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Accumulating evidence indicates that hypertension is associated with "ion channel remodeling" of vascular smooth muscle cells (VSMCs). The objective of this study was to determine the effects of exercise intensity/volume on hypertension-associated changes in large-conductance Ca2+-activated K+ (BKCa) channels in mesenteric arteries (MAs) from spontaneously hypertensive rats (SHR). Male SHRs were randomly assigned to three groups: a low-intensity aerobic exercise group (SHR-L: 14 m/min), a moderate-intensity aerobic exercise group (SHR-M: 20 m/min), and a sedentary group (SHR). Age-matched Wistar-Kyoto rats (WKYs) were used as normotensive controls. Exercise groups completed an 8-week exercise program. Elevation of the α and β1 proteins was unequal in MA myocytes from SHRs, with the β1 subunit increasing more than the α subunit. BKCa contribution to vascular tone regulation was higher in the myocytes and arteries of SHRs compared to WKYs. SHR BKCa channel subunit protein expression, β1/α ratio, whole cell current density and single-channel open probability was also increased compared with WKYs. Aerobic exercise lowered systemic blood pressure and normalized hypertension-associated BKCa alterations to normotensive control levels in the SHRs. These effects were more pronounced in the moderate-intensity group than in the low-intensity group. There is a dose-effect for aerobic exercise training in the range of low to moderate-intensity and accompanying volume for the correction of the pathological adaptation of BKCa channels in myocytes of MAs from SHR. [ABSTRACT FROM AUTHOR]

The effect of lipopolysaccharide (LPS)-based neuroinflammation following cerebral ischemia/reperfusion (I/R) on the genotypic transformation of reactive astrocytes and its relationship with endogenous hydrogen sulfide (H 2 S) were investigated in present study. We found that LPS promoted the cerebral I/R-induced A1 astrocytes proliferation in mouse hippocampal tissues and deteriorated the reduction of hydrogen sulfide (H 2 S) content in mouse sera, H 2 S donor NaHS could inhibit A1 astrocytes proliferation. Similarly, knockout of cystathionine γ-lyase (CSE), one of endogenous H 2 S synthases, likewise up-regulated the cerebral I/R-induced A1 astrocytes proliferation, which could also be blocked by NaHS. Besides, supplement with H 2 S promoted the A2 astrocytes proliferation in hippocampal tissues of CSE knockout (CSE KO) mice or LPS-treated mice following cerebral I/R. In the oxygen glucose deprivation/reoxygenation (OGD/R) model of astrocytes, H 2 S also promoted the transformation of astrocytes into A2 subtype. Moreover, we found that H 2 S could up-regulate the expression of α-subunit of large-conductance Ca2+-activated K+ (BK Ca) channels in astrocytes, and the channel opener BMS-191011 likewise promoted the transformation of astrocyte into A2 subtype. In conclusion, H 2 S inhibits the proliferation of A1 astrocytes induced by LPS-based neuroinflammation following cerebral I/R and promotes the transformation of astrocytes into A2 subtype, which may be related to up-regulation of BK Ca channels. [Display omitted] [ABSTRACT FROM AUTHOR]

Background and Purpose. Caveolae act as signalling hubs in endothelial and smooth muscle cells. Caveolar disruption by the membrane cholesterol depleting agent methyl-β-cyclodextrin (M-β-CD) has various functional effects on arteries including (i) impairment of endothelium-dependent relaxation, and (ii) alteration of smooth muscle cell (SMC) contraction independently of the endothelium. The aim of this study was to explore the effects of M-β-CD on rat femoral arteries.Methods. Isometric force was measured in rat femoral arteries stimulated to contract with a solution containing 20 mM K+ and 200 nM Bay K 8644 (20 K/Bay K) or with one containing 80 mM K+(80 K).Results. Incubation of arteries with M-β-CD (5 mM, 60 min) increased force in response to 20 K/Bay K but not that induced by 80 K. Application of cholesterol saturated M-β-CD (Ch-MCD, 5 mM, 50 min) reversed the effects of M-β-CD. After mechanical removal of endothelial cells M-β-CD caused only a small enhancement of contractions to 20 K/Bay K. This result suggests M-β-CD acts via altering release of an endothelial-derived vasodilator or vasoconstrictor. When nitric oxide synthase was blocked by pre-incubation of arteries with L-NAME (250 µM) the contraction of arteries to 20 K/Bay K was enhanced, and this effect was abolished by pre-treatment with M-β-CD. This suggests M-β-CD is inhibiting endothelial NO release. Inhibition of large conductance voltage- and Ca2+-activated (BKCa) channels with 2 mM TEA+ or 100 nM Iberiotoxin (IbTX) enhanced 20 K/Bay K contractions. L-NAME attenuated the contractile effect of IbTX, as did endothelial removal.Conclusions. Our results suggest caveolar disruption results in decreased release of endothelial-derived nitric oxide in rat femoral artery, resulting in a reduced contribution of BKCa channels to the smooth muscle cell membrane potential, causing depolarisation and contraction.

