Vasodilation Of Pulmonary Arteries Research Articles

Abstract 257: Unselective Pulmonary Vasodilation is an Important Factor in Sodium Nitroprusside Enhanced Cardiopulmonary Resuscitation Improved Blood Flow

Introduction: Sodium nitroprusside enhanced CPR (SNPeCPR) is a novel CPR method that includes a potent vasodilator, active compression-decompression CPR, an inspiratory impedance threshold device and abdominal binding. SNPeCPR has been shown to improve vital organ flow and functional survival outcomes compared to standard CPR methods in animals. We hypothesize that one of the main effects of SNPeCPR mediated increase in cardiac output during prolonged resuscitation is profound pulmonary artery vasodilation. Methods: After electrically induced VF was left untreated for 3 min, 20 (44-48Kg) pigs were randomized to receive SNPeCPR (10) or standard CPR (10) for a total of 30 min; the first 10 minutes were BLS CPR followed by twenty minutes of ACLS. During ACLS, animals were given IV SNP (1mg bolus) or standard epinephrine (0.5mg) q5 min until ROSC or 45 min total CPR. Shocks were delivered after 30 minutes of CPR at 300J. If ROSC was achieved, animal was monitored until 4-hour endpoint. Ventilations were provided with 10ml/kg at 10/min with a mechanical ventilator. Initially during CPR, room air was used and FiO2 was adjusted q5 minutes to maintain O 2 %saturation &gt 92% based on ABG. Lactic acid was also measured. Aortic, right atrial, and coronary artery pressures and carotid blood flow were recorded continuously. A-a oxygen gradient was measured with standard technique. Results: SNPeCPR animals documented a significantly higher mean CPP, lower lactic acid and 3x higher carotid blood flow over 30 minutes compared to standard CPR as previously documented. A-a oxygen gradient was dramatically increased in the SNPeCPR and coincided with a decreased lactate level (see Figure 1). Discussion: SNPeCPR causes profound pulmonary vasodilation and increases flow through non-ventilated lung areas. Despite that, the overall increase in forward flow leads to higher minute O 2 delivery and improved tissue perfusion. SNPeCPR should be used with 100% oxygen in the first human clinical trial.

ACUTE COR PULMONALE AS THE INITIAL PRESENTATION OF LIMITED SYSTEMIC SCLEROSIS

SESSION TITLE: Medical Student/Resident Pulmonary Vascular Disease 2 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 pm - 02:15 pm INTRODUCTION: Acute Cor pulmonale is a common presentation of severe pulmonary arterial hypertension (PAH). PAH affects up to 12% of patients with systemic sclerosis (SS) and associated with a poor prognosis. We present a case of a patient presenting with acute RV failure from severe pulmonary hypertension secondary to limited SS. CASE PRESENTATION: A 63-year-old African American female presented with worsening dyspnea. Past medical history was significant for COPD, severe pulmonary hypertension (PASP of 86 mmHg on previous echocardiogram), obesity and OSA. On arrival to the hospital, patient was tachypneic to 22 breaths/minute with a blood pressure of 92/70. Her oxygen saturation was noted to be 95% on 6L via nasal cannula. She suffered a syncopal episode while walking to the bathroom after being admitted to the hospital, which prompted a rapid response team to be alerted. Her blood pressure was 70/40 mmHg on arrival of the rapid response team (RRT). Pulmonary artery catheterization (PAC) was performed after point-of-care ultrasound suggested significant RV failure. PAC revealed RA 21mmHg, RV 109/20mmHg, PA 115/31 (mean of 62), PCWP 12 mmHg. TTE was performed revealing normal LV function, EF 60-65%. Abnormal septal motion and flat intraventricular septum consistent with RV overload, with an estimated PASP 103mmHg. While in the ICU, patient had continued hypotension requiring vasopressor support with norepinephrine. She was started on furosemide infusion to achieve diuresis. She was also started on intravenous epoprostenol as a pulmonary arterial vasodilator. Given her persistent hypotension and decreased cardiac output, a milrinone infusion was started as well. Despite these efforts, patient continued to deteriorate. The etiology for her decompensation remained unclear, she was noted to have significant worsening of her PASP on review of her previous echocardiography. She was started on a heparin infusion due to concerns for possible pulmonary embolism causing the acute decompensation. Further workup was pursued to evaluate for possible causes of PAH, given the decreased likelihood that her acute worsening was secondary to her history of OSA & COPD. Anti-centromere titers > 8 were revealed suggesting a diagnosis of limited SS. Unfortunately, patient’s clinical status continued to decline and patient expired. DISCUSSION: Acute cor pulmonale from PAH has an in-hospital mortality of 50% when requiring vasopressor and/or inotropic support. PAH affects up to 12% of patients with systemic sclerosis and is the leading cause of death in this patient population. Currently there are no guidelines on appropriate screening tools to identify patients with limited SS complicated by PAH. CONCLUSIONS: Acute cor pulmonale in the setting of SS portends a poor prognosis with associated 50% mortality. More studies are needed to identify strategies for early identification that will improve outcomes in this population. Reference #1: Chaisson et al. Systemic Sclerosis-Associated Pulmonary Arterial Hypertension. Chest. 2013;144(4):1346-1356. doi:10.1378/chest.12-2396. Reference #2: Jentzer et al. Pulmonary Hypertension in the Intensive Care Unit. J Intensive Care Med. 2016 Jul;31(6):369-85. doi: 10.1177/0885066615583652. DISCLOSURES: No relevant relationships by Navneet Kaur, source=Web Response No relevant relationships by Adnan Khalif, source=Web Response

