On the expression of cytosolic calcium-independent phospholipase A2 (88 kDa) in immature and mature myeloid cells and its role in leukotriene synthesis in human granulocytes

The human calcium-independent phospholipase A(2) (iPLA(2); 88 kDa) has recently been cloned (Larsson, P.K.A., Claesson, H.-E. and Kennedy, B.P. (1998) J. Biol. Chem. 272, 207-214), Here we demonstrate the expression of the human iPLA(2) mRNA and its splice variants in blood progenitor cells, immature leukemic cells and mature granulocytes, Chromatographical resolvable iPLA(2) activity was found in the cytosolic fraction of granulocytes and the activity was inhibited by the iPLA(2) inhibitor bromoenol lactone, This drug also inhibited leukotriene synthesis in human granulocytes, induced by low concentration of calcium ionophore A23187 (0.10-0.15 mu M) or opsonized zymosan, These results suggest that iPLA(2) is involved in the regulation of the pool of arachidonic acid destined for leukotriene synthesis in human granulocytes. (C) 1998 Federation of European Biochemical Societies.