title: Prostaglandin E2 EP3 receptor regulates cyclooxygenase-2 expression in the kidney.
abstract: Cyclooxygenase-2 (COX-2) is constitutively expressed and highly regulated in the thick ascending limb (TAL). As COX-2 inhibitors (Coxibs) increase COX-2 expression, we tested the hypothesis that a negative feedback mechanism involving PGE(2) EP3 receptors regulates COX-2 expression in the TAL. Sprague-Dawley rats were treated with a Coxib [celecoxib (20 mg·kg(-1)·day(-1)) or rofecoxib (10 mg·kg(-1)·day(-1))], with or without sulprostone (20 μg·kg(-1)·day(-1)). Sulprostone was given using two protocols, namely, previous to Coxib treatment (prevention effect; Sulp7-Coxib5 group) and 5 days after initiation of Coxib treatment (regression effect; Coxib10-Sulp5 group). Immunohistochemical and morphometric analysis revealed that the stained area for COX-2-positive TAL cells (μm(2)/field) increased in Coxib-treated rats (Sham: 412 ± 56.3, Coxib: 794 ± 153.3). The Coxib effect was inhibited when sulprostone was used in either the prevention (285 ± 56.9) or regression (345 ± 51.1) protocols. Western blot analysis revealed a 2.1 ± 0.3-fold increase in COX-2 protein expression in the Coxib-treated group, an effect abolished by sulprostone using either the prevention (1.2 ± 0.3-fold) or regression (0.6 ± 0.4-fold vs. control, P < 0.05) protocols. Similarly, the 6.4 ± 0.6-fold increase in COX-2 mRNA abundance induced by Coxibs (P < 0.05) was inhibited by sulprostone; prevention: 0.9 ± 0.3-fold (P < 0.05) and regression: 0.6 ± 0.1 (P < 0.05). Administration of a selective EP3 receptor antagonist, L-798106, also increased the area for COX-2-stained cells, COX-2 mRNA accumulation, and protein expression in the TAL. Collectively, the data suggest that COX-2 levels are regulated by a novel negative feedback loop mediated by PGE(2) acting on its EP3 receptor in the TAL.
authors.affiliation: Dept. of Physiology, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Alameda 340, Santiago, Chile. cvio@uc.cl
authors.forename: Carlos P
authors.initials: CP
authors.lastname: Vio
authors.forename: Mariana
authors.initials: M
authors.lastname: Quiroz-Munoz
authors.forename: Catherina A
authors.initials: CA
authors.lastname: Cuevas
authors.forename: Carlos
authors.initials: C
authors.lastname: Cespedes
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Ferreri
mesh_terms: D000818:Animals; D015153:Blotting, Western; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology; D025461:Feedback, Physiological / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D007150:Immunohistochemistry; D007668:Kidney / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009399:Nephrons / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000378:metabolism; D058308:Receptors, Prostaglandin E, EP3 Subtype / Q000187:drug effects / Q000502:physiology*
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D058306:Receptors, Prostaglandin E, EP1 Subtype; D058308:Receptors, Prostaglandin E, EP3 Subtype; C016767:sulprostone; D012313:RNA; D051546:Cyclooxygenase 2; D015232:Dinoprostone