Background: Resveratrol, a phytoalexin found in grapes and red wine, exhibits diverse pharmacological activities. However, relatively little is known about whether resveratrol modulates the ion channels in cortical neurons. The large-conductance calcium-activated potassium channels (BKCa) and voltage-gated sodium channels were expressed in cortical neurons and play important roles in regulation of neuronal excitability. The present study aimed to determine the effects of resveratrol on BKCa currents and voltage-gated sodium currents in cortical neurons. Results: Resveratrol concentration-dependently increased the current amplitude and the opening activity of BKCa channels, but suppressed the amplitude of voltage-gated sodium currents. Similar to the BKCa channel opener NS1619, resveratrol decreased the firing rate of action potentials. In addition, the enhancing effects of BKCa channel blockers tetraethylammonium (TEA) and paxilline on action potential firing were sensitive to resveratrol. Our results indicated that the attenuation of action potential firing rate by resveratrol might be mediated through opening the BKCa channels and closing the voltage-gated sodium channels. Conclusions: As BKCa channels and sodium channels are critical molecular determinants for seizure generation, our findings suggest that regulation of these two channels in cortical neurons probably makes a considerable contribution to the antiseizure activity of resveratrol. [ABSTRACT FROM AUTHOR]

Aerobic exercise showed beneficial influence on cardiovascular systems in aging, and mechanisms underlying vascular adaption remain unclear. Large-conductance Ca2+-activated K+ (BKCa) channels play critical roles in regulating cellular excitability and vascular tone. This study determined the effects of aerobic exercise on aging-associated functional changes in BKCa channels in cerebrovascular myocytes, Male Wistar rats aged 20-22 months were randomly assigned to sedentary (O-SED), low training frequency (O-EXL), and high training frequency group (O-EXH). Young rats were used as control. Compared to young rats, whole-cell BKCa current was decreased, and amplitude of spontaneous transient outward currents were reduced. The open probability and Ca2+/voltage sensitivity of single BKCa channel were declined in O-SED, accompanied with a reduction of tamoxifen-induced BKCa activation; the mean open time of BKCa channels was shortened whereas close time was prolonged. Aerobic exercise training markedly alleviated the aging-associated decline independent of training frequency. Exercise three times rather than five times weekly may be a time and cost-saving training volume required to offer beneficial effects to offset the functional declines of BKCa during aging. [ABSTRACT FROM AUTHOR]

This study investigated the molecular mechanism of the effect of sulfur dioxide (SO2) on the expression of adenosine triphosphate (ATP)-sensitive potassium ion (K+; KATP) channel, big-conductance calcium ion (Ca2+)-activated K+ (BKCa) channel, and L-type (L-Ca2+) channel subunits in rat aortas with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot. The results showed that the messenger RNA and protein levels of the KATP channel subunits Kir6.1, Kir6.2, and sulfonylurea receptor 2B (SUR2B) of rat aortas were significantly increased by SO2 at 14 mg/m3, whereas the levels of SUR2A were not changed. SO2 at all the treated concentrations markedly raised the expression of the BKCa channel subunits α and β1. SO2 at 14 mg/m3 significantly decreased the expression of the L-Ca2+ channel Cav1.2 and Cav1.3. The histological examination of rat aorta tissues showed moderate injury of tunica media in the presence of SO2 at 14 mg/m3. These suggest that SO2 can activate the KATP and BKCa channels by upregulating the expression of Kir6.1, Kir6.2, SUR2B, BKCa α, and BKCa β1, while inhibit the L-Ca2+ channels by downregulating the expression of Cav1.2 and Cav1.3 in rat aortas. The molecular mechanism of SO2-induced vasorelaxant effect might be linked to the changes in expression of these channel subunits, which plays an important role in the pathogenesis of SO2-associated cardiovascular diseases. [ABSTRACT FROM AUTHOR]

