Inflammation, growth factors, and pulmonary vascular remodeling

Galectin-3 Levels Are Elevated and Predictive of Mortality in Pulmonary Hypertension

BACKGROUND

Galectin-3, a novel binding-lectin involved in inflammation and fibrosis, is elevated in heart failure and is independently predictive of mortality in this condition. We sought to evaluate galectin-3 levels and its prognostic value in patients with pulmonary hypertension (PH), a known inflammatory state, in the setting of pulmonary arterial hypertension (PAH) and in heart failure with preserved ejection fraction-associated PH (HFpEF-PH).

METHODS

We measured galectin-3 levels in 76 patients with PH; 37 patients with PAH and 39 patients with HFpEF-PH. Baseline characteristics, and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels were assessed. Univariate and multivariate analyses were used to assess the prognostic value of galectin-3.

RESULTS

Median (IQR) galectin-3 (ng/mL) for the entire cohort was 24.65 (IQR=10.39, 32.90); 22.33 (IQR=18.94, 27.30) and 28.94 (IQR=21.67, 39.85) in the PAH and HFpEF-PH, respectively (p=0.07). After evaluation of the galectin-3 levels by tertile, mortality rates were 16% (4/25), 34.6% (9/26), and 48% (12/25) in tertiles 1-3, respectively, and Kaplan-Meier analysis revealed a significant increase in mortality across increasing galectin-3 tertiles (log-rank p=0.014). On Cox regression analysis, galectin-3 was a strong predictor of mortality on both univariate HR=2.09 per tertile (95% CI=1.21, 3.62 per tertile; p-trend=0.008) and multivariate analysis HR=2.19 per tertile (95% CI=1.06, 4.54; p-trend=0.035) after adjusting for age, sex, race, glomerular filtration rate (eGFR), NT-proBNP, medications, and aetiology of PH (PAH vs. HFpEF-PH).

CONCLUSION

Galectin-3 is a strong, independent prognostic marker in PH, regardless of aetiology. Larger studies should further evaluate the role of galectin-3 as a prognostic biomarker and possible therapeutic target in PH.

Non-infectious pulmonary disorders in HIV

INTRODUCTION

Since the advent of antiretroviral therapy (ART), non-infectious pulmonary disorders have become common comorbidities in the human immunodeficiency virus (HIV) positive population. Clinicians caring for those with HIV disease should be aware of the prevalence of non-infectious pulmonary disorders. A comprehensive understanding is required to diagnosis and manage these syndromes appropriately. Areas covered: This review focuses on the epidemiology, risk factors, pathogenesis, clinical feature and diagnosis, and treatment of HIV-related chronic obstructive pulmonary disease (COPD), lung cancer, pulmonary hypertension. Expert Commentary: The prevalence of COPD in the HIV population is frequent and requires appropriate diagnosis and treatment. HIV-positive individuals with lung cancer carry a poorer prognosis and require early diagnosis and treatment. A complex condition exists with pulmonary hypertension in the HIV population and requires a high degree of clinical suspicion for early diagnosis.

Dimethyl Fumarate ameliorates pulmonary arterial hypertension and lung fibrosis by targeting multiple pathways

Pulmonary arterial hypertension (PAH) is a fatal condition for which there is no cure. Dimethyl Fumarate (DMF) is an FDA approved anti-oxidative and anti-inflammatory agent with a favorable safety record. The goal of this study was to assess the effectiveness of DMF as a therapy for PAH using patient-derived cells and murine models. We show that DMF treatment is effective in reversing hemodynamic changes, reducing inflammation, oxidative damage, and fibrosis in the experimental models of PAH and lung fibrosis. Our findings indicate that effects of DMF are facilitated by inhibiting pro-inflammatory NFκB, STAT3 and cJUN signaling, as well as βTRCP-dependent degradation of the pro-fibrogenic mediators Sp1, TAZ and β-catenin. These results provide a novel insight into the mechanism of its action. Collectively, preclinical results demonstrate beneficial effects of DMF on key molecular pathways contributing to PAH, and support its testing in PAH treatment in patients.

Subclinical Pulmonary Hypertension in Childhood Systemic Lupus Erythematosus Associated with Minor Disease Manifestations

The aim of this study was to evaluate pulmonary hypertension (PH) in 852 childhood-onset systemic lupus erythematosus (cSLE) patients. This was a large multicenter study conducted in 10 Pediatric Rheumatology Services of São Paulo state, Brazil. PH was defined as systolic pulmonary artery pressure >35 mmHg and/or measurement of the mean pulmonary artery pressure >25 mmHg and/or diastolic pressure >15 mmHg by transthoracic echocardiogram. Demographic data, clinical manifestations, disease activity score (SLEDAI-2K), disease damage score (SLICC/ACR-DI) and treatments were also evaluated. Statistical analysis was performed using Bonferroni correction (p < 0.002). PH was observed in 17/852 (2%) cSLE patients. Effort dyspnea occurred in 3/17, chest pain in 1/17 and right ventricle dysfunction in 3/17 cSLE patients. None had pulmonary thromboembolism or antiphospholipid syndrome. Further comparison between 17 cSLE with PH and 85 cSLE control patients without PH with similar disease duration [15 (0-151) vs. 15 (0-153) months, p = 0.448], evaluated at the last visit, revealed higher frequencies of fever (47 vs. 9%, p < 0.001), reticuloendothelial manifestations (41 vs. 7%, p < 0.001) and serositis (35 vs. 5%, p = 0.001) in the former group. Frequencies of renal and neuropsychiatric involvements and antiphospholipid syndrome, as well as the median of SLEDAI-2K and SLICC/ACR-DI scores, were comparable in both groups (p > 0.002). Normal transthoracic echocardiography was evidenced in 9/17 (53%), with median cSLE duration of 17.5 months (1-40) after PH standard treatment. PH was a rare manifestation of cSLE occurring in the first two years of disease. The majority of patients were asymptomatic with mild lupus manifestations. The underlying mechanism seemed not to be related to pulmonary thromboembolism and/or antiphospholipid syndrome.

Apparent Aortic Stiffness in Children With Pulmonary Arterial Hypertension: Existence of Vascular Interdependency?

BACKGROUND

Left ventricular dysfunction, mediated by ventricular interdependence, has been associated with negative outcomes in children with pulmonary arterial hypertension (PAH). Considering the dilation of the pulmonary arteries as a paramount sign of PAH, we hypothesized that the ascending aorta will present signs of apparent stiffness in children with PAH and that this effect may be because of mechanical interaction with the dilated main pulmonary artery (MPA).

METHODS AND RESULTS

Forty-two children with PAH and 26 age- and size-matched controls underwent comprehensive cardiac magnetic resonance evaluation. Assessment of aortic stiffness was evaluated by measuring pulse wave velocity, aortic strain, and distensibility. Children with PAH had significantly increased pulse wave velocity in the ascending aorta (3.4 versus 2.3 m/s for PAH and controls, respectively; P=0.001) and reduced aortic strain (23% versus 29%; P<0.0001) and distensibility (0.47 versus 0.64%/mm Hg; P=0.02). Indexed MPA diameter correlated with pulse wave velocity (P=0.04) and with aortic strain (P=0.02). The ratio of MPA to aortic size correlated with pulse wave velocity (P=0.0098), strain (P=0.0099), and distensibility (P=0.015). Furthermore, aortic relative area change was associated with left ventricular ejection fraction (P=0.045) and ventricular-vascular coupling ratio (P=0.042).

CONCLUSIONS

Pediatric PAH patients have increased apparent ascending aortic stiffness, which was strongly associated with the degree of MPA distension. We speculate that distension of the MPA may play a major role in limiting full aortic expansion during systole, which modulates left ventricular performance and impacts systemic hemodynamics in pediatric PAH.

Three-dimensional micro computed tomography analysis of the lung vasculature and differential adipose proteomics in the Sugen/hypoxia rat model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disease characterized by significant vascular remodeling. The obesity epidemic has produced great interest in the relationship between small visceral adipose tissue depots producing localized inflammatory conditions, which may link metabolism, innate immunity, and vascular remodeling. This study used novel micro computed tomography (microCT) three-dimensional modeling to investigate the degree of remodeling of the lung vasculature and differential proteomics to determine small visceral adipose dysfunction in rats with severe PAH. Sprague-Dawley rats were subjected to a subcutaneous injection of vascular endothelial growth factor receptor blocker (Sugen 5416) with subsequent hypoxia exposure for 3 weeks (SU/hyp). At 12 weeks after hypoxia, microCT analysis showed a decrease in the ratio of vascular to total tissue volume within the SU/hyp group (mean ± standard deviation: 0.27 ± 0.066; P = 0.02) with increased vascular separation (0.37 ± 0.062 mm; P = 0.02) when compared with the control (0.34 ± 0.084 and 0.30 ± 0.072 mm). Differential proteomics detected an up-regulation of complement protein 3 (C3; SU/hyp∶control ratio = 2.86) and the adipose tissue-specific fatty acid binding protein-4 (FABP4, 2.66) in the heart adipose of the SU/hyp. Significant remodeling of the lung vasculature validates the efficacy of the SU/hyp rat for modeling human PAH. The upregulation of C3 and FABP4 within the heart adipose implicates small visceral adipose dysfunction. C3 has been associated with vascular stiffness, and FABP4 suppresses peroxisome proliferator-activated receptor, which is a major regulator of adipose function and known to be downregulated in PAH. These findings reveal that small visceral adipose tissue within the SU/hyp model provides mechanistic links for vascular remodeling and adipose dysfunction in the pathophysiology of PAH.

