Genetic Ablation of PDGF-Dependent Signaling Pathways Abolishes Vascular Remodeling and Experimental Pulmonary Hypertension

A novel PDGFR inhibitor WQ-C-401 prevents pulmonary vascular remodeling in rats with monocrotaline-induced pulmonary arterial hypertension

Platelet-derived growth factor (PDGF) is one of the most important cytokines associated with pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). PDGF receptor (PDGFR) inhibition exerted therapeutic effects on PAH in clinical trials, but serious side effects warrant the withdrawal of existing drugs. In this study, a novel highly selective PDGFR inhibitor WQ-C-401 was developed, and its effects on PDGFR signaling pathway and pulmonary vascular remodeling in PAH were investigated. Cell proliferation assays and Western blot analysis of PDGFRα/β phosphorylation showed that WQ-C-401 inhibited PDGFR-mediated cell proliferation assay and suppressed PDGFR phosphorylation in a concentration-dependent manner. DiscoverX's KinomeScanTM technology confirmed the good kinome selectivity of WQ-C-401 (S score (1) of PDGFR = (0.01)). In monocrotaline (MCT)-induced PAH rats, intragastric administration of WQ-C-401 (25, 50, 100 mg/kg/d) or imatinib (50 mg/kg/d, positive control) significantly decreased right ventricular systolic pressure (RVSP). Histological analysis demonstrated that WQ-C-401 inhibited pulmonary vascular remodeling by reducing muscularization and fibrosis, as well as alleviated right ventricular hypertrophy in MCT-treated rats. In addition, WQ-C-401 suppressed MCT-induced cell hyperproliferation and CD68+ macrophage infiltration around the pulmonary artery. In vitro, WQ-C-401 inhibited PDGF-BB-induced proliferation and migration of human pulmonary arterial smooth muscle cells (PASMCs). Moreover, Western blot analysis showed that WQ-C-401 concertration-dependently inhibited PDGF-BB-induced phosphorylation of ERK1/2 and PDGFRβ Y751, decreased collagen Ⅰ synthesis and increased alpha smooth muscle actin (α-SMA) expression in PASMCs. Collectively, our results suggest that WQ-C-401 is a selective and potent PDGFR inhibitor which could be a promising drug for the therapeutics of PAH by preventing pulmonary vascular remodeling.

Seralutinib in adults with pulmonary arterial hypertension (TORREY): a randomised, double-blind, placebo-controlled phase 2 trial

BACKGROUND

Morbidity and mortality in pulmonary arterial hypertension (PAH) remain high. Activation of platelet-derived growth factor receptor, colony stimulating factor 1 receptor, and mast or stem cell growth factor receptor kinases stimulates inflammatory, proliferative, and fibrotic pathways driving pulmonary vascular remodelling in PAH. Seralutinib, an inhaled kinase inhibitor, targets these pathways. We aimed to evaluate the efficacy and safety of seralutinib in patients with PAH receiving standard background therapy.

METHODS

The TORREY trial was a phase 2, randomised, multicentre, multinational, double-blind, placebo-controlled study. Patients with PAH from 40 hospital and community sites were randomly assigned 1:1 via interactive response technologies to receive seralutinib (60 mg twice daily for 2 weeks, then increased to 90 mg twice daily as tolerated) or placebo by dry powder inhaler twice daily for 24 weeks. Randomisation was stratified by baseline pulmonary vascular resistance (PVR; <800 dyne·s/cm5 and ≥800 dyne·s/cm5). Patients were eligible if classified as WHO Group 1 PH (PAH), WHO Functional Class II or III, with a PVR of 400 dyne·s/cm5 or more, and a 6 min walk distance of between 150 m and 550 m. The primary endpoint was change in PVR from baseline to 24 weeks. Analyses for efficacy endpoints were conducted in randomly assigned patients (intention-to-treat population). Safety analyses included all patients who received the study drug. TORREY was registered with ClinicalTrials.gov (NCT04456998) and EudraCT (2019-002669-37) and is completed.

FINDINGS

From Nov 12, 2020, to April 20, 2022, 151 patients were screened for eligibility, and following exclusions, 86 adults receiving PAH background therapy were randomly assigned to seralutinib (n=44; four male, 40 female) or placebo (n=42; four male, 38 female), and comprised the intention-to-treat population. At baseline, treatment groups were balanced except for a higher representation of WHO Functional Class II patients in the seralutinib group. The least squares mean change from baseline to week 24 in PVR was 21·2 dyne·s/cm5 (95% CI -37·4 to 79·8) for the placebo group and -74·9 dyne·s/cm5 (-139·7 to -10·2) for the seralutinib group. The least squares mean difference between the seralutinib and placebo groups for change in PVR was -96·1 dyne·s/cm5 (95% CI -183·5 to -8·8; p=0·03). The most common treatment-emergent adverse event in both treatment groups was cough: 16 (38%) of 42 patients in the placebo group; 19 (43%) of 44 patients in the seralutinib group.

INTERPRETATION

Treatment with inhaled seralutinib significantly decreased PVR, meeting the primary endpoint of the study among patients receiving background therapy for PAH.

FUNDING

Gossamer Bio.

C-type natriuretic peptide/cGMP/FoxO3 signaling attenuates hyperproliferation of pericytes from patients with pulmonary arterial hypertension

Pericyte dysfunction, with excessive migration, hyperproliferation, and differentiation into smooth muscle-like cells contributes to vascular remodeling in Pulmonary Arterial Hypertension (PAH). Augmented expression and action of growth factors trigger these pathological changes. Endogenous factors opposing such alterations are barely known. Here, we examine whether and how the endothelial hormone C-type natriuretic peptide (CNP), signaling through the cyclic guanosine monophosphate (cGMP) -producing guanylyl cyclase B (GC-B) receptor, attenuates the pericyte dysfunction observed in PAH. The results demonstrate that CNP/GC-B/cGMP signaling is preserved in lung pericytes from patients with PAH and prevents their growth factor-induced proliferation, migration, and transdifferentiation. The anti-proliferative effect of CNP is mediated by cGMP-dependent protein kinase I and inhibition of the Phosphoinositide 3-kinase (PI3K)/AKT pathway, ultimately leading to the nuclear stabilization and activation of the Forkhead Box O 3 (FoxO3) transcription factor. Augmentation of the CNP/GC-B/cGMP/FoxO3 signaling pathway might be a target for novel therapeutics in the field of PAH.

IMPAHCT: A randomized phase 2b/3 study of inhaled imatinib for pulmonary arterial hypertension

AV-101 (imatinib) powder for inhalation, an investigational dry powder inhaled formulation of imatinib designed to target the underlying pathobiology of pulmonary arterial hypertension, was generally well tolerated in healthy adults in a phase 1 single and multiple ascending dose study. Inhaled Imatinib Pulmonary Arterial Hypertension Clinical Trial (IMPAHCT; NCT05036135) is a phase 2b/3, randomized, double-blind, placebo-controlled, dose-ranging, and confirmatory study. IMPAHCT is designed to identify an optimal AV-101 dose (phase 2b primary endpoint: pulmonary vascular resistance) and assess the efficacy (phase 3 primary endpoint: 6-min walk distance), safety, and tolerability of AV-101 dose levels in subjects with pulmonary arterial hypertension using background therapies. The study has an operationally seamless, adaptive design allowing for continuous recruitment. It includes three parts; subjects enrolled in Part 1 (phase 2b dose-response portion) or Part 2 (phase 3 intermediate portion) will be randomized 1:1:1:1 to 10, 35, 70 mg AV-101, or placebo (twice daily), respectively. Subjects enrolled in Part 3 (phase 3 optimal dose portion) will be randomized 1:1 to the optimal dose of AV-101 and placebo (twice daily), respectively. All study parts include a screening period, a 24-week treatment period, and a 30-day safety follow-up period; the total duration is ∼32 weeks. Participation is possible in only one study part. IMPAHCT has the potential to advance therapies for patients with pulmonary arterial hypertension by assessing the efficacy and safety of a novel investigational drug-device combination (AV-101) using an improved study design that has the potential to save 6-12 months of development time. ClinicalTrials.gov Identifier: NCT05036135.

