Ceramide inhibits Kv currents and contributes to TP-receptor-induced vasoconstriction in rat and human pulmonary arteries

Neutral sphingomyelinase (nSMase)-derived ceramide has been proposed as a mediator of hypoxic pulmonary vasoconstriction (HPV), a specific response of the pulmonary circulation. Voltage-gated K+ (Kv) channels are modulated by numerous vasoactive factors, including hypoxia, and their inhibition has been involved in HPV. Herein, we have analyzed the effects of ceramide on Kv currents and contractility in rat pulmonary arteries (PA) and in mesenteric arteries (MA). The ceramide analog C6-ceramide inhibited Kv currents in PA smooth muscle cells (PASMC). Similar effects were obtained after the addition of bacterial sphingomyelinase (SMase), indicating a role for endogenous ceramide in Kv channel regulation. Kv current was reduced by stromatoxin and diphenylphosphine oxide-1 (DPO-1), selective inhibitors of Kv2.1 and Kv1.5 channels, respectively. The inhibitory effect of ceramide was still present in the presence of stromatoxin or DPO-1, suggesting that this sphingolipid inhibited both components of the native Kv current. Accordingly, ceramide inhibited Kv1.5 and Kv2.1 channels expressed in Ltk− cells. Ceramide-induced effects were reduced in human embryonic kidney 293 cells expressing Kv1.5 channels but not the regulatory subunit Kvβ2.1. The nSMase inhibitor GW4869 reduced the thromboxane-endoperoxide receptor agonist U46619-induced, but not endothelin-1-induced pulmonary vasoconstriction that was partly restored after addition of exogenous ceramide. The PKC-ζ pseudosubstrate inhibitor (PKCζ-PI) inhibited the Kv inhibitory and contractile effects of ceramide. In MA ceramide had no effect on Kv currents and GW4869 did not affect U46619-induced contraction. The effects of SMase were also observed in human PA. These results suggest that ceramide represents a crucial signaling mediator in the pulmonary vasculature.

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Development of the pulmonary vasculature in newborn lambs: structure-function relationships

Journal of Applied Physiology ◽

10.1152/jappl.1991.70.3.1255 ◽

1991 ◽

Vol 70 (3) ◽

pp. 1255-1264 ◽

Cited By ~ 18

Author(s):

R. P. Michel ◽

J. B. Gordon ◽

K. Chu

Keyword(s):

Light Microscopy ◽

Hypoxic Pulmonary Vasoconstriction ◽

Venous Pressure ◽

Pulmonary Arteries ◽

Muscle Thickness ◽

Pulmonary Vasculature ◽

Pressure Gradients ◽

Middle Segment ◽

Pulmonary Vasoconstriction ◽

Quantitative Light Microscopy

Our objectives were 1) to describe the quantitative light microscopy and ultrastructure of newborn lamb lungs and 2) to correlate hemodynamic changes during normoxia and hypoxia with the morphology. By light microscopy, we measured the percent muscle thickness (%MT) and peripheral muscularization of pulmonary arteries and veins from 25 lambs aged less than 24 h, 2-4 days, 2 wk, and 1 mo. At the same ages, lungs were isolated and perfused in situ and, after cyclooxygenase blockade with indomethacin, total, arterial (delta Pa), middle (delta Pm), and venous pressure gradients at inspired O2 fractions of 0.28 (mild hyperoxia) and 0.04 (hypoxia) were determined with inflow-outflow occlusion. During mild hyperoxia, delta Pa and delta Pm fell significantly between 2-4 days and 2 wk, whereas during hypoxia, only delta Pm fell. The %MT of all arteries (less than 50 to greater than 1,000 microns diam) decreased, and peripheral muscularization of less than 100-microns-diam arteries fell between less than 4 days and greater than 2 wk. Our data suggest that 1) the %MT of arteries determines normoxic pulmonary vascular resistance, because only arterial and middle segment resistance fell, 2) peripheral muscularization is a major determinant of hypoxic pulmonary vasoconstriction, because we observed a fall with age in peripheral muscularization of less than 100-micron-diam arteries and in delta Pm with hypoxia, and 3) the arterial limit of the middle segment defined by inflow-outflow occlusion lies in 100- to 1,000-microns-diam arteries.

