CD44 expression in plexiform lesions of idiopathic pulmonary arterial hypertension

Inflammation and DKK1-induced AKT activation contribute to endothelial dysfunction following NR2F2 loss

NR2F2 is expressed in endothelial cells (ECs) and Nr2f2 knockout produces lethal cardiovascular defects. In humans, reduced NR2F2 expression is associated with cardiovascular diseases including congenital heart disease and atherosclerosis. Here, NR2F2 silencing in human primary ECs led to inflammation, endothelial-to-mesenchymal transition (EndMT), proliferation, hypermigration, apoptosis-resistance, and increased production of reactive oxygen species. These changes were associated with STAT and AKT activation along with increased production of DKK1. Co-silencing DKK1 and NR2F2 prevented NR2F2-loss-induced STAT and AKT activation and reversed EndMT. Serum DKK1 concentrations were elevated in patients with pulmonary arterial hypertension (PAH) and DKK1 was secreted by ECs in response to in vitro loss of either BMPR2 or CAV1, which are genetic defects associated with the development of PAH. In human primary ECs, NR2F2 suppressed DKK1, whereas its loss conversely induced DKK1 and disrupted endothelial homeostasis, promoting phenotypic abnormalities associated with pathologic vascular remodeling. Activating NR2F2 or blocking DKK1 may be useful therapeutic targets for treating chronic vascular diseases associated with EC dysfunction.NEW & NOTEWORTHY NR2F2 loss in the endothelial lining of blood vessels is associated with cardiovascular disease. Here, NR2F2-silenced human endothelial cells were inflammatory, proliferative, hypermigratory, and apoptosis-resistant with increased oxidant stress and endothelial-to-mesenchymal transition. DKK1 was induced in NR2F2-silenced endothelial cells, while co-silencing NR2F2 and DKK1 prevented NR2F2-loss-associated abnormalities in endothelial signaling and phenotype. Activating NR2F2 or blocking DKK1 may be useful therapeutic targets for treating vascular diseases associated with endothelial dysfunction.

Osteopontin in Pulmonary Hypertension

Pulmonary hypertension (PH) is a pathological condition with multifactorial etiology, which is characterized by elevated pulmonary arterial pressure and pulmonary vascular remodeling. The underlying pathogenetic mechanisms remain poorly understood. Accumulating clinical evidence suggests that circulating osteopontin may serve as a biomarker of PH progression, severity, and prognosis, as well as an indicator of maladaptive right ventricular remodeling and dysfunction. Moreover, preclinical studies in rodent models have implicated osteopontin in PH pathogenesis. Osteopontin modulates a plethora of cellular processes within the pulmonary vasculature, including cell proliferation, migration, apoptosis, extracellular matrix synthesis, and inflammation via binding to various receptors such as integrins and CD44. In this article, we provide a comprehensive overview of the current understanding of osteopontin regulation and its impact on pulmonary vascular remodeling, as well as consider research issues required for the development of therapeutics targeting osteopontin as a potential strategy for the management of PH.

Potential contribution of early endothelial progenitor cell (eEPC)-to-macrophage switching in the development of pulmonary plexogenic lesion

Background

Plexiform lesions, which have a dynamic appearance in structure and cellular composition, are the histological hallmark of severe pulmonary arterial hypertension in humans. The pathogenesis of the lesion development remains largely unknown, although it may be related to local inflammation and dysfunction in early progenitor endothelial cells (eEPCs). We tested the hypothesis that eEPCs contribute to the development of plexiform lesions by differentiating into macrophages in the setting of chronic inflammation.

Methods

The eEPC markers CD133 and VEGFR-2, macrophage lineage marker mannose receptor C-type 1 (MRC1), TNFα and nuclear factor erythroid 2-related factor 2 (Nrf2) in plexiform lesions in a broiler model were determined by immunohistochemistry. eEPCs derived from peripheral blood mononuclear cells were exposed to TNFα, and macrophage differentiation and angiogenic capacity of the cells were evaluated by phagocytotic and Matrigel plug assays, respectively. The role of Nrf2 in eEPC-to-macrophage transition as well as in MRC1 expression was also evaluated. Intratracheal installation of TNFα was conducted to determine the effect of local inflammation on the formation of plexiform lesions.

