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Ferris HR, Stine NC, Hill-Eubanks DC, Nelson MT, Wellman GC, Koide M. Epidermal Growth Factor Receptors in Vascular Endothelial Cells Contribute to Functional Hyperemia in the Brain. Int J Mol Sci 2023; 24:16284. [PMID: 38003472 PMCID: PMC10671586 DOI: 10.3390/ijms242216284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/06/2023] [Accepted: 11/12/2023] [Indexed: 11/26/2023] Open
Abstract
Functional hyperemia-activity-dependent increases in local blood perfusion-underlies the on-demand delivery of blood to regions of enhanced neuronal activity, a process that is crucial for brain health. Importantly, functional hyperemia deficits have been linked to multiple dementia risk factors, including aging, chronic hypertension, and cerebral small vessel disease (cSVD). We previously reported crippled functional hyperemia in a mouse model of genetic cSVD that was likely caused by depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) in capillary endothelial cells (EC) downstream of impaired epidermal growth factor receptor (EGFR) signaling. Here, using EC-specific EGFR-knockout (KO) mice, we directly examined the role of endothelial EGFR signaling in functional hyperemia, assessed by measuring increases in cerebral blood flow in response to contralateral whisker stimulation using laser Doppler flowmetry. Molecular characterizations showed that EGFR expression was dramatically decreased in freshly isolated capillaries from EC-EGFR-KO mice, as expected. Notably, whisker stimulation-induced functional hyperemia was significantly impaired in these mice, an effect that was rescued by administration of PIP2, but not by the EGFR ligand, HB-EGF. These data suggest that the deletion of the EGFR specifically in ECs attenuates functional hyperemia, likely via depleting PIP2 and subsequently incapacitating Kir2.1 channel functionality in capillary ECs. Thus, our study underscores the role of endothelial EGFR signaling in functional hyperemia of the brain.
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Affiliation(s)
- Hannah R. Ferris
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Nathan C. Stine
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - David C. Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA
- Division of Cardiovascular Sciences, University of Manchester, Manchester M13 9PL, UK
| | - George C. Wellman
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
| | - Masayo Koide
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA; (H.R.F.); (N.C.S.)
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT 05405, USA
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2
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Ferris HR, Hill-Eubanks DC, Nelson MT, Wellman GC, Koide M. Epidermal growth factor receptors in vascular endothelial cells contribute to functional hyperemia in the brain. bioRxiv 2023:2023.09.15.557981. [PMID: 37745396 PMCID: PMC10516026 DOI: 10.1101/2023.09.15.557981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Functional hyperemia - activity-dependent increases in local blood perfusion - underlies the on-demand delivery of blood to regions of enhanced neuronal activity, a process that is crucial for brain health. Importantly, functional hyperemia deficits have been linked to multiple dementia risk factors, including aging, chronic hypertension, and cerebral small vessel disease (cSVD). We previously reported crippled functional hyperemia in a mouse model of genetic cSVD that was likely caused by depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) in capillary endothelial cells (EC) downstream of impaired epidermal growth factor receptor (EGFR) signaling. Here, using EC-specific EGFR-knockout (KO) mice, we directly examined the role of endothelial EGFR signaling in functional hyperemia, assessed by measuring increases in cerebral blood flow in response to contralateral whisker stimulation using laser Doppler flowmetry. Molecular characterizations showed that EGFR expression was dramatically decreased in freshly isolated capillaries from EC-EGFR-KO mice, as expected. Notably, whisker stimulation-induced functional hyperemia was significantly impaired in these mice, an effect that was rescued by exogenous administration of PIP2, but not by the EGFR ligand, HB-EGF. These data suggest that the deletion of the EGFR specifically in ECs depletes PIP2 and attenuates functional hyperemia, underscoring the central role of the endothelial EGFR signaling in cerebral blood flow regulation.
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Affiliation(s)
- Hannah R. Ferris
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - David C. Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - George C. Wellman
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
| | - Masayo Koide
- Department of Pharmacology, Larner College of Medicine University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine University of Vermont, Burlington, VT, USA
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3
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Abstract
Capillaries are equipped to sense neurovascular coupling agents released onto the outer wall of a capillary, translating these external signals into electrical/Ca2+ changes that play a crucial role in blood flow regulation and ensuring that neuronal demands are met. However, control mechanisms attributable to forces imposed onto the lumen are less clear. Here, we show that Piezo1 channels act as mechanosensors in central nervous system capillaries. Electrophysiological analyses confirmed expression and function of Piezo1 channels in brain cortical and retinal capillaries. Activation of Piezo1 channels evoked currents that were sensitive to endothelial cell-specific Piezo1 deletion. Using genetically encoded Ca2+ indicator mice and an ex vivo pressurized retina preparation, we found that activation of Piezo1 channels by mechanical forces triggered Ca2+ signals in capillary endothelial cells. Collectively, these findings indicate that Piezo1 channels are capillary mechanosensors that initiate crucial Ca2+ signals and could, therefore, have a profound impact on central nervous system blood flow control.
