ISOENZYME-SPECIFIC CYCLOOXYGENASE INHIBITORS - A WHOLE-CELL ASSAY SYSTEM USING THE HUMAN ERYTHROLEUKEMIC CELL-LINE HEL AND THE HUMAN MONOCYTIC CELL-LINE MONO-MAC-6

NSAIDs inhibit the conversion of arachidonic acid into Prostaglandin G (2) and Prostaglandin H-2 which is catalyzed by the enzyme cyclooxygen ase (COX). Two genetically distinct isoforms have been discovered, COX -1 and COX-2. While COX-1 is thought to account for homeostatic amount s of eicosanoids, COX-2 is induced during inflammation leading to path ologic amounts of eicosanoids. Since NSAIDs inhibit both COX isoforms, antiinflammatory drug research has refocused to discovering COX-2 inh ibitors that do not inhibit COX-1. For this purpose, we have developed a whole cell assay system using the human erythroleukemic cell line H EL as a source for COX-1 and the human monocytic cell line Mono Mac 6 as a source for COX-2. Mono Mac 6 cells express high amounts of COX-2 upon stimulation with lipopolysaccharide (LPS) in the absence of any d etectable COX-1 protein. On the other hand, we find HEL cells to natur ally express COX-1 protein, but not COX-2. Testing of a panel of NSAID s as well as some COX-2 specific inhibitors showed that this assay sys tem is suitable for identifying compounds that selectively inhibit eit her COX-1 or COX-2. This test system offers the advantage of assessing COX-1 and COX-2 inhibitors within the human species, within a similar test set-up, and circumvents the need for tedious purification of eit her platelets or peripheral blood monocytes. (C) 1997 Elsevier Science Inc.