title: Comparison of the cyclooxygenase-1 inhibitory properties of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors, using sensitive microsomal and platelet assays.
abstract: Two forms of cyclooxygenase (COX) activity are involved in the synthesis of prostaglandins, prostacyclins, and thromboxanes in mammalian cells. There is now convincing evidence, obtained with a number of structurally distinct inhibitors, that selective COX-2 inhibitors possess anti-inflammatory effects with an improved gastrointestinal tolerability compared with conventional nonsteroidal anti-inflammatory drugs (NSAIDs) affecting both COX-1 and COX-2. As more selective COX-2 inhibitors are being developed, assays with a high degree of sensitivity to inhibition are needed to compare the relative effects of compounds on COX-1 activity. In the present report, we describe a sensitive assay for the inhibition of human COX-1 based on the production of prostaglandin E2 by microsomes from U937 cells incubated with a subsaturating concentration of arachidonic acid. More than 45 NSAIDs and selective COX-2 inhibitors were tested in this assay. IC50 values ranged from 1 nM for flunixin and flurbiprofen to about 200-500 microM for salicylate and acetaminophen. Potent and nonselective NSAIDs such as sulindac sulfide, diclofenac, and indomethacin showed IC50 values of < 20 nM. Among the compounds that have been reported to show selectivity for COX-2, the rank order of potency against COX-1 was DuP 697 > SC-58451 > celecoxib > nimesulide-meloxicam-piroxicam-NS-398-RS-57067 > SC-57666 > SC-58125 > flosulide > etodolac > L-745,337 > DFU-T-614, with IC50 values ranging from 7 nM to 17 microM. A good correlation was obtained between the IC50 values for the inhibition of microsomal COX-1 and both the inhibition of TXB2 production by Ca2+ ionophore challenged platelets and the inhibition of prostaglandin E2 production by CHO cells stably expressing human COX-1. However, the microsomal assay was more sensitive to inhibition than cell-based assays and allowed the detection of inhibitory effects on COX-1 for all NSAIDs and selective COX-2 inhibitors examined with discrimination of their potency under conditions of limited availability of arachidonic acid.
authors.affiliation: Merck Frosst Centre for Therapeutic Research, Kirkland, QC, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Riendeau
authors.forename: S
authors.initials: S
authors.lastname: Charleson
authors.forename: W
authors.initials: W
authors.lastname: Cromlish
authors.forename: J A
authors.initials: JA
authors.lastname: Mancini
authors.forename: E
authors.initials: E
authors.lastname: Wong
authors.forename: J
authors.initials: J
authors.lastname: Guay
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D016718:Arachidonic Acid / Q000378:metabolism; D001792:Blood Platelets / Q000201:enzymology; D016466:CHO Cells; D000001:Calcimycin / Q000494:pharmacology; D002460:Cell Line; D006224:Cricetinae; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D015232:Dinoprostone / Q000037:antagonists & inhibitors; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects*; D008565:Membrane Proteins; D008861:Microsomes / Q000201:enzymology; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects*; D012680:Sensitivity and Specificity; D013929:Thromboxane B2 / Q000037:antagonists & inhibitors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007476:Ionophores; D007527:Isoenzymes; D008565:Membrane Proteins; D016718:Arachidonic Acid; D000001:Calcimycin; D013929:Thromboxane B2; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone