Human mononuclear phagocytes (HMP) can be identified in elevated numbers in periodontally diseased tissues and can be stimulated to release physiologically significant amounts of arachidonic acid (AA) metabolites including prostaglandin E2 (PGE2) and thromboxane B2 (TSB2). PGE2 has particular relevance to periodontal disease due to its capacity to stimulate bone resorption and regulate immune function. Bacterial endotoxin, a complex lipopolysaccharide (LPS) implicated in the pathogenisis of periodontal disease, is a potent stimulator of AA metabolite release from HMP. However, the mechanisms by which LPS regulates AA metabolism in HMP remains virtually unexplored. The goal of this proposal is examine in detail LPS regulation of AA metabolite release from HMP. Specific points to be addressed in this proposal include 1) LPS stimulation of AA metabolite release from HMP in the absence of C3b stimulatory effects, 2) the apparent cellular compartmentalization of PGE2 and TXB2 production and release from HMP following stimulation with LPS, and 3) whether HMP possess significant amounts of ether-acyl and alkyl-acyl phospholipids and whether LPS selectively regulates AA release from these lipids. Initial experiments will characterize time and dose dependent metabolite release from HMP following stimulation with several LPS preparations including the biologically active lipid A moiety of LPS. AA metabolite release will be monitored by RIA as well as by the production of labelled metabolites following HMP prelabelling with 3H-AA and/or 14C-AA. In addition, HMP phospholipid content will be extensively characterized with specific emphasis on ether-acyl and alkyl-acyl phospholipid content. The time course of labelled metabolite appearance will then be correlated with alterations in phospholipid labelling. These studies will provide additional insight into the biological interaction between LPS and HMP and will provide additional support for the role of the monocyte/macrophage in chronic inflammatory disease processes including periodontal disease.
