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Holmes H, Saini BS, Moir OJ, Darby JRT, Morrison JL, Sun L, Seed M. Pulmonary Vascular Regulation in the Fetal and Transitional Lung. Clin Perinatol 2024; 51:1-19. [PMID: 38325936 DOI: 10.1016/j.clp.2023.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Fetal lungs have fewer and smaller arteries with higher pulmonary vascular resistance (PVR) than a newborn. As gestation advances, the pulmonary circulation becomes more sensitive to changes in pulmonary arterial oxygen tension, which prepares them for the dramatic drop in PVR and increase in pulmonary blood flow (PBF) that occur when the baby takes its first few breaths of air, thus driving the transition from fetal to postnatal circulation. Dynamic and intricate regulatory mechanisms control PBF throughout development and are essential in supporting gas exchange after birth. Understanding these concepts is crucial given the role the pulmonary vasculature plays in the development of complications with transition, such as in the setting of persistent pulmonary hypertension of the newborn and congenital heart disease. An improved understanding of pulmonary vascular regulation may reveal opportunities for better clinical management.
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Affiliation(s)
- Hannah Holmes
- Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Brahmdeep S Saini
- Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Olivia J Moir
- Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Jack R T Darby
- Early Origins of Adult Health Research Group, University of South Australia, Adelaide, South Australia, 5001, Australia
| | - Janna L Morrison
- Early Origins of Adult Health Research Group, University of South Australia, Adelaide, South Australia, 5001, Australia; Department of Physiology, Faculty of Medicine, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada; Translational Medicine Program, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada
| | - Liqun Sun
- Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Mike Seed
- Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada; Translational Medicine Program, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada; Research Institute, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada; Department of Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada.
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Cookson MW, Abman SH, Kinsella JP, Mandell EW. Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension. Semin Fetal Neonatal Med 2022; 27:101367. [PMID: 35688685 PMCID: PMC10329862 DOI: 10.1016/j.siny.2022.101367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.
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Affiliation(s)
- Michael W Cookson
- Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States; Pediatric Heart Lung Center, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States.
| | - Steven H Abman
- Pediatric Heart Lung Center, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States; Section of Pulmonary Medicine, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States
| | - John P Kinsella
- Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States; Pediatric Heart Lung Center, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States
| | - Erica W Mandell
- Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States; Pediatric Heart Lung Center, Department of Pediatrics, University of Colorado Anschutz School of Medicine and Children's Hospital Colorado, Aurora, CO, United States
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Jain A, Giesinger RE, Dakshinamurti S, ElSayed Y, Jankov RP, Weisz DE, Lakshminrusimha S, Mitra S, Mazwi ML, Ting J, Narvey M, McNamara PJ. Care of the critically ill neonate with hypoxemic respiratory failure and acute pulmonary hypertension: framework for practice based on consensus opinion of neonatal hemodynamics working group. J Perinatol 2022; 42:3-13. [PMID: 35013586 DOI: 10.1038/s41372-021-01296-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 11/17/2021] [Accepted: 12/02/2021] [Indexed: 11/09/2022]
Abstract
Circulatory transition after birth presents a critical period whereby the pulmonary vascular bed and right ventricle must adapt to rapidly changing loading conditions. Failure of postnatal transition may present as hypoxemic respiratory failure, with disordered pulmonary and systemic blood flow. In this review, we present the biological and clinical contributors to pathophysiology and present a management framework.
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Affiliation(s)
- Amish Jain
- Department of Pediatrics, University of Toronto, Toronto, ON, Canada
| | | | | | - Yasser ElSayed
- Department of Pediatrics, University of Manitoba, Winnipeg, MB, Canada
| | - Robert P Jankov
- Department of Pediatrics, University of Ottawa, Ottawa, ON, Canada
| | - Dany E Weisz
- Department of Pediatrics, University of Toronto, Toronto, ON, Canada
| | | | - Souvik Mitra
- Department of Pediatrics, Dalhousie University, Halifax, NS, Canada
| | - Mjaye L Mazwi
- Department of Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Joseph Ting
- Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada
| | - Michael Narvey
- Department of Pediatrics, University of Manitoba, Winnipeg, MB, Canada
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Mandell E, Kinsella JP, Abman SH. Persistent pulmonary hypertension of the newborn. Pediatr Pulmonol 2021; 56:661-669. [PMID: 32930508 DOI: 10.1002/ppul.25073] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 11/07/2022]
Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is a significant clinical problem characterized by refractory and severe hypoxemia secondary to elevated pulmonary vascular resistance resulting in right-to-left extrapulmonary shunting of deoxygenated blood. PPHN is associated with diverse cardiopulmonary disorders and a high early mortality rate for infants with severe PPHN. Surviving infants with PPHN have an increased risk of long-term morbidities. PPHN physiology can be categorized by (1) maladaptation: pulmonary vessels have normal structure and number but have abnormal vasoreactivity; (2) excessive muscularization: increased smooth muscle cell thickness and increased distal extension of muscle to vessels that are usually not muscularized; and (3) underdevelopment: lung hypoplasia associated with decreased pulmonary artery number. Treatment involves adequate lung recruitment, optimization of cardiac output and left ventricular function, and pulmonary vasodilators such as inhaled nitric oxide. Infants who fail to respond to conventional therapy should be evaluated for lethal lung disorders including alveolar-capillary dysplasia, T-box transcription factor 4 gene, thyroid transcription factor-1, ATP-binding cassette A3 gene, and surfactant protein diseases.
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Affiliation(s)
- Erica Mandell
- Department of Pediatrics, The Pediatric Heart Lung Center, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
- Section of Neonatology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
| | - John P Kinsella
- Department of Pediatrics, The Pediatric Heart Lung Center, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
- Section of Neonatology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
| | - Steven H Abman
- Department of Pediatrics, The Pediatric Heart Lung Center, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
- Section of Pulmonary Medicine, Department of Pediatrics, Children's Hospital Colorado, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
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Le Duc K, Mur S, Sharma D, Aubry E, Recher M, Rakza T, Storme L. Prostaglandin E1 in infants with congenital diaphragmatic hernia (CDH) and life-threatening pulmonary hypertension. J Pediatr Surg 2020; 55:1872-1878. [PMID: 32061366 DOI: 10.1016/j.jpedsurg.2020.01.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 12/18/2019] [Accepted: 01/09/2020] [Indexed: 10/25/2022]
Abstract
BACKGROUND Suprasystemic pulmonary hypertension (PH) is highly predictive of pulmonary morbidity and death in infants with congenital diaphragmatic hernia (CDH). OBJECTIVES To report the effects and tolerability of Prostaglandin E1 (PGE1) in newborns with severe CDH and life-threatening PH. METHODS Newborn infants with isolated CDH and life-threatening PH defined by an acute worsening of the cardiorespiratory function, and bidirectional or exclusive right-to-left shunting across the ductus arteriosus (DA) with an acceleration of the blood flow >1.5 m.s-1 assessed by Doppler echocardiography. Serial measurements of cardiorespiratory variables have been recorded before and after PGE1. RESULTS 18 infants (out of 102 in the cohort) were included in the study (gestational age: 39 ± 2 weeks). The median FiO2, and preductal and postductal SpO2 were 80% [50; 100], 91% [88; 95] and 86% [82; 91], respectively, before treatment. FiO2 decreased to 35% [30-40] (p = 0.001) at H6. Maximal blood flow velocities in the DA decreased after starting PGE1 from 2.2 m.s-1 [1.5-2.5] to 1 m.s-1 [0.55-1.2] (p < 0.001). CONCLUSIONS PGE1 treatment improved oxygenation and circulatory function in newborn infants with severe CDH and life-threatening PH. Our data provide evidence that restrictive DA may result in suprasystemic pulmonary hypertension in CDH infants, and that PGE1 may improve cardiorespiratory failure through reopening of the DA. TYPE OF STUDY Treatment study. LEVEL OF EVIDENCE Level III.
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Affiliation(s)
- Kévin Le Duc
- Department of Neonatology, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France.
| | - Sébastien Mur
- Department of Neonatology, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
| | - Dyuti Sharma
- Department of Pediatric Surgery, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
| | - Estelle Aubry
- Department of Pediatric Surgery, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
| | - Morgan Recher
- Paediatric Intensive Care Unit, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
| | - Thameur Rakza
- Department of Neonatology, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
| | - Laurent Storme
- Department of Neonatology, Jeanne de Flandre Hospital, University Hospital of Lille, F-59000, France
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Sheak JR, Weise-Cross L, deKay RJ, Walker BR, Jernigan NL, Resta TC. Enhanced NO-dependent pulmonary vasodilation limits increased vasoconstrictor sensitivity in neonatal chronic hypoxia. Am J Physiol Heart Circ Physiol 2017; 313:H828-H838. [PMID: 28733445 DOI: 10.1152/ajpheart.00123.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 02/03/2023]
Abstract
Augmented vasoconstrictor reactivity is thought to play an important role in the development of chronic hypoxia (CH)-induced neonatal pulmonary hypertension. However, whether this response to CH results from pulmonary endothelial dysfunction and reduced nitric oxide (NO)-mediated vasodilation is not well understood. We hypothesized that neonatal CH enhances basal tone and pulmonary vasoconstrictor sensitivity by limiting NO-dependent pulmonary vasodilation. To test this hypothesis, we assessed the effects of the NO synthase (NOS) inhibitor Nω-nitro-l-arginine (l-NNA) on baseline pulmonary vascular resistance (PVR) and vasoconstrictor sensitivity to the thromboxane mimetic U-46619 in saline-perfused lungs (in situ) from 2-wk-old control and CH (12-day exposure, 0.5 atm) Sprague-Dawley rats. Basal tone was defined as that reversed by exogenous NO (spermine NONOate). CH neonates displayed elevated right ventricular systolic pressure (in vivo) and right ventricular hypertrophy, indicative of pulmonary hypertension. Perfused lungs from CH rats demonstrated greater baseline PVR, basal tone, and U-46619-mediated vasoconstriction compared with control rats in the absence of l-NNA. l-NNA markedly increased baseline PVR and reactivity to U-46619 in lungs from CH neonates, further augmenting vasoconstrictor sensitivity compared with control lungs. Exposure to CH also enhanced NO-dependent vasodilation to arginine vasopressin, pulmonary expression of NOS III [endothelial NOS (eNOS)], and eNOS phosphorylation at activation residue Ser1177 However, CH did not alter lung nitrotyrosine levels, a posttranslational modification reflecting [Formula: see text] scavenging of NO. We conclude that, in contrast to our hypothesis, enhanced basal tone and agonist-induced vasoconstriction after neonatal CH is limited by increased NO-dependent pulmonary vasodilation resulting from greater eNOS expression and phosphorylation at activation residue Ser1177NEW & NOTEWORTHY This research is the first to demonstrate enhanced nitric oxide-dependent vasodilation that limits increased vasoconstrictor reactivity in neonatal pulmonary hypertension. These results suggest that augmented vasoconstriction in this setting reflects changes in smooth muscle reactivity rather than a reduction in nitric oxide-dependent pulmonary vasodilation.
