Ultrastructural Localization of Prostaglandin Endoperoxide Synthase (Cyclooxygenase) to Isolated, Purified Fractions of Guinea Pig Peritoneal Macrophage and Line 10 Hepatocarcinoma Cell Lipid Bodies

Abstract

Subcellular fractions of purified cytoplasmic, nonmembrane-bound lipid bodies were prepared from [³H]-arachidonic acid-labeled guinea pig peritoneal macrophages and line 10 hepatocarcinoma cells. These fractions, which contained [³H]-arachidonyl lipids, were shown to be devoid of contaminating cellular membranes by electron microscopy, and to contain prostaglandin endoperoxide (PGH) synthase by postembedding immunogold electron microscopy. These findings support a proposed role for these lipid-rich organelles in the generation of eicosanoids by oxidative metabolism of arachidonate in the cyclooxygenase pathway of inflammatory and neoplastic cells.

Hyperosmolarity-induced lipid droplet formation depends on ceramide production by neutral sphingomyelinase 2

“…The cellular function of LDs is considered both detrimental as well as protective. The fi rst is illustrated by eicosanoids production from the FFAs released during triglyceride (TG) hydrolysis ( 14 ), whereas the protective effect was hinted at by longer survival under stress of cells that produce TGs ( 15 ). Membrane phospholipids provide the building blocks for stress-induced LD synthesis ( 16 ).…”

Monocyte Chemoattractant Protein-1 and 5-Lipoxygenase Products Recruit Leukocytes in Response to Platelet-Activating Factor-Like Lipids in Oxidized Low-Density Lipoprotein

“…Lipid bodies serve as sites for localization of esterified arachidonate and eicosanoid-forming enzymes (25,29), and certain leukotrienes mediate some of the effects of PAF in vivo (30 -32). We asked whether the cellular response to oxidized phospholipids required these eicosanoids.…”

Lipid Bodies Are Reservoirs of Cyclooxygenase-2 and Sites of Prostaglandin-E2 Synthesis in Colon Cancer Cells

“…However, mechanisms that regulate lipid body formation and their functional significance to the cellular biology of the tumor are not known. Recent studies based on lipid body content have shown that lipid bodies, beside their rich lipid content, contain several functionally diverse types of proteins, including adipose differentiation-related protein (ADRP) and caveolin (6)(7)(8)(9), lipid metabolic enzymes and proteins of Rab family (10)(11)(12), eicosanoid-forming enzymes (13,14), and protein kinases, such as phosphoinositide 3-kinase (PI3K), mitogenactivated protein kinase, and protein kinase C (PKC; refs. [15][16][17].…”