Signal transduction pathways of muscarinic receptors in the murine urinary bladder smooth muscle

Abstract

Overactive bladder (OAB) is a clinical condition characterized by symptoms of frequency, urgency with/without incontinence. Despite of the fact that OAB affects millions of patients’ quality of life significantly, its etiology is still poorly understood. Currently, antimuscarinics are the first-line medical therapy for the management of OAB. However, their application is limited due to the decrease of patients’ compliance because of several adverse effects (e.g. dry mouth, obstipation).Our aim was to further analyze the signaling pathways of muscarinic receptors in detrusor muscle contraction with the goal of better understanding the intracellular regulation of micturition and identifying potential novel therapeutic targets for OAB.Experiments were performed on adult, male, wild-type (WT), M 2 , M 3 , M 2 /M 3 , Gα q/11 knockout (KO) and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were measured in the urinary bladder smooth muscle (UBSM).Contractile responses induced by the muscarinic receptor agonist carbamoylcholine (CCh) in UBSM associated with increased activity of RhoA and were reduced in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632. The CCh-induced contractions were markedly reduced in detrusor strips lacking either M 2 or M 3 receptors and were abolished in UBSM from M 2 /M 3 KO mice. The RhoA activation was decreased in both M 2 KO and M 3 KO bladders and it was completely reduced in M 2 /M 3 KO UBSM. Inhibition of Gα i -coupled signaling by PTX-treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. CCh-induced contractile responses were markedly decreased in Gα q/11 KO mice, however, RhoA activation was unaffected.In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M 2 and M 3 receptors. Furthermore, CCh-induced contractions involve simultaneously the classical Gα q/11 - and the Gα i -coupled signaling pathways, but the RhoA activation appears to be mediated exclusively by the Gα i proteins. These findings may aid the identification of more specific therapeutic targets for OAB. Hungarian NRDIO K-125174, K-135683, K-139230 and PD-132851, Ministry for Innovation and Technology from the Hungarian NRDI fund (2020-1.1.6-JÖVÖ-2021-00010, TKP2021-EGA-25), STIA-KFI-2021, EFOP-3.6.3-VEKOP-16-2017-00009 grants and Gedeon Richter Plc Talent Foundation This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.