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

Abstract

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 μM) 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.