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Affiliation(s)
- Osama F. Harraz
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, VT, USA
| | - Nicholas R. Klug
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, USA
| | - Amanda J. Senatore
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, USA
| | - David C. Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, USA
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT, USA
- Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, VT, USA
- Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, UK
- Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Group, University of Manchester, UK
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4
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Koide M, Harraz OF, Dabertrand F, Longden TA, Ferris HR, Wellman GC, Hill-Eubanks DC, Greenstein AS, Nelson MT. Differential restoration of functional hyperemia by antihypertensive drug classes in hypertension-related cerebral small vessel disease. J Clin Invest 2021; 131:e149029. [PMID: 34351870 PMCID: PMC8439604 DOI: 10.1172/jci149029] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 07/28/2021] [Indexed: 02/05/2023] Open
Abstract
Dementia resulting from small vessel diseases (SVDs) of the brain is an emerging epidemic for which there is no treatment. Hypertension is the major risk factor for SVDs, but how hypertension damages the brain microcirculation is unclear. Here, we show that chronic hypertension in a mouse model progressively disrupts on-demand delivery of blood to metabolically active areas of the brain (functional hyperemia) through diminished activity of the capillary endothelial cell inward-rectifier potassium channel, Kir2.1. Despite similar efficacy in reducing blood pressure, amlodipine, a voltage-dependent calcium-channel blocker, prevented hypertension-related damage to functional hyperemia whereas losartan, an angiotensin II type 1 receptor blocker, did not. We attribute this drug class effect to losartan-induced aldosterone breakthrough, a phenomenon triggered by pharmacological interruption of the renin-angiotensin pathway leading to elevated plasma aldosterone levels. This hypothesis is supported by the finding that combining losartan with the aldosterone receptor antagonist eplerenone prevented the hypertension-related decline in functional hyperemia. Collectively, these data suggest Kir2.1 as a possible therapeutic target in vascular dementia and indicate that concurrent mineralocorticoid aldosterone receptor blockade may aid in protecting against late-life cognitive decline in hypertensive patients treated with angiotensin II type 1 receptor blockers.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA
| | - Osama F. Harraz
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA
| | - Fabrice Dabertrand
- Department of Pharmacology, Larner College of Medicine, and,Department of Anesthesiology and,Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Thomas A. Longden
- Department of Pharmacology, Larner College of Medicine, and,Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | | | - Adam S. Greenstein
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA.,Division of Cardiovascular Sciences, School of Medical Sciences and,Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Group, University of Manchester, Manchester, United Kingdom
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine, and,Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, USA.,Division of Cardiovascular Sciences, School of Medical Sciences and,Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Group, University of Manchester, Manchester, United Kingdom
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5
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Koide M, Moshkforoush A, Tsoukias NM, Hill-Eubanks DC, Wellman GC, Nelson MT, Dabertrand F. The yin and yang of K V channels in cerebral small vessel pathologies. Microcirculation 2018; 25. [PMID: 29247493 DOI: 10.1111/micc.12436] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 12/08/2017] [Indexed: 12/14/2022]
Abstract
Cerebral SVDs encompass a group of genetic and sporadic pathological processes leading to brain lesions, cognitive decline, and stroke. There is no specific treatment for SVDs, which progress silently for years before becoming clinically symptomatic. Here, we examine parallels in the functional defects of PAs in CADASIL, a monogenic form of SVD, and in response to SAH, a common type of hemorrhagic stroke that also targets the brain microvasculature. Both animal models exhibit dysregulation of the voltage-gated potassium channel, KV 1, in arteriolar myocytes, an impairment that compromises responses to vasoactive stimuli and impacts CBF autoregulation and local dilatory responses to neuronal activity (NVC). However, the extent to which this channelopathy-like defect ultimately contributes to these pathologies is unknown. Combining experimental data with computational modeling, we describe the role of KV 1 channels in the regulation of myocyte membrane potential at rest and during the modest increase in extracellular potassium associated with NVC. We conclude that PA resting membrane potential and myogenic tone depend strongly on KV 1.2/1.5 channel density, and that reciprocal changes in KV channel density in CADASIL and SAH produce opposite effects on extracellular potassium-mediated dilation during NVC.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | - Arash Moshkforoush
- Department of Biomedical Engineering, Florida International University, Miami, FL, USA
| | - Nikolaos M Tsoukias
- Department of Biomedical Engineering, Florida International University, Miami, FL, USA
| | | | - George C Wellman
- 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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6
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Baylie R, Ahmed M, Bonev AD, Hill-Eubanks DC, Heppner TJ, Nelson MT, Greenstein AS. Lack of direct effect of adiponectin on vascular smooth muscle cell BK Ca channels or Ca 2+ signaling in the regulation of small artery pressure-induced constriction. Physiol Rep 2018; 5:5/16/e13337. [PMID: 28830977 PMCID: PMC5582259 DOI: 10.14814/phy2.13337] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/18/2017] [Accepted: 05/20/2017] [Indexed: 12/23/2022] Open
Abstract
The aim of this study was to investigate mechanisms by which adiponectin influences vascular Ca2+ signaling, K+ channel activity and thus contractile tone of small arteries. Vasodilation to adiponectin was studied in mesenteric resistance arteries constricted with intraluminal pressure. Ca2+ signals were characterized using high speed confocal microscopy of intact arteries. Patch clamp investigated the effect of adiponectin on individual VSMC potassium (K+) channel currents. Adiponectin dilated arteries constricted with pressure‐induced tone by approximately 5% and the induced vasodilation was only transient. The dilation to adiponectin was reduced by pharmacological interruption of the Ca2+ spark/large conductance activated K+ (BK) channel pathway but from a physiological perspective, interpretation of the data was limited by the small effect. Neither Adiponectin nor the presence of intact perivascular adipose tissue (PVAT) influenced Ca2+ spark or Ca2+ wave frequency or characteristics. Studied using a perforated patch approach, Adiponectin marginally increased current through the VSMC BK channel but this effect was lost using the whole cell technique with dialysis of the cytoplasm. Adiponectin did not change the frequency or amplitude of Ca2+ spark‐induced transient outward currents (STOC). Overall, our study shows that Adiponectin induces only a small and transient dilation of pressure constricted mesenteric arteries. This vasodilatory effect is likely to be independent of Ca2+ sparks or direct BK channel activation.
