertension: double hit injury

: Improved survival among HIV-1-infected individuals with the advent of antiretroviral therapy has clearly led to a greater prevalence of noninfectious complications. One of the most devastating sequelae in these individuals is the development of pulmonary arterial hypertension (PAH). Various epidemiological studies suggest worse survival of HIV-PAH patients when compared with other forms of PAH. Given that only a subset and not all HIV-infected individuals develop HIV-PAH, it is suggested that an additional second-hit of genetic or environmental trigger is needed for the development of PAH. In this context, it has been well documented that HIV patients who abuse illicit drugs such as stimulants, opioids, and the like, are more susceptible to develop PAH. In this review, we highlight the studies that support the significance of a double hit of HIV and drug abuse in the incidence of PAH and focus on the research that has been undertaken to unravel the pathobiology and vascular remodeling mechanisms underlying the deleterious synergy between HIV infection and drugs of abuse in orchestrating the development of PAH.

Role of SMURF1 ubiquitin ligase in BMP receptor trafficking and signaling

Heterozygous germline mutations in the bone morphogenetic protein type II receptor gene (BMPRII) are associated with hereditary pulmonary arterial hypertension (HPAH). Missense mutations, both in the extracellular ligand-binding and cytoplasmic kinase domains, mostly involve substitution of conserved Cys residues. Singular substitution at any of those Cys residues causes cytoplasmic, perinuclear localization of BMPR with reduced cell surface expression and BMP signaling. The present study examined the effect of Cys residue substitution on BMPR endocytic trafficking and lysosome degradation. We demonstrate that endocytosis/lysosomal degradation of BMPR occurs by two distinct pathways. SMURF1 ubiquitin ligase induces lysosomal degradation of BMPR, while ligase-inactive SMURF1 maintains BMPR protein level and cell surface expression. Substitution of BMPR Cys residues increases lysosomal degradation which is blocked by ligase-inactive SMURF1, elevating protein levels of Cys-substituted BMPRs. Expression of Cys-substituted BMPR suppresses basal BMP signaling activity which is also up-regulated by ligase-inactive SMURF1. Cys-residue substitution thus appears to cause BMPR endocytosis to lysosomes in a SMURF1 ubiquitin ligase-associated pathway. Kinase-activated BMPR undergoes endocytic/lysosomal degradation by a pathway with certain unique properties. Therefore, our results describe a novel mechanism whereby SMURF1 ubiquitin ligase regulates constitutive endocytosis of BMPR which may be mediated by its conserved Cys residues.

Sexually Dimorphic Regulation of EET Synthesis and Metabolism: Roles of Estrogen

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid via cytochrome P450 (CYP)/epoxygenase and are hydrolyzed by soluble epoxide hydrolase (sEH). Circulating and tissue levels of EETs are controlled by CYP (EET synthesis) and sEH (EET degradation). Therefore, both increases in CYP activity and decreases in sEH expression potentiate EET bioavailability, responses that prevail in the female sex as a function of estrogen. This mini review, based on subtitles listed, briefly summarizes studies focusing specifically on (1) female-specific potentiation of CYP/epoxygenase activity to compensate for the endothelial dysfunction; and (2) estrogen-dependent downregulation of sEH expression, which yields divergent actions in both systemic and pulmonary circulation, respectively.

Estrogen-Potentiating EET Synthesis in Response to Endothelial Dysfunction: This section summarizes the current understanding regarding the roles of estrogen in facilitating EET synthesis in response to endothelial dysfunction. In this regard, estrogen recruitment of EET-driven signaling serves as a back-up mechanism, which compensates for NO deficiency to preserve endothelium-dependent vasodilator responses and maintain normal blood pressure.

Estrogen-Dependent Downregulation of Ephx2/sEH Expression: This section focuses on molecular mechanisms responsible for the female-specific downregulation of sEH expression.