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Affiliation(s)
- Joshua R Sheak
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Laura Weise-Cross
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Ray J deKay
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Benjimen R Walker
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Nikki L Jernigan
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Thomas C Resta
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
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7
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Affiliation(s)
- Lucy R. Green
- Centre for Fetal Origins of Adult Disease, Universiy of Southampton, 887(F) Princess Anne Hospital, Coxford Road, Southanmpton SO16 5YA United Kingdom
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Abstract
The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed.
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Affiliation(s)
- Karthik Suresh
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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Wedgwood S, Lakshminrusimha S, Schumacker PT, Steinhorn RH. Cyclic stretch stimulates mitochondrial reactive oxygen species and Nox4 signaling in pulmonary artery smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2015; 309:L196-203. [PMID: 26024892 DOI: 10.1152/ajplung.00097.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 05/26/2015] [Indexed: 02/07/2023] Open
Abstract
This study was designed to determine whether cyclic stretch induces a persistent pulmonary hypertension of the newborn (PPHN) phenotype of increased NADPH oxidase (Nox) 4 signaling in control pulmonary artery smooth muscle cells (PASMC), and to identify the signal transduction molecules involved. To achieve this, PPHN was induced in lambs by antenatal ligation of the ductus arteriosus at 128 days gestation. After 9 days, lungs and PASMC were isolated from control (twin) and PPHN lambs. Control PASMC were exposed to cyclic stretch at 1 Hz and 15% elongation for 24 h. Stretch-induced Nox4 expression was attenuated by inhibition of mitochondrial complex III and NF-κB, and stretch-induced protein thiol oxidation was attenuated by Nox4 small interfering RNA and complex III inhibition. NF-κB activity was increased by stretch in a complex III-dependent fashion, and stretch-induced cyclin D1 expression was attenuated by complex III inhibition and Nox4 small interfering RNA. This is the first study to show that cyclic stretch increases Nox4 expression via mitochondrial complex III-induced activation of NF-κB in fetal PASMC, resulting in ROS signaling and increased cyclin D1 expression. Targeting these signaling molecules may attenuate pulmonary vascular remodeling associated with PPHN.
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Affiliation(s)
- Stephen Wedgwood
- Department of Pediatrics, University of California Davis Medical Center, Sacramento, California;
| | - Satyan Lakshminrusimha
- Department of Pediatrics, State University of New York at Buffalo, Buffalo, New York; and
| | - Paul T Schumacker
- Department of Pediatrics, Northwestern University, Chicago, Illinois
| | - Robin H Steinhorn
- Department of Pediatrics, University of California Davis Medical Center, Sacramento, California
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Wedgwood S, Lakshminrusimha S, Schumacker PT, Steinhorn RH. Hypoxia inducible factor signaling and experimental persistent pulmonary hypertension of the newborn. Front Pharmacol 2015; 6:47. [PMID: 25814954 PMCID: PMC4356070 DOI: 10.3389/fphar.2015.00047] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/24/2015] [Indexed: 01/18/2023] Open
Abstract
Background: Mitochondrial reactive oxygen species (ROS) levels and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activity are increased in a lamb model of persistent pulmonary hypertension of the newborn (PPHN). These events can trigger hypoxia inducible factor (HIF) signaling in response to hypoxia, which has been shown to contribute to pulmonary vascular remodeling in rodent models of pulmonary hypertension. However, the role of HIF signaling in chronic intrauterine pulmonary hypertension is not well understood. Aim: To determine if HIF signaling is increased in the lamb model of PPHN, and to identify the underlying mechanisms. Results: PPHN was induced in lambs by antenatal ligation of the ductus arteriosus at 128 days gestation. After 9 days, lungs and pulmonary artery smooth muscle cells (PASMC) were isolated from control and PPHN lambs. HIF-1α expression was increased in PPHN lungs and HIF activity was increased in PPHN PASMC relative to controls. Hypoxia increased HIF activity to a greater degree in PPHN vs. control PASMC. Control PASMC were exposed to cyclic stretch at 1 Hz and 15% elongation for 24 h, as an in vitro model of vascular stress. Stretch increased HIF activity, which was attenuated by inhibition of mitochondrial complex III and NFκB. Conclusion: Increased HIF signaling in PPHN is triggered by stretch, via mechanisms involving mitochondrial ROS and NFκB. Hypoxia substantially amplifies HIF activity in PPHN vascular cells. Targeting these signaling molecules may attenuate and reverse pulmonary vascular remodeling associated with PPHN.
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Affiliation(s)
- Stephen Wedgwood
- Department of Pediatrics, University of California Davis Medical Center Sacramento, CA, USA
| | | | | | - Robin H Steinhorn
- Department of Pediatrics, University of California Davis Medical Center Sacramento, CA, USA
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Kulik TJ. Pulmonary hypertension caused by pulmonary venous hypertension. Pulm Circ 2015; 4:581-95. [PMID: 25610595 DOI: 10.1086/678471] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 04/16/2014] [Indexed: 12/21/2022] Open
Abstract
The effect of pulmonary venous hypertension (PVH) on the pulmonary circulation is extraordinarily variable, ranging from no impact on pulmonary vascular resistance (PVR) to a marked increase. The reasons for this are unknown. Both acutely reversible pulmonary vasoconstriction and pathological remodeling (especially medial hypertrophy and intimal hyperplasia) account for increased PVR when present. The mechanisms involved in vasoconstriction and remodeling are not clearly defined, but increased wall stress, especially in small pulmonary arteries, presumably plays an important role. Myogenic contraction may account for increased vascular tone and also indirectly stimulate remodeling of the vessel wall. Increased wall stress may also directly cause smooth muscle growth, migration, and intimal hyperplasia. Even long-standing and severe pulmonary hypertension (PH) usually abates with elimination of PVH, but PVH-PH is an important clinical problem, especially because PVH due to left ventricular noncompliance lacks definitive therapy. The role of targeted PH therapy in patients with PVH-PH is unclear at this time. Most prospective studies indicate that these medications are not helpful or worse, but there is ample reason to think that a subset of patients with PVH-PH may benefit from phosphodiesterase inhibitors or other agents. A different approach to evaluating possible pharmacologic therapy for PVH-PH may be required to better define its possible utility.
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Affiliation(s)
- Thomas J Kulik
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA; and Department of Cardiology, Division of Cardiac Critical Care, and the Pulmonary Hypertension Program, Boston Children's Hospital, Boston, Massachusetts, USA
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12
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Fediuk J, Dakshinamurti S. A role for actin polymerization in persistent pulmonary hypertension of the newborn. Can J Physiol Pharmacol 2015; 93:185-94. [PMID: 25695400 DOI: 10.1139/cjpp-2014-0413] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is defined as the failure of normal pulmonary vascular relaxation at birth. Hypoxia is known to impede postnatal disassembly of the actin cytoskeleton in pulmonary arterial myocytes, resulting in elevation of smooth muscle α-actin and γ-actin content in elastic and resistance pulmonary arteries in PPHN compared with age-matched controls. This review examines the original histological characterization of PPHN with attention to cytoskeletal structural remodeling and actin isoform abundance, reviews the existing evidence for understanding the biophysical and biochemical forces at play during neonatal circulatory transition, and specifically addresses the role of the cortical actin architecture, primarily identified as γ-actin, in the transduction of mechanical force in the hypoxic PPHN pulmonary circuit.
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Affiliation(s)
- Jena Fediuk
- Biology of Breathing Group, Manitoba Institute of Child Health, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada., Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
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Papamatheakis DG, Blood AB, Kim JH, Wilson SM. Antenatal hypoxia and pulmonary vascular function and remodeling. Curr Vasc Pharmacol 2014; 11:616-40. [PMID: 24063380 DOI: 10.2174/1570161111311050006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/25/2012] [Accepted: 07/12/2012] [Indexed: 01/02/2023]
Abstract
This review provides evidence that antenatal hypoxia, which represents a significant and worldwide problem, causes prenatal programming of the lung. A general overview of lung development is provided along with some background regarding transcriptional and signaling systems of the lung. The review illustrates that antenatal hypoxic stress can induce a continuum of responses depending on the species examined. Fetuses and newborns of certain species and specific human populations are well acclimated to antenatal hypoxia. However, antenatal hypoxia causes pulmonary vascular disease in fetuses and newborns of most mammalian species and humans. Disease can range from mild pulmonary hypertension, to severe vascular remodeling and dangerous elevations in pressure. The timing, length, and magnitude of the intrauterine hypoxic stress are important to disease development, however there is also a genetic-environmental relationship that is not yet completely understood. Determining the origins of pulmonary vascular remodeling and pulmonary hypertension and their associated effects is a challenging task, but is necessary in order to develop targeted therapies for pulmonary hypertension in the newborn due to antenatal hypoxia that can both treat the symptoms and curtail or reverse disease progression.
