Distal Pulmonary Artery Research Articles

Central role of ubiquitin-specific protease 8 in leptin signaling pathway in pulmonary arterial hypertension

Leptin receptor (ObR-b) is overexpressed in pulmonary artery smooth muscle cells (PA-SMCs) from patients with pulmonary arterial hypertension (PAH) and is implicated in both mechanisms that contribute to pulmonary vascular remodeling: hyperproliferation and inflammation. Our aim was to investigate the role of ubiquitin-specific peptidase 8 (USP8) in ObR-b overexpression in PAH. We performed in situ and in vitro experiments in human lung specimens and isolated PA-SMCs combined with 2 different in vivo models in rodents and we generated a mouse with an inducible USP8 deletion specifically in smooth muscles. Our results showed an upregulation of USP8 in the smooth muscle layer of distal pulmonary arteries from patients with PAH, and upregulation of USP8 expression in PAH PA-SMCs, compared to controls. USP8 inhibition in PAH PA-SMCs significantly blocked both ObR-b protein expression level at the cell surface as well as ObR-b-dependant intracellular signaling pathway as shown by a significant decrease in pSTAT3 expression. USP8 was required for ObR-b activation in PA-SMCs and its inhibition prevented Ob-mediated cell proliferation through STAT3 pathway. USP8 inhibition by the chemical inhibitor DUBs-IN-2 protected against the development of experimental PH in the 2 established experimental models of PH. Targeting USP8 specifically in smooth muscle cells in a transgenic mouse model also protected against the development of experimental PH. Our findings highlight the role of USP8 in ObR-b overexpression and pulmonary vascular remodeling in PAH.

Study of the Relationship between Pulmonary Artery Pressure and Heart Valve Vibration Sound Based on Mock Loop.

The vibration of the heart valves' closure is an important component of the heart sound and contains important information about the mechanical activity of a heart. Stenosis of the distal pulmonary artery can lead to pulmonary hypertension (PH). Therefore, in this paper, the relationship between the vibration sound of heart valves and the pulmonary artery blood pressure was investigated to contribute to the noninvasive detection of PH. In this paper, a lumped parameter circuit platform of pulmonary circulation was first set to guide the establishment of a mock loop of circulation. By adjusting the distal vascular resistance of the pulmonary artery, six different pulmonary arterial pressure states were achieved. In the experiment, pulmonary artery blood pressure, right ventricular blood pressure, and the vibration sound of the pulmonary valve and tricuspid valve were measured synchronously. Features of the time domain and frequency domain of two valves' vibration sound were extracted. By conducting a significance analysis of the inter-group features, it was found that the amplitude, energy and frequency features of vibration sounds changed significantly. Finally, the continuously varied pulmonary arterial blood pressure and valves' vibration sound were obtained by continuously adjusting the resistance of the distal pulmonary artery. A backward propagation neural network and deep learning model were used, respectively, to estimate the features of pulmonary arterial blood pressure, pulmonary artery systolic blood pressure, the maximum rising rate of pulmonary artery blood pressure and the maximum falling rate of pulmonary artery blood pressure by the vibration sound of the pulmonary and tricuspid valves. The results showed that the pulmonary artery pressure parameters can be well estimated by valve vibration sounds.

Microenvironmental regulation of T-cells in pulmonary hypertension.

