Vasodilation Of Pulmonary Arteries Research Articles

Optimizing management of chronic pulmonary hypertension in preterm infants: strategies for a complex population.

Pulmonary hypertension (PH) is commonly observed in premature infants with bronchopulmonary dysplasia (BPD) and is associated with poor outcomes and increased mortality. This review explores the management of this intricate condition of the pulmonary vasculature, which exhibits heterogeneous effects and may involve both arterial and postcapillary components. Current management of BPD-PH should focus on optimizing ventilatory support, which involves treatment of underlying lung disease, transitioning to a chronic phase ventilation strategy and evaluation of the airway. Data on management is limited to observational studies. Diuretics are considered a part of the initial management, particularly in infants with right ventricular dilation. In many cases, pulmonary vasodilator therapy is required to induce pulmonary arterial vasodilation, reduce right ventricular strain, and prevent coronary ischemia and heart failure. Echocardiography plays a pivotal role in guiding treatment decisions and monitoring disease progression. BPD-PH confers a heightened risk of mortality and long-term cardio-respiratory adverse outcomes. Echocardiography has been advocated for screening, while catheterization allows for confirmation in select more complex cases. Successful management of BPD-PH requires a multidisciplinary approach, focusing on optimizing BPD treatment and addressing underlying pathologies.

The Vasodilator Effect and Mechanism of 18β-glycyrrhetinic Acid on Isolated Pulmonary Artery Rings in Rats

Background: The purpose of this study was to evaluate the effect of 18β-glycyrrhetinic acid (18β-GA) on isolated rat pulmonary artery vascular rings as well as the mechanism that lies behind the diastolic effects of this compound. Methods: To examine the effects of various doses of 18β-GA on resting normal vascular rings, we used isolated rat pulmonary artery vascular rings. The isolated rat pulmonary artery vascular ring was precontracted with phenylephrine (PE) and potassium chloride solution (KCl), which allowed for the observation of the diastolic effects of 18β-GA, as well as the effects of various concentrations of 18β-GA on blocking the four potassium channels of glibenclamide, barium chloride (BaCl2), tetraethylamine (TEA), or 4-aminopyridine; the impact of various 18β-GA concentrations on the pulmonary artery vasodilation effect pre-use of the nitric oxide synthase inhibitors l-nitroarginine methyl ester and indomethacin. Results: It was shown that 18β-GA has concentration-dependent diastolic effects on isolated rat pulmonary vascular rings that have been precontracted with PE and KCl but it has no effect on resting isolated thoracic aortic vascular rings. Conclusion: The two Kir and Kv channels may be connected to the endothelium-dependent vasodilation mechanism of 18β-GA.

Updates in the Pharmacotherapy of Pulmonary Hypertension in Patients with Heart Failure with Preserved Ejection Fraction.

Pulmonary hypertension (PH) associated with left heart disease (LHD) is a complex cardiopulmonary condition where a variable degree of pulmonary congestion, arterial vasoconstriction and vascular remodeling can lead to PH and right heart strain. Right heart dysfunction has a significant prognostic impact on these patients. Therefore, preserving right ventricular (RV) function is an important treatment goal. However, the treatment of PH in patients with left heart disease has produced conflicting evidence. The transition from pure LHD to LHD with PH is a continuum and clinically challenging. The heart failure with preserved ejection fraction (HFpEF) patient population is heterogeneous when it comes to PH and RV function. Appropriate clinical and hemodynamic phenotyping of patients with HFpEF and concomitant PH is paramount to making the appropriate treatment decision. This manuscript will summarize the current evidence for the use of pulmonary arterial vasodilators in patients with HFpEF.

Aloperine protects pulmonary hypertension via triggering PPARγ signaling and inhibiting calcium regulatory pathway in pulmonary arterial smooth muscle cells.

Previous studies have reported the beneficial role of Aloperine (ALO), an active vasodilator purified from the seeds and leaves of the herbal plant Sophora alopecuroides L., on experimental pulmonary hypertension (PH); however, detailed mechanisms remain unclear. In this study, monocrotaline-induced PH (MCT-PH) rat model and primarily cultured rat distal pulmonary arterial smooth muscle cells (PASMCs) were used to investigate the mechanisms of ALO on experimental PH, pulmonary vascular remodeling, and excessive proliferation of PASMCs. Results showed that first, ALO significantly prevented the disease development of MCT-PH by inhibiting right ventricular systolic pressure (RVSP) and right ventricular hypertrophy indexed by the Fulton Index, normalizing the pulmonary arterials (PAs) remodeling and improving the right ventricular function indexed by transthoracic echocardiography. ALO inhibited the excessive proliferation of both PAs and PASMCs. Then, isometric tension measurements showed vasodilation of ALO on precontracted PAs isolated from both control and MCT-PH rats via activating the KCNQ channel, which was blocked by specific KCNQ potassium channel inhibitor linopirdine. Moreover, by using immunofluorescence staining and nuclear/cytosol fractionation, we further observed that ALO significantly enhanced the PPARγ nuclear translocation and activation in PASMCs. Transcriptome analyses also revealed activated PPARγ signaling and suppressed calcium regulatory pathway in lungs from MCT-PH rats treated with ALO. In summary, ALO could attenuate MCT-PH through both transient vasodilation of PAs and chronic activation of PPARγ signaling pathway, which exerted antiproliferative roles on PASMCs and remodeled PAs.NEW & NOTEWORTHY Aloperine attenuates monocrotaline-induced pulmonary hypertension (MCT-PH) in rats by inhibiting the pulmonary vascular remodeling and proliferation of pulmonary arterial smooth muscle cells (PASMCs). In mechanism, Aloperine not only exerts a transient KCNQ-dependent vasodilation in precontracted pulmonary arteries (PAs) from both control and MCT-PH rats but also activates PPARγ nuclear translocation and signaling transduction in PASMCs, which chronically inhibits the calcium regulatory pathway and proliferation of PASMCs.

Oxidant activation of endothelial PKG regulates TRPV4-mediated vasodilation in mesenteric and pulmonary resistance arteries

Smooth muscle protein kinase G (PKG) mediates vasodilation whether activated by the NO/cGMP signalling pathway or by oxidation of cysteine residues in the PKGIα subunit1. PKG is also present in endothelial cells, where it is proposed to inhibit Ca2+ influx through heteromeric TRPV4-TRPC channels2. We tested the hypothesis that oxidant activation of PKG regulates vasodilation by modulating endothelial TRPV4 channel activity. Endothelium-dependent dilation was evoked in pulmonary arteries (PA), which employ NO as the mediator, and mesenteric arteries (MA), where Ca2+ entry via TRP4 channels leads to endothelial and smooth muscle hyperpolarisation. Arteries from PKG[C42S]KI mice, which lack the cysteine based PKG oxidant sensor1, were compared with wild type (WT) mice using pressure (MA) and wire (PA) myography and en face imaging of fluo-4 loaded endothelium with spinning disc confocal microscopy. Ca2+ signals were measured in the absence (pulsars) and presence (sparklets) of 1 μM cyclopiazonic acid to deplete Ca2+ stores2. TRPV4 currents were recorded from mesenteric endothelial cells using whole-cell patch-clamp. Muscarinic agonists caused concentration-dependent dilation of both arteries from WT mice, as well as PA, but not MA, from PKG[C42S]KI mice. They also stimulated the activity of Ca2+ pulsars in the endothelium of both WT arteries and in PA, but not MA, from PKG[C42S]KI mice. The response in WT MA was suppressed by reducing the availability of endogenous H2O2 with PEG-catalase. The TRPV4 agonist, GSK1016709A (1-100 nM), evoked endothelium and concentration-dependent relaxation of PA and MA from WT mice but was nearly 10-fold less potent in both vessels from PKG[C42S]KI mice. At 10 nM, GSK1016709A activated endothelial TRPV4 sparklets in PA and MA, but was less effective in vessels from PKG[C42S]KI mice. GSK1016709A was also 10-fold less potent at activating TRPV-4 current in mesenteric endothelial cells from PKG[C42S]KI mice, compared with WT mice.The loss of endothelium-dependent relaxation to GSK1016790A in PKG[C42S]KI arteries, along with the reduced ability of GSK1016790A to generate endothelial currents and Ca2+ sparklets, indicates that vasodilation mediated by endothelial TRPV4 channels requires PKG activation by endogenous oxidants. The differential ability of muscarinic agonists to dilate MA and PA from PKG[C42S]KI mice is consistent with the central role of TRP4 channels in endothelium-dependent dilation of MA, compared with a lack of TRPV4 contribution in PA.1. Burgoyne JR, Madhani M, Cuello F, Charles RL, Brennan JP, Schroder E, Browning, DD, Eaton P (2007). Cysteine redox sensor in PKGIα enables oxidant-induced activation. Science 317: 1393-13972. Zhang, P., Mao, Aq., Sun, Cy. et al. Translocation of PKG1α acts on TRPV4-C1 heteromeric channels to inhibit endothelial Ca2+ entry. Acta Pharmacol Sin 37, 1199–1207 (2016).3. Sonkusare SK, Bonev AD, Ledoux J, Liedtke W, Kotlikoff MI, Heppner TJ, Hill-Eubanks DC, Nel British Heart Foundation; Amman Arab University, University of Malaya, Ministry of Higher Education Malaysia This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cigarette smoke induces pulmonary arterial dysfunction through an imbalance in the redox status of the soluble guanylyl cyclase.

Chronic obstructive pulmonary disease (COPD), whose main risk factor is cigarette smoking (CS), is one of the most common diseases globally. Some COPD patients also develop pulmonary hypertension (PH), a severe complication that leads to premature death. Evidence suggests reactive oxygen species (ROS) involvement in COPD and PH, especially regarding pulmonary artery smooth muscle cells (PASMC) dysfunction. However, the effects of CS-driven oxidative stress on the pulmonary vasculature are not completely understood. Herein we provide evidence on the effects of CS extract (CSE) exposure on PASMC regarding ROS production, antioxidant response and its consequences on vascular tone dysregulation. Our results indicate that CSE exposure promotes mitochondrial fission, mitochondrial membrane depolarization and increased mitochondrial superoxide levels. However, this superoxide increase did not parallel a counterbalancing antioxidant response in human pulmonary artery (PA) cells. Interestingly, the mitochondrial superoxide scavenger mitoTEMPO reduced mitochondrial fission and membrane potential depolarization caused by CSE. As we have previously shown, CSE reduces PA vasoconstriction and vasodilation. In this respect, mitoTEMPO prevented the impaired nitric oxide-mediated vasodilation, while vasoconstriction remained reduced. Finally, we observed a CSE-driven downregulation of the Cyb5R3 enzyme, which prevents soluble guanylyl cyclase oxidation in PASMC. This might explain the CSE-mediated decrease in PA vasodilation. These results provide evidence that there might be a connection between mitochondrial ROS and altered vasodilation responses in PH secondary to COPD, and strongly support the potential of antioxidant strategies specifically targeting mitochondria as a new therapy for these diseases.