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Affiliation(s)
- Demosthenes G Papamatheakis
- Center for Perinatal Biology, Loma Linda University School of Medicine, 11234 Anderson Street, Loma Linda, 92350 CA, USA.
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14
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Storme L, Aubry E, Rakza T, Houeijeh A, Debarge V, Tourneux P, Deruelle P, Pennaforte T. Pathophysiology of persistent pulmonary hypertension of the newborn: impact of the perinatal environment. Arch Cardiovasc Dis 2013; 106:169-77. [PMID: 23582679 DOI: 10.1016/j.acvd.2012.12.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 12/08/2012] [Accepted: 12/11/2012] [Indexed: 01/11/2023]
Abstract
The main cause of pulmonary hypertension in newborn babies results from the failure of the pulmonary circulation to dilate at birth, termed 'persistent pulmonary hypertension of the newborn' (PPHN). This syndrome is characterized by sustained elevation of pulmonary vascular resistance, causing extrapulmonary right-to-left shunting of blood across the ductus arteriosus and foramen ovale and severe hypoxaemia. It can also lead to life-threatening circulatory failure. There are many controversial and unresolved issues regarding the pathophysiology of PPHN, and these are discussed. PPHN is generally associated with factors such as congenital diaphragmatic hernia, birth asphyxia, sepsis, meconium aspiration and respiratory distress syndrome. However, the perinatal environment-exposure to nicotine and certain medications, maternal obesity and diabetes, epigenetics, painful stimuli and birth by Caesarean section-may also affect the maladaptation of the lung circulation at birth. In infants with PPHN, it is important to optimize circulatory function. Suggested management strategies for PPHN include: avoidance of environmental factors that worsen PPHN (e.g. noxious stimuli, lung overdistension); adequate lung recruitment and alveolar ventilation; inhaled nitric oxide (or sildenafil, if inhaled nitric oxide is not available); haemodynamic assessment; appropriate fluid and cardiovascular resuscitation and inotropic and vasoactive agents.
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Affiliation(s)
- Laurent Storme
- EA4489, Environnement Périnatal et Croissance, Faculté de Médecine, Université Lille-2, Lille, France.
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Smolich JJ, Penny DJ, Mynard JP. Increased right ventricular output and central pulmonary reservoir function support rise in pulmonary blood flow during adenosine infusion in the ovine fetus. Am J Physiol Regul Integr Comp Physiol 2012; 302:R1450-7. [PMID: 22513745 DOI: 10.1152/ajpregu.00653.2011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although adenosine markedly increases fetal pulmonary blood flow, the specific changes in pulmonary trunk (PT), ductus arteriosus (DA), and conduit pulmonary artery (PA) flow interactions that support this increased flow are unknown. To address this issue, seven anesthetized late-gestation fetal sheep were instrumented with PT, DA, and left PA micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and after adenosine infusion to increase PA flow approximately fivefold. With adenosine infusion, DA mean and phasic flows were unchanged, but increases in mean PT (500 ± 256 ml/min, P = 0.002) and the combined left and right PA flow (479 ± 181 ml/min, P < 0.001) were similar (P > 0.7) and related to a larger flow-increasing forward-running compression wave arising from right ventricular (RV) impulsive contraction. Moreover, while the increased PT flow was confined to systole, the rise in PA flow spanned systole (316 ml/min) and diastole (163 ml/min). This elevated PA diastolic flow was accompanied by a 170% greater discharge from a PT and main PA reservoir filled in systole (P < 0.001), but loss of retrograde blood discharge from a conduit PA reservoir that was evident at baseline. These data suggest that 1) an increase in fetal pulmonary blood flow produced by adenosine infusion is primarily supported by a higher PT blood flow (i.e., RV output); 2) about two-thirds of this increased RV output passes into the pulmonary circulation during systole; and 3) the remainder is transiently stored in a central PT and main PA systolic reservoir, from where it discharges into the lungs in diastole.
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Affiliation(s)
- Joseph J Smolich
- Heart Research Group, Murdoch Childrens Research Institute, Flemington Road, Parkville, Victoria 3052, Australia.
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Smolich JJ, Penny DJ, Mynard JP. Enhanced central and conduit pulmonary arterial reservoir function offsets reduced ductal systolic outflow during constriction of the fetal ductus arteriosus. Am J Physiol Regul Integr Comp Physiol 2011; 302:R175-83. [PMID: 21993527 DOI: 10.1152/ajpregu.00459.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Constriction of the fetal ductus arteriosus (DA) has disparate effects on mean and phasic hemodynamics, as mean DA blood flow is preserved until constriction is severe, but DA systolic and diastolic blood velocities change with only mild constriction. To determine the basis of this disparity and its physiological significance, seven anesthetized late-gestation fetal sheep were instrumented with pulmonary trunk (PT), DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and during mild, moderate, and severe DA constriction (defined as pulmonary-aortic mean pressure differences of 4, 8, and 14 mmHg, respectively), produced with an adjustable snare. With DA constriction, mean DA flow was initially maintained but decreased with severe constriction (P < 0.05) in conjunction with a reduction (P < 0.05) in PT flow (i.e., right ventricular output). By contrast, DA systolic flow fell progressively during DA constriction (P < 0.001), due to decreased transmission of both early and midsystolic proximal flow-enhancing forward-running compression waves into the DA. However, DA constriction was also accompanied by greater systolic storage of blood in the PT and main PA (P < 0.025), and increased retrograde diastolic flow from compliant major branch PA (P < 0.001). Transductal discharge of these central and conduit PA blood reservoirs in diastole offset systolic DA flow reductions. These data suggest that, during DA constriction in the fetus, enhanced central and conduit PA reservoir function constitutes an important compensatory mechanism that contributes to preservation of mean DA flow via a systolic-to-diastolic redistribution of phasic DA flow.
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Affiliation(s)
- Joseph J Smolich
- Heart Research Group, Murdoch Childrens Research Institute, Melbourne, Australia.
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Houfflin-Debarge V, Sabbah-Briffaut E, Aubry E, Deruelle P, Alexandre C, Storme L. Effects of environmental tobacco smoke on the pulmonary circulation in the ovine fetus. Am J Obstet Gynecol 2011; 204:450.e8-450.e14. [PMID: 21333966 DOI: 10.1016/j.ajog.2010.12.049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 12/21/2010] [Accepted: 12/30/2010] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Epidemiologic studies have highlighted an association between maternal smoking and persistent pulmonary hypertension of the newborn infant. However, the impact of exposure to tobacco smoke on the perinatal pulmonary circulation is currently unknown. The purpose of this study was to assess the pulmonary vascular effects of environmental tobacco smoke in the fetus. STUDY DESIGN We performed surgery on 16 fetal lambs and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic blood flow transducer was placed around the left pulmonary artery to measure blood flow. The ewes were exposed to tobacco smoke for 2 hours. In another set of experiments, the pulmonary vascular response to increased fetal O(2) tension has been assessed after 2 hours of tobacco smoke inhalation or not (control group). RESULTS Exposure to tobacco smoke decreased pulmonary blood flow by 30% and elevated pulmonary vascular resistance by 40%. The vasodilator response to increased O(2) tension was blunted after smoke inhalation compared with control animals. Smoke inhalation was associated with a decrease in fetal PaO(2) and SaO(2). CONCLUSION Exposure to environmental tobacco smoke in pregnant ewes impairs both basal tone and vascular reactivity of the fetal lung.
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Dumas de la Roque E, Storme L, Mauriat P, Bonnet S. [Pulmonary hypertension in pediatric and neonatal intensive care unit. Part I: Physiopathology]. Arch Pediatr 2010; 18:68-75. [PMID: 21130624 DOI: 10.1016/j.arcped.2010.10.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/24/2010] [Accepted: 10/20/2010] [Indexed: 12/01/2022]
Abstract
Pulmonary hypertension may be encountered in the pediatric and neonatal intensive care unit. Managing these patients in the intensive care unit can prove extremely challenging, particularly when they become hemodynamically unstable. Pulmonary hypertension in pediatric patients is frequently associated with critical illnesses such as congenital heart disease, acute respiratory disease, and left heart failure. In neonates, pulmonary hypertension is idiopathic or related to respiratory distress or congenital heart failure. This review discusses the pathogenesis and physiology of pulmonary hypertension, the cardiopulmonary interactions in this pathology, and the adaptation to extra-uterine life.
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Affiliation(s)
- E Dumas de la Roque
- Service de réanimation néonatale, CHU de Bordeaux, place Amélie-Raba-Léon, Bordeaux, France.
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Abstract
During the development of the pulmonary vasculature in the fetus, many structural and functional changes occur to prepare the lung for the transition to air breathing. The development of the pulmonary circulation is genetically controlled by an array of mitogenic factors in a temporo-spatial order. With advancing gestation, pulmonary vessels acquire increased vasoreactivity. The fetal pulmonary vasculature is exposed to a low oxygen tension environment that promotes high intrinsic myogenic tone and high vasocontractility. At birth, a dramatic reduction in pulmonary arterial pressure and resistance occurs with an increase in oxygen tension and blood flow. The striking hemodynamic differences in the pulmonary circulation of the fetus and newborn are regulated by various factors and vasoactive agents. Among them, nitric oxide, endothelin-1, and prostaglandin I2 are mainly derived from endothelial cells and exert their effects via cGMP, cAMP, and Rho kinase signaling pathways. Alterations in these signaling pathways may lead to vascular remodeling, high vasocontractility, and persistent pulmonary hypertension of the newborn.