Results

Cells composed of the early lesions have a typical eEPC phenotype whereas those in more mature lesions display molecular and morphological characteristics of macrophages. Increased TNFα production in plexiform lesions was observed with lesion progression. In vitro studies showed that chronic TNFα challenge directed eEPCs to macrophage differentiation accompanied by hyperactivation of Nrf2, a stress-responsive transcription factor. Nrf2 activation (Keap1 knockdown) caused a marked downregulation in CD133 but upregulation in MRC1 mRNA. Dual luciferase reporter assay demonstrated that Nrf2 binds to the promoter of MRC1 to trigger its expression. In good agreement with the in vitro observation, TNFα exposure induced macrophage differentiation of eEPCs in Matrigel plugs, resulting in reduced neovascularization of the plugs. Intratracheal installation of TNFα resulted in a significant increase in plexiform lesion density.

Conclusions

This work provides evidence suggesting that macrophage differentiation of eEPCs resulting from chronic inflammatory stimulation contributes to the development of plexiform lesions. Given the key role of Nrf2 in the phenotypic switching of eEPCs to macrophages, targeting this molecular might be beneficial for intervention of plexiform lesions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02210-7.

Cardiovascular Effects Mediated by HMMR and CD44

Cardiovascular disease (CVD) is the leading cause of death worldwide. The most dangerous life-threatening symptoms of CVD are myocardial infarction and stroke. The causes of CVD are not entirely clear, and new therapeutic targets are still being sought. One of the factors involved in CVD development among vascular damage and oxidative stress is chronic inflammation. It is known that hyaluronic acid plays an important role in inflammation and is regulated by numerous stimuli, including proinflammatory cytokines. The main receptors for hyaluronic acid are CD44 and RHAMM. These receptors are membrane proteins that differ in structure, but it seems that they can perform similar or synergistic functions in many diseases. Both RHAMM and CD44 are involved in cell migration and wound healing. However, their close association with CVD is not fully understood. In this review, we describe the role of both receptors in CVD.

Irbesartan ameliorates chronic mountain sickness in a rat model via the cholesterol metabolism: An iTRAQ -based proteomics analysis

OBJECTIVE

To study the effects of irbesartan on pulmonary artery lesions in a rat model with chronic mountain sickness (CMS) and identify the biomarkers involved.

METHODS

In this study, we used a rat model of CMS to evaluate the therapeutic effect of irbesartan by measuring pulmonary artery pressure and evaluating the histopathology of the pulmonary artery. We also used proteomics technology to identify differentially expressed proteins (DEPs) in the serum and performed bioinformatics analysis. Results were then verified by enzyme linked immunosorbent assay (ELISA) and immunohistochemistry (IHC).

RESULTS

Irbesartan treatment induced a significant decrease (P < 0.05) in the pulmonary artery pressure of CMS rats. Histopathological and electron microscope further confirmed that high altitude hypoxia induced changes in the structure of the pulmonary artery tissue and caused ultrastructural lesions. Proteomics analysis identified 40 DEPs; bioinformatics analysis further revealed that the cholesterol metabolism pathway plays a crucial role in the occurrence of CMS. ELISA and IHC verified that several DEPs (Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1) represent critical biological markers in pulmonary artery disease caused by CMS.

CONCLUSIONS

Irbesartan significantly improved pulmonary artery damage in a rat model of CMS possibly by impacting on the cholesterol metabolism pathway and by reducing damage to vascular endothelial cells. Irbesartan also inhibited the expression levels of IGF-1, Profilin1 and Col1a1 to relieve pulmonary artery pressure and improve lung function by inhibiting vascular remodeling. Several proteins were identified as potential biomarkers of CMS, including Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1.

