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Barnes EA, Lee L, Barnes SL, Brenner R, Alvira CM, Cornfield DN. β1-Subunit of the calcium-sensitive potassium channel modulates the pulmonary vascular smooth muscle cell response to hypoxia. Am J Physiol Lung Cell Mol Physiol 2018; 315:L265-L275. [PMID: 29644895 PMCID: PMC6139656 DOI: 10.1152/ajplung.00060.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/04/2018] [Accepted: 04/05/2018] [Indexed: 11/22/2022] Open
Abstract
Accessory subunits associated with the calcium-sensitive potassium channel (BKCa), a major determinant of vascular tone, confer functional and anatomical diversity. The β1 subunit increases Ca2+ and voltagesensitivity of the BKCa channel and is expressed exclusively in smooth muscle cells. Evidence supporting the physiological significance of the β1 subunit includes the observations that murine models with deletion of the β1 subunit are hypertensive and that humans with a gain-of-function β1 mutation are at a decreased risk of diastolic hypertension. However, whether the β1 subunit of the BKCa channel contributes to the low tone that characterizes the normal pulmonary circulation or modulates the pulmonary vascular response to hypoxia remains unknown. To determine the role of the BKCa channel β1 subunit in the regulation of pulmonary vascular tone and the response to acute and chronic hypoxia, mice with deletion of the Kcnmb1 gene that encodes for the β1 subunit ( Kcnmb1-/-) were placed in chronic hypoxia (10% O2) for 21-24 days. In normoxia, right ventricular systolic pressure (RVSP) did not differ between Kcnmb1+/+ (controls) and Kcnmb1-/- mice. After exposure to either acute or chronic hypoxia, RVSP was higher in Kcnmb1-/- mice compared with Kcnmb1+/+ mice, without increased vascular remodeling. β1 subunit expression was predominantly confined to pulmonary artery smooth muscle cells (PASMCs) from vessels ≤ 150 µm. Peripheral PASMCs contracted collagen gels irrespective of β1 expression. Focal adhesion expression and Rho kinase activity were greater in Kcnmb1-/- compared with Kcnmb1+/+ PASMCs. Compromised PASMC β1 function may contribute to the heightened microvascular vasoconstriction that characterizes pulmonary hypertension.
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MESH Headings
- Acute Disease
- Animals
- Chronic Disease
- Focal Adhesions/genetics
- Focal Adhesions/metabolism
- Focal Adhesions/pathology
- Gene Deletion
- Hypertension, Pulmonary/genetics
- Hypertension, Pulmonary/metabolism
- Hypertension, Pulmonary/pathology
- Hypoxia/genetics
- Hypoxia/metabolism
- Hypoxia/pathology
- Large-Conductance Calcium-Activated Potassium Channel beta Subunits/genetics
- Large-Conductance Calcium-Activated Potassium Channel beta Subunits/metabolism
- Lung/blood supply
- Lung/metabolism
- Lung/pathology
- Mice
- Mice, Knockout
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/pathology
- Pulmonary Artery/metabolism
- Pulmonary Artery/pathology
- Vasoconstriction
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Affiliation(s)
- Elizabeth A Barnes
- Division of Pulmonary Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
| | - Lori Lee
- Division of Pulmonary Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
| | - Shayna L Barnes
- Division of Pulmonary Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
| | - Robert Brenner
- Department of Cellular and Integrative Physiology, School of Medicine, University of Texas Health Sciences Center , San Antonio, Texas
| | - Cristina M Alvira
- Division of Pulmonary Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
- Division of Critical Care Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
| | - David N Cornfield
- Division of Pulmonary Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
- Division of Critical Care Medicine, Department of Pediatrics, Stanford University School of Medicine , Stanford, California
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2
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Gao Y, Cornfield DN, Stenmark KR, Thébaud B, Abman SH, Raj JU. Unique aspects of the developing lung circulation: structural development and regulation of vasomotor tone. Pulm Circ 2017; 6:407-425. [PMID: 27942377 DOI: 10.1086/688890] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
This review summarizes our current knowledge on lung vasculogenesis and angiogenesis during normal lung development and the regulation of fetal and postnatal pulmonary vascular tone. In comparison to that of the adult, the pulmonary circulation of the fetus and newborn displays many unique characteristics. Moreover, altered development of pulmonary vasculature plays a more prominent role in compromised pulmonary vasoreactivity than in the adult. Clinically, a better understanding of the developmental changes in pulmonary vasculature and vasomotor tone and the mechanisms that are disrupted in disease states can lead to the development of new therapies for lung diseases characterized by impaired alveolar structure and pulmonary hypertension.