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Affiliation(s)
- Rachael Baylie
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Majid Ahmed
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Adrian D Bonev
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | | | - Thomas J Heppner
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | - Mark T Nelson
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.,Department of Pharmacology, University of Vermont, Burlington, Vermont
| | - Adam S Greenstein
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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7
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Khavandi K, Baylie RA, Sugden SA, Ahmed M, Csato V, Eaton P, Hill-Eubanks DC, Bonev AD, Nelson MT, Greenstein AS. Pressure-induced oxidative activation of PKG enables vasoregulation by Ca2+ sparks and BK channels. Sci Signal 2016; 9:ra100. [PMID: 27729550 DOI: 10.1126/scisignal.aaf6625] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Activation of Ca2+-sensitive, large-conductance potassium (BK) channels in vascular smooth muscle cells (VSMCs) by local, ryanodine receptor-mediated Ca2+ signals (Ca2+ sparks) acts as a brake on pressure-induced (myogenic) vasoconstriction-a fundamental mechanism that regulates blood flow in small resistance arteries. We report that physiological intraluminal pressure within resistance arteries activated cGMP-dependent protein kinase (PKG) in VSMCs through oxidant-induced formation of an intermolecular disulfide bond between cysteine residues. Oxidant-activated PKG was required to trigger Ca2+ sparks, BK channel activity, and vasodilation in response to pressure. VSMCs from arteries from mice expressing a form of PKG that could not be activated by oxidants showed reduced Ca2+ spark frequency, and arterial preparations from these mice had decreased pressure-induced activation of BK channels. Thus, the absence of oxidative activation of PKG disabled the BK channel-mediated negative feedback regulation of vasoconstriction. Our results support the concept of a negative feedback control mechanism that regulates arterial diameter through mechanosensitive production of oxidants to activate PKG and enhance Ca2+ sparks.
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Affiliation(s)
- Kaivan Khavandi
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK.,King's College London, Cardiovascular Division, The British Heart Foundation Centre of Excellence, The Rayne Institute, Saint Thomas' Hospital, London, SE1 7EH, UK
| | - Rachael A Baylie
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK
| | - Sarah A Sugden
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK
| | - Majid Ahmed
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK.,Department of Pharmacology, University of Vermont, Vermont, 05405-0068, USA
| | - Viktoria Csato
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK.,Division of Clinical Physiology, Institute of Cardiology, Research Centre for Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen 4012, Hungary
| | - Philip Eaton
- King's College London, Cardiovascular Division, The British Heart Foundation Centre of Excellence, The Rayne Institute, Saint Thomas' Hospital, London, SE1 7EH, UK
| | | | - Adrian D Bonev
- Department of Pharmacology, University of Vermont, Vermont, 05405-0068, USA
| | - Mark T Nelson
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK.,Department of Pharmacology, University of Vermont, Vermont, 05405-0068, USA
| | - Adam S Greenstein
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Center, Manchester, M13 9NT, UK
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Povlsen GK, Longden TA, Bonev AD, Hill-Eubanks DC, Nelson MT. Uncoupling of neurovascular communication after transient global cerebral ischemia is caused by impaired parenchymal smooth muscle Kir channel function. J Cereb Blood Flow Metab 2016; 36:1195-201. [PMID: 27052838 PMCID: PMC4929704 DOI: 10.1177/0271678x16638350] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 01/18/2016] [Accepted: 01/18/2016] [Indexed: 12/28/2022]
Abstract
Transient global cerebral ischemia is often followed by delayed disturbances of cerebral blood flow, contributing to neuronal injury. The pathophysiological processes underlying such disturbances are incompletely understood. Here, using an established model of transient global cerebral ischemia, we identify dramatically impaired neurovascular coupling following ischemia. This impairment results from the loss of functional inward rectifier potassium (KIR) channels in the smooth muscle of parenchymal arterioles. Therapeutic strategies aimed at protecting or restoring cerebrovascular KIR channel function may therefore improve outcomes following ischemia.
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Affiliation(s)
- Gro Klitgaard Povlsen
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA Department of Clinical Experimental Research, Glostrup Research Institute, Glostrup University Hospital, Glostrup, Denmark
| | - Thomas A Longden
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Adrian D Bonev
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA
| | | | - Mark T Nelson
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK
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9
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Villalba N, Sackheim AM, Nunez IA, Hill-Eubanks DC, Nelson MT, Wellman GC, Freeman K. Traumatic Brain Injury Causes Endothelial Dysfunction in the Systemic Microcirculation through Arginase-1-Dependent Uncoupling of Endothelial Nitric Oxide Synthase. J Neurotrauma 2016; 34:192-203. [PMID: 26757855 DOI: 10.1089/neu.2015.4340] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Endothelial dysfunction is a hallmark of many chronic diseases, including diabetes and long-term hypertension. We show that acute traumatic brain injury (TBI) leads to endothelial dysfunction in rat mesenteric arteries. Endothelial-dependent dilation was greatly diminished 24 h after TBI because of impaired nitric oxide (NO) production. The activity of arginase, which competes with endothelial NO synthase (eNOS) for the common substrate l-arginine, were also significantly increased in arteries, suggesting that arginase-mediated depletion of l-arginine underlies diminished NO production. Consistent with this, substrate restoration by exogenous application of l-arginine or inhibition of arginase recovered endothelial function. Moreover, evidence for increased reactive oxygen species production, a consequence of l-arginine starvation-dependent eNOS uncoupling, was detected in endothelium and plasma. Collectively, our findings demonstrate endothelial dysfunction in a remote vascular bed after TBI, manifesting as impaired endothelial-dependent vasodilation, with increased arginase activity, decreased generation of NO, and increased O2- production. We conclude that blood vessels have a "molecular memory" of neurotrauma, 24 h after injury, because of functional changes in vascular endothelial cells; these effects are pertinent to understanding the systemic inflammatory response that occurs after TBI even in the absence of polytrauma.
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Affiliation(s)
- Nuria Villalba
- 1 Department of Pharmacology, University of Vermont , Burlington, Vermont
| | - Adrian M Sackheim
- 2 Department of Surgery, University of Vermont , Burlington, Vermont
| | - Ivette A Nunez
- 2 Department of Surgery, University of Vermont , Burlington, Vermont
| | | | - Mark T Nelson
- 1 Department of Pharmacology, University of Vermont , Burlington, Vermont.,2 Department of Surgery, University of Vermont , Burlington, Vermont.,3 Institute of Cardiovascular Sciences, University of Manchester , Manchester, United Kingdom
| | - George C Wellman
- 1 Department of Pharmacology, University of Vermont , Burlington, Vermont.,2 Department of Surgery, University of Vermont , Burlington, Vermont
| | - Kalev Freeman
- 1 Department of Pharmacology, University of Vermont , Burlington, Vermont.,2 Department of Surgery, University of Vermont , Burlington, Vermont
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10
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 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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11
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Collier DM, Hill-Eubanks DC, Nelson MT. Orchestrating Ca2+ influx through Ca(V)1.2 and Ca(V)3.x channels in human cerebral arteries. J Gen Physiol 2015; 145:481-3. [PMID: 26009543 PMCID: PMC4442783 DOI: 10.1085/jgp.201511411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Daniel M Collier
- Department of Pharmacology, University of Vermont, Burlington, VT 05405
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT 05405
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12
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Hill-Eubanks DC, Gonzales AL, Sonkusare SK, Nelson MT. Vascular TRP channels: performing under pressure and going with the flow. Physiology (Bethesda) 2015; 29:343-60. [PMID: 25180264 DOI: 10.1152/physiol.00009.2014] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial cells and smooth muscle cells of resistance arteries mediate opposing responses to mechanical forces acting on the vasculature, promoting dilation in response to flow and constriction in response to pressure, respectively. In this review, we explore the role of TRP channels, particularly endothelial TRPV4 and smooth muscle TRPC6 and TRPM4 channels, in vascular mechanosensing circuits, placing their putative mechanosensitivity in context with other proposed upstream and downstream signaling pathways.
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Affiliation(s)
| | - Albert L Gonzales
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, Vermont
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13
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Sonkusare SK, Dalsgaard T, Bonev AD, Hill-Eubanks DC, Kotlikoff MI, Scott JD, Santana LF, Nelson MT. AKAP150-dependent cooperative TRPV4 channel gating is central to endothelium-dependent vasodilation and is disrupted in hypertension. Sci Signal 2014; 7:ra66. [PMID: 25005230 DOI: 10.1126/scisignal.2005052] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Endothelial cell dysfunction, characterized by a diminished response to endothelial cell-dependent vasodilators, is a hallmark of hypertension. TRPV4 channels play a major role in endothelial-dependent vasodilation, a function mediated by local Ca(2+) influx through clusters of functionally coupled TRPV4 channels rather than by a global increase in endothelial cell Ca(2+). We showed that stimulation of muscarinic acetylcholine receptors on endothelial cells of mouse arteries exclusively activated TRPV4 channels that were localized at myoendothelial projections (MEPs), specialized regions of endothelial cells that contact smooth muscle cells. Muscarinic receptor-mediated activation of TRPV4 depended on protein kinase C (PKC) and the PKC-anchoring protein AKAP150, which was concentrated at MEPs. Cooperative opening of clustered TRPV4 channels specifically amplified Ca(2+) influx at MEPs. Cooperativity of TRPV4 channels at non-MEP sites was much lower, and cooperativity at MEPs was greatly reduced by chelation of intracellular Ca(2+) or AKAP150 knockout, suggesting that Ca(2+) entering through adjacent channels underlies the AKAP150-dependent potentiation of TRPV4 activity. In a mouse model of angiotensin II-induced hypertension, MEP localization of AKAP150 was disrupted, muscarinic receptor stimulation did not activate TRPV4 channels, cooperativity among TRPV4 channels at MEPs was weaker, and vasodilation in response to muscarinic receptor stimulation was reduced. Thus, endothelial-dependent dilation of resistance arteries is enabled by MEP-localized AKAP150, which ensures the proximity of PKC to TRPV4 channels and the coupled channel gating necessary for efficient communication from endothelial to smooth muscle cells in arteries. Disruption of this molecular assembly may contribute to altered blood flow in hypertension.
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Affiliation(s)
- Swapnil K Sonkusare
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05403, USA
| | - Thomas Dalsgaard
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05403, USA
| | - Adrian D Bonev
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05403, USA
| | - David C Hill-Eubanks
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05403, USA
| | - Michael I Kotlikoff
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - John D Scott
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Luis F Santana
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - Mark T Nelson
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05403, USA. Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9NT, UK.