Activation of Endothelial Potassium Channels Lowers Pulmonary Arterial Pressure in Pulmonary Hypertension

Endothelium‐dependent vasodilation of small pulmonary arteries (PAs) lowers the resting pulmonary arterial pressure (PAP). Moreover, a loss of endothelium‐dependent vasodilation is a major contributor to elevated PAP in pulmonary hypertension (PH). Therefore, therapeutic strategies specifically targeting endothelial vasodilatory mechanisms may have beneficial effects on PAP in PH. In this regard, endothelial Ca2+ signaling mechanisms promote PA dilation and may present potential therapeutic targets for lowering PAP in PH. Under homeostatic conditions, Ca2+ signals activate endothelial nitric oxide synthase (eNOS) and Ca2+‐sensitive intermediate and small conductance potassium (IK and SK) channels to dilate PAs. eNOS activity and NO signaling are impaired in PH. However, the activity of IK/SK channels and its effect on PAP in PH have not been investigated. We hypothesized that IK/SK channels can be targeted for lowering PAP in PH. A mouse model of PH (chronic hypoxia + Sugen 5416, hereafter CH+Su, for 3 weeks) showed elevated right ventricular systolic pressure (RVSP, an indirect indicator of PAP) and development of pulmonary arterial lesions. We recently showed that adenosine triphosphate (ATP) dilates PAs through Ca2+‐dependent activation of eNOS in normal mice (Daneva et al., PNAS, 2021). PA pressure myography experiments demonstrated that ATP was unable to dilate PAs from CH+Su mice, confirming a loss of eNOS‐dependent vasodilation in these mice. However, PA dilation in response to IK/SK channel agonist NS309 (1 μM) was not different between PAs from control and CH+Su mice. Whole‐cell patch‐clamp studies in freshly isolated endothelial cells showed that IK/SK channel activity is not impaired in the endothelium from CH+Su mice. Finally, intraperitoneal administration of the IK/SK channel activator better suited for in vivo treatment, SKA‐31 (30 mg/kg), lowered the RVSP in CH+Su mice. Cardiac functional magnetic resonance imaging studies revealed that acute SKA‐31 administration does not alter the heart rate, stroke volume, ejection fraction, and cardiac output. Importantly, the RVSP‐lowering effect of SKA‐31 was not observed in normal mice. Collectively, our data reveal unaltered IK/SK channel activity in PH and provide proof of principle that IK/SK activation can be used as a strategy for lowering PAP in PH.

Clinical Pharmacology of Sildenafil in Infants and Children

Sildenafil is a competitive and selective inhibitor of phosphodiesterase 5. Sildenafil is cleared by hepatic CYP3A (major route) and CYP2C9 (minor route) and concomitant administration of potent CYP3A inducers (e.g., bosentan) causes decreases in plasma levels of sildenafil. CYP3A4 inhibitors (erythromycin and cimetidine) inhibit sildenafil metabolism prolonging the half-life and elevating blood levels of sildenafil. Sildenafil is a pulmonary arterial vasodilator and it has been used in the treatment of persistent pulmonary hypertension. The initial oral dose is 250 to 500 µg/kg 4 times-daily in infants and the oral dose is 10 to 20 mg thrice-daily in children with a body-weight up to 20 kg or > 20 kg, respectively. Sildenafil has been found efficacy and safe in infants and children but it may induce adverse-effects. Following an oral dosing, the absorption rate constant is 0.343 h-1, and the elimination half-life is 2.41 hours in children suggesting that sildenafil is rapidly absorbed and eliminated. The interaction of sildenafil with drugs and the metabolism of sildenafil have been extensively studied. The principal routes of sildenafil metabolism are: N-demethylation, oxidation, and aliphatic dihydroxylation, and the major metabolite is N-desmethyl sildenafil. The treatment of infants and children with sildenafil has been extensively studied. Sildenafil citrate and sildenafil cross the human placenta and sildenafil migrates into the breast-milk in significant amounts. The aim of this study is to review the sildenafil dosing, efficacy and safety, effects, adverse-effects, pharmacokinetics, interaction with drugs, metabolism, treatments, and sildenafil placental transfer and migration into the breast-milk.

Aryl hydrocarbon receptor is essential for the pathogenesis of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by arteriopathy in the small to medium-sized distal pulmonary arteries, often accompanied by infiltration of inflammatory cells. Aryl hydrocarbon receptor (AHR), a nuclear receptor/transcription factor, detoxifies xenobiotics and regulates the differentiation and function of various immune cells. However, the role of AHR in the pathogenesis of PAH is largely unknown. Here, we explore the role of AHR in the pathogenesis of PAH. AHR agonistic activity in serum was significantly higher in PAH patients than in healthy volunteers and was associated with poor prognosis of PAH. Sprague-Dawley rats treated with the potent endogenous AHR agonist, 6-formylindolo[3,2-b]carbazole, in combination with hypoxia develop severe pulmonary hypertension (PH) with plexiform-like lesions, whereas Sprague-Dawley rats treated with the potent vascular endothelial growth factor receptor 2 inhibitors did not. Ahr-knockout (Ahr-/- ) rats generated using the CRISPR/Cas9 system did not develop PH in the SU5416/hypoxia model. A diet containing Qing-Dai, a Chinese herbal drug, in combination with hypoxia led to development of PH in Ahr+/+ rats, but not in Ahr-/- rats. RNA-seq analysis, chromatin immunoprecipitation (ChIP)-seq analysis, immunohistochemical analysis, and bone marrow transplantation experiments show that activation of several inflammatory signaling pathways was up-regulated in endothelial cells and peripheral blood mononuclear cells, which led to infiltration of CD4+ IL-21+ T cells and MRC1+ macrophages into vascular lesions in an AHR-dependent manner. Taken together, AHR plays crucial roles in the development and progression of PAH, and the AHR-signaling pathway represents a promising therapeutic target for PAH.

Abstract 16629: Endothelial Caveolin-1-trpv4 Regulation of Pulmonary Arterial Pressure and Impairment in Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a degenerative disorder that is characterized by elevated vascular resistance and pulmonary arterial pressure (PAP). Endothelial transient receptor potential vanilloid 4 (TRPV4 EC ) ion channels represent an important Ca 2+ influx signaling mechanism that promotes vasodilation of small pulmonary arteries (PAs). Scaffolding protein caveolin-1 (Cav-1) has been shown to precipitate with TRPV4 channels in pulmonary endothelial cells in culture. Hypothesis: We hypothesized that the endothelial Cav-1-TRPV4 channel signaling in small PAs lowers PAP, and is impaired in PH. Methods: Inducible endothelium-specific KO mice for TRPV4 channel or Cav-1 were used to study the role of Cav-1-TRPV4 signaling in the regulation of resting PAP. Endothelium-specific P2Y2 receptor KO mice were used to test if Cav-1 provides a signaling scaffold for purinergic activation of TRPV4 EC channels. Endothelial Cav-1-TRPV4 signaling was assessed in PAs from two PH mouse models and PH patients. The role of NADPH oxidase (NOX1)- and inducible nitric oxide synthase (iNOS)-mediated peroxynitrite (PN), an oxidant molecule, in impairing Cav-1-TRPV4 signaling in PH was evaluated using NOX1-/- and iNOS-/- mice and pharmacological inhibitors. Results: We show that endothelial Cav-1-TRPV4 signaling in small PAs lowers resting PAP, and protects against the pathogenesis of PH. Endothelial Cav-1 provides a signaling scaffold for the activation of TRPV4 channels by endogenous purinergic receptor signaling. Moreover, TRPV4 EC channel activity and Cav-1-TRPV4 signaling are impaired in small PAs from two mouse models of PH and PH patients. Elevated levels of NOX1 and iNOS enzymes in caveolae resulted in PN formation close to Cav-1 in PH. Elevated PN targeted Cav-1 to lower Cav-1-TRPV4 signaling, thereby contributing to impaired vasodilation and increased PAP. Pharmacological inhibition of NOX1, iNOS, or PN rescued TRPV4 EC channel activity and vasodilation in PH. Conclusion: This study provides novel evidence that endothelial Cav-1-TRPV4 signaling lowers PAP and is impaired in PH. Inhibiting NOX1 or iNOS activity, or lowering endothelial PN levels may represent a novel strategy for restoring TRPV4 EC channel activity, vasodilation, and PAP.

Loss of Alpha Globin Genes in Human Subjects Is Associated with Improved Nitric Oxide-Mediated Vascular Perfusion

