title: Sildenafil-induced vasorelaxation is associated with increases in the phosphorylation of the heat shock-related protein 20 (HSP20).
abstract: OBJECTIVE
  Sildenafil is an oral phosphodiesterase type 5 inhibitor that is a vasodilator used in the treatment of erectile dysfunction. Cyclic nucleotide-dependent vasorelaxation is associated with increases in the phosphorylation of the heat shock related protein 20 (HSP20). The purpose of this study was to determine if sildenafil-induced vasorelaxation is associated with increases in the phosphorylation of HSP20.
  
  
  METHODS
  Peptides containing an 11 amino acid enhanced protein transduction domain (PTD) and the functional 13 amino acid sequence of HSP20 with a phosphoserine (PTD-pHSP20) were synthesized using F-MOC technology. Rings of porcine coronary artery were suspended in a muscle bath and sub-maximally contracted with serotonin. Increasing concentrations of sodium nitroprusside (SNP; 0.01-10 microM), sildenafil (0.01-100 microM), or PTD-pHSP20 (0.1-1.0 mM) were added to the baths and the percent relaxation was recorded. To determine if sildenafil-induced vasorelaxation was associated with increases in the phosphorylation of HSP20, rings of porcine coronary artery were untreated (control) or treated with SNP (10 microM) or sildenafil (100 microM) for 2, 5, and 10 min and then snap frozen. Extracted proteins were then separated using two-dimensional SDS-PAGE, transferred to a membrane, and probed for HSP20.
  
  
  RESULTS
  Sildenafil induced vasorelaxation of pre-contracted coronary artery in a dose-dependent manner. Sildenafil-induced vasorelaxation was associated with an increase in the phosphorylation of HSP20. Transduction of peptide analogues of pHSP20 led to a dose-dependent relaxation of pre-contracted porcine coronary artery.
  
  
  CONCLUSIONS
  These findings suggest that sildenafil-induced vasorelaxation is associated with increases in the phosphorylation of HSP20 and that transduction of phosphopeptide analogues of HSP20 is sufficient for relaxation of vascular smooth muscle.
authors.affiliation: Department of Kinesiology, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Deron J
authors.initials: DJ
authors.lastname: Tessier
authors.forename: Padmini
authors.initials: P
authors.lastname: Komalavilas
authors.forename: Elisabeth
authors.initials: E
authors.lastname: McLemore
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Thresher
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Brophy
mesh_terms: D000818:Animals; D001158:Arteries; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism*; D066298:In Vitro Techniques; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate