title: Glucocorticoids protect renal mesangial cells from apoptosis by increasing cellular sphingosine-1-phosphate.
abstract: Neutral ceramidase (NCDase) and sphingosine kinases (SphKs) are key enzymes regulating cellular sphingosine-1-phosphate (S1P) levels. In this study we found that stress factor-induced apoptosis of rat renal mesangial cells was significantly reduced by dexamethasone treatment. Concomitantly, dexamethasone increased cellular S1P levels, suggesting an activation of sphingolipid-metabolizing enzymes. The cell-protective effect of glucocorticoids was reversed by a SphK inhibitor, was completely absent in SphK1-deficient cells, and was associated with upregulated mRNA and protein expression of NCDase and SphK1. Additionally, in vivo experiments in mice showed that dexamethasone also upregulated SphK1 mRNA and activity, and NCDase protein expression in the kidney. Fragments (2285, 1724, and 1126 bp) of the rat NCDase promoter linked to a luciferase reporter were transfected into rat kidney fibroblasts and mesangial cells. There was enhanced NCDase promoter activity upon glucocorticoids treatment that was abolished by the glucocorticoid receptor antagonist RU-486. Single and double mutations of the two putative glucocorticoid response element sites within the promoter reduced the dexamethasone effect, suggesting that both glucocorticoid response elements are functionally active and required for induction. Our study shows that glucocorticoids exert a protective effect on stress-induced mesangial cell apoptosis in vitro and in vivo by upregulating NCDase and SphK1 expression and activity, resulting in enhanced levels of the protective lipid second messenger S1P.
authors.affiliation: Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
authors.forename: Ankathrin
authors.initials: A
authors.lastname: Förster
authors.forename: Tanja
authors.initials: T
authors.lastname: Emmler
authors.forename: Stephanie
authors.initials: S
authors.lastname: Schwalm
authors.forename: Mahsa
authors.initials: M
authors.lastname: Ebadi
authors.forename: Dagmar Meyer Zu
authors.initials: DM
authors.lastname: Heringdorf
authors.forename: Barbara
authors.initials: B
authors.lastname: Nieuwenhuis
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Kleuser
authors.forename: Andrea
authors.initials: A
authors.lastname: Huwiler
authors.forename: Josef
authors.initials: J
authors.lastname: Pfeilschifter
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002477:Cells / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005347:Fibroblasts / Q000378:metabolism; D005938:Glucocorticoids / Q000235:genetics / Q000494:pharmacology*; D008246:Lysophospholipids; D050527:Mesangial Cells / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D015735:Mifepristone / Q000494:pharmacology; D055576:Neutral Ceramidase; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D020218:Response Elements / Q000187:drug effects; D013107:Sphingolipids / Q000235:genetics / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives; D000099157:Sphingosine Kinase
chemical_list: D003907:Dexamethasone; D005938:Glucocorticoids; D008246:Lysophospholipids; D015735:Mifepristone; D055576:Neutral Ceramidase; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D013107:Sphingolipids; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate