scholarly journals Regulation of endothelial BK channels by heme oxygenase-derived carbon monoxide and caveolin-1

2012 ◽  
Vol 303 (1) ◽  
pp. C92-C101 ◽  
Author(s):  
Melissa A. Riddle ◽  
Benjimen R. Walker
Keyword(s):  
Carbon Monoxide ◽  
Heme Oxygenase ◽  
Barometric Pressure ◽  
Inhibitory Effect ◽  
Bk Channels ◽  
Bk Channel ◽  
Channel Activity ◽  
Outward Currents ◽  
In Cells

A novel vasodilatory influence of endothelial cell (EC) large-conductance Ca2+-activated K+ (BK) channels is present after in vivo exposure to chronic hypoxia (CH) and may exist in other pathological states. However, the mechanism of channel activation that results in altered vasoreactivity is unknown. Previously, we demonstrated that inhibition of either BK channels or heme oxygenase (HO) restores vasoconstrictor reactivity after CH. Additionally, administration of the scaffolding domain of caveolin (Cav)-1 inhibits EC BK activity and restores vasoconstrictor reactivity in this setting. These results led us to hypothesize that CH exposure results in a loss in Cav-1 inhibition of EC BK channels, resulting in their activation by HO-derived carbon monoxide (CO). Experiments were conducted on freshly dispersed aortic ECs from control and CH-exposed (barometric pressure: 380 mmHg for 48 h) rats. In electrophysiology experiments, outward currents were greater in cells from CH rats as well as from cells from control rats treated with the cholesterol-depleting agent methyl-β-cyclodextrin. These enhanced currents were returned to control by HO inhibition. Channel activity could be restored by the CO donor CO-releasing molecule (CORM)-2 during HO inhibition. Administration of the Cav-1 scaffolding domain eliminated BK currents in cells from CH rats, and current was not restored by the addition of CORM-2. Colocalization experiments in ECs from control and CH rats demonstrated an association between HO-2, Cav-1, and BK. We conclude that EC BK channel activity is HO dependent in the absence of the inhibitory effect of the Cav-1 scaffolding domain.

Peroxynitrite reversibly inhibits Ca2+-activated K+ channels in rat cerebral artery smooth muscle cells

2000 ◽  
Vol 278 (6) ◽  
pp. H1883-H1890 ◽  
Author(s):  
Anna K. Brzezinska ◽  
Debebe Gebremedhin ◽  
William M. Chilian ◽  
Balaraman Kalyanaraman ◽  
Stephen J. Elliott
Keyword(s):  
Single Channel ◽  
Cerebral Arteries ◽  
Ionic Current ◽  
Inhibitory Effect ◽  
Bk Channels ◽  
Bk Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Whole Cell ◽  
Cell Current

Peroxynitrite (ONOO−) is a contractile agonist of rat middle cerebral arteries. To determine the mechanism responsible for this component of ONOO−bioactivity, the present study examined the effect of ONOO− on ionic current and channel activity in rat cerebral arteries. Whole cell recordings of voltage-clamped cells were made under conditions designed to optimize K+ current. The effects of iberiotoxin, a selective inhibitor of large-conductance Ca2+-activated K+ (BK) channels, and ONOO− (10–100 μM) were determined. At a pipette potential of +50 mV, ONOO− inhibited 39% of iberiotoxin-sensitive current. ONOO− was selective for iberiotoxin-sensitive current, whereas decomposed ONOO− had no effect. In excised, inside-out membrane patches, channel activity was recorded using symmetrical K+solutions. Unitary currents were sensitive to increases in internal Ca2+ concentration, consistent with activity due to BK channels. Internal ONOO− dose dependently inhibited channel activity by decreasing open probability and mean open times. The inhibitory effect of ONOO− could be overcome by reduced glutathione. Glutathione, added after ONOO−, restored whole cell current amplitude to control levels and reverted single-channel gating to control behavior. The inhibitory effect of ONOO− on membrane K+ current is consistent with its contractile effects in isolated cerebral arteries and single myocytes. Taken together, our data suggest that ONOO− has the potential to alter cerebral vascular tone by inhibiting BK channel activity.