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Analysis of flow resistance in the pulmonary arterial circulation: Implications for hypoxic pulmonary vasoconstriction

Journal of Applied Physiology ◽

10.1152/japplphysiol.00128.2021 ◽

2021 ◽

Author(s):

David Walter Johnson ◽

Tuhin K. Roy ◽

Timothy W. Secomb

Keyword(s):

Essential Role ◽

Scaling Laws ◽

Hypoxic Pulmonary Vasoconstriction ◽

Pulmonary Arteries ◽

Blood Oxygenation ◽

Pulmonary Vasculature ◽

Arterial Circulation ◽

Pulmonary Vasoconstriction ◽

Hypoxic Vasoconstriction ◽

Pulmonary Arterial

Hypoxic pulmonary vasoconstriction (HPV) plays an essential role in distributing blood in the lung to enhance ventilation-perfusion matching and blood oxygenation. In this study, a theoretical model of the pulmonary vasculature is used to predict the effects of vasoconstriction over specified ranges of vessel diameters on pulmonary vascular resistance (PVR). The model is used to evaluate the ability of hypothesized mechanisms of HPV to account for observed levels of PVR elevation during hypoxia. The vascular structure from pulmonary arteries to capillaries is represented using scaling laws. Vessel segments are modeled as resistive elements and blood flow rates are computed from physical principles. Direct vascular responses to intravascular oxygen levels have been proposed as a mechanism of HPV. In the lung, significant changes in oxygen level occur only in vessels less than 60 μm in diameter. The model shows that observed levels of hypoxic vasoconstriction in these vessels alone cannot account for the elevation of PVR associated with HPV. However, the elevation in PVR associated with HPV can be accounted for if larger upstream vessels also constrict. These results imply that upstream signaling by conducted responses to engage constriction of arterioles plays an essential role in the elevation of PVR during HPV.

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Influence of bronchial arterial PO2 on pulmonary vascular resistance

Journal of Applied Physiology ◽

10.1152/jappl.1991.70.1.405 ◽

1991 ◽

Vol 70 (1) ◽

pp. 405-415 ◽

Cited By ~ 32

Author(s):

B. E. Marshall ◽

C. Marshall ◽

M. Magno ◽

P. Lilagan ◽

G. G. Pietra

Keyword(s):

Vascular Resistance ◽

Bronchial Artery ◽

Hypoxic Pulmonary Vasoconstriction ◽

Pulmonary Arteries ◽

Vasa Vasorum ◽

Pulmonary Vasculature ◽

Mechanically Ventilated ◽

Bronchial Circulation ◽

Pulmonary Vasodilation ◽

Pulmonary Vasoconstriction

In six anesthetized and mechanically ventilated adult sheep, the bronchial artery was perfused with blood from an oxygenator-pump circuit. When the lungs were ventilated with 100% O2 and the bronchial O2 tension (PbrO2) was approximately 600 Torr, the mean of the pulmonary vascular resistances (PVR) measured at the beginning (3.32 +/- 0.29 units) and end (3.17 +/- 0.13 units) of the experiment was 3.24 +/- 0.20 units. When the PbrO2 was changed to 58 +/- 1 Torr, the PVR (2.99 +/- 0.14 units) did not change significantly. However, when the lungs were ventilated with air as PbrO2 was decreased to 91 +/- 4, 77 +/- 3, 56 +/- 2, and 42 +/- 1 Torr, the PVR increased to 3.67 +/- 0.18, 4.03 +/- 0.16, 4.79 +/- 0.19, and 4.71 +/- 0.35 units, respectively. However, when the PbrO2 was decreased further to 26 +/- 1 and 13 +/- 1 Torr, the PVR decreased to 3.77 +/- 0.28 and 3.91 +/- 0.30 units, respectively. In contrast, the bronchial vascular resistance decreased monotonically as PbrO2 decreased. The bronchial circulation supplies vasa vasorum to the walls of all but the smallest pulmonary arteries, and it is therefore suggested that the PO2 of the bronchial circulation is responsible for the bimodal response of the pulmonary vasculature, with stimulation of hypoxic pulmonary vasoconstriction at moderate hypoxemia and of hypoxic pulmonary vasodilation at profound hypoxemia. The physiological and pathophysiological significance of the influence of systemic PO2 on pulmonary vascular tone is discussed.

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Inhibition of hypoxic pulmonary vasoconstriction by antagonists of store-operated Ca2+ and nonselective cation channels

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00044.2005 ◽

2005 ◽

Vol 289 (1) ◽

pp. L5-L13 ◽

Cited By ~ 87

Author(s):

Letitia Weigand ◽

Joshua Foxson ◽

Jian Wang ◽

Larissa A. Shimoda ◽

J. T. Sylvester

Keyword(s):

