scholarly journals Chloroform Extract ofArtemisia annuaL. Relaxes Mouse Airway Smooth Muscle

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Jun Huang ◽  
Li-Qun Ma ◽  
Yongle Yang ◽  
Nana Wen ◽  
Wan Zhou ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Single Channel ◽  
Artemisia Annua ◽  
Chloroform Extract ◽  
Bk Channels ◽  
Bk Channel ◽  
Airway Smooth Muscle Cells ◽  
Patch Clamp Technique ◽  
Channel Currents

Artemisia annuaL. belongs to the Asteraceae family, which is indigenous to China. It has valuable pharmacological properties, such as antimalarial, anti-inflammatory, and anticancer properties. However, whether it possesses antiasthma properties is unknown. In the current study, chloroform extract ofArtemisia annuaL. (CEAA) was prepared, and we found that CEAA completely eliminated acetylcholine (ACh) or high K+-elicited (80 mM) contractions of mouse tracheal rings (TRs). Patch-clamp technique and ion channel blockers were employed to explore the underlying mechanisms of the relaxant effect of CEAA. In whole-cell current recording, CEAA almost fully abolished voltage-dependent Ca2+channel (VDCC) currents and markedly enhanced large conductance Ca2+-activated K+(BK) channel currents on airway smooth muscle cells (ASMCs). In single channel current recording, CEAA increased the opening probability but had no effect on the single channel conductance of BK channels. However, under paxilline-preincubated (a selective BK channel blocker) conditions, CEAA only slightly increased BK channel currents. These results indicate that CEAA may contain active components with potent antiasthma activity. The abolished VDCCs by CEAA may mainly contribute to the underlying mechanism through which it acts as an effective antiasthmatic compound, but the enhanced BK currents might play a less important role in the antiasthmatic effects.

scholarly journals Chronic Prenatal Hypoxia Down-Regulated BK Channel Β1 Subunits in Mesenteric Artery Smooth Muscle Cells of the Offspring

2018 ◽  
Vol 45 (4) ◽  
pp. 1603-1616 ◽  
Author(s):  
Bailin Liu ◽  
Yanping Liu ◽  
Ruixiu Shi ◽  
Xueqin Feng ◽  
Xiang Li ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Single Channel ◽  
Muscle Cells ◽  
Bk Channels ◽  
Bk Channel ◽  
Mesenteric Arteries ◽  
Prenatal Hypoxia ◽  
Pregnant Rats ◽  
Α Subunit

Background/Aims: Chronic hypoxia in utero could impair vascular functions in the offspring, underlying mechanisms are unclear. This study investigated functional alteration in large-conductance Ca2+-activated K+ (BK) channels in offspring mesenteric arteries following prenatal hypoxia. Methods: Pregnant rats were exposed to normoxic control (21% O2, Con) or hypoxic (10.5% O2, Hy) conditions from gestational day 5 to 21, their 7-month-old adult male offspring were tested for blood pressure, vascular BK channel functions and expression using patch clamp and wire myograh technique, western blotting, and qRT-PCR. Results: Prenatal hypoxia increased pressor responses and vasoconstrictions to phenylephrine in the offspring. Whole-cell currents density of BK channels and amplitude of spontaneous transient outward currents (STOCs), not the frequency, were significantly reduced in Hy vascular myocytes. The sensitivity of BK channels to voltage, Ca2+, and tamoxifen were reduced in Hy myocytes, whereas the number of channels per patch and the single-channel conductance were unchanged. Prenatal hypoxia impaired NS1102- and tamoxifen-mediated relaxation in mesenteric arteries precontracted with phenylephrine in the presence of Nω-nitro-L-arginine methyl ester. The mRNA and protein expression of BK channel β1, not the α-subunit, was decreased in Hy mesenteric arteries. Conclusions: Impaired BK channel β1-subunits in vascular smooth muscle cells contributed to vascular dysfunction in the offspring exposed to prenatal hypoxia.

