Phosphodiesterase type 5 inhibitors improve male lower urinary tract symptoms

An animal study to compare the degree of the suppressive effects on the afferent pathways of micturition between tamsulosin and sildenafil

Background

Tamsulosin, an α1-adrenoceptor antagonist, and sildenafil, a phosphodiesterase (PDE) inhibitor, are reported to improve lower urinary tract symptoms including overactive bladder (OAB). This study is aimed at investing the effects of tamsulosin and sildenafil and comparing the degree of the suppressive effects on the afferent pathways of micturition between them using an animal model of OAB, the spontaneously hypertensive rat (SHR).

Results

The cystometric parameters, the basal pressure and duration of bladder contraction, were significantly increased in the SHR group as compared with the Wistar-Kyoto (WKY) group. The intercontraction interval also significantly decreased in the SHR group. In the SHR-Tam 0.01 mg/kg group and the SHR-Sil 1 mg/kg group, however, the basal pressure and duration were significantly reduced and the intercontraction interval was significantly prolonged. Moreover, the degree of the expression of c-Fos and NGF was significantly higher in the SHR group as compared with the WKY group. But it was significantly reduced in the SHR-Tam 0.01 mg/kg group and the SHR-Sil 1 mg/kg group. Furthermore, tamsulosin had a higher degree of effect as compared with sildenafil.

Conclusions

In conclusion, α1-adrenergic receptor antagonists and PDE-5 inhibitors may have an effect in improving the voiding functions through an inhibition of the neuronal activity in the afferent pathways of micturition.

Selective inhibition of phosphodiesterase 1 relaxes urinary bladder smooth muscle: role for ryanodine receptor-mediated BK channel activation

The large conductance voltage- and Ca(2+)-activated K(+) (BK) channel is a major regulator of detrusor smooth muscle (DSM) excitability and contractility. Recently, we showed that nonselective phosphodiesterase (PDE) inhibition reduces guinea pig DSM excitability and contractility by increasing BK channel activity. Here, we investigated how DSM excitability and contractility changes upon selective inhibition of PDE type 1 (PDE1) and the underlying cellular mechanism involving ryanodine receptors (RyRs) and BK channels. PDE1 inhibition with 8-methoxymethyl-3-isobutyl-1-methylxanthine (8MM-IBMX; 10 μM) increased the cAMP levels in guinea pig DSM cells. Patch-clamp experiments on freshly isolated DSM cells showed that 8MM-IBMX increased transient BK currents and the spontaneous transient hyperpolarization (STH) frequency by ∼2.5- and ∼1.8-fold, respectively. 8MM-IBMX hyperpolarized guinea pig and human DSM cell membrane potential and significantly decreased the intracellular Ca(2+) levels in guinea pig DSM cells. Blocking BK channels with 1 μM paxilline or inhibiting RyRs with 30 μM ryanodine abolished the STHs and the 8MM-IBMX inhibitory effects on the DSM cell membrane potential. Isometric DSM tension recordings showed that 8MM-IBMX significantly reduced the spontaneous phasic contraction amplitude, muscle force integral, duration, frequency, and tone of DSM isolated strips. The electrical field stimulation-induced DSM contraction amplitude, muscle force integral, and duration were also attenuated by 10 μM 8MM-IBMX. Blocking BK channels with paxilline abolished the 8MM-IBMX effects on DSM contractions. Our data provide evidence that PDE1 inhibition relaxes DSM by raising cellular cAMP levels and subsequently stimulates RyRs, which leads to BK channel activation, membrane potential hyperpolarization, and decrease in intracellular Ca(2+) levels.

Signalling pathways involved in sildenafil-induced relaxation of human bladder dome smooth muscle

BACKGROUND AND PURPOSE

The mechanism(s) of action responsible for the beneficial effects of phosphodiesterase 5 (PDE5) inhibitors including sildenafil on lower urinary tract symptoms suggestive of benign prostate hyperplasia are unclear. In particular, the role of the NO-cGMP signalling pathway in regulating human bladder dome smooth muscle relaxation is questionable. Thus, we assessed the ability of a PDE5 inhibitor, sildenafil, to relax such tissue, and identified the signalling pathways involved in this relaxation.

EXPERIMENTAL APPROACH

Human bladder samples were obtained from 20 patients with no overactive bladder undergoing cystectomy for bladder cancer. Detrusor strips were mounted isometrically in Krebs-HEPES solution. Concentration-response curves for sildenafil (10 nM-30 microM) were generated in the presence of various inhibitors on carbachol-induced pre-contraction.

KEY RESULTS

Sildenafil relaxed carbachol-pre-contracted human detrusor strips, starting at 3 microM. This effect was not modified by NO donors, S-nitroso-N-acetylpenicillamine (10 microM) or sodium nitroprusside (300 nM), but was significantly inhibited by inhibition of guanylate cyclase (with ODQ, 10 microM) or adenylyl cyclase (with MDL-12,330A, 10 microM), by the ATP-sensitive potassium channel inhibitor, glibenclamide (10 microM), or inhibition of the large (with iberiotoxin, 30 nM) or small (with apamin, 100 nM) conductance calcium-activated potassium channels.

CONCLUSIONS AND IMPLICATIONS

Sildenafil-induced relaxation of human detrusor smooth muscle involved cGMP-, cAMP- and K(+) channel-dependent signalling pathways, with a minor contribution from NO. The effect of this sildenafil-induced relaxation on the clinical benefit of PDE5 inhibitors on urinary storage symptoms in men deserves further investigation.

Vardenafil can improve continence recovery after bilateral nerve sparing prostatectomy: results of a randomized, double blind, placebo-controlled pilot study

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5-I) have acquired an established role in the treatment of post-prostatectomy erectile dysfunction (ED). Several trials in men with ED and lower urinary tract symptoms associated with benign prostatic hyperplasia suggest that PDE5-I could improve both erectile function and urinary symptoms.

AIM

To assess the role of vardenafil in continence recovery after bilateral nerve sparing radical prostatectomy (BNS-RP).

METHODS

Thirty-nine patients with prostate cancer were recruited. After BNS-RP, patients were double-blinded assigned to three arms: a) vardenafil on demand; b) vardenafil nightly; and c) placebo.

MAIN OUTCOMES MEASURES

Urinary function (UF) and urinary bother (UB) of University of California-Los Angeles Prostate Cancer Index questionnaire were assessed preoperatively and at 1, 3, 6, 9, 10, and 12 months. Twelve-month outcomes were compared to 1 month with a t-test. The differences in UF and UB (at 3, 6, 9, 10, and 12 months) between the three treatment arms were calculated by an analysis of variance. With ALLFIT we estimated half-maximal recovery times (ER50) and maximal recovery (R(max)) in three groups.

RESULTS

The improvement of UF and UB between 1 and 12 months was significant in all arms except for placebo (UF: P = 0.125; UB: P = 0.089). Nightly resulted in greater UF at 3, 6, and 9 months and greater UB at 6 months compared with placebo (P = 0.042, P = 0.044 and P = 0.039); after nightly administration, patients presented higher UB than after on-demand use, 3 and 6 months postoperatively (P = 0.036 and P = 0.017). ALLFIT demonstrated a similar ER50 in all groups (2.6 months for both UF and UB) and indicated that nightly administration induced significant improvements in R(max) compared with placebo (both <0.0001).

CONCLUSIONS

Vardenafil can improve continence recovery after BNS-RP compared with placebo. The daily use of vardenafil seems to provide better continence rate, although it does not seem to influence the timing needed to achieve full continence.