Role of Ca2+ entry in the modulation of airway tone by hypoxia

1993 ◽  
Vol 264 (3) ◽  
pp. L284-L289 ◽  
Author(s):  
L. B. Fernandes ◽  
K. Stuart-Smith ◽  
T. L. Croxton ◽  
C. A. Hirshman

To evaluate the cellular mechanisms involved in hypoxic relaxation of airway smooth muscle, we investigated the effects of hypoxia on the behavior of third- and fourth-order porcine bronchial rings contracted with either carbachol or KCl. In one series of experiments, hypoxia (95% N2-5% CO2) was imposed and rings were then exposed to increasing concentrations of carbachol or KCl. In separate experiments, rings were first contracted with carbachol (10(-6) M) or KCl (40 mM) and were then exposed to solutions bubbled with decreasing concentrations of O2. The CO2 concentration was maintained constant at 5% in all experiments. The initial magnitude of KCl-induced but not carbachol-induced contractions was profoundly reduced by 95% N2-5% CO2. The sensitivity of the airway to carbachol was unchanged. In rings precontracted with either carbachol or KCl, hypoxia caused similar losses of airway smooth muscle tone in a reversible and concentration-dependent manner. The effects of hypoxia were independent of the presence of an intact epithelium and were not inhibited by the cyclooxygenase inhibitor indomethacin (5 microM), the soluble guanylate cyclase inhibitor methylene blue (50 microM), or the beta-adrenoceptor antagonist propranolol (1 microM). The impairment by hypoxia of the initiation phase of KCl-induced contractions and of the maintenance phase of both KCl- and carbachol-induced contractions, but not the initiation phase of carbachol-induced contractions, suggests that changes in O2 tension modulate airway tone by altering the entry of extracellular calcium into the airway smooth muscle.

2015 ◽  
Vol 309 (6) ◽  
pp. L537-L542 ◽  
Author(s):  
Rodney D. Britt ◽  
Michael A. Thompson ◽  
Ine Kuipers ◽  
Alecia Stewart ◽  
Elizabeth R. Vogel ◽  
...  

Exposure to moderate hyperoxia in prematurity contributes to subsequent airway dysfunction and increases the risk of developing recurrent wheeze and asthma. The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic GMP (cGMP) axis modulates airway tone by regulating airway smooth muscle (ASM) intracellular Ca2+ ([Ca2+]i) and contractility. However, the effects of hyperoxia on this axis in the context of Ca2+/contractility are not known. In developing human ASM, we explored the effects of novel drugs that activate sGC independent of NO on alleviating hyperoxia (50% oxygen)-induced enhancement of Ca2+ responses to bronchoconstrictor agonists. Treatment with BAY 41–2272 (sGC stimulator) and BAY 60-2770 (sGC activator) increased cGMP levels during exposure to 50% O2. Although 50% O2 did not alter sGCα1 or sGCβ1 expression, BAY 60-2770 did increase sGCβ1 expression. BAY 41-2272 and BAY 60-2770 blunted Ca2+ responses to histamine in cells exposed to 50% O2. The effects of BAY 41-2272 and BAY 60-2770 were reversed by protein kinase G inhibition. These novel data demonstrate that BAY 41-2272 and BAY 60-2770 stimulate production of cGMP and blunt hyperoxia-induced increases in Ca2+ responses in developing ASM. Accordingly, sGC stimulators/activators may be a useful therapeutic strategy in improving bronchodilation in preterm infants.


2009 ◽  
Vol 297 (2) ◽  
pp. L347-L361 ◽  
Author(s):  
Yan Bai ◽  
Martin Edelmann ◽  
Michael J. Sanderson