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14
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Gonzales AL, Yang Y, Sullivan MN, Sanders L, Dabertrand F, Hill-Eubanks DC, Nelson MT, Earley S. A PLCγ1-dependent, force-sensitive signaling network in the myogenic constriction of cerebral arteries. Sci Signal 2014; 7:ra49. [PMID: 24866019 DOI: 10.1126/scisignal.2004732] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Maintaining constant blood flow in the face of fluctuations in blood pressure is a critical autoregulatory feature of cerebral arteries. An increase in pressure within the artery lumen causes the vessel to constrict through depolarization and contraction of the encircling smooth muscle cells. This pressure-sensing mechanism involves activation of two types of transient receptor potential (TRP) channels: TRPC6 and TRPM4. We provide evidence that the activation of the γ1 isoform of phospholipase C (PLCγ1) is critical for pressure sensing in cerebral arteries. Inositol 1,4,5-trisphosphate (IP3), generated by PLCγ1 in response to pressure, sensitized IP3 receptors (IP3Rs) to Ca(2+) influx mediated by the mechanosensitive TRPC6 channel, synergistically increasing IP3R-mediated Ca(2+) release to activate TRPM4 currents, leading to smooth muscle depolarization and constriction of isolated cerebral arteries. Proximity ligation assays demonstrated colocalization of PLCγ1 and TRPC6 with TRPM4, suggesting the presence of a force-sensitive, local signaling network comprising PLCγ1, TRPC6, TRPM4, and IP3Rs. Src tyrosine kinase activity was necessary for stretch-induced TRPM4 activation and myogenic constriction, consistent with the ability of Src to activate PLCγ isoforms. We conclude that contraction of cerebral artery smooth muscle cells requires the integration of pressure-sensing signaling pathways and their convergence on IP3Rs, which mediate localized Ca(2+)-dependent depolarization through the activation of TRPM4.
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Affiliation(s)
- Albert L Gonzales
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. Department of Pharmacology, University of Vermont, Burlington, VT 05405, USA
| | - Ying Yang
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Michelle N Sullivan
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Lindsey Sanders
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Fabrice Dabertrand
- Department of Pharmacology, University of Vermont, Burlington, VT 05405, USA
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT 05405, USA. Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9NT, UK
| | - Scott Earley
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557-0318, USA.
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15
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Dabertrand F, Hannah RM, Pearson JM, Hill-Eubanks DC, Brayden JE, Nelson MT. Prostaglandin E2, a postulated astrocyte-derived neurovascular coupling agent, constricts rather than dilates parenchymal arterioles. J Cereb Blood Flow Metab 2013; 33:479-82. [PMID: 23385200 PMCID: PMC3618402 DOI: 10.1038/jcbfm.2013.9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It has been proposed that prostaglandin E(2) (PGE(2)) is released from astrocytic endfeet to dilate parenchymal arterioles through activation of prostanoid (EP(4)) receptors during neurovascular coupling. However, the direct effects of PGE(2) on isolated parenchymal arterioles have not been tested. Here, we examined the effects of PGE(2) on the diameter of isolated pressurized parenchymal arterioles from rat and mouse brain. Contrary to the prevailing assumption, we found that PGE(2) (0.1, 1, and 5 μmol/L) constricted rather than dilated parenchymal arterioles. Vasoconstriction to PGE(2) was prevented by inhibitors of EP(1) receptors. These results strongly argue against a direct role of PGE(2) on arterioles during neurovascular coupling.
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Affiliation(s)
- Fabrice Dabertrand
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405-0068, USA
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16
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Sonkusare SK, Bonev AD, Ledoux J, Liedtke W, Kotlikoff MI, Heppner TJ, Hill-Eubanks DC, Nelson MT. Elementary Ca2+ signals through endothelial TRPV4 channels regulate vascular function. Science 2012; 336:597-601. [PMID: 22556255 DOI: 10.1126/science.1216283] [Citation(s) in RCA: 417] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Major features of the transcellular signaling mechanism responsible for endothelium-dependent regulation of vascular smooth muscle tone are unresolved. We identified local calcium (Ca(2+)) signals ("sparklets") in the vascular endothelium of resistance arteries that represent Ca(2+) influx through single TRPV4 cation channels. Gating of individual TRPV4 channels within a four-channel cluster was cooperative, with activation of as few as three channels per cell causing maximal dilation through activation of endothelial cell intermediate (IK)- and small (SK)-conductance, Ca(2+)-sensitive potassium (K(+)) channels. Endothelial-dependent muscarinic receptor signaling also acted largely through TRPV4 sparklet-mediated stimulation of IK and SK channels to promote vasodilation. These results support the concept that Ca(2+) influx through single TRPV4 channels is leveraged by the amplifier effect of cooperative channel gating and the high Ca(2+) sensitivity of IK and SK channels to cause vasodilation.
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Affiliation(s)
- Swapnil K Sonkusare
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA
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17
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Abstract
Changes in intracellular Ca(2+) are central to the function of smooth muscle, which lines the walls of all hollow organs. These changes take a variety of forms, from sustained, cell-wide increases to temporally varying, localized changes. The nature of the Ca(2+) signal is a reflection of the source of Ca(2+) (extracellular or intracellular) and the molecular entity responsible for generating it. Depending on the specific channel involved and the detection technology employed, extracellular Ca(2+) entry may be detected optically as graded elevations in intracellular Ca(2+), junctional Ca(2+) transients, Ca(2+) flashes, or Ca(2+) sparklets, whereas release of Ca(2+) from intracellular stores may manifest as Ca(2+) sparks, Ca(2+) puffs, or Ca(2+) waves. These diverse Ca(2+) signals collectively regulate a variety of functions. Some functions, such as contractility, are unique to smooth muscle; others are common to other excitable cells (e.g., modulation of membrane potential) and nonexcitable cells (e.g., regulation of gene expression).
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Affiliation(s)
- David C Hill-Eubanks
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA
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18
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Hill-Eubanks DC, Werner ME, Nelson MT. Local elementary purinergic-induced Ca2+ transients: from optical mapping of nerve activity to local Ca2+ signaling networks. ACTA ACUST UNITED AC 2010; 136:149-54. [PMID: 20660658 PMCID: PMC2912073 DOI: 10.1085/jgp.201010402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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19
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Layne JJ, Werner ME, Hill-Eubanks DC, Nelson MT. NFATc3 regulates BK channel function in murine urinary bladder smooth muscle. Am J Physiol Cell Physiol 2008; 295:C611-23. [PMID: 18579799 DOI: 10.1152/ajpcell.00435.2007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The nuclear factor of activated T-cells (NFAT) is a Ca(2+)-dependent transcription factor that has been reported to regulate the expression of smooth muscle contractile proteins and ion channels. Here we report that large conductance Ca(2+)-sensitive potassium (BK) channels and voltage-gated K(+) (K(V)) channels may be regulatory targets of NFATc3 in urinary bladder smooth muscle (UBSM). UBSM myocytes from NFATc3-null mice displayed a reduction in iberiotoxin (IBTX)-sensitive BK currents, a decrease in mRNA for the pore-forming alpha-subunit of the BK channel, and a reduction in BK channel density compared with myocytes from wild-type mice. Tetraethylammonium chloride-sensitive K(V) currents were elevated in UBSM myocytes from NFATc3-null mice, as was mRNA for the Shab family member K(V)2.1. Despite K(V) current upregulation, bladder strips from NFATc3-null mice displayed an elevated contractile response to electrical field stimulation relative to strips from wild-type mice, but this difference was abrogated in the presence of the BK channel blocker IBTX. These results support a role for the transcription factor NFATc3 in regulating UBSM contractility, primarily through an NFATc3-dependent increase in BK channel activity.
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Affiliation(s)
- J J Layne
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA
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20
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Gonzalez Bosc LV, Layne JJ, Nelson MT, Hill-Eubanks DC. Nuclear factor of activated T cells and serum response factor cooperatively regulate the activity of an alpha-actin intronic enhancer. J Biol Chem 2005; 280:26113-20. [PMID: 15857835 DOI: 10.1074/jbc.m411972200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Expression of alpha-actin in smooth muscle cells (SMCs) is regulated, in part, by an intronic serum response factor (SRF)-binding CArG element. We have identified a conserved nuclear factor of activated T cells (NFAT) binding site that overlaps this CArG box and tested the hypothesis that this site plays a previously unrecognized role in regulating alpha-actin expression. A reporter construct prepared using a 56-bp region of the mouse alpha-actin first intron containing SRF, NFAT, and AP-1 sites (SNAP) acted as an enhancer element in the context of a minimal thymidine kinase promoter. Basal reporter activity following expression in SMCs was robust and sensitive to the calcineurin-NFAT pathway inhibitors cyclosporin A and FK506. Mutating either the NFAT or SRF binding site essentially abolished reporter activity, suggesting that both NFAT and SRF binding are required. Basal activity in non-smooth muscle HEK293 cells was SRF-dependent but NFAT-independent and approximately 8-fold lower than that in SMCs. Activation of NFAT in HEK293 cells induced an approximately 4-fold increase in activity that was dependent on the integrity of both NFAT and SRF binding sites. NFATc3.SRF complex formation, demonstrated by co-immunoprecipitation, was facilitated by the presence of SNAP oligonucleotide. Inhibition of the calcineurin-NFAT pathway decreased alpha-actin expression in cultured SMCs, suggesting that the molecular interaction of NFAT and SRF at SNAP may be physiologically relevant. These data provide the first evidence that NFAT and SRF may interact to cooperatively regulate SMC-specific gene expression and support a role for NFAT in the phenotypic maintenance of smooth muscle.
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Affiliation(s)
- Laura V Gonzalez Bosc
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA
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21
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Gonzalez Bosc LV, Wilkerson MK, Bradley KN, Eckman DM, Hill-Eubanks DC, Nelson MT. Intraluminal pressure is a stimulus for NFATc3 nuclear accumulation: role of calcium, endothelium-derived nitric oxide, and cGMP-dependent protein kinase. J Biol Chem 2003; 279:10702-9. [PMID: 14688253 DOI: 10.1074/jbc.m312920200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor NFAT (nuclear factor of activated T-cells) is implicated in cardiac hypertrophy and vasculogenesis. NFAT activation, reflecting dephosphorylation by the calcium-dependent phosphatase, calcineurin, and subsequent nuclear localization, is generally thought to require a sustained increase in intracellular calcium. However, in smooth muscle we have found that elevation of calcium by membrane depolarization fails to induce an increase in nuclear localization of the NFATc3 isoform. Here, we demonstrate that physiological intravascular pressure (100 mm Hg) induces an increase in NFATc3 nuclear localization in mouse cerebral arteries. Pressure-induced NFATc3 nuclear accumulation is abrogated by endothelial denudation and by nitric-oxide synthase, cGMP-dependent kinase (PKG), and voltage-dependent calcium channels inhibition. We further show that exogenous nitric oxide, in combination with an elevation in calcium, is an effective stimulus for NFATc3 nuclear accumulation. c-Jun terminal kinase 2 (JNK) activity, which has been shown to regulate NFATc3 nuclear export, is also reduced by pressure, an effect that is prevented by pretreatment with a PKG inhibitor. Consistent with this, pressure-induced NFATc3 nuclear accumulation is independent of PKG in arteries from JNK2(-/-) mice. Collectively, our results indicate that both activation of the NO/PKG pathway and elevation of smooth muscle calcium are required for NFATc3 nuclear accumulation and that PKG inhibits JNK2 to decrease NFAT nuclear export. Our findings suggest that at physiological intravascular pressures NFATc3 is localized to the nucleus in smooth muscle cells of intact arteries and indicate a novel and unexpected role for nitric oxide/PKG in NFAT activation.
