The structural basis of pulmonary hypertension in chronic lung disease: remodelling, rarefaction or angiogenesis?

Pulmonary Vasodilator Therapy in Severe Pulmonary Hypertension Due to Chronic Obstructive Pulmonary Disease (Severe PH-COPD): A Systematic Review and Meta-Analysis

Background: Chronic obstructive pulmonary disease-associated pulmonary hypertension (PH-COPD) results in a significant impact on symptoms, quality of life, and survival. There is scant and conflicting evidence about the use of pulmonary hypertension (PH) specific therapy in patients with PH-COPD. Study Design and Methods: PubMed, OVID, CINAHL, Cochrane, Embase, and Web of Science were searched using various MESH terms to identify randomized controlled trials (RCTs) or observational studies investigating PH-specific therapies in patients with severe PH-COPD, defined by mean pulmonary artery pressure (mPAP) of more than 35 mm Hg or pulmonary vascular resistance (PVR) of more than 5 woods units on right heart catheterization. The primary outcome was a change in mPAP and PVR. Secondary outcomes were changes in six-minute walk distance (6MWD), changes in the brain-natriuretic peptide (BNP), New York Heart Association (NYHA) functional class, oxygenation, and survival. Results: Thirteen studies satisfied the inclusion criteria, including a total of 328 patients with severe PH-COPD. Out of these, 308 patients received some type of specific therapy for PH. There was a significant reduction in mPAP (mean difference (MD) -3.68, 95% CI [-2.03, -5.32], p < 0.0001) and PVR (MD -1.40 Wood units, 95% CI [-1.97, -0.82], p < 0.00001). There was a significant increase in the cardiac index as well (MD 0.26 L/min/m2, 95% CI [0.14, 0.39], p < 0.0001). There were fewer patients who had NYHA class III/lV symptoms, with an odds ratio of 0.55 (95% CI [0.30, 1.01], p = 0.05). There was no significant difference in the 6MWD (12.62 m, 95% CI [-8.55, 33.79], p = 0.24), PaO2 (MD -2.20 mm Hg, 95% CI [-4.62, 0.22], p = 0.08), or BNP or NT-proBNP therapy (MD -0.15, 95% CI [-0.46, 0.17], p = 0.36). Conclusion: The use of PH-specific therapies in severe PH-COPD resulted in a significant reduction in mPAP and PVR and increased CI, with fewer patients remaining in NYHA functional class III/IV. However, no significant difference in the 6MWD, biomarkers of right ventricular dysfunction, or oxygenation was identified, demonstrating a lack of hypoxemia worsening with treatment. Further studies are needed to investigate the use of PH medications in patients with severe PH-COPD.

[Pathophysiology, diagnosis, prognosis and treatment of pulmonary hypertension associated with chronic lung disease]

The pathophysiology of pulmonary hypertension associated with chronic lung disease (PH-CLD) is complex, multifactorial, and not consistent among pulmonary diseases. However, pulmonary vasculopathy triggered by various factors, such as chronic alveolar hypoxia or cigarette smoking, seems to play a central role in the pathogenesis of PH-CLD. While the initial workup of PH-CLD is usually complicated by an overlap of symptoms of PH and the underlying lung disease, PH-CLD should be considered when there is a discrepancy between symptoms (especially exertional dyspnea) and pulmonary function tests. Clinical suspicion of PH-CLD can be strengthened by noninvasive diagnostic tools such as transthoracic echocardiography (TTE) or N-terminal pro-B-type natriuretic peptide (NT-pro-BNP). However, a right heart catheterization should only be performed in specialized centers to establish the diagnosis if therapeutic consequences for the patient were expected.The basic treatment of PH-CLD is optimal management of the underlying lung disease. Among the existing interventional and registry-based studies, only a small number of data suggests favorable outcomes when treating PH-CLD patients with PAH-specific medications. Some publications even suggest negative effects. Nevertheless, recent data on inhaled vasoactive therapy in PH-CLD showed positive results for inhaled Treprostinil, although long-term data for this therapeutic approach are still lacking. Treatment of PH-CLD patients with PAH-specific drugs should only be performed in specialized centers and preferably in the context of clinical trials.

A topological data analysis study on murine pulmonary arterial trees with pulmonary hypertension

Pulmonary hypertension (PH), defined by a mean pulmonary arterial blood pressure above 20 mmHg in the main pulmonary artery, is a cardiovascular disease impacting the pulmonary vasculature. PH is accompanied by chronic vascular remodeling, wherein vessels become stiffer, large vessels dilate, and smaller vessels constrict. Some types of PH, including hypoxia-induced PH (HPH), also lead to microvascular rarefaction. This study analyzes the change in pulmonary arterial morphometry in the presence of HPH using novel methods from topological data analysis (TDA). We employ persistent homology to quantify arterial morphometry for control and HPH mice characterizing normalized arterial trees extracted from micro-computed tomography (micro-CT) images. We normalize generated trees using three pruning algorithms before comparing the topology of control and HPH trees. This proof-of-concept study shows that the pruning method affects the spatial tree statistics and complexity. We find that HPH trees are stiffer than control trees but have more branches and a higher depth. Relative directional complexities are lower in HPH animals in the right, ventral, and posterior directions. For the radius pruned trees, this difference is more significant at lower perfusion pressures enabling analysis of remodeling of larger vessels. At higher pressures, the arterial networks include more distal vessels. Results show that the right, ventral, and posterior relative directional complexities increase in HPH trees, indicating the remodeling of distal vessels in these directions. Strahler order pruning enables us to generate trees of comparable size, and results, at all pressure, show that HPH trees have lower complexity than the control trees. Our analysis is based on data from 6 animals (3 control and 3 HPH mice), and even though our analysis is performed in a small dataset, this study provides a framework and proof-of-concept for analyzing properties of biological trees using tools from Topological Data Analysis (TDA). Findings derived from this study bring us a step closer to extracting relevant information for quantifying remodeling in HPH.

Microcomputed tomography visualization and quantitation of the pulmonary arterial microvascular tree in mouse models of chronic lung disease

Pulmonary vascular dysfunction is characterized by remodeling and loss of microvessels in the lung and is a major manifestation of chronic lung diseases (CLD). In murine models of CLD, the small arterioles and capillaries are the first and most prevalent vessels that are affected by pruning and remodeling. Thus, visualization of the pulmonary arterial vasculature in three dimensions is essential to define pruning and remodeling both temporally and spatially and its role in the pathogenesis of CLD, aging, and tissue repair. To this end, we have developed a novel method to visualize and quantitate the murine pulmonary arterial circulation using microcomputed tomography (µCT) imaging. Using this perfusion technique, we can quantitate microvessels to approximately 6 µM in diameter. We hypothesize that bleomycin-induced injury would have a significant impact on the arterial vascular structure. As proof of principle, we demonstrated that as a result of bleomycin-induced injury at peak fibrosis, significant alterations in arterial vessel structure were visible in the three-dimensional models as well as quantification. Thus, we have successfully developed a perfusion methodology and complementary analysis techniques, which allows for the reconstruction, visualization, and quantitation of the mouse pulmonary arterial microvasculature in three-dimensions. This tool will further support the examination and understanding of angiogenesis during the development of CLD as well as repair following injury.

Endotyping COPD: hypoxia-inducible factor-2 as a molecular "switch" between the vascular and airway phenotypes?

COPD is a heterogeneous disease with multiple clinical phenotypes. COPD endotypes can be determined by different expressions of hypoxia-inducible factors (HIFs), which, in combination with individual susceptibility and environmental factors, may cause predominant airway or vascular changes in the lung. The pulmonary vascular phenotype is relatively rare among COPD patients and characterised by out-of-proportion pulmonary hypertension (PH) and low diffusing capacity of the lung for carbon monoxide, but only mild-to-moderate airway obstruction. Its histologic feature, severe remodelling of the small pulmonary arteries, can be mediated by HIF-2 overexpression in experimental PH models. HIF-2 is not only involved in the vascular remodelling but also in the parenchyma destruction. Endothelial cells from human emphysema lungs express reduced HIF-2α levels, and the deletion of pulmonary endothelial Hif-2α leads to emphysema in mice. This means that both upregulation and downregulation of HIF-2 have adverse effects and that HIF-2 may represent a molecular "switch" between the development of the vascular and airway phenotypes in COPD. The mechanisms of HIF-2 dysregulation in the lung are only partly understood. HIF-2 levels may be controlled by NAD(P)H oxidases via iron- and redox-dependent mechanisms. A better understanding of these mechanisms may lead to the development of new therapeutic targets.

Pharmacology and Emerging Therapies for Group 3 Pulmonary Hypertension Due to Chronic Lung Disease

Pulmonary hypertension (PH) frequently complicates chronic lung disease and is associated with high morbidity and poor outcomes. Individuals with interstitial lung disease and chronic obstructive pulmonary disease develop PH due to structural changes associated with the destruction of lung parenchyma and vasculature with concurrent vasoconstriction and pulmonary vascular remodeling similar to what is observed in idiopathic pulmonary arterial hypertension (PAH). Treatment for PH due to chronic lung disease is largely supportive and therapies specific to PAH have had minimal success in this population with exception of the recently FDA-approved inhaled prostacyclin analogue treprostinil. Given the significant disease burden of PH due to chronic lung diseases and its associated mortality, a great need exists for improved understanding of molecular mechanisms leading to vascular remodeling in this population. This review will discuss the current understanding of pathophysiology and emerging therapeutic targets and potential pharmaceuticals.

Quantitative CT Evaluation of Small Pulmonary Vessels Has Functional and Prognostic Value in Pulmonary Hypertension

Background The in vivo relationship between peel pulmonary vessels, small pulmonary vessels, and pulmonary hypertension (PH) is not fully understood. Purpose To quantitatively assess peel pulmonary vessel volumes (PPVVs) and small pulmonary vessel volumes (SPVVs) as estimated from CT pulmonary angiography (CTPA) in different subtypes of PH compared with controls, their relationship to pulmonary function and right heart catheter metrics, and their prognostic value. Materials and Methods In this retrospective single-center study performed from January 2008 to February 2018, quantitative CTPA analysis of total SPVV (TSPVV) (0.4- to 2-mm vessel diameter) and PPVV (within 15, 30, and 45 mm from the lung surface) was performed. Results A total of 1823 patients (mean age, 69 years ± 13 [SD]; 1192 women [65%]) were retrospectively analyzed; 1593 patients with PH (mean pulmonary arterial pressure [mPAP], 43 mmHg ± 13 [SD]) were compared with 230 patient controls (mPAP, 19 mm Hg ± 3). The mean vessel volumes in pulmonary peels at 15-, 30-, and 45-mm depths were higher in pulmonary arterial hypertension (PAH) and PH secondary to lung disease compared with chronic thromboembolic PH (45-mm peel, mean difference: 6.4 mL [95% CI: 1, 11] [P < .001] vs 6.8 mL [95% CI: 1, 12] [P = .01]). Mean small vessel volumes at a diameter of less than 2 mm were lower in PAH and PH associated with left heart disease compared with controls (1.6-mm vessels, mean difference: -4.3 mL [95% CI: -8, -0.1] [P = .03] vs -6.8 mL [95% CI: -11, -2] [P < .001]). In patients with PH, the most significant positive correlation was noted with forced vital capacity percentage predicted (r = 0.30-0.40 [all P < .001] for TSPVVs and r = 0.21-0.25 [all P < .001] for PPVVs). Conclusion The volume of pulmonary small vessels is reduced in pulmonary arterial hypertension and pulmonary hypertension (PH) associated with left heart disease, with similar volume of peel vessels compared with controls. For chronic thromboembolic PH, the volume of peel vessels is reduced. In PH, small pulmonary vessel volume is associated with pulmonary function tests. Clinical trial registration no. NCT02565030 Published under a CC BY 4.0 license Online supplemental material is available for this article.

CLINICAL SIGNIFICANCE OF PULMONARY HYPERTENSION IN INTERSTITIAL LUNG DISEASE A Consensus Statement from The Pulmonary Vascular Research Institute's Innovative Drug Development Initiative ‐ Group 3 Pulmonary Hypertension

Pulmonary hypertension (PH) has been linked to worse outcomes in chronic lung diseases. The presence of PH in the setting of underlying Interstitial Lung Disease (ILD) is strongly associated with decreased exercise and functional capacity, an increased risk of hospitalizations and death. Examining the scope of this issue and its impact on patients is the first step in trying to define a roadmap to facilitate and encourage future research in this area. The aim of our working group is to strengthen the communities understanding of PH due to lung diseases and to improve the care and quality of life of affected patients. This introductory statement provides a broad overview and lays the foundation for further in‐depth papers on specific topics pertaining to PH‐ILD.

Treprostinil palmitil inhibits the hemodynamic and histopathological changes in the pulmonary vasculature and heart in an animal model of pulmonary arterial hypertension

Treprostinil palmitil (TP) is a long-acting inhaled pulmonary vasodilator prodrug of treprostinil (TRE). In this study, TP was delivered by inhalation (treprostinil palmitil inhalation suspension, TPIS) in a rat Sugen 5416 (Su)/hypoxia (Hx) model of pulmonary arterial hypertension (PAH) to evaluate its effects on hemodynamics, pulmonary vascular remodeling, and cardiac performance and histopathology. Male Sprague-Dawley rats received Su (20 mg/kg, s.c), three weeks of Hx (10% O2) and 5 or 10 weeks of normoxia (Nx). TPIS was given during the 5-10 week Nx period after the Su/Hx challenge. Su/Hx increased the mean pulmonary arterial blood pressure (mPAP) and right heart size (Fulton index), reduced cardiac output (CO), stroke volume (SV) and heart rate (HR), and increased the thickness and muscularization of the pulmonary arteries along with obliteration of small pulmonary vessels. In both the 8- and 13-week experiments, TPIS at inhaled doses ranging from 39.6 to 134.1 μg/kg, QD, dose-dependently improved pulmonary vascular hemodynamics, reduced the increase in right heart size, enhanced cardiac performance, and attenuated most of the histological changes induced by the Su/Hx challenge. The PDE5 inhibitor sildenafil, administered at an oral dose of 50 mg/kg, BID for 10 weeks, was not as effective as TPIS. These results in Su/Hx challenged rats demonstrate that inhaled TPIS may have superior effects to oral sildenafil. We speculate that the improvement of the pathobiology in this PAH model induced by TPIS involves effects on pulmonary vascular remodeling due to the local effects of TRE in the lungs.

The effect of COPD on the incidence and mortality of hospitalized patients with pulmonary embolism: A nationwide population-based study (2016-2018)

BACKGROUND

To examine the incidence, clinical characteristics, and in-hospital outcomes of pulmonary embolism (PE) among hospitalized patients with or without chronic obstructive pulmonary disease (COPD) in Spain, and to identify predictors of in-hospital-mortality (IHM) after PE among patients with and without COPD.

METHODS

We included all patients aged ≥ 40 years who were hospitalised for PE between 2016 and 2018. Data were collected from the Spanish National Hospital Discharge Database.

RESULTS

We identified 47,190 hospitalizations for PE during the study period, 7.49% with COPD. Adjusted incidence of PE was higher in COPD patients than in those without COPD (IRR 1.16; 95%CI 1.13-1.19). Crude IHM was significantly higher in PE hospitalized patients with COPD than in those without COPD (9.86% vs 3.59%; p<0.001). Predictor factors of IHM in COPD patients with PE included older age, higher Charlson comorbidity index, atrial fibrillation, massive PE and dependence on oxygen prior to hospital admission. However, obesity was associated with lower IHM. For PE hospitalized patients, suffering COPD increased the probability of dying in the hospital (adjusted OR 2.84; 95%CI 2.27-3.55).

CONCLUSIONS

Our results revealed that incidence of PE was higher in COPD patients than in those without COPD. Furthermore, COPD was a risk factor for IHM after PE.