In pulmonary hypertension (PH), pulmonary arterial remodeling is often accompanied by perivascular inflammation. The inflammation is characterized by the accumulation of activated macrophages and lymphocytes within the adventitial stroma, which is comprised primarily of fibroblasts. The well-known ability of fibroblasts to secrete interleukins and chemokines has previously been implicated as contributing to this tissue-specific inflammation in PH vessels. We were interested if pulmonary fibroblasts from PH arteries contribute to microenvironmental changes that could activate and polarize T-cells in PH. We used single-cell RNA sequencing of intact bovine distal pulmonary arteries (dPAs) from PH and control animals and flow cytometry, mRNA expression analysis, and respirometry analysis of blood-derived bovine/human T-cells exposed to conditioned media obtained from pulmonary fibroblasts of PH/control animals and IPAH/control patients (CM-(h)PH Fibs vs CM-(h)CO Fibs). Single-cell RNA sequencing of intact bovine dPAs from PH and control animals revealed a pro-inflammatory phenotype of CD4+ T-cells and simultaneous absence of regulatory T-cells (FoxP3+ Tregs). By exposing T-cells to CM-(h)PH Fibs we stimulated their proinflammatory differentiation documented by increased IFNγ and decreased IL4, IL10, and TGFβ mRNA and protein expression. Interestingly, we demonstrated a reduction in the number of suppressive T-cell subsets, i.e., human/bovine Tregs and bovine γδ T-cells treated with CM-(h)PH-Fibs. We also noted inhibition of anti-inflammatory cytokine expression (IL10, TGFβ, IL4). Pro-inflammatory polarization of bovine T-cells exposed to CM-PH Fibs correlated with metabolic shift to glycolysis and lactate production with increased prooxidant intracellular status as well as increased proliferation of T-cells. To determine whether metabolic reprogramming of PH-Fibs was directly contributing to the effects of PH-Fibs conditioned media on T-cell polarization, we treated PH-Fibs with the HDAC inhibitor SAHA, which was previously shown to normalize metabolic status and examined the effects of the conditioned media. We observed significant suppression of inflammatory polarization associated with decreased T-cell proliferation and recovery of mitochondrial energy metabolism. This study demonstrates how the pulmonary fibroblast-derived microenvironment can activate and differentiate T-cells to trigger local inflammation, which is part of the vascular wall remodeling process in PH.

MANAGEMENT OF PULMONAL HYPERTENSION IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Chronic obstructive pulmonary disease (COPD) is an obstructive pulmonary disease due to inflammatory processes of the respiratory tract and lung parenchyma. In some cases of COPD, changes in the pulmonary vessels are found which are not uncommon, causing impaired gas exchange and causing pulmonary hypertension which is associated with increased morbidity and mortality. Pulmonary hypertension is an increase in the mean pulmonary artery pressure (Pulmonary Arterial Pressure) greater than or equal to 25 mmHg at rest as assessed by a right heart catheterization procedure. Pulmonary hypertension (HP) can exacerbate the occurrence of COPD where HP patients with COPD must receive optimal COPD management according to GOLD guidelines. Pulmonary hypertension can be caused by a variety of conditions which WHO divides into five major groups. Pulmonary hypertension in patients with COPD belongs to the third group. The pathophysiology of pulmonary hypertension in patients with hypoxia or chronic lung disease is caused by tunica media hypertrophy and tunica intima proliferation leading to distal pulmonary artery obstruction. Clinical and physical symptoms in HP patients in COPD usually overlap. If HP is suspected, echocardiography is the best initial examination. Definitive diagnosis obtained through right heart catheterization. In contrast to idiopathic pulmonary hypertension, examination of the vasoreactivity of blood vessels during right heart catheterization in this group is not recommended. The goal of therapy is improvement of clinical symptoms, hemodynamic status, right ventricular function and ultimately increase in quality of life and life expectancy. Oxygen therapy is the main therapy in HP and COPD after medical therapy. Providing adequate therapy for HP with COPD is expected to provide good outcomes for patients.