Roles of EETs in Systemic Circulation, as a Function of Estrogen-Dependent Downregulation of sEH: This section summarizes studies conducted on animals that are either deficient in the Ephx2 gene (sEH-KO) or have been treated with sEH inhibitors (sEHIs), and exhibit EET-mediated cardiovascular protections in the cerebral, coronary, skeletal, and splanchnic circulations. In particular, the estrogen-inherent silencing of the Ephx2 gene duplicates the action of sEH deficiency, yielding comparable adaptations in attenuated myogenic vasoconstriction, enhanced shear stress-induced vasodilation, and improved cardiac contractility among female WT mice, male sEH-KO and sEHI-treated mice.

Roles of Estrogen-Driven EET Production in Pulmonary Circulation: This section reviews epidemiological and clinical studies that provide the correlation between the polymorphism, or mutation of gene(s) involving estrogen metabolism and female predisposition to pulmonary hypertension, and specifically addresses an intrinsic causation between the estrogen-dependent downregulation of Ephx2 gene/sEH expression and female-susceptibility of being pulmonary hypertensive, a topic that has never been explored before. Additionally, the issue of the “estrogen paradox” in the incidence and prognosis of pulmonary hypertension is discussed.

Pulmonary Arterial Hypertension

This article provides an overview of pulmonary arterial hypertension (PAH), beginning with the initial pathologic recognition of pulmonary hypertension more than 100 years ago and progressing to the current diagnostic categorization of PAH. It reviews the epidemiology, pathophysiology, genetics, and modern treatment of PAH. The article discusses several important recent studies that have highlighted the importance of new management strategies, including serial risk assessment and combination pharmacotherapy.

Genetic analysis of over 1 million people identifies 535 new loci associated with blood pressure traits

High blood pressure is a highly heritable and modifiable risk factor for cardiovascular disease. We report the largest genetic association study of blood pressure traits (systolic, diastolic and pulse pressure) to date in over 1 million people of European ancestry. We identify 535 novel blood pressure loci that not only offer new biological insights into blood pressure regulation but also highlight shared genetic architecture between blood pressure and lifestyle exposures. Our findings identify new biological pathways for blood pressure regulation with potential for improved cardiovascular disease prevention in the future.

Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension

BACKGROUND

In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, because of mutations in KCNK3, was identified as a genetic cause and pharmacological target.

METHODS

Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult-onset group I PAH patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult-onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis.

RESULTS

We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes SUR1 (sulfonylurea receptor 1)-a regulatory subunit of the ATP-sensitive potassium channel. We observed loss of ATP-sensitive potassium channel function for all ABCC8 variants evaluated and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide.

CONCLUSIONS

Novel and rare missense variants in ABCC8 are associated with PAH. Identified ABCC8 mutations decreased ATP-sensitive potassium channel function, which was pharmacologically recovered.

Inhibitory Antibodies against Activin A and TGF-β Reduce Self-Supported, but Not Soluble Factors-Induced Growth of Human Pulmonary Arterial Vascular Smooth Muscle Cells in Pulmonary Arterial Hypertension

Increased growth and proliferation of distal pulmonary artery vascular smooth muscle cells (PAVSMC) is an important pathological component of pulmonary arterial hypertension (PAH). Transforming Growth Factor-β (TGF-β) superfamily plays a critical role in PAH, but relative impacts of self-secreted Activin A, Gremlin1, and TGF-β on PAH PAVSMC growth and proliferation are not studied. Here we report that hyper-proliferative human PAH PAVSMC have elevated secretion of TGF-β1 and, to a lesser extent, Activin A, but not Gremlin 1, and significantly reduced Ser^465/467-Smad2 and Ser^423/425-Smad3 phosphorylation compared to controls. Media, conditioned by PAH PAVSMC, markedly increased Ser^465/467-Smad2, Ser^423/425-Smad3, and Ser^463/465-Smad1/5 phosphorylation, up-regulated Akt, ERK1/2, and p38 MAPK, and induced significant proliferation of non-diseased PAVSMC. Inhibitory anti-Activin A antibody reduced PAH PAVSMC growth without affecting canonical (Smads) or non-canonical (Akt, ERK1/2, p38 MAPK) effectors. Inhibitory anti-TGF-β antibody significantly reduced P-Smad3, P-ERK1/2 and proliferation of PAH PAVSMC, while anti-Gremlin 1 had no anti-proliferative effect. PDGF-BB diminished inhibitory effects of anti-Activin A and anti-TGF-β antibodies. None of the antibodies affected growth and proliferation of non-diseased PAVSMC induced by PAH PAVSMC-secreted factors. Together, these data demonstrate that human PAH PAVSMC have secretory, proliferative phenotype that could be targeted by anti-Activin A and anti-TGF-β antibodies; potential cross-talk with PDGF-BB should be considered while developing therapeutic interventions.

