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Wen X, Peng Y, Peng Y, Zhu Y, Yu F, Geng L, Zhou T, Wang X, Feng L, Meng Q. Aortic smooth muscle TRPV4 channels regulate vasoconstriction in high salt-induced hypertension. Hypertens Res 2023; 46:2356-2367. [PMID: 37532951 DOI: 10.1038/s41440-023-01363-2] [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: 02/14/2023] [Revised: 06/21/2023] [Accepted: 06/23/2023] [Indexed: 08/04/2023]
Abstract
Recent studies have focused on the contribution of vascular endothelial transient receptor potential vanilloid 4 (TRPV4) channels to hypertension. However, in hypertension, TRPV4 channels in vascular smooth muscle remain unexplored. In the present study, we performed wire myograph experiments in isolated aortas from endothelial cell specific TRPV4 channel knockout (TRPV4EC-/-) mice to demonstrate that GSK1016790A (a specific TRPV4 channel agonist) triggered aortic smooth muscle-dependent contractions from mice on a normal-salt diet, and the contractions were enhanced in high-salt diet (HSD) mice. Intracellular Ca2+ concentration ([Ca2+]i) and Ca2+ imaging assays showed that TRPV4-induced [Ca2+]i was significantly higher in aortic smooth muscle cells (ASMCs) from HSD-induced hypertensive mice, and application of an inositol trisphosphate receptor (IP3R) inhibitor markedly attenuated TRPV4-induced [Ca2+]i. IP3R2 expression was enhanced in ASMCs from HSD-induced hypertensive mice and the contractile response induced by TRPV4 was inhibited by the IP3R inhibitor. Whole-transcriptome analysis by RNA-seq and western blot assays revealed the involvement of interferon regulatory factor 7 (IRF7) in TRPV4-IRF7-IP3R2 signaling in HSD-induced hypertension. These results suggested that TRPV4 channels regulate smooth muscle-dependent contractions in high salt-induced hypertension, and this contraction involves increased [Ca2+]i, IP3R2, and IRF7 activity. Our study revealed a considerable effect of TRPV4 channels in smooth muscle-dependent contraction in mice during high-salt induced hypertension.
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Affiliation(s)
- Xin Wen
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Yidi Peng
- School of Pharmaceutical Sciences, Jiangnan University, Wuxi, 214000, China
| | - Yuefeng Peng
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Yuzhong Zhu
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Fan Yu
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Li Geng
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Tingting Zhou
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Xianfeng Wang
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Lei Feng
- Wuxi School of Medicine, Jiangnan University, Wuxi, 214000, China
| | - Qingyou Meng
- Department of Vascular Surgery, General Surgery Clinical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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2
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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: 14] [Impact Index Per Article: 4.7] [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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3
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Tengah A, Syed NIH, Talip STA, Bujang SNB, Kennedy C. Comparison of signalling mechanisms underlying UTP-evoked vasoconstriction of rat pulmonary and tail arteries. Eur J Pharmacol 2018; 837:45-52. [PMID: 30170065 DOI: 10.1016/j.ejphar.2018.08.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 08/22/2018] [Accepted: 08/24/2018] [Indexed: 12/16/2022]
Abstract
The endogenous nucleotide, UTP, acts at smooth muscle P2Y receptors to constrict rat pulmonary and tail arteries, but the underlying signalling pathways are poorly understood. The aim was to characterise the contribution of Ca2+ release and influx, rho kinase and protein kinase C to these contractions. Isometric tension was recorded from endothelium-denuded rat intralobar pulmonary and tail artery rings mounted on a wire myograph. Contractions were evoked by UTP and peak amplitude measured. Thapsigargin (1 µM), but not ryanodine (10 µM), significantly depressed contractions in both by 30-40% (P < 0.05). Nifedipine (1 µM) significantly reduced contractions in tail artery by ~60% (P < 0.01). Y27632 (10 µM), a rho kinase inhibitor and GF109203X (10 µM), a protein kinase C inhibitor, each significantly reduced pulmonary vasoconstriction by ~20%, and tail artery contractions by ~80% and ~40%, respectively (P < 0.01). In pulmonary artery, Y27632, GF109203X and thapsigargin, acted in an additive manner, but nifedipine less so. Adding all four together abolished the UTP response. In tail artery, Y27632 plus thapsigargin or GF109203X or nifedipine abolished contractions. Thapsigargin, GF109203X and nifedipine, coapplied pair-wise, acted additively and applying all three together abolished UTP-evoked contractions. So, Ca2+ release from the sarcoplasmic reticulum and influx through Cav1.2 channels, but not ryanodine receptors, play significant roles in UTP-evoked vasoconstriction of rat pulmonary and tail arteries. Rho kinase and protein kinase C are also involved, but more so in tail artery. Thus UTP activates multiple signalling mechanisms that lead to vasoconstriction, but their relative importance differs in pulmonary compared with systemic arteries.
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Affiliation(s)
- Asrin Tengah
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Nawazish-I-Husain Syed
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Siti Tajidah Abdul Talip
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Siti Nur Basirah Bujang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
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Leo MD, Zhai X, Muralidharan P, Kuruvilla KP, Bulley S, Boop FA, Jaggar JH. Membrane depolarization activates BK channels through ROCK-mediated β1 subunit surface trafficking to limit vasoconstriction. Sci Signal 2017; 10:10/478/eaah5417. [PMID: 28487419 DOI: 10.1126/scisignal.aah5417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Membrane depolarization of smooth muscle cells (myocytes) in the small arteries that regulate regional organ blood flow leads to vasoconstriction. Membrane depolarization also activates large-conductance calcium (Ca2+)-activated potassium (BK) channels, which limits Ca2+ channel activity that promotes vasoconstriction, thus leading to vasodilation. We showed that in human and rat arterial myocytes, membrane depolarization rapidly increased the cell surface abundance of auxiliary BK β1 subunits but not that of the pore-forming BKα channels. Membrane depolarization stimulated voltage-dependent Ca2+ channels, leading to Ca2+ influx and the activation of Rho kinase (ROCK) 1 and 2. ROCK1/2-mediated activation of Rab11A promoted the delivery of β1 subunits to the plasma membrane by Rab11A-positive recycling endosomes. These additional β1 subunits associated with BKα channels already at the plasma membrane, leading to an increase in apparent Ca2+ sensitivity and activation of the channels in pressurized arterial myocytes and vasodilation. Thus, membrane depolarization activates BK channels through stimulation of ROCK- and Rab11A-dependent trafficking of β1 subunits to the surface of arterial myocytes.
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Affiliation(s)
- M Dennis Leo
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Xue Zhai
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Padmapriya Muralidharan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Korah P Kuruvilla
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Simon Bulley
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Frederick A Boop
- Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Jonathan H Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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5
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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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6
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Lin Q, Zhao G, Fang X, Peng X, Tang H, Wang H, Jing R, Liu J, Lederer WJ, Chen J, Ouyang K. IP 3 receptors regulate vascular smooth muscle contractility and hypertension. JCI Insight 2016; 1:e89402. [PMID: 27777977 DOI: 10.1172/jci.insight.89402] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Inositol 1, 4, 5-trisphosphate receptor-mediated (IP3R-mediated) calcium (Ca2+) release has been proposed to play an important role in regulating vascular smooth muscle cell (VSMC) contraction for decades. However, whether and how IP3R regulates blood pressure in vivo remains unclear. To address these questions, we have generated a smooth muscle-specific IP3R triple-knockout (smTKO) mouse model using a tamoxifen-inducible system. In this study, the role of IP3R-mediated Ca2+ release in adult VSMCs on aortic vascular contractility and blood pressure was assessed following tamoxifen induction. We demonstrated that deletion of IP3Rs significantly reduced aortic contractile responses to vasoconstrictors, including phenylephrine, U46619, serotonin, and endothelin 1. Deletion of IP3Rs also dramatically reduced the phosphorylation of MLC20 and MYPT1 induced by U46619. Furthermore, although the basal blood pressure of smTKO mice remained similar to that of wild-type controls, the increase in systolic blood pressure upon chronic infusion of angiotensin II was significantly attenuated in smTKO mice. Taken together, our results demonstrate an important role for IP3R-mediated Ca2+ release in VSMCs in regulating vascular contractility and hypertension.
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Affiliation(s)
- Qingsong Lin
- Drug Discovery Center, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Guiling Zhao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Xi Fang
- University of California San Diego, School of Medicine, Department of Medicine, La Jolla, California, USA
| | - Xiaohong Peng
- Drug Discovery Center, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Huayuan Tang
- Drug Discovery Center, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Hong Wang
- Drug Discovery Center, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Ran Jing
- Xiangya Hospital, Central South University, Changsha, China
| | - Jie Liu
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Ju Chen
- University of California San Diego, School of Medicine, Department of Medicine, La Jolla, California, USA
| | - Kunfu Ouyang
- Drug Discovery Center, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, China
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7
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Ghosh D, Syed AU, Prada MP, Nystoriak MA, Santana LF, Nieves-Cintrón M, Navedo MF. Calcium Channels in Vascular Smooth Muscle. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:49-87. [PMID: 28212803 DOI: 10.1016/bs.apha.2016.08.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Calcium (Ca2+) plays a central role in excitation, contraction, transcription, and proliferation of vascular smooth muscle cells (VSMs). Precise regulation of intracellular Ca2+ concentration ([Ca2+]i) is crucial for proper physiological VSM function. Studies over the last several decades have revealed that VSMs express a variety of Ca2+-permeable channels that orchestrate a dynamic, yet finely tuned regulation of [Ca2+]i. In this review, we discuss the major Ca2+-permeable channels expressed in VSM and their contribution to vascular physiology and pathology.
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Affiliation(s)
- D Ghosh
- University of California, Davis, CA, United States
| | - A U Syed
- University of California, Davis, CA, United States
| | - M P Prada
- University of California, Davis, CA, United States
| | - M A Nystoriak
- Diabetes and Obesity Center, University of Louisville, Louisville, KY, United States
| | - L F Santana
- University of California, Davis, CA, United States
| | | | - M F Navedo
- University of California, Davis, CA, United States.
