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Foote CA, Ramirez-Perez FI, Smith JA, Ghiarone T, Morales-Quinones M, McMillan NJ, Augenreich MA, Power G, Burr K, Aroor AR, Bender SB, Manrique-Acevedo C, Padilla J, Martinez-Lemus LA. Neuraminidase inhibition improves endothelial function in diabetic mice. Am J Physiol Heart Circ Physiol 2023; 325:H1337-H1353. [PMID: 37801046 PMCID: PMC10908409 DOI: 10.1152/ajpheart.00337.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/29/2023] [Accepted: 09/29/2023] [Indexed: 10/07/2023]
Abstract
Neuraminidases cleave sialic acids from glycocalyx structures and plasma neuraminidase activity is elevated in type 2 diabetes (T2D). Therefore, we hypothesize circulating neuraminidase degrades the endothelial glycocalyx and diminishes flow-mediated dilation (FMD), whereas its inhibition restores shear mechanosensation and endothelial function in T2D settings. We found that compared with controls, subjects with T2D have higher plasma neuraminidase activity, reduced plasma nitrite concentrations, and diminished FMD. Ex vivo and in vivo neuraminidase exposure diminished FMD and reduced endothelial glycocalyx presence in mouse arteries. In cultured endothelial cells, neuraminidase reduced glycocalyx coverage. Inhalation of the neuraminidase inhibitor, zanamivir, reduced plasma neuraminidase activity, enhanced endothelial glycocalyx length, and improved FMD in diabetic mice. In humans, a single-arm trial (NCT04867707) of zanamivir inhalation did not reduce plasma neuraminidase activity, improved glycocalyx length, or enhanced FMD. Although zanamivir plasma concentrations in mice reached 225.8 ± 22.0 ng/mL, in humans were only 40.0 ± 7.2 ng/mL. These results highlight the potential of neuraminidase inhibition for ameliorating endothelial dysfunction in T2D and suggest the current Food and Drug Administration-approved inhaled dosage of zanamivir is insufficient to achieve desired outcomes in humans.NEW & NOTEWORTHY This work identifies neuraminidase as a key mediator of endothelial dysfunction in type 2 diabetes that may serve as a biomarker for impaired endothelial function and predictive of development and progression of cardiovascular pathologies associated with type 2 diabetes (T2D). Data show that intervention with the neuraminidase inhibitor zanamivir at effective plasma concentrations may represent a novel pharmacological strategy for restoring the glycocalyx and ameliorating endothelial dysfunction.
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Affiliation(s)
- Christopher A Foote
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, United States
| | | | - James A Smith
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Thaysa Ghiarone
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
| | | | - Neil J McMillan
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Marc A Augenreich
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Gavin Power
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Katherine Burr
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
| | - Annayya R Aroor
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Missouri, Columbia, Missouri, United States
- Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
| | - Shawn B Bender
- Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, United States
| | - Camila Manrique-Acevedo
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Missouri, Columbia, Missouri, United States
- Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
| | - Jaume Padilla
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
- Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
| | - Luis A Martinez-Lemus
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, United States
- Department of Medicine, Center for Precision Medicine, University of Missouri, Columbia, Missouri, United States
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2
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Logsdon AF, Rhea EM, Reed M, Banks WA, Erickson MA. The neurovascular extracellular matrix in health and disease. Exp Biol Med (Maywood) 2021; 246:835-844. [PMID: 33302738 PMCID: PMC8719034 DOI: 10.1177/1535370220977195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The blood-brain barrier (BBB) is a vital interface that supports normal brain functions. Endothelial cells (ECs) are the main component of the BBB and are highly specialized to govern the transfer of substances into brain. The EC lumen is enmeshed with an extracellular matrix (ECM), known as the endothelial glycocalyx layer (EGL). The lumen-facing EGL is primarily comprised of proteoglycans (PGs) and glycosaminoglycans (GAGs), which function as the first line of defense for blood-to-brain transfer of substances. Circulating factors must first penetrate the EGL before interacting with the EC. The abundance and composition of the PG and GAGs can dictate EGL function, and determine which circulating substances communicate with the ECs. The EGL can interact with circulating factors through physio-chemical interactions with the EC. Some disease states reveal a "thinning" of the EGL that may increase EC interactions with components of the systemic circulation and alter BBB function. EGL changes may also contribute to the cognitive complications of systemic diseases, such as sepsis and diabetes. For decades, researchers have measured how genetic and environmental factors influence the peripheral EGL constituents; however, much less is known about the neurovascular EGL. In this mini-review, we introduce components of the EGL and innovative ways to measure their abundance and composition that may contribute to BBB dysfunction.