Pharmacology and Rationale for Seralutinib in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by vascular remodeling and a consequent increase in pulmonary vascular resistance. The histologic hallmarks of PAH include plexiform and neointimal lesions of the pulmonary arterioles, which are composed of dysregulated, apoptosis-resistant endothelial cells and myofibroblasts. Platelet-derived growth factor receptors (PDGFR) α and β, colony stimulating factor 1 receptor (CSF1R), and mast/stem cell growth factor receptor kit (c-KIT) are closely related kinases that have been implicated in PAH progression. In addition, emerging data indicate significant crosstalk between PDGF signaling and the bone morphogenetic protein receptor type 2 (BMPR2)/transforming growth factor β (TGFβ) receptor axis. This review will discuss the importance of the PDGFR-CSF1R-c-KIT signaling network in PAH pathogenesis, present evidence that the inhibition of all three nodes in this kinase network is a potential therapeutic approach for PAH, and highlight the therapeutic potential of seralutinib, currently in development for PAH, which targets these pathways.

Parainfectious cerebral vasculopathy complicating bacterial meningitis: Acute-short lived vasospasm followed by delayed-long lasting vasculitis

Bacterial meningitis is a serious, life-threatening infection of the meninges. Several radiological studies highlight prominent structural alterations occurring in the cerebral vasculature, leading to significant cerebrovascular consequences during bacterial meningitis. Beginning with reflexive arterial vasospasm , cerebrovascular disease during bacterial meningitis proceeds through a orderly sequence of arterial vasculitis with inflammatory cell infiltration, medial smooth muscle migration and proliferation, medial necrosis, adventitial fibrosis and eventual intimal stenosis. As such, this review focuses on changes occurring within cerebral arteries during disease progression, highlighting the various structural modifications occurring in the arterial vessels that contribute to disturbances in cerebral hemodynamics and, ultimately, cerebrovascular consequences during bacterial meningitis.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Vascular pathobiology of pulmonary hypertension

Pulmonary hypertension (PH), increased blood pressure in the pulmonary arteries, is a morbid and lethal disease. PH is classified into several groups based on etiology, but pathological remodeling of the pulmonary vasculature is a common feature. Endothelial cell dysfunction and excess smooth muscle cell proliferation and migration are central to the vascular pathogenesis. In addition, other cell types, including fibroblasts, pericytes, inflammatory cells and platelets contribute as well. Herein, we briefly note most of the main cell types active in PH and for each cell type, highlight select signaling pathway(s) highly implicated in that cell type in this disease. Among others, the role of hypoxia-inducible factors, growth factors (e.g., vascular endothelial growth factor, platelet-derived growth factor, transforming growth factor-β and bone morphogenetic protein), vasoactive molecules, NOTCH3, Kruppel-like factor 4 and forkhead box proteins are discussed. Additionally, deregulated processes of endothelial-to-mesenchymal transition, extracellular matrix remodeling and intercellular crosstalk are noted. This brief review touches upon select critical facets of PH pathobiology and aims to incite further investigation that will result in discoveries with much-needed clinical impact for this devastating disease.

Inhaled seralutinib exhibits potent efficacy in models of pulmonary arterial hypertension

BACKGROUND

Signalling through platelet-derived growth factor receptor (PDGFR), colony-stimulating factor 1 receptor (CSF1R) and mast/stem cell growth factor receptor kit (c-KIT) plays a critical role in pulmonary arterial hypertension (PAH). We examined the preclinical efficacy of inhaled seralutinib, a unique small-molecule PDGFR/CSF1R/c-KIT kinase inhibitor in clinical development for PAH, in comparison to a proof-of-concept kinase inhibitor, imatinib.

METHODS

Seralutinib and imatinib potency and selectivity were compared. Inhaled seralutinib pharmacokinetics/pharmacodynamics were studied in healthy rats. Efficacy was evaluated in two rat models of PAH: SU5416/Hypoxia (SU5416/H) and monocrotaline pneumonectomy (MCTPN). Effects on inflammatory/cytokine signalling were examined. PDGFR, CSF1R and c-KIT immunohistochemistry in rat and human PAH lung samples and microRNA (miRNA) analysis in the SU5416/H model were performed.

RESULTS

Seralutinib potently inhibited PDGFRα/β, CSF1R and c-KIT. Inhaled seralutinib demonstrated dose-dependent inhibition of lung PDGFR and c-KIT signalling and increased bone morphogenetic protein receptor type 2 (BMPR2). Seralutinib improved cardiopulmonary haemodynamic parameters and reduced small pulmonary artery muscularisation and right ventricle hypertrophy in both models. In the SU5416/H model, seralutinib improved cardiopulmonary haemodynamic parameters, restored lung BMPR2 protein levels and decreased N-terminal pro-brain natriuretic peptide (NT-proBNP), more than imatinib. Quantitative immunohistochemistry in human lung PAH samples demonstrated increased PDGFR, CSF1R and c-KIT. miRNA analysis revealed candidates that could mediate seralutinib effects on BMPR2.

CONCLUSIONS

Inhaled seralutinib was an effective treatment of severe PAH in two animal models, with improved cardiopulmonary haemodynamic parameters, a reduction in NT-proBNP, reverse remodelling of pulmonary vascular pathology and improvement in inflammatory biomarkers. Seralutinib showed greater efficacy compared to imatinib in a preclinical study.

Methylation-mediated silencing of PTPRD induces pulmonary hypertension by promoting pulmonary arterial smooth muscle cell migration via the PDGFRB/PLCγ1 axis

OBJECTIVE

Pulmonary hypertension is a lethal disease characterized by pulmonary vascular remodeling and is mediated by abnormal proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). Platelet-derived growth factor BB (PDGF-BB) is the most potent mitogen for PASMCs and is involved in vascular remodeling in pulmonary hypertension development. Therefore, the objective of our study is to identify novel mechanisms underlying vascular remodeling in pulmonary hypertension.

METHODS

We explored the effects and mechanisms of PTPRD downregulation in PASMCs and PTPRD knockdown rats in pulmonary hypertension induced by hypoxia.

RESULTS

We demonstrated that PTPRD is dramatically downregulated in PDGF-BB-treated PASMCs, pulmonary arteries from pulmonary hypertension rats, and blood and pulmonary arteries from lung specimens of patients with hypoxic pulmonary arterial hypertension (HPAH) and idiopathic PAH (iPAH). Subsequently, we found that PTPRD was downregulated by promoter methylation via DNMT1. Moreover, we found that PTPRD knockdown altered cell morphology and migration in PASMCs via modulating focal adhesion and cell cytoskeleton. We have demonstrated that the increase in cell migration is mediated by the PDGFRB/PLCγ1 pathway. Furthermore, under hypoxic condition, we observed significant pulmonary arterial remodeling and exacerbation of pulmonary hypertension in heterozygous PTPRD knock-out rats compared with the wild-type group. We also demonstrated that HET group treated with chronic hypoxia have higher expression and activity of PLCγ1 in the pulmonary arteries compared with wild-type group.

