title: Phosphodiesterase-5 inhibition with sildenafil attenuates cardiomyocyte apoptosis and left ventricular dysfunction in a chronic model of doxorubicin cardiotoxicity.
abstract: BACKGROUND
  Sildenafil, a phosphodiesterase-5 inhibitor, induces cardioprotection against ischemia/reperfusion injury via opening of mitochondrial K(ATP) channels. It is unclear whether sildenafil would provide similar protection from doxorubicin-induced cardiotoxicity.
  
  
  RESULTS
  Male ICR mice were randomized to 1 of 4 treatments: saline, sildenafil, doxorubicin (5 mg/kg IP), and sildenafil (0.7 mg/kg IP) plus doxorubicin (n=6 per group). Apoptosis was assessed with the use of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and in situ oligo ligation methods. Desmin distribution was determined via immunofluorescence. Bcl-2 expression was analyzed by Western blot. Left ventricular function was assessed by measuring developed pressure and rate pressure product in Langendorff mode. ECG changes indicative of doxorubicin cardiotoxicity were also measured. For in vitro studies, adult ventricular cardiomyocytes were exposed to doxorubicin (1 micromol/L), sildenafil (1 micromol/L) with or without N(G)-nitro-L-arginine methyl ester (L-NAME) (100 micromol/L), or 5-hydroxydecanoate (100 micromol/L) 1 hour before doxorubicin and incubated for 18 hours. Doxorubicin-treated mice demonstrated increased apoptosis and desmin disruption, which was attenuated in the sildenafil+doxorubicin group. Bcl-2 was decreased in the doxorubicin group but was maintained at basal levels in the sildenafil+doxorubicin group. Left ventricular developed pressure and rate pressure product were significantly depressed in the doxorubicin group but were attenuated in the sildenafil+doxorubicin group. ST interval was significantly increased in the doxorubicin group over 8 weeks. In the sildenafil+doxorubicin group, ST interval remained unchanged from baseline. Doxorubicin caused a significant increase in apoptosis, caspase-3 activation, and disruption of mitochondrial membrane potential in vitro. In contrast, sildenafil significantly protected against doxorubicin cardiotoxicity; however, this protection was abolished by both L-NAME and 5-hydroxydecanoate.
  
  
  CONCLUSIONS
  Prophylactic treatment with sildenafil prevented apoptosis and left ventricular dysfunction in a chronic model of doxorubicin-induced cardiomyopathy.
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University Medical Center, Richmond 23298, USA.
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Fisher
authors.forename: Fadi
authors.initials: F
authors.lastname: Salloum
authors.forename: Anindita
authors.initials: A
authors.lastname: Das
authors.forename: Haroon
authors.initials: H
authors.lastname: Hyder
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Kukreja
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D009202:Cardiomyopathies / Q000139:chemically induced* / Q000188:drug therapy; D002908:Chronic Disease; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004317:Doxorubicin / Q000009:adverse effects; D004359:Drug Therapy, Combination; D006333:Heart Failure / Q000517:prevention & control; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000473:pathology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D010727:Phosphoric Diester Hydrolases / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology* / Q000627:therapeutic use; D011292:Premedication; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D018487:Ventricular Dysfunction, Left / Q000188:drug therapy*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D004317:Doxorubicin; D000068677:Sildenafil Citrate; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517382:Pde5a protein, mouse