Endothelial TRPV4 Channel Function is Impaired in Pulmonary Arterial Hypertension

Endothelial dysfunction contributes to the pathogenesis of pulmonary arterial hypertension (PAH) by reducing arterial vasodilation. Endothelium‐dependent vasodilation is an important regulator of pulmonary vascular resistance (PVR) and overall pulmonary arterial pressure (PAP). We recently identified endothelial TRPV4 (transient receptor potential vanilloid 4) channels as important regulators of vasodilation in pulmonary arteries (PAs), and showed that unitary Ca2+ influx events through TRPV4 channels, termed TRPV4 sparklets, activate endothelial nitric oxide synthase (eNOS) to cause vasodilation. Reduced NO bioavailability is a hallmark of endothelial dysfunction in PAH. However, the mechanisms underlying reduced NO bioavailability in PAH are not well understood. We hypothesized that impairment of TRPV4 channel function attenuates NO release in PAH. PAH was induced in mice using three‐week chronic hypoxia (CH) and Sugen 5416 + CH models. Mouse right ventricular pressures (RVP) were measured as an indicator of PAP. RVP was significantly higher in TRPV4−/− mice when compared to the control mice after three weeks of CH. High‐speed Ca2+ imaging was used to analyze TRPV4 sparklets in the native endothelium from resistance‐sized, fourth‐order PAs. Vascular diameter studies were performed on isolated, pressurized (15 mmHg), small PAs. Ca2+ imaging studies were also performed in PAs obtained from control and PAH patients. In CH and Sugen 5416 + CH models, TRPV4 sparklet activity and TRPV4 channel‐dependent vasodilation were significantly lower compared to normoxic control mice. However, TRPV4 mRNA expression and immunofluorescence were not altered in both mouse models of PAH, suggesting an impairment in the regulation of channel function rather than channel expression. TRPV4 sparklet activity was also consistently lower in PAs from PAH patients, when compared to control patients. Elevated levels of superoxide radicals have been shown to contribute to the development of PAH. Superoxides can react with NO to form peroxynitrite (PN). A PN scavenger, uric acid, restored TRPV4 channel activity in CH mice. We, therefore, hypothesized that PN‐induced impairment of TRPV4‐dependent Ca2+ signaling inhibits endothelial function in PAH. Indeed, PN attenuated TRPV4 sparklet activity in a reversible manner. Our results support the concept that PN‐induced regulation of TRPV4‐dependent Ca2+ signaling may contribute to the development of PAH. Moreover, altered TRPV4 channel activity may contribute to the reduced NO bioavailability in PAH.Support or Funding Information1R56HL138496, 5R00HL121484, 17PRE33660762This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Beta Adrenergic Induced Pulmonary Arterial Vasodilation Following Long Term Hypoxia in Fetal and Adult Sheep

Long term high altitude exposure is known to cause tissue hypoxia and exposure of fetuses as well as adults to rarefied environments increases morbidity and mortality. In particular, hypoxia can cause developmental abnormalities in the fetal pulmonary vasculature and contribute to pulmonary arterial hypertension in the adult. β2 adrenergic receptor (β‐AR) agonists are a major treatment for asthma, however far less is known about their role in pulmonary arterial function. Even still, previous evidence illustrates that β‐AR stimulation holds promise for the treatment of pulmonary arterial hypertension. Other evidence illustrates that β‐AR stimulation modulates the activity of Ca2+‐activated K+ channels (KCa), which are important mediators of pulmonary vasorelaxation. Dysregulation of KCa may contribute to chronic hypoxia induced pulmonary hypertension and β‐AR signaling may be involved in the process. In these studies we tested the hypothesis that β‐AR ‐ mediated pulmonary arterial vasodilation may be preserved following long term high altitude hypoxia due to dependency on KCa channels. This hypothesis was addressed in isolated pulmonary arteries from adult or fetal sheep that gestated at 700 meters (normoxic) or 3,801 meters for 110+ days (hypoxic). Myography was performed on pulmonary arterial rings to evaluate the vasorelaxation in response to the β‐AR agonist isoproterenol (ISO) and the methylxanthine phosphodiesterase inhibitor, IBMX. ISO‐mediated relaxation was preserved following hypoxia in fetal sheep and relaxation was greater in arteries from adult hypoxic animals relative to fetuses. Inhibition of BKCa with TEA blunted ISO‐mediated vasorelaxation in fetal normoxic and adult hypoxic arteries. IBMX caused a dose dependent relaxation in arteries from all groups and TEA did not influence this effect. Overall, these studies provide evidence that β‐AR stimulated pathways cause pulmonary arterial vasodilation, but with varying reliance on BKCa activation. Targeting β‐AR signaling pathways could therefore be therapeutically significant and functional alterations in the pathways may contribute to the development of disease.Support or Funding InformationThis material is based upon work supported by NIH HD‐069746, P01HD083132, and P20MD006988. MA and BP were Walter E Macpherson Medical Student Summer Research Fellows while AV was an Undergraduate Summer Research Fellow through the Center for Health Disparities and Molecular Mechanisms at Loma Linda University.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cyclic Nucleotides Reduce Ryanodine Receptor Mediated Ca2+ Spark Activation Independent of Long Term Hypoxia in Ovine Fetal Pulmonary Arterial Myocytes

