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McGarr GW, Muia CM, Saci S, Fujii N, Kenny GP. K Ca channels are major contributors to ATP-induced cutaneous vasodilation in healthy older adults. Microvasc Res 2020; 133:104096. [PMID: 33058899 DOI: 10.1016/j.mvr.2020.104096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 08/30/2020] [Accepted: 10/08/2020] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To examine the contributions of calcium-activated K+ (KCa) channels and nitric oxide synthase (NOS) to adenosine triphosphate (ATP)-induced cutaneous vasodilation in healthy older adults. METHODS In eleven older adults (69 ± 2 years, 5 females), cutaneous vascular conductance, normalized to maximum vasodilation (%CVCmax) was assessed at four dorsal forearm skin sites that were continuously perfused with either 1) lactated Ringer solution (Control), 2) 50 mM tetraethylammonium (TEA, KCa channel blocker), 3) 10 mM Nω-nitro-L-arginine (L-NNA, NOS inhibitor), or 4) combined 50 mM TEA +10 mM L-NNA, via microdialysis. Local skin temperature was fixed at 33 °C at all sites with local heaters throughout the protocol while the cutaneous vasodilator response was assessed during coadministration of ATP (0.03, 0.3, 3, 30, 300 mM; 20 min per dose), followed by 50 mM sodium nitroprusside and local skin heating to 43 °C to achieve maximum vasodilation (20-30 min). RESULTS Blockade of KCa channels blunted %CVCmax relative to Control from 0.3 to 300 mM ATP (All P < 0.05). A similar response was observed for the combined KCa channel blockade and NOS inhibition site from 3 to 300 mM ATP (All P < 0.05). Conversely, NOS inhibition alone did not influence %CVCmax across all ATP doses (All P > 0.05). CONCLUSION In healthy older adults, KCa channels play an important role in modulating ATP-induced cutaneous vasodilation, while the NOS contribution to this response is negligible.
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Affiliation(s)
- Gregory W McGarr
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Caroline M Muia
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Samah Saci
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Naoto Fujii
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada; Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.
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2
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Fan C, Sukomon N, Flood E, Rheinberger J, Allen TW, Nimigean CM. Ball-and-chain inactivation in a calcium-gated potassium channel. Nature 2020; 580:288-293. [PMID: 32269335 PMCID: PMC7153497 DOI: 10.1038/s41586-020-2116-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 01/15/2020] [Indexed: 01/21/2023]
Abstract
Inactivation is the process by which ion channels terminate ion flux through their pores while the opening stimulus is still present1. In neurons, inactivation of both sodium and potassium channels is crucial for the generation of action potentials and regulation of firing frequency1,2. A cytoplasmic domain of either the channel or an accessory subunit is thought to plug the open pore to inactivate the channel via a 'ball-and-chain' mechanism3-7. Here we use cryo-electron microscopy to identify the molecular gating mechanism in calcium-activated potassium channels by obtaining structures of the MthK channel from Methanobacterium thermoautotrophicum-a purely calcium-gated and inactivating channel-in a lipid environment. In the absence of Ca2+, we obtained a single structure in a closed state, which was shown by atomistic simulations to be highly flexible in lipid bilayers at ambient temperature, with large rocking motions of the gating ring and bending of pore-lining helices. In Ca2+-bound conditions, we obtained several structures, including multiple open-inactivated conformations, further indication of a highly dynamic protein. These different channel conformations are distinguished by rocking of the gating rings with respect to the transmembrane region, indicating symmetry breakage across the channel. Furthermore, in all conformations displaying open channel pores, the N terminus of one subunit of the channel tetramer sticks into the pore and plugs it, with free energy simulations showing that this is a strong interaction. Deletion of this N terminus leads to functionally non-inactivating channels and structures of open states without a pore plug, indicating that this previously unresolved N-terminal peptide is responsible for a ball-and-chain inactivation mechanism.
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Affiliation(s)
- Chen Fan
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Nattakan Sukomon
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Emelie Flood
- School of Science, RMIT University, Melbourne, Victoria, Australia
| | - Jan Rheinberger
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
- Department of Structural Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, Victoria, Australia
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA.
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA.
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3
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Xu J, Zeug A, Riederer B, Yeruva S, Griesbeck O, Daniel H, Tuo B, Ponimaskin E, Dong H, Seidler U. Calcium-sensing receptor regulates intestinal dipeptide absorption via Ca 2+ signaling and IK Ca activation. Physiol Rep 2020; 8:e14337. [PMID: 31960592 PMCID: PMC6971415 DOI: 10.14814/phy2.14337] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Although absorption of di- and tripeptides into intestinal epithelial cells occurs via the peptide transporter 1 (PEPT1, also called solute carrier family 15 member 1 (SLC15A1)), the detailed regulatory mechanisms are not fully understood. We examined: (a) whether dipeptide absorption in villous enterocytes is associated with a rise in cytosolic Ca2+ ([Ca2+ ]cyt ), (b) whether the calcium sensing receptor (CaSR) is involved in dipeptide-elicited [Ca2+ ]cyt signaling, and (c) what potential consequences of [Ca2+ ]cyt signaling may enhance enterocyte dipeptide absorption. Dipeptide Gly-Sar and CaSR agonist spermine markedly raised [Ca2+ ]cyt in villous enterocytes, which was abolished by NPS-2143, a selective CaSR antagonist and U73122, an phospholipase C (PLC) inhibitor. Apical application of Gly-Sar induced a jejunal short-circuit current (Isc), which was reduced by NPS-2143. CaSR expression was identified in the lamina propria and on the basal enterocyte membrane of mouse jejunal mucosa in both WT and Slc15a1-/- animals, but Gly-Sar-induced [Ca2+ ]cyt signaling was significantly decreased in Slc15a1-/- villi. Clotrimazole and TRM-34, two selective blockers of the intermediate conductance Ca2+ -activated K+ channel (IKCa ), but not iberiotoxin, a selective blocker of the large-conductance K+ channel (BKCa ) and apamin, a selective blocker of the small-conductance K+ channel (SKCa ), significantly inhibited Gly-Sar-induced Isc in native tissues. We reveal a novel CaSR-PLC-Ca2+ -IKCa pathway in the regulation of small intestinal dipeptide absorption, which may be exploited as a target for future drug development in human nutritional disorders.
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Affiliation(s)
- Jingyu Xu
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
- Research GastroenterologyAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Andre Zeug
- Cellular NeurophysiologyHannover Medical SchoolHannoverGermany
| | - Brigitte Riederer
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
| | - Sunil Yeruva
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
| | | | - Hannelore Daniel
- Nutritional PhysiologyTechnical University of MunichFreisingGermany
| | - Biguang Tuo
- Research GastroenterologyAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | | | - Hui Dong
- Department of MedicineUniversity of California, San DiegoLa JollaCAUSA
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
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4
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Dickerson MT, Dadi PK, Altman MK, Verlage KR, Thorson AS, Jordan KL, Vierra NC, Amarnath G, Jacobson DA. Glucose-mediated inhibition of calcium-activated potassium channels limits α-cell calcium influx and glucagon secretion. Am J Physiol Endocrinol Metab 2019; 316:E646-E659. [PMID: 30694690 PMCID: PMC6482666 DOI: 10.1152/ajpendo.00342.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Pancreatic α-cells exhibit oscillations in cytosolic Ca2+ (Ca2+c), which control pulsatile glucagon (GCG) secretion. However, the mechanisms that modulate α-cell Ca2+c oscillations have not been elucidated. As β-cell Ca2+c oscillations are regulated in part by Ca2+-activated K+ (Kslow) currents, this work investigated the role of Kslow in α-cell Ca2+ handling and GCG secretion. α-Cells displayed Kslow currents that were dependent on Ca2+ influx through L- and P/Q-type voltage-dependent Ca2+ channels (VDCCs) as well as Ca2+ released from endoplasmic reticulum stores. α-Cell Kslow was decreased by small-conductance Ca2+-activated K+ (SK) channel inhibitors apamin and UCL 1684, large-conductance Ca2+-activated K+ (BK) channel inhibitor iberiotoxin (IbTx), and intermediate-conductance Ca2+-activated K+ (IK) channel inhibitor TRAM 34. Moreover, partial inhibition of α-cell Kslow with apamin depolarized membrane potential ( Vm) (3.8 ± 0.7 mV) and reduced action potential (AP) amplitude (10.4 ± 1.9 mV). Although apamin transiently increased Ca2+ influx into α-cells at low glucose (42.9 ± 10.6%), sustained SK (38.5 ± 10.4%) or BK channel inhibition (31.0 ± 11.7%) decreased α-cell Ca2+ influx. Total α-cell Ca2+c was similarly reduced (28.3 ± 11.1%) following prolonged treatment with high glucose, but it was not decreased further by SK or BK channel inhibition. Consistent with reduced α-cell Ca2+c following prolonged Kslow inhibition, apamin decreased GCG secretion from mouse (20.4 ± 4.2%) and human (27.7 ± 13.1%) islets at low glucose. These data demonstrate that Kslow activation provides a hyperpolarizing influence on α-cell Vm that sustains Ca2+ entry during hypoglycemic conditions, presumably by preventing voltage-dependent inactivation of P/Q-type VDCCs. Thus, when α-cell Ca2+c is elevated during secretagogue stimulation, Kslow activation helps to preserve GCG secretion.
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Affiliation(s)
- Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
| | - Molly K Altman
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
| | - Kenneth R Verlage
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
- School of Medicine, Texas Tech University Health Sciences Center , Lubbock, Texas
- Department of Urology, Oregon Health and Science University , Portland, Oregon
| | - Ariel S Thorson
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
| | - Kelli L Jordan
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
| | - Nicholas C Vierra
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
- Department of Neurobiology, Physiology and Behavior University of California , Davis, California
| | - Gautami Amarnath
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
- Experimental and Clinical Neurosciences, University of Regensburg , Regensburg , Germany
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University , Nashville, Tennessee
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5
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Cocozza G, di Castro MA, Carbonari L, Grimaldi A, Antonangeli F, Garofalo S, Porzia A, Madonna M, Mainiero F, Santoni A, Grassi F, Wulff H, D'Alessandro G, Limatola C. Ca 2+-activated K + channels modulate microglia affecting motor neuron survival in hSOD1 G93A mice. Brain Behav Immun 2018; 73:584-595. [PMID: 29981425 PMCID: PMC6129409 DOI: 10.1016/j.bbi.2018.07.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 06/28/2018] [Accepted: 07/02/2018] [Indexed: 12/13/2022] Open
Abstract
Recent studies described a critical role for microglia in amyotrophic lateral sclerosis (ALS), where these CNS-resident immune cells participate in the establishment of an inflammatory microenvironment that contributes to motor neuron degeneration. Understanding the mechanisms leading to microglia activation in ALS could help to identify specific molecular pathways which could be targeted to reduce or delay motor neuron degeneration and muscle paralysis in patients. The intermediate-conductance calcium-activated potassium channel KCa3.1 has been reported to modulate the "pro-inflammatory" phenotype of microglia in different pathological conditions. We here investigated the effects of blocking KCa3.1 activity in the hSOD1G93AALS mouse model, which recapitulates many features of the human disease. We report that treatment of hSOD1G93A mice with a selective KCa3.1 inhibitor, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), attenuates the "pro-inflammatory" phenotype of microglia in the spinal cord, reduces motor neuron death, delays onset of muscle weakness, and increases survival. Specifically, inhibition of KCa3.1 channels slowed muscle denervation, decreased the expression of the fetal acetylcholine receptor γ subunit and reduced neuromuscular junction damage. Taken together, these results demonstrate a key role for KCa3.1 in driving a pro-inflammatory microglia phenotype in ALS.
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Affiliation(s)
- Germana Cocozza
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy; Center for Life Nanoscience - Istituto Italiano di Tecnologia@Sapienza, Rome, Italy
| | | | - Laura Carbonari
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Alfonso Grimaldi
- Center for Life Nanoscience - Istituto Italiano di Tecnologia@Sapienza, Rome, Italy
| | - Fabrizio Antonangeli
- Department of Molecular Medicine, Sapienza University, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Rome, Italy
| | - Stefano Garofalo
- Department of Physiology and Pharmacology, Sapienza University, Laboratory affiliated to Istituto Pasteur Italia, Fondazione Cenci Bolognetti, Rome, Italy
| | | | | | - Fabrizio Mainiero
- Department of Experimental Medicine, Sapienza University, Rome, Italy
| | - Angela Santoni
- Department of Molecular Medicine, Sapienza University, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Rome, Italy; IRCCS Neuromed, Pozzilli, IS, Italy
| | - Francesca Grassi
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Heike Wulff
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | | | - Cristina Limatola
- Department of Physiology and Pharmacology, Sapienza University, Laboratory affiliated to Istituto Pasteur Italia, Fondazione Cenci Bolognetti, Rome, Italy; IRCCS Neuromed, Pozzilli, IS, Italy.