Characteristics of Ca2+ release for activation of K+ current and contractile system in some smooth muscles

1996 ◽  
Vol 271 (3) ◽  
pp. C772-C782 ◽  
Author(s):  
Y. Imaizumi ◽  
S. Henmi ◽  
Y. Uyama ◽  
K. Atsuki ◽  
Y. Torii ◽  
...  
Keyword(s):  
Single Cells ◽  
Smooth Muscles ◽  
Bk Channels ◽  
Bk Channel ◽  
Channel Activity ◽  
Acetoxymethyl Ester ◽  
Contractile System ◽  
Outward Currents ◽  
K Current ◽  
Spontaneous Transient Outward Currents

Characteristics of Ca2+ release from stores were investigated in strips from ileum and portal vein and in isolated myocytes from ileum and urinary bladder of the guinea pig with use of caffeine and 9-methyl-7-bromoeudistomin D (MBED), a potent releaser of Ca2+ from skeletal muscle sarcoplasmic reticulum. In skinned strips, 1-30 mM caffeine elicited a transient contraction, but 10-300 microM MBED did not. Pretreatment with 100 microM MBED did not affect the subsequent caffeine-induced contraction. In single cells loaded with indo 1-acetoxymethyl ester, 10 mM caffeine increased cytoplasmic Ca2+ concentration, whereas 100 microM MBED elicited a small or no increase. Under whole cell clamp, spontaneous transient outward currents through Ca(2+)-dependent K+ (BK) channels were first enhanced and then suppressed by 30 microM MBED or 5 mM caffeine. The amplitude of Ca(2+)-dependent transient K+ current on depolarization was reduced by MBED and caffeine (50% inhibitory concentrations = 20 microM and 1 mM, respectively). Other currents and single BK channel activity were not significantly affected by MBED. The Ca2+ release from stores responsible for BK channel activation may be resolved from that for the activation of the contractile system by MBED in these smooth muscle cells.

scholarly journals Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle

2014 ◽  
Vol 306 (5) ◽  
pp. C460-C470 ◽  
Author(s):  
Kiril L. Hristov ◽  
Amy C. Smith ◽  
Shankar P. Parajuli ◽  
John Malysz ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Guinea Pig ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Channel Regulation ◽  
Pkc Activation

Large-conductance voltage- and Ca2+-activated K+ (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca2+ imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca2+ sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca2+ levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca2+-dependent mechanism, thus increasing DSM contractility.

Disruption of TRPV1-mediated coupling of coronary blood flow to cardiac metabolism in diabetic mice: role of nitric oxide and BK channels

2012 ◽  
Vol 303 (2) ◽  
pp. H216-H223 ◽  
Author(s):  
Giacinta Guarini ◽  
Vahagn A. Ohanyan ◽  
John G. Kmetz ◽  
Daniel J. DelloStritto ◽  
Roslin J. Thoppil ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Coronary Blood Flow ◽  
Cardiac Metabolism ◽  
Bk Channels ◽  
Bk Channel ◽  
Transient Receptor Potential Vanilloid ◽  
Trpv1 Channels ◽  
Channel Dependent

We have previously shown transient receptor potential vanilloid subtype 1 (TRPV1) channel-dependent coronary function is compromised in pigs with metabolic syndrome (MetS). However, the mechanisms through which TRPV1 channels couple coronary blood flow to metabolism are not fully understood. We employed mice lacking TRPV1 [TRPV1(−/−)], db/db diabetic, and control C57BKS/J mice to determine the extent to which TRPV1 channels modulate coronary function and contribute to vascular dysfunction in diabetic cardiomyopathy. Animals were subjected to in vivo infusion of the TRPV1 agonist capsaicin to examine the hemodynamic actions of TRPV1 activation. Capsaicin (1–100 μg·kg−1·min−1) dose dependently increased coronary blood flow in control mice, which was inhibited by the TRPV1 antagonist capsazepine or the nitric oxide synthase (NOS) inhibitor N-nitro-l-arginine methyl ester (l-NAME). In addition, the capsaicin-mediated increase in blood flow was attenuated in db/db mice. TRPV1(−/−) mice exhibited no changes in coronary blood flow in response to capsaicin. Vasoreactivity studies in isolated pressurized mouse coronary microvessels revealed a capsaicin-dependent relaxation that was inhibited by the TRPV1 inhibitor SB366791 l-NAME and to the large conductance calcium-sensitive potassium channel (BK) inhibitors iberiotoxin and Penetrim A. Similar to in vivo responses, capsaicin-mediated relaxation was impaired in db/db mice compared with controls. Changes in pH (pH 7.4–6.0) relaxed coronary vessels contracted to the thromboxane mimetic U46619 in all three groups of mice; however, pH-mediated relaxation was blunted in vessels obtained from TRPV1(−/−) and db/db mice compared with controls. Western blot analysis revealed decreased myocardial TRPV1 protein expression in db/db mice compared with controls. Our data reveal TRPV1 channels mediate coupling of myocardial blood flow to cardiac metabolism via a nitric oxide-dependent, BK channel-dependent pathway that is corrupted in diabetes.

