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Kaur G, Harris NR. Endothelial glycocalyx in retina, hyperglycemia, and diabetic retinopathy. Am J Physiol Cell Physiol 2023; 324:C1061-C1077. [PMID: 36939202 PMCID: PMC10125029 DOI: 10.1152/ajpcell.00188.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 02/28/2023] [Accepted: 03/16/2023] [Indexed: 03/21/2023]
Abstract
The endothelial glycocalyx (EG) is a meshlike network present on the apical surface of the endothelium. Membrane-bound proteoglycans, the major backbone molecules of the EG, consist of glycosaminoglycans attached to core proteins. In addition to maintaining the integrity of the endothelial barrier, the EG regulates inflammation and perfusion and acts as a mechanosensor. The loss of the EG can cause endothelial dysfunction and drive the progression of vascular diseases including diabetic retinopathy. Therefore, the EG presents a novel therapeutic target for treatment of vascular complications. In this review article, we provide an overview of the structure and function of the EG in the retina. Our particular focus is on hyperglycemia-induced perturbations in the glycocalyx structure in the retina, potential underlying mechanisms, and clinical trials studying protective treatments against degradation of the EG.
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Affiliation(s)
- Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana, United States
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana, United States
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Kaur G, Song Y, Xia K, McCarthy K, Zhang F, Linhardt RJ, Harris NR. Effect of high glucose on glycosaminoglycans in cultured retinal endothelial cells and rat retina. Glycobiology 2022; 32:720-734. [PMID: 35552402 PMCID: PMC9280546 DOI: 10.1093/glycob/cwac029] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/07/2022] [Accepted: 04/29/2022] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION The endothelial glycocalyx regulates vascular permeability, inflammation, and coagulation, and acts as a mechanosensor. The loss of glycocalyx can cause endothelial injury and contribute to several microvascular complications and, therefore, may promote diabetic retinopathy. Studies have shown a partial loss of retinal glycocalyx in diabetes, but with few molecular details of the changes in glycosaminoglycan (GAG) composition. Therefore, the purpose of our study was to investigate the effect of hyperglycemia on GAGs of the retinal endothelial glycocalyx. METHODS GAGs were isolated from rat retinal microvascular endothelial cells (RRMECs), media, and retinas, followed by liquid chromatography-mass spectrometry assays. Quantitative real-time polymerase chain reaction was used to study mRNA transcripts of the enzymes involved in GAG biosynthesis. RESULTS AND CONCLUSIONS Hyperglycemia significantly increased the shedding of heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). There were no changes to the levels of HS in RRMEC monolayers grown in high-glucose media, but the levels of CS and HA decreased dramatically. Similarly, while HA decreased in the retinas of diabetic rats, the total GAG and CS levels increased. Hyperglycemia in RRMECs caused a significant increase in the mRNA levels of the enzymes involved in GAG biosynthesis (including EXTL-1,2,3, EXT-1,2, ChSY-1,3, and HAS-2,3), with these increases potentially being compensatory responses to overall glycocalyx loss. Both RRMECs and retinas of diabetic rats exhibited glucose-induced alterations in the disaccharide compositions and sulfation of HS and CS, with the changes in sulfation including N,6-O-sulfation on HS and 4-O-sulfation on CS.
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Affiliation(s)
- Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
| | - Yuefan Song
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Ke Xia
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Kevin McCarthy
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
| | - Fuming Zhang
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Robert J Linhardt
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
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Cooper S, Teoh H, Campeau MA, Verma S, Leask RL. Empagliflozin restores the integrity of the endothelial glycocalyx in vitro. Mol Cell Biochem 2019; 459:121-130. [PMID: 31127491 DOI: 10.1007/s11010-019-03555-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 05/14/2019] [Indexed: 12/22/2022]
Abstract
The antihyperglycemic agent empagliflozin not only improves glycemic control but has also been associated with clinically meaningful reductions in cardiovascular events. Studies have shown that empagliflozin significantly reduces cardiovascular death and heart failure-associated hospitalizations. Given that endothelial dysfunction is closely linked with the pathogenesis of atherosclerotic cardiovascular disease, we hypothesized that the cardiovascular benefits observed with empagliflozin may be a result of its positive impact on the health of the endothelial glycocalyx (GCX), a critical component for the endothelium homeostasis. Human abdominal aortic endothelial cells (HAAECs) were either statically cultured or subjected to a steady wall shear stress of 10 dyne/cm2. Empagliflozin (50 µM, 24 h) restored heparinase III-mediated GCX disruption and the normal mechanotransduction responses in GCX-compromised HAAECs while reducing the attachment of all-trans retinoic acid-transformed NB4 cells to HAAECs. The current body of work suggests that the cardioprotective properties previously reported for empagliflozin may in part be due to the ability of empagliflozin to preserve and restore the structural integrity of the GCX, which in turn helps to maintain vascular health by promoting an anti-inflammatory endothelium, in the presence of a pro-inflammatory environment. Further studies are needed to fully understand the mechanisms underlying the cardiovascular benefits of empagliflozin.