Introduction Absence of alpha globin genes has long been known to influence the physiology of sickle cell disease (SCD). Individuals with SCD who are missing one or two alpha globin genes have decreased rates of cerebral vasculopathy, stroke, acute chest syndrome, and leg ulcers (Bernaudin, Blood 2008; Flanagan, Blood 2011; Nolan, Br J Haematol 2006). Although there is laboratory evidence of decreased hemolytic rate in these patients (Higgs, N Engl J Med 1982), the mechanism for their improved clinical outcomes has not been identified. Recently, the alpha globin protein has been shown to be present in the endothelial wall of human arterioles, where it modulates nitric oxide (NO) scavenging during vasoconstriction (Straub, Nature 2012). In mice, pharmacological inhibition of alpha globin leads to increased endothelial NO activity, independently of NO production, and results in increased blood perfusion, reduced systemic hypertension, and increased pulmonary artery vasodilation (Keller, Hypertension 2016; Alvarez, Am J Respir Cell Mol Biol 2017). The relationship between absence of alpha globin and arterial vasodilation, and the role of alpha globin in NO-mediated vascular signaling are potential mechanisms that could explain the beneficial effect of missing alpha globin genes in SCD. Using alpha thalassemia as a naturally occurring human model of alpha globin gene knockout, we hypothesized that loss of alpha globin genes leads to improvement in microvascular blood flow in thalassemia trait subjects without hemolysis. Methods Alpha thalassemia trait subjects missing one or two alpha globin genes, and healthy controls were recruited to the study, which was approved by the Children's Hospital Los Angeles Institutional Review Board. Blood samples were obtained from all subjects to test for hemoglobin, mean corpuscular volume (MCV), reticulocyte count, plasma hemoglobin, lactate dehydrogenase, and alpha globin genotype. We assessed flow-mediated dilation (FMD) of the brachial artery following distal forearm occlusion (Detterich, Blood 2015) simultaneously with laser Doppler flowmetry (LDF) and photoplethysmography (PPG) in the fingertip. We also measured the increase in microvascular perfusion with a thermal stimulus. The maximal change in vascular perfusion after provocation indicates vasodilatory capacity. Statistical analysis was performed in JMP® version 14 (SAS Institute Inc., USA). Results Twenty-seven subjects were enrolled, including 12 controls (4 alpha globin genes), 10 patients with 3 alpha globin genes and 5 with 2. The mean MCV was lower in subjects missing alpha globin genes than in controls (p=0.0099). Importantly, hemoglobin levels and markers of hemolysis were normal in both groups. There was no detectable difference in FMD between individuals missing one and two alpha globin genes; thus, these groups were combined and labeled as alpha trait for further analyses. FMD was significantly higher in alpha trait subjects after adjusting for age (Figure 1, p=0.0357). Missing alpha globin genes had no effect on microvascular flow by LDF or PPG (data not shown). Discussion FMD is an established and specific predictor of NO bioavailability (Thijssen, Am J Physiol Heart Circ Physiol 2011), and, in addition to shear-mediated NO circulation in conduit vessels, it reflects the sum of flow in multiple arteriolar networks downstream of the conduit artery. Using this method, a difference in endothelial function between control and alpha thalassemia trait was easily detected (Figure 1). Because endothelial alpha globin is present in arterioles rather than conduit vessels (Butcher, Free Radic Biol Med 2014), we measured microvascular flow in a 1-mm3 volume in the skin using a laser Doppler sensor, and in the fingertip by PPG, but were unable to detect an effect of alpha trait. As none of the subjects had anemia or evidence of hemolysis, the significantly increased FMD associated with loss of alpha globin genes is most likely due to increased NO as a result of decreased scavenging by alpha globin. The finding reported here that lower alpha globin gene number is associated with increased NO-related perfusion in humans may explain the beneficial effect of alpha thalassemia trait in SCD and suggests that the presence of alpha thalassemia trait may also play a role in other types of vascular disease. Disclosures Wood: BiomedInformatics: Consultancy; Imago Biosciences: Consultancy; BluebirdBio: Consultancy; Celgene: Consultancy; WorldcareClinical: Consultancy; Philips Medical Systems: Research Funding. Coates:apo pharma (Chiesi Pharma): Consultancy, Honoraria; Sangamo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios pharma: Consultancy, Honoraria; Vifor Pharma: Consultancy, Honoraria; Celgene, BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Prostanoid receptor subtypes involved in treprostinil-mediated vasodilation of rat pulmonary arteries and in treprostinil-mediated inhibition of collagen gene expression of human lung fibroblasts

Treprostinil (TRE) is a potent pulmonary vasodilator with effects on other pathological aspects of pulmonary arterial hypertension. In this study, the prostanoid receptors involved in TRE-induced relaxation of isolated rat pulmonary arteries and TRE-induced inhibition of increased gene expression in collagen synthesis and contractility of human lung fibroblasts were determined. TRE (0.01−100 μM) relaxed prostaglandin F2α-precontracted rat pulmonary arteries which was attenuated by denudation of the vascular endothelium. TRE-induced relaxation was predominantly blocked by the IP receptor antagonist RO3244194 (1 μM), with slightly greater inhibition in endothelium-denuded tissue. At higher TRE concentrations (> 1 μM), the DP1 receptor antagonist BW A868C (1 μM) also inhibited relaxation reaching significance above 10 μM. In contrast, the EP3 receptor antagonist L798106 (1 μM) accentuated TRE-induced relaxation of pulmonary arteries with intact endothelium. In human lung fibroblasts, the EP2 receptor antagonist PF-04418948 (1 μM) blocked transforming growth factor β1 (TGF-β1)-increased expression of collagen synthesis (COL1A1 and COL1A2) and fibroblast contractility (ACTG2) genes in presence of TRE (0.1 μM). In conclusion, the IP receptor located on rat pulmonary vascular smooth muscle and endothelium is the primary receptor mediating vasorelaxation, while the DP1 receptor present on the rat endothelium is involved only at higher TRE concentrations. In human lung fibroblasts, the EP2 receptor is the dominant receptor subtype involved in suppression of increased collagen synthesis and fibroblast contractility gene expression induced by TGF-β1 in the presence of TRE.

Novel technique of repairing right partial anomalous pulmonary venous connection with intact atrial septum using in situ interatrial septum as a flap in a 68-year-old-woman: a case report

BackgroundPartial anomalous pulmonary venous connection draining into the right atrium with an intact atrial septum is a very rare clinical entity in the adult population. Partial anomalous pulmonary venous connection must be suspected as a differential diagnosis when the cause of right heart enlargement and pulmonary artery hypertension is unknown.Case presentationThis study describes the surgical case of an isolated right partial anomalous pulmonary venous connection to the right atrium in a 68-year-old woman, who underwent tricuspid ring annuloplasty and right-sided maze procedure simultaneously. She had complaints of gradually progressing dyspnea on exertion. However, a diagnosis could not be established despite consultations at multiple hospitals for over a year. Right heart catheterization revealed severe pulmonary artery hypertension with a mean pulmonary artery pressure of 46 mmHg, step-up phenomenon of oxygen saturation at the mid-level of the right atrium with a pulmonary-to-systemic blood flow ratio of 2.4, and a pulmonary vascular resistance of 3.1 Wood Units. As medical treatment with pulmonary artery vasodilator therapy did not improve her symptoms, she underwent surgical repair. An atrial septal defect was created surgically with a curvilinear tongue-shaped cut. The right anomalous pulmonary veins were rerouted through the surgically created atrial septal defect into the left atrium with a baffle comprised of the interatrial septum flap, kept in continuity with the anterior margin and sutured while mobilizing the enlarged right atrium. The patient had an uneventful postoperative course and remains asymptomatic.ConclusionsThe described surgical technique could be considered an effective alternative for patients undergoing surgical repair for a partial anomalous pulmonary venous connection isolated to the right atrium. The indication for surgery must be judged on a case-by-case basis in these patients with prevalent systemic-to-pulmonary shunting.

