Abstract
BackgroundProtein Kinase C (PKC) dysfunction is implicated in a variety of smooth muscle disorders including detrusor overactivity associated with frequency and urgency of micturition. In this study, we aimed to evaluate the modulatory effects of endogenous PKC-dependent pathways on bladder storage and emptying function.MethodsWe utilized in vivo cystometry and in vitro organ bath studies using isolated bladder muscle strips (BMS) from rats to measure contractility, intravesical pressure, and voided volume. Both in vitro and in vivo results were statistically analyzed using one-way repeated measures ANOVA between the groups followed by Bonferroni’s post-test, as appropriate (Systat Software Inc., San Jose, CA).ResultsEffects of PKC activators, phorbol-12,13-dibutyrate (PDBu), and phorbol-12,13-myristate (PMA), were concentration-dependent, with high concentrations increasing frequency of micturition, and sensitivity of intramural nerves to electrical field stimulation (EFS), in vitro, while lower concentrations had no effect on BMS sensitivity to EFS. The PKC inhibitors, bisindolylmaleimide1 (Bim-1), (28 nM), and Ro318220 (50 μM) triggered an increase in the number of non-voiding contractions (NVC), and a decrease in the voided volume associated with reduced ability to maintain contractile force upon EFS, but did not affect peak force in vitro. Both low (50 nM) and high PDBu 1 micromolar (1uM) decreased the sensitivity of BMS to carbachol. Application of a low concentration of PDBu inhibited spontaneous contractions, in vitro, and Bim-1-induced NVC, and restored normal voiding frequency during urodynamic recordings in vivo.ConclusionsIn summary, the effects of low PKC stimulation include inhibition of smooth muscle contractile responses, whereas high levels of PKC stimulation increased nerve-mediated contractions in vitro, and micturition contractions in vivo. These results indicate that endogenous PKC signaling displays a concentration-dependent contraction profile in the urinary bladder via both smooth muscle and nerve-mediated pathways.
Highlights
Protein Kinase C (PKC) dysfunction is implicated in a variety of smooth muscle disorders including detrusor overactivity associated with frequency and urgency of micturition
It was previously established that a number of detrusor smooth muscle (DSM) pathologies are linked to the changes in signaling proteins including, but not limited to, protein kinase C (PKC), Rho-associated kinase (ROK), and large conductance Ca2+-activated potassium (BK) channels [5,13,16,17,18,19,20,21,22,23,24,25,26]
This phenomenon has been previously reported in urothelium denuded bladder smooth muscle (BSM) strips isolated from the rabbit urinary bladder, and confirmed that the urothelium did not play a role in PKC-induced inhibition of bladder contractions [22]
Summary
Protein Kinase C (PKC) dysfunction is implicated in a variety of smooth muscle disorders including detrusor overactivity associated with frequency and urgency of micturition. Among identified mechanisms are neurogenic and myogenic alterations of detrusor contractility, as well as changes in bladder stiffness, and ion channels associated with partial bladder outlet obstruction (PBOO), and other pathological conditions of the urinary bladder [3,8,9,10,11,12,13,14,15]. It was previously established that a number of DSM pathologies are linked to the changes in signaling proteins including, but not limited to, protein kinase C (PKC), Rho-associated kinase (ROK), and large conductance Ca2+-activated potassium (BK) channels [5,13,16,17,18,19,20,21,22,23,24,25,26]. Social stress in rats may induce bladder overactivity, frequency of micturition, and decreased voided volumes [34]
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