Hypoxia and its preconditioning on cardiac and vascular remodelling in experimental animals

Since oxygen (O₂) is indispensable for mammalian life, every cell in the body is endowed with mechanisms to detect and to respond to changes in the O₂ levels in the microenvironment. The heart and the brain are the two most vital, life-supporting organs requiring a continuous supply of O₂ to sustain their high metabolic rate. On being challenged with hypoxia, maintenance of O₂ supply to these organs even at the cost of others becomes a priority. This review describes the cardiovascular, skeletal muscle vascular, pulmonary vascular and cerebrovascular remodelling in face of chronic mild hypoxia exposure and the underlying mechanisms, with special reference to the role of oxidative stress, hypoxia signalling, autonomic nervous mechanisms. The significance of the normalized wall index (NWI) in assessing the remodelling of the vessels particularly of the intramyocardial coronary artery has been underscored. The review also highlights the basic concepts of hypoxic preconditioning and the subsequent protection of the brain against an acute ischemic insult in preclinical studies hinting towards its possible therapeutic potential in the management of ischemic stroke.

Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung

Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O2 saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca2+ signaling and Ca2+ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca2+ or Ca2+ influx through various Ca2+-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca2+ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca2+ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca2+-sensing receptors (by 30 µM NPS2143, an allosteric Ca2+-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca2+ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca2+ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca2+-mediated activation of Ca2+-sensing receptors and the cell-cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.

NFATc3 regulation of collagen V expression contributes to cellular immunity to collagen type V and hypoxic pulmonary hypertension

Chronic hypoxia (CH)-induced pulmonary hypertension (PH) results, in part, from T helper-17 (T_H17) cell-mediated perivascular inflammation. However, the antigen(s) involved is unknown. Cellular immunity to collagen type V (col V) develops after ischemia-reperfusion injury during lung transplant and is mediated by naturally occurring (n)T_H17 cells. Col5a1 gene codifies for the α1-helix of col V, which is normally hidden from the immune system within type I collagen in the extracellular matrix. COL5A1 promoter analysis revealed nuclear factor of activated T cells, cytoplasmic 3 (NFATc3) binding sites. Therefore, we hypothesized that smooth muscle NFATc3 upregulates col V expression, leading to nT_H17 cell-mediated autoimmunity to col V in response to CH, representing an upstream mechanism in PH development. To test our hypothesis, we measured indexes of PH in inducible smooth muscle cell (SMC)-specific NFATc3 knockout (KO) mice exposed to either CH (380 mmHg) or normoxia and compared them with wild-type (WT) mice. KO mice did not develop PH. In addition, COL5A1 was one of the 1,792 genes differentially affected by both CH and SMC NFATc3 in isolated intrapulmonary arteries, which was confirmed by RT-PCR and immunostaining. Cellular immunity to col V was determined using a trans vivo delayed-type hypersensitivity assay (Tv-DTH). Tv-DTH response was evident only when splenocytes were used from control mice exposed to CH but not from KO mice, and mediated by nT_H17 cells. Our results suggest that SMC NFATc3 is important for CH-induced PH in adult mice, in part, by regulating the expression of the lung self-antigen COL5A1 protein contributing to col V-reactive nT_H17-mediated inflammation and hypertension.

Interruption of vascular endothelial growth factor receptor 2 signaling induces a proliferative pulmonary vasculopathy and pulmonary hypertension

Pulmonary arterial hypertension is a severe and progressive disease characterized by a pulmonary vascular remodeling process with expansion of collateral endothelial cells and total vessel occlusion. Endothelial cells are believed to be at the forefront of the disease process. Vascular endothelial growth factor (VEGF) and its tyrosine kinase receptor, VEGF receptor-2 (VEGFR-2), play a central role in angiogenesis, endothelial cell protection, but also in the destabilization of endothelial barrier function. Therefore, we investigated the consequences of altered VEGF signaling in an experimental model, and looked for translational correlates of this observation in patients. We performed an endothelial cell-specific conditional deletion of the kinase insert domain protein receptor (kdr) gene, coding for VEGFR-2, in C57/BL6 mice (Kdr^∆end) and held them in an environmental chamber with 10% FiO₂ or under normoxia for 6 weeks. Kdr knockout led to a mild PH phenotype under normoxia that worsened under hypoxia. Kdr^∆end mice exhibited a significant increase in pulmonary arterial wall thickness, muscularization, and VEGFR-3⁺ endothelial cells obliterating the pulmonary artery vessel lumen. We observed the same proliferative vasculopathy in our rodent model as seen in patients receiving anti-angiogenic therapy. Serum VEGF-a levels were elevated both in the experimental model and in humans receiving bevacizumab. Interrupted VEGF signaling leads to a pulmonary proliferative arteriopathy in rodents after direct ablative gene manipulation of Kdr. Histologically, similar vascular lesions can be observed in patients receiving anti-VEGF treatment. Our findings illustrate the importance of VEGF signaling for maintenance of pulmonary vascular patency.

Mesenchymal Regulation of the Microvascular Niche in Chronic Lung Diseases

The adult lung is comprised of diverse vascular, epithelial, and mesenchymal progenitor cell populations that reside in distinct niches. Mesenchymal progenitor cells (MPCs) are intimately associated with both the epithelium and the vasculature, and new evidence is emerging to describe their functional roles in these niches. Also emerging, following lineage analysis and single cell sequencing, is a new understanding of the diversity of mesenchymal cell subpopulations in the lung. However, several gaps in knowledge remain, including how newly defined MPC lineages interact with cells in the vascular niche and the role of adult lung MPCs during lung repair and regeneration following injury, especially in chronic lung diseases. Here we summarize how the current evidence on MPC regulation of the microvasculature during tissue homeostasis and injury may inform studies on understanding their role in chronic lung disease pathogenesis or repair. © 2019 American Physiological Society. Compr Physiol 9:1431-1441, 2019.

Secretory immunoglobulin A induces human lung fibroblasts to produce inflammatory cytokines and undergo activation

Immunoglobulin (Ig)A is the most abundant immunoglobulin in humans, and in the airway mucosa secretory IgA (sIgA) plays a pivotal role in first-line defense against invading pathogens and antigens. IgA has been reported to also have pathogenic effects, including possible worsening of the prognosis of idiopathic pulmonary fibrosis (IPF). However, the precise effects of IgA on lung fibroblasts remain unclear, and we aimed to elucidate how IgA activates human lung fibroblasts. We found that sIgA, but not monomeric IgA (mIgA), induced interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF) production by normal human lung fibroblasts (NHLFs) at both the protein and mRNA levels. sIgA also promoted proliferation of NHLFs and collagen gel contraction comparable to with transforming growth factor (TGF)-β, which is involved in fibrogenesis in IPF. Also, Western blot analysis and real-time quantitative polymerase chain reaction (PCR) revealed that sIgA enhanced production of α-smooth muscle actin (α-SMA) and collagen type I (Col I) by NHLFs. Flow cytometry showed that NHLFs bound sIgA, and among the known IgA receptors, NHLFs significantly expressed CD71 (transferrin receptor). Transfection of siRNA targeting CD71 partially but significantly suppressed cytokine production by NHLFs co-cultured with sIgA. Our findings suggest that sIgA may promote human lung inflammation and fibrosis by enhancing production of inflammatory or fibrogenic cytokines as well as extracellular matrix, inducing fibroblast differentiation into myofibroblasts and promoting human lung fibroblast proliferation. sIgA's enhancement of cytokine production may be due partially to its binding to CD71 or the secretory component.