BK channel β1-subunit regulation of calcium handling and constriction in tracheal smooth muscle

2006 ◽  
Vol 291 (4) ◽  
pp. L802-L810 ◽  
Author(s):  
Iurii Semenov ◽  
Bin Wang ◽  
Jeremiah T. Herlihy ◽  
Robert Brenner
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Cell Types ◽  
Bk Channels ◽  
Bk Channel ◽  
Tracheal Smooth Muscle ◽  
Calcium Handling ◽  
Cholinergic Signaling ◽  
Smooth Muscle Function ◽  
Voltage Dependent

The large-conductance, Ca2+-activated K+ (BK) channels are regulators of voltage-dependent Ca2+ entry in many cell types. The BK channel accessory β1-subunit promotes channel activation in smooth muscle and is required for proper tone in the vasculature and bladder. However, although BK channels have also been implicated in airway smooth muscle function, their regulation by the β1-subunit has not been investigated. Utilizing the gene-targeted mice for the β1-subunit gene, we have investigated the role of the β1-subunit in tracheal smooth muscle. In mice with the β1-subunit-knockout allele, BK channel activity was significantly reduced in excised tracheal smooth muscle patches and spontaneous BK currents were reduced in whole tracheal smooth muscle cells. Knockout of the β1-subunit resulted in an increase in resting Ca2+ levels and an increase in the sustained component of Ca2+ influx after cholinergic signaling. Tracheal constriction studies demonstrate that the level of constriction is the same with knockout of the β1-subunit and BK channel block with paxillin, indicating that BK channels contribute little to airway relaxation in the absence of the β1-subunit. Utilizing nifedipine, we found that the increased constriction caused by knockout of the β1-subunit could be accounted for by an increased recruitment of L-type voltage-dependent Ca2+ channels. These results indicate that the β1-subunit is required in airway smooth muscle for control of voltage-dependent Ca2+ influx during rest and after cholinergic signaling in BK channels.

scholarly journals Suppression of human detrusor smooth muscle excitability and contractility via pharmacological activation of large conductance Ca2+-activated K+channels

2012 ◽  
Vol 302 (11) ◽  
pp. C1632-C1641 ◽  
Author(s):  
Kiril L. Hristov ◽  
Shankar P. Parajuli ◽  
Rupal P. Soder ◽  
Qiuping Cheng ◽  
Eric S. Rovner ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Electrical Field Stimulation ◽  
Bk Channels ◽  
Bk Channel ◽  
Resting Membrane Potential ◽  
Force Frequency ◽  
Detrusor Smooth Muscle ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Current Clamp Mode

Overactive bladder syndrome is frequently associated with increased detrusor smooth muscle (DSM) contractility. We tested the hypothesis that pharmacological activation of the large-conductance voltage- and Ca2+-activated K+(BK) channel with NS-1619, a selective BK channel opener, reduces the excitability and contractility of human DSM. We used the amphotericin-perforated whole cell patch-clamp technique on freshly isolated human DSM cells, live-cell Ca2+imaging, and isometric DSM tension recordings of human DSM strips obtained from open bladder surgeries. NS-1619 (30 μM) significantly increased the amplitude of the voltage step-induced whole cell BK currents, and this effect was abolished by pretreatment with 200 nM iberiotoxin (IBTX), a selective BK channel inhibitor. In current-clamp mode, NS-1619 (30 μM) significantly hyperpolarized the resting membrane potential, and the hyperpolarization was reversed by IBTX (200 nM). NS-1619 (30 μM) significantly decreased the intracellular Ca2+level in isolated human DSM cells. BK channel activation with NS-1619 (30 μM) significantly inhibited the amplitude, muscle force, frequency, duration, and tone of the spontaneous phasic and pharmacologically induced DSM contractions from human DSM isolated strips. IBTX (200 nM) suppressed the inhibitory effects of NS-1619 on spontaneous contractions. The amplitude of electrical field stimulation (0.5–50 Hz)-induced contractions was significantly reduced by NS-1619 (30 μM). Our data suggest that pharmacological activation of BK channels could represent a novel treatment option to control bladder dysfunction in humans.

scholarly journals Large-conductance voltage- and Ca2+-activated K+ channels regulate human detrusor smooth muscle function

2011 ◽  
Vol 301 (4) ◽  
pp. C903-C912 ◽  
Author(s):  
Kiril L. Hristov ◽  
Muyan Chen ◽  
Whitney F. Kellett ◽  
Eric S. Rovner ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Specific Inhibitor ◽  
Bk Channels ◽  
Bk Channel ◽  
Bladder Function ◽  
Detrusor Smooth Muscle ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Human Detrusor