Ryanodine receptors (RyR) release Ca2+ from smooth muscle sarcoplasmic reticulum in rapid events known as Ca2+ sparks. These Ca2+ sparks activate voltage and Ca2+ gated potassium channels (BK channels) that cause cell repolarization. Ca2+ spark‐BK channel mediated cell repolarization dilates many types of vessels and is essential to pulmonary arterial (PA) vasodilation during the fetal transition to breathing air. Infants who do not successfully negotiate this transition are at risk of developing pulmonary hypertension, which has significant morbidity and mortality. Previous work shows that long term hypoxia (LTH) decreases Ca2+ spark events in fetal pulmonary arterial smooth muscle cells (PASMCs) even though the Ca2+ stores have functional RyRs. Additional studies illustrate that cyclic nucleotides can increase RyR activity, which led us to test the hypothesis that cyclic nucleotides could rescue RyR activity in myocytes of LTH fetuses. This was examined by treating PAs isolated from low (700m; LA) and high altitude (3801m; HA) near‐term fetal sheep with exogenous cyclic AMP (cAMP) and cyclic GMP (cGMP) or the methylxanthine IBMX, a non‐specific cAMP and cGMP phosphodiesterase inhibitor. RyR activity was measured by confocal imaging of Ca2+ sparks in fluo‐4 labeled PASMCs. The spatial and temporal aspects to the Ca2+ sparks were evaluated using SparkLab, a custom software package. Contrary to our hypothesis, the prevalence of Ca2+ sparks decreased in the presence of cAMP, cGMP, and IBMX for PASMC from both LA and HA fetal sheep. These data suggest that cyclic nucleotides reduce instead of increase vasodilatory capacity via RyR‐BK channel coupling mechanisms. Furthermore, increased cyclic nucleotides had no effect on the spatial‐temporal aspects to the Ca2+ sparks. Even though the signaling pathway remains unclear, the reduction of Ca2+ sparks by cyclic nucleotides is potentially a novel mechanism of RyR modulation in sheep fetal PASMC. This data suggests that increasing cyclic nucleotides may be contra‐indicated in newborn infants who are at risk of developing pulmonary hypertension.Support or Funding InformationThis work is supported by The National Institutes of Health, Eunice Kennedy Shriver National Institute of Child Health and Human Development grant number HD083132, by the National Science Foundation under Grant No. MRI 0923559, and the Loma Linda University School of Medicine. SH was a Loma Linda University Summer Undergraduate Research Fellow.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

RIGHT VENTRICULAR MYOCARDIAL INFARCTION IN A PATIENT WITH CHRONIC THROMBOEMBOLIC PULMONARY HYPERTENSION AGAINST THE BACKGROUND OF SMALL CORONARY ARTERIES

Most often acute myocardial infarction of the right ventricle is diagnosed in patients with acute left ventricular lesion and is associated with an atherosclerotic process in the coronary arteries. Isolated acute myocardial infarction of the right ventricle is rarely diagnosed and is often detected only during autopsy. Previously it was believed that in the absence of a significant lesion of the coronary arteries, an acute myocardial infarction of the right ventricle is associated with hypertrophy of the right ventricular myocardium. The results of a study in which acute myocardial infarction of the right ventricle were found in patients who died due to acute massive pulmonary embolism and who did not have right ventricular hypertrophy appeared later. There are many questions regarding the tactics of therapy for this complication, especially in patients with pulmonary hypertension who are on treatment with pulmonary arterial vasodilators. The article describes a rare clinical case of postmortem detection of myocardial infarction of the right ventricle against the background of small coronary arteries in a 41-year-old patient with a diagnosis of chronic thromboembolic pulmonary hypertension, the difficulties of intravital diagnosis and the restriction of drug therapy.

Diminished Cardiac Performance and Left Ventricular Dimensions in Neonates with Congenital Diaphragmatic Hernia.

Newborns with congenital diaphragmatic hernia (CDH) have varying degrees of pulmonary hypoplasia and pulmonary hypertension (PH), and there is limited evidence that cardiac dysfunction is present. We sought to study early neonatal biventricular function and performance in these patients by reviewing early post-natal echocardiography (ECHO) measurements and comparing them to normal term newborns. Retrospective case-control study reviewing clinical and ECHO data on term newborns with CDH and normal controls born between 2009 and 2016. Patients were excluded if major anomalies, genetic syndromes, or no ECHO available. PH was assessed by ductal shunting and tricuspid regurgitant jet velocity. Speckle-tracking echocardiography was used to assess myocardial deformation using velocity vector imaging. Forty-four patients with CDH and 18 age-matched controls were analyzed. Pulmonary pressures were significantly higher in the CDH cohort (systolic pulmonary arterial pressure to systolic blood pressure of 103 ± 13 vs. 78 ± 29%, p = 0.0001). CDH patients had decreased RV fractional area change (FAC - 28.6 ± 11.1 vs. 36.2 ± 9.6%, p = 0.02), tricuspid annular plane of systolic excursion (TAPSE-5.6 ± 1.6 vs. 8.6 ± 1.6mm, p = 0.0001), and RV outflow tract stroke distance (8.6 ± 2.7 vs. 14.0 ± 4.5cm, p = 0.0001) compared with controls. The left ventricular (LV) ejection fraction was similar in both groups, but CDH patients had a decreased LV end-diastolic volume by Simpson's rule (2.7 ± 1.0 vs. 5.0 ± 1.8mL, p = 0.0001) and LVOT stroke distance (9.7 ± 3.4 vs. 12.6 ± 3.6cm, p = 0.004). Biventricular global longitudinal strain (GLS) was markedly decreased in the CDH population compared to controls (RV-GLS: - 9.0 ± 5.3 vs. - 19.5 ± 1.4%, p = 0.0001; LV GLS: - 13.2 ± 5.8 vs. - 20.8 ± 3.5%, p = 0.0001). CDH newborns have evidence of biventricular dysfunction and decreased cardiac output. Abnormal function may be a factor in the non-response to pulmonary arterial vasodilators in CDH patients. A two-pronged management strategy aimed at improving cardiac function, as well as reducing pulmonary artery pressure in CDH newborns, may be warranted.

Tissue-Resident TSP1-CD47 Signaling Promotes Sickle Cell-Associated Arterial Vasculopathy and Pulmonary Hypertension

Pulmonary hypertension (PH) is a chronic pulmonary complication of sickle cell disease (SCD) and a leading cause of death in adults. The exact molecular causes of SCD-associated PH are unknown although pathologic hemolysis related to chronic nitric oxide depletion and oxidative stress are recognized as contributing factors. We have reported that the protein thrombospondin-1 (TSP1) is elevated in the plasma of patients with SCD and by interacting with its receptor CD47 limits vasodilation of distal pulmonary arteries ex vivo . We hypothesized that the TSP1-CD47 interaction may promote PH in the BERK sickle mouse model. To test this hypothesis, we inquired whether TSP1 and CD47 are upregulated in the lungs of BERK mice and patients with SCD-associated PH. We found that lungs of age matched male 13-14 months old BERK sickle mice overexpressed TSP1 and CD47 as compared to both C57BL/6J and Hemi BERK mice and also confirmed our prior findings that sickle mice develop PH as they age. Immunohistochemistry of lung sections from 6 patients with SCD-associated PH revealed increased levels of CD47 as compared to sections from patients without PH or overt lung disease. We interrogated the TSP1-CD47 axis in vivo by generating chimeric animals with a sickle erythropoiesis on a CD47KO background by transplanting BERK sickle bone marrow into C57BL/6J (n=24) and CD47 knockout (CD47KO, n=27) mice. Fully engrafted chimeric mice underwent pulmonary hemodynamic assessment after 6 months. Right ventricular (RV) pressures were lower in Sickle-to-CD47KO chimeras as compared to Sickle-to-C57BL/6J chimeras as shown by the reduced maximum pressure of the RV (22.1 ± 3.6 vs. 28.1 ± 8.8 mmHg, p=0.013) and mean pulmonary artery pressure (15.3 ± 2.6 vs. 18.8 ± 5.7 mmHg, p=0.020). The afterload of the Sickle-to-CD47KO chimeras was lower compared to Sickle-to-C57BL/6J chimeras as shown by the diminished pulmonary vascular resistance (1.2 ± 0.7 vs. 2.4 ± 2.2 Wood units, p=0.024) and RV effective arterial elastance (1.5 ± 0.9 vs. 2.7 ± 2.6 mmHg/µL, p=0.052). The RV diastolic function as measured by the RV dP/dtmin also showed a trend towards improvement as compared to Sickle-to-C57BL/6J chimeras (-1297.0 ± 318.2 vs. -1604.0 ± 668.2 mmHg/s, p=0.059). Finally, the Sickle-to-CD47KO chimeras had a tendency for less RV hypertrophy as evidenced by lower RV free wall weight as compared to Sickle-to-C57BL/6J chimeras (21.45 ± 5.0 vs. 24.63 ± 6.0 mg, p=0.056). Interestingly, plasma levels of soluble TSP1 were reduced in Sickle-to-CD47KO chimeras (61.45 ± 10.11 vs. 76.89 ± 10.84 pg/mL, p=0.012). On myography, aortic segments from Sickle-to-CD47KO chimeras had improved relaxation to the endothelial activator acetylcholine. We hypothesized that in SCD TSP1-CD47 signaling promotes PH, in part, by increasing ROS generation. Treatment with exogenous TSP1 (2.2x10-9 M, a concentration found in the plasma of SCD patients) stimulated increased levels of superoxide and hydrogen peroxide in human pulmonary artery endothelial cells by cytochrome C and Amplex Red assays, respectively. Furthermore, lungs of CD47KO chimeras had decreased oxidative damage as measured by reduced 4-hydroxynonenal and 3-nitrotyrosine staining vs. Sickle-to-C57BL/6J chimeras. Finally, suppression of CD47 with a morpholino (10 mg/kg body weight i.p. weekly) for 8 weeks (n=8 animals) also reduced pulmonary pressures in BERK mice. Our results show that genetic deletion or suppression of CD47 ameliorates SCD-associated PH, which may be due, in part, to decreased ROS levels. Targeting TSP1-CD47 may provide a new molecular approach to the treatment of SCD-associated PH. DisclosuresIsenberg:Tioma Therapeutics: Equity Ownership; Radiation Control Technologies, Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Nitric Oxide-Dependent Feedback Loop Regulates Transient Receptor Potential Vanilloid 4 (TRPV4) Channel Cooperativity and Endothelial Function in Small Pulmonary Arteries.