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6
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Tiwari MN, Mohan S, Biala Y, Yaari Y. Differential contributions of Ca 2+ -activated K + channels and Na + /K + -ATPases to the generation of the slow afterhyperpolarization in CA1 pyramidal cells. Hippocampus 2018; 28:338-357. [PMID: 29431274 PMCID: PMC5947627 DOI: 10.1002/hipo.22836] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 12/17/2017] [Accepted: 02/05/2018] [Indexed: 12/13/2022]
Abstract
In many types of CNS neurons, repetitive spiking produces a slow afterhyperpolarization (sAHP), providing sustained, intrinsically generated negative feedback to neuronal excitation. Changes in the sAHP have been implicated in learning behaviors, in cognitive decline in aging, and in epileptogenesis. Despite its importance in brain function, the mechanisms generating the sAHP are still controversial. Here we have addressed the roles of M-type K+ current (IM ), Ca2+ -gated K+ currents (ICa(K) 's) and Na+ /K+ -ATPases (NKAs) current to sAHP generation in adult rat CA1 pyramidal cells maintained at near-physiological temperature (35 °C). No evidence for IM contribution to the sAHP was found in these neurons. Both ICa(K) 's and NKA current contributed to sAHP generation, the latter being the predominant generator of the sAHP, particularly when evoked with short trains of spikes. Of the different NKA isoenzymes, α1 -NKA played the key role, endowing the sAHP a steep voltage-dependence. Thus normal and pathological changes in α1 -NKA expression or function may affect cognitive processes by modulating the inhibitory efficacy of the sAHP.
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Affiliation(s)
- Manindra Nath Tiwari
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Sandesh Mohan
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Yoav Biala
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Yoel Yaari
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
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7
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Mathew John C, Khaddaj Mallat R, George G, Kim T, Mishra RC, Braun AP. Pharmacologic targeting of endothelial Ca 2+-activated K + channels: A strategy to improve cardiovascular function. Channels (Austin) 2018; 12:126-136. [PMID: 29577810 PMCID: PMC5972810 DOI: 10.1080/19336950.2018.1454814] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 03/15/2018] [Indexed: 12/17/2022] Open
Abstract
Endothelial small and intermediate-conductance, Ca2+-activated K+ channels (KCa2.3 and KCa3.1, respectively) play an important role in the regulation of vascular function and systemic blood pressure. Growing evidence indicates that they are intimately involved in agonist-evoked vasodilation of small resistance arteries throughout the circulation. Small molecule activators of KCa2.x and 3.1 channels, such as SKA-31, can acutely inhibit myogenic tone in isolated resistance arteries, induce effective vasodilation in intact vascular beds, such as the coronary circulation, and acutely decrease systemic blood pressure in vivo. The blood pressure-lowering effect of SKA-31, and early indications of improvement in endothelial dysfunction suggest that endothelial KCa channel activators could eventually be developed into a new class of endothelial targeted agents to combat hypertension or atherosclerosis. This review summarises recent insights into the activation of endothelial Ca2+ activated K+ channels in various vascular beds, and how tools, such as SKA-31, may be beneficial in disease-related conditions.
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Affiliation(s)
- Cini Mathew John
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Rayan Khaddaj Mallat
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Grace George
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Taeyeob Kim
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ramesh C. Mishra
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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8
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Honrath B, Krabbendam IE, Culmsee C, Dolga AM. Small conductance Ca 2+-activated K + channels in the plasma membrane, mitochondria and the ER: Pharmacology and implications in neuronal diseases. Neurochem Int 2017; 109:13-23. [PMID: 28511953 DOI: 10.1016/j.neuint.2017.05.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 04/24/2017] [Accepted: 05/08/2017] [Indexed: 12/14/2022]
Abstract
Ca2+-activated K+ (KCa) channels regulate after-hyperpolarization in many types of neurons in the central and peripheral nervous system. Small conductance Ca2+-activated K+ (KCa2/SK) channels, a subfamily of KCa channels, are widely expressed in the nervous system, and in the cardiovascular system. Voltage-independent SK channels are activated by alterations in intracellular Ca2+ ([Ca2+]i) which facilitates the opening of these channels through binding of Ca2+ to calmodulin that is constitutively bound to the SK2 C-terminus. In neurons, SK channels regulate synaptic plasticity and [Ca2+]i homeostasis, and a number of recent studies elaborated on the emerging neuroprotective potential of SK channel activation in conditions of excitotoxicity and cerebral ischemia, as well as endoplasmic reticulum (ER) stress and oxidative cell death. Recently, SK channels were discovered in the inner mitochondrial membrane and in the membrane of the endoplasmic reticulum which sheds new light on the underlying molecular mechanisms and pathways involved in SK channel-mediated protective effects. In this review, we will discuss the protective properties of pharmacological SK channel modulation with particular emphasis on intracellularly located SK channels as potential therapeutic targets in paradigms of neuronal dysfunction.
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Affiliation(s)
- Birgit Honrath
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Inge E Krabbendam
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany
| | - Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands.
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9
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Ozkor MA, Hayek SS, Rahman AM, Murrow JR, Kavtaradze N, Lin J, Manatunga A, Quyyumi AA. Contribution of endothelium-derived hyperpolarizing factor to exercise-induced vasodilation in health and hypercholesterolemia. Vasc Med 2015; 20:14-22. [PMID: 25648989 PMCID: PMC9135050 DOI: 10.1177/1358863x14565374] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The role of endothelium-derived hyperpolarizing factor (EDHF) in either the healthy circulation or in those with hypercholesterolemia is unknown. In healthy and hypercholesterolemic subjects, we measured forearm blood flow (FBF) using strain-gauge plethysmography at rest, during graded handgrip exercise, and after sodium nitroprusside infusion. Measurements were repeated after l-NMMA, tetraethylammonium (TEA), and combined infusions. At rest, l-NMMA infusion reduced FBF in healthy but not hypercholesterolemic subjects. At peak exercise, vasodilation was lower in hypercholesterolemic compared to healthy subjects (274% vs 438% increase in FBF, p=0.017). TEA infusion reduced exercise-induced vasodilation in both healthy and hypercholesterolemic subjects (27%, p<0.0001 and -20%, p<0.0001, respectively). The addition of l-NMMA to TEA further reduced FBF in healthy (-14%, p=0.012) but not in hypercholesterolemic subjects, indicating a reduced nitric oxide and greater EDHF-mediated contribution to exercise-induced vasodilation in hypercholesterolemia. In conclusion, exercise-induced vasodilation is impaired and predominantly mediated by EDHF in hypercholesterolemic subjects. CLINICAL TRIAL REGISTRATION IDENTIFIER NCT00166166:
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Affiliation(s)
- Muhiddin A Ozkor
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Salim S Hayek
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Ayaz M Rahman
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Jonathan R Murrow
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Nino Kavtaradze
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Ji Lin
- Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Amita Manatunga
- Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Arshed A Quyyumi
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
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10
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Modgil A, Guo L, O’Rourke ST, Sun C. Apelin-13 inhibits large-conductance Ca2+-activated K+ channels in cerebral artery smooth muscle cells via a PI3-kinase dependent mechanism. PLoS One 2013; 8:e83051. [PMID: 24386141 PMCID: PMC3873301 DOI: 10.1371/journal.pone.0083051] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 11/04/2013] [Indexed: 11/25/2022] Open
Abstract
Apelin-13 causes vasoconstriction by acting directly on APJ receptors in vascular smooth muscle (VSM) cells; however, the ionic mechanisms underlying this action at the cellular level remain unclear. Large-conductance Ca2+-activated K+ (BKCa) channels in VSM cells are critical regulators of membrane potential and vascular tone. In the present study, we examined the effect of apelin-13 on BKCa channel activity in VSM cells, freshly isolated from rat middle cerebral arteries. In whole-cell patch clamp mode, apelin-13 (0.001-1 μM) caused concentration-dependent inhibition of BKCa in VSM cells. Apelin-13 (0.1 µM) significantly decreased BKCa current density from 71.25±8.14 pA/pF to 44.52±7.10 pA/pF (n=14 cells, P<0.05). This inhibitory effect of apelin-13 was confirmed by single channel recording in cell-attached patches, in which extracellular application of apelin-13 (0.1 µM) decreased the open-state probability (NPo) of BKCa channels in freshly isolated VSM cells. However, in inside-out patches, extracellular application of apelin-13 (0.1µM) did not alter the NPo of BKCa channels, suggesting that the inhibitory effect of apelin-13 on BKCa is not mediated by a direct action on BKCa. In whole cell patches, pretreatment of VSM cells with LY-294002, a PI3-kinase inhibitor, markedly attenuated the apelin-13-induced decrease in BKCa current density. In addition, treatment of arteries with apelin-13 (0.1 µM) significantly increased the ratio of phosphorylated-Akt/total Akt, indicating that apelin-13 significantly increases PI3-kinase activity. Taken together, the data suggest that apelin-13 inhibits BKCa channel via a PI3-kinase-dependent signaling pathway in cerebral artery VSM cells, which may contribute to its regulatory action in the control of vascular tone.
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Affiliation(s)
- Amit Modgil
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America
| | - Lirong Guo
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin, China
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America
- * E-mail: (CS); (LG)
| | - Stephen T. O’Rourke
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America
| | - Chengwen Sun
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America
- * E-mail: (CS); (LG)
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11
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Fan F, Sun CW, Maier KG, Williams JM, Pabbidi MR, Didion SP, Falck JR, Zhuo J, Roman RJ. 20-Hydroxyeicosatetraenoic acid contributes to the inhibition of K+ channel activity and vasoconstrictor response to angiotensin II in rat renal microvessels. PLoS One 2013; 8:e82482. [PMID: 24324797 PMCID: PMC3853207 DOI: 10.1371/journal.pone.0082482] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/02/2013] [Indexed: 11/24/2022] Open
Abstract
The present study examined whether 20-hydroxyeicosatetraenoic acid (HETE) contributes to the vasoconstrictor effect of angiotensin II (ANG II) in renal microvessels by preventing activation of the large conductance Ca2+-activated K+ channel (KCa) in vascular smooth muscle (VSM) cells. ANG II increased the production of 20-HETE in rat renal microvessels. This response was attenuated by the 20-HETE synthesis inhibitors, 17-ODYA and HET0016, a phospholipase A2 inhibitor AACOF3, and the AT1 receptor blocker, Losartan, but not by the AT2 receptor blocker, PD123319. ANG II (10-11 to 10-6 M) dose-dependently decreased the diameter of renal microvessels by 41 ± 5%. This effect was blocked by 17-ODYA. ANG II (10-7 M) did not alter KCa channel activity recorded from cell-attached patches on renal VSM cells under control conditions. However, it did reduce the NPo of the KCa channel by 93.4 ± 3.1% after the channels were activated by increasing intracellular calcium levels with ionomycin. The inhibitory effect of ANG II on KCa channel activity in the presence of ionomycin was attenuated by 17-ODYA, AACOF3, and the phospholipase C (PLC) inhibitor U-73122. ANG II induced a peak followed by a steady-state increase in intracellular calcium concentration in renal VSM cells. 17-ODYA (10-5 M) had no effect on the peak response, but it blocked the steady-state increase. These results indicate that ANG II stimulates the formation of 20-HETE in rat renal microvessels via the AT1 receptor activation and that 20-HETE contributes to the vasoconstrictor response to ANG II by blocking activation of KCa channel and facilitating calcium entry.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Calcium/metabolism
- Gene Expression
- Hydroxyeicosatetraenoic Acids/metabolism
- Ionomycin/pharmacology
- Male
- Microvessels/drug effects
- Microvessels/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Phospholipases A2/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels/metabolism
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Rats
- Receptors, Angiotensin/genetics
- Receptors, Angiotensin/metabolism
- Renal Circulation/drug effects
- Renal Circulation/physiology
- Type C Phospholipases/metabolism
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Fan Fan
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Cheng-Wen Sun
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America
| | - Kristopher G. Maier
- Division of Vascular Surgery and Endovascular Services, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Jan M. Williams
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Malikarjuna R. Pabbidi
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Sean P. Didion
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - John R. Falck
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Jialong Zhuo
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Richard J. Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
- * E-mail:
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12
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Tricarico D, Mele A, Calzolaro S, Cannone G, Camerino GM, Dinardo MM, Latorre R, Conte Camerino D. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation. PLoS One 2013; 8:e69551. [PMID: 23874973 PMCID: PMC3712936 DOI: 10.1371/journal.pone.0069551] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 06/10/2013] [Indexed: 11/18/2022] Open
Abstract
Emerging evidences suggest that Ca2+activated-K+-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10-11-10-3M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2x10-7M-5x10-3M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the cell proliferation induced by hyperkalemia. These findings may have relevance in disorders associated with abnormal K+ ion homeostasis including periodic paralysis and myotonia.
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13
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Yang D, Arifhodzic L, Ganellin CR, Jenkinson DH. Further studies on bis-charged tetraazacyclophanes as potent inhibitors of small conductance Ca(2+)-activated K+ channels. Eur J Med Chem 2013; 63:907-23. [PMID: 23685886 DOI: 10.1016/j.ejmech.2013.02.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 02/21/2013] [Accepted: 02/22/2013] [Indexed: 11/20/2022]
Abstract
Previously, quinolinium-based tetraazacyclophanes, such as UCL 1684 and UCL 1848, have been shown to be extraordinarily sensitive to changes in chemical structure (especially to the size of the cyclophane system) with respect to activity as potent non-peptidic blockers of the small conductance Ca(2+)-activated K(+) ion channels (SKCa). The present work has sought to optimize the structure of the linking chains in UCL 1848. We report the synthesis and SKCa channel-blocking activity of 29 analogues of UCL 1848 in which the central CH2 of UCL 1848 is replaced by other groups X or Y = O, S, CF2, CO, CHOH, CC, CHCH, CHMe to explore whether subtle changes in bond length or flexibility can improve potency still further. The possibility of improving potency by introducing ring substituents has also been explored by synthesizing and testing 25 analogues of UCL 1684 and UCL 1848 with substituents (NO2, NH2, CF3, F, Cl, CH3, OCH3, OCF3, OH) in the 5, 6 or 7 positions of the aminoquinolinium rings. As in our earlier work, each compound was assayed for inhibition of the afterhyperpolarization (AHP) in rat sympathetic neurons, an action mediated by the SK3 subtype of the SKCa channel. One of the new compounds (39, R(7) = Cl, UCL 2053) is twice as potent as UCL 1848 and UCL 1684: seven are comparable in activity.
