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Abstract
Pericytes, attached to the surface of capillaries, play an important role in regulating local blood flow. Using optogenetic tools and genetically encoded reporters in conjunction with confocal and multiphoton imaging techniques, the 3D structure, anatomical organization, and physiology of pericytes have recently been the subject of detailed examination. This work has revealed novel functions of pericytes and morphological features such as tunneling nanotubes in brain and tunneling microtubes in heart. Here, we discuss the state of our current understanding of the roles of pericytes in blood flow control in brain and heart, where functions may differ due to the distinct spatiotemporal metabolic requirements of these tissues. We also outline the novel concept of electro-metabolic signaling, a universal mechanistic framework that links tissue metabolic state with blood flow regulation by pericytes and vascular smooth muscle cells, with capillary KATP and Kir2.1 channels as primary sensors. Finally, we present major unresolved questions and outline how they can be addressed.
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Affiliation(s)
- Thomas A Longden
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; ,
- Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Guiling Zhao
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; ,
- Laboratory of Molecular Cardiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Ashwini Hariharan
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; ,
- Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - W Jonathan Lederer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; ,
- Laboratory of Molecular Cardiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
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2
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Abstract
Vascular smooth muscle cells (VSMCs) of small peripheral arteries contribute to blood pressure control by adapting their contractile state. These adaptations depend on the VSMC cytosolic Ca2+ concentration, regulated by complex local elementary Ca2+ signaling pathways. Ca2+ sparks represent local, transient, rapid calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial SMCs, Ca2+ sparks activate nearby calcium-dependent potassium channels, cause membrane hyperpolarization and thus decrease the global intracellular [Ca2+] to oppose vasoconstriction. Arterial SMC Cav1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux through RyRs. Cav3.2 T-type channels contribute to a minor extend to Ca2+ spark generation in certain types of arteries. Their localization within cell membrane caveolae is essential. We summarize present data on local elementary calcium signaling (Ca2+ sparks) in arterial SMCs with focus on RyR isoforms, large-conductance calcium-dependent potassium (BKCa) channels, and cell membrane-bound calcium channels (Cav1.2 and Cav3.2), particularly in caveolar microdomains.
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Affiliation(s)
- Gang Fan
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany
| | - Yingqiu Cui
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany
| | - Maik Gollasch
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Berlin, Germany
| | - Mario Kassmann
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Berlin, Germany
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Kaßmann M, Szijártó IA, García‐Prieto CF, Fan G, Schleifenbaum J, Anistan Y, Tabeling C, Shi Y, le Noble F, Witzenrath M, Huang Y, Markó L, Nelson MT, Gollasch M. Role of Ryanodine Type 2 Receptors in Elementary Ca 2+ Signaling in Arteries and Vascular Adaptive Responses. J Am Heart Assoc 2019; 8:e010090. [PMID: 31030596 PMCID: PMC6512102 DOI: 10.1161/jaha.118.010090] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 02/07/2019] [Indexed: 12/29/2022]
Abstract
Background Hypertension is the major risk factor for cardiovascular disease, the most common cause of death worldwide. Resistance arteries are capable of adapting their diameter independently in response to pressure and flow-associated shear stress. Ryanodine receptors (RyRs) are major Ca2+-release channels in the sarcoplasmic reticulum membrane of myocytes that contribute to the regulation of contractility. Vascular smooth muscle cells exhibit 3 different RyR isoforms (RyR1, RyR2, and RyR3), but the impact of individual RyR isoforms on adaptive vascular responses is largely unknown. Herein, we generated tamoxifen-inducible smooth muscle cell-specific RyR2-deficient mice and tested the hypothesis that vascular smooth muscle cell RyR2s play a specific role in elementary Ca2+ signaling and adaptive vascular responses to vascular pressure and/or flow. Methods and Results Targeted deletion of the Ryr2 gene resulted in a complete loss of sarcoplasmic reticulum-mediated Ca2+-release events and associated Ca2+-activated, large-conductance K+ channel currents in peripheral arteries, leading to increased myogenic tone and systemic blood pressure. In the absence of RyR2, the pulmonary artery pressure response to sustained hypoxia was enhanced, but flow-dependent effects, including blood flow recovery in ischemic hind limbs, were unaffected. Conclusions Our results establish that RyR2-mediated Ca2+-release events in VSCM s specifically regulate myogenic tone (systemic circulation) and arterial adaptation in response to changes in pressure (hypoxic lung model), but not flow. They further suggest that vascular smooth muscle cell-expressed RyR2 deserves scrutiny as a therapeutic target for the treatment of vascular responses in hypertension and chronic vascular diseases.
