Temporal and pharmacological division of fibroblast cyclooxygenase expression into transcriptional and translational phases.

Abstract

We have recently shown that the synthesis of cyclooxygenase [also called prostaglandin (PG) activity.Previous studies in our laboratory (1) and by others (2) have demonstrated that the cytokine interleukin 1 (IL-1) stimulates formation of prostaglandin E2 (PGE2) in cultured human dermal fibroblasts. We further showed that IL-1-containing monocyte-conditioned medium produced increased Vmas of fibroblast prostaglandin (PG) endoperoxide synthase (also called PG synthase and cyclooxygenase; 8,11,14-icosatrienoate, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.1), which appeared to be blocked by RNA and protein synthesis inhibitors (3). More recently, we have shown (4) that IL-1 stimulates the synthesis in fibroblasts of PG synthase in a time-and dose-dependent manner. Overall, these results (1-4) suggest an IL-1-dependent transcriptional regulation of the synthesis of PG synthase. Previous studies have shown that the tumor promoter phorbol 12-myristate 13-acetate (PMA) stimulated PGE2 production in a variety of cell types by: (i) increasing phospholipase A2 activity to release arachidonic acid (5, 6), (ii) inhibiting the reacylation enzymes arachidonoyl-CoA synthetase (EC 6.2.1.15) and lysophosphatide acyltransferase (EC 2.3.1.23; refs. 7 and 8), or (iii) increasing the level of cellular PG synthase (9). In the studies reported here, we tested the hypothesis that activation of protein kinase C plays a critical role in the signal transduction mechanism for the IL-1 and PMA induction of PG synthase synthesis.Glucocorticoids are known to inhibit icosanoid production when administered both in vivo and in vitro to cells or tissues (10). Evidence from numerous studies indicated that the mechanism of this glucocorticoid effect involves the synthesis ofa group ofproteins (collectively termed lipocortins) that inhibit the activity of phospholipase A2 and thereby the production of various icosanoids (10). Recent reports, however, have raised some doubts with regard to the validity of this mechanism. Davidson et al. (11) and Aarsman et al. (12) have demonstrated that lipocortins do not directly interact with or inhibit the activity of phospholipase A2 but rather interact with substrate phospholipids. Furthermore, in some studies, glucocorticoids failed to inhibit cellular phospholipase A2 (13) and also failed to induce synthesis of either the mRNA for lipocortin I or the lipocortin mass (14). Other studies (15, 16) have suggested that glucocorticoids may exert their inhibitory action on PG biosynthesis by inhibiting PG synthase activity. In support of this, Pash and Bailey (17) recently reported that dexamethasone inhibited the epidermal growth factor stimulation of PG synthase activity in aortic smooth muscle cells.The present studies were designed to establish incubation conditions that will afford a temporal separation of the transcriptional and translational phases of PG synthase synthesis, so that we could study the regulation of the enzyme synthesis at each of these phases. Lacking a PG synthase cDNA pro...

Glucocorticoids inhibit prostaglandin synthesis not only at the level of phospholipase A2 but also at the level of cyclo‐oxygenase/PGE isomerase

“…A similar inhibition of prostaglandin synthase in rats was also shown by Moore & Hoult (1980). After this manuscript was submitted, Bailey et al (1988) showed decreased mRNA levels of cyclooxygenase in vascular smooth muscle cells and Raz et al (1989) showed decreased levels of cyclo-oxygenase in fibroblasts. This indicates that the effects of glucocorticoids on cyclo-oxygenase are not restricted to a certain cell type but seem to be of more general nature.…”

Induction of cyclooxygenase ii in human synovial microvessel endothelial cells by interleukin‐1

“…We present herein evidence that microvessel endothelial cells derived from rheumatoid synovium produce increased amounts of PGE, when treated with IL-1. This increase in PGE, biosynthesis is mediated, at least in part, by an increase in the de induction by cytokines appears to be a consistent property of the inducible COX in divergent cell types and species (10,13,15,16,30). HSE cells were treated with exogenous AA to assess the COX activity following treatment of the cells with cytokines.…”

“…HSE cells were treated with exogenous AA to assess the COX activity following treatment of the cells with cytokines. IL-1 has been shown to increase PG release from cells by increasing the release of AA from membranes, a result of phospholipase A, activity (31,32), and to induce the synthesis of COX, which converts AA to PGH, (10,13,15). Basal PGE, release, as well as ionophore A23 187-stimulated PGE, release, require phospholipase-mediated release of AA from membranes in addition to AA metabolism by COX.…”

“…At least 2 forms of COX have been identified and their genes cloned (8)(9)(10)(11)(12). Type I COX is considered to be expressed constitutively, while type I1 COX is highly inducible by growth factors and cytokines (1 1, [13][14][15]. COX I1 is apparently expressed only in certain cell types such as monocytes (15) and fibroblasts (13,16).…”

Spatial Requirements for 15-(R)-Hydroxy-5Z,8Z,11Z,13E-eicosatetraenoic Acid Synthesis within the Cyclooxygenase Active Site of Murine COX-2

“…The discovery of a second isoform of COX, the expression of which is induced by a number of cytokines and growth factors (23)(24)(25)(26), has been the catalyst for significant efforts by numerous academic and pharmaceutical groups to isolate isoform selective inhibitors. One of the best known and oldest NSAIDs, aspirin, along with the new more COX-2-selective version of aspirin, APHS (7), differ from all other NSAIDs in that they covalently modify the same serine residue (Ser-530) in both COX-1 (6) and COX-2 (7,21,27).…”