The role of nuclear factor of activated T cells in pulmonary arterial hypertension

Nuclear factor of activated T cells (NFAT) was first identified as a transcription factor about 3 decades ago and was not well studied until the development of immunosuppressant. Numerous studies confirm that calcineurin/NFAT signaling is very important in the development of vasculature and cardiovascular system during embryogenesis and is involved in the development of vascular diseases such as hypertension, atherosclerosis and restenosis. Recent studies demonstrated that NFAT proteins also regulate immune response and vascular cells in the pulmonary microenvironment. In this review, we will discuss how different NFAT isoforms contribute to pulmonary vascular remodeling and potential new therapeutic targets for treating pulmonary arterial hypertension.

A stimuli responsive liposome loaded hydrogel provides flexible on-demand release of therapeutic agents

Lysolipid-based thermosensitive liposomes (LTSL) embedded in a chitosan-based thermoresponsive hydrogel matrix (denoted Lipogel) represents a novel approach for the spatiotemporal release of therapeutic agents. The entrapment of drug-loaded liposomes in an injectable hydrogel permits local liposome retention, thus providing a prolonged release in target tissues. Moreover, release can be controlled through the use of a minimally invasive external hyperthermic stimulus. Temporal control of release is particularly important for complex multi-step physiological processes, such as angiogenesis, in which different signals are required at different times in order to produce a robust vasculature. In the present work, we demonstrate the ability of Lipogel to provide a flexible, easily modifiable release platform. It is possible to tune the release kinetics of different drugs providing a passive release of one therapeutic agent loaded within the gel and activating the release of a second LTSL encapsulated agent via a hyperthermic stimulus. In addition, it was possible to modify the drug dosage within Lipogel by varying the duration of hyperthermia. This can allow for adaption of drug dosing in real time. As an in vitro proof of concept with this system, we investigated Lipogels ability to recruit stem cells and then elevate their production of vascular endothelial growth factor (VEGF) by controlling the release of a pro-angiogenic drug, desferroxamine (DFO) with an external hyperthermic stimulus. Initial cell recruitment was accomplished by the passive release of hepatocyte growth factor (HGF) from the hydrogel, inducing a migratory response in cells, followed by the delayed release of DFO from thermosensitive liposomes, resulting in a significant increase in VEGF expression. This delayed release could be controlled up to 14days. Moreover, by changing the duration of the hyperthermic pulse, a fine control over the amount of DFO released was achieved. The ability to trigger the release of therapeutic agents at a specific timepoint and control dosing level through changes in duration of hyperthermia enables sequential multi-dose profiles.

STATEMENT OF SIGNIFICANCE

This paper details the development of a heat responsive liposome loaded hydrogel for the controlled release of pro-angiogenic therapeutics. Lysolipid-based thermosensitive liposomes (LTSLs) embedded in a chitosan-based thermoresponsive hydrogel matrix represents a novel approach for the spatiotemporal release of therapeutic agents. This hydrogel platform demonstrates remarkable flexibility in terms of drug scheduling and sequencing, enabling the release of multiple agents and the ability to control drug dosing in a minimally invasive fashion. The possibility to tune the release kinetics of different drugs independently represents an innovative platform to utilise for a variety of treatments. This approach allows a significant degree of flexibility in achieving a desired release profile via a minimally invasive stimulus, enabling treatments to be tuned in response to changing symptoms and complications.

Treatment of Vasodilator-resistant Mixed Connective Tissue Disease-associated Pulmonary Arterial Hypertension with Glucocorticoid and Cyclophosphamide

Pulmonary arterial hypertension (PAH) associated with systemic lupus erythematosus (SLE) or mixed connective tissue disease (MTCD), in contrast to other types of PAH, may respond to immunosuppressive therapy. Most PAH cases with an immunosuppressant response were in the early stages of the disease (WHO functional class III or less). The present case was a 34-year-old woman with MCTD-associated PAH (WHO functional class IV) who was resistant to a combination of three vasodilators. Afterwards, she was treated with glucocorticoid and cyclophosphamide. This case suggested the potential benefit of immunosuppressants in patients with severe MCTD-associated PAH.

Adventitial Fibroblast Nox4 Expression and ROS Signaling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease arising from remodeling and narrowing of pulmonary arteries (PA) resulting in high pulmonary arterial blood pressure and ultimately right ventricular failure. Elevated production of reactive oxygen species (ROS) by NADPH oxidase 4 (Nox4), a constitutively active enzyme, has been associated with oxygen sensing, vasomotor control, cellular proliferation, differentiation, migration, apoptosis, senescence, fibrosis, and angiogenesis. Further, elevated expression of Nox4 has been reported in a number of cardiovascular diseases, including atherosclerosis, hypertension, cardiac failure, ischemic stroke, and PAH. However, the cellular location of Nox4 and its contribution to aberrant vascular remodeling in PAH remains poorly understood. The goal of this review is to summarize the recent literature on the enzymatic regulation of Nox4 in the production of ROS in PAH. In the vascular wall, Nox4 is present in fibroblasts, a primary cell of the adventitia, and matches the adventitial location of ROS production in PAH. Further, in adventitial fibroblasts, Nox4 overexpression stimulates migration and proliferation as well as matrix gene expression. Collectively, reports indicate that Nox4 contributes to altered fibroblast behavior, ROS production leading to hypertensive vascular remodeling and the development of PAH. Finally, we address the functional significance of Nox4 in fibroblasts, and also suggest an "outside in" (adventitial) process of vascular remodeling that is mediated by Nox4, which although has physiological roles in the intimal layer (i.e., endothelium), may also have pathologic importance in the adventitial layer of the vascular wall through signaling in fibroblasts.

Reactive Oxygen Species in COPD-Related Vascular Remodeling

The pathogenesis of chronic obstructive pulmonary disease (COPD) is a multifaceted process involving the alteration of pulmonary vasculature. Such vascular remodeling can be associated with inflammation, shear stress, and hypoxia-conditions commonly seen in patients with lung diseases. Particularly, the overproduction of reactive oxygen species (ROS) in the diseased lungs contributes greatly to pulmonary vascular remodeling. ROS play an important role in vascular homeostasis, yet excessive ROS can alter pulmonary vasculature and impair lung function, as implicated in COPD at all stages. Increased inflammatory cell infiltration and endothelial dysfunction both correspond to the severity of COPD. As a byproduct of vascular remodeling, pulmonary hypertension negatively affects the long-term survival rate of COPD patients. While there is currently no cure for COPD, several treatment options have focused on alleviating COPD symptoms. Interventions such as long-term oxygen therapy, endothelium-targeted treatment, and pharmacological therapies show promising results in improving the life span of COPD patients and attenuating the progression of pulmonary hypertension. In this chapter, we aim to discuss the contributing factors of pulmonary vascular remodeling in COPD with an emphasis on the ROS, as well as potential redox treatments for COPD-related vascular remodeling.

Pulmonary vascular remodeling in pulmonary hypertension

Pulmonary vascular remodeling is the key structural alteration in pulmonary hypertension and involves changes in the intima, media and adventitia, often with the interplay of inflammatory cells. This review examines the pathology of these changes and highlights some of the pathogenetic mechanisms that underlie the remodeling process.

Endothelial cell signaling and ventilator-induced lung injury: molecular mechanisms, genomic analyses, and therapeutic targets

Mechanical ventilation is a life-saving intervention in critically ill patients with respiratory failure due to acute respiratory distress syndrome (ARDS). Paradoxically, mechanical ventilation also creates excessive mechanical stress that directly augments lung injury, a syndrome known as ventilator-induced lung injury (VILI). The pathobiology of VILI and ARDS shares many inflammatory features including increases in lung vascular permeability due to loss of endothelial cell barrier integrity resulting in alveolar flooding. While there have been advances in the understanding of certain elements of VILI and ARDS pathobiology, such as defining the importance of lung inflammatory leukocyte infiltration and highly induced cytokine expression, a deep understanding of the initiating and regulatory pathways involved in these inflammatory responses remains poorly understood. Prevailing evidence indicates that loss of endothelial barrier function plays a primary role in the development of VILI and ARDS. Thus this review will focus on the latest knowledge related to 1) the key role of the endothelium in the pathogenesis of VILI; 2) the transcription factors that relay the effects of excessive mechanical stress in the endothelium; 3) the mechanical stress-induced posttranslational modifications that influence key signaling pathways involved in VILI responses in the endothelium; 4) the genetic and epigenetic regulation of key target genes in the endothelium that are involved in VILI responses; and 5) the need for novel therapeutic strategies for VILI that can preserve endothelial barrier function.