TGF-β and BMPR2 Signaling in PAH: Two Black Sheep in One Family

Knowledge pertaining to the involvement of transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) signaling in pulmonary arterial hypertension (PAH) is continuously increasing. There is a growing understanding of the function of individual components involved in the pathway, but a clear synthesis of how these interact in PAH is currently lacking. Most of the focus has been on signaling downstream of BMPR2, but it is imperative to include the role of TGF-β signaling in PAH. This review gives a state of the art overview of disturbed signaling through the receptors of the TGF-β family with respect to vascular remodeling and cardiac effects as observed in PAH. Recent (pre)-clinical studies in which these two pathways were targeted will be discussed with an extended view on cardiovascular research fields outside of PAH, indicating novel future perspectives.

Consequences of BMPR2 Deficiency in the Pulmonary Vasculature and Beyond: Contributions to Pulmonary Arterial Hypertension

Since its association with familial pulmonary arterial hypertension (PAH) in 2000, Bone Morphogenetic Protein Receptor II (BMPR2) and its related signaling pathway have become recognized as a key regulator of pulmonary vascular homeostasis. Herein, we define BMPR2 deficiency as either an inactivation of the receptor, decreased receptor expression, or an impairment of the receptor’s downstream signaling pathway. Although traditionally the phenotypic consequences of BMPR2 deficiency in PAH have been thought to be limited to the pulmonary vasculature, there is evidence that abnormalities in BMPR2 signaling may have consequences in many other organ systems and cellular compartments. Revisiting how BMPR2 functions throughout health and disease in cells and organs beyond the lung vasculature may provide insight into the contribution of these organ systems to PAH pathogenesis as well as the potential systemic manifestation of PAH. Here we review our knowledge of the consequences of BMPR2 deficiency across multiple organ systems.

Recent advances in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a high mortality rate. Treatment options have improved in the last 20 years, but patients still die prematurely of right heart failure. Though rare, it is heterogeneous at the genetic and molecular level, and understanding and exploiting this is key to the development of more effective treatments. BMPR2, encoding bone morphogenetic receptor type 2, is the most commonly affected gene in both familial and non-familial PAH, but rare mutations have been identified in other genes. Transcriptomic, proteomic, and metabolomic studies looking for endophenotypes are under way. There is no shortage of candidate new drug targets for PAH, but the selection and prioritisation of these are challenges for the research community.

Pulmonary arterial hypertension in congenital heart disease: translational opportunities to study the reversibility of pulmonary vascular disease

Pulmonary arterial hypertension (PAH) is a progressive and lethal pulmonary vascular disease (PVD). Although in recent years outcome has improved by new treatments that delay disease progression, a cure has not yet been achieved. In PAH associated with congenital heart disease (CHD), remodeling of the pulmonary vasculature reaches an irreversible phenotype similar to all forms of end-stage PAH. In PAH-CHD, however, also an early stage is recognised, which can be completely reversible. This reversible phase has never been recognised in other forms of PAH, most likely because these patients are only diagnosed once advanced disease has developed. We propose that the clinical model of PAH-CHD, with an early reversible and advanced irreversible stage, offers unique opportunities to study pathophysiological and molecular mechanisms that orchestrate the transition from reversible medial hypertrophy into irreversible plexiform lesions. Comprehension of these mechanisms is not only pivotal in clinical assessment of disease progression and operability of patients with PAH-CHD; specific targeting of these mechanisms may also lead to pharmacological interventions that transform 'irreversible' plexiform lesions into a reversible PVD: one that is amenable for a cure. In recent years, significant steps have been made in the strive to 'reverse the irreversible'. This review provides an overview of current clinical and experimental knowledge on the reversibility of PAH, focussing on flow-associated mechanisms, and the near-future potential to advance this field.

