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Inderwiedenstraße L, Kienitz MC. Angiotensin receptors and α 1B-adrenergic receptors regulate native IK (ACh) and phosphorylation-deficient GIRK4 (S418A) channels through different PKC isoforms. Pflugers Arch 2024; 476:1041-1064. [PMID: 38658400 DOI: 10.1007/s00424-024-02966-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/03/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024]
Abstract
Signaling of G protein-activated inwardly rectifying K+ (GIRK) channels is an important mechanism of the parasympathetic regulation of the heart rate and cardiac excitability. GIRK channels are inhibited during stimulation of Gq-coupled receptors (GqPCRs) by depletion of phosphatidyl-4,5-bisphosphate (PIP2) and/or channel phosphorylation by protein kinase C (PKC). The GqPCR-dependent modulation of GIRK currents in terms of specific PKC isoform activation was analyzed in voltage-clamp experiments in rat atrial myocytes and in CHO or HEK 293 cells. By using specific PKC inhibitors, we identified the receptor-activated PKC isoforms that contribute to phenylephrine- and angiotensin-induced GIRK channel inhibition. We demonstrate that the cPKC isoform PKCα significantly contributes to GIRK inhibition during stimulation of wildtype α1B-adrenergic receptors (α1B-ARs). Deletion of the α1B-AR serine residues S396 and S400 results in a preferential regulation of GIRK activity by PKCβ. As a novel finding, we report that the AT1-receptor-induced GIRK inhibition depends on the activation of the nPKC isoform PKCε whereas PKCα and PKCβ do not mainly participate in the angiotensin-mediated GIRK reduction. Expression of the dominant negative (DN) PKCε prolonged the onset of GIRK inhibition and significantly reduced AT1-R desensitization, indicating that PKCε regulates both GIRK channel activity and the strength of the receptor signal via a negative feedback mechanism. The serine residue S418 represents an important phosphorylation site for PKCε in the GIRK4 subunit. To analyze the functional impact of this PKC phosphorylation site for receptor-specific GIRK channel modulation, we monitored the activity of a phosphorylation-deficient (GIRK4 (S418A)) GIRK4 channel mutant during stimulation of α1B-ARs or AT1-receptors. Mutation of S418 did not impede α1B-AR-mediated GIRK inhibition, suggesting that S418 within the GIRK4 subunit is not subject to PKCα-induced phosphorylation. Furthermore, activation of angiotensin receptors induced pronounced GIRK4 (S418A) channel inhibition, excluding that this phosphorylation site contributes to the AT1-R-induced GIRK reduction. Instead, phosphorylation of S418 has a facilitative effect on GIRK activity that was abolished in the GIRK4 (S418A) mutant. To summarize, the present study shows that the receptor-dependent regulation of atrial GIRK channels is attributed to the GqPCR-specific activation of different PKC isoforms. Receptor-specific activated PKC isoforms target distinct phosphorylation sites within the GIRK4 subunit, resulting in differential regulation of GIRK channel activity with either facilitative or inhibitory effects on GIRK currents.
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Affiliation(s)
- Leonie Inderwiedenstraße
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany
| | - Marie-Cécile Kienitz
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany.
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Li C, Yang Y. Advancements in the study of inward rectifying potassium channels on vascular cells. Channels (Austin) 2023; 17:2237303. [PMID: 37463317 PMCID: PMC10355679 DOI: 10.1080/19336950.2023.2237303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/20/2023] [Accepted: 07/04/2023] [Indexed: 07/20/2023] Open
Abstract
Inward rectifier potassium channels (Kir channels) exist in a variety of cells and are involved in maintaining resting membrane potential and signal transduction in most cells, as well as connecting metabolism and membrane excitability of body cells. It is closely related to normal physiological functions of body and the occurrence and development of some diseases. Although the functional expression of Kir channels and their role in disease have been studied, they have not been fully elucidated. In this paper, the functional expression of Kir channels in vascular endothelial cells and smooth muscle cells and their changes in disease states were reviewed, especially the recent research progress of Kir channels in stem cells was introduced, in order to have a deeper understanding of Kir channels in vascular tissues and provide new ideas and directions for the treatment of related ion channel diseases.
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Affiliation(s)
- Chunshu Li
- Key Lab of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yan Yang
- Key Lab of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
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Ottolini M, Sonkusare SK. The Calcium Signaling Mechanisms in Arterial Smooth Muscle and Endothelial Cells. Compr Physiol 2021; 11:1831-1869. [PMID: 33792900 PMCID: PMC10388069 DOI: 10.1002/cphy.c200030] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The contractile state of resistance arteries and arterioles is a crucial determinant of blood pressure and blood flow. Physiological regulation of arterial contractility requires constant communication between endothelial and smooth muscle cells. Various Ca2+ signals and Ca2+ -sensitive targets ensure dynamic control of intercellular communications in the vascular wall. The functional effect of a Ca2+ signal on arterial contractility depends on the type of Ca2+ -sensitive target engaged by that signal. Recent studies using advanced imaging methods have identified the spatiotemporal signatures of individual Ca2+ signals that control arterial and arteriolar contractility. Broadly speaking, intracellular Ca2+ is increased by ion channels and transporters on the plasma membrane and endoplasmic reticular membrane. Physiological roles for many vascular Ca2+ signals have already been confirmed, while further investigation is needed for other Ca2+ signals. This article focuses on endothelial and smooth muscle Ca2+ signaling mechanisms in resistance arteries and arterioles. We discuss the Ca2+ entry pathways at the plasma membrane, Ca2+ release signals from the intracellular stores, the functional and physiological relevance of Ca2+ signals, and their regulatory mechanisms. Finally, we describe the contribution of abnormal endothelial and smooth muscle Ca2+ signals to the pathogenesis of vascular disorders. © 2021 American Physiological Society. Compr Physiol 11:1831-1869, 2021.