Contribution of TRPC channels in human and experimental pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is due to progressive distal pulmonary artery (PA) obstruction leading to right ventricular hypertrophy and failure. Exacerbated store-operated Ca2+ entry (SOCE) contributes to PAH pathogenesis, mediating human PA smooth muscle cells (hPASMCs) abnormalities. The transient receptor potential canonical channels (TRPC family) are Ca2+-permeable channels contributing to SOCE in different cell types, including PASMCs. However, the properties, signaling pathways, and contribution to Ca2+ signaling of each TRPC isoform are unclear in human PAH. We studied in vitro the impact of TRPC knockdown on control and PAH-hPASMCs function. In vivo, we analyzed the consequences of pharmacological TRPC inhibition using the experimental model of pulmonary hypertension (PH) induced by monocrotaline (MCT)-exposure. Compared to control-hPASMCs cells, in PAH-hPASMCs, we found a decreased TRPC4 expression, overexpression of TRPC3 and TRPC6, and unchanged TRPC1 expression. Using the siRNA strategy, we found that the knockdown of TRPC1-C3-C4-C6 reduced the SOCE and the proliferation rate of PAH-hPASMCs. Only TRPC1 knockdown decreased the migration capacity of PAH-hPASMCs. After PAH-hPASMCs exposure to the apoptosis inducer staurosporine, TRPC1-C3-C4-C6 knockdown increased the percentage of apoptotic cells, suggesting that these channels promote apoptosis resistance. Only TRPC3 function contributed to exacerbated calcineurin activity. In the MCT-PH rats' model, only TRPC3 protein expression was increased in lungs compared to control rats, and in vivo "curative" administration of a TRPC3 inhibitor attenuated PH development in rats. These results suggest that TRPC channels contribute to PAH-hPASMCs dysfunctions, including SOCE, proliferation, migration, apoptosis resistance, and could be considered as therapeutic targets in PAH.

Quantitative Proteomic and Phosphoproteomic Profiling of Lung Tissues from Pulmonary Arterial Hypertension Rat Model.

Pulmonary arterial hypertension (PAH) is a rare but fatal disease characterized by elevated pulmonary vascular resistance and increased pressure in the distal pulmonary arteries. Systematic analysis of the proteins and pathways involved in the progression of PAH is crucial for understanding the underlying molecular mechanism. In this study, we performed tandem mass tags (TMT)-based relative quantitative proteomic profiling of lung tissues from rats treated with monocrotaline (MCT) for 1, 2, 3 and 4 weeks. A total of 6759 proteins were quantified, among which 2660 proteins exhibited significant changes (p-value < 0.05, fold change < 0.83 or >1.2). Notably, these changes included several known PAH-related proteins, such as Retnla (resistin-like alpha) and arginase-1. Furthermore, the expression of potential PAH-related proteins, including Aurora kinase B and Cyclin-A2, was verified via Western blot analysis. In addition, we performed quantitative phosphoproteomic analysis on the lungs from MCT-induced PAH rats and identified 1412 upregulated phosphopeptides and 390 downregulated phosphopeptides. Pathway enrichment analysis revealed significant involvement of pathways such as complement and coagulation cascades and the signaling pathway of vascular smooth muscle contraction. Overall, this comprehensive analysis of proteins and phosphoproteins involved in the development and progression of PAH in lung tissues provides valuable insights for the development of potential diagnostic and treatment targets for PAH.

The Right Time for Certification

The Right Time for Certification

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

Percutaneous approach to residual pulmonary bifurcation stenosis in conotruncal diseases.

Residual stenosis after right ventricle outflow tract surgery represents a major issue to manage in the children and adult patient with conotruncal defects. Despite a detailed multimodality imaging, the anatomy of distal pulmonary trunk and pulmonary artery bifurcation may be challenging in these patients.The aim of this study was to analyse retrospectively the outcome of the percutaneous transcatheter treatment in children with post-surgical stenosis of pulmonary artery bifurcation.We enrolled 39 patients with a median age of 6.0 years. Standard high-pressure balloon dilation was attempted in 33 patients, effective in 5 of them. Pulmonary branch stenting was performed in 10 patients, effective in 6. A kissing balloon approach was chosen in 17 patients (6 after angioplasty or stenting failure), and this technique was effective in 16 cases. Finally, a bifurcation stenting was performed in 10 patients (second step in 9 cases), effective in all the cases. None of the patients approached by kissing balloon needed a bifurcation stenting.In conclusion, standard balloon angioplasty and standard stenting might be ineffective in post-surgical stenosis involving pulmonary artery bifurcation. In this population, kissing balloon or bifurcation stenting, followed by side branch de-jailing, may be more effective in relieving the gradient.

