Abstract

The microvascular endothelium serves as the major barrier that controls the transport of blood constituents across the vessel wall. Barrier leakage occurs during infection or sterile inflammation, allowing plasma fluid and cells to extravasate and accumulate in surrounding tissues, an important pathology underlying a variety of infectious diseases and immune disorders. The leak process is triggered and regulated by bidirectional communications between circulating cells and vascular cells at the blood-vessel interface. While the molecular mechanisms underlying this complex process remain incompletely understood, emerging evidence supports the roles of neutrophil-endothelium interaction and neutrophil-derived products, including neutrophil extracellular traps and vesicles, in the pathogenesis of vascular barrier injury. In this review, we summarize the current knowledge on neutrophil-induced changes in endothelial barrier structures, with a detailed presentation of recently characterized molecular pathways involved in the production and effects of neutrophil extracellular traps and extracellular vesicles. Additionally, we discuss the therapeutic implications of altering neutrophil interactions with the endothelial barrier in treating inflammatory diseases.

Highlights

  • Serving as the blood-tissue interface, the vascular endothelial barrier plays a critical role in regulating host defense against infection or injury

  • We have recently identified a new lipidation pathway, endothelial protein palmitoylation mediated by palmitoyl acyltransferase DHHC21, in promoting neutrophil-endothelium adhesion and microvascular permeability [33]

  • We show that syndecan-3/4 can be cleaved by thrombin to produce ectodomain fragments, and these fragments trigger adherens junctions (AJs) disorganization and stress fiber formation, causing elevated para-cellular permeability [42]

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Summary

INTRODUCTION

Serving as the blood-tissue interface, the vascular endothelial barrier plays a critical role in regulating host defense against infection or injury. Endothelial hyperpermeability is considered an important cause, as well as consequence, of inflammatory/immune responses associated with sepsis, trauma, ischemia-reperfusion injury, diabetes, and metastatic tumor development [1, 2]. This pathological process involves complex cell-cell communications and molecular signaling. Among the multiple subtypes of leukocytes in the circulation, polymorphonuclear granulocytes (PMNs), or neutrophils, are the most impactful cells to vascular permeability, as they can alter endothelial barrier properties via direct contacts (adhesion and transmigration) and/or by secreting bioactive products capable of disrupting the barrier structure. We discuss the effects of neutrophil-endothelium contact and neutrophil-derived factors on endothelial permeability

Neutrophils and Microvascular Permeability
ENDOTHELIAL BARRIER
Focal Adhesions
PMN REGULATION OF ENDOTEHLIAL PERMEABILITY
PMN Adhesion and Endothelial Permeability
PMN Secretion and Endothelial Permeability
THERAPEUTIC IMPLICATIONS
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