BackgroundRecent studies demonstrate that spatially restricted, local Ca2+ signals are key regulators of endothelium‐dependent vasodilation in systemic circulation. There are drastic functional differences between pulmonary arteries (PAs) and systemic arteries, but the local Ca2+ signals that control endothelium‐dependent vasodilation of PAs are not known. Localized, unitary Ca2+ influx events through transient receptor potential vanilloid 4 (TRPV4) channels, termed TRPV4 sparklets, regulate endothelium‐dependent vasodilation in resistance‐sized mesenteric arteries via activation of Ca2+‐dependent K+ channels. The objective of this study was to determine the unique functional roles, signaling targets, and endogenous regulators of TRPV4 sparklets in resistance‐sized PAs.Methods and ResultsUsing confocal imaging, custom image analysis, and pressure myography in fourth‐order PAs in conjunction with knockout mouse models, we report a novel Ca2+ signaling mechanism that regulates endothelium‐dependent vasodilation in resistance‐sized PAs. TRPV4 sparklets exhibit distinct spatial localization in PAs when compared with mesenteric arteries, and preferentially activate endothelial nitric oxide synthase (eNOS). Nitric oxide released by TRPV4‐endothelial nitric oxide synthase signaling not only promotes vasodilation, but also initiates a guanylyl cyclase‐protein kinase G‐dependent negative feedback loop that inhibits cooperative openings of TRPV4 channels, thus limiting sparklet activity. Moreover, we discovered that adenosine triphosphate dilates PAs through a P2 purinergic receptor‐dependent activation of TRPV4 sparklets.ConclusionsOur results reveal a spatially distinct TRPV4‐endothelial nitric oxide synthase signaling mechanism and its novel endogenous regulators in resistance‐sized PAs.

Computational simulation of postoperative pulmonary flow distribution in Alagille patients with peripheral pulmonary artery stenosis.

Up to 90% of individuals with Alagille syndrome have congenital heart diseases. Peripheral pulmonary artery stenosis (PPS), resulting in right ventricular hypertension and pulmonary flow disparity, is one of the most common abnormalities, yet the hemodynamic effects are ill-defined, and optimal patient management and treatment strategies are not well established. The purpose of this pilot study is to use recently refined computational simulation in the setting of multiple surgical strategies, to examine the influence of pulmonary artery reconstruction on hemodynamics in this population. Based on computed tomography angiography and cardiac catheterization data, preoperative pulmonary artery models were constructed for 4 patients with Alagille syndrome with PPS (all male, age range: 0.6-2.9 years), and flow simulations with deformable walls were performed. Surgeon directed virtual surgery, mimicking the surgical procedure, was then performed to derive postoperative models. Postoperative simulation-derived hemodynamics and blood flow distribution were then compared with the clinical results. Simulations confirmed substantial resistance, resulting from preoperative severe ostial stenoses, and the use of newly developed adaptive outflow boundary conditions led to excellent agreement with in vivo measurements. Relief of PPS decreased pulmonary artery pressures and improved pulmonary flow distribution both in vivo and in silico with good correlation. Using adaptive outflow boundary conditions, computational simulations can estimate postoperative overall pulmonary flow distribution in patients with Alagille syndrome after pulmonary artery reconstruction. Obstruction relief along with pulmonary artery vasodilation determines postoperative pulmonary flow distribution and newer methods can incorporate these physiologic changes. Evolving blood flow simulations may be useful in surgical or transcatheter planning and in understanding the complex interplay among various obstructions in patients with peripheral pulmonary stenosis.

Sex differences in pulmonary vascular control: focus on the nitric oxide pathway.

Although the incidence of pulmonary hypertension is higher in females, the severity and prognosis of pulmonary vascular disease in both neonates and adults have been shown to be worse in male subjects. Studies of sex differences in pulmonary hypertension have mainly focused on the role of sex hormones. However, the contribution of sex differences in terms of vascular signaling pathways regulating pulmonary vascular function remains incompletely understood. Consequently, we investigated pulmonary vascular function of male and female swine in vivo, both at rest and during exercise, and in isolated small pulmonary arteries in vitro, with a particular focus on the NO‐cGMP‐PDE5 pathway. Pulmonary hemodynamics at rest and during exercise were virtually identical in male and female swine. Moreover, NO synthase inhibition resulted in a similar degree of pulmonary vasoconstriction in male and female swine. However, NO synthase inhibition blunted bradykinin‐induced vasodilation in pulmonary small arteries to a greater extent in male than in female swine. PDE5 inhibition resulted in a similar degree of vasodilation in male and female swine at rest, while during exercise there was a trend towards a larger effect in male swine. In small pulmonary arteries, PDE5 inhibition failed to augment bradykinin‐induced vasodilation in either sex. Finally, in the presence of NO synthase inhibition, the pulmonary vasodilator effect of PDE5 inhibition was significantly larger in female swine both in vivo and in vitro. In conclusion, the present study demonstrated significant sex differences in the regulation of pulmonary vascular tone, which may contribute to understanding sex differences in incidence, treatment response, and prognosis of pulmonary vascular disease.

Evidence Supporting the Existence of a Distinct Obese Phenotype of Heart Failure With Preserved Ejection Fraction.