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Affiliation(s)
- Aric F Logsdon
- Geriatrics Research Education and Clinical Center,
Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108,
USA
- Division of Gerontology and Geriatric Medicine,
Department of Medicine, University of Washington School of Medicine,
Seattle, WA 98159, USA
| | - Elizabeth M Rhea
- Geriatrics Research Education and Clinical Center,
Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108,
USA
- Division of Gerontology and Geriatric Medicine,
Department of Medicine, University of Washington School of Medicine,
Seattle, WA 98159, USA
| | - May Reed
- Geriatrics Research Education and Clinical Center,
Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108,
USA
- Division of Gerontology and Geriatric Medicine,
Department of Medicine, University of Washington School of Medicine,
Seattle, WA 98159, USA
| | - William A Banks
- Geriatrics Research Education and Clinical Center,
Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108,
USA
- Division of Gerontology and Geriatric Medicine,
Department of Medicine, University of Washington School of Medicine,
Seattle, WA 98159, USA
| | - Michelle A Erickson
- Geriatrics Research Education and Clinical Center,
Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108,
USA
- Division of Gerontology and Geriatric Medicine,
Department of Medicine, University of Washington School of Medicine,
Seattle, WA 98159, USA
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3
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Araibi H, van der Merwe E, Gwanyanya A, Kelly-Laubscher R. The effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion injury in the isolated rat heart. Microcirculation 2020; 27:e12612. [PMID: 32017300 DOI: 10.1111/micc.12612] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 01/24/2020] [Accepted: 01/30/2020] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Sphingosine-1-phosphate is a natural metabolite that is cardioprotective, but its effects on endothelial glycocalyx damage during ischemia-reperfusion are unknown. Therefore, we investigated the effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion. METHODS Isolated hearts from Wistar rats were perfused on a Langendorff system with Krebs-Henseleit buffer and pretreated with sphingosine-1-phosphate (10 nmol/L) before ischemia-reperfusion. Infarct size was measured by triphenyl tetrazolium chloride staining (n ≥ 6 per group). Cardiac edema was assessed by calculating total water content (n = 7 per group) and histologically quantifying the interstitial compartment (n ≥ 3 per group). The post-ischemic coronary release of syndecan-1 was quantified using ELISA. Syndecan-1 immunostaining intensity was assessed in perfusion-fixed hearts (n ≥ 3 per group). RESULTS Pretreatment with sphingosine-1-phosphate decreased infarct size in isolated hearts subjected to ischemia-reperfusion (P = .01 vs ischemia-reperfusion). However, sphingosine-1-phosphate had no effect on syndecan-1 levels in the coronary effluent or on the intensity of the syndecan-1 immunostaining signal in cardiac tissue. Heart total water content was not significantly different between control and ischemic groups but was significantly decreased in hearts treated with sphingosine-1-phosphate alone. CONCLUSION These results suggest that sphingosine-1-phosphate-induced cardioprotection against ischemia-reperfusion injury is not mediated by the maintenance of syndecan-1 in the endothelial glycocalyx.
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Affiliation(s)
- Hala Araibi
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Elizabeth van der Merwe
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Roisin Kelly-Laubscher
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Department of Biological Sciences, Faculty of Science, University of Cape Town, Cape Town, South Africa.,Department of Pharmacology & Therapeutics, The College of Medicine and Health, University College Cork, Cork, Ireland
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4
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Silva AT, Rouf F, Semola OA, Payton ME, Lovern PC. Placental growth factor levels in quadriceps muscle are reduced by a Western diet in association with advanced glycation end products. Am J Physiol Heart Circ Physiol 2019; 317:H851-H866. [PMID: 31397166 DOI: 10.1152/ajpheart.00511.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In peripheral artery disease (PAD), atherosclerotic occlusion chronically impairs limb blood flow. Arteriogenesis (collateral artery remodeling) is a vital adaptive response to PAD that protects tissue from ischemia. People with type II diabetes have a high risk of developing PAD and would benefit from arteriogenesis. However, arteriogenesis is suppressed in people with diabetes by a multifaceted mechanism which remains incompletely defined. Upregulation of placental growth factor (PLGF) is a key early step in arteriogenesis. Therefore, we hypothesized that metabolic dysfunction would impair PLGF expression in skeletal muscle. We tested this hypothesis in C57BL/6J and ApoE-/- mice of both sexes fed a Western diet (WD) for 24 wk. We first assessed baseline levels of PLGF, vascular endothelial growth factor (VEGF-A), and VEGF receptor 1 (VEGFR1) protein in hindlimb skeletal muscle. Only PLGF was consistently decreased by the WD. We next investigated the effect of 24 wk of the WD on the response of PLGF, VEGF-A, VEGFR1, and monocyte chemoattractant protein-1 (MCP-1) to the physiological stimulus of vascular occlusion. Hindlimb ischemia was induced in mice by gradual femoral artery occlusion using an ameroid constrictor. Growth factor levels were measured 3-28 days postsurgery. In C57BL/6J mice, the WD decreased and delayed upregulation of PLGF and abolished upregulation of VEGF-A and VEGFR1 but had no effect on MCP-1. In ApoE-/- mice fed either diet, all factors tested failed to respond to occlusion. Metabolic phenotyping of mice and in vitro studies suggest that an advanced glycation end product/TNFα-mediated mechanism could contribute to the effects observed in vivo.NEW & NOTEWORTHY In this study, we tested the effect of a Western diet on expression of the arteriogenic growth factor placental growth factor (PLGF) in mouse skeletal muscle. We provide the first demonstration that a Western diet interferes with both baseline expression and hindlimb ischemia-induced upregulation of PLGF. We further identify a potential role for advanced glycation end product/TNFα signaling as a negative regulator of PLGF. These studies provide insight into one possible mechanism by which type II diabetes may limit collateral growth.