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8
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Adenosine monophosphate-activated protein kinase activation and suppression of inflammatory response by cell stretching in rabbit synovial fibroblasts. Mol Cell Biochem 2016; 423:175-185. [PMID: 27686453 DOI: 10.1007/s11010-016-2835-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 09/23/2016] [Indexed: 10/20/2022]
Abstract
Joint mobilization is known to be beneficial in osteoarthritis (OA) patients. This study aimed to investigate the effect of stretching on adenosine monophosphate-activated protein kinase (AMPK) activity and its role in modulating inflammation in rabbit synovial fibroblasts. Uniaxial stretching of isolated rabbit synovial fibroblasts for ten min was performed. Stretching-induced AMPK activation, its underlying mechanism, and its anti-inflammatory effect were investigated using Western blot. Static stretching at 20 % of initial length resulted in AMPK activation characterized by expression of phosphorylated AMPK and phosphorylated acetyl-Co A carboxylase. AMP-activated protein kinase phosphorylation peaked 1 h after stretching and declined toward resting activity. Using cell viability assays, static stretching did not appear to cause cellular damage. Activation of AMPK involves Ca2+ influx via a mechanosensitive L-type Ca2+ channel, which subsequently raises intracellular Ca2+ and activates AMPK via Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ). Interestingly, stretching suppressed TNFα-induced expression of COX-2, iNOS, and phosphorylated NF-κB. These effects were prevented by pretreatment with compound C, an AMPK inhibitor. These results suggest that mechanical stretching suppressed inflammatory responses in synovial fibroblasts via a L-type Ca2+-channel-CaMKKβ-AMPK-dependent pathway which may underlie joint mobilization's ability to alleviate OA symptoms.
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9
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Wang Q, Leo MD, Narayanan D, Kuruvilla KP, Jaggar JH. Local coupling of TRPC6 to ANO1/TMEM16A channels in smooth muscle cells amplifies vasoconstriction in cerebral arteries. Am J Physiol Cell Physiol 2016; 310:C1001-9. [PMID: 27147559 DOI: 10.1152/ajpcell.00092.2016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 04/28/2016] [Indexed: 11/22/2022]
Abstract
Anoctamin-1 [ANO1, also known as transmembrane protein 16A (TMEM16A)] is a Ca(2+)-activated Cl(-) channel expressed in arterial myocytes that regulates membrane potential and contractility. Signaling mechanisms that control ANO1 activity in arterial myocytes are poorly understood. In cerebral artery myocytes, ANO1 channels are activated by local Ca(2+) signals generated by plasma membrane nonselective cation channels, but the molecular identity of these proteins is unclear. Arterial myocytes express several different nonselective cation channels, including multiple members of the transient receptor potential receptor (TRP) family. The goal of this study was to identify localized ion channels that control ANO1 currents in cerebral artery myocytes. Coimmunoprecipitation and immunofluorescence resonance energy transfer microscopy experiments indicate that ANO1 and canonical TRP 6 (TRPC6) channels are present in the same macromolecular complex and localize in close spatial proximity in the myocyte plasma membrane. In contrast, ANO1 is not near TRPC3, TRP melastatin 4, or inositol trisphosphate receptor 1 channels. Hyp9, a selective TRPC6 channel activator, stimulated Cl(-) currents in myocytes that were blocked by T16Ainh-A01, an ANO1 inhibitor, ANO1 knockdown using siRNA, and equimolar replacement of intracellular EGTA with BAPTA, a fast Ca(2+) chelator that abolishes local Ca(2+) signaling. Hyp9 constricted pressurized cerebral arteries, and this response was attenuated by T16Ainh-A01. In contrast, T16Ainh-A01 did not alter depolarization-induced (60 mM K(+)) vasoconstriction. These data indicate that TRPC6 channels generate a local intracellular Ca(2+) signal that activates nearby ANO1 channels in myocytes to stimulate vasoconstriction.
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Affiliation(s)
- Qian Wang
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - M Dennis Leo
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Korah P Kuruvilla
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Jonathan H Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
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10
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Parajuli SP, Zheng YM, Levin R, Wang YX. Big-conductance Ca 2+-activated K + channels in physiological and pathophysiological urinary bladder smooth muscle cells. Channels (Austin) 2016; 10:355-364. [PMID: 27101440 DOI: 10.1080/19336950.2016.1180488] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Contraction and relaxation of urinary bladder smooth muscle cells (UBSMCs) represent the important physiological functions of the bladder. Contractile responses in UBSMCs are regulated by a number of ion channels including big-conductance Ca2+- activated K+ (BK) channels. Great progress has been made in studies of BK channels in UBSMCs. The intent of this review is to summarize recent exciting findings with respect to the functional interactions of BK channels with muscarinic receptors, ryanodine receptors (RyRs) and inositol triphosphate receptors (IP3Rs) as well as their functional importance under normal and pathophysiological conditions. BK channels are highly expressed in UBSMCs. Activation of muscarinic M3 receptors inhibits the BK channel activity, facilitates opening of voltage-dependent Ca2+ (CaV) channels, and thereby enhances excitability and contractility of UBSMCs. Signaling molecules and regulatory mechanisms involving RyRs and IP3Rs have a significant effect on functions of BK channels and thereby regulate cellular responses in UBSMCs under normal and pathophysiological conditions including overactive bladders. Moreover, BK channels may represent a novel target for the treatment of bladder dysfunctions.
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Affiliation(s)
- Shankar P Parajuli
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
| | - Yun-Min Zheng
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
| | - Robert Levin
- b Stratton VA Medical Center , Albany , NY , USA
| | - Yong-Xiao Wang
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
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Bannister JP, Bulley S, Leo MD, Kidd MW, Jaggar JH. Rab25 influences functional Cav1.2 channel surface expression in arterial smooth muscle cells. Am J Physiol Cell Physiol 2016; 310:C885-93. [PMID: 27076616 DOI: 10.1152/ajpcell.00345.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/24/2016] [Indexed: 11/22/2022]
Abstract
Plasma membrane-localized CaV1.2 channels are the primary calcium (Ca(2+)) influx pathway in arterial smooth muscle cells (myocytes). CaV1.2 channels regulate several cellular functions, including contractility and gene expression, but the trafficking pathways that control the surface expression of these proteins are unclear. Similarly, expression and physiological functions of small Rab GTPases, proteins that control vesicular trafficking in arterial myocytes, are poorly understood. Here, we investigated Rab proteins that control functional surface abundance of CaV1.2 channels in cerebral artery myocytes. Western blotting indicated that Rab25, a GTPase previously associated with apical recycling endosomes, is expressed in cerebral artery myocytes. Immunofluorescence Förster resonance energy transfer (immunoFRET) microscopy demonstrated that Rab25 locates in close spatial proximity to CaV1.2 channels in myocytes. Rab25 knockdown using siRNA reduced CaV1.2 surface and intracellular abundance in arteries, as determined using arterial biotinylation. In contrast, CaV1.2 was not located nearby Rab11A or Rab4 and CaV1.2 protein was unaltered by Rab11A or Rab4A knockdown. Rab25 knockdown resulted in CaV1.2 degradation by a mechanism involving both lysosomal and proteasomal pathways and reduced whole cell CaV1.2 current density but did not alter voltage dependence of current activation or inactivation in isolated myocytes. Rab25 knockdown also inhibited depolarization (20-60 mM K(+)) and pressure-induced vasoconstriction (myogenic tone) in cerebral arteries. These data indicate that Rab25 is expressed in arterial myocytes where it promotes surface expression of CaV1.2 channels to control pressure- and depolarization-induced vasoconstriction.
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Affiliation(s)
- John P Bannister
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Simon Bulley
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - M Dennis Leo
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Michael W Kidd
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Jonathan H Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
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12
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Longden TA, Hill-Eubanks DC, Nelson MT. Ion channel networks in the control of cerebral blood flow. J Cereb Blood Flow Metab 2016; 36:492-512. [PMID: 26661232 PMCID: PMC4794103 DOI: 10.1177/0271678x15616138] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/17/2015] [Accepted: 10/14/2015] [Indexed: 12/26/2022]
Abstract
One hundred and twenty five years ago, Roy and Sherrington made the seminal observation that neuronal stimulation evokes an increase in cerebral blood flow.(1) Since this discovery, researchers have attempted to uncover how the cells of the neurovascular unit-neurons, astrocytes, vascular smooth muscle cells, vascular endothelial cells and pericytes-coordinate their activity to control this phenomenon. Recent work has revealed that ionic fluxes through a diverse array of ion channel species allow the cells of the neurovascular unit to engage in multicellular signaling processes that dictate local hemodynamics.In this review we center our discussion on two major themes: (1) the roles of ion channels in the dynamic modulation of parenchymal arteriole smooth muscle membrane potential, which is central to the control of arteriolar diameter and therefore must be harnessed to permit changes in downstream cerebral blood flow, and (2) the striking similarities in the ion channel complements employed in astrocytic endfeet and endothelial cells, enabling dual control of smooth muscle from either side of the blood-brain barrier. We conclude with a discussion of the emerging roles of pericyte and capillary endothelial cell ion channels in neurovascular coupling, which will provide fertile ground for future breakthroughs in the field.
