title: Adenosine signaling, priapism and novel therapies.
abstract: BACKGROUND
  Priapism is defined as abnormal prolonged penile erection lasting at least for 4 hours occurring without sexual interest. Forty percent of sickle cell disease (SCD) patients display priapism. The disorder is dangerous and urgent given its association with ischemia-mediated erectile tissue damage and subsequent erectile dysfunction. Current strategies to manage the disorder are poor due to lack of fundamental understanding of the molecular mechanisms of priapism. Adenosine is a signaling nucleoside that elicits many pathophysiological effects by engaging membrane receptors. Recent evidence shows that adenosine may play an important role in priapism via adenosine receptor.
  
  
  OBJECTIVE
  To summarize the recent findings on the importance of adenosine signaling in the pathogenesis of priapism.
  
  
  METHODS
  Evidence in the literature on the association between adenosine signaling and the development of priapism.
  
  
  METHODS
  This article reviews the literature that relates to the contributory role of adenosine signaling in priapism in multiple animal models and humans.
  
  
  RESULTS
  Excessive adenosine accumulation in the penis, coupled with increased A(2B)R signaling, contributes to priapism in two independent lines of mutant mice. One is adenosine deaminase (ADA)-deficient mice, the only animal displaying spontaneously prolonged penile erection, and the other is SCD transgenic mice, a well-accepted priapic animal model. Both polyethylene glycol-modified ADA (PEG-ADA) enzyme therapy and A(2B)R antagonists are capable of inhibiting potent corpus cavernosal vascular relaxation associated with priapic-like activity seen in both ADA-deficient mice and SCD transgenic mice, indicating that PEG-ADA enzyme therapy is likely to be a novel therapy for such a dangerous urological disorder.
  
  
  CONCLUSIONS
  Overall, the research reviewed here raises the intriguing possibility that elevated adenosine signaling contributes to priapism in general and that this signaling pathway represents a potentially important therapeutic target for the treatment of priapism.
authors.affiliation: University of Texas at Houston Medical School, Biochemistry and Molecular Biology, Houston, TX 77030, USA.
authors.forename: Yingbo
authors.initials: Y
authors.lastname: Dai
authors.forename: Yujin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Prasad
authors.initials: P
authors.lastname: Phatarpekar
authors.forename: Tiejuan
authors.initials: T
authors.lastname: Mi
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blackburn
authors.forename: Yang
authors.initials: Y
authors.lastname: Xia
mesh_terms: D000241:Adenosine / Q000378:metabolism / Q000502:physiology*; D000243:Adenosine Deaminase / Q000378:metabolism*; D000818:Animals; D004730:Endothelium, Vascular / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology; D005355:Fibrosis / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051379:Mice; D009130:Muscle, Smooth / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D010413:Penis / Q000473:pathology / Q000503:physiopathology; D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use*; D011317:Priapism / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors; D000243:Adenosine Deaminase; C051409:pegademase bovine; D000241:Adenosine