Pulmonary Arterial Hypertension: Pathophysiology and Treatment

Pulmonary arterial hypertension (PAH), the first category of pulmonary hypertension, is a chronic and progressive disorder characterised by angioproliferative vasculopathy in the pulmonary arterioles, leading to endothelial and smooth muscle proliferation and dysfunction, inflammation and thrombosis. These changes increase pulmonary vascular resistance and subsequent pulmonary arterial pressure, causing right ventricular failure which leads to eventual death if untreated. The management of PAH has advanced rapidly in recent years due to improved understanding of the condition's pathophysiology, specifically the nitric oxide, prostacyclin-thromboxane and endothelin-1 pathways. Five classes of drugs targeting these pathways are now available: phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, prostacyclin analogues, prostacyclin receptor agonists and endothelin receptor antagonists. These developments have led to substantial improvements in mortality rate in recent decades. Recently, long-term studies have demonstrated sustained progression-free survival and have created a new paradigm of initial combination therapy. Despite these targeted therapies, PAH is still associated with significant morbidity and mortality. As such, further research into broadening our understanding of PAH pathophysiology is underway with potential of increasing the repertoire of drugs available.

Genetic analyses in a cohort of 191 pulmonary arterial hypertension patients

Background

Pulmonary arterial hypertension (PAH) is a progressive and fatal disorder associated with high pulmonary artery pressure. Genetic testing enables early diagnosis and offers an opportunity for family screening. To identify genetic mutations and help make a precise diagnosis, we performed genetic testing in 191 probands with PAH and tried to analyze the genotype-phenotype correlation.

Methods

Initially, PAH samples (n = 119) were submitted to BMPR2 screening using Sanger sequencing. Later, we developed a PAH panel test to identify causal mutations in 13 genes related to PAH and tried to call BMPR2 copy number variations (CNVs) with the panel data. Multiplex ligation-dependent probe amplification (MLPA) was used to search for CNVs in BMPR2, ACVRL1 and ENG. Notably, EIF2AK4 gene was also involved in the panel, which allowed to distinguish pulmonary veno-occlusive disease (PVOD)/pulmonary capillary hemangiomatosis (PCH) patients from idiopathic PAH (IPAH). Characteristics of patients were compared using t test for continuous variables.

Results

Pathogenic BMPR2 mutations were detected most frequently in 32 (17.9%) IPAH and 5 (41.7%) heritable PAH (HPAH) patients by sequencing, and 12 BMPR2 CNVs called from the panel data were all successfully confirmed by MLPA analysis. In addition, homozygous or compound heterozygous EIF2AK4 mutations were identified in 6 patients, who should be corrected to a diagnosis of PVOD/PCH. Genotype-phenotype correlation analysis revealed that PAH patients with BMPR2 mutations were younger at diagnosis (27.2y vs. 31.6y, p = 0.0003) and exhibited more severe pulmonary hemodynamic impairment and a worse cardiac index compared with those without BMPR2 mutations.

Conclusions

The panel assay represented a highly valuable tool in PAH genetic testing, not only for the detection of small sequence alterations, but also for an indication of BMPR2 CNVs, which had implications for the specific samples to perform further MLPA assay. Analyses of PAH causal genes have a great help to clinical diagnosis and deep implications in disease treatment.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0789-9) contains supplementary material, which is available to authorized users.