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Affiliation(s)
- Mario Kaßmann
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
- DZHK (German Centre for Cardiovascular Research), partner site BerlinBerlinGermany
| | - István András Szijártó
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Concha F. García‐Prieto
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
- Department of Pharmaceutical and Health SciencesFacultad de FarmaciaUniversidad CEU San PabloMadridSpain
| | - Gang Fan
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Johanna Schleifenbaum
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Yoland‐Marie Anistan
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Christoph Tabeling
- Department of Infectious Diseases and Pulmonary MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Yu Shi
- Medical Clinic for Hematology, Oncology and Tumor ImmunologyCharité–Universitätsmedizin BerlinBerlinGermany
| | - Ferdinand le Noble
- Department of Cell and Developmental BiologyITG (Institute of Toxicology and Genetics)Karlsruhe Institute of TechnologyKarlsruheGermany
| | - Martin Witzenrath
- Department of Infectious Diseases and Pulmonary MedicineCharité–Universitätsmedizin BerlinBerlinGermany
| | - Yu Huang
- Institute of Vascular Medicine and School of Biomedical SciencesChinese University of Hong KongChina
| | - Lajos Markó
- Medical Clinic for Hematology, Oncology and Tumor ImmunologyCharité–Universitätsmedizin BerlinBerlinGermany
| | - Mark T. Nelson
- Department of PharmacologyCollege of MedicineThe University of VermontBurlingtonVT
| | - Maik Gollasch
- Experimental and Clinical Research Centera joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular MedicineCharité–Universitätsmedizin BerlinBerlinGermany
- DZHK (German Centre for Cardiovascular Research), partner site BerlinBerlinGermany
- Medical Clinic for Nephrology and Internal Intensive CareCharité–Universitätsmedizin BerlinBerlinGermany
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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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Kuo KH, Leo JM. Enhancement of Vascular Smooth Muscle Contractility by Alterations of Membranous Architecture. Anat Rec (Hoboken) 2018; 302:186-192. [PMID: 30299599 DOI: 10.1002/ar.23946] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 01/28/2018] [Accepted: 02/15/2018] [Indexed: 11/11/2022]
Abstract
Plasma membrane (PM) of smooth muscle cells hosts channel molecules regulating the flow of various ions. An intact architecture of PM is essential to orchestrate proper channel functions in order to complete agonist-mediated contraction, which includes Ca2+ release from the sarcoplasmic reticulum (SR) to initiate contraction, and subsequent Ca2+ refilling into SR through PM to sustain muscle contraction. The Junctional Complex (JC), comprising of junctional SR, and its apposing PM and neighboring caveolae, provides a quasi-enclosed microdomain housing receptors as well as ion channels and also restricting ion diffusions into the cytosol so the cell achieves optimal performance. The spatial arrangement of the JC is believed to ensure an uninterrupted Ca2+ cycling route. Full understanding of the functional role of the JC is the key to elucidating the contractile mechanisms of vascular smooth muscle and the physiological function of vessel contraction. The JC can be further divided into two sub-divisions, namely the PM-SR and caveolar regions. Previously, we demonstrated the role of the PM-SR region in the initiation of muscle contraction using pharmacological tools on the inferior vena cava (IVC) of rabbit. In the current study, we further dissected the caveolar region using a cholesterol-disrupting agent to investigate the role of the caveolar region. We conclude that disruption of the caveolar region in rabbit IVC smooth muscle results in augmented muscle contraction in response to adrenergic stimulation and the altered Ca2+ signaling may underlie the augmented contractility. Anat Rec, 302:186-192, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Kuo-Hsing Kuo
- Northern Medical Program, University of Northern British Columbia, Prince George, British Columbia, Canada
| | - Joyce M Leo
- Department of Laboratory Medicine, Victoria Royal Jubilee Hospital, Victoria, British Columbia, Canada
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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: 222] [Impact Index Per Article: 31.7] [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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7
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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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Gutterman DD, Chabowski DS, Kadlec AO, Durand MJ, Freed JK, Ait-Aissa K, Beyer AM. The Human Microcirculation: Regulation of Flow and Beyond. Circ Res 2016; 118:157-72. [PMID: 26837746 DOI: 10.1161/circresaha.115.305364] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The microcirculation is responsible for orchestrating adjustments in vascular tone to match local tissue perfusion with oxygen demand. Beyond this metabolic dilation, the microvasculature plays a critical role in modulating vascular tone by endothelial release of an unusually diverse family of compounds including nitric oxide, other reactive oxygen species, and arachidonic acid metabolites. Animal models have provided excellent insight into mechanisms of vasoregulation in health and disease. However, there are unique aspects of the human microcirculation that serve as the focus of this review. The concept is put forth that vasculoparenchymal communication is multimodal, with vascular release of nitric oxide eliciting dilation and preserving normal parenchymal function by inhibiting inflammation and proliferation. Likewise, in disease or stress, endothelial release of reactive oxygen species mediates both dilation and parenchymal inflammation leading to cellular dysfunction, thrombosis, and fibrosis. Some pathways responsible for this stress-induced shift in mediator of vasodilation are proposed. This paradigm may help explain why microvascular dysfunction is such a powerful predictor of cardiovascular events and help identify new approaches to treatment and prevention.
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Affiliation(s)
- David D Gutterman
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee.
| | - Dawid S Chabowski
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
| | - Andrew O Kadlec
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
| | - Matthew J Durand
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
| | - Julie K Freed
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
| | - Karima Ait-Aissa
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
| | - Andreas M Beyer
- From the Cardiovascular Center (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A., M.J.D.), Departments of Medicine (A.M.B., A.O.K., D.D.G., D.S.C., J.K.F., K.A.-A.), Pharmacology and Toxicology (D.S.C., J.K.F.), Physiology (A.M.B., A.O.K.), Physical Medicine and Rehabilitation (M.J.D.), and Anesthesiology (J.K.F.), Medical College of Wisconsin, Milwaukee
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Tano JY, Gollasch M. Calcium-activated potassium channels in ischemia reperfusion: a brief update. Front Physiol 2014; 5:381. [PMID: 25339909 PMCID: PMC4186282 DOI: 10.3389/fphys.2014.00381] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/13/2014] [Indexed: 12/24/2022] Open
Abstract
Ischemia and reperfusion (IR) injury constitutes one of the major causes of cardiovascular morbidity and mortality. The discovery of new therapies to block/mediate the effects of IR is therefore an important goal in the biomedical sciences. Dysfunction associated with IR involves modification of calcium-activated potassium channels (KCa) through different mechanisms, which are still under study. Respectively, the KCa family, major contributors to plasma membrane calcium influx in cells and essential players in the regulation of the vascular tone are interesting candidates. This family is divided into two groups including the large conductance (BKCa) and the small/intermediate conductance (SKCa/IKCa) K(+) channels. In the heart and brain, these channels have been described to offer protection against IR injury. BKCa and SKCa channels deserve special attention since new data demonstrate that these channels are also expressed in mitochondria. More studies are however needed to fully determine their potential use as therapeutic targets.