Small Airway Disease in Pulmonary Hypertension-Additional Diagnostic Value of Multiple Breath Washout and Impulse Oscillometry

Airways obstruction is frequent in patients with pulmonary hypertension (PH). Small airway disease (SAD) was identified as a major contributor to resistance and symptoms. However, it is easily missed using current diagnostic approaches. We aimed to evaluate more elaborate diagnostic tests such as impulse oscillometry (IOS) and SF₆-multiple-breath-washout (MBW) for the assessment of SAD in PH. Twenty-five PH patients undergoing body-plethysmography, IOS and MBW testing were prospectively included and equally matched to pulmonary healthy and non-healthy controls. Lung clearance index (LCI) and acinar ventilation heterogeneity (S_acin) differed significantly between PH, healthy and non-healthy controls. Likewise, differences were found for all IOS parameters between PH and healthy, but not non-healthy controls. Transfer factor corrected for ventilated alveolar volume (TLCO/VA), frequency dependency of resistance (D5-20), resonance frequency (F_res) and S_acin allowed complete differentiation between PH and healthy controls (AUC (area under the curve) = 1.0). Likewise, PH patients were separated from non-healthy controls (AUC 0.762) by D5-20, LCI and conductive ventilation heterogeneity (S_cond). Maximal expiratory flow (MEF) values were not associated with additional diagnostic values. MBW and IOS are feasible in PH patients both providing additional information. This can be used to discriminate PH from healthy and non-healthy controls. Therefore, further research targeting SAD in PH and evaluation of therapeutic implications is justified.

EXPRESS: Gremlin1 blocks vascular endothelial growth factor signalling in the pulmonary microvascular endothelium

The bone morphogenetic protein (BMP) antagonist gremlin 1 plays a central role in the pathogenesis of hypoxic pulmonary hypertension (HPH). Recently, non-canonical functions of gremlin 1 have been identified, including specific binding to the vascular endothelial growth factor receptor-2 (VEGFR2). We tested the hypothesis that gremlin 1 modulates VEGFR2 signaling in the pulmonary microvascular endothelium.

We examined the effect of gremlin 1 haploinsufficiency on the expression of VEGF responsive genes and proteins in the hypoxic (10% O2) murine lung in vivo. Using human microvascular endothelial cells in vitro we examined the effect of gremlin 1 on VEGF signaling.

Gremlin 1 haploinsufficiency (Grem1+/–) attenuated the hypoxia-induced increase in gremlin 1 observed in the wild-type mouse lung. Reduced gremlin 1 expression in hypoxic Grem1+/– mice restored VEGFR2 expression and endothelial nitric oxide synthase (eNOS) expression and activity to normoxic values. Recombinant monomeric gremlin 1 inhibited VEGFA-induced VEGFR2 activation, downstream signaling, and VEGF-induced increases in Bcl-2, cell number, and the anti-apoptotic effect of VEGFA in vitro.

These results show that the monomeric form of gremlin 1 acts as an antagonist of VEGFR2 activation in the pulmonary microvascular endothelium. Given the previous demonstration that inhibition of VEGFR2 causes marked worsening of HPH, our results suggest that increased gremlin 1 in the hypoxic lung, in addition to blocking BMP receptor type-2 (BMPR2) signaling, contributes importantly to the development of PH by a non-canonical VEGFR2 blocking activity.

Maternal omega-3 PUFA supplementation prevents hyperoxia-induced pulmonary hypertension in the offspring

Pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) affect 16-25% of premature infants with bronchopulmonary dysplasia (BPD), contributing significantly to perinatal morbidity and mortality. Omega-3 polyunsaturated fatty acids (PUFA ω-3) can improve vascular remodeling, angiogenesis, and inflammation under pathophysiological conditions. However, the effects of PUFA ω-3 supplementation in BPD-associated PH are unknown. The present study aimed to evaluate the effects of PUFA ω-3 on pulmonary vascular remodeling, angiogenesis, and inflammatory response in a hyperoxia-induced rat model of PH. From embryonic day 15, pregnant Sprague-Dawley rats were supplemented daily with PUFA ω-3, PUFA ω-6, or normal saline (0.2 ml/day). After birth, pups were pooled, assigned as 12 per litter, randomly assigned to either air or continuous oxygen exposure (fraction of inspired oxygen = 85%) for 20 days, and then euthanized for pulmonary hemodynamic and morphometric analysis. We found that PUFA ω-3 supplementation improved survival, decreased right ventricular systolic pressure and RVH caused by hyperoxia, and significantly improved alveolarization, vascular remodeling, and vascular density. PUFA ω-3 supplementation produced a higher level of total ω-3 in lung tissue and breast milk and was found to reverse the reduced levels of VEGFA, VEGF receptor 2, angiopoietin-1 (ANGPT1), endothelial TEK tyrosine kinase, endothelial nitric oxide synthase, and nitric oxide concentrations in lung tissue and the increased ANGPT2 levels in hyperoxia-exposed rats. The beneficial effects of PUFA ω-3 in improving lung injuries were also associated with an inhibition of leukocyte infiltration and reduced expression of the proinflammatory cytokines IL-1β, IL-6, and TNF-α. These data indicate that maternal PUFA ω-3 supplementation strategies could effectively protect against infant PH induced by hyperoxia.

PLCγ1-PKCε-IP3R1 signaling plays an important role in hypoxia-induced calcium response in pulmonary artery smooth muscle cells

Hypoxia-induced pulmonary vasoconstriction (HPV) is attributed to an increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in pulmonary artery smooth muscle cells (PASMCs). We have reported that phospholipase C-γ1 (PLCγ1) plays a significant role in the hypoxia-induced increase in [Ca²⁺]_i in PASMCs and attendant HPV. In this study, we intended to determine molecular mechanisms for hypoxic Ca²⁺ and contractile responses in PASMCs. Our data reveal that hypoxic vasoconstriction occurs in pulmonary arteries, but not in mesenteric arteries. Hypoxia caused a large increase in [Ca²⁺]_i in PASMCs, which is diminished by the PLC inhibitor U73122 and not by its inactive analog U73433 . Hypoxia augments PLCγ1-dependent inositol 1,4,5-trisphosphate (IP₃) generation. Exogenous ROS, hydrogen peroxide (H₂O₂), increases PLCγ1 phosphorylation at tyrosine-783 and IP₃ production. IP₃ receptor-1 (IP₃R1) knock-down remarkably diminishes hypoxia- or H₂O₂-induced increase in [Ca²⁺]_i. Hypoxia or H₂O₂ increases the activity of IP₃Rs, which is significantly reduced in protein kinase C-ε (PKCε) knockout PASMCs. A higher PLCγ1 expression, activity, and basal [Ca²⁺]_i are found in PASMCs, but not in mesenteric artery smooth muscle cells from mice exposed to chronic hypoxia (CH) for 21 days. CH enhances H₂O₂- and ATP-induced increase in [Ca²⁺]_i in PASMCs and PLC-dependent, norepinephrine-evoked pulmonary vasoconstriction. In conclusion, acute hypoxia uniquely causes ROS-dependent PLCγ1 activation, IP₃ production, PKCε activation, IP₃R1 opening, Ca²⁺ release, and contraction in mouse PASMCs; CH enhances PASM PLCγ1 expression, activity, and function, playing an essential role in pulmonary hypertension in mice.

Deregulated angiogenesis in chronic lung diseases: a possible role for lung mesenchymal progenitor cells (2017 Grover Conference Series)

Chronic lung disease (CLD), including pulmonary fibrosis (PF) and chronic obstructive pulmonary disease (COPD), is the fourth leading cause of mortality worldwide. Both are debilitating pathologies that impede overall tissue function. A common co-morbidity in CLD is vasculopathy, characterized by deregulated angiogenesis, remodeling, and loss of microvessels. This substantially worsens prognosis and limits survival, with most current therapeutic strategies being largely palliative. The relevance of angiogenesis, both capillary and lymph, to the pathophysiology of CLD has not been resolved as conflicting evidence depicts angiogenesis as both reparative or pathologic. Therefore, we must begin to understand and model the underlying pathobiology of pulmonary vascular deregulation, alone and in response to injury induced disease, to define cell interactions necessary to maintain normal function and promote repair. Capillary and lymphangiogenesis are deregulated in both PF and COPD, although the mechanisms by which they co-regulate and underlie early pathogenesis of disease are unknown. The cell-specific mechanisms that regulate lung vascular homeostasis, repair, and remodeling represent a significant gap in knowledge, which presents an opportunity to develop targeted therapies. We have shown that that ABCG2^pos multipotent adult mesenchymal stem or progenitor cells (MPC) influence the function of the capillary microvasculature as well as lymphangiogenesis. A balance of both is required for normal tissue homeostasis and repair. Our current models suggest that when lymph and capillary angiogenesis are out of balance, the non-equivalence appears to support the progression of disease and tissue remodeling. The angiogenic regulatory mechanisms underlying CLD likely impact other interstitial lung diseases, tuberous sclerosis, and lymphangioleiomyomatosis.

