Login to Access Video or Poster Abstract: MP26-08
Sources of Funding: none

Introduction

Phosphodiesterase 5 (PDE5) inhibitor, tadalafil, improves lower urinary tract symptoms suggestive of benign prostatic hyperplasia. The mechanism is believed to smooth muscle relaxation, increased blood perfusion and modulation of sensory stimuli via increased activity of the NO/cGMP/protein kinase G pathway. However study for tadalafil in urothelium is few, here we investigated the distribution of PDE5, as well as the molecular mechanism for tadalafil in signal transduction focusing on transient receptor potential (TRP) channels and ATP release of bladder urothelium.

Methods

All experiments were performed by using10-12 week old male Sprague-Dawley rats and C57BL/6 mice. PDE5 expressions were detected by immunochemistry and western blotting in rat bladder tissues and primary bladder urothelial cell cultures. Ca2+ influx was evaluated by in vitro calcium imaging system under exposure to isotonic (340mOsm), hypotonic (200mOsm), cannabidiol (CAD, TRPV2-selective agonist) (10?M), GSK1016790A (GSK, TRPV4-selective agonist) (30nM), ATP (P2X and Y agonist) (5?M) and PIP2 (TRPM7 agonist) (4?M) stimuli respectively with or without tadalafil (10?M). ATP concentration induced by stretch was measured in mouse bladder with or without tadalafil (100 ?M) by using the luciferase reagent.

Results

Immunochemistry and western blotting demonstrated abundant expression of PDE5 in rat bladder urothelium (Fig.1) as well as primary rat urothelial cell cultures. Ca2+ influx responded to hypotonic stimuli was significantly inhibited by pretreatment of tadalafil in primary rat bladder urothelial cell cultures. (Control (C): 13.1% v.s. tadalafil (T): 4.9%) (Fig.2). Ca2+ influx evoked by GSK (C: 74.7% v.s. T: 68.8%) or CAD (C: 52.2% v.s. T: 25.9%) was significantly inhibited by pretreatment of tadalafil. While Ca2+ influx caused by the stimulation of ATP (C: 49.6% v.s. T: 49.0%) could not be attenuated. PIP2 at the concentration of 4?M did not evoke Ca2+ influx. ATP release in the tadalafil pretreated-bladder was significantly smaller than control bladder.

Conclusions

Tadalafil attenuated Ca2+ influx via TRPV4 and TRPV2 channels and inhibited ATP release in bladder urothelium. Tadalafil could act an inhibitory role in urothelial signal transduction.

Funding

none