Ca2+ sensitization during sustained hypoxic pulmonary vasoconstriction is endothelium dependent

2003 ◽  
Vol 284 (6) ◽  
pp. L1121-L1126 ◽  
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.

ROK contribution to endothelin-mediated contraction in aorta and mesenteric arteries following intermittent hypoxia/hypercapnia in rats

2007 ◽  
Vol 293 (5) ◽  
pp. H2911-H2918 ◽  
Author(s):  
Kyan J. Allahdadi ◽  
Benjimen R. Walker ◽  
Nancy L. Kanagy
Keyword(s):  
Arterial Pressure ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Intermittent Hypoxia ◽  
Myosin Light Chain ◽  
Mesenteric Arteries ◽  
Endothelin 1 ◽  
Second Messenger Systems ◽  
Intracellular Ca ◽  
Inner Diameter

We reported previously that intermittent hypoxia with CO2 to maintain eucapnia (IH-C) elevates plasma endothelin-1 (ET-1) and arterial pressure. In small mesenteric arteries (sMA; inner diameter = 150 μm), IH-C augments ET-1 constrictor sensitivity but diminishes ET-1-induced increases in intracellular Ca2+ concentration, suggesting IH-C exposure increases both ET-1 levels and ET-1-stimulated Ca2+ sensitization. Because Rho-associated kinase (ROK) can mediate Ca2+ sensitization, we hypothesized that augmented vasoconstrictor sensitivity to ET-1 in arteries from IH-C-exposed rats is dependent on ROK activation. In thoracic aortic rings, ET-1 contraction was not different between groups, but ROK inhibition (Y-27632, 3 and 10 μM) attenuated ET-1 contraction more in IH-C than in sham arteries (50 ± 11 and 78 ± 7% vs. 41 ± 12 and 48 ± 9% inhibition, respectively). Therefore, ROK appears to contribute more to ET-1 contraction in IH-C than in sham aorta. In sMA, ROK inhibitors did not affect ET-1-mediated constriction in sham arteries and only modestly inhibited it in IH-C arteries. In ionomycin-permeabilized sMA with intracellular Ca2+ concentration held at basal levels, Y-27632 did not affect ET-1-mediated constriction in either IH-C or sham sMA and ET-1 did not stimulate ROK translocation. In contrast, inhibition of myosin light-chain kinase (ML-9, 100 μM) prevented ET-1-mediated constriction in sMA from both groups. Therefore, IH-C exposure increases ET-1 vasoconstrictor sensitivity in sMA but not in aorta. Furthermore, ET-1 constriction is myosin light-chain kinase dependent and mediated by Ca2+ sensitization that is independent of ROK activation in sMA but not aorta. Thus ET-1-mediated signaling in aorta and sMA is altered by IH-C but is dependent on different second messenger systems in small vs. large arteries.

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

2005 ◽  
Vol 289 (1) ◽  
pp. L5-L13 ◽  
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.

Hypoxic pulmonary vasoconstriction in intact rat intrapulmonary arteries is not initiated by inhibition of Na+-Ca2+ exchange

2007 ◽  
Vol 293 (4) ◽  
pp. L982-L990 ◽  
Author(s):  
Silke Becker ◽  
Lyn M. Moir ◽  
Vladimir A. Snetkov ◽  
Philip I. Aaronson
Keyword(s):  
Hypoxic Pulmonary Vasoconstriction ◽  
Combined Treatment ◽  
Physiological Saline ◽  
Isometric Tension ◽  
Acetoxymethyl Ester ◽  
Tension Development ◽  
Reverse Mode ◽  
Pulmonary Vasoconstriction ◽  
Physiological Saline Solution ◽  
Intracellular Ca