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Affiliation(s)
- Donglai Yang
- Department of Chemistry, University College London, Gower Street, London WC1E 6BT, UK
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14
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Gao Q, Hu J, Hu J, Yu Y, Ye H, Li Z, Guan S. Calcium activated potassium channel and protein kinase C participate in the cardiac protection of remote post conditioning. Pak J Pharm Sci 2013; 26:285-290. [PMID: 23455198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The present study was designed to investigate the roles of Ca(2+) activated K(+) channel (KCa) and protein kinase C (PKC) in the protective mechanisms of remote ischemic post conditioning (RPostC) when rat heart was subjected to ischemia/reperfusion (I/R) injury in vivo. Rat heart was subjected to regional ischemia for 45 min and reperfusion for 180 min in vivo to mimic I/R injury. RPostC was induced by 5 min right femoral artery occlusion followed by 5 min reperfusion for 3 cycles (totally 30 min) after 15 min of cardiac ischemia. Delayed remote ischemic post conditioning (delayed RPostC) was induced after 10 min of cardiac reperfusion. The hemodynamic parameters including mean arterial blood pressure and heart rate (HR) were recorded, and lactate dehydrogenase (LDH) release in plasma and infarct size were determined, and arrhythmia scores were calculated. In contrast to I/R, RPostC reduced infarct size and LDH release during reperfusion, the occurrence of arrhythmia was decreased, but no changes in delayed RPostC. The specific inhibitor of KCa iberiotoxin and PKC inhibitor chelerythrine both attenuated the role of RPostC. The findings indicated that RPostC had a protective effect on myocardial ischemia/reperfusion injury. Opening of KCa and activating of PKC may be involved in the mechanisms of RPostC.
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Affiliation(s)
- Qin Gao
- Department of Physiology, Bengbu Medical College, Bengbu, China
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15
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Brereton MF, Wareing M, Jones RL, Greenwood SL. Characterisation of K+ channels in human fetoplacental vascular smooth muscle cells. PLoS One 2013; 8:e57451. [PMID: 23437391 PMCID: PMC3578819 DOI: 10.1371/journal.pone.0057451] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/24/2013] [Indexed: 11/18/2022] Open
Abstract
Adequate blood flow through placental chorionic plate resistance arteries (CPAs) is necessary for oxygen and nutrient transfer to the fetus and a successful pregnancy. In non-placental vascular smooth muscle cells (SMCs), K(+) channels regulate contraction, vascular tone and blood flow. Previous studies showed that K(+) channel modulators alter CPA tone, but did not distinguish between effects on K(+) channels in endothelial cells and SMCs. In this study, we developed a preparation of freshly isolated CPASMCs of normal pregnancy and investigated K(+) channel expression and function. CPASMCs were isolated from normal human term placentas using enzymatic digestion. Purity and phenotype was confirmed with immunocytochemistry. Whole-cell patch clamp was used to assess K(+) channel currents, and mRNA and protein expression was determined in intact CPAs and isolated SMCs with RT-PCR and immunostaining. Isolated SMCs expressed α-actin but not CD31, a marker of endothelial cells. CPASMCs and intact CPAs expressed h-caldesmon and non-muscle myosin heavy chain-2; phenotypic markers of contractile and synthetic SMCs respectively. Whole-cell currents were inhibited by 4-AP, TEA, charybdotoxin and iberiotoxin implicating functional K(v) and BK(Ca) channels. 1-EBIO enhanced whole cell currents which were abolished by TRAM-34 and reduced by apamin indicating activation of IK(Ca) and SK(Ca) respectively. BK(Ca), IK(Ca) and SK(Ca)3 mRNA and/or protein were expressed in CPASMCs and intact CPAs. This study provides the first direct evidence for functional K(v), BK(Ca,) IK(Ca) and SK(Ca) channels in CPASMCs. These cells display a mixed phenotype implicating a dual role for CPASMCs in controlling both fetoplacental vascular resistance and vasculogenesis.
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MESH Headings
- Actins/genetics
- Actins/metabolism
- Calcium/metabolism
- Calmodulin-Binding Proteins/genetics
- Calmodulin-Binding Proteins/metabolism
- Chorion/blood supply
- Chorion/cytology
- Chorion/drug effects
- Chorion/metabolism
- Female
- Fetus
- Gene Expression/drug effects
- Humans
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myosin Heavy Chains/genetics
- Myosin Heavy Chains/metabolism
- Patch-Clamp Techniques
- Placenta/blood supply
- Placenta/cytology
- Placenta/drug effects
- Placenta/metabolism
- Potassium/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/classification
- Potassium Channels, Calcium-Activated/genetics
- Potassium Channels, Calcium-Activated/metabolism
- Potassium Channels, Voltage-Gated/antagonists & inhibitors
- Potassium Channels, Voltage-Gated/classification
- Potassium Channels, Voltage-Gated/genetics
- Potassium Channels, Voltage-Gated/metabolism
- Pregnancy
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Affiliation(s)
- Melissa F Brereton
- Maternal and Fetal Health Research Centre, Institute of Human Development, University of Manchester, St. Mary's Hospital, Manchester, United Kingdom.
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16
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Shimanskaia TV, Strutinskaia NA, Vavilova GL, Goshovskaia IV, Semenikhina EN, Sagach VF. [Cyclosporin A-sensitive mitochondrial pore as a target of cardioprotective action of hydrogen sulfide donor]. Ross Fiziol Zh Im I M Sechenova 2013; 99:261-272. [PMID: 23650739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In experiments on a model of ischemia-reperfusion in Langendorff isolated rat hearts and isolated mitochondria we studied the role of hydrogen sulfide donor - sodium hydrosulfide (NaHS, 7.4 mg/kg) in modulating the sensitivity ofmitochondrial permeability transition pore opening. It was shown that NaHS increased the reserves of rat myocardium and had cardioprotective effects from ischemia-reperfusion. In experiments on isolated mitochondria NaHS in concentrations of 10(-6), 10(-5) and 5 x 10(-5) mol/L inhibited Ca(2+)-induced swelling of mitochondria. Preincubation of isolated mitochondria with K+(ATphi)-channels inhibitor 5-hydroxydecanoate (10(-4) mol/L) reduced the protective effect of NaHS (10(-5) mol/L). Thus, we consider that NaHS protective effect from reperfusion disturbances of heart function was realized via inhibition of Ca(2+)-induced mitochondrial permeability transition pore opening.
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17
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Sitdikova GF, Khaertdinov NN, Zefirov AL. Role of calcium and potassium channels in effects of hydrogen sulfide on frog myocardial contractility. Bull Exp Biol Med 2012; 151:163-6. [PMID: 22238741 DOI: 10.1007/s10517-011-1280-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The effects of sodium hydrosulfide NaHS, a donor of hydrogen sulfide H2S, on the force of muscle contraction were examined on isolated myocardial strips from frog ventricles. NaHS decreased the amplitude of muscle contractions in a dose-dependent manner under normal conditions and during inhibition of Ca channels with nifedipine. In contrast, under conditions of blockade of ATP-dependent potassium channels with glibenclamide, NaHS exerted a positive inotropic effect from the first minute of application. Neither blockade, nor activation of ATP-dependent K-channels with glibenclamide modulated the negative inotropic effect of NaHS. Inhibition of K-channels with tetraethylammonium (TEA) (3, 5, 10 mM) or 4-aminopyridine increased the amplitude of myocardial contractions. Preliminary application of 4-aminopyridine or TEA (3 mM) did not eliminate NaHS-induced negative inotropic effect, although higher TEA concentrations (5 or 10 mM) prevented it. The data indicate that the targets of H(2)S in frog myocardium are ATP-dependent, Ca-activated, and voltage-dependent K-channels.
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Affiliation(s)
- G F Sitdikova
- Department of Human and Animal Physiology, Kazan (Privolzhskii) Federal University, Russia.
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18
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Buxton SK, Neveu C, Charvet CL, Robertson AP, Martin RJ. On the mode of action of emodepside: slow effects on membrane potential and voltage-activated currents in Ascaris suum. Br J Pharmacol 2011; 164:453-70. [PMID: 21486286 PMCID: PMC3188918 DOI: 10.1111/j.1476-5381.2011.01428.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 01/17/2011] [Accepted: 03/28/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Anthelmintics are required for treatment and prophylaxis of nematode parasites of humans and domestic animals. Emodepside, a cyclooctadepsipeptide, is a modern anthelmintic that has a novel mode of action involving a Ca-activated K channel (SLO-1) in Caenorhabditis elegans, sometimes mediated by a latrophilin (LAT) receptor. We examined mechanisms of action of emodepside in a parasitic nematode, Ascaris suum. EXPERIMENTAL APPROACH RT-PCR was used to investigate expression of slo-1 and lat-1 in A. suum muscle flaps, and two-micropipette current-clamp and voltage-clamp techniques were used to record electrophysiological effects of emodepside. KEY RESULTS Expression of slo-1 and lat-1 were detected. Emodepside produced a slow time-dependent (20 min), 4-aminopyridine sensitive, concentration-dependent hyperpolarization and increase in voltage-activated K currents. Sodium nitroprusside increased the hyperpolarizations and K currents. N-nitro-L-arginine inhibited the hyperpolarizations and K currents. Phorbol-12-myristate-13 acetate increased the K currents, while staurosporine inhibited the hyperpolarizations and K currents. Iberiotoxin reduced these emodepside K currents. The effect of emodepside was reduced in Ca-free solutions. Emodepside had no effect on voltage-activated Ca currents. CONCLUSIONS AND IMPLICATIONS Asu-slo-1 and Asu-lat-1 are expressed in adult A. suum muscle flaps and emodepside produces slow activation of voltage-activated Ca-dependent SLO-1-like K channels. The effect of emodepside was enhanced by stimulation of protein kinase C and NO pathways. The data are consistent with a model in which NO, PKC and emodepside signalling pathways are separate and converge on the K channels, or in which emodepside activates NO and PKC signalling pathways to increase opening of the K channels.
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Affiliation(s)
- S K Buxton
- Department of Biomedical Sciences, Iowa State University, Ames, IA, USA
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19
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Beleznai TZ, Yarova PL, Yuill KH, Dora KA. Smooth muscle Ca(2+) -activated and voltage-gated K+ channels modulate conducted dilation in rat isolated small mesenteric arteries. Microcirculation 2011; 18:487-500. [PMID: 21535295 PMCID: PMC4826745 DOI: 10.1111/j.1549-8719.2011.00109.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To assess the influence of blocking smooth muscle large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels on the conducted dilation to ACh and isoproterenol. MATERIALS AND METHODS Rat mesenteric arteries were isolated with a bifurcation, triple-cannulated, pressurized and imaged using confocal microscopy. Phenylephrine was added to the superfusate to generate tone, and agonists perfused into a sidebranch to evoke local dilation and subsequent conducted dilation into the feed artery. RESULTS Both ACh- and isoproterenol-stimulated local and conducted dilation with similar magnitudes of decay with distance along the feed artery (2000μm: ∼15% maximum dilation). The gap junction uncoupler carbenoxolone prevented both conducted dilation and intercellular spread of dye through gap junctions. IbTx, TEA or 4-AP, blockers of large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels, did not affect conducted dilation to either agonist. A combination of either IbTx or TEA with 4-AP markedly improved the extent of conducted dilation to both agonists (2000μm: >50% maximum dilation). The enhanced conducted dilation was reflected in the hyperpolarization to ACh (2000μm: Control, 4±1 mV, n = 3; TEA with 4-AP, 14±3mV, n=4), and was dependent on the endothelium. CONCLUSIONS These data show that activated BK(Ca) and K(V) -channels serve to reduce the effectiveness of conducted dilation.