CONCLUSION

We propose that PTPRD likely plays an important role in the process of pulmonary vascular remodeling and development of pulmonary hypertension in vivo .

The Provenance, Providence, and Position of Endothelial Cells in Injured Spinal Cord Vascular Pathology

Endothelial cells (ECs) and pericytes are present in all blood vessels. Their position confers an important role in controlling oxygen and nutrient transportation to the different organs. ECs can adopt different morphologies based on their need and functions. Both ECs and pericytes express different surface markers that help in their identification, but heterogeneity and overlapping between markers among different cells pose a challenge for their precise identification. Spatiotemporal association of ECs and pericytes have great importance in sprout formation and vessel stabilization. Any traumatic injury in CNS may lead to vascular damage along with neuronal damage. Hence, ECs-pericyte interaction by physical contact and paracrine molecules is crucial in recovering the epicenter region by promoting angiogenesis. ECs can transform into other types of cells through endothelial-mesenchymal transition (EndMT), promoting wound healing in the epicenter region. Various signaling pathways mediate the interaction of ECs with pericytes that have an extensive role in angiogenesis. In this review, we discussed ECs and pericytes surface markers, the spatiotemporal association and interaction of ECs-pericytes, and signaling associated with the pathology of traumatic SCI. Linking the brain or spinal cord-specific pathologies and human vascular pathology will pave the way toward identifying new therapeutic targets and developing innovative preventive strategies. Endothelial-pericyte interaction strategic for formation of functional neo-vessels that are crucial for neurological recovery.

The Platelet-Derived Growth Factor Pathway in Pulmonary Arterial Hypertension: Still an Interesting Target?

The lack of curative options for pulmonary arterial hypertension drives important research to understand the mechanisms underlying this devastating disease. Among the main identified pathways, the platelet-derived growth factor (PDGF) pathway was established to control vascular remodeling and anti-PDGF receptor (PDGFR) drugs were shown to reverse the disease in experimental models. Four different isoforms of PDGF are produced by various cell types in the lung. PDGFs control vascular cells migration, proliferation and survival through binding to their receptors PDGFRα and β. They elicit multiple intracellular signaling pathways which have been particularly studied in pulmonary smooth muscle cells. Activation of the PDGF pathway has been demonstrated both in patients and in pulmonary hypertension (PH) experimental models. Tyrosine kinase inhibitors (TKI) are numerous but without real specificity and Imatinib, one of the most specific, resulted in beneficial effects. However, adverse events and treatment discontinuation discouraged to pursue this therapy. Novel therapeutic strategies are currently under experimental evaluation. For TKI, they include intratracheal drug administration, low dosage or nanoparticles delivery. Specific anti-PDGF and anti-PDGFR molecules can also be designed such as new TKI, soluble receptors, aptamers or oligonucleotides.

Platelet‐Derived Growth Factor Receptor Type α Activation Drives Pulmonary Vascular Remodeling Via Progenitor Cell Proliferation and Induces Pulmonary Hypertension

Background

Platelet‐derived growth factor is a major regulator of the vascular remodeling associated with pulmonary arterial hypertension. We previously showed that protein widely 1 (PW1⁺) vascular progenitor cells participate in early vessel neomuscularization during experimental pulmonary hypertension (PH) and we addressed the role of the platelet‐derived growth factor receptor type α (PDGFRα) pathway in progenitor cell‐dependent vascular remodeling and in PH development.

Methods and Results

Remodeled pulmonary arteries from patients with idiopathic pulmonary arterial hypertension showed an increased number of perivascular and vascular PW1⁺ cells expressing PDGFRα. PW1^nLacZ reporter mice were used to follow the fate of pulmonary PW1⁺ progenitor cells in a model of chronic hypoxia–induced PH development. Under chronic hypoxia, PDGFRα inhibition prevented the increase in PW1⁺ progenitor cell proliferation and differentiation into vascular smooth muscle cells and reduced pulmonary vessel neomuscularization, but did not prevent an increased right ventricular systolic pressure or the development of right ventricular hypertrophy. Conversely, constitutive PDGFRα activation led to neomuscularization via PW1⁺ progenitor cell differentiation into new smooth muscle cells and to PH development in male mice without fibrosis. In vitro, PW1⁺ progenitor cell proliferation, but not differentiation, was dependent on PDGFRα activity.

Conclusions

These results demonstrate a major role of PDGFRα signaling in progenitor cell–dependent lung vessel neomuscularization and vascular remodeling contributing to PH development, including in idiopathic pulmonary arterial hypertension patients. Our findings suggest that PDGFRα blockers may offer a therapeutic add‐on strategy to combine with current pulmonary arterial hypertension treatments to reduce vascular remodeling. Furthermore, our study highlights constitutive PDGFRα activation as a novel experimental PH model.

TRPC6, a therapeutic target for pulmonary hypertension

Idiopathic pulmonary arterial hypertension (PAH) is a fatal and progressive disease. Sustained vasoconstriction due to pulmonary arterial smooth muscle cell (PASMC) contraction and concentric arterial remodeling due partially to PASMC proliferation are the major causes for increased pulmonary vascular resistance and increased pulmonary arterial pressure in patients with precapillary pulmonary hypertension (PH) including PAH and PH due to respiratory diseases or hypoxemia. We and others observed upregulation of TRPC6 channels in PASMCs from patients with PAH. A rise in cytosolic Ca2+ concentration ([Ca2+]cyt) in PASMC triggers PASMC contraction and vasoconstriction, while Ca2+-dependent activation of PI3K/AKT/mTOR pathway is a pivotal signaling cascade for cell proliferation and gene expression. Despite evidence supporting a pathological role of TRPC6, no selective and orally bioavailable TRPC6 antagonist has yet been developed and tested for treatment of PAH or PH. In this study, we sought to investigate whether block of receptor-operated Ca2+ channels using a nonselective blocker of cation channels, 2-aminoethyl diphenylborinate (2-APB, administered intraperitoneally) and a selective blocker of TRPC6, BI-749327 (administered orally) can reverse established PH in mice. The results from the study show that intrapulmonary application of 2-APB (40 µM) or BI-749327 (3-10 µM) significantly and reversibly inhibited acute alveolar hypoxia-induced pulmonary vasoconstriction. Intraperitoneal injection of 2-APB (1 mg/kg per day) significantly attenuated the development of PH and partially reversed established PH in mice. Oral gavage of BI-749327 (30 mg/kg, every day, for 2 wk) reversed established PH by ∼50% via regression of pulmonary vascular remodeling. Furthermore, 2-APB and BI-749327 both significantly inhibited PDGF- and serum-mediated phosphorylation of AKT and mTOR in PASMC. In summary, the receptor-operated and mechanosensitive TRPC6 channel is a good target for developing novel treatment for PAH/PH. BI-749327, a selective TRPC6 blocker, is potentially a novel and effective drug for treating PAH and PH due to respiratory diseases or hypoxemia.

Disrupted PI3K subunit p110α signaling protects against pulmonary hypertension and reverses established disease in rodents

Enhanced signaling via RTKs in pulmonary hypertension (PH) impedes current treatment options because it perpetuates proliferation and apoptosis resistance of pulmonary arterial smooth muscle cells (PASMCs). Here, we demonstrated hyperphosphorylation of multiple RTKs in diseased human vessels and increased activation of their common downstream effector phosphatidylinositol 3'-kinase (PI3K), which thus emerged as an attractive therapeutic target. Systematic characterization of class IA catalytic PI3K isoforms identified p110α as the key regulator of pathogenic signaling pathways and PASMC responses (proliferation, migration, survival) downstream of multiple RTKs. Smooth muscle cell-specific genetic ablation or pharmacological inhibition of p110α prevented onset and progression of pulmonary hypertension (PH) as well as right heart hypertrophy in vivo and even reversed established vascular remodeling and PH in various animal models. These effects were attributable to both inhibition of vascular proliferation and induction of apoptosis. Since this pathway is abundantly activated in human disease, p110α represents a central target in PH.