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Affiliation(s)
- Scott Cooper
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, QC, H3A 2B2, Canada
| | - Hwee Teoh
- Division of Endocrinology and Metabolism, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada.,Division of Cardiac Surgery, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada
| | - Marc Antoine Campeau
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, QC, H3A 2B2, Canada
| | - Subodh Verma
- Division of Cardiac Surgery, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.,Departments of Surgery, and Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - Richard L Leask
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, QC, H3A 2B2, Canada. .,Montreal Heart Institute, Montréal, QC, Canada.
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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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FACE analysis as a fast and reliable methodology to monitor the sulfation and total amount of chondroitin sulfate in biological samples of clinical importance. Molecules 2014; 19:7959-80. [PMID: 24927366 PMCID: PMC6271866 DOI: 10.3390/molecules19067959] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/23/2014] [Accepted: 05/27/2014] [Indexed: 01/11/2023] Open
Abstract
Glycosaminoglycans (GAGs) due to their hydrophilic character and high anionic charge densities play important roles in various (patho)physiological processes. The identification and quantification of GAGs in biological samples and tissues could be useful prognostic and diagnostic tools in pathological conditions. Despite the noteworthy progress in the development of sensitive and accurate methodologies for the determination of GAGs, there is a significant lack in methodologies regarding sample preparation and reliable fast analysis methods enabling the simultaneous analysis of several biological samples. In this report, developed protocols for the isolation of GAGs in biological samples were applied to analyze various sulfated chondroitin sulfate- and hyaluronan-derived disaccharides using fluorophore-assisted carbohydrate electrophoresis (FACE). Applications to biologic samples of clinical importance include blood serum, lens capsule tissue and urine. The sample preparation protocol followed by FACE analysis allows quantification with an optimal linearity over the concentration range 1.0–220.0 µg/mL, affording a limit of quantitation of 50 ng of disaccharides. Validation of FACE results was performed by capillary electrophoresis and high performance liquid chromatography techniques.
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Wang P, Keijer J, Bunschoten A, Bouwman F, Renes J, Mariman E. Insulin modulates the secretion of proteins from mature 3T3-L1 adipocytes: a role for transcriptional regulation of processing. Diabetologia 2006; 49:2453-62. [PMID: 16896944 DOI: 10.1007/s00125-006-0321-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Accepted: 04/19/2006] [Indexed: 01/31/2023]
Abstract
AIMS/HYPOTHESIS Under conditions of insulin resistance and type 2 diabetes, fat cells are subjected to increased levels of insulin, which may have a major impact on the secretion of adipokines. MATERIALS AND METHODS Using transcriptomics and proteomics, we investigated how insulin affects the transcription and protein secretion profile of mature 3T3-L1 adipocytes. RESULTS We found that insulin has a significant impact on protein secretion of 3T3-L1 adipocytes. However, transcription is not the major regulation point for these secreted proteins. For extracellular matrix components, our data suggest that the mRNA level of processing enzymes, but not of target proteins, is the regulating point at which insulin stimulates secretion and function of the relevant proteins. Among these enzymes, we report a novel finding, namely that sulfatase 2 gene is regulated by insulin, which may induce a functional change in cultured adipocytes. CONCLUSIONS/INTERPRETATION We propose that enhancement of protein processing and secretion rather than transcription of the secreted protein genes is part of the strategic role of insulin in the induction of cellular responses.