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Affiliation(s)
- Timea Z Beleznai
- Department of Pharmacology, University of Oxford, Oxford, UK Department of Pharmacy and Pharmacology, University of Bath, Bath, UK
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20
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Tishkin SM, Rekalov VV, Ivanova IV, MoreLand RS, Soloviev AI. Ionizing non-fatal whole-body irradiation inhibits Ca2+-dependent K+channels in endothelial cells of rat coronary artery: Possible contribution to depression of endothelium-dependent vascular relaxation. Int J Radiat Biol 2009; 83:161-9. [PMID: 17378524 DOI: 10.1080/09553000601146931] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE The goal of this study was to evaluate the influence of ionizing irradiation on large conductance Ca2+-dependent potassium (BKCa) channels in rat coronary endothelial cells. MATERIALS AND METHODS Rats were exposed to a 6 Gy dose from a cobalt60 source. Experimental design of this study comprised recording of contractile force using isolated rat aortic rings and whole-cell patch clamp techniques to study whole-cell potassium currents in isolated rat coronary artery endothelial cells. RESULTS It has been shown that outward potassium currents in endothelial cells 9 days after irradiation appear to be suppressed or even totally abolished. The reversal potential for these currents in irradiated cells was shifted to more positive values. Paxilline (500 nM), an inhibitor of BKCa channels, had no or only a negligible effect on irradiated cells. The experiments using isolated aortic rings demonstrated that both paxilline and irradiation significantly shifted the acetylcholine dependent concentration-relaxation response curve to the right. Irradiated tissues were insensitive to paxilline. CONCLUSION The results suggest that non-fatal, whole-body gamma-irradiation suppresses large conductance, calcium-activated potassium channels, which control the driving force for Ca2+ entry and therefore Ca2+ dependent nitric oxide (NO) synthesis in endothelial cells. This may contribute, in part, to radiation-induced endothelium dysfunction and an increase in arterial blood pressure.
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Affiliation(s)
- Sergey M Tishkin
- Institute of Pharmacology and Toxicology, Academy of Medical Sciences, Kiev, Ukraine
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21
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Abstract
GnRH receptor activation elicits release of intracellular Ca(2+), which leads to secretion and also activates Ca(2+)-activated ion channels underlying membrane voltage changes. The predominant Ca(2+)-activated ion channels in rat and mouse gonadotrophs are Ca(2+)-activated K(+) channels. To establish the temporal relationship between GnRH-induced changes in intracellular [Ca(2+)] ([Ca(2+)](i)) and membrane current (I(m)), and to identify specific Ca(2+)-activated K(+) channels linking GnRH-induced increase in [Ca(2+)](i) to changes in plasma membrane electrical activity, we used single female mouse gonadotrophs in the perforated patch configuration of the patch-clamp technique, which preserves signaling pathways. Simultaneous measurement of [Ca(2+)](i) and I(m) in voltage-clamped gonadotrophs revealed that GnRH stimulates an increase in [Ca(2+)](i) that precedes outward I(m), and that activates two kinetically distinct currents identified, using specific toxin inhibitors, as small conductance Ca(2+)-activated K(+) (SK) current (I(SK)) and large (big) conductance voltage- and Ca(2+)-activated K(+) (BK) current (I(BK)). We show that the apamin-sensitive current has an IC(50) of 69 pM, consistent with the SK2 channel subtype and confirmed by immunocytochemistry. The magnitude of the SK current response to GnRH was attenuated by 17beta-estradiol (E(2)) pretreatment. Iberiotoxin, an inhibitor of BK channels, completely blocked the residual apamin-insensitive outward I(m), substantiating that I(BK) is a component of the GnRH-induced outward I(m). In contrast to its suppression of I(SK), E(2) pretreatment augmented peak I(BK). SK or BK channel inhibition modulated GnRH-stimulated LH secretion, implicating a role for these channels in gonadotroph function. In summary, in mouse gonadotrophs the GnRH-stimulated increase in [Ca(2+)](i) activates I(SK) and I(BK), which are differentially regulated by E(2) and which may be targets for E(2) positive feedback in LH secretion.
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Affiliation(s)
- Dennis W Waring
- Division of Endocrinology, Department of Internal Medicine, University of California, One Shields Avenue, Davis, California 95616, USA.
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22
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Abstract
The intermediate-conductance Ca(2+)-activated K(+) channel (K(Ca)3.1) was first described by Gardos in erythrocytes and later confirmed to play a significant role in T-cell activation and the immune response. More recently, K(Ca)3.1 has been characterized in numerous cell types which contribute to the development of vascular disease, such as T-cells, B-cells, endothelial cells, fibroblasts, macrophages, and dedifferentiated smooth muscle cells (SMCs). Physiologically, K(Ca)3.1 has been demonstrated to play a role in acetylcholine and endothelium-derived hyperpolarizing factor (EDHF) induced hyperpolarization, and thus control of blood pressure. Pathophysiologically, K(Ca)3.1 contributes to proliferation of T-cells, B-cells, fibroblasts, and vascular SMCs, as well as the migration of SMCs and macrophages and platelet coagulation. Recent studies have indicated that blockade of K(Ca)3.1, by specific blockers such as TRAM-34, could prove to be an effective treatment for vascular disease by inhibiting T-cell activation as well as preventing proliferation and migration of macrophages, endothelial cells, and SMCs. This vasculoprotective potential of K(Ca)3.1 inhibition has been confirmed in both rodent and swine models of restenosis. In this review, we will discuss the physiological and pathophysiological role of K(Ca)3.1 in cells closely associated with vascular biology, and the effect of K(Ca)3.1 blockers on the initiation and progression of vascular disease.
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Affiliation(s)
- D L Tharp
- Department of Biomedical Sciences, University of Missouri, 1600 E. Rollins, Columbia, MO 65211, USA
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Hirukawa K, Muraki K, Ohya S, Imaizumi Y, Togari A. Electrophysiological properties of a novel Ca(2+)-activated K(+) channel expressed in human osteoblasts. Calcif Tissue Int 2008; 83:222-9. [PMID: 18787886 DOI: 10.1007/s00223-008-9167-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 08/04/2008] [Indexed: 11/28/2022]
Abstract
Intracellular Ca(2+) mobilization plays important roles in cell survival, proliferation, and differentiation of osteoblasts. In this study, we identified a novel type of Ca(2+)-activated K(+) channel in human osteoblasts and investigated its physiological roles. Using RT-PCR methods and single-channel analysis in the patch-clamp technique, we found that BK and IK channels were genetically expressed in human osteoblasts and had electrophysiological properties similar to those reported previously for the channels in other organs (conductance, voltage dependence, and sensitivity to intracellular Ca(2+)). Taking advantage of the fact that ATP induces elevation of the intracellular Ca(2+) concentration in human osteoblasts, we successfully demonstrated that ATP-induced hyperpolarization was effectively inhibited by the IK channel blockers charybdotoxin and clotrimazole and by a P2 purinergic receptor antagonist, suramin, but not by the BK channel blockers tetraethylammonium chloride and iberiotoxin under the current-clamp mode of whole-cell clamp. The present study is the first to demonstrate the electrophysiological properties and functional expression of IK channels in human osteoblasts, findings which suggest that IK channels are regulators of membrane potential that give rise to intracellular Ca(2+) mobilization by physiological stimulation.
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Affiliation(s)
- Koji Hirukawa
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan
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24
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Awumey EM, Hill SK, Diz DI, Bukoski RD. Cytochrome P-450 metabolites of 2-arachidonoylglycerol play a role in Ca2+-induced relaxation of rat mesenteric arteries. Am J Physiol Heart Circ Physiol 2008; 294:H2363-70. [PMID: 18375719 PMCID: PMC10433144 DOI: 10.1152/ajpheart.01042.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The perivascular sensory nerve (PvN) Ca(2+)-sensing receptor (CaR) is implicated in Ca(2+)-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries, which involves the vascular endogenous cannabinoid system. We determined the effect of inhibition of diacylglycerol (DAG) lipase (DAGL), phospholipase A(2) (PLA(2)), and cytochrome P-450 (CYP) on Ca(2+)-induced relaxation of PE-contracted rat mesenteric arteries. Our findings indicate that Ca(2+)-induced vasorelaxation is not dependent on the endothelium. The DAGL inhibitor RHC 802675 (1 microM) and the CYP and PLA(2) inhibitors quinacrine (5 microM) (EC(50): RHC 802675 2.8 +/- 0.4 mM vs. control 1.4 +/- 0.3 mM; quinacrine 4.8 +/- 0.4 mM vs. control 2.0 +/- 0.3 mM; n = 5) and arachidonyltrifluoromethyl ketone (AACOCF(3), 1 microM) reduced Ca(2+)-induced relaxation of mesenteric arteries. Synthetic 2-arachidonoylglycerol (2-AG) and glycerated epoxyeicosatrienoic acids (GEETs) induced concentration-dependent relaxation of isolated arteries. 2-AG relaxations were blocked by iberiotoxin (IBTX) (EC(50): control 0.96 +/- 0.14 nM, IBTX 1.3 +/- 0.5 microM) and miconazole (48 +/- 3%), and 11,12-GEET responses were blocked by IBTX (EC(50): control 55 +/- 9 nM, IBTX 690 +/- 96 nM) and SR-141716A. The data suggest that activation of the CaR in the PvN network by Ca(2+) leads to synthesis and/or release of metabolites of the CYP epoxygenase pathway and metabolism of DAG to 2-AG and subsequently to GEETs. The findings indicate a role for 2-AG and its metabolites in Ca(2+)-induced relaxation of resistance arteries; therefore this receptor may be a potential target for the development of new vasodilator compounds for antihypertensive therapy.
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MESH Headings
- 8,11,14-Eicosatrienoic Acid/metabolism
- Acetylcholine/pharmacology
- Animals
- Arachidonic Acids/metabolism
- Arachidonic Acids/pharmacology
- Calcium/metabolism
- Cytochrome P-450 Enzyme Inhibitors
- Cytochrome P-450 Enzyme System/metabolism
- Dose-Response Relationship, Drug
- Endocannabinoids
- Enzyme Inhibitors/pharmacology
- Glycerides/metabolism
- Lipoprotein Lipase/antagonists & inhibitors
- Lipoprotein Lipase/metabolism
- Male
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/enzymology
- Mesenteric Arteries/metabolism
- Miconazole/pharmacology
- Peptides/pharmacology
- Phenylephrine/pharmacology
- Phospholipase A2 Inhibitors
- Phospholipases A2/metabolism
- Piperidines/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Pyrazoles/pharmacology
- Quinacrine/pharmacology
- Rats
- Rats, Wistar
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/metabolism
- Receptors, Calcium-Sensing/metabolism
- Rimonabant
- Signal Transduction/drug effects
- Vasoconstrictor Agents/pharmacology
- Vasodilation
- Vasodilator Agents/pharmacology
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Affiliation(s)
- Emmanuel M Awumey
- Cardiovascular Disease Research Program, Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA.
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25
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Martins M, Viveiros M, Amaral L. Inhibitors of Ca2+ and K+ transport enhance intracellular killing of M. tuberculosis by non-killing macrophages. In Vivo 2008; 22:69-75. [PMID: 18396785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
BACKGROUND Human monocyte-derived macrophages that have little killing activity of their own kill intracellular Staphylococcus aureus when cultured in the presence of inhibitors of calcium and potassium efflux pumps. The aim of this study was to evaluate the effect of inhibitors such as ouabain, reserpine and verapamil in the killing activity of macrophages infected with Mycobacterium tuberculosis. MATERIALS AND METHODS Macrophages obtained from peripheral blood were infected with M. tuberculosis ATCC27294 H37Rv and treated with reserpine, ouabain and verapamil. RESULTS After three days post-infection, macrophages treated with the inhibitors demonstrated an enhancement of the killing activity destroying the internalized bacteria. CONCLUSION Whereas drugs that target the bacterium are predicted to lose effectiveness due to mutation of the bacterial target, drugs that enhance killing by macrophages that normally do not kill mycobacteria may yield a more effective form of infections therapy caused by multidrug resistant M. tuberculosis.
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Affiliation(s)
- Marta Martins
- Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, 1349-008 Lisboa, Portugal
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26
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Berkan O, Bagcivan I, Kaya T, Yildirim K, Yildirim S, Doğan K. Investigation of the vasorelaxant effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) and diethylamine/nitric oxide (DEA/NO) on the human radial artery used as coronary bypass graft. Can J Physiol Pharmacol 2007; 85:521-6. [PMID: 17632587 DOI: 10.1139/y07-033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The radial artery (RA) is used as a spastic coronary bypass graft. This study was designed to investigate the mechanism of vasorelaxant effects of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole), a nitric oxide (NO)-independent soluble guanylate cyclase (sGC) activator, and DEA/NO (diethylamine/nitric oxide), a NO-nucleophile adduct, on the human RA. RA segments (n = 25) were obtained from coronary artery bypass grafting patients and were divided into 3-4 mm vascular rings. Using the isolated tissue bath technique, the endothelium-independent vasodilatation function was tested in vitro by the addition of cumulative concentrations of YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) following vasocontraction by phenylephrine in the presence or absence of 10-5 mol/L ODQ (1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one), the selective sGC inhibitor, 10-7 mol/L iberiotoxin, a blocker of Ca2+-activated K+ channels, or 10-5 mol/L ODQ plus 10-7 mol/L iberiotoxin. We also evaluated the effect of YC-1 and DEA/NO on the cGMP levels in vascular rings obtained from human radial artery (n = 6 for each drug). YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) caused the concentration-dependent vasorelaxation in RA rings precontracted with phenylephrine (10-5 mol/L) (n = 20 for each drug). Pre-incubation of RA rings with ODQ, iberiotoxin, or ODQ plus iberiotoxin significantly inhibited the vasorelaxant effect of YC-1, but the inhibitor effect of ODQ plus iberiotoxin was significantly more than that of ODQ and iberiotoxin alone (p < 0.05). The vasorelaxant effect of DEA/NO almost completely abolished in the presence of ODQ and iberiotoxin plus ODQ, but did not significantly change in the presence of iberiotoxin alone (p > 0.05). The pEC50 value of DEA/NO was significantly lower than those for YC-1 (p < 0.01), with no change Emax values in RA rings. In addition, YC-1-stimulated RA rings showed more elevation in cGMP than that of DEA/NO (p < 0.05). These findings indicate that YC-1 is a more potent relaxant than DEA/NO in the human RA. The relaxant effects of YC-1 could be due to the stimulation of the sGC and Ca2+-sensitive K+channels, whereas the relaxant effects of DEA/NO could be completely due to the stimulation of the sGC. YC-1 and DEA/NO may be effective as vasodilator for the short-term treatment of perioperative spasm of coronary bypass grafts.