Galectin-3 inhibition ameliorates hypoxia-induced pulmonary artery hypertension

Galectin-3 (Gal-3) is a β-galactoside-binding lectin, which is important in inflammation, fibrosis and heart failure. The present study aimed to investigate the role and mechanism of Gal-3 in hypoxia-induced pulmonary arterial hypertension (PAH). Male C57BL/6J and Gal-3^−/− mice were exposed to hypoxia, then the right ventricular systolic pressure (RVSP) and Fulton's index were measured, and Gal-3 mRNA and protein expression in the pulmonary arteries was analyzed by reverse transcription-quantitative polymerase chain reaction and western blotting. Compared with the control, hypoxia increased the mRNA and protein expression levels of Gal-3 in wild type murine pulmonary arteries. Gal-3 deletion reduced the hypoxia-induced upregulation of RVSP and Fulton's index. Furthermore, human pulmonary arterial endothelial cells (HPAECs) and human pulmonary arterial smooth muscle cells (HPASMCs) were stimulated by hypoxia in vitro, and Gal-3 expression was inhibited by small interfering RNA. The inflammatory response of HPAECs, and the proliferation and cell cycle distribution of HPASMCs was also analyzed. Gal-3 inhibition alleviated the hypoxia-induced inflammatory response in HPAECs, including tumor necrosis factor-α and interleukin-1 secretion, expression of intercellular adhesion molecule-1 and adhesion of THP-1 monocytes. Gal-3 inhibition also reduced hypoxia-induced proliferation of HPASMCs, partially by reducing cyclin D1 expression and increasing p27 expression. Furthermore, Gal-3 inhibition suppressed HPASMC switching from a ‘contractile’ to a ‘synthetic’ phenotype. In conclusion, Gal-3 serves a fundamental role in hypoxia-induced PAH, and inhibition of Gal-3 may represent a novel therapeutic target for the treatment of hypoxia-induced PAH.

A case of pulmonary arterial hypertension associated with adult hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is an aggressive, life-threatening syndrome of excessive immune activation. Presentation is most common among the pediatric population, and cases in adults are rare. The number of nonhematologic presentations described in relation to HLH has been growing. We present a case involving a woman who developed HLH after autologous stem cell transplantation for mantle cell lymphoma. Months later, she received a diagnosis of pulmonary arterial hypertension (PAH) while undergoing treatment for her HLH. To our knowledge, PAH associated with adult HLH has only been described in the literature once before. PAH may now be a potential differential diagnosis for patients with HLH who present with respiratory symptoms.

BMPRII influences the response of pulmonary microvascular endothelial cells to inflammatory mediators

Mutations in the bone morphogenetic protein receptor (BMPR2) gene have been observed in 70 % of patients with heritable pulmonary arterial hypertension (HPAH) and in 11-40 % with idiopathic PAH (IPAH). However, carriers of a BMPR2 mutation have only 20 % risk of developing PAH. Since inflammatory mediators are increased and predict survival in PAH, they could act as a second hit inducing the development of pulmonary hypertension in BMPR2 mutation carriers. Our specific aim was to determine whether inflammatory mediators could contribute to pulmonary vascular cell dysfunction in PAH patients with and without a BMPR2 mutation. Pulmonary microvascular endothelial cells (PMEC) and arterial smooth muscle cells (PASMC) were isolated from lung parenchyma of transplanted PAH patients, carriers of a BMPR2 mutation or not, and from lobectomy patients or lung donors. The effects of CRP and TNFα on mitogenic activity, adhesiveness capacity, and expression of adhesion molecules were investigated in PMECs and PASMCs. PMECs from BMPR2 mutation carriers induced an increase in PASMC mitogenic activity; moreover, endothelin-1 secretion by PMECs from carriers was higher than by PMECs from non-carriers. Recruitment of monocytes by PMECs isolated from carriers was higher compared to PMECs from non-carriers and from controls, with an elevated ICAM-1 expression. CRP increased adhesion of monocytes to PMECs in carriers and non-carriers, and TNFα only in carriers. PMEC from BMPR2 mutation carriers have enhanced adhesiveness for monocytes in response to inflammatory mediators, suggesting that BMPR2 mutation could generate susceptibility to an inflammatory insult in PAH.

Microvolt T-wave alternans profiles in patients with pulmonary arterial hypertension compared to patients with left ventricular systolic dysfunction and a group of healthy volunteers

OBJECTIVE

Microvolt T-wave alternans (MTWA) is a well-examined parameter for the risk stratification of sudden cardiac death (SCD) in patients with left ventricular dysfunction (LVD). However, the role of MTWA in pulmonary arterial hypertension (PAH) remains obscure. Consequently, the present study aimed to analyze the profile of MTWA among PAH patients in comparison with LVD patients and healthy volunteers.

METHODS

The prospectively study included 22 patients with PAH (mean pulmonary artery pressure ≥ 25 mm Hg and pulmonary capillary wedge pressure ≤15 mm Hg during right heart catheterization; mean age, 40±17 years); 24 with LVD [left ventricular ejection fraction (LVEF) ≤35%; mean age, 40±11 years]; and 28 healthy volunteers (mean age, 41±8 years). Patients with persistent atrial arrhythmia were excluded. The MTWA (spectral method) categories were positive, negative, or indeterminate (MTWA_pos, MTWA_neg, or MTWA_ind, respectively). MTWA_pos and MTWA_ind were qualified as abnormal (MTWA_abn). Statistical analyses (Mann-Whitney U, chi-square with Yates's correction, Fisher's exact test) were performed.

RESULTS

PAH patients had higher LVEF than LVD patients (61±7% vs. 27±7%; p<0.05). MTWA_abn was observed more frequently in the PAH and LVD groups than in the healthy volunteers. Patients with PAH were characterized by a considerable percentage of MTWA_pos and MTWA_abn (59% and 73%, respectively), but this did not differ from LVD patients.

CONCLUSION

Patients with PAH are characterized by a high rate of MTWA abnormalities similar to LVD patients, despite the relevant differences in LVEF. Further research is required to elucidate the clinical significance and prognostic value of this data, particularly in the context of SCDunderlying mechanisms in PAH patients.

Elevated serum levels of soluble CD146 in patients with systemic sclerosis

CD146, a transmembrane glycoprotein member of the immunoglobulin superfamily, acts as an adhesion molecule that helps maintain the cell monolayer. Human endothelial cells expressing CD146 are involved in angiogenesis and inflammation. Recently, we developed a sandwich ELISA for detecting soluble CD146 (sCD146) in human serum specimens. The aim of this study is to determine serum levels of sCD146 in patients with systemic sclerosis (SSc) and to examine the relationship between sCD146 levels and clinical manifestations. We quantified serum sCD146 levels in 47 serum samples from patients fulfilling criteria for SSc, 23 serum samples from patients fulfilling criteria for rheumatoid arthritis (RA), and 25 healthy controls. We also investigated the relationship between sCD146 levels and various clinical characteristics with SSc patients. Levels of sCD146 were significantly higher in the 47 patients with SSc than in the 25 healthy controls and 23 patients with RA (12.50 vs. 6.91 vs. 9.95 ng/ml; p < 0.001). Serum sCD146 levels in SSc patients with pulmonary arterial hypertension (PAH) were lower than in SSc patients without PAH (10.12 vs.13.17 ng/ml; p < 0.01). The serum levels of sCD146 were elevated in patients with SSc. However, decreased sCD146 levels were observed in SSc patients with PAH. Further studies are necessary to elucidate the sources and the mechanisms.

Role of noncoding RNA in vascular remodelling

PURPOSE OF REVIEW

Noncoding RNAs (ncRNAs), such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are becoming fundamentally important in the pathophysiology relating to injury-induced vascular remodelling. We highlight recent studies that demonstrate the involvement of ncRNAs in vein graft disease, in in-stent restenosis and in pulmonary arterial hypertension, with a particular focus on endothelial cell and vascular smooth muscle cell function. We also briefly discuss the emerging role of exosomal-derived ncRNAs and how this mechanism impacts on vascular function.

RECENT FINDINGS

ncRNAs have been described as novel regulators in the pathophysiology of vascular injury, inflammation, and vessel wall remodelling. In particular, several studies have demonstrated that manipulation of miRNAs can reduce the burden of pathological vascular remodelling. Such studies have also shown that exosomal miRNA-mediated, cell-to-cell communication between endothelial cells and vascular smooth muscle cells is critical in the disease process. In addition to miRNAs, lncRNAs are emerging as regulators of vascular function in health and disease. Although lncRNAs are complex in both their sheer numbers and mechanisms of action, identifying their contribution to vascular disease is essential.

