title: Transcriptional inhibition of protease-activated receptor-1 expression by prostacyclin in human vascular smooth muscle cells.
abstract: OBJECTIVE
  Stimulation of protease-activated receptor-1 (PAR-1) by thrombin causes vascular smooth muscle cell (SMC) mitogenesis and has been implicated in the vascular response to injury. Vascular injury is also associated with enhanced formation of PGE2 and PGI2 (prostacyclin). This study investigates whether PGI2 and PGE2 modify the expression of PAR-1 and the cellular response to thrombin in human SMC.
  
  
  RESULTS
  The PGI2-mimetic iloprost (1 to 100 nmol/L) attenuated mRNA, total protein, and cell surface expression of PAR-1. This was associated with inhibition of thrombin-induced mitogenesis and migration. Comparable inhibition of PAR-1 expression was observed with the selective IP-receptor agonist cicaprost, the adenylyl cyclase activator forskolin, the phosphodiesterase inhibitor isobutylmethylxanthine and the PKA activator dibutyryl-cAMP. Similar effects of PGE2 required micromolar concentrations. The specific PKA-inhibitor Myr-PKI prevented PAR-1 downregulation by iloprost. The potential role of Rho family GTPases in PAR-1 regulation was also investigated. Iloprost decreased Rac1 mRNA and the Rac1 inhibitor NSC23766 mimicked the inhibitory effects of iloprost on PAR-1 protein--but not mRNA. The Rho kinase inhibitor Y27632 did not influence PAR-1 expression.
  
  
  CONCLUSIONS
  IP-receptor agonists may limit the mitogenic actions of thrombin in human SMC by downregulating PAR-1 via modulation of cAMP-/PKA- and Rac1-dependent signaling pathways.
authors.affiliation: Institut für Pharmakologie und Klinische Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Pape
authors.forename: Bernhard H
authors.initials: BH
authors.lastname: Rauch
authors.forename: Anke C
authors.initials: AC
authors.lastname: Rosenkranz
authors.forename: Gernot
authors.initials: G
authors.lastname: Kaber
authors.forename: Karsten
authors.initials: K
authors.lastname: Schrör
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology / Q000502:physiology; D015536:Down-Regulation; D011464:Epoprostenol / Q000494:pharmacology / Q000502:physiology*; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D016285:Iloprost / Q000378:metabolism* / Q000494:pharmacology; D007150:Immunohistochemistry; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012501:Saphenous Vein / Q000166:cytology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D044463:Receptor, PAR-1; D011464:Epoprostenol; D016285:Iloprost; D015232:Dinoprostone