Regulation of Ca
            <sup>2+</sup>
            Homeostasis by Atypical Na
            <sup>+</sup>
            Currents in Cultured Human Coronary Myocytes

Boccara, Gilles; Choby, Cécile; Frapier, Jean Marc; Quignard, Jean-François; Nargeot, Joël; Dayanithi, Govindan; Richard, Sylvain

doi:10.1161/01.res.85.7.606

Cited by 26 publications

(47 citation statements)

References 24 publications

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“…The present study demonstrates the biophysical and molecular characteristics of I Na in cultured hASMCs, consistent with the previous reports in human cultured myocytes (3,17,23,25). We also demonstrate that the expression of SCN9A is limited to cultured and diseased conditions in human and rabbit aorta smooth muscle cells and is absent in isolated native aorta.…”

Section: Discussionsupporting

confidence: 92%

“…After being cleaned of connective tissue and adhered fat tissue, isolated arteries were cut open longitudinally and the endothelium was removed by gently rubbing with a cotton swab. The aorta was cut into small pieces about 1-3 mm 3 and then incubated in a gently shaking bath at 37°C in Ca 2ϩ -free Tyrode solution containing 0.4 mg/ml collagenase type IA (Sigma) for 90 min. The isolated cells were then used for later experiments.…”

Section: Methodsmentioning

confidence: 99%

“…At present, 10 ␣-subunit (SCN1-6, 8-11A) and 4 ␤-subunit (SCN␤ [1][2][3][4] ) genes have been identified with isoform expression dependent on cell types (24). I Na has also been identified in cultured smooth muscle cells such as coronary arterial (3), pulmonary arterial (25), and bronchial (17) smooth muscle cells.…”

Section: Voltage-gated Namentioning

confidence: 99%

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Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells

Meguro¹,

Iida²,

Takano³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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Na ϩ channel currents (INa) are expressed in several types of smooth muscle cells. The purpose of this study was to evaluate the expression of INa, its functional role, pathophysiology in cultured human (hASMCs) and rabbit aortic smooth muscle cells (rASMCs), and its association with vascular intimal hyperplasia. In whole cell voltage clamp, I Na was observed at potential positive to Ϫ40 mV, was blocked by tetrodotoxin (TTX), and replacing extracellular Na ϩ with N-methyl-D-glucamine in cultured hASMCs. In contrast to native aorta, cultured hASMCs strongly expressed SCN9A encoding NaV1.7, as determined by quantitative RT-PCR. I Na was abolished by the treatment with SCN9A small-interfering (si)RNA (P Ͻ 0.01). TTX and SCN9A siRNA significantly inhibited cell migration (P Ͻ 0.01, respectively) and horseradish peroxidase uptake (P Ͻ 0.01, respectively). TTX also significantly reduced the secretion of matrix metalloproteinase-2 6 and 12 h after the treatment (P Ͻ 0.01 and P Ͻ 0.05, respectively). However, neither TTX nor siRNA had any effect on cell proliferation. L-type Ca 2ϩ channel current was recorded, and INa was not observed in freshly isolated rASMCs, whereas TTX-sensitive I Na was recorded in cultured rASMCs. Quantitative RT-PCR and immunostaining for NaV1.7 revealed the prominent expression of SCN9A in cultured rASMCs and aorta 48 h after balloon injury but not in native aorta. In conclusion, these studies show that INa is expressed in cultured and diseased conditions but not in normal aorta. The NaV1.7 plays an important role in cell migration, endocytosis, and secretion. NaV1.7 is also expressed in aorta after balloon injury, suggesting a potential role for NaV1.7 in the progression of intimal hyperplasia. vascular smooth muscle; sodium channel; SCN9A; balloon injury VOLTAGE-GATED NA ϩ CHANNELS (I Na ) are generally involved in the generation and propagation of action potentials in nerve fiber (5), skeletal muscle, and cardiac muscle (13). At present, 10 ␣-subunit (SCN1-6, 8-11A) and 4 ␤-subunit (SCN␤ 1-4 ) genes have been identified with isoform expression dependent on cell types (24). I Na has also been identified in cultured smooth muscle cells such as coronary arterial (3), pulmonary arterial (25), and bronchial (17) smooth muscle cells. However, the pathophysiology and function of I Na and its molecular characteristics are not fully understood in cultured human aortic smooth muscle cells (hASMCs).Vascular smooth muscle cells undergo cellular proliferation and migration in the formation of atherosclerosis and intimal hyperplasia (6,30). Smooth muscle cells in atherosclerotic plaques or neointimal hyperplasia are different from native contractile smooth muscle cells, but rather resemble cultured vascular smooth muscle cells (36). Since I Na is expressed only in the cultured and proliferative state, but not in the freshly isolated aortic smooth muscle cells (7), it is likely that this phenotypical change contributes to the cell proliferation, migration, and endocytosis, which mirrors exocytosis (33) in ...