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Affiliation(s)
- Yuangsheng Gao
- Department of Pediatrics, University of Illinois College of Medicine at Chicago, Chicago, Illinois, USA
| | - David N Cornfield
- Section of Pulmonary and Critical Care Medicine, Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
| | - Kurt R Stenmark
- Section of Critical Care Medicine, Department of Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado, USA
| | - Bernard Thébaud
- Sinclair Centre for Regenerative Medicine, Ottawa Hospital Research Institute; and Children's Hospital of Eastern Ontario Research Institute; University of Ottawa, Ottawa, Ontario, Canada
| | - Steven H Abman
- Section of Pulmonary Medicine, Department of Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado, USA
| | - J Usha Raj
- Department of Pediatrics, University of Illinois College of Medicine at Chicago, Chicago, Illinois, USA
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3
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Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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Affiliation(s)
- J. T. Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Larissa A. Shimoda
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Philip I. Aaronson
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Jeremy P. T. Ward
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
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4
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Ahn YT, Kim YM, Adams E, Lyu SC, Alvira CM, Cornfield DN. Hypoxia-inducible factor-1α regulates KCNMB1 expression in human pulmonary artery smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2011; 302:L352-9. [PMID: 22114151 DOI: 10.1152/ajplung.00302.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously, we observed that hypoxia increases the expression of the β1-subunit (KCNMB1) of the calcium-sensitive potassium channel (BK(Ca)). Herein, we elucidate the mechanism whereby hypoxia increases KCNMB1 expression in human pulmonary artery smooth muscle cells (hPASMC). In response to hypoxia, the expression of both the transcription factor hypoxia-inducible factor 1-α (HIF-1α) and KCNMB1 are increased. Knockdown of HIF-1α using a shRNA plasmid blocked the hypoxic induction of KCNMB1 expression. Chromatin immunoprecipitation (ChIP) demonstrated HIF-1α binding to three discrete regions of the human KCNMB1 promoter known to contain hypoxia response elements (HREs). A KCNMB1 promoter reporter assay combined with site-directed mutagenesis identified two adjacent HREs located between -3,540 bp and -3,311 bp that are essential for the hypoxic induction of KCNMB1 promoter activity. Furthermore, additional ChIP assays demonstrated recruitment of the HIF-1α transcriptional coactivator, p300, to this same promoter region. Treatment of hPASMC with the histone deacetylase inhibitor, trichostatin, prolonged the increase in KCNMB1 observed with hypoxia, suggesting that alterations in chromatin remodeling function to limit the hypoxic induction of KCNMB1. Finally, KCNMB1 knockdown potentiated the hypoxia-induced increase in cytosolic calcium in hPASMC, highlighting the contribution of the β1-subunit in modulating vascular SMC tone in response to acute hypoxia. In conclusion, HIF-1α increases KCNMB1 expression in response to hypoxia in hPASMC by binding to two HREs located at -3,540 to -3,311 of the KCNMB1 promoter. We speculate that selective modulation of KCNMB1 expression may serve as a novel therapeutic approach to address diseases characterized by an increase in vascular tone.
