title: Sildenafil-mediated acute cardioprotection is independent of the NO/cGMP pathway.
abstract: Sildenafil, a potent inhibitor of phosphodiesterase type 5, has recently been investigated in animal models of myocardial ischemia-reperfusion (MI/R) injury. Previous studies have suggested that the protective effects of sildenafil are mediated via activation of endothelial nitric oxide (NO) synthesis (eNOS) and inducible NOS (iNOS). To further investigate the protective mechanism of sildenafil, we subjected wild-type, eNOS, and iNOS null animals to 30 min of myocardial ischemia and 24 h of reperfusion. Treatment with 0.06 mg/kg sildenafil 5 min before reperfusion significantly reduced myocardial infarct size in wild-type, eNOS null mice (eNOS(-/-)), and iNOS(-/-) animals. Additionally, the low dose utilized in this study did not alter myocardial cGMP. These results suggest that acute low-dose sildenafil-mediated cardioprotection is independent of eNOS, iNOS, and cGMP. In a second series of experiments, we investigated sildenafil in db/db diabetic mice subjected to MI/R. We found that sildenafil failed to protect diabetic mice against MI/R. However, NO(.) donor therapy was found to significantly protect against MI/R injury in both nondiabetic and diabetic mice, suggesting that protection could be conferred in diabetic mice and that the upstream modulator of soluble guanylyl cyclase, NO(.), may mediate protection independent of cGMP signaling. The present study suggests that further research is needed to delineate the precise mechanisms by which sildenafil exerts cardioprotection.
authors.affiliation: Dept. of Medicine-Div. of Cardiology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Elrod
authors.forename: James J M
authors.initials: JJ
authors.lastname: Greer
authors.forename: David J
authors.initials: DJ
authors.lastname: Lefer
mesh_terms: D000208:Acute Disease; D000818:Animals; D002316:Cardiotonic Agents / Q000008:administration & dosage*; D006152:Cyclic GMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control*; D009569:Nitric Oxide / Q000378:metabolism*; D010879:Piperazines / Q000008:administration & dosage*; D011687:Purines; D015398:Signal Transduction / Q000187:drug effects*; D000068677:Sildenafil Citrate; D013450:Sulfones; D016896:Treatment Outcome
chemical_list: D002316:Cardiotonic Agents; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D009569:Nitric Oxide; D000068677:Sildenafil Citrate; D006152:Cyclic GMP