Antisense inhibition of group VI Ca2+-independent phospholipase A(2) blocks phospholipid fatty acid remodeling in murine P388D(1) macrophages

A major issue in lipid signaling relates to the role of particular phospholipase A(2) isoforms in mediating receptor-triggered responses, This has been difficult to study because of the lack of isoform specific inhibitors, Based on the use of the Group VI Ca2+-independent phospholipase A(2) (iPLA(2)) inhibitor bromoenol lactone (EEL), we previously suggested a role for the iPLA(2) in mediating phospholipid fatty acid turnover (Balsinde, J,, Bianco, I, D,, Ackermann, E, J,, Conde-Frieboes, K., and Dennis, E, A. (1995) Proc, Natl, Acad, Sci, U, S, A, 92: 8527-8531), We have now further evaluated the role of the iPLA(2) in phospholipid remodeling by using antisense RNA technology, We show herein that inhibition of iPLA(2) expression by a specific antisense oligonucleotide decreases both the steady-state levels of lysophosphatidylcholine and the capacity of the cell to incorporate arachidonic acid into membrane phospholipids. These effects correlate with a decrease in both iPLA(2) activity and protein in the antisense-treated cells. Collectively these data provide further evidence that the iPLA(2) plays a major role in regulating phospholipid fatty acyl turnover in P388D(1) macrophages. In stark contrast, experiments with activated cells confirmed that the iPLA(2) does not play a significant role in receptor-coupled arachidonate mobilization in these cells, as manifested by the lack of an effect of the iPLA(2) antisense oligonucleotide on PAF-stimulated arachidonate release.