Hypoxic Pulmonary Vasoconstriction ◽

Acute Hypoxia ◽

Pulmonary Arteries ◽

Cation Channels ◽

Pulmonary Vasoconstriction ◽

Nonselective Cation Channels ◽

Pressor Responses ◽

Intracellular Ca ◽

Pulmonary Arterial

Previous studies indicated that acute hypoxia increased intracellular Ca2+ concentration ([Ca2+]i), Ca2+ influx, and capacitative Ca2+ entry (CCE) through store-operated Ca2+ channels (SOCC) in smooth muscle cells from distal pulmonary arteries (PASMC), which are thought to be a major locus of hypoxic pulmonary vasoconstriction (HPV). Moreover, these effects were blocked by Ca2+-free conditions and antagonists of SOCC and nonselective cation channels (NSCC). To test the hypothesis that in vivo HPV requires CCE, we measured the effects of SOCC/NSCC antagonists (SKF-96365, NiCl2, and LaCl3) on pulmonary arterial pressor responses to 2% O2 and high-KCl concentrations in isolated rat lungs. At concentrations that blocked CCE and [Ca2+]i responses to hypoxia in PASMC, SKF-96365 and NiCl2 prevented and reversed HPV but did not alter pressor responses to KCl. At 10 μM, LaCl3 had similar effects, but higher concentrations (30 and 100 μM) caused vasoconstriction during normoxia and potentiated HPV, indicating actions other than SOCC blockade. Ca2+-free perfusate and the voltage-operated Ca2+ channel (VOCC) antagonist nifedipine were potent inhibitors of pressor responses to both hypoxia and KCl. We conclude that HPV required influx of Ca2+ through both SOCC and VOCC. This dual requirement and virtual abolition of HPV by either SOCC or VOCC antagonists suggests that neither channel provided enough Ca2+ on its own to trigger PASMC contraction and/or that during hypoxia, SOCC-dependent depolarization caused secondary activation of VOCC.

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Abstract 276: Heme Oxygenase-1 Induction Modulates Hypoxic Pulmonary Vasoconstriction

Circulation ◽

10.1161/circ.116.suppl_16.ii_35-b ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Mansoor Ahmad ◽

Nader G Abraham ◽

Michael S Wolin

Keyword(s):

Organ Culture ◽

Heme Oxygenase ◽

Cobalt Chloride ◽

Hypoxic Pulmonary Vasoconstriction ◽

Pulmonary Arteries ◽

Heme Oxygenase 1 ◽

Force Development ◽

Pulmonary Vasoconstriction ◽

Copper Chelator ◽

Relaxing Effect

Endothelium removed Bovine pulmonary arteries (BPA) contract to hypoxia through a mechanism potentially involving lowering of superoxide-derived hydrogen peroxide and removing its basal relaxing effect. Induction of heme oxygenase-1 (HO-1) in BPA by 24 hr organ culture with 0.1mM cobalt chloride was accompanied by a decrease in 5μM lucigenin-detectable superoxide and an increase in horseradish peroxidase-luminol detectable peroxide levels. Force development to 20mM KCl in BPA was not affected by HO-1, but hypoxic pulmonary vasoconstriction (HPV) was significantly reduced. Organ culture with a HO-1 inhibitor (10μM chromium mesoporphyrin) reversed the effects of HO-1 on HPV and peroxide. Pretreatment of BPA with a copper chelator 10mM diethyldithiocarbamate (DETCA) to inactivate Cu,Zn-SOD, prevented the conversion of superoxide to peroxide, and attenuated HPV. DETCA treatment increased superoxide and decreased peroxide to similar levels in control and HO-1 induced BPA. Peroxide scavenging with 0.1mM ebselen increased force development to 20mM KCl and partially reversed the decrease in HPV seen on induction of HO-1. Thus HO-1 induction in BPA causes an increase in superoxide scavenging by Cu,Zn-SOD resulting in increased levels of peroxide, leading to an attenuation of HPV. The generation of superoxide in BPA is not affected by HO-1 induction as DETCA treated control and HO-1 BPA show similar levels of superoxide. Thus, HO-1 induction appears to attenuate HPV in BPA by increasing the conversion of superoxide to peroxide, leading to peroxide levels which may not be adequately lowered by hypoxia.

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Hypoxic induction of Ca2+-dependent action potentials in small pulmonary arteries of the cat

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.5.1389 ◽

1985 ◽

Vol 59 (5) ◽

pp. 1389-1393 ◽

Cited By ~ 73

Author(s):

D. R. Harder ◽

J. A. Madden ◽

C. Dawson

Keyword(s):