Antiproliferative effect of selexipag active metabolite MRE-269 on pulmonary arterial smooth muscle cells from patients with chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a group 4 pulmonary hypertension (PH) characterized by nonresolving thromboembolism in the central pulmonary artery and vascular occlusion in the proximal and distal pulmonary artery. Medical therapy is chosen for patients who are ineligible for pulmonary endarterectomy or balloon pulmonary angioplasty or who have symptomatic residual PH after surgery or intervention. Selexipag, an oral prostacyclin receptor agonist and potent vasodilator, was approved for CTEPH in Japan in 2021. To evaluate the pharmacological effect of selexipag on vascular occlusion in CTEPH, we examined how its active metabolite MRE-269 affects platelet-derived growth factor-stimulated pulmonary arterial smooth muscle cells (PASMCs) from CTEPH patients. MRE-269 showed a more potent antiproliferative effect on PASMCs from CTEPH patients than on those from normal subjects. DNA-binding protein inhibitor (ID) genes ID1 and ID3 were found by RNA sequencing and real-time quantitative polymerase chain reaction to be expressed at lower levels in PASMCs from CTEPH patients than in those from normal subjects and were upregulated by MRE-269 treatment. ID1 and ID3 upregulation by MRE-269 was blocked by co-incubation with a prostacyclin receptor antagonist, and ID1 knockdown by small interfering RNA transfection attenuated the antiproliferative effect of MRE-269. ID signaling may be involved in the antiproliferative effect of MRE-269 on PASMCs. This is the first study to demonstrate the pharmacological effects on PASMCs from CTEPH patients of a drug approved for the treatment of CTEPH. Both the vasodilatory and the antiproliferative effect of MRE-269 may contribute to the efficacy of selexipag in CTEPH.

(975) A Case of Diffuse Distal Congenital Pulmonary Artery Hypoplasia Successfully Treated with Pulmonary Artery Stenting

(975) A Case of Diffuse Distal Congenital Pulmonary Artery Hypoplasia Successfully Treated with Pulmonary Artery Stenting

Acute oxygen sensing by vascular smooth muscle cells.

An adequate supply of oxygen (O2) is essential for most life forms on earth, making the delivery of appropriate levels of O2 to tissues a fundamental physiological challenge. When O2 levels in the alveoli and/or blood are low, compensatory adaptive reflexes are produced that increase the uptake of O2 and its distribution to tissues within a few seconds. This paper analyzes the most important acute vasomotor responses to lack of O2 (hypoxia): hypoxic pulmonary vasoconstriction (HPV) and hypoxic vasodilation (HVD). HPV affects distal pulmonary (resistance) arteries, with its homeostatic role being to divert blood to well ventilated alveoli to thereby optimize the ventilation/perfusion ratio. HVD is produced in most systemic arteries, in particular in the skeletal muscle, coronary, and cerebral circulations, to increase blood supply to poorly oxygenated tissues. Although vasomotor responses to hypoxia are modulated by endothelial factors and autonomic innervation, it is well established that arterial smooth muscle cells contain an acute O2 sensing system capable of detecting changes in O2 tension and to signal membrane ion channels, which in turn regulate cytosolic Ca2+ levels and myocyte contraction. Here, we summarize current knowledge on the nature of O2 sensing and signaling systems underlying acute vasomotor responses to hypoxia. We also discuss similarities and differences existing in O2 sensors and effectors in the various arterial territories.