The large-conductance voltage- and Ca2+-activated K+ channel (BKCa) is an important regulator of membrane excitability in a wide variety of cells and tissues. In myometrial smooth muscle, activation of BKCa plays essential roles in buffering contractility to maintain uterine quiescence during pregnancy and in the transition to a more contractile state at the onset of labor. Multiple mechanisms of modulation have been described to alter BKCa channel activity, expression, and cellular localization. In the myometrium, BKCa is regulated by alternative splicing, protein targeting to the plasma membrane, compartmentation in membrane microdomains, and posttranslational modifications. In addition, interaction with auxiliary proteins (i.e., β1- and β2-subunits), association with G-protein coupled receptor signaling pathways, such as those activated by adrenergic and oxytocin receptors, and hormonal regulation provide further mechanisms of variable modulation of BKCa channel function in myometrial smooth muscle. Here, we provide an overview of these mechanisms of BKCa channel modulation and provide a context for them in relation to myometrial function.

Introduction The BKCa channel has been reported to play an important role in erectile function. Recently, novel BKCa channel activator, LDD175, was introduced. Aim This study aims to investigate whether LDD175 relaxes corporal smooth muscle ( CSM) via BKCa channel activation. Methods After isolation of CSM strip from a male rabbit model, contraction studies using organ bath was performed. Isolating human tissue and cell cultures, electrophysiological studies were done via whole-cell patch-clamp recording. Main Outcome Measures Vasodilatory effects of LDD175 were evaluated by cumulative addition ranging from 10−7 to 10−4 M in corpus cavernosal strips after precontraction with 10−5 M phenylephrine via organ bath system. Using cultured human CSM cells, patch-clamp recording was performed. Erectile function was measured by in vivo rat cavernous nerve stimulation. Results LDD175 caused an endothelium-independent relaxation of corporal tissues, and this effect was abolished by pretreatment with iberiotoxin. The relaxation effect of 10−4 M LDD175 was greater than that of 10−6 M udenafil (54.0 ± 3.1% vs. 34.5 ± 3.9%, P < 0.05); 10−5 M LDD175 with 10−6 M udenafil caused a greater relaxation effect on strips than 10−5 M LDD175 or 10−6 M udenafil alone (50.7%, 34.1%, vs. 20.7%, respectively, P < 0.001). In patch-clamp recordings, LDD175 increased K+ currents in a dose-dependent manner, and washout of LDD175 or the addition of iberiotoxin fully reversed the increase. Intravenous LDD175 improved erectile function measured by area under the curve ( AUC) of the intracavernosal pressure (ICP)/arterial blood pressure (ABP) ratio (1,612.1 ± 135.6 vs. 1,093.7 ± 123.1, P < 0.05). There was no difference between 10 mg/kg LDD175 and 1 mg/kg udenafil regarding maximal ICP, maximal ICP/ ABP ratio, and the AUC of the ICP/ ABP ratio ( P > 0.05). Conclusions LDD175 leads to an endothelium-independent relaxation of erectile tissue, primarily through the opening of BKCa channels. The results suggest that LDD175 might be a new candidate treatment for erectile dysfunction. Sung HH, Choo SH, Han DH, Chae MR, Kang SJ, Park C-S, So I, Park JK, and Lee SW. Effect of the novel BKCa channel opener LDD175 on the modulation of corporal smooth muscle tone. J Sex Med 2015;12:29-38. [ABSTRACT FROM AUTHOR]