The relative contribution of inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) and ryanodine receptors (RyRs) to agonist-induced Ca2+ signaling in mouse airway smooth muscle cells (SMCs) was investigated in lung slices with phase-contrast or laser scanning microscopy. At room temperature (RT), methacholine (MCh) or 5-hydroxytryptamine (5-HT) induced Ca2+ oscillations and an associated contraction in small airway SMCs. The subsequent exposure to an IP3R antagonist, 2-aminoethoxydiphenyl borate (2-APB), inhibited the Ca2+ oscillations and induced airway relaxation in a concentration-dependent manner. 2-APB also inhibited Ca2+ waves generated by the photolytic release of IP3. However, the RyR antagonist ryanodine had no significant effect, at any concentration, on airway contraction or agonist- or IP3-induced Ca2+ oscillations or Ca2+ wave propagation. By contrast, a second RyR antagonist, tetracaine, relaxed agonist-contracted airways and inhibited agonist-induced Ca2+ oscillations in a concentration-dependent manner. However, tetracaine did not affect IP3-induced Ca2+ release or wave propagation nor the Ca2+ content of SMC Ca2+ stores as evaluated by Ca2+-release induced by caffeine. Conversely, both ryanodine and tetracaine completely blocked agonist-independent slow Ca2+ oscillations induced by KCl. The inhibitory effects of 2-APB and absence of an effect of ryanodine on MCh-induced airway contraction or Ca2+ oscillations of SMCs were also observed at 37°C. In Ca2+-permeable SMCs, tetracaine inhibited agonist-induced contraction without affecting intracellular Ca2+ levels indicating that relaxation also resulted from a reduction in Ca2+ sensitivity. These results indicate that agonist-induced Ca2+ oscillations in mouse small airway SMCs are primary mediated via IP3Rs and that tetracaine induces relaxation by both decreasing Ca2+ sensitivity and inhibiting agonist-induced Ca2+ oscillations via an IP3-dependent mechanism.


2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Li Tan ◽  
Weiwei Chen ◽  
Ming-Yu Wei ◽  
Jinhua Shen ◽  
Meng-Fei Yu ◽  
...  

The traditional herbPlumula Nelumbinisis widely used in the world because it has many biological activities, such as anti-inflammation, antioxidant, antihypertension, and butyrylcholinesterase inhibition. However, the action ofPlumula Nelumbinison airway smooth muscle (ASM) relaxation has not been investigated. A chloroform extract ofPlumula Nelumbinis(CEPN) was prepared, which completely inhibited precontraction induced by high K+in a concentration-dependent manner in mouse tracheal rings, but it had no effect on resting tension. CEPN also blocked voltage-dependent L-type Ca2+channel- (VDCC-) mediated currents. In addition, ACh-induced precontraction was also completely blocked by CEPN and partially inhibited by nifedipine or pyrazole 3. Besides, CEPN partially reduced ACh-activated nonselective cation channel (NSCC) currents. Taken together, our data demonstrate that CEPN blocked VDCC and NSCC to inhibit Ca2+influx, resulting in relaxation of precontracted ASM. This finding indicates that CEPN would be a candidate of new potent bronchodilators.


2001 ◽  
Vol 280 (3) ◽  
pp. H1113-H1121 ◽  
Author(s):  
Phillip F. Pratt ◽  
Pinlan Li ◽  
Cecilia J. Hillard ◽  
Jason Kurian ◽  
William B. Campbell

Endothelium-derived hyperpolarizing factor (EDHF) is released in response to agonists such as ACh and bradykinin and regulates vascular smooth muscle tone. Several studies have indicated that ouabain blocks agonist-induced, endothelium-dependent hyperpolarization of smooth muscle. We have demonstrated that epoxyeicosatrienoic acids (EETs), cytochrome P-450 metabolites of arachidonic acid, function as EDHFs. To further test the hypothesis that EETs represent EDHFs, we have examined the effects of ouabain on the electrical and mechanical effects of 14,15- and 11,12-EET in bovine coronary arteries. These arteries are relaxed in a concentration-dependent manner to 14,15- and 11,12-EET (EC50 = 6 × 10−7 M), bradykinin (EC50 = 1 × 10−9 M), sodium nitroprusside (SNP; EC50 = 2 × 10−7 M), and bimakalim (BMK; EC50 = 1 × 10−7 M). 11,12-EET-induced relaxations were identical in vessels with and without an endothelium. Potassium chloride (1–15 × 10−3 M) inhibited [3H]ouabain binding to smooth muscle cells but failed to relax the arteries. Ouabain (10−5 to 10−4 M) increased basal tone and inhibited the relaxations to bradykinin, 11,12-EET, and 14,15-EET, but not to SNP or BMK. Barium (3 × 10−5 M) did not alter EET-induced relaxations and ouabain plus barium was similar to ouabain alone. Resting membrane potential ( E m) of isolated smooth muscle cells was −50.2 ± 0.5 mV. Ouabain (3 × 10−5 and 1 × 10−4 M) decreased E m(−48.4 ± 0.2 mV), whereas 11,12-EET (10−7 M) increased E m (−59.2 ± 2.2 mV). Ouabain inhibited the 11,12-EET-induced increase in E m. In cell-attached patch clamp studies, 11,12-EET significantly increased the open-state probability ( NP o) of a calcium-activated potassium channel compared with control cells (0.26 ± 0.06 vs. 0.02 ± 0.01). Ouabain did not change NP o but blocked the 14,15-EET-induced increase in NP o. These results indicate that: 1) EETs relax coronary arteries in an endothelium-independent manner, 2) unlike EETs, potassium chloride does not relax the coronary artery, and 3) ouabain inhibits bradykinin- and EET-induced relaxations as has been reported for EDHF. These findings provide further evidence that EETs are EDHFs.