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Affiliation(s)
- Asitha T Silva
- Department of Physiological Sciences, Oklahoma State University, Stillwater, Oklahoma
| | - Farzana Rouf
- Department of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma
| | - Oluwayemisi A Semola
- Department of Physiological Sciences, Oklahoma State University, Stillwater, Oklahoma
| | - Mark E Payton
- Department of Statistics, Oklahoma State University, Stillwater, Oklahoma
| | - Pamela C Lovern
- Department of Physiological Sciences, Oklahoma State University, Stillwater, Oklahoma
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5
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Mundi S, Massaro M, Scoditti E, Carluccio MA, van Hinsbergh VWM, Iruela-Arispe ML, De Caterina R. Endothelial permeability, LDL deposition, and cardiovascular risk factors-a review. Cardiovasc Res 2019; 114:35-52. [PMID: 29228169 DOI: 10.1093/cvr/cvx226] [Citation(s) in RCA: 182] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 12/05/2017] [Indexed: 12/21/2022] Open
Abstract
Early atherosclerosis features functional and structural changes in the endothelial barrier function that affect the traffic of molecules and solutes between the vessel lumen and the vascular wall. Such changes are mechanistically related to the development of atherosclerosis. Proatherogenic stimuli and cardiovascular risk factors, such as dyslipidaemias, diabetes, obesity, and smoking, all increase endothelial permeability sharing a common signalling denominator: an imbalance in the production/disposal of reactive oxygen species (ROS), broadly termed oxidative stress. Mostly as a consequence of the activation of enzymatic systems leading to ROS overproduction, proatherogenic factors lead to a pro-inflammatory status that translates in changes in gene expression and functional rearrangements, including changes in the transendothelial transport of molecules, leading to the deposition of low-density lipoproteins (LDL) and the subsequent infiltration of circulating leucocytes in the intima. In this review, we focus on such early changes in atherogenesis and on the concept that proatherogenic stimuli and risk factors for cardiovascular disease, by altering the endothelial barrier properties, co-ordinately trigger the accumulation of LDL in the intima and ultimately plaque formation.
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Affiliation(s)
- Santa Mundi
- Department of Biological and Environmental Science and Technology (DISTEBA), University of Salento, via Monteroni, 73100, Lecce, Italy
| | - Marika Massaro
- National Research Council (CNR), Department of Biomedical sciences, Institute of Clinical Physiology, Via Monteroni, 73100, Lecce, Italy
| | - Egeria Scoditti
- National Research Council (CNR), Department of Biomedical sciences, Institute of Clinical Physiology, Via Monteroni, 73100, Lecce, Italy
| | - Maria Annunziata Carluccio
- National Research Council (CNR), Department of Biomedical sciences, Institute of Clinical Physiology, Via Monteroni, 73100, Lecce, Italy
| | - Victor W M van Hinsbergh
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat, NL-1081 BT, Amsterdam, The Netherlands
| | - Marial Luisa Iruela-Arispe
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, 610 Charles E Young Dr S, 90095, Los Angeles, USA; and
| | - Raffaele De Caterina
- Department of Neuroscience, Imaging and Clinical Science and Institute of Advanced Biomedical Technologies, University G. D'Annunzio, via dei Vestini, 66100 Chieti, Italy
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6
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Dogné S, Flamion B, Caron N. Endothelial Glycocalyx as a Shield Against Diabetic Vascular Complications: Involvement of Hyaluronan and Hyaluronidases. Arterioscler Thromb Vasc Biol 2018; 38:1427-1439. [PMID: 29880486 PMCID: PMC6039403 DOI: 10.1161/atvbaha.118.310839] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 05/21/2018] [Indexed: 12/24/2022]
Abstract
The endothelial glycocalyx (EG), which covers the apical surface of the endothelial cells and floats into the lumen of the vessels, is a key player in vascular integrity and cardiovascular homeostasis. The EG is composed of PGs (proteoglycans), glycoproteins, glycolipids, and glycosaminoglycans, in particular hyaluronan (HA). HA seems to be implicated in most of the functions described for EG such as creating a space between blood and the endothelium, controlling vessel permeability, restricting leukocyte and platelet adhesion, and allowing an appropriate endothelial response to flow variation through mechanosensing. The amount of HA in the EG may be regulated by HYAL (hyaluronidase) 1, the most active somatic hyaluronidase. HYAL1 seems enriched in endothelial cells through endocytosis from the bloodstream. The role of the other main somatic hyaluronidase, HYAL2, in the EG is uncertain. Damage to the EG, accompanied by shedding of one or more of its components, is an early sign of various pathologies including diabetes mellitus. Shedding increases the blood or plasma concentration of several EG components, such as HA, heparan sulfate, and syndecan. The plasma levels of these molecules can then be used as sensitive markers of EG degradation. This has been shown in type 1 and type 2 diabetic patients. Recent experimental studies suggest that preserving the size and amount of EG HA in the face of diabetic insults could be a useful novel therapeutic strategy to slow diabetic complications. One way to achieve this goal, as suggested by a murine model of HYAL1 deficiency, may be to inhibit the function of HYAL1. The same approach may succeed in other pathological situations involving endothelial dysfunction and EG damage.
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Affiliation(s)
- Sophie Dogné
- From the Molecular Physiology Research Unit-URPhyM, Namur Research Institute for Life Sciences (NARILIS), University of Namur (Unamur), Belgium.
