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Transendothelial neutrophil migration. Role of neutrophil-derived proteases and relationship to transendothelial
G Cepinskas1, R Noseworthy, P R Kvietys
1Division of Vascular Biology, London Health Sciences Centre-Research, Ontario, Canada.
Abstract:
During an acute inflammatory response polymorphonuclear leukocytes (PMNs) adhere to and emigrate across the venular microvasculature. There is general agreement on the mechanisms involved in PMN adhesive interactions. However, the mechanisms by which PMNs migrate across the endothelial lining remain controversial, particularly with respect to the role of elastase. In the present study, we used human umbilical vein endothelial cells (HUVECs) and PMNs to test the hypothesis that the relative role of PMN-derived elastase may be dependent on the degree of HUVEC retraction within monolayers. A high (10(-7) mol/L), but not a low (10(-10) mol/L), concentration of platelet-activating factor (PAF) caused HUVEC retraction of sufficient magnitude to increase transendothelial protein movement. Elastase inhibitors prevented PMN transendothelial migration in response to the low, but not the high, concentration of PAF. These findings suggest that PMN migration across confluent endothelial cells is elastase dependent, whereas PMN migration across retracted endothelial cells is elastase independent. However, under the latter condition (high concentration of PAF), the two endogenous proteases, alpha 2-macroglobulin and alpha 1-antitrypsin, could interfere with PAF-induced PMN transendothelial migration. Thus, as the concentration of PAF is increased, migrating PMNs use other proteases, in addition to elastase. We also noted that transendothelial protein movement is closely coupled to PMN migration.
Insights
Polymorphonuclear leukocyte (PMN) migration across endothelial cells depends on endothelial cell retraction. PMN elastase is crucial for migration across intact cells but less so for retracted cells, where other proteases are involved.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Polymorphonuclear leukocytes (PMNs) emigrate across venular microvasculature during inflammation.
- Mechanisms of PMN adhesion are understood, but PMN transmigration across endothelium is debated, especially regarding elastase's role.
Purpose of the Study:
- To investigate the role of PMN-derived elastase in PMN transmigration across human umbilical vein endothelial cells (HUVECs).
- To test if the role of elastase depends on the degree of HUVEC retraction.
Main Methods:
- Used HUVECs and PMNs to study PMN transendothelial migration.
- Applied varying concentrations of platelet-activating factor (PAF) to induce HUVEC retraction.
- Utilized elastase inhibitors and monitored transendothelial protein movement.
Main Results:
- High PAF concentration (10(-7) mol/L) caused HUVEC retraction and increased protein movement.
- Elastase inhibitors blocked PMN migration with low PAF (10(-10) mol/L) but not high PAF.
- High PAF concentrations involved other proteases (alpha 2-macroglobulin, alpha 1-antitrypsin) in PMN migration.
- PMN migration correlated with transendothelial protein movement.
Conclusions:
- PMN migration across confluent endothelial cells is elastase-dependent.
- PMN migration across retracted endothelial cells is elastase-independent, involving other proteases.
- Transendothelial protein movement is tightly linked to PMN migration during inflammation.