Spontaneous tricuspid valve chordal rupture in a dog with severe, irreversible pulmonary hypertension caused by Angiostrongylus vasorum infection

BackgroundThe adult worms of Angiostrongylus vasorum reside in the pulmonary artery of dogs and can lead to cardiac, respiratory, and central neurologic signs. Due to luminal obstruction and perivascular inflammation of the pulmonary artery branches, pulmonary hypertension can arise. Pulmonary hypertension, in turn, can lead to severe damage of the right-sided cardiac structures, leading to right ventricular remodeling and tricuspid valve regurgitation.Case presentationAn 8-year-old neutered female English Cocker Spaniel was presented to the author’s institution because of abdominal distention and exercise intolerance. Ascites caused by congestive right-sided heart failure was found to be responsible for these problems. The underlying etiology of the right-sided heart failure was a severe pulmonary hypertension caused by Angiostrongylus vasorum infection. Echocardiography revealed, in addition to a severe concentric and eccentric right ventricular hypertrophy, right atrial and pulmonary trunk dilation, severe tricuspid valve regurgitation, and a systolic flail of the anterior leaflet of the tricuspid valve, resulting from ruptured chordae tendineae. As a coincidental finding, a congenital mitral stenosis was found. Oral therapy was initiated with daily administration of fenbendazole for 2 weeks along with daily administration of oral sildenafil until the re-check examination. At the 6-week re-check the dog showed full clinical and partial echocardiographic recovery, and both the blood antigen test for Angiostrongylus vasorum and the fecal Baermann larva isolation test were negative. When the sildenafil therapy was ceased after tapering the daily dosage, the owner reported recurrence of abdominal distension. Re-starting the sildenafil therapy resulted in resolution of this problem. The dog was reported to be clinically healthy with daily sildenafil administration 7 months after the initial presentation.ConclusionsThe present case report describes a dog where angiostrongylosis led to congestive right-sided heart failure resulting from severe pulmonary hypertension. The secondary right ventricular eccentric hypertrophy together with suspected papillary muscular ischemia were the suspected cause of the ruptured major tricuspid chordae tendineae, which led to a severe tricuspid valve regurgitation. Despite eradication of the worms, the severe pulmonary hypertension persisted. Treatment with daily oral sildenafil, a pulmonary arterial vasodilator, was enough to keep the dog free of clinically apparent ascites.

“Spatial localization determines preferential calcium signal‐target coupling in microvascular endothelium”

Endothelial cell layer is an important regulator of vascular resistance. Localized, spatially restricted Ca2+ signals in endothelial cells promote vasodilation in systemic and pulmonary arteries, thereby lowering vascular resistance. Ca2+ signals are known to activate two main vasodilatory targets in endothelial cells: intermediate and small conductance Ca2+‐activated K+ (IK and SK, respectively) channels and endothelial nitric oxide synthase (eNOS). The goal of this study was to determine the specific mechanisms underlying preferential Ca2+ signal to vasodilatory target coupling. Based on the literature, we used resistance mesenteric arteries (MA) as a prototype for Ca2+ signal‐IK/SK channel coupling, and resistance pulmonary arteries (PA) as a prototype for Ca2+ signal‐eNOS coupling. Unitary Ca2+ influx signals through endothelial transient receptor potential vanilloid 4 (TRPV4) channels, termed TRPV4 sparklets, dilate both mesenteric and pulmonary arteries, thereby lowering resting systemic and pulmonary arterial pressures. Therefore, the study focused on the coupling of endothelial TRPV4 channels with their vasodilator targets. Whole‐cell patch clamp studies in freshly isolated endothelial cells showed that TRPV4 channel activator GSK1016790A (GSK101, 10 nM) induced IK/SK currents in MA endothelial cells, but not in PA endothelial cells. However, direct IK/SK channel activator NS309 (1 mM) or 3 mM intracellular Ca2+ was able to elicit similar IK/SK currents in both MA and PA endothelial cells, confirming the presence of IK/SK channels in endothelial cells from PA and supporting a lack of TRPV4‐IK/SK channel coupling in PAs. NO measurements with fluorescent indicator DAF‐FM showed increased endothelial NO levels in response to GSK101 in PAs but not in MAs, supporting a lack of TRPV4 sparklet‐eNOS coupling in MAs. Because of the localized nature of TRPV4 sparklets, we hypothesized that spatial co‐localization determines Ca2+ signal‐vasodilator target coupling. While TRPV4 channels were localized at endothelial projections to smooth muscle or myoendothelial projections (MEPs) in both MAs and PAs, IK/SK channels were seen at MEPs only in MAs, supporting the importance of spatial co‐localization for TRPV4‐IK/SK channel coupling. Interestingly, eNOS was localized at MEPs in both MAs and PAs, raising the question why TRPV4 sparklets cannot activate eNOS in MAs despite the spatial proximity. Therefore, we postulated that hemoglobin α (Hbα), which is known to bind eNOS and scavenge NO, silences TRPV4 channel‐eNOS coupling in MAs. Hbα immunostaining was seen mostly at MEPs in MAs, but was absent in PA endothelium. Moreover, Hbα existed in nanometer proximity with eNOS in MAs. Finally, a synthetic peptide that disrupts eNOS‐Hbα interaction uncovered the TRPV4‐eNOS coupling in MAs. Our results suggest that spatial co‐localization and the presence of Hbα determine Ca2+ signal‐vasodilator target coupling in endothelial cells. Understanding the differential coupling mechanisms may lead to novel therapeutic approaches that can selectively dilate pulmonary versus systemic vasculature.Support or Funding InformationHL121484‐01, HL138496

