Effect of dexamethasone on voltage-gated Na+ channel in cultured human bronchial smooth muscle cells

Nakajima, Toshiaki; Jo, Taisuke; Meguro, Kentaro; Oonuma, Hitoshi; Ma, Ji; Kubota, Naoki; Imuta, Hiroyuki; Takano, Haruhito; Iida, Hidehiro; Nagase, Takahide; Nagata, Toshiaki

doi:10.1016/j.lfs.2008.04.007

Cited by 12 publications

(19 citation statements)

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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%

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%

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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“…These values were also similar to those reported for Na V 1.5, although such results must be interpreted with the caveat that voltage-dependent kinetics may be influenced by expression of ␤-subunits, different expression systems, and different recording conditions (5). However, the expression of ␤-subunits may be less of a problem than originally anticipated, as ␤ 1 -subunits are endogenously expressed in ASMC and HEK-293 cells (22,24). ␤-Subunits are known to produce modest shifts in the voltage-dependent kinetics and to abolish a slow component of inactivation that results in a large persistent current.…”

Section: Discussionsupporting

confidence: 83%

“…In airway smooth muscle, a direct comparison was made between cultured and freshly dispersed human bronchial smooth muscle cells, where Na ϩ current was found only in the cultured cells (32). The presence of this current in cultured human bronchial myocytes, probably due to expression of Na V 1.7, was later confirmed by two other studies (18,24).In the present study, we set out to reexamine the membrane currents in rabbit smooth muscle cells freshly dispersed from small bronchi. We used a short digestion with collagenase and avoided use of papain to minimize digestion of ion channel proteins.…”

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confidence: 72%

“…The authors of these studies suggested that VGSC might be important in airway remodeling in asthma and, interestingly, showed that expression of Na V 1.7 in cultured cells was inhibited by dexamethasone (24).…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 83%

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The cardiac sodium current Na_v1.5 is functionally expressed in rabbit bronchial smooth muscle cells

Bradley

Webb

Hollywood

et al. 2013

American Journal of Physiology-Cell Physiology

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Bradley E, Webb TI, Hollywood MA, Sergeant GP, McHale NG, Thornbury KD. The cardiac sodium current Nav1.5 is functionally expressed in rabbit bronchial smooth muscle cells. Am J Physiol Cell Physiol 305: C427-C435, 2013. First published June 19, 2013 doi:10.1152/ajpcell.00034.2013.-A collagenase-proteinase mixture was used to isolate airway smooth muscle cells (ASMC) from rabbit bronchi, and membrane currents were recorded using the whole cell patch-clamp technique. Stepping from Ϫ100 mV to a test potential of Ϫ40 mV evoked a fast voltage-dependent Na ϩ current, sometimes with an amplitude of several nanoamperes. The current disappeared within 15 min of exposure to papain ϩ DTT (n ϭ 6). Comparison of the current in ASMC with current mediated by NaV1.5 ␣-subunits expressed in human embryonic kidney cells revealed similar voltage dependences of activation (V1/2 ϭ Ϫ42 mV for NaV1.5) and sensitivities to TTX (IC50 ϭ 1.1 and 1.2 M for ASMC and NaV1.5, respectively). The current in ASMC was also blocked by lidocaine (IC50 ϭ 160 M). Although veratridine, an agonist of voltage-gated Na ϩ channels, reduced the peak current by 33%, it slowed inactivation, resulting in a fourfold increase in sustained current (measured at 25 ms after onset). In current-clamp mode, veratridine prolonged evoked action potentials from 37 Ϯ 9 to 1,053 Ϯ 410 ms (n ϭ 8). Primers for NaV1.2-1.9 were used to amplify mRNA from groups of ϳ20 isolated ASMC and from whole bronchial tissue by RT-PCR. Transcripts for NaV1.2, NaV1.3, and NaV1.5-1.9 were detected in whole tissue, but only NaV1.2 and NaV1.5 were detected in single cells. We conclude that freshly dispersed rabbit ASMC express a fast voltage-gated Na ϩ current that is mediated mainly by the NaV1.5 subtype. sodium current; Nav1.5; airway smooth muscle; patch clamp VOLTAGE-GATED SODIUM CHANNELS (VGSC) are normally associated with excitable cells, such as neurons and skeletal and cardiac myocytes, where they are responsible for the initiation and propagation of the action potential. They are classified according to their pore-forming ␣-subunits, of which there are nine known subtypes, designated Na V 1.1-1.9, encoded by the SCN gene family (SCN1A-5A and SCN8A-11A) (5). Perhaps surprisingly, VGSC have also been found in some nonexcitable cell types, including Schwann cells, cultured fibroblasts, cultured vascular endothelial cells, and metastatic cancer cells, although their role in these cells is poorly understood (1,4,6,8,11,12,19,26). In freshly dispersed smooth muscle cells, VGSC were previously regarded as a rarity, but evidence for their existence in this cell type has been gradually accumulating. In phasic tissues, such as uterine, lymphatic, vas deferens, portal vein, and gastrointestinal smooth muscle, they may play a part in the generation and/or propagation of spontaneous electrical activity underlying myogenic contractions (14,15,29,31,38). However, they have also been found in a variety of tonic arterial smooth muscles (7,9,21,27), although mostly only in cultured cells, suggestin...