Micromolar Ca2+ from sparks activates Ca2+-sensitive K+ channels in rat cerebral artery smooth muscle

2001 ◽  
Vol 281 (6) ◽  
pp. C1769-C1775 ◽  
Author(s):  
Guillermo J. Pérez ◽  
Adrian D. Bonev ◽  
Mark T. Nelson
Keyword(s):  
Smooth Muscle ◽  
Laser Scanning ◽  
Cerebral Arteries ◽  
Bk Channels ◽  
Bk Channel ◽  
Hill Coefficient ◽  
Channel Activity ◽  
Acetoxymethyl Ester ◽  
Open Probability ◽  
Apparent Dissociation Constant

The goal of the present study was to test the hypothesis that local Ca2+ release events (Ca2+ sparks) deliver high local Ca2+concentration to activate nearby Ca2+-sensitive K+ (BK) channels in the cell membrane of arterial smooth muscle cells. Ca2+ sparks and BK channels were examined in isolated myocytes from rat cerebral arteries with laser scanning confocal microscopy and patch-clamp techniques. BK channels had an apparent dissociation constant for Ca2+ of 19 μM and a Hill coefficient of 2.9 at −40 mV. At near-physiological intracellular Ca2+ concentration ([Ca2+]i; 100 nM) and membrane potential (−40 mV), the open probability of a single BK channel was low (1.2 × 10−6). A Ca2+spark increased BK channel activity to 18. Assuming that 1–100% of the BK channels are activated by a single Ca2+ spark, BK channel activity increases 6 × 105-fold to 6 × 103-fold, which corresponds to ∼30 μM to 4 μM spark Ca2+ concentration. 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid acetoxymethyl ester caused the disappearance of all Ca2+sparks while leaving the transient BK currents unchanged. Our results support the idea that Ca2+ spark sites are in close proximity to the BK channels and that local [Ca2+]i reaches micromolar levels to activate BK channels.

scholarly journals OSR1 and SPAK Sensitivity of Large-Conductance Ca2+ Activated K+ Channel

2016 ◽  
Vol 38 (4) ◽  
pp. 1652-1662 ◽  
Author(s):  
Bernat Elvira ◽  
Yogesh Singh ◽  
Jamshed Warsi ◽  
Carlos Munoz ◽  
Florian Lang
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Cell Volume Regulation ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Xenopus Laevis Oocytes ◽  
Channel Activity ◽  
Wild Type ◽  
Constitutively Active

Background/Aims: The oxidative stress-responsive kinase 1 (OSR1) and the serine/threonine kinases SPAK (SPS1-related proline/alanine-rich kinase) are under the control of WNK (with-no-K [Lys]) kinases. OSR1 and SPAK participate in diverse functions including cell volume regulation and neuronal excitability. Cell volume and neuronal excitation are further modified by the large conductance Ca2+-activated K+ channels (maxi K+ channel or BK channels). An influence of OSR1 and/or SPAK on BK channel activity has, however, never been shown. The present study thus explored whether OSR1 and/or SPAK modify the activity of BK channels. Methods: cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+Δ899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type OSR1 or wild-type SPAK, constitutively active T185EOSR1, catalytically inactive D164AOSR1, constitutively active T233ESPAK or catalytically inactive D212ASPAK. K+ channel activity was measured utilizing dual electrode voltage clamp. Results: BK channel activity in BKM513I+Δ899-903 expressing oocytes was significantly decreased by co-expression of OSR1 or SPAK. The effect of wild-type OSR1/SPAK was mimicked by T185EOSR1 and T233ESPAK, but not by D164AOSR1 or D212ASPAK. Conclusions: OSR1 and SPAK suppress BK channels, an effect possibly contributing to cell volume regulation and neuroexcitability.