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Affiliation(s)
- Jean-Yves Tano
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
| | - Maik Gollasch
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
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Krishnamoorthy G, Regehr K, Berge S, Scherer EQ, Wangemann P. Calcium sparks in the intact gerbil spiral modiolar artery. BMC PHYSIOLOGY 2011; 11:15. [PMID: 21871098 PMCID: PMC3170618 DOI: 10.1186/1472-6793-11-15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 08/26/2011] [Indexed: 11/18/2022]
Abstract
Background Calcium sparks are ryanodine receptor mediated transient calcium signals that have been shown to hyperpolarize the membrane potential by activating large conductance calcium activated potassium (BK) channels in vascular smooth muscle cells. Along with voltage-dependent calcium channels, they form a signaling unit that has a vasodilatory influence on vascular diameter and regulation of myogenic tone. The existence and role of calcium sparks has hitherto been unexplored in the spiral modiolar artery, the end artery that controls blood flow to the cochlea. The goal of the present study was to determine the presence and properties of calcium sparks in the intact gerbil spiral modiolar artery. Results Calcium sparks were recorded from smooth muscle cells of intact arteries loaded with fluo-4 AM. Calcium sparks occurred with a frequency of 2.6 Hz, a rise time of 17 ms and a time to half-decay of 20 ms. Ryanodine reduced spark frequency within 3 min from 2.6 to 0.6 Hz. Caffeine (1 mM) increased spark frequency from 2.3 to 3.3 Hz and prolonged rise and half-decay times from 17 to 19 ms and from 20 to 23 ms, respectively. Elevation of potassium (3.6 to 37.5 mM), presumably via depolarization, increased spark frequency from 2.4 to 3.2 Hz. Neither ryanodine nor depolarization changed rise or decay times. Conclusions This is the first characterization of calcium sparks in smooth muscle cells of the spiral modiolar artery. The results suggest that calcium sparks may regulate the diameter of the spiral modiolar artery and cochlear blood flow.
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Adesse D, Lisanti MP, Spray DC, Machado FS, Meirelles MDN, Tanowitz HB, Garzoni LR. Trypanosoma cruzi infection results in the reduced expression of caveolin-3 in the heart. Cell Cycle 2010; 9:1639-46. [PMID: 20372051 DOI: 10.4161/cc.9.8.11509] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Caveolae are motile, membrane-bound compartments that contain a number of molecules that participate in cell signaling. Caveolins are protein markers of caveolae and function in a variety of biological processes. Caveolin-3 (Cav-3) is expressed in muscle cells and Cav-3 null mice display a cardiomyopathic phenotype. Ultrastructural cytochemistry, confocal microscopy and immunoblotting revealed a reduction in Cav-3 expression and an activation of ERK (extracellular-signal-regulated kinase) 48 hours after Trypanosoma cruzi infection of cultured cardiac myocytes. CD-1 mice infected with the Brazil strain of T. cruzi displayed reduced expression of Cav-3 and activation of ERK 66 days post infection (dpi). By 180 dpi there was a normalization of these values. These data suggest that the reduction in Cav-3 expression and the activation of ERK during the early phase of infection may contribute to the pathogenesis of chagasic cardiomyopathy.
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Affiliation(s)
- Daniel Adesse
- Instituto Oswaldo Cruz/FIOCRUZ, Rio de Janeiro, Brazil
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12
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Stimulation of the adenosine A3 receptor reverses vascular hyporeactivity after hemorrhagic shock in rats. Acta Pharmacol Sin 2010; 31:413-20. [PMID: 20348945 DOI: 10.1038/aps.2010.18] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
AIM To investigate whether adenosine A(3) receptors (A(3)AR) stimulation restore vascular reactivity after hemorrhagic shock through a ryanodine receptor (RyR)-mediated and large conductance calcium-activated potassium (BK(Ca)) channel-dependent pathway. METHODS Rat hemorrhagic shock model (40 mmHg) and vascular smooth muscle cell (VSMC) hypoxic model were used. The expression of A(3)AR was determined by Western blot and RT-PCR. The effect of A(3)AR stimulation on RyR-mediated Ca(2+) release in VSMCs was analyzed by the Fura-3/AM loading Ca(2+) imaging. The modulation of vascular reactivity to norepinephrine (NE) by A(3)AR stimulation was monitored by an isolated organ tension instrument. RESULTS Decrease of A(3)AR expression is consistent with the loss of vasoreactivity to NE in hemorrhagic shock rats. The stimulation of A(3)AR with a selective agonist, IB-MECA, could partly but significantly restore the vasoreactivity in the rats, and this restorative effect could be counteracted by MRS1523, a selective A(3)AR antagonist. In hypoxic VSMCs, RyR activation by caffeine significantly evoked the rise of [Ca(2+)] compared with the control cells, a phenomenon closely associated with the development of vascular hyporeactivity in hemorrhagic shock rats. The stimulation of A(3)AR with IB-MECA significantly blocked this over activation of RyR-mediated Ca(2+) release. RyR activation by caffeine and BK(Ca) channel activation by NS1619 attenuated the restoration of vasoreactivity to NE resulting from A(3)AR stimulation by IB-MECA after hemorrhagic shock; this attenuation effect could be antagonized by a selective BK(Ca) channel blocker. CONCLUSION These findings suggest that A(3)AR is involved in the modulation of vasoreactivity after hemorrhagic shock and that stimulation of A(3)AR can restore the decreased vasoreactivity to NE through a RyR-mediated, BK(Ca) channel-dependent signal pathway.
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13
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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14
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Dick GM, Tune JD. Role of potassium channels in coronary vasodilation. Exp Biol Med (Maywood) 2010; 235:10-22. [DOI: 10.1258/ebm.2009.009201] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
K+ channels in coronary arterial smooth muscle cells (CASMC) determine the resting membrane potential ( Em) and serve as targets of endogenous and therapeutic vasodilators. Em in CASMC is in the voltage range for activation of L-type Ca2+ channels; therefore, when K+ channel activity changes, Ca2+ influx and arterial tone change. This is why both Ca2+ channel blockers and K+ channel openers have such profound effects on coronary blood flow; the former directly inhibits Ca2+ influx through L-type Ca2+ channels, while the latter indirectly inhibits Ca2+ influx by hyperpolarizing Em and reducing Ca2+ channel activity. K+ channels in CASMC play important roles in vasodilation to endothelial, ischemic and metabolic stimuli. The purpose of this article is to review the types of K+ channels expressed in CASMC, discuss the regulation of their activity by physiological mechanisms and examine impairments related to cardiovascular disease.