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Affiliation(s)
- Thomas A Longden
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT, USA Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK
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Mufti RE, Zechariah A, Sancho M, Mazumdar N, Brett SE, Welsh DG. Implications of αvβ3 Integrin Signaling in the Regulation of Ca2+ Waves and Myogenic Tone in Cerebral Arteries. Arterioscler Thromb Vasc Biol 2015; 35:2571-8. [PMID: 26494230 DOI: 10.1161/atvbaha.115.305619] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 10/09/2015] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The myogenic response is central to blood flow regulation in the brain. Its induction is tied to elevated cytosolic [Ca(2+)], a response primarily driven by voltage-gated Ca(2+) channels and secondarily by Ca(2+) wave production. Although the signaling events leading to the former are well studied, those driving Ca(2+) waves remain uncertain. APPROACH AND RESULTS We postulated that αvβ3 integrin signaling is integral to the generation of pressure-induced Ca(2+) waves and cerebral arterial tone. This hypothesis was tested in rat cerebral arteries using the synergistic strengths of pressure myography, rapid Ca(2+) imaging, and Western blot analysis. GRGDSP, a peptide that preferentially blocks αvβ3 integrin, attenuated myogenic tone, indicating the modest role for sarcoplasmic reticulum Ca(2+) release in myogenic tone generation. The RGD peptide was subsequently shown to impair Ca(2+) wave generation and myosin light chain 20 (MLC20) phosphorylation, the latter of which was attributed to the modulation of MLC kinase and MLC phosphatase via MYPT1-T855 phosphorylation. Subsequent experiments revealed that elevated pressure enhanced phospholipase Cγ1 phosphorylation in an RGD-dependent manner and that phospholipase C inhibition attenuated Ca(2+) wave generation. Direct inhibition of inositol 1, 4, 5-triphosphate receptors also impaired Ca(2+) wave generation, myogenic tone, and MLC20 phosphorylation, partly through the T-855 phosphorylation site of MYPT1. CONCLUSIONS Our investigation reveals a hitherto unknown role for αvβ3 integrin as a cerebral arterial pressure sensor. The membrane receptor facilitates Ca(2+) wave generation through a signaling cascade, involving phospholipase Cγ1, inositol 1,3,4 triphosphate production, and inositol 1, 4, 5-triphosphate receptor activation. These discrete asynchronous Ca(2+) events facilitate MLC20 phosphorylation and, in part, myogenic tone by influencing both MLC kinase and MLC phosphatase activity.
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Affiliation(s)
- Rania E Mufti
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.)
| | - Anil Zechariah
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.)
| | - Maria Sancho
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.)
| | - Neil Mazumdar
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.)
| | - Suzanne E Brett
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.)
| | - Donald G Welsh
- From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
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14
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Leo MD, Bulley S, Bannister JP, Kuruvilla KP, Narayanan D, Jaggar JH. Angiotensin II stimulates internalization and degradation of arterial myocyte plasma membrane BK channels to induce vasoconstriction. Am J Physiol Cell Physiol 2015; 309:C392-402. [PMID: 26179602 DOI: 10.1152/ajpcell.00127.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 06/29/2015] [Indexed: 11/22/2022]
Abstract
Arterial smooth muscle cells (myocytes) express large-conductance Ca(2+)-activated K(+) (BK) channel α and auxiliary β1 subunits that modulate arterial contractility. In arterial myocytes, β1 subunits are stored within highly mobile rab11A-positive recycling endosomes. In contrast, BKα subunits are primarily plasma membrane-localized. Trafficking pathways for BKα and whether physiological stimuli that regulate arterial contractility alter BKα localization in arterial myocytes are unclear. Here, using biotinylation, immunofluorescence resonance energy transfer (immunoFRET) microscopy, and RNAi-mediated knockdown, we demonstrate that rab4A-positive early endosomes traffic BKα to the plasma membrane in myocytes of resistance-size cerebral arteries. Angiotensin II (ANG II), a vasoconstrictor, reduced both surface and total BKα, an effect blocked by bisindolylmaleimide-II, concanavalin A, and dynasore, protein kinase C (PKC), internalization, and endocytosis inhibitors, respectively. In contrast, ANG II did not reduce BKα mRNA, and sodium nitroprusside, a nitric oxide donor, did not alter surface BKα protein over the same time course. MG132 and bafilomycin A, proteasomal and lysosomal inhibitors, respectively, also inhibited the ANG II-induced reduction in surface and total BKα, resulting in intracellular BKα accumulation. ANG II-mediated BK channel degradation reduced BK currents in isolated myocytes and functional responses to iberiotoxin, a BK channel blocker, and NS1619, a BK activator, in pressurized (60 mmHg) cerebral arteries. These data indicate that rab4A-positive early endosomes traffic BKα to the plasma membrane in arterial myocytes. We also show that ANG II stimulates PKC-dependent BKα internalization and degradation. These data describe a unique mechanism by which ANG II inhibits arterial myocyte BK currents, by reducing surface channel number, to induce vasoconstriction.
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Affiliation(s)
- M Dennis Leo
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Simon Bulley
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - John P Bannister
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Korah P Kuruvilla
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Jonathan H Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
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15
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Abstract
There are nineteen different receptor proteins for adenosine, adenine and uridine nucleotides, and nucleotide sugars, belonging to three families of G protein-coupled adenosine and P2Y receptors, and ionotropic P2X receptors. The majority are functionally expressed in blood vessels, as purinergic receptors in perivascular nerves, smooth muscle and endothelial cells, and roles in regulation of vascular contractility, immune function and growth have been identified. The endogenous ligands for purine receptors, ATP, ADP, UTP, UDP and adenosine, can be released from different cell types within the vasculature, as well as from circulating blood cells, including erythrocytes and platelets. Many purine receptors can be activated by two or more of the endogenous ligands. Further complexity arises because of interconversion between ligands, notably adenosine formation from the metabolism of ATP, leading to complex integrated responses through activation of different subtypes of purine receptors. The enzymes responsible for this conversion, ectonucleotidases, are present on the surface of smooth muscle and endothelial cells, and may be coreleased with neurotransmitters from nerves. What selectivity there is for the actions of purines/pyrimidines comes from differential expression of their receptors within the vasculature. P2X1 receptors mediate the vasocontractile actions of ATP released as a neurotransmitter with noradrenaline (NA) from sympathetic perivascular nerves, and are located on the vascular smooth muscle adjacent to the nerve varicosities, the sites of neurotransmitter release. The relative contribution of ATP and NA as functional cotransmitters varies with species, type and size of blood vessel, neuronal firing pattern, the tone/pressure of the blood vessel, and in ageing and disease. ATP is also a neurotransmitter in non-adrenergic non-cholinergic perivascular nerves and mediates vasorelaxation via smooth muscle P2Y-like receptors. ATP and adenosine can act as neuromodulators, with the most robust evidence being for prejunctional inhibition of neurotransmission via A1 adenosine receptors, but also prejunctional excitation and inhibition of neurotransmission via P2X and P2Y receptors, respectively. P2Y2, P2Y4 and P2Y6 receptors expressed on the vascular smooth muscle are coupled to vasocontraction, and may have a role in pathophysiological conditions, when purines are released from damaged cells, or when there is damage to the protective barrier that is the endothelium. Adenosine is released during hypoxia to increase blood flow via vasodilator A2A and A2B receptors expressed on the endothelium and smooth muscle. ATP is released from endothelial cells during hypoxia and shear stress and can act at P2Y and P2X4 receptors expressed on the endothelium to increase local blood flow. Activation of endothelial purine receptors leads to the release of nitric oxide, hyperpolarising factors and prostacyclin, which inhibits platelet aggregation and thus ensures patent blood flow. Vascular purine receptors also regulate endothelial and smooth muscle growth, and inflammation, and thus are involved in the underlying processes of a number of cardiovascular diseases.
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Affiliation(s)
- Vera Ralevic
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, United Kingdom.
| | - William R Dunn
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, United Kingdom
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16
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Crystal structure of phospholipase PA2-Vb, a protease-activated receptor agonist from theTrimeresurus stejnegerisnake venom. FEBS Lett 2014; 588:4604-12. [DOI: 10.1016/j.febslet.2014.10.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 10/07/2014] [Accepted: 10/27/2014] [Indexed: 11/20/2022]
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17
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The proteome of mouse cerebral arteries. J Cereb Blood Flow Metab 2014; 34:1033-46. [PMID: 24667914 PMCID: PMC4050249 DOI: 10.1038/jcbfm.2014.52] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 02/12/2014] [Accepted: 02/28/2014] [Indexed: 12/29/2022]
Abstract
The cerebral vasculature ensures proper cerebral function by transporting oxygen, nutrients, and other substances to the brain. Distribution of oxygenated blood throughout the neuroaxis takes place at the level of the circle of Willis (CW). While morphologic and functional alterations in CW arteries and its main branches have been reported in cerebrovascular and neurodegenerative diseases, accompanying changes in protein expression profiles remain largely uncharacterized. In this study, we performed proteomics to compile a novel list of proteins present in mouse CW arteries and its ramifications. Circle of Willis arteries were surgically removed from 6-month-old wild-type mice, proteins extracted and analyzed by two proteomics approaches, gel-free nanoLC-mass spectrometry (MS)/MS and gel-based GelLC-MS/MS, using nanoAcquity UPLC coupled with ESI-LTQ Orbitrap XL. The two approaches helped maximize arterial proteome coverage. Six biologic and two technical replicates were performed. In all, 2,188 proteins with at least 2 unique high-scoring peptides were identified (6,630 proteins total). Proteins were classified according to vasoactivity, blood-brain barrier specificity, tight junction and adhesion molecules, membrane transporters/channels, and extracellular matrix/basal lamina proteins. Furthermore, we compared the identified CW arterial proteome with the published brain microvascular proteome. Our database provides a vital resource for the study of CW cerebral arterial protein expression profiles in health and disease.
