Extracellular Histones Bind Vascular Glycosaminoglycans and Inhibit the Anti-Inflammatory Function of Antithrombin

Binding of histones to molecular pattern recognition receptors on endothelial cells and leukocytes provokes proinflammatory responses and promotes activation of coagulation. Histones also bind therapeutic heparins, thereby neutralizing their anticoagulant functions. The aim of this study was to test...

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Bibliographic Details
Published in:Cellular physiology and biochemistry Vol. 55; no. 5; pp. 605 - 617
Main Authors: Biswas, Indranil, Panicker, Sumith R, Cai, Xiaofeng S, Giri, Hemant, Rezaie, Alireza R
Format: Journal Article
Language:English
Published: Germany Cell Physiol Biochem Press GmbH & Co KG 16.10.2021
Subjects:
Antithrombin III - metabolism
Blood Coagulation
Endothelial Cells - metabolism
Glycosaminoglycans - metabolism
Histones - metabolism
Human Umbilical Vein Endothelial Cells
Humans
Inflammation - blood
Inflammation - metabolism
Protein Binding
Histones; Antithrombin; Glycosaminoglycans; Signaling
ISSN:1015-8987, 1421-9778, 1421-9778
Online Access:Get full text
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Summary:Binding of histones to molecular pattern recognition receptors on endothelial cells and leukocytes provokes proinflammatory responses and promotes activation of coagulation. Histones also bind therapeutic heparins, thereby neutralizing their anticoagulant functions. The aim of this study was to test the hypothesis that histones can interact with the antithrombin (AT)-binding vascular glycosaminoglycans (GAGs) to induce inflammation and inhibit the anti-inflammatory function of AT. METHODS: We evaluated the heparin-binding function of histones by an AT-dependent protease-inhibition assay. Furthermore, we treated endothelial cells with histones in the absence and presence of AT and monitored cellular phenotypes employing established signaling assays. RESULTS: Histones neutralized AT-dependent anticoagulant function of heparin in both purified protease-inhibition and plasma-based assays. Histones also disrupted endothelial cell barrier-permeability function by a GAG-dependent mechanism as evidenced by the GAG-antagonist, surfen, abrogating their disruptive effects. Further studies revealed histones and AT compete for overlapping binding-sites on GAGs, thus increasing concentrations of one protein abrogated effects of the other. Histones elicited proapoptotic effects by inducing nuclear localization of PKC-δ in endothelial cells and barrier-disruptive effects by destabilizing VE-cadherin, which were inhibited by AT, but not by a D-helix mutant of AT incapable of interacting with GAGs. Finally, histones induced release of Weibel-Palade body contents, VWF and angiopoietin-2, and promoted expression of cell adhesion molecules on endothelial cells, which were all downregulated by AT but not by D-helix mutant of AT. CONCLUSION: We conclude that histones and AT compete for overlapping binding sites on vascular GAGs to modulate coagulation and inflammation.
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Author Contributions
I.B. designed and performed all inhibition kinetics and endothelial cell signaling assays; S.R.P. conducted flow cytometry; X.S.C. and H.G. designed immunofluorescence experiments and analyzed phosphorylation of signaling molecules; and A.R.R. designed experiments, analyzed data, wrote the manuscript and supervised the project. All authors approved the final version of the manuscript.
ISSN:1015-8987
1421-9778
1421-9778
DOI:10.33594/000000438