Heart failure (HF) with preserved ejection fraction (HFpEF) is a heterogeneous syndrome. Phenotyping patients into pathophysiologically homogeneous groups may enable better targeting of treatment. Obesity is common in HFpEF and has many cardiovascular effects, suggesting that it may be a viable candidate for phenotyping. We compared cardiovascular structure, function, and reserve capacity in subjects with obese HFpEF, those with nonobese HFpEF, and control subjects. Subjects with obese HFpEF (body mass index ≥35 kg/m2; n=99), nonobese HFpEF (body mass index <30 kg/m2; n=96), and nonobese control subjects free of HF (n=71) underwent detailed clinical assessment, echocardiography, and invasive hemodynamic exercise testing. Compared with both subjects with nonobese HFpEF and control subjects, subjects with obese HFpEF displayed increased plasma volume (3907 mL [3563-4333 mL] versus 2772 mL [2555-3133 mL], and 2680 mL [2380-3006 mL]; P<0.0001), more concentric left ventricular remodeling, greater right ventricular dilatation (base, 34±7 versus 31±6 and 30±6 mm, P=0.0005; length, 66±7 versus 61±7 and 61±7 mm, P<0.0001), more right ventricular dysfunction, increased epicardial fat thickness (10±2 versus 7±2 and 6±2 mm; P<0.0001), and greater total epicardial heart volume (945 mL [831-1105 mL] versus 797 mL [643-979 mL] and 632 mL [517-768 mL]; P<0.0001), despite lower N-terminal pro-B-type natriuretic peptide levels. Pulmonary capillary wedge pressure was correlated with body mass and plasma volume in obese HFpEF (r=0.22 and 0.27, both P<0.05) but not in nonobese HFpEF (P≥0.3). The increase in heart volumes in obese HFpEF was associated with greater pericardial restraint and heightened ventricular interdependence, reflected by increased ratio of right- to left-sided heart filling pressures (0.64±0.17 versus 0.56±0.19 and 0.53±0.20; P=0.0004), higher pulmonary venous pressure relative to left ventricular transmural pressure, and greater left ventricular eccentricity index (1.10±0.19 versus 0.99±0.06 and 0.97±0.12; P<0.0001). Interdependence was enhanced as pulmonary artery pressure load increased (P for interaction <0.05). Compared with those with nonobese HFpEF and control subjects, obese patients with HFpEF displayed worse exercise capacity (peak oxygen consumption, 7.7±2.3 versus 10.0±3.4 and12.9±4.0 mL/min·kg; P<0.0001), higher biventricular filling pressures with exercise, and depressed pulmonary artery vasodilator reserve. Obesity-related HFpEF is a genuine form of cardiac failure and a clinically relevant phenotype that may require specific treatments.

Nitric Oxide Inhibits Functional Coupling Among Endothelial TRPV4 Channels and Limits Vasodilation in Small Pulmonary Arteries

Vasodilatory function of endothelial cells (ECs) is regulated by localized increases in intracellular Ca2+. TRPV4 (transient receptor potential vanilloid 4) channels on the EC membrane are a major Ca2+ influx pathway in the systemic and pulmonary endothelium, and a key determinant of endothelial vasodilations to physiological stimuli. We recently showed that localized, unitary Ca2+ influx events through TRPV4 channels (TRPV4 Ca2+ sparklets) on the EC membranes dilate resistance‐sized pulmonary arteries (PAs) through selective activation of endothelial nitric oxide synthase (eNOS) (Marziano et al., FASEB J, 2016) and NO release. Studies in the expression system have shown that NO can modify the activity of TRPV4 channels. Based on the predominant role for NO in TRPV4‐dependent vasodilations in the PAs, we hypothesized that NO released by TRPV4‐eNOS activation alters TRPV4 channel function in the native PA endothelium, exerting a finer control over TRPV4‐mediated vasodilations. In en face 4th order PAs loaded with Fluo‐4, NOS inhibitor (L‐NG‐Nitroarginine or L‐NNA; 100 μM) produced a 2‐fold increase in TRPV4 sparklet activity, whereas a NO donor (Spermine NONOate or NONOate; 30 μM) inhibited TRPV4 sparklet activity by ~70%, confirming NO‐inhibition of TRPV4 sparklet activity. Inhibitors of S‐nitrosylation did not alter the effect of NO on TRPV4 channel activity ruling out a role for S‐nitrosylation in NO‐inhibition of the channel. However, guanylyl cyclase (GC) and protein kinase G (PKG) inhibitors (ODQ; 3 μM and Rp‐8‐Br‐PET‐cGMPS or PET; 30 μM, respectively) caused a 2‐fold increase in TRPV4 sparklet activity, and abolished the effect of NONOate on TRPV4 sparklets. Concurrently, cannulated and pressurized 4th order PAs showed a significantly higher dilation to the specific TRPV4 channel activator GSK1016790A (3–30 nM) in the presence of ODQ when compared to control arteries. These results revealed the negative feedback inhibition of TRPV4 activity and vasodilations by NO‐GC‐PKG signaling in PAs. Recent studies demonstrate that cooperative openings of TRPV4 channels at an individual sparklet site determine Ca2+ influx through the channels, and are dependent on Ca2+‐potentiation of the channel (Sonkusare et al., Sci Signal., 2014). To determine whether PKG altered TRPV4 channel cooperativity we used a coupled Markov chain model to examine the coupling strength/cooperativity among TRPV4 channels at individual sparklet sites. Whereas L‐NNA stimulated the coupling among TRPV4 channels, NONOate reduced the coupling. Moreover, both PET and ODQ increased the coupling strength and inhibited the effect of NONOate. Chelating local Ca2+ with membrane permeable EGTA‐AM (5 μM) also inhibited the effect of NONOate on sparklet activity, indicating that NO‐GC‐PKG activation disrupted Ca2+‐dependent cooperativity among TRPV4 channels. Together these data reveal a novel NO‐dependent regulatory mechanism that mediates and limits TRPV4‐vasodilations in PAs. Perturbations in the endothelial GC‐PKG dependent negative‐feedback mechanism can be particularly important in pulmonary disorders including pulmonary hypertension, pulmonary edema and lung injury that are associated with endothelial dysfunction.Support or Funding InformationThis study was supported by a grant from NIH (HL121484‐01) to S.K.S and (4T32HL007284‐40) to C.M.

