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Mediation of endothelial injury following neutrophil adherence to extracellular matrix
R A Kaslovsky1, L Lai, K Parker
1Department of Pediatrics, Albany Medical College of Union University, New York 12208.
Abstract:
Since polymorphonuclear leukocytes (PMN) rapidly migrate across the endothelial barrier and attach to extracellular matrix components, we tested the hypothesis that adhesion of PMN to matrix proteins can mediate endothelial injury following PMN activation. Studies were made using gelatin- and fibronectin-coated polycarbonate microporous filters (10 microns thick) on which confluent monolayers of bovine pulmonary microvessel endothelial cells were grown. PMN were layered either directly onto endothelial cells (at a ratio of 10:1) ("upright system") or onto gelatin- and fibronectin-coated filters with the endothelial monolayer grown on the underside of the filter without contact between PMN and endothelial cells ("inverted system"). PMN were activated with phorbol 12-myristate 13-acetate (PMA; 5 x 10(-9) M) in both systems. PMN activation increased endothelial permeability to 125I-labeled albumin in upright as well as inverted systems. Pretreatment of PMN with anti-CD18 monoclonal antibodies IB4 or R15.7, which inhibited PMN adherence to matrix constituents as well as to endothelial cells, prevented the permeability increase in both configurations. This effect of anti-CD18 monoclonal antibodies (mAbs) was not ascribed to a reduction in PMN activation, since PMA-induced superoxide generation was unaffected. We conclude that activation of PMN adherent to extracellular matrix proteins increases endothelial permeability to albumin and that this response is dependent on PMN adhesion to the matrix. The results support the concept that PMN-mediated increase in endothelial permeability is the result of "targeted" release of PMN products independent of whether the PMN are adherent to the extracellular matrix or the endothelium.
Insights
Polymorphonuclear leukocyte (PMN) activation increases endothelial permeability when adhering to extracellular matrix proteins. This PMN-mediated endothelial injury is dependent on PMN adhesion to the matrix, not direct contact with endothelial cells.
Area of Science:
- Immunology
- Cell Biology
- Vascular Biology
Background:
- Polymorphonuclear leukocytes (PMNs) are critical immune cells that rapidly traverse endothelial barriers.
- PMN adhesion to extracellular matrix (ECM) components is a key step in their migration and potential role in tissue injury.
- Understanding the mechanisms of PMN-induced endothelial injury is vital for treating inflammatory conditions.
Purpose of the Study:
- To investigate whether PMN adhesion to matrix proteins, independent of direct endothelial contact, can mediate endothelial injury upon PMN activation.
- To elucidate the role of PMN-endothelial cell interactions and PMN-matrix interactions in increasing endothelial permeability.
Main Methods:
- Utilized gelatin- and fibronectin-coated microporous filters with bovine pulmonary microvessel endothelial cell monolayers.
- Employed "upright" (PMN on endothelial cells) and "inverted" (PMN on matrix, endothelial cells on underside) systems to differentiate direct contact from matrix adhesion.
- Activated PMNs with phorbol 12-myristate 13-acetate (PMA) and assessed endothelial permeability to 125I-labeled albumin.
- Investigated the role of anti-CD18 monoclonal antibodies (mAbs) in inhibiting PMN adherence and subsequent endothelial permeability changes.
Main Results:
- PMN activation significantly increased endothelial permeability to albumin in both upright and inverted systems.
- Pretreatment with anti-CD18 mAbs (IB4, R15.7) inhibited PMN adherence to both matrix and endothelial cells, preventing the permeability increase.
- The protective effect of anti-CD18 mAbs was observed without reducing PMN activation (superoxide generation).
Conclusions:
- Activation of PMNs adherent to extracellular matrix proteins directly contributes to increased endothelial permeability.
- PMN-mediated endothelial injury is dependent on PMN adhesion to the matrix, highlighting the significance of the PMN-ECM interaction.
- The findings support a model where PMN products are "targeted" upon adhesion, leading to endothelial dysfunction irrespective of direct PMN-endothelial cell contact.