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Affiliation(s)
- Gregory M Dick
- Department of Exercise Physiology and Center for Cardiovascular & Respiratory Sciences, West Virginia University School of Medicine, Morgantown, WV 26506
| | - Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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15
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Song YH, Cho H, Ryu SY, Yoon JY, Park SH, Noh CI, Lee SH, Ho WK. L-type Ca(2+) channel facilitation mediated by H(2)O(2)-induced activation of CaMKII in rat ventricular myocytes. J Mol Cell Cardiol 2009; 48:773-80. [PMID: 19883656 DOI: 10.1016/j.yjmcc.2009.10.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 10/17/2009] [Accepted: 10/26/2009] [Indexed: 10/20/2022]
Abstract
The Ca(2+)-dependent facilitation (CDF) of L-type Ca(2+) channels, a major mechanism for force-frequency relationship of cardiac contraction, is mediated by Ca(2+)/CaM-dependent kinase II (CaMKII). Recently, CaMKII was shown to be activated by methionine oxidation. We investigated whether oxidation-dependent CaMKII activation is involved in the regulation of L-type Ca(2+) currents (I(Ca,L)) by H(2)O(2) and whether Ca(2+) is required in this process. Using patch clamp, I(Ca)(,L) was measured in rat ventricular myocytes. H(2)O(2) induced an increase in I(Ca,L) amplitude and slowed inactivation of I(Ca)(,L). This oxidation-dependent facilitation (ODF) of I(Ca)(,L) was abolished by a CaMKII blocker KN-93, but not by its inactive analog KN-92, indicating that CaMKII is involved in ODF. ODF was not affected by replacement of external Ca(2+) with Ba(2+) or presence of EGTA in the internal solutions. However, ODF was abolished by adding BAPTA to the internal solution or by depleting sarcoplasmic reticulum (SR) Ca(2+) stores using caffeine and thapsigargin. Alkaline phosphatase, beta-iminoadenosine 5'-triphosphate (AMP-PNP), an autophosphorylation inhibitor autocamtide-2-related inhibitory peptide (AIP), or a catalytic domain blocker (CaM-KIINtide) did not affect ODF. In conclusion, oxidation-dependent facilitation of L-type Ca(2+) channels is mediated by oxidation-dependent CaMKII activation, in which local Ca(2+) increases induced by SR Ca(2+) release is required.
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Affiliation(s)
- Young-Hwan Song
- Department of Pediatrics, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea
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16
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Abstract
The calcium ion (Ca(2+)) is the simplest and most versatile intracellular messenger known. The discovery of Ca(2+) sparks and a related family of elementary Ca(2+) signaling events has revealed fundamental principles of the Ca(2+) signaling system. A newly appreciated "digital" subsystem consisting of brief, high Ca(2+) concentration over short distances (nanometers to microns) comingles with an "analog" global Ca(2+) signaling subsystem. Over the past 15 years, much has been learned about the theoretical and practical aspects of spark formation and detection. The quest for the spark mechanisms [the activation, coordination, and termination of Ca(2+) release units (CRUs)] has met unexpected challenges, however, and raised vexing questions about CRU operation in situ. Ample evidence shows that Ca(2+) sparks catalyze many high-threshold Ca(2+) processes involved in cardiac and skeletal muscle excitation-contraction coupling, vascular tone regulation, membrane excitability, and neuronal secretion. Investigation of Ca(2+) sparks in diseases has also begun to provide novel insights into hypertension, cardiac arrhythmias, heart failure, and muscular dystrophy. An emerging view is that spatially and temporally patterned activation of the digital subsystem confers on intracellular Ca(2+) signaling an exquisite architecture in space, time, and intensity, which underpins signaling efficiency, stability, specificity, and diversity. These recent advances in "sparkology" thus promise to unify the simplicity and complexity of Ca(2+) signaling in biology.
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Affiliation(s)
- Heping Cheng
- Institute of Molecular Medicine, National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, China.
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17
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Activation of high conductance Ca2+-activated K+ channels by sodium tanshinoneII-A sulfonate (DS-201) in porcine coronary artery smooth muscle cells. Eur J Pharmacol 2008; 598:9-15. [DOI: 10.1016/j.ejphar.2008.09.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 08/28/2008] [Accepted: 09/09/2008] [Indexed: 11/18/2022]
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18
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Essin K, Welling A, Hofmann F, Luft FC, Gollasch M, Moosmang S. Indirect coupling between Cav1.2 channels and ryanodine receptors to generate Ca2+ sparks in murine arterial smooth muscle cells. J Physiol 2007; 584:205-19. [PMID: 17673505 PMCID: PMC2277062 DOI: 10.1113/jphysiol.2007.138982] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In arterial vascular smooth muscle cells (VSMCs), Ca(2+) sparks stimulate nearby Ca(2+)-activated K(+) (BK) channels that hyperpolarize the membrane and close L-type Ca(2+) channels. We tested the contribution of L-type Ca(v)1.2 channels to Ca(2+) spark regulation in tibial and cerebral artery VSMCs using VSMC-specific Ca(v)1.2 channel gene disruption in (SMAKO) mice and an approach based on Poisson statistical analysis of activation frequency and first latency of elementary events. Ca(v)1.2 channel gene inactivation reduced Ca(2+) spark frequency and amplitude by approximately 50% and approximately 80%, respectively. These effects were associated with lower global cytosolic Ca(2+) levels and reduced sarcoplasmic reticulum (SR) Ca(2+) load. Elevating cytosolic Ca(2+) levels reversed the effects completely. The activation frequency and first latency of elementary events in both wild-type and SMAKO VSMCs weakly reflected the voltage dependency of L-type channels. This study provides evidence that local and tight coupling between the Ca(v)1.2 channels and ryanodine receptors (RyRs) is not required to initiate Ca(2+) sparks. Instead, Ca(v)1.2 channels contribute to global cytosolic [Ca(2+)], which in turn influences luminal SR calcium and thus Ca(2+) sparks.