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Affiliation(s)
- Ocal Berkan
- Department of Cardiovascular Surgery, Cumhuriyet University School of Medicine, 58140 Sivas, Turkey.
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Abstract
Developments in the treatment of sickle cell disease (SCD) have not kept pace with advances in understanding the pathophysiology of this haemoglobinopathy. Drugs undergoing preclinical and clinical assessment for the therapy of these globin gene disorders are discussed in this article. Beginning with investigational agents for treatment of SCD as a whole, the discussion proceeds to drugs being developed for specific manifestations or iatrogenic complications. Despite being licensed in the USA, the prototype antisickling agent, hydroxycarbamide, has not attained worldwide clinical use because of concerns about long-term toxicity. The less toxic decitabine, which (as with hydroxycarbamide) increases fetal haemoglobin level, cannot be administered orally; therefore, the search continues for effective and safe antisickling drugs that can be taken orally. The naturally occurring benzaldehyde 5-hydroxymethyl-2-furfural has shown promising antisickling properties in vitro, and when administered to transgenic sickle mice. These effects are surpassed by the new synthetic pyridyl derivatives of benzaldehyde. Studies in humans with SCD are required to assess the clinical efficacy of these benzaldehydes. Niprisan, another antisickling agent with significant clinical efficacy and an attractive safety profile, is undergoing further development. The prospects of antiadhesion therapy in SCD are demonstrated by a recombinant protein containing the Fc fragment of IgG fused to the natural ligand for selectins: the conjugate significantly inhibited blood vessel occlusion in transgenic sickle mice. Whereas the orally administrable iron-chelating agent deferasirox is likely to increasingly take the place of desferioxamine (which can only be given parenterally), effective treatment of priapism in SCD remains a distressing challenge.
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MESH Headings
- Acetamides/pharmacology
- Acetamides/therapeutic use
- Anemia, Sickle Cell/complications
- Anemia, Sickle Cell/drug therapy
- Anemia, Sickle Cell/metabolism
- Anemia, Sickle Cell/therapy
- Animals
- Antihypertensive Agents/therapeutic use
- Antisickling Agents/pharmacology
- Antisickling Agents/therapeutic use
- Benzaldehydes/pharmacology
- Benzaldehydes/therapeutic use
- Benzoates/administration & dosage
- Benzoates/therapeutic use
- Carnitine/therapeutic use
- Cell Adhesion
- Deferasirox
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Etilefrine/therapeutic use
- Female
- Genetic Therapy/methods
- Hematopoietic Stem Cell Transplantation
- Humans
- Hydroxyurea/pharmacology
- Hydroxyurea/therapeutic use
- Hypertension, Pulmonary/drug therapy
- Hypertension, Pulmonary/etiology
- Iron Chelating Agents/administration & dosage
- Iron Chelating Agents/therapeutic use
- Male
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/pharmacology
- Membrane Glycoproteins/therapeutic use
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Priapism/drug therapy
- Priapism/etiology
- Recombinant Fusion Proteins/pharmacology
- Recombinant Fusion Proteins/therapeutic use
- Triazoles/administration & dosage
- Triazoles/therapeutic use
- Trityl Compounds/pharmacology
- Trityl Compounds/therapeutic use
- Vasoconstrictor Agents/therapeutic use
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Affiliation(s)
- Iheanyi Okpala
- St Thomas' Hospital, University of London, London SE1 7EH, UK.
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28
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Yang YY, Lin HC, Huang YT, Lee TY, Hou MC, Wang YW, Lee FY, Lee SD. Role of Ca2+-dependent potassium channels in in vitro anandamide-mediated mesenteric vasorelaxation in rats with biliary cirrhosis. Liver Int 2007; 27:1045-55. [PMID: 17845532 DOI: 10.1111/j.1478-3231.2007.01551.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND/AIM Anandamide can activate potassium (K(+)) channels to induce an endothelium-dependent vasorelaxation in normal rat mesenteric arteries. Cannabinoids contribute partly to the splanchnic vasodilation in cirrhosis. This study investigated the roles of vascular K(+) channels in anandamide-induced mesenteric vasorelaxation in isolated rat cirrhotic vessels. METHODS The effects of the pretreatment of AM251, a specific CB(1) receptor antagonist, were assessed on the vascular reactivity to phenylephrine (PE), potassium chloride (KCl), acetylcholine (ACh) and sodium nitroprusside (SNP). Additionally, cannabinoid (CB(1) and CB(2)) receptors' protein expression and the effects of different K(+) channel blockers on vascular reactivity to anandamide were also studied. RESULTS Cirrhotic mesenteric arteries showed an overexpression of CB(1) receptor associated with hyporeactivity to PE and KCl, and hyper-response to ACh, SNP and anandamide. Pretreatment with AM251 significantly improved the hyporeactivity to KCl and ameliorated the hyper-response to ACh in cirrhotic vessels. Increased relaxation response to anandamide was suppressed by combinations of vascular Ca(2+)-dependent K(+) channel blockers (including apamin+charybdotoxin+iberiotoxin or apamin+TRAM-34+iberiotoxin) (TRAM-34, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole). CONCLUSIONS In cirrhotic mesenteric arteries, vascular CB(1) receptor and anandamide contribute to the in vitro hyporeactivity to KCl. In addition, hyper-response to ACh may probably act through the modulation of vascular Ca(2+)-dependent K(+) channels.
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MESH Headings
- Acetylcholine/pharmacology
- Animals
- Apamin/pharmacology
- Arachidonic Acids/metabolism
- Cannabinoid Receptor Modulators/metabolism
- Charybdotoxin/pharmacology
- Common Bile Duct/surgery
- Dose-Response Relationship, Drug
- Endocannabinoids
- Glyburide/pharmacology
- Ligation
- Liver Cirrhosis, Biliary/metabolism
- Liver Cirrhosis, Biliary/physiopathology
- Liver Cirrhosis, Experimental/metabolism
- Liver Cirrhosis, Experimental/physiopathology
- Male
- Mesenteric Artery, Superior/drug effects
- Mesenteric Artery, Superior/metabolism
- Mesenteric Artery, Superior/physiopathology
- Nitroprusside/pharmacology
- Peptides/pharmacology
- Phenylephrine/pharmacology
- Piperidines/pharmacology
- Polyunsaturated Alkamides/metabolism
- Potassium/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Potassium Chloride/pharmacology
- Pyrazoles/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/metabolism
- Receptor, Cannabinoid, CB2/metabolism
- Vasoconstrictor Agents/pharmacology
- Vasodilation/drug effects
- Vasodilator Agents/pharmacology
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Affiliation(s)
- Ying-Ying Yang
- Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
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29
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Díaz-Ríos M, Dombeck DA, Webb WW, Harris-Warrick RM. Serotonin Modulates Dendritic Calcium Influx in Commissural Interneurons in the Mouse Spinal Locomotor Network. J Neurophysiol 2007; 98:2157-67. [PMID: 17581844 DOI: 10.1152/jn.00430.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Commissural interneurons (CINs) help to coordinate left–right alternating bursting activity during fictive locomotion in the neonatal mouse spinal cord. Serotonin (5-HT) plays an active role in the induction of fictive locomotion in the isolated spinal cord, but the cellular targets and mechanisms of its actions are relatively unknown. We investigated the possible role of serotonin in modifying dendritic calcium currents, using a combination of two-photon microscopy and patch-clamp recordings, in identified CINs in the upper lumbar region. Dendritic calcium responses to applied somatic voltage-clamp steps were measured using fluorescent calcium indicator imaging. Serotonin evoked significant reductions in voltage-dependent dendritic calcium influx in about 40% of the dendritic sites studied, with no detectable effect in the remaining sites. We also detected differential effects of serotonin in different dendritic sites of the same neuron; serotonin could decrease voltage-sensitive calcium influx at one site, with no effect at a nearby site. Voltage-clamp studies confirmed that serotonin reduces the voltage-dependent calcium current in CINs. Current-clamp experiments showed that the serotonin-evoked decreases in dendritic calcium influx were coupled with increases in neuronal excitability; we discuss possible mechanisms by which these two seemingly opposing results can be reconciled. This research demonstrates that dendritic calcium currents are targets of serotonin modulation in a group of spinal interneurons that are components of the mouse locomotor network.
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Affiliation(s)
- Manuel Díaz-Ríos
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
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30
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Gebremedhin D, Yamaura K, Harder DR. Role of 20-HETE in the hypoxia-induced activation of Ca2+-activated K+ channel currents in rat cerebral arterial muscle cells. Am J Physiol Heart Circ Physiol 2007; 294:H107-20. [PMID: 17906097 DOI: 10.1152/ajpheart.01416.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mechanism of sensing hypoxia and hypoxia-induced activation of cerebral arterial Ca(2+)-activated K(+) (K(Ca)) channel currents and vasodilation is not known. We investigated the roles of the cytochrome P-450 4A (CYP 4A) omega-hydroxylase metabolite of arachidonic acid, 20-hydroxyeicosatetraenoic acid (20-HETE), and generation of superoxide in the hypoxia-evoked activation of the K(Ca) channel current in rat cerebral arterial muscle cells (CAMCs) and cerebral vasodilation. Patch-clamp analysis of K(+) channel current identified a voltage- and Ca(2+)-dependent 238 +/- 21-pS unitary K(+) currents that are inhibitable by tetraethylammonium (TEA, 1 mM) or iberiotoxin (100 nM). Hypoxia (<2% O(2)) reversibly enhanced the open-state probability (NP(o)) of the 238-pS unitary K(Ca) current in cell-attached patches. This effect of hypoxia was not observed on unitary K(Ca) currents recorded from either excised inside-out or outside-out membrane patches. Inhibition of CYP 4A omega-hydroxylase activity increased the NP(o) of K(Ca) single-channel current. Hypoxia reduced the basal endogenous level of 20-HETE by 47 +/- 3% as well as catalytic formation of 20-HETE in cerebral arterial muscle homogenates as determined by liquid chromatography-mass spectrometry analysis. The concentration of authentic 20-HETE was reduced when incubated with the superoxide donor KO(2). Exogenous 20-HETE (100 nM) attenuated the hypoxia-induced activation of the K(Ca) current in CAMCs. Hypoxia did not augment the increase in NP(o) of K(Ca) channel current induced by suicide inhibition of endogenous CYP 4A omega-hydroxylase activity with 17-octadecynoic acid. In pressure (80 mmHg)-constricted cerebral arterial segments, hypoxia induced dilation that was partly attenuated by 20-HETE or by the K(Ca) channel blocker TEA. Exposure to hypoxia caused the generation of intracellular superoxide as evidenced by intense staining of arterial muscle with the fluorescent probe hydroethidine, by quantitation using fluorescent HPLC analysis, and by attenuation of the hypoxia-induced activation of the K(Ca) channel current by superoxide dismutation. These results suggest that the exposure of CAMCs to hypoxia results in the generation of superoxide and reduction in endogenous level of 20-HETE that may account for the hypoxia-induced activation of arterial K(Ca) channel currents and cerebral vasodilation.
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MESH Headings
- Animals
- Antioxidants/pharmacology
- Calcium/metabolism
- Cell Hypoxia
- Cerebral Arteries/metabolism
- Chromatography, High Pressure Liquid
- Cyclic N-Oxides/pharmacology
- Cytochrome P-450 CYP4A/antagonists & inhibitors
- Cytochrome P-450 CYP4A/metabolism
- Enzyme Inhibitors/pharmacology
- Fatty Acids, Unsaturated/pharmacology
- Hydroxyeicosatetraenoic Acids/metabolism
- Hydroxylation
- In Vitro Techniques
- Ion Channel Gating
- Male
- Mass Spectrometry
- Membrane Potentials
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/metabolism
- Patch-Clamp Techniques
- Peptides/pharmacology
- Potassium/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Rats
- Rats, Sprague-Dawley
- Signal Transduction/drug effects
- Spectrometry, Fluorescence
- Spin Labels
- Superoxides/metabolism
- Tetraethylammonium/pharmacology
- Vasodilation/drug effects
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Affiliation(s)
- Debebe Gebremedhin
- Cardiovascular Research Center, Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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31
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Yin LT, Fu YJ, Xu QL, Yang J, Liu ZL, Liang AH, Fan XJ, Xu CG. Potential biochemical therapy of glioma cancer. Biochem Biophys Res Commun 2007; 362:225-9. [PMID: 17707767 DOI: 10.1016/j.bbrc.2007.07.167] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 07/24/2007] [Indexed: 10/23/2022]
Abstract
Glioma is a highly invasive, rapidly spreading form of brain cancer that is resistant to surgical and medical treatment. The recent progresses made in intracellular and ion channels of glioma cells provide a potential new approach for biochemical therapy of brain tumor. In this paper, we reviewed clinical data on chemotherapy by temozolomide and results from new studies on voltage-gated potassium channels, large-conductance Ca(2+)-activated K(+) channels, volume-activated chloride channels, glioma-specific chloride channel and their modulators. These new findings may represent future directions for brain tumor studies and treatment.