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Affiliation(s)
- Yuansheng Gao
- Department of Physiology and Pathophysiology, Peking University, Health Science Center, Beijing, China; and Department of Pediatrics, University of Illinois, College of Medicine at Chicago, Chicago, Illinois
| | - J. Usha Raj
- Department of Physiology and Pathophysiology, Peking University, Health Science Center, Beijing, China; and Department of Pediatrics, University of Illinois, College of Medicine at Chicago, Chicago, Illinois
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Allison BJ, Crossley KJ, Flecknoe SJ, Morley CJ, Polglase GR, Hooper SB. Pulmonary hemodynamic responses to in utero ventilation in very immature fetal sheep. Respir Res 2010; 11:111. [PMID: 20723253 PMCID: PMC2944277 DOI: 10.1186/1465-9921-11-111] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 08/19/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The onset of ventilation at birth decreases pulmonary vascular resistance (PVR) resulting in a large increase in pulmonary blood flow (PBF). As the large cross sectional area of the pulmonary vascular bed develops late in gestation, we have investigated whether the ventilation-induced increase in PBF is reduced in immature lungs. METHODS Surgery was performed in fetal sheep at 105 d GA (n = 7; term ~147 d) to insert an endotracheal tube, which was connected to a neonatal ventilation circuit, and a transonic flow probe was placed around the left pulmonary artery. At 110 d GA, fetuses (n = 7) were ventilated in utero (IUV) for 12 hrs while continuous measurements of PBF were made, fetuses were allowed to develop in utero for a further 7 days following ventilation. RESULTS PBF changes were highly variable between animals, increasing from 12.2 ± 6.6 mL/min to a maximum of 78.1 ± 23.1 mL/min in four fetuses after 10 minutes of ventilation. In the remaining three fetuses, little change in PBF was measured in response to IUV. The increases in PBF measured in responding fetuses were not sustained throughout the ventilation period and by 2 hrs of IUV had returned to pre-IUV control values. DISCUSSION AND CONCLUSION Ventilation of very immature fetal sheep in utero increased PBF in 57% of fetuses but this increase was not sustained for more than 2 hrs, despite continuing ventilation. Immature lungs can increase PBF during ventilation, however, the present studies show these changes are transient and highly variable.
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Affiliation(s)
- Beth J Allison
- Department of Physiology, Monash University, Melbourne, Australia.
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Hsu JH, Oishi P, Wiseman DA, Hou Y, Chikovani O, Datar S, Sajti E, Johengen MJ, Harmon C, Black SM, Fineman JR. Nitric oxide alterations following acute ductal constriction in the fetal lamb: a role for superoxide. Am J Physiol Lung Cell Mol Physiol 2010; 298:L880-7. [PMID: 20363848 DOI: 10.1152/ajplung.00384.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acute partial compression of the fetal ductus arteriosus (DA) results in an initial abrupt increase in pulmonary blood flow (PBF), which is followed by a significant reduction in PBF to baseline values over the ensuing 2-4 h. We have previously demonstrated that this potent vasoconstricting response is due, in part, to an endothelin-1 (ET-1)-mediated decrease in nitric oxide synthase (NOS) activity. In addition, in vitro data demonstrate that ET-1 increases superoxide levels in pulmonary arterial smooth muscle cells and that oxidative stress alters NOS activity. Therefore, the objectives of this study were to determine the potential role of superoxide in the alterations of hemodynamics and NOS activity following acute ductal constriction in the late-gestation fetal lamb. Eighteen anesthetized near-term fetal lambs were instrumented, and a lung biopsy was performed. After a 48-h recovery, acute constriction of the DA was performed by inflating a vascular occluder. Polyethylene glycol-superoxide dismutase (PEG-SOD; 1,000-1,500 units/kg, n = 7) or PEG-alone (vehicle control group, n = 5) was injected into the pulmonary artery before ductal constriction. Six animals had a sham operation. In PEG-alone-treated lambs, acute ductal constriction rapidly decreased pulmonary vascular resistance (PVR) by 88%. However, by 4 h, PVR returned to preconstriction baseline. This vasoconstriction was associated with an increase in lung superoxide levels (82%), a decrease in total NOS activity (50%), and an increase in P-eNOS-Thr495 (52%) (P < 0.05). PEG-SOD prevented the increase of superoxide after ductal constriction, attenuated the vasoconstriction, preserved NOS activity, and increased P-eNOS Ser1177 (307%, P < 0.05). Sham procedure induced no changes. These data suggest that an acute decrease in NOS activity that is mediated, in part, by increased superoxide levels, and alterations in the phosphorylation status of the endothelial NOS isoform, underlie the pulmonary vascular response to acute ductal constriction.
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Affiliation(s)
- Jong-Hau Hsu
- Department of Pediatrics, University of California, San Francisco, California 94143-0106, USA
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Tourneux P, Chester M, Grover T, Abman SH. Fasudil inhibits the myogenic response in the fetal pulmonary circulation. Am J Physiol Heart Circ Physiol 2008; 295:H1505-13. [PMID: 18676688 DOI: 10.1152/ajpheart.00490.2008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In addition to high pulmonary vascular resistance (PVR) and low pulmonary blood flow, the fetal pulmonary circulation is characterized by mechanisms that oppose vasodilation. Past work suggests that high myogenic tone contributes to high PVR and may contribute to autoregulation of blood flow in the fetal lung. Rho-kinase (ROCK) can mediate the myogenic response in the adult systemic circulation, but whether high ROCK activity contributes to the myogenic response and modulates time-dependent vasodilation in the developing lung circulation are unknown. We studied the effects of fasudil, a ROCK inhibitor, on the hemodynamic response during acute compression of the ductus arteriosus (DA) in chronically prepared, late-gestation fetal sheep. Acute DA compression simultaneously induces two opposing responses: 1) blood flow-induced vasodilation through increased shear stress that is mediated by NO release and 2) stretch-induced vasoconstriction (i.e., the myogenic response). The myogenic response was assessed during acute DA compression after treatment with N(omega)-nitro-L-arginine, an inhibitor of nitric oxide synthase, to block flow-induced vasodilation and unmask the myogenic response. Intrapulmonary fasudil infusion (100 microg over 10 min) did not enhance flow-induced vasodilation during brief DA compression but reduced the myogenic response by 90% (P<0.05). During prolonged DA compression, fasudil prevented the time-dependent decline in left pulmonary artery blood flow at 2 h (183+/-29 vs. 110+/-11 ml/min with and without fasudil, respectively; P<0.001). We conclude that high ROCK activity opposes pulmonary vasodilation in utero and that the myogenic response maintains high PVR in the normal fetal lung through ROCK activation.
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Affiliation(s)
- Pierre Tourneux
- The Pediatric Heart Lung Center, Sections of Neonatology and Pulmonary Medicine, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA.
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Smolich JJ, Mynard JP, Penny DJ. Simultaneous pulmonary trunk and pulmonary arterial wave intensity analysis in fetal lambs: evidence for cyclical, midsystolic pulmonary vasoconstriction. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1554-62. [PMID: 18287223 DOI: 10.1152/ajpregu.00743.2007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The physiological basis of a characteristically low blood flow to the fetal lungs is incompletely understood. To determine the potential role of pulmonary vascular interaction in this phenomenon, simultaneous wave intensity analysis (WIA) was performed in the pulmonary trunk (PT) and left pulmonary artery (LPA) of 10 anesthetized late-gestation fetal sheep instrumented with PT and LPA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity (U). Studies were performed at rest and during brief complete occlusion of the ductus arteriosus to augment pulmonary vasoconstriction (n = 4) or main pulmonary artery to abolish wave transmission from the lungs (n = 3). Wave intensity (dI(W)) was calculated as the product of the P and U rates of change. Forward and backward components of dI(W) were determined after calculation of wave speed. PT and LPA WIA displayed an early systolic forward compression wave (FCW(is)) increasing P and U, and a late systolic forward expansion wave decreasing P and U. However, a marked midsystolic fall in LPA U to near-zero was related to an extremely prominent midsystolic backward compression wave (BCW(ms)) that arose approximately 5 cm distal to the LPA, was threefold larger than the PT BCW(ms) (P < 0.001), of similar size to FCW(is) at rest (P > 0.6), larger than FCW(is) following ductal occlusion (P < 0.05) and abolished after main pulmonary artery occlusion. These findings suggest that the absence of pulmonary arterial midsystolic forward flow which accompanies a low fetal lung blood flow is due to a BCW(ms) generated in part by cyclical vasoconstriction within the pulmonary microcirculation.
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Affiliation(s)
- Joseph J Smolich
- Australia and New Zealand Children's Heart Research Centre, Murdoch Children's Research Institute, Melbourne, Australia.