Retrospective evaluation of pimobendan and sildenafil therapy for severe pulmonary hypertension due to lung disease and hypoxia in 28 dogs (2007-2013).

Pulmonary hypertension (PH) is the persistent abnormal increase in pulmonary artery (PA) pressure and in dogs is usually secondary to congenital disease causing pulmonary over circulation, chronic respiratory disease and elevated left atrial pressure. Sildenafil (SF) is a phosphodiesterase (PDE) V inhibitor that causes pulmonary artery (PA) vasodilation by increasing pulmonary vascular concentrations of cyclic guanosine monophosphate which subsequently increases the activity of endogenous nitric oxide. Pimobendan (PB) is a PDE III inhibitor with calcium sensitizing effects thereby exerting positive inotropy and vasodilation. The purpose of this retrospective study was to evaluate the long‐term survival of dogs with severe PH treated with SF and PB compared to SF alone. The use of PB in combination with SF did not result in a statistically significant increase in survival times in dogs with pulmonary hypertension secondary to chronic respiratory disease compared to SF alone.

&amp;lt;i&amp;gt;In Vitro&amp;lt;/i&amp;gt; Characterisation of Pharmacological Effect of Prostacyclin Analogues in Comparison to Phosphodiesterase Inhibitors on Small Human Pulmonary Vessels

Background and Aim of Study: The phosphodiesterase inhibitors (Sildenafil and Milrinone), Nitric Oxide donor Sodium Nitroprusside (SNP) and prostacyclin analogs are commonly used pulmonary vasodilators to treat pulmonary hypertension. In the past few years, we have used human pulmonary artery rings in vitro to evaluate pulmonary vascular resistance. The main objective of the current study is to document the pharmacological impact of clinically used prostacyclin analogs on the human pulmonary system in parallel with phosphodiesterase inhibitors and SNP. Methods: The study used human pulmonary artery rings of internal diameter of 2 - 4 mm and length of 2 mm. These were extracted from patients with lung resections. These rings were then mounted on a multiwire myograph, and changes in isometric tension were noted. Then, concentration response curves were constructed to Sildenafil (Sd), Milrinone (Mil), Sodium Nitroprusside (SNP), Epoprostenol (Ep), Iloprost (Ip) and Treprostinil (Tp). Results: 52 pulmonary artery rings were used in these experiments. Sildenafil, Milrinone, SNP, Epoprostenol, Iloprost and Treprostinil caused a concentration-dependent vasodilation in small human pulmonary arteries (pEC50: 5.97 ± 0.22, 5.99 ± 0.12, 7.64 ± 0.08, 7.53 ± 0.14, 8.84 ± 0.15 and 9.48 ± 0.13 respectively, n = 8 to 12). The efficacy for the same was in the order: Tp = Ip > Ep > Mil > SNP > Sd. The potency varied in the order: Tp > Ip > SNP > Ep > Mil > Sd. Conclusion: This research showed the efficacy as well as the potency of SNP and phosphodiesterase inhibitors and prostacyclin analogs on the human pulmonary vasculature. Treprostinil and Iloprost exhibited maximum relaxation. However, Sildenafil and SNP showed lesser impact. These effects need to be considered for clinical studies for enhanced patient outcomes.

PP.26.04] THE STATUS OF VASOREACTIVITY AND CYTOKINES LEVELS OF PATIENTS WITH IDIOPATHIC PULMONARY ARTERIAL HYPERTENSION

Objective: to assess serum cytokines levels in patients with idiopathic pulmonary arterial hypertension (IPAH) depending on the result of acute vasoreactivity test (AVT).Design and method: In the study we included 61 IPAH patients (mean age 32,4 ± 3,2 years). Patients were divided into two groups depending on pulmonary artery vasodilator reactivity. In all patients were investigated by serum cytokines levels. Results were compared with control group, 10 healthy volunteers served of control group. Results: In all IPAH patients the levels of IL–1β were not different and were within normal range (p > 0,05) (Table 1). But at one-third of patients the levels of IL–1β were higher than in the control group. In both groups the level of IL-6 TNFα, MIP1α, sVCAM was significantly higher as compared to control levels. A high level of IL-6 evidence about the formation of an noadequate response organism on injury or inflammation. Intensity of inflammation and endothelial dysfunction and their interaction, noting the existence of a significant positive correlation between IL-6 and ET-1 (r = 0,421; p < 0,05). High levels of IL-6 TNFα and MIP1α indicate the presence of inflammation at all stages of development IPAH. IL-8 levels was significantly higher in nonresponder group and pointed to a more pronounced inflammatory reactions sharpness. The differences between the groups of responders and nonresponders confirms a significant correlation between IL-8 and NT-proANP (r = 0,342; p < 0,05), NT-proBNP (r = 0,428; p < 0,05), and NA (r = 0,468; p < 0,05). In all IPAH patients the level of IL-10 was higher than control values. Only in nonresponder group the level of INFγ was lower than in the control group. The marker of vascular injury s ICAM was significantly higher than in the control group and the maximum concentration observed in patients without reserve vasoreactivity. Conclusions: The levels of inflammatory cytokines were significantly increased in the nonresponder group in compare with responder group. The most elevated levels of inflammatory mediator were IL-8 and s ICAM.