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Affiliation(s)
- Kirill Essin
- Department of Nephrology and Medical Intensive Care, Charité Campus Virchow-Klinikum, Berlin, Germany
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19
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Hotta S, Morimura K, Ohya S, Muraki K, Takeshima H, Imaizumi Y. Ryanodine receptor type 2 deficiency changes excitation-contraction coupling and membrane potential in urinary bladder smooth muscle. J Physiol 2007; 582:489-506. [PMID: 17363382 PMCID: PMC2075324 DOI: 10.1113/jphysiol.2007.130302] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The possibility that the ryanodine receptor type 2 (RyR2) can function as the major Ca(2+)-induced Ca(2+) release (CICR) channel in excitation-contraction (E-C) coupling was examined in smooth muscle cells (SMCs) isolated from urinary bladder (UB) of RyR2 heterozygous KO mice (RyR2+/-). RyR2 mRNA expression in UB from RyR2+/- was much lower than that in wild-type (RyR2+/+. In single UBSMCs from RyR2+/+, membrane depolarization under voltage clamp initially induced several local Ca(2+) transients (hot spots) in peripheral areas of the cell. Then, Ca(2+) waves spread from Ca(2+) hot spots to other areas of the myocyte. The number of Ca(2+) hot spots elicited by a short depolarization (< 20 ms) in UBSMCs of RyR2+/- was significantly smaller than in those of RyR2+/+. The force development induced either by direct electrical stimulation or by 10 microm acetylcholine in tissue segments of RyR2+/- was smaller than and comparable to those in RyR2+/+, respectively. The frequency of spontaneous transient outward currents in single myocytes and the membrane depolarization by 1 microm paxilline in tissue segments from RyR2+/- were significantly lower and smaller than those in RyR2+/+, respectively. The urination frequency and volume per voiding in RyR2+/- were significantly increased and reduced, respectively, compared with RyR2+/+. In conclusion, RyR2 plays a crucial role in the regulation of CICR during E-C coupling and also in the regulation of resting membrane potential, presumably via the modulation of Ca(2+)-dependent K(+) channel activity in UBSMCs and, thereby, has a pivotal role in the control of bladder activity.
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Affiliation(s)
- Shingo Hotta
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Science, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
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20
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Effect of endogenous and exogenous nitric oxide on calcium sparks as targets for vasodilation in rat cerebral artery. Nitric Oxide 2006; 16:104-9. [PMID: 16899379 DOI: 10.1016/j.niox.2006.06.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2006] [Revised: 06/06/2006] [Accepted: 06/09/2006] [Indexed: 10/24/2022]
Abstract
The potent vasodilator nitric oxide (NO), produced mainly by the endothelium, acts through a BK(Ca)-dependent mechanism to increase the frequency of calcium sparks (Ca(2+) sparks) in myocyte isolated from rat cerebral arteries. Our present aim has been to assess the role of endogenous and exogenous NO on the Ca(2+) sparks through ryanodine-sensitive channels in the sarcoplasmic reticulum of an intact artery. Calcium sparks, detected with fluo-4 and laser scanning confocal microscopy, were examined in isolated pressurized rat posterior cerebral arteries with (intact) and without endothelium (denuded). Addition of the NO donor, DEA-NONOate (N-(2-aminoethyl)-N-(2-hydroxy-2-nitrosohydrazino)-1,2-ethylenediamine), did not change the amplitude and frequency of Ca(2+) sparks in the intact artery. However, inhibition of nitric oxide synthase with N-omega-nitro-L-arginine or removal of endothelium reduced Ca(2+) sparks frequency by about 50%. Under these conditions (i.e., absence of endogenous NO production), DEA-NONOate, increased Ca(2+) spark frequency 3- to 4-fold. These results suggest that endothelial NO modulates local Ca(2+) release events in the arterial smooth muscle and that this mechanism may contribute to the actions of nitrovasodilators.
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21
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Laporte R, Hui A, Laher I. Pharmacological modulation of sarcoplasmic reticulum function in smooth muscle. Pharmacol Rev 2005; 56:439-513. [PMID: 15602008 DOI: 10.1124/pr.56.4.1] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The sarco/endoplasmic reticulum (SR/ER) is the primary storage and release site of intracellular calcium (Ca2+) in many excitable cells. The SR is a tubular network, which in smooth muscle (SM) cells distributes close to cellular periphery (superficial SR) and in deeper aspects of the cell (deep SR). Recent attention has focused on the regulation of cell function by the superficial SR, which can act as a buffer and also as a regulator of membrane channels and transporters. Ca2+ is released from the SR via two types of ionic channels [ryanodine- and inositol 1,4,5-trisphosphate-gated], whereas accumulation from thecytoplasm occurs exclusively by an energy-dependent sarco-endoplasmic reticulum Ca2+-ATPase pump (SERCA). Within the SR, Ca2+ is bound to various storage proteins. Emerging evidence also suggests that the perinuclear portion of the SR may play an important role in nuclear transcription. In this review, we detail the pharmacology of agents that alter the functions of Ca2+ release channels and of SERCA. We describe their use and selectivity and indicate the concentrations used in investigating various SM preparations. Important aspects of cell regulation and excitation-contractile activity coupling in SM have been uncovered through the use of such activators and inhibitors of processes that determine SR function. Likewise, they were instrumental in the recent finding of an interaction of the SR with other cellular organelles such as mitochondria. Thus, an appreciation of the pharmacology and selectivity of agents that interfere with SR function in SM has greatly assisted in unveiling the multifaceted nature of the SR.