SUMMARY

Given the important roles of ncRNAs in vascular injury and remodelling together will their capacity for cell-to-cell communication, manipulating ncRNA might provide novel therapeutic interventions.

Notch activation of Ca2+-sensing receptor mediates hypoxia-induced pulmonary hypertension

A recent study from our group demonstrated that the Ca²⁺-sensing receptor (CaSR) was upregulated and that the extracellular Ca²⁺-induced increase in the cytosolic Ca²⁺ concentration [Ca²⁺]_cyt was enhanced in pulmonary arterial smooth muscle cells (PASMCs) from patients with idiopathic pulmonary arterial hypertension. Here, we examined whether hypoxia-induced activation of Notch signaling leads to the activation and upregulation of CaSR in hypoxia-induced pulmonary hypertension (HPH). The activation of Notch signaling with Jag-1, a Notch ligand, can activate the function and increase the expression of CaSR in acute and chronic hypoxic PASMCs. Downregulation of Notch3 with a siRNA attenuates the extracellular Ca²⁺-induced increase in [Ca²⁺]_cyt and the increase in hypoxia-induced PASMC proliferation in acute hypoxic rat PASMCs. Furthermore, we tested the prevention and rescue effects of a γ-secretase inhibitor (DAPT) in HPH rats. For the Jag-1-treated group, right ventricular systolic pressure (RVSP), right heart hypertrophy (RV/LV+S ratio), and the level of right ventricular myocardial fibrosis were higher than the hypoxia alone group. Meanwhile, DAPT treatment prevented and rescued pulmonary hypertension in HPH rats. The Notch activation of CaSR mediates hypoxia-induced pulmonary hypertension. Understanding the new molecular mechanisms that regulate [Ca²⁺]_cyt and PASMC proliferation is critical to elucidating the pathogenesis of HPH and the development of novel therapies for pulmonary hypertension.

Deletion of LR11 Attenuates Hypoxia-Induced Pulmonary Arterial Smooth Muscle Cell Proliferation With Medial Thickening in Mice

OBJECTIVE

We aimed to determine whether LR11 (low-density lipoprotein receptor with 11 binding repeats) is a potential key regulator of smooth muscle cell (SMC) proliferation during the progression of hypoxia-induced medial thickening in mice and whether sLR11 (soluble LR11) can serve as a biomarker in patients with pulmonary arterial hypertension.

APPROACH AND RESULTS

The role of LR11 in pulmonary arterial hypertension was investigated using mouse and cell models of induced hypoxia. The expression of LR11 and of hypoxia-inducible factor-1α was significantly increased in lung tissues from C57Bl/6 mice after 3 weeks of exposure to hypoxia compared with normoxia. Serum sLR11 levels were also increased. Physiological and histochemical analyses showed that increased right ventricular systolic pressure, right ventricular hypertrophy, and medial thickening induced under hypoxia in wild-type mice were attenuated in LR11(-/-) mice. The proliferation rates stimulated by hypoxia or platelet-derived growth factor-BB were attenuated in SMC derived from LR11(-/-) mice, compared with those from wild-type mice. Exogenous sLR11 protein increased the proliferation rates of SMC from wild-type mice. The expression of LR11 and hypoxia-inducible factor-1α was increased in cultured SMC under hypoxic conditions, and hypoxia-inducible factor-1α knockdown almost abolished the induction of LR11. Serum sLR11 levels were significantly higher in patients with, rather than without, pulmonary arterial hypertension. sLR11 levels positively correlated with pulmonary vascular resistance and mean pulmonary arterial pressure.

CONCLUSIONS

LR11 regulated SMC proliferation during the progression of hypoxia-induced medial thickening in mice. The findings obtained from mice, together with those in humans, indicate that sLR11 could serve as a novel biomarker that reflects the pathophysiology of proliferating medial SMC in pulmonary arterial hypertension.

Lung-specific RNA interference of coupling factor 6, a novel peptide, attenuates pulmonary arterial hypertension in rats

Background

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease associated with high morbidity and mortality rates. However, the exact regulatory mechanism of PAH is unknown. Although coupling factor 6 (CF6) is known to function as a repressor, its role in PAH has not been explored. Here, we investigated the involvement of endogenous CF6 in the development of PAH.

Methods

PAH was induced with monocrotaline (MCT), as demonstrated by significant increases in pulmonary artery pressure and vessel wall thickness. The adeno-associated virus (AAV) carrying CF6 short hairpin RNA (shRNA) or control vector (2×10¹⁰ gp) was intratracheally transfected into the lungs of rats 2 weeks before or after MCT injection.

Results

A 2-6-fold increase in CF6 was observed in the lungs and circulation of the MCT-injected rats as confirmed by qRT-PCR and ELISA. Immunohistochemistry analysis revealed a small quantity of CF6 localized to endothelial cells (ECs) under physiological conditions spread to surrounding tissues in a paracrine manner in PAH lungs. Notably, CF6 shRNA effectively inhibited CF6 expression, abolished lung macrophage infiltration, reversed endothelial dysfunction and vascular remodeling, and ameliorated the severity of pulmonary hypertension and right ventricular dysfunction at 4 weeks both as a pretreatment and rescue intervention. In addition, the circulating and lung levels of 6-keto-PGF1a, a stable metabolite of prostacyclin, were reversed by CF6 inhibition, suggesting that the effect of CF6 inhibition may partly be mediated through prostacyclin.

Conclusions

CF6 contributes to the pathogenesis of PAH, probably in association with downregulation of prostacyclin. The blockage of CF6 might be applied as a novel therapeutic approach for PAH and PA remodeling.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0409-5) contains supplementary material, which is available to authorized users.

[The new endothelin receptor antagonist macitentan: Prospects for therapy of pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a clinical group of severe and rare diseases with similar morphological, hemodynamic, and therapeutic characteristics. One of the novel drugs to treat PAH is macitentan, a new double endothelin ETA and ETB receptor antagonist that is characterized by special physicochemical properties, ensuring the penetration of the drug into tissues and its improved receptor-binding properties. The SERAPHIN trial has demonstrated that therapy with macitentan 10 mg versus placebo statistically significantly reduces the risk of poor outcomes and death by 45%. The treatment with macitentan 10 is observed to be highly effective regardless of the presence/absence of basic PAH-specific therapy. The drug considerably improves clinically important outcomes, including 6-minute walk distance and WHO functional class. Macitentan exerts a steady-state therapeutic effect, by improving pulmonary hemodynamics. Macitentan 10 mg statistically significantly reduces the risk of PAH, frequency of its related hospitalizations, and the number of days spent in hospital. The drug has a favorable safety profile; its most common side effects are headache, nasopharyngitis, and anemia. Macitentan is an effective first-line drug to improve long-term outcomes in patients with newly and previously diagnosed PAH.

Role of interleukin-1 receptor 1/MyD88 signalling in the development and progression of pulmonary hypertension

Pulmonary artery smooth muscle cell (PA-SMC) proliferation and inflammation are key components of pulmonary arterial hypertension (PAH). Interleukin (IL)-1β binds to IL-1 receptor (R)1, thereby recruiting the molecular adaptor myeloid differentiation primary response protein 88 (MyD88) (involved in IL-1R1 and Toll-like receptor signal transduction) and inducing IL-1, IL-6 and tumour necrosis factor-α synthesis through nuclear factor-κB activation.

We investigated the IL-1R1/MyD88 pathway in the pathogenesis of pulmonary hypertension.

Marked IL-1R1 and MyD88 expression with predominant PA-SMC immunostaining was found in lungs from patients with idiopathic PAH, mice with hypoxia-induced pulmonary hypertension and SM22-5-HTT+mice. Elevations in lung IL-1β, IL-1R1, MyD88 and IL-6 preceded pulmonary hypertension in hypoxic mice. IL-1R1−/−, MyD88−/−and control mice given the IL-1R1 antagonist anakinra were protected similarly against hypoxic pulmonary hypertension and perivascular macrophage recruitment. Anakinra reversed pulmonary hypertension partially in SM22-5-HTT+mice and markedly in monocrotaline-treated rats. IL-1β-mediated stimulation of mouse PA-SMC growth was abolished by anakinra and absent in IL-1R1−/−and MyD88−/−mice. Gene deletion confined to the myeloid lineage (M.lys-Cre MyD88fl/flmice) decreased pulmonary hypertension severityversuscontrols, suggesting IL-1β-mediated effects on PA-SMCs and macrophages. The growth-promoting effect of media conditioned by M1 or M2 macrophages from M.lys-Cre MyD88fl/flmice was attenuated.

Pulmonary vessel remodelling and inflammation during pulmonary hypertension require IL-1R1/MyD88 signalling. Targeting the IL-1β/IL-1R1 pathway may hold promise for treating human PAH.