Single-Cell Transcriptomics Reveals the Cellular Heterogeneity of Cardiovascular Diseases

"A world in a wild flower, and a bodhi in a leaf," small cells contain huge secrets. The vasculature is composed of many multifunctional cell subpopulations, each of which is involved in the occurrence and development of cardiovascular diseases. Single-cell transcriptomics captures the full picture of genes expressed within individual cells, identifies rare or de novo cell subpopulations, analyzes single-cell trajectory and stem cell or progenitor cell lineage conversion, and compares healthy tissue and disease-related tissue at single-cell resolution. Single-cell transcriptomics has had a profound effect on the field of cardiovascular research over the past decade, as evidenced by the construction of cardiovascular cell landscape, as well as the clarification of cardiovascular diseases and the mechanism of stem cell or progenitor cell differentiation. The classification and proportion of cell subpopulations in vasculature vary with species, location, genotype, and disease, exhibiting unique gene expression characteristics in organ development, disease progression, and regression. Specific gene markers are expected to be the diagnostic criteria, therapeutic targets, or prognostic indicators of diseases. Therefore, treatment of vascular disease still has lots of potentials to develop. Herein, we summarize the cell clusters and gene expression patterns in normal vasculature and atherosclerosis, aortic aneurysm, and pulmonary hypertension to reveal vascular heterogeneity and new regulatory factors of cardiovascular disease in the use of single-cell transcriptomics and discuss its current limitations and promising clinical potential.

Progenitor/Stem Cells in Vascular Remodeling during Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by an important occlusive vascular remodeling with the production of new endothelial cells, smooth muscle cells, myofibroblasts, and fibroblasts. Identifying the cellular processes leading to vascular proliferation and dysfunction is a major goal in order to decipher the mechanisms leading to PAH development. In addition to in situ proliferation of vascular cells, studies from the past 20 years have unveiled the role of circulating and resident vascular in pulmonary vascular remodeling. This review aims at summarizing the current knowledge on the different progenitor and stem cells that have been shown to participate in pulmonary vascular lesions and on the pathways regulating their recruitment during PAH. Finally, this review also addresses the therapeutic potential of circulating endothelial progenitor cells and mesenchymal stem cells.

Macrophage-derived PDGF-B induces muscularization in murine and human pulmonary hypertension

Excess macrophages and smooth muscle cells (SMCs) characterize many cardiovascular diseases, but crosstalk between these cell types is poorly defined. Pulmonary hypertension (PH) is a lethal disease in which lung arteriole SMCs proliferate and migrate, coating the normally unmuscularized distal arteriole. We hypothesized that increased macrophage platelet-derived growth factor–B (PDGF-B) induces pathological SMC burden in PH. Our results indicate that clodronate attenuates hypoxia-induced macrophage accumulation, distal muscularization, PH, and right ventricle hypertrophy (RVH). With hypoxia exposure, macrophage Pdgfb mRNA was upregulated in mice, and LysM‑Cre mice carrying floxed alleles for hypoxia-inducible factor 1a, hypoxia-inducible factor 2a, or Pdgfb had reduced macrophage Pdgfb and were protected against distal muscularization and PH. Conversely, LysM‑Cre von-Hippel Lindau^fl/fl mice had increased macrophage Hifa and Pdgfb and developed distal muscularization, PH, and RVH in normoxia. Similarly, Pdgfb was upregulated in macrophages from human idiopathic or systemic sclerosis–induced pulmonary arterial hypertension patients, and macrophage-conditioned medium from these patients increased SMC proliferation and migration via PDGF-B. Finally, in mice, orotracheal administration of nanoparticles loaded with Pdgfb siRNA specifically reduced lung macrophage Pdgfb and prevented hypoxia-induced distal muscularization, PH, and RVH. Thus, macrophage-derived PDGF-B is critical for pathological SMC expansion in PH, and nanoparticle-mediated inhibition of lung macrophage PDGF-B has profound implications as an interventional strategy for PH.

mTOR Signaling in Pulmonary Vascular Disease: Pathogenic Role and Therapeutic Target

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease without a cure. The exact pathogenic mechanisms of PAH are complex and poorly understood, yet a number of abnormally expressed genes and regulatory pathways contribute to sustained vasoconstriction and vascular remodeling of the distal pulmonary arteries. Mammalian target of rapamycin (mTOR) is one of the major signaling pathways implicated in regulating cell proliferation, migration, differentiation, and protein synthesis. Here we will describe the canonical mTOR pathway, structural and functional differences between mTOR complexes 1 and 2, as well as the crosstalk with other important signaling cascades in the development of PAH. The pathogenic role of mTOR in pulmonary vascular remodeling and sustained vasoconstriction due to its contribution to proliferation, migration, phenotypic transition, and gene regulation in pulmonary artery smooth muscle and endothelial cells will be discussed. Despite the progress in our elucidation of the etiology and pathogenesis of PAH over the two last decades, there is a lack of effective therapeutic agents to treat PAH patients representing a significant unmet clinical need. In this review, we will explore the possibility and therapeutic potential to use inhibitors of mTOR signaling cascade to treat PAH.

Growth factors in pulmonary arterial hypertension: Focus on preserving right ventricular function

Pulmonary arterial hypertension (PAH) is a rare and progressive disease, characterized by increased vascular resistance leading to right ventricle (RV) failure. The extent of right ventricular dysfunction crucially influences disease prognosis; however, currently no therapies have specific cardioprotective effects. Besides discussing the pathophysiology of right ventricular adaptation in PAH, this review focuses on the roles of growth factors (GFs) in disease pathomechanism. We also summarize the involvement of GFs in the preservation of cardiomyocyte function, to evaluate their potential as cardioprotective biomarkers and novel therapeutic targets in PAH.

Endothelial platelet-derived growth factor-mediated activation of smooth muscle platelet-derived growth factor receptors in pulmonary arterial hypertension