Action Potentials ◽

Hypoxic Pulmonary Vasoconstriction ◽

Pulmonary Arteries ◽

Input Resistance ◽

Potential Generation ◽

Applied Current ◽

Pulmonary Vasoconstriction ◽

Ionic Conductances ◽

The Relationship ◽

K Permeability

Small pulmonary arteries (less than 300 micron) from cats were mounted in myographs to record mechanical and electrical responses to hypoxia. When these preparations were exposed to a PO2 of 30–50 Torr after equilibration at 300 Torr they consistently developed active force, which increased or decreased in amplitude as [Ca2+] was raised or lowered, respectively, and was blocked on addition of verapamil. Intracellular electrical recording with glass microelectrodes demonstrated membrane depolarization and action potential generation when PO2 was lowered. Steady-state voltage vs. applied current curves obtained before and during hypoxia showed a significant reduction in input resistance. The relationship between membrane potential and extracellular K+ was not different during hypoxia compared with control, suggesting that there were not marked changes in K+ permeability under this condition. In the presence of verapamil to block Ca2+ inward current the hypoxia-induced action potentials were abolished concomitant with partial membrane repolarization. The results of these studies suggest that in certain isolated pulmonary arteries hypoxia induces contraction by a mechanism involving an increased Ca2+ conductance. These data suggest that the sensor involved in hypoxic pulmonary vasoconstriction may lie within the vessel wall and somehow mediates changes in smooth muscle ionic conductances.

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Ca2+ sensitization during sustained hypoxic pulmonary vasoconstriction is endothelium dependent

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00422.2002 ◽

2003 ◽

Vol 284 (6) ◽

pp. L1121-L1126 ◽

Cited By ~ 43

Author(s):

Tom P. Robertson ◽

Philip I. Aaronson ◽

Jeremy P. T. Ward

Keyword(s):

Hypoxic Pulmonary Vasoconstriction ◽

Mesenteric Arteries ◽

Initial Transient ◽

Endothelin 1 ◽

Pulmonary Vasoconstriction ◽

Endothelial Denudation ◽

Transient Rise ◽

Intracellular Ca ◽

Prostaglandin F

The main aim of this study was to determine the effects of endothelium removal on tension and intracellular Ca2+([Ca2+]i) during hypoxic pulmonary vasoconstriction (HPV) in rat isolated intrapulmonary arteries (IPA). Rat IPA and mesenteric arteries (MA) were mounted on myographs and loaded with the Ca2+-sensitive fluorophore fura PE-3. Arteries were precontracted with prostaglandin F2α, and the effects of hypoxia were examined. HPV in isolated IPA consisted of a transient constriction superimposed on a second sustained phase. Only the latter phase was abolished by endothelial denudation. However, removal of the endothelium had no effect on [Ca2+]i at any point during HPV. The endothelin-1 antagonists BQ-123 and BQ-788 did not affect HPV, although constriction induced by 100 nM endothelin-1 was abolished. In MA, hypoxia induced an initial transient rise in tension and [Ca2+]i, followed by vasodilatation and a fall in [Ca2+]i to (but not below) prehypoxic levels. These results are consistent with sustained HPV being mediated by an endothelium-derived constrictor factor that is distinct from endothelin-1 and that elicits vasoconstriction via Ca2+sensitization.

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Responses of isolated guinea pig pulmonary venules to hypoxia and anoxia

Journal of Applied Physiology ◽

10.1152/jappl.1989.67.5.2147 ◽

1989 ◽

Vol 67 (5) ◽

pp. 2147-2153 ◽

Cited By ~ 8

Author(s):

W. R. Tracey ◽

J. T. Hamilton ◽

I. D. Craig ◽

N. A. Paterson

Keyword(s):

Guinea Pig ◽

Hypoxic Pulmonary Vasoconstriction ◽

Pulmonary Arteries ◽

Major Site ◽

Sustained Contraction ◽

Pulmonary Vasoconstriction ◽

Ph Dependent

Because small pulmonary arteries are believed to be the major site of hypoxic pulmonary vasoconstriction (HPV), pulmonary venular responses to hypoxia have received little attention. Therefore the responses of isolated guinea pig pulmonary venules to hypoxia (bath PO2, 25 Torr) and anoxia (bath PO2, 0 Torr) were characterized. Pulmonary venules [effective lumen radius (ELR), 116 +/- 2 microns] with an adherent layer of parenchyma responded to hypoxia and anoxia with a graded sustained contraction (hypoxia, 0.03 +/- 0.01; anoxia, 0.26 +/- 0.03 mN/mm), whereas paired femoral venules (ELR, 184 +/- 7 microns) contracted to anoxia only (0.05 +/- 0.02 mN/mm). Repeated challenges with hypoxia and anoxia continued to elicit sustained pulmonary venular contractions; femoral venule contractions to anoxia were not repeatable. Hypoxia- and anoxia-induced pulmonary venular contractions were calcium and pH dependent. Dissection of the parenchyma from pulmonary venules did not alter contractions to decreased PO2. Anoxic contractions of pulmonary venules were variably reduced by replacement of the bath fluid; however, the release of a contractile mediator(s) from pulmonary venules during hypoxia or anoxia was not demonstrated. Pulmonary venular responses to hypoxia and anoxia are similar to those induced by hypoxia in vivo, and results obtained from this model may be useful in predicting mechanisms of HPV.

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