| | - Bruno Flamion
- From the Molecular Physiology Research Unit-URPhyM, Namur Research Institute for Life Sciences (NARILIS), University of Namur (Unamur), Belgium
| | - Nathalie Caron
- From the Molecular Physiology Research Unit-URPhyM, Namur Research Institute for Life Sciences (NARILIS), University of Namur (Unamur), Belgium
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7
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Dogné S, Rath G, Jouret F, Caron N, Dessy C, Flamion B. Hyaluronidase 1 Deficiency Preserves Endothelial Function and Glycocalyx Integrity in Early Streptozotocin-Induced Diabetes. Diabetes 2016; 65:2742-53. [PMID: 27246914 DOI: 10.2337/db15-1662] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 05/23/2016] [Indexed: 11/13/2022]
Abstract
Hyaluronic acid (HA) is a major component of the glycocalyx involved in the vascular wall and endothelial glomerular permeability barrier. Endocytosed hyaluronidase HYAL1 is known to degrade HA into small fragments in different cell types, including endothelial cells. In diabetes, the size and permeability of the glycocalyx are altered. In addition, patients with type 1 diabetes present increased plasma levels of both HA and HYAL1. To investigate the potential implication of HYAL1 in the development of diabetes-induced endothelium dysfunction, we measured endothelial markers, endothelium-dependent vasodilation, arteriolar glycocalyx size, and glomerular barrier properties in wild-type and HYAL1 knockout (KO) mice with or without streptozotocin (STZ)-induced diabetes. We observed that 4 weeks after STZ injections, the lack of HYAL1 1) prevents diabetes-induced increases in soluble P-selectin concentrations and limits the impact of the disease on endothelium-dependent hyperpolarization (EDH)-mediated vasorelaxation; 2) increases glycocalyx thickness and maintains glycocalyx structure and HA content during diabetes; and 3) prevents diabetes-induced glomerular barrier dysfunction assessed using the urinary albumin-to-creatinine ratio and urinary ratio of 70- to 40-kDa dextran. Our findings suggest that HYAL1 contributes to endothelial and glycocalyx dysfunction induced by diabetes. HYAL1 inhibitors could be explored as a new therapeutic approach to prevent vascular complications in diabetes.
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Affiliation(s)
- Sophie Dogné
- Molecular Physiology Research Unit, Namur Research Institute for Life Sciences, University of Namur, Namur, Belgium
| | - Géraldine Rath
- Pole of Pharmacology and Therapeutics, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - François Jouret
- Groupe Interdisciplinaire de Génoprotéomique Appliquée, Cardiovascular Sciences, University of Liège, Liège, Belgium
| | - Nathalie Caron
- Molecular Physiology Research Unit, Namur Research Institute for Life Sciences, University of Namur, Namur, Belgium
| | - Chantal Dessy
- Pole of Pharmacology and Therapeutics, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Bruno Flamion
- Molecular Physiology Research Unit, Namur Research Institute for Life Sciences, University of Namur, Namur, Belgium
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8
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Abstract
The vascular endothelium is an interface between the blood stream and the vessel wall. Changes in this single cell layer of the artery wall are believed of primary importance in the pathogenesis of vascular disease/atherosclerosis. The endothelium responds to humoral, neural and especially hemodynamic stimuli and regulates platelet function, inflammatory responses, vascular smooth muscle cell growth and migration, in addition to modulating vascular tone by synthesizing and releasing vasoactive substances. Compromised endothelial function contributes to the pathogenesis of cardiovascular disease; endothelial 'dysfunction' is associated with risk factors, correlates with disease progression, and predicts cardiovascular events. Therapies for atherosclerosis have been developed, therefore, that are directed towards improving endothelial function.
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9
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Siegel G, Meyer-Rath G, Ermilov E, Rodríguez M, Malmsten M, Claesson P, Saunders R, Hetzer R, Lindman B. Flow sensing in the cardiovascular system. Colloids Surf A Physicochem Eng Asp 2015. [DOI: 10.1016/j.colsurfa.2014.10.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Cheng H, Harris RC. Renal endothelial dysfunction in diabetic nephropathy. Cardiovasc Hematol Disord Drug Targets 2015; 14:22-33. [PMID: 24720460 DOI: 10.2174/1871529x14666140401110841] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 03/21/2014] [Accepted: 03/26/2014] [Indexed: 12/24/2022]
Abstract
Endothelial dysfunction has been posited to play an important role in the pathogenesis of diabetic nephropathy (DN). Due to the heterogeneity of endothelial cells (ECs), it is difficult to generalize about endothelial responses to diabetic stimuli. At present, there are limited techniques fordirectly measuring EC function in vivo, so diagnosis of endothelial disorders still largely depends on indirect assessment of mediators arising from EC injury. In the kidney microcirculation, both afferent and efferent arteries, arterioles and glomerular endothelial cells (GEnC) have all been implicated as targets of diabetic injury. Both hyperglycemia per se, as well as the metabolic consequences of glucose dysregulation, are thought to lead to endothelial cell dysfunction. In this regard, endothelial nitric oxide synthase (eNOS) plays a central role in EC dysfunction. Impaired eNOS activity can occur at numerous levels, including enzyme uncoupling, post-translational modifications, internalization and decreased expression. Reduced nitric oxide (NO) bioavailability exacerbates oxidative stress, further promoting endothelial dysfunction and injury. The injured ECs may then function as active signal transducers of metabolic, hemodynamic and inflammatory factors that modify the function and morphology of the vessel wall and interact with adjacent cells, which may activate a cascade of inflammatory and proliferative and profibrotic responses in progressive DN. Both pharmacological approaches and potential regenerative therapies hold promise for restoration of impaired endothelial cells in diabetic nephropathy.
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Affiliation(s)
| | - Raymond C Harris
- Division of Nephrology, S3223 MCN, Vanderbilt University School of Medicine, and Nashville Veterans Affairs Hospital, Nashville, TN 37232, USA.
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11
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Greyling A, Schreuder THA, Landman T, Draijer R, Verheggen RJHM, Hopman MTE, Thijssen DHJ. Elevation in blood flow and shear rate prevents hyperglycemia-induced endothelial dysfunction in healthy subjects and those with type 2 diabetes. J Appl Physiol (1985) 2015; 118:579-85. [PMID: 25593286 DOI: 10.1152/japplphysiol.00936.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Hyperglycemia, commonly present after a meal, causes transient impairment in endothelial function. We examined whether increases in blood flow (BF) protect against the hyperglycemia-mediated decrease in endothelial function in healthy subjects and patients with type 2 diabetes mellitus (T2DM). Ten healthy subjects and 10 age- and sex-matched patients with T2DM underwent simultaneous bilateral assessment of brachial artery endothelial function by means of flow-mediated dilation (FMD) using high-resolution echo-Doppler. FMD was examined before and 60, 120, and 150 min after a 75-g oral glucose challenge. We unilaterally manipulated BF by heating one arm between minute 30 and minute 60. Oral glucose administration caused a statistically significant, transient increase in blood glucose in both groups (P < 0.001). Forearm skin temperature, brachial artery BF, and shear rate significantly increased in the heated arm (P < 0.001), and to a greater extent compared with the nonheated arm in both groups (interaction effect P < 0.001). The glucose load caused a transient decrease in FMD% (P < 0.05), whereas heating significantly prevented the decline (interaction effect P < 0.01). Also, when correcting for changes in diameter and shear rate, we found that the hyperglycemia-induced decrease in FMD can be prevented by local heating (P < 0.05). These effects on FMD were observed in both groups. Our data indicate that nonmetabolically driven elevation in BF and shear rate can similarly prevent the hyperglycemia-induced decline in conduit artery endothelial function in healthy volunteers and in patients with type 2 diabetes. Additional research is warranted to confirm that other interventions that increase BF and shear rate equally protect the endothelium when challenged by hyperglycemia.
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Affiliation(s)
- Arno Greyling
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands; Unilever R&D Vlaardingen, The Netherlands; and
| | - Tim H A Schreuder
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Thijs Landman
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | - Maria T E Hopman
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Dick H J Thijssen
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands; Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
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12
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Markos F, Shortt CM, Edge D, Ruane-O'Hora T, Noble MIM. Immediate direct peripheral vasoconstriction in response to hyperinsulinemia and metformin in the anesthetized pig. Physiol Res 2014; 63:559-66. [PMID: 24908091 DOI: 10.33549/physiolres.932736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Elevated levels of insulin have been reported to induce both an arterial vasodilation mediated by nitric oxide (NO), and vasoconstriction mediated by endothelin and reactive oxygen radicals. Metformin, used to control blood glucose levels in type 2 diabetes, has also been shown to cause NO-mediated dilation of conduit arteries. It is possible that these contradictory vascular effects are due to a non-direct action on arteries. Therefore, the direct effect of high levels of insulin and metformin infusion on resistance artery diameter was evaluated. Experiments were carried out on the anesthetized pig; blood flow and pressure were measured in the iliac artery. An adjustable snare was applied to the iliac above the pressure and flow measurement site to induce step decreases (3-4 occlusions at 5 min intervals were performed for each infusion) in blood flow, and hence iliac pressure, and the conductance (deltaflow / deltapressure) calculated. Saline, insulin (20 and 40 mUSP/l/min), and metformin (1 microg/ml/min) were infused separately downstream of the adjustable snare and their effect on arterial conductance assessed. Insulin at both infusion rates and metformin caused a significant reduction in peripheral vascular conductance. In conclusion, hyperinsulinemia and metformin infusion constrict resistance arterial vessels in vivo.
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Affiliation(s)
- F Markos
- Department of Physiology, University College Cork, Cork, Ireland.
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Modulation of endothelial glycocalyx structure under inflammatory conditions. Mediators Inflamm 2014; 2014:694312. [PMID: 24803742 PMCID: PMC3997148 DOI: 10.1155/2014/694312] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 03/03/2014] [Indexed: 01/08/2023] Open
Abstract
The glycocalyx of the endothelium is an intravascular compartment that creates a barrier between circulating blood and the vessel wall. The glycocalyx is suggested to play an important role in numerous physiological processes including the regulation of vascular permeability, the prevention of the margination of blood cells to the vessel wall, and the transmission of shear stress. Various theoretical models and experimental approaches provide data about changes to the structure and functions of the glycocalyx under various types of inflammatory conditions. These alterations are suggested to promote inflammatory processes in vessels and contribute to the pathogenesis of number of diseases. In this review we summarize current knowledge about the modulation of the glycocalyx under inflammatory conditions and the consequences for the course of inflammation in vessels. The structure and functions of endothelial glycocalyx are briefly discussed in the context of methodological approaches regarding the determination of endothelial glycocalyx and the uncertainty and challenges involved in glycocalyx structure determination. In addition, the modulation of glycocalyx structure under inflammatory conditions and the possible consequences for pathogenesis of selected diseases and medical conditions (in particular, diabetes, atherosclerosis, ischemia/reperfusion, and sepsis) are summarized. Finally, therapeutic strategies to ameliorate glycocalyx dysfunction suggested by various authors are discussed.