Distal vessel pulmonary thromboendarterectomy: Results from a single institution

Chronic thromboembolic pulmonary hypertension (CTEPH) is primarily managed by pulmonary thromboendarterectomy (PTE). As advanced surgical techniques permit resection at the segmental and subsegmental level, PTE can now be curative for CTEPH mostly involving the distal pulmonary arteries. Between January 2017 and June 2021, consecutive patients undergoing PTE were categorized according to the most proximal level of chronic thrombus resection: Level I (main pulmonary artery), Level II (lobar), Level III (segmental) and Level IV (subsegmental). Proximal disease patients (any Level I or II) were compared to distal disease (Level III or IV bilaterally) patients. Demographics, medical history, preoperative pulmonary hemodynamics, and immediate postoperative outcomes were obtained for each group. During the study period, 794 patients underwent PTE, 563 with proximal disease and 231 with distal disease. Patients with distal disease more frequently had a history of an indwelling intravenous device, splenectomy, upper extremity thrombosis or use thyroid replacement and less often had prior lower extremity thrombosis or hypercoagulable state. Despite more use of PAH-targeted medications in the distal disease group (63.2% vs 50.1%, p < 0.001), preoperative hemodynamics were similar. Both patient groups exhibited significant improvements in pulmonary hemodynamics postoperatively with comparable in-hospital mortality rates. Compared to proximal disease, a lower percentage of patients with distal disease showed residual pulmonary hypertension (3.1% vs 6.9%, p=0.039) and airway hemorrhage (3.0% vs 6.6%, p=0.047) postoperatively. Thromboendarterectomy for distal (segmental and subsegmental) CTEPH is technically feasible and may result in favorable pulmonary hemodynamic outcomes, without increased mortality or morbidity.

Microvascular lung vessels obstructive thromboinflammatory syndrome in patients with COVID-19: Insights from lung intravascular optical coherence tomography.

Microvascular lung vessels obstructive thromboinflammatory syndrome has been proposed as a possible mechanism of respiratory failure in COVID-19 patients. However, it has only been observed in post-mortem studies and has never been documented in vivo, probably because of a lack of CT scan sensitivity in small pulmonary arteries. The aim of the present study was to assess the safety, tolerability, and diagnostic value of optical coherence tomography (OCT) for the assessment of patients with COVID-19 pneumonia for pulmonary microvascular thromboinflammatory syndrome. The COVID-OCT trial was a multicenter, open-label, prospective, interventional clinical study. Two cohorts of patients were included in the study and underwent pulmonary OCT evaluation. Cohort A consisted of patients with COVID-19 with a negative CT scan for pulmonary thrombosis and elevated thromboinflammatory markers (D-dimer > 10,000 ng/mL or 5,000 < D-dimer < 10,000 ng/mL and one of: C-reactive Protein > 100 mg/dL, IL-6 > 6 pg/mL, or ferritin > 900 ng/L). Cohort B consisted of patients with COVID-19 and a CT scan positive for pulmonary thrombosis. The primary endpoints of the study were: (i) to evaluate the overall safety of OCT investigation in patients with COVID-19 pneumonia, and (ii) to report on the potential value of OCT as a novel diagnostic tool for the diagnosis of microvascular pulmonary thrombosis in COVID-19 patients. A total of 13 patients were enrolled. The mean number of OCT runs performed in each patient was 6.1 ± 2.0, both in ground glass and healthy lung areas, achieving a good evaluation of the distal pulmonary arteries. Overall, OCT runs identified microvascular thrombosis in 8 patients (61.5%): 5 cases of red thrombus, 1 case of white thrombus, and 2 cases of mixed thrombus. In Cohort A, the minimal lumen area was 3.5 ± 4.6 mm2, with stenosis of 60.9 ± 35.9% of the area, and the mean length of thrombus-containing lesions was 5.4 ± 3.0 mm. In Cohort B, the percentage area obstruction was 92.6 ± 2.6, and the mean thrombus-containing lesion length was 14.1 ± 13.9 mm. No peri-procedural complications occurred in any of the 13 patients. OCT appears to be a safe and accurate method of evaluating the distal pulmonary arteries in hospitalized COVID-19 patients. Here, it enabled the first in vivo documentation of distal pulmonary arterial thrombosis in patients with elevated thromboinflammatory markers, even when their CT angiogram was negative for pulmonary thrombosis. ClinicalTrial.gov, identifier NCT04410549.

