Platelet-Activating Factor and Angiogenesis

Abstract

Platelet-activating factor (PAF) is a phospholipid autacoid with a spectrum of diverse and potent biological properties relevant for the development of inflammatory reaction and septic shock¹. Recently, PAF has been also implicated in the embryogenesis and cell differentiation^2,3. Researchers believe that PAF is a mediator of cell to cell communication which may function both as intercellular and intracellular messenger. Since PAF is produced after appropriate stimulation by many cell types, including most inflammatory cells, it has been implicated in the pathogenesis of a variety of diseases⁴. Moreover, human endothelial cells (EC) were found to produce PAF after stimulation by several inflammatory mediators^5,6. Many cell types that synthesized PAF, including EC, are also target for PAF^7,8 and express PAF-binding sites on their surface⁹. PAF, indeed, directly stimulates the endothelium, as it enhances the permeability of EC monolayer and induces changes of the cell cytoskeleton, leading to cell retraction and formation of intercellular gaps⁸. Moreover, it was observed that, in sub-confluent EC cultures, the redistribution of cytoskeleton was characteristic of cells undergoing translational movements⁸. These observations prompted us to evaluate whether PAF may stimulate the migration of EC in vitro.