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Affiliation(s)
- Matteo Ottolini
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA
| | - Swapnil K Sonkusare
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA.,Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia, USA.,Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia, USA
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Prostanoids contribute to regulation of inwardly rectifying K + channels in intrarenal arterial smooth muscle cells. Life Sci 2020; 250:117586. [PMID: 32222464 DOI: 10.1016/j.lfs.2020.117586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 03/19/2020] [Accepted: 03/19/2020] [Indexed: 11/23/2022]
Abstract
AIM The inward rectifier K+ (Kir) channels and prostanoids are important factors in regulating vascular tone, but the relationship between them has not been well studied. We aimed to study the involvement of prostanoids in regulating Kir activity in the rat intrarenal arteries (RIRAs). MAIN METHODS The vascular tone of isolated RIRAs was recorded with a wire myograph. The intracellular Ca2+ concentrations ([Ca2+]i) and Kir currents were measured with a Ca2+-sensitive fluorescence probe and patch clamp, respectively, in the arterial smooth muscle cell (ASMC) freshly isolated from RIRAs. Kir2.1 expression in RIRAs was assayed by Western blotting. KEY FINDINGS At 0.03-1.0 mM, BaCl2 (a specific Kir blocker) concentration-dependently contracted RIRAs and elevated [Ca2+]i levels. Mild stimulations with various vasoconstrictors at low concentrations significantly potentiated RIRA contraction induced by Kir closure with BaCl2. In both the quiescent and the stimulated RIRAs, cyclooxygenase inhibition and thromboxane-prostanoid receptor (TPR) antagonism depressed BaCl2-induced RIRA contraction, while nitric oxide (NO) synthetase inhibition and endothelium-denudation enhanced the contraction. Kir2.1 expression was significantly more abundant in smaller RIRAs. Ba2+-sensitive Kir currents were depressed by TPR agonist U46619 while increased by NO donor sodium nitroprusside. SIGNIFICANCE The present results reveal that vasoconstrictor stimulation augments RIRA contraction induced by Kir closure with Ba+ and indicate that prostanoid synthesis followed by TPR activation is involved in the modulation of the myocyte Kir activity. This study suggests that prostanoid synthesis and TPR may be potential targets for dysfunctions in renal blood circulation.
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Dogan MF, Yildiz O, Arslan SO, Ulusoy KG. Potassium channels in vascular smooth muscle: a pathophysiological and pharmacological perspective. Fundam Clin Pharmacol 2019; 33:504-523. [PMID: 30851197 DOI: 10.1111/fcp.12461] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/23/2022]
Abstract
Potassium (K+ ) ion channel activity is an important determinant of vascular tone by regulating cell membrane potential (MP). Activation of K+ channels leads to membrane hyperpolarization and subsequently vasodilatation, while inhibition of the channels causes membrane depolarization and then vasoconstriction. So far five distinct types of K+ channels have been identified in vascular smooth muscle cells (VSMCs): Ca+2 -activated K+ channels (BKC a ), voltage-dependent K+ channels (KV ), ATP-sensitive K+ channels (KATP ), inward rectifier K+ channels (Kir ), and tandem two-pore K+ channels (K2 P). The activity and expression of vascular K+ channels are changed during major vascular diseases such as hypertension, pulmonary hypertension, hypercholesterolemia, atherosclerosis, and diabetes mellitus. The defective function of K+ channels is commonly associated with impaired vascular responses and is likely to become as a result of changes in K+ channels during vascular diseases. Increased K+ channel function and expression may also help to compensate for increased abnormal vascular tone. There are many pharmacological and genotypic studies which were carried out on the subtypes of K+ channels expressed in variable amounts in different vascular beds. Modulation of K+ channel activity by molecular approaches and selective drug development may be a novel treatment modality for vascular dysfunction in the future. This review presents the basic properties, physiological functions, pathophysiological, and pharmacological roles of the five major classes of K+ channels that have been determined in VSMCs.
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Affiliation(s)
- Muhammed Fatih Dogan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Oguzhan Yildiz
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
| | - Seyfullah Oktay Arslan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Kemal Gokhan Ulusoy
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
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Liu Z, Khalil RA. Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease. Biochem Pharmacol 2018; 153:91-122. [PMID: 29452094 PMCID: PMC5959760 DOI: 10.1016/j.bcp.2018.02.012] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 02/12/2018] [Indexed: 12/11/2022]
Abstract
Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.
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Affiliation(s)
- Zhongwei Liu
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA
| | - Raouf A Khalil
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA.
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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Vetri F, Qi M, Xu H, Oberholzer J, Paisansathan C. Impairment of neurovascular coupling in Type 1 Diabetes Mellitus in rats is prevented by pancreatic islet transplantation and reversed by a semi-selective PKC inhibitor. Brain Res 2016; 1655:48-54. [PMID: 27865779 DOI: 10.1016/j.brainres.2016.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/07/2016] [Accepted: 11/09/2016] [Indexed: 12/15/2022]
Abstract
Streptozotocin (STZ)-induced chronic hyperglycemia has a detrimental effect on neurovascular coupling, linked to increased PKC-mediated phosphorylation and PKC isoform expression changes. Here, we sought to determine whether: 1) selective PKC-α/β/γ inhibitor, GF109203X, could reverse the effects of chronic hyperglycemia on cerebrovascular reactivity; 2) pancreatic islet transplantation could prevent the development of cerebrovascular impairment seen in a rat model of Type 1 Diabetes. We studied the effect of GF109203X in diabetic (DM), non-diabetic (ND), and transplanted (TR) Lewis rats during either sciatic nerve stimulation (SNS) or the topical applications of the large-conductance Ca2+-operated K+(BKCa) channel opener, NS1619, or the K+ inward rectifier (Kir) channel agonist, KCl. Pial arteriole diameter changes were monitored using a closed cranial window in vivo microscopy technique. The pial arteriole dilatory response associated with SNS was decreased by ~45%, when comparing DM vs either ND or TR rats. Also, pial arteriolar dilations to topical KCl and NS1619 were largely attenuated in DM rats, but not in ND or TR animals. These responses were completely restored by the acute application of GF109203X to the brain surface. The PKC inhibitor had no effect on vascular responses in normoglycemic and TR animals. In conclusion, DM-associated chronic impairment of neurovascular coupling may be readily reversed by a PKC-α/β/γ inhibitor or prevented via pancreatic islet transplantation. We believe that specific PCK isoforms (α/β/γ) are mechanistically linked to the neurovascular uncoupling seen with hyperglycemia.