The large-conductance voltage- and Ca2+-activated K+ (BK) channel is expressed in many smooth muscle types, but its role in human detrusor smooth muscle (DSM) is unclear. With a multidisciplinary approach spanning channel molecules, single-channel activity, freshly isolated human DSM cells, intact DSM preparations, and the BK channel specific inhibitor iberiotoxin, we elucidated human DSM BK channel function and regulation. Native human DSM tissues were obtained during open surgeries from patients with no preoperative history of overactive bladder. RT-PCR experiments on single human DSM cells showed mRNA expression of BK channel α-, β1-, and β4-subunits. Western blot and immunocytochemistry confirmed BK channel α, β1, and β4 protein expression. Native human BK channel properties were described using the perforated whole cell configuration of the patch-clamp technique. In freshly isolated human DSM cells, BK channel blockade with iberiotoxin inhibited a significant portion of the total voltage step-induced whole cell K+ current. From single BK channel recordings, human BK channel conductance was calculated to be 136 pS. Voltage-dependent iberiotoxin- and ryanodine-sensitive transient BK currents were identified in human DSM cells. In current-clamp mode, iberiotoxin inhibited the hyperpolarizing membrane potential transients and depolarized the cell resting membrane potential. Isometric DSM tension recordings revealed that BK channels principally control the contractions of isolated human DSM strips. Collectively, our results indicate that BK channels are fundamental regulators of DSM excitability and contractility and may represent new targets for pharmacological or genetic control of urinary bladder function in humans.

scholarly journals Testosterone decreases urinary bladder smooth muscle excitability via novel signaling mechanism involving direct activation of the BK channels

2016 ◽  
Vol 311 (6) ◽  
pp. F1253-F1259 ◽  
Author(s):  
Kiril L. Hristov ◽  
Shankar P. Parajuli ◽  
Aaron Provence ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Single Channel ◽  
Bk Channels ◽  
Bk Channel ◽  
Bladder Pressure ◽  
Resting Membrane Potential ◽  
Open Probability ◽  
Membrane Hyperpolarization ◽  
Whole Cell ◽  
Inside Out

In addition to improving sexual function, testosterone has been reported to have beneficial effects in ameliorating lower urinary tract symptoms by increasing bladder capacity and compliance, while decreasing bladder pressure. However, the cellular mechanisms by which testosterone regulates detrusor smooth muscle (DSM) excitability have not been elucidated. Here, we used amphotericin-B perforated whole cell patch-clamp and single channel recordings on inside-out excised membrane patches to investigate the regulatory role of testosterone in guinea pig DSM excitability. Testosterone (100 nM) significantly increased the depolarization-induced whole cell outward currents in DSM cells. The selective pharmacological inhibition of the large-conductance voltage- and Ca2+-activated K+ (BK) channels with paxilline (1 μM) completely abolished this stimulatory effect of testosterone, suggesting a mechanism involving BK channels. At a holding potential of −20 mV, DSM cells exhibited transient BK currents (TBKCs). Testosterone (100 nM) significantly increased TBKC activity in DSM cells. In current-clamp mode, testosterone (100 nM) significantly hyperpolarized the DSM cell resting membrane potential and increased spontaneous transient hyperpolarizations. Testosterone (100 nM) rapidly increased the single BK channel open probability in inside-out excised membrane patches from DSM cells, clearly suggesting a direct BK channel activation via a nongenomic mechanism. Live-cell Ca2+ imaging showed that testosterone (100 nM) caused a decrease in global intracellular Ca2+ concentration, consistent with testosterone-induced membrane hyperpolarization. In conclusion, the data provide compelling mechanistic evidence that under physiological conditions, testosterone at nanomolar concentrations directly activates BK channels in DSM cells, independent from genomic testosterone receptors, and thus regulates DSM excitability.

Deglycosylation of the β1-subunit of the BK channel changes its biophysical properties

2006 ◽  
Vol 291 (4) ◽  
pp. C750-C756 ◽  
Author(s):  
Brian M. Hagen ◽  
Kenton M. Sanders
Keyword(s):  
Smooth Muscle ◽  
Molecular Mass ◽  
Single Channel ◽  
Bk Channels ◽  
Bk Channel ◽  
Dependent Manner ◽  
Biophysical Properties ◽  
Single Channel Recordings ◽  
Inside Out ◽  
Α Subunits

