Lipid bodies: intracellular sites for eicosanoid formation.

Lipid bodies, therefore, represent specialized intracellular domains that form rapidly in response to agents that activate protein kinase C. These structures contain eicosanoid-precursor arachidonate esterified in specific phospholipids. Arachidonate-releasing phospholipases probably act at lipid bodies, and an eicosanoid-forming enzyme, PGH synthase (cyclooxygenase), definitely localizes to lipid bodies. In addition, the heightened presence of lipid bodies in cells likely to be producing eicosanoids as part of inflammatory reactions indicates that lipid bodies are dynamic, specialized intracellular domains with roles pertinent to the metabolic transformation of arachidonate into paracrine mediators of inflammation. With their prominence in cells in association with inflammation, lipid bodies constitute specialized sites at which eicosanoid formation could occur for the heightened generation of eosinophil eicosanoid mediators of inflammation. This compartmentalization of eicosanoid formation at lipid bodies would provide a nonmembrane pool of arachidonate whose metabolic utilization could occur without perturbation of membranes if membranes were the sole stores of substrate fatty acid used for quantities of eicosanoids synthesized as paracrine mediators of inflammation. Moreover, lipid bodies would serve as sites at which the coordinated and regulated enzymatic events involved in arachidonate mobilization and oxidative metabolism could occur.