Pristane/Hypoxia (PriHx) Mouse as a Novel Model of Pulmonary Hypertension Reflecting Inflammation and Fibrosis

BACKGROUND

Pulmonary arterial hypertension (PAH), particularly connective tissue disease-associated PAH (CTD-PAH), is a progressive disease and novel therapeutic agents based on the specific molecular pathogenesis are desired. In the pathogenesis of CTD-PAH, inflammation, immune cell abnormality, and fibrosis play important roles. However, the existing mouse pulmonary hypertension (PH) models do not reflect these features enough. The relationship between inflammation and hypoxia is still unclear.

METHODS AND RESULTS

Intraperitoneal administration of pristane, a kind of mineral oil, and exposure to chronic hypoxia were combined, and this model is referred to as pristane/hypoxia (PriHx) mice. Hemodynamic and histological analyses showed that the PriHx mice showed a more severe phenotype of PH than pristane or hypoxia alone. Immunohistological and flow cytometric analyses revealed infiltration of immune cells, including hemosiderin-laden macrophages and activated CD4+helper T lymphocytes in the lungs of PriHx mice. Pristane administration exacerbated lung fibrosis and elevated the expression of fibrosis-related genes. Inflammation-related genes such asIl6andCxcl2were also upregulated in the lungs of PriHx mice, and interleukin (IL)-6 blockade by monoclonal anti-IL-6 receptor antibody MR16-1 ameliorated PH of PriHx mice.

CONCLUSIONS

A PriHx model, a novel mouse model of PH reflecting the pathological features of CTD-PAH, was developed through a combination of pristane administration and exposure to chronic hypoxia.

Arteritis and Plexiform Lesion in Intralobar Pulmonary Sequestration: The First Case With Such Two Distinct Complex Lesions Associated With Local Pulmonary Hypertension

In intralobar pulmonary sequestrations, vascular changes similar to those in pulmonary hypertension (PH) are generally observed, such as intimal proliferation and plexiform lesions. However, to our knowledge, a sequestrated lung manifesting vascular changes with both arteritis and a plexiform lesion has never been reported. A 25-year-old man was diagnosed with intralobar pulmonary sequestration. Pathologically, both arteritis and a plexiform lesion were observed in the sequestrated lung. Systemic vasculitis syndrome was clinically excluded, and the pathological findings appeared to be associated with local PH. Arteritis is an extremely rare finding; only one case of arteritis associated with local PH has been reported in intralobar sequestration. In this case, the artery near the plexiform lesion had milder inflammation and fibrosis, suggesting that the arteritis formed prior to the plexiform lesion. This is the first case of arteritis and a plexiform lesion co-occurring in intralobar pulmonary sequestration associated with local PH. This case may shed light on the formation of plexiform lesions and their association with arteritis.

Role of miR-223-3p in pulmonary arterial hypertension via targeting ITGB3 in the ECM pathway

Objectives

To investigate the functions of miR‐223‐3p and ITGB3 in pulmonary arterial hypertension (PAH).

Materials and Methods

Microarray analysis was used to detect differentially expressed genes and microRNAs. In in vitro models, the expressions of miR‐223‐3p and ITGB3 were detected by qRT‐PCR and Western blot. α‐SMA expression and cell proliferation were analysed by immunofluorescence and MTT assay, respectively. In in vivo models, PAH progressions were determined by measuring the levels of mPAP and RVSP. Lung and myocardial tissues were subjected to HE staining and Masson and Sirius red‐saturated carbazotic acid staining to investigate the pathological features.

Results

The microarray analysis revealed that ITGB3 was upregulated, while hsa‐miR‐223‐3p was downregulated in PAH. After the induction of hypoxia, miR‐223‐3p was downregulated and ITGB3 was upregulated in PASMCs. Hypoxia induction promoted cell proliferation and inhibited α‐SMA expression in PASMCs. Both the upregulation of miR‐223‐3p and the downregulation of ITGB3 attenuated the aberrant proliferation induced by hypoxia conditions. After approximately 4 weeks, the mPAP and RVSP levels of rats injected with MCT were decreased by the overexpression of miR‐223‐3p or the silencing of ITGB3. The staining results revealed that both miR‐223‐3p overexpression and ITGB3 knockdown alleviated the pulmonary vascular remodelling and improved the PAH pathological features of rats.

