Ultrastructural immunogold localization of prostaglandin endoperoxide synthase (cyclooxygenase) to non-membrane-bound cytoplasmic lipid bodies in human lung mast cells, alveolar macrophages, type II pneumocytes, and neutrophils.

Abstract

Lipid bodies are non-membrane-bound, lipid-rich cytoplasmic inclusions that occur in many mammalian cell types. Because lipid bodies are more prominent in cells associated with inflammation and are repositories of arachidonylphospholipids, a role for lipid bodies in the oxidative metabolism of arachidonic acid to form eicosanoids has been suggested. To evaluate further whether lipid bodies, in addition to serving as non-membranous sources of substrate arachidonate, are involved in eicosanoid formation, we used cells isolated from human lung to investigate the intracellular localization of prostaglandin endoperoxide (PGH) synthase (cyclmxygenase), the key initial, rate-limiting enzyme in the formation of prostaglandins and thromboxanes. Isolated lung cells containing a mixture of mast cells, alveolar macrophages, Type 11 alveolar pneumocytes, and neutrophils from short-term cultures were fted in suspension in a dilute aldehyde mixture, post-fixed in osmium tetroxide, stained en bloc with uranyl acetate, dehydrated in a graded series of alcohols, and embedded in Epon. A post-embedding immunogold procedure was used with a primary PGH synthase monoclonal antibody and 20-nm gold-conjugated sec-

Not Just Fat: The Structure and Function of the Lipid Droplet

“…However, some morphological studies show the presence of proteins, including soluble ones, in the LD core (Dvorak et al 1992;Bozza et al 1997;Robenek et al 2004Robenek et al , 2005. It is not plausible that hydrophilic proteins exist alone in the core, but amphiphilic proteins may complex with phospholipids to make structures compatible with the hydrophobic environment.…”

Mechanisms of leukocyte lipid body formation and function in inflammation

“…By using immunocytochemistry at the light level and ultrastructural postembedding immunogold, cyclooxygenase has been reported to localize at eosinophil lipid bodies, both in naturally formed lipid bodies in eosinophils from HES patients and in PAF-induced lipid bodies (Dvorak et al 1992, 1993, Bozza et al 1997. Previous studies on the intracellular localization of 5-LO have shown that 5-LO localization is cell type-specific and also varies according to the activation state of the cell.…”

Mechanisms of formation and function of eosinophil lipid bodies: inducible intracellular sites involved in arachidonic acid metabolism

“…By using immunocytochemistry at the light level and ultrastructural postembedding immunogold, cyclooxygenase has been reported to localize at eosinophil lipid bodies, both in naturally formed lipid bodies in eosinophils from HES patients and in PAF-induced lipid bodies (Dvorak et al 1992. Previous studies on the intracellular localization of 5-LO have shown that 5-LO localization is cell typespecific and also varies according to the activation state of the cell (Rouzer & Kargman 1988, Reid et al 1990, Woods et al 1993, Brock et al 1994).…”

“…Together our findings support a role for lipid bodies to function as specific sites for eicosanoid formation. The compartmentalization of arachidonate substrate (Weller et al 1989(Weller et al , 1991, cPLA 2 , and eicosanoid-forming enzymes (Dvorak et al 1992) provides in one locale an efficient mean to regulate arachidonate release and directly couple it with the enzymes to form eicosanoids.…”