Platelet-derived growth factor is one of the major growth factors found in human and mammalian serum and tissues. Abnormal activation of platelet-derived growth factor signaling pathway through platelet-derived growth factor receptors may contribute to the development and progression of pulmonary vascular remodeling and obliterative vascular lesions in patients with pulmonary arterial hypertension. In this study, we examined the expression of platelet-derived growth factor receptor isoforms in pulmonary arterial smooth muscle and pulmonary arterial endothelial cells and investigated whether platelet-derived growth factor secreted from pulmonary arterial smooth muscle cell or pulmonary arterial endothelial cell promotes pulmonary arterial smooth muscle cell proliferation. Our results showed that the protein expression of platelet-derived growth factor receptor α and platelet-derived growth factor receptor β in pulmonary arterial smooth muscle cell was upregulated in patients with idiopathic pulmonary arterial hypertension compared to normal subjects. Platelet-derived growth factor activated platelet-derived growth factor receptor α and platelet-derived growth factor receptor β in pulmonary arterial smooth muscle cell, as determined by phosphorylation of platelet-derived growth factor receptor α and platelet-derived growth factor receptor β. The platelet-derived growth factor-mediated activation of platelet-derived growth factor receptor α/platelet-derived growth factor receptor β was enhanced in idiopathic pulmonary arterial hypertension-pulmonary arterial smooth muscle cell compared to normal cells. Expression level of platelet-derived growth factor-AA and platelet-derived growth factor-BB was greater in the conditioned media collected from idiopathic pulmonary arterial hypertension-pulmonary arterial endothelial cell than from normal pulmonary arterial endothelial cell. Furthermore, incubation of idiopathic pulmonary arterial hypertension-pulmonary arterial smooth muscle cell with conditioned culture media from normal pulmonary arterial endothelial cell induced more platelet-derived growth factor receptor α activation than in normal pulmonary arterial smooth muscle cell. Accordingly, the conditioned media from idiopathic pulmonary arterial hypertension-pulmonary arterial endothelial cell resulted in more pulmonary arterial smooth muscle cell proliferation than the media from normal pulmonary arterial endothelial cell. These data indicate that (a) the expression and activity of platelet-derived growth factor receptor are increased in idiopathic pulmonary arterial hypertension-pulmonary arterial smooth muscle cell compared to normal pulmonary arterial smooth muscle cell, and (b) pulmonary arterial endothelial cell from idiopathic pulmonary arterial hypertension patients secretes higher level of platelet-derived growth factor than pulmonary arterial endothelial cell from normal subjects. The enhanced secretion (and production) of platelet-derived growth factor from idiopathic pulmonary arterial hypertension-pulmonary arterial endothelial cell and upregulated platelet-derived growth factor receptor expression (and function) in idiopathic pulmonary arterial hypertension-pulmonary arterial smooth muscle cell may contribute to enhancing platelet-derived growth factor/platelet-derived growth factor receptor-associated pulmonary vascular remodeling in pulmonary arterial hypertension.

LncRNA-SMILR modulates RhoA/ROCK signaling by targeting miR-141 to regulate vascular remodeling in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a fatal progressive disease characterized by an increased blood pressure in the pulmonary arteries. RhoA/Rho-kinase (RhoA/ROCK) signaling activation is often associated with PAH. The purpose of this study is to investigate the role and mechanisms of long noncoding RNA (lncRNA) smooth muscle-induced lncRNA (SMILR) to activate the RhoA/ROCK pathway in PAH. SMILR, microRNA-141 (miR-141), and RhoA were identified by qRT-PCR in PAH patients' serum. 3-(4,5-Dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT), wound-healing assay, cell counting kit-8 (CCK-8) assay, and flow cytometry were performed to determine cell viability, migration, proliferation, and cell cycle in human pulmonary arterial smooth muscle cells (hPASMCs) and primary PASMCs from PAH patients. We also performed bioinformatical prediction, luciferase reporter assay, and RNA-binding protein immunoprecipitation (RIP) to assess the interaction among SMILR, miR-141, and RhoA. The RhoA/ROCK pathway and proliferation-related proteins were measured by Western blotting. Finally, we introduced the small hairpin (sh)SMILR to monocrotaline-induced PAH rat model and used the hemodynamic measurement, qRT-PCR, and immunohistochemistry to examine the therapeutic effects of shSMILR. SMILR and RhoA expression were upregulated, while miR-141 expression was downregulated in PAH patients. SMILR directly interacted with miR-141 and negatively regulated its expression. Knockdown of SMILR suppressed PASMC proliferation and migration induced by hypoxia. Furthermore, overexpression of miR-141 could inhibit the RhoA/ROCK pathway by binding to RhoA, thereby repressing cell proliferation-related signals. Knockdown of SMILR significantly inhibited the Rho/ROCK activation and vascular remodeling in monocrotaline-induced rats. Knockdown of SMILR effectively elevated miR-141 expression and in turn inhibited the RhoA/ROCK pathway to regulate vascular remodeling and reduce blood pressure in PAH.NEW & NOTEWORTHY Smooth muscle enriched long noncoding RNA (SMILR), as a long noncoding RNA (lncRNA), was increased in pulmonary arterial hypertension (PAH) patients and in vitro and in vivo models. SMILR activated RhoA/ROCK signaling by targeting miR-141 to disinhibit its downstream target RhoA. SMILR knockdown or miR-141 overexpression inhibited hypoxia-induced cell proliferation and migration via repressing RhoA/ROCK signaling in pulmonary arterial smooth muscle cells (PASMCs), which was confirmed in vivo experiments that knockdown of SMILR inhibited vascular remodeling and alleviated PAH in rats. SMILR may be a promising and novel therapeutic target for the treatment and drug development of PAH.

3D in vitro Model of Vascular Medial Thickening in Pulmonary Arterial Hypertension

In pulmonary arterial hypertension (PAH), excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) causes vascular medial thickening. Medial thickening is a histopathological hallmark of pulmonary vascular remodeling, the central disease process driving PAH progression. Pulmonary vascular remodeling causes stenosis and/or obstruction of small pulmonary arteries. This leads to increased pulmonary vascular resistance, elevated pulmonary arterial pressure, and ultimately right heart failure. To improve the survival of PAH patients, which remains at approximately 60% at 3 years after diagnosis, the development of novel PAH-targeted drugs is desired. To this end, a detailed understanding of the mechanisms underlying excessive PASMC proliferation and the medial thickening that ensues is necessary. However, a lack of in vitro models that recapitulate medial thickening impedes our deeper understanding of the pathogenetic mechanisms involved. In the present study, we applied 3-dimensional (3D) cell culture technology to develop a novel in vitro model of the pulmonary artery medial layer using human PAH patient-derived PASMCs. The addition of platelet-derived growth factor (PDGF)-BB, a mitogen known to promote excessive PASMC proliferation in PAH, resulted in increased thickness of the 3D-PAH media tissues. Conversely, administration of the PDGF receptor inhibitor imatinib or other clinical PAH drugs inhibited this medial thickening-inducing effect of PDGF-BB. Altogether, by using 3D cell culture technology, we report the generation of an in vitro model of medial thickening in PAH, which had hitherto not been successfully modeled in vitro. This model is potentially useful for assessing the ability of candidate PAH drugs to suppress medial thickening.

Endothelial Twist1-PDGFB signaling mediates hypoxia-induced proliferation and migration of αSMA-positive cells

Remodeling of distal pulmonary arterioles (PAs) associated with marked accumulation of pulmonary artery smooth muscle cells (PASMCs) represents one of the major pathologic features of pulmonary hypertension (PH). We have reported that the transcription factor Twist1 mediates hypoxia-induced PH. However, the mechanism by which endothelial Twist1 stimulates SMC accumulation to distal PAs in PH remains unclear. Here, we have demonstrated that Twist1 overexpression increases the expression of platelet-derived growth factor (PDGFB) in human pulmonary arterial endothelial (HPAE) cells. Hypoxia upregulates the levels of Twist1 and PDGFB in HPAE cells. When we implant hydrogel supplemented with endothelial cells (ECs) on the mouse lung, these ECs form vascular lumen structures and hypoxia upregulates PDGFB expression and stimulates accumulation of αSMA–positive cells in the gel, while knockdown of endothelial Twist1 suppresses the effects. The levels of Twist1 and PDGFB are higher in PAE cells isolated from idiopathic pulmonary arterial hypertension (IPAH) patients compared to those from healthy controls. IPAH patient-derived PAE cells stimulate accumulation of αSMA–positive cells in the implanted gel, while Twist1 knockdown in PAE cells inhibits the effects. Endothelial Twist1-PDGFB signaling plays a key role in αSMA–positive cell proliferation and migration in PH.