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Affiliation(s)
- Yong-Tae Ahn
- Ctr. for Excellence in Pulmonary Biology, Division of Pediatric Pulmonary, Asthma and Critical Care Medicine, Stanford Univ. Medical School Medicine, Stanford, CA 94305, USA
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5
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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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6
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Resnik E, Herron J, Keck M, Sukovich D, Linden B, Cornfield DN. Chronic intrauterine pulmonary hypertension selectively modifies pulmonary artery smooth muscle cell gene expression. Am J Physiol Lung Cell Mol Physiol 2006; 290:L426-33. [PMID: 16467248 DOI: 10.1152/ajplung.00281.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary artery smooth muscle cell (PASMC) relaxation at birth results from an increase in cytosolic cGMP, cGMP-dependent and kinase-mediated activation of the Ca2+-sensitive K+channel (KCa), and closure of voltage-operated Ca2+channels (VOCC). How chronic intrauterine pulmonary hypertension compromises perinatal pulmonary vasodilation remains unknown. We tested the hypothesis that chronic intrauterine pulmonary hypertension selectively modifies gene expression to mitigate perinatal pulmonary vasodilation mediated by the cGMP kinase-KCa-VOCC pathway. PASMC were isolated from late-gestation fetal lambs that had undergone either ligation of the ductus arteriosus (hypertensive) or sham operation (control) at 127 days of gestation and were maintained under either hypoxic (∼25 Torr) or normoxic (∼120 Torr) conditions in primary culture. We studied mRNA levels for cGMP kinase Iα (PKG-1α), the α-chain of VOCC (Cav1.2), and the α-subunit of the KCachannel. Compared with control PASMC, hypertensive PASMC had decreased VOCC, KCa, and PKG-1α expression. In response to sustained normoxia, expression of VOCC and KCachannel decreased and expression of PKG-1α increased. In contrast, sustained normoxia had no effect on PKG-1α levels and an attenuated effect on VOCC and KCachannel expression in hypertensive PASMC. Protein expression of PKG-1α was consistent with the mRNA data. We conclude that chronic intrauterine pulmonary hypertension decreases PKG expression and mitigates the genetic effects of sustained normoxia on pulmonary vasodilation, because gene expression remains compromised even after sustained exposure to normoxia.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium-Transporting ATPases
- Cells, Cultured
- Chronic Disease
- Cyclic GMP-Dependent Protein Kinase Type I
- Cyclic GMP-Dependent Protein Kinases/genetics
- Cyclic GMP-Dependent Protein Kinases/metabolism
- Female
- Fetal Diseases/metabolism
- Fetal Diseases/physiopathology
- Fetus
- Gene Expression
- Hypertension, Pulmonary/metabolism
- Hypertension, Pulmonary/physiopathology
- Hypoxia/metabolism
- Hypoxia/physiopathology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/physiology
- Oxygen/pharmacology
- Potassium Channels/genetics
- Potassium Channels/metabolism
- Pregnancy
- Pregnancy, Animal
- Pulmonary Artery/cytology
- Pulmonary Artery/physiology
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sarcoplasmic Reticulum Calcium-Transporting ATPases
- Sheep
- Vasodilation/physiology
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Affiliation(s)
- Ernesto Resnik
- Dept. of Pediatrics, Stanford University School of Medicine, 300 Pasteur Dr., Stanford, CA 94304, USA
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7
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8
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Resnik E, Herron J, Fu R, Ivy DD, Cornfield DN. Oxygen tension modulates the expression of pulmonary vascular BKCa channel alpha- and beta-subunits. Am J Physiol Lung Cell Mol Physiol 2005; 290:L761-L768. [PMID: 16284215 DOI: 10.1152/ajplung.00283.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At birth, the lung environment changes from low to relatively high O(2) tension. Pulmonary blood flow increases and pulmonary artery pressure decreases. Recent data suggest that pulmonary vascular calcium-sensitive K(+) channel (BK(Ca)) activation mediates perinatal pulmonary vasodilation. Although BK(Ca) channel expression is developmentally regulated, the molecular mechanisms responsible for BK(Ca) expression remain unknown. We tested the hypothesis that the low-O(2) tension environment of the normal fetus modulates BK(Ca) channel expression. We analyzed BK(Ca) expression under conditions of hypoxia and normoxia both in vitro and in vivo. BK(Ca) alpha-subunit mRNA expression increased twofold in ovine pulmonary artery smooth muscle cell (PASMC) primary cultures maintained in hypoxia. In vivo, BK(Ca) expression was similarly affected by hypoxia. When adult Sprague-Dawley rats were placed in hypobaric hypoxic chambers for 3 wk, hypoxic animals showed an increase of threefold in the expression of BK(Ca) alpha- and more than twofold in the expression of BK(Ca) beta(1)-subunit mRNA. Immunochemical staining was consistent with the genetic data. To assess transcriptional activation of the beta-subunit of the BK(Ca), both BK(Ca) beta(1)- and beta(2)-subunit luciferase (K(Ca) beta:luc(+)) reporter genes were constructed. Hypoxia increased PASMC K(Ca) beta(1):luc(+) reporter expression by threefold and K(Ca) beta(2):luc(+) expression by 35%. Fetal PASMC treated with the hypoxia-inducible factor-1 mimetic deferoxamine showed a 63 and 41% increase in BK(Ca) channel alpha- and beta(1)-subunit expression, respectively. Together, these results suggest that oxygen tension modulates BK(Ca) channel subunit mRNA expression, and the regulation is, at least in part, at the transcriptional level.
