title: PPARγ agonists upregulate sphingosine 1-phosphate (S1P) receptor 1 expression, which in turn reduces S1P-induced [Ca(2+)]i increases in renal mesangial cells.
abstract: We previously identified peroxisome proliferator-activated receptor gamma (PPARγ) agonists (thiazolidinediones, TZDs) as modulators of the sphingolipid metabolism in renal mesangial cells. TZDs upregulated sphingosine kinase 1 (SK-1) and increased the formation of intracellular sphingosine 1-phosphate (S1P), which in turn reduced the expression of pro-fibrotic connective tissue growth factor. Since S1P also acts as extracellular ligand at specific S1P receptors (S1PR, S1P1-5), we investigated here the effect of TZDs on S1PR expression in mesangial cells and evaluated the functional consequences by measuring S1P-induced increases in intracellular free Ca(2+) concentration ([Ca(2+)]i). Treatment with two different TZDs, troglitazone and rosiglitazone, enhanced S1P1 mRNA and protein expression in rat mesangial cells, whereas S1P2-5 expression levels were not altered. Upregulation of S1P1 mRNA upon TZD treatment was also detected in human mesangial cells and mouse glomeruli. PPARγ antagonism and promoter studies revealed that the TZD-dependent S1P1 mRNA induction involved a functional PPAR response element in the S1P1 promoter. Pharmacological approaches disclosed that S1P-induced [Ca(2+)]i increases in rat mesangial cells were predominantly mediated by S1P2 and S1P3. Interestingly, the transcriptional upregulation of S1P1 by TZDs resulted in a reduction of S1P-induced [Ca(2+)]i increases, which was reversed by the S1P1/3 antagonist VPC-23019, the protein kinase C (PKC) inhibitor PKC-412, and by S1P1 siRNA. These data suggest that PPARγ-dependent upregulation of S1P1 leads to an inhibition of S1P-induced Ca(2+) signaling in a PKC-dependent manner. Overall, these results reveal that TZDs not only modulate intracellular S1P levels but also regulate S1PR signaling by increasing S1P1 expression in mesangial cells.
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: koch@med.uni-frankfurt.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Koch
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: voelzke@med.uni-frankfurt.de.
authors.forename: Anja
authors.initials: A
authors.lastname: Völzke
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: bianca.puff@web.de.
authors.forename: Bianca
authors.initials: B
authors.lastname: Puff
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: kblanken@stud.uni-frankfurt.de.
authors.forename: Kira
authors.initials: K
authors.lastname: Blankenbach
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: heringdorf@med.uni-frankfurt.de.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Meyer Zu Heringdorf
authors.affiliation: Institute of Pharmacology, University of Bern, Friedbühlstrasse 49, CH-3011 Bern, Switzerland. Electronic address: huwiler@pki.unibe.ch.
authors.forename: Andrea
authors.initials: A
authors.lastname: Huwiler
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany. Electronic address: pfeilschifter@em.uni-frankfurt.de.
authors.forename: Josef
authors.initials: J
authors.lastname: Pfeilschifter
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D050527:Mesangial Cells / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D047495:PPAR gamma / Q000819:agonists / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D049349:Receptors, Lysosphingolipid / Q000235:genetics / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology*
chemical_list: D008246:Lysophospholipids; D047495:PPAR gamma; D049349:Receptors, Lysosphingolipid; D045162:Thiazolidinediones; C060506:sphingosine 1-phosphate; C089946:2,4-thiazolidinedione; D013110:Sphingosine; D002118:Calcium
keywords: CTGF; Calcium signaling; GAPDH; Mesangial cells; PKC; PPAR responsive element; PPARγ; PPRE; RSG; S1P; S1P receptor; S1P receptors; S1PR; SK; Sphingosine 1-phosphate; TRO; TZDs; [Ca(2+)](i); connective tissue growth factor; glyceraldehyde 3-phosphate dehydrogenase; intracellular free Ca(2+) concentration; peroxisome proliferator-activated receptor gamma; protein kinase C; rosiglitazone; sphingosine 1-phosphate; sphingosine kinase; thiazolidinediones; troglitazone