Inhibition of Cytosolic Phospholipase A_2 Suppresses Production of Cholesteryl Ester through the Reesterification of Free Cholesterol but not Formation of Foam Cells in Oxidized LDL-Stimulated Macrophages(Highlighted paper selected by Editor-in-chief,Bioc

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Macrophage-derived foam cells are formed as a result of the accumulation of cholesteryl ester (CE) not only in cytoplasm where CE is produced by the reesterification of free cholesterol derived from oxidized low density lipoprotein (OxLDL) undergoing hydrolysis, but also in lysosomes where the remaining CE of OxLDL is deposited. We examined the possible involvement of cytosolic phospholipase A_2s (cPLA_2s) in the production of CE through the reesterification and in the formation of foam cells. In [^3H]oleic acid-labeled human acute monocytic leukemia (THP-1) cell-derived macrophages (THP-M) and mouse peritoneal macrophages (MPM), which possessed at least cPLA_2α and cPLA_2γ, stimulation with OxLDL induced the production of [^3H]cholesteryl oleate ([^3H]CE).The production was suppressed by an inhibitor of cPAL_2s. However, the inhibitor tended to slightly decrease total intracellular levels of CE, and did not affect the formation of foam cells, as estimated by staining with Oil Red O. In cPLA_2α-knockout MPM, OxLDL-induced increases in [^3H]CE and total CE did not differ from those in wild-type MPM. Our results suggest that cPLA_2s other than cPLA_2α contribute to the supply of fatty acids, which are utilized for the production of CE through the reesterification, in OxLDL-stimulated macrophages. However, the formation of foam cells could not be inhibited only by the suppression of cPLA_2-mediated CE production.
2008-01-01