The flavonoid quercetin reverses pulmonary hypertension in rats.

Quercetin is a dietary flavonoid which exerts vasodilator, antiplatelet and antiproliferative effects and reduces blood pressure, oxidative status and end-organ damage in humans and animal models of systemic hypertension. We hypothesized that oral quercetin treatment might be protective in a rat model of pulmonary arterial hypertension. Three weeks after injection of monocrotaline, quercetin (10 mg/kg/d per os) or vehicle was administered for 10 days to adult Wistar rats. Quercetin significantly reduced mortality. In surviving animals, quercetin decreased pulmonary arterial pressure, right ventricular hypertrophy and muscularization of small pulmonary arteries. Classic biomarkers of pulmonary arterial hypertension such as the downregulated expression of lung BMPR2, Kv1.5, Kv2.1, upregulated survivin, endothelial dysfunction and hyperresponsiveness to 5-HT were unaffected by quercetin. Quercetin significantly restored the decrease in Kv currents, the upregulation of 5-HT2A receptors and reduced the Akt and S6 phosphorylation. In vitro, quercetin induced pulmonary artery vasodilator effects, inhibited pulmonary artery smooth muscle cell proliferation and induced apoptosis. In conclusion, quercetin is partially protective in this rat model of PAH. It delayed mortality by lowering PAP, RVH and vascular remodeling. Quercetin exerted effective vasodilator effects in isolated PA, inhibited cell proliferation and induced apoptosis in PASMCs. These effects were associated with decreased 5-HT2A receptor expression and Akt and S6 phosphorylation and partially restored Kv currents. Therefore, quercetin could be useful in the treatment of PAH.

Liposomal nanoparticles encapsulating iloprost exhibit enhanced vasodilation in pulmonary arteries.

Prostacyclin analogues are standard therapeutic options for vasoconstrictive diseases, including pulmonary hypertension and Raynaud’s phenomenon. Although effective, these treatment strategies are expensive and have several side effects. To improve drug efficiency, we tested liposomal nanoparticles as carrier systems. In this study, we synthesized liposomal nanoparticles tailored for the prostacyclin analogue iloprost and evaluated their pharmacologic efficacy on mouse intrapulmonary arteries, using a wire myograph. The use of cationic lipids, stearylamine, or 1,2-di-(9Z-octadecenoyl)-3-trimethylammonium-propane (DOTAP) in liposomes promoted iloprost encapsulation to at least 50%. The addition of cholesterol modestly reduced iloprost encapsulation. The liposomal nanoparticle formulations were tested for toxicity and pharmacologic efficacy in vivo and ex vivo, respectively. The liposomes did not affect the viability of human pulmonary artery smooth muscle cells. Compared with an equivalent concentration of free iloprost, four out of the six polymer-coated liposomal formulations exhibited significantly enhanced vasodilation of mouse pulmonary arteries. Iloprost that was encapsulated in liposomes containing the polymer polyethylene glycol exhibited concentration-dependent relaxation of arteries. Strikingly, half the concentration of iloprost in liposomes elicited similar pharmacologic efficacy as nonencapsulated iloprost. Cationic liposomes can encapsulate iloprost with high efficacy and can serve as potential iloprost carriers to improve its therapeutic efficacy.

Dehydroabietic acid isolated from Commiphora opobalsamum causes endothelium-dependent relaxation of pulmonary artery via PI3K/Akt-eNOS signaling pathway.

Commiphora opobalsamum is a Traditional Chinese Medicine used to treat traumatic injury, mainly by relaxing blood vessels. In this study, two diterpenes, dehydroabietic acid (DA) and sandaracopimaric acid (SA) were obtained from it by a bioassay-guided approach using isolated rat pulmonary artery rings. The structures of the two compounds were elucidated by spectroscopic methods (IR, 1H- and 13C-NMR, HR-ESI-MS). Both DA and SA reduced the contraction of phenylephrine-induced pulmonary arteries in a concentration-dependent manner, and endothelium contributed greatly to the vasodilatory effect of DA. This effect of DA was attenuated by NG-Nitro-L-arginine methyl ester (L-NAME, an eNOS inhibitor). Meanwhile, DA increased nitric oxide (NO) production, along with the increase of phosphorylation level of eNOS and Akt in endothelial cells. LY294002 (a PI3K inhibitor) could reverse this effect, which suggested the endothelial PI3K/Akt pathway involved in the mechanism underlying DA-induced relaxation of pulmonary artery. This work provided evidence of vasorelaxant substances in Commiphora opobalsamum and validated that PI3K/Akt-eNOS pathway was associated with DA-induced pulmonary artery vasodilation.

Severe pulmonary hypertension in adult pulmonary Langerhans cell histiocytosis: the effect of sildenafil as a bridge to lung transplantation.

Severe pulmonary hypertension (PH) often develops in patients with pulmonary Langerhans cell histiocytosis (PLCH). Supplemental oxygen treatment is often used, whereas pulmonary arterial hypertension-specific vasodilators are generally considered hazardous because of the possible development of pulmonary edema and deterioration of hypoxia. In the present report, we herein describe a PLCH patient with severe PH in whom sildenafil, a phosphodiesterase 5 (PDE5) inhibitor, substantially improved the pulmonary hemodynamics before lung transplantation. An immunohistochemical study of the resected lung revealed positive staining for PDE5 on the diseased pulmonary arteries. These observations suggest that sildenafil can be a promising therapeutic option for PH in patients with PLCH.