title: Sildenafil effect on the human bladder involves the L-cysteine/hydrogen sulfide pathway: a novel mechanism of action of phosphodiesterase type 5 inhibitors.
abstract: BACKGROUND
  Phosphodiesterase type 5 inhibitors (PDE5-Is) are effective in the treatment of lower urinary tract symptom (LUTS), although their mechanism of action is still unclear. PDE5-Is cause bladder detrusor relaxation, and this effect is partially independent of nitric oxide. Hydrogen sulfide (H(2)S) is a newly discovered transmitter with myorelaxant properties. It is predominantly formed from L-cysteine by cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE).
  
  
  OBJECTIVE
  To evaluate whether the L-cysteine/H(2)S pathway contributes to the relaxing effect of sildenafil on the human detrusor dome.
  
  
  METHODS
  Samples of bladders obtained from men undergoing open prostatectomy for benign prostatic hyperplasia (BPH) were used. The presence of CBS and CSE enzymes was assessed by western blot. H(2)S production was measured by a colorimetric assay in basal and stimulated conditions with L-cysteine and in response to sildenafil (1, 3, 10, and 30 μM), 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP; 100 μM) or dibutyryl-cyclic adenosine monophosphate (dibutyryl-cAMP; 100 μM). A curve concentration effect of sodium hydrosulfide (NaHS), H(2)S donor (0.1 μM to 10mM), L-cysteine (0.1 μM to 10mM), and sildenafil (0.1-10 μM) was performed on precontracted detrusor dome strips. To investigate H(2)S signaling in a sildenafil effect, CBS and CSE inhibitors were used.
  
  
  METHODS
  Analysis of variance was used, followed by the Bonferroni post hoc test.
  
  
  CONCLUSIONS
  CBS and CSE are present in the human bladder dome and efficiently convert L-cysteine into H(2)S. Both NaHS and L-cysteine relaxed human strips. Sildenafil caused (1) a relaxation of bladder dome strips and (2) a concentration-dependent increase in H(2)S production. Both effects were significantly reduced by CBS and CSE inhibitors. Similar to sildenafil, both 8-bromo-cGMP and dibutyryl-cAMP caused an increase in H(2)S production.
  
  
  CONCLUSIONS
  The sildenafil relaxant effect on the human bladder involves the H(2)S signaling pathway. This effect may account in part for the efficacy of PDE5-Is in LUTS. A better definition of the pathophysiologic role of the H(2)S pathway in the human bladder may open new therapeutic approaches.
authors: Interdepartmental Centre for Sexual Medicine, University of Naples, Federico II, Naples, Italy.
authors: Ferdinando
authors: F
authors: Fusco
authors: Roberta d'Emmanuele
authors: Rd
authors: di Villa Bianca
authors: Emma
authors: E
authors: Mitidieri
authors: Giuseppe
authors: G
authors: Cirino
authors: Raffaella
authors: R
authors: Sorrentino
authors: Vincenzo
authors: V
authors: Mirone
mesh_terms: D000368:Aged; D003545:Cysteine / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology; D015398:Signal Transduction; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate; D003545:Cysteine; D006862:Hydrogen Sulfide