TY - JOUR T1 - BMS-229724 Is a Tight-Binding Inhibitor of Cytosolic Phospholipase A<sub>2</sub> That Acts at the Lipid/Water Interface and Possesses Anti-Inflammatory Activity in Skin Inflammation Models JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 376 LP - 385 VL - 298 IS - 1 AU - James R. Burke AU - Lynda B. Davern AU - Paul L. Stanley AU - Kurt R. Gregor AU - Jacques Banville AU - Roger Remillard AU - John W. Russell AU - Patrick J. Brassil AU - Mark R. Witmer AU - Graham Johnson AU - Jeffrey A. Tredup AU - Kenneth M. Tramposch Y1 - 2001/07/01 UR - http://jpet.aspetjournals.org/content/298/1/376.abstract N2 - Cytosolic phospholipase A2 (cPLA2) 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 cPLA2(IC50 = 2.8 μM) in that it did not inhibit secreted phospholipase A2 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 (KI*app) was determined to be 1 · 10−5 mol% versus an apparent dissociation constant for the arachidonate-containing phospholipid of 0.35 mol%. The unit of concentration in the interface is mole fraction (or mol%), which is related to the surface concentration of substrate, rather than bulk concentration that has units of molarity. Thus, BMS-229724 represents a novel inhibitor of cPLA2, which partitions into the phospholipid bilayer and competes with phospholipid substrate for the active site. This potent inhibition of the enzyme translated into anti-inflammatory activity when applied topically (5%, w/v) to a phorbol ester-induced chronic inflammation model in mouse ears, inhibiting edema and neutrophil infiltration, as well as prostaglandin and leukotriene levels in the skin. In hairless guinea pigs, BMS-229724 was active orally (10 mg/kg) in a UVB-induced skin erythema model in hairless guinea pigs. The American Society for Pharmacology and Experimental Therapeutics ER -