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Affiliation(s)
- Laura V Gonzalez Bosc
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA
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22
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Gomez MF, Bosc LVG, Stevenson AS, Wilkerson MK, Hill-Eubanks DC, Nelson MT. Constitutively elevated nuclear export activity opposes Ca2+-dependent NFATc3 nuclear accumulation in vascular smooth muscle: role of JNK2 and Crm-1. J Biol Chem 2003; 278:46847-53. [PMID: 12954637 DOI: 10.1074/jbc.m304765200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor NFAT (nuclear factor of activated T-cells) is a cytosolic phosphoprotein that accumulates in the nucleus following dephosphorylation by the calcium (Ca2+)/calmodulin-dependent phosphatase, calcineurin. A defining feature of stimuli that induce NFAT nuclear accumulation/activation is a sustained increase in global intracellular Ca2+. Contrary to expectations, we have found that a sustained elevation of intracellular Ca2+, induced by membrane potential depolarization and mediated by voltage-dependent Ca2+ channels, does not result in nuclear localization of the NFATc3 isoform in smooth muscle. However, vasoconstrictors (e.g. uridine triphosphate (UTP)) and growth factors, which elevate intracellular Ca2+ and engage multiple intracellular signaling pathways, induce a robust increase in smooth muscle nuclear NFATc3. Here we show that depolarizing stimuli that normally fail to induce NFATc3 nuclear accumulation in arterial smooth muscle effectively induce nuclear accumulation under conditions in which Crm-1-dependent or JNK2-mediated nuclear export processes are disrupted. Consistent with an important regulatory role for JNK, UTP exerts a suppressive effect on JNK activity in smooth muscle. Export of nuclear NFATc3 following UTP-induced nuclear accumulation is dramatically slowed in cerebral arteries from JNK2-/- animals. These data indicate that in smooth muscle, stimulation of Ca2+-dependent, calcineurin-mediated nuclear import and suppression of Crm-1/JNK-dependent nuclear export are both required for induction of NFATc3 nuclear accumulation. These results highlight the dynamic interplay between influences that promote and oppose NFAT nuclear accumulation and suggest that in arterial smooth muscle suppression of constitutive nuclear export activity is an important property of NFAT-activating stimuli.
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Affiliation(s)
- Maria F Gomez
- Department of Pharmacology, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405, USA
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23
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Abstract
First identified in activated T cells, the calcium (Ca2+)-dependent transcription factor, nuclear factor of activated T cells (NFAT), has since been shown to play a role in nonimmune cells, including cells of the cardiovascular system. In arterial smooth muscle, the diverse array of calcium-signaling modalities, the functional interplay between smooth muscle and endothelial cells, and the influence of intravascular pressure on calcium and other signaling pathways creates a calcium-regulatory environment that is arguably unique. This review focuses on mechanisms that control the initial Ca2+/calcineurin-dependent events in NFAT activation, with a particular emphasis on NFAT regulation in native vascular smooth muscle. Also addressed is the role of additional mechanisms that act to modulate calcineurin-dependent NFAT nuclear import/export, mechanisms that may have particular relevance in this tissue.
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Affiliation(s)
- David C Hill-Eubanks
- Department of Pharmacology, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405, USA
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Gomez MF, Stevenson AS, Bonev AD, Hill-Eubanks DC, Nelson MT. Opposing actions of inositol 1,4,5-trisphosphate and ryanodine receptors on nuclear factor of activated T-cells regulation in smooth muscle. J Biol Chem 2002; 277:37756-64. [PMID: 12145283 DOI: 10.1074/jbc.m203596200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nuclear factor of activated T-cells (NFAT), originally identified in T-cells, has since been shown to play a role in mediating Ca(2+)-dependent gene transcription in diverse cell types outside of the immune system. We have previously shown that nuclear accumulation of NFATc3 is induced in ileal smooth muscle by platelet-derived growth factor in a manner that depends on Ca(2+) influx through L-type, voltage-dependent Ca(2+) channels. Here we show that NFATc3 is also the predominant NFAT isoform expressed in cerebral artery smooth muscle and is induced to accumulate in the nucleus by UTP and other G(q/11)-coupled receptor agonists. This induction is mediated by calcineurin and is dependent on sarcoplasmic reticulum Ca(2+) release through inositol 1,4,5-trisphosphate receptors and extracellular Ca(2+) influx through L-type, voltage-dependent Ca(2+) channels. Consistent with results obtained in ileal smooth muscle, depolarization-induced Ca(2+) influx fails to induce NFAT nuclear accumulation in cerebral arteries. We also provide evidence that Ca(2+) release by ryanodine receptors in the form of Ca(2+) sparks may exert an inhibitory influence on UTP-induced NFATc3 nuclear accumulation and further suggest that UTP may act, in part, by inhibiting Ca(2+) sparks. These results are consistent with a multifactorial regulation of NFAT nuclear accumulation in smooth muscle that is likely to involve several intracellular signaling pathways, including local effects of sarcoplasmic reticulum Ca(2+) release and effects attributable to global elevations in intracellular Ca(2+).
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Affiliation(s)
- Maria F Gomez
- Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA
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25
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Abstract
The transcription factor NFAT (nuclear factor of activated T-cells) plays a central role in mediating Ca(2+)-dependent gene transcription in a variety of cell types. Sustained increases in intracellular calcium concentration ([Ca(2+)]i) are presumed to be required for NFAT dephosphorylation by the Ca(2+)/calmodulin-dependent protein calcineurin and its subsequent nuclear translocation. Here, we provide the first identification and characterization of NFAT in native smooth muscle, showing that NFAT4 is the predominant isoform detected by reverse transcriptase-polymerase chain reaction and Western blot analysis. PDGF induces NFAT4 translocation in smooth muscle, leading to an increase in NFAT transcriptional activity. NFAT4 activation by PDGF depends on Ca(2+) entry through voltage-dependent Ca(2+) channels, because its nuclear accumulation is prevented by the Ca(2+) channel blocker nisoldipine and the K(+) channel opener pinacidil. Interestingly, elevation of [Ca(2+)]i by membrane depolarization or ionomycin treatment are not effective stimuli for NFAT4 nuclear accumulation, indicating that Ca(2+) influx is necessary but not sufficient for NFAT4 activation. In contrast, membrane depolarization readily activates the Ca(2+)-dependent transcription factor CREB (cAMP-responsive element-binding protein). The calcineurin blockers CsA and FK506 also prevented the PDGF-induced NFAT4 nuclear localization. These results indicate that both the nature of the calcium signal and PDGF-induced modulation of nuclear import-export of NFAT are critical for NFAT4 activation in this tissue.
