Platelet-Activating Factor (PAF): Signalling and Adhesion in Cell-Cell Interactions

ω-3 Fatty acids suppress monocyte adhesion to human endothelial cells: role of endothelial PAF generation

“…Cultured HUVEC demonstrate hardly any P-selectin expression after stimulation with TNF-␣. This study did not address the question whether adhesive forces between PAF and its receptor may directly contribute to the firm monocyte attachment on the endothelial cells or whether the PAF system is largely operative via monocyte activation and enhanced mononuclear integrin expression and/or avidity as suggested as juxtacrine PAF-induced mechanisms (22,49). Receptor-operated regulation of integrin affinity has, indeed, been disclosed as an important mechanism inducing rapid leukocyte adhesion to endothelial cell surfaces (26,40,43).…”

“…PAF synthesis in endothelial cells was first described in HUVEC (5, 31) but is in fact a function of endothelial cells from all vascular beds activated by receptor-operated stimuli or undergoing injurious attack (3,18). Endothelial PAF remains associated with the cell surface, even in the presence of albumin for binding of this hydrophobic molecule, and studies from Zimmerman and co-workers (20,48,49) suggested that binding of endothelial PAF and the leukocyte PAF receptor contribute to adhesive interactions between endothelial cells and monocytes, followed by a juxtacrine activation of the adherent mononuclear cells. This concept is fully supported by the Fig.…”

Endothelial cell functions

“…As well, PAF synthesis is also triggered by endothelial cell activation. PAF remains into the endothelial cell plasma membrane (Zimmerman et al, 1996). As chemokines, PAF is specifically recognized by a seven-transmembrane spanning receptors present on the leukocyte surface and participates in triggering firm adhesion (Prescott et al, 2001).…”

PAF-acetylhydrolase expressed during megakaryocyte differentiation inactivates PAF-like lipids

“…3 Both PAF and PAF-like lipids are substrates of a small subset of phospholipases A2, the PAF-acetylhydrolases (PAF-AHs), which quench signaling by both types of PAFR ligands. 4 Although the PAF signaling system has been studied extensively in endothelial cells and circulating leukocytes, platelets, and other human cells, 2,[4][5][6][7] its roles in the bone marrow compartment are less characterized. PAF is present in human bone marrow where it regulates the function of stem cell progenitors.…”