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Key Words
- BKCa, large-conductance Ca2+-operated K+ channel
- DM, diabetic
- Diabetes mellitus type 1
- GF109203X
- Kir, K+ inward rectifier channel
- ND, non-diabetic
- NVC, neurovascular coupling
- Neurovascular coupling
- PKC
- PKC, protein kinase C
- Pancreatic islet transplantation
- Potassium channels
- SEPs, somatosensory evoked potentials
- STZ, streptozotocin
- TR, transplanted rats
- aCSF, artificial cerebrospinal fluid
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Affiliation(s)
- Francesco Vetri
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA.
| | - Meirigeng Qi
- Division of Transplantation, Department of Surgery, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Haoliang Xu
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Jose Oberholzer
- Division of Transplantation, Department of Surgery, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Chanannait Paisansathan
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
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Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:89-144. [PMID: 28212804 DOI: 10.1016/bs.apha.2016.07.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+, and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. VSM cells express multiple isoforms of at least five classes of K+ channels that contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression, and function of large conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells.
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Ringvold HC, Khalil RA. Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:203-301. [PMID: 28212798 PMCID: PMC5319769 DOI: 10.1016/bs.apha.2016.06.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.
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Affiliation(s)
- H C Ringvold
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States
| | - R A Khalil
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States.
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Vetri F, Chavez R, Xu HL, Paisansathan C, Pelligrino DA. Complex modulation of the expression of PKC isoforms in the rat brain during chronic type 1 diabetes mellitus. Brain Res 2012; 1490:202-9. [PMID: 23103504 DOI: 10.1016/j.brainres.2012.10.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/06/2012] [Accepted: 10/16/2012] [Indexed: 10/27/2022]
Abstract
We previously demonstrated that chronic hyperglycemia has a detrimental influence on neurovascular coupling in the brain-an effect linked to an alteration in the protein kinase C (PKC)-mediated phosphorylation pattern. Moreover, the activity of PKC was increased, in diabetic rat brain, in a tissue fraction composed primarily of the superficial glia limitans and pial vessels, but trended toward a decrease in cerebral cortical gray matter. However, that study did not examine the expression patterns of PKC isoforms in the rat brain. Thus, in a rat model of streptozotocin (STZ)-induced chronic type 1 diabetes mellitus (T1DM), and in non-diabetic (ND) controls, two hypotheses were addressed. First, chronic T1DM is accompanied by changes in the expression of PKC-α, βII, γ, δ, and ε Second, those changes differ when comparing cerebral cortex and glio-pial tissue. In addition, we analyzed the expression of a form of PKC-γ, phosphorylated on threonine 514 (pT514-PKC-γ), as well as the receptor for activated C kinase 1 (RACK1). The expression pattern of different PKC isoforms was altered in a complex and tissue-specific manner during chronic hyperglycemia. Notably, in the gray matter, PKC-α expression significantly decreased, while pT514-PKC-γ expression increased. However, PKC-βII, -γ, -δ, -ε, and RACK1 expressions did not change. Conversely, in glio-pial tissue, PKC-α and RACK1 were upregulated, whereas PKC-γ, pT514-PKC-γ, and PKC-ε were downregulated. PKC-βII, and PKC-δ, were unchanged. These findings suggest that the PKC activity increase previously seen in the glio-pial tissue of diabetic rats may be due to the selective upregulation of PKC-α, and ultimately lead to the impairment of neurovascular coupling.
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Affiliation(s)
- Francesco Vetri
- Neuroanesthesia Research Laboratory, Department of Anesthesiology, University of Illinois, Chicago, IL 60612, USA.
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Hald BO, Jacobsen JCB, Braunstein TH, Inoue R, Ito Y, Sørensen PG, Holstein-Rathlou NH, Jensen LJ. BKCa and KV channels limit conducted vasomotor responses in rat mesenteric terminal arterioles. Pflugers Arch 2011; 463:279-95. [PMID: 22052159 DOI: 10.1007/s00424-011-1049-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 09/15/2011] [Accepted: 10/16/2011] [Indexed: 11/28/2022]
Abstract
Intracellular Ca(2+) signals underlying conducted vasoconstriction to local application of a brief depolarizing KCl stimulus was investigated in rat mesenteric terminal arterioles (<40 μm). Using a computer model of an arteriole segment comprised of coupled endothelial cells (EC) and vascular smooth muscle cells (VSMC) simulations of both membrane potential and intracellular [Ca(2+)] were performed. The "characteristic" length constant, λ, was approximated using a modified cable equation in both experiments and simulations. We hypothesized that K(+) conductance in the arteriolar wall limit the electrotonic spread of a local depolarization along arterioles by current dissipation across the VSMC plasma membrane. Thus, we anticipated an increased λ by inhibition of voltage-activated K(+) channels. Application of the BK(Ca) channel blocker iberiotoxin (100 nM) onto mesenteric arterioles in vitro and inhibition of BK(Ca) channel current in silico increased λ by 34% and 32%, respectively. Similarly, inhibition of K(V) channels in vitro (4-aminopyridine, 1 mM) or in silico increased λ by 41% and 21%, respectively. Immunofluorescence microscopy demonstrated expression of BK(Ca), Kv1.5, Kv2.1, but not Kv1.2, in VSMCs of rat mesenteric terminal arterioles. Our results demonstrate that inhibition of voltage-activated K(+) channels enhance vascular-conducted responses to local depolarization in terminal arterioles by increasing the membrane resistance of VSMCs. These data contribute to our understanding of how differential expression patterns of voltage-activated K(+) channels may influence conducted vasoconstriction in small arteriolar networks. This finding is potentially relevant to understanding the compromised microcirculatory blood flow in systemic vascular diseases such as diabetes mellitus and hypertension.
