Involvement of calcium-independent phospholipase A2 in uterine stromal cell phospholipid remodelling

The role of Ca2+-independent phospholipase A(2) (iPLA(2)) in arachidonic (AA) and docosahexaenoic (DHA) acid incorporation and phospholipid remodelling in rat uterine stromal cells (U-III cells) was studied. Incorporation of AA and DHA into Um cell phospholipids was Ca2+-independent, Bromoenollactone (BEL), a patent inhibitor of iPLA(2), reduced lysophosphatidylcholine level and AA incorporation into phospholipids by approximate to 20%. DHA incorporation was not affected by EEL, indicating that the pathways for AA and DHA incorporation are partially different. In control cells, the transfer of AA occurred mainly from diacyl-glycerophosphocholine (GroPCho) to alkenylacyl-glycerophosphoethanolamine (GroPEtn) and to a lesser extent from diacyl-GroPCho to diacyl-GroPEtn. [H-3]DHA was redistributed from diacyl-GroPCho and alkylacyl-GroPEtn to alkenylacyl-GroPEtn, EEL treatment inhibited completely the redistribution of AA within diacyl-GroPCho and diacyl -GroPEtn and reduced the [H-3]DHA content of diacyl-GroPEtn, indicating that a EEL-sensitive iPLA(2) controls the redistribution of polyunsaturated fatty acids to diacyl-GroPEtn. In contrast the redistribution of radioactive AA and DHA to alkenylacyl-GroPEtn was almost insensitive to EEL. The analysis of substrate specificity and EEL sensitivity of iPLA(2) activity indicates that UIII cells exhibit at least two isoforms of iPLA(2), one of which is EEL-sensitive and quite selective of diacyl species, and another one that is insensitive to EEL and selective for alkenylacyl-GroPEtn. Taken together, these results suggest that several iPLA(2) participate independently in the remodelling of Um cell phospholipids.