title: The cAMP-producing agonist beraprost inhibits human vascular smooth muscle cell migration via exchange protein directly activated by cAMP.
abstract: OBJECTIVE
  During restenosis, vascular smooth muscle cells (VSMCs) migrate from the vascular media to the developing neointima. Preventing VSMC migration is therefore a therapeutic target for restenosis. Drugs, such as prostacyclin analogues, that increase the intracellular concentration of cyclic adenosine monophosphate (cAMP) can inhibit VSMC migration, but the mechanisms via which this occurs are unknown. Two main downstream mediators of cAMP are protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac). This study has examined the effects of the prostacyclin analogue beraprost on VSMC migration and investigated the intracellular pathways involved.
  
  
  RESULTS
  In a chemotaxis chamber, human saphenous vein VSMC migrated towards a platelet-derived growth-factor-BB (PDGF) chemogradient. Incubation with therapeutically relevant concentrations of cAMP-producing agonist beraprost significantly decreased PDGF-induced migration. Direct activation of either PKA or Epac inhibited migration whereas inhibition of PKA did not prevent the anti-migratory effect of beraprost. Direct activation of Epac also prevented hyperplasia in ex vivo serum-treated human veins. Using fluorescence resonance energy transfer, we demonstrated that beraprost activated Epac but not PKA. The mechanisms of this Epac-mediated effect involved activation of Rap1 with subsequent inhibition of RhoA. Cytoskeletal rearrangement at the leading edge of the cell was consequently inhibited. Interestingly, Epac1 was localized to the leading edge of migrating VSMC.
  
  
  CONCLUSIONS
  These results indicate that therapeutically relevant concentrations of beraprost can inhibit VSMC migration via a previously unknown mechanism involving the cAMP mediator Epac. This may provide a novel target that could blunt neointimal formation.
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK.
authors.forename: Jenny S
authors.initials: JS
authors.lastname: McKean
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK.
authors.forename: Fiona
authors.initials: F
authors.lastname: Murray
authors.affiliation: Department of Cardiothoracic Surgery, Aberdeen Royal Infirmary, Aberdeen, UK.
authors.forename: George
authors.initials: G
authors.lastname: Gibson
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK.
authors.forename: Derryck A
authors.initials: DA
authors.lastname: Shewan
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Tucker
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK g.f.nixon@abdn.ac.uk.
authors.forename: Graeme F
authors.initials: GF
authors.lastname: Nixon
mesh_terms: D002465:Cell Movement / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D011464:Epoprostenol / Q000031:analogs & derivatives* / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D020662:Guanine Nucleotide Exchange Factors; C048081:beraprost; D011464:Epoprostenol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Epac; Migration; Prostacyclin; Vascular smooth muscle cell; cAMP