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Affiliation(s)
- Bjørn Olav Hald
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Song CY, Xi HJ, Yang L, Qu LH, Zi-YongYue, Zhou J, Cui XG, Gao W, Wang N, Pan ZW, Li WZ. Propofol inhibited the delayed rectifier potassium current (Ik) via activation of protein kinase C epsilon in rat parietal cortical neurons. Eur J Pharmacol 2011; 653:16-20. [DOI: 10.1016/j.ejphar.2010.10.072] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 10/06/2010] [Accepted: 10/22/2010] [Indexed: 11/24/2022]
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14
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Potentiation of EDHF-mediated relaxation by chloride channel blockers. Acta Pharmacol Sin 2010; 31:1303-11. [PMID: 20835269 DOI: 10.1038/aps.2010.157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
AIM To investigate the involvement of Cl⁻ channels in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in rat mesenteric arteries. METHODS Cl⁻ channel and K(ir) channel activities were studied using whole-cell patch clamping in rat mesenteric arterial smooth muscle cells. Isometric tension of arterial rings was measured in organ chambers. RESULTS The volume-activated Cl⁻ current in rat mesenteric arterial smooth muscle cells was abolished by Cl⁻ channel blockers NPPB or DIDS. The EDHF-mediated vasorelaxation was potentiated by NPPB and DIDS. The EDHF response was diminished by a combination of apamin and charybdotoxin, which agreed with the hypothesis that EDHF response involves the release of K(+) via the Ca²(+)-activated K(+) channels in endothelial cells. The elevation of K(+) concentration in bathing solution from 1.2 mmol/L to 11.2 mmol/L induced an arterial relaxation, which was abolished by the combination of BaCl₂ and ouabain. It is consistent to the hypothesis that K(+) activates K(+)/Na(+)-ATPase and inward rectifier K(+) (K(ir)) channels, leading to the hyperpolarization and relaxation of vascular smooth muscle. The K(+)-induced relaxation was augmented by NPPB, DIDS, or withdrawal of Cl⁻ from the bathing solution, which could be reversed by BaCl₂, but not ouabain. The potentiating effect of Cl⁻ channel blockers on K(+)-induced relaxation was probably due to the interaction between Cl⁻ channels and K(ir) channels. Moreover, the K(+)-induced relaxation was potentiated when the arteries were incubated in hyperosmotic solution, which is known to inhibit volume-activated Cl⁻ channels. CONCLUSION The inhibition of Cl⁻ channels, particularly the volume-activated Cl⁻ channels, may potentiate the EDHF-induced vasorelaxation through the K(ir) channels.
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15
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Park WS, Ko JH, Ko EA, Son YK, Hong DH, Jung ID, Park YM, Choi TH, Kim N, Han J. The guanylyl cyclase activator YC-1 directly inhibits the voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells. J Pharmacol Sci 2010; 112:64-72. [PMID: 20093789 DOI: 10.1254/jphs.09228fp] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
We investigated the effects of YC-1, an activator of soluble guanylyl cyclase (sGC), on voltage-dependent K+ (Kv) channels in smooth muscle cells from freshly isolated rabbit coronary arteries by using the whole-cell patch clamp technique. YC-1 inhibited the Kv current in a dose-dependent fashion with an apparent K(d) of 9.67 microM. It accelerated the decay rate of Kv channel inactivation without altering the kinetics of current activation. The rate constants of association and dissociation for YC-1 were 0.36 +/- 0.01 microM(-1) x s(-1) and 3.44 +/- 0.22 s(-1), respectively. YC-1 did not have a significant effect on the steady-state activation and inactivation curves. The recovery time constant from inactivation was decreased in the presence of YC-1, and application of train pulses (1 or 2 Hz) caused a progressive increase in the YC-1 blockade, indicating that YC-1-induced inhibition of Kv currents is use-dependent. Pretreatment with Bay 41-2272 (also a sGC activator), ODQ (a sGC inhibitor), or Rp-8-Br-PET-cGMPs (a protein kinase G inhibitor) did not affect the basal Kv current and also did not significantly alter the inhibitory effect of YC-1. From these results, we suggest that YC-1 directly inhibits the Kv current independently of sGC activation and in a state-, time-, and use-dependent fashion.
