Selectivity of nonsteroidal antiinflammatory drugs as inhibitors of constitutive and inducible cyclooxygenase.

Abstract

Constitutive cyclooxygenase (COX-1; prostaglandin-endoperoxide synthase, EC 1.14.99.1) is present in cells under physiological conditions, whereas COX-2 is induced by some cytokines, mitogens, and endotoxin presumably in pathological conditions, such as inflammation. Therefore, we have assessed the relative inhibitory effects of some nonsteroidal antiinflammatory drugs on the activities of COX-1 (in bovine aortic endothelial cells) and COX-2 (in endotoxinactivated J774.2 macrophages) in intact ceils, broken cells, and purified enzyme preparations (COX-1 in sheep seminal vesicles; COX-2 in sheep placenta). Similar potencies of aspfrin, indomethacin, and ibuprofen against the broken cell and purified enzyme preparations indicated no influence of species. Aspirin, indomethacin, and ibuprofen were more potent inhibitors of COX-1 than COX-2 in all models used. The relative potencies of aspirin and indomethacin varied only slightly between models, although the IC50 values were different.Ibuprofen was more potent as an inhibitor of COX-2 in intact cells than in either broken cells or purified enzymes. Sodium salicylate was a weak inhibitor of both COX isoforms in intact cells and was inactive against COX in either broken cells or purified enzyme preparations. Diclofenac, BW755C, acetaminophen, and naproxen were approximately equipotent inhibitors of COX-1 and COX-2 in intact cells. BF 389, an experimental drug currently being tested in humans, was the most potent and most selective inhibitor of COX-2 in intact cells. Thus, there are clear pharmacological differences between the two enzymes. The use of such models of COX-1 and COX-2 activity will lead to the identification of selective inhibitors of COX-2 with presumably less side effects than present therapies. Some inhibitors had higher activity in intact cells than against purified enzymes, suggesting that pure enzyme preparations may not be predictive of therapeutic action.Cyclo-oxygenase (COX; prostaglandin-endoperoxide synthase, EC 1.14.99.1) converts arachidonic acid to prostaglandin (PG) H2, which is then further metabolized by other enzymes to various PGs, prostacyclin, and thromboxanes (1). COX exists in at least two isoforms with similar molecular weights ("'70 kDa). COX-1 is expressed constitutively and was first characterized, purified, and cloned from sheep vesicular glands (2-7). Activation of COX-1 leads, for instance, to the production of prostacyclin, which when released by the endothelium is antithrombogenic (8) and by the gastric mucosa is cytoprotective (9). COX-2 is induced in cells exposed to proinflammatory agents, including cytokines (10), mitogens (11) and endotoxin (12,13 COX-2 may well explain their therapeutic utility as antiinflammatory drugs, whereas inhibition of COX-1 may explain their unwanted side effects, such as gastric and renal damage.After establishing that bovine aortic endothelial cells in culture contain COX-1 and that endotoxin-activated J774.2 macrophages contain COX-2, we have investigated the inhibitory effects of s...

Regulation of cyclooxygenase activity by metamizol

“…1995 . Our data also indicate that, although breaking the integrity of the cell plasma membrane should facilitate the access of metamizol to the endoplasmic reticulum and nuclear envelope, where cyclooxygenase-2 is located Ž . Morita et al, 1995 , cell purified enzymes have also been described for other Ž NSAIDs Barnett et al, 1994;Mitchell et al, 1994;. Carabaza et al, 1996 .…”

“…The NSAID BF 389, for example, exhibits a 250-fold lower IC value for cyclooxygenase -2 50 in intact cells when compared with the IC obtained with 50 Ž . the purified enzyme Mitchell et al, 1994 . The reasons for these differences in the IC values depending on assay 50 conditions remain to be established.…”

“…Ž Section 3 or other classical NSAIDs Smith and DeWitt, . 1994;Mitchell et al, 1994;Cashman, 1996 . The IC 50 value obtained for cyclooxygenase-1 in human platelets is about 15-fold higher than the blood levels of metamizol Ž .…”

“…BAEC cells do not contain cyclooxygenase-2 but a constitutive cyclooxygenase-1 activity, which results in a release of prostaglandins to the Ž . extracellular medium Mitchell et al, 1994 . High concentrations of metamizol in the incubation media resulted in a We next decided to test the capacity of metamizol to inhibit cyclooxygenase-1 activity in human platelets as a model of freshly isolated intact human cells.…”

“…Murine monocyte-macrophage J774A.1 cells have been used as a model to determine cyclooxygenase-2 activity Mitchell et al, 1994 . No prostaglandin E levels were 2 detected in the incubation media, unless cells were stimulated with lipopolysaccharide for 12 h. In these conditions, and as a result of inducing cyclooxygenase-2 expression, the concentration of prostaglandin E released to the incu- …”