PAF, a putative mediator of oral inflammation

PAF, or platelet-activating factor, is a family of structurally related pho spholipids ( 1-O-alkyl/acyl/alkenyl-2-acetyl-sn-glycero-3-phosphocholine) w hich possesses a wide spectrum of potent pro-inflammatory actions. These ph ospholipids are synthesized by a diverse array of cells, including neutroph ilic polymorphonuclear leukocytes (PMN), platelets, mast cells, monocytes/m acrophages, Vascular endothelial cells, and lymphocytes. PAF targets these and other cells via specific, G-protein-coupled receptors to initiate intra crine. autocrine, paracrine, and juxtacrine cell activation. Of important, these unique acetylated phospholipids are frequently synthesized in concert with pro-inflammatory lipid mediators derived from arachidonic acid. Since PAF synergizes with these and other mediators to amplify the inflammatory response, it seems likely that PAF plays an integral, perhaps pivotal, role in acute and chronic inflammatory processes. PAF is present in the mixed s aliva of dentate, but not edentulous, human subjects. The levels of PAF in mixed saliva or in gingival crevicular fluid and tissues are significantly increased during oral inflammatory conditions such as periodontitis and muc ositis, interestingly, the levels of salivary PAF correlate with the extent /severity of these oral diseases. These observations suggest that PAF may p articipate in pathophysiologic events during the course of oral inflammatio n. The availability of specific PAF receptor antagonists and human recombin ant PAF-acetylhydrolase (PAF-AH), a plasma enzyme which rapidly destroys PA F, should provide clinical tools for the investigation of the role of PAF i n these and other inflammatory disorders; and perhaps, ultimately, some of these reagents may prove to be therapeutically useful in the treatment and management of these conditions.