Impaired Endothelial Caveolin‐1‐TRPV4 Channel Signaling Contributes to Endothelial Dysfunction in Pulmonary Hypertension

Impaired endothelium‐dependent vasodilation is a key contributor to elevated pulmonary arterial pressure (PAP) in pulmonary hypertension (PH). While the mechanisms of pathogenesis of PH remain elusive, recent studies show that spatially localized Ca2+ influx via endothelial transient receptor potential vanilloid 4 (TRPV4EC) channels promotes vasodilation in resistance‐sized pulmonary arteries (PAs) by activating endothelial nitric oxide synthase (eNOS) and releasing nitric oxide (NO). Caveolin‐1 (Cav‐1EC) is an essential structural protein within the pulmonary endothelium, where it has been found to associate with TRPV4EC channels in cultured endothelial cells. We hypothesized that Cav‐1EC regulates TRPV4EC channel activity and PAP, and that impaired Cav‐1EC‐TRPV4EC signaling contributes to elevated PAP in PH. To test these hypotheses, we used right ventricular systolic pressure (RVSP) and PAP measurements in normoxic or chronic hypoxic Cav‐1EC−/− and TRPV4EC−/− mice, and pressure myography and high‐speed Ca2+ imaging studies in PAs from these mice. TRPV4EC channel activity and TRPV4EC‐mediated vasodilation were significantly impaired in PAs from Cav‐1EC−/− mice, suggesting that Cav‐1EC enhances TRPV4EC channel activity in PAs. Purinergic signaling plays an important role in pulmonary circulation, and we recently identified adenosine triphosphate (ATP) as a novel physiological activator of TRPV4EC channels in PAs. ATP activation of TRPV4EC channels was abolished by protein kinase C (PKC) inhibition, and was absent in the arteries from Cav‐1EC−/− mice, supporting a Cav‐1EC‐PKC‐TRPV4EC signaling that enables ATP activation of TRPV4‐EC channels. Resting RVSP and PAP were elevated in Cav‐1EC−/− and TRPV4EC−/− mice supporting the concept that Cav‐1EC‐TRPV4EC signaling lowers resting PAP. Moreover, exposure to chronic hypoxia (CH, 3 weeks) resulted in higher increases in RVSPs in Cav‐1EC−/− and TRPV4EC−/− mice when compared to the respective wild‐type control mice, suggesting that Cav‐1EC‐TRPV4EC channel signaling is protective against CH‐induced PH. We further used two well‐established models of PH— CH and sugen 5416 injection + CH. TRPV4EC channel activity, and ATP‐ and PKC‐activation of TRPV4EC channels were impaired in PAs from both the models of PH, suggesting that Cav‐1EC‐PKC‐TRPV4EC signaling may be impaired in PH. Taken together, these results suggest that Cav‐1EC‐PKC‐TRPV4EC signaling lowers resting PAP, and is impaired in PH. Deciphering the mechanisms that impair the Cav‐1EC‐PKC‐TRPV4EC signaling in PH may lead to novel therapeutic strategies to restore endothelium‐dependent vasodilation in PH.Support or Funding InformationHL121484‐01, HL‐138496

Therapeutic Challenges And Advances In The Management Of Systemic Sclerosis-Related Pulmonary Arterial Hypertension (SSc-PAH).

Systemic sclerosis (SSc) is a rare autoimmune disorder with multi-organ involvement. SSc-associated pulmonary arterial hypertension (SSc-PAH) is one of the leading causes of morbidity and mortality in the SSc population. With advances in our understanding of pulmonary arterial hypertension (PAH) diagnosis and treatment, outcomes for all PAH patients have significantly improved. While SSc-PAH patients have also benefited from these advances, significant challenges remain. Diagnosis of PAH is a challenging endeavor in SSc patients who often have many co-existing pulmonary and cardiac comorbidities. Given the significantly elevated prevalence and lifetime risk of PAH in the SSc population, screening for SSc-PAH is a critically useful strategy. Treatment with pulmonary arterial (PA) vasodilators has resulted in a dramatic improvement in the survival and quality of life of PAH patients. While therapy with PA vasodilators is beneficial in SSc-PAH patients, therapy effects appear to be attenuated when compared to responses in patients with idiopathic PAH (IPAH). This review attempts to chronicle and summarize the advances in our understanding of the optimal screening strategies to identify PAH in patients with SSc. The article also reviews the advances in the therapeutic and risk stratification strategies for SSc-PAH patients.

