BMS-229724 Is a Tight-Binding Inhibitor of Cytosolic Phospholipase A 2 That Acts at the Lipid/Water Interface and Possesses Anti-Inflammatory Activity in Skin Inflammation Models

ABSTRACT Cytosolic phospholipase A 2 (cPLA 2 ) catalyzes the selective release of arachidonic acid from the sn-2 position of phospholipids and is believed to play a key cellular role in the generation of arachidonic acid. BMS-229724 (4-[4-[2-[2-[bis(4-chlorophenyl)methoxy]ethyl-sulfonyl]ethoxy]phenyl]-1,1,1-trifluoro-2-butanone) was found to be a selective inhibitor of cPLA 2 (IC 50 ϭ 2.8 M) in that it did not inhibit secreted phospholipase A 2 in vitro, nor phospholipase C and phospholipase D in cells. The compound was active in inhibiting arachidonate and eicosanoid production in U937 cells, neutrophils, platelets, monocytes, and mast cells. With a synthetic covesicle substrate system, the dose-dependent inhibition could be defined by kinetic equations describing competitive inhibition at the lipid/water interface. The apparent equilibrium dissociation constant for the inhibitor bound to the enzyme at the interface (K