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18
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Burnstock G, Ralevic V. Purinergic signaling and blood vessels in health and disease. Pharmacol Rev 2013; 66:102-92. [PMID: 24335194 DOI: 10.1124/pr.113.008029] [Citation(s) in RCA: 219] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Purinergic signaling plays important roles in control of vascular tone and remodeling. There is dual control of vascular tone by ATP released as a cotransmitter with noradrenaline from perivascular sympathetic nerves to cause vasoconstriction via P2X1 receptors, whereas ATP released from endothelial cells in response to changes in blood flow (producing shear stress) or hypoxia acts on P2X and P2Y receptors on endothelial cells to produce nitric oxide and endothelium-derived hyperpolarizing factor, which dilates vessels. ATP is also released from sensory-motor nerves during antidromic reflex activity to produce relaxation of some blood vessels. In this review, we stress the differences in neural and endothelial factors in purinergic control of different blood vessels. The long-term (trophic) actions of purine and pyrimidine nucleosides and nucleotides in promoting migration and proliferation of both vascular smooth muscle and endothelial cells via P1 and P2Y receptors during angiogenesis and vessel remodeling during restenosis after angioplasty are described. The pathophysiology of blood vessels and therapeutic potential of purinergic agents in diseases, including hypertension, atherosclerosis, ischemia, thrombosis and stroke, diabetes, and migraine, is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London NW3 2PF, UK; and Department of Pharmacology, The University of Melbourne, Australia.
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19
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Narayanan D, Bulley S, Leo MD, Burris SK, Gabrick KS, Boop FA, Jaggar JH. Smooth muscle cell transient receptor potential polycystin-2 (TRPP2) channels contribute to the myogenic response in cerebral arteries. J Physiol 2013; 591:5031-46. [PMID: 23858011 PMCID: PMC3810807 DOI: 10.1113/jphysiol.2013.258319] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 07/10/2013] [Indexed: 12/29/2022] Open
Abstract
Intravascular pressure-induced vasoconstriction is a smooth muscle cell-specific mechanism that controls systemic blood pressure and organ regional blood flow. Smooth muscle cell polycystin-1 and -2 (TRPP1 and -2) proteins modulate the myogenic response in mesenteric arteries, but involvement in other vascular beds is unclear. Here, we examined TRPP2 expression, cellular distribution, cation currents (ICat), and physiological functions in smooth muscle cells of rat and human cerebral arteries. We demonstrate that TRPP2 is the major TRPP isoform expressed in cerebral artery smooth muscle cells, with message levels higher than those of TRPP1. Arterial biotinylation and immunofluorescence indicated that TRPP2 is located primarily (∼88%) in the smooth muscle cell plasma membrane. RNA interference reduced TRPP2 expression by ∼55% compared to control, but did not alter levels of TRPP1, TRPC1, TRPC3, TRPC6, TRPM4, ANO1/TMEM16A, or voltage-dependent Ca(2+) (CaV1.2) channels, other ion channel proteins that modulate myogenic tone. Cell swelling induced by hyposmotic (250 osmol (l solution)(-1)) bath solution stimulated Gd(3+)-sensitive ICat in smooth muscle cells that were reduced by selective TRPP2 knockdown. TRPP2 knockdown did not alter myogenic tone at 20 mmHg but reduced tone between ∼28 and 39% over an intravascular pressure range between 40 and 100 mmHg. In contrast, TRPP2 knockdown did not alter depolarization-induced (60 mmol l K(+)) vasoconstriction. In summary, we show that TRPP2 is expressed in smooth muscle cells of resistance-size cerebral arteries, resides primarily in the plasma membrane, and contributes to the myogenic response. Data also suggest that TRPP2 differentially regulates the myogenic response in cerebral and mesenteric arteries.
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Affiliation(s)
- Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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20
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Dabertrand F, Nelson MT, Brayden JE. Ryanodine receptors, calcium signaling, and regulation of vascular tone in the cerebral parenchymal microcirculation. Microcirculation 2013; 20:307-16. [PMID: 23216877 PMCID: PMC3612564 DOI: 10.1111/micc.12027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 11/21/2012] [Indexed: 11/27/2022]
Abstract
The cerebral blood supply is delivered by a surface network of pial arteries and arterioles from which arise (parenchymal) arterioles that penetrate into the cortex and terminate in a rich capillary bed. The critical regulation of CBF, locally and globally, requires precise vasomotor regulation of the intracerebral microvasculature. This vascular region is anatomically unique as illustrated by the presence of astrocytic processes that envelope almost the entire basolateral surface of PAs. There are, moreover, notable functional differences between pial arteries and PAs. For example, in pial VSMCs, local calcium release events ("calcium sparks") through ryanodine receptor (RyR) channels in SR membrane activate large conductance, calcium-sensitive potassium channels to modulate vascular diameter. In contrast, VSMCs in PAs express functional RyR and BK channels, but under physiological conditions, these channels do not oppose pressure-induced vasoconstriction. Here, we summarize the roles of ryanodine receptors in the parenchymal microvasculature under physiologic and pathologic conditions, and discuss their importance in the control of CBF.
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Affiliation(s)
- Fabrice Dabertrand
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA.
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21
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Verma G, Bhatia H, Datta M. JNK1/2 regulates ER-mitochondrial Ca2+ cross-talk during IL-1β-mediated cell death in RINm5F and human primary β-cells. Mol Biol Cell 2013; 24:2058-71. [PMID: 23615449 PMCID: PMC3681707 DOI: 10.1091/mbc.e12-12-0885] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Elevated interleukin-1β (IL-1β) induces apoptosis in pancreatic β-cells through endoplasmic reticulum (ER) stress induction and subsequent c-jun-N-terminal kinase 1/2 (JNK1/2) activation. In earlier work we showed that JNK1/2 activation is initiated before ER stress and apoptotic induction in response to IL-1β. However, the detailed regulatory mechanisms are not completely understood. Because the ER is the organelle responsible for Ca(2+) handling and storage, here we examine the effects of IL-1β on cellular Ca(2+) movement and mitochondrial dysfunction and evaluate the role of JNK1/2. Our results show that in RINm5F cells and human primary β-cells, IL-1β alters mitochondrial membrane potential, mitochondrial permeability transition pore opening, ATP content, and reactive oxygen species production and these alterations are preceded by ER Ca(2+) release via IP3R channels and mitochondrial Ca(2+) uptake. All these events are prevented by JNK1/2 small interfering RNA (siRNA), indicating the mediating role of JNK1/2 in IL-1β-induced cellular alteration. This is accompanied by IL-1β-induced apoptosis, which is prevented by JNK1/2 siRNA and the IP3R inhibitor xestospongin C. This suggests a regulatory role of JNK1/2 in modulating the ER-mitochondrial-Ca(2+) axis by IL-1β in apoptotic cell death.
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Affiliation(s)
- Gaurav Verma
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110 007, India
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22
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Abstract
Myogenic tone is a fundamental aspect of vascular behavior in resistance arteries. This contractile response to changes in intravascular pressure is critically involved in blood flow autoregulation in tissues such as the brain, kidneys, and heart. Myogenic tone also helps regulate precapillary pressure and provides a level of background tone upon which vasodilator stimuli act to increase tissue perfusion when appropriate. Despite the importance of these processes in the brain, little is known about the mechanisms involved in control of myogenic tone in the cerebral microcirculation. Here, we report that pharmacological inhibition of P2Y4 and P2Y6 pyrimidine receptors nearly abolished myogenic tone in cerebral parenchymal arterioles (PAs). Molecular suppression of either P2Y4 or P2Y6 receptors using antisense oligodeoxynucleotides reduced myogenic tone by 44%±8% and 45%±7%, respectively. These results indicate that both receptor isoforms are activated by increased intravascular pressure, which enhances the activity of voltage-dependent calcium channels and increases myogenic tone in PAs. Enhancement or inhibition of ectonucleotidase activity had no effect on parenchymal arteriolar myogenic tone, indicating that this response is not mediated by local release of nucleotides, but rather may involve direct mechanical activation of P2Y receptors in the smooth muscle cells.
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23
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Schwingshackl A, Teng B, Ghosh M, Lim KG, Tigyi G, Narayanan D, Jaggar JH, Waters CM. Regulation of interleukin-6 secretion by the two-pore-domain potassium channel Trek-1 in alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2012; 304:L276-86. [PMID: 23275623 DOI: 10.1152/ajplung.00299.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We recently proposed a role for the two-pore-domain K(+) (K2P) channel Trek-1 in the regulation of cytokine release from mouse alveolar epithelial cells (AECs) by demonstrating decreased interleukin-6 (IL-6) secretion from Trek-1-deficient cells, but the underlying mechanisms remained unknown. This study was designed to investigate the mechanisms by which Trek-1 decreases IL-6 secretion. We hypothesized that Trek-1 regulates tumor necrosis factor-α (TNF-α)-induced IL-6 release via NF-κB-, p38-, and PKC-dependent pathways. We found that Trek-1 deficiency decreased IL-6 secretion from mouse and human AECs at both transcriptional and translational levels. While NF-κB/p65 phosphorylation was unchanged, p38 phosphorylation was decreased in Trek-1-deficient cells, and pharmacological inhibition of p38 decreased IL-6 secretion in control but not Trek-1-deficient cells. Similarly, pharmacological inhibition of PKC also decreased IL-6 release, and we found decreased phosphorylation of the isoforms PKC/PKDμ (Ser(744/748)), PKCθ, PKCδ, PKCα/βII, and PKCζ/λ, but not PKC/PKDμ (Ser(916)) in Trek-1-deficient AECs. Phosphorylation of PKCθ, a Ca(2+)-independent isoform, was intact in control cells but impaired in Trek-1-deficient cells. Furthermore, TNF-α did not elevate the intracellular Ca(2+) concentration in control or Trek-1-deficient cells, and removal of extracellular Ca(2+) did not impair IL-6 release. In summary, we report the expression of Trek-1 in human AECs and propose that Trek-1 deficiency may alter both IL-6 translation and transcription in AECs without affecting Ca(2+) signaling. The results of this study identify Trek-1 as a new potential target for the development of novel treatment strategies against acute lung injury.
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Affiliation(s)
- Andreas Schwingshackl
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38103, USA.