Rare variants in RNF213, a susceptibility gene for moyamoya disease, are found in patients with pulmonary hypertension and aggravate hypoxia-induced pulmonary hypertension in mice

Ring finger 213 (RNF213) is a susceptibility gene for moyamoya disease (MMD), a progressive cerebrovascular disease. Recent studies suggest that RNF213 plays an important role not only in MMD, but also in extracranial vascular diseases, such as pulmonary hypertension (PH). In this study, we undertook genetic screening of RNF213 in patients with PH and performed functional analysis of an RNF213 variant using mouse models. Direct sequencing of the exons in the C-terminal region of RNF213, where MMD-associated mutations are highly clustered, and of the entire coding exons of BMPR2 and CAV1, the causative genes for PH, was performed in 27 Japanese patients with PH. Two MMD-associated rare variants (p.R4810K and p.A4399T) in RNF213 were identified in two patients, three BMPR2 mutations (p.Q92H, p.L198Rfs*4, and p.S930X) were found in three patients, whereas no CAV1 mutations were identified. To test the effect of the RNF213 variants on PH, vascular endothelial cell (EC)-specific Rnf213 mutant transgenic mice were exposed to hypoxia. Overexpression of the EC-specific Rnf213 mutant, but neither Rnf213 ablation nor EC-specific wild-type Rnf213 overexpression, aggravated the hypoxia-induced PH phenotype (high right ventricular pressure, right ventricular hypertrophy, and muscularization of pulmonary vessels). Under hypoxia, electron microscopy showed unique EC detachment in pulmonary vessels, and western blots demonstrated a significant reduction in caveolin-1 (encoded by CAV1), a key molecule involved in EC functions, in lungs of EC-specific Rnf213 mutant transgenic mice, suggestive of EC dysfunction. RNF213 appears to be a genetic risk factor for PH and could play a role in systemic vasculopathy.

Oxidative stress increases M1dG, a major peroxidation-derived DNA adduct, in mitochondrial DNA

Reactive oxygen species (ROS) are formed in mitochondria during electron transport and energy generation. Elevated levels of ROS lead to increased amounts of mitochondrial DNA (mtDNA) damage. We report that levels of M1dG, a major endogenous peroxidation-derived DNA adduct, are 50-100-fold higher in mtDNA than in nuclear DNA in several different human cell lines. Treatment of cells with agents that either increase or decrease mitochondrial superoxide levels leads to increased or decreased levels of M1dG in mtDNA, respectively. Sequence analysis of adducted mtDNA suggests that M1dG residues are randomly distributed throughout the mitochondrial genome. Basal levels of M1dG in mtDNA from pulmonary microvascular endothelial cells (PMVECs) from transgenic bone morphogenetic protein receptor 2 mutant mice (BMPR2R899X) (four adducts per 106 dG) are twice as high as adduct levels in wild-type cells. A similar increase was observed in mtDNA from heterozygous null (BMPR2+/-) compared to wild-type PMVECs. Pulmonary arterial hypertension is observed in the presence of BMPR2 signaling disruptions, which are also associated with mitochondrial dysfunction and oxidant injury to endothelial tissue. Persistence of M1dG adducts in mtDNA could have implications for mutagenesis and mitochondrial gene expression, thereby contributing to the role of mitochondrial dysfunction in diseases.

Precision medicine and personalising therapy in pulmonary hypertension: seeing the light from the dawn of a new era

Pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH) include different cardiopulmonary disorders in which the interaction of multiple genes with environmental and behavioural factors modulates the onset and the progression of these severe conditions. Although the development of therapeutic agents that modulate abnormalities in three major pathobiological pathways for PAH has revolutionised our approach to the treatment of PAH, the long-term survival rate remains unsatisfactory. Accumulating evidence has underlined that clinical outcomes and responses to therapy in PAH are modified by multiple factors, including genetic variations, which will be different for each individual. Since precision medicine, also known as stratified medicine or personalised medicine, aims to better target intervention to the individual while maximising benefit and minimising harm, it has significant potential advantages. This article aims to assemble and discuss the different initiatives that are currently underway in the PH/PAH fields together with the opportunities and prospects for their use in the near future.

Development of precision medicine strategies will be the next frontier in the evolution of PAH treatmenthttp://ow.ly/8T8730j7e36

Identification of rare sequence variation underlying heritable pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within components of the transforming growth factor-β pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlies most heritable forms of PAH. To identify the missing heritability we perform whole-genome sequencing in 1038 PAH index cases and 6385 PAH-negative control subjects. Case-control analyses reveal significant overrepresentation of rare variants in ATP13A3, AQP1 and SOX17, and provide independent validation of a critical role for GDF2 in PAH. We demonstrate familial segregation of mutations in SOX17 and AQP1 with PAH. Mutations in GDF2, encoding a BMPR2 ligand, lead to reduced secretion from transfected cells. In addition, we identify pathogenic mutations in the majority of previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings contribute new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.