Background: Trigeminal neuralgia is a disorder of paroxysmal and severely disabling facial pain and continues to be a real therapeutic challenge. At present there are few effective drugs. Here the aim of this study was to investigate the role of BKCa channels in trigeminal neuropathic pain.Methods: Rats were divided into two groups: a sham and a chronic constriction injury of infraorbital branch of trigeminalnerve (ION-CCI) group. Nociceptive behavior testing, immunohistochemistry, RT-PCR, Western blotting and whole-cellpatch clamp recording were used.Results: Relative to the sham group, rats with ION-CCI consistently displayed lower mechanical pain thresholds in thevibrissal pad region from day 6 to 42 after ION-CCI operation. ION-CCI induced a significant down-regulation of BKCachannels both in mRNA and protein levels in the ipsilateral trigeminal ganglion (TG), a lower threshold intensity of actionpotential, and decreased total BKCa currents in cultured TG neurons. TG target injection of NS1619 (20–100 mg), anopener of BKCa channels, dose-dependently increased the mechanical pain threshold, which was blocked by the BKCachannel inhibitor iberiotoxin (IbTX, 20 mg). NS1619 (10 mM) significantly increased the mean threshold intensities ofaction potentials in ION-CCI rats, while failing to affect those in the sham rats.The levels of phosphorylated extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinases (JNK) in TG were significantly increased after ION-CCI operation. The ERK1/2 antagonist U0126, p38 antagonist SB203580 and JNK antagonist SP600125 significantly reversed the facial mechanical allodynia in ION-CCI rats. However, the ERK1/2 antagonist U0126, p38 antagonist SB203580 but not JNK antagonist SP600125 significantly increased BKCa currents in ION-CCI TG neurons.Conclusions: Our results indicate the important involvement of mainly ERK and p38 MAPK pathways in modulating BKCa channels in ION-CCI TG neurons. BKCa channels represent a new therapeutic target for the clinical treatment of trigeminal neuropathic pain. [ABSTRACT FROM AUTHOR]

Altered lipid metabolism in obesity causes pregnancy complications in humans and animals. Leptin levels increase in pregnancy, as well as obesity. However, the effect of obesity on uterine leptin receptors and its distal signaling is not clear. The present study aimed to understand the effect of increased fat on leptin signaling in rat uterus. Wistar female rats were fed with an HF diet (40% Fat, 17% Sucrose, 1.25% Cholesterol, 0.75% Cholic acid) for 6 weeks before the mating and during pregnancy. HF diet significantly increased the fat depots, liver weight, serum, and tissue cholesterol levels. It produced fatty degeneration in the liver and caused infiltration of inflammatory cells, cystic endometrial glands, and sub endometrial fibrosis of the uterus. In isometric tension experiments, leptin caused a significant increase in uterine contractions in high fat-fed animals compared to control animals. Analysis of receptor expressions revealed no significant difference between the groups. However, a significant decrease in the JAK2 and BKCaα mRNA expression was observed in the uterus of high fat-fed rats. No change in the BKCaβ, eNOS, iNOS, MLCP, and MLCK mRNA expressions was noticed in the HF group compared to the control. The findings of the present study suggest that the contractile response to leptin in the uterus of high fat-fed rats may be attributed to reduced signaling through JAK2 and, lowered expressions of BKCa channel α subunits. [ABSTRACT FROM AUTHOR]

