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 o f O-2(radical anion) are required for monocyte-mediated low density li poprotein (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 i nvestigated 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 mos t well-studied cPLA(2), has a molecular mass of 85 kDa and has been re ported to be regulated by both Ca2+ and phosphorylation. We found that cPLA(2) protein levels and cPLA(2) enzymatic activity mere induced up on activation of human monocytes by opsonized zymosan, Pharmacologic i nhibition 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 n ot 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 lip id 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 oligon ucleotides did not affect cPLA(2) protein expression, cPLA(2) enzymati c activity, O-2(radical anion) production, or monoctye-mediated LDL Li pid oxidation. These studies support the proposal that cPLA(2) activit y is required for activated monocytes to oxidize LDL Lipids.