2005 ◽  
Vol 288 (3) ◽  
pp. L460-L470 ◽  
Author(s):  
É Rousseau ◽  
Martin Cloutier ◽  
Caroline Morin ◽  
Sonia Proteau

The aim of this study was to delineate the mode of action of 20-hydroxy-eicosatetraenoic acid (20-HETE) in airway smooth muscle (ASM) cells. ASM metabolizes arachidonic acid by various enzymatic pathways, including the cytochrome P-450 (CYP-450) ω-hydroxylase, which leads to the production of 20-HETE, a bronchoconstrictive eicosanoid. The present study demonstrated that 20-HETE induced concentration-dependent tonic responses in ASM, whereas transient responses were recorded in Ca2+-free solution, suggesting an intracellular Ca2+ release process. 20-HETE inotropic responses were abolished by 36 μM 2-aminoethoxydiphenyl borate or 1 μM thapsigargin but were insensitive to 10 μM ryanodine, indicating that inositol triphosphate receptors likely control the release of intracellular Ca2+. Sustained tension, which required Ca2+ entry, was partially blocked by 1 μM nifedipine (an L-type) and 100 μM Gd3+ (a nonselective cationic channel blocker). Moreover, in the absence of selective 20-HETE receptor antagonists, 20-HETE tonic responses were inhibited in a concentration-dependent manner (0.1–10 μM) by capsazepine, a well-characterized vanilloid receptor antagonist. Capsazepine was also observed to reverse cumulative responses to 20-HETE and capsaicin, a TRPV1 agonist. In addition, capsazepine pretreatment largely modified the sustained inotropic responses to 20-HETE, suggesting that 20-HETE cross-reacted with TRPV1 receptors with a low affinity (μM) or that its specific receptor was inhibited by the vanilloid antagonist. Data obtained using RHC-80267, ONO-RS-082, and eicosatetraynoic acid, respective inhibitors of diacylglycerol-lipase, phospholipase A2, and CYP-450 ω-hydroxylase, reveal that intracellular arachidonic acid production and its 20-HETE metabolite may be responsible for the activation of nonselective cationic channels and tonic responses.


2002 ◽  
Vol 283 (5) ◽  
pp. L1151-L1159 ◽  
Author(s):  
Adriana Catalli ◽  
Dawei Zhang ◽  
Luke J. Janssen