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Affiliation(s)
- Régent Laporte
- Ferring Research Institute, Inc., Ferring Pharmaceuticals, San Diego, California, USA
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22
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Fry CH, Hussain M, McCarthy C, Ikeda Y, Sui GP, Wu C. Recent advances in detrusor muscle function. ACTA ACUST UNITED AC 2005:20-5. [PMID: 15545193 DOI: 10.1080/03008880410015138] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Contractile activation of detrusor smooth muscle is initiated by the release of transmitters from motor nerves. Acetylcholine is a ubiquitous transmitter, as also is adenosine triphosphate (ATP) in many animal bladders and in people from several patient groups with pathological bladder function. In recent years there has been progress in explaining several cellular mechanisms that link transmitter release to contraction and these will be considered. The lifetime of ATP in the neuromuscular junction is finite and broken down ultimately to adenosine, which can exert modulatory control of contractile activation. Adenosine depresses nerve-mediated contractions and two sites of action have been proposed: an action on the motor nerves via A receptors to depress further transmitter release and a less well-defined depressant effect on the detrusor muscle. The Ca2+ ions that activate the contractile proteins are derived from intracellular stores, which releases their content via IP receptor activation and Ca2+-induced Ca2+ release. Filling of the stores in the rest interval is mediated via transmembrane flux of Ca2+through Ca2+ channels. Activation of the channels is regulated by the level of the intracellular [Ca2+], via activation and inactivation of Ca2+-sensitive K channels. Thus, Ca2+ store filling is regulated by intracellular [Ca2+] via a negative feedback process. The presence and physiological function of spontaneous contractions in detrusor remain contentious and little is known about their origin. One possibility is that they originate from random Ca2+ sparks, i.e. localized transient increases of [Ca2+] that may eventually progress to generate a cellular Ca2+ transient. Observations by confocal microscopy have revealed the presence of such sparks, especially near the cell membrane, and thus provide a cellular basis for spontaneous contractions. Finally, the questions arises as to whether detrusor smooth muscle is a functional syncitium. The demonstration of small gap junctions by electron microscopy and the demonstration of the gap junction protein connexin45 indicate that the muscle mass may indeed be functionally connected. The implications regarding the spread of excitation are discussed.
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Affiliation(s)
- C H Fry
- The Institute of Urology and Nephrology, London, UK.
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23
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Curtis TM, Tumelty J, Dawicki J, Scholfield CN, McGeown JG. Identification and spatiotemporal characterization of spontaneous Ca2+ sparks and global Ca2+ oscillations in retinal arteriolar smooth muscle cells. Invest Ophthalmol Vis Sci 2005; 45:4409-14. [PMID: 15557449 PMCID: PMC2590679 DOI: 10.1167/iovs.04-0719] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To identify spontaneous Ca(2+) sparks and global Ca(2+) oscillations in microvascular smooth muscle (MVSM) cells within intact retinal arterioles and to characterize their spatiotemporal properties and physiological functions. METHODS Retinal arterioles were mechanically dispersed from freshly isolated rat retinas and loaded with Fluo-4, a Ca(2+)-sensitive dye. Changes in [Ca(2+)](i) were imaged in MVSM cells in situ by confocal scanning laser microscopy in x-y mode or line-scan mode. RESULTS The x-y scans revealed discretely localized, spontaneous Ca(2+) events resembling Ca(2+) sparks and more global and prolonged Ca(2+) transients, which sometimes led to cell contraction. In line scans, Ca(2+) sparks were similar to those previously described in other types of smooth muscle, with an amplitude (DeltaF/F(0)) of 0.81 +/- 0.04 (mean +/- SE), full duration at half maximum (FDHM) of 23.62 +/- 1.15 ms, full width at half maximum (FWHM) of 1.25 +/- 0.05 mum, and frequency of 0.56 +/- 0.06 seconds(-1). Approximately 35% of sparks had a prolonged tail (>80 ms), similar to the Ca(2+)"embers" described in skeletal muscle. Sparks often summated to generate global and prolonged Ca(2+) elevations on which Ca(2+) sparks were superimposed. These sparks occurred more frequently (2.86 +/- 025 seconds(-1)) and spread farther across the cell (FWHM = 1.67 +/- 0.08 microm), but were smaller (DeltaF/F(0) = 0.69 +/- 0.04). CONCLUSIONS Retinal arterioles generate Ca(2+) sparks with characteristics that vary during different phases of the spontaneous Ca(2+)-signaling cycle. Sparks summate to produce sustained Ca(2+) transients associated with contraction and thus may play an important excitatory role in initiating vessel constriction. This deserves further study, not least because Ca(2+) sparks appear to inhibit contraction in many other smooth muscle cells.
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Affiliation(s)
- Tim M Curtis
- Ophthalmic Research Centre, The Queen's University of Belfast, Institute of Clinical Sciences, The Royal Victoria Hospital, Belfast, Northern Ireland
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24
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Robinson JA, Jenkins NS, Holman NA, Roberts-Thomson SJ, Monteith GR. Ratiometric and nonratiometric Ca2+ indicators for the assessment of intracellular free Ca2+ in a breast cancer cell line using a fluorescence microplate reader. ACTA ACUST UNITED AC 2004; 58:227-37. [PMID: 15026209 DOI: 10.1016/j.jbbm.2003.11.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2003] [Revised: 10/27/2003] [Accepted: 11/20/2003] [Indexed: 11/29/2022]
Abstract
Transporters of Ca2+ are potential drug targets and Ca2+ is a useful signal in the assessment of G-protein-coupled receptor activation. Assays involving the assessment of intracellular Ca2+ using microplate readers most often use Ca2+ indicators which do not exhibit a spectra shift on Ca2+ binding (e.g. fluo-3). Indicators that do exhibit a spectral shift upon Ca2+ binding (e.g. fura-2) offer potential advantages for the calibration of intracellular Ca2+ levels. However, experimental limitations may limit the use of ratiometric dyes in microplate readers capable of screening. In this study, we compared the assessment of intracellular Ca2+ in adherent breast cancer cells using ratiometric and nonratiometric Ca2+ indicators. Our results demonstrate that both fluo-3 and fura-2 detect ATP dose-dependent increases in intracellular Ca2+ in the MCF-7 breast cancer cell line and that some of the limitations in the use of fura-2 appear to be overcome by the use of glass bottom microplates. The calibrated intracellular Ca2+ levels derived using fura-2 are consistent with those from microscopy and cuvette-based studies. Fura-2 may be useful in microplate studies, where cell lines with different properties are compared or where screening treatments lead to differences in the number of cells or dye loading.
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Affiliation(s)
- Jodie A Robinson
- The School of Pharmacy, The University of Queensland, 4072, St. Lucia, Queensland, Australia.
