Alteration in TRPV1 and Muscarinic (M3) receptor expression and function in idiopathic overactive bladder urothelial cells.
OBJECTIVE
To examine function of both cholinergic (muscarinic) and TRPV1 receptors in human bladder urothelial (HBUC) from non-neurogenic overactive bladder (OAB) patients as compared to control subjects.


METHODS
Primary HBUC cultures were derived from cystoscopic biopsies from OAB and control subjects. Muscarinic and TRPV1 function was assessed by acetylcholine (5 μm) or capsaicin (0.5 μm) evoked ATP release, measured by luciferase assay. Overall, expression of TRPV1 and muscarinic M3 receptors in bladder urothelial cells was accomplished using western immunoblotting.


RESULTS
Our findings revealed that the response to acetylcholine in OAB HBUC cultures (which was blocked by the nonselective muscarinic antagonist, atropine methyl nitrate or AMN) was not significantly different than from controls. The acetylcholine M3 receptor was slightly decreased as compared to control. In contrast, OAB HBUC cultures exhibited a capsaicin hypersensitivity and augmented release of ATP (3.2 fold higher), which was blocked by the antagonist capsazepine. The increase in capsaicin sensitivity correlated with increased urothelial TRPV1 expression.


CONCLUSIONS
Though characterized in a small number of subjects, augmented release of urothelial-derived transmitters such as ATP could 'amplify' signalling between and within urothelial cells and nearby afferent nerves.
Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA. lbirder@pitt.edu
L A
LA
Birder
A S
AS
Wolf-Johnston
Y
Y
Sun
T C
TC
Chai
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D002211:Capsaicin / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D061251:Primary Cell Culture; D043587:Receptor, Muscarinic M3 / Q000378:metabolism*; D018689:Sensory System Agents / Q000494:pharmacology; D013268:Stimulation, Chemical; D050916:TRPV Cation Channels / Q000378:metabolism*; D053201:Urinary Bladder, Overactive / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D019459:Urothelium / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology
D018679:Cholinergic Agonists; D043587:Receptor, Muscarinic M3; D018689:Sensory System Agents; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D000255:Adenosine Triphosphate; D000109:Acetylcholine; D002211:Capsaicin