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Section: Discussionsupporting

confidence: 92%

Section: Methodsmentioning

confidence: 99%

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Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells

Meguro¹,

Iida²,

Takano³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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“…The inward I Na we observed in human PASMC possessed biophysical and pharmacological characteristics similar to those previously identified in other human VSMC [4,5,7,16,28]: sensitivity to TTX (EC 50 17.5 nM), -60 to -50 mV activation threshold, -15 to 0 mV peak amplitude potential, -70 to -65 mV half-inactivation voltage, -25 to -15 mV half-activation voltage, and activation (τ act ∼1 ms) and inactivation time (τ inact ≤ 4 ms) constants. Similarities in the window currents, -60 to -10 mV in 3human PASMC and other VSMC [4,7], also suggest that Na + channels are active over a wide range of physiological E m , and that they may contribute to the regulation of resting E m in human PASMC. However, in unpublished observations, we found that TTX did not significantly alter human PASMC E m (-41.2±2.6 mV, -46.2±3.1 mVin TTX, n=4, data not shown) indicating that Na + channel activity does not modulate E m in cultured normal human PASMC.…”

supporting

confidence: 82%

Identification of functional voltage-gated Na+ channels in cultured human pulmonary artery smooth muscle cells

Platoshyn

Remillard

Fantozzi

et al. 2005

Pflugers Arch - Eur J Physiol

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Electrical excitability, which plays an important role in excitation-contraction coupling in the pulmonary vasculature, is regulated by transmembrane ion flux in pulmonary artery smooth muscle cells (PASMC). This study aimed to characterize the electrophysiological properties and molecular identities of voltage-gated Na + channels in cultured human PASMC. We recorded tetrodotoxinsensitive and rapidly inactivating Na + currents with properties similar to those described in cardiac myocytes. Using RT-PCR, we detected transcripts of seven Na + channel α genes (SCN2A, 3A, 4A, 7A, 8A, 9A, and 11A), and two β subunit genes (SCN1B and 2B). Our results demonstrate that human PASMC express TTX-sensitive voltage-gated Na + channels. Their physiological functions remain unresolved, although our data suggest that Na + channel activity does not directly influence membrane potential, intracellular Ca 2+ release, or proliferation in normal human PASMC. Whether their expression and/or activity are heightened in the pathological state is discussed.Keywords membrane potential; Na + channels; vascular smooth muscle; pulmonary Voltage-gated Na + channels play a major role in regulating cell excitability, particularly as it pertains to the generation of action potentials in neurons, skeletal muscle, and cardiac myocytes. Evidence has shown that, in vascular smooth muscle, action potentials are not dependent on Na + channels since tetrodotoxin (TTX) has no effect on amplitude and duration of action potentials [18], leading to the belief that these channels might not be present or prominent in these tissues. Nonetheless, Na + currents (I Na ) have been measured in visceral smooth muscles such as myometrium and uterus (pregnant), colon, esophagus, stomach, and ureter as well as in certain vascular smooth muscles such as the portal and azygos veins [2,8,[24][25][26]31,33,34]. The identification of functional voltage-gated Na + channels in quiescent and proliferating vascular smooth muscle cells (VSMC), however, has not been as forthcoming. Currently, I Na have been measured in smooth muscle cells isolated from the coronary artery, aorta, vena cava, and pulmonary artery of various species, including humans [5,16,23,27]. On only rare occasions have I Na been recorded in freshly dissociated human VSMC, although they are readily detected when the same cells are cultured [28]. In isolated cases, I Na have been recorded in both freshly dispersed rabbit [27] de-differentiation and proliferation [28]. More specifically, voltage-gated Na + channel expression and activity may be required either to facilitate the transition or to promote the de-differentiation of cells from "contractile" to "synthetic" or "proliferative" phenotypes [20,30]. This raises the possibility that the expression of functional voltage-gated Na + channels in cultured cells act as a trigger for cell de-differentiation and proliferation, possibly via enhanced cytoplasmic free Ca 2+ concentration ([Ca 2+ ] cyt ).The molecular identification of the subunits that make ...

