Regulation of urinary bladder function by protein kinase C in physiology and pathophysiology

Pharmacological study on the enhancing effects of U46619 on guinea pig urinary bladder smooth muscle contraction induced by acetylcholine and α,β-methylene ATP and the possible involvement of protein kinase C

We examined whether U46619 (a prostanoid TP receptor agonist) could enhance the contractions of guinea pig urinary bladder smooth muscle (UBSM) in response to acetylcholine (ACh) and an ATP analog (α,β-methylene ATP (αβ-MeATP)) through stimulation of the UBSM TP receptor and whether protein kinase C (PKC) is involved. U46619 (10-7 M) markedly enhanced UBSM contractions induced by electrical field stimulation and ACh/αβ-MeATP (3 × 10-6 M each), the potentiation of which was completely suppressed by SQ 29,548 (a TP receptor antagonist, 6 × 10-7 M). PKC inhibitors did not attenuate the ACh-induced contractions enhanced by U46619 although they partly suppressed the U46619-enhanced, αβ-MeATP-induced contractions. While phorbol 12-myristate 13-acetate (PMA, a PKC activator, 10-6 M) did not enhance ACh-induced contractions, it enhanced αβ-MeATP-induced contractions, an effect that was completely suppressed by PKC inhibitors. αβ-MeATP-induced contractions, both with and without U46619 enhancement, were strongly inhibited by diltiazem. U46619/PMA enhanced 50 mM KCl-induced contractions, the potentiation of which was partly/completely attenuated by PKC inhibitors. These findings suggest that U46619 potentiates parasympathetic nerve-associated UBSM contractions by stimulating UBSM TP receptors. PKC-increased Ca2+ influx through voltage-dependent Ca2+ channels may partially play a role in purinergic receptor-mediated UBSM contractions enhanced by TP receptor stimulation.

The role of rhoA/rho-kinase and PKC in the inhibitory effect of L-cysteine/H2S pathway on the carbachol-mediated contraction of mouse bladder smooth muscle

We investigated the role of RhoA/Rho-kinase (ROCK) and PKC in the inhibitory effect of L-cysteine/hydrogen sulfide (H2S) pathway on the carbachol-mediated contraction of mouse bladder smooth muscle. Carbachol (10-8-10-4 M) induced a concentration-dependent contraction in bladder tissues. L-cysteine (H2S precursor; 10-2 M) and exogenous H2S (NaHS; 10-3 M) reduced the contractions evoked by carbachol by ~ 49 and ~ 53%, respectively, relative to control. The inhibitory effect of L-cysteine on contractions to carbachol was reversed by 10-2 M PAG (~ 40%) and 10-3 M AOAA (~ 55%), cystathionine-gamma-lyase (CSE) and cystathionine-β-synthase (CBS) inhibitor, respectively. Y-27632 (10-6 M) and GF 109203X (10-6 M), a specific ROCK and PKC inhibitor, respectively, reduced contractions evoked by carbachol (~ 18 and ~ 24% respectively), and the inhibitory effect of Y-27632 and GF 109203X on contractions was reversed by PAG (~ 29 and ~ 19%, respectively) but not by AOAA. Also, Y-27632 and GF 109203X reduced the inhibitory responses of L-cysteine on the carbachol-induced contractions (~ 38 and ~ 52% respectively), and PAG abolished the inhibitory effect of L-cysteine on the contractions in the presence of Y-27632 (~ 38%). Also, the protein expressions of CSE, CBS, and 3-MST enzymes responsible for endogenous H2S synthesis were detected by Western blot method. H2S level was increased by L-cysteine, Y-27632, and GF 109203X (from 0.12 ± 0.02 to 0.47 ± 0.13, 0.26 ± 0.03, and 0.23 ± 0.06 nmol/mg respectively), and this augmentation in H2S level decreased with PAG (0.17 ± 0.02, 0.15 ± 0.03, and 0.07 ± 0.04 nmol/mg respectively). Furthermore, L-cysteine and NaHS reduced carbachol-induced ROCK-1, pMYPT1, and pMLC20 levels. Inhibitory effects of L-cysteine on ROCK-1, pMYPT1, and pMLC20 levels, but not of NaHS, were reversed by PAG. These results suggest that there is an interaction between L-cysteine/H2S and RhoA/ROCK pathway via inhibition of ROCK-1, pMYPT1, and pMLC20, and the inhibition of RhoA/ROCK and/or PKC signal pathway may be mediated by the CSE-generated H2S in mouse bladder.

Machine Learning on a Genome-wide Association Study to Predict Late Genitourinary Toxicity After Prostate Radiation Therapy

PURPOSE

Late genitourinary (GU) toxicity after radiation therapy limits the quality of life of prostate cancer survivors; however, efforts to explain GU toxicity using patient and dose information have remained unsuccessful. We identified patients with a greater congenital GU toxicity risk by identifying and integrating patterns in genome-wide single nucleotide polymorphisms (SNPs).

METHODS AND MATERIALS

We applied a preconditioned random forest regression method for predicting risk from the genome-wide data to combine the effects of multiple SNPs and overcome the statistical power limitations of single-SNP analysis. We studied a cohort of 324 prostate cancer patients who were self-assessed for 4 urinary symptoms at 2 years after radiation therapy using the International Prostate Symptom Score.

RESULTS

The predictive accuracy of the method varied across the symptoms. Only for the weak stream endpoint did it achieve a significant area under the curve of 0.70 (95% confidence interval 0.54-0.86; P = .01) on hold-out validation data that outperformed competing methods. Gene ontology analysis highlighted key biological processes, such as neurogenesis and ion transport, from the genes known to be important for urinary tract functions.

CONCLUSIONS

We applied machine learning methods and bioinformatics tools to genome-wide data to predict and explain GU toxicity. Our approach enabled the design of a more powerful predictive model and the determination of plausible biomarkers and biological processes associated with GU toxicity.

Developmental changes in contractile responses to cholinergic stimuli: role of calcium sensitization and related pathways

This study was performed to analyze the developmental changes in bladder response to cholinergic stimulation in detail, highlighting calcium sensitization (CS) and its related pathways. Rats were divided into three groups in accordance with reported time of developmental milestones (newborns, days 1–4; youngsters, days 5–14; and grown-ups, days 15–28). Following cholinergic stimulation (carbachol, 5 µM), the contractile response to detrusor was analyzed with respect to three phases (initial phasic, tonic, and superimposed phasic contractions). Contractile responses were analyzed by their dynamic and kinetic aspects. The responses were further compared in varying external calcium concentrations and in the presence of inhibitors of protein kinase C (PKC) and Rho kinase (ROCK), which are involved in CS. The responses of newborns contrasted with the others by their short and brisk initial phasic contractions, prominent tonic contractions, and delayed participation of irregular superimposed phasic contractions. With development, phasic contractions became prominent, and tonic contractions diminished. These developmental changes in phasic contractions were reproduced when exposed to increasing calcium concentrations. Application of specific inhibitors and molecular phasic analysis revealed that PKC was functional in tonic contractions of the newborns, whereas ROCK took over its role with development. Within a few days of birth, rats’ bladders experienced drastic changes in contractile mechanisms. This included dominance of phasic contractions over tonic contractions due to increased calcium dependence and the maturational shift of the calcium sensitivity mechanism from PKC to ROCK.

Non-neurogenic Chronic Urinary Retention: What Are We Treating?

PURPOSE OF REVIEW

This review examines current terminology used to define non-neurogenic chronic urinary retention (CUR), describes the pathophysiology of urinary retention, and highlights contemporary diagnostic and treatment algorithms.

RECENT FINDINGS

There is no standardized definition for the condition, but volumes >300 ml are commonly used to describe CUR. It is a clinical diagnosis which does not require urodynamics. Pathophysiologic causes of CUR be from myogenic, neurogenic, bladder outlet obstruction, or a combination of these sources. Treatment algorithms recommend stratifying patients with chronic urinary retention by risk and by symptoms before initiating treatment. Common CUR outcome endpoints need to be better utilized so that treatment modalities can be compared. Non-neurogenic CUR is a heterogeneous condition that has multiple definitions, underlying physiologies, and possible endpoints. Standardization is needed to better understand and treat CUR.

Big-conductance Ca2+-activated K+ channels in physiological and pathophysiological urinary bladder smooth muscle cells

Contraction and relaxation of urinary bladder smooth muscle cells (UBSMCs) represent the important physiological functions of the bladder. Contractile responses in UBSMCs are regulated by a number of ion channels including big-conductance Ca²⁺- activated K⁺ (BK) channels. Great progress has been made in studies of BK channels in UBSMCs. The intent of this review is to summarize recent exciting findings with respect to the functional interactions of BK channels with muscarinic receptors, ryanodine receptors (RyRs) and inositol triphosphate receptors (IP₃Rs) as well as their functional importance under normal and pathophysiological conditions. BK channels are highly expressed in UBSMCs. Activation of muscarinic M₃ receptors inhibits the BK channel activity, facilitates opening of voltage-dependent Ca²⁺ (Ca_V) channels, and thereby enhances excitability and contractility of UBSMCs. Signaling molecules and regulatory mechanisms involving RyRs and IP₃Rs have a significant effect on functions of BK channels and thereby regulate cellular responses in UBSMCs under normal and pathophysiological conditions including overactive bladders. Moreover, BK channels may represent a novel target for the treatment of bladder dysfunctions.