Large-conductance Ca2+-activated potassium (BK) channels are composed of pore-forming α-subunits and auxiliary β-subunits. The α-subunits are widely expressed in many cell types, whereas the β-subunits are more tissue specific and influence diverse aspects of channel function. In the current study, we identified the presence of the smooth muscle-specific β1-subunit in murine colonic tissue using Western blotting. The native β1-subunits migrated in SDS-PAGE as two molecular mass bands. Enzymatic removal of N-linked glycosylations from the β1-subunit resulted in a single band that migrated at a lower molecular mass than the native β1-subunit bands, suggesting that the native β1-subunit exists in either a core glycosylated or highly glycosylated form. We investigated the functional consequence of deglycosylating the β1-subunit during inside-out single-channel recordings. During inside-out single-channel recordings, with N-glycosidase F in the pipette solution, the open probability ( Po) and mean open time of BK channels increased in a time-dependent manner. Deglycosylation of BK channels did not affect the conductance but shifted the steady-state voltage of activation toward more positive potentials without affecting slope when Ca2+ concentration was <1 μM. Treatment of myocytes lacking the β1-subunits of the BK channel with N-glycosidase F had no effect. These data suggest that glycosylations on the β1-subunit in smooth muscle cells can modify the biophysical properties of BK channels.

scholarly journals Nanoscale coupling of junctophilin-2 and ryanodine receptors regulates vascular smooth muscle cell contractility

2019 ◽  
Vol 116 (43) ◽  
pp. 21874-21881 ◽  
Author(s):  
Harry A. T. Pritchard ◽  
Caoimhin S. Griffin ◽  
Evan Yamasaki ◽  
Pratish Thakore ◽  
Conor Lane ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Cerebral Arteries ◽  
Ryanodine Receptors ◽  
Bk Channels ◽  
Bk Channel ◽  
Functional Coupling ◽  
Superresolution Microscopy ◽  
Cell Contractility ◽  
Channel Currents

Junctophilin proteins maintain close contacts between the endoplasmic/sarcoplasmic reticulum (ER/SR) and the plasma membrane in many types of cells, as typified by junctophilin-2 (JPH2), which is necessary for the formation of the cardiac dyad. Here, we report that JPH2 is the most abundant junctophilin isotype in native smooth muscle cells (SMCs) isolated from cerebral arteries and that acute knockdown diminishes the area of sites of interaction between the SR and plasma membrane. Superresolution microscopy revealed nanometer-scale colocalization of JPH2 clusters with type 2 ryanodine receptor (RyR2) clusters near the cell surface. Knockdown of JPH2 had no effect on the frequency, amplitude, or kinetics of spontaneous Ca2+ sparks generated by transient release of Ca2+ from the SR through RyR2s, but it did nearly abolish Ca2+ spark-activated, large-conductance, Ca2+-activated K+ (BK) channel currents. We also found that JPH2 knockdown was associated with hypercontractility of intact cerebral arteries. We conclude that JPH2 maintains functional coupling between RyR2s and BK channels and is critically important for cerebral arterial function.

Inhibition of slow-wave repolarization and Ca(2+)-activated K+ channels by quaternary ammonium ions

1993 ◽  
Vol 264 (3) ◽  
pp. C625-C631 ◽  
Author(s):  
A. Carl ◽  
B. W. Frey ◽  
S. M. Ward ◽  
K. M. Sanders ◽  
J. L. Kenyon
Keyword(s):  
Smooth Muscle ◽  
Binding Site ◽  
Slow Wave ◽  
Voltage Dependence ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Circular Smooth Muscle

We studied the effects of the K+ channel blocker tetrapentylammonium (TPeA) on the electrical activity of intact circular smooth muscle from canine colon. TPeA (10 and 20 microM) increased slow-wave duration and "locked" the membrane potential around -30 mV plateau potential after several minutes of application, suggesting that K+ channels are essential for termination of colonic slow waves. Repolarization and normal slow-wave activity resumed after 20-30 min of washout. The patch-clamp technique was used to study the block of large-conductance Ca(2+)-activated K+ channels (BK channels) by TPeA and tetraethylammonium (TEA) in excised and cell-attached patches from isolated colonic smooth muscle cells. Channel block was characterized by a voltage-dependent dissociation constant [Kd(V)] for the binding of TEA and TPeA to a blocking site located a fraction of the distance across the membrane field (delta). The extracellular TEA binding site had a Kd(0) of 0.33 mM and a delta of 0.23. The extracellular TPeA binding site had a Kd(0) of 2.2 mM but showed significantly less voltage dependence (delta = 0.02). The intracellular binding site for TEA was of low affinity [Kd(0) = 76 mM]. Intracellular TPeA was the most potent blocker of BK channel current [Kd(0) = 11.7 microM]. The voltage dependence of block by intracellular TPeA (delta = -0.21) was not significantly different from that of intracellular TEA (delta = -0.3). Internal TPeA (10 microM) also blocked a 70-pS K+ channel and a 23-pS K+ channel.(ABSTRACT TRUNCATED AT 250 WORDS)