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Affiliation(s)
- Li-Tian Yin
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, PR China
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32
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Bai X, Ma J, Pan Z, Song YH, Freyberg S, Yan Y, Vykoukal D, Alt E. Electrophysiological properties of human adipose tissue-derived stem cells. Am J Physiol Cell Physiol 2007; 293:C1539-50. [PMID: 17687001 DOI: 10.1152/ajpcell.00089.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human adipose tissue-derived stem cells (hASCs) represent a potentially valuable cell source for clinical therapeutic applications. The present study was designed to investigate properties of ionic channel currents present in undifferentiated hASCs and their impact on hASCs proliferation. The functional ion channels in hASCs were analyzed by whole-cell patch-clamp recording and their mRNA expression levels detected by RT-PCR. Four types of ion channels were found to be present in hASCs: most of the hASCs (73%) showed a delayed rectifier-like K(+) current (I(KDR)); Ca(2+)-activated K(+) current (I(KCa)) was detected in examined cells; a transient outward K(+) current (I(to)) was recorded in 19% of the cells; a small percentage of cells (8%) displayed a TTX-sensitive transient inward sodium current (I(Na.TTX)). RT-PCR results confirmed the presence of ion channels at the mRNA level: Kv1.1, Kv2.1, Kv1.5, Kv7.3, Kv11.1, and hEAG1, possibly encoding I(KDR); MaxiK, KCNN3, and KCNN4 for I(KCa); Kv1.4, Kv4.1, Kv4.2, and Kv4.3 for I(to) and hNE-Na for I(Na.TTX). The I(KDR) was inhibited by tetraethyl ammonium (TEA) and 4-aminopyridine (4-AP), which significantly reduced the proliferation of hASCs in a dose-dependent manner (P < 0.05), as suggested by bromodeoxyurindine (BrdU) incorporation. Other selective potassium channel blockers, including linopiridine, iberiotoxin, clotrimazole, and apamin also significantly inhibited I(KDR). TTX completely abolished I(Na.TTX). This study demonstrates for the first time that multiple functional ion channel currents such as I(KDR), I(KCa), I(to), and I(Na.TTX) are present in undifferentiated hASCs and their potential physiological function in these cells as a basic understanding for future in vitro experiments and in vivo clinical investigations.
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Affiliation(s)
- Xiaowen Bai
- Department of Molecular Pathology, University of Texas, MD Anderson Cancer Center, Houston, Texas 77054, USA
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33
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Wang GY, Song CM, Zhang LN, Li Q, Yue H, Feng JK, Wang N. [Roles of potassium channel in effects of resveratrol on isolated myocardial contractility and heart rate research in guinea pig]. Zhongguo Zhong Yao Za Zhi 2007; 32:1317-9. [PMID: 17879735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
OBJECTIVE To study the effects of resvaratrol derivatives on spontaneous HR and CF of isolated guinea pig atrium. METHOD The dose-effect curve of resvaratrol was observed. The possible mechanism of potassium channels responsible for changes of CF and HR after administering with resvaratrol was measured. RESULT Resvaratrol reduced the spontaneous HR and weakened the CF in a dose-dependent manner ranging from 10(-6) to 3 x 10(-4) mol x L(-1) (P < 0.05). As compared with Res group, the effects were partly blocked by Gli (P < 0.05) and TEA (P < 0.01), but not blocked by 4-AP, BaCl2, Atropine. CONCLUSION Resvaratrol can induce negative chronotropic action and negative (inotropic action. The mechanism(s) may relate to the opening of K(ATP) and Kc(Ca).
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Affiliation(s)
- Gui-ying Wang
- Department of Physiology, Basic Medical College, Hebei Medical University, Shijiazhuang 050091, China.
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Kito Y, Suzuki H. Role of K+ channels in the regulation of electrical spontaneous activity of the mouse small intestine. Pflugers Arch 2007; 455:505-14. [PMID: 17602242 DOI: 10.1007/s00424-007-0306-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 05/25/2007] [Accepted: 06/01/2007] [Indexed: 10/23/2022]
Abstract
The roles of K(+) channels in the regulation of slow waves and pacemaker potentials recorded from mouse small intestine were investigated using intracellular recording techniques in the presence of nifedipine. Iberiotoxin (0.1 microM) and charybdotoxin (0.1 microM) had no effect on the generation of slow waves recorded from circular smooth muscle cells. Apamin (0.3 microM) depolarized the membrane and decreased the amplitude of early, rapid repolarization of slow waves, without altering the amplitude, frequency, duration, or maximum rate of rise of the initial upstroke phase (dV/dt(max)). The early, rapid repolarization was enhanced by phenylephrine (15 microM). 4-Aminopyridine (4-AP, 5 mM) depolarized the membrane and increased the amplitude and dV/dt(max) of slow waves. Both apamin and 4-AP depolarized the membrane and decreased the amplitude and dV/dt(max) of pacemaker potentials recorded from interstitial cells of Cajal distributed in the myenteric region (ICC-MY). Membrane depolarization with a high-K(+) solution decreased the amplitude and dV/dt(max) of slow waves. These results suggest that apamin-sensitive K(+) conductance and 4-AP-sensitive K(+) conductance may contribute to the resting membrane potential of circular smooth muscle cells. The early, rapid repolarization of slow waves appears to result from the opening of apamin-sensitive K(+) conductance. 4-AP-sensitive K(+) conductance is likely to be activated in the initial upstroke component (primary component) of slow waves. In ICC-MY, membrane depolarization induced by apamin or 4-AP may result from electrotonic spread from smooth muscle cells.
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Affiliation(s)
- Yoshihiko Kito
- Department of Physiology, Nagoya City University Medical School, Nagoya, Japan.
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Seto SW, Au ALS, Lam TY, Chim SSC, Lee SMY, Wan S, Tjiu DCS, Shigemura N, Yim APC, Chan SW, Tsui SKW, Leung GPH, Kwan YW. Modulation by simvastatin of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine coronary artery smooth muscle cells. Br J Pharmacol 2007; 151:987-97. [PMID: 17558433 PMCID: PMC2042927 DOI: 10.1038/sj.bjp.0707327] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG CoA) reductase inhibitors) have been demonstrated to reduce cardiovascular mortality. It is unclear how the expression level of HMG CoA reductase in cardiovascular tissues compares with that in cells derived from the liver. We hypothesized that this enzyme exists in different cardiovascular tissues, and simvastatin modulates the vascular iberiotoxin-sensitive Ca2+-activated K(+) (BK(Ca)) channels. EXPERIMENTAL APPROACHES Expression of HMG CoA reductase in different cardiovascular preparations was measured. Effects of simvastatin on BK(Ca) channel gatings of porcine coronary artery smooth muscle cells were evaluated. KEY RESULTS Western immunoblots revealed the biochemical existence of HMG CoA reductase in human cardiovascular tissues and porcine coronary artery. In porcine coronary artery smooth muscle cells, extracellular simvastatin (1, 3 and 10 microM) (hydrophobic), but not simvastatin Na+ (hydrophilic), inhibited the BK(Ca) channels with a minimal recovery upon washout. Isopimaric acid (10 microM)-mediated enhancement of the BK(Ca) amplitude was reversed by external simvastatin. Simvastatin Na+ (10 microM, applied internally), markedly attenuated isopimaric acid (10 microM)-induced enhancement of the BK(Ca) amplitude. Reduced glutathione (5 mM; in the pipette solution) abolished simvastatin -elicited inhibition. Mevalonolactone (500 microM) and geranylgeranyl pyrophosphate (20 microM) only prevented simvastatin (1 and 3 microM)-induced responses. simvastatin (10 microM ) caused a rottlerin (1 microM)-sensitive (cycloheximide (10 microM)-insensitive) increase of PKC-delta protein expression. CONCLUSIONS AND IMPLICATIONS Our results demonstrated the biochemical presence of HMG CoA reductase in different cardiovascular tissues, and that simvastatin inhibited the BK(Ca) channels of the arterial smooth muscle cells through multiple intracellular pathways.
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MESH Headings
- Adult
- Aged
- Animals
- Blotting, Western
- Caveolin 1/biosynthesis
- Cell Line
- Cell Line, Tumor
- Coronary Vessels/cytology
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Dose-Response Relationship, Drug
- Enzyme Activation/drug effects
- Female
- Humans
- Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology
- Imidazoles/pharmacology
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Middle Aged
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/physiology
- Peptides/pharmacology
- Phorbol Esters/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Potassium Channels, Calcium-Activated/physiology
- Protein Kinase C-delta/metabolism
- Pyridines/pharmacology
- Simvastatin/chemistry
- Simvastatin/pharmacology
- Swine
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Affiliation(s)
- S W Seto
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - A L S Au
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - T Y Lam
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S S C Chim
- Department of Obstetrics and Gynaecology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S M Y Lee
- Institute of Chinese Medical Sciences, University of Macau Macau, PR China
| | - S Wan
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - D C S Tjiu
- Department of Surgery, United Christian Hospital, The Hong Kong Polytechnic University Hong Kong SAR, PR China
| | - N Shigemura
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - A P C Yim
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S W Chan
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University Hong Kong SAR, PR China
| | - S K W Tsui
- Department of Biochemistry, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong SAR, PR China
| | - G P H Leung
- Department of Pharmacology, University of Hong Kong Hong Kong SAR, PR China
| | - Y W Kwan
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
- Author for correspondence:
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Morin C, Sirois M, Echave V, Gomes MM, Rousseau E. Relaxing effects of 5-oxo-ETE on human bronchi involve BKCa channel activation. Prostaglandins Other Lipid Mediat 2007; 83:311-9. [PMID: 17499751 DOI: 10.1016/j.prostaglandins.2007.03.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 02/27/2007] [Accepted: 03/01/2007] [Indexed: 10/23/2022]
Abstract
The present study investigated the ability of 5-oxo-EicosaTetraEnoic acid (5-oxo-ETE) for modulating airway smooth muscle (ASM) tone in human bronchi. 5-Oxo-ETE induced a concentration-dependent relaxing effect on human bronchi pre-contracted with methacholine (MCh) and arachidonic acid (AA). This relaxing response was highly sensitive to Iberiotoxin (IbTx), a large conducting Ca(2+)-activated K(+) channel (BK(Ca)) inhibitor. Furthermore, microelectrode measurements revealed that 5-oxo-ETE (0.1-10 microM) hyperpolarizes the membrane potential of human bronchial ASM cells. These hyperpolarizing effects were also inhibited in the presence of 10nM IbTx. Lastly, 5-oxo-ETE was shown to directly activate reconstituted BK(Ca) channels derived from human airway smooth muscles. In summary, the 5-oxo-ETE eicosanoid activates a specific K(+) conductance, involved in membrane hyperpolarization, which in turn reduces Ca(2+) entry and facilitates relaxation of smooth muscle cells.
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Affiliation(s)
- Caroline Morin
- Le Bilarium, Department of Physiology and Biophysics, Faculty of Medicine and Health Sciences, Université de Sherbrooke 3001, 12th Avenue North, Sherbrooke J1H 5N4, Que., Canada
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Absi M, Burnham MP, Weston AH, Harno E, Rogers M, Edwards G. Effects of methyl beta-cyclodextrin on EDHF responses in pig and rat arteries; association between SK(Ca) channels and caveolin-rich domains. Br J Pharmacol 2007; 151:332-40. [PMID: 17450174 PMCID: PMC2013982 DOI: 10.1038/sj.bjp.0707222] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The small and intermediate conductance, Ca2+-sensitive K+ channels (SK(Ca) and IK(Ca), respectively) which are pivotal in the EDHF pathway may be differentially activated. The importance of caveolae in the functioning of IK(Ca) and SK(Ca) channels was investigated. EXPERIMENTAL APPROACH The effect of the caveolae-disrupting agent methyl-beta-cyclodextrin (MbetaCD) on IK(Ca) and SK(Ca) localization and function was determined. KEY RESULTS EDHF-mediated, SK(Ca)-dependent myocyte hyperpolarizations evoked by acetylcholine in rat mesenteric arteries (following blockade of IK(Ca) with TRAM-34) were inhibited by MbetaCD. Hyperpolarizations evoked by direct SK(Ca) channel activation (using NS309 in the presence of TRAM-34) were also inhibited by MbetaCD, an effect reversed by cholesterol. In contrast, IK(Ca)-dependent hyperpolarizations (in the presence of apamin) were unaffected by MbetaCD. Similarly, in porcine coronary arteries, EDHF-mediated, SK(Ca)-dependent (but not IK(Ca)-dependent) endothelial cell hyperpolarizations evoked by substance P were inhibited by MbetaCD. In mesenteric artery homogenates subjected to sucrose-density centrifugation, caveolin-1 and SK3 (SK(Ca)) proteins but not IK1 (IK(Ca)) protein migrated to the buoyant, caveolin-rich fraction. MbetaCD pretreatment redistributed caveolin-1 and SK3 proteins into more dense fractions. In immunofluorescence images of porcine coronary artery endothelium, SK3 (but not IK1) and caveolin-1 were co-localized. Furthermore, caveolin-1 immunoprecipitates prepared from native porcine coronary artery endothelium contained SK3 but not IK1 protein. CONCLUSIONS AND IMPLICATIONS These data provide strong evidence that endothelial cell SK(Ca) channels are located in caveolae while the IK(Ca) channels reside in a different membrane compartment. These studies reveal cellular organisation as a further complexity in the EDHF pathway signalling cascade.