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Affiliation(s)
- Won Sun Park
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, College of Medicine, Cardiovascular and Metabolic Disease Center, FIRST Mitochondrial Research Group, Biomarker Medical Research Center, Inje University, Korea
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16
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Schwartz IF, Chernichovski T, Schwartz D. Aortic arginine transport is attenuated, through post-translational modulation of CAT-1 by PKCalpha, in old male rats. Vasc Med 2009; 15:55-9. [PMID: 19843630 DOI: 10.1177/1358863x09346659] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Experimental models using rats suggest that decreased endothelial nitric oxide synthase (eNOS) activity in old males promotes renal atherosclerosis, whereas females are protected. We aimed to explore whether aging alters aortic arginine uptake by CAT-1, the selective arginine supplier to eNOS in rats. Arginine uptake by freshly harvested aortic rings from young males (9 weeks) was significantly higher than in young females. Old males (18 months) exhibited a significant decrease in arginine transport compared to young males, whereas no differences were observed between old and young females. Cationic amino acid transporter-1 (CAT-1) abundance remained unchanged in all experimental groups. The abundance of protein kinase C alpha (PKCalpha), a CAT-1 inhibitor, was significantly augmented in old versus young males while no differences were detected between old and young females. Phosphorylated PKCalpha was significantly increased in old rats of both sexes. alphaTocopherol, a PKC inhibitor, produced a significant increase in arginine transport in old males only. In conclusion, aortic arginine transport by CAT-1 is attenuated in old male rats through upregulation of PKCalpha. In old females, aortic arginine transport is protected from the effects of PKCalpha by an unknown mechanism.
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Affiliation(s)
- Idit F Schwartz
- Department of Nephrology, Tel Aviv Sourasky Medical Center, Tel Aviv University, Sackler School of Medicine, Tel Aviv, Israel
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17
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Wu ZX, Yu BP, Xu L, Xia H. Emodin Inhibits Voltage-Dependent Potassium Current in Guinea Pig Gallbladder Smooth Muscle. Basic Clin Pharmacol Toxicol 2009; 105:167-72. [DOI: 10.1111/j.1742-7843.2009.00419.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Park WS, Ko EA, Jung ID, Son YK, Kim HK, Kim N, Park SY, Hong KW, Park YM, Choi TH, Han J. APE1/Ref-1 promotes the effect of angiotensin II on Ca2+ -activated K+ channel in human endothelial cells via suppression of NADPH oxidase. Arch Pharm Res 2008; 31:1291-301. [PMID: 18958420 DOI: 10.1007/s12272-001-2109-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2008] [Revised: 08/07/2008] [Accepted: 08/08/2008] [Indexed: 11/24/2022]
Abstract
The effects of angiotensin II (Ang II) on whole-cell large conductance Ca(2+)-activated K(+) (BK(Ca)) currents was investigated in control and Apurinic/apyrimidinic endonuclease1/redox factor 1 (APE1/Ref-1)-overexpressing human umbilical vein endothelial cells (HUVECs). Ang II blocked the BK(Ca) current in a dose-dependent fashion, and this inhibition was greater in APE1/Ref-1-overexpressing HUVECs than in control HUVECs (half-inhibition values of 102.81+/-9.54 nM and 11.34+/-0.39 nM in control and APE1/Ref-1-overexpressing HUVECs, respectively). Pretreatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) or knock down of NADPH oxidase (p22 phox) using siRNA increased the inhibitory effect of Ang II on the BK(Ca) currents, similar to the effect of APE1/Ref-1 overexpression. In addition, application of Ang II increased the superoxide and hydrogen peroxide levels in the control HUVECs but not in APE1/Ref-1-overexpressing HUVECs. Furthermore, direct application of hydrogen peroxide increased BK(Ca) channel activity. Finally, the inhibitory effect of Ang II on the BK(Ca) current was blocked by an antagonist of the Ang II type 1 (AT(1)) receptor in both control and APE1/Ref-1-overexpressing HUVECs. From these results, we conclude that the inhibitory effect of Ang II on BK(Ca) channel function is NADPH oxidase-dependent and may be promoted by APE1/Ref-1.
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Affiliation(s)
- Won Sun Park
- National Research Laboratory for Mitochondrial Signaling Laboratory, FIRST Mitochondria Research Group, Department of Physiology and Biophysics, College of Medicine, Medical Research Center, Inje University, Busan, Korea
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19
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Nelson CP, Willets JM, Davies NW, Challiss RAJ, Standen NB. Visualizing the temporal effects of vasoconstrictors on PKC translocation and Ca2+ signaling in single resistance arterial smooth muscle cells. Am J Physiol Cell Physiol 2008; 295:C1590-601. [PMID: 18829899 DOI: 10.1152/ajpcell.00365.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Arterial smooth muscle (ASM) contraction plays a critical role in regulating blood distribution and blood pressure. Vasoconstrictors activate cell surface receptors to initiate signaling cascades involving increased intracellular Ca(2+) concentration ([Ca(2+)](i)) and recruitment of protein kinase C (PKC), leading to ASM contraction, though the PKC isoenzymes involved vary between different vasoconstrictors and their actions. Here, we have used confocal microscopy of enhanced green fluorescence protein (eGFP)-labeled PKC isoenzymes to visualize PKC translocation in primary rat mesenteric ASM cells in response to physiological vasoconstrictors, with simultaneous imaging of Ca(2+) signaling. Endothelin-1, angiotensin II, and uridine triphosphate all caused translocation of each of the PKC isoenzymes alpha, delta, and epsilon; however, the kinetics of translocation varied between agonists and PKC isoenzymes. Translocation of eGFP-PKCalpha mirrored the rise in [Ca(2+)](i), while that of eGFP-PKCdelta or -epsilon occurred more slowly. Endothelin-induced translocation of eGFP-PKCepsilon was often sustained for several minutes, while responses to angiotensin II were always transient. In addition, preventing [Ca(2+)](i) increases using 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra-(acetoxymethyl) ester prevented eGFP-PKCalpha translocation, while eGFP-PKCdelta translocated more rapidly. Our results suggest that PKC isoenzyme specificity of vasoconstrictor actions occurs downstream of PKC recruitment and demonstrate the varied kinetics and complex interplay between Ca(2+) and PKC responses to different vasoconstrictors in ASM.
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Affiliation(s)
- Carl P Nelson
- Department of Cell Physiology & Pharmacology, Univ. of Leicester, LE1 9HN, UK.