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Frati Munari AC. Importancia médica del glucocáliz endotelial. Parte 2: su papel en enfermedades vasculares y complicaciones de la diabetes mellitus. ARCHIVOS DE CARDIOLOGIA DE MEXICO 2014; 84:110-6. [DOI: 10.1016/j.acmx.2013.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 10/15/2013] [Accepted: 10/21/2013] [Indexed: 10/25/2022] Open
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Ruane-O’Hora T, Shortt CM, Edge D, Markos F, Noble MI. Intraluminal hyperglycaemia causes conduit and resistance artery dilatation and inhibits vascular autoregulation in the anaesthetised pig. Can J Physiol Pharmacol 2013; 91:1031-6. [DOI: 10.1139/cjpp-2013-0206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of intraluminal hyperglycaemia was investigated in the iliac artery of 11 anaesthetised pigs. Following isolation of a test segment, hyperglycaemic blood (40 mmol·L–1) caused a significant dilatation of the artery of 167 ± 208 μm (mean ± SD; n = 6, P = 0.031). Dilatations were reduced by N(G)-nitro-l-arginine methyl esther (250 μg·mL–1) from 145 ± 199 to 38 ± 5 μm), but this was not statistically significant (n = 6, P = 0.18). Intra-arterial infusions of d-glucose (20–40 mmol·L–1·min–1), during graded constrictions, caused statistically significant increases in blood flow (n = 11, P = 0.0013). Vasodilatation was confirmed by measurements of the ratio of immediate pressure steps to flow steps (∂P/∂F) during the graded obstruction experiments, showing a decrease in instantaneous vascular resistance from a control of 0.62 ± 0.30 to 0.33 ± 0.34 mm Hg·mL–1·min–1 (n = 7, P = 0.016). Autoregulation was assessed from the slopes of the plots of steady-state flow versus pressure. There were significant increases in the slope from 2.32 ± 1.03 to 5.88 ± 5.60 mL·min–1·(mm Hg)–1 (n = 7, P = 0.0078), indicating significant impairment of autoregulation. In conclusion, luminal hyperglycaemia relaxes both arterial and resistance vessel smooth muscle.
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Affiliation(s)
| | | | - Deirdre Edge
- Department of Physiology, University College Cork, Cork, Ireland
| | - Farouk Markos
- Department of Physiology, University College Cork, Cork, Ireland
| | - Mark I.M. Noble
- Cardiovascular Medicine, University of Aberdeen, Scotland, UK
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Frati-Munari AC. [Medical significance of endothelial glycocalyx]. ARCHIVOS DE CARDIOLOGIA DE MEXICO 2013; 83:303-12. [PMID: 24280179 DOI: 10.1016/j.acmx.2013.04.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 04/15/2013] [Accepted: 04/16/2013] [Indexed: 10/26/2022] Open
Abstract
Endothelial glycocalyx is a layer composed by glycosaminoglycans, proteoglycans and glycoproteins attached to the vascular endothelial luminal surface. It has several physiological roles: shear stress mechanotransduction to the endothelial cells, regulation of fluids and macromolecules vascular permeability, of coagulation cascade activation and fibrinolysis, and protects the endothelium from platelets and leukocytes adhesion. In general, glycocalyx protects vascular wall against pathogenic insults. The glycocalyx may be damaged by abnormal shear stress, reactive oxygen species, hypernatremia, hyperglycemia, hypercholesterolemia and inflammatory molecules, resulting in endothelial dysfunction, enhanced vascular permeability, lipoproteins leakage to subendothelial space, activation of plasma coagulation, and increased adherence of platelets and leukocytes to the endothelial cells. Shredding of glycocalyx appears as an important initial step in the pathophysiology of vascular diseases.
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Markos F, Ruane O'Hora T, Noble MIM. What is the mechanism of flow-mediated arterial dilatation. Clin Exp Pharmacol Physiol 2013; 40:489-94. [DOI: 10.1111/1440-1681.12120] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 05/14/2013] [Accepted: 05/16/2013] [Indexed: 02/05/2023]
Affiliation(s)
- Farouk Markos
- Department of Physiology; University College Cork; Cork Ireland
| | | | - Mark IM Noble
- Cardiovascular Medicine; University of Aberdeen; Aberdeen UK
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Metformin causes nitric oxide-mediated dilatation in a shorter time than insulin in the iliac artery of the anesthetized pig. J Cardiovasc Pharmacol 2012; 59:182-7. [PMID: 22048751 DOI: 10.1097/fjc.0b013e31823b4b94] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We tested the hypothesis that metformin produces arterial dilatation indirectly, by directly exposing the endothelial surface, of an occluded test segment of the pig iliac artery in vivo, to test blood containing metformin or excess insulin, with and without the presence of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester hydrochloride. Such exposure to metformin 1 μg/mL caused the artery to dilate at constant pressure, and this was abolished when NG-nitro-L-arginine methyl ester hydrochloride was coadministered with metformin. The onset of dilatation occurred approximately 4 minutes after the commencement of endothelial exposure to metformin; this contrasts with the approximate 10 minutes required for a similar response to luminal hyperinsulinemia. After the release of flow occlusion, the subsequent flow-mediated dilatation was slightly but significantly enhanced compared with control for metformin; the effect of insulin on flow-mediated dilatation was not statistically significant. The hypothesis was disproved, as we have shown that insulin and metformin, like insulin, directly stimulate NO production by endothelium of a conduit artery; this function may be of value in delaying the atherothrombotic process. The time taken for the commencement of NO production is shorter for metformin than for insulin; the clinical relevance of this finding is unclear.