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Affiliation(s)
- M Absi
- Faculty of Life Sciences, University of Manchester, Core Technology Facility Manchester, UK
| | - M P Burnham
- Faculty of Life Sciences, University of Manchester, Core Technology Facility Manchester, UK
| | - A H Weston
- Faculty of Life Sciences, University of Manchester, Core Technology Facility Manchester, UK
| | - E Harno
- Faculty of Life Sciences, University of Manchester, Core Technology Facility Manchester, UK
| | - M Rogers
- Imaging Science and Biomedical Engineering, The University of Manchester Manchester, UK
| | - G Edwards
- Faculty of Life Sciences, University of Manchester, Core Technology Facility Manchester, UK
- Author for correspondence:
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Abstract
BACKGROUND AND PURPOSE NO/prostanoid independent, EDHF-mediated hyperpolarization and dilation in rat middle cerebral arteries is mediated solely by endothelial cell IK(Ca). However, when the NO-pathway is also active, both SK(Ca) and IK(Ca) contribute to EDHF responses. As the SK(Ca) component can be inhibited by stimulation of thromboxane A(2) (TxA(2)) TP receptors and NO has the potential ability to inhibit thromboxane synthesis, we investigated whether TxA(2) might explain loss of functional input from SK(Ca) during NOS inhibition in cerebral arteries. EXPERIMENTAL APPROACH Rat middle cerebral arteries were mounted in a wire myograph. Endothelium-dependent responses to the PAR2 agonist, SLIGRL were assessed as simultaneous changes in smooth muscle membrane potential and tension. KEY RESULTS Responses were obtained in the presence of L-NAME as appropriate. Inhibition of TP receptors with either ICI 192,605 or SQ 29,548, did not affect EDHF mediated hyperpolarization and relaxation, but in their presence neither TRAM-34 nor apamin (to block IK(Ca) and SK(Ca) respectively) individually affected the EDHF response. However, in combination they virtually abolished it. Similar effects were obtained in the presence of the thromboxane synthase inhibitor, furegrelate, which additionally revealed an iberiotoxin-sensitive residual EDHF hyperpolarization and relaxation in the combined presence of TRAM-34 and apamin. CONCLUSIONS AND IMPLICATIONS In the rat middle cerebral artery, inhibition of NOS leads to a loss of the SK(Ca) component of EDHF responses. Either antagonism of TP receptors or block of thromboxane synthase restores an input through SK(Ca). These data indicate that NO normally enables SK(Ca) activity in rat middle cerebral arteries.
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Affiliation(s)
- A J McNeish
- Department of Pharmacy and Pharmacology, the University of Bath Claverton Down, Bath, UK
| | - C J Garland
- Department of Pharmacy and Pharmacology, the University of Bath Claverton Down, Bath, UK
- Author for correspondence:
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Kalifa J, Bernard M, Gout B, Bril A, Cozma D, Laurent P, Chalvidan T, Deharo JC, Djiane P, Cozzone P, Maixent JM. Anti-arrhythmic effects of I (Na), I (Kr), and combined I (Kr)-I (CaL) blockade in an experimental model of acute stretch-related atrial fibrillation. Cardiovasc Drugs Ther 2007; 21:47-53. [PMID: 17356910 DOI: 10.1007/s10557-007-6001-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 10/05/2006] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Atrial dilatation is commonly associated with atrial fibrillation (AF), but the electrophysiological mechanisms and the implications for anti-arrhythmic therapy are poorly understood. In a model of acute stretch-related AF in isolated rabbit hearts, we evaluated the electrophysiological effects of three different anti-arrhythmic drugs: dofetilide, flecainide and BRL-32872 (associating I (Kr) and I (CaL) blocking properties). METHODS After 30 min of sustained stretch-related AF, we perfused BRL 10-7 M, BRL 3.10-7 M, BRL 10-6 M, flecainide 2.4 10-6 M and dofetilide 10-7 M and iteratively measured atrial effective refractory periods (ERPs), AF inducibility and AF cycle length (AFCL) 15, 30 and 60 min after drug perfusion, respectively. RESULTS After a significant shortening of the ERPs by acute atrial stretch in the five groups individually (p < 0.001, stretch vs baseline for each group individually), drug perfusion led to a strong lengthening of AFCL, a very significant prolongation of ERPs (p < 0.001 vs stretch) and a reduction of AF inducibility (p < 0.01 vs control group) for each of the five experimental groups. The relative ERP increase was comparable in all groups, whereas a significantly lower AF inducibility was observed in the BRL 10-6 M group (p < 0.05 vs other BRL concentrations). CONCLUSION In a model of acute stretch-related AF, dofetilide, flecainide and BRL-32872 terminated AF and prevented its immediate reinduction after having comparatively prolonged AFCL and ERPs. These comparative results suggest that those drugs are equally efficacious, albeit with different mechanisms, in the setting of acute atrial stretch.
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Affiliation(s)
- J Kalifa
- Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine, 27 Bd Jean Moulin, 13005, Marseille, France.
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Hu J, Yuan X, Ko MK, Yin D, Sacapano MR, Wang X, Konda BM, Espinoza A, Prosolovich K, Ong JM, Irvin D, Black KL. Calcium-activated potassium channels mediated blood-brain tumor barrier opening in a rat metastatic brain tumor model. Mol Cancer 2007; 6:22. [PMID: 17359538 PMCID: PMC1831484 DOI: 10.1186/1476-4598-6-22] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 03/14/2007] [Indexed: 11/16/2022] Open
Abstract
Background The blood-brain tumor barrier (BTB) impedes the delivery of therapeutic agents to brain tumors. While adequate delivery of drugs occurs in systemic tumors, the BTB limits delivery of anti-tumor agents into brain metastases. Results In this study, we examined the function and regulation of calcium-activated potassium (KCa) channels in a rat metastatic brain tumor model. We showed that intravenous infusion of NS1619, a KCa channel agonist, and bradykinin selectively enhanced BTB permeability in brain tumors, but not in normal brain. Iberiotoxin, a KCa channel antagonist, significantly attenuated NS1619-induced BTB permeability increase. We found KCa channels and bradykinin type 2 receptors (B2R) expressed in cultured human metastatic brain tumor cells (CRL-5904, non-small cell lung cancer, metastasized to brain), human brain microvessel endothelial cells (HBMEC) and human lung cancer brain metastasis tissues. Potentiometric assays demonstrated the activity of KCa channels in metastatic brain tumor cells and HBMEC. Furthermore, we detected higher expression of KCa channels in the metastatic brain tumor tissue and tumor capillary endothelia as compared to normal brain tissue. Co-culture of metastatic brain tumor cells and brain microvessel endothelial cells showed an upregulation of KCa channels, which may contribute to the overexpression of KCa channels in tumor microvessels and selectivity of BTB opening. Conclusion These findings suggest that KCa channels in metastatic brain tumors may serve as an effective target for biochemical modulation of BTB permeability to enhance selective delivery of chemotherapeutic drugs to metastatic brain tumors.
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MESH Headings
- Animals
- Blood-Brain Barrier/pathology
- Brain Neoplasms/metabolism
- Brain Neoplasms/pathology
- Brain Neoplasms/secondary
- Coculture Techniques
- Disease Models, Animal
- Endothelial Cells/cytology
- Endothelial Cells/metabolism
- Gene Expression Regulation, Neoplastic
- Humans
- Lung Neoplasms/pathology
- Permeability/drug effects
- Potassium Channels, Calcium-Activated/agonists
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/genetics
- Potassium Channels, Calcium-Activated/metabolism
- Potentiometry
- Protein Transport
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Receptor, Bradykinin B2/metabolism
- Tumor Cells, Cultured
- Xenograft Model Antitumor Assays
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Affiliation(s)
- Jinwei Hu
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Xiangpeng Yuan
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - MinHee K Ko
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Dali Yin
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Manuel R Sacapano
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Xiao Wang
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Bindu M Konda
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Andres Espinoza
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Ksenia Prosolovich
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - John M Ong
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Dwain Irvin
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
| | - Keith L Black
- Department of Neurosurgery, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048. USA
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Selemidis S, Cocks T. Smooth muscle mediates circumferential conduction of hyperpolarization and relaxation to focal endothelial cell activation in large coronary arteries. Naunyn Schmiedebergs Arch Pharmacol 2007; 375:85-94. [PMID: 17340126 DOI: 10.1007/s00210-007-0149-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Accepted: 02/20/2007] [Indexed: 10/23/2022]
Abstract
Longitudinal conduction of endothelium-dependent vasodilatation is mediated by intercellular spread of hyperpolarization via gap junctions along the endothelium. If similar electrical signals from the endothelium conduct around the circumference of arteries via smooth muscle cells, then, both longitudinal and circumferential spread of such signals would make it possible for a wide annulus of a large blood vessel like an epicardial coronary artery to dilate to local stimuli. To examine this in vitro, we developed a dual-chambered organ bath in which both membrane potential and force are independently determined in endothelium-intact and -denuded regions of a single annulus of artery. Hyperpolarizations and relaxations to endothelium-dependent vasodilators like bradykinin (BK) and substance P in smooth muscle cells immediately beneath the local endothelium-intact region (local responses) are conducted via smooth muscle cells around the circumference of the artery. The local relaxation was partially inhibited by the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine (L-NOARG), and subsequently abolished by further treatment with a combination of two characteristic inhibitors of endothelium-dependent hyperpolarization-the Ca2+ -activated potassium channel (KCa) channel inhibitors, apamin and charybdotoxin. The conducted hyperpolarizations and relaxations to BK were unaffected by L-NOARG, but were abolished by apamin and charybdotoxin. In conclusion, these studies demonstrate for the first time that NO acts only as a local vasodilator, whereas endothelium-dependent hyperpolarization (EDH) causes local and remote vasodilatation in large coronary arteries. We propose that such a remote EDH-dependent signalling mechanism compensates for the loss of the local NO-dependent vasodilatation in diseased arteries.
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Affiliation(s)
- Stavros Selemidis
- Department of Pharmacology, Monash University, Wellington Road, Clayton, Victoria, 3800, Australia.
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Shmygol A, Noble K, Wray S. Depletion of membrane cholesterol eliminates the Ca2+-activated component of outward potassium current and decreases membrane capacitance in rat uterine myocytes. J Physiol 2007; 581:445-56. [PMID: 17331986 PMCID: PMC2075177 DOI: 10.1113/jphysiol.2007.129452] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Changes in membrane cholesterol content have potent effects on cell signalling and contractility in rat myometrium and other smooth muscles. We have previously shown that depletion of cholesterol with methyl-beta-cyclodextrin (MCD) disrupts caveolar microdomains. The aim of this work was to determine the mechanism underlying the increase in Ca(2+) signalling and contractility occurring in the myometrium with MCD. Patch clamp data obtained on freshly isolated myocytes from the uterus of day 19-21 rats showed that outward K(+) current was significantly reduced by MCD. Membrane capacitance was also reduced. Cholesterol-saturated MCD had no effect on the amplitude of outward current suggesting that the reduction in the outward current was due to cholesterol depletion induced by MCD rather than a direct inhibitory action of MCD on the K(+) channels. Confocal visualization of the membrane bound indicator Calcium Green C18, revealed internalization of the surface membrane with MCD treatment. Large conductance, Ca(2+)-sensitive K(+) channel proteins have been shown to localize to caveolae. When these channels were blocked by iberiotoxin outward current was significantly reduced in the uterine myocytes; MCD treatment reduced the density of outward current. Following reduction of outward current by MCD pretreatment, iberiotoxin was unable to produce any additional decrease in the current, suggesting a common target. MCD treatment also increased the amplitude and frequency of spontaneous rises in cytosolic Ca(2+) level ([Ca(2+)](i) transients) in isolated myocytes. In intact rat myometrium, MCD treatment increased Ca(2+) signalling and contractility, consistent with previous findings, and this effect was also found to be reduced by BK channel inhibition. These data suggest that (1) disruption of cholesterol-rich microdomains and caveolae by MCD leads to a decrease in the BK channel current thus increasing cell excitability, and (2) the changes in membrane excitability produced by MCD underlie the changes found in Ca(2+) signalling and uterine contractility.