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20
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Edwards A, Pallone TL. Mechanisms underlying angiotensin II-induced calcium oscillations. Am J Physiol Renal Physiol 2008; 295:F568-84. [PMID: 18562632 DOI: 10.1152/ajprenal.00107.2008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To gain insight into the mechanisms that underlie angiotensin II (ANG II)-induced cytoplasmic Ca2+ concentration ([Ca]cyt) oscillations in medullary pericytes, we expanded a prior model of ion fluxes. ANG II stimulation was simulated by doubling maximal inositol trisphosphate (IP3) production and imposing a 90% blockade of K+ channels. We investigated two configurations, one in which ryanodine receptors (RyR) and IP3 receptors (IP3R) occupy a common store and a second in which they reside on separate stores. Our results suggest that Ca2+ release from stores and import from the extracellular space are key determinants of oscillations because both raise [Ca] in subplasmalemmal spaces near RyR. When the Ca2+-induced Ca2+ release (CICR) threshold of RyR is exceeded, the ensuing Ca2+ release is limited by Ca2+ reuptake into stores and export across the plasmalemma. If sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pumps do not remain saturated and sarcoplasmic reticulum Ca2+ stores are replenished, that phase is followed by a resumption of leak from internal stores that leads either to [Ca]cyt elevation below the CICR threshold (no oscillations) or to elevation above it (oscillations). Our model predicts that oscillations are more prone to occur when IP3R and RyR stores are separate because, in that case, Ca2+ released by RyR during CICR can enhance filling of adjacent IP3 stores to favor a high subsequent leak that generates further CICR events. Moreover, the existence or absence of oscillations depends on the set points of several parameters, so that biological variation might well explain the presence or absence of oscillations in individual pericytes.
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Affiliation(s)
- Aurélie Edwards
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, USA.
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21
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Reshef R, Schwartz D, Ingbir M, Shtabsky A, Chernichovski T, Isserlin BA, Chernin G, Levo Y, Schwartz IF. A profound decrease in maternal arginine uptake provokes endothelial nitration in the pregnant rat. Am J Physiol Heart Circ Physiol 2008; 294:H1156-63. [DOI: 10.1152/ajpheart.01051.2007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
While a specific role for nitric oxide (NO) in inducing the hemodynamic alterations of pregnancy is somewhat controversial, it is widely accepted that excess NO is generated during pregnancy. l-Arginine is the sole precursor for NO biosynthesis. Among several transporters that mediate l-arginine uptake, cationic amino acid transporter-1 (CAT-1) acts as the specific arginine transporter for endothelial NO synthase. The present study was designed to test the hypothesis that, during pregnancy, when arginine consumption by the fetus is significantly increased, compensatory changes in maternal arginine uptake affect the endothelium. Uptake of radiolabeled arginine (l-[3H]arginine) by freshly harvested maternal aortic rings from pregnant rats decreased by 65 and 30% in mid- and late pregnancy, respectively, compared with those obtained from virgin animals. This decrease was associated with a significant increase in endothelial protein nitration (the footprint of peroxynitrite generation), as shown by both Western blotting and immunohistochemistry utilizing anti-nitrotyrosine antibodies, reflecting endothelial damage. Northern blot analysis revealed that steady-state aortic CAT-1 mRNA levels did not change throughout pregnancy, whereas CAT-1 protein abundance was significantly increased, peaking at mid-pregnancy. Protein content of protein kinase C (PKC)-α, which was previously shown to decrease CAT-1 activity, increased significantly in the pregnant animals and was associated with a significant increase in CAT-1 phosphorylation. Intraperitoneal injection of α-tocopherol, a PKC-α inhibitor, prevented the decrease in arginine transport and attenuated protein nitration. In conclusion, aortic arginine uptake is reduced during pregnancy, through posttranslational modulation of CAT-1 protein, presumably via upregulation of PKC-α. The aforementioned findings are associated with an increase in protein nitration and, therefore, in selected individuals, may lead to the development of certain forms of endothelial dysfunction, like preeclampsia.
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22
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Ko EA, Han J, Jung ID, Park WS. Physiological roles of K + channels in vascular smooth muscle cells. J Smooth Muscle Res 2008; 44:65-81. [DOI: 10.1540/jsmr.44.65] [Citation(s) in RCA: 317] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Eun A Ko
- National Research Laboratory for Mitochondrial Signaling, FIRST Mitochondria Research Group, Department of Physiology and Biophysics, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University
| | - Jin Han
- National Research Laboratory for Mitochondrial Signaling, FIRST Mitochondria Research Group, Department of Physiology and Biophysics, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University
| | - In Duk Jung
- Department of Microbiology and Immunology and National Research Laboratory of Dentritic, Cell Differentiation and Regulation, Pusan National University, College of Medicine
| | - Won Sun Park
- National Research Laboratory for Mitochondrial Signaling, FIRST Mitochondria Research Group, Department of Physiology and Biophysics, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University
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Sun H, Zhao H, Sharpe GM, Arrick DM, Mayhan WG. Influence of chronic alcohol consumption on inward rectifier potassium channels in cerebral arterioles. Microvasc Res 2007; 75:367-72. [PMID: 18191159 DOI: 10.1016/j.mvr.2007.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 10/23/2007] [Accepted: 11/26/2007] [Indexed: 11/17/2022]
Abstract
Inward rectifier potassium (K(IR)) channels appear to play an important role in the regulation of cerebral blood flow. Our goal was to examine the influence of chronic alcohol exposure on K(IR) channels in cerebral arterioles. Sprague-Dawley rats were fed liquid diets with or without alcohol for 8-12 weeks. Using intravital microscope, we measured diameter of pial arterioles in response to an inhibitor, BaCl(2), and an activator, KCl, of K(IR) channels in the absence and presence of a scavenger of reactive oxygen species, tempol, or an inhibitor of NAD(P)H oxidase, apocynin. Application of BaCl(2) (30 and 100 microM) produced dose-related vasoconstriction in non-alcohol-fed, but not in alcohol-fed rats. In addition, application of KCl (3, 10, and 30 mM) produced dose-related dilation in non-alcohol-fed and alcohol-fed rats, but the magnitude of vasodilatation was less in alcohol-fed rats. In contrast, nitroglycerin-induced vasodilation was similar in non-alcohol-fed and alcohol-fed rats. Superfusion of cranial window with tempol (0.1 mM) or apocynin (1 mM) did not alter baseline diameter and nitroglycerin-induced dilation of pial arterioles in non-alcohol-fed and alcohol-fed rats but significantly improved impaired KCl-induced dilation in alcohol-fed rats. Our findings suggest that chronic alcohol consumption impairs the role of K(IR) channels in basal tone and KCl-induced dilation of cerebral arterioles. In addition, impaired KCl-induced dilation of cerebral arterioles during alcohol consumption may be related to enhanced release of oxygen-derived free radicals via NAD(P)H oxidase.