Using muscle bath techniques, we examined the inhibitory activities of several E- and F-ring isoprostanes in canine and porcine airway smooth muscle. 8-Isoprostaglandin E1 and 8-isoprostaglandin E2 (8-iso PGE2) reversed cholinergic tone in a concentration-dependent manner, whereas the F-ring isoprostanes were ineffective. Desensitization with 8-iso-PGE2 and PGE2 implicated isoprostane activity at the PGE2 receptor (EP). We found that the inhibitory E-ring isoprostane responses were significantly augmented by rolipram (a type IV phosphodiesterase inhibitor), while 1 H-[1,2,4]-oxadiazolo[4,3- a]quinoxalin-1-one (a guanylate cyclase inhibitor) had no effect, suggesting a role for cAMP in isoprostane-mediated relaxations. 8-Iso-PGE2 did not reverse KCl tone, suggesting that voltage-dependent Ca2+ influx and myosin light chain kinase are not suppressed by isoprostanes. Patch-clamp studies showed marked suppression of K+ currents by 8-iso-PGE2. We conclude that E-ring isoprostanes exert PGE2receptor-directed, cAMP-dependent relaxations in canine and porcine airway smooth muscle. This activity is not dependent on K+channel activation or the direct inhibition of voltage-operated Ca2+ influx or myosin light chain kinase.


2000 ◽  
Vol 278 (3) ◽  
pp. H907-H912 ◽  
Author(s):  
Takaaki Ishine ◽  
Isabelle Bouchelet ◽  
Edith Hamel ◽  
Tony J. F. Lee

Isolated porcine pial veins in the presence of active muscle tone have been shown to exhibit rhythmic contractions (RC) that are inhibited by serotonin (5-HT) in a concentration-dependent manner. The 5-HT inhibition of RC is mediated by an as yet unidentified 5-HT receptor subtype located on the vascular smooth muscle. 5-carboxamidotryptamine, which is a potent but nonselective agonist at 5-HT7receptors, has been shown to be the most potent inhibitor of RC in porcine pial veins. Therefore, the present study was designed to determine if the 5-HT-mediated inhibition of RC in pial veins is mediated by 5-HT7 receptors and if 5-HT7 receptor mRNA is expressed in endothelium-denuded pial veins; the study was done with the use of an in vitro tissue bath and RT-PCR techniques. Our findings indicated that 5-HT inhibition of RC in porcine pial veins was prevented by 5-HT7-receptor antagonists (clozapine, pimozide, and LY-215840) in a concentration-dependent manner. Furthermore, a strong PCR signal for the 5-HT7 receptor was consistently detected in endothelium-denuded pial veins. Sequence analysis of the amplified products confirmed their high degree of homology with the porcine and/or human 5-HT7-receptor gene. Taken together, these data suggest that the 5-HT-induced inhibition of RC in porcine pial veins is at least in part mediated by 5-HT7 receptors located on the venous smooth muscle.


2002 ◽  
Vol 96 (2) ◽  
pp. 428-437 ◽  
Author(s):  
Chie Sakihara ◽  
Keith A. Jones ◽  
Robert R. Lorenz ◽  
William J. Perkins ◽  
David O. Warner

Background The investigation examined whether primary alcohols could be used as tools to explore the mechanism of anesthetic actions in airway smooth muscle (ASM). The hypothesis was that, like volatile anesthetics, the primary alcohols relax intact ASM by decreasing intracellular Ca2+ concentration ([Ca2+]i) and by inhibiting agonist-induced increases in the force developed for a given [Ca2+]i (Ca2+ sensitivity). Method The effects of butanol, hexanol, and octanol on isometric force in canine tracheal smooth muscle were examined. The effects of hexanol on [Ca2+]i (measured with fura-2) and the relationship between force and [Ca2+]i were studied during membrane depolarization provided by KCl and during muscarinic stimulation provided by acetylcholine. Results The primary alcohols relaxed ASM contracted by KCl or acetylcholine in a concentration-dependent manner, with potency increasing as chain length increased. The alcohols could completely relax the strips, even during maximal stimulation with 10 microM acetylcholine (median effective concentrations of 28 +/- 12, 1.3 +/- 0.4, and 0.14 +/- 0.05 mM [mean +/- SD] for butanol, hexanol, and octanol, respectively). Hexanol decreased both [Ca2+]i and force in a concentration-dependent manner. Hexanol decreased Ca2+ sensitivity during muscarinic stimulation but had no effect on the force-[Ca2+]i relationship in its absence. Conclusions Primary alcohols produce reversible, complete relaxation of ASM, with potency increasing as chain length increases, by decreasing [Ca2+]i and inhibiting increases in Ca2+ sensitivity produced by muscarinic receptor stimulation. These actions mimic those of volatile anesthetics on ASM, a circumstance suggesting that the primary alcohols may be useful tools for further exploring mechanisms of anesthetic effects on ASM.