Global Proteomics Deciphered Novel-Function of Osthole Against Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive cardiovascular-disease with high mortality lacking high-efficiency drug. Our efforts attempted to delineate therapeutic action of osthole produced by Angelica Pubescens Maxim, which has the capacity to treat PAH by exploiting an iTRAQ-based proteomic method. Excitingly, osthole was observed to significantly restore 98 of 315 differential proteins significantly modified by PAH progression. They were primarily annotated into 24 signaling pathways. Four mostly affected proteins (RPL15, Cathepsin S, Histone H3.3 and HMGB1) were experimentially validated which belonged to ribosome pathway, oxidative phosphorylation pathway, systemic lupus erythematosus pathway, complement and coagulation cascades pathway, whose modifications and modulations mostly accounted for therapeutic capacity of this compound against PAH. Altogether, our findings demonstrated that global proteomics is a promising systems-biology approach for deciphering therapeutic actions and associated mechanisms of natural products derived from traditional Chinese medicine. Importantly, osthole is supposed to be a candidate compound for new drug development to treat PAH.

The integrated stress response regulates BMP signalling through effects on translation

Background

Developmental pathways must be responsive to the environment. Phosphorylation of eIF2α enables a family of stress-sensing kinases to trigger the integrated stress response (ISR), which has pro-survival and developmental consequences. Bone morphogenetic proteins (BMPs) regulate multiple developmental processes in organisms from insects to mammals.

Results

Here we show in Drosophila that GCN2 antagonises BMP signalling through direct effects on translation and indirectly via the transcription factor crc (dATF4). Expression of a constitutively active GCN2 or loss of the eIF2α phosphatase dPPP1R15 impairs developmental BMP signalling in flies. In cells, inhibition of translation by GCN2 blocks downstream BMP signalling. Moreover, loss of d4E-BP, a target of crc, augments BMP signalling in vitro and rescues tissue development in vivo.

Conclusion

These results identify a novel mechanism by which the ISR modulates BMP signalling during development.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0503-x) contains supplementary material, which is available to authorized users.

Bone Morphogenetic Protein-Based Therapeutic Approaches

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the transforming growth factor (TGF)-β family of ligands and exert most of their effects through the canonical effectors Smad1, 5, and 8. Appropriate regulation of BMP signaling is critical for the development and homeostasis of numerous human organ systems. Aberrations in BMP pathways or their regulation are increasingly associated with diverse human pathologies, and there is an urgent and growing need to develop effective approaches to modulate BMP signaling in the clinic. In this review, we provide a wide perspective on diseases and/or conditions associated with dysregulated BMP signal transduction, outline the current strategies available to modulate BMP pathways, highlight emerging second-generation technologies, and postulate prospective avenues for future investigation.

BMPR2 mutations and endothelial dysfunction in pulmonary arterial hypertension (2017 Grover Conference Series)

Despite the discovery more than 15 years ago that patients with hereditary pulmonary arterial hypertension (HPAH) inherit BMP type 2 receptor ( BMPR2) mutations, it is still unclear how these mutations cause disease. In part, this is attributable to the rarity of HPAH and difficulty obtaining tissue samples from patients with early disease. However, in addition, limitations to the approaches used to study the effects of BMPR2 mutations on the pulmonary vasculature have restricted our ability to determine how individual mutations give rise to progressive pulmonary vascular pathology in HPAH. The importance of understanding the mechanisms by which BMPR2 mutations cause disease in patients with HPAH is underscored by evidence that there is reduced BMPR2 expression in patients with other, more common, non-hereditary form of PAH, and that restoration of BMPR2 expression reverses established disease in experimental models of pulmonary hypertension. In this paper, we focus on the effects on endothelial function. We discuss some of the controversies and challenges that have faced investigators exploring the role of BMPR2 mutations in HPAH, focusing specifically on the effects different BMPR2 mutation have on endothelial function, and whether there are qualitative differences between different BMPR2 mutations. We discuss evidence that BMPR2 signaling regulates a number of responses that may account for endothelial abnormalities in HPAH and summarize limitations of the models that are used to study these effects. Finally, we discuss evidence that BMPR2-dependent effects on endothelial metabolism provides a unifying explanation for the many of the BMPR2 mutation-dependent effects that have been described in patients with HPAH.