Dysregulated Smooth Muscle Cell BMPR2-ARRB2 Axis Causes Pulmonary Hypertension.

Mutations in BMPR2 (bone morphogenetic protein receptor 2) are associated with familial and sporadic pulmonary arterial hypertension (PAH). The functional and molecular link between loss of BMPR2 in pulmonary artery smooth muscle cells (PASMC) and PAH pathogenesis warrants further investigation, as most investigations focus on BMPR2 in pulmonary artery endothelial cells. Our goal was to determine whether and how decreased BMPR2 is related to the abnormal phenotype of PASMC in PAH. SMC-specific Bmpr2-/- mice (BKOSMC) were created and compared to controls in room air, after 3 weeks of hypoxia as a second hit, and following 4 weeks of normoxic recovery. Echocardiography, right ventricular systolic pressure, and right ventricular hypertrophy were assessed as indices of pulmonary hypertension. Proliferation, contractility, gene and protein expression of PASMC from BKOSMC mice, human PASMC with BMPR2 reduced by small interference RNA, and PASMC from PAH patients with a BMPR2 mutation were compared to controls, to investigate the phenotype and underlying mechanism. BKOSMC mice showed reduced hypoxia-induced vasoconstriction and persistent pulmonary hypertension following recovery from hypoxia, associated with sustained muscularization of distal pulmonary arteries. PASMC from mutant compared to control mice displayed reduced contractility at baseline and in response to angiotensin II, increased proliferation and apoptosis resistance. Human PASMC with reduced BMPR2 by small interference RNA, and PASMC from PAH patients with a BMPR2 mutation showed a similar phenotype related to upregulation of pERK1/2 (phosphorylated extracellular signal related kinase 1/2)-pP38-pSMAD2/3 mediating elevation in ARRB2 (β-arrestin2), pAKT (phosphorylated protein kinase B) inactivation of GSK3-beta, CTNNB1 (β-catenin) nuclear translocation and reduction in RHOA (Ras homolog family member A) and RAC1 (Ras-related C3 botulinum toxin substrate 1). Decreasing ARRB2 in PASMC with reduced BMPR2 restored normal signaling, reversed impaired contractility and attenuated heightened proliferation and in mice with inducible loss of BMPR2 in SMC, decreasing ARRB2 prevented persistent pulmonary hypertension. Agents that neutralize the elevated ARRB2 resulting from loss of BMPR2 in PASMC could prevent or reverse the aberrant hypocontractile and hyperproliferative phenotype of these cells in PAH.

Reconstruction of a large pulmonary artery aneurysm using a vascular prosthesis

A pulmonary artery aneurysm is a rare, heterogeneous disease for which there are currently no surgical guidelines. We present the case of a symptomatic patient presenting with a large aneurysm of the distal pulmonary trunk and left pulmonary artery. The aneurysm was resected through a full median sternotomy under cardiopulmonary bypass and aortic cross-clamping. The reconstruction was performed using a straight vascular prosthesis to connect the proximal pulmonary trunk to the left pulmonary artery with the lateral reimplantation of the right pulmonary artery. We find this surgical technique to be simple, effective, and reproducible by colleagues encountering similar cases.