Peroxynitrite Impairs Caveolin‐1‐TRPV4 Channel Signaling in Pulmonary Hypertension

The endothelium is an important regulator of vascular resistance and overall pulmonary arterial pressure (PAP). Endothelial dysfunction in small, resistance pulmonary arteries (PAs) leads to impaired vasodilation, increased PAP, and the development of pulmonary hypertension (PH). However, the mechanisms leading to endothelial dysfunction in PH remain unknown. We recently identified endothelial TRPV4 (transient receptor potential vanilloid 4‐TRPV4EC) channels as important regulators of endothelium‐dependent vasodilation in small PAs, and showed that localized Ca2+ influx events through TRPV4EC channels activate an endothelial nitric oxide (eNOS)‐dependent vasodilatory pathway. Furthermore, inducible endothelium‐specific TRPV4 knockout (TRPV4EC−/−) mice have impaired vasodilation and elevated PAP, revealing TRPV4EC channels as critical regulators of resting PAP. However, the signaling pathways that regulate TRPV4EC channels and how they may be impaired in PH remain unknown. Caveolin‐1 (Cav‐1EC) is an important structural protein that is known to associate with TRPV4 channels in cultured endothelial cells, and global Cav‐1−/− mice were shown to have high PAP. We, therefore, hypothesized that impairment in Cav‐1EC‐TRPV4EC signaling regulation contributes to endothelial dysfunction in PH. PH was induced using a three week‐chronic hypoxia (CH) model. TRPV4EC channel function was studied using high‐speed Ca2+ imaging, which records Ca2+ influx events through TRPV4EC channels (TRPV4EC sparklets) in the intact endothelium of small PAs. Pressure myography in small PAs was used to determine the functional outcome of TRPV4EC channel signaling. Right ventricular systolic pressure (RVSP) was measured as an indicator of PAP. In normal PAs, Cav‐1EC anchoring of protein kinase C (PKC) increased TRPV4EC sparklet activity and TRPV4EC‐‐dependent vasodilation. However, in CH, decreased Cav‐1EC‐PKC localization resulted in impaired TRPV4EC sparklet activity and endotheliumdependent vasodilation. Elevated peroxynitrite (PN) levels have been shown to contribute to the development of PH. PN levels, as indicated by nitrotyrosine staining, were elevated in PAs from CH mice. PN scavenger, FeTPPS, rescued TRPV4EC sparklet activity and vasodilation in PAs obtained from CH mice. Furthermore, acute injection of FeTPPS significantly lowered PAP in CH mice. Exogenous PN significantly decreased TRPV4EC sparklet activity and vasodilation in control mice but had no effect on PAs from inducible Cav‐1EC−/− mice, indicating that the effect of PN on TRPV4EC channel activity is Cav‐1EC‐dependent. Our results support the idea that elevated PN levels in PH impairs Cav‐1EC‐PKC‐dependent potentiation of TRPV4EC channel activity. Inhibition of TRPV4EC channel activity by PN contributes to impaired vasodilation and elevated PAP observed in PH.Support or Funding Information17PRE33660762, HL138496This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Vascular TSP1-CD47 signaling promotes sickle cell-associated arterial vasculopathy and pulmonary hypertension in mice.

Pulmonary hypertension (PH) is a leading cause of death in sickle cell disease (SCD) patients. Hemolysis and oxidative stress contribute to SCD-associated PH. 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 SCD. We found that TSP1 and CD47 are upregulated in the lungs of Berkeley (BERK) sickling (Sickle) mice and patients with SCD-associated PH. We then generated chimeric animals by transplanting BERK bone marrow into C57BL/6J (n = 24) and CD47 knockout (CD47KO, n = 27) mice. Right ventricular (RV) pressure was lower in fully engrafted Sickle-to-CD47KO than Sickle-to-C57BL/6J chimeras, as shown by the reduced maximum RV pressure (P = 0.013) and mean pulmonary artery pressure (P = 0.020). The afterload of the sickle-to-CD47KO chimeras was also lower, as shown by the diminished pulmonary vascular resistance (P = 0.024) and RV effective arterial elastance (P = 0.052). On myography, aortic segments from Sickle-to-CD47KO chimeras showed improved relaxation to acetylcholine. We hypothesized that, in SCD, TSP1-CD47 signaling promotes PH, in part, by increasing reactive oxygen species (ROS) generation. In human pulmonary artery endothelial cells, treatment with TSP1 stimulated ROS generation, which was abrogated by CD47 blockade. Explanted lungs of CD47KO chimeras had less vascular congestion and a smaller oxidative footprint. Our results show that genetic absence of CD47 ameliorates SCD-associated PH, which may be due to decreased ROS levels. Modulation of TSP1-CD47 may provide a new molecular approach to the treatment of SCD-associated PH.

Design, synthesis and evaluation of N2,N4-diaminoquinazoline based inhibitors of phosphodiesterase type 5

We describe the design, synthesis and evaluation of a series of N2,N4-diaminoquinazoline analogs as PDE5 inhibitors. Twenty compounds were prepared and these were assessed in terms of their PDE5 and PDE6 activity, ex-vivo vasodilation response, mammalian cytotoxicity and aqueous solubility. Molecular docking was used to determine the binding mode of the series and this was demonstrated to be consistent with the observed SAR. Compound 15 was the most active PDE5 inhibitor (IC50 = 0.072 ± 0.008 µM) and exhibited 4.6-fold selectivity over PDE6. Ex-vivo assessment of 15 and 22 in a rat pulmonary artery vasodilation model demonstrated EC50s of 1.63 ± 0.72 µM and 2.28 ± 0.74 µM respectively.