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Broughton BRS, Walker BR, Resta TC. Chronic hypoxia induces Rho kinase-dependent myogenic tone in small pulmonary arteries. Am J Physiol Lung Cell Mol Physiol 2008; 294:L797-806. [PMID: 18263668 DOI: 10.1152/ajplung.00253.2007] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myogenic tone in the pulmonary vasculature of normoxic adult animals is minimal or nonexistent. Whereas chronic hypoxia (CH) increases basal tone in pulmonary arteries, it is unclear if a portion of this elevated tone is due to development of myogenicity. Since basal arterial RhoA activity and Rho kinase (ROK) expression are augmented by CH, we hypothesized that CH elicits myogenic reactivity in pulmonary arteries through ROK-dependent vascular smooth muscle (VSM) Ca(2+) sensitization. To test this hypothesis, we assessed the contribution of ROK to basal tone and pressure-induced vasoconstriction in endothelium-disrupted pulmonary arteries [50-300 microm inner diameter (ID)] from control and CH [4 wk at 0.5 atmosphere (atm)] rats. Arteries were loaded with fura-2 AM to continuously monitor VSM intracellular Ca(2+) concentration ([Ca(2+)](i)). Basal VSM [Ca(2+)](i) was not different between groups. The ROK inhibitor, HA-1077 (100 nM to 30 microM), caused a concentration-dependent reduction of basal tone in CH arteries but had no effect in control vessels. In contrast, PKC inhibition with GF109203X (1 microM) did not alter basal tone. Furthermore, significant vasoconstriction in response to stepwise increases in intraluminal pressure (5-45 mmHg) was observed at 12, 15, 25, and 35 mmHg in arteries (50-200 microm ID) from CH rats. This myogenic reactivity was abolished by HA-1077 (10 microM) but not by GF109203X. VSM [Ca(2+)](i) was unaltered by HA-1077, GF109203X, or increases in pressure in either group. Myogenicity was not observed in larger vessels (200-300 microm ID). We conclude that CH induces myogenic tone in small pulmonary arteries through ROK-dependent myofilament Ca(2+) sensitization.
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Affiliation(s)
- Brad R S Broughton
- Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-0001, USA
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Sandoval RJ, Injeti ER, Williams JM, Georthoffer WT, Pearce WJ. Myogenic contractility is more dependent on myofilament calcium sensitization in term fetal than adult ovine cerebral arteries. Am J Physiol Heart Circ Physiol 2007; 293:H548-56. [PMID: 17384133 DOI: 10.1152/ajpheart.00134.2007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Regulation of cytosolic calcium and myofilament calcium sensitivity varies considerably with postnatal age in cerebral arteries. Because these mechanisms also govern myogenic tone, the present study used graded stretch to examine the hypothesis that myogenic tone is less dependent on calcium influx and more dependent on myofilament calcium sensitization in term fetal compared with adult cerebral arteries. Term fetal and adult posterior communicating cerebral arteries exhibited similar myogenic responses, with peak tensions averaging 24 and 26% of maximum contractile force produced in any given tissue in response to an isotonic Krebs buffer containing 122 mM K+ (Kmax) at optimum stretch ratios (working diameter/unstressed diameter) of 2.19 and 2.23, respectively. Graded stretch increased cytosolic Ca2+ concentration at stretch ratios >2.0 in adult arteries, but increased Ca2+ concentration only at stretch ratios >2.3 in fetal arteries. In permeabilized arteries, myogenic tone peaked at a stretch ratio of 2.1 in both fetal and adult arteries. The fetal %Kmax values at peak myogenic tone were not significantly different at either pCa 7.0 (23%) or pCa 5.5 (25%) but were significantly less at pCa 8.0 (8.4 ± 2.3%). Conversely, adult %Kmax values at peak myogenic tone were significantly less at both pCa 8.0 (10.4 ± 1.8%) and pCa 7.0 (16%) than at pCa 5.5 (27%). The maximal extents of stretch-induced increases in myosin light chain phosphorylation in intact fetal (20%) and adult (17%) arteries were similar. The data demonstrate that the cerebrovascular myogenic response is highly conserved during postnatal maturation but is mediated differently in fetal and adult cerebral arteries.
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Affiliation(s)
- Renan J Sandoval
- Department of Physiology and Pharmacology, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
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Houfflin Debarge V, Sicot B, Jaillard S, Gueorgiva I, Delelis A, Deruelle P, Ducloy AS, Storme L. The Mechanisms of Pain-Induced Pulmonary Vasoconstriction: An Experimental Study in Fetal Lambs. Anesth Analg 2007; 104:799-806. [PMID: 17377085 DOI: 10.1213/01.ane.0000259013.59084.bd] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Nociceptive stimulation induces pulmonary vasoconstriction in fetuses and newborns. The mechanism of this response is not fully understood. As the systemic hemodynamic response to pain is mainly mediated by sympathetic stimulation, we hypothesized that pain-induced pulmonary vasoconstriction results from the activation of catecholaminergic receptors. To test this hypothesis, we studied the pulmonary vascular response to nociceptive stimuli in fetal lambs before and after alpha-adrenoceptor blockade. METHODS Surgery was performed in fetal lambs. Catheters were placed into the ascending aorta, superior vena cava, and main pulmonary artery. An ultrasonic flow transducer was placed around the left pulmonary artery, and subcutaneous catheters were placed in the limb. The hemodynamic responses to (1) subcutaneous injection of formalin (which is used as nociceptive stimulus in experimental studies), (2) prazosin (specific alpha(1)-adrenoceptor antagonist), and (3) formalin during prazosin infusion were evaluated. Plasma cortisol and catecholamine concentrations were measured. RESULTS Pulmonary vascular resistance (PVR) increased by 50% (P < 0.01) after the formalin test. PVR did not change after the formalin test during prazosin infusion or during prazosin infusion alone. Catecholamine and cortisol levels did not change during any of the protocols. DISCUSSION Our results indicate that the fetal pulmonary vasoconstrictive response to pain involves alpha(1)-adrenoceptors activation. As plasma catecholamine concentrations did not change after the formalin test, we speculate that the pulmonary vascular response to nociceptive stimuli could be triggered by a local release of catecholamine induced by sympathetic stimulation.
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Abman SH. Recent advances in the pathogenesis and treatment of persistent pulmonary hypertension of the newborn. Neonatology 2007; 91:283-90. [PMID: 17575471 DOI: 10.1159/000101343] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is a clinical syndrome characterized by failure of the lung circulation to achieve or sustain the normal drop in pulmonary vascular resistance (PVR) at birth. Past laboratory studies identified the important role of nitric oxide (NO)-cGMP signaling in the regulation of the perinatal lung circulation, leading to the development and application of inhaled NO therapy for PPHN. Although inhaled NO therapy has improved the clinical course and outcomes of many infants, pulmonary hypertension can be refractory to inhaled NO, suggesting the need for additional approaches to severe PPHN. To develop novel therapeutic strategies for PPHN, ongoing studies continue to explore basic mechanisms underlying the pathobiology of PPHN in experimental models, including strategies to enhance NO-cGMP signaling. Recent studies have demonstrated that impaired vascular endothelial growth factor (VEGF) signaling may contribute to the pathogenesis of PPHN. Lung VEGF expression is markedly decreased in an experimental model of PPHN in sheep; inhibition of VEGF mimics the structural and functional abnormalities of PPHN, and VEGF treatment improves pulmonary hypertension through upregulation of NO production. Other studies have shown that enhanced NO-cGMP activity through the use of cGMP-specific phosphodiesterase inhibitors (sildenafil), soluble guanylate cyclase activators (BAY 41-2272), superoxide scavengers (superoxide dismutase), and rho-kinase inhibitors (fasudil) can lead to potent and sustained pulmonary vasodilation in experimental PPHN. Overall, these laboratory studies suggest novel pharmacologic strategies for the treatment of refractory PPHN.
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Affiliation(s)
- Steven H Abman
- Department of Pediatrics, University of Colorado School of Medicine and The Children's Hospital, Denver, CO 80218-1088, USA.
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Jaillard S, Larrue B, Deruelle P, Delelis A, Rakza T, Butrous G, Storme L. Effects of Phosphodiesterase 5 Inhibitor on Pulmonary Vascular Reactivity in the Fetal Lamb. Ann Thorac Surg 2006; 81:935-42. [PMID: 16488698 DOI: 10.1016/j.athoracsur.2005.09.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2005] [Revised: 09/04/2005] [Accepted: 09/09/2005] [Indexed: 11/20/2022]
Abstract
BACKGROUND Nitric oxide released by pulmonary vascular endothelium is a potent vasodilator related to increased cyclic guanosine monophosphate (cGMP) content. Hydrolysis of cGMP is achieved predominately by cGMP-specific phosphodiesterases. Sildenafil is a selective phosphodiesterase-5 (PDE5) inhibitor. The purpose of the study is to assess the effects of sildenafil on pulmonary vascular circulation during the perinatal period. METHODS Thirty-two pregnant ewes were operated on at the end of gestation, and fetal lambs were prepared with catheters placed into the aorta, vena cava, pulmonary artery, and left atrium. An ultrasonic flow transducer and an inflatable vascular occluder were placed respectively around the left pulmonary artery and the ductus arteriosus. Fetal lambs were randomly divided into two groups: (1) sildenafil group, infused continuously with sildenafil for 24 hours at a rate of 1 mg/h; or (2) control group, infused with saline for 24 hours. After 24 hours of infusion, we compared basal pulmonary vascular resistance and the pulmonary vascular responses to increase in fetal PaO2 and to acute ductus arteriosus compression causing "shear stress." RESULTS Sildenafil infusion did not change mean aortic and pulmonary artery pressures, increased mean left pulmonary blood flow by 160%, and decreased pulmonary vascular resistance by 60% (p < 0.05). However, both mean flow (Q) and pulmonary vascular resistance returned to baseline values after 2 hours of sildenafil infusion. Despite similar baseline values, pulmonary vascular resistance during maternal O2 inhalation was lower in the sildenafil group than in the control group (0.21 +/- 0.03 versus 0.33 +/- 0.03 mm Hg.mL(-1).min(-1), respectively; p < 0.01). Furthermore, drop in pulmonary vascular resistance during acute ductus arteriosus compression was greater in the sildenafil group (from 0.56 +/- 0.06 to 0.26 +/- 0.04 mm Hg.mL(-1).min(-1)) than in the control group (from 0.55 +/- 0.05 to 0.39 +/- 0.03 mm Hg.mL(-1).min(-1); p < 0.01). CONCLUSIONS Although sildenafil induces a transient pulmonary vasodilation, it mediates a sustained change in vascular reactivity, especially to birth-related stimuli in the ovine fetal lung. These data suggest that PDE5 is involved in the regulation of pulmonary vascular reactivity during the perinatal period and may potentiate birth-related pulmonary vasodilator stimuli.
