title: Corticosteroids induce COX-2 expression in cardiomyocytes: role of glucocorticoid receptor and C/EBP-beta.
abstract: Psychological stress increases the level of glucocorticoids in the circulating system. We found that dexamethasone administration in adult mice elevates the expression of COX-2 in the myocardium. With isolated neonatal cardiomyocytes, corticosterone (CT) at physiologically relevant doses (0.01-1 microM) induces the expression of COX-2 gene. The induction first appeared at 4 h and remained for at least 24 h with 1 microM CT treatment. This response is likely cardiomyocyte cell type specific since CT did not induce COX-2 expression in cardiac fibroblasts and glucocorticoids are known to suppress the expression of COX-2 in lymphocytes and several organs. Corticosteroids, but not estrogen or progesterone, induce COX-2 expression. The glucocorticoid receptor (GR) antagonist mifepristone (MF) prevented CT from inducing COX-2 gene, suggesting a GR-dependent induction in cardiomyocytes. COX-2 gene promoter deletion and mutation studies indicate a role of CCAAT/enhancer binding protein-beta (C/EBP-beta) in CT-induced COX-2 gene expression. Chromatin immunoprecipitation assays revealed that CT caused the binding of both GR and C/EBP-beta to COX-2 promoter, while MF pretreatment blocked such binding. Coimmunoprecipitation experiments demonstrated that CT treatment induced the interaction of GR with C/EBP-beta. Small interfering RNA against C/EBP-beta prevented CT from activating COX-2 promoter or elevating COX-2 protein. Our data suggest that the interaction between GR and C/EBP-beta contributes to elevated COX-2 gene transcription by CT in cardiomyocytes.
authors.affiliation: Interdisciplinary Graduate Program of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona 85724, USA.
authors.forename: Haipeng
authors.initials: H
authors.lastname: Sun
authors.forename: Elena
authors.initials: E
authors.lastname: Sheveleva
authors.forename: Beibei
authors.initials: B
authors.lastname: Xu
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Inoue
authors.forename: Tim G
authors.initials: TG
authors.lastname: Bowden
authors.forename: Qin M
authors.initials: QM
authors.lastname: Chen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003345:Corticosterone / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D022782:CCAAT-Enhancer-Binding Protein-beta; D034741:RNA, Small Interfering; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D051546:Cyclooxygenase 2; D003345:Corticosterone