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Affiliation(s)
- P Wang
- Functional Genomics Group, Research Institute NUTRIM, Department of Human Biology, Maastricht University, Maastricht, The Netherlands
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Brecher AS, Adamu MT. The effect of glycosaminoglycans with acetaldehyde on the activation of prothrombin. Can J Physiol Pharmacol 2005; 83:431-8. [PMID: 15897925 DOI: 10.1139/y05-017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heparin17–19k, (25, 50, and 100 ng), heparin6k(50 and 100 ng), heparin3k(50, 100, and 200 µg), chondroitin sulfates B (dermatan sulfate) (0.25, 0.5, and 1.0 µg), C (1 and 10 µg), and A (1 and 10 µg) each prolong the activated partial thromboplastin time (APTT) when preincubated with prothrombin to a greater extent than when preincubated with Factor II-deficient plasma prior to their mixing and subsequent additions of APTT reagent and Ca2+. In all cases statistical significance (p ≤ 0.05) was observed except with the 2 lower levels of heparin3k. These results suggest that the glycosaminoglycans (GAGs) may exert a direct effect upon prothrombin (FII) in their anticoagulant activity. Pre mix tures of [(FII/25 ng H17–19k) + 447 mmol acetaldehyde (AcH)/L] as well as [(AcH/H) + FII] and [(FII/AcH) + H] each exert a synergistic anticoagulant effect upon APTT. At low AcH concentrations (44.7 mmol/L), neither a synergistic nor an additive effect is seen. H6kand H3k, on premixing with 447 mmol AcH/L, exhibit an additive effect on APTT prolongation but no synergism. Similarly, premixtures of CSB/447 mmol AcH/L/FII show a greater anticoagulant effect than do [(CSB/AcH) + FII] or [(FII/AcH) + CSB] premixtures. CSC–AcH and CSA–AcH patterns are analogous to those of CSB (DS). These data suggest the possibility that AcH, the primary product of ethanol metabolism, may serve as a crosslinking adduct with proteins, in this case, prothrombin, as well as GAGs. Thus ternary complexes between the zymogen form of coagulation factors, GAGs, and AcH are possible, further influencing coagulopathy.Key words: prothrombin, alcoholism, acetaldehyde, glycosaminoglycans, heparins, chondroitin sulfates.
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Affiliation(s)
- Arthur S Brecher
- Department of Chemistry, Bowling Green State University, OH 43403, USA.
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Brecher AS, Hommema EL. The influence of acetaldehyde and glycosaminoglycans upon factor Xa- and factor X-deficient plasma. Can J Physiol Pharmacol 2002; 80:879-86. [PMID: 12430983 DOI: 10.1139/y02-111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The comparative effects of glycosaminoglycans and acetaldehyde (AcH)--glycosaminoglycan (GAG) mixtures upon Factor Xa- (FXa) and Factor X-deficient plasma (FXDP) have been studied by activated partial thromboplastin time (APTT) studies. Heparin at 0.025, 0.030, 0.04, and 0.05 U statistically prolonged the APTT when pre-incubated with FXa at 37 degrees C for 3 min prior to addition to FXDP and subsequent addition of Ca2+. Upon addition of 0.25, 0.375, and 0.5 microg heparin-6000 (H6k) to FXa, significant increases in APTT were observed. Similarly, profound increases in APTT were observed when 0.5, 0.75, and 1.0 microg heparin-3000 (H3k) was added to FXa. The chondroitin sulfates (CSA, CSB, CSC) had far less impact upon APTT with the FXa-FXDP system. In examining the effects of AcH-GAG mixtures upon the clotting factor, it was observed that 44.3 and 443 mM AcH synergistically prolonged the APTT in a statistically significant manner regardless of the order of premixing the three components. Hence, AcH may play a role in prolonging APTT in alcoholics. It synergistically prolonged APTT in concert with GAGs and FXa at the AcH levels used in this study. The effect of the GAGs upon FXDP is far less than its effect upon FXa.
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Affiliation(s)
- Arthur S Brecher
- Department of Chemistry, Bowling Green State University, OH 43403, USA.
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