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Parker TA, Grover TR, Kinsella JP, Falck JR, Abman SH. Inhibition of 20-HETE abolishes the myogenic response during NOS antagonism in the ovine fetal pulmonary circulation. Am J Physiol Lung Cell Mol Physiol 2005; 289:L261-7. [PMID: 15821014 DOI: 10.1152/ajplung.00315.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanisms that maintain high pulmonary vascular resistance (PVR) and oppose vasodilation in the fetal lung are poorly understood. In fetal lambs, increased pulmonary artery pressure evokes a potent vasoconstriction, suggesting that a myogenic response contributes to high PVR in the fetus. In adult systemic circulations, the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) has been shown to modulate the myogenic response, but its role in the fetal lung is unknown. We hypothesized that acute increases in pulmonary artery pressure release 20-HETE, which causes vasoconstriction, or a myogenic response, in the fetal lung. To address this hypothesis, we studied the hemodynamic effects of N-methylsufonyl-12,12-dibromododec-11-enamide (DDMS), a specific inhibitor of 20-HETE production, on the pulmonary vasoconstriction caused by acute compression of the ductus arteriosus (DA) in chronically prepared fetal sheep. An inflatable vascular occluder around the DA was used to increase pulmonary artery pressure under three study conditions: control, after pretreatment with nitro-l-arginine (l-NA; to inhibit shear-stress vasodilation), and after combined treatment with both l-NA and a specific 20-HETE inhibitor, DDMS. We found that DA compression after l-NA treatment increased PVR by 44 ± 12%. Although intrapulmonary DDMS infusion did not affect basal PVR, DDMS completely abolished the vasoconstrictor response to DA compression in the presence of l-NA (44 ± 12% vs. 2 ± 4% change in PVR, l-NA vs. l-NA + DDMS, P < 0.05). We conclude that 20-HETE mediates the myogenic response in the fetal pulmonary circulation and speculate that pharmacological inhibition of 20-HETE might have a therapeutic role in neonatal conditions characterized by pulmonary hypertension.
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Affiliation(s)
- Thomas A Parker
- Pediatric Heart Lung Center, University of Colorado School of Medicine, Denver, Colorado 80045, USA.
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Deruelle P, Grover TR, Abman SH. Pulmonary vascular effects of nitric oxide-cGMP augmentation in a model of chronic pulmonary hypertension in fetal and neonatal sheep. Am J Physiol Lung Cell Mol Physiol 2005; 289:L798-806. [PMID: 15964898 DOI: 10.1152/ajplung.00119.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is partly due to impaired nitric oxide (NO)-cGMP signaling. BAY 41-2272 is a novel direct activator of soluble guanylate cyclase, but whether this drug may be an effective therapy for PPHN is unknown. We hypothesized that BAY 41-2272 would cause pulmonary vasodilation in a model of severe PPHN. To test this hypothesis, we compared the hemodynamic response of BAY 41-2272 to acetylcholine, an endothelium-dependent vasodilator, and sildenafil, a selective inhibitor of PDE5 in chronically instrumented fetal lambs at 1 and 5 days after partial ligation of the ductus arteriosus. After 9 days, we delivered the animals by cesarean section to measure their hemodynamic responses to inhaled NO (iNO), sildenafil, and BAY 41-2272 alone or combined with iNO. BAY 41-2272 caused marked pulmonary vasodilation, as characterized by a twofold increase in blood flow and a nearly 60% fall in PVR at day 1. Effectiveness of BAY 41-2272-induced pulmonary vasodilation increased during the development of pulmonary hypertension. Despite a similar effect at day 1, the pulmonary vasodilator response to BAY 41-2272 was greater than sildenafil at day 5. At birth, BAY 41-2272 dramatically reduced PVR and augmented the pulmonary vasodilation induced by iNO. We concluded that BAY 41-2272 causes potent pulmonary vasodilation in fetal and neonatal sheep with severe pulmonary hypertension. We speculate that BAY 41-2272 may provide a novel treatment for severe PPHN, especially in newborns with partial response to iNO therapy.
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Affiliation(s)
- Philippe Deruelle
- Pediatric Heart Lung Center, University of Colorado School of Medicine, Denver, Colorado, USA
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Abstract
Persistent pulmonary hypertension of the newborn (PPHN), among the most rapidly progressive and potentially fatal of vasculopathies, is a disorder of vascular transition from fetal to neonatal circulation, manifesting as hypoxemic respiratory failure. PPHN represents a common pathway of vascular injury activated by numerous perinatal stresses: hypoxia, hypoglycemia, cold stress, sepsis, and direct lung injury. As with other multifactorial diseases, a single inciting event may be augmented by multiple concurrent/subsequent phenomena that result in differing courses of disease progression. I review the various mechanisms of vascular injury involved in neonatal pulmonary hypertension: endothelial dysfunction, inflammation, hypoxia, and mechanical strain, in the context of downstream effects on pulmonary vascular endothelial-myocyte interactions and myocyte phenotypic plasticity.
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Affiliation(s)
- S Dakshinamurti
- Department of Pediatrics, University of Manitoba, Manitoba Institute of Child Health, Winnipeg, Canada.
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Larrue B, Jaillard S, Lorthioir M, Roubliova X, Butrous G, Rakza T, Warembourg H, Storme L. Pulmonary vascular effects of sildenafil on the development of chronic pulmonary hypertension in the ovine fetus. Am J Physiol Lung Cell Mol Physiol 2005; 288:L1193-200. [PMID: 15681394 DOI: 10.1152/ajplung.00405.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the pulmonary vascular effects of prophylactic use of sildenafil, a specific phosphodiesterase-5 inhibitor, in late-gestation fetal lambs with chronic pulmonary hypertension. Fetal lambs were operated on at 129 +/- 1 days gestation (term = 147 days). Ductus arteriosus (DA) was compressed for 8 days to cause chronic pulmonary hypertension. Fetuses were treated with sildenafil (24 mg/day) or saline. Pulmonary vascular responses to increase in shear stress and in fetal PaO2 were studied at, respectively, day 4 and 6. Percent wall thickness of small pulmonary arteries (%WT) and the right ventricle-to-left ventricle plus septum ratio (RVH) were measured after completion of the study. In the control group, DA compression increased PA pressure (48 +/- 5 to 72 +/- 8 mmHg, P < 0.01) and pulmonary vascular resistance (PVR) (0.62 +/- 0.08 to 1.15 +/- 0.11 mmHg x ml(-1) x min(-1), P < 0.05). Similar increase in PAP was observed in the sildenafil group, but PVR did not change significantly (0.54 +/- 0.06 to 0.64 +/- 0.09 mmHg x ml(-1) x min(-1)). Acute DA compression, after brief decompression, elevated PVR 25% in controls and decreased PVR 35% in the sildenafil group. Increased fetal PaO2 did not change PVR in controls but decreased PVR 60% in the sildenafil group. %WT and RVH were not different between groups. Prophylactic sildenafil treatment prevents the rise in pulmonary vascular tone and altered vasoreactivity caused by DA compression in fetal lambs. These results support the hypothesis that elevated PDE5 activity is involved in the consequences of chronic pulmonary hypertension in the perinatal lung.
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Affiliation(s)
- B Larrue
- Department of Cardiothoracic Surgery, Centre Hospitalier Régional Universitaire de Lille, France
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Deruelle P, Grover TR, Storme L, Abman SH. Effects of BAY 41-2272, a soluble guanylate cyclase activator, on pulmonary vascular reactivity in the ovine fetus. Am J Physiol Lung Cell Mol Physiol 2004; 288:L727-33. [PMID: 15608146 DOI: 10.1152/ajplung.00409.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitric oxide (NO)-cGMP signaling plays a critical role during the transition of the pulmonary circulation at birth. BAY 41-2272 is a novel NO-independent direct stimulator of soluble guanylate cyclase that causes vasodilation in systemic and local circulations. However, the hemodynamic effects of BAY 41-2272 have not been studied in the perinatal pulmonary circulation. We hypothesized that BAY 41-2272 causes potent and sustained fetal pulmonary vasodilation. We performed surgery on 14 fetal lambs (125-130 days gestation; term = 147 days) and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic flow transducer was placed on the left pulmonary artery (LPA) to measure blood flow, and a catheter was placed in the LPA for drug infusion. Pulmonary vascular resistance (PVR) was calculated as pulmonary artery pressure minus left atrial pressure divided by LPA blood flow. BAY 41-2272 caused dose-related increases in pulmonary blood flow up to threefold above baseline and reduced PVR by 75% (P < 0.01). Prolonged infusion of BAY 41-2272 caused sustained pulmonary vasodilation throughout the 120-min infusion period. The pulmonary vasodilator effect of BAY 41-2272 was not attenuated by N(omega)-nitro-l-arginine, a NO synthase inhibitor. In addition, compared with sildenafil, a phosphodiesterase 5 inhibitor, the pulmonary vasodilator response to BAY 41-2272 was more prolonged. We conclude that BAY 41-2272 causes potent and sustained fetal pulmonary vasodilation independent of NO release. We speculate that BAY 41-2272 may have therapeutic potential for pulmonary hypertension associated with failure to circulatory adaptation at birth, especially in the setting of impaired NO production.
