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PAF mediates neutrophil adhesion to thrombin or TNF-stimulated endothelial cells under shear stress
Abstract:
Platelet-activating factor (PAF) is known to modulate polymorphonuclear leukocyte (PMN) adhesion to endothelial cells cultured under static conditions and activated by thrombin. In contrast, there are no data on the role of PAF in PMN adhesion to cells exposed to flow conditions and activated by stimuli other than thrombin. Here we used the PAF receptor antagonist L-659,989 to evaluate PMN adhesion to human umbilical vein endothelial cells (HUVEC) in basal conditions or upon challenge with thrombin or tumor necrosis factor-alpha (TNF-alpha). Experiments were performed under dynamic flow using a parallel-plate flow chamber and a computer-based image analysis system. Rolling and adhesion of PMNs to endothelial cells significantly increased upon stimulation with thrombin. Thrombin-stimulated HUVEC also synthesized higher amounts of PAF than untreated cells. Pretreatment of PMNs with L-659,989 significantly reduced their rolling and adhesion to thrombin-activated HUVEC. Stimulation of HUVEC with TNF-alpha significantly increased the number of rolling and adherent PMNs as compared with untreated cells. Adhesion of PMNs to and migration across TNF-alpha-stimulated HUVEC were reduced by L-659,989, whereas cell rolling was unchanged. We conclude that PAF mediates leukocyte interaction under flow conditions with HUVEC activated by inflammatory stimuli.
Insights
Platelet-activating factor (PAF) mediates polymorphonuclear leukocyte (PMN) adhesion to activated endothelial cells under flow. Blocking PAF reduced PMN interaction with thrombin- or TNF-alpha-stimulated cells.
Area of Science:
- Immunology
- Cell Biology
- Vascular Biology
Background:
- Platelet-activating factor (PAF) influences leukocyte adhesion to endothelial cells under static conditions.
- The role of PAF in leukocyte adhesion under dynamic flow and inflammatory conditions is not well understood.
Purpose of the Study:
- To investigate the role of PAF in polymorphonuclear leukocyte (PMN) adhesion to human umbilical vein endothelial cells (HUVEC) under flow conditions.
- To assess the effect of PAF receptor antagonism on PMN adhesion stimulated by thrombin and tumor necrosis factor-alpha (TNF-alpha).
Main Methods:
- Utilized a parallel-plate flow chamber to simulate dynamic flow conditions.
- Employed a PAF receptor antagonist (L-659,989) to block PAF signaling.
- Quantified PMN rolling and adhesion to HUVEC using a computer-based image analysis system.
Main Results:
- Thrombin stimulation significantly increased PMN rolling and adhesion to HUVEC, accompanied by increased PAF synthesis.
- PAF receptor antagonism with L-659,989 significantly reduced PMN rolling and adhesion to thrombin-activated HUVEC.
- TNF-alpha stimulation increased PMN rolling and adhesion; L-659,989 reduced adhesion and transmigration but not rolling.
Conclusions:
- PAF plays a significant role in mediating PMN adhesion and migration to inflammatory-activated HUVEC under flow.
- PAF signaling is crucial for leukocyte-endothelial cell interactions during inflammation in a flow environment.