It has been proposed that a hypoxia-induced inhibition of the Na+-Ca2+ exchanger (NCX) contributes to hypoxic pulmonary vasoconstriction (HPV). By recording isometric tension development in rat intrapulmonary arteries (IPA), we examined the effect on HPV of maneuvers that reduce the ability of NCX to regulate intracellular Ca2+ concentration ([Ca2+]i). In some experiments, fura pentakis(acetoxymethyl) ester-3 (fura PE-3) was also used to monitor [Ca2+]i. HPV was elicited in IPA that were pretreated with 10 μM diltiazem and slightly preconstricted with PGF2α, which enhances the hypoxic response. Substitution of Na+ with Li+ increased HPV and the associated rise in [Ca2+]i. Pretreatment with ouabain (100 μM) to diminish the Na+ gradient or with the reverse-mode NCX inhibitor KB-R7943 (3 or 10 μM) had no significant effect on HPV. Combined treatment with ouabain and low-[Na+] (24 mM) solution enhanced HPV strongly. The role of NCX in Ca2+ extrusion was examined by assessing the decrease in [Ca2+]i in Ca2+-free physiological saline solution either containing or lacking Na+ following a high K+-induced loading of cellular [Ca2+]. Although the large initial rapid fall in [Ca2+] was Na+ independent, final recovery of [Ca2+] to its basal level was delayed in the absence of Na+. Therefore, HPV persisted or was increased under conditions in which forward-mode NCX was already attenuated or prevented, demonstrating that inhibition of NCX by hypoxia is unlikely to initiate HPV. Instead, NCX appears to act to inhibit HPV as would be expected if it is functioning to extrude Ca2+.

Abstract 658: Suppressed Hypoxic Pulmonary Vasoconstriction in Malonyl-CoA-Decarboxylase Knock-Out Mice

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Gopinath Sutendra ◽  
Sebastien Bonnet ◽  
Alois Haromy ◽  
Gary Lopaschuk ◽  
Jason Dyck ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Exercise Tolerance ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Acute Hypoxia ◽  
Metabolic Enzyme ◽  
Acid Oxidation ◽  
Wild Mice ◽  
Pulmonary Vasoconstriction ◽  
Malonyl Coa ◽  
Intracellular Ca

Background : Hypoxic pulmonary vasoconstriction (HPV) is intrinsic to the pulmonary artery smooth muscle cells (PASMC). A recently proposed mechanism for HPV suggests that hypoxia is sensed within the mitochondria, altering the production of activated oxygen species (AOS) in response to changes in PO 2 . Decreased AOS (like H 2 O 2 ) inhibit Kv channels, depolarize PASMC, increase influx of Ca ++ , causing PASMC contraction. Malonyl-CoA-Decarboxylase (MCD) is a metabolic enzyme, that when inhibited suppresses the mitochondrial-based fatty acid oxidation, promoting glucose oxidation. We have shown that knockout mice lacking MCD (KO-MCD) are resistant to chronic-hypoxia-induced pulmonary hypertension (CH-PHT) but they have a normal phenotype in normoxia. We hypothesized that KO-MCD mice have suppressed HPV. Methods and Results : We compared KO-MCD to wild mice (W-MCD) using PASMC patch clamping, intracellular Ca ++ (fura-2), mitochondrial membrane potential (ΔΨm, using TMRM and confocal microscopy), mitochondrial AOS production (mitosox and confocal microscopy) and isolated intact resistance PA rings; we also studied exercise tolerance (distance covered in a treadmill) during normoxia and acute hypoxia (n =7–10 mice/group for all studies). As expected, in W-MCD mice acute hypoxia inhibited K + current (Ik), increased intracellular Ca ++ and mitochondrial ΔΨm, decreased mitochondrial AOS production, increased PA tone and decreased exercise tolerance (due to the rapid increase in PA pressure and decrease in cardiac output). In contrast, KO-MCD showed an impressive lack of response to acute hypoxia in all the parameters studied (table ). Conclusions : Our data show that acute hypoxia is not sensed in W-MCD mice and might offer at least a partial explanation for the resistance to CH-PHT in these mice. They also offer a novel insight into the metabolic basis of pulmonary vascular reactivity and HPV.

Acute and chronic hypoxic pulmonary vasoconstriction: a central role for endothelin-1?