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24
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Adebiyi A, Thomas-Gatewood CM, Leo MD, Kidd MW, Neeb ZP, Jaggar JH. An elevation in physical coupling of type 1 inositol 1,4,5-trisphosphate (IP3) receptors to transient receptor potential 3 (TRPC3) channels constricts mesenteric arteries in genetic hypertension. Hypertension 2012; 60:1213-9. [PMID: 23045459 DOI: 10.1161/hypertensionaha.112.198820] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hypertension is associated with an elevation in agonist-induced vasoconstriction, but mechanisms involved require further investigation. Many vasoconstrictors bind to phospholipase C-coupled receptors, leading to an elevation in inositol 1,4,5-trisphosphate (IP(3)) that activates sarcoplasmic reticulum IP(3) receptors. In cerebral artery myocytes, IP(3) receptors release sarcoplasmic reticulum Ca(2+) and can physically couple to canonical transient receptor potential 3 (TRPC3) channels in a caveolin-1-containing macromolecular complex, leading to cation current activation that stimulates vasoconstriction. Here, we investigated mechanisms by which IP(3) receptors control vascular contractility in systemic arteries and IP(3)R involvement in elevated agonist-induced vasoconstriction during hypertension. Total and plasma membrane-localized TRPC3 protein was ≈2.7- and 2-fold higher in mesenteric arteries of spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rat controls, respectively. In contrast, IP(3)R1, TRPC1, TRPC6, and caveolin-1 expression was similar. TRPC3 expression was also similar in arteries of pre-SHRs and WKY rats. Control, IP(3)-induced and endothelin-1 (ET-1)-induced fluorescence resonance energy transfer between IP3R1 and TRPC3 was higher in SHR than WKY myocytes. IP3-induced cation current was ≈3-fold larger in SHR myocytes. Pyr3, a selective TRPC3 channel blocker, and calmodulin and IP(3) receptor binding domain peptide, an IP(3)R-TRP physical coupling inhibitor, reduced IP(3)-induced cation current and ET-1-induced vasoconstriction more in SHR than WKY myocytes and arteries. Thapsigargin, a sarcoplasmic reticulum Ca(2+)-ATPase blocker, did not alter ET-1-stimulated vasoconstriction in SHR or WKY arteries. These data indicate that ET-1 stimulates physical coupling of IP(3)R1 to TRPC3 channels in mesenteric artery myocytes, leading to vasoconstriction. Furthermore, an elevation in IP(3)R1 to TRPC3 channel molecular coupling augments ET-1-induced vasoconstriction during hypertension.
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Affiliation(s)
- Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Ave, Memphis, TN 38163, USA
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Bulley S, Neeb ZP, Burris SK, Bannister JP, Thomas-Gatewood CM, Jangsangthong W, Jaggar JH. TMEM16A/ANO1 channels contribute to the myogenic response in cerebral arteries. Circ Res 2012; 111:1027-36. [PMID: 22872152 DOI: 10.1161/circresaha.112.277145] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE Pressure-induced arterial depolarization and constriction (the myogenic response) is a smooth muscle cell (myocyte)-specific mechanism that controls regional organ blood flow and systemic blood pressure. Several different nonselective cation channels contribute to pressure-induced depolarization, but signaling mechanisms involved are unclear. Similarly uncertain is the contribution of anion channels to the myogenic response and physiological functions and mechanisms of regulation of recently discovered transmembrane 16A (TMEM16A), also termed Anoctamin 1, chloride (Cl(-)) channels in arterial myocytes. OBJECTIVE To investigate the hypothesis that myocyte TMEM16A channels control membrane potential and contractility and contribute to the myogenic response in cerebral arteries. METHODS AND RESULTS Cell swelling induced by hyposmotic bath solution stimulated Cl(-) currents in arterial myocytes that were blocked by TMEM16A channel inhibitory antibodies, RNAi-mediated selective TMEM16A channel knockdown, removal of extracellular calcium (Ca(2+)), replacement of intracellular EGTA with BAPTA, a fast Ca(2+) chelator, and Gd(3+) and SKF-96365, nonselective cation channel blockers. In contrast, nimodipine, a voltage-dependent Ca(2+) channel inhibitor, or thapsigargin, which depletes intracellular Ca(2+) stores, did not alter swelling-activated TMEM16A currents. Pressure-induced (-40 mm Hg) membrane stretch activated ion channels in arterial myocyte cell-attached patches that were inhibited by TMEM16A antibodies and were of similar amplitude to recombinant TMEM16A channels. TMEM16A knockdown reduced intravascular pressure-induced depolarization and vasoconstriction but did not alter depolarization-induced (60 mmol/L K(+)) vasoconstriction. CONCLUSIONS Membrane stretch activates arterial myocyte TMEM16A channels, leading to membrane depolarization and vasoconstriction. Data also provide a mechanism by which a local Ca(2+) signal generated by nonselective cation channels stimulates TMEM16A channels to induce myogenic constriction.
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Affiliation(s)
- Simon Bulley
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Narayanan D, Adebiyi A, Jaggar JH. Inositol trisphosphate receptors in smooth muscle cells. Am J Physiol Heart Circ Physiol 2012; 302:H2190-210. [PMID: 22447942 DOI: 10.1152/ajpheart.01146.2011] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are a family of tetrameric intracellular calcium (Ca(2+)) release channels that are located on the sarcoplasmic reticulum (SR) membrane of virtually all mammalian cell types, including smooth muscle cells (SMC). Here, we have reviewed literature investigating IP(3)R expression, cellular localization, tissue distribution, activity regulation, communication with ion channels and organelles, generation of Ca(2+) signals, modulation of physiological functions, and alterations in pathologies in SMCs. Three IP(3)R isoforms have been identified, with relative expression and cellular localization of each contributing to signaling differences in diverse SMC types. Several endogenous ligands, kinases, proteins, and other modulators control SMC IP(3)R channel activity. SMC IP(3)Rs communicate with nearby ryanodine-sensitive Ca(2+) channels and mitochondria to influence SR Ca(2+) release and reactive oxygen species generation. IP(3)R-mediated Ca(2+) release can stimulate plasma membrane-localized channels, including transient receptor potential (TRP) channels and store-operated Ca(2+) channels. SMC IP(3)Rs also signal to other proteins via SR Ca(2+) release-independent mechanisms through physical coupling to TRP channels and local communication with large-conductance Ca(2+)-activated potassium channels. IP(3)R-mediated Ca(2+) release generates a wide variety of intracellular Ca(2+) signals, which vary with respect to frequency, amplitude, spatial, and temporal properties. IP(3)R signaling controls multiple SMC functions, including contraction, gene expression, migration, and proliferation. IP(3)R expression and cellular signaling are altered in several SMC diseases, notably asthma, atherosclerosis, diabetes, and hypertension. In summary, IP(3)R-mediated pathways control diverse SMC physiological functions, with pathological alterations in IP(3)R signaling contributing to disease.
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Affiliation(s)
- Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, 38163, USA
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Westcott EB, Goodwin EL, Segal SS, Jackson WF. Function and expression of ryanodine receptors and inositol 1,4,5-trisphosphate receptors in smooth muscle cells of murine feed arteries and arterioles. J Physiol 2012; 590:1849-69. [PMID: 22331418 DOI: 10.1113/jphysiol.2011.222083] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We tested the hypothesis that vasomotor control is differentially regulated between feed arteries and downstream arterioles from the cremaster muscle of C57BL/6 mice. In isolated pressurized arteries, confocal Ca(2+) imaging of smooth muscle cells (SMCs) revealed Ca(2+) sparks and Ca(2+) waves. Ryanodine receptor (RyR) antagonists (ryanodine and tetracaine) inhibited both sparks and waves but increased global Ca(2+) and myogenic tone. In arterioles, SMCs exhibited only Ca(2+) waves that were insensitive to ryanodine or tetracaine. Pharmacological interventions indicated that RyRs are functionally coupled to large-conductance, Ca(2+)-activated K(+) channels (BK(Ca)) in SMCs of arteries, whereas BK(Ca) appear functionally coupled to voltage-gated Ca2+ channels in SMCs of arterioles. Inositol 1,4,5-trisphosphate receptor (IP3R) antagonists (xestospongin D or 2-aminoethoxydiphenyl borate) or a phospholipase C inhibitor (U73122) attenuated Ca(2+) waves, global Ca(2+) and myogenic tone in arteries and arterioles but had no effect on arterial sparks. Real-time PCR of isolated SMCs revealed RyR2 as the most abundant isoform transcript; arteries expressed twice the RyR2 but only 65% the RyR3 of arterioles and neither vessel expressed RyR1. Immunofluorescent localisation of RyR protein indicated bright, clustered staining of arterial SMCs in contrast to diffuse staining in arteriolar SMCs. Expression of IP(3)R transcripts and protein immunofluorescence were similar in SMCs of both vessels with IP(3)R1>>IP(3)R2>IP(3)R3. Despite similar expression of IP(3)Rs and dependence of Ca(2+) waves on IP(3)Rs, these data illustrate pronounced regional heterogeneity in function and expression of RyRs between SMCs of the same vascular resistance network. We conclude that vasomotor control is differentially regulated in feed arteries vs. downstream arterioles.
