Mouse Urinary Bladder Identifying Targets to Treat Overactive Bladder

Searl, Timothy; Silinsky, Eugene

Abstract

Overactive bladder (OAB) is a major cause of distress for patients and their caregivers. The long term objective of this proposal is to identify novel therapeutic intervention sites for treating OAB. As the purinergic component of contraction of the bladder detrusor muscle (mediated by ATP) is increased in OAB relative to the normal cholinergic component, we propose that prejunctional mechanisms governing ATP release will provide impactful targets for controlling detrusor activity and voiding behavior. We will use electrophysiological and muscle contraction techniques in mouse and human tissues to address 3 Specific Aims.
SPECIFIC AIM 1 : Determine the pre-junctional physiological mechanisms controlling the detrusor muscle of the bladder by: A. measuring the contributions of neuronal Ca2+ channel subtypes in controlling ATP versus acetylcholine (ACh) release;. B. Defining the therapeutic effects of the bolultinum toxin (Botx) fractions (A-E) as they cleave specific components of the nerve terminal secretory apparatus, and C. Determine the effects of (-)-vesamicol (ACh uptake inhibitor) on the purinergic and cholinergic components.
SPECIFIC AIM 2 : Determine the actions of adenosine receptors on detrusor neurotransmission. Our preliminary experiments show that A1 adenosine receptor analogs modulate detrusor activity. To exploit this we will define the role of these receptors as neuromodulators and measure the influence of epithelial components (urothelium/suburothelium) on neurotransmission and release. This is critical as we recently found that urothelial adenosine derivatives inhibit detrusor contractions suggesting a mechanism for modulating activity and symptoms. Such translational findings will be tested in human detrusor confirming the site and mechanism of adenosine-mediated inhibition.
SPECIFIC AIM 3 : To study murine models of OAB and bladder dysfunction utilizing a newly developed in vivo voiding mouse that mimics human OAB, we will: A. Determine purinergic/cholinergic transmission ratios and B. Test the effects of Ca2+ channel blockers, adenosine analogs, and BoTx fractions. These studies will integrate the murine and human findings in a setting that confirms clinical targets and therapeutic pathways.

Public Health Relevance

Studies show that current FDA approved therapies for urinary incontinence are either ineffective or poorly tolerated by many patients. The purpose of the proposed studies is to determine the mechanisms of regulating detrusor transmission to help to identify novel mechanisms and targets for the development of new classes of therapies for patients suffering from OAB and to confirm the results using human specimens.