The large-conductance Ca2+-activated K+ channel (BK Ca channel) is involved in repolarizing the membrane potential and has a variety of cellular functions. The BK Ca channel is highly expressed in bladder smooth muscle and mediates muscle relaxation. Compounds that activate the BK Ca channel have therapeutic potential against pathological symptoms associated with the overactivity of bladder smooth muscle. In this regard, we screened a chemical library of 9938 compounds to identify novel BK Ca channel activators. A cell-based fluorescence assay identified a structural family of compounds containing a common tricyclic quinazoline ring that activated the BK Ca channel. The most potent compound TTQC-1 (7-bromo-N-(3-methylphenyl)-5-oxo-1-thioxo-4,5-dihydro[1,3]thiazolo[3,4-a]quinazoline-3-carboxamide) directly and reversibly activated the macroscopic current of BK Ca channels expressed in Xenopus oocytes from both sides of the cellular membrane. TTQC-1 increased the maximum conductance and shifted the half activation voltage to the left. The apparent half-maximal effective concentration and dissociation constant were 2.8 μM and 7.95 μM, respectively. TTQC-1 delayed the kinetics of channel deactivation without affecting channel activation. The activation effects were observed over a wide range of intracellular Ca2+ concentrations and dependent on the co-expression of β1 and β4 auxiliary subunits, which are highly expressed in urinary bladder. In the isolated smooth muscle cells of rat urinary bladder, TTQC-1 increased the K+ currents which can be blocked by iberiotoxin. Finally, oral administration of TTQC-1 to hypertensive rats decreased the urination frequency. Therefore, TTQC-1 is a BK Ca channel activator with a novel structure that is a potential therapeutic candidate for BK Ca channel-related diseases, such as overactive bladder syndrome. • A quinazoline derivative, TTQC-1 was discovered as a potent activator of BK Ca channels. • The channel activation effects were dependent on the type of BK Ca β subunit. • Oral administration of TTQC-1 reduced the increased urination frequency of SHRs representing OAB symptoms. [ABSTRACT FROM AUTHOR]

Large conductance, voltage- and Ca 2+ -gated K + (BK Ca ) channels play a critical role in smooth muscle contractility and thus represent an emerging therapeutic target for drug development to treat vascular disease, gastrointestinal, bladder and uterine disorders. Several compounds are known to target the ubiquitously expressed BK Ca channel-forming α subunit. In contrast, just a few are known to target the BK Ca modulatory β 1 subunit, which is highly expressed in smooth muscle and scarce in most other tissues. Lack of available high-resolution structural data makes structure-based pharmacophore modeling of β 1 subunit-dependent BK Ca channel activators a major challenge. Following recent discoveries of novel BK Ca channel activators that act via β 1 subunit recognition, we performed ligand-based pharmacophore modeling that led to the successful creation and fine-tuning of a pharmacophore over several generations. Initial models were developed using physiologically active cholane steroids (bile acids) as template. However, as more compounds that act on BK Ca β 1 have been discovered, our model has been refined to improve accuracy. Database searching with our best-performing model has uncovered several novel compounds as candidate BK Ca β 1 subunit ligands. Eight of the identified compounds were experimentally screened and two proved to be activators of recombinant BK Ca β 1 complexes. One of these activators, sobetirome, differs substantially in structure from any previously reported activator. [ABSTRACT FROM AUTHOR]

Background Potassium-channels in the carotid body and the brainstem are important regulators of ventilation. The BKCa-channel contains response elements for CO, O2, and CO2. Its block increases carotid body signalling, phrenic nerve activity, and respiratory drive. GAL-021, a new BKCa-channel blocker, increases minute ventilation in rats and non-human primates. This study assessed the single-dose safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of GAL-021 in healthy volunteers. Methods Thirty subjects participated in a nine-period, randomized, double-blinded, placebo-controlled, crossover, ascending dose, first-in-human study with i.v. infusions of 0.1–0.96 mg kg−1 h−1 for 1 h and intermediate doses up to 4 h. Results Adverse event rates were generally similar among dose levels and between placebo- and GAL-021-treated subjects. At higher GAL-021 doses, a mild/moderate burning sensation at the infusion site occurred during the infusion. No clinically significant changes in vital signs or clinical chemistries were noted. Minute ventilation increased (AUE0–1 h ≈ 16%, P<0.05) and end-tidal carbon dioxide (ECO2′) decreased (AUE0–1 h ≈ 6%, P<0.05) during the first hour at 0.96 mg kg−1 h−1 with 1/2-maximal V˙E and ECO2′-change occurring by 7.5 min. Drug concentration rose rapidly during the infusion and decreased rapidly initially (distribution t1/2 of 30 min) and then more slowly (terminal t1/2 of 5.6 h). Conclusions GAL-021 was safe and generally well tolerated with adverse events comparable with placebo except for an infusion site burning sensation. GAL-021 stimulated ventilation at the highest doses suggesting that greater infusion rates may be required for maximum PD effects. GAL-021 had PK characteristics consistent with an acute care medication. [ABSTRACT FROM AUTHOR]