scholarly journals Inhibition of Apoptosis by Gamma Interferon in Cells and Mice Infected with Chlamydia muridarum (the Mouse Pneumonitis Strain of Chlamydia trachomatis)

2002 ◽  
Vol 70 (5) ◽  
pp. 2559-2565 ◽  
Author(s):  
Jean-Luc Perfettini ◽  
Toni Darville ◽  
Alice Dautry-Varsat ◽  
Roger G. Rank ◽  
David M. Ojcius
Keyword(s):  
Chlamydia Trachomatis ◽  
Inhibitory Effect ◽  
Gamma Interferon ◽  
Apoptotic Cells ◽  
Chlamydia Muridarum ◽  
Infected Cells ◽  
Heterogenous Population ◽  
Ifn Γ ◽  
In Cells

ABSTRACT The effect of gamma interferon (IFN-γ) on apoptosis due to infection by Chlamydia muridarum (the mouse pneumonitis strain of Chlamydia trachomatis) was studied in epithelial cells in culture and in the genital tracts of mice. IFN-γ concentrations that induce the formation of aberrant, persistent chlamydiae inhibit apoptosis due to C. muridarum infection. In cells treated with an IFN-γ concentration that leads to the development of a heterogenous population of normal and aberrant Chlamydia vacuoles, apoptosis was inhibited preferentially in cells that contained the aberrant vacuoles. The inhibitory effect of IFN-γ appears to be due in part to expression of host cell indoleamine 2,3-dioxygenase activity, since inhibition of apoptosis could be partially reversed through coincubation with exogenous tryptophan. Apoptotic cells were observed in the genital tracts of wild-type mice infected with C. muridarum, and a significantly larger number of apoptotic cells was detected in infected IFN-γ-deficient mice. These results suggest that IFN-γ may contribute to pathogenesis of persistent Chlamydia infections in vivo by preventing apoptosis of infected cells.

scholarly journals G protein pathway suppressor 2 enhanced the renal large-conductance Ca2+-activated potassium channel expression via inhibiting ERK1/2 signaling pathway

2018 ◽  
Vol 315 (3) ◽  
pp. F503-F511 ◽  
Author(s):  
Zhizhi Zhuang ◽  
Jia Xiao ◽  
Xinxin Chen ◽  
Xiaohan Hu ◽  
Ruidian Li ◽  
...  
Keyword(s):  
Protein Expression ◽  
Signaling Pathway ◽  
G Protein ◽  
Mapk Signaling ◽  
Bk Channels ◽  
Bk Channel ◽  
Mapk Signaling Pathway ◽  
Dependent Manner ◽  
Channel Activity ◽  
Open Probability

G protein pathway suppressor 2 (GPS2) is a multifunctional protein and transcriptional regulation factor that is involved in the G protein MAPK signaling pathway. It has been shown that the MAPK signaling pathway plays an important role in the regulation of renal large-conductance Ca2+-activated potassium (BK) channels. In this study, we investigated the effects of GPS2 on BK channel activity and protein expression. In human embryonic kidney (HEK) BK stably expressing cells transfected with either GPS2 or its vector control, a single-cell recording showed that GPS2 significantly increased BK channel activity ( NPo), increasing BK open probability ( Po), and channel number ( N) compared with the control. In Cos-7 cells and HEK 293 T cells, GPS2 overexpression significantly enhanced the total protein expression of BK in a dose-dependent manner. Knockdown of GPS2 expression significantly decreased BK protein expression, while increasing ERK1/2 phosphorylation. Knockdown of ERK1/2 expression reversed the GPS2 siRNA-mediated inhibition of BK protein expression in Cos-7 cells. Pretreatments of Cos-7 cells with either the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 partially reversed the inhibitory effects of GPS2 siRNA on BK protein expression. In addition, feeding a high-potassium diet significantly increased both GPS2 and BK protein abundance in mice. These data suggest that GPS2 enhances BK channel activity and its protein expression by reducing ERK1/2 signaling-mediated degradation of the channel.