Hypoxia-inducible factor-1 α deletion in myeloid lineage attenuates hypoxia-induced pulmonary hypertension

Hypoxemia is seen in patients with pulmonary hypertension and hypoxic pulmonary vasoconstriction worsens their clinical condition. However, vasoconstriction is not the only aspect through which hypoxia induces the progression to pulmonary hypertension. Hypoxia‐inducible factor‐1α (HIF‐1α) is a transcription factor responding to hypoxic conditions by regulating hundreds of genes involved in angiogenesis, erythropoiesis, inflammation, and proliferation. We sought to determine the contribution of HIF‐1α in myeloid lineage cells to the pulmonary vascular response to chronic exposure to hypoxia. We generated myeloid‐specific HIF‐1α knockout (MyeHIF1KO) mice by using Cre‐lox P system, and exposed them to hypoxic conditions for 3 weeks to induce pulmonary hypertension. Macrophages from MyeHIF1KO and control mice were used for western blotting, RT‐qPCR, chemotaxis assay, and ATP assay. MyeHIF1KO mice exposed to hypoxia for 3 weeks exhibited a significant reduction in the right ventricular systolic pressure accompanied by a decrease in the ratio of the right ventricular weight to left ventricular weight, muscularization of the small pulmonary arteries, and infiltration of macrophages into the lung and right ventricle compared with control mice. HIF‐1α‐deficient peritoneal macrophages showed less migration toward monocyte chemoattractant protein‐1 and a decrease in intracellular ATP levels. These results indicate that HIF‐1α in macrophages contributes to the progression of pulmonary vascular remodeling and pulmonary hypertension induced by chronic exposure to hypoxic conditions. The inhibition of myeloid‐specific HIF‐1α may be a novel therapeutic strategy for the treatment of pulmonary hypertension.

Redox Regulation of Ion Channels and Receptors in Pulmonary Hypertension

Significance: Pulmonary hypertension (PH) is characterized by elevated vascular resistance due to vasoconstriction and remodeling of the normally low-pressure pulmonary vasculature. Redox stress contributes to the pathophysiology of this disease by altering the regulation and activity of membrane receptors, K+ channels, and intracellular Ca2+ homeostasis. Recent Advances: Antioxidant therapies have had limited success in treating PH, leading to a growing appreciation that reductive stress, in addition to oxidative stress, plays a role in metabolic and cell signaling dysfunction in pulmonary vascular cells. Reactive oxygen species generation from mitochondria and NADPH oxidases has substantial effects on K+ conductance and membrane potential, and both receptor-operated and store-operated Ca2+ entry. Critical Issues: Some specific redox changes resulting from oxidation, S-nitrosylation, and S-glutathionylation are known to modulate membrane receptor and ion channel activity in PH. However, many sites of regulation that have been elucidated in nonpulmonary cell types have not been tested in the pulmonary vasculature, and context-specific molecular mechanisms are lacking. Future Directions: Here, we review what is known about redox regulation of membrane receptors and ion channels in PH. Further investigation of the mechanisms involved is needed to better understand the etiology of PH and develop better targeted treatment strategies.

MicroRNA‑132 mediates proliferation and migration of pulmonary smooth muscle cells via targeting PTEN

Pulmonary arterial hypertension (PAH) is a severe and progressive disease characterized by the remodeling of small pulmonary arteries. The aberrant proliferation of pulmonary arterial smooth muscle cells (PASMCs) is the primary feature of PAH. MicroRNA (miR)‑132 has been demonstrated to inhibit the proliferation of vascular smooth muscle cells and repress neointimal formation. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a direct target of miR‑132 that has been revealed to be involved in the development of PAH. However, the role of miR‑132 in PAH remains unclear. The present study demonstrated that miR‑132 expression was upregulated in monocrotaline‑induced PAH rats and platelet‑derived growth factor‑induced PASMCs. In addition, treatment of PASMCs with miR‑132 mimics inhibited their proliferation, whereas miR‑132 inhibition exhibited the opposite effects. Furthermore, miR‑132 mimics promoted cell migration and maintained the PASMC contractile phenotype. Finally, the expression levels of PTEN were significantly decreased in PAH and PASMCs treated with miR‑132 mimics. Taken collectively, the data suggested that miR‑132 regulated PASMC function via PTEN and that it may be used as a potential target for the treatment of PAH.

Platelet-derived growth factor up-regulates Ca2+-sensing receptors in idiopathic pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease associated with remodeling of the pulmonary artery. We previously reported that the Ca²⁺-sensing receptor (CaSR) is up-regulated in pulmonary arterial smooth muscle cells (PASMCs) from patients with idiopathic PAH (IPAH) and contributes to enhanced Ca²⁺ responses and excessive cell proliferation. However, the mechanisms underlying the up-regulation of CaSR have not yet been elucidated. We herein examined involvement of platelet-derived growth factor (PDGF) on CaSR expression, Ca²⁺ responses, and proliferation in PASMCs. The expression of PDGF receptors was higher in PASMCs from patients with IPAH than in PASMCs from normal subjects. In addition, PDGF-induced activation of PDGF receptors and their downstream molecules [ERK1/2, p38, protein kinase B, and signal transducer and activator of transcription (STAT) 1/3] were sustained longer in PASMCs from patients with IPAH. The PDGF-induced CaSR up-regulation was attenuated by small interfering RNA knockdown of PDGF receptors and STAT1/3, and by the treatment with imatinib. In monocrotaline-induced pulmonary hypertensive rats, the up-regulation of CaSR was reduced by imatinib. The combination of NPS2143 and imatinib additively inhibited the development of pulmonary hypertension. These results suggest that enhanced PDGF signaling is involved in CaSR up-regulation, leading to excessive PASMC proliferation and vascular remodeling in patients with IPAH. The linkage between CaSR and PDGF signals is a novel pathophysiological mechanism contributing to the development of PAH.-Yamamura, A., Nayeem, M. J., Al Mamun, A., Takahashi, R., Hayashi, H., Sato, M. Platelet-derived growth factor up-regulates Ca²⁺-sensing receptors in idiopathic pulmonary arterial hypertension.

Pulmonary arterial remodelling by deficiency of peroxisome proliferator-activated receptor-γ in murine vascular smooth muscle cells occurs independently of obesity-related pulmonary hypertension

Background

Obesity is associated with cardiovascular complications, including pulmonary hypertension (PH). Reports suggest that peroxisome proliferator-activated receptor-γ (PPARγ) has direct action in preventing vascular remodelling in PH. Here we dissected the specific role of high-fat-diet (HFD)-induced obesity and vascular smooth muscle cell (VSMC)-PPARγ for remodelling of small pulmonary arteries.

Methods

Wild-type (WT) and VSMC-specific PPARγ-knockout (SmPparγ^−/−) mice were fed a low-fat-diet (LFD, 10% kcal from fat) or HFD (60% kcal from fat) for 24 weeks. Mice were metabolically phenotyped (e.g. weight development, insulin/glucose tolerance) at the beginning, and after 12 and 24 weeks, respectively. At 24 weeks additionally pulmonary pressure, heart structure, pulmonary vascular muscularization together with gene and protein expression in heart and lung tissues were determined.

Results

HFD increased right ventricular systolic pressure (RVSP) to a similar extent in WT and SmPparγ^−/− mice. HFD decreased glucose tolerance and insulin sensitivity in both WT and SmPparγ^−/− mice. Importantly, the increase in RVSP correlated with the degree of insulin resistance. However, VSMC-PPARγ deficiency increased pulmonary vascular muscularization independently of the diet-induced rise in RVSP. This increase was associated with elevated expression of early growth response protein 1 in heart and osteopontin in lung tissue.

Conclusions

Here we demonstrate a correlation of insulin resistance and pulmonary pressure. Further, deficiency of PPARγ in VSMCs diet-independently leads to increased pulmonary vascular muscularization.