Our previous study reported that cerebrosides from traditional Chinese medicine Baifuzi directly interact with the STREX domain of BKCa channels, which in turn results in the therapeutic effect of Baifuzi on ischemic stroke. However, it is not known how cerebrosides in the plasma membrane could interact with the STREX domain that is in the cytoplasmic side. Using patch-clamp technique, effects of different cerebrosides on the BKCa channel were studied by measuring single channel currents in CHO cells expressing wild type or mutated BKCa channels. Palmitoylation of the STREX domain was removed either by site-directed mutagenesis or pharmacological inhibition. Removal of palmitoylation sites at C646 and C647 by mutating the residues to Ala abolished the ability of cerebrosides to activate the BKCa channel. In contrast, the mutation neither changed the single channel conductance nor voltage sensitivity of the channel. Both palmitoylation inhibitors tunicamycin and palmitic acid analog 2-bromopalmitate attenuated the activation of the BKCa channel by cerebrosides. Furthermore, confocal images on STREX-EGFP fragments demonstrated that STREX fragments no longer associated with the plasma membrane when the palmitoylation was removed or blocked. These findings suggest that palmitoylation of the STREX domain is necessary for cerebrosides to activate the BKCa channel and provide insight into the mechanism of how Baifuzi could exert therapeutic effect on ischemic stroke. [ABSTRACT FROM AUTHOR]

Our previous study demonstrated that pregnancy increased large-conductance Ca(2+)-activated potassium channel β1 subunit (BKβ1) expression and large-conductance Ca(2+)-activated potassium channel activity in uterine arteries, which were abrogated by chronic hypoxia. The present study tested the hypothesis that promoter methylation/demethylation is a key mechanism in epigenetic reprogramming of BKβ1 expression patterns in uterine arteries. Ovine BKβ1 promoter of 2315 bp spanning from -2211 to +104 of the transcription start site was cloned, and an Sp1-380 binding site that contains CpG dinucleotide in its core binding sequences was identified. Site-directed deletion of the Sp1 site significantly decreased the BKβ1 promoter activity. Estrogen receptor-α bound to the Sp1 site through tethering to Sp1 and upregulated the expression of BKβ1. The Sp1 binding site at BKβ1 promoter was highly methylated in uterine arteries of nonpregnant sheep, and methylation inhibited transcription factor binding and BKβ1 promoter activity. Pregnancy caused a significant decrease in CpG methylation at the Sp1 binding site and increased Sp1 binding to the BKβ1 promoter and BKβ1 mRNA abundance. Chronic hypoxia during gestation abrogated this pregnancy-induced demethylation and upregulation of BKβ1 expression. The results provide evidence of a novel mechanism of promoter demethylation in pregnancy-induced reprogramming of large-conductance Ca(2+)-activated potassium channel expression and function in uterine arteries and suggest new insights of epigenetic mechanisms linking gestational hypoxia to aberrant uteroplacental circulation and increased risk of preeclampsia. [ABSTRACT FROM AUTHOR]

Background Fragile X Syndrome (FXS) is the most common form of inherited intellectual disability and is also associated with autism spectrum disorders. Previous studies implicated BKCa channels in the neuropathogenesis of FXS, but the main question was whether pharmacological BKCa stimulation would be able to rescue FXS neurobehavioral phenotypes. Methods and results We used a selective BKCa channel opener molecule (BMS-204352) to address this issue in Fmr1 KO mice, modeling the FXS pathophysiology. In vitro, acute BMS-204352 treatment (10 µM) restored the abnormal dendritic spine phenotype. In vivo, a single injection of BMS-204352 (2 mg/kg) rescued the hippocampal glutamate homeostasis and the behavioral phenotype. Indeed, disturbances in social recognition and interaction, non-social anxiety, and spatial memory were corrected by BMS-204352 in Fmr1 KO mice. Conclusion These results demonstrate that the BKCa channel is a new therapeutic target for FXS. We show that BMS-204352 rescues a broad spectrum of behavioral impairments (social, emotional and cognitive) in an animal model of FXS. This pharmacological molecule might open new ways for FXS therapy. [ABSTRACT FROM AUTHOR]