Pulmonary Hypertension and Indicators of Right Ventricular Function

Pulmonary hypertension (PH) is a rare disease, whose underlying mechanisms are not fully understood. It is characterized by pulmonary arterial vasoconstriction and vessels wall thickening, mainly intimal and medial layers. Several molecular pathways have been studied, but their respective roles remain unknown. Cardiac repercussions of PH are hypertrophy, dilation, and progressive right ventricular dysfunction. Multiple echocardiographic parameters are being used, in order to assess anatomy and cardiac function, but there are no guidelines edited about their usefulness. Thus, it is now recommended to associate the best-known parameters, such as atrial and ventricular diameters or tricuspid annular plane systolic excursion. Cardiac catheterization remains necessary to establish the diagnosis of PH and to assess pulmonary hemodynamic state. Concerning energetic metabolism, free fatty acids, normally used to provide energy for myocardial contraction, are replaced by glucose uptake. These abnormalities are illustrated by increased (18)F-fluorodeoxyglucose ((18)F-FDG) uptake on positron emission tomography/computed tomography, which seems to be correlated with echocardiographic and hemodynamic parameters.

Iptakalim influences the proliferation and apoptosis of human pulmonary artery smooth muscle cells

The aim of the present study was to determine the effect of an ATP-sensitive K+ (KATP) channel opener iptakalim (IPT) on the proliferation and apoptosis of human pulmonary artery smooth muscle cells (HPASMCs), and examine the potential value of IPT to hypoxic pulmonary hyper-tension (HPH) at a cellular level. HPASMCs were divided into the control, ET-1, ET-1+IPT and ET-1+IPT+glibenclamide (GLI) groups. GLI was administered 30 min prior to ET-1 and IPT. The 4 groups were incubated with corresponding reagents for 24 h. Cell viability was evaluated using a CCK-8 assay, cell proliferation by 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, and cell apoptosis via the expression of apoptosis-related proteins, i.e., Bcl-2-associated X protein (Bax) and B-cell lymphoma 2 (Bcl-2) using western blotting. We incubated HPASMCs with varying concentrations of ET-1 for 24, 48 and 72 h, and found that cell survival rate was increased in a dose-dependent manner (P<0.05) rather than in a time-dependent manner (P>0.05). After co-incubation of HPASMCs with varying concentrations of IPT and ET-1 for 24 h, the cell survival rate was decreased in a dose-dependent manner. The cell survival rate in the IPT+ET-1 group was significantly lower than that in the ET-1 group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1 group were higher than those in the control group, and the expression of Bax/Bcl-2 was lower than the control group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1+IPT group were lower than those in the ET-1 group, and the expression of Bax/Bcl-2 was higher than that in the ET-1 group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1+IPT+GLI group were higher than those in the ET-1+IPT group, and the expression of Bax/Bcl-2 was lower than that in the ET-1+IPT group (P<0.05). In conclusion, IPT inhibited ET-1‑induced HPASMC proliferation and promoted cell apoptosis. Thus, it may play an important role in the treatment of HPH.

Histone deacetylation contributes to low extracellular superoxide dismutase expression in human idiopathic pulmonary arterial hypertension

Epigenetic mechanisms, including DNA methylation and histone acetylation, regulate gene expression in idiopathic pulmonary arterial hypertension (IPAH). These mechanisms can modulate expression of extracellular superoxide dismutase (SOD3 or EC-SOD), a key vascular antioxidant enzyme, and loss of vascular SOD3 worsens outcomes in animal models of pulmonary arterial hypertension. We hypothesized that SOD3 gene expression is decreased in patients with IPAH due to aberrant DNA methylation and/or histone deacetylation. We used lung tissue and pulmonary artery smooth muscle cells (PASMC) from subjects with IPAH at transplantation and from failed donors (FD). Lung SOD3 mRNA expression and activity was decreased in IPAH vs. FD. In contrast, mitochondrial SOD (Mn-SOD or SOD2) protein expression was unchanged and intracellular SOD activity was unchanged. Using bisulfite sequencing in genomic lung or PASMC DNA, we found the methylation status of the SOD3 promoter was similar between FD and IPAH. Furthermore, treatment with 5-aza-2'-deoxycytidine did not increase PASMC SOD3 mRNA, suggesting DNA methylation was not responsible for PASMC SOD3 expression. Though total histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity, acetylated histones, and acetylated SP1 were similar between IPAH and FD, treatment with two selective class I HDAC inhibitors increased SOD3 only in IPAH PASMC. Class I HDAC3 siRNA also increased SOD3 expression. Trichostatin A, a pan-HDAC inhibitor, decreased proliferation in IPAH, but not in FD PASMC. These data indicate that histone deacetylation, specifically via class I HDAC3, decreases SOD3 expression in PASMC and HDAC inhibitors may protect IPAH in part by increasing PASMC SOD3 expression.

Morphological changes in small pulmonary vessels are associated with severe acute exacerbation in chronic obstructive pulmonary disease

BACKGROUND

Pulmonary vascular remodeling is essential for understanding the pathogenesis of chronic obstructive pulmonary disease (COPD). The total cross-sectional area (CSA) of small pulmonary vessels has been reported to correlate with the pulmonary artery pressure, and this technique has enabled the assessment of pulmonary vascular involvements. We investigated the contribution of morphological alterations in the pulmonary vessels to severe acute exacerbation of COPD (AE-COPD).

METHODS

This study enrolled 81 patients with COPD and 28 non-COPD subjects as control and assessed the percentage of CSA (%CSA) less than 5 mm(2) (%CSA<5) and %CSA in the range of 5-10 mm(2) (%CSA5-10) on high-resolution computed tomography images.

RESULTS

Compared with the non-COPD subjects, the COPD patients had lower %CSA<5. %CSA<5 was positively correlated with airflow limitation and negatively correlated with the extent of emphysema. COPD patients with lower %CSA<5 showed significantly increased incidences of severe AE-COPD (Gray's test; P=0.011). Furthermore, lower %CSA<5 was significantly associated with severe AE-COPD (hazard ratio, 2.668; 95% confidence interval, 1.225-5.636; P=0.010).

CONCLUSION

%CSA<5 was associated with an increased risk of severe AE-COPD. The distal pruning of the small pulmonary vessels is a part of the risk associated with AE-COPD, and %CSA<5 might be a surrogate marker for predicting AE-COPD.

Blockade of Astrocytic Calcineurin/NFAT Signaling Helps to Normalize Hippocampal Synaptic Function and Plasticity in a Rat Model of Traumatic Brain Injury

Increasing evidence suggests that the calcineurin (CN)-dependent transcription factor NFAT (Nuclear Factor of Activated T cells) mediates deleterious effects of astrocytes in progressive neurodegenerative conditions. However, the impact of astrocytic CN/NFAT signaling on neural function/recovery after acute injury has not been investigated extensively. Using a controlled cortical impact (CCI) procedure in rats, we show that traumatic brain injury is associated with an increase in the activities of NFATs 1 and 4 in the hippocampus at 7 d after injury. NFAT4, but not NFAT1, exhibited extensive labeling in astrocytes and was found throughout the axon/dendrite layers of CA1 and the dentate gyrus. Blockade of the astrocytic CN/NFAT pathway in rats using adeno-associated virus (AAV) vectors expressing the astrocyte-specific promoter Gfa2 and the NFAT-inhibitory peptide VIVIT prevented the injury-related loss of basal CA1 synaptic strength and key synaptic proteins and reduced the susceptibility to induction of long-term depression. In conjunction with these seemingly beneficial effects, VIVIT treatment elicited a marked increase in the expression of the prosynaptogenic factor SPARCL1 (hevin), especially in hippocampal tissue ipsilateral to the CCI injury. However, in contrast to previous work on Alzheimer's mouse models, AAV-Gfa2-VIVIT had no effects on the levels of GFAP and Iba1, suggesting that synaptic benefits of VIVIT were not attributable to a reduction in glial activation per se. Together, the results implicate the astrocytic CN/NFAT4 pathway as a key mechanism for disrupting synaptic remodeling and homeostasis in the hippocampus after acute injury.

SIGNIFICANCE STATEMENT

Similar to microglia, astrocytes become strongly "activated" with neural damage and exhibit numerous morphologic/biochemical changes, including an increase in the expression/activity of the protein phosphatase calcineurin. Using adeno-associated virus (AAV) to inhibit the calcineurin-dependent activation of the transcription factor NFAT (Nuclear Factor of Activated T cells) selectively, we have shown that activated astrocytes contribute to neural dysfunction in animal models characterized by progressive/chronic neuropathology. Here, we show that the suppression of astrocytic calcineurin/NFATs helps to protect synaptic function and plasticity in an animal model in which pathology arises from a single traumatic brain injury. The findings suggest that at least some astrocyte functions impair recovery after trauma and may provide druggable targets for treating victims of acute nervous system injury.