Potential markers and metabolic processes involved in the mechanism of radiation-induced heart injury

Irradiation of normal tissues leads to acute increase in reactive oxygen/nitrogen species that serve as intra- and inter-cellular signaling to alter cell and tissue function. In the case of chest irradiation, it can affect the heart, blood vessels, and lungs, with consequent tissue remodelation and adverse side effects and symptoms. This complex process is orchestrated by a large number of interacting molecular signals, including cytokines, chemokines, and growth factors. Inflammation, endothelial cell dysfunction, thrombogenesis, organ dysfunction, and ultimate failing of the heart occur as a pathological entity - "radiation-induced heart disease" (RIHD) that is major source of morbidity and mortality. The purpose of this review is to bring insights into the basic mechanisms of RIHD that may lead to the identification of targets for intervention in the radiotherapy side effect. Studies of authors also provide knowledge about how to select targeted drugs or biological molecules to modify the progression of radiation damage in the heart. New prospective studies are needed to validate that assessed factors and changes are useful as early markers of cardiac damage.

Effect of pulmonary hyperinflation on central blood volume: An MRI study

Pulmonary hyperinflation attained by glossopharyngeal insufflation (GPI) challenges the circulation by compressing the heart and pulmonary vasculature. Our aim was to determine the amount of blood translocated from the central blood volume during GPI. Cardiac output and cardiac chamber volumes were assessed by magnetic resonance imaging in twelve breath-hold divers at rest and during apnea with GPI. Pulmonary blood volume was determined from pulmonary blood flow and transit times for gadolinium during first-pass perfusion after intravenous injection. During GPI, the lung volume increased by 0.8±0.6L (11±7%) above the total lung capacity. All cardiac chambers decreased in volume and despite a heart rate increase of 24±29 bpm (39±50%), pulmonary blood flow decreased by 2783±1820mL (43±20%). The pulmonary transit time remained unchanged at 7.5±2.2s and pulmonary blood volume decreased by 354±176mL (47±15%). In total, central blood volume decreased by 532±248mL (46±14%). Voluntary pulmonary hyperinflation leads to ∼50% decrease in pulmonary and central blood volume.

A review of imaging modalities in pulmonary hypertension

Pulmonary hypertension (PH) is defined as resting mean pulmonary artery pressure ≥25 mmHg measured by right heart catheterization. PH is a progressive, life-threatening disease with a variety of etiologies. Swift and accurate diagnosis of PH and appropriate classification in etiologic group will allow for earlier treatment and improved outcomes. A number of imaging tools are utilized in the evaluation of PH, such as chest X-ray, computed tomography (CT), ventilation/perfusion (V/Q) scan, and cardiac magnetic resonance imaging. Newer imaging tools such as dual-energy CT and single-photon emission computed tomography/computed tomography V/Q scanning have also emerged; however, their place in the diagnostic evaluation of PH remains to be determined. In general, each imaging technique provides incremental information, with varying degrees of sensitivity and specificity, which helps suspect the presence and identify the etiology of PH. The present study aims to provide a comprehensive review of the utility, advantages, and shortcomings of the imaging modalities that may be used to evaluate patients with PH.

Prominent Intrapulmonary Bronchopulmonary Anastomoses and Abnormal Lung Development in Infants and Children with Down Syndrome

OBJECTIVES

To determine the frequency of histologic features of impaired lung vascular and alveolar development and to identify the presence of intrapulmonary bronchopulmonary anastomoses (IBA) in infants and children who died with Down syndrome.

STUDY DESIGN

A retrospective review of autopsy reports and lung histology from 13 children with Down syndrome (ages: 0-8 years) was performed. Histologic features of abnormal lung development were identified and semiquantified, including the presence of IBA. Three-dimensional reconstructions of IBA were also performed. Comparisons were made with 4 age-matched patients without Down syndrome with congenital heart defects who underwent autopsies during this time period.

RESULTS

Of the 13 subjects with Down syndrome, 69% died from cardiac events, 77% had a congenital heart defect, and 46% had a clinical diagnosis of pulmonary hypertension. Lung histology from all subjects with Down syndrome demonstrated alveolar simplification, and 92% had signs of persistence of a double capillary network in the distal lung. The lungs from the subjects with Down syndrome frequently had features of pulmonary arterial hypertensive remodeling (85%), and prominent bronchial vessels and IBA were observed in all subjects with Down syndrome. These features were more frequent in subjects with Down syndrome compared with control subjects.

CONCLUSIONS

Children with Down syndrome who died of cardiopulmonary diseases often have histologic evidence of impaired lung alveolar and vascular development, including the presence of prominent IBA and pulmonary hypertension. We speculate that children with Down syndrome are at risk for reduced lung surface area and recruitment of IBA, which may worsen gas exchange in subjects with Down syndrome.

Relationship between polycythemia and in-hospital mortality in chronic obstructive pulmonary disease patients with low-risk pulmonary embolism

BACKGROUNDS

Pulmonary embolism (PE) is frequent in subjects with chronic obstructive pulmonary disease (COPD) and associated with high mortality. This multi-center retrospective study was performed to investigate if secondary polycythemia is associated with in-hospital mortality in COPD patients with low-risk PE.

METHODS

We identified COPD patients with proven PE between October, 2005 and October, 2015. Patients in risk classes III-V on the basis of the PESI score were excluded. We extracted demographic, clinical and laboratory information at the time of admission from medical records. All subjects were followed until hospital discharge to identify all-cause mortality.

RESULTS

We enrolled 629 consecutive patients with COPD and PE at low risk: 132 of them (21.0%) with and 497 (79.0%) without secondary polycythemia. Compared with those without polycythemia, the polycythemia group had significantly lower forced expiratory volume in one second (FEV₁) level (0.9±0.3 vs. 1.4±0.5, P=0.000), lower PaO₂ and SpO₂ as well as higher PaCO₂ (P=0.03, P=0.03 and P=0.000, respectively). COPD patients with polycythemia had a higher proportion of arrhythmia in electrocardiogram (ECG) (49.5% vs. 35.7%, P=0.02), a longer hospital duration time (15.3±10.1 vs. 9.7±9.1, P=0.001), a higher mechanical ventilation rate (noninvasive and invasive, 51.7% vs. 30.3%, P=0.04 and 31.0% vs. 7.9%, P=0.04, respectively), and a higher in-hospital mortality (12.1% vs. 6.6%, P=0.04). Multivariate logistic regression analysis revealed that polycythemia was associated with mortality in COPD patients with low-risk PE (adjusted OR 1.11; 95% CI, 1.04-1.66).

CONCLUSIONS

Polycythemia is an independent risk factor for all-cause in-hospital mortality in COPD patients with PE at low risk.

A method for evaluating the murine pulmonary vasculature using micro-computed tomography

BACKGROUND

Significant mortality and morbidity are associated with alterations in the pulmonary vasculature. While techniques have been described for quantitative morphometry of whole-lung arterial trees in larger animals, no methods have been described in mice. We report a method for the quantitative assessment of murine pulmonary arterial vasculature using high-resolution computed tomography scanning.

METHODS

Mice were harvested at 2 weeks, 4 weeks, and 3 months of age. The pulmonary artery vascular tree was pressure perfused to maximal dilation with a radio-opaque casting material with viscosity and pressure set to prevent capillary transit and venous filling. The lungs were fixed and scanned on a specimen computed tomography scanner at 8-μm resolution, and the vessels were segmented. Vessels were grouped into categories based on lumen diameter and branch generation.

RESULTS

Robust high-resolution segmentation was achieved, permitting detailed quantitation of pulmonary vascular morphometrics. As expected, postnatal lung development was associated with progressive increase in small-vessel number and arterial branching complexity.

CONCLUSIONS

These methods for quantitative analysis of the pulmonary vasculature in postnatal and adult mice provide a useful tool for the evaluation of mouse models of disease that affect the pulmonary vasculature.

