Resting calcium influx in airway smooth muscle

2005 ◽  
Vol 83 (8-9) ◽  
pp. 717-723 ◽  
Author(s):  
Luis M Montaño ◽  
Blanca Bazán-Perkins
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Calcium Influx ◽  
Physiological Role ◽  
Resting Membrane Potential ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Influx Pathways

Plasma membrane Ca2+ leak remains the most uncertain of the cellular Ca2+ regulation pathways. During passive Ca2+ influx in non-stimulated smooth muscle cells, basal activity of constitutive Ca2+ channels seems to be involved. In vascular smooth muscle, the 3 following Ca2+ entry pathways contribute to this phenomenon: (i) via voltage-dependent Ca2+ channels, (ii) receptor gated Ca2+ channels, and (iii) store operated Ca2+ channels, although, in airway smooth muscle it seems only 2 passive Ca2+ influx pathways are implicated, one sensitive to SKF 96365 (receptor gated Ca2+ channels) and the other to Ni2+ (store operated Ca2+ channels). Resting Ca2+ entry could provide a sufficient amount of Ca2+ and contribute to resting intracellular Ca2+ concentration ([Ca2+]i), maintenance of the resting membrane potential, myogenic tone, and sarcoplasmic reticulum-Ca2+ refilling. However, further research, especially in airway smooth muscle, is required to better explore the physiological role of this passive Ca2+ influx pathway as it could be involved in airway hyperresponsiveness.Key words: basal Ca2+ entry, constitutive Ca2+ channels, airway and vascular smooth muscle, SKF 96365, Ni2+.

Ionic mechanisms and Ca2+ regulation in airway smooth muscle contraction: do the data contradict dogma?

2002 ◽  
Vol 282 (6) ◽  
pp. L1161-L1178 ◽  
Author(s):  
Luke J. Janssen
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Smooth Muscle Contraction ◽  
Channel Blockers ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Spatial And Temporal Heterogeneity ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Ionic Mechanisms

In general, excitation-contraction coupling in muscle is dependent on membrane depolarization and hyperpolarization to regulate the opening of voltage-dependent Ca2+ channels and, thereby, influence intracellular Ca2+ concentration ([Ca2+]i). Thus Ca2+ channel blockers and K+ channel openers are important tools in the arsenals against hypertension, stroke, and myocardial infarction, etc. Airway smooth muscle (ASM) also exhibits robust Ca2+, K+, and Cl− currents, and there are elaborate signaling pathways that regulate them. It is easy, then, to presume that these also play a central role in contraction/relaxation of ASM. However, several lines of evidence speak to the contrary. Also, too many researchers in the ASM field view the sarcoplasmic reticulum as being centrally located and displacing its contents uniformly throughout the cell, and they have focused almost exclusively on the initial single [Ca2+] spike evoked by excitatory agonists. Several recent studies have revealed complex spatial and temporal heterogeneity in [Ca2+]i, the significance of which is only just beginning to be appreciated. In this review, we will compare what is known about ion channels in ASM with what is believed to be their roles in ASM physiology. Also, we will examine some novel ionic mechanisms in the context of Ca2+ handling and excitation-contraction coupling in ASM.

Calcium signaling pathways utilized by P2X receptors in freshly isolated preglomerular MVSMC

2001 ◽  
Vol 280 (6) ◽  
pp. F1054-F1061 ◽  
Author(s):  
Steven M. White ◽  
John D. Imig ◽  
Thu-Thuy Kim ◽  
Benjamin C. Hauschild ◽  
Edward W. Inscho
Keyword(s):  
Calcium Influx ◽  
Receptor Activation ◽  
P2x Receptors ◽  
Transient Increase ◽  
P2x Receptor ◽  
The Novel ◽  
Peak Response ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Influx Pathways

This study tested the hypothesis that P2X receptor activation increases intracellular Ca2+concentration ([Ca2+]i) in preglomerular microvascular smooth muscle cells (MVSMC) by evoking voltage-dependent calcium influx. MVSMC were obtained and loaded with the calcium-sensitive dye fura 2 and studied by using single-cell fluorescence microscopy. The effect of P2X receptor activation on [Ca2+]i was assessed by using the P2X receptor-selective agonist α,β-methylene-ATP and was compared with responses elicited by the endogenous P2 receptor agonist ATP. α,β-Methylene-ATP increased [Ca2+]i dose dependently. Peak increases in [Ca2+]iaveraged 37 ± 11, 73 ± 15, and 103 ± 21 nM at agonist concentrations of 0.1, 1, and 10 μM, respectively. The average peak response elicited by 10 μM α,β-methylene-ATP was ∼34% of the response obtained with 10 μM ATP. α,β-Methylene-ATP induced a transient increase in [Ca2+]i before [Ca2+]i returned to baseline, whereas ATP induced a biphasic response including a peak response followed by a sustained plateau. In Ca2+-free medium, ATP induced a sharp transient increase in [Ca2+]i, whereas the response to α,β-methylene-ATP was abolished. Ca2+channel blockade with 10 μM diltiazem or nifedipine attenuated the response to α,β-methylene-ATP, whereas nonspecific blockade of Ca2+ influx pathways with 5 mM Ni2+ abolished the response. Blockade of P2X receptors with the novel P2X receptor antagonist NF-279 completely but reversibly abolished the response to α,β-methylene-ATP. These results indicate that P2X receptor activation by α,β-methylene-ATP increases [Ca2+]i in preglomerular MVSMC, in part, by stimulating voltage-dependent Ca2+ influx through L-type Ca2+ channels.

