PhD Scientific Days 2023

Translational Medicine - Posters P

Signal Transduction Pathways of Muscarinic Receptors in the Murine Urinary Bladder

Text of the abstract

Overactive bladder (OAB) is a clinical condition characterized by symptoms of frequency, urgency with/without incontinence. Despite of the fact, 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 their 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), M2, M3, M2/M3, Gαq/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 M2 or M3 receptors and were abolished in UBSM from M2/M3 KO mice. The RhoA activation was significantly decreased in both M2 KO and M3 KO bladders and it was completely declined in M2/M3 KO UBSM. Inhibition of Gαi-coupled signaling by PTX-treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. Detrusor muscle contractions evoked by CCh were further decreased in Gαq/11 KO mice, whereas RhoA activation was unaffected in Gαq/11 KO animals compared to controls.
In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Furthermore, CCh-induced contractions involve simultaneously the classical Gαq/11- and the Gαi-coupled signaling pathways, but the RhoA activation appears to be mediated exclusively by the Gαi 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-JÖVŐ-2021-00010, TKP2021-EGA-25), EFOP-3.6.3-VEKOP-16-2017-00009 grants and by Gedeon Richter Plc Talent Foundation