PhD Scientific Days 2024

Theoretical and Translational Medicine III.

The Role of the Rho-ROCK Pathway in the Regulation of Detrusor Muscle Contraction

Text of the abstract

The muscarinic acetylcholine receptors (mAChR) play a pivotal role in the regulation of micturition and antimuscarinic drugs are mainstays of the treatment for overactive bladder syndrome (OAB). Nevertheless, the exact signaling pathway of mAChRs is obscure even though a more detailed understanding of the signal transduction pathway may help to find more specific drug targets with fewer adverse effects for OAB.
Thus, we aimed to further analyze the signal transduction of mAChRs concentrating on the interaction with the Rho-ROCK pathway in the urinary bladder smooth muscle (UBSM). Our final goal is to provide more specific medication for OAB with fewer adverse effects.
Experiments were performed on adult, male, wild-type, M2, M3, M2/M3, Gq/11 knockout (KO) and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were quantified in the urinary bladder smooth muscle (UBSM).
Contractile responses induced by the mAChR agonist carbamoylcholine (CCh) in UBSM were found to be associated with increased activity of RhoA and were reduced in the presence of the ROCK inhibitor Y-27632. The CCh-induced contractions were significantly reduced in detrusor strips lacking either M2 or M3 receptors and were abolished in UBSM from M2/M3 KO mice. The RhoA activation was decreased in both M2 KO and M3 KO bladders and it was diminished in M2/M3 KO UBSM. Inhibition of Gi-coupled signaling by PTX-treatment shifted the concentration-response curve of CCh to the right and completely decreased RhoA activation. CCh-induced contractile responses were markedly reduced in Gq/11 KO mice but RhoA activation was unaffected.
In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Moreover, CCh-induced contractions involve simultaneously the classical Gq/11- and the Gi-coupled signaling pathways, but the RhoA activation appears to be mediated exclusively by the Gi proteins. These observations can support the development of more specific therapeutic targets that can help to improve patient adherence and facilitate the implementation of more effective and cost-effective therapeutic strategies for OAB.

Hungarian NRDIO K-125174, K-135683, K-139230 and PD-132851, 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