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Affiliation(s)
- Erika B Westcott
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Thomas-Gatewood C, Neeb ZP, Bulley S, Adebiyi A, Bannister JP, Leo MD, Jaggar JH. TMEM16A channels generate Ca²⁺-activated Cl⁻ currents in cerebral artery smooth muscle cells. Am J Physiol Heart Circ Physiol 2011; 301:H1819-27. [PMID: 21856902 DOI: 10.1152/ajpheart.00404.2011] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transmembrane protein (TMEM)16A channels are recently discovered membrane proteins that display electrophysiological properties similar to classic Ca(2+)-activated Cl(-) (Cl(Ca)) channels in native cells. The molecular identity of proteins that generate Cl(Ca) currents in smooth muscle cells (SMCs) of resistance-size arteries is unclear. Similarly, whether cerebral artery SMCs generate Cl(Ca) currents is controversial. Here, using molecular biology and patch-clamp electrophysiology, we examined TMEM16A channel expression and characterized Cl(-) currents in arterial SMCs of resistance-size rat cerebral arteries. RT-PCR amplified transcripts for TMEM16A but not TMEM16B-TMEM16H, TMEM16J, or TMEM16K family members in isolated pure cerebral artery SMCs. Western blot analysis using an antibody that recognized recombinant (r)TMEM16A channels detected TMEM16A protein in cerebral artery lysates. Arterial surface biotinylation and immunofluorescence indicated that TMEM16A channels are located primarily within the arterial SMC plasma membrane. Whole cell Cl(Ca) currents in arterial SMCs displayed properties similar to those generated by rTMEM16A channels, including Ca(2+) dependence, current-voltage relationship linearization by an elevation in intracellular Ca(2+) concentration, a Nerstian shift in reversal potential induced by reducing the extracellular Cl(-) concentration, and a negative reversal potential shift when substituting extracellular I(-) for Cl(-). A pore-targeting TMEM16A antibody similarly inhibited both arterial SMC Cl(Ca) and rTMEM16A currents. TMEM16A knockdown using small interfering RNA also inhibited arterial SMC Cl(Ca) currents. In summary, these data indicate that TMEM16A channels are expressed, insert into the plasma membrane, and generate Cl(Ca) currents in cerebral artery SMCs.
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Affiliation(s)
- Candice Thomas-Gatewood
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Adebiyi A, McNally EM, Jaggar JH. Vasodilation induced by oxygen/glucose deprivation is attenuated in cerebral arteries of SUR2 null mice. Am J Physiol Heart Circ Physiol 2011; 301:H1360-8. [PMID: 21784985 DOI: 10.1152/ajpheart.00406.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Physiological functions of arterial smooth muscle cell ATP-sensitive K(+) (K(ATP)) channels, which are composed of inwardly rectifying K(+) channel 6.1 and sulfonylurea receptor (SUR)-2 subunits, during metabolic inhibition are unresolved. In the present study, we used a genetic model to investigate the physiological functions of SUR2-containing K(ATP) channels in mediating vasodilation to hypoxia, oxygen and glucose deprivation (OGD) or metabolic inhibition, and functional recovery following these insults. Data indicate that SUR2B is the only SUR isoform expressed in murine cerebral artery smooth muscle cells. Pressurized SUR2 wild-type (SUR2(wt)) and SUR2 null (SUR2(nl)) mouse cerebral arteries developed similar levels of myogenic tone and dilated similarly to hypoxia (<10 mmHg Po(2)). In contrast, vasodilation induced by pinacidil, a K(ATP) channel opener, was ∼71% smaller in SUR2(nl) arteries. Human cerebral arteries also expressed SUR2B, developed myogenic tone, and dilated in response to hypoxia and pinacidil. OGD, oligomycin B (a mitochondrial ATP synthase blocker), and CCCP (a mitochondrial uncoupler) all induced vasodilations that were ∼39-61% smaller in SUR2(nl) than in SUR2(wt) arteries. The restoration of oxygen and glucose following OGD or removal of oligomycin B and CCCP resulted in partial recovery of tone in both SUR2(wt) and SUR2(nl) cerebral arteries. However, SUR(nl) arteries regained ∼60-82% more tone than did SUR2(wt) arteries. These data indicate that SUR2-containing K(ATP) channels are functional molecular targets for OGD, but not hypoxic, vasodilation in cerebral arteries. In addition, OGD activation of SUR2-containing K(ATP) channels may contribute to postischemic loss of myogenic tone.
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Affiliation(s)
- Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Mujica PE, González FG. Interaction between IP3 receptors and BK channels in arterial smooth muscle: non-canonical IP3 signaling at work. J Gen Physiol 2011; 137:473-7. [PMID: 21482693 PMCID: PMC3082923 DOI: 10.1085/jgp.201110607] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Patricio E. Mujica
- Graduate School of Biomedical Sciences, Newark Division, and Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07101
- Graduate School of Biomedical Sciences, Newark Division, and Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07101
| | - Francisco G. González
- Graduate School of Biomedical Sciences, Newark Division, and Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07101
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Bannister JP, Thomas-Gatewood CM, Neeb ZP, Adebiyi A, Cheng X, Jaggar JH. Ca(V)1.2 channel N-terminal splice variants modulate functional surface expression in resistance size artery smooth muscle cells. J Biol Chem 2011; 286:15058-66. [PMID: 21357696 DOI: 10.1074/jbc.m110.182816] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Voltage-dependent Ca(2+) (Ca(V)1.2) channels are the primary Ca(2+) influx pathway in arterial smooth muscle cells and are essential for contractility regulation by a variety of stimuli, including intravascular pressure. Arterial smooth muscle cell Ca(V)1.2 mRNA is alternatively spliced at exon 1 (e1), generating e1b or e1c variants, with e1c exhibiting relatively smooth muscle-specific expression in the cardiovascular system. Here, we examined physiological functions of Ca(V)1.2e1 variants and tested the hypothesis that targeting Ca(V)1.2e1 modulates resistance size cerebral artery contractility. Custom antibodies that selectively recognize Ca(V)1.2 channel proteins containing sequences encoded by either e1b (Ca(V)1.2e1b) or e1c (Ca(V)1.2e1c) both detected Ca(V)1.2 in rat and human cerebral arteries. shRNA targeting e1b or e1c reduced expression of that Ca(V)1.2 variant, induced compensatory up-regulation of the other variant, decreased total Ca(V)1.2, and reduced intravascular pressure- and depolarization-induced vasoconstriction. Ca(V)1.2e1b and Ca(V)1.2e1c knockdown reduced whole cell Ca(V)1.2 currents, with Ca(V)1.2e1c knockdown most effectively reducing total Ca(V)1.2 and inducing the largest vasodilation. Knockdown of α(2)δ-1, a Ca(V)1.2 auxiliary subunit, reduced surface expression of both Ca(V)1.2e1 variants, inhibiting Ca(V)1.2e1c more than Ca(V)1.2e1b. e1b or e1c overexpression reduced Ca(V)1.2 surface expression and whole cell currents, leading to vasodilation, with e1c overexpression inducing the largest effect. In summary, data indicate that arterial smooth muscle cells express Ca(V)1.2 channels containing e1b or e1c-encoded N termini that contribute to Ca(V)1.2 surface expression, α(2)δ-1 preferentially traffics the Ca(V)1.2e1c variant to the plasma membrane, and targeting of Ca(V)1.2e1 message or the Ca(V)1.2 channel proximal N terminus induces vasodilation.
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Affiliation(s)
- John P Bannister
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Westcott EB, Jackson WF. Heterogeneous function of ryanodine receptors, but not IP3 receptors, in hamster cremaster muscle feed arteries and arterioles. Am J Physiol Heart Circ Physiol 2011; 300:H1616-30. [PMID: 21357503 DOI: 10.1152/ajpheart.00728.2010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The roles played by ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP₃Rs) in vascular smooth muscle in the microcirculation remain unclear. Therefore, the function of both RyRs and IP₃Rs in Ca(²+) signals and myogenic tone in hamster cremaster muscle feed arteries and downstream arterioles were assessed using confocal imaging and pressure myography. Feed artery vascular smooth muscle displayed Ca(²+) sparks and Ca(²+) waves, which were inhibited by the RyR antagonists ryanodine (10 μM) or tetracaine (100 μM). Despite the inhibition of sparks and waves, ryanodine or tetracaine increased global intracellular Ca(²+) and constricted the arteries. The blockade of IP₃Rs with xestospongin D (5 μM) or 2-aminoethoxydiphenyl borate (100 μM) or the inhibition of phospholipase C using U-73122 (10 μM) also attenuated Ca(2+) waves without affecting Ca(²+) sparks. Importantly, the IP₃Rs and phospholipase C antagonists decreased global intracellular Ca(2+) and dilated the arteries. In contrast, cremaster arterioles displayed only Ca(²+) waves: Ca(²+) sparks were not observed, and neither ryanodine (10-50 μM) nor tetracaine (100 μM) affected either Ca(²+) signals or arteriolar tone despite the presence of functional RyRs as assessed by responses to the RyR agonist caffeine (10 mM). As in feed arteries, arteriolar Ca(²+) waves were attenuated by xestospongin D (5 μM), 2-aminoethoxydiphenyl borate (100 μM), and U-73122 (10 μM), accompanied by decreased global intracellular Ca(²+) and vasodilation. These findings highlight the contrasting roles played by RyRs and IP₃Rs in Ca(²+) signals and myogenic tone in feed arteries and demonstrate important differences in the function of RyRs between feed arteries and downstream arterioles.
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Affiliation(s)
- Erika B Westcott
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA.