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Markos F, Ruane O’Hora T, Wainwright CL, Noble MIM. Dependence of smooth muscle tone upon pulsatility in the iliac artery of the anaesthetised pig. Pflugers Arch 2012; 463:679-84. [DOI: 10.1007/s00424-012-1076-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 01/20/2012] [Accepted: 01/23/2012] [Indexed: 10/28/2022]
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Diabetes impairs arteriogenesis in the peripheral circulation: review of molecular mechanisms. Clin Sci (Lond) 2010; 119:225-38. [PMID: 20545627 DOI: 10.1042/cs20100082] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Patients suffering from both diabetes and PAD (peripheral arterial disease) are at risk of developing critical limb ischaemia and ulceration, and potentially requiring limb amputation. In addition, diabetes complicates surgical treatment of PAD and impairs arteriogenesis. Arteriogenesis is defined as the remodelling of pre-existing arterioles into conductance vessels to restore the perfusion distal to the occluded artery. Several strategies to promote arteriogenesis in the peripheral circulation have been devised, but the mechanisms through which diabetes impairs arteriogenesis are poorly understood. The present review provides an overview of the current literature on the deteriorating effects of diabetes on the key players in the arteriogenesis process. Diabetes affects arteriogenesis at a number of levels. First, it elevates vasomotor tone and attenuates sensing of shear stress and the response to vasodilatory stimuli, reducing the recruitment and dilatation of collateral arteries. Secondly, diabetes impairs the downstream signalling of monocytes, without decreasing monocyte attraction. In addition, EPC (endothelial progenitor cell) function is attenuated in diabetes. There is ample evidence that growth factor signalling is impaired in diabetic arteriogenesis. Although these defects could be restored in animal experiments, clinical results have been disappointing. Furthermore, the diabetes-induced impairment of eNOS (endothelial NO synthase) strongly affects outward remodelling, as NO signalling plays a key role in several remodelling processes. Finally, in the structural phase of arteriogenesis, diabetes impairs matrix turnover, smooth muscle cell proliferation and fibroblast migration. The review concludes with suggestions for new and more sophisticated therapeutic approaches for the diabetic population.
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Noble MIM, Drake-Holland AJ. Review: Hyperglycaemia and the vascular glycocalyx: the key to microalbuminuria and cardiovascular disease in diabetes mellitus? ACTA ACUST UNITED AC 2010. [DOI: 10.1177/1474651409357035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The vascular glycocalyx is a gel layer between endothelium and the blood, 0.5 µm thick. Evidence is presented from published studies to indicate that hyperglycaemia causes damage to the vascular glycocalyx. This damage results in microalbuminuria, excess fluid transfer to the interstitium, reduction in nitric oxide (NO) production by arterial endothelium, and leukocyte and platelet adhesion to endothelium leading to atherothrombosis. The lack of NO production proceeds from the fact that glycocalyx is the mechanotransducer transmitting the signal for increased shear stress between blood and arterial wall, and this function is inhibited by hyperglycaemia. When hyperinsulinaemia is also present, the problem is compounded by general arterial dilatation leading to low shear rates throughout the arterial tree. These findings explain the predisposition to atherothrombosis in the pre-diabetic condition of insulin resistance/metabolic syndrome/obesity and diabetes mellitus. It is proposed that greater efforts than ever are required to detect occult insulin resistance, to treat such patients and diabetics with ever more strict blood glucose control while minimising insulin levels, and to carry out further research into how glycocalyx structure and function can be preserved.
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Affiliation(s)
- Mark IM Noble
- Cardiovascular Medicine, University of Aberdeen, Aberdeen, UK
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Brower JB, Targovnik JH, Caplan MR, Massia SP. High glucose-mediated loss of cell surface heparan sulfate proteoglycan impairs the endothelial shear stress response. Cytoskeleton (Hoboken) 2010; 67:135-41. [DOI: 10.1002/cm.20430] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Connell P, Walshe T, Ferguson G, Gao W, O'Brien C, Cahill PA. Elevated Glucose Attenuates Agonist- and Flow-Stimulated Endothelial Nitric Oxide Synthase Activity in Microvascular Retinal Endothelial Cells. ACTA ACUST UNITED AC 2009; 14:17-24. [PMID: 17364893 DOI: 10.1080/10623320601177213] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Impaired vasoactive release of opposing vasodilator and vasoconstrictor mediators due to endothelial dysfunction is integral to the pathogenesis of diabetic retinopathy. The aim of this study was to determine the effect of hyperglycemia on the expression of endothelial nitric oxide synthase (eNOS) and the release of nitric oxide (NO) in bovine microvascular retinal endothelial cells (BRECs) under both static (basal and acetylcholine stimulated) and flow (laminar shear stress [10 dynes/cm2 and pulsatile flow 0.3 to 23 dynes/cm2) conditions using a laminar shear apparatus and an in vitro perfused transcapillary culture system. The activity and expression of eNOS, measured by nitrate levels and immunoblot, respectively, were determined following exposure of BRECs to varying concentrations of glucose and mannitol (0 to 25 mM). Under static conditions the expression of eNOS decreased significantly following exposure to increasing concentrations of glucose when compared to osmotic mannitol controls and was accompanied by a significant dose-dependent decrease in nitrate levels in conditioned medium. The acetylcholine stimulated increase in NO release (2.0 +/- 0.3-fold) was significantly reduced by 55% +/- 5% and 65% +/- 4.5% following exposure to 16 and 25 mM glucose, respectively, when compared to osmotic controls. In parallel studies, glucose significantly inhibited both laminar shear stress and pulsatile flow-induced activity when compared to mannitol. We conclude that hyperglycemia impairs agonist- and flow-dependent release of NO in retinal microvascular endothelial cells and may thus contribute to the vascular endothelial dysfunction and impaired autoregulation of diabetic retinopathy.