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Affiliation(s)
- Hong Sun
- Department of Cellular and Integrative Physiology 985850, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA.
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24
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Nakamura J. Protein kinase C-dependent antilipolysis by insulin in rat adipocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:1195-201. [PMID: 17689141 DOI: 10.1016/j.bbalip.2007.06.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 05/19/2007] [Accepted: 06/27/2007] [Indexed: 01/19/2023]
Abstract
Recently, we have shown that protein kinase C (PKC) activated by phorbol 12-myristate 13-acetate (PMA) attenuates the beta1-adrenergic receptor (beta1-AR)-mediated lipolysis in rat adipocytes. Stimulation of cells by insulin, angiotensin II, and alpha1-AR agonist is known to cause activation of PKC. In this study, we found that lipolysis induced by the beta1-AR agonist dobutamine is decreased and is no longer inhibited by PMA in adipocytes that have been treated with 20 nM insulin for 30 min followed by washing out insulin. Such effects on lipolysis were not found after pretreatment with angiotensin II and alpha1-AR agonists. The rate of lipolysis in the insulin-treated cells was normalized by the PKCalpha- and beta-specific inhibitor Gö 6976 and PKCbeta-specific inhibitor LY 333531. In the insulin-treated cells, wortmannin increased lipolysis and recovered the lipolysis-attenuating effect of PMA. Western blot analysis revealed that insulin slightly increases membrane-bound PKCalpha, betaI, and delta, and wortmannin decreases PKCbetaI, betaII, and delta in the membrane fraction. These results indicate that stimulation of insulin receptor induces a sustained activation of PKC-dependent antilipolysis in rat adipocytes.
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Affiliation(s)
- Jiro Nakamura
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba-shi, Ibaraki-ken, 305-8575, Japan.
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25
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Park WS, Ko JH, Kim N, Son YK, Kang SH, Warda M, Jung ID, Park YM, Han J. Increased inhibition of inward rectifier K+ channels by angiotensin II in small-diameter coronary artery of isoproterenol-induced hypertrophied model. Arterioscler Thromb Vasc Biol 2007; 27:1768-75. [PMID: 17525364 DOI: 10.1161/atvbaha.107.143339] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE We investigated the effects of angiotensin II (Ang II) on inward rectifier K+ (Kir) channels in small-diameter coronary arterial smooth muscle cells (SCASMCs) of control and isoproterenol (Iso)-induced hypertrophied rabbits. METHODS AND RESULTS Kir current amplitude and Kir channel protein expression were definitely lower in the Iso-induced hypertrophied model than in the control. In a pressurized arterial experiment, 15 mmol/L K+-induced vasodilation was greater in the control arteries than in the arteries of Iso-induced hypertrophied model. Ang II reduced the Kir current in a concentration-dependent manner, and this inhibition was greater in SCASMCs from Iso-induced hypertrophied model than from control. Although, there was no difference in the expression of Ang II type 2 (AT2) receptor between SCASMCs of control and Iso-induced hypertrophied model, the expression of Ang II type 1 (AT1) receptor and phosphorylated PKC alpha were greater in SCASMCs of Iso-induced hypertrophied model than of control. CONCLUSION Ang II inhibits Kir channels more prominently in SCASMCs of Iso-induced hypertrophied model owing to increases in the expression of AT1 receptor and the activation of PKC alpha. Our findings about the differential expression of Kir channels and different modulation of Kir channels by a vasoconstrictor (Ang II) in a hypertrophy model are important for better understanding the responsiveness of small-diameter arteries during hypertrophy.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Blotting, Western
- Cardiomyopathy, Hypertrophic/pathology
- Cells, Cultured
- Coronary Vessels/cytology
- Disease Models, Animal
- Electrophysiology
- Endothelium, Vascular/pathology
- Male
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Potassium Channels, Inwardly Rectifying/drug effects
- Potassium Channels, Inwardly Rectifying/metabolism
- Probability
- Rabbits
- Random Allocation
- Reference Values
- Sensitivity and Specificity
- Vasoconstrictor Agents/pharmacology
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- Won Sun Park
- Mitochondrial Signaling Laboratory, Department of Physiology & Biophysics, College of Medicine, Biohealth Products Research Center, Inje University 633-165 Gaegeum-Dong, Busanjin-Gu, Busan 613-735, Korea
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26
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Park WS, Son YK, Kim N, Ko JH, Kang SH, Warda M, Earm YE, Jung ID, Park YM, Han J. Acute hypoxia induces vasodilation and increases coronary blood flow by activating inward rectifier K(+) channels. Pflugers Arch 2007; 454:1023-30. [PMID: 17486361 DOI: 10.1007/s00424-007-0269-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2007] [Accepted: 04/12/2007] [Indexed: 10/23/2022]
Abstract
We examined the effects of acute hypoxia on vascular tone and coronary blood flow (CBF) in rabbit coronary arteries. In the pressurized arterial preparation of small arteries (<100 mum) and the Langendorff-perfused rabbit hearts, hypoxia induced coronary vasodilation and increased CBF in the presence of glibenclamide (K(ATP) channel blocker), Rp-8-Br-PET-cGMPs [cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor, Rp-cGMPs], and methionyl transfer RNA synthetase (MRS) 1334 (adenosine A(3) receptor inhibitor); these increases were inhibited by the inward rectifier K(+) (Kir) channel inhibitor, Ba(2+). These effects were blocked by the adenylyl cyclase inhibitor SQ 22536 and by the cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) inhibitors Rp-8-CPT-cAMPs (Rp-cAMPs) and KT 5720. However, cGMP-dependent protein kinase was not involved in the hypoxia-induced increases of the vascular diameter and CBF. In summary, our results suggest that acute hypoxia can induce the opening of Kir channels in coronary artery that has small diameter (<100 mum) by activating the cAMP and PKA signalling pathway, which could contribute to vasodilation and, therefore, increased CBF.