Conclusions

MiR‐223‐3p alleviated the progression of PAH by suppressing the expression of ITGB3, a finding which provides novel targets for clinical treatment.

Pharmacokinetics of drugs for pediatric pulmonary hypertension

BACKGROUND

Over the past few years, several drugs, each with a different mechanism, have been developed for the treatment of pulmonary hypertension (PH) and are now prescribed in the clinical setting. While the optimal doses of these drugs in adults have been determined, the optimal dose in children, however, is unclear. The aim of this study was therefore, to measure blood drug levels and analyze the pharmacokinetics of two such drugs in children.

METHODS

From April 2010 to May 2015, we prospectively enrolled 23 children with PH for treatment with bosentan and/or tadalafil. Twenty children were treated with bosentan and 19 received tadalafil. Sixteen children were given both drugs. Blood samples were collected after 2 weeks of treatment, and blood drug levels measured using high-performance liquid chromatography.

RESULTS

For both drugs, the peak plasma concentration was lower and the half-life was shorter than the known values in adults. The blood trough level of bosentan significantly correlated with its dose, but no such correlation was seen for tadalafil. For both drugs, no correlation was observed between age and blood drug levels.

CONCLUSIONS

Oral dosing with bosentan and tadalafil in children may not achieve therapeutic blood concentration. Thus, the optimal dosing must be established individually while monitoring blood drug level.

Modification of hyaluronan by heavy chains of inter-α-inhibitor in idiopathic pulmonary arterial hypertension

We previously reported an altered hyaluronan (HA) metabolism in idiopathic pulmonary arterial hypertension (IPAH) lung tissue and cultured smooth muscle cells. Hyaluronan was present in the smooth muscle cell layer surrounding the pulmonary vasculature and in plexigenic lesions. Additionally, cultured pulmonary artery smooth muscle cells produced spontaneous HA "cable" structures, without additional stimuli, that were leukocyte-adhesive. We now present evidence that the HA that accumulates in IPAH plexigenic lesions is a pathological form of HA in which heavy chains (HCs) from the serum-derived proteoglycan inter-α-inhibitor are covalently attached to the HA backbone to form a pathological HC-HA complex. CD45-positive leukocytes were identified within these HC-HA matrices. Elevated mRNA levels of the enzyme that transfers HCs to HA, known as tumor necrosis factor-stimulated gene 6, were detected in IPAH lung tissue.

The emergence of new therapeutic targets in pulmonary arterial hypertension: from now to the near future

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease that pathologically increases pulmonary vascular resistance. Ultimately, this leads to right ventricular failure and premature death. Current therapeutic strategies are mainly designed to induce relaxation of the pulmonary arteries, but are not directly aimed to improve vascular remodeling that characterize PAH. Although these treatments modestly improve patient symptoms, pulmonary hemodynamics and survival, none of them are curative and approximately 15% of patients die within 1 year of medical follow-up despite treatment. Within the last 5 years, tremendous advances in our understanding of the PAH pathophysiology have arisen. These advances have a high potential for the development of better patient care by providing novel therapeutic targets. The goal of this report is to review the current PAH treatments, as well as novel therapies that will pave the future in this devastating disease.

Signal transduction in the development of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a unique disease. Properly speaking, it is not a disease of the lung. It can be seen more as a microvascular disease occurring mainly in the lungs and affecting the heart. At the cellular level, the PAH paradigm is characterized by inflammation, vascular tone imbalance, pulmonary arterial smooth muscle cell proliferation and resistance to apoptosis and the presence of in situ thrombosis. At a clinical level, the aforementioned abnormal vascular properties alter physically the pulmonary circulation and ventilation, which greatly influence the right ventricle function as it highly correlates with disease severity. Consequently, right heart failure remains the principal cause of death within this cohort of patients. While current treatment modestly improve patients' conditions, none of them are curative and, as of today, new therapies are lacking. However, the future holds potential new therapies that might have positive influence on the quality of life of the patient. This article will first review the clinical presentation of the disease and the different molecular pathways implicated in the pathobiology of PAH. The second part will review tomorrow's future putative therapies for PAH.