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Albert AP. Gating Mechanisms of Canonical Transient Receptor Potential Channel Proteins: Role of Phosphoinositols and Diacylglycerol. TRANSIENT RECEPTOR POTENTIAL CHANNELS 2011; 704:391-411. [DOI: 10.1007/978-94-007-0265-3_22] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Adebiyi A, Narayanan D, Jaggar JH. Caveolin-1 assembles type 1 inositol 1,4,5-trisphosphate receptors and canonical transient receptor potential 3 channels into a functional signaling complex in arterial smooth muscle cells. J Biol Chem 2010; 286:4341-8. [PMID: 21098487 DOI: 10.1074/jbc.m110.179747] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Physical coupling of sarcoplasmic reticulum (SR) type 1 inositol 1,4,5-trisphosphate receptors (IP(3)R1) to plasma membrane canonical transient receptor potential 3 (TRPC3) channels activates a cation current (I(Cat)) in arterial smooth muscle cells that induces vasoconstriction. However, structural components that enable IP(3)R1 and TRPC3 channels to communicate locally are unclear. Caveolae are plasma membrane microdomains that can compartmentalize proteins. Here, we tested the hypothesis that caveolae and specifically caveolin-1 (cav-1), a caveolae scaffolding protein, facilitate functional IP(3)R1 to TRPC3 coupling in smooth muscle cells of resistance-size cerebral arteries. Methyl-β-cyclodextrin (MβCD), which disassembles caveolae, reduced IP(3)-induced I(Cat) activation in smooth muscle cells and vasoconstriction in pressurized arteries. Cholesterol replenishment reversed these effects. Cav-1 knockdown using shRNA attenuated IP(3)-induced vasoconstriction, but did not alter TRPC3 and IP(3)R1 expression. A synthetic peptide corresponding to the cav-1 scaffolding domain (CSD) sequence (amino acids 82-101) also attenuated IP(3)-induced I(Cat) activation and vasoconstriction. A cav-1 antibody co-immunoprecipitated cav-1, TRPC3, and IP(3)R1 from cerebral artery lysate. ImmunoFRET indicated that cav-1, TRPC3 channels and IP(3)R1 are spatially co-localized in arterial smooth muscle cells. IP(3)R1 and TRPC3 channel spatial localization was disrupted by MβCD and a CSD peptide. Cholesterol replenishment re-established IP(3)R1 and TRPC3 channel close spatial proximity. Taken together, these data indicate that in arterial smooth muscle cells, cav-1 co-localizes SR IP(3)R1 and plasma membrane TRPC3 channels in close spatial proximity thereby enabling IP(3)-induced physical coupling of these proteins, leading to I(Cat) generation and vasoconstriction.
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Affiliation(s)
- Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Zhao G, Neeb ZP, Leo MD, Pachuau J, Adebiyi A, Ouyang K, Chen J, Jaggar JH. Type 1 IP3 receptors activate BKCa channels via local molecular coupling in arterial smooth muscle cells. ACTA ACUST UNITED AC 2010; 136:283-91. [PMID: 20713546 PMCID: PMC2931145 DOI: 10.1085/jgp.201010453] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Plasma membrane large-conductance Ca2+-activated K+ (BKCa) channels and sarcoplasmic reticulum inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are expressed in a wide variety of cell types, including arterial smooth muscle cells. Here, we studied BKCa channel regulation by IP3 and IP3Rs in rat and mouse cerebral artery smooth muscle cells. IP3 activated BKCa channels both in intact cells and in excised inside-out membrane patches. IP3 caused concentration-dependent BKCa channel activation with an apparent dissociation constant (Kd) of ∼4 µM at physiological voltage (−40 mV) and intracellular Ca2+ concentration ([Ca2+]i; 10 µM). IP3 also caused a leftward-shift in BKCa channel apparent Ca2+ sensitivity and reduced the Kd for free [Ca2+]i from ∼20 to 12 µM, but did not alter the slope or maximal Po. BAPTA, a fast Ca2+ buffer, or an elevation in extracellular Ca2+ concentration did not alter IP3-induced BKCa channel activation. Heparin, an IP3R inhibitor, and a monoclonal type 1 IP3R (IP3R1) antibody blocked IP3-induced BKCa channel activation. Adenophostin A, an IP3R agonist, also activated BKCa channels. IP3 activated BKCa channels in inside-out patches from wild-type (IP3R1+/+) mouse arterial smooth muscle cells, but had no effect on BKCa channels of IP3R1-deficient (IP3R1−/−) mice. Immunofluorescence resonance energy transfer microscopy indicated that IP3R1 is located in close spatial proximity to BKCa α subunits. The IP3R1 monoclonal antibody coimmunoprecipitated IP3R1 and BKCa channel α and β1 subunits from cerebral arteries. In summary, data indicate that IP3R1 activation elevates BKCa channel apparent Ca2+ sensitivity through local molecular coupling in arterial smooth muscle cells.
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Affiliation(s)
- Guiling Zhao
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Vaithianathan T, Narayanan D, Asuncion-Chin MT, Jeyakumar LH, Liu J, Fleischer S, Jaggar JH, Dopico AM. Subtype identification and functional characterization of ryanodine receptors in rat cerebral artery myocytes. Am J Physiol Cell Physiol 2010; 299:C264-78. [PMID: 20445169 PMCID: PMC2928634 DOI: 10.1152/ajpcell.00318.2009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 05/04/2010] [Indexed: 11/22/2022]
Abstract
Ryanodine receptors (RyRs) regulate contractility in resistance-size cerebral artery smooth muscle, yet their molecular identity, subcellular location, and phenotype in this tissue remain unknown. Following rat resistance-size cerebral artery myocyte sarcoplasmic reticulum (SR) purification and incorporation into POPE-POPS-POPC (5:3:2; wt/wt) bilayers, unitary conductances of 110 +/- 8, 334 +/- 15, and 441 +/- 27 pS in symmetric 300 mM Cs(+) were usually detected. The most frequent (34/40 bilayers) conductance (334 pS) decreased to
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Affiliation(s)
- Thirumalini Vaithianathan
- Department Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Abstract
The substantia nigra pars reticulata (SNr) is a key basal ganglia output nucleus critical for movement control. A hallmark of the SNr gamma-aminobutyric acid (GABA)-containing projection neurons is their depolarized membrane potential, accompanied by rapid spontaneous spikes. Parkinsonian movement disorders are often associated with abnormalities in SNr GABA neuron firing intensity and/or pattern. A fundamental question is the molecular identity of the ion channels that drive these neurons to a depolarized membrane potential. Recent data show that SNr GABA projection neurons selectively express type 3 canonical transient receptor potential (TRPC3) channels. Such channels are tonically active and mediate an inward, Na(+)-dependent current, leading to a substantial depolarization and ensuring appropriate firing intensity and pattern in SNr GABA projection neurons. Equally important, TRPC3 channels in SNr GABA neurons are up-regulated by dopamine (DA) released from neighboring nigral DA neuron dendrites. Co-activation of D1 and D5 DA receptors leads to a TRPC3 channel-mediated inward current and increased firing in SNr GABA neurons, whereas D1-like receptor blockade reduces SNr GABA neuron firing frequency and increases their firing irregularity. TRPC3 channels serve as the effector channels mediating an ultra-short SNc-->SNr DA pathway that regulates the firing intensity and pattern of the basal ganglia output neurons.
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Affiliation(s)
- Fu-Ming Zhou
- Department of Pharmacology, University of Tennessee College of Medicine, Memphis TN 38163, USA.
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Narayanan D, Xi Q, Pfeffer LM, Jaggar JH. Mitochondria control functional CaV1.2 expression in smooth muscle cells of cerebral arteries. Circ Res 2010; 107:631-41. [PMID: 20616314 DOI: 10.1161/circresaha.110.224345] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RATIONALE Physiological functions of mitochondria in contractile arterial myocytes are poorly understood. Mitochondria can uptake calcium (Ca(2+)), but intracellular Ca(2+) signals that regulate mitochondrial Ca(2+) concentration ([Ca(2+)](mito)) and physiological functions of changes in [Ca(2+)](mito) in arterial myocytes are unclear. OBJECTIVE To identify Ca(2+) signals that regulate [Ca(2+)](mito), examine the significance of changes in [Ca(2+)](mito), and test the hypothesis that [Ca(2+)](mito) controls functional ion channel transcription in myocytes of resistance-size cerebral arteries. METHODS AND RESULTS Endothelin (ET)-1 activated Ca(2+) waves and elevated global Ca(2+) concentration ([Ca(2+)](i)) via inositol 1,4,5-trisphosphate receptor (IP(3)R) activation. IP(3)R-mediated sarcoplasmic reticulum (SR) Ca(2+) release increased [Ca(2+)](mito) and induced mitochondrial depolarization, which stimulated mitochondrial reactive oxygen species (mitoROS) generation that elevated cytosolic ROS. In contrast, a global [Ca(2+)](i) elevation did not alter [Ca(2+)](mito), mitochondrial potential, or mitoROS generation. ET-1 stimulated nuclear translocation of nuclear factor (NF)-kappaB p50 subunit and ET-1-induced IP(3)R-mediated mitoROS elevated NF-kappaB-dependent transcriptional activity. ET-1 elevated voltage-dependent Ca(2+) (Ca(V)1.2) channel expression, leading to an increase in both pressure (myogenic tone)- and depolarization-induced vasoconstriction. Baseline Ca(V)1.2 expression and the ET-1-induced elevation in Ca(V)1.2 expression were both reduced by IP(3)R inhibition, mitochondrial electron transport chain block, antioxidant treatment, and NF-kappaB subunit knockdown, leading to vasodilation. CONCLUSIONS IP(3)R-mediated SR Ca(2+) release elevates [Ca(2+)](mito), which induces mitoROS generation. MitoROS activate NF-kappaB, which stimulates Ca(V)1.2 channel transcription. Thus, mitochondria sense IP(3)R-mediated SR Ca(2+) release to control NF-kappaB-dependent Ca(V)1.2 channel expression in arterial myocytes, thereby modulating arterial contractility.