scholarly journals The role of calcium influx pathways in phospholipase D activation in bovine adrenal glomerulosa cells

2009 ◽  
Vol 202 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Haixia Qin ◽  
Patricia Kent ◽  
Carlos M Isales ◽  
Peter M Parker ◽  
Mariya V Wilson ◽  
...  
Keyword(s):  
Phospholipase D ◽  
Calcium Influx ◽  
Cell Model ◽  
Primary Cultures ◽  
Extracellular Potassium ◽  
Voltage Dependent ◽  
H295r Cells ◽  
Glomerulosa Cells ◽  
Influx Pathways

The steroid hormone aldosterone maintains sodium homeostasis and is therefore important in the control of blood volume and pressure. Angiotensin II (AngII) and elevated extracellular potassium concentrations ([K+]e), the prime physiologic regulators of aldosterone secretion from adrenal glomerulosa cells, activate phospholipase D (PLD) in these cells. The role of Ca2+ in the activation by these agents is unknown, although nitrendipine, a voltage-dependent Ca2+ channel antagonist, does not inhibit AngII-elicited PLD activation, despite the fact that this compound blocked elevated [K+]e-stimulated PLD activity. PLD activation triggered by AngII was also unaffected by the T-type calcium channel inhibitor nickel. Nevertheless, Ca2+ influx was required for AngII-induced PLD activation in both primary cultures of bovine adrenal glomerulosa cells and a glomerulosa cell model, the NCI H295R adrenocortical carcinoma cell line. The involvement of store-operated Ca2+ (SOC) influx and Ca2+ release-activated Ca2+ (CRAC) influx pathways in PLD activation was investigated using thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor that empties the store to induce SOC influx, and the SOC inhibitor YM-58483 (BTP2), as well as a CRAC inhibitor, tyrphostin A9. In bovine glomerulosa cells, tyrphostin A9 inhibited AngII-induced PLD activation without affecting elevated [K+]e-stimulated enzyme activity. On the other hand, differences were observed between the bovine adrenal glomerulosa and H295R cells in the involvement of Ca2+ influx pathways in PLD activation, with the involvement of the SOC pathway suggested in the H295R cells. In summary, our results indicate that Ca2+ entry only through certain Ca2+ influx pathways is linked to PLD activation.

Role of G proteins in agonist-induced Ca2+ sensitization of tracheal smooth muscle

1998 ◽  
Vol 275 (4) ◽  
pp. L748-L755 ◽  
Author(s):  
Thomas L. Croxton ◽  
Boris Lande ◽  
Carol A. Hirshman
Keyword(s):  
Smooth Muscle ◽  
G Proteins ◽  
Airway Smooth Muscle ◽  
Tracheal Smooth Muscle ◽  
Heterotrimeric G Proteins ◽  
Contractile Responses ◽  
Intracellular Ca ◽  
Increased Sensitivity ◽  
Rho Family

Increased sensitivity to intracellular Ca2+ concentration ([Ca2+]) is an important mechanism for agonist-induced contraction of airway smooth muscle, but the signal transduction pathways involved are uncertain. We studied Ca2+ sensitization with acetylcholine (ACh) and endothelin (ET)-1 in porcine tracheal smooth muscle by measuring contractions at a constant [Ca2+] in strips permeabilized with α-toxin or β-escin. The peptide inhibitor G protein antagonist 2A (GP Ant-2A), which has selectivity for Gq over Gi, inhibited contractile responses to ET-1, ACh, and guanosine 5′- O-(3-thiotriphosphate) (GTPγS), but the proportional inhibition of ACh responses was less than that of ET-1. Pretreatment with pertussis toxin reduced ACh contractions but had no effect on those of ET-1 or GTPγS. Clostridium botulinum C3 exoenzyme, which inactivates Rho family monomeric G proteins, caused similar reductions in contractile responses to ACh, ET-1, and GTPγS. Farnesyltransferase inhibition, which inhibits Ras G proteins, reduced responses to ET-1. We conclude that the heterotrimeric G proteins Gq and Gi both contribute to Ca2+ sensitization by ACh, whereas ET-1 responses involve Gq but not Gi. Both Gq and Gi pathways likely involve Rho family small G proteins. A Ras-mediated pathway also contributes to Ca2+ sensitization by ET-1 in airway smooth muscle.