Abstract 10904: Integrins Signaling Represents an Exciting Therapeutic Avenue to Counter Vascular Remodeling and Right Ventricular Failure in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by progressive obstruction of pulmonary arteries (PAs), culminating in right ventricular (RV) failure and premature death. Like cancer cells, PA smooth muscle cells (PASMCs) isolated from PAH patients exhibit exaggerated proliferation and resistance to apoptosis in response to extracellular matrix remodeling. Integrins, members of the cell adhesion receptors superfamily, are known to promote cell proliferation, survival, hypertrophic growth and fibrosis, which are key elements contributing to PAs remodeling and RV failure. Therefore, we hypothesized that integrins signaling could promote PAH-PASMC proliferation and resistance to apoptosis contributing to PAs vascular remodeling, and RV maladaptive hypertrophy and fibrosis, leading to RV failure. Using NanoString, we found that members of the fibronectin-binding integrin (FiBI) family were the most abundantly expressed in PASMCs and RV fibroblasts (RVFbs) isolated from PAH patients. By western blot (WB), we showed that FiBIs expression is significantly changed in distal PAs, PASMCs, PA endothelial cells and decompensated RV from PAH patients compared to controls (p&lt;0.05). In vitro , pharmacological inhibition of FiBIs decreases PAH-PASMCs proliferation (WB: PLK1; Ki67 labeling; p&lt;0.05, n=5) and resistance to apoptosis (WB: Survivin; Annexin V labeling; p&lt;0.05, n=5). These effects were associated with a decreased activation of FiBIs downstream signaling, FAK and MAPK pathways. In adult rat cardiomyocytes and human RVFbs, FiBIs inhibition decreases phenylephrine-induced hypertrophy (f-actin labeling; p&lt;0.001) and TGFβ1-induced RVFb activation (WB: αSMA, and Col1; p&lt;0.05). In vivo , in both moncrotaline and sugen/hypoxia rats with established PAH, pharmacological inhibition of FiBIs alone or in combination with macitentan and tadalafil improves hemodynamic (mPAP, CO, TAPSE, RVFAC; p&lt;0.05) and vascular remodeling (EVG; p&lt;0.01). In the PA banding rat model, inhibition of FiBIs attenuates RV failure (CO, TAPSE, RVEDP, RVFAC; p&lt;0.01). Our results suggest that integrins play a key role in the pathophysiology of PAH in both the lungs and the RV. Their inhibition provided significant beneficial effects both in vitro and in vivo .

Abstract 10202: DNA-PKcs: A Novel Therapeutic Target in Pulmonary Arterial Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by vascular obliteration of small pulmonary arteries (PAs), notably due to excessive proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs). Accumulating evidence indicates that PAH-PASMCs have acquired an over-efficient DNA damage response (DDR) ensuring sensing, signaling, and repair of DNA damages, accounting for their enhanced capacity to survive and proliferate under stressful conditions. DNA-dependent protein kinase (DNA-PK) is a pivotal component of the DNA repair machinery which plays an instrumental role in the overall survival and proliferation of cancer cells. Based on similarities between PAH and cancer cells, we thus hypothesized that increased expression of DNA-PK contributes to vascular remodeling in PAH. Methods and Results: Using Western blot (WB) and immunohistochemistry, we found that expression and activity of DNA-PK were increased in PAH-PASMCs (n=6) compared to controls (n=6, p&lt;0.01). Similarly, DNA-PK was significantly up-regulated in distal PAs from PAH animal models (i.e. MCT rats and Su/Hx rats and mice, n=5/group, p&lt;0.01). In vitro, the pharmacological inhibition of DNA-PK using AZD-7648 or Nedisertib attenuates PAH-PASMC proliferation (Ki67 and EdU labeling, MCM2, PLK1, and PNCA by WB; p&lt;0.05) and resistance to apoptosis (AnnexinV labeling, Survivin by WB)(n=5 cell lines; p&lt;0.05). These effects were associated with reduced expression of gH2AX. As assessed by echocardiography and right heart catheterization, treatment with AZD7648 improved pulmonary hemodynamics (RVSP, mPAP, and TPR) and right ventricular function (CO, PAT/PET, TAPSE) in Su/Hx mice with established PAH (n=10/group; all p&lt;0.01). Accordingly, pulmonary vascular remodeling (EVG) and the proportion of PCNA-positive PASMCs were reduced in AZD7648-treated Su/Hx mice when compared to vehicle-treated Su/Hx mice (p&lt;0.001). Conclusions: We showed for the first time that DNA-PK is overexpressed in human and experimental PAH and contributes to the pro-proliferative and anti-apoptotic phenotype of PAH-PASMCs.