The Dual Role of Bone Morphogenetic Proteins in Cancer

Bone morphogenetic proteins (BMPs) are a diverse class of molecules with over 20 growth factor proteins that belong to the transforming growth factor-β (TGF-β) family and are highly associated with bone formation and disease development. Aberrant expression of various BMPs has been reported in several cancer tissues. Biological function studies have elicited the dual role of BMPs in both cancer development and suppression. Furthermore, a variety of BMP antagonists, ligands, and receptors have been shown to reduce or enhance tumorigenesis and metastasis. Knockout mouse models of BMP signaling components have also revealed that the suppression of BMP signaling impairs cancer metastasis. Herein, we highlight the basic clinical background and involvement of BMPs in modulating cancer progression and their dynamic interactions (e.g., with microRNAs) in the tumor microenvironment in addition to their mutations and roles in chemoprevention. We also suggest that BMPs should be considered a powerful putative therapeutic target in tumorigenesis and bone metastasis.

Clinical significance linked to functional defects in bone morphogenetic protein type 2 receptor, BMPR2

Bone morphogenetic protein type 2 receptor (BMPR2) is one of the transforming growth factor-β (TGF-β) superfamily receptors, performing diverse roles during embryonic development, vasculogenesis, and osteogenesis. Human BMPR2 consists of 1,038 amino acids, and contains functionally conserved extracellular, transmembrane, kinase, and C-terminal cytoplasmic domains. Bone morphogenetic proteins (BMPs) engage the tetrameric complex, composed of BMPR2 and its corresponding type 1 receptors, which initiates SMAD proteins-mediated signal transduction leading to the expression of target genes implicated in the development or differentiation of the embryo, organs and bones. In particular, genetic alterations of BMPR2 gene are associated with several clinical disorders, including representative pulmonary arterial hypertension, cancers, and metabolic diseases, thus demonstrating the physiological importance of BMPR2. In this mini review, we summarize recent findings regarding the molecular basis of BMPR2 functions in BMP signaling, and the versatile roles of BMPR2. In addition, various aspects of experimentally validated pathogenic mutations of BMPR2 and the linked human diseases will also be discussed, which are important in clinical settings for diagnostics and treatment.

Elevated microRNA-135a is associated with pulmonary arterial hypertension in experimental mouse model

Multiple causes are associated with the complex mechanism of pathogenesis of pulmonary arterial hypertension (PAH), but the molecular pathway in the pathogenesis of PAH is still insufficiently understood. In this study, we investigated epigenetic changes that cause PAH induced by exposure to combined Th2 antigen (Ovalbumin, OVA) and urban particulate matter (PM) in mice. To address that, we focused on the epigenetic mechanism, linked to microRNA (miR)-135a. We found that miR-135a levels were significantly increased, and levels of bone morphogenetic protein receptor type II (BMPR2) which is the target of miR-135a, were significantly decreased in this experimental PAH mouse model. Therefore to evaluate the role of miR-135a, we injected AntagomiR-135a into this mouse model. AntagomiR-135a injected mice showed decreased right ventricular systolic pressures (RVSPs), right ventricular hypertrophy (RVH), and the percentage of severely thickened pulmonary arteries compared to control scrambled miRNA injected mice. Both mRNA and protein expression of BMPR2 were recovered in the AntagomiR-135a injected mice compared to control mice. Our study understands if miR-135a could serve as a biomarker helping to manage PAH. The blocking of miR-135a could lead to new therapeutic modalities to alleviate exacerbation of PAH caused by exposure to Th2 antigen and urban air pollution.