Inhibition of Shp2 ameliorates monocrotaline-induced pulmonary arterial hypertension in rats

Background

Src homology 2 containing protein tyrosine phosphatase (PTP) 2 (Shp2) is a typical tyrosine phosphatase interacting with receptor tyrosine kinase to regulate multiple signaling pathways in diverse pathological processes. Here, we will investigate the effect of Shp2 inhibition on pulmonary arterial hypertension (PAH) in a rat model and its potential cellular and molecular mechanisms underlying.

Methods

Monocrotaline (MCT)-induced PAH rat model was used in this study. Phps-1, a highly selective inhibitor for Shp2, was administered from 21 days to 35 days after MCT single-injection. Microcatheter method was applied to detected hemodynamic parameters. Histological methods were used to determine PVR changes in PAH rats. Moreover, cultured pulmonary artery smooth muscle cells (PASMCs) treated by platelet-derived growth factor (PDGF) with or without Phps-1 was used to investigate the potential cellular and molecular mechanisms underlying in vitro.

Results

Inhibition of Shp2 significantly attenuated MCT-induced increases of mean pulmonary arterial pressure (mPAP), right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH) in rats. Shp2 inhibition effectively decreased thickening of pulmonary artery media and cardiomyocyte hypertrophy as well as perivascular and myocardial fibrosis in MCT-treated rats. Moreover, Shp2 inhibition ameliorated muscularization of pulmonary arterioles in MCT-induced PAH rats. Shp2 inhibition significantly reduced platelet-derived growth factor (PDGF)-triggered proliferation and migration of human pulmonary artery smooth muscle cells (PASMCs), which might be attributed to the inactivations of Akt and Stat3 pathways.

Conclusions

Shp2 contributes to the development of PAH in rats, which might be a potential target for the treatment of PAH.

MiR-339 inhibits proliferation of pulmonary artery smooth muscle cell by targeting FGF signaling

Pulmonary artery hypertension (PAH) is a fatal disorder. Recent studies suggest that microRNA (miRNA) plays an important role in regulating proliferation of pulmonary artery smooth muscle cells (PASMC), which underlies the pathology of PAH. However, the exact mechanism of action of miRNAs remains elusive. In this study, we found that miR‐339 was highly expressed in the cardiovascular system and was downregulated by a group of cytokines and growth factors, especially PDGF‐BB and FGF2. Functional analyses revealed that miR‐339 can inhibit proliferation of PASMC. Also, miR‐339 inhibited FGF2‐induced proliferation, but had no effect on proliferation induced by PDGF‐BB. The fibroblast growth factor receptor substrate 2 (FRS2) was identified as a potential direct target of miR‐339. Consistent with the actions of miR‐339, knockdown of FRS2 only inhibited FGF2‐ but not PDGF‐BB‐induced proliferation of PASMC. In addition, our results showed that inhibition of ERK and PI3K abrogated the downregulation of miR‐339 induced by PDGF‐BB. Finally, miR‐339 expression was found to be decreased in the pulmonary arteries of rats with MCT‐induced PAH. Our study is the first report on the biological role of miR‐339 in regulating proliferation of PASMC by targeting FGF signaling, providing new mechanistic insights into PASMC proliferation and pathogenesis of PAH.

Extracellular retention of PDGF-B directs vascular remodeling in mouse hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a lethal condition, and current vasodilator therapy has limited effect. Antiproliferative strategies targeting platelet-derived growth factor (PDGF) receptors, such as imatinib, have generated promising results in animal studies. Imatinib is, however, a nonspecific tyrosine kinase inhibitor and has in clinical studies caused unacceptable adverse events. Further studies are needed on the role of PDGF signaling in PH. Here, mice expressing a variant of PDGF-B with no retention motif ( Pdgfb^ret/ret), resulting in defective binding to extracellular matrix, were studied. Following 4 wk of hypoxia, right ventricular systolic pressure, right ventricular hypertrophy, and vascular remodeling were examined. Pdgfb^ret/ret mice did not develop PH, as assessed by hemodynamic parameters. Hypoxia did, however, induce vascular remodeling in Pdgfb^ret/ret mice; but unlike the situation in controls where the remodeling led to an increased concentric muscularization of arteries, the vascular remodeling in Pdgfb^ret/ret mice was characterized by a diffuse muscularization, in which cells expressing smooth muscle cell markers were found in the interalveolar septa detached from the normally muscularized intra-acinar vessels. Additionally, fewer NG2-positive perivascular cells were found in Pdgfb^ret/ret lungs, and mRNA analyses showed significantly increased levels of Il6 following hypoxia, a known promigratory factor for pericytes. No differences in proliferation were detected at 4 wk. This study emphasizes the importance of extracellular matrix-growth factor interactions and adds to previous knowledge of PDGF-B in PH pathobiology. In summary, Pdgfb^ret/ret mice have unaltered hemodynamic parameters following chronic hypoxia, possibly secondary to a disorganized vascular muscularization.

Phosphatidylinositol 3-Kinase-DNA Methyltransferase 1-miR-1281-Histone Deacetylase 4 Regulatory Axis Mediates Platelet-Derived Growth Factor-Induced Proliferation and Migration of Pulmonary Artery Smooth Muscle Cells

BACKGROUND

Platelet-derived growth factor BB, a potent mitogen of pulmonary artery smooth muscle cells (PASMCs), has been implicated in pulmonary arterial remodeling, which is a key pathogenic feature of pulmonary arterial hypertension. Previous microRNA profiling in platelet-derived growth factor BB-treated PASMCs found a significantly downregulated microRNA, miR-1281, but it has not been associated with any cellular function, and we investigated the possibility.

METHODS AND RESULTS

Real-time quantitative reverse transcription-polymerase chain reaction assay proved that downregulation of miR-1281 was a conserved phenomenon in human and rat PASMCs. Overexpression and inhibition of miR-1281 in PASMCs promoted and suppressed, respectively, the cell proliferation and migration. Bioinformatic prediction and 3'-untranslated region reporter assay identified histone deacetylase 4 to be a direct target of miR-1281. Supporting this, proliferation and migration assay demonstrated the cellular function of histone deacetylase 4 is inversely correlated with that of miR-1281. Mechanistically, it is found that platelet-derived growth factor BB activates the phosphatidylinositol 3-kinase pathway, which then induces the expression of DNA methyltransferase 1, leading to enhanced methylation of a flanking CpG island and repressed miR-1281 expression. Finally, a reduced miR-1281 level was consistently identified in hypoxic PASMCs in vitro, in pulmonary arteries of rats with monocrotaline-induced pulmonary arterial hypertension, and in serum of patients with coronary heart disease-pulmonary arterial hypertension. These data suggest that there may be a diagnostic and therapeutic use for miR-1281.

CONCLUSIONS

Herein, we report a novel regulatory axis, phosphatidylinositol 3-kinase-DNA methyltransferase 1-miR-1281-histone deacetylase 4, integrating multiple epigenetic regulators that participate in platelet-derived growth factor BB-stimulated PASMC proliferation and migration and pulmonary vascular remodeling.

Cardiac pathophysiology in response to environmental stress: a current review

Purpose

Environmental stressors are disturbing our ecosystem at an accelerating rate. An increasingly relevant stressor are air pollutants, whose levels are increasing worldwide with threats to human health. These air pollutants are associated with increased mortality and morbidity from cardiovascular diseases. In this review we discuss environmental stressors focusing mainly on the various types of air pollutants, their short-term and long-term cardiovascular effects, and providing the epidemiological evidence associated with adverse cardiovascular outcomes. Direct and indirect pathophysiological mechanisms are also linked with cardiovascular complications such as thrombosis, fibrinolysis, hypertension, ischemic heart diseases and arrhythmias.