2002 ◽  
Vol 132 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Larissa A Shimoda ◽  
James S.K Sham ◽  
Qiang Liu ◽  
J.T Sylvester
Keyword(s):  
Hypoxic Pulmonary Vasoconstriction ◽  
Endothelin 1 ◽  
Pulmonary Vasoconstriction

Ca2+ signaling in hypoxic pulmonary vasoconstriction: effects of myosin light chain and Rho kinase antagonists

2007 ◽  
Vol 293 (3) ◽  
pp. L674-L685 ◽  
Author(s):  
Jian Wang ◽  
Letitia Weigand ◽  
Joshua Foxson ◽  
Larissa A. Shimoda ◽  
J. T. Sylvester
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Rho Kinase ◽  
Pulmonary Vasoconstriction ◽  
Dependent Inhibition ◽  
Intracellular Ca ◽  
Myosin Motors ◽  
Isolated Lungs ◽  
Cellular Components

Antagonists of myosin light chain (MLC) kinase (MLCK) and Rho kinase (ROK) are thought to inhibit hypoxic pulmonary vasoconstriction (HPV) by decreasing the concentration of phosphorylated MLC at any intracellular Ca2+ concentration ([Ca2+]i) in pulmonary arterial smooth muscle cells (PASMC); however, these antagonists can also decrease [Ca2+]i. To determine whether MLCK and ROK antagonists alter Ca2+ signaling in HPV, we measured the effects of ML-9, ML-7, Y-27632, and HA-1077 on [Ca2+]i, Ca2+ entry, and Ca2+ release in rat distal PASMC exposed to hypoxia or depolarizing concentrations of KCl. We performed parallel experiments in isolated rat lungs to confirm the inhibitory effects of these agents on pulmonary vasoconstriction. Our results demonstrate that MLCK and ROK antagonists caused concentration-dependent inhibition of hypoxia-induced increases in [Ca2+]i in PASMC and HPV in isolated lungs and suggest that this inhibition was due to blockade of Ca2+ release from the sarcoplasmic reticulum and Ca2+ entry through store- and voltage-operated Ca2+ channels in PASMC. Thus MLCK and ROK antagonists might block HPV by inhibiting Ca2+ signaling, as well as the actin-myosin interaction, in PASMC. If effects on Ca2+ signaling were due to decreased phosphorylated myosin light chain concentration, their diversity suggests that MLCK and ROK antagonists may have acted by inhibiting myosin motors and/or altering the cytoskeleton in a manner that prevented achievement of required spatial relationships among the cellular components of the response.

Hypoxic constriction of porcine distal pulmonary arteries: endothelium and endothelin dependence

2001 ◽  
Vol 280 (5) ◽  
pp. L856-L865 ◽  
Author(s):  
Q. Liu ◽  
J. S. K. Sham ◽  
L. A. Shimoda ◽  
J. T. Sylvester
Keyword(s):  
Hypoxic Pulmonary Vasoconstriction ◽  
Pulmonary Arteries ◽  
Bronchial Arteries ◽  
Pulmonary Vasoconstriction ◽  
Endothelial Denudation ◽  
Basal Release ◽  
Pulmonary Arterial ◽  
Pulmonary Arterial Smooth Muscle

To determine the role of endothelium in hypoxic pulmonary vasoconstriction (HPV), we measured vasomotor responses to hypoxia in isolated seventh-generation porcine pulmonary arteries < 300 μm in diameter with (E+) and without endothelium. In E+ pulmonary arteries, hypoxia decreased the vascular intraluminal diameter measured at a constant transmural pressure. These constrictions were complete in 30–40 min; maximum at Po 2 of 2 mmHg; half-maximal at Po 2 of 40 mmHg; blocked by exposure to Ca2+-free conditions, nifedipine, or ryanodine; and absent in E+ bronchial arteries of similar size. Hypoxic constrictions were unaltered by indomethacin, enhanced by indomethacin plus N G-nitro-l-arginine methyl ester, abolished by BQ-123 or endothelial denudation, and restored in endothelium-denuded pulmonary arteries pretreated with 10−10 M endothelin-1 (ET-1). Given previous demonstrations that hypoxia caused contractions in isolated pulmonary arterial myocytes and that ET-1 receptor antagonists inhibited HPV in intact animals, our results suggest that full in vivo expression of HPV requires basal release of ET-1 from the endothelium to facilitate mechanisms of hypoxic reactivity in pulmonary arterial smooth muscle.

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