Nitric Oxide and Other Novel Therapies for Pulmonary Hypertension

Pulmonary hypertension is an uncommon, yet devastating, syndrome with a complex underlying pathobiology. Hypoxia, inflammation, and increased shear stress appear to be the primary pathogenic events; however, mechanisms by which these processes lead to pulmonary hypertension remain incompletely understood. The ultimate increase in pulmonary vascular resistance is attributed to remodelling of the walls of resistance vessels, which can lead to encroachment on and reduction of the vascular lumen. The number of blood vessels per unit of cross-sectional area in the hypertensive lung is also reduced, which can contribute to increased vascular resistance. Regardless of its etiology, endothelial dysfunction underlies pulmonary hypertension, one manifestation of which is the attenuated production of bioactive nitric oxide. Nitric oxide administration can exert beneficial effects at various stages of the disease. Here we review the known pathobiology of pulmonary hypertension, with a principal focus on endothelial nitric oxide, and also summarize the data on nitric oxide replacement therapy and other novel therapies that relate to nitric oxide as one approach to treatment.

Study of cardiovascular function using a coupled left ventricle and systemic circulation model

To gain insight into cardio-arterial interactions, a coupled left ventricle-systemic artery (LV–SA) model is developed that incorporates a three-dimensional finite-strain left ventricle (LV), and a physiologically-based one-dimensional model for the systemic arteries (SA). The coupling of the LV model and the SA model is achieved by matching the pressure and the flow rate at the aortic root, i.e. the SA model feeds back the pressure as a boundary condition to the LV model, and the aortic flow rate from the LV model is used as the input for the SA model. The governing equations of the coupled system are solved using a combined immersed-boundary finite-element (IB/FE) method and a Lax–Wendroff scheme. A baseline case using physiological measurements of healthy subjects, and four exemplar cases based on different physiological and pathological scenarios are studied using the LV–SA model. The results of the baseline case agree well with published experimental data. The four exemplar cases predict varied pathological responses of the cardiovascular system, which are also supported by clinical observations. The new model can be used to gain insight into cardio-arterial interactions across a range of clinical applications.

Epidemiology of chronic thromboembolic pulmonary hypertension in Korea: results from the Korean registry

BACKGROUND/AIMS

The diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH) is difficult for numerous reasons and is related with a poor prognosis. In Korea, the incidence of CTEPH and its clinical features are unknown. Thus, in this study, we evaluated the clinical characteristics and outcomes of CTEPH in a Korean cohort.

METHODS

This study included South Korean patients diagnosed with CTEPH between September 2008 and October 2011. Baseline characteristics, treatments and outcomes were analyzed.

RESULTS

A total of 134 patients were included in this study with 76 females (56.7%). Their median age was 58.3 ± 15.9 years and dyspnea (112 patients, 83.5%) was the most common presenting symptom. Sixty-three patients (47%) had a history of acute pulmonary embolism or deep vein thrombosis, and six (4.5%) had pulmonary tuberculosis. In total, 28 patients (21%) underwent pulmonary thromboendarterectomy (PTE), and 99 patients had medical therapy. During the study period, 18 patients (13.4%) died. In a multivariate analysis, higher hemoglobin (relative risk [RR], 1.516; 95% confidence interval [CI], 1.053 to 2.184; p = 0.025) and lower total cholesterol levels (RR, 0.982; 95% CI, 0.965 to 0.999; p = 0.037) were associated with increased mortality.

CONCLUSIONS

This was the first national cohort study of Korean patients with CTEPH. Accurate diagnosis, characterization and distributions of CTEPH are imperative for prompt treatment in patients, particularly those undergoing PTE.

Pulmonary Arterial Pressure Response During Exercise in COPD: A Correlation with C-Reactive Protein (hsCRP)

Background:

The non-invasive assessment of pulmonary haemodynamics during exercise provides complementary data for the evaluation of exercise tolerance in patients with COPD.

Methods:

Exercise echocardiography in the semi-supine position was performed in 27 patients with COPD (C) with a forced expiratory volume in one second (FEV1) of 36±12% predicted and 13 age and gender-matched non-COPD subjects (NC). COPD patients also underwent cardiopulmonary exercise testing with gas exchange detection (CPET). Furthermore, serum high sensitive C-reactive protein (hsCRP), a marker of systemic inflammation, was also measured.

Results:

The maximal work rate (WRmax) and aerobic capacity (VO2peak) were significantly reduced (WRmax: 77±33 Watt, VO2peak: 50±14 %pred) in COPD. Pulmonary arterial systolic pressure (PAPs) was higher in COPD versus controls both at rest (39±5 vs. 31±2 mmHg, p<0.001), and at peak exercise (72±12 vs. 52±8 mmHg, p<0.001). In 19 (70%) COPD patients, the increase in PAPs was above 22 mmHg. The change in pressure (dPAPs) correlated with hsCRP (r2=0.53, p<0.0001) and forced vital capacity (FVC) (r2=0.18, p<0.001).

Conclusion:

PAPs at rest and during exercise were significantly higher in COPD patients and correlated with higher hsCRP. This may indicate a role for systemic inflammation and hyperinflation in the pulmonary vasculature in COPD.

The study was registered at ClinicalTrials.gov webpage with NCT00949195 registration number.

Neovascularization in the pulmonary endothelium is regulated by the endosome: Rab4-mediated trafficking and p18-dependent signaling

Neovascularization, the formation of new blood vessels, requires multiple processes including vascular leak, migration, and adhesion. Endosomal proteins, such as Rabs, regulate trafficking of key signaling proteins involved in neovascularization. The novel endosome protein, p18, enhances vascular endothelial (VE)-cadherin recycling from early endosome to cell junction to improve pulmonary endothelial barrier function. Since endothelial barrier integrity is vital in neovascularization, we sought to elucidate the role for endosome proteins p18 and Rab4, Rab7, and Rab9 in the process of vessel formation within the pulmonary vasculature. Overexpression of wild-type p18 (p18(wt)), but not the nonendosomal-binding mutant (p18(N39)), significantly increased lung microvascular endothelial cell migration, adhesion, and both in vitro and in vivo tube formation. Chemical inhibition of mTOR or p38 attenuated the proneovascularization role of p18(wt). Similar to the effect of p18(wt), overexpression of prorecycling wild-type (Rab4(WT)) and endosome-anchored (Rab4(Q67L)) Rab4 enhanced neovascularization processes, whereas molecular inhibition of Rab4, by using the nonendosomal-binding mutant (Rab4(S22N)) attenuated VEGF-induced neovascularization. Unlike p18, Rab4-induced neovascularization was independent of mTOR or p38 inhibition but was dependent on p18 expression. This study shows for the first time that neovascularization within the pulmonary vasculature is dependent on the prorecycling endocytic proteins Rab4 and p18.

Elevated plasma CXCL12α is associated with a poorer prognosis in pulmonary arterial hypertension

RATIONALE

Recent work in preclinical models suggests that signalling via the pro-angiogenic and pro-inflammatory cytokine, CXCL12 (SDF-1), plays an important pathogenic role in pulmonary hypertension (PH). The objective of this study was to establish whether circulating concentrations of CXCL12α were elevated in patients with PAH and related to mortality.

METHODS

Plasma samples were collected from patients with idiopathic pulmonary arterial hypertension (IPAH) and PAH associated with connective tissue diseases (CTD-PAH) attending two pulmonary hypertension referral centres (n = 95) and from age and gender matched healthy controls (n = 44). Patients were subsequently monitored throughout a period of five years.

RESULTS

CXCL12α concentrations were elevated in PAH groups compared to controls (P<0.05) and receiver-operating-characteristic analysis showed that plasma CXCL12α concentrations discriminated patients from healthy controls (AUC 0.80, 95% confidence interval 0.73-0.88). Kaplan Meier analysis indicated that elevated plasma CXCL12α concentration was associated with reduced survival (P<0.01). Multivariate Cox proportional hazards model showed that elevated CXCL12α independently predicted (P<0.05) earlier death in PAH with a hazard ratio (95% confidence interval) of 2.25 (1.01-5.00). In the largest subset by WHO functional class (Class 3, 65% of patients) elevated CXCL12α independently predicted (P<0.05) earlier death, hazard ratio 2.27 (1.05-4.89).

