Selective inhibition of cytosolic phospholipase A(2) in activated human monocytes - Regulation of superoxide anion production and low density lipoprotein oxidation

Our previous studies have shown that monocyte activation and release of O-2(radical anion) are required for monocyte-mediated low density lipoprotein (LDL) lipid oxidation. We have also found that intracellular Ca2+ levels and protein kinase C activity are requisite participants in this potentially pathogenic process. In these studies, we further investigated the mechanisms involved in the oxidation of LDL lipids by activated human monocytes, particularly the potential contributions of the cytosolic phospholipase A(2) (cPLA(2)) signaling pathway. The most well-studied cPLA(2), has a molecular mass of 85 kDa and has been reported to be regulated by both Ca2+ and phosphorylation. We found that cPLA(2) protein levels and cPLA(2) enzymatic activity mere induced upon activation of human monocytes by opsonized zymosan, Pharmacologic inhibition of cPLA(2) activity by AA-COOF3, which has been reported to be a specific inhibitor of cPLA(2) as compared with sPLA(2), caused a dose-dependent inhibition of cPLA(2) enzymatic activity and LDL lipid oxidation by activated human monocytes, whereas sPLA(2) activity was not affected. To corroborate these findings, we used specific antisense oligonucleotides to inhibit cPLA(2). We observed that treatment with antisense oligonucleotides caused suppression of both cPLA(2) protein expression and enzymatic activity as well as monocyte-mediated LDL lipid oxidation. Furthermore, antisense oligonucleotide treatment caused a substantial inhibition of O-2(radicl anion) production by activated human monocytes. In parallel experimental groups, cPLA(2) sense oligonucleotides did not affect cPLA(2) protein expression, cPLA(2) enzymatic activity, O-2(radical anion) production, or monoctye-mediated LDL Lipid oxidation. These studies support the proposal that cPLA(2) activity is required for activated monocytes to oxidize LDL Lipids.