title: Feedback regulation of cyclooxygenase-2 transcription ex vivo and in vivo.
abstract: Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme for prostaglandin biosynthesis. Its inducible expression is regulated by complex pathways. To monitor Cox-2 transcriptional activity in vivo, we generated a knock-in mouse expressing a firefly luciferase reporter. In this study we examined, by comparing luciferase activity of Cox-2(luc/+) and Cox-2(luc/-) cells and mice, effects of prostanoid products on Cox-2 promoter transcriptional activation. In peritoneal macrophages, luciferase induction by LPS in Cox-2(luc/-) cells was less than that of Cox-2(luc/+) cells. However, in the presence of PGE(2), induction was comparable, suggesting positive Cox-2 feedback regulation by PGE(2) occurs for macrophages. In contrast, feedback modulation was not observed in TPA-induced Cox-2(luc/+) and Cox-2(luc/-) mouse embryonic fibroblasts (MEFs). Using non-invasive in vivo imaging, we observed negative feedback regulation of Cox-2 expression during paw inflammation in living mice. Our results suggest Cox-2 expression is regulated by cell type specific feedback mechanisms, both in cultured cells and in living animals.
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, 341 Boyer Hall, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA.
authors.forename: Tomo-O
authors.initials: TO
authors.lastname: Ishikawa
authors.forename: Naveen
authors.initials: N
authors.lastname: Jain
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Herschman
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2 / Q000235:genetics*; D015536:Down-Regulation; D025461:Feedback, Physiological; D015971:Gene Expression Regulation, Enzymologic; D055879:Gene Knock-In Techniques; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D008817:Mice, Mutant Strains; D014158:Transcription, Genetic
chemical_list: C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2