Contractions of ex-vivo mouse bladder driven by activation of channelrhodopsin-2 expressed in urothelial cells

Signaling molecules released from the urothelium by mechanical stretch are known to play a sensory role in bladder contractions via neuronal signaling. It is also theorized that these molecules released from the urothelium could act locally to induce urothelial cell-mediated local bladder contractions. In this study, we specifically stimulated the urothelial cells using optogenetics to investigate how the urothelial released signaling molecules can influence bladder contractions locally. Using an ex-vivo whole bladder preparation, we stimulated the urothelial cells by activating channelrhodopsin-2 (ChR2) with blue light and initiated the urothelial cell-mediated local bladder contractions. The P2X receptor antagonist, PPADS, nearly abolished the contractions. The muscarinic receptor antagonist, atropine, significantly inhibited the contractions. Nifedipine, which blocks extracellular Ca²⁺ entry, abolished the contractions. G protein-coupled receptor inhibitor YM-254,890 significantly inhibited the contractions. Hemichannel inhibitor carbenoxolone disodium and the exocytotic pathway of transmitter release inhibitor brefeldin A also showed significant inhibition of the contractions. In conclusion, we validated the previous hypothesis that urothelial release factors can influence bladder contractions locally without the need for signaling from the central nervous system. Further studies are needed to determine the relevance of this signaling pathway in normal bladder physiology and pathophysiologic conditions.