48-h Hypoxic exposure results in endothelium-dependent systemic vascular smooth muscle cell hyperpolarization

2002 ◽  
Vol 283 (1) ◽  
pp. R79-R85 ◽  
Author(s):  
Scott Earley ◽  
Jay S. Naik ◽  
Benjimen R. Walker
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Vascular Smooth Muscle ◽  
Vessel Wall ◽  
Hypoxic Exposure ◽  
Resting Membrane Potential ◽  
Resistance Arteries ◽  
Adrenergic Agonist ◽  
Intracellular Ca ◽  
Oxide Synthase

Chronic hypoxia (CH) results in reduced sensitivity to vasoconstrictors in conscious rats that persists upon restoration of normoxia. We hypothesized that this effect is due to endothelium-dependent hyperpolarization of vascular smooth muscle (VSM) cells after CH. VSM cell resting membrane potential was determined for superior mesenteric artery strips isolated from CH rats (Pb = 380 Torr for 48 h) and normoxic controls. VSM cells from CH rats studied under normoxia were hyperpolarized compared with controls. Resting vessel wall intracellular Ca2+ concentration ([Ca2+]i) and pressure-induced vasoconstriction were reduced in vessels isolated from CH rats compared with controls. Vasoconstriction and increases in vessel wall [Ca2+]i in response to the α1-adrenergic agonist phenylephrine (PE) were also blunted in resistance arteries from CH rats. Removal of the endothelium normalized resting membrane potential, resting vessel wall [Ca2+]i, pressure-induced vasoconstrictor responses, and PE-induced constrictor and Ca2+ responses between groups. Whereas VSM cell hyperpolarization persisted in the presence of nitric oxide synthase inhibition, heme oxygenase inhibition restored VSM cell resting membrane potential in vessels from CH rats to control levels. We conclude that endothelial derived CO accounts for persistent VSM cell hyperpolarization and vasoconstrictor hyporeactivity after CH.

Defective autophagy in vascular smooth muscle cells alters contractility and Ca2+ homeostasis in mice

2015 ◽  
Vol 308 (6) ◽  
pp. H557-H567 ◽  
Author(s):  
Cédéric F. Michiels ◽  
Paul Fransen ◽  
Dorien G. De Munck ◽  
Guido R. Y. De Meyer ◽  
Wim Martinet
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Vascular Smooth Muscle ◽  
Vascular Reactivity ◽  
Contractile Function ◽  
Cell Types ◽  
Resting Membrane Potential ◽  
Plasmic Reticulum ◽  
Old Mice

Autophagy is an evolutionary preserved process that prevents the accumulation of unwanted cytosolic material through the formation of autophagosomes. Although autophagy has been extensively studied to understand its function in normal physiology, the role of vascular smooth muscle (SM) cell (VSMC) autophagy in Ca2+ mobilization and contraction remains poorly understood. Recent evidence shows that autophagy is involved in controlling contractile function and Ca2+ homeostasis in certain cell types. Therefore, autophagy might also regulate contractile capacity and Ca2+-mobilizing pathways in VSMCs. Contractility (organ chambers) and Ca2+ homeostasis (myograph) were investigated in aortic segments of 3.5-mo-old mice containing a SM cell-specific deletion of autophagy-related 7 ( Atg7; Atg7 fl/ fl SM22α -Cre+ mice) and in segments of corresponding control mice ( Atg7+/+ SM22α -Cre+). Our results indicate that voltage-gated Ca2+ channels (VGCCs) of Atg7 fl/ fl SM22α -Cre+ VSMCs were more sensitive to depolarization, independent of changes in resting membrane potential. Contractions elicited with K+ (50 mM) or the VGCC agonist BAY K8644 (100 nM) were significantly higher due to increased VGCC expression and activity. Interestingly, the sarcoplasmic reticulum of Atg7 fl/ fl SM22α -Cre+ VSMCs was enlarged, which, combined with increased sarco(endo)plasmic reticulum Ca2+-ATPase 2 expression and higher store-operated Ca2+ entry, promoted inositol 1,4,5-trisphosphate-mediated contractions of Atg7 fl/ fl SM22α -Cre+ segments and maximized the Ca2+ storing capacity of the sarcoplasmic reticulum. Moreover, decreased plasma membrane Ca2+-ATPase expression in Atg7 fl/ fl SM22α -Cre+ VSMCs hampered Ca2+ extrusion to the extracellular environment. Overall, our study indicates that defective autophagy in VSMCs leads to an imbalance between Ca2+ release/influx and Ca2+ reuptake/extrusion, resulting in higher basal Ca2+ concentrations and significant effects on vascular reactivity.

