Radiation-induced increased platelet-activating factor activity in mixed saliva

BACKGROUND: Platelet-activating factor (PAF), a family of structurally- related phospholipid mediators of inflammation, is present in normal human mixed saliva; however, its role in oral biology and the homeostasis of oral host defense mechanisms remains to be established. EXPERIMENTAL DESIGN: The current study was designed to evaluate the salivary levels of PAF in patients with oral mucositis that developed as a complication of head and neck irradiation for oral cancer. PAF activity was assessed in platelet bioassay and expressed relative to the activity of authentic PAF, 1-O-hexadecyl-2- acetyl-sn-glycero-3-phosphocholine (C16:0-AGEPC). RESULTS: A significant increase in salivary PAF levels was observed in patients with mucositis (47,032 ± 12,731 C16:0-AGEPC fmole equivalents/ml of saliva, mean ± SE, N = 7) as compared with normal subjects (5,568 ± 1,135 C16:0-AGEPC fmole equivalents/ml of saliva, N = 27). Phospholipid fractionation of the PAF isolated from the saliva of patients with mucositis by reverse phase high performance liquid chromatography revealed a single peak of activity that corresponded with the elution profile of C16:0-AGEPC, the most biologically active molecular species of PAF. In contrast, the PAF isolated from normal human mixed saliva contained multiple molecular species of PAF. CONCLUSIONS: These results suggest that this potent phospholipid inflammatory mediator may play a role in the inflammation and tissue injury associated with mucositis resulting from radiation treatment for oral cancer.