title: Sildenafil promotes eNOS activation and inhibits NADPH oxidase in the transgenic sickle cell mouse penis.
abstract: BACKGROUND
  Sickle cell disease (SCD)-associated vasculopathy in the penis is characterized by aberrant nitric oxide and phosphodiesterase (PDE) 5 signaling, and by increased oxidative stress. Preliminary clinical trials show that continuous treatment with PDE5 inhibitor sildenafil unassociated with sexual activity decreases priapic activity in patients with SCD. However, the mechanism of its vasculoprotective effect in the penis remains unclear.
  
  
  OBJECTIVE
  We evaluated whether continuous administration of PDE5 inhibitor sildenafil promotes eNOS function at posttranslational levels and decreases superoxide-producing enzyme NADPH oxidase activity in the sickle cell mouse penis.
  
  
  METHODS
  SCD transgenic mice were used as an animal model of SCD. WT mice served as controls. Mice received treatment with the PDE5 inhibitor sildenafil (100 mg/kg/day) or vehicle for 3 weeks. eNOS phosphorylation on Ser-1177 (positive regulatory site), eNOS interactions with heat-shock protein 90 (HSP90) (positive regulator), phosphorylated AKT (upstream mediator of eNOS phosphorylation on Ser-1177), an NADPH oxidase catalytic subunit gp91(phox), and a marker of oxidative stress (4-hydroxy-2-nonenal [HNE]) were measured by Western blot.
  
  
  METHODS
  Effect of continuous sildenafil treatment on eNOS posttranslational activation, NADPH oxidase catalytic subunit, and oxidative stress in the penis of the sickle cell mouse.
  
  
  RESULTS
  Continuous treatment with sildenafil reversed (P < 0.05) the abnormalities in protein expressions of P-eNOS (Ser-1177), eNOS/HSP90 interaction, P-AKT, protein expression of gp91(phox), and 4-HNE, in the sickle cell mouse penis. Sildenafil treatment of WT mice did not affect any of these parameters.
  
  
  CONCLUSIONS
  Our findings that sildenafil enhances eNOS activation and inhibits NADPH oxidase function in the sickle cell mouse penis offers a vasculoprotective molecular basis for the therapeutic effect of sildenafil in the penis in association with SCD.
authors.affiliation: The James Buchanan Brady Urological Institute, Department of Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Biljana
authors.initials: B
authors.lastname: Musicki
authors.forename: Trinity J
authors.initials: TJ
authors.lastname: Bivalacqua
authors.forename: Hunter C
authors.initials: HC
authors.lastname: Champion
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Burnett
mesh_terms: D000447:Aldehydes; D000755:Anemia, Sickle Cell / Q000150:complications* / Q000201:enzymology / Q000235:genetics; D000818:Animals; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000096:biosynthesis*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D010413:Penis / Q000098:blood supply / Q000187:drug effects / Q000201:enzymology*; D058986:Phosphodiesterase 5 Inhibitors / Q000627:therapeutic use*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000627:therapeutic use*; D011317:Priapism / Q000188:drug therapy* / Q000201:enzymology / Q000209:etiology; D011687:Purines / Q000627:therapeutic use; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000627:therapeutic use*; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000447:Aldehydes; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D013481:Superoxides; D009569:Nitric Oxide; D000068677:Sildenafil Citrate; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019255:NADPH Oxidases; C027576:4-hydroxy-2-nonenal
keywords: 4-HNE; AKT; HSP90; Oxidative Stress; eNOS Phosphorylation