2013 ◽  
Vol 304 (9) ◽  
pp. R734-R743 ◽  
Author(s):  
Richard B. Thorpe ◽  
Sara L. Stockman ◽  
James M. Williams ◽  
Thomas M. Lincoln ◽  
William J. Pearce

Chronic hypoxia attenuates soluble guanylate cyclase-induced vasorelaxation in serotonin (5-HT)-contracted ovine carotid arteries. Because protein kinase G (PKG) mediates many effects of soluble guanylate cyclase activation through phosphorylation of multiple kinase targets in vascular smooth muscle, we tested the hypothesis that chronic hypoxia reduces the ability of PKG to phosphorylate its target proteins, which attenuates the ability of PKG to induce vasorelaxation. We also tested the hypothesis that hypoxia attenuates PKG expression and/or activity. Arteries from normoxic and chronically hypoxic (altitude of 3,820 m for 110 days) fetal and adult sheep were denuded of endothelium and equilibrated with 95% O2-5% CO2 in the presence of nitro-l-arginine methyl ester (l-NAME) and NG-nitro-l-arginine (l-NNA) to inhibit residual endothelial nitric oxide synthase. Concentration-response relations for 5-HT were determined in the presence of prazosin to minimize activation of α-adrenergic receptors. The PKG activator 8-( p-chlorophenylthio)-guanosine 3′,5′-cyclic monophosphate (8-pCTP-cGMP) reduced agonist binding affinity of the 5-HT receptor in a concentration-dependent manner that was attenuated by hypoxia. Expression and activity of PKG-I was not significantly affected by chronic hypoxia in either fetal or adult arteries, although PKG-I abundance was greater in fetal arteries. Pretreatment with the large conductance calcium-sensitive potassium channel (BK) inhibitor iberiotoxin attenuated the vasorelaxation induced by 8-pCPT-cGMP in normoxic but not chronically hypoxic arteries. These results support the hypothesis that hypoxia attenuates the vasorelaxant effects of PKG through suppression of the ability of PKG to activate large conductance calcium-sensitive potassium channels in arterial smooth muscle. The results also reveal that this hypoxic effect is greater in fetal than adult arteries and that chronic maternal hypoxia can profoundly affect fetal vascular function.


1998 ◽  
Vol 274 (6) ◽  
pp. L997-L1005 ◽  
Author(s):  
Mark E. Wylam ◽  
Nesli Gungor ◽  
Richard W. Mitchell ◽  
Jason G. Umans

Previous studies in vivo or in isolated airway preparations have suggested that eosinophil-derived polycationic proteins enhance airway smooth muscle tone in an epithelium-dependent manner. We assessed the direct effects of activated human eosinophil supernatant, major basic protein (MBP), and polycationic polypeptides on basal and agonist-stimulated intracellular Ca2+concentrations ([Ca2+]i) in cultured bovine tracheal smooth muscle (TSM) cells. A 1-h incubation of myocytes with activated eosinophil buffer resulted in a doubling of basal [Ca2+]iand increased responsivity to histamine compared with myocytes that were exposed to sham-activated eosinophil buffer. In addition, concentration-dependent acute transient increases and subsequent 1-h sustained elevations of basal [Ca2+]iwere observed immediately after addition of MBP and model polycationic proteins. Finally, both peak and plateau [Ca2+]iresponses to bradykinin addition were augmented significantly in cultured myocytes that had been exposed to low concentrations of MBP or model polycationic proteins but were inhibited at greater concentrations. This elevated [Ca2+]ito polycationic proteins was manifest in epithelium-denuded bovine TSM strips as concentration-dependent increased basal tone. We conclude that activated eosinophil supernatant, MBP, and other polycationic proteins have a direct effect on both basal and subsequent agonist-elicited Ca2+mobilization in cultured TSM cells; TSM strips in vitro demonstrated, respectively, augmented and diminished responses to the contractile agonist acetylcholine. It is possible that alteration in myocyte Ca2+mobilization induced by these substances may influence clinical states of altered airway tone, such as asthma.


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