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9
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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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10
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Houfflin-Debarge V, Delelis A, Jaillard S, Larrue B, Deruelle P, Ducloy AS, Puech F, Storme L. Effects of nociceptive stimuli on the pulmonary circulation in the ovine fetus. Am J Physiol Regul Integr Comp Physiol 2005; 288:R547-53. [PMID: 15637175 DOI: 10.1152/ajpregu.00433.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The fetus is able to exhibit a stress response to painful events, and stress hormones have been shown to modulate pulmonary vascular tone. At birth, the increased level of stress hormones plays a significant role in the adaptation to postnatal life. We therefore hypothesized that pain may alter pulmonary circulation in the perinatal period. The hemodynamic response to subcutaneous injection of formalin, which is used in experimental studies as nociceptive stimulus, was evaluated in chronically prepared, fetal lambs. Fetal lambs were operated on at 128 days gestation. 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. Three subcutaneous catheters were placed in the lambs' limb. The hemodynamic responses to subcutaneous injection of formalin, to formalin after fetal analgesia by sufentanil, and to sufentanil alone were recorded. Cortisol and catecholamine concentrations were also measured. Pulmonary vascular resistances (PVR) increased by 42% ( P < 0.0001) after formalin injection. Cortisol increased by 54% ( P = 0.05). During sufentanil infusion, PVR did not change significantly after formalin. Cortisol increased by 56% ( P < 0.05). PVR did not change during sufentanil infusion. Norepinephrine levels did not change during any of the protocols. Our results indicate that nociceptive stimuli may increase the pulmonary vascular tone. This response is not mediated by an increase in circulating catecholamine levels. Analgesia prevents this effect. We speculate that this pulmonary vascular response to nociceptive stimulation may explain some hypoxemic events observed in newborn infants during painful intensive care procedures.
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Affiliation(s)
- V Houfflin-Debarge
- Department of Obstetrics, Centre Hospitalier Régional Universitaire de Lille, Lille, France.
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11
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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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12
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Linden BC, Resnik ER, Hendrickson KJ, Herron JM, O'Connor TJ, Cornfield DN. Chronic intrauterine pulmonary hypertension compromises fetal pulmonary artery smooth muscle cell O2 sensing. Am J Physiol Lung Cell Mol Physiol 2003; 285:L1354-61. [PMID: 12882761 DOI: 10.1152/ajplung.00091.2003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test the hypothesis that chronic intrauterine pulmonary hypertension (PHTN) compromises pulmonary artery (PA) smooth muscle cell (SMC) O2 sensing, fluorescence microscopy was used to study the effect of an acute increase in Po2 on the cytosolic Ca2+ concentration ([Ca2+]i) of chronically hypoxic subconfluent monolayers of PA SMC in primary culture. PA SMCs were derived from fetal lambs with PHTN due to intrauterine ligation of the ductus arteriosus. Acute normoxia decreased [Ca2+]i in control but not PHTN PA SMC. In control PA SMC, [Ca2+]i increased after Ca2+-sensitive (KCa) and voltage-sensitive (Kv) K+ channel blockade and decreased after diltiazem treatment. In PHTN PA SMC, KCa blockade had no effect, whereas Kv blockade and diltiazem increased [Ca2+]i. Inhibition of sarcoplasmic reticulum Ca2+ ATPase activity caused a greater increase in [Ca2+]i in controls compared with PHTN PA SMC. Conversely, ryanodine caused a greater increase of [Ca2+]i in PHTN compared with control PA SMC. KCa channel mRNA is decreased and Kv channel mRNA is unchanged in PHTN PA SMC compared with controls. We conclude that PHTN compromises PA SMC O2 sensing, alters intracellular Ca2+ homeostasis, and changes the predominant ion channel that determines basal [Ca2+]i from KCa to Kv.
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Affiliation(s)
- Bradley C Linden
- Department of Surgery, University of Minnesota Medical School, 420 Delaware St. SE, Minneapolis, MN 55455, USA.
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13
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Cornfield DN, Resnik ER, Herron JM, Reinhartz O, Fineman JR. Pulmonary vascular K+ channel expression and vasoreactivity in a model of congenital heart disease. Am J Physiol Lung Cell Mol Physiol 2002; 283:L1210-9. [PMID: 12388350 DOI: 10.1152/ajplung.00428.2001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
K+ channels play an important role in mediating pulmonary vasodilation caused by increased oxygen tension, nitric oxide, alkalosis, and shear stress. To test the hypothesis that lung K+ channel gene expression may be altered by chronic increases in pulmonary blood flow, we measured gene and protein expression of calcium-sensitive (K Ca ) and voltage-gated (Kv2.1) K+ channels, and a pH-sensitive K+ channel (TASK), in distal lung from fetal lambs in which an aortopulmonary shunt was placed at 139 days gestation. Under baseline conditions, animals with an aortopulmonary shunt showed elevated pulmonary artery pressure and pulmonary blood flow compared with twin controls. Hypoxia caused a greater increase in pulmonary vascular tone in shunt animals compared with controls. Alkalosis caused pulmonary vasodilation in control but not shunt animals. To determine lung K+ channel mRNA levels, we performed quantitative RT-PCR. In comparison with control animals, lung K Ca channel mRNA content was increased in shunt animals, whereas TASK mRNA levels were decreased. There was no difference in Kv2.1 mRNA levels. Channel protein expression was consistent with these findings. We conclude that, in the presence of elevated pulmonary blood flow, K Ca channel expression is increased and TASK is decreased.
