Platelet-Activating Factor and Calcium Signaling: Its Implication in Cellular Responses

Platelet-activating factor (PAF), a potent phospholipid inflammatory mediator, known to affect cellular phosphoinositide metabolism, through formation of inositol triphosphate, transiently releases intracellular calcium. This highly sensitive cellular signaling process is involved in a great variety of cellular responses in many organs, and it may play a pivotal role in regulating meditor release in the cell. Through activating phospholipase A2, leading to arachidonic acid release and eicosanoid generation, PAF may induce downregulation of mediator release, an important process to maintain normal cell metabolism. On the other hand, via interacting with various cytokines or bacterial lipopolysaccharides, PAF may up-regulate mediator release, initiating an important role for the phospholipid noy only under normal conditions, but also in pathophysiological alterations of cellular responses and metabolism.