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Ion Channel Modulators and Urinary Tract Function

Brading

Brain

2011

Handbook of Experimental Pharmacology

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The membrane potential fulfils an important role in initiating smooth muscle contraction, through its depolarization and the subsequent influx of Ca(2+) through voltage-gated Ca(2+) channels. Changes in membrane potential can also coordinate contraction across great distances, utilizing the speed of electrical current flow through gap junctions. Hence, regulating membrane potential can greatly influence smooth muscle function. In this chapter, we will consider the influence of ion channels, as dynamic gatekeepers of membrane permeability, on urogenital function. Through their ability to act as key regulators of both the resting membrane potential and its dynamic changes, they provide important pharmacological targets for influencing urogenital function.Urogenital smooth muscle and urothelia contain a diverse range of molecularly and functionally distinct K(+) channels, which are key to regulating the resting membrane and for re-establishing the normal membrane potential following both active and passive changes. The voltage-gated Ca(2+) channels are key to initiating contraction and causing rapid depolarization, supplemented in some smooth muscles by rapid Na(+) conductances. The Cl(-) channels, often assumed to be passive, can actively change the membrane potential, and hence, cellular function, because Cl(-) is not usually at its equilibrium potential. The useful ways in which these ion channels can be targeted therapeutically in the ureter, bladder and urethra are discussed, focussing particularly on treatments for ureteric obstruction and detrusor overactivity. Current treatments for many urinary tract disorders, particularly the overactive bladder, are complicated by side effects. While ion channels have traditionally been considered as poor therapeutic targets by the pharmaceutical industry, our increasing knowledge of the molecular diversity of K(+) and Cl(-) channels gives new hope for more narrowly focused drug targeting, while the exciting discoveries of active currents in interstitial cells give us a new set of cellular targets for drugs.

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Effect of dexamethasone on voltage-gated Na+ channel in cultured human bronchial smooth muscle cells

Cited by 12 publications

References 40 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

The cardiac sodium current Na_v1.5 is functionally expressed in rabbit bronchial smooth muscle cells

Ion Channel Modulators and Urinary Tract Function

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Effect of dexamethasone on voltage-gated Na+ channel in cultured human bronchial smooth muscle cells

Cited by 12 publications

References 40 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

The cardiac sodium current Nav1.5 is functionally expressed in rabbit bronchial smooth muscle cells

Ion Channel Modulators and Urinary Tract Function

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Product

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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

The cardiac sodium current Na_v1.5 is functionally expressed in rabbit bronchial smooth muscle cells