The large-conductance voltage- and Ca2+-activated K+ channel (BKCa) is an important regulator of membrane excitability in a wide variety of cells and tissues. In myometrial smooth muscle, activation of BKCa plays essential roles in buffering contractility to maintain uterine quiescence during pregnancy and in the transition to a more contractile state at the onset of labor. Multiple mechanisms of modulation have been described to alter BKCa channel activity, expression, and cellular localization. In the myometrium, BKCa is regulated by alternative splicing, protein targeting to the plasma membrane, compartmentation in membrane microdomains, and posttranslational modifications. In addition, interaction with auxiliary proteins (i.e., β1- and β2-subunits), association with G-protein coupled receptor signaling pathways, such as those activated by adrenergic and oxytocin receptors, and hormonal regulation provide further mechanisms of variable modulation of BKCa channel function in myometrial smooth muscle. Here, we provide an overview of these mechanisms of BKCa channel modulation and provide a context for them in relation to myometrial function. [ABSTRACT FROM AUTHOR]

Background: The inhibition of potassium (K+) channels plays an important role in pulmonary circulation for its close relationship with hypoxic pulmonary vasoconstriction (HPV). Docosahexaenoic acid (DHA), a n-3 polyunsaturated fatty acid, is well known for its prevention and treatment of cardiovascular diseases. However the role which DHA plays in HPV remains unclear. Here, we tested the hypothesis that DHA contributes to pulmonary vascular tone by activating the large conductance Ca2+-activated K+ (BKCa) channels via calcium sparks. Methods and results: Isolated resistance pulmonary artery preparation was used to study the vasomotor response to DHA. Pulmonary artery smooth muscle cells (PASMCs) were isolated from third- to fourth order branches of pulmonary arteries by collagenase digestion method. BKCa and the voltage-dependent potassium channel (Kv) currents in PASMCs were measured by the whole-cell patch-clamp technique. Fluo-8 was used as a fluorescence indicator for the real-time measurement of calcium dynamics in PASMCs. DHA dilated resistance pulmonary arteries in a dose-dependent manner in hypoxic or normoxic solution, and the effects of DHA were abolished after pre-treatment with heparin (100 μg/ml), a 1,4,5-triphosphate (IP3) receptor (IP3R) inhibitor or iberiotoxin (100 nmol/L), a specific inhibitor of BKCa channel. DHA activated BKCa channels in a dose-dependent manner, however, the activation induced by DHA was not seen in PASMCs pre-incubated with heparin. While the Kv currents decreased from 102.6 ± 5.4 to 36.5 ± 6.7 pA/pF by addition of 10 μmol/L DHA. DHA also caused calcium sparks in PASMCs. Moreover, hypoxia inhibited BKCa currents in PASMCs, but this inhibition was reversed by DHA. Conclusion: Our findings suggest that DHA is a novel BKCa opener in PASMCs, which may indicate a potential therapeutic role in HPV. [ABSTRACT FROM AUTHOR]

Abstract: Our previous study reported that a mixture of cerebrosides from traditional Chinese medicine Baifuzi could activate BKCa channel. It is curious to know the effect of each single cerebroside on the channel. Here we isolated 5 pure cerebrosides from the mixture and determined their chemical structures. The most potent one increased the single channel open probability 6 folds with EC50 value of 1.0 μM. The structure–activity relationship revealed that acyl chain length of cerebrosides has potent effect, while configuration of double bond at C8–C9 on their long chain base has weak effect on the channel activity. Thus, this research provides a guide for design and synthesis of a lead cerebroside with more potent effect on the BKCa channel. [Copyright &y& Elsevier]

Highlights: [•] BKCa channels were specifically labeled using streptavidin-coated quantum dots. [•] Diffusional movement of BKCa channels in live COS-7 cells was monitored and analyzed. [•] Palmitoylation-deficient BKCa channels showed less confined lateral diffusion. [•] Lipid rafts were not involved in the confined diffusion of BKCa channels. [ABSTRACT FROM AUTHOR]