title: Regulation of prostaglandin E synthases: effects of siRNA-mediated inhibition of microsomal prostaglandin E synthase-1.
abstract: Prostaglandin E2 (PGE2) is a key mediator involved in several inflammatory conditions. In this study, we investigated the expression and regulation of the terminal PGE2 synthesizing enzyme prostaglandin E synthases (mPGES-1, mPGES-2 and cPGES) in gingival fibroblasts stimulated with pro-inflammatory cytokines. We used siRNA knockdown of mPGES-1 to elucidate the impact of mPGES-1 inhibition on mPGES-2 and cPGES expression, as well as on PGE2 production. The cytokines TNFalpha and IL-1beta increased protein expression and activity of mPGES-1, accompanied by increased COX-2 expression and PGE2 production. The isoenzymes mPGES-2 and cPGES, constitutively expressed at mRNA and protein levels, were unaffected by the pro-inflammatory cytokines. We show for the first time that treatment with mPGES-1 siRNA down-regulated the cytokine-induced mPGES-1 protein expression and activity. Interestingly, mPGES-1 siRNA did not affect the cytokine-stimulated PGE2 production, whereas PGF(2alpha) levels were enhanced. Neither mPGES-2 nor cPGES expression was affected by siRNA silencing of mPGES-1. Dexamethasone and MK-886 both inhibited the cytokine-induced mPGES-1 expression while mPGES-2 and cPGES expression remained unaffected. In conclusion, mPGES-1 siRNA down-regulates mPGES-1 expression, and neither mPGES-2 nor cPGES substituted for mPGES-1 in a knockdown setting in gingival fibroblasts. Moreover, mPGES-1 siRNA did not affect PGE2 levels, whereas PGF(2alpha) increased, suggesting a compensatory pathway of PGE2 synthesis when mPGES-1 is knocked down.
authors: Department of Pediatric Dentistry, Institute of Odontology, Karolinska Institutet, Huddinge, Sweden. tove.bage@ki.se
authors: Tove
authors: T
authors: Båge
authors: Thomas
authors: T
authors: Modéer
authors: Tomomi
authors: T
authors: Kawakami
authors: Hernan Concha
authors: HC
authors: Quezada
authors: Tülay
authors: T
authors: Yucel-Lindberg
mesh_terms: D002478:Cells, Cultured; D002648:Child; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D016207:Cytokines / Q000502:physiology; D003600:Cytosol / Q000201:enzymology; D015232:Dinoprostone / Q000096:biosynthesis; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology; D005881:Gingiva / Q000201:enzymology; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D008861:Microsomes / Q000201:enzymology*; D000071876:Prostaglandin-E Synthases; D034741:RNA, Small Interfering / Q000235:genetics*; D015398:Signal Transduction
chemical_list: D016207:Cytokines; D007527:Isoenzymes; D034741:RNA, Small Interfering; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; C000605863:PTGES2 protein, human; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone