SELECTIVE-INHIBITION OF CYTOSOLIC PHOSPHOLIPASE A(2) IN ACTIVATED HUMAN MONOCYTES - REGULATION OF SUPEROXIDE ANION PRODUCTION AND LOW-DENSITY-LIPOPROTEIN OXIDATION
Q. Li et Mk. Cathcart, SELECTIVE-INHIBITION OF CYTOSOLIC PHOSPHOLIPASE A(2) IN ACTIVATED HUMAN MONOCYTES - REGULATION OF SUPEROXIDE ANION PRODUCTION AND LOW-DENSITY-LIPOPROTEIN OXIDATION, The Journal of biological chemistry, 272(4), 1997, pp. 2404-2411
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.