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Affiliation(s)
- David N Cornfield
- Division of Pediatric Pulmonology and Critical Care Medicine, Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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14
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Olschewski A, Hong Z, Linden BC, Porter VA, Weir EK, Cornfield DN. Contribution of the K(Ca) channel to membrane potential and O2 sensitivity is decreased in an ovine PPHN model. Am J Physiol Lung Cell Mol Physiol 2002; 283:L1103-9. [PMID: 12376364 DOI: 10.1152/ajplung.00100.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca2+-sensitive K+ (K(Ca)) channels play an important role in mediating perinatal pulmonary vasodilation. We hypothesized that lung K(Ca) channel function may be decreased in persistent pulmonary hypertension of the newborn (PPHN). To test this hypothesis, pulmonary artery smooth muscle cells (PASMC) were isolated from fetal lambs with severe pulmonary hypertension induced by ligation of the ductus arteriosus in fetal lambs at 125-128 days gestation. Fetal lambs were killed after pulmonary hypertension had been maintained for at least 7 days. Age-matched, sham-operated animals were used as controls. PASMC K+ currents and membrane potentials were recorded using amphotericin B-perforated patch-clamp techniques. The increase in whole cell current normally seen in response to normoxia was decreased (333.9 +/- 63.6% in control vs. 133.1 +/- 16.0% in hypertensive fetuses). The contribution of the K(Ca) channel to the whole cell current was diminished in hypertensive, compared with control, fetal PASMC. In PASMC from hypertensive fetuses, a change from hypoxia to normoxia caused no change in membrane potential compared with a -14.6 +/- 2.8 mV decrease in membrane potential in PASMC from control animals. In PASMC from animals with pulmonary hypertension, 4-aminopyridine (4-AP) caused a larger depolarization than iberiotoxin, whereas in PASMC from control animals, iberiotoxin caused a larger depolarization than 4-AP. These data confirm the hypothesis that the contribution of the K(Ca) channel to membrane potential and O2 sensitivity is decreased in an ovine model of PPHN, and this may contribute to the abnormal perinatal pulmonary vasoreactivity associated with PPHN.
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MESH Headings
- 4-Aminopyridine/pharmacology
- Animals
- Animals, Newborn
- Disease Models, Animal
- Female
- Gestational Age
- Hypertension, Pulmonary/embryology
- Hypertension, Pulmonary/physiopathology
- Membrane Potentials/physiology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/embryology
- Muscle, Smooth, Vascular/physiopathology
- Peptides/pharmacology
- Potassium Channels, Calcium-Activated/physiology
- Pregnancy
- Pulmonary Artery/drug effects
- Pulmonary Artery/embryology
- Pulmonary Artery/physiopathology
- Pulmonary Circulation/drug effects
- Pulmonary Circulation/physiology
- Sheep
- Tetrodotoxin/pharmacology
- Vasodilation/physiology
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Affiliation(s)
- Andrea Olschewski
- Department of Anesthesiology, Justus Liebig University, 35392 Giessen, Germany
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15
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Hopkins N, McLoughlin P. The structural basis of pulmonary hypertension in chronic lung disease: remodelling, rarefaction or angiogenesis? J Anat 2002; 201:335-48. [PMID: 12430958 PMCID: PMC1570922 DOI: 10.1046/j.1469-7580.2002.00096.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chronic lung disease in humans is frequently complicated by the development of secondary pulmonary hypertension, which is associated with increased morbidity and mortality. Hypoxia, inflammation and increased shear stress are the primary stimuli although the exact pathways through which these initiating events lead to pulmonary hypertension remain to be completely elucidated. The increase in pulmonary vascular resistance is attributed, in part, to remodelling of the walls of resistance vessels. This consists of intimal, medial and adventitial hypertrophy, which can lead to encroachment into and reduction of the vascular lumen. In addition, it has been reported that there is a reduction in the number of blood vessels in the hypertensive lung, which could also contribute to increased vascular resistance. The pulmonary endothelium plays a key role in mediating and modulating these changes. These structural alterations in the pulmonary vasculature contrast sharply with the responses of the systemic vasculature to the same stimuli. In systemic organs, both hypoxia and inflammation cause angiogenesis. Furthermore, remodelling of the walls of resistance vessels is not observed in these conditions. Thus it has been generally stated that, in the adult pulmonary circulation, angiogenesis does not occur. Prompted by previous observations that chronic airway inflammation can lead to pulmonary vascular remodelling without hypertension, we have recently shown, using quantitative stereological techniques, that angiogenesis can occur in the adult pulmonary circulation. Pulmonary angiogenesis has also been reported in some other conditions including post-pneumonectomy lung growth, metastatic disease of the lung and in biliary cirrhosis. Such angiogenesis may serve to prevent or attenuate increased vascular resistance in lung disease. In view of these more recent data, the role of structural alterations in the pulmonary vasculature in the development of pulmonary hypertension should be carefully reconsidered.
