Participation of the arachidonic acid cascade pathway in macrophage binding/uptake of oxidized low density lipoprotein

Arachidonic acid cascade inhibitors. including phospholipase A, inhibitors, dexamethasone and quinacrine (mepacrine). cyclooxygenase inhibitors. indomethacin and aspirin. and lipoxygenase inhibitor AA861, prevented foam cell formation and cholesterol accumulation in the incubation of thioglycollate-induced mouse peritoneal macrophages with oxidized low density lipoprotein (LDL) at 37 degreesC for 24 h. These inhibitors similarly prevented foam cell formation of fibronectin- and Ca ionophore A23187-stimulated macrophages. Binding and/or uptake of Dil (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine)-acetyl LDL by macrophages at 37 degreesC for 3 h and arachidonic acid release from macrophages at 37degreesC for 4h were inhibited by dexamethasone. Exogenously added phospholipase A, of bee venom and Crotalus adamanteous venom increased arachidonic acid release during incubation for 2 h. and increased macrophage binding and/or uptake of Dil-acetyl LDL at 37degreesC for 3 h, and foam cell formation at 37degreesC for 24h. Protein kinase inhibitors. ML-9 and staurosporine. that inhibited macrophage binding and/or uptake of Dil-acetyl LDL did not inhibit arachidonic acid release, indicating that protein phosphorylation was not involved in the arachidonic acid pathway in the macrophage scavenger receptor activation. Nordihydroguaiaretic acid that inhibited arachidonic acid release prevented binding and/or uptake of Dil-acetyl LDL. The release of arachidonic acid was not enhanced by fibronectin-stimulation. indicating that Ca influx-dependent stimulation of macrophage activity was not through the activation of phospholipase A(2). These results indicate that. as well as the fibronectin-stimulated Ca influx pathway and protein phosphorylation pathway. the arachidonic acid pathway participated in the activation of macrophages to hind and take up oxidized.