Antisense oligonucleotide inhibition of type II phospholipase A2 expression, release and activity in vitro

Phospholipase A2 (PLA2) enzymes that regulate the release of arachidonic acid from cell membrane phospholipids represent a crucial rate-limiting step for the prostaglandin biosynthetic pathway. The aim of this study was to determine the mechanism of action and effects of type II PLA2 antisense oligonucleotides on type II PLA2 mRNA relative abundance, and the release of PLA2 enzymatic activity and prostaglandin F2alpha (PGF2alpha) in vitro. A human placental explant system was used to evaluate the effects of the type II PLA2 specific antisense oligonucleotides A (5'-GGGTGGGTATAGAAGGGCTCC-3', complementary to the base sequence 697-717 of the type II PLA2 gene) and B (5'-TTTTTGATTTGCTAATTGCTT-3', complementary to the base sequence 821-841 of the type II PLA2 gene). PLA2 activity released from explants was quantified by radiolabelled substrate assay using 14C-phosphatidylethanolamine (PE), and PGF2alpha content was analyzed by radioimmunoassay. Compared with control, the release of PLA2 activity and PGF2alpha was significantly reduced over the 24-h period by treatment with both antisense oligonucleotides (P< 0.05). At this concentration, type II PLA2 mRNA abundance was also significantly reduced by both antisense oligonucleotides A and B (P< 0.05). This data demonstrates the efficacy of antisense oligonucleotide inhibition of secretory PLA2 (sPLA2) expression and activity, and the contribution of sPLA2 to placental prostaglandin production.