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Affiliation(s)
- Philippe Deruelle
- Pediatric Heart Lung Center, University of Colorado School of Medicine, Denver, CO 80218-1088, USA
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Naik JS, Earley S, Resta TC, Walker BR. Pressure-induced smooth muscle cell depolarization in pulmonary arteries from control and chronically hypoxic rats does not cause myogenic vasoconstriction. J Appl Physiol (1985) 2004; 98:1119-24. [PMID: 15501924 DOI: 10.1152/japplphysiol.00819.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic obstructive pulmonary diseases, as well as prolonged residence at high altitude, can result in generalized airway hypoxia, eliciting an increase in pulmonary vascular resistance. We hypothesized that a portion of the elevated pulmonary vascular resistance following chronic hypoxia (CH) is due to the development of myogenic tone. Isolated, pressurized small pulmonary arteries from control (barometric pressure congruent with 630 Torr) and CH (4 wk, barometric pressure = 380 Torr) rats were loaded with fura 2-AM and perfused with warm (37 degrees C), aerated (21% O(2)-6% CO(2)-balance N(2)) physiological saline solution. Vascular smooth muscle (VSM) intracellular Ca(2+) concentration ([Ca(2+)](i)) and diameter responses to increasing intraluminal pressure were determined. Diameter and VSM cell [Ca(2+)](i) responses to KCl were also determined. In a separate set of experiments, VSM cell membrane potential responses to increasing luminal pressure were determined in arteries from control and CH rats. VSM cell membrane potential in arteries from CH animals was depolarized relative to control at each pressure step. VSM cells from both groups exhibited a further depolarization in response to step increases in intraluminal pressure. However, arteries from both control and CH rats distended passively to increasing intraluminal pressure, and VSM cell [Ca(2+)](i) was not affected. KCl elicited a dose-dependent vasoconstriction that was nearly identical between control and CH groups. Whereas KCl administration resulted in a dose-dependent increase in VSM cell [Ca(2+)](i) in arteries taken from control animals, this stimulus elicited only a slight increase in VSM cell [Ca(2+)](i) in arteries from CH animals. We conclude that the pulmonary circulation of the rat does not demonstrate pressure-induced vasoconstriction.
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Affiliation(s)
- Jay S Naik
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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36
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Jouannic JM, Bonnet D, Hislop AA, Roussin R, Dinh-Xuan AT. Noninvasive assessment of fetal pulmonary blood flow in experimental pulmonary hypertension in the fetal lamb. Pediatr Res 2004; 56:385-90. [PMID: 15240856 DOI: 10.1203/01.pdr.0000136286.65985.7c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aim of this study was to assess pulmonary arterial blood flow changes induced by the creation of a systemic arteriovenous fistula (120 d gestation) in the fetal lamb using Doppler technique. Doppler echocardiographic assessment of the pulmonary artery blood flow performed 1, 6, and 14 d after surgery showed that mean pulmonary arterial blood flow in the left or right pulmonary artery was 224 +/- 58 mL/min at day 1 in the fistula group, significantly higher than in the control group (113 +/- 22 mL/min; p < 0.01, ANOVA test) whether no difference was found at days 6 and 14. The mean inner diameter of the left pulmonary artery measured on postmortem lung arteriograms compared favorably to the one measured on day 14 at the same level on ultrasound. The mean left pulmonary arterial blood flow, measured at birth on day 14 after surgery, using ultrasonic flow transducer, was not statistically different from the one measured by Doppler on day 14. Our data demonstrate that echocardiography allows accurate assessment of pulmonary arterial blood flow in utero, providing evidence suggesting transient high pulmonary blood flow that did not last >6 d after the creation of a systemic fistula.
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Affiliation(s)
- Jean-Marie Jouannic
- Service de Gynécologie-Obstérique, Hôpital Rothschild, AP-HP Paris VI, Paris, France.
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37
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Abstract
Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator. In randomised trials, iNO increased gas exchange modestly and had no effect on the outcome (survival, chronic lung disease, CLD) in very low birth-weight (VLBW) infants. NO is an important component of the innate immune system and a lipid- soluble free radical scavenger that interacts with the surfactant system. VLBW infants with pneumonia and therapy-resistant, severe respiratory failure soon after birth were studied. Despite their infection, there was no detectable alveolar inducible NO synthase or nitrotyrosine, which is a toxic oxidation product of NO. These infants do not respond to exogenous surfactant and demonstrate severe pulmonary hypertension. However, they require exogenous surfactant prior to iNO. In most cases the disease is complicated by pneumonia and prolonged rupture of fetal membranes. We have shown evidence that iNO given within a few hours after birth reverses the progressive course of respiratory failure and pulmonary hypertension in VLBW infants.
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Affiliation(s)
- Mikko Hallman
- Department of Pediatrics and Biocenter Oulu, University of Oulu, Oulu, Finland.
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Ovadia B, Bekker JM, Fitzgerald RK, Kon A, Thelitz S, Johengen MJ, Hendricks-Munoz K, Gerrets R, Black SM, Fineman JR. Nitric oxide-endothelin-1 interactions after acute ductal constriction in fetal lambs. Am J Physiol Heart Circ Physiol 2002; 282:H862-71. [PMID: 11834480 DOI: 10.1152/ajpheart.00417.2001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acute partial compression of the fetal ductus arteriosus (DA) results in an initial increase in pulmonary blood flow (PBF) that is followed by acute vasoconstriction. The objective of the present study was to determine the role of nitric oxide (NO)-endothelin-1 (ET-1) interactions in the acute changes in pulmonary vascular tone after in utero partial constriction of the DA. Twelve late-gestation fetal lambs (132-140 days) were instrumented to measure vascular pressures and left PBF. After a 24-h recovery period, acute constriction of the DA was performed by partially inflating a vascular occluder, and the hemodynamic variables were observed for 4 h. In control lambs (n = 7), acute ductal constriction initially increased PBF by 627% (P < 0.05). However, this was followed by active vasoconstriction, such that PBF was restored to preconstriction values by 4 h. This was associated with a 43% decrease in total NO synthase (NOS) activity (P < 0.05) and a 106% increase in plasma ET-1 levels (P < 0.05). Western blot analysis demonstrated no changes in lung tissue endothelial NOS, preproET-1, endothelin-converting enzyme-1, or ET(B) receptor protein levels. The infusion of PD-156707 (an ET(A) receptor antagonist, n = 5) completely blocked the vasoconstriction and preserved NOS activity. These data suggest that the fetal pulmonary vasoconstriction after acute constriction of the DA is mediated by NO-ET-1 interactions. These include an increase in ET(A) receptor-mediated vasoconstriction and an ET(A) receptor-mediated decrease in NOS activity. The mechanisms of these NO-ET-1 interactions, and their role in mediating acute changes in PBF, warrant further studies.
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Affiliation(s)
- Boaz Ovadia
- Department of Pediatrics, University of California, San Francisco, California 94143-0106, USA
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39
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Ghanayem NS, Gordon JB. Modulation of pulmonary vasomotor tone in the fetus and neonate. Respir Res 2002; 2:139-44. [PMID: 11686877 PMCID: PMC2002072 DOI: 10.1186/rr50] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2001] [Revised: 02/12/2001] [Accepted: 02/13/2001] [Indexed: 11/18/2022] Open
Abstract
The high pulmonary vascular resistance (PVR) of atelectatic, hypoxic, fetal lungs limits intrauterine pulmonary blood flow (PBF) to less than 10% of combined right and left ventricular output. At birth, PVR decreases precipitously to accommodate the entire cardiac output. The present review focuses on the role of endothelium-derived nitric oxide (NO), prostacyclin, and vascular smooth muscle potassium channels in mediating the decrease in PVR that occurs at birth, and in maintaining reduced pulmonary vasomotor tone during the neonatal period. The contribution of vasodilator and vasoconstrictor modulator activity to the pathophysiology of neonatal pulmonary hypertension is also addressed.
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Affiliation(s)
- Nancy S Ghanayem
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - John B Gordon
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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40
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Storme L, Parker TA, Kinsella JP, Rairigh RL, Abman SH. Chronic hypertension impairs flow-induced vasodilation and augments the myogenic response in fetal lung. Am J Physiol Lung Cell Mol Physiol 2002; 282:L56-66. [PMID: 11741816 DOI: 10.1152/ajplung.2002.282.1.l56] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that altered vasoreactivity in perinatal pulmonary hypertension (PH) is characterized by abnormal responses to hemodynamic stress, including the loss of flow-induced vasodilation and an augmented myogenic response. Therefore, we studied the acute hemodynamic effects of brief compression of the ductus arteriosus (DA) in control fetal lambs and in lambs during exposure to chronic PH. In both groups, acute DA compression decreased pulmonary vascular resistance (PVR) by 20% at baseline (day 0). After 2 days of hypertension, acute DA compression paradoxically increased PVR by 50% in PH lambs, whereas PVR decreased by 25% in controls. During the 8-day study period, PVR increased during acute DA compression in PH lambs, whereas acute DA compression continued to cause vasodilation in controls. Brief treatment with the nitric oxide (NO) synthase inhibitor nitro-L-arginine (L-NA) increased basal PVR in control but not PH lambs, suggesting decreased NO production in PH lambs. Chronic hypertension increased the myogenic response after L-NA in PH lambs, whereas the myogenic response remained unchanged in controls. The myogenic response was inhibited by nifedipine in PH lambs, suggesting that the myogenic response is dependent upon the influx of extracellular calcium. We conclude that chronic PH impairs flow-induced vasodilation and increases the myogenic response in fetal lung. We speculate that decreased NO signaling and an augmented myogenic response contributes to abnormal vasoreactivity in PH.