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Affiliation(s)
- A Shmygol
- Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV2 2DX, UK
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Abstract
TRAM-34 has been demonstrated to inhibit intermediate-conductance Ca(2+)-activated K(+) channels in a wide variety of cell types, including immune cells. In the present study, we investigated effects of TRAM-34 on microglial cells stimulated with lysophosphatidylcholine (LPC). LPC-induced increases in the intracellular Ca(2+) concentration of microglial cells were effectively reduced in the presence of TRAM-34. At a concentration of 1 microM, TRAM-34 inhibited LPC-induced Ca(2+) signals by 60%. The TRAM-34-induced reduction of LPC-induced Ca(2+) increases cannot be related to the inhibition of Ca(2+)-activated K(+) channels. In contrast to TRAM-34, the Ca(2+)-activated K(+) channel inhibitor charybdotoxin did not affect LPC-induced increases in the intracellular Ca(2+) concentration of microglial cells. Patch clamp experiments revealed a direct inhibitory effect of TRAM-34 on nonselective cation channels. Half-maximal inhibition of LPC-induced nonselective cation currents was determined at 38 nM TRAM-34. These data indicate that TRAM-34 may cause additional effects on immune cells that are unrelated to the well-described inhibition of Ca(2+)-activated K(+) channels.
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Affiliation(s)
- Tom Schilling
- Institute of Physiology, Medical Faculty Charité, Tucholskystrasse 2, 10117 Berlin, Germany
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Ataga KI, Orringer EP, Styles L, Vichinsky EP, Swerdlow P, Davis GA, Desimone PA, Stocker JW. Dose-escalation study of ICA-17043 in patients with sickle cell disease. Pharmacotherapy 2007; 26:1557-64. [PMID: 17064199 DOI: 10.1592/phco.26.11.1557] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE To determine the dose tolerance, safety, and pharmacokinetics of a single oral dose of ICA-17043 in patients with sickle cell disease. DESIGN Phase I, randomized, double-blind, placebo-controlled, single-dose, dose-escalation study. SETTING Four university medical centers. PATIENTS Twenty-eight patients with sickle cell disease, aged 18-60 years, who were otherwise healthy and in a noncrisis state. INTERVENTION Patients in three separate dose cohorts--50 mg, 100 mg, and 150 mg--received single doses of ICA-17043 or placebo. MEASUREMENTS AND MAIN RESULTS The mean area under the concentration-time curve from time zero extrapolated to infinity (AUC(0-infinity)) for ICA-17043 increased in a dose-related manner (11,827, 19,697, and 30,676 ng.hr/ml for 50, 100, and 150 mg, respectively). Overall mean half-life was 12.8 days. Mean peak plasma concentrations rose between the 50- and 100-mg dose levels but plateaued at 150 mg (59.1, 108.7, and 109.1 ng/ml, respectively). Weekly pharmacokinetic and safety assessments were conducted in each patient during the follow-up phase for 56 days. No dose-limiting adverse events were noted in any of the patients. CONCLUSION Total systemic exposure of ICA-17043 after a single oral dose, as measured by AUC(0-infinity), increased nearly proportionally with the dose. The rate of absorption, however, appeared to be delayed at doses greater than 100 mg. With the long half-life of ICA-17043 demonstrated in this study, once-daily dosing is probably adequate to maintain steady-state plasma concentrations. In addition, single doses of ICA-17043 were well tolerated.
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Affiliation(s)
- Kenneth I Ataga
- Division of Hematology-Oncology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7305, USA.
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Abstract
Preliminary clinical studies of testosterone therapy in male patients with coronary artery disease obtained promising results. However, little is known about the in vitro effects of testosterone in human isolated arteries. We investigated the effect of testosterone on contractile tone of human isolated radial artery (RA). Testosterone was added (0.1 - 300 microM ) cumulatively to organ baths after precontraction with KCl (45 mM) and phenylephrine (PE, 10 microM). Testosterone-induced relaxations were tested in the presence of the cyclooxygenase inhibitor indomethacin (10 microM), nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM), non-selective large conductance Ca(2+)-activated and voltage-sensitive K(+) channel inhibitor tetraethylammonium (TEA, 1 mM), ATP-sensitive K(+) channel inhibitor glibenclamide (GLI, 10 microM), and voltage-sensitive K(+) channel inhibitor 4-aminopyridine (4-AP, 1 mM). Testosterone produced relaxation in human RA (E(max): 53.03 +/- 2.76% and 66.83 +/- 1.97% of KCl and PE-induced contraction, respectively). Except for GLI, the relaxation to testosterone is affected by neither K(+) channel inhibitors (TEA, BaCl(2), and 4-AP), L-NAME, nor indomethacin. We report for the first time that supraphysiological concentrations of testosterone induces relaxation in RA. This response may occur in part via ATP-sensitive K(+) channel opening action.
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Affiliation(s)
- Melik Seyrek
- Department of Pharmacology, Gulhane School of Medicine, Ankara, Turkey
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Kryshtal' DO, Nesin VV, Shuba MF. [Effect of paxilline on Ca(2+)-dependent K+ current in smooth muscle cells isolated from rat vas deferens]. Fiziol Zh (1994) 2007; 53:67-74. [PMID: 18080495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The properties of the outward Ca(2+)-dependent K+ current (KCa) were investigated in single smooth muscle cells (SMCs) isolated from epididymal part of the rat vas deferens (RVD) using amphotericin B perforated patch-clamp technique. The complex kinetic of the net outward current elicited by positive voltage steps from -80 mV to +40 mV suggested the presence of several components of this current. KCa current was separated from the net outward current by removal of Ca2+ from the external solution. KCa was characterized by slow kinetics of current activation and decay. Mycotoxin paxilline, the selective blocker of the large conductance KCa channels, inhibited KCa current in a dose-dependent manner. At the concentration of 70 nM paxilline evoked 50% inhibition of KCa and at 1 mkM complete suppression of KCa current was achieved. The blocking effect of low concentrations of a nonselective KCa channels inhibitor tetraethylammonium (TEA) was compared to that of paxilline. The external application of 0.3 mM TEA inhibited KCa current similarly to 1 mkM of paxilline. Finally, we studied the effect of paxilline on the resting membrane potential ofRVD SMCs. Paxilline (1 mkM) did not affect the membrane potential of SMCs with the resting potential in the range of -60 to -40 mV. However, at potentials more positive than -40 mV application of paxilline significantly (up to 15 mV) depolarized the membrane of SMCs. These results suggest that the large conductance KCa channels in RVD SMCs do not contribute to the resting membrane potential but could serve as a hyperpolarizing mechanism at the significant membrane depolarizations.
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Buryĭ VO, Hurkovs'ka AV, Sukhanova KI, Sahach VF. [Involvement of voltge dependent potassium channels in rabbit corpus cavernosum responses to oxidative stress]. Fiziol Zh (1994) 2007; 53:34-39. [PMID: 18309629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Previously we have demonstrated that oxidative stress produces a complex response of the rabbit corporal smooth muscle cells consisting of transient relaxation followed by contraction. We used 4-AP and TEA, selective blockers for voltage- and Ca(2+)-dependent K+ channels to investigate possible contribution of these channels in maintaining of basal cavernosal tone as well as in mediating of contractile response caused by oxidative stress. TEA in concentration of 1 mmol/l caused contraction of corporal smooth muscle. Application of hydrogen peroxide (H2O2) in the presence of TEA caused contraction similar to that in control conditions. This argues against involvement of Ca(2+)-dependent K+ channels in contractile response caused by oxidative stress. On the other hand, contractile response on inhibition of Ca(2+)-dependent K+ channels suggests their contribution in maintaining of corporal tone. 4-AP in concentration of 5 mmol/l caused contraction resembling that, evoked by TEA. Thus, voltage-dependent similar to Ca(2+)-dependent K+ channels contribute to corporal tone. In the presence of 4-AP H2O2 induced contraction was essentially decreased. The most probable explanation of this result is that population of channels modulated by 4-AP and H2O2 is common for both factors. We previously reported that H2O2 induced contraction could be inhibited by indometacine. Together these results suggest, that H2O2 induced contraction could be a result of inhibition of 4-AP-sensitive voltage-dependent K+ channels that is mediated by metabolite products of arachinoide acid via cyclooxigenase pathway.
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Bournaud R, Hidalgo J, Yu H, Girard E, Shimahara T. Catecholamine secretion from rat foetal adrenal chromaffin cells and hypoxia sensitivity. Pflugers Arch 2006; 454:83-92. [PMID: 17165071 DOI: 10.1007/s00424-006-0185-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Revised: 07/21/2006] [Accepted: 11/26/2006] [Indexed: 01/07/2023]
Abstract
The adrenal medulla chromaffin cells (AMCs) secrete catecholamines in response to various types of stress. We examined the hypoxia-sensitivity of catecholamine secretion by rat foetal chromaffin cells in which the innervation by the splanchnic nerve is not established. The experiments were performed in primary cultured cells from two different ages of foetuses (F15 and F19). Membrane potential of AMCs was monitored with the patch clamp technique, and the catecholamine secretion was detected by amperometry. We found that: (1) AMCs from F19 foetuses showed hypoxia-induced catecholamine release. (2) This hypoxia-induced secretion is produced by membrane depolarization generated by an inhibition of Ca(2+)-activated K(+) current [I (K(Ca))] current. (3) Chromaffin precursor cells from F15 foetuses secrete catecholamine. The quantal release is calcium-dependent, but the size of the quantum is reduced. (4) In the precursor cells, a hypoxia-induced membrane hyperpolarization is originated by an ATP-sensitive K(+) current [I (K(ATP))] activation. (5) During the prenatal period, at F15, the percentage of the total outward current for I (K(ATP)) and I (K(Ca)) was 50 and 29.5%, respectively, whereas at F19, I (K(ATP)) is reduced to 14%, and I (K(Ca)) became 64% of the total current. We conclude that before birth, the age-dependent hypoxia response of chromaffin cells is modulated by the functional activity of K(ATP) and K(Ca) channels.
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Affiliation(s)
- R Bournaud
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, Institut Alfred Fessard CNRS UPR 9040, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France.
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Greenwood IA, Leblanc N. Overlapping pharmacology of Ca2+-activated Cl- and K+ channels. Trends Pharmacol Sci 2006; 28:1-5. [PMID: 17150263 DOI: 10.1016/j.tips.2006.11.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Revised: 10/13/2006] [Accepted: 11/22/2006] [Indexed: 11/22/2022]
Abstract
Research into Ca2+-activated Cl- channels is hampered by the inability to decipher their molecular identity and the fact that all extant Cl- channel blockers have effects on other ion channels. Most notably, Cl- channel blockers such as the fenamates (e.g. niflumic acid and flufenamic acid) activate Ca2+-dependent K+ channels, although other pharmacological overlaps have been discovered. In this article, we highlight the complex pharmacology of Ca2+-activated Cl- channels and the caveats associated with using these blockers--a necessary requirement because many researchers use Cl- channel blockers as probes for Cl- channel activity. Moreover, we discuss the argument for a common structural motif between Ca2+-activated Cl- channels and Ca2+-dependent K+ channels, which has led to the possibility that the molecular identity of Cl- channels will be revealed by research in this new direction, in addition to the use of existing candidates such as the CLCA, Bestrophin and tweety genes.
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Affiliation(s)
- Iain A Greenwood
- Ion Channels and Cell Signalling Research Centre, Division of Basic Medical Sciences, St George's, University of London, London SW17 0RE, UK.
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Domeier TL, Segal SS. Electromechanical and pharmacomechanical signalling pathways for conducted vasodilatation along endothelium of hamster feed arteries. J Physiol 2006; 579:175-86. [PMID: 17138602 PMCID: PMC2075370 DOI: 10.1113/jphysiol.2006.124529] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Conducted vasodilatation (CVD) reflects the initiation and rapid (>mm s(-1)) spread of hyperpolarization along the endothelium and into smooth muscle. The ion channels that initiate CVD remain unclear as do signalling pathways that may complement electromechanical relaxation. Using isolated pressurized (75 mmHg; 37 degrees C) feed arteries (n=63; diameter: rest: 53 +/- 2 microm, maximal: 98 +/- 2 microm) from hamster retractor skeletal muscle, we investigated the contribution of calcium-activated potassium channels (KCa) and endothelium-derived autacoids to CVD. Local delivery (1 microm micropipette tip; 500-2000 ms pulse) of acetylcholine (ACh) at the downstream end initiated a local increase in endothelial cell [Ca2+]i (Fura-PE3; Deltaratio 340/380 nm = 0.215 +/- 0.032) that preceded CVD along the entire vessel. During local perifusion with KCa antagonists, iberiotoxin (5 microm) had no effect, but charybdotoxin (CTX, 5 microm) + apamin (APA, 10 microm) abolished CVD reversibly. Remarkably, this local inhibition of KCa unmasked a 'slow-conducted vasodilatation' (SCVD) that spread >1200 microm at approximately 21 microm s(-1) (n=27). Recorded 500 microm upstream from the ACh stimulus, a rise in endothelial cell [Ca2+]i (Deltaratio 340/380 nm) = 0.146 +/- 0.017; P<0.05) preceded SCVD (Deltadiameter = 14 +/- 3 microm) by approximately 10 s. Before KCa inhibition, antagonism of nitric oxide synthase (Nomega-nitro-L-arginine, 250 microm; l-NNA) and cyclooxygenase (indomethacin, 5 microm; INDO) had no effect on the amplitude of CVD yet response duration decreased by one-third (P<0.05). During local CTX + APA perifusion, L-NNA + INDO abolished SCVD while conducted [Ca2+]i responses remained intact. Thus, ACh triggers electromechanical relaxation of smooth muscle cells along the vessel initiated by local KCa, and the ensuing 'wave' of Ca2+ along the endothelium releases autacoids to promote pharmacomechanical relaxation.
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