Transforming growth factor beta 1 induced endothelin-1 release is peroxisome proliferator-activated receptor gamma dependent in A549 cells

Background

Endothelin-1 (ET-1) is involved in pulmonary vascular remodeling. The aim of this study was to investigate the biochemical interactions between PPAR-γ, TGF-β1 and ET-1 in vitro.

Methods

A549 cells were pre-treated with S2505 (10 μM), S2871 (10 μM) with/without SB203580 (10 μM) for 60 min following 2 h treatment with 10 ng/mL TGF-β1. A549 cells were also transfected with positive or negative PPAR-γ plasmids for comparison. RT-PCR, ELISA, western blotting and confocal laser scanning microscopy (CLSM) were used to measure the relevant expression of mRNA, protein, mediators of pathways and nuclear factor translocation.

Results

SB203580 inhibited TGF-β1 induced ET-1 expression in A549 cells. S2871 decreased PPAR-γ mRNA and increase TGF-β1-induced ET-1 expression. S2871 increased phosphorylation of p38 MAPK and Smad2. Cells transfected with PPAR-γ negative plasmid increased TGF-β1 induced ET-1 expression, and increased the expression of phospho-p38 MAPK and phospho-Smad2. S2505 increased PPAR-γ mRNA expression, suppressed the increased TGF-β1-induced expression of ET-1. S2505 inhibited TGF-β1 induced phosphorylation of p38 MAPK and Smad2, also the nuclear translocation of Smad2. Cells transfected with PPAR-γ positive plasmid reduced TGF-β1-induced ET-1 expression, and inhibited the expression of phospho-p38 MAPK and phospho-Smad2.

Conclusions

TGF-β1 induced release of endothelin-1 is PPAR-γ dependent in cultured A549 cells.

Effect of Perflubron-Induced Lung Growth on Pulmonary Vascular Remodeling in Congenital Diaphragmatic Hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) involves lung hypoplasia and pulmonary hypertension (PH). Post-natal Perflubron ventilation induces lung growth. This phenomenon is called Perflubon-induced lung growth (PILG). However, it does not appear to ameliorate PH in CDH. We aim to determine the effect of PILG on pulmonary vascular remodeling in neonates with CDH and PH requiring extracorporeal membrane oxygenation (ECMO).

METHODS

Lung tissue from four patients was obtained, three treated with PILG + ECMO, and one maintained on conventional ventilation + ECMO (control). The distribution of collagen was assessed with Masson's trichrome stain. Immunohistochemistry was done to assess cell proliferation and immunofluorescence to assess vascular morphology.

RESULTS

Comparing PILG vs. control, there was an increase in vessel wall diameter (6.85 μm, 10.28 μm, and 10.35 μm vs. 4.34 μm), increase in collagen thickness in two PILG patients (35.66 μm, 14.23 μm, and 38.46 μm vs. 22.16 μm), and decrease in lumen diameter despite similar total area (48.99 μm, 41.74 μm, and 36.32 μm vs. 51.56 μm) for each PILG patient vs. the control patient, respectively.

CONCLUSION

PILG does not appear to improve pulmonary vascular remodeling that occurs with PH. The findings are descriptive and will require larger samples to validate the significance of the findings. Overall, further studies will be required to identify the mechanistic causes of PH in CDH to create effective treatments.

MicroRNA-140-5p and SMURF1 regulate pulmonary arterial hypertension

Loss of the growth-suppressive effects of bone morphogenetic protein (BMP) signaling has been demonstrated to promote pulmonary arterial endothelial cell dysfunction and induce pulmonary arterial smooth muscle cell (PASMC) proliferation, leading to the development of pulmonary arterial hypertension (PAH). MicroRNAs (miRs) mediate higher order regulation of cellular function through coordinated modulation of mRNA targets; however, miR expression is altered by disease development and drug therapy. Here, we examined treatment-naive patients and experimental models of PAH and identified a reduction in the levels of miR-140-5p. Inhibition of miR-140-5p promoted PASMC proliferation and migration in vitro. In rat models of PAH, nebulized delivery of miR-140-5p mimic prevented the development of PAH and attenuated the progression of established PAH. Network and pathway analysis identified SMAD-specific E3 ubiquitin protein ligase 1 (SMURF1) as a key miR-140-5p target and regulator of BMP signaling. Evaluation of human tissue revealed that SMURF1 is increased in patients with PAH. miR-140-5p mimic or SMURF1 knockdown in PASMCs altered BMP signaling, further supporting these factors as regulators of BMP signaling. Finally, Smurf1 deletion protected mice from PAH, demonstrating a critical role in disease development. Together, these studies identify both miR-140-5p and SMURF1 as key regulators of disease pathology and as potential therapeutic targets for the treatment of PAH.

Reduced force of diaphragm muscle fibers in patients with chronic thromboembolic pulmonary hypertension

Patients with pulmonary hypertension (PH) suffer from inspiratory muscle weakness. However, the pathophysiology of inspiratory muscle dysfunction in PH is unknown. We hypothesized that weakness of the diaphragm, the main inspiratory muscle, is an important contributor to inspiratory muscle dysfunction in PH patients. Our objective was to combine ex vivo diaphragm muscle fiber contractility measurements with measures of in vivo inspiratory muscle function in chronic thromboembolic pulmonary hypertension (CTEPH) patients. To assess diaphragm muscle contractility, function was studied in vivo by maximum inspiratory pressure (MIP) and ex vivo in diaphragm biopsies of the same CTEPH patients (N = 13) obtained during pulmonary endarterectomy. Patients undergoing elective lung surgery served as controls (N = 15). Muscle fiber cross-sectional area (CSA) was determined in cryosections and contractility in permeabilized muscle fibers. Diaphragm muscle fiber CSA was not significantly different between control and CTEPH patients in both slow-twitch and fast-twitch fibers. Maximal force-generating capacity was significantly lower in slow-twitch muscle fibers of CTEPH patients, whereas no difference was observed in fast-twitch muscle fibers. The maximal force of diaphragm muscle fibers correlated significantly with MIP. The calcium sensitivity of force generation was significantly reduced in fast-twitch muscle fibers of CTEPH patients, resulting in a ∼40% reduction of submaximal force generation. The fast skeletal troponin activator CK-2066260 (5 μM) restored submaximal force generation to levels exceeding those observed in control subjects. In conclusion, diaphragm muscle fiber contractility is hampered in CTEPH patients and contributes to the reduced function of the inspiratory muscles in CTEPH patients.

Bosentan reverses the hypoxia-induced downregulation of the bone morphogenetic protein signaling in pulmonary artery smooth muscle cells

AIMS

Pulmonary hypertension (PH) is a common complication of chronic hypoxic lung diseases. Bone morphogenetic protein (BMP) and endothelin-1 signaling pathways have been shown to be altered in hypoxic PH and to play crucial roles in the associated pulmonary artery remodeling. We, therefore, aimed to study the potential link between hypoxia and the alteration of BMP and endothelin-1 signaling observed in pulmonary artery smooth muscle cells (PA-SMCs) in hypoxic PH.

MATERIALS AND METHODS

Human PA-SMCs were treated with hypoxia-mimetic agent cobalt chloride (CoCl2; 100μM), with or without pretreatment with a dual endothelin receptor antagonist bosentan (10μM). Expressions of preproendothelin-1 (PPET1), BMP type 2 receptor (BMPR-2), and one BMP signaling target gene, the inhibitor of DNA binding 1 (ID1) were evaluated by real time quantitative polymerase chain reaction. BMP2-treated PA-SMCs were assessed for Smad1/5/8 signaling activation by Western Blotting.

KEY FINDINGS

Treatment of PA-SMCs with CoCl2 increased PPET1 gene expression, while it did not alter expressions of endothelin converting enzyme, endothelin receptor type A or type B. Hypoxia-mimetic agent CoCl2 decreased the expressions of BMPR-2 and ID1 maximally after 3- and 6-hour treatment respectively, while CoCl2 treatment progressively increased noggin expression. Bosentan pretreatment restored expressions of BMPR-2 and ID1, as well as the activation (by phosphorylation) of Smad1/5/8 signaling induced by BMP2.

SIGNIFICANCE

Hypoxia induces the downregulation of the BMP signaling in PA-SMCs, at least, partly through the endothelin system. In hypoxic PH, increased endothelin-1 production might therefore contribute to the altered BMP signaling and subsequent PA-SMC hyperplasia.

Pharmacokinetics of the novel oral prostacyclin receptor agonist selexipag in subjects with hepatic or renal impairment

AIM

The aim of the present study was to explore the effect of hepatic or renal dysfunction on the pharmacokinetics (PK), tolerability and safety of selexipag, an orally active prostacyclin receptor agonist.

METHODS

Two prospective, open-label studies evaluated the PK of selexipag and its active metabolite ACT-333679 in healthy subjects and in subjects with mild, moderate and severe hepatic impairment or severe renal function impairment (SRFI). A single dose of 200 μg or 400 μg was administered. The PK parameters were derived from plasma concentration-time profiles.