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Affiliation(s)
- Won Sun Park
- Department of Physiology and Biophysics, College of Medicine, Cardiovascular and Metabolic Disease Research Center, Biohealth Products Research Center, Inje University, 633-165 Gaegeum-Dong, Busanjin-Gu, Busan, 613-735, South Korea
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27
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Wu BN, Luykenaar KD, Brayden JE, Giles WR, Corteling RL, Wiehler WB, Welsh DG. Hyposmotic challenge inhibits inward rectifying K+ channels in cerebral arterial smooth muscle cells. Am J Physiol Heart Circ Physiol 2006; 292:H1085-94. [PMID: 17056667 DOI: 10.1152/ajpheart.00926.2006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study sought to define whether inward rectifying K(+) (K(IR)) channels were modulated by vasoactive stimuli known to depolarize and constrict intact cerebral arteries. Using pressure myography and patch-clamp electrophysiology, initial experiments revealed a Ba(2+)-sensitive K(IR) current in cerebral arterial smooth muscle cells that was active over a physiological range of membrane potentials and whose inhibition led to arterial depolarization and constriction. Real-time PCR, Western blot, and immunohistochemical analyses established the expression of both K(IR)2.1 and K(IR)2.2 in cerebral arterial smooth muscle cells. Vasoconstrictor agonists known to depolarize and constrict rat cerebral arteries, including uridine triphosphate, U46619, and 5-HT, had no discernable effect on whole cell K(IR) activity. Control experiments confirmed that vasoconstrictor agonists could inhibit the voltage-dependent delayed rectifier K(+) (K(DR)) current. In contrast to these observations, a hyposmotic challenge that activates mechanosensitive ion channels elicited a rapid and sustained inhibition of the K(IR) but not the K(DR) current. The hyposmotic-induced inhibition of K(IR) was 1) mimicked by phorbol-12-myristate-13-acetate, a PKC agonist; and 2) inhibited by calphostin C, a PKC inhibitor. These findings suggest that, by modulating PKC, mechanical stimuli can regulate K(IR) activity and consequently the electrical and mechanical state of intact cerebral arteries. We propose that the mechanoregulation of K(IR) channels plays a role in the development of myogenic tone.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Cerebral Arteries/drug effects
- Cerebral Arteries/metabolism
- Female
- Hypotonic Solutions
- In Vitro Techniques
- Membrane Potentials/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Naphthalenes/pharmacology
- Patch-Clamp Techniques
- Potassium Channels, Inwardly Rectifying/drug effects
- Potassium Channels, Inwardly Rectifying/metabolism
- Protein Kinase C/metabolism
- Protein Kinase Inhibitors/pharmacology
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Serotonin/pharmacology
- Tetradecanoylphorbol Acetate/analogs & derivatives
- Tetradecanoylphorbol Acetate/pharmacology
- Uridine Triphosphate/pharmacology
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Bin-Nan Wu
- Department and Graduate Institute of Pharmacology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
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28
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Bae YM, Kim A, Kim J, Park SW, Kim TK, Lee YR, Kim B, Cho SI. Serotonin depolarizes the membrane potential in rat mesenteric artery myocytes by decreasing voltage-gated K+ currents. Biochem Biophys Res Commun 2006; 347:468-76. [PMID: 16828462 DOI: 10.1016/j.bbrc.2006.06.116] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Accepted: 06/21/2006] [Indexed: 11/21/2022]
Abstract
We hypothesized that voltage-gated K+ (Kv) currents regulate the resting membrane potential (Em), and that serotonin (5-HT) causes Em depolarization by reducing Kv currents in rat mesenteric artery smooth muscle cells (MASMCs). The resting Em was about -40 mV in the nystatin-perforated patch configuration, and the inhibition of Kv currents by 4-aminopyridine caused marked Em depolarization. The inhibition of Ca2+-activated K+ (KCa) currents had no effect on Em. 5-HT (1 microM) depolarized Em by approximately 11 mV and reduced the Kv currents to approximately 63% of the control at -20 mV. Similar 5-HT effects were observed with the conventional whole-cell configuration with a weak Ca2+ buffer in the pipette solution, but not with a strong Ca2+ buffer. In the presence of tetraethylammonium (1mM), 5-HT caused Em depolarization similar to the control condition. These results indicate that the resting Em is largely under the regulation of Kv currents in rat MASMCs, and that 5-HT depolarizes Em by reducing Kv currents in a [Ca2+]i-dependent manner.
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Affiliation(s)
- Young Min Bae
- Artificial Muscle Research Center, College of Medicine, Konkuk University 322 Danwol-dong, Choongju 380-701, Republic of Korea.
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