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Affiliation(s)
- A S Stevenson
- Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA
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26
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Hill-Eubanks DC, Lollar P. von Willebrand factor is a cofactor for thrombin-catalyzed cleavage of the factor VIII light chain. J Biol Chem 1990; 265:17854-8. [PMID: 2120219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The proteolytic activation of highly purified, heterodimeric porcine factor VIII and factor VIII-von Willebrand factor complex by thrombin was compared at I 0.17, pH 7.0, 22 degrees C. During the activation of factor VIII, heavy-chain cleavage is necessary to activate the procoagulant function, whereas light-chain cleavage is required to dissociate factor VIII from von Willebrand factor. The kinetics of activation of free factor VIII and factor VIII-von Willebrand factor complex were identical. The steady-state kinetics of thrombin-catalyzed heavy-chain cleavages and light-chain cleavage of factor VIII either free or in complex with von Willebrand factor were studied using sodium dodecyl sulfate-polyacrylamide gel radioelectrophoresis and scanning densitometry of fragments derived from 125I-labeled factor VIII. Association of factor VIII with von Willebrand factor resulted in an 8-fold increase in the catalytic efficiency (kcat/Km) of light-chain cleavage (from 7 x 10(6) to 54 x 10(6) M-1 s-1). The catalytic efficiencies of heavy-chain cleavage at position 372 (approximately 6 x 10(6) M-1 s-1) and position 740 (approximately 100 x 10(6) M-1 s-1) were not affected by von Willebrand factor. We conclude that von Willebrand factor promotes cleavage of the factor VIII light chain by thrombin which is followed by rapid dissociation of the complex, so that the rate-limiting step becomes heavy-chain cleavage at position 372. This accounts for the observation that von Willebrand factor has no effect on the kinetics of activation of factor VIII by thrombin.
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Abstract
Blood coagulation factor VIII (fVIII) is a plasma protein that is decreased or absent in hemophilia A. It is isolated as a mixture of heterodimers that contain a variably sized heavy chain and a common light chain. Thrombin catalyzes the activation of fVIII in a reaction that is associated with cleavages in both types of chain. We isolated a serine protease from Bothrops jararacussu snake venom that catalyzes thrombin-like heavy-chain cleavage but not light-chain cleavage in porcine fVIII as judged by NaDodSO4/PAGE and N-terminal sequence analysis. Using a plasma-free assay of the ability of activated fVIII to function as a cofactor in the activation of factor X by factor IXa, we found that fVIII is activated by the venom enzyme. The venom enzyme-activated fVIII was isolated in stable form by cation-exchange HPLC. von Willebrand factor inhibited venom enzyme-activated fVIII but not thrombin-activated fVIII. These results suggest that the binding of fVIII to von Willebrand factor depends on the presence of an intact light chain and that activated fVIII must dissociate from von Willebrand factor to exert its cofactor effect. Thus, proteolytic activation of fVIII-von Willebrand factor complex appears to be differentially regulated by light-chain cleavage to dissociate the complex and heavy-chain cleavage to activate the cofactor function.
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Affiliation(s)
- D C Hill-Eubanks
- Department of Biochemistry, University of Vermont, Burlington 05405
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29
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Lollar P, Hill-Eubanks DC, Parker CG. Association of the factor VIII light chain with von Willebrand factor. J Biol Chem 1988; 263:10451-5. [PMID: 3134349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Coagulation factor VIII (fVIII) is isolated from porcine blood as a set of three heterodimers because of proteolytic cleavages in the middle, or B region, of the parent single-chain molecule. A single 80-kDa COOH-terminal fragment, the light chain (fVIIILC), is associated with one of three forms of heavy chain (fVIIIHCs) by a calcium-dependent linkage. The purified heterodimers were dissociated using EDTA and fVIIILC, and fVIIIHCs were isolated by high pressure liquid chromatography under nondenaturing conditions. The association of fVIII, fVIIILC, and fVIIIHCs with multimeric human von Willebrand factor (vWF) was studied using analytical velocity sedimentation. A previous study using this method with an intact, single heterodimeric species of fVIII has shown that one molecule of fVIII can bind to each subunit of vWF (Lollar, P., and Parker, C.G. (1987) J. Biol. Chem. 262, 17572-17576). fVIIILC bound vWF as judged by the increase in the plateau height and sedimentation coefficient of the fVIIILC.vWF complex compared to vWF at 42,000 x g and by the decrease in the plateau height of the 4.8 S fVIIILC boundary sedimenting at 240,000 x g. Titration of a fixed concentration of fVIIILC with vWF yielded a stoichiometry of one fVIIILC molecule per subunit of vWF. Proteolytic cleavage by thrombin to remove an acidic 41-residue NH2-terminal peptide from fVIIILC completely abolished its binding to vWF. In contrast, no binding of fVIIIHCs to vWF was observed. Additionally, intact fVIII bound to vWF was completely dissociated after proteolysis by thrombin. These data are consistent with the hypothesis that a critical step in blood coagulation is the release of all regions of fVIII from vWF following a single proteolytic cleavage of fVIIILC.
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Affiliation(s)
- P Lollar
- Department of Medicine and Biochemistry, University of Vermont, Burlington 05405
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