Urodynamic properties and neurotransmitter dependence of urinary bladder contractility in the BK channel deletion model of overactive bladder

2005 ◽  
Vol 289 (3) ◽  
pp. F604-F610 ◽  
Author(s):  
K. S. Thorneloe ◽  
A. L. Meredith ◽  
A. M. Knorn ◽  
R. W. Aldrich ◽  
M. T. Nelson
Keyword(s):  
Urinary Bladder ◽  
Overactive Bladder ◽  
Bk Channels ◽  
Bk Channel ◽  
Bladder Pressure ◽  
Bladder Smooth Muscle ◽  
Medical Issues ◽  
Urinary Bladder Smooth Muscle ◽  
Important Therapeutic Target

Overactive bladder and incontinence are major medical issues, which lack effective therapy. Previously, we showed (Meredith AL, Thornloe KS, Werner ME, Nelson MT, and Aldrich RW. J Biol Chem 279: 36746–36752, 2004) that the gene mSlo1 encodes large-conductance Ca2+-activated K+ (BK) channels of urinary bladder smooth muscle (UBSM) and that ablation of mSlo1 leads to enhanced myogenic and nerve-mediated contractility and increased urination frequency. Here, we examine the in vivo urodynamic consequences and neurotransmitter dependence in the absence of the BK channel. The sensitivity of contractility to nerve stimulation was greatly enhanced in UBSM strips from Slo−/− mice. The stimulation frequency required to obtain a 50% maximal contraction was 8.3 ± 0.9 and 19.1 ± 1.8 Hz in Slo−/− and Slo +/+ mice, respectively. This enhancement is at least partially due to alterations in UBSM excitability, as muscarinic-induced Slo−/− contractility is elevated in the absence of neuronal activity. Muscarinic-induced Slo−/− contractility was mimicked by blocking BK channels with iberiotoxin (IBTX) in Slo +/+ strips, whereas IBTX had no effect on Slo−/− strips. IBTX also enhanced purinergic contractions of Slo +/+ UBSM but was without effect on purinergic contractions of Slo−/− strips. In vivo bladder pressure and urine output measurements (cystometry) were performed on conscious, freely moving mice. Slo−/− mice exhibited increased bladder pressures, pronounced pressure oscillations, and urine dripping. Our results indicate that the BK channel in UBSM has a very significant role in urinary function and dysfunction and as such likely represents an important therapeutic target.

scholarly journals Nitric oxide inhibits basolateral 10-pS Cl− channels through the cGMP/PKG signaling pathway in the thick ascending limb of C57BL/6 mice

2016 ◽  
Vol 310 (8) ◽  
pp. F755-F762 ◽  
Author(s):  
Peng Wu ◽  
Zhongxiuzi Gao ◽  
Shiwei Ye ◽  
Zhi Qi
Keyword(s):  
Nitric Oxide ◽  
Soluble Guanylyl Cyclase ◽  
Inhibitory Effect ◽  
No Synthase ◽  
Thick Ascending Limb ◽  
Channel Activity ◽  
No Donor ◽  
Cgmp Analog ◽  
Synthase Inhibitor

We used patch-clamp techniques to examine whether nitric oxide (NO) decreases NaCl reabsorption by suppressing basolateral 10-pS Cl− channels in the thick ascending limb (TAL). Both the NO synthase substrate l-arginine (l-Arg) and the NO donor S-nitroso- N-acetylpenicillamine significantly inhibited 10-pS Cl− channel activity in the TAL. The inhibitory effect of l-Arg on Cl− channels was completely abolished in the presence of the NO synthase inhibitor or NO scavenger. Moreover, inhibition of soluble guanylyl cyclase abrogated the effect of l-Arg on Cl− channels, whereas the cGMP analog 8-bromo-cGMP (8-BrcGMP) mimicked the effect of l-Arg and significantly decreased 10-pS Cl− channel activity, indicating that NO inhibits basolateral Cl− channels by increasing cGMP production. Furthermore, treatment of the TAL with a PKG inhibitor blocked the effect of l-Arg and 8-BrcGMP on Cl− channels, respectively. In contrast, a phosphodiesterase 2 inhibitor had no significant effect on l-Arg or 8-BrcGMP-induced inhibition of Cl− channels. Therefore, we conclude that NO decreases basolateral 10-pS Cl− channel activity through a cGMP-dependent PKG pathway, which may contribute to the natriuretic and diuretic effects of NO in vivo.

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