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“…Measurement of Intracellular Ca 2ϩ -Intracellular Ca 2ϩ level was measured in single cells, as previously described (21). Briefly, the dual excitation ratiometric Ca 2ϩ -sensitive dye, Fura-2, was used for [Ca 2ϩ ] i imaging measurements by means of an Olympus-LSR system (MER-LIN; Life Science Resources Ltd., Cambridge, UK).…”

Section: Methodsmentioning

confidence: 99%

Permissive Effect of Voltage on mGlu 7 Receptor Subtype Signaling in Neurons

Perroy

Richard

Nargeot

et al. 2002

Journal of Biological Chemistry

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G protein-coupled receptors mobilize neuronal signaling cascades which until now have not been shown to depend on the state of membrane depolarization. Thus we have previously shown that the metabotropic glutamate receptor type 7 (mGlu7 receptor) blocks P/Q-type Ca 2؉ channels via activation of a G o protein and PKC, in cerebellar granule cells. We show here that the transient depolarizations used to evoke the studied Ca 2؉ current were indeed permissive to activate this pathway by a mGlu7 receptor agonist. Indeed, sustained depolarization to 0 mV was sufficient to inhibit P/Q-type Ca 2؉ channels. This effect involved a conformational change in voltage-gated sodium channel independently of Na ؉ flux, activation of a pertussis toxin-sensitive G-protein, inositol trisphosphate formation, intracellular Ca 2؉ release, and PKC activity. Subliminal sustained membrane depolarization became efficient in inducing inositol trisphosphate formation, release of intracellular Ca 2؉ and in blocking Ca 2؉ channels, when applied concomitantly with the mGlu7a receptor agonist, D,L-aminophosphonobutyrate. This synergistic effect of membrane depolarization and mGlu7 receptor activation provides a mechanism by which neuronal excitation could control action of the mGlu7 receptor in neurons.The excitatory neurotransmitter, glutamate, mediates its effects by activating ionotropic and metabotropic (mGlu) receptors. Eight genes encoding mGlu receptors have been identified and classified into three groups. The group I (mGlu1 and mGlu5 receptors) activates PLC through a G q protein, whereas group II (mGlu2 and mGlu3 receptors) and group III (mGlu4, mGlu6, mGlu7, and mGlu8 receptors) are coupled to G i /G o proteins (1). These receptors are widely distributed throughout the mammalian brain (2-5), but only the mGlu7 receptor subtype is almost exclusively localized at presynaptic sites (6 -8).Group II and III mGlu receptors, and particularly the mGlu7 receptor subtype, inhibit synaptic transmission (1, 9). Thus in vitro studies have shown that stimulation of mGlu7 receptors decreases release of glutamate in cerebellar cultures (10) and GABA in striatal cultures (11), promoting neuroprotection and excitotoxicity, respectively. Moreover, we have recently shown that mGlu7 receptors selectively block P/Q-type Ca 2ϩ channels in neurons (12), and these channels control transmitter release (13). Together these studies suggest that mGlu7 receptors play an important role in the modulation of synaptic transmission.Recent studies have pointed out that in the rat locus coeruleus, group III mGlu receptor agonists down-regulate high but not low frequency synaptic activity (14), suggesting that this receptor action depends on the state of neuronal depolarization. Moreover, a voltage-dependent activation of a G o protein has recently been shown in rat brain synaptoneurosomes (15). In light of these results, and because the mGlu7 receptor is coupled to a G o protein, this receptor is a potential candidate for mobilization of both voltage-and G o protein-depen...

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Regulation of Ca ²⁺ Homeostasis by Atypical Na ⁺ Currents in Cultured Human Coronary Myocytes

Cited by 26 publications

References 24 publications

Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells

Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells

Identification of functional voltage-gated Na+ channels in cultured human pulmonary artery smooth muscle cells

Permissive Effect of Voltage on mGlu 7 Receptor Subtype Signaling in Neurons

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Regulation of Ca 2+ Homeostasis by Atypical Na + Currents in Cultured Human Coronary Myocytes

Cited by 26 publications

References 24 publications

Function and role of voltage-gated sodium channel NaV1.7 expressed in aortic smooth muscle cells

Function and role of voltage-gated sodium channel NaV1.7 expressed in aortic smooth muscle cells

Identification of functional voltage-gated Na+ channels in cultured human pulmonary artery smooth muscle cells

Permissive Effect of Voltage on mGlu 7 Receptor Subtype Signaling in Neurons

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Product

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Regulation of Ca ²⁺ Homeostasis by Atypical Na ⁺ Currents in Cultured Human Coronary Myocytes

Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells

Function and role of voltage-gated sodium channel Na_V1.7 expressed in aortic smooth muscle cells