CONCLUSIONS

Our data show that elevated concentrations of circulating CXCL12α in PAH predicted poorer survival. Furthermore, elevated circulating CXCL12α was an independent risk factor for death that could potentially be included in a prognostic model and guide therapy.

Transdifferentiation of endothelial cells to smooth muscle cells play an important role in vascular remodelling

Pulmonary artery remodelling it is a major feature of pulmonary hypertension (PH). It is characterised by cellular and structural changes of the pulmonary arteries causing higher pulmonar vascular resistance and right ventricular failure. Abnormal deposition of smooth muscle-like (SM-like) cells in normally non-muscular, small diameter vessels and a deregulated control of endothelial cells are considered pathological features of PH. The origin of the SM-like cells and the mechanisms underlying the development and progression of this remodelling process are not understood. Endothelial cells within the intima may migrate from their organised layer of cells and transition to mesenchymal or SM-like phenotype in a process called endothelial-mesenchymal transition (EnMT). Traditionally, Waddington's epigenetic landscape illustrates that fates of somatic cells are progressively determined to compulsorily follow a downhill differentiation pathway. EnMT induces the transformation of cells with stem cell traits, therefore contrasting Waddington's theory and confirming that cell fate seems to be far more flexible than previously thought. The prospect of therapeutic inhibition of EnMT to delay or prevent PH may represent a promising new treatment modality.

Cardiopulmonary coupling in chronic obstructive pulmonary disease: the role of imaging

Chronic obstructive pulmonary disorder (COPD) is a systemic disease that affects the cardiovascular system through multiple pathways. Pulmonary hypertension, ventricular dysfunction, and atherosclerosis are associated with smoking and COPD, causing significant morbidity and poor prognosis. Coupling between the pulmonary and cardiovascular system involves mechanical interdependence and inflammatory pathways that potentially affect the entire circulation. Although treatments specific for COPD-related cardiovascular and pulmonary vascular disease are limited, early diagnosis, study of pathophysiology, and monitoring the effects of treatment are enhanced with improved imaging techniques. In this article, we review recent advancements in the imaging of the vasculature and the heart in patients with COPD. We also explore the potential mechanism of coupling between the progression of COPD and vascular disease. Imaging methods reviewed include specific implementations of computed tomography, magnetic resonance imaging, dual-energy computed tomography, positron emission tomography, and echocardiography. Specific applications to the proximal and distal pulmonary vasculature, as well as to the heart and systemic circulation, are also discussed.

Pulmonary hypertension survival effects and treatment options in cystic fibrosis

PURPOSE OF REVIEW

This review discusses the current impact of pulmonary hypertension on the outcome and treatment of cystic fibrosis (CF).

RECENT FINDINGS

Pulmonary hypertension is commonly encountered in advanced lung diseases such as CF. The prevalence of pulmonary hypertension in CF patients varies based on disease severity and methodology used for diagnosis. Chronic alveolar hypoxia is the most likely cause. The majority of recent studies have shown worse survival in CF patients who develop pulmonary hypertension. The impact of pulmonary hypertension-specific therapies on symptomatology and outcomes in CF patients has not been well studied.

SUMMARY

Pulmonary hypertension is common in patients with CF and it occurs largely because of hypoxemia. The presence of pulmonary hypertension in patients with CF is likely associated with worse outcome; however, it remains unknown whether treatment with pulmonary hypertension-specific therapies would be beneficial.

Pulmonary hypertension after pneumonectomy for lung cancer

Background

We aimed to consolidate our clinical observations regarding the development of pulmonary hypertension following pneumonectomy for lung cancer.

Methods

Sixty-nine of 82 initially selected patients without pulmonary or cardiac comorbidities, who underwent pneumonectomy for lung cancer between October 2009 and October 2011, accomplished our protocol. Mean patient age was 60.6 years (range 44–78 years) and 10.1% were women.

Results

Postoperative complications occurred in 16 (23.2%) patients. Mortality at 1, 12, and 18 months postoperatively was 4.3%, 15.9%, and 29%, respectively. One year postoperatively, 37.9% of patients developed mild to moderate pulmonary hypertension and 3.4% had severe pulmonary hypertension. The calculated mean pulmonary artery systolic pressure at 1, 6, and 12 months postoperatively was 21.9 ± 6.6, 27.3 ± 9.3, and 34.1 ± 14 mm Hg, respectively ( p < 0.001). Receiver operating characteristic curve analysis showed a cutoff point at 35.5 mm Hg for late postoperative (at 12 months) pulmonary artery systolic pressure (sensitivity 80%, specificity 82%; p < 0.001) related to suboptimal clinical outcomes (decreased performance status or death), with a detected 18-fold risk for these patients ( p < 0.001).

Conclusions

Pulmonary hypertension may occur after pneumonectomy with its known adverse effects. Patients with late postoperative pulmonary artery systolic pressure > 35.5 mm Hg are at higher risk of a suboptimal clinical outcome.

Physiological and pathological angiogenesis in the adult pulmonary circulation

Angiogenesis occurs during growth and physiological adaptation in many systemic organs, for example, exercise-induced skeletal and cardiac muscle hypertrophy, ovulation, and tissue repair. Disordered angiogenesis contributes to chronic inflammatory disease processes and to tumor growth and metastasis. Although it was previously thought that the adult pulmonary circulation was incapable of supporting new vessel growth, over that past 10 years new data have shown that angiogenesis within this circulation occurs both during physiological adaptive processes and as part of the pathogenic mechanisms of lung diseases. Here we review the expression of vascular growth factors in the adult lung, their essential role in pulmonary vascular homeostasis and the changes in their expression that occur in response to physiological challenges and in disease. We consider the evidence for adaptive neovascularization in the pulmonary circulation in response to alveolar hypoxia and during lung growth following pneumonectomy in the adult lung. In addition, we review the role of disordered angiogenesis in specific lung diseases including idiopathic pulmonary fibrosis, acute adult distress syndrome and both primary and metastatic tumors of the lung. Finally, we examine recent experimental data showing that therapeutic enhancement of pulmonary angiogenesis has the potential to treat lung diseases characterized by vessel loss.

Endothelin-1 decreases endothelial PPARγ signaling and impairs angiogenesis after chronic intrauterine pulmonary hypertension

Increased endothelin-1 (ET-1) disrupts angiogenesis in persistent pulmonary hypertension of the newborn (PPHN), but pathogenic mechanisms are unclear. Peroxisome proliferator activated receptor γ (PPARγ) is decreased in adult pulmonary hypertension, but whether ET-1-PPARγ interactions impair endothelial cell function and angiogenesis in PPHN remains unknown. We hypothesized that increased PPHN pulmonary artery endothelial cell (PAEC) ET-1 production decreases PPARγ signaling and impairs tube formation in vitro. Proximal PAECs were harvested from fetal sheep after partial ligation of the ductus arteriosus in utero (PPHN) and controls. PPARγ and phospho-PPARγ protein were compared between normal and PPHN PAECs ± ET-1 and bosentan (ETA/ETB receptor blocker). Tube formation was assessed in response to PPARγ agonists ± ET-1, N-nitro-l-arginine (LNA) (NOS inhibitor), and PPARγ siRNA. Endothelial NO synthase (eNOS), phospho-eNOS, and NO production were measured after exposure to PPARγ agonists and PPARγ siRNA. At baseline, PPHN PAECs demonstrate decreased tube formation and PPARγ protein expression and activity. PPARγ agonists restored PPHN tube formation to normal. ET-1 decreased normal and PPHN PAEC tube formation, which was rescued by PPARγ agonists. ET-1 decreased PPARγ protein and activity, which was prevented by bosentan. PPARγ agonists increased eNOS protein and activity and NO production in normal and PPHN PAECs. LNA inhibited the effect of PPARγ agonists on tube formation. PPARγ siRNA decreased eNOS protein and tube formation in normal PAECs. We conclude that ET-1 decreases PPARγ signaling and contributes to PAEC dysfunction and impaired angiogenesis in PPHN. We speculate that therapies aimed at decreasing ET-1 production will restore PPARγ signaling, preserve endothelial function, and improve angiogenesis in PPHN.

The α and Δ isoforms of CREB1 are required to maintain normal pulmonary vascular resistance

Chronic hypoxia causes pulmonary hypertension associated with structural alterations in pulmonary vessels and sustained vasoconstriction. The transcriptional mechanisms responsible for these distinctive changes are unclear. We have previously reported that CREB1 is activated in the lung in response to alveolar hypoxia but not in other organs. To directly investigate the role of α and Δ isoforms of CREB1 in the regulation of pulmonary vascular resistance we examined the responses of mice in which these isoforms of CREB1 had been inactivated by gene mutation, leaving only the β isoform intact (CREB(αΔ) mice). Here we report that expression of CREB regulated genes was altered in the lungs of CREB(αΔ) mice. CREB(αΔ) mice had greater pulmonary vascular resistance than wild types, both basally in normoxia and following exposure to hypoxic conditions for three weeks. There was no difference in rho kinase mediated vasoconstriction between CREB(αΔ) and wild type mice. Stereological analysis of pulmonary vascular structure showed characteristic wall thickening and lumen reduction in hypoxic wild-type mice, with similar changes observed in CREB(αΔ). CREB(αΔ) mice had larger lungs with reduced epithelial surface density suggesting increased pulmonary compliance. These findings show that α and Δ isoforms of CREB1 regulate homeostatic gene expression in the lung and that normal activity of these isoforms is essential to maintain low pulmonary vascular resistance in both normoxic and hypoxic conditions and to maintain the normal alveolar structure. Interventions that enhance the actions of α and Δ isoforms of CREB1 warrant further investigation in hypoxic lung diseases.

Reactive oxygen species in pulmonary vascular remodeling

The pathogenesis of pulmonary hypertension is a complex multifactorial process that involves the remodeling of pulmonary arteries. This remodeling process encompasses concentric medial thickening of small arterioles, neomuscularization of previously nonmuscular capillary-like vessels, and structural wall changes in larger pulmonary arteries. The pulmonary arterial muscularization is characterized by vascular smooth muscle cell hyperplasia and hypertrophy. In addition, in uncontrolled pulmonary hypertension, the clonal expansion of apoptosis-resistant endothelial cells leads to the formation of plexiform lesions. Based upon a large number of studies in animal models, the three major stimuli that drive the vascular remodeling process are inflammation, shear stress, and hypoxia. Although, the precise mechanisms by which these stimuli impair pulmonary vascular function and structure are unknown, reactive oxygen species (ROS)-mediated oxidative damage appears to play an important role. ROS are highly reactive due to their unpaired valence shell electron. Oxidative damage occurs when the production of ROS exceeds the quenching capacity of the antioxidant mechanisms of the cell. ROS can be produced from complexes in the cell membrane (nicotinamide adenine dinucleotide phosphate-oxidase), cellular organelles (peroxisomes and mitochondria), and in the cytoplasm (xanthine oxidase). Furthermore, low levels of tetrahydrobiopterin (BH4) and L-arginine the rate limiting cofactor and substrate for endothelial nitric oxide synthase (eNOS), can cause the uncoupling of eNOS, resulting in decreased NO production and increased ROS production. This review will focus on the ROS generation systems, scavenger antioxidants, and oxidative stress associated alterations in vascular remodeling in pulmonary hypertension.

Lactate dehydrogenase a expression is necessary to sustain rapid angiogenesis of pulmonary microvascular endothelium

Angiogenesis is a fundamental property of endothelium, yet not all endothelial cells display equivalent angiogenic responses; pulmonary microvascular endothelial cells undergo rapid angiogenesis when compared to endothelial cells isolated from conduit vessels. At present it is not clear how pulmonary microvascular endothelial cells fulfill the bioenergetic demands that are necessary to sustain such rapid blood vessel formation. We have previously established that pulmonary microvascular endothelial cells utilize aerobic glycolysis to generate ATP during growth, a process that requires the expression of lactate dehydrogenase A to convert pyruvate to lactate. Here, we test the hypothesis that lactate dehydrogenase A is required for pulmonary microvascular endothelial cells to sustain rapid angiogenesis. To test this hypothesis, Tet-On and Tet-Off conditional expression systems were developed in pulmonary microvascular endothelial cells, where doxycycline is utilized to induce lactate dehydrogenase A shRNA expression. Expression of LDH-A shRNA induced a time-dependent decrease in LDH-A protein, which corresponded with a decrease in glucose consumption from the media, lactate production and cell growth; re-expression of LDH-A rescued each of these parameters. LDH-A silencing greatly reduced network formation on Matrigel in vitro, and decreased blood vessel formation in Matrigel in vivo. These findings demonstrate that LDH-A is critically important for sustaining the rapid angiogenesis of pulmonary microvascular endothelial cells.

Wall shear stress measured by phase contrast cardiovascular magnetic resonance in children and adolescents with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a devastating disease with significant morbidity and mortality. At the macroscopic level, disease progression is observed as a complex interplay between mean pulmonary artery pressure, pulmonary vascular resistance, pulmonary vascular stiffness, arterial size, and flow. Wall shear stress (WSS) is known to mediate or be dependent on a number of these factors. Given that WSS is known to promote architectural vessel remodeling, it is imperative that the changes of this factor be quantified in the presence of PAH.

METHODS

In this study, we analyzed phase contrast imaging of the right pulmonary artery derived from cardiovascular magnetic resonance to quantify the local, temporal and circumferentially averaged WSS of a PAH population and a pediatric control population. In addition, information about flow and relative area change were derived.

RESULTS

Although the normotensive and PAH shear waveform exhibited a WSS profile which is uniform in magnitude and direction along the vessel circumference at systole, time-averaged WSS (2.2 ± 1.6 vs. 6.6 ± 3.4 dynes/cm(2), P = 0.018) and systolic WSS (8.2 ± 5.0 v. 20.0 ± 9.1 dynes/cm(2), P = 0.018) was significantly depressed in the PAH population as compared to the controls. BSA-indexed PA diameter was significantly larger in the PAH population (1.5 ± 0.4 vs. 0.7 ± 0.1 cm/m(2), P = 0.003).

CONCLUSIONS

In the presence of preserved flow rates through a large PAH pulmonary artery, WSS is significantly decreased. This may have implications for proximal pulmonary artery remodeling and cellular function in the progression of PAH.

Balancing the risks and benefits of oxygen therapy in critically III adults

Oxygen therapy is an integral part of the treatment of critically ill patients. Maintenance of adequate oxygen delivery to vital organs often requires the administration of supplemental oxygen, sometimes at high concentrations. Although oxygen therapy is lifesaving, it may be associated with deleterious effects when administered for prolonged periods at high concentrations. Here, we review the recent advances in our understanding of the molecular responses to hypoxia and high levels of oxygen and review the current guidelines for oxygen therapy in critically ill patients.

Iptakalim, a novel ATP-sensitive potassium channel opener, inhibits pulmonary arterial smooth muscle cell proliferation by downregulation of PKC-α

Iptakalim is a new ATP-sensitive potassium (K_ATP) channel opener, and it inhibits the proliferation of pulmonary arterial smooth muscle cells (PASMCs) and pulmonary vascular remodeling. However, the underlying mechanism remains unclear. In the present study, we found that iptakalim significantly decreased pulmonary artery pressure, inhibited pulmonary ariery remodeling and PKC-α overexpression in chronic hypoxia in a rat pulmonary hypertension model. Iptakalim reduced hypoxia-induced expression of PKC-α, and abolished the effect of hypoxia on PASMC proliferation significantly in a dose-dependent manner in vitro. Moreover, these effects were abolished by glibenclamide, a selective K_ATP channel antagonist. These results indicate that iptakalim inhibits PASMC proliferation and pulmonary vascular remodeling induced by hypoxia through downregulating the expression of PKC-α. Iptakalim can serve as a novel promising treatment for hypoxic pulmonary hypertension.