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Zenge JP, Rairigh RL, Grover TR, Storme L, Parker TA, Kinsella JP, Abman SH. NO and prostaglandin interactions during hemodynamic stress in the fetal ovine pulmonary circulation. Am J Physiol Lung Cell Mol Physiol 2001; 281:L1157-63. [PMID: 11597907 DOI: 10.1152/ajplung.2001.281.5.l1157] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitric oxide (NO) and prostacyclin (PGI(2)) are potent fetal pulmonary vasodilators, but their relative roles and interactions in the regulation of the perinatal pulmonary circulation are poorly understood. We compared the separate and combined effects of nitric oxide synthase (NOS) and cyclooxygenase (COX) inhibition during acute hemodynamic stress caused by brief mechanical compression of the ductus arteriosus (DA) in chronically prepared fetal lambs. Nitro-L-arginine (L-NNA; NOS antagonist), meclofenamate (Mec; COX inhibitor), combined drugs (L-NNA-Mec), or saline (control) was infused into the left pulmonary artery (LPA) before DA compression. In controls, DA compression decreased pulmonary vascular resistance (PVR) by 43% (P < 0.01). L-NNA, but not Mec, treatment completely blocked vasodilation and caused a paradoxical increase in PVR (+31%; P < 0.05). The effects of L-NNA-Mec and L-NNA on PVR were similar. To determine if the vasodilator effect of PGI(2) is partly mediated by NO release, we studied PGI(2)-induced vasodilation before and after NOS inhibition. L-NNA treatment blocked the PGI(2)-induced rise in LPA blood flow by 73% (P < 0.001). We conclude that NO has a greater role than PGs in fetal pulmonary vasoregulation during acute hemodynamic stress and that PGI(2)-induced pulmonary vasodilation is largely mediated by NO release in the fetal lung.
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Affiliation(s)
- J P Zenge
- Section of Neonatology, Pediatric Heart Lung Center, Department of Pediatrics, University of Colorado School of Medicine, Denver, Colorado 80262, USA.
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42
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Rairigh RL, Parker TA, Ivy DD, Kinsella JP, Fan ID, Abman SH. Role of inducible nitric oxide synthase in the pulmonary vascular response to birth-related stimuli in the ovine fetus. Circ Res 2001; 88:721-6. [PMID: 11304495 DOI: 10.1161/hh0701.088683] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To determine whether type II nitric oxide synthase (NOS II) contributes to the NO-mediated fall in pulmonary vascular resistance (PVR) at birth, we studied the effects of selective NOS II antagonists N-(3-aminomethyl) benzylacetamidine dihydrochloride (1400W) and aminoguanidine (AG) and a nonselective NOS antagonist, nitro-L-arginine (L-NA), during mechanical ventilation with low FIO(2) (<10%), high FIO(2) (100%), and inhaled NO (20 ppm) in 23 near-term fetal lambs. Intrapulmonary infusions of AG, 1400W, and L-NA increased basal PVR before delivery (P<0.05). In control animals, ventilation with low and high FIO(2) decreased PVR by 62% and 85%, respectively. Treatment with AG and 1400W attenuated the fall in PVR by 50% during ventilation with low and high FIO(2) (control versus treatment, P<0.05 for each intervention). L-NA treatment attenuated the fall in PVR during ventilation with low and high FIO(2) to a similar degree as the NOS II antagonists. To test the selectivity of the NOS II antagonists, we studied the effects of acetylcholine and inhaled NO in each study group. Acetylcholine-induced pulmonary vasodilation remained intact after treatment with selective NOS II antagonists but not after treatment with nonselective NOS blockade with L-NA. In contrast, the response to inhaled NO was similar between treatment groups. We conclude that selective NOS II inhibition is as effective as nonselective NOS blockade in attenuating pulmonary vasodilation at birth and speculate that NOS II activity contributes to NO-mediated pulmonary vasodilation at birth. We additionally speculate that stimulation of the airway epithelium by rhythmic distension and increased FIO(2) may activate NOS II release at birth.
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Affiliation(s)
- R L Rairigh
- Pediatric Heart Lung Center and the Sections of Neonatology, Department of Pediatrics, University of Colorado School of Medicine, Denver, Colorado, USA
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43
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Abstract
Inhaled nitric oxide (iNO), a selective pulmonary vasodilator, is available for treatment of persistent pulmonary hypertension of the newborn in term and near-term neonates. iNO decreases pulmonary vascular resistance leading to diminished extrapulmonary shunt and also has a microselective effect which improves ventilation/perfusion matching. Clinical trials indicate the need for extracorporeal membrane oxygenation (ECMO) is diminished by iNO. Information suggests a 20 ppm starting dose; doses greater than 40 ppm offer no advantage. The typical duration of therapy in responders is less than one week. Several approaches to weaning have been successful. Abrupt discontinuation should be avoided. Ventilatory management remains important when parenchymal lung disease accompanies pulmonary hypertension of the newborn; HFOV used to optimize lung inflation facilitates the action of iNO. Non-ECMO centers should be able to provide iNO during transport to an ECMO center. Data suggest a possible role for iNO in preterms with hypoxemic respiratory failure and studies in this group should proceed.
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Affiliation(s)
- J P Kinsella
- Department of Pediatrics, and The Children's Hospital and the University of Colorado School of Medicine, Denver, CO, USA.
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44
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Ivy DD, Parker TA, Abman SH. Prolonged endothelin B receptor blockade causes pulmonary hypertension in the ovine fetus. Am J Physiol Lung Cell Mol Physiol 2000; 279:L758-65. [PMID: 11000137 DOI: 10.1152/ajplung.2000.279.4.l758] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelin (ET)-1 contributes to regulation of pulmonary vascular tone and structure in the normal ovine fetus and in models of perinatal pulmonary hypertension. The hemodynamic effects of ET-1 are due to activation of its receptors. The ET(A) receptor mediates vasoconstriction and smooth muscle cell proliferation, whereas the ET(B) receptor mediates vasodilation. In a lamb model of chronic intrauterine pulmonary hypertension, ET(B) receptor activity and gene expression are decreased. To determine whether prolonged ET(B) receptor blockade causes pulmonary hypertension, we studied the hemodynamic effects of selective ET(B) receptor blockade with BQ-788. Animals were treated with an infusion of either BQ-788 or vehicle for 7 days. Prolonged BQ-788 treatment increased pulmonary arterial pressure and pulmonary vascular resistance (P < 0.05). The pulmonary vasodilator response to sarafotoxin 6c, a selective ET(B) receptor agonist, was attenuated after 7 days of BQ-788 treatment, demonstrating pharmacological blockade of the ET(B) receptor. Animals treated with BQ-788 had greater right ventricular hypertrophy and muscularization of small pulmonary arteries (P < 0. 05). Lung ET-1 levels were threefold higher in the animals treated with BQ-788 (P < 0.05). We conclude that prolonged selective ET(B) receptor blockade causes severe pulmonary hypertension and pulmonary vascular remodeling in the late-gestation ovine fetus.
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Affiliation(s)
- D D Ivy
- Section of Cardiology, Pediatric Heart Lung Center, University of Colorado School of Medicine, and The Children's Hospital, Denver, Colorado 80218, USA.
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45
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Kinsella JP, Abman SH. Clinical approach to inhaled nitric oxide therapy in newborn with hypoxemia. The journal The Journal of Pediatrics 2000. [DOI: 10.1016/s0022-3476(00)10660-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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46
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Storme L, Rairigh RL, Parker TA, Kinsella JP, Abman SH. Acute intrauterine pulmonary hypertension impairs endothelium-dependent vasodilation in the ovine fetus. Pediatr Res 1999; 45:575-81. [PMID: 10203151 DOI: 10.1203/00006450-199904010-00018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To determine whether acute pulmonary hypertension in utero alters fetal pulmonary vascular reactivity, we compared pulmonary vasodilation with an endothelium-dependent agonist, acetylcholine, with that of an endothelium-independent agonist, 8-bromo-guanosine 3',5'-cylic monophosphate. Acute pulmonary hypertension was produced in chronically prepared, late-gestation fetal lambs by 3 repeated 30-minute partial occlusions of the ductus arteriosus (DA). The first DA compression increased LPA blood flow from 80 +/- 10 to 180 +/- 21 mL/min (p < 0.01) and decreased pulmonary vascular resistance. In contrast, LPA blood flow did not change and pulmonary vascular resistance increased by 25% during the third period of DA compression. Pulmonary vasodilation during acetylcholine infusion after serial DA compressions was decreased in comparison with the acetylcholine-induced vasodilator response achieved during the baseline period (fall in pulmonary vascular resistance = -49 +/- 7% (baseline) versus -25 +/- 5% after repeated DA compressions; p < 0.05). In contrast, the vasodilator response to 8-bromo-guanosine 3',5'-cylic monophosphate remained intact. To determine whether decreased nitric oxide (NO) production may contribute to altered vasoreactivity after acute pulmonary hypertension, repeated DA compressions were performed after treatment with a nonspecific NO synthase inhibitor (nitro-L-arginine). NO synthase inhibition blocked the pulmonary vasodilation during the first DA compression period, and repeated DA compressions after NO synthase inhibition did not further alter the hemodynamic response to DA compression. These findings support the hypothesis that brief hypertension due to DA compression impairs endothelium-dependent pulmonary vasodilation in the fetus, and that this may be due to decreased NO production.
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Affiliation(s)
- L Storme
- The Service de Medecine Neonatale, Hopital jeanne de Flandre, CHRU de Lille, France
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