RESULTS

Evidence to date suggests that humans are constantly being exposed to unhealthy levels of environmental toxicants with the potential of serious health conditions. Environmental stressors adversely affect the cardiovascular system and pose an increased risk for cardiovascular diseases for those who reside in highly polluted areas.

CONCLUSION

People with existing risk factors and those with established cardiovascular disease have increased susceptibility to environmental stressors. The literature reviewed in this article thus support public health policies aimed at reducing pollutant exposure to benefit public health.

PDGF in organ fibrosis

Fibrosis is part of a tissue repair response to injury, defined as increased deposition of extracellular matrix. In some instances, fibrosis is beneficial; however, in the majority of diseases fibrosis is detrimental. Virtually all chronic progressive diseases are associated with fibrosis, representing a huge number of patients worldwide. Fibrosis occurs in all organs and tissues, becomes irreversible with time and further drives loss of tissue function. Various cells types initiate and perpetuate pathological fibrosis by paracrine activation of the principal cellular executors of fibrosis, i.e. stromal mesenchymal cells like fibroblasts, pericytes and myofibroblasts. Multiple pathways are involved in fibrosis, platelet-derived growth factor (PDGF)-signaling being one of the central mediators. Stromal mesenchymal cells express both PDGF receptors (PDGFR) α and β, activation of which drives proliferation, migration and production of extracellular matrix, i.e. the principal processes of fibrosis. Here, we review the role of PDGF signaling in organ fibrosis, with particular focus on the more recently described ligands PDGF-C and -D. We discuss the potential challenges, opportunities and open questions in using PDGF as a potential target for anti-fibrotic therapies.

Use of multitarget tyrosine kinase inhibitors to attenuate platelet-derived growth factor signalling in lung disease

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) play a fundamental role in the embryonic development of the lung. Aberrant PDGF signalling has been documented convincingly in a large variety of pulmonary diseases, including idiopathic pulmonary arterial hypertension, lung cancer and lung fibrosis. Targeting PDGF signalling has been proven to be effective in these diseases. In clinical practice, the most effective way to block PDGF signalling is to inhibit the activity of the intracellular PDGFR kinases. Although the mechanism of action of such drugs is not specific for PDGF signalling, the medications have a broad therapeutic index that allows clinical use. The safety profile and therapeutic opportunities of these and future medications that target PDGFs and PDGFRs are reviewed.

An increasing role for PDGF signalling inhibitors in clinical trials for the treatment of various pulmonary diseaseshttp://ow.ly/buaI30f9HcN

Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) levels in the cerebrospinal fluid of children with influenza-associated encephalopathy

INTRODUCTION

To search for an index of neurologic prognosis of children with influenza-associated encephalopathy (IAE), involvement of angiogenesis-related growth factors in the pathology was investigated.

PATIENTS AND METHODS

The subjects were 11 IAE patients, 6 patients with bacterial meningitis (BM), and 24 patients with non-central nervous system infection as a control group admitted to our hospital. The correlation between the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) levels in cerebrospinal fluid and the relationship with an index of inflammatory marker, interleukin (IL)-6, were investigated. Using the Pediatric Cerebral Performance Categories (PCPC) score as a prognostic indicator, we evaluated the association between the biomarkers and neurologic prognosis.

RESULT

PDGF significantly increased in the IAE group compared with that in the BM group. Cerebrospinal fluid VEGF and PDGF increased in all IAE and BM patients compared with that in the control group, and VEGF and PDGF were positively correlated in the 2 groups. No correlation was found between the cerebrospinal fluid VEGF and PDGF levels and IL-6 level in the IAE group, whereas a correlation was found in the BM group. All these factors increased in patients with poor neurologic prognosis.

DISCUSSION

It is possible that the disease state of IAE can be evaluated based on vascular endothelial disorder-related markers.

Inhibitory effect of NBL1 on PDGF-BB-induced human PASMC proliferation through blockade of PDGFβ-p38MAPK pathway

Pulmonary artery remodelling is a key feature in the pathological progress of pulmonary arterial hypertension (PAH). Moreover, excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs) plays a critical role in the pathogenesis of pulmonary artery remodelling. Neuroblastoma suppressor of tumorigenicity 1 (NBL1) has been previously shown to induce growth inhibition in tumour cells. However, the effect of NBL1 in the regulation of human PASMC proliferation remains unclear. In cultured human PASMCs, we observed a dose-dependent inhibitory effect of NBL1 on platelet derived growth factor (PDGF)-BB-induced cell growth, DNA synthesis and proliferating cell nuclear antigen (PCNA) expression, as measured by MTS assay, 5-ethynil-2-deoxyuridine (EdU) analysis and western blots respectively. We also detected the expression and activities of cell-cycle positive regulators (cyclin D1, cyclin E, CDK2, CDK4 and CDK6) and negative regulators (p21 and p27) in human PASMCs by western blots and co-immuoprecipitation (IP). Our results show that NBL1-induced growth suppression is associated with the decreased activity of cyclin D1–CDK4 and the decreased phosphorylation of p27 in PDGF-BB-treated human PASMCs. By western blots using the phosphor-specific antibodies, we further demonstrated that NBL1 induced growth suppression is mediated by blockade of the up-stream PDGF-receptor β (PDGFRβ)-p38 mitogen-activated protein kinase (MAPK). In conclusion, our results suggest that NBL1 could inhibit PDGF-BB-induced human PASMC proliferation, and the underlying mechanism is associated with the decreased cyclin D1–CDK4 activity and up-regulated p27 by decreasing the phosphorylation of p27 via blockade of PDGFRβ-p38MAPK signal cascade. Our findings may provide a potential therapeutic target for PAH.

Teleocidin A2 inhibits human proteinase-activated receptor 2 signaling in tumor cells

Enhanced expression of the proteinase‐activated receptor 2 (PAR2) is linked to cell proliferation and migration in many cancer cell types. The role of PAR2 in cancer progression strongly illustrates the need for PAR2‐inhibiting compounds. However, to date, potent and selective PAR2 antagonists have not been reported. The natural product teleocidin A2 was characterized against PAR2‐activating peptide SLIGKV‐NH₂, and trypsin‐induced PAR2‐dependent intracellular Ca²⁺ mobilization in tumor and in primary endothelial or epithelial cells. Further biochemical and cell‐based studies were conducted to evaluate teleocidin specificity. The antagonizing effect of teleocidin A2 was confirmed in PAR2‐dependent cell migration and rearrangement of actin cytoskeleton of human breast adenocarcinoma cell line (MDA‐MB 231) breast cancer cells. Teleocidin A2 antagonizes PAR2‐dependent intracellular Ca²⁺ mobilization induced by either SLIGKV‐NH₂ or trypsin with IC₅₀ values from 15 to 25 nmol/L in MDA‐MB 231, lung carcinoma cell line, and human umbilical vein endothelial cell. Half maximal inhibition of either PAR1 or P2Y receptor‐dependent Ca²⁺ release is only achieved with 10‐ to 20‐fold higher concentrations of teleocidin A2. In low nanomolar concentrations, teleocidin A2 reverses both SLIGKV‐NH₂ and trypsin‐mediated PAR2‐dependent migration of MDA‐MB 231 cells, and has no effect itself on cell migration and no effect on cell viability. Teleocidin A2 further controls PAR2‐induced actin cytoskeleton rearrangement of MDA‐MB 231 cells. Thus, for the first time, the small molecule natural product teleocidin A2 exhibiting PAR2 antagonism in the low nanomolar range with potent antimigratory activity is described.