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Affiliation(s)
- Paul Connell
- Vascular Health Research Centre, Faculty of Science and Health, Dublin City University, Dublin, Ireland
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Vascular endothelial dysfunction: A tug of war in diabetic nephropathy? Biomed Pharmacother 2009; 63:171-9. [DOI: 10.1016/j.biopha.2008.08.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Accepted: 08/19/2008] [Indexed: 11/18/2022] Open
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Markos F, Ruane-O'Hora T, Snow HM, Kelly R, Wainwright C, Skene K, Drake-Holland AJ, Noble MIM. Dilatation in the femoral vascular bed does not cause retrograde relaxation of the iliac artery in the anaesthetized pig. Acta Physiol (Oxf) 2008; 194:207-13. [PMID: 18577181 DOI: 10.1111/j.1748-1716.2008.01882.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM We tested the hypothesis that dilatation of a feeding artery may be elicited by transmission of a signal through the tissue of the arterial wall from a vasodilated peripheral vascular bed. METHODS In eight pentobarbital anaesthetized pigs, acetylcholine (ACh, an endothelium-dependent vasodilator) was injected intra-arterially above (upstream) and below (downstream) a test segment of the left iliac artery, the diameter of which was measured continuously by sonomicrometry. RESULTS Under control conditions, ACh injections upstream and downstream of the test segment caused dilatation. Downstream injection dilated the peripheral arterioles, resulting in increased blood flow and proximal dilatation. This is a shear stress, nitric oxide (NO)-dependent response. The experiment was then repeated after applying a stenosis to prevent the increased flow caused by downstream injection of ACh; the stenosis was placed either above the site of diameter measurement to allow retrograde conduction, or below that site to prevent distally injected ACh reaching the measurement site. Under these conditions, downstream injection of ACh had a minimal effect on the shear stress of the test segment with no increase in test segment diameter. This was not due to endothelial damage or dysfunction as injection of ACh upstream still caused a large increase in test segment diameter. CONCLUSIONS Our results indicate that dilatation of the feeding artery of a vasodilated bed is caused by increased shear stress within the feeding artery and not via a signal transmitted through the arterial wall from below.
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Affiliation(s)
- F Markos
- Department of Physiology, University College Cork, Cork, Ireland.
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Noble MIM, Drake-Holland AJ, Vink H. Hypothesis: arterial glycocalyx dysfunction is the first step in the atherothrombotic process. QJM 2008; 101:513-8. [PMID: 18319293 DOI: 10.1093/qjmed/hcn024] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We present evidence that the 0.5 microm thick gel layer, lining the inner wall of healthy blood vessels, the glycocalyx, is the first line of defence against atherothrombotic disease. All blood vessel linings are coated with this gel, a highly negatively charged structure, rich in anionic sites mostly represented by the sialic acid moieties of glycoproteins and the sulphate and carboxyl groups of heparan-sulphate proteoglycans. Blood flow in arteries is associated with a shear stress at the glycocalyx, which signals the underlying endothelial cells to release nitric oxide (NO), an anti-atherogenic factor. Sites of low shear stress in the arterial tree are more susceptible to atheroma due to lack of NO generation through this mechanism, whereas exercise, by increasing blood flow and shear stress, is protective. We postulate that risk factors for atherothrombosis act by impairing glycocalyx function. That luminal hyperglycaemia causes glycocalyx dysfunction has already been shown; we postulate this to be the first step in the atherothrombotic process in patients with diabetes mellitus and metabolic syndrome (insulin resistance). There is also evidence of glycocalyx defects from exposure to oxidized low-density lipoprotein. We postulate that other risk factors will have a similar action on the glycocalyx as the initiating factor in the disease process, e.g. smoking, hyperlipidaemias and hyperhomocystenaemia. These predictions can now be tested in a large animal model of shear-stress-mediated arterial dilatation.
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Affiliation(s)
- M I M Noble
- Department of Medicine and Therapeutics, Polwarth Building, Foresterhill, Aberdeen AB25 2ZH, UK.
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Kelly RF, Snow HM. Characteristics of the response of the iliac artery to wall shear stress in the anaesthetized pig. J Physiol 2007; 582:731-43. [PMID: 17412772 PMCID: PMC2075330 DOI: 10.1113/jphysiol.2007.128736] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The functional significance of shear stress-induced vasodilatation in large conduit arteries is unclear since changes in the diameter have little effect on the resistance to blood flow. However, changes in diameter have a relatively large effect on wall shear stress which suggests that the function of flow-mediated dilatation is to reduce wall shear stress. The mean and pulsatile components of shear stress vary widely throughout the arterial system and areas of low mean and high amplitude of wall shear stress are prone to the development of atheroma. In this study, using an in vivo model with the ability to control flow rate and amplitude of flow independently, we investigated the characteristics of the response of the iliac artery to variations in both the mean and amplitude of wall shear stress. The results of this study confirm that increases in mean wall shear stress are an important stimulus for the release of nitric oxide by the endothelium as indicated by changes in arterial diameter and show for the first time, in vivo, that increases in the amplitude of the pulsatile component of shear stress have a small but significant inhibitory effect on this response. A negative feedback mechanism was identified whereby increases in shear stress brought about by increases in blood flow are reduced by the release of nitric oxide from the endothelium causing dilatation of the artery, thus decreasing the stimulus to cell adhesion and, through a direct action of nitric oxide, inhibiting the process of cell adhesion. The results also provide an explanation for the uneven distribution of atheroma throughout the arterial system, which is related to the ratio of pulsatile to mean shear stress and consequent variability in the production of NO.
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Affiliation(s)
- R F Kelly
- Biological Services Unit and Department of Physiology, University College Cork, Cork, Ireland.
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