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Affiliation(s)
- Natalie Hopkins
- Department of Human Anatomy and Physiology, Conway Institute of Biomolecular and Biomedical Research, Dublin, Ireland
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16
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Porter VA, Rhodes MT, Reeve HL, Cornfield DN. Oxygen-induced fetal pulmonary vasodilation is mediated by intracellular calcium activation of K(Ca) channels. Am J Physiol Lung Cell Mol Physiol 2001; 281:L1379-85. [PMID: 11704533 DOI: 10.1152/ajplung.2001.281.6.l1379] [Citation(s) in RCA: 31] [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
O(2) sensing in fetal pulmonary artery smooth muscle is critically important in the successful transition to air breathing at birth. However, the mechanism by which the fetal pulmonary vasculature senses and responds to an acute increase in O(2) tension is not known. Isolated fetal pulmonary artery smooth muscle cells were kept in primary culture for 5-14 days in a hypoxic environment (20-30 mmHg). These cells showed a 25.1 +/- 1.7% decrease in intracellular calcium in response to an acute increase in O(2) tension. Low concentrations of caffeine (0.5 mM) and diltiazem also decreased intracellular calcium. The decrease in intracellular calcium concentration in response to increasing O(2) was inhibited by iberiotoxin and ryanodine. Freshly isolated fetal pulmonary artery smooth muscle cells exhibited "spontaneous transient outward currents," indicative of intracellular calcium spark activation of calcium-sensitive potassium channels. The frequency of spontaneous transient outward currents increased when O(2) tension was increased to normoxic levels. Increasing fetal pulmonary O(2) tension in acutely instrumented fetal sheep increased fetal pulmonary blood flow. Ryanodine attenuated O(2)-induced pulmonary vasodilation. This study demonstrates that fetal pulmonary vascular smooth muscle cells are capable of responding to an acute increase in O(2) tension and that this O(2) response is mediated by intracellular calcium activation of calcium-sensitive potassium channels.
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Affiliation(s)
- V A Porter
- Division of Pediatric Pulmonology and Critical Care Medicine, Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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17
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Abstract
Endothelial cells (EC) form a unique signal-transducing surface in the vascular system. The abundance of ion channels in the plasma membrane of these nonexcitable cells has raised questions about their functional role. This review presents evidence for the involvement of ion channels in endothelial cell functions controlled by intracellular Ca(2+) signals, such as the production and release of many vasoactive factors, e.g., nitric oxide and PGI(2). In addition, ion channels may be involved in the regulation of the traffic of macromolecules by endocytosis, transcytosis, the biosynthetic-secretory pathway, and exocytosis, e.g., tissue factor pathway inhibitor, von Willebrand factor, and tissue plasminogen activator. Ion channels are also involved in controlling intercellular permeability, EC proliferation, and angiogenesis. These functions are supported or triggered via ion channels, which either provide Ca(2+)-entry pathways or stabilize the driving force for Ca(2+) influx through these pathways. These Ca(2+)-entry pathways comprise agonist-activated nonselective Ca(2+)-permeable cation channels, cyclic nucleotide-activated nonselective cation channels, and store-operated Ca(2+) channels or capacitative Ca(2+) entry. At least some of these channels appear to be expressed by genes of the trp family. The driving force for Ca(2+) entry is mainly controlled by large-conductance Ca(2+)-dependent BK(Ca) channels (slo), inwardly rectifying K(+) channels (Kir2.1), and at least two types of Cl( -) channels, i.e., the Ca(2+)-activated Cl(-) channel and the housekeeping, volume-regulated anion channel (VRAC). In addition to their essential function in Ca(2+) signaling, VRAC channels are multifunctional, operate as a transport pathway for amino acids and organic osmolytes, and are possibly involved in endothelial cell proliferation and angiogenesis. Finally, we have also highlighted the role of ion channels as mechanosensors in EC. Plasmalemmal ion channels may signal rapid changes in hemodynamic forces, such as shear stress and biaxial tensile stress, but also changes in cell shape and cell volume to the cytoskeleton and the intracellular machinery for metabolite traffic and gene expression.