RESULTS

Exposure increased with the severity of hepatic impairment. Geometric mean ratios and 90% confidence intervals of the area under the concentration-time curve from time zero to infinity (AUC0-∞ ) for selexipag and ACT-333679 increased 2.1-fold (1.7-2.6) and 1.2-fold (0.9-1.6) in subjects with mild hepatic impairment, and 4.5-fold (3.4-5.8) and 2.2-fold (1.7-2.8) in subjects with moderate hepatic impairment when compared with healthy subjects. The two subjects with severe hepatic impairment showed similar dose-normalized exposure to that of subjects with moderate hepatic impairment. A 1.7-fold increase in the AUC0-∞ of selexipag and ACT-333679 was observed with SRFI compared with healthy subjects. Although exposure to selexipag and/or ACT-333679 was higher in subjects with mild or moderate hepatic impairment or SRFI vs. healthy subjects, no safety concerns were raised in these groups.

CONCLUSIONS

Based on these observations, the PK data suggest that the clinically used starting dose needs no adjustments in patients with mild or moderate hepatic impairment or SRFI. However, doses should be up-titrated with caution in these patients. The small number of subjects limits the interpretation of selexipag PK in subjects with severe hepatic impairment.

Challenges and opportunities in treating inflammation associated with pulmonary hypertension

INTRODUCTION

Inflammatory cells are present in the lungs from patients with many, if not all, forms of severe pulmonary hypertension.

AREAS COVERED

Historically the first inflammatory cell identified in the pulmonary vascular lesions was the mast cell. T and B lymphocytes, as well as macrophages, are present in and around the pulmonary arterioles and many patients have elevated blood levels of interleukin 1 and 6; some patients show elevated levels of leukotriene B4. An overlap between collagen-vascular disease-associated pulmonary arterial hypertension (PAH) and idiopathic PAH exists, yet only a few studies have been designed that evaluate the effect of anti-inflammatory treatments. Here we review the pertinent data that connect PAH and inflammation/autoimmune dysregulation and evaluate experimental models of severe PAH with an emphasis on the Sugen/athymic rat model of severe PAH. Expert commentary: We postulate that there are several inflammatory phenotypes and predict that there will be several anti-inflammatory treatment strategies for severe PAH.

Right ventricular failure due to chronic pressure load: What have we learned in animal models since the NIH working group statement?

Right ventricular (RV) failure determines outcome in patients with pulmonary hypertension, congenital heart diseases and in left ventricular failure. In 2006, the Working Group on Cellular and Molecular Mechanisms of Right Heart Failure of the NIH advocated the development of preclinical models to study the pathophysiology and pathobiology of RV failure. In this review, we summarize the progress of research into the pathobiology of RV failure and potential therapeutic interventions. The picture emerging from this research is that RV adaptation to increased afterload is characterized by increased contractility, dilatation and hypertrophy. Clinical RV failure is associated with progressive diastolic deterioration and disturbed ventricular–arterial coupling in the presence of increased contractility. The pathobiology of the failing RV shows similarities with that of the LV and is marked by lack of adequate increase in capillary density leading to a hypoxic environment and oxidative stress and a metabolic switch from fatty acids to glucose utilization. However, RV failure also has characteristic features. So far, therapies aiming to specifically improve RV function have had limited success. The use of beta blockers and sildenafil may hold promise, but new therapies have to be developed. The use of recently developed animal models will aid in further understanding of the pathobiology of RV failure and development of new therapeutic strategies.

Calpain-2 activates Akt via TGF-β1-mTORC2 pathway in pulmonary artery smooth muscle cells

Calpain is a family of calcium-dependent nonlysosomal neutral cysteine endopeptidases. Akt is a serine/threonine kinase that belongs to AGC kinases and plays important roles in cell survival, growth, proliferation, angiogenesis, and cell metabolism. Both calpain and Akt are the downstream signaling molecules of platelet-derived growth factor (PDGF) and mediate PDGF-induced collagen synthesis and proliferation of pulmonary artery smooth muscle cells (PASMCs) in pulmonary vascular remodeling. We found that inhibitions of calpain-2 by using calpain inhibitor MDL28170 and calpain-2 small interfering RNA attenuated Akt phosphorylations at serine-473 (S473) and threonine-308 (T308), as well as collagen synthesis and cell proliferation of PASMCs induced by PDGF. Overexpression of calpain-2 in PASMCs induced dramatic increases in Akt phosphorylations at S473 and T308. Moreover, knockout of calpain attenuated Akt phosphorylations at S473 and T308 in smooth muscle of pulmonary arterioles of mice with chronic hypoxic pulmonary hypertension. The cell-permeable-specific transforming growth factor (TGF)-β receptor inhibitor SB431542 attenuated Akt phosphorylations at both S473 and T308 induced by PDGF and by overexpressed calpain-2 in PASMCs. Furthermore, SB-431452 and knocking down activin receptor-like kinase-5 significantly reduced PDGF-induced collagen synthesis and cell proliferation of PASMCs. Nevertheless, neutralizing extracellular TGF-β1 using a cell-impermeable TGF-β1 neutralizing antibody did not affect PDGF-induced Akt phosphorylations at S473 and T308. Furthermore, inhibition of mammalian target of rapamycin complex 2 (mTORC2) by knocking down its component protein Rictor prevented Akt phosphorylations at S473 and T308 induced by PDGF and by overexpressed calpain-2. These data provide first evidence supporting that calpain-2 upregulates PDGF-induced Akt phosphorylation in pulmonary vascular remodeling via an intracrine TGF-β1/mTORC2 mechanism.

Adhesion Molecules: Master Controllers of the Circulatory System

This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

CXCL13 in idiopathic pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

BACKGROUND

Chemokine CXC ligand 13 (CXCL13) has been implicated in perivascular inflammation and pulmonary vascular remodeling in patients with idiopathic pulmonary artery hypertension (IPAH). We wondered whether CXCL13 may also play a role in chronic thromboembolic pulmonary hypertension (CTEPH) and whether serum levels of CXCL13 might serve as biomarkers in these conditions.

METHODS

Lung tissue from patients with IPAH or CTEPH was immunostained for CXCL13. Serum samples were obtained from patients with IPAH (n = 42) or CTEPH (n = 50) and from healthy controls (n = 13). Serum CXCL13 concentrations were measured by enzyme-linked immunosorbent assay technology and were evaluated for associations with markers of disease severity and survival.

RESULTS

CXCL13 was expressed in pulmonary vascular lesions and lymphocytes of patients with IPAH and inoperable CTEPH, respectively. Serum CXCL13 was elevated in patients compared to healthy controls [median, interquartile range, 83 (55,114) pg/ml versus 40 (28, 48) pg/ml; p < 0.001]. Serum CXCL13 showed only weak and inconsistent correlations with markers of inflammation or disease severity. In both populations, patients with serum CXCL13 above the median of the respective groups did not have a higher risk of death than patients with lower serum CXCL13.

CONCLUSIONS

CXCL13 was overexpressed in pulmonary vascular lesions of patients with IPAH and CTEPH, and increased serum concentrations were found in patients with IPAH and CTEPH, suggesting a potential pathogenic role of CXCL13 in both diseases. However, given the weak associations between serum CXCL13 and markers of disease severity and outcome, CXCL13 is unlikely to become a promising biomarker in these patient populations.

Role of Nerve Growth Factor in Development and Persistence of Experimental Pulmonary Hypertension

RATIONALE

Pulmonary hypertension (PH) is characterized by a progressive elevation in mean pulmonary arterial pressure, often leading to right ventricular failure and death. Growth factors play significant roles in the pathogenesis of PH, and their targeting may therefore offer novel therapeutic strategies in this disease.

OBJECTIVES

To evaluate the nerve growth factor (NGF) as a potential new target in PH.

METHODS

Expression and/or activation of NGF and its receptors were evaluated in rat experimental PH induced by chronic hypoxia or monocrotaline and in human PH (idiopathic or associated with chronic obstructive pulmonary disease). Effects of exogenous NGF were evaluated ex vivo on pulmonary arterial inflammation and contraction, and in vitro on pulmonary vascular cell proliferation, migration, and cytokine secretion. Effects of NGF inhibition were evaluated in vivo with anti-NGF blocking antibodies administered both in rat chronic hypoxia- and monocrotaline-induced PH.

MEASUREMENTS AND MAIN RESULTS

Our results show increased expression of NGF and/or increased expression/activation of its receptors in experimental and human PH. Ex vivo/in vitro, we found out that NGF promotes pulmonary vascular cell proliferation and migration, pulmonary arterial hyperreactivity, and secretion of proinflammatory cytokines. In vivo, we demonstrated that anti-NGF blocking antibodies prevent and reverse PH in rats through significant reduction of pulmonary arterial inflammation, hyperreactivity, and remodeling.