Contractile agonists activate voltage-dependent calcium channels in airway smooth muscle cells

1992 ◽  
Vol 263 (1) ◽  
pp. C106-C113 ◽  
Author(s):  
M. Tomasic ◽  
J. P. Boyle ◽  
J. F. Worley ◽  
M. I. Kotlikoff
Keyword(s):  
Smooth Muscle ◽  
Calcium Channels ◽  
Smooth Muscle Cells ◽  
Calcium Channel ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Cell Types ◽  
State Probability ◽  
Airway Smooth Muscle Cells ◽  
Channel Currents

To determine whether agents that cause contraction of airway smooth muscle affect sarcolemmal calcium channel activity, unitary calcium channel currents (using Ba2+ as the charge carrier) were recorded in on-cell configuration from acutely dissociated (dog, pig, and ferret) and cultured (human) airway smooth muscle cells. Addition of the contractile agonists methacholine or bradykinin increased the open-state probability of the large-conductance calcium channel 37.2- and 45-fold, respectively. The increase in open-state probability was not due to cellular depolarization because increases occurred in the absence of depolarization. Channel activation by the agonist was determined to result in the favoring of a long (16.5 +/- 5.0 ms) open lifetime for the channel, which was not observed under control conditions, in the absence of BAY K 8644. We also report the unitary calcium channel currents from a second, smaller conductance calcium channel. This channel was present in all cell types and had a mean conductance of 9.5 +/- 0.8 pS (80 mM Ba2+). Exposure of cells to agonist also resulted in an increase in the open-channel probability of the small-conductance calcium channel (10.4-fold), which did not result from cellular depolarization. These experiments demonstrate that the molecular pathways exist between contractile agonist receptors and sarcolemmal calcium channels in airway smooth muscle cells. Because membrane patches were not directly exposed to agonist, receptor-channel linkage probably occurs via a second messenger-coupling pathway.

scholarly journals Inhibition of phosphodiesterases relaxes detrusor smooth muscle via activation of the large-conductance voltage- and Ca2+-activated K+ channel

2012 ◽  
Vol 302 (9) ◽  
pp. C1361-C1370 ◽  
Author(s):  
Wenkuan Xin ◽  
Qiuping Cheng ◽  
Rupal P. Soder ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Bk Channels ◽  
Bk Channel ◽  
Dependent Manner ◽  
Detrusor Smooth Muscle ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Membrane Hyperpolarization ◽  
Pde Inhibition

Detrusor smooth muscle (DSM) exhibits increased spontaneous phasic contractions under pathophysiological conditions such as detrusor overactivity (DO). Our previous studies showed that activation of cAMP signaling pathways reduces DSM contractility by increasing the large-conductance voltage- and Ca2+-activated K+ (BK) channel activity. Here, we tested the hypothesis whether inhibition of phosphodiesterases (PDEs) can reduce guinea pig DSM excitability and contractility by increasing BK channel activity. Utilizing isometric tension recordings of DSM isolated strips and the perforated patch-clamp technique on freshly isolated DSM cells, we examined the mechanism of DSM relaxation induced by PDE inhibition. Inhibition of PDEs by 3-isobutyl-1-methylxanthine (IBMX), a nonselective PDE inhibitor, significantly reduced DSM spontaneous and carbachol-induced contraction amplitude, frequency, duration, muscle force integral, and tone in a concentration-dependent manner. IBMX significantly reduced electrical field stimulation-induced contractions of DSM strips. Blocking BK channels with paxilline diminished the inhibitory effects of IBMX on DSM contractility, indicating a role for BK channels in DSM relaxation mediated by PDE inhibition. IBMX increased the transient BK currents (TBKCs) frequency by ∼3-fold without affecting the TBKCs amplitude. IBMX increased the frequency of the spontaneous transient hyperpolarizations by ∼2-fold and hyperpolarized the DSM cell resting membrane potential by ∼6 mV. Blocking the BK channels with paxilline abolished the IBMX hyperpolarizing effects. Under conditions of blocked Ca2+ sources for BK channel activation, IBMX did not affect the depolarization-induced steady-state whole cell BK currents. Our data reveal that PDE inhibition with IBMX relaxes guinea pig DSM via TBKCs activation and subsequent DSM cell membrane hyperpolarization.

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