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Affiliation(s)
- Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Avenue, Memphis TN 38163, USA
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Adebiyi A, Zhao G, Narayanan D, Thomas-Gatewood CM, Bannister JP, Jaggar JH. Isoform-selective physical coupling of TRPC3 channels to IP3 receptors in smooth muscle cells regulates arterial contractility. Circ Res 2010; 106:1603-12. [PMID: 20378853 DOI: 10.1161/circresaha.110.216804] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Inositol 1,4,5-trisphosphate (IP(3))-induced vasoconstriction can occur independently of intracellular Ca(2+) release and via IP(3) receptor (IP(3)R) and canonical transient receptor potential (TRPC) channel activation, but functional signaling mechanisms mediating this effect are unclear. OBJECTIVES Study mechanisms by which IP(3)Rs stimulate TRPC channels in myocytes of resistance-size cerebral arteries. METHODS AND RESULTS Immunofluorescence resonance energy transfer (immuno-FRET) microscopy using isoform-selective antibodies indicated that endogenous type 1 IP(3)Rs (IP(3)R1) are in close spatial proximity to TRPC3, but distant from TRPC6 or TRPM4 channels in arterial myocytes. Endothelin-1 (ET-1), a phospholipase C-coupled receptor agonist, elevated immuno-FRET between IP(3)R1 and TRPC3, but not between IP(3)R1 and TRPC6 or TRPM4. TRPC3, but not TRPC6, coimmunoprecipitated with IP(3)R1. TRPC3 and TRPC6 antibodies selectively inhibited recombinant channels, but only the TRPC3 antibody blocked IP(3)-induced nonselective cation current (I(Cat)) in myocytes. TRPC3 knockdown attenuated immuno-FRET between IP(3)R1 and TRPC3, IP(3)-induced I(Cat) activation, and ET-1 and IP(3)-induced vasoconstriction, whereas TRPC6 channel knockdown had no effect. ET-1 did not alter total or plasma membrane-localized TRPC3, as determined using surface biotinylation. RT-PCR demonstrated that C-terminal calmodulin and IP(3)R binding (CIRB) domains are present in myocyte TRPC3 and TRPC6 channels. A peptide corresponding to the IP(3)R N-terminal region that can interact with TRPC channels activated I(Cat). A TRPC3 CIRB domain peptide attenuated IP(3)- and ET-1-induced I(Cat) activation and vasoconstriction. CONCLUSIONS IP(3) stimulates direct coupling between IP(3)R1 and membrane-resident TRPC3 channels in arterial myocytes, leading to I(Cat) activation and vasoconstriction. Close spatial proximity between IP(3)R1 and TRPC3 establishes this isoform-selective functional interaction.
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Affiliation(s)
- Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38139, USA
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Toll-like receptor 4 mediates neutrophil sequestration and lung injury induced by endotoxin and hyperinflation. Crit Care Med 2010; 38:194-201. [PMID: 19789446 DOI: 10.1097/ccm.0b013e3181bc7c17] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To address the role of Toll-like receptor 4 signaling in mediating neutrophil recruitment and lung injury induced by lipopolysaccharide challenge coupled to lung hyperinflation, using Toll-like receptor 4 knockout (tlr4) mice. Infiltration of polymorphonuclear neutrophils into the lung is an important feature of ventilator-induced lung injury associated with pneumonia, but the mechanisms involved in neutrophil recruitment are poorly understood. DESIGN Experimental animal model. SETTING University laboratory. SUBJECTS tlr4 and wild-type C57BL/6 mice. INTERVENTIONS Wild-type or tlr4 mice were challenged by intratracheal instillation of lipopolysaccharide (0.3 mg/kg) for 2 hrs and then subjected to normal (7 mL/kg) or high (28 mL/kg) tidal volume ventilation for another 2 hrs. In other studies, neutrophils from wild-type or tlr4 mice were pretreated with lipopolysaccharide for 30 mins and then infused into the isolated lung preparation for 30 mins as the lungs were ventilated with 25 cm H2O peak inspiratory pressure. MEASUREMENTS AND MAIN RESULTS Lipopolysaccharide-challenged wild-type mice ventilated with a 28 mL/kg tidal volume exhibited 12-fold increase in neutrophil sequestration, 6-fold increase in bronchoalveolar lavage albumin concentration, and 1.6-fold increase in lung water content compared with unchallenged mice exposed to normal tidal volume ventilation. However, tlr4 mice showed negligible neutrophil sequestration, microvascular barrier breakdown, or edema formation. Mechanical ventilation alone or combined with lipopolysaccharide caused activation of circulating neutrophils and pulmonary endothelium in wild-type mice, whereas this was prevented in tlr4 mice. CONCLUSIONS High tidal volume ventilation during pneumonia/sepsis induces lung neutrophil sequestration and injury via the Toll-like receptor 4-dependent signaling pathway. The results suggest an important role of Toll-like receptor 4 in the mechanism of lung neutrophil sequestration and acute lung injury when pneumonia/sepsis is coupled to lung hyperinflation.
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Katakam PVG, Domoki F, Lenti L, Gáspár T, Institoris A, Snipes JA, Busija DW. Cerebrovascular responses to insulin in rats. J Cereb Blood Flow Metab 2009; 29:1955-67. [PMID: 19724283 PMCID: PMC2814524 DOI: 10.1038/jcbfm.2009.177] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Effects of insulin on cerebral arteries have never been examined. Therefore, we determined cerebrovascular actions of insulin in rats. Both PCR and immunoblot studies identified insulin receptor expression in cerebral arteries and in cultured cerebral microvascular endothelial cells (CMVECs). Diameter measurements (% change) of isolated rat cerebral arteries showed a biphasic dose response to insulin with an initial vasoconstriction at 0.1 ng/mL (-9.7%+/-1.6%), followed by vasodilation at 1 to 100 ng/mL (31.9%+/-1.4%). Insulin also increased cortical blood flow in vivo (30%+/-8% at 120 ng/mL) when applied topically. Removal of reactive oxygen species (ROS) abolished the vasoconstriction to insulin. Endothelial denudation, inhibition of K(+) channels, and nitric oxide (NO) synthase, all diminished insulin-induced vasodilation. Inhibition of cytochrome P450 enhanced vasodilation in endothelium-intact arteries, but promoted vasoconstriction after endothelial denudation. Inhibition of cyclooxygenase abolished vasoconstriction and enhanced vasodilation to insulin in all arteries. Inhibition of endothelin type A receptors enhanced vasodilation, whereas endothelin type B receptor blockade diminished vasodilation. Insulin treatment in vitro increased Akt phosphorylation in cerebral arteries and CMVECs. Fluorescence studies of CMVECs showed that insulin increased intracellular calcium and enhanced the generation of NO and ROS. Thus, cerebrovascular responses to insulin were mediated by complex mechanisms originating in both the endothelium and smooth muscle.
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Bannister JP, Adebiyi A, Zhao G, Narayanan D, Thomas CM, Feng JY, Jaggar JH. Smooth muscle cell alpha2delta-1 subunits are essential for vasoregulation by CaV1.2 channels. Circ Res 2009; 105:948-55. [PMID: 19797702 DOI: 10.1161/circresaha.109.203620] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Voltage-dependent L-type (Ca(V)1.2) Ca(2+) channels are a heteromeric complex formed from pore-forming alpha(1) and auxiliary alpha(2)delta and beta subunits. Ca(V)1.2 channels are the principal Ca(2+) influx pathway in arterial myocytes and regulate multiple physiological functions, including contraction. The macromolecular composition of arterial myocyte Ca(V)1.2 channels remains poorly understood, with no studies having examined the molecular identity or physiological functions of alpha(2)delta subunits. OBJECTIVE We investigated the functional significance of alpha(2)delta subunits in myocytes of resistance-size (100 to 200 mum diameter) cerebral arteries. METHODS AND RESULTS alpha(2)delta-1 was the only alpha(2)delta isoform expressed in cerebral artery myocytes. Pregabalin, an alpha(2)delta-1/-2 ligand, and an alpha(2)delta-1 antibody, inhibited Ca(V)1.2 currents in isolated myocytes. Acute pregabalin application reversibly dilated pressurized arteries. Using a novel application of surface biotinylation, data indicated that >95% of Ca(V)1.2 alpha(1) and alpha(2)delta-1 subunits were present in the arterial myocyte plasma membrane. Alpha(2)delta-1 knockdown using short hairpin RNA reduced plasma membrane-localized Ca(V)1.2 alpha(1) subunits, caused a corresponding elevation in cytosolic Ca(V)1.2 alpha(1) subunits, decreased intracellular Ca(2+) concentration, inhibited pressure-induced vasoconstriction ("myogenic tone"), and attenuated pregabalin-induced vasodilation. Prolonged (24-hour) pregabalin exposure did not alter total alpha(2)delta-1 or Ca(V)1.2 alpha(1) proteins but decreased plasma membrane expression of each subunit, which reduced myogenic tone. CONCLUSIONS alpha(2)delta-1 is essential for plasma membrane expression of arterial myocyte Ca(V)1.2 alpha(1) subunits. alpha(2)delta-1 targeting can block Ca(V)1.2 channels directly and inhibit surface expression of Ca(V)1.2 alpha(1) subunits, leading to vasodilation. These data identify alpha(2)delta-1 as a novel molecular target in arterial myocytes, the manipulation of which regulates contractility.
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Affiliation(s)
- John P Bannister
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Abstract
Substantia nigra pars reticulata (SNr) is a key basal ganglia output nucleus critical for movement control. Its GABA-containing projection neurons intermingle with nigral dopamine (DA) neuron dendrites. Here we show that SNr GABA neurons coexpress dopamine D(1) and D(5) receptor mRNAs and also mRNA for TRPC3 channels. Dopamine induced an inward current in these neurons and increased their firing frequency. These effects were mimicked by D(1)-like agonists, blocked by a D(1)-like antagonist. D(1)-like receptor blockade reduced SNr GABA neuron firing frequency and increased their firing irregularity. These D(1)-like effects were absent in D(1) or D(5) receptor knock-out mice and inhibited by intracellularly applied D(1) or D(5) receptor antibody. These D(1)-like effects were also inhibited when the tonically active TRPC3 channels were inhibited by intracellularly applied TRPC3 channel antibody. Furthermore, stimulation of DA neurons induced a direct inward current in SNr GABA neurons that was sensitive to D(1)-like blockade. Manipulation of DA neuron activity and DA release and inhibition of dopamine reuptake affected SNr GABA neuron activity in a D(1)-like receptor-dependent manner. Together, our findings indicate that dendritically released dopamine tonically excites SNr GABA neurons via D(1)-D(5) receptor coactivation that enhances constitutively active TRPC3 channels, forming an ultra-short substantia nigra pars compacta --> SNr dopamine pathway that regulates the firing intensity and pattern of these basal ganglia output neurons.
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