cAMP-dependent regulation of RhoA/Rho-kinase attenuates detrusor overactivity in a novel mouse experimental model

Abstract

Objective: To investigate detrusor function and cAMP activation as a possible target for detrusor overactivity in an experimental model lacking a key denitrosylation enzyme, S-nitrosoglutathione reductase (GSNOR).

Materials and methods: GSNOR-deficient (GSNOR^-/- ) (n = 30) and wild-type (WT) mice (n = 26) were treated for 7 days with the cAMP activator, colforsin (1 mg/kg), or vehicle intraperitoneally. Cystometric studies or molecular analyses of bladder specimens were performed. Bladder function indices and expression levels of proteins that regulate detrusor relaxation (nitric oxide synthase pathway) or contraction (RhoA/Rho-kinase pathway) and oxidative stress were assessed. For statistical analysis the Student's t-test and one-way analysis of variance were used.

Results: GSNOR^-/- mice had significantly higher (P < 0.05) voiding and non-voiding contraction frequencies compared to WT mice (Cohen's effect size values d = 1.82 and 2.52, respectively). Colforsin normalised these abnormalities (Cohen's effect size values d = 1.85 and 1.28, respectively). Western blot analyses showed an up-regulation of the RhoA/Rho-kinase pathway reflected by significantly higher (P < 0.05) phosphorylated myosin phosphatase target subunit 1 (P-MYPT-1) expression in GSNOR^-/- mouse bladders, which was reversed by colforsin treatment. There was a higher level (P < 0.05) of gp91^phox expression in the bladders of GSNOR^-/- mice without significant change after colforsin treatment. Neuronal and endothelial nitric oxide synthase phosphorylation on Ser-1412 and Ser-1177, respectively, did not differ between GSNOR^-/- and WT mouse bladders irrespective of colforsin treatment.

Conclusion: Impaired denitrosylation is associated with detrusor overactivity, which is linked with upregulated RhoA/Rho-kinase signalling. Colforsin reverses physiological and molecular abnormalities. This study describes a novel model of detrusor overactivity and suggests a possible basis for its treatment.

Keywords: animal model; cystometry; nitric oxide; overactive bladder; transnitrosylation.