Caveolae facilitate muscarinic receptor-mediated intracellular Ca2+ mobilization and contraction in airway smooth muscle

2007 ◽  
Vol 293 (6) ◽  
pp. L1406-L1418 ◽  
Author(s):  
Reinoud Gosens ◽  
Gerald L. Stelmack ◽  
Gordon Dueck ◽  
Mark M. Mutawe ◽  
Martha Hinton ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Muscarinic Receptor ◽  
Airway Smooth Muscle ◽  
Isometric Force ◽  
Signaling Proteins ◽  
Muscarinic Agonist ◽  
Caveolin 1 ◽  
Intracellular Ca ◽  
Domain Peptide

Contractile responses of airway smooth muscle (ASM) determine airway resistance in health and disease. Caveolae microdomains in the plasma membrane are marked by caveolin proteins and are abundant in contractile smooth muscle in association with nanospaces involved in Ca2+ homeostasis. Caveolin-1 can modulate localization and activity of signaling proteins, including trimeric G proteins, via a scaffolding domain. We investigated the role of caveolae in contraction and intracellular Ca2+ ([Ca2+]i) mobilization of ASM induced by the physiological muscarinic receptor agonist, acetylcholine (ACh). Human and canine ASM tissues and cells predominantly express caveolin-1. Muscarinic M3 receptors (M3R) and Gαq/11 cofractionate with caveolin-1-rich membranes of ASM tissue. Caveolae disruption with β-cyclodextrin in canine tracheal strips reduced sensitivity but not maximum isometric force induced by ACh. In fura-2-loaded canine and human ASM cells, exposure to methyl-β-cyclodextrin (mβCD) reduced sensitivity but not maximum [Ca2+]i induced by ACh. In contrast, both parameters were reduced for the partial muscarinic agonist, pilocarpine. Fluorescence microscopy revealed that mβCD disrupted the colocalization of caveolae-1 and M3R, but [ N-methyl-3H]scopolamine receptor-binding assay revealed no effect on muscarinic receptor availability or affinity. To dissect the role of caveolin-1 in ACh-induced [Ca2+]i flux, we disrupted its binding to signaling proteins using either a cell-permeable caveolin-1 scaffolding domain peptide mimetic or by small interfering RNA knockdown. Similar to the effects of mβCD, direct targeting of caveolin-1 reduced sensitivity to ACh, but maximum [Ca2+]i mobilization was unaffected. These results indicate caveolae and caveolin-1 facilitate [Ca2+]i mobilization leading to ASM contraction induced by submaximal concentrations of ACh.

Antisense inhibition of Na+/Ca2+ exchange in primary cultured arterial myocytes

1995 ◽  
Vol 269 (5) ◽  
pp. C1340-C1345 ◽  
Author(s):  
M. K. Slodzinski ◽  
M. Juhaszova ◽  
M. P. Blaustein
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Digital Imaging ◽  
Mesenteric Artery ◽  
Physiological Role ◽  
Antisense Oligodeoxynucleotides ◽  
Antisense Inhibition ◽  
Fura 2 ◽  
Rat Mesenteric Artery

The effects of chimeric phosphorothioated antisense oligodeoxynucleotides (AS-oligos) targeted against the Na+/Ca2+ exchanger (NCX) were tested in primary cultured rat mesenteric artery myocytes. In parallel cultures, myocytes proliferated and were morphologically normal in the presence of scrambled nonsense (NS-) or AS-oligos or no oligos (controls). NCX function was examined with digital imaging, using fura 2 to estimate the cytosolic free Ca2+ concentration ([Ca2+]cyt). Resting [Ca2+]cyt was higher (145 +/- 4 nM; P < 0.05) in AS-oligo-treated cells than in controls (125 +/- 5 nM) or NS-oligo-treated cells (131 +/- 4 nM). Lowering external Na+, to promote Ca2+ entry via NCX, increased [Ca2+]cyt transiently in controls and NS-oligo-treated cells but not in AS-oligo-treated cells. Raising the cytosolic free Na+ concentration with ouabain augmented the low-Na(+)-induced rise in [Ca2+]cyt in controls and NS-oligo-treated cells, but AS-oligo-treated cells still did not respond. Nevertheless, serotonin (5-HT) increased [Ca2+]cyt in all three groups. Thus AS-oligos selectively blocked NCX activity but not the 5-HT response. To determine the effect of NCX knockdown on the modulation of stored Ca2+, the 5-HT response was tested immediately after removal of external Ca2+. Ouabain augmented the 5-HT-induced rise in [Ca2+]cyt in control and NS-oligo-treated cells but not AS-oligo-treated cells. This indicates that the NCX can modulate intracellular Ca2+ stores. We conclude that AS-oligos are useful for investigating the physiological role of NCX in vascular smooth muscle.

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