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25
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Wellman GC, Nelson MT. Signaling between SR and plasmalemma in smooth muscle: sparks and the activation of Ca2+-sensitive ion channels. Cell Calcium 2003; 34:211-29. [PMID: 12887969 DOI: 10.1016/s0143-4160(03)00124-6] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Intracellular calcium ions are involved in the regulation of nearly every aspect of cell function. In smooth muscle, Ca2+ can be delivered to Ca2+-sensitive effector molecules either by influx through plasma membrane ion channels or by intracellular Ca2+ release events. Ca2+ sparks are transient local increases in intracellular Ca2+ that arise from the opening of ryanodine-sensitive Ca2+ release channels (ryanodine receptors) located in the sarcoplasmic reticulum. In arterial myocytes, Ca2+ sparks occur near the plasma membrane and act to deliver high (microM) local Ca2+ to plasmalemmal Ca2+-sensitive ion channels, without directly altering global cytosolic Ca2+ concentrations. The two major ion channel targets of Ca2+ sparks are Ca2+-activated chloride (Cl(Ca)) channels and large-conductance Ca2+-activated potassium (BK) channels. The activation of BK channels by Ca2+ sparks play an important role in the regulation of arterial diameter and appear to be involved in the action of a variety of vasodilators. The coupling of Ca2+ sparks to BK channels can be influenced by a number of factors including membrane potential and modulatory beta subunits of BK channels. Cl(Ca) channels, while not present in all smooth muscle, can also be activated by Ca2+ sparks in some types of smooth muscle. Ca2+ sparks can also influence the activity of Ca2+-dependent transcription factors and expression of immediate early response genes such as c-fos. In summary, Ca2+ sparks are local Ca2+ signaling events that in smooth muscle can act on plasma membrane ion channels to influence excitation-contraction coupling as well as gene expression.
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Affiliation(s)
- George C Wellman
- Department of Pharmacology, The University of Vermont College of Medicine, Given Building, Room B-321, 89 Beaumont Avenue, Burlington, VT 05405, USA.
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26
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Burdyga T, Shmygol A, Eisner DA, Wray S. A new technique for simultaneous and in situ measurements of Ca2+ signals in arteriolar smooth muscle and endothelial cells. Cell Calcium 2003; 34:27-33. [PMID: 12767890 DOI: 10.1016/s0143-4160(03)00019-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We report here the first local and global Ca(2+) measurements made from in situ terminal arterioles. The advantages of the method are that there is minimal disturbance to the vessels, which retain their relationship to the tissue they are supplying (rat ureter) and the small size of vessel that can be studied. Good loading with the Ca(2+) indicator, Fluo-4 was obtained, and confocal sectioning through the tissue enabled vascular smooth muscle and endothelial cells to be clearly seen, along with red blood cells, nerve endings and the ureteric smooth muscle cells. We find the terminal arterioles to be extremely active, both spontaneously and in response to nor-adrenaline stimulation, with Ca(2+) sparks occurring in the vascular myocytes and Ca(2+) puffs in the endothelial cells. Even under resting conditions, endothelial cells produced oscillations and waves, which could pass from cell to cell, whereas the vascular myocytes only produced waves in response to agonist stimulation, and with no increase in the frequency of Ca(2+) sparks, and no spread from cell to cell. We compare our data to those obtained in dissected intact vessels and single cells. We conclude that this approach is a convenient and useful method for studying inter- and intracellular Ca(2+) signalling events and communication between cell types, particularly in very small vessels.
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MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Aniline Compounds
- Animals
- Arterioles/cytology
- Arterioles/metabolism
- Calcium/analysis
- Calcium/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Histocytochemistry/instrumentation
- Histocytochemistry/methods
- Microscopy, Confocal/instrumentation
- Microscopy, Confocal/methods
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Norepinephrine/pharmacology
- Rats
- Ureter/blood supply
- Ureter/cytology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Xanthenes
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Affiliation(s)
- T Burdyga
- The Physiological Laboratory, Department of Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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Remillard CV, Zhang WM, Shimoda LA, Sham JSK. Physiological properties and functions of Ca(2+) sparks in rat intrapulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2002; 283:L433-44. [PMID: 12114206 DOI: 10.1152/ajplung.00468.2001] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca(+) spark has been implicated as a pivotal feedback mechanism for regulating membrane potential and vasomotor tone in systemic arterial smooth muscle cells (SASMCs), but little is known about its properties in pulmonary arterial smooth muscle cells (PASMCs). Using confocal microscopy, we identified spontaneous Ca(2+) sparks in rat intralobar PASMCs and characterized their spatiotemporal properties and physiological functions. Ca(2+) sparks of PASMCs had a lower frequency and smaller amplitude than cardiac sparks. They were abolished by inhibition of ryanodine receptors but not by inhibition of inositol trisphosphate receptors and L-type Ca(2+) channels. Enhanced Ca(2+) influx by BAY K8644, K(+), or high Ca(2+) caused a significant increase in spark frequency. Functionally, enhancing Ca(2+) sparks with caffeine (0.5 mM) caused membrane depolarization in PASMCs, in contrast to hyperpolarization in SASMCs. Norepinephrine and endothelin-1 both caused global elevations in cytosolic Ca(2+) concentration ([Ca(2+)]), but only endothelin-1 increased spark frequency. These results suggest that Ca(2+) sparks of PASMCs are similar to those of SASMCs, originate from ryanodine receptors, and are enhanced by Ca(2+) influx. However, they play a different modulatory role on membrane potential and are under agonist-specific regulation independent of global [Ca(2+)].
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Affiliation(s)
- Carmelle V Remillard
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA
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Wellman GC, Nathan DJ, Saundry CM, Perez G, Bonev AD, Penar PL, Tranmer BI, Nelson MT. Ca2+ sparks and their function in human cerebral arteries. Stroke 2002; 33:802-8. [PMID: 11872907 DOI: 10.1161/hs0302.104089] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Local Ca2+ release events (Ca2+ sparks) caused by the opening of ryanodine-sensitive Ca2+ channels in the sarcoplasmic reticulum have been suggested to oppose constriction in cerebral arteries through the activation of large-conductance Ca2+-activated K+ (BK) channels. We report the first identification and characterization of Ca2+ sparks and associated BK channel currents in smooth muscle cells isolated from human cerebral arteries. METHODS Membrane currents and intracellular Ca2+ were measured with the use of the patch-clamp technique and laser scanning confocal microscopy. RESULTS Ca2+ sparks with a peak fractional fluorescence change (F/F0) of 2.02 +/- 0.04 and size of 8.2 +/- 0.5 microm2 (n=108) occurred at a frequency of approximately 1 Hz in freshly isolated, cerebral artery myocytes from humans. At a holding potential of -40 mV, the majority of, but not all, Ca2+ sparks (61 of 85 sparks) were associated with transient BK currents. Consistent with a role for Ca2+ sparks in the control of cerebral artery diameter, agents that block Ca2+ sparks (ryanodine) or BK channels (iberiotoxin) were found to contract human cerebral arteries. CONCLUSIONS This study provides evidence for local Ca2+ signaling in human arterial myocytes and suggests that these events may play an important role in control of cerebral artery diameter in humans.