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Affiliation(s)
- B Nilius
- Department of Physiology, KU Leuven, Campus Gasthuisberg, Leuven, Belgium.
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18
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Rhodes MT, Porter VA, Saqueton CB, Herron JM, Resnik ER, Cornfield DN. Pulmonary vascular response to normoxia and K(Ca) channel activity is developmentally regulated. Am J Physiol Lung Cell Mol Physiol 2001; 280:L1250-7. [PMID: 11350805 DOI: 10.1152/ajplung.2001.280.6.l1250] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To address developmental regulation of pulmonary vascular O(2) sensing, we tested the hypotheses that 1) fetal but not adult pulmonary artery smooth muscle cells (PASMCs) can directly sense an acute increase in O(2), 2) Ca2+-sensitive K(+) (K(Ca)) channel activity decreases with maturation, and 3) PASMC K(Ca) channel expression decreases with maturation. We used fluorescence microscopy to confirm that fetal but not adult PASMCs are able to sense an acute increase in O(2) tension. Acute normoxia induced a 22 +/- 2% decrease in cytosolic Ca2+ concentration ([Ca2+](i)) in fetal PASMCs and no change in ([Ca2+](i)) in adult PASMCs (P < 0.01). The effects of K(+) channel antagonists were studied on fetal and adult PASMC ([Ca2+](i)). Iberiotoxin (10(-9) M) caused PASMC ([Ca2+](i)) to increase by 694 +/- 22% in the fetus and caused no change in adult PASMCs. K(Ca) channel expression and mRNA levels in distal pulmonary arteries from fetal and adult sheep were examined. Both K(Ca) channel protein and mRNA expression in the distal pulmonary vasculature decreased with maturation. We conclude that maturation-dependent changes in PASMC O(2) sensing render the fetal PASMCs uniquely sensitive to an acute increase in O(2) tension at a biologically critical time point.
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MESH Headings
- Aging/metabolism
- Animals
- Calcium/metabolism
- Cells, Cultured
- Cytosol/metabolism
- Dose-Response Relationship, Drug
- Fetus
- Gene Expression Regulation, Developmental/drug effects
- Immunoblotting
- Microscopy, Fluorescence
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Oxygen/metabolism
- Oxygen/pharmacology
- Peptides/pharmacology
- Potassium Channel Blockers
- Potassium Channels/genetics
- Potassium Channels/metabolism
- Pulmonary Artery/cytology
- Pulmonary Artery/embryology
- Pulmonary Artery/metabolism
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Tetraethylammonium/pharmacology
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Affiliation(s)
- M T Rhodes
- Division of Pediatric Pulmonology and Critical Care Medicine, Department of Pediatrics, University of Minnesota, 420 Delaware St., Minneapolis, MN 55455, USA
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19
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Cornfield DN, Resnik ER, Herron JM, Abman SH. Chronic intrauterine pulmonary hypertension decreases calcium-sensitive potassium channel mRNA expression. Am J Physiol Lung Cell Mol Physiol 2000; 279:L857-62. [PMID: 11053020 DOI: 10.1152/ajplung.2000.279.5.l857] [Citation(s) in RCA: 16] [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
Calcium-sensitive potassium (K(Ca)) channels play a critical role in mediating perinatal pulmonary vasodilation. Because infants with persistent pulmonary hypertension of the newborn (PPHN) have blunted vasodilator responses to birth-related stimuli, we hypothesized that lung K(Ca) channel gene expression is decreased in PPHN. To test this hypothesis, we measured K(Ca) channel gene expression in distal lung homogenates from both fetal lambs with severe pulmonary hypertension caused by prolonged compression of the ductus arteriosus and age-matched, sham-operated animals (controls). After at least 9 days of compression of the ductus arteriosus, fetal lambs were killed. To determine lung K(Ca) channel mRNA levels, primers were designed against the known sequence of the K(Ca) channel and used in semiquantitative RT-PCR, with lung 18S rRNA content as an internal control. Compared to that in control lambs, lung K(Ca) channel mRNA content in the PPHN group was reduced by 26 +/- 6% (P < 0.02), whereas lung voltage-gated K(+) 2.1 mRNA content was unchanged. We conclude that lung K(Ca) channel mRNA expression is decreased in an ovine model of PPHN. Decreased K(Ca) channel gene expression may contribute to the abnormal pulmonary vascular reactivity associated with PPHN.