CONCLUSIONS

This study highlights the critical role of NGF in PH. Because of the recent development of anti-NGF blocking antibodies as a possible new pain treatment, such a therapeutic strategy of NGF inhibition may be of interest in PH.

Novel biomarkers for risk stratification in pulmonary arterial hypertension

Risk stratification in pulmonary arterial hypertension (PAH) is paramount to identifying individuals at highest risk of death. So far, there are only limited parameters for prognostication in patients with PAH.

95 patients with confirmed PAH were included in the present analysis and followed for a total of 4 years. Blood samples were analysed for serum levels of N-terminal pro-brain natriuretic peptide, high-sensitivity troponin T (hsTnT), pro-atrial natriuretic peptide (proANP), growth differentiation factor 15, soluble fms-like tyrosine kinase 1 and placental growth factor.

27 (28.4%) patients died during a follow-up of 4 years. Levels of all tested biomarkers, except for placental growth factor, were significantly elevated in nonsurvivors compared with survivors. Receiver operating characteristic analyses demonstrated that cardiac biomarkers had the highest power in predicting mortality. In particular, proANP exhibited the highest area under the curve, followed by N-terminal pro-brain natriuretic peptide and hsTnT. Furthermore, proANP and hsTnT added significant additive prognostic value to the established markers in categorical and continuous net reclassification index. Moreover, after Cox regression, proANP (hazard ratio (HR) 1.91), hsTnT (HR 1.41), echocardiographic right ventricular impairment (HR 1.30) and 6-min walk test (HR 0.97 per 10 m) remained the only significant parameters in prognostication of mortality.

Our data suggest benefits of the implementation of proANP and hsTnT as additive biomarkers for risk stratification in patients with PAH.

The cardiac biomarkers proANP and hsTnT may be of use in the assessment of risk stratification in PAH patientshttp://ow.ly/RJFtn

Inhibition of Excessive Cell Proliferation by Calcilytics in Idiopathic Pulmonary Arterial Hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is a rare and progressive disease of unknown pathogenesis. Vascular remodeling due to excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs) is a critical pathogenic event that leads to early morbidity and mortality. The excessive cell proliferation is closely linked to the augmented Ca2+ signaling in PASMCs. More recently, we have shown by an siRNA knockdown method that the Ca2+-sensing receptor (CaSR) is upregulated in PASMCs from IPAH patients, involved in the enhanced Ca2+ response and subsequent excessive cell proliferation. In this study, we examined whether pharmacological blockade of CaSR attenuated the excessive proliferation of PASMCs from IPAH patients by MTT assay. The proliferation rate of PASMCs from IPAH patients was much higher (~1.5-fold) than that of PASMCs from normal subjects and patients with chronic thromboembolic pulmonary hypertension (CTEPH). Treatment with NPS2143, an antagonist of CaSR or calcilytic, clearly suppressed the cell proliferation in a concentration-dependent manner (IC50 = 2.64 μM) in IPAH-PASMCs, but not in normal and CTEPH PASMCs. Another calcilytic, Calhex 231, which is structurally unrelated to NPS2143, also concentration-dependently inhibited the excessive proliferation of IPAH-PASMCs (IC50 = 1.89 μM). In contrast, R568, an activator of CaSR or calcimimetic, significantly facilitated the proliferation of IPAH-PASMCs (EC50 = 0.33 μM). Similar results were obtained by BrdU incorporation assay. These results reveal that the excessive PASMC proliferation was modulated by pharmacological tools of CaSR, showing us that calcilytics are useful for a novel therapeutic approach for pulmonary arterial hypertension.

Potassium channels in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating cardiopulmonary disorder with various origins. All forms of PAH share a common pulmonary arteriopathy characterised by vasoconstriction, remodelling of the pre-capillary pulmonary vessel wall, and in situ thrombosis. Although the pathogenesis of PAH is recognised as a complex and multifactorial process, there is growing evidence that potassium channels dysfunction in pulmonary artery smooth muscle cells is a hallmark of PAH. Besides regulating many physiological functions, reduced potassium channels expression and/or activity have significant effects on PAH establishment and progression. This review describes the molecular mechanisms and physiological consequences of potassium channel modulation. Special emphasis is placed on KCNA5 (Kv1.5) and KCNK3 (TASK1), which are considered to play a central role in determining pulmonary vascular tone and may represent attractive therapeutic targets in the treatment of PAH.

Contribution of inflammation and impaired angiogenesis to the pathobiology of chronic thromboembolic pulmonary hypertension

Deficient angiogenesis and systemic inflammation could be involved in the pathophysiology of chronic thromboembolic pulmonary hypertension (CTEPH). We aimed to characterise the histopathology of pulmonary vascular lesions from 52 CTEPH patients who underwent a pulmonary endarterectomy (PEA) and investigate a potential link between clinical, biological and morphometric parameters.

Collagen, elastin, fibrin, lipid, endothelial, smooth muscle and inflammatory cell content was investigated using immunohistochemistry. Qualitative changes were evaluated using severity scores. Circulating levels of inflammatory mediators were measured using ELISA.

Neointima, thrombotic, recanalised and atherosclerotic lesions were found. Accumulation of macrophages, T-lymphocytes and neutrophils was found mainly in atherosclerotic and thrombotic lesions. Angiogenesis was observed in all kinds of lesions; low-scored angiogenesis predicted adverse outcome, including persistent pulmonary hypertension post-PEA, start of medical therapy and poor survival. C-reactive protein (CRP), interleukin-10, monocyte chemotactic protein-1, macrophage inflammatory protein-1α and matrix metalloproteinase (MMP)-9 were significantly elevated in CTEPH patients. Plasma CRP and MMP-9 levels correlated with neutrophil and macrophage accumulation, respectively.

Enhanced systemic inflammation parallels local inflammatory cell infiltration in major pulmonary arteries at advanced stages of CTEPH. Impaired neovascularisation is associated with poor survival, start of medical treatment and persistent pulmonary hypertension post-PEA. These findings suggest that inflammation and impaired angiogenesis could contribute to the progression of the disease.

The striated muscles in pulmonary arterial hypertension: adaptations beyond the right ventricle

Pulmonary arterial hypertension (PAH) is a fatal lung disease characterised by progressive remodelling of the small pulmonary vessels. The daily-life activities of patients with PAH are severely limited by exertional fatigue and dyspnoea. Typically, these symptoms have been explained by right heart failure. However, an increasing number of studies reveal that the impact of the PAH reaches further than the pulmonary circulation. Striated muscles other than the right ventricle are affected in PAH, such as the left ventricle, the diaphragm and peripheral skeletal muscles. Alterations in these striated muscles are associated with exercise intolerance and reduced quality of life. In this Back to Basics article on striated muscle function in PAH, we provide insight into the pathophysiological mechanisms causing muscle dysfunction in PAH and discuss potential new therapeutic strategies to restore muscle dysfunction.

The Effects of Antigen-Specific IgG1 Antibody for the Pulmonary-Hypertension-Phenotype and B Cells for Inflammation in Mice Exposed to Antigen and Fine Particles from Air Pollution

Air pollution is known to exacerbate chronic inflammatory conditions of the lungs including pulmonary hypertension, cardiovascular diseases and autoimmune diseases. Directly pathogenic antibodies bind pro-inflammatory cell receptors and cause or exacerbate inflammation. In contrast, anti-inflammatory antibody isotypes (e.g. mouse immunoglobulin G1, IgG1) bind inhibitory cell receptors and can inhibit inflammation. Our previous studies showed that co-exposure to antigen and urban ambient particulate matter (PM_2.5) induced severe pulmonary arterial thickening and increased right ventricular systolic pressures in mice via T-cell produced cytokines, Interleukin (IL)-13 and IL-17A. The aim of the current study was to understand how B cell and antibody responses integrate into this T cell cytokine network for the pulmonary hypertension phenotype. Special focus was on antigen-specific IgG1 that is the predominant antibody in the experimental response to antigen and urban ambient PM_2.5. Wild type and B cell-deficient mice were primed with antigen and then challenged with antigen and urban particulate matter and injected with antibodies as appropriate. Our data surprisingly showed that B cells were necessary for the development of increased right ventricular pressures and molecular changes in the right heart in response to sensitization and intranasal challenge with antigen and PM_2.5. Further, our studies showed that both, the increase in right ventricular systolic pressure and right ventricular molecular changes were restored by reconstituting the B cell KO mice with antigen specific IgG1. In addition, our studies identified a critical, non-redundant role of B cells for the IL-17A-directed inflammation in response to exposure with antigen and PM_2.5, which was not corrected with antigen-specific IgG1. In contrast, IL-13-directed inflammatory markers, as well as severe pulmonary arterial remodeling induced by challenge with antigen and PM_2.5 were similar in B cell-deficient and wild type mice. Our studies have identified B cells and antigen specific IgG1 as potential therapeutic targets for pulmonary hypertension associated with immune dysfunction and environmental exposures.