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Affiliation(s)
- George C Wellman
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405-0068, USA.
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Löhn M, Jessner W, Fürstenau M, Wellner M, Sorrentino V, Haller H, Luft FC, Gollasch M. Regulation of calcium sparks and spontaneous transient outward currents by RyR3 in arterial vascular smooth muscle cells. Circ Res 2001; 89:1051-7. [PMID: 11717163 DOI: 10.1161/hh2301.100250] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Intracellular Ca(2+) levels control both contraction and relaxation in vascular smooth muscle cells (VSMCs). Ca(2+)-dependent relaxation is mediated by discretely localized Ca(2+) release events through ryanodine receptor (RyR) channels in the sarcoplasmic reticulum (SR). These local increases in Ca(2+) concentration, termed sparks, stimulate nearby Ca(2+)-activated K(+) (BK) channels causing BK currents (spontaneous transient outward currents or STOCs). STOCs are hyperpolarizing currents that oppose vasoconstriction. Several RyR isoforms are coexpressed in VSMCs; however, their role in Ca(2+) spark generation is unknown. To provide molecular information on RyR cluster function and assembly, we examined Ca(2+) sparks and STOCs in RyR3-deficient freshly isolated myocytes of resistance-sized cerebral arteries from knockout mice and compared them to Ca(2+) sparks in cells from wild-type mice. We used RT-PCR to identify RyR1, RyR2, and RyR3 mRNA in cerebral arteries. Ca(2+) sparks in RyR3-deficient cells were similar in peak amplitude (measured as F/F(0)), width at half-maximal amplitude, and duration compared with wild-type cell Ca(2+) sparks. However, the frequency of STOCs (between -60 mV and -20 mV) was significantly higher in RyR3-deficient cells than in wild-type cells. Ca(2+) sparks and STOCs in both RyR3-deficient and wild-type cells were inhibited by ryanodine (10 micromol/L), external Ca(2+) removal, and depletion of SR Ca(2+) stores by caffeine (1 mmol/L). Isolated, pressurized cerebral arteries of RyR3-deficient mice developed reduced myogenic tone. Our results suggest that RyR3 is part of the SR Ca(2+) spark release unit and plays a specific molecular role in the regulation of STOCs frequency in mouse cerebral artery VSMCs after decreased arterial tone.
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Affiliation(s)
- M Löhn
- HELIOS Klinikum-Berlin, Franz Volhard Clinic and Max Delbrück Center for Molecular Medicine, Medical Faculty of the Charité, Humboldt University Berlin, Germany
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Ohi Y, Yamamura H, Nagano N, Ohya S, Muraki K, Watanabe M, Imaizumi Y. Local Ca(2+) transients and distribution of BK channels and ryanodine receptors in smooth muscle cells of guinea-pig vas deferens and urinary bladder. J Physiol 2001; 534:313-26. [PMID: 11454953 PMCID: PMC2278703 DOI: 10.1111/j.1469-7793.2001.t01-3-00313.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. The relationship between Ca(2+) sparks spontaneously occurring at rest and local Ca(2+) transients elicited by depolarization was analysed using two-dimensional confocal Ca(2+) images of single smooth muscle cells isolated from guinea-pig vas deferens and urinary bladder. The current activation by these Ca(2+) events was also recorded simultaneously under whole-cell voltage clamp. 2. Spontaneous transient outward currents (STOCs) and Ca(2+) sparks were simultaneously detected at -40 mV in approximately 50 % of myocytes of either type. Ca(2+) sparks and corresponding STOCs occurred repetitively in several discrete sites in the subplasmalemmal area. Large conductance Ca(2+)-dependent K(+) (BK) channel density in the plasmalemma near the Ca(2+) spark sites generating STOCs was calculated to be 21 channels microm(-2). 3. When myocytes were depolarized from -60 to 0 mV, several local Ca(2+) transients were elicited within 20 ms in exactly the same peripheral sites where sparks occurred at rest. The local Ca(2+) transients often lasted over 300 ms and spread into other areas. The appearance of local Ca(2+) transients occurred synchronously with the activation of Ca(2+)-dependent K(+) current (I(K,Ca)). 4. Immunofluorescence staining of the BK channel alpha-subunit (BKalpha) revealed a spot-like pattern on the plasmalemma, in contrast to the uniform staining of voltage-dependent Ca(2+) channel alpha1C subunits along the plasmalemma. Ryanodine receptor (RyR) immunostaining also suggested punctate localization predominantly in the periphery. Double staining of BKalpha and RyRs revealed spot-like co-localization on/beneath the plasmalemma. 5. Using pipettes of relatively low resistance, inside-out patches that included both clustered BK channels at a density of over 20 channels microm(-2) and functional Ca(2+) storage sites were obtained at a low probability of approximately 5%. The averaged BK channel density was 3-4 channels microm(-2) in both types of myocyte. 6. These results support the idea that a limited number of discrete sarcoplasmic reticulum (SR) fragments in the subplasmalemmal area play key roles in the control of BK channel activity in two ways: (i) by generating Ca(2+) sparks at rest to activate STOCs and (ii) by generating Ca(2+) transients presumably triggered by sparks during an action potential to activate a large I(K,Ca) and also induce a contraction. BK channels and RyRs may co-localize densely at the junctional areas of plasmalemma and SR fragments, where Ca(2+) sparks occur to elicit STOCs.
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Affiliation(s)
- Y Ohi
- Department of Molecular and Cellular Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
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