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Affiliation(s)
- D N Cornfield
- Division of Pediatric Pulmonology and Critical Care Medicine, Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
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20
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Porter VA, Reeve HL, Cornfield DN. Fetal rabbit pulmonary artery smooth muscle cell response to ryanodine is developmentally regulated. Am J Physiol Lung Cell Mol Physiol 2000; 279:L751-7. [PMID: 11000136 DOI: 10.1152/ajplung.2000.279.4.l751] [Citation(s) in RCA: 24] [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
To study developmental changes in intracellular calcium handling in pulmonary artery smooth muscle cells (PASMCs), cells were isolated from distal and proximal pulmonary arteries from rabbits at different developmental stages: juvenile (4-6 wk old), newborn (<48 h), and full-term fetal. Isolated PASMCs were studied using the calcium-sensitive dye fura 2. Cells from each age group responded to caffeine with an increase in calcium; however, ryanodine (50 microM) only increased calcium in fetal distal PASMCs. The ryanodine-induced increase was due to influx of extracellular calcium because it was blocked by removal of extracellular calcium or by diltiazem. The calcium-sensitive potassium (K(Ca)) channel blocker iberiotoxin produced a transient increase in calcium in the fetal distal PASMCs, which could be inhibited by prior application of ryanodine. Conversely, the ryanodine response was inhibited if iberiotoxin was given first. With the use of electrophysiology and confocal microscopy, fetal PASMCs were shown to exhibit spontaneous transient outward currents and calcium sparks, respectively. These observations suggest that ryanodine-sensitive release of calcium from the sarcoplasmic reticulum and K(Ca) channels act together to control intracellular calcium only in fetal distal PASMCs.
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Affiliation(s)
- V A Porter
- Division of Pediatric Pulmonology and Critical Care Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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21
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Cornfield DN, Saqueton CB, Porter VA, Herron J, Resnik E, Haddad IY, Reeve HL. Voltage-gated K(+)-channel activity in ovine pulmonary vasculature is developmentally regulated. Am J Physiol Lung Cell Mol Physiol 2000; 278:L1297-304. [PMID: 10835337 DOI: 10.1152/ajplung.2000.278.6.l1297] [Citation(s) in RCA: 32] [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
To examine mechanisms underlying developmental changes in pulmonary vascular tone, we tested the hypotheses that 1) maturation-related changes in the ability of the pulmonary vasculature to respond to hypoxia are intrinsic to the pulmonary artery (PA) smooth muscle cells (SMCs); 2) voltage-gated K(+) (K(v))-channel activity increases with maturation; and 3) O(2)-sensitive Kv2.1 channel expression and message increase with maturation. To confirm that maturational differences are intrinsic to PASMCs, we used fluorescence microscopy to study the effect of acute hypoxia on cytosolic Ca(2+) concentration ([Ca(2+)](i)) in SMCs isolated from adult and fetal PAs. Although PASMCs from both fetal and adult circulations were able to sense an acute decrease in O(2) tension, acute hypoxia induced a more rapid and greater change in [Ca(2+)](i) in magnitude in PASMCs from adult compared with fetal PAs. To determine developmental changes in K(v)-channel activity, the effects of the K(+)-channel antagonist 4-aminopyridine (4-AP) were studied on fetal and adult PASMC [Ca(2+)](i). 4-AP (1 mM) caused PASMC [Ca(2+)](i) to increase by 94 +/- 22% in the fetus and 303 +/- 46% in the adult. K(v)-channel expression and mRNA levels in distal pulmonary arteries from fetal, neonatal, and adult sheep were determined through the use of immunoblotting and semiquantitative RT-PCR. Both Kv2.1-channel protein and mRNA expression in distal pulmonary vasculature increased with maturation. We conclude that there are maturation-dependent changes in PASMC O(2) sensing that may render the adult PASMCs more responsive to acute hypoxia.
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Affiliation(s)
- D N Cornfield
- Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA.
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