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Polymorphonuclear leukocytes induce PDGF release from IL-1beta-treated endothelial cells: role of adhesion molecules
L Totani1, A Cumashi, A Piccoli
1"Antonio Taticchi" Unit for Atherosclerosis and Thrombosis, Department of Vascular Medicine and Pharmacology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy.
Abstract:
Polymorphonuclear leukocytes (PMNs) and endothelial cells interact at sites of vascular injury during inflammatory response and during the development of atherosclerotic lesions. Such close proximity leads to the modulation of several of the biological functions of the 2 cell types. Because we have shown previously that PMNs enhance release of growth factors from resting endothelial cells, we decided to evaluate whether coincubation of PMNs with interleukin-1beta (IL-1beta)-stimulated human umbilical vein endothelial cells (HUVEC) could further modulate mitogen release from HUVEC. We found that PMN-HUVEC coincubation resulted in a 10-fold increase in mitogen release, compared with HUVEC alone (14+/-6 versus 1.3+/-0.1). When PMNs were incubated with IL-1beta-treated HUVEC, a further increase in mitogen release (up to 35-fold) was observed. The mitogenic activity was immunologically related to platelet-derived growth factor (PDGF) because the activity was abolished by an anti-PDGF antibody. PDGF-AB antigen, detected in low concentrations in conditioned medium from HUVEC alone, was increased 4-fold when IL-1beta or PMNs were incubated with HUVEC and dramatically upregulated (up to 40-fold) when PMNs were cocultured with IL-1beta-treated HUVEC. The presence of the protease inhibitor eglin C abolished mitogenic activity generation, suggesting a role for PMN-derived elastase and cathepsin G. Indeed, purified elastase and cathepsin G mimicked PMN-induced mitogen release from HUVEC. Because PMNs firmly adhered to IL-1beta-treated HUVEC, we investigated the role of cell-cell adhesion in mitogen release. Adhesion and PDGF release were inhibited by approximately 60% in the presence of anti-CD11a/CD18 and anti-intercellular adhesion molecule-1 monoclonal antibodies. This study suggests a new role for PMNs and their interaction with endothelium in pathological conditions in which intimal hyperplasia is a common feature.
Insights
Polymorphonuclear leukocytes (PMNs) interacting with endothelial cells significantly increase mitogen release, particularly platelet-derived growth factor (PDGF). This interaction, mediated by proteases and cell adhesion molecules, plays a role in vascular pathologies like intimal hyperplasia.
Area of Science:
- Immunology
- Cell Biology
- Vascular Biology
Background:
- Polymorphonuclear leukocytes (PMNs) and endothelial cells interact during vascular injury and atherosclerosis.
- Previous studies showed PMNs enhance growth factor release from resting endothelial cells.
Purpose of the Study:
- To evaluate if PMN-endothelial cell interaction modulates mitogen release from IL-1beta-stimulated HUVEC.
- To identify the mechanisms involved in PMN-induced mitogen release.
Main Methods:
- Coincubation of PMNs with IL-1beta-stimulated HUVEC.
- Measurement of mitogen release and PDGF-AB antigen levels.
- Use of anti-PDGF antibodies, protease inhibitors (eglin C), and monoclonal antibodies against adhesion molecules (anti-CD11a/CD18, anti-ICAM-1).
Main Results:
- PMN-HUVEC coincubation increased mitogen release 10-fold; IL-1beta stimulation further increased it up to 35-fold.
- Mitogenic activity was identified as PDGF, with antigen levels upregulated up to 40-fold.
- PMN-derived proteases (elastase, cathepsin G) and cell adhesion (via CD11a/CD18, ICAM-1) were crucial for PDGF release.
Conclusions:
- PMNs significantly enhance PDGF release from IL-1beta-stimulated HUVEC.
- This process involves PMN proteases and endothelial cell adhesion molecules.
- The PMN-endothelial cell interaction contributes to pathological conditions like intimal hyperplasia.