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

The human calcium-independent phospholipase A2 (iPLA2; 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 iPLA2 mRNA and its splice variants in blood progenitor cells, immature leukemic cells and mature granulocytes. Chromatographical resolvable iPLA2 activity was found in the cytosolic fraction of granulocytes and the activity was inhibited by the iPLA2 inhibitor bromoenol lactone. This drug also inhibited leukotriene synthesis in human granulocytes, induced by low concentration of calcium ionophore A23187 (0.10-0.15 microM) or opsonized zymosan. These results suggest that iPLA2 is involved in the regulation of the pool of arachidonic acid destined for leukotriene synthesis in human granulocytes.