Abstract 11687: Diagnosis and Management of High-Risk Pulmonary Embolism in a Term Neonate

Case Presentation: A 5 day old, term infant born to a 39-year-old G1P0 with a history of diet-controlled gestational diabetes mellitus presented with hypernatremic dehydration in the setting of poor feeding. On hospital day 2, the infant suffered a bradycardic cardiac arrest requiring 2 minutes of CPR prior to return of spontaneous circulation. An echocardiogram (Figure 1A) revealed moderately depressed right ventricular (RV) function, elevated RV pressure and a large mobile mass extending from the main pulmonary artery (PA) into the left PA with obstruction of flow. D-dimer was markedly elevated at 2740 ng/mL. A subsequent CT angiogram revealed acute pulmonary emboli in the distal left and right branch PAs (Figure 1B). Additional imaging was obtained and showed dural venous sinus, left portal vein and right cephalic vein thromboses. The infant was managed with a heparin infusion and supportive therapy for the RV dysfunction and pulmonary hypertension including mechanical ventilation, inhaled nitric oxide as well as epinephrine and milrinone infusions. Over the course of two weeks, the infant improved clinically with normalization of RV function. Discussion: Neonatal pulmonary arterial thrombosis is an exceedingly rare phenomenon. The majority of cases described in the literature are associated with either an inherited thrombophilia or with underlying congenital heart disease, which were not found to be present in this case. However, this patient presented with severe dehydration and a history of maternal diabetes, both of which are risk factors for neonatal thrombosis. Fortunately, this patient responded to treatment with anticoagulation alone and did not require more invasive therapies, such as surgical thrombectomy or systemic and catheter-directed thrombolysis. Although rare, neonatal pulmonary arterial thrombosis can occur and delays in recognition and treatment may lead to significant RV dysfunction, morbidity, and even death.

Abstract 9359: Orai1 Inhibitors as Potential Treatments for Pulmonary Arterial Hypertension

Rationale: Pulmonary arterial hypertension (PAH) is characterized by progressive distal pulmonary artery (PA) obstruction, leading to right ventricular hypertrophy and failure. Exacerbated intracellular calcium (Ca 2+ ) signaling contributes to abnormalities in PA smooth muscle cells (PASMCs), including aberrant proliferation, apoptosis resistance, exacerbated migration, and arterial contractility. Store-operated Ca 2+ entry (SOCE) is involved in Ca 2+ homeostasis in PASMCs, but its properties in PAH are unclear. Methods: Using a combination of Ca 2+ imaging, molecular biology, in vitro , ex vivo , and in vivo approaches, we investigated the roles of SOCE channel Orai1 in PA remodeling in PAH, and determined the consequences of pharmacological Orai1 inhibition in vivo using experimental models of pulmonary hypertension (PH). Results: Human PASMCs (hPASMCs) from patients with PAH (PAH-hPASMCs) showed upregulation of SOCE and Orai1 expression, in which ERK1/2, nuclear factor of activated T cells (NFAT), and nuclear factor-kappa B (NFκB) were contributing factors. Using siRNA and two Orai1 inhibitors, we found that Orai1 inhibition reduced SOCE, mitochondrial Ca 2+ entry, aberrant proliferation, apoptosis resistance, migration, and excessive calcineurin activity in PAH-hPASMCs. Orai1 inhibitors reduced agonist-evoked constriction in human PAs. In experimental rat models of PH evoked by chronic-hypoxia or monocrotaline or Sugen/hypoxia, administration of Orai1 inhibitors (BTP2, JPIII, or 5J4) protected against PH. Conclusions: In human PAH and experimental PH, Orai1 expression and activity are increased. Orai1 inhibition normalizes the PAH-hPASMC phenotype and attenuates PH in rat models, suggesting that Orai1 should be considered as a relevant therapeutic target for PAH.