The role of Rho-kinase in human urinary bladder smooth muscle contraction induced by inflammatory mediators
Authors: Borsodi Kinga , Balla Helga , Molnár Péter , Lénárt Ádám , Dér Bálint , Kenessey István , Horváth András , Keszthelyi Attila , Romics Miklós , Majoros Attila , Nyirády Péter , Benyó Zoltán 
Published: May 2023

Urinary bladder smooth muscle (UBSM) dysfunctions (overactive bladder, detrusor overactivity) affect millions of people worldwide, however their etiology is still poorly understood. Nevertheless, inflammatory mediators including isoprostanes (isoP) and bradykinin (BK) have been proposed as potential pathogenic factors in detrusor overactivity. Our preliminary data gained from mouse bladders proved that these mediators are potent constrictors of murine UBSM and the RhoA – Rho-kinase (ROCK) pathway plays a prominent role in mediating their effects.The present study aimed to investigate the signal transducion of isoP- and BK-induced contractions focusing on the role of RhoA – ROCK signaling in human UBSM. Our goal is to better understand the molecular mechanism of micturition and identifying potential novel therapeutic targets of its disorders.Experiments were performed on human bladders which were surgically removed due to bladder malignancy. UBSM strips were dissected from a macroscopically tumor-free area, approved by a pathologist, then they were mounted on a myograph system. The force and time course of their contractile responses were registered under isometric conditions BK and isoPs (8-iso-PGF2α and 8-iso-PGE2) induced concentration-dependent contractions in human UBSM. BK’s effect was significantly inhibited by the B2 receptor antagonist HOE-140, whereas it remained unaltered following incubation with B1 receptor antagonist R-715. Consistently with these findings, pharmacological stimulation of B2 but not B1 receptors resembled the effect of BK.Similarly, isoPs also induced concentration-dependent potent contractions in human bladder strips, which were inhibited by the thromboxane prostanoid (TP) receptor antagonist SQ29548. For further investigating the downstream signaling of B2 and TP receptors, we focused on the RhoA – ROCK pathway. Thus, we applied the specific ROCK-inhibitor, Y27632, which substantially reduced human UBSM contractions induced by BK or isoPs.Our results clearly demonstrate that both isoPs and BK induce potent contractions in human detrusor muscle. BK’s effect is mediated mainly via B2 receptors, while isoP-induced contractions are dependent on TP receptor activation in human bladders. Inhibition of ROCK enzyme reduced the contractions induced by these inflammatory mediators, identifying this enzyme, together with B2 or TP receptors as potential targets for treating bladder smooth muscle dysfunctions assocated with local